• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.230-237
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• 2004

In this paper the effects of inverter ripple currents to the Proton Exchange Membrane Fuel Cell Stack (PEMFCS) is analyzed by the impedance model. The proposed method employs the frequency analysis technique to derive an equivalent impedance model of the fuel cell stack and the effects of the inverter ripple current are investigated. The calculated results m then verified by means of experiments on commercially available PEMFCSs. The experimental results show that the ripple current can contribute up to 10[%] reduction in the available output power.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.285-293
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• 1999

In this paper, the novel digital frequency/phase controller, to control the invelter fed traveling wave type ultra-sonic m motor(USM) is proposed. This controller is used to control the drive frequency, phase difference and applied voltages of e each phase of the motor. Proposed digital controller has constructed with digital logic only, no more use digitallongleftarrowanalog h hybrid method of the conventional controller, in order to generate drive frequency and phase difference. Therefore, the c control system has become to velY simple structure. T\rvo types of controllers are designed, one is to control drive f frequency and phase difference, another has added voltage control function of each phase. Two full digital voltage/phase c controllers are implemented by using custom LSI and EPLD, the control pelformance and the simplicity ofthe proposed c controller is verified by expeJimental results.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.533-539
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• 1999

Integration methods of a Gas Turbine and a Air Separation Unit have a potential to improve plant performance and cost of IFCC. Several studies on those integrations schemes were carried out. Then some of the methods were accually in commercial plants. Thus paper reviewed the integration schemes of a Gas Turbine and a Air Separation Unit. In order to compare the plant performance of IGCC with each scheme, simulation model was developed for IGCC power cycle with Texaco Quench gasification process. The simulation results showed that the thermal efficiency of the plant was appeared to be the best when all of the air consumption required for Air Separation Unit was supplied from the Gas Turbine and the net plant power output was maximized when 75% of the total ASU an requirement was supplied from Gas Turbine.

• Journal of Information Management
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• v.30 no.1
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• pp.11-28
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• 1999

STN(The Scientific & Technical Information Network) is a fee-based, comprehensive, online search service that provides. accurate, up-to-date information from over 200 scientific, technical, business, and patent databases. STN Easy(http: //stneasy.cas.org) provides point-and-click access to 59 selected key STN databases on the web, and it gives drawings and 3-dimensional chemical structures as well as citation-abstract informations. And information searchers are now able to access full-text documents from key scientific publishers and patent offices through STN Easy via the ChemPort(http://www.chemport.org) connection.

• Annual Conference of KIPS
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• 2014.04a
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• pp.325-327
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• 2014

애플의 iOS가 처음 출시되고 앱 마켓이 공급자와 소비자 모두에게 각광을 받으며 성공하자 구글에서도 Android를 내세워 구글 마켓을 오픈하였고 결국 다양한 종류, 높은 품질의 애플리케이션들이 사용자들에게 공급되게 되었다. 언제 어디서나 스마트 폰을 통해 고품질의 다양한 앱을 이용할 수 있다는 점이 부각되어 각 마켓의 다운로드 횟수가 급증하는 등 폭발적인 앱 시장을 이룩하게 되었다. 하지만 개발자의 입장에서는 같은 솔루션을 개발할 때 모든 플랫폼을 지원하기 위해 각각의 OS에 맞게 따로 개발하기 때문에 오히려 전체 개발기간이 늦어지는 요소가 되었다. 이런 비효율적인 개발 기간을 단축하기 위해 상용엔진을 구매하여 적용하는 경우가 있지만 영세한 규모의 프로젝트 팀에서 적용하기에는 무리가 있으며 엔진 자체를 배우거나 개발하려는 앱을 위한 커스터마이징하는 기간 역시 짧지 않아 좋은 선택이 될 수 없다. 이에 본 논문에서는 모바일 OS 크로스 플랫폼 지원이 가능한 게임 엔진을 구축하기 위한 방법을 설명하고 이를 활용하여 개발된 프로젝트를 테스트하여 초당 54~61frame 이라는 그래픽 출력 속도를 보임으로써 해당 엔진의 활용 가능성을 증명하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.270-270
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• 2020

자연재해저감종합계획의 주요 사항은 하천, 내수, 사면, 토사, 바람, 가뭄, 대설재해 등 자연재해로 인명피해나 재산피해가 발생할 수 있는 지역을 선정하고, 이에 적절한 저감대책을 수립하는 것이다. 다른 부분별 계획과 달리 자연재해저감종합계획은 다양한 자연재해를 대상으로 하므로 재해 유형별로 서로 다른 공학적 기법을 적용해야 한다. 실무에서는 자연재해저감종합계획 수립시 HEC-RAS, HEC-HMS(하천재해), XP-SWMM(내수재해), RUSLE(토사재해) 등 다양한 수치모형과 ArcGIS, QGIS 등 GIS 분석도구를 종합적으로 활용한다. 이 때, 모형별로 요구되는 입·출력 자료의 형식이 다양하다 보니 자료를 변환하는 등 번거로움이 발생한다. 이러한 배경에서 자연재해저감종합계획 수립에 GDP Tools의 적용가능성을 검토하고자 한다. GDP Tools는 방재설계 편의를 위해 개발된 도구로 자연재해저감종합계획에서 다루는 대부분의 재해유형에 대한 분석을 지원한다. GDP Tools를 이용하면 별도로 자료 형식을 변환할 필요가 없고, 분석 결과를 도면화하는 등 다양한 편의 기능을 활용할 수 있는 장점이 있다. 본 논문에서는 GDP Tools를 활용하여 자연재해 발생가능성을 검토하고, 그 결과를 기존 방법(상용 모형)의 결과와 비교하여 GDP Tools의 성능을 평가하고자 한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.93-103
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• 1999

