Optimum design of large span concrete filled steel tubular arch bridge based on static,stability and modal analysis

A three-dimensional finite element model was established for a large span concrete filled steel tubular (CFST) arch bridge which is currently under construction. The arch rib, the spandrel columns, the prestressed concrete box-beam, the cast-in-situ concrete plate of bridge deck, the steel box-beam and the crossbeams connecting the two pieces of arch ribs, were modeled by three-dimensional Timoshenko beam elements (3DTBE). The suspenders were modeled by three-dimensional cable elements (3DCE). Both geometric nonlinearity and prestress effect could be included in each kind of element. At the same time a second finite element model with the same geometric and material properties excepted for the sectional dimension of arch rib was set up. Static dynamic analyses were performed to determine the corresponding characteristics of the structure. The results showed that the arch rib's axial rigidity could be determined by static analysis. The stability and vibration of this system could be separated into in-plane modes, out-of-plane modes and coupled modes. The in-plane stability and dynamic characteristics are determined by the arch rib's vertical stiffness and that of out-of-plane is determined by the crossbeams' stiffness and arch rib's lateral stiffness mainly. The in-plane stiffness is much greater than that of out-of-plane for this kind of bridge . The effect of geometric nonlinearity and prestress effect on bridge behavior is insignificant.     

Measuring in-plane micro-motion of micro-structure using optical flow

Optical flow method is one of the most important methods of analyzing motion images.Optical flow field is used to analyze characteristics of motion objects.According to motion features of micro-electronic mechanical system(MEMS)micro-structure,the optical algorithm based on label field and neighborhood optimization is presented to analyze the in-plane micro-motion of micro-structure.Firstly,high speed motion states for each frequency segment of micro-structure in cyclic motion are frozen based on stroboscopic principle.Thus a series of image sequences,and can obtain reliable and precise optical field and reduce computing time.As micro-resonator of urement precision of the presented algorithm is high,and measurement repeatability reaches 40 am under the same experiment condition.     

Mask synthesis and verification based on geometric model for surface micro-machined MEMS

Traditional MEMS (microelectromechanical system) design methodology is not a structured method and has become an obstacle for MEMS creative design. In this paper, a novel method of mask synthesis and verification for surface micro-machined MEMS is proposed, which is based on the geometric model of a MEMS device. The emphasis is focused on synthesizing the masks at the basis of the layer model generated from the geometric model of the MEMS device. The method is comprised of several steps: the correction of the layer model, the generation of initial masks and final masks including multi-layer etch masks, and mask simulation. Finally some test results are given.     

Science Letters：Mask synthesis and verification based on geometric model for surface micro-machined MEMS

INTRODUCTION When designers develop microelectromechani- cal system (MEMS) devices with the traditional ap- proach, they should devise the mask-layouts and fabrication process instead of the function and shape of the MEMS device. The geometric model of the MEMS device is then derived based on the simulated fabrication according to the devised mask layout and the process. This is analogous to generating a geo- metric model from the NC tool paths in the macro world. Obviously it is uni…     

基于垂直扫描显微干涉技术的高精度轮廓仪

A profilometer used for 3 dimension measurement of micro-surface topography is presented. The instrument is based on the vertical scanning microscopic interferometry （VSMI）. A Linnik type interference microscope is used and the interferograms which present changes of surface profile are recorded with a CCD camera. A developed nano-positioning work stage with an integrated optical grating displacement measuring system realizes the precise vertical scanning motion during profile measurement. By a white-light phase shifting algorithm of arbitrary step, frames of interferograms are processed by a computer to rebuild and evaluate the measured profile. Because of the specialty of VSMI, the profilometer is suitable for both smooth and rough surface measurement. It can also be used to measure curved surfaces, dimension of micro electro mechanical systems （MEMS）, etc. The vertical resolution of the profilometer is 0.5 nm, and lateral resolution 0.5 μm.     

MEMS薄膜平均应力梯度在线测量方法

结构层淀积是MEMS加工过程中的重要工艺步骤,淀积薄膜的应力梯度是影响MEMS器件性能的一个重要的力学参数．文中介绍了几种常见的平均应力梯度在线测量方法,阐明了其测试结构及测量原理,并对这些测量方法进行了比较．     

基于Minitab的MEMS测量系统偏倚及线性研究

对测量误差的大小及能否接受的判断需要进行测量系统分析,从而可以减少因仪器设备引起的误差,并得到测试数据中所隐含的信息。介绍了进行测量系统偏倚及线性分析的概念及方法,在消音室用B&K测试仪对MEMS微传声器频响、灵敏度测得了参考值并使用在线测量系统对标准样品测得了相关数据,运用Minitab软件对测量系统在0.10、1.00、3.15和8.00 kHz等不同频点的偏倚及线性进行了分析,提出了复合测量系统的概念,并对此进行了有效的分析。根据研究结果,找到了运用整体偏倚值对测量系统进行修正的方法,并用Minitab对改善后的测量系统进行了预测,应用于生产实际后,大大提高了MEMS微传声器测量系统测试数据的可靠性。     

Shaking Table Test on Out-of-Plane Stability of Infill Masonry Wall

The behaviors of infill wall in earthquakes show that infill masonry walls,which are used as nonstructural elements of concrete frames,are vulnerable when they are subjected to earthquake.In order to achieve an optimal antiseismic behavior,or even stability,two methods of connection are investigated.The shaking table tests,with 1:3 scale walls of two-storey model subjected to horizontal earthquake loads,were carried out to investigate the out-of-plane behaviors with different connections between walls and beams.The test results show that the connection methods employed between walls and beams have a significant effect on the out-of-plane stability of infill walls.The walls bound by bars with the beams perform better than those with inclined bricks without gaps.     

