• 제목/요약/키워드: interphase

검색결과 197건 처리시간 0.02초

Modern State of Models for Fundamental Adhesion - A Review Extended Abstract

  • Possart, Wulff
    • 접착 및 계면
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    • 제3권1호
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    • pp.43-51
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    • 2002
  • Advanced adhesive technologies and demanding applications of adhesive joints can no longer be developed successfully by the traditional "trial and error" approach. Appropriate technical solutions require reference to a reliable basis of well-established scientific knowledge about the elementary mechanisms of adhesion (i.e. the 'fundamental adhesion') as they are responsible for the capability of the compound w transmit mechanical force between the adhesive and the substrate surface (i.e. the 'practical adhesion'). Adhesion mechanisms also influence the formation of polymer structure in the adhesive and the resulting macromolecular dynamics in the interphase that is formed in the adhesive near to the substrate. These manifold molecular factors rule the macroscopic behaviour of an adhesive bond line in terms of mechanical and other physical properties as well as in terms of durability. This paper reviews the level of refinement that understanding of fundamental adhesion has achieved up to now.

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잠겨진 가스분사장치에서의 2상 유동 및 열전달 특성 (Two-phase flow and heat transfer characteristics in a submerged gas injection system)

  • 최청렬;김창녕
    • 설비공학논문집
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    • 제11권6호
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    • pp.824-834
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    • 1999
  • Characteristics of two-phase flow and heat transfer were numerically investigated in a submerged gas injection system when temperature of the injected gas was different from that of the liquid. The Eulerian approach was used for both the continuous and dispersed phases. The turbulence in the liquid phase was modeled using the standard $k-\varepsilon$$\varepsilon$ turbulence model. The interphase friction and heat transfer coefficient were calculated from the correlations available in the literature. The turbulent dispersion of the phases was modeled by a "dispersion Prandtl number". In the case with heat transfer where the temperature of the injected gas is higher than the mean liquid temperature, the axial and the radial velocities are lower in comparison with the case of homogeneous temperatures. The results in the present research are of interest in the design and operation of a wide variety of material and chemical processes.

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평판에서 층류 막응축의 근사해 (Approximate Solutions for Laminar Film Condensation on a Flat Plate)

  • 이승홍;권장렬;이억수
    • 설비공학논문집
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    • 제3권4호
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    • pp.215-221
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    • 1991
  • Laminar film condensation of a saturated vapor in forced flow over a flat plate is analyzed by using integral method. Laminar condensate film is so thin that the inertia and thermal convection terms in liquid flow can be neglected. Approximate solutions for water are presented and well agreed with the similarity solutions over the wide range of physical parameter, Cp1(Ts-Tw)/Pr.hfg. For the strong condensation case, it is found that magnitude of the interfacial shear stress at the liquid-vapor interphase boundary is approximately equal to the momentum transferred by condensation, i.e., ${\tau}_i{\simeq}\dot{m}(U_O-U_i)$.

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삼상 유도전동기의 고효율 운전을 위한 SW-VVVF 시스템에 관한 연구 (SW-VVVF System for High Efficiency Drive of Induction Motor)

  • 유철로;이공희;이성룡
    • 대한전기학회논문지
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    • 제38권2호
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    • pp.93-99
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    • 1989
  • This paper describes Sinusoidal Wave-Variable Voltage Variable Fequency (SW-VVVF) system for the high efficiency drive of a 3-phase induction motor. SW-VVVF system consists of a 3-phase 24-pulse converter and a SPWM inverter. The converter with additional 2 tap diode circuits in interphase reactor reduces harmonics in input current. The SPWM inverter consists of an improved PLL system and a V/F controller, which reduces harmonics in output current and performs a high efficiency algorithm by maintaining a constant slip frequency and compensating for the velocity variation of the induction motor with the change of load. Therefore, this system reduces harmonics in input and output currents, and also can drive an induction motor with high efficiency in an economical way. We have proved its utility through experiment.

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Local nanofiller volume concentration effect on elastic properties of polymer nanocomposites

  • Shin, Hyunseong;Han, Jin-Gyu;Chang, Seongmin;Cho, Maenghyo
    • Multiscale and Multiphysics Mechanics
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    • 제1권1호
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    • pp.65-76
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    • 2016
  • In this study, an influence of local variation of nanoparticulate volume fraction on the homogenized elastic properties is investigated. It is well known that interface effect is dependent on the radius and volume fraction of reinforced nanofillers. However, there is no study on the multiscale modeling and analysis of polymer nanocomposites including polydispersed nanoparticles with consideration of interphase zone, which is dependent on the volume fraction of corresponding nanoparticles. As results of numerical examples, it is confirmed that an influence of local variation of nanoparticulate volume fraction should be considered for non-dilute system such as cluster of nanoparticles. Therefore representative volume element analysis is conducted by considering local variation of nanoparticle volume fraction in order to analyze the practical size of cell including hundreds of nanoparticles. It is expected that this study could be extended to the multiparticulate nanocomposite systems including polydispersed nanoparticles.

Actin-related protein BAF53 is essential for the formation of replication foci

  • Kwon, Su-Jin;Kwon, Hyock-Man
    • Animal cells and systems
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    • 제16권3호
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    • pp.183-189
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    • 2012
  • It has been suggested that chromatin is organized into the stable structures that provide fundamental units of chromosome architecture in interphase mammalian cells. The stable structures of chromatin can be visualized as replication foci when replicating DNA is labeled with thymidine analogs. Previously, we showed that the chromosome territory expanded after BAF53 knockdown. In this study, we found that BAF53 is required for the formation of replication foci. DNA replication was not impaired in BAF53 knockdown cells, suggesting that the decrease in the number of replication foci is due to disintegration of replication foci, but not suppression of DNA replication. The attractive forces that maintain structural integrity of replication foci could be disrupted by BAF53 knockdown, and it may be responsible, at least in part, for the expansion of chromosome territories after BAF53 knockdown.

