• Journal of Broadcast Engineering
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• v.3 no.2
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• pp.146-154
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• 1998

시간적 표본화를 채택한 다중경로방법에 의한 장면전환 검출방법은 전 동영상에 대해 매 프레임마다 순차적으로 검색하는 방법에 비해서 빠르며, 동일한 정확성을 갖고 있다. 그러나, 검출 시간을 최소화하기 위한 적절한 검출 간격을 선택하는 어떠한 기준이나 방법도 제시되지 않았으며 검출 간격을 경험에 의해 선택할 수밖에 없다. 이 논문에서는 장면 전환 검출 시간, 검출 간격과 실제 장면 전환 간격으로부터 검출 시간을 최소화하는 최적 검출 간격을 얻을 수 있음을 보였다. 평균 장면 전환 간격이 알려져 있지 않은 동영상에 대해서 최적 검출 간격을 추정할 수 있는 알고리듬을 제안하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.202-203
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• 2001

21세기 고도 정보화 사회는 실감형 3차원 입체 멀티미디어 서비스로 발전할 것으로 전망됨에 따라 3차원 입체 영상 디스플레이 기술에 대한 관심이 높아져서 국내외적으로 기술개발이 활발하게 진행되고 있다. 최근 3차원 영상 디스플레이 시스템을 구현하기 위해 입력이미지는 공간광변조기에 의해 디스플레이 되는데, 이때 사용될 수 있는 공간광변조기는 LCD, DMD,(deformable mirror device), MOD(magento optic device)등이 있다. (중략)

• 한국ITS학회:학술대회논문집
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• 2002.11a
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• pp.210-213
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• 2002

차량 대기열 측정에 관한 연구는 효과적인 교통 통제를 위해서 필수적인 요소이다. 이를 위해 본 논문에서는 영역기반 영상처리를 이용한 차량 대기열 분석에 관한 방법을 제안한다. 도로 영상에서 영역을 설정하고 각 영역에서의 차량 검출방법을 통하여 차량 대기열의 길이를 계산하였다. 이때 차량의 검출은 영역 처리를 이용하였고 대기열 측정은 검출된 차량의 최종단 위치를 파악하여 계산하였다. 이러한 방법은 차량 통행량 분석에 이용하여 능동적 교통 신호 체계에 응용될 수 있다.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.1
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• pp.1-10
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• 2010

Purpose: The effect of artifact was analyzed, which occurs from fiducial marker during the liver Image Guided Radiation Therapy (IGRT) using the fiducial marker. Materials and Methods: The size of artifact of fixed fiducial marker and length of mobile fiducial marker locus were measured using the On-Board Imager system (OBI) and CT simulator, and 2D-2D matching and 3D-3D matching were carried out, respectively, and at this time, the coordinates transition value of couch was analyzed. Results: The measurement of fixed fiducial marker artifact size indicated CT 4.90, 8.10, 12.90, 19.70 mm and OBI 5.60, 10.60, 14.70, 29.40 mm based on the reference CT slice thickness of 1.25, 2.50, 5.00, and 10.00 mm. Meanwhile, the measurement of mobile fiducial marker locus length indicated CT 42.00, 43.10, 46.50 mm, and OBI 43.40, 46.00, 49.30 mm. The coordinates transition of 1.00, 2.00, and 8.00 mm occurred between 2D-2D matching and 3D-3D matching. Conclusion: It was confirmed that the therapy error increased during IGRT due to the influence of artifact when CT slice thickness increased. Thus, it may be desirable to acquire the image less than 2.50 mm in slice thickness when IGRT is implemented using the fiducial marker.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.17-24
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• 2020

The purpose of this study was to evaluate the accuracy and precision of the three-dimensional (3D) imaging system of children's facial soft tissue by comparing linear measurements. The subjects of the study were 15 children between the ages of 7 and 12. Twenty-three landmarks were pointed on the face of each subject and 16 linear measurements were directly obtained 2 times using an electronic caliper. Two sets of 3D facial images were made by the 3D scanner. The same 16 measurements were obtained on each 3D image. In the accuracy test, the total average difference was 0.9 mm. The precision of 3D photogrammetry was almost equivalent to that of direct measurement. Thus, 3D photogrammetry by the 3D scanner in children had sufficient accuracy and precision to be used in clinical setting. However, the 3D imaging system requires the subject's compliance for exact images. If the clinicians provide specific instructions to children while obtaining 3D images, the 3D device is useful for investigating children's facial growth and development. Also the device can be a valuable tool for evaluating the results of orthodontic and orthopedic treatments.

