• Journal of the Korean Ceramic Society
• /
• v.24 no.5
• /
• pp.431-436
• /
• 1987

High purity Al2O3 has been extracted from serlcite of clayminerals, selicite was treated by H2SO4(2N∼18N) solution, NH4OH treatment(PH8.5∼10.0) and metallic impurities such as Fe were removed by NaOH treatment. The tendency of extraction yield of ${\alpha}$-Al2O3 have been investigated by relating reaction time, acid concentration. Reaction products were analyzed by DT-TGA, chemical analysis and X-ray diffractometer. Prepared ${\alpha}$-Al2O3 power is fired in air at 1400$^{\circ}C$, 1600$^{\circ}C$ 2hr. The results are as follows; 1. The most suitable extracting conditions of ${\alpha}$-Al2O3 from Selicite were N-H2SO4, 120 min acidtreating time. 2. The optimum pH condition was 9.0. 3. Physical properties of sintered Al2O3 bodies were as follows. Relative density is 99%. Water absorption is 0.26%. Rock well hardness is 89.

• Journal of Photoscience
• /
• v.10 no.1
• /
• pp.89-96
• /
• 2003

Two important types of $\alpha$-heterolytic fragmentation reactions of aminium radicals are discussed. In these fragmentation processes, transfer of electrofugal groups from the aminium radicals to either Lowry-Bronsted or Lewis bases produces $\alpha$-amino radicals. The results of recent studies that provided key information about the dynamics of the important aminium radical fragmentation reactions, deprotonation, desilylation, are summarized. Finally, selected examples, which demonstrate how knowledge of the relative rates of aminium radical cleavage can be used to design synthetically relevant SET-promoted photocyclization reactions, are presented.

• Journal of Nutrition and Health
• /
• v.30 no.9
• /
• pp.1102-1108
• /
• 1997

The purpose of this study was to find the extent of lipid peroxidation of erythrocytes in cigarette smokers, and to determine the relative effectiveness of $\beta$-carotene, canthaxanthin , and $\alpha$-tocopherol as antioxidants. Thirty smokers and 30 nonsmokers participated in this study . No significant differences according to age, sex, and height were shown. Cigarette smokers in this study had higher hemoglobin concentrations and more oxidation of hemoglobin than non-smokers. In addition, the erythrocytes of cigarette smokers had significantly higher MDA concentrations than crythrocytes of nonsmokers, which suggests that smokers may have tocopherol were studied in vitro by measuring the concentration of malondialdehyde(MDA) and precent hemolysis of erythrocytes. The addition of any antioxidant to erythrocytes significantly decreased MDA concentrations(p<0.05) while antioxidants showed nonsignificant inhibition of hemolysis. Among the antioxidant used in this study, canthaxanthin showed the greatest inhibition of both lipid peroxidationand hemolysis. Meanwhile, $\alpha$-tocopherol showed potent inhibition of lipid peroxidation, but not of hemolysis.

• Journal of Environmental Health Sciences
• /
• v.29 no.4
• /
• pp.48-54
• /
• 2003

This study investigated retrogradation properties of Jeungpyun substituted for cereals with dietary fibers of 60% of brown rice, and barley. Quality changes during storage periods of the functional Jeungpyun, were studied using $\alpha$-amylase iodine enzyme digestion methods, X-ray diffraction patterns, and differential scanning calorimetry (DSC). The barley substituted samples showed significantly lower retrogrdation rates than those of control when examined by $\alpha$-amylase method. The Relative crystallity by X-ray diffraction patterns had typical A type in all samples with appealing big crystallity around its diffraction angle 23$^{\circ}$degrees as storage periods were increased. The brown rice and barley Jeunpyun made smaller crystallity than that of control, representing slower retrogradation rates. The batter controls had significantly lower ΔH than the other compared samples when measured by DSC, but had significantly higher ΔH after 30 days of storage, implying that the control required more energy for regelatinization after the 30 days of storage.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1433-1435
• /
• 2001

The mechanical and phase transformation of the cold isostatically pressed $\beta$-SiC ceramic were investigated as a function of the sintering temperature. The result of phase analysis revealed 6H, 4H, 3C and phase transformation between 3C and 4H showed over 2000$^{\circ}C$ and the $\beta$ ${\rightarrow}$ $\alpha$ phase transformation was in saturation at 2200$^{\circ}C$. The relative density and the mechanical properties of $\alpha$-SiC ceramic was increased with increased sintering temperature. The flexural strength showed the highest value of 230 MPa at 2200$^{\circ}C$. This reason is because crack was propagated through surface flaw. The fracture toughness showed the highest value of 4.2 $MPa{\cdot}m^{1/2}$ at 2200$^{\circ}C$.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.61 no.1
• /
• pp.55-58
• /
• 2012

By using EEG and HRV, subjects were estimated on their psychological and physiological reaction when reading psychrometric chart in 7 point century font, in an environmental test room in the condition of temperature 25[$^{\circ}C$], relative humidity 50[RH%], air current speed 0.02[m/sec], giving variation in illuminance to 0.1, 300, 600, 1000, 1300 and 1600[lux]. As a result, it was at 1300[lux] that absolute ${\alpha}$ wave, SMR, SDNN were most vitalized, and also both sides ${\alpha}$ wave asymmetry index, SEF50, HRT, stress and fatigue degree were at the lowest. It was found that a certain illuminance which minimizes psychological stress and fatigue degree while enhancing concentration and task achievement stably does exist.

