System Reliability

We present a foundational theory of software system re-liability based on components. The theory describes how component developers can design and test their components to produce measurements that are later used by system de-signers to calculate composite system reliability — ...

Secondary elements such as barriers, sidewalks, and diaphragms may increase the load carrying capacity of girder bridges. This in turn affects reliability. The objective of this study is to evaluate the potential benefit of secondary elements on the system reliability of girder bridges, if these elements are designed with the structural system to participate resisting vehicular live loads. Simple span,

This paper proposes a methodology to apply Bayesian networks to structural system reliability reassessment, with the incorporation of two important features of large structures: (1) multiple failure sequences, and (2) correlations between component-level limit states. The proposed method is validated by analytical comparison with the traditional reliability analysis methods for series and parallel systems. The Bayesian network approach is combined with the branch-and-bound method to improve its efficiency and to facilitate its application to large structures. A framed structure with multiple potential locations of plastic hinges and multiple failure sequences is analyzed to illustrate the proposed method.

As high-performance computing (HPC) systems continue to increase in scale, their mean-time to interrupt decreases respectively. The current state of practice for fault toler- ance (FT) is checkpoint/restart. However, with increasing error rates, increasing aggregate memory and not propor- tionally increasing I/O capabilities, it is becoming less effi- cient. Proactive FT avoids experiencing failures through preventative measures, such as by migrating application parts away from nodes that are "about to fail". This paper presents a proactive FT framework that performs environ- mental monitoring, event logging, parallel job monitoring and resource monitoring to analyze HPC system reliability and to perform FT through such preventative actions.

The main objective of this study is to run a complete structural reliability analysis of an existing villa, located in Lebanon. The structural components, such as slabs, beams, columns, and footings, are first analyzed independently, and the reliability index for each failure mode, is being evaluated at the component level. The structural failure modes are grouped into two categories: the

ABSTRAK Kertas kerja ini membincangkan rekabentuk dan implementasi Programmable Logic Controller (PLC) untuk aplikasi miniatur pembuatan pembotolan (Modular Automation Production System - MAPS). PLC digunakan untuk menjalankan sistem supaya bekerja secara automatik dan digunakan untuk aplikasi sistem yang berulang. Penggunaan PLC dalam industri bertujuan meminimumkan kos pengeluaran, meningkatkan produktiviti, meningkatkan kualiti dan kebolehpercayaan sistem. Rekabentuk dan implementasi sistem automasi dilakukan dengan menggunakan MAPS. MAPS adalah suatu sistem modular yang dibangunkan dengan menggunakan beberapa stesen menjadi sistem terintegrasi. Di dalam kajian ini, MAPS digunakan sebagai miniatur pengeluaran pembotolan yang sebenar dan merupakan integrasi beberapa sistem iaitu PLC, pengesan, pneumatik, mekanik, elektronik dan sistem kawalan. Kata kunci: Automasi; PLC; pembuatan pembotolan; MAPS ABSTRACT This paper discusses the design and implementation of Programmable Logic Con...

In this paper an approach for obtaining depth and section modulus of the cantilever sheet pile wall using inverse reliability method is described. The proposed procedure employs inverse first order reliability method to obtain the design penetration depth and section modulus of the steel sheet pile wall in order that the reliability of the wall against failure modes must meet a desired level of safety. Sensitivity analysis is conducted to assess the effect of uncertainties in design parameters on the reliability of cantilever sheet pile walls. The analysis is performed by treating back fill soil properties, depth of the water table from the top of the sheet pile wall, yield strength of steel and section modulus of steel pile as random variables. Two limit states, viz., rotational and flexural failure of sheet pile wall are considered. The results using this approach are used to develop a set of reliability based design charts for different coefficients of variation of friction angle of the backfill (5%, 10% and 15%). System reliability considerations in terms of series and parallel systems are also studied.

Self-healing is increasingly becoming a promising approach to designing reliable digital systems, and it refers to the ability of a system to detect faults or failures and fix them through healing or repairing. Digital systems with architecture for self-healing are expected to compensate faults. However, there are a few research challenges that need to be overcome before self-healing becomes a mainstream approach. For example, current self-healing techniques face challenges such as scalability, reliability, area overhead, and mapping. This paper explains the self-healing concept and investigates the self-healing approaches related to digital design in the literature. It gives a general overview of the topic and explains levels of abstraction at which self-healing can be used: hardware level, application level, and system level. The paper presents multiple related works at each level of abstraction. In the faulted phase, different types of faults and fault detection methods are described. For the evaluation of a self-healing technique, this paper presents the parameters which can be used to evaluate a self-healing method. These parameters are redundancy rate, the maximum ratio of repair, self-healing time consumption, reliability, and area overhead. The paper also presents a comparison between previous works of self-healing in terms of evaluation techniques. Implementations using VHDL and ISE Xilinx Vertex-5 for self-healing on Embryonic Hardware (EmHW) and Network-on-Chip (NoC) are also presented. The simulation results show the contribution of self-healing to improve system reliability and mean time to failure.

There is a need for efficient bridge evaluation procedures. A considerable number of existing bridges in the United States require repair and/or replacement. Accurate estimate of the current strength and the remaining life time is essential for optimum distribution of the available limited resources. The major parameters which determine the structural performance are random variables. Statistical models of load and resistance can be derived from the test data, observations and analysis. For bridge members the reliability can be calculated using this available data, observations and analysis. considerable discrepancy between the reliability level of individual members and the overall bridge reliability. Due to load sharing and redundancies, the actual load-carrying capacity often exceeds the theoretical value. System reliability methods allow us to reveal an actual safety reserve in the structure. This paper summarizes the practical bridge reliability models. Using a special sampling technique, the reliability is evaluated for typical girder bridges.

Details pertaining to two groups of preventable accidents, both caused by transient events, are presented. The accidents could have been avoided if there had been better coordination during the design process, during system construction and during operation. Moreover, a number of common beliefs, inherited from the period when computer simulations were rare, as well as ill-informed attempts to mimic "good solutions", influenced design decisions and contributed to the performance difficulties. The two examples illustrate transient analysis in complex systems and raise crucial issues about the lines of responsibility; although such problems also exist in small systems, the damage is typically proportionally smaller, and thus small systems have tended to receive less attention. The first case presented involves the Abattemarco pipeline in Italy. In this case, an unauthorized decision to marginally decrease capital costs by reducing the pipe's pressure class significantly compromised system reliability. In the second case, involving a desalination plant, it was erroneously believed that such a low-pressure system would not be susceptible to transients and that, in any case, a higher pressure class would invariably cover all contingencies. The operation of this second system was further complicated by a decision to oversize the pumps, a choice that increased both capital and running costs and simultaneously diminished the reliability of the already vulnerable system.