• Journal of the Korea Computer Graphics Society
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• v.14 no.3
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• pp.31-46
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• 2008

The depth of field is the range that the objects inside of this range treated to be focused. Objects that are placed out of this range are out of focus and become blurred. In computer graphics, generating depth of field effects gives a great reality to rendered images. The previous researches on the depth of field in computer graphics can be divided into two major categories. One of them is the distributed ray tracing that samples the lens area against each pixel. It is possible to obtain precise results without noise if enough number of samples are taken. However, to make a good result, a great number of samples are needed, resulting in an enormous timing requirement. The other approach is the method that approximates depth of field effect by post-processing an image and its depth values computed using a pin-hole camera. Though the second technique is not that physically correct like distributed ray tracing, many approaches which using this idea have been introduced because it is much faster than the first approach. But the post-processing have some limitations because of the lack of ray information. In this paper, we first present an improvement technique that corrects the previous post-processing methods and then propose another one that accelerates the distributed ray tracing by using a radiance caching method.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.2
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• pp.1-14
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• 2000

The rosette-scan seeker, mounted on the infrared guided missile, is a device that tracks the target It can acquire the 2D image of the target by scanning a space about target in rosette pattern with a single detector Since the detected image is changed according to the position of the object in the field of view and the number of the object is not fixed, the unsupervised methods are employed in clustering it The conventional ISODATA method clusters the objects by using the distance between the seed points and pixels So, the clustering result varies in accordance with the shape of the object or the values of the merging and splitting parameters In this paper, we propose an Array Linkage Clustering Algorithm (ALCA) as a new clustering algorithm improving the conventional method The ALCA has no need for the initial seed points and the merging and splitting parameters since it clusters the object using the connectivity of the array number of the memory stored the pixel Therefore, the ALCA can cluster the object regardless of its shape With the clustering results using the conventional method and the proposed one, we confirm that our method is better than the conventional one in terms of the clustering performance We simulate the rosette scanning infrared seeker (RSIS) using the proposed ALCA as an infrared counter countermeasure The simulation results show that the RSIS using our method is better than the conventional one in terms of the tracking performance.

• Journal of Bio-Environment Control
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• v.20 no.2
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• pp.63-71
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• 2011

Pattern recognition of a cucumber were conducted to detect directly the binary images by using thresholding method, which have the threshold level at the optimum intensity value. By restricting conditions of learning pattern, output patterns could be extracted from the same and similar input patterns by the algorithm. The algorithm of pattern recognition was developed to determine the position of the cucumber from a real image within working condition. The algorithm, designed and developed for this project, learned two, three or four learning pattern, and each learning pattern applied it to twenty sample patterns. The restored success rate of output pattern to sample pattern form two, three or four learning pattern was 65.0%, 45.0%, 12.5% respectively. The more number of learning pattern had, the more number of different out pattern detected when it was conversed. Detection of feature pattern of cucumber was processed by using auto scanning with real image of 30 by 30 pixel. The computing times required to execute the processing time of cucumber recognition took 0.5 to 1 second. Also, five real images tested, false pattern to the learning pattern is found that it has an elimination rate which is range from 96 to 98%. Some output patterns was recognized as a cucumber by the algorithm with the conditions. the rate of false recognition was range from 0.1 to 4.2%.

• The KIPS Transactions:PartB
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• v.19B no.2
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• pp.99-106
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• 2012

The purpose of this study was to determine the evaluation parameters' osteoporosis predictability in accordance with measuring regions by analyzing the correlations between bone mineral density and trabecular patterns derived from different measuring regions. Experimental subjects were a total of 40 female patients after menopause aged over 40 years, and were classified into 20 control and 20 osteoporotic groups according to the T-score. Bone mineral density was measured on femoral neck, trochanter and ward's triangle by DEXA(Dual Energy X-ray Absorptiometry). We designated ROI(Region of Interest) with $50{\times}50$ pixel size on each measuring regions, and extracted trabecular patterns by using existing image processing method. We also selected a total of eight evaluation parameters that are categorized into structural(mean gray level, area, perimeter, thickness and terminal distance), skeletonized parameters(number, length) and fractal dimension. As a result, it was observed that area, perimeter, thickness, terminal distance, number, length and fractal dimension reflected the bone mineral density with high statistical validity(p<0.003). We also confirmed that the evaluation parameters could predict the osteoporosis more efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1C
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• pp.1-8
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• 2003

