基于虚拟变量法的结构可靠度参数敏感性分析

在结构可靠度分析中,功能函数通常是强非线性的,并且随机变量之间往往存在相关性,这给基于一次二阶矩法原理的参数敏感性分析带来了困难。为此,提出了一种基于虚拟变量法的结构可靠度参数敏感性分析方法,推导了相关随机变量的敏感性计算公式,在计算可靠指标时无须求偏导,计算效率高。工程算例分析表明,在功能函数为非线性、变量之间相关的情况下,该计算方法是一种有效的结构可靠度敏感性分析方法。     

A SIX－YEAR RETROSPECTIVE STUDY ON THE RELATIONSHIP OF SODIUM－LITHIUM COUNTERTRANSPORT WITH BLOOD PRESSURE AND SODIUM SENSITIV

ＡＳＩＸ－ＹＥＡＲＲＥＴＲＯＳＰＥＣＴＩＶＥＳＴＵＤＹＯＮＴＨＥＲＥＬＡＴＩＯＮＳＨＩＰＯＦＳＯＤＩＵＭ－ＬＩＴＨＩＵＭＣＯＵＮＴＥＲＴＲＡＮＳＰＯＲＴＷＩＴＨＢＬＯＯＤＰＲＥＳＳＵＲＥＡＮＤＳＯＤＩＵＭＳＥＮＳＩＴＩＶＩＴＹＩＮＣＨＩＬＤＲＥＮ（牟...     

西部地区县乡公路设计参数敏感性分析及土基等级划分

分析西部地区县乡公路沥青路面典型结构设计参数的敏感性.通过对路基路面设计参数(结构层厚度和材料模量)的变化对路基路面工作状态影响的研究,得到路面结构强度随各结构层设计参数变化规律,确定路面结构的敏感性层位,推荐出设计参数的建议值,为县乡公路土基强度等级划分及路基路面的结构优化设计提供依据.     

西部地区县乡公路设计参数敏感性分析及土基等级划分

分析西部地区县乡公路沥青路面典型结构设计参数的敏感性.通过对路基路面设计参数(结构层厚度和材料模量)的变化对路基路面工作状态影响的研究,得到路面结构强度随各结构层设计参数变化规律,确定路面结构的敏感性层位,推荐出设计参数的建议值,为县乡公路土基强度等级划分及路基路面的结构优化设计提供依据.     

基于敏感性分析的改扩建高速公路安全性评价

随着我国高速公路建设事业的快速发展,不少高速公路由于先期建成路段设计标准较低、超长中服役等原因,已经无法适应目前大交通量的需求,面临着改扩建等问题。文章采用敏感性分析,找出影响改扩建高速公路的敏感因素;从影响交通安全的风险因子发生概率、严重程度2个方面进行单因素敏感性分析和多因素敏感性综合分析,根据分析结果采用模糊综合评价方法对改扩建高速公路的安全性进行评价,并提出相应的优化措施。     

Inverse identification of wheel–rail contact forces based on observation of wheel disc strains: an evaluation of three numerical algorithms

In this paper, three numerical algorithms for the identification of wheel–rail contact forces based on measured wheel disc strains on an instrumented railway wheelset are discussed and compared. The three algorithms include one approach resting on static calibration, one that is applying a Kalman filter and the third is exploiting an inverse identification scheme. To demonstrate and evaluate the alternative methods, two load cases including periodic excitation by sinusoidal wheel–rail irregularities and transient excitation by an insulated rail joint are considered. Based on a previously presented vehicle–track interaction model in the time domain, load scenarios are defined by taking the calculated vertical wheel–rail contact forces as the reference force to be re-identified by the proposed algorithms. The reference contact forces are applied on a finite element model of the wheel to generate synthetic observation data, that is, radial strains at the positions of the strain gauges, serving as input to the identification procedures. It is concluded that the inverse identification scheme leads to superior accuracy at higher computational cost. If on-line implementation and evaluation is required, the Kalman filter generates better accuracy than the static calibration approach.     

钹式水听器的改进和测试

钹式水听器体积小，灵敏度高，但其接收性能不够稳定，接收频带较窄．为了克服这些弱点，对其结构进行改进．运用双片陶瓷并联代替单片陶瓷，并缩小陶瓷半径．再通过有限元仿真实验和水池实验，对改进前后的钹式水听器进行测试，结果表明，改进后的钹式水听器接收性能更加稳定，接收频带也明显增加，同时其灵敏度依然较高．     

气相色谱仪灵敏度的测量不确定度的评定

为了检定气相色谱仪数据的准确性,要考虑检定不确定度的影响.通过对气相色谱仪热导检测器(TCD)灵敏度进行校准过程中引入的不确定度分量进行了评定.TCD灵敏度的相对不确定度为2.1%,扩展不确定度为4.2%(k=2),所有检定项目中,标准样品进样量的不确定度是最大的.此方法简单、实用,可用于带色谱工作站的GC的校准.     

On the scattering of test data and the significance of the standard coefficients ‘dynamic stiffness’ and ‘loss angle’ for hydraulic engine mounts

Based on the test results, a study on the scattering of the standard coefficients c _dyn and δ within the test cycles on a standard testing machine as well as within the samples of a batch of hydraulic engine mounts is performed; furthermore, an estimate for the systematic error caused by the testing machine is given. By a simulated example, the pronounced sensitivity of the response of the engine to the scattering of c _dyn and δ as well as to even small deviations of the hysteresis curves for otherwise identical values of the standard coefficients is demonstrated. As a main result, it is found that the most important source of uncertainty is scattering within the batch, which, in conjunction with the observed sensitivity of the response of the engine, raises the question for the meaningful level of sophistication of a model for predictive purposes.