A modular modelling approach to stochastic simulation of production – logistic systems

The economic scenario today is highly competitive in terms of costs and number of competitors, so it isnecessary to adopt strategies that allow the constant improvement of manufacturing processes withinthe spending constrains. Simulation models are useful to support and drive company management inimproving the performances of production and logistic systems. The costs of simulation modeldevelopment could be reduced by the reuse of some of its parts. This work presents a case studyconcerning stochastic modeling of a small manufacture operating into the wood products field. Amodular simulation model composed of reusable sub-models has been developed using AutoMod™software package. The aim of the modular architecture is to allow the use of sub-models in differentproduction systems with little changes, decreasing the costs of development in order to became moreaffordable in a SME (small medium enterprise) contest

Designing Fault-Injection Experiments for the Reliability of Embedded Systems

This paper considers the long-standing problem of conducting fault-injections experiments to establish the ultra-reliability of embedded systems. There have been extensive efforts in fault injection, and this paper offers a partial summary of the efforts, but these previous efforts have focused on realism and efficiency. Fault injections have been used to examine diagnostics and to test algorithms, but the literature does not contain any framework that says how to conduct fault-injection experiments to establish ultra-reliability. A solution to this problem integrates field-data, arguments-from-design, and fault-injection into a seamless whole. The solution in this paper is to derive a model reduction theorem for a class of semi-Markov models suitable for describing ultra-reliable embedded systems. The derivation shows that a tight upper bound on the probability of system failure can be obtained using only the means of system-recovery times, thus reducing the experimental effort to estimating a reasonable number of easily-observed parameters. The paper includes an example of a system subject to both permanent and transient faults. There is a discussion of integrating fault-injection with field-data and arguments-from-design