Small arm transfers and state complicity in international law： Challenging the limitations

合集下载

机械手毕业设计外文翻译--最小化传感级别不确定性联合策略的机械手控制

毕业设计(论文)有关外文翻译院系：机械电子工程学院专业：自动化姓名：学号：指导教师：完成时间：2009-4-25说明1、将与课题有关的专业外文翻译成中文是毕业设计（论文）中的一个不可缺少的环节。

此环节是培养学生阅读专业外文和检验学生专业外文阅读能力的一个重要环节。

通过此环节进一步提高学生阅读专业外文的能力以及使用外文资料为毕业设计服务，并为今后科研工作打下扎实的基础。

2、要求学生查阅与课题相关的外文文献3篇以上作为课题参考文献，并将其中1篇（不少于3000字）的外文翻译成中文。

中文的排版按后面格式进行填写。

外文内容是否与课题有关由指导教师把关，外文原文附在后面。

3、指导教师应将此外文翻译格式文件电子版拷给所指导的学生，统一按照此排版格式进行填写，完成后打印出来。

4、请将封面、译文与外文原文装订成册。

5、此环节在开题后毕业设计完成前完成。

6、指导教师应从查阅的外文文献与课题紧密相关性、翻译的准确性、是否通顺以及格式是否规范等方面去进行评价。

最小化传感级别不确定性联合策略的机械手控制摘要：人形机器人的应用应该要求机器人的行为和举止表现得象人。

下面的决定和控制自己在很大程度上的不确定性并存在于获取信息感觉器官的非结构化动态环境中的软件计算方法人一样能想得到。

在机器人领域，关键问题之一是在感官数据中提取有用的知识，然后对信息以及感觉的不确定性划分为各个层次。

本文提出了一种基于广义融合杂交分类（人工神经网络的力量，论坛渔业局）已制定和申请验证的生成合成数据观测模型，以及从实际硬件机器人。

选择这个融合，主要的目标是根据内部（联合传感器）和外部（ Vision 摄像头）感觉信息最大限度地减少不确定性机器人操纵的任务。

目前已被广泛有效的一种方法论就是研究专门配置5个自由度的实验室机器人和模型模拟视觉控制的机械手。

在最近调查的主要不确定性的处理方法包括加权参数选择（几何融合），并指出经过训练在标准操纵机器人控制器的设计的神经网络是无法使用的。

Optimizedstairca...

Optimized staircase profiles for diffractive optical devices made from absorbing materialsBernd Nöhammer,Christian David,and Jens GobrechtLaboratory for Micro-and Nanotechnology,Paul Scherrer Institut,CH-5232Villigen,SwitzerlandHans Peter HerzigInstitute of Microtechnology,University of Neuchâtel,CH-2000Neuchâtel,Switzerland We report on the optimization of staircase grating profiles for the case of absorbing grating inga simple numerical algorithm,we determined the grating parameters,maximizing the first-order diffractionefficiency for different numbers of staircase steps.The results show that there is a significant differencebetween the staircase profiles for nonnegligible and negligible absorption.The obtained solutions are ofimportance for diffractive optics in the soft-x-ray and extreme-ultraviolet ranges.Because of the progress in lithography and replicationtechniques that permit low-cost mass fabrication, diffractive optical elements(DOEs)have becomeimportant optical devices.1The most important andalso simplest form of DOE is gratings.There are also many other types of DOE that are generalized formsof gratings with a varying grating constant,such asFresnel zone plates or computer-generated holograms. Consequently the task of finding the optimum surfacerelief of a DOE can often be simplified to the problemof finding the optimum shape of a grating.In conventional optics the absorption of the gratingmaterial is usually negligible;therefore only the phase-shifting properties of the material(described by the real part of the refractive index)have to be taken intoaccount for this shape-optimization process.However,for wavelengths l in the extreme-ultraviolet(EUV)and x-ray ranges,where the refractive index n is conve-niently written as n͑l͒෇12d͑l͒1i b͑l͒,d and b areoften of the same order of magnitude;therefore absorp-tion(described by b)also has to be taken into accountfor the calculation of optimized grating profiles.A requirement for many applications is to diffract as much light as possible in a single(e.g.,the first)diffraction order.In the case in which absorption isnegligible,this is achieved by use of a blazed grating structure that has a sawtoothlike shape and a heighth c calculated from h c෇l͞j d j[Fig.1(A),dashed lines]. However,when absorption of the diffracting structures plays a role,the shape of the grating that gives maxi-mum first-order diffraction efficiency is quite different.Tatchyn et al.2have shown that in this general case the optimum profile is still sawtooth shaped and has the same slope as in the case of zero absorption[Fig.1(A), solid lines],but the structures are narrower,resulting in an open part b1.The size of the open fraction b1͞b depends on the ratio d͞b as indicated in Fig.1(B)and has to be calculated numerically.In practice,fabrication of a continuous sawtooth pro-file with the required accuracy is difficult.There-fore the ideal profile is often approximated by a stair-case profile(Fig.2).Such staircase profiles can be fabricated by use of several aligned lithography stepsand subsequent etching or deposition of the gratingmaterial.3For the case of staircase profiles optimized for neg-ligible absorption,the N distinct steps of the staircasehave equal width(w i෇w j;i,j෇1,...,N)and the heights,h i,of the steps follow the ideal profile for zeroabsorption,leading to h i෇͓͑i21͒͞N͔l͞j d j.Such pro-files give good results for optics in the visible spectral range,where absorption is normally negligible.Also, in the case of the first x-ray optics with staircase pro-files,which have been recently reported,4–6b was suf-ficiently small for the relevant photon energies in the hard-x-ray range.However,when considering optics in the EUV and soft-x-ray region,in most cases ab-sorption will play a role.In the current work we show how to optimize the design of a staircase profile to ob-tain maximum first-order diffraction efficiency for this case of nonnegligible absorption.In the EUV and soft-x-ray spectral ranges,thewavelength of the light is typically smallcomparedFig.1.(A)Design of a transmission grating maximizing the first-order diffraction efficiency in the case of absorbing grating material(solid lines)and in the case of negligible absorption(dashed lines).(B)Correlation between free de-sign parameter b1and the optical properties of the grating material(quantif ied by d͞b).Published in Optics Letters 28, issue 13, 1087-1089, 2003which should be used for any reference to this work1Fig.2.General form of a staircase profile enabling the optimization of the first-order diffraction efficiency.with the period b and the height of the gratings used;therefore in most cases a grating can be treated as a thin structure,and the thin-element approximation can be used (for a discussion of the validity of the thin-element approximation see,for example,Ref.1).In addition,d and b are typically very small;conse-quently ref lections at surfaces between different materials are negligible.With these approximations the diffraction efficiency h can be calculated with the aid of a Fourier analysis of the transmission function.For a discrete profile we get 1h ෇ÉNX i ෇1f i É2,(1)wheref i ෇exp ͑22p h i b ͞d ͒exp ͓2p i ͑h i 2x i ͔͒sin ͑p w i ͒͞p ,(2)and the normalized heights (h i ),widths (w i )andmiddle positions (x i )of the steps are denotedh i ෇h i j d j ͞l ,w i ෇w i ͞b ,x i ෇x i ͞b .(3)Equation (1)is a sum of contributions from each step of the staircase profile shown in Fig.2.The first term in Eq.(2)describes the absorption within one step.The second term gives the phase of each contribution,originating from the material phase shift (h i )and the position of the step within the grating (x i ).The third term is obtained from the Fourier transform of a rect-angular function with width w i .The analytical treat-ment of the problem would be rather complex since the efficiency is a complicated sum over functions of all staircase parameters.Therefore we used a numerical approach,applying a local search algorithm 7to find the optimum values for the parameters in Eq.(3)with respect to diffraction efficiency.The principle of the algorithm is to make small,ran-dom,trial changes in the actual profile,where the change is allowed to take place only if the new profile (the new set of parameters h i ,w i ,and x i )has a higher diffraction efficiency than the previous one.By re-peating this step until a large number (n trial .100)of subsequent trial changes fails to improve the diffrac-tion efficiency,an optimum set of values of h i ,w i ,and x i will ultimately be reached.This kind of algorithm could fail because of the presence of local maxima and as a consequence would never yield reasonable results for the design parame-ters of the grating.However,the numerical resultsshow that the total number of maxima is rather small;therefore it is sufficient to repeat the whole algorithm a few (typically 20)times with different,randomly chosen starting parameters for the grating in order to obtain a parameter set that represents the global optimum with respect to diffraction efficiency.Figure 3shows the numerical results of using this algorithm in the case of a staircase profile with four levels.For low values of absorption (high values of d ͞b )we obtain the expected staircase profile,which has steps with equal width and normalized heights of 0,1͞4,1͞2,and 3͞4.When we go to higher values of absorption,the widths (as well as the heights)of the second and the third steps decrease and finally approach zero.The widths of the first and the fourth steps both increase,and for values of d ͞b near zero they both approach a value equal to half of the grating period b .Therefore in the limit of infinite absorption a conventional binary amplitude grating is obtained.These results for high values of absorption can be qualitatively understood because the staircase profile always has to provide an optimum approximation of the ideal profile in terms of diffraction efficiency.For the ideal grating in the case of strong absorption the main contributions to the diffraction efficiency come from regions of the grating with smallheight.Fig.3.Optimum normalized widths w i (A)and heights h i (B)of a four-step staircase profile as a function of d ͞b of the grating material.Fig.4.First-order diffraction efficiency of a four-step pro-file (solid curve)featuring optimal values for the heights and widths of the steps.In addition,the diffraction ef-ficiency of the ideal continuous profile (see Fig.1)and a four-step profile optimized for negligible absorption aredepicted.Fig.5.First-order diffraction efficiency for different opti-mized grating designs.Therefore it is important to get a good approximation of the region with zero height (provided by the first step with w 1ഠb 1)and a short region with small height at the beginning of the sawtooth (provided by the second and third steps,which therefore tend to have rather small widths and heights in the case of high absorption).In Fig.4the diffraction efficiency of a four-step pro-file with optimal values for h i ,w i ,and x i is depicted.In addition,the diffraction efficiency of the ideal con-tinuous profile and a four-step profile with the con-ventional design rule optimized for zero absorption are plotted for comparison.For high values of d ͞b thetwo different staircase profiles nearly have the same diffraction efficiency,whereas for values of d ͞b below 10a significant difference can be observed.There-fore the optimal design of the staircase profile has to be used in this case to guarantee maximum diffrac-tion efficiency (e.g.,for d ෇2the optimum four-step profile gives 22%diffraction efficiency in comparison with only 16%for a four-step profile optimized for zero absorption).When different step numbers N of the staircase profile are used,similar results are found.For high values of d ͞b (typically d ͞b .10)the anticipated profile optimized for zero absorption [w i ෇w j and h i ෇͑i 21͒͞N ]is obtained.For the case of high absorption the staircase profile gives a good approxi-mation of the ideal continuous profile in regions with small or zero structure height and an inferior approximation in regions of large structure heights,as expected.Figure 5shows the first-order diffraction efficiencies of optimized profiles with different step numbers N .For small values of absorption a larger number N of steps leads to a strongly improved diffraction efficiency,whereas for strong absorption very little difference is found among all profiles.This is because,for all profiles,the normalized width of the region with zero height approaches 1͞2,going to small values of d ͞b .Consequently in the limit of infinite absorption all the staircase profiles will have the same optical properties as a binary amplitude grating.In summary,we have shown that material absorp-tion has to be taken into account for the optimization of gratings in the EUV and x-ray ranges.By use of a numerical local search algorithm we were able to calculate the optimum parameters for maximum first-order diffraction efficiency of gratings with staircase profiles.This work was funded by the Swiss National Sci-ence Foundation. B.N öhammer ’s e-mail address is **********************.References1.H.P.Herzig,ed.,Micro-optics (Taylor &Francis,Lon-don,1998).2.R.Tatchyn,P.L.Csonka,and I.Lindau,J.Opt.Soc.Am.72,1630–1639(1982).3.M.B.Stern,in Micro-optics ,H.P.Herzig,ed.(Taylor &Francis,London,1998),pp.53–86.4.E.Di Fabrizio,F.Romanato,M.Gentili,S.Cabrini,B.Kaulich,J.Susini,and R.Barrett,Nature 401,895–898(1999).5.W.Yun,i,A.A.Krasnoperova,E.Di Fabrizio,Z.Cai,F.Cerrina,Z.Chen,M.Gentili,and E.Gluskin,Rev.Sci.Instrum.70,3537–3541(1999).6.B.N öhammer,J.Hoszowska,H.P.Herzig,and C.David,presented at the X-Ray Microscopy Conference 2002,Grenoble,France,July 29–August 2,2002.7.E.Aarts and J.K.Lenstra,Local Search in Combinato-rial Optimization (Wiley,Chichester,U.K.,1997).。