Isolation of Luteolin 7-O-rutinoside and Esculetin with Potential Antioxidant Activity from the Aerial Parts of Artemisia montana

  • Kim, Na-Mee;Kim, Jong;Chung, Hae-Young;Chol, Jae-Sue
    • Archives of Pharmacal Research
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    • 제23권3호
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    • pp.237-239
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    • 2000
  • The antioxidant activity of Artemisia montana was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and inhibitory activity against free radical generation of hepatocytes ($AC_2$F). The methanol extract of A. montana showed strong radical scavenging activity at a concentration of $10.1{\mu}g/m{\ell}$, and thus fractionated by solvent extraction. Esculetin and luteolin 7-O-rutinoside (scolymoside) were isolated as the active principles from the EtOAc and interphase fractions, respectively. The antioxidant activity of these compounds were comparable to that of L-ascorbic acid.

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A micromechanics-based time-domain viscoelastic constitutive model for particulate composites: Theory and experimental validation

  • You, Hangil;Lim, Hyoung Jun;Yun, Gun Jin
    • Advances in aircraft and spacecraft science
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    • 제9권3호
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    • pp.217-242
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    • 2022
  • This paper proposes a novel time-domain homogenization model combining the viscoelastic constitutive law with Eshelby's inclusion theory-based micromechanics model to predict the mechanical behavior of the particle reinforced composite material. The proposed model is intuitive and straightforward capable of predicting composites' viscoelastic behavior in the time domain. The isotropization technique for non-uniform stress-strain fields and incremental Mori-Tanaka schemes for high volume fraction are adopted in this study. Effects of the imperfectly bonded interphase layer on the viscoelastic behavior on the dynamic mechanical behavior are also investigated. The proposed model is verified by the direct numerical simulation and DMA (dynamic mechanical analysis) experimental results. The proposed model is useful for multiscale analysis of viscoelastic composite materials, and it can also be extended to predict the nonlinear viscoelastic response of composite materials.

EC:MA 혼합전해질에서 카본 전극의 용량 특성 - I. 전기화학적 특성에 대한 혼합비의 영향 - (Properties of Capacity on Carbon Electrode in EC:MA Electrolytes - I. Effect of Mixing Ratio on the Electrochemical Properties -)

  • 박동원;김우성;손동언;김성필;최용국
    • 공업화학
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    • 제17권2호
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    • pp.183-187
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    • 2006
  • 리튬-이온 전지에서 전해질 용액에 대한 용매의 선택은 충방전 특성의 개선을 위해 매우 중요하다. 여러 가지 용매 시스템이 리튬-이온 전지의 전해질로서 광범위하게 연구 되어졌다. 본 연구는 다양한 혼합비에서 제조한 1 M $LiPF_6/EC$ (ethylene carbonate) : MA (methyl acetate) (x:y) 전해질 용액의 용매 분해 전위와 카본 부극 표면에 형성된 Solid Electrolyte Interphase 피막의 전기화학적 성질을 시간대 전위법, 순환 전압- 전류법, 임피던스법을 이용하여 관찰하였다. 용매분해 전위는 전해질의 이온 전도도에 따라 전위가 달라졌고, 용매의 혼합비에 따라 피막의 전기화학적 특성이 변화되었음을 확인하였다. 결과적으로, 1 M $LiPF_6/(EC+MA)$ 시스템에서 가장 적절한 EC와 MA의 혼합비는 대략 1:3 (EC:MA, 부피비)이었다.

LiBOB 전해액 첨가제 도입에 따른 Li(Ni1/3Co1/3Mn1/3)O2/graphite 전지의 고온특성 (Effects of Lithium Bis(Oxalate) Borate as an Electrolyte Additive on High-Temperature Performance of Li(Ni1/3Co1/3Mn1/3)O2/Graphite Cells)

  • 정지선;이혜원;이후길;유명현;이용민
    • 전기화학회지
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    • 제18권2호
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    • pp.58-67
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    • 2015
  • 음극 표면에 solid electrolyte interphase (SEI)를 형성하는 전해질 첨가제인 lithium bis(oxalate) borate (LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), 2-(triphenylphosphoranylidene) succinic anhydride (TPSA)를 $Li(Ni_{1/3}Co_{1/3}Mn_{1/3})O_2$ (NCM)/graphite 전지에 도입하여 고온 저장 특성을 비교하였다. 각 전지를 50%의 충전상태(stage of charge, SOC)에서, 고온 저장($60^{\circ}C$, 20일) 시킨 이후의 용량 유지율을 확인한 결과, LiBOB 1 wt.%가 가장 우수한 용량 유지 특성(초기 방전용량 대비 86.7%)을 나타내었다. LiBOB 1 wt.%의 경우 고온 저장 전후의 전지 저항 증가 및 SEI 두께 변화가 가장 적었고, 이는 음극 SEI에 포함된 다량의 semi-carbonate 물질과 연관성이 높다고 판단된다. 또한, LiBOB 1 wt.%가 포함된 NCM/graphite 전지의 상온($25^{\circ}C$) 및 고온수명($60^{\circ}C$) 특성도 기준 전해액(1.15 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate/ethyl methyl carbonate (EC/EMC, 3/7 by volume))보다 각각 6%와 9% 향상된 결과를 보여주었다. 따라서, LiBOB이 상온 성능을 동등 이상으로 유지하면서도 고온 특성을 개선할 수 있는 우수한 전해액 첨가제로 판단된다.