• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.227-237
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• 1999

As the interface bonding phenomenon between the matrix and the reinforcements has a large effect on the mechanical properties of MMCs, a sugestion of the strength analysis technique considering the residual stress and the interface bonding phenomenon is very important for the design of pans and the estimation of fatigue behavior. In this paper the three dimensional finite element anaysis is performed during the elasto-plastic deformation of the particulate reinforced metal matrix composites. It was analyzed with the volume fractions in view of microscale. Bonding strength. interface separation and matrix void growth between the matrix and the reinforcements will be predicted on deformation under tensile loading. An interface seperation is estimated by the fracture criterion which is a critical value of generalized plastic work per unit volume. The shape of the reinforcement is assumed to be a perfect sphere. And the type of the reinforcement distribution is assumed as FCC array. The thermal residual stress in MMCs is induced by the heat treatment. It is included at the simulation as an initial residual stress. The element birth and death method of the ANSYS program is used for the estimation of the interface bonding strength, void generation and propagation. It is assumed that the fracture in the matrix region begin to occur under the external loading when the plastic work per unit volume is equal to the critical value. The fracture strain will be defined. The experimental data of the extruded $SiC_p$>/606l Al composites are compared with the theoretical results.

• 한국항공우주학회지
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• 제36권2호
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• pp.185-194
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• 2008

본 논문에서는 3차원 사용자 인터페이스를 PC 클러스터에 기반한 타일 가시화 시스템에 효율적으로 연동시킬 수 있는 방법을 제안하였다. 사용자 편의성을 증대하기 위해 개발된 3차원 사용자 인터페이스 소프트웨어에는 모델 자세조종 명령어를 비롯한 각종 메뉴가 포함되어있으며, 3차원 사용자 인터페이스 장비에서 발생되는 신호 잡음을 없애기 위해 박스형 필터를 사용하였다. 또한 타일 가시화 시스템과 3차원 사용자 인터페이스 사이에서 신호 대기로 인해 발생하는 모델 운동 지연 문제를 해결하기 위해 비동기식 통신형태에 기반한 새로운 ‘통신 분리’ 알고리듬을 제안하였으며, 검증 테스트를 통해 제안된 방안의 효율성을 확인하였다.

• 방송공학회논문지
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• 제19권1호
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• pp.83-95
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• 2014

최근 손과 손가락을 인식하는 기술은 HCI(human computer interaction)에서 자연스럽고 친숙한 환경을 제공하기 위한 기술로 주목 받고 있다. 본 논문에서는 깊이 카메라를 이용하여 손과 손가락의 모양을 검출 및 인식하는 방법을 제안하고, 그 인식 결과를 활용하여 다양한 기기와 상호연동 할 수 있는 MPEG-U 기반 향상된 사용자 상호작용 인터페이스 시스템을 제안한다. 제안하는 시스템은 깊이 카메라를 이용하여 손을 검출한 후, 손목의 위치를 찾아 최소 손 영역을 검출한다. 이어서 검출된 최소 손 영역으로부터 손가락 끝점을 검출 한 후, 최소 손 영역의 중심점과 손가락 끝점간의 뼈대를 만든다. 이렇게 만든 뼈대의 길이와 인접 뼈대간의 각도차를 분석하여 손가락을 판별한다. 또한, 제안하는 시스템은 사용자가 MPEG-U에서 정의하는 다양한 심벌들을 손 자세로 취하였을 때 제안 방법을 이용하여 손 자세를 인식하고, 인식 결과를 상호연동 가능한 MPEG-U 스키마 구조로 표현한다. 실험에서는 다양한 환경에서 제안하는 손 자세 인식 방법의 성능을 보인다. 또한, 제안 시스템의 상호연동성을 보이기 위해 인식 결과를 MPEG-U part2 표준에 맞는 XML 문서로 표현하고, MPEG-U 참조 소프트웨어를 이용하여 그 표현 결과에 대한 표준 부합성을 검증한다.

• Carbon letters
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• 제13권1호
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• pp.1-16
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• 2012

The near explosion of attention given to graphene has attracted many to its research field. As new studies and findings about graphene synthesis, properties, electronic quality control, and possible applications simultaneous burgeon in the scientific community, it is quite hard to grasp the breadth of graphene history. At this stage, graphene's many fascinating qualities have been amply reported and its potential for various electronic applications are increasing, pulling in ever more newcomers to the field of graphene. Thus it has become important as a community to have an equal understanding of how this material was discovered, why it is stirring up the scientific community and what sort of progress has been made and for what purposes. Since the first discovery, the hype has expediently led to near accomplishment of industrial-sized production of graphene. This review covers the progress and development of synthesis and transfer techniques with an emphasis on the most recent technique of chemical vapor deposition, and explores the potential applications of graphene that are made possible with the improved synthesis and transfer.

• Current Photovoltaic Research
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• 제8권1호
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• pp.17-26
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• 2020

It is clear that monocrystalline Silicon (Si) ingots are the key raw material for semiconductors devices. In the present industries markets, most of monocrystalline Silicon (Si) ingots are made by Czochralski Process due to their advantages with low production cost and the big crystal diameters in comparison with other manufacturing process such as Float-Zone technique. However, the disadvantage of Czochralski Process is the presence of impurities such as oxygen or carbon from the quartz and graphite crucible which later will resulted in defects and then lowering the efficiency of Si wafer. The heat transfer plays an important role in the formation of Si ingots. However, the heat transfer generates convection in Si molten state which induces the defects in Si crystal. In this study, a crystal growth simulation software was used to optimize the Si crystal growth process. The furnace and system design were modified. The results showed the melt-crystal interface shape can affect the Si crystal growth rate and defect points. In this study, the defect points and desired interface shape were controlled by specific crystal growth rate condition.

