• Journal of the Korean Society for Precision Engineering
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• v.7 no.2
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• pp.74-84
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• 1990

The machine tool structures for ultra-precision machining muxt be manufactured with materials which have high static and dynamic stiffness, high damping, a long term dimensional and thermal stability. This study aims at the development of new composite material Epoxy-Granite which exhibits the satisfactory characteristics as a material of ultra-precision mchine tool bed. The Epoxy-Granite testpieces that use epoxy resins as a binder and granite particles as a aggregate have been manufactured so as to examine the material properties about mechanical, thermal and damping characteristics. Experiments were carried out to obtain the proper manufacturing conditions of Expoxy-Granite specimens by varying the several testing conditions such as types of epoxy resins, particle sizes of granite and mixture ratio of epoxy resin and aggregate. Also, when Epoxy-Granite was compared with cast iron, GRANITAN which was imported from CMS of U.K. and granite materials, it has exhibited the superior or almost the same mechanical and damping properties and thermal conductivity, except for the thermal expansion.

• Bulletin of the Korean Chemical Society
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• v.26 no.4
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• pp.523-528
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• 2005

Diblock copolymers with different poly($\varepsilon$-caprolactone) (PCL) block lengths were synthesized by ringopening polymerization of $\varepsilon$-caprolactone in the presence of monomethoxy poly(ethylene glycol) (mPEG-OH, MW 2000) as initiator. The self-aggregation behaviors of the diblock copolymer nanoparticle, prepared by the diafiltration method, were investigated by using $^1H$ NMR, dynamic light scattering (DLS), and fluorescence spectroscopy. The PEG-PCL block copolymers formed the nano-sized self-aggregate in an aqueous environment by intrsa- and/or intermolecular association between hydrophobic PCL chains. The critical aggregation concentrations (cac) of the block copolymer self-aggregate became lower with increasing hydrophobic PCL block length. On the other hand, reverse trends of mean hydrodynamic diameters were measured by DLS owing to the increasing bulkiness of the hydrophobic chains and hydrophobic interaction between the PCL microdomains. The hydrodynamic diameters of the block copolymer nanoparticles, measured by DLS, were in the range of 65-270 nm. Furthermore, the size of the nanoparticles was scarcely affected by the concentration of the block copolymers in the range of 0.125-5 mg/mL owing to the negligible interparticular aggregation between the self-aggregated nanoparticles. Considered with the fairly low cac and nanoparticle stability, the PEG-PCL nanoparticles can be considered a potential candidate for biomedical applications such as drug carrier or imaging agent.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.39-48
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• 2006

A laboratory investigation was conducted wherein smooth, rounded, siliceous river gravel aggregates were coated with fine-grained polyethylene, carpet co-product, or cement + styrene butadiene rubber latex and used to prepare hot mix asphalt concrete specimens. Only the coarse (+ No.4) aggregates were coated. The concept was that the coatings would enhance surface roughness of the aggregates and, thus, produce asphalt mixtures with superior engineering properties. Hot mix asphalt specimens were prepared and evaluated using several standard and non-standard test procedures. Based on experiences during the coating processes and analyses of these limited test results, the following was concluded: All three aggregate coating materials increased Hveem and Marshall stability, tensile strength, and resilient modulus(stiffness). These findings are indicative of improved resistance to rutting and cracking in hot mix asphalt pavements prepared using coated gravel aggregates in comparison to similar uncoated gravel aggregates.

• Journal of the Korean Professional Engineers Association
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• v.16 no.3
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• pp.41-53
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• 1983

