外文翻译原文
外文文献翻译译稿和原文
外文文献翻译译稿1卡尔曼滤波的一个典型实例是从一组有限的，包含噪声的，通过对物体位置的观察序列（可能有偏差）预测出物体的位置的坐标及速度。
在很多工程应用（如雷达、计算机视觉）中都可以找到它的身影。
同时，卡尔曼滤波也是控制理论以及控制系统工程中的一个重要课题。
例如，对于雷达来说，人们感兴趣的是其能够跟踪目标。
但目标的位置、速度、加速度的测量值往往在任何时候都有噪声。
卡尔曼滤波利用目标的动态信息，设法去掉噪声的影响，得到一个关于目标位置的好的估计。
这个估计可以是对当前目标位置的估计（滤波），也可以是对于将来位置的估计（预测），也可以是对过去位置的估计（插值或平滑）。
命名[编辑]这种滤波方法以它的发明者鲁道夫.E.卡尔曼（Rudolph E. Kalman）命名，但是根据文献可知实际上Peter Swerling在更早之前就提出了一种类似的算法。
斯坦利。
施密特（Stanley Schmidt）首次实现了卡尔曼滤波器。
卡尔曼在NASA埃姆斯研究中心访问时，发现他的方法对于解决阿波罗计划的轨道预测很有用，后来阿波罗飞船的导航电脑便使用了这种滤波器。
关于这种滤波器的论文由Swerling（1958）、Kalman (1960)与Kalman and Bucy（1961）发表。
目前，卡尔曼滤波已经有很多不同的实现。
卡尔曼最初提出的形式现在一般称为简单卡尔曼滤波器。
除此以外，还有施密特扩展滤波器、信息滤波器以及很多Bierman, Thornton开发的平方根滤波器的变种。
也许最常见的卡尔曼滤波器是锁相环，它在收音机、计算机和几乎任何视频或通讯设备中广泛存在。
以下的讨论需要线性代数以及概率论的一般知识。
卡尔曼滤波建立在线性代数和隐马尔可夫模型（hidden Markov model）上。
其基本动态系统可以用一个马尔可夫链表示，该马尔可夫链建立在一个被高斯噪声（即正态分布的噪声）干扰的线性算子上的。
系统的状态可以用一个元素为实数的向量表示。
毕业论文外文翻译(中英文)
译文交通拥堵和城市交通系统的可持续发展摘要:城市化和机动化的快速增长,通常有助于城市交通系统的发展，是经济性，环境性和社会可持续性的体现,但其结果是交通量无情增加，导致交通拥挤。
道路拥挤定价已经提出了很多次，作为一个经济措施缓解城市交通拥挤，但还没有见过在实践中广泛使用，因为道路收费的一些潜在的影响仍然不明。
本文首先回顾可持续运输系统的概念,它应该满足集体经济发展,环境保护和社会正义的目标.然后,根据可持续交通系统的特点，使拥挤收费能够促进经济增长，环境保护和社会正义。
研究结果表明,交通拥堵收费是一个切实有效的方式，可以促进城市交通系统的可持续发展。
一、介绍城市交通是一个在世界各地的大城市迫切关注的话题。
随着中国的城市化和机动化的快速发展,交通拥堵已成为一个越来越严重的问题,造成较大的时间延迟,增加能源消耗和空气污染，减少了道路网络的可靠性．在许多城市,交通挤塞情况被看作是经济发展的障碍.我们可以使用多种方法来解决交通挤塞,包括新的基础设施建设，改善基础设施的维护和操作,并利用现有的基础设施,通过需求管理策略,包括定价机制,更有效地减少运输密度.交通拥堵收费在很久以前就已提出，作为一种有效的措施,来缓解的交通挤塞情况。
交通拥堵收费的原则与目标是通过对选择在高峰拥挤时段的设施的使用实施附加收费,以纾缓拥堵情况．转移非高峰期一些出行路线,远离拥挤的设施或高占用车辆，或完全阻止一些出行,交通拥堵收费计划将在节省时间和降低经营成本的基础上,改善空气中的质量，减少能源消耗和改善过境生产力。
此计划在世界很多国家和地方都有成功的应用。
继在2０世纪70年代初和8０年代中期挪威与新加坡实行收费环,在20０３年2月伦敦金融城推出了面积收费；直至现在,它都是已经开始实施拥挤收费的大都市圈中一个最知名的例子。
然而,交通拥堵收费由于理论和政治的原因未能在实践中广泛使用。
道路收费的一些潜在的影响尚不清楚,和城市发展的拥塞定价可持续性,需要进一步研究。
外文翻译及原文
Pyrolysis of oil sludge first by thermogravimetry/mass spectroscopy (TG/MS) and then in a horizontal quartz reactor with an electrical laboratory furnace under different pyrolysis conditions was carried out. The influence of heating rate from 5 to 20 °Camin-1, final pyrolysis temperature from 400 to 700 °C, various interval holding stage, and catalyst on the products were investigated in detail. The TG/MS results show that pyrolysis reaction of oil sludge starts at a low temperature of about 200 °C, and the maximum evolution rate is observed between the temperatures of 350-500 °C. A higher final pyrolysis temperature, an interval holding stage, and adding catalyst can promote the pyrolysis conversion (in terms of less solid residue production). In all parameters, an interval holding stage for 20 min near the peak temperature of 400 °C can enhance the yield of oil and improve its quality. Three additives used in this work as catalysts do not improve oil product quality markedly in spite of increasing pyrolysis conversion greatly.油泥的裂解首先通过热重/质谱分析（TG / MS），然后在水平石英反应器中具有不同热解条件下的电气实验室炉进行。
自动化专业-外文文献-英文文献-外文翻译-plc方面
1、外文原文（复印件)A: Fundamentals of Single-chip MicrocomputerTh e si ng le-ch i p mi cr oc om pu ter is t he c ul mi nat i on o f bo th t h e d ev el op me nt o f th e d ig it al com p ut er an d t he int e gr at ed ci rc ui ta r gu ab ly th e t ow m os t s i gn if ic ant i nv en ti on s o f t h e 20t h c en tu ry[1].Th es e to w t ype s o f a rc hi te ct ur e a re fo un d i n s i ng le—ch ip m i cr oc om pu te r。
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3-5A-2.In g en er al te r ms a s in gl e—ch i p mi cr oc om pu ter isc h ar ac te ri zed b y the i nc or po ra tio n of al l t he uni t s o f a co mp ut er i n to a s in gl e de v i ce，as s ho wn i n F ig3—5A—3。
外文翻译英语原文编号01
Vol.25 No.2 PANG Chaoming et al: Methods of Modifying the Brittle (156)DOI 10.1007/s11595-010-1156-yMethods of Modifying the Brittle Behavior ofCementitious CompositesPANG Chaoming1, SUN Wei1, LEUNG Christopher KY2(1.College of Materials Science and Engineering, Southeast University, Jiangsu Key laboratory of Construction Materials, Nanjing 211189,China;2. Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong, China SAR)Abstract: We put forward effective methods of increasing the tensile strain of cementitiouscomposites with 2% PVA fiber and high fly ash content. The test results show that curing condition hasa significantly effect on the tensile performance. It is approved that the specimens incorporated ap-propriate volume fraction rubber powder and lightweight aggregate greatly increase the tensile strain ofcomposites at medium-term age, but indefinitely at long-term age. To a certain extent, EVA can limitedlyenhance the tensile performance of comentitious composites owing to the formation of polymer membraneand the hindered hydration of cement.Key word: high-ductility cementitious composites (HDCC); tensile properties; high content offly ash; rubber powder; light aggregate; ethylene vinyl alcohol latex powder1 IntroductionCementitious composites are widely used as the majority of structural materials. However, cementitious composites are limited to some special projects due to the inherently brittle behavior. Most efforts have been made to modify the brittle behavior of cementitious composites all along. As a result, the fiber reinforced cementitious composites (FRCC) occurred. In comparison to plain concrete, FRC usually deteriorates the tensile or bending properties by the formation of several cracks and a main crack. In the past two decades, Li, Leung and Wu etc[1-3] investigated the bridging stress of fiber and proposed the theory for high-ductility cementitious composites (here-after abbreviated as HDCCs) or pseudo ductility cemen-titious composites or pseudo strain hardening cementi-tious composites, based on the two nondimensionalized parameters energy absorption rate and normalized flaw size. It has been demonstrated that the ductility behaviors of brittle materials can be achieved by multiple cracks in steady state along the length of the specimen and behave pseudo strain hardening (abbr. PSH). Hereafter, the theories for PSH in the cementitious composites were gradually developed by Li and his co-workers, and the particular theory for “composite design”, based on the micro mechanics parameter, by emphasizing the proper integrant materials and interface was proposed[4,5]. The cementitious composite with high tensile strain capacity of 3%-6%, whose strain capacity is far outperforming conventional cementitious composites, was achieved[6].Recently increasing researchers are interesting to the new type of fiber reinforced cementitious composite. However, it is not easy to achieve PSH in discontinuous random fiber reinforced. Strain due to a little deviation of raw materials occur even if the well-known same mixture proportion of ECC is used due to a little deviation of raw materials. Meanwhile, the design method of existing theory depend on known experimental micro mechanics parameters, such as the fracture toughness, fiber content, fiber strength, fiber distribution, the bridging stress and interface properties between fiber matrix, etc. Moreover, it is very difficult to achieve the accurate fiber distribu-tion and bridging stress due to the randomization and inhomogeneity of the distribution of fiber in composites. But the micromechanical parameters and the ductile be-havior is strongly affected by the bridging stress governed by fiber debonding, fiber bending, fiber rupture, matrix spalling and their coupling[2].The focus in the current study is to discover the ef-ficacious methods to increase the tensile strain of HDCC. It is well know that curing conditions have a significantly©Wuhan University of Technology and Springer-Verlag Berlin Heidelberg 2010 (Received: Jan. 6, 2009; Accepted: Oct. 16, 2009)PANG Chaoming(庞超明): Ph D candidate; E-mail: pangchao@seu. edu. cnJournal of Wuhan University of Technology-Mater. Sci. Ed. Feb.2010157conditions were used for comparison, considering that the structures in practice project are often exposed to different environment and different curing condition are usually applied according to the lab environment in the different researches. For the brittle cementitious com-posites, the matrix cracking strength, which is determined by the matrix toughness and the largest crack or flaw in the stress section of specimen provided that the matrix cracking is controlled by fracture process, does not de-crease unlimitedly but reaches a lower bound at steady state cracking stress with the growing flaw size [7]. Moreover, the discontinuous pre-existing flaw or mi-cro-voids may relax the crack-tip stress triaxiality, dif-fuse the intensity of crack-tip stress singularity and consume more energy. To ensure the formation of multiple cracks, it is desirable to introduce a rtificial flaws in the matrix to reduce its crack tip toughness and increase the crack size due to energy absorption of flaw [8]. Therefore, different materials, such as rubber powder and fine lightweight aggregate, were added to the composites to increase the strain capacity.2 ExperimentalSpecial green island brand P·II 52.5 cement was used. The range of particle size of fly ash is mainly 2-10 μm, and the active index of compressive strength at 7 days, 28 days and 90 days are the 86%, 84% and 96% respectively followed by ASTM C311-04. Polyvinyl alcohol fiber (abbr. PVAF) produced by Japan Kuraray Limited Corporation was used, and its density, length, diameter were 1.3 g/cm 3, 12 mm, 38 μm respectively,also its elastic modulus and rate of elongation is 33 GPaand 6.5% respectively.The particle size of silica fume, silica filler and silica sand used is 1-20 μm, 1-15 μm and 50-200 μm respec-tively. ADVA105 superplastics admixture (abbr. Sp) was ％produced by Grace Co.LTD and its solid content is 23. SP4000 (abbr. SP4), which is ethylene vinyl alcohol (abbr. EVA) latex powder and is produced by Japan Kuraray Trading Co.LTD, was used in this study. The particle size of lightweight aggregate (abbr. LA) is between 1 mm and 3 mm, whose specific density is 1 500 kg/m 3, and the loose volume weight is about 780 kg/m 3. Rubber pow-der with the particle size of 0.4 mm was also used.The specimen was demoulded 24 hours after casting, where the temperature and relative humidity was about 20±2 ℃ and (60±5)％ respectively, then cured in water at curing room , where the temperature is 27 ℃ (ac-cording to the BS standard). The nominal sizes used for tensile performance and compressive performance are about 350×50×15 mm and 40×40×40 mm respec-tively. The dimensions of the specimen were accurately measured by vernier caliper and all the specimens were polished to smooth surface before testing to obtain ac-curate experimental results, and at least three specimens were tested at each age.The tensile performance was tested under the dis-placement control in the MTS810-25 kN materials test-ing system with the displacement rate of 0.15 mm/min. Linear variable displacement transducer was used to measure the displacement at the gage length of 150 mm for the more accuracy purpose. The first crack strain εfc , the peak strain εp and the maximum strain εm repre-sent to the strain corresponding to the first crack stress σTc when the first crack occurred, peak stress σTp when the stress reaches the peak, and the strain when the stress descends up to 90% σTp , respectively.3 Results3.1 Effect of curing conditions on me-chanical properties of HDCCAccording to previous work, two mix proportions shown in Table 1 were used, i e , SP4 and W1 with high volume fraction fly ash and low ratio of water to binder (cement and fly ash). Table 1 Mix proportion in mass of HDCC No. cement FA SP4 sand water Sp PVAF SP4 1 3.9 0.1 1.0 1.1 0.022 0.090 W1 1 4.0 0 1.0 1.0 0.023 0.096For the purpose of comparing the effect of different curing condition on the tensile performance, four types of curing conditions were applied in mixture SP4 as fol-lowing: full dry curing in room temperature condition after demoulded, which corresponds to symbol D in the denominated title in Table 2, dry curing in room tem-perature condition after 3-day curing in water corre-sponding to symbol W3D, dry curing in room tempera-ture condition after 7-day water curing corresponding to symbol W7D, and 28-day water curing corresponding to symbol W. The only two types of curing conditions wereused in mixture W1: dry curing in room temperature condition after 7 days water curing and full water curing. Table 2 list the test results of the tensile strength and strain and compressive strength on different curing con-ditions at the age of 7-day and 28-day.Vol.25 No.2 PANG Chaoming et al : Methods of Modifying the Brittle …1583.2 Effect of rubber powder on mechanic-al properties of HDCCThe specimen without rubber powder is regarded as control specimen, and two mixtures of HDCCs with the rubber powder were prepared. SR7 and SR11 represent for HDCC of the volume fraction of 7% and 11%, re-spectively. For estimating the long-term performance, the accelerated curing method was conducted, that is, after cured in water for 7 days, at least three specimens were put to the heat curing room for 72 hours, where the temperature and relative humidity are 80 ℃％and 95respectively, the mechanical performance was measured after being cooled down in the room temperature condi-tion. The mix proportion used and test results are sum-marized in Table 3, Table 4 respectively. Heat curing corresponds to symbol HC. Fig.1 shows the tensile stress versus strain curves of SR7 and SR11 at 28 days.3.3 Effect of lightweight aggregate onmechanical properties of HDCC For the purpose of researching the effect of light-weight aggregate on the tensile strain of HDCC with highflyash content, the volume fraction of 3.5% was incor-porated into the mixture, and the mix proportion was listed in Table 5. The specimen FA3 and FA3LA corre-spond to control specimen and specimen with lightweight aggregate, respectively.The test results are shown in Table 6. The condition of heat curing is the same as mentioned above. Fig.2(a) and Fig.2(b) showed the typical stress vs strain curve of FA3 and FA3LA3.5 at different age: 7 days, 28 days and heat curing 3 days.Table 2 Test results of HDCC on different curing conditionsSP4D SP4W3D SP4W7D SP4W W1 7-day 28-day 7-day 28-day 28-day 90-day 7-day 28-day W7 W28 W7DσTfc /MPa 2.68 2.36 2.91 2.54 3.26 3.28 2.70 3.36 2.76 3.65 3.62 εfc /% 0.080 0.069 0.075 0.096 0.080 0.089 0.119 0.060 0.088 0.047 0.128 σTp /MPa 3.30 3.39 3.76 3.14 4.07 3.62 3.17 4.02 3.27 3.81 4.69εp /% 1.53 3.95 2.69 2.56 2.82 2.58 2.78 0.77 1.050.35 2.94 εm /% 1.69 4.28 2.80 2.79 3.54 2.66 2.97 1.81 1.360.54 3.39 σcom /MPa 22.8 27.2 — — — — 23.4 36.0 35.8 58.9 — Table 3 Mix proportion in mass of HDCC with different volume fraction of rubber powder No. Cement FA Filler Sand Rubber Water Sp PVAFControl 1 1.50 0.25 1.00 0 0.63 0.015 0.057 SR7 1 1.50 0.25 0.65 0.163 0.58 0.020 0.055 SR11 1 1.50 0.25 0.40 0.263 0.58 0.020 0.055 Table 4 Test results of HDCCs with different volume fraction of rubber powderControl SR7 SR117-day 28-day 90-day 7-day 28-day HC 7-day 28-day HCσTfc /MPa 3.58 4.61 3.81 2.31 2.60 3.63 2.19 2.31 3.28 εfc /% 0.050 0.042 0.027 0.036 0.022 0.039 0.034 0.051 0.041 σTp/MPa 4.30 5.05 4.53 2.49 3.00 3.81 2.72 3.18 3.57 εp /% 1.33 0.84 0.29 0.31 0.58 0.16 1.04 2.15 0.20 εm/% 1.59 0.98 0.39 0.54 1.07 0.71 1.40 2.49 0.34 σcom /MPa 49.6 66.2 — 29.7 35.7 40.5 24.8 31.4 37.0 Table 5 Mix proportion in mass No. Cement FA LA Sand Water Sp PVAF FA3 1 3 — 1 1 0.025 0.056 FA3LA 1 3 0.16 1 1 0.028 0.056 Table 6 Test results of HDCCs with or without lightweightaggregate FA3 FA3LA 7 d 28 d 90 d HC 7 d 28 d 90 d HCσTfc /MPa 1.42 2.68 3.60 4.38 2.86 3.15 3.25 6.42εfc /% 0.015 0.044 0.031 0.022 0.025 0.045 0.040 0.037 σTp /MPa 2.91 3.46 4.86 4.86 2.86 3.91 3.92 6.49εp /% 0.04 0.58 0.29 0.08 0.03 1.96 0.23 0.04 εm /% 1.16 0.96 0.66 0.31 1.40 2.07 0.54 0.38 σcom/MPa 21.5 44.7 69.5— 19.0 44.2 74.8 —Journal of Wuhan University of Technology-Mater. Sci. Ed. Feb.20101593.4 Effect of EVA powder on mechanicalproperties of HDCCA series of HDCCs specimens with or without EVA powder were also prepared, cured and tested at prescribed age followed by the test procedure. The condition of heat curing is also the same as mentioned above. The mix proportion used is listed in Table 7, and test results of tensile properties are presented in Table 8 and Fig.2(c) respectively. S is the control specimen, and SS4 is representative for HDCC with EVA powder.4 Discussion It can be concluded that the curing conditions have a great effect on the tensile properties from Table 1 and Table 2. The tensile properties exhibit a great difference at 28 days due to different curing condition for mixture SP4 and mixture W1. The HDCC cured in water per-forms better than that in room temperature condition atthe early age, however, as the age increases, the tensileperformance of HDCCs cured in room temperature condition shows an increasing tendency while that curedin the water decreases. The tensile strain of specimensthat of W3D is similar to that of W7D at 28 days, whichtest results also show the ultimate tensile strength has not direct relationship with the tensile strain, and high tensile strain do not mean low tensile strength, and vice versa . That can be explained as follows: curing condi-tion plays a significant influence on microstructure and macroscopical performance of cementitious composites. For fiber reinforced cementitious composites, there exists a distinctive layer of interface zone about 30-50 μm away from the fiber surface [9]. Also the interface will strongly influence the toughness of the compositesand frictional bond [10]. Generally the interface zone is considerable weaker than the matrix due to the large calcium hydroxide crystals and higher porosity for the FRCCs with steel fiber or polypropylene fiber [9], but thePVA fiber is a special organic fiber to the cementitiouscomposites. The majority of fibers used to the cementi-tious composites, such as steel fiber, polypropylenefiber,etc , will not react with the hydration products of cement, but the investigations by Akers show that [11], the PVA fiber performs surprisingly high chemical bonding between the PVA fiber and cement hydrationproducts due to the strong hydrophilic characteristic or hydrogen intermolecular bond induced by the hydroxyl groups, and as the age increase, while there are no evi-dent change in fiber properties, the bonding strengthbetween fiber and cement-based matrix will increase due to an increase in interface bond with age. The re-searches by Kanda T etc also shows that the apparent chemical bonding between PVA fiber and cement ma-，trix independent of the water-to cement ratio of matrix, is relatively stable and up to 30-40 MPa, but the value of friction bond, affected by water to cement ratio, is be-tween 2.2 MPa to 4.4 MPa when the water to cementvaries from 0.62 to 0.27[12]. Through the investigation by Li and his co-workers [3], only the FRCC with the appropriate fracture toughness of matrix and frictional Table 7 Mix proportion with or without EVA in mass No. Cement FA SF SP4 Sand Water Sp PVAF S 1 3.85 0.1 — 1 1.21 0.033 0.096 SS4 1 3.60 0.1 0.1 1 1.21 0.032 0.096 Table 8 Test results of HDCCs with or without EVAS SS47 d 28 d HC 7 d 28 d HCσTfc /MPa 1.15 3.32 4.37 1.86 3.14 3.89 εfc/% 0.021 0.067 0.029 0.057 0.086 0.049 σTp /MPa 1.94 3.43 4.90 2.03 3.42 4.75 εp /% 0.20 1.18 0.33 0.49 1.24 0.60εm /% 0.54 1.63 0.40 1.55 1.73 0.74 σcom /MPa 13.0 33.5 — 13.0 35.4 — (a) FA3 (b) FA3LA (c) S and SS4Fig.2 Stresses vs. Strain curves of FA3, FA3LA, S and SS4 at different ageVol.25 No.2 PANG Chaoming et al: Methods of Modifying the Brittle (160)and high strain capacity of FRCC can dominantly be achieved by using PVA fiber, and the interfacial fric-tional stress for FRCC with PSH behavior show the relative definite requirement and shall preferably be between 0.8 to 2.0 MPa[13], and the value can be achieved by applying oil agent[14]. In the present study, the PVA fiber, which had been coated with the oiling agent by Japan Kuraray Co. LTD, was employed. Ow-ing to low water to binder ratio and high content of fly ash (W/B＝0.20, FA/C＝4.0), and the specimens were kept only for 0-7 days in water and then longer than 20 days cured in room temperature condition, where there is no enough water for cement hydration, therefore they exhibit relative lower hydration degree and larger shrinkage than those cured in the water in all time. The lower hydration degree and larger shrinkage result in relatively lower frictional bond and weaker interface between PVA fiber and matrix[15]. Therefore, the former forms relatively looser structure and satisfies the re-quirement of low interfacial frictional stress, therefore performs better in strain hardening. Also the failure pat-tern of fiber rupture can be observed in testing process of the latter.In general, the definite range of interfacial fric-tional stress for achieving PSH behavior of FRCC, lower ratio of cement to binder, high fly ash content and PVA fiber properties contribute to the effect of curing condition on the tensile behavior.It can be deduced from Table 4, Table 6, Fig.1 and Fig.2 that the tensile strength of HDCC with rubber powder or light aggregate keep on growing, while the tensile strain also increases as the age increases from 7 days to 28 days, then decreased as the age continually grows up to 90 days or when heat curing was applied. That is because the fiber/matrix bond strength should saturate in a duration of less than 14-28 days, and ma-ture much earlier than matrix properties in cementi-tious[16]. But the high content of fly ash will considera-bly lower the chemical bond and delay the mature due to diluting the metal cation concentration on the fiber surface at early age and as a result the strain increases from 7 days to 28 days[17]. But the friction strength and the facture toughness of matrix continue to develop as age increase to 28 days as the second hydration of fly ash continually develop due to activity effect of fly ash under high temperature or at long age. When the imbal-ance of develop rate occurs, the strain decreases with the continual increasing age.From Table 4 and Table 6, not all the specimens show better tensile performance than the control specimen, only the tensile strain of the specimens with 11% volume fraction rubber powder or 3.5% light-weight aggregate increase comparing to the control specimen at 28 days. The specimens FA3 and FA3LA rapidly reach ultimate strength then crack, and only few cracks develop due to the high fracture toughness of matrix and the low friction between matrix and PVA fiber at 7 days, but the specimen can still maintain the considerable strain after cracking owing to fiber gradu-ally being pulled out. And the SR7 also shows the similar tendency at 28 days. It is possible that the frac-ture toughness of matrix develops faster than the chemical bond and the frictional bond due to the low ratio of water to binder and high content fly ash. However, the specimen with the 11% volume fraction rubber pow-der reaches 2.15% in comparison with only 0.84% for the corresponding control specimen and the ultimate strain of with or without lightweight aggregate varies from 1.96% to 0.58%. The similar test results, i e, pre-existing flaw or micro-voids can modify the brittle behavior of HDCC, were observed in the reference[8] as the pre-existing flaw can relax the crack-tip triaxiality, diffuse the intensity of crack-tip stress and consume more energy, and the lager flaw will not influence the cracking strength but reached a lower bound at a steady state of cracking stress.Table 8 and Fig.2 present that the EVA latex powder show a little positive effect on the tensile strain at different age. It is possible that the EVA as a polymer can form a layer polymer membrane, which hinders the hydration of cementitious materials, but the membrane only influences a little hydration process owing to the lower content, about 1% volume fraction, in compos-ites.In summary, the appropriate fracture toughness of matrix and frictional bond between fiber and matrix is necessary conditions to achieve the PSH behavior or high strain capability. The curing condition emphasize particularly on the influence of friction bond, but the incorporation of rubber powder and lightweight lay particular stress on the fracture toughness of matrix. However the incorporation of rubber powder and lightweight aggregate lower the fracture toughness of matrix and facilitate the crack of matrix, which will possibly lower the effect of curing condition on the tensile properties.Journal of Wuhan University of Technology-Mater. Sci. Ed. Feb.2010 1615 ConclusionsSome methods to modifying the brittle behavior of HDCC with high content fly ash are proposed. It is undoubted that curing condition will strongly influence the microstructure of cementitious composites. The test results show that curing condition has a significant ef-fect on the tensile strain of HDCC with high content fly ash, and dry curing condition will show the clear trend to increase the tensile strain of HDCC with high content fly ash. Not all the specimens but the specimens with appropriate volume fracture rubber powder and light-weight aggregate greatly enhance the tensile strain of HDCC at medium-term age, but indefinitely at long-term age impossibly because disconnected pre-existing flaw or micro-voids may relax the crack-tip, diffuse the intensity of crack-tip stress and significantly consume energy. To a certain extent, EVA can enhance the tensile performance of HDCC owing to the hindered hydration of cement based materials as a result of the formation of polymer membrane. But it is possible that the incorporation of rubber powder and lightweight will lower the effect of curing condition on the tensile per-formance.It also experimentally demonstrates that some specimens rapidly reach ultimate strength and crack, but some specimen can still maintain the considerable strain after cracking owing to fiber gradually being pulled out. The tensile stress keeps increasing, but the tensile strain firstly increases then decreases as the age continually grows because of the imbalance of develop rate between bond strength and matrix properties. References[1]LI V C and LEUNG C K Y. Steady-state and MultipleCracking of Short Random Fiber Composites[J]. Journal ofEngineering Mechanics, 1992, 118(11): 2 246-2 264[2]LEUNG C K Y and LI V C. Effect of Fiber Inclination onCrack Bridging Stress in Fiber Reinforced Brittle MatrixComposites[J]. Journal of Mechanical Physics, 1992, 40(6):1 333-1 362[3]LI V C and WU H C. Conditions for PseudoStrain-Hardening in Fiber Reinforced Brittle MatrixComposites[J]. Applied Mechanics Revolution, 1992, 45(8):390-398[4]LI V C, MISHRA D K and WU H C. Matrix Design forPseudo-Strain-Hardening Fiber Reinforced CementitiousComposites[J]. Materials and Structures, 1995, 28: 586-595 [5]KANDA T, LI V C and Member of ASCE. New Micro-mechanics Design Theory for Pseudostrain Hardness Ce-mentitious Composite[J]. Journal of Engineering Me-chanics, 1999, 125(4): 373-381[6]LI V C, WANG S and WU C. Tensile Strain- HardeningBehavior or Polyvinyl Alcohol Engineered CementitiousComposite (PVA-ECC)[J]. ACI Materials Journal, 2001,98(6): 483-492[7]MAESHALL D B, COX B N and EVANS A G. The Mechan-ics of Matrix Cracking in Brittle Matrix Fiber Composites[J].ACTA Metallurgical, 1985, 33(11): 2 013-2 021[8]WANG S and LI V C. Tailoring of Pre-Existing Flaw inECC Matrix for Saturated Strain Hardening[C]. Proceed-ings of the Fifth International Conference on FractureMechanics of Concrete and Concrete Structures. Colorado:Ia-FraMCos, 2004: 1 005-1 012[9]Li V C, WU H C, and CHAN Y W. Interfacial PropertyTailoring for Pseudo Strain-Hardening Cementitious Composites[C]. Advanced Technology on Design and Fabrication of Composite Materials and Structures. Neth-erlands: Kluwer Acad. Publ., 1995: 261-268[10]SUN W, MANDEL J A and SAID Samir. Studies of theProperties of the Fiber-Matrix Interface in Steel Fiber Re-inforced Mortar[J]. ACI Materials Journal, 1987, 84(12):101-109[11]AKERS S A S. Long Term Durability of PVA ReinforcingFibers in a Cement Matrix[J]. The International Journal ofCement Composite and Lightweight Concrete, 1989, 11:79-91[12]KANDA T and LI V C. Interface Property and ApparentStrength of High-Strength Hydrophilic Fiber in CementMatrix[J]. Journal of Materials in Civil Engineering, 1998,10(1): 5-13[13]LI V C and WANG S. Process for Increasing the Ductilityof High Performance Fiber-Reinforced Brittle Matrix Composites and Composites Produced Thereby[P]. US Patent 7169224. 2007-01-30[14]REDON C. Measuring and Modifying Interface Propertiesof PVA Fibers in ECC Matrix[J]. ASCE J. Materials inCivil Engineering, 2001, 13(6): 399-406[15]CHEN H SUN W and PIET S. Interfacial Transition ZoneBetween Aggregate and Paste in Cementitious Composites(II): Mechanism of Formation and Degradation of Interfa-cial Transition Zone Microstructure and Its Influence Factors[J].Journal of the Cement Ceramic Society, 2004, 32(1): 70-80 [16]CHAN Y W and LI V C. Age Effect on the Characteristicsof Fibre/Cement Interfacial Properties[J]. Journal of Ma-terials Science, 1997, 32: 5 287-5 292[17]WANG S and LI V C. Engineered Cementitious Compos-ites with High-Volume Fly Ash[J]. ACI Materials Journal,2007, 104(3): 233-241。
