• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.5
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• pp.179-186
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• 2007

Single crystal $CdGa_2Se_4$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with the hot wall epitaxy(HWE) system by evaporating the polycrystal source of $CdGa_2Se_4$ at $630^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of single crystal $CdGa_2Se_4$ thin films measured with Hall effect by van der Pauw method are $8.27{\times}10^{17}cm^{-3},\;345cm^2/V{\cdot}s$ at 293 K, respectively. The photocurrent and the absorption spectra of $CdGa_2Se_4/SI$(Semi-Insulated) GaAs(100) are measured ranging from 293 K to 10 K. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation $E_g(T)=2.6400eV-(7.721{\times}10^{-4}eV/K)T^2/(T+399K)$. Using the photocurrent spectra and the Hopfield quasicubic model, the crystal field energy(${\Delta}cr$) and the spin-orbit splitting energy(${\Delta}so$) far the valence band of the $CdGa_2Se_4$ have been estimated to be 106.5 meV and 418.9 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-},\;B_{1^-},\;and\;C_{11}-exciton$ peaks.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.1
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• pp.21-30
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• 1991

In Summer, oxygen-deficient water masses were developed extensively in the closed eutrophic bays such as Chinhae Bay which results in mass mortality of marine organisms and severe decrease the production of the bay every year. Under the circumstances, this study was performed to investigate the oxygen depletion relating to eutrophication, and also to evaluate self-purfication capacity of Buk Bay by dissolved oxygen mass balance in 1988. The mean concentration of total inorganic nitrogen, phosphate phosphorus and chlorophyll-a were $11.06{\mu}g-at/l,\;0.80{\mu}g-at/l\;and\;1.11mg/m^3$ respectively, which were over eutrophication criteria. Oxygen-deficient water mass was formed in July with the minimum concentration of 2.08ml/l(mean) at the bottom of all stations and recovered slowly in August. The decay and reaeration coefficient calculated from dissloved oxygen sag curve were 0.222/day and 0.018ml/l/day, respectively. To maintain above 4ml/l of oxygen to prevent oxygen-deficient water mass, it is recommendable to supply as much as 0.856ml/l/day of dissolved oxygen or should be reduced the same mass loading of BOD from watershed by the construction of wastewater treatment plant.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.6
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• pp.921-925
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• 2003

To control blood glucose level as close to normal is the major goal of treatment of diabetes mellitus. $\alpha$-glucosidase is the enzyme to digest dietary carbohydrate and inhibition of $\alpha$-glucosidase could suppress postprandial hyperglycemia. The methanol extract of soybean sprout was tested for the inhibitory activities against $\alpha$-glucosidase in vitro. Soybean sprout extract inhibited yeast $\alpha$-glucosidase activity by 24.5% at the concentration of 5 mg/mL. The methanol extract of soybean sprout was subsequently subjected to sequential fractionation with hexane, ethyl acetate, butanol and water. Among the fractions tested ethyl acetate-soluble fraction showed relatively strong inhibition against $\alpha$-glucosidase by 36.3% at the concentration of 5 mg/mL. Acarbose, standard $\alpha$-glucosidase inhibitor, inhibited $\alpha$-glucosidase activity by 40.1%. The ability of soybean sprout extract to lower postprandial glucose was studied in streptozotocin-induced diabetic rats. Starch solution (1 g/kg) with and without the methanol extract of soybean sprout (500 mg/kg) was administered to diabetic rats after an overnight-fast by gastric intubation. A single oral dose of soybean sprout extract inhibited the increase in blood glucose levels significantly at 60, 90, 120, 180 min (p<0.05) and decreased incremental response areas under the glycemic response curve significantly (p<0.05). These results suggest that soybean sprout might exert hypoglycemic effect by inhibiting $\alpha$-glucosidase activity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.609-615
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• 2005

