• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.267-270
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• 1999

We measured the dielectr~c constant of undoped GaN thin films grown on (0001) sapphire substrates In 0.8 - 4.5 eV energy (276 - 1550 nm wavelength) range by spectroscopic ellipsometry. For more accurate data analysis we also performed X-ray diffraction, photolurninescence and Rutherford backscattering spectroscopy on samples. Data were analyzed with a four-phase model. The dielectric constant of GaN thin films was obtained not only in the transparent region but also around the absorption edge. Absorption edge energy, $3.3992{\pm}0.002$eV was determined from the obtained dielectric function.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.128-132
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• 2013

L-Arginine semi-oxalate (LASO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Photoluminescence studies confirm the violet fluorescence emission peak at 395 nm. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV-VIS-NIR spectrum. The dielectric constant, dielectric loss and ac conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. The solid state parameters such as plasma energy, Penn gap, Fermi energy and polarizability were calculated to analyze second harmonic generation (SHG). Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.

• KIEE International Transactions on Power Engineering
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• v.5A no.3
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• pp.280-285
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• 2005

This paper proposes a novel method for determining the kind and rating of power quality solutions. To determine the kind of solution, event cause and direction are utilized. According to the event cause and direction, an adequate type of solution is determined for effective compensation. To rate the required capacity of solution, the concept of lost energy is adopted. Lost voltage, lost power and lost energy are calculated and the rating of the solution is determined to compensate a specific event. The rating method that utilizes the result of stochastic diagnosis is also proposed. A power quality index such as CP95 is adopted for solution suggestion. The method developed in this paper is applied to the test system and proved to be useful for enhancing the power quality of the customer system. It can provide customers with information pertaining to what is a proper and cost-effective solution among various compensating devices.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.582-587
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• 2016

연료효율에 대한 선주들의 요구와 그린쉽이라는 사회적 흐름에 맞춰 현재 연료 절감 장치에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 KVLCC2M의 반류개선 및 연료효율 증가를 위한 반원형 덕트의 변수 연구를 진행하였으며, 계산의 신뢰도를 검증하기 위해 서울대학교 선박저항성능 연구실에서 실시한 모형 시험결과와 비교하였다. 반원형 덕트의 크기와 길이방향 위치를 설계변수로 설정하여, 총 12가지 경우에 대한 CFD 계산을 시행하였으며, 계산 결과를 유동 정류를 통한 저항 감소와 반류 개선을 통한 프로펠러의 성능 개선 이라는 두 가지 기준으로 최적 조건을 선정하였다. 또한, 후처리를 통해 계산 결과를 추가적으로 분석하여 에너지 절감의 이론적인 배경을 찾았으며, 이를 바탕으로 반원형 덕트를 개선하여 부채꼴형 덕트를 새로이 설계하였다. 이에 대한 추가적인 계산 결과 최대 4%의 연료절감 효과를 최종 확인하였다.

• Bulletin of the Korean Chemical Society
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• v.15 no.6
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• pp.453-455
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• 1994

Semiempirical MO calculations are applied to estimate the substituent effects on acylations of the nonfused N-vinyl-2-amino $\beta-lactams$ having frameworks analogous to 3-cephems. The stabilization energy for the reaction intermediate of the nucleophilic attack by the hydroxide ion is selected as the reactivity index and calculated by AM1 and PM3 methods for the model $\beta-lactams$ with substituents at the C1 and N-vinyl terminal positions. The reactivities are larger for -SH connected to the C1 and strong $\pi-acceptors$ at the N-vinyl terminal implying the large reactivity for known active cephalosporins. Quantum chemical calculation of stabilization energy could be useful in correlating antibiotic activities of many compounds obtained as derivatives of a lead compound.

• Nuclear Engineering and Technology
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• v.36 no.5
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• pp.430-449
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• 2004

A quantitative model for a control system that integrates human operators, systems, and their interactions is developed based on discrete functions. After identifying the major entities and the key factors that are important to each entity in the control system, a quantitative analysis to estimate the recovery failure probability from an abnormal state is performed. A numerical analysis based on assumed values of related variables shows that this model produces reasonable results. The concept of 'relative sensitivity' is introduced to identify the major factors affecting the reliability of the control system. The analysis shows that the hardware factor and the design factor of the instrumentation system have the highest relative sensitivities in this model. T도 probability of human operators performing incorrect actions, along with factors related to human operators, are also found to have high relative sensitivities. This model is applied to an analysis of the TMI-2 nuclear power plant accident and systematically explains how the accident took place.

• Nuclear Engineering and Technology
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• v.18 no.2
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• pp.85-91
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• 1986

A single comparator method with its accuracy has been studied for determining multielement by reactor neutron activation analysis. Spectral index at the irradiation position of each sample was determined using two flux monitors of Au and Co, one of which was used as a single comparator. The uncertainties of nuclear data related to the method were investigated for 18 elements and the error of the analytical result due to the uncertainties of nuclear data related is found to be less than 6%. The analytical results of 4 USGS reference samples agree well within 15% deviation with the results evaluated by USGS.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.17 no.1
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• pp.47-53
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• 2022

Objectives This case study aimed to investigate the effect of acupotomy and fascia chuna therapy on talipes cavus-type plantar fasciitis. Methods We classified the foot arch type using a podoscope and estimated the outcome by evaluating the numeric rating scale, pain disability index, and EuroQol-5-dimension measurement. Results After treatment, heel pain decreased and the quality-of-life score improved. Conclusions This study suggests that treatment with acupotomy and muscle energy techniques based on the foot arch type may be effective for plantar fasciitis. A limitation of this study is the small number of cases. Further clinical studies are required.

• Journal of Hydrogen and New Energy
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• v.33 no.4
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• pp.318-329
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• 2022

This study analyzed keyword networks and Author's Affiliation networks of hydrogen-related papers published in Korea Citation Index (KCI) journals from 2016 to 2020. The study investigated co-occurrence patterns of institutions over time to examine collaboration trends of hydrogen scholars. The study also conducted frequency analysis of keyword networks to identify key topics and visualized keyword networks to explore topic trends. The result showed Collaborative research between institutions has not yet been extensively expanded. However, collaboration trends were much more pronounced with local universities. Keyword network analysis exhibited continuing diversification of topics in hydrogen research of Korea. In addition centrality analysis found hydrogen research mostly deals with multi-disciplinary and complex aspects like hydrogen production, transportation, and public policy.

• Journal of the Korean Ceramic Society
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• v.42 no.1
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• pp.28-32
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• 2005

The optical properties and intrinsic stress of $Ta_{2}O_{5}$ thin films deposited by Dual ion-Beam Sputtering: (DIBS) and Single ion-Beam Sputtering (SIBS) were studied as a function of the substrate temperature and assist ion beam voltage. The refractive index showed the maximum value (n = 2.144) at $150^{circ}C$ in the SIBS process. When the substrate temperature has above $150^{circ}C$ in the SIBS process the refractive index decreased. In the DIBS process, the increase of the substrate temperature affected the increase of the refractive index at a maximum value (n = 2.1117, at $200^{circ}C$). The low temperature process $(<100^{circ}C)$ can greatly reduce residual stress with the assist ion gun, but the high temperature process was unaffected. As the assist ion beam voltage increase from 250 to 350 V the refractive index increased to 2.185. However, the refractive index was decreased at the range of 350-650 V, As the assist ion beam voltage increased, the stress of the deposited film decreased to 0.1834 GPa at 650 V.