• 융합보안논문지
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• 제24권2호
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• pp.123-132
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• 2024

사물 인터넷 시대를 맞아 700억대 이상의 다양한 기기들이 세계를 연결하고 있다. 초연결 시대로 다양한 기기들의 정보 보안은 중요한 기술 요소이다. 기밀성, 무결성, 인증 등 주요 보안 기능을 구현하기 위해 다양한 기기들의 실난수 발생기를 구현하는 것은 중요하다. 이 연구는 실난수 발생기의 난수성을 빠르게 측정하는 방법을 제안한다. 국제 표준을 통해 난수 발생기출력의 난수성을 측정하는 방법이 있다. 하지만, 공식적인 국제 표준은 평가를 위한 많은 시간 및 비용을 소비한다. 따라서, 실난수 발생기를 구현하는 입장에서 난수성과 예측 불가능성을 빠르게 측정하는 것은 실난수 발생기를 설계하고 구현하는 입장에서 시간과 비용에 효율성을 높여준다. 첫째, 아날로그 신호의 경우 자기 상관 및 상호 상관 측정을 통해 예측 불가능성을 빠르게 측정하는 것을 제안한다. 둘째, 디지털 신호의 경우 결합 엔트로피 및 상호 정보 측정을 통해 예측 불가능성을 더 명확히 측정하는 것을 제안한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1664_1665
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• 2009

Many years ago, most of thermal power plants built in this country were of subcritical pressure, of medium or small size, of constant pressure operations and of drum type steam generators with circulation type boilers. But, nowadays almost all of them were of high efficiency, of supercritical pressure, of big capacity, of sliding pressure operations, and of once through type steam generator. It has such advantage as the reduction of startup duration, but it control system and operation method are very complicated. It has a big difference in operation method of turbine and boiler. The feedforward control needs to be introduced to prevent such problems as thermal shock during the transit from normal operation into bypass operation. This paper introduces the turbine control and turbine bypass control during startup of thermal power plants.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권3호
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• pp.330-335
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• 2012

Brushless doubly-fed machine (BDFM) doesn't use brush and slip ring, and has advantages such as high system reliability, small capacity of its frequency converter, low system cost, adjustable power factor and speed, etc. At the same time, it has good applicable potentials on the variable frequency motors and the variable speed constant frequency generators. However, due to the complicacy and particularity of BDFM in the structure and operating mechanism, the effect of magnetic field modulation directly influences the operating efficiency of BDFM. To study the effect of different cage rotor structures on the magnetic field modulation of BDFM, the rotor magnetomotive force (MMF) of BDFM with cage rotor is studied by the analytical method. The components and features of rotor harmonic MMFs are discussed. At the same time, the method to weaken the higher harmonics is analyzed by the theoretic formulae. Furthermore, the magnetic field modulation mechanism is expounded on in detail and the relationship between the magnetic field modulation effect and the operating efficiency of BDFM is established. And then, a new method for estimating the magnetic field modulation effect is proposed. At last, the magnetic field modulation effects of four BDFM prototypes with different cage rotor structures are compared by the MMF analysis and the efficiency data of electromagnetic design. The results verify the effectiveness of the new method for estimating the magnetic field modulation effect of BDFM with cage rotor.

• 대한기계학회논문집
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• 제19권1호
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• pp.231-239
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• 1995

This paper describes a computer simulation of the triple effect, water-lithium bromide absorption cooling cycles. The performance of the absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature, the working solution concentrations, the ratio of the amount of the weak solution to the high, middle and low temperature generators, and the temperature difference of each solution heat exchanger. The efficiency of different cycles has been studied and the simulation results show that higher coefficient of performance could be obtained for the parallel cycle of constant solution distribution rate. As a result of this analysis, the optimum designs and operating conditions were determined based on the operating conditions and coefficient of performance.

