• 한국물환경학회지
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• 제27권4호
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• pp.438-444
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• 2011

Magnesium is one of the abundant natural resources in the earth crust and seawater, which is directly related to various organisms activities interconnecting with water-rock system. In aqueous system, magnesium is known to predominantly exist in the form of $Mg^{2+}$ ion which is verified in its $E_h-pH$ diagram. When it is at equilibrium in aqueous system, temperature takes an essential role to complete equilibrium states. This study represents the change of the stable region of magnesium ion according to temperature, and how the consequences would affect aquatic organisms. It was revealed that there is a noticeable tendency shrinking the stable region of magnesium ion in a diagram as temperature increases, and as a result, aquatic bio-species presumably have difficulties to absorb the nutrient. Also, it was considered that the water system would be acidified by decreasing alkalinity.

• 대한금속재료학회지
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• 제48권6호
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• pp.523-532
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• 2010

Co-application of organic coating and cathodic protection has not provided enough durability to low-alloyed steels inseawater ballast tank (SBT) environments. An attempt has made to study the effect of alloy elements (Al, Cr, Cu, Mo, Ni, Si, W) on general and localized corrosion resistance of steels as basic research to develop new low-allowed steels resistive to corrosion in SBT environments. For this study, we measured the corrosion rate by the weigh loss method after periodic immersion in synthetic seawater at $60^{\circ}C$, evaluated the localized corrosion resistance by an immersion test in concentrated chloride solution with the critical pH depending on the alloy element (Fe, Cr, Al, Ni), determined the permeability of chloride ion across the rust layer by measuring the membrane potential, and finally, we analyzed the rust layer by EPMA mapping and compared the result with the E-pH diagram calculated in the study. The immersion test of up to 55 days in the synthetic seawater showed that chromium, aluminium, and nickel are beneficial but the other elements are detrimental to corrosion resistance. Among the beneficial elements, chromium and aluminium effectively decreased the corrosion rate of the steels during the initial immersion, while nickel effectively decreased the corrosion rate in a longer than 30-day immersion. The low corrosion rate of Cr- or Al-alloyed steel in the initial period was due to the formation of $Cr_2FeO_4$ or $Al_2FeO_4$, respectively -the predicted oxide in the E-pH diagram- which is known as a more protective oxide than $Fe_3O_4$. The increased corrosion rate of Cr-alloyed steels with alonger than 30-day exposure was due to low localized corrosion resistance, which is explained bythe effect of the alloying element on a critical pH. In the meantime, the low corrosion rate of Ni-alloyed steel with a longer than 30-day exposure wasdue to an Ni enriched layer containing $Fe_2NiO_4$, the predicted oxide in the E-pH diagram. Finally, the measurement of the membrane potential depending on the alloying element showed that a lower permeability of chloride ion does not always result in higher corrosion resistance in seawater.

• The Korean Journal of Ecology
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• 제19권1호
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• pp.71-80
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• 1996

The effects of simulated acid rain on the growth and interspecific competition of Echinochloa crus-galli and Digitaria sanguinalis were studied. Changes of growth in height and dry weight were examined and competition between the two species was investigated using the experimental model proposed by de Wit (1960). The experiments were carried out in the greenhouse, and test plants were germinated and grown for 4 weeks and then sprayed with simulated acid rain of pH 5.6, 4.2 and 2.8 for another 8 weeks. In de Wit replacement experiments, the variation of density and the treatment of simulated acid rain showed little effect on the interspecific competition between E. Crus-galli and D.sanguinalis. The ratio diagram, another method to reveal the interrelations between two competing species, always showed the predominance of E. crus-galli in competition, regardless of density and pH. The interspecific competition of the two species, represented by relative yield total (RYT), revealed that intraspecific competition was stronger than interspecific competition in both species.The treatment of simulated acid rain showed little effect on the growth of E. Crus-galli and D. sanguinalis. Height growth of both species did not differ from that of control (pH 5.6), but root/shoot ratio increased with the decrease in pH of simulated acid rain. Growth of tatal dry weight of E. crus-galli and D. sanguinalis was not influenced by the change of pH, except that D.sanguinalis showed a decrease in the total dry weight at pH 2.8 along with a visible sign of white spots on leaves. Physical environmental conditions can exert an effect on the interrelationships between the two species, but this experiment did not show the reversion of competition, and showed that E.crus-gilli was competitively dominant under any environmental conditions given in this study.

