• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.133-138
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• 1997

The technology of removing phosphorous, considered as one of the most important control nutrients causing eutrophication in various water bodies, have been investigated by many researchers. Recently, phosphorous crystallization process is emerging as a new technology for phosphorous removal. In this study, waste oyster shells which can be easily obtained from the ocean, were used as a seed crystal, and their effects of several physical/chemical factors on the phosphorous removal efficiencies were examined by batch tests. Ca$^{2+}$ and pH affected phosphorous crystallization process using waste oyster shells. As alkalinity of wastewater increased, phosphorous removal efficiencies gradually decreased. Phosphorous removal efficiencies were increased, as specific area and contact efficiency per unit area of waste oyster shells were increased. In case of high temperature, phosphorous crystallization process was rapidly advanced and phosphorous removal efficiencies were increased. Dependig on X-ray diffraction analysis, it was showed that generation materials extracted from the surface of waste oyster shells with short reaction time were dominated by $CaHPO_4\cdot 2H_2O$, but progressed to $Ca_5(OH)(PO_4)_3$. The SEM observation reveals that the evident variations were hardly seen, but particle sizes of waste oyster shells were relatively bigger and showed forms of smaller plate than before.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1343-1354
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• 2007

Secondary batteries become more important in our lives as the use of portable electric devices, such as camera, cellular phone, laptop, etc. Especially, because of their high energy densities and high voltage, lithium-ion batteries are being used in many systems. For the optimum design of such systems which include lithium-ion batteries, virtual prototype is required generally. However, since the complex chemical and physical processes are involved, the behavior of battery becomes harder to be predicted compared with that of electric and mechanic devices. This paper, proposes a new static model of lithium secondary battery, which accounts for nonlinear equilibrium potentials, rate and temperature dependencies, thermal effects, lifetime characteristic. The results of the simulation of the model are analysed and compared with experimental data to inspect their validity.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.3
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• pp.254-260
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• 1999

This experiment was carried out to evaluate the effect of improvement of soil physical property such as deep plowing and chiseling and diagnostic application of N, P, K fetilizers. Latex Coated Urea(LCU), compost, sillicate for increasing yielding and enchancing N-use efficiency in puddled-soil drill seeding of Rice. The soil physical properties, such as bulk density, hardness and porosity were increased by deep plowing and chiseling, as well as chemical propeties were highly enhanced soil productivity due to increase the content of organic matter, available $P_2O_5$ and K as compare with control. The amount of $NH_4-N$ in soil was highly increased by diagnostic fertilization and chiseling, while recovery rate of V fertilizer was the highest at LCU 80% applied with chiseling. The rice yield increased by 23% under the diagnositic application of LCU 80% applied base with chiseling.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.132-138
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• 2007

Carbon nanotubes (CNTs) arc grown on Ni catalysts employing an inductively-coupled plasma chemical vapor deposition (ICP-CVD) method. The structural and field-emissive properties of the CNTs grown are characterized in terms of the substrate-bias applied. Characterization using the various techniques, such as field-omission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Auger spectroscopy (AES), and Raman spectroscopy, shows that the structural properties of the CNTs, including their physical dimensions and crystal qualities, as well as the nature of vertical growth, are strongly dependent upon the application of substrate bias during CNT growth. It is for the first time observed that the provailing growth mechanism of CNTs, which is either due to tip-driven growth or based-on-catalyst growth, may be influenced by substrate biasing. It is also seen that negatively substrate-biasing would promote the vertical-alignment of the CNTs grown, compared to positively substrate-biasing. However, the CNTs grown under the positively-biased condition display a higher electron-emission capability than those grown under the negatively-biased condition or without any bias applied.

• Journal of Periodontal and Implant Science
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• v.27 no.4
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• pp.949-961
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• 1997

To date, various clinical procedures have been used to restore periodontal apparatus destroyed by periodontal disease. And then, many experimental approaches have been proceeded to develop treatment methods to promote periodontal regeneration. Mechanical, chemical treatments to enhance the attachment of periodontal tissue cells as changing the physical properties of root surfaces, bone graft procedure, and treatments for guided tissue regeneration have been used for periodontal regeneration. However, recent studies have revealed that biologic factors such as growth factors promote biologic mechanism associated with periodontal regeneration. This study was done to enucleate how ELF stimulus affect the periodontal regeneration. We can have following conclusions from this experimental results. The influence of low frequency(ELF) electric stimulus (30Hz at $lO{\mu}A$) known to promote bone formation in vivo, was evaluated for its ability to affect bone cell function in vitro. After 12 hour exposure of ELF stimulus at most appropriate densities ($5{\times}10^4\;cells/cm^2$) to increase osteoblastic cells normally, rat calvarial cells were incubated for 60 hours were used in this study. We have found ELF stimulus suppress calvarial cell proliferation and the ability of protein synthesis, enhance the alkaline phosphatase activity significantly.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.318-321
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• 2000

