• 한국진공학회지
• /
• 제14권2호
• /
• pp.78-83
• /
• 2005

지난 10년 동안 유전체 내부에 형성된 나노미터 크기의 규소알갱이는 발광센터로서 주목 받아왔다 나노미터 크기인 결정질 규소의 엑시토닉 전자-홀의 쌍들이 발광결합에 기여한다고 여겨진다. 그러나 규소결정에 존재하는 여러가지 결함들은 비발광 천이의 경로가 되어 나노규소결접립의 발광천이와 경쟁하여 발광효율을 저하시키는 요인이 된다. 이러한 결정 결함들은 고온 열처리과정에서 대부분 소멸되나 $1000^{\circ}C$ 이상의 공정 에서도 나노규소와 유전체의 계면에 존재하는 결함들은 나노규소결정립의 발광을 억제하게 된다. 일반적으로 수소로서 규소결정립의 계면을 마감처리하게 되면 규소결정립의 발광효율이 획기적으로 향상되나 불행하게도 매질 내 수소의 높은 이동성으로 말미암아 후속 열처 리 과정에서 수소마감효과는 쉽게 손실된다. 따라서 본 연구에서는 온도가역적인 수소 대신 인을 이온주입 방법으로 첨가하여 수소와 같은 계면 마감효과를 얻으며 또한 후속 고온공정 에 대한 내구력을 증대시켰다. 모재인 산화규소 기판에 400keV, $1\times10^{17}\; Si/cm^2$와 그 주위에 균일한 함량을 도핑하기 위하여 다중에너지의 인을 주입하였다. 규소와 인을 이온주입 후 Ar 분위기에서 $1100^{\circ}C$ , 두 시간의 후열처리를 통하여 규소결정립을 형성하였으며 향상된 내열효과를 시험하기 위하여 Ar 분위기에서 $1000^{\circ}C$까지 열처리하였다. 인으로 마감된 나노미터 크기인 규소 결정립의 향상된 광-발광(PL)효과와 감쇄시간, 그리고 발광파장의 변화에 대하여 논의하였다.

• 대한본초학회지
• /
• 제29권6호
• /
• pp.1-6
• /
• 2014

Objectives : This study was aimed to compare Gyejibokryeong-hwan (GBH) decoctions produced using different pressure levels for various extraction times to find the optimal extraction conditions through extraction yield, total soluble solids content (TSSC), hydrogen ion concentration (pH), and the contents of chemical compounds. Methods : Decoctions of GBH were prepared under the pressure levels of 0 or $1kgf/cm^2$ for 30-180 min using water as extraction solvent. The extraction yield, TSSC, and pH were measured, and the amounts of the chemical compounds were determined using high performance liquid chromatography-photodiode array detector. Results : The higher pressure and longer extraction time increased the values of TSSC and extraction yield, while decreased the pH value. The decoctions produced in 180 min by pressurized method and produced in 150 min by non-pressurized method showed maximum values of extraction yield and TSSC with minimum value of pH. The amounts of chemical compounds showed variations in pressurized and non-pressurized decoction during overall extraction times. The influences of pressure and extraction time on extraction yield, TSSC, pH, and the contents of chemical compounds were confirmed by regression analysis, which showed that all extraction values were significantly affected by at least one of two extraction factors, pressure and extraction time. Conclusions : This study suggests that the pressure and extraction time can significantly affect the extraction efficiency of components from GBH decoctions. However, optimal extraction conditions could not be chosen due to the variation of the amounts of chemical compounds.

• Journal of Electrochemical Science and Technology
• /
• 제8권4호
• /
• pp.265-273
• /
• 2017

Solid-state alkaline water electrolysis is a promising method for producing hydrogen using renewable energy sources such as wind and solar power. Despite active investigations of component development for anion exchange membrane water electrolysis (AEMWE), understanding of the device performance remains insufficient for the commercialization of AEMWE. The study of assembled AEMWE devices is essential to validate the activity and stability of developed catalysts and electrolyte membranes, as well as the dependence of the performance on the device operating conditions. Herein, we review the development of catalysts and membranes reported by different AEMWE companies such as ACTA S.p.A. and Proton OnSite and device operating conditions that significantly affect the AEMWE performance. For example, $CuCoO_x$ and $LiCoO_2$ have been studied as oxygen evolution catalysts by Acta S.p.A and Proton OnSite, respectively. Anion exchange membranes based on polyethylene and polysulfone are also investigated for use as electrolyte membranes in AEMWE devices. In addition, operation factors, including temperature, electrolyte concentration and acidity, and solution feed methods, are reviewed in terms of their influence on the AEMWE performance. The reaction rate of water splitting generally increases with increase in operating temperature because of the facilitated kinetics and higher ion conductivity. The effect of solution feeding configuration on the AEMWE performance is explained, with a brief discussion on current AEMWE performance and device durability.