The Dangri Crushed Stone Quarry is located in Dangridong, Busan City, and around the estuary of the Nagdong River. The quarry is considered to be a very promised one in the urban area from the standpoints of the assessment of the aggregate rank, the environmental impacts and the transportation distance. The crushed stones for aggregate of the quarry marks the higher rank in the gravity, the absorption ratio, the abrasion ratio, and the stability in comparison with the JISA 5005. The basement vibrations of the residential section in the vicinity of the quarry, which are arised by the millisecond blasting at the quarry site using the gelatin dynamites less than 39kg in weight, are measured to assess the vibration nuisance. The values of acceleration and the magnitudes are less than eight gals and O on the Richter scale respectively, the vibration nuisance thus can be ignored in such scales of the experiments. The traffic vibrations of the residential section are slightly susceptible. In the experiments, the traffic vibrations appears to be sensibler to the basement than the explosion vibration. The explosion noises in the experiments are not checked not only on the RION Sound Level Meter but also to our ears. The values of traffic noises also are in the safety values of the noise nuisance. The crush dust suspends in the air toward the upper valley in the opposite side of the residential area because of the influences of the sea breeze and the valley wind in the daytime, and the monsoon and the topographic disposition. the dust nuisance thus would not be remained in problem. The quarry is operated in the daytime only. The traffic dust in the residential area will be reduced by the faultless pavement and the careful driving. The elaborate survey on the ridges and peaks surrounded the quarry is recommended to prevent in advance the accidents of the rock slide. Moreover, it is required to make an advisory committee to develop the industry and to save the techniques. The most important matter is the accomodation between the attitude of the enterprising man for the social responsibility to the public nuisance and the cooperative spirit of the inhabitants for the industry.

• Resources Recycling
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• v.18 no.3
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• pp.36-41
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• 2009

The objectives of this study are focusing on the issue with efficiently recycling for EAF slag as construction material such as an aggregate of concrete. This study can be classified mainly into two categories: the first section is the carbonation treatment of Electric Arc Furnace(EAF)-slag for obtaining soundness as using aggregate of concrete. And the second section is the application of carbonated EAF-slag on the mortar test to evaluate the stability and mechanical property, which is compressive strength, according to the replacement of EAF-slag on the mortar. It was known that pH of EAF-Slagle according to carbonation time decreases drastically to 7 within several sec of carbonation, and a calcite is formed on the surface of EAF slag. The formation of calcite during the carbonation process of EAF slag lead to fill at pore in the texture of EAF-Slag surface, and than the porosity of EAF-slag decreases with carbonation process. In the mortar test, compressive strength, according to the replacement of EAF-Slag to sand on the mortar, the compressive strength of mortar increased as the 50% replacement ratio of EAF slag for sand was above 10% higher than that of reference mortar according to 50% replacement of EAF slag.

• Korean Journal of Social Welfare
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• v.54
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• pp.321-345
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• 2003

Aggregate income stability depends heavily on labor market institutions that stabilize or de-stabilize earnings. But, with the expansion of sate welfare programmes, public income transfers are also important sources of income stability for individual and families. Moreover, income stability is determinant factor of individual and family well being, there are another strategies of income stability in society. Family-based and community-based strategies are particularly important. Accordingly, the distribution of income stability in a given society depends on such institutional arrangements as market, family, state, and community. The purpose of this study is to analyse the income stabilizing role of family, state, and community. I found that stabilizing effect of the family and community was very strong in Korea. When institutional features of labor market and the state leave individuals exposed to market risk, they may be respond by relying more on family-based or community-based strategies of income stabilization. But, I can't deny the possibility of an inadequacy of these strategies in according to the rapid changes of family structures and informal networks. Therefore, state-based strategies of income stabilization should be more strengthened in Korea.

• Analytical Science and Technology
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• v.29 no.3
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• pp.105-113
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• 2016

The present study investigated the immobilization of lipases on silica nanoparticles and silica-coated magnetite nanoparticles as supports with a functional group to enhance the stability of lipase. The influence of functional groups, such as the epoxy group and the amine group, on the activity and stability of immobilized lipase was also studied. The epoxy group and the amino group were introduced onto the surface of nanoparticles by glycidyl methacrylate and aminopropyl triethoxysilane, respectively. Immobilized Candida rugosa lipase on silica nanoparticles and silica-coated magnetite nanoparticles with a functional group showed slightly lower initial enzyme activities than free enzyme; however, the immobilized Candida rugosa lipase retained over 92 % of the initial activity, even after 3 times reuse. Lipase was also immobilized on the silica-coated magnetite nanoparticles by cross-linked enzyme aggregate (CLEA) using glutaraldehyde and covalent binding, respectively, were also studied. Immobilized Candida rugosa lipase on silica nanoparticles and silica-coated magnetite nanoparticles by CLEA and covalent binding showed higher enzyme activities than free enzyme, while immobilized Candida rugosa lipase retained over 73 % of the initial activity after 5 times reuse.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.145-150
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• 2005

