• 대한안전경영과학회:학술대회논문집
• /
• 대한안전경영과학회 2004년도 추계학술대회
• /
• pp.197-203
• /
• 2004

Railway system is consisted of various resources such as rail-line, signal, and railcar. It is necessary to efficiently utilize these limited and expensive resources as much as possible up to given line capacity. So far, we treat the line capacity as the criteria for evaluating investment alternatives or for restricting train frequencies, and this criteria is calculated statical and experimental numerical formula. But, line capacity has special attribute that changes dynamically according to operational conditions, so there is a need of new line capacity estimation system. In this paper, we present an improved systematic line capacity model. The proposed model has three main components ; TPS(lain performance simulator), PES(parameter evaluation simulator), LCS(line capacity simulator). The concept of each sub-component is described, including the evaluation method of capacity parameters. And capacity parameter evaluation and estimation results using sample line section data are presented.

• 설비공학논문집
• /
• 제12권6호
• /
• pp.599-608
• /
• 2000

One dimensional numerical modeling was carried out for the melting behavior of dry snow and the unsaturated flow when heat was supplied from the bottom surface. Discrepancy between the previous experimental data and the present numerical results is substantially reduced by considering the density change of water permeation layer due to the infiltration of meltwater. In the parametric study for effective thermal conductivity, it was found that the effect of this parameter to the behavior of snow melting is minor. Sensitivity analysis showed that the melting time is most sensitive to changes in supplied heat flux, snow temperature, and bulk density, whereas snow bulk density and residual saturation have a significant effect on the height of water permeation layer in snow.

• Journal of the Korean Statistical Society
• /
• 제19권2호
• /
• pp.128-138
• /
• 1990

In this paper we study the properties of nonparametric tests for testing the null hypothesis of no changes against one sided and two sideds alternatives in scale parameter at unknown point. We first propose two types of nonparametric tests based on linear rank statistics and rank-like statistics, respectively. For these statistics, we drive the asymptotic distributions under the null and contiguous alternatives. The main theoreticla tools used for derivation are the stochastic process representation of the test staistic and the Brownian bridge approximation. We evaluate the Pitman efficiencies of the test for the contiguous alternatives, and also compute empirical power by Monte Carlo simulation.

• 대한물리의학회지
• /
• 제4권4호
• /
• pp.249-255
• /
• 2009

Purpose：To investigate of gait component in Parkinson's Disease patient. Methods：participated Parkinson's Disease patient(n=12) and Normal adult(n=13). gait measure used by GaitRite. Results：SPSS for win version 12 was used for statistic analysis and independent t-test used to find between two groups. In the comparison of temporal parameter of gait between groups, the swing phase was significant decreased in Parkinson's groups, in the stance phase was significant increased in Normal groups, in the single support was significant decreased in Parkinson's groups and in the double support was significant increased in Parkinson's groups(p<.05). In the asymmetrical ratio of singele support was significant increased in Parkinson's groups(p<.05), and the swing phase and stance phase was significant increased in Parkinson's groups(p<.05). Conclusion：In the Parkinson's Disease patient gait showed temporal and spatial component variable changes comparison normal adult. therefore, it was seems to very important considerable at gait tranning in clinical intervention.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.666-669
• /
• 2004

Substructures position is considered as design parameter to obtain optimal structural changes to raise its dynamic characteristics. In conventional SDM (structural dynamics modification) method, the layout of modifying substructures position is first fixed and at that condition the structural optimization is performed by using the substructures size and/or material property as design parameters. But in this paper as a design variable substructures global translational and rotational position is treated. For effective structural modification the eigenvalue sensitivity with respect to that design parameter is derived based on measured frequency response function. The optimal structural modification is calculated by combining eigenvalue sensitivities and eigenvalue reanalysis technique iteratively. Numerical examples are presented to the case of beam stiffener optimization to raise the natural frequency of plate.

