• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.307-308
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• 2006

In recent, displays have very good properties at high luminance, fast response, and size. Also They have good quality in terms of color according to the development of the gamut extension and color reproduction. However, despite these merits, there is a characteristic that at a high luminance display, observer perceive the different color from the originally re-producted color due to the change of perceived luminance in human visual system. In this paper, we propose a model that is the hue shift phenomenon between a normal display and a high luminance display, and then an algorithm which compensate the color between two devices, so that observer can perceive the same color.

• 한국정보통신학회논문지
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• 제20권7호
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• pp.1376-1382
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• 2016

본 논문에서는, 배경 잡음 제거 알고리즘을 적용하여 일반적인 3차원 광자 계수 집적 영상의 화질을 개선하는 방법을 설명한다. 광자 계수 영상법은 광자가 매우 희박한 환경에서 소수의 광자를 검출하여 영상을 시각화 하는 방법이다. 하지만, 배경에서 발생되는 광자의 수가 많을 때, 원하는 물체의 광자 검출은 매우 어렵다. 이로 인해, 복원된 영상의 화질이 저하되는 문제점이 있다. 따라서, 본 논문에서는 불필요한 배경 잡음을 제거하고 오로지 원하는 물체에서만 광자를 검출하는 새로운 광자 계수 영상법을 제안한다. 또한, 3차원 정보를 획득하기 위해 집적 영상을 사용한다. 제안된 알고리즘의 유용성을 증명하기 위하여 광학적 실험을 수행하고 성능 평가를 위해 평균 제곱 오류 값을 계산한다.

• 한국전문물리치료학회지
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• 제23권3호
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• pp.21-28
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• 2016

Background: The toe-spread-out (TSO) exercise has been introduced as a strengthening exercise for the abductor hallucis muscle in subjects with hallux valgus. Visual biofeedback using ultrasound imaging during exercise, may increase the ability to selectively contract the abductor hallucis muscle, compared with exercise alone. Objects: The aim of this study was to investigate the effects of ultrasound imaging visual feedback during the TSO exercise with respect to its influence on the angle of the first metatarsophalangeal joint (1st MPJ) and the cross-sectional area (CSA) of the abductor hallucis muscle in subjects with hallux valgus. Methods: Twenty-five healthy young subjects with a mean average age of 22.5 years, and a standard deviation of 2.3 years, were recruited for this study. Hallux valgus was defined as an angles greater than $15^{\circ}$ angle of 1st MPJ. Goniometric measurement was used to determine the angle of 1st MPJ. In addition, an ultrasound system was used to collect the CSA of the abductor hallucis muscle in each foot. The angle of the 1st MPJ and CSA of the abductor hallucis were measured in three positions; the resting position, during TSO exercise, and during TSO exercise in conjunction with real-time ultrasound imaging feedback. All data analyzed using a repeated analysis of variance with Bonferroni correction in order to compare the dependent variables in all three positions. Statistical level of significance was set up as p<.05. Results: The angle of the 1st MPJ was noted to be significantly reduced and the CSA of the abductor hallucis to be significantly greater during TSO exercise used in conjunction with ultrasound imaging visual feedback, compared to when the values were recorded during TSO exercise alone (p<.05). Conclusion: Based on these findings, it can be concluded that the application of ultrasound imaging visual feedback during TSO exercise is more effective in contracting selectively the abductor hallucis than the use of exercise alone.

• Investigative Magnetic Resonance Imaging
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• 제25권1호
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• pp.23-34
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• 2021

