• 제목/요약/키워드: 가소성

검색결과 449건 처리시간 0.027초

Replication Characteristics of Micropatterns According to Mold Temperature in Ultrasonic Imprinting (초음파 임프린팅에서 금형온도에 따른 미세패턴의 전사특성 연구)

  • Min, Kyeong Bin;Park, Jong Han;Park, Chang Yong;Park, Keun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제38권1호
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    • pp.51-57
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    • 2014
  • Ultrasonic imprinting is a novel process for replicating micropatterns on thermoplastic polymer substrates with low energy consumption and short cycle time. The polymer substrate is softened by the frictional heat and repetitive deformation energy under ultrasonic excitation; thus, a number of micropatterns are replicated on the softened polymer substrate. In the present work, the effect of mold temperature on the replication characteristics of ultrasonic imprinting is investigated. The temperature change in the patterned region is measured by varying the mold temperature. Numerical simulation is then performed for investigating pattern replication characteristics under various mold temperatures. In addition, pattern replication ratio and uniformity are compared through various experimental measurements. Through the results of these comparisons, it is found that the mold temperature has a significant positive effect on the replication characteristics of ultrasonic imprinting.

Numerical Analysis for Separation of Carbon Dioxide by Hollow Fiber Membrane with Cocurrent Flow (병류흐름의 중공사 분리막에 의한 이산화탄소 분리 수치 해석)

  • Lee Yong-Taek;Song In-Ho;Ahn Hyo-Seong;Lee Young-Jin;Jeon Hyun-Soo;Kim Jeong-Hoon;Lee Soo-Bok
    • Membrane Journal
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    • 제16권3호
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    • pp.204-212
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    • 2006
  • A numerical analysis was carried out for separation of carbon dioxide from carbon dioxide/nitrogen gas mixture by a polyethersulfone hollow fiber membrane which has shown a good stability against plasticization by carbon dioxide and an excellent separation efficiency fur carbon dioxide from its gas mixture. A computer program for carbon dioxide separation was developed using the Compaq Visual Fortran 6.6 software. Governing module equations were thought to be an initial-value problem and the nonlinear ordinary differential equations were simultaneously solved using the Runge-Kutta-Verner fifth-order method. From results of numerical analysis, the carbon dioxide partial pressure of the feed stream, the pressure ratio of the feed side to the permeate side and the feed gas residence time at the inside of a membrane were found to be very important factors to affect the permeation characteristics of carbon dioxide.

The Neurobiology of Anxiety (불안의 생물학적 근원)

  • Seok Jeong-Ho;Kim Se-Joo;Kim Chan-Hyung
    • Anxiety and mood
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    • 제1권1호
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    • pp.7-13
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    • 2005
  • Anxiety is one of the basic emotions which human experiences across different cultures in the world and it can be observed in mammals. Our understanding of the neurobiology of this emotion has made some advances, even though it has not been completed, with the development and advance in the investigation method including neuroimaging, neurochemical, and genetic approaches. In this article, the neuroanatomical and neurochemical basis of anxiety is reviewed. The amygdaloid complex has been known to playa key role in processing of anxiety or fear. It has extensive afferent and/or efferent connections with cortical and subcortical structures. The mesial temporal structures including hippocampus appear to be involved in acquisition of anxiety and related behaviors. The prefrontal cortical structures appear to play important roles in conscious awareness of anxiety and in modulating anxiety and related behavior. The bed nucleus of the stria terminalis (BNST) is known to playa critical role in unconditioned fear response. The central noradrenergic system and hypothalamo-pituitary-adrenal axis are known to play important roles in modulating and expressing anxiety-related responses. Anxiety has been gathering attentions from many investigators and numerous preclinical and clinical investigations of anxiety and anxiety disorders have been done. In particular, neural plasticity in critical period and the psychobiological factors related to resilience to extreme stress and anxiety are important issues in this field.

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EPD(Electrophoretic Deposition)를 이용한 Ni-$Al_2O_3$ 경사기능재료(FGM) 코팅에 관한 연구

