• Journal of Environmental Science International
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• v.13 no.12
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• pp.1089-1102
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• 2004

Seasonal variation of biogeochemical characteristics was determined in Lake Shihwa from October 2002 to August 2003. When the lake was artificially constructed for the freshwater reservoir in 1988, the development of the strong haline density stratification resulted in two-layered system in water column and hypoxic/anoxic environment prevailed in the bottom layer due to oxidation of accumulated organic matters in the lake. Recently, seawater flux to the lake through the sluice has been increased to improve water quality in the lake since 2000, but seasonal stratification and hypoxic bottom layer of the lake still developed in the summer due to the nature of artificially enclosed lake system. As the lake is still receiving tremendous amount of organic matters and other pollutants from neighboring streams during the rainy summer season, limited seawater flux sluicing into the lake may not be enough for the physical and biogeochemical mass balance especially in the summer. The excess of accumulated organic matters in the bottom layer apparently exhausted dissolved oxygen and affected biogeochemical distributions and processes of organic and inorganic compounds in the stratified two-layered environment in the summer. During the summer, ammonia and dissolved organic carbon remarkably increased in the bottom layer due to the hypoxic/anoxic condition in the bottom layer. Phosphate also increased as the result of benthic flux from the bottom sediment. Meanwhile, dissolved organic carbon showed the highest value at the upstream area and decreased along the salinity gradient in the lake. In addition to the sources from the upstream, autochthonous origin of particulate organic carbon from algal bloom in the lake might be more important for sustaining aggravated water quality and development of deteriorated bottom environment in the summer. The removal of trace metals could be attributed to scavenging by strong insoluble metal-sulfide compounds in the hypoxic/anoxic bottom layer in the summer.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.527-534
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• 2006

The purpose of this study is the development of more effective filter-type polymer adsorbent for removal of anionic pollutants from wastewater. In order to synthesize the polymer adsorbent that possesses anionic exchangeable function, carboxyl(-COOH) group of PP-g-AA nonwoven fabric was converted into amine($-NH_2$) group by the chemical modification using diethylene triamine(DETA). FT-IR data indicate that amine group was introduced into PP-g-AA through amidation of grafted acrylic acid by reaction with DETA. The degree of amination increased with increase in the reaction time and temperature of the chemical modification process, and was significantly improved by the pre-swelling treatment of PP-g-AA with solvent and addition of metal chlorides as a catalyst in following order as $NH_4OH>MeOH{\geq}HCl{\geq}H_2O\;and\;AlCl_3>FeCl_3{\geq}SnCl_2{\gg}ZnCl_2{\geq}FeCl_2$, respectively. However, the addition of catalyst limited the reusability of DETA, hence was less useful from the viewpoint of cost effectiveness and waste management. The anion exchange capacity of the aminated PP-g-AA(PP-g-AA-Am) increased with increase in the degree of amination, but it reached maximum value at the degree of amination as about $50{\sim}60%$. The anion exchange capacity of PP-g-AA-Am was higher than those of commercial anion resins.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.169-169
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• 2008

To keep pace with scaling trends of CMOS technologies, high-k metal oxides are to be introduced. Due to their high permittivity, high-k materials can achieve the required capacitance with stacks of higher physical thickness to reduce the leakage current through the scaled gate oxide, which make it become much more promising materials to instead of $SiO_2$. As further studying on high-k, an understanding of the relation between the etch characteristics of high-k dielectric materials and plasma properties is required for the low damaged removal process to match standard processing procedure. There are some reports on the dry etching of different high-k materials in ICP and ECR plasma with various plasma parameters, such as different gas combinations ($Cl_2$, $Cl_2/BCl_3$, $Cl_2$/Ar, $SF_6$/Ar, and $CH_4/H_2$/Ar etc). Understanding of the complex behavior of particles at surfaces requires detailed knowledge of both macroscopic and microscopic processes that take place; also certain processes depend critically on temperature and gas pressure. The choice of $BCl_3$ as the chemically active gas results from the fact that it is widely used for the etching o the materials covered by the native oxides due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. In this study, the surface reactions and the etch rate of $Al_2O_3$ films in $BCl_3/Cl_2$/Ar plasma were investigated in an inductively coupled plasma(ICP) reactor in terms of the gas mixing ratio, RF power, DC bias and chamber pressure. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by AFM and SEM. The chemical states of film was investigated using X-ray photoelectron spectroscopy (XPS), which confirmed the existence of nonvolatile etch byproducts.

