An experimental study on variation of thermal fields during the deformation of a compressive en

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髋关节关节软骨负重区和非负重区力学性能的实验研究硕士论文

天津医科大学
硕士学位论文
髋关节关节软骨负重区和非负重区力学性能的实验研究
姓名：***
申请学位级别：硕士
专业：骨科学
指导教师：***
20060520
天津医科大学硕士学位论文第二部分２股骨头
股骨颈骨折（头颈型）
股骨头冠切面（关节软骨厚度从上之下逐渐变薄）
股骨头冠切面
天津医科大学硕士学位论文第三部分附图
１．对照组
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番红０染ＩＩ型胶原免疫组化染色
２．空气暴露组
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１小时２小时Ｍａｓｓｏｎ三色染色法
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１小时番红０染色
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林格氏液组关节软骨显微镜下观察
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科学实验的英语作文

科学实验的英语作文Scientific Experiment。

Scientific experiments are an essential part of the scientific process. They are conducted to test hypotheses, gather data, and draw conclusions about the natural world. Experiments can be conducted in a variety of ways, depending on the question being asked and the resources available.There are several key components of a scientific experiment. First, there is the hypothesis, which is a proposed explanation for a phenomenon. The hypothesis is then tested through an experiment, which involves manipulating one or more variables and observing the effects on the system being studied. The results of the experiment are then analyzed and used to draw conclusions about the hypothesis.One important aspect of scientific experiments is theuse of controls. Controls are variables that are kept constant throughout the experiment, so that any changes observed can be attributed to the manipulated variable. For example, if an experiment is testing the effect of a new fertilizer on plant growth, the amount of water, sunlight, and soil type should be kept constant for all plants in the experiment, except for the ones receiving the newfertilizer.Another important consideration in scientific experiments is the sample size. The sample size refers to the number of individuals or objects being studied. Alarger sample size generally leads to more reliable results, as it reduces the impact of random variation.In addition to these basic components, there are many other factors that can affect the outcome of a scientific experiment. These include the choice of experimental design, the accuracy of the measurements taken, and the potentialfor bias in the data analysis.Despite the many challenges involved in conductingscientific experiments, they remain a crucial tool for advancing our understanding of the natural world. Through careful observation, experimentation, and analysis, scientists are able to uncover new insights into the workings of the universe and develop innovative solutions to complex problems.In conclusion, scientific experiments are a vital component of the scientific process. They allow us to test hypotheses, gather data, and draw conclusions about the natural world. By carefully controlling variables, using appropriate sample sizes, and considering a range offactors that can affect the outcome, scientists are able to conduct experiments that yield reliable and meaningful results.。

