• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권6호
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• pp.247-253
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• 2003

A novel finite element mesh regeneration method is presented for 3D shape optimization of electromagnetic devices. The method has its theoretical basis in the structural deformation of an elastic body. When the shape of the electromagnetic devices changes during the optimization process, a proper 3D finite element mesh can be easily obtained using the method from the initial mesh. For real engineering problems, the method guarantees a smooth shape with proper mesh quality, and maintains the same mesh topology as the initial mesh. Application of the optimum design of an electromagnetic shielding plate shows the effectiveness of the presented method.

• 한국컴퓨터그래픽스학회논문지
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• 제17권3호
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• pp.43-50
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• 2011

본 논문에서는 2차원 입력 형상에 대하여 계층 메쉬를 이용한 빠르고, 품질 저하가 적은 평면 형상변형 기법을 제시한다. 입력으로 주어진 2차원형상의 내부와 경계를 조밀하게 샘플링한 정점의 집합으로 구성된 형상 메쉬와, 입력 형상을 근사적으로 둘러싸는 형상 메쉬의 일부 정점으로 구성된 제어 메쉬를 구성한다. 이때, 형상 메쉬 정점은 제어 메쉬의 정점에 대한 평균값 좌표로 표현한다. 사용자의 형상 변형 입력에 대하여 기존의 비선형 최소자승법을 사용한 메쉬 최적화문제를 풀어 제어 메쉬 정점의 변형될 위치를 구하고, 형상 메쉬는 변형된 제어 메쉬의 정점으로부터 평균값 좌표를 이용하여 최종적인 형상의 변형을 빠르게 계산한다. 형상 메쉬는 입력 형상을 정확히 표현하기 위해 많은 수의 정점으로 구성되는 반면에 제어 메쉬는 상대적으로 적은 수의 정점으로 구성된다. 계산양이 많은 최적화 방법은 제어 메쉬에만 적용되기 때문에 전체 수행시간은 매우 빠르지만, 제어 메쉬의 품질저하에 따라 형상변형의 품질 또한 저하된다. 본 논문에서는 형상 변형의 결과를 조절하고 품질 저하를 보정하기 위해서 사용자 제한에 방위 제어를 포함시켜 형상변형의 강성도를 조절하는 방법을 제시한다. 실험적인 결과에 의하면 본 논문에서 제시한 방법은 비교적 적은 수의 정점을 사용하여 형상 변형의 수행속도가 빠르면서, 변형의 시각적인 품질은 부드럽게 유지된다. 본 논문의 결과는 휴대폰이나 타블렛 PC와 같이 계산속도가 느린 임베디드 시스템에서 형상 변형을 이용한 2차원 애니메이션 제작과 같은 응용문제에 효과적으로 사용될 수 있다.

• International Journal of Contents
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• 제5권4호
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• pp.1-6
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• 2009

In this paper, we propose a mesh smoothing method for mesh models with noise. The proposed method enables not only the removal of noise from the vertexes but the preservation and smoothing of shape recognized as edges and comers. The magnitude ratio of 2D area and 3D volume in mesh data is adopted for the smoothing of noise. Comparing with previous smoothing methods, this method does not need many iteration of the smoothing process and could preserve the shape of original model. Experimental results demonstrate improved performance of the proposed approach in 3D mesh smoothing.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권7호
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• pp.307-314
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• 2003

This paper presents a 3D shape optimization algorithm for electromagnetic devices using the design sensitivity analysis with finite element method. The structural deformation analysis based on the deformation theory of the elastic body under stress is used for mesh renewing. The design sensitivity and adjoint variable formulae are derived for the 3D finite element method with edge element. The results of sensitivity analysis are used as the input data of the structural analysis to calculate the relocation of the nodal points. This method makes it possible that the new mesh of analysis region can be obtained from the initial mesh without regeneration. The proposed algorithm is applied to the shape optimization of 3D electromagnet pole to net a uniform flux density at the target region.

• 한국분말재료학회지
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• 제2권2호
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• pp.135-141
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• 1995

As the first step of study on fabrication of ceramic powders from phytoliths in rice, especially in rice husks, pulverization method of rice husks and the properties of milled rice husks were investigated. Impact methods, such as ball milling, were not meaningful for pulverizing elastic and thin fabric structure of rice husks. The most effective one was cutting method. In the present work, a rotating knife cutting method was applied to pulverizing rice husks. A 40-mesh screen was inserted under the rotating knives. The most portion of the milled powder was found in -50/+100 mesh section. Morphology of the milled rice husks revealed that the husks larger than 70 mesh were flake-like shape, at -70/+100 mesh section relatively equi-axed shape, at -170/+325 mesh section rod-like shape, and below 325 mesh section dust-like shape. Tap density of raw rice husks was about 0.1 $g/cm^3$, while those of milled rice husks were over $0.4 g/cm^3$. This meant that, for a given volume of reactor, raw material charge can be increased more that 4 times when using milled rice husks than unmilled one. True densities of unmilled and milled rice husks were higher than $1.4 g/cm^3$, and increased with decreasing milled sizes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.87-90
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• 1988

