• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.695-698
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• 2007

최근 유 무선 홈 네트워크를 위한 다양한 기술들이 개발되고 있는데, 이러한 기술들을 수용하여 가정내 유무선 정보가전기들을 인터넷을 통해서도 통합제어 가능한 효율적인 미들웨어를 필요로 한다. UPnP(Universal Plug and Play)는 기본적으로 표준 TCP/IP 프로토콜에 근거하여 PnP(Pulg and Play)개념을 네트워킹에 확장한 것이다. 지능형 가전, 무선기기 및 모든 종류의 PC들을 연결하기 위한 파급력이 있는 P2P(Peer to Peer) 네트워크 연결 구조를 지닌다. UPnP는 TCP/IP를 기본으로 하여 가정내 정보가전들을 통합제어 하기위한 홈 네트워크 미들웨어로 제시되어 상용화 되고 있지만 그 한계가 내부 네트워크에 국한되고 기능의 한계와 다른 기기들을 제어하기가 힘들다. 본 논문에서는 인터넷 홈 네트워크 가전 제어를 위해 UPnP를 확장하여 인터넷 게이트웨이를 통하여 인터넷망을 통하여 서로간의 모든 기능 및 컨트롤이 가능한 시스템 구축을 연구한다.

• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.449-453
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• 2021

Interest and investment in renewable energy have increased worldwide, highlighting the need for renewable energy. Solar energy was the most promising energy of all renewable energy sources, and it has the highest investment value. Because photovoltaics require a certain amount of area for installation, high density and high output performance are required. Shingled module is a promising technology in that they are featured by higher density and higher output compared to the conventional modules. Shingled technology uses a laser scribing to divide solar cells that are to be bonded with electrically conductive adhesive (ECA) to produce and connect strings, which has a higher output in the same area than the conventional modules. In the process of producing solar modules, metal ribbons are used to interconnect cells, but they are also needed for string connections in shingled solar cells. Accordingly, in this study, we researched the interconnection that best suits the connector that joins the string to the string. The module outputs produced under the conditions of the string interconnection were compared and analyzed.

• 전기학회논문지P
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• 제55권3호
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• pp.146-152
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• 2006

In order to analyze the characteristics of series arcs that could happen in poor connections of electrical facilities, we made an apparatus which is similar to actual situation. series arcs are generated between copper and copper, copper and bronze, copper and brass, bronze and bronze, and then oxidation growth and voltage waveform were measured. A very small vibration with constant movement is needed to grow oxidation initially, whereas oxidation growth proceeded without a vibration after a certain amount of time. At first, blue white flame was generated initially between copper and copper, and then yellow flame was generated. In case of contact between copper and copper, the length of oxidation growth was about 7.1[mm] in 90[min]. In case of contact between copper and brass, the length of oxidation growth was about 4.3[mm] in 90[min], When bronze is contacted with copper, the lengths of oxidation growth were about 1.4[mm] in 20[min] and 2.7[mm] in 40[min] respectively, and no more oxidation growth was shown after that. In case of contact between brass and brass, the length of oxidation growth was about 1.2[mm] in 90[min], so it was the smallest compared to other cases. When copper is contacted with copper, the current through the load was about 1.6[A] and the power dissipation increased from 19[W] to 31[W]. In case of oxidation growth between copper and brass, the voltage changed from 8.4[V] to 11[V]. However, the voltage drop and the power dissipation between copper and brass were small compared to oxidation growth between copper and copper. When series arcs were generated between bronze and copper, a peak was shown at the beginning of voltage increase, and 40[min] later, oxidation material was not grown any longer. When oxidation growth occurred, voltage waveform showed irregular waveforms with tiny ripples.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2003년도 추계학술발표논문집 (상)
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• pp.201-204
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• 2003

At a consequence of WWW large popularity, the internet has suffered from various performance problems, such as network congestion and overloaded servers. These days, it is not uncommon to find servers refusing connections because they are overloaded. Web server performance has always been a key issue in the design and operation of on-line systems. With regard to Internet, performance is also critical, because users want fast and easy access to all objects (e.g., documents, graphics, audio, and video) available on the net. To solve this problem, a number of companies are exploring the benefits of having multiple geographically or locally distributed Internet sites. This requires a comprehensive scheme for traffic management, which includes the principle of an optimal load balancing of client requests across multiple clusters of real servers. This paper focuses on the performance analysis of Web server and we apply these results to load balancing in clustering web server. It also discusses the mam steps needed to carry out a WWW performance analysis effort and shows relations between the workload characteristics and system resource usage. Also, we will introduce an optimal load balancing algorithm base on the RTSM (Real-Time Server Monitor) and Fuzzy Inference Engine for the local status of a real server, and the benefits is provided with of the suggested method.