Journal of Reinforced Plastics and Composites-2014-Geng-0731684413518619

Original ArticleComparison of drill wear mechanismbetween rotary ultrasonic ellipticalmachining and conventional drilling ofCFRPDaxi Geng1,Deyuan Zhang1,Y onggang Xu1,Fengtao He2andFuqiang Liu1AbstractCarbon fiber-reinforced plastic(CFRP)is widely used as aircraft structural components for its superior mechanical and physical properties.Meanwhile,the rotary ultrasonic elliptical machining(RUEM),as a new drilling method in which an elliptical ultrasonic vibration is imposed on the end of the drill,can reduce tool wear effectively.In this paper,we firstly presented an investigation on the wear mechanism of diamond core drill in RUEM of CFRP in comparison with the conventional drilling(CD).A series of drilling experiments were performed including the drilling force measurement,the observation of drill topographies,and machined hole surface.The experiment results indicated that the drill performance in RUEM of CFRP was improved significantly in comparison with that in CD.Because the length of steady region rised by 39%and the tool life increased by28%in RUEM than those in CD,respectively.With the observation of drill surface under a microscope,it was validated that less chip adhesion and more grain micro-fracture appeared in RUEM,which had a positive effect on the better drilling performance,such as lower drilling force,smoother hole surface.KeywordsCarbon fiber-reinforced plastic,rotary ultrasonic elliptical machining,diamond core drill wear,chip adhesion,grain micro-fractureIntroductionIn recent years,the demand for the CFRP composites is increasing greatly to meet the wide applications such as aircraft skin,wind turbine blades,robot structures and automotive parts due to their low density,high strength-to-weight ration,large stiﬀ-to-weight ratio, high chemical and corrosion resistance,and other superior properties.1,2The abrasivity of the CFRP causes severe damage to the cutting tool,not only shortening the tool life but also aﬀecting the surface quality.2So the cost-consuming and time-consuming machining process happens in CFRP machining.Drilling has been employed as the most frequent method on machining CFRP owing to the assemble need ofﬁxing the composite parts to other structures,3,4 such as joining the CFRP skin to the titanium alloy beams in aircraft wings assembly process.Meanwhile, many typical problems exist in drilling CFRP including short tool life,delamination,burrs,swelling,splinter-ing,ﬁber pullout,and low machining precision.The tool performance plays a dominant role in drilling pro-cess.In order to improve the performance of drilling tools,tools with diﬀerent geometry including twist drills,saw drills,mutifacet drills,candle stick drills, core-center drills,and diamond core drills were fabri-cated.4–9Furthermore,the cutting mode in which the drill tool was assisted by ultrasonic vibration could 1School of Mechanical Engineering and Automation,Beihang University, Beijing,China2Chengdu Aircraft Industrial(Group)Co.Ltd.,Chengdu,China Corresponding author:Daxi Geng,School of Mechanical Engineering and Automation,Beihang University,Beijing100191,China.Email:dxgeng@Journal of Reinforced Plasticsand Composites0(00)1–13!The Author(s)2014Reprints and permissions:/journalsPermissions.navDOI:10.1177/0731684413518619improve the tool performance signiﬁcantly in experi-ments,which indicated that the cutting mechanism was modiﬁed in this process.10Ultrasonic-assisted drilling has been applied in dif-ferent modes to develop cost-eﬀective and high surface quality drilling technology,which resulted in tool life extension and drilling force decrement.As a typical one-dimensional ultrasonic-assisted drilling(UEV), rotary ultrasonic machining(RUM)is adopted exten-sively,in which the ultrasonic vibration applied to the drill is generated in the direction vertical to the work-face.10–12Recently,RUM has been successfully used in drilling holes in CFRP.A comparison of RUM and twist drilling,eﬀects of variables on output variables and temperature,and a comparison of diﬀerent cooling conditions were studied.11,13–17However,the RUM coolant limited the RUM technology application in the aircraft assembly due to the high cost of the cutting ﬂuid deployment,the waste cuttingﬂuid treatment,the health and environment hazard.11,12,14In order to fur-ther enhance the machining eﬃciency and improve the quality of hole surface in ultrasonic-assisted drilling, Ma et al.proposed a two-dimensional UEV technique. He utilized a drill bit and a special aluminum alloy workpiece that ultrasonically vibrated in an elliptical mode vertical to the drill axial direction.18The investi-gation showed that the axial drilling force,the variation of the radial drilling force,and the chip thickness of drilling were reduced in UEV under dry condition. After then,the technique of UEV(later called rotary ultrasonic elliptical machining,RUEM)was success-fully applied to the machining of CFRP,and the via-bility of RUEM on CFRP was studied for theﬁrst time by Liu et al.12In the experiment,the diamond core drill vibrated ultrasonically in two directions by using an elliptical ultrasonic vibrator.Dry machining was used to avoid the problems related to cuttingﬂuids.The experimental results showed that,in comparison of CD,the tool wear and thrust force were signiﬁcantly reduced,and the hole precision as well as surface qual-ity was enhanced markedly.Therefore,RUEM was considered to be a new eﬀective method for CFRP dril-ling under dry condition.However,the core drill wear in RUEM of CFRP was simply measured by the wear size of core drill,and the analysis of the ultrasonic vibration eﬀect on tool wear was not conducted in this paper.As for the tool wear in RUM,the ratio of the removed material weight to the tool wear weight was often used to evaluate the speciﬁc tool wear.19The eﬀects of process parameters in RUM on speciﬁc tool wear were investigated experimentally,such as static load,ultrasonic vibration amplitude,diamond type, grit size,bond materials,strength,and so on.10,11,20 However,the conventional speciﬁc tool wear measurements can reveal little about the tool wear mechanism in RUM.Based on the microscope tech-niques used to investigate the wear mechanism of grind-ing wheel,Zeng et al.studied the diamond core drill wear in RUM of advanced ceramics by examining the drill surface under a digital microscope with magniﬁca-tion50.21Although there were a lot of investigations on the tool wear mechanism in both CD and RUM,few stu-dies were carried out to reveal the wear behavior in RUEM.It is well known that the investigation on the evolution of drill wear is essential to quantitatively evaluate the drill cutting ability.This paper,for the ﬁrst time in the literature,presented an experimental observation and analysis on tool wear in RUEM of CFRP.The experimental investigation was conducted to study the diamond core drill wear behavior by carry-ing out the RUEM operations on CFRP without cool-ant on an ultra-precision lathe.The drill surface topographies until losing the cutting ability were used to evaluate the tool wear evolution condition.In add-ition,in order to deeply understand the wear behavior in RUEM,the CD experimental works in the same drilling conditions were also conducted.Finally,the experiments results in RUEM were fully analyzed to investigate the wear mechanism of diamond core drill in comparison of that in CD.ExperimentExperimental set-upThe experimental set-up is shown in Figure1(a).It mainly consisted of an ultra-precision lathe(a Harding lathe by Harding Co.,Ltd.,NY,USA),an ultrasonic drilling unit,and a data acquisition system.The ultra-sonic drilling unit was composed of an elliptical ultra-sonic transducer,a power supply,and a slip ring which supplied electricity to the rotary ultrasonic transducer. Theﬁxture clamping the specimen was mounted on a3D dynamometerﬁxed to the lathe working platform.The ultrasonic elliptical transducer and vibration modes are shown in Figure1(b).The designed trans-ducer was a sandwiched piezoelectric structure which was composed of a diamond core drill,a front cylinder (titanium alloy),two groups of piezoelectric plates (PZTs),and a back cylinder(stainless steel).The bend-ing vibrations were incited by the two orthogonal groups of PZTs.When the alternating voltages were applied to the two groups of PZTs,respectively,with the same frequency and a phase shift,two ultrasonic bending vibrations were generated in x-and y-direc-tions simultaneously.The synthesis of the two bending vibrations generated an elliptical mode vibration in the x–y-plane at the end of the vibrator.As a diamond core2Journal of Reinforced Plastics and Composites0(00)drill was mounted onto the end of the transducer,the vibration amplitude of the diamond core drill tip was magniﬁed by the stepped horn and reached maximized value.The elliptical vibration locus is shown in Figure 1(c).Once a feed motion was provided to the specimen ﬁxed on the lathe platform,the diamond core drill held on the rotating spindle would remove the work material.In this case,as the elliptical ultrasonic vibration of the vibra-tor was applied,an RUEM operation was performed.Measurement procedure and conditionsRUEM experiments were performed on an experimental apparatus without coolant (i.e.dry machining).The dril-ling force was measured by a three-dimensional (3D)piezoelectric dynamometer (9256A1by Kistler Japan Co.,Ltd.,Winterthur,Switzerland),and the data acquisi-tion system is shown in Figure 1(a).The surface roughness of the drilled holes across the axial direction was obtained using a texture measuring instrument (Surfcom408A by Tokyo Seimitsu Co.Ltd.,Tokyo,Japan).In order to obtain the elliptical ultrasonic vibration of the tool end,the frequency,the amplitude,and phase shift of the applied AC voltages were set as 20.6kHz,50V and 250 ,respectively.In this condition,the elliptical vibra-tion amplitude of the drill end was measured with twolaser Doppler vibrometers (LV-1610of Ono Sokki Co.,Ltd.,Yokohama,Japan),the amplitude of circular locus was 10m m (i.e.a ¼b ¼5m m)(see Figure 1c).A sample of CFRP was used as the workpiece,which was provided by Chengdu Aircraft Industrial (Group)Co.,Ltd.,Chengdu,China,with a dimension of 200mm Â200mm Â10mm.The material properties of workpiece are shown in Table 1.The cutting tools were diamond core drills (Figure 2)provided by Beijing Aeronautical Manufacturing Technology Research Institude,Beijing,China.The grit size,the drill outer diameter,and the inner diameter were 80#(the screen hole size was 0.18mm),10.7mm,and 8.1mm,respect-ively.The diamond grains were welded to the tool sur-face by vacuum brazing process.The surface density of diamond grains on drill face was about 15grains per unit area (i.e.15/mm 2)and few diamond grains existed on the drill inner face,so it could improve drill sharp-ness,machining quality,and prevent rod jamming eﬀectively.Two drills were used to drill the specimen in CD and RUEM.After particular drilling tests,the diamond core drills were removed from the lathe spin-dle and cleaned by an ultrasonic washing machine.The surface conditions were observed using a digital optical microscope (Nikon E950by Nikon Co.,Ltd.,Tokyo,Japan)to grasp the evolution of drill wear.The mag-niﬁcation of the microscope was 30to 500.Once the tool was dull enough to generate severe delamination and burrs at the hole exit position,a repairing oper-ation was needed.In this experiment,the tool life ofaFigure 1.Experimental set-up and ultrasonic transducer of RUEM.(a)Experimental set-up of RUEM,(b)Ultrasonic elliptical transducer and (c)Partial view A of the diamond core drill.T able 1.Workpiece material properties.PropertyUnit ValueDensitykg/m 3155Hardness (Rockwell)HRB 70–75Elasticity Modulus of epoxy GPa 2.06–2.15T ensile strength of epoxyMPa 80–85Elasticity Modulus of carbon fiber GPa 230T ensile strength of carbon fiberMPa4900Figure 2.3D view of the diamond core drill.Geng et al.3diamond core drill was deﬁned as the drilled hole number before repairing.The details of experiment conditions are tabulated in Table2. Experimental resultsDrilling forceFigure3shows the mean drilling force along the axial direction(i.e.mean thrust force)as a function of the drilling tests number.The drilling force which is dir-ectly related to the sliding friction at the interface between the drill and the workpiece is generally a cru-cial factor for the evaluation of the drill wear condi-tions.The mean drilling force in this experiment was deﬁned by F mF m¼Z t iF zidtTð1Þwhere F ziis the real-time axial drilling force at t i,and t iand T are the real-time cutting time and the cuttingduration during drilling,respectively.It can be obtained that the mean drilling force inRUEM was much smaller than that in CD.In thestudy of Zeng et al.,21the tool wear in RUM of cer-amics was divided into two stages until most of dia-mond grains were dislodged from the drill end faceaccording to the wear mode.Moreover,the results con-ﬁrmed an obvious relationship between the evaluationof drill wear and the maximum drilling force.Thus,according to the trend of the mean drilling force,thecore drill wear process either in RUEM or CD could bedivided into three stages,i.e.an initial region,a steadyregion,and a deteriorated region:1.Initial region:It covered the drilling test times<5in CD or3inRUEM.In this region,the drilling force increasedobviously.2.Steady region:It covered the drilling test times from5to28in CDor from3to35in RUEM.In this region,the drillingforce in CD increased slightly with a smallﬂuctuation.The drilling force in RUEM also increased slightly andcompared with CD,the steady region in RUEM was39%longer.3.Deteriorated region:This region covered the drilling test times larger than28in CD or35and RUEM,respectively.The experi-ments were terminated at the32nd drilling test in CDand the41st drilling test in RUEM due to severe delam-ination and burrs at hole exit position.In this region,the drilling force increased sharply with the test numberboth in CD and RUEM,while the increasing rate inCD was larger than that in RUEM.Moreover,itshould be noted that,the tool life in RUEM and CDwas41holes and32holes,respectively,and thus,thetool life in RUEM was28%longer in comparison withthat in CD.Topographic features of drill surfaceWear of tool end face.Figures4–8show the images of thedrill end face after the5th,15th,25th and32nd drillingtest both in CD and RUEM,and the41st drilling test inRUEM,respectively.It can be seen that there were few visible changes ofdrill end faces afterﬁve times drilling tests except somegrain pullout and slight grain micro-fracture both inT able2.Details of experiment conditions.Parameters(unit)ValueCoolant Dry conditionInput voltage amplitude(V)U¼50Input voltage frequency(kHz)f¼20.6Input voltages phase shift( )É¼250Elliptical vibration amplitude(m m)a¼b¼5Rotary speed(r/min) s¼5000Feedrate(mm/s) f¼0.33Depth of drilling(mm)d¼10Figure3.Mean drilling force versus the number of drillingtests.4Journal of Reinforced Plastics and Composites0(00)CD and RUEM.The number of dislodged grains in CD was obviously larger than that in RUEM,while the number of grains with slight micro-fracture in RUEM was larger than that in CD at the whole drill end pared with the wear condition of other grains,the premature dislodged grains had not reachedits eﬀective working life.Although some grain pullout occurred in CD and RUEM,there were still lots of active cutting edges at the drill end face,which were considered as main cutting edges during drilling.Compared with the drill end face after ﬁve drilling test times,more grains were dislodged and more sharp cutting edges were worn signiﬁcantly in mode of attri-tious wear after drilling 15holes,especially in CD (see Figure 5).Both wear modes eﬀectively decreased in active cutting edge density which was deﬁned as the number of active cutting edges per unit area on the drill end face.The bond fracture resulting in grain pull-out and slight chip adhesion in the bulky pits occurred at the edge of the drill end face in CD.Although the bond fracture,grain pullout,and cutting edges worn were also observed in RUEM,the chip adhesion rarely appeared and obvious grain micro-fracture could be found.This meant that the drill in RUEM maintained a higher drilling performance than that in CD.As the drilling tests were raised to 25times (see Figure 6),bond fracture and grain pullout increased markedly in CD and RUEM.However,moregrainFigure 4.2D microscopic images of drill end face after the 5th drilling tests.(a)CD and (b)RUEM.Figure 5.2D microscopic images of drill end face after the 15th drilling tests.(a)CD and (b)RUEM.Figure 6.2D microscopic images of drill end face after the 25th drilling test.(a)CD and (b)RUEM.Geng et al.5micro-fracture and less chip adhesion occurred in RUEM in comparison with CD.It indicated that the core drill became poor after drilling 25holes in CD,while the core drill was still sharp in RUEM.After the 32nd drilling test (see Figure 7),the chip adhesion and bond fracture became severe in CD,and about 80%of the end face was blocked with adhesion layer,which was made up of the epoxy debris,the cut carbon ﬁbers,the diamond and metal solder debris.In this situation,the cutting edge density decreased so sig-niﬁcantly that the drilling force became large enough to produce severe delamination and burrs at the exit pos-ition of drilled holes.Thus,the drill in CD lost the cutting ability and the repairing operation wasnecessary.Meanwhile,in RUEM,the active cutting edges on the end face were still obvious,and slight chip adhesion was observed at the bulky pits where grains were dislodged.Therefore,the drill still owned some cutting ability in RUEM.Once the drilling tests number was increased to 41in RUEM (see Figure 8),grain pullout and bond fracture became so severe that there were no obvious sharp grains left on the drill end face,so the repairing oper-ation was needed.The microscopic features of drill end face indicated that the grain wear modes changed signiﬁcantly with the increase of drilling test times.The obvious variation was the number decrement of active diamond grains and the area increment of chip adhesion on the drill end face.Active diamond grains are deﬁned as the grains with sharp cutting edges (i.e.sharp grains).The active diamond grain number on the end face during drilling is shown in Figure 9(a).The number of active grains on the drill end face during drilling was obtained by a microscope,and then the percentage of the active diamond grain number to the total grain number on the drill initial end face was calculated.The number of active grains on the drill end face decreased with the increase of drilling test times.The descent in the initial region and the deteriorated region was sharper than that in the steady region either in CD or RUEM.The number of active grains in RUEM was always larger than that in CD during drilling.This indicated that drill dullness could be constrained eﬀectively in RUEM.The variation of the chip adhesion area with the dril-ling test number is shown in Figure 9(b).The area of chip adhesion was measured with the 2D microscopic images of drill end face and VK Analyzer software.The percentage of the chip adhesion could be calculated by the software after the area of the chip adhesion was determined.It was obvious that the chip adhesion area in CD increased signiﬁcantly in steady region,and once the drilling test number exceeded 25times,the increasing rate became muchgreater.Figure 8.2D microscopic images of drill end face after the 41st drilling test inRUEM.Figure 7.2D microscopic images of drill end face after the 32nd drilling test.(a)CD and (b)RUEM.6Journal of Reinforced Plastics and Composites 0(00)By contrast,the chip adhesion area in RUEM increased slightly and was much less than that in CD,which indi-cated that better chip removal condition could be achieved in RUEM.Wear of tool lateral face.Figures 10and 11show the images of the drill lateral face after the 15th and 32nd drilling tests,respectively.Figure 10shows that some grain pullout occurred in CD or RUEM after 15dril-ling test times,especially at the edge.Obvious chip adhesion occurred in the hollow space in CD while some grain micro-fracture was observed in RUEM.It indicated that the drill lateral face in RUEM kept a better cutting ability compared with that inCD.Figure 9.Variation of active diamond grains and chip adhesion during drilling.(a)active diamond grains and (b)chipadhesion.Figure 10.2D microscopic images of the lateral face after the 15th drilling test.(a)CD and (b)RUEM.Figure 11.2D microscopic images of the lateral face after the 32nd drilling test.(a)CD and (b)RUEM.Geng et al.7After the 32nd drilling test (Figure 11)in CD,the severe chip adhesion and bond fracture occurred due to the poor chip removal character and great friction between the drill and the workpiece.In RUEM,although the bond fracture and grain pullout also occurred at the lateral face,obvious chip adhesion did not appear.It was mainly attributed to the better chip removal and heat conduction in RUEM.12Machined surface quality.The topographic features of the machined surface at the entrance as well as the exit location both in CD and RUEM after 15and 32dril-ling test times are shown in Figures 12and 13,respect-ively.It could be obtained that the hole surface quality in RUEM was much better than that in CD at the entrance or the exit position during drilling.Moreover,in CD,the hole surface quality after 32dril-ling test times became much worse than that after 15drilling test times,especially at the exit position,due to obvious delamination and marked surface roughness.Conversely,in RUEM,the hole surface quality either at the entrance or the exit location had a less worsening trend after 32drilling test times compared with that after 15drilling test times.The variations of machined surface roughness at the exit and entrance location during drilling both in CD and RUEM are shown in Figure 14.It was obtained that the machined surface roughness in RUEM was obviously better than that in CD,espe-cially at the exit location.For the roughness at the exit location (Figure 14a),it could be seen that the hole surface roughness increased rapidly in the initial region,and then decreased slightly in steady region with some ﬂuctuation,and ﬁnally it had a steady increasing trend in the deteriorate region.In contrast,although the hole surface roughness at the exit pos-ition in the deteriorated region rose obviously,the roughness in the initial or steady regions was lower in RUEM than that in CD.As for the roughness variation trends at the entrance location (Figure 14b),it could be seen that the entrance surface rough-ness was increasing slightly with small ﬂuctuation in all the regions of the two drilling process,and the roughness in RUEM was also better than that in CD.The diﬀerence of surface roughness in the two drilling process showed that the drill wear during RUEM had a positive eﬀect on maintaining the high surfacequality.Figure 12.T opographic features of the machined surface after 15drilling test times.(a)entrance in CD,(b)entrance in RUEM,(c)exit in CD,and (d)exit in RUEM.8Journal of Reinforced Plastics and Composites 0(00)DiscussionAs described earlier,the diamond core drill wear behav-ior either in CD or RUEM can be divided into three stages:the initial region,the steady region,and thedeteriorated region,according to the obtained drilling force and drill surface topographic features.Since RUEM is a hybrid machining process of grind-ing and ultrasonic machining,the wheel wear mechan-ism in grinding is the basis to understand tool wear mechanisms in RUEM.The research conductedbyFigure 13.T opographic features of the machined surface after 32drilling test times.(a)entrance in CD,(b)entrance in RUEM,(c)exit in CD,and (d)exit inRUEM.Figure 14.Variation of surface roughness during drilling.(a)at the exit location and (b)at the entrance location.Geng et al.9Malkin et al.indicated that there were three main modes of wheel wear:attritious wear,grain micro-frac-ture,and bond fracture.22Attritious wear included the dulling of abrasive grains and the growth of wear ﬂats owing to rubbing against the workpiece by grains.Grain micro-fracture involved the removal of abrasive fragments by fractures within the grains.Bond fracture causes dislodging of grains from the binder.It was vali-dated that attritious wear and grain micro-fracture resulted in only a few percent of the tool weight loss while bond fracture was mainly responsible for the loss in the wheel radius.However,the attritious wear led to the increase of ﬂat area and determined the magnitude of the grinding force and the quality of machined sur-face,while the grain micro-fracture and bond fracture exposed new cutting edges to be responsible for the self-sharping of grinding wheels.23,24Figure 15(a)shows the full view of drill end face which is the initial drill topography before drilling and Figure 15(b)is the sectional view (e.g.A-A)of the diamond core drill.Some fragile grains were created due to the abrasive grain primary cracks and some weak joining of abrasive grains.It was diﬃcult to avoid the weak joining during vacuum brazing process in manufacturing of diamond core drills.The typical mechanism of drill wear for diﬀerent regions in CD and RUEM are summarized as the models from Figures 16to 18.In the initial wear region,the wear patterns in CD included grain pullout and slight grain micro-fracture (see Figure 16(a)),while the wear patterns in RUEM included slighter grain pullout and more obvious grain micro-fracture (see Figure 16(b))due to the smaller drilling force and greater impulse impacts by elliptical ultrasonic vibration in RUEM.The fragile grains did not adhere to the solder ﬁrmly,which made these grains lower mechanical strength than others.Thus in the ini-tial wear region,the drill end face was worn easily,caused a rapid increasing cutting force either in CD or RUEM.Furthermore,the initial wear regionofFigure 15.The end face and sectional view of core drill.(a)the core drill end face and (b)the initial drill topography beforedrilling.Figure 16.Mechanism of core drill wear in the initial region.(a)CD and (b)RUEM.10Journal of Reinforced Plastics and Composites 0(00)RUEM was shorter than that of CD,and the reason was the impulse impacts on the grains which resulted in the faster drill wear.In the steady wear region,the drill end face wear in CD could be mainly characterized by the following modes:attritious wear,chip adhesion,and grain pull-out,as shown in Figure 17(a).And the drill end face wear in RUEM could be characterized by three pat-terns:attritious wear,grain micro-fracture,and grain pullout,as shown in Figure 17(b).These drill wear modes are completely determined by the interaction between the grains and the workpiece,such as grain cutting action,chip deformation,friction eﬀect,and other factors.The wear mechanism of drill end face is modiﬁed by the elliptical ultrasonic vibration of grains on the drill end face.Firstly,the grain cutting action is changed by using elliptical ultrasonic vibration.The orientation of the grain cutting edges in CD is consistent with the direc-tion of the cutting velocity,so only the same cutting edges are employed to cut the workpiece until the edges are worn.However,the cutting edges are always chan-ging in RUEM due to the continuous variable cutting direction along the spiral cutting path of the grains.As the grain position and cutting direction in RUEM is changed,the negative rake angle and the interaction area between the grain and the workpiece are also chan-ged.Therefore,with the aid of elliptical ultrasonic vibration,the attritious wear of grains at the drill end face is restrained to some extent,the sharpness of grains was maintained in RUEM.Secondly,the grain micro-fracture appears easier due to the continuous impacts of elliptical ultrasonic vibration on grain cutting edges,resulting in higher cutting edge density in RUEM.However,it is not con-sistent with the observations reported for RUM of advanced ceramics by Zeng et al.22They concluded that,in RUM of advanced ceramics,the tool wear pat-tern of grain micro-fracture which was commonly seen in metal grinding and conventional grinding (CG)ofFigure 17.Mechanism of core drill wear in the steady region.(a)CD and (b)RUEM.Figure 18.Mechanism of core drill wear in the deteriorated region.(a)CD and (b)RUEM.Geng et al.11。

