• Interaction and multiscale mechanics
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• 제1권2호
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• pp.211-230
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• 2008

Owing to the growing size of the eigenvalue problem and the growing number of eigenvalues desired, solution methods of iterative nature are becoming more popular than ever, which however suffer from low efficiency and lack of proper convergence criteria. In this paper, three efficient iterative eigenvalue algorithms are considered, i.e., subspace iteration method, iterative Ritz vector method and iterative Lanczos method based on the cell sparse fast solver and loop-unrolling. They are examined under the mode error criterion, i.e., the ratio of the out-of-balance nodal forces and the maximum elastic nodal point forces. Averagely speaking, the iterative Ritz vector method is the most efficient one among the three. Based on the mode error convergence criteria, the eigenvalue solvers are shown to be more stable than those based on eigenvalues only. Compared with ANSYS's subspace iteration and block Lanczos approaches, the subspace iteration presented here appears to be more efficient, while the Lanczos approach has roughly equal efficiency. The methods proposed are robust and efficient. Large size tests show that the improvement in terms of CPU time and storage is tremendous. Also reported is an aggressive shifting technique for the subspace iteration method, based on the mode error convergence criteria. A backward technique is introduced when the shift is not located in the right region. The efficiency of such a technique was demonstrated in the numerical tests.

• 한국전기전자재료학회논문지
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• 제37권4호
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• pp.412-419
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• 2024

Mn-doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_2/3Nb_1/3)O₃-PbTiO₃ (Mn:PIN-PMN-PT) single crystals, which exhibit improved phase transition temperatures and coercive field properties compared to Pb(In_1/2Nb_1/2)O₃-Pb(Mg_2/3Nb_1/3)O₃-PbTiO₃ (PIN-PMN-PT) single crystals, are expected to be utilized in high-power acoustic transducers. Bridgeman method, growing single crystals along the axial direction from melt, is most widely used method for single crystal growth with large size and high quality. However, single crystal boules grown by the Bridgeman method demonstrate a PT compositional variation, giving rise a distribution of crystal structure and material properties along the growing axis. To employ piezoelectric single crystals grown by the Bridgeman method for acoustic transducers, it is essential to investigate their overall property distribution. In this study, the compositional distribution and property variation of Mn:PIN-PMN-PT single crystals grown by the Bridgeman method was investigated. Measured compositional distribution of PT was from 29% to 32.5% in the Rhombohedral crystal region of the boule. Two types of specimen, [011]-poled Mn:PIN-PMN-29PT and Mn:PIN-PMN-32PT single crystals, were fabricated and tested to obtain full property variation at both ends of the Rhombohedral crystal region. The properties related to the 32 directional vibration mode and the properties related to high-power driving were measured to confirm the overall distribution of properties by composition.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 춘계학술대회
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• pp.646-648
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• 2012

본 논문에서는 다양한 휴대단말 환경에서 획득한 영상에서 관심 객체의 특성을 추출하여 검출하는 내용 기반 영상 검색 기술을 제안한다. 검출하고자 하는 모델 영상의 HSI 컬러 정보를 이용한 컬러 히스토그램 정합법을 사용하여 관심 객체가 존재하는 템플릿을 검출한다. 해당 영역에서 해리스코너 검출 기법을 사용하여 코너 포인트를 검출 후 영역 성장법을 적용하여 관심 객체를 검출해내는 기법을 제안한다. 객체 검출 성능을 향상시키며 휴대단말 간의 속도를 향상시키기 위해 색상(Hue) 영역 정보만을 이용하여 연산량을 감소시키며 실시간 처리가 가능하도록 한다.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권12호
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• pp.651-658
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• 2000

This paper presents a new method to extract traffic information such as number of passing vehicles and average speed by a pair of stereo road images. The whole process consists of the extraction of vehicles and the tracking of the extracted vehicles. For the extraction of vehicles, the outline of each vehicle is obtained by using binary region growing technique applied to disparity map based on multi-resolution stereo matching. The Kalman filter tracking algorithm is applied to the extracted vehicle outlines to determine the flow of vehicles. Experimental results show that the proposed method significantly improved recognition rate of vehicles over the conventional methods-frame difference and background elimination methods.

• 대한전자공학회논문지SP
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• 제40권1호
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• pp.51-62
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• 2003

본 논문에서는 분할기반 영상 부호화를 위한 새로운 영상 분할 알고리즘을 제안한다. 제안된 방법은 움직임과 밝기 정보에 기반한 새로운 유사성 척도를 사용한다. 그리고 하나의 분할 단계 내에 밝기와 움직임 정보가 함께 결합된다. 영상 분할은 분수령 알고리즘에 기반한 영역 확장법을 통해 이루처지며, 연속된 프레임에 대한 분할은 분할결과가 시간축으로 일관성을 유지하도록 추적방법을 통해 이루어진다. 모의실험결과, 제안된 방법이 통계적 척도만을 사용한 방법과는 달리, 물체의 경계를 결정하는데 효과적임을 보였다.