  • Kim, Hyeong-Seop;Yang, Seung-Gyu;Lee, Seon-Yeong
    • Proceedings of the Materials Research Society of Korea Conference
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    • 한국재료학회 2012년도 춘계학술발표대회
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    • pp.104.2-104.2
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    • 2012
  • 이종 재료의 접합에 대한 연구는 단일 재료에서 얻을 수 없는 물리적/기계적 특성과 이종 재료의 우수한 특성을 얻을 수 있다는 장점이 있어 국내외 적으로 연구가 활발히 진행되고 있다. 이러한 이종 접합 기술은 구조재료와 에너지 변환분야에 가장 많이 사용되고 있으며, 그 외 광촉매와 Thin film, 경량구조재료 등에도 사용되고 있다. 그 중 FGM(Functional Graded Materials)는 조성의 점진적인 변화를 통하여 접합하는 방법으로 이종 재료 접합 시 발생하는 내부 응력을 해소해줌으로써 적합한 방법이라고 할 수 있다. FGM 제작에 사용되는 방법으로 널리 알려진 것들로는 plasma spraying, 원심주조, 분말 야금법, PVD, CVD 그리고 EPD(electrophoretic deposition) 등이 있다. 이중에서 EPD는 수용액이나 유기용매와 같은 분산매체 중에 콜로이드 입자의 표면에 대전되는 전하를 이용하여, 외부에서 전장을 걸어서 입자의 움직임을 제어하는 기술이다 EPD는 코팅 속도가 상대적으로 빠르고 두꺼운 코팅 층 제작이 가능하다. 또한 바인더, 윤활제 또는 가소제를 사용하지 않고 다양한 종류와 모양의 기판 위에 균일한 코팅이 가능하다는 장점이 있다. 본 연구에서는 Ni substrate를 이용하여 그 위에 Ni과 $Al_2O_3$의 조성을 점진적으로 변화시켜 FGM을 EPD 방법으로 코팅하였다. 여기서 사용된 Ni은 높은 녹는점과 좋은 연성으로 인해 성형이 용이하여 구조재료로 적합하며, $Al_2O_3$는 고내열성과 내부식성을 가지며 경도가 높다는 장점이 있다. 본 연구에서는 EPD 방식을 이용하여 Ni/$Al_2O_3$ FGM을 코팅하였으며, 코팅 후 발생하는 substrate와의 접착력 문제를 해결하기 위해서 건조 방식과 substrate의 표면 상태를 최적화하여 다층의 Ni/$Al_2O_3$ FGM을 코팅 및 소결하였다. Zeta-potential 측정을 통해 electrophoretic mobility와 suspension의 분산 안정도를 평가 할 수 있었으며, X-ray 회절 분석(XRD)을 통하여 Ni 의 환원 여부를 확인하였다. 또한 Scanning electron microscopy(SEM) 분석을 통하여 미세구조 분석을 하였고, 최종적으로 Electron Probe Micro Analyzer (EPMA) 를 이용하여 다층 구조의 조성변화를 확인함으로 Ni/$Al_2O_3$의 FGM 코팅이 이루어졌음을 확인하였다.

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Analytical method of phthalates in children's products (어린이 용품 중 프탈레이트류 함유량 및 전이량 분석방법 고찰)

  • Kang, Young-Yeul;Shin, Sun-Kyoung;Park, Jin-Soo;Kim, Woo-Il;Chun, Jin-Won;Heo, Hwa-Jin;Koo, So-Hyun
    • Analytical Science and Technology
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    • 제23권4호
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    • pp.357-362
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    • 2010
  • Phthalate plasticizer is not human carcinogens which has been classified as environmentally hazardous substance. Phthalates are absorbed into the body and cause tumors and ecological mutation to human potentially as reproductive toxic substances. For this reason, in some countries the use of phthalates in products for children has been banned. In this study, we proposed the analytical method of phthalate content and migration rate for children's product which was compared and reviewed to the analytical method of various countries, United States, Japan, European Union. The children's product on the proposed analytical method was analysed to consider of the correlation between the phthalate content and migration rate, but there was no correlation both of them.

Analysis of Soil Contamination by Phthalate Ester around Tributaries to the Han River (한강지류 하천 주변 토양의 Phthalate ester 오염 분석)

  • Ahn, Seung-Hyun;Lee, Jong-Hoon;Hong, Yeon-Pyo;Kim, Min-Kyun
    • Applied Biological Chemistry
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    • 제45권2호
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    • pp.97-100
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    • 2002
  • Phthalate esters are used as additives in plastics to improve mechanical properties, particularly flexibility. The contamination of soil samples by phthalate esters around four tributaries to the nm river was analyzed based on gas chromatography-mass spectrometry (GC-MS). All soil samples collected from the four tributaries, which include Anyangcheon and Seohocheon (expected polluted areas), and Gapyeongcheon and Namhan river (expected clean areas), were found to be contaminated by his(2-ethylhexyl) phthalate (DEHP). Soil around Anyangcheon was the most contaminated (113 ppb), about twofold higher than the ones around Seohpcheon (64 ppb), Gapyeongcheon and Namhan river (50 ppb). Based on the fact that DEHP contamination in sediments of the river tributaries around the country is as high as 2.04 ppm, it was concluded that DEHP contamination of the soils around the tributaries to the Han river is relatively low.

