• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1625_1626
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• 2009

최근 세라믹 메탈할라이드 램프의 사용이 증가함에 따라 고연색성, 장수명에 대한 기대치가 높아지고 있다. 이런 추세에 의하여 현재 정격수명이 15,000 ~ 20,000시간의 세라믹 메탈할라이드 램프가 개발되고 있으며 신뢰성에 대한 문제 또한 부각되고 있는 실정이다. 본 논문에서는 이러한 세라믹 메탈할라이드 램프의 수명 특성을 알아보기 위하여 "신뢰성기준 RS C 0085"를 바탕으로 램프를 20분 점등후 20분 소등을 한 주기로 하여 1,200회를 반복한 후 광학적 특성 및 전기적 특성을 측정하여 실험 전 초기 특성과 비교 분석하였다. 광학적 특성으로 광속과 효율은 3.1 [%] 감소, 연색성은 2.3 [%] 감소, 색온도 변화를 가져왔다. 전기적 특성으로는 램프 열화로 인한 내부저항의 변화로 인해 전압이 1.4 [V] 증가, 전류가 0.02 [A] 감소하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.14 no.1
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• pp.49-58
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• 1996

This paper deals with the gravimetric solution of geoid by Fast Fourier Transform(FFT) technique in and around Korean Peninsula. The used reference surface is OSU91A geopotential model up to degree and order 180 refered to GRS80. The remove and restore technique was applied to obtain the geoidal height in this paper. And the FFT with 20% window was applied to compute the medium wavelength effect from terrestrial gravity anomalies. For the comparison of computed results, the geometric geoidal height was derived from GPS/Levelling data. According to the comparison, the mean value and RMSE of the differences are 0.3819m and 0.4695m respectively.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.78-84
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• 2011

CFD simulation has been conducted on a small scaled 4 nozzle clustered engine operating with air. In the present paper, the effects of grid size, turbulence models, flux difference methods have been compared. The results show that the base flows are somewhat different as the turbulence models, while Roe and AUSM flux differences produced almost the same results. Spalart-Allmaras turbulence model produces more accurate results rather than famous SST k-w model. The calculated Mach number and pressure profile in the engine base reveal the complex base flow structure, which is somewhat different from the generally estimated flow fields.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1361-1373
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• 2001

In the firewall systems of 3-tier client/server systems, in general, data transmission speed is declined rapidly according to the duplicated proxy services in application server and fire wall server. In this paper, an application server configuration containing the proxy functions of firewall system is proposed so that the high speed data transmission can be achieved. The proposed application server can form the dual-homed gateway by means of the additional network interface card. The screened router of application server forms the screened subnet gateway that can separate the internal network. The proposed server configuration is more effective in traffic control than the traditional firewall systems and provides high speed data transmission with the functions of firewall. It can be also cost-effective alternative to the firewall system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.9
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• pp.616-623
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• 2001

Effects of the grating period fluctuation on the wavelength distribution have been studied by an effective index transfer matrix method in quarter wavelength shifted (QWS) DFB lasers. The wavelength distribution is expressed by a probability density that is an analytical function of the correlation coefficient and normalized standard deviation of the grating period fluctuation. The probability density function of wavelength distribution is shown to be nearly Gaussian, and its standard deviation increases with normalized standard deviation of the grating period fluctuation, and decreases with the negative correlation between adjacent half-periods.

• Journal of the Korea Society for Simulation
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• v.23 no.3
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• pp.33-40
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• 2014

Drifter is equipment which is hard to localize. Performance of prototype hasn't performed well compared to product of leading companies even though advanced foreign firm's product were dead copied. This study shows cases of approaching the factor which produces performance gap through drifter hydraulic analysis model which is core component of rock drill. Progression of procedure is following. 1) Securing reliability of the analysis model by comparing impact test result with analysis result. 2) Drawing a graph which indicates performance gap between prototype and drifter of advanced foreign firm by using analysis model. 3) Approaching the factor which produces performance gap with analysing variable of the analysis model. Software used for this analysis is SimulationX.

• Journal of The Korean Association of Information Education
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• v.13 no.4
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• pp.479-487
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• 2009

In the existing curriculum of the Elementary computer Education emphasizes students' problem-solving ability and knowledge of informatics. However, current computer education focus on using application program. In order to raise students' problem-solving ability and logical thinking ability, it is necessary to learning about computer science education. Thereupon, this study applied unplugged learning method to the elementary student. To apply the play-based unplugged learning method to the area of information representation. As a result, unplugged learning method produced higher academic achievement than the lecture model. Also it was more positive in the affective area than the lecture model.

• Journal of The Korean Association of Information Education
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• v.11 no.4
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• pp.497-504
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• 2007

This study proposed the unplugged learning strategy of computer science that makes more easily to understand learning contents and to improve logical thinking of learners in elementary school. We reorganized the contents of data structure in computer science. The students write project papers from their own experiences and daily lives in the classroom, not in the computer room as applying unplugged learning methods. The result of this study shows that students can better understand computer through a study method of computer science on their step of growth. Through this study, the learners can be the abilities of organizing digital data and increasing the logical thinking, based on information education.

• KIISE Transactions on Computing Practices
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• v.21 no.2
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• pp.132-137
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• 2015

A real-time system is a system wherein the behavior of the system depends not only on the input but also on the timing of the input. Timed automata is a widely used model for real-time system modeling and analysis. Model-based testing is employed to check whether the system under test (SUT) works according to the model specifications by using test cases generated from models that represent software requirements. In this paper, a case study was performed applying the timed automata based testing tools, UPPAAL-TRON, UPPAAL-COVER and SYMBOLRT, to the same system. Comparison of the testing approaches and tools is then made based on the results of the case study.

• Proceedings of the Korea Contents Association Conference
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• 2013.05a
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• pp.73-74
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• 2013

차세대 웹 기술인 시맨틱 웹(Semantic Web)이 각광을 받음에 따라, 시맨틱 웹과 관련된 다양한 기술들이 활발히 연구되고 있다. 특히, 시맨틱 웹의 핵심 사례인 링크드 데이터(Linked Data)는 웹으로 접근 가능한 형태의 URI로 시맨틱 데이터를 표현하고 서로 연결함으로써, 오픈 데이터로서 상호운용성 극대화 및 데이터의 통합을 용이하게 한다. 이는 바이오인포매틱스 기술 발전과 결합하여 웹에서 바로 이용 가능한 많은 의학 링크드 데이터 생산과 이를 활용한 다양한 의학용어 검색 서비스 개발 결과를 가져왔다. 하지만, 기존 의학용어 검색 서비스들은 각 기관이 보유하고 있는 의학정보를 기반으로 서비스되기 때문에 다양하고 정확한 정보를 얻기 위해서는 많은 시간과 노력을 투자해야 한다. 그래서 본 논문에서는 척추 분야 의학 관련 링크드 데이터를 활용해 정확도가 높고 확장이 용이한 척추정보 검색 서비스를 제안한다.