Purpose: Differentiating between glioblastoma and solitary metastasis is very important for the planning of further workup and treatment. We assessed the ability of various morphological parameters using conventional MRI and diffusion-based techniques to distinguish between glioblastomas and solitary metastases in tumoral and peritumoral regions. Materials and Methods: We included 38 patients with solitary brain tumors (21 glioblastomas, 17 solitary metastases). To find out if there were differences in the morphologic parameters of enhancing tumors, we analyzed their shape, margins, and enhancement patterns on postcontrast T1-weighted images. During analyses of peritumoral regions, we assessed the extent of peritumoral non-enhancing lesion on T2- and postcontrast T1-weighted images. We also aimed to detect peritumoral neoplastic cell infiltration by visual assessment of T2-weighted and diffusion-based images, including DWI, ADC maps, and exponential DWI, and evaluated which sequence depicted peritumoral neoplastic cell infiltration most clearly. Results: The shapes, margins, and enhancement patterns of tumors all significantly differentiated glioblastomas from metastases. Glioblastomas had an irregular shape, ill-defined margins, and a heterogeneous enhancement pattern; on the other hand, metastases had an ovoid or round shape, well-defined margins, and homogeneous enhancement. Metastases had significantly more extensive peritumoral T2 high signal intensity than glioblastomas had. In visual assessment of peritumoral neoplastic cell infiltration using T2-weighted and diffusion-based images, all sequences differed significantly between the two groups. Exponential DWI had the highest sensitivity for the diagnosis of both glioblastoma (100%) and metastasis (70.6%). A combination of exponential DWI and ADC maps was optimal for the depiction of peritumoral neoplastic cell infiltration in glioblastoma. Conclusion: In the differentiation of glioblastoma from solitary metastatic lesions, visual morphologic assessment of tumoral and peritumoral regions using conventional MRI and diffusion-based techniques can also offer diagnostic information.

• 천문학논총
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• 제30권2호
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• pp.223-224
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• 2015

We present the results of visual double stars speckle observations from 2013 using a Zeiss Double Refractor 60 cm with visual focal length f = 1,078 cm, and CCD SBIG ST-402 MEA. A Bessel V filter with ${\lambda}=550nm$ was placed in front of the CCD camera to reduce the chromatic aberration of the objective lens. The objects selected for this observation were calibration candidates and program stars with separations ranging from 0.9-6 arc second, and were located in both the northern and southern hemispheres. Seeing at Bosscha Observatory is generally 1-2 arc second, imposing a limit on visual double star separation below which the system cannot be resolved by long exposure imaging (longer than ~50 ms). Speckle interferometry methods are used to resolve double stars with separations below the typical size of seeing effects. A series of images were captured in fast short-time exposures (~50 ms) using a CCD camera. The result of our experiment shows that our system can be used to measure separations of 0.9 arc second (for systems with small ${\Delta}m$) and ${\Delta}m{\approx}3.7$ (for wide systems).

• Journal of Korean Neurosurgical Society
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• 제49권5호
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• pp.296-298
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• 2011

Spinal intradural cysticercosis is a rare manifestation of neurocysticercosis. We report a unique patient who showed visual symptoms and normal imaging of the brain caused by isolated spinal neurocysticercosis. A 59-year-old male patient was admitted to the emergency unit with a history of severe headache and progressive blurred vision. Brain computed tomographic scanning and magnetic resonance imaging showed normal cerebral anatomy without hydrocephalus. The fundoscopic evaluation by an ophthalmologist showed bilateral papilledema. Perimetry studies revealed visual field defects in both eyes. With the diagnosis of pseudotumor cerebri, a lumbar tap was attempted; however, we could not drain the cerebrospinal fluid in spite of appropriate attempts. Lumbar magnetic resonance imaging revealed multilevel intraspinal lesions that were confirmed histologically to be neurocysticercosis. An intraoperative lumbar puncture revealed an increased opening pressure and cytochemical analysis showed elevated cerebrospinal fluid protein level. The headache resolved immediately after surgery. However, the visual symptoms remained and recovered only marginally despite antihelminthic medications after six months of operation.

• Korean Journal of Radiology
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• 제22권7호
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• pp.1213-1224
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• 2021