• Nuclear Engineering and Technology
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• 제42권5호
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• pp.552-561
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• 2010

This study investigates the solubility of neptunium (Np) in the deep natural groundwater of the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT). According to a Pourbaix diagram (pH-$E_h$ diagram) that was calculated using the geochemical modeling program PHREEQC 2.0, the redox potential and the carbonate ion concentration both control the solubility of neptunium. The carbonate effect becomes pronounced when the total carbonate concentration is higher than $1.5\;{\times}\;10^{-2}$ M at $E_h$ = -200 mV and the pH value is 10. Given the assumption that the solubility-limiting stable solid phase is $Np(OH)_4(am)$ under the reducing condition relevant to KURT, the soluble neptunium concentrations were in the range of $1\;{\times}\;10^{-9}$ M to $3\;{\times}\;10^{-9}$ M under natural groundwater conditions. However, the solubility of neptunium, which was calculated with the formation constants of neptunium complexes selected in an OECD-NEA TDB review, strongly deviates from the value measured in natural groundwater. Thus, it is highly recommended that a prediction of neptunium solubility is based on the formation constants of ternary Np(IV) hydroxo-carbonato complexes, even though the presence of those complexes is deficient in terms of the characterization of neptunium species. Based on a comparison of the measurements and calculations of geochemical modeling, the formation constants for the "upper limit" of the Np(IV) hydroxo-carbonato complexes, namely $Np(OH)_y(CO_3)_z^{4-y-2z}$, were appraised as follows: log $K^{\circ}_{122}\;=\;-3.0{\pm}0.5$ for $Np(OH)_2(CO_3)_2^{2-}$, log $K^{\circ}_{131}\;=\;-5.0{\pm}0.5$ for $Np(OH)_3(CO_3)^-$, and log $K^{\circ}_{141}\;=\;-6.0{\pm}0.5$ for $Np(OH)_4(CO_3)^{2-}$.

• Preventive Nutrition and Food Science
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• 제13권4호
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• pp.306-312
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• 2008

This study investigated the influence of pH on the color development of melanoidins formed from amino acid enantiomer model systems. For this, the color development was evaluated by measuring browning at 420 nm and color measurements by spectrophotometry and colorimetry. The browning and browning index showed no difference according to the type of amino acid enantiomers, while that formed from the D-Asn system was the only difference according to pH level. The tristimulus value of melanoidins formed from all model systems was located on a dominant wavelength of 475 nm, the blue zone of the diagram. In addition, the $L^*$, $a^*$, $b^*$, $C^*_{ab}$ values, and ${\Delta}E^*$ index on the basis of the type of amino acid enantiomers, the differences were markedly found at pH 4.0. At pH 7.0, significantly differences were found in the $L^*$, $a^*$, $b^*$ values, and ${\Delta}E^*$ index and not in the case of the lysine enantiomers. In addition, at pH 10.0, the differences were found in the $a^*$ and $b^*$ values from the lysine enantiomers and $C^*_{ab}$ value from the asparagine enantiomers. Therefore, the color development of melanoidins was influenced by the type of amino acid enantiomers and pH levels. Especially, it is thought that the $a^*$ and $b^*$ values can be used to explain the differences among the amino acid enantiomers in the color development of melanoidins.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2543-2551
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• 2020

Calculations of chemical equilibrium for multicomponent aqueous systems of the HyBRID dissolution of magnetite were performed by using the HSC Chemistry. They were done by using a Pitzer-based aqueous solution model with the recipe of raw materials in experiments conducted at KAERI. The change in the amounts of species and ions and the pH values of the solution at equilibrium was observed as functions of temperature and raw amount of CuSO₄. Precipitation of Cu₂O occurred at a large amount of CuSO₄ added to the solution, while no precipitation of Cu(OH)₂ was found at any amounts of CuSO₄. The E-pH diagrams for Cu were constructed at various Cu concentrations to provide the effect of the Cu concentration on the pH values at boundaries where the coexistence of Cu⁺ ion and Cu₂O solid occurred. To prevent Cu⁺ ions from being precipitated to Cu₂O, the raw amount of CuSO₄ should be adjusted so that the pH value of the solution from the equilibrium calculation is less than that from the E-pH diagram. We provided guidelines for the raw amount of CuSO₄ and the pH value of the solution, which prevent the formation of Cu₂O precipitates in the HyBRID dissolution experiments for magnetite.

• 지질공학
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• 제11권2호
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• pp.175-190
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• 2001

오염된 연약지반에 편재하중이 작용하는 경우에 있어서 지반의 소성화에 따른 측방유동에 대한 거동을 규명하기 위하여 기존의 이론적인 배경을 고찰하고, 모형실험을 통하여 실측한 결과를 상호 비교.분석하였다. 모형실험은 모형재하장치인 토조와 재하틀 및 재하판을 제작하여 토조 안에 함수비를 일정하게 유지한 상태에서 자연지반의 시료와 오염물질을 점진적으로 증가시킨 지반시료에 대하여 일정한 시간 간격으로 편재하중을 증가시키면서 침하량과 측방변위량 및 융기량 등을 관측하였다. 그 결과 한계하중은 실험값이 Tschebotarioff(q$_{cr}$=3.0$_{cu}$)의 제안값과 Meyerhof(q$_{cr}$=(B/2H+$\pi$/2)$_{cu}$)의 제안값에 근접하여 q$_{cr}$=2.78$_{cu}$값을 나타냈고, 극한하중은 Prandtl의 제안값에 근접하여 q$_{ult}$=4.84$_{cu}$값을 나타냈다. 측방유동압은 Matsui.Hong의 이론식에 의해서 산정함이 비교적 적절하며, 측방유동압의 최대값은 토층두께(H)의 0.3H 부근에서 발생하였으며, 복합형과 Poulos의 분포형태 및 오염되지 않는 연약점토(CL, CH)지반 보다 지표면측으로 상승하여 발생하였다. 안정관리방법은 지반의 측방유동에 의한 소성변위량을 많이 이용하고 있는 부영.교본, 자전.관구, 송미.천촌 등의 안정관리도에 적용한 결과 송미.천촌의{S$_{v}$-(Y$_{m}$/S$_{v}$)}관리도와 자전.관구의 {(q/Y$_{m}$)-q}관리도에서 얻어진 극한하중은 하중-침하량곡선 (q-S$_{v}$)에서 얻어진 극한하중 보다 적은 경향을 나타냈다.

