• 인터넷정보학회논문지
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• 제10권5호
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• pp.165-181
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• 2009

본 논문은 해마의 형상 분석을 위한 효과적인 모델 표현 방법과 분석 과정에서의 실제감을 향상시키는 스테레오-햅틱 장치 기반의 대화형 가상 환경을 제공한다. 매개변수형 표면 모델과 골격 표현은 해마의 형상을 효과적으로 표현하고 이러한 정보를 옥트리 자료 구조에 저장하여 대화형의 형상 분석 작업을 가능하게 한다. 그리고 골격 기반 정규화 방법은 다양한 모달리티를 갖는 의료 영상으로부터 생성된 3차원 해마 모델들의 위치와 방위를 정확하게 맞추어주는 기능을 수행한다. 또한 본 논문에서는 정상인 해마 형상 집단과 간질 환자 해마 형상 집단의 정확한 분류 작업을 수행하기 위하여 SVM 알고리즘 기반의 분류기 모델을 구축하였다. 실험 결과를 통하여 본 논문에서 제안한 표현 구조는 다양한 단계의 형상 표현을 제공하며 SVM 기반 분류기는 두 집단간 형상 차이를 분석하기 위한 효과적이었음을 확인하였다. 또한 스테레오 디스플레이 장치와 햅틱 장치를 결합한 가상환경은 사용자에게 향상된 공간 인지와 조작력을 제공하기 때문에 의료 분야에서의 해마 모델과 같은 다양한 해부학적 구조에 대한 분석 작업에 효과적으로 활용될 수 있다.

• 설비공학논문집
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• 제27권12호
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• pp.652-658
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• 2015

The Bubble Jet Loop Heat Pipe (BJLHP) is designed to operate in the horizontal orientation. The motion of the bubble generated by boiling working fluid on a heater surface in the evaporating section of the BJLHP helps the working fluid transfer heat to the condensing portion. In this study, we changed the position of the heater in the evaporating section from concentric to eccentric. The concentric heater is located at the center of the tube in the evaporating part, and the eccentric heater is located at the bottom of the inner surface of the same tube. We used R-134a as the working fluid, and the charging ratio was 50%vol. We measured the temperatures of the evaporating and condensing sections by changing the input electric power from 50 W to 200 W, measuring every 50 W. The results of the experiment show that the effective thermal conductivity of BJLHP using an eccentric heater is four times higher than the BJLHP obtained using a concentric heater. Additionally, we conducted a visualization experiment on the evaporating portion of BJLHP to determine why the effective thermal conductivity was higher. The working fluid was water, and we took pictures of the flow visualization for BJLHP. Nucleate boiling with the eccentric heater was more intense and generated more bubbles. Therefore, the eccentric heater was more saturated by the liquefied working fluid.

• 한국컴퓨터그래픽스학회논문지
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• 제21권4호
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• pp.19-26
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• 2015

본 논문에서는 양팔을 이용한 물체 들기 자세를 최적화 하는 기술을 소개한다. 입력 값은 인체 모델과 임의의 모양의 물체이다. 물체는 크기가 크고 무거워서 두 팔을 사용해서만이 들 수 있다고 가정한다. 작은 물체와 달리 큰 물체는 물리적 안정성을 유지하면서 들고 있는 것이 쉽지 않다. 물체의 방향 그리고 손, 팔, 몸통 등 상체의 자세가 적절한 경우에만 물리적 안정성이 보장될 수 있고, 그러한 자세의 범위는 매우 제한적이다. 본 논문에서는 먼저 렌치스페이스 개념을 사용하여 주어진 인체 자세에 대해 안정성을 평가하는 알고리즘을 제시한다. 다음 전체 형태 공간을 정의 하고 형태 공간 내에서 안정성 평가 점수가 가장 높은 자세를 찾아내는 방법을 소개한다. 여러 가지 모양의 물체와 사용자 요구 조건이 주어졌을 때 최적화 된 들기 자세를 찾아내는 실험을 통해 유용성을 증명한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.788-791
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• 2005

Nodal displacements are referred to the Initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian formulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid fer structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacements and traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One closed loop structure undergoing large deformations is analyzed to demonstrate the efficiency and validity of the proposed method.

