• Journal of Nutrition and Health
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• v.36 no.9
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• pp.918-923
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• 2003

L-theanine Is an amino acid in green tea and has been known to decrease serotonin and increase norepinephrine in rat brains, and also reported to produce mental relaxation, lower blood pressure and improve learning ability in human beings. But, few studies on these effects for human beings have been conducted so far. This study was conducted to evaluate the effect of L-theanine on the release of brain alpha waves known to be related with mental relaxation and concentration. Twenty healthy male volunteers aged 18 to 30 years without any Physical and Psychological diseases were recruited through written advertisement. Alpha power values of EEG as a surrogate marker of mental relaxation and concentration were measured in frontal and occipital regions for 40 minutes after administration of four placebo or test tablets and 20 minute resting period. The same procedure crossed over at 7-day intervals. We analyzed average alpha power values in frontal and occipital regions at 10 minute intervals. Repeated ANOVA revealed that there were significant differences of occipital alpha power values between placebo and test groups with high anxiety (p < 0.05). The mean values at 20,30,40,50 and 60 minute intervals were 0.23, 024, 0.28, 0.25 and 0.34 in placebo, respectively and 0.23, 0.29, 0.40, 0.34, and 0.45 in test, respectively. But there were no significant differences of frontal and occipital alpha power values between placebo and test groups with low anxiety (p > 0.05) . The results of this study suggest that L-theanine containing tablets promote the release of alpha waves related to mental relaxation and concentration in young adult males.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.155-159
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• 2001

Beta radiation is measured for an environmental monitoring purpose or for an internal radiation exposure monitoring of nuclear power plant's worker. In korea, strontium 89 and strontium 90 is measured for an environmental monitoring purpose. Also tritium and carbon 14 contained in urine is measured for an internal radiation exposure monitoring of nuclear power plant's worker. Because above isotopes emits low energy beta radiations having a wide range of energy, very complicated isotope separation preprocess is needed. In this study, two mixed beta emitting isotopes are measured simultaneously using a liquid scintillation counter(LSC) and analyzed by using a developed statistical method. Banded least square method is used to analyze the mixed spectrum, and the goodness-of-fitness test is proposed. Test results show that the developed procedure can be very useful for analyzing a mixed beta emitting isotopes.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.63-69
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• 2013

Most washing machines are now produced as a drum-type, where a washing drum mounted on a suspension system with springs and dampers, to minimize the transmittance of the vibration from the drum to the frame. A low-cost MR damper, using magneto-rheological fluids, can produce variable damping forces by changing the current values in the magnetic coil. Experimental results show the comparison of the vibration attenuation performances between two different dampers. One test set-up uses a passive damper and another one uses a MR fluid damper. The test results showed that the vibration amplitude of the washing machine with the MR damper is much smaller than the case with the passive damper.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.33-35
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• 1999

This paper describes the test results of the single phase 3kVA high temperature superconducting power trans-former. The tapes are made with Bi-2223 and have silver alloy as the matrix. Four double pancake windings are used in total. Among them two double pancake windings are connected in series for high voltage winding and two double pancake windings are connected in parallel for low voltage winding. The rated voltages of each winding are 220/110 V. Fundamental characteristics are obtained through short circuit and no load tests. The over load capability and characteristics are investigated.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.39-44
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• 2015

The fracture toughness of 2.25Cr-1Mo cast steel (SA217-WC9) samples which were taken from the check valves of feed water piping of Korean Standard Nuclear Power Plant(KSNPP) was measured by Master Curve method. The measured $T_0$ reference temperature of SA217-WC9 steel was $-30^{\circ}C$. The obtained $T_0$ was compared to the derived value from Charpy impact test data following to SINTEP procedure. The heat-to-heat variation in fracture toughness of SA217-WC9 steel was observed. It was found that the low toughness of a heat of SA217-WC9 steel was attributed to the coarse MnS inclusion originated by high sulfur content as the results of microanalyses.

• Proceedings of the Korean Society for Quality Management Conference
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• 2009.10a
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• pp.234-240
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• 2009

The growing mobile products market is expected energy efficiency. So product design is more important focusing on reducing power consumption than improving technology of color sense. A Organic light emission diode is in limelight of the best display to satisfy market expectation. A Organic light emission diode is achieved low power consumption, pixel response which was fast for its time, high contrast of brightness and wide color reproduction raio. Therefore there is a fierce competition for the organic light emission diode development between a country and another country over business. The technical value's life is short because of a fierce development competition, and there is little probability that technical success become business success. In this study, the purpose is reduce the time for life test by accelerated current and it can do production possible design by accelerated life model in design phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.499-499
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• 2008

High voltage transformer of Diagnostic X-ray system has been contributed to wiping out disease to get a good quality images from patients. High voltage transformer of diagnostic X-ray system has been usefully used for diagnostic purpose but if high voltage transformer performances are deteriorated, low quality image will be archived. In this case, operator has to exposure to get a more good quality images. In this case, unexpected radiation could be exposed to patient and it is very harmful to the patient. And I would like to design and make equipment to checkable high voltage transformer performance after that I wish to test and study what it is most influences in radiation output quality.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.335-339
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• 2001

The recent advancements in power electronic switching devices have enabled high frequency switching operation and have improved the performance of pulse-width modulated (PWM) inverters for driving induction motors. But, the insulation failures of stator winding have attracted much concern due to high dv/dt of IGBT PWM inverter. In this paper, the test results for evaluation on the stator winding insulation of low-voltage induction motors for IGBT PWM inverter applications are presented. The insulation characteristics are analyzed with partial discharge and dissipation factor tests. Also, insulation breakdown tests by switching pulse voltage are performed. An effective insulation technique to enhance the insulation strength is suggested from the test results.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.4 s.37
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• pp.331-338
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• 2005

The rapid advances in high power light sources and arrays as encountered in incandescent lamps have induced dramatic increases in die heat flux and power consumption at all levels of high power LED packaging. The lifetime of such devices and device arrays is determined by their temperature and thermal transients controlled by the powering and cooling, because they are usually operated under rough environmental conditions. The reliability of packaged electronics strongly depends on the die attach quality, because any void or a small delamination may cause instant temperature increase in the die, leading sooner or later to failure in the operation. Die attach materials have a key role in the thermal management of high power LED packages by providing the low thermal resistance between the heat generating LED chips and the heat dissipating heat slug. In this paper, thermal transient characteristics of die attach in high power LED package have been studied based on the thermal transient analysis using the evaluation of the structure function of the heat flow path. With high power LED packages fabricated by die attach materials such as Ag paste, solder paste and Au/Sn eutectic bonding, we have demonstrated characteristics such as cross-section analysis, shear test and visual inspection after shear test of die attach and how to detect die attach failures and to measure thermal resistance values of die attach in high power LED package. From the structure function oi the thermal transient characteristics, we could know the result that die attach quality of Au/Sn eutectic bonding presented the thermal resistance of about 3.5K/W. It was much better than those of Ag paste and solder paste presented the thermal resistance of about 11.5${\~}$14.2K/W and 4.4${\~}$4.6K/W, respectively.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.905-909
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• 1995

We constructed the large 3-axis square Helmholtz coil system for the power frequency magnetic field immunity test. We measured the coil factors and magnetic field homogeneities of the fabricated 3-axis square Helmholtz coil. The experimental results for the field homogeneities are in agreement with the theoretical data. From these results, we determined the effective areas for the immunity test. We also confirmed that the low current using the multi-turns coil can be applicable to the immunity test for the high field in short duration.