• 산업경영시스템학회지
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• 제20권43호
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• pp.153-162
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• 1997

M/G/1 queueing system is one of the most widely used one to model the real system. When operating a real systems, since it often takes cost, some control policies that change the operation scheme are adopted. In particular, the N-policy is the most popular among many control policies. Almost all researches on queueing system are based on the assumption that the arrival rates of customers into the queueing system is constant, In this paper, we consider the M/G/1 queueing system whose arrival rate varies according to the servers status : idle, set-up and busy states. For this study, we construct the steady state equations of queue lengths by means of the supplementary variable method, and derive the PGF(probability generating function) of them. The L-S-T(Laplace Stieltjes transform) of waiting time and average waiting time are also presented. We also develop an algorithm to find the optimal N-value from which the server starts his set-up. An analysis on the performance measures to minimize total operation cost of queueing system is included. We finally investigate the behavior of system operation cost as the optimal N and arrival rate change by a numerical study.

• 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.

• 한국항행학회논문지
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• 제18권4호
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• pp.347-352
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• 2014

본 논문에서는 멀티 서비스 무선 인지 망에서 2 차 사용자의 비 실시간 호의 강제 종료율을 줄이기 위한 마르코프 큐잉모델(M/M/1)을 기반으로 하는 호 수락제어를 제안한다. 멀티 서비스 무선 인지 망에서 2 차 사용자 호를 제어하는 기존의 방법에서는 가용 스펙트럼 홀을 실시간 사용자에게 우선 할당함으로써 비실시간 사용자 호의 강제 종료율이 증가하게 된다. 이를 해결하기 위해 제안된 기법은 비실시간 호의 서비스 품질 특성을 고려하여 가용채널이 생길 때까지 큐잉 시스템에서 대기한 후, 서비스를 지속하게 하여 강제 종료율을 줄인다. 1 차 사용자의 재출현은 신경망 기법으로 예측한다. 시뮬레이션을 통하여 2 차 사용자 호의 강제 종료율, 지연특성, 스펙트럼 사용효율을 분석하고, 기존의 방법과 비교하여 비실시간 호의 강제 종료율을 줄일 수 있음을 보인다.

• 한국콘텐츠학회논문지
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• 제16권7호
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• pp.146-153
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• 2016

본 연구에서는 연속시간 M/M/1 대기행렬 시스템에서 고객들의 평형행동과 서버의 최적 가격책정 전략에 대해 다룬다. 본 연구에서는 두가지 유형의 가격지불 모형을 고려한다. 첫 번째로, 정액지불 모형은 고객의 시스템 내 체류시간에 관계없이 고정된 요금을 부과한다. 두 번째로, 정률지불 모형은 고객의 시스템 내 체류시간에 비례하여 요금을 부과한다. 각 지불 모형에서 시스템을 이탈하는 고객의 보상은 체류시간에 반비례한다. 본 연구는 각 가격지불 모형에서 단위시간당 서버의 기대수익을 최대화하기 위한 가격책정 전략과 그 전략에 따른 고객의 시스템 입장행동에 대해 분석한다. 마지막으로 수치예제를 통해 정액지불 모형과 정률지불 모형을 비교분석하고, 서버측면에서 어떤 가격지불 모형을 선택해야하는 지를 살펴본다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2000년도 춘계공동학술대회 논문집
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• pp.253-256
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• 2000

In general, Automated Storage/Retrieval Systems (AS/RS ) have racks of equal sized cells to utilize the concept of unit-load. Most of the techniques for the performance estimation of a unit-load AS/RS are a static model or computer simulation. Especially, their models were developed under assumption that the Storage/Retrieval (S/R) machine performs only single command (SC) or dual command (DC). In reality, defending on the operating policy and the status of the system at a particular time, the S/B machine performs a SC or a DC, or becomes .: idle. In order to resolve these weak points, we propose a stochastic model for the performance estimation of unit-load AS/RS by using a single-server queueing model. Expected numbers of waiting storage and retrieval commands are found

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.215-217
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• 2005

