• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.129-130
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• 2009

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.615-616
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• 2010

• 한국정보과학회논문지:소프트웨어및응용
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• 제34권12호
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• pp.1045-1055
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• 2007

잠재토픽모델(latent topic model)은 데이타에 내재된 특징적 패턴이나 데이타 정의 자질들 간의 상호 관련성을 확률적으로 모델링하고 자동 추출하는 모델로서 최근 텍스트 문서로부터의 의미 자질 자동 추출, 이미지를 비롯한 멀티미디어 데이타 분석, 생물정보학 분야 등에서 많이 응용되고 있다. 이러한 잠재토픽모델의 대규모 데이타에 대한 적용 시 그 효과 증대를 위한 중요한 이슈 중의 하나는 모델의 효율적 학습에 관한 것이다. 본 논문에서는 대표적 잠재토픽모델 중의 하나인 PLSA (probabilistic latent semantic analysis) 기법을 대상으로 점진적 EM 알고리즘을 활용한, 기본 EM 알고리즘 기반의 기존 학습에 대한 학습속도 증진 기법을 제안한다. 점진적 EM 알고리즘은 토픽 추론 시 전체 데이타에 대한 일괄적 E-step 대신에 일부 데이타에 대한 일련의 부분적 E-step을 수행하는 특징이 있으며 이전 데이터 일부에 대한 학습 결과를 바로 다음 데이타 학습에 반영함으로써 모델 학습의 가속화를 기대할 수 있다. 또한 이론적인 측면에서 지역해로의 수렴성이 보장되고 기존 알고리즘의 큰 수정 없이 구현이 용이하다는 장점이 있다. 논문에서는 해당 알고리즘의 기본적인 응용과 더불어 실제 적용과정 상에서의 가능한 데이터 분할법들을 제시하고 모델 학습 속도 개선 면에서의 성능을 실험적으로 비교 분석한다. 실세계 뉴스 문서 데이타에 대한 실험을 통해, 제안하는 기법이 기존 PLSA 학습 기법에 비해 유의미한 수준에서 학습 속도 증진을 달성할 수 있음을 보이며 추가적으로 모델의 병렬 학습 기법과의 조합을 통한 실험 결과를 간략히 제시한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.529-530
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• 2006

Manufacturing industry is changing rapidly. Prototyping with rapid manufacturing is a part of every business in many companies and prototypes are used efficiently as a part of the production development process. Sheet metal forming has traditionally been a technology area where prototyping has been extremely expensive and efficient options for low volume have been limited. This paper describes the process for incremental sheet forming technologies to make the prototype for a brake dust shield of vehicles, which includes the remodeling method to make a base mold and tool path for sheet metal forming and 5-axes laser cutting machine to trim the prototype product.

• Interaction and multiscale mechanics
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• 제6권2호
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• pp.211-235
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• 2013

An incompressible smoothed particle hydrodynamics (ISPH) method based on the incremental pressure projection method is developed in this study. The Rayleigh-B$\acute{e}$nard convection in a square enclosure is used as a validation case and the results obtained by the proposed ISPH model are compared to the benchmark solutions. The comparison shows that the established ISPH method has a good performance in terms of accuracy. Subsequently, the proposed ISPH method is employed to simulate natural convection from a heated cylinder in a square enclosure. It shows that the predictions obtained by the ISPH method are in good agreements with the results obtained by previous studies using alternative numerical methods. A rotating and heated cylinder is also considered to study the effect of the rotation on the heat transfer process in the enclosure space. The numerical results show that for a square enclosure at, the addition of kinetic energy in the form of rotation does not enhance the heat transfer process. The method is also applied to simulate forced convection from a circular cylinder in an unbounded uniform flow. In terms of results, it turns out that the proposed ISPH model is capable to simulate heat transfer problems with the complex and moving boundaries.

• 한국항만학회지
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• 제14권3호
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• pp.331-340
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• 2000

For the rational and economic design of the structural elements of ships which is built using welding, the ultimate strength analyses of the plates having initial imperfections, such as welding residual stresses and strains, are needful. The welding deformation usually relied on approximative equations or based on expert's experience. But in this paper, for the thermal elasto-plastic analysis of plates, the finite element analysis was performed, based on initial strain method. In formulating the incremental analysis, unbalanced force terns were included. In the plastic domain during the incremental process, the 2nd order terns stress increment and yield stress increment were considered, so that time increment could be controlled for a more stable solution. The ultimate strength analysis program of the plates having initial imperfections was made. The ultimate strength analysis was carried out based on the results of the welding deformations of this paper. In the ultimate strength analysis the Rayleigh-Ritz method based on the minimum potential theory was used.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 봄 학술발표회 논문집
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• pp.17-27
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• 1995

For the post-buckling and elasto-plastic analysis of shell structures, the total Lagrangian formulation is presented based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors in the iteration process and evaluating the total Green-Lagrange stain corresponding U total displacements. In the calculation of the stiffness matrix, the element formulation takes into account the effect of finite rotation increments by retaining second order rotation terms in the incremental displacement field. The selective or reduced integration scheme using the heterosis element is applied in order to overcome both shear locking phenomena and the zero energy mode. The load/displacement incremental scheme is adopted for geometric non-linear F .E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with references's results.

• 소성∙가공
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• 제4권2호
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• pp.131-140
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• 1995

In this paper damage propagation of a material during forming is investigated with the concept of continuum damage mechanics. An isotropic damage model based on the theory of materials of type N is adopted to describe the damage process of a ductile material with large elasto-viscoplastic deformation. The stiffness degradation of the loaded material is chosen as a damage measure. The highly nonlinear equilibrium equations are reduced to the incremental weak form and approximated by the total Lagrangian finite element method. To simulate contact condition, extended interior penalty method with modified coulomb friction law is adopted. The displacement control method along with the modified Riks' continuation technique is used to solve the incremental iterative equations. As numerical examples, upsetting problem and backward extrusion problem are simulated and the results of damage propagation and $J_2$ stress contours with and without friction are presented.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.122-126
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• 2000

In particle or short-fiber reinforced composites cracking of the reinforcements is a significant damage mode because the broken reinformcements lose load carrying capacity . The average stress in the inhomogeneity represents its load carrying capacity and the difference between the average stresses of the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The composite in damage process contains intact and broken reinforcements in a matrix, An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori-Tanaka's mean field concept. influence of the cracking damage on the Eshelby's equivalent inclusion method and Mori-Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.929-932
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• 1995

In the work, a new computerized incremental forming method having high flexibility has been developed. In the mothod, the ordinary tools are replaced by various small tools, and only the small local region of a sheet blank is incrementally by movement of these tools. Since a small tool moves over the arbitrary surface ofthe dies using a NC machine, it is possible to produce three-dimensional and non-symmetric parts directly from CAD data. Arbitrarily shaped dies are made by LOM(Laminated Object Manufacturing), which is one of the Rapid Prototyping Methods. A forming machine is designed and developed by introducing a computer to control the movement of the tools.