• Journal of Radiation Protection and Research
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• 제36권3호
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• pp.107-118
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• 2011

Conventional (SRS) and fractionated (FSRS) stereotactic radiosurgery necessarily require stringent overall target point accuracy and precision. We determine three-dimensional intracranial target point deviations (TPDs) in a whole treatment procedure using magnetic resonance image (MRI)-based polymer-gel dosimetry, and suggest a technique for overall system tests. TPDs were measured using a custom-made head phantom and gel dosimetry. We calculated TPDs using a treatment planning system. Then, we compared TPDs using mid bi-plane and three-dimensional volume methods with spherical and elliptical targets to determine their inherent analysis errors; finally, we analyzed regional TPDs using the latter method. Average and maximum additive errors for ellipses were 0.62 and 0.69 mm, respectively. Total displacements were 0.92 ${\pm}$ 0.25 and 0.77 ${\pm}$ 0.15 mm for virtual SRS and FSRS, respectively. Average TPDtotal at peripheral regions was greater than that at central regions for both. Overall system accuracy was similar to that reported previously. Our technique could be used as an overall system accuracy test that considers the real radiation field shape.

• 한국수자원학회논문집
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• 제38권11호
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• pp.973-984
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• 2005

3차원 열동수역학 모형을 개발하여 지형학적으로 복잡한 자연 저수지에서 안정한 성층류의 선택 취수를 부정류 모의하였다. 지배방정식은 2차 정확도의 유한체적법을 이용하여 해석하였다. 개발된 수치모형을 3차원 난류, 성층화된 전단층흐름에 적용하여 검정을 하였다. 수치해석결과는 실험실에서 관측된 선택취수시의 속도 및 온도분포의 일반적인 형상을 양호하게 예측하는 것으로 나타났으나, 자연 저수지에서의 흐름에 대한 적용시에는 속도의 크기를 과대모의 하는 것으로 나타났다. 수치모의에서 구해진 선택취수의 물리적 특성을 논하였다.

• 패션비즈니스
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• 제8권6호
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• pp.68-77
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• 2004

Hollow filament yarns provide better warmth to the touch, lighter in weight, increased opacity, and subtle luster compared to the regular synthetic filament yarns. However, luster properties of textile fibers or fabrics are often difficult to characterize, partly due to the fineness of the surface texture, the anisotropic nature of the weave structure, the complexity of the fiber array comprising a yarn, and the fiber structure itself. In this study, the fabric surface luster image was analyzed using image analysis methods after image acquisition. The hollow filament fiber was modeled using a three-dimensional modeling software. It was then ray-traced for comparing the virtual luster images of the hollow fiber and the regular fiber models based on shading models including photon mapping. The luster object size of the actual hollow filament fabric was smaller than that of the regular filament fabric. The shape of the luster object of the hollow filament fabric was dual peak type while that of the regular filament was single.

• 한국자동차공학회논문집
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• 제3권5호
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• pp.82-89
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• 1995

The three-dimensional fluid motion through the intake port and cylinder of a single DOHC SI engine was investigated with a commercial computational fluid dynamics simulation program, STAR-CD. This domain includes the intake port, intake valves and combustion chamber. Steady induction port flows for various valve lifts have been simulated for an actual engine configuration. The geometry was obtained by direct interface with a three-dimensional CAD software for complicated port and valve shape. The computational grid was generated using the commercial preprocessor ICEM CFD/CAE. Detailed procedures were presented on the generation of the geometry and the block-structured mesh. A standard k-${\varepsilon}$ turbulent model was applied to consider the complexity of the geometry and the fluid motion. The global flow patterns and the distributions of various quantities, such as pressure, velocity magnitude around the valve seat etc., were examined. The computational results, such as mass flow rate, discharge coefficient etc., for various valve lifts were compard with the experimental results and the computational results were found in good agreement with the experiment.

• 대한조선학회지
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• 제27권3호
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• pp.73-88
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• 1990

본 논문에서는 이론적인 방법과 실험적인 방법에 의해서 구와 플레어 형상을 갖는 축대칭 물체와 같이 3차원 물체에 대한 충격력을 검토하였다. 플레어 형상을 갖는 축대칭물체는 선수와 유사한 형상을 갖고 있다. 플레어 형상물체는 연직운동에 대한 것만을 검토한 반면 구에 대해서는 연직운동만이 아니라 사각 충격에 대해서도 검토하였다. 다이폴분포와 등포텐시얼 자유표면문제를 푼 계산결과와 실험결과를 비교하였다. 경계치문제는 알려진 내부유동을 사용함으로써 계산시간을 단축하였다. 이론과 실험의 비교로부터 물체형상에 따라 최대 충격력의 이론추정치는 실험치보다 더 크거나 작을 수 있다는 것을 보여주고 있다. 그러나, 이론치가 실용적으로 사용될 수 있음을 보여주고 있다.