The steady-state performance analysis program for turboprop engine which was used for a small, middle industrial aircraft and a basic trainer aircraft was developed and linear Gas Path Analysis method was applied to Engine Health Monitoring for Turboprop engine. This program was compared with TURBOMARCH program which is well known with performance and power according to flight Mach No. at the standard atmospheric condition to prove a steady-state performance analysis program. From the result, inlet, exit temperature and pressure of each component had error within 3% and especially power according to flight Mach No. had error within 2.4% so that this program could be assured. To make sure if linear Gas Path Analysis is reasonable four cases were selected. The first is the case that fouling is occurred in compressor only. The second is the case that fouling is occurred in compressor and erosion is occurred in turbine. The third is the case that erosion is occurred in both compressor and turbine and power turbine at the same time. Finally, the case that fouling and erosion are occurred in compressor, compressor turbine and power turbine was selected. Different parameters were selected impartially among the independent parameters so that the effect of measurement parameter selection was observed. From the result, the more measurement parameters the smaller RMS error and even though the number of measurement parameters was the same, the RMS error was obtained differently according to which measurement parameters were selected. The case using eight instrument parameters of case IV-4 had small error comparably and was economic and it was important to select optimal number of measurement and optimal measurement parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.777-784
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• 2017

Energy harvesting through a thermoelectric module normally makes use of the temperature gradient in the system's operational environment. Therefore, it is difficult to obtain the desired output power when the system is subjected to an environment in which a low temperature gradient is generated across the module, because the power generation efficiency of the thermoelectric device is not optimized. The utilization of solar energy, which is a form of renewable energy abundant in nature, has mostly been limited to photovoltaic solar cells and solar thermal energy generation. However, photovoltaic power generation is capable of utilizing only a narrow wavelength band from the sunlight and, thus, the power generation efficiency might be lowered by light scattering. In the case of solar thermal energy generation, the system usually requires large-scale facilities. In this study, a simple and small size thermoelectric power generation system with a solar concentrator was designed to create a large temperature gradient for enhanced performance. A solar tracking system was used to concentrate the solar thermal energy during the experiments and a liquid circulating chiller was installed to maintain a large temperature gradient in order to avoid heat transfer to the bottom of the thermoelectric module. Then, the setup was tested through a series of experiments and the performance of the system was analyzed for the purpose of evaluating its feasibility and validity.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.116-121
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• 2014

In order to study the improvement of the multi stage regeneration cycles, muti-stage processes were applied to the cycles, respectively or together. The kinds of the cycles are multi stage reheater cycle (MS) and multi stage reheater regeneration cycle (MSR). Working fluid used was R134a and R245fa. Temperature of the heat source was $65^{\circ}C$, $75^{\circ}C$, and $85^{\circ}C$, and temperature of the heat sink was $5^{\circ}C$. Optimization simulation was conducted for improving the gross power and efficiency with multi stage reheater regeneration cycle for ocean thermal energy conversion(OTEC) with changing of a heat source, kind of the working fluid, and type of the cycle. Performance analysis of the various components was simulated by using the Aspen HYSYS for analysis of the thermodynamic cycle. R245fa shows better performance than R134a. This paper showed the most suitable working fluid with changing of a heat source and the kinds of working cycle. Compared to each other, MS showed better performance at gross power and MSR showed higher cycle efficiency.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.1
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• pp.56-69
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• 2021

In this paper, the PV system with a link to the commercial system needs some advantages like small capacity, high power factor, high reliability, low harmonic output, maximum power operation of solar cell, and low cost, etc. as well as the properties of inverter. To transfer the PV energy of photovoltaic power generation system to the system and load, it requires PCS in both directions. The purpose of this paper is to confirm the stable power supply through the load leveling by presenting the PCS considering ESS of photovoltaic power generation. In order to achieve these purpose, 5 step process of operation mode algorithm were used according to the solar insolation amount and load capacity and the controller for charging/ discharging control was designed. For bidirectional and effective energy transfer, the bidirectional converter and battery at DC-link stage were connected and the DC-link voltage and inverter output voltage through the interactive inverter were controlled. In order to prove the validity of the suggested system, the simulation using PSIM was performed and were reviewed for its validity and stability. The 3[kW] PCS was manufactured and its test was conducted in order to check this situation. In addition, the system characteristics suggested through the test results was verified and the PCS system presented in this study was excellent and stronger than that of before system.