共查询到19条相似文献,搜索用时 62 毫秒
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采用交流法测量大功率商用钛酸钡(BT)陶瓷加热器的电阻和加热功率随温度的变化关系,结果显示,BT陶瓷的电导特性在80℃附近出现了明显的转变,从低温时的极化于跳跃导电转变为高温时的能带导电,此时,电阻出现极小值,而加热功率出现极大值. 相似文献
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介绍了利用导电橡胶对薄膜霍尔效应装置的改进方案及对新装置的性能测试结果.初步证实了将导电橡胶应用于薄膜霍尔效应测量装置时,具有电流线平行、不损伤薄膜、装片方便、接触电阻低、接触稳定等优点. 相似文献
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室温下用3MeV的硅离子对聚苯乙烯(PS)进行辐照,对辐照后的样品在室温至液氮温度范围的导电特性进行了测量.结果表明,当辐照剂量在1×1012cm-2附近,PS的室温电阻发生突变.随着温度的降低,PS电阻增大,在低辐照剂量下,电阻在155K附近急剧增加.对于高辐射剂量样品,在较高的温度下呈现热激活导电,在低温下电子通过隧穿传导.分析认为,PS电阻随温度的变化是由于不同剂量辐照离子在聚合物中形成的对电子传导有贡献的导电中心密度不同.通过拟合样品的渗流临界特性,分析了样品电阻随辐照剂量的变化
关键词:
聚苯乙烯
硅离子辐照
低温导电 相似文献
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以均苯四甲酸二酐、4,4'-二氨基二苯醚、炭黑为主要原材料制成填充型导电PI/纳米炭黑复合材料.经电子显微镜及伏安法等对其性能进行表征,结果发现:掺入纳米炭黑能使PI的导电能力增强,且这种能力随炭黑掺入量增加而提高,但是炭黑含量继续增加却会引起聚合物体系中团聚现象的加剧,导致导电能力下降,当掺入量为6%时复合材料导电性能达最好,电阻为4.02×106 Ω. 相似文献
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读了《物理实验》第7卷第5期姜仁滨、王宛珏的“导电薄膜上两点间电阻的计算”一文,觉得其中的一些提法欠妥,兹提出我们的看法以供讨论. 一、导电介质中放任意的两电极(图1),不论导电介质是三维,还是二维(导电薄膜),它们之间的电阻值理论上都是可 相似文献
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测量了液氮温区导电聚吡咯薄膜在直流电场下的电阻,发现电阻对电场有依赖关系。所有的结果在变程跳跃理论上得到很的解释。 相似文献
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The method of time-ordered cumulants is used to investigate the behavior of heat pulses in a one-dimensional medium in which the thermal conductivity is random. A partial differential equation is obtained for the average temperature profile; it is the heat equation modified by the addition of a fourth-order spatial derivative. A solution is obtained by asymptotic series. The first two spatial moments of the average temperature profile are evaluated and are shown to tend to those of a Gaussian whent is large. Finally, an equation is obtained for the covariance function.Alfred P. Sloan Fellow. 相似文献
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Hao Chen 《Frontiers of Physics in China》2009,4(3):327-336
We used the self-consistent method-based density functional theory (DFT) and non-equilibrium Green’s function (NEGF) to simulate
molecular transport. Our numerical calculations for the organic molecular measurement made by Reichert et al. (Phys. Rev. Lett., 2002, 88: 176804) and for the alkanedithiols measurement made by Xu et al. (Science, 2003, 301: 1221) met the related experimental values quite well. This means that the first-principles calculations
based on DFT and NEGF can well explain the conduction measurements of some large molecules. The numerical study reveals the
fact that molecular conduction does not obey the classic law; in stead it illustrates the quantum behavior. We designed active
molecular transistors controlled by the gate bias with high working frequency. They may be the next generation electronic
devices.
相似文献
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Information filtering via weighted heat conduction algorithm 总被引:3,自引:0,他引:3
In this paper, by taking into account effects of the user and object correlations on a heat conduction (HC) algorithm, a weighted heat conduction (WHC) algorithm is presented. We argue that the edge weight of the user-object bipartite network should be embedded into the HC algorithm to measure the object similarity. The numerical results indicate that both the accuracy and diversity could be improved greatly compared with the standard HC algorithm and the optimal values reached simultaneously. On the Movielens and Netflix datasets, the algorithmic accuracy, measured by the average ranking score, can be improved by 39.7% and 56.1% in the optimal case, respectively, and the diversity could reach 0.9587 and 0.9317 when the recommendation list equals to 5. Further statistical analysis indicates that, in the optimal case, the distributions of the edge weight are changed to the Poisson form, which may be the reason why HC algorithm performance could be improved. This work highlights the effect of edge weight on a personalized recommendation study, which maybe an important factor affecting personalized recommendation performance. 相似文献
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根据爱因斯坦的质能等效关系式,热能具有的等效质量称为热质,从而在固态和气态介质中分别建立了声子气质量和热子气质量的概念.应用牛顿定律建立了含有驱动力、阻力和惯性力的热质(声子气或热子气)运动的动量守恒方程.由于热量在介质中的传递本质上就是热质(声子气和热子气)在介质中的运动,所以热质动量守恒方程就是普适的导热定律,能够统一描述各种条件下的导热规律.当热流密度不是很大从而热质惯性力可以忽略时,热质动量守恒方程就退化为傅里叶导热定律,这表明傅里叶导热定律是特殊条件下的导热定律,对于微纳尺度条件下的导热,热流密度可以极高,由速度空间变化引起的惯性力不能忽略,在稳态导热情况下也将出现非傅里叶导热,此时在计算或者实验中不能用热流密度除温度梯度求导热系数.在超快速加热条件下,必需考虑惯性力,与基于CV导热模型的波动方程相比,普适的导热定律增加了因速度空间变化引起的惯性力项,所以在介质中热波叠加时不会出现产生负温度的非物理现象,表明基于热质运动概念的普适导热定律更为合理.
关键词:
傅里叶导热定律
普适导热定律
热质运动
非傅里叶导热 相似文献
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A linear irreversible thermodynamic framework of heat conduction in rigid conductors is introduced. The deviation from local equilibrium is characterized by a single internal variable and a current multiplier. A general constitutive evolution equation of the current density of the internal energy is derived by introducing a linear relationship between the thermodynamic forces and fluxes. The well‐known Fourier, Maxwell–Cattaneo–Vernotte, Guyer–Krumhansl, Jeffreys‐type, and Green–Naghdi‐type equations of heat conduction are obtained as special cases. The universal character of the approach is demonstrated by two examples. Solutions illustrating the properties of the equation with jump boundary conditions are given. 相似文献
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《Current Applied Physics》2018,18(12):1492-1495
This paper studies the influence of temperature on electrical resistivity in α-InAs thin films between 30 K-2K based on the analysis of Mott VRH model and ES VRH model. The effect of the interactions between electrons at lower temperature must be considered, therefore, ES VRH conduction will dominate mechanism, and the crossover from Mott to ES VRH conduction is observed about 7 K. Based on available experiment data and VRH conduction model, the parameters of VRH conduction are determined. And the calculated values of TC are consistent with the experimental results. In addition, RM/ξ, ΔM/kT, RES/ξ and ΔES/kT are satisfied with the validity of Mott and ES models. Furthermore, the temperature dependence of resistivity at low temperature obeys a universal scaling law, which well describes the overall temperature range of VRH conduction. However, the values of T’M from the universal function are two order of magnitudes lower than TM deduced from fitting experiment. 相似文献