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Contact Interface (contact + interface)
Selected AbstractsHigh-Performance Air-Processed Polymer,Fullerene Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Chang-Yong Nam Abstract High photovoltaic device performance is demonstrated in ambient-air-processed bulk heterojunction solar cells having an active blend layer of organic poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), with power conversion efficiencies as high as 4.1%, which is comparable to state-of-the-art bulk heterojunction devices fabricated in air-free environments. High-resolution transmission electron microscopy is combined with detailed analysis of electronic carrier transport in order to quantitatively understand the effects of oxygen exposure and different thermal treatments on electronic conduction through the highly nanostructured active blend network. Improvement in photovoltaic device performance by suitable post-fabrication thermal processing results from the reduced oxygen charge trap density in the active blend layer and is consistent with a corresponding slight increase in thickness of an ,4,nm aluminum oxide hole-blocking layer present at the electron-collecting contact interface. [source] Transient scattering of plane waves from an inclusion with a unilateral frictional contact interface,a 2D time domain boundary element analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2004Yang-De Feng Abstract This paper is the continuity of our previous work (Commun Numer Meth Engng 2003; 19: 25,36) which applies the 2D time domain boundary element method (BEM) to solve the transient scattering of SH waves by an inclusion with a unilateral frictional contact interface. The case of the plane wave (P and/or SV wave) incidence is studied. Localized slip and separation at the interface caused by strong incident waves are considered. Therefore the interface involves three different kinds of unknown intervals: slip, separation and stick regions. In order to determine the unknown intervals, an iterative technique is developed. As an example, we compute the scattering of P waves by a cylinder of circular cross-section embedded in an infinite solid. Numerical results for the near field solutions are presented. The distortion of the response waves and the variation of the interface states are discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Finite element modelling of rock alteration and metamorphic process in hydrothermal systemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2001Chongbin Zhao Abstract We use the finite element method to simulate the rock alteration and metamorphic process in hydrothermal systems. In particular, we consider the fluid,rock interaction problems in pore-fluid saturated porous rocks. Since the fluid,rock interaction takes place at the contact interface between the pore-fluid and solid minerals, it is governed by the chemical reaction which usually takes place very slowly at this contact interface, from the geochemical point of view. Due to the relative slowness of the rate of the chemical reaction to the velocity of the pore-fluid flow in the hydrothermal system to be considered, there exists a retardation zone, in which the conventional static theory in geochemistry does not hold true. Since this issue is often overlooked by some purely numerical modellers, it is emphasized in this paper. The related results from a typical rock alteration and metamorphic problem in a hydrothermal system have shown not only the detailed rock alteration and metamorphic process, but also the size of the retardation zone in the hydrothermal system. Copyright © 2001 John Wiley & Sons, Ltd. [source] A numerical,analytical combined method for vibration of a beam excited by a moving flexible bodyINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2007Huajiang Ouyang Abstract The vibration of a beam excited by a moving simple oscillator has been extensively studied. However, the vibration of a beam excited by an elastic body with conformal contact has attracted much less attention. This is the subject of the present paper. The established model is more complicated but has a much wider range of applications than the moving-oscillator model. Because the moving body is flexible, the moving loads at the contact interface are not known a priori and must be determined together with the dynamics of the whole system. In this paper, the equation of motion of the beam and the moving body are established separately using a numerical,analytical combined approach. It is found from the numerical results of the simulated example that the vibrations of the moving body and the beam excited by the moving body are significantly influenced by the travelling speed. At very low or very high speeds the dynamic effect is small and the beam deforms to take the shape of its static deflection. Vibrations tend to be greater in the intermediate speed range and the total moving force at the interface of the beam and the moving body can be compressive and tensile. Copyright © 2007 John Wiley & Sons, Ltd. [source] The least-squares meshfree method for elasto-plasticity and its application to metal forming analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2005Kie-Chan Kwon Abstract A new meshfree method for the analysis of elasto-plastic deformation is presented. The method is based on the proposed first-order least-squares formulation for elasto-plasticity and the moving least-squares approximation. The least-squares formulation for classical elasto-plasticity and its extension to an incrementally objective formulation for finite deformation are proposed. In the formulation, equilibrium equation and flow rule are enforced