毕业论文外文翻译范例
外文原文(一)Savigny and his Anglo-American Disciple s*M. H. HoeflichFriedrich Carl von Savigny, nobleman, law reformer, champion of the revived German professoriate, and founder of the Historical School of jurisprudence, not only helped to revolutionize the study of law and legal institutions in Germany and in other civil law countries, but also exercised a profound influence on many of the most creative jurists and legal scholars in England and the United States. Nevertheless, tracing the influence of an individual is always a difficult task. It is especially difficult as regards Savigny and the approach to law and legal sources propounded by the Historical School. This difficulty arises, in part, because Savigny was not alone in adopting this approach. Hugo, for instance, espoused quite similar ideas in Germany; George Long echoed many of these concepts in England during the 1850s, and, of course, Sir Henry Sumner Maine also espoused many of these same concepts central to historical jurisprudence in England in the 1860s and 1870s. Thus, when one looks at the doctrinal writings of British and American jurists and legal scholars in the period before 1875, it is often impossible to say with any certainty that a particular idea which sounds very much the sort of thing that might, indeed, have been derived from Savigny's works, was, in fact, so derived. It is possible, nevertheless, to trace much of the influence of Savigny and his legal writings in the United States and in Great Britain during this period with some certainty because so great was his fame and so great was the respect accorded to his published work that explicit references to him and to his work abound in the doctrinal writing of this period, as well as in actual law cases in the courts. Thus, Max Gutzwiller, in his classic study Der einfluss Savignys auf die Entwicklung des International privatrechts, was able to show how Savigny's ideas on conflict of laws influenced such English and American scholars as Story, Phillimore, Burge, and Dicey. Similarly, Andreas Schwarz, in his "Einflusse Deutscher Zivilistik im Auslande," briefly sketched Savigny's influence upon John Austin, Frederick Pollock, and James Bryce. In this article I wish to examine Savigny's influence over a broader spectrum and to draw a picture of his general fame and reputation both in Britain and in the United States as the leading Romanist, legal historian, and German legal academic of his day. The picture of this Anglo-American respect accorded to Savigny and the historical school of jurisprudence which emerges from these sources is fascinating. It sheds light not only upon Savigny’s trans-channel, trans-Atlantic fame, but also upon the extraordinarily*M.H.Hoeflich, Savigny and his Anglo-American Disciples, American Journal of Comparative Law, vol.37, No.1, 1989.cosmopolitan outlook of many of the leading American and English jurists of the time. Of course, when one sets out to trace the influence of a particular individual and his work, it is necessary to demonstrate, if possible, precisely how knowledge of the man and his work was transmitted. In the case of Savigny and his work on Roman law and ideas of historical jurisprudence, there were three principal modes of transmission. First, there was the direct influence he exercised through his contacts with American lawyers and scholars. Second, there was the influence he exercised through his books. Third, there was the influence he exerted indirectly through intermediate scholars and their works. Let us examine each mode separately.I.INFLUENCE OF THE TRANSLATED WORKSWhile American and British interest in German legal scholarship was high in the antebellum period, the number of American and English jurists who could read German fluently was relatively low. Even those who borrowed from the Germans, for instance, Joseph Story, most often had to depend upon translations. It is thus quite important that Savigny’s works were amongst the most frequently translated into English, both in the United States and in Great Britain. His most influential early work, the Vom Beruf unserer Zeitfur Rechtsgeschichte und Gestzgebung, was translated into English by Abraham Hayward and published in London in 1831. Two years earlier the first volume of his History of Roman Law in the Middle Ages was translated by Cathcart and published in Edinburgh. In 1830, as well, a French translation was published at Paris. Sir Erskine Perry's translation of Savigny's Treatise on Possession was published in London in 1848. This was followed by Archibald Brown's epitome of the treatise on possession in 1872 and Rattigan's translation of the second volume of the System as Jural Relations or the Law of Persons in 1884. Guthrie published a translation of the seventh volume of the System as Private International Law at Edinburgh in 1869. Indeed, two English translations were even published in the far flung corners of the British Raj. A translation of the first volume of the System was published by William Holloway at Madras in 1867 and the volume on possession was translated by Kelleher and published at Calcutta in 1888. Thus, the determined English-speaking scholar had ample access to Savigny's works throughout the nineteenth century.Equally important for the dissemination of Savigny's ideas were those books and articles published in English that explained and analyzed his works. A number of these must have played an important role in this process. One of the earliest of these is John Reddie's Historical Notices of the Roman law and of the Progress of its Study in Germany, published at Edinburgh in 1826. Reddie was a noted Scots jurist and held the Gottingen J.U.D. The book, significantly, is dedicated to Gustav Hugo. It is of that genre known as an external history of Roman law-not so much a history of substantive Roman legal doctrine but rather a historyof Roman legal institutions and of the study of Roman law from antiquity through the nineteenth century. It is very much a polemic for the study of Roman law and for the Historical School. It imparts to the reader the excitement of Savigny and his followers about the study of law historically and it is clear that no reader of the work could possibly be left unmoved. It is, in short, the first work of public relations in English on behalf of Savigny and his ideas.Having mentioned Reddie's promotion of Savigny and the Historical School, it is important to understand the level of excitement with which things Roman and especially Roman law were greeted during this period. Many of the finest American jurists were attracted-to use Peter Stein's term-to Roman and Civil law, but attracted in a way that, at times, seems to have been more enthusiastic than intellectual. Similarly, Roman and Civil law excited much interest in Great Britain, as illustrated by the distinctly Roman influence to be found in the work of John Austin. The attraction of Roman and Civil law can be illustrated and best understood, perhaps, in the context of the publicity and excitement in the English-speaking world surrounding the discovery of the only complete manuscript of the classical Roman jurist Gaius' Institutes in Italy in 1816 by the ancient historian and German consul at Rome, B.G. Niebuhr. Niebuhr, the greatest ancient historian of his time, turned to Savigny for help with the Gaius manuscript (indeed, it was Savigny who recognized the manuscript for what it was) and, almost immediately, the books and journals-not just law journals by any means-were filled with accounts of the discovery, its importance to legal historical studies, and, of course, what it said. For instance, the second volume of the American Jurist contains a long article on the civil law by the scholarly Boston lawyer and classicist, John Pickering. The first quarter of the article is a gushing account of the discovery and first publication of the Gaius manuscript and a paean to Niebuhr and Savigny for their role in this. Similarly, in an article published in the London Law Magazine in 1829 on the civil law, the author contemptuously refers to a certain professor who continued to tell his students that the text of Gaius' Institutes was lost for all time. What could better show his ignorance of all things legal and literary than to be unaware of Niebuhr's great discovery?Another example of this reaction to the discovery of the Gaius palimpsest is to be found in David Irving's Introduction to the Study of the Civil Law. This volume is also more a history of Roman legal scholarship and sources than a study of substantive Roman law. Its pages are filled with references to Savigny's Geschichte and its approach clearly reflects the influence of the Historical School. Indeed, Irving speaks of Savigny's work as "one of the most remarkable productions of the age." He must have been truly impressed with German scholarship and must also have been able to convince the Faculty of Advocates, forwhom he was librarian, of the worth of German scholarship, for in 1820 the Faculty sent him to Gottingen so that he might study their law libraries. Irving devotes several pages of his elementary textbook on Roman law to the praise of the "remarkable" discovery of the Gaius palimpsest. He traces the discovery of the text by Niebuhr and Savigny in language that would have befitted an adventure tale. He elaborates on the various labors required to produce a new edition of the text and was particularly impressed by the use of a then new chemical process to make the under text of the palimpsest visible. He speaks of the reception of the new text as being greeted with "ardor and exultation" strong words for those who spend their lives amidst the "musty tomes" of the Roman law.This excitement over the Verona Gaius is really rather strange. Much of the substance of the Gaius text was already known to legal historians and civil lawyers from its incorporation into Justinian's Institutes and so, from a substantive legal perspective, the find was not crucial. The Gaius did provide new information on Roman procedural rules and it did also provide additional information for those scholars attempting to reconstruct pre-Justinianic Roman law. Nevertheless, these contributions alone seem hardly able to justify the excitement the discovery caused. Instead, I think that the Verona Gaius discovery simply hit a chord in the literary and legal community much the same as did the discovery of the Rosetta Stone or of Schliemann’s Troy. Here was a monument of a great civilization brought newly to light and able to be read for the first time in millenia. And just as the Rosetta Stone helped to establish the modern discipline of Egyptology and Schliemann's discoveries assured the development of classical archaeology as a modern academic discipline, the discovery of the Verona Gaius added to the attraction Roman law held for scholars and for lawyers, even amongst those who were not Romanists by profession. Ancillary to this, the discovery and publication of the Gaius manuscript also added to the fame of the two principals involved in the discovery, Niebuhr and Savigny. What this meant in the English-speaking world is that even those who could not or did not wish to read Savigny's technical works knew of him as one of the discoverers of the Gaius text. This fame itself may well have helped in spreading Savigny's legal and philosophical ideas, for, I would suggest, the Gaius "connection" may well have disposed people to read other of Savigny's writings, unconnected to the Gaius, because they were already familiar with his name.Another example of an English-speaking promoter of Savigny is Luther Stearns Cushing, a noted Boston lawyer who lectured on Roman law at the Harvard Law School in 1848-49 and again in 1851- 1852.Cushing published his lectures at Boston in 1854 under the title An Introduction to the Study of Roman Law. He devoted a full chapter to a description of the historical school and to the controversy betweenSavigny and Thibaut over codification. While Cushing attempted to portray fairly the arguments of both sides, he left no doubt as to his preference for Savigny's approach:The labors of the historical school have established an entirely new and distinct era in the study of the Roman jurisprudence; and though these writers cannot be said to have thrown their predecessors into the shade, it seems to be generally admitted, that almost every branch of the Roman law has received some important modification at their hands, and that a knowledge of their writings, to some extent, at least, is essentially necessary to its acquisition.译文(一)萨维尼和他的英美信徒们*M·H·豪弗里奇弗雷德里奇·卡尔·冯·萨维尼出身贵族，是一位出色的法律改革家，也是一位倡导重建德国教授协会的拥护者，还是历史法学派的创建人之一。
毕业论文文献外文翻译----危机管理：预防,诊断和干预文献翻译-中英文文献对照翻译
第1页 共19页中文3572字毕业论文（设计）外文翻译标题：危机管理-预防，诊断和干预一、外文原文标题：标题：Crisis management: prevention, diagnosis and Crisis management: prevention, diagnosis andintervention 原文：原文：The Thepremise of this paper is that crises can be managed much more effectively if the company prepares for them. Therefore, the paper shall review some recent crises, theway they were dealt with, and what can be learned from them. Later, we shall deal with the anatomy of a crisis by looking at some symptoms, and lastly discuss the stages of a crisis andrecommend methods for prevention and intervention. Crisis acknowledgmentAlthough many business leaders will acknowledge thatcrises are a given for virtually every business firm, many of these firms do not take productive steps to address crisis situations. As one survey of Chief Executive officers of Fortune 500 companies discovered, 85 percent said that a crisisin business is inevitable, but only 50 percent of these had taken any productive action in preparing a crisis plan(Augustine, 1995). Companies generally go to great lengths to plan their financial growth and success. But when it comes to crisis management, they often fail to think and prepare for those eventualities that may lead to a company’s total failure.Safety violations, plants in need of repairs, union contracts, management succession, and choosing a brand name, etc. can become crises for which many companies fail to be prepared untilit is too late.The tendency, in general, is to look at the company as a perpetual entity that requires plans for growth. Ignoring the probabilities of disaster is not going to eliminate or delay their occurrences. Strategic planning without inclusion ofcrisis management is like sustaining life without guaranteeinglife. One reason so many companies fail to take steps to proactively plan for crisis events, is that they fail to acknowledge the possibility of a disaster occurring. Like an ostrich with its head in the sand, they simply choose to ignorethe situation, with the hope that by not talking about it, it will not come to pass. Hal Walker, a management consultant, points out “that decisions will be more rational and better received, and the crisis will be of shorter duration, forcompanies who prepare a proactive crisis plan” (Maynard, 1993) .It is said that “there are two kinds of crises: those that thatyou manage, and those that manage you” (Augustine, 1995). Proactive planning helps managers to control and resolve a crisis. Ignoring the possibility of a crisis, on the other hand,could lead to the crisis taking a life of its own. In 1979, theThree-Mile Island nuclear power plant experienced a crisis whenwarning signals indicated nuclear reactors were at risk of a meltdown. The system was equipped with a hundred or more different alarms and they all went off. But for those who shouldhave taken the necessary steps to resolve the situation, therewere no planned instructions as to what should be done first. Hence, the crisis was not acknowledged in the beginning and itbecame a chronic event.In June 1997, Nike faced a crisis for which they had no existi existing frame of reference. A new design on the company’s ng frame of reference. A new design on the company’s Summer Hoop line of basketball shoes - with the word air writtenin flaming letters - had sparked a protest by Muslims, who complained the logo resembled the Arabic word for Allah, or God.The council of American-Islamic Relations threatened aa globalNike boycott. Nike apologized, recalled 38,000 pairs of shoes,and discontinued the line (Brindley, 1997). To create the brand,Nike had spent a considerable amount of time and money, but hadnever put together a general framework or policy to deal with such controversies. To their dismay, and financial loss, Nike officials had no choice but to react to the crisis. This incident has definitely signaled to the company that spending a little more time would have prevented the crisis. Nonetheless,it has taught the company a lesson in strategic crisis management planning.In a business organization, symptoms or signals can alert the strategic planners or executives of an eminent crisis. Slipping market share, losing strategic synergy anddiminishing productivity per man hour, as well as trends, issues and developments in the socio-economic, political and competitive environments, can signal crises, the effects of which can be very detrimental. After all, business failures and bankruptcies are not intended. They do not usually happen overnight. They occur more because of the lack of attention to symptoms than any other factor.Stages of a crisisMost crises do not occur suddenly. The signals can usuallybe picked up and the symptoms checked as they emerge. A company determined to address these issues realizes that the real challenge is not just to recognize crises, but to recognize themin a timely fashion (Darling et al., 1996). A crisis can consistof four different and distinct stages (Fink, 1986). The phasesare: prodromal crisis stage, acute crisis stage, chronic crisisstage and crisis resolution stage.Modern organizations are often called “organic” due tothe fact that they are not immune from the elements of their surrounding environments. Very much like a living organism, organizations can be affected by environmental factors both positively and negatively. But today’s successfulorganizations are characterized by the ability to adapt by recognizing important environmental factors, analyzing them, evaluating the impacts and reacting to them. The art of strategic planning (as it relates to crisis management)involves all of the above activities. The right strategy, in general, provides for preventive measures, and treatment or resolution efforts both proactively and reactively. It wouldbe quite appropriate to examine the first three stages of acrisis before taking up the treatment, resolution or intervention stage.Prodromal crisis stageIn the field of medicine, a prodrome is a symptom of the onset of a disease. It gives a warning signal. In business organizations, the warning lights are always blinking. No matter how successful the organization, a number of issues andtrends may concern the business if proper and timely attentionis paid to them. For example, in 1995, Baring Bank, a UK financial institution which had been in existence since 1763,ample opportunitysuddenly and unexpectedly failed. There wasfor the bank to catch the signals that something bad was on thehorizon, but the company’s efforts to detect that were thwarted by an internal structure that allowed a single employee both to conduct and to oversee his own investment trades, and the breakdown of management oversight and internalcontrol systems (Mitroff et al., 1996). Likewise, looking in retrospect, McDonald’s fast food chain was given the prodromalsymptoms before the elderly lady sued them for the spilling ofa very hot cup of coffee on her lap - an event that resulted in a substantial financial loss and tarnished image of thecompany. Numerous consumers had complained about thetemperature of the coffee. The warning light was on, but the company did not pay attention. It would have been much simplerto pick up the signal, or to check the symptom, than facing the consequences.In another case, Jack in the Box, a fast food chain, had several customers suffer intestinal distress after eating at their restaurants. The prodromal symptom was there, but the company took evasive action. Their initial approach was to lookaround for someone to blame. The lack of attention, the evasiveness and the carelessness angered all the constituent groups, including their customers. The unfortunate deaths thatptoms,occurred as a result of the company’s ignoring thesymand the financial losses that followed, caused the company to realize that it would have been easier to manage the crisis directly in the prodromal stage rather than trying to shift theblame.Acute crisis stageA prodromal stage may be oblique and hard to detect. The examples given above, are obvious prodromal, but no action wasWebster’s New Collegiate Dictionary, an acute stage occursacutewhen a symptom “demands urgent attention.” Whether the acutesymptom emerges suddenly or is a transformation of a prodromalstage, an immediate action is required. Diverting funds and other resources to this emerging situation may cause disequilibrium and disturbance in the whole system. It is onlythose organizations that have already prepared a framework forthese crises that can sustain their normal operations. For example, the US public roads and bridges have for a long time reflected a prodromal stage of crisis awareness by showing cracks and occasionally a collapse. It is perhaps in light of the obsessive decision to balance the Federal budget that reacting to the problem has been delayed and ignored. This situation has entered an acute stage and at the time of this writing, it was reported that a bridge in Maryland had just collapsed.The reason why prodromes are so important to catch is thatit is much easier to manage a crisis in this stage. In the caseof most crises, it is much easier and more reliable to take careof the problem before it becomes acute, before it erupts and causes possible complications (Darling et al., 1996). In andamage. However, the losses are incurred. Intel, the largest producer of computer chips in the USA, had to pay an expensiveprice for initially refusing to recall computer chips that proved unreliable o n on certain calculations. The f irmfirm attempted to play the issue down and later learned its lesson. At an acutestage, when accusations were made that the Pentium Chips were not as fast as they claimed, Intel quickly admitted the problem,apologized for it, and set about fixing it (Mitroff et al., 1996). Chronic crisis stageDuring this stage, the symptoms are quite evident and always present. I t isIt is a period of “make or break.” Being the third stage, chronic problems may prompt the company’s management to once and for all do something about the situation. It may be the beginning of recovery for some firms, and a deathknell for others. For example, the Chrysler Corporation was only marginallysuccessful throughout the 1970s. It was not, however, until the company was nearly bankrupt that amanagement shake-out occurred. The drawback at the chronic stage is that, like in a human patient, the company may get used to “quick fixes” and “band “band--aid”approaches. After all, the ailment, the problem and the crisis have become an integral partoverwhelmed by prodromal and acute problems that no time or attention is paid to the chronic problems, or the managers perceive the situation to be tolerable, thus putting the crisison a back burner.Crisis resolutionCrises could be detected at various stages of their development. Since the existing symptoms may be related todifferent problems or crises, there is a great possibility thatthey may be misinterpreted. Therefore, the people in charge maybelieve they have resolved the problem. However, in practicethe symptom is often neglected. In such situations, the symptomwill offer another chance for resolution when it becomes acute,thereby demanding urgent care. Studies indicate that today anincreasing number of companies are issue-oriented and searchfor symptoms. Nevertheless, the lack of experience in resolvinga situation and/or inappropriate handling of a crisis can leadto a chronic stage. Of course, there is this last opportunityto resolve the crisis at the chronic stage. No attempt to resolve the crisis, or improper resolution, can lead to grim consequences that will ultimately plague the organization or even destroy it.It must be noted that an unsolved crisis may not destroy the company. But, its weakening effects can ripple through the organization and create a host of other complications.Preventive effortsThe heart of the resolution of a crisis is in the preventiveefforts the company has initiated. This step, similar to a humanbody, is actually the least expensive, but quite often the mostoverlooked. Preventive measures deal with sensing potential problems (Gonzales-Herrero and Pratt, 1995). Major internalfunctions of a company such as finance, production, procurement, operations, marketing and human resources are sensitive to thesocio-economic, political-legal, competitive, technological, demographic, global and ethical factors of the external environment. What is imminently more sensible and much more manageable, is to identify the processes necessary forassessing and dealing with future crises as they arise (Jacksonand Schantz, 1993). At the core of this process are appropriate information systems, planning procedures, anddecision-making techniques. A soundly-based information system will scan the environment, gather appropriate data, interpret this data into opportunities and challenges, and provide a concretefoundation for strategies that could function as much to avoid crises as to intervene and resolve them.Preventive efforts, as stated before, require preparations before any crisis symptoms set in. Generally strategic forecasting, contingency planning, issues analysis, and scenario analysis help to provide a framework that could be used in avoiding and encountering crises.出处：出处：Toby TobyJ. Kash and John R. Darling . Crisis management: prevention, diagnosis 179-186二、翻译文章标题：危机管理：预防，诊断和干预译文：本文的前提是，如果该公司做好准备得话，危机可以更有效地进行管理。
5、外文文献翻译(附原文)产业集群,区域品牌,Industrial cluster ,Regional brand
外文文献翻译（附原文）外文译文一：产业集群的竞争优势——以中国大连软件工业园为例Weilin Zhao,Chihiro Watanabe，Charla-Griffy-Brown[J]. Marketing Science,2009(2):123-125.摘要：本文本着为促进工业的发展的初衷探讨了中国软件公园的竞争优势。
产业集群深植于当地的制度系统，因此拥有特殊的竞争优势。
根据波特的“钻石”模型、SWOT模型的测试结果对中国大连软件园的案例进行了定性的分析。
产业集群是包括一系列在指定地理上集聚的公司，它扎根于当地政府、行业和学术的当地制度系统，以此获得大量的资源，从而获得产业经济发展的竞争优势。
为了成功驾驭中国经济范式从批量生产到开发新产品的转换，持续加强产业集群的竞争优势,促进工业和区域的经济发展是非常有必要的。
关键词：竞争优势；产业集群；当地制度系统；大连软件工业园；中国；科技园区；创新；区域发展产业集群产业集群是波特[1]也推而广之的一个经济发展的前沿概念。
作为一个在全球经济战略公认的专家,他指出了产业集群在促进区域经济发展中的作用。
他写道：集群的概念,“或出现在特定的地理位置与产业相关联的公司、供应商和机构，已成为了公司和政府思考和评估当地竞争优势和制定公共决策的一种新的要素。
但是，他至今也没有对产业集群做出准确的定义。
最近根据德瑞克、泰克拉[2]和李维[3]检查的关于产业集群和识别为“地理浓度的行业优势的文献取得了进展”。
“地理集中”定义了产业集群的一个关键而鲜明的基本性质。
产业由地区上特定的众多公司集聚而成,他们通常有共同市场、,有着共同的供应商,交易对象,教育机构和其它像知识及信息一样无形的东西，同样地,他们也面临相似的机会和威胁。
在全球产业集群有许多种发展模式。
比如美国加州的硅谷和马萨诸塞州的128鲁特都是知名的产业集群。
前者以微电子、生物技术、和风险资本市场而闻名,而后者则是以软件、计算机和通讯硬件享誉天下[4]。
外文翻译原文.