【北京市自然科学基金】_设计_基金支持热词逐年推荐_【万方软件创新助手】_20140729

53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106
107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160
黄芩苷黄芩鲁棒性'输出跟踪鲁棒性高速高级加密标准高繁殖力高科技厂房高斯模型高层钢结构骨缺损骨架骨形态发生蛋白受体ib基因骨密度马赫-曾德尔干涉仪马蔺首尔饲料配方系统风力发电机频率响应颈动脉颅内动脉瘤面向服务的体系结构非脆弱非线性系统非线性度非线性动态系统辨识非定常计算需求侧管理集成框架集成服务平台集成式石英谐振器集成学习集团企业集中柔度隶属度函数隧道工程隔舌隐私性隐私保护隐式授权随机故障随机性检测降噪阻遏蛋白质类阻尼比闪耀光纤光栅锻模优化设计锥束ct重建错配碱基错误拒绝率锅炉链球菌,变异铁电存储器
模态分析桥梁柔顺机构机械设计机器人有限元无源性数据流图敏度分析拓扑优化抗震设计承载力戴尔福特菌性能分析并联柔性机器人嵌入式系统嵌入式数据库小干扰rna 天然气大范围形变多网格编码调制均匀设计地下结构合成叶轮进口流动可视化发酵罐反馈线性化压型钢板压力脉动博弈单片机动应力动力学功率控制分类标准分子对接减震技术克隆催化燃烧信息融合二值化 xbrl实例生成器 web服务 rna干扰 rice信道 lagrange方程 ked方法 dsp canopen ansys 龙芯2号微处理器龙芯2号处理器齿兰环斑病毒

CitedReferences：引用的参考文献

Cited References:1. Chen, B.; Eddaoudi, M.; Hyde, S. T.; O'Keeffe, M.; Yaghi, O. M., InterwovenMetal-Organic Framework on a Periodic Minimal Surface with Extra-Large Pores.Science 2001, 291, (5506), 1021-1023.2. Yaghi, O. M.; O'Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J.,Reticular synthesis and the design of new materials. Nature 2003, 423, (6941),705-714.3. Ferey, G.; Mellot-Draznieks, C.; Serre, C.; Millange, F.; Dutour, J.; Surble, S.;Margiolaki, I., A Chromium Terephthalate-Based Solid with Unusually LargePore Volumes and Surface Area. Science 2005, 309, (5743), 2040-2042.4. Hoskins, B. F.; Robson, R., Design and construction of a new class ofscaffolding-like materials comprising infinite polymeric frameworks of 3D-linked molecular rods. A reappraisal of the zinc cyanide and cadmium cyanide structures and the synthesis and structure of the diamond-related frameworks [N(CH3)4][CuIZnII(CN)4] and CuI[4,4',4'',4'''-tetracyanotetraphenylmethane]BF4.xC6H5NO2. J. Am. Chem. Soc. 1990, 112, (4), 1546-1554.5. Li, H.; Eddaoudi, M.; O'Keeffe, M.; Yaghi, O. M., Design and synthesis of anexceptionally stable and highly porous metal-organic framework. Nature 1999,402, (6759), 276-279.6. Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O'Keeffe, M.; Yaghi,O. M., Hydrogen Storage in Microporous Metal-Organic Frameworks. Science2003, 300, (5622), 1127-1129.7. Tannenbaum, R., Three-Dimensional Coordination Polymers of Ruthenium(II)with 1,4-Diisolcyanobenzene Ligands and Their Catalytic Activity. Chem. Mater.1994, 6, 550-555.8. Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K., Preparation, Clathration Ability,and Catalysis of a Two-Dimensional Square Network Material Composed ofCadmium(II) and 4,4'-Bipyridine. J. Am. Chem. Soc. 1994, 116, (3), 1151-1152. 9. Kepert, C. J.; Prior, T. J.; Rosseinsky, M. J., Hydrogen Bond-Directed HexagonalFrameworks Based on Coordinated 1,3,5-Benzenetricarboxylate. J. Solid StateChem. 2000, 152, 261-270.10. Kepert, C. J.; Prior, T. J.; Rosseinsky, M. J., A Versatile Family ofInterconvertible Microporous Chiral Molecular Frameworks: The First Exampleof Ligand Control of Network Chirality. J. Am. Chem. Soc. 2000, 122, (21), 5158-5168.11. Bradshaw, D.; Prior, T. J.; Cussen, E. J.; Claridge, J. B.; Rosseinsky, M. J.,Permanent Microporosity and Enantioselective Sorption in a Chiral OpenFramework. J. Am. Chem. Soc. 2004, 126, (19), 6106-6114.12. Seo, J. S.; Whang, D.; Lee, H.; Jun, S. I.; Oh, J.; Jeon, Y. J.; Kim, K., Ahomochiral metal-organic porous material for enantioselective separation andcatalysis. Nature 2000, 404, (6781), 982-986.13. Evans, O. R.; Ngo, H. L.; Lin, W., Chiral Porous Solids Based on LamellarLanthanide Phosphonates. J. Am. Chem. Soc. 2001, 123, (42), 10395-10396.14. Hu, A.; Ngo, H. L.; Lin, W., Chiral Porous Hybrid Solids for PracticalHeterogeneous Asymmetric Hydrogenation of Aromatic Ketones. J. Am. Chem.Soc. 2003, 125, (38), 11490-11491.15. Doucet, H.; Ohkuma, T.; Murata, K.; Yokozawa, T.; Kozawa, M.; Katayama, E.;England, A. F.; Ikariya, T.; Ryoji, N., trans-[RuCl2(phosphane)2(1,2-diamine)]and Chiral trans-[RuCl2(diphosphane)(1,2-diamine)]: Shelf-Stable Precatalystsfor the Rapid, Productive, and Stereoselective Hydrogenation of Ketones. Angew.Chem., Int. Ed. Engl. 1998, 37, (12), 1703-1707.16. Hu, A.; Ngo, H. L.; Lin, W., Chiral, Porous, Hybrid Solids for HighlyEnantioselective Heterogeneous Asymmetric Hydrogenation of α,β-Keto Esters.Angew. Chem., Int. Ed. Engl. 2003, 42, (48), 6000-6003.17. van den Berg, M.; Minnaard, A. J.; Schudde, E. P.; van Esch, J.; de Vries, A. H.M.; de Vries, J. G.; Feringa, B. L., Highly Enantioselective Rhodium-CatalyzedHydrogenation with Monodentate Ligands. J. Am. Chem. Soc. 2000, 122, (46),11539-11540.18. Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.; Souchi, T.; Noyori,R., Synthesis of 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), anatropisomeric chiral bis(triaryl)phosphine, and its use in the rhodium(I)-catalyzedasymmetric hydrogenation of .alpha.-(acylamino)acrylic acids. J. Am. Chem. Soc.1980, 102, (27), 7932-7934.19. Jia, X.; Guo, R.; Li, X.; Yao, X.; Chan, A. S. C., Highly enantioselectivehydrogenation of enamides catalyzed by rhodium-monodentate phosphoramiditecomplex. Tetrahedron Lett. 2002, 43, (32), 5541-5544.20. Wang, X.; Ding, K., Self-Supported Heterogeneous Catalysts for EnantioselectiveHydrogenation. J. Am. Chem. Soc. 2004, 126, (34), 10524-10525.21. Yuan, Y.; Zhang, X.; Ding, K., Quasi Solvent-Free Enantioselective Carbonyl-Ene Reaction with Extremely Low Catalyst Loading. Angew. Chem., Int. Ed. Engl.2003, 42, (44), 5478-5480.22. Takizawa, S.; Somei, H.; Jayaprakash, D.; Sasai, H., Metal-Bridged Polymers asInsoluble Multicomponent Asymmetric Catalysts with High Enantiocontrol: AnApproach for the Immobilization of Catalysts without Using any Support. Angew.Chem., Int. Ed. Engl. 2003, 42, (46), 5711-5714.23. Wang, X.; Shi, L.; Li, M.; Ding, K., Heterogenization of Shibasaki's Binol/LaCatalyst for Enantioselective Epoxidation of α,β-Unsaturated Ketones withMultitopic Binol Ligands: The Impact of Bridging Spacers. Angew. Chem., Int.Ed. Engl. 2005, 44, (39), 6362-6366.24. Cho, S.-H.; Ma, B.; Nguyen, S. T.; Hupp, J. T.; Albrecht-Schmitt, T. E., A metal-organic framework material that functions as an enantioselective catalyst forolefin epoxidation. Chem. Comm. 2006, (24), 2563-2565.25. Wu, C. D.; Hu, A.; Zhang, L.; Lin, W., A Homochiral Porous Metal-OrganicFramework for Highly Enantioselective Heterogeneous Asymmetric Catalysis. J.Am. Chem. Soc. 2005, 127, (25), 8940-8941.26. Dybtsev, D. N.; Nuzhdin, A. L.; Chun, H.; Bryliakov, K. P.; Talsi, E. P.; Fedin, V.P.; Kim, K., A Homochiral Metal-Organic Material with Permanent Porosity,Enantioselective Sorption Properties, and Catalytic Activity. Angew. Chem., Int.Ed. Engl. 2006, 45, (6), 916-920.27. Hasegawa, S.; Horike, S.; Matsuda, R.; Furukawa, S.; Mochizuki, K.; Kinoshita,Y.; Kitagawa, S., Three-Dimensional Porous Coordination PolymerFunctionalized with Amide Groups Based on Tridentate Ligand: SelectiveSorption and Catalysis. J. Am. Chem. Soc. 2007, 129, (9), 2607-2614.Reviews and Books:28. Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; O'Keeffe, M.;Yaghi, O. M., Modular Chemistry: Secondary Building Units as a Basis for theDesign of Highly Porous and Robust Metal-Organic Carboxylate Frameworks.Acc. Chem. Res. 2001, 34, (4), 319-330.29. McMorn, P.; Hutchings, G. J., Heterogeneous enantioselective catalysts:strategies for the immobilisation of homogeneous catalysts. Chem. Soc. Rev. 2004, 33, (2), 108-122.30. Song, C.; Garces, J. M.; Sugi, Y., Shape-Selective Catalysis: Chemical Synthesisand Hydrocarbon Processing. American Chemical Society: Washington DC,1999; Vol. 738, p 410.31. Kitagawa, S.; Kitaura, R.; Noro, S.-i., Functional Porous Coordination Polymers.Angew. Chem., Int. Ed. Engl. 2004, 43, (18), 2334-2375.32. Ding, K.; Wang, Z.; Wang, X.; Liang, Y.; Wang, X., Self-Supported ChiralCatalysts for Heterogeneous Enantioselective Reactions. Chemistry a EuropeanJournal 2006, 12, (20), 5188-5197.33. Bradshaw, D.; Claridge, J. B.; Cussen, E. J.; Prior, T. J.; Rosseinsky, M. J.,Design, Chirality, and Flexibility in Nanoporous Molecule-Based Materials. Acc.Chem. Res. 2005, 38, (4), 273-282.34. Mueller, U.; Schubert, M.; Teich, F.; Puetter, H.; Schierle-Arndt, K.; Pastre, J.,Metal-organic frameworks-prospective industrial applications. J. Mater. Chem.2006, 16, (7), 626-636.35. Maspoch, D.; Ruiz-Molina, D.; Veciana, J., Old materials with new tricks:multifunctional open-framework materials. Chem. Soc. Rev. 2007, 36, (5), 770-818.。

The Alternate Arm Converter A New Hybrid Multilevel Converter With DC-Fault Blocking Capability

