• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.843-850
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• 1991

There is a growing demend for absorptive electromagentic shielding materials for wide band frequency application. In this study, the absorber which consists of a rubber plus Ni-Zn ferrite which have been prepared by direct-wet method. A rubber ferrite composite for electromagnetic shielding, it is most importan facter the homogeneous ultra fine size and high dispersitive ferrite powder. Direct-wet method and solid-solid reaction method for preparing of ultra fine ferrite powder was used. It has been experimentally verified that the powder which prepared by direct-wet method was very fine and almost same size spherical powder, the composite ferrite have excellent electromagnetic wave absorption in X-band.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.184-186
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• 2002

The evolution of texture and microstructure during warm rolling and subsequent annealing in aluminium 3004 alloy sheet was investigated by X-ray texture measurements and microstructure observations. Warm rolling at 250$^{\circ}C$ led to the development of strong through thickness texture gradients with shear textures at the surface layer and a regular rolling texture in the center of the sheets. FEM simulations indicated that these texture gradients are caused by pronounced strain gradients throughout the sheet thickness. Upon recrystallization annealing, in the sheet center the characteristic cube-recrystallization texture developed, while in the surface layers with a pronounced shear texture continuous recrystallization took place which led to the formation of a very fine grained microstructure. It is concluded that the very complex strain history in the near-surface layers together with the resulting high work-hardening rate gave rise to the formation of the ultra-fine grains with an average size smaller than 2$\mu\textrm{m}$.

• Korean Journal of Materials Research
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• v.32 no.4
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• pp.223-229
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• 2022

A porous photocatalyst concrete filter was successfully produced to remove NOx, by mixing TiO₂ photocatalyst with lightweight aerated concrete. Ultra Fine Bubbles were used to form continuous pores inside the porous photocatalytic concrete filter, which was mixed via a bubble generation experiment. The optimal mixing condition was determined to be with 4 % of the bubble generation agent B. NO removal specimens were prepared for various photocatalytic loading conditions, and the specimen containing 3 % P-25 removed NO at a concentration of 1.03 µmol in 1 h. The NO removal rate of the porous photocatalytic concrete filter prepared in this study was 10.99 %. This photocatalytic filter performance was more than 9 times the amount of NO removed by a general photocatalytic filter. The porous photocatalyst concrete filter for removing NOx developed in this study can be applied to various construction sites and the air quality can be solved by reducing NOx contributing to the formation of fine particles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.613-614
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• 2012

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.86-95
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• 2011

Ultra-precision machining technology is the essential core technology in today's micro-electronics and electro-optical industries. The needs for processing systems to manufacture products to nanometer(nm) accuracy and sub-nanometer resolutions are increased recently. By using ion beam, it is possible to fabricate ultra-precision and ultra-fine products with nm accuracy and sub-nm resolution. In this paper, the basic research trends of ultra precision machining technology in domestic are surveyed, and the ways to reach to the world-leading level of basic research capabilities in the field of ultra-precision machining technology in domestic is suggested.

• Journal of Oriental Neuropsychiatry
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• v.22 no.2
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• pp.107-128
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• 2011

Objectives : This experiment was designed to investigate the efficacy of DDTCMT hot water extract & ultra-fine powder on Alzheimer's Disease Model. Methods : The effects of the DDTCMT hot water extract on expression of IL-$1{\beta}$, IL-6, TNF-${\alpha}$, COX-2, NOS-II, IL-10, IL-1 receptor antagonist mRNA and production of IL-$1{\beta}$, IL-6, TNF-${\alpha}$ in BV2 microglial cell line treated by lipopolysacchaide(LPS) were investigated. Expression of NO, ROS in BV2 microglial cell line treated by LPS and AChE activity in PC-12 cell treated by NGF were investigated. anti-AChE was observed through Western blot analysis. The effects of the DDTCMT hot water extract & ultra-fine powder on the behavior of the memory deficit mice induced by scopolamine were investigated. Results : 1. The DDTCMT hot water extract significantly decreased the production of mIL-6, mNOS-II, mTNF-${\alpha}$, and increased the production of mIL-10, mIL-1 receptor antagonist. 2. The DDTCMT hot water extract significantly suppressed the production of IL-$1{\beta}$, IL-6, TNF-${\alpha}$ in BV2 microglial cell line treated by LPS. 3. The DDTCMT hot water extract significantly suppressed the NO and ROS production in BV2 microglial cell line treated by LPS. 4. The DDTCMT hot water extract groups showed inhibition of AChE activity in NGF treated PC-12 cell line. 5. The DDTCMT hot water extract suppressed anti-AChE expression in NGF treated PC-12 cell line was observed by Western blot analysis. 6. The DDTCMT hot water extract & ultra-fine powder groups showed significantly inhibitory effect on the scopolamine -induced impairment of memory in the experiment of Morris water maze. Conclusions : These results suggest that the DDTCMT hot water extract & ultra-fine powder may be effective for the prevention and treatment of Alzheimer's disease.

• Food Science and Preservation
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• v.23 no.6
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• pp.899-905
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• 2016

In this study, beauty food activities were determined for extracts of Saurus chinensis as functional beauty food. Tyrosinase inhibitory effect was increased as more 4 folds by ultra-fine grind technology than normal grind technology in ethanol extracts from Saurus chinensis. A ultra-fine ground technology was used to increase the extraction yield for bioactive compounds from medicinal plants. Tyrosinase inhibitory activity, which is related to skin-whitening, was confirmed to be 100% for ethanol extracts at 1,000 ppm of phenolics. Anti-wrinkle activity was determined showing 30% of inhibition effect at above 1,000 ppm phenolic concentration. The elastase inhibitory activity of water and ethanol extracts from ultra-fine ground Saurus chinensis showed higher inhibition activity than compared to extracts from normal ground Saurus chinensis. Astringent activity in ethanol extracts was determined showing over 70% at 250 ppm of phenolics. Based on these results, Saurus chinensis extracts can be used as a functional beauty food and cosmetic with whitening, anti-wrinkle and pore contraction effects.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.211-212
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• 2011

It was very important to evaluate concrete experimentally at elevated temperature because concrete was filled with aggregate of concrete volume about 70 percent. Concrete exposure to high temperatures produces changes in its internal structure, for instance loss of its strength and deformation capacity, in extreme cases risking the service life of the structure. The work of this paper is performed to evaluate the thermal behavior of ultra-high strength concrete having different water to cement ratio (strength), fine aggregate to aggregate ratio and maximum size of coarse aggregate. For exposure to 500℃ during 1 hour, residual mechanical properties of the ultra-high strength concrete decreased as the s/a ratio decreases and the maximum size of coarse aggregate increases.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.431-440
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• 2011

Concrete structures exposed to fire produce changes in their internal structure, resulting in their service life reduction due to the deterioration of its strength and performance capacity. The deterioration level are dependent on the temperature, exposure time, concrete mix proportions, aggregate property, and material properties. This study was performed to evaluate the thermal behavior of ultra-high strength concrete for the parameters of water to cement ratio (compressive strength), fine to total aggregate ratio, and maximum coarse aggregate size. At room temperature and $500^{\circ}C$, tests of ultrasonic pulse velocity, resonance frequency, static modulus of elasticity, and compressive strength are performed using ${\varnothing}100{\times}200\;mm$ cylindrical concrete specimens. The results showed that the residual mechanical properties of ultra-high strength concrete heated to $500^{\circ}C$ is influenced by variation of a water to binder ratio, fine to total aggregate ratio, and maximum coarse aggregate size.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.411-417
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• 1996

Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.