结直肠癌发生过程中普拉梭菌丰度变化的研究

tients and colorectal cancer patients. It includes three families: ruminococcaceae, bifidobacteriaceae and clostridi-
dae, among which ruminococcaceae includes ruminococcaceae and faecobacter. The relative abundance of Faeca-
Study on the variation of Faecalibacterium prausnitzii abundance in colorectal cancer
Zhong Huage, Yan Linhai, Chen Yi, Wu Changtao, Tang Weizhong. (Departmentof Gastrointestinal Surgery, The
· 1078 ·
＜0.05). Conclusion:Decrease in the abundance of Faecalibacterium prausnitzii is an event thatoccurs in the whole process of healthy-adenoma-adenocarcinoma, which may be related to the occurrence of colorectal cancer, and may become a microbiologicalobservation point for the occurrence of colorectal cancer. Keywords colon cancer; GMrepo; metagenomic sequencing; Faecalibacterium prausnitzii

科技英语写作高级教程参考答案

科技英语写作高级教程参考答案科技英语写作高级教程参考答案V、练习参考答案练习1I、1、the(各项均为负。

)2、the; a (功率额定值是电阻器不会引起温度太大的上升而能安全地耗散的最大功率。

)3、an(这是均方根值伏特计。

)4、The; a(该设备的成功设计需要详细地了解性能指标。

)5、the; a; a(在氢原子的布尔模型中，一个电子绕一个质子以半径为R的圆周运转。

)6、the(电阻的单位是欧姆。

)7、an (这是一个h参数。

)8、/; /(图5,1画出了Oersted的实验。

)9、A; a; a(机器是能够传递力来完成某一确定目的的一种设备。

)10、/(水压机将在第14章加以考虑。

)11、the; the [/](我们容易确定参数μ的值。

)12、/; the(根据式(2,1)，我们得到以下的关系式。

)13、the; /(作者工作在位于阿林顿的得克萨斯大学。

)14、an(甚至当积分区间并不是无穷时，能够恰当地显示一个时函数的傅氏变换的仪器是多么重要啊～)II、1. Dr. Emmet graduated from Harvard University in 2001.2. Professor Li earned his Ph.D. degree in mechanical engineeringfrom the Xi’anUniversity of Technology in 1988.3. Now we shall turn to the discussion of local area networks.4. The Bainbridge mass spectrometer is as important aninstrument as the opticalspectrometer.5. How long a time [或How much time] is required to this experiment? The densityof a substance is its mass per unit volume.6. An increase in pressure always causes a decrease in volume.7. Fig. (2-5) shows what is expressed by Eq. (2-2).8. The unit of inductance is the henry.III、1. The UASMA protocol employs a unique frame structure.2. Finally, a broad stepped impedance transformer is designed bythis method.3. Dynamic analysis and evaluation of the security of a proactive secret sharingsystem4. The approach can be applied to the one-dimensional potentialbarrier with anarbitrary profile.5. We propose a numerical method based on Newton’s iterative method.练习2I、1. This circuit consists of a battery, an inductor and a capacitor.2. Compute the electric fields at points a, b, and c.3. This satellite is used for communications between the United States and Great Britain, France and Italy.4. We assume that the antenna is vertical and that its loss iszero.5. Chapters 6, 7, and 8 deal with transmission lines.II、121. Its error is six parts in 10.2. This computer stores four times more information than that one (does).3. The demand for this kind of equipment in the near future will be 20 times what it is.4. The voltage across this component is a few tenths of a volt.5. Now its internal pressure is one sixteenth what it was.III、1. This object is over five times heavier than that one is.2. Unless otherwise stated, it is assumed that silicon transistors are used and that I CBOcan be neglected.3. This circuit has the advantages of simple structure and easy adjustment.4. Figs. 1, 2, and 3 show this process in detail.5. For further information, consult references [3, 5, 9].练习3I、1. This new type of computer has many advantages over the general type.2. It is not difficult to solve this differential equation for the unknown quantity.3. Of these five new chapters, the first one deals with the basic principles of negative feedback.o4. At this point/time, current differs in phase from voltage by 90.5. By analyzing [By the analysis of] the parameters of the instrument, we canunderstand its performance.6. We will find out its average velocity over this distance.7. The science of electronics is too important in the world today.8. They solved this problem with great difficulty.II、1. For x,1, there is no solution to this equation [this equation has no solution].2. Upon [On] substituting [substitution of] these values into [in] theequation, we obtained the following expression..3. This circuit is similar in operation to that of Fig. 1-10.4. This computer is very good in performance.5. These waves travel only in one direction.III、1. This paper presents a new method for the recognition of radar targets.2. The influence of the moving state of the target on the tracking accuracy of the EKF is great.th3. Another comsat was launched on the morning of the 8 of October.4. Voltage is measured in volts.5. They will leave for Beijing to attend an international conference on mobile communication.6. Unless otherwise stated, it is assumed that silicon transistors are used and that I can be neglected. CBO7.练习4I、1. The force acts perpendicular to the surface of the table.2. The three coefficients here remains to be determined.3. The two equations below will be often (frequently) used in later chapters/in thechapters which follow.4. Here we use two metal balls 10 cm apart.5. The output remains/stays constant/unchanged/fixed/unaltered/the same.6. All the textbooks available discuss this problem.7. Accurate in operation and high in speed, computers have found wide applications.8. The answer to this problem looks correct.9. Two parallel wi res a distance (o f)δapart carry the currenti.10. The problem now is how to measure the voltage across this component.11. These data will be sent to the computing center 2 kilometers away.12. Upon rearranging the equation above, we have [get, obtain] the following expression.13. These charges can interact with other charges present.14. Forces can be transmitted without contact, contrary to the common belief.15. This coefficient is typically 0.35.II、1. In this case, the input does not fall; nor [neither] does the output. […; the output does not fall, either.]2. The resistance of a conductor depends not only on the material of which theconductor is made, but also on the size and temperature of the conductor.3. These scientists are very interested in this topic.4. This parameter can hardly be measured.5. In this laboratory, this instrument is more expensive than any other one/ any oneelse.6. The features of this device are small size and light weight.练习5I、1. This equation can be solved in either of the following two ways/the two wayswhich follow.2. This baseball will soon come to rest because of its interaction with the ground.3. Our choice of this coefficient as 1 is correct.4. From its definition as the ratio of a force to a length, we can see that k has thesame unit as work (does).5. Our analysis of the machine is of great significance.6. This facilitates their use in circuit analysis.II、1. This police car is equipped with a receiver the size of a matchbox.2. Wires one hundredth the diameter of a silk thread are used to connect thesecomponents.3. We must water cool these equipments/devices.4. In the past, telephone calls were operator connected.5. AC can be changed/turned/converted/transformed/translated into/to DC, a process called/known as/referred to as rectification.6. A magnet attracts iron materials, a familiar phenomenon.7. Computers are capable of processing information, a process that previouslycould be accomplished only inside our heads.8. An instrument for measuring current, voltage, and resistance, the multimeter iswidely used in electrical engineering.III、1. Secs. 1.1 and 1.2 will discuss several other problems.2. Problems are listed/given on pp. 1-5.3. In the equations above, all h’s a re the hybrid parame ters.4. The mass of the standard pound is equal to 0.4535924277 kilograms.5. All a’s and b’s in Eq. (5-1) are related to the impedance R. o6. We must take the effect of temperature on [upon] semiconductorsintoaccount.7. In this case, the variation of output with input is very small.8. This curve shows the dependence of distance on/upon speed.IV、1. None of them can solve this special type of differential equation.2. They do not know whether this material can stand so largea force or not.3. There are M polygons altogether, each of which has N vertexes.4. These two engineers are busy (in) designing a new kind ofsoftware.5. Iron is almost as good a conductor as aluminum.练习6I、1. This image, it will be noticed, is a real image.2. This technical problem, we hope, will be solved soon.103. 2 is approximately 1000, a fact that we think is very useful in the study of digitalelectronics.4. A resistor of say 100 ohms should be used here.II、1. None of those textbooks have/has mentioned this point.2. All of these x values cannot satisfy the equation.3. Neither of the two conditions is satisfied here.4. In the preceding/previous chapter, we discussed all kinds of force.5. This paper describes a new method for designing aircraft.6. By the end of the last century, the company had manufactured 5 000 radars.7. Since 2008, this research institute has been developing a special kind of robot. III、1. In Section 1-2, the concept of force was introduced.2. As early as the 1940s, it was found that semiconductors are very useful.3. This result can also be arrived at in another way.4. At that time no use was made of this phenomenon/…, thisphenomenon was made no use of.5. This point will be dealt with in the next section.IV、1. This computer works much better than that one(does)/This computer is much betterin performance than that one (is)..2. This computer requires many more components that that one (does).3. The distance of the moon from the earth is as great as 240 000 miles.4. The greater the resistance, the longer time it takes for the capacitor to reach itsmaximum voltage/…, the longer time is required for the capacitor to reach its maximumvoltage.)5. The current as small as 0.1 A cannot produce enough heat.V、1. It is easy for us to determine the weight of the body. 或:We can determine theweight of the body easily.2. The two engineers are busy (in) designing a new type of computer.3. We find this concept very difficult to explain.4. None of these windows can withstand so large a force.5. Work equals [is equal to] force multiplied by/times distance.6. The results obtained agree with the experimental values. [… arein agreement withthe experimental values.]练习7I、1. It will take a few months to design this kind of aircraft withthe help of a computer.2. It is left as a problem to [for] the reader to show that this expression holds.3. The program to be executed is stored in this unit.4. This valley acts as the foundation on which to build the dam.5. In this laboratory there are many kinds of instrument forstudents to choose from.6. Let t equal/be equal to zero. 07. The farther away the target (is), the longer time it takes forthe echo to return.8. For the series to converge, x must be less than 1.9. We find this concept very difficult to understand.10. This method makes it much easier to detect targets.11. This factor will affect the ability of a computer to store information.12. We have to find out how large to make r so as for the series to converge.13. This is a pen to draw pictures with.14. Elasticity is the tendency of a body to return to its original condition after beingdeformed.15. Ordinary matter is said to be electrically neutral.16.This property makes it possible for metals to be made into any shape.17. This table is unfit for a student to do experiments on.18. Now we consider what path of integration to take.II、1. The sine law of the variation of light intensity with the cylinder diameter has beenemphasized.2. Not only do temperature and light affect the conductivity, but the addition ofimpurities to semiconductors also makes it change greatly.3. Various satellites are frequently launched to obtain information about/on space.4. Our semiconductor industry came into being at the end of the 1950s.5. My colleagues and I would like to express our thanks to Professor W. Smith for hisgreat help.练习8I、1. The amplifier amplifies the received signals.2. Moving molecules have kinetic energy.5. Fig. 1 – 3 shows the photo of a freely falling body.3. Speed equals distance divided by time.4. Voltage equals/is equal to current multiplied by resistance.5. The resistance of air increases with the increased/increasing/an increase in speed.6. A transformer is a device consisting of two or more coils wound on/round an iron core.7. It is necessary to find out the current flowing through this component.8. This book, properly used, will be of great help to the reader.9. Flowing through a circuit, the current will lose part of its energy.10. Given/Knowing time and speed, we/one can find out distance.11. Having studied this chapter, the student will understand/will have understood theprinciple of a computer.12. The speed of light being extremely great, we cannot measure it by ordinary methods.13. Several comsats were launched, all of them (being) high-altitude satellites.14. Called “the mother of all networks,” the Internet is a widely used internationalnetwork.15. This force can be resolved into two components, one (being) horizontal and the othervertical.II、1. Let us construct/draw a circle with the origin as the center and of radius R.2. This parameter should be measured with E grounded.3. With no resistance in the circuit,the current will increase indefinitely.4. With this in view, we have written this book.5. This paper introduces a new design method/technique, with emphasis on its principle. III、1. Let us consider designing a computer.2. We refer to these components as being passive.3. This involves taking the Fourier transform.4. On/Upon rearranging the above equations, we obtain the following set ofequations.5. In using this equation, it does not matter which plane is considered as 1.IV、1. Given/Knowing resistance and current, one/we candetermine/calculate voltage.2. The price of this instrument is high.3. A robot is a special kind of electronic device.4. The current starts flowing at the very moment we close thecircuit.5. They have been designing a new type of computer these six months.练习9I、1. The problem was not solved until a completely different method was introduced.2. Nearly 100 years passed before the existence/presence of subatomic particles was confirmed by experiment/experimentally.3. The year this device was invented, World War II broke out.4. Small as they are, atoms are made up of still smaller particles.5. These two resistors should be selected/chosen so that the transistor can operate normally.6. The body is in such a state that it can do work.II、1. The relation that voltage is the product of current andresistance applies to all the dc circuits.2. The discovery that magnetism can produce current is extremely important in the field of electricity.3. An equation is an algebraic statement that two algebraic expressions are equal.4. There is evidence that no life exists on the moon.5. The question now arises whether the algorithm is of practical use.6. In this case there is no guarantee that the series is convergent.7. There is a growing/increasing awareness that thesetechniques/methods are veryuseful.8. One of/Among the most noteworthy achievements at that time wasthe realization thatlight consists of electromagnetic waves.9. This is due to/is caused by/results from the fact that there are many free electrons inconductors.10. Besides/In addition to the fact that the properties of thematerial should be included inthe analytical model, we must take other factors into account.III、1. These features make it difficult for electronic counter-measure systemsto intercept, analyze and jam this kind of signal.2. The existence of and the ability to control these phenomena make those devicespossible.3. The variation of/in the number of the filter’s teeth has a greater effect on the performance of its passband than the variationof/in its dimensions.4. Scalar detection will result in the loss of some phase information.5. Fig. 6 shows the schematic diagram of measuring scatter parameters by the natural parameter transformation method.练习10I、1. Now it remains to be determined when the series converges.2. It is clear from Dubamel’s Theorem that this limit exists.3. It follows from Maxwell’s hypo thesis that whenever there is a change in an electricfield, a magnetic field is produced.4. It does not matter whether the magnet is moved in this case.5. Temperature determines in what direction the transfer of heat will take place.6. It is now a well-known fact that all matter consists of tiny particles.II、1. What a generator does is (to) change mechanical energy into electrical energy.2. What this chapter describes/What is described in this chapter is of great importance.3. Matter is what can occupy space.4. What we have discovered in this experiment is the entirely new realm of electricalphenomenon.5. This direction is opposite to what has been assumed.6. Magnitude, direction, and place of application are what we call the three elements of aforce.7. These numbers constitute what is known as the real number system.8. In what follows, we shall acquaint ourselves with somebasic concepts. III、1. An x-band wave-guide test system is shown in Fig.7. [或:Fig.7 shows …].2. This method lowers the requirement for the hardware of a sample network.3. On the basis of the above analysis of the decomposition of the polynomial, a novelconfiguration results. [或:The above analysis of the decompositionof the polynomial resultsin a novel configuration.]4. Finally, an analysis of packet loss probability is made bycomputer simulation.5. The sparse ratio of the resulting impedance matrix is as high as 40%.练习11I、1. The meter (that/which) we use to measure the voltage across a resistor is called avoltmeter.2. Computers are the most efficient assistants (that) man has ever had.3. Now this disease is no longer the serious problem (that) it once was.4. Radar can measure the time (that) it takes for the radio echo to return.5. We must calculate the distance (that/through which) the body is lifted.6. The direction (that/in which) a body moves is also very important.7. The number of times (that/by which) this particle vibrates per/a second iscalled/termed/named/known as/spoken of as/referred to as frequency.。

