• Journal of Communications and Networks
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• 제5권2호
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• pp.104-115
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• 2003

It is well known that Multiple Input Multiple Output (MIMO) systems offer the promise of achieving very high spectrum efficiencies (many tens of bit/s/Hz) in a mobile environment. The gains in MIMO capacity are sensitive to the presence of spatial and temporal correlation introduced by the radio environment. In this paper, we examine how MIMO capacity is influenced by a number of factors e.g., a) temporal correlation b) various combinations of low/high spatial correlations at either end, c) combined spatial and temporal correlations. In all cases, we compare the channel capacity that would be achievable under independent fading. We investigate the behaviour of "capacity fades," examine how often the capacity experiences the fades, develop a method to determine level crossing rates and average fade durations and relate these to antenna numbers. We also evaluate the influence of channel correlation on the capacity autocorrelation and assess the fit of a Gaussian random process to the temporal capacity sequence. Finally we note that the particular spatial correlation structure of the MIMO channel is influenced by a large number of factors. For simplicity, it is desirable to use a single overall correlation measure which parameterizes the effect of correlation on capacity. We verify this single parameter concept by simulating a large number of different spatially correlated channels.

• 산업경영시스템학회지
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• 제34권3호
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• pp.49-56
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• 2011

Estimating optimum hardware capacity of an e-learning system is very important process to grasp reasonable size of designing technique architecture and budget during step of ISP(information strategic planning) and development. It hugely influences cost and quality of the whole project. While investment on information system hardware has been continuously increased, there was no certified hardware capacity estimating method in e-learning system development. A guideline for hardware sizing of information systems was established by Telecommunication Technology Association in 2008. However, the guideline is not appropriate for estimating optimum hardware capacity of an e-learning system because it was designed to provide general standards for estimating hardware capacity of various types of projects. The purpose of this paper is to provide a methodology for estimating optimum hardware capacity in e-learning system development. To develop the methodology, this study, first of all, analyzes two e-learning development projects, in which the guideline was applied to estimate optimum hardware capacity. Then, this study finds out several key factors influencing on hardware capacity. Finally, this study suggests a methodology for estimating optimum hardware capacity of an e-learning system, in which weights for the factors are determined through AHP analysis.

• 한국구조물진단유지관리공학회 논문집
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• 제7권4호
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• pp.225-233
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• 2003

최근 성능에 근거한 설계법의 개발과 더불어, 변위설계에 대한 관심이 증가하고 있다. 본 연구에서는 다층 RC 골조의 변위성능을 보다 정확하게 평가할 수 있는 방법을 제시하고자 한다. 이를 위해, 골조의 횡변위를 계산하기 위해서 보와 기둥의 변형뿐만 아니라 정착부와 조인트 부분의 변형을 변위 산정시 고려하였다. 기존의 실험 및 계산결과의 비교로부터, 본 연구에서 제시한 방법의 적합성을 확인하였고, 이를 강한 기둥-약한 보의 설계개념을 설계된 다층 RC골조 건물에 적용하여 그 거동을 예측하였다. 그 결과, 보다 정확한 건물의 변위성능을 평가하기 위해서는 정착부와 조인트의 변형을 반드시 반영하여야 하는 것으로 나타났다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.183-184
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• 2004

High capacity container carrier has been considered for many decades to transport the more containers at the same time. Therefore, it is required for high capacity container ship to be applied thicker plate to accomodate a number of containers compared to that of general container ship. To maintain the same productivity of this thicker plate, new welding process should be considered. One of the process for vertical-up position is 2 electrodes EGW(Electro Gas Welding). 2 ectrodes EGW was applied and evaluated whether it can be applicable or not. The heat input used for 72mm thick plate was 520k11cm. from the mechanical test, it is considered that this process can be applicable, showing satisfaction of mechanical properties such as tensile strength, elongation and impact property.

• 한국시뮬레이션학회논문지
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• 제8권2호
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• pp.73-85
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• 1999

In this paper, the productivity estimation of the painting line in an automobile plant is studied. To improve the bottleneck and the weak point of the process, computer simulations are performed. In determining the system specification, the status of the conveyor lines and the other physical facilities are considered in order not to intervene with each other and to satisfy the painting facility restrictions. As simulation parameters, production performance ratio, number of hanger and dolley, down time, speed of conveyor and the pitch of a painting body are chosen on the basis of exhaustive field evaluation to study their effects on the capacity of the process. The results of the simulation show that we can improve the capability of they system without additional investment to the plant facility. The best condition for the maximum capacity of the process is selected by comparing the alternative computer simulation results. As a simulation language, Promodel is used which is very useful and easy to use in manufacturing oriented simulation.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1999년도 춘계학술대회 논문집
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• pp.105-109
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• 1999

Tool shop of the D Heavy Industries Co.(DHI) fabricates engines for a bus, truck, small ship. In order to increase the production capacity of engines, DHI will be established the new tool shop that consists of a block line, head line, assembly line, test line and AS/RS in 1999. In order to assure the production capacity designed of the new tool shop for producing engines and improve the production process of it, it is needed to find a bottleneck process and an optimal way of allocating workloads among machines and workers to maximize the production. In a way to solve this, we model the engine fabrication process of the tool shop and analyze its performance by computer simulation. In this study, we at first identify the bottleneck processes of the engine fabrication process under the designed operation policy. Then, we derive some alternative operating policies applicable to the new tool shop of an engine, and analyze the optimal operation policy by comparing the performance of the tool shop following each alternative policy.