Objective: To develop a machine learning (ML) pipeline based on radiomics to predict Coronavirus Disease 2019 (COVID-19) severity and the future deterioration to critical illness using CT and clinical variables. Materials and Methods: Clinical data were collected from 981 patients from a multi-institutional international cohort with real-time polymerase chain reaction-confirmed COVID-19. Radiomics features were extracted from chest CT of the patients. The data of the cohort were randomly divided into training, validation, and test sets using a 7:1:2 ratio. A ML pipeline consisting of a model to predict severity and time-to-event model to predict progression to critical illness were trained on radiomics features and clinical variables. The receiver operating characteristic area under the curve (ROC-AUC), concordance index (C-index), and time-dependent ROC-AUC were calculated to determine model performance, which was compared with consensus CT severity scores obtained by visual interpretation by radiologists. Results: Among 981 patients with confirmed COVID-19, 274 patients developed critical illness. Radiomics features and clinical variables resulted in the best performance for the prediction of disease severity with a highest test ROC-AUC of 0.76 compared with 0.70 (0.76 vs. 0.70, p = 0.023) for visual CT severity score and clinical variables. The progression prediction model achieved a test C-index of 0.868 when it was based on the combination of CT radiomics and clinical variables compared with 0.767 when based on CT radiomics features alone (p < 0.001), 0.847 when based on clinical variables alone (p = 0.110), and 0.860 when based on the combination of visual CT severity scores and clinical variables (p = 0.549). Furthermore, the model based on the combination of CT radiomics and clinical variables achieved time-dependent ROC-AUCs of 0.897, 0.933, and 0.927 for the prediction of progression risks at 3, 5 and 7 days, respectively. Conclusion: CT radiomics features combined with clinical variables were predictive of COVID-19 severity and progression to critical illness with fairly high accuracy.

• 제어로봇시스템학회논문지
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• 제5권8호
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• pp.995-1000
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• 1999

This paper presents a optic system and a visual inspection algorithm looking for solder joint defects of J-lead chip which are more integrate and smaller than ones with Gull-wing on PCBs(Printed Circuit Boards). The visual inspection system is composed of three sections : host PC, imaging and driving parts. The host PC part controls the inspection devices and executes the inspection algorithm. The imaging part acquires and processes image data. And the driving part controls XY-table for automatic inspection. In this paper, the most important five features are extracted from input images to categorize four classes of solder joint defects in the case of J-lead chip and utilized to a back-propagation network for classification. Consequently, good accuracy of classification performance and effectiveness of chosen five features are examined by experiment using proposed inspection algorithm.

• Current Optics and Photonics
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• 제3권4호
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• pp.329-335
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• 2019

Wide FOV imaging systems are important for acquiring rich visual information. A conventional catadioptric imaging system deploys a camera in front of a curved mirror to acquire a wide FOV image. This is a cumbersome setup and causes unnecessary occlusions in the acquired image. In order to reduce both the burden of the camera deployment and the occlusions in the images, this study uses a secondary planar mirror in the catadioptric imaging system. A compact design of the catadioptric imaging system and a condition for the position of the secondary planar mirror to satisfy the central imaging are presented. The image acquisition model of the catadioptric imaging system with a secondary planar mirror is discussed based on the principles of geometric optics in this study. As a backward mapping, the acquired image is restored to a distortion-free image in the experiments.

• 한국융합학회논문지
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• 제12권11호
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• pp.207-220
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• 2021

최근 센서 경험을 위한 새로운 매체들의 발전은 프로젝션맵핑, 가상현실과 같은 비디오 설치 미술의 시각적 표현을 더욱 확장시키고 있다. 예술가들은 새로운 매체들들 통해 새로운 시각적 표현 기법을 개발하고 발전시킬 수 있다. 프로젝션맵핑 기술은 지속적으로 미디어아트 작품의 시각적 표현에 다양한 가능성을 부여하고 있다. 본 논문은 프로젝션맵핑 기술에 기반한 시각 표현이 인간의 감각 체험으로 전이되고 확장되는 과정을 연구하기 위해서, 매체가 갖는 '복제성,' '전파성,' '가상성' 그리고 '인터랙션'의 특징을 분석함으로써 시각적 표현을 정의하고 의미를 기술하였다. 작품 분석을 통해 '반복과 중첩,' '시뮬라이크롬과 은유,' '치환과 전환'의 시각적 표현 기법에 대해 분석하고, 프로젝션맵핑 작품인 에 적용함으로써 시각 표현 기법이 인간의 감각 체험으로 확장되는 과정을 연구하였다. 시각적 표현의 확장성 연구는 작품을 제작하는 예술가들이나 관람하는 관객들에게 작품의 의미를 전달하거나 해석하는데 필요한 핵심 요소이다.