• Proceedings of the Korean Information Science Society Conference
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• 2007.06b
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• pp.350-353
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• 2007

기존의 시스템 개발 환경은 동질성, 신뢰성 그리고 보안성 등을 중요시하는 중앙 집중 형태로 운영되어 왔다. 그러나 최근의 컴퓨팅 환경은 분산된 자원들 사이에서의 협업이나 자원 고유를 위한 상호 운영 방향으로 변모되어가고 있다. 이러한 상호 연결 시스템으로는 그리드 컴퓨팅이 활발하게 연구가 진행되고 있다. 그리드 환경에서 고려해야 할 사항은 필요 자원의 사용 대기시간을 줄이는 작업 분배 알고리즘과 고장 감내이며 이들을 중요한 연구 대상으로 하고 있다. 특히, 한정된 지역 정보만을 사용하는 n-Cycle 오버레이 네트워크는 효율적이고 고른 작업 분배 알고리즘을 제공하지만 고장 감내에 대한 대처를 하지 못하는 단점을 지니고 있다. 본 논문에서 부분 복구 기법을 제안함으로써 고장 노드에 의해 발생되는 작업 메시지의 누락율을 줄이고 전체 네트워크 토폴로지의 성능을 향상 시킨다. 또한 고장 노드가 발생하면 전체의 오버레이 네트워크를 재구성해야 하는 문제점을 해결한다. 실험을 통해 부분 복구 기법으로 노드의 고장에 따른 성능 저하율이 현저히 낮아짐을 보인다.

• The KIPS Transactions:PartA
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• v.13A no.4 s.101
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• pp.323-334
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• 2006

A metadata service is one of the important factors to affect the performance of cluster file systems. We propose a content-based load balancing algorithm that dynamically distributes client requests to appropriate metadata servers based on the types of metadata operations. By replicating metadatas and logging update messages in each server, rather than moving metadatas across servers, we significantly reduced the response time and evenly distributed client's requests among metadata servers.

• Annual Conference of KIPS
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• 2022.11a
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• pp.347-349
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• 2022

과열되는 배달 시장의 경쟁 속에서 수많은 배달원이 속도전에 내몰리고 있다. 배달 앱 시장에서는 속도전의 승리를 위해 단건 배달 서비스를 내놓았지만 이러한 배달 경쟁은 배달비 인상으로 이어져 소비자의 부담으로 돌아왔다. 본 논문에서는 배달 업무의 고른 분배를 통해 배달원들의 경쟁을 완화하고 전체 배달 시스템의 처리량과 신뢰도를 향상하고자 하였다. 따라서 목적함수의 최적화와 무작위성이라는 특징을 가진 유전 알고리즘을 활용하여 배달원들 간 배달 업무의 고른 분배를 통해 시스템 성능을 향상시켰다. 실험을 통해 기존의 배치 기법에 비하여 제안 알고리즘에서의 성능이 향상되었음을 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3546-3552
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• 2009

In this study, an analysis code was created for a 190*650*25-mm (W*H*D) parallel-flow evaporator, and research was done on how to increase the heat transfer rate of aluminum PF heat exchanger for application in IDU. After varying the R410A refrigerant up-down flow to two and three passes and the distribution ratio to 1:1:1 and 1:2:2, it was determined that the two-pass flow has a 30% higher partial heat transfer rate and a 25% lower heat transfer coefficient compared to the three-pass flow. As for the distribution ratios of the three-pass flow, 1:1:1 was found to have a lower refrigerant pressure loss than 1:2:2 distribution. It was assumed, though, that the refrigerant distribution had a uniform flow and that its value was thus overestimated in the actual case of maldistribution in each pass.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.2
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• pp.184-191
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• 2000

We discussed load CUlTent sharing for Master/Slave convertedMSC) type two DC-DC Converters parallel operation using a single current sensor method. In the conventional method, two CTs have been used to share t the load CUlTent equally with two coηverters‘ This paper presents a novel load CUlTent distribution method u using a single CUlTent sensor that can share load CUlTent effectively with only one CT in the Master-Slave C conveη:ers(MSCs) type. To confirm parallel operational performance of proposed DC-DC converters parallel operation, two experimental prototype converters were designed, implemented and experimented under three a arbitrary conditions. A load cur‘rent shahring perforrnance of the proposed method was compared with that of a c conventional peak CUt${\gamma}$ent method requmng two CTs. Those experimental results show that load cUlTent s sharing performance of paralleled two converters using a single CUlTent sensor was good and operated as well a as conventional method (ex, Pe밟 CUlTent Method)

