• Advances in aircraft and spacecraft science
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• 제2권2호
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• pp.217-232
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• 2015

To prevent over-testing of the test-item during random vibration testing Scharton proposed and discussed the force limited random vibration testing (FLVT) in a number of publications. Besides the random vibration specification, the total mass and the turn-over frequency of the load (test item), $C^2$ is a very important parameter for FLVT. A number of computational methods to estimate $C^2$ are described in the literature, i.e., the simple and the complex two degrees of freedom system, STDFS and CTDFS, respectively. The motivation of this work is to evaluate the method for the computation of a realistic value of $C^2$ to perform a representative random vibration test based on force limitation, when the adjacent structure (source) description is more or less unknown. Marchand discussed the formal description of getting $C^2$, using the maximum PSD of the acceleration and maximum PSD of the force, both at the interface between load and source. Stevens presented the coupled systems modal approach (CSMA), where simplified asparagus patch models (parallel-oscillator representation) of load and source are connected, consisting of modal effective masses and the spring stiffness's associated with the natural frequencies. When the random acceleration vibration specification is given the CSMA method is suitable to compute the value of the parameter $C^2$. When no mathematical model of the source can be made available, estimations of the value $C^2$ can be find in literature. In this paper a probabilistic mathematical representation of the unknown source is proposed, such that the asparagus patch model of the source can be approximated. The chosen probabilistic design parameters have a uniform distribution. The computation of the value $C^2$ can be done in conjunction with the CSMA method, knowing the apparent mass of the load and the random acceleration specification at the interface between load and source, respectively. Data of two cases available from literature have been analyzed and discussed to get more knowledge about the applicability of the probabilistic method.

• 인터넷정보학회논문지
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• 제4권1호
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• pp.27-37
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• 2003

본 논문에서는 가상공간과 데이터베이스 처리를 필요로 하는 웹 서비스 생성 시스템 개발을 기술한다. 본 시스템의 주요 특성은 가상공간의 변화와, 가상공간내 객체들의 속성을 포함하는 데이터베이스 내용이 상호 연동되며, 일반사용자가 가상공간상의 각 객체의 속성을 직접 변화시킬 수 있도록 VRML 노드 정보를 시각화해서 객체 정보를 화면상에서 직접 수정할 수 있는 인터페이스를 제공하는 점이다. VRML 파일의 노드들은 트리(Tree)구조로 시각화되었으며 이 인터페이스를 통해 가상공간상의 각 객체에 접근할 수 있도록 구성하였다. 변화된 속성은 데이터베이스에 자동 기록되며, 이에 따라 가상공간을 사용하는 웹 서비스의 내용을 자동 변동시키는 구조로 되어있다. 또한, 일반 사진을 이용하여 텍스춰매핑을 실행시킬 때 각 장면 구성을 위해 사진 3장을 이용한 가중치 적용 보간 방법을 정의한다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.699-722
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• 2019

It is difficult to observe the potential risks of lifting or turn-over operations in the early stages before a real operation. Therefore, many dynamic simulations have been designed to predict the risks and to reduce the possibility of accidents. These simulations, however, have usually been performed for predetermined and fixed scenarios, so they do not reflect the real-time control of an operator that is one of the most important influential factors in an operation; additionally, lifting or turn-over operations should be a collaboration involving more than two operators. Therefore, this study presents an integrated method for a collaborative simulation that allows multiple workers to operate together in the virtual world. The proposed method is composed of four components. The first component is a dynamic analysis that is based on multibody-system dynamics. The second component is VR (virtual reality) for the generation of realistic views for the operators. The third component comprises the control devices and the scenario generator to handle the crane in the virtual environment. Lastly, the fourth component is the HLA (high-level architecture)-based integrated simulation interface for the convenient and efficient exchange of the data through the middleware. To show the applicability of the proposed method, it has been applied to a block turn-over simulation for which one floating crane and two crawler cranes were used, and an offshore module installation for which a DCR (dual-crane rig) was used. In conclusion, the execution of the proposed method of this study is successful regarding the above two applications for which multiple workers were involved.

