• 시큐리티연구
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• 제51호
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• pp.199-219
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• 2017

이 연구는 초등학교 주변에 설치된 방범용CCTV가 범죄를 감소하는 효과가 있는지를 검증하였다. 이를 위해 춘천시에 설치된 9개의 방범용CCTV의 위치와 종류에 관한 데이터 및 춘천시의 범죄데이터가 수집되었다. 분석단위로 월 단위가 사용되었으며, 날짜, 월평균 온도, 범죄 추이를 통제한 후 포아송 회귀분석을 이용하여 분석하였다. 분석결과는 초등학교 주변에 설치된 방범용CCTV로 인해 전체범죄와 중범죄가 감소하였음을 보여주었다. 그러나 경범죄에서는 그러한 결과가 나타나지 않았다. 본 연구는 방범용CCTV가 초등학교 인근에 설치되었을 때 중범죄율과 전체범죄율을 낮추는 데 도움을 줄 수 있음을 시사한다.

• 한국측량학회지
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• 제32권6호
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• pp.591-597
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• 2014

A wide variety of image application methods, such as aerial image, terrestrial image, terrestrial laser, and stereo image point are currently under investigation to develop three-dimensional 3D geospatial information. In this study, matching points, which are needed to build a 3D model, were examined under diverse weather conditions by analyzing the stereo images recorded by closed circuit television (CCTV) cameras installed in the U-City. The tests on illuminance and precipitation conditions showed that the changes in the number of matching points were very sensitively correlated with the changes in the illuminance levels. Based on the performances of the CCTV cameras used in the test, this study was able to identify the optimal values of the shutter speed and iris. As a result, compared to an automatic control mode, improved matching points may be obtained for images filmed using the data obtained through this test in relation to different weather and illuminance conditions.

• 한국자동차공학회논문집
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• 제15권4호
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• pp.139-145
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• 2007

The motion of single-rod cylinder is typically controlled by the directional control valve. In some case, the hydraulic system should be energized by the man power and at the same time the motion of a cylinder is controlled manually. It may be confusing for a man to do two things at the same time. The solution is to make up the closed hydraulic circuit with the bi-directional pump and single-rod cylinder without using a directional control valve. In the case of single-rod cylinder, the flows at the rod side and head side are so different that several valves should be installed to make the motion of single-rod cylinder possible. The hydraulic system is composed of a bi-directional pump, a single-rod cylinder, pilot operated check valves, a check valve and a counter balance valve for the purpose of actuating the lifter. The characteristics of a suggested system are analysized mathematically and numerically.

• 한국축산시설환경학회지
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• 제20권4호
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• pp.173-176
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• 2014

This study was conducted to investigate the effect of weaning period on the vocalization frequency of Hanwoo calf. Twelve Hanwoo calves were allocated into 4 groups, control (forced weaning on 90days) and treatment (weaning on 70, 90 and 120days with 5 adaptation days). After weaning, behavior and vocalization of Hanwoo calves were recorded on 3 consecutive days with closed circuit television (DTC-R5254, Digite Co., Ltd., Korea) and digital audio tape recorder (SR-900, Idamtech Co., Ltd., Korea). Vocalization frequency of Hanwoo calf were not significance difference with control and treatment group. Thus, additional studies of feed intake and body weight gain were needed to determine the weaning period of Hanwoo calves.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.2148-2150
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• 1998

This paper proposes a constant frequency controlled zero voltage switching method that can reduce switching losses caused by emf on inductance in DC motor. The zero voltage switching method is used more than a zero current switching method because of reducing switching losses by capacitance of depletion region of MOSFET. To simplify the controller circuit, we propose constant frequency controlled zero voltage switching method in the paper. The control method is more stable than a variable frequency control method because it can optimize bandwidth of a closed-loop and reactances. Therefore, we construct a constant frequency controlled zero voltage switching converter and improve zero switching losses in high switching frequency. In the process, we can control low-losses in full range on variable voltage and load. We simulate the proposed converter with P-SPICE and compare results obtained through the experiment.

