• 한국철도학회논문집
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• 제11권1호
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• pp.39-44
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• 2008

본 연구에서는 실측 주행시험 결과데이터를 바탕으로 윤축 진동과 설계변수간의 관계를 규명하고자 2 자유도계 모델을 구성하였다. 특히 2차 현가장치인 공기스프링의 점탄성 특성을 반영하기 위해 니시무라 공기스프링 모델을 적용하였다. 수치해석 결과 내부 압력 감소 및 보조 공기탱크 체적 증가 시 객차 가속도응답이 감소하는 것을 확인할 수 있었다. 이에 안정성을 헤치지 않는 범위 내에서 현가장치의 강성을 조정해 볼 필요가 있음을 알았다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.315-320
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• 2009

Thermoeconomics or exergoeconomics can be classified into the three fields of cost estimating, cost optimization, and internal cost analysis. The objective of cost estimating is to estimate each unit cost of product and allocate each cost flow of product such as electricity or hot water. The objective of optimization is to minimize the input costs of capital and energy resource or maximize the output costs of products under the given constraints. The objective of internal cost analysis is to find out the cost formation process and calculate the amount of cost flow at each state, each component, and overall system. In this study, a new thermoeconomic methodology was proposed in the three fields. The proposed methodology is very simple and obvious. That is, the equation is only each one, and there are no auxiliary equations. Any energy including enthalpy and exergy can be applied and evaluated by this equation. As a new field, the cost allocation methodology on cool air or hot air produced from an air-condition system was proposed. Extending this concept, the proposed methodology can be applied to any complex system.

• 환경영향평가
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• 제11권2호
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• pp.67-77
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• 2002

Air traffic increased 12% annually in Korea since 1988 after the Olympics, this rate is two times than the rate of the world average. In order to accommodate fast growing aviation demand, Incheon International Airport is operated at Yongjong Island since March, 2001. The Incheon airport project will continue till 2020. After the final phase in 2020, Incheon International Airport will handle 100 million passengers, 530,000 flights and 7 million tons of cargo annually. In this study, air pollution from aircraft and other sources are calculated and assessed in Incheon International Airport area by EDMS(Emission and Dispersion Modeling System), which is a combined emission and dispersion model for airport. EDMS could also be considered power plant, incinerator and aircraft support equipment such as ground support equipment, aerospace ground equipment, auxiliary power units. And EDMS is recommended as preferred model for air quality assessment of the airport area by U.S. EP A. The result of this study shows that NOx emission from aircraft and support utility is estimated as 27,000 - 35,000 ton/yr and Namdong-Gu area in Incheon city is affected as 30-60 ppb by the NOx emission from these sources in 2020, the final phase of Incheon international airport construction.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.397-416
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• 2020

Investigations of the commercial aircraft impact effect on nuclear island infrastructures have been drawing extensive attention, and this paper aims to perform the safety assessment of Generation III nuclear power plant (NPP) buildings subjected to typical commercial aircrafts crash. At present Part II, based on the verified finite element (FE) models of aircrafts Airbus A320 and A380, as well as the NPP containment and auxiliary buildings in Part I of this paper, the whole collision process is reproduced numerically by adopting the coupled missile-target interaction approach with the finite element code LS-DYNA. The impact induced damage of NPP plant under four impact locations of containment (cylinder, air intake, conical roof and PCS water tank) and two impact locations of auxiliary buildings (exterior wall and roof of spent fuel pool room) are evaluated. Furthermore, by considering the inner structures in the containment and raft foundation of NPP, the structural vibration analyses are conducted under two impact locations (middle height of cylinder, main control room in the auxiliary buildings). It indicates that, within the discussed scenarios, NPP structures can withstand the impact of both two aircrafts, while the functionality of internal equipment on higher floors will be affected to some extent under impact induced vibrations, and A380 aircraft will cause more serious structural damage and vibrations than A320 aircraft. The present work can provide helpful references to assess the safety of the structures and inner equipment of NPP plant under commercial aircraft impact.

• 한국정보통신학회논문지
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• 제23권10호
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• pp.1188-1194
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• 2019

유체의 흐름을 측정하는 여러 방법 중 열선 풍속 센서는 유체의 열전달에 의해 속도나 온도를 측정하는 장치로 비정상 속도 및 난류 속도 성분을 측정하는데 유용하다. 하지만 열선 풍속 센서는 외부의 환경 요인에 민감하며, 주변 온도, 습도, 신호 잡음 등에 의해 정확도가 떨어지는 단점이 있다. 이런 단점을 보완하는 방법으로 온도 보상 회로를 추가하는 기술이 나오고 있지만 가격 경쟁력을 갖출 수 없는 상황이다. 이를 해결하기 위해 본 논문에서는 온도 보상이 필요 없는 풍속 감지 센서에 대해 연구를 진행하였다. 열선식 풍속 센서는 외부 환경 요인 중에서도 주변 온도에 매우 취약하다. 주변 온도로는 전자 회로에 의한 발열의 영향이 가장 크게 미치고 있으며, 이를 개선하는 방법으로 발열체에 보조 발열체를 추가로 장착하여 보조발열체와 발열체의 일정한 온도차를 제어하는 것이다. 이와 같이 기존 기술에 비해 복잡하지 않은 방법으로 동등한 성능을 확보할 수 있다는 것을 확인할 수 있었다.