• 센서학회지
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• 제32권2호
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• pp.110-117
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• 2023

Reconstructing underwater geometry in real time with forward-looking sonar is critical for applications such as localization, mapping, and path planning. Geometrical data must be repeatedly calculated and overwritten in real time because the reliability of the acoustic data is affected by various factors. Moreover, scattering of signal data during the coordinate conversion process may lead to geometrical errors, which lowers the accuracy of the information obtained by the sensor system. In this study, we propose a three-step data processing method with low computational cost for real-time operation. First, the number of data points to be interpolated is determined with respect to the distance between each point and the size of the data grid in a Cartesian coordinate system. Then, the data are processed with a nonlinear interpolation so that they exhibit linear properties in the coordinate system. Finally, the data are transformed based on variations in the position and orientation of the sonar over time. The results of an evaluation of our proposed approach in a simulation show that the nonlinear interpolation operation constructed a continuous underwater geometry dataset with low geometrical error.

• Advances in aircraft and spacecraft science
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• 제3권4호
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• pp.427-445
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• 2016

Star sensors are the attitude estimation sensors of the satellite orbiting in its path. It gives information to the control station on the earth about where the satellite is heading towards. It captures the images of a predetermined reference star. By comparing this image with that of the one captured from the earth, exact position of the satellite is determined. In the process of imaging, stray lights are eliminated from reaching the optic lens by the mechanical enclosures of the star sensors called Baffles. Research in space domain in the last few years is mainly focused on increased payload capacity and reduction in launch cost. In this paper, a star sensor baffle made of Aluminium is considered for the study. In order to minimize the component weight, material wastage and to improve the structural performance, an alternate material to Aluminium is investigated. Carbon Fiber Reinforced Polymer is found to be a better substitute in this regard. Design optimisation studies are carried out by adopting suitable design modifications like implementing an additional L-shaped flange, Upward flange projections, downward flange projections etc. A better configuration of the baffle, satisfying the design requirements and achieving manufacturing feasibility is attained. Geometrical modeling of the baffle is done by using UNIGRAPHICS-Nx7.5(R). Structural behavior of the baffle is analysed by FE analysis such as normal mode analysis, linear static analysis, and linear buckling analysis using MSC/PATRAN(R), MSC-NASTRAN(R) as the solver to validate the stiffness, strength and stability requirements respectively. Effect of the layup sequence and the fiber orientation angle of the composite layup on the stiffness are also studied.

• 복식
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• 제56권7호
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• pp.69-78
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• 2006

In the early Joseon when royal authority was not still firmly established, King Taejong, or Lee Bang Won tried to make their political position guaranteed through relationships with Ming, making efforts to develop relations with the Chinese nation positively. This political orientation towards Ming by of the king Taejong was also clearly reflected in the settlement of official uniform in the early Joseon, which can be described as follows. Gaoming(誥命), Yinxin(印信) and Mianfu(冕服) granted by Ming for the first time since the foundation of Joseon suggested that the Chinese nation recognized the formal settlement of Joseon dynasty and the inauguration of King Taejong. presumedly, the grants played a critical role in the firm establishment by King Taejong of his royal authority under unstable political conditions. Under the reign of King Taejong, Joseon tried to abolish ancient regime and, instead, accept systems and institutions of Ming as it maintained smooth relations with the Chinese nation. King Taejong whose royal authority was locally deemed lack in legitimacy and morality wanted to receive the moral recognition of his reign. So the monarch tried to not only strengthen his authority, but also take in advanced culture and civilization through submissive diplomatic relations with Ming. This was a practical diplomatic strategy that was clearly discriminated from toadyism. It was a policy towards Ming, pursuing substantial national benefit. Therefore, official uniform system under the reign of King Taejong should be understood accordingly.

