• 산업경영시스템학회지
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• 제37권1호
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• pp.96-103
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• 2014

A steady-state controllable M/G/1 queueing model operating under the (TN) policy is considered where the (TN) policy is defined as the next busy period will be initiated either after T time units elapsed from the end of the previous busy period if at least one customer arrives at the system during that time period, or the time instant when Nth customer arrives at the system after T time units elapsed without customers' arrivals during that time period. After deriving the necessary system characteristics such as the expected number of customers in the system, the expected length of busy period and so on, the total expected cost function per unit time in the system operation is constructed to determine the optimal operating policy. To do so, the cost elements associated with such system characteristics including the customers' waiting cost in the system and the server's removal and activating cost are defined. Then, the optimal values of the decision variables included in the operating policies are determined by minimizing the total expected cost function per unit time to operate the system under consideration.

• 한국항해항만학회지
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• 제41권3호
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• pp.137-148
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• 2017

항만의 서비스 수준은 항만의 운영 및 관리 주체인 터미널운영사(TOC), 항만공사 및 정부의 입장에서 항만간 경쟁력의 기준이 되며, 항만의 이용 주체인 선사 및 화주의 입장에서는 어느 항만을 선택할 지를 결정하는 중요 지표로도 활용된다. 이러한 지표의 중요성을 고려하여 컨테이너 부두 및 벌크부두를 대상으로 중요 서비스 지표인 선석 점유율, 선박 대기율, 선석 처리량, 접안 척수, 평균 대기 척수, 평균 대기 시간과 같은 6개 지표를 객관적으로 정의하고 관리할 수 있는 소프트웨어를 개발하였다. 컨테이너 부두는 1개 선석부터 6개 선석까지와 벌크 부두는 1개 선석부터 4개 선석까지를 선택적으로 활용할 수 있도록 6개의 서비스 지표를 산정하여 예측이 가능토록 하였다. 이를 활용하면 선석점유율 대비 선박 대기율, 선석 처리량, 접안 척수, 평균 대기 척수, 평균 대기 시간을 예측할 수 있다. 추가하여 선박의 도착 패턴에 따라 선박 대기율과 항만의 생산성 지표인 연간 처리량도 어떻게 변화되는지를 예측할 수 있도록 하였다. 결과적으로, TOC 입장에서는 서비스 지표인 선박 대기율과 생산성 지표인 연간 처리량의 관계에서 최적의 운영 수준을 전략적으로 선택(Trade-off)할 수 있으므로 경쟁 항만에 대비하여 더 많은 선사 및 화주를 유치할 수 있으므로 터미널 수입도 극대화할 수 있다.

• 품질경영학회지
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• 제20권1호
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• pp.48-58
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• 1992

This paper deals with a test procedures on reliablity using hybrid censoring when failure time follows two parameter Weibull distribution. In each case of single and two stage test with hybrid censoring, we construct a operating characteristic curve, and then obtain the censoring number and sample size which the producer's risk and the consumer's risk are both satisfied. This study suggests to determine the expected waiting time at a decision.

• 산업경영시스템학회지
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• 제45권4호
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• pp.53-60
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• 2022

In a group-testing method, instead of testing a sample, for example, blood individually, a batch of samples are pooled and tested simultaneously. If the pooled test is positive (or defective), each sample is tested individually. However, if negative (or good), the test is terminated at one pooled test because all samples in the batch are negative. This paper considers a queueing system with a two-stage group-testing policy. Samples arrive at the system according to a Poisson process. The system has a single server which starts a two-stage group test in a batch whenever the number of samples in the system reaches exactly a predetermined size. In the first stage, samples are pooled and tested simultaneously. If the pooled test is negative, the test is terminated. However, if positive, the samples are divided into two equally sized subgroups and each subgroup is applied to a group test in the second stage, respectively. The server performs pooled tests and individual tests sequentially. The testing time of a sample and a batch follow general distributions, respectively. In this paper, we derive the steady-state probability generating function of the system size at an arbitrary time, applying a bulk queuing model. In addition, we present queuing performance metrics such as the offered load, output rate, allowable input rate, and mean waiting time. In numerical examples with various prevalence rates, we show that the second-stage group-testing system can be more efficient than a one-stage group-testing system or an individual-testing system in terms of the allowable input rates and the waiting time. The two-stage group-testing system considered in this paper is very simple, so it is expected to be applicable in the field of COVID-19.

