• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권9호
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• pp.430-435
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• 2002

The $SF_{6}$ gas insulated power equipments have the insulation systems which are composed of $SF_{6}$ gas and insulation paper. It is repored that their insulation abilities are influenced by the $SF_{6}$ gas gaps in those insulation systems and gas pressures. This paper describes partial discharge phenomena with $SF_{6}$ gas pressures in insulation system of $SF_{6}$ gas-insulation paper Specimens of $SF_{6}$ gas-insulation paper were prepared and aramid paper was used as insulation paper. Partial discharge inception voltages(PDIV) and breakdown voltages for the existence of $SF_{6}$ gas gaps were measured by short term tests with gas pressures. Also, average PD quantities and pulse counts, life times of each specimens were calculated from the results of long term aging tests with gas pressures. It was found that the $SF_{6}$ gas gaps decrease increasing rates of PDIV and brealdown voltages according to gas pressure increase and the insulation breakdown caused by the smaller PD quantities than 1[pC] at the high gas pressure of 300kPa is due to the increase of energy density with increase of gas pressure.

• 센서학회지
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• 제5권5호
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• pp.11-20
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• 1996

본 연구에서는 가속기에서 발생하는 치료방사선을 방사선원으로 사용하여 다이오드 치료방사선 검출센서의 특성을 조사하였다. 방사선량에 따른 선형성, 재현성, 오차율, 에너지의존성, 방사선조사후의 감도변화량, 다이오드의 숫자에 따른 출력값 측정 및 Portal 영상을 위한 가능성 검사를 위해서 핵계측기를 이용한 펄스 성형(成形)을 시도하였다. 제작된 시스템의 효율성을 검증하기 위하여 구성된 다이오드 센서로 조사야(照射野)별 심부량(深部量)를 백분율을 기존의 측정장치인 기체 전리함을 이용한 값과 상호 비교하여 보았다. 또한 다이오드의 선량측정회로를 다채널로 구성하여 A/D 변환후 컴퓨터 상에서 치료영역의 범위를 읽을 수 있었다. 모형인체(模型人體)를 치료대 위에 놓고 읽은 출력값과 모형인체(模型人體)없이 직접 읽은 출력값을 비교하여 Portal 영상을 위한 가능성을 제시하여 보았다.

• 한국항공우주학회지
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• 제44권9호
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• pp.789-795
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• 2016

이차 추진제로 많이 쓰이는 알루미늄을 고출력 레이저를 조사하여 공기 중의 산소와 반응시켜 발생되는 알루미늄과 산소의 화학 반응을 레이저 분광분석법을 이용하여 연구를 수행 하였다. 7ns의 펄스 주기와 1064nm의 주파수를 가진 Q-switched Nd:YAG 레이저로 40 - 2500mJ($6.88{\times}10^{10}-6.53{\times}10^{11}W/cm^2$)의 에너지가 공급되었으며, 플라즈마 빛은 echelle 회절 분광기와 ICCD 카메라로 감지하였다. 분광분석을 통하여 알루미늄과 산소의 원자/분자 신호 분석과 현상이 일어나는 플라즈마 환경의 특성 연구를 위해 들뜸 온도(2200K~6600K) 및 전자밀도($3.15{\times}10^{15}{\sim}2.38{\times}10^{16}cm^{-3}$) 계산, 그리고 알루미늄 표면의 크레이터(Crater) 분석을 수행하였다. 본 연구는 고 레이저 복사 조도 환경하에서 발생되는 화학 반응과 플라즈마의 특성을 파악하는 방법을 제시하고 있다.

• 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.

• Journal of the Korean Wood Science and Technology
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• 제41권2호
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• pp.164-172
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• 2013

The purpose of this research was development of quantitative ultrasonic test methodology for detecting internal defects in members of ancient wooden building. Connection part between wooden members and/or contacted or hidden part by wall of ceiling or other construction materials make it hard to apply direct way of ultrasonic test. So indirect way of ultrasonic test needed to be applied. Test methodology with newly developed prototype of ultrasonic system was proposed. Homogeneous material with polypropylene was also tested for establishing the criterion. Results showed that TOF(time of flight)-energy and pulse length were found out to be proper ultrasonic parameters for predicting depth of defect in wood different from polypropylene. It was not possible to directly apply prediction equation derived from polypropylene. Newly established prediction equation shows coefficient of determination of 0.73 for wood. Finally, defect of replaced rafter members was predicted with the coefficient of determination of 0.32. Various aspects of ultrasound propagation in wood including anisotropy need to be carefully considered to raise up the prediction accuracy.

