Multi-channel micro neural probe fabricated with SOI

Silicon-on-insulator(SOI) substrate is widely used in micro-electro-mechanical systems(MEMS).With the buried oxide layer of SOI acting as an etching stop,silicon based micro neural probe can be fabri-cated with improved uniformity and manufacturability.A seven-record-site neural probe was formed by inductive-coupled plasma(ICP) dry etching of an SOI substrate.The thickness of the probe is 15 μm.The shaft of the probe has dimensions of 3 mm×100 μm×15 μm with typical area of the record site of 78.5 μm2.The im...     

振片式超声波马达的研究

超声波马达是一种由超声振动而获得驱动力的新型马达。它利用作为定子的压电陶瓷振子,通过压电效应产生高频振动并依靠摩擦力来驱动压置在其上的转子运动。     

Application of time reversal mirror technique in microwave-induced thermo-acoustic tomography system

Microwave-induced thermo-acoustic tomography (MITAT) is a promising technique with great potential in biomedical imaging. It has both the high contrast of the microwave imaging and the high resolution of the ultrasound imaging. In this paper, the proportional relationship between the absorbed microwave energy distribution and the induced ultrasound source distribution is derived. Further, the time reversal mirror (TRM) technique based on the pseudo-spectral time domain (PSTD) method is applied to MITAT system. The simulation results show that high contrast and resolution can be achieved by the TRM technique based on PSTD method even for the received signals with very low signal-to-noise ratio (SNR) and the model parameter with random fluctuation. Supported by the National Natural Science Foundation of China (Grant No. 60771042), the National Hi-Tech Research and Development Program (“863” Project) (Grant No. 2007AA12Z159), 111 Project (Grant No. B07046), SiChuan Excellent Youth Foundation (Grant No. 08ZQ026-039), Program for New Century Excellent Talents in University of China and Program for Changjiang Scholars     

Optimizing loading path and die linetype of large length-to-diameter ratio metal stator screw lining hydroforming

In order to meet the high temperature environment requirement of deep and superdeep well exploitation, a technology of large length-to-diameter ratio metal stator screw lining meshing with rotor is presented. Based on the elastic-plasticity theory, and under the consideration of the effect of tube size, material mechanical parameters, friction coefficient and loading paths, the external pressure plastic forming mechanical model of metal stator screw lining is established, to study the optimal loading path of metal stator lining tube hydroforming process. The results show that wall thickness reduction of the external pressure tube hydroforming(THF) is about 4%, and three evaluation criteria of metal stator screw lining forming quality are presented: fillet stick mold coefficient, thickness relative error and forming quality coefficient. The smaller the three criteria are, the better the forming quality is.Each indicator has a trend of increase with the loading rate reducing, and the adjustment laws of die arc transition zone equidistance profile curve are acquired for improving tube forming quality. Hence, the research results prove the feasibility of external pressure THF used for processing high-accuracy large length-to-diameter ratio metal stator screw lining, and provide theoretical basis for designing new kind of stator structure which has better performance and longer service life.     

Design of a control system for a macro-micro dual-drive high acceleration high precision positioning stage for IC packaging

A macro-micro dual-drive positioning system showing good potential for high acceleration and high precision positioning required in IC packaging applications is devised in this paper. The dual-drive positioning stage uses a VCM (voice coil motor) driven macro positioning stage and a PZT piezo-electric driven micro positioning stage. The coupling characteristics of the system are analyzed to produce a control structure with a micro positioning stage that can dynamically compensate for the positioning error produced by the macro positioning stage. Models of the two positioning stages are described. The models cover both the mechanism and the actuator. For the macro positioning stage, friction characteristics are taken into account, and a controller with an LQG (linear-quadratic-Gaussian) control algorithm combining a feed-forward compensation algorithm is derived. A PID controller is used to control the micro positioning stage. Detailed designs are derived for the proposed approach, and the performance is validated by simulation. Supported by the National Natural Science Foundation of China (Grant No. 50705027), the National High Technology Research and Development Program of China (“863” Program) (Grant No. 2007AA04Z315) and Self-Planned Task of State Key Laboratory of Robotics and System (HIT) (Grant No. SKLRS200804B)     

