A new measure for evaluating spatially related properties of traffic information credibility

With the wide applications of sensor network technology in traffic information acquisition systems, a new measure will be quite necessary to evaluate spatially related properties of traffic information credibility. The heterogeneity of spatial distribution of information credibility from sensor networks is analyzed and a new measure, information credibility function （ICF）, is proposed to describe this heterogeneity. Three possible functional forms of sensor ICF and their corresponding expressions are presented. Then, two feasible operations of spatial superposition of sensor ICFs are discussed. Finally, a numerical example is introduced to show the calibration method of sensor ICF and obtain the spatially related properties of expressway in Beijing. The results show that the sensor ICF of expressway in Beijing possesses a negative exponent property. The traffic information is more abundant at or near the locations of sensor, while with the distance away from the sensor increasing, the traffic information credibility will be declined by an exponential trend. The new measure provides theoretical bases for the optimal locations of traffic sensor networks and the mechanism research of spatial distribution of traffic information credibility.     

Geometric Structures of Stable Time-Variant State Feedback Systems

A new technique for considering the stabilizing time-variant state feedback gains is proposed from the viewpoint of information geometry. First, parametrization of the set of all stabilizing time-variant state feedback gains is given. Moreover, a diffeomorphic structure between the set of stabilizing time-variant state feedback gains and the Cartesian product of positive definite matrix and skew symmetric matrix satisfying certain algebraic conditions is constructed. Furthermore, an immersion and some results about the eigenvalue locations of stable state feedback systems are derived.     

Truss structural damage identification based on principal component analysis and multivariate control chart

The present paper addresses the subject of truss damage identification using measured frequency response functions (FRF). Damage identification matrix is formed using measured FRFs obtained from truss dynamic test. Then using principal component analysis (PCA),the variable space dimensions of damage identification matrix can be reduced,and original data characters of FRFs can be analyzed and extracted from lower dimension variable space. Thus truss damages can be identified using the multivariate control chart of first several order principal components which contain almost all of original data information. Without the need for modal parameters,the method avoids the errors of modal fitting. In order to validate the reliability of the method,a whole size truss was tested with six types of damage case concerning single or two element damages. The experimental result shows that the proposed method is straightforward and reliable for truss damage identification. Especially,the method has good applicability for the truss under noisy environment and non-linear cases.     

AGENT based structural static and dynamic collaborative optimization

A static and dynamic collaborative optimization mode for complex machine system and its ontology project relationship are put forward, on which an agent-based structural static and dynamic collaborative optimization system is constructed as two agent colonies: optimization agent colony and finite element analysis colony. And a two-level solving strategy as well as the necessity and possibility for handing with finite element analysis model in multi-level mode is discussed. Furthermore, the cooperation of all FEA agents for optimal design of complicated structural is studied in detail. Structural static and dynamic collaborative optimization of hydraulic excavator working equimpent is taken as an example to show that the system is reliable.     

A new method of rapid quality detection of vacuum insulation panels

A new method of measuring gas pressure in vacuum insulation panels(VIPs)is reported in this study,which provides a fast and efficient quality control option of production.Although there are different methods of measuring gas pressure for VIPs,connecting an internal measurement gauge to external data acquisition units is problematic.The thin high barrier film covering the panel’s core usually prevents external electrical wires or mechanical devices being connected to the inside of the VIPs.To solve this problem,a micro capacitive pressure sensor with 0 to 250 Pa detection range is developed to detect the vacuum pressure.The sensor has high linearity and a sensitivity of 10 mV/Pa.Moreover,through the communication mode study,an ultrasound communications system for VIPs is designed.It shows from operation that this system is stable and reliable,and quick for communication speed.This new method enables the quality detection of VIPs to be completed within 1 second.The minimum detectable pressure of VIPs is below 1 Pa,and the measurement error can be controlled around 5%.     

