• 소성∙가공
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• 제1권1호
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• pp.52-65
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• 1992

In this study a new simplified three-dimensional numerical method and the associated computer program have been developed to simulate the non-axisymmetric extrusion processes. The two-dimensional rigid-plastic finite element method under the generalized plane-strain condition is combined with the slab method. To define the die geometry for a non-axisymmetric extrusion. area mapping technique was used. Streamlined die surface was used to minimize the total extrusion pressure. Extrusion of square, hexagonal and 'T' section from round billet have been simulated and experimented with a model material. The computed results were in good agreement with the experiments in cross-sectional grid distortion. Computational results will be valuable for designing tool geometries and corresponding processes.

• 한국광학회:학술대회논문집
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• 한국광학회 2004년도 제15회 정기총회 및 동계학술발표회
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• pp.272-273
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• 2004

Optical connector is prone to take environment attack since it is exposed to various environmental conditions. As the data bit rate is increased in the modern optical communication system. the stability of optical connector becomes more important issue in complex network comprising of many connection by connectors. In this research, to estimate the influence of defects of connector, especially surface scratches, on the transmission, surface scratches were intentionally introduced on the cross sectional surface of optical connector and the insertion loss, return loss. and BER were measured as functions of geometry and density of scratches, Environmental conditioning was also performed onto these connectors and the variations of basic optical characteristics mentioned above were measured. Based on this measurement the lifetime of connectors was estimated by statistical prediction method.

• 소음진동
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• 제3권3호
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• pp.271-278
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• 1993

Acoustic characteristics of silencer system are affected by various geometric parameters such as cross sectional geometry, size of chamber, and location of inlet-outlet port. It is impossible to obtain exact solutions of the equations of acoustic wave propagation except few simple cases. So, we resort to numerical techniques to analyze performance of acoustic system. In this work, finite element formulation has been obtained to predict transmission loss of an arbitrary 3-dimensional muffler in the presence of mean flow of low mach number. The effect of the degree of the ellipticity of expansion chambers on the transmission loss has been studied using the resulting finite element equation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.49-53
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• 2003

In this study, the geometric design parameters of ejector system were investigated. The critical parameters were primary nozzle area ratio, 2nd-throat cross sectional area and 2nd-throat L/D ratio. At every geometry cases, primary pressure and secondary pressure were measured simultaneously according to secondary mass flow rate. From the results, the ejector starting pressure, unstarting pressure and minimum secondary flow pressure were found and we got the effect of geometric parameters to ejector performance and the way to optimal design of ejector system for chemical lasers operating. Also the experiments of changing secondary flow temperature were carried out.

• 융복합기술연구소 논문집
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• 제1권1호
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• pp.24-28
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• 2011

The purposes of this study are predictions of the changes in the section geometry and determination of the initial cross section so that opposite side in height direction is exactly parallel after coiling process. Finite element analysis is carried out for the calculation of the sectional changes for mold spring item. Analysis results reveal that the slope of the top and bottom sides varies in the range of 5 to 8 degrees and the amount depends on the dimension of the outer diameter. The slopes of the sides should be defined first among design variables.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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• pp.395-397
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• 2006

Air interlacing serves to protect the yarn against damage, strengthens inter-filament compactness or cohesion, and ensures fabric consistency. The air interlacing nozzle is used to introduce intermittent nips to a filament yarn so as to improve its performance in textile processing. The effect of various interlacing nozzle geometries on the interlacing process was studied. The geometries of interlacing nozzles with single or multiple air inlets located across the width of yarn channels are investigated. The basis case is the yarn channel, with a perpendicular main air inlet in the middle. Other cases have main air inlets, slightly inclined double sub air inlets, The yarn channel cross sectional shapes are either semicircular or rectangular shapes. The compressed impinging jet from the main air inlet hole hits the opposing bottom wall of the yarn channel, is divided into two branches, joins with the compressed air coming out from sub air inlet at the bottom and creates two free jets at both ends of the yarn channel. The compressed air movement in the cross-section consists of two opposing directional vortices. The CFD-FASTRAN flow parallel solver was used to perform steady simulations of impinging jet flow inside of the interlace nozzles. The vortical structure and the flow pattern such as pressure contour, particle traces, velocity vector plots inside of interlace nozzle geometry are discussed in this pater.