• 한국세라믹학회지
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• 제34권10호
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• pp.1027-1036
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• 1997

The reology and several physical properties of cements are studied by varying the different mineral composition and particle size distribution(PSD) of cements with closed circuit ball mill for high workability, low heat of hydration, and high strength. In this study, we found that the workability of concretes is related to the viscosity of cement, and affects to strength. Here, this workability is affected by mineral composition (C3A) and the PSD. Especially, rosin-rammer index and 44${\mu}{\textrm}{m}$ residue in the PSD of cements are affected to water demand, casting property, slump loss, strength of cements. From the above results, the conditions of cement for high workability, low heat of hydration and high strength are to use low C3A clinker, 5-10% slag addition, and to grind cement below 0.7 rosin-rammer index, above 3.5-4.5% 44 ${\mu}{\textrm}{m}$ residue, 4000$\pm$100 $\textrm{cm}^2$/g blaine. Such cements are, therefore, supurior to super low heat cement and slag-blended cement in comparing the physical properties of strength, slump, slump-flow, adiabetic temperature, etc.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.653-658
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• 2008

Service areas in the urban transit need to construct the intelligent integrated surveillance system, because they are the public places that many people get together at one time. In past, analogue, closed-circuit televisions and analogue video recorders are used to construct the surveillance system. Now, a lot parts of the analogue systems that depend on the images have been changed to the complicated system, which consists of sensors and images and also, to be digitalized. In past, the surveillance system was used as an inspection devices to examine the spots after happening some events. But, with a high level of the computer and communication technologies, it is possible that the digitalized data leads the intelligence systems to prevent some accidents by using the various analysis techniques. And the data could be used to decide surveillance policies and provide some information on the safety and management policies as well as surveillance policies. In this paper, we define the intelligent surveillance system and suggest the major functions of the system. Also, we suggest the fundamental functions that every part should get and describe the way to develop the system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.106-108
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• 2008

This paper deals with the design for speed controller to drive PMSM by matrix converter without DC-link circuit as the power conversion system of AC servo motor drive. To design the speed controller of PMSM drive, the closed-loop transfer function of speed controller is calculated and then the frequency-domain response characteristics are analyzed by bode plot using Matlab. Based on the results by bode plot, the speed control gains are determined. As the real effects of controller designed in the frequency-domain display in the time-domain, the performance of speed controller is confirmed by the step response of speed controller. The design examples are shown and its validity of the design method mentioned in the paper is verified through PSIM simulation.

• 전자공학회논문지SC
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• 제39권6호
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• pp.59-70
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• 2002

본 논문에서는 최적 효율과 고성능으로 동작하는 SynRM(Synchronous Reluctance Motor)을 위한 위치 및 속도 센서리스 벡터제어를 제시한다. 제시한 제어 방법은 고정자 전압과 전류의 자속 추정에 기초한다. 그리고 동손과 철손을 최소화하는 효율 최적화의 전류각 조건은 SynRM의 등가회로를 기초로 유도한다. 폐루프 위치 및 속도 제어의 연구결과는 최적화 제어의 입증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.522-524
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• 2018

A New Direct AC LED Driver has been proposed for wide output power range and precise constant current regulation using an advanced auto commutation topology. The conventional shunt regulation method provides a stepped input current shape by fixed regulation references in the linear regulator of the each channel, which results in poor current regulation and high THD. The conventional method needs to assign a linear regulator in each LED channel so that the number of linear regulator increases when extending the number of channels especially at high power application. The proposed regulation method can drive multiple switches to regulate each LED channel current by a single amplifier with sinusoidal reference so that large number of LED channel can be simply extended with less BOM cost and low THD is obtained with the accurate current regulation thanks to the sinusoidal input current control in the closed loop control. To confirm the validity of the proposed circuit, theoretical analysis and experimental results from a 20-W LED driver prototype are presented.