Carrier fringe method of moire interferometry for tiny strain measurements in micro-field

In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the specimen surface, and the strain can be deduced from the changes in carrier fringes before and after the deformation of an object. Four coherent laser beams are used to obtain the carrier fringe patterns of field U and V. Both theoretical analysis and numerical simulation indicate that the ideal accuracy of strain can be controlled within a range of ±1με. Case study of a plane extension experiment shows that the measurement accuracy of strain can be controlled within the range of ±10με. The average strain values of every row of field U and every column of field V can be obtained by using this method, and approximated strain of every pixel in the whole-field can be further acquired, and thus it is possible to measure tiny strains occurred in a micro-field. The technology in this paper can provide comprehensive information for analyzing related mechanical content in the field of MEMS.

Effects of different irrigation methods on micro-environments and root distribution in winter wheat fields

The irrigation method used in winter wheat fields affects micro-environment factors, such as relative humidity（RH） within canopy, soil temperature, topsoil bulk density, soil matric potential, and soil nutrients, and these changes may affect plant root growth.An experiment was carried out to explore the effects of irrigation method on micro-environments and root distribution in a winter wheat field in the 2007–2008 and 2008–2009 growing seasons.The results showed that border irrigation（BI）, sprinkler irrigation（SI）, and surface drip irrigation（SDI） had no significant effects on soil temperature.Topsoil bulk density, RH within the canopy, soil available N distribution, and soil matric potential were significantly affected by the three treatments.The change in soil matric potential was the key reason for the altered root profile distribution patterns.Additionally, more fine roots were produced in the BI treatment when soil water content was low and topsoil bulk density was high.Root growth was most stimulated in the top soil layers and inhibited in the deep layers in the SDI treatment, followed by SI and BI, which was due to the different water application frequencies.As a result, the root profile distribution differed, depending on the irrigation method used.The root distribution pattern changes could be described by the power level variation in the exponential function.A good knowledge of root distribution patterns is important when attempting to model water and nutrient movements and when studying soil-plant interactions.

HIGH PERFORMANCE ELECTRIC FIELD MICRO SENSOR WITH COMBINED DIFFERENTIAL STRUCTURE

This paper presents a high performance electric field micro sensor with combined differential structure.The sensor consists of two backward laid micro-machined chips,each packaged by polymer and metal.The novel combined differential structure effectively reduces various environmental affections,such as thermal drift,humidity drift and electrostatic charge accumulation.The sensor is tested in near-ground place as well as balloon-borne sounding.In different weather conditions,the measurement results showed good agreement with those of the commercial electric field mill.

Velocity distribution of the flow field in the cyclonic zone of cyclone-static micro-bubble flotation column

Laboratory experiments have been conducted to study the flow field in a cyclone static micro-bubble flotation column. The method of Particle Image Velocimetry (PIV) was used. The flow field velocity distribution in both cross section and longitudinal section within cyclonic zone was studied for different circulating volumes. The cross sectional vortex was also analyzed. The results show that in cross section as the circulating volume increases from 0.187 to 0.350 m 3 /h, the flow velocity ranges from 0 to 0.68 m/s. The flow field is mainly a non-vortex potential flow that forms a free vortex without outside energy input. In the cyclonic region the vortex deviates from the center of the flotation column because a single tangential opening introduces circulating fluid into the column. The tangential component of the velocity plays a defining role in the cross section. In the longitudinal section the velocity ranges from 0 to 0.08 m/s. The flow velocity increases as does the circulating volume. Advantageous mineral separation conditions arise from the combined effects of cyclonic flow in cross and longitudinal section.

Evaluation of micro-behavior of strain field in Chinese mainland with the GPS time se-ries

Based on the time series of GPS station coordinate in the international Earth reference frame （ITRF）, we evaluate annual micro-behavior of strain field in Chinese mainland with the triangle method. The results show that the annual micro-behavior of strain field is divided into two parts by the north-south earthquake belt in the research region. The prevailing direction of compressive principal strain field is nearly consistent in the western region. From west to east, the direction varies from NS to NE. It is in accordance with the direction of the modem compressive principal strain field. This suggests that geologic deformation in western region was mainly caused by that India tectonic plate pushes the research region northward and the Siberia plate pushes it southward relatively. It is an inheritance of new tectonic motion. The prevailing direction of the compressive principal strain field does not exist in the eastern region .The annual biggest shear strain is different greatly in every grid-cell. The values varies from 4.13×10^-8 to 7.0×10^-10. By and large the annual biggest shear strain in the western region is bigger than that in the eastern region. And so is the variation between any two consecutive biggest annual shear strains in the same grid-cell. The annual surface dilatation show that in most grid-cells of the research region the surface dilatation is in compressibility, and the variation between any two consecutive annual surface dilatation in the same grid-cell is small.

