• Journal of Power System Engineering
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• v.20 no.5
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• pp.29-36
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• 2016

Aluminum alloys have been widely used in engine materials, cold & hot-water storage vessels and piping etc., Furthermore, the aluminum alloy of AC8A have been widely used in mold casting material of engine piston for various vehicles because of its properties of temperature, wear and corrosion resistance. Therefore, it is considered that evaluation of corrosion resistance as well as wear resistance of AC8A material is also important to improve its property and to prolong its lifetime. In previous paper, the effect of solution($510^{\circ}C$:4hrs) and tempering($190^{\circ}C$: 16, 24, and 36 hrs)heat treatments to corrosion resistance and hardness were investigated using electrochemical method. In this study, in order to examine completely the effect of the tempering hours to hardness variation and corrosion resistance, the results of solution($510^{\circ}C$:4hrs) and tempering($190^{\circ}C$: 2, 4, 8 and 12hrs)heat treatments to hardness and corrosion resistance were investigated using electrochemical method. The hardness decreased with solution heat treatment compared to mold casting condition, but its value increased with tempering heat treatment. Furthermore, the corrosion resistance increased with decreasing of the hardness, and decreased with increasing of the hardness reversely. And the tempering heat treatment temperature at $190^{\circ}C$ for 8 hrs exhibited the highest value of the hardness and also indicated the highest corrosion current density. However, the values of hardness and corrosion current density was again increasingly decreased with increasing of tempering hours than 8 hrs, Consequently, it is suggested that decision of the optimum. tempering hours is very important to improve the corrosion or wear resistance.

• Journal of the Korean Vacuum Society
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• v.14 no.4
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• pp.258-262
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• 2005

We report on the field emission properties from vertically aligned carbon nanotubes (CNTs) produced by a triode PECVD with a SiNx capping layer on metal catalyst. It is found that the CNTs density can be controlled by the capping layer thickness and decreases with increasing SiNx thickness. The CNT density of $\~$ 104/$cm^{2}$ exhibited highest electron emission characteristics, the threshold field of 1.2 V/$\mu$m and the current density of 0.17 mA/$cm^{2}$ at 3.6 V/$\mu$m. We have carried out investigation of electron emission stability under ambient gas of N2. The electron emission stability was improved with decreasing CNT density. Under $1\times$$10^{-5}$ Torr ambient pressure, the CNTs in 5 $\mu$m hole show electron emission current higher than $1\times$$10^{-4}$ A/cm2 and it's electron emission uniformity has $2\%$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.4
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• pp.35-40
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• 2002

Ultra-power-saving SBR has been fabricated by using vanadium and molybdenum with low work function. Because reverse leakage current is increased in inverse proportion to work function, we implanted argon ion on the n-Si layer for decreasing leakage current. The dose and acceleration energy of the argon implantation in the silicon was 1$\times$10$^{14}$ ion/$\textrm{cm}^2$, 40 keV, respectively. The forward voltages drop of fabricated V-SBR and Mo-SBR were 0.25 V and 0.39 V at the same forward current density of 60 A/$\textrm{cm}^2$. As a result, it was found that the reverse leakage current of the fabricated V-SBR was reduced over 20$mutextrm{A}$ by the argon implantation in comparison with the no implanted V-SBR. Also, owing to argon implantation, the inferiority of characteristic of the SBR was not detected.

• Nutrition Research and Practice
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• v.9 no.1
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• pp.37-42
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• 2015