• 한국환경보건학회지
• /
• 제44권2호
• /
• pp.133-142
• /
• 2018

Objectives: The pathogenic Vibrios genus denotes halophilic bacteria that are distributed in aquatic environments, including both sea and freshwater. Vibrio cholerae, Vibrio vulnificus, and Vibrio parahaemolyticus are the most important species since they can be potent human pathogens and leading causes of septicemia, wound infections, and seafood borne gastroenteritis. The recent emergence of a potential pandemic clone, V. cholera serotype O1 and the cholera outbreak in South Korea in 2016 indicates the importance of consistent surveillance of pathogenic Vibrio genus within coastal areas. Methods: The present study was undertaken to determine where and how vibrios live in the aquatic environment adjacent to coastal areas of South Korea. For this survey, a total of 838 samples were obtained at 35 different sites in South Korean coastal areas during the period from January 2016 to December 2016. Pathogenic vibrios was determined using the real-time PCR method, and its clones were isolated using three selective plating media. We also monitored changes in seawater and atmospheric temperature, salinity, turbidity, and hydrogen ion concentration at the collection points. Results: The total isolation rates of V. vulnificus, V. cholera (non-pathogenic, non-O1, non-O139 serogroups), and V. parahaemolyticus from seawater specimens in 2016 were 14.2, 13.48, and 67.06%, respectively. Conclusions: The isolation rates of pathogenic vibrios genus showed a positive correlation with temperature of seawater and atmosphere but were negatively correlated with salinity and turbidity.

• 한국치위생학회지
• /
• 제19권6호
• /
• pp.1099-1107
• /
• 2019

Objectives: The purpose of this study was to investigate the changes in pH in the oral cavity using the probiotic intake method. Methods: A total of 109 participants were enrolled and randomly assigned to three groups. Participants in the control group did not ingest powdered probiotics, those in experimental group 1 ingested powdered probiotics by dissolving them on the tongue, and those in experimental group 2 dissolved powdered probiotics on the tongue and rinsed with water. pH values were measured 5 times in all. The significance of each group was examined by the Kruskal-Wallis test. The trend over time was expressed as a graph with groupwise means and confidence intervals, considering repeated measurement data. Results: A significant difference was found between the control group and experimental group 1 at two time-points, i.e., immediately after intake and 3 min after ingestion. As a result of the time trend, the pH value of experimental group 2 was smaller than that of experimental group 1, compared to the control group. Conclusions: Studies have shown that taking probiotics with water may help reduce changes in oral pH. Probiotics should be aware of live bacteria and provide consumers with more detailed information on proper dosage and precautions.

• 공업화학
• /
• 제16권1호
• /
• pp.107-111
• /
• 2005

$V_2O_5$ 분말을 과산화수소에 용해시켜 $V_2O_5$ 겔을 졸-겔법으로 합성한 후 물성과 전기화학적 특성을 NMR, 선형전압전류법 등을 이용하여 조사하였다. $V_2O_5$ xerogel에 삽입된 $Li^+$ 이온의 량에 따라 NMR 스펙트라의 화학적이동값이 다르게 나타났으며 xerogel 구조 내에서 다른 환경의 리튬이온 자리가 존재함을 알 수 있었다. 합성에 이용한 $V_2O_5$의 초기농도 변화와 pH 변화에 따른 xerogel의 전기화학적 특성은 큰 차이가 나타나지 않았으며, 전지용량은 이온교환수지법으로 제조한 xerogel과 비슷한 140 mAh/g으로 나타났다.

• 한국콘텐츠학회논문지
• /
• 제9권8호
• /
• pp.1-8
• /
• 2009

IT 융합 기술의 발전에 따라 정부의 4대강 복원을 위한 마스터플랜이 구축되면서, 환경 친화적인 수질 오염 관리의 중요성이 부각되고 있다. 본 논문에서는 친환경 저수조의 수질 향상과 온라인 관리를 하기 위해서 저수조 자동 분류를 이용한 효과적인 수질 오염 관리를 제안하였다. 제안된 방법에서는 수질오염 평가의 7가지 요소들을 정의하였고 센서를 이용하여 수소이온농도(pH), 화학적 산소요구량(COD),부유 물질량(SS), 용존 산소량(DO), 대장균군수(MPN), 총인 (T-P), 총질소(T-N)에 따른 적합한 수질 오염 관리를 하였다. 저수조의 7가지의 수질 오염 요소간의 측정치를 평가하고 [1,9] 사이에 분포하도록 정규화하였다. 저수조 자동 분류를 이용한 수질 오염 관리 시스템의 성능 평가를 하기 위해 F-측정식을 이용하여 유용성을 검증하였다. 평가 결과, 기존 시스템에 대한 만족도의 차이가 통계적으로 의미가 있음을 증명하였다.

