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Using the RTM/NEGF method, which is a first-principles calculation tool for the quantum transport through nanostructures between electrodes, we study the effects of atomic-scale contacts on the transport properties through single molecules. Electronic states and current-voltage (I-V) characteristics are investigated in various contact conditions with and without single molecules between electrodes. We find that similar nonlinear behaviors appear in the I-V characteristics. Such nonlinear behaviors are determined not only by the HOMO-LUMO electronic states of single molecules between electrodes, but also by the atomic-scale contact conditions. We show that the transitions from tunneling to ballistic regimes affect the I-V characteristics significantly. 相似文献
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The chemorheology and curing kinetics of a new high performance resin transfer molding benzoxazine resin was investigated. A chemorheological model based on a modified Arrhenius equation that describes the resin viscosity as a function of temperature and time was proposed. The model, which agreed well with the experimental data, can provide theoretical support for the mold-filling stage in the resin transfer molding process. The average activation energies of the polymerization reaction were obtained by means of gelation times at different temperatures based on the Arrhenius equation and from dynamic differential scanning calorimetry (DSC) results based on the Kissinger and Ozawa methods; the values were 96.0,84.0 and 87.8 KJ/mol, respectively. A plot of activation energy vs. conversion in the curing process was obtained using the Flynn-Wall-Ozawa model. The reaction orders were estimated from isothermal DSC based on a modified Kamal kinetics model which can describe both the autocatalytic and diffusion-controlled curing mechanism. 相似文献
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Kenji Hirose Nobuhiko Kobayashi 《Physica E: Low-dimensional Systems and Nanostructures》2005,29(3-4):515
Using the recursion-transfer-matrix (RTM) method combined with nonequilibrium Green's function (NEGF) method, we study the electronic states and current–voltage (I–V) characteristics of junction systems with atomic-scale nanocontacts as a function of the distance between electrodes. We observe a strong nonlinear behavior in the I–V characteristics and correspondingly a gap structure appears in conductance. We find that such a nonlinear behavior emerges when the transport properties change from tunneling to ballistic regimes. 相似文献
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RTM充模分析的隐式控制体积法及其迭代方法 总被引:1,自引:0,他引:1
江顺亮 《南昌大学学报(理科版)》2006,30(2):187-191
RTM充模分析的隐式方法需要迭代来决定树脂注满的区域。为了改善隐式方法的迭代过程,在本文中提出了一种基于界面更新的隐式方法。该方法只对已注满结点进行求解,然后更新界面结点的体积函数以便决定是否要更新界面。采用不同求解方法对该方法进行了试算。计算表明了本文的方法性能良好,计算速度比显式方法有明显改进。 相似文献
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The stochastic nonlinear complementarity problem has been recently reformulated as an expected residual minimization problem which minimizes an expected residual function defined by an NCP function. In this work, we show that the expected residual function defined by the Fischer–Burmeister function is an RTM2SW-1-11/0?wchp=dGLzVlz-zSkzV" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=13 width="24"/> function. 相似文献
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Smoothed Particle Hydrodynamics Modeling of Transverse Flow in Randomly Aligned Fibrous Porous Media
The Lagrangian smoothed particle hydrodynamics (SPH) method is employed to obtain a meso-/micro-scopic pore-scale insight
into the transverse flow across the randomly aligned fibrous porous media in a 2D domain. Fluid is driven by an external body
force, and a square domain with periodic boundary conditions imposed at both the streamwise and transverse flow direction
is assumed. The porous matrix is established by randomly embedding a certain number of fibers in the square domain. Fibers
are represented by position-fixed SPH particles, which exert viscous forces upon, and contribute to the density variations
of, the nearby fluid particles. An additional repulsive force, similar in form to the 12-6 Lennard-Jones potential between
atoms, is introduced to consider the no-penetrating restraint prescribed by the solid pore structure. This force is initiated
from the fixed solid material particle and may act on its neighboring moving fluid particles. Fluid flow is visualized by
plotting the local velocity vector field; the meandering fluid flow around the porous microstructures always follow the paths
of least resistance. The simulated steady-state flow field is further used to calculate the macroscopic permeability. The
dimensionless permeability (normalized by the squared characteristic dimension of the fiber cross section) exhibits an exponential
dependence on the porosity within the intermediate porosity range, and the derived dimensionless permeability—porosity relation
is found to have only minor dependence on either the relative arrangement condition among fibers or the fiber cross section
(shape or area). 相似文献
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Samson Rwawiire Blanka Tomkova Jiri Militky Bandu Madhukar Kale Petr Prucha 《International Journal of Polymer Analysis and Characterization》2015,20(2):160-171
The quest for sustainable materials as a consequence of a global drive to mitigate climate change has led to a focus on natural fiber–reinforced composite materials. In this study, skillful ply angle arrangement of bark cloth–reinforced laminar epoxy composites was carried out for the first time using vacuum-assisted resin transfer molding, and the composites fabricated were characterized for the effect of the layering pattern on their static and dynamic mechanical properties. Tensile strength and flexural strength were shown to be dependent on the ply angle arrangement. Dynamic mechanical analysis of the composites showed a glass transition temperature of 70°C, and the storage modulus and mechanical damping properties showed that the developed composites can withstand considerable loads and have excellent fiber-to-matrix adhesion. 相似文献
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A novel performance matrix, coded as LCRTM, with low cure and post‐cure temperature (≤ 200°C) for fabricating advanced polymer composites via resin transfer molding (RTM), was successfully developed, made up of 4,4′‐bismaleimidodiphenylmethane (BDM) and N‐allyl diaminodiphenylether (ADDE). Investigations show that the stoichiometry of BDM and ADDE has great effect on the processing and performance parameters of the resultant resins. In the case of the optimum formulation (the mole ratio of BDM and ADDE is 1:0.55), the injection temperature range is between 70–82°C, and the pot life at 80°C is 300 min, moreover, the cured resin has desirable thermal and mechanical properties after being cured at 200°C for 6 hr, reflecting a great potential as high performance matrices for fabricating advanced composites via the RTM technique. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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M. Frauenhofer T. Ströhlein S. Fabig S. Böhm L. Herbeck K. Dilger 《Mechanics of Composite Materials》2008,44(5):523-530
The prepreg technology is a state-of-the-art method to produce high-performance CFRP parts. Due to the high material prices,
the restricted process rate, and limitations to the component complexity, in future, more and more parts will be assembled
by using liquid composite moulding. Especially in the case of series larger than 100 parts per year, the LCM technology offers
the best cost-effectiveness. This technology is based on resin injection into dry multilayer fibre textiles (preforms). The
Institute of Joining and Welding (TU, Braunschweig), together with the Institute of Composite Structures and Adaptive Systems
(DLR), has elaborated a new technology to speed up the preform process, which is the most labour-intensive step within the
LCM process chain. A novel concept to consolidate binder-coated fabrics is under development. By applying the high energy
transfer rate of induction technology, it is possible to heat up a preform with rates up to 50 K/s to melt the binder and
consolidate the preform.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 747–756, September–October, 2008. 相似文献