• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.142-142
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• 2000

We performed a total energy calculation of clean alumunum surfaces of three low indices based on a density functional theory with a local density approximation, using the Ceperly-Alder exhange correlation parametrized by Perdew and Zunger. Pseudopotentials were generated for Al of which the plane wave cut-off was 15Ry. We used Gaussian broadening of a Fermi level to accelerate the convergence of our calculation with the Gaussian energy smearing parameter of 0.005Ry. First, we determine the lattice constant of the aluminum of an face-centered-cubic structure to be 3.96 which is comparable to the experimental data of 4.05 . The cohesive energy of 4.20eV/atom and the bulk modulus of 0.775$\times$1012dyne/cm2 are also comparable to the experimental values of 3.39eV/atom and 0.772$\times$1012dyne/cm2, respectively. Then we investigated the surface relaxation of (100), (110) and (111) surfaces using a 9-layer slab separated by 6-layer thick vacuum. The results are consistent with the existing experimental results.

• 한국정밀공학회지
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• 제10권3호
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• pp.87-96
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• 1993

In this study, the peak stress of a fuillet in elastic structure was optimized to have minimum value by using quadratic isoparametric element. The method of auomatic gridding was also developed along with shape algorithm and design element technique was adopted in selecting design variables. The computer program developed was combined with the Hooke-Jeeves direct algorithm of optimization techniques in order to minimize the peak stress of the fillet. The imployment of design element technique significantly cut down computer time by the reduction in design variables, and the opitmum fillet shape with uniform minimum stress was obtained by varying design variables along x and y directions in improving the shape compared to other results. By using automatic gridding, in which Bezier surfaces and Coons surfaces of cubic interpolation were employed, the irregular boundary was removed resulting in smoother anbd more accurate fillet shape possessing uniform minimum stress.

• 소성∙가공
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• 제13권1호
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• pp.33-38
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• 2004

A new approach for the design of extrusion die surface of arbitrarily shaped section is presented. In order to generate the extrusion die surface. an automatic surface construction method based on B-spline surface and scalar field theory is proposed. The isothermal lines and stream lines designed in the scalar field are introduced to find the control points which are used in constructing B-spline surfaces. Intersected points between the isothermal lines and stream lines are used to construct B-spline surfaces. The inlet and outlet profiles are precisely described with B-spline curves by using the centripetal method for uniform parameterization. The extrusion die surface is generated by using the cubic curve interpolation in the u- and v-directions. A quantitative measure for the control of surface is suggested by introducing the tangential vectors at the inlet and outlet sections. To verify the validity and effectiveness of the proposed method, automatic surface generation is carried out for extrusion dies of arbitrarily shaped sections.

• Restorative Dentistry and Endodontics
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• 제45권4호
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• pp.52.1-52.11
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• 2020

Objectives: Yttria-stabilized tetragonal phase zirconia has been used as a dental restorative material for over a decade. While it is still the strongest and toughest ceramic, its translucency remains as a significant drawback. To overcome this, stabilizing the translucency zirconia to a significant cubic crystalline phase by increasing the yttria content to more than 8 mol% (8YTZP). However, the biocompatibility of a high amount of yttria is still an important topic that needs to be investigated. Materials and Methods: Commercially available 8YTZP plates were used. To enhance cell adhesion, proliferation, and differentiation, the surface of the 8YTZP is sequentially polished with a SiC-coated abrasive paper and surface coating with type I collagen. Fibroblast-like cells L929 used for cell adherence and cell proliferation analysis, and mouse bone marrow-derived mesenchymal stem cells (BMSC) used for cell differentiation analysis. Results: The results revealed that all samples, regardless of the surface treatment, are hydrophilic and showed a strong affinity for water. Even the cell culture results indicate that simple surface polishing and coating can affect cellular behavior by enhancing cell adhesion and proliferation. Both L929 cells and BMSC were nicely adhered to and proliferated in all conditions. Conclusions: The results demonstrate the biocompatibility of the cubic phase zirconia with 8 mol% yttria and suggest that yttria with a higher zirconia content are not toxic to the cells, support a strong adhesion of cells on their surfaces, and promote cell proliferation and differentiation. All these confirm its potential use in tissue engineering.

