• Journal of Power System Engineering
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• v.8 no.1
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• pp.36-40
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• 2004

Two-phase loop systems using the latent heat capacity of their working fluids can meet the increasing power requirements and are well suited to thermal management systems of future large applications, due to its abilities to handle large heat loads and to provide them at uniform temperatures regardless of the changes in the heat loads. Therefore some experiments on the effect of the gas and liquid superficial velocities, $j_G,\;j_L$ on flow pattern transition, void fraction and frictional pressure loss were performed on a co-current air-water flow in an adiabatic horizontal tube. The flow patterns were depended on the superficial velocity of each phase. It snowed that the increasing $j_L$, resulted in a significant increase in the frictional pressure loss for all flow patterns, at a constant $j_G$. The experimental results were also evaluated with some of existing models and correlations.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.04a
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• pp.9-25
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• 2001

Fairchild has been developing a new class IPM called SPM consisting of dramatic Packaging technology to achieve the lowest cost rind better performance for low power home appliances and industrial AC drive applications. The first Fairchild SPM development with IGBT 600V/15A for washing machine application started in 1999 and was completed successfully. Fairchild SPMs are going to be the best solution for low power inverter-driven AC drive system after 2001. The new SPM Packages like SPM ∥ and SPIM for the next generation IPM with the highest competitiveness (cost & performance) shall be continuouslly developed.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2433-2435
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• 1998

원자력발전소의 증기발생기는 기능상으로도 중요한 역할을 하지만 증기발생기 내의 전열관 손상이나 누설은 바로 방사능 누출의 원인이 되므로 원자력 발전소의 안전성 측면에서 보면 매우 중요한 설비이다. 따라서, 증기발생기 전열관은 정기보수시 마다 전열관 각각에 대해 비파괴검사의 일종인 와전류검사(Eddy Current Testing, ECT)를 통해 건전성을 평가하고 있다. 현재는 신호를 취득하고 평가하는 업무가 별개의 기관에서 수행하고 있으며 이를 위해 현장에 관련 인력과 장비가 이동되어야 한다. 그러나, 취득한 신호를 평가자가 on-line으로 받을 수 있고 그 결과를 이용하여 즉시 피드백이 가능하다면 평가기관의 인력은 현장에 있지 않더라도 평가가 가능하다. 그러므로, 원격 평가 환경을 구축한다는 것은 평가자가 굳이 현장에 가지 않더라도 지역에 상관없이 LAN을 활용하여 전국 어디서든 평가가 가능하도록 하고자 함에 있다.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1381-1383
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• 2000

A multi-train operation simulation software is under development, in this G7 Project for a High Speed Train System, to simulate the running performance, power consumption, signalling and operation. In the first stage, a Train Performance Simulation (TPS) software is introduced in this paper. This is a core module of whole system and gives some parameters of a train, e.g., its position, speed traction and braking power and electric power system state, etc. In this paper, calculation technique was used for voltage drop at the train's positions and major posts along the catenary line. The final program will be used as an evaluation tool for system performance in constructing a new line or introducing a new train system.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.403-405
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• 1999

Dissoved oxygen(DO) control by deaerator has a great effect on the integrity of S/G in nuclear power plant. The goal of this study based on the theoretical basis and the extensive surveys is to identify the effect of deaerator in feedwater system on steam generator to clear the need of installation of deaerator. In addition, this paper discusses the review to understand the mechanism of DO formation as well as removal. The conclusion is that the installation of deaerator improve the integrity of S/G and is contributed to the whole nuclear power plant safety.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.479-481
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• 2007

This paper presented a actual conditions on a false-tripping of ELB(Earth Leakage Breakers) and an assessment of the harmonics due to non-linear electronic equipment such as personal computers, rectifier, electric furnace and test equipments in plant installations. Actual conditions on a failure of ELB were surveyed and analyzed by making up a question to safety managers of plant installations. Also, power quality measurements such as harmonic currents, voltage and current waveform and current imbalance were made at various plant installations where nuisance tripping of ELB is often occurred. The results of this study can be used in making decisions regarding cause of ELB trip and operating and tripping characteristics test of ELB when subjected to distorted current waveform.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.3
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• pp.101-109
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• 2002

It is a very difficult to control the S/G(Steam Generator) levels for not only automatic operation mode but also manual operation made by operators in case of start up or low power plants. The object of this study is to develop and applicate a DCS(Digital Control System) that process the reliable control algorithm in order to control S/G levels automatically from a start-up to full power operation mode for nuclear power plants.

• Journal of Korean Vacuum Science & Technology
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• v.2 no.2
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• pp.133-138
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• 1998

To enhance the ionization level of I-PVD and reduce the coil voltage two approaches were tried and as a diagnostic, optical emission spectroscopy and impedance analysis of the plasma was done with a range of Ar pressures and RF power along with XRD analysis of deposited Ag films. RF sputtering power was pulsed with various on/off time scales to recover the ICP quenched by sputtered metals. This in average enhances the ionization of the sputtered atoms with 10 ms/10 ms and 100 ms/100ms pulse on/off time duration and gives higher (200) preferred orientation over (111) in deposited Ag films. Secondly, Small axial B field about 8G remarkably reduced RF coil sputtering and showed scaled relationship between RF power and magnetic field strength for optimal process condition. From OES of Ar0 and Ar+, wave-like dispersion structure appeared and reduced the coil voltage about 20% at very weak field strength of 8G. This should be studied further to have nay relation with low mode helicon wave launching.

• Journal of applied mathematics & informatics
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• v.39 no.5_6
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• pp.689-701
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• 2021

The purpose of this paper is to optimize the number of source places required for the unique representation of the destination using the tools of graph theory. A subset S of vertices of a graph G is called a rational resolving set of G if for each pair u, v ∈ V - S, there is a vertex s ∈ S such that d(u/s) ≠ d(v/s), where d(x/s) denotes the mean of the distances from the vertex s to all those y ∈ N[x]. A rational resolving set is called minimal rational resolving set if no proper subset of it is a rational resolving set. In this paper we study varieties of minimal rational resolving sets defined on the basis of its complements and compute the minimum and maximum cardinality of such sets, respectively called as lower and upper rational metric dimensions for power of a path P_n analysing various possibilities.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.919-926
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• 2021

In this paper, a study was conducted on the miniaturization of an e-Mobility battery charger module using GaN-FET. GaN-FET is one of the types of WBG devices, and it is a device that exceeds the performance of existing Si power semiconductors. In particular, GaN-FET has the advantage of small packaging size and high switching frequency operation, which is advantageous for miniaturization of power converters. Therefore, a bidirectional DC/DC converter module for e-mobility charging using GaN-FET was developed. To apply to the converter to be developed, analysis is performed on the characteristics of GaN-FET, and after manufacturing a prototype of a bidirectional DC/DC converter module, the efficiency and temperature data of the power converter are analyzed to verify its feasibility.