• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.329-337
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• 2001

This simulator is developed for the analysis of a MOSFET based on Thermally Coupled Energy Transport Model(TCETM). The simulator has the ability to calculate not only stationary characteristics but also non - stationary characteristics of a MOSFET. It solves basic semiconductor devices equations including Possion equation, current continuity equations for electrons and holes, energy balance equation for electrons and heat flow equation, using finite difference method. The conventional semiconductor device simulation technique, based on the Drift-Diffusion Model (DDM), neglects the thermal and other energy-related properties of a miniaturized device. I, therefore, developed a simulator based on the Thermally Coupled Energy Transport Model (TCETM) which treats not only steady-state but also transient phenomena of such a small-size MOSFET. In particular, the present paper investigates the breakdown characteristics in transient conditions. As a result, we found that the breakdown voltage has been largely underestimated by the DDM in transient conditions.

• Journal of Korean Association for Spatial Structures
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• v.1 no.1 s.1
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• pp.157-166
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• 2001

In general, the cutting pattern of the membrane structures is determined by dividing the complicated curved 3-D surface into several 2-D plane strip by using flattening technique. In this procedure, however, some discrepancies ore occurred between actual stresses of equilibrated state and designed uniform stresses because the material properties are not considered. These deviations can cause the critical structural problems, wrinkling or overstress, and thus a optimization process should be considered. In this paper, a new analytical method for determining an optimum cutting pattern considering material properties is presented. Here, iterative procedure is introduced to decrease the errors caused in numerical process. The optimization method proposed can diminish the deviations occurred by material properties and numerical errors, simultaneously. As a results, it is shown that the final stress distributions for the HP shell model are sufficiently near to design stress distributions, and it can be concluded that this method can be used to obtain the optimized cutting pattern of membrane structures.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.134-139
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• 2007

A delivery ship is used to handle the cargo with the crane to/from the ships. The ship is inclined in the direction of a cargo which is hung on a crane. In this case, a arc shaped rail should be in the equilibrium state to get good anti-rolling performance. In this study, a device and control algorithm are developed to take accurate and quick equilibrium of the rail. The device is composed of a hinged immovable support, screw jack and damper. And the control system is based on I-PD control law to consider of control input saturation and overshoot. The controller is composed of integral controller of feedforward path and proportional-derivative controller of feedback path. The parameters of controller is designed to follow the reference signal and to remove overshoot. The simulation results show that the desirable control performance is achieved.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.325-332
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• 1999

As part of the conceptual disign of cable and membrane structures, the adequate shape is decisive with respect to load bearing behaviour and aesthetic expression of the structure. The force densities which are the force-length ratio are very useful parameters for the description of equilibrium state of any general cable-net structures. Because equilibrium states are obtained by solving linear equations the force desity method has a advantage compared with other solution strategies. But if there are futher restrainted conditions in force density the linear method will be extended to nonlinear one. The numeriacl methods are based upon least square and general inverse method for sieving nonlinear eqations. In this paper, the results from two methods is compared through several examples.

• Korean Membrane Journal
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• v.1 no.1
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• pp.8-24
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• 1999

free volume in polymers is defined as the difference of the specific volume and the volume which is not available for the particular molecular motion which is responsible or the process that is considered . Relations between free volume and viscosity free volume and diffusion coefficient are pre-sented both in the case of simple low molecular weight liquids and in the case of polymers. Molecular models and free volume models are reminded starting from the equilibrium state equation of Simha and Somcynski. The non equilibrium situations of specific volume of glass polymers below Tg are shown introducing different relaxation volume equations which involve different material's parameters and con-cept of the fictitious temperature. The diffusivity equations of Vrentas and Duda are introduced both for the glassy and rubbery states. The possibility of introducing time relaxation functions is also suggested. The importance of finding experimental evidences of the free volume is stressed. highlights of the free volume measurement methods are given in particular as to dilatometry photocromy fluorescence electron spin resonance small angle X-ray scattering positron annihilation spectroscopy.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.732-737
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• 2018

Experimental data of phase equilibria are reported for the binary mixture of 1-phenyl-2-pyrrolidone in supercritical carbon dioxide. Phase behavior data was measured in a synthetic method at a temperature ranging from 333.2 to 393.2 K and at pressures up to 97.14 MPa. The solubility of 1-phenyl-2-pyrrolidone in the carbon dioxide + 1-phenyl-2-pyrrolidone system increased as temperature increased at a constant pressure and it exhibited the type-I phase behavior. The experimental data for the binary mixture were correlated with the Peng-Robinson equation of state using mixing rule and the critical properties of 1-phenyl-2-pyrrolidone were predicted with the Joback and Lyderson method.

• International Journal of High-Rise Buildings
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• v.1 no.4
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• pp.247-254
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• 2012

In order to improve the seismic behaviors of traditional steel-concrete mixed structure, a novel steel concrete mixed structure consisting of steel frames braced with buckling restrained braces (BRBs) and a concrete tube is proposed. Based on several assumptions, the simplified mechanical model of the novel mixed structure is established, and the shear and bending stiffness formulas of the steel frames, BRBs and concrete tube are respectively introduced. The equilibrium differential equation of the novel mixed structure under horizontal load is developed based on the structural elastic theory. The simplified algorithms to determine the lateral displacement and internal forces of the novel mixed structure under the inverted-triangle distributed load, uniformly load and top-concentrated load are then obtained considering several boundary conditions and compatible deformation conditions. The effectiveness of the simplified algorithms is verified by FEM comparison.

• Geomechanics and Engineering
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• v.4 no.2
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• pp.105-120
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• 2012

In this paper, the ultimate pullout capacity of a vertical plate strip anchors in cohesion-less soil is analyzed with the consideration of active and passive state of equilibrium in the soil. K$\ddot{o}$tter's equation is used to compute the active and passive thrusts (along with their point of application) which are subsequently used in the analysis in which, all the equation of equilibrium are properly interpreted. A comparison of the results with the experimental results vis-$\grave{a}$-vis available theoretical/empirical solutions shows that, the proposed analysis provides a better estimate of the pullout capacity.

• Nuclear Engineering and Technology
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• v.35 no.4
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• pp.336-346
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• 2003

This study is intended to evaluate the dependency of TRU recycling characteristics on the neutron spectrum shift in a Pb-Bi cooled core. Considering two Pb-Bi cooled cores with the soft and the hard spectrum, respectively, various characteristics of the recycled core are carefully examined and compared with each other. Assuming very simplified fuel cycle management with the homogeneous and single region fuel loading, the burnup calculations are performed until the recycled core reached to the (quasi-) equilibrium state. The mechanism of TRU recycling toward the equilibrium is analyzed in terms of burnup reactivity and the isotopic compositions of TRU fuel. In the comparative analyses, the difference in the recycling behavior between the two cores is clarified. In addition, the basic safety characteristics of the recycled core are also discussed in terms of the Doppler coefficient, the coolant loss reactivity coefficient, and the effective delayed neutron fraction.

• Journal of Drive and Control
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• v.11 no.3
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• pp.22-30
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• 2014

In this research, the energy stability level method is used for examining the stable state of Field Robot under effects of swing motion, at particular postures of manipulator, and terrain conditions. The energy stability level is calculated by using the dynamic models of Field Robot, subjected to the concept of equilibrium plane and support boundary. The results, simulated by using computing program for estimating the potential overturning of Field Robot, supply useful predictions of stability analysis for designers and operators.