• 한국의학물리학회지:의학물리
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• 제23권4호
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• pp.303-308
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• 2012

뇌정위 방사선수술의 선량계산을 위해 Geant4 기반의 응용 프로그램을 개발 하였다. 선형가속기에서 발생하는 방사선의 스펙트럼을 입력하기 위하여 사전에 실행하여 구한 스펙트럼에 각 에너지별로 구한 가중치를 곱하여 확률밀도를 구하였다. 이를 누적밀도로 변환하여 입력하도록 하였다. 메신저 클래스를 이용하여 다양한 형태의 MLC 조사면을 설정할 수 있도록 하였다. 갠트리와 테이블의 회전을 모사하기 위하여 rotateX와 rotateY라는 회전행렬을 사용하였다. 월드좌표 속에서 갠트리와 테이블을 정의하여 각각 회전을 구현하였다. 실제 환자의 자료는 CT의 dicom 파일에서 픽셀 크기, 매트릭스 크기 등의 정보와 픽셀의 HU를 밀도로 변환한 파일을 생성한 다음 이 파일을 이용 환자의 모델링에 이용 하였다. 환자의 모델링은 팬텀월드 안에 픽셀의 크기에 해당하는 복셀을 정의하고 이 복셀에 픽셀의 밀도와 이 밀도에 해당하는 물질을 할당해주었다.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제2권5호
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• pp.347-352
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• 2013

임펄스 잡음 제거 기법들에서 윈도우의 크기는 매우 중요한데, 보통 잡음의 밀도에 따라 적당한 크기의 윈도우를 사용한다. 이때 윈도우가 너무 작으면 잡음을 충분히 제거하지 못하며, 너무 크면 영상 내의 에지나 미세한 형태를 제대로 복원하지 못하고 흐릿하게 만들 수 있다. 또한 잡음이 있는 중앙 화소를 복원하기 위해 이러한 윈도우 내의 모든 화소들이 이용된다. 본 논문에서는 이러한 기존 방법과 달리 작은 크기의 윈도우를 사용하고 잡음이 없이 깨끗한 화소만을 사용하여 임펄스 잡음을 제거하는 새로운 반복적인 알고리즘을 제안한다. 제안된 방법은 모든 잡음 화소가 새로 계산된 추정치로 대체될 때까지 반복된다. 잡음 화소에 대해 최적의 값을 유추하기 위해 제안된 방법에서는 무잡음 화소를 이용한 유전자 프로그래밍 (GP) 기반의 추정자를 제안하는데, 이것은 윈도우 내의 무잡음 화소와, 산술 연산자 및 랜덤 상수들로 이루어진다. 실험을 통해 제안된 방법이 영상 내의 미세한 형태들을 잘 유지하면서 임펄스 잡음을 효과적으로 제거할 수 있음을 알 수 있었는데, 특히 심하게 잡음이 가해진 데이터의 복원에 매우 효과적임을 알 수 있었다.

• 대한치과교정학회지
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• 제50권2호
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• pp.108-119
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• 2020

Objective: The primary objective of this study was to quantitatively analyze the bone parameters (thickness and density) at four different interdental areas from the distal region of the canine to the mesial region of the second molar in the maxilla and the mandible. The secondary aim was to compare and contrast the bone parameters at these specific locations in terms of sex, growth status, and facial type. Methods: This retrospective cone-beam computed tomography (CBCT) study reviewed 290 CBCT images of patients seeking orthodontic treatment. Cortical bone thickness in millimeters (mm) and density in pixel intensity value were measured for the regions (1) between the canine and first premolar, (2) between the first and second premolars, (3) between the second premolar and first molar, and (4) between the first and second molars. At each location, the bone thickness and density were measured at distances of 2, 6, and 10 mm from the alveolar crest. Results: The sex comparison (male vs. female) in cortical bone thickness showed no significant difference (p > 0.001). The bone density in growing subjects was significantly (p < 0.001) lower than that in non-growing subjects for most locations. There was no significant difference (p > 0.001) in bone parameters in relation to facial pattern in the maxilla and mandible for most sites. Conclusions: There was no significant sex-related difference in cortical bone thickness. The buccal cortical bone density was higher in females than in males. Bone parameters were similar for subjects with hyperdivergent, hypodivergent, and normodivergent facial patterns.

• 센서학회지
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• 제29권1호
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• pp.27-32
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• 2020

This study proposes a pixel-patterning method for organic light-emitting diodes (OLEDs) based on thermal transfer. An infrared lamp was introduced as a heat source, and glass type donor element, which absorbs infrared and generates heat and then transfers the organic layer to the substrate, was designed to selectively sublimate the organic material. A 200 nm-thick layer of molybdenum (Mo) was used as the lightto-heat conversion (LTHC) layer, and a 300 nm-thick layer of patterned silicon dioxide (SiO₂), featuring a low heat-transfer coefficient, was formed on top of the LTHC layer to selectively block heat transfer. To prevent the thermal oxidation and diffusion of the LTHC material, a 100 nm-thick layer of silicon nitride (SiN_x) was coated on the material. The fabricated donor glass exhibited appropriate temperature-increment property until 249 ℃, which is enough to evaporate the organic materials. The alpha-step thickness profiler and X-ray reflection (XRR) analysis revealed that the thickness of the transferred film decreased with increase in film density. In the patterning test, we achieved a 100 ㎛-long line and dot pattern with a high transfer accuracy and a mean deviation of ± 4.49 ㎛. By using the thermal-transfer process, we also fabricated a red phosphorescent device to confirm that the emissive layer was transferred well without the separation of the host and the dopant owing to a difference in their evaporation temperatures. Consequently, its efficiency suffered a minor decline owing to the oxidation of the material caused by the poor vacuum pressure of the process chamber; however, it exhibited an identical color property.

