• Journal of Advanced Marine Engineering and Technology
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• 제8권1호
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• pp.17-36
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• 1984

Since 1973, the competition on the development of fuel saving type internal combustion engines has become severe by the two times oil shock, and new type engines are reported every several months. Whenever these new type engines are developed, new designs are required and they will be offered in the market after performing the endurance test for a long time. But the engine market is faced with a heavy burden of finance, as the developing of a new engine requires tremendous expenses. For this reason, the computer simulation method has been lately developed to cope with it. The computer simulation method can be available to perform the reasonable research works by the theoretical analysis before carrying out practical experiments. With these processes, the developing expenses are cut down and the period of development is curtailed. The object of this study is the development of simulation computer program for the small naturally aspirated four-stroke diesel engine which is intended to product by the original design of our country. The process of simulation is firstly investigated for the ideal engine cycle, and secondly for the real engine cycle. In the ideal engine cycle, each step of the cycle is simulated by the energy balance according to the first law of thermodynamics, and then the engine performance is calculated. In the real cycle imulation program, the injection rate, the preparation rate and the combustion rate of fuel and the heat transfer through the wall of combustion chamber are considered. In this case, the injection rate is supposed as constant through the crank angle interval of injection and the combustion rate is calculated by the Whitehouse-Way equation and the heat transfer is calculated by the Annand's equation. The simulated values are compared with measured values of the YANMAR NS90(C) engine and Mitsubishi 4D30 engine, and the following conclusions are drawn. 1. The heat loss by the exhaust gas is well agree with each other in the lower load, but the measured value is greater than the calculated value in the higher load. The maximum error rate is about 15% in the full load. 2. The calculated quantity of heat transfer to the cooling water is greater than the measured value. The maximum error rate is about 11.8%. 3. The mean effective pressure, the fuel consumption, the power and the torque are well agree with each other. The maximum error is occurred in the fuel consumption, and its error rate is about 7%. From the above remarks, it may be concluded that the prediction of the engine performance is possibly by using the developed program, although the program needs to reform by adding the simulation of intake and exhaust process and assumping more reliable mechanical efficiency, volumetric efficiency, preparation rate and combustion rate.

• 한국전자파학회논문지
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• 제28권8호
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• pp.603-609
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• 2017

전개형 솔리드 안테나에서 패널 전개 시 발생할 수 있는 구조적인 오차가 안테나 성능에 미치는 영향을 분석하였다. 위성에서 활용되는 전개형 안테나는 지상에서 접힌 상태로 발사되어 우주 공간에서 펼쳐지며, 전개 시 발생할 수 있는 오차의 형태를 분류하여 각각의 경우에 성능에 미치는 영향을 분석하였다. 패널 하나에만 전개 오차가 있을 때는 불완전 전개 패널에 해당하는 쪽에서 안테나 성능의 열화가 발생하였다. 패널 전개 오차가 코사인 함수의 형태로 분포한다고 가정하여 오차의 크기와 오차 형태에 따른 영향을 계산하고 분석하였다. 안테나 패널 오차가 균일한 경우에는 오차크기에 비례하여 이득이 감소하고, 패턴은 대칭이다. 코사인 1 또는 3주기의 패널 오차에 대해서는 주엽의 기울어짐이 나타나며, 코사인 2 또는 4주기의 패널 오차에 대해서는 패턴은 대칭이며, 이득이 감소한다.

• 지역연구
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• 제33권3호
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• pp.3-19
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• 2017

본 연구의 목적은 지역의 산업다양성이 지역의 경기변동에 어떤 영향을 주는지를 분석하는 데 있다. 지역의 경기변동은 고용시장과 생산활동의 측면에서 측정하였고 2005년 1월부터 2016년 2월을 분석기간으로 설정하였다. 우리나라의 주요 항만도시를 대상으로 선정하였고 지역의 특성을 통제하기 위하여 패널 벡터오차수정모형의 그룹평균 추정량과 통합그룹평균 추정량을 사용하였다. 산업의 구성이 다양한 지역에서는 단기적으로 실업률의 변동의 폭이 작았지만, 제조업 생산지수의 변동성은 장기적인 경우에만 낮게 나타났다.

