• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.116-120
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• 2007

In this study, it is presented analytic results of bending problems in the anisotropic curved thick beam and the anisotropic curved thin beam. The anisotropy is that the material properties are different in each directions and it is difficult to solve the analytical solutions because the behavior is complex. In applying numerical method to solve differential equations of anisotropic curved beams, this study uses the finite element method. Both thin beam theory and thick beam theory are used as the basic governing equations of bending problems in the anisotropic beams. The analytic results are compared between the anisotropic curved thick beams and the anisotropic curved thin beams.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1529-1540
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• 1993

The quenching of steels by water is one of the imprtant problems in the applications of heat treatment, but the fundamental researches by way of theoretical approaches have not been satisfactorily improbed yet. This study aimed at measuring the exact subcooled transient boiling curve for cylindrical specimens and at conducting the analytical researches into the prediction of cooling curves, including the latent heat of phase transformation of steel. Experiments of quenching were made with cylindrical specimens of carbon steel S45C of diameters from 12 to 30 mm and with Cu specimens of 12 mm diameter respectively. The internal temperature of specimens during the quenching process was measured by C-A sheathed thermocouple. The heat fluxes were numerically calculated by the numerical method of inverse heat conduction problem, using the measured inner temperature of specimen as a boundary condition. In case of ${\Delta}T_{sub}=80K$, $q_{s}$ is as follows $q_{s}=2.02{\times}10^{5}{\Delta}T_{set}^{0.05}:{\Delta}T_{set}\le500K.$ And the numerical analysis of unsteady heat conduction during the quenching process was made and the cooling curves were calculated by TDMA method.

• Journal of the Korean Magnetics Society
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• v.8 no.1
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• pp.34-41
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• 1998

We have theoretically investigated torque curve shapes of simple uniaxial magnetic materials by considering conditions for round peaks to exist. These conditions are functions of an applied field, anisotropy field, ans lowest critical field $h_0$ for a domain wall to move or nucleate. The peak having a height of 2h appears when h is lower than h$_1$, the peak having a height of 1 appears when h is higher than h$_2$, ans two peaks having heights of 1 and -1 appear when h is higher than h$_3$. It was found that torque curves of simple uniaxial magnetic materials could be classified into 8 distinct types depending on the existence of hysteresis, the number of the round peaks, and the reversal mechanisms. Simple uniaxial magnetic materials also found to be classifed into the 5 groups depending on $h_0$.

• The KIPS Transactions:PartB
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• v.10B no.5
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• pp.521-526
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• 2003

In this paper, we propose a geometric active contour model based on intensity information and curve evolution for detecting region boundaries. We put boundary extraction problem as the minimization of the difference between the average intensity of the region and the intensity of the expanding closed curves. We used level set theory to implement the curve evolution for optimal solution. It offered much more freedom in the initial curve position than a general active contour model. Our methods could detect regions whose boundaries are not necessarily defiened by gradient compared to general edge based methods and detect multiple boundaries at the same time. We could improve the result by using anisotropic diffusion filter in image preprocessing. The performance of our model was demonstrated on several data sets like CT and MRI medical images.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.440-447
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• 2001

This study investigate experimentally the effect of in height, thickness, and clearance on the boiling heat transfer. The heat surfaces having copper fin array is tested for pool boiling. The gas-liquid exchange interference is investigated based on fin array clearance. These test results can be applied to the design of tube bundle system. The fin height of 2 mm is found to be effective. Effects of heat transfer promotion reaches the highest level when the fin clearance is 0.5mm. Also, heat flux is increased when the fin thickness is smaller. But0.2 mm fin thickness is highly recommended.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1770-1773
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• 2008

수위-유량 관계 곡선식에 포함되어져 있는 매개변수를 추정하기 위해 많이 사용되는 로그선형 회귀분석은 잔차의 비등분산성(heterocesdascity)을 고려하지 못하므로 본 연구에서는 의사우도추정법(Pseudo-likelihood Estimation, P-LE)에 의해 분산함수를 추정하고 이와 함께 회귀계수를 추정할 수 있는 방법을 제시하였다. 이 과정에서 제시된 회귀잔차를 최소화하기 위하여 SA(simulated annealing)이라는 전역 최적화 알고리즘을 적용하였다. 또한 수위-유량 관계 곡선식은 단면 등의 영향으로 인해 구간에 따라 각각 다르게 구축되어져야 하므로 이를 보다 객관적으로 판단하고 분리 위치를 정확히 추정하기 위하여 Heaviside 함수를 의사우도함수에 포함시켜 결과를 추정하도록 하였으며, 2개의 구간을 가지는 유량자료를 이용하여 제시된 방법의 합리성을 통계적으로 실험하였다. 이와 같이 통계적 실험을 통해 제시된 방법들이 기존 방법과 비교하여 가질 수 있는 장점을 파악하였으며, 제시된 방법들을 금강유역 5개 지점에서 대해 수행하여 효율성을 검증하였다.

• Journal of the Korean Magnetics Society
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• v.3 no.2
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• pp.121-124
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• 1993

보자력이 큰 강자성체의 자기이력곡선, 자기변형, 자기이방성등의 측정에 사용할수 있는 펄스전자석을 설계제작하였다. 철심의 형상이 주어졌을때 권선의 회수에 따른 전자석의 여러특성과 축전기 방전시의 전류진폭 감쇄비등을 계산하는 일반식을 유도하고 그것에 의하여 철심단면적 46 nm * 32 nm, 공기간격 28nm의 전자석을 설계 제작하여 20 mT/A의 기울기로 0.49 T까지 직선적인 자기장 대 전류특성을 얻었다. 이 전자석에 에너로그 적분기에 의한 자속계를 부쳐서 박막 또는 박대시료의 major 및 minor 이력곡선을 단번에 쉽게 얻을 수 있는 자기이력곡선 측정기가 구성되었다.

• The Journal of the Korea Contents Association
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• v.5 no.6
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• pp.138-145
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• 2005

This paper describes a technique for detecting the boundary of the optic disk in digital image of the retina using inward and outward curve evolution. This paper offers medical information about glaucoma progresses. For accurate boundary detection, image inpainting based on texture synthesis removes blood vessels crossing the optic disk. For removing noises and preserving boundary of optic disk in image inpainting process, the anisotropic diffusion filtering is necessary. After pre-processing, the optic disk boundary is determined using inward and outward curve evolution. The experimental results show that the algorithm is effective for detection of optic disk boundary.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.2
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• pp.36-43
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• 1993

Real quality and axial void fraction distribution of subcooled refrigerant flow is very important to predict the heat transfer rate and pressure drop in the design of refrigerating system. In the subcooled boiling region, the liquid bulk temperature is still below the corresponding saturation temperature. But beyond the net vapor generation point, bubble detachment is occured actively from the vapor layer formed on the wall. A reliable method to predict the vapor fraction from the liquid bulk temperature is suggested in this paper. And also the actual quality of the subcooled R-113 flow is calculated in the range of 261-1239kg/$m^2$s mass velocity and 10-30K subcooling.

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.102-103
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• 1998