A framework to integrate software behavior into dynamic probabilistic risk assessment

Software plays an increasingly important role in modern safety-critical systems. Although, research has been done to integrate software into the classical probabilistic risk assessment (PRA) framework, current PRA practice overwhelmingly neglects the contribution of software to system risk. Dynamic probabilistic risk assessment (DPRA) is considered to be the next generation of PRA techniques. DPRA is a set of methods and techniques in which simulation models that represent the behavior of the elements of a system are exercised in order to identify risks and vulnerabilities of the system. The fact remains, however, that modeling software for use in the DPRA framework is also quite complex and very little has been done to address the question directly and comprehensively. This paper develops a methodology to integrate software contributions in the DPRA environment. The framework includes a software representation, and an approach to incorporate the software representation into the DPRA environment SimPRA. The software representation is based on multi-level objects and the paper also proposes a framework to simulate the multi-level objects in the simulation-based DPRA environment. This is a new methodology to address the state explosion problem in the DPRA environment. This study is the first systematic effort to integrate software risk contributions into DPRA environments.     

Tailored toolkit to enable seamless supply chains

Despite many individual well-documented and high-profile business process re-engineering success stories, the achievement of such enhanced performance still tends to be the exception rather than the norm. What is missing from the equation is a robust, generic, methodology that will help practitioners to plan, execute and successfully re-engineer supply chains. The aim of the present paper is to assist in this process by providing a tailored toolkit to enable a seamless supply chain based on the concept of smooth material flow and associated information flow. This toolkit is tested in-depth via observations on 40 real-world value streams covering a range of market sectors. The applicability of each of the 12 rules forming the toolkit is then assessed and prioritized in relation to a range of operational factors including product marketing characteristics and product delivery processes. The consequence of the present research is the segmentation of the rules into those found to have universal applicability and those which are especially important in specific product-related scenarios. There is further partitioning into rules that are primarily of internal application and those requiring considerable external collaboration.     

DSD: a generic software package for model-based fault diagnosis in dynamic systems

A user-friendly, interactive software package is described that can be used for fault diagnosis in dynamic systems. The methodology is based on the representation of system evolution in time as probability of transitions between sets of magnitude intervals in the state/parameter space. The software is developed in C++ for Windows NT platform. The display capabilities of the software and its implementation are illustrated using a second order system.     

Fast multi-tau real-time software correlator for dynamic light scattering

We present a PC-based multi-tau software correlator suitable for processing dynamic light-scattering data. The correlator is based on a simple algorithm that was developed with the graphical programming language LabVIEW, according to which the incoming data are processed on line without any storage on the hard disk. By use of a standard photon-counting unit, a National Instruments Model 6602-PCI timer-counter, and a 550-MHz Pentium III personal computer, correlation functions can be worked out in full real-time over time scales of ~5 mus and in batch processing down to time scales of ~300 ns. The latter limit is imposed by the speed of data transfer between the counter and the PC's memory and thus is prone to be progressively reduced with future technological development. Testing of the correlator and evaluation of its performances were carried out by use of dilute solutions of calibrated polystyrene spheres. Our results indicate that the correlation functions are determined with such precision that the corresponding particle diameters can be recovered to within an accuracy of a few percent rms.     

Numerical studies in dynamic fracture mechanics

This paper provides a summary of recent studies concerning numerical modeling of dynamic crack-propagation, Both stationary mesh as well as moving mesh finite-element procedures are examined. Simple procedures, using a moving mesh of conventional isoparametric elements in conjunction with certain path-independent integrals for the evaluation of stress-intensity factors for a dynamically propagating crack are presented.

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Résumé Le mémoire fournit des synthèses des études récentes relatives à la modélisation numérique de la propagation de fissures dynamiques. On examine, à la fois, le maillage stationaire et le maillage mobile utilisés dans les procédures d'éléments finis. On présente des procédures simples utilisant un maillage mobile d'éléments conventionnels isoparamétriques utilisé avec certaines intégrales indépendantes du parcours, en vue d'évaluer les facteurs d'intensité de contrainte dans le cas d'une fissure en cours de propagation dynamique.

     

Numerical analysis of dynamic crack propagation: Generation and prediction studies

Results of “generation” (determination of dynamic stress-intensity factor variation with time, for a specified crack-propagation history) studies, as well as “prediction” (determination of crack-propagation history for specified dynamic fracture toughness vs crack-velocity relationships) studies of dynamic crack propagation in plane-stress/strain situations are presented and discussed in detail. These studies were conducted by using a transient finite element method wherein the propagating stress-singularities near the propagating crack-tip have been accounted for. Details of numerical procedures for both the generation and prediction calculations are succinctly described. In both the generation and prediction studies, the present numerical results are compared with available experimental data. It is found that the important problem of dynamic crack propagation prediction can be accurately handled with the present procedures.     