There are two types of packet loss probabilities used in both the network layer and the physical layer within the wireless transmitter such as a queueing discard probability and transmission loss probability. We analyze these loss performances in order to guarantee Quality of Service (QoS) which is the basic of the future network. The queuing loss probability is caused by a maximum allowable delay time and the transmission loss probability is caused by a wireless channel error. These two types of packet loss probabilities are not easily analyzed due to recursive feedback which, originates as a result at a queueing delay and a number of retransmission attempts. We consider a wireless transmitter to a M/D/1 queueing model. We configurate the model to have a finite-size FIFO buffer in order to analyze the real-time traffic streams. Then we present the approaches used for evaluating the loss probabilities of this M/D/1/K queueing model. To analyze the two types of probabilities which have mutual feedbacks with each other, we drive the solutions recursively. The validity and accuracy of the analysis are confirmed by the computer simulation. From the following solutions, we suggest a minimum of 'a Maximum Allowable Delay Time' for real-time traffic in order to initially guarantee the QoS. Finally, we analyze the required service rate for each type utilizing real-time traffic and we apply our valuable analysis to a N-user's wireless network in order to get the fundamental information (types of supportable real-type traffics, types of supportable QoS, supportable maximum number of users) for network design.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2000년도 추계학술대회 및 정기총회
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• pp.59-62
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• 2000

Many of the previous researchers have been studied for the performance estimation of an AS/RS with a static model or computer simulation. Especially, they assumes that the storage/retrieval (S/R) machine performs either only single command (SC) or dual command (DC) and their requests are known in advance. However, the S/R machine performs a SC or a DC. or both or becomes idle according to the operating policy and the status of system at an arbitrary point of time. In this paper, we propose a stochastic model for the performance estimation of a unit-load AS/RS by using a M/G/1 queueing model with a single-server and two queues. Expected numbers of waiting storage and retrieval commands, and the waiting time in queues for the storage and retrieval commands are found

• 대한산업공학회지
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• 제27권1호
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• pp.111-117
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• 2001

Most of the techniques for the performance estimation of unit-load AS/RS are a static model or computer simulation. Especially, their models have been developed under the assumption that the Storage/Retrieval (S/R) machine performs either single command(SC) or dual command(DC) only. In reality, depending on the operating policy and the status of the system at a particular time, the S/R machine performs a SC or a DC, or becomes idle. In order to resolve this weak point, we propose a stochastic model for the performance estimation of unit-load ASIRS by using a M/G/1 queueing model with a single server and two queues. Server utilization, expected numbers of waiting storage and retrieval commands and mean time spent in queue and system are found.

• 한국BIM학회 논문집
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• 제5권2호
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• pp.1-11
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• 2015

Despite a lot of research on BIM, there is no quantitative study to measure accurately the performance of BIM coordination service. Thus, this study suggested method to measure the performace of BIM coordination services, applying queueing models in the field of management science. To analyze queuing system of BIM coordination services, a group of BIM coordinator were selected. Through focus group interviews with experts were used in the analysis to derive mean arrival rate(${\lambda}$), mean service rate(${\mu}$) of BIM coordination services. Single-server queuing model(M/M/1), multiple server queuing model(M/M/s) is utilized for the BIM coordination services performance measurement in construction phase. This study has significant quantitative performance measurement approaches that can be utilized in the decision-making for the improvement of the BIM coordination services and to support the review of the alternatives accordingly. But There is a limit but it is difficult to take into account the increase or decrease of the cost of alternatives according to the review.

• 경영과학
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• 제27권1호
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• pp.17-31
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• 2010

Patients entering an emergency care center in a hospital usually visit medical processes in different orders depending on the urgency level and the medical treatments required. We formulate the patient flows among diverse processes in an emergency care center using the Jackson network, which is one of the queueing networks, in order to evaluate the system performances such as the expected queue length and the expected waiting time. We present a case study based on actual data collected from an emergency care center in a hospital, in order to prove the validity of applying the Jackson network model in practice. After assessing the current system performances, we provide operational strategies to reduce waiting at the bottleneck processes and evaluate the impact of those strategies on the entire system.