• 한국결정성장학회:학술대회논문집
• /
• 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
• /
• pp.422-448
• /
• 1996

Low-temperature epitaxial growth of Si and SiGe layers of Si is one of the important processes for the fabrication of the high-speed Si-based heterostructure devices such as heterojunction bipolar transistors. Low-temperature growth ensures the abrupt compositional and doping concentration profiles for future novel devices. Especially in SiGe epitaxy, low-temperature growth is a prerequisite for two-dimensional growth mode for the growth of thin, uniform layers. UHV-ECRCVD is a new growth technique for Si and SiGe epilayers and it is possible to grow epilayers at even lower temperatures than conventional CVD's. SiH and GeH and dopant gases are dissociated by an ECR plasma in an ultrahigh vacuum growth chamber. In situ hydrogen plasma cleaning of the Si native oxide before the epitaxial growth is successfully developed in UHV-ECRCVD. Structural quality of the epilayers are examined by reflection high energy electron diffraction, transmission electron microscopy, Nomarski microscope and atomic force microscope. Device-quality Si and SiGe epilayers are successfully grown at temperatures lower than 600℃ after proper optimization of process parameters such as temperature, total pressure, partial pressures of input gases, plasma power, and substrate dc bias. Dopant incorporation and activation for B in Si and SiGe are studied by secondary ion mass spectrometry and spreading resistance profilometry. Silicon p-n homojunction diodes are fabricated from in situ doped Si layers. I-V characteristics of the diodes shows that the ideality factor is 1.2, implying that the low-temperature silicon epilayers grown by UHV-ECRCVD is truly of device-quality.

• 대한토목학회논문집
• /
• 제2권1호
• /
• pp.63-68
• /
• 1982

본(本) 연구(硏究)는 국산천연(國産天然) 제오라이트를 이용한 중금속(重金屬) 산업폐수(產業廢水) 처리공정(處理工程)을 개발(開發)할 목적(目的)으로 수행(遂行)되었으며 본 논문에서는 1차적으로 알카리 처리된 제오라이트를 이용하여 Batch Test를 통한 기초실험(基礎實驗) 결과(結果)를 수록하였다. 제오라이트에 의한 중금속 흡착(吸着)공정에 미치는 pH의 영향(影響), 흡착 Isotherm Model 결정, 흡착속도 및 온도(溫度)의 영향을 중점적으로 평가분석(評價分析)하였으며 그 결과 최적(最適) pH는 4~5이상, 카드미움 흡착은 BET Model이 적합하며, 반응시간(反應時間)은 10분 이상이 소요됨을 알았으며 또한 온도가 증가하면 비례하여 흡착능(吸着能)도 증가하므로서 단순한 물리흡착(物理吸着)만이 아닌 화학흡착(化學吸着)도 병행하여 일어나고 있다고 판단된다. 본 연구 결과로 판단컨대, 국산 천연 제오라이트를 이용한 중금속 폐수처리는 그 전망이 밝으며 앞으로 Column Test를 통하여 합성(合成)폐수는 물론 실제폐수의 처리도(處理度)를 실험하므로서 처리공정설계 조건을 도출할 수 없으며 이와 같은 공정의 개발로서 우리나라의 중금속 폐수처리에 획기적인 공헌이 기대된다.

• 대한한의학회지
• /
• 제34권4호
• /
• pp.12-20
• /
• 2013

Objectives: This study compared Gumiganghwal-tang (GGT) decoctions produced using different pressure levels for various extraction times to determine the optimal extraction conditions through hydrogen ion concentration (pH), total soluble solids content (TSSC), extraction yield, and content of chemical compounds. Methods: Decoctions were prepared by the pressure levels of 0 or $1kgf/cm^2$ for 30-180 min. The pH and TSSC were measured, the extraction yield was calculated, and the amounts of the chemical compounds were determined using high performance liquid chromatography. Results: The higher pressure and longer extraction time decreased the pH value, while those conditions increased TSSC and extraction yield: the decoction produced in 180 min by pressurized method showed the minimum value of pH, but maximum values of TSSC and extraction yield. The chemical compounds showed higher amounts in decoctions produced by non-pressurized methods than pressurized methods and their amounts were decreased over the peak extraction time in both pressurized and non-pressurized methods. The results of regression analysis confirmed the correlative influences of the pressure and extraction time on pH, TSSC, and extraction yield. Conclusions: This study suggests that pressure and extraction time influence the compositional constituents in GGT decoctions, and the non-pressurized method for 120 min should be chosen as the optimal extraction condition for the preparation of GGT decoction.