• 대한방사선기술학회지:방사선기술과학
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• 제10권1호
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• pp.31-35
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• 1987

Authors have investigated actual conditions of 22 hospitals throughout the Seoul district to evaluate of chest radiographic systems. The results are as followed: 1. Concerning exposure factors, most hospitals have used low tube voltage, merely two hospitals high tube voltage, that is, over 120 kVp. Roughly halves of intensifying screens have been used in hospitals were medium speed screens, and the rests were high speed screens. 2, Surface doses existed within wide range of $10{\sim}63.5mR$, and image quality value were $5.60{\sim}7.49$. 3. The minimum perceptibility of Burger Phantom have been increased with contrast improvement.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.327-327
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• 2011

A nonthermal bioplasma source was developed for application to human liquid fluids by making use of nano-size tungsten tips. Characteristics of the plasma source are investigated. Here we have used the AC voltage system. The bioplasma source generated by a tungsten tip with quartz tube and ground electrode is a low-temperature plasma without making any noticeable damage to cells at a low power operation. The breakdown voltage and current signals are measured by high voltage probe (Tektronix P6015A) and current probe (P6021). Variation of breakdown temperature near the tip electrode is larger than that in the neighborhood of ground electrode. Bubble formation during discharge has been recorded and investigated by using the high speed camera. The existence and behavior of hydroxyl and superoxide radicals are detected and measured by spectrometers. The electrical and optical properties of breakdown characteristics are also investigated.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.194-197
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• 2003

The actively addressable carbon nanotube (CNT) emitters have been studied for stable and low-voltage driving field emission display (FED). The a-Si TFT and screen-printed CNT emitters were successfully integrated to fabricate the diode type active-matrix cathode and FED panel. Also, we propose a new FED architecture based on the actively controlled triode CNT emitters showing the properties of ideal triode type cathode with electron beam focusing effect.

• 전기학회논문지
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• 제57권3호
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• pp.403-408
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• 2008

The gyroscope is the sensor for detecting the rotation in inertial reference frame and constitute the navigation system together an accelerometer. As the inertial reference equipment for attitude determination and control in the satellite, the mechanical gyroscope has been used but it bring the disturbance for mass unbalance so the disturbance give a bad influence to the observation satellite mission because the mechanical gyroscope has the rotation parts. During the launch. The mechanical gyroscope is weak in vibration, shock and has the defect of narrow operating temperature range so it need the special design in integration. Recently the low orbit observation satellite for seeking the high pointing accuracy of image camera payload accept the FOG(Fiber Optic Gyro) or RLG(Ring Laser Gyro) for the attitude determination and control. The Ring Laser Gyro makes use of the Sanac effect within a resonant ring cavity of a He-Ne laser and has more accuracy than the other gyros. It need the 1000V DC to create the He-Ne plasma in discharge tube. In this paper, the design process of the High Voltage Power Supply for RLG(Ring Laser Gyroscope) is described. The specification for High Voltage Power Supply (HVPS) is proposed. Also, The analysis of flyback converter topology is explained. The Design for the HVPS is composed of the inverter circuit, feedback control circuit, high frequency switching transformer design and voltage doubler circuit.

• Imaging Science in Dentistry
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• 제48권2호
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• pp.103-109
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• 2018

Purpose: To analyze cone-beam computed tomography (CBCT) use, indications, and exposure parameters in San $Jos{\acute{e}}$, Costa Rica. Materials and Methods: A cross-sectional study was performed. All CBCT examinations over a period of 6 months at 2 radiological centers in San $Jos{\acute{e}}$, Costa Rica were evaluated. The examinations were performed with Veraview EPOC X550 and Veraviewepocs 3D R100 equipment. The patients' age and sex, clinical indication for CBCT, region of interest (ROI), repeat examinations, specialty of the referring dentist, field-of-view (FOV), tube voltage (kV), tube current (mA), and radiation dose (${\mu}Gy$) were evaluated. Patients were classified by age as children (${\leq}12years$), adolescents(13-18 years), and adults(${\geq}19years$). Results: The mean age of the 526 patients was 49.4 years. The main indications were implant dentistry and dental trauma. The most frequent ROIs were posterior, while anterior ROIs were much less common. The highest percentage of repeat examinations was in children. Fifty-six percent of the referring dentists were specialists. The most commonly used FOV was small. The mean tube voltage and current were 79.8 kV and 7.4 mA for Veraview EPOC X550 and 89.9 kV and 6 mA for Veraviewepocs 3D R100, respectively. The mean doses for children, adolescents, and adults were $6.9{\mu}Gy$, $8.4{\mu}Gy$, and $7.8{\mu}Gy$, respectively. Conclusion: Although CBCT was most commonly used in adults for implant dentistry, most repeat examinations were in children, and the highest mean dose was in adolescents. Additional dose optimization efforts should be made by introducing low-dose protocols for children and adolescents.

