• Communications for Statistical Applications and Methods
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• 제7권2호
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• pp.489-497
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• 2000

The M/M/1 queue with impatient customers is studied. Impatient customers wait for service only for limited time K/0 and leave the system if their services do not start during that time. Notice that in the analysis of virtual waiting time, the impatient customer can be considered as the customer who enters the system only when his/her waiting time does not exceed K. In this paper, we apply martingale methods to the virtual waiting time and obtain the expected period from origin to the point where the virtual waiting time crosses over K or reaches 0, and the variance of this period. With this results, we obtain the expected busy period of the queue, the distribution, expectation and variance of the number of times the virtual waiting time exceeding level K during a busy period, and the probability of there being no impatient customers in a busy period.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2004년도 학술발표논문집
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• pp.289-294
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• 2004

We consider M/G/1 queue in which the customers are classified into n+1 classes by their impatience time. First, we analyze the model of two types of customers; one is the customer with constant impatience duration k and the other is patient customer. The expected busy period of the server and the limiting distribution of the virtual waiting time process are obtained. Then, the model is generalized to the one in which there are classes of customers according to their impatience duration.

• International Journal of Reliability and Applications
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• 제3권4호
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• pp.165-171
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• 2002

An optimization of the M/M/1 queue with impatient customers is studied. The impatient customer does not enter the system if his or her virtual waiting time exceeds the threshold K ＞ 0. After assigning three costs to the system, a cost proportional to the virtual waiting time, a penalty to each impatient customer, and also a penalty to each unit of the idle period of the server, we show that there exists a threshold K which minimizes the long-run average cost per unit time.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.49-52
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• 2003

IEEE 802.11 MAC uses a distributed coordination function (DCF) known as carrier sense multiple access with collision avoidance (CSMA/CA) for medium access. Random back-off algorithm helps to avoid the collision. This paper proposes virtual back-off and modified back-off algorithm for reduce a waiting time by back-off and reduce the collision. The modified DCF is consisted of these two algorithms. We expect to reduce the average waiting time of each transmission by using the modified DCF algorithm.

• 한국간호교육학회지
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• 제29권4호
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• pp.339-351
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• 2023

Purpose: The purpose of this study is to identify the educational needs of virtual reality simulations that can be applied to novice nurses during the waiting period before starting work in a hospital. Methods: A convergent mixed methods was used. The survey data were collected from 230 novice nurses, and a focus group interview was conducted with 6 new nurses. The data were collected from November 2022 to January 2023. Descriptive statistics, a frequency analysis, independent t-test, and an Importance-Performance Analysis were performed using SPSS 24.0. Results: Appropriate topics for virtual reality simulation education were indicated to be medications and intravenous injections, which are high priority topics in quantitative and qualitative research. The novice nurses wanted group activity training three to four times a week for two weeks before beginning work in a hospital. They also wanted an immersive virtual reality system based on a real hospital environment. Conclusion: Based on the above results, this study provides basic data for the development of a virtual reality simulation education that can improve the adaptation of novice nurses to clinical practice. A strategy was suggested to utilize the waiting time before beginning work in a hospital as educational time.

• 한국멀티미디어학회논문지
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• 제9권2호
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• pp.208-214
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• 2006

가상환경에 참여하는 참여자들의 하드웨어와 네트워크 성능은 매우 다를 수 있으므로 다양한 환경 하에 있는 참여자들에게 동일한 대우를 하는 공정성과 적절한 응답성의 보장과 이를 위한 동기화는 반드시 해결되어야 할 과제이다. 동기화를 위하여 메시지를 받은 즉시 처리하지 않고 일정한 대기시간이 지난 후 처리하는 방법을 사용할 수 있다. 대기시간이 길어질수록 공정성은 좋아지나 응답성이 떨어지므로 적절한 대기시간을 결정하는 것은 쉬운 문제가 아니다. 본 논문에서는 참여자들의 네트워크 지연시간 중 일정 비율을 제외한 나머지만을 고려하여 대기시간을 결정하는 방법을 제안하고 이 방법의 효용성을 검증했다. 이를 위해 가상환경을 구축하고 메시지를 생성하여 모의실험을 하였다. 실험에서는 본 논문에서 제안한 방범이 대부분의 경우에 좋은 결과를 보여 네트워크로 연결된 가상환경에서 메시지를 동기화 하는데 효과적인 방법임을 입증하였다.

