• Bulletin of the Korean Chemical Society
• /
• v.33 no.8
• /
• pp.2546-2552
• /
• 2012

A novel biguanide-functionalized $Fe_3O_4/SiO_2$ magnetite nanoparticle with a core-shell structure was developed for utilization as a heterogeneous organosuperbase in chemical transformations. The structural, surface, and magnetic characteristics of the nanosized catalyst were investigated by various techniques such as transmission electron microscopy (TEM), powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), elemental analyzer (EA), thermogravimetric analysis (TGA), $N_2$ adsorption-desorption (BET and BJH) and FT-IR. The biguanide-functionalized $Fe_3O_4/SiO_2$ nanoparticles showed a superpara-magnetic property with a saturation magnetization value of 46.7 emu/g, indicating great potential for application in magnetically separation technologies. In application point of view, the prepared catalyst was found to act as an efficient recoverable nanocatalyst in nitroaldol and domino Knoevenagel condensation/Michael addition/cyclization reactions in aqueous media under mild condition. Additionally, the catalyst was reused six times without significant degradation in catalytic activity and performance.

• Journal of the Korean institute of surface engineering
• /
• v.34 no.6
• /
• pp.531-536
• /
• 2001

Co-22 %Cr alloy films are promising for high-density perpendicular magnetic recording media with their perpendicular anisotropy and large coercivity of 3000 Oe. We observed that a self organized nano structure (SONS) of fine ferromagnetic Co-enriched phase and paramagnetic Cr-enriched phase appears inside the grain of Co-Cr magnetic alloy thin films at the elevated substrate temperature after do-sputtering. The periodic fine Co-enriched phase and Cr-enriched phase is the plate shape of 80 (equation omitted)-wide and 1000 (equation omitted)-long. Cr-enriched phases are located at the center of grains. We prepared 5000 (equation omitted) -thick Co-22 %Cr films on polyimide substrate with varying substrate temperature of $ 30^{\circ}C$, $ 150^{\circ}C$ ,200 $^{\circ}C$, $300^{\circ}C$, and $400^{\circ}C$, respectively. A transmission electron microscope equipped with energy dispersive X-ray analyzer is employed to observe the microstructure of each samples after Co-enri-ched phase are etched selectively. The self organized nano structure of Co-enriched and Cr-enriched lamellar is observed above the substrate temperture of $150^{\circ}C$. No compositional change is observed with substrate temperature. The compositional phase separation in self organized structure becomes clear as the substrate temperature increases. Our results implies that the self organized nano structure in Co-22 %Cr film is ideal for ultra high density recording media by recording selectively on Co-enri-ohed phase.

• Hwankyungkyoyuk
• /
• v.18 no.2 s.27
• /
• pp.1-13
• /
• 2005

The purpose of this study was to investigate the environmental awareness and attitude of elementary school teachers. For this study, 100 elementary school teachers from H graduate school of education were sampled. The results of this study were summarized as follows. First, the biggest concern of environmental problems were water-pollution and garbage problems by the lack of understanding about the environment and injudicious development. Second, most teachers recognized the need for environmental education and they answered that they were doing best to teach students with the main purpose of helping them develop values of environmental preservation. Third, most environmental education was carried out during class using current events and the emphasis on garbage separation and recycling. They also showed the lack of teaching materials and field trips for environmental education. Fourth, it appeared to come from media-oriented environmental education. Most teachers mainly used newspapers and visual materials. 1'hey were obtaining knowledge and information related to environmental education through the media. Since in-service teachers' conceptions could directly effect present education, it is necessary to establish a more systematic educational system for environmental education, for in-service elementary school teachers.

