• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1056-1062
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• 2008

The interaction between thrust plume and satellite base region was investigated by using direct simulate Monte-Carlo calculations. For the accurate simulation of N2 and H2 collisions and rotation-translation transition, a variable soft-sphere model and a recent rotational relaxation model of N2 and H2 were used. For the investigation of the interaction between thrust plume and base region, the number density distribution for each species, translational and rotational temperature distributions, heat flux, and pressure were examined by direct simulation of Monte-Carlo calculations. It was found that most of the surface properties are affected by H2 collisions and a strong non-equilibrium state is observed at the base region. It was demonstrated that an accurate model is needed to simulate H2 collisions and the rotation-translation transition. The results by the present calculation are more accurate than previous direct simulation Monte-Carlo calculations because more accurate rotational relaxation models were used in simulating the inelastic collisions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1115-1128
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• 1994

The condition of temperature gradients in asphaltic concrete (Ascon) pavement have been analyzed based on the data collected from 5 major sites in Korea. From this. considering heat transfer by insolation flux and air temperature within pavement slab. temperature variation on the surface of pavement was computed and numerical model using the theory of thermal conductivity was applied to estimate the temperature gradients in depth. To investigate the present condition of asphalt generally used in Korea. the asphalt property tests were applicated on 5 different AP-3 (AC 85~100), and AP-5 (AC 60~70) asphalts classified by penetration index. Uniaxial compression test and indirect tensile test were also carried out for varying temperature conditions to analyze the effect of temperature on the deformation characteristics of Ascon pavement by calculating the variation of static elastic modulus and layer coefficients.

• Fire Science and Engineering
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• v.25 no.5
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• pp.1-7
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• 2011

In this study, standards and test methods for building materials of domestic and foreign countries were compared and analyzed to propose evaluation methods for the fire-retardant performance of HANOK components (Traditional house). IBC and NFPA codes recently have been adopted in the US, and the properties such as critical heat flux, fire spread index and smoke density are being used as an evaluation reference. In Europe, the unified Euroclass has been adopted and the surface flammability, prototype fire test or cone calorimeter test are conducted for the performance test. Japan has the similar system as Korea where the class is classified into 3 grades. We tried to study a quantitative evaluation method of fire retardant performance for the HANOK components based on the analysis results of the several countries' standards and test methods for building materials.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1257-1264
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• 2011

This paper presents 3D simulation by STAR-CCM+ for lean premixed combustion in a stationary gas turbine combustor with separate pilot and main nozzles. The constant for the source term in the flame area density transport equation was modified to account for a low global equivalence ratio and validated against measurement data. A Partially-premixed Coherent Flame Model(PCFM) involves propagation of a laminar premixed flame with the predicted flame surface density and equilibrium assumption in the burned gas with spatial inhomogeneity. The conditions for cooling by radiation and convection are considered for accurate determination of the heat flux on the wall. A parametric study is of the pilot-fuel-to-total-fuel-ratio is carried out. A chemical reactor network (CRN) was constructed on the basis of the 3D simulation results and compared against measurements of NOx.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.9-14
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• 2002

A higher order zig-zag plate theory is developed to accurately predict fully coupled mechanical, thermal, and electric behaviors. Both the in-plane displacement and temperature fields through the thickness are constructed by superimposing linear zig-zag field to the smooth globally cubic varying field. Smooth parabolic distribution through the thickness is assumed in the transverse deflection in order to consider transverse normal deformation. Linear zig-zag form is adopted in the electric field. The layer-dependent degrees of freedom of displacement and temperature fields are expressed in tern-is of reference primary degrees of freedom by applying interface continuity conditions as well as bounding surface conditions of transverse shear stresses and transverse heat flux. The numerical examples of coupled and uncoupled analysis demonstrate the accuracy and efficiency of the present theory. The present theory is suitable for the predictions of fully coupled behaviors of thick smart composite plate under mechanical, thermal, and electric loadings combined.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.117-119
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• 2008

