• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.3
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• pp.127-131
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• 2005

Big fire such as mountain fire may cause the prevention of the functions of the overhead cables and insulators, which may affect the operation of the transmission lines. In the worst case, this kind of disaster may have a huge effect on the whole industry of a country. However, the study on the effect of the mountain fire on the transmission line is very rare. Therefore, in order to understand the effect of the mountain fire on the polymeric insulator for transmission lines, the author observed the deformation of the sheds of the polymeric insulators and the change of the discs of the porcelain insulators under fire, varying the ignition time using the artificial ignition testing equipment which simulates the mountain fire, and investigated the electrical and mechanical characteristics of the insulators after the ignition test. For the test, the miniature insulators made of polymeric material and porcelain have been utilized. As the result, the following conclusions were obtained. First, the porcelain insulator was degraded in electrical characteristics when the insulator was subjected to the fire for approximately 5 minutes; whereas, the polymeric insulator was not degraded though there were some damage on its sheds. Second, after 20 minute exposure to the fire, the polymeric insulator lost a lot of parts of sheds, but the electrical characteristics was lowered by around $20\%$, but the porcelain insulators were electrically degraded by more than $80\%$.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2193-2199
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• 2012

A series of novel polytriazoleimides were prepared from various aromatic dianhydrides and a new kind of 1,2,3-triazole-containing aromatic diamine synthesized by the Cu (I)-catalyzed 1,3-dipolar cycloaddition reaction in DMAc, and characterized by FT-IR, $^1H$-NMR, XRD, DSC and TGA techniques. The results show the polytriazoleimides are soluble in most of strong polar solvents and have inherent viscosity values of 0.51-0.62 dL/g(DMAc). The polytriazoleimide films exhibit a tensile strength of 62.3-104.5 MPa and an elongation at breakage of 4.0-8.1%, a glass transition temperature ($T_g$) of $257-275^{\circ}C$, a decomposition temperature (at 5% weight loss) of $350-401^{\circ}C$ in $N_2$ atmosphere, and a dielectric constant of 2.47-3.01 at 10 MHz, which depend on the structure of the polymers. The polytriazoleimides perform good resistance to acid and alkali solution.

• Macromolecular Research
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• v.14 no.3
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• pp.272-286
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• 2006

Dendritic hyperbranched poly(methyl methacrylate)s (PMMA)s, whose branched architectures resemble the 'dendron' part(s) of dendrimer, were synthesized by an iterative methodology consisting of two reactions in each iteration process: (a) a coupling reaction of u-functionalized, living, anionic PMMA having two tert-butyldimethylsilyloxymethylphenyl(SMP) groups with benzyl bromide(BnBr)-chain-end-functionalized PMMA, and (b) a transformation reaction of the introduced SMP groups into BnBr functionalities. These two reactions, (a) and (b), were repeated three times to afford a series of dendron-like, hyperbranched (PMMA)s up to third generation. Three dendron-like, hyperbranched (PMMA)s different in branched architecture were also synthesized by the same iterative methodology using a low molecular weight, functionalized 1,1-diphenylalkyl anion prepared from sec-BuLi and 1,1-bis(3-tert-butyldime-thylsilyloxymethylphenyl)ethylene in the reaction step (b) in each iterative process. Furthermore, structurally similar, dendron-like, hyperbranched block copolymers could be successfully synthesized by the iterative methodology using $\alpha$-functionalized, living, anionic poly(2-(perfluorobutyl) ethyl methacrylate) (PRfMA) in addition to $\alpha$-functionalized, living PMMA. Accordingly, the resulting block copolymers were comprised of both PMMA and PRfMA segments with different sequential orders. After the block copolymers were cast into films and annealed, their surface structures were characterized by angle-dependent XPS and contact angle measurements. All three samples showed significant segregation and enrichment of PRfMA segments at the surfaces.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.39 no.2
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• pp.89-96
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• 2013

This study demonstrate that polymeric microspheres composed of poly (ethylene adipate) (PEA) and poly (methyl methacrylate) (PMMA) can encapsulate and remarkably stabilize Broussonetia kazinoki root extract. We compared the long-term stability and the activity of Broussonetia kazinoki root extract in polymeric microspheres fabricated with different polymer ratio of PEA and PMMA. PMMA was incorporated to the PEA microsphere in order to reinforce the physical strength of microsphere, and there was no noticeable negative effect on the activity of Broussonetia kazinoki root extract. Optical microscope (OM), polarized microscope (PM), and scanning electron microscope (SEM) results showed that PMMA incorporated microspheres were very spherical and had smoothsurface. On the other hand, PEA microspheres showed relatively irregular morphology due to the low physical strength of microspheres. Moreover, the mushroom tyrosinase activities were measured for testing the inhibitory activity of Broussonetia kazinoki root extract encapsulated in polymeric microspheres, and these microspheres showed the effective suppression of mushroom tyrosinase activity. Consequently, polymeric microspheres produced in this study may be beneficial for the research of improving stability and protecting labile substances incorporated into the polymeric microspheres.

