Ho-Gyun Kim

Reliability‐redundancy optimization using simulated annealing algorithms

Purpose – This paper aims to present a simulated annealing (SA) algorithm to search the optimal solution of reliability‐redundancy allocation problems (RRAP) with nonlinear resource constraints.Design/methodology/approach – The developed SA algorithm is coded in C++ and is applied to reliability design problems which include the series system (P1(a) and P1(b)), the series‐parallel system (P2), and the complex (bridge) system (P3). The numerical experiments are executed on an IBM‐PC compatible with a Pentium IV 2.0 GHz. The results are compared with those of previous studies.Findings – The SA algorithm can find better solutions comparable to the previous studies in all problems except the problem P1(b). The difference on the order of 10−4 between the best and worst for all problems indicates good solution convergence of the SA algorithm. Note that the CPU times for these problems are within a few seconds by Pentium IV 2.0 GHz (P1(a) =2.78 sec, P1(b) =3.37 sec, P2=1.38 sec, and P3=1.40 sec).Originality/valu...

Business values of ISO 9000:2000 to Korean shipbuilding machinery manufacturing enterprises

Purpose – The purpose of this article is to furnish empirical evidence on the degree of performance of the 23 major requirements of the ISO 9001:2000 standard implemented at Korean shipbuilding machinery manufacturing companies.Design/methodology/approach – Deep interviews and surveys were made to measure how well the companies comply with the requirements of the new standard. Correlation analysis, standard t‐tests, and one‐way ANOVA were employed to identify significant differences for each major requirement depending on company size, top management type, implementation motive, and operating period.Findings – Large‐sized companies achieved compliance with monitoring and measurement better than small‐sized ones; professional manager‐CEOs accomplished compliance with nine major requirements better than owner‐CEOs; companies that certified because of internal development reasons performed compliance with seven major requirements better than those that certified because of customer request; companies with di...

Multiple multi-level redundancy allocation in series systems

This paper deals with a multiple multi-level redundancy allocation problem (MMRAP) in which all available items for redundancy (system, module and component) can be simultaneously chosen. Due to a well-known principle that the redundancy at the component level (component redundancy) is more effective than the redundancy at the system level (system redundancy), the object of redundancy allocation has been limited to the component redundancy. In addition, multi-level redundancy allocation problems (MRAP) have been addressed, considering the redundancy at the subsystem level (modular redundancy). In this paper, the MMRAP is formulated and a GA algorithm is presented to solve the problem. Some numerical examples are illustrated.

Performance analysis for closed-loop production systems with unreliable machines and random processing times

In this paper we propose new approximate methods for the performance analysis of closed-loop production systems with unreliable machines and random processing times. Each approximate method decomposes the production system consisting of K machines into a set of K subsystems, each subsystem consisting of two machines separated by a finite buffer. Then, each subsystem is analyzed by three different analyzing methods in isolation. The population constraint of the closed-loop production system is taken into account by prescribing that the sum of average buffer levels in the subsystems is equal to the number of customers in the closed-loop production system. We establish a set of equations that characterize unknown parameters of the servers in the subsystems. An iterative procedure is then used to determine the unknown parameters. Experimental results show that these methods provide a good estimation of the throughput.

A robust design of simulated annealing approach for mixed-model sequencing

The effectiveness of the solution method based on simulated annealing (SA) mainly depends on how to determine the SA-related parameters. A scheme as well as parameter values for defining an annealing schedule should be appropriately determined, since various schemes and their corresponding parameter values have a significant impact on the performance of SA algorithms. In this paper, based on robust design we propose a new annealing parameter design method for the mixed-model sequencing problem which is known to be NP-hard. To show the effectiveness of the proposed method, extensive computation experiments are conducted. It was found that the robust designed method outperforms the SA algorithm by McMullen and Frazier [McMullen, P.R., & Frazier, G.V. (2000). A simulated annealing approach to mixed-model sequencing with multiple objectives on a just-in-time line. IIE Transactions, 32, 679-686].

SIMULATED ANNEALING ALGORITHM FOR REDUNDANCY OPTIMIZATION WITH MULTIPLE COMPONENT CHOICES

This paper considers the series-parallel redundant reliability problem where each subsystem has multiple component choices. The subsystems are characterized by their reliability and resources such as cost and volume. If resource constraints comprise nonlinear functions, the problem becomes an NP-hard problem of combinatorial optimization problems. In this paper, a simulated annealing (SA) algorithm which determines the maximal reliability of series-parallel system configuration subject to the resources is proposed. To show its effectiveness, several test problems are experimented and the results are compared with those of previous studies.

Understanding of Audit Results from Demonstration Companies toward Green Management System Certificate

Climate changes and environmental pollution recently became a matter of global interest. Korean government established low carbon green growth act in the light of international environment regulation and started demonstration certificate project for GMS (Green Management System). We aim to explore audit data resulted from demonstration companies that pursued the GMS certificate. The demonstration companies are consisted of 11 companies that a certification body L gave the certificate. The audit data results were formed by minor nonconformities detected in the field evaluation based on GMS standards, KS I 7001/2 : 2011. We found out significant differences for minor nonconformities between types of industry and between major clauses of Part 1 and Part 2 in GMS standards. We make an effort to figure out the implication of causes of the significant differences. These results are expected to contribute to understand GMS operation situations and are utilized as a reference for energy management, social responsibility, and green gas reduction.