• Nuclear Engineering and Technology
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• v.26 no.2
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• pp.225-236
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• 1994

The sudden discharge of the loop seal water, which is present upstream of the SEBIM POSRV, creates large momentum and inertia forces on the downstream of the discharge piping system. This study provides the procedures and results of analysis of the thermal-hydraulic transient in the SEBIM POSRV discharge piping during the valve opening. The analysis is peformed by RELAP5/MOD3. The appropriate modeling of the discharge piping system, SEBIM POSRV opening characteristics, and loop seal water discharge for the RELAP5/MOD3 analysis is suggested. Also performed is the sensitivity study for the selection of proper options for the junction and volume control. flags. The analysis results demonstrate the adequacy of the RELAP5/HOD3 for the thermal-hydraulic transient analysis of the loop seal water discharge of the SEBIM POSRV discharge piping system. From the sensitivity analysis results, it is shown that the smooth area change option with reasonable geometric pressure drop distribution, non-equilibrium option, and proper time step should be selected for loop seal water discharge analysis.

• Journal of the Korean GEO-environmental Society
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• v.20 no.10
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• pp.39-46
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• 2019

The interaction between the ground and structures should be considered for seismic design of group piles supporting the superstructure. The p-y curve has been used widely for the analysis of nonlinear relationship between the ground and structures, and various researches have conducted to apply the dynamic p-y curve for seismic design of group piles. This curve considers the interaction between the ground and structures under the dynamic load such as an earthquake. However the supported effect by the pile cap and the interaction by inertia behavior of superstructures. Therefore, the shaking table test was conducted to verify the effect of the change of the pile cap in group piles supporting superstructures embedded in sandy soil. The test condition is that the arrangement and distance between centers of piles are fixed and the length of the pile cap is changed for various distances between the pile cap side and the pile center. The result shows that the distance between the pile cap side and the pile center have an effect on the dynamic p-y curve and the effect of group piles.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.9-19
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• 2020

An integrated finite element model composed of a boiler and its supporting steel structure for a 375-MW coal-fired power plant was developed. This study used the developed model for seismic analysis using SAP2000 software. For the complex superheaters, reheaters, economizers, and membrane walls of the boiler, which consisted of numerous tubes, a method of modeling them by the equivalent elements in the viewpoint of stiffness and/or inertia was proposed. In addition, a method of modeling for the connection between the boiler and steel structure was proposed. Many hangers that connect the boiler to the girders of a steel structure were transformed into equivalent hangers by decreasing the number. The displacements of the boiler stoppers on the buckstay and the posts of the steel structure were coupled by considering their interface condition. Static analysis under the self-loading condition for the developed integrated model was implemented, and the results of deformation indicated that the behavior of the steel members and the major components of the boiler were appropriate. In conclusion, the integrated model developed in this study can be used to evaluate the safety of the boiler and steel structure under seismic loads.

• Journal of KSNVE
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• v.6 no.1
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• pp.107-114
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• 1996

The damping characteristics of a cylindrical structure containing oil and bearing balls is investigated for external bending forces. The experimental data obtained through the use of bearing balls with viscous oil in a column is given and analyzed. The viscous action of the oil and inertia effects of the balls on the inside of column create a drag force. The drag force dampens the vibration of the column. This study aims to search for an optimum combination of oil and balls which would produce maximum damping. Machining oils of various viscosities along with ball bearings of various sizes place inside cantilevered aluminium tubes of various diameters to create a rig on which the damping properties of the oil and balls can be studied. The contileved tubes are studied in both horizontal and vertical positions in order to gauge the effect of gravity on the system. The actions of the ball in the column and damping characteristics are investigated according to the dimensionless terms. The Buckingham theorem is used to reduce the variables and to predict the damping of an oil ball column. Though the damping ratio remains fairly constant in the horizontal position of column, the damping ratio begins to increase as the ratio of the number of balls and column length rise above 0.28 in the vertical position of oil ball column. The ratio of the ball diameter to column diameter influences the damping ratio with an optimum diameter ratio. Slenderness ratio and gravity effects on the damping ratio ane investigated.

• Journal of Korean Orthopaedic Sports Medicine
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• v.3 no.1
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• pp.66-72
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• 2004

Purpose: To evaluate the compensatory mechanism in vivo and develop the treatment guide by performing the comprehensive functional tests of the posterior cruciate ligament (PCL) deficient subjects. Material and Methods: 10 PCL deficient subjects and 10 healthy control group were evaluated. Performed functional tests were range of motion, posterior drawer test, Telos, 30$^{\circ}$ flexion wt-bearing view, KT-1000 arthrometer, gait analysis, EMG test and isokinetic tests. Results: Physical, KT-1000, Telos posterior tests showed significant differences, but 300 full weight bearing lateral view, muscle strength test revealed no difference between two groups. Less knee flexion at initial contact and reduced maximum valgus moment were observed in PCL deficient group. In vertical drop landing, PCL group had increased plantar flexion angle at initial contact. Conclusion: Compensatory mechanisms such as reduced unstable components and absorbing the maximal load of the joint were occurred after PCL insufficiency, which result in good clinical and functional outcomes. Further investigations would be needed to understand the functional adaptations of PCL deficient subjects.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.12-18
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• 2021

The purpose of this study is to effectively mitigate the bending displacement that occurs in the bridge due to forced vibration. We developed CTMD (Combine Tuned Mass Damper) that combines the relationship between spring and mass to control the bending behavior of simple beams. The experiment was conducted to confirm the control effect according to the change in the mass ratio of the developed CTMD. The developed CTMD is designed and manufactured so that the mass ratio can be adjusted according to the characteristics of the bridge. The maximum load of the spring applied to CTMD was fixed at 33.15 N. In order to evaluate the performance of the developed CTMD, a simple beam composed of hinges and rollers as boundary conditions was fabricated. In the experimental method, a CTMD was installed in the center of a simple beam and the deflection displacement according to the mass ratio was measured. The shaking condition was shaken at 3 Hz to induce the maximum bending behavior of the simple beam. As a result of the experiment, it was confirmed that when the optimal mass ratio was 2.1, the damping rate of the bending behavior displacement was about 71.2 %, indicating the best control effect.