• KEPCO Journal on Electric Power and Energy
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• 제7권2호
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• pp.277-283
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• 2021

Power plant simulators have been used for operator training, control verification and engineering verification. In general, simulators can be used in the place where they are installed by only single user group at a time. Considering high cost of simulator development, a lot of available scenarios, the diversity of user level and accessibility based on users' work location, development of simulator system that can be used by multiple user groups regardless of location is required in order to enhance utilization of simulators. In this paper, the simulator system that can be used by multiple user group simultaneously without location limitation is proposed. The simulator system is composed of simulator servers, database servers, HMI servers, a web server, web clients. Simulator server consists of control model, process model that are developed for Circulating Fluidized Bed power plant located overseas. A web server manages user accounts, operation procedures, multiple server access between web client group and simulator server group. In other words, a web server makes a user group select a simulator server at a time. The developed simulator system is integrated after implementing process model, control model, HMI, and web server. Web client systems are installed on local site where power plant is located, while simulator servers, HMI servers, database servers, and a web server are located in KEPCO RI. The developed simulator system is verified by steady-state test, malfunction test and so on via remote access.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권1호
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• pp.119-131
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• 2013

With the explosive growth of computer networks, many remote service providing servers and multi-server network architecture are provided and it is extremely inconvenient for users to remember numerous different identities and passwords. Therefore, it is important to provide a mechanism for a remote user to use single identity and password to access multi-server network architecture without repetitive registration and various multi-server authentication schemes have been proposed in recent years. Recently, Tsaur et al. proposed an efficient and secure smart card based user authentication and key agreement scheme for multi-server environments. They claimed that their scheme satisfies all of the requirements needed for achieving secure password authentication in multi-server environments and gives the formal proof on the execution of the proposed authenticated key agreement scheme. However, we find that Tsaur et al.'s scheme is still vulnerable to impersonation attack and many logged-in users' attack. We propose an extended scheme that not only removes the aforementioned weaknesses on their scheme but also achieves user anonymity for hiding login user's real identity. Compared with other previous related schemes, our proposed scheme keeps the efficiency and security and is more suitable for the practical applications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권5호
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• pp.444-460
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• 2009

In this paper, we propose an expanded patching technique in order to reduce the server network bandwidth requirements to support true VoD services in VoD Systems. Double Patching, which is a typical multicast technique, ensures that a long patching stream delivers not only essential video data for the current client but also extra video data for future clients. Since the extra data may include useless data, it results in server network bandwidth wastage. In order to prevent a server from transmitting useless data, the proposed patching technique uses a new kind of stream called a linking stream. A linking stream is transmitted to clients that have received short patching streams, and it plays a linking role between a patching stream and a regular stream. The linking stream enables a server to avoid transmitting unnecessary data delivered by a long patching stream in Double Patching, so the server never wastes its network bandwidth. Mathematical analysis shows that the proposed technique requires less server network bandwidth to support true VoD services than Double Patching. Moreover, simulation results show that it has better average service latency and client defection rate compared with Double Patching.

• 융합보안논문지
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• 제6권1호
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• pp.13-23
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• 2006

악성 코드로 인한 피해에 적극 대응하기 위해서는 클라이언트가 아닌 서버 측에서 실행되는 안티바이러스 소프트웨어가 필요하다. 그러나 서버용 안티바이러스 소프트웨어로 인하여 서버의 부하가 가중되는 것은 바람직하지 않다. 본 논문에서는 모니터/에이전트 구조로 멀티프로세서 환경의 서버 시스템에서 수행되는 안티바이러스 소프트웨어를 개발하였다. 이 소프트웨어는 안티바이러스 엔진의 주요 특징을 반영하여 서버에서 동적 부하 균형을 지원해줌으로써 효율적인 수행 환경을 제공한다. 악성코드 검색율과 검색 속도에 대한 성능 측정 결과는 서버용 안티바이러스 소프트웨어로서의 장점과 특징을 입증해준다.

• 정보보호학회논문지
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• 제25권1호
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• pp.95-105
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• 2015

본 논문은 서버 가상화 시스템의 보안 함수를 개발하기 위해 선행해야 할, 보안 요구 사항을 제안하는 것에 그 목적을 두고 있다. 도출된 보안 요구 사항은 서버 가상화 시스템에 대한 보안 위협을 기반으로 하며, 제안 된 요구 사항이 보안 위협 사항을 방어할 수 있는 것을 보임으로써 보안 요구 사항의 타당성을 검증한다. 또한, 클라우드 컴퓨팅 보안 위협에서 서버 가상화 시스템에 가해지는 보안 위협을 도출하기 위해서, 보안 위협과 서버 가상화 시스템의 보안 이슈 사항의 관계를 분석 및 제시한다.