• 센서학회지
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• 제26권1호
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• pp.28-34
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• 2017

An NIR grism Si optical area sensor spectrometer with in-band reference wavelength is designed and fabricated. It is composed of a transmission type diffraction grating (spatial density 300 line/mm), a rectangular N-BK7 prism (apex angle 30 degree), NIR filter(cutoff wavelength 720 nm), an imaging convex lens(focal length 50 mm F1.8) and an IR modified DSLR camera (Canon EOS40D) of Si optical area sensor ($3,888{\times}2,592$ pixels, pixel size $5.710{\mu}m$). "In-band reference wavelength function" is implemented using non-dispersive 0th diffraction order optical beam. The NIR grism spectrometer is tested in a laboratory using a halogen lamp and a Neon lamp. And the spectrometer is used in an astronomy field for obtaining the planet Jupiter NIR spectrum. In-band reference wavelength i.e. un-deviation wavelength is 846 nm, an wavelength resolution is 0.3027 nm/pixel, an wavelength resolving power is 2,794 and an wavelength range is 650~1,000 nm.

• 정보처리학회논문지B
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• 제17B권1호
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• pp.15-22
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• 2010

비디오 감시 시스템에서 정확한 물체 추적을 위해서는 움직이는 물체가 없는 정적인 배경 영상이 필수적이다. 하지만 기존의 배경 생성 방법들은 주로 시간 축에 따른 화소 정보를 이용하여 오랫동안 정지해 있는 물체들이 존재하는 경우에는 적용하기 어려운 단점이 있다. 이러한 문제점을 해결하기 위해 본 논문에서는 mean-shift와 fast marching method(FMM)을 이용해 시간 축 화소 정보와 공간 축 화소 정보를 이용하여 배경을 생성하는 방법을 제안한다. mean-shift를 이용해 시간 축에 따른 화소 값의 최빈값을 추정하여 배경을 생성하고, FMM을 이용해공간 축에 따른 화소 정보를 이용하여 일정 기간 동안 움직이지 않은 물체가 있는 환경에서 바람직한 배경을 생성한다. 실험 결과는 제안한 방법이 기존의 시간에 따른 빈도만을 이용하는 방법보다 더 효율적임을 보여준다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2007년도 한국컴퓨터종합학술대회논문집 Vol.34 No.1 (C)
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• pp.477-481
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• 2007

A background is a part where do not vary too much or frequently change in an image sequence. Using this assumption, it is presented a background acquisition algorithm for not only static but also dynamic view in this paper. For generating background, we detect a region, where has high correlation rate compared within selected region in the prior pyramid image, from the searching region in the current image. Between a detected region in the current image and a selected region in the prior image, we calculate movement vector for each regions in time sequence. After we calculate whole movement vectors for two successive images, vector histogram is used to determine the camera movement. The vector which has the highest density in the histogram is determined a camera movement. Using determined camera movement, we classify clusters based on pixel intensities which pixels are matched with prior pixels following camera movement. Finally we eliminate clusters which have lower weight than threshold, and combine remained clusters for each pixel to generate multiple background clusters. Experimental results show that we can automatically detect background whether camera move or not.

• 전기학회논문지
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• 제56권1호
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• pp.112-116
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• 2007

We have investigated the hysteresis phenomenon of a hydrogenated amorphous silicon thin film transistor (a-Si:H TFT) and analyzed the effect of hysteresis phenomenon when a-Si:H TFT is a pixel element of active matrix organic light emitting diode (AMOLED). When a-Si:H TFT is addressed to different starting gate voltages, such as 10V and 5V, the measured transfer characteristics with 1uA at $V_{DS}$ = 10V shows that the gate voltage shift of 0.15V is occurred due to the different quantities of trapped charge. When the step gate-voltage in the transfer curve is decreased from 0.5V to 0.05V, the gate-voltage shift is decreased from 0.78V to 0.39V due to the change of charge do-trapping rate. The measured OLED current in the widely used 2-TFT pixel show that a gate-voltage of TFT in the previous frame can influence OLED current in the present frame by 35% due to the change of interface trap density induced by different starting gate voltages.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.520-524
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• 2009

In compressed color images, colors are usually represented by luminance and chrominance (YCbCr) components. Considering characteristics of human vision system, chrominance (CbCr) components are generally represented more coarsely than luminance component. Aiming at possible recovery of chrominance components, we propose a model-based chrominance estimation algorithm where color images are modeled by a Markov random field (MRF). A simple MRF model is here used whose local conditional probability density function (pdf) for a color vector of a pixel is a Gaussian pdf depending on color vectors of its neighboring pixels. Chrominance components of a pixel are estimated by maximizing the conditional pdf given its luminance component and its neighboring color vectors. Experimental results show that the proposed chrominance estimation algorithm is effective for quality improvement of compressed color images such as JPEG and JPEG2000.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.3873-3887
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• 2018

In this paper, we propose a novel method to recover images corrupted by impulse noise. The proposed method uses two stages: noise detection and filtering. In the first stage, we use pixel values, rank-ordered logarithmic difference values, and median values to train a neural-network-based impulse noise detector. After training, we apply the network to detect noisy pixels in images. In the next stage, we use group-based weighted couple sparse representation to filter the noisy pixels. During this second stage, conventional methods generally use only clean pixels to recover corrupted pixels, which can yield unsuccessful dictionary learning if the noise density is high and the number of useful clean pixels is inadequate. Therefore, we use reconstructed pixels to balance the deficiency. Experimental results show that the proposed noise detector has better performance than the conventional noise detectors. Also, with the information of noisy pixel location, the proposed impulse-noise removal method performs better than the conventional methods, through the recovered images resulting in better quality.