e c o l o g i c a l e n g i n e e r i n g 28(2006124–130a v a i l ab l e a t w w w.sc i e n c ed i re c t.c omj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /e c o l e n gPlant-biofilm oxidation ditch for in situ treatm ent of polluted watersQi-Tang Wu a ,∗,Ting Gao a ,Shucai Zeng a ,Hong Chua ba College of Natural Resources and Environment,South China Agricultural University,Guangzhou 510642,ChinabDepartment of Civil and Structural Engineering,Hong Kong Polytechnic University,Hung Hom,Kowloon,Hong Kong SAR,Chinaa r t i c l ei n f o Article history:Received 17December 2005Received in revised form 16May 2006Accepted 18May 2006Keywords:Plant-biofilm oxidation ditch (PBFODIn situWastewater treatmenta b s t r a c tEutrophication of surface water bodies is a problem of increasing environmental and ecolog-ical concern worldwide and is particularly serious in China.In the present study,oxidation ditches were connected to a lake receiving municipal sewage sludges.T wo 24m 2(width 2m,length 12mparallel plastic oxidation ditches material were installed on a lake near the inlet of the municipal sewage.Zizania caduciflora and Canna generalis were grown in the ditches with plastic floating supporters for the removal of N and P from the sewage.The experiment was conducted firstly with municipal sewage in autumn–winter seasons for about 150daysunder the following conditions:2m 3/h influent flow,0.75kW jet-flow aerator(air/water of 5,18h HRT (hydrological retention timeand a return ratio of 10.Then it was run with the polluted lake water in summer–autumn for about 160days with an aerator of 1.25kW and an influent of 6m 3/h (air/water 3.3,HRT 6h.The performance was quite stable during the experimental period for the municipal sewage treatment.The average removal rates of COD (chemical oxygen demand,SS (suspended solids,TP (total phosphorus,NH 4+-N and inorganic-N were 70.6,75.8,72.6,52.1and50.3%,respectively.For the polluted lake water treatment,the average concentrations of COD,NH 4+-N and TP were 42.7,13.1and 1.09mg/L,respectively,in the influent and were 25.1,6.4and 0.38mg/L,respectively,in the effluent.The capacity of the plants to remove N and P by direct uptake was limited,but the indi-rect mechanisms also occurred.The proposed process,transforming the natural lake into a wastewater treatment plant,could evidently reduce the costs of the sewage collection,the land space requirement and the construction compared with conventional sewage treat-ment plants,and is especially suited to conditions in south China and south-east Asia.©2006Elsevier B.V .All rights reserved.1.IntroductionMany water bodies are subject to eutrophication due to eco-nomic constraints in reducing point sources of nutrients and/or to a high proportion of diffuse sources,and the prob-lem is particularly common in China because the proportion of treated municipal sewage is still low due to the relatively high capital investmentrequired.Accordingly,43.5%of 130investi-gated major lakes in China were found to be highly eutrophied∗Corresponding author .Tel.:+862085280296;fax:+862085288326.E-mail address:qitangwu@ (Q.-T.Wu.and 45%were of intermediate status (Li et al.,2000.These pol-luted lakes were mainly located in economically developed regions and especially around cities where large amounts of municipal sewage are discharged without appropriate treat-ment.Increasingly,natural or constructed wetlands,including buffer zones(Correll,2005,are being used for removal of pol-lutants from wastewater or for treatment of stormwater runoff from agricultural land and other non-point sources (Mitsch ete c o l o g i c a l e n g i n e e r i n g28(2006124–130125Table1–COD and BOD5of the study lake sampled at three points for5days inMay2003COD(mg/LBOD5(mg/LBOD5/COD13May89.5135.700.4083.3334.500.4189.5136.600.4114May55.5624.800.4589.5135.200.3949.3820.900.4227May105.1141.300.3981.0832.300.40111.1141.000.3728May60.0026.830.4563.3327.700.4463.3327.000.4329May90.0035.700.4093.3337.000.40117.9949.400.42al.,2000;Coveney et al.,2002;Belmont et al.,2004.However, this method requires a large land area in addition to the lake in question.For in situ treatment of hypereutrophic water bodies where the transparency of the water does not allow regrowth of submerged macrophytes,phosphorus precipitation in eutrophic lakes by iron application(Deppe and Benndorf, 2002or by additions of lime(Walpersdorf et al.,2004has been reported.Aeration of river water has been employed to remediate polluted rivers since the1970s(Wang et al.,1999. Increasing oxygen transfer inflow by stones placed in rivers was studied by Cokgor and Kucukali(2004.Growingfloating aquatic macrophytes(Sooknah and Wilkie,2004or terrestrial green plants usingfloating supports(Li and Wu,1997,physical ecological engineering(PEEN(Pu et al.,1998,and biotic addi-tives have also been applied(Chen,2003.However,these sim-ple designs do not constitute a real water treatment system and the efficiencies of these treatments are unsatisfactory.Activated sludge systems have been proved efficient treat-ing municipal sewage since the1960s(Ray,1995.However, this type of system has not been used for in situ remediation of polluted lakes or rivers.In the present study,the oxidation ditch technique was adopted on a lake receiving municipal sewage sludge.Floating green plants and the biofilms com-prisingfloating materials and plant roots were also added to enhance N and P removal.A pilot scale experiment was set up to test the feasibility and performance of the plant-enhanced oxidation ditch for in situ treatment ofboth the municipal sewage and the polluted lake water.2.Experimental2.1.Site descriptionThe study lake was situated at South China Agricultural Uni-versity,Guangzhou,China.The area of the lake was about 10000m2and the depth0.5–3m.This lake received the munic-ipal sewage from the residential area around the university.Fig.1–Surface arrangement of the plant-biofilm oxidation ditch and the waterflows.(1Wall of nylon tissue;(2nets of5mm;(3nets of0.25mm;(4oxidation ditch;(5jet-flow aerator;(6water pump;(7floating green plants;(8sewage entry.2.2.Establishment of the plant-biofilm oxidationditchesT wo24m2(width2m,length12mparallel oxidation ditches made of plastic materials were installed along the lake bank near the sewage inlet.The inner ditch was made of cement and the outer ditch was isolated with nylon tissues andfix-ing PVC(polyvinyl chloridetubes.Fig.1showsthe surface arrangement and the waterflow path.The coarse suspended solids in the influent werefiltered by two pl astic nets,one with a pore size of5mm and the other with a pore size of0.25mm,whereas the suspended solids in the effluent werefiltered by a plastic net with a pore size of 0.25mm.Zizania caduciflora and Canna generalis were grown in the ditch with theplast icfloating supporters which held the plants in position.Thefloating supporters were made of closed126e c o l o g i c a l e n g i n e e r i n g28(2006124–130PVC tubes and nylon nets and each was3.6m2.Zizania caduci-flora was grown on twofloating supporters an d Canna gener-alis on another two supporters.The plants were planted in four columns andfive lines.The twofloating supporters with Canna generalis were near the influent and the two with Zizania caduciflora were near the effluent.The entire disposal system is shown in Photo1.2.3.Conduct of the experimentsAn experiment was conductedfirstly on municipal sewage in autumn–winter seasons of2003–2004for about150days. The aeration of the oxidation ditch was achieved using a jet-flow aerator of0.75kW(Aqua Co.,Italy;air generation10m3/h, water jet rate22–28m3/h.The water sampling started on18 September2003and endedon12February2004.The influent was2m3/h created by a water pump of0.37kW.With the jet-flow aerator of0.75kW the theoretical air/water ratio was5, HRT was18h and the return ratio was10–13.The system was then run with the polluted lake water in summer and autumn2004for about160days with an aerator of1.25kW and with an influent of6m3/h(air/water3.3,HRT 6h.The influent was not created by water pump but by the driving fo rce of the jet-flow aerator.The water sampling for the second run started on15May2004and endedon15October 2004.2.4.Sampling and analysisThe influent and effluent were sampled every3–5days at 08:00–09:00a.m.andat17:00–18:00p.m.,each with three sam-pling re plicates for thefirst run.For the second run,the influ-ent and effluent were sampled1day a week.The water sam-pler took0–30cm surface water.The samples were analyzed for COD Cr,BOD5,SS,TP,NO3−-N,NH4+-N and pH according to standard methods(APHA,1995.The plant s were transplanted ontofloating supporters two weeks before water sampling and thefirst harvest was carried out60days later and at the termination of thefirst run for the municipal sewage.The plant biomass and N and P con-tents were measured according to the methods proposed by the Soil and Agro-Chemical Analysis Committee of China(Lu, 2000.The total uptakes of N and P were calculated and com-pared with the total removal of these elements calculated by the cumulative removal each day following measurement of a water sample.Total N removal=(average N in influent−average N in effluent×48×D iwhere48was the treated water volume per day in m3/day;D i was the number of days following the water sampling and before the next sampling.3.Results and discussionTable2shows the removal of COD Cr and SS by plant-biofilm oxidation ditch for the treatment of the municipal sewage in autumn–winter seasons of2003–2004.The removal of COD Cr varied from60to79%with an average of70%for the influent COD Cr ranging from100to200mg/L,a nd resulted in effluent COD Cr valuesfrom30to55mg/L(Table2,Fig.2.The average removal percentage was about75%for SS and variedfrom68to82%(Table2.The effluent SS was about 30mg/L which is the effluent limit value of the second grade for the sewage treatment plants in China(GB18918,2002 (Fig.3,for the influents varying from60to240mg/L.The average NH4+-N removal from influent was52%,which was lower in winter than in autumn(Table3.This may be due to lower bacterial activity in winter,but theinfluent NH4+-NTable2–Removal of COD and SS by the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage each month in autumn–winter seasons of2003–2004Period Sampled days Water temperature(◦CInfluent(mg/LEffluent(mg/LRemoval(%COD Cr18–30September528.0118.54(3.01a34.34(7.8367.74 3–28October826.1123.91(4.0333.51(4.2672.661–7November326.0153.94(2.7337.60(3.8175.4918–28November423.1170.22(4.2835.45(5.3778.711–15December419.3180.36(8.2039.24(7.0677.6511–31January314.5128.46(3.6652.04(5.2359.504–12February216.8178.35(4.1662.86(5.8362.47Average150.54(4.3042.15(5.6370.60SS18–30September528.0160.4041.6074.18 3–28October826.1144.3826.2581.171–7November326.0116.0033.3370.7918–28November423.1111.7521.5080.981–15December419.390.5028.5068.4211–31January314.5104.0017.3382.384–12February216.8120.5033.0072.57Average121.0828.7975.78e c o l o g i c a l e n g i n e e r i n g28(2006124–130127Fig.2–COD in the influent and effluent of the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.was also higher in winter(Fig.4probably because of lower water consumption in the cold season.The total inorganic-N removal was similar to that for NH4+-N(Table3.NO3−-N concentrations were rather similar in the influent and the effluent.The total P removal varied from63to78%and was higher and more regular than N removal(Table3.The P concentra-tion in treated effluent was about1mg/L(Fig.5and conformed to the Chinese municipal sewage treatment standard which is set to3mg/L for second grade regions and1.5forfirst grade regions(GB18918,2002.Fig.6shows typical changes in the water quality param-eters for the sampling points from inlet to outlet.Thisindi-Fig.3–Suspended solids concentration in the influent and effluent of the p lant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.cates that COD and SS decreased gradually,but NH4+-N and TP dropped substantially following the mixing with the return water by the aerator and then decreased slowly,while NO3−-N and pH of the water remained virtually unchanged.The water DO increased dramatically following the aeration,decreased slowly thereafter and remained rather high even in the efflu-ent(about5.5mg/L.For the second run treating the polluted lake water on-site,the average influent COD Cr was42.7mg/L and the effluent 25.1mg/L for about160days during summer–autumn seasons (Fig.7.The removal of NH4+-N was about50%from about13.1 to6.4mg/L.Total-P in the effluents was rather stable,bei ngTable3–The removal of N and P by the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage for each month in autumn–winter seasons of2003–2004Period Sampled days Water temperature(◦CInfluent(mg/LEffluent(mg/LRemoval(%NH4+-N18–30September528.020.60(0.30a7.16(0.2264.72 3–28October826.126.55(0.2310.15(0.2061.671–7November326.030.00(0.4113.67(0.2254.5118–28November423.135.15(0.7915.95(0.2653.991–15December419.335.89(0.3515.93(0.2755.1511–31January314.530.57(0.6918.59(0.2236.634–12February216.835.23(0.0521.61(0.0637.72Average30.57(0.4014.72(0.2152.06NH4+-N+NO3−-N18–30September528.023.06(0.159.24(0.1159.94 3–28October826.128.31(0.1212.01(0.1457.571–7November326.031.42(0.2114.58(0.1153.5918–28November423.136.32(0.4016.81(0.1353.721–15December419.337.41(0.1917.54(0.1453.1111–31January314.531.96(0.3720.07(0.1337.204–12February216.837.11(0.0323.35(0.0337.08Average32.23(0.2116.23(0.1150.32TP18–30September528.0 3.56(0.070.81(0.0475.56 3–28October826.1 4.01(0.140.87(0.0478.241–7November326.0 4.37(0.13 1.20(0.0472.5618–28November423.1 4.89(0.16 1.13(0.0776.661–15December319.5 4.86(0.80 1.38(0.2371.07 11–31January314.5 3.75(0.45 1.35(0.0363.32 4–12February216.8 4.75(0.10 1.51(0.0566.20 Average 4.31(0.16 1.16(0.0471.89128e c o l o g i c a l e n g i n e e r i n g 28(2006 124–130Fig.4–NH 4+-N concentration in the influent and effluent of the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.Fig.5–Total-P concentration in the influent and effluent of the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.Fig.6–T ypical changes in the pollutants in theplant-biofilm oxidation ditch during the in situ treatment ofFig.7–The influent and effluent concentrations of COD (up,NH 4+-N (medianand total-P (bottomin theplant-biofilm oxidation ditch treating polluted lake water.about 0.38mg/L from an average of 1.09mg/L in the influents.The removal of COD Cr ,NH 4+-N and Total-P was then quite sat-isfactory both for the municipal sewage and the polluted lake water.The removal of N and P was somewhat higher than con-ventional oxidation ditches,perhaps due to the existence of the plant-biofilm in the studiedsystem.However,the direct uptake rates of N and P by green plants were almost negligi-ble compared to the total removal of these elements by the whole system (Table4.However,the plants may have cre-ated localized anaerobic conditions by their root exudates and dead biomass and enhance the denitrification of N by micro-organisms as occurs in constructed wetlands (Hone,2000.Besides the green plants,the proposed system also con-tains biofilm coated to the plastic materials.The high velocity of return-fluent was different to the conventional oxidation ditch.Kugaprasatham et al.(1982showed that the increase of the fluent velocity could increase the density of the biofilm if the nutrient conditions were suitable for bacteria growth.Simultaneous nitrification/denitrification (SND(Van Mun ch etal.,1996may also occur in the system.Concerning the P removal of the system,biological phos-phate removal processes may occur but were not significant because there was no sludge removal and very little sludge precipitation after the run for treatment of municipal sewage.This may partly due to the existence of some ferric chains which were added to precipitate and fix the nylon tissue to the lake bottom,with formation of precipitates of ferric phos-e c o l o g i c a l e n g i n e e r i n g 2 8 ( 2 0 0 6 124–130 129 Table 4 – Proportions of N and P uptake by plants and total removal in the plant-biofilm oxidation ditch treating municipal sewage Date Days ZCa Harvested fresh biomass (g CG ZC 5 September–4 November 5 November–6 January Total or average a Plant uptake (g N CG 5.30 13.03 System removal (kg N CG P Percent of plant uptake N (% P (% P ZC 0.88 0.24 2.79 60 63 123 2200 625 9725 2750 4150 4.85 1.20 24.38 0.72 0.95 37.63 65.45 103.1 7.13 12.78 19.91 0.03 0.02 0.02 0.02 0.01 0.01 ZC: Zizania caduciflo ra; CG: Canna generalis. tained for at least 1 year. The actual mechanisms still remain to be identified. The oxidation ditch has been used for many years worldwide as an economical and efficient wastewater treatment technology that can remove COD, nitrogen and a fraction of the phosphorusefficiently. Anaerobic tanks (Liu et al., 2002 and phased isolation ditch systems with intra-channel clarifier (Hong et al., 2003 were added to the system to increase the TP removal efficiency. The proposed process takes an artificial process in combination with natural purification, transforming the natural lake into the wastewater treatment plant, and could evidently reduce the costs of sewage collection, the landspace requirement and the construction costs compared with the conventional sewage treatment plants. This process could be especially suitable to subtropical regions and to many water bodies in south China and southeast Asia where sewage treatment facilities are not well established. China. The authors are grateful to Dr. P. Christie, Department of Agricultural and Environmental Science, Queen’s University Belfast, UK, and Dr. Y. Ouyang, Department of Water Resources, St. Johns River Water Management District, Palatka, FL, USA, for their valuable suggestions and language corrections. references 4. Conclusions The present study adapted the oxidation ditch on the lake surface for in situ treatment of municipal sewage or polluted lake water in combination with plant biofilms for performing N and P removal, and running experiments at pilot scale for about 1.5 years resulted in the following observations: (1 The system was quite satisfactory and stable for treatment of municipal sewage and polluted lake water in removing COD, NH4 + -N and P. (2 The direct uptake of N and P by plants was negligible in comparison with the totalremoval by the system, but indirect mechanisms via plant root exudates and biofilms merit further studies. (3 The proposed process could dramatically reduce the costs of sewage collection, the land-space requirement and the construction costs compared with conventional sewage treatment plants; might be suitable for treatment of both municipal sewage and polluted lake water; and could lead to the promotion of wastewater treatment in many developing countries. Acknowledgements This study was funded by Department of Science and Technology of Guangdong Province (Grant no. 2004B33301007, American Public Health Association (APHA, 1995. Standards Methods for the Examination of Water and Wastewater, 19th ed. American Public Health Association, Washington, DC. Belmont, M.A., Cantellano, E., Thompson, S., Williamson, M.,S’anchez, A., Metcalfe, C.D., 2004. Treatment of domestic wastewater in a pilot-scale natural treatment system in central Mexico. Ecol. Eng. 23, 299–311. Chen, Y.C., 2003. Bioremediation Engineering of Polluted Environment. Chemical Industry Press, Beijing, p. 304 (in Chinese. Cokgor, S., Kucukali, S., 2004. Oxygen transfer in flow around and over stones placed in a laboratory flume. Ecol. Eng. 23, 205–219. Correll, D.L., 2005. Principles of planning and establishment of buffer zones. Ecol. Eng. 24, 433–439. Coveney, M.F., Stites, D.L., Lowe, E.F., Battoe, L.E., Conrow, R., 2002. Nutrient removal from eutrophic lake water by wetland filtration. Ecol. Eng. 19, 141–159. Deppe, T., Benndorf, J., 2002. Phosphorus reduction in a shallow hypereutrophic reservoir by in-lake dosage of ferrous iron. Water Res. 36, 4525–4534. Hone, A.J., 2000. Phytoremediation by constructed wetlands. In: Terry, N., Banuelos, G. (Eds., Phytoremediation of Contaminated Soil and Water. Lewis Publishers, pp. 13–40. Hong, K.H., Chang, D., Hur, J.M., Han, S.B., 2003. Novel phased isolation ditch system for enhanced nutrient removal and its optimal operating strategy. J. Environ. Sci. Health Part A 38, 2179–2189. Kugaprasatham, S., Nagaoka, H., Ohgaki, S., 1982. Effect of turbulence on nitrifying biofilms at non-limiting substrate conditions. Water Res. 26, 1629–1638. Li, F.X., Xin, Y., Chen, W., 2000. Assessment of eutrophication level of lakes. Chongqing Environ. Sci. 22, 10–11 (in Chinese. Li, F.B., Wu, Q.T., 1997.Domestic wastewater treatment with means of soilless cultivated plants. Chin. J. Appl. Ecol. 8, 88–92 (in Chinese. Liu, J.X., Wang, B.Z., van Groenestijn, J.W., Doddema, H.J., 2002. Addition of anaerobic tanks to an oxidation ditch system to enhance removal of phosphorus from wastewater. J. Environ. Sci. 14, 245–249.130 e c o l o g i c a l e n g i n e e r i n g 2 8 ( 2 0 0 6 124–130 Lu, R.K., 2000. Soil and Agricultural Chemistry Analysis. China Agriculture Press, Beijing (in Chinese. Mitsch, W.J., Horne, A.J., Nairn, R.W., 2000. Nitrogen and phosphorus retention in wetlands—ecological approaches to solving excess nutrient problems. Ecol. Eng. 14, 1–7. Pu, P., Hu, W., Yan, J., Wang, G., Hu, C., 1998. A physico-ecological engineering experiment for water treatment in a hypertrophic lake in China. Ecol. Eng. 10, 179–190. Ray, B.T., 1995. Environmental Engineering. PWS Publishing Company, New York, pp. 299–341. Sooknah, R.D., Wilkie, A.C., 2004. Nutrient removal by floating aquatic macrophytes cultured in anaerobically digested flushed dairy manure wastewater. Ecol. Eng. 22, 27–42. Van Munch, E.P., Land, P., Keller, J., 1996. Simultaneous nitrification and denitrification in bench-scale sequencing batch reactors. Water Sci. Technol. 20,277–284. Wang, C.X., Lin, H., Shi, K.H., 1999. Restoration of polluted river by pure oxygen aeration. Shanghai Environ. Sci. 18, 411–413 (in Chinese. Walpersdorf, E., Neumann, T., Stuben, D., 2004. Efficiency of natural calcite precipitation compared to lake marl application used for water quality improvement in an eutrophic lake. Appl. Geochem. 19, 1687–1698.。
外文翻译原文及配套译文
Business process re-engineering –saviour or just another fad?One UK health care perspectiveAnjali PatwardhanHealth Service Management Centre,Birmingham,UK,and Dhruv Patwardhan University of Newcastle,Newcastle upon Tyne,UKAbstractPurpose –Pressure to change is politically driven owing to escalating healthcare costs and an emphasis on efficiency gains,value for money and improved performance proof in terms of productivity and recently to some extent by demands from less satisfied patients and stakeholders.In a background of newly immerging expensive techniques and drugs,there is an increasing consumer expectation,i.e.quality services.At the same time,health system managers and practitioners are finding it difficult to cope with demand and quality expectations.Clinicians are frustrated because they are not recognised for their contribution.Managers are frustrated because meaningful dialogue with clinicians is lacking,which has intensified the need for change to a more efficient system that satisfies all arguments about cost effectiveness and sustainable quality services.Various strategies,originally developed by management quality “gurus”for engineering industries,have been applied to health industries with variable success,which largely depends on the type of health care system to which they are applied.Design/methodology/approach –Business process re-engineering is examined as a quality management tool using past and recent publications.Findings –The paper finds that applying business process re-engineering in the right circumstances and selected settings for quality improvement is critical for its success.It is certainly “not for everybody”.Originality/value –The paper provides a critical appraisal of business process re-engineering experiences in UK healthcare.Lessons learned regarding selecting organisations and agreeing realistic expectations are addressed.Business process re-engineering has been evaluated and reviewed since 1987in US managed health care,with no clear lessons learned possibly because unit selection and simultaneous comparison between two units virtually performing at opposite ends has never been done before.Two UK pilot studies,however,add useful insights.Keywords Business process re-engineering,Total quality management,Continuous improvement,Medical management,Health services,United KingdomPaper type ViewpointHistory of quality management in health careTo know how health care organisations became interested in industrial quality development tools and how business process re-engineering (BPR)emerged as an option,we have to go back to 1987when the Quality Improvement in Health Care National Demonstration Project (NDP)was launched as an experiment (Godfrey,n.d.).A total of 21health-care organisations participated and promised to support this study lasting eight-months.The aim was to look at the applicability of industrial quality-improvement methods to health care.Support included free consulting,The current issue and full text archive of this journal is available at/0952-6862.htmBPR –saviour or just a fad?289Received 29November 2006Revised 10February 2007Accepted 25May 2007International Journal of Health Care Quality Assurance Vol.21No.3,2008pp.289-296q Emerald Group Publishing Limited 0952-6862DOI 10.1108/09526860810868229materials,access to training courses and reviews.The funding companies included many of the USA’s leading organisations such as Corning,Ford,Hewlett-Packard,IBM and Xerox.At the final stages of the project evaluations it was clear that out of 21organisations,15health care organisations made significant progress –mainly financial and patient satisfaction gains,target and project time keeping and investment in research and development.The NDP was extended for three years,which eventuallyevolved into the Institute for Healthcare Improvement,a not-for-profit organisation –dedicated to providing health-care quality management ter,BPR emerged as an alternative for managers in organisations frustrated with slow improvements,not encompassing the whole organisation experiencing total quality management (TQM).The TQM key target was to convert an organisation’s structure,culture and services to patient/consumer rather than organisation-focused goals (Harvey and Millett,1999).Why change?Traditionally health care systems were mostly “governed”by clinicians (Shutt,2003)because patient outcomes;that is,recovery from illness,were the sole responsibility of all professionals directly involved in patient plexity and variance in health care studies reveal that outcome has many determinants;i.e.pharmacy,pathology,technical support and information technology.It was also realised that cost containment and good quality care needed teamwork,communication,time management,etc.(Shutt,2003).Sir Roy Griffiths,in the early 1980s,developed hospital general management and the greater involvement of clinicians in resource management initiatives (DHSS,1984).Today,apart from political motives,change is driven by escalating health care costs,increased demands for quality care,value for money services,patient expectation and third-party payers in managed health care systems.These intensified the need for change to more efficient health care systems.What is BPR?BPR,also known business transformation and process change management,was introduced to the business world by Frederick Taylor in his article The Principles of Scientific Management in the 1900s (wikipedia,2006).In the 1990s,Hammer and Champy (1993)introduced Reengineering the Corporation ,which gave birth to BPR.BPR is “the analysis and design of workflows and processes within and between organizations”(Devenport and Short,1990,p.11).Teng et al.(1994)on the other hand,defined BPR as critical analysis and radical redesign of existing business processes to achieve breakthrough improvements in performance measures.Hammer and Champy (1993),similarly,defined BPR as fundamentally rethinking and radically redesigning business processes to achieve dramatic improvements in critical contemporary performance measures such as cost,quality,service and speed.From a health care viewpoint,BPR is a management approach that rethinks present practices and processes in business and its interactions.It attempts to improve underlying process efficiency by applying fundamental and radical approaches by either modifying or eliminating non-value adding activities and redeveloping the process/structure/culture (McNulty and Ferlie,2000).However,in the health sector,a wide variety of patient groups make the health care service a complex project to redesign along these lines,thereby rendering changes context and time sensitive.IJHCQA 21,3290BPR key featuresHealth care’s BPR approach means starting with clean slate and rethinking services using a patient-focused approach.With the benefit of hindsight BPR identifies delays caused by unnecessary steps or potential errors that are built into processes.It is presumed that redesigning processes by removing these errors dramatically improves care quality.The BPR approach,therefore,raises expectations about dramatic results. Consequently,high returns on investment are anticipated.The process,planned strategically,is explained in Taylor’s BPR framework(wikipedia,2006): .defining BPR’s purpose and goal;.identifying requirements that meet clients’needs;.defining project scope,including appropriate activities such as process mapping;.assessing the environment using,for example,force-field analyses;.re-engineering business processes and activities;.implementing redesigned processes;and.monitoring redesign success and failure.BPR vs TQMComparing BPR with other popular quality management methods helps us to appreciate and highlight key features in a health care context(Harvey and Millett,1999).TQM or continuous quality improvement(CQI)refers to programmes and initiatives that emphasise incremental improvement in work processes and outputs over an open-ended time period.In contrast,BPR refers to discrete initiatives intended to radically redesign and improve work processes within a time frame.Some people think TQM is best suited to quality in health care improvement though it is an incremental stepwise,slow but holistic approach.In practice,TQM and BPR are customer-oriented and both encourage managers and practitioners to take a customer view point.Both are team approaches that involve process control.The TQM protagonists assume that existing health care practices and systems are principally right but improvements are needed.The BPR supporters,on the other hand,assume that health care systems and practices areflawed and need replacing.Those using TQM expect and believe in stepwise increments in performance as opposed to BPR experts who look for dramatic results.TQM aims to improve all levels for all stakeholders and at all steps,while BPR aims at specified areas only.Standardisation and supporting documentation is a TQM key point.Believing in consistent and cost-effective performance and minimising process or system defects, prevents rather than corrects problems(Field and Swift,1996).Those that use the BPR approach,on the other hand,areflexible and assume that standardisation increases process complexity(Harvey and Millett,1999).Nevertheless,BPR is a drastic change leading to staff resistance.Moreover,it is a top-down approach,so management support and commitment is vital to success.Innovation,therefore,is a risky process when used for“sick organisations”.The TQM incremental method,on the other hand,follows a gradual approach that is mostly bottom-up.It involves employees and often based on Deming’s principles that direct improvements through plan-do-study-act(PDSA)cycle.TQM,therefore,is suitable for improving quality in any organisation,although some amendments to suit context may be needed.Application in managed health care generated different results BPR–saviour or just a fad?291when dissimilar processes were applied in different scenarios.Business process re-engineering,therefore,may not suite everyone because it works better when applied to sick organisations or in fundamentally defective systems (Bashein et al.,1994).The TQM approach is about a cultural change as it is built into practices hooked on daily routines.The BPR method is a target-oriented process that is time sensitive because if not completed as planned then success may be jeopardised.The TQM primary enableris statistical process control,while in BPR it is information and technology (Harvey and Millett,1999).Advantages of applying BPR to health service quality improvementUsing BPR in the health sector was a response to frustrations amongst managers in organisations who perceived TQM’s incrementalism and ability to achieve organisation-wide change had failed.King’s College Hospital experience (Grimes,2000;Harrison et al.,1992)suggests that BPR could be best tried to achieve previously unachieved levels of efficiency in scenarios when other efforts/methods had been unsuccessful.The driving forces for change were aspirations to develop a more efficient system that satisfies consumers’demands for service quality and value for money (Bowns and McNulty,1999).At the same time,BPR makes it possible to sustain such quality without necessarily costing more,even though we know that health care costs are rising steeply.The third and most important aspiration in the King’s project was to improve professionals’job satisfaction,what they felt they always deserved.The aim was to orient health care towards and focus on patients rather than organisation needs.The BPR approach focuses on rethinking and redesigning processes from scratch,giving staff opportunities to revisit services in detail,thereby pointing out improvement areas.It strips all non-value adding and unnecessary steps from the process to make services more efficient.Although it is managed top-down and dominated by managers and leaders,decision making is done at the coal-face,thereby empowering the team.The BPR approach provides a flexible work environment,culture and work practices.It can be valuable for organisations in deep difficulties and performing poorly.In such a crisis,re-engineering may be the only way organisations can survive (Harvey and Millett,1999).Where major structural and cultural deficiencies are identified or are