• 한국산학기술학회논문지
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• 제10권10호
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• pp.2589-2595
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• 2009

본 연구에서는 장하분배법(Load Distribution Method) 및 등가회로법(Equivalent Circuit Method)을 이용하여 액체금속이송을 위한 전자기펌프를 설계하고 제작하였다. 제작된 전자기펌프의 구동전력과 이에 상응하는 액체의 유량관계를 구하였다. 액체금속유동에 가하는 전자기 힘(Lorentz force)의 크기에 따른 유속과 유량을 수치해석기법을 이용하여 계산하였다. 수치해석결과를 상용코드인 FLUENT를 이용하여 계산한 결과와 비교하고 분석하였다. 다양한 전자기력의 크기에 대한 액체금속(우드메탈)의 평균속도에 대한 결과는 FLUENT의 결과와 5%이내의 오차 내에서 잘 일치하였다.

• 산경연구논집
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• 제9권9호
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• pp.7-14
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• 2018

Purpose - Social welfare is a social insurance system that provides funds and services for all citizens to maximize their life quality. Its ultimate goal is to alleviate social contradictions. Therefore, this paper explores the determinants of social welfare in terms of macroeconomics. Research design, data, and methodology - Based on the vector error correction model, the annual time series from 1990 to 2017 will be used to conduct an empirical analysis. The real GDP, the real income, the inflation and the degree of openness will be treated as independent variables. The input of social welfare will be treated as a dependent variable. These variables will be used to perform the cointegration test and the vector error correction model to explore how the macroeconomic variables affect social welfare both in long run and short run. Result - Via the empirical analysis, it can be summarized that the real GDP, the real income and the degree of openness are the driving determinants to enlarge the social welfare. Conversely, the inflation is the obstructive determinant to reduce the social welfare. Conclusion - The positive and negative determinants of social welfare exist simultaneously, China's government should take macroeconomic regulation and control to balance them to enlarge social welfare.

• 전력전자학회논문지
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• 제19권2호
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• pp.99-105
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• 2014

This paper proposes the reliability improvement of H-Bridge Multi-level (HBM) inverter. This reliability can be implemented through modularization of power circuit, distribution of controller, duplication of controller and communication, and continuous operation method in case of power cell failure for driving medium-voltage & high-power induction motor. It is shown that the modularization and expansion characteristics of the HBM inverter are improved since the individual inverter modules operate more independently when using the proposed concept. Also the fault tolerance is increased by using power cell bypass. The proposed design and control methods are described in detail and the validity of the proposed system is verified experimentally in various industrial fields.

• Tribology and Lubricants
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• 제27권2호
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• pp.88-94
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• 2011

The tribological characteristics of the swash plate surface of a compressor which is for automobile were investigated. For surface treatments, PTFE and $MoS_2$ are used as a solid lubricant, together with copper alloy. Test condition is set considering actual driving condition. Wear testing is conducted using pin on disk type tester, and the coefficient of friction and the temperature on friction surface are measured. Also, to determine the wear patterns, cross-section of friction surface is analyzed by SEM(scanning electrode microscope). The $MoS_2$, both at dry and lubricated conditions, friction surface and the coefficient of friction maintained rather stable results. But, the PTFE, at oil less condition, sample resulted in rather unstable condition. In case of copper alloy, quite higher friction coefficients(higher than 0.1) were obtained at dry condition. At the temperature of $125^{\circ}C$, seizure has occurred.

• Tribology and Lubricants
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• 제29권2호
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• pp.105-110
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• 2013

Refrigeration and air-conditioning compressors used in home appliances, including refrigerators and air conditioners, are typically hermetic-type reciprocating compressors. Because the shell is sealed by welding, it should be designed to have a semi-permanent life. The energy consumption of a hermetic-type reciprocating compressor is low, but because it operates continuously to maintain a constant temperature inside the refrigerator, it has a certain base load. In this type of compressor, the driving motor operates at a high speed (about 3,000 - 3,600 rpm), which causes valve damage, friction, wear, and high-frequency noise. Many studies have been conducted to solve these problems. To enhance the reliability and efficiency of the reciprocating compressor, the design conditions and operating environment of journal bearings should be considered. Dynamic behavior analysis should be carried out in terms of the discharge pressure. The results showed that the load (discharge pressure) increases in the forward lookup zone and decreases in the backward lookup zone. When the revolution speed is increased, the maximum load decreases in the region where the maximum load operates.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.526-529
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• 2009

본 연구에서는 Lab-Scale의 하이브리드 연소기를 이용하여 하이브리드 로켓의 추력제어 범위와 연소 시간에 따른 추진제의 후퇴거리를 분석하기 위하여 산화제 유량에 따른 추진제별 연소 특성을 파악하였다. 산화제 유량을 제어하기 위해서 니들 밸브와 스텝모터를 결합하여 스텝모터의 구동에 의해 니들밸브의 개폐량을 조절할 수 있도록 배관 시스템을 설계하였다. 산화제 유량 변화를 통해 추진제에 따른 질유량과 후퇴율 관계식을 유도하였다. 추력제어를 하면서 명령 추력 값에 따른 산화제 유량을 통해 후퇴거리를 예측하였으며 실제 추력제어 연소 실험을 통해 신뢰성을 확인하였다.