• 접착 및 계면
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• 제5권2호
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• pp.14-26
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• 2004

For reliable determination of mechanical characteristics of adhesively bonded joints used e.g. as input data for computer-aided design of complex components, the thick-adherend tensile-shear test according to ISO 11003-2 is the most important material testing method. Although the total displacement of the joint is measured across the polymer layer directly in the overlap zone in order to minimize the influence of the stepped adherends, the substrate deformation must be taken into account within the framework of the evaluation of the shear modulus and the maximum shear strain, at least when high-strength adhesives are applied. In the standard ISO 11003-2 version of 1993, it was prescribed to perform the substrate deformation correction by means of testing a one-piece reference specimen. The authors, however, pointed to the excessive demands on the measuring accuracy of the extensometers connected with this technique in industrial practice and alternatively proposed a numerical deformation analysis of a dummy specimen. This idea of a mathematical correction was included in the revised ISO 11003-2 version of 2001 but in the simplified form of an analytical method based on Hooke's law of elasticity for small strains. In the present work, it is shown that both calculation techniques yield considerably discordant results. As experimental assessment would require high-precision distance determination (e.g. laser extensometer), finite element analyses of the deformation behavior of the bonded joint are performed in order to estimate the accuracy of the obtained substrate deformation corrections. These simulations reveal that the numerical correction technique based on the finite element deformation modeling of the reference specimen leads to considerably more realistic results.

• 정보처리학회논문지B
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• 제14B권5호
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• pp.343-350
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• 2007

가상환경이란 사용자들에게 실감나는 감각적 체험과 인터랙션을 제공하여 마치 실제 공간에 있는 것 같은 느낌을 주는 멀티미디어 환경을 일컫는다. 이런 가상환경에 일반 사용자들에게 친숙한 2차원 인터페이스를 활용하여 사용자 인터랙션을 쉽게 도와주는 연구가 많았는데, 주로 특정 가상환경에서만 사용할 수 있고 일반적으로 적용하기 어려운 문제가 있었다. 이런 점을 개선하기 위해 가상환경을 위한 2차원 사용자 인터페이스 저작 프레임워크 개발 시도가 있었으나 사용성이나 유연성이 부족했다. 본 연구에서는 XML과 스크립트 언어를 활용하고 동적으로 모듈을 적재하고 설정하는 기능과 이벤트 처리 메커니즘을 제공하여 사용성과 유연성을 지원하는 새로운 가상현실 인터페이스 제작 툴킷인 HIVE 프레임워크를 만들었다. 본 논문에서는 먼저 HIVE프레임워크에 대해 설명하고, HIVE를 이용하여 다양한 인터페이스를 개발한 예를 보여주며, 향후 연구방향에 대해 논한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.763-764
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• 2013

A three-dimensional image capturing device and its signal processing algorithm and apparatus are presented. Three dimensional information is one of emerging differentiators that provides consumers with more realistic and immersive experiences in user interface, game, 3D-virtual reality, and 3D display. It has the depth information of a scene together with conventional color image so that full-information of real life that human eyes experience can be captured, recorded and reproduced. 20 Mega-Hertz-switching high speed image shutter device for 3D image capturing and its application to system prototype are presented[1,2]. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of 20MHz high-speed micro-optical image modulator, so called 'optical resonator'. The high speed image modulation is obtained using the electro-optic operation of the multi-layer stacked structure having diffractive mirrors and optical resonance cavity which maximizes the magnitude of optical modulation[3,4]. The optical resonator is specially designed and fabricated realizing low resistance-capacitance cell structures having small RC-time constant. The optical shutter is positioned in front of a standard high resolution CMOS image sensor and modulates the IR image reflected from the object to capture a depth image (Figure 1). Suggested novel optical resonator enables capturing of a full HD depth image with depth accuracy of mm-scale, which is the largest depth image resolution among the-state-of-the-arts, which have been limited up to VGA. The 3D camera prototype realizes color/depth concurrent sensing optical architecture to capture 14Mp color and full HD depth images, simultaneously (Figure 2,3). The resulting high definition color/depth image and its capturing device have crucial impact on 3D business eco-system in IT industry especially as 3D image sensing means in the fields of 3D camera, gesture recognition, user interface, and 3D display. This paper presents MEMS-based optical resonator design, fabrication, 3D camera system prototype and signal processing algorithms.