obvious as a poor performance cause,BPR is the best way to handle that scenario –evident from King’s College Hospital experiences (Bowns and McNulty,1999).BPR limitations in health care quality improvementWe know that BPR is a top-down approach that staff may resist.It is cited by autonomous clinical professionals as “a brutal and inappropriate technique”(Jones,1996,p.4284).Implementing BPR in health care scenarios,where clinicians are key players,therefore,is not only difficult but also unsafe (McNulty and Ferlie,2000).Thus,BPR may lead to ownership loss and employee de-motivation because they are not involved in planning and change management.Generally,change processes are less-well understood by employees (Jones,1996,p.4284):Quality would seem unlikely to be forthcoming if re-engineering is imposed from the top down in a rigid and mechanistic fashion ...If organizational change is to be effective and sustainable,this will also require the active engagement of,and learning by,employees rather than grudging compliance with management diktat.IJHCQA 21,3292Quality improvement in European public services elaborated health care TQM and BPR as quality improvement tools.It was acknowledged that many business approaches to quality improvement,including TQM and re-engineering,failed to take account of health care’s complexity and the nature of professionalised knowledge.The language and values used in most of these projects were alien to clinicians and so were rejected as management fads.It seems that BPR requires massive culture and structure change if it is to improve quality of the same magnitude.It may be that radical overnight transformation may sound impressive but unrealistic.Structural and cultural change needs time to develop,be accepted and absorbed at all levels, particularly in health care settings.In short,BPR is a high-cost and high-risk project. Seventy-percent of all industries could not achieve their targets–a BPR success rate around30per cent.In the health care sector,on the other hand,from the literature we reviewed,there is no successfigure available.BPR carries an unrealistic scope and expectation most of the time,which may be a reason for its70per cent failure rate.Its top-down nature and success depends on sustained management commitment and inspirational leadership,which is not easily measured and may not be available up to the threshold needed.BPR may make only a unit change in time.To be meaningful,it needs to be followed by a CQI exercise.Once changes are brought about,BPR-based change needs CQI projects to have sustained results.It is always contested that BPR does not take account of human processes–evident from Jones’(1996,p.4284) quotation:Such a perspective is seen as promoting the idea that you can design a perfect process, implement it exactly as you planned and the organizational machine will carry it out faultlessly.Setting on one side questions about the reliability of this whole process,it is evident that BPR neglects the important role of human creativity in making process work. As we raised earlier,BPR usually innovates one process at a time rather than a whole organisation approach.The process that is changed,therefore,might not have an effect on overall organisational performance that can be measured especially those perceived by consumers.In other words,BPR may have a drastic effect on one specific process but none or very little on total organisational performance.A simple illustration for improving inpatient admissions shows that BPR alone cannot improve services.There will be need also to improve day care,outpatient,primary care and emergency services. All have an effect on an organisation’s inpatient services because they are interlinked and interdependent.Moreover,BPR’s effect can be difficult to assess in this context since NHS organisations lack specific measures(Bowns and McNulty,1999).The extent to which BPR is applicable to health care systemsThe UK BPR health care experience comes from two centrally funded pilot studies:(1)King’s College Hospital,London(KCH);and(2)Leicester Royal Infirmary(LRI).The KCH project was evaluated by a Brunel team(Packwood et al.,1998;Grimes,2000) and the LRI scheme by Sheffield and Warwick(Bowns and McNulty,1999).Employees in these organisations shared their BPR experiences during evaluation.Consequently, both studies generated interesting and valuablefindings as they highlighted to what extent BPR could be applied to health care systems.However,the two hospitals were BPR–saviour or just a fad?293extremes,i.e.KCH was a “sick”unit at the time of the study.LRI,on the other hand,was one of the best teaching hospitals (McNulty and Ferlie,2000)with little scope to improve.At the end of the pilot studies it was evident from reports that both hospitals could not reach expectations especially the drastic changes and improvements anticipated at the beginning of the BPR projects.Both reduced waiting times and length of stay along with faster diagnostic processes.King’s,over and above theseimprovements,also made £1million savings (Grimes,2000)–attributed to “waste reduction”by process mapping followed by removing non-value adding activities and by increasing efficiency in the renewed system (Packwood et al.1998).This suggests that BPR is not for everybody and that selecting units to which BPR can be applied is important to achieve desired results.When the two trusts ran the pilot,they also continued to work on their generic and core improvement initiatives at different levels in the process and so it was difficult to attribute success to BPR alone or to assess its relative contribution to overall improvements.One approach to identify suitable sub processes for applying BPR is process mapping from “door to door”,which helps capture all the process components and applying a lean approach (Jones and Mitchell,2006,p.23).Identifying value-added activities highlights the non-value-added ones.Each non-value-added activity can be measured and analysed to assess its impact and ways to eliminate activity.Resource availability,deadline,cost,generic skills and above all,urgency to change help users select the right improvement tool.Also,as raised earlier,change management success is closely related to team morale,ownership and motivation.To achieve quality in health care services,therefore,two key staff groups –managers and clinicians,who come from different cultural backgrounds and are knowledgeable in different ways,need to work as a team.Understanding and cooperation are crucial if difficult tasks are to be accomplished (Shortell et al.1998).However,BPR’s failure to consider the human aspects of processes may make it difficult to integrate BPR into health care services.The BPR approach sounds impressive but unrealistic because soft structural and cultural change need time to develop particularly in health care settings.We believe that BPR can help to improve health services if it is meticulously planned and applied diligently.In short,even with all BPR’s limitations,it is still capable of delivering dramatic results not least because it forces staff to think from outside the scenario or process as a whole and work to deadlines (Bowns and McNulty,1999).Conclusions and recommendationsHealth care is a more complex system than any manufacturing industry.As a service provider with a major human component there are safety and efficiency issues rather than cost and efficacy,which separates health care from industry.BPR,like other single approaches to improve service quality,are likely to be unsuitable for health care (Shortell and Ferlie,2001),which is comprised of a number of sub processes.It has many stakeholders at different levels and there is wide variation in its internal customer (e.g.,fellow professionals)and external customer (i.e.patients)needs.We accept that BPR can be used as a tool for improving some sub-process or sub-unit activity.An example could be what happened in the LRI where BPR was tried as a quality improvement tool in bed management,pathology and OPD service innovation,etc.;but not applied in areas where clinician’s precision was paramount or where BPR was accepted less-well.In these areas,therefore,views on the methods’suitability forIJHCQA 21,3294quality improvements were mixed.That is,TQM and BPR ideally should always be followed by CQI methods for service improvement to be sustainable and effective.In short,quality management tools designed for industry should be applied to health services with proper selection,caution and care.ReferencesBashein,B.J.,Markus,M.L.and Riley,P.(1994),“Preconditions for BPR success:and how to prevent failures”,Information Systems Management,Vol.11No.2,pp.7-13.Bowns,I.R.and McNulty,T.(1999),Re-engineering Leicester Royal Infirmary–Executive Summary,School of Health and Related Research,University of Sheffield,Sheffield. Devenport,T.and Short,J.(1990),“The new industrial engineering information technology and BPR”,Sloan Management Review,Summer,pp.11-27.DHSS(1984),Health Services Management:Implementation of the NHS Management Inquiry, DHSS Circular HC(84)13,DHSS,London.Field,S.W.and Swift,K.G.(1996),Effecting a Quality Change:An Engineering Approach,Arnold, London.Godfrey,B.(n.d.),“Quality health care”,Quality Digest,available at:/ sep96/health.htm(accessed on15October2006).Grimes,K.(2000),Changing the Change Team,King’s College Hospital,London.Hammer,M.and Champy,J.(1993),Reengineering the Corporation:A Manifesto for Business Revolution,Harper Business Books,New York,NY.Harrison,S.,Hunter,D.,Marnoch,G.and Pollitt,C.(1992),Just Managing:Power and Culture in the NHS,Macmillan,Basingstoke.Harvey,S.and Millett,B.(1999),“OD,TQM and BPR:a comparative approach”,Australian Journal of Management and Organizational Behavior,Vol.2No.3,pp.30-42.Jones,D.and Mitchell,A.(2006),Lean Thinking for the NHS:A Report Commissioned by the NHS Confederation,pamphlet RA395.G7,NHS Confederation,London.Jones,M.(1996),“Re-engineering”,in Warner,M.(Ed.),International Encyclopedia of Business and Management,Routledge,London.McNulty,T.and Ferlie,E.(2000),Reengineering Health Care:The Complexities of Organisational Transformation,Oxford University Press,Oxford.Packwood,T.,Pollitt,C.and Roberts,S.(1998),“Good medicine?A case study of business process reengineering in a hospital”,Policy and Politics,Vol.26No.4,pp.401-15. Shortell,S.and Ferlie,E.(2001),“Improving quality of healthcare in the United Kingdom and the United States:a framework for change”,The Milbank Quarterly,Vol.79No.2,May, pp.281-315.Shortell,S.M.,Waters,T.M.and Clarke,K.W.B.(1998),“Physicians as double agents: maintaining trust in an era of multiple accountabilities”,Journal of the American Medical Association,Vol.280No.12,pp.1102-8.Shutt,J.A.(2003),“Balancing the health care scorecard”,Managed Care,September,pp.42-6. Teng,J.T.C.,Grover,V.and Fiedler,K.(1994),“Business process reengineering:charting a strategic path for the information age”,California Management Review,Vol.36No.3, pp.9-31.wikipedia(2006),“Frederick Winslow Taylor”,available at:/wiki/ Frederick_Winslow_Taylor(accessed2December2006).BPR–saviour or just a fad?295Further reading Davies,H.T.O.(2000),“Organizational culture and quality of health care”,Quality in Health Care ,Vol.9No.2,pp.111-9.Malhotra,Y.(1998),“Business process redesign:an overview”,IEEE Engineering Management Review ,Vol.26No.3,pp.214-25.Pollitt,C.(1996),“Business approaches to quality improvement:why are they hard for the NHS toswallow?”,Quality in Health Care ,Vol.5No.2,pp.104-10.Raymond,L.,Bergeron, F.and Rivard,S.(1980),“Determinants of business processreengineering success in small and large enterprises:an empirical study in the Canadian context”,Journal of Small Business Management ,Vol.36,pp.72-85.Corresponding authorAnjali Patwardhan can be contacted at:doctoranjali@IJHCQA 21,3296To purchase reprints of this article please e-mail:reprints@ Or visit our web site for further details:/reprints。
3-电气工程及其自动化专业 外文文献 英文文献 外文翻译
3-电气工程及其自动化专业外文文献英文文献外文翻译1、外文原文(复印件)A: Fundamentals of Single-chip MicrocomputerThe single-chip microcomputer is the culmination of both the development of the digital computer and the integrated circuit arguably the tow most significant inventions of the 20th century [1].These tow types of architecture are found in single-chip microcomputer. Some employ the split program/data memory of the Harvard architecture, shown in Fig.3-5A-1, others follow the philosophy, widely adapted for general-purpose computers and microprocessors, of making no logical distinction between program and data memory as in the Princeton architecture, shown in Fig.3-5A-2.In general terms a single-chip microcomputer is characterized by the incorporation of all the units of a computer into a single device, as shown in Fig3-5A-3.ProgramInput& memoryOutputCPU unitDatamemoryFig.3-5A-1 A Harvard typeInput&Output CPU memoryunitFig.3-5A-2. A conventional Princeton computerExternal Timer/ System Timing Counter clock componentsSerial I/OReset ROMPrarallelI/OInterrupts RAMCPUPowerFig3-5A-3. Principal features of a microcomputerRead only memory (ROM).ROM is usually for the permanent,non-volatile storage of an applications program .Many microcomputers and microcontrollers are intended for high-volume applications and hence the economical manufacture of the devices requires that the contents of the program memory be committed permanently during the manufacture of chips . Clearly, this implies a rigorous approach to ROM code development since changes cannot be made after manufacture .This development process may involve emulation using a sophisticated development system with a hardware emulation capability as well as the use of powerful software tools.Some manufacturers provide additional ROM options by including in their range devices with (or intended for use with) user programmablememory. The simplest of these is usually device which can operate in a microprocessor mode by using some of the input/output lines as an address and data bus for accessing external memory. This type of device can behave functionally as the single chip microcomputer from which itis derived albeit with restricted I/O and a modified external circuit. The use of these ROMlessdevices is common even in production circuits where the volume does not justify the development costs of custom on-chip ROM[2];there canstill be a significant saving in I/O and other chips compared to a conventional microprocessor based circuit. More exact replacement for ROM devices can be obtained in the form of variants with 'piggy-back' EPROM(Erasable programmable ROM )sockets or devices with EPROM instead of ROM 。
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外文文献翻译原文+译文
外文文献翻译原文Analysis of Con tin uous Prestressed Concrete BeamsChris BurgoyneMarch 26, 20051、IntroductionThis conference is devoted to the development of structural analysis rather than the strength of materials, but the effective use of prestressed concrete relies on an appropriate combination of structural analysis techniques with knowledge of the material behaviour. Design of prestressed concrete structures is usually left to specialists; the unwary will either make mistakes or spend inordinate time trying to extract a solution from the various equations.There are a number of fundamental differences between the behaviour of prestressed concrete and that of other materials. Structures are not unstressed when unloaded; the design space of feasible solutions is totally bounded；in hyperstatic structures, various states of self-stress can be induced by altering the cable profile, and all of these factors get influenced by creep and thermal effects. How were these problems recognised and how have they been tackled?Ever since the development of reinforced concrete by Hennebique at the end of the 19th century (Cusack 1984), it was recognised that steel and concrete could be more effectively combined if the steel was pretensioned, putting the concrete into compression. Cracking could be reduced, if not prevented altogether, which would increase stiffness and improve durability. Early attempts all failed because the initial prestress soon vanished, leaving the structure to be- have as though it was reinforced; good descriptions of these attempts are given by Leonhardt (1964) and Abeles (1964).It was Freyssineti’s observations of the sagging of the shallow arches on three bridges that he had just completed in 1927 over the River Allier near Vichy which led directly to prestressed concrete (Freyssinet 1956). Only the bridge at Boutiron survived WWII (Fig 1). Hitherto, it had been assumed that concrete had a Young’s modulus which remained fixed, but he recognised that the de- ferred strains due to creep explained why the prestress had been lost in the early trials. Freyssinet (Fig. 2) also correctly reasoned that high tensile steel had to be used, so that some prestress would remain after the creep had occurred, and alsothat high quality concrete should be used, since this minimised the total amount of creep. The history of Freyssineti’s early prestressed concrete work is written elsewhereFigure1:Boutiron Bridge,Vic h yFigure 2: Eugen FreyssinetAt about the same time work was underway on creep at the BRE laboratory in England ((Glanville 1930) and (1933)). It is debatable which man should be given credit for the discovery of creep but Freyssinet clearly gets the credit for successfully using the knowledge to prestress concrete.There are still problems associated with understanding how prestressed concrete works, partly because there is more than one way of thinking about it. These different philosophies are to some extent contradictory, and certainly confusing to the young engineer. It is also reflected, to a certain extent, in the various codes of practice.Permissible stress design philosophy sees prestressed concrete as a way of avoiding cracking by eliminating tensile stresses; the objective is for sufficient compression to remain after creep losses. Untensionedreinforcement, which attracts prestress due to creep, is anathema. This philosophy derives directly from Freyssinet’s logic and is primarily a working stress concept.Ultimate strength philosophy sees prestressing as a way of utilising high tensile steel as reinforcement. High strength steels have high elastic strain capacity, which could not be utilised when used as reinforcement; if the steel is pretensioned, much of that strain capacity is taken out before bonding the steel to the concrete. Structures designed this way are normally designed to be in compression everywhere under permanent loads, but allowed to crack under high live load. The idea derives directly from the work of Dischinger (1936) and his work on the bridge at Aue in 1939 (Schonberg and Fichter 1939), as well as that of Finsterwalder (1939). It is primarily an ultimate load concept. The idea of partial prestressing derives from these ideas.The Load-Balancing philosophy, introduced by T.Y. Lin, uses prestressing to counter the effect of the permanent loads (Lin 1963). The sag of the cables causes an upward force on the beam, which counteracts the load on the beam. Clearly, only one load can be balanced, but if this is taken as the total dead weight, then under that load the beam will perceive only the net axial prestress and will have no tendency to creep up or down.These three philosophies all have their champions, and heated debates take place between them as to which is the most fundamental.2、Section designFrom the outset it was recognised that prestressed concrete has to be checked at both the working load and the ultimate load. For steel structures, and those made from reinforced concrete, there is a fairly direct relationship between the load capacity under an allowable stress design, and that at the ultimate load under an ultimate strength design. Older codes were based on permissible stresses at the working load; new codes use moment capacities at the ultimate load. Different load factors are used in the two codes, but a structure which passes one code is likely to be acceptable under the other.For prestressed concrete, those ideas do not hold, since the structure is highly stressed, even when unloaded. A small increase of load can cause some stress limits to be breached, while a large increase in load might be needed to cross other limits. The designer has considerable freedom to vary both the working load and ultimate load capacities independently; both need to be checked.A designer normally has to check the tensile and compressive stresses, in both the top and bottom fibre of the section, for every load case. The critical sections are normally, but not always, the mid-span and the sections over piers but other sections may become critical ，when the cable profile has to be determined.The stresses at any position are made up of three components, one of which normally has a different sign from the other two; consistency of sign convention is essential.If P is the prestressing force and e its eccentricity, A and Z are the area of the cross-section and its elastic section modulus, while M is the applied moment, then where ft and fc are the permissible stresses in tension and compression.c e t f ZM Z P A P f ≤-+≤Thus, for any combination of P and M , the designer already has four in- equalities to deal with.The prestressing force differs over time, due to creep losses, and a designer isusually faced with at least three combinations of prestressing force and moment;• the applied moment at the time the prestress is first applied, before creep losses occur,• the maximum applied moment after creep losses, and• the minimum applied moment after creep losses.Figure 4: Gustave MagnelOther combinations may be needed in more complex cases. There are at least twelve inequalities that have to be satisfied at any cross-section, but since an I-section can be defined by six variables, and two are needed to define the prestress, the problem is over-specified and it is not immediately obvious which conditions are superfluous. In the hands of inexperienced engineers, the design process can be very long-winded. However, it is possible to separate out the design of the cross-section from the design of the prestress. By considering pairs of stress limits on the same fibre, but for different load cases, the effects of the prestress can be eliminated, leaving expressions of the form:rangestress e Perm issibl Range Mom entZ These inequalities, which can be evaluated exhaustively with little difficulty, allow the minimum size of the cross-section to be determined.Once a suitable cross-section has been found, the prestress can be designed using a construction due to Magnel (Fig.4). The stress limits can all be rearranged into the form:()M fZ PA Z e ++-≤1 By plotting these on a diagram of eccentricity versus the reciprocal of the prestressing force, a series of bound lines will be formed. Provided the inequalities (2) are satisfied, these bound lines will always leave a zone showing all feasible combinations of P and e. The most economical design, using the minimum prestress, usually lies on the right hand side of the diagram, where the design is limited by the permissible tensile stresses.Plotting the eccentricity on the vertical axis allows direct comparison with the crosssection, as shown in Fig. 5. Inequalities (3) make no reference to the physical dimensions of the structure, but these practical cover limits can be shown as wellA good designer knows how changes to the design and the loadings alter the Magnel diagram. Changing both the maximum andminimum bending moments, but keeping the range the same, raises and lowers the feasible region. If the moments become more sagging the feasible region gets lower in the beam.In general, as spans increase, the dead load moments increase in proportion to the live load. A stage will be reached where the economic point (A on Fig.5) moves outside the physical limits of the beam; Guyon (1951a) denoted the limiting condition as the critical span. Shorter spans will be governed by tensile stresses in the two extreme fibres, while longer spans will be governed by the limiting eccentricity and tensile stresses in the bottom fibre. However, it does not take a large increase in moment ，at which point compressive stresses will govern in the bottom fibre under maximum moment.Only when much longer spans are required, and the feasible region moves as far down as possible, does the structure become governed by compressive stresses in both fibres.3、Continuous beamsThe design of statically determinate beams is relatively straightforward; the engineer can work on the basis of the design of individual cross-sections, as outlined above. A number of complications arise when the structure is indeterminate which means that the designer has to consider, not only a critical section,but also the behaviour of the beam as a whole. These are due to the interaction of a number of factors, such as Creep, Temperature effects and Construction Sequence effects. It is the development of these ideas whichforms the core of this paper. The problems of continuity were addressed at a conference in London (Andrew and Witt 1951). The basic principles, and nomenclature, were already in use, but to modern eyes concentration on hand analysis techniques was unusual, and one of the principle concerns seems to have been the difficulty of estimating losses of prestressing force.3.1 Secondary MomentsA prestressing cable in a beam causes the structure to deflect. Unlike the statically determinate beam, where this motion is unrestrained, the movement causes a redistribution of the support reactions which in turn induces additional moments. These are often termed Secondary Moments, but they are not always small, or Parasitic Moments, but they are not always bad.Freyssinet’s bridge across the Marne at Luzancy, started in 1941 but not completed until 1946, is often thought of as a simply supported beam, but it was actually built as a two-hinged arch (Harris 1986), with support reactions adjusted by means of flat jacks and wedges which were later grouted-in (Fig.6). The same principles were applied in the later and larger beams built over the same river.Magnel built the first indeterminate beam bridge at Sclayn, in Belgium (Fig.7) in 1946. The cables are virtually straight, but he adjusted the deck profile so that the cables were close to the soffit near mid-span. Even with straight cables the sagging secondary momentsare large; about 50% of the hogging moment at the central support caused by dead and live load.The secondary moments cannot be found until the profile is known but the cablecannot be designed until the secondary moments are known. Guyon (1951b) introduced the concept of the concordant profile, which is a profile that causes no secondary moments; es and ep thus coincide. Any line of thrust is itself a concordant profile.The designer is then faced with a slightly simpler problem; a cable profile has to be chosen which not only satisfies the eccentricity limits (3) but is also concordant. That in itself is not a trivial operation, but is helped by the fact that the bending moment diagram that results from any load applied to a beam will itself be a concordant profile for a cable of constant force. Such loads are termed notional loads to distinguish them from the real loads on the structure. Superposition can be used to progressively build up a set of notional loads whose bending moment diagram gives the desired concordant profile.3.2 Temperature effectsTemperature variations apply to all structures but the effect on prestressed concrete beams can be more pronounced than in other structures. The temperature profile through the depth of a beam (Emerson 1973) can be split into three components for the purposes of calculation (Hambly 1991). The first causes a longitudinal expansion, which is normally released by the articulation of the structure; the second causes curvature which leads to deflection in all beams and reactant moments in continuous beams, while the third causes a set of self-equilibrating set of stresses across the cross-section.The reactant moments can be calculated and allowed-for, but it is the self- equilibrating stresses that cause the main problems for prestressed concrete beams. These beams normally have high thermal mass which means that daily temperature variations do not penetrate to the core of the structure. The result is a very non-uniform temperature distribution across the depth which in turn leads to significant self-equilibrating stresses. If the core of the structure is warm, while the surface is cool, such as at night, then quite large tensile stresses can be developed on the top and bottom surfaces. However, they only penetrate a very short distance into the concrete and the potential crack width is very small. It can be very expensive to overcome the tensile stress by changing the section or the prestress。
王德龙外文翻译原文
DC Switching Power Supply Protection Technology1、IntroductionDC switching regulator used in the price of more expensive high-power switching devices,the control circuit is also more complex,In addition,the load switching regulators are generally used a large number of highly integrated electronic systems installed devices. Transistors and integrated device tolerance electricity,less heat shocks.Switching Regulators therefore should take into account the protection of voltage regulators and load their own safety.Many different types of circuit protection,polarity protection,introduced here,the program protection,over-current protection,over-voltage protection,under-voltage protection and over-temperature protection ually chosen to be some combination of protection,constitutes a complete protection system.2、polarity protectionDC switching regulator input are generally not regulated DC power supply.Operating errors or accidents as a result of the situation will take its wrong polarity,switching power supply will be damaged.Polarity protection purposes,is to make the switching regulator only when the correct polarity is not connected to DC power supply regulator to work at. Connecting a single device can achieve power polarity protection.Since the diode D to flow through switching regulator input total current,this circuit applied in a low-power switching regulator more suitable.Power in the larger occasion,while the polarity protection circuit as a procedure to protect a link,save the power required for polarity protection diodes,power consumption will be reduced.In order to easy to operate,make it easier to identify the correct polarity or not,collect the next light.3、procedures to protectSwitching power supply circuit is rather complicated,basically can be divided into low-power and high-power part of the control part of the switch.Switch is a high-power transistors,for the protection of the transistor switch is turned on or off power safety,we must first modulator,amplifier and other low-power control circuit.To this end,the boot to ensure the correct procedures.Switching Regulators generally take the input of a small inductor,the input filter capacitor.Moment in the boot,filter capacitor will flow a lot of surge current,the surge current can be several times more than the normal input current. Such a large surge current may contact the general power switch or relay contact melting,and the input fuse fuse.In addition,the capacitor surge current will damage to shorten the life span of premature damage.To this end,the boot should be access to a current limiting resistor,through the current limiting resistor to capacitor charging.In order not to make the current limiting resistor excessive power consumption,thus affecting the normal switching regulator,and the transient process in the boot after a short period then automatically relays it to DC power supply directly to the switching regulator power supply.This circuit switching regulator called a"soft start"circuit.Switching regulator control circuit of the logic components required or op-amp auxiliary power supply.To this end,the auxiliary power supply must be in the switch circuit. This control circuit can be used to ensure the boot.Normal boot process is:to identify the polarity of input power,voltage protection procedures→boot→auxiliary power supply circuit and through current limiting resistor R of the switching regulator input capacitor C→charge modulation switching regulator circuit,→short-circuit current limiting resistor stability switching regulator.In the switching regulator,the machines just because the output capacitance,and charge to the rated output voltage value of the need for a certain period of time.During this time, sampling the output amplifier with low input voltage sampling,closed-loop regulation characteristics of the system will force the switching of the transistor conduction time lengthened,so that switching transistor during this period will tend to continuous conduction, and easily damaged.To this end,the requirements of this paragraph in the boot time,the switch to switch the output modulation circuit transistor base drive signal of the pulse width modulation,can guarantee the switching transistor by the cut-off switches are becoming more and more normal state,therefore the protection of the setting up of a boot to tie in with the soft start.4、over-current protectionWhen the load short-circuit,overload control circuit failure or unforeseen circumstances,such as would cause the flow of switching voltage regulator transistor current is too large,so that increased power tubes,fever,if there is no over-current protection device, high power switching transistor may be damaged.Therefore,the switching regulator in the over-current protection is commonly used.The most economical way is to use simple fuse. As a result of the heat capacity of small transistors,general fuse protection in general can not play a role in the rapid fuse common fuse.This method has the advantage of the protectionof vulnerable,but it needs to switch transistor in accordance with specific security requirements of the work area to select the fuse specifications.This disadvantage is over-current protection measures brought about by the inconvenience of frequent replacement of fuses.Linear voltage regulator commonly used in the protection and current limiting to protect the cut-off in the switching regulator can be applied.However,according to the characteristics of switching regulators,the protection circuit can not directly control the output transistor switches,and