• Title, Summary, Keyword: EPR

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Miscibility and Properties of Ethyl-Branched Polyethylene/Ethylene-Propylene Rubber Blends (II) (에틸 가지화된 폴리에틸렌과 에틸렌-프로필렌 고무 블렌드의 혼화성과 물성(II))

  • Cho, Ur-Ryong
    • Elastomers and Composites
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    • v.37 no.2
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    • pp.79-85
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    • 2002
  • Ethyl-branched polyethylene [PE(2)] containing 2mole% ethyl branch and three ethylene-propylene rubbers (EPR's) having the same ethylene(E)-propylene(P) molar ratio(E/P=50/50) with different stereoregularity, that is, random EPR (r-EPR), alternating-EPR (alt-EPR) and isotactic-alternating-EPR (iso-alt-EPR) were mixed for the investigation or their properties depending on the stereoregularity. Crystallinity of the prepared blends decreased with increasing content of amorphous EPR because of a decrease in both the degree of annealing and kinetics of diffusion of the crystallizable polymer content. With blend composition, crystallinity was reduced with the stereoregularity in EPR. The thermodynamic interaction parameter(x) for the three blend systems approximately equals to zero near the melting point. These systems were determined to be miscible on a molecular scale near or above the crystalline melting point or the crystalline PE(2). From the measurement of $T_m$ vs. $T_c$, the behavior of PE(2) is mainly due to a diluent effect of EPR component. The spherulite size measured by small angle light scattering (SALS) technique depended upon blend composition, and stereoregularity of EPR. The size of spherulite was enlarged with the content of rubbery EPR and the decrease of stereoregularity in EPR.

Miscibility and Properties of Ethyl-Branched Polyethylene/Ethylene-Propylene Rubber Blends( I ) (에틸 가지화된 폴리에틸렌과 에틸렌-프로필렌 고무 블렌드의 혼화성와 물성( I ))

  • Cho, Ur-Ryong
    • Elastomers and Composites
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    • v.36 no.3
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    • pp.169-176
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    • 2001
  • Ethyl-branched polyethylene[PE(2)] containing 2mole% ethyl branch and three ethylene-propylene rubbers(EPR's) haying the same ethylene(E)-propylene(P) molar ratio(E/P=50/50) with different stereoregularity, that is, random EPR(r-EPR), alternating-EPR(alt-FPR) and isotactic-alternating-EPR(iso-alt-EPR) were mixed for the investigation of their properties depending on the stereoregurarity. The three blends were immiscible at room temperature, and showed the simple additivity effect in density behavior. The melting point depression with blend composition increased in order of PE(2)/r-EPR>PE(2)/alt-EPR>PE(2)/iso-alt-EPR. In the tensile test, this blend systems have the lowest value or the breaking strength at FE(2) fraction of 0.5. This phenomenon results from the greastest separated phase morphology at this blend composition.

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Rheological Properties of Ethylene-Propylene Rubber Modified Nylon-6 (EP 고무로 개질한 Nylon-6의 유변학적 성질)

  • Haw, Jung-Rim;Lee, Sung;Kim, Byeong-Cheol;Lee, Dai-Soo
    • The Korean Journal of Rheology
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    • v.5 no.2
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    • pp.144-148
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    • 1993
  • Nylon-6의 내충격성을 개선하기 위한 개질제로써 에틸렌-프로필렌 고무(EPR)와 에 틸렌-아크릴 에스터-무수말레산 공중합체(EAM)를 첨가한 nylon-6/EPR/EAM 블렌드 시스 템의 유변학적 특성을 24$0^{\circ}C$에서 조사하였다. 개질제중 EAM의 점도는 조성물 가운데 가장 낮음에도 불구하고 첨가량을 증가함에 따라 블렌드의 점도는 증가하였다. 또한 EPR(I)의 점 도가 EPR(II)의 점도보다 낮지만 EAM 함량이 증가함에 따라 nylon-6/EPR(I)/EAM의 점도 는 nylon-6/EPR(II)/EAM의 점도보다 높아지는 현상이 관찰되었다. 이러한 특성을 분산상의 morphology 변화와 전단력하에서 변형이 어려워지기 때문인 것으로 해석하였다.