• 지능정보연구
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• 제15권4호
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• pp.37-51
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• 2009

서비스 인적자원 운용의 효율성 제고와 부품 또는 시설 할당의 적정성 향상을 위해 서비스센터를 통해 접수되는 서비스 요청 건수를 보다 정확하게 예측하고자 하는 필요성이 제조업을 중심으로 증가하고 있다. 본 연구에서는 제품의 특성을 반영하여 제품수명주기 별로 제품들을 군집화하고 군집 별로 적절한 예측모형을 구축한 후 예측 값을 통합하는 개별예측방식을 LCD 모니터 제조사의 사례를 통해 제시한다. 또한 예측 결과를 총량방식 및 기존에 기업이 사용하고 있는 방식과 비교. 평가하여 우수성을 증명함으로써 제품이나 산업의 특성을 반영한 맞춤형 수요예측 기법 도입의 필요성을 부각하고, 그에 따른 이론적, 실무적 가이드라인을 제공한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.382-386
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• 2002

The tapping is machining process that makes a female screw on the parts to be assembly together. It is used for the high-speed tapping machine with synchronizing function for the high productivity. This paper describes the development of the ultra high-speed tapping machine with 10,000rpm. The key factors in the tapping speed are the acceleration/deceleration velocity and the synchronizing errors between the spindle motor and feeding motor. To minimizing acceleration/deceleration time, the low inertia spindle with synchronous built-in servo motor is developed. To minimizing synchronizing errors, the tapping cycle algorithm under open architecture CNC environment is optimized. The developed tapping machine has 0.13sec/10,000rpm in acceleration/deceleration time and the synchronizing error below 4.0%. It has 0.55sec for cycle time of one female screw, M3 tap, 2 times depth of tap diameter.

• 한국정보시스템학회지:정보시스템연구
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• 제14권2호
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• pp.257-276
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• 2005

This study adopts diffusion of innovation theory and analyses product life cycle on two different information communication technology (ICT) products. One is telematics located on introduction and the other one is MP3 located on maturity. The analytical results were mixed. ordinary least square (OLS) result showed that adoption of MP3 player is affected by white noise error ($\varepsilon$) and telematics is influenced by innovation effect (p coefficient) rather than imitation effect (q coefficient) or white noise error. However, nonlinear least square (NLS) result showed that adoption of MP3 player is affected by imitation effect (q coefficient) rather than innovation effect (p coefficient). In addition, the ratio of imitation effect/innovation effect of MP3 player is larger than that of telematics.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.470-475
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• 2002

Instantaneous following PWM control technique is pulsed nonlinear dynamic control method. This new control technique using analog integrator is proposed to control the duty ratio D of do-dc converter. In this control method, the duty ratio of a switch is exactly equal In or proportional to the control reference in the steady state or in a transient. Proposed control method compensates power source perturbation in one switching cycle, and the average value of the dynamic reference in one switching cycle. There is no steady state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with buck converter have demonstrated the robustness of the control method and verified theoretical prediction. The control method is very general and applicable to all type PWM

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.378-381
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• 2002

Instantaneous following PWM control technique is pulsed nonlinear dynamic control method. This new control technique using analog integrator is proposed to control the duty ratio D of DC-DC converter. In this control method, the duty ratio of a switch is exactly equal to or proportional to the control reference in the steady state or in a transient. Proposed control method compensates power source perturbation in one switching cycle, and the average value of the dynamic reference in one switching cycle. There is no steady state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with buck converter have demonstrated the robustness of the control method and verified theoretical prediction. The control method is very general and applicable to all type PWM.

• 설비공학논문집
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• 제14권10호
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• pp.854-862
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• 2002

In the previous research, a simplified correlation method was developed as an easy prediction tool for comparing energy use of cooling plants. The purpose of this paper is to test the applicability of this method for economic evaluation with two zones of a 20-story commercial building in Seoul. The results of this method were compared with the DOE-2 simulation and actual measured data. Then, Comparisons of life cycle cost were carried out for three types of cooling plants. Testing of one zone showed good agreement of within 10% error in cooling energy use and within 2% error in LCC. But testing of the other zone indicated that the use of this method were invalid when input variables were used beyond its valid range.

• Journal of the Optical Society of Korea
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• 제12권3호
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• pp.205-209
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• 2008

We demonstrated a simple way of evaluating the duty cycle error in periodically polled lithium niobate(PPLN) based on the method of binary phase diffraction grating. To demonstrate this method, -Z face etched PPLN of desired periods were fabricated by the standard electric field poling technique. The etched PPLN was considered as a surface-relief binary phase grating. The diffraction patterns were recorded for different spatial locations along the length of the sample. The experimentally observed efficiencies of the diffracted orders were compared with the theoretically calculated values to estimate the duty cycle error.