• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1623-1630
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• 2002

Recently, much attention is imposed on the design of the fuel assemblies in the Pressurized Light Water Reactor (PWR). Spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water, and maintains a coolable geometry from the external impact loads. In this research, a new shape of the spacer grid is designed by the axiomatic approach. The Independence axiom is utilized for the design. For conceptual design, functional requirements (FRs) are defined and corresponding design parameters (DPs) are found to satisfy FRs in sequence. Overall configuration and shapes are determined in this process. Detail design is carried out based on the result of the axiomatic design. For the detail design, the system performances are evaluated by using linear and nonlinear finite element analysis. The dimensions are determined by optimization. Some commercial codes are utilized for the analysis and design.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.6
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• pp.403-410
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• 2006

Eddy current testing (ECT) signals produced by a differential bobbin coil probe vary according to probe design parameters such as the number of turns, geometry and coil gap size. In the present study, the characteristics of a differential bobbin coil probe signals are investigated by numerical simulation in order to determine the optimum coil gap. For verification of numerical simulation accuracy, a specially designed bobbin probe of which the coil gap can be adjusted is fabricated and a series of experiments to acquire signals from two kinds of standard tubes with the variation in coil gap is performed. Then, the experimental signals are compared to the simulation results. Based on this investigation, a decision on the optimum range of coil gap is made. The theoretically predicted signals agree very well to the experimental signals. In fact, this excellent agreement demonstrates a high potential of the simulation as a design optimization tool for ECT bobbin probes.

• Journal of KSNVE
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• v.6 no.3
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• pp.349-355
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• 1996

For a rail traffic noise, a typical source has a length of 200m - 400m so that the noise pollution areas have been located in the transition regions where the sound level drops between 3dB/dd and 6dB/dd. Therefore, in this region, parameters such as a horizontal distance from the track, the geometry of the ground surface, the environmental effect, and the boundary impedance condition play import roles, especially in our nation's situation. In this study, modelling techniques for the finite length of noise source have been investigated in order to evaluate the rail traffic noise level. Then. noise correction value .${\Delta}$SPL for various location in the track region is represented by the non-dimensionalized horizontal and parallel distance from the track. As an application, a high speed train is examined. Beas on the noise data measured for a Eurostar in France, the sound power value per unit length $H_1$is calcuated. It turns out that$H_1$is 109 dB. Overall sound power from the highspeed train to be serviced in our country is expected to 135 dBA.

• Water for future
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• v.15 no.1
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• pp.33-42
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• 1982

In recent years owing to extensive land reclamation, increased river engineering activites and morer intense flood plain use, river geomorphology has attracted considerable attention. One of outstanding problems has been maintenance of river meanders and nearly all natural river exhibit the tendency to meander. Often the meander geometry was fitted in to various idealized model. COnsequently, both the selection of data and the methods to determine the geometric parameters were highly subject to individual preferences. This study applied statistical analysis in tipifying their shape and analysised meander characteristics by channel model of line generalization algorithm. This method is applied to Geum river system. The results show that the variance of curvature is a better index to describe the meander intensity and the kurtosis is a good index to characterize the total length of the straight sections for a given reach. The results also show that channel model of line generalization algorithm is a good model in analysis of meander characterisitics.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.211-216
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• 1996

Since the middle of the eighties of this century a research program both for heating reactor and investigation of heating reactor thermal-hydraulics has been carried out in Institute of Nuclear Energy Technology(INET) of Tsinghua university in China. This kind of heating reactor is a light water cooled and integrated natural circulation reactor with low system pressure and low quality at the exit of core. Because of relatively long riser and low system pressure. a little change of the quality at the exit of the core will result in a relatively large variation of void fraction in the riser. Two full scale test loops. HRTL-5 and HRTL-200 simulating the HR-5 and HR-200 heating reactors in geometry and operation parameters respectively, and some test results from the HRTL-200 test facility are shown in this paper. The range of studied system pressure is from 1.0MPa to 4.0MPa, the largest heat flux is about 50 W/cm2, and the quality at the exit of test section is less than 5%.