• Korean Journal of Mathematics
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• 제18권3호
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• pp.323-334
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• 2010

We give a theorem for the existence of at least three solutions for the fourth order elliptic boundary value problem with the square growth variable coefficient nonlinear term. We use the variational reduction method and the critical point theory for the associated functional on the finite dimensional subspace to prove our main result. We investigate the shape of the graph of the associated functional on the finite dimensional subspace, (P.S.) condition and the behavior of the associated functional in the neighborhood of the origin on the finite dimensional reduction subspace.

• 제어로봇시스템학회논문지
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• 제5권3호
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• pp.353-362
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• 1999

This paper presents a shape reconstruction method for automatic inspection of the solder joints on PCBs using X-ray. Shape reconstruction from X-ray radiographic image has been very important since X-ray equipment was used for improving the reliability of inspection result. For this purpose there have been lots of previous works using tomography, which reconstructs the correct shape, laminography or tomosynthesis, which are very fast algorithm. Latter two methods show outstanding performance in cross-sectional image reconstruction of lead type component, but they are also known to show some fatal limitations to some kinds of components such as BGA, because of shadow effect. Although conventional tomography does not have any shadow effect, the shape of PCB prohibits it from being applied to shape reconstruction of solder joints on PCB. This paper shows that tomography using Iterative Reconstruction Technique(IRT) can be applied to this difficult problem without any limitations. This makes conventional radiographic instrument used for shape reconstruction without shadow effect. This means that the new method makes cost down and shadow-free shape reconstruction. To verify the effectiveness of IRT, we develop three dimensional model of BGA solder ball, make projection model to obtain X-ray projection data. and perform a simulation study of shape reconstruction. To compare the performance of IRT with that of conventional laminography or tomosynthesis, reconstruction data are reorganized and error analysis between the original model are also performed.

• 한국유체기계학회 논문집
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• 제10권2호
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• pp.7-15
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• 2007

A numerical procedure for optimizing the shape of three-dimensional channel with V-shaped ribs extruded on both walls has been carried out to enhance the turbulent heat transfer. The response surface based optimization is used as an optimization technique with Reynolds-averaged Wavier-stoked analysis. Shear stress transport (SST) turbulence model is used as a turbulence closure. Computational results for average heat transfer rate show good agreements with experimental data. The objective function is defined as a linear combination of heat transfer and friction loss-related terms with a weighting factor. Three dimensionless variables such as, rib pitch-to-rib height ratio, rib height-to-channel height ratio, and the attack angle of the rib are chosen as design variables. Nineteen training points obtained by D-optimal designs for three design variables construct a reliable response surface. In the sensitivity analysis, it is found that the objective function is most sensitive to the ratio of rib height-to-channel height ratio. And, optimal values of design variables have been obtained in a range of the weighting factor.

• 한국해양공학회지
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• 제13권3호통권33호
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• pp.21-28
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• 1999

In this paper, a finite element method for the determination of initial blank shape in sheet metal forming process will be introduced. The initial blank shape is determined by the only one step from the final to the initial blank. The used finite element inverse method adopted Henky's deformation theory, Hill's anisotropic yield criterion and simplified boundary conditions. Based on this theory. a three-dimensional membrane finite element code was developed. The developed code will be applied to several sheet metal forming examples for the demonstration of its validity.

• 대한기계학회논문집B
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• 제28권8호
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• pp.929-936
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• 2004

In the present work, shape of the mixing vane in Plus7 fuel assembly has been optimized numerically using three-dimensional Reynolds-averaged Navier-Stokes analysis of flow and heat transfer. Standard $k-{\epsilon}$ model is used as a turbulence closure. The Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of friction loss. Bend angle and base length of mixing vane are selected as design variables. Thermal-hydraulic performances for different shapes of mixing vane have been discussed, and optimum shape has been obtained as a function of weighting factor in the objective function.