• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.1020-1027
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• 2000

A simple model for describing the non-spherical particle growth phenomena has been developed. In this model, we solve simultaneously particle volume and surface area conservation sectional equations that consider particles' non-sphericity. From the correlation between two conserved properties of sections, we can predict the evolution of the aggregates' morphology. This model was compared with a simple monodisperse-assumed model and more rigorous two-dimensional sectional model. For comparison, formation and growth of silica particles have been simulated in a constant temperature reactor environment. This new model showed good agreement with the detailed two-dimensional sectional model in total number concentration and primary particle size. The present model successfully predicted particle size distribution and morphology without costing very heavy computation load and memory needed for the analysis of two dimensional aerosol dynamics.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.4
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• pp.3-11
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• 2004

A finite volume model is developed to simulate the surface irrigation at a paddy field. The model's capabilities are validated through comparison with the simulafed results and the observed data obtained by various experimental tests, and the simulated results are in good agreement with the observed pending depth. The result of surface irrigation simulation shows that the longer the paddy field's the length of long-sided becomes, the longer the advance and storage time is taken. To analyze surface irrigation performance with variable inflow rate, three patterns of flow variation-constant rate, initially high then low, and initially low then high-were studied. The results show that at the pattern with initially high followed by low during the latter half of the irrigation the advance time is shortest, but the pending depth of irrigation completion and irrigation effiency are the little difference between irrigation patterns.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1681-1690
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• 2003

The effect of roughness is a change in the velocity and turbulence distributions near the surface. Turbulence models with surface roughness effect are applied to the fully developed flow in a two-dimensional, rough wall channel. Modified wall function model, low-Reynolds number k-$\varepsilon$ model, and k-$\omega$ model are selected for comparison. In order to make a fair comparison, the calculation results are compared with the experimental data. The modified wall function model and the low-Reynolds number k-$\varepsilon$ model require further refinement, while the k-$\omega$ model of Wilcox performs remarkably well over a wide range of roughness values.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.331-334
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• 2009

In this paper, we present a surface relaxation model in atomistic calculations for thin nanofilms. This surface relaxation model is very simple model which have only two degrees of freedoms to determine the atomic positions of nanofilms. Whereas in conventional molecular statics simulations, the same number of degrees of freedoms at all atom positions are used as unknown variables. In order to prove the reliability of the presented model, we present the results of self-equilibrium strain calculations with the surface parameters obtained from this model.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.39-46
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• 2018

Two surfaces that have relative motion show different characteristics according to surface roughness or surface patterns in all lubrication areas. For two rough surfaces with mixed lubrication, this paper proposes a new approach that includes the contact characteristics of the surfaces and a probabilistic method for a numerical analysis of lubrication. As the contact area of the two surfaces changes according to the loading conditions, asperity contact is very important. An average flow model developed by Patir-Cheng is central to the study of lubrication for rough surfaces. This average flow model also refers to a multi-asperity contact model for deriving a modified Reynolds equation and calculating the lubricant characteristics of a bearing surface with random roughness during fluid flow. Based on the average flow model, this paper carried out a numerical analysis of lubrication using a contact model by considering a load change made by the actual contact of asperities between two surfaces. Lubrication properties show different characteristics according to the surface patterns. This study modeled various geometric surface patterns and calculated the characteristics of lubrication.

• Geomechanics and Engineering
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• v.14 no.1
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• pp.61-69
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• 2018

The first part shows the optimal contact surface for T-shaped combined footings to obtain the most economical dimensioning on the soil (optimal area). This paper presents the second part of a new model for T-shaped combined footings, this part shows a the mathematical model for design of such foundations subject to axial load and moments in two directions to each column considering the soil real pressure acting on the contact surface of the footing with one or two property lines restricted, the pressure is presented in terms of an axial load, moment around the axis "X" and moment around the axis "Y" to each column, and the methodology is developed using the principle that the derived of the moment is the shear force. The classic model considers an axial load and a moment around the axis "X" (transverse axis) applied to each column, i.e., the resultant force from the applied loads is located on the axis "Y" (longitudinal axis), and its position must match with the geometric center of the footing, and when the axial load and moments in two directions are presented, the maximum pressure and uniform applied throughout the contact surface of the footing is considered the same. To illustrate the validity of the new model, a numerical example is presented to obtain the design for T-shaped combined footings subjected to an axial load and moments in two directions applied to each column. The mathematical approach suggested in this paper produces results that have a tangible accuracy for all problems.

• KSTLE International Journal
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• v.5 no.1
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• pp.14-22
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• 2004

The sub-surface stress field beneath the gear's contact surface caused by the surface pressure in lubricated condition is analyzed. To evaluate the influence of the clearances between a gear tooth and a pinion tooth on the stress field, two kinds of tooth profile models - conventional cylinder contact model and new numerical model - were chosen. Kinematics of the gear is taken into account to obtain the numerical model which is the accurate geometric clearances between a gear tooth and a pinion tooth. Transient elasto-hydrodynamic lubrication (EHL) analysis is performed to get the surface pressure. The sub-stress field is obtained by using Love's rectangular patch solution. The analysis results show that the sub-surface stress is quite dependent on both the surface pressures and the profile models. The maximum effective stress of the new model is lower than that of the old model. The depth where the maximum effective stress occurs in the new model is not proportional to the intensity of the external load.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.3
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• pp.91-100
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• 1999

Tow constitutive models for weathered granite soil, Yasufuku's constitutive model with a single yield surface and Lade's constitutive model with two intersectiong yield surface compared in terms of their capabilities to accurately capture the observed behavior of compacted weathered grainite soil for various stress-paths. Both the single surface and the double surface models capture the experimentally observed behavior at a variety of stress-paths with good accuracy. The double surface model may model the observed compacted weathered granite soil behavior with better accuracy for proportational loading with increasing stress, but the single surface model may model dilatancy property with better accuracy for p-constant loading with increasing stress ratio.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.562-566
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• 2010

Numerical analysis of 150kW Huels-type arc jet was performed using compressible Navier-Stokes CFD code. To consider chemical reaction by high temperature, the flow was assumed to be chemical equilibrium states. As a turbulence and a radiation model, the two-equation k-epsilon model and the 3-band radiation model were adopted, respectively. Mass flow rate and current density were given as conditions for calculations. In this study, two kinds of mechanisms for injection of air flow wire considered. One is that air is provided by left wall surface and the other is that air is injected from upper wall surface. The pressure, density and temperature contours of two cases were compared and heat transfer rates were estimated. The numerical results of two cases were not much different to each other. However, in real 150KW device, air is injected from upper wall surface with swirl. To calculate more accurately, swirl effect is must be considered.

• Journal of the Korean Solar Energy Society
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• v.22 no.1
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• pp.73-80
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• 2002

This is study of the planning of thermal insulation to prevent heat loss in a basement, is aimed at investigating the heat loss from the basement space and basement structures. The results analyzed in these researches are as follows; To analyze the heat loss from basement structures, this study experimented on the heat flow phenomenon of a non-insulation structure and two insulation structure models. From the result, the interior surface temperature of two insulation structures(B, C, model) showed an equal temperature, but the interior surface temperature of a non-insulation structure (A model) is different from the two models, Therefore, we understand that the insulator constructed in the basement structure makes a role of preventing the heat loss from the basement. In addition, the exterior surface temperature of two insulation structure models showed an equal temperature. Specially, judging from the temperature difference of C model. we understand that the performance of insulator is low under the definite depth of underground. The thermal insulation design should be constructed under the definite depth of underground considering outdoor and building conditions.