• Bulletin of the Korean Chemical Society
• /
• 제12권5호
• /
• pp.540-544
• /
• 1991

Thin film being formed on the surface of cobalt in the early stage of electrochemically induced passivation was studied by the three-parameter ellipsometry. The growth of the passive film was complete in a few seconds from the onset of the passivating potential, and was followed by a slight decrease in the thickness in 4-40 seconds. The optical constants of the passive film changed gradually during the changes in the thickness. The thickness and the optical properties at the steady state of passivation depended on the potential of the electrode. From the coulometric data and the optical properties, the composition of the passive films was deduced to be close to those of CoO, ${Co_3}{O_4}$ and ${Co_2}{O_3}$ depending on the potential. Cathodic reduction in the presence of EDTA was found to be an efficient way to obtain film-free reference surface of cobalt.

• Steel and Composite Structures
• /
• 제33권1호
• /
• pp.133-142
• /
• 2019

In the present study, microstructure-dependent static stability analysis of inhomogeneous tapered micro-columns is performed. It is considered that the micro column is made of functionally graded materials and has a variable cross-section. The material and geometrical properties of micro column vary continuously throughout the axial direction. Euler-Bernoulli beam and modified couple stress theories are used to model the nonhomogeneous micro column with variable cross section. Rayleigh-Ritz solution method is implemented to obtain the critical buckling loads for various parameters. A detailed parametric study is performed to examine the influences of taper ratio, material gradation, length scale parameter, and boundary conditions. The validity of the present results is demonstrated by comparing them with some related results available in the literature. It can be emphasized that the size-dependency on the critical buckling loads is more prominent for bigger length scale parameter-to-thickness ratio and changes in the material gradation and taper ratio affect significantly the values of critical buckling loads.

• 고무기술
• /
• 제5권2호
• /
• pp.94-103
• /
• 2004

The present work describes modification of dual phase filler by electron beam irradiation in presence of multifunctional acrylates like trimethylol propane triacrylate (TMPTA) or silane coupling agent like bis (3-triethoxysilylpropyltetrasulphide) and in-fluence of the modified fillers on the physical properties of styrene-butadiene rubber (SBR) vulcanizates. Modulus at 300 % elongation increases whereas the tensile strength decreases with increase in radiation dose for the dual phase filler loaded styrene-butadiene rubber vulcanizates (SBR). However, modulus and tensile strength significantly increase, which is more, pronounced at higher filler loadings for TMPTA modified dual phase filler loaded SBR. These changes in properties are explained by the equilibrium swelling data and Kraus plot interpreting the polymer-filler interaction. Electron beam modification of the filler results in a reduction of tan ${\delta}$ at $70^{\circ}C$, a parameter for rolling resistance and increase in tan ${\delta}$ at $0^{\circ}C$, a parameter for wet skid resistance of the SBR vulcanizates. Finally, the influence of modified fillers on the properties like abrasion resistance, tear strength and fatigue failure and the improvement in the properties have been explained in terms of polymer-filler interaction.

• Bulletin of the Korean Chemical Society
• /
• 제16권3호
• /
• pp.214-216
• /
• 1995

Passive films formed on chromium surface in citrate buffer solution were investigated by means of three-parameter ellipsometry. The citrate buffer was found to be a suitable medium in which oxide film on chromium could be removed by cathodic treatment, providing a reference surface for the optical study. The passive film effectively protecting the chromium surface from corrosion was found to have thicknesses in the range 0.65 to 1.25 nm depending on the potential in the range of -0.20 to 0.60 V (0.1M KCl calomel electrode). The complex refractive index of the passive film did not show significant potential-dependent changes, indicating that the composition of the film material does not depend on potential.

• 반도체디스플레이기술학회지
• /
• 제20권4호
• /
• pp.167-170
• /
• 2021

Integrated passive device (IPD) technology has emerged with the need for 5G. In order to integrate and miniaturize capacitors inside IPD, various studies are actively performed using high-k materials and trench structures. In this paper, an EM(Electromagnetic) simulation study was performed by applying an oxide dielectric to the capacitors having a various trench type structures. Commercially available materials HfO₂, Al₂O₃, and Ta₂O₅ are applied to non, circle, trefoil, and quatrefoil type trench structures to confirm changes in each material or structure. As a result, the bigger the capacitor area and the higher dielectric constant of the oxide dielectric, the insertion loss tended to decrease.