• 대한화학회지
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• 제56권5호
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• pp.628-637
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• 2012

이 연구에서는 1945년 교수요목기의 교과서부터 2009 개정 교육과정 화학II 교과서까지 수용액에서 강산의 이온화도에 대한 내용을 분석하고, 현직 화학 교사 50명을 대상으로 수용액에서 강산의 화학종에 대한 인식과 이온화도를 고려하였을 때의 인식 차이를 알아보는 설문과 면담을 실시하였다. 연구 결과, 우리나라 교사들은 교과서에 제시된 이온화도 값을 근거로 강산의 수용액 안에 존재하는 화학종에 대한 생각을 하고 있었으며, 강산의 정의와 교과서에 제시된 이온화도 값이 서로 일치하지 않은 문제를 생각하지 못하거나, 문제를 인식하는 경우에도 그에 대한 해결을 하지 못한 것으로 나타났다.

• 대한화학회지
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• 제59권3호
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• pp.238-245
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• 2015

The crystallization and morphology change of amorphous titanias by hydrothermal treatment have been investigated. The amorphous titanias were prepared by pure water hydrolysis of two different precursors, titanium tetraisopropoxide (TTIP) and TTIP modified with acetic acid (HOAc) and characterized prior to hydrothermal treatment. In order to avoid complicate situation, the hydrothermal treatment was performed in a single solvent water with and without strong acids at various temperatures. The effects of strong acid, temperature and time were systematically investigated on the transformation of amorphous titania to crystalline TiO₂ under simple hydrothermal condition. Without strong acid the titanias were transformed into only anatase phase nanoparticle regardless of precursor type, temperature and time herein used (up to 250 ℃ and 48 hours). The treatment temperature and time effected only on the crystalline size, not on the crystal phase et al. However, it was clearly revealed that the strong acids such as HNO₃ and HCl catalyzed the formation of rutile phase depending on temperature. HCl was slightly better than HNO₃ in this catalytic activity. The morphology of rutile TiO₂ formed was also a little affected by the type of acid. The precursor modifier, HOAc slightly reduced the catalytic activity of the strong acids in rutile phase formation.

• 전자공학회논문지
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• 제50권7호
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• pp.269-274
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• 2013

전해 산성이온수는 알칼리성 이온수에 비해 응용분야가 음용을 목적으로 하는 알칼리이온수와 많이 다르게 이용되고 있으며 ph 농도에 따라 강산성인 경우 잔류염소에 의한 살균 목적의 소독제로 사용되고, 중산성인 경우 세척과 세안으로 사용하고, 약산성인 경우 식재료와 혼합하여 요리에 널리 사용할 수 있다. 이런 산성이온수를 생성하기 위해서는 물을 전기분해 하여 사용하는데 전기분해 하는 과정에서 염소가스와 수산화나트륨 등의 물질로 살균력을 가지며, 전기분해시 +전극 쪽으로 -이온을 띤 염소, 인, 유황 등의 유기물이 모여져 산성이온수를 만든다. 또한 산성수와 알칼리수를 분리하기 위해서 격막을 사용했다. ph 농도변화의 구현방법은 Microprocessor를 이용하여 강산성에서 약산성 사이의 ph 농도를 PWM(pulse width modulation) 제어로 3종류의 PWM 전압을 전해조 전극에 인가하여 PWM제어에 의한 연속적으로 농도가 조절된 산성수가 생성되게 구현하였다.

• Corrosion Science and Technology
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• 제7권4호
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• pp.237-242
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• 2008

Physical properties of water, such as dielectric constant and ionic product, significantly vary with the density of water. In the supercritical conditions, since density of water widely varies with pressure, pressure has a strong influence on physical properties of water. Dielectric constant represents a character of water as a solvent, which determines solubility of an inorganic compound including metal oxides. Dissociation equilibrium of an acid is also strongly dependent on water density. Dissociation constant of acid rises with increased density of water, resulting in drop of pH. Density of water and the density-related physical properties of water, therefore, are the major governing factors of corrosion and environmentally assisted cracking of metals in supercritical aqueous solutions. This paper discusses importance of "physical properties of water" in understanding corrosion and cracking behavior of alloys in supercritical water environments, based on experimental data and estimated solubility of metal oxides. It has been pointed out that the water density can have significant effects on stress corrosion cracking (SCC) susceptibility of metals in supercritical water, when dissolution of metal plays the key role in the cracking phenomena.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1841-1846
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• 2000

To examine the effect of acid fog on the corrosion fatigue behavior in structural steel, fatigue tests under acid fog atmosphere were carried out in comparison with distilled water. The corrosive c omponents contained in acid fog pile up the corrosion products on crack face and show a crack branching and crack tip blunting. Therefore, due to these workings crack growth rate was reduced by decreasing the effective stress range in crack tip rather than under distilled water. Also the effect of sulfuric acid, which is the main component of acid fog, and testing speed on fatigue crack growth were examined. It was found that corrosion behavior was remarkably dependent upon pH and Hz rather than components of acid fog. According as pH and testing speed decrease below a specific value, crack growth was accelerated in comparison with distilled water. This reveals that due to liquid having strong acidity and slow speed of test the crack face dissolution was promoted, so crack closure was disturbed in the process of stress descent.