ELECTRIC FIELD MICROSENSOR BASED ON THE STRUCTURE OF PIEZOELECTRIC INTERDIGITATED CANTILEVER BEAMS

This paper presents the design, fabrication, and preliminary experimental result of an electric field microsensor based on the structure of piezoelectric interdigitated cantilevers with staggered vertical vibration mode. The working principle of this electric field microsensor is demonstrated, and the induced charges and structural parameters of this microsensor are simulated by the finite element method. The electric field microsensor was fabricated by Micro-Electro Mechanical Systems(MEMS) technique. Each cantilever is a multilayer compound structure(Al/Si3N4/ Pt/PZT/Pt/ Ti/SiO 2/Si), and Piezoelectric, PieZ oelectric ceramic Transducer(PZT)(PbZ rxTi(1–x)O3) layer, prepared by sol-gel method, is used as the piezoelectric material to drive the cantilevers vibrating. This electric field microsensor was tested under the DC electric field with the field intensity from 0 to 5×104 V/m. The output voltage signal of the electric field microsensor has a good linear relationship to the intensity of applied electric field. The performance could be improved with the optimized design of structure, and reformative fabrication processes of PZT material.

A Fractional Micro-Macro Model for Crowds of Pedestrians Based on Fractional Mean Field Games

Modeling a crowd of pedestrians has been considered in this paper from different aspects. Based on fractional microscopic model that may be much more close to reality, a fractional macroscopic model has been proposed using conservation law of mass. Then in order to characterize the competitive and cooperative interactions among pedestrians, fractional mean field games are utilized in the modeling problem when the number of pedestrians goes to infinity and fractional dynamic model composed of fractional backward and fractional forward equations are constructed in macro scale. Fractional micromacro model for crowds of pedestrians are obtained in the end. Simulation results are also included to illustrate the proposed fractional microscopic model and fractional macroscopic model, respectively. © 2014 Chinese Association of Automation.

微通道内流流场的数值模拟及Micro-PIV测量

采用数值模拟与实验研究方法对直管微通道内流流场进行了详细研究.实验测量借助Micro-PIV技术,采用3μm荧光示踪粒子、10倍显微物镜和14位灰阶CCD相机获取微尺度流场速度分布.利用Fluent数值计算软件,将微尺度通道壁面粗糙元抽象为多孔介质模型,采用realizable k-ε两方程模型,对边长为600μm和800μm的方形断面微尺度直通道分别在Re=100和Re=300条件下进行数值模拟,模拟结果与同工况下Micro-PIV实验测量结果进行对比,结果表明基于多孔介质模拟壁面粗糙元的realizable k-ε两方程模型能够良好地模拟微尺度管流流动,并且获得了多孔介质厚度采用微尺度通道的相对粗糙度折算,多孔介质的粘性阻力系数和惯性阻力系数由多孔介质区域内的流态及阻力计算的方法.

场驱动医疗微机器人:材料制备工艺不断优化的应用前景

背景:微机器人具有体积小、灵活、靶向性强等特点,可以在狭窄的环境下通过单体或集群的方式完成复杂的工作。随着材料、制备工艺以及驱动方式的不断优化,其在生物医学领域内显示出越来越重要的应用价值。目的:分析场驱动微机器人在生物医学领域的应用并展望其应用前景。方法:以“微机器人,纳米机器人,驱动,生物医学,医疗”为中文关键词,以“microrobots,micro-robots,nanorobots,micromachine,microswimmer,medical”为英文关键词,分别检索万方以及Pub Med数据库,检索时间范围重点为2010年1月至2024年1月,同时纳入少数远期文献。通过阅读文题、摘要初步筛选,排除重复性研究、低质量期刊以及与内容不相关的文献,阅读全文后最终纳入66篇文献进行综述。结果与结论:场驱动医疗微机器人涵盖了磁、光、热、超声及多种混合因素驱动机器人。场驱动机器人已被应用于肠道诊断、药物靶向治疗及干细胞治疗等多个领域。尽管医用微机器人在临床医学中已有少数应用,但大多数还处于理论和实验阶段。医用微机器人的未来面临诸多挑战,如实现大规模制备、进一步提升精确控制、解决回收或体内降解问题,以及所用材料是否会对人体产生不良反应等,此外微机器人还需与相应的微创医学手术相配合。