An extensive numerical analysis is carried out to investigate the slope stability of the wasted mine tailing landfill constructed by the utilization of fine recycled-concrete aggregates. To do this, first, the physical and mechanical properties of the fine recycled-concrete aggregates and the wasted mine tailing are investigated, and the settlement and the change of material properly of the fine recycled-concrete aggregates resulted from reaction with water are also examined. The $OH^-$ elution from the fine recycled-concrete aggregates reacted with water slightly causes the change of material properties such as porosity, permeability and waster absorption, but the settlement does not happen noticeably. The results of numerical analysis of the landfill slope built with wasted mine tailing and recycled-concrete aggregates in alternate layer indicate that slope stability increases with decreasing the slope ratio, with decreasing the groundwater level inside slope, and with increasing the depth of fine recycled-concrete aggregate layer. Based on this study, thus, engineers working in related to the wasted mine tailing landfill design and construction using the fine recycled-concrete aggregates should be considered the slope ratio, the groundwater level, the depth of fine recycled-concrete aggregate layer.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.1
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• pp.29-34
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• 1987

This experiment was designed to find out the effects of soil conditioner, Polyacrylamide (PAM) and Bitumen, on the changes of soil aggregate properties and crop yields. The soil conditioners were treated at the rates of 0.5% and 1% to sandy loam and silty clay loam soils. The aggregate stability, wetting angle, mean weight diameter and air permeability were analyzed. Pot experiments were carried out to investigate the soybean growths and soil property changes after the soil conditioners were sprayed to surface soils. Soil aggregate stability was increased remarkably by the soil conditioner, PAM and Bitumen, treatments. PAM was more effective in sandy loam than silty clay loam, but Bitumen was better in silty clay loam. Wetting angle of the soil was changed slightly by PAM treatment, but it was greatly changed to hydrophobic by Bitumen treatment. Air permeability, water infiltration rate and moisture retention of the soils were increased by surface application of soil conditioners, PAM and Bitumen. The growths of soybean in conditioner applicated pots were better than those of untreated pots from early stage, and the yields were increased 6-13%.

• Microbiology and Biotechnology Letters
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• v.46 no.3
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• pp.234-243
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• 2018

The Antarctic Ocean contains numerous microorganisms that produce novel biocatalysts that can have applications in various industries. We screened various psychrophilic bacterial strains isolated from the Ross Sea and found that a Croceibacter atlanticus strain (Stock No. 40-F12) showed high lipolytic activity on a tributyrin plate. We isolated the corresponding lipase gene (lipCA) by shotgun cloning and expressed the LipCA enzyme in Escherichia coli cells. Homology modeling of LipCA was carried out using the Spain Arreo lake metagenome alpha/beta hydrolase as a template. According to the model, LipCA has an ${\alpha}/{\beta}$ hydrolase fold, Gly-X-Ser-X-Glymotif, and lid sequence, indicating that LipCA is a typical lipase enzyme. Active LipCA enzyme was purified fromthe cell-free extract by ammonium sulfate precipitation and gel filtration chromatography. We determined its enzymatic properties including optimum temperature and pH, stability, substrate specificity, and organic solvent stability. LipCA was immobilized by the cross-linked enzyme aggregate (CLEA) method and its enzymatic properties were compared to those of free LipCA. After cross-linking, temperature, pH, and organic solvent stability increased considerably, whereas substrate specificities did not changed. The LipCA CLEA was recovered by centrifugation and showed approximately 40% activity after 4th recovery. This is the first report of the expression, characterization, and immobilization of a C. atlanticus lipase, and this lipase could have potential industrial application.