• 한국정밀공학회지
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• 제17권1호
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• pp.185-191
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• 2000

Direct ＆ adaptive slicing of sculptured surfaces in RP improves, quality ＆ accuracy of the final product, compared to the slicing with uniform layer thickness or the slicing of facets (ie, STL). Present D＆A slicing procedures adaptively compute the next layer thickness based on the surface information of current sliced contour, which assumes constant normal curvature values. In some cases, however. such assumption leads to intolerable slicing result which cannot correctly consider the entire local feature shape. We propose improved adaptive slicing algorithms which can determine near-optimal layer thickness, including illustrated examples.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.237-238
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• 2010

• 대한수학회보
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• 제35권4호
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• pp.741-755
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• 1998

We prove the asymptotic lens equivalence in manifolds without conjugate points. By using this property we show that under a metric condition of asymptotically Euclidean and the curvature condition decaying faster than quadratic, any surface $(R^2,g)$ without conjugate points is Euclidean.

• 한국자동차공학회논문집
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• 제4권4호
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• pp.118-129
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• 1996

In this study, three dimensional flow analysis in a HVAC duct was performed computationally using various turbulence models and compared numerical predictions such as outlet flow split, surface pressure distribution along the duct to experimental data. It's well known that accuracy of computational predictions of flow heavily dependent on turbulent models and discritization method. Therefore, in this work, to assess the ability of turbulent models to predict characteristics of duct flow, three kinds of models, namely standard $k-\varepsilon$, RNG $k-\varepsilon$ and modified $k-\varepsilon$, containing parameter for the effect of streamline curvature were employed and validated one another by comparing with experimental data. In results, modified $k-\varepsilon$ turbulence model allows a successful prediction of static pressure distribution particulary at around strong curvature but little improvement flow split. In the futrue, adoption of CFD to design HVAC duct with modified $k-\varepsilon$ model will bring benefits of producing more accurate prediction, and also give designers more detail information much more than now.

• 한국전기전자재료학회논문지
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• 제33권3호
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• pp.163-168
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• 2020

We studied the change of photovoltaic properties of a flexible CuIn_xGa(_1-x)Se₂ (CIGS) solar cell fabricated on polyimide by mechanical bending with curvature radii of 75 mm (75R) and 20 mm (20R). The flexible CIGS cells were flattened on a PET film, then placed and forced against the surface of a curved block fabricated with pre-designed curvatures. Both up (compressive) and down (tensile) bending were applied to a specimen of CIGS on PET with curvatures of 75R and 20R for 10,000 times and 2,000 times, respectively. From J-V measurements, we found that the conversion efficiency (Eff.) was reduced by 3% and 4% for up-and down-bending, respectively, at curvature 75R; it was greatly reduced by 15% for curvature 20R in the up-bending. However, the open circuit voltage (V_oc) and short-circuit current density (J_sc) seemed to change little, within 3%, for the applied mechanical stresses. The degradation in Eff. resulted from the deterioration of the series (R_s) and shunt (R_sh) resistances of the solar cell.

• Physical Therapy Rehabilitation Science
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• 제11권1호
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• pp.88-96
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• 2022

Objective: Purpose of this study was to compare muscle activity ratio of multifidus to erector spinalis according to various cueing including tactile stimulation to provide an effective strategy to provide verbal and tactile feedback during exercise to provoke multifidus muscle activation. Design: Cross-sectional study. Methods: Participants of this study included 28 healthy adults. Muscle activities of the multifidus and erector spinalis were measured while the participants performed tasks according to the three different methods of verbal cueing and three different tactile stimulation. Surface EMG was used to measure the muscular activity of the muscles during all the tasks. Results: Tactile stimulation to abdomen and lumbar vertebrae showed no significant difference in the muscle activity ratio (p>0.05). However, muscle activity ratio of the multifidus in relation to the erector spinalis was increased when subjects were given verbal instructions to make lumbar curvature with little force and to make lumbar curvature while pulling navel (p<0.05). However, it was decreased when they were provided with verbal instruction to make lumbar curvature with strong force (p<0.05). Conclusions: According to the results, proper verbal instruction was an effective tool to increase the muscular activity of multifidus. This study aimed to find and provide the most appropriate verbal cueing while doing exercises to activate multifidus.

• 한국CDE학회논문집
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• 제9권2호
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• pp.143-147
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• 2004

To design parts satisfying physical property in the continuous region, we do it in the discrete rectangular mesh points. Then we obtain points data from parts design and usually construct the surface using least squares method. In such case, that surface has an oscillation in the ineffective region which is inadequate for physical phenomena or NC machining. To solve both problems simultaneously, we extend the surface smoothly to have small curvature in the extended region. Up to now, we use the least squares method for the parts design in Color Picture Tube or Color Display Tube but in this paper, we use functions which is easily controllable. This surface has no error within the effective region compared to the least squares method.

• 한국해양공학회지
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• 제11권2호
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• pp.138-144
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• 1997

This is describes the automatic mesh generation on the ship hull surface. At first ship hull is defined as a cillocation of composite surface patches which satisfy the geometic continuity between adjoining patches by using Gregory surface method. Node points that would be mesh points are ganerated by considering the surface curvature. The triangulation of the node points is by the combination of Ohtsubo's method and Choi's one. After triangulation, shape improvement and quadrilateralization is done with specific criterin. An application to the actual ship and the results are shown.

• 대한기계학회논문집A
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• 제29권6호
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• pp.895-903
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• 2005

In this paper, we present a cutter location (CL) surface deformation approach for constant scallop height tool path generation from triangular mesh. The triangular mesh model of the stereo lithography (STL) format is offset to the CL surface and then deformed in accordance with the deformation vectors, which are computed by the slope and the curvature of the CL surface. In addition, the tool path which is computed by slicing the deformed CL surface is inversely deformed by those same deformation vectors to a tool path with a constant scallop height. The proposed method is implemented, and a tool path generated by the proposed method is tested by simulation and by numerical control (NC) machining. The scallop height was found to be constant over the entire machined surface, demonstrating much better quality than that of mesh slicing, under the same constraints for machining time.

• 대한조선학회논문집
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• 제28권2호
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• pp.21-27
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• 1991

이 논문에서는 periodic 균일 knot vector 뿐만아니라 open 균일 knot vector를 사용하여 선체형상을 Bi-cubic B-spline곡면으로 수식화하는 방법을 보인다. B-spline곡면을 형성하기 위한 B-spline control vertex는 기본 함수의 pseudoinverse matrix를 사용하여 결정된다. 주어진 offset과 형성된 선체곡면을 비교한 결과 잘 일치하였다. 곡면의 순정을 검토하기 위하여 Gaussian곡률을 많은 작은 곡면조각에 대해 계산하여 흑백의 농도 차이를 이용하여 도시화하였다.