in least-squares sense, i.e. their squared residuals are minimized, and hardening law and loading/unloading condition are enforced pointwise at each integration point. The closest point projection method for the integration of rate-form constitutive equation is inherently involved in the formulation, and thus the radial-return mapping algorithm is not performed explicitly. The proposed formulation is a mixed-type method since the residuals are represented in a form of first-order differential system using displacement and stress components as nodal unknowns. Also the penalty schemes for the enforcement of boundary and frictional contact conditions are devised and the reshaping of nodal supports is introduced to avoid the difficulties due to the severe local deformation near contact interface. The proposed method does not employ structure of extrinsic cells for any purpose. Through some numerical examples of metal forming processes, the validity and effectiveness of the method are discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effect of metallised carbon content of collector strip on the wear of contact wire,collector strip pair in railway systemsLUBRICATION SCIENCE, Issue 1 2007B. Pizzigoni Abstract Among the topics related to the interaction between the contact wire of the overhead line and the collector strip, the wear that takes place at the contact interface, depending on both electrical and mechanical quantities, represents an important aspect of maintenance costs, affecting the mean lifetime of collectors, in terms of travelled kilometers (in terms of tenth of thousands), and contact line duration, in terms of years (between 15 and 40). Due to its importance in the global maintenance of both rolling stock and infrastructure, this topic deserved the attention of several regulations in the last decade. In order to investigate the effects of electro-mechanical wear on both contact wire and contact strip, a new test equipment has been designed and installed at Politecnico di Milano. A series of tests have been performed, involving different kinds of collector strip materials and contact conditions, tested at varying speeds and current intensities. This investigation concerned different collector strip configurations intended for 3kV D.C. lines. The combination of different contents of copper and metallised carbon in the collector has been found to influence the wear rate of both collector strip and contact wire. Differences in wear up to four times for the former and up to six times for the latter have been found depending on the composition of the collector. Copyright © 2006 John Wiley & Sons, Ltd. [source] An approach to combined rock physics and seismic modelling of fluid substitution effectsGEOPHYSICAL PROSPECTING, Issue 2 2002Tor Arne Johansen ABSTRACT The aim of seismic reservoir monitoring is to map the spatial and temporal distributions and contact interfaces of various hydrocarbon fluids and water within a reservoir rock. During the production of hydrocarbons, the fluids produced are generally displaced by an injection fluid. We discuss possible seismic effects which may occur when the pore volume contains two or more fluids. In particular, we investigate the effect of immiscible pore fluids, i.e. when the pore fluids occupy different parts of the pore volume. The modelling of seismic velocities is performed using a differential effective-medium theory in which the various pore fluids are allowed to occupy the pore space in different ways. The P-wave velocity is seen to depend strongly on the bulk modulus of the pore fluids in the most compliant (low aspect ratio) pores. Various scenarios of the microscopic fluid distribution across a gas,oil contact (GOC) zone have been designed, and the corresponding seismic properties modelled. Such GOC transition zones generally give diffuse reflection regions instead of the typical distinct GOC interface. Hence, such transition zones generally should be modelled by finite-difference or finite-element techniques. We have combined rock physics modelling and seismic modelling to simulate the seismic responses of some gas,oil zones, applying various fluid-distribution models. The seismic responses may vary both in the reflection time, amplitude and phase characteristics. Our results indicate that when performing a reservoir monitoring experiment, erroneous conclusions about a GOC movement may be drawn if the microscopic fluid-distribution effects are neglected. [source] Structure of tetragonal crystals of human erythrocyte catalaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2001Martin K. Safo The structure of catalase from human erythrocytes (HEC) was determined in tetragonal crystals of space group I41 by molecular-replacement methods, using the orthorhombic crystal structure as a search model. It was then refined in a unit cell of dimensions a = b = 203.6 and c = 144.6,Å, yielding R and Rfree of 0.196 and 0.244, respectively, for all data at 2.4,Å resolution. A major difference of the HEC structure in the tetragonal crystal compared with the orthorhombic structure was the omission of a 20-residue N-terminal segment corresponding to the first exon of the human catalase gene. The overall structures were otherwise identical in both crystal forms. The NADPH-binding sites were empty in all four subunits and bound water molecules were observed at the active sites. The structure of the C-terminal segment, which corresponds to the last exon, remained undetermined. The tetragonal crystals showed a pseudo-4122 symmetry in molecular packing. Two similar types of lattice contact interfaces between the HEC tetramers were observed; they were related by the pseudo-dyad axes. [source] | ||||||||||