• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.79-85
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• 1997

In order to improve the surface characteristics of polymethylmethacrylate(PMMA), oxide thin film coatings were applied using the sol-gel dip-coating technique. The $Si(OC_2H_5)_4$, tetra-ethyl-ortho-silicate(TEOS) was used as a starting material for $SiO_2$ coating. The hardness of the alkoxy-derived oxide-coated PMMA was increased from 190 MPa for non-coated PMMA with increasing film thickness. By optimizing the heating conditions and the hydrolysis conditions, a maximum apparent hardness obtained In the present study was achieved 310 MPa using the withdrawal velocity of 5cm/min and heat treatment at $90^{\circ}C$ for 5 hours, which is about 1.6 times larger than that of uncoated PMMA.

• Journal of the Korean Applied Science and Technology
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• v.7 no.1
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• pp.87-91
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• 1990

1,3-Di(2-octadecanoyl)-2,7-dioxy-l,3,6,8-tetra aza cyclodecane [DDTC] was synthesized by reacting octadecanoic acid, 2,2'-di-aminodiethyl amine with urea. O/W type softner (STA) was prepared by blending DDTC and pentaerithritol monostearate with polyoxysthylene (20) oleyl ether, polyoxyethylene (10) castor oil, and PEG #1000-lauric acid ester. Treating STA to all cotton fabrics, the physical properties, such as tear strength, crease recovery, flexing abrasion resistance, and so on were measured. Resulting the measurements, STA was found to be durable softner with softness.

• Journal of the Korean Applied Science and Technology
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• v.7 no.1
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• pp.49-62
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• 1990

In order to synthesize N,N-di-(polyoxyethylene) perfluoroacyl amines and the surface active monoperfluoroacyl aza crown ethers, it is performed as follow. Six of N,N-di(polyoxyethylene) perfluoro acyl amines were synthesized from perfluoroalkanoic acids with ethanol followed by oxyethylation with triethylene glycol mono chloride or tetra ethylene glycol mono chloride and six of N-perfluor acyl monoaza crown ethers by cyclization of corresponding N,N-di(polyoxy ethylene} perfluoro acyl amines with p-toluene suflonic chloride-NaOH/dioxane, p-toluene sulfonyl chloride KOH/dioxane and benzene sulfonic chloride-KOH/dioxane systems.

• Journal of the Korean Applied Science and Technology
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• v.11 no.2
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• pp.147-150
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• 1994

Ultra thin films of HDSM-CuPc(Tetra-3-hexadecylsulphamoylcopperphthalocya-nine) were formed on various substrates by Langmuir-Blodgett method, where HDSM-CuPc was synthesized by attaching long-chain alkylamine(hexa-decylamine) to CuPc. The reaction product was identified with FT- IR, UV-visible absorption spectroscopies, elemental analysis and thin layer chromatography. The formation of ultrathin films of HDSM-CuPc was confirmed by FT-IR and UV-visible spectroscpies.

• Macromolecular Research
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• v.9 no.5
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• pp.247-252
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• 2001

Tricyclic aliphatic dianhydride monomer, tricycle[4.2.2.0]dec-9-ene exo, endo-3,4: 7,8-tetra-carboxylicdianhydride (TCDDA), was synthesized by photochemical reaction and poly(amic acid)s from TCDDA and diamines such as 1,4-bis-(4-aminophenoxy)benzene (BAB), 2,2-bis(4-(4-aminophenoxy) phenyl) propane (BAPP), 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (BAPHF), bis(4-(4-ami-nophenoxy) phenyl)sulfone (BAPS), and 1,4-bis-(4-aminophenoxy)biphenyl (BABP) were prepared. The inherent viscosities of the poly(amic acid)s were between 0.39 and 0.50 dL/g. The poly(amic acid)s were converted to polyimide films by thermal imidization. The glass transition temperatures (T$\_$g/) of the polyimides were in the range of 201-263$\^{C}$. The thermogravimetric analysis (TGA) thermogram of these polyimides showed the temperatures of 5% weight losses between 375 and 393$\^{C}$ in nitrogen atmosphere. To show their utility for image generation, degradations of these polyimides in UV exposure were investigated by UV spectroscopy.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.724-727
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• 2002