• 제어로봇시스템학회논문지
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• 제10권9호
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• pp.847-854
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• 2004

In this paper, It is studied to control and to monitor the remote system state using HTTP(Hyper Text Transfer Protocol) object communication. The remote control system is controlled by using a web browser or a application program. This system is organized by three different part depending on functionality-server part, client part, controller part. The java technology is used to composite the server part and the client part and C language is used for a controller. The server part is waiting for the request of client part and then the request is reached, the server part saves client data to the database and send a command set to the client part. The administrator can control the remote system just using a web browser. Remote part is worked by timer that is activated per 1 second. It gets the measurement data of the controller part, and then send the request to the server part and get a command set in the command repository of server part using the client ID. After interpreting the command set, the client part transfers the command set to the controller part. Controller part can be activated by the client part. If send command is transmitted by the client part, it sends sensor monitoring data to the client part and command set is transmitted then setting up the value of the controlled system.

• Interdisciplinary Bio Central
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• 제3권3호
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• pp.12.1-12.3
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• 2011

Bioinformatics tools and databases are useful for understanding and processing various biological data. Numerous resources are being published each year. It is not a trivial task to find up-to-date relevant tools and databases. Moreover, no server is available to provide comprehensive coverage on bioinformatics resources in all biological fields. Here, we present a directory server called IntoPub that provides information on web resources. First, we downloaded XML-formatted abstracts containing web URLs from the NCBI PubMed database by using 'ESearch-EFetch' function in the NCBI E-utilities. The information is obtained from abstracts in the PubMed by extracting 'www' or 'http' prefixes. Then, we cu-rate the downloaded abstracts both in automatic and manual fashion. As of July 2011, the IntoPub database has 12,118 abstracts containing web URLs from 174 journals. Our anal-ysis shows that the number of abstracts containing web resources has increased signifi-cantly every year. The server has been tested by many biologists from several countries to get opinion on user satisfaction, usefulness, practicability, and ease of use since January 2010. In the IntoPub web server, users can easily find relevant bioinformatics resources, as compared to searching in PubMed. IntoPub will continue to update and incorporate new web resources from PubMed and other literature databases. IntoPub, available at http://into.kobic.re.kr/, is updated every day.

• 응용통계연구
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• 제22권3호
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• pp.541-551
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• 2009

Generalized processor sharing(GPS) service policy is a scheduling algorithm to allocate the bandwidth of a queueing system with multi-class input traffic. In a queueing system with single-class traffic, the stationary queue length becomes larger stochastically when the bandwidth (i.e. the service rate) of the system decreases. For a given GPS server, we consider the similar problem to this. We define the monotonicity for the head of the line processor sharing(HLPS) servers in which the units in the heads of the queues are served simultaneously and the bandwidth allocated to each queue are determined by the numbers of units in the queues. GPS is a type of monotonic HLPS. We obtain the HLPS server whose queue length of a class stochastically bounds upper that of corresponding class in the given monotonic HLPS server for all classes. The queue lengths process of all classes in the obtained HLPS server has the stationary distribution of product form. When the given monotonic HLPS server is GPS server, we obtain the explicit form of the stationary queue lengths distribution of the bounding HLPS server. Numerical result shows how tight the stochastic bound is.

• 전기전자학회논문지
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• 제7권2호
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• pp.265-270
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• 2003

본 논문에서는 웹 서버의 부하 분산을 위해 네트워크를 LAN 내부와 LAN 외부로 나누고 이들에 각각의 웹 서버를 할당한다. LAN 내부의 노드들에 의한 접속만이 가능한 웹 서버의 성능은 RTO(Retransmission Time Out : 재전송타임아웃)라는 TCP 파라미터에 의해 많은 영향을 받는다. 웹 서버의 운영체제 내에 디폴트로 설정된 RTO 값은 LAN에서는 지나치게 큰 값으로 네트워크와 웹 서버의 성능을 저하시킨다. 이에 본 논문에서는 기존의 재전송 타임아웃의 알고리즘 방식을 이용하지 않고, 조정된 RTO값을 사용하여 LAN 내부의 웹 서버 성능을 향상시킬 수 있음을 확인하였다.

• 전기전자학회논문지
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• 제21권4호
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• pp.353-357
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• 2017

엔터프라이즈 및 데이터센터환경에서 사용되는 수많은 서버시스템을 유지하기 위해서 가장 중요한 것은 각각의 서버시스템에서 UE(Uncorrectable Error)의 발생을 방지하는 것이다. 최근 클라우드 서비스의 발전으로 더 많은 용량의 메모리 모듈이 기존보다 더 많이 사용되고 있는 반면에 서버시스템의 동작 주파수는 높아지고 또한 메모리를 개발하기 위한 공정은 계속해서 축소되어 이전보다 불량이 발생될 확률이 매우 높아졌다. 이런 환경에서 서버시스템에서 직접 메모리 불량을 교체할 수 있는 방법이 제공되고 있지만 이를 효과적으로 사용할 수 있는 가이드라인이 현재 제공되지 않고 있다. 본 논문에서는 기존 시스템에서의 메모리 불량현상을 관찰하고 분석한 결과를 토대로 서버 시스템에서 효율적으로 메모리 불량을 방지하고 대처할 수 있는 방안을 제시하였다.