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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) 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 Geun ),정승호 ( Jeong Seung Ho ) 대한설비관리학회 2003 대한설비관리학회지 Vol.8 No.3
N/A Infant mortality failures have critical effects on the reliability of items and result in considerable expenses to both producer and customer. In the electronic industry, two types of reliability testing to decrease these risks are common : Environmental Stress Screening(ESS) and Bum-in. In this study, 2-level program where perform ESS at part level and bum-in at unit level is employed. The effective screening durations to satisfy the failure rate of system immediately after burn-in or mission reliability at specified time after shipment are determined. Also, two optimal screening durations are obtained by minimizing the life-cycle cost with a failure rate or mission reliability constraint. Numerical experiments to investigate effects on optimal screening times of input parameter values are conducted.
일반논문 : 확률적 피로한도모형하에서 계단형 피로시험의 설계
서순근 ( Sun Keun Seo ),박정은 ( Jung Eun Park ),조유희 ( You Hee Cho ),송서일 ( Suh Il Song ) 한국품질경영학회 2007 품질경영학회지 Vol.35 No.3
The fatigue has been considered the most failure mode of metal, ceramic, and composite materials. In this paper, numerical experiments to asses the usefulness of two Dixon`s methods (small and large samples) and 14 S-N methods on assumptions of lognormal fatigue limit distribution under RFL (Random Fatigue Limit) model are conducted for staircase (or up-and-down) test and compared by MSE (Mean Squared Error) and bias for estimates of mean log-fatigue limit. Also, guidelines for staircase test plans to choose initial stress level and step size are recommended from numerical experiments including sensitivity analyses. In addition, the parametric bootstrap method to construct a confidence interval for the mean of log-fatigue limit by the percentile method using a transition probability matrix of Markov chain is presented and illustrated with an example.
와이블과 대수정규 수명분포를 따를 때 새로운 가속수명시험 계획의 개발
서순근(Sun-Keun Seo) 한국신뢰성학회 2014 신뢰성응용연구 Vol.14 No.3
This paper presents new practical accelerated life test plans with different censoring times at three levels of stress for Weibull and lognormal lifetime distributions, respectively. The proposed plans are compared with the corresponding two-level statistically optimal plans and three-level compromise and practical plans. Computational results indicate that new practical plans have been more precise and effective than the existing three-level plans under a constraint of total testing time. In addition, a procedure to determine useful ALT plans is illustrated with a numerical example.
서순근 ( Seo Sun-keun ) 한국경영공학회 2017 한국경영공학회지 Vol.22 No.1
Since the depreciation method affects taxable income in future periods, the companies try to minimize the present worth of future tax payments by choosing a depreciation method optimally. This paper reexamines the preference between straight-line(SL) and declining balance(DB) methods stipulated by Korean Corporate Tax Act, because the latter has a different and unique form from ones of USA and Japan. By relaxing the assumption of positive taxable income with uncertain revenue, two depreciation methods are compared and discussed. Also, the situations under progressive tax structure and where net-operating losses may be carried-forward in time are examined and illustrated with numerical examples. Under these situations, this paper formulates models and establishes conditions that allow SL method to be preferred over DB method.