• 대한의용생체공학회:의공학회지
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• 제26권6호
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• pp.383-391
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• 2005

Age-related White Matter Changes (WMC) on Magnetic Resonance Imaging (MRI) are known to appear frequently in Multiple sclerosis (MS) and Alzheimer's disease and to be related to cognitive impairment. The characterization of these WMC is very important to the study of psychology and aging. These changes consist of periventricular and subcortical types, however it is difficult to detect and segment WMC using only intensity-based methods, because their intensity, level IS similar to th~t of the gray matter (GM). In this paper, we propose a new method of segmenting periventricular WMC using K-means clustering and morphological features.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2010년도 춘계학술발표대회
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• pp.455-458
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• 2010

Extracting the brain from magnetic resonance imaging head scans is an essential preprocessing step of which the accuracy greatly affects subsequent image analysis. The currently popular Brain Extraction Tool produces a brain mask which may be too smooth for practical use to reduce the accuracy. This paper presents a novel and indirect brain extraction method based on non-brain tissue segmentation. Based on ITK, the proposed method allows a non-brain contour by using region growing to match with the original image naturally and extract the brain tissue. Experiments on two set of MRI data and 2D brain image in horizontal plane and 3D brain model indicate successful extraction of brain tissue from a head.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2009년도 추계학술발표대회
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• pp.345-346
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• 2009

The segmentation of vessel including portal vein, hepatic vein and artery, from Computed Tomography (CT) images plays an important role in the therapeutic strategies for hepatic diseases. Representing segmented vessels in three dimensional spaces is extremely useful for doctors to plan liver surgery. In this paper, proposed method is focused on smoothing technique of segmented 3D liver vessels, which derived from 3D region growing approach. A pixel expand algorithm has been developed first to avoid vessel lose and disconnection cased by the next smoothing technique. And then a binary volume filtering technique has been implemented and applied to make the segmented binary vessel volume qualitatively smoother. This strategy uses an iterative relaxation process to extract isosurfaces from binary volumes while retaining anatomical structure and important features in the volume. Hard and irregular place in volume image has been eliminated as shown in the result part, which also demonstrated that proposed method is a suitable smoothing solution for post processing of fine vessel segmentation.

• Computers and Concrete
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• 제32권6호
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• pp.615-623
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• 2023

Crack detection is an essential method to ensure the safety of dam concrete structures. Low-quality crack images of dam concrete structures limit the application of neural network methods in crack detection. This research proposes a modified attentional mechanism model to reduce the disturbance caused by uneven light, shadow, and water spots in crack images. Also, the focal loss function solves the small ratio of crack information. The dataset collects from the network, laboratory and actual inspection dataset of dam concrete structures. This research proposes a novel method for crack detection of dam concrete structures based on the U-Net neural network, namely AF-UNet. A mutual comparison of OTSU, Canny, region growing, DeepLab V3+, SegFormer, U-Net, and AF-UNet (proposed) verified the detection accuracy. A binocular camera detects cracks in the experimental scene. The smallest measurement width of the system is 0.27 mm. The potential goal is to achieve real-time detection and localization of cracks in dam concrete structures.

• 디지털콘텐츠학회 논문지
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• 제7권4호
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• pp.287-294
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• 2006

대량 주문 생산은 의류 시장에서 고속으로 성장하는 분야이다. 의류 대량 주문 생산 분야에서 2D 가상 착의 시스템은 생산하기 전에 의류를 판매하는 것을 가능하게 해주고 제품 개발과 제조와 관련된 시간과 비용을 절감할 수 있도록 지원하는 비주얼 도구들 중 하나이다. 본 논문은 2D 실사 기반 가상 착의 시스템의 직물 컬러 매핑 방법에 관한 것이다 제안된 방법은 의류 모델 영상에서 영역 성장 기법을 통해 원하는 의류 형상을 분할한 후, 분할된 의류 형상 영역의 명도 차분 맵에 기반하여, 사용자가 선택한 새로운 직물 컬러를 해당 의류 형상 영역에 매핑시킨다. 2D 가상 착의 시스템에서 제안된 방법을 이용할 경우, 모델 의류의 컬러나 명도에 관계없이, 선택된 의류 형상 영역의 음영 및 조명 특성을 유지하면서 직물 컬러를 가상적으로 변경시킬 수 있다. 또한 각기 다른 스타일 혹은 전체 차림새를 위한 다양한 직물 컬러 조합을 신속하고 용이하게 시뮬레이션하고 비교 선택할 수 있다.