Measuring the evolutionary stability of software systems: case studies of Linux and FreeBSD

In software evolution, stability is defined as the ability of a module to remain largely unchanged when faced with newer requirements and/or changes in the environment. Although stability is an important long-term design characteristic for hardware systems, it has not been studied deeply for software systems. Stability is directly related to software evolvability and maintainability; and it affects the software evolution process. A model based on software version differences is presented to measure the evolutionary stability of software modules. This model represents and normalises two distances: the source code and the structure distances, between two versions of an evolving software module. As a case study based on this model, the evolutionary stability of Linux and FreeBSD modules is compared. The results of the study shows that the evolutionary stability of a software module in Linux and FreeBSD depends more on its function type and less on the system environment.     

Enhancing software safety by fault trees: experiences from an application to flight critical software

The fault tree analysis is a well-established method in system safety and reliability assessment. We transferred the principles of this technique to an assembler code analysis, regarding any incorrect output of the software as the undesired top-level event. Starting from the instructions providing the outputs and tracking back to all instructions contributing to these outputs a hierarchical system of references is generated that may graphically be represented as a fault tree. To cope with the large number of relations in the code, a tool suite has been developed, which automatically creates these references and checks for unfulfilled preconditions of instructions. The tool was applied to the operational software of an inertial measurement unit, which provides safety critical signals for artificial stabilization of an aircraft. The method and its implementation as a software tool is presented and the benefits, surprising results, and limitations we have experienced were discussed.     

Adaboosting‐based dynamic weighted combination of software reliability growth models

Software reliability growth models (SRGMs) are very important for software reliability estimation and prediction and have been successfully applied in the critical airborne software. However, there is no general model which can perform well for different cases. Thus, some researchers proposed to obtain more accurate estimation and prediction than one single model by combining various individual SRGMs together. AdaBoosting is a commonly used machine learning algorithm for combining several weak predictors into a single strong predictor to significantly improve the estimating and forecasting accuracy, which may be very suitable for the combination of SRGMs. Hence, two novel AdaBoosting‐based combination approaches for improving the parametric SRGMs are presented in this paper. The first one selects several variations of one original SRGM for obtaining the self‐combination model (ASCM). The second selects several various candidate SRGMs for obtaining the multi‐combinational model (AMCM). Finally, two case studies are presented and the results show that: (1) the ASCM is fairly effective and applicable for improving the estimation and prediction performance of its corresponding original SRGM without adding any other factors and assumptions; (2) the AMCM is notably effective and applicable for combining SRGMs because it has well applicability and provides a significantly better reliability estimation and prediction power than the traditional SRGMs and also yields a better estimation and prediction power than the neural‐network‐based combinational model. Copyright © 2011 John Wiley & Sons, Ltd.     

Theoretical dynamic simulation software for slider crank mechanism of V8 engines

This paper proposes a low‐cost technique for the evaluation of the forces in a kinematic mechanism of a slider crank system and provides these results for further use. By implementing the exact equations for kinematic and dynamic analysis in an object oriented programming module under the Visual Basic Net programming package, a theoretical dynamic simulation software was developed. All forces were extracted as graphical outputs on diagrams and as data tables, and are to be further applied as input files to Finite Element analysis systems for fatigue and stress analysis of a range of engine components.     

The dynamic of professional knowledge utilized in software applications for process controlling

Main objective of the presented paper is the examination of the professional knowledge used in intelligent software applications for process controlling.It concerns in particular the user instruction and the realization of corresponding interaction as well as the interface design.Regular approach for service of the different user groups is evaluated and extended in means of flexibility in the time.The rules decisive for the user interaction with the application are outlined.They represent the interdependency between quality of professional knowledge to be utilized and user group characteristics alter in time.An application scenario for knowledge visualization is presented to show the practicability of the concept developed.     

基于动态正常模型和免疫计算的软件故障高精度处理

针对软件故障的检测、消除和修复的问题,用动态正常模型和免疫计算的方法进行了软件故障高精度处理的研究.动态的正常模型用来提高软件故障检测的精度,免疫计算用来提高软件系统对软件故障的免疫力和修复能力.用正常软件系统中所有组件的时空属性唯一确定了该系统的正常状态,设计了软件故障检测、消除与修复的免疫算法,包括自体/软件故障的检测算法、已知软件故障的识别算法、未知软件故障的识别算法、软件故障的消除算法和受损系统的修复算法.在时间属性正确的条件下,软件系统的正常模型大大提高了对软件故障的检测率(理论上可达到100%),降低了误检率.正常模型和免疫计算有助于从精度和智能两方面同时解决软件系统的安全性问题,为未来软件的设计与工程化提供有用的创新思路.     

Optimal hardware and software design of an image-based system for capturing dynamic movements

In contrast to conventional image-capture systems, which attempt to minimize the amount of data collected during capture, typically by using hardware filters, the more general condition of using all information captured on a camera sensor is much more challenging and requires rigorous consideration of the hardware and software pipelines to obtain accurate tracking results. In this paper, this issue is specifically addressed by describing a unique hardware and software design implemented for use as a fully image-based capture system. An attempt is made to minimize the cost of this system by maximizing hardware control through software implementation. The hardware and software requirements are described in the context of the desired high-speed capture suitable for earthquake motions or other dynamic movements in a scene. Experiments are conducted and presented illustrating the good performance and stability of the system. This system is deemed suitable for the general condition of a building interior.