• 대한산업공학회지
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• 제29권3호
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• pp.222-229
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• 2003

In this paper, we address a layout design problem, PTN[2], for determining an appropriate 2-class-based dedicated storage layout in a class of unit load storage systems. Our strong conjecture is that PTNI2] is NP-hard. Restricting PTN[2], we provide three solvable cases of PTN[2] in which an optimal solution to the solvable cases is one of the partitions based on the PAI(product activity index)-nonincreasing ordering. However, we show with a counterexample that a solution based on the PAI-non increasing ordering does not always give an optimal solution to PTN[2]. Utilizing the derived properties, we construct an effective heuristic algorithm for solving PTN[2] based on a PAI-non increasing ordering with performance ratio bound. Our algorithm with O($n^2$) is effective in the sense that it guarantees a better class-based storage layout than a randomized storage layout in terms of the expected single command travel time.

• Journal of Power Electronics
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• 제15권4호
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• pp.929-938
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• 2015

Maximum power point tracking (MPPT) and battery charging control are two important functions for a solar battery charger. The former improves utilization of the available solar energy, while the latter ensures a prolonged battery life. Nevertheless, complete implementation of both functions can be complex and costly, especially for low voltage application such as standalone street lamps. In this paper, the operation of a solar battery charger for standalone street light systems is investigated. Using only one voltage sensor, the solar charger is able to operate in both MPPT and constant voltage (CV) charging mode, hence providing high performance at a low cost. Using a lab prototype and a solar simulator, the operation of the charger system is demonstrated and its performance under varying irradiance is validated.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.73-81
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• 2006

A commercial diesel engine was converted into a dedicated natural gas engine to reduce the exhaust emissions in a retrofit of a diesel-fueled vehicle. The cylinder head and piston were remodeled into engine parts suited for a spark ignition engine using natural gas. The remodeling of the combustion chamber changed the compression ratio from 21.5 to 10.5. A multi-point port injection(MPI) system for a dedicated natural gas engine was also adopted to increase the engine power and torque through improved volumetric efficiency, to allow a rapid engine response to changes in throttle position, and to control the precise equivalence ratio during cold-start and engine warm-up. The performance and exhaust emissions of the retrofitted natural gas engine after remodeling a diesel engine are investigated. The emissions of the retrofitted natural gas engine were low enough to satisfy the limits for a transitional low emission vehicle(TLEV) in Korea. We concluded that a diesel engine can be effectively converted into a dedicated natural gas engine without any deterioration in engine performance or exhaust emissions.

• 한국통신학회논문지
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• 제25권8A호
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• pp.1186-1197
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• 2000

본 논문에서는 국내 지능형 교통시스템 (ITS : Intelligent Transportation System) 서비스에 사용될 예정인 5.8GHz 대역의 근거리 전용 패킷통신 시스템의 성능 평가 및 분석을 수행하였고 근거리 전용 통신 시스템에 적합한 변조방식과 물리 계층의 성능 향상방안으로 간섭 성분을 제거하는 기술에 대해 분석하였으며 DSRC(Dedicated Short Range Communication) 상항링크에 다중 접속 제어 프로토콜 적용시 이에 적합한 프로토콜을 제시하였다 아울러 DSRC 물리계층의 정확한 성능평가를 위해 노변 기지국(RSU)과 이동국 단말(OBE) 사이의 채널 모델링을 제시하고 이의 타당성을 수치해석 결과를 통해 보여주었다.

• 산업경영시스템학회지
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• 제44권3호
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• pp.22-32
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• 2021

To meet rapidly changing market demands, manufacturers strive to increase both of productivity and diversity at the same time. As a part of those effort, they are applying flexible manufacturing systems that produce multiple types and/or options of products at a single production line. This paper studies such flexible manufacturing system with multiple types of products, multiple Bernoulli reliability machines and dedicated buffers between them for each of product types. As one of the prevalent control policies, priority based policy is applied at each machines to select the product to be processed. To analyze such system and its performance measures exactly, Markov chain models are applied. Because it is too complex to define all relative transient and its probabilities for each state, an algorithm to update transient state probability are introduced. Based on the steady state probability, some performance measures such as production rate, WIP-based measures, blocking probability and starvation probability are derived. Some system properties are also addressed. There is a property of non-conservation of flow, which means the product ratio at the input flow is not conserved at the succeeding flows. In addition, it is also found that increased buffer capacity does not guarantee improved production rate in this system.