It is very important to protect life, property at sea from any fire. Recommendation on improved fire test procedures for surface flammability of bulkhead, ceiling and deck finish materials specifies a procedure for measuring fire characterizing their flammability and thus their suitability for use in marine construction. In this paper, we investigated the positive expected by fire test procedures for flammability of bulkhead, ceiling and deck finish materials. Also, unusual materials were analyzed. Finally, we suggest methods to solve several problems related to unusual materials.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.20-25
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• 1998

Solar irradiation controls the exchange of heat energy between atmosphere and land or ocean, and becomes an important factors to the radiance flux at the surface and the biosphere. In order to estimate solar irradiance and earth albedo In Korea peninsula during 1996, GMS date and paramaterization model was combinationally used. In clear sky, the paramaterization model was used to estimate solar iradiance. Also in cloudy sky, the earth albedo was used to calculate the Interceptive effect of solar irradiance. The hourly solar irradiance [the hourly earth albedo] showed generally very low values with <1.00 MJ/m$^2$hr [high values with >0.65] on the middle part (36.00-36.50$^{\circ}$S) and the Southeastern part (near 34.50$^{\circ}$S) in Korea peninsula, respectively. Satellite estimates (GMS data) with pyramometer measurements (in-situ data) were compared for 21 observed stations. Totally, correlation coefficient showed high values with 0.85. In the monthly variation, correlation coefficient of the spring and summer with rms=about 0.42 MJ/m$^2$hr was better than the autumn and winter with rms >0.5 MJ/m$^2$hr. Generally monthly variations of correlation coefficient between satellite estimetes and pyranometer measurements showed r=0.936 in clear sky during 1 year except only May, June, July and August.

• Fire Science and Engineering
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• v.30 no.5
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• pp.116-123
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• 2016

The quantitative risk assessment methods for thermal failure in targets were studied using fire modeling. To this end, Fire Dynamics Simulator (FDS), as a representative fire model, was used and the probabilities related to thermal damage to an electrical cable were evaluated according to the change in fire area inside a specific compartment. 'The maximum probability of exceeding the damage thresholds' adopted in a conservative point of view and 'the probability of failure' including the time to damage were compared. The probability of failure suggested in the present study could evaluate the quantitative fire risk more realistically, compared to the maximum probability of exceeding the damage thresholds with the assumption that thermal damage occurred the instant the target reached its minimum failure criteria in terms of the surface temperature and heat flux.

• Membrane Journal
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• v.6 no.1
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• pp.44-52
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• 1996

For the purpose of the optimal design of a frame and plate type of pervaporation module, model equations which can predict the effects of feed flow condition on the temperature distribution of the feed developed in the module were established and the temperature distribution with feed flow condition was investigated through the model si$$\mu$ation. With increasing the Reynolds number of feed flow in the module, the flow velocity gradient in the channel height-direction as well as the volume rate of feed which acts as energy source for the evaporation of perrneants on the permeate-side surface of a membrane increased to such an extent that both mass and heat flux in the channel height direction could increase and the temperature drop of feed due to the evaporation of the permeant could be reduced correspondingly. A decrease in channel height caused the temperature drop of feed because of decreasing feed flow in the module. It was observed that the si$$\mu$ation result on the effect of Re on the temperature distribution of feed in the module has an agreement with experiment.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1185-1186
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• 2007

The UTM-01 developed in 1998 was the first maglev vehicle in Korea for the urban transit maglev (UTM) system. Through the improvement of UTM-01 and development of UTM02, the commercialization of the UTM system is being prepared now. In order to prepare for the commercialization of maglev, it is necessary that an optimal design of the levitation magnet should be provided for the safe operation of the vehicle. The levitation force is formed through the function of magnetic flux density on the top of magnet poles and gap between magnet pole and guide rail. To generate a magnetic field that is high enough to levitate the vehicle, ferromagnetic materials, such as pure iron for magnet pole and SS400 for guide rail, were used. The heat generated by $I^2R$ loss of magnet conductor makes the thermal convection on the surface of magnet including coil and poles. As these two characteristics are nonlinear phenomena, this paper deals with the nonlinear analysis on the magnetic and thermal properties of the U-type levitation magnet by using 3-D finite element method (FEM). Base on the analysis results, a small scale U-type magnet was designed, manufactured, and tested and it was verified that the magnet manufactured was satisfactory to all the design specifications.