• Polymer(Korea)
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• v.31 no.2
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• pp.130-135
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• 2007

To enhance the thermo-mechanical properties of polyimide films which have potential application for the FCCL, we have synthesized the poly (amic acid) s composed of 4-components PMDA/BTDA and PDA/ODA as monomer system, u4 then they were effectively converted into 4-component polyimide films by thermal imidization process. It has been found that CTE values in the range of $100\sim200^{\circ}C$ decreased with the amount of PDA, which also caused 36% and 59% increases in tensile modulus and strength respectively. And also, peel test results on 3-layered copper clad laminate using 4-component polyimide films showed excellent adhesion strength above 1.8 kgf/cm. On the basis of obtained results it can be concluded that 4-component polyimide films may be applied for the high performance FCCL base films.

• Journal of Adhesion and Interface
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• v.4 no.4
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• pp.15-21
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• 2003

Polysulfone/organophilic layered silicate nanocomposites were prepared in the range of 0.25 to 9 wt% of organophilic-layered silicate by solution blend. Nano-hybridized films were cast from the blend solution. Exfoliation and intercalation of the polysulfone/organophiliclayered silicate nanocomposite films were confirmed by an X-ray diffractometer and a transmission electron microscope. Surface morphologies of polysulfone/organophilic layered silicate nanocomposite films were determined by a scanning electronic microscope and an atomic force microscope. When the organophilic layered silicate was added more than 1.5 wt%, the surface roughness (RMS) was rapidly increased because clusters of intercalated organophilic layered silicate particles existed on the polysulfone/organophilic-layered silicate film surface. Surface tension revealed an upward tendency over the contents of 1.5 wt% organophilic layered silicate in polysulfone/organophilic layered silicate nanocomposite. The change of surface morphology in polysulfone/organophilic layered silicate nanocomposite were affected by nano scale dispersed and intercalated organophilic layered silicate particles.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.22 no.1
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• pp.72-79
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• 2019

Purpose: The efficacy of exclusive enteral nutrition (EEN) with a polymeric diet has not been confirmed in Korean pediatric patients with Crohn's disease (CD). This study aimed to compare the effectiveness of EEN with a specific polymeric diet ($Encover^{(R)}$) and corticosteroids (CSs) for the induction of remission in Korean pediatric CD patients. Methods: We retrospectively compared data from 51 pediatric CD patients who underwent induction therapy with EEN (n=19) or CSs (n=32) at Severance Children's Hospital or Incheon St. Mary's Hospital in Korea. The primary endpoint of this study was the rate of clinical remission, defined as a Pediatric Crohn's Disease Activity Index (PCDAI) score <10, after 8 weeks of induction treatment. Clinical, laboratory, and growth data at post-induction as well as their changes from baseline were also compared between groups. Results: After 8 weeks of induction therapy, clinical remission rates were 78.9% (15/19) and 65.6% (21/32) in the EEN and CS groups, respectively (p=0.313). No significant differences in PCDAI scores, laboratory variables, and growth parameters were noted between the two groups at post-induction. However, significant changes in albumin levels at post-induction were observed in the EEN group compared to the CS group (p=0.038). Conclusion: Our results suggest that the effectiveness of EEN with a polymeric diet and CSs for induction therapy did not differ in Korean pediatric CD patients. EEN with a polymeric diet is a good first-line treatment option for the induction of remission in these patients.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.123-132
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• 1995

During compression molding of fiber-reinforced polymeric composites, microstructural changes such as the fiber-matrix separation and the fiber orientation are occurred by the flow of composite materials. Since the nonhomogeneity and anisotropy of composites are caused by the separation and orientation of fibers. On the other hand, the separation and the orientation of fibers are inseparably related to each other. In this paper the degree of nonhomogeneity which is a measure of the separation is obtained using one-dimensional rectangular shaped part compression molding. And the orientation function is measured by the image processing using soft X-rayed photograph and image scanner. We study effects of the mold temperature on the degree of nonhomogeneity and the orientation function.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.197-208
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• 1995

${\gamma}$-LiAlO2 fibers for fiber reinforced molten carbonate fuel cell (MCFC) matrix have been produced from LiAlO2 complex polymeric sols using the sol-gel process. The stable and spinnable LiAlO2 sols could be synthesized by mixing LiNO3 alcohol solutions in aluminum complex polymeric sols prepared through the condensationpolymerization reaction of 1 more of aluminum tri-sec-butoxide with 0.55 mole of mixed chelates (mole ratio of acetylaceton/triethanolamine=0.25/0.3). It was found that the viscosity range for fiber-spinning should be higher than 30 poise. The defect-free flexible ${\gamma}$-LiAlO2 fibers with the average tensile strength of 350 MPa could be obtained when the spinned fibers were heat-treated to 120$0^{\circ}C$ on the specified heating schedule after dried at room temperature.

• Tribology and Lubricants
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• v.19 no.2
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• pp.109-115
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• 2003

Nanotribological characteristics between a Si$_3$N$_4$ AFM tip and hydrophobic thin films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM (atomic force microscope) and LFM (lateral force microscope) modes in various .ranges of normal load. Plasma-modified thin polymeric films were deposited on Si-wafer (100). Results showed that wetting angle of plasma-modified thin polymeric film increased with the treating time, which resulted in the hydrophobic surface and the decrease of adhesion and friction. Nanotribological characteristics of these surfaces were compared with those of other hydrophobic surfaces, such as DLC, OTS and IBAD-Ag coated surfaces. Those of OTS coated surface were superior to those of others, though wetting angle of plasma-modified thin polymeric film is higher.