The Alternate Arm Converter:A NewHybrid Multilevel Converter With DC-FaultBlocking CapabilityMichaël M.C.Merlin,Member,IEEE,Tim C.Green,Senior Member,IEEE,Paul D.Mitcheson,Senior Member,IEEE,David R.Trainer,Roger Critchley,Will Crookes,and Fainan HassanAbstract—This paper explains the working principles,sup-ported by simulation results,of a new converter topology intended for HVDC applications,called the alternate arm converter(AAC). It is a hybrid between the modular multilevel converter,because of the presence of H-bridge cells,and the two-level converter,in the form of director switches in each arm.This converter is able to generate a multilevel ac voltage and since its stacks of cells consist of H-bridge cells instead of half-bridge cells,they are able to gen-erate higher ac voltage than the dc terminal voltage.This allows the AAC to operate at an optimal point,called the“sweet spot,”where the ac and dc energyﬂows equal.The director switches in the AAC are responsible for alternating the conduction period of each arm,leading to a signiﬁcant reduction in the number of cells in the stacks.Furthermore,the AAC can keep control of the current in the phase reactor even in case of a dc-side fault and support the ac grid,through a STATCOM mode.Simulation results and loss calculations are presented in this paper in order to support the claimed features of the AAC.Index Terms—AC–DC power converters,emerging topologies, fault tolerance,HVDC transmission,multilevel converters,power system faults,STATCOM.I.I NTRODUCTIONI NCREASING attention is being paid to HVDC transmis-sion systems,especially because most of the new schemes are intended to connect remote renewable sources to the grid and the most effective way to do it is to transmit the generated power using HVDC instead of HV AC[1].For offshore HVDC applica-tions,voltage-source converters(VSCs)are more suitable than current-source converters(CSCs)[2]due to to their black-start capability and ability to operate in weak ac grids,such as a net-work of wind turbine generators.However,compared to CSCs, their power ratings are limited and their efﬁciency is somewhatManuscript received August27,2012;revised May22,2013and August09, 2013;accepted September04,2013.Date of publication October07,2013;date of current version January21,2014.This work was supported in part by the Supergen FlexNet Research Consortium(ESPRC Grant EP/E04011X/1)and in part by Alstom Grid.Paper no.TPWRD-00896-2012.M.M.C.Merlin,T.C.Green,and P.D.Mitcheson are with the Department of Electrical and Electronics Engineering,Imperial College,London SW7 2AZ,U.K.(e-mail:michael.merlin@;t.green@;paul.mitch-eson@).D.R.Trainer,R.Critchley,R.W.Crookes,and F.Hassan are with Al-stom Grid,Stafford ST174LX,U.K.(e-mail:david.trainer@; roger.critchley@;will.crookes@).Color versions of one or more of theﬁgures in this paper are available online at .Digital Object Identiﬁer10.1109/TPWRD.2013.2282171poorer although recent developments in semiconductor devices are closing the gap in both cases so that VSCs are becoming economically viable as technological solutions in large HVDC schemes;some of them[3],[4]to be commissioned in the next couple of years.Since the1990s,a great deal of research effort has been directed to improving converters primarily to make them more power efﬁcient than theﬁrst generation of VSCs[5]–[8]. The modular multilevel converter(MMC),published in1998 for STATCOM applications[9],published in2003for HVDC Power Transmission[10],and followed up in[11]–[13],brought several new features to VSC.It replaced the series-connected insulated-gate biploar transistor(IGBT)in each arm of the two-level converter by a stack of half-bridge cells which con-sist of a charged capacitor and a set of IGBTs.Sincet the voltage of each cell is small compared to the ac and dc voltages,a large number of cells are placed in series in each stack,resulting in the creation of a voltage waveform with numerous steps.This characteristic has two main consequences:1)the generated ac current is very close to a sine wave and no longer requires any ﬁltering,thus saving the implementation of bulky and costly acﬁlters and2)the converter does not rely on high-frequency PWM to syntheses voltage waveforms,thus greatly reducing the switching loss and thereby improving the overall efﬁciency of the converter.Notwithstanding the advantages brought by this new gener-ation of converters,there are some aspects that can still be im-proved.The avoidance of the acﬁlter means that the cells are now one of the bulkiest components of the converter station and cell format requires a physically large capacitor in addition to the set of IGBTs.Half-bridge cells are normally used in pref-erence to H-bridge cells(both illustrated in Fig.1)in order to reduce the number of devices in conduction at any time and, therefore,reduce the conduction power loss.Even if this choice is justiﬁed by the large cost associated with the power losses,it also means that the converter is vulnerable to a dc-side fault in a similar way to a two-level converter whereas an H-bridge ver-sion would not be.The inability of half-bridge cells to produce a negative voltage results in the conduction of the antiparallel diodes connected to the IGBTs,thus creating an uncontrollable current path in case of a collapse of the dc bus voltage.Since the dc breakers for high-power applications are still under de-velopment[14],[15],the lack of other fast protective mecha-nisms[16]makes this loss of a means to control dc fault current problematic.In[17],the double-clamped submodule(DCS)was0885-8977©2013IEEE.Personal use is permitted,but republication/redistribution requires IEEE permission.See /publications_standards/publications/rights/index.html for more information.Fig.1.Electrical schematic of half-bridge cells(left)and H-bridge cells(right). suggested as a new type of cell to deal with this issue.The DCS connects two half-bridge cells together into one cell through one additional IGBT and two diodes.This conﬁguration offers the possibility of switching in a reverse voltage,similar to the H-bridge cell,in order to respond to the need for negative stack voltage in case of a dc-side fault.However the DCS does not fully solve the dc fault issue because:1)only half the available positive voltage can be translated into negative voltage,leavinga voltage deﬁcit from that needed to fully control the current and2)the power losses are increased by50%compared to using two half-bridge cells during normal operation because of the addi-tional IGBT in the conduction path.This paper presents the analysis of a new converter topology, which is part of a new generation of VSCs[18],[19],based on the multilevel approach but also takes some characteristics from the two-level VSC.As explained through this paper,one of the features of this topology lies in its ability to retain control of the phase current during the loss of the dc-bus voltage,thanks to the presence of H-bridge cells in the arms.The key advantage of this new topology lies in its reduced number of cells;thus, it does not compromise the efﬁciency of the converter,nor on the number of devices and even saves volume because of the reduced number of cells per arm.A component level simulation of a20-MW converter is used to conﬁrm the claimed character-istics of this new topology.II.D ESCRIPTION OF THE T OPOLOGYA.Basic OperationBrieﬂy presented in[20],the alternate arm converter(AAC) is a hybrid topology which combines features of the two-level and multilevel converter topologies.As illustrated in Fig.2, each phase of the converter consists of two arms,each with a stack of H-bridge cells,a director switch,and a small arm in-ductor.The stack of cells is responsible for the multistep voltage generation,as in a multilevel converter.Since H-bridge cells are used,the voltage produced by the stack can be either positive or negative;thus,the converter is able to push its ac voltage higher than the dc terminal voltage if required.The director switch is composed of IGBTs connected in series in order to withstand the maximum voltage which could be applied across the director switch when it is in the open state.The main role of thisdirector Fig.2.Schematic of the alternate arm converter,with the optional middle-point connection shown in a dashedline.Fig.3.Idealized voltage and current waveforms over one cycle in a phase con-verter of the AAC,showing the working period of each arm.switch is to determine which arm is used to conduct the ac cur-rent.Indeed,the key feature of this topology is to use essentially one arm per half cycle to produce the ac voltage.By using the upper arm to construct the positive half-cycle of the ac sine wave and the lower arm for the negative part,the maximum voltage that each stack of cells has to produce is equal to half of the dc bus voltage,which is approximately half the rating of the arm of the MMC.The resulting voltage and current waveforms of the cells and reactor switches are illustrated in Fig.3.The aim of the AAC is to reduce the number of cells,hence the volume and losses of the converter station.The short period of time when one armﬁnishes its working period and hands over conduction of the phase current to the op-posite arm is called the overlap period.Since each arm has an ac-tive stack of cells,it can fully control the arm current to zero be-fore opening the director switch,hence achieving soft-switchingFig.4.STATCOM modes of the AAC during a dc-side fault:alternate arms (mode A),single working arm(mode B),and dual working arms(mode C). of the director switch,further lowering the power losses.Al-though normally short,the overlap period can provide additional control features,such as controlling the amount of energy stored in the stacks,as explained in Section II-C.B.DC Fault ManagementOne of the important characteristics of this converter is the ability of its arms to produce negative voltage.In fact,the AAC already uses this ability to produce a converter voltage higher than the dc terminal voltage without requiring the opposite arm to also produce a higher than normal positive voltage from its stack of cells,provided that the director switch is suitably rated. This ability is put to use in normal operation when the converter produces a voltage which is higher than the dc bus voltage.It can be extended to the case when the dc bus voltage collapses to a low level,for example,a fault on the dc side.Since enough cells are present in the stacks to oppose the ac grid voltage,the converter is thus able to keep all of its internal currents under control,in contrast to the two-level converter or half-bridge ver-sion of the MMC.Furthermore,even if the absence of a dc bus voltage means that it is no longer possible to export ac-tive power to the dc side,it does not prevent reactive power exchange with the ac side.Since the arms of the AAC are still operational,the entire converter can now act as a STATCOM, similar to that in[9].There are some choices over how the di-rector switches are used in this mode,as illustrated in Fig.4, which lead to different modes that can be achieved by the AAC during a dc-side fault:one arm conducts per half cycle simi-larly to normal operation,one arm works continuously or the two arms working together,potentially increasing the reactive power capability to2.0p.u.This STATCOM mode of managing the converter during dc fault can help to support the ac grid during a dc outage,in contrast to the worsening effect that can be brought about by other topologies because of their inability to control dc-side fault current.C.Energy BalanceThe ability of the converter to generate relativelyﬁne voltage steps comes from its cells and,more speciﬁcally,from the charged capacitors inside.However,since the resulting ac current isﬂowing through them,the charge of these capacitors willﬂuctuate over time,depending on the direction of the current and the switching states of the cells.Due to the large number of cells,it is easier to look at the amount of energy which is stored by the stacks of cells as a whole.Assuming that this charge is evenly distributed among the various cells, thanks to some rotation mechanisms,the only requirement left to ensure satisfactory operation of the converter is to keep the energy of the stacks close to their nominal value.To achieve this,the converter has to be operated in such way that the net energy exchange for the stacks over each half cycle is strictly zero.Based on the time functions(1)of and(1) The energy exchange corresponds to the difference between the amount of energy coming from the ac side(2)and going to the dc side(3)(2)(3) By equating these two energies,an ideal operating point is identiﬁed as described in(4).This operating point is called the “sweet spot”and is deﬁned by a ratio of the ac voltage magni-tude to dc voltage magnitude(4) It is important to remark that this sweet spot speciﬁes an ac peak voltage higher than the dc terminal voltage,that is,half the dc bus voltage.The converter is thus required to generate its ac voltage in overmodulation mode,at a level of approximately 27%higher than the dc terminal voltage. The presence of H-bridge cells is thus fully justiﬁed since these cells are required to provide a negative voltage,thus pushing the voltage higher than the dc terminal voltage.By choosing the turns ratio of the transformer between the converter and the ac grid in order to obtain the ac voltage of the sweet spot,the con-verted energy willﬂow through the converter without a deﬁcit or surplus being exchanged with the stacks.In practice,discrepancies between the converter and its the-oretical model[used to derived(2)and(3)leading to(4)]will lead to a small fraction of the converted energy being exchanged with the stack.To remedy this,the overlap period(i.e.,the small period of time when one arm hands over conduction of the phase current to the other arm)can be used to run a small dc current through both arms to the dc side.This will result in an exchange of energy between the stacks and the dc capacitor,which can be used to balance the energy in the stacks.D.Number of DevicesThe device count in the AAC can be obtained by following a series of steps,given the particular operating mechanism described before.The calculation presented below only gives the minimal requirement under normal operation.An additional margin has to be added to comply with the different operating conditions applied to each project.It is,however,important to note that the stacks of the AAC can generate as much negative voltage as positive voltage;thus,the AAC is able to provide an ac voltage up to200%of the dc terminal voltage without requiring extra cells.First,the number of cells is obtained by calculating the max-imum voltage that a stack has to produce.Since the two arms of a single-phase converter have to support at least the total dc bus voltage,and assuming a symmetrical construction,this maximum voltage has to be at least half the dc bus voltage.Fur-thermore,given that this topology is intended to have dc-fault blocking capability,the arms should be able to produce at least the ac peak voltage in order to maintain control over the current in the phase reactor with the dc voltage reduced to zero.There-fore,the stacks should be rated to deliver the ac peak voltage. Since the sweet spot deﬁnes the ac peak voltage as27%higher than half the dc bus voltage,the minimum requirement can then be increased up to the ac peak voltage.However,if dc-fault blocking is not a requirement,this voltage can remain at half the dc bus voltage.Furthermore,the maximum voltage of the stacks also deﬁnes how long an arm can stay active beyond the zero-crossing point of the converter voltage in order to provide an overlap period.The longer the overlap period,the higher the voltage that the stack has to produce,hence the more cells are required.Once the maximum voltage of the stack is set,the number of cells is directly obtained by dividing this voltage by the nominal voltage of a cell.Second,the required number of series IGBTs,which form the director switch,is determined based on the maximum voltage applied across the director switch,as illustrated in Fig.3.This voltage is the difference between the converter voltage and the voltage at the other end of the director switch,which is con-nected to the(nonconducting)stack of cells.The nonconducting stack can be set to maximize its voltage in order to lower the voltage across the director switch,taking care not to reverse the voltage across the director switch.Equation(5)summarizes all of these arguments and presents the maximum voltage across the director switch.By implementing the sweet spot deﬁnition (4)into(5),it yields(6),a function of the dc bus voltage and the peak stack voltage(5)(6) Table I summarizes the voltage ratings required of the stack of cells and the director switch given three choices made over the need to block dc fault current and the extent of overlap.In deﬁning these voltages,these choices will also determine the number of semiconductor devices in the AAC.TABLE IV OLTAGE R ATINGS OF THE S TACKS AND D IRECTOR SWITCHESThe resulting number of cells per stack is given by(7),where is the nominal voltage of a cell(7) Equation(8)presents the total number of semiconductor de-vices()in a three-phase AAC,with being the number series-IGBTs in the director switch obtained by dividing the maximum voltage of a director switch()by the voltage applied to an IGBT,here assumed to be the same to the voltage of a cell().(8)Using the dc-fault blocking case(given in Table I)and the deﬁnition of the sweet spot(4),the total number of semicon-ductor devices becomes the value of the following equation:(9)III.S IMULATION R ESULTSA.Model CharacteristicsIn order to conﬁrm the operation of this new topology,a sim-ulation model has been realised in Matlab/Simulink using the SimPowerSystems toolbox.The characteristics of this model have been chosen in order to reﬂect a realistic power system, albeit at medium voltage(MV),and key parameters are sum-marized in Table II.The transformer interfacing the ac grid and the converter has its turns ratio deﬁned such that the con-verter operates close to the sweet-spot ac voltage,as deﬁned in Section II-C.The number of cells chosen for each stack follows the second case from Table II so that dc-side fault blocking is available.A small additional allowance was made so that the converter can still operate and block faults with an ac voltage of1.05p.u.The choice is therefore for nine cells charged at1.5 kV each per stack.The minimum number of cells for operation without overlap(sweet spot operation only)and without fault blocking would be seven cells.The choice of nine cells per stack allows the AAC to operate with1-ms overlap period which is sufﬁcient to internally manage the energy storage within the cur-rent rating of the IGBTs(1.2kA).Finally,a dcﬁlter has been ﬁtted to the AAC model,as illustrated in Fig.2,and tuned to have critical damping and a cutoff frequency at50Hz;well below theﬁrst frequency component expected on the dc side which is a six-pulse ripple(i.e.,300Hz in this model).C HARACTERISTICS OF THE 20-MW AAC MODELB.Performance Under Normal ConditionsBased on this model,the behavior of the AAC was simulated under normal conditions in order to test its performance.In this section,the converter is running in recti ﬁer mode,converting 20MW and providing 5-MV Ar capacitive reactive power.Fig.5shows the waveforms generated by the AAC in this simulation.First,the converter is very responsive.Second,the waveform of the phase current in the ac grid connection is high quality with only very low amplitude harmonics,as shown by the Fourier analysis in Fig.6.Third,the dc current exhibits the character-istic six-pulse ripple inherent in the recti ﬁcation method of this converter,but attenuated by an inductor placed between the con-verter and the dc grid.Fourth,this recti ﬁcation action of the cur-rent is particularly observable in the fourth graph which shows the arm currents in phase A,indicating when an arm is con-ducting.Finally,the ﬁfth graph presents the average voltage of the cells in both stacks of phase A,with their offstate voltage being controlled to stay at the reference value of 1.5kV.The voltage and current waveforms have been postprocessed together with the switching commands sent to the converter from the controller,in order to determine the generated power losses.For this example,all of the semiconductor devices were based on the same IGBT device [21]from which the losses curves have been extracted to compute the energy lost through conduction and switching at every simulation time step (2s).A simulation of 1.5s was used in which the ﬁrst 0.5s was ignored in order to focus only on the steady-state portion.The obtained results are summarized in Table III.As can be observed in Table III,the switching loss relative to the total power losses is low,as could be expected from a mul-tilevel converter,meaning that the conduction loss isdominant.Fig.5.Simulation results of a 20-MW AAC model running in recti ﬁer mode under normalconditions.Fig.6.Fourier transform of the grid-side ac current generated by the AAC.However,the conduction loss is kept small despite the use of H-bridge cells by the fact that the stacks do not have to be rated for the full dc bus voltage because of the presence of the di-rector switches;the conduction loss of a director switch device is less than that of an H-bridge cell.The director switches do not incur any switching loss thanks to the soft-switching capability of the arms (through controlling the arm current to zero before opening of the director switch).Finally,a large amount of the power losses comes from the dc inductor but this is not repre-sentative of a large converter.In this scale model of 20MW,the current at 1kA is typical of a much later converter and it is the voltage that has been scalded down by reducing the number of cells and levels (while keeping the cell voltage at a value typicalB REAKDOWN OF THE P OWER L OSSES AT 20MWof a larger converter 1.5kV).Since the Q factor of the inductor and the current have not been scaled,the loss in the in-ductor is proportionately large.C.Robustness Against AC FaultsSince the AAC is a type of VSC,it does not rely on a strong ac voltage to operate.As a consequence,the AAC is able to cope with ac-side faults.Fig.7shows the results of the simulation where the ac voltage drops to 0.3-p.u.retained voltage between 0.20and 0.35s,similar to a major fault on the ac grid.The con-verter switches into voltage-control mode and supplies 1.0-p.u.capacitive reactive power current.When the ac voltage returns to its nominal value,the converter switches back to normal op-eration and full power is reapplied with a ramp function of more than 50ms.Several observations can be made.First,the converter is able to react quickly to the fault and reduces the power as a conse-quence.Second,the quality of the ac current waveform deteri-orates during the fault,mainly because fewer levels are needed to construct the reduced converter voltage waveform.Third,the cell capacitors display greater voltage ﬂuctuation during the fault because the converter is running far away from the sweet spot,but this does not prevent the AAC from generating reac-tive power during the outage.D.DC Fault Blocking CapabilityThe intended ability to block current during dc faults was tested by simulating the temporary reduction of the dc bus voltage to zero,equivalent to a dc-side fault.The graph in Fig.8shows the waveforms generated during this simulation,where the dc bus voltage is lost between 0.20and 0.35s followed by a ramp up back to normal operations.When observing the sequence of events during this simula-tion,it can be seen that when the dc voltage collapses to zero,it leads to a rapid discharge of the dc bus capacitor which is out-side the control of the converter in opposition to the cell capac-itors.At the moment of fault,the dc ﬁlter behaves similar to an RLC circuit with a precharged capacitor (20kV)and inductorFig.7.Simulation results of a 20-MW AAC model running in recti ﬁer mode when an ac-side fault occurs between 0.20and 0.35s.(1kA),resulting in a theoretical peak current of 5.1kA which is close to the current spike observed in the third graph.However,the fourth graph shows that the converter is able to keep control of the ac reactor current and its arm currents so that no fault cur-rent ﬂows from the ac side to the dc side,demonstrating the dc fault blocking capability of the converter itself.Since the converter is no longer able to exchange active power with its dc bus voltage at zero,the active currents are controlled back to zero.Then,from 0.25s,the AAC starts injecting 1.0-p.u.reactive current,thus acting as a STATCOM supporting the ac grid during the outage of the dc link.The stack in conduction at the instance of the fault sees its stored energy rise because it temporarily stores the still incoming en-ergy (while the active current is being reduced),but converges back to its reference value over the period when the fault is present.Finally,when the dc voltage has returned,the converter is able to resume operation quickly.This simulation shows the ability of the AAC to cope with the dc-side fault and even run as a STATCOM to support the ac grid,in the absence of dc bus voltage.Furthermore,in the current simulation,the AAC keeps the same alternating mechanisms of its arms (mode A in Fig.4)but,by activating both arms continuously (mode C in Fig.4),the maximum reactive power could reach up to 2.0-p.u.current.Fig.8.Simulation results of a20-MW AAC model running in rectiﬁer mode when a dc-side fault occurs between0.20and0.35s.IV.C ONCLUSIONThe AAC is a hybrid topology between the two-level con-verter and the modular multilevel converter.By combining stacks of H-bridge cells with director switches,it is able to generate almost harmonic-free ac current,as does the modular multilevel approach.And by activating only one arm per half cycle,like the two-level converter,it can be built with fewer cells than the MMC.Since this topology includes cells with capacitors which are switched into the current path,special attention needs to be paid to keeping their stored energy(equivalently,the cell capacitor voltage)from drifting away from their nominal value.By ex-amining the equations,which govern the exchange of energy between the ac and dc sides,an ideal operating condition has been identiﬁed,called the“sweet spot.”When the converter is running at this condition,the energy levels of the stacks return to their initial values at the end of each cycle without any addi-tional action.In cases where this equilibrium is not attained,an overlap period can be used to run a small dc current in order to balance the stacks by sending the excess energy back to the dc capacitors.A discussion of the total number of devices required by this topology has also been presented.Providing dc fault blocking and overlap both require more than the bare minimum number of cells,and adding cells does lead to increased conduction power loss which gives rise to a design tradeoff. Simulations of a small-scale model show that this converter is able to deliver performance under normal conditions,in terms of efﬁciency and current waveform quality,and provide rapid responses in the case of ac-or dc-side faults.Its ability to keep control of the current even during dc faults is a signiﬁcant ad-vantage,especially in multiterminal HVDC applications,and can be extended into STATCOM operation in order to support the ac grid during the outage,by providing potentially up to 2.0-p.u.reactive current.R EFERENCES[1]T.Hammons,V.Lescale,K.Uecker,M.Haeusler,D.Retzmann,K.Staschus,and S.Lepy,“State of the art in ultrahigh-voltage transmis-sion,”Proc.IEEE,vol.100,no.2,pp.360–390,Feb.2012.[2]D.Jovcic,D.van Hertem,K.Linden,J.-P.Taisne,and W.Grieshaber,“Feasibility of dc transmission networks,”in Proc.2nd IEEE PowerEnergy Soc.Int.Conf.Exhibit.Innovative Smart Grid Technol.,Dec.2011,pp.1–8.[3]SIEMENS,Borwin2press release,2010.[4]Energinet.dk Svenska Kraftnät Vattenfall Europe Transmission,AnAnalysis of Offshore Grid Connection at Kriegers Flak in the BalticSea,Joint Pre-feasibility study Energinet.dk.,2009[Online].Avail-able:http://www.svk.se/global/02_press_info/090507_kriegers-ﬂak-pre-feasibility-report-ﬁnal-version.pdf,Tech.Rep.[5]B.Andersen,L.Xu,P.Horton,and P.Cartwright,“Topologies for vsctransmission,”Power Eng.J.,vol.16,no.3,pp.142–150,2002.[6]R.Jose,L.Jih-Sheng,and P.Fangzheng,“Multilevel inverters:Asurvey of topologies,controls,applications,”IEEE Trans.Ind.Elec-tron.,vol.49,no.4,pp.724–738,Aug.2002.[7]M.Bahrman and B.Johnson,“The abcs of hvdc transmission technolo-gies,”IEEE Power Energy Mag.,vol.5,no.2,pp.32–44,Mar.2007.[8]High-V oltage Direct Current(HVDC)Power Transmission UsingV oltage Sourced Converter(VSC)BSi,2011,pD IEC/TR62543:2011.[9]J.Ainsworth,M.Davies,P.Fitz,K.Owen,and D.Trainer,“Staticvar compensator(statcom)based on single-phase chain circuit con-verters,”Proc.Inst.Elect.Eng.,Gen.,Transm.Distrib.,vol.145,no.4,pp.381–386,Jul.1998.[10]A.Lesnicar and R.Marquardt,“An innovative modular multilevel con-verter topology suitable for a wide power range,”presented at the IEEEBologna Power Tech Conf.,Bologna,Italy,Jun.2003.[11]S.Allebrod,R.Hamerski,and R.Marquardt,“New transformerless,scalable modular multilevel converters for hvdc-transmission,”inProc.IEEE Power Electron.Specialists Conf.,Jun.2008,pp.174–179.[12]J.Dorn,H.Huang,and D.Retzmann,“Novel voltage sourced con-verters for hvdc and facts applications,”in Proc.CIGRE,Osaka,Japan,2007.[13]R.Marquardt,“Modular multilevel converter:An universal concept forhvdc-networks and extended dc-bus-applications,”in Proc.Int.PowerElectron.Conf.,Jun.2010,pp.502–507.[14]C.Franck,“Hvdc circuit breakers:A review identifying future researchneeds,”IEEE Trans.Power Del.,vol.26,no.2,pp.998–1007,Apr.2011.[15]J.Hafner and B.Jacobson,“Proactive hybrid hvdc breakers—A keyinnovation for reliable hvdc grids,”in Proc.CIGRE,Bologna,Italy,2011.[16]J.Yang,J.Fletcher,and J.O’Reilly,“Multi-terminal dc wind farm col-lection and transmission system internal fault analysis,”in Proc.IEEEInt.Symp.Ind.Electron.,Jul.2010,pp.2437–2442.[17]R.Marquardt,“Modular multilevel converter topologies with dc-shortcircuit current limitation,”in Proc.IEEE8th Int.Conf.Power Electron.ECCE Asia,,Jun.2011,pp.1425–1431.[18]D.Trainer,C.Davidson,C.Oates,N.Macleod,D.Critchley,and R.Crookes,“A new hybrid voltage-sourced converter for HVDC powertransmission,”in CIGRE Session,2010.[19]C.Davidson and D.Trainer,“Innovative concepts for hybrid multi-level converters for hvdc power transmission,”in Proc.9th IET Int.Conf.AC DC Power Transm.,Oct.2010,pp.1–5.[20]M.Merlin,T.Green,P.Mitcheson,D.Trainer,D.Critchley,and R.Crookes,“A new hybrid multi-level voltage-source converter with dcfault blocking capability,”presented at the9th IET Int.Conf.AC DCPower Transm,London,U.K.,Oct.2010.。