• 한국정보전자통신기술학회논문지
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• 제12권5호
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• pp.475-481
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• 2019

스플린트는 마비, 구축 등이 나타난 환측에 적용하는 대표적인 보조기로서 전통적으로 숙련된 전문가의 수작업을 통해 제작된다. 제작과정은 열가소성 소재를 가열한 후 부드러워진 소재를 환측 부위에 접촉하며 해당 부위의 표면에 피팅시키는 과정을 반복하여 이루어진다. 이러한 전통적 방식은 저온화상의 위험, 제작자의 숙련도에 따른 완성도의 차이 등 여러 문제점을 가지고 있다. 이러한 단점을 보완하기 위하여 3D 프린팅 기술을 이용한 다양한 접근이 시도되고 있으나 3D 스캐너를 이용하는 경우 고비용의 문제, 수작업 측정의 경우 정확도의 문제 등의 단점을 나타내고 있다. 본 연구는 인체의 좌우 대칭성에 착안하여 건측 아래팔의 기하 특징을 이용하여 환측 스플린트를 3D 프린팅 기술로 제작하는 가능성에 관한 사전 연구이다. 디지털 사진과 사진측량기법을 이용하여 건강한 성인 남성으로부터 양측 아래팔의 3차원 가상 모델을 생성하고, 매 20mm 위치마다 둘레 길이 및 단면적을 측정하였다. 동일한 피험자네서 우세측과 비우세측 사이의 둘레 길이 및 단면적은 허용할 만한 수준의 차이를 나타냈으며, 우세측과 비우세측 사이에서 동일한 변수들 간에 높은 수준의 양의 상관관계를 나타냈다. 이러한 결과로부터 건측 아래팔의 기하 특징을 이용하여 3D 프린팅 기술의 적용을 통해 환측 스플린트 제작 가능성을 확인하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.397-401
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• 2008

Knowledge of dynamic characteristics of structural elements often can make difference between success and failure in the design of structure due to resonance effect. In this paper an analytical model of a cantilever beam having midpoint load is considered for structural optimization. This involves creating the geometry which allows parametric study of all design variables. For that purpose optimization of cantilever beam is elaborated in order to find the optimum geometry which minimizes its volume eventually for minimum weight using ANSYS. But such geometry could be obtained by different combinations of width and height, so that it may have the same cross sectional area yet different dynamic behavior. So for optimum safe design, besides minimum volume it should have minimum vibration as well. In order to predict vibration different dynamic analyses are performed simultaneously to solve the eigenvalues problem assuming no damping initially through MATLAB simulations using state space form for modal analysis, which identifies the resonant frequencies and mode shapes belonging to the lowest three modes of vibration. And next by introducing damping effects tip displacement, bending stress and the vertical reaction force at the fixed end is evaluated under some dynamic load of varying frequency, and finally it is discussed how resonance can be avoided for particular design. Investigation of results clearly shows that only structural analysis is not enough to predict the optimum values of dimension for safe design. Potentially this technique will meet maintenance and cost goals of many organizations particularly for the application where dynamic loading is invertible and helps a lot ensuring that the proposed design will be safe for both static and dynamic conditions.

• 한국콘텐츠학회논문지
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• 제11권10호
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• pp.488-493
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• 2011

한국과학기술정보연구원과 가톨릭대학교 의과대학 가톨릭응용해부연구소에서는 척추 연구자들이 쉽게 사용할 수 있는 기초 자료를 구축하고 있다. 척추 형상 정보를 제공하기 위해 60-80대 기증시신 20여 표본을 활용하여 고해상도 척추 (whole spine) CT (pixel dimension : 0.4x mm, thickness: 0.6mm)를 촬영하고 이를 3차원 모델링 소프트웨어(Mimics, Ver.14, Materialise, Belgium)를 사용하여 3차원 형상 모델(shell model, STL format)로 구축하고, 목, 등, 허리 척추의 주요 부위를 계측하여 수치화 하였다. 시신기반 자료의 한계를 극복하기 위해 고령자 호발 질환을 중심으로 대상 환자를 선정하여 X-Ray, CT, BMD 자료를 구축하여 보강하고 있다. 물리적 성질 정보 구축은 기증시신 10여 표본을 활용하여 임상적, 물리적 골밀도를 측정하고, 목척추(cervical), 등척추(thoracic), 허리척추(lumbar) 부분의 굽힘-폄(flexion-extension), 가쪽 굽힘(lateral bending), 회전(torsion), 압축(body/disc compression) 시험을 수행하여 작용력과 굽힘량의 관계를 구축하고 있다. 구축된 물성 시험 결과는 형상 모델과 함께 제공되어 자료의 활용도를 높이고 있으며, 이를 이용하여 한국인 특성이 반영된 척추 관련 연구 및 제품 개발에 활용 될 수 있다.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.98-103
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• 2009

The environment and energy related problem has become one of the most important global issues in recent years. One of the most effective ways of improving the fuel efficiency of automobiles is the weight reduction. In order to obtain this goal the hydroforming technology has been adapting for the high strength steel and its application is being widened. In present study, the chassis components (mainly cross members of engine cradle) simulation and development by hydroforming technology to apply high strength steel having tensile strength of 440 MPa grade is studied. In the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydroformability in details. Overall possibility of hydroformable chassis parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, performing and hydroforming. In the die design stage, all the components of prototyping tool were designed and interference with press was investigated from the point of geometry and thinning.