• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.2
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• pp.71-77
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• 2019

This study proposes a circulating current reduction method that uses high-frequency voltage compensation when carrier phase difference occurs between two inverters in MSIS. In MSIS, inverters are configured in parallel to increase power capacity and to increase efficiency by using inverters only as needed. However, in the parallel inverter structure, circulating current is inevitably generated. Circulating current increases the stress on the switch, adversely affects the current control performance, and renders load sharing difficult. The proposed method compensates for the output voltage reference of the slave module by using the high-frequency voltage so that the switching pattern of each module is matched even in asynchronous carriers. The validity of the proposed method is verified by simulations and experiments with 600 W IPMSM.

• Journal of Welding and Joining
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• v.25 no.6
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• pp.59-63
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• 2007

The weld-induced deformation is more serious in thin plates than in thick plates because heat affect zone of thin plates is wider than that of thick plates and in addition internal and external constraints have much more influence upon weld-induced deformation of thin plates. This paper deals with the application of the mechanical tensioning method to butt weld of thin plates to reduce the transverse and longitudinal deformation. In order to investigate the quantitative effect of tensioning method upon the reduction of angular deformation and shrinkage in longitudinal and transverse direction of weld line, butt welding test has been carried out for several thin plate specimens with varying plate thickness and magnitude of tensile load. From the present experimental study, it has been found that the tensioning method is very effective in reducing the weld-induced residual stress as well as the weld-induced deformation.

• Journal of the Korean Institute of Gas
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• v.10 no.4 s.33
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• pp.23-28
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• 2006

This paper presents the strength safety and the weight reduction analysis of nine gas valve models for a LPG cylinder using a finite element analysis program, MARC and Taguchi's experimental method. The maximum Von Mises stress of a gas valve body represents a safety of a brass valve structure for the given gas pressure of $91kg/cm^2$, which considered a safety factor of a LPG gas cylinder. The weight reduction analysis is very important for reducing a gas flow friction loss and a manufacturing cost as a design parameter. The calculated results present an design model 9 as an optimized design data with 10mm radius of a lower part gas flow pipe A, 6mm radius of an upper part gas flow pipe B and a connecting length 2 mm of tapered pipe D between lower and upper pipes.

• Journal of Society of Preventive Korean Medicine
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• v.18 no.2
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• pp.59-67
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• 2014

Objective : This study was to examine the effects of Doin-Angyo program, evidenced by East Asian Medicine literatures, on stress among smoking adolescents. Method : This study was a prospective community trial using a one-group, pretest-posttest design. As an intervention, Doin-Angyo program was implemented for 10 minutes per session, 3 days a week, for 6 weeks to smoking students who attend a Girl's high school. Psychological stress was measured by self-report questionnaire and physiological stress was measured by salivary cortisol. The final sample for the questionnaire included 18 participants. In addition, pre- and post-salivary cortisol levels of 24 adolescents participating in the last session were compared in order to identify the acute effects of Doin-Angyo program in reducing stress. Results : There were no significant differences in overall stress-test results from the comparisons before and after the intervention. However, we found a significant going-down of the stress level(p = .032) in the question, "About School-work" among six sub-category questions. From the salivary cortisol tests in the last session, we found, in comparison with the standard salivary cortisol density level, $0.3{\mu}g/dL$, the density level tended to go down(p = .062) when higher than the standard, and it went up(p = .001) when lower than the standard, after 10 minute session. Conclusion : The results of this pilot study supported the partial effect of Doin-Angyo program in reducing the stress levels. The study protocol and results can be used to elaborate the community trials design aiming to prove the effect of Korean Medicine based health promotion modalities.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.292-297
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• 1986

Measurements of internal stress .sigma.$_{i}$, anelastic strain .epsilon.$_{A}$ and recovery rate .gamma. were made in steady state creep of 2024 Al alloys over a wide range of stresses at temperatures between 260.deg. C and 380.deg. C, for the purpose of investigating the relations among the three parameters. Values of .sigma.$_{i}$ were obtained by the method of strain transient dip test, and those of .epsilon.$_{A}$ and .gamma. were determined from the results of sudden stress removal or reduction tests. As a main result, it is thought that the anelastic behavior and recovery process are basically dependent on same deformation mechanisms.sms.sms.