Mass Transfer Issues in Micro- and Nanoscale

Issues in Micro- and Nanoscale
Nadapana Vasu and Sirshendu De Contents 11.1 Introduction....................................................................................................................... 318 11.2 Mass Transfer Issues Pertaining to Microscales........................................................... 319 11.3 Sherwood Number Correlation...................................................................................... 320 11.4 Mass Transfer Issues Pertaining to Nanoscale............................................................. 321 11.5 Dividing Line between Devices at Microscale and Nanoscale.................................. 321 11.6 Advantages at Microscale................................................................................................ 321 11.6.1 Effe

2006年天津大学校级领导班子述职会-天津大学研究生e-Learning平台

天津大学 Tianjin University
13
天津大学 Tianjin University
14
天津大学 Tianjin University
8
三，研究目标和内容
分析水下环境制约因素
在Matlab/simulink中搭建水下声学传感器通信模型
构建协作MIMO通信系统
利用Stackelberg博弈模型进行协作节点选择和功率分配
天津大学 Tianjin University
9
四，技术问题和方法
天津大学 Tianjin University
12
五，工作条件和计划
2013.9——2013.12 熟悉协作MIMO和博弈论理论知识，掌握相关仿真软件的使用方法； 2014.1——2014.2 考虑水下声学通信环境的多样性，搭建水下声通信系统模型； 2014.3——2014.5 提出适合于水下节点通信的协作MIMO通信模型并进行验证； 2014.6——2014.8 设计基于Stackelberg博弈的协作MIMO通信模型，并对模型、算法的可行性和有效性进行仿真和验证； 2014.9——2014.11 撰写毕业论文，准备答辩。
10
四，技术问题和方法
针对问题3： ——构建基于Stackelberg博弈的买家-卖家模型，按照节点位置和信道优劣状况设定协作节点的功率价格，计算源节点和协作节点的效益函数
U Sn =CSn Rm PRmSn
m 1 M
U Rm =( Rm c) PRm Sn
n 1
N
——限制协作节点个数，可以设定一常数作为单位功率获得的效益阈值，某节点被选择后，若源节点单位功率获得的效益大于此阈值，则选择该节点，否则不选

单分子综述-NATURE NANOTECHNOLOGY-Single-molecule junctions beyond electronic transport-2013

