• 대한의용생체공학회:의공학회지
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• 제29권5호
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• pp.364-370
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• 2008

Recent development in large area flat-panel x-ray detector technology enables clinical application of digital tomosyntesis. Unlike conventional motion tomography using x-ray films, flat-panel x-ray detectors provide projection images in digital formats so that tomographic images can be synthesized in a more flexible way. For the digital tomosynthesis, precise movements of the x-ray source and the x-ray detector with respect to a fulcrum point are necessary. In this study, we apply the digital tomosynthesis technique to the flat-panel detector based micro-CT in which the flat-panel detector and the x-ray source rotate together on a circular arc. The experimental results suggest that flat-panel detector based 3D CTs can be used for digital tomosynthesis in the clinical environment.

• 한국정보전자통신기술학회논문지
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• 제12권1호
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• pp.78-82
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• 2019

본 논문에서는 수배전반 내 코로나 및 직렬아크 발생 시 나타나는 초음파 신호의 측정 및 분석에 대해 기술하였다. 휴대용 초음파 감지기는 전기 시스템에서 발생하는 코로나와 같은 방전 현상 감지에 유용하다. 그러나 일반적인 휴대용 초음파 감지기는 방전 여부에 대한 판단 결과가 사용자의 주관적 반응에 영향을 미치며, 음향 특성을 듣고 결과를 예측함으로써 문제 유형을 판별하는 것이 어렵다는 단점을 가지고 있다. 따라서 초음파 특성을 구별하는 새로운 분석 방법이 필요하다. 본 논문에서는 초음파 감지기로 측정 한 초음파 음향을 시각화하기 위한 초음파 분석 사례를 연구하였다. 실험 결과 초음파탐지계통은 외부소음의 영향을 받지 않고 배전반에서 코로나 및 직렬 아크 방전을 검출할 수 있었다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.379-381
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• 2002

A single CdZnTe detector is tested for suitability in a prototype CT/ SPECT system designed to acquire both emission and transmission data. The detector has the size of 1${\times}$l-cm$^2$ with 4${\times}$4 1.5${\times}$l.5mm$^2$ pixellated anodes. Since the detector is smaller than imaged object, we translated it in an arc centered at the x-ray tube to image larger objects. Pulse counting electronics with very short shaping time (50 ns) are used to satisfy high photon rates in x-ray imaging, and response linearity up to 3${\times}$10$\^$5/ counts per second per detector element is achieved. The energy resolution of 122-keV gamma-ray is measured to be 14%. We have characterized the system performance by scanning a radiographic resolution phantom .and the Hoffman brain phantom. The spatial resolution of CT and SPECT are about 1 mm and 7 mm, respectively.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.407-410
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• 2002

A three-phase 6/8 structure Switched Reluctance Motor drive, the construction of the stator and the rotor. in the motor, the scheme of the rotor position detector and the main circuit of the power converter are described. The range of the stator pole arc factor and the rotor pole arc factor of the motor are analyzed in the linear region. The optimum range of the stator pole arc factor and the optimum range of the turn-off angle of the main switches in the power converter are given with the 2-D finite element electro-magnetic field calculation of the motor and the nonlinear simulation. Test jesuits of the developed prototype are discussed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.9-11
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• 2018

This paper studies on the development of an electric fire prevention system with the detection and alarm in case of parallel arc fault occurrence in low voltage distribution lines. The proposed detector has the characteristics of high speed operation responsibility and superior system reliability from composition using a large number of semiconductor devices. The line voltage is always feedback, and when an arc or a spark occurs, these are detected by the microcomputer. In addition, we design and develop algorithms using high speed and high precision microcomputer. A new conceptual control technique is adopted that RCD cuts-off by forming a forced short circuit between the phase voltage and ground in the event of an electrical accident. Some experimental tests of the proposed system also confirm practicality and the validity of the analytical results.

• Current Optics and Photonics
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• 제5권4호
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• pp.375-383
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• 2021

We present a simulation method to design antireflection coating (ARCs) for fiber-coupled superconducting nanowire single-photon detectors. Using a finite-element method, the absorptance of the nanowire is calculated for a defined unit-cell structure consisting of a fiber, ARC layer, nanowire absorber, distributed Bragg reflector (DBR) mirror, and air gap. We develop a method to evaluate the uncertainty in absorptance due to the uncontrollable parameter of air-gap distance. The validity of the simulation method is tested by comparison to an experimental realization for a case of single-layer ARC, which results in good agreement. We show finally a double-layer ARC design optimized for a system detection efficiency of higher than 95%, with a reduced uncertainty due to the air-gap distance.