2,7-dibromo-9, 9-dialkyl-substituted-fluorene derivatives were prepared by the alkylation of 2,7-dibromofluorene with various alkyl groups under two-phase phase transfer catalysis (PTC) conditions, as monomers for synthesizing poly(dialkylfluorene)s. Tetra-nbutylammonium hydrogen sulfate (TBAHS) was used as a phase transfer catalyst to enhance nucleophilic substitution. In addition, NaOH in water (25M) was used as a base to generate anions. Compared to conventional alkylation using butyllithium(BuLi), the reaction using the PTC technique attained high selectivity and substantial conversion of reactants, due to the enhanced reaction rate, while the reaction was carried out under moderate conditions. An approximately 90% yield was obtained from the reaction and the reaction time was remarkably reduced. 2,7-dibromo-9,9-dihexyl-fluorene, 2,7-dibromo-9,9-dioctyl-fluorene, and 2,7-dibromo-9,9-di(2-ethylhexyl)-fluorene were effectively synthesized by phase transfer catalytic reaction.

• The KSFM Journal of Fluid Machinery
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• v.11 no.1
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• pp.46-51
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• 2008

A stability analysis has been made for a newly designed gate of intake tower of reservoir. The analysis is composed of finding the natural frequency of the gate and the frequency induced by water flowing over and through the gate. ANSYS is employed to calculate the natural frequency of the gate and SC/Tetra is utilized for calculating flow field around the gate, which in turn gives the frequency of pressure force fluctuation on the gate. In addition to the safety analysis, the present study presents how the gate selectively intakes a muddy water layer located in the middle depth of reservoir.

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.29-34
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• 2010

In this paper, aerodynamic noise of axial flow fans for outdoor unit of air-conditioner was analyzed by both experiment and numerical simulation. The three-dimensional incompressible turbulent flow was predicted by the commercial computational fluid dynamics code SC/Tetra, while the aeroacoustic noise of an axial flow fan was predicted by FlowNoise. Computations and experiments were performed with two types of axial flow fans, in which very different noise source distributions were presented. The results obtained from this study are expected to show the way to reduce the noise of axial flow fans in industrial applications.

• Journal of Powder Materials
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• v.4 no.1
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• pp.9-17
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• 1997

The mullite-zirconia composites were prepared by the pressureless sintering with addition of 10~20 vol% ZrO$_2$(TZ3Y) in the fused mullite and sol-gel mullite matrix. The densification rate of sol-gel mullite was higher than that of fused mullite, and the addition of ZrO$_2$(TZ3Y) was effective on the densification of fused mullite. The enhancement of densification and anisotropic growth of mullite in ZrO$_2$added specimen can be explained by the solid solution effect of $Zr^{+4}$ ion in mullite. Both mechanical strength and fracture toughness of mullite-zirconia composite were enhanced compared to those of mullite. The enhancement of mechanical properties is attributed to the hinderance of grain growth and the combined toughening effects of tetra-mono phase transformation and crack deflection due to the residual stress between mullite/ZrO$_2$.

• Journal of Veterinary Clinics
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• v.23 no.2
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• pp.218-221
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• 2006

This report described clinical findings and Magnetic resonance image (MRI) results in two small breed dogs with fibrocartilaginous embolism (FCE). They were admitted with asymmetric acute-onset tetra/paraparesis with superficial pain sensation. In addition, there were no back pain and no progression of clinical signs. Cerebrospinal fluid and laboratory findings were evaluated. MRI revealed a similar focal intramedullary lesion of hyperintensive signals on T2-weighted images. Based on these findings, it was diagnosed as fibrocartilaginous embolic myelopathy in those two dogs.