基于改进自适应加权的多传感器融合监测

针对加注系统多传感器测量数据融合,为满足融合的可靠性与准确性需求,提出了一种改进的自适应加权融合算法。加权融合算法的关键是如何准确判定测量数据权重值,在总结分析当前权重值判定方法优缺点的基础上,将证据理论中的修正证据距离引入测量数据间距离计算,生成融合权重值,完成传感器数据融合。通过一般算例与加注系统典型算例,对所提融合算法进行验证,结果表明算法融合效果较好、鲁棒性强,具有一定的理论意义和较好的工程实用价值。     

一种链式无线路由协议的液压支架压力监测系统设计

本文研究并设计了一种基于无线传感器网络的液压支架压力信息采集节点,并以此为基础搭建了监测系统平台。首先对无线网络拓扑结构分析,以提高网络整体生命周期为目的,设计了一种链式结构的简单无线路由协议。在此基础上,以CC2530为主处理器完成压力采集节点软、硬件设计。最后,给出了系统采集到的液压支架工作阻力数据。测试结果表明,系统能够实现液压支架压力实时监测功能,满足应用需求。     

N,N-二甲基硫代乙酰胺S3(ππ*)态的衰变动力学 (cited: 1)

采用共振拉曼光谱和完全活化空间自洽场方法研究了N,N-二甲基硫代乙酰胺在被激发至S₃(ππ^*)态后的衰减动力学. 指认了紫外吸收光谱和振动光谱. 获得了乙腈、甲醇和水溶剂中不同激发波长下的A带共振拉曼光谱,以探测Franck-Condon区域的结构动力学. 开展了CASSCF计算以确定低能单重激发态和锥形交叉点的电子激发能和优化几何结构. 通过共振拉曼强度分析和CASSCF计算获得了结构参数、A带结构动力学和S₃(ππ^*)态衰减机制. 提出了主要衰减通道为_3,FC(ππ^*)→S₃(ππ^*)/S₁(nπ^*)→_1(nπ^*).     

含裂纹一维欧拉梁的裂纹无效位置分析

基于集中柔度模型,建立了含裂纹一维欧拉梁的频率方程,以此为基础探讨了裂纹无效位置的求解方法。数值计算结果显示,裂纹无效位置和位移振型节点并不一致。进一步的理论推导证明裂纹无效位置就是曲率模态振型的零点位置,从曲率和力学性能基本参数的关系分析,这一结论是合理的。本文结论对于实验、测试方案设计有指导意义。     

Study on transient aerodynamic characteristics of parachute opening process

In the research of parachute, canopy inflation process modeling is one of the most complicated tasks. As canopy often experiences the largest deformations and loadings during a very short time, it is of great difficulty for theoretical analysis and experimental measurements. In this paper, aerodynamic equations and structural dynamics equations were developed for describing parachute opening process, and an iterative coupling solving strategy incorporating the above equations was proposed for a small-scale, flexible and flat-circular parachute. Then, analyses were carried out for canopy geometry, time-dependent pressure difference between the inside and outside of the canopy, transient vortex around the canopy and the flow field in the radial plane as a sequence in opening process. The mechanism of the canopy shape development was explained from perspective of transient flow fields during the inflation process. Experiments of the parachute opening process were conducted in a wind tunnel, in which instantaneous shape of the canopy was measured by high velocity camera and the opening loading was measured by dynamometer balance. The theoretical predictions were found in good agreement with the experimental results, validating the proposed approach. This numerical method can improve the situation of strong dependence of parachute research on wind tunnel tests, and is of significance to the understanding of the mechanics of parachute inflation process. The project supported by the National Natural Science Foundation of China (10377006). The English text was polished by Yunming Chen.     

Buckling of a cylindrical shell subject to a wrench

We examine the axisymmetric buckling of a generalized Kirchhoff cylindrical shell under an axial wrench. If the shell is non-linear elastic, we provide a boundary value problem amenable to the bifurcation theory of Poincaré. Using this theory we prove a non-uniqueness theorem and obtain the critical loads and critical states. In the hyperelastic case, by exploiting the variational character of the problem, a global existence and non-uniqueness theorem is also proved.

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Sommario Viene esaminato un problema di buckling per un guscio cilindrico, del tipo di Kirchhoff generalizzato, sotto un carico ai bordi di trazione-torsione. Nel caso elastico non lineare, si perviene ad un problema ai valori al contorno, cui si può applicare la teoria delle biforcazioni di Poincaré. In tal modo si dimostra un teorema di non unicità della soluzione e si ottengono i punti di biforcazione e i carichi critici. Nel caso iperclastico, facendo ricorso all'aspetto variazionale del problema, viene dimostrato un teorema globale di esistenza e non unicità della soluzione.

     

地铁隧道工程的应力监测

本文利用应变电测法，对天津地铁隧道工程进行现场应力监测。为保证施工安全和优化工程设计，提供了可靠测试数据。     

Mixed-mode stress intensity factors and critical angles of cracks in bolted joints by weight function method

Summary   Mechanical joints, such as bolted or riveted joints, are widely used in structural components. Reliable determination of stress intensity factors for cracks in bolted joints is required to evaluate their safety and fatigue life. The weight function method is an efficient technique to calculate stress intensity factors for various loading conditions by the stress analysis of an uncracked model. In this paper, the mixed-mode stress intensity factors for cracks in bolted joints are analyzed by the weight function method, and coefficients included in the weight function are determined by finite element analysis for reference loadings. The critical angle at which mode I stress intensity factor becomes maximum is determined, and the effects of the amount of clearance and crack length on the critical angle are investigated. Received 28 February 2001; accepted for publication 22 June 2001 RID=" ID=" The authors are grateful for the support provided by a grant from the Korea Science & Engineering Foundation (KOSEF) and Safety and Structural Integrity Research Center at the Sungkyunkwan University.     

Sequential non-linear least-square estimation for damage identification of structures with unknown inputs and unknown outputs

The detection of structural damages real-time on-line, based on vibration data measured from sensors, is an important but challenging research topic, and it has received considerable attentions recently. Due to practical limitations, it is highly desirable to install as few sensors as possible in the structural health monitoring system, leading to incomplete measurements of structural responses and excitations. The traditional time-domain analysis techniques, such as the least-square estimation (LSE) method and the extended Kalman filter (EKF) approach, require that all the external excitations (inputs) be available, which may not be the case for most structural health monitoring systems. Recently, the adaptive sequential non-linear least-square estimate (SNLSE) method has been proposed for the on-line identification of structural damages. In this paper, we extend the SNLSE method to cover the general case with unknown (unmeasured) excitations (inputs) and unknown (unmeasured) acceleration responses (outputs) in order to reduce the number of sensors required in the structural health monitoring system, referred to as the SNLSE-UI-UO. Analytic recursive solutions for the new approach are derived and presented. The accuracy and effectiveness of the proposed approach have been demonstrated using the Phase I ASCE structural health monitoring benchmark building, a 5-degree-of-freedom non-linear hysteretic building model, and a 3-story steel frame finite-element model. Simulation results indicate that the proposed approach is capable of tracking the changes of structural parameters leading to the identification of damages.     

楔形双滑面稳定性动态分析及其在削坡治理中的应用──以神府-东胜和准格尔煤田露天采场斜坡为例

本文提出了可以连续地计算任何坡高不同坡角的双滑面楔形四面滑体的稳定系数, 以便求得某一稳定性系数的最优化坡角。本方法经神府-东胜及准格尔煤田采场斜坡验算, 得知两煤田采场斜坡还有较大的安全储备。