• 한국항행학회논문지
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• 제10권1호
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• pp.7-12
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• 2006

본 논문에서는 지능형 교통망 시스템 서비스에 사용될 5.8GHz 대역에서 OFDM을 이용한 단거리 전용 통신 시스템의 성능 평가 및 분석하였다. DSRC 채널은 차량의 이동 속도가 최대 180km/h 로 빠른 속도를 가지며, 이로 인하여 핸드 오프가 발생하지 않을 경우, 다양한 정보를 제공하기에는 서비스 시간이 매우 짧다. 따라서, 교통정보와 다양한 멀티미디어 서비스 등을 하기 위해서 더 높은 전송속도가 요구되며, 현재 차세대 DSRC 시스템의 데이터 전송 속도는 10Mbps 이상으로 추진되고 있다. 본 논문에서는 라이시안 채널에서의 수신 신호를 컴퓨터 시뮬레이터를 이용하여 실험하였고, BCH 부호화 기법을 적용하여 시스템의 성능을 분석하였다.

• 한국재료학회지
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• 제29권6호
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• pp.363-370
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• 2019

The recent development of information and communication technologies brings new changes to automobile traffic systems. The most typical example is the advancement of dedicated short range communication(DSRC). DSRC mainly consists of an intelligent transportation system(ITS), an electronic toll collection system(ETCS) and an advanced traveler information system(ATIS). These wireless communications often cause unnecessary electromagnetic waves, and these electromagnetic waves, in turn, cause frequent system malfunction. To solve this problem, an absorber of electromagnetic waves is suggested. In this research, various materials, such as powdered metal and iron oxides, are used to test the possibility for an effective absorption of the unnecessary electromagnetic waves. The various metal powders are made into a thin sheet form by compositing through processing. The electromagnetic characteristics(complex permittivity, complex permeability) of the fabricated sheet are measured. As a result, we achieve -6.5 dB at 940 MHz(77.6 % absorption rate) with a 1.0 mm-thickness electromagnet wave absorber, and -9.5 dB at 940 MHz(88.8 % absorption rate) with a 2.0 mm-thickness absorber.

• 경영과학
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• 제28권3호
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• pp.15-29
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• 2011

In this paper, we consider a system working at both primary service and secondary service. A server can switch between the primary service and the secondary service or it can be assigned to secondary service as a dedicated server. A service policy is characterized by the number of servers dedicated to the secondary service and a rule for switching the remaining servers between two services. The primary service system is modelled as a Markovian queueing system and the throughput is a function of the number of servers, buffer capacity, and service policy. And the secondary service system has a service level requirement strategically determined to perform the service assigned. There is a revenue obtained from throughput and costs due to servers and buffers. We study the problem of simultaneously determining the optimal total number of servers, buffers, and service policy to maximize profit of the system subject to both an expected customer waiting time constraint of the primary service and a service level constraint of the secondary service and develop an algorithm which can be successfully applied with the small number of computations.

• 디지털산업정보학회논문지
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• 제8권4호
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• pp.135-142
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• 2012

DSRC system is a communication system that consists of road side equipment and on board equipment to provide services of communication technology for intelligent transportation systems. In this paper, we carry out a short-range dedicated high-speed wireless communications via DSRC system based on board equipment that is installed in the vehicle and road side equipment through wireless channels of communication. on board equipment is system that have a memory which initialization information is stored, it loads physical layer and MAC layer, LLC layer, L7 layer in turn. In the upper, it should analyze the various commands that are sent from roadside base stations, and carry out the operation which is in accordance with the command. and also it designs the structure of protocol stack which is TRM Layer loaded that is to initialize on L7 layer and MAC layer and efficiently designs operation between on board equipment and the road side equipment.

• 산업경영시스템학회지
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• 제22권51호
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• pp.89-97
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• 1999

본 논문에서는 음성호 및 데이타호를 동시에 서비스하는 계층구조를 가지는 CDMA 셀룰러 시스템에서 트래픽 특성을 고려한 효율적인 채널 할당 알고리듬을 제안한다. 제안된 채널할당 알고리듬은 신규호나 핸드오프호가 마이크로셀에 접속을 시도하고 만약 여유채널이 존재하지 않으면 상위계층인 매크로셀로 오버플로우(Overflow)되는 방식을 Birth-Death Process를 이용한 Stochastic Model로써 모델링한다. 특히, 이 모델에서는 핸드오프 전용채널을 두고 이 핸드오프 전용채널의 수에 따른 블록킹확률을 구한다. 이 결과를 이용하여 적정한 서비스품질(QoS)을 만족하는 핸드오프 전용채널의 수를 결정한다.