• Nuclear Engineering and Technology
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• v.42 no.6
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• pp.670-679
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• 2010

In this paper, a new approach using a pixel-based correction method was developed to fix the non-uniform responses of flat-bed type scanners used for radiochromic film dosimetry. In order to validate the method's performance, two cases were tested: the first consisted of simple dose distributions delivered by a single port; the second was a complicated dose distribution composed of multiple beams. In the case of the simple individual dose condition, ten different doses, from 8.3 cGy to 307.1 cGy, were measured, horizontal profiles were analyzed using the pixel-based correcton method and compared with results measured by an ionization chamber and results corrected using the existing correction method. A complicated inverse pyramid dose distribution was made by piling up four different field shapes, which were measured with GAFCHROMIC$^{(R)}$EBT film and compared with the Monte Carlo calculation; as well as the dose distribution corrected using a conventional method. The results showed that a pixel-based correction method reduced dose difference from the reference measurement down to 1% in the flat dose distribution region or 2 mm in a steep dose gradient region compared to the reference data, which were ionization chamber measurement data for simple cases and the MC computed data for the complicated case, with an exception for very low doses of less than about 10 cGy in the simple case. Therefore, the pixel-based scanner correction method is expected to enhance the accuracy of GAFCHROMIC$^{(R)}$EBT film dosimetry, which is a widely used tool for two-dimensional dosimetry.

• Radiation Oncology Journal
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• v.1 no.1
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• pp.29-36
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• 1983

The treatment of tumors along curved surfaces with stationary electron beams using cone collimation may lead to non-uniform dose distributions due to a varying air gap between the cone surface and patient. For large tumors, more than one port may have to be used in irradiation of the chest wall, often leading to regions of high or low dose at the junction of the adjacent ports. Electron-beam arc therapy may elimination many of these fixed port problems. When treating breast tumors with electrons, the energy of the internal mammary port is usually higher than that of the chest wall port. Bolus is used to increase the skin dose or limit the range of the electrons. We invertiaged the effect of various arc beam parameters in the isodose distributions, and combined into a single arc port for adjacent fixed ports of different electron beam eneries. The higher fixed port energy would be used as the arc beam energy while the beam penetration in the lower energy region would be controlled by a proper thickness of bolus. We obtained the results of following: 1. It is more uniform dose distribution of electron to use rotation than stationary irradiation. 2. Increasing isocenter depth on arc irradiation, increased depth of maximum dose, reduction in surface dose and an increasing penetration of the linear portion of the curve. 3. The deeper penetration of the depth dose curve and higher X-ray background for the smaller field sized. 4. If the isocenter depth increase, the field effect is small. 5. The decreasing arc beam penetration with decreasing isocenter depth and the isocenter depth effect appears at a greater depth as the energy increases. 6. The addition of bolus produces a shift in the penetration that is the same for all depths leaving the shape of the curves unchanged. 7. Lead strips 5 mm thick were placed at both ends of the arc to produce a rapid dose drop-off.

• Progress in Superconductivity
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• v.12 no.1
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• pp.6-11
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• 2010

The milling effects of a precursor $Y_2BaCuO_5$ (Y211) powder having 1 wt.% $CeO_2$ on the microstructure and critical current density ($J_c$) of liquid infiltration growth (LIG) processed $YBa_2Cu_3O_{7-y}$ (Y-123) bulk superconductors were investigated. The microstructure analysis revealed that the Y211 size in the final Y-123 products decreased with increasing the milling time and a relatively high density and uniform distribution of Y211 inclusions were observed in the sample prepared using 8 h milled powder. However, the unexpected Y211 particles coarsening was observed from the 4 h milled sample which was further increased for 10 h milled sample. Critical current density ($J_c$) of the LIG processed Y-123 bulk superconductors was found to be dependent on the milling time of the Y211 precursor powder. The $J_c$ increased with the increase of milling time and reached up to a maximum at 8 h in the self field while 10 h milled sample showed lower $J_c$ at the same field which might be due to the exaggerated growth and non-uniform distribution of Y211 particles.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1168-1179
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• 2006