overcurrent protection must be converted to pulse output commands to control the modulator to protect the transistor switch.In order to achieve over-current protection are generally required sampling resistor in series in the circuit,this will affect the efficiency of power supply,so more for low-power switching regulator of occasions.In the high-power switching power supply,by taking into account the power consumption should be avoided as far as possible access to the sampling resistor.Therefore, there will usually be converted to over-current protection,and under-voltage protection.5、over-voltage protectionSwitching regulator's input over-voltage protection,including over-voltage protection and output over-voltage protection.Switching regulator is not used in DC power supply voltage regulator and rectifier,such as battery voltage,if too high,so switching regulator is not working properly,or even damage to internal devices,therefore,it is necessary to use the input over-voltage protection ing transistors and relays protection circuit.In the circuit,when the input DC power supply voltage higher than the voltage regulator diode breakdown voltage value,the breakdown voltage regulator tube,a current flowing through resistor R,so that V turn-on transistor,relay,normally closed contact off open,cut off the input.Voltage regulator voltage regulator which controls the value of Vz= ESrmax-UBE.The polarity of input power with the input protection circuit can be combined with over-voltage protection,polarity protection constitute a differential circuit and overvoltage protection.Output over-voltage protection switching power supply is essential.In particular,for the5V output of the switching regulator,it is a lot of load on a high level of integration of the logic device.If at work,switching regulator sudden damage to the switch transistor,the output potential may be increased immediately to the importation of non-regulated DC power supply voltage value,causing great loss monly used method isshort-circuit protection thyristor.The simplest over-voltage protection circuit.When the output voltage is too high,the regulator tube breakdown triggered thyristor turn-on,the output short-circuit,resulting in over-current through the fuse or circuit protective device to cut off the input to protect the load.This circuit is equivalent to the response time of the opening time of thyristor is about5~10μs.The disadvantage is that its action is fixed voltage,temperature coefficient,and action points of instability.In addition,there is a voltage regulator control parameters of the discrete,model over-voltage start-up the same but has different values,difficult to debug.Esc a sudden increase in output voltage, transistors V1,V2conduction,the thyristor conduction.Reference voltage Vz by type.6、under-voltage protectionOutput voltage below the value to reflect the input DC power supply,switching regulator output load internal or unusual occurrence.Input DC power supply voltage drops below the specified value would result in switching regulator output voltage drops,the input current increases,not only endanger the switching transistor,but also endanger the input power.Therefore,in order to set up due to voltage protection.Due to simple voltage protection.When no voltage regulator input normal,ZD breakdown voltage regulator tube, transistors V conduction,the relay action,contact pull-in,power-switching regulator.When the input below the minimum allowable voltage value,the regulator tube ZD barrier,V cut-off,contact Kai-hop,switching regulator can not work.Internal switching regulator,as the control switch transistor circuit disorders or failure will decrease the output voltage;load short-circuit output voltage will also decline.Especially in the reversed-phase step-up or step-up switching regulator DC voltage of the protection due to over-current protection with closely related and therefore more important.Implementation of Switching Regulators in the termination of the output voltage comparators.Normally,there is no comparator output,once the voltage drops below the allowable value in the comparator on the flip,drive alarm circuit;also fed back to the switching regulator control circuit,so that switching transistor cut-off or cut off the input power.7、over-temperature protectionSwitching regulator and the high level of integration of light-weight small volume,with its unit volume greatly increased the power density,power supply components to its workwithin the requirements of the ambient temperature is also a corresponding increase. Otherwise,the circuit performance will deteriorate,premature component failure.Therefore, in high-power switching regulator should be set up over-temperature protection.Relays used to detect the temperature inside the power supply temperature,when the internally generated power supply overheating,the temperature of the relay on the action,so that whole circuit in a warning alarm,and the realization of the power supply over-temperature protection.Temperature relay can be placed in the vicinity of the switching transistor,the general high-power tube shell to allow the maximum temperature is75℃, adjust the temperature setting to60℃.When the shell after the temperature exceeds the allowable value to cut off electrical relay on the switch protection.Semiconductor switching device thermal"hot thyristor,"in the over-temperature protection,played an important role. It can be used as directed circuit temperature.Under the control of p-hot-gate thyristor (TT102)characteristics,by RT value to determine the temperature of the device turn-on,RT greater the temperature the lower the turn-on.When placed near the power switching transistor or power device,it will be able to play the role of temperature instructions.When the power control the temperature of the shell or the internal device temperature exceeds the allowed value,the heat conduction thyristor on,so that LED warning light.If the optocoupler with,would enable the whole circuit alarm action to protect the switching regulator.It can also be used as a power transistor as the over-temperature protection,crystal switch the base current by n-type gate control thyristor TT201thermal bypass,cut-off switch to cut off the collector current to prevent overheating.8、ConclusionDiscussed above in the switching regulator of a variety of conservation,and introduces a number of specific ways to achieve.Of a given switching power supply is concerned,but also protection from the whole to consider the following points:1)the switching regulator used in the switching transistor in the DC security restrictions on the work of regional work.The transistor switches selected by the manual available transistors get DC safe working area.According to the maximum collector current to determine the input value of over-current protection.However,the instantaneous maximum value should be converted to the average current.At rated output current and output voltage conditions,the switch of the dynamic load line does not exceed a safe working area DC maximum input voltage,input over-voltage protection is the voltage value.2)the switching regulator output limit given by the technical indicators within.Work within the required temperature range,the switching regulator's output voltage,the lower limit of the output is off,due to the voltage value of voltage protection.Over-current protection can be based on the maximum output current to determine.False alarm in order not to protect the value of a certain margin to remain appropriate.3)from the above two methods to determine the protection after the power supply device in accordance with the needs of measures to determine the alarm.Measures the general alarm sound and light alarm two police.Voice of the police applied to more complex machines,power supply parts and do not stand out in a place,it can give staff an effective warning of failure;optical Police instructions can be eye-catching and fault alarm and pointed out that the fault location and type.Protection measures should be protected as to determine the location.In the high-power,multi-channel power supply,always paying,DC circuit breakers,relays,etc.high-sensitivity auto-protection measures,to cut off the input power supply to stop working the system from damage.Through the logic control circuit to make the appropriate program cut-off switch transistor is sensitive it is convenient and economic.This eliminated large,long response time,the price of your high-power relay or circuit breaker.4)the power of putting in the protection circuit will be affected after the reliability of the system,for which want to protect the reliability of the circuit itself is higher in order to improve the reliability of the entire power system,thereby increasing its own power supply MTBF.This requires the protection of strict logic,the circuit is simple,at least components, In addition to the protection circuit should also be considered a failure of maintenance of their difficulty and their power to protect the damage.Therefore,we must be comprehensive and systematic consideration of a variety of switching power supply protection measures to ensure the normal operation of switching power supplies and high-efficiency and high reliability.。
应收账款【外文翻译】
外文文献翻译一、外文原文原文：Accounts Receivable IssuesFor many companies, the accounts receivable portfolio is its largest asset. Thus, it deserves special care and attention. Effective handling of the portfolio can add to the bottom line, while neglect can cost companies in unseen losses.Accounts Receivable Strategies to Energize the Bottom LineDon’t be surprised to find the big shots from finance suddenly looking over your shoulder questioning the ways your credit department operates. Accounts receivable has become the darling of those executives desperate to optimize working capital and improve their balance sheet.Here’s a roundup of some of the tactics that have been collected from the best credit managers to squeeze every last cent out of their accounts receivable portfolio: ·Have invoices printed and mailed as quickly as possible. Most customers start the clock ticking when the invoice arrives in their offices. The sooner you can get the invoice to them, the sooner they will pay you. While this strategy will not affect days sales outstanding(DSO),it will improve the bottom line.·Look for ways to improve invoice accuracy without delaying the mail date.·Offer more stringent terms where appropriate in your annual credit reviews and with new customers. Consider whether shorter terms might be better for you company.·Offer financial inducements to customers who agree to pay your invoices electronically.·If you have not had a lockbox study performed in the last few years, have one done to determine your optimal lockbox location.·With customers who have a history of paying late, begin your collection effortsbefore the due date. Call to inquire whether they have the invoice and if everything is in order. Resolve any problems quickly at this point.·If you have been giving a grace period to those taking discounts after the discount period, reduce or eliminate it.·Resolve all discrepancies quickly so payment can be made promptly.·If a customer indicates it has a problem with part of an invoice, authorize partial payments.·Keep a log of customer problems and analyze it once a month to discover weaknesses in your procedures that cause these quandaries.·Apply cash the same day the payment is received. Collectors can then spend their time with customers who have not paid rather than annoying ones who have already sent their payment.·Deal with a bank that makes lockbox information available immediately by fax, or preferably, online. Then when a customer claims it has made a payment , the collector will be able to verify this.·Look into ways to accept P-cards from customers placing small orders and those who cannot be extended credit on open account terms.·Benchmark department and individual collectors’ performance to pinpoint those areas and individuals in need of additional training.Review your own policies and procedures to determine if there are any areas that could be tweaked to improve cash flow. Then, when the call comes from executive quarters, you will be ready, and they will be hard pressed to find ways that you fell down on the job.Dealing with Purchase OrdersLeading credit managers have learned to pay attention to the purchase orders that their companies receive. Specifically, they want to ensure that the purchase order accepted by the salesperson does not include clause that will ultimately cause trouble for their companies, or even legal difficulties later on. Realistically, the salesperson should have caught the problem, but he or she rarely does. When the customer doesn’tpay due to one of these techn icalities, it’s not the salesperson who will get blamed.To help avoid a purchase order disaster, credit professionals can take the following steps:1．Simply read the purchase order. Vendors often slip clauses into purchase orders that you would never agree to. One favorite is to include a statementsaying the seller will be paid as soon as its customer pays the buyer. This is arisk few companies are willing to tolerate.2．Prioritize attachments. Typically, buyers write purchase orders that contain attachments. These include drawings, specifications, supplementary termsand conditions for work done on company premises, or safety rules for thesupplier.When including attachments, it is recommended that one of them be a listof priorities to guard against any inconsistencies in the documents. Thepurchase order should “clearly reference all the attachments, and there shouldbe a recitation as to which attachments are controlling over the others.” In theevent of any inconsistency between or among these documents, the purchaseorder shall be controlling over any attachments, and the attachments shall beinterpreted using the priority listed.3．Take care when reference is made to a buyer’s documents in the purchase order. There are likely to be both helpful and harmful statements in thosedocuments that reference the buyer’s material. The buyer may have printedits own terms and conditions on the back of a document. By referring to thedocument in the purchase order, you may inadvertently refer not only to theprice, but also to terms and conditions, which may include warrantydisclaimers and limitations of remedies that your company does not intend togive.Instead, the recommendation is not to refer to the buyers’ documents.Insist that the information is specified in the purchase order. If this is notpractical, the following language might work:” Any reference to thepurchaser’s quotation contained in this purchase order is a reference forconvenience only, and no such reference shall be deemed to include any ofthe purchaser’s standard terms and conditions of sale. The seller expresslyrejects anything in any of the buyer’s documents that is inconsistent with theseller’s standard terms and conditions.”Another favorite is to include terms and conditions on the back of thepurchase order written in very small print and a pale (almost undecipherable)color.4．Be careful of confirming purchase orders. Often, buyers will place orders via telephone, only to later confirm them with a written purchase order. In oralcontracts, the buyer will often want the purchase order to be more than justan offer. Therefore, the buyer will try to show on the purchase order that it isa confirming purchase order and cement the oral contract made over thephone. If the buyer does so, the confirming purchase order will satisfy theUniform Commerical Code (UCC) requirement of a written confirmationunless the other side objects to it within ten days.More than one cunning purchaser has slipped terms into a confirmingpurchase order that were nothing like those agreed to orally. Don’t fall intothe trap of assuming that the confirming purchase order confirms what wasactually said on the phone.Credit professionals who take these few extra steps with regard to purchase orders will limit their troubles.Quality of Accounts Receivable: Days Sales OutstandingMany credit professionals are measured on their effectiveness by reviewing the accounts receivable portfolio. The most common measurement is the length of time a sale stays outstanding before being paid. The Credit Research Foundation (CRF) defines DSO as the average time in days that receivables are outstanding. It helps determine if a change in receivables is due to a change in sales, or to another factor such as a change in selling terms. An analyst might compare the day’s sales in receivables with the company’s credit terms as an indication of how efficiently thecompany manages its receivables. Days sales outstanding is occasionally referred to as days receivable outstanding, as well. The formula to calculate DSO is:365e Re Sales t N Annual ceivablesGrossQuality of Accounts Receivable: Collection Effectiveness IndexSome feel that the quality of the portfolio is dependent to a large extent on the efforts of the collection staff. This is measured by the collection effectiveness index (CEI). The CRF says this percentage expresses the effectiveness of collection efforts over time. The closer to 100% the ratio gets, the more effective the collection effort. It is a measure of the quality of collection of receivables, not of time. Here’s the formula to calculate the CEI:Daysor Months of Number N ceivables Current Ending N Sales Credit ceivables Beginning ceivablesTotal Ending N Sales Credit ceivables Beginning =⨯-+-+100Re )(Re Re )(ReQuality of Accounts Receivable: Best Possible Days Sales OutstandingMany credit professionals find fault with using DSO to measure theirperformance. They feel that a better measure is one based on average terms based on customer payment patterns. The CRF says that this figure expresses the best possible level of receivables. The CRF believes this measure should be used together with DSO. The closer the overall DSO is to the average terms based on customer payment patterns (best possible DSO [BPDSO])，the closer the receivables are to the optimal level. The formula for calculating BPDSO is:AnalyzedPeriod for Sales Credit Analyzed Period in Days of Number ceivables Current ⨯ReBad-Debt ReservesInevitably, no matter how good the credit professional, a company will have a customer that does not pay its debts. Most companies understand that bad debts are simply part of doing business and reserve for bad debts. In fact, many believe that acompany with no bad debts is not doing a good job. The reason that being that if the company loosened its credit terms slightly, the company would greatly increase its sales and, even after accounting for the bad debts, its profits. Thus, most companies plan for bad debt, monitor it, and periodically, depending on the company’s outlook, revise projections and credit policy to allow for an increase or decrease.For example, as the economy goes into a recession, most companies will experience an increase in bad debts if their credit policy remains static. So, in light of declining economic conditions, companies should either increase their bad-debt reserves or tighten the credit policy. Similarly, if the economy is improving, a company would take reverse actions, either decreasing the reserve for bad debts or loosening the credit policy.Many companies take advantage or a favorable economy to expand their customer base. They might simultaneously increase the bad-debt reserve and loosen credit policy. Obviously, these decisions are typically made at a fairly high level. Other factors will also come into play in establishing a bad-debt reserve. Industry conditions are key and can often be quite different than the state of the economy. This is especially true when competition comes from foreign markets.There is no one set way to calculate the reserve for bad debts. Many simply take a percentage of sales or outstanding accounts receivable, or they make some other relatively uncomplicated calculation.How to Reduce Your Bad-Debt Write-OffsMost credit and collection professionals would love to be able to brag about having no bad-debt write-offs. Few can. While a goal of reducing the amount of bad debt write-offs to zero might be unrealistic in most industries, keeping that number as low as possible is something within the control of today’s credit managers. The following seven techniques will help you keep your numbers as low as possible:1.Call early. Don’t wait until the ac count goes 30 or even 60 days past duebefore calling customers about late payments. Such delays can mean that, in the case of a financially unstable company, a second and perhaps even a thirdshipment will be made to a customer who ultimately will pay for naught. Some professionals even call a few days before the payment is due to ensure that everything is in order and the customer has everything it needs to make a timely payment. By beginning your calling campaign as early as possible, it is possible o uncover shaky situations. Even if payment is not received for the first delivery, future order are not accepted, effectively reducing bad-debt write-offs.municate, communicate, communicate. Keep the dialogue open with everyone involved. This not only includes your customers, but the sales force as well. In many cases, they are in a better position than the credit manager to know when a customer is on thin ice. With good lines of communication between sales and credit, it is possible to avoid taking some of those orders that will ultimately have to be written off.3.Follow up, follow up, follow up. Continual follow up with customers is important, whether you’re trying to collect on a timely basis or attempting to avoid a bad-debt write-off. If the customer knows you will call every few days or will be calling to track the status of promises made, it is much more likely to pay. This can also be the case of the squeaky wheel getting the grease, or in this case the money, when cash is tight.4.Systematize. Many collection professionals keep track of promises and deadlines by hand, on a pad or calendar. Items tend to fall through the cracks with this approach. Invest some money either in prepackaged software or in developing your own in-house, and the likelihood of losing track of customers diminishes. Some accounting programs have a tracking capability that many have not taken the time to learn. If your software has such a facility, use it.5.Specialize. Set up a group of one or more individuals who do nothing but try to collect receivables that are overdue. By having experts on staff to handle such work, you will improve your collection rate and speed.6.Credit hold. Putting customers on credit hole early in the picture will sometimes entice a payment from someone who really had no intention of paying you. This technique is particularly effective with customers who rely heavily onyour product and would be hard put to get it elsewhere. Of course, if you sell something that many other vendors sell as well, putting a potentially good customer on hold could backfire.7.Small claims court. Some credit professionals have had great success incollecting smaller amounts by taking the customer to small claims court. The limits for such actions vary by state but can be as high as $10,000.While these techniques will not necessarily squeeze money from a bankrupt client, they will help you get as much as possible as soon as possible from as many of your customers as possible. This can be especially important in avoiding preference actions with clients who eventually do file. The quicker you get the clock ticking, the more likely you are to be able to avoid preference claims.Source: Mary S. Schaeffer, 2002, Essentials of Credit, Collections, and Accounts Receivable, John Wiley & Sons, Inc.( October 01, 2002 ):pp81-102.二、翻译文章译文：应收账款对许多公司来说，应收账款是其最大的资产。
毕业设计英文 翻译(原文)
编号：毕业设计(论文)外文翻译（原文）院（系）：桂林电子科技大学专业：电子信息工程学生姓名： xx学号： xxxxxxxxxxxxx 指导教师单位：桂林电子科技大学姓名： xxxx职称： xx2014年x月xx日Timing on and off power supplyusesThe switching power supply products are widely used in industrial automation and control, military equipment, scientific equipment, LED lighting, industrial equipment,communications equipment,electrical equipment,instrumentation, medical equipment, semiconductor cooling and heating, air purifiers, electronic refrigerator, LCD monitor, LED lighting, communications equipment, audio-visual products, security, computer chassis, digital products and equipment and other fields.IntroductionWith the rapid development of power electronics technology, power electronics equipment and people's work, the relationship of life become increasingly close, and electronic equipment without reliable power, into the 1980s, computer power and the full realization of the switching power supply, the first to complete the computer Power new generation to enter the switching power supply in the 1990s have entered into a variety of electronic, electrical devices, program-controlled switchboards, communications, electronic testing equipment power control equipment, power supply, etc. have been widely used in switching power supply, but also to promote the rapid development of the switching power supply technology .Switching power supply is the use of modern power electronics technology to control the ratio of the switching transistor to turn on and off to maintain a stable output voltage power supply, switching power supply is generally controlled by pulse width modulation (PWM) ICs and switching devices (MOSFET, BJT) composition. Switching power supply and linear power compared to both the cost and growth with the increase of output power, but the two different growth rates. A power point, linear power supply costs, but higher than the switching power supply. With the development of power electronics technology and innovation, making the switching power supply technology to continue to innovate, the turning points of this cost is increasingly move to the low output power side, the switching power supply provides a broad space for development.The direction of its development is the high-frequency switching power supply, high frequency switching power supply miniaturization, and switching power supply into a wider range of application areas, especially in high-tech fields, and promote the miniaturization of high-tech products, light of. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.classificationModern switching power supply, there are two: one is the DC switching power supply; the other is the AC switching power supply. Introduces only DC switching power supply and its function is poor power quality of the original eco-power (coarse) - such as mains power or battery power, converted to meet the equipment requirements of high-quality DC voltage (Varitronix) . The core of the DC switching power supply DC / DC converter. DC switching power supply classification is dependent on the classification of DC / DC converter. In other words, the classification of the classification of the DC switching power supply and DC/DC converter is the classification of essentially the same, the DC / DC converter is basically a classification of the DC switching power supply.DC /DC converter between the input and output electrical isolation can be divided into two categories: one is isolated called isolated DC/DC converter; the other is not isolated as non-isolated DC / DC converter.Isolated DC / DC converter can also be classified by the number of active power devices. The single tube of DC / DC converter Forward (Forward), Feedback (Feedback) two. The double-barreled double-barreled DC/ DC converter Forward (Double Transistor Forward Converter), twin-tube feedback (Double Transistor Feedback Converter), Push-Pull (Push the Pull Converter) and half-bridge (Half-Bridge Converter) four. Four DC / DC converter is the full-bridge DC / DC converter (Full-Bridge Converter).Non-isolated DC / DC converter, according to the number of active power devices can be divided into single-tube, double pipe, and four three categories. Single tube to a total of six of the DC / DC converter, step-down (Buck) DC / DC converter, step-up (Boost) DC / DC converters, DC / DC converter, boost buck (Buck Boost) device of Cuk the DC / DC converter, the Zeta DC / DC converter and SEPIC, the DC / DC converter. DC / DC converters, the Buck and Boost type DC / DC converter is the basic buck-boost of Cuk, Zeta, SEPIC, type DC / DC converter is derived from a single tube in this six. The twin-tube cascaded double-barreled boost (buck-boost) DC / DC converter DC / DC converter. Four DC / DC converter is used, the full-bridge DC / DC converter (Full-Bridge Converter).Isolated DC / DC converter input and output electrical isolation is usually transformer to achieve the function of the transformer has a transformer, so conducive to the expansion of the converter output range of applications, but also easy to achieve different voltage output , or a variety of the same voltage output.Power switch voltage and current rating, the converter's output power is usually proportional to the number of switch. The more the number of switch, the greater the output power of the DC / DC converter, four type than the two output power is twice as large,single-tube output power of only four 1/4.A combination of non-isolated converters and isolated converters can be a single converter does not have their own characteristics. Energy transmission points, one-way transmission and two-way transmission of two DC / DC converter. DC / DC converter with bi-directional transmission function, either side of the transmission power from the power of lateral load power from the load-lateral side of the transmission power.DC / DC converter can be divided into self-excited and separately controlled. With the positive feedback signal converter to switch to self-sustaining periodic switching converter, called self-excited converter, such as the the Luo Yeer (Royer,) converter is a typical push-pull self-oscillating converter. Controlled DC / DC converter switching device control signal is generated by specialized external control circuit.the switching power supply.People in the field of switching power supply technology side of the development of power electronic devices, while the development of the switching inverter technology, the two promote each other to promote the switching power supply annual growth rate of more than two digits toward the light, small, thin, low-noise, high reliability, the direction of development of anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, AC / AC DC / AC, such as inverters, DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardization, and has been recognized by the user, but AC / DC modular, its own characteristics make the modular process, encounter more complex technology and manufacturing process. Hereinafter to illustrate the structure and characteristics of the two types of switching power supply.Self-excited: no external signal source can be self-oscillation, completely self-excited to see it as feedback oscillation circuit of a transformer.Separate excitation: entirely dependent on external sustain oscillations, excited used widely in practical applications. According to the excitation signal structure classification; can be divided into pulse-width-modulated and pulse amplitude modulated two pulse width modulated control the width of the signal is frequency, pulse amplitude modulation control signal amplitude between the same effect are the oscillation frequency to maintain within a certain range to achieve the effect of voltage stability. The winding of the transformer can generally be divided into three types, one group is involved in the oscillation of the primary winding, a group of sustained oscillations in the feedback winding, there is a group of load winding. Such as Shanghai is used in household appliances art technological production of switching power supply, 220V AC bridge rectifier, changing to about 300V DC filter added tothe collector of the switch into the transformer for high frequency oscillation, the feedback winding feedback to the base to maintain the circuit oscillating load winding induction signal, the DC voltage by the rectifier, filter, regulator to provide power to the load. Load winding to provide power at the same time, take up the ability to voltage stability, the principle is the voltage output circuit connected to a voltage sampling device to monitor the output voltage changes, and timely feedback to the oscillator circuit to adjust the oscillation frequency, so as to achieve stable voltage purposes, in order to avoid the interference of the circuit, the feedback voltage back to the oscillator circuit with optocoupler isolation.technology developmentsThe high-frequency switching power supply is the direction of its development, high-frequency switching power supply miniaturization, and switching power supply into the broader field of application, especially in high-tech fields, and promote the development and advancement of the switching power supply, an annual more than two-digit growth rate toward the light, small, thin, low noise, high reliability, the direction of the anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, the DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardized, and has been recognized by the user, but modular AC / DC, because of its own characteristics makes the modular process, encounter more complex technology and manufacturing process. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.The switching power supply applications in power electronic devices as diodes, IGBT and MOSFET.SCR switching power supply input rectifier circuit and soft start circuit, a small amount of applications, the GTR drive difficult, low switching frequency, gradually replace the IGBT and MOSFET.Direction of development of the switching power supply is a high-frequency, high reliability, low power, low noise, jamming and modular. Small, thin, and the key technology is the high frequency switching power supply light, so foreign major switching power supply manufacturers have committed to synchronize the development of new intelligent components, in particular, is to improve the secondary rectifier loss, and the power of iron Oxygen materials to increase scientific and technological innovation in order to improve the magnetic properties of high frequency and large magnetic flux density (Bs), and capacitor miniaturization is a key technology. SMT technology allows the switching power supply has made considerable progress, the arrangement of the components in the circuit board on bothsides, to ensure that the light of the switching power supply, a small, thin. High-frequency switching power supply is bound to the traditional PWM switching technology innovation, realization of ZVS, ZCS soft-switching technology has become the mainstream technology of the switching power supply, and a substantial increase in the efficiency of the switching power supply. Indicators for high reliability, switching power supply manufacturers in the United States by reducing the operating current, reducing the junction temperature and other measures to reduce the stress of the device, greatly improve the reliability of products.Modularity is the overall trend of switching power supply, distributed power systems can be composed of modular power supply, can be designed to N +1 redundant power system, and the parallel capacity expansion. For this shortcoming of the switching power supply running noise, separate the pursuit of high frequency noise will also increase, while the use of part of the resonant converter circuit technology to achieve high frequency, in theory, but also reduce noise, but some The practical application of the resonant converter technology, there are still technical problems, it is still a lot of work in this field, so that the technology to be practical.Power electronics technology innovation, switching power supply industry has broad prospects for development. To accelerate the pace of development of the switching power supply industry in China, it must take the road of technological innovation, out of joint production and research development path with Chinese characteristics and contribute to the rapid development of China's national economy.Developments and trends of the switching power supply1955 U.S. Royer (Roger) invented the self-oscillating push-pull transistor single-transformer DC-DC converter is the beginning of the high-frequency conversion control circuit 1957 check race Jen, Sen, invented a self-oscillating push-pull dual transformers, 1964, U.S. scientists canceled frequency transformer in series the idea of switching power supply, the power supply to the size and weight of the decline in a fundamental way. 1969 increased due to the pressure of the high-power silicon transistor, diode reverse recovery time shortened and other components to improve, and finally made a 25-kHz switching power supply.At present, the switching power supply to the small, lightweight and high efficiency characteristics are widely used in a variety of computer-oriented terminal equipment, communications equipment, etc. Almost all electronic equipment is indispensable for a rapid development of today's electronic information industry power mode. Bipolar transistor made of 100kHz, 500kHz power MOS-FET made, though already the practical switching power supply is currently available on the market, but its frequency to be further improved. Toimprove the switching frequency, it is necessary to reduce the switching losses, and to reduce the switching losses, the need for high-speed switch components. However, the switching speed will be affected by the distribution of the charge stored in the inductance and capacitance, or diode circuit to produce a surge or noise. This will not only affect the surrounding electronic equipment, but also greatly reduce the reliability of the power supply itself. Which, in order to prevent the switching Kai - closed the voltage surge, RC or LC buffers can be used, and the current surge can be caused by the diode stored charge of amorphous and other core made of magnetic buffer . However, the high frequency more than 1MHz, the resonant circuit to make the switch on the voltage or current through the switch was a sine wave, which can reduce switching losses, but also to control the occurrence of surges. This switch is called the resonant switch. Of this switching power supply is active, you can, in theory, because in this way do not need to greatly improve the switching speed of the switching losses reduced to zero, and the noise is expected to become one of the high-frequency switching power supply The main ways. At present, many countries in the world are committed to several trillion Hz converter utility.the principle of IntroductionThe switching power supply of the process is quite easy to understand, linear power supplies, power transistors operating in the linear mode and linear power, the PWM switching power supply to the power transistor turns on and off state, in both states, on the power transistor V - security product is very small (conduction, low voltage, large current; shutdown, voltage, current) V oltammetric product / power device is power semiconductor devices on the loss.Compared with the linear power supply, the PWM switching power supply more efficient process is achieved by "chopping", that is cut into the amplitude of the input DC voltage equal to the input voltage amplitude of the pulse voltage. The pulse duty cycle is adjusted by the switching power supply controller. Once the input voltage is cut into the AC square wave, its amplitude through the transformer to raise or lower. Number of groups of output voltage can be increased by increasing the number of primary and secondary windings of the transformer. After the last AC waveform after the rectifier filter the DC output voltage.The main purpose of the controller is to maintain the stability of the output voltage, the course of their work is very similar to the linear form of the controller. That is the function blocks of the controller, the voltage reference and error amplifier can be designed the same as the linear regulator. Their difference lies in the error amplifier output (error voltage) in the drive before the power tube to go through a voltage / pulse-width conversion unit.Switching power supply There are two main ways of working: Forward transformand boost transformation. Although they are all part of the layout difference is small, but the course of their work vary greatly, have advantages in specific applications.the circuit schematicThe so-called switching power supply, as the name implies, is a door, a door power through a closed power to stop by, then what is the door, the switching power supply using SCR, some switch, these two component performance is similar, are relying on the base switch control pole (SCR), coupled with the pulse signal to complete the on and off, the pulse signal is half attentive to control the pole voltage increases, the switch or transistor conduction, the filter output voltage of 300V, 220V rectifier conduction, transmitted through the switching transformer secondary through the transformer to the voltage increase or decrease for each circuit work. Oscillation pulse of negative semi-attentive to the power regulator, base, or SCR control voltage lower than the original set voltage power regulator cut-off, 300V power is off, switch the transformer secondary no voltage, then each circuit The required operating voltage, depends on this secondary road rectifier filter capacitor discharge to maintain. Repeat the process until the next pulse cycle is a half weeks when the signal arrival. This switch transformer is called the high-frequency transformer, because the operating frequency is higher than the 50HZ low frequency. Then promote the pulse of the switch or SCR, which requires the oscillator circuit, we know, the transistor has a characteristic, is the base-emitter voltage is 0.65-0.7V is the zoom state, 0.7V These are the saturated hydraulic conductivity state-0.1V-0.3V in the oscillatory state, then the operating point after a good tune, to rely on the deep negative feedback to generate a negative pressure, so that the oscillating tube onset, the frequency of the oscillating tube capacitor charging and discharging of the length of time from the base to determine the oscillation frequency of the output pulse amplitude, and vice versa on the small, which determines the size of the output voltage of the power regulator. Transformer secondary output voltage regulator, usually switching transformer, single around a set of coils, the voltage at its upper end, as the reference voltage after the rectifier filter, then through the optocoupler, this benchmark voltage return to the base of the oscillating tube pole to adjust the level of the oscillation frequency, if the transformer secondary voltage is increased, the sampling coil output voltage increases, the positive feedback voltage obtained through the optocoupler is also increased, this voltage is applied oscillating tube base, so that oscillation frequency is reduced, played a stable secondary output voltage stability, too small do not have to go into detail, nor it is necessary to understand the fine, such a high-power voltage transformer by switching transmission, separated and after the class returned by sampling the voltage from the opto-coupler pass separated after class, so before the mains voltage, and after the classseparation, which is called cold plate, it is safe, transformers before power is independent, which is called switching power supply.the DC / DC conversionDC / DC converter is a fixed DC voltage transformation into a variable DC voltage, also known as the DC chopper. There are two ways of working chopper, one Ts constant pulse width modulation mode, change the ton (General), the second is the frequency modulation, the same ton to change the Ts, (easy to produce interference). Circuit by the following categories:Buck circuit - the step-down chopper, the average output voltage U0 is less than the input voltage Ui, the same polarity.Boost Circuit - step-up chopper, the average output voltage switching power supply schematic U0 is greater than the input voltage Ui, the same polarity.Buck-Boost circuit - buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, the inductance transmission.Cuk circuit - a buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, capacitance transmission.The above-mentioned non-isolated circuit, the isolation circuit forward circuits, feedback circuit, the half-bridge circuit, the full bridge circuit, push-pull circuit. Today's soft-switching technology makes a qualitative leap in the DC / DC the U.S. VICOR company design and manufacture a variety of ECI soft-switching DC / DC converter, the maximum output power 300W, 600W, 800W, etc., the corresponding power density (6.2 , 10,17) W/cm3 efficiency (80-90)%. A the Japanese Nemic Lambda latest using soft-switching technology, high frequency switching power supply module RM Series, its switching frequency (200 to 300) kHz, power density has reached 27W/cm3 with synchronous rectifier (MOSFETs instead of Schottky diodes ), so that the whole circuit efficiency by up to 90%.AC / DC conversionAC / DC conversion will transform AC to DC, the power flow can be bi-directional power flow by the power flow to load known as the "rectification", referred to as "active inverter power flow returned by the load power. AC / DC converter input 50/60Hz AC due must be rectified, filtered, so the volume is relatively large filter capacitor is essential, while experiencing safety standards (such as UL, CCEE, etc.) and EMC Directive restrictions (such as IEC, FCC, CSA) in the AC input side must be added to the EMC filter and use meets the safety standards of the components, thus limiting the miniaturization of the volume of AC / DC power, In addition, due to internal frequency, high voltage, current switching, making the problem difficult to solve EMC also high demands on the internal high-density mountingcircuit design, for the same reason, the high voltage, high current switch makes power supply loss increases, limiting the AC / DC converter modular process, and therefore must be used to power system optimal design method to make it work efficiency to reach a certain level of satisfaction.AC / DC conversion circuit wiring can be divided into half-wave circuit, full-wave circuit. Press the power phase can be divided into single-phase three-phase, multiphase. Can be divided into a quadrant, two quadrant, three quadrants, four-quadrant circuit work quadrant.he selection of the switching power supplySwitching power supply input on the anti-jamming performance, compared to its circuit structure characteristics (multi-level series), the input disturbances, such as surge voltage is difficult to pass on the stability of the output voltage of the technical indicators and linear power have greater advantages, the output voltage stability up to (0.5)%. Switching power supply module as an integrated power electronic devices should be selected。
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Project Management ProcessDurgesh BurdeAbstract:There are the rules of project management. Project management skills are indispensable for project managers, and other managers who control intricate actions and responsibilities, because intricate responsibilities are projects. Project management skills are necessary for any intricate responsibility, where diverse results are feasible, requiring plan and assess alternatives, and organizing actions and assets to deliver an outcome. Projects arrive in all forms and dimensions, from the little and simple to extremely big and highly intricate. Project management may be concerned with everything such as:- public, products, finance, buildings and premises, acquisition, services, purchasing, resources, construction, plant and equipment, training, culture, divestment, storage, distribution, logistics, IT and communications, staffing and management, administration, sales, selling, marketing, human resources, etc. Project management, for projects large or small, should follow the simple process:Project management process1.Detailed requirement for the project.2.Plan the project - time, team, activities, resources, and financials.3.Correspond the project plan to the project group.4.Consent and allot project actions.5.Control, encourage, notify, promote, and facilitate the project team.6.Verify, assess, evaluate project development; regulate project procedure, andnotify the project members and others.7.Finish project; evaluation and report on project performance; Admire and thanksto the project members.1. Detailed requirement for the projectFrequently called the project 'terms of reference', the project requirement should be an exact depiction of what the project aspires to accomplish, and the criteria and flexibilities concerned, its factors, scope, range, outputs, sources, participants, budgets and timescales.The project manager must discuss with others and then consent the project requirement with superiors, or with relevant authorities. The requirement may engage several drafts before it is agreed. A project requirement is essential in that it creates a measurable accountability for anyone wishing at any time to assess how the project is going, or its success on completion. Project terms of reference also provide an essential discipline and framework to keep the project on track, and concerned with the original agreed aims and parameters. A properly formulated and agreed project requirement also protects the project manager from being held to account for issues that are outside the original scope of the project or beyond the project manager's control.This is the step to agree special circumstances or exceptions with those in authority. Once you have published the terms of reference you have created a very firm set of expectations by which you will be judged. So if you have any concerns, or want to renegotiate, now's the time to do it.The largest projects can require several weeks to produce and agree project terms of reference. Most normal business projects however require a few days thinking and consulting to produce a suitable project requirement. Establishing and agreeing a project requirement is an important process even if your task is simple one.An outline for a project requirement:1.Describe purpose, aims and deliverables.2.State factors (timescales, budgets, range, scope, territory, authority).3.State people involved and the way the team will work (frequency of meetings,decision-making process).4.Establish 'break-points' at which to review and check progress, and how progressand results will be measured.2. Plan the project - time, team, activities, resources, and financials.Plan the various steps and tasks of the project. A valuable tip is to work backwards from the end aim, identifying all the things that need to be put in place and done, in reverse order. First, idea generation will help to gather most of the points and issues. For complex projects, or when you lack experience of the issues, involve others in the idea generation process. Thereafter it is a question of putting the issues in the right order, and establishing relationships and links between each issue. Complex projects will have a number of tasks running in parallel. Some parts of the project will need other parts of the project to be completed before they can begin or progress. Some projects will require a feasibility step before the completion of a detailed plan.a) Project timescalesMost projects come in late - that is just the way it is - so do not plan a timescale that is over-ambitious. Preferably, plan for some adversaries. If you have been given a fixed deadline, plan to meet it earlier, and work back from that earlier date. Build some slippage or leeway into each phase of the project. Err on the side of caution where you can. Otherwise, you will be making a rod for your own back.b) The project teamAnother important part of the planning stage is picking your team. Take great care, especially if you have team-members imposed on you by the project brief. Selecting and gaining commitment from the best team members - whether directly employed, freelance, contractors, suppliers, consultants or other partners - is crucial to the quality of the project, and the ease with which you are able to manage it. Generally try to establish yourteam as soon as possible. Identifying or appointing one or two people even during the terms of reference stage is possible sometimes. Appointing the team early maximizes their ownership and buy-in to the project, and maximizes what they can contribute. But be very cautious of appointing people before you are sure how good they are, and not until they have committed themselves to the project upon terms that are clearly understood and acceptable. Do not imagine that teams need to be full of paid and official project team members. Some of the most valuable team members are informal advisors, mentors, helpers, who want nothing other than to be involved and a few words of thanks. Project management on a tight budget can be a lonely business - get some help from good people you can trust, whatever the budget.To plan and manage large complex projects with various parallel and dependent tasks you will need to put together a 'Critical Path Analysis' and a spreadsheet on MS Excel or equivalent. Critical Path Analysis will show you the order in which tasks must be performed, and the relative importance of tasks. Some tasks can appear small and insignificant when they might actually be hugely influential in enabling much bigger activities to proceed or give best results. A Gantt chart is a useful way of showing blocks of activities over time, at a given cost, and for managing the project and its costs along the way.Various project management software is available, much of which is useful, but before trying it, you should understand and concentrate on developing the pure project management skills, which are described in this process. The best software in the world will not help you if you cannot do the key things.c) The project 'critical path analysis''Critical Path Analysis' sounds very complicated, but it's a very logical and effective method for planning and managing complex projects. This is how to create a critical path analysis. As an example, the project is a simple one - making a fried breakfast.First note down all the issues (resources and activities in a rough order):Assemble crockery and utensils, assemble ingredients, prepare equipment, make toast, fry sausages and eggs, grill bacon and tomatoes, lay table, warm plates, serve.Note that some of these activities must happen in parallel. That is to say, if you tried to make a fried breakfast by doing one task at a time, and one after the other, things would go wrong. Certain tasks must be started before others, and certain tasks must be completed in order for others to begin. The plates need to be warming while other activities are going on. The toast needs to be toasting while the sausages are frying, and at the same time the bacon and sausages are under the grill. The eggs need to be fried last. A critical path analysis is a diagrammatical representation of what needs done and when. Timescales and costs can be applied to each activity and resource. Here's the critical path analysis for making a fried breakfast:This critical path analysis example below shows just a few activities over a few minutes. Normal business projects would see the analysis extending several times wider than this example, and the time line would be based on weeks or months. It is possible to use MS Excel or a similar spreadsheet to create a critical path analysis, which allows financial totals and time totals to be planned and tracked. Various specialized project management software enable the same thing. Beware however of spending weeks on the intricacies of computer modeling, when in the early stages especially, a carefully hand drawn diagram - which requires no computer training at all - can put 90% of the thinking and structure in place.d) Gantt chartsGantt Charts are extremely useful project management tools. You can construct a Gantt Chart using MSExcel or a similar spreadsheet. Every activity has a separate line. Create a time-line for the duration of the project (the breakfast example shows minutes, but normally you would use weeks, or for very big long-term projects, months). You can colour code the time blocks to denote type of activity (e.g. intense, watching brief, directly managed, delegated and left to run, etc.) You can schedule review and break points. At the end of each line you can show as many cost columns for the activities as you need. The breakfast example shows just the capital cost of the consumable items and a revenue cost for labour and fuel. A Gantt chart like this can be used to keep track of progress for each activity and how the costs are running. You can move the time blocks around to report on actuals versus planned, and to re-schedule, and to create new plan updates. Costs columns can show plan and actuals and variances, and calculate whatever totals, averages, ratios, etc you need. Gantt Charts are the most flexible and useful of all project management tools, but remember they do not show the importance and inter-dependence of related parallel activities, and they will not show the necessity to complete one task before another can begin, as a critical path analysis will do, so you need both tools, especially at the planning stage.e) Project financial planning and reportingFor projects, involving more than petty cash you will need a spreadsheet to plan and report planned and actual expenditure. Use MSExcel or similar. If you do not know how to put together a basic financial plan, get some help from someone who knows. Make sure you bring a good friendly, flexible financial person into your team - it is a key function of project management, and if you cannot manage the financial processes your self, you need to be able to rely completely on whoever does it for you. The spreadsheet must enable you to plan, administer and report the detailed finances of your project. Create a cost line for main expenditure activity, and break this down into individual elements. Create a system for allocating incoming invoices to the correct activities (your bought-ledger people will not know unless you tell them), and showing when the costs hit the project account. Establish clear payment terms with all suppliers and stick to them. Projects develop problems when team members get dissatisfied; rest assured, non- or late-payment is a primary cause of dissatisfaction.Remember to set some budget aside for 'contingencies' - you will need it.f) Project contingency planningPlanning for and anticipating the unforeseen, or the possibility that things may not go as expected, is called 'contingency planning'. Contingency planning is vital in any task when results and outcomes cannot be absolutely guaranteed. Often a contingency budget needs to be planned, as there are usually costs associated. Contingency planning is about preparing fallback actions, and making sure that leeway for time, activity and resource exists to rectify or replace first-choice plans. A simple contingency plan for the fried breakfast would be to plan for the possibility of breaking the yolk of an egg, in which case spare resource (eggs) should be budgeted for and available if needed. Another might be to prepare some hash browns and mushrooms in the event that any of the diners are vegetarian. It may be difficult to anticipate precisely what contingency to plan for in complex long-term projects, in which case simply a contingency budget is provided, to be allocated later when and if required.3. Correspond the project plan to the project group.This serves two purposes: it informs people what is happening, and it obtains essential support, agreement and commitment. If your project is complex and involves a team, then you should involve the team in the planning process to maximize buy-in, ownership, and thereby accountability. Your project will also benefit from input and consultation from relevant people at an early stage.4. Consent and allot project actions.Your plan will have identified those responsible for each activity. Activities need to be very clearly described, including all relevant parameters, timescales, costs, and deliverables. When delegated tasks fail this is typically because they have not been explained clearly, agreed with the other person, or supported and checked while in progress. So publish the full plan to all in the team, but do not issue all the tasks unless the recipients are capable of their own forward planning. Long-term complex projects need to be planned in more detail and great care must be taken in delegating and supporting them. Do not delegate anything unless it makes sure for perfection.5. Control, encourage, notify, promote, and facilitate the project team.Manage the team and activities by meeting, communicating, supporting, and helping with decisions. Admire vociferously; charge quietly. One of the big challenges for a project manager is deciding how much freedom to give for each delegated activity. Tight parameters and lots of checking are necessary for inexperienced people who like clear instructions, but this approach is the kiss of death to experienced, entrepreneurial and creative people. They need a wider brief, more freedom, and less checking. Manage these people by the results they get - not how they get them. Look out for differences in personality and working styles in your team. They can get in the way of understandingand cooperation. Your role here is to enable and translate. Face to face meetings, when you can bring team members together, are generally the best way to avoid issues and relationships becoming personalized and emotional. Communicate progress and successes regularly to everyone. Give the people in your team the applause, particularly when someone high up expresses satisfaction - You must take the blame for anything that goes wrong - never dump on anyone in your team.6. Verify, assess, evaluate project development; regulate project procedure, and notify the project members and others.Check the progress of activities against the plan. Review performance regularly and at the stipulated review points, and confirm the validity and relevance of the remainder of the plan. Adjust the plan if necessary in light of performance, changing circumstances, and new information, but remain on track and within the original terms of reference. Be sure to use transparent, pre-agreed measurements when judging performance. Identify, agree and delegate new actions as appropriate. Inform team members and those in authority about developments, clearly, concisely and in writing. Plan team review meetings. Stick to the monitoring systems you established. Probe the apparent situations to get at the real facts. Examine causes and learn from mistakes. Identify reliable advisors and experts in the team and use them. Keep talking to people, and make yourself available to all.7. Finish project; evaluation and report on project performance; Admire and thanks to the project members.At the end of your successful project, hold a review with the team. Ensure you understand what happened and why. Replicate on any failures and mistakes positively, objectively, and without allocating personal blame. Reflect on successes gratefully and realistically. Write a review report, and make observations and recommendations about follow up issues and priorities - there will be plenty.As project manager, to be at the end of a project and to report that the project plan has been fully met, on time and on budget, is a significant achievement, whatever the project size and complexity. The mix of skills required is such that good project managers can manage anything.Conclusions:Businesses sometimes use formal systems development processes. These help assure that systems are developed successfully. A formal process is more effective in creating strong controls, and auditors should review this process to confirm that it is well designed and is followed in practice. A good formal systems development plan outlines: • A strategy to align development with the organization’s broader objectives•Standards for new systems•Project management policies for timing and budgeting•Procedures describing the processRegardless of the methodology used, the project development process will have the same above major stages: requirement for the project, Plan the project, project group, project actions, project team, evaluate project development, regulate project procedure and finish project; evaluation and report on project performance; Admire and thanks to the project members.References:1.Project Management Guidebook2.How to Manage Projects, Priorites and Deadlines3.Project Manager Today, January 2008.4.The Big Project, July 2008.<><><><><><><><><><><><><><><><>><><><><><><>><><><><><><><><> © Durgesh Burde. The author can be reached at durgesh19@ . The author is freelance writer and his area of research is project management and human development.。
