• Korean Journal of Microbiology
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• v.50 no.1
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• pp.73-83
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• 2014

The objective of the this study was to investigate the binding capacity and removal ability of lactic acid bacterial strains obtained from Korean soybean paste for mutagenic heterocyclic amines (HCAs) formed during cooking of protein-rich food at high temperature. Among 19 strains identified by carbohydrate fermentation and 16S rRNA sequencing, the live cell or cell-free culture supernatant of Lactobacillus acidophilus D11, Enterococcus faecium D12, Pediococcus acidilactici D19, L. acidophilus D38, Lactobacillus sakei D44, Enterococcus faecalis D66, and Lactobacillus plantarum D70 inhibited the mutagenesis caused by either 3-amino-1,4-dimethyl-5H-pyrido[4,3-b] indole (Trp-P-1) or 3-amino-1-methyl-5H-pyrido[4,3-b] indole (Trp-P-2) in Salmonella typhimurium TA98 and TA100. The bacterial cells of the isolated strains showed greater binding activity than the pure cell wall, exopolysaccharide, and pepetidoglycan. The carbohydrate moieties of the cell wall or protein molecules on the cell surface have a significant role in binding Trp-P-1 and Trp-P-2, since protease, heating, sodium metaperiodate, or acidic pH treatments significantly (P<0.05) reduced the binding efficacy of the tested bacteria. Addition of metal ions or sodium dodecyl sulfate decreased the binding ability of E. faecium D12, L. acidophilus D38, and E. faecalis D66. Therefore, the binding mechanisms of these strains may consist of ion-exchange and hydrophobic bonds. Especially, the high mutagen binding by L. acidophilus D38 and L. plantarum D70 may reduce the accumulation or absorption of Trp-P-1 and Trp-P-2 in the small intestine via increased excretion of a mutagen-bacteria complex.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.310-315
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• 2009

Perovskite-type ceramic powder, $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$, have been synthesized successfully by the citrate method. As a result of TGA for precursor, metal-citrate complex in precursor was decomposed in the temperature range of $150{\sim}650^{\circ}C$. XRD analysis showed the single perovskite structure was observed over $1,000^{\circ}C$ without impurities. Typical dense membrane with 1.6 mm thickness has been prepared using as-prepared powder by pressing unilaterally and sintering at $1,300^{\circ}C$. The electrical conductivity of $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ membrane increased with increasing temperature at atmosphere of air and then decreased over $600^{\circ}C$ due to oxygen loss from the crystal lattice. The oxygen flux of $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ membrane in the range of 700 to $950^{\circ}C$ increased with the increasing temperature from 0.045 to $0.415ml/cm^2{\cdot}min$. The activation energy for oxygen permeation was calculated to be 89.17 kJ/mol.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.535-541
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• 2017

On the basis of 200 ppm of Ag and 120 l/h of feed flow rate, we built a pilot plant of an ion exchange fiber system having an double tube type ion exchange chamber with strong base ion exchange fiber (FIVAN A-6) which was designed to replace fibers easily and to eliminate the need for a fixture. The following results were obtained for the double tube type of ion exchange fiber system with an ion exchange capacity of 4.6 meq/g for Ag. The adsorption process was operated in the range of 40~90 l/h after confirming the effect of the flow rate and, pH did not affect formation of complex ion of Ag in the range of pH 7~12. In the case of backwash process, the recovery rate of Ag was tested in the range of 60~120 l/h and comparative experiments were carried out using NaOH, $NH_4Cl$, and NaCl as the chemicals for backwash. Although the desorption time was shortened at higher concentration, the desorption efficiency per mol was lowered. Therefore, it was confirmed that the desorption time and the concentration should be well balanced to operate economically. The desorption pattern of the backwash process is slower than the adsorption process and takes a lot of time. The results showed that the Ag adsorption ratio was 99.5% or more and the Ag recovery ratio was 96% or more, and commercialization was possible.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.94-101
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• 2019

In this study, the FEM technique was applied to design the shape of the horn that transmits ultrasonic vibration energy to the base material, and the shape of the welding horn with a one-wavelength bar shape used in the 20kHz region was designed. The shape design of the horn was performed by applying the rod longitudinal vibration theory to Ansys APDL (Ansys Parametric Design Language). Twenty-five models were designed using the ratio of the area of the input and output surfaces of the vibration and the length of the horn to derive the appropriate horn shape. The horn was designed with a total length of 130mm, a step length of 65mm, and an output area of 28.79mm. The horn was fabricated using the optimized dimensions, and the vibration and displacement characteristics of the horn were evaluated using the measurement system. Finally, a uniform longitudinal step horn was designed, and more than 97.4% of the uniformity of the tip was secured. The amplitude ratio of the optimized horn was improved by 51%.