The validity of an unsteady two-dimensional(2-D) numerical hydrodynamic and pollutant dispersion model(2DNHPDM) was evaluated using the data obtained from I-sa streams in Sooncheon, Chonnam, during rain-fall run-off. Field observations was conducted for 35 hours during the 10 hours rainfall event on 7th May 2005. The water level, 2-D velocity, flow field, and COD at seven points selected along the river were measured at intervals of one hour. The model was applied to describe two-dimensional movement of dissolved pollutants in meandering non-uniform river. Major physical processes affecting the lateral and horizontal mixing of the river flow were simulated. The model was proved effective in describing the hydrodynamics and dispersion of the river pollutants from its major tributaries as well as non-point sources.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.643-648
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• 2004

This paper is dedicated to the thermoelastic modeling and dynamic response of the rotating blades made of functionally graded ceramic-metal based materials. The blades modeled as non-uniform thin walled beams fixed at the hub with various selected values of setting angles and pre-twisted angles. In this study, the blade is rotating with a constant angular velocity and exposed to a steady temperature field as well as external excitation. Moreover, the effect of the temperature gradient through the blade thickness is considered. Material properties are graded in the thickness direction of the blade according to the volume fraction power law distribution. The numerical results highlight the effects of the volume fraction, temperature gradient, taper ratio, setting angle and pre-twisted angle on the dynamic response of bending-bending coupled beam characteristics are provided for the case of a biconvex cross section and pertinent conclusions are outlined.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.93-100
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• 2003

This paper describes the thermoelastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation. In a conventional disc brake analysis, heat generation is only related with wheel speed and friction material and the interface pressure between disc and pad is assumed constant. But under dynamic braking conditions, the frictional heat causes the thermoelastic distortion that leads to more concentrated contact pressure distribution and hence more and more non-uniform temperature. In this paper, to complete the solution of the thermomechanically coupled problem, the linear relation model between pressure and temperature is proposed and demonstrated in examples of a simple two dimensional contact problem. And the two dimensional model has been extended to an annular three dimensional disc model in order to consider more realistic geometry and to provide a more accurate critical speed for automotive brake systems.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.80-86
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• 2003

Arc-spot welding is generally used in joining of precise parts such as case and core in electric compressor. It is important to control joining deformation in electric compressor because clearance control of micrometer order is needed for excellent airtightness and anti-nose. The countermeasures for this deformation in field have mainly been dependent on rule of try and error by operator's experience because of productivities. For control this deformation problem without influence on productivities, development of exact simulation model should be needed. In this study, on the basis of previous study, the analysis model io predict deformation of precise order in arc-spot welded structure with non-uniform stiffness is brought up through feedback and tuning between monitoring data and analysis results. For this, deformation monitoring system was built and boundary condition considering mechanical melting temperature was applied.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1322-1329
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• 2018

In this paper, the reliability test of three kinds of epoxy resin for GIS Spacer, which is a high voltage based heavy electric machine, AC electrical treeing experiments were performed. Three types of epoxy resins, Araldite B41, CT 5531 CI and B46, have slight viscosity differences. An non-uniform electric field, E = 1149.4 kV/mm, as the needle to plate electrode, a power source with a frequency of 1 kHz was applied to the tree electrode for accelerated deterioration. The treeing phenomena of the three kinds of epoxy resin all initiated, propagated, and destroyed by the branch tree. Epoxy Resin B46 was 145 times longer than B41 and 53 times longer than CT 5531CI. I think that the choice of epoxy resin is very important in choosing high voltage heavy electric machine insulation materials.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.4
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• pp.317-323
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• 2014

This study is concerned with the free vibration analysis of an inextensible uniform rope with a spring-mass system at the tip. The rope is hanged vertically in a gravitational field. This problem is related to the free vibration of an elevator rope connected to an elevator cage. The equation of motion and the corresponding boundary conditions are derived by using the Hamilton's principle. The general solution of the governing equation of motion is expressed in terms of Bessel functions. The characteristic equation was derived by applying the boundary conditions. The characteristic values which are in fact non-dimensionalized natural frequencies were obtained numerically. The effects of mass and spring constant were investigated. The numerical results show how the tip mass and spring affect the natural frequencies of the rope.

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.70-70
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• 2004

Lower thermospheric winds are forced primarily by non-uniform solar heating, atmospheric tides and other waves coming from below, and energy and momentum forcing associated with high-latitude magnetosphere-ionosphere coupling, particularly ion drag and Joule heating. To understand the physical processes that control the thermospheric dynamics, we quantify the momentum forces that are mainly responsible for maintaining the high-latitude lower thermospheric wind system and examine the resulting momentum balance with the aid of the Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM) developed by the National Center for Atmospheric Research. (omitted)