• 디지털산업정보학회논문지
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• 제16권2호
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• pp.35-43
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• 2020

Cloud computing integrates computing resources such as servers, storage, and networks with virtualization technology to provide suitable services according to user needs. Due to the structural characteristics of sharing physical resources based on virtualization technology, threats to availability can occur, so it is essential to respond to availability threats in cloud computing. Existing over-provisioning method is not suitable because it can generate idle resources and cause under-provisioning to degrade or disconnect service. System resources must be allocated in real-time according to the system load to guarantee the cloud system's availability. Through appropriate management measures, it is necessary to reduce the system load and increase the performance of the system. This paper analyzes the work response time according to the allocation or migration of virtual machines and discusses an efficient resource management method considering the system load.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2002년도 춘계학술발표논문집 (상)
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• pp.381-384
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• 2002

This paper describes the motivation, design and performance of bi-active Load balancer in Linux Virtual Server. The goal of bi-active Load balancer is to provide a framework to build highly scalable, fault-tolerant services using a large cluster of commodity servers. The TCP/IP stack of Linux Kernel is extended to support three IP load balancing techniques, which can make parallel services of different kinds of server clusters to appear as a service on a single IP address. Scalability is achieved by transparently adding or removing a node in the cluster. and high availability is provided by detecting node or daemon failures and reconfiguring the system appropriately. Extensive simulation reveals that the proposed approach improves the reply rate about 20% compared to earlier design.

• Journal of Power Electronics
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• 제19권2호
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• pp.580-590
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• 2019

The concept of virtual synchronous generators (VSGs) is a valuable means for improving the frequency stability of microgrids (MGs). However, a great virtual inertia in a VSG's controller may cause power oscillation, thereby deteriorating system stability. In this study, a small-signal model of an MG with two paralleled VSGs is established, and a control strategy for maintaining a constant inertial time with an increasing active-frequency droop coefficient (m) is proposed on the basis of a root locus analysis. The power oscillation is suppressed by adjusting virtual synchronous reactance, damping coefficient, and load frequency coefficient under the same inertial time constant. In addition, the dynamic load distribution is sensitive to the controller parameters, especially under the parallel operation of VSGs with different capacities. Therefore, an active power increment method is introduced to improve the precision of active power sharing in dynamic response. Simulation and experimental is used to verify the theoretical analysis findings.

• 융합보안논문지
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• 제8권4호
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• pp.51-56
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• 2008

VPN(Virtual Private Network)과 DSL, 케이블과 같은 다이얼업 접속의 조합은 저렴한 비용으로 임대라인 기반의 사설망의 대안이 되고 있다. VPN 장비의 고가용성(High Availability, HA)에 대한 기업의 요구가 증대되고 있다. 본 논문에서 VPN 게이트웨이에서 링크 이중화를 통한 액티브-액티브 방식을 이용해 네트웍 접근성의 고가용성과 네트웍 부하 분산 기법을 제안한다. 네트웍 링크의 고가용성/부하분산은 외부 내트웍 접근을 독립적인 두 개의 라인으로 이중화하는 것으로 달성할 수 있다. 이것은 둘 중 하나의 링크에 문제가 발생하더라도 내부 사용자에게 지속적인 네트웍 접근을 제공할 수 있다. 뿐만 아니라, 네트웍 부하를 두 개의 라인으로 분산시킴으로써 두 배에 가까운 네트웍 대역폭을 제공할 수 있다. 네트웍 링크의 부하 분배를 위해 정적인 알고리즘과 동적인 알고리즘을 제안한다.

• 한국의상디자인학회지
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• 제23권3호
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• pp.1-10
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• 2021

Harnesses are used in a variety of industries, such as rescue operations, medicine, and entertainment. However, conventional harnesses have problems as they are uncomfortable to wear and causes continuous pain. Therefore, in this study, the load and pressure applied to the body in the flying state when using a conventional harness were measured in real time and the distribution change was observed. Load and pressure were measured using a modified corset harness, a pressure sensor, and a human mannequin to measure the maximum and average pressure on the waist. As a result, it was confirmed that the load concentrated on the waist in the flying state was 104 N, and the pressure was applied to the left and right sides was 800 kPa or greater. The pressure distribution showed a pressure of 3-45 kPa in 73% in all measurable pressures. The results of the load and pressure distribution are presented as basic data for improving the wearability and reducing the discomfort of harnesses in the future, aid in the development of a harnesses that can minimize discomfort for various activities, and increase the concentration on experiential activities. In addition, using the CLO 3D program, which is a 3D virtual wearing system, a harness was put on a virtual model, and the compression level was checked and compared with the actual pressure distribution. As a result of comparing the measured pressure values in the flying state with the clothing pressure wearing the harness in the CLO 3D program, the total pressure value was found to be about 68% of the actual measured value. This helps develop a harness that can minimize discomfort during activities by predicting the load and pressure on the body by first applying new designs to a virtual wearing system during development. These new harness patterns can solve the problems of conventional harnesses.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.74-76
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• 2001