基于机器视觉的螺纹缺陷检测方法

为了满足现代制造业自动化生产装配中在线检测要求,提出利用机器视觉的方法对螺纹缺陷进行检测.检测算法主要包括图像预处理、二值化、感兴趣区域提取、螺纹的边缘提取、螺纹的缺陷检测、缺陷量值的计算与存储.该算法由Visual C++6.0编程实现.实验结果表明,基于这种螺纹缺陷检测方法的准确率能够达到99.5%,一个螺纹的检测时间在300 ms以内,达到既定要求与目标.     

A load simulation method of piezoelectric actuator in FEM for smart structures

More and more piezoelectric materials and structures have been used for structure control in aviation and aerospace industry. More efficient and convenient computation method for large complex structure with piezoelectric actuation devices is required. A load simulation method of piezoelectric actuation is presented in this paper. By this method, the freedom degree of finite element simulation is significantly reduced, the difficulty in defining in-plane voltage for multi-layers piezoelectric composite is overcome and the transfer computation between material main direction and the element main direction is simplified. The concept of simulation load is comprehensible and suitable for engineers of structure strength in shape and vibration control, thereby is valuable for promoting the application of piezoelectric material and structures in practical aviation and aerospace fields. Supported by the National Natural Science Foundation of China (Grant Nos. 10772183 and 10532070) and Foundation Program of Chinese Academy of Sciences (Grant No. KJCX2-YW-L07)     

三维信息存储读出信号振幅的计算机仿真

针对信息存储低容量、低速率的现状,提出了将阵列激光器、波分复用技术(密集型波分复用)和多层镀膜相结合实现三维信息存储的方法。该方法利用光纤光学头的耦合物镜实现对光斑的自动近场聚焦,可实现海量信息的并行读写,并能极大地减少三维存储的寻道时间。对光电探测器检测的光信号幅度进行了计算机仿真分析,这种并行存储的探索是实现高密度、大容量的重要基础研究。     

异步电机的直接转矩控制仿真

采用空间矢量建立异步电机数学模型,利用Matlab中的Simulink库搭建了完整的仿真系统,并对仿真系统中的异步电机模块、逆变器模块和控制模块的搭建做了详细的描述。控制模块基于定子坐标系计算出转矩和定子磁链,根据转矩值和定子磁链值再发出控制开关量,以获得转矩的高动态性能。直接转矩控制与矢量控制相比,省去了复杂的坐标变换,克服了对电机转子参数的依赖性,具有转矩响应快的优点。仿真结果表明,直接转矩控制在异步电机中高速工况下具有良好的控制效果。     

磁悬浮列车用直线电机的有限元分析和电感计算

为研究磁悬浮列车长定子直线电机的性能,以德国TR08型磁悬浮列车长定子直线同步电机尺寸为基础,基于有限元方法建立了一个悬浮电磁铁模块的分析模型,对其牵引和悬浮电磁场进行了较为系统的分析,得到了不同动子极距下牵引和悬浮力的变化曲线.重点研究了长定子直线同步电机在分别改变定、动子电流和气隙大小的情况下,以及定动子绕组交直轴电感的变化情况,并通过多项式拟合和傅立叶分解得到了交直轴电感的经验公式.仿真结果表明,定子电流对气隙磁场和电感影响较小,当动子极距为266.5 mm时电机性能较佳,拟合得到的经验公式具有较高的精确度,平均误差小于5％.     