• Journal of Nutrition and Health
• /
• v.27 no.6
• /
• pp.574-582
• /
• 1994

The effects of age and dietary fatty acid composition on prostagladin production was investigated in Sprague-Dawley strain male rats. Animals weighing 88.6$\pm$2.2g were fed 10% dietary fat(W/W, 20% of total energy). The P/S ratios of dietary lipid were three levels(0.5, 1, 2) and there were three different levels of n-6/n-3 fatty acid ratio(2, 4, 8) in each P/S ratio. The experimental period were 1 month and 12 months, respectively. The results of this study were as follows. As the age of rats increased, the plasma thromboxane B2 production increased, but aorta 6-keto prostaglandin F1$\alpha$ decreased. When a higher amount of n-3 fatty acid was fed in each P/S ratio, the relative percentage of linolenic acid and EPA in platelet increased.

• Science of Emotion and Sensibility
• /
• v.3 no.1
• /
• pp.17-24
• /
• 2000

본 연구는 일반 컴퓨터 게임과 뇌파를 이용한 바이오피드백 게임의 수행에 따른 뇌파의 변화를 비교하고자 하였다. 뇌파는 게임을 수행하는 동안 변화된 slow alpha파와 fast beta파의 relative power change를 실시간으로 분석하였다. slow alpha파와 fast beta파만을 분석한 이유는 두 뇌파 유형이 시시각각으로 변하는 게임 상황에서 수행자의 정신활동을 잘 반영하는 것으로 고려되었기 때문이다. 두 가지 게임을 수행 전반기와 후반기로 나누어 안정기와 비교하여 변화된 뇌파를 비교, 분석한 결과, 전반적으로 뇌파 게임은 수행 전반기에 비해 후반기에 slow alpha파가 증가하였고, 이와는 반대로 컴퓨터 게임은 전반기에 비해 후반기로 갈수록 fast beta파가 증가하였다. 특히 이러한 변화는 F3, Fp2, 그리고 T4 부위에서 두드러지게 관찰되었다. 이는 뇌파게임이 일반 컴퓨터 게임에 비해서 안정된 정서를 발달시킬 수 있다는 가능성을 시사한다.

• Korean Journal of Acupuncture
• /
• v.36 no.4
• /
• pp.241-251
• /
• 2019

Objectives : The purpose of this study was to examine the effects of electroacupuncture at GB14, on brain activity assessed on an electroencephalogram(EEG). Methods : (1) Thirty-four healthy participants were randomly divided into two groups, receiving either real acupuncture or non-penetrating sham acupuncture at GB14. (2) EEG measurements were conducted simultaneously before and after a 5-minute electroacupuncture stimulation, and the differences in the resulting EEG parameters were compared between the test and control groups. Results : (1) Absolute power increased significantly in the theta-wave channel of the occipital region and in the entire alpha-wave channel. (2) Relative power decreased significantly in the theta-wave channels of the frontal and occipital regions. (3) Coherence decreased significantly in the theta- and beta-wave channels of the parietal and occipital regions, and increased significantly in the alpha-wave channels of most areas. Conclusions : This study shows that electroacupuncture stimulation at GB14 activates the alpha frequency band in particular.

• The Journal of Asian Finance, Economics and Business
• /
• v.2 no.4
• /
• pp.5-11
• /
• 2015

This study is the first to analyze performance of Taiwanese domestic equity funds between January 2009 and October 2014, the period during which quantitative redirected capital flows toward developing economies and the Taiwanese Stock Exchange Weighted Index compounded at approximately 12.9% annually. Adopting methods endorsed by earlier research, we evaluated 15 Taiwanese equity funds' performance relative to market averages using the Sharpe (1966) and Treynor (1965) ratios and Jensen's alpha method (1968). To test market timing proficiency, we applied the Treynor and Mazuy (1966) and Henriksson and Merton (1981) regression analysis methods. Jensen's alpha method (1968) was used to measure fund managers' stock selection skills. Results revealed that funds significantly under-performed Taiwan's average annual market return and demonstrated no exceptional stock-selection skills and market timing proficiency during the era of quantitative easing.