• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.227-235
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• 2010

This paper introduces the design of a bridge transport system with a telescopic tube for positioning equipment to perform remote handling tasks in a radioactive facility. It consists of an extensible and retractable telescopic tube assembly for z-direction motion, a cabling system for management of power and signal cables, and a trolley system for transverse motion and accommodating servo drives. The working environment for the bridge transport system with the telescopic tube requires strict geometrical constraints, including a short height, short telescopic tube length when retracted, and a long stroke. These constraints were met by solving a nonlinear programming problem involving the optimal dimensions. This paper introduces a cabling system for effective management of cables with changeable lengths to accommodate telescopic motions and a selection guide for servo drives that are sufficient to drive the system.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1782-1798
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• 2004

A numerical study of a natural convection in a rectangular cavity with the low-Reynolds-number differential stress and flux model is presented. The primary emphasis of the study is placed on the investigation of the accuracy and numerical stability of the low-Reynolds-number differential stress and flux model for a natural convection problem. The turbulence model considered in the study is that developed by Peeters and Henkes (1992) and further refined by Dol and Hanjalic (2001), and this model is applied to the prediction of a natural convection in a rectangular cavity together with the two-layer model, the shear stress transport model and the time-scale bound ν$^2$- f model, all with an algebraic heat flux model. The computed results are compared with the experimental data commonly used for the validation of the turbulence models. It is shown that the low-Reynolds-number differential stress and flux model predicts well the mean velocity and temperature, the vertical velocity fluctuation, the Reynolds shear stress, the horizontal turbulent heat flux, the local Nusselt number and the wall shear stress, but slightly under-predicts the vertical turbulent heat flux. The performance of the ν$^2$- f model is comparable to that of the low-Reynolds-number differential stress and flux model except for the over-prediction of the horizontal turbulent heat flux. The two-layer model predicts poorly the mean vertical velocity component and under-predicts the wall shear stress and the local Nusselt number. The shear stress transport model predicts well the mean velocity, but the general performance of the shear stress transport model is nearly the same as that of the two-layer model, under-predicting the local Nusselt number and the turbulent quantities.

• Electrical & Electronic Materials
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• v.10 no.3
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• pp.268-273
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• 1997

In this paper the transient electron transport in GaAs bulk is simulated by using ensemble Monte Carlo method. To analyze the transient electron transport the 10000 electrons in the .GAMMA. valley are simulated simultaneously for 10 picoseconds. The electric field-velocity relation is obtained. The high impurity density reduces the negative differential resistance effect. The result of transient average velocity shows the electron velocity in the transient state is faster than that in the steady state. This transient velocity overshoot is caused by the intervalley scattering mechanism. And we confirmed the fact that the energy relaxation time is longer than the momentum relaxation time.

• Earthquakes and Structures
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• v.18 no.5
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• pp.599-607
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• 2020

This paper deals with the experimental investigation on the behavior of RCS beam-column exterior joints. Two full-scale specimens of joints between reinforced concrete columns and steel beams are tested under cyclic loading. The objective of the test is to study the effect of steel fiber reinforced concrete (SFRC) on the seismic behavior of RCS joints. The load bearing capacity, story drift capacity, ductility, energy dissipation, and stiffness degradation of specimens are evaluated. The experimental results point out that the FRC joint is increased 20% of load carrying capacity and 30% of energy dissipation capacity in comparison with the RC joint. Besides, the FRC joint shown lower damage and better ductility than RC joint.

• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.825-836
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• 2014

Predicting radioactive fission product (FP) behaviors in the reactor coolant system and the containment of a nuclear power plant (NPP) is one of the major concerns in the field of reactor safety, since the amount of radioactive FP released into the environment during the postulated accident sequences is one of the major regulatory issues. Radioactive FPs circulating in the primary coolant loop and released into the containment are basically in the form of gas or aerosol. In this study, a multi-component and multi-sectional analysis module for aerosol fission products has been developed based on the MAEROS model [1,2], and the aerosol transport model has been developed and verified against an analytic solution. The deposition of aerosol FPs to the surrounding structural surfaces is modeled with recent research achievements. The developed aerosol analysis model has been successfully validated against the STORM SR-11 experimental data [3], which is International Standard Problem No. 40. Future studies include the development of the resuspension, growth, and chemical reaction models of aerosol fission products.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.4
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• pp.40-50
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• 1993

In this paper, MODFET devices with various gate length are simulated using the Monte-Carlo method. The number of superparticle is 5000 and the Poisson equation is solved to obtain field distribution. The structure of MODFET is n-AlGaAs/i-AlGaAs/iGaAs and doping concentration of n-AlGaAs layer is 1${\times}10^{17}/cm^{3}$ and the thickness is 500.angs., and the thickness of i-AlGaAs is 50$\AA$. The devices with gate length 0.2$\mu$m, 0.5$\mu$m, 1.0$\mu$m respctively are simulated and the current-voltage curves and transport characteristics of that devices are obtained. Occupancy of each subband and electron energy distribution and conduction energy band in channel have been analyzed to obtain transport characteristics, and particles transposed from source to drain have been analyzed to current-voltage curves. Current level is highest for the device of Lg=0.2$\mu$m and transconductance of this device is 310mS/mm.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.489-496
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• 2021

The performandce of polymer electrolyte membrane fuel cell depends on the effective management of heat and product water by the electrochemical reaction. This study is designed to investigate the parametric change of heat management along the channel of polymer electrolyte membrane. The model was developed by an aspen custom modeler that it can solve differential equation with distretization model. The model can simulate water transport through the membrane electrolyte that is coupled with heat generation. In order to verify the model, it is compared with the experimental data. The water transport behavior is then evaluated with the simulation model.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.375-388
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• 2024

In this study, to evaluate the shock and vibration load characteristics of used fuel, a sea transportation test was conducted using simulated fuel assemblies under normal transport conditions. An overall test data analysis was performed based on the measured strain and acceleration data obtained from cruise, rotation, acceleration, braking, depth of water, and rolling tests. In addition, shock response spectrum and power spectral densities were obtained for each test case. Amplification and attenuation characteristics were investigated based on the load path. The load was amplified as it passed from the overpack to the simulated used fuel-assembly. As a result of the RMS trend analysis, the fuel-loading position of the transportation package affected the measured strain in the fuel rod, and the maximum strains were obtained at the spans with large spacing. However, even these maximum strains were very small compared to the fatigue strength and the cladding yield strength. Moreover, the fuel rods located on the side exhibited a larger strain value than those at the center.

• Nuclear Engineering and Technology
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• v.44 no.2
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• pp.207-224
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• 2012

This article discusses selects of some outstanding problems in nuclear reactor analysis, with proposed approaches thereto and numerical test results, as follows: i) multi-group approximation in the transport equation, ii) homogenization based on isolated single-assembly calculation, and iii) critical spectrum in Monte Carlo depletion.

• Nuclear Engineering and Technology
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• v.41 no.4
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• pp.381-390
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• 2009

This article provides selects of outstanding problems in computational neutron transport, with some suggested approaches thereto, as follows: i) ray effect in discrete ordinates method, ii) diffusion synthetic acceleration in strongly heterogeneous problems, iii) method of characteristics extension to three-dimensional geometry, iv) fission source and $k_{eff}$ convergence in Monte Carlo, v) depletion in Monte Carlo, vi) nuclear data evaluation, and vii) uncertainty estimation, including covariance data.