• 한국분무공학회지
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• 제25권1호
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• pp.8-14
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• 2020

Recently, 1-D model-based engine development using virtual engine system is getting more attention than experimental-based engine development due to the advantages in time and cost. Injection rate profile is the one of the main parameters that determine the start and end of combustion. Therefore, it is essential to set up a sophisticated model to accurately predict the injection rate as starting point of virtual engine system. In this research, procedure of 1-D model setup based on AMESim is introduced to predict the dynamic behavior and injection rate of diesel injector. As a first step, detailed 3D cross-sectional drawing of the injector was achieved, which can be done with help of precision measurement system. Then an approximate AMESim model was provided based on the 3D drawing, which is composed of three part such as solenoid part, control chamber part and needle and nozzle orifice part. However, validation results in terms of total injection quantity showed some errors over the acceptable level. Therefore, experimental work including needle movement visualization, solenoid part analysis and flow characteristics of injector part was performed together to provide more accuracy of 1-D model. Finally, 1-D model with the accuracy of less than 10% of error compared with experimental result in terms of injection quantity and injection rate shape under normal temperature and single injection condition was established. Further work considering fuel temperature and multiple injection will be performed.

• 제어로봇시스템학회논문지
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• 제10권3호
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• pp.286-293
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• 2004

This paper presents the result of a study on the starter control for a turbo generator. Because a starter in gear box type turbo-generator system is composed of gearbox and brush DC motor, it should be replaced with High Speed Generator(HSG)) in HSG type Turbo-generator. There-ore, it is necessary to design a new starting algorithm and starter. In gearbox type system, brush DC motor is rotated to the designed speed using low voltage-high current battery power. After brush DC motor speed is increased to several times by gearbox, gas turbine engine can be rotated to designed starting speed. If we implement a starter with High Speed Generator(HSG), it is necessary to drive high-speed generator to high-speed motor. High-speed generator with permanent magnet on rotor has a low leakage inductance fur driving high-speed rotation, and it is necessary high DC link voltage for inverter when High-speed generator is driven to high speed. This paper presents result of development of the boost converter for converting high voltage DC from low battery voltage and design of the inverter for controlling a high frequency current to be injected to motor winding. Also, we show performance of the designed starter by driving the turbo generator.

• 항공우주기술
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• 제7권2호
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• pp.170-175
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• 2008

본 연구에서는 다양한 기체를 사용한 액체로켓엔진의 시동특성 및 적합성, 그리고 호환성 등에 대해 고찰하였다. 엔진의 시동특성은 파이로 시동기 및 헬륨 기체 시동에 대해 고찰하였으며, 파이로 시동기 및 헬륨, 수소+질소 혼합기체 그리고 공기 등을 구동매질로 할 때의 시험 적합성과 호환성 등에 대해 고찰하였다. 대부분의 기체가 엔진의 시동특성과 호환성을 만족시키는 것을 알 수 있었으나, 공기의 경우 저추력의 경우에만 사용할 수 있는 것을 알 수 있었다.

• 인터넷정보학회논문지
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• 제9권3호
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• pp.79-90
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• 2008

본 논문은 전문가시스템 기법인 전향추론 기법을 이용하여 프로야구의 효율적인 선발 라인업 시스템을 설계 및 구현한다. 지식베이스는 선수 286명 148개 평가 항목으로 구성되어 있으며, 선수들의 경쟁력을 포인트로 평가하였다. 1차 포인트는 정적인 정보에 의해 산출된 포인트이며, 2차 포인트는 동적인 정보에 의해 산출된 포인트이다. 1, 2차 포인트를 통해 종합 포인트가 산출된다. 이를 이용하여 주어진 환경과 상대에 대한 효율적인 라인업 시스템 구현한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.641-644
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• 2011

축소형 2차목 초음속 디퓨저를 설계/제작하여 디퓨저 주요 설계 변수에 따른 성능 특성 변화를 파악하고자 한다. 디퓨저 주요 설계 변수로 디퓨저 입구 길이(Ld), 2차목 길이(Lst), 확산부 길이(Ls)를 선정하였고, 상온의 질소를 사용한 실험을 통하여 디퓨저 성능 특성을 파악하였다. 실험 결과 디퓨저 입구 길이에 따른 변화는 크게 없었으며, 2차목 길이, 확산부 길이에 따라서 시동압력의 영향이 있었고, 2차목 길이대 2차목 직경비(Lst/Dst)가 8 이상에서는 시동압력의 변화가 없는 것으로 확인되었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.216-220
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• 2006

본 연구에서는 다양한 기체를 사용한 액체로켓엔진의 시동특성 및 적합성, 그리고 호환성 등에 대해 고찰하였다. 엔진의 시동특성은 파이로 시동기 및 He 기체 시동에 대해 고찰하였으며, 파이로 시동기 및 He, H2+N2 혼합기체 그리고 공기 등을 구동매질로 할 때의 시험 적합성과 호환성 등에 대해 고찰하였다. 대부분의 기체가 엔진의 시동특성과 호환성을 만족시키는 것을 알 수 있었으나, 공기의 경우 저추력의 경우에만 사용할 수 있는 것을 알 수 있었다.