• 한국항해학회지
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• 제10권1호
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• pp.101-127
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• 1986

Transportation provides an infrastructure vital to economic growth, and it is an integral part of production . As a port is the interface between the maritime transport and domestic transport sectors, it certainly plays a key role in any economic development. Therefore, it is doubtless that inadequacy of a nation's port will depress the level of throughput, to the level where it fails to meet the target set by the national economic planning schemes. Korea is surrounded by the seas and the economic structure of Korea consists of processing trades, so that it cannot be overstated that substantial economy in maritime transport coasts can be achieved through the improvement of the port transport system. This paper treats the transportation process in Pusan Port by Queueing Simulation method, and the reasonable size of Pusan Port is suggested from the point of view of efficiency maximization. The results of the analysis are summarized as follows; 1) the utility rate is 47.91 percents in general piers, 85-52 percents in container piers, and waiting time 5.2hrs, in general piers, 0.8 hrs, in container piers, and the probability of maximum queue length 12 ships in general piers, 2 ships in container piers, and the probability of waiting is 44 percents in general piers, 8 percents in container pier. 2) in general piers, the improvement of app. 30 percents in port capacity is desirable for operating effectively concerning the current arrival rate. By introducing the traffic control ion container piers, there is no apparent necessity of port investment, but I is expected to reduce invisible congestion occurred along the waiting line. 3) On Pusan Port, the optimal utility rate and the optimal arrival rate for reducing waiting time are 3.5 to 4.0(hrs./ship) in general piers, 5.1 to 6.0(hrs./ship) in container piers.

• 산업경영시스템학회지
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• 제39권3호
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• pp.147-155
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• 2016

Industry 4.0's goal is the 'Smart Factory' that integrates and controls production process, procurement, distribution and service based on the fundamental technology such as internet of the things, cyber physical system, sensor, etc. Basic requirement for successful promotion of this Industry 4.0 is the large supply of semiconductor. However, company I who produces dicing blades has difficulty to meet the increasing demand and has hard time to increase revenue because its raw material includes high price diamond, and requires very complex and sensitive process for production. Therefore, this study is focused on understanding the problems and presenting optimal plan to increase productivity of dicing blade manufacturing processes. We carried out a study as follows to accomplish the above purposes. First, previous researches were investigated. Second, the bottlenecks in manufacturing processes were identified using simulation tool (Arena 14.3). Third, we calculate investment amount according to added equipments purchase and perform economic analysis according to cost and sales increase. Finally, we derive optimum plan for productivity improvement and analyze its expected effect. To summarize these results as follows : First, daily average blade production volume can be increased two times from 60 ea. to 120 ea. by performing mixing job in the day before. Second, work flow can be smoother due to reduced waiting time if more machines are added to improve setting process. It was found that average waiting time of 23 minutes can be reduced to around 9 minutes from current process. Third, it was found through simulation that the whole processing line can compose smoother production line by performing mixing process in advance, and add setting and sintering machines. In the course of this study, it was found that adding more machines to reduce waiting time is not the best alternative.