• Resources Recycling
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• v.16 no.6
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• pp.3-9
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• 2007

Although the ferrous material was separated by the magnetic separation before the incineration process, the municipal solid waste incineration bottom ash generated during incinerator in metropolitan area consists of many iron products which account for about $3{\sim}11%$ as well as ceramics and glasses. The formation of $NiFe_2O_4$ and $FeCr_2O_4$ with a $Fe_3O_4-Fe_2O_3$ (similar to pure Fe) on the surface of iron product was found during air-annealing in the incinerator at $1000^{\circ}C$, because Ni and Cr has a chemical attraction about iron is using to coat with Ni and Cr metals for poish or to prevent corrosion. Therefore, Fe-Ni Cr oxide can be formed on durface of the iron product and it can be separated from bottom ash through the magnetic separation. So, in this study, the separation ratio of heavy metals as magnetic separation and mineralogical formation of Fe-ion(heavy metal) in ferrous metals corroded were investigated. As the result, the separation ratio of Ni and Cr based on particle sizes accounted for about $45{\sim}50%$, and Cu and Pb accounted for below 20%. Also, the leaching concentration of Ni and Cr in bottom ash separated by magnetic separation was lower than that in fresh bottom ash.

• Clean Technology
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• v.6 no.2
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• pp.121-127
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• 2000

There are several kinds of hazardous materials in incinerator flue gas, such as particulate matter, acid gas, heavy metal, dioxin, etc. The activated carbon adsorption is considered as one of the methods removing dioxin from flue gas. Without any additional equipment and facilities, the activated carbon was mixed with lime and sprayed in the semi-drying reactor of an incinerator and filtered in the bag filter, and its efficiency of removing hazardous organic material was investigated. 1,2-dichlorobenzene (o-DCB) was used as a precursor material of dioxin and the effects of the activated carbon amount, the operating temperature of the reactor, and the atomizer r.p.m were measured and analyzed. Experimental results showed that the optimum outlet temperature of the reactor was $145^{\circ}C$ considering the performance of the bag filter, and the adsorption performance improved with the increase of the atomizer r.p.m. Also the performance of removing o-DCB in the bag filter is higher than of the semi-drying reactor.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.165-173
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• 2006

Purpose: With gold electroforming system fir the double crown, the secondary crown is electroformed directly onto the primary crown. An even thick layer of high precision can be acquired. It is thought that the retention of electroformed outer crown is primarily acquired by the adhesive force (surface tension) through the saliva which is interposed between precisely fitted inner and outer crown. The purpose of this study was to investigate the effect of taper and surface area of inner crown on the retentive force of electroformed outer crown according to the presence of saliva. Materials and methods: 32 titanium inner crowns with cervical diameter of 8 mm and cone angles of 0, 2, 4, 6 degrees, which had same surface area by regulated height, were machined on a lathe. Another 32 titanium inner crowns with cone angles of 0, 2, 4, 6 degrees, which had doubled surface area by increased cervical diameter. were fabricated. Eight specimens of each group, for a total of 64 titanium inner crowns, were prepared. The electroformed outer crowns were fabricated directly on the inner crowns by using electroforming machine(GAMMAT free, Gramm Technik, Germany). The tertiary frameworks were waxed-up on the electroformed outer crown and cast using nonprecious alloy($Rexillium^(R)III,\;Jeneric^(R)/Pentronh^(R)$ Inc., USA). The cast metal frameworks were sandblasted with alubimium oxides and cemented using resin cement(Superbond C&B, Sun Medical Co., Japan) over the electroformed copings of each specimen. Then, artificial saliva($Taliva^(R)$, Halim Pharm. Co., Korea) was sprayed between the inner and outer crown, and they were connected under 5 kg force. The retentive force was measured by the universal testing machine(Tinius Olsen 1000, Tinius Olsen, USA) with a cross-head speed of 66.67 mm/sec. The direction of cross-head travel was exactly aligned with the path of removal of the respective specimens. This measurement procedures for retentive force of electroformed outer crown with artificial saliva were repeated in the same way without presence of artificial saliva. Results and Conclusion: The following conclusions were drawn: 1. The retentive force of electroformed outer crown was decreased according to increased taper of inner crown(P<.05). 2. The retentive force of electroformed outer crown showed no significant differences according to surface area and the presence of artificial saliva(P>.05).