• Nutrition Research and Practice
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• 제9권5호
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• pp.496-502
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• 2015

BACKGROUND/OBJECTIVES: This study was performed to investigate the association between the dietary intake of fish and shellfish, and omega-3 polyunsaturated fatty acids (PUFAs) and cardiovascular disease (CVD) risk factors in the middle-aged Korean female patients with Type 2 diabetes (T2D). SUBJECTS/METHODS: A cross-sectional analysis was performed with 356 female patients (means age: 55.5 years), who were recruited from the Huh's Diabetes Clinic in Seoul, Korea between 2005 and 2011. The dietary intake was assessed by a validated semi-quantitative food frequency questionnaire and analyzed using the Computer Aided Nutritional Analysis program (CAN-Pro) version 4.0 software. RESULTS: In a multiple regression analysis after the adjustment for confounding factors such as age, BMI, duration of diagnosed T2D, alcohol consumption, fiber intake, sodium intake, and total energy intake, fish and shellfish intake of the subjects was negatively associated with triglyceride and pulse wave velocity (PWV). Omega-3 PUFAs intake was negatively associated with triglyceride, systolic blood pressures, diastolic blood pressures, and PWV. The multiple logistic regression analysis with the covariates showed a significant inverse relationship between the omega-3 PUFAs consumption and prevalence of hypertriglyceridemia [OR (95% CI) for greater than the median compared to less than the median: 0.395 (0.207-0.753)]. CONCLUSIONS: These results suggest that the consumption of fish and shellfish, good sources of omega-3 PUFAs, may reduce the risk factors for CVD in the middle-aged female patients with T2D.

• 디지털융복합연구
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• 제16권12호
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• pp.309-315
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• 2018

방전 현상을 에너지로 이용하여 금속을 가공하는, 특히 초경 및 난삭 소재의 가공과 정밀가공에 효과적인 방전가공 시 빠른 가공속도와 향상된 정밀도 및 면조도를 달성하기 위하여 효율적인 아크의 검출과 제어방법에 대해 연구하였다. 단일 방전 파형을 Td(Time-Delay), Ton(Time-on), Toff(Time-off)의 세 가지 구간으로 나누어 HDL 언어를 이용하여 게이트 제어 타이밍을 시뮬레이션 하고, 실제 방전가공기에 적용하여 파형을 실측하였으며, 비교기 회로를 통한 Td 구간의 샘플링을 통해 서보기구의 동작을 결정함으로써 전극과 가공물 간의 간격 제어와 가공 결과에 미치는 영향을 분석하였다. 분석결과 형성되는 파형의 Td 구간을 보다 정밀하게 고속으로 샘플링하여 이를 토대로 전극과 가공물 간의 gap 제어에 적용하였을 때 보다 향상된 결과를 나타내었다.

• 한국인터넷방송통신학회논문지
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• 제18권6호
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• pp.99-105
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• 2018

본 논문은 VLC (Visible Light Communication)의 컬러그리드 변조방식을 이용하여 스마트 도어락 시스템을 구현하기 위한 다중접속 방식을 제안한다. 컬러그리드 변조방식을 이용하여 도어락으로 접근하는 다수의 사용자를 인식하고 인증하기 위하여 가시광 신호를 다중으로 접속하는 방법이다. 기존 인프라를 이용하여 가시광 다중 접속을 가능하게 하기 위해서는 신호의 심벌 에너지 간격을 최대한 넓게 해야한다. 따라서 이와 같은 가시광 컬러그리드 기반 심벌을 모듈레이션하여 가시광 채널에서 제안된 시스템의 성능을 측정한다. 다중 접속 사용자의 수를 인식하는 도어락 시스템을 구현하기 위한 변조신호의 실제 채널 실험 결과를 보인다.

• Journal of Ceramic Processing Research
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• 제20권5호
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• pp.484-489
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• 2019

VO2 is an attractive candidate as a transition metal oxide switching material as a selection device for reduction of sneak-path current. We demonstrate deposition of nanoscale VO2 thin films via thermal atomic layer deposition (ALD) with H2O reactant. Using this method, we demonstrate VO2 thin films with high-quality characteristics, including crystallinity, reproducibility using X-ray diffraction, and X-ray photoelectron spectroscopy measurement. We also present a method that can increase uniformity and thin film quality by splitting the pulse cycle into two using scanning electron microscope measurement. We demonstrate an ON / OFF ratio of about 40, which is caused by metal insulator transition (MIT) of VO2 thin film. ALD-deposited VO2 films with high film uniformity can be applied to next-generation nonvolatile memory devices with high density due to their metal-insulator transition characteristic with high current density, fast switching speed, and high ON / OFF ratio.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.939-946
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• 2023

Comprehensive Research Facility for Fusion Technology (CRAFT) is an integration of different demonstrating or testing facilities, which aim to develop the critical technology or composition system towards the fusion reactor. Due to the importance and challenge of the negative ion based neutral beam injection (NNBI), a NNBI test facility is included in the framework of CRAFT. The initial object of CRAFT NNBI test facility is to obtain a H⁰ beam power of 2 MW at the energy of 200-400 keV for the pulse duration of 100 s. Inside the negative ion accelerator of NNBI system, the interactions of the negative ions with the background gas and electrodes can generate abundant stray electrons. The stray electrons can be further accelerated and dumped on the electrodes or eject from the accelerator. The stray electrons, including the ejecting electrons, cause the unwanted particle and heat flux onto the electrodes and the inner components of beamline (especially the temperature sensitive cryopump). The suppression of the stray electrons from the CRAFT accelerator is carried out via a series of design and simulation works. The paper focuses the influence of different magnetic field configurations on the stray electrons and the character of the ejecting electrons.