추계적 계획법을 이용한 수술실 예약 모델과 Newsvendor 비율의 자원 효율성에 대한 영향 분석

민대기(Daiki Min) 한국경영과학회 2011 經營 科學 Vol.28 No.2

The purpose of this paper is to schedule elective surgery patients using a stochastic programming approach and to illustrate how operating room utilization behaves when a decision-maker varies costs associated with utilization. Because of the uncertainty in surgery durations, the underage and overage costs that a decision-maker considers plays an important role in allocating surgery cases into available operating room capacity. We formulate the problem as a stochastic mixed integer programming and propose a sampling-based approximation method for a computational purpose. Newsvendor model is employed to explain the results from numerical experiments that are conducted with the actual data from a hospital. The results show that the operating room utilization is more sensitive when the unit overtime cost is relatively larger than the unit cost for underutilized time.

상향식-하향식 DEA 모형을 이용한 온실가스 감축량 배분

민대기(Daiki Min),정광헌(Kwanghun Chung) 한국경영과학회 2018 經營 科學 Vol.35 No.3

In this paper, we develop a model that adjusts the GHG (Green House Gas) reduction targets by taking account of the bottom-up allocation approach in addition to the top-down allocations. Using environmental efficiency instead of the amount of GHG emissions, we propose a DEA (Data Envelopment Analysis)-based model to allocate the reduction target. By comparing the top-down allocations with the bottom-up allocations, we identify how much each company can reduce or should require the amount of GHG emission permits. In this regard, the purpose of this research includes the development of mathematical models, collecting data sets for empirical analysis, and showing managerial implications. The top-down model allocates the GHG reductions into companies while maximizing the total efficiency so as to accomplish fair allocations. The bottom-up model determines the maximum amount of GHG reductions with aims to maximize the efficiency of individual company. We perform empirical analysis to see differences between the top-down and bottom-up allocations. We obtain data from 36 Korean domestic companies in steel industry. Our empirical analysis provides the guideline how much each company should buy or can sell GHG emissions.

정기발주 재고모형에서 공급자 수율 정보 공유의 기대효과 분석

민대기(Daiki Min) 한국경영과학회 2011 한국경영과학회지 Vol.36 No.3

The objective of this study is to evaluate the effects of sharing uncertain yield information with a downstream supply chain player. We are interested in understanding how the amount of yield uncertainty affects the supply-side benefits and/or costs, which has not been considered in the literature, in addition to the customer-side benefits. With that purpose, this work evaluates a supplier who provides yield information in comparison with another supplier who shares no information. We simulate an order-up-to type heuristic policy that is adapted from the literature and reasonably modified to represent yield information sharing with error. From the simulation study, we argue that the customer would experience cost reduction, but the cost for supplier’s inventory is increasing when sharing yield information. Furthermore, the amount of benefits and costs are situational and affected by level of yield uncertainty and demand variance. Based on the simulation study, we finally make several recommendations for the supply-side approaches to yield information sharing.

예약기반 서비스 시스템에서의 고객 도착 프로세스 분석

민대기(Daiki Min) 한국경영과학회 2012 한국경영과학회지 Vol.37 No.2

Delivery of a good quality of service in an efficient manner requires matching the supply of capacity with customer demand. Much research has employed queueing models that analyzed the service system on the basis of independent and stationary customer arrivals. However, the appointment system, which is widely used to facilitate customer access to service in many industries including healthcare, has significant influence on the customer arrival process so that the independent and stationary assumption does not hold in an appointment-based service system. In this regard, this paper aims to propose a model for accurate illustration of the appointment-based customer arrival process. The use of the proposed model allows us to evaluate the overall system performance such as mean waiting time and service level under various appointment policies instead of conducting simulation studies.

탄소 배출권거래 비용을 고려한 직배송 물류전략의 효과성 평가

민대기(Daiki Min) 한국생산관리학회 2013 한국생산관리학회지 Vol.24 No.3

최근 탄소배출관리는 물류 산업에서도 매우 중요한 고려대상이 되었다. 본 연구는 탄소배출권거래 시스템 아래에서 직배송 물류전략의 성능을 평가하기 위한 분석 모형을 제시한다. 본 논문에서 제안한 분석 모형을 이용하여 탄소배출비용을 고려한 직배송 물류전략의 효과성이 차량의 효율성(utilization) 뿐만이 아니라 탄소배출비용과 관련이 있음을 확인하였다. 특히, 탄소배출비용 자체보다는 탄소배출을 고려한 경우의 단위 수송(재고)비용과 탄소배출을 고려하지 경우의 단위 수송(재고)비용 사이의 상대적 비율이 효과성의 결정에 중요함을 제시하였다. 분석결과는 기업이 탄소비용을 고려하는 경우 직배송 물류전략의 효과성을 향상시키는데 활용될 수 있다. 본 논문에서 제안한 분석모형의 타당성을 수치예제를 통하여 검증하였으며, 실험결과 6% 이하의 오류수준에서 물류전략의 효과성을 정확하게 추정하였다. Managing carbon emission has become a major challenge in logistics operations. In this paper, we propose an analytic method to evaluate performance of the direct shipment strategy under a carbon emission trading constraint. With the method, we demonstrate that the effectiveness of direct shipment strategy considering carbon costs is associated not only with the utilization of vehicle capacity but also with the ratio of costs for transportation and inventory without considering carbon emission to those with carbon emission. The method provides insights that help a company to understand how to improve the performance of the direct shipment strategy when considering the carbon emission trading system. We validate the proposed method using a numerical example. The results show that the lower bound of the effectiveness developed in this work successfully estimates the actual effectiveness with an error of less than 6%.