• 정보교육학회논문지
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• 제15권1호
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• pp.67-76
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• 2011

본 논문은 스마트 기기의 터치 인터페이스를 활용하여 학습자가 직접 입체 학습 콘텐츠를 제어함으로써 보다 실감적인 교육 환경을 구축하고자 한다. 또한 기존의 입체 학습 콘텐츠는 제작의 어려움으로 인해 콘텐츠 확보와 제공에 한계가 있어 교사 및 학습자가 직접 콘텐츠를 제작하고 공유할 수 있도록 프레임워크를 설계하였다. 프레임워크는 직관적인 XML 언어로 구성되고 안드로이드가 탑재된 기기에서 재생 및 저작이 가능하도록 어플리케이션을 구현하였으며 콘텐츠 공유를 위한 서버 환경도 구축하였다. 제안한 프레임워크는 전문가 평가를 통해 타당성을 검증한 결과 새로운 학습 콘텐츠 활용 가능성 면에서 긍정적으로 분석되었다.

• 한국전산유체공학회지
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• 제4권1호
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• pp.19-26
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• 1999

This paper describes a numerical method for predicting the incompressible unsteady laminar three-dimensional flows with free-surface. The Navier-Stokes equations governing the flows have been discretized by means of finite-difference approximations, and the resulting equations have been solved via the SIMPLE-C algorithm. The free-surface is defined by the motion of a set of marker particles and the interface behaviour was investigated by means of a "Lagrangian" technique. Using the GALA concept of Spalding, the conventional mass continuity equation is modified to form a volumetric or bulk-continuity equation. The use of this bulk-continuity relation allows the hydrodynamic variables to be computed over the entire flow domain including both liquid and gas regions. Thus, the free-surface boundary conditions are imposed implicitly and the problem formulation is greatly simplified. The numerical procedure is validated by comparing the predicted results of a periodic standing waves problems with analytic solutions. The results show that this numerical method produces accurate and physically realistic predictions of three-dimensional free-surface flows.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.55-58
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• 2008

산업 제품을 디자인하는 디자이너들은 CAD(Computer Aided Design)과 같은 방법을 사용하여 새로운 디자인을 만들어내고, 이를 적용한 가상의 3D 모델을 통해 살펴본다. 이 방법은 직접 손으로 도면을 그리고 단순히 한쪽 면만 살펴볼 수 있었던 기존의 방법에 비해서 컴퓨터로 인한 자동화와 다양한 각도에서 제품에 적용된 새로운 디자인을 살펴봄으로써 시간과 비용을 절감할 수 있다. 이에 우리는 앞서 언급한 디자인 방법에 Augmented Reality와 Rapid Prototyping의 개념을 더해 현실적이고 인터랙티브한 산업제품의 디자인 방법을 고안하였다. 이것은 스티로폼과 같은 재질로 만들어진 mockup을 조립하여 만들고, 3D 모델의 컬러, 재질, 버튼 등의 인터페이스 요소와 실제 제품을 조작하는 것과 같은 인터랙티브한 요소들을 적용시킴으로써 제품을 디자인할 수 있는 증강현실기반 시스템이다.

• 대한기계학회논문집B
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• 제20권7호
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• pp.2397-2408
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• 1996

A numerical study was made of the control of transient oscillatory flow modes in Czochralski convection. The reduction of temperature oscillation was achieved by changing the rotation rate of crystal rod, .OMEGA.$_{S}$=.OMEG $A_{S0}$(1+ $A_{S}$sin(2.pi. $f_{S}$/ $t_{p}$t)). The temporal behavior of oscillation flow was scrutinized over broad ranges of two parameters, i.e., the rotation amplitude( $A_{S}$.leq.0.5) and the nondimensional frequency (0.9.leq. $f_{S}$.leq.1.5). The mixed convection parameter was ranged 0.225.leq.Ra/PrR $e^{2}$.leq.0.929, which encompassed the buoyancy-and forced-dominant convection regimes. Computational results revealed that the temperature oscillations could be reduced effectively by a proper adjustment of the control parameters. The uniformity of temperature distribution near the crystal rod was examined. The control of oscillatory flow modes was also made for a realistic, low value of Pr.