• 한국정밀공학회지
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• 제28권1호
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• pp.19-23
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• 2011

Recently, focused ion beam (FIB) applications have been investigated for the modification of VLSI circuit, the MEMS processing, and the localized ion doping, A multi aperture FIB system has been introduced as the demands of FIB applications for high speed and large area processing increase. A liquid metal ion source has problems, a large angular divergence and a metal contamination into a substrate. In this study, a gas ion source was introduced to replace a liquid metal ion source. The gas ion source generated inductively coupled plasma (ICP) in a quartz tube (diameter: 45 mm). Ar gas fed into the quartz was ionized by a 2 turned radio frequency antenna. The Ar ions were extracted by 2 extraction grids. The maximum extraction voltage was 10 kV. A numerical simulation was used to optimize the design of extraction grids and to predict an ion trajectory. As a result, the maximum ion current density was 38 $mA/cm^2$ and the spread of ion energy was 1.6 % for the extraction voltage.

• Journal of Nutrition and Health
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• 제13권1호
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• pp.9-14
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• 1980

A total of 35 hospitals throughout Korea were surveyed for the assessment of the educational function of dietitians. The current situation and the depth of practices were diagnosed in such areas as: 1. The continuing education for the hospital dietitians 2. The characteristics of patient consultation performed by the hospital dietitians 3. Systems and methods of patient instruction practiced by the dietitians, and 4. Prospectives in establishing the nutrition education center for the in-and out-patients. The major findings are: 1. Approximately half of the hospital dietitians feel positive about the practicality of their college education for the job. Extremely small number of them are on any kind of continuing education program 2) The monthly average of only 20 patients at one hospital receive diet consultation or nutrition education service from dietitians. The 50% of the consultation cases is taken up by the patients with diabetes and various circulartory diseases followed by the tube feedings, liver and renal diseases with less frequencies 3) Not even a single hospital has an office for the diet consultation and nutrition education for the in-or out-patients. Very few hospital dietetics have educational aids and/or any feedback system to evaluate the effect of the consultation. Charting is not practiced by most dietitians leaving no record of their contributions to the patient care. 4) Although the necessity of the nutrition education center in the hospital is strong1y recognized among dietitians the progress has been blocked by such obstacles as the poor system in the hospital administration in general, short in funds, lack of preparation in the dietetics and the lack of recognition both by the hospital administration and by the dietitian themselves.

• Nutrition Research and Practice
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• 제11권3호
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• pp.240-246
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• 2017

BACKGROUND/OBJECTIVES: Folic acid supplementation before pregnancy is known to significantly reduce the risk of having a baby with neural tube defects (NTDs). Therefore, it is important for women to be aware of the effects of folic acid supplementation before pregnancy. The purpose of this study was to investigate the awareness and preconceptional use of folic acid and to assess the current knowledge about folic acid among low-income pregnant women in Korea. SUBJECTS/METHODS: A questionnaire survey was conducted in 2012. Five hundred pregnant women were selected from the waiting list for the Nutriplus program implemented in public health centers using a multistage clustered probability sampling design. Data from 439 women were analyzed after excluding ones with incomplete answers. RESULTS: Among women who responded to the questionnaire, 65.6% had heard of folic acid before pregnancy, and 26.4% reported on the preconceptional use of folic acid. Women with a university degree or higher education were more likely to be aware of folic acid and to take folic acid in the preconception period. In a multivariate logistic regression, when age, education level, household income, employment status, gravidity, parity, and folic acid awareness were included in the model, folic acid awareness was a strong predictor of preconceptional folic acid use. As of interview, 85.4% and 77.7% of women were aware of the NTD-preventive role of folic acid and the appropriate time to take folic acid, respectively. The main sources of information on folic acid were healthcare professionals (41.2%), friends and family members (31.2%), and the media (26.5%). CONCLUSIONS: Our results suggest that public health strategies are needed to increase the preconceptional use of folic acid among Korean women.

