• Korean Journal of Environmental Biology
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• v.30 no.3
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• pp.272-279
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• 2012

This was the second study on the ecological characteristics of the epiphytes on seagrass leaf. The objective of this study was to understand the variation of epiphytes on seagrass leaf depending on the change of physico-chemical factors such as salinity, nutrients, and etc. This study showed the four results. 1) The eelgrass growth was influenced by water temperature, suggesting the positive correlation between eelgrass growth and water temperature. 2) The epiphytes growth on seagrass leaves did not show the correlation with water temperature, but negatively correlated with salinity. 3) The eelgrass growth decreased when the concentraion of nitrogen increased. 4) However, loads of epiphytes increased when the concentration of total nitogen (TN), nitrate ($NO_3^-$), and nitrite ($NO_2^-$) were high. This increase of epiphytes growth could be suggested in the cause-effect pathway of nutrient enrichment leading to seagrasses loss.

• Journal of the Mineralogical Society of Korea
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• v.17 no.1
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• pp.23-35
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• 2004

The weathering characteristics of periodically submerged sedimentary rocks in the Sayeon dam, Ulsan was examined by field work, electron probe micro-analysis, X-ray diffraction, and X-ray fluorescence spectrometry. Analysis of fracture zone and exfoliation showed the submerged sedimentary rocks have undergone severe mechanical weathering. Mechanical weathering in the water-rock interface accelerated chemical weathering, such as dissolution and alteration of the most of minerals except for quartz in the weathering zone. The dissolution of carbonates specially calcite, is remarkable creating the cavities, whereas formation of minerals including clay minerals is not active. The sedimentary rocks have been periodically submerged for a certain period of time, and have repeated freezing and thawing. This mechanical weathering favored infiltration, which accelerated mineral dissolution. The high content of easily soluble carbonate of the sedimentary rocks is likely the major cause of intense chemical weathering. The dissolved elements within the infiltrated water interrupted the occurrence of clay and weathering minerals, and expend fractures by infiltrated water accelerated weathering process.

• Membrane and Water Treatment
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• v.9 no.3
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• pp.181-188
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• 2018

A sidestream contains the filtrate or concentrate from the belt filter press, filter backwash and supernatant from sludge digesters. The sidestream flow, which heads back into the sewage treatment train, is about 1-3% less than the influent flow. However, the sidestream can increase the nutrient load since it contains high concentrations of phosphorus and nitrogen. In this study, the removal of PO4-P with organic matter characteristics and bacteriological changes during the sidestream treatment via ladle furnace (LF) slag was investigated. The sidestream used in this study consisted of 11-14% PO4-P and 3.2-3.6% soluble chemical oxygen demand in influent loading rates. LF slag, which had a relatively high $Ca^{2+}$ release compared to other slags, was used to remove $PO_4-P$ from the sidestream. The phosphate removal rates increased as the slag particle size decreased 19.1% (2.0-4.0 mm, 25.2% (1.0-2.0 mm) and 79.9% (0.5-1.0 mm). The removal rates of dissolved organic carbon, soluble chemical oxygen demand, color and aromatic organic matter ($UV_{254}$) were 17.6, 41.7, 90.2 and 77.3%, respectively. Fluorescence excitation-emission matrices and liquid chromatography-organic carbon detection demonstrated that the sidestream treatment via LF slag was effective in the removal of biopolymers. However, the removal of dissolved organic matter was not significant during the treatment. The intact bacterial biomass decreased from $1.64{\times}10^8cells/mL$ to $1.05{\times}10^8cells/mL$. The use of LF slag was effective for the removal of phosphate and the removal efficiency of phosphate was greater than 80% for up to 100 bed volumes.

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1047-1053
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• 2009

The future use of hydrogen as an energy source is expected to increase on account of its environmentally friendliness. In order to enhance the production of hydrogen, Pd ions (0.01, 0.05, 0.1, and 0.5 mol%) were incorporated $TiO_2$ (Pd-$TiO_2$) and used as a photocatalyst. The UV-visible absorbance decreased with increasing level of palladium incorporation without a wavelength shift. Although all the absorption plots showed excitation characteristics, there was an asymmetric tail observed towards a higher wavelength caused by scattering. However, the intensity of the photoluminescence (PL) curves of Pd-$TiO_2$ was smaller, with the smallest case being observed at 0.1 and 0.5 mol% Pd-$TiO_2$, which was attributedto recombination between the excited electrons and holes. Based on these optical characteristics, the evolution of $H_2$ from methanol/water (1:1) photo-splitting over Pd-$TiO_2$ in the liquid system was enhanced, compared with that over pure $TiO_2$. In particular, 2.4 mL of $H_2$ gas was produced after 8 h when 0.5 g of a 1.0 mol% Pd-$TiO_2$ catalyst was used. $H_2$ was stably evolved even after 28 h without catalytic deactivation, and the amount of $H_2$ produced reached 14.5 mL after 28 h. This is in contrast to the case of the Pd 0.1 mol% impregnated $TiO_2$ of $H_2$ evolution of 17.5 mL due to the more decreasedelectron-hole recombination.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.1
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• pp.65-69
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• 2005

We have developed a new method of manufacturing salts by horizontal spray drying technique, using the concentrated deep ocean water after desalination processes. We studied the chemical characteristics of the spray-dried salts. Sodium content in the spray salts is $28.4\%$, which is $10-30\%$ lower than that of bay salts, bamboo salts and boiling salts $(32-38.2\%)$. However, the contents of magnesium, potassium and calcium of the spray salts are 2.5 times, 3 times and 4.5 times higher relative to those of bay salts, respectively. On the one hand, sulfur content in spray salts is 14 times lower than those of bay salts, which is caused by their volatilization during spray and vaporization of the concentrated seawater. Enrichment factors of Mg (0.8), K (0.9) and Ca (1.0) in the spray salts are relatively higher than those in bay salt (0.2-0.3), bamboo salt (0.15-0.4) and boiled salt (0.4-0.7), respectively. On the contrary, enrichment factor of sulfur in spray salts is observed to be 0.07, which is considerably lower than those in other salts (0.3-0.7). It means that the minerals like Mg, K and Ca can be well conserved from seawater to salts through spray drying techniques, while volatile elements like sulfur, lead, mercury and organic compounds can be easily removed from seawater via spray and heating processes.