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MCU-Based Aquaculture System V. B. De Leon, A. H. Ballado Jr., P. Dychitan Jr., R. GustiloAbstract—Developments in the field of control technology stretched the limits of its application in the field of aquaculture. Hence, this study was carried out to utilize microcontrollers to provide the necessary control of several variables or parameters i.e., pH, temperature and water level in an aquaculture system. The versatility of microcontroller programming allowed the manipulation of the range of parameter values, which could be altered depending on the needs of the system. Likewise, other features of the study included ease of monitoring and data logging. The construction of a simulation tank exhibiting different water quality conditions was carried out to capture dynamic aquacultural situations. Remote monitoring and data collection were an integral part of this study. However, the researcher welcomes further improvements in terms of additional parameters - oxygen level, salinity, phosphate level, and the like - necessary for optimum fish growth, and the use of modern advanced control algorithms to improve the system’s efficiency and speed.Index Terms -microcontroller, aquaculture system, remote terminal unit, data loggerI.I NTRODUCTIONIt is relatively fitting that tilapia can be called colloquially as “aquatic chicken” because of its high growth rate, adaptability to a wide range of environmental conditions, growth and reproduction even in captivity. Not quite surprisingly, this fish has become an excellent candidate for aquaculture, especially in tropical and subtropical environments. Raising tilapia as an inexpensive meat source can be very promising considering the health risks and high costs associated with the consumption of red meat.Tilapia culture is believed to have originated more than 4000 years ago, but very little information was available on their culture during those ancient times. Tilapia farming began from the Nile Valley and spread to central and western Africa.Manuscript reviewed February 28, 2011; revised June 29, 2011. This work was supported by the ERDT program of the Department of Science and Technology.V. B. de Leon finished his MS ECE in Mapúa Institute of Technology. He also holds a MS Math degree from Ateneo de Manila University. He finished his BS ECE from Rizal Technological University. He is currently pursuing his PhD in ECE in Mapúa Institute of Technology. (email: Voltaire.deleon@).A. H. Ballado Jr. received his BS ECE in 1995 from Mapúa Institute of Technology Manila, Philippines. He earned his MS in Electronics Engineering also from the same Institute, in 1999. Currently, he is a candidate for a PhD in Electronics Engineering at the De La Salle University, Philippines. Presently, he is a professor and the program chair of the Electronics Engineering program in Mapúa. (e-mail: ahballado@.ph).P. M. Dychitan Jr. finished his BS ECE in Don Bosco Technical College in 1993. He is at present the president of Dychitan Electronics Corporation. (e-mail: jun@).R. C. Gustilo earned his MS ECE from Ateneo. He obtained his BS ECE from the Technological Institute of the Philippines. He taught at various schools and universities like Mapúa and Adamson. He is currently a PhD candidate in ECE in De La Salle University (e-mail:reghie@).The first trials of tilapia aquaculture were recorded in Kenya in the 1920s, while artificial introductions of this species in many Asian and some Pacific Island countries started in the 1950s [1]. Since then, breeding of tilapia has been established in many tropical and subtropical regions, and even in areas beyond their native ranges, where they have been introduced for various purposes. As a result, considerable attention has been paid to tilapia aquaculture during the past three decades. Tilapia farming is expanding worldwide in both developed and developing countries because this group of fish can be cultured under very basic conditions. While it is ideal for rural subsistence farming, tilapia is amenable to more sophisticated, market-oriented culture programs, for these fish have high reproductive and growth rates, are relatively disease-free and hardy in nature [2]. Tilapia aquaculture is currently practiced in more than a hundred countries all around the globe yet alongside the popularity of culturing tilapia are important growth factors that need to be considered which include pH, temperature, and water level (depth); hence, the monitoring and control of these parameters through the utilization of control systems will be the goal of this research.Through the use and application of control systems, this study will monitor and control each factor based on set values of parameters affecting the growth of the fish. The resulting controlled environment after the application or implementation of process control mechanisms will be crucial in determining the success of growing excellent quality tilapia fit for high-demand human consumption. Generally, the objective of this research is to construct/ build a control system for aquaculture. Specifically, this research seeks to:create an algorithm incorporating the monitoring andcontrol of pH, temperature and water level of theaquatic environment;design a control system for monitoring and control ofthe three growth factors: pH, temperature, and waterlevel;provide means/ solutions for maintaining the ph,temperature, and depth of the water environment basedon specified set values; andutilize C language for the source code or program toimplement the algorithm.II.M ETHODOLOGYThe procedures in designing and building the control system in automating tilapia aquaculture will be discussed systematically in this section. The block diagram of the proposed system is shown in Fig.1.The process algorithm that will provide control for pH, temperature, and water level of aquarium water is presented in Fig. 2.Sensors being used as transducers will send appropriate signals to the microcontroller which will adjust the factor/s that need/s to be corrected. Altogether, these devices will give the control necessary to maintain set values of parameters for tilapia aquaculture.Fig. 1. Block diagram for the control system implementation for tilapiaaquaculture.Fig.2. Process algorithm. The simulation tank holding 15gallons of water will be equipped with temperature, pH, and water level sensors strategically placed inside the tank. It is provided with a drain valve that would flush out water in the event of water-quality correction. An aerator (with abuilt-in filter) installed in the system will distribute oxygen evenly in the water. The tank comes with two reservoirs, one containing alkaline water and tap water on the other, which will neutralize acidity or alkalinity beyond the specified range of values ideal for tilapia growth. Likewise, a reservoir for cold water for water temperature correction is also supplied.Pumps are attached within the tanks to hasten the flow of water/ solution from the reservoirs. Similarly, a pumpwas attached to the drain valve to ensure faster water exit.Data will be gathered every 15 minutes and can be monitored indefinitely. For this study, six hours of monitoring were observed for a given date. If water-correcting action is being done, this will be included within the data log. A visual display showing the status of parameters and sensoractions for periodical inspection was also supplied. Range of values of parameters can be interactively altered with this display using the microcomputer. The microcontroller comes with a data logger where one can monitor the status of the system.The following are the considerations and parameters involved in the operation of the MCU-based aquaculture system:At the heartof the system is an RCM 4300 RabbitCoreMicroController Unit which will be usedto provide control. It comes with a data logger andequipped with relays.ThepH sensor (8205 Digital pH Transmitter/ Burkert, Germany) will measure the acidityof aquarium water. Depending onthe detected water chemistry, it will send the appropriate signal to themicrocontroller which will in turn perform thenecessary control action with the opening or closingof water-composition-correcting valves throughrelays.The temperature sensor (8400 Screw-in TemperatureSensor, Burkert, Germany) will measure thetemperature of aquarium water. If water is too warmbased on a given set of values, it will send a signal tothe microcontroller which will in turn trigger theopening of the cold-water reservoir valve (mineralwater dispenser).Two float level switches/ sensors (top level/ bottomlevel sensors) will detect the depth of water in thetank. Both switches are closed when submerged inwater and opens when water level is below theswitch.Indicators (LEDs) in the relay board will indicatewhich valve is open or close to indicate correctingaction.Alkaline reservoir which contains limewater solution(hydrated calcium oxide) will provide the base toneutralize acidity (neutralization reaction).Tap water reservoir will supply water into the tank ascorrecting action if aquarium water gets too basic orif water level dips below the level sensors.Cold-water reservoir will provide the water forcooling action if aquarium water gets too warm.Solenoid valves (6013 Compact Solenoid Valve,Burkert, Germany) 1/8 ” diameter will open/ closeappropriately in the process of water chemistrycorrection and are connected to the drain, tap andalkaline solution reservoir.Water is circulated around the system with asubmersible pump.The simulation tank is a 15-gallon translucentaquarium for easy observation.For the initial conditions in the design of the aquaculturesystem, the parameters ideal for tilapia growth were used.These were the following:a)pH range of 6.5 – 8.0 [3]b)temperature of 30 °C or less [4]c)water level just above the top level sensor [5]From tilapia culture literature, it was noted that the fish willattain optimal growth if water quality is maintained with a pHof 6.5 to 8.0. Values that would exceed the range above orbelow and maintained for several days would be fatal to thefish. Likewise, temperature exceeding 30 °C for prolongedperiods will eventually result to fish kill. But temperaturesbelow it, even lower than 25 degrees will have little effect onthe fish.It could be noted from the algorithm that pH control takesprecedence over temperature control while water level isalways maintained for every corrective action. Since the setupis indoors, temperature is a secondary consideration forcontrol unlike pH level which could abruptly change thechemistry of the water resulting from the decay of feeds givento the fish and wastes coming from them in the form ofdissolved salts [6]. Temperature change could be a slowerprocess compared to pH change. Hence, if all parametersneed to be corrected, it would be pH that would be givenpriority as evidenced from the main program.The following status entries were used in the system todescribe certain conditions:High pH correction- a state where the pH ofaquarium water is greater than 8.0Low pH correction- a state where the pH of aquariumwater is below 6.5High Temperature correction- a state where thetemperature of aquarium water is more than 30 °CPassive - a state where corrections had already beenintroduced followed by a time of inactivityMonitoring- a state where the system is “waiting” forwater-quality deviations to occurA.High pH Correction AlgorithmThe system is pre-programmed to control the pH level from6.5 to 8.0. When the pH of aquarium water regardless of itstemperature exceeds a pH of 8.0 as sensed by the pHtransmitter, the microcontroller will send a signal to the relayswitch which will open the drain valve. Water will escapefrom the aquarium for a period of 60 seconds (preset timedelay). During this time, the top-level sensor would be opensince water would have escaped already. No corrective actionwill take place if this time delay has not yet elapsed. Oncethis time elapsed, the drain valve will close and the correctiveaction will take place. Since the water quality is basic/alkaline, it will open the tap water valve which would allowtap water from the tap water reservoir to flow to the aquarium.This process would continue until the top-level sensor closes.Once closed, the passive state will set in. This is the stagewhere no action takes place to give time for the system toadjust the correction done (settling time). Once the passivedelay has elapsed (system has been preset with a passive delayof 60 seconds), the pH of the water will be measured again. Ifit falls within the range, then temperature will now bemonitored with the water level maintained. Otherwise, the pHwill be corrected again and the process above will be repeated.Refer to Figure 3.Fig. 3. High pH correction.B.Low pH Correction AlgorithmWhen the pH of aquarium water regardless of itstemperature falls below a pH of 6.5 as sensed by the pHtransmitter, the microcontroller will send a signal to the relayswitch which will open the drain valve. Water will escapefrom the aquarium for a period of 60 seconds (preset timedelay). During this time, the top-level sensor would opensince water would have escaped already. No corrective actionwilltake place if this time delay has not yet elapsed. Oncethis time elapsed, the drain valve will close and the correctiveaction will take place. Since the water quality is acidic, it willopen the alkaline water valve which would allow alkalinewater from the alkaline water reservoir to flow to theaquarium. This process would continue until the top-levelsensor closes. Once closed, the passive state will set in. Thisis the stage where no action takes place to give time for the system to adjust the correction done (settling time). Once the passive delay has elapsed (system has been preset with a passive delay of 60 seconds), the pH of the water will be measured again. If it falls within the range, then temperature will now be monitored with the water level maintained. Otherwise, the pH will be corrected again and the process above will be repeated.C.High Temperature Correction AlgorithmWhen the temperature of aquarium water reaches more than 30 °C as sensed by the temperature transmitter, the microcontroller will send a signal to the relay switch which will open the drain valve. Water will escape from the aquarium for a period of 60 seconds (preset time delay). During this time, the top-level sensor would open since water would have escaped already. No corrective action will take place if this time delay has not yet elapsed. Once this time elapses, the drain valve will close and the corrective action will take place. Since the water quality is warm, it will open the cold-water valve which would allow cold water from the cold-water reservoir to flow to the aquarium. This process would continue until the top-level sensor closes. Once closed, the passive state will set in. This is the stage where no action takes place to give time for the system to adjust the correction done (settling time). Once the passive delay has elapsed (system has been preset with a passive delay of 60 seconds), the temperature of the water will be measured again. If it still falls above 30°C, then the temperature will be corrected again and the process above will be repeated.D.Automated pH Correction System DisplayThe aquaculture system is provided with a display operating in real-time to provide an update of what is happening to the system as exhibited in Fig. 4.Fig. 4. Sample screen display.The Status field will tell us the condition of the system whether it is in high pH correction, low pH correction, high temperature correction, passive status, or monitoring status.The pH Level field will indicate the alkalinity or acidity of the aquarium water. The Temperature field will show us the present temperature of aquarium water. The Top Level Sensor field will tell us if water level in the aquarium is above or below it.The Drain Valve field will indicate if the drain valve is close or open. An open drain valve lets water out of the aquarium.The Lime Water field will show us if alkaline water valve is open or close. An open limewater lets alkaline water out of the alkaline water reservoir to neutralize acidity.The Tap Water field will tell us if the tap water valve is open or close. An open tap water means that tap water is introduced into the system to correct high pH or low water level.The Cold Tap Water field indicates if the cold-water valve is open or close. An open cold tap water introduces cold water into the system to correct high water temperature.The Date/ Time field shows the present time and date.E.Configuration DisplayAn aquaculturist can alter the pH range and temperature setting of the system as depicted in Fig. 5. Likewise, the time delay and passive delay could be changed. The time delay for the system is defined as the time taken for the drain valve to release water from the aquarium.Fig.5. Configuration display screen.Passive delay for the system is defined as the time it takes for the system to remain in a state where no corrective action takes place. This is also the time aquarium water settles down after being corrected.The pH Lower Limit and pH Upper Limit field could be changed to accommodate a range of pH values appropriate for the type of fish in to be cultured.The Temp Upper Limit can be altered to allow a new temperature set point to be maintained.The Time and Passive delay could likewise be reset.III.R ESULTSSimulating different water conditions were done through the use of concentrated alkaline solution, muriatic acid (hydrochloric acid), and water heater. For this simulation lasting six hours, the results were noted using the output of thedata logger.The entries in the data log are in the following order: date, time of monitoring, status, pH level, temperature, top-level sensor status, and bottom- level sensor status.A.Simulation and Data LoggingData logging started on the first of December, 2010 at 3: 17 pm (System, Start up) and ended at 9:15 pm. For presentation purposes, time was expressed in minutes and pH values were the same numerical figures recorded in the data logger. The range of pH values maintained by the control system is from 6.5 to 8.0.As presented in the data log, there were three instances when the graph was above the eighth pH mark (High pH Correction). The system responded to correct the high pH during the first simulated pH change. The pH was already correct at 7.96 recorded at 3:50 pm. We could conclude that it took around 27 minutes for this correction to take place. The second “shock” happened at 4: 42 pm. The pH of aquarium water was already correct at 4: 58 after more than 16 minutes. The last correction took place at 5:32 pm. The system corrected the pH after more than 15 minutes. The system stabilized at 5:52 pm.The temperature to be maintained by the control system is 30 °C or less.There were three instances where the graph was above the 30 °C mark indicative of a high temperature status of aquarium water. The system responded to correct the high temperature during the first simulated temperature change. The temperature was already correct at 29.6 °C recorded at 3:57 pm. We could conclude that it took around 15 minutes for this correction to take place. The second “shock” happened at 4:33 pm. The temperature of aquarium water was already correct at 4:42 after 9 minutes. The last recorded high temperature situation took place at 5:02 pm. The temperature stabilized at 5:09 pm.When water level goes above a sensor (top or bottom), the status of the sensor would read “above”. The opposite is true when water level is below the sensor, thus, the status of the sensor woul d read “below”. A s monitored from 3:17 pm until 9:15 pm, the status of the two sensors was “below”. This will not come as a surprise, since water level is always maintained for every change in pH or temperature that will happen. One may also refer to the flowchart (see fig. 3) and note that water level is always checked or monitored every step of the way. B.SMS MonitoringData logging apart from being directly done with a laptop computer via Wi-Fi can also be accomplished remotely through Short Message Service. The procedure would be carried by typing “1234 status” on a mobile phone and sending this message to 09279221966. Then, an SMS text message will be received by the sender displaying the status, date, time, pH level, temperature, water level condition (above or below), drain valve condition (open or close), alkaline valve condition (open or close), tap water valve condition (open or close) and cold water valve condition (open or close).IV.C ONCLUSIONAn MCU-based aquaculture system proved that monitoring and control of different parameters or factors for optimum fish growth can be done easily and remotely. Unlike the earlier means of monitoring and control that involved actual visit to the site, these things could now be done conveniently through a mobile phone, or a laptop computer connected to the Internet.Based on the results of controlling several variables altogether, we could conclude that one factor is related to another when simulations were done in the system, that is, temperature, pH, and water volume are all functions of each other. Consequently, a change in a variable will favor a corresponding change in the other. Also, the monitoring of pH based on the sampled monitoring period showed that pH correction is relatively faster than temperature correction. However, in the course of simulation, an outlier was observed. Temperature correction alone took a while before settling in the desired value. See Figure 6. This may be attributed to the fact that water volume is a function of specific heat. The greater volume of water, the greater time will be spent to heat it up. The pH of water could be easily changed depending on the concentration of the acid or base to be used. The result of the study showed that the pH of aquarium water responded fast with the addition of either acid or base. Therefore, microcontrollers are versatile and sound devices that produce the desired output with considerable accuracy and efficiency.R EFERENCES[1]S. Nandlal, Tilapia Hatchery Operation, Tilapia fish farming in PacificIsland Countries, vol. I, 2004.[2] A. El-Sayed, Tilapia Culture, 2006.[3]P. Fowler, D. Baird, R. Bucklin, S. Yerlan, C. Watson, and F.Chapman,“Microcontrollers in recirculating aquaculture,” EES-326, University of Florida, 1994.[4]Balarin, J.D. and Haller, R.D., Recent Advances in Aquaculture, 1982.[5]El-Sayed, A.-F.M., Mansour, C.R. and Ezzat, A. Aquaculture, pp. 619–632.[6]Wangead, et al (1988) Effects of acid water on survival and growth rateof Nile tilapia (Oreochromis niloticus). In: Pullin, R.S.V., Bhukaswan, T., Tonguthai, K. and Maclean, J.L. (eds) Proceedings of the Second International Symposium on Tilapia in Aquaculture.Fig.6. pH vs. time chart。
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编号：毕业设计(论文)外文翻译（原文）学院：计算机科学与工程学院专业：计算机科学与技术专业学生姓名：覃龙学号：0700720222指导教师单位：计算机科学与工程学院姓名：黄廷磊职称：教授2011年5月30 日Block RAM SummaryThe block RAM in Virtex-5 FPGAs stores up to 36K bits of data and can be configured aseither two independent 18 Kb RAMs, or one 36 Kb RAM. Each 36 Kb block RAM can beconfigured as a 64K x 1 (when cascaded with an adjacent 36 Kb block RAM), 32K x 1,16K x 2, 8K x 4, 4K x 9, 2K x 18, or 1K x 36 memory. Each 18 Kb block RAM can beconfigured as a 16K x 1, 8K x2 , 4K x 4, 2K x 9, or 1K x 18 memory.Similar to the Virtex-4 FPGA block RAMs, Write and Read are synchronous operations; thetwo ports are symmetrical and totally independent, sharing only the stored data. Each portcan beconfigured in one of the available widths, independent of the other port. Inaddition, the read port width can be different from the write port width for eac h port. Thememory content can be initialized or cleared by the configuration bitstream. During awrite operation the memory can be set to have the data output either remain unchanged,reflect the new data being written or the previous data now being overwritten.Virtex-5 FPGA block RAM enhancements include:I ncreased memory storage capability per block. Each block RAM can store up to 36Kbits of data.S upport of two independent 18K blocks, or a single 36K block RAM.E ach 36K block RAM can be set to simple dual-port mode, doubling data width of theblock RAM to 72 bits. The 18K block RAM can also be set to simple dual-port mode,doubling data width to 36 bits.Simple dual-port mode is defined as having one readonlyport and one write-only port with independent clocks.T wo adjacent block RAMs can be combined to one deeper 64K x 1 memory withoutany external logic.O ne 64-bit Error Correction Coding block is provided per 36 Kb block RAM or 36 KbFIFO. Separate encode/decode functionality is available.S ynchronous Set/Reset of the outputs to an initial value is available for both the latchand register modes of the block RAM output.A n attribute to configure the block RAM as a synchronous FIFO to eliminate flaglatency uncertainty.T he Virtex-5 FIFO does not have FULL flag assertion latency.Virtex-5 FPGA block RAM features:18, 36, or 72-bit wide ports can have an individual write enable per byte. This featureis popular for interfacing to an on-chip microprocessor.E ach block RAM contains optional address sequencing and control circuitry to operate as a built-in multirate FIFO memory. In Virtex-5 architecture, the block RAM can be configured as an18Kb or 36Kb FIFO.A ll inputs are registered with the port clock and have a setup-to-clock timing specification.A ll outputs have a read function or a read-during-write function, depending on the state of the write enable (WE) pin. The outputs are available after the clock-to-out timing interval. The read-during-write outputs have one of three operating modes:WRITE_FIRST, READ_FIRST, and NO_CHANGE.A write o peration requires one clock edge.A read operation requires one clock edge.A ll output ports are latched. The state of the output port does not change until the port executes another read or write operation. The default block RAM output is latch mode.T he output data path has an optional internal pipeline register. Using the regist ermode is strongly recommended. This allows a higher clock rate, however, it adds a clock cycle latency of one. Virtex-5 FPGA block RAM usage rules:T he Synchronous Set/R eset (SSR) port cannot be used when the ECC decoder is enabled (EN_ECC_READ = TRUE).T he setup time of the block RAM address and write enable pins must not be violated. Violating the address setup time (even if write enable is Low) will corrupt the datacontents of the block RAM.T he block RAM register mode SSR requires REGCE = 1 to reset the output DO register value. The block RAM array data output latch does not get reset in this mode. The block RAM latch mode SSR requires the block RAM enable, EN = 1, to reset the output DO latch value.A lthough RAMB18SDP (x36 18k block RAM) and RAMB36SDP (x72 36k block RAM)are simple dual-port primitives, the true dual-port primitives (RAMB18 and RAMB36) can be used with one read-only port and one write-only port. For example: a RAMB18s READ_WIDTH_A = 18, WRITE_WIDTH_B = 9, with WEA = 0 and WEB = 1 is effectively a simple dual-port block RAM with a smaller port width having been derived from the true dual-port primitive. Similarly, a ROM function can be built out of either the true dual-port (RAMB18 or RAMB36) or the simple dual-portblock RAM primitives (RAMB18SDP or RAMB36SDP).D ifferent read and write port width choices are available when using specific block RAM primitives. The parity bits are only available for the x9, x18, and x36 port widths. The parity bits should not be used when the read width is x1, x2, or x4. If the read width is x1, x2 or x4, the effective write width is x1, x2, x4, x8, x16, or x32. Similarly, when a write width is x1, x2, or x4, the actual available read width is x1, x2, x4, x8, x16, or x32 even though the primitive attribute isset to 1, 2, 4, 9, 18, or 36respectively. Table 4-1 shows some possible scenarios.Table 4-1: Parity Use SceneriesNotes:1. Do not use parity bits DIP/DOP when one port widths is less than nine and another port width is nineBlock RAM IntroductionIn addition to distributed RAM memory and high-speed SelectIO™ memory interfaces, Virtex-5devices feature a large number of 36 Kb block RAMs. Each 36 Kb block RAM contains two independently controlled 18 Kb RAMs. Block RAMs are placed in columns, and the total number of block RAM memory depends on the size of the Virtex-5 device. The 36 Kb blocks are cascadable to enable a deeper and wider memory implementation, with a minimal timing penalty. Embedded dual- or single-port RAM modules, ROM modules, synchronous FIFOs, and data width converters are easily implemented using the Xilinx CORE Generator™ block memory modules. Multirate FIFOs can be generated using the CORE Generator FIFO Generator module. The synchronous or asynchronous (multirate) FIFO implementation does not require additional CLB resources for the FIFO control logicsince it uses dedicated hardware resources.Synchronous Dual-Port and Single-Port RAMsData FlowThe true dual-port 36 Kb block RAM dual-port memories consist of a 36 Kb storage area and two completely independent access ports, A and B. Similarly, each 18 Kb b lock RAM dual-port memory consists of an 18 Kb storage area and two completely independent access ports, A and B. The structure is fully symmetrical, and both ports are interchangeable. Figure 4-1 illustrates the true dual-port data flow. Table 4-2 lists the port names and descriptions. Data can be written to either or both ports and can be read from either or both ports. Each write operation is synchronous, each port has its own address, data in, data out, clock, clock enable, and write enable. The read and write operations are synchronousand require a clock edge. There is no dedicated monitor to arbitrate the effect of identical addresses onboth ports. It is up to the user to time the two clocks appropriately. Conflicting simultaneous writes to the same location never cause any physical damage but can result in data uncertainty.Read OperationIn latch mode, the read operation uses one clock edge. The read address is registered on the read port, and the stored data is loaded into the output latches after the RAM access time. When using the outputregister, the read operation will take one extra latency cycle.Write OperationA write operation is a single clock-edge operation. The write address is registered on the write port, andthe data input is stored in memory.Write ModesThree settings of the write mode determines the behavior of the data available on the output latches after a write clock edge: W RITE_FIRST, REA D_FIRST, and NO_CHANGE. Write mode selection is set by configuration. The Write mode attribute can be individually selected for each port. The default mode is WRITE_FIRST. W RITE_FIRST outputs thenewly written data onto the output bus. REA D_FIRST outputs the previously stored data while new data is being written. NO_CHANGE maintains the output previously generated by a read operation. For the simple dual port block RAM, the Write mode is always READ_FIRST in ECC configuration,and therefore no collision can occur when used in synchronous mode.WRITE_FIRST or Transparent Mode (Default)In WRITE_FIRST mode, the input data is simultaneously written into memory an d stored in the data output (transparent write), as shown in Figure 4-2. These waveforms correspond to latch modewhetREAD_FIRST or Read-Before-Write ModeIn REA D_FIRST mode, data previously stored at the write address appears on the output latches, while the input data is being stored in memory (read before write). The waveforms in Figure 4-3 correspond to latch mode when the optional output pipeline register is not usdedNO_CHANGE ModeIn NO_CHANGE mode, the output latches remain unchanged during a write operation. As shown in Figure 4-4, data output remains the last read data and is unaffected by a write operation on the same port. These waveforms correspond to latch mode when the optional output pipeline register is not used.Conflict AvoidanceVirtex-5 FPGA block RAM memory is a true dual-port RAM where both ports can access any memory location at any time. When accessing the same memory location from both ports, the user must, however, observe certain restrictions. There are two fundamentally different situations: The two ports either have a common clock (synchronous clocking), or the clock frequency and phase is different for the two ports (asynchronous clocking).Asynchronous ClockingAsynchronous clocking is the more general case, where the active edges of both clocks do not occur simultaneously:T here are no timing constraints when both ports perform a read operation.W hen one port performs a write operation, the other port must not read- or writeaccess the same memory location. The simulation model will produce an error if this condition is violated. If this restriction is ignored, a read or write operation willproduce unpredictable results. There is, however, no risk of physical damage to the device. If a read and write operation is performed, then the write will store valid data at the write location. Synchronous ClockingSynchronous clocking is the special case, where the active edges of both port clocks occur simultaneously:T here are no timing constraints when both ports perform a read operation.W hen one port performs a write operation, the other port must not write into the same location, unless both ports write identical data.W hen one port performs a write operation, the write operation succeeds; the other port can reliably read data from the same location if the write port is in READ_FIRST mode. DATA_OUT on bothports will then reflect the previously stored data. If the write port is in either WRITE_FIRST or inNO_CHA NGE mode, then the DATAOUT on the read port would become invalid (unreliable). Themode setting of the read-port does not affect this operation.Additional Block RAM Features in Virtex-5 Devices Optional Output RegistersThe optional output registers improve design performance by eliminating routing delay to the CLB flip-flops for pipelined operation. An independent clock and clock enable input is provided for these output registers. As a result the output data registers hold the value independent of the input register operation. Figure 4-5 shows the optional output register.Independent Read and Write Port Width SelectionEach block RAM port has control over data width and address depth (aspect ratio). The true dual-portblock RAM in Virtex-5 FPGAs extends this flexibility to Read and Write where each individual portcan be configured with different data bit widths. For example, port A can have a 36-bit Read width anda 9-bit Write width, and port B can have a 18-bit Read width and a 36-bit Write width. See “BlockRAM Attributes,” page 126. If the Read port width differs from the Write port width, and is configuredin WRITE_FIRST mode, then DO shows valid new data for all the enabled write bytes. The DO portoutputs the original data stored in memory for all not enabled bytes. Independent Read and Write portwidth selection increases the efficiency of implementing a content addressable memory (CAM) inblock RAM. Th is option is available for all Virtex-5 FPGA true dual-port RAM port sizes and modes. Simple Dual-Port Block RAMEach 18 Kb block and 36 Kb block can also be configured in a simple dual-port RAM mode. In this mode, the block RAM port width doubles to 36 bits for the 18 Kb block RAM and 72 bits for the 36 Kb block RAM. In simple dual-port mode, independent Read and Write operations can occur simultaneously, where port A is designated as the Read port and port B as the Write port. When the Read and Write port access the same data location at the same time, it is treated as a collision, similar to the port collision in true dual-port mode. Readback through the configuration port is not supported in simple dual-port block RAM mode. Figure 4-6 shows the simple dual-port data flowCascadable Block RAMIn the Virtex-5 block RAM architecture, two 32K x 1 RAMs can be combined to form one 64K x 1 RAM without using local interconnect or additional CLB logic resources. Any two adjacent block RAMs can be cascaded to generate a 64K x 1 block RAM. Increasing the depth of the block RAM by cascading two block RAMs is available only in the 64K x 1 mode. Further information on cascadable block RAM is described in the “Additional RAMB18 and RAMB36 Primitive Design Considerations” section. For other wider and/or deeper sizes, consult the Creating Larger RAM Structures section. Figure 4-7 shows the block RAM with the appropriate ports connected in the Cascadable mode.Byte-wide Write EnableThe byte-wide write enable feature of the block RAM gives the capability to write eight bit (one byte) portions of incoming data. There are four independent byte-wide write enable inputs to the RAMB36 true dual-port RAM. There are eight independent byte-wide write enable inputs to block RAM in simple dual-port mode (RAMB36SDP). Table 4-4 summarizes the byte-wide write enables for the 36K and 18K block RAM. Each byte-wide write enable is associated with one byte of input data and one parity bit. A ll byte-wide write enable inputs must be driven in all data width configurations. This feature is useful when using block RAM to interface with a microprocessor. Byte-wide write enable is not available in the multirate FIFO or ECC mode. Byte-wide write enable is further described in the “Additional RAMB18 and RAMB36 Primitive Design Considerations” section.Figure 4-8 shows the byte-wide write-enable timing diagram for the RAMB36.When the RAMB36 is configured for a 36-bit or 18-bit wide data path, any port can restrict writing to specified byte locations within the data word. If configured in READ_FIRST mode, the DO bus shows the previous content of the whole addressed word. In WRITE_FIRST mode, DO shows a combination of the newly written enabled byte(s), and the initial memory contents of the unwritten bytes.Block RAM Error Correction CodeBoth