• 산업기술연구
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• 제17권
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• pp.291-295
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• 1997

The tests of stress corrosion cracking in structural carbon steel were carried out under the conditions of acid fog and general water. As the result of measurement SCC rupture time under acid fog was observed to be much shorter than that of general water at the same stress level. Therefore, acid fog drops the SCC strength in structural carbon steel due to strong corrosion. In the SCC process by acid fog, crack initiation was caused by pit corrosion and local stress concentration, and distinctive feature of crack growth shows branching since crack grows to the corrosion direction. Moreover, corrosion products were observed by clevage corrosion on the crack surfaces.

• Environmental Analysis Health and Toxicology
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• 제1권1호
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• pp.77-80
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• 1986

$N^{G}$ -Mono［$^{14}$ C-Methyl］-L-arginine을 방사선화학적 방법으로 mono ［$^{14}$ C］-Methylamine 으로부터 합성한후 양이온 교환수지에 흡착시킨 다음 암모니아수로 용출시켜 정제하였으며 flavianic acid를 사용하여 결정상태로 얻었다. 한편 flavianate와 음이온 교환수지 를 함께 실온 이하의 온도에서 교반혼합함으로서 유리 상태의 amino acid를 쉽게 만들수 있으며 박층크로마토그라피, 박층전기영동 및 섬광분광분석법으로 순도를 조사하였다.

• Journal of Photoscience
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• 제1권1호
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• pp.25-29
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• 1994

Diffuse reflectance and emission spectra of 7-hydroxyquinoline intercalated in the supercage of X and Y zeolites are compared with the absorption and emission spectra of aqueous 7-hydroxyquinoline solutions at various pH to understand protropic and photophysical properties of 7-hydroxyquinoline in zeolite microenvironments. Predominance of zwitterionic spedes with significant existences of the other three protropic equilibrium species, normal, protonated and deprotonated species in zeolite samples indicates that the major fraction of the molecules interact with strong acid and base sites of zeolite at an adsorbed position. Observed zeolite pHs of near neutrality are established by a near balance in numbers of many strong acid and base sites rather than by'small numbers or weakness of acid and base sites. Excitations of nonzwitterionic species such as deprotonated species also give prevailing zwitterionic fluorescence, indicating that excited and ground proton transfer cycles of protropic species can be triggered by photons in organized zeolite media as well as in water.

• 한국축산식품학회지
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• 제31권3호
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• pp.349-355
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• 2011

Russian deer velvet antlers were divided into three parts and subjected to a extraction process using hot water at 100, 110, and $120^{\circ}C$ or an extraction with 70% ethanol. Each extract was analyzed for its biochemical components, including uronic acid, sulfated-glycosaminoglycans (sulfated-GAGs), and sialic acid, and the antioxidant and anti-acetylcholinesterase activities were investigated. Different levels of uronic acid and sulfated-GAGs were observed in the extracts according to the water temperature used for the extraction, and contents decreased with increasing extraction temperature. The upper layer of each extract showed high amounts of uronic acid and sulfated-GAGs, followed by the middle and base layers. Ethanol extraction was more effective for recovering uronic acid than sulfated-GAGs. Sialic acid content was the highest in the $110^{\circ}C$ extracts but was not observed in the ethanol extracts. Velvet antler extracts showed strong antioxidant activities against DPPH and hydrogen peroxide as well as strong reducing power in a dose-dependent manner. However, the antioxidant activities were different in each layer and according to the extraction method. Additionally, velvet antler extracts exhibited inhibitory activity against acetylcholinesterase, which is associated with Alzheimer's disease, in a dose-dependent manner. These results suggest that velvet antler extracts are useful as a functional food ingredient and/or a pharmaceutical.

• 한국식품영양과학회지
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• 제28권6호
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• pp.1310-1315
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• 1999

Polyphenolic compounds widely occurring in the traditional medicine plants have been reported to possess strong antioxidant activity. The antioxidative substances of water soluble extract from leaves, stem bark, root bark and fruit powder of Cudrania tricuspidata were tested in three different in vitro experimental models. In oxidation models using DPPH( , ' diphenyl picrylhydrazyl) method, Fe2+ induced linoleic acid peroxidation, and autooxidation of hepatic microsomal membranes, the antioxidative activities of water soluble extract from stem bark were strong than that from leaves and root bark. Fruits of Cudrania tricuspidata contained the highest amounts of polyphenolic compounds among the parts of this plant. The changes in polyphenolic compound contents of fruit powder caused by heat treatment (20oC, 40oC, and 60oC) were also monitored. After water blanching, contents of phenolic compounds was increased slightly in the following order; 20oC(1454mg), 40oC(1487mg), and 60oC(1511mg). These results supports that water soluble extracts from Cudrania tricuspidata contain antioxidative compounds.