• 한국자동차공학회논문집
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• 제21권5호
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• pp.67-73
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• 2013

This experimental work described the effect of flow control valve type on the performance of wobble plate type fuel pump for the stable DME fuel supply. In order to study this, different four types of flow control valves (ITV, SCV, IMV and MPROP) were installed on the wobble plate fuel pump, and fuel flow rate, torque, and temperature variation of pump were investigated under various operating conditions by using pump performance test system. It was revealed that wobble plate type fuel pump worked well with ITV and SCV control valve, and the flow rate and torque of fuel pump was in proportion to the value of valve open duty. The maximum flow rate and torque of fuel pump were achieved around the 50% duty of control valve. Temperature variation at all pump measuring points were under $60^{\circ}C$ which is acceptable.

• 한국전자파학회논문지
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• 제14권12호
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• pp.1311-1320
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• 2003

본 논문에서는 RF 전자기장을 사용한 동물 및 세포 실험에서 전자기장 노출량의 정확성을 평가할 수 있는 방법을 제안하였다. 이를 위해 전자파 흡수율(SAR)을 전자기장 노출량의 단위로 사용한 동물 및 세포 연구 논문과 휴대폰 및 PDA에 대한 전자파 흡수율 시험 성적서를 대상으로 출력 전력, 전력 밀도 등과 SAR의 상관 관계 및 회귀 관계를 분석하였다. 동물 실험의 경우 전력 밀도와 SAR이, 세포 실험의 경우 출력 전력이 duty factor를 고려한 SAR과 통계적으로 유의한 상관 관계를 보였다. 회귀분석에서의 노출 불확실성을 평가하기 위해 결정계수값을 분석하였다. 각각의 실험장치 및 방법에 대한 해석 또는 측정 기법의 분석 이전에 본 연구 방법을 실시하여 대상 연구군의 특성을 고찰한다면 보다 효율적인 전자기장노출신뢰성 평가를 실시할 수 있을 것으로 판단된다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.229-234
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• 2002

Under the hostile influence of the extreme space environmental conditions due to the deep space and direct solar flux, the thermal control in space applications is especially of major importance. There are tight temperature range restrictions for electro-optical elements while on the other hand there are low power consumption requirements due to the limited energy sources on the spacecraft. So, we usually have strong requirement of thermal and power control module in space applications. In this paper, the design concept of a thermal and power control module in the MSC(Multi-Spectral Camera) system which will be a payload on KOMPSATII is described in terms of H/W & S/W. This thermal and power control module, called THTM(Thermal and Telemetry Module) in MSC, resides inside the PMU(Payload Management Unit) which is responsible for the proper management of the MSC payload for controlling and monitoring the temperature insides the EOS(Electro-Optic System) and gathering all the analog telemetry from all the MSC sub-units, etc. Particularly, the designed heater controller has the special mode of "duty cycle" in addition to normal closed loop control mode as usual. THTM controls heaters in open loop according to on/off set time designed through analysis in duty cycle mode in case of all thermistor failure whereas it controls heaters by comparing the thermistor value to temperature based on closed loop in normal mode. And a designed THTM provides a checking and protection method against the failure in thermal control command using the test pulse in command itself.

• 시큐리티연구
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• 제28호
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• pp.79-102
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• 2011

본 연구는 오재환(2010)의 후속연구로 개선된 교육 프로그램이 민간경비원의 직무만족 및 직무성과에 미치는 영향을 확인하는 것이 목적이다. 이를 위해 오재환(2010) 연구에서 선정된 서울, 경기 지역에 거주하고 있는 민간경비원 170명을 대상으로 유의 표집하여 설문조사를 실시하였다. 수집된 자료는 SPSS 15.0를 활용하여 빈도분석, 상관분석, 다중 회귀분석을 실시하였다. 설문지의 신뢰도 Cronbach's ${\alpha}$ 값은 0.800 이상으로 나타났다. 본 연구의 분석 결과는 다음과 같다. 해당 프로그램의 교육훈련 내용이 증가하면 직무만족 및 직무성과가 증가되는 것으로 나타났다. 이는 개선된 교육프로그램의 내용이 METT, 행동촉발질문과 같은 과학적이고 체계적인 기법이 포함되어 있고, 실무교육이 적절하게 구성되어 있어 민간경비원으로 하여금 자신감 있는 근무를 할 수 있게 하고, 시대의 흐름을 적절하게 반영하였으며, 민간경비원의 업무와도 직접적으로 관련성이 높아 업무에 활용될 수 있는 가능성이 높다는 것을 의미한다.