• Journal of Energy Engineering
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• v.14 no.3 s.43
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• pp.194-202
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• 2005

The present study was analytically and experimentally carried out to predict the absorption characteristics on combined heat and mass transfer process in a vertical falling film of variable absorbers. Heat and mass transfer enhancements were analytically investigated. Effects of geometric parameters by insert device (spring) and corrugate, flow pattern on absorption performances has been also investigated. Especially, the optimal values of absorber geometry (ID=22.8mm, L=1150m) and kinetic variables (solution flow rate, flow pattern) for maximum absorption performance has been predicted by the numerical analysis. The maximum absorption performance in a numerical analysis and experiment was shown at the wavy-flow by insert device (spring).

• The KSFM Journal of Fluid Machinery
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• v.2 no.2 s.3
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• pp.64-73
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• 1999

The three-dimensional numerical study of a water jet pump was carried out to investigate the relationship between performance and the geometric variables of nozzle space, area ratio, and throat length. Because of the complex geometry, the multiblock technique was adopted for numerical analysis and a special treatment for transferring data from each of the block interfaces was implemented in order to maintain the conserved properties. To validate the present code, flow passing through a square duct with a 90-deg bend was computed, our results show good accordance with other experimental and computational results. The numerical simulation was done with the flow of the water jet pump having a 180-deg bend in order to calculate the performance at different operating conditions. The performance of the water jet pump can be improved by study of parameters which clarify the relations between the geometric variables and the flow characteristics of vortex strength and location.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.212-219
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• 1998

During machining of dies and molds with sculptured surfaces. the cutter contact area changes continuously and results in cutting force variation. In order to implement cutting force prediction model into a CAM system, an effective and fast method is necessary. In this paper. a new method is proposed to predict mean cutting force. The cutter contact area in the spherical part of the cutter is obtained using Z-map, and expressed by the grids on the cutter plane orthogonal to the cutter axis. New empirical cutting parameters were defined to describe the cutting force in the spherical part of cutter. Before the mean cutting force calculation, the cutting force density in each grid is calculated and saved to force map on the cutter plane. The mean cutting force in an arbitrary cutter contact area can be easily calculated by summing up the cutting force density of the engaged grid of the force map. The proposed method was verifed through the slotting and slanted surface machining with various inclination angles. It was shown that the mean force can be calculated fast and effectively through the proposed method for any geometry including sculptured surfaces with cusp marks and holes.

• Journal of the Korean Solar Energy Society
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• v.21 no.4
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• pp.29-35
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• 2001

The chemical heat storage as the one way of utilization for high temperature solar energy was considered. The stram reforming reaction of methane was chosen for endothermic reaction. The reactor was made of stainless steel tube and it's dimension was 0.635 cm I.D. and 30 cm long, coiled tube because of the geometry requirement of solar receiver The effects of space velocity and reactants mole ratio on the methane conversion and CO selectivity were examined. From the experimental results, the optimum steam/methane mole ratio was determined.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.232-237
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• 2004

Anatahan Volcano in the Commonwealth of the Northern Mariana Islands (CNMI) erupted for the first time in recorded history on 10 May 2003. The underwater acoustic records of earthquakes, explosions, and tremor produced during the eruption were recorded on a sound-channel hydrophone deployed in February 2003. Acoustic propagation models show the seismic to acoustic conversion at Anatahan is particularly efficient, aided by the slope of the seamount toward the hydrophone. The hydrophone records confirm the onset of earthquake activity at 01:53Z on 10 May, as well as the onset (at ${\~}$06:20Z) of continuous, low-frequency (5-40 Hz) acoustic energy that is likely volcanic tremor related to magma intrusion. The hydrophone recorded a total of 458 earthquakes associated with the eruption. To predict the character of acoustic signals generated from Anatahan, we developed a moment-tensor representation of a volcano-seismic source that is governed by the geometry of the source and the physical properties of the magma. A buried magmatic pipe model was adopted, and numerically modeling source parameters such as the pipe radius and magma viscosity enable us to grasp the inward nature of Anatahan Volcano.