• East Asian mathematical journal
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• 제27권1호
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• pp.23-33
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• 2011

Due to underutilization of spectrum under current inefficient and static spectrum management policy, various kinds of opportunistic spectrum access (OSA) strategies have appeared. Myopic policy is a simple and robust OSA strategy with reduced complexity that maximizes immediate throughput. In this paper, we propose mathematical models to evaluate the throughput and the MAC delay of a myopic policy under saturation tra c conditions. Using the MAC delay distribution, we evaluate the packet delay of secondary users under nonsaturation conditions. Numerical results are given to show the performance of the myopic policy in cognitive radio networks.

• Journal of Preventive Medicine and Public Health
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• 제26권4호
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• pp.650-660
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• 1993

This study aims to describe the causes of medically unnecessary hospital stay at a teaching tertiary hospital, using modified version of Delay Tool in which the causes of delay are divided into slx major categories : delay related to test scheduling, test results, surgery, medical staff, patient/family, and administration. For the analysis of hospital stay, 6,479 inpatient-days were reviewed in two medical and four surgical departments for one month. Initially inappropriate hospital stays were identified using Appropriateness Evaluation Protocol (AEP), and causes of delay listed in Delay Tool were assigned to each of them. In both medical and surgical services, the most important cause of delay was related to medical staffs, ranging from 3.6% to 51.6% of total inpatient days. Next important category was delay related to test scheduling in medical services ($4.7{\sim}9.2%$), and delay related to surgery in surgical services ($7.3{\sim}15.0%$). Among subcategories of delay related to medical staffs, delay due to conservative care was the most important cause of inappropriate hospital stay ($2.9{\sim}6.4%$). Each clinical departments had different distribution among delay categories, which could not be fully justified by their clinical charateristics. The Delay Tool would be helpful in exploring factors related to the inefficient use of hospital beds. As a measurement tool of inappropriate hospital stay, however, the Delay Tool should be refined in the definitions of categories and its contents.

• 한국정보통신학회논문지
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• 제17권5호
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• pp.1101-1105
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• 2013

정적 스펙트럼 관리 방식 아래에서 스펙트럼의 낮은 이용 효율을 개선하기 위하여 다양한 종류의 동적 스펙트럼 접속 방식이 제안되어 왔다. 동적 스펙트럼 접속 방식 중 하나인 myopic 방식은 즉각적인 처리율을 최대로 하는 방식으로 복잡하지 않고 단순하면서도 효율적인 것이 장점이다. 본 논문에서는 myopic 방식의 매체 접속 지연 시간의 분포를 포화 트래픽 환경에서 분석하고, 이를 이용하여 포화 상태가 아닌 정상 상태에서의 시스템 지연 시간을 구한다. 이러한 분석 방법과 결과는 이차 사용자의 실시간 트래픽에 대한 지연 성능 보장을 위한 자료로 사용될 수 있다.

• 인터넷정보학회논문지
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• 제5권6호
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• pp.11-20
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• 2004

Proportional Fair (PF) share policy has been adopted as a downlink scheduling scheme in CDMA2000 l×EV-DO standard. Although It offers optimal performance in aggregate throughput conditioned on equal time share among users, it cannot provide a bandwidth guarantee and a strict delay bound. which is essential requirements of real-time (RT) applications. In this study, we propose a new scheduling policy that provides quality-of-service (QoS) guarantees to a variety of traffic types demanding diverse service requirements. In our policy data traffic is categorized Into three classes, depending on sensitivity of Its performance to delay or throughput. And the primary components of our policy, namely, Proportional Fair (PF), Weighted Fair Queuing (WFQ), and delay-based prioritized scheme are intelligently combined to satisfy QoS requirements of each traffic type. In our policy all the traffic categories run on the PF policy as a basis. However the level of emphasis on each of those ingredient policies is changed in an adaptive manner by taking into account the channel conditions and QoS requirements. Such flexibility of our proposed policy leads to offering QoS guarantees effectively and. at the same time, maximizing the throughput. Simulations are used to verify the performance of the proposed scheduling policy. Experimental results show that our proposal can provide guaranteed throughput and maximum delay bound more efficiently compared to other policies.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.92-94
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• 2007

This paper considers an optimal control problem for a remote control to an electrical drive system with a DC motor. Since it is a linear control system with time-delay subject to unknown but bounded disturbance, we construct a worst-case feedback control policy. This policy can guarantee that, for all admissible uncertain disturbances, the real system state should be in a prescribed neighborhood of a desired value, and the cost functional takes the best guarantee value. The worst-case feedback control policy is allowed to be corrected at one correction point between the initial to the final time, which is equivalent to solving a 1-level min-max problem. Since the min-max problem at the stage does not yield a simple analytical solution, we consider an approximate control policy, which is equivalent and can be solved explicitly m the numerical experiments.

