Buckling analysis with the aska program system

The theoretical and practical considerations involved in extending the very large, general purpose finite element program system ASKA to include linear buckling mode analysis are presented. The main analysis features and their software implementation are discussed in the context of modular processors and data operands. A broader interpretation of buckling load factors and modes in relation to mode superposition is given, and typical applications are presented to illustrate both classical bifurcation buckling analyses and buckling mode superposition response.     

A sequel to the article “buckling analysis with the aska program system”

In the above-mentioned article [1]buckling of an axially compressed open cylindrical shell was used as a qualification test by comparing the ASKA results with experimental results published [2]. ASKA predicted bifurcation buckling at a load level slightly larger than that at which the shell collapsed in the experiment. However, the marked nonlinearities in the prebuckling range, reported in [2], could only be explained by assuming geometrical imperfections with an order of magnitude of the shell thickness. No indication, however, on the order of magnitude of possible imperfections in the experiment is given in [2].In a different publication [3] a complete numerical solution is presented for the considered problem, including specific imperfections in loading and geometry. This solution is evaluated, however, for slightly different dimensions, elasticity data and boundary conditions than those used in [1]and in [2].Thus, to confirm the ASKA results, one of the configurations evaluated in [3](including geometrical imperfections) has been reanalyzed, and fairly good agreement between the ASKA results and those of [3] has been obtained. The comparison gives some insight into the performance and limits of the buckling mode superposition method adopted in ASKA for the treatment of nonlinear prebuckling behaviour.     

Extensions to the fuzzy pointed set with applications to imageprocessing

In all man-machine systems with image processing functions, an important unsolved problem arises in the treatment of uncertain and incomplete image information. Several frameworks have been suggested for handling uncertain image information including; expert systems, fuzzification, likelihood estimation, and neural networks. In this paper we review those methods. We also present a new method for handling uncertainties by unifying the representations of gray-values and uncertainty into one framework in a way that parallels fuzzy logic. This new framework is based on the application of the extended fuzzy pointed set and an associated algebra to handle uncertain information. We further show how this framework can be used in image processing and artificial intelligence     

Extensions of infinitesimal perturbation analysis

An extension of the concept of perturbation analysis (PA) is introduced that can be applied to cases where sample path discontinuity with respect to system parameters has prevented the application of simple PA rules. Both Markov and generalized semi-Markov processes are considered. The robustness of the extended PA is examined and it is found to be sufficiently robust     

An information-leak analysis system based on program slicing

For programs using secret information such as credit card numbers, preventing information-leaks is important. Denning, for example, has proposed a mechanism to certify that a given program does not violate a security policy. Kuninobu, on the other hand, has proposed a more practical framework for calculating the secrecy level of each output value from the secrecy level set to each input value, but no implementation has been yet explored. In this paper, we propose an implementation method for information-leak analysis, and show a system we have implemented based on program slicing. We have applied this system to a credit card program. Our results show that information-leak analysis before practical use of the program is important.     

程序动态分析系统中插装方式的改进

动态分析是程序理解的重要方法,而插装技术是其中常用的关键技术之一.介绍了QESat/C 中动态分析子系统的插装策略,在其基础上提出并实现了新的插装器并改进了插装探针库的效率.实验表明,改进后的动态分析子系统具有插装速度快、动态结果文件小、动态信息合并效率高的优点.展望了现有系统如何支持新的动态分析技术,最后对全文进行了总结.     

Variational sensitivity analysis of elastoplastic structures applied to optimal shape of specimens

Structural and Multidisciplinary Optimization - The aim of this paper is to improve the shape of specimens for biaxial experiments with respect to optimal stress states, characterized by the stress...     

Nonlinear elastoplastic dynamic analysis of single-layer reticulated shells subjected to earthquake excitation

A nonlinear dynamic finite element technique is developed to analyze the elastoplastic dynamic response of single-layer reticulated shells under strong earthquake excitation, in which the nonlinear three-dimensional beam elements are employed. An elastoplastic tangent stiffness matrix of three-dimensional beam element is derived by using the updated Lagrangian formulation, in which the isotropic hardening model, the Von-Mises yield criterion and the Prandtl-Reuss flow relations are applied to this study. This procedure considers both geometric and material nonlinearities. In this paper, several condensation and reduction techniques in matrices and degrees of freedom are used to simplify the analysis. An incremental-iterative technique based on the Newmark direct integration method and the modified Newton-Raphson method is employed for obtaining the solutions of the nonlinear dynamic equilibrium equations. Moreover, an accurate method is developed to compute the large rotations of space structures. As a numerical example, the elastoplastic dynamic response of a single-layer reticulated shell under strong seismic excitation is investigated. It is shown through the numerical example that the method developed in this paper is efficient for the nonlinear dynamic response analysis and plastic design of space structures.     