High resolution angular-displacement sensor based on whispering gallery mode resonance in bent optical fibers

A simple fiber sensor to measure angular displacement with high resolution,which is based on whispering gallery mode(WGM)resonance in bent optical fibers,is proposed.The sensor is composed of a single loop formed by loosely tying a knot using single mode fiber.To measure the transmission spectra,a tunable laser and an optic power meter are connected to the two ends of fiber loop,respectively.Significant WGM resonances occur over the investigated wavelength range for all the sensors with different bend radius.The angular-displacement sensitivity is studied in the range from-0.1°to 0.1°.The detection limit of1.49×10-7 rad can be achieved for the detecting system with the resolution of 1pm.The simple loopstructure fiber sensor has potential application prospect in the field of architecture or bridge building with low detection limit and low cost.     

Application of fuzzy theory on earthquake damage rate estimation of buildings

Variations between earthquakes result in many factors that influence post-earthquake building damage （e.g., ground motion parameters, building structure, site information, and quality of construction）. Consequently, it is necessary to develop an appropriate building damage-rate estimation model. The building damage survey data were recorded and constructed into files by the Architecture and Building Research Institute （ABRI）, Taiwan for the 1999 Chi-Chi earthquake in the Nantou region as a basis for developing a building damage rate estimation model by applying fuzzy theory to express the fragility curves of buildings as a membership function. Empirical verification was performed using post-earthquake building damage data in the Taichung city that suffered relatively severe damage. Results indicate that fuzzy theory can be applied to predict building damage rates and that the estimated results are similar to actual disaster figures. Prediction of disaster damage using building damage rates can provide a reference for immediate disaster response during earthquakes and for regular disaster prevention and rescue planning.     

Research on CAD/CAE/MDO integrated system for nuclear valve products

In order to realize rapid response to performance-driven design for nuclear valve products, a rapid design platform is constructed by combining the structural features with the multi-characteristic optimization requirement, which integrates parametric design, multi-characteristic simulation, and multidisciplinary design optimization of nuclear power valves together. Through the integration of heterogeneous CAX/MDO software, such as UG, ANSYS and iSIGHT, the analytical efficiency is enhanced by coupling respective and unique advantage of various software systems, and the mutual coordination and information sharing are realized between the heterogeneous systems. The application example shows that the system is convenient operation that improves the automation in design and analysis on nuclear valves. The results can provide a practical and effective development method and technical reference of the integrated design system for valve products.     

传感器布置及结构损伤识别的优化方法

假设测试噪音空间非均匀分布的情况,研究了传感器最优布置问题,提出了针对结构损伤识别的传感器最优布置方法。基于结构损伤演化过程的物理特征,将结构损伤识别问题等价为一个优化问题进行求解,通过采用同步优化策略,避免了结构动力特征方程的求解和动力参数灵敏度的计算。算例分析表明,根据传感器布置方案获得的测试数据以及同步优化模式,能够准确高效地得到存在噪音下的结构损伤位置和损伤程度等损伤识别结果。     

结构损伤参量灵敏度分析的传感器数量位置优化

为判断结构是否存在一定水平的损伤,对结构健康监测系统中所需的加速度传感器的最小数目及其位置进行计算.以损伤参量的灵敏度技术为基础,根据结构损伤对各种损伤参量的影响范围的不同,以遗传算法为工具,针对各种损伤参量得出所需传感器的最小数目以及其配置位置.通过对19自由度的简支梁进行仿真分析,得到对于不同损伤参量进行损伤识别所需加速度传感器最小数目和位置,结果表明对于该算例,柔度法所需传感器数目较少,但是损伤位置比较难确定,而对于模态曲率和模态应变能所需传感器比较多.通过该布置方法可以对结构损伤情况的损伤位置有大致评估,对多损伤状态的最大损伤处有初步定位.     

基于应变模态变化率的弯曲薄板结构损伤研究

以应变模态变化率作为识别参数,以弯曲薄板为研究对象,采用改变单元厚度的方法模拟结构损伤,应用有限元对结构进行模态分析和瞬态分析.模态分析获取板结构应变模态,以对称位置应变模态变化率的改变确定损伤,以改变值的差值大小判断损伤程度;瞬态分析以单元处应变模态变化率突变值,作为损伤定位和损伤程度判断.结果表明:应变模态改变率对于结构的损伤的敏感性强,易于定位.在此基础上给出了通过模态变化率直方图进行损伤识别定位的新方法,与应变模态的损伤识别方法比较表明验证该方法是有效的.     