• 한국전자거래학회지
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• 제6권2호
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• pp.87-99
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• 2001

Along with the rapid emergence of the Internet and e-commerce, online auctions are hitting the spotlights. The inconveniences found in off-line auctions, such as time and place restriction and limited number of items, are solved in the online auction. However, not so many auction sites have integrated auction information systems, which monitor the present status of auctions, resulting in greater inconvenience for the online auction users. Moreover, there is no auction site that suggests the appropriate starting or closing price that is useful for users when they make, their bids, What the online auction users need is an auction system that can solve such problems. This study is purported for solving the problems by designing and implementing a real time auction system that applies the comparison search functions and the agent functions. In other words, an integrated database system using a bidder-oriented agent for providing information is built so that the users can search and compare the information on the item they are interested in and make a faster and more accurate purchase. Also the appropriate starting and closing prices are offered to the sellers and bidders through the integrated system for a closer and more accurate comparison and analysis of the prices. For future work, the product recommendation service, which accurately reflects the bidding patterns, and the methods for studying the multi bidding pattern will be applied to the suggested system to realize a real time auction information system that supports CRM(Customer Relationship Management) .

• Journal of Biosystems Engineering
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• 제40권2호
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• pp.95-101
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• 2015

Purpose: During the start-up period, the response time of a hydraulic system increases in the winter because of the increased oil viscosity caused by the cold weather. The problems of delayed tractor starting and excessive wear of the clutch disk occur for these reasons. Therefore, this study develops an analysis model using the commercial hydraulic analysis program AMESim to examine the characteristics of delays in power shuttle starting at different oil temperatures. Methods: In the experiment, a tractor was stationary on a flat surface with the engine running at a constant speed of 1,080 rpm. The forward lever was then pressed to activate the power shuttle at three different oil temperatures, and the pressure changes were measured. The pressure on the forward clutch control valve was measured by a pressure gauge installed on the hydraulic line supplied to the transmission from the main valve. An analysis model was also developed and verified with actual tests. Results: The trend of the simulated pressures of the power shuttle is similar to that of the measured pressures, and a constant modulation period was observed in both the simulation and test results. However, the difference found between the simulation and test results was the initial pressure required to overcome the initial force of the clutch spring. Conclusions: This study also examines the characteristics of the delayed startup of the power shuttle at different oil temperatures through simulations.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.157-163
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• 2008

The HCCI combustion mode poses its own set of narrow engine operating by knocking. In order to solve this, inhomogeneity method of mixture and temperature is suggested. The purpose of this research is to get fundamental knowledge about the effect of thermal stratification on HCCI combustion of PRF -Air mixture. The temperature stratification is made by buoyancy effect in combustion chamber of RCM. The analysis items are pressure, temperature of in-cylinder gas and combustion duration. In addition, the structure of flames using the two dimensional chemiluminescence's images by a framing camera are analyzed. Under stratification, the LTR starting time and the HTR starting time are advanced than that of homogeneous. Further, the LTR period of homogeneous conditions became shorter than that of the stratified conditions. With the case of homogeneous condition, the luminosity duration becomes shorter than the case of stratified condition. Additionally, under stratified condition, the brightest luminosity intensity is delayed longer than at homogeneous condition.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.774-780
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• 2021

회전익 항공기의 보조동력장치(APU, Auxiliary Power Unit)는 지상 운용/비행 중 주 동력 기관의 시동, 환경제어시스템용 고압 공기 공급, 비상발전기 등의 역할을 수행한다. 보조동력장치(이하 'APU')는 소형 가스터빈엔진형태로 구성되어 있으며, 해당 구성품의 시동 원리는 전기 시동 모터를 사용하는 방식으로, 축을 회전시켜 시동에 필요한 동력을 발생시킨다. 본 연구에서는 회전익 항공기에 장착된 APU의 시동 모터 운용성 확보를 위해 APU와 APU 시동 모터 간 축간 분리 장치(Over-Running Clutch) 적용을 통한 품질개선을 수행하였다. APU 시동 모터는 초기 APU 시동이 주 역할이지만, 운용 시 실제 작동 시간 이후에도 APU 기어축의 회전력에 의해 무 부하 회전을 하게 되어 구성품/부품 간 과도한 마찰력이 지속적으로 발생하였다. 이러한 현상은 시동 모터 내부 브러시 마모를 유발하게 되고, 결과적으로 항공기 운용을 위한 APU 작동 시간 증가 시 브러시 운용 수명 감소와 APU의 운용성에 영향을 미치게 된다. 따라서 본 연구에서는 APU 시동 모터의 운용성/내구성 향상을 위하여 시동 모터 브러시 마모와 APU 작동시간의 연동성을 분리하는 축간 분리 장치(Over-Running Clutch)적용하여 시험으로 효과를 검증하였고, 설계변경에 따른 기술적 타당성을 분석하였다.