• Korean Journal of Environmental Agriculture
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• v.6 no.2
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• pp.46-52
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• 1987

This study of adsorption and column percolation was conducted to examine the utilization of natural zeolite for the removal of heavy metals from waste water to compare with that of absorption activated carbon. The adsorption of heavy metals by natural zeolite was conformed to the Freundlich isotherm (1/n values: $0.12{\sim}0.45$, K values: $18.77{\sim}59.48$) and natural zeolite was turned out to be an effective adsorbent of heavy metals. At the same particle size and percolation velocity, zeolite adsorbed a greater amount of heavy metals was adsorbed on natural zeolite than activated carbon. The smaller the particle size, the more heavy metals that were adsorbed. It was postulated that the most effective size as an adsorbent of heavy metals from waste water ranged from 0.5 to 2.0mm. The slower the percolation velocity that of the heavy metal solution in column, the more heavy metals were adsorbed. Natural zeolite in a single solution adsorbed more heavy metals than that in mixed solution, and the order of the adsorption amount on natural zeolite was Cu>Zn>Cd.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.291-298
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• 2016

Electrochemical water treatment process as a useful treatment method for the removal of non-degradable matter has been consistently studied for several decades. Key process of electrochemical water treatment are oxidation reaction from an anode and reduction from a cathode. In this study, the effect of pre-treatment methods in the insoluble electrode manufacturing process for the water treatment has been evaluated for the life time of electrode The results of this study showed that pre-treatment methods of a base metal such as surface roughness, clean method and interlayer formation influenced to life time of electrode when the same condition (catalyst electrode layer coating method and material system) was applied for pre-treatment methods. This study was conducted by using $IrO_2/Ti$ electrode In the test of sand-blasting process, an electrode manufactured by using sanding media of different sizes resulted in the most effective electrode life time when the size of alumina was used for $212{\sim}180{\mu}m$ praticle size (#80). The most effective method was considered using arc plasma in the additional roughness control and cleaning process, sputtering method to form Ta type interlayer formation process.

• Korean Journal of Microbiology
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• v.53 no.4
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• pp.251-256
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• 2017

Some rhizobacteria were isolated, that have copper resistance and can confer copper resistance to plants allowing growth under copper stress. Isolated strains Pseudomonas veronii MS1 and P. migulae MS2 produced 0.13 and 0.26 mmol/ml of siderophore, that is a metal-chelating agent, and also showed 64.6 and 77.9% of biosorption ability for Cu in 20 mg/L Cu solution, respectively. Copper can catalyze a formation of harmful free radicals, which may cause oxidative stress in organisms. Removal activity of 1,1-diphenyl-2-picryl hydrazyl radical and antioxidant capacity of strains MS1 and MS2 increased up to 82.6 and 78.1%, respectively compared to those of control at 24 h of incubation. They exhibited 7.10 and $6.42{\mu}mol$ ${\alpha}$-ketobutyrate mg/h of 1-aminocyclopropane-1-carboxylic acid deaminase activity, respectively, which reduced levels of stress hormone, ethylene in plants, and also produced indole-3-acetic acid and salicyclic acid that can help plant growth under abiotic stress. All these results indicated that these copper-resistant rhizobacteria could confer copper resistance and growth promotion to plants.

• Journal of the Korean Applied Science and Technology
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• v.38 no.5
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• pp.1302-1313
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• 2021

In this study, Gami-Sumiwon (GS; Cynanchi wilfordii R., Angelica gigantis R., Lycium chinense M., Betula platyphylla S., Cryptotympana atrata F. and Carthamus tinctorius L.) and/or Sinomenium acutum R. (SC) was extracted with 70% ethanol or water. And We investigated the antioxidant activity effect of GS±SC. The following experimental techniques were used to evaluate the antioxidant efficacy of GS±SC. HPLC chromatogram, heavy metal content, ABTS/DPPH radical scavenging analysis, SOD-like activity assay, FACS, and NO assay. As a result of the experiment, the sinomenine content was found to be higher in DW extracts, and decursin was found to be higher in 80% ethanol extracts. And, the amount of heavy metals in all extracts was below the standard value. ABTS, and DPPH radical scavenging activity was identified that GS±SC(EtOH) was found to have a higher scavenging activity than GS±SC(DW). But, SOD showed the opposite result. No cytotoxicity of GS was observed on Raw 264.7 cells at concentration of 1~100 ㎍/㎖. The ROS production was significantly decreased that GS±SC(DW) was found to have a higher scavenging activity than GS±SC(EtOH). However, NO production showed the opposite result. Looking at the results of SOD and ROS analysis, SC does not seem to have a function of prevention. SC is thought to have an effect on the removal of free radicals generated after oxidative stress. This result objectively confirmed the antioxidant effect of GS±SCs. We will continue to conduct in-depth research. Therefore, it is believed that the possibility of using GS±SCs as a functional material can be established. The more diverse the objectives, the higher the value of GS utilization is thought to be.