• 대한전기학회논문지:전력기술부문A
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• 제51권6호
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• pp.255-261
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• 2002

Recently, traction motors in trains are supplied with single phase a.c. power. After this power is converted to d.c. power, it is inverted to three phase power to operate traction motors. As going through the process of the conversion, harmonic current is generated in train. The method of conventional analysis on harmonics, studied by RTRI, is modeled with equivalent circuit of ac AT-fed electric railroad system using by the distributed constant circuit. However, this circuit as two-port network model has some difference in comparison with real system. The reason why the conventional method is different from the real system is that the conventional method dose not include three conductor groups, that is catenary, rail, and feeder, and admittance between the conductors for line capacitance. Therefore, this method has a little error. This paper proposes new method to more effectively estimate Harmonic current. In this method, numerous components in electric railway are categorized and each component is defined as a four- port network model. The equivalent circuit for the entire power supply system is also described into a four-port network model with connections of these components. In order to evaluate the efficiency and the accuracy of a proposed method, it is compared with values measured in Kyung-Bu high speed line and ones calculated by the conventional method.

• 인터넷정보학회논문지
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• 제15권2호
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• pp.9-18
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• 2014

인체에 부착된 센서들의 위치는 인간의 신체적 활동에 따라 자주 이동된다. 이에 따른 노드 위치 이동과 비가시선상의 문제들은 무선 인체 통신망에서 핫 스팟과 에너지 효율, 그리고 신뢰적인 통신 성능에 영향을 미친다. 우리는 빈번히 변화하는 네트워크 토폴로지와 채널 조건을 고려한 포워딩을 결정하는 방법을 제안하였다. 본 논문에서는 각 노드의 라우팅 레벨에서 입, 출력 링크들의 비율에 근거하여 포워딩 비율과 패킷들의 크기를 제어한다. 또한 패킷 크기와 포워딩 비율 제어를 지원하는 격자 기반의 연결을 확장함으로써 네트워크 토폴로지를 견고하게 한다. 본 논문의 시뮬레이션은 이러한 접근들이 네트워크 수명을 48.2% 증가시키는 것뿐 아니라 약 6.08%의 패킷 전달율의 증가가 있음을 증명한다. 또한 핫 스팟 문제도 본 제안을 통해 해결된다.

• 전기전자학회논문지
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• 제23권2호
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• pp.529-533
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• 2019

오늘날 복합 화력 발전소는 전력 생산을 위해 많이 사용되고 있고, 최근에는 운전 매개 변수를 기반으로 발전 출력을 예측하는 것이 주요 관심사이다. 본 논문에서는 복합 화력 발전소의 출력을 예측하기 위해 컴퓨터 지능 기법을 이용하는 방법을 제시한다. 컴퓨터 지능 기술은 지속적으로 발전되어 많은 실제 문제에 적용되어 왔다. 본 논문에서는 트리 구조의 퍼지 뉴럴 네트워크를 이용하여 발전 출력을 예측하고자 한다. 트리 구조의 퍼지 뉴럴 네트워크는 퍼지 뉴런을 노드로 선택하고 관련 입력을 최적으로 선택하여 규칙 수를 줄이는 장점이 있다. 네트워크의 최적화를 위해 2 단계 최적화 방법이 사용된다. 유전 알고리즘은 최적의 노드와 리프를 선택하여 네트워크의 이진 구조를 최적화 한 다음 랜덤 신호 기반 학습을 수행하여 최적화 된 이진 연결을 단위 구간에서 미세 학습한다. 제안 된 방법의 유용성을 검증하기 위해 UCI Machine Learning Repository Database에서 얻은 복합 화력 발전소 데이터를 사용한다.

