전방십자인대 파열시 후방십자인대의 자기공명영상의 소견

김동형,최남홍 대한슬관절학회 1999 대한슬관절학회지 Vol.11 No.1

The purpose of this retrospective study was to compare the morphologic change of the posterior cruciate ligament (PCL) in the anterior cruciate ligament (ACL) tear group and control group by the quantitative analysis. The study groups of patients were; acute ACL tear group (21 patients), chronic ACL tear group (31 patients), and meniscus tear group (20 patients) that undertaken partial meniscectomy. To express curved shape of the PCL quantitatively, the authors made a line (basal line) between the femoral attachment and tibial attachment of the PCL and decided the point (apex) that was located most far away from the base line. And the authors made a line (line 1) between the femoral attachment and the apex of the PCL, another line (line 2) between the tibial attachment and the apex of the PCL, and quartered the base line; first quartile, Hl, second quartile, H2, and third quartile, H3. The authors measured the each angle between basal line and line 1 (angle a), between basal line and line 2 (angle b), each height of the PCL at each quartile (Hl, H2, H3) and at the apex of the PCL on the basal line (H4). Three groups were compared and examined which factor was able to decide whether the ACL was ruptured or nnt. Angle a was significantly higher in chronic ACL tear group than acute ACL tear group and meniscus tear group. In conclusion, the PCL of $quot;sigmoid$quot; or $quot;curled up$quot; shape is a more constant finding of chronic ACL tear than acute ACL tear.

조대술 후 구강내 접근술을 통한 거대 법랑모세포종의 치험례 : 증례보고

김동형,조성웅,서동원,강지연,심재환,이동근,김상중,Kim, Dong-Hyung,Cho, Sung-Woong,Seo, Dong-Won,Kang, Ji-Yeon,Sim, Jae-Hwan,Lee, Dong-Keun,Kim, Sang-Jung 대한구강악안면외과학회 2008 대한구강악안면외과학회지 Vol.34 No.2

Ameloblastoma is the most frequently accuring odontogenic tumor in mouth. The biologic behavior of this neoplasm is locally invasive tumor with a high rate of recurrence. But in case of unicystic ameloblastoma, it was known that the neoplasm can be treated by marsupialization and the recurrence rate is lower. In our clinic, we tried to treat one of ameloblastoma cases by marsupialization and finished the treatment by enucleation via intra-oral approach with sagittal ramus osteotomy. This is a report of that case about 29 years old female patient.

H.264/AVC비디오의 고속 부호화를 위한 인트라모드 선택 알고리듬

김동형,정제창,Kim, Dong-Hyung,Jeong, Je-Chang 한국통신학회 2007 韓國通信學會論文誌 Vol.32 No.6c

H.264 부호화 표준은 부호화 효율을 높이기 위해 1/4 화소 단위의 움직임 추정, 다중 참조 프레임, 인트라 예측, 루프 필터, 다양한 블록 크기의 지원 등과 같은 새로운 부호화 도구들을 사용한다. 이를 통해 이전의 비디오 부호화 표준들에 비해 율-왜곡(率-歪曲) 관점에서 높은 성능을 보이지만 그로 인해 부호기의 복잡도는 상당히 증가한다. 본 논문은 부호기 복잡도의 증가를 초래하는 주요 부호화 도구들 중 인트라 매크로블록 모드 선택의 복잡도 감소에 주안(主眼)점을 두며, 이를 위한 고속 부호화 알고리듬을 제시한다. 제안하는 알고리듬은 먼저 간단한 전처리과정을 통해서 Intra4x4 모드의 예측모드를 한정하고, 선택된 Intra4x4의 예측모드를 사용하여 다른 인트라 모드들의 예측모드를 결정한다. 실험결과 제안하는 알고리듬은 기존의 방법보다 높은 성능을 보이며 참조소프트웨어와 비교하여 약 82%의 속도향상을 가져오는 것으로 나타난다. For the improvement of coding efficiency, the H.264 standard uses new coding tools such as VBS, 1/4-pel accurate ME, multiple references, intra prediction, loop filter, etc. Using these coding tools, H.264 has achieved significant improvements from rate-distortion point of view compared to existing standards. However, the encoder complexity is greatly increased due to these coding tools. We focus on the complexity reduction method of intra-mode decision. Our algorithm first restricts selective prediction modes of Intra4x4 using a simple preprocessing. The prediction modes of Intra4x4 are used for restricting those of the other inter-modes. Simulation results show that the proposed method outperforms other conventional methods and save about 82% of total encoding time.

H.264에서 에러은닉을 위한 Optical Flow기반의 움직임벡터 복원 기법

김동형,정제창 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.2

이미지 보간을 위한 의사결정나무 분류 기법의 적용 및 구현

김동형 (사)디지털산업정보학회 2020 디지털산업정보학회논문지 Vol.16 No.1

With the development of display hardware, image interpolation techniques have been used in various fields such as image zooming and medical imaging. Traditional image interpolation methods, such as bi-linear interpolation, bi-cubic interpolation and edge direction-based interpolation, perform interpolation in the spatial domain. Recently, interpolation techniques in the discrete cosine transform or wavelet domain are also proposed. Using these various existing interpolation methods and machine learning, we propose decision tree classification-based image interpolation methods. In other words, this paper is about the method of adaptively applying various existing interpolation methods, not the interpolation method itself. To obtain the decision model, we used Weka's J48 library with the C4.5 decision tree algorithm. The proposed method first constructs attribute set and select classes that means interpolation methods for classification model. And after training, interpolation is performed using different interpolation methods according to attributes characteristics. Simulation results show that the proposed method yields reasonable performance.

