• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.541-546
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• 1987

An experimental study has been conducted to investigate the suction performance of a designed inlet. Total pressure distortion in the inlet S-duct was measured and the effect of lip thickness and throat area was analyzed. The volume flow rate of air into the turbojet engine was controlled to observe the effect of engine RPM to the total pressure distortion. The pressure data from 36 air tubes were obtained using scanivalve, pressure transducer, and visicoder system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권9호
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• pp.4123-4144
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• 2016

Vehicular Ad Hoc Networks (VANETs) utilize radio propagation models (RPMs) to predict path loss in vehicular environment. Modern urban vehicular environment contains road infrastructure units that include road tunnels, straight roads, curved roads flyovers and underpasses. Different RPMs were proposed in the past to predict path loss, but modern road infrastructure units especially flyovers and underpasses are neglected previously. Most of the existing RPMs are computationally complex and ignore some of the critical features such as impact of infrastructure units on the signal propagation and the effect of both static and moving radio obstacles on signal attenuation. Therefore, the existing RPMs are incapable of predicting path loss in flyovers and underpass accurately. This paper proposes an RPM to predict path loss for vehicular communication on flyovers and inside underpasses that considers both the static and moving radio obstacles while requiring only marginal overhead. The proposed RPM is validated based upon the field measurements in 5 GHz frequency band. A close agreement is found between the measured and predicted values of path loss.

• 한국정보통신학회논문지
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• 제2권4호
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• pp.627-634
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• 1998

본 논문에서는 관성 모멘트 동정에 의해 상태관측기의 성능 및 유도전동기의 저속운전 특성을 개선하는 알고리즘을 제안하였다 저속운전 영역에서 저 분해능 엔코더를 사용하는 속도 검출법은 속도 주기내에 펄스수가 너무 적어 정확한 속도정보를 얻을 수 없다 이러한 문제점을 개선하고자 속도와 외란을 추정할 수 있는 고피나스 이론에 근거한 상태관측기를 설계하여, 외란이 제거된 제어를 수행하였다. 또한 추정된 속도와 외란의 오차를 최소화하기 위하여 전동기의 관성 모멘트를 추정하고, 관측기의 공칭 관성 린멘트를 동정하였다. 시뮬레이션과 실험결과로부터 제안된 알고리즘은 6［rpm］ 이하의 저속영역에서 과도응답 특성의 향상을 보여주었다.

• 한국분무공학회지
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• 제18권4호
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• pp.188-195
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• 2013

An investigation on spray characteristics of fuels which diesel and di-methyl ether (DME) with change of injection pressure used the multi-injection in constant volume combustion chamber (CVCC). Diesel was already used famous fuel which we could use. DME showed similar features with diesel like as cetane number, auto-ignition temperature. High cetane number of diesel and DME could make possible to compression ignition. DME showed different atomization from diesel due to evaporating pressures and boiling points. Experiments were carried out in CVCC equipped with Delphi solenoid 6-hole type injector and the spray characteristics of diesel and DME were tested the various pre and pilot injection. Terms of injections and a number of injections in multi-injection has been controlled. Experiments were performed in 2 types that 1500 rpm, 2000 rpm and under the condition of injection ranging from 100 bar to 500 bar. From the results of this experiment diesel showed longer spray penetration than DME. That result showed different of atomization speed DME and diesel. Result of high injection pressure condition showed similar spray characteristics diesel and DME. After this investigation, new conditions and experiments using laser light to go forward and add the fuels like as the biodiesel and diesel and DME blend.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.250-257
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• 2001

Low NPSH and high pressure pumps are widely used for turbopump systems, which have an inducer and operate at high rotating speeds In this paper, a meanline method has been established for the preliminary design and performance prediction of pumps having an inducer for cavitating or non-cavitating conditions and at design or off-design points. The method was applied for the performance prediction of a fuel pump, which had been developed by Hyundai Mobis in collaboration with KeRC for a liquid rocket engine. The engine uses liquid methane and liquid oxygen as working fluids and rotates at 50,000 rpm KeRC carried out a model testing of the fuel pump with water as a working fluid at the reduced speed (10,000 ${\~}$ 15,000 rpm). Predicted performances by the method are shown to be in good agreement with experimental results for cavitating and non-cavitating conditions. The established meanline method can be used for the performance prediction and preliminary design of high speed pumps which have a inducer, impeller and volute.