织物增强混凝土薄板的高温力学性能与微观界面黏结破坏性分析

研究目的：探讨不同温度和持续时间对织物增强混凝土（TRC）薄板裂缝行为和承载能力的影响。通过微观扫描电镜观测观测,分析纤维编织网与基体混凝土间的界面黏结破坏机理。创新要点：明确了高温后纤维编纵网与基体混凝土之间界向粘结破坏的主要原因。以温度和持时为基本参数,对TRC构件的耐高温性能进行正确评价。研究方法：通过三点弯曲试验（地图3）,对高温后试什的力学件能（见图4、5）进行测试。通过微观扫揣电镜观测（见图8～10）,了解高温下纤维编织网、坏氧树脂及基体混凝土的形态。重要结论：1．环氧树脂任200℃高温作用90min时劣化严重,造成纤维网与基体之间的界血黏结破坏,这是导致试件破坏的主要原因;2．在常温或120℃作用下,掺加聚丙烯（PP）纤维可以较大幅度地提高TRC构件的乐载能力;但在200℃、持续时间较长的高温作用下,PP纤维的掺入对试件的乐载力几乎没有影响。     

人体无线内窥微机电系统设计中若干关键问题

研究讨论了人体无线内窥微机电系统设计中的若干关键问题,包括电源系统的设计问题,无线发射电路的设计问题,图像采集与保存问题。在它们的设计过程中,综合考虑了无线内窥微机电系统的性能、功耗与尺寸要求,并都给出了合理的最终解决方案。     

System competence modelling: Theoretical foundation and empirical validation of a model involving natural,social and human‐environment systems

Constituting a metacognitive strategy, system competence or systems thinking can only assume its assigned key function as a basic concept for the school subject of geography in Germany after a theoretical and empirical foundation has been established. A measurement instrument is required which is suitable both for supporting students and for the evaluation of methodical‐didactic measures. Such a tool is theoretically anchored in an empirically validated geography‐didactic and cognition‐psychological competence model, providing a differentiated representation of both the internal structure of a competency and the proficiency levels. The starting point of this foundation was the development of a normative‐theoretically derived model of geographic system competence. Its empirical validation was performed in different phases aimed at operationalising the competence model by means of test problems. In order to analyse the factor structure of the theoretical model, various item response models were estimated. The item levels of difficulty expected in the competence model were related to the empirical levels of difficulty and predicted by means of ordinary least squares regression to verify the model for proficiency levels. The two‐dimensional competence model – with the two dimensions ‘system organisation and behaviour’ and ‘system‐adequate intention to act’ – exhibits a better fit in reference to the model fit criteria than the one‐dimensional and three‐dimensional models. The correlations between the expected and empirical item difficulties are positive. Items that should be more difficult according to the competence model are actually shown to be more difficult. These findings suggest the reliability and validity of this new measurement instrument for diagnosing and promoting geographical system competence. It has to be implemented in practice as the next step.     

基于HALCON和VC＋＋混合编程的视觉测量系统设计

视觉测量是采用机器视觉精确测量和定位空间几何尺寸的技术,能够有效提高工业检测的精度和效率。运用基于HALCON和VC＋＋混合编程方法开发了电子元件视觉测量软件工具,实现了测量图像采集与显示、视觉测量等核心算法及其功能;设计并构建了由工业数字摄像机、工业镜头、光源等仪器组成的电子元件视觉测量硬件平台,并依此对软件工具的可靠性和稳定性进行试验验证,结果表明系统检测速度快、检测精度达到预期技术指标。     

Design and fabrication of an surface acoustic wave resonator based on AlN/4H-SiC material for harsh environments

Surface acoustic wave (SAW) sensors and micro-electromechanical system (MEMS) technology provide a promising solution for measurement in harsh environments such as gas turbines. In this paper, a SAW resonator (size: 1107 μm× 721 μm) based on the AlN/4H-SiC multilayer structure is designed and simulated. A MEMS-compatible fabrication process is employed to fabricate the resonator. The results show that highly c-axis-oriented AlN thin films deposited on the 4H-SiC substrate are obtained, with that the diffraction peak of AlN is 36.10° and the lowest full width at half maximum (FWHM) value is only 1.19°. The test results of the network analyzer are consistent with the simulation curve, which is very encouraging and indicates that our work is a significant attempt to solve the measurement problems mainly including high temperature stability of sensitive structures and the heat transmission of leads in harsh environments. It is essential to get the best performance of SAW resonator, optimize and characterize the behaviors in high temperatures in future research.     

