• 콘크리트학회논문집
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• 제17권5호
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• pp.857-868
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• 2005

This paper deals with the accumulated damage in concrete structures due to the cyclic freeze-thaw as an environmental load. The cyclic ice body nucleation and growth processes in porous systems are affected by the thermo-physical and mass transport properties, and gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and diffusion of chloride ion effects are hard to be identified in tests, and there has been no analytic model for the combined degradations. The main objective is to determine the driving force and evaluate the reduced strength and stiffness by freeze-thaw. For the development of computational model of those coupled deterioration, micro-pore structure characterization, pore pressure based on the thermodynamic equilibrium, time and temperature dependent super-cooling with or without deicing salts, nonlinear-fracture constitutive relation for the evaluation of internal damage, and the effect of entrained air pores (EA) has been modeled numerically. As a result, the amount of ice volume with temperature dependent surface tensions, freezing pressure and resulting deformations, and cycle and temperature dependent pore volume has been calculated and compared with available test results. The developed computational program can be combined with DuCOM, which can calculate the early aged strength, heat of hydration, micro-pore volume, shrinkage, transportation of free water in concrete. Therefore, the developed model can be applied to evaluate those various practical degradation cases as well.

• Membrane and Water Treatment
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• 제6권2호
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• pp.113-126
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• 2015

Salinity gradient power (SGP) systems have strong potential to generate sustainable clean electricity for 24 hours. Here, we introduce a solid-salt pressure-retarded osmosis (PRO) system using crystal salt powders rather than seawater. Solid salts have advantages such as a small storage volume, controllable solubility, high Gibbs dissolution energy, and a single type of water intake, low pretreatment costs. The power densities with 3 M draw solutions were $11W/m^2$ with exothermic energy and $8.9W/m^2$ without at 35 bar using a HTI FO membrane (water permeability $A=0.375L\;m^{-2}h^{-1}bar^{-1}$). These empirical power densities are ~13% of the theoretical value.

• Journal of Microbiology and Biotechnology
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• 제12권2호
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• pp.209-216
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• 2002

Bacillus sp. A56 was studied, because of its high flocculating activity. The flocculating substance produced by this strain was purified by ethanol precipitation, cetylpyridinium chloride (CPC) precipitation, and gel permeation chromatography (GPC). The FT-IR spectrum of the purified bioflocculant, designated as BF-56, showed typical characteristics of polysaccharides. The non-sugar substituents, and sugar components of BF-56 containing glucose, fucose, glucuronic acid, and galactose in an approximate molar ratio of 2.76:1.10:1:0.12, suggested that it was a novel bioflocculant with an estimated molecular mass of over $7{\times}10^3$ kDa. Rheological analysis of BF-56 revealed that it was a pseudoplastic that had higher apparent viscosity rate at dilute concentrations than those of zooglan. The solution of bioflocculant BF-56 exhibited non-Newtonian characteristics and it was compatible to high concentrations of salts such as KCl, NaCl, $CaCl_2,\;or\;FeCl_3.$ The present results suggested strong possibility of bioflocculant BF-56 to be fully applicable to industries such as wastewater treatment.

• 한국환경보건학회지
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• 제14권1호
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• pp.33-38
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• 1988

Natural mineral water is generally quite different from ordinary drinking water due to its original nature and various properties. The complexity of natural mineral water requires, therefore, not only to identify its nature and proper characteristics, but also to classify them by a reasonable scientific basis of comparison. The study was concentrated on a possible classification technique to natural mineral waters by their constitutions and physico-ehemical properties. The classification was carried out by the computation of such numerical parameters as ionic equivalent percentage, electrolytic conductance or mobility, ionic molecular weight, molecular concentration, equivalent conductivity and degree of ionization in consideration of the determinative criteria as follows -particular single element or molecule -major components of natural waters as bicarbonate, sulphate, chloride,caloride, calcium, magnesium, and sodium -moleculat concentration related to blood osmotic pressure -water temperature at emergence from spring -contents of free carbon dioxide (CO2) -pH value of water -total dissolved solids or salts (NaCl) The results obtained proved out to be clearly distinguhhable from ordinary drinking water as far as concern natural mineral water as an example on the subject -simple water -bicarbonate-predominating water -cold spring -carbonated-non gaseous water -weak alkaline water -non saline water Putting these various results together, the sample turned out to be a kind of natural mineral water that can be used as a drinking water if microbiologically safe.

• 한국안전학회지
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• 제31권6호
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• pp.12-18
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• 2016

This paper describes an optimal design of electric snow melting mat on vulnerable walk zone. In order to design an optimal electric power of snow melting mat and protect pedestrians with a nonslip mat, with considering protection of environmental pollution from abusing of the de-icing salts added calcium chloride. We analyzed nine snow melting mats through verification experiment in the condition of $-5^{\circ}C$, depending on three different kinds of heating material, electric heating cable, carbon heating film and carbon textile film. As a consequence, the $150W/m^2$ carbon textile film mat for snow melting was identified as an optimal power input and functional performance for pedestrians' safety on vulnerable walk zone. It is expected that the $150W/m^2$ carbon textile film mat would be useful to reduce slip down accidents by human error.