• Journal of KIISE:Software and Applications
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• v.36 no.12
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• pp.1034-1037
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• 2009

Sign language spotting is the task of detecting the start and end points of signs from continuous data and recognizing the detected signs in the predefined vocabulary. The difficulty with sign language spotting is that instances of signs vary in both motion and shape. Moreover, signs have variable motion in terms of both trajectory and length. Especially, variable sign lengths result in problems with spotting signs in a video sequence, because short signs involve less information and fewer changes than long signs. In this paper, we propose a method for spotting variable lengths signs based on semi-CRF (semi-Markov Conditional Random Field). We performed experiments with ASL (American Sign Language) and KSL (Korean Sign Language) dataset of continuous sign sentences to demonstrate the efficiency of the proposed method. Experimental results show that the proposed method outperforms both HMM and CRF.

• Journal of Korea Multimedia Society
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• v.5 no.2
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• pp.158-166
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• 2002

In this paper, we proposed a contour shape description method which use the CFR(contour fluctuation ratio) feature. The CFR is the ratio of the line length to the curve length of a contour segment. The line length means the distance of two end points on a contour segment, and the curve length means the sum of distance of all adjacent two points on a contour segment. We should acquire rotation and scale invariant contour segments because each CFR is computed from contour segments. By using the interleaved contour segment of which length is proportion to the entire contour length and which is generated from all the points on contour, we could acquire rotation and scale invariant contour segments. The CFR can describes the local or global feature of contour shape according to the unit length of contour segment. Therefore we describe the shape of objects with the feature vector which represents the distribution of CFRs, and calculate the similarity by comparing the feature vector of corresponding unit length segments. We implemented the proposed method and experimented with rotated and scaled 165 fish images of fifteen types. The experimental result shows that the proposed method is not only invariant to rotation and scale but also superior to NCCH and TRP method in the clustering power.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.129-137
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• 2001

Matching pursuit algorithm was successfully demonstrated useful in low bit-rate video coding, However, one of the practical concerns related to applying the matching pursuit algorithm to application is its massive computation required for finding bases whose weighted sum best approximates the given input image. The main contribution of this paper is that we provide a new method that can drastically reduce the computational load without any degradation of image quality. Its main idea is based on reducing the number of inner product calculation required for finding best bases because the complexity of matching pursuit algorithm is due to the exhaustive local inner product calculation. As the first step, we compute a matrix which is the 1-D inner product of the given motion-compensated error input image with the 1-D vertical Gabor functions using the separable property of Gabor bases. In the second step, we calculate length of each vector in the matrix that corresponds to 1-D horizontal Gabor function, and compare the length with the current maximum absolute inner product value so far. According to the result of this comparison, one can decide whether or not to calculate the inner product. Since most of them do not need to calculate the inner product value, one can significantly reduce the computational load. Experimental results show that proposed method reduces about 70% of inner product calculation compared to the Neff's fast algorithm without any degradation of image quality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6C
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• pp.614-622
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• 2006

In this paper, we propose an efficient packetization method to reduce the packetization overhead. For the purpose, we firstly verify the relationship between packet length and packet loss rate. The empirical results show that as the packet length is larger than the path MTU, the packet loss rate is drastically increased, producing poor visual quality at the receiver side. However, as the length of the packet is reduced, we should transmit more packets per frame and the packetization overhead will be increased. This increase in the packetization overhead reduces the number of bits allocated to the video data, resulting in the low visual quality. Therefore, each packet should be packetized to have the packet length close to the path MTU. In this paper, we show that the this process of the packetization with the constraint on the packet length is very similar to the dynamic storage allocation in the operating system. We had thoroughly surveyed the dynamic storage allocation methods used in the recent operating systems and propose to use the allocation methods for the video packetization. We empirically show that the proposed method can reduce the packetization overhead upto 28.3%, compared with the conventional sequential packetization method which have been widely used in Internet video transmission.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.6-17
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• 2009

Objective: The purpose of this study was to evaluate the possibility of using a digital model and cone beam computed tomograph(CBCT) image for model analysis. Methods: Model analyses of CBCT images, plaster models, and digital models of 20 orthodontic patients with a permanent dentition with no proximal metal restorations, were compared. Results: The average differences of tooth size measurements were 0.01 to 0.20 mm, and the average difference of arch length discrepancy measurements were 0.41 mm in the maxilla and 0.82 mm in the mandible. The difference in Bolton discrepancy measurements was 0.17 mm for the anterior region and 0.44 mm overall but with no statistically significant difference. When comparing CBCT images with plaster models, the average differences in tooth size measurements were -0.22 to 0.01 mm, and the average differences in arch length discrepancy measurements were 0.43 mm in the maxilla and 0.32 mm in the mandible. Difference in Bolton discrepancy measurements were 0.35 mm in the anterior region and 1.25 mm overall. CBCT images showed significantly smaller overall Bolton discrepancy measurements. Conclusions: Although there were statistically significant differences in some model analysis measurements, the ranges of measurement errors of the digital model and CBCT images were clinically acceptable. Therefore, a digital model and CBCT image can be used for model analysis.