• Proceedings of the KSME Conference
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• 2002.08a
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• pp.47-50
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• 2002

The numerical simulation of a 271-rod fuel assembly of nuclear Liquid-Metal Fast Reactor (LMFR) with an infernal blockage has been carried out. Internal blockage within a subassembly is addressed in the safety assessment because it potentially has very serious consequences for the reactor as a whole. Three dimensional calculations were performed using the SABRE4 computer code for the range of blockage positions and sizes to investigate the seriousness and detectability of the internal blockage. The magnitude and location of the peak temperatures together with the temperature distribution at the subassembly exit were calculated in order to look at the potential for damage within the subassembly, and the possibility of blockage detection. The analysis result shows that the 6-subchannel blockage causes large temperature rise within a assembly with practically no change in mixed mean temperature at the assembly exit.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.280-282
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• 2002

As EG(Embedded Generation : photo-voltaic, wind, combined heat and power, fuel cell, small hydro etc.) grows fast in adopting to peak load reducing at the middle or the end of distribution system, there much has been interested in interconnection of EG. This paper discusses the various issue of a embedded generator to power system and shows the simulation of its various situation that could happen (focusing on load-flow by EG) by using a commercial software CYME(PSAF) for load-flow. With a result of above simulation, this paper shows a way of possible solution briefly.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.167-172
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• 2016

The high temperature deformation behavior of $Ni_3Al$ and $Ni_3(Al,Mo)$ single crystals that were oriented near <112> was investigated at low strain rates in the temperature range above the flow stress peak temperature. Three types of behavior were found under the present experimental conditions. In the relatively high strain rate region, the strain rate dependence of the flow stress is small, and the deformation may be controlled by the dislocation glide mainly on the {001} slip plane in both crystals. At low strain rates, the octahedral glide is still active in $Ni_3Al$ above the peak temperature, but the active slip system in $Ni_3(Al,Mo)$ changes from octahedral glide to cube glide at the peak temperature. These results suggest that the deformation rate controlling mechanism of $Ni_3Al$ is viscous glide of dislocations by the <110>{111} slip, whereas that of $Ni_3(Al,Mo)$ is a recovery process of dislocation climb in the substructures formed by the <110>{001} slip. The results of TEM observation show that the characteristics of dislocation structures are uniform distribution in $Ni_3Al$ and subboundary formation in $Ni_3(Al,Mo)$. Activation energies for deformation in $Ni_3Al$ and $Ni_3(Al,Mo)$ were obtained in the low strain rate region. The values of the activation energy are 360 kJ/mol for $Ni_3Al$ and 300 kJ/mol for $Ni_3(Al,Mo)$.

• Tuberculosis and Respiratory Diseases
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• v.44 no.2
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• pp.298-308
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• 1997

Background : Portable devices for measuring peak expiratory flow(PEF) are now of proved value in the diagnosis and management of asthma and many lightweight PEF meters have become available. However, it is necessary to determine whether peak expiratory flow rate(PEFR) measurements measured with peak flowmeters is accurate and reproducible for clinical application. The aim of the present study is to define accuracy, agreement, and precision of mini-Wright peak flow meter(MPFM) against standard pneumotachygraph. Methods : The lung function tests by standard pneumotachygraph and PEFR measurement by MPFM were performed in a random order for 2 hours in 22 normal and 17 asthmatic subjects and also were performed for 3 successive days in 22 normals. Results : The PEFR measured with MPFM was significantly related to the PEFR and $FEV_1$ measured with standard pneumotachygraph in normal and asthmatics(for PEFR, r = 0.92 ; p < 0.001 ; for $FEV_1$, r = 0.78 ; p < 0.001). The accuracy of MPFM was within 100(limits of accuracy recommeded by NAEP) in all the subjects or 22 normal, mean difference from standard pneumotachygraph being 16.5L/min(percentage of difference being 2.90%) or 10.6L/min(percentage of difference being 1.75%), respectively. According to the method proposed by Bland and Altman, the 95% limits of the distribution of differences between MPFM and standard pneumotachygraph after correction of PEFR using our regression equation were +38.2 and -71.5L/min in all the subjects or 20.49~+9.49L/min in 22 normal and was similar to the intraindividual agreements for 3 successive days in normal. There was no statistically significant difference of PEFR measured with MPFM and standard pneumotachygraph among three days(p > 0.05) and the coefficient of variation($2.4{\pm}1.2%$) of PEFR measured with MPFM was significantly lower than that($5.2{\pm}3.5%$) with standard pneumotachygraph in normal (p < 0.05). Conclusion : This results suggest that the MPFM was as accurate and reproducible as standard pneumotachygraph for monitoring of PEFR in the asthmatic subjects.