In this paper, performance of the CPC(complex phase code) which is recently proposed as a practical phase encoding method for phase-code multiplexes holographic memory system is comparatively analyzed with those of the conventional phase codes such as PR(pure random code), RCE(random code with equality), WHM(Walsh Hadamard Matrix). In computer simulation, the size of an address bean is fixed at 32$\times$32 pixels and 0%-25% phase-error ratio in a pixel are intentionally added to the real phase values to consider the nonlinear phase-modulation characteristics of the practical spatial light modulator. From comparative analysis of crosstalks and signal-to-noise ratios for these phase codes by calculating auto-correlation and cross-correlation, it is found that the CPC have the lowest cross-correlation mean value of 0.021, the lowest standard deviation of 0.0113 and the highest signal-to-noise ratio(SNR) of 27.4 among the four types of phase code. In addition, from the calculation of the number of all possible address beams for these four types of phase code as the size of the address beam is fixed to 3232 pixels, the CPC is found to have 6.334$\times$10$^{49}$ address beams, which are relatively higher number than that of the conventional phase codes.

• Imaging Science in Dentistry
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• v.33 no.2
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• pp.113-119
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• 2003

Purpose : To evaluate the relationship between morphometric analysis of bone microstructure from digital radiographic image and trabecular bone strength. Materials and Methods : One hundred eleven bone specimens with 5 mm thickness were obtained from the mandibles of 5 pigs. Digital images of specimens were taken using a direct digital intraoral radiographic system. After selection of ROI (100 × 100 pixel) within the trabecular bone, mean gray level and standard deviation were obtained. Fractal dimension and the variants of morphometric analysis (trabecular area, periphery, length of skeletonized trabeculae, number of terminal point, number of branch point) were obtained from ROI. Punch sheer strength analysis was performed using Instron (model 4465, Instron Corp., USA). The loading force (loading speed 1 mm/min) was applied to ROI of bone specimen by a 2 mm diameter punch. Stress-deformation curve was obtained from the punch sheer strength analysis and maximum stress, yield stress, Young's modulus were measured. Results: Maximum stress had a negative linear correlation with mean gray level and fractal dimension significantly (p<0.05). Yield stress had a negative linear correlation with mean gray level, periphery, fractal dimension and the length of skeletonized trabeculae significantly (p < 0.05). Young's modulus had a negative linear correlation with mean gray level and fractal dimension significantly (p < 0.05). Conclusions : The strength of cancellous bone exhibited a significantly linear relationship between mean gray level, fractal dimension and morphometric analysis. The methods described above can be easily used to evaluate bone quality clinically.

• Journal of Periodontal and Implant Science
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• v.31 no.3
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• pp.565-571
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• 2001

The purpose of this study is to determine if a relationship exists among osteoporosis, alveolar bone density and periodontal disease in postmenopausal osteoporotic women and postmenopausal healthy women. Twenty-two women were evaluated for this study. They were attending the postmenopausal clinic, Seoul National University Hospital and generally healthy except osteoporosis. They had experienced menopause not less than one year when we began to examine them. Bone densities of lumbar area(L2-L4) was determined by DEXA(LUNAR-expert Co,. U.S.A). We diagnosed osteoporosis when T-score was below -2.5 and healthy state when T-score was over -1. Osteoporotic(10 female), not hormone-treated group and healthy control group(12 female) were asked for their age, menopausal age, menopausal period and the number of remaining teeth and examined clinically for plaque index(PI), gingival index(GI), clinical attachment loss(CAL) on their 6 Ramfjord index teeth. Intraoral radiographs were taken in maxillary anterior zone. All films were equally exposed and developed. Each films was digitized and analysed using image processing software, Scion image. Alveolar bone regions of interest were selected and Intensity of each pixel was quantized in the array ranging from 0(white) to 255(black). The two groups were comparable with respect age, menopausal age, menopausal period and number of remaining teeth. The osteoporotic women had significantly lower alveolar bone density than controls in maxilla. But no significant difference was found with respect clinical attachment loss, plaque index and gingival index. Supported by the Ministry of Public Health and Welfare, Korea (HMP-00-CH-10-0009).