• 보건행정학회지
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• 제13권4호
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• pp.115-130
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• 2003

Reperfusion delay in patients with acute myocardial infarction leads to increased morbidity and mortality. We sought to measure the rates of reperfusion delay and to identify factors associated with reperfusion delay after arrival to hospitals. We included 360 patients who had acute myocardial infarction with ST-elevation or left bundle branch block on electrocardiogram and received reperfusion therapy from the three participating academic medical centers from 1997 to 2000. Through retrospective chart review, we collected data about time to reperfusion therapy, patient and hospital factors potentially associated with reperfusion delay. Factors independently associated with reperfusion delay were determined by logistic regression analysis. Median door­to­needle time was 60.0 minutes, and median door­to­balloon time was 102.5 minutes. According to recommendation of the American College of Cardiology/American Heart Association Guidelines, 226 out of 264(85.6％) of thrombolytic patients and 43 out of 96(44.8％) percutaneous transluminal coronary angioplasty(PTCA) patients experienced reperfusion delay. The significant factors associated with delay were type of reperfusion therapy, patient factors including hypertension and delayed symptom onset to presentation(>4 hours), and hospital factors including nocturnal presentation(6pm∼8am), weekend, and an individual hospital. A significant proportion of patients experienced reperfusion delay. The identified predictors of reperfusion delay may help design a hospital system to reduce the delay in reperfusion therapy

• 한국콘텐츠학회논문지
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• 제21권9호
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• pp.458-470
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• 2021

한국의 정책 현실에서는 사회적으로 큰 이슈가 되지만 막상 정책 결정이 이루어지지 않는 경우가 많이 있다. 이렇게 정책 결정이 지연되는 이유로는 적정한 정책 절차를 거치기 위해서 지연되는 경우, 이해관계자의 동의가 이루어지지 않아 지연되는 경우 등도 존재하지만, 이와 같은 사유만으로 정당화되지 않는 정책 지연도 다수 발생하고 있다. 본 연구는 현재 한국의 정책 결정 과정에서 정당화되지 않는 정책 지연은 정부에 의한 의도적인 무의사결정으로 설명할 수 있다는 점을 제시하고자 하였다. 이에 대한 사례로 상암동 롯데복합쇼핑몰을 제시하고, 상암동 롯데복합쇼핑몰 정책 과정을 무의사결정의 시각에서 분석하였다. 엘리트층의 존재, 목적, 정책수단, 정책과정, 결과 등의 요소들을 기반으로 분석한 결과 상암동 롯데복합쇼핑몰 건립 지연 사례는 정부의 적극적이고 전략적인 무의사결정에 의한 것으로 추정될 수 있었다. 소극행정과 구분되는 정부의 전략적인 무의사결정에 대해 향후 다양한 검토가 이루어질 필요가 있다.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2000년도 추계학술대회
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• pp.329-333
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• 2000

Delay time analysis is a pragmatic mathematical concept readily embraced by engineers which has been developed as a means to model maintenance decision problem. This paper considers an inspection period using delay time analysis for fishing vessel equipment. We assume that delay time distribution is Weibull and inspections are perfect. In this paper, we determine the optimal inspection period which minimize the expected downtime per unit time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권2호
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• pp.733-750
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• 2019

Software Defined Networking (SDN) is a new network paradigm, allowing administrators to manage networks through central controllers by separating control plane from data plane. So, one or more controllers must locate outside switches. However, this separation may cause delay problems between controllers and switches. In this paper, we therefore propose a Priority-based Scheduling policy for OpenFlow (PSO) to reduce the delay of some significant traffic. Our PSO is based on packet prioritization mechanisms in both OpenFlow switches and controllers. In addition, we have prototyped and experimented on PSO using a network simulator (ns-3). From the experimental results, PSO has demonstrated low delay for targeted traffic in the out-of-brand control network. The targeted traffic can acquire forwarding rules with lower delay under network congestion in control links (with normalized load > 0.8), comparing to traditional OpenFlow. Furthermore, PSO is helpful in the in-band control network to prioritize OpenFlow messages over data packets.

• 항공우주정책ㆍ법학회지
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• 제18권
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• pp.77-103
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• 2003