• 대한의용생체공학회:의공학회지
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• 제37권2호
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• pp.68-74
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• 2016

In this study, we investigated the rotational characteristics which were comprised of directionality and linearity of target registration error (TRE) as a study in advance to enhance the accuracy of contour-based registration in neuronavigation. For the experiment, two rigid head phantoms that have different faces with specially designed target frame fixed inside of the phantoms were used. Three-dimensional coordinates of facial surface point cloud and target point of the phantoms were acquired using computed tomography (CT) and 3D scanner. Iterative closest point (ICP) method was used for registration of two different point cloud and the directionality and linearity of TRE in overall head were calculated by using 3D position of targets after registration. As a result, it was represented that TRE had consistent direction in overall head region and was increased in linear fashion as distance from facial surface, but did not show high linearity. These results indicated that it is possible for decrease TRE by controlling orientation of facial surface point cloud acquired from scanner, and the prediction of TRE from surface registration error can decrease the registration accuracy in lesion. In the further studies, we have to develop the contour-based registration method for improvement of accuracy by considering rotational characteristics of TRE.

• Elastomers and Composites
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• 제51권1호
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• pp.1-9
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• 2016

Characterization of the UV oxidation for raw natural rubber (NR) was investigated in controlled conditions through image and FT-IR analysis. The UV oxidation was performed on a thin film of natural rubber coated on a KBr window at 254 nm and room temperature to exclude the thermal oxidation. Before or after exposure to UV light, image of the NR thin film was observed at a right or tilted angle. FT-IR absorption spectra were measured in transmission mode with the UV irradiation time. The UV oxidation of NR was examined by the changes of absorption peaks at 3425, 1717, 1084, 1477, 1377, and $833cm^{-1}$ which were assigned to hydroxyl group (-OH), carbonyl group (-C=O), carbon-oxygen bond (-C-O), methylene group $(-CH_2-)$, methyl group $(-CH_3)$, and cis-methine group $(cis-CCH_3=CH-)$, respectively. During the initial exposure period, the results indicated that the appearance of carbonyl group was directly related to the reduction of cis-methine group containing carbon-carbon double bond (-C=C-). Most of aldehydes or ketones from carbon-carbon double bonds were formed very fast by chain scission. A lot of long wide cracks with one orientation at regular intervals which resulted in consecutive chain scission were observed by image analysis. During all exposure periods, on the other hand, it was considered that the continuous increment of hydroxyl and carbonyl group was closely related to the decrement of methylene and methyl group in the allylic position. Therefore, two possible mechanisms for the UV oxidation of NR were suggested.

• 한국전자통신학회논문지
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• 제8권12호
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• pp.1923-1932
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• 2013

본 논문에서는 광각 카메라로 촬영한 영상에서 생기는 영상의 왜곡 문제를 해결하기 위하여, 카메라 모델의 추정과 검증을 통하여 광각 카메라 영상에서의 방사형 왜곡을 보정하는 방법을 제안한다. 먼저, 교정 패턴으로부터 렌즈의 초점 거리와 주점의 위치 등으로 구성된 내부 파라미터와 회전과 위치 정보로 구성된 외부 파라미터를 찾음으로써 카메라의 왜곡 모델을 추정한다. 다음으로, 추정된 카메라 모델로부터 역으로 코너점을 다시 추출하여 검증하고, 마지막으로, 검증된 카메라 모델을 이용하여 영상의 왜곡을 보정한다. 일반 웹 카메라와 광각 카메라로부터 격자 모양의 교정 패턴을 촬영한 영상을 이용하여 방사형 왜곡을 보정하는 실험을 수행한 결과, 제안된 방법이 80% 이상의 개선 성능을 보임을 확인하였다.