• 한국콘텐츠학회논문지
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• 제18권10호
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• pp.478-489
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• 2018

본 연구에서는 사용자의 현재와 기대 스크립트를 기반으로 커피 전문점의 서비스디자인을 위한 규준 스크립트를 설계하였다. 1) 현재와 기대 스크립트에 포함된 활동들을 확인하였다. 2) 현재와 기대 스크립트에서 고빈도의 활동들을 선정하였다. 그런 후 이 둘을 통합하여 장면별로 분류하였다. 3) 통합된 장면과 활동들에 대한 중요도를 평가하였다. 4) 일정한 규칙에 따라 불필요한 활동들을 삭제하거나 선택 항목으로 제외하였다. 그리고 나머지 활동들을 장면별로 분류하고 순서대로 나열하여 하나의 규준 스크립트를 완성하였다. 각 장면에 속한 활동들 하나하나가 서비스 접점이 되었다. 장면은 '들어가기', '자리 정하기', '주문하기', '음료 기다리기', '음료 받기', '음료를 마시며 시간 보내기', '화장실 가기', 그리고 '나가기'로 구성되었다. '들어가기'에는 2개, '자리 정하기'에는 6개, '주문하기'에는 11개, '음료 기다리기'에는 2개, '음료 받기'에는 4개, '음료를 마시며 시간 보내기'에는 6개, '화장실 가기'에는 3개, 그리고 '나가기'에는 4개의 활동들이 포함되었다. 이러한 결과들과 함께 특이점을 논의하였으며, 마지막에는 연구의 의의와 제한점을 추가하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1881-1888
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• 2008

As the ticket issuing methods have been diversified for the convenience of the passengers such as ticketless service(SMS ticket, e-ticket, home ticket), automatic ticket issuing machine and consignment ticket sale, maintaining the current number of ticket booth has been becoming a issue. Too many booth can cause the inefficiency of the cost of labor. According to the Charter of Customer Service of Korail, on the other hand, 95% of passengers have to purchase a train ticket within 5 minutes. This study was designed to present a decision making model for the optimum number of ticket booth which can affect an efficient operation of train station and improvement of customer convenience. And, this paper shows the proper manpower of ticket booth and the change of customer waiting time by analyzing the arrival and ticket issuing time of passengers based on 'Queueing Theory'. However, it is insufficient to be generalized due to some limitations of analysis. This study will contribute to improve customer satisfaction by reducing the waiting time at the ticket booth. In addition, presenting the optimum number of booth is expected to have an effect on the increase of productivity and cost savings.

• 사물인터넷융복합논문지
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• 제10권2호
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• pp.103-108
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• 2024

본 논문에서는 YOLO(You only look once)v5를 기반으로 한 실시간 객체 검출 기술을 활용하여 스마트 엘리베이터 시스템을 연구하였다. 외부 엘리베이터 버튼이 눌러지면 YOLOv5 모델이 카메라 영상을 분석하여 대기자의 유무를 판별하고, 대기자가 없다고 판별되면 해당 버튼을 자동으로 취소시킨다. 연구에서는 YOLOv5와 사물인터넷에서 활용되는 MQTT(Message Queuing Telemetry Transport)를 통한 객체 탐지 및 통신 기술의 효과적인 구현 방법을 소개한다. 그리고 이를 활용하여 대기자 유무를 실시간으로 판별하는 스마트 엘리베이터 시스템을 구현하였다. 제안한 시스템은 불필요한 소비 전력을 절감하면서 CCTV(closed-circuit television)의 역할을 할 수 있다. 따라서 제안한 스마트 엘리베이터 시스템은 안전 및 치안 문제에도 기여할 수 있을 것으로 기대한다.

• 한국국방경영분석학회지
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• 제24권1호
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• pp.98-109
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• 1998

This study develops a maintenance strategy for a reparable 2-unit standby system. The maintenance strategy implies the waiting time to call the repair facility when the unit-1 fails. Almeida and Souza set up the multi-attribute utility function consisting of system availability and repair cost for several maintenance strategies and decide the optimal maintenance strategy that maximize the expected value of the utility function. We decide the optimal maintenance strategy satisfying the following two criteria about the utility function : maximum variance using Almeida and Souza's utility function. It both criteria are not satisfied at the same time for every strategies, the strategy maximizing the lower confidence limit for expected utility function is regarded as an optimal one.