• 한국인터넷방송통신학회논문지
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• 제16권5호
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• pp.7-12
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• 2016

일반적으로 은행, 관공서, 병원과 같이 사람이 많은 장소에서는 대체로 고객에게 일정 시간의 대기시간이 요구되며, 이로 인해 고객의 방문 순서에 따라 고객 대기번호가 기재된 순번대기표를 뽑아 순번을 기다리게 된다. 이와 같은 방법에서는 대기 중인 고객은 현재 처리중인 대기 순서를 항상 확인해야 하므로 대기번호표시부가 보이는 장소 내에 있어야 하는 제약이 있어 다른 장소에서 별도의 업무를 볼 수 없다는 문제점이 있다. 본 논문은 스마트폰을 이용한 대기번호를 발급하는 어플리케이션인 SmartQ 시스템을 개발하였다. SmartQ는 스마트폰을 이용하여 기존의 대기번호 발권기를 대체하여 편리하게 순번대기 서비스를 이용할 수 있도록 지원하며, 서비스 알림, 대기인원, 시간대별/업무별 예상대기시간 등을 실시간으로 제공한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.39-60
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• 2017

In the Cloud, for the scheduling of parallel jobs, there are many tasks in a job and those tasks are executed concurrently on different VMs (Visual machines), where each task of the job will be executed synchronously. The goal of scheduling is to reduce the execution time and to keep the fairness between jobs to prevent some jobs from waiting more time than others. We propose a Cloud model which has multiple Clouds, and under this model, jobs are in different lists according to the waiting time of the jobs and every job has different parallelism. At the same time, a new method-ZOMT (the scheduling parallel tasks based on ZERO-ONE scheduling with multiple targets) is proposed to solve the problem of scheduling parallel jobs in the Cloud. Simulations of ZOMT, AFCFS (Adapted First Come First Served), LJFS (Largest Job First Served) and Fair are executed to test the performance of those methods. Metrics about the waiting time, and response time are used to test the performance of ZOMT. The simulation results have shown that ZOMT not only reduces waiting time and response time, but also provides fairness to jobs.

• 대한산업공학회지
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• 제40권1호
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• pp.135-139
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• 2014

In a connection-oriented packet switching network, the data communication starts after a virtual circuit is established between source and destination. The virtual circuit establishment time includes the queue waiting times in the direction from source to destination and the other way around. We use this two-way queueing delay to evaluate scheduling policies of a packet switching processor through simulation studies. In this letter, we also suggest user testing functions for the packet switching processor to manage virtual circuits. By detecting error causes, the user testing helps the packet switching processor provide reliable connection-oriented services.

• 한국게임학회 논문지
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• 제5권4호
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• pp.33-38
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• 2005

인터넷을 이용하여 수천 명이 동시에 접속할 수 있는 온라인 게임에서는 참여자들의 하드웨어와 네트워크 성능은 매우 다를 수 있으므로 메시지 동기화는 반드시 해결되어야 할 과제이다. 동기화를 위하여 메시지를 받은 즉시 처리하지 않고 일정한 대기시간이 지난 후 처 리하는 방법이 많이 사용되는데, 대기시간이 길어질수록 공정성은 좋아지나 응답성이 떨어지므로 적절한 대기시간을 결정하는 것은 쉬운 문제가 아니다. 본 논문에서는 대용량 일인칭 액션 게임의 특징과 참여자간의 상호작용 확률을 고려한 대기시간 결정 방법을 제안했다. 제안된 방법을 구현하고 가상환경 하에서 메시지를 생성하는 모의실험을 하여 제안된 방법의 효용성을 검증했다.