Study on pure silica core optical fibers

An optimal refractive index profile of pure silica core optical fiber (PSCF) was designed, in combination with the characters of the modified chemical vapor deposition (MCVD) process. Techniques of preform fabrication by a new furnace round heating MCVD process and fiber drawing process were reviewed. Difficulties in doping fluorine in silica, widening the depressed-index cladding and maintaining the index of fiber core were discussed. Methods used to overcome these difficulties were given at the same time. Additionally, the optimal refractive index profiles of PSCF were presented. Supported by the Hi-Tech Research and Development Program of China (Grant No. 2002AA312190), National Natural Science Foundation of China (Grant No. 60477017), Program for the New Century Excellent Talents in University (Grant No. NCET-06-0076), Beijing Natural Science Foundation (Grant No. 4052023) and the Beijing Jiaotong University Foundation (Grant No. 2006XM003)     

Numerical study on the separation and superposition of the influences from up- and downstream rotors

A three-dimensional Navier-Stokes solver is used to investigate the separation and superposition of the influences from upstream and downstream rotors in an axial-radial combined compressor for unsteady design applications. The data from rotor/stator and stator/rotor configurations show that the unsteady flow response in axial stator passage is caused only by one rotor. The results from the rotor/stator/rotor configuration revealed the superimposed characteristic of influences from upstream and downstream the rotor. The impact of the superimposed characteristic was studied by analyzing the virtual relative flow angle at the stator exit. The results show that the axial velocity in the passage of axial stator can be influenced by wake from upstream axial rotor and potential field of downstream radial rotor. While they are coupled to have an effect on the unsteady flow in axial statot passage, the excitation or suppression phenomena appear and lead to different levels of deterministic fluctuation kinetic energy. Their locations are determined by the frequencies of the involved influences. In addition, the variability of superimposed characteristic （ excitation and suppression） at the stator exit modulates the inlet flow angle for downstream rotor.     

Frequency-domain analysis of computer-controlled optical surfacing processes

Mid-high spatial frequency errors are often induced on optical surfaces polished by computer-controlled optical surfacing (CCOS) processes. In order to efficiently remove these errors, which would degrade the performances of optical systems, the ability of a CCOS process to correct the errors have been investigated based on the convolution integral model in view of the availability of material removal. To quantify the ability, some conceptions, such as figure correcting ability and material removal availability (MRA), have been proposed. The research result reveals that the MRA of the CCOS process to correct a single spatial frequency error is determined by its tool removal function (TRF), and it equals the normalized amplitude spectrum of the Fourier transform of its TRF. Finally, three sine surfaces were etched using ion beam figuring (IBF), which is a typical CCOS process. The experimental results have verified the theoretical analysis. The employed method and the conclusions of this work provide a useful mathematical basis to analyze and optimize CCOS processes. Supported by the National Basic Research Program of China (“973” Project) and the National Natural Science Foundation of China (Grant No. 50775215)     

Optical property of amorphous semiconductor mercury cadmium telluride from first-principles study

The structural and optical properties of amorphous semiconductor mercury cadmium telluride (a-MCT) are obtained by the first principles calculations. The total pair distribution functions and the density of states show that the a-MCT has the semiconductor characteristic. The calculated results of dielectric function show that E ₂ peak of the imaginary of dielectric function for the crystal mercury cadmium telluride abruptly disappears in the amorphous case due to the long-range disorders. And the imaginary of dielectric function of a-MCT shows a large broad peak, which is in agreement with the available results of other amorphous semiconductors. From the linear extrapolation of the curve ħωɛ ₂(ω)^1/2 versus ħω, it can be obtained that the optical energy gap of amorphous semiconductor Hg_0.5Cd_0.5Te is 0.51±0.05 eV. Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2007CB613205), the National Natural Science Foundation of China (Grant Nos.10725418, 10734090, 60576068), the Key Fund of Shanghai Science and Technology Foundation (Grant No. 08JC1421100) and the Knowledge Innovation Program of the Chinese Academy of Sciences     

Numerical modeling of concrete hydraulic fracturing with extended finite element method

The extended finite element method (XFEM) is a new numerical method for modeling discontinuity. Research about numerical modeling for concrete hydraulic fracturing by XFEM is explored. By building the virtual work principle of the fracture problem considering water pressure on the crack surface, the governing equations of XFEM for hydraulic fracture modeling are derived. Implementation of the XFEM for hydraulic fracturing is presented. Finally, the method is verified by two examples and the advan- tages of ...     

