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51.
High temperature thermoelectric properties of highly c-axis oriented Bi2Sr2Co2Oy thin films fabricated by pulsed laser deposition 下载免费PDF全文
High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa (001). Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices, 相似文献
52.
Mostefa Sayhi Nasreddine Haine Belkacem Belaabed Valérie Vigneras 《Journal of Macromolecular Science: Physics》2015,54(10):1183-1195
Conducting polymer blends were prepared using polyaniline doped with para- toluene sulfonic acid (PTSA-PANI) and a polyester polyol-based polyurethane (PU). The morphological, thermal and dielectric properties of the PTSA-PANI/PU blends in the frequency range of 1–5 GHz (S band) were investigated. It was found that the morphology of the samples was affected by the PTSA-PANI loading, resulting in the formation of agglomerates and pathways when above 10 wt%. The thermal stability of the composites was improved with increased PTSA-PANI loading. The electrical conductivity percolation threshold was obtained at 2.5% of PTSA-PANI loading and the electrical conductivity reached the value of 0.13 S/m at a PTSA-PANI loading of 30 wt%. The obtained results for the PTSA-PANI/PU blends prepared indicate a high potential for their successful use in electrical and electromagnetic applications. 相似文献
53.
Ziad Khattari Mufeed MaghrabiTony McNally Saadi Abdul Jawad 《Physica B: Condensed Matter》2012,407(4):759-764
The dielectric behavior of polymethyl methacrylate/multi-walled carbon nanocomposites (PMMA/MWCNTs) was investigated using impedance spectroscopy technique. The composites were prepared using melt mixing with MWCNTs loading ranging from 0.01 to 10 wt%. The experimental results showed that the measured impedance reflects the insulating behavior of the host material (PMMA) with no appreciable effects of the filler less than 8.5 wt%. However, for the sample containing 10 wt%, the calculated value of dc conductivity increases with increasing temperature from 2.0×10−6 (Ω m)−1 to attain a value of 4.8×10−6 (Ω m)−1 at 110 °C. The percolation threshold derived from the dielectric data was estimated to be higher than 8.5 wt% and lower than 10 wt%. A temperature dependent electrical relaxation phenomenon was only observed in the sample containing 10 wt% of MWCNTs. The frequency dependence of the ac conductivity data followed a power law. 相似文献
54.
High temperature thermoelectric properties of highly c-axis oriented Bi<sub>2</sub>Sr<sub>2</sub>Co<sub>2</sub>O<sub>y</sub> thin films fabricated by pulsed laser deposition 下载免费PDF全文
High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co2Oy thin films prepared by pulsed laser deposition on LaAlO3(001).Both the electric resistivity ρ and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m·Ω· cm and 202 μV/K at 980 K,resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples.A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature.The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application in high temperature thin film thermoelectric devices. 相似文献
55.
A. Saichev D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(3):443-459
Several recent works point out that the crowd of small unobservable
earthquakes (with magnitudes below the detection threshold md) may
play a significant and perhaps dominant role in triggering future
seismicity. Using the ETAS branching model of triggered seismicity, we
apply the formalism of generating probability functions to investigate
how the statistical properties of observable earthquakes differ from the
statistics of all events. The ETAS (epidemic-type aftershock sequence)
model assumes that each earthquake can trigger other earthquakes
(“aftershocks”). An aftershock sequence results in this model from the
cascade of aftershocks of each past earthquake. The triggering
efficiency of earthquakes is assumed to vanish below a lower magnitude
limit m0, in order to ensure the convergence of the theory and may
reflect the physics of state-and-velocity frictional rupture. We show
that, to a good approximation, the statistical distribution of seismic
rates of events with magnitudes above md generated by an ETAS model
with branching ratio n is the same as that of events generated by
another ETAS model with effective parameter n(md). Our present
analysis thus confirms, for the full statistical (time-independent
or large time-window approximation)
properties, the results obtained previously by one of us and Werner,
based solely on the average seismic rates (the first-order moment of the
statistics). Our analysis also demonstrates that this correspondence is
not exact, as there are small corrections which can be systematically
calculated, in terms of additional contributions that can be mapped onto
a different branching model. We also show that this approximate correspondence
of the ETAS model onto itself obtained by changing m0 into md, and n into
n(md) holds only with respect to its statistical properties
and not for all its space-time properties. 相似文献
56.
We prove some results concerning the decay of connectivities in the low-temperature phase of the two-dimensional Ising model. These provide the bounds necessary to establish, nonperturbatively, large-deviation properties for block magnetizations in these systems. We also obtain estimates on the rate at which the finite-volume, plus-boundary-condition expectation of the spin at the origin converges to the spontaneous magnetization.On leave from São Paulo University, Brazil. 相似文献
57.
给定图$G$,对图$G$的每条边确定一个方向,称为$G$的定向图$G^\sigma$, $G$称为$G^\sigma$的基础图. $G^\sigma$的斜邻接矩阵$S(G^\sigma)$是反对称矩阵,其特征值是0或纯虚数. $S(G^\sigma)$所有特征值的$k$次幂之和称为$G^\sigma$的$k$阶斜谱矩,其中$k$是非负整数.斜谱矩序列可用于对图进行排序.本文主要研究定向树和定向单圈图的斜谱矩,并对这两类图的斜谱矩序列依照字典序进行排序.首先确定了直径为$d$的树作为基础图的所有定向树中,斜谱矩序最大的$2\lfloor\frac{d}{4}\rfloor$个图; 然后确定以围长为$g$的单圈图作为基础图的所有定向单圈图中, 斜谱矩序最大的$2\lfloor\frac{g}{4}\rfloor+1$个图. 相似文献
58.
Scaling theory predicts complete localization in d = 2 in quantum systems belonging to the orthogonal class(i.e., with timereversal symmetry and spin-rotation symmetry). The conductance g behaves as g^exp(-L/l) with system size L and localization length l in the strong disorder limit. However, classical systems can always have metallic states in which Ohm’s law shows a constant g in d=2. We study a two-dimensional quantum percolation model by controlling dephasing effects. The numerical investigation of g aims at simulating a quantum-to-classical percolation evolution. An unexpected metallic phase, where g increases with L, generates immense interest before the system becomes completely classical. Furthermore, the analysis of the scaling plot of g indicates a metal-insulator crossover. 相似文献
59.
基于面向对象技术的多媒体CAI素材库系统 总被引:1,自引:0,他引:1
建立实用、高效的多媒体CAI素材库是高效率、高质量开发CAI软件的基础和关键.本文从数据模型、面向对象分析和存储模式三方面入手,提出一种支撑CAI制作工具的素材库体系结构,并讨论该体系结构的特性和进一步研究的问题. 相似文献
60.
Y. C. Jean Y. Rhee Y. Lou D. Shelby G. L. Wilkes 《Journal of Polymer Science.Polymer Physics》1996,34(17):2979-2985
Two-dimensional angular correlation of annihilation radiation (2D-ACAR) experiments have been performed on an uniaxially oriented polymer, bisphenol-A polycarbonate. The two-dimensional hole structures of unoriented and oriented polymers, determined from the momentum distributions, are found to be spherical and ellipsoidal, respectively. The average hole radii are determined to be 2.9 Å in the unoriented sample and between 2.3 and 3.8 Å in the oriented sample. Applications of the 2D-ACAR method to image the three-dimensional hole structures of polymeric materials are discussed. © 1996 John Wiley & Sons, Inc. 相似文献