MPS方法模拟三维圆柱形液舱晃荡问题

MPS方法模拟三维圆柱形液舱晃荡问题田鑫;万德成【摘要】[目的]为了研究在单自由度横荡激励下,激励频率对液舱晃荡现象的影响,将移动粒子半隐式(MPS)方法应用于水平圆柱形液舱晃荡问题.[方法]基于改进的MPS方法和GPU并行加速技术,课题组将自主开发的无网格粒子法求解器MPSGPU-SJTU应用到三维圆柱形液舱晃荡问题中.首先,进行模型验证,对激励频率为一阶固有频率时的晃荡现象进行模拟.然后,在此基础上进行不同激励频率下的晃荡现象计算,并将激励频率在1.2 Hz的模拟结果与实验结果进行对比.最后,在此基础上模拟不同激励频率下液舱的横荡运动.[结果]结果显示,MPSGPU-SJTU求解器能够较好地模拟圆柱形液舱内的液体晃荡现象,也能较为精确地计算液舱受力;当激励频率在固有频率附近时,晃荡现象十分剧烈,当远离固有频率时,晃荡会迅速变弱,液舱受力也随之迅速减小.[结论]所得模拟结果能够为圆柱形液舱的设计应用提供有效参考.【期刊名称】《中国舰船研究》【年(卷),期】2019(014)003【总页数】6页(P116-121)【关键词】液舱晃荡;圆柱形液舱;移动粒子半隐式方法;MPSGPU-SJTU求解器【作者】田鑫;万德成【作者单位】上海交通大学船舶海洋与建筑工程学院,上海200240;上海交通大学海洋工程国家重点实验室,上海200240;高新船舶与深海开发装备协同创新中心,上海200240;上海交通大学船舶海洋与建筑工程学院,上海200240;上海交通大学海洋工程国家重点实验室,上海200240;高新船舶与深海开发装备协同创新中心,上海200240【正文语种】中文【中图分类】U663.850 引言液舱晃荡是指在外部激励作用下，舱内装载的部分液体所产生的波动及其与舱壁结构相互作用的现象。

随着世界航运业的发展以及对能源需求的不断提高，相继开发应用了大型原油货轮、液化石油气船以及液化天然气船等载液货船。

这些容积巨大的船装载着巨量的液体货物，其内部产生晃荡现象往往会对船舶产生巨大危害，因此晃荡现象成为船舶与海洋工程研究的热点问题。

变工况条件下单螺杆膨胀机膨胀比的实验研究

ε internal =
pin pout
(3)
式中， pin 为进气瞬间压力(即进气结束时基元容积内的压力)， pout 为排气瞬间压力(即膨胀结束时基元容积内的压力)，单位为 MPa。单螺杆膨胀机外膨胀比的关系式如下：
ε duct =
p1 p2
(4)
式中， p1 为进气管道压力、 p2 为排气管道压力，单位为 MPa。
收稿日期：2017年11月24日；录用日期：2017年12月7日；发布日期：2017年12月14日
摘
要
在中低温余热回收利用中，有机朗肯循环被认为是具有较大潜力的技术方向。膨胀机作为有机朗肯循环的输出动力设备起着至关重要的作用，而单螺杆膨胀机由于其独特的结构和工作特性使得其在节能和可再生能源利用领域具有较好的应用前景。除了膨胀机效率，膨胀比是膨胀机另一个重要的性能参数，其对有机朗肯循环系统的热效率影响很大。本文通过对本实验室设计的单螺杆膨胀机样机进行实验研究，分析了单螺杆膨胀机内、外膨胀比随工况的变化规律。实验结果发现，内膨胀比随着转速的增加逐渐增大，外膨胀比则逐渐下降。单螺杆膨胀机内、外膨胀比都随着进气压力的增加而增加。当进气压力区间为0.4~0.65 MPa时，外膨胀比变化范围为3.26~3.73，内膨胀比变化范围为4.8~8.0。可以发现，单螺杆膨胀机内膨胀比受工况的影响较大，外膨胀比受背压影响，但变化幅度较小。
2.2. 实验台简介
2.2.1. 单螺杆膨胀机的工艺流程实验台主要针对本实验室设计的单螺杆膨胀机样机进行性能测试，选用压缩空气作为测试工质。单螺杆膨胀机样机的性能测试实验平台的流程如图 1 所示。压缩机提供的高压空气进入单螺杆膨胀机内膨胀做功，做完功的气体经油气分离器引至室外排出。膨胀机输出的轴功通过扭矩仪测出，同时用涡流测功机为假负载消耗轴功。在膨胀机的进出口管路上布置有各种传感器，用于监测膨胀机进出口的压力、温度以及流量参数。

memory test 项目介绍

MemTest86 Test AlgorithmsMemTest86 uses two algorithms that provide a reasonable approximation of the ideal test strategy above. The first of these strategies is called moving inversions. The moving inversion test works as follows:1. Fill memory with a pattern2. Starting at the lowest addresso check that the pattern has not changedo write the patterns complemento increment the addresso repeat3. Starting at the highest addresso check that the pattern has not changedo write the patterns complemento decrement the addresso repeatThis algorithm is a good approximation of an ideal memory test but there are some limitations. Most high density chips today store data 4 to 16 bits wide. With chips that are more than one bit wide it is impossible to selectively read or write just one bit. This means that we cannot guarantee that all adjacent cells have been tested for interaction. In this case the best we can do is to use some patterns to insure that all adjacent cells have at least been written with all possible one and zero combinations.It can also be seen that caching, buffering and out of order execution will interfere with the moving inversions algorithm and make less effective. It is possible to turn off cache but the memory buffering in new high performance chips can not be disabled. To address this limitation a new algorithm I call Modulo-X was created. This algorithm is not affected by cache or buffering. The algorithm works as follows:1. For starting offsets of 0 - 20 doo write every 20th location with a patterno write all other locations with the patterns complemento repeat above one or more timeso check every 20th location for the patternThis algorithm accomplishes nearly the same level of adjacency testing as moving inversions but is not affected by caching or buffering. Since separate write passes (1a, 1b) and the read pass (1c) are done for all of memory we can be assured that all of the buffers and cache have been flushedbetween passes. The selection of 20 as the stride size was somewhat arbitrary. Larger strides may be more effective but would take longer to execute. The choice of 20 seemed to be a reasonable compromise between speed and thoroughness.Individual Test DescriptionsMemTest86 executes a series of numbered test sections to check for errors. These test sections consist of a combination of test algorithm, data pattern and cache setting. The execution order for these tests were arranged so that errors will be detected as rapidly as possible. A description of each of the test sections follows:Test 0 [Address test, walking ones, no cache]Tests all address bits in all memory banks by using a walking ones address pattern.Test 1 [Address test, own address, Sequential]Each address is written with its own address and then is checked for consistency. In theory previous tests should have caught any memory addressing problems. This test should catch any addressing errors that somehow were not previously detected. This test is done sequentially with each available CPU.Test 2 [Address test, own address, Parallel]Same as test 1 but the testing is done in parallel using all CPUs and using overlapping addresses. Test 3 [Moving inversions, ones&zeros, Parallel]This test uses the moving inversions algorithm with patterns of all ones and zeros. Cache is enabled even though it interferes to some degree with the test algorithm. With cache enabled this test does not take long and should quickly find all "hard" errors and some more subtle errors. This is done in parallel using all CPUs.Test 4 [Moving inversions, 8 bit pattern]This is the same as test 3 but uses a 8 bit wide pattern of "walking" ones and zeros. This test will better detect subtle errors in "wide" memory chips.Test 5 [Moving inversions, random pattern]Test 5 uses the same algorithm as test 4 but the data pattern is a random number and it's complement. This test is particularly effective in finding difficult to detect data sensitive errors. The random number sequence is different with each pass so multiple passes increase effectiveness.Test 6 [Block move, 64 moves]This test stresses memory by using block move (movsl) instructions and is based on Robert Redelmeier's burnBX test. Memory is initialized with shifting patterns that are inverted every 8 bytes. Then 4mb blocks of memory are moved around using the movsl instruction. After the moves are completed the data patterns are checked. Because the data is checked only after the memory moves are completed it is not possible to know where the error occurred. The addresses reported are only for where the bad pattern was found. Since the moves are constrained to a 8mb segment of memory the failing address will always be less than 8mb away from the reported address. Errors from this test are not used to calculate BadRAM patterns.Test 7 [Moving inversions, 32 bit pattern]This is a variation of the moving inversions algorithm that shifts the data pattern left one bit for each successive address. The starting bit position is shifted left for each pass. To use all possible data patterns 32 passes are required. This test is quite effective at detecting data sensitive errors but the execution time is long.Test 8 [Random number sequence]This test writes a series of random numbers into memory. By resetting the seed for the random number the same sequence of number can be created for a reference. The initial pattern is checked and then complemented and checked again on the next pass. However, unlike the moving inversions test writing and checking can only be done in the forward direction.Test 9 [Modulo 20, Random pattern]Using the Modulo-X algorithm should uncover errors that are not detected by moving inversions due to cache and buffering interference with the algorithm.Test 10 [Bit fade test, 2 patterns]The bit fade test initializes all of memory with a pattern and then sleeps for a few minutes. Then memory is examined to see if any memory bits have changed. All ones and all zero patterns are used.Test 11 [Random number sequence, 64-bit]This test is the same as Test 8, but native 64-bit instructions are used.Test 12 [Random number sequence, 128-bit]This test is the same as Test 8, but native SIMD (128-bit) instructions are used.Test 13 [Hammer Test]The row hammer test exposes a fundamental defect with RAM modules 2010 or later. This defect can lead to disturbance errors when repeatedly accessing addresses in the same memory bank but different rows in a short period of time. The repeated opening/closing of rows causes charge leakage in adjacent rows, potentially causing bits to flip.This test 'hammers' rows by alternatively reading two addresses in a repeated fashion, then verifying the contents of other addresses for disturbance errors. For more details on DRAM disturbance errors, see Flipping Bits in Memory Without Accessing Them: An Experimental Study of DRAM Disturbance Errors by Yoongu Kim et al.Starting from MemTest86 v6.2, potentially two passes of row hammer testing are performed. On the first pass, address pairs are hammered at the highest possible rate. If errors are detected on the first pass, errors are not immediately reported and a second pass is started. In this pass, address pairs are hammered at a lower rate deemed as the worst case scenario by memory vendors (200K accesses per 64ms). If errors are also detected in this pass, the errors are reported to the user as normal. However, if only the first pass produces an error, a warning message is instead displayed to the user.。

应用语言学课程教学大纲

《应用语言学》课程教学大纲课程代码：ENGL2049课程类别：专业选修课授课对象：英语、英语师范专业开课学期：秋（第7学期）学分： 2主讲教师：王宇指定教材：1.《应用语言学》（第二版），乐眉云主编，南京师范大学出版社，2004年。

2.《第二语言习得研究与外语学习》，丁言仁，上海外语教育出版社，2004年。

教学目的（含课程内容和考核方式）应用语言学有狭义和广义之分。

狭义的应用语言学专指语言教学，特别是指第二语言教学或外语教学。

广义的应用语言学则涵盖所有与语言和语言学应用有关的学科，包括第二语言习得、社会语言学、心理语言学、神经语言学等等。

本课程将重点选取与学生英语学习密切相关的领域——即第二语言习得和第二语言教学——进行分析和讨论。

本课程是面向英语和英语教育专业所有学生的一门专业选修课，其教学目的为：●帮助学生了解第二语言习得和第二语言教学方面的基本理论和主要论题，培养学生的研究兴趣和一定的批评能力；●引导学生自觉地运用应用语言学原理指导和促进英语学习；●掌握基本的应用语言学研究方法，为撰写毕业论文打下基础。

本课程分三个模块，主要内容包括：模块一：第二语言习得，包括学习者语言/中介语、影响第二语言习得的外在因素、第二语言习得的内在机制、学习者个体差异、二语习得理论、课堂教学与第二语言习得等。

