• 한국멀티미디어학회논문지
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• 제11권9호
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• pp.1277-1285
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• 2008

본 논문에서는 WiMAX 와 HSDPA 모드를 모두 지원하는 SCA 기반 다중모드 SDR 단말의 컴포넌트를 설계하고 블럭도를 제시하였으며, 실제 실험을 통한 경량화 대상 분석을 통해 SDR 단말 구현 시 어느 구성요소를 경량화해야 하는 지 분석해 보았다. 또한, 컴포넌트 재구성 분석을 통하여 동적 재구성 전체 시간 측정을 위한 일반 식을 도출하였고, 분석 결과를 토대로 SCA 규격의 인터페이스와 수행절차를 위배하지 않는 범위 안에서 총 22단계에 걸친 컴포넌트 레벨 동적 재구성 알고리즘을 설계하였다.

• Journal of Power Electronics
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• 제12권3호
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• pp.410-417
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• 2012

In this paper, a direct current control method based on a one-cycle controller (DCOCC) for double frequency buck converters (DF buck) is proposed. This control method can make the average current through the high frequency and low frequency inductors of a DF buck converter equal. This is similar to the average current control method. However, the design of the loop compensator is much easier when compared with the average current control. Since the average current though the high frequency and low frequency inductors is equivalent, the current stress of the high frequency switches and the switch losses are minimized. Therefore, the efficiency of the DF buck converter is improved. Firstly, the operation principle of DCOCC is described, then the small signal models of a one cycle controller and a DF buck converter are presented based on the state space average method. Eventually, a system block diagram of the DCOCC controlled DF buck is established and the compensator is designed. Finally, simulation and experiment results are given to verify the correction of the theory analysis.

• Journal of Power Electronics
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• 제7권1호
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• pp.38-43
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• 2007

An External Electrode Fluorescent Lamp (EEFL) has longer lifespan, higher power efficiency and higher luminance than a Cold Cathode Fluorescent Lamp (CCFL). Moreover, it is easy to drive them in parallel. Therefore, the EEFL is expected to quickly replace the CCFL in LCD backlight systems. However, the EEFL has more complex characteristics than the CCFL with a resistive component, because it has both a resistive component by plasma and a capacitive component by external electrode. In this paper, values of resistance and capacitance are measured at several power levels and at several operating frequencies. They are expressed by a numeral formula based on a linear approximation that represents the equivalent resistance and capacitance as a function of power. Then we made block diagram of the equivalent circuit model using numerical expressions. Simulation waveforms and experimental results are presented to verify the feasibility of the equivalent model.

• 한국기술혁신학회:학술대회논문집
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• 한국기술혁신학회 2000년도 추계 학술대회(The 2000 Autumn Conference of korea Technology Inovation Society)(한국기술혁신학회)
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• pp.45-67
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• 2000

Broadband access technologies plays an important role in the national information infrastructure. In the evolution path of the information infrastructure, the relative economics of alternative access technology is the most critical determining factor. In this paper, we discuss the economics of local loop access technologies of existing technologies, such as, ADSL, HFC, and new PLC. To do this, we suggest appropriate configuration of access network system and its associated numerical equations. To modelize access network system and drive the numerical equations, we consider the DS (Double Star) and the T&B (Tree ＆ Brench) architecture and analyse the adequate block diagram of each access system for each technology We introduce the density of subscriber as a key variable and the equation of allocating optimal number of cell in a service area. We analyze the relative economics of local loop architecture in two different situations, that is, urban and rural. From the empirical implementation, we found that for the case of urban area, where the cost of cable and infrastructure is not necessary, there is not much difference in the cost per one subscriber. However, for the case of rural region, we found that there is remarkable difference in the cost per one subscriber among technologies. Therefore we conclude that the economics of local loop architecture is depend on the density of subscriber and existing network infrastructures. we hope that this paper contribute to the optimal technology selection of consmer, technology Providers, and government.

• 대한전기학회논문지
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• 제39권11호
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• pp.1174-1182
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• 1990

A hgih efficiency and good dynamic performance drive system of an induction motor is presented in this paper using vector control technique. If the induction motor is driven under light loads with rated flux, the iron loss is excessively large compared with the copper loss, resulting in poor motor efficiency. High efficiency drive of an induction motor can be achieved by adjusting the flux level which leads the total motor loss to be a minimum value. Generally reducing the flux degrades the dynamic performance, but the dynamic performance of the proposed system is also maintained high. If the d-axis is coincident with rotor flux phasor in synchronous rotating reference frame, the stator current can be decoupled as flux component and torque component. At steady state, the developed motor torque is proportional to the product of the flux and torque component. The combination of the two components minimizing the motor loss could be found with numerical method. As the procedure to obtain the optimal combination is too hard, it is found experimentally. The system block diagram is suggested for maximum efficiency control. The proposed system is studied through digital simulation and verified with experiment. The experimental results show the possiblity of a high efficiency drive with good dynamic performance of maximum efficiency control.