• Progress in Superconductivity
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• 제9권1호
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• pp.62-67
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• 2007

The effects of the heat-treatment temperature on the carbon (C) substitution amount, full width at half maximum (FWHM) value, critical temperature ($T_c$), critical current density ($J_c$) have been investigated for 10 wt % malic acid ($C_4H_6O_5$)-doped $MgB_2/Fe$ wires. All the samples were fabricated by the in-situ powder-in-tube (PIT) method and heat-treated within a temperature range of $650^{\circ}C$ to $1000^{\circ}C$. As the heat-treatment temperature increased, it seemed that the lattice distortion was increased by a more active C substitution into the boron sites from the malic acid addition. These increased electron scattering defects seemed to enhance the $J_c-H$ properties in spite of an improvement in the crystallinity, such as a decrease of the FWHM value and an increase of the $T_c$. Compared to the un-doped wire heat-treated at $650^{\circ}C$ for 30 min, the $J_c$ was enhanced by the C doping in a high-field regime. The wire heat-treated at $900^{\circ}C$ resulted in a higher magnetic $J_c$ of approximately $10^4\;A/cm^2$ at 5 K and 8 T.

• 한국전기전자재료학회논문지
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• 제30권3호
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• pp.139-143
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• 2017

N-type crystalline silicon solar cells have high metal impurity tolerance and higher minority carrier lifetime that increases conversion efficiency. However, junction quality between the boron diffused layer and the n-type substrate is more important for increased efficiency. In this paper, the current status and prospects for boron diffused layers in N-type crystalline silicon solar cell applications are described. Boron diffused layer formation methods (thermal diffusion and co-diffusion using $a-SiO_X:B$), boron rich layer (BRL) and boron silicate glass (BSG) reactions, and analysis of the effects to improve junction characteristics are discussed. In-situ oxidation is performed to remove the boron rich layer. The oxidation process after diffusion shows a lower B-O peak than before the Oxidation process was changed into $SiO_2$ phase by FTIR and BRL. The $a-SiO_X:B$ layer is deposited by PECVD using $SiH_4$, $B_2H_6$, $H_2$, $CO_2$ gases in N-type wafer and annealed by thermal tube furnace for performing the P+ layer. MCLT (minority carrier lifetime) is improved by increasing $SiH_4$ and $B_2H_6$. When $a-SiO_X:B$ is removed, the Si-O peak decreases and the B-H peak declines a little, but MCLT is improved by hydrogen passivated inactive boron atoms. In this paper, we focused on the boron emitter for N-type crystalline solar cells.

• 한국강구조학회 논문집
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• 제24권6호
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• pp.743-751
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• 2012

본 논문은 HSB 강재를 보다 다양한 분야에 적용하기 위한 기본적인 연구로 HSB600 강재를 적용한 6개의 원형강관 기둥을 제작하여 구조적 특성을 고찰하고 현행 설계기준(KBC, Eurocode 3)의 적합성을 검토하였다. 실험의 주요변수는 세장비(KLe/r = 12, 14, 40, 65), 지름두께비(D/t = 25, 40), 편심비(e/D = 0, 0.5)이다. 실험결과를 현행 규준식과 비교한 결과 압축강도와 보-기둥 강도 모두 안전측으로 평가되어 현행 규준을 HSB600 강재에 적용할 수 있는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제28권3호
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• pp.482-490
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• 2018

Candida albicans infections are often problematic to treat owing to antifungal resistance, as such infections are mostly associated with biofilms. The ability of C. albicans to switch from a budding yeast to filamentous hyphae and to adhere to host cells or various surfaces supports biofilm formation. Previously, the ethanol extract from Paeonia lactiflora was reported to inhibit cell wall synthesis and cause depolarization and permeabilization of the cell membrane in C. albicans. In this study, the P. lactiflora extract was found to significantly reduce the initial stage of C. albicans biofilms from 12 clinical isolates by 38.4%. Thus, to assess the action mechanism, the effect of the P. lactiflora extract on the adhesion of C. albicans cells to polystyrene and germ tube formation was investigated using a microscopic analysis. The density of the adherent cells was diminished following incubation with the P. lactiflora extract in an acidic medium. Additionally, the P. lactiflora-treated C. albicans cells were mostly composed of less virulent pseudohyphae, and ruptured debris was found in the serum-containing medium. A quantitative real-time PCR analysis indicated that P. lactiflora downregulated the expression of C. albicans hypha-specific genes: ALS3 by 65% (p = 0.004), ECE1 by 34.9% (p = 0.001), HWP1 by 29.2% (p = 0.002), and SAP1 by 37.5% (p = 0.001), matching the microscopic analysis of the P. lactiflora action on biofilm formation. Therefore, the current findings demonstrate that the P. lactiflora ethanol extract is effective in inhibiting C. albicans biofilms in vitro, suggesting its therapeutic potential for the treatment of biofilm-associated infections.

