• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.309-316
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• 2010

When the horizontal and vertical curves are superimposed in railway alignments, which affects the running stability, ride comfort, and track maintenance costs. However, when designing new lines or realigning existing ones, there are many cases of superimposition caused by the existing fixed points (bridge, tunnel, turnout, and catenary system, etc) on the conventional lines and undesirable impacts on the environment, etc. In this study, when the horizontal and vertical curves are superimposed, in order to optimize the horizontal curve in aspect of the ride comfort, the object function was developed and verified by vehicle dynamic analysis. Also, the solution algorithm for simplified evaluation method was presented.

• Environmental Engineering Research
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• v.25 no.3
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• pp.439-445
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• 2020

In the estimation of the aerosol single fiber efficiency using fibrous filters, there is a size range, where the particles penetrate most effectively through the fibrous collectors, and corresponding minimum single fiber efficiency. For small particles in which the diffusion mechanism is dominant, the Cunningham slip correction factor (C_c) affects the single fiber efficiency and the most penetrating particle size (MPPS). Therefore, for accurate estimation, C_c is essential to be considered. However, many previous studies have neglected this factor because of its complexity and the associated difficulty in deriving the appropriate parameterization particularly for the MPPS. In this study, the expression for the MPPS, and the corresponding expression for the minimum single fiber efficiency are analytically derived, and the effects of C_c are determined. In order to accommodate the slip factor for all particle-size ranges, C_c is simplified and modified. Overall, the obtained analytical expression for the MPPS is in a good agreement with the exact solution.

• Journal of Powder Materials
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• v.11 no.5
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• pp.399-411
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• 2004

Crack generation during die compaction and distortion during sintering have been critical problems for the conventional pressing and sintering process. Until now, trial and error approach with engineers' industrial experiences has been only solution to protect the crack generation and distortion. However, with complexity in shape and process it is very difficult to design process conditions without CAE analysis. We developed the exclusive CAE software (PMsolver/Compaction) for die compaction process. The accuracy of PMsolver is verified by comparing the finite element simulation results with experimental results. The simplified procedures to find material properties are proposed and verified with iron based powder and tungsten carbide powder. Based on the accurate simulation result by PMsolver, the optimal process conditions are designed to get uniform density distribution in a powder compact after die compaction process by using a derivative based optimization scheme. In addition, the effect of non-uniform density distribution in a powder compact on distortion during sintering is shown in case of the fabrication of tungsten carbide insert.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.833-841
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• 1994

In this paper we develop an approximation formalism for the queue length distribution of general queueing models. Our formalism is based on two steps of analytic approximation employing both the lower and upper bound techniques. It is favorable to a fast numerical calcuation for the queue length distribution of a superposition of a superposition of arbitary type traffic sources. In the application. M+ N D /M/1 is considered. The calculated result for queue length distribution measured by arriving or leaving customers show a good agreement with the direct simulation of the system. Especially, we demonstrate that our formula for M/M/1 is equivalent to the exact solution, while that D/M/1 is simplified in an analytic form.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.224-227
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• 1998

Linear motors are increasingly employed as direct actuators replacing the more conventional systems composed by a rotating motor and a mechanical device. Linear DC motor is useful in a high speed and high accuracy positioning system with a feedback controller. Because of these advantages, linear DC motors have already been used as motors of pen recorders and magnetic disk storage devices, these are moving coil type linear DC motors as these movers are light. Moving magnet type linear DC motor has advantages at long stroke motors because its mover's feeding wires for driving is not necessary. This paper is concerned with the analysis of linear DC motor that is moving magnet type with unipolar. In order to analyze the dynamic behaviour a mathematical model based on a simplified field analysis developed. A two dimensional finite element field solution is employed in order to illustrate the effect of yoke saturation and motor performance. It is deduced the relation between the limit value of the thrust of the linear DC motor and the dimension of the yokes.