• KIPS Transactions on Software and Data Engineering
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• v.3 no.9
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• pp.361-368
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• 2014

The LPR(License plate recognition) system has been developed to efficient control for complex traffic environment and currently be used in many places. However, because of light, noise, background changes, environmental changes, damaged plate, it only works limited environment, so it is difficult to use in real-time. This paper presents a heuristic segmentation algorithm for robust to noise and illumination changes and introduce a real-time license plate recognition system using it. In first step, We detect the plate utilized Haar-like feature and Adaboost. This method is possible to rapid detection used integral image and cascade structure. Second step, we determine the type of license plate with adaptive histogram equalization, bilateral filtering for denoise and segment accurate character based on adaptive threshold, pixel projection and associated with the prior knowledge. The last step is character recognition that used histogram of oriented gradients (HOG) and multi-layer perceptron(MLP) for number recognition and support vector machine(SVM) for number and Korean character classifier respectively. The experimental results show license plate detection rate of 94.29%, license plate false alarm rate of 2.94%. In character segmentation method, character hit rate is 97.23% and character false alarm rate is 1.37%. And in character recognition, the average character recognition rate is 98.38%. Total average running time in our proposed method is 140ms. It is possible to be real-time system with efficiency and robustness.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.99-111
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• 2009

The result of Image segmentation, an indispensable process in image processing, significantly affects the analysis of an image. Despite the significance of image segmentation, it produces some problems when the variation of pixel values is large, or the boundary between background and an object is not clear. Also, these problems occur frequently when many objects in an image are placed very close by. In this paper, when the shape of objects in an image is circular, we proposed an algorithm which segment an each object in an image using the geometric characteristic of circular shape. The proposed algorithm is composed of 4 steps. First is the boundary edge extraction of whole object. Second step is to find the candidate points for further segmentation using the boundary edge in the first step. Calculating the representative circles using the candidate points is the third step. Final step is to draw the line connecting the overlapped points produced by the several erosions and dilations of the representative circles. To verify the efficiency of the proposed algorithm, the algorithm is compared with the three well-known cell segmentation algorithms. Comparison is conducted by the number of segmented region and the correctness of the inner segment line. As the result, the proposed algorithm is better than the well-known algorithms in both the number of segmented region and the correctness of the inner segment line by 16.7% and 21.8%, respectively.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.885-901
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• 2021

This paper illustratesthe impact of the temporal gap between satellite images and targetsize in mesoscale atmospheric motion vector (AMV) algorithm. A test has been performed using GEO-KOMPSAT-2A (GK2A) rapid-scan data sets with a temporal gap varying between 2 and 10 minutes and a targetsize between 8×8 and 40×40. Resultsshow the variation of the number of AMVs produced, mean AMV speed, and validation scores as a function of temporal gap and target size. As a results, it was confirmed that the change in the number of vectors and the normalized root-mean squared vector difference (NRMSVD) became more pronounced when smaller targets are used. In addition, it was advantageous to use shorter temporal gap and smaller target size for the AMV calculation in the lower layer, where the average speed is low and the spatio-temporal scale of atmospheric phenomena is small. The temporal gap and the targetsize are closely related to the spatial and temporalscale of the atmospheric circulation to be observed with AMVs. Thus, selecting the target size and temporal gap for an optimum calculation of AMVsrequires considering them. This paper recommendsthat the optimized configuration to be used operationally for the near-real time analysis of mesoscale meteorological phenomena is 4-min temporal gap and 16×16 pixel target size, respectively.