模糊支撑半径变量贝叶斯网络多态系统故障概率分析

针对现有隶属函数描述系统及部件故障状态的不足,构建了一种含模糊支撑半径变量的隶属函数来描述部件故障状态,提出了一种基于模糊支撑半径变量的贝叶斯网络多态系统故障概率计算方法。在隶属函数的构造中,用变量代替精确值描述隶属函数模糊支撑半径,建立了含模糊支撑半径变量的隶属函数;并将其引入贝叶斯网络,利用桶消元法对多态系统叶节点故障概率进行分析,得到叶节点故障概率变化曲线。将所提出的方法与文献中基于模糊支撑半径为定值的隶属函数贝叶斯网络方法相比较,验证了方法的有效性。最后,将该方法应用到数控机床主轴系统故障分析实例中,对叶节点故障概率进行计算。结果表明,该方法能够有效解决多态系统故障状态隶属函数选择中的主观性问题。     

主动结构的控制律辨识研究

主动控制结构主要运用于包括振动、声学、转子动力学的一些工程项目中。对于各种主动结构,其控制律显然是最能反映主动结构动力学特征的参数。在对相关参数进行了初步的探讨后,得到了在单点控制单点反馈条件下,对其反馈信号类型及其反馈增益的辨识公式。该方法由频响函数直接构造,其表达简洁,具有一定的工程实用价值。通过实例的数值计算也证实了该方法的正确性。     

HY-2卫星地面应用系统综述

海洋二号(HY-2)卫星地面应用系统是HY-2卫星工程五大系统之一,具备HY-2卫星数据的接收、处理、定标和验证以及数据应用等功能。HY-2卫星地面应用系统具备稳定可靠运行的卫星接收系统,接收我国南海、东海、黄海、渤海及东北亚周边海域的实时数据;建设了包括多星运行计划管理、接收预处理、精密定轨、运控通信、数据处理、产品存档及分发服务和业务应用在内的HY-2卫星数据处理中心,每天处理海洋动力环境产品并向国内外用户提供数据分发及应用服务。为了全面的介绍HY-2卫星地面应用系统,本文分别对地面应用系统中主要分系统的组成、功能和业务流程等进行了综述。     

镁合金管材挤压变形动态再结晶流函数法研究

为研究热挤压成形镁合金管材过程中动态再结晶现象,首先采用流函数方法建立了挤压锥杯内变形区的应变速率张量场、等效应变速率场、最小剪切应变速率场以及应变张量场等数学模型,然后通过热模拟实验测得镁合金AZ91D高温力学性能数据,计算并建立了AZ91D镁合金高温变形时发生动态再结晶的临界应变函数;结合镁合金管材挤压过程应变速率及应变场等,建立了挤压过程变形区内产生初始动态再结晶的判定准则及分布规律。最后通过经实验验证了该准则及分布规律的准确性,为实际生产工艺的制定提供了理论依据。     

Synthesis and evaluation of ciprofloxacin-loaded carboxymethyl tamarind kernel polysaccharide nanoparticles

Nanotechnology is currently employed as a tool to fight more efficiently against human pathogens. Nanoparticles can be prepared from a variety of materials such as protein, biodegradable polymers and synthetic polymers. Tamarindus indica Linn. or tamarind is one of the most important biodegradable polymer. In the present study, chemically modified polymer of tamarind ‘carboxymethyl tamarind kernel polysaccharide’ (CMTKP) is used for the synthesis of nanoparticulate formulation. Antibacterial activity of CMTKP was analysed which was then enhanced by incorporating a flouroquinolone antibiotic, ciprofloxacin to it. Ciprofloxacin-loaded CMTKP nanoparticles were synthesised via ionotropic gelation technique. Nanosuspension so formed was lyophilised by addition of a cryoprotectant. Nanoparticles obtained were characterised for its particle size, morphology and stability. Interaction studies were confirmed by Fourier transform infrared spectroscopy (FT-IR). Antibacterial activities of ciprofloxacin, CMTKP and ciprofloxacin-loaded CMTKP nanoparticles were tested against two Gram negative and positive bacteria. The antibacterial assay results revealed greatest zone of inhibition by ciprofloxacin-loaded CMTKP nanoparticles in Micrococcus luteus. Toxicity analysis of the prepared formulation was carried out on vero cell lines via resazurin assay which revealed its minimum toxicity.     