• 조명전기설비학회논문지
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• 제22권2호
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• pp.10-18
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• 2008

본 논문은 주파수 변조 기법을 도입하여 메탈 핼라이드 램프의 음향공명 현상을 제거한 수동 PFC 구조의 전자식 안정기를 설계 및 구현하였다. 제안하는 안정기는 EMI 필터, 수동 PFC 회로, 풀 브리지 인버터 및 LC 공진 타입의 점화기, 그리고 음향공명 현상을 제거하기 위한 회로로 구성되었다. 주파수 변조 기법의 도입으로 단일 주파수 구동시 문제점이였던 램프의 수명 경과에 따른 음향공명 대역이 변화와 동일한 크기의 방전관이라도 램프 제조 사마다 아크 튜브 내부에 봉입되는 물질과 압력차에 의한 음향공명 대역의 차이를 해결하였다. 개발된 prototype 1[kW] 메탈 핼라이드 램프용 전자식 안정기의 광변환 효율, 입력 PF, 입력 전류의 THD, 그리고 전력 변환 효율을 측정함으로써 성능을 입증하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.368-368
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• 2008

Ion implantation has been widely developed during the past decades to become a standard industrial tool. To comply with the growing needs in ion implantation, innovative technology for the control of ion beam parameters is required. Beam current, beam profile, ion fractions are of great interest when uniformity of the implant is an issue. Especially, it is important to measure the spatial distribution of beam power and also the energy distribution of accelerated ions. This energy distribution is influenced by the proportion of mass for ion in the plasma generator(ion source) and by charge exchange and dissociation within the accelerator structure and also by possible collective effects in the neutralizer which may affect the energy and divergence of ions. Hydrogen atom has been the object of a good study to investigate the energy distribution. Hydrogen ion sources typically produce multi-momentum beams consisting of atomic ion ($H^+$) and molecular ion ($H_2^+$ and $H_3^+$). In the beam injector, the molecular ions pass through a charge-exchanges gas cell and break up into atomic with one-half (from $H_2^+$) or one-third (from $H_3^+$) according to their accelerated energy. Burrell et al. have observed the Doppler shifted lines from incident $H^+$, $H_2^+$, and $H_3^+$ using a Doppler shift spectroscopy. Several authors have measured the proportion of mass for hydrogen ion and deuterium using an ion source equipped with a magnetic dipole filter. We developed an ion implanter with 50-KeV and 20-mA ion source and 100-keV accelerator tube, aiming at commercial uses. In order to measure the proportion of mass for ions, we designed a filter system which can be used to measure the ion fraction in any type of ion source. The hydrogen and helium ion species compositions are used a filter system with the two magnets configurations.

• 한국과학교육학회지
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• 제23권2호
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• pp.176-188
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• 2003

자체 유도 현상은 고등학교의 모든 물리II 교과서에서 다뤄지고 있는 중요한 개념이다. 자체 유도 현상에 대한 설문 조사 결과, 코일로 구성된 회로에서 스위치를 열기만 하면 고압의 유도기전력이 발생한다는 과 일반화된 사고는 일반고등학교 학생뿐만 아니라 과학고등학교 학생들에서도 심각할 정도로 많이 나타난다. 자체 유도 현상에 대한 학생들의 일반화된 사고의 원인을 현행 물리II 교과서 분석을 통해 찾아볼 수 있었다. 그 결과, 특정 회로에서의 네온 전구의 점등 현상을 바탕으로 학생들의 직관적 사고에 의존한 막연한 설명이 주된 원인으로 나타났다. 자체 유도 현상에 대한 과학자적 이해를 돕기 위하여 정량적 해석을 시도 하였으며, 이를 바탕으로 학생들에게 자체 유도 현상을 효과적으로 이해시킬 수 있는 정상적인 접근 방법을 찾아보았다.