• 전기학회논문지
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• 제59권4호
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• pp.768-773
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• 2010

In this paper, we study on an optimal design of a triple-band PIFA (Planar Inverted-F Antenna) of 433 MHz, 912 MHz and 2.45 GHz by using evolution strategy. Generally, the resonant frequency of the PIFA is determined by the width and length of a U-type slot used. However the resonant frequencies of the multiple U slots are varied by the mutual effect of the slots. Thus the optimal width and length of U-type slots are determined by using an optimal design program based on the evolution strategy. To achieve this, an interface program between a commercial EM analysis tool and the optimal design program is constructed for implementing the evolution strategy technique that seeks a global optimum of the objective function through the iterative design process consisting of variation and reproduction. The resonant frequencies of initial model are 439.5 MHz, 981.5 MHz and 2.563 GHz. However, the resonant frequencies of the triple-band PIFA yielded by the optimal design program are 430.5 MHz, 907 MHz and 2.4515 GHz. Measured resonant frequencies are 433.5 MHz, 905.5 MHz and 2.454GHz, which show a good agreement with the simulation results.

• 대한교통학회지
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• 제13권3호
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• pp.67-86
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• 1995

It requires the detector system which can collect highly reliable traffic data in order to perform the real-time traffic signal control. This study is to decide the optimal shape of inductive loop for the real-time traffic signal control .This loop is located at the stopline in the signalized intersection for DS(Degree of Saturation) control. In order to find out the optimal shape of loop, 6types of experiments were performed . The results of the basic experiments of loops are as follows ; -the optimal number of turns for loop is 3 turns. -the impedance values of the loop detectors are similar to that of NEMA standards -the 1.8${\times}$4.5M loop is excellent for sensitivity in actual detection range of car length comparing to other shape of inductive loops. At the experimental of establishments of the optimal loop shape, it found that 1.8 4.5M loop has the highest values of $\DeltaL$ comparing to other types of loops, It means that the range of Lead-in cable length of this loop. And this loop is highly reliable in occpupancy time. Conclusivley, the 1.8${\times}$4.5M inductive loop is the optimal solution as a stop line loop detector for real -time traffic signal control.

• 한국항공우주학회지
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• 제32권4호
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• pp.53-60
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• 2004

F-4E를 모선으로 하는 초소형 위성을 탑재할 수 있는 공중발사체 1단 부스터용 하이브리드 모터의 최적설계를 실시하였다. 설계변수는 포트개수, 초기 산화제 플럭스, 연소실 압력, 그리고 노즐 팽창비 등을 사용하였다. 또한 서로 다른 최적화 알고리듬의 적용 가능성을 검증하기 위하여 구배법 (GBM)과 유전자 알고리듬 (GA) 방법을 각각 사용하였으며, 목적함수의 선택에 따른 최적화 결과의 변화를 살펴보기 위하여 두 가지 종류의 목적함수 (모터 중량과 모터 길이)를 사용하여 그 결과를 상호 비교하였다. 최적화 알고리듬, 그리고 목적함수의 선택과 무관하게 거의 같은 설계결과로 수렴함을 확인하였다. 최적화결과로 설계요구조건을 만족하는 총중량 704.74kg, 1단 길이 3.74m의 하이브리드 모터를 설계 할 수 있었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.137-140
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• 2003

In this paper, we propose a new construction algorithm for the reversible variable-length code (RVLC) using a simplified average length function of the optimal Huffman code. RVLC is introduced as one of the error resilience tools in H.263+ and MPEG-4 owing to its error-correcting capability. The proposed algorithm demonstrates an improved performance in terms of the average codeword length over the existing HVLC algorithms.

• 한국정보과학회논문지:정보통신
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• 제28권4호
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• pp.657-664
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• 2001

선행 논문(제1부)[13]에서는 광 베니언-형 교환 망에 있어 누화를 야기하는 멀티캐스트 접속들간의 관계를 그래프로 표현하고, 해당 그래프의 차수의 상한을 제시하였다. 본 논문(제2부)에서는 교환소자를 달리하는 멀티캐스팅의 스케줄링에서의 라우팅 횟수 즉, 스케줄링 길이에 대해 다룬다. 최적의 스케줄링 길이를 구하는 문제는 NP-complete이므로 최적 길이의 상한의 두 배 이내의 길이를 제공하는 근사 알고리즘을 제시한다. 아울러, 링크를 달리하는(즉, 넌블럭킹) 멀티캐스팅에 관한 스케줄링 길이를 고찰한다. 얻어진 스케줄링 길이 하에서 다양한 넌블럭킹 베니언-형 멀티캐스팅 망들을 규명한다.

