• Journal of Nutrition and Health
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• 제29권9호
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• pp.981-990
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• 1996

To define the risk facots of subclinical vitamin D deficiency in postmenopausal women, circulating serum 25-hydroxyvitamin D levels, known to be the indicator of vitamin D status, were measured and risk faxtors affecting it were investigated in 27 women with low 25-hydoxyvitamin d level(ie, the study group : serum 25-hydroxyvitamin D<10ng/ml) by comparing to 55 age-matched control(the control group) were analyzed. The serum level of 25-hydorxyvitamin D was analyzed by HPLC(High Pressure Liquid Chor-matography) and analyzed biochemical parameter. The following information was obtained by interviews : sociodemographic charateristics, the intake of food containing vitamin D, proxy measure of sunlight exposure(time spent outdoors), and reprocuctive histpry of the subjects. The study group had significantly lower levels of serum calcium, increased levels of iPTH and alkaline phosphatase, Among the dietary determents, energy, protein, fat, calcium, phophorus, and vitamin D intakes were lower in the study group than the normal group. The time spent outdoors in a day was not significantly different between the two groups. However, during the day, a specific time of time spent out doors between 12:00 and 14:00 was significantly lower in the study group. Logistic analysis revealed that vitamin D and calcium intake were more important affecting factors than the time spent outdoors in post menopausal women.

• Geomechanics and Engineering
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• 제22권4호
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• pp.329-337
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• 2020

Polyacrylamide (PAM) possesses high water absorption capacity and a unique pH-dependent behavior that confer large potential to enhance the engineering performance of clays. In this study, calcium bentonite was treated with a nonionic PAM. Flexible-wall permeability test and the consolidation test were performed at different pH values to evaluate the effects of PAM treatment on the hydraulic and consolidation properties. Test results demonstrate that index properties are affected by the adsorbed PAM on clay surface: a decrease in specific gravity, a decrease in net zeta potential, and an increase in liquid limit are observed due to the PAM treatment. At a given pH, the compressibility of the treated clay is greater than that of the untreated clay. However, the compression indices of untreated and treated clays can be expressed as a single function of the initial void ratio, regardless of pH. Hydraulic conductivity is reduced by PAM treatment about 5 times at both neutral and alkaline pH conditions under similar void ratios, because of the reduction in size of the water flow channel by PAM expansion. However, at acidic pH, the hydraulic conductivity of the treated clay is slightly higher than the untreated clay. This reflects that the treated bentonite with PAM can be beneficially used in barrier system for highly alkaline residues.

• 한국세라믹학회지
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• 제53권4호
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• pp.429-434
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• 2016

Here, we introduce a means of utilizing waste oyster shells which were obtained from temporary storage near coastal workplaces as $CO_2$ adsorbents. The calcined CaO can be easily dissociated to $Ca^{2+}$ cation and $CO_3{^{2-}}$ anion by hydrolysis and gas-liquid carbonation reaction and converted to precipitated calcium carbonate (PCC) in algae-containing water. The calcium hydroxide and carbonation combination in algae-containing water significantly contributed to improving water quality which is very dependent on the addition amount of calcined powders.

• Advances in concrete construction
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• 제5권4호
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• pp.377-390
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• 2017

This study proposes a mix design method for geopolymer concrete (GPC) using low calcium fly ash and alccofine, with the focus on achieving the required compressive strength and workability at heat and ambient curing. Key factors identified and nine mixes with varied fly ash content (350, 375 and $400kg/m^3$) and different molarity (8, 12 and 16M) of NaOH solutions were prepared. The cubes prepared were cured at different temperatures ($27^{\circ}C$, $60^{\circ}C$ and $90^{\circ}C$) and tested for its compressive strength after 3, 7 and 28 days of curing. Fly ash content has been considered as the direct measure of workability and strength. The suggested mix design approach has been verified with the help of the example and targets well the requirements of fresh and hardened concrete.

• The Korean Journal of Ceramics
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• 제2권2호
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• pp.63-69
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• 1996

Barium titanyl oxalates, strontium titanyl oxalates and calcium zirconyl oxalates were prepared with variation of solution concentration and method of adding mixed metal ion solution into oxalic acid. Then they were aged in distilled water, ethanol or methanol, respectively. Barium titanyl oxalates and calcium zironyl oxalates were grown in water and strontium titanyl oxalates were groun in both water and methanol. They were supposed to be grown through the solutionl and reprecipitation mechanism. Nonuniform dispersion of particles in liquid phase is thought to cause abnormal particle growth.

• 대한금속재료학회지
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• 제50권11호
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• pp.823-828
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• 2012

Direct reduction of $Ta_2O_5$ using liquid calcium was investigated. The experiment was conducted in a closed stainless steel chamber in an Ar atmosphere for 5-120 minutes. Most of $Ta_2O_5$ was reduced to ${\alpha}-Ta$ in 30 minutes above 1173 K and at a molar ratio of Ca and $Ta_2O_5$ above 10. The particles size increased with the reaction temperature, but it did not change much above 1223 K. The oxygen content of metal Ta was about 1 wt%.

