一种压电喷墨打印机喷头的动力学特性研究

为研究压电薄膜驱动的应用,介绍了一种MEMS压电喷墨打印机喷头的工作原理.重点研究了逆压电效应作用产生的机械振动特性.模型结构由一种耐热玻璃与沉积在其表面的压电薄膜复合而成.针对圆形、方形两种形状的压电薄膜,利用有限元分析软件ANSYS分别求得复合结构的最大静位移0.57μm和0.36 μm,一阶固有频率23.90 kHz和22.30 kHz,并比较了两种情况下的动力特性.仿真结果表明,所施加驱动交流电压的频率对该结构可产生很大的影响,其最大机械变形主要取决于谐振频率,从而为喷墨打印机喷头及类似器件的设计提供参考.     

大位移压电陶瓷驱动器的设计与试验

针对大位移压电陶瓷驱动器，研究了压电陶瓷双晶片的驱动效能。基于压电陶瓷材料的逆压电效应，应用压电陶瓷双晶片在机械自由、电学短路状态下，一片加正向电压缩短另一片加反向电压伸长共同作用产生弯曲变形，通过组合设计将压电陶瓷双晶片的弯曲变形位移叠加起来，实现了压电陶瓷驱动器的大位移输出。在相同电压的条件下，此压电陶瓷驱动器的输出位移量比叠层驱动器有较大的增加，达200μm，结构尺寸也大大减小。该驱动器不需要位移放大机构，可直接应用于有大位移要求的机构驱动。     

新型压电陶瓷驱动器的特性分析

讨论了一种基于压电陶瓷的新型叠堆驱动器,并阐述了其工作原理,推导出该驱动器的力学性能公式。基于压电陶瓷材料的机电耦合特性,运用ANSYS有限元软件对此驱动器进行了数值分析,研究了其驱动性能,分析结果表明,其输出位移和输出力均与输入电压呈线性关系,在较低电压下可获得较大变形量,且具有良好的动态响应特性。该叠堆压电驱动器结构简单、尺寸小、成本低,通过输入电压即可实现位移控制,可作为较好的自适应控制驱动器应用于智能摩擦阻尼器的驱动装置。     

基于压电喷墨印刷的墨滴速度大小的理论研究

通过分析压电喷墨印刷的驱动原理及波传导理论,并结合牛顿第二定律、压电驱动器的在驱动电压下的体积位移和窄通道下压力波的算法公式,推导出了墨滴速度的算法公式,最后分析了其影响因素。     

四自由度压电微夹钳的结构设计及尺寸参数优化

为提高微夹钳操作微对象时的灵活性,探索四自由度压电微夹钳的实现问题,将制成相应形状并分割驱动电极的两片压电陶瓷晶片进行粘结,制作出微夹钳,并将两组空间垂直交叉的横向逆压电效应作用于钳指上,使单个钳指产生夹持方向和垂直于夹持方向的微位移,从而使整个微夹钳(两个钳指)具有4个自由度.在综合考虑微夹钳输出位移、固有频率、制作工艺的情况下,采用有限元分析方法,对钳指长度、宽度、厚度进行了优化,对优化后微夹钳的输出位移和振型进行了分析.对微夹钳的输出位移进行了测试,结果表明:在60 V的最高驱动电压作用下,左、右两钳指沿夹持方向的最大位移分别为25.6μm、24.3μm,沿垂直于夹持方向的最大位移分别为32.1μm、30.9μm;两钳指的输出位移具有良好的重复性.     

基于电流控制的压电陶瓷驱动器

为了解决电压控制型压电陶瓷驱动器驱动压电陶瓷时存在的迟滞、蠕变和带宽窄的问题，设计了基于电流控制的压电陶瓷驱动器，利用压电陶瓷致动器位移与其所带电荷量间的线性关系，该驱动器通过控制压电陶瓷的充电电流和时间控制其位移量．在此基础上，提出了以分辨率换取稳定性的动态保持控制方法，采用该电流型驱动器，实现了开环下对压电陶瓷致动器的稳定、快速、高精度定位．实验结果表明，该驱动器驱动行程为10μm的压电陶瓷时，满行程带宽大于1．5kHz，重复定位精度小于4nm（0．4％）．     

结构表面电激厚剪压电驱动器动态特性研究

该文对粘贴在各向同性半平面结构表面的高频激励厚度剪切压电驱动器所产生的波传播特性提供了一种实用的解析与数值的分析方法.首先选用压电驱动器振动模式为厚度剪切模式,而驱动器下的半平面弹性体波传播的解析解则根据弹性力学应变积分求位移特解的方法得到,然后根据边界条件得到了整个结构中波传播的求解方案,通过数值模拟计算了半平面体上...     

新型纳米分辨率位移定位平移台的研制

为克服已有压电驱动器存在的结构及控制系统复杂、定位行程小等缺陷,利用压电陶瓷的逆压电效应设计并制作了一种新型的压电纳米步进驱动器,建立光栅测试系统对这种压电驱动器的动态性能进行了测试.将压电纳米步进驱动器与电磁伺服马达耦合,设计新颖驱动结构,利用微机通过步进运动控制卡统一控制,实现大范围一维纳米分辨率位移定位.系统样机解决了所研制压电纳米步进驱动器双向运动、实用定位等问题.位移定位分辨率为50 nm,定位行程为100mm,纳米分辨率定位最大速度为0.6 mm/s.     

压电厚膜驱动的高刚度微变形镜的制备

研究制备了一种压电厚膜微变形镜,微变形镜的连续薄膜式单晶硅镜面由61单元压电厚膜致动器阵列驱动.以镜面冲程与工作频带宽为目标,对微变形镜的结构参数进行优化设计,根据优化参数采用硅微加工技术试制了61单元致动器的微变形镜.镜面、压电陶瓷与弹性支撑层厚度分别为100μm、60μm与60μm,单元间距为5mm,通光口径为40 mm.对制备的样品性能进行了测试,微变形镜在100 V电压驱动下变形量约为2.84μm,工作带宽大于10 kHz.测试结果还表明压电厚膜驱动的微变形镜拥有较高刚度,有利于提高镜面初始平面度.     

压电薄膜微传感器振动模态的仿真分析

以压电本构方程为基础，建立了压电薄膜微传感器机电耦合的有限元模型，采用有限元分析软件ANSYS7．0对压电薄膜微传感器进行了模态分析，同时分析了压电薄膜微传感器的结构尺寸对振动模态的影响，探讨了影响压电薄膜微传感器工作稳定性和响应速度的关键因素，结果表明为了提高压电薄膜微传感器的工作稳定性和响应速度，应该在符合工艺要求和保证其它特性的前提下，尽量减小微悬臂梁结构长度，增加多晶硅层厚度，限制PZT层厚度，而微悬臂梁宽度的影响较小。     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

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