• 터널과지하공간
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• 제20권6호
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• pp.465-474
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• 2010

중규모 터널(연장 1 km 이내) 건설은 최근 매년 30% 이상의 증가율을 보이고 있으나 환기 및 방재시설 설치기준은 제정되어 있지 않은 상태라 장대터널을 대상으로 한 설치기준을 따르고 있다. 이에 따라 중규모터널 환기 및 방재시설의 최적화 노력이 요구되고 있다. 본 연구에서는 중규모 터널 내 20 MW 규모의 화재 시 발생하는 화재연 역류거리, 고온 열기류 확산범위, 가시거리 20 m 이하(상류) 구간분포, 임계풍속 확보여부, 대피시간 등을 CFD 분석을 통해 방재팬의 적정 초기 가동시간을 도출하여 방재시스템의 최적운전 방안의 제시를 목적으로 한다.

• Journal of Communications and Networks
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• 제14권2호
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• pp.121-129
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• 2012

In this paper, we consider a source node that operates over a time varying channel with energy harvesting capability. The goal of the source is to maximize the average number of successfully delivered packets per time slot. The source is able to choose whether to transmit a packet or defer the transmission in each time slot. The decision which is chosen by the source depends on the channel information available and the length of the energy queue. We formulate the problem of finding the optimal policy as a Markovian decision problem. We show some properties of the value function that represents the discounted number of successfully delivered packets per time slot. We prove that the optimal policy is a threshold type policy depending on the state of the channel and the length of the energy queue. We also derive an upper bound for the average number of packets per time slots successfully received by the destination. We show using numerical results that this bound is a tight bound on the performance of the optimal policy. And we consider the case of time varying channel but without channel state information (CSI). Then, we study the impact of channel time varying nature and the availability of CSI. In this case, we show that the optimal policy is a greedy policy. The performance of this greedy policy is also calculated.

• Journal of the Korean Data and Information Science Society
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• 제17권2호
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• pp.367-377
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• 2006

This paper develops a periodic preventive maintenance(PM) policy following the expiration of warranty. Two types of warranty are considered: renewing warranty and non-renewing warranty. Also, we consider the situation where each PM cost is an increasing function of the PM effect. We determine the optimal number of PM's before replacing the system by a new one and the optimal length of period for the periodic PM following the expiration of warranty. Explicit solutions to determine the optimal periodic PM are presented for the Weibull distribution case.

• 한국농공학회지
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• 제45권6호
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• pp.83-95
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• 2003

In this study, a new concept in a paddy consolidation project is introduced in that curved parallel terracing with contour-lined layout is adopted in sloping areas instead of conventional rectangular terracing. The contoured layout reduces earth-moving considerably compared to rectangular methods in consolidation projects. The objective of the paper is to develop a combinatorial optimization model using the network theory for the design of contour-lined plots which minimizes the volume of earth moving. The results showed that as the length of short side of plot is longer or the land slope is steeper, the volume of earth moving for land leveling increases. The developed optimization model is applied for three consolidated districts and the resulting optimal earth moving is compared with the volume of earth from the conventional method. The shorter is the minimum length of short side of a polt with increases the number of plots, the less is the volume of earth. As the minimum length of short side is 20 m for efficient field works by farm machinery, the volume of earth moving of optimal plot is less by 21.0∼27.1 % than that of the conventional consolidated plots.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권5호
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• pp.1554-1566
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• 2014

Cloud Computing allows application providers seamlessly scaling their services and enables users scaling their usage according to their needs. In this paper, using queuing game model, we present service scheduling schemes which are used in software as a service (SaaS). The object is maximizing the Cloud Computing platform's (CCP's) payoff via controlling the service requests whether to join or balk, and controlling the value of CCP's admission fee. Firstly, we treat the CCP as one virtual machine (VM) and analyze the optimal queue length with a fixed admission fee distribution. If the position number of a new service request is bigger than the optimal queue length, it balks. Otherwise, it joins in. Under this scheme, the CCP's payoff can be maximized. Secondly, we extend this achievement to the multiple VMs situation. A big difference between single VM and multiple VMs is that the latter one needs to decide which VM the service requests turn to for service. We use a corresponding algorithm solve it. Simulation results demonstrate the good performance of our schemes.