• 한국유기농업학회지
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• 제19권4호
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• pp.577-587
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• 2011

This study was carried out to evaluate the manufacturing characteristics of organic liquid fertilizer with poultry manure, soybean meal, and rice bran at plastic house in Chungbuk Agricultural Research and Extension Service. Treatment was given 3 treatments; poultry manure+soybean meal (PM+SM), poultry manure+rice bran (PM+RB), and soybean meal+rice bran (SM+RB). The obtained results from this study were summarized as follows; The pH in liquid fertilizer was consistently increased in PM+SM treatment, and was increased after decreased at early season in PM+RB and SM+RB treatments. The electriacl conductivity(EC) in liquid fertilizer was rapidly increased from $2^{nd}$ weeks to $4^{th}$ weeks after fermentation in PM+SM and PM+RB treatments, and was rapidly increased from $4^{th}$ weeks to 6th weeks after fermentation in SM+RB treatment. The amount of $H_2S$ gas occurrence was the highest as $1,200\;mg{\cdot}kg^{-1}$ in early season, and was the lowest as $50\;mg{\cdot}kg^{-1}$ at $12^{th}$ weeks after fermentation of organic liquid fertilizer. The temperature of organic liquid fertilizer was stabilizing in $4^{th}$ weeks after fermentation. The yield of well of nitrogen, phosphate, and potassium was increased with increasing fermentation periods. It was not change from $4^{th}$ weeks after fermentation in content of calcium, magnesium and sodium in organic liquid fertilizer.

• 대한화학회지
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• 제38권2호
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• pp.129-135
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• 1994

Acyclic polyether dicarboxylic acid는 액체막계에서 금속이온의 운반체로 연구되었다. 수소이온이 이온화될 수 있는 리간드는 금속이온의 이동에 수소이온이 반대방향으로 이동된다. 이와 같은 리간드는 pH를 변화시키면 효과적으로 금속이온을 분리할 수 있고 농축시킬 수도 있다. 금속이온의 이동은 source phase의 염기의 농도와 receiving phase의 산의 농도를 증가시키면 증가된다. Acyclic polyether dicarboxylic acids를 운반체로 사용한 경쟁이동반응에서 칼슘이온을 선택적으로 분리할 가능성이 있다.

• Korean Chemical Engineering Research
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• 제49권1호
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• pp.109-113
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• 2011

탄산칼슘의 Biomineralization 반응을 수행하기 위해 aspartic acid와 lysine을 $CaCl_2$ 용액에 첨가하여 기-액 반응으로 염화칼슘과 $NH_4HCO_3$을 사용하여 탄산칼슘 결정화 실험을 하였다. 결정화 반응시간, aspartic acid와 lysine의 첨가양, $CaCl_2$의 양, $NH_4HCO_3$의 양을 변경하여 탄산칼슘 결정의 다형체인 calcite와 vaterite의 비를 조사하였다. 결정 분석을 수행하기 위해 FT-IR spectrometer(model IR Prestige-21, Shimadzu, Kyoto, Japan) 장치를 사용하였고 FT-IR 스펙트럼으로 calcite와 vaterite 결정을 확인하였다. $CaCl_2$의 양을 변경하였을 때, $NH_4HCO_3$ 10 g에서 0.15 M의 $CaCl_2$ 농도 전후에서 vaterite 결정의 증가가 감소로 변하다가 0.20M에서는 다시 증가하여 0.25 M에서 가장 많은 vaterite 결정이 관찰되었다. $NH_4HCO_3$ 20 g에서는 0.10 M의 $CaCl_2$를 전환점으로 하여 vaterite 결정이 증가에서 감소추세를 보이다가 0.25M에서 다시 증가하는 것으로 나타났다. 첨가제로 lysine을 이용하였을 때는 반응시간이 2일을 기점으로 vaterite양의 증가가 감소로 변하였고 aspartic acid를 첨가하였을 때는 반대의 경향을 보였다.

• 한국유기농업학회지
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• 제20권3호
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• pp.345-356
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• 2012

본 연구는 2009년에 친환경 농산물 재배 농가들이 사용하는 자가 제조 액비 실태를 파악하고자 친환경 농산물 인증을 받은 29농가를 대상으로 액비의 종류, 재료, 제조과정, 활용방법 및 효과 등에 대해서 조사를 실시하였다. 농가에서 사용하는 액비의 재료는 대부분 주변에서 쉽게 구할 수 있는 것들이었고 제조방법은 주재료에 미생물의 에너지원으로 사용할 수 있는 당밀이나 흑설탕을 첨가하고 그리고 발효 미생물원으로 부엽토, 시판미생물, 시군센터에서 보급하는 미생물 또는 토착미생물 배양체를 사용하고 있었다. 농가에서 제조하여 활용하고 있는 액비 종류는 발효액비, 천혜녹즙, 아미노산액비, 칼슘액비, 인산액비 등 이었고 이들 액비는 생육촉진, 개화촉진, 꽃눈형성, 당도증가, 저장성 증대, 병해충 저항성 증가, 그리고 고온장해 억제 등의 효과가 있는 것으로 조사되었다. 수집된 액비의 성분분석 결과, pH와 EC의 범위는 시료간의 차이가 크며 질소, 인산 등 다량원소 함량은 대부분 적었으며 같은 재료를 이용하여 제조된 액비라도 제조방법에 따라 양분함량이 각각 다른 것으로 조사되었다.