• KSBB Journal
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• v.5 no.2
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• pp.183-189
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• 1990

An efficient method has been developed for the purification of urokinase from 1, 000 liter batches of human urine. The procedure involved precipitation of urokinase with 2mM zinc chloride, resuspension of the precipitate with 0.1M EDTA/0.5M Glycine solution, and CM-Toyopearl and benzamidine-Sepharose column chromatography. The purified urokinase was fully active and possessed a specific activity of 1.07$\times$105IU/mg. The recoveries ranged from 42 to 65% in several preparations(mean value was 51%). And the urokinase purified by this process consisted of about 13% of single chain urokinase (pro-urokinase) as evaluated by SDS-polyacrylamide gel electrophoresis in reducing condition and by S-2444 amldolytic activity under plasmin treatment.

• Computers and Concrete
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• v.19 no.2
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• pp.143-152
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• 2017

This paper has numerically investigated the changes of loading-induced stress in concrete with the corrosion time in the sulfate-containing environment. Firstly, based on Fick's law and reaction kinetics, a diffusion-reaction equation of sulfate ion in concrete is proposed, and it is numerically solved to obtain the spatial and temporal distribution of sulfate ion concentration in concrete by the finite difference method. Secondly, by fitting the existed experimental data of concrete in sodium sulfate solutions, the chemical damage of concrete associated with sulfate ion concentration and corrosion time is quantitatively presented. Thirdly, depending on the plastic-damage mechanics, while considering the influence of sulfate attack on concrete properties, a simplified chemo-mechanical damage model, with stress-based plasticity and strain-driven damage, for concrete under axial loading and sulfate attack is determined by introducing the chemical damage degree. Finally, an axially compressed concrete prism immersed into the sodium sulfate solution is regarded as an object to investigate the time-varying stress in concrete subjected to the couplings of axial loading and sulfate attack.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.247-256
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• 2008

This research is to develop product retrieval system through simplified communication by applying intelligent agent technology based on automatically created domain ontology to present solution on problems with e-commerce system which searches in the web documents with a simple keyword. Ontology development extracts representative term based on classification information of international product classification code(UNSPSC) and jewelry websites that is applied to analogy relationship thesaurus to establish standardized ontology. The intelligent agent technology is applied to retrieval stage to support efficiency of information collection for users by designing and developing e-commerce system supported with semantic web. Moreover, it designs user profile to personalized search environment and provide personalized retrieval agent and retrieval environment with inference function to make available with fast information collection and accurate information search.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.121-133
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• 1995

It is well known that two-dimensional simplified third-order theories satisfy the layer interface continuity of transverse shear strains, thus these theories violate the continuity of transverse shear stresses when two consecutive layers differ either in fibre orientation or material. The third-order theories considered herein involve four/or five dependent unknowns in the displacement field and satisfy the condition of vanishing of transverse shear stresses at the bounding planes of the plate. The objective of this investigation is to examine (i) the flexural response prediction accuracy of these third-order theories compared to exact elasticity solution (ii) the effect of layer interface continuity conditions on the flexural response. To investigate the effect of layer interface continuity conditions, three-dimensional elasticity solutions are developed by enforcing the continuity of different combinations of transverse stresses and/or strains at the layer interfaces. Three dimensional twenty node solid finite element (having three translational displacements as degrees of freedom) without the imposition of any of the conditions on the transverse stresses and strains is also employed for the flexural analysis of the laminated plates for the purposes of comparison with the above theories. These shear deformation theories and elasticity approaches in terms of accuracy, adequacy and applicability are examined through extensive numerical examples.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.245-248
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• 2001

Recently, with the advancement of internet network the system has been needed to be controllable and observable through internet at industrial workplace. In this study, we developed the digital timer which has a communication function to control and observe many kinds of devices by combining relay and timer used for each type of control panel to realize control solution based on internet to be easily applicable at workplace with low cost and adding 485 serial communication module to have parallel expansibility and safety. And, this system was experimented and designed for easy system management and status check from remote station through internet. appling the developed digital timer to parallel sequence control of motor. As the result of experiment, the circuit configuration would be more simplified than the existing, and it is expected that multi-connection control and monitoring can be simply implemented with low cost equipment at industrial workplace.