• Proceedings of the KWS Conference
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• 1999.10a
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• pp.310-313
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• 1999

This paper represents to develop a computer software system which is capable to analyze the phase transformation of high strength steel(BV-AH32) and to predict heat transfer, residual stress due to phase transformation during Gas Metal Arc(GMA) welding. The developed model was taken into account temperature dependent of young's modules, coefficient of thermal expansion and yield stress as well as the double ellipsoidal heat distribution by the moving arc. The results showed that the longitudinal and transverse residual stresses calculated by the coupled analysis of heat transfer, residual stress and phase transformation are in good agreement with the experimental data. In addition, the temperature distribution as well as longitudinal and transverse residual stresses of weldment were determined at the 1-pass and 2-pass of welding.

• Kyungpook Mathematical Journal
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• v.61 no.2
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• pp.323-351
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• 2021

The present paper addresses magnetohydrodynamic pulsating flow and heat transfer of two immiscible, incompressible, and conducting couple stress fluids between two permeable beds. The flow between the permeable beds is assumed to be governed by Stokes' [28] couple stress fluid flow equations, whereas the dynamics of permeable beds is determined by Darcy's law. In this study, matching conditions were used at the fluid-fluid interface, whereas the B-J slip boundary condition was employed at the fluid-porous interface. The governing equations were solved analytically, and the expressions for velocity, temperature, mass flux, skin friction, and rate of heat transfer were obtained. The analytical expressions were numerically evaluated, and the results are presented through graphs and tables.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2003.10a
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• pp.97-97
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• 2003

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.7
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• pp.588-594
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• 2001

The purpose of this study is to investigate the thermal and hydrodynamic characteristics of the channel in corrugated plate type heat exchangers numerically. Numerical work has been conducted using the Reynolds Stress Model(RSM) by utilizing the commercial finite-volume code, FLUENT. Based on this model, the dependence of heat transfer and friction factor on geometrical parameters have been investigated. It is found that larger corrugation angle give higher values of heat transfer coefficients and friction factors. As the reynolds number increases, the heat transfer coefficient also increases. It is also observed that the heat transfer coefficient reaches maximum while the friction factor stays relatively low at same corrugation angle. Through the analysis, it is found that the optimum corrugation angle for the heat exchanger performance exists. It is noted that the flow repulsions at the contact point of the two fluid streams make the low mixing more active for larger corrugation angle and high reynolds number.

• Journal of Power Electronics
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• v.13 no.2
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• pp.186-196
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• 2013

This paper presents a low voltage-stress AC-linked charge equalizing system for balancing the energy in a serially connected, valve-regulated lead acid battery string using a modular converter that consists of multiple transformers coupled together. Each converter was coupled through an AC-linked bus to increase the overall energy transfer efficiency of the system and to eliminate the problem of the unbalanced charging of batteries. Previous solutions are based on centralized and modularized topologies. A centralized topology requires a redesign of the hardware and related components. It also faces a high voltage stress when the number of batteries is expanded. Modularized solutions use low-voltage-stress, double-stage, DC-linked topologies which leads to poor energy transfer efficiency. The proposed solution uses a low-voltage stress, AC-linked, modularized topology that makes adding more batteries easier. It also has a better energy transfer efficiency. To ensure that the charge equalization system operates smoothly and safely charges batteries, a small intelligent microcontroller was used in the control section. The efficiency of this charge equalization system is 85%, which is 21% better than other low-voltage-stress DC-linked charging techniques. The validity of this approach was confirmed by experimental results.