Stimulated by the initial proposal that molecules could be used as the functional building blocks in electronic devices 1, researchers around the world have been probing transport phenomena at the single-molecule level both experimentally and theoretically 2–11. Recent experimental advances include the demonstration of conductance switching 12–16, rectification 17–21, and illustrations on how quantum interference effects 22–26 play a critical role in the electronic properties of single metal–molecule–metal junctions. The focus of these experiments has been to both provide a fundamental understanding of transport phenomena in nanoscale devices as well as to demonstrate the engineering of functionality from rational chemical design in single-molecule junctions. Although so far there are no ‘molecular electronics’ devices manufactured commercially, basic research in this area has advanced significantly. Specifically, the drive to create functional molecular devices has pushed the frontiers of both measurement capabilities and our fundamental understanding of varied physi-cal phenomena at the single-molecule level, including mechan-ics, thermoelectrics, optoelectronics and spintronics in addition to electronic transport characterizations. Metal–molecule–metal junctions thus represent a powerful template for understanding and controlling these physical and chemical properties at the atomic- and molecular-length scales. I n this realm, molecular devices have atomically defined precision that is beyond what is achievable at present with quantum dots. Combined with the vast toolkit afforded by rational molecular design 27, these techniques hold a significant promise towards the development of actual devices that can transduce a variety of physical stimuli, beyond their proposed utility as electronic elements 28.n this Review we discuss recent measurements of physi-cal properties of single metal–molecule–metal junctions that go beyond electronic transport characterizations (Fig. 1). We present insights into experimental investigations of single-molecule junc-tions under different stimuli: mechanical force, optical illumina-tion and thermal gradients. We then review recent progress in spin- and quantum interference-based phenomena in molecular devices. I n what follows, we discuss the emerging experimentalSingle-molecule junctions beyond electronic transportSriharsha V. Aradhya and Latha Venkataraman*The id ea of using ind ivid ual molecules as active electronic components provid ed the impetus to d evelop a variety of experimental platforms to probe their electronic transport properties. Among these, single-molecule junctions in a metal–molecule–metal motif have contributed significantly to our fundamental understanding of the principles required to realize molecular-scale electronic components from resistive wires to reversible switches. The success of these techniques and the growing interest of other disciplines in single-molecule-level characterization are prompting new approaches to investigate metal–molecule–metal junctions with multiple probes. Going beyond electronic transport characterization, these new studies are highlighting both the fundamental and applied aspects of mechanical, optical and thermoelectric properties at the atomic and molecular scales. Furthermore, experimental demonstrations of quantum interference and manipulation of electronic and nuclear spins in single-molecule circuits are heralding new device concepts with no classical analogues. In this Review, we present the emerging methods being used to interrogate multiple properties in single molecule-based devices, detail how these measurements have advanced our understanding of the structure–function relationships in molecular junctions, and discuss the potential for future research and applications.methods, focusing on the scientific significance of investigations enabled by these methods, and their potential for future scientific and technological progress. The details and comparisons of the dif-ferent experimental platforms used for electronic transport char-acterization of single-molecule junctions can be found in ref. 29. Together, these varied investigations underscore the importance of single-molecule junctions in current and future research aimed at understanding and controlling a variety of physical interactions at the atomic- and molecular-length scale.Structure–function correlations using mechanicsMeasurements of electronic properties of nanoscale and molecu-lar junctions do not, in general, provide direct structural informa-tion about the junction. Direct imaging with atomic resolution as demonstrated by Ohnishi et al.30 for monoatomic Au wires can be used to correlate structure with electronic properties, however this has not proved feasible for investigating metal–molecule–metal junctions in which carbon-based organic molecules are used. Simultaneous mechanical and electronic measurements provide an alternate method to address questions relating to the struc-ture of atomic-size junctions 31. Specifically, the measurements of forces across single metal–molecule–metal junctions and of metal point contacts provide independent mechanical information, which can be used to: (1) relate junction structure to conduct-ance, (2) quantify bonding at the molecular scale, and (3) provide a mechanical ‘knob’ that can be used to control transport through nanoscale devices. The first simultaneous measurements of force and conductance in nanoscale junctions were carried out for Au point contacts by Rubio et al.32, where it was shown that the force data was unambiguously correlated to the quantized changes in conductance. Using a conducting atomic force microscope (AFM) set-up, Tao and coworkers 33 demonstrated simultaneous force and conductance measurements on Au metal–molecule–metal junc-tions; these experiments were performed at room temperature in a solution of molecules, analogous to the scanning tunnelling microscope (STM)-based break-junction scheme 8 that has now been widely adopted to perform conductance measurements.Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA. *e-mail: lv2117@DOI: 10.1038/NNANO.2013.91These initial experiments relied on the so-called static mode of AFM-based force spectroscopy, where the force on the canti-lever is monitored as a function of junction elongation. I n this method the deflection of the AFM cantilever is directly related to the force on the junction by Hooke’s law (force = cantilever stiff-ness × cantilever deflection). Concurrently, advances in dynamic force spectroscopy — particularly the introduction of the ‘q-Plus’ configuration 34 that utilizes a very stiff tuning fork as a force sen-sor — are enabling high-resolution measurements of atomic-size junctions. In this technique, the frequency shift of an AFM cantilever under forced near-resonance oscillation is measuredas a function of junction elongation. This frequency shift can be related to the gradient of the tip–sample force. The underlying advantage of this approach is that frequency-domain measure-ments of high-Q resonators is significantly easier to carry out with high precision. However, in contrast to the static mode, recover-ing the junction force from frequency shifts — especially in the presence of dissipation and dynamic structural changes during junction elongation experiments — is non-trivial and a detailed understanding remains to be developed 35.The most basic information that can be determined throughsimultaneous measurement of force and conductance in metalThermoelectricsSpintronics andMechanicsOptoelectronicsHotColdFigure 1 | Probing multiple properties of single-molecule junctions. phenomena in addition to demonstrations of quantum mechanical spin- and interference-dependent transport concepts for which there are no analogues in conventional electronics.contacts is the relation between the measured current and force. An experimental study by Ternes et al.36 attempted to resolve a long-standing theoretical prediction 37 that indicated that both the tunnelling current and force between two atomic-scale metal contacts scale similarly with distance (recently revisited by Jelinek et al.38). Using the dynamic force microscopy technique, Ternes et al. effectively probed the interplay between short-range forces and conductance under ultrahigh-vacuum conditions at liquid helium temperatures. As illustrated in Fig. 2a, the tunnel-ling current through the gap between the metallic AFM probe and the substrate, and the force on the cantilever were recorded, and both were found to decay exponentially with increasing distance with nearly the same decay constant. Although an exponential decay in current with distance is easily explained by considering an orbital overlap of the tip and sample wavefunctions through a tunnel barrier using Simmons’ model 39, the exponential decay in the short-range forces indicated that perhaps the same orbital controlled the interatomic short-range forces (Fig. 2b).Using such dynamic force microscopy techniques, research-ers have also studied, under ultrahigh-vacuum conditions, forces and conductance across junctions with diatomic adsorbates such as CO (refs 40,41) and more recently with fullerenes 42, address-ing the interplay between electronic transport, binding ener-getics and structural evolution. I n one such experiment, Tautz and coworkers 43 have demonstrated simultaneous conduct-ance and stiffness measurements during the lifting of a PTCDA (3,4,9,10-perylene-tetracarboxylicacid-dianhydride) molecule from a Ag(111) substrate using the dynamic mode method with an Ag-covered tungsten AFM tip. The authors were able to follow the lifting process (Fig. 2c,d) monitoring the junction stiffness as the molecule was peeled off the surface to yield a vertically bound molecule, which could also be characterized electronically to determine the conductance through the vertical metal–molecule–metal junction with an idealized geometry. These measurements were supported by force field-based model calculations (Fig. 2c and dashed black line in Fig. 2d), presenting a way to correlate local geometry to the electronic transport.Extending the work from metal point contacts, ambient meas-urements of force and conductance across single-molecule junc-tions have been carried out using the static AFM mode 33. These measurements allow correlation of the bond rupture forces with the chemistry of the linker group and molecular backbone. Single-molecule junctions are formed between a Au-metal sub-strate and a Au-coated cantilever in an environment of molecules. Measurements of current through the junction under an applied bias determine conductance, while simultaneous measurements of cantilever deflection relate to the force applied across the junction as shown in Fig. 2e. Although measurements of current throughzF zyxCantileverIVabConductance G (G 0)1 2 3Tip–sample distance d (Å)S h o r t -r a n g e f o r c e F z (n N )10−310−210−11110−110−210−3e10−410−210C o n d u c t a n c e (G 0)Displacement86420Force (nN)0.5 nm420−2F o r c e (n N )−0.4−0.200.20.4Displacement (nm)SSfIncreasing rupture forcegc(iv)(i)(iii)(ii)Low HighCounts d9630−3d F /d z (n N n m −1)(i)(iv)(iii)(ii)A p p r o a chL i ft i n g110−210−4G (2e 2/h )2051510z (Å)H 2NNH 2H 2NNH 2NNFigure 2 | Simultaneous measurements of electronic transport and mechanics. a , A conducting AFM set-up with a stiff probe (shown schematically) enabled the atomic-resolution imaging of a Pt adsorbate on a Pt(111) surface (tan colour topography), before the simultaneous measurement of interatomic forces and currents. F z , short-range force. b , Semilogarithmic plot of tunnelling conductance and F z measured over the Pt atom. A similar decay constant for current and force as a function of interatomic distance is seen. The blue dashed lines are exponential fits to the data. c , Structural snapshots showing a molecular mechanics simulation of a PTCDA molecule held between a Ag substrate and tip (read right to left). It shows the evolution of the Ag–PTCDA–Ag molecular junction as a function of tip–surface distance. d , Upper panel shows experimental stiffness (d F /d z ) measurements during the lifting process performed with a conducting AFM. The calculated values from the simulation are overlaid (dashed black line). Lower panel shows simultaneously measured conductance (G ). e , Simultaneously measured conductance (red) and force (blue) measurements showing evolution of a molecular junction as a function of junction elongation. A Au point contact is first formed, followed by the formation of a single-molecule junction, which then ruptures on further elongation. f , A two-dimensional histogram of thousands of single-molecule junctionrupture events (for 1,4-bis(methyl sulphide) butane; inset), constructed by redefining the rupture location as the zero displacement point. The most frequently measured rupture force is the drop in force (shown by the double-headed arrow) at the rupture location in the statistically averaged force trace (overlaid black curve). g , Beyond the expected dependence on the terminal group, the rupture force is also sensitive to the molecular backbone, highlighting the interplay between chemical structure and mechanics. In the case of nitrogen-terminated molecules, rupture force increases fromaromatic amines to aliphatic amines and the highest rupture force is for molecules with pyridyl moieties. Figure reproduced with permission from: a ,b , ref. 36, © 2011 APS; c ,d , ref. 43, © 2011 APS.DOI: 10.1038/NNANO.2013.91such junctions are easily accomplished using standard instru-mentation, measurements of forces with high resolution are not straightforward. This is because a rather stiff cantilever (with a typical spring constant of ~50 N m−1) is typically required to break the Au point contact that is first formed between the tip and sub-strate, before the molecular junctions are created. The force reso-lution is then limited by the smallest deflection of the cantilever that can be measured. With a custom-designed system24 our group has achieved a cantilever displacement resolution of ~2 pm (com-pare with Au atomic diameter of ~280 pm) using an optical detec-tion scheme, allowing the force noise floor of the AFM set-up to be as low as 0.1 nN even with these stiff cantilevers (Fig. 2e). With this system, and a novel analysis technique using two-dimensional force–displacement histograms as illustrated in Fig. 2f, we have been able to systematically probe the influence of the chemical linker group44,45 and the molecular backbone46 on single-molecule junction rupture force as illustrated in Fig. 2g.Significant future opportunities with force measurements exist for investigations that go beyond characterizations of the junc-tion rupture force. In two independent reports, one by our group47 and another by Wagner et al.48, force measurements were used to quantitatively measure the contribution of van der Waals interac-tions at the single-molecule level. Wagner et al. used the stiffness data from the lifting of PTCDA molecules on a Au(111) surface, and fitted it to the stiffness calculated from model potentials to estimate the contribution of the various interactions between the molecule and the surface48. By measuring force and conductance across single 4,4’-bipyridine molecules attached to Au electrodes, we were able to directly quantify the contribution of van der Waals interactions to single-molecule-junction stiffness and rupture force47. These experimental measurements can help benchmark the several theoretical frameworks currently under development aiming to reliably capture van der Waals interactions at metal/ organic interfaces due to their importance in diverse areas includ-ing catalysis, electronic devices and self-assembly.In most of the experiments mentioned thus far, the measured forces were typically used as a secondary probe of junction prop-erties, instead relying on the junction conductance as the primary signature for the formation of the junction. However, as is the case in large biological molecules49, forces measured across single-mol-ecule junctions can also provide the primary signature, thereby making it possible to characterize non-conducting molecules that nonetheless do form junctions. Furthermore, molecules pos-sess many internal degrees of motion (including vibrations and rotations) that can directly influence the electronic transport50, and the measurement of forces with such molecules can open up new avenues for mechanochemistry51. This potential of using force measurements to elucidate the fundamentals of electronic transport and binding interactions at the single-molecule level is prompting new activity in this area of research52–54. Optoelectronics and optical spectroscopyAddressing optical properties and understanding their influence on electronic transport in individual molecular-scale devices, col-lectively referred to as ‘molecular optoelectronics’, is an area with potentially important applications55. However, the fundamental mismatch between the optical (typically, approximately at the micrometre scale) and molecular-length scales has historically presented a barrier to experimental investigations. The motiva-tions for single-molecule