• 한국산학기술학회논문지
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• 제20권11호
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• pp.239-249
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• 2019

최근, 정부는 신재생에너지전원을 확대하는 정책을 시행하고 있으며, 이에 따라 다수의 대용량 태양광전원이 배전계통에 활발하게 연계되고 있는 실정이다. 하지만, 이러한 태양광전원이 배전계통에 연계되는 경우, 역조류 현상에 의하여 수용가 전압이 규정전압범위를 벗어날 가능성이 있다. 이러한 문제점을 해결하기 위하여, 배전계통에서 태양광전원의 수용성을 향상시키기 위한 연구가 활발히 이루어지고 있다. 따라서, 본 논문에서는 선로절체에 의한 태양광전원의 수용성 향상을 위하여, 배전계통 상용해석 프로그램인 PSCAD/EMTDC를 이용하여, 3분할 3연계로 구성된 배전계통의 모델링을 제시하고, 태양광전원을 최대한 수용할 수 있는 선로절체 평가알고리즘을 제시한다. 또한, 배전선로 절체 구간 및 태양광전원 연계 용량 등의 다양한 운용 시나리오에 기반하여, 변압기 2차측 직하 수용가전압을 규정전압범위 이내로 유지하는 최대 태양광전원 용량을 산정하기 위하여 최적의 선로절체 구간을 산정한다. 제안한 배전계통의 수용성 평가알고리즘과 모델링을 바탕으로 수용가전압 특성을 분석한 결과, 대용량 태양광전원이 연계된 배전선로를 용량의 여유가 남아있는 선로와 절체하여 재구성하게 되면, 더 많은 용량의 태양광전원의 연계가 가능하여, 본 논문의 유용성을 확인하였다.

• Structural Engineering and Mechanics
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• 제28권1호
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• pp.53-67
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• 2008

Anisotropic materials are increasingly required in modern technological applications. Certainly, civil, mechanical and naval engineers frequently deal with the situation of analyzing the dynamical behaviour of structural elements being composed of such materials. For example, panels of anisotropic materials must sometimes support electromechanical engines, and besides, holes are performed in them for operational reasons e.g., conduits, ducts or electrical connections. This study is concerned with the natural frequencies and normal modes of vibration of rectangular anisotropic plates supported by different combinations of the classical boundary conditions: clamped, simply - supported and free, and with additional complexities such holes of free boundaries and attached concentrated masses. A variational approach (the well known Ritz method) is used, where the displacement amplitude is approximated by a set of beam functions in each coordinate direction corresponding to the sides of the rectangular plate. Consequently each coordinate function satisfies the essential boundary conditions at the outer edge of the plate. The influence of the position and magnitude of both hole and mass, on the natural frequencies and modal shapes of vibration are studied for a generic anisotropic material. The classical Ritz method with beam functions as spatial approximation proved to be a suitable procedure to solve a problem of such analytical complexity.

• 대한기계학회논문집A
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• 제32권3호
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• pp.280-289
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• 2008

This paper presents design of the quantitative feedback control system of the three axes hydraulic road simulator with respect to the dummy wheel for uncertain multiple input-output(MIMO) feedback systems. This simulator has the uncertain parameters such as fluid compressibility, fluid leakage, electrical servo components and nonlinear mechanical connections. This works have reproduced the random input signal to implement the real road vibration's data in the lab. The replaced $m^2$ MISO equivalent control systems satisfied the design specifications of the original $m^*m$ MIMO control system and developed the mathematical method using quantitative feedback theory based on schauder's fixed point theorem. This control system illustrates a tracking performance of the closed-loop controller with low order transfer function G(s) and pre-filter F(s) having the minimum bandwidth for parameters of uncertain plant. The efficacy of the designed controller is verified through the dynamic simulation with combined hydraulic model and Adams simulator model. The Matlab simulation results to connect with Adams simulator model show that the proposed control technique works well under uncertain hydraulic plant system. The designed control system has satisfied robust performance with stability bounds, tracking bounds and disturbance. The Hydraulic road simulator consists of the specimen, hydraulic pump, servo valve, hydraulic actuator and its control equipments