• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1996년도 학술대회
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• pp.175-180
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• 1996

In this paper, a new image segmentation method based on merging of two low contrast neighbor regions iteratively is proposed. It is suitable for very low bit rate coding. The proposed method reduces efficiently contour information and preserves subjective and objective image quality. It consists of image segmentation using 4-level hierarchical structure based on mathematical morphology and 1-level region merging structure using the contrast difference of two adjacent neighbor regions. For each segmented region of the third level, two adjacent neighbor regions having low contrast difference value in fourth level based on contrast difference value is merged iteratively. It preserves image quality and shows the noticeable reduction of the contour information, so that it can improve the bottleneck problem of segmentation-based coding at very low bit rate.

• 대한원격탐사학회지
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• 제28권3호
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• pp.287-296
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• 2012

Although low spatial resolution satellite images like MODIS and GOCI can be important to observe land surface, it is often difficult to visually interpret the imagery because of the low contrast by prevailing cloud covers. We proposed a simple and adaptive stretching algorithm to enhance image contrast over land areas in cloudy images. The proposed method is basically a linear algorithm that stretches only non-cloud pixels. The adaptive linear stretch method uses two values: the low limit (L) from image statistics and upper limit (U) from low boundary value of cloud pixels. The cloud pixel value was automatically determined by pre-developed empirical function for each spectral band. We used MODIS and GOCI images having various types of cloud distributions and coverage. The adaptive contrast stretching method was evaluated by both visual interpretation and statistical distribution of displayed brightness values.

• 한국자기공명학회논문지
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• 제23권1호
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• pp.12-19
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• 2019

A former study has shown that the spin-lattice relaxation time ($T_1$) in cancerous prostate tissue had enhanced contrast at an ultra-low magnetic field, $132{\mu}T$. To study the field dependence and the origin of the contrast we measured $T_1$ in pairs of ex-vivo prostate tissues at the Earth's magnetic field. A portable and coil-based nuclear magnetic resonance (NMR) system was adopted for $T_1$ measurements at $40{\mu}T$. The $T_1$ contrast, ${\delta}=1-T_1$ (more cancer)/$T_1$(less cancer), was calculated from each pair. Additionally, we performed pathological examinations such as Gleason's score, cell proliferation index, and micro-vessel density (MVD), to quantify correlations between the pathological parameters and $T_1$ of the cancerous prostate tissues.

• Fisheries and Aquatic Sciences
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• 제14권2호
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• pp.130-137
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• 2011

Visual stimuli of nets, which affect fishing selectivity, vary by twine diameter, color, and material under different light conditions and visual geometries. In this study, two cylindrical model codends of two mesh sizes, 28 and 43 mm, were made of high-contrast, dark brown polyethylene (PE) netting twine and low contrast, light-blue polyamid (PA) monofilament twine. Each model codend was filled with juvenile seabream and set in the water channel of a light-blue circular tank under a flow speed 0.8 m/s for 30 min. Light conditions were set to relatively bright, dim, and dark. The resulting retention rates of juvenile seabream were 15-35% lower for the low-contrast codend with PA monofilament than for the high contrast PE twine netting under bright and dim light conditions, while no difference was observed under dark conditions. The effects of mesh size and netting contrast on the retention rate were dependent on the light level, while the retention rate due to netting contrast was independent of mesh size. Therefore, low-contrast nets in the codend could help to reduce juvenile bycatch by disturbing the orderly optomotor response.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2002년도 추계학술대회 및 정기총회
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• pp.295-299
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• 2002

This paper presents an image contrast enhancement technique for improving low contrast images. We applied fuzzy logic to develop an image contrast enhancement technique in the viewpoint of considering that the low pictorial information of a low contrast image is due to the vaguness or fuzziness of the multivalued levels of brightness rather than randomness. The fuzzy image contrast enhancement technique consists of three main stages, namely, image fuzzification, modification of membership values, and image defuzzification. In the stage of image fuzzification, we need to select a crossover point. To select the crossover point automatically the K-means algorithm is used. The problem of crossover point selection can be considered as the two-category, object and background, classification problem. The proposed method is applied to an experimental image with 256 gray levels and the result of the proposed method is compared with that of the histogram equalization technique. We used the index of fuzziness as a measure of image quality. The result shows that the proposed method is better than the histogram equalization technique.