• 항공우주시스템공학회지
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• 제14권1호
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• pp.8-15
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• 2020

본 논문은 위성을 발사장까지 안전하게 운반하기 위해, 열이나 외부 온도가 심하게 변화하는 조건에서 위성 컨테이너 내부 온도를 일정하게 유지할 수 있도록 컨테이너 벽면 및 경계층 단열 설계 방법을 제시하고 위성 운반용 컨테이너 외부 환경에 대한 열 유동 해석 및 위성 내부 열 전달 해석을 통해 위성 컨테이너 내부 온도가 일정하게 유지되는지 분석하였다. 컨테이너 내부 유동 해석을 통해 컨테이너 내 위성 주변의 유동이 원활 한지 유동 분포를 확인하였으며, 보조 팬 및 공조시스템과 특별한 그릴 가이드 구조 설계 안을 제시하고자 한다.

• 전기학회논문지
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• 제64권9호
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• pp.1385-1390
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• 2015

This paper is analysis of multiple factor that should be considered in the design of an eddy current brake used as auxiliary brake system. The eddy current brake is a brake that generates a braking torque in a rotational direction opposite to the direction of the rotor by using a time-varying magnetic flux. The eddy current brake has the advantage of being able to take high current densities because this is used for a short period of time. Also, the eddy current brake is influenced by multiple factor such as number of slots, teeth width, coating thickness, air-gap length and so on. Therefore the eddy current brake was designed for use in railway application in consideration of the operation region and critical parameters.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권5호
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• pp.238-245
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• 2001

During an AC motor's start-up accelerating period, a large amount of current is required to reach to the rating speed. This is called in-rush current. This peak in-rush current can be more than about several times the operating or steady-state current in the full load rating of the motor. In-rush current is present in both and electronic ballasts. The main area of concern is the tripping of circuit breaker and fuses which can affect electrical system components From this, we can see that the electrical power controllers will be rather concerned, since they have to supply the actual current necessary to start the motor. This paper presents a new method to reducing in-rush current and energy saving of the single-phase induction motor used in air-conditioner. It can be obtained that proposed system is low cost and small size as compared with other controller. Experiments are focused on a capacitor starting single-phase induction motor. The optimal power saving and in-rush current limiting by phase angle control are verified by experimental results. Also, auxiliary winding was controlled by electronic starting switch.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1238-1240
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• 2003

A new soft switching technique that improves performance of the high power factor boost rectifier by reducing switching losses is introduced. The losses are reduced by air active snubber which consists of an inductor, a capacitor a rectifier, and an auxiliary switch. Since the boost switch turns off with zero current, this technique is well suited for implementations with insulated gate bipolar transistors. The reverse recovery related losses of the rectifier are also reduced by the snubber inductor which is connected in series with the boost switch and the boost rectifier. In addition, the auxiliary switch operates with zero voltage switching. A complete design procedure and extensive performance evaluation of the proposed active snubber using a 1.2[kW] high power factor boost rectifier operating from a 90 [$V_{rms}$] input are also presented.

• Journal of Biosystems Engineering
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• 제38권1호
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• pp.41-47
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• 2013

Purpose: The objectives of this study were to construct the solar drying system with evacuated tubular solar collector and to investigate its performance in comparison with indoor and outdoor dryings. Methods: Solar drying system was constructed with using CPC (compound parabolic concentrator) evacuated tubular solar collector. Solar drying system is mainly composed of evacuated tubular solar collector with CPC reflector, storage tank, water-to-air heat exchanger, auxiliary heater, and drying chamber. Performance test of solar drying system was conducted with drying of agricultural products such as sliced radish, potato, carrot, and oyster mushroom. Drying characteristics of agricultural products in solar drying system were compared with those of indoor and outdoor ones. Results: Solar drying system showed considerable effect on reducing the half drying time for all drying samples. However, outdoor drying was more effective than indoor drying on shortening the half drying time for all of drying samples. Solar drying system and outdoor drying for oyster mushroom showed the same half drying time. Conclusions: Oyster mushroom could be dried easily under outdoor drying until MR (Moisture Ratio) was reached to about 0.2. However, solar drying system showed great effect on drying for most samples compared with indoor and outdoor dryings, when MR was less than 0.5.