• Journal of the Korean GEO-environmental Society
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• v.22 no.8
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• pp.5-12
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• 2021

Climate change caused by global warming increases the frequency of occurrence of super typhoons and causes various types of sediment disasters such as debris flows in the mountainous area. This study is to evaluate the behavior of debris flow according to the multiplier value of the precipitation characteristics and the quantity of debris flow according to the typhoon category. For the analysis of the debris flow, the finite difference method for time elapse was applied. The larger the typhoon category, the higher the peak value of the flow discharge of debris flow and the faster the arrival time. When the precipitation characteristic multiplier is large, the fluctuation amplitude is high and the bandwidth is wide. When the slope angle was steeper, water discharge increased by 2~2.5 times or more, and the fluctuation of the flow discharge of debris flow increased. All of the velocities of debris flow were included to the class of "Very rapid", and the distribution of the erosion or sedimentation velocity of debris flows showed that the magnitude of erosion increased from the beginning, large-scale erosion occurred, and flowed downstream. The results of this study will provide information for predicting debris flow disasters, structural countermeasures and establishing countermeasures for reinforcing resilience in vulnerable areas.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.9
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• pp.843-852
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• 2000

The flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices were studied experimentally. The test facility consisted of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta winglet protruding from the surface. In order to control the strength of the longitudinal vortices, the angles of attack of the vortex generators were varied from $\pm20\;degree\;to\;\pm45$ degree, but spacings between the vortex generators were fixed to 4 cm. The 3-dimensional mean velocity measurements were made using a five-hole pressure probe. Heat transfer measurements were made using the thermochromatic liquid to provide the local distribution of the heat transfer coefficient. By using the method mentioned above, the following conclusions were obtained from the present experiment. The boundary layer was thinned in the regions where the secondary flow was directed toward the wall and thickened where it was directed away from the wall. The peak augmentation of the local heat transfer coefficient occurred in the downwash region near the point of minimum boundary-layer thickness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.84-91
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• 2003

Flow-Induced Vibration of steam generator tubes may result in fretting wear damage at the tube-to-support locations. KSNP(Korean Standard Nuclear Power plant) steam generators experienced fretting wear in the upper part of U-bend above the central cavity region of steam generators. This region has conditions susceptible to the flow-induced vibration, such as high flow velocity, high void fraction, and longer unsupported span. To improve its performance, APR1400 steam generator is designed with additional supports in this region to reduce unsupported span and to reduce peak velocity in the central cavity region. In this paper, we examined its performance improvement using ATHOS code. The thermal-hydraulic condition in the region of secondary side of APR1400 steam generator is obtained using the ATHOS3 code. The effective mass for modal analysis is calculated using the void fraction, enthalpy, and operating pressure information from ATHOS3 code result. With the effective mass distribution along the tube, natural frequency and mode shape is obtained using ANSYS code. Finally, stability ratios and real mean squared displacements for selected tubes of the APR1400 steam generator are computed. From these results, the current design of the APR1400 steam generator are examined.

• Wind and Structures
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• v.9 no.1
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• pp.23-35
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• 2006

The effect of buildings on flow in urban canopy is one of the most important problems in local/micro-scale meteorology. A large eddy simulation model is used to simulate the flow structure in an urban neighborhood and the bulk effect of the buildings on surrounding flows is analyzed. The results demonstrate that: (a) The inflow conditions affect the detailed flow characteristics much in the building group, including: the distortion or disappearance of the wake vortexes, the change of funneling effect area and the change of location, size of the static-wind area. (b) The bulk effect of the buildings leads to a loss of wind speed in the low layer where height is less than four times of the average building height, and this loss effect changes little when the inflow direction changes. (c) In the bulk effect to environmental fields, the change of inflow direction affects the vertical distribution of turbulence greatly. The peak value of the turbulence energy appears at the height of the average building height. The attribution of fluctuations of different components to turbulence changes greatly at different height levels, in the low levels the horizontal speed fluctuation attribute mostly, while the vertical speed fluctuation does in high levels.

• Journal of the Korean institute of surface engineering
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• v.46 no.3
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• pp.133-138
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• 2013

We have developed a 2D axi-symmetric numerical model for an inductively coupled plasma system in order to analyze gas mixing effect through a narrow gap shower head. For frictional flow, holes of 0.5 mm diameter and 2 mm length are approximately modeled in 2D. Gas velocity distribution 10 mm below the shower head showed 2 times difference between the center and the edge at 10 mTorr. At 10 mm above the wafer, it was increased to 6 times difference due to the pumping duct effect. The model with a 5 mm height buffer region of a shower head showed reasonable behavior of Ar discharge. The density of Ar metastable showed additional peak inside the buffer region around the edge holes.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.37-43
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• 2003

The objective of this work is to investigate the effect of swirl, injection pressure and pilot injection on D.I. diesel combustion by using a transparent engine system. The test engine is equipped with common rail injection system to obtain high pressure and to control injection timing and duration. In this study, the combustion analysis and steady flow test were conducted to estimate the heat release rate from in-cylinder pressure. Soot distribution in diffusion flame according to swirl ratio, injection pressure and pilot injection was investigated by using LII technique. As the results, high injection pressure was found to shorten ignition delay as well as enhance peak pressure and heat release rate was greatly affected by injection timing and pilot injection. In addition, the results showed that the period of soot formation corresponded to the diffusion flame.