模块二：第二语言教学，包括语言技能（包括听、说、读、写）的教学和语言评估。

模块三：应用语言学的研究方法和论文写作。

考核方式：课堂讨论（20%），课外文献阅读（30%），以小组为单位的项目报告（50%）。

第一课 Orientation课时：第一周，共2课时教学内容：第一节What is applied linguistics?The Role of Applied LinguisticsThe Nature of Applied Linguistics第二节Why should we study applied linguistics?Applied Linguistics and the Language Teacher思考题:1.What is the relationship between Linguistics and applied linguistics:hierarchy or partnership?2.Can there be a unitary theory of applied linguistics, or indeed dotheories of applied linguistics exist at all?3.Should applied linguists be theoretical?模块一（第2课——第8课）：Essential Concepts and Theories in SLA第二课 Puzzles in SLA & The Influence of Behaviorism课时：第二周，共2课时教学内容第一节SLA as a Field of LearningIssues for Exploration第二节The “Interference” of L1The behaviorist Understanding of SLAContrastive AnalysisCriticism from Empirical Research思考题：1.Think of more features on which students make errors sometimes butdo fairly well other times. Describe the conditions under which they tend to err and those under which they tend to get it correct.2.Think of a few areas of difficulty for advanced Chinese learners ofEnglish. Do there areas represent features that are overtly or slightly different from their Chinese counterparts?第三课 The “Chomskyan Revolution”课时：第三周，共2课时教学内容第一节Chomskyan LinguisticsCriticisms of Chomskyan Linguistics第二节Interlanguage HypothesisError analysis思考题：1.Give examples of errors young children make when they are learningto speak Chinese. You may recall the errors you yourself made when you were little.2.Sometimes sentences may look similar, but their functions can be verydifferent. Compare “Jack comes here”with “Here comes Jack.”What are their differences? Think of situations in which you can use one but not the other.第四课 Natural Order and comprehensible Input课时：第四周，共2课时教学内容第一节Natural Order HypothesisMorpheme Studies and Their findings第二节Problems with Error Analysis and Morpheme StudiesComprehensible Input Hypothesis思考题：1.If you know any international students or any other non-nativespeakers of Chinese, carefully observe their speech. Do they make errors that are similar to those you once made when you were a child?2.What are the flaws in Krashen’s Comprehensible Input Hypothesis?第五课 Variability in Performance and Acquisition课时：第五周，共2课时教学内容第一节Variability in L1 UseVariability in L2 Language Learner第二节Role of Variability in SLALearner Variation思考题：1.Discuss the possible reasons for the L2 performance variation foundin the Foster and Skehan study and Zhu Lingzhi’s study.2.Think of as many categories as you can that would characterize yourcurrent and former classmates, such as extroverts, introverts, bookworms, athletes, loners, born leaders, social butterflies, teachers’pets, to name a few. Discuss, in small groups, how different character traits affect language learning differently, and what traits are associated with good language learning and why.第六课 Input and Interaction课时：第六周，共2课时教学内容第一节Input and Interaction in L1 AcquisitionInput and Interaction in Natural SettingsInput and Interaction in Classroom SettingsEffects of Input and Interaction on SLA第二节Criticism of the Interaction HypothesisSwain’s Output HypothesisEmpirical Studies on the Role of Interaction思考题：1.In China, we use Chinese all the time, but we may still suddenly failto recall a term (or name of a person) we want to use. What do you do if this happens to you when you are (1) shopping, (2) visiting a university president, or (3) delivering a speech to a large audience?2.Recall one of your encounters with a person from overseas who was usingChinese as his or her L2. How soon did you become aware that this person might have trouble following you? What did you do to modify your speech so that you could be correctly understood?第七课 Learner Strategies课时：第七周，共2课时教学内容第一节Production StrategiesCommunication Strategies第二节Learning StrategiesThe Role of Memorization Strategies思考题：1.Presumably, production strategies will help us with production andcommunication, but will they also help us with L2 learning? Are there any strategies that do not facilitate our learning?2.Go over the list of cognitive strategies in Table 7.1 (P.167-170) again.Of the 15 strategies listed, how many of them have to do with understanding the auditory or printed material? How many of them have to do with memorizing words and phrases? How many of them have to do with learning and applying syntactic rules?第八课 Noticing the Native Speaker Selection课时：第八周，共2课时教学内容第一节The Noticing HypothesisEffects of the Noticing Hypothesis第二节Noticing the Native Speaker SelectionA New Model of Language思考题：1.How would you compare Schumann’s research with Schmidt’s? Which ofthem is closer to your own experience of learning English or another foreign language?2.Give an example of a situation in which you yourself succeeded inunderstanding or communication even though you did not have the necessary vocabulary.模块二（第9课——第13课）：Language Skills and Assessment第九课 Listening课时：第九周，共2课时教学内容第一节What is listening?Issues in listening第二节How do we gain insights in listening?From Theory to Practice: Issues in Teaching L2 Listening思考题：1.What do you think are the difficulty factors in listening?2.In many Chinese ESL classrooms, teachers are mostly “testing”ratherthan teaching listening. What is your opinion about this phenomenon?What can the teachers do to “teach” the students how to listen?第十课 Speaking and Pronunciation课时：第十周，共2课时教学内容第一节What are Speaking and Pronunciation?Issues in SpeakingIssues in Pronunciation第二节Implications for Pedagogy思考题：1.Should speaking activities focus on texts or sentences?2.What procedures are there specifically for pronunciation teaching?第十一课 Reading课时：第十一周，共2课时教学内容第一节What is Reading?Reading in a Second LanguageL2 Reading vs L1 Reading第二节Issues in L2 ReadingImplications of L2 Research for Instruction思考题：1.Discuss the contributing role of vocabulary knowledge for L2 readingabilities.2.It is generally agreed that extensive reading should be a componentof almost any reading program. To what extent should extensive reading be balanced with an intensive reading program containing well-considered reading instruction (for example, in reading strategies, in vocabulary, etc.)?第十二课 Writing课时：第十二周，共2课时教学内容第一节Demystifying WritingAspects of Writing第二节Second Language Writing: Theory, Research, and Pedagogy思考题：ment on the three L2 writing approaches: controlled composition,the paragraph pattern approach and the process approach.第十三课 Assessment课时：第十三周，共2课时教学内容第一节What is Language Assessment?Fundamental Issues in Language Assessment第二节Language Assessment and Language Teaching思考题：1.Define the term “validity”.2.Discuss the relationship between language assessment and languageteaching.模块三（第十四周——第十八周）: Research Methods and Thesis Writing第十四课 Research Methods in Applied linguistics课时：第十四周，共2课时教学内容第一节What is research?Developing research questionsSelecting research designs第二节A survey studyAn experimental studyA case study思考题：1.What tasks does a researcher have to accomplish if a piece of researchis conducted effectively?2.What are the important differences between quantitative andqualitative designs?第十五课 Writing Up a Research Report课时：第十五周，共2课时教学内容第一节The structure of a thesis / research reportWriting an introductionWriting a literature reviewDescribing methodologyReporting results and discussionWriting the conclusion chapter第二节Academic writing styleAPA writing format思考题：1.Try to get a copy of an undergraduate thesis or an MA thesis. Work witha group to comment on its structure, language, format, etc. Reading Week (第十六周)第十七课 Project Report (1)第十八课 Project Report (2)主要参考文献：1.《英语语言学纲要》，丁言仁、郝克，上海外语教育出版社，2001年。

variance和variation的用法

variance和variation的用法Variance and variation are terms commonly used in statistics and probability to describe the extent, dispersion, or spread of data. While they are related concepts, there are subtle differences in their usage. In this essay, we will explore the definitions, applications, and significance of variance and variation in various fields.Variance is a statistical measure that quantifies how spread out or dispersed a set of values is. It is calculated as the average of the squared differences from the mean of the data set. The basic idea behind variance is to determine the average distance between each data point and the mean. A larger variance indicates a greater spread or dispersion of data, while a smaller variance indicates a more concentrated cluster of values around the mean.Variance is widely used in fields such as finance, economics, engineering, and physics. In finance, for example, variance is a key measure of volatility in asset prices. Higher variance implies greater price fluctuations, making an investment riskier. Economists use variance to assess the volatility of economic indicators like GDP, inflation rates, and stock market returns. In engineering, variance helps evaluate the consistency and reliability of processes or systems. For instance, in manufacturing, measuring the variance of product dimensions ensures quality control. In physics, variance is used to analyze the fluctuations or noise in experimental measurements.On the other hand, variation refers to the range or diversity of values within a data set or population. It provides a measure of how different individual observations are from one another. Variation can be expressed in several ways, such as the range (maximum minus minimum), interquartile range (middle 50% of observations), or coefficient of variation (standard deviation divided by the mean). Variation is used in fields including biology, genetics, ecology, and social sciences. In biology and genetics, variation is crucial for understanding the diversity of traits within a species or population. It helps researchers study genetic variability, evolution, and adaptability. In ecology, variation is used to analyze how different environmental factors impact species diversity, population dynamics, and ecosystem stability. Social scientists use variation to investigate differences in attitudes, behaviors, socioeconomic factors, or cultural practices across different groups or regions.While variance and variation share similarities, they serve distinct purposes in statistics. Variance focuses specifically on the dispersion or spread of data around the mean. It provides a quantitative measure of the average distance between individual values and the central tendency of the data set. On the other hand, variation encompasses a broader concept that considers the entire range of values or patterns in a data set. It quantifies the degree of diversity, heterogeneity, or variability within the set. Both variance and variation play vital roles in hypothesis testing, modeling, and decision-making. They help researchers and practitioners make inferences, draw comparisons, and evaluate statistical significance. For example, when testing the effectiveness of a new drug, variance allows researchers to assess the consistency and reliability of treatment outcomes. In a manufacturing process, variation analysis helps identify sources of defects, optimize performance, and minimize waste. Moreover, in social sciences, analyzing variation across different groups provides insights into social inequalities,policy implications, or cultural differences.In conclusion, variance and variation are critical statistical measures used to analyze the spread, diversity, or dispersion of data. Variance focuses on the differences between individual values and the mean, providing a measure of how spread out the values are. Variation, on the other hand, considers the entire range of values or patterns within a data set, quantifying the degree of diversity or heterogeneity. Both concepts are extensively applied in various fields and are instrumental in decision-making, evaluating statistical significance, and understanding patterns in data.。

豌豆杂交实验整理笔记

豌豆杂交实验整理笔记Last month, I conducted an experimental study on pea hybridization, which involved cross-breeding different varieties of peas to observe the characteristics of the offspring.上个月，我进行了豌豆杂交的实验研究，其中涉及跨品种杂交豌豆，以观察后代的特征。

The aim of the experiment was to understand how different traits are inherited in pea plants, such as seed color, pod shape, and plant height. By conducting controlled crosses and observing the resulting offspring, we hoped to gain insights into the inheritance patterns of these traits.实验的目的是了解不同特征在豌豆植物中是如何遗传的，比如种子颜色、荚形和植株高度。

通过进行受控交配并观察所得后代，我们希望能够深入了解这些特征的遗传模式。

The process involved selecting specific pea plants with desired traits, such as yellow seeds and smooth pods, and then crossing them withother pea plants that exhibited different traits. This allowed us to create a diverse range of offspring and observe how the traits were expressed in the new generation.这个过程涉及选择具有所需特征的特定豌豆植株，比如黄色种子和光滑荚，然后将它们与表现出不同特征的其他豌豆植株进行杂交。

A CFD parametric study of geometrical variations on the pressure pulsations and performance