Evaluation of in-plane shear test methods for composite material laminates

In-plane shear properties of composite material laminates are very important in structural design of composite material. Four commonly used in-plane shear test methods were introduced in this paper. In order to study the differences of various shear test methods, two ASTM standard in-plane shear test methods for composite material laminates were experimentally investigated. They are ±45° tensile shear test (ASTM D3518) and V-notched rail shear test (ASTM D7078). Five types of composite material laminates composed of E-glass fiber fabric and vinyl ester resin were utilized, whose stacking sequences are 03s, 0/903s, CSM/0/902s, ±453s and (0/90)2/(±45)2/(0/90)2s, respectively. The test results indicate that the ±45° tensile shear test can predict shear moduli of composite material laminates accurately. However, the predictions of shear strength using ±45° tensile shear test are significantly lower than those of V-notched rail shear test.     

Detecting Multidimensional DIF in Polytomous Items with IRT Methods and Estimation Approaches

The purpose of this study was to investigate multidimensional DIF with a simple and nonsimple structure in the context of multidimensional Graded Response Model (MGRM). This study examined and compared the performance of the IRT-LR and Wald test using MML-EM and MHRM estimation approaches with different test factors and test structures in simulation studies and applying real data sets. When the test structure included two dimensions, the IRT-LR (MML-EM) generally performed better than the Wald test and provided higher power rates. If the test included three dimensions, the methods provided similar performance in DIF detection. In contrast to these results, when the number of dimensions in the test was four, MML-EM estimation completely lost precision in estimating the nonuniform DIF, even with large sample sizes. The Wald with MHRM estimation approaches outperformed the Wald test (MML-EM) and IRT-LR (MML-EM). The Wald test had higher power rate and acceptable type I error rates for nonuniform DIF with the MHRM estimation approach.The small and/or unbalanced sample sizes, small DIF magnitudes, unequal ability distributions between groups, number of dimensions, estimation methods and test structure were evaluated as important test factors for detecting multidimensional DIF.     

身体锻炼对大学新生一般自我效能感和应对方式的影响

为考察身体锻炼与大学新生一般自我效能感和应对方式的关系,采用文献资料法、心理测量法、数理统计法,对大学新生进行调查分析。结果表明：大学新生一般自我效能感存在性别差异,男生明显高于女生;女生在求助维度上明显好于男生,文科生比理科生更少使用情绪取向和消极应对方式;身体锻炼与新生一般自我效能感及应对方式显著相关。     

A Study of Sensori-Motor and Conceptual Thinking in Children between the Ages of Nine and Eighteen

In this research, the author addresses whether the application of unidimensional item response models provides valid interpretation of test results when administering items sensitive to multiple latent dimensions. Overall, the present study found that unidimensional models are quite robust to the violation of the unidimensionality assumption due to secondary dimensions from sensitive items. When secondary dimensions are highly correlated with main construct, unidimensional models generally fit and the accuracy of ability estimation is comparable to that of strictly unidimensional tests. In addition, longer tests are more robust to the violation of the essential unidimensionality assumption than shorter ones. The author also shows that unidimensional item response theory models estimate item difficulty parameter better than item discrimination parameter in tests with secondary dimensions.     

基于CCD的氨基甲酸酯类农药荧光检测系统

根据氨基甲酸酯类农药在紫外光的照射下能够发出荧光的机理,设计了一种基于电荷耦合器件（CCD）的检测该类有机农药残留的光纤荧光测量系统。该系统以脉冲氙灯为激发光源,利用光纤探测和传输荧光,采用线阵CCD代替传统的光电倍增管作为荧光信号的光电检测元件,同时配备A／D高速数据采集卡,实现了单片机控制下荧光信号的光电转换以及数据采集,进而实现了对西维因和克百威农药浓度的测量。实验结果表明,在激发波长分别为280nm和285nm时,西维因和克百威的荧光强度分别在330nm和315nm处达到最大,最低检出限分别为3．7ug／L和6．5ug/L。在5～1000ug/L范围内,荧光强度和溶液浓度基本呈线性关系。该测量系统灵敏度高,线性范围宽,可以满足荧光检测的要求。     

一种基于MEMS倾角测量仪的设计与验证

在MEMS传感器的基础上设计并制作了具有大量程、高精度的倾角仪。测量单元采用3个正交的MEMS加速度传感器,在保证测量精度的同时加大了倾角的测量范围。硬件设计分别采用线性电源、高频控制芯片及高分辨率模数转换芯片实现倾角仪的小型化。对倾角仪测量时的测量误差通过建模提出了多位置标定补偿技术、分段式温度补偿技术及现场快速标定技术,实时保证倾角仪具备较高的测量精度。通过三轴温控转台对提出的3种标定方法进行了实验验证,不但证明了3种标定技术的有效性及实用性,且对倾角仪的标定精度均可达0.01°。