Most compressive strengths commonly used in the construction field are in a range of 240 to 300 kgf/$\textrm{cm}^2$ at 28 days. To get this rage of strengths, however, high-flowing concrete requires cementitious binders more than 400 to 450 kg/$\textrm{cm}^2$ for preventing segregation and sedimentation of aggregates. This amount of cementitious binder generates a large emission of excessive hydration heat, which may consequently induce harmful cracks in concrete structure. In order to reduce excessive hydration heat, thus, this paper aims at fabricating a high-flowing concrete under the condition that cement content is kept as low as 350kg/$\textrm{cm}^3$ by using viscose agents. In a parametric study, effects of cement types such as a ternary blended cement and Type V on he physical characteristics of high-flowing concrete were evaluated. In addition, the influence of viscosity was also investigated by applying two different viscose agents, one in a range of 6,000 to 10,000 cps and the others of 10,000 to 14,000 cps. In terms of chemical admixtures used in concrete mixture, the superplasticizer was Sulfonated Melamine-Formaldehyde Condensate with about 30,000 of molecular weight, and main component of viscose agent was HPMC (Hydroxy Propyl Methyl Cellulose). Slump flow was fixed at 50cm with different dosages of superplasticizer in weight.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.678-685
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• 1992

The effects of functional monomers on the pressure sensitive adhesive proporties were studied. Acrylic acid and other monomers were copolymerized by radical solution polymerization and their properties were measured. The desirability function methodology was applied to obtain optimum pressure sensitive adhesive properties. Acrylic acid showed more effective than acrylamide on peel strength increase. On the other hand acrylamide showed more effective than acrylic acid on tack decrease. The optimum monomer ratio of the acrylic pressure sensitive adhesive recipe containing n-butylacrylate 81.7 mole%, acrylic acid 8.0 mole%, acrylamide 2.1 mole% and vinylacetate 8.2 mole% was obtained to result from the statistical analysis with the desirability function methodology. The estimated regression equation of desirability function(D) is as follows: $D=.857+.072X_1-.114X_2-.027X_3-.126X_1{^2}-.046X_1{\cdot}X_2-.063X_1{\cdot}X_3-.152X_2{^2}+.027X2{\cdot}X_3-.120X_3{^2}$ $X_1$:coded acylic acid, $X_2$:coded acylamide, $X_3$:coded vinylacetate

• Journal of the Korean Chemical Society
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• v.54 no.4
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• pp.460-464
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• 2010

We manufactured functional contact lens materials using 2-hydroxy-4-methoxy-benzophenone, titanium(VI) isopropoxide and nanogold, nanoplatinum with UV-blocking and antimicrobial effects. Contact lens was manufactured by cast mould method. The resulting mixture was copolymerized by heating at $70^{\circ}C$ for about 40 min, at $80^{\circ}C$ for about 40 min, and finally at $100^{\circ}C$ for about 40 min. The refractive index of 1.434 ~ 1.436, water content of 35.24 ~ 36.32%, and visible transmittance of 88.3 ~ 90.8% were obtained for the contact lens materials. The polymer materials satisfied the physical properties required to make the material suitable to be applied as a functional material for ophthalmological purposes.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.109-121
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• 1992

For the purpose of mineralogical and chemical study on the topazes from various localities of world(Brzail, China, India, Nigeria and Sri Lanka), electron microprobe analysis(EPMA), neutron activation analysis(NAA), X-ray diffractometry, Raman spectroscopy, etch test, scanning electron microscopy, refractive index, specific gravity, fluid inclusion were performed. The chemical composition in topaz was discussed along with its physical and structural properties. Variations in the unit-cell dimension and physical properties of topaz were found to have a close relations in the unit-cell dimension and physical properties of topaz were found to have a close relationship with extent of substitution of $OH^-\;for\;F^-$. According to neutron activation analyses, the trace elements had no effects on the physical properties of topaz. Raman spectra showed that the peaks of topaz were different in intensity from one locality to another. Etching defects in topaz includes negative crystal defect o point-bottom pit(India, Nigeria) and net work defect of curl-bottom pit(Brazil, China). Fluid inclusions in topaz may be classiffied into liquid $CO_2$-bearing inclusion, gaseous inclusion, halite, sylvite-bearing inclusion and liquid inclusion. The results of this study can be useful to devising artificial coloring methods for topaz with different mineralogical compositions.

• Polymer(Korea)
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• v.33 no.3
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• pp.263-267
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• 2009

In order to improve the hydrophilic property on the surface of d-PMMA(deuterated poly-(methyl methacrylate)) film, it was exposed to oxygen plasma, All experimental conditions were same except to plasma exposure time that was varied from 0 to 180 s, The effects according to the exposure time were identified using contact angles, X-ray reflectometer(XRR), neutron reflectometer(NR), and X-ray photoelectron spectroscopy(XPS). By confirming that as the exposure time increases, water contact angle decreases while the composition of oxygen increases, it was confirmed that the composition of oxygen has a huge influence on improving the hydrophilic property. The physical characters as a function of the exposure time were investigated by the XRR. By analyzing complementally the results of the XRR, NR, and XPS, more detailed chemical bonding conditions were studied by obtaining not only composition of the carbon and oxygen but that of the hydrogen.