• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.87-95
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• 2016

In this study, we develop a model of an open center and load-sensing system and for a main control valve to analyze system characteristics and efficiency using SimulationX. In order to analyze the operating characteristics of the pressure and flow of the main control valve of an open center system, a test was performed at each port. The reliability of the model was confirmed by comparing the similarity of the analysis results with the test results before analyzing the operating characteristics of the system. Development of the load sensing main control valve was performed by adding a flow sharing valve and a notched shape to the open center system based on it's the proven reliability. The authors performed the simulation under the same load conditions in order to compare the efficiency of the systems. Additionally, the combined operation performance was investigated by means of analyzing the characteristics of flow distribution under different load conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.348-357
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• 2012

Recently, smartphone, notebook, PC and other supporting wireless LAN device have come into wide use. By increasing user that use wireless LAN device, wireless traffic also increased. If wireless traffic through one AP is increase, it causes throughput decrease. To solve this problem, wireless LAN service provider install more AP where overload occurred. But this is not enough. Because stations can't know AP's load factor, and APs do nothing for load balancing. In this paper, we propose Multi-Interface Access Point(MIAP) to solve this problem. MIAP operate same as multiple APs with multi-interface, and MIAP measure each interface's load periodically. If MIAP detect overloaded interface, MIAP transfer station from overloaded interface to under-loaded interface. We conducted an experiment for verifying existing problem, and we found this problem occurred. We plan an experiment scenario for a comparison between existing AP and MIAP, and excute these experiment. In the result, we show MIAP with load balancing can improve total throughput about 72% and stabilize delay jitter than existing AP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2230-2237
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• 2015

Inspired by the synchronization phenomena observed in the Nature, we propose an autonomous load balancing method for a wireless network. We model the load balancing problem of cells providing wireless access services as a synchronization problem in the Nature and design an algorithm for each cell to distribute loads in a self-determining way based on the load differences among its neighbor cells. Through simulations, we verify the feasibility of the proposed method in that cell loads can be balanced efficiently eve if cells make decision autonomously using their local information.

• 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)

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1485-1488
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• 2001

최근 들어 매우 인기 있는 웹 사이트는 우수한 성능의 단일 서버 또는 미러(mirror) 사이트에만 의존 할 수 없을 정도로 인터넷 사용이 급증하였다. 늘어나는 트래픽을 감당해내며 사용자를 만족시키기 위해서는 클라이언트의 요청들을 여러 대의 서버에 분산 처리 할 수 있는 고성능 웹서버 클러스터링 시스템에서는 제공되어야 한다. 본 논문에서는 부하 분배기를 이용한 로드 밸런싱을 소개하고 지역성과 로드밸런싱의 균형을 이루는 분배 알고리즘을 제시한다. 본 논문에서 제안된 알고리즘은 정적 웹 환경에서의 각 요청들은 작업 시간이 고정되어 있지 않다는 점에 착안하여 유효 요청의 수와 잔여량을 고려한 부하 분배 알고리즘을 개발하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.13-15
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• 2004

CC-NUMA 시스템은 메모리를 분산시켜 트랜잭션을 지역화 함으로써 고성능 및 확장성을 꾀하는 구조이다. 그러나 CC-NUMA 시스템에서 여러 병렬 프로그램들이 수행될 경우, 각 프로그램의 부하 차이에 의하여 균등한 네트워크 활용율을 나타내지 못하며. 이중 링 CC-NUMA 시스템에서 이러한 불균등한 네트워크 부하로 인한 성능 감소가 발생한다. 본 논문은 이중 연결 구조중 하나를 건너뜀 연결을 갖도록 배치하여 균등한 네트워크 부하를 나타내도록 하며, 이중 링에 비하여 균등한 네트워크 부하를 나타냄을 시뮬레이션을 통하여 검증한다.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.550-558
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• 2001

Although the web is becoming a widely accepted medium, it provides relatively poor performance and low availability. A cluster consists of a collection of interconnected stand-alone computers working together and provides a high-availability solution in application area such as web services or information systems. In this paper, we propose a load balancer architecture under the web server cluster that provides high-availability, high performance and scalability. In addtion, we propose an efficient load balancing algorithm that considers access rate and size of documents. Specially, our algorithm does not require the nodes running under similar configurations and the same operating system. Also, server cache can be utilized more efficiently.

• The KIPS Transactions:PartA
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• v.10A no.6
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• pp.729-736
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• 2003

With the rapid growth of the Internet, popular Web sites are visited so frequently that these cannot be constructed with a single server or mirror site of high performance. The rapid increase of Internet uses and uses raised the problems of overweighted transmission traffic and difficult load balancing. To solve these, various schemes of server clustering have been surveyed. Especially, in order to fully utilize the performance of computer systems in a cluster, a good scheduling method that distributes user requests evenly to servers in required. In this paper, we propose a new method for reducing the service latency. In our method, each Web server in the cluster has different content. This helps to reduce the complexity of load balancing algorithm and the service latency The Web server that received a request from the load balancer responds to the client directly without passing through the load balancer. Simulation studies show that our method performs better than other traditional methods. In terms of response time, our method shows shorter latency than RR (Round Robin) and LC (Least Connection) by about 16%, 14% respectively.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10a
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• pp.669-672
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• 2000

회선분배장치를 제어관리하는 W/S의 Daemon 중에서 Event 처리를 담당하는 EvtProc Daemon의 경우를 들어 효율적인 부하 분산 알고리즘을 설계하였다. 본 논문에서는 대량의 Event 발생 시 담당 프로세스가 연속적으로 fork, exec 하지 않고 일정시간 대기하므로써 fork 와 exec 의 오버헤드를 줄이고 같은 Op Code의 연이은 Event 발생에 대기중인 프로세스가 이를 처리함으로써 더욱더 오버헤드를 줄일 수 있다. 그리고 Event를 처리하는 Child 생성에 있어 주 Child 가 부하분산을 담당하게 함으로써 효율적이고 안정적으로 관리할 수 있는 방안을 제시하였고 이를 구현 분석하였다.

• 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.