• 한국정보통신학회논문지
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• 제6권6호
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• pp.879-884
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• 2002

산업 현장에서 필수적인 설비인 공기 압축기는 스크루, 왕복동 및 터보 압축기가 사용되고 있다. 근래에 터보 압축기가 넓이 사용되고 있는데, 터보 압축기는 구조적으로 임펠러를 고속회전 시켜야한다. 범용전동기에 높은 기어비를 가진 기어박스를 이용하여 구현하였는데, 이는 관성 모멘트, 마찰손 및 압축기의 크기를 증가시켰다. 최근에 터보 압축기의 연구는 초고속 동기전동기를 장착하여 기어박스를 제거하여 크기와 마찰손을 최소화하는 방향으로 진행되고 있다. 본 연구에서는 150마력 70,000rpm 직접 구동방식의 터보 압축기를 개발하기 위하여 초고속 동기전동기 센서리스 벡터 구동시스템을 개발하였고, 이를 적용하여 직접 구동방식 터보 압축기를 개발하였다.

• Tribology and Lubricants
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• 제28권5호
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• pp.197-202
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• 2012

In this study, with the purpose of fundamentally improving the unbalance response vibration of a large PRT motor-generator rotor by design, a performance improvement design analysis is carried-out by retrofitting tilting pad bearings, replacing the plain partial journal bearings that were originally applied for operation at a rated speed of 1,800 rpm. In this process, a goal of the design analysis is to obtain a design solution for maximizing the direct stiffness of the bearings while satisfying the key basic lubrication performance requirements such as the minimum lift-off speed and maximum oil-film temperature. The results show that with a careful design application of tilting pad journal bearings for operation at such a relatively low speed of 1,800 rpm, direct stiffness increment of the bearings by about two times can be effectively achieved. Prevention of pad unloading is also considered in the analysis. Moreover, the designs of elliptical and offset half journal bearings are also analyzed and reviewed.

• 한국분무공학회지
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• 제27권2호
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• pp.94-100
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• 2022

Even in non-road UTV (Utility Terrain Vehicle), spark ignition engines are often used to reduce emissions. In this study, gasoline and LPG (Liquified Petroleum Gas) fuels were applied to UTV engines, and the exhaust gas and combustion stability were compared through engine tests. A 0.8-liter two-cylinder SI engine was used in the experiment. Experiments were conducted while changing the IVO (Intake Valve Open) and EVC (Exhaust Valve Close) at 1500 rpm 14 N·m, 40 N·m, and 3000 rpm 17 N·m, 44 N·m conditions. As a result of the experiment, when the valve overlap increased according to the change of IVO and EVC, combustion stability decreased and THC emission increased, but NOx decreased. Comparing the LPG engine with the gasoline engine, the amount of CO₂ and PN (Particulate Number) generation decreased in the LPG engine, and the combustion stability was good.

• 공업화학
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• 제4권4호
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• pp.739-745
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• 1993

본 연구에서는 제올라이트에 의하여 Cs 및 Sr을 분리하는 무기이온 교환계에 있어서 물질전달 특성을 규명하는데 중점을 두었다. Cs이온의 경우 선택도가 우수한 AW300 및 AW500 제올라이트, Sr이온의 경우는 4A, 13X 제올라이트를 각각 선정하여 물질전달실험을 수행하였다. 실험조건으로는 $25^{\circ}C$, 교반속도 300rpm, 제올라이트량 4g, Cs 및 Sr 용액의 농도, 부피는 각각 1000ppm, 2000ppm의 $0.5{\ell}$에서 회분식의 이온교환 방식을 채택하였다. 물질전달속도는 경막내 확산에 의해 지배됨을 알았으며, 경막 내 물질 전달계수는 $10^{-4}{\sim}10^{-3}cm/sec$, 입자내 겉보기 확산계수는 $10^{-8}cm^2/sec$의 차수를 나타내었다.

• 수산해양기술연구
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• 제37권1호
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• pp.57-65
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• 2001

본 연구에서는 2차자속을 파라미터로 하는 순시토크제어법에 근거한 속도센서리스 제어방식을 제안하였고, 2차자속 정보를 이용하여 운전중 변동하는 2차저항을 속도추정과 동시에 동정할 수 있음을 제시하였다. 수치시뮬레이션을 통해 얻은 결과는 다음과 같다. 1) 2차자속을 교류를 중첩한 형태로 토크응답, 속도응답과는 독립적인 제어가 가능하다. 2) 수치실험상으로 무부하시 0[rpm]을 포함하는 저속영역에서도 양호한 속도추정이 이루어졌다. 3) 위의 속도추정을 바탕으로 수[rpm]대의 저속 영역에서 양호한 속도센서리스제어가 이루어졌다. 4) 2차저항값은 제안된 동정식을 통해 실제 2차 저항값에 수렴하는 특성을 보임으로써 2차저항의 동시동정과 속도센서리스제어가 가능함을 확인하였다.