• 한국철도학회논문집
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• 제10권4호
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• pp.438-443
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• 2007

This paper proposes an integrated SE process for the development of railway systems with safety assessment included. Although the safety assessment process must be performed with SE process properly with good coordination, the interfaces between the two processes have not been clear. Thus, in many of safety critical system developments in Korea, it is difficult to assess safety in proper development phase. The process model proposed in this paper is based on both the concept of system life cycle and the repetitive use of SE process. In each of development phases, appropriate safety assessment methods are described. Also the evaluation of the integrated system incorporating safety factors is described. The resultant process model is expressed by the Enhanced Functional Flow Block Diagram (EFFBD) using a CASE tool. The model also allows timeline analysis for identifying activity flow and data flow, resulting in the effective management of process. In conclusion, the integrated process enable both the SE process and safety assessment process to cooperate with each other from early development phase throughout the whole system life cycle.

• 한국태양에너지학회 논문집
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• 제31권5호
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• pp.134-139
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• 2011

Since large and small scale photovoltaic(PV) systems have been commercialized in many countries, it is necessary to assess the effects of PV systems on the electric power system. For this, the development of accurate simulation model of PV arrays is very important. PSCAD/EMTDC, a widely used simulation tool for analyzing the transient behavior of electrical apparatus and networks, does not have a standard model of a PV array. Therefore in order to simulate the PV array, users have to develop their own simulation model. However, the block-diagram-based model is very complicated, and it is hard to modify the model parameters. In this study, we develop the user-defined model of a PV array by using the Design Editor, which is provided by PSCAD program. The mathematical model of a PV array and the method to determine the parameters of nonlinear I-V equation are implemented in a Fortran code. The graphical user interface provides the users with easy and simple way to modify the PV array parameters and simulation conditions. In order to help the users, this model also provides the parameters of 10 commercial PV arrays.

• 대한안전경영과학회지
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• 제10권4호
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• pp.73-81
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• 2008

The current electrical safety plan developed for the national electricity system has been playing an important role in handling a variety of electrical accidents. However, it can be more effective to prevent or reduce those accidents if a preventive electrical safety plan is available. In this paper, an approach to developing the safety plan is described. We first discuss the contents that should be included in the plan. Noting that an effective plan requires the system level consideration of all the factors affecting the safety issues, an operation concept document (OCD) is considered. The OCD can allow us to understand the behavior of the safety system based on the operation environment, the system functions, the performance requirements, all at the system level of the safety system. Thus, the OCD can be useful in developing the safety plan. A detailed description then follows on how the OCD is developed for the electrical safety system under study. Finally, we discuss how the developed OCD can be used in deriving the preventive electrical safety plan.

• 한국추진공학회지
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• 제9권3호
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• pp.120-126
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• 2005

액체산소(LOx)와 케로신(Kerosene)을 연료로 사용하는 액체로켓엔진 시험설비에서 지상연소시험을 수행할 경우에 발생하는 위험도를 감소시키는 방법을 연구하였다. 본 방법은 잠재적인 사고 발생확률을 낮추고 그에 따른 발생 가능한 손실을 낮추기 위해서 사고 발생 가능한 한계선에 대한 연구와 기술적 해결방법을 바탕으로 하고 있다. 시험설비에서 사고 상황을 야기 할 수 있는 위험한 상황에 관한 개략도와 추진제 유출 사고시 발전 양상 및 발전 프로세스에 대한 도표, 기술적인 해결방법, 위험성 감소 평가 방법을 제시함으로써 기존의 확률적인 통계 값을 바탕으로 하는 것과는 또 다른 방법으로써 위험도 감소를 위한 대안으로 사용하고자 한다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.1054-1057
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• 2015

실제적인 산업분야에서 실시간 처리는 중요하다. 본 논문에서는 LabVIEW를 이용하여 RS-485 직렬통신 기반 Modbus/RTU 프로토콜을 구현하였다. 토크(Torque) 센서와 전압/전류계로부터 측정값을 입력받기 위하여 Modbus/RTU 프로토콜을 구현하였다. 입력받은 토크 값, 전압, 전류 값을 이용하여 기계적인 손실을 계산할 수 있다. LabVIEW 툴을 이용하여 소스코드를 작성하였고, 이러한 소스코드는 실제 산업현장에 적용할 수 있음을 확인하였다.