• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1022-1025
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• 2003

Although the globe is the most typical valve to control high pressure drop in piping system, it is very hard to figure out the characteristics of flow field in the globe valve caused by its complex geometry. So there is very few studies to find out flow characteristics of globe valve. In this study, numerical analysis for flow field in the globe valve is carried out using the Fluent code which is commercial CFD program. Pressure drop through the globe valve is also measured to verify the results come from numerical analysis. Comparing experiment with numerical analysis, two results are very close to each other. Also finite element method is employed to evaluate the safety of globe valve using the results coming from the flow analysis to make the boundary conditions for FEM analysis. Maximum stress appears on the inlet channel of valve where inlet flow runs against. Because the maximum stress between 11.7 MPa to 3.6 MPa is within 3.4% of yield stress. the structural safety of valve is considered to be very sound

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.77-86
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• 2008

The reliability of leaded and lead-free solders of BGA type packages on a printed circuit board was investigated by employing the standard drop test and 4-point bending test. Tested solder joints were examined by optical microscopy to identify associated failure mode. Three-dimensional finite element analysis(FEM) with ANSYS Workbench v.11 was carried out to understand the mechanical behavior of solder joints under the influence of bending or drop impact. The results of numerical analysis are in good agreement with those obtained by experiments. Packages in the center of the PCB experienced higher stress than those in the perimeter of the PCB. The solder joints located in the outermost comer of the package suffered from higher stress than those located in center region. In both drop and bending impact tests, the lead-free solder showed better performances than the leaded solders. The numerical analysis results indicated that stress and strain behavior of solder joint were dependent on various effective parameters.

• Journal of the Korean Institute of Gas
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• v.25 no.5
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• pp.37-51
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• 2021

The pressure drop phenomenon that occurs when the same flow rate is supplied to the gas regulator was analyzed. The regulator moves the position of the piston through the interaction of the force acting on the upper and lower parts of the piston and the spring tension to release the pressure of a specific range in a specific environment as constant pressure, thereby maintaining the pressure. The flow characteristics and pressure control process of the regulator were investigated through a numerical analysis technique as the volume of the fluid inside the regulator changed. As the gap between the piston and the piston seat decreased, the pressure drop increased and the flow velocity increased. It was verified through numerical analysis that the piston was positioned at 0.12mm under the same conditions as the pressure-flow test (inlet pressure 3MPa, outlet pressure 0.8MPa, flow rate 70kg/h).

• Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.19-25
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• 2013

Smoothed Particle Hydrodynamics(SPH) method uses a grid of historical analysis and is not Lagrangian particles using the grid method. The Navier-Stokes equations were used to solve the viscous flow of the non-compressed. In this study, the numerical analysis of the three-dimensional Coin Drop Simulation using SPH method was performed, and the analysis results are compared with experimental results, and a similar behavior can be seen. The commercial program used was Abaqus/Explicit. SPH method to reduce the error by comparing the existing flow analysis or interpretation of the continuing research is needed in the future. That will enable real-time analysis of material obtained as a result of these numerical simulations similar to the actual flow phenomena, depending on the development of computer graphics technology to show visually. As a result, this method can be applied to the analysis fluid - structure interaction problems in a variety of fields.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.24-29
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• 2017

There is a need for explosion experiments for explosion-related research. However, there are many restrictions in performing an actual experiment. Therefore, in this paper, an alternative method of overcoming the constraints of an explosion experiment has been conducted using a passenger behavior analysis program called MADYMO to assess and analyze the human body injury due to explosion load. To increase the reliability of the analysis, a drop test has been conducted with the analysis. We provide a new framework for performing the analysis. In future, we will further develop our research with the goal of reducing the opportunity cost for the study of the human body injury.

• Korean Journal of Applied Biomechanics
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• v.31 no.3
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• pp.168-175
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• 2021

Objective: To investigate the static and dynamic analysis of ankle joint complex between subjects with chronic ankle instability (CAI) and healthy controls. Method: A total of 38 subjects and CAI group (N=19) and healthy control (N=19) participated in this first study. Variables that were measured in this study were as follows: 1) Subtalar joint axis inclination and deviation 2) Rearfoot angle 3) Navicular drop test 4) Heel alignment view in alignment analysis. Intra Correlation Coefficient (ICC) is used for reliability. A secondary 17 subjects are recruited including 9 of CAI and healthy for gait analysis between group. Lower extremity sagittal, frontal, and transverse kinematics were measured. All data were analyzed to ensemble curve analysis. Results: 1) There were statistically significant differences in standing rearfoot, navicular drop, heel alignment view, subtalar joint (STJ) inclination and deviation. 2) Only in sagittal, meaningful difference is showed during walking in gait analysis. Conclusion: Morphological problem can affect ankle sprain in aspect of structure with no relation to compensation of neuromuscular.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.541-547
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• 2022

Before making a prototype, we predicted the inlet/outlet differential pressure and flow coefficient, which are the most basic design data for the valve through the design and numerical analysis of the trim, which is the most important in the localization development of the 1500Ib high differential pressure control valve used for boiler feed water. As a result, the design value and the analysis value were found to be about 98% similar. The flow field within the fluid velocity of 23m/s to prevent cavitation was also found. The result of the numerical analysis on thermal stress due to the characteristics of valves exposed to high temperatures showed that it was found to be about 18% less than the allowable stress of the bolt fixing the trim. When all loads such as pressure, self-weight, and vibration are applied, however, it is judged to go beyond the currently calculated thermal stress, exceeding the allowable stress.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1114-1116
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• 2002

The characteristics of voltage drop and THD for parallel operating 11 PCRs (Phase Controlled Rectifiers) are analysed. The PCRs are used to drive high current (1.6 kA ${\sim}$ 3.7 kADC) electromagnetic coils for electromagnets. All the PCRs operate simultaneously in pulsed mode, and the pulse shot occurs every 150 seconds. During the pulse operation the PCR output current ramps up for 4 seconds, and then keeps flat top state for 2 seconds, and finally ramps down for 4 seconds. For the flat top mode a severe voltage drop and distortion appear in the power system because transformers for the PCRs are designed considering pulsed mode operation. It is expected that the analysis method can be applied to improve the system performance including power factor and design of high power pulsed mode operating power supply systems.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1659-1663
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• 2011

Precast concrete slab track is a track structure to be installed by transporting and assembling precast concrete slabs manufactured at the factory. This method can improve concrete quality, provide easy maintenance and reduce construction time, compared with in-situ concrete track. However, the concrete slabs being continuously connected in longitudinal direction, due to the temperature change between summer and winter, the openings at slab joints have occurred. Thus, in this study, to identify the cause of this opening of slab joint, the joint opening caused by temperature drop in the longitudinally continuous precast concrete slab track has been predicted using three-dimensional finite element analysis, and compared with field measurements. Based on the proven model, the slab joint opening, and the stress pattern of concrete slab and steel reinforcement according to concrete slab-base friction properties, concrete-reinforcement bond properties, and prestressing were analyzed.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1424-1429
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• 2004

To seek the fan operating point on a cooling system with fans, it is very important to determine the system impedance and it has been usually examined with the fan tester(wind tunnel) based on ASHRAE standard and AMCA standard. This leads to a large investment in time and cost, because it could not be executed until the system is made actually. Therefore it is necessary to predict the system impedance curve through numerical analysis so that we could reduce the measurement effort. This paper presents how the system impedance curve (pressure drop curve) is computed by CFD in substitute for experiment. In reverse order to the experimental principle of the fan tester, pressure difference was adopted first as inlet and outlet boundary conditions of the system and then flow rate was calculated.