可靠性灵敏度函数及其特征指标的条件概率模拟求解方法

可靠性分析中基本变量分布参数为区间均匀变量时,失效概率为分布参数的函数。基于条件概率马尔科夫链模拟,提出了一种可靠性灵敏度函数的求解方法,并提出了一种新的可靠性灵敏度度量指标,它为参数可靠性灵敏度函数在参数空间上的期望。文中推导了线性极限状态正态变量下全局灵敏度函数及新指标的计算式.并提出了高效的基于条件概率马尔科夫链...     

考虑非概率可靠性的结构柔顺度拓扑优化设计

实际工程中广泛存在的不确定性可能对结构拓扑设计产生重要影响。基于不确定性的多椭球凸模型描述及非概率可靠性指标的定义,建立了材料体积约束和不确定参数范围约束下、结构柔顺度极小极大化为目标的非概率可靠性拓扑优化数学模型。结合移动渐进线方法,基于单循环策略实现该连续Minimax优化问题的求解。经典算例尺寸优化设计结果说明了...     

Enhancing software reliability modeling and prediction through the introduction of time-variable fault reduction factor

Over the past three decades, many software reliability models with different parameters, reflecting various testing characteristics, have been proposed for estimating the reliability growth of software products. We have noticed that one of the most important parameters controlling software reliability growth is the fault reduction factor (FRF) proposed by Musa. FRF is generally defined as the ratio of net fault reduction to failures experienced. During the software testing process, FRF could be influenced by many environmental factors, such as imperfect debugging, debugging time lag, etc. Thus, in this paper, we first analyze some real data to observe the trends of FRF, and consider FRF to be a time-variable function. We further study how to integrate time-variable FRF into software reliability growth modeling. Some experimental results show that the proposed models can improve the accuracy of software reliability estimation. Finally, sensitivity analyses of various optimal release times based on cost and reliability requirements are discussed. The analytic results indicate that adjusting the value of FRF may affect the release time as well as the development cost.     

一类修复不如新的可修复系统的可靠性分析

用增补变量的方法建立了在人为错误下修复不如新的两相同部件并联可修复系统.通过选取空间和定义系统算子,将模型方程转化成为了抽象Cauchy问题.然后利用线性算子半群理论研究了系统解的存在唯一性和渐近稳定性,进一步对系统的可用度做了比较分析.     

基于Copula的部件相依并联系统可靠性分析

应用Copula函数,研究了部件相依的并联系统可靠性问题,给出了F-G-M Copula函数下并联系统的可靠度、平均寿命、失效率的表达式,讨论了部件下象限相关下并联系统的平均寿命与部件独立时系统的平均寿命的关系,通过算例分析了部件个数与部件相依关系对系统平均寿命的影响。     

Grundlegende technische Forderungen an Radioisotopen-Meßgeräte

In zunehmendem Maße werden Meßgeräte unter Verwendung von Radionuklid-Strahlungsquellen in der Industrie zum Zweck der Prozeßüberwachung, -messung und -regelung eingesetzt. Unter den rauhen Umgebungsbedingungen kommt es dabei besonders auf eine hohe Zuverlässigkeit der Geräte an, da Störungen oder Ausfälle der Meßtechnik – je nach dem Einsatzort – mitunter sehr unangenehme Ausfälle im Produktionsprozeß zur Folge haben. Ein Beispiel für den Einsatz eines Radioisotopen-Meßgerätes in der industriellen Fertigungstechnik ist die Flächengewichtsmeßanlage FMM 24004. Aus der Vielfalt der bei der Entwicklung solcher Geräte zu beachtenden Festlegungen, Vorschriften und Randbedingungen werden in dieser Arbeit, ohne Anspruch auf Vollständigkeit erheben zu können, einige wesentliche Aspekte dargestellt.     

基于等效静态载荷法的区间参数结构可靠性拓扑优化

研究了用等效静态载荷法,解决动态响应约束下的区间参数结构可靠性拓扑优化问题。对等效静态载荷赋予了新的含义:由等效静态载荷产生的区间静态响应与由动态载荷产生的区间动态响应,其对应的中值与离差均相等。利用泰勒展开计算出区间参数结构动态响应所有可能值组成的集合,再根据集合映射获得包含结构所有不确定信息的等效静态载荷集合,继而建立静态可靠性拓扑优化数学模型。通过集合映射和区间自然扩展,获得静态位移响应区间。基于区间非概率可靠性指标的定义,给出区间非概率可靠性约束的伴随法灵敏度分析算法。采用移动渐近线法完成此优化问题的求解。数值算例验证了模型的正确性和算法的有效性。     

平稳随机激励下耦合Newmark滑移系统的可靠性分析

基于随机激励的离散形式,对耦合Newmark系统的动力可靠度问题进行解析分析。平稳随机激励下,耦合Newmark系统初始滑移极限状态方程可以写成n个标准正态随机变量的显式线性函数,并能给出可靠度指标的理论解。对于以相对滑移量为临界状态的情况,极限状态方程是n个标准正态随机变量的隐式函数,可借助静力可靠度方法进行求解。算例表明,系统初始滑移的设计点激励是以潜在滑动体自振频率为主频,振幅渐增的谐振时程;后者的失效概率与摩擦系数成非线性关系,存在合适的摩擦系数使失效概率最小。     

Improving spectral resolution in spatial encoding dimension of single-scan nuclear magnetic resonance 2D spin echo correlated spectroscopy

The spatial encoding technique can be used to accelerate the acquisition of multi-dimensional nuclear magnetic resonance spectra. However, with this technique, we have to make trade-offs between the spectral width and the resolution in the spatial encoding dimension (F1 dimension), resulting in the difficulty of covering large spectral widths while preserving acceptable resolutions for spatial encoding spectra. In this study, a selective shifting method is proposed to overcome the aforementioned drawback. This method is capable of narrowing spectral widths and improving spectral resolutions in spatial encoding dimensions by selectively shifting certain peaks in spectra of the ultrafast version of spin echo correlated spectroscopy (UFSECSY). This method can also serve as a powerful tool to obtain high-resolution correlated spectra in inhomogeneous magnetic fields for its resistance to any inhomogeneity in the F1 dimension inherited from UFSECSY. Theoretical derivations and experiments have been carried out to demonstrate performances of the proposed method. Results show that the spectral width in spatial encoding dimension can be reduced by shortening distances between cross peaks and axial peaks with the proposed method and the expected resolution improvement can be achieved. Finally, the shifting-absent spectrum can be recovered readily by post-processing.     

横波速度径向层析成像方法及应用研究

近来三维声波成像技术的一个重要进展是利用偶极子弯曲波反演地层径向横波速度剖面。确定地层径向横波速度变化对评价井壁稳定性、估算地应力和优化油藏生产等有着重要的意义。偶极横波测井激发的弯曲波低频探测较深,高频探测较浅,本文根据偶极弯曲波的频散特征,采用约束反演的方法求取地层径向横波速度变化。在实际测井中,经常会遇到偶极子弯曲波的频散曲线在高频时缺失或者不准确的情况,这会使约束反演方法产生误差。针对这一现象,本文提出利用理论频散数据进行高频约束,并通过数值模拟验证了改进后约束反演方法的正确性。本文给出了一个致密气层的横波速度径向剖面综合应用实例,发现地层径向横波速度变化程度与岩石脆性有很好的对应关系,最终的压裂效果由压前、压后正交偶极横波各向异性的变化得到了印证,压裂后油气产量提高。