灌水器内流道流场Micro-PIV试验分析

采用Micro-PIV测量技术,在雷诺数Re=200情况下分别对方形截面平角和圆角齿形结构微尺度通道内流流体运动进行测量并加以比较,寻找灌水器内流流动规律和流道堵塞机理。试验使用10倍显微物镜、14位灰阶PCO.1600相机、3?m荧光示踪粒子和仅允许610nm红光透过的滤光镜相配合获取清晰的粒子图像,通过图像处理技术得到高分辨率的流场速度矢量分布图和流线图。试验发现各类微通道齿间内流充分发展后是一种重复性流动,平角微通道顶角和转角内侧存在低速涡旋区,圆角微通道只在转角内侧出现回流,颗粒在低速涡旋区易发生沉积,是造成堵塞的主要原因。若缩小断面尺寸则低速回流区范围有所扩大,顶角转向处出现回流趋势,对防堵不利。

非牛顿流体微流场测量Micro-PIV系统研究

介绍了一种专用于非牛顿流体微流动测量Micro-PIV系统,主要包括微流场激发、微流动观察记录与数据处理三大部分。针对非牛顿流体流动激发形式多样性的特点,微流场激发部分包括显微镜冷热台、波形发生器和磁场发生仪,可以产生激发非牛顿流体为流场所需的电、磁及温度场。观察记录部分主要包括荧光显微镜、CCD等,用于观察并记录荧光示踪粒子的运动,获取荧光示踪粒子运动的视频文件。数据处理部分用于将视频文件进行图像处理以得到所需流场数据。应用该系统对非牛顿流体5CB液晶在电场作用下所激发的微流动进行了测量,重点测量了液晶盒侧面的速度剖面图,所得到的试验结果与计算结果非常吻合,且比传统测量方法更加快速、准确。此外,对温度场变化产生的液晶缺陷进行了试验研究,得到了连续加热冷却状态下的液晶缺陷形成温度变化趋势,即形成缺陷的温度逐渐升高,从开始的31.25℃逐渐升高至34.4℃后保持平稳。

Splitting Regularities of Thin Ferrofluid Layer Manipulated by Vertical Magnetic Field

The regular distribution of micro-droplets splitting from thin ferrofluid layer is systematic experimentally investigated, as the layer is placed in a vertical magnetic field. In this work, the field is applied in an instant manner and a slow manner, respectively; the field strength is linear increased. With instantly raising the field, it is observed that the ferrofluid layer is split into several regularly distributed micro-droplets, and that the number of micro-droplets is linear to the magnetic field strength and the thickness of the liquid layers. When the field is slowly increased, a liquid ring together with several micro-droplets appears from the ferrofluid layer splitting. A spatial drift of the micro-droplets is also observed in the process of increasing the magnetic field. Our results are useful for manipulating the splitting regularities of ferrofluid layers by magnetic field, which may be used in non-contact segmentation, and magnetically manipulated drug carriers for targeting the therapy, etc.

Finite element analysis of the effect of micro-pore defect on linear friction welding of medium carbon steel

Micro-pore is a very common material defect. In the present paper, the temperature fields of medium carbon steel joints with and without micro-pore defect during linear friction welding （LFW） were investigated by using finite element method. The effect of micro-pore defect on the axial shortening of joints during LFW was examined. The x- and y-direction displacements of micro-pore during the LFW process were also studied. In addition, the shape of micro-pore after LFW was observed. The heat conducted from the weld inteace to the specimen interior. The fluctuation range of the temperature curves for the joint with micro-pore is larger than that without micro-pore. Position of micro-pore changes with the change of the friction time. The circular shape of micro-pore becomes oval after welding.

不同形状疏水性微肋阵内流场Micro-PIV流动可视化研究

运用Micro-PIV显微粒子图像测速系统对不同截面形状、不同接触角微肋阵的流动特性展开可视化研究.通过制备接触角为83°、99.5°、121.5°、151.5°的疏水表面,研究Re数为100~450时工质绕流圆形、椭圆形和菱形微肋阵速度与流线变化,并对流场进行分析.实验结果表明,在圆形微肋阵中尾涡的出现相比于宏观尺度有明显延迟,直到Re达到250时在中间的圆柱尾部才出现对称漩涡.对比3种形状微肋阵可发现,椭圆形具有的流线型结构和菱形具有的细长结构不易发生边界层分离.在经过疏水性处理后,圆形针肋尾部的边界层分离明显延迟,接触角为151.5°的表面边界层最晚分离.