• 전산구조공학
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• 제9권1호
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• pp.93-99
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• 1996

서로 다른 두 재료의 접합면에 균열이 수직으로 위치하고 있을 때, 균열에서의 응력특이성차수는 두 재료의 재료특성치에 따라서 변화하게 된다. 이와 같은 균열문제를 해석하기 위하여 다영역경계요소법을 사용하였다. 균열을 포함하는 등매개 경계요소 중간절점의 위치를 적절히 이동하여 놓음으로써 변위에 대한 정확한 형상함수를 나타내었으며, 아울러 트랙션에 대해서도 정확한 보간차수를 나타내도록 시도하였다. 3절점 경계요소를 이용하여 수치해석을 수행하였으며, 이의 결과를 기존의 해석결과와 비교 검토하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.102-107
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• 2001

Interfacial cracks between an isotropic and orthotropic material, subjected to static far field tensile loading are analyzed using the technique of photoelasticity. The fracture parameters are extracted from the full-field isochromatic data and the same are compared with that obtained using boundary collocation method. Dynamic Photoelasticity combined with high-speed digital photography is employed for capturing the isochromatics in the case of propagating interfacial cracks. The normalized stress intensity factors for static crack is greater when $\alpha=90^{\circ}C$ (fibers perpendicular to the interface) than when $\alpha=0^{\circ}C$ (fiber parallel to the interface) and those when $\alpha=90^{\circ}C$ are similar to ones of isotropic material. The dynamic stress intensity factors for interfacial propagating crack are greater when $\alpha=0^{\circ}C$ than $\alpha=90^{\circ}C$. The relationship between complex dynamic stress intensity factor $|K_D|$ and crack speed C is similar to that for isotropic homogeneous materials, the rate of increase of energy release rate G or $|K_D|$ with crack speed is not as drastic as that reported for homogeneous materials.

• 로봇학회논문지
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• 제3권1호
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• pp.58-67
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• 2008

This study developed a novel augmented reality interface for minimally invasive surgery. The augmented reality technique can alleviate the sensory feedback problem inherent to laparoscopic surgery. An augmented reality system merges real laparoscope image and reconstructed 3D patient model based on diagnostic medical image such as CT, MRI data. By using reconstructed 3D patient model, AR interface could express structure of patient body that is invisible outside visual field of laparoscope. Therefore, an augmented reality system improved sight information of limited laparoscope. In our augmented reality system, the laparoscopic view is located at the center of a wide-angle concave screen and reconstructed 3D patient model is displayed outside the laparoscope. By using a joystick, the laparoscopic view and the reconstructed 3D patient model view are changed concurrently. With our augmented reality system, the surgeon can see the peritoneal cavity from a wide angle of view, without having to move the laparoscope. Since the concave screen serves immersive environments, the surgeon can feel as if she is in the patient body. For these reasons, a surgeon can recognize easily depth information about inner parts of patient and position information of surgical instruments without laparoscope motion. It is possible for surgeon to manipulate surgical instruments more exact and fast. Therefore immersive augmented reality interface for minimally invasive surgery will reduce bodily, environmental load of a surgeon and increase efficiency of MIS.

• 대한조선학회논문집
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• 제30권2호
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• pp.30-36
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• 1993

본 논문에서는 설계 경험이 적은 설계자가 효율적으로 선급규정을 이용하여 선체설계를 할 수 있도록, 범용 전문가시스템 쉘(Shell)인 NEXPERT를 이용하여, 선체 구조설계를 지원할 수 있는 전문가 시스템을 개발하였다. 먼저, 기존의 Rule Scantling프로그램으로 부터 지식을 추출하고, 이를 바탕으로 객체지향개념에 의해 지식의 그룹핑과 계층화를 시도하였다. 또한, NEXPERT가 갖고 있는 외부 프로그램과의 접속기능(Callable Interface)을 이용하여 각종 설계에 필요한 프로그램과 실적선 데이타베이스를 접속하였다. 특히, Motif를 이용한 그래픽 사용자 인터페이스(Graphical User Interface : GUI)를 도입하였고, 설계자가 결과에 대해 검토를 할 수 있도록 Knowledge tracing 기능을 부여함으로써, 사용자 지향의 구조부재 치수 결정 지원 전문가 시스템을 개발하였다.

• Structural Engineering and Mechanics
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• 제25권4호
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• pp.383-403
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• 2007

The contact problem for an elastic layer resting on an elastic half plane is considered according to the theory of elasticity with integral transformation technique. External loads P and Q are transmitted to the layer by means of two dissimilar rigid flat punches. Widths of punches are different and the thickness of the layer is h. All surfaces are frictionless and it is assumed that the layer is subjected to uniform vertical body force due to effect of gravity. The contact along the interface between elastic layer and half plane will be continuous, if the value of load factor, ${\lambda}$, is less than a critical value, ${\lambda}_{cr}$. However, if tensile tractions are not allowed on the interface, for ${\lambda}$ > ${\lambda}_{cr}$ the layer separates from the interface along a certain finite region. First the continuous contact problem is reduced to singular integral equations and solved numerically using appropriate Gauss-Chebyshev integration formulas. Initial separation loads, ${\lambda}_{cr}$, initial separation points, $x_{cr}$, are determined. Also the required distance between the punches to avoid any separation between the punches and the layer is studied and the limit distance between punches that ends interaction of punches, is investigated. Then discontinuous contact problem is formulated in terms of singular integral equations. The numerical results for initial and end points of the separation region, displacements of the region and the contact stress distribution along the interface between elastic layer and half plane is determined for various dimensionless quantities.