• 대한방사선기술학회지:방사선기술과학
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• 제43권2호
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• pp.79-85
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• 2020

The influence of metal artifact in CT image depends on the type of metal materialsm, the reconstruction algorithm, and scan parameters. The presence of metal artifacts was quantitatively evaluated by applying the standard and MAR algorithms through the phantom study. In the change of tube voltage applied the standard algorithm, metal artifact decreased to 44.9% for 80 vs 120 kVp, 24% for 100 vs 120 kVp, while the image taken at 140 kVp increased the artifact by 19% compared to 120 kVp. When the tube current was increased from 100 to 300 mA, there was no significant difference in the CT value and noise. Black band and white strike artifacts occurred up to 65.9% in the adjacent ROI of the metal driver, whereas titanium screw produced lesser metal artifact than that of the metal driver. The combination of 120kVp or higher tube voltage-standard algorithm was effective in removing black band artifacts as well as white streak by high density materials. However, MAR reconstruction algorithm was useful in improving image quality under the environment of low kVp and high density materials, without increase of radiation exposure.

• 한국방사선학회논문지
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• 제17권6호
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• pp.859-863
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• 2023

본 연구에서는 엑스선 증감지와 광센서, 마이크로컨트롤러(MCU)를 이용하여 휴대와 이동이 용이한 교육용 방사선검출기를 제안하였다. 광센서와 증감지로 이루어진 검출부와 마이크로컨트롤부로 간단하게 구성되어 제작이 쉽고 소형화 및 휴대형으로 적합하게 제작되었다. 검출기의 성능 확인을 위해 전압을 50에서 100 kVp까지 변경하며 검출시스템과 흡수선량계를 이용하여 방사선을 측정하였다. 관전류량은 100 mAs, SDD는 100 cm로 고정하였고 각 관전압에서 10회 반복 측정하였다. 측정값을 이용하여 검출기의 응답과 선형성을 확인하였다. 검출기와 흡수선량계의 측정결과 비교에서 높은 상관성(r:0.998, p<.001)을 보임을 확인하였다. 이러한 결과를 통하여 본 연구에서 제안된 증감지와 마이크로컨트롤러 기반의 검출기의 사용가능성을 확인할 수 있었으며, 휴대형 방사선검출시스템이 소형, 저가형, 휴대형 시스템으로 교육용으로 적용이 가능할 것으로 판단되었다.

• 한국융합학회논문지
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• 제10권12호
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• pp.129-134
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• 2019

의료기관에서 많이 사용되는 방사선 차폐 재료인 납을 대처할 수 있는 플라스틱 제품으로 PVC를 선택하였다. 방사선 차폐 의복 이외에 저선량 영역에서 의료기기 부품, 산업용 차폐 재료로 사용이 가능한지 평가하고자 한다. 상업용 PVC는 밀도가 3.68 g/㎠ 으로 재료의 유연성과 경제성 등 일정 방사선 영역에서는 충분한 차폐 효과를 긍정적으로 기대할 수 있으며, 다양한 형태로 변형이 가능하고, 경량의 차폐벽으로 사용할 수 있다. 의료기관에서 임상 검사 시 사용되는 의료방사선 영역 대에서 3mm PVC 5장을 두께로 조절하여 차폐 성능을 실험하였다. 의료방사선의 관전압 기준으로 실효에너지에 대한 차폐 성능을 평가하였다. PVC는 두께가 두꺼울수록 관전압과 실효에너지가 낮을수록 차폐효과는 크게 나타났으며, 차폐효과는 12mm 두께에 관전압 80kVp에서 70%의 차폐효과가 있었다. 따라서 PVC 재료의 차폐효과는 두께의 의존율이 높게 나타났다. 앞으로는 차폐 성능을 높이면서 얇고 가벼운 친환경 제품을 만들기 위한 지속적인 연구가 필요하다.

• 한국방사선학회논문지
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• 제13권7호
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• pp.941-946
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• 2019

환자의 진단 및 치료를 결정할 때 전산화단층촬영 (computed tomography; CT)은 우수한 해부학 정보를 제공하기 때문에 진단에 큰 도움이 되어 있다. 그에 따른 사용빈도가 증가하고 있으며, 활용 및 응용범위도 확대되어가는 추세이다. 저관전압을 사용해서 CT 검사를 하면 노이즈가 증가한다. 기존의 여러 연구에서는 영상재구성법에 대한 노출조건을 조절하는 방법 등을 시도해서 최적의 화질을 찾는 방법을 찾고 있으나 근본적 문제해결은 되지 못한다. 입력 영상의 신호를 유지하고 노이즈만을 최대한 제거하기 위해서 이중 트리웨이블릿 알고리즘을 적용하였다. 실험결과 100kVp, 회전시간 0.5sec의 영상에서 complex oriented 2d 방을 사용 할 경우 노이즈는 8.53에서 4.51로 줄어들었다. 본 연구를 통해서 저관전압 두부 CT에서 발생하는 높은 수준의 노이즈를 최적의 노이즈제거 알고리즘으로 노이즈를 제거하고 환자선 량을 낮출 수 있었다. 본 연구결과를 임상에서 사용 시 저선량의 CT 사용이 가능하고 환자 피폭을 줄일 것으로 판단한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.89-92
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• 2001

Silent gas discharge method has been widely applied for ozone production, ultraviolet light and UV laser generation. Since ozone and ultraviolet applications have tendency to spread widely in industry, the development of efficient and low-cost power supply for such systems is a task of great impotency. This paper introduces high-frequency inverter type mode power supply designed for ozone generation tube and ultraviolet generation excimer lamp and considerations on this inverter and pulse density modulation control strategy applied in it.