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.3
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• pp.311-317
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• 2019

We first numerically analyzed the characteristics of a silicon-based grating structure for beam steering. The analysis includes the basic principle of the grating structure according to the wavelength, peak radiation angle, radiation efficiency, and full-width at the half maximum(FWHM) of the radiation angle. Based on the analysis, we propose a silicon-based grating structure integrated with distributed Bragg reflector(DBR) to obtain a high radiation efficiency and narrow beam width simultaneously. We performed the numerical optimization of the radiation efficiency and FWHM of the radiation angle according to the DBR position. By the design optimization using the proposed grating structure compatible with the complementary metal-oxide semiconductor(CMOS) process, we achieved a maximum radiation efficiency of 87.1% and minimum FWHM of radiation angle of $4.68^{\circ}$.

• Journal of KIISE:Information Networking
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• v.29 no.5
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• pp.466-472
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• 2002

We investigate the load sharing problem between the umbrella cell and the overlaid tells in hierarchical cell structure. A load sharing strategy is proposed and its performance is evaluated by simulation when it is used for transmission of the mobile Internet traffic using the High Speed Downlink Packet Access scheme. The results show that, with the proposed strategy, the microcell backs well the overlaid picocells up, especially when a specific picocell cluster suffers unusual heavy load condition. By using the strategy, we can reduce the installation cost, otherwise needed for increasing the system capacity of every picocell cluster to cope with the unusual heavy load.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.5
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• pp.581-587
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• 2007

In order to suggest the methodology for improving the equality of flow distribution in a distribution channel, wet tests were carried out for pilot plant which was scaled down to 1/8 of full scale distribution channel being operated in domestic K_water treatment plant. The correlation between various hydraulic variables and their effects on the equality of flow distribution was evaluated through wet tests using pilot plant. From the results of wet tests, the longitudinal baffle with orifices was installed in the distribution channel, the equality of flow distribution was improved on the condition that the Froude number in pilot plant was similar with that in the full scale channel. Also, the opening ratio of the orifices on the longitudinal baffled did not have influence on the performance of the equality of flow distribution when the average flow velocity and Froud number were relatively low (Froude number ${\fallingdotseq} 0.01$). In the other hand, the performance of the equality of flow distribution was improved with increasing the opening ration of on the longitudinal baffle under conditions of relatively high average flow velocity and high Froud number(${\gtrsim}0.1$)

• Journal of Korean Society of Water and Wastewater
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• v.21 no.5
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• pp.571-579
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• 2007

This study was conducted to qualify the equality of the flow distribution from open channel between rapid mixing basin and flocculation basins in a domestic full-scale water treatment plant, and suggest a remedy for improving the equality. In order to evaluate the feasibility of the suggested remedy, computational fluid dynamics (CFD) technique are used, and for verifying the CFD simulation results wet tests were carried out for the pilot scale channel based on geometric similarity. From the results of CFD simulation and wet tests, it was investigated that the modification of hydraulic structure in the distribution channel, which is to install the longitudinal orifice baffle in flow direction, could improve the equality of the flow distribution. Also, in the case that Froude number is relatively small (Froude number <<0.03), the open ratio of orifices on the installed baffle hardly affects the equality of flow distribution.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.651-657
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• 2008

A new approach for maximizing torque capability of low efficient reaction wheel assembly is addressed in this paper. At first, to find out a solution in constrainted field, weighted pseudo-inverse and momentum minimized allocation are suggested instead of a general control allocation called pseudo-inverse. The second method is a structural manner to enlarge torque capability of specific axis by changing installed skew angle of wheels. Two proposed methods are applied to large angle maneuvers of satellite. Improvement of control performance and feasibility for applying to commercial satellite attitude control are demonstrated by numeric simulations.