A CFD parametric study of geometrical variations on the pressure pulsations and performance characteristics of a centrifugal pumpR.Spence a,*,J.Amaral-Teixeira ba Clyde Pumps Limited,149Newlands Road,Cathcart,Glasgow G444EX,UKbSchool of Engineering,Cranﬁeld University,Cranﬁeld,Bedfordshire ML430AL,UKa r t i c l e i n f o Article history:Received 2April 2008Received in revised form 8October 2008Accepted 26November 2008Available online 6December 2008a b s t r a c tPressure pulsations may be troublesome during the operation and performance of centrifugal pumps.Such pressure pulsations have traditionally been investigated experimentally but numerical analysis techniques allow these effects to be explored.The multi-block,structured grid CFD code TASCﬂow has been used to investigate the time variation of pressure within a complete double entry,double volute centrifugal pump.This investigation has taken the form of a parametric study covering four geometric parameters,namely the cutwater gap,vane arrangement,snubber gap and the sidewall clearance.Tagu-chi methods allowed the number of transient analyses to be limited to a total of 27.Three ﬂow rates were investigated and the pulsations were extracted at 15different locations covering important pump regions.Taguchi post-processing analysis tools were used to rank the relative importance of the four geo-metric parameters at each location for each ﬂow rate.The cutwater gap and vane arrangement were found to exert the greatest inﬂuence across the various monitored locations and the ﬂow range.A ratio-nalisation process aimed at increased component life and reduced noise/vibration through reductions in pressure pulsations has produced geometric recommendations,which should be useful to designers.Ó2008Elsevier Ltd.All rights reserved.1.IntroductionCentrifugal pumps are used in a wide range of applications and they can handle a variety of liquids at relatively high pressures and/or temperatures.The present work focuses on a scaled down version of a high energy,double entry double volute pump.Double entry pumps are used in applications that would require a high ﬂow in a single stage pump.However,due to the high energies in-volved these pumps tend to suffer more from pressure pulsations than single entry pumps.A number of investigators have considered the effect of geome-try modiﬁcations on the pressure variations within pumps,either by monitoring the pressure directly or through changes in the axial and/or radial thrust.Uchida et al.[1]performed tests that involved monitoring the radial force and pump performance for different volute cutwater gaps and cutwater shapes using a single entry end suction pump.In 1978,Makay and Szamody [2]reported research into the ma-jor causes of pump failure (see also Ref.[3]).They suggested that emphasis on gaining high efﬁciencies at design conditions led to undesirable ﬂow features at part load operation and provided a thorough examination of pumps and pump design relating to per-formance difﬁculties.Makay and Szamody highlighted the impor-tance of internal pump clearances,especially those betweenrotating and stationary parts where high gradients exist.A later re-port [4],which covered similar ground recommended that the safe minimum ﬂow for a large feed pump should be 25%of the design ﬂow condition;also that on double entry impellers the impeller blade should be staggered (or clocked)to minimise hydraulic forces and that for double entry impellers the central shroud should be extended to the impeller outer diameter.Unfortunately,these recommendations were not presented with any back up information or discussion of the possible performance changes in the pump due to either design modiﬁcation.Sudo et al.[5]provide some experimental information concerning the variation in pres-sure pulsations at the pump discharge due to the cutwater gap,skew of the cutwater tongue and the clocking of the impeller.Sudo et al.report that the staggered impeller vanes produce pulsation amplitudes of around a quarter of those present for an inline impeller arrangement,but their measurements were some dis-tance from the pump discharge.It has generally been accepted that while the accuracy of CFD analyses has not yet achieved a level that is equivalent to experi-mental techniques,its ability to correctly predict the direction of any changes is reliable [6].Others consider that CFD can be partic-ularly adept in aiding understanding of the effect of ranges of parameters [7].Yet little has been published regarding CFD being used for parametric studies,although work performed at the Uni-versity of Oviedo has recently compared two impeller diameters,i.e.González-Pérez et al.[8]and Blanco et al.[9].Earlier work by Spence and Teixeira [10]has shown the feasibility of generating0045-7930/$-see front matter Ó2008Elsevier Ltd.All rights reserved.doi:10.1016/pﬂuid.2008.11.013*Corresponding author.E-mail address:reemull@ (R.Spence).Computers &Fluids 38(2009)1243–1257Contents lists available at ScienceDirectComputers &Fluidsj ou r na l h om e pa ge :w w w.e lse vi e r.c om /lo c at e /c om pﬂuida numerical model of a complete pump geometry and conducting CFD analyses using this model over aﬂow range from1.00Qn (BEP)down to0.25Qn.That study also compared the pressure pul-sations from the numerical analysis at locations within the impel-ler,volute and leakageﬂow passages with experimental test data and reasonable agreement was found.The numerical model was also found to correctly predict pressure pulsation trends for differ-ent pump geometries.Additionally,information relating to some of the internalﬂow features observed within the pump both at BEP and reducedﬂow rates has also been published[11].This present paper uses the analysis in[10]to provide a wider parametric study that investigates the effect of various geometry features on the pressure pulsations in the pump.A survey of liter-ature and industrial experience provided a shortlist of key param-eters in the design process and that are likely to have an effect on the pressure variation in the pump.These key areas are,the cutwa-ter clearance gap[radial distance between impeller blade tip and the volute cutwater],the snubber clearance gap[radial distance between the shroud outer diameter and the volute casing],side-wall clearance[minimum axial distance between the impeller shroud and the volute casing]and blade clocking or stagger[on a double entry impeller this is the practice of offsetting the arrange-ment of blades on one side of the impeller so that they do not coin-cide with the blades on the opposite side].The parametric study utilises a Taguchi array to reduce the number of analyses required at eachﬂow rate,with threeﬂow rates being investigated,namely 1.00Qn,0.50Qn and0.25Qn.The array provides a framework for the post-processing of the results and allows the reduction of the pressure pulsations in conjunction with the adjustment of the above variables.This is a rationalisation process that does not so-lely focus on reducing the pressure pulsation since other critical factors,such as the pump generated head,are also considered. Broadly,the objective of this rationalisation is to assist the devel-opment of pump designs,which will achieve reduced levels of pul-sations without signiﬁcant loss in performance.2.Pump geometryThe centrifugal pump simulated is of a double entry,double vo-lute type,shown in Fig.1,with a speciﬁc speed of0.74.The double entry impeller has a maximum diameter of366mm,with6back-wards curved blades per side.It should be noted that the largest impeller diameter used in the investigation was deliberately over-sized for the pump design.The impeller blade has average inlet and outlet angles of26°and22.5°,respectively,with the blade wrap angle being102°.The cutwater tongue is at a diameter of 380mm,with a radius of12mm.The pump operates at a speed of1400rpm,with a dutyﬂow condition of550m3/h.The dutyﬂow condition used in all analyses relates to the designﬂow rate for the original pump and so the pump will not be operating at its optimal ﬂow condition.Table1provides a list of the main characteristics of the pump.The geometrical factors considered for the parametric study are shown in Fig.2and the values given in Table2.Three cutwater gaps are considered,3.83%,6.00%and7.95%,based on the actual blade diameter.The change in cutwater gap was achieved by reducing the impeller blade diameter(corresponding impeller blade diameters are366,358.5and352mm,respectively).Three snubber gap sizes are also considered,namely0.27%,1.10%and 1.27%,also based on the shroud diameter,along with three side-wall leakageﬂow clearances that are for convenience termed 100%,50%and25%where100%corresponds with a12mm clear-ance in this case.Finally three different impeller arrangements are considered,an inline or straight arrangement,a mid position stagger(30°)and a quarter position stagger(15°).Fig.3shows the different impeller arrangements.It should be noted that the staggered impeller arrangements contain a central hub extended to the outer impeller diameter,while the inline impeller termi-nates the hub at a radius part way through the impeller.Table2 provides information relating to the various arrangements analysed.3.Numerical modelThe numerical simulation is conducted using CFX-TASCﬂow, which utilises aﬁnite element basedﬁnite volume method to solve the unsteady three-dimensional Navier–Stoker equations on a structured grid.CFX-TASCﬂow also has the advantages of including some turbomachinery speciﬁc capabilities at the pre-and post-stages of the simulation.As has been noted earlier,a previous paper[10]contains de-tailed information concerning the generation of the numericalNomenclatureb2impeller outlet widthB3volute widthD d discharge branch diameterD s suction branch diameterD2impeller outlet diameterEff hydraulic efﬁciencyn pj number of level factor trials[n pj=3]p pressurep j factor totals:summation of the results relating to a par-ticular factor levelpÃr normalised relative pressure;pÃr¼ðpÀp1Þ=ðq u22=2Þp1pump suction pressureQ n nominalﬂow rateR L leading edge blade radiusR1inlet eye radiusR3radius to cutwatert B blade thicknessu2circumferential speed at the impeller outlety GM the grand mean(average of all response values) y P the predicted response z blade number(per side)b L average leading edge blade angleD p peak-to-peak pressure pulsationD pÃnormalised pressure pulsation;D pÃ¼D p=ðq u22=2ÞD P effect for factor p,where D P¼ðp1=n p1ÞÀðpÀ1=n pÀ1Þ(D P/2)half effect for factor ph total blade wrap angleq density of theﬂuidSufﬁxesi1denotes inlet2denotes outlet3denotes cutwater j level of Taguchi factor(À1:low,0:mid,+1:high) p denotes geometric factorA cutwater gapB snubber gapC sidewall clearanceD vane arrangementAB interaction of factors A and B1244R.Spence,J.Amaral-Teixeira/Computers&Fluids38(2009)1243–1257model.This previous paper includes descriptions of the grid inde-pendence checks conducted,in addition to the examination of dif-ferent boundary conditions and turbulence models with a view toachieving a robust analysis in a reasonable timeframe while pre-serving the accuracy of the rmation relating to the interpretation of the data gained from the analyses and compari-sons with industrial experimental tests are also provided in this previous work.A brief summary of this work is contained below.3.1.Grid generationThe pump is split into a number of component parts for model-ling.The component parts included:(a)the double suction inlet,(b)the leakage ﬂow paths comprising the snubber gap,sidewall clearance and wear ring gaps,(c)the pump impeller (both sides),(d)the double volute and (e)a mid block between the two sides of the impeller (the mid block is only present for staggered impel-ler arrangements).Due to the size and complexity of the pump care was taken regarding the distribution of grid elements in the model.A detailed grid independence check was conducted for the impeller grid using single passageway sizes ranging from 10,000to 85,000elements,with the inﬂuence of the volute on the ﬂow in the impel-ler grid being factored into the check.This concluded that an impeller grid size of 22,000elements/nodes per passageway was sufﬁcient to reliably model the pressure in the impeller.The impel-ler model consisted of 12passageways and totalled 227,126ele-ments.Care was taken to concentrate grid in the cutwater region of the volute and the axial distribution at the impeller interface replicated the impeller grid distribution.In total,391,848elements were used to model the volute.The leakage ﬂow path model was generated in such a way that multiple snubber and sidewall geo-metric arrangements could be analysed through use of a single grid and the block-off feature in CFX-TASCﬂow.The leakage ﬂow pathTable 1Main characteristics of pump arrangements.Location DescriptionParameter Value Double entry impellerInlet eye diameter (m)D 10.177Average leading edge blade angle (o )b L 26Maximum impeller outlet diameter (m)D 20.366Average trailing edge blade angle (o )b T 22.5Impeller outlet width (m)b 20.061Blade number (per side)z 6Total blade wrap angle (o )h 102Blade thickness (m)t B 0.007Leading edge blade radius (m)r 0.002Double voluteSuction branch diameter (m)D s 0.400Discharge branch diameter (m)D d 0.300Volute width (m)B 30.105Radius to cutwater (m)R 30.190Fig.2.Geometric factor locations within thepump.Fig.1.Pump type with horizontal cross section.Table 2Geometric conﬁguration of Taguchi arrangements.Experimental arrangement Cutwater gap Snubber gap Sidewall clearance Vanearrangement 1 3.83%[À1]0.27%[À1]100%[+1]0°[À1]2 3.83%[À1] 1.10%[0]50%[0]15°[0]3 3.83%[À1] 1.64%[+1]25%[À1]30°[+1]4 6.00%[0]0.27%[À1]50%[0]30°[+1]5 6.00%[0] 1.10%[0]25%[À1]0°[À1]6 6.00%[0] 1.64%[+1]100%[+1]15°[0]77.95%[+1]0.27%[À1]25%[À1]15°[0]87.95%[+1] 1.10%[0]50%[0]30°[+1]97.95%[+1]1.64%[+1]100%[+1]0°[À1]R.Spence,J.Amaral-Teixeira /Computers &Fluids 38(2009)1243–12571245comprised161,760grid elements.The suction inlet model con-sisted of89,756elements.The model was assembled using a step-by-step iterative process that allowed each component grid model to be examined and reﬁned in order to improve the interac-tion of theﬂow between components.This was a time consuming process,but gives conﬁdence in the large,complex numerical mod-el since each component was capable of modelling not only its internalﬂow satisfactorily,but had also been generated with con-sideration of interactive effects with other components.Once com-plete the total pump model consisted of870,500hexahedral elements.Fig.4provides an indication of the overall model mesh.3.2.Pre-processingThe pre-processing set up of the pump model was conducted with consideration of the limitations involved with gaining a stable transient analysis while performing analyses over a wide range of ﬂow conditions.The impeller and leakageﬂow grid components were set in a rotating frame of reference.The interfaces between rotating and stationary frames were modelled using the rotor/sta-tor interface option;interfaces between components in the same frame of reference use the general grid interface(GGI)option. Although a number of boundary conditions were examined,the parametric study was conducted using a massﬂow at inlet and sta-tic pressure at outlet as this set of boundary conditions had been found to be more stable and converge faster than other combina-tions without a signiﬁcant loss in accuracy.As noted above the dutyﬂow condition for all geometry conﬁgurations was550m3/h. This decision was made to ensure consistency with experimental work that was conducted with a single dutyﬂow rate.Theﬂow rates chosen for examination in this project were deliberately se-lected at signiﬁcant spacing to preserve general trends with varying ﬂow rate.It was calculated that the extremes of geometry would indicate a best efﬁciency point shift of less than5%in theﬂow rate. The internal and external impeller surfaces were modelled using a rotating wall,while all other walls were stationary.Turbulence was modelled with a standard k-epsilon model; wall functions based on the logarithmic law were used.A second order discretisation process was employed in the transient analy-ses.The calculations were conducted serially on computers that contain two Intel3GHz processors with6GB of shared memory apiece.The time taken per iteration is dependent on the arrange-ment andﬂowrate analysed,but is approximately one iteration per hour.Typically periodic unsteady convergence was achieved in four toﬁve impeller revolutions.The timestep selected for use in the current analyses was1.488Â10À4s,as this provided288 Fig.3.Different impeller arrangements:left to right–inline,15°and30°arrangements.Fig.4.Total pump grid model.1246R.Spence,J.Amaral-Teixeira/Computers&Fluids38(2009)1243–1257time steps per impeller rotation(48time steps per blade passage). This timestep was chosen based upon the work of Koumoutsos[12] who conducted transient analyses of a centrifugal pump using time steps equivalent to250and500time steps per revolution and con-cluded that250time steps per revolution(50time steps per revo-lution)was adequate for a reliable and accurate analysis.Thus,the selection of the timestep,giving a greater number of time steps per impeller revolution,was considered to have preserved the accu-racy and stability of the analysis,with the Courant Freidrich Levy (CFL)number being less than30.Transient resultsﬁles were cre-ated after every second iterative loop.3.3.Pressure pulsation monitoring locationsThe pressure pulsation level was investigated at15locations around the pump.Fig.5provides the circumferential position of a number of the locations in the volute and leakageﬂow passage.Leakageﬂow locations(in casing wall in leakageﬂow path at back of impeller)C1–60mm ahead of the leading edge cutwater(not shown).C2–30mm ahead of the leading edge cutwater.C3–at the leading edge cutwater.C4–30mm past the leading edge cutwater.C10–60mm ahead of the leading edge cutwater,opposite to C1 (not shown).Volute locations(at splitter,25mm axially offset from pump centreline)C5–5mm back from the cutwater leading edge.C6–15mm back from the cutwater leading edge.C7–30mm back from the cutwater leading edge.C8–50mm back from the cutwater leading edge.C9–Top,centre of the pump(not shown).Cd–Pump discharge(not shown).Impeller positions(all not shown)Shroud B(above blade)–shroud outer diameter,positioned above an impeller blade.Shroud M(mid passage)–shroud outer diameter,positioned mid way between two impeller blades.Blade P–located on the pressure face of an impeller blade at the trailing edge.Blade S–located on the suction face of an impeller blade at the trailing edge.In order to keep the presentation manageable the results given in this paper are restricted to a single monitoring position in each of the major pump regions,e.g.C4for leakageﬂow path,C6for vo-lute cutwater,C9for general volute/towards discharge and Blade P for the impeller outlet.Results at some of the other positions will be mentioned in discussion.3.4.Summary of experimental comparisonThe uncertainty in the present analysis has been minimised and assessed through two approaches.Firstly through convergence studies as described in Section3.1and by comparison with indus-trial based experiments.The former have shown that the present mesh size,for the impeller,is within3%of a muchﬁner grid.The latter is described in detail in Refs.[10,11]but the results are sum-marised here for convenience.Table3provides a comparison of the CFD simulation(arrange-ment2)with experimental data for the0.25Qn and1.00Qnﬂow rates.The table gives an indication of the percentage variation of the CFD simulation with the industrial test results at a selection of locations around the pump(with the difference being divided by the experimental value).The agreement at the impeller shroud where the pulsation levels are relatively high is excellent and typ-ically the differences are signiﬁcantly lower for allﬂow rates than the average,being as low as7%.It should be pointed out that the C5 and C6positions(which show a higher difference)are very sensi-tive to the actual monitored location because of the high pressure pulsation gradients in the vicinity of the cutwater tongue.The shroud and C9(towards the discharge)positions are important locations for monitoring within the pump as the estimation of fa-tigue levels in the impeller requires information at the impeller shroud and the C9position can be used to provide a more general indication of pressure pulsations within the pump.At these loca-tions the variations are better than average and can reach levels as low as3%.Generally within the pump,the differences have an average value across all locations being between25%and30%, but it is important to note that all of these comparisons show sub-stantial improvement over previous pulsation work performed by Longatte and Kueny[13]and Talha[14]who,respectively,reported over prediction of pulsations by1000%and300%in comparison with experimental tests.In general the relationship between the numerical simulation and experimental test is rather complex.The percentage variation with the experimental values does not appear to show any identi-ﬁable improvement atﬂow rates closer to the BEPﬂow condition. However,the pulsation variation at1.00Qn is approximately half that calculated for0.25Qn for both arrangements when averaged across all measured locations.Unfortunately only limited experi-mental performance data is available for comparison,i.e.noFig.5.Sketch of the circumferential position of the volute cutwater(C5,C6,C7andC8)and sidewall(C2,C3and C4)monitoring locations.Table3Percentage variations for pressure pulsations and generated head with industrialexperimental tests for arrangement2.Pump location Arrangement2Percentage variation Normalised pulsation value(Â10À3)1.00Qn0.25Qn 1.00Qn0.25QnC1351256101C382056169C4402267189C52716231315C62127200268C820381330C93224967Shroud127128281Head 3.9 6.8––R.Spence,J.Amaral-Teixeira/Computers&Fluids38(2009)1243–12571247efﬁciency information was recorded.However,for the arrange-ment shown,the comparison of the available data indicates that the CFD simulation predicts the pump generated head to within 4%of the experiment at the 1.00Qn ﬂow rate,with this increasing to 7%at the lowest ﬂow condition.3.5.Presentation and discussion of resultsThe output from the CFD analyses provided a time history of the pressure variation and performance characteristics as the impeller rotated in the volute.Fig.6provides sample time histories of the normalised relative pressure at the four selected locations around the pump for the ﬁfth geometrical arrangement (shown in Table 2)and at 1.00Qn.The relation of the pressure pulsation to the move-ment of the blade relative to the cutwater can be described using Fig.6a (i.e.a location at the cutwater).The highest pressure,occur-ring at 0°and every 60°thereafter,takes place just before the pres-sure face of the impeller blade reaches the cutwater.As the blade passes the cutwater the effect of the wake impinging on the cutwa-ter causes a sharp decrease in the pressure,with a minimum being reached as the suction face of the impeller blade passes the cutwa-ter.Then,as the impeller blade continues past the cutwater the pressure rises rapidly.The time period for this pulsation in pres-sure is short,relating to under half the time for each blade pass.The C4position (in the leakage ﬂow passageway),Fig.6b records a regular pulsation with the pulsation frequency corresponding to blade rate.The amplitude of pulsation is generally half that experienced at the cutwater.Fig.6c illustrates that the pulsations at C9(approaching the outlet)are approximately a quarter of those recorded at the cutwater;the location does identify the peaks cor-responding with the blade passing frequency.The impeller blade pressure face location time history,Fig.6d,shows two larger peaks corresponding to the blade passing the splitter (180°)and the cut-water (0°/360°),respectively.It can be observed that although the splitter and cutwater have been designed to be as alike as possible,the pulsation at the splitter is signiﬁcantly larger.There is also sig-niﬁcant difference in the pressure variation from the cutwater to splitter (0°–180°)than from the splitter to the cutwater (180°–360°).The positive pressure gradient in the initial half of the casing is likely due to the use of an oversize impeller in the analyses indi-cating that the 1.00Qn ﬂow condition is actually lower than the optimum design ﬂow rate.This indicates that slight differences in each half of the volute geometry results in them having different optimised ﬂow conditions.It should be noted that although peak-to-peak pulsations are investigated for each location,the purpose of the investigation is to gain an indication of the change (and rate of change)of these maxima with differing geometries rather than identify the location of the highest pressure pulsation within the pump.In order to present the parametric results in a concise fashion,themaximumFig.6.Time history of pressure variation at selected locations for arrangement 5at 1.00Qn.1248R.Spence,J.Amaral-Teixeira /Computers &Fluids 38(2009)1243–1257peak-to-peak pressure pulsations results for all nine arrangements and the threeﬂow rates have been extracted from graphs similar to Fig.6.These are presented in Tables4–6,respectively.It is clear that the pressure pulsations increase as theﬂow decreases and that the largest pulsations exist at the trailing edge of the impeller blade.The pulsations at the volute cutwater are larger than those in the leakage region and the cutwater gap and vane arrangement are the geometric parameters with the strongest effects.4.Taguchi backgroundTaguchi’s concept was to design a quality product rather than inspecting a product to determine if it was a quality product.The Taguchi methodology optimises the conﬁgurations used in a para-metric study such that fewer conﬁgurations are required to iden-tify the relative importance of the selected parameters.The Taguchi approach sets out conﬁgurations(or arrangements)to be conducted using an appropriate orthogonal array;the terminology used in these arrays includes‘‘factors”–an item that is to be varied during the simulations,‘‘level”–the number of times a factor is to be varied during the simulations and‘‘conﬁguration number”–the number of simulations that are required to be run to complete the analysis.Thus,the cutwater gap is a‘‘factor”,which has three lev-els(i.e.3.83%,6.00%and7.95%).In total,the simulations conducted in this work are to investigate four,three level factors(i.e.cutwater gap,snubber gap,sidewall clearance and vane arrangement).The selection of an appropriate Taguchi array is dependent on the number of factors and the levels of the factors to be analysed. The letter L and a subscript number identify the arrays.Roy[15] provides a table of common orthogonal arrays and their related number of factors and levels,which indicates that for the current requirement the L9array is appropriate.To produce a full factorialTable4Normalised pressure pulsation(Â10À3)and pump performance results for1.00Qnﬂow rate.Arr.Single rotation average performance Normalised pressure pulsations(Â10À3)Head(m)Hyd.eff.(%)Leakageﬂow path locations Volute locations Impeller outlet locationsC1C2C10C3C4C5C6C7C8C9Blade press.face Blade suct.faceShroudblade pos.Shroudmid pos.136.185.79487949010125325921716772411185181149 234.786.756436156672312001348149332254128115 335.287.3383537639526420818011925381234178160 432.787.4303033384817214012294222471897873 533.886.88975898510924220318514365327207206137 632.988.35645494042133108796740228167122114 730.988.35044454142118968374341751317562 830.388.62319252736134988350151481267468 931.886.672707373771991531491134420615512984Table5Normalised pressure pulsation and pump performance results for0.50Qnﬂow rate.Arr.Single rotation average performance Normalised pressure pulsations(Â10À3)Head(m)Hyd.eff.(%)Leakageﬂow path locations Volute locations Impeller outlet locationsC1C2C10C3C4C5C6C7C8C9Blade press.face Blade suct.faceShroudblade pos.Shroudmid pos.139.344.15863568310723326334031686693444432540 239.042.0385142739428922121818544628291228355 339.042.0252930638722522620417336582319295364 437.339.6424342546426021018815928526373217261 537.941.54550498913230823728727868578333275359 637.039.5332526355017713612415432423338197275 735.737.7262627294315911614016336416347191279 836.037.8243029374514312411110921421312196214 936.339.3605558687922316318619649455297260252Table6Normalised pressure pulsation and pump performance results for0.25Qnﬂow rate.Arr.Single rotation average performance Normalised pressure pulsations(Â10À3)Head(m)Hyd.eff.(%)Leakageﬂow path locations Volute locations Impeller outlet locationsC1C2C10C3C4C5C6C7C8C9Blade press.face Blade suct.faceShroud bladepos.Shroud midpos.139.533.1114115125123132313283330293113648373355522238.233.21011247716918931526830933067580291281328339.432.86359509811127226430318244714319340388437.530.4495043627220621618416034576380270353538.432.395909011213620923329829480611379288483637.330.15977599610217617417415146430338253367735.928.3424046455822317113616543427347201359835.828.038474555612311731581242646831254283936.032.6998294888721422722717068473351261388R.Spence,J.Amaral-Teixeira/Computers&Fluids38(2009)1243–12571249。

