• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.2
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• pp.56-64
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• 2006

Rapid progress in many branches of technology has led to a demand on new materials such as high strength light weight alloys, powdered alloys and composite materials. The hydrostatic extrusion is essentially a method of extruding a clad rod through a die. In order to investigate the effect of the process conditions such as friction heat, deformation and clad thickness on the clad extrusion process, viscoplastic finite element simulations were conducted. A specific model for theoretical analysis used in this study is The single scalar variable version of Hart's model. An experiment also has been carried out using 1.5MN hydrostatic extruder with variable speed ram, LVDT and load cell for comparison. It is found that the hydrostatic extrusion pressure considering the effect of heat dissipation in this theoretical work was closer to the experimental pressure than the isothermal hydrostatic extrusion pressure.

• Membrane and Water Treatment
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• v.5 no.1
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• pp.57-71
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• 2014

In this study, a theoretical model for the transport phenomena in an Air Gap Membrane Distillation used for desalination was developed. The model is based on the conservation equations for the mass, momentum, energy and species within the feed water solution as well as on the mass and energy balances on the membrane sides. The rarefaction impacts are taken into consideration showing their effects on process parameters particularly permeate flow and thermal efficiency. The theoretical model was validated with available data and was found in good agreement especially when the slip condition is introduced. The rarefaction impact was found considerable inducing an increase in the permeate flux and the thermal efficiency.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.371-374
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• 2003

The degree of changes in mechanical properties of fire-damaged reinforced concrete column depends mostly on sectional geometry, duration exposed to fire, and moisture containment. In order to reasonably assess the deterioration of structural capacity of fire-damaged reinforced concrete column, it is necessary to develop a theoretical model predicting column behavior based on nonlinear heat transfer equation in addition to the traditional mechanics. This research focuses on the development of theoretical model to predict moment-curvature relations of fire-damaged reinforced column. The model is used for the assessment of structural capacity of fire-damaged column in terms of moment-curvature relations and PM interaction curves.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.201-210
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• 1994

A theoretical heat-flow model incorporating with a constant moving CO$_{2}$ laser beam has been analyzed to predict depth and the shape of bead section during last beam welding. The laser beam is exponentially attenuated with an abosrption coefficient in the material. The solution can be expressed in terms of normalized variables. The experimental data were generated by usint CW 2 CO$_{2}$ laser with multi beam mode and CW 3 kW CO$_{2}$laser with Gaussian mode. The specimens were made as bead-on-plate welds for SM 10C, STS 304, STS 316, STS 420 and pure Nickel. The maximum possible penetration depth and the shape of beas section for given sources of laser power, travel speed and beam spot size can be prdicted with this model in a given material.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.464-469
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• 2003

The traditional and still most widely used, test methods for concrete structures are destructive method, such as coring, drilling or otherwise removing part of the structure to permit visual inspection of the interior. While these methods are highly reliable, they are also time consuming and expensive, and the defects they leave behind often become focal point for deterioration. In this study, tomography by theoretical inversion method in case of elastic wave using impact-echo method among concrete non-destruction test method was made. Taken model experiments are theoretical inversion method and time domain and frequency domain test on pier test model at laboratory level. Also experiment concerning frequency domain on 3 kinds of tunnel model with I-dimension form was carried out.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.902-907
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• 2003

Substantial experimental and theoretical work exists on the bond characteristics of FRP-concrete adhesive joints. Analytic solutions based on fracture mechanics are most commonly accepted for theoretical work on joint. The solutions may be derived for the simple form of the shear strees-slip curve. And it is difficult to determine the model parameters consisting the curve. In this study, the bilinear curve with softening branch is introduced. The model parameters are determined by the method described by the companion paper with comparison of test results. There are many uncertainties in the test results of CFRP sheet adhesive joints, so that test results used for the construction of the regression problem should be reasonably selected.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.124-133
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• 1995

A theoretical self-consistent thermoelectric model has been developed for optimal thermal design in the self-signal processing infraed detectors. The model is achived by employing the coupled thermoelectric equation which allows which allows the simultaneous investigation of the termal and electrical aspects of device behavior. The thermal limitation of detectivity and responsivity are determined by the enegy gap, carrier concentration, lifetime, and mobility as a function of the temperature. The calculated results indicate that the detectivity is decreased at bias fields above about 50 V/cm, because the performence is limiting by temperature when the bias voltage reached the level associated with Joule heating. It has been also found that the improvement in the mid-band modulation transfer function(MTF) may be restricted by increasing the bias fields. Further, the important paramerers in the thermal optimization of SPIR detector, such as temperature in the device, ambipolar velocity, element thickness and length, are also considered. The analytical study provides a mathematical basis for optimal design of such a photoconductive IR detector and the agreement between the experimental and theoretical results are seen to be good.

• Asia pacific journal of information systems
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• v.9 no.2
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• pp.39-58
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• 1999

This paper determines the interactive effects of information technologies(IT) on corporate performances. IT was measured inclusively in terms of technology level, information level, functional level, and management level. Corporate performances were composed of the effectiveness of IT and the financial performance of a corporation. The effectiveness of IT was measured in terms of satisfaction with the support of IT department and with output information, whereas financial performance of corporation was measured in terms of market growth and profitability. Theoretical and empirical analyses lead to the followings. In the theoretical aspect, IT in a corporation needs to be measured broadly. And a study of IT related to corporate performance needs to use either a conversion effectiveness model or an intermediate effect model rather than a direct effect model. In the empirical aspect, the effectiveness of IT within an organization improves with some of the interactive effect of ITs including technology level, information level, functional level, and management level. So do some of the financial performances of a corporation.

• Journal of Information Display
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• v.10 no.4
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• pp.143-148
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• 2009

The theoretical current density equations for organic semiconductors was derived according to the internal carrier emission equation based on the diffusion model at the Schottky barrier contact and the mobility equation based on the field dependence model, the so-called "Poole-Frenkel mobility model." The electric field becomes constant because of the absence of a space charge effect in the case of a higher injection barrier height and a lower sample thickness, but there is distribution in the electric field because of the space charge effect in the case of a lower injection barrier height and a higher sample thickness. The transition between the injection- and bulk-limited currents was presented according to the Schottky barrier height and the sample thickness change.

• Journal of the Korean Operations Research and Management Science Society
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• v.27 no.4
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• pp.11-27
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• 2002

This paper is aimed at surveying the method that supports logical and theoretical back grounds of electricity service pricing, to investigate whether the ESPM can reflect comprehensively the various interests of parties and persons concerned with electricity supply and demand, and analyzing the practical applicability of the model in short-term perspectives. The major findings of this study can be summarized as fellows. First, the ESPM explains what process the equilibrium price is attained through, which is the essential concept and object in evaluating the value of public enterprises or utilities and the price of electricity Second, the ESPM provides the logics and methods that can objectify the discrete price by each electricity user. Third, the ESPM presents theoretical logics and practical methods that can calculate the basic price and the variable price per electricity unit which are key concepts in the two-part tariff. Fourth, the ESPM has powerful practical applicabilities in the reasonable electricity pricing and in the explanation for the balance between parties and persons interested with electricity supply and demand.