改进粒子群算法的两阶段梁式结构损伤识别

针对实际工程监测时损伤识别误差大的问题,提出一种基于改进粒子群算法的两阶段识别方案。第1阶段利用D-S证据理论融合算法进行损伤定位;第2阶段利用改进的粒子群算法,对定位结果进行修正,同时准确定量损伤。仿真算例和实验分析结果表明：由于第1阶段损伤定位减少了可能损伤单元的数量,第2阶段基于改进粒子群算法的搜索范围减小,能更准确地识别多损伤和小损伤的位置和程度,且抗噪性能良好。     

基于灵敏度分析的弧门主框架多损伤检测方法

以频率作为弧形闸门主框架结构多损伤识别的主要动力参数,基于灵敏度分析方法,建立结构损伤位置及程度与结构多阶固有频率的关系矩阵,并根据此矩阵和实测频率的变化情况反解出结构的损伤位置与程度。为了反映结构不同位置的损伤对频率的影响,同时减小方程的未知量个数,给出了弧门主框架频率与损伤位置和程度的灵敏度关系图。计算结果表明：基于灵敏度分析的结构多损伤检测方法可识别弧形闸门主框架多位置发生损伤的情况,可为水工结构动力检测与损伤评估提供技术参考。     

结构健康监测中传感器优化设置方法研究

首先探讨了3种基于数据信息最大化准则的传统传感器优化布置方法,即有效独立法、有效独立驱动点-残差法及运动能法.其中前2种基于Fisher信息阵最大化,而第3种基于运动能最大化.然后运用结构振动模态和三样条插值模态之间的均方差最小和抗噪性能最好,这两种比较准则来确定最优的传感器设置方法.数值分析表明:这3种传感器优化布置法都是有效的,而有效独立-驱动点残差法的效果最好.     

采用有效信号段自提取算法识别结构多损伤位置

为识别结构中的多处损伤,提出了一种采用有效Lamb波信号段自提取算法计算结构损伤指标的多损伤识别成像方法.该方法将结构的待检测区域划分为数个子区域,并根据Lamb波的传播时间和波速从传感器接收到的信号中自动提取出包含结构信息的有效信号.以该有效信号作为输入,计算每个子区域中基于信号相关系数所获得的损伤指标,最后采用RAPID算法对全部识别区域内的损伤位置进行识别和成像.以航空铝板为研究对象进行了实验验证研究,结果表明,该方法能快速有效地识别出多个损伤,并较为准确地实现损伤成像以描述损伤的位置.     

结构损伤识别的改进曲率模态方法

结构损伤识别是结构健康监测和结构状态评估的主要前提之一。尽早了解结构的损伤状况和损伤位置有助于提高结构的预期可靠性和安全性,同时降低了结构的维修费用。论文主要研究了如何采用改进的曲率模态方法识别结构的损伤以提高识别精度。基于曲率模态对结构局部损伤比较敏感和频率指标测试简单方便、精度高的特点,论文提出了一种以结构的曲率模态为基础,综合考虑频率变化的改进曲率模态识别结构损伤位置的方法。最后用一数值模拟的简支混凝土梁对该方法与曲率模态方法进行了对比验证。结果表明,改进的曲率模态方法能够更精确地识别出结构的损伤位置。     

剪切型框架模态参数的损伤敏感性分析

探讨了剪切型框架结构模态参数对损伤的敏感性,有助于进行进一步的结构损伤识别。从结构的固有振动方程出发,根据剪切型框架结构刚度矩阵特性,导出了结构固有频率、振型和振型斜率的敏感性系数表达式。对一个10层剪切型框架结构的数值分析表明,对于绝对敏感性系数,高阶模态参数比低阶模态参数对损伤敏感;对于相对敏感性系数,同一阶频率对不同处损伤的敏感性及不同阶频率对同一处损伤的敏感性均不相同;振型和振型斜率相对敏感性系数的最大值一般发生在最靠近振型节点的自由度处和振型斜率绝对值最小处,不能反映结构的损伤位置信息。