Finer fractal geometry for analytic families of conformal dynamical systems

We prove several results establishing real analyticity of Hausdorff dimensions of limit sets of analytic families of conformal graph directed Markov systems. With this tool and with iterated function systems resulting from the existence of nice sets in the sense of Rivera-Letelier, we prove that the canonical Hausdorff measure restricted to the radial Julia set of a tame meromorphic function (can be rational) is σ-finite and that the Hausdorff dimension of the radial Julia sets for fairly general families of meromorphic functions (can be rational) is real analytic.     

A dissection solver with kernel detection for symmetric finite element matrices on shared memory computers

A direct solver for symmetric sparse matrices from finite element problems is presented. The solver is supposed to work as a local solver of domain decomposition methods for hybrid parallelization on cluster systems of multi‐core CPUs, and then it is required to run on shared memory computers and to have an ability of kernel detection. Symmetric pivoting with a given threshold factorizes a matrix with a decomposition introduced by a nested bisection and selects suspicious null pivots from the threshold. The Schur complement constructed from the suspicious null pivots is examined by a factorization with 1 × 1 and 2 × 2 pivoting and by a robust kernel detection algorithm based on measurement of residuals with orthogonal projections onto supposed image spaces. A static data structure from the nested bisection and a block sub‐structure for Schur complements at all bisection levels can use level 3 BLAS routines efficiently. Asynchronous task execution for each block can reduce idle time of processors drastically, and as a result, the solver has high parallel efficiency. Competitive performance of the developed solver to Intel Pardiso on shared memory computers is shown by numerical experiments. Copyright © 2014 John Wiley & Sons, Ltd.     

Novel computational methods for high‐dimensional stochastic sensitivity analysis

This paper presents three new computational methods for calculating design sensitivities of statistical moments and reliability of high‐dimensional complex systems subject to random input. The first method represents a novel integration of the polynomial dimensional decomposition (PDD) of a multivariate stochastic response function and score functions. Applied to the statistical moments, the method provides mean‐square convergent analytical expressions of design sensitivities of the first two moments of a stochastic response. The second and third methods, relevant to probability distribution or reliability analysis, exploit two distinct combinations built on PDD: the PDD‐saddlepoint approximation (SPA) or PDD‐SPA method, entailing SPA and score functions; and the PDD‐Monte Carlo simulation (MCS) or PDD‐MCS method, utilizing the embedded MCS of the PDD approximation and score functions. For all three methods developed, the statistical moments or failure probabilities and their design sensitivities are both determined concurrently from a single stochastic analysis or simulation. Numerical examples, including a 100‐dimensional mathematical problem, indicate that the new methods developed provide not only theoretically convergent or accurate design sensitivities, but also computationally efficient solutions. A practical example involving robust design optimization of a three‐hole bracket illustrates the usefulness of the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.     

A displacement‐based finite element formulation for general polyhedra using harmonic shape functions

A displacement‐based continuous‐Galerkin finite element formulation for general polyhedra is presented for applications in nonlinear solid mechanics. The polyhedra can have an arbitrary number of vertices or faces. The faces of the polyhedra can have an arbitrary number of edges and can be nonplanar. The polyhedra can be nonconvex with only the mild restriction of star convexity with respect to the vertex‐averaged centroid. Conforming shape functions are constructed using harmonic functions defined on the undeformed configuration, thus requiring the use of a total‐Lagrangian finite element formulation in large deformation applications. For nonlinear applications with computationally intensive constitutive models, it is important to minimize the number of element quadrature points. For this reason, an integration scheme is adopted in which the number of quadrature points is equal to the number of vertices. As a first step toward verifying the element behavior in the general nonlinear setting, several linear verification examples are presented using both random Voronoi meshes and distorted hexahedral meshes. For the hexahedral meshes, results for the polyhedral formulation are compared to those of the standard trilinear hexahedral formulation. The element behavior in the nearly incompressible regime is also examined. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantitative Analysis of Dynamic Fault Trees Based on the Structure Function

This paper presents a probabilistic model of dynamic gates which allows to perform the quantitative analysis of any dynamic fault tree (DFT) from its structure function. Both these probabilistic models and the quantitative analysis which can be performed thanks to them can accommodate any failure distribution of basic events. We illustrate our approach on a DFT example from the literature. Copyright © 2013 John Wiley & Sons, Ltd.