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김유일(Yuil Kim),신은경(Eunkyoung Shin),홍태호(Taeho Hong) 한국인터넷전자상거래학회 2004 인터넷전자상거래연구 Vol.4 No.3
This study presents the comparative analysis of data mining performance for the prediction of stock price index using neural networks and support vector machine. The prediction of stock price index was performed on the basis of technical analysis using technical indicators which is able to find the change of the present and future prices in the market. Neural networks have a few problems such as the lack of explanation and over-fitting although their outstanding performance in the financial prediction area. On the other side, SVM is capable of generalizing the model because it can be explained mathematically and minimize the structured risk.<br/> In this study, we predicted the stock price index using neural networks and SVM and compared their performance with the prediction performance of discriminant analysis and logit, called statistical techniques. For the comparison of performance among each models, KOSPI 200 and S&P 500 index are utilized to experiments and the results are tested statistically. In addition, we analyzed the experimental results considering the characteristics of data in Korea and US.
지식공유 영향요인들이 형식지와 잠재지의 공유에 미치는 영향의 차이에 관한 연구
김진완(Jinwan Kim),이경진(Kyungjin Lee),김유일(Yuil Kim) 한국인터넷전자상거래학회 2004 인터넷전자상거래연구 Vol.4 No.3
Factors affecting knowledge sharing in terms of organizational, knowledge trait and knowledge management system were identified. And the differences between their effect on actual sharing of explicit and implicit knowledge were surveyed. The subject of this study was organizations using any forms of knowledge management system. 108 questionnaires were collected and analyzed. The results are as follows. First of all, explicit knowledge sharing factors are support for knowledge management infrastructure, evaluation and compensation, and top management support in the organizational context. Codifiability and dependability are also identified in view of knowledge trait. In addition. perceived ease of KMS use and perceived KMS usefulness were identified as system factors. Secondly, we extracted implicit knowledge sharing factors, which are evaluation and compensation, top management support in the organizational context, codifiability in knowledge trait view, and perceived ease of KMS use in system view. The results show us that the extent of knowledge standardization is related with determination factors affecting knowledge sharing. Finally, organizational factors, knowledge trait factors and system factors are all affecting knowledge sharing irrespective of knowledge classification.
UAV 추진기관의 현황 및 차세대 UAV 추진기관의 개발 전망
이동훈(Donghun Lee),팽기석(Kisuk Paeng),김유일(Yuil Kim),박부민(Poomin Par),최성만(Seongman Choi),허환일(Hwanil Huh) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.11
현재 운용중인 UAV(Unmanned Aerial Vehicle) 추진기관의 현황 및 추진기관 종류에 따른 장, 단점을 분석하였으며, 차세대 UAV 추진기관의 개발 전망 및 UAV 추진기관에 적용될 가스터빈 엔진의 특성 및 요구조건을 제시하였다. The characteristics and present state of UAV engine which is operating currently were studied and advantages/disadvantages of UAV engines were also analyzed. Forecast of next generation UAV engine development trend was presented and the performance demand of gas turbine engine for UAV were suggested.
습도 영향을 고려한 초소형 터보제트 엔진 성능시험 소개
이보화(BoHwa Lee),이경재(KyungJae Lee),양수석(SooSeok Yang),김유일(Yuil Kim) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.11
대기 중의 수증기는 가스터빈엔진의 주요성능에 많은 영향을 끼친다. 습공기의 영향은 기온 및 기압이 높은 여름철 해면 고도, 높은 비행 마하수 그리고 낮은 엔진 회전수에서 그 영향이 더욱 두드러진다. 이러한 습공기 유입에 따른 가스터빈 엔진의 성능변화의 정도를 살펴보고자 200lbf 급 초소형 터보제트 엔진의 고공환경 성능시험을 통해 습도가 엔진성능에 미치는 영향에 대하여 알아보았다. 고공환경 엔진시험을 통해, 건공기 유입에 비해 습공기 유입 시 순추력에서 2.826% 낮게, 비연료소모율에서 1.325% 높게 측정되었다. The moisture in the atmosphere exerts a lot of influence upon Gas turbine engine performances. There is a noticeable influence of wet air at the summer sea level, high flight mach number and low engine rpm increasingly. An altitude Engine Test Facility is used to accomplish the engine performance tests at dry air condition and wet air condition, through which engine performance results is revealed. In the result, net thrust and specific fuel consumption measured -2.826% and 1.325%, respectively at wet air condition compared to dry air condition.
팽기석(Kiseok Paeng),안철주(Chulju Ahn),민성기(Seongki Min),김유일(Yuil Kim) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.11
추력 150 lbf 급의 초소형 터보제트 엔진이 개발되었다. 본 엔진은 소형 무인항공기(UAV), 기만기, 대공망 제압용 유도무기 등 다양한 무기체계에 적용이 될 수 있도록 고성능, 소형, 저가로 설계되었으며, 시제엔진을 제작하여 지상 성능 시험 및 고도 시험을 수행하였다. 본 논문에서는 소형, 저가, 고효율 터보제트 엔진을 구성하는 각 엔진 구성품의 특징, 구조, 구성품 및 엔진 시험 결과 등에 대하여 기술하였다. A 150 lbf-thrust class micro turbojet engine has been developed. The engine could be applied to power plant for small aviation vehicle such as UAV, decoy and anti-radar missile and was designed with concepts that has small size, low-cost and high performance. A prototype was manufactured and performed the ground static test and high altitude test. This paper outlines the features and layout of 150 lbf turbojet engine and also describes the design characteristics and test results of the engine and components.