• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1595-1603
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• 2003

Droplet combustion at high ambient pressures is studied numerically by formulating one dimensional combustion model in the mixture of n-heptane fuel and air. The ambient pressure is supercritical conditions. The modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties to account for the real gas effect on fluid p-v-T properties in high pressure conditions. Non-ideal thermodynamic and transport property at near critical and supercritical conditions are also considered. Several parametric studies are performed by changing ambient pressure and initial droplet diameter. Droplet lifetime decreased with increasing pressure. Surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• Steel and Composite Structures
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• v.14 no.3
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• pp.243-265
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• 2013

Distortional and local buckling are important factors that influences the bearing capacity of steel-concrete composite box-beam. Through theoretical analysis of distortional buckling forms, a stability analysis calculation model of composite box beam considering rotation of steel beam top flange is presented. The critical bending moment calculation formula of distortional buckling is established. In addition, mechanical behaviors of a steel beam web in the negative moment zone subjected separately to bending stress, shear stress and combined stress are investigated. Elastic buckling factors of steel web under different stress conditions are calculated. On the basis of local buckling analysis results, a limiting value for height-to thickness ratio of a steel web in the elastic stage is proposed. Numerical examples are presented to verify the proposed models.

• Steel and Composite Structures
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• v.2 no.5
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• pp.397-410
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• 2002

The main aim of the present paper is to present the results of a full-scale experimental investigation to study the structural behaviour of composite steel beams. The composite beam was made of cold-formed steel section shapes filled with reinforced concrete. First a comprehensive description of the experimental results in terms of: deflections, deformations, slippage and stress levels on critical steps of the load path is presented. The experimental results were then compared to theoretical values obtained by the use of an analytical model based on ultimate limit state stress blocks. Finally, a practical application of the use of this structural solution is depicted.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.4
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• pp.158-163
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• 2001

Magnetization losses of a Bi-2223 tape in magnetic fields parallel to the tape surface were measured by a room temperature cancellation and a cryogenic temperature cancellation. The results indicate that the same loss data are observed for both methods. The magnetization losses are hysteretic because the measured losses agree well with calculated ones based on a critical state model. In the full field penetration cases the magnetization losses increase with the frequency but in the partial field penetration cases the influence of the frequency is opposite.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.8-14
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• 2004

Characteristics of droplet vaporization at high ambient pressures and temperatures which are supercritical conditions is studied numerically by formulating one dimensional vaporization model in liquid dodecane and air. Modified Soave-Redlich-Kwong state equation is used to condider real gas effect. Non-ideal behavior of properties at near critical and supercritical conditions is considered in the high pressure condition. Characteristic spatial distribution of properties with various conditions of pressure and temperature is evaluated in order to understand vaporizing evolution.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.103-106
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• 2000

We have studied the magnetic properties in Bi$_2$Sr$_2$CaCu$_2$O$_8$ single crystal with columnar defects using micro Hall-probe array. We found that fold profiles inside sample were similar to the Bean's critical state model from the magnetic hysteresis measurement. In the magnetic relaxation measurement, the normalized relaxation rates were maximum near the center and decreased toward the edge of the sample expect zero gauss. The relaxation rates as a function of the temperature were maximum near the 40K and rapidly decreased both sides of the peak.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1061-1064
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• 2006

Optimal design of functionally graded plates is investigated considering stress and critical temperature. Material properties are assumed to be temperature dependent and varied continuously in the thickness direction. The effective material properties are obtained by applying linear rule of mixtures. The 3-D finite element model is adopted using an 18-node solid element to analyze more accurately the variation of material properties and temperature field in the thickness direction. For stress analysis, the tensile stress ratio and compressive stress ratio of the structure under mechanical load are investigated. In the thermo-mechanical buckling analysis, temperature at each node is obtained by solving the steady-state heat transfer problem and Newton-Raphson method is used for material nonlinear analysis. Finally, the optimal design of FGM plates is studied for stress reduction and improving thermo-mechanical buckling behavior, simultaneously.

• 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.

• Polymer(Korea)
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• v.24 no.5
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• pp.682-689
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• 2000

The information related to the interaction energy between repeat units is essential for the production of useful polymer blends via molecular structure design. Based on the interaction energies obtained here, a method for the fabrication of miscible blend was suggested. An investigation related to the equilibrium phase behavior of polymer blends of various polycarbonates with various polymethacrylates was performed and then based on the obtained interaction information miscible polymer blends were produced by controling molecular structure of polymer. Binary interaction energies between repeat units were calculated from the lower critical solution temperature-type phase boundary using an equation of state combined with binary interaction model.

• Computational Structural Engineering
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• v.7 no.2
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• pp.61-67
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• 1994

The objective of this numerical analysis is to trace the hysteretic behavior of steel angles under very-low-cycle loading test, especially the history and cumulative state of local stress-strain at their critical parts. The computer model is based on a three-dimensional, non-linear analysis by using the finite element program, MSC/NASTRAN, which includes the effects of the material and geometric non-linearities. The analysis was performed as two stage procedures, namely Analysis I and II. The overall behavior from this analysis showed good agreement with the experiment.