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PRELIMINARY STUDY OF WATER CONTENTS AND SIGNAL BEHAVIOR IN FINGERNAIL/EPR DOSIMETRY

  • Choi, Hoon;Choi, Sul A;Lee, Byungil
    • Journal of Radiation Protection and Research
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    • v.38 no.4
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    • pp.185-188
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    • 2013
  • Heating method using electric heater was used to reduce water content in fingernail clippings. Authors found that low water content is helpful to measure EPR signal of fingernail sample with enhanced variability. Generally, natural dehydration happens in normal room condition at least one month and needs much time for using in experiment. So, artificial heating method is applied in this study for time savings. Fingernail samples were tested to find effect of water content to the EPR signal on microwave power levels for dosimetry. Low water content in fingernail reduced variability of EPR signal and makes it possible to measure accurate EPR signal. It also made it possible to measure constant movement of EPR signals on several microwave power levels. Although this method was difficult to apply directly in fingernail/EPR dosimetry, we, authors, believe that this heating method would be useful to differentiate MIS2 and RIS which are generally located at the same g-factor and almost impossible to be identified with each other.

Normal State EPR Study of the n-type High-Tc Superconductors

  • Lee, Cheol-Eui;Kim, W.S.;Noh, S.J
    • Journal of Magnetics
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    • v.3 no.2
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    • pp.39-40
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    • 1998
  • Normal state EPR signals have been studied for the n-type$ high-T_c$ superconductors $Nd_{1.85}Ce_{0.15}CuO_{4-x} and Nd_2CuO_{3.6-x}F_{0.4-y}.$ Since EPR signals were observed only in quenched non-superconducting samples and were absent in furnace-cooled samples, our results suggest that no normal state EPR signals come from pure phase n-type hihg-Tc superconductors. Our observation is consistent with previously reported absence of nomal state EPR signals in the p-type high-Tc superconductors.

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Cosmetic Potency of Puerariae Radix in Dermal Fibroblasts

  • Lee, Jae Yun;Park, Seo A;Woo, Won Hong;Mun, Yeun Ja
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.33 no.1
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    • pp.63-67
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    • 2019
  • Interaction between epidermis and dermis plays an important role in wound healing and hair follicle formation. This study focused on investigating the potency of ethanol extract of Puerariae Radix (EPR) as cosmetic ingredient using human dermal fibroblasts (hDFn). Our results revealed that EPR suppressed collagenase activity dose-dependently. EPR inhibited activity of $5{\alpha}$-reductase I and II at the final concentration of $25{\mu}g/ml$ in hDFn cells. Also, EPR promoted the proliferation and the ERK activation of cells. ERK phosphorylation by EPR was blocked by specific inhibitor of ERK, PD98059. EPR-induced cell proliferation was blocked by PD98059. This means that EPR could promote the proliferation of hDFn cells via the activation ERK. Collectively, these results suggest that EPR may be used as a new cosmetic ingredient.

A Study on Research of Pending Issues for Recovery and Recycling Expansion of Domestic Waste in B City According to EPR Target Extension (EPR대상품목 확대에 따른 B시 생활계폐기물 중심의 회수율과 재활용 확대를 위한 현안조사 연구)

  • Ha, Sang-An;Kim, Dong-Kyun;Nam, Gil-Woo;Wang, Jei-Pil
    • Resources Recycling
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    • v.25 no.1
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    • pp.68-75
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    • 2016
  • Realization of zero waste society, which includes reduction, recycling and reuse of waste, has been a huge issue in Korea recently, and many experts are proposing various improvement plans in the establishment of political system. In particular, the current EPR system is partially agreed on its external achievement, but many problems are arising from the enforcement of the system. Therefore, flexible revisions and modifications on recycling policy are necessary. In order to understand the insufficiency and problem of the expansion of items in current EPR system, this study examined the actual generation and basic unit in small, medium and large-scale apartment complexes in B City and predicted the items that do not appear in the statistics to compare and analyze the problems in current recycling based on their result value; a survey was conducted on 137 experts and students of relevant major that live in B City on the items of EPR system and their perceptions to indicate the error in the necessity of items in EPR system that are generally underperceived by people and the error of current recycling system, and solution plans were sought to establish smooth future system.