Effects of Zinc Stearates on the Thermal and Rheological Properties of Polystyrene Ionomers (폴리스티렌 이오노머의 열적·유변학적 성질에 미치는 스테아린산 아연의 영향)

  • Kim, Jong-sang;Doo, Jun Kil;Lee, Dai Soo
    • Applied Chemistry for Engineering
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    • 제10권8호
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    • pp.1216-1220
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    • 1999
  • Different amounts of zinc stearate were incorporated as a plasticizer into poly(styrene-co-sodium methacrylate) ionomers prepared by bulk-suspension plymerization and neutralization with sodium hydroxide and effects of the zinc stearate on the thermal and rheological properties were investigated. It was obseved that the crystallization of zinc stearate in the ionomers were partially suppressed depending on the content of ionic moieties. It is postulated that the ionic moieties dissolved zinc stearate and suppressed crystallization of the zinc stearates. We speculated that 0.4~0.6 mole of zinc stearate was dissolved by one mole of the ionic moiety. Poly(styrene-co-sodium methacrylate) containing only the dissolved zinc stearates showed typical rheological properties of homogeneous systems in Cox-Mertz plots. However, poly(styrene-co-sodium methacrylate) containing crystallizable zinc stearates as well as dissolved ones showed typical rheological properties of heterogeneous systems.

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Expression of Calponin 3 in the Striatum Following 3-Nitropropionic Acid-induced Neurotoxicity (선조체에서 3-nitropropionic acid 투여 후 calponin 3의 발현 연구)

  • Choi, Yun-Sik
    • Journal of Life Science
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    • 제23권1호
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    • pp.125-130
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    • 2013
  • Calponin 3 is an F-actin-binding protein and plays a key role in regulating spine plasticity and synaptic activity in neurons. Unlike the other subtypes, calponin 1 and 2, which are expressed in smooth and cardiac muscle cells, calponin 3 is highly expressed in the brain. The goal of this study was to elucidate the spatiotemporal expression pattern of calponin 3 following repeated administration of 3-nitropropionic acid in mice. The repeated administration of 3-nitropropionic acid generated necrotic neuronal cell death in the striatum. Calponin 3 was up-regulated in the neuroprotective penimbral region from 1.5 days after the last injection and thereafter. Double immunofluorescence study revealed that calponin 3 was induced in GFAP-positive astrocytes. These results suggest that calponin 3 induction in the neuroprotective penumbral area following 3-nitropropionic acid intoxication may play a key role in reactive astrogliosis in the striatum.

Electrochemical Characterization and Mechanical Properties of PEO-like Solid Polymer Electrolyte Based on Bisphenol A Ethoxylate Diacrylate (Bisphenol A ethoxylate diacrylate를 가교제로 사용한 PEO계 고분자 전해질의 전기화학적 특성 및 물성)

  • Kim, Seok-Koo;Kang, Yong-Ku;Rhee, Hee-Woo;Lee, Chang-Jin
    • Polymer(Korea)
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    • 제25권4호
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    • pp.568-574
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    • 2001
  • PEO-like solid polymer electrolytes based on bisphenol A ethoxylate acrylate were synthesized and their electrochemical properties and mechanical stability were studied. Low molecular weight poly(ethylene glycol) dimethyl ether (PEGDMe) was added to increase the conductivity of the electrolyte. The maximum conductivity of the resulting polymer electrolyte was found to be 1.0 ${\times}$ 10$^{-3}$ S/cm [Bisphenol A ethoxylate diacrylate ([EO]/[phenol]= 15), PEGDMe250 80 wt%, LiCF$_3SO_3$] at 30$^{\circ}$C. Tensile strength of the free standing polymer electrolyte films was measured to be in the range of 0.4 ~ 5 MPa and these polymer electrolyte films did not show a crack even in 90$^{\circ}$ and 180$^{\circ}$ bending against ${\phi}$=3 mm bar. These electrolytes showed oxidation stability up to 4.5 V vs. lithium reference electrode.

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Studies on the Oxygen Permeability and It's Proofness of the Various Commercial Polymer Films (상업용 고분자 필름의 산소투과도 및 산소투과 방지도에 관한 연구)

  • Suh, Hwan-Kyu;Kim, Joon-Soo;Lee, Jung-Keun
    • Elastomers and Composites
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    • 제15권1호
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    • pp.3-9
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    • 1980
  • The oxygen permeability and it's proofness of te various commercial polymer films have been investigated at the constant pressure and temperature. Oxygen proofness, the reciprocals of the oxygen permeability for the various samples, were determined by means of a coulometric oxygen permeability tester. The testing of sample films was performed at constant temperature $(23{\pm}1^{\circ}C)$ under 1 atm. for 24 hours. The order of the relative proofness observed are as follows; oriented Nylon (O. Nylon)> oriented Polyester (O. PET)>nonoriented Nylon (N. Nylon)>nonoriented Polyester (N.PET)> rigid Polyvinyl chloride (Rigid PVC)>semirigid Polyvinyl chloride (Semirigid PVC)> oriented Polypropylene (O. PP)>plasticized Polyvinyl chloride (P. PVC)> casted Polypropylene (C. PP)> low density Polyethylene (LDPE)>high density Polyethylene (HDPE, Inflation)> high density-polyethylene (HDPE, T-die) The oxygen proofness of the films was increased with the polarity cf polymer, the film thickness and mechanical orientation and decreased with the addition of plasticizer in PVC. For the use of wrapping materials, one film with the polar property in the main chain of the polymer molecule and the others with nonpolar property in it are laminated for the protection from oxygen and moisture.

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