沸石转轮脱附后废气温度_概述说明以及解释

沸石转轮脱附后废气温度概述说明以及解释1. 引言1.1 概述本文对于沸石转轮脱附后废气温度进行了深入的研究和探讨。

沸石转轮脱附是一种常见的废气处理技术，其通过沸石材料的选择性吸附和脱附能力，实现了有机废气中有害物质的去除。

而废气温度作为一个重要的指标，直接影响着整个脱附过程中处理效果以及设备的稳定运行。

因此，深入了解并解释沸石转轮脱附后废气温度的变化规律具有重要的理论与应用价值。

1.2 文章结构文章首先将介绍沸石转轮脱附后废气温度变化的背景和意义。

接着，文章将详细阐述沸石转轮脱附原理以及废气温度受到影响的因素。

在这个基础上，文章将解释废气温度随时间变化的规律，并给出相关数据和实验结果进行支撑。

最后，文章总结了沸石转轮脱附后废气温度的重要性，并展望了其在相关工业领域中的应用前景。

1.3 目的本文旨在全面地了解和解释沸石转轮脱附后废气温度的变化规律，揭示影响废气温度的因素，并探索废气温度对于整个脱附过程的重要性。

通过深入研究废气温度变化规律，我们可以为进一步优化沸石转轮脱附技术、提高废气处理效率以及保证设备安全运行提供理论指导与参考依据。

同时，我们希望通过文章的介绍和解释，让读者更好地理解并认识到沸石转轮脱附后废气温度对于工业领域的重要性，并激发更多关于该领域的研究兴趣和创新思路。

2. 正文在沸石转轮脱附后废气温度方面，是指经过沸石转轮脱附处理后产生的废气的温度变化情况。

沸石转轮脱附是一种常用的工业废气处理技术，其可以有效去除废气中的有害物质，提高环境质量。

沸石转轮脱附原理是利用沸石催化剂具有较强的吸附能力，在加热过程中将吸附在催化剂上的有害物质释放出来。

催化剂会通过一个转动的转轮循环进行吸附和脱附操作。

当废气通过装置时，有害物质被催化剂吸附，此时废气温度会上升。

废气温度的变化受多种因素影响。

首先是原始废气中有害物质的类型和浓度。

不同类型和浓度的有害物质对催化剂的吸附和脱附能力会产生不同影响，导致废气温度变化程度也不同。

the study a number of experiments

the study a number of experimentsThe Study of a Number of ExperimentsThe scientific method, at its core, relies heavily on experiments to validate or refute hypotheses. Experiments are designed to test specific predictions or theories under controlled conditions. They are an integral part of the scientific process, allowing researchers to gather data, analyze it, and draw conclusions based on observable evidence.When a number of experiments are conducted, it's not just about accumulating more data points; it's about building a stronger foundation of evidence. Each experiment contributes to the overall understanding of a phenomenon, either confirming or refuting previous findings. By comparing and contrasting the results of different experiments, scientists can identify patterns, trends, and outliers that might suggest underlying mechanisms or principles.Moreover, conducting multiple experiments allows for the identification and correction of potential errors. Single experiments can be subject to various biases, such as sampling errors, instrument malfunctions, or operator error. However, when multiple experiments are conducted, these biases often cancel each other out, providing a more accurate and reliable picture.Furthermore, a series of experiments can help establish causality. By manipulating different variables and observing the effects on the outcome, scientists can determine which factors are responsible for specific changes. This is crucial in science, as understanding the cause-and-effect relationships underlying natural phenomena is key to making predictions and developing theories.In conclusion, the study of a number of experiments is crucial in the scientific process. It not only provides a more comprehensive understanding of a phenomenon but also helps to establish causality, correct errors, and build a robust foundation of evidence. By conducting multiple experiments, scientists can move closer to the truth, piecing together the complex puzzle of how the world works.。

深基坑开挖和降水对紧邻既有地铁隧道的影响

深基坑开挖和降水对紧邻既有地铁隧道的影响陈志伟; 缪海波【期刊名称】《《科学技术与工程》》【年(卷),期】2019(019)030【总页数】6页(P297-302)【关键词】地铁隧道; 基坑开挖和降水; 数值计算; 渗流场; 变形【作者】陈志伟; 缪海波【作者单位】安徽理工大学土木建筑学院淮南232001【正文语种】中文【中图分类】TU43近年来，基坑工程安全事故和引发的环境问题频繁发生，占总工程量的10%～15%[1]，其中渗流破坏比重最大，约为23.37%[2]，其原因是基坑开挖、降水和后续施工会导致土体中应力重新分布，从而对邻近既有工程产生附加应力和位移[3]。

