A knowledge management system for series-parallel availability optimization and design Ying-Shen Juang a,c, * , Shui-Shun Lin b , Hsing-Pei Kao c a Department of Business Administration, Chung-Hua University, Taiwan, ROC b Department of Business Administration, National Chinyi Institute of Technology, Taiwan, ROC c Institute of Industrial Management, National Central University, Taiwan, ROC Abstract System availability is an important subject in the design field of industrial system as the system structure becomes more complicated. While improving the system’s reliability, the cost is also on the upswing. The availability is increased by a redundancy system. Redun- dancy Allocation Problem (RAP) of a series-parallel system is traditionally resolved by experienced system designers. We proposed a genetic algorithm based optimization model to improve the design efficiency. The objective is to determine the most economical policy of components’ mean-time-between-failure (MTBF) and mean time-to-repair (MTTR). We also developed a knowledge-based interac- tive decision support system to assist the designers set up and to store component parameters during the intact design process of repair- able series-parallel system. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Knowledge management system; Availability optimization; Genetic algorithms; Series-parallel system 1. Introduction In 1952, the Advisory Group on the Reliability of Elec- tronic Equipment (AGREE) defined the reliability in a broader sense: reliability indicates the probability imple- menting specific performance or function of products and achieving successfully the objectives within a time schedule under a certain environment (Wang, 1992). In general, a higher priority is placed on quality control rather than reli- ability in the process of manufacturing. Nonetheless, high quality is not equivalent to high reliability. For example, a certain component, which has passed quality control pro- cedure in conformity to the specifications, may lead to problems when operating with other components. This involves reliability design that is related to electrical or mechanical interface compatibility among spare parts. With the rapid technological progress and increasing complexity of system structure, any failure of any compo- nent may lead to system malfunction or serious damage. For instance, a weapon system is a precise and sophisti- cated system that comprises several sub-systems, compo- nents and spare parts. Failure of even a single element will likely have adverse impact upon the operability of the weapon system, or even threat the national security. System availability, a concept closely related to reliabil- ity, refers to the scale of measuring the reliability of a repairable system. Repairable system indicates a system that can be repaired to operate normally in the event of any failure, such as computer network, manufacturing sys- tem, power plant or fire prevention system. Availability comprises ‘‘reliability’’ and ‘‘recovery part of unreliability after repair’’, indicating the probability that repairable sys- tems, machines or components maintain the function at a specific moment’’ (Wang, 1992). It is generally expressed as the operable time over total time. 0957-4174/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.eswa.2006.08.023 * Corresponding author. Address: Department of Business Administra- tion, Chung-Hua University, Taiwan, ROC. Tel.: +886 3 5186060; fax: +886 3 5186570. E-mail addresses: ysjuang@chu.edu.tw, yes.ebada@gmail.com (Y.-S. Juang). www.elsevier.com/locate/eswa Expert Systems with Applications 34 (2008) 181–193 Expert Systems with Applications