基于Micro-PIV的不同截面形状微柱群内部流场特性研究

采用显微粒子测速技术(Micro-PIV)对圆形、椭圆形及菱形等不同截面形状错排微柱群绕流流动进行研究,得到了不同雷诺数(Re)下微柱群内部的速度场、流线等绕流流场信息,分析了Re与截面形状对绕流流场结构的影响规律。研究结果表明,微柱体绕流过程中漩涡脱落相对于常规尺度具有一定的滞后性;圆形微柱体背风区最早发生流动分离,菱形、椭圆形次之;随着Re的增大,微柱体尾流区出现涡结构,回流长度逐渐增大,在三种截面形状微柱群绕流流动中圆形截面微柱群的回流长度和回流区域最大。

基于Micro-PIV和LBM的土壤孔隙网络中流体速度分布表征

土壤孔隙结构复杂多变,揭示其内部流场特性对于描述和预测土壤中水分传输、溶质迁移等现象至关重要.基于规则性的土壤孔隙网络模型,采用Micro-PIV(Micro-scale Particle Image Velocimetry,显微粒子成像测速系统)技术分析不同雷诺数下孔隙结构中流体运动的特征,通过LBM方法(Lattice Boltzmann Method,晶格玻尔兹曼方法)对孔隙结构中流场分布进行数值模拟研究.结果表明:微观尺度下孔隙网络模型中不同孔隙区域流速分布差异明显,中线区域流场呈规律性分布,孔喉处为高速区,流速达到0.001 4 m/s,水平方向相邻两圆柱靠近边界处存在低速区,速度不高于0.000 2 m/s,在垂直于流向方向上速度场具有良好的对称性;靠近上下边界的大孔隙区域流体优先通过,流体的速度可达到0.003 0 m/s.LBM方法模拟的孔隙网络模型中流场分布结果与试验获得的流场分布吻合,其平均均方根误差为0.009 4 m/s,表明土壤孔隙网络模型能有效模拟土壤孔隙,捕捉微观尺度上的流体运动特征,为应用孔隙网络模型研究土壤孔隙中溶质运移和反应等问题提供了微观尺度的度量工具.

PDMS微流控芯片微筛阵列流场的Micro-PIV分析

针对微流控芯片上的细胞培养技术,很多微流控芯片设计力图追求高通量,但并未考虑芯片中流场的分布状态,导致细胞培养效果不佳.本文介绍了直径1μm的荧光粒子以30μL/min的速度注入芯片中,利用Micro-PIV技术对设计的含有16μm微筛阵列的PDMS微流控芯片进行流场、流速的测试与分析,得到高分辨率的流场、速度矢量分布图,并且与ANSYS软件模拟结果进行比较.实验结果表明:液体经过微筛阵列时,流速逐渐减小,流场分布稳定均一,模拟结果与实际结果吻合.

Effects of aging in electric field on 2024 alloy

The effect of heat treatment in an electric field on micro plastic deformation characteristics of 2024 Al alloy was investigated. The mechanism of aging in an electric field affecting the micro plastic deformation behavior was preliminarily discussed. The results show that the resistance to micro plastic deformation of the alloy can be greatly increased by aging in an electric field. Aging temperature, aging time and electric field strength are selected by adopting the orthogonal design method and the optimum technological parameters are obtained.

Simulation of GaN micro-structured neutron detectors for improving electrical properties

Nowadays,the superior detection performance of semiconductor neutron detectors is a challenging task.In this paper,we deal with a novel GaN micro-structured neutron detector(GaN-MSND)and compare three different methods such as the method of modulating the trench depth,the method of introducing dielectric layer and p-type inversion region to improve the width of depletion region(W).It is observed that the intensity of electric field can be modulated by scaling the trench depth.On the other hand,the electron blocking region is formed in the detector enveloped with a dielectric layer.Furthermore,the introducing of p-type inversion region produces new p/n junction,which not only promotes the further expansion of the depletion region but also reduces the intensity of electric field produced by main junction.It can be realized that all these methods can considerably enhance the working voltage as well as W.Of them,the improvement on W of GaN-MSND with the p-type inversion region is the most significant and the value of W could reach 12.8μm when the carrier concentration of p-type inversion region is 10^17 cm^-3.Consequently,the value of W is observed to improve 200%for the designed GaN-MSND as compared with that without additional design.This work ensures to the researchers and scientific community the fabrication of GaN-MSND having superior detection limit in the field of intense radiation.

复杂微型构件特种能场辅助微成形研究进展

随着复杂微型构件特征尺寸的不断减小,尺度范围不断扩大,材料种类日益增多,单纯依靠模具施加载荷的塑性微成形技术受到越来越多的挑战,成为制约微型构件实际应用的关键技术瓶颈。特种能场微成形技术利用超声场、电场和电磁场等能场与材料相互作用产生的特殊物理效应进行微加工,可以明显改善材料的塑性流动,降低微成形载荷,从而显著提高微型构件成形质量。本文综述了超声场、电场和电磁场等特种能场作用下塑性微成形的研究进展。首先探讨了特种能场作用下材料力学性能响应机制及微成形尺度极限,其次介绍了特种能场作用下微成形过程中材料微观组织结构演化与缺陷形成机理,最后总结了特种能场辅助微成形的关键工艺参数及其对成形质量的影响规律,强调了通过优化工艺参数实现高精度成形的重要性,为复杂微型构件的低成本、高效制造提供了新的技术路径。