optoelectronic studies are twofold: first, optical spectroscopies (especially Raman spectroscopy) could lead to a significantly better characterization of the local junction structure. The nanostructured metallic electrodes used to real-ize single-molecule junctions are coincidentally some of the best candidates for local field enhancement due to plasmons (coupled excitations of surface electrons and incident photons). This there-fore provides an excellent opportunity for understanding the interaction of plasmons with molecules at the nanoscale. Second, controlling the electronic transport properties using light as an external stimulus has long been sought as an attractive alternative to a molecular-scale field-effect transistor.Two independent groups have recently demonstrated simulta-neous optical and electrical measurements on molecular junctions with the aim of providing structural information using an optical probe. First, Ward et al.56 used Au nanogaps formed by electromi-gration57 to create molecular junctions with a few molecules. They then irradiated these junctions with a laser operating at a wavelength that is close to the plasmon resonance of these Au nanogaps to observe a Raman signal attributable to the molecules58 (Fig. 3a). As shown in Fig. 3b, they observed correlations between the intensity of the Raman features and magnitude of the junction conductance, providing direct evidence that Raman signatures could be used to identify junction structures. They later extended this experimental approach to estimate vibrational and electronic heating in molecu-lar junctions59. For this work, they measured the ratio of the Raman Stokes and anti-Stokes intensities, which were then related to the junction temperature as a function of the applied bias voltage. They found that the anti-Stokes intensity changed with bias voltage while the Stokes intensity remained constant, indicating that the effective temperature of the Raman-active mode was affected by passing cur-rent through the junction60. Interestingly, Ward et al. found that the vibrational mode temperatures exceeded several hundred kelvin, whereas earlier work by Tao and co-workers, who used models for junction rupture derived from biomolecule research, had indicated a much smaller value (~10 K) for electronic heating61. Whether this high temperature determined from the ratio of the anti-Stokes to Stokes intensities indicates that the electronic temperature is also similarly elevated is still being debated55, however, one can definitely conclude that such measurements under a high bias (few hundred millivolts) are clearly in a non-equilibrium transport regime, and much more research needs to be performed to understand the details of electronic heating.Concurrently, Liu et al.62 used the STM-based break-junction technique8 and combined this with Raman spectroscopy to per-form simultaneous conductance and Raman measurements on single-molecule junctions formed between a Au STM tip and a Au(111) substrate. They coupled a laser to a molecular junction as shown in Fig. 3c with a 4,4’-bipyridine molecule bridging the STM tip (top) and the substrate (bottom). Pyridines show clear surface-enhanced Raman signatures on metal58, and 4,4’-bipy-ridine is known to form single-molecule junctions in the STM break-junction set-up8,15. Similar to the study of Ward et al.56, Liu et al.62 found that conducting molecular junctions had a Raman signature that was distinct from the broken molecu-lar junctions. Furthermore, the authors studied the spectra of 4,4’-bipyridine at different bias voltages, ranging from 10 to 800 mV, and reported a reversible splitting of the 1,609 cm–1 peak (Fig. 3d). Because this Raman signature is due to a ring-stretching mode, they interpreted this splitting as arising from the break-ing of the degeneracy between the rings connected to the source and drain electrodes at high biases (Fig. 3c). Innovative experi-ments such as these have demonstrated that there is new physics to be learned through optical probing of molecular junctions, and are initiating further interest in understanding the effect of local structure and vibrational effects on electronic transport63. Experiments that probe electroluminescence — photon emis-sion induced by a tunnelling current — in these types of molec-ular junction can also offer insight into structure–conductance correlations. Ho and co-workers have demonstrated simultaneous measurement of differential conductance and photon emissionDOI: 10.1038/NNANO.2013.91from individual molecules at a submolecular-length scale using an STM 64,65. Instead of depositing molecules directly on a metal sur-face, they used an insulating layer to decouple the molecule from the metal 64,65 (Fig. 3e). This critical factor, combined with the vac-uum gap with the STM tip, ensures that the metal electrodes do not quench the radiated photons, and therefore the emitted photons carry molecular fingerprints. Indeed, the experimental observation of molecular electroluminescence of C 60 monolayers on Au(110) by Berndt et al.66 was later attributed to plasmon-mediated emission of the metallic electrodes, indirectly modulated by the molecule 67. The challenge of finding the correct insulator–molecule combination and performing the experiments at low temperature makes electro-luminescence relatively uncommon compared with the numerous Raman studies; however, progress is being made on both theoretical and experimental fronts to understand and exploit emission pro-cesses in single-molecule junctions 68.Beyond measurements of the Raman spectra of molecular junctions, light could be used to control transport in junctions formed with photochromic molecular backbones that occur in two (or more) stable and optically accessible states. Some common examples include azobenzene derivatives, which occur in a cis or trans form, as well as diarylene compounds that can be switched between a conducting conjugated form and a non-conducting cross-conjugated form 69. Experiments probing the conductance changes in molecular devices formed with such compounds have been reviewed in depth elsewhere 70,71. However, in the single-mol-ecule context, there are relatively few examples of optical modula-tion of conductance. To a large extent, this is due to the fact that although many molecular systems are known to switch reliably in solution, contact to metallic electrodes can dramatically alter switching properties, presenting a significant challenge to experi-ments at the single-molecule level.Two recent experiments have attempted to overcome this chal-lenge and have probed conductance changes in single-molecule junctions while simultaneously illuminating the junctions with visible light 72,73. Battacharyya et al.72 used a porphyrin-C 60 ‘dyad’ molecule deposited on an indium tin oxide (I TO) substrate to demonstrate the light-induced creation of an excited-state mol-ecule with a different conductance. The unconventional transpar-ent ITO electrode was chosen to provide optical access while also acting as a conducting electrode. The porphyrin segment of the molecule was the chromophore, whereas the C 60 segment served as the electron acceptor. The authors found, surprisingly, that the charge-separated molecule had a much longer lifetime on ITO than in solution. I n the break-junction experiments, the illuminated junctions showed a conductance feature that was absent without1 μm Raman shift (cm –1)1,609 cm –1(–)Source 1,609 cm–1Drain (+)Low voltage High voltageMgPNiAl(110)STM tip (Ag)VacuumThin alumina 1.4 1.5 1.6 1.701020 3040200400Photon energy (eV)3.00 V 2.90 V 2.80 V 2.70 V 2.60 V2.55 V 2.50 VP h o t o n c o u n t s (a .u .)888 829 777731Wavelength (nm)Oxideacebd f Raman intensity (CCD counts)1,5001,00050000.40.30.20.10.01,590 cm −11,498 cm −1d I /d V (μA V –1)1,609 cm –11,631 cm–11 μm1 μmTime (s)Figure 3 | Simultaneous studies of optical effects and transport. a , A scanning electron micrograph (left) of an electromigrated Au junction (light contrast) lithographically defined on a Si substrate (darker contrast). The nanoscale gap results in a ‘hot spot’ where Raman signals are enhanced, as seen in the optical image (right). b , Simultaneously measured differential conductance (black, bottom) and amplitudes of two molecular Raman features (blue traces, middle and top) as a function of time in a p-mercaptoaniline junction. c , Schematic representation of a bipyridine junction formed between a Au STM tip and a Au(111) substrate, where the tip enhancement from the atomically sharp STM tip results in a large enhancement of the Raman signal. d , The measured Raman spectra as a function of applied bias indicate breaking of symmetry in the bound molecule. e , Schematic representation of a Mg-porphyrin (MgP) molecule sandwiched between a Ag STM tip and a NiAl(110) substrate. A subnanometre alumina insulating layer is a key factor in measuring the molecular electroluminescence, which would otherwise be overshadowed by the metallic substrate. f , Emission spectra of a single Mg-porphyrin molecule as a function of bias voltage (data is vertically offset for clarity). At high biases, individual vibronic peaks become apparent. The spectra from a bare oxide layer (grey) is shown for reference. Figure reproduced with permission from: a ,b , ref. 56, © 2008 ACS; c ,d , ref. 62, © 2011 NPG; e ,f , ref. 65, © 2008 APS.DOI: 10.1038/NNANO.2013.91light, which the authors assigned to the charge-separated state. In another approach, Lara-Avila et al.73 have reported investigations of a dihydroazulene (DHA)/vinylheptafulvene (VHF) molecule switch, utilizing nanofabricated gaps to perform measurements of Au–DHA–Au single-molecule junctions. Based on the early work by Daub et al.74, DHA was known to switch to VHF under illumina-tion by 353-nm light and switch back to DHA thermally. In three of four devices, the authors observed a conductance increase after irradiating for a period of 10–20 min. In one of those three devices, they also reported reversible switching after a few hours. Although much more detailed studies are needed to establish the reliability of optical single-molecule switches, these experiments provide new platforms to perform in situ investigations of single-molecule con-ductance under illumination.We conclude this section by briefly pointing to the rapid pro-gress occurring in the development of optical probes at the single-molecule scale, which is also motivated by the tremendous interest in plasmonics and nano-optics. As mentioned previously, light can be coupled into nanoscale gaps, overcoming experimental chal-lenges such as local heating. Banerjee et al.75 have exploited these concepts to demonstrate plasmon-induced electrical conduction in a network of Au nanoparticles that form metal–molecule–metal junctions between them (Fig. 3f). Although not a single-molecule measurement, the control of molecular conductance through plas-monic coupling can benefit tremendously from the diverse set of new concepts under development in this area, such as nanofabri-cated transmission lines 76, adiabatic focusing of surface plasmons, electrical excitation of surface plasmons and nanoparticle optical antennas. The convergence of plasmonics and electronics at the fundamental atomic- and molecular-length scales can be expected to provide significant opportunities for new studies of light–mat-ter interaction 77–79.Thermoelectric characterization of single-molecule junctions Understanding the electronic response to heating in a single-mole-cule junction is not only of basic scientific interest; it can have a tech-nological impact by improving our ability to convert wasted heat into usable electricity through the thermoelectric effect, where a temper-ature difference between two sides of a device induces a voltage drop across it. The efficiency of such a device depends on its thermopower (S ; also known as the Seebeck coefficient), its electric and thermal conductivity 80. Strategies for increasing the efficiency of thermoelec-tric devices turned to nanoscale devices a decade ago 81, where one could, in principle, increase the electronic conductivity and ther-mopower while independently minimizing the thermal conductiv-ity 82. This has motivated the need for a fundamental understandingof thermoelectrics at the single-molecule level 83, and in particular, the measurement of the Seebeck coefficient in such junctions. The Seebeck coefficient, S = −(ΔV /ΔT )|I = 0, determines the magnitude of the voltage developed across the junction when a temperature dif-ference ΔT is applied, as illustrated in Fig. 4a; this definition holds both for bulk devices and for single-molecule junctions. If an addi-tional external voltage ΔV exists across the junction, then the cur-rent I through the junction is given by I = G ΔV + GS ΔT where G is the junction conductance 83. Transport through molecular junctions is typically in the coherent regime where conductance, which is pro-portional to the electronic transmission probability, is given by the Landauer formula 84. The Seebeck coefficient at zero applied voltage is then related to the derivative of the transmission probability at the metal Fermi energy (in the off-resonance limit), with, S = −∂E ∂ln( (E ))π2k 2B T E 3ewhere k B is the Boltzmann constant, e is the charge of the electron, T (E ) is the energy-dependent transmission function and E F is the Fermi energy. When the transmission function for the junction takes on a simple Lorentzian form 85, and transport is in the off-resonance limit, the sign of S can be used to deduce the nature of charge carriers in molecular junctions. In such cases, a positive S results from hole transport through the highest occupied molecu-lar orbital (HOMO) whereas a negative S indicates electron trans-port through the lowest unoccupied molecular orbital (LUMO). Much work has been performed on investigating the low-bias con-ductance of molecular junctions using a variety of chemical linker groups 86–89, which, in principle, can change the nature of charge carriers through the junction. Molecular junction thermopower measurements can thus be used to determine the nature of charge carriers, correlating the backbone and linker chemistry with elec-tronic aspects of conduction.Experimental measurements of S and conductance were first reported by Ludoph and Ruitenbeek 90 in Au point contacts at liquid helium temperatures. This work provided a method to carry out thermoelectric measurements on molecular junctions. Reddy et al.91 implemented a similar technique in the STM geome-try to measure S of molecular junctions, although due to electronic limitations, they could not simultaneously measure conductance. They used thiol-terminated oligophenyls with 1-3-benzene units and found a positive S that increased with increasing molecular length (Fig. 4b). These pioneering experiments allowed the iden-tification of hole transport through thiol-terminated molecular junctions, while also introducing a method to quantify S from statistically significant datasets. Following this work, our group measured the thermoelectric current through a molecular junction held under zero external bias voltage to determine S and the con-ductance through the same junction at a finite bias to determine G (ref. 92). Our measurements showed that amine-terminated mol-ecules conduct through the HOMO whereas pyridine-terminatedmolecules conduct through the LUMO (Fig. 4b) in good agree-ment with calculations.S has now been measured on a variety of molecular junctionsdemonstrating both hole and electron transport 91–95. Although the magnitude of S measured for molecular junctions is small, the fact that it can be tuned by changing the molecule makes these experiments interesting from a scientific perspective. Future work on the measurements of the thermal conductance at the molecu-lar level can be expected to establish a relation between chemical structure and the figure of merit, which defines the thermoelec-tric efficiencies of such devices and determines their viability for practical applications.SpintronicsWhereas most of the explorations of metal–molecule–metal junc-tions have been motivated by the quest for the ultimate minia-turization of electronic components, the quantum-mechanical aspects that are inherent to single-molecule junctions are inspir-ing entirely new device concepts with no classical analogues. In this section, we review recent experiments that demonstrate the capability of controlling spin (both electronic and nuclear) in single-molecule devices 96. The early experiments by the groups of McEuen and Ralph 97, and Park 98 in 2002 explored spin-depend-ent transport and the Kondo effect in single-molecule devices, and this topic has recently been reviewed in detail by Scott and Natelson 99. Here, we focus on new types of experiment that are attempting to control the spin state of a molecule or of the elec-trons flowing through the molecular junction. These studies aremotivated by the appeal of miniaturization and coherent trans-port afforded by molecular electronics, combined with the great potential of spintronics to create devices for data storage and quan-tum computation 100. The experimental platforms for conducting DOI: 10.1038/NNANO.2013.91。

