• Korean Journal of Microbiology
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• v.27 no.2
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• pp.130-138
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• 1989

Microbiological parameters such as bacterial biovolume and biomass in Soyang Reservoir was statistically analyzed with the physico-chemical enviromental factors. Analysis of correlation and multiple regression showed that temperature affects most of microbiological parameters. Variations of total bacterial number, total bacterial biovolume and saprophyte number were highly correlatd with the concentrations of chlorophyll a and pheophytin a. Bacterial production by the $^{3}H$-thymidine incorporation rate was largely affected by Seston. It suggests that microbiological factors such as bacterial biovolume and bacterial biomass were controled by the concentration of seston and distribution of phytoplankton which acts as carbon and energy source for the bacterial community in the water column of Soyang Reservoir.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.4
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• pp.309-316
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• 2001

Helianthus tuberosus has been known to inhibit the growth of weeds and other plants sharing its habitat. This study was conducted to identify the allelochemicals of Helianthus tuberosus which were extracted with water and solvents. Aqueous extracts of leaf, stem, root, tuber and tuber peel of Helianthus tuberosus except tuber did not show significant differences in phytotoxicity to alfalfa seedlings. It was considered that Helianthus tuberosus contained fewer or less potential water-soluble substances that were toxic to alfalfa. Methanol extract of leaves of Helianthus tuberosus was sequentially partitioned in increasing polarity with n-hexane, ethylacetate and n-butanol. Each extract had a yield of 148, 12, 15.7 and 9.5g, respectively. Inhibitory effects on germination of alfalfa seeds treated with four fractions were not significantly different. But the significant reductions on hypocotyl length were observed for all the solvent extracts. Among the four fractions, the ethylacetate fraction showed the most significant inhibition effect on bioassay with alfalfa. Further separation of the active ethylacetate fraction by open column chromatography led to the 25 subfractions. In bioassay of each sub-fraction with alfalfa seeds, sub-fraction No. 13 showed the most inhibitory effect on seedling growth. $^1$H NMR and gas chromatography-mass spectrometry analysis revealed that sub-fraction No. 13 was the mixture of straight-chain saturated fatty acids.

• Korean Journal of Food Science and Technology
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• v.22 no.7
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• pp.793-798
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• 1990

As a search for natural antioxidants, antioxidative fractions in pueraria root were extracted and identified using column chromatography, thin layer chromatography and high performance liquid chromatography. Components which have most effective antioxidative activities were futher identified by IR and GC/MS. The strongest antioxidative component of pueraria root methanol extract was identified as puerarin. Puerarin obtained from pueraria root was practically effective as antioxidant at the level of 100 ppm. Antioxidative activity of the puerarin was higher in linoleic acid-water system than in a linoleic acid substrate. Puerarin, daidzin and daidzein contents in pueraria root juice were 0.39%, 0.45% and 0,03%, respectively.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.172-176
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• 2006

Fe(III)-Coated Star Fish (ICSF) was prepared by reaction of calcined Star Fish (SF) with Fe(III) solution at an elevated temperature. To investigate the stability of ICSF at acidic condition, dissolution of Fe was studied at pH 2 as a function of time. Extracted iron was negligible over the entire reaction time. This stability test suggests the applicability of ICSF in the treatment of wastewater even at low pH. Adsorption capacity of Cu(II) onto SF and ICSF was investigated in a batch and a column test. In the pH-edge adsorption, adsorption of copper onto SF and ICSF was quite similar over the entire pH range due to the presence of an important amount of Fe in SF itself. From the adsorption isotherm obtained with variation of the concentration of Cu(II), ICSF showed 1.6 times greater adsorption capacity than SF. Also, ICSF showed a greater removal capacity of Cu(II) in the column test.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1324-1328
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• 2003

The simultaneous determination of anions ($SO_4 ^{2-},\;Cl^-,\;and\;NO_3^-$) and cations ($Na^+,\;NH^{4+},\;K^+,\;Mg^{2+},\;and\;Ca^{2+}$) in natural water obtained by Nakdong River waters system in Korea were performed by ion-exclusion/cationexchange chromatography with conductimetric detection. The stationary phase was a polymethacrylate-based weakly acidic cation-exchange resin column in the $H^+$-form and a weak-acid eluent. When using only a 1.4 mM sulfosalicylic acid/6 mM 18-crown-6 ether as an eluent, good resolution of both anions and cations, minimum time required for the separation, and satisfactory detection sensitivity were obtained in a reasonable time. The method was successfully applied to the simultaneous determination of anions and cations in natural waters.

• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1781-1784
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• 2003

Determination of Co(II) ion as a 4-(2-thiazolylazo)resorcinol(TAR) or 5-methyl-4-(2-thiazolylazo)resorcinol(5MTAR) chelate was accomplished by reversed-phase capillary high-performance liquid chromatography (RP-Capillary-HPLC) using a Vydac $C_4$ column and MeCN-water mixture as mobile phase. The effect of change in pH and MeCN percentage of the mobile phase on the retention factor, k and peak intensity were evaluated. It was found that 30% MeCN (v/v) of pH 5.60 or 7.20 was adequate as mobile phase when TAR or 5MTAR is used. Detection limit (D.L., S/N=3) in each case was $2.0\;{\times}\;10^{-7}$M (11.8 ppb) and $3.0\;{\times}\;10^{-7}$ M (17.7 ppb). The Co(II) ion in mineral and waste water was determined with the optimum column and mobile phase.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.22-28
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• 2006

The motion and wave drift forces of floating BBDB (backward-bent duct buoy) wave energy absorbers in regular waves are calculated, taking account of the oscillating surface-pressure due to the pressure drop in the air chamber above the oscillating water column, within the scope of the linear wave theory. A series of model tests has been conducted in order to order to verify the motion and time mean wave drift force reponses in regular waves at the ocean engineering basin, MOERI/KORDI. The pneumatic damping through an orifice-type duct for the BBDB wave energy device are deducted from experimental research. Numerical simulation for motion and drift force responses of the BBDB wave energy device, considering pneumatic damping coefficients, has been carried out, and the results are compared with those of model tests.

• KSBB Journal
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• v.16 no.4
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• pp.327-331
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• 2001

Catechin compounds from the Green tea cultivated in Bosung (Chollanamdo) were extracted using supercritical fluid and various additives, and analyzed by reversed-phase high performance liquid chromatography (RP-HPLC). The chromatographic column was packed with LiChrospher 100RP-18(15 $\mu$m), and water was used as the mobile phase with 0.05% phosphoric acid and acetonitrile. Gradient election was applied to separate EGCG by changing the mobile phase compositions. Comparing the extraction yield of three different types of supercritical fluids, pure CO$_2$, with additives of water and ethanol (5 wt,%), the extraction amount of EGCG was most abundant in the suprcritical CO$_2$with ethanol. However, more was extracted and pure higher purity was achieved by solvent extraction using ethanol.

• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.900-906
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• 2004

An RPLC-postcolumn detection method has been developed for the fluorimetric determination of dichloroacetamide (DCAD) in water. After ammonia and DCAD were separated on a $C_{18}$ nonpolar stationary phase with 2.5% methanol-0.02 M phosphate buffer at pH 3, the column eluant was reacted with post column reagents, o-phthaldialdehyde (OPA) and sulfite ion at pH 11.5, to produce a highly fluorescent isoindole fluorophore, which was measured with a fluorescence detector ( ${\lambda}_{ex}$ = 363 nm, ${\lambda}_{em}$ = 425 nm). With the optimized conditions for RPLC and the postcolumn derivatization, the calibration curve was found to be linear in the concentration ranges of 0.5 and 20 ${\mu}$M for DCAD, and the detection limit for DCAD was 0.18 ${\mu}$M (23${\mu}$g/L). This corresponded to 18 pmol per 100 ${\mu}$L injection volume for a signal-to-noise ratio of 3, and the repeatability and reproducibility of this method were 1.0% and 2.5% for five replicate analyzes of 2 ${\mu}$M DCAD, respectively. The degradation yields DCAD to ammonia were 94 and 99%, and the percent recoveries of DCAD from 4 and 6 ${\mu}$M DCAD-spiked tap water were shown mean more than 97%.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.47-52
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• 2010

The wave energy absorption efficiency and the first-order and the time-mean second-order wave loads of a three-dimensional bottom-mounted oscillating water column (OWC) chamber structure are studied. The potential problem is solved by making use of a hybrid Green integral equation associated with the finite-waterdepth free-surface Green function outside a twin chamber and the Rankine Green function inside taking account of the fluctuating air pressure inside the chamber. Numerical results of the primary wave energy converting efficiency and the oscillating and steady wave loads of a three-dimensional bottom-mounted OWC pilot plant have been presented.