• Membrane Journal
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• v.15 no.2
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• pp.105-113
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• 2005

Silica membranes were prepared on a porous metal sheet by ultrasonic spray pyrolysis method for gas separation at high temperatures. In order to improve the permselectivity, silica was deposited in the sol-gel derived $silica/\gamma-alumina$ intermediate layer by pyrolysis of tetraethyl orthosilicate (TEOS) at 873 K. The pyrolysis with forced cross flow through the porous wall of the support was very effective in plugging mesopores, Knudsen diffusion regime, that were left unplugged in the membranes. At permeation temperature of 523 K, the silica/alumina composite membrane showed $H_2/N_2$ and water/methanol selectivity as high as 17 and 16, respectively, by molecular sieve effect.

• Membrane Journal
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• v.18 no.4
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• pp.274-281
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• 2008

Covalent-crosslinked sulfonated poly(arylene ether sulfone) (SPAES) copolymers were synthesized copolymerization technique and additionally crosslinked with divinylbenzene (DVB). To optimize the reaction condition, a concentration of crosslinking agent and a reaction time were varied in the ranges of $30{\sim}90\;v/v%$ and $30{\sim}720\;min$. The properties of the crosslinked membranes were investigated by SEM, TGA and the measurement of proton conductivity. It was found that the proton conductivity of crosslinked membranes decreased depending on a degree of crosslinking while water uptake and methanol permeability reduced.

• Journal of Korean Society on Water Environment
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• v.23 no.1
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• pp.111-121
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• 2007

The experimental design and response surface methodologies haven been applied to the investigation of the chemical coagulation of livestock wastewater. The chemical coagulation reactions were mathematically described as a function of parameters raping mixing (rpm) of chemical coagulation ($X_1$), slow mixing (rpm) of chemical coagulation ($X_2$), $FeCl_3 $ concentration (mg/L) ($X_3$) and pH ($X_4$) being modeled by use of the central composite design. Empirical models were developed to describe relationship between the experimental variables and response. Statistical analysis indicates that three factors ($X_1$: raping mixing (rpm), $X_2$: slow mixing (rpm), $X_3$: $FeCl_3 $ concentration (mg/L) on the linear term (main effect), slow mixing (rpm) (${X_2}^2$) on the non-linear term (quadratic), and two factors ($X_1-X_3$, $X_2-X_3$) on the non-linear term (cross-product) had significant effects, respectively. The estimated ridge of maximum responses and optimal conditions for CODcr using canonical analysis was 87.44% ($X_1$: 229 rpm, $X_2$: 51 rpm, $X_3$: 877 mg/L, $X_4$: 4.3). To confirm this optimum condition, three additional experiments were performed and the mean CODcr removal (%) and concentration (mg/L) with a standard deviation of $87{\pm}1.2%$ ($576{\pm}34ppm$) were obtained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.163-170
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• 2007

To evaluate on the applicability of Chemical Compaction Pile (CCP) method to weak soil improvement, two kinds of testing chambers were fabricated and the changes of water content and shear stress associated with soil types, ages and distances from the center of pile were measured with different mixing proportions of CCP such as bottom ash, lime powder and added admixture. As results of test, it was noted that water content and shear stress of ground are mainly affected by the amount of lime powder and increase of the amount corresponds to rapid improvement of soil. And the improvement depended greatly on the types of soil also. It was finally found that CCP developed can be applicable to bearing pile as well as soil improvement since CCP has a bearing capacity enough to carry loads.

• Advances in concrete construction
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• v.10 no.5
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• pp.381-391
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• 2020

This study aimed to develop reference materials (RMs) for mortar that can simulate the initial flow characteristics with constant quality over a long period. Through the previous research on the development of RMs for cement paste, the combination of limestone, glycerol, and water was used as the basic matrix for developing RMs for mortar in this study. In addition, glass beads of three particle sizes (0.5, 1.0, and 2.0 mm) and ISO standard sand were selected as tentative candidates to derive fine aggregate substitutes. The mixture of glass beads could simulate the initial flow characteristics of mortar, but under the same mixing ratio, replicates showed an unstable tendency to indicate inconsistent values due to the generation of electrostatic properties between materials and equipment. On the other hand, the mixture using ISO standard Sand not only simulates the constant flow characteristics for a long period of time, but also shows stable results with little error in replicates. Therefore, limestone, glycerol, ISO standard sand, and water were finally determined as components that met the required properties of RMs for mortar. The effect of each component on the flow characteristics of RMs was analyzed. It was found that glycerol increased the cohesion between the particles of standard sand, resulting in a constant increase both in the plastic viscosity and yield stress. Both limestone and standard sand had a dominant effect on the yield stress. The relationships between various mortar mixing ratios and the corresponding mixing ratios of RMs were established. In addition, the results of the verification experiment showed that the rheological properties of the RMs obtained through the relationships correlated with various water/cement ratios and the fine aggregate volume fractions of mortar obtained with same manner. In other words, the RMs for mortar developed in this study can be used as standard samples because they can simulate the initial flow characteristics of mortar of various mixing ratios for a long period without any chemical changes.