• 융복합기술연구소 논문집
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• 제2권1호
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• pp.24-30
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• 2012

In this study, the trucks(2.9-liter) have been developed to use DME as fuel, and performance test of the vehicle's DME engine, power, emissions, fuel economy and vehicle aspects was conducted. For experiments, the fuel system(common-rail injectors and high-pressure pump included) and the engine control logic was developed, and ECU mapping was performed. As a result, the rail pressure from 40MPa to approximately 65% increase compared to the base injector has been confirmed that. Also, the pump discharge flow is 15.5 kg/h when the fuel rail pressure is 400rpm(40 MPa), and the pump discharge flow is 92.1 kg/h when the fuel rail pressure is 2,000rpm(40MPa). The maximum value of full-load torque capability is 25.5kgfm(based on 2,000rpm), and more than 90% compared to the level of the diesel engine were obtained. The DME vehicle was developed in this study, 120 km/h can drive to the stable, and calculated in accordance with the carbon-balance method of fuel consumptions is 5.7 km/L.

• 한국수소및신에너지학회논문집
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• 제12권3호
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• pp.169-176
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• 2001

The purpose of study is to obtain low-emission and high-efficiency in LPG engine with hydrogen enrichment. The test engine was named heavy-duty variable compression ratio single cylinder engine (VCSCE). The fuel supply system provides LPG/hydrogen mixtures based on same heating value. Various sensors such as crank shaft position sensor (CPS) and hall sensor supply spark timing data to ignition controller. Displacement of VCSCE is $1858.2cm^3$. VCSCE was runned 1400rpm with compression ratio 8. Spark timing was set MBT without knocking. Relative air-fuel ratio(${\lambda}$) of this work was varied between 0.76 and 1.5. As a result, i) Maximum thermal efficiency occurred at ${\lambda}$ value 1.0. It was shown that thermal efficiency was increased approximately 5% with hydrogen enrichment at same ${\lambda}$ value. ii) Engine-out carbon monoxide (CO) emissions were decreased at a great rate under LPG/hydrogen mixture fuelling. iii) Total hydrocarbon (THC) emission was much exhausted in rich zone, same as CO. But THC was exhausted a little bit more in lean zone. iv) Finally, engine-out oxides of nitrogen (NOx) was increased with ${\lambda}$ value 1.0 zone at a greater rate with hydrogen enrichment due to high adiabatic flame temperature.

• Journal of Power Electronics
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• 제12권1호
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• pp.164-171
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• 2012

Variable step size maximum power point trackers (MPPTs) are widely used in photovoltaic (PV) systems to extract the peak array power which depends on solar irradiation and array temperature. One essential factor which judges system dynamics and steady state performances is the scaling factor (N), which is used to update the controlling equation in the tracking algorithm to determine a new duty cycle. This paper proposes a novel stability study of variable step size incremental resistance maximum power point tracking (INR MPPT). The main contribution of this analysis appears when developing the overall small signal model of the PV system. Therefore, by using linear control theory, the boundary value of the scaling factor can be determined. The theoretical analysis and the design principle of the proposed stability analysis have been validated using MATLAB simulations, and experimentally using a fixed point digital signal processor (TMS320F2808).

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권6호
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• pp.299-305
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• 2006

In this paper, we suggest a new space vector PWM modulation method with very short processing time which does not need identification of nearest three vectors(NTV) and duty ratio for each vector. The suggested PWM method makes mean value of phase voltage to be same as reference during every modulation period by use of a triangle in small hexagon on multi-level vector space. This paper described the suggested modulation method can be successfully applied to the space vector modulation use of multi-level inverter by computer simulations and experiments.

• 한국재료학회지
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• 제17권1호
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• pp.56-59
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• 2007

Recently, requirement for the ultra thin copper foil increases with smaller and miniaturized electronic components. In this study, we evaluated the surface morphology, crystal phase ana surface roughness of the copper film electrodeposited by pulse method without using additives. Homogeneous and dense copper crystals were formed on the titanium substrate, and the optimum condition was 25% duty cycle. Moreover, the surface roughness(Ra), $0.295{\mu}m$, is the smallest value in this condition. It is thought that this copper foil is good for electromigration inhibition due to the preferential crystal growth of Cu (111)

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.171-172
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• 2011

The paper proposes a close loop control algorithm for Z-source inverter. The algorithm is realized by PWM duty ratio control in order to improve the output voltage to it's desired level. The controller consist of the output voltage PID controller and DC input voltage P controller. Using the DQ coordinate transformation simplify the controller design. The PSIM simulation results verify the validity by means of comparing the system with or without compensation and estimating if the system has output consistency function when ZSI's load and input voltage value changing.