• Journal of the Korean Electrochemical Society
• /
• v.10 no.3
• /
• pp.159-168
• /
• 2007

An electrochemical study related to the redox characteristics of Ethyl-3-acetyl-6-methyl-1, 4-diphenyl-4, 3a-dihydro-1, 3, 4-triazolino[3, 4-a] pyrimidine-5-carboxylate ester and its derivatives (1a-f) and (2a-e) in nonaqueous solvents such as 1, 2-dichloroethane (DCE), dichloromethane (DCM), acetonitrile (AN), dimethylsulphoxide (DMSO) and tetrahydrofurane (THF) using $0.1\;mol\;dm^{-3}$ tetrabutylammonium perchlorate (TBAP) as a supporting electrolyte at platinum, glassy carbon and gold electrodes, has been performed using cyclic voltammetry (CV). Controlled potential electrolysis (CPE) is also carried out to elucidate the course of different electrochemical reactions through the separation and identification of the intermediates and final electrolysis products. The redox mechanism is suggested and proved. It was found that all the investigated compounds in all solvents are oxidized in a single irreversible one electron donating process following the well known pattern of the EC-mechanism to give a dimer. On the other hand, these compounds are reduced in a single irreversible one electron step to form the anion radical, which is basic enough to proton from the media forming the radical which undergoes tautomerization and then dimerization processes to give also another bis-compound through N-N linkage formation.

• Preventive Nutrition and Food Science
• /
• v.7 no.1
• /
• pp.28-32
• /
• 2002

A Micrococcus sp. producing catalase was isolated from soil, and a commercial-scathe cultivation and purification of catalase were conducted. The maximum catalase activity was about 103 BU/mL obtained after 46 hr of cultivation in a 30 L fermenter containing 2% glucose, 2% peptone, 4% yeast extract, and 0.5% NaCl. Soybean sauce, CSL (corn steep liquor), and yeast extract were also studied as media substitutes in the media 30 L fermenter. The optimum medium components for the production catalase were found to be 2% glucose, 4% soybean sauce, and 16% CSL. In a 18 kL fermenter, the stationary phase in the cell growth and maximum catalase activity (112 BU/mL) were reached after 46 hr of cultivation, which was the same result as in the 30 L fermenter. The catalase activity was purified with over 17 folds in four steps with a 33.6% yield. From 104,250 mg of protein after cell lysis, 1,966 mg of the purified enzyme with a specific activity of 192.7 kBU/mg was obtained. The residual activity with the addition of 10% NaCl exhibited more than 100%. The use of just NaCl produced a higher residual activity than combination of bencol (benzyldimethyl ammoniumchloride) and PG (propyleneglycol).

• Membrane and Water Treatment
• /
• v.10 no.2
• /
• pp.105-112
• /
• 2019

On the purpose of conform the more stringent government regulation for turbid stormwater from construction sites, the feasibility and availability of synthetic fiber placing after the conventional protection barrier were tested in this study. Initially, comparative work on the filtering performance of fiber media and conventional gravel filter was carried out, 27% higher filtration capacity was obtained under the similar operational conditions. The filter efficiency was about 20 to 52% with a varying filter depth of 5 to 15cm, presuming at extreme storm flow conditions (800-1500 m/day of filtration rates). Fiber filter was found to have a similar filtration prosperity as grain media; namely, the separation efficiency is directly and inversely proportional to filter depth and rate, respectively. The effects of filter aid (polyaluminium chloride) on filter performance was also investigated, it greatly affected the turbidity reduction at the dosage of 2 mg/L. At the time of breakthrough, a simple filter washing was carried out, herein, the solid recovery achieved over than 88% and greatly determined by operational parameters. Based on the operational data, the empirical models aimed for predicting filtration efficiency were established, which can effectively determine the required filter depth and filtration area in field.

• Journal of Environmental Health Sciences
• /
• v.21 no.3
• /
• pp.48-55
• /
• 1995

