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방사형 물류체계에서 수송장비의 보유대수 결정과 분배정책
서순근,이병호,Seo, Sun-Keun,Lee, Byung-Ho 대한산업공학회 1998 산업공학 Vol.11 No.1
Fleet sizing and distribution of empty equipments are two of the most critical problems in managing transportation system. This paper develops a cost model for sizing a fleet and establishing decentralized redistribution polices of empty equipments by building from inventory theory of multi-echelon system in hub-and-spoke network. An analytical approach to determine control variables of redistribution policies in each terminal and fleet size of the transportation system is proposed and its results are validated by simulation model. Numerical experiments are conducted with respect to parameters of the model and test results for assumptions of the model are discussed.
서순근(Sun Keun Seo),하천수(Chen Soo Ha),김갑석(Kab Seok Kim) 한국품질경영학회 2001 품질경영학회지 Vol.29 No.3
This paper presents new compromise ALT plan which is applied to situations that true relationship between stress and parameters is not known exactly. The assumed failure distribution of this study is one of location-scale family, i. e., exponential, Weibull, and lognormal distributions which have been ones of the popular choices of failure distributions. The method of applying the stress is constant, and the censoring mechanism is Type I censoring. Compared with existing compromise plans under true simple linear model in terms of statistical efficiency, the efficiency of new compromise plan is better than the corresponding other compromise ones in most cases. For case when true model is quadratic, this plan can be used without any severe loss in statistical efficiency. The proposed new compromise ALT plan is illustrated with a numerical example and sensitivity analyses are conducted to study effects of pre-estimates of design parameters.
서순근(Sun-Keun Seo) 한국신뢰성학회 2016 신뢰성응용연구 Vol.16 No.4
Purpose: Recently, Jiang defines the tradeoff B life to minimize a sum of life lost by preventive maintenance (PM) and corrective maintenance (CM) contribution parts and sets up an optimal replacement age of age replacement policy as this tradeoff life. In this paper, Jiang’s model only considering the known lifetime distribution is extended by assigning different weights to two parts of PM and CM in order to reflect the practical maintenance situations in application. Methods: The new age replacement model is formulated and the meaning of a weight factor is expressed with the implied cost of failure under asymptotic expected cost model and also discussed with one-cycle expected cost criterion. Results: The proposed model is applied to Weibull and lognormal lifetime distributions and optimum PM replacement ages are derived with corresponding implied cost of failure. Conclusion: The new age replacement policy to escape the estimation of cost of failure in classical asymptotic expected cost criterion based on the renewal process is provided.
서순근 ( Seo Sun-keun ),허지희 ( Hur Ji Hee ) 한국경영공학회 2020 한국경영공학회지 Vol.25 No.4
Purpose Present Worth (PW) and Internal Rate of Return (IRR) are two popular economic decision criteria in engineering economic analysis, but PW is preferred to IRR because of several deficiencies including multiple internal rates of return (MROR). Research in MROR has mainly focused on two areas: conditions for MROR occurrence and unique positive IRR, and solutions to MROR. This paper discusses MROR problems in depth. Methods In two areas of MROR, main and recent research streams are reviewed and illustrated with numerical examples. Also, a concrete measure to clarify the meaning of AIRR(Average IRR) proposed by Magni(2010) to resolve several problems of IRR is provided. Results Scopes and levels to cover MROR problems in textbooks of engineering economy (EE) field are surveyed and a new pedagogical proposal for instructors to teach MROR problems in EE class is presented. Conclusion Despite several drawbacks including MROR, surveys for managers have consistently shown that substantial practitioners still favor IRR. Results and proposals in this article will be helpful to enhance the study achievement for IRR in EE class of university.
서순근(Sun Keun Seo),이성재(Sung Jae Lee) 대한설비관리학회 2000 대한설비관리학회지 Vol.5 No.3
N/A Because manufacturing lot sizes continue to shrink, statistical process control(SPC) methods for short production runs are increasingly important. In this study, four short run SPC techniques(the standardized, Q, EWMA-Q and EWMA control chart) are reviewe
서순근 ( Seo Sun Keun ) 한국품질경영학회 2016 품질경영학회지 Vol.44 No.3
Purpose: This paper evaluates the performance of the pre-control(PC), an alternative to statistical process control techniques and compares with a control chart considering the tolerance of process. Methods: The previous studies for PC have drawbacks that PC with two linked stages, qualification and running, are discussed separately and independently. Hence this paper analyzes the performance of PC by integrating two stages. Results: Average outgoing quality limits to grasp the outcome of PC are provided by computational results for two process capability indexes, <sub>p</sub> and <sub>pk</sub> and the usefulness of PC from comparative experiments with modified control charts is commented. Conclusion: Helpful guidelines for quality managers to apply PC in practice and areas of process for PC to be more benefit are presented.