冉龙等[4]利用模型试验结合数值模拟得出基坑渗透破坏时，坑内的平均水力梯度要大于太沙基理论的结果；黄戡等[5]通过建立三维仿真模型，得出基坑周围土体渗流呈现空间与时间差异性，降水速度对基坑周围土层变形影响较小；马昌慧等[6]通过数值软件建立基坑渗流场，得出水头损失在帷幕处影响显著，增加帷幕深度可进一步提高降水效果；薛丽影等[7]通过设计基坑模型试验测出基坑流网变化规律，水头差对水位降深和基坑渗流量的影响；Wang等[8]对上海基坑帷幕建立概念模型和数学模型得出地铁基坑降水是不可避免的，无法用帷幕隔断渗流路径是造成地面沉降的重要原因之一。

依托深圳某深基坑工程，利用Midas-GTS数值分析软件，采取流固耦合的分析方法模拟基坑开挖和坑内降水的全过程，研究开挖和降水对既有地铁隧道的影响，以期为实际的基坑设计和施工提供重要的数据参考，进而降低施工的风险性和基坑事故的发生率。

1 深基坑工程概况该深基坑于深圳福田区福华路和新洲路交叉口东北角，南侧紧邻地铁一号线隧道。

临近地铁侧开挖深度为17.8 m，远离地铁侧21.7～23 m，属于非等深基坑。

基坑整体近似梯形，长约90 m，宽约26～46 m，周长约260 m。

隧道与基坑最小净距为4.3 m。

快速鉴定新菠萝灰粉蚧的分子标记技术

快速鉴定新菠萝灰粉蚧的分子标记技术马光昌;王晓妮;牛黎明;龚治;温海波;金启安;彭正强【摘要】新菠萝灰粉蚧Dysmicoccus neobrevipes(Beardsley)是一种严重为害剑麻、番荔枝等经济作物的入侵性害虫.由于粉蚧类昆虫体型较小,且外部形态十分相似,难以达到快速准确识别.本文利用分子标记技术,研究了新菠萝灰粉蚧的快速鉴定方法.通过对新菠萝灰粉蚧、扶桑绵粉蚧、双条拂粉蚧、杰克贝尔氏粉蚧、大洋臀纹粉蚧、木槿曼粉蚧、甘蔗粉蚧和木瓜粉蚧等8种粉蚧的序列进行分析,针对新菠萝灰粉蚧设计了1对特异性引物,其扩增片段大小为552 bp(GenBank登录号为MF 363108),该引物对其它7种粉蚧没有扩增能力.该引物不仅对新菠萝灰粉蚧成虫具有扩增效能,对1龄若虫、2龄若虫和3龄若虫都具有同样的扩增能力,其最低检出阈值为437.5 pg/μL.该技术的建立,实现了在剑麻等苗木调运过程中对新菠萝灰粉蚧的快速准确鉴定,同时对新菠萝灰粉蚧的检疫和监测也具有重要的意义.%Dysmicoccus neobrevipes (Beardsley) is an invasive pest, which tremendously harms economic crops including Agave sisalana and Annona squamosa. It is very hard to rapidly and accurately distinguishing mealybugs because of their small size and similarity in external morphology. In this study, we had developed a method for the rapid differentiation of D. neobrevipes by molecular marker technique. Sequences of D. neobrevipes、Phenacoccus solenopsis Tinsley、Ferrisia virgata Cockerell、Pseudococcus jackbeardsleyi、Planococcus minor Maskell、Maconellicoccus hirsutus、Saccharicoccus sacchari Cockerell and Paracoccus marginatus were analysed. A pair of specific primers which is specific to D. neobrevipes was designed. A single 552 bp (GenBankaccession number: MF 363108) fragment was amplified using the specific primers only in D. neobrevipes. No fragments were amplified using the specific primers in other mealybugs. The amplification ability of specific primer was proved to be capable for not only adults but also 1st, 2nd and 3rd instar of D. neobrevipes. Moreover, the assays was capable of detecting 437.5 pg/μL. This technique should be useful tool for pes t rapid diagnosis, quarantine and monitoring during transportation of seedlings like A. sisalana.【期刊名称】《环境昆虫学报》【年(卷),期】2017(039)004【总页数】5页(P893-897)【关键词】新菠萝灰粉蚧;分子标记;快速鉴定;特异性扩增【作者】马光昌;王晓妮;牛黎明;龚治;温海波;金启安;彭正强【作者单位】中国热带农业科学院环境与植物保护研究所,海口 571101;中国热带农业科学院环境与植物保护研究所,海口 571101;中国热带农业科学院环境与植物保护研究所,海口 571101;中国热带农业科学院环境与植物保护研究所,海口571101;中国热带农业科学院环境与植物保护研究所,海口 571101;中国热带农业科学院环境与植物保护研究所,海口 571101;中国热带农业科学院环境与植物保护研究所,海口 571101【正文语种】中文【中图分类】Q963;S412新菠萝灰粉蚧Dysmicoccus neobrevipes(Beardsley)属半翅目Hemiptera，粉蚧科Pseudococcidae，洁粉蚧属Dysmicoccus(Beardsley，1959)，被我国列为进境植物检疫性有害生物。

开题报告书参考文献

开题报告书参考文献1. 引言引言的作用是对研究的背景和意义进行简要的介绍。

在开题报告中，引言部分可以通过引用相关文献来支持研究背景和问题陈述的合理性。

参考文献：1.Smith, A.B., Johnson, C.D., & Lee, H. (2018). The impact of climatechange on agricultural production: A literature review. EnvironmentalResearch Letters, 13(10), 103001.2.Zhang, Y., Wu, X., & Liu, J. (2019). The effects of air pollution on humanhealth: A comprehensive review. Journal of Environmental Health Science and Engineering, 17(1), 577-598.2. 研究背景研究背景部分需要对目前相关领域的研究进行综述，并论述当前研究中存在的问题和不足之处。

为了支持研究背景的描述，可以引用一些相关的文献。

参考文献：1.Anderson, J.T., Inouye, R.S., McKinney, A.M., & Colautti, R.I. (2012).Historical analysis reveals low genetic variation in Western North Americanpopulations of winter‐annual Arabidopsis thaliana. Journal of Heredity, 103(6), 794-803.2.Ren, C., Zhang, L., Ma, X., Luo, J., & Sun, W. (2018). Genetic diversityand population structure of Taraxacum erythrospermum and its geneticrelationship with T. kok‐sanshin. Ecology and Evolution, 8(18), 9151-9163.3. 研究目的与意义研究目的与意义部分需要明确研究的目标，并解释为什么这个研究是有意义的。

不同粒径支撑剂组合导流能力变化规律实验研究

第51卷第5期辽宁化工 Vol.51，No. 5 2022年5月 Liaoning Chemical Industry May，2022收稿日期： 2021-08-08 不同粒径支撑剂组合导流能力变化规律实验研究陈庆栋，周际永，陈维余，高双，宋爱莉，张宸，安恒序（中海油能源发展股份有限公司工程技术分公司，天津 300452）摘要：形成具有一定渗流能力的支撑裂缝是水力压裂实现高效改造的重要前提，在压裂的不同阶段往往会加入不同粒径的支撑剂，目前对多种支撑剂混合后导流能力变化规律研究尚不系统和深入。

因此，通过对20/40、30/50、40/70目陶粒及其不同组合下导流能力开展了实验评价，并通过导流能力保留率这一参数对其变化规律进行分析。

结果表明：支撑剂导流能力与支撑剂粒径成正相关的关系；不同粒径支撑剂组合的导流能力介于该组合的最大最小两种支撑剂的导流能力区间之内；支撑剂组合的导流能力值更接近于占比更高的支撑剂；当支撑剂粒径差别大时，会导致导流能力变低、导流能力保留率较低且受闭合压力的影响大。

研究成果得到了不同粒径支撑剂组合下导流能力的变化规律，为现场压裂施工中支撑剂优选及压裂效果预测提供了重要的指导。

关键词：压裂；支撑剂组合；导流能力；变化规律中图分类号：TE357.12 文献标识码： A 文章编号： 1004-0935（2022）05-0593-03随着低渗、特低渗及其他非常规储层的不断动用和开发，水力压裂作为此类储层高效改造的重要技术，起到越来越重要的作用[1-3]。

在水力压裂工艺中，形成具有较大渗流能力的支撑裂缝是实现高效改造的重要指标[4-5]。

在压裂施工效果预测中，需使用到裂缝的导流能力这一关键参数[6-8]。

在进行压裂工艺改造中，在施工的不同阶段往往会泵入不同粒径的支撑剂[9-10]，当不同粒径的支撑剂混合后，其导流能力与单一粒径的支撑剂相比会产生一定的变化，无法使用单一支撑剂导流能力进行计算[11-12]。

沁水盆地典型煤矿区煤的流速敏感性实验及控制机理

沁水盆地典型煤矿区煤的流速敏感性实验及控制机理孟召平;侯安琪;张鹏;郝海金;武杰【摘要】采用沁水盆地3个典型煤矿中、高煤阶煤样,开展了实验室煤样流速敏感性实验,分析了不同流速条件下煤样渗透率的变化规律,建立了煤储层渗透性与流速之间的关系和模型,揭示了中、高煤阶煤储层流速敏感性的控制机理.研究结果表明,煤样渗透率随流速发生变化,且存在一个临界流速.在临界流速之前随着注入流量(或流速)的增加煤样渗透率增加,当流速超过临界流速后,煤样的渗透率随着流体流速的增加反而减少.煤储层流速敏感性主要受控于煤储层物性和煤中速敏矿物.随着煤储层孔隙度、渗透率和流体流量的增高,煤储层速敏损害率按对数函数关系增高.实验煤样黏土矿物占矿物质含量为66.63％～99.89％,主要以高岭石、伊利石为主,存在潜在的速敏伤害,速敏实验结果表明,本区实验煤样存在不同程度的速敏损害,煤样速敏损害程度由弱至中等偏强,临界流速低.随着煤中黏土矿物含量的增加,煤储层速敏损害率也增高.在煤层气并排采过程中,寺河煤矿和西山煤矿煤层气井排采降速应为赵庄煤矿的6倍左右.%By using medium and high rank coal samples from three typical coal mines in Qinshui Basin,an experimental study on flow rate sensitivity has been carried out.The permeability variation under different flow conditions is analyzed and the relationship models between coal reservoir permeability and flow rate are established.Furthermore,the control mechanisms of flow rate sensitivity about medium and high-rank coals are revealed.It is shown that the coal sample permeability varies with the flow rate,and there is a critical flow velocity.Before the critical flow rate,with the increase of injection flow rate (or velocity),the permeability of coal sample increases.When the velocity exceeds the critical value,coalpermeability will decrease with the rise of injection flow rate.The flow rate sensitivity is mainly controlled by coal physical properties and flow rate sensitive minerals.With the increase of porosity,permeability and fluid flow rate of coal reservoir,the flow sensitive damage rate of coal reservoir increases as logarithmic function.The clay minerals in the experimental coal samples accounts for 66.63％-99.89％,and are mainly kaolinite and illite.So it indicates these coals exist potential flow rate sensitive damage.The results of flow rate sensitive experiment show that the coal samples in this area have different degrees of flow rate sensitive damage,and the flow rate sensitive damage degree of coal sample is from weak to moderate strong,the critical velocity is lower.With the increase of clay mineral content in coal,the flow sensitive damage rate of coal reservoir is also increased.In the process of CBM well drainage,pressure drop rate of Sihe and Xishan Coal Mine should be about six times of that of Zhaozhuang Coal Mine.【期刊名称】《煤炭学报》【年(卷),期】2017(042)010【总页数】8页(P2649-2656)【关键词】沁水盆地;煤储层;流速敏感性;控制机理【作者】孟召平;侯安琪;张鹏;郝海金;武杰【作者单位】中国矿业大学(北京)地球科学与测绘工程学院,北京100083;山西晋城无烟煤矿业集团有限责任公司煤与煤层气共采国家重点实验室,山西晋城048000;中国矿业大学(北京)地球科学与测绘工程学院,北京100083;中国矿业大学(北京)地球科学与测绘工程学院,北京100083;山西晋城无烟煤矿业集团有限责任公司煤与煤层气共采国家重点实验室,山西晋城048000;山西晋城无烟煤矿业集团有限责任公司煤与煤层气共采国家重点实验室,山西晋城048000【正文语种】中文【中图分类】P618.11煤储层流速敏感性是影响煤层气井产能的重要因素之一，在煤层气井排采过程中排采强度过大不仅会造成压裂砂的返吐，而且会引起煤层激动，使裂隙产生堵塞效应，降低渗透率，妨碍煤层整体降压，影响煤层气开采效果。

7-蒋瑞年-混凝土无破损应力检测.

Larose & Hall, Monitoring stress related velocity variation in concrete with a 2.10−5 relative resolution using diffuse ultrasound
试验：
尾波干涉技术
Simon Christian Stählerand Christoph Sens-Schönfelder, Monitoring stress changes in a concrete bridge with coda wave interferometry
声波参数对混凝土应力的敏感性
波谱面积随应力的变化 Variation of Spectrum Area with Stress
LIN Jun-zhi 等，AN EXPERIMENTAL RESEARCH ON THE CORRELATION OF ACOUSTIC PARAMETERS AND STRESS OF CONCRETE, Chinese Journal of Rock Mechanics and Engineering, Aug. 2005, vol. 24, 4988-4996.
混凝土应力检测常用方法
无损检测技术 • 声发射技术 • 声弹性应力测试技术 • 尾波干涉技术 • 非线性超声波技术
声波参数对混凝土应力的敏感性
波速随应力的变化 Variation of Pulse Velocity with Stress
LIN Jun-zhi 等，AN EXPERIMENTAL RESEARCH ON THE CORRELATION OF ACOUSTIC PARAMETERS AND STRESS OF CONCRETE, Chinese Journal of Rock Mechanics and Engineering, Aug. 2005, vol. 24, 4988-4996.