• 산업기술연구
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• 제24권A호
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• pp.119-126
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• 2004

BLDC Motor is one of the widely utilizable motors in servo system. The accurate calculation of the power loss for the IGBT and Inverse diode with Bipolar and Unipolar switching modes the driving modes is important for the design of drives for their heat treatment. If it were not for temperature-sensors in devices, it is difficult to get direct power loss, so. Power losses may be modeled by computer modeling to obtain the Calculation of the Power loss for Inverter in BLDC Motor with switching modes which is presented in this paper. The computer modeling is carried out by Matlab simulation. The power loss consists of conduction losses Conduction losses are the source of occurrence due to The IGBT and Inverse diode currents. Switching losses are the source of occurrence due to switching on/off in the devices, and gives the dominant influence to the loss. As a result, the unipolar I mode is best in reducing the heat losses.

• 한국지능시스템학회논문지
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• 제22권1호
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• pp.1-6
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• 2012

이동로봇에 관한 연구가 널리 진행되고 있다. 본 논문에서는 미지의 공간에서 효과적으로 장애물을 회피할 수 있는 SFLC(single-input fuzzy logic controller) 기반의 이동로봇의 주행 제어기 설계와 구현을 제안한다. 장애물의 위치와 거리 인식을 위해 초음파센서를 사용하였으며, 좌, 우측 바퀴의 각속도 출력 제어를 위하여 퍼지논리시스템 기반의 제어기를 설계하였다. 퍼지제어기의 퍼지화 방법은 싱글톤 방법, 추론법은 간략화된 Mamdani의 추론법, 비퍼지화 방법은 간략화된 무게중심법을 사용하였다. 제안한 퍼지제어기의 성능 및 실제 적용 가능성의 평가를 위해 이동로봇의 모델링에 근거한 컴퓨터 시뮬레이션을 수행하였다. 그 결과 이동로봇이 장애물을 피하면서 목표지점에 정확히 도착함을 확인하였다. 더욱이 기존의 2-입력 퍼지논리시스템 기반의 제어기로부터 단일 입력을 가지는 단순구조 퍼지논리제어기를 설계할 수 있음도 보였다.

• 한국화재소방학회논문지
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• 제25권5호
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• pp.32-38
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• 2011

호버크래프트는 수륙양용으로 운용이 가능하고, 일반 보트에 비해 연비가 좋은 관계로 보트의 대체 수단 및 레저용으로 이용이 증가하는 추세이다. 아울러 우리나라도 소방서의 인명구조구급용으로의 수요가 점차 많아지고 있다. 본 논문에서는 호버크래프트의 전진과 후진을 자유롭게 하기 위해 후진 시 방향을 제어할 수 있는 후진 버켓 컴퓨터 시스템 제어기를 개발하였다. 제안한 시스템제어기의 타당성을 입증하기 위하여 Matlab으로 시뮬레이션 한 다음, 실제 소방서에 납품하는 기종에 장착하여 실증 실험을 수행하 였다. 그 결과 호버크래프트는 추진 공기의 흐름에 대하여 좌 우 및 역 추진이 용이하였으며 인명 구조시나 고속 주행시 등에서도 안정된 운용이 가능함을 확인 하였다.

• Nuclear Engineering and Technology
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• 제34권5호
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• pp.494-501
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• 2002

Radioactive Corrosion Products (CRUD) which are generated by the neutron activation of general corrosion products at the nuclear power plant are the major source of occupational radiation exposure. Most of the CRUD has a characteristic of showing strong ferrimagnetisms. Along with the new development and production of permanent magnet (rare earth magnet) which generates much stronger magnetic field than the conventional magnet, new type of magnetic filter that can separate CRUD efficiently and eventually reduce radiation exposure of personnel at nuclear power plant is suggested. This separator consists of inner and outer magnet assemblies, coolant channel and container surrounding the outer magnet assembly. The rotational motion of the inner and outer permanent magnet assemblies surrounding the coolant channel by driving motor system produces moving alternating magnetic fields in the coolant channel. The CRUD can be separated from the coolant by the moving alternating magnetic field. This study describes the results of preliminary experiment performed with the different flow rates of coolant and rotation velocities of magnet assemblies. This new magnetic filter shows better performance results of filtering the magnetite at coolant (water). How rates, rotating velocities of magnet assemblies and particle sizes turn out to be very important design parameters.