BACKGROUND/OBJECTIVES: Red grape seeds as functional food are a good source of important bioactive components such as phenolics and antioxidants, which decrease oxidative stress that contributes to the pathogenesis of hepatotoxicity. The current study was conducted in order to evaluate the protective effect of red grape dried seeds (RGDS) on antioxidant properties, lipid metabolism, and liver and kidney functions of rats with paracetamol (750 mg/kg) induced hepatotoxicity. MATERIALS/METHODS: RGDS was added to the basal diet at 5, 10, and 20%. Thirty five adult male rats were assigned to five groups (n = 7) for a six-week feeding period; group (1) normal control, group (2) induced control, groups (3, 4, and 5) fed a diet with RGPS at different levels, 5, 10, and 20%, respectively. At the end of the feeding period, animals' blood and tissues were collected for estimation of serum lipid profile, serum liver, and kidney biomarkers. The protection was measured by detecting lipid peroxidation (LPO), glutathione (GSH), superoxide dismutase (SOD), Catalase (CAT) (in liver tissues), and liver histological examination. RESULTS: The results showed a significant (P < 0.05) decrease in levels of serum cholesterol, triglycerides, low density lipoprotein (LDL-C), and very low density lipoprotein (VLDL-C), with a significant increase in level of high density lipoprotein (HDL-C) for RGDS groups compared to induced control. Rats administered a diet containing RGDS levels produced significant (P < 0.05) hepatoprotection by decreasing the activities of liver enzymes, kidney parameters, and lipid peroxidation, while levels of GSH, SOD, and CAT were increased significantly to near the normal levels. CONCLUSION: The RGDS 20% group was more effective than others against hepatotoxicity of paracetamol, which may be attributed to RGDS total phenols and antioxidant contents, which were 1.438 mg and 1.231 mg, respectively.

• Journal of the Korean Wood Science and Technology
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• v.48 no.1
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• pp.41-49
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• 2020

Jabon (Anthocephalus cadamba) is a fast-growing wood species that is widely utilized for light construction and other purposes in Indonesia. The objectives of the current study were to determine the effects of monoethylene glycol (MEG) and SiO₂ nanoparticles (nano SiO₂) impregnation treatment on the dimensional stability and density of jabon wood and to identify the characteristics of impregnated jabon wood. Wood samples were immersed in water (as untreated), MEG, 0.5% MEGSiO₂, then impregnated by applying 0.5 bar of vacuum for 60 min, and then applying 2.5 bar of pressure for 120 min. The results showed that impregnation with MEG and Nano SiO₂ had a significant effect on the dimensional stability of jabon wood. Polymers can fill cell walls in wood indicated by increasing weight percentgain, antiswelling efficiency, bulking effect, and density, then decreasing in water uptake value. Jabon wood morphology by using SEM showed that MEGSiO₂ polymers can cover part of the pitsin the wood vessel wall of jabon. This finding was reinforced by EDX results showing that the silicon content was increased due to the addition of SiO₂ nano. The XRD diffraction pattern indicated that MEGSiO₂ treatment increased the degree of crystallinity in wood samples. Overall, treatment with 0.5% MEGSiO₂ led to the most improvement in the dimensional stability of 5-year-old jabon wood in this study.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.613-620
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• 2021

A flow channel shape of PEMFC has an influence on the internal flow uniformity. If the reactant distribution in a flow path is not uniform during operation, both catalyst deactivation and mechanical damage of membrane could occur resulting in decreasing the membrane electrode assembly (MEA) durability. Numerous studies concerning flow design have been conducted to make smooth supply and uniform distribution of reactants in fuel cells. The baffle of flow path could improve fuel cell performance through the forced convection effect. A sub-channel, as an additional air flow path, could increase the reactant concentration and reduce the mass transfer loss via a smooth water discharge. In this study, computational fluid dynamics (CFD) was used to analyze the effect of blocks and sub-channels on the current density and oxygen concentration of the fuel cell. As a result, the limit current density and oxygen concentration at a rear block increased when using blocks and sub-channels in a flow channel. In particular, the current density increased significantly when the sub-channel was placed between two blocks. Also, the sub-channel position was optimized by analyzing the oxygen concentration, and the oxygen concentration was recovered at a rear block in the fuel cell.

