We consider the transient performance analysis of failure-prone manufacturing systems producing multiple part types. We decompose the exact monolithic model into: 1) a slower time scale structure state process modeling the failure and repair, and 2) a faster time scale performance model describing the part processing and the material movement. We combine the solution of these two models to show that the accumulated reward over a given time interval is a solution of a set of forward or adjoint multidimensional linear hyperbolic partial differential equations. This result generalizes the existing results on composite performance-dependability analysis of manufacturing systems. We also present efficient numerical methods for computing the distribution of the cumulative operational time, and the mean and variance of the cumulative production over a given time interval. Further, we bring out the significance of these results in the manufacturing systems context through several examples.>

Performance evaluation of failure-prone manufacturing systems is of significant practical interest. In this paper, the authors consider the parametric sensitivity analysis of manufacturing systems producing multiple part types. This involves transient analysis of the Markov model of the system and computation of the derivative of the cumulative throughput with respect to the varying parameters. Such an analysis would be useful in studying the effects of various not exactly known parameters on the system performance, identifying the bottlenecks and hot spots and in system optimization studies. In this paper, the authors derive expressions for the sensitivity of the first two moments of the throughput-related performability with respect to failure and repair rates of various subsystems such as machines, guided vehicles, robots, etc. The authors also present two examples to illustrate the theoretical results of this paper.>

A modified version of the multiple attribute tree (MAT) database organization, which uses a compact directory, is discussed. An efficient algorithm to process the directory for carrying out the node searches is presented. Statistical procedures are developed to estimate the number of nodes searched and the number of data blocks retrieved for most general and complex queries. The performance of inverted file and modified MAT organizations are compared using six real-life databases and four types of query complexities. Careful tradeoffs are established in terms of storage and access times for directory and data, query complexities, and database characteristics.