When a Bus voltage is low, the Load-Flour is generally blown up. If Bus voltage is normalized. the convergence of Load-flow is improved. This paper introduces virtual bus with tap. In that case, the Bus admittance will be considered. And the convergence of Load-Flow in applying virtual bus is debated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.5694-5711
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• 2017

The technology of cloud computing is growing very quickly, thus it is required to manage the process of resource allocation. In this paper, load balancing algorithm based on honey bee behavior (LBA_HB) is proposed. Its main goal is distribute workload of multiple network links in the way that avoid underutilization and over utilization of the resources. This can be achieved by allocating the incoming task to a virtual machine (VM) which meets two conditions; number of tasks currently processing by this VM is less than number of tasks currently processing by other VMs and the deviation of this VM processing time from average processing time of all VMs is less than a threshold value. The proposed algorithm is compared with different scheduling algorithms; honey bee, ant colony, modified throttled and round robin algorithms. The results of experiments show the efficiency of the proposed algorithm in terms of execution time, response time, makespan, standard deviation of load, and degree of imbalance.

• 한국공간정보시스템학회 논문지
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• 제10권4호
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• pp.21-26
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• 2008

본 연구에서는 대용량의 항공 레이저 스캔 자료를 효율적으로 처리하기 병렬처리 기법과 가상격자 구조를 도입하였으며 제안한 방법의 실효성을 평가하기 위하여 IDW(Inverse Distance Weighting) 방식으로 정규격자 DSM을 생성하였다. 즉, 대용량 항공 레이저 스캔 자료의 신속한 보간을 위하여 병렬처리 기법을 이용하고 불규칙적으로 분포된 포인트의 검색 효율성을 제고하기 위하여 가상격자(virtual grid)를 사용하였다. 마스터 노드와 6대의 슬래이브 노드로 구성된 클러스터를 사용하여 처리 시간을 측정한 결과 노드의 수가 증가하더라도 1에 가까운 efficiency를 나타내었으며 load scalability의 특성도 만족시켰다. 또한 용량의 한계로 인하여 단일 시스템에서 처리할 수 없는 크기의 자료를 클러스터 시스템으로 처리할 수 있음을 확인하였다.

• 정보처리학회논문지A
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• 제8A권4호
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• pp.299-310
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• 2001

본 연구에서는 리눅스 가상 서버(LVS：Linux Virtual Server) 클러스터 시스템에서 실제 서버의 상태에 기초한 사용자의 요청을 분배하는 방법론을 연구하고자 한다. LVS 클러스터 시스템에서 사용자의 요청을 분배하는데 적용되는 기존 WLC(Weighted Least Connection) 방법론이 검토되었고, 실제 서버의 부하를 고려하여 각 서버에 요청을 할당하는 부하 분산 방법론을 제안하고자 한다. 부하 측정을 위한 실험은 가상의 부하를 생성하는 툴을 사용하여 서버에 부하를 부과하여 실행되었다. 본 연구에서 제시된 부하 분산 방법론이 기존의 WLC 방법론보다 실제 서버의 메모리 사용측면에서 효율을 기대할 수 있어 제안하고자 하며, 또한 서버 자원을 균형적으로 분배시키고 가중치의 변화에 대한 교정력(correction potentiality)이 어느 정도 개선됨을 확인할 수 있었다.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2002년도 춘계학술대회 논문집
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• pp.34-38
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• 2002

A virtual human which can evaluate Kansei such as comfort, pain, etc. when the virtual human uses some product is developed. In this paper, method of the evaluation of Kansei by the virtual human is presented. The body of our virtual human is modeled as an uniform non-linear elastic one with a skeleton. The deformation of the body on the contact with some product is simulated using a FEM analysis, and by using of the simulated results (load distribution, strain, etc.) on the contact surface the Kansei is predicted. As examples of the application, comfort of buttocks on seating and pain of arm on hanging of bag are shown. This virtual human can apply for the design of virtual products and also the simulation of medical care.