• 한국철도학회논문집
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• 제13권1호
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• pp.37-43
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• 2010

전차선과 팬터그래프는 전기철도차량에 전력을 공급하기 위해 사용된다. 전기철도차량 운행 시 전차선과 팬터그래프 사이의 불안정한 접촉에 의하여 아크가 발생하며 이는 고장 및 사고의 원인이 된다. 따라서 아크를 검출하고 전차선 유지보수를 위한 아크 검측 시스템의 필요성이 요구되고 있다. 본 논문에서는 이러한 전차선 아크 검측 시스템의 개발에 관하여 기술하였다. 아크는 광 검출기를 이용하여 간접 측정하며 가선 전압/전류, 전차선의 높이, 주행속도, 발생위치와 온/습도를 동영상과 함께 저장한다. 개발된 시스템은 서울-동대구간 하행선에서 시험 검측하고 평가하였다. 실험 결과, 아크 발생 및 강도는 가신 전압/전류, 팬터그래프의 높이, 속도에 크게 영향을 받는 것으로 나타났다.

• 전기학회논문지
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• 제63권6호
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• pp.855-859
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• 2014

Quality criteria for interaction between a pantograph and overhead contact wire is a most important requirement to assess of the performance for the current collection system. Interaction performance between pantograph and catenary system is subject to approval by the infrastructure manager when a new design and contraction of overhead contact line and pantograph are installed. Among the various performance, percentage of arcing at maximum line speed is a simple test method compared with contact force of pantograph due to direct sensing of pantagraph, calibrations, installations of train, and etc. On the other hand, percentage of arcing is need to reliable arcing detector and general requirements with accordance with EN 50317. In this paper, percentage of arcing are investigated on the function of duration of arc and proposed which is satiable of percentage of arcing. As a results, we proposed which duration of arcs are unsuitable from infrastructures point of view as performance testing for quality of current collection.

• 전기학회논문지
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• 제61권8호
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• pp.1216-1220
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• 2012

The current collection between pantograph and contact wire is a more critical component for need to train speed up in electric railway. The basic purpose of this paper is to establish a measure of determining arc by developing an arc detector assessment system. The system was designed under conditions of EN 50317 and simulations were conducted using the developed device. According to the results, it was possible to conduct certification tests following regulations of international standards. To check the validity of our approach for the intended application, we analysis contact loss of catenary system using developed arcing measurement system in Korea. The proposed arcing measurement system is expected to enhance precision of current collection quality performance assessment methods at high-speed lines and conventional lines.

• Radiation Oncology Journal
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• 제20권4호
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• pp.391-395
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• 2002

목적 : 서울대학교병원에서 개발한 정위방사선수술 시스템에서의 표준적 정위방사선수술기법을 적용시 중심점에서의 방사선량 오차를 확인하고자 하였다. 재료 및 방법 : 내경 10 mm 20 mm인 원통형의 3차 콜리메이터를 장착후 5개의 호형(arc)으로 구성된 표준형 정위방사선수술계획에 따라 시행한 정위방사선수술시의 선량을 측정하였다. 방사선은 CL2100C 선형가속기에서 발생하는 6 MV X-선을 사용하였고 자체 개발한 다용도 팬톰에서 0.125 cc 전리함 및 다이오드 검출기로 중심점 선량을 측정하였다. 결과 : 내경 20 mm인 3차 콜리메이터를 장착한 정위방사선수술 시행시 호형에 따른 계획선량과 측정선량 간 오차는 0.125 cc 전리함 측정시 $-0.73\%$ 내지 $-2.69\%$, 다이오드 검출기 측정시 $-1.29\%$ 내지 $-2.91\%$이었다. 내경 10 mm 인 3차 콜리메이터 장착한 경우의 오차는 다이오드 검출기로 측정하였을 때 $-2.39\%$ 내지 $-4.25\%$이었다. 결론 : 중심점 선량 오차는 약 $3\%$ 정도로서 DICOM 3.0 표준형식을 통한 영상자료 처리 등의 개선책을 통한 최소화 노력이 필요하다.