• 한국미생물·생명공학회지
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• 제23권3호
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• pp.269-274
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• 1995

For the screening of a new functional exopolysaccharide, sugar composition and rheological properties of exopolysaccharide produced from Xanthomonas sp. EPS-1 were investigated. The average molecular weight of exopolysaccharide was determined to be approximately 2.l $\times$ 10$^{6}$ dalton. The new exopolysaccharide EPS-1 was composed of mannose, glucose, galactose and gluco- samine. IR analysis showed that the exopolysaccharide EPS-1 was assumed to be polymer with carbohydrates. NMR analysis showed that exopolysaccharide EPS-1 was presumed to be 4 units of sugar and trace of CH$_{3}$ group. Exopolysaccharide EPS-1 solution showed a characteristic of non-Newtonian fluid properties. At the concentration of 1.0%, the consistency index and the flow behavior index were shown at 10.8352 poise-sec and 0.4419, respectively. All dispersions were pseudoplastic fluids described accurately by Power-law model. Exopolysaccharide EPS-1 was highly viscous at low concentration, with good stability over a wide range of pH 5 to 13. The excellent compatibility of exopolysaccharide EPS-1 was represented with salts such as sodium chloride.

• Nuclear Engineering and Technology
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• 제43권3호
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• pp.195-204
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• 2011

The effects on pool boiling heat transfer of aqueous solutions of boric acid ($H_3BO_3$) and sodium chloride (NaCl) as working fluids have been studied. Borated and NaCl water were prepared by dissolving 0.5~5% volume concentration of boric acid and NaCl in distilled-deionized water. The pool boiling tests were conducted using $1{\times}1\;cm^2$ flat heaters at 1 atm. The critical heat flux (CHF) dramatically increased compared to boiling pure water. At the end of boiling tests it was observed that particles of boric acid and NaCl had deposited and formed a coating on the heater surface. The CHF enhancement and surface modification during boiling tests were very similar to those obtained from boiling with nanofluids. Additional experiments were carried out to investigate the reliability of the additives deposition in pure water. The boric acid and NaCl coatings disappeared after repeated boiling tests on the same surface due to the soluble nature of the coatings, thus CHF enhancement no longer existed. These results demonstrate that not only insoluble nanoparticles but also soluble salts can be deposited during boiling process and the deposited layer is solely responsible for significant CHF enhancement.

• 미생물학회지
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• 제13권1호
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• pp.37-44
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• 1975

As a basic study to elucidate nutritional physiology and composition of synthetic medium of red rotting bacteria, Erwinia carotovora, of ginseng, the effects of hydrogen ion concentration, various kinds of carbon sources, nitrogen source, micrometallic salts and it's concentration on the gorwth of the bacteria were investigated and the results were as follows. Optimal pH in the basal medium for the growth of the bacteria was 6.5. After incubation the pH in culture media was neutralized. Among the various kinds of carbon sources, sucrose, glucose mannitol, but organic acids were not utilized effectively as nutrients. After incubation the pH turned acidic. Alanine as organic nitrogen sources nad ammonium sulfate as inorganic nitrogen promoted the growth, but L-valine and sodium nitrite were the least effective. Ferric chloride 1.0mg/dl and ferrous sulfate 100mg/dl were the most effective as micrometallic sources. Control and boric acid were the least effective. New synthetic medium based on the above results was follows ; Alanine 1.0g, $KH_2PO_4$ 1.0g, sucrose 30.0g, $MgSo_4$ $7H_2$O 0.5g, $FeCl_36H_2$O 1.0mg thiamine 200.gamma.g, and distilled water 1000ml, pH6.5.

• 생명과학회지
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• 제15권4호
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• pp.578-583
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• 2005

Cell-free culture broth of marine halophilic bacterium, Kordia algicida was shown to possess specific algicidal ability against red tide organism, Cochlodinium polykrikides. Physiochemical characteristics of algicidal material originated in the bacterial culture broth were analyzed that its molecular weight was estimated to a 3,000 dalton and it was stable in heat and pH treatment. The algicidal fraction against C. polykrikoides obtained from gel permeable chromatography contained high concentration of ammonium ion as analyzed by ICP/Mass spectrum. C. polykrikoides by the fraction was quickly lysed within 1 min. It was shown that the effective concentration for algicide against C. polykrikoides was over 1mM of ammonium chloride. On the other hand, other metal ions presented in the algicidal fraction showed no algicidal effect against C. polykrikoides. In additon, ammonium ion exhibited species-specific killing spectrum for two species of red tide organisms, C. polykrikoides and Gymnodinium sanguieum. Therefore, further researches on the killing mechanism against C. polykrikoides exerted by ammonium ion, and subsequent development of replaceable algicidal materials will perform to provide useful tools for the control of red tide.

• Journal of Pharmaceutical Investigation
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• 제29권3호
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• pp.171-177
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• 1999

Lidocaine(2-Diethylaminoaceto-2', 6'-xylidide) was transdennally delivered by iontophoresis and the effect of enhancer on the delivery of lidocaine was studied. We delivered lidocaine through the skin of hairless mouse using diffusion cell and investigated the effect of the amount of cation salts such as sodium chloride, calcium acetate, zinc acetate and aluminum acetate on the drug delivery. The amounts of transported drugs and adsorbed metal ions were measured by HPLC(High Perfonnance Liquid Chromatography) and AAS(Atomic Absorption Spectrophotometry), respectively. The addition of zinc acetate and aluminum acetate greatly enhanced the delivery of lidocaine. The detection of two metal ions by AAS seemed to support the idea that the astringency effect of these ions were the main reason for the enhancement of transdermal delivery.