• Journal of Korean Academy of Nursing
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• v.33 no.6
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• pp.693-704
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• 2003

Purpose: The purpose of this study was to determine whether a relaxing music was effective in reducing stress response of patients admitted to a coronary care unit with the diagnosis of acute myocardial infarction. Method: The research design was the chosen convenience sample of a randomized control group pre-posttest quasi-experimental design. Forty patients, 20 for an experimental group and another 20 for control group. The study was to provide the patients three different kinds of relaxing music. The experimental group listened to relaxing music for a 20-minute one time a day for 3days. The control group was just provided with a 20-minute period of rest. Test for hypothesis was done by repeated measured ANOV A. Result: The experimental group which received relaxing music showed a significantly lower level of electrodermal response, myocardial oxygen consumption and respiration rate, and a higher level of peripheral skin temperature than the control group. The experimental group which received relaxing music showed a significant reduction in state anxiety than the control group. Conclusion: The results showed that relaxing music is an effective nursing intervention for reducing physiologic and psychologic stress response of the patients with acute myocardial infarction in a critical intensive care unit.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.491-499
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• 2010

This study was carried out to investigate the consolidation characteristics of the remolded clay by the oedometer and the constant rate of strain(CRS) consolidation tests. As the rate of strain increases, the settlement rapidly decreased. As the ratio of the sand in the specimen increases, its effect on the rate of strain to the settlement was reduced. As the effective stress increased, the void ratio decreased, while the rate of strain increased, it did not show a clear variation. The reduction of the void ratio was shown to be less than the oedometer test. The coefficient of vertical consolidation with effective stress showed very large variation around preconsolidation stress, but the rate of strain did not provide significant effects. The rate of strain with effective stress gradually decreased at all tests and mixed ratio of sand. The rate of strain at the constant rate of strain tests showed smaller than in the oedometer test. The coefficient of consolidation at the constant rate of strain tests showed much more increase than in the oedometer test. The ratio of the vertical coefficient of consolidation by the odometer and the constant rate of strain tests showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to designing the soft ground improvement.

• Child Health Nursing Research
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• v.11 no.1
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• pp.125-131
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• 2005

Purpose: This study was done to evaluate the effects of massage on the level of stress hormone in the urine in preterm infants. Method: The design was a nonequivalent control group pretest-posttest design quasi experimental study. Fifty-eight preterm infants were assigned to the experimental(31) or control group(27). The data were collected from March 2002 to August 2003. The massage stimulation was provided to infants in the experimental group for 15-minutes twice a day for 10 days. On day 1 and day 10 of the study, a 24 hour-urine sample was collected for norepinephrine, epinephrine, and cortisol assays. In data analysis, SPSSWIN 10.0 program was utilized for descriptive statistics, ANOVA and t-test. Results: General characteristics of the two groups showed no significant differences, thus the two groups were found to be homogenous. The 24 hour-urine cortisol of the massage group (t=4.61, p=.000) was significantly reduced compared to the control group after 10 days. Conclusions: The results suggest that the massage stimulation can be used to reduce 24 hour-urine cortisol in preterm infants. Therefore, massage provided in the incubator is recommended for reduction of stress in preterm infants who are hospitalized in neonatal intensive care units.

• 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.

• The Korean Journal of Ceramics
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• v.3 no.1
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• pp.1-4
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• 1997

Diamond film (24$\mu\textrm{m}$) were prepared by Microwave Plasma Chemical Vapor Deposition method from a reactive CO/H$_2$ mixtures. Micro-Raman spectroscopy and micro-cathodoluminescence study were carried out along the crosssection and correlated to SEM observation. CL image of cross-section was also investigated. Peak position, FWHM of Raman spectrum were determined using Lorentzing fit. The stress in this sample is 0.4~0.7 GPa compressive stress, and along the distance the compressive stress reduced. The Raman peak broadening is dominated by phonon life time reduction at grain boundaries and defect sites. Defects and impurities were mainly present inside the film, not at Silicon/Diamond interface.