• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.87-91
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• 2004

It is definitely required to control dispersion of the rocket engine performance in order to accomplish the mission of launch vehicle successfully. We performed the dispersion analysis of gas generator cycle LRE (liquid rocket engine) accompanied with ANASYN. As a result, the vacuum thrust dispersion of the engine was $+5.34\%,\;-5.27\%$ and the mixture ratio deviated $+9.07\%,\;-9.82\%$ from the nominal value due to the errors of components and engine inlet condition of propellants. By applying the gas generator regulator only, the dispersion of the engine performance increases. Error in turbine efficiency is the most influential factor to the dispersion of engine performance.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.4
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• pp.197-208
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• 1991

A depth-averaged X-Y numerical model with transformed coordinates is developed to analyze the salinity dispersion in estuaries. Simulation of intertidal zones, residual current and closed boundary condition are examined. Especially. the improvements in stability and accuracy of the numerical algorithm are made by adopting fractional step method for the dispersion term of the governing equation. The model being applied to the Keum River Esturary, velocity fields and salinity fields are reproduced satisfactorily and the estimation of the dispersion coefficient with respect to the flow fold is also studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.10 s.241
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• pp.1075-1082
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• 2005

The characteristics of longitudinal dispersion enhancement by the flow oscillation are numerically studied according to various groove geometries in a 2-D channel in the present study. The length of expanded section l$_{1}$/h$_{1}$ is varied from 0 to 8.75. The oscillating flow condition is given at both side ends, i.e., u = Asin ($2{\pi}ft$) The non-dimensional temperatures at both side ends are set to zero. The bottom and top walls are adiabatic. The local heat sources are located at the middle of the groove wall. In order to solve the governing equations, the SIMPIER algorithm is employed. The present results indicate that maximum longitudinal thermal dispersion can be achieved when the area ratio of the expanded section to the contracted section in the grooved channel becomes 1.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1330-1337
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• 1994

This study is to predict the lateral dispersion of the particles with time in a vertical pipe. Particle is released downward and located in the center of a pipe through which stationary, homogeneous turbulent air is flowing. We assume that gas turbulence velocities have a Gaussian probability density distribution and the presence of particle is not to alter turbulent structures. Particle trajectory is computed by numerically integrating the particle Lagrangian equation of motion, with a random sampling to determine the fluctuating air velocity experienced by each particle, which considered inertia effect and crossing-trajectories effect. The result shows characterestics of particle dispersion according to flow field condition and droplet size by using the parameters and scales, which expressed characterestics of flow field and particle. Predictions agree reasonably with experimental data.

• Composites Research
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• v.28 no.4
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• pp.232-238
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• 2015

As a new method to predict the degree of dispersion in carbon nanocomposites, the electrical resistance (ER) method has been evaluated. After CNT epoxy resin was dropped on CF tow, the change in electrical resistance of carbon fiber tow was measured to evaluate dispersion condition in CNT epoxy resin. Good dispersion of CNTs in carbon nanocomposite exhibited low change in ER due to wetted resin penetrated on CF tow. However, because CNT network was formed among CFs, non-uniform dispersion occurred due to nanoparticle filtering effect by CF tow. The change in ER for poor dispersion exhibited large ER signal change. The change in ER was used for the dispersion evaluation of CNT epoxy resin. Correlation between interlaminar shear strength (ILSS) and dispersion condition by ER method was established. Good CNT dispersion in nanocomposites led to good interfacial properties of fiberreinforced nanocomposites.

• Textile Coloration and Finishing
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• v.24 no.1
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• pp.69-78
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• 2012

This paper surveys the physical properties of the MWNT dispersion solution dispersed with the three types of solvents and of the polyurethane composite film for improvement of mechanical properties and electrical characteristics of PU/MWNT composite film. For this purpose, the MWNT dispersed solution was mixed with three types of solvent such as IPA, MEK and Toluene and then mixed with polyurethane (100part) with variation of loading content (0, 10, 20, 30, 40, 50 part) of MWNT dispersed solution in the ultrasonic wave dispersion apparatus. And eighteen PU/MWNT composite films were prepared as specimens. The various physical properties of these PU/MWNT films were measured and discussed with the loading content of three types of MWNT dispersed solutions. The highest absorbancy among the three types of dispersed solutions was shown in the IPA/MWNT solution. But the absorbancy of PU/MWNT films was not same as the solution. The low electrical surface and volume resistivity of PU/MWNT film were shown at the condition of 20 and 10 parts loading of IPA/MWNT dispersed solution, respectively. The low triboelectricity of PU/MWNT film was shown at the condition of above 30part loading of IPA/MWNT dispersed solution. The breaking strength and strain of PU/MWNT film prepared with IPA/MWNT dispersed solution were decreased with increasing loading content of IPA/MWNT from 10 to 40 parts. The maximum breaking strength and breaking strain according to the dispersion solution were shown on the IPA/MWNT dispersed solution. The uniform dispersion of PU/MWNT film according to the loading content of MWNT solution was shown by surface image analysis on the films dispersed with IPA.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.248-249
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• 2005

• 한국전기화학회:학술대회논문집
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• 2005.04a
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• pp.47-47
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• 2005

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.575-586
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• 2003

In case of continuous input of a pollutant, dispersion characteristics do not change much with changing dispersion coefficient, but that of an instantaneous input is very sensitive to the changes of dispersion coefficient. The characteristics of behavior of instantaneous input of a pollutant at the downstream of Han river were analyzed in this paper Field measurement of hydraulic and water quality factors at the downstream of Han river were conducted at low flow condition. The hydraulic factors were used to estimate the longitudinal dispersion coefficient, and the reasonable empirical equations for longitudinal dispersion coefficient at the downstream of Han river were suggested. The measured concentrations of BOD were closely matched with the calculated ones from RMA-4 model. In case of instantaneous input, range of dispersion, transport pathway and the traveltimes of the first and maximum concentration with variation of the longitudinal dispersion coefficients and water levels of downstream boundary were evaluated in this paper.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.899-906
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• 2018

The irradiation performance of $U_3Si$ dispersion fuel in an Al matrix, $U_3Si-Al$, under the Hi-Flux Advanced Neutron Application Reactor (HANARO) design full-power condition of 30 MW was tested for full-power qualification of the fuel. A test assembly was fabricated containing 18 fuel rods made with atomized $U_3Si$ powder manufactured at the Korea Atomic Energy Research Institute. The test assembly was irradiated for 188 full-power operation days in the HANARO subject to the normal fuel-loading scheme and achieved about 60 at% U-235 average burnup and 75 at% U-235 peak burnup. The maximum linear power of the test assembly was 98 kW/m. Nondestructive and destructive postirradiation examinations were conducted. The measured postirradiation examination data were compared with data from previous irradiations and the design criteria required for HANARO fuel. Consequently, it was concluded that in-pile performance was acceptable and fuel integrity was maintained, and the behavior satisfied the fuel design requirements.