• Journal of the Korean Chemical Society
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• v.35 no.5
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• pp.545-552
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• 1991

A mercury ion-sensitive carbon-paste electrode (CPE) was constructed with l-sparteine. Mercury (II) ion was chemically deposited by the complexation with l-sparteine onto the CPE. The surface of CPEs was characterized by cyclic voltammetry and anodic stripping voltammetry in an acetate buffer solution, separately. Exposure of CPEs to acid solution could regenerate surface and reuse it for deposition. In 5 deposition/measurement/regeneration cycle, the response was reproducible and in licnear up to $2.0\;{\times}\;10^{-6}$ M with linear sweep voltammetry. In case of using the differential pulse technique, we have obtained the linear response up to $7.0 {\times}10^{-7}$ M with relative standard deviation of ${\pm}5.1$%. The detection limit was $5.0{\times}10^{-7}$ M for 20 minutes of the deposition. We have investigated the interference effect of various metal ions, which are expected to form the complex with ligand. Silver (I) ion of these has interfered with the analysis of Hg (II) ions. However, pretreatment of the silver (I) ion with potassium chloride led to no interference on the analysis of mercury ions in aqueous solution.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.11
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• pp.1054-1062
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• 2010

Oxidative coupling reactions of humic substances (HS) can be catalyzed by a variety of natural extracellular enzymes and metal oxides. In this study, property changes of HS induced by a natural enzyme, horseradish peroxidase (HRP), and the effect of it to microfiltration (MF) were investigated. PAHA was transformed by oxidative coupling reaction with HRP and hydrogen peroxide ($H_2O_2$), verifying the catalytic effects of the HRP. Size exclusion chromatography (SEC) revealed that weight-average molecular weight (MWw) of PAHA was proportionally increased with the dosages of HRP and $H_2O_2$, indicating the transform action of HS into larger and complex molecules. An increase in the conformational stability of HS was achieved through the promotion of intermolecular covalent bondings between heterogeneous humic molecules. Spectroscopic analysis (fluorescence and infrared spectroscopy) proved that functional groups were transformed by the reaction. Additionally, HS and transformed products were undergone microfiltration (MF) to examine the treatment potential of them in a water treatment facility. Original HS could not be removed by MF but larger molecules of transformed products could be removed. Meanwhile, transformed products caused more fouling on the filtration than original HS. This results proved that natural organic matter (NOM) can be removed by MF after its increase in molecular size by oxidative coupling reaction.

• Analytical Science and Technology
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• v.8 no.1
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• pp.1-7
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• 1995

Spectrophotometric determination of U(VI) and Th(IV) by Flow injection method is described. Chrome Azurol S forms water soluble complexes with U(VI) and Th(IV) in the presence of cethyltrimethylammonium bromide. The maximum adsorption of U(VI) and Th(IV) complexes are at 600nm with molar absorptivity of $2.3{\times}10^5Lmol^{-1}cm^{-1}$ and 611nm with molar absorptivity of $3.8{\times}10^5Lmol^{-1}cm^{-1}$ in acetate buffer medium having pH 5.0 and 5.5. The calibration curves of U(VI) and Th(IV) are linear over the range of 0.1~0.8ppm and the correlation coefficients are ca. 0.9960 and 0.9930 respectively. The detection limits(S/N) are 20ppb for U(VI) and 15ppb for Th(IV). The relative standard deviation are ${\pm}1.8%$ for U(VI) and ${\pm}2.1%$ for Th(IV). The sample throughput was ca. $50hr^{-1}$.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.108-108
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• 2009