• 한국컴퓨터그래픽스학회논문지
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• 제21권2호
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• pp.1-10
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• 2015

본 논문에서는 방향성이 있는 포인트 클라우드로부터 3차원 개체의 표면을 복구하는 향상된 기법을 제안한다. 본 방법은 기존에 널리 사용되고 있는 최소 자승법에 기초하고 있지만, 7-방향 박스-스플라인과 체심입방(BCC: Body-Centered)격자를 활용하여 카티시안 격자와 B-스플라인에 기반한 기존의 방법들에 비해 좀 더 나은 품질의 곡면을 빠른 시간에 얻을 수 있다. 구체적으로는, 기존의 두 방법론과 비교해 보았을 때 본 방법은 평균적으로 약 53%의 연산시간만에 좀 더 나은 품질의 곡면을 얻을 수 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.141-141
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• 2013

Shape control of metal nanocrystals has broad applications, including catalysis, plasmonics, and sensing. It was found that controlling the atomic arrangement on metal nanocrystal surfaces affects many properties, including the electronic dipole or work function. Tuning the surface structure of exposed facets of metal nanocrystals was enabled by shape control. We investigated the effect of shape on nanomechanical properties, including friction and adhesion forces. Two nanoparticles systems, high-index {321} and low-index {100}, were used as model nanoparticle surfaces. Scanning force microscopy was used to probe nanoscale friction and adhesion. Because of the abundant presence of high-density atomic steps and kinks, high-index faceted nanoparticles have a higher surface energy than low-index faceted cubic nanoparticles. Due to this high surface energy, high-index faceted particles have shown stronger adhesion and higher friction than low-index nanoparticles. We discuss the results in light of the differences in surface energy as well as the effect of capping layers in the measurement.

• 한국기계가공학회지
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• 제20권2호
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• pp.23-31
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• 2021

Surface texturing is a promising route to reduce the friction forces between two surfaces in sliding contact. To this end, the fabrication of micro dimples is one of the most widely used surface texturing methods. According to published results, textured surfaces with elliptical micro dimples offer the best friction performance. Therefore, we fabricated elliptical micro dimples on carbon steel (SM45C) by using dual frequency vibration assisted machining. High and low frequencies of 16.3 kHz and 230 Hz were applied to the 3D resonant elliptical vibrator. The 3D resonant elliptical vibrator with a triangular cubic boron nitride insert was assembled on a computer numerically controlled turning lathe. Oval micro dimples of various profiles were manufactured on carbon steel. In terms of the profile of the elliptical micro dimples, the experimental results indicated that the average micro dimple width and depth were 112 ㎛ and 7.7 ㎛. These dimensions are closely related to the cutting conditions and can be easily controlled.

• 한국CDE학회논문집
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• 제1권1호
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• pp.76-83
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• 1996

A three dimensional FE mesh generation scheme based on mapping approach is proposed in this study. A volume in Eucledian space is represented by composite hyperpatches which are piecewise cubic functions in parameters u, v, w. A key idea in the proposed approach is that I sampled grid data points lying only on the boundary surfaces are needed for the shape representation. Inner points which are necessary to form a hyperpatch are internally generated by Coons patches. This approach is most appropriate for the shapes which are compositions of hexahedronlike shapes and also severely curved.

• 산업기술연구
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• 제22권A호
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• pp.83-87
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• 2002

Many industrial products such as paints, ink and adhesives are composed of the ingredients of a mixture. In mixture experiments, the characteristics of quality(response) depends only on the proportions of the ingredients and does not depend on the total amount of the mixture. This article discusses the constrained mixture experimental design, the data analysis, and the optimum formulation of ingredients based on the two quality characteristics - taste and flavor. It IS shown that efficient designs can be constructed from D-optimal criterion. Special cubic models were selected as the final mixture response surfaces for both reponses. The desirability function was used for the optimization of the two responses.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book I
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• pp.686-697
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• 2003

A new colloidal silver (Ag) system is present in which a fine colloidal Ag is in situ deposited onto functionalized porous poly (ethylene glycol dimethacrylate) (poly (EGDMA)) microspheres. The effectiveness of Ag deposition was investigated considering the surface characteristics of poly (EGDMA) microspheres. The result reported in this study illustrates that the control of surface area and surface functionality (in this study, a hydroxyl group) of poly (EGDMA) microspheres is an important factor that determines practically the degree of deposition of colloidal Ag. The x-ray analysis showed that Ag nanoparticles were dispersed evenly inner and outer surfaces and had a face center cubic (fee) phase. In the preservative efficacy test, the Ag-containing poly (EGDMA) microspheres had a powerful anti-bacterial activity, showing a high potential for a new preservative in cosmetic industry.