• 대한방사선기술학회지:방사선기술과학
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• 제39권1호
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• pp.71-79
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• 2016

본 연구는 전산화단층검사(computed tomography; CT)에서 저농도 조영제와 저관전압 기법이 선량과 영상에 미치는 유용성을 팬텀으로 평가하였다. 조영제 농도별로 희석정도를 달리하여 실험팬텀에 삽입 후 관전압과 관전류를 단계적으로 변화하여 촬영하였고, 획득된 팬텀영상을 통해 선량과 HU를 평가하였다. 그 결과 표준조건(350 mgI/ml, 120 kV)보다 저농도 조영제와 저관전압 조건(300 mgI/ml, 100 kV)설정이 체적 선량평가(CTDIvol; computed tomography dose $index_{vol}$)에서 평균 21% 감소하였다. SNR은 저농도 조영제와 저관전압 조건이 팬텀에서 측정한 모든 깊이(center, 4.5cm, 2.25cm)의 조영제와 생리식염수를 1:10, 1:20으로 희석한 실험에서 각각 12.2(26%), 6.2(17%) 증가하였다. CNR은 각각 11.5(32%), 6.3(26%) 증가하였다. CT 검사에서 조영제 부작용 감소를 위한 저농도 조영제의 사용과 피폭선량 감소를 위한 저관전압 사용으로 영상에서 높은 감약계수를 통한 다양한 연구가 필요할 것으로 사료된다.

• 방송공학회논문지
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• 제17권2호
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• pp.284-294
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• 2012

본 논문은 OLED 디스플레이를 위한 저전력 화질 개선 기법을 제안한다. 제안하는 알고리즘은 영상의 대조비를 향상하면서 동시에 OLED 디스플레이의 소비 전력을 감소하는 변환을 선형 변환 함수에 기반하여 유도한다. 또한 영상의 지역적 특성을 고려하여 블록 단위로 변환 함수를 적용하여 영상의 지역적 특성에 적응적인 대조비 개선 알고리즘을 개발한다. 컴퓨터 모의실험을 통해 제안하는 알고리즘이 전력 소비를 줄이고 동시에 영상의 대조비를 향상시키는 것을 확인한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.485-486
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• 2012

• 대한건축학회논문집:구조계
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• 제35권5호
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• pp.191-202
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• 2019

This study examines the effect of luminance contrast ratio of character on readability and visual fatigue during an hour-long reading session while using a tablet PC in ambient environments having low luminance limited to $25cd/m^2$. Experiments were conducted with four patterns of the tablet's luminance contrast ratio of characters, namely 1:2.5, 1:4.5, 1:6.5, and 1:8.5, in low ambient luminance of $9cd/m^2$ and $25cd/m^2$. The obtained results show that the characters can be easily read at the luminance contrast ratio of character of 1:8.5 under surface luminance of $25cd/m^2$. Visual fatigue was evaluated through a subjective survey of symptoms. Physical, psychological, and visual fatigue were observed at a surface luminance of $9cd/m^2$, whereas solely visual fatigue was felt at a surface luminance of $25cd/m^2$. By assessing the physical fatigue using the value, it has been found that smaller the luminance contrast ratio of character, greater is the CFF variation rate. Furthermore, readability is poor and visual fatigue can be observed when the surface luminance is lower than the ambient luminance. However, readability can be improved by increasing the luminance contrast ratio of character to a value of 1:8.5. Thus, in low luminance environments, luminance contrast ratio of characters can affect readability and fatigue. Consider providing the full form of "CFF" so that the acronym can be used unambiguously throughout the manuscript.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2001년도 추계학술대회 학술발표 논문집
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• pp.279-282
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• 2001

This paper presents an image contrast enhancement technique for improving the low contrast images using the improved IAFC(Integrated Adaptive Fuzzy Clustering) Model. The low pictorial information of a low contrast image is due to the vagueness or fuzziness of the multivalued levels of brightness rather than randomness. Fuzzy image processing has three main stages, namely, image fuzzification, modification of membership values, and image defuzzification. Using a new model of automatic crossover point selection, optimal crossover point is selected automatically. The problem of crossover point selection can be considered as the two-category classification problem. The improved MEC can classify the image into two classes with unsupervised teaming rule. The proposed method is applied to some experimental images with 256 gray levels and the results are compared with those of the histogram equalization technique. We utilized the index of fuzziness as a measure of image quality. The results show that the proposed method is better than the histogram equalization technique.