• 한국안전학회지
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• 제7권3호
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• pp.30-34
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• 1992

This study is conducted to evaluate the airborne concentration of mercury, as well as installation and efficiency of local exhaust ventilation system for 57 factories manufactured fluorescence lamps, mercury lamps and thermometers for July and August 1990. Results and conclusion are as fellows : 1) Mercury treatment factories are 32 among 57 ones, which are 18 fluorescence lamp manufacturing ones and 6 mercury lamp ones and 3 thermometer ones and 5 other ones. 2) Mean airborne concentrations of mercury for factories manufactured mercury lamps are 0.01 mg/ ㎥ in injection process and 0.0155mg/㎥ in exhaust process, and mean airborne concentration of mercury for factories manufactured thermometer are 0.023mg/㎥ in injection process and 0.012mg/㎥ in selection process. All of these airborne concentrations of mercury are lower than PEL(Permissible Exposure Limit ), 0.05mg/㎥. 3) Mean airborne concentrations of mercury for factories manufactured fluorescence lamps are 0.094mg/㎥ in injection process and 0.087mg/㎥ in exhaust process, and 0.052mg/㎥ in sealing process and 0.085mg/㎥ in other process, respectively. All of these air borne concentrations of mercury are exceeded to PEL. More than 60% among 32 factories manufactured mercury are exceeded to PEL. 4) Nine factories among 18 factories manufactured fluorestence lamps are equipped with local exhaust ventilation system, and 7 factories among 9 factories are required for the improvement of suction capacity and structure. Five factories among 14 factories manufactured mercury lamps and the other ones are equipped with local exhaust ventilation system, and 2 factories are required for the improvement of suction capacity and structure.

• 전기학회논문지
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• 제67권1호
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• pp.22-28
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• 2018

In case of developing a combined system by a number of distributed resources with storage device, a number of application suggests a huge capacity can derive operational flexibility both power supply issues or when unexpected situation imposed. However, it is important to determine a resonable energy capacity because the device have many controversial cost issues in current power system industry. An ESS application which focusing essentially required points can induce appropriate storage capacity that required in economic operation. In this paper, a curtailment supporting algorithm based on storage device is introduced, and applied in the capacity calculation method. The main algorithm pursues handling minor exceeding quantities which can cause mechanical load at blade; This paper tries to include it for configuring hybrid algorithm with pitch control. Several fluctuating conditions are utilized in simulation to reflect critical situation. The analyzing process focuses on the control feasibility with applied capacity and control method.

• 약학회지
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• 제36권5호
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• pp.449-454
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• 1992

The effect of radioprotective ginseng protein fraction on DNA repair capacity was determined by measuring the amount of $^{3}H-thymidine$ incorporated into DNA in the process of repair synthesis for UV damaged DNA. CHO-Kl cells were prepared whose semiconservative replication was inhibited by trimethylpsoralen plus near-UV(PUVA) treatment. When the cells were exposed to UV light alone, the DNA repair capacity was increased at first and then decreased as UV dose increased. However, when the ginseng fraction was treated to the cells, the DNA repair capacity was kept increasing regardless of UV dose increment. When the concentration of protein contained in the added fraction was increased gradually, the repair capacity was also increased almost linearly showing dose-response relationship of the effect. These results suggest that the enhancement of DNA repair capacity of the cell can be one of the mechanisms of radioprotection by the ginseng fraction.

• The Korean Journal of Ecology
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• 제26권2호
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• pp.53-58
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• 2003

Ever-growing recreation, tourism and ecotourism worldwide have become a significant factor of resource degradation in many protected areas. Managers of these areas are increasingly challenged to implement policies, strategies and actions that would protect the resource base while providing quality visitor experience. One major issue in managing protected area visitations is that of carrying capacity, or the question of "how much use is too much\ulcorner". Scientific studies of visitor impacts, often known as recreation ecology, has generated a knowledge base that provides valuable input to the visitor carrying capacity management process adopted by the U.S. National Park Service. This paper aims at (a) providing an overview of recreation ecology research and its application in managing visitor carrying capacity, and (b) examining the relevance of recreation ecology to East Asian protected areas with special reference to the visitor capacity issue.ity issue.