自由能之天线系统

自由能之天线系统天线系统, 自由能pdf格式英文原文下载：自由能之天线系统google翻译自由能之天线系统如下：人们普遍认为，天线是不是能够搜集多少权力。

流行的概念是，唯一的电力供应是低级别从遥远的无线电发射器的无线电波，虽然它的确，无线电波可以挑选进行航空up ，权力的真正源头不无线电发射机。

例如，我们将寻求在从赫尔曼Plauston任何信息，他认为他的这次访问没有产生一个搒购物中心不是一个功率超过100千瓦以上，？系统天线系统。

托马斯亨利马里向观众展示了他的系统反复，在高达50千瓦的水平拉。

这些电源水平是不生产的电台信号。

尼古拉特斯拉抯系统。

尼古拉特斯拉产生了空中装置，值得一提。

这是5月21日申请专利1901年是主要的辐射能量的使用情况揂pparatus ？美国专利号码685957 。

该装置看似简单，但特斯拉指出，电容需要搊f 大量静电容量呢，他建议使用最优质的云母建造它作为1897年在他的专利号577671 。

该电路通过一个绝缘的绘制，有光泽的金属板的力量。

绝缘可喷涂在塑料。

盘越大，就越能回升。

越高板升高，更大的回升。

这种特斯拉抯系统拿起能源白天和黑夜。

电容得到被控和振动开关多次放电电容为降压变压器。

变压器降低电压，并提出了当前可用的输出功率，然后利用电力负荷。

看来，这可能主要是从器件的静电，一些人认为是零点能源领域的体现。

特斯拉抯设备操作时，很可能由马达驱动的威姆斯赫斯特机，而不是一个大的空中板喂食。

家建威姆斯赫斯特设备的详细资料在书中提供慔omemade闪电？由RA福特，书号0-07-021528-6 。

但是，应该认识到，特斯拉描述两种不同形式的能量回升。

首先是静电，拿起从非常轻微与零点能透过它流场接机板互动，和其他正在回升的动力辐射能活动，通常由雷击。

在一个偶然一瞥，一般人不会认为是一个可行的能源来源闪电，但事实并非如此，因为有大约200雷击每秒- 主要是在热带-与人们普遍不理解的是，他们辐射能事件及其影响即刻感受到作为传输地球上任何地方通过零点能在任何领域的瞬时距离。

A New Approach for Filtering Nonlinear Systems

computational overhead as the number of calculations demanded for the generation of the Jacobian and the predictions of state estimate and covariance are large. In this paper we describe a new approach to generalising the Kalman ﬁlter to systems with nonlinear state transition and observation models. In Section 2 we describe the basic ﬁltering problem and the notation used in this paper. In Section 3 we describe the new ﬁlter. The fourth section presents a summary of the theoretical analysis of the performance of the new ﬁlter against that of the EKF. In Section 5 we demonstrate the new ﬁlter in a highly nonlinear application and we conclude with a discussion of the implications of this new ﬁlter1
Tቤተ መጻሕፍቲ ባይዱ
= = =
δij Q(i), δij R(i), 0, ∀i, j.
(3) (4) (5)

水稻耐冷害图位克隆COLD1 Confers Chilling Tolerance in Rice

Highlights
d
QTL COLD1 regulates G-protein signaling to confer chilling tolerance in rice SNP2 in COLD1jap/ind enhances its ability to activate Gprotein a GTPase COLD1 interacts with G protein to activate the Ca2+ channel for temperature sensing The SNP2-containing allele is selected during japonica rice domestication
INTRODUCTION Rice, which is both a model plant and one that feeds more than half of the world’s population (Sasaki and Burr, 2000), evolved in tropical and subtropical areas and is sensitive to chilling stress (Kovach et al., 2007; Saito et al., 2001; Sang and Ge, 2007). Extreme temperature thus represents a key factor limiting global rice plant distribution. Super hybrid rice cultivars produce high yields in tropical or subtropical climates but are frequently harmed by chilling. Therefore, molecular genetic tools have been urgently sought to improve rice chilling tolerance in order to maintain rice production in current regions and expand it into northern areas with lower yearly temperatures. Asian cultivated rice (Oryza sativa) was domesticated from its wild relatives Oryza nivara and O. ruﬁpogon. It consists of two