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10 kHz decrease from 550 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kV/cm decrease from $1.64\times10^{-6}$ to $1.26\times10^{-7}\;A/cm^2$. In the results of hysteresis loops measured at $\pm170kV/cm$, the remanent polarization and the coercive field increase from 6.62 to $12.86{\mu}C/cm^2$ and from 32.15 to 56.45 kV/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying $10^9$ square pulses with $\pm5V$, the remanent polarization of the PLZT (10/40/60) thin film decreases $50\%$ from the initial state while that of the PLZT (10/0/100) thin film decreases $28\%$. In the results of retention measurements of 10s s, the remanent polarization of the PLZT (10/0/100) thin film dec.eases only $10\%$ from the initial state, while that of the PLZT (10/40/60) thin film decreases $40\%$.

• Resources Recycling
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• v.14 no.4 s.66
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• pp.47-52
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• 2005

Carbonate species in aqueous solution play an important role in the determination of chemical properties of water in relation with alkalinity, buffer capacity, biological productivity, and so on. These compounds also have reactive characteristics such as interphasal reactions between solid, liquid, and gas phases. In the absence of solid materials, the total amount and relative abundance of each carbonate species are directly influenced by the partial pressure of $CO_2$ gas in the atmosphere, which in turn significantly affects the properties of aquatic system. In the water/wastewater treatment process along with the wastes treatment and recycling process which occurring in aquatic environment, it is essential to figure out its characteristics for their optimization and one of its most influential features upon these processes is determined by carbonate species. To understand the fundamental aspect of the relationship between the partial pressure of $CO_2$ gas and chemical features of water, especially pH, the working partial pressure of pure $CO_2$ gas that produced by contacting the dry ice with water has been estimated based on equilibrium calculation. The equilibrium constants for the dissociation ot carbonic acid were determined using van't Hoff equation and the distribution diagram of carbonate species according to the pH has been constructed to substantiate the results of equilibrium calculation. The estimated working partial pressure of pure $CO_2$ gas was found to be a function of the concentration of carbonates in solution, which suggesting that Prior evaluation of the working partial pressure of gas is essential for a better understanding of aquatic interactions.

• Journal of the Korean Electrochemical Society
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• v.6 no.4
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• pp.242-249
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• 2003

Zn electrode was widely used as an anode material in alkaline battery systems in highly concentrated KOH electrolyte, however it was well known that its cycle life is significantly shortened by growth of dendrite due to the high dissolution of $Zn(OH)_2$ and rapid electrochemical reaction. In this study when by the additives such as $Ca(OH)_2$, Citrate, tartrate and Gluconate were added to $40\%$ KOH electrolyte at solution temperature of $25^{\circ}C$ and the amount of $5wt\%\;Pb_3O_4$ was mixed to Zn electrode and then the effect of $Pb_3O_4$ and additives on the electrochemical behavior of Zn electrode was investigated by Potentiodynamic Polarization Curves, Cyclic Voltammetry, Accelerated Life Cycle lest, and SEM image analyses. The addition of $Pb_3O_4$ reduced the corrosion rate of Zn electrode. The corrosion potential of Zn electrode with $Pb_3O_4$ was higher or lower than that of pure Zn electrode however was not influenced practically to the open circuit voltage. And the addition of 4 type additives had an important role in improving both cycle life in accelerated cycle life test and corrosion resistance. Furthermore the additive of Tartrate indicated comparatively a good effect to corrosion resistance as well as charging-discharging property Improvement among those four type additives.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.973-977
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• 2013

These studies were attempted to investigate the change of microbial community of anode of microbial fuel cell using swine wastewater in the enrichment step with the lapse of time. Microbial fuel cells enriched by a 1 : 1 mixture of anaerobic digestive juices of the sewage treatment plant and livestock wastewater. Enrichment culture step was divided into three stages to indentify the microorganisms. It was separated by each lag phase, exponential phase, and stationary phase. These steps were determined by the change of the current value. The current after enrichment was generated about $0.84{\pm}0.06mA$. We were cut out the different 17 bands in the DGGE fingerprint gel to do sequencing. The bands which the concentration was increasing or newly appearing with the lapse of time were included for this study. In the lag and exponential phase, Clostridium, Rhodocyclaceae, Bacteriodetes, and Uncultured bacterium etc. were detected. There were in the stationary phase Geobacter sp., Rhodocyclaceae, Candidatus, Nitrospira, Flavobactriaceae and uncultured bacterium etc. Geobactor among microorganisms detected in this study is known as the Electrochemically active microorganisms. It may include electrochemically active microorganisms to be considered as electrical activity microorganisms.