• 자원환경지질
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• 제34권6호
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• pp.523-537
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• 2001

운정동위생매립장 입구부근의 잡용수가 유입되는 지점의 하천수는 주변 하천수에 비하여 pH, EC, turbidity, TDS, NaCl(%) 등이 높게 나타나고 있으며, 유기물의 부화로 인한 낮은 DO가 관측되어 매립자의 잡용수에 의한 오염을 시사하고 있다. 잡용수가 합류한 하천에 인접한 C 지점의 지하수에서 EC, TDS, NaCl(%) 등이 높게 나타나고 있으며, A 와 F 지점의 지하수에서도 B ,D , 그리고 E 지점의 지하수에 비하여 이러한 특성들이 높게 나타나는 특징을 보인다. 특히 이들 지하수는 piper diagram에서도 공통적으로 Na-Cl형으로 분류되어 운정동위생매립장의 침출수와 잡용수에 의한 오염을 강력하게 지시하고 있다. 연구지역의 지하수와 하천수 오염특성은 건기인 겨울철시료에 비하여 우기인 여름철시료에서 더 높게 나타나고 있음을 확인하였다. 지하수와 하천수에 대한 요인분석결과, 침출수중의 함량이 높게 나타나는 원소들(Ca, Ma, Na, K, $Cl­^{-}$­, $SO_4^{2-}$, $F­^{-}$)의 명료한 수반관계를 확인하였으며 이들을 매립장 주변 수계의 오염지시자로 활용할 수 있을 것이다.

• 한국산림과학회지
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• 제80권2호
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• pp.210-219
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• 1991

P-V 곡선법(曲線法)을 적용(適用)하여 20종(種)의 낙엽활엽수(落葉闊葉樹)에 대한 내건성진단(耐乾性診斷)을 하였다. 엽(葉)의 수분특성인자(水分特性因子) 중 내건성판별(耐乾性判別)에 적합(適合)한 인자(因子)는 최대포수시(最大飽水時)의 삼투(滲透)포텐셜 (${\Psi}_0{^{sat}}$), 초기원형질분리점(初期原形質分離點)의 삼투(滲透)포텐셜(${\Psi}_0{^{tlp}}$), 세포막(細胞膜)의 최대탄성계수(最大彈性係數)($E_{max}$), 초기원형질분리점(初期原形質分離點)의 상대함수율(相對含水率)($RWC^{tlp}$)였으며, 그 밖에 상대함수율(相對含水率)(FWC)와 워터포텐셜(${\Psi}_L$)과의 관계, 팽압(膨壓)($P_{vat}$)과 ${\Psi}_L$과의 관계, H$\ddot{o}$fler diagram등의 그림을 내건성진단(耐乾性診斷)에 사용하였다. 이와같은 수분특성인자(水分特性因子)로 고찰(考察)할 때 물푸레나무, 상수리나무, 졸참나무, 갈참나무, 현사시등은 비교적 내건성(耐乾性)이 높은 수종(樹種)으로, 들메나무, 자작나무, 이태리포플러, 음나무, 서어나무, 까치박달, 산벚나무, 개벚나무, 층층나무등은 비교적 내건성(耐乾性)이 약(弱)한 수종(樹種)으로, 그리고 신갈나무, 고로쇠, 복자기, 당단풍, 느릅나무, 느티나무등은 중간(中間) 수종(樹種)으로 판별(判別)되었다.

• 한국식품영양과학회지
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• 제19권3호
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• pp.263-269
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• 1990

Aqueous solution pigment produced by Steptomyces californicus KS-89 showed a vivid bluish purple pigment and purified by silica gel column chromatography. The pigment indicated a deep purple color zone by the C. I. E chromatic diagram and showed UV absorption maxima at 575nm. The color intensity in aqueous solution was fairly stable in the ranges of pH5-8 and was not affected by UV light however sometimes it had faded slightly by the heat. It was possible to prevent significantly by the addition of metal salt. Especially this pigment has no mutagenicity and antitumor activity and it appears to be devoid of antibiotic activity.