H.264에서의 시방향(時方向) 에러은닉 기법

김동형,정제창,Kim, Dong-Hyung,Jeong, Je-Chang 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.2C

H.264/AVC 동영상 부호화 표준에서는 새로운 부호화 도구들이 추가되었으며 이를 통하여 보다 높은 압축 효율을 보인다. 추가된 부호화 도구들로 인하여 H.264내의 매크로블록은 이전의 부호화 표준들에 비하여 보다 많은 정보를 포함한다. H.264 부호화 표준에서는 하나의 매크로블록이 최대 16개까지의 서로 다른 움직임벡터를 가질 수 있으며 최대 4개의 서로 다른 참조프레임을 가질 수 있다. 또한 다양한 블록크기로의 움직임 추정하며 이는 매크로블록 모드로서 정의된다. 따라서 H.264내의 매크로블록은 기존보다 많은 움직임벡터를 가질 뿐만 아니라 기존에는 없던 참조프레임과 매크로블록 모드의 정보를 새로이 포함하고 있다. 본 논문은 H.264 부호화 표준의 특성을 고려하여 매크로블록이 포함하고 있는 다양한 크기의 움직임 벡터 및 참조 프레임 뿐 아니라 주변 매크로 블록들의 모드를 이용하여 서로 다른 블록 크기로 에러를 은닉함으로써 매크로블록이 포함하고 있는 정보를 최대한 활용하고 이를 통한 효율적인 에러은닉 알고리듬을 제안한다. 제안하는 알고리듬은 기존의 시방향 에러은닉 기법과 비교하여 적은 연산양만을 가지면서도 비트율에 관계없이 향상된 객관적 화질을 나타낸다. For the improvement of coding efficiency, the H.264 standard uses new coding tools. Using these coding tools, H.264 has achieved significant improvements from rate-distortion point of view. The adoption of these tools enables a macroblock in H.264 to have more information, sixteen motion vectors, four reference frames and a macroblock mode. In this paper, we present an efficient temporal error concealment algorithm by using not only motion vectors and reference frames but also macroblock mode of neighbor macroblocks. Our algorithm conceals the macroblock error with variable sizes, $16{\times}16,\;16{\times}8,\;8{\times}16,\;8{\times}8$ depending on the macroblock modes of neighbor macroblocks. Simulation results show that the proposed method increase the objective quality regardless of bit-rate and block error rate.

복원화소의 신뢰도 기반 가중 평균 필터를 활용한 Salt-and-Pepper 잡음 제거 알고리즘

김동형 (사)디지털산업정보학회 2021 디지털산업정보학회논문지 Vol.17 No.2

Salt and pepper is a type of impulse noise. It may appear due to an error in the image transmission process and image storage memory. This noise changes the pixel value at any position in the image to 0 (in case of pepper noise) or 255 (in case of salt noise). In this paper, we present an algorithm for SAP noise reduction. The proposed method consists of three steps. In the first step, the location of the SAP noise is detected, and in the second step, the pixel value of the detected location is restored using a weighted average of the surrounding pixel values. In the last step, a reliability matrix around the reconstructed pixels is constructed, and additional correction is performed with a weighted average using this. As a result of the experiment, the proposed method appears to have similar or higher objective and subjective image quality than previous methods for almost all SAP noise ratios.

Error Concealment Using Intra-Mode Information Included in H.264/AVC-Coded Bitstream

김동형,Seyoon Jeong,Jin Soo Choi,전광길,김승종,Jechang Jeong 한국전자통신연구원 2008 ETRI Journal Vol.30 No.4

The H.264/AVC standard has adopted new coding tools such as intra-prediction, variable block size, motion estimation with quarter-pixel-accuracy, loop filter, and so on. The adoption of these tools enables an H.264/AVC-coded bitstream to have more information than was possible with previous standards. In this paper, we propose an effective spatial error concealment method with low complexity in H.264/AVC intra-frame. From information included in an H.264/AVC-coded bitstream, we use prediction modes of intra-blocks to recover a damaged block. This is because the prediction direction in each prediction mode is highly correlated to the edge direction. We first estimate the edge direction of a damaged block using the prediction modes of the intra-blocks adjacent to a damaged block and classify the area inside the damaged block into edge and flat areas. Our method then recovers pixel values in the edge area using edge-directed interpolation, and recovers pixel values in the flat area using weighted interpolation. Simulation results show that the proposed method yields better video quality than conventional approaches.

Color Domain 및 Gamma Correction 적용에 따른 Retinex 기반 영상개선 알고리즘의 효과 분석

김동형 (사)디지털산업정보학회 2019 디지털산업정보학회논문지 Vol.15 No.1

Retinex-based image enhancement is a technique that utilizes the property that the human visual characteristics are sensitive to the difference from the surrounding pixel value rather than the pixel value itself. These Retinex-based algorithms show different characteristics of the improved image depending on the applied color space or gamma correction. In this paper, we set eight different experimental conditions according to the application of color space and gamma correction, and analyze the objective and subjective performance of each Retinex based image enhancement algorithm and apply it to the implementation of Retinex based algorithm. In the case of gamma correction, quantitative low entropy images and low contrast images are obtained. The application of Retinex technique in HSI color space rather than RGB color space is found to be high in overall subjective image quality as well as maintaining color.

H.264/AVC 비디오의 고속 부호화를 위한 인트라모드 선택 알고리듬

김동형,정제창 한국통신학회 2007 韓國通信學會論文誌 Vol.32 No.6