This paper reports a simple posteriori error estimate method for adaptive finite element mesh generation using quadratic shape function especially for the magnetic field problems. The elements of quadratic shape function have more precise solution than those of linear shape function. Therefore, the difference of two solutions gives error quantity. The method uses the magnetic flux density error as a basis for refinement. This estimator is tested on two dimensional problem which has singular points. The estimated error is always under estimated but in same order as exact error, and this method is much simpler and more convenient than other methods. The result shows that the adaptive mesh gives even better rate of convergence in global error than the uniform mesh.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.313-313
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• 2016

Transparent conductive oxide (TCO) films have many disadvantages, such as rarity, possible exhaustion, process temperature limitations, and brittleness on a flexible substrate. In particular, as display technology moves toward flexible displays, TCO will become completely unsuitable due to its brittleness. To address theses issue, many researchers have been studying TCO substitutes. In recent efforts, metal nanowires, conducting polymers, carbon nanotube networks, graphene films, hybrid thin films, and metal meshes/grids have been evaluated as candidates to replace TCO electrodes. In this study, we fabricated the TCO film with Ag meshes shape using polystyrene (PS) beads monolayer on the substrate. The PS beads were used as a template to create the mesh pattern. We fabricated the monolayer on the flexible substrate (PES) with the well-aligned PS beads. Electrodes with Ag mesh shape were formed using this patterned monolayer. We could fabricated the Ag mesh electrode with the sheet resistance with $8ohm{\Omega}/{\Box}$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.79-82
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• 2004

In this study, a new refinement technique for 3-dimensional hexahedral element mesh is proposed, which is aimed at the control of mesh density. With the proposed scheme the mesh is refined adaptively to the elemental error which is estimated by 'a posteriori' error estimator based on the energy norm. A desired accuracy of an analysis i.e. a limit of error defines the new desired mesh density map on the current mesh. To obtain the desired mesh density, the refinement procedure is repeated iteratively until no more elements to be refined exist. In the algorithm, at first the regions of mesh to be refined are defined and, then, the zero-thickness element layers are inserted into the interfaces between the regions. All the meshes in the regions, in which the zero-thickness layers are inserted, are to be regularized in order to improve the shape of the slender elements on the interfaces. This algorithm is tested on a simple shape of 2-d quadrilateral element mesh and 3-d hexahedral element mesh. A numerical example of elastic deformation of a plate with a hole shows the effectiveness of the proposed refinement scheme.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.77-83
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• 2009

In this study, we conducted resistance and propulsion performance test of ship composed of the Resistance Test, Propeller Open Water Test and Self Propulsion Test using the CFD(Computational Fluid Dynamics). We used commercial RANS(Reynolds Averaged Navier Stokes equation) solver, as a calculating tool. The unstructured grids were used in a bow and stern of ship, having complex shape, for a convenience of generating grids, and the structured grids were adopted in a central hull and rest of hull having a relatively simple shape which is called hybrid grid method. In addition, The sliding mesh method was adopted to rotate a propeller directly in the Propeller Open Water and Self Propulsion Test. The Resistance Test and Self Propulsion Test were calculated using Volume of Fluid (VOF) model and considering a free surface. And all The three cases were applied realizable k-epsilon model as the turbulence model. The results of calculations were verified for the suitability of calculations by comparing MOERI's EFD results.

• 대한기계학회논문집A
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• 제28권9호
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• pp.1359-1367
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• 2004

The purpose of this study is to predict the dynamic transmission error of the helical gear system. To do so, the equations of motion in the helical gear system which consists of motor, coupling, gear, torque sensor, and brake are derived. As the input parameters, the mass moment of inertia by a 3D CAD software and the equivalent stiffness of the bearings and shaft are calculated and the coupling stiffness is measured. The static transmission error as an excitation is calculated by in-house program. Dynamic transmission error is predicted by solving the equations of motion. Mode shape, the dynamic mesh force and the bearing force are also calculated. In this analysis, the relationship between the dynamic mesh force and the bearing force and mode shape behavior in gear mesh are checked. As a result, the magnitude of mesh force is highly related with the gear mesh behavior in mode shape. The finite element analysis is conducted to find out the natural frequency of gear system. The natural frequencies by finite element analysis have a good agreement with the results by equation of motion. Finally, dynamic transmission error is measured by the specially designed experiment and the results by equation of motion are validated.