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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 ) 한국품질경영학회 2014 품질경영학회지 Vol.42 No.4
Purpose: This paper reviews popular measurement system indices and proposes a procedure for assessing a measurement system using two parameters with intraclass correlation and a factor for process capability. Methods: Gage Repeatability and Reproducibility(GR&R), precision-to-tolerance ratio(PTR), number of distinct categories, producer’s and consumer’s risks are employed to assess the measurement capabilities and discuss the relationships between measurement system metrics. Results: Two-dimensional plot by two parameters is presented to assess adequacy of the measurement system and process capability. A numerical example and previously studied case study are provided for illustration. Conclusion: The procedure proposed in this paper using two-dimension parameters provides a valuable procedure and helpful guidelines to quality and production managers in assessing the capabilities of a measurement system and choosing the needed actions to be the most benefit.
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 ) 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.
서순근(Seo, Sun-Keun) 한국신뢰성학회 2012 신뢰성응용연구 Vol.12 No.3
Successive and simultaneous sudden death tests are compared with the complete and Type II censored samples in terms of expected test duration and Total Time on Test(TTT) subject to the same number of failures in order to maintain the equal statistical precision under Weibull lifetime distribution with known shape parameter. Also, two sudden death tests under a proposed cost model are discussed and a numerical example is provided to illustrate the use of the proposed cost model.
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.
와이블 수명분포와 대수정규 수리시간분포 하에서 가용도의 추정과 실증시험계획
서순근(Seo, Sun-Keun) 한국신뢰성학회 2014 신뢰성응용연구 Vol.14 No.1
One important measure of performance for a repairable system is steady-state availability. In this paper, a method to estimate and establish confidence interval for the steady-state availability under Weibull lifetime and lognormal repair time distributions is proposed. Also, bias and mean squared error of a point estimator for an availability are investigated. In addition, a procedure to derive the sample size and critical value for availability demonstration test is presented and illustrated with a numerical example.