• Analytical Science and Technology
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• v.15 no.4
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• pp.329-334
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• 2002

Tributyl phosphate(TBP) is used in solvent extraction process for radioactive waste. This compound may be degraded to dibutyl phosphate($DBP^-$), monobutyl phosphate($MBP^{2-}$) and ${PO_4}^{3-}$ by radioactive material. Amount of $DBP^-$ and $MBP^{2-}$ in TBP must be monitored because they production of these compounds means degradation of which leads to a decrease in the extraction yield. Retention behavior for $DBP^-$, $MBP^{2-}$, $F^-$, $Cl^-$, ${NO_2}^-$, ${NO_3}^-$, ${SO_4}^{2-}$ and ${PO_4}^{3-}$ are studied with AS4A-SC(Dionex) analytical column and $Na_2CO_3$/NaOH eluent by Ion chromatography. Optimum condition for these anions is 2 mM $Na_2CO_3$/1 mM NaOH eluent. All anions by this condition is well separated within 15min. Dynamic range is $10{\mu}g/mL$ - $100{\mu}g/mL$ for DBP and $5{\mu}g/mL$ - $50{\mu}g/mL$ for $MBP^{2-}$, respectively. The Detection limit for AS4A-SC are $1{\mu}g/mL$ for $DBP^-$ and $0.5{\mu}g/mL$ for $MBP^{2-}$ in this system with a $25{\mu}L$ sample loop.

• The Korean Journal of Pesticide Science
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• v.13 no.2
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• pp.79-86
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• 2009

In order to elucidate the residual characteristics of the insecticides, bifenthrin and imidacloprid, the pesticides were sprayed onto the squash and their residues were analyzed with GC-ECD and HPLC. Detection limits of the pesticides were $0.005\;mg;kg^{-1}$ and recoveries of bifenthrin and imidacloprid in squash were from 100.87 to 104.31 and from 79.71 to 92.54%, respectively. Half-lives of bifenthrin and imidacloprid in squash were from 1.8 to 2.9 and from 1.5 to 2.5 days, respectively. Initial concentration of bifenthrin and imidacloprid sprayed at the recommended rate and double rate of recommendation were less than their MRLs. And also, residueal concentrations of the pesticides were rapidly decreased in squash with time. At harvest, estimated daily intakes (EDIs) of the pesticides were less than 0.6% of their acceptable daily intakes (ADIs).

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.55-61
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• 2003

The objective of this study was to investigate the characteristics of nitrate removal by conducting the column test in order to see the performance of surfactant modified zeolite (SMZ) as a permeable reactive barrier material. The prediction of nitrate removal was tested using the one-dimensional advective-dispersive model fitted to the experimental breakthrough curve. A methodology for scaling up to in-situ permeable reactive barrier was also proposed. The breakthrough of nitrate in the column packed with SMZ was well predicted using linear equilibrium adsorption model. The breakthrough time and half-life obtained by breakthrough experiment with variation of flowrates were decreased with the increase of flowrates. When 10㎥/day of groundwater containing the 50 mg/l of nitrate is to be treated to satisfy the potable water quality criteria (10 mg/l) by SMZ reactive barrier, 300 tons of SMZ and about 6 years of breakthrough time will be required, suggesting that 165 million wons are needed as barrier material expenses in each 6 years besides the initial design and construction expenses and the minimal monitoring and maintenance expenses.