This study was performed to investigate the inhibitory effect of Aloe vera on the growth and aflatoxin production of Aspergillus parasiticus. Spore suspension of A. parasiticus ATCC 15517 was inoculated on the yeast-extract sucrose broth containing 0.1%, 0.5%, 1.0% and 10.0% of chloroform extract of Aloe vera and then incubated at 30$\circ$C for 7 days. Mycelial weight was 160.7 mg/5ml in control group and decreased by the addition of the extract with no significance. The mold caused decrease in pH of the media with and without the extract. pH in the group contained 10.0% of the extract showed significantly higher value of 5.10 than that of 4.90 in control group (p<0.05). Fluorescence spots of four aflatoxins were observed under the 365 nm of UV light after extraction of the media and TLC. In the result of separation and determination by HPLC, the aflatoxins were produced in the order of $B_1, G_1, B_2$ and $G_2$ in all groups. Production of aflatoxins $B_1, B_2$ and $G_1$ was reduced by the addition of the extract and decreased as amount of the extract increased. The production of aflatoxins $B_1$ and $B_2$ significantly reduced when the media contained more than 1.0% of the extract, and $G_1$ more than 0.5%, respectively(p<0.05). No reduction and no significant difference among groups were observed in case of aflatoxin $G_2$. With the above result, the extract of Aloe vera reduced the production of aflatoxin by A. parasiticus though it did not inhibit mycelial growth.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.4
• /
• pp.619-627
• /
• 2015

This paper presents a speech enhancement method using non-negative matrix factorization (NMF). In the training phase, each basis matrix of source signal is obtained from a proper database, and these basis matrices are utilized for the source separation. In this case, the performance of speech enhancement relies heavily on the basis matrix. The proposed method for which speech basis matrix is made a high reconstruction error for noise signal shows a better performance than the standard NMF which basis matrix is trained independently. For comparison, we propose another method, and evaluate one of previous method. In the experiment result, the performance is evaluated by perceptual evaluation speech quality and signal to distortion ratio, and the proposed method outperformed the other methods.

• Journal of Environmental Science International
• /
• v.15 no.10
• /
• pp.945-949
• /
• 2006

For a membrane bio-reactor, it is possible to fillet and separate activated sludge and effluent by head loss of centimeters, if non-woven fabric material is used as titration media. However, if non-woven fabric material is used to thicken high-concentration sludge, excessive sludge attachment causes the rapid decrease of flux. Mesh with fore sizes of $100{\mu}m,\;150{\mu}m,\;and\;200{\mu}m$ allows for easy separation of attached sludge. This study examined the possibility of mesh as filtration media. Existing close-flow filtration process, which requires maintaining sludge movement, makes It difficult to obtain high thickening rate. With a view of complementing this weakness, this study has made an experimental examination on how high-concentration sludge (about 3,000mg/L to 10,000mg/L) will be filtered and thickened when mesh module is submersed in the bio-reactor. Effluent flowed from the bottom of the bio-reactor by head loss of 65cm. In case of pore size of $100{\mu}m$, SS showed high recovery of 80% to 96%; therefore, it has been decided that mesh can be used as filtration media. Filtration lasted for more than 9 hours, until sludge with 9,000mg/L in MLSS concentration was thickened 9 times as dense. In the range from 3,610mg/L to 9,060mg/L in MLSS concentration, it was possible to obtain effluent with less than 2mg/L in MLSS concentration within 10 minutes.

• Journal of Environmental Impact Assessment
• /
• v.28 no.3
• /
• pp.332-345
• /
• 2019

The purpose of the study is to evaluate the treatability of contaminated groundwater with TPH and (or) $Cr^{6+}$. Laboratory scale tests were performed for oil/water separation, dissolved air flotation (DAF), coagulation and precipitation, and filtration with sand and activated carbon respectively. Two times of oil/water separation tests for total 40 minutes of separation or separating time shows 90.2 % of TPH removal rate. In case of DAF test for high TPH sample, the TPH removal rates were not varied significantly by the variation of microbubble size. However, tests for low TPH samples show that TPH removal rate increases as microbubbles are smaller. When coagulant was added to sample for DAF test, TPH removal rate was increased 12.3 %. SS removal rate by DAF was 97.9 % at $16-40{\mu}m$ and it was increased as the size of microbubble is reduced. Tests for coagulation and precipitation were performed to evaluate the removal of $Cr^{6+}$ in groundwater. The increase of $FeSO_4$ dosage increased $Cr^{6+}$ removal rate in the coagulation and precipitation process. As the amount of activated carbon in the filter media increased TPH removal rate in the filtration process. SS removal rate by the filtration was 96.7 % similar to the results of DAF process tests. The filtration process treats TPH and SS. Best design parameters are determined as the size of sand is $425-850{\mu}m$ and the ratio of activated carbon and sand is 50:50.