Extensions of principle component analysis with applications on vision based computing

This paper mainly focuses on the principle component analysis (PCA) and its applications on vision based computing. The underlying mechanism of PCA given and several significant factors, involved with subspace training are discussed theoretically in detail including principle components energy, residuals assessment, and decomposition computation. The typical extensions, including probabilistic PCA (PPCA), kernel PCA (KPCA), multi-dimensional PCA and robust PCA (RPCA), have been presented with critical analysis on both mechanisms and computations. Combining with the studies on, such as, image compression, visual tracking, image recognition and super-resolution image reconstruction, PCA and its extensions applied to computer vision are critically reviewed and evaluated on the targeted issues in each application as well as the role they played at specific tasks to the characteristics, cost and suitable situations of each PCA based vision processing technique.     

An elastoplastic cracked-beam finite element for structural analysis

A finite element model has been developed in this paper to analyse statically indeterminate skeletal cracked structures. The model is based on elastic-plastic fracture mechanics techniques in order to consider the crack tip plasticity in the analysis. Stiffness matrices for single-edge and double-edge cracked structural elements have been derived using transfer matrix theory. These matrices take into account the effects of axial, flexural and shear deformations due to crack presence. The present model has been applied to investigate the effects of crack size, structure cross-section depth and crack tip plasticity on the redistribution of internal forces in structures. Hence, this analysis can be employed to identify the overstressed regions in cracked structures.     

A logical approach to program analysis

This paper describesMicroScope, a framework for developing analysis tools for Lisp programs. MicroScope uses a knowledge-intensive approach for program representation and analysis. The analysis tools share a common object oriented program database, and a common Prolog inference engine. The use of Prolog and a declarative representation for programs permits sharing of information, and provides high bandwidth communication between diverse analysis tools. It also supports program specification and debugging activities in the same framework. Extensions to Prolog to support analysis are described, and two tools, theCritic and theExpector, are presented.This work supported in part by Hewlett-Packard Company, the National Science foundation Under Grant Number MCS81-21750 and the Defense Advanced Research Projects Agency under contract number DAAK11-84-K-0017.     

面向程序分析的插桩技术研究

为了满足测试覆盖分析和软件调试等程序分析技术对插桩技术的需求,提出了插桩模型,开发了一款实用的插桩工具。基于双缓冲技术,构建词法分析器和语法分析器。在语法分析归约时同步收集插桩信息,然后根据插桩策略执行插桩,生成目标文件。得到的程序运行时信息被应用于影响广泛的四种软件自动调试分析方法。对于这四种方法。缺陷语句均被准确识别为最可疑语句。应用结果表明,该方法能够为准确高效的程序分析提供必要的运行时信息。     

A unified approach to finite deformation elastoplastic analysis based on the use of hyperelastic constitutive equations

By assuming from the outset hyperelastic constitutive behavior, an alternative approach to finite deformation plasticity and viscoplasticity is proposed whereby the need for integration of spatial rate constitutive equations is entirely bypassed. To enhance the applicability of the method, reference is made to a general formulation of plasticity and viscoplasticity which embodies both the multiplicative and additive theories. A new return mapping algorithm capable of accommodating general yield conditions, arbitrary flow and hardening rules and non-constant tangent elasticities is proposed. Finally, a numerical example is presented which illustrates the excellent performance of the method for very large time steps.     

Extensions to the design of sampled integrating regulators

The stability properties and design rules for a class of robust integrating regulators are considered. Passivity arguments are employed to define bounds on the parameters of an extended PID regulator and to establish the robustness of the closed-loop stability properties in the presence of sector-bounded non-linear elements in the feedback loop. This approach allows linear and non-linear single-input/single-output and multi-input/multi-oulput systems to be considered in the same framework.