• Phonetics and Speech Sciences
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• v.10 no.1
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• pp.9-14
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• 2018

This study compared the relative contributions of intensity, F0, duration and vowel spectra of L2 English lexical stress by Japanese and Korean learners of English. Recordings of Japanese, Korean and native English speakers reading eighteen 2 to 4 syllable words in a carrier sentence were analyzed using multiple regression to investigate the influence of each acoustic correlate in determining whether a vowel was stressed. The relative contribution of each correlate was calculated by converting the coefficients to percentages. The Japanese learner group showed phonological transfer of L1 phonology to L2 lexical prosody and relied mostly on F0 and duration in manifesting L2 English stress. This is consistent with the results of the previous studies. However, advanced Japanese speakers in the group showed less reliance on F0, and more use of intensity, which is another parameter used in native English stress accents. On the other hand, there was little influence of F0 on L2 English stress by the Korean learners, probably due to the transfer of the Korean intonation pattern to L2 English prosody. Hence, this study shows that L1 transfer happens at the prosodic level for Japanese learners of English and at the intonational level for Korean learners.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.835-843
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• 2002

The goal of this paper is to understand the stress-transfer mechanism of concrete-filled tubular column to H-beam connection with external T stiffener through the elasto-plastic finite element method and to offer basic data for the design of T stiffener. For the accuracy, analysis results are compared with experimental results. It makes use of several stress and strain indices to understand the stress-transfer mechanism of connection. An alternative plan that decreases the stress concentration of beam flange to horizontal stiffener connection is proposed through the elasto-plastic finite element method.

• Proceedings of the KWS Conference
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• v.43
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• pp.58-60
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• 2004

In the field of welding the behavior of a welded structure under consideration may be predicted via heat transfer and residual stress analysis. In order to facilitate the industrial applications of welding, numerical modeling of heat transfer and residual stress in weldment has been carried out applying Finite Element Method (FEM) and the analysis with the external load including this residual stress due to welding has been done. The present work includes the specialized finite element codes for the calculation of nonlinear heat transfer details and residual stress redistributed along with the external load in the welded structures. A basic interface, which allows models, built in commercial preprocessing package access to the data necessary to build standard input decks for these specialized FEM codes, which are not supported by commercial package. The results from the FEM codes are imported back into commercial package for visualization. In addition the residual stress values are exported to commercial package (such as ANSYS, PATRAN etc.) for further analysis with the external loads, which make the FEM codes fully applicable to the industrial purpose.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.3
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• pp.41-52
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• 1990

In this study are determined the unsteady temperature and thermal stress fields for a domestic 4-cylinder, 4-cycle gasoline engine cylinder head by the three-dimensional finite element method. A representative part of the cylinder head is modelled as a combination of hexahedron isoparametric elements, and the time-dependent temperature and the heat transfer coefficient of the gas are imposed as the thermal boundary conditions for the engine speeds of 500 rpm and 2000 rpm. The obtained results, which are represented graphically, indicate that the amplitudes of temperature fluctuation during a cycle are about 10.deg. C and 3.deg. C respectively on the surface of combustion chamber, and the maximum temperature fields occur at 30.deg. , 10.deg. respectively before the initiation of the exhaust stroke. Thermal stress fields due to non-uniform temperature distributions show that compressive stress is much larger than tensile stress throughout a cycle. It is also found that the compressive stress varies with substantial amplitude between the exhaust port and ignition plug hole, and the high tensile stress with small fluctuation occurs between exhaust port and the adjacent head bolt hole.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.239-245
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• 2005

The reduction of heat transfer rate to the stored liquid hydrogen from outside condition is extremely important to keep the liquid hydrogen longer. In this paper the highly efficient support system for the liquid hydrogen storage vessel was newly developed and analysed. The support system was composed of a spherical ball in the center of supporter to reduce the heat transfer area, with its above and below supporting blocks which are the SUS and PTFE blocks inserted in the SUS tube. The heat transfer rate and temperature distribution of the support system were evaluated by FLUENT, and the thermal stress and strain were estimated by ANSYS software. The results showed that the heat transfer rate from outer vessel to inner one was extremely decreased compared with the common method which is simply SUS tubes inserted between inner and outer tanks. The thermal stress and strain were obtained well below the limited values. As a result, it was the most efficient support system of storage vessel for liquid hydrogen and most cryogenic fluids.