block RAM and FIFO implementations of the 36 Kb block RAM support a 64-bit Error Correction Code (ECC) implementation. The code is used to detect single and double-bit errors inblock RAM data read out. Single-bit errors are then corrected in the output data.Block RAM Library PrimitivesThe Virtex-5 FPGA block RAM library primitives, RAMB18 and RAMB36, are the basic building blocks for all block RAM configurations. Other block RAM primitives and macros are based on these primitives. Some block RAM attributes can only be configured usingone of these primitives (e.g., pipeline register, cascade, etc.). See the “Block RAM Attributes” section. The input and output data buses are represented by two buses for 9-bit width (8 + 1), 18-bit width (16 + 2), and 36-bit width (32 + 4) configurations. The ninth bit associated with each byte can store parity/error correction bits or serve as additional data bits. No specific function is performed on the ninth bit. The separate bus for parity bits facilitates some designs. However, other designs safely use a 9-bit, 18-bit, or 36-bit bus by merging the regular data bus with the parity bus. Read/write and storage operations are identical for all bits, including the parity bits.Block RAM Port SignalsEach block RAM port operates independently of the other while accessing the same set of 36K-bit memory cells.Clock - CLK[A|B]Each port is fully synchronous with independent clock pins. All port input pins have setup time referenced to the port CLK pin. The output data bus has a clock-to-out time referenced to the CLK pin. Clock polarity is configurable (rising edge by default).Enable - EN[A|B]The enable pin affects the read, write, and set/reset functionality of the port. Ports with an inactive enable pin keep the output pins in the previous state and do not write data to the memory cells. Enable polarity is configurable (active High by default).Byte-wide Write Enable - WE[A|B]To write the content of the data input bus into the addressed memory location, both EN and WE must be active within a set-up time before the active clock edge. The output latches are loaded or not loaded according to the write configuration (W RITE_FIRST, READ_FIRST, NO_CHA NGE). When inactive, a read operation occurs, and the contents of the memory cells referenced by the address bus appear on the data-out bus, regardless of the write mode attribute. Write enable polarity is not configurable (active High).Register Enable - REGCE[A|B]The register enable pin (REGCE) controls the optional output register. When the RAM is in register mode, REGCE = 1 registers the output into a register at a clock edge. The polarity of REGCE is not configurable (active High).Set/Reset - SSR[A|B]In latch mode, the SSR pin forces the data output latches, to contain the value SRVA L. See“Block RAM Attributes,” pag e 126. When the optional output registers are enabled, the data output registers can also be forced by the SSR pin to contain the value SRVA L. SSR does not affect the latched value. The data output latches or output registers are synchronously asserted to 0 or 1, including the parity bit. Each port has an independent SRVA L[A|B] attribute of 36 bits. This operation does not affect RAM memory cells and does not disturb write operations on the other port. Similar to the read and write operation, the set/reset function is active only when the enable pin of the port is active. Set/reset polarity is configurable (active High by default).Address Bus - ADDR[A|B]<13:#><14:#><15:#>The address bus selects the memory cells for read or write. The data bit width of the port determinesthe required address bus width for a single RAMB18 or RAMB36, as shown in Table 4-6 and Table 4-7.For cascadable block RAM using the RAMB36, the data width is one bit, and the address bus is 16 bits <15:0>. The address bit 15 is only used in cascadable block RAM. For noncascading block RAM, connect High. Data and address pin mapping is further described in the “Additional RAMB18 and RAMB36 Prim itive Design Considerations”section.Data-In Buses - DI[A|B]<#:0> & DIP[A|B]<#:0>Data-in buses provide the new data value to be written into RAM. The regular data-in bus (DI), plus the parity data-in bus (DIP) when available, have a total width equal to the port width. For example the 36-bit port data width is represented by DI<31:0> and DIP<3:0>, as shown in Table 4-6 and Table 4-7. Data-Out Buses - DO[A|B]<#:0> and DOP[A|B]<#:0>Data-out buses reflect the contents of memory cells referenced by the address bus at the last active clock edge during a read operation. During a write operation (WRITE_FIRST or READ_FIRST configuration), the data-out buses reflect either the data being written or the stored value before write. During a write operation in NO_CHANGE mode, data-out buses are not changed. The regular data-out bus (DO) plus the parity data-out bus (DOP) (when available) have a total width equal to the port width, as shown in Table 4-6 and Table 4-7.Cascade In - CASCADEINLAT[A|B] and CASCADEINREG[A|B]The CASCA DEIN pins are used to connect two block RAMs to form the 64K x 1 mode (Figure 4-10.) This pin is used when the block RAM is the UPPER block RAM, and is connected to the CASCADEOUT pins of the LOW ER block RAM of the same port. When cascade mode is not used, this pin does not need to be connected. Refer to the “Cascadable Block RAM” for further information.CascadeOut - CASCADEOUTLAT[A|B] and CASCADEOUTREG[A|B]The CASCA DEOUT pins are used to connect two block RAMs to form the 64K x 1 mode. This pin is used when the block RAM is the LOW ER block RAM, and is connected to the CASCADEIN pins of the UPPER block RAM of the same port. When cascade mode is not used, this pin does not need to be connected. Refer to the “Cascadable Block RAM” for further information.Inverting Control PinsFor each port, the six control pins (CLK, EN, and SSR) each have an individual inversion option. EN and SSR control signals can be configured as active High or Low, and the clock can be active on a rising or falling edge (active High on rising edge by default), without requiring other logic resources. GSRThe global set/reset (GSR) signal of a Virtex-5 device is an asynchronous global signal that is active at the end of device configuration. The GSR can also restore the initial Virtex-5 device state at any time. The GSR signal initializes the output latches to the INIT (simple dual port), or to the INIT_A and INIT_B value (true dual port.) See “Block RAM Attributes.” A GSR signal has no impact on internal memory contents. Because it is a global signal, the GSR has no input pin at the functional level (block RAM primitive).Unused InputsUnused data and/or address inputs should be connected HighBlock RAM Address MappingEach port accesses the same set of 18,432 or 36,864 memory cells using an addressing scheme dependent on whether it is a RAMB18 or RAMB36. The physical RAM locations addressed for a particular width are determined using the following formula (of interest only when the two ports use different aspect ratios):END = ((A DDR + 1) Width) -1START = A DDR WidthTable 4-8 shows low-order address mapping for each port width.Block RAM AttributesAll attribute code examples are discussed in the “Block RAM Initialization in VHDL or Verilog Code” section. Further information on using these attributes is available in the“Additional RAMB18 and RAMB36 Primitive Design Considerations” section.Content Initialization - INIT_xxINIT_xx attributes define the initial memory contents. By default, block RAM memory is initialized with all zeros during the device configuration sequence. The 64 initialization attributes from INIT_00 through INIT_3F for the RAMB18, and the 128 initialization attributes from INIT_00 through INIT_7F for the RAMB36 represent the regular memory contents. Each INIT_xx is a 64-digit hex-encoded bit vector. The memory contents can be partially initialized and are automatically completed with zeros. The following formula is used for determining the bit positions for each INIT_xx attribute. Given yy = conversion hex-encoded to decimal (xx), INIT_xx corresponds to the memorycells as follows:f rom [(yy + 1) 256] – 1t o (yy) 256For example, for the attribute INIT_1F, the conversion is as follows:y y = conversion hex-encoded to decimal (xx) “1F” = 31f rom [(31+1) 256] – 1 = 8191t o 31 256 = 7936More examples are given in Table 4-9.Content Initialization - INITP_xxINITP_xx attributes define the initial contents of the memory cells corresponding to DIP/DOP buses (parity bits). By default these memory cells are also initialized to all zeros. The initialization attributes represent the memory contents of the parity bits. The eight initialization attributes are INITP_00 through INITP_07 for the RAMB18. The 16 initialization attributes are INITP_00 through INITP_0F for the RAMB36. Each INITP_xx is a 64-digit hex-encoded bit vector with a regular INIT_xx attribute behavior. The same formula can be used to calculate the bit positions initialized by a particular INITP_xx attribute.Output Latches Initialization - INIT (INIT_A or INIT_B)The INIT (single-port) or INIT_A and INIT_B (dual-port) attributes define the output latches or output register values after configuration. The width of the INIT (INIT_A andINIT_B) attribute is the port width, as shown in Table 4-10. These attributes are hexencoded bit vectors, and the default value is 0. In cascade mode, both the upper and lower block RAM should be initialized to the same value. Output Latches/Registers Synchronous Set/Reset (SRVAL_[A|B])The SRVA L (single-port) or SRVA L_A and SRVA L_B (dual-port) attributes define output latch values when the SSR input is asserted. The width of the SRVA L (SRVA L_A and SRVA L_B) attribute is the port width, as shown in Table 4-10. These attributes are hexencoded bit vectors and the default value is 0. This attribute sets the value of the output register when the optional output register attribute is set. When the register is not used, the latch gets set to the SRVA L instead. In the 36-bit mode, SRVA L[35:32] corresponds toDP[3:0].Output Latches/Registers Synchronous Set/Reset (SRVAL_[A|B])The SRVA L (single-port) or SRVA L_A and SRVA L_B (dual-port) attributes define output latch values when the SSR input is asserted. The width of the SRVA L (SRVA L_A and SRVA L_B) attribute is the port width, as shown in Table 4-10. These attributes are hexencoded bit vectors and the default value is 0. This attribute sets the value of the output register when the optional output register attribute is set. When the register is not used, the latch gets set to the SRVA L instead. In the 36-bit mode, SRVA L[35:32] corresponds toDP[3:0].Optional Output Register On/Off Switch - DO[A|B]_REGThis attribute sets the number of pipeline register at A/B output of the block RAM. The valid values are 0 (default) or 1.Extended Mode Address Determinant - RAM_EXTENSION_[A|B]This attribute determines whether the block RAM of interest has its A/B port as UPPER/LOW ER address when using the cascade mode. Refer to the “Cascadable Block RAM”section. When the block RAM is not used in cascade mode, the default value isNONE.Read Width - READ_WIDTH_[A|B]This attribute determines the A/B read port width of the block RAM. The valid values are:0 (default), 1, 2, 4, 9, 18, and 36.Write Width - WRITE_WIDTH_[A|B]This attribute determines the A/B write port width of the block RAM. The valid values are:0 (default), 1, 2, 4, 9, 18, and 36.Write Mode - WRITE_MODE_[A|B]This attribute determines the write mode of the A/B input ports. The possible values are WRITE_FIRST (default), READ_FIRST, and NO_CHANGE. Additional information on the write modes is in the “Write Modes” sectionBlock RAM Location ConstraintsBlock RAM instances can have LOC properties attached to them to constrain placement. Block RAM placement locations differ from the convention used for naming CLB locations, allowing LOC properties to transfer easily from array to array. The LOC properties use the following form:。
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J. Serb. Chem. Soc. 75 (5) 689–701 (2010) UDC 665.941+547.281+661.717.52–JSCS–3999 12:66.095.26:543.51Original scientific paperdoi: 10.2298/JSC091030036G689Molar-mass distribution of urea–formaldehyde resins of different degrees of polymerisation by MALDI-TOF mass spectrometryIVANA GAVRILOVI Ć-GRMUŠA 1*, OLIVERA NEŠKOVI Ć2,MILANKA ĐIPOROVI Ć-MOM ČILOVI Ć1 and MLA ĐAN POPOVI Ć11Faculty of Forestry, University of Belgrade, Kneza Viseslava 1, 11030 Belgrade and 2Department of Physical Chemistry, Institute “Vin ča” Belgrade,Mike Petrovi ća-Alasa 12–14, 11351 Belgrade, Serbia(Received 30 October 2009, revised 25 January 2010)Abstract : This paper describes some results obtained in an investigation ofurea–formaldehyde (UF) resins of different degrees of polymerisation by ma-trix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) massspectrometry (MS). MALDI-TOF MS proved to be an appropriate techniquefor analyzing these types of polymers, bearing in mind that the results of theanalysis correspond with previous physical and chemical measurements. Thistechnique enables a relatively swift determination of the degree of polymerri-sation through the monitoring of key changes in the structure of a polymer.Thus, in the analysis of UF resins, it may be possible to monitor a decrease inthe intensity of the monohydroxymethyl urea (MMU) signal, which corres-ponds to an increase of the mass spectra values in the mass range of higherhomologues, above 1000 g mol -1. A noticeable difference concerns the signalintensities in the higher mass ranges (up to 1400 g mol -1), which corresponds tomore branched and longer homologues of the polymers. Especially, a signi-ficantly more intensive signal of MMU was registered. The average molecularweight (MW) of the examined samples was between 936 and 1324 g mol -1,with a maximal deviation of 20 %, depending on the ratios of the reactants.Keywords : urea-formaldehyde resins; molar ratio; molecular structure; degreeof polymerisation; MALDI-TOF.INTRODUCTIONUrea–formaldehyde, UF, resins are the most important type of adhesives inthe wood industry. They are widely used for the production of wood-based com-posite panels, such as particleboards, fibreboards and plywood.1* Corresponding author. E-mail: ivana.grmusa@sfb.rs690 GAVRILOVIĆ-GRMUŠA et al.UF resins are based on a manifold reaction of two monomers, urea and formaldehyde.2 By using different reaction and preparation conditions, a more or less innumerable variety of condensed structures is possible.3 In the application stage, UF resins are still soluble or dispersed in water. They also can be supplied in the form of spray-dried water-soluble powders. Such structures consist of li-near or branched polymeric molecules of various molecular masses. After har-dening, UF resins form insoluble three-dimensional networks of thermosetting duromers.4Although UF resins consist of only two main components, i.e., urea and for-maldehyde, they present a broad variety of possible reactions and structures.5 This variety leads to a wide range of molar mass distributions in UF resins, from low molar mass molecules up to more or less polymeric structures. The highest molar masses in UF resin cannot be clearly determined, but it is estimated that molar masses of 100000 to 500000 g mol–1 can successfully describe the macromolecule structure of UF resins.3,6–8From the viewpoint of end-use applications of UF resins, the molar mass distribution is a very important chemical characteristic, having an influence on several important properties of the resin, such as: viscosity, flow ability, pene-tration into the wood surface,9,10 distribution on the wood furnish (particles or fibres), water dilute ability,11etc. The molar mass distribution can be determined by means of gel permeation chromatography (GPC),12 but it is very difficult be-cause an increase in the molecular weight of the soluble macromolecules and in the degree of branching leads to the formation of insoluble products.13 In addi-tion, analysis of the structural components can be performed by various spectro-scopic methods, such as: infrared (IR);14–19 nuclear magnetic resonance (NMR), i.e., 1H-NMR,20–2313C-NMR,14,24–2815N-NMR9,30 and Raman spectroscopy.31Matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry has greatly expanded the use of mass spectrometry towards large molecules and has been demonstrated to be a powerful method for the characte-rization of both synthetic and natural polymers. This technique is usually com-bined with a time-of-flight (TOF) mass analyzer, which has the advantages of being capable of providing a complete mass spectrum per event, having a virtu-ally unlimited mass range, requiring a small amount of analyte and relatively low cost equipment.32–34Generally, the polycondensation structures of UF resins have not been stu-died thoroughly by the MALDI-TOF technique. Therefore, the objective of this research was a MALDI-TOF investigation of the molar mass distribution of UF resin samples obtained from the same reactor batch, but having three different degrees of polymerisations.MALDI-TOF ANALYSIS OF UF RESINS 691EXPERIMENTALPreparation of urea–formaldehyde (UF) resins with various viscositiesUrea–formaldehyde resins were synthesized via the reaction between formalin at a concentration of 47.69 % and urea by DUKOL Ostrava (the Czech Republic). Four samples of about 1 L, designated as I, II, III and IV, were taken from the same reactor batch when the viscosity values showed that different degrees of polymerisation had been attained. Samples I–III were prepared at an F:U molar ratio of 2:1. Sample IV was prepared by modification of sample III by the addition of formaldehyde to give an F:U ratio of 1.45:1. All the samples were kept in a refrigerator before further use.The samples were tested for viscosity, dry matter content, pH value, gel time and pot life. The obtained results are presented in Table I.In order to determine the dry matter content, 2.0 g of resin were dried in a laboratory oven at 105 ± 2 °C until constant mass was reached.The viscosity of the four UF resins was determined by the Brookfield method. The test values registered on the Brookfield instrument together with factors based on the employed combination of the type of rotating spindle and the rotation speed were used to calculate the viscosity in Pa s.The pH value of each UF resin sample was determined by inserting a glass electrode directly into the emulsion.The gel time of the resins containing hardener was determined by the boiling water test. The time measurement began when a test tube containing approximately 2.0 g of resin to-gether with the hardener ammonium sulphate (1 % based on the adhesive dry matter) was immersed into boiling water. The resin in the test tube was gently stirred throughout the test. The gel time was taken as the time elapsed from immersion of the test tube until hardening of the resin, when stirring was no longer possible.The densities of the resins were determined at 20 °C using a pycnometer of 25 mL nominal volume, the exact volume of which was determined using distilled water. Preparation of the MALDI matrixA saturated solution of α-cyano-4-hydroxycinnamic acid (CHCA) was prepared by dis-solving the matrix in 50 % acetonitrile with 0.10 % trifluoracetic acid. The solution was vortexed thoroughly and sonicated in a water bath for several minutes at room temperature. The solution was used for the preparation of samples for MALDI-TOF MS. All employed chemicals were of p.a. purity, originating from Sigma-Aldrich (St. Louis, WI, USA).Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometryAn aliquot of each sample solutions containing an internal standard was combined 1:1 with the CHCA matrix and mixed thoroughly. Aliquots (0.50 μL) of the mixtures were spotted onto a 100-spot sample plate (Applied Biosystems) and air-dried. Mass analysis was performed in the positive ion reflector mode using a 200 Hz frequency pulsed N2 laser operating at 327 nm. Five spectra at each of 10 randomly selected positions were accumulated per spot between 170 and 500 g mol-1 using the MS positive ion reflector mode acquisition method. Calibration of the instrument was realised using Calibration mixture 2 as the external standard. To generate spectra with high mass accuracy, an internal calibration was performed. Sample preparationFor the analysis of silver clusters, 1.0 mg mL-1 solutions in 0.10 % trifluoracetic acid were prepared. 0.50 μL of these solutions was placed onto 0.50 μL of CHCA solution on the target.692 GAVRILOVIĆ-GRMUŠA et al.Data analysisSamples of the UF resins (I–IV) were mixed with the CHCA matrix in ratios of 1:100 and 1:10, v/v. The concentration of CHCA was 10 mg mL-1, diluted in a 1:1 acetonitrile and water solution. After dilution, 0.50 μL volumes of samples were placed on the MALDI plate. Samples were air dried and analyzed on a 4800 Plus MALDI TOF/TOF analyser (Applied Biosystems, Foster City, CA, USA) in the positive mode. Data Explorer, version 4.9, was used for the analysis of the recorded spectra. Ions of the CHCA matrix were used for internal calibration, based on the theoretically calculated masses of CHCA monomers, dimers and trimers at m/z 190.05 (molecular formula C10H7NO3), 379.09 (molecular formula C20H14N2O6) and 568.14 (molecular formula C30H21N3O9), respectively. The mass spectrum of the matrix alone was recorded in order to eliminate the signals generated by the matrix itself. Baseline correction and Gaussian smoothing was applied to each mass spectrum.Positively charged ions were analysed in the reflector mode using delayed ion extraction. The spectra were recorded with a 200 Hz frequency data-sampling rate. Unless otherwise stated, the extraction delay time was 150 ns and deflection was used to suppress ions up to m/z 500. The spectra were recorded using the reflector mode of the TOF analyzer under delayed extraction conditions, thus improving the mass accuracy and resolution. The extraction vol-tage was 20 kV in all cases. Other instrument parameters were tuned for optimal resolution. All instrument high voltages were left on between all analyses to ensure a stable instrument performance. After short interruptions (< 7 min), while exchanging the sample plate, the high voltages of the instrument were switched on 50 min prior to spectra acquisition. The applied laser intensity was between 10 and 30 % of the maximum available laser power.The spectra were acquired without a low mass gate and each spectrum represents an average of at least 100 single laser shots.RESULTS AND DISCUSSIONPhysical characteristics of UF resinsThe characteristics of UF resins (Table I) showed no significant differences between samples I–III, except for the viscosity, sample III having a viscosity of 555 mPa s, while the viscosities of samples I and II were 218 and 281 mPa s, respectively. All the determined physical properties were significantly increased for sample IV in comparison to the other samples, which clearly distinguishes sample IV from samples I–III. The viscosity of sample IV was 2052 mPa s, a value 3 to 9 times higher when compared with the other samples. It will be quite evident later that increased content of higher homologues increased the viscosity of this resin.TABLE I. The characteristics of the UF resins (Samples I–IV)No. PropertyUF SampleI II III IV1 Drymatter,% 53.7 53.6 53.8 65.62 Brookfield viscosity (at 20 °C), mPa s 218 282 555 20523 pH 7.8 7.9 8.0 7.74 Gel time, s 58 59 58 595 Density, g cm3 1.24 1.24 1.25 1.30MALDI-TOF ANALYSIS OF UF RESINS 693Degree of polymerisationThe recorded spectra of samples I–IV (Figs. 1 and 2), obtained on the MALDI-TOF/TOF instrument, implicate a close relationship between viscosity, dry matter content and degree of polymerisation of the UF resin samples. A com-parison of spectra revealed sample I had the lowest degree of polymerisation and also the lowest viscosity.Fig. 1. MALDI-TOF Mass spectra of samples I and II in the m/z range 561–953.Results of the analysis showed that samples I and II had similar degrees of polymerisation, but with a slightly higher amount of branching in sample I, as in-dicated by its more pronounced mass signals in the m/z range 561–953 (Fig. 1). Although, both samples had a similar dry matter content, they differed in visco-sity, with sample II having an approximately 30 % higher viscosity than sample I.Due to its higher viscosity, an increased amount of homologues with a high-er degree of polymerisation is to be expected in sample II. However, the differ-rence between the signal intensity of the higher homologues in samples I and II was negligible (also when compared with samples III and IV).The dry matter content of samples I, II and III were similar. On the other hand, the viscosity of sample III was almost twice that of samples I and II. A higher viscosity implies a higher degree of polymerisation, which can be observed in the mass spectrum of sample III, shown in Fig. 2.In addition, three times more intense signals in the same mass range of the higher polymerisation homologues were registered for sample III (data not given) than for samples I and II (shown in Fig. 1).694 GAVRILOVIĆ-GRMUŠA et al.According to its physical and chemical parameters, sample IV had no simi-larities with samples I–III, having an almost one order of magnitude higher vis-cosity compared with the other three samples, a 10 % higher dry matter content and a significantly increased degree of polymerisation of higher homologues, as shown in Fig. 2.Fig. 2. MALDI-TOF Mass spectra of sample III (maximum registered polymer mass1052 g mol-1) and sample IV (maximum registered polymer mass 1324 g mol-1).Comparison of the polymer structures of samples I, II, III and IVHigher homologue products of the polymerisation processes, which are re-gistered in the m/z range 200–1200, may be described through a combination of the residues in the general structure. Confirmation of such structures was basedMALDI-TOF ANALYSIS OF UF RESINS 695 on both external and internal calibration. The external calibration was applied on the mass spectra shown in Figs. 1 and 2, with an experimental error of 0.10 g mol–1 of the mass value. In addition, the mass spectra were internally calibrated (see later in the text Figs. 5–7) using signals originating from the ions of the CHCA matrix, which increased the mass measurement accuracy to 5 ppm (third of the four decimal digits of the mass value). Accurate mass measurement leads to a better determination of the elemental ion composition and, in this sense, the molecular formula of a link can be established. As the polymers consisted of a series of links, it was impossible to determine the molecular formulas of all the polymers. However, it was possible to determine the constitutive elements of the polymer structure.The true mass and molecular formula were determined using the signals of the highest intensity in order to identify the structure of the higher homologues. Within the observed mass range and according to the signal intensity, it is pos-sible to determine the type of homologue and the preferred form of branching. NMR research indicated that the formation of mono-, di- and tri-hydroxymethyl urea under alkaline conditions amounts to 45–60 % and partial polymerisation to dimethyl ethers to 10–20 % (i.e., –NH–CH2OH 45–60 % and –N(CH2OH)2 10–15 %).35 In addition, 10–15 % of the formaldehyde remained unreacted. The for-mation of methylol groups mostly depended on the F/U molar ratio, with higher molar ratios increasing the tendency to form highly methylolated species.36,37 The significant intensive signal of MMU can be seen at m/z 91 in the MALDI-TOF mass spectra of samples I–IV shown in Fig. 3. Some examples of polymer chains of ether homologues are demonstrated in Figs. 4 and 5, from which, it is possible to determine the representative type of molecular structure originating in the branching process and growth of the polymer chains. This might reveal if the method of synthesis favours the creation of ether or methyl bonds and, furthermore, allow an estimation of the preferred number of hydroxyl groups per number of carbons in the chain. As expected, the highest MMU intensity of 68,000 was registered for sample I, in comparison to sample IV, with an MMU intensity of 22000. Contrary to sample IV, which had an increased ratio of higher homologues, sample I had increased amounts of simple MMU structures, 3.1 times higher when compared to sample IV, suggesting poor branching in sample I and a high degree of polymerisation of sample IV. The relations between sam-ples II and III were similar to those of samples I and IV. Thus, sample III had a higher ratio of higher polymer structures in comparison to sample II, while sample II had a 2.7 times more intensive MMU signal when compared to sample III.Structures A, B and C shown in Fig. 5 may also belong to structures with hydroxymethyl groups with secondary and tertiary amines in different positions. Thus, the molecular formulas of structures A C8H18N4O5, B C9H20N4O6 and C C10H22N4O7 would have to be preserved. Mass spectra showing the intensity of the structures A, B and C are shown in Fig. 6.696 GAVRILOVIĆ-GRMUŠA et al.Fig. 3. MALDI-TOF Mass spectra of samples I–IV, with a significant intense signal ofmonohydroxymethylurea (MMU) at m/z 91.MALDI-TOF ANALYSIS OF UF RESINS 697Fig. 4. Molecules formed through reaction of urea and formaldehyde under alkaline conditions, registered in the m/z range of 250–312.698 GAVRILOVIĆ-GRMUŠA et al.Fig. 5. Molecules formed through reaction of urea and formaldehyde under alkaline conditions, registered in the m/z range of 250–312. The associated theoreticalm/z values for structures A, B and C are 251.14, 281.14 and 311.16, respectively.The mass spectrum of sample IV for the selected region is shown in Fig. 6. Identical mass spectra were obtained for samples I–III. According to the signal intensity of the ion structures A, B and C, it may be concluded that the homo-logues containing ether bonds are more abundant than those of homologues with methylene bonds are. It may also be concluded that the most intensive signals in the spectra belong to structures with terminal di- and tetrahydroxymethylene groups (structures A and C). The calculation of molecular formulas in regards to theFig. 6. MALDI-TOF Mass spectra of sample IV with the A, B and C structures designated.MALDI-TOF ANALYSIS OF UF RESINS 699 measured molecular masses for structures A–C were possible because a maxi-mum measurement error of 5 ppm was achieved.Methylene bridges, branching polymer structures, are present over the whole spectrum and signify the difference between peaks of 12 g mol–1 or 12.0072 g mol–1 as measured and shown in Fig. 7.Fig. 7. MALDI-TOF Mass spectrum of sample IV with noticeably constant differences of 12 g mol-1 between the most intensive signals in the spectrum.CONCLUSIONSThis paper describes some results obtained in an investigation of urea–for-maldehyde (UF) resins of different degrees of polymerisation by MALDI-TOF mass spectrometry. Each of the four samples gave a contribution to the eluci-dation of the establishment of the molar masses of the resins. The interpretation and combination of the results led to following conclusions:1) The average MW of the examined samples I–IV of UF resin was between 936 and 1324 g mol–1, with a maximal deviation of 20 %, depending on the ratios of the reactants.2) The signal intensities and their positions regarding samples I–IV showed no differences. The only noticeable difference concerned the signal intensities in the higher mass ranges (up to 1400 g mol–1), which corresponds to more branched and longer homologues of the polymers.3) Sample IV had, by far, the highest degree of branching and polymerisa-tion when compared to samples I–III, which was evidenced as it was the polymer giving the highest recorded mass of 1324 g mol–1 and multiple higher signal in-tensities in the m/z range of 250–1000.4) MALDI-TOF proved to be an appropriate technique for analyzing these types of polymers, bearing in mind that the results of analysis corresponded with the results of physical and chemical measurements (dry matter content, viscosity,700 GAVRILOVIĆ-GRMUŠA et al.gel time, etc.). For routine polymer analysis, this technique enables a relatively swift and simple determination of the degree of polymerisation, through the mo-nitoring of key changes in the polymer structure. It may be possible to monitor a decrease in the intensity of the MMU signal, which corresponds to an increase of the mass spectra values in the mass range of higher homologues, above 1000 g mol–1.Acknowledgements.The research work presented in this paper was financed by the Mi-nistry of Science and Technological Development of the Republic of Serbia, Project “Wood biomass as a resource of sustainable development of Serbia”, 20070-TP.ИЗВОДРАСПОДЕЛАМОЛАРНЕМАСЕУРЕА–ФОРМАЛДЕХИДНИХСМОЛАРАЗЛИЧИТОГСТЕПЕНАПОЛИМЕРИЗАЦИЈЕОДРЕЂЕНАМАСЕНОМСПЕКТРОМЕТРИЈОМ MALDI-TOFИВАНАГАВРИЛОВИЋ-ГРМУША1, ОЛИВЕРАНЕШКОВИЋ2, МИЛАНКАЂИПОРОВИЋ-МОМЧИЛОВИЋ1ИМЛАЂАНПОПОВИЋ11[umarski fakultet, Univerzitet u Beogradu, Kneza Vi{eslava 1, 11030 Beograd i 2Laboratorija za fizi~ku hemiju, Institut“Vin~a”, Mike Petrovi}a-Alasa 12–14, 11351 Beograd Уциљукарактеризацијечетириузоракауреа–формалдехидне (УФ) смоле, коришћенајеметодамасенеспектроскопије MALDI-TOF (матрицомпотпомогнуталасерскадесорп-ција/јонизација-времепрелета). Каоједанодвидоваанализеполимера, поменутатехникаомогућујерелативнобрзоодређивањестепенапилокондензацијепутемпраћењакључнихпроменауструктуриполимера. ПрианализиузоракаУФсмолеутврђено je дасмањењеин-тензитетаММУсигналаодговараповећањувредностимасеногспектрауопсегувишиххо-мологаизнад 1000 g mol-1. Значајнаразликаодносисенаинтензитетсигналапривишеммасеномопсегу(до 1400 g mol–1), штоодговараразгранатијимидужимполимернимхомолозима. СредњаМwиспитиванихузораканалазисеуопсегуод 936 до 1324 g mol–1, самаксималномдевијацијомод 20 % узависностиодкомпоненти.(Примљено 30. октобра 2009, ревидирано 25. јануара 2010)REFERENCES1.M. Dunky, A. Pizzi, Wood adhesives, in Adhesion Science and Engineering –2. Surfaces,Chemistry and Applications, Amsterdam, 2002, p. 10392. A. Pizzy, Wood Adhesives, Chemistry and Technology, Marcel Decker Inc., New York,19833.M. Dunky, In Proceedings of 5th Pacific Rim Bio-Based Composites Symposium,Cambera, Australia, 2000, p. 2054.M. Dunky, Int. J. Adhes. 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