压电式胎压报警器供电装置的发电特性

提出利用压电发电装置替代电池为胎压报警器提供实时电能。根据胎压报警器结构特点,提出将压电发电装置安装在车轮轮毂上,利用车轮转动中的振动来发电的方案。通过试验的方法研究了压电振子在轮毂上不同安装方式下的发电特性。试验结果表明,在既垂直于轮毂又垂直于车轮滚动方向的安装方式下,压电振子可以有效克服离心力的影响并吸收来自车轮所在平面多个方向的振动,压电发电装置发电效果较佳,适合为胎压报警器供电。利用4片45mm×15mm×0.2mm的悬臂梁型压电振子并联为胎压报警器供电,其产生的能量能够满足胎压报警器的工作要求。     

圆锥外螺纹的线阵CCD非接触检测方法

为了提高圆锥外螺纹尺寸检测的精度并实现自动化测量,提出了基于线阵CCD的非接触测量方法.建立了包括计算机运动控制、图像数据自动采集和尺寸计算的测量系统,该系统通过控制高精度的线阵CCD扫描外圆锥螺纹在平行光场中的投影来获取螺纹图像.针对正投影时螺旋线对螺纹牙的投影产生局部遮挡的现象,通过调整螺纹轴线与光轴的角度消除遮挡,获取完整的螺纹牙投影.1维CCD图像信号经过中值滤波处理后进行一阶差分提取螺纹牙的轮廓点.对螺纹轮廓分段拟合并以亚像素级的轮廓推导出螺纹尺寸的计算公式.实验表明,该系统可以完成各项螺纹参数测量,精度高于5μm,重复性好,易于实现自动化测量.     

A new type counter electrode for dye-sensitized solar cells

A new type counter electrode for dye-sensitized solar cells (DSCs) was proposed which consists of substrate, aluminum film and platinum film. The new type counter electrode can obviously improve the photoelectric conversion efficiency of DSCs from 3.46% to 7.07% under the standard AM1.5 irradiation condition. Advantages and shortcomings of this new type counter electrode in terms of electrical properties, optical properties and anti-corrosive properties were analyzed. As a result, some improvements were proposed. Supported by the Key Foundation for Fundamental Research of Tianjin Municipal Science & Technology Commission in China ( Grant No. 06YFJZJC01700) and the National Basic Research Program of China (“973“ Project) (Grant Nos. 2006CB20260, 2006CB202603)     

红外镜头光学定心方法研究

针对红外镜头的材料特点和精度要求,提出了一种适用于科研生产的双向光学定心加工方法.从相对180°方向,用两台定心仪同时观察、测量红外透镜组件的两个球心像,根据测量结果重复调节专用的球心像调整工装,调两球心像相对轴线的位置,确定红外透镜组件的理想光轴.结果表明:某红外测量镜头的系统同轴度小于或等于0.02 mm,镜头的焦距相对误差仅为0.2%.     

Analysis for Rotor Losses of High Speed Permanent Magnet Synchronous Motor

OINTRoDUCTIONPermanentMagnetSynchronousMotor(PMSM)havebeeninawideapplicationforsuchgoodfeaturesaslowlosses,hightorquecapacity,higheffciency,stablespeed.NowwiththedevelopmentofNdFeB,muchatten-tionhasbeengiventoradialfluxPMSMasahighspeedmotor.ThespeedofPMSMisusuallyintherangeofloOOOrpmtol8OoOOrpmandevenhigher.ThelossesofhighspeedPMSMshouldbeconsideredseriously.Ifthelossesaretoomuch,theperformanceofthemotorwouldbeheavilyaffected.Amongallthelosses,thero-torlossisthemostharmful.Exc…