외래병원 환경에서 UHF 수동형 RFID 기술을 활용한 태그 추적 시스템 개발

민대기(Daiki Min) 한국전자거래학회 2011 한국전자거래학회지 Vol.16 No.3

RFID 시스템은 초기 공급사슬관리 영역에서 다양한 영역으로 확산되고 있다. 의료분야 또한 환자, 의료진, 의료기기 등의 위치추적 관리, 의약품 추적관리 등의 영역에 RFID 시스템 도입을 진행하고 있다. 본 연구는 외래병원에서 태그의 위치추적을 위한 수동형 RFID 기술 기반의 시스템 구축 사례를 4계층의 시스템 구조를 활용하여 분석하였다. 특히 일반적으로 수동형 RFID 기술에서 경험하는 불안정한 인식 데이터 문제를 해결하기 위하여 두 계층으로 구성된 데이터 처리 절차를 제시하였다. 본 논문에서 제시한 데이터 처리 절차를 실제 사례에서 취합한 데이터에 적용하여 태그의 위치를 정확하게 파악하고 추가적인 업무 정보를 도출하는 것이 가능함을 확인하였다. 마지막으로 보다 안정적이고 효과적인 RFID 시스템 구축을 위하여 사례분석에서 경험한 추가적인 논의사항과 연구방향을 제시하였다. An RFID system has been widely applied in many areas over the initial SCM application. In the literature enormous RFID applications in healthcare are documented to improve patient safety, patient/provider logistics, and the efficiency of collecting data. Based on the proposed 4-layered RFID system architecture, we introduce a case that implemented an UHF passive RFID-based tracking system in an outpatient clinic. Particularly, we propose a method to process RFID data that contains noise and missing reads. The proposed method for processing unreliable RFID data is capable to locate the tag accurately and provide additional business information. We finally conclude the paper with identifying obstacles and what is necessary to ensure system reliability.

탈원전・탈석탄・신재생 에너지 확대 정책에 따른 신규 전원구성의 수급 안정성 평가

민대기(Daiki Min),류종현(Jong-hyun Ryu),최동구(Dong Gu Choi) 에너지경제연구원 2018 에너지경제연구 Vol.17 No.1

발전용 대형 가스터빈 개발 기획

민대기(DaiKi Min),송성진(Seung Jin Song),강신형(Shin Hyoung Kang) 한국유체기계학회 2010 한국유체기계학회 학술대회 논문집 Vol.2010 No.12

순회배송 물류전략에서 탄소배출 비용의 효과 분석

민대기(Daiki Min) 한국경영과학회 2015 한국경영과학회지 Vol.40 No.1

This paper develops an analytic model for minimizing the cost of distributing items by truck from one supplier to many customers under Milk run logistics strategy. The model derives formulas for not only inventory and transportation costs but also costs associated with carbon emission trading scheme. In addition, monetary investment for reducing carbon emissions is considered. We analyze how to determine optimal shipment size and carbon emission reduction investment. The purpose of this work is to evaluate the effects of carbon emission trading scheme on the Milk run logistics strategy in terms of how much to reduce carbon emissions and/or inventory and transportation costs. We analytically show that it is possible to reduce carbon emissions while reducing inventory and transportation costs by introducing cap-and-trade carbon emission trading scheme under certain conditions.

탄소배출권거래제도에서의 공급망 조정 모형

민대기(Daiki Min) 대한산업공학회 2015 대한산업공학회지 Vol.41 No.3

This paper considers a supply chain consisting of a manufacturer under the cap-and-trade emissions regulation and a permit supplier. We study joint production quantity and investment in reducing permit production cost decisions for centralized and decentralized supply chains. We formulate two supply chain contracts with aims to coordinate the decentralized supply chain; wholesale price contract and cost-sharing contract. Under the cost-sharing contract, the manufacturer shares a part of the investment in reducing permit production cost and then is allowed to purchase emission permit at a lower price. We analytically find that the proposed cost-sharing contract with reasonable parameters can coordinate the supply chain whereas the wholesale price contract is not desirable to achieve the system-wide profit. Numerical example is followed to support the analysis.