AVisuallyServoedMEMSManipulator

A Visually Servoed MEMS ManipulatorYu Sun,Michael A.Greminger,David P.Potasek,and Bradley J.Nelson Department of Mechanical EngineeringUniversity of MinnesotaMN55455,USA*************.eduAbstract.This paper reports on a visual servoing system capable of2DOF nanoposition-ing using a novel multi-axis electrostatic MEMS(MicroElectroMechanical System)device. The high aspect ratio micromanipulator was fabricated using a high yield process with Deep Reactive Ion Etching(DRIE)on Silicon-On-Insulator(SOI)wafers,which produces larger electrostatic forces and requires lower actuation voltages compared to most existing elec-trostatic microactuators.A real-time sub-pixel parameterized feature tracking algorithm of resolution is incorporated into the visual servoing loop.The resulting system is capable of visually servoing to a precision of in two axes using the inexpensive bulk micromachined multi-axis electrostatic micromanipulator and standard microscope op-tics with a CCD camera.Potential applications of the system are in the manipulation of subcellular structures within biological cells,and microassembly of hybrid MEMS devices. 1IntroductionMany microrobotic applications require multi-degree-of-freedom positioning at mi-cro and nanoscales.Actuation technologies capable of providing motion at this scale include piezoactuators[1],microstepping motors[2],highly geared electromagnetic servomotors[3],and Lorentz force-type actuators such as voice coil motors[4]. Typically these positioning systems are expensive and require extensive calibra-tion procedures.This paper reports on a visual servoing system capable of2DOF nanopositioning using a novel multi-axis electrostatic MEMS(MicroElectroMe-chanical System)manipulator.The3-D high aspect ratio transverse comb drive micromanipulator,formed by Deep Reactive Ion Etching(DRIE)on Silicon-On-Insulator(SOI)wafers,produces two orders of magnitude larger electrostatic forces than surface micromachined lateral comb drive microactuators[5][6][7][8][9][10]while the required actuation voltages are approximately ten times smaller.By removing the substrate beneath the comb drive structure,this reported micromanipulator does not require the use of a ground plane as a typical electrostatic microactuator,and the movable structure does not suffer from the leviation effect[11],i.e.,an unbalanced electricﬁled distribution forces the structure to move out of the actuation plane.When a micromanipulation system is used in micromanipulation,such as mi-crorobotic surgery or cell manipulation,precise positioning is required.To increase the positioning precision,a sub-pixel vision tracking algorithm of resolu-tion[12]was developed to provide feedback in the visual servo loop.B. Siciliano and P. Dario (Eds.): Experimental Robotics VIII, STAR 5, pp. 255--264, 2003Springer-Verlag Berlin Heidelberg 2003256Y.Sun et al.The resulting system is capable of visually servoing to a precision of us-ing a novel and inexpensive bulk micromachined multi-axis electrostatic manipulator and standard microscope optics with a CCD camera.Minimal system calibration is required.Potential applications of the device are in the manipulation of subcellular structures within biological cells[13]shown in Fig.1,microassembly of hybrid MEMS devices,and manipulation of large molecules such as DNA or proteins.Fig.1.Microrobotic pronuclei DNA injection of a mouse embryo2MEMS-based electrostatic micromanipulator2.1Manipulator designThe design of the2DOF electrostatic manipulator is based on the use of offset electrostatic interdigitated comb drives and curved springs that serve asﬂexure hinges to allow planar motion in and.Fig.2shows the solid model of the micromanipulator design.The constrained outer frame and the inner movable plate are connected by four curved springs.When a voltage difference is applied on comb drive1and comb drive4,the generated electrostatic force causes the movable plate to move in,resulting in the movement of the manipulator for micromanipulation.To create motion along,comb drive2 and comb drive5are conﬁgured to be orthogonal to the comb drives in.The offset comb drive model is shown in Fig.3,where is the displacement of the movableﬁngers from the equilibrium position.The electrostatic force acting on the movable combﬁngers isA Visually Servoed MEMS Manipulator257Fig.2.Solid model of the two-axis micromanipulator(1) where is the number of parallel capacitor pairs;is the dielectric constant for the material(for air);is the permittivity of free space;;;is the overlapping area of eachﬁnger pair;and is the applied actuation voltage.The spring dimensions determine the system stiffness.Structural analysis was performed numerically.The force-deﬂection model of the spring in both and is(2) where is the deﬂection;is the force acting on the springs;is the YoungŠs modulus of silicon;is the width of the springs;is the height of the springs;in,and in.Finite element simulations of structural and electrostatic properties were per-formed in order to ensure that a range of motion of can be achieved in both and with actuation voltages less than in and in.2.2MicrofabricationThe main fabrication steps are illustrated in Fig.4.Fig.5shows the completed device.258Y.Sun et al.Fig.3.Offset comb drive modelStep A.Start from a double polished P-type wafer with crystal orientation of <100>.Step B.LPCVD(Low Pressure Chemical Vapor Deposition)1SiO.Step C.Fusion bond the wafer with SiO with another P-type wafer.Step D.CMP(Chemical Mechanical Polishing)the top wafer down to50;this forms an SOI wafer.Step E.E-beam evaporate Al to form Ohmic contacts;Liftoff to pattern Al.Step F.DRIE(Deep Reactive Ion Etching)to form the features on the back side such as the outer frame and movable plates.The buried1SiO layer acts as an etch stop layer and also as an insulator between the capacitors.Step G.DRIE the top side to form capacitive combﬁngers and curved springs.Step H.RIE(Reactive Ion Etching)to remove the buried SiO layer;This releases the devices and ends the fabrication process.The released devices were then wire bonded.A yield of86.4%has been achieved without signiﬁcant process optimization.3Nanometer vision tracking algorithm3.1The template matching algorithmIn traditional template matching algorithms[14],objects are typically located to one pixel resolution and no change in orientation is assumed.To overcome these limitations,the template and the image are represented as a list of edge vertices obtained by the Canny edge operator[15]rather than a2D array of pixels.The template vertices and image vertices are related by the homogeneous transformation given by(3)A Visually Servoed MEMS Manipulator259Fig.4.Fabrication sequenceFig.5.SEM micrograph of the device260Y.Sun et al.where is a template vertex coordinate with respect to the-coordinate sys-tem;is the template vertex coordinate with respect to the-coordinate system;and is a homogeneous transformation matrix.The error function is given by(4)where is the scale factor of the template about its origin;is the rotation of the template about its origin;and are the and components of the translation of the origin of the template coordinate system with respect to the image coordinate system;are the coordinates the th edge pixel of the template transformed by(3);are the coordinates of the edge pixel in the image that is nearest to the point;and is the number of edge pixels in the template.By minimizing(4),the values of,,,and that best match the image in a least squares sense can be determined.3.2Performance optimizationsThe error function(4)is minimized by aﬁrst-order multi-variable minimization technique called the Broydon-Fletcher-Goldfarb-Shanno(BFGS)method[16].Like the steepest decent method,the BFGS method is a gradient based minimization technique.The BFGS method differs from the steepest decent method in that it uses information from previous iterations in the choice of a new search direction giving it faster convergence rates than the steepest decent method.The error function(4)is computationally expensive because for each template vertex it is necessary to locate the image vertex that is nearest to it.The data structure employed to organize the pixel data is the KD-Tree[17].A KD-Tree canﬁnd the nearest image vertex with operations as opposed to the operations required toﬁnd the nearest pixel without using a spacial data structure,where is the number of vertex points in the image.3.3Resolution of the template matching algorithmWhen using a50X objective lens with0.42NA,the template matching algorithm is capable of tracking position to within a1uncertainty interval of using the least squares error measure(4).By using the least squares error measure,a normal error distribution is assumed[18],which may not always be the case for a microscopy image.The following robust error measure based on the Cauchy distribution[19]is used(5)where is the distance from each template pixel to the nearest image ing the Cauchy estimator,the1uncertainty interval of the tracking algorithm wasA Visually Servoed MEMS Manipulator261 reduced to.This gain in resolution by using a robust error measure can be attributed to the existence of noise in the image with a non-normal distribution.4Visual servoingThe two-axis micromanipulator is modelled individually in and as two spring-mass-damper systems.(6) where.The system in and consists of linear equations of motionand nonlinear electrostatic forces.In this section,the variables,,,,,, and coincide with the ones deﬁned for(1).The approach to visual servoing is a position-based one.A proportional-integral ()PI visual servoing control architecture with a feedforward component as shown in Fig.6,was implemented.The feedforward component, which signiﬁcantly increases system response and reduces system overshoot,is given as(7) Table1lists the recognized system stiffness from calibration and the results fromFig.6.Visual servoing scheme for nanopositioningﬁnite element structural analysis.The measurement of the motion of the features,denoted in Fig.6by, must be done continuously and quickly.The nanometer visual tracking algorithm operates at a full to measure this motion.Fig.7shows the template used to track the manipulator tip.A tracking resolution of was achieved.262Y.Sun et al.Table1.System stiffness determined from calibration and simulationstiffness in()in()simulation 3.31110.75calibration 2.81104.10Fig.7.Template used to track manipulator tipThe feedforward section increases system response.The visual servoing framework allows the device to be positioned precisely despite the nonlinear characteristics exhibited by the electrostatic actuator and the fact that signiﬁcant hysteresis inthe device occurs when the comb drive is overdriven and capacitor pull-in occurs. Despite a control rate of which reduces disturbance rejection capability,results demonstrate that a controllable motion range of along and can be obtained to a precision of limited by the tracking algorithm and the microscope optics,which consisted of a50X objective with0.42NA.Another factor limiting thepositioning precision is environmental vibration,though aﬂoating table was used to reduce this.Using the visual servoing framework,desired system response can be obtained forthe micromanipulation system.For example,when the system is used in microrobotic surgery and cell manipulation,an overdamped system response is desirable.Fig.8 shows system step responses along two axes.5ConclusionsExperimental results show that the novel inexpensive MEMS micromanipulator is visually servoed to a precision of with voltages ranging from in and in as predicted by FEA.The vision tracking algorithm demon-strates precision with a variance half that of sum-of-squared-differences least-squares trackers.Potential applications of the system are in the manipulation of subcellular structures within biological cells,and microassembly of hybrid MEMS devices.A Visually Servoed MEMS Manipulator263Fig.8.Step response of the system;(a)in;(b)inReferences1.Szita N.,Sutter R.,Dual J.,and Buser R.A.(2001)A micropipettor with integratedsensors.Sensors and Actuators A89,No.1-2,112–1182.Navathe C.P.,Dashora B.L.,Roy U.N.,Singh R.,Maheswari S.,and Kukreja L.M.(1998)Control system for Langmuir-Blodgett film deposition set-up based on microstepping.Measurement Science and Technology9,No.3,540–5413.Barth O.(2000)Harmonic piezodrive miniaturized servo motor.Mechatronics10,No.4-5,545–5544.Molenaar A.,Zaaijer E.H.,and Beek H.F.(1998)A novel long stroke planar magneticbearing actuator.The4th International Conference on Motion and Vibration Control, Zurich,Switzerland,1071–10765.Harness T.and Syms R.R.A.(2000)Characteristic modes of electrostatic comb-driveX-Y microactuators.J.Micromech.Microeng.10,7–146.Indermuehle P.F.,Linder C.,Brugger J.,Jaecklin V.P.,and Rooij N.F.(1994)Designand fabrication of and overhanging xy-microactuator with integrated tip for scanning surface profiling.Sensor and Actuators A43346–3507.Indermuhle P.F.,Jaecklin V.P.,Brugger J.,Linder C.,and Rooij N.F.(1995)AFMimaging with an XY-micropostioner with integrated tip.Sensors and Actuators A46-47 562–5658.Hirano T.,Furuhata T.,Gabriel K.J.,and Fujita H.(1992)Design,fabrication,and oper-ation of submicron gap comb-drive microactuators.Journal of Microelectromechanical Systems1,No.1,52–599.Tang W.C.,Nguyen T.H.,Judy M.W.,and Howe R.T.(1990)Electrostatic-comb driveof lateral polysilicon resonators.Sensors and Actuators A21-23328–33110.Yeh J.L.A.,Jiang H.,and Tien N.C.(1999)Integrated polysilicon and DRIE bulk siliconmicromachining for an electrostatic torsional actuator.Journal of Microelectromechan-ical Systems8,No.4,456–46511.Tang W.C.,Lim M.G.,and Howe R.T.(1992)Electrostatic comb drive levitation andcontrol method.Journal of Microelectromechanical systems1,No.4,170–17812.Greminger M.A.and Nelson B.J.(2001)Vision-based force sensing at nanonewtonscales.SPIE Microrobotics and Microassembly III,78–89264Y.Sun et al.13.Sun Y.and Nelson B.J.(2001)Microrobotic cell injection.IEEE International Confer-ence on Robotics and Automation1,620–62514.Pratt W.(1991)Digital Image Processing.John Wiley and Sons,New York15.Canny J.A.(1986)A computational approach to edge detection.IEEE Transactions onPattern Analysis and Machine Intelligence,8,No.6,679–69816.Vanderplaats G.(1984)Numerical Optimization Techniques for Engineering Design.McGraw-Hill,New York17.Samet H.(1990)The Design and Analysis of Spatial Data Structures.Addison-Wesley,Reading,MA.18.Draper N.R.(1998)Applied Regression Analysis,3rd Edition.John Wiley and Sons,New York19.Stewart C.V.(1999)Robust parameter estimation in computer vision.SIAM Review,41,No.3,513–537。

ARM11_Microarchitecture_White_Paper 的翻译

ARM11_Microarchitecture_White_Paper.docx 的翻译ARM11_Microarchitecture_White_Paper.docx 的翻译The ARM11 ™Microarchitecture ARM11™微April 2002 2002年4月The ARM11 ™Microarchitecture ARM11™微David Cormie 大卫CormieARM Ltd ARM公司The ARM11 microarchitecture is the first implementation of the ARMv6instruction set 的ARM11微架构是在ARMv6指令集的第一个实施architecture, and forms the basis of a new family of ARM11 cores.架构，并形成一个新的家庭ARM11内核的基础上。

The microarchitecture 微架构is the detailed definition of the internal design, and hardware resources,which supports 详细定义的内部设计，硬件资源，支持the ARMv6 architectural specification. ARMv6的建筑规范。

The key objective in developing the ARM11 microarchitecture was to deliverhigh 在发展中国家的ARM11微架构的主要目的是提供高performance at low power and low cost. 在低功耗和低成本的性能。

This paper examines thespecific features of the 本文探讨的具体特点new microarchitecture, and explains why the design meets the needs of next-generation 新的微架构，并解释了为什么设计满足下一代的需求wireless and portable consumer products. 无线和便携式消费电子产品。

Armchair for formation and correction of human spi

专利名称：Armchair for formation and correction ofhuman spine发明人：Michael V. Baranov,Vladimir M.Baranov,Stanislav Bezugly申请号：US11103400申请日：20050408公开号：US20060238006A1公开日：20061026专利内容由知识产权出版社提供专利附图：摘要：An armchair includes a base with a seat placed upon it, a backrest, the arm rest,and a feet platform with adjustable feet fixation limiters. Said seat is able to turn inhorizontal flatness and to regulate its height. Said backrest includes at least two back supports, which are independent and can be regulated and fixated in the vertical and horizontal directions. The seat belt attached to the backrest is supposed to fixate the correct torso positioning of the user's spine relatively to the armchair backrest. The arm supports (elbow-rests) are connected with the armchair seat and are regulated in the desired height and incline in vertical flatness. The feet, platform is attached to the base and equipped with the adjustable feet limiters to keep the user's feet from moving during his/her seat turning.申请人：Michael V. Baranov,Vladimir M. Baranov,Stanislav Bezugly地址：Brooklyn NY US,Flushing NY US,Staten Island NY US国籍：US,US,US更多信息请下载全文后查看。

Quasi-Two-Dimentional Modeling of the Self Gravitating Gas

2
relations of the QTDA method have been used: ∇2 Φ(r, z )ds = ∇Φ(r, z ) · ds = ∇ · A(r, z )ds = d dz d dz d dz dΦ(z ) dz
S S
S (z ) +
L(z )
S (z )
n · ∇Φ(r, z ) dl, cos ϑ
3
The QTD Model of the Weak Transverse Nonhomogeneity Approximation
The QTDA equations are the result of application of the QTDA method represented by (3) - (10) to equations of continuity, Poisson, and (2) in the system of coordinate related to the wave. In this model we studing the eﬀects related to the small perturbations of the physical values. According to this 3
there P is pressure, υ - thermal speed, Φ - gravitational potential, ρ - gas density, t - time, A = const. This system describes the ideal classic gas with self gravitation. In the system of coordinate related to the stationary wave the derivative of time disappear [1] from the system (4). An addition to (4) we’ll use also the radius component of the equation of motion multiplyed by ρ(z, r )r : 2 ∂P ∂Φ 1 ∂υr ρr +r = −ρr . (5) 2 ∂r ∂r ∂r

monoaminergictract 单胺能束

monoaminergictract 单胺能束下载提示：该文档是本店铺精心编制而成的，希望大家下载后，能够帮助大家解决实际问题。

文档下载后可定制修改，请根据实际需要进行调整和使用，谢谢!本店铺为大家提供各种类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by this editor. I hope that after you download it, it can help you solve practical problems. The document can be customized and modified after downloading, please adjust and use it according to actual needs, thank you! In addition, this shop provides you with various types of practical materials, such as educational essays, diary appreciation, sentence excerpts, ancient poems, classic articles, topic composition, work summary, word parsing, copy excerpts, other materials and so on, want to know different data formats and writing methods, please pay attention!单胺能束是神经系统中调节情绪、注意力和意识等功能的重要组成部分。

Small-Bowel Obstruction(小肠梗阻)

3. Strangulated obstruction indicates that blood flow is compromised, which may lead to intestinal ischemia, necrosis, and perforation.
4. Closed-loop obstruction occurs when a segment of bowel is obstructed at two points along its course, resulting in progressive accumulation of fluid in gas within the isolated loop, placing it at risk for volvulus and subsFindings
CT Findings
Figure 7: Images in an 81-year-old woman with nausea and vo miting. (a) Axial unenhanced CT scan shows dilated loops of ileum fille d with contrast material (arrow). Note the contrast material doe s not pass into decompressed distal loops of small bowel (arro whead). (b) Unenhanced axial CT scan at the level of the pubic symphy sis shows protrusion of ileum (arrow) into the obturator canal. (c) Unenhanced axial CT scan shows ileum trapped in the obtur ator canal between the obturator externus and pectineus muscl es (arrow). (d) Coronal reformation shows the herniated and obstructed ile um protruding into the obturator canal (arrow).

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。