• Journal of Oriental Neuropsychiatry
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• v.25 no.4
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• pp.411-422
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• 2014

Objectives: A large number of patients require psychiatric therapy. We attempted to determine the present situation regarding psychotherapy and neuropsychological tests for dementia in Korean medicine for the benefit of the Health Insurance Review and Assessment Service (HIRAS). The aim of this study was to aware of the current status about psychotherapy and neuropsychological test for dementia in Korean medicine. Methods: We searched the medical practice records for psychotherapy and neuropsychological tests in oriental neuropsychiatry between 2009 and 2013 using the Health Insurance Review and Assessment Service (HIRAS) database. The search categories were: IJeongByunGi (Medical practice code:59001), JiUnGoRoen (59002), Kyungjapyungji (59003), OhJiSangSeung (59004), neuropsychological test for dementia (29005). Results: 1. The number of patients treated with Korean Medical Psychotherapy increased annually by 151%. The total number of patients treated with Korean Medical Psychotherapy was 4,289 in 2013. 2. The total cost for patients treated with Korean medical Psychotherapy in the public health medical insurance budget was 268,032,000 won in 2013. The average medical cost for one therapy was 17,000 won in 2013. 3. The number of patients in local clinics is increasing faster than the number in Korean medical hospitals. 4. The age group between 20~30 years of age, for both men and women, is the group with the greatest density in Korean Medical Psychotherapy. 5. Neuropsychological Testing for Dementia in Korean Medicine is slowly decreasing. Conclusions: The prevalence of mental illness in Korea is increasing, therefore, the demand for Korean Medical Psychotherapy has increased recently. Authorizing Korean Medical psychiatrists to utilize Korean mental Health resources is essential. This study could be helpful in understanding the current status for the purpose of expanding Korean Medical Psychotherapy.

• Fire Science and Engineering
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• v.32 no.6
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• pp.134-140
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• 2018

This study examined the adequacy of a school classroom's occupant load density standard to cope with the issues associated with the decreasing number of students and regional variations. Therefore, this study analyzed the occupant load density standards of kindergarten, elementary school, middle school, high school, and universities using the data open to the public by the Ministry of Education. The results revealed a high variance in the occupant load density according to the school type. The median values were 1.49, 3.45, 2.64, 2.45, and $3.41m^2/person$ for kindergarten, elementary school, middle school, high school, and universities, respectively. Although the occupant load density was higher than the current standard ($1.9m^2/person$), except for kindergarten, the present standard did not need to be improved immediately, considering the purpose of calculating the maximum occupancy. On the other hand, if improvements are made in line with other enhancements of a national education policy, it will be possible to mitigate the measure to $2.5m^2/person$ based on the survey results.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.398-400
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• 2003

The YMnO$_3$ thin films were prepared on platinized-silicon substrates by chemical solution deposition and annealed at 750 to 85$0^{\circ}C$ for 1 h under various oxygen pressures, from 2 mTorr to 760 Torr. Effects of annealing oxygen pressures on the crystallization behavior and electrical properties of YMnO$_3$ thin films were investigated. Crystallinity and c-axis preferred orientation of YMnO$_3$ thin film were improved by decreasing the oxygen pressure but were deteriorated at extremely low oxygen pressure, 2 mTorr. Leakage current density of the YMn03 thin film decreased as the oxygen pressure decreased. The film annealed at 80$0^{\circ}C$ under 2 Torr, which had the best crystallinity and the highest c-axis preferred orientation. showed the best-developed ferroelectric C-V hysteresis.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.66-70
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• 2003

In a HTS transformer, the perpendicular component of magnetic flux density ($B_r$) applied to HTS tapes of pancake windings becomes larger than that of solenoid winding, thereby decreasing the critical current in the HTS tapes. This paper introduces several methods to reduce $B_r$ applied to the HTS tapes in the transformer with double pancake windings by changing winding arrangements and the relative permeability of flux diverters. We have conducted a winding design for a single-phase 1MVA 22.9kV/6.6kV HTS transformer. We observed a change of $B_r$ due to a variation of gap-length between the high voltage windings and the low voltage windings, reciprocal arrangement and an increase of the number of the high voltage pancake. We also observed a change of Br on the HTS tapes due to variation of the relative permeability of flux diverters placed between the high voltage winding and the low voltage winding. Finally, we have designed a 1MVA 22.9kV/6.6kV HTS transformer winding using suggested methods and calculated transformer parameters by the 3D finite element method.