• 전력전자학회논문지
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• 제17권4호
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• pp.368-376
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• 2012

According to developed distributed generators, Solid State Circuit Breaker(SSCB) is essential for high power quality of DC Grid. In this paper, a simple and new structure of DC SSCB with a fast circuit breaker and fault current limiter is proposed. It can help to choice low specification of elements because of the limiting of fault current and achieve economic efficiency for minimizing auxiliary SCRs. Also all of SCRs have little switching loss because they operate under ZVS and ZCS. Through simulations and experiments of short-circuit fault, the performance characteristic of proposed circuit is verified and a guideline is so suggested that the DC SSCB is applied for a different DC grid using formulas.

• 대한전기학회논문지:전력기술부문A
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• 제49권2호
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• pp.43-49
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• 2000

It is a complex process to analyze power system voltage stability problems with all of the dynamics of a system, because a large power network system sophisticatedly consists of generators, lines, loads and so forth. So we considered the dynamics of loads so as to analyze voltage stability method- by carrying out an analysis of steady state voltage stability and dynamic voltage stability simultaneously. To perform a steady state voltage stability program in advance makes it possible to cut down on laborious calculations so that an analysis of dynamic voltage stability becomes concise. The validity and efficiency of the method presented in this paper were verified by applying the IEEE 14 bus system.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권5호
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• pp.264-267
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• 2004

Recently the pulsed power systems have been widely used in many fields such as E/P(Electrostatic Precipitator), DeNOx/DeSOx power systems, ozone generators and power sources of the laser beam. In this paper, we studied various electrical characteristics for arc suppression of line-to-line electrodes in air and removal of the metaloxide using our pulsed power system. To obtain high efficiency of the pulsed power system, we repeatedly experimented and tested their characteristics. by adjusting electrode length of the load. As a result, when the value of the electrode length and pulse repetition rate were changed at the load, the value of the arc voltage changed at the electrode load. In conclusion, we controlled arc voltage of the load by ,changing electrode length and pulse repetition rate. Also. we stydied removal area of the metaloxide using area discharge according to pulse repetition rate.

• 전기학회논문지
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• 제61권7호
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• pp.950-956
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• 2012

As development of battery technologies, the installation of Battery Energy Storage System (BESS) increased. The BESS can be used for various purposes such like frequency response, load leveling, and fluctuation mitigation of renewable energy generators. In this paper, three state BESS model is proposed. the BESS model considering charge, discharge and keeping efficiency, and life cycle according to depth of discharge (DOD). Then, the benefit and cost of BESS installed at substation for load leveling are summarized. The economic evaluation of BESS is analyzed using net present values (NPV) analysis. In case study, the NPV analysis of NaS battery system is carried out using the proposed BESS model. Because the result of economic evaluation of BESS using nowadays cost data is not positive, the sensitivity analysis of BESS is conducted by changing the capital cost and energy cost.

• Elastomers and Composites
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• 제56권2호
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• pp.57-64
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• 2021

This paper reviews recent developments and applications of dielectric elastomers (DEs) and suggests various techniques to improve DE properties. DEs as smart materials are a variety of electro-active polymers (EAPs) that convert electrical energy into mechanical energy and cause a large deformation when a voltage is applied. The dielectric constant, modulus, and dielectric loss of DEs determine the efficiency of deformation. Among these, the dielectric constant significantly affects their performance. Therefore, various recent approaches to improve the dielectric constant are reviewed, including the enhancement of polarization, introduction of microporous structures in the matrix, and introduction of ferroelectric fillers. Furthermore, the basic principles of DEs are examined, as well as their various applications such as actuators, generators, sensors, and artificial muscles.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1371-1379
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• 2013

Application of induction machines in wind turbine driven generators is a good alternative due to their good characteristics such as efficiency, reliability and low cost. Nevertheless, when isolated operation is required, the application of external capacitive bank, connected to the stator windings, to provide self-excitation results in a rather complex analysis. This paper presents an analysis of self-excited induction generator connected to a load either directly or by an intermediate of a power converter. At first a dynamic model of the induction generator accounting for magnetic saturation is developed. Then a number of balanced and unbalanced capacitors, passive and active loads are verified. Experimental results obtained from laboratory tests are compared to those simulated; the two are shown to be in good agreement.