Precipitation hardening nickel base alloys strengthened by intermetallic compounds are extensively used to manufacture on the components of the hot section of gas turbine engines. To ensure structural stability and maintenance of strength properties for a long time, nickel alloys are normally subjected to complex alloying with elements to form ${\gamma}'$(gamma prime). Such alloys have a limited weldability, are normally welded in high temperature. However, laser welding have a merit that applies in room temperature as easy control of welding parameter and heat input. In this study, $CO_2$ laser welding is applied on STS304 plate with good ductility and precipitation hardening nickel base alloy (GTD111DS) used blade material. Also, several welding parameters are applied on powder, power and travel speed. There are no cracks in Rene 80 and IN 625 powder when STS304 plate is used. But IN 625 powder has no cracks and Rene 80 have some cracks in welds with GTD111DS substrate. Adjusting of welding parameter is tried to apply Rene 80 having a good strength compare to IN 625. In the result of adjusted welding parameter, optimized welding parameters are set with low power, low feed rate and high welding speed. Tensile strength of GTD111DS substrate with Rene 80 powder is same and over than the one of base metal in room temp and high temp($760^{\circ}C$).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.144-154
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• 1999

Masan Bay is highly polluted by the discharge of large quantities of effluents from the industrial complex and domestic sewage of Masan City, Southeast Korea. Surface sediments from 9 stations were used for geochemical and foraminiferal analyses in order to investigate foraminiferal response to sedimentary pollution in the Bay. The heavy metal concentrations in sediments are relatively higher than those in Kyeonggi Bay and Daesan area, west coastal region of Korea. Zn, Cd, Pb, and As are more concentrated than in world average shale, indicating that the municipal and industrial effluents cause sediment contamination. Responses of benthic foraminifera to the sedimentary pollution effect document a degree of pollution in Masan Bay. The species number and diversity in Masan Bay had lower values than those in Gadeog Channel. In Masan Bay, agglutinated foraminifera are abundant and calcareous foraminiferal tests were frequently pyritized. Eggerella advena and Trochammina pacifica dominated at levels of pollution and could be opportunistic species. These data will provide a baseline for future assessments of environmental quality in Masan Bay.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.72-72
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• 2012

Lithium rechargeable batteries have been widely used as key power sources for portable devices for the last couple of decades. Their high energy density and power have allowed the proliferation of ever more complex portable devices such as cellular phones, laptops and PDA's. For larger scale applications, such as batteries in plug-in hybrid electric vehicles (PHEV) or power tools, higher standards of the battery, especially in term of the rate (power) capability and energy density, are required. In PHEV, the materials in the rechargeable battery must be able to charge and discharge (power capability) with sufficient speed to take advantage of regenerative braking and give the desirable power to accelerate the car. The driving mileage of the electric car is simply a function of the energy density of the batteries. Since the successful launch of recent Ni-MH (Nickel Metal Hydride)-based HEVs (Hybrid Electric Vehicles) in the market, there has been intense demand for the high power-capable Li battery with higher energy density and reduced cost to make HEV vehicles more efficient and reduce emissions. However, current Li rechargeable battery technology has to improve significantly to meet the requirements for HEV applications not to mention PHEV. In an effort to design and develop an advanced electrode material with high power and energy for Li rechargeable batteries, we approached to this in two different length scales - Atomic and Nano engineering of materials. In the atomic design of electrode materials, we have combined theoretical investigation using ab initio calculations with experimental realization. Based on fundamental understanding on Li diffusion, polaronic conduction, operating potential, electronic structure and atomic bonding nature of electrode materials by theoretical calculations, we could identify and define the problems of existing electrode materials, suggest possible strategy and experimentally improve the electrochemical property. This approach often leads to a design of completely new compounds with new crystal structures. In this seminar, I will talk about two examples of electrode material study under this approach; $LiNi_{0.5}Mn_{0.5}O_2$ based layered materials and olivine based multi-component systems. In the other scale of approach; nano engineering; the morphology of electrode materials are controlled in nano scales to explore new electrochemical properties arising from the limited length scales and nano scale electrode architecture. Power, energy and cycle stability are demonstrated to be sensitively affected by electrode architecture in nano scales. This part of story will be only given summarized in the talk.