新型推挽激励的谐振式微机械静电场传感器

为了提高传感器的信噪比(signal-to-noise ratio,SNR),降低器件的耦合干扰,基于表面微机械工艺设计制作了一种新型推挽激励方案的谐振式微型静电场传感器.该传感器敏感结构主要包括静电梳齿激励电极、屏蔽电极和感应电极3部分.工作时,在该传感器敏感结构同一侧梳齿的固定端上加入反相相等的激励信号,实现差分激励,使屏蔽电极在谐振频率处振动,从而在感应电极上感应出差分电流信号,通过相关检测方式检测出传感器该输出信号的二次谐波分量,即可获得被测静电场强度大小.该传感器的新型结构设计和激励检测方案可获得最大电场响应灵敏度,并有效抑制了同频耦合串扰和共模噪声.常压室温(约25℃)测试结果表明,在量程(-15 kV/m～15 kV/m)内,只需要5 Vpp激励电压,其中线性度(端基线性度)达到了1.03%,分辨率优于200 V/m.     

新型便携式薄膜体声波谐振气体传感器的研制与应用

基于MEMS工艺的新型阵列化薄膜体声波谐振器(FBAR),可实现对多种挥发性气体的高通量检测.本文通过对薄膜体声波谐振器表面进行不同的化学官能团修饰,形成了传感器阵列,挥发性气体可以在不同化学官能团修饰的器件界面进行选择性沉积,通过监测传感器的谐振频率变化,形成气体响应的特征条形码,由此实现了对不同挥发性气体更加准确的检测.相对于传统的气体检测手段,由于采用了MEMS工艺,该传感器具备体积小巧、反应快捷、灵敏度高等优势,同时通过多化学官能团修饰的阵列化传感器可以实现一套传感装置对不同气体的检测,大大提高了气体检测的效率、识别能力和准确性.     

高灵敏Love波传感器及其关键材料

Love波传感器是声表面波传感器的一种,其灵敏度最高.对Love波生物、化学传感器的研究现状进行了综述,着重分析了波导材料及其厚度、基板材料及其切向对传感器的灵敏度及温度稳定性的影响关系.指出采用高频谐振型的器件结构并结合聚合物波导的方案可进一步提高Love波传感器的灵敏度.     

一种基于光纤F-P腔的石墨烯谐振式压力传感器

谐振式传感器具有良好的重复性、分辨率和稳定性,全光纤谐振式微型传感器则集合了微纳结构与光纤传感特性两者的优点。石墨烯作为近年来发现的一种新型材料,具有良好的热学和力学特性,可以作为谐振式传感器中的敏感元件。本文提出了一种基于光纤F-P结构的石墨烯谐振式压力传感器,其兼具微机械传感器和光纤谐振器的优点,具有较高的谐振频率,在测量压力的实验中展现出良好的性能,压力灵敏度最高可达2. 93Hz/Pa,具有重要的应用价值。     

新型高灵敏度GLV光学电流传感器设计与性能分析

本文结合GLV技术设计了一种适于检测高压交流电的新型光学电流传感器.这一设计具有温度稳定性好、大电流下灵敏度高、频率响应范围宽等特点,且测量芯片制作工艺简单、成本低廉.通过有限元分析和数值计算对器件的模态、工作性能、热膨胀特性等进行了分析模拟,结果表明:测量芯片量程达500A～2000A,并可通过改变设计参数灵活调整;一阶固有频率接近60kHz,大电流下灵敏度接近0.2dB/A,外界温度变化±50K时传感器测试误差在0.7%以内.     

基于集成氮化硅微腔的光学传感芯片研究

近年来随着传感器在生物探测领域的应用,提高传感器芯片的灵敏度成为研究的热点。利用氮化硅微腔灵敏度高、成本低、易于集成的优点,设计制造了1550 nm波长下二维、三维结构品质因子分别为1.6×104和4×103的悬空耦合传感器芯片,并详细研究了集成氮化硅微腔光学传感芯片在折射率测量方面的应用。     

共平面低功耗CO气体传感器的设计及制作

设计了一种新型的共平面微结构气体传感器,利用MEMS技术制作了传感器样品.实验测得该传感器对于体积分数为50×10~(-6)CO气体的灵敏度为8.6(R0/R),功耗为82mW,响应时间约5s,恢复时间约22s,该传感器的灵敏度是同种敏感材料烧结型传感器(测体积分数50×10~(-6) CO气体)的2.5倍,而功耗却是同种敏感材料烧结型传感器的1/2,是一种具备了体积小、重量轻、功耗低、灵敏度高、便于与其它器件集成等特点,而且制作工艺简单,成本较低的微结构CO气体传感器.     

工艺特性对二维微加速度传感器性能的影响

工艺特性在很大程度上决定了MEMS器件最终的功能特性.本文针对自主设计的二维微加速度传感器,在概念设计阶段定量分析了工艺特性对传感器性能的影响,主要包括质量偏心、梁加工误差、结构对称性、非平行效应等.结果表明:质量偏心会引起角位移变化,但对主轴刚度无影响,传感器不会有输出;在现有工艺条件下,可忽略梁厚误差的影响,但需严格控制梁宽误差;各种不对称方案对传感器主轴刚度和横向灵敏度的影响程度不同,不对称方案对横向灵敏度的影响随着不对称性的加剧而增大;非平行效应使得在相同外载荷作用下敏感轴向位移减小,但静态灵敏度却有所增加.     

用于挥发性有机化合物探测的微悬臂梁传感器

在研制成功的用于化学气体探测的热驱动微悬臂梁谐振器的基础上,提出了基于这种微悬臂梁谐振器,并以聚合物涂层作为挥发性有机化合物吸附敏感层的谐振式气体传感器.利用3种聚合物材料：聚氧化乙烯（PEO）、聚乙烯醇（PVA）和聚乙二醇乙醚醋酸酯（PEVA）,在微悬臂梁谐振器上制备气体敏感层,探测6种挥发性有机化合物：甲苯、苯、乙醇、丙酮、己烷和辛烷.通过有限元分析估计了聚合物涂层的工作温度.用喷射法制备了PVA和PE-VA涂层,用点滴法制备了PEO涂层.测试了传感器的开环幅频特性,实验检测了气体传感器的谐振频率变化与分析物蒸气浓度的关系以及传感器对相对湿度的响应,分析了传感器的灵敏度和线性度.实验结果表明,这种涂覆聚合物敏感层的热驱动微悬臂梁谐振器为探测挥发性有机化合物提供了良好的平台.根据实验结果,可开发几种基于不同聚合物敏感层的高灵敏度微型气体传感器.     

新型谐振式硅微机械加速度计

制作出一种新型结构的谐振式硅微加速度计，其输出频率信号可以克服微机电系统器件输出微弱信号检测的困难、采用双端固定音叉作为谐振器，在加速度作用下，质量块的惯性力通过悬臂梁施加于音叉轴向，利用音叉谐振频率的变化测量加速度．在每个音叉臂上制作了梳齿结构，用梳齿间的静电力激励音叉产生谐振，并利用其构成的电容检测其振动频率．该加速度计采用体硅工艺制作，文中给出了工艺流程、用有限元方法仿真估算，得到传感器的灵敏度约为2／gHz．     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

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.     

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.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

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.