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991.
Abstract Transformation kinetics from hBN to cBN has been studied at 6 GPa with changing reaction temperature and content of catalyst mixed with hBN powder. At lower catalyst content (3–10 wt %), rate of transformation was extraordinary rapid between 1300 and 1350 C. At higher catalyst content (30–50 wt %), rate of transformation was decreased. Normal nucleation kinetics was observed at about 1500 C. The rapid transformation temperature region correlates characteristic behavior of the sintering process. 相似文献
992.
热场致发射阴极所产生的强流电子束具有很强的空间电荷效应,为研究该效应对热场致发射过程中诺廷汉(Nottingham)效应的影响机理,在理论分析的基础上,用数值方法研究了不同逸出功和多个外加电场条件下考虑空间电荷效应对诺廷汉效应结果的影响,并与不考虑空间电荷效应时的情形进行了对比. 结果表明:空间电荷效应的强弱会显著影响到阴极表面的稳态电场,进而对诺廷汉效应产生不可忽略的影响;当逸出功在3.0–4.52 eV、外加电场在3×109–9×109 V/m范围内时,考虑空间电荷效应的影响后,热场致发射电子所带走的平均能量较不考虑空间电荷效应时增加0–2.5 eV,且温度越高或外加电场越大时,该增加值越大;考虑空间电荷效应对诺廷汉效应的影响后,热场致发射电子从阴极带走的平均能量随外加电场的增加呈非线性下降规律;当阴极表面温度较高时,诺廷汉效应中的冷却效应随二极管间隙距离的变大而增强.
关键词:
热场致发射
诺廷汉效应
空间电荷效应
阴极表面电场 相似文献
993.
高强混凝土立方强度尺寸效应的分析计算 总被引:1,自引:0,他引:1
王岩 《数学的实践与认识》2006,36(8):144-147
对55组高强混凝土立方强度实测数据作了分析,并给出了计算公式.表明高强混凝土立方强度尺寸效应不同于普通混凝土. 相似文献
994.
Jean-Louis Féménias 《Journal of Molecular Spectroscopy》2005,232(1):80-101
Applications of the χ2 test, the F test, the Durbin-Watson d test, and the f (or Sign) test, to examples of correlated data treatment, show important drawbacks with the d test and (apparently) with the f test. An analytical approach based on residual analysis suggests an improvement in their use that leads to better results at lowest order; it also points out a distinction between goodness-of-fit tests, as the f test, and goodness-of-modeling tests, as the χ2 and F tests. The residual analysis method is applied to the same examples; it looks faster, simpler, and often more accurate than the classical ones. 相似文献
995.
Helmut R. Brand Charles R. Doering Robert E. Ecke 《Journal of statistical physics》1989,54(5-6):1111-1119
A brief introduction to the field is given together with an overview of the lectures given at the workshop on External Noise and its Interaction with Spatial Degrees of Freedom in Nonlinear Dissipative Systems organized by the Center for Nonlinear Studies at Los Alamos, March 28–31, 1988. It is hoped that the publication of papers presented at the workshop in a single issue of theJournal of Statistical Physics will help draw attention to the recent developments in this rapidly area of nonequilibrium phenomena. 相似文献
996.
997.
Equality of Types for the Distribution of the Maximum for Two Values of n Implies Extreme Value Type
In this note, we prove a characterization of extreme value distributions. We show that, under some conditions, if the distribution of the maximum of n i.i.d. variables is of the same type for two distinct values of n then the distribution is one of the three extreme value types. This is an analogue of the well known result that if the sum of two i.i.d. random variables with finite second moment is of the same type as the original distribution then the distribution is Gaussian (Kagan et al., 1973). Our result was motivated by study of the m out of n bootstrap. 相似文献
998.
S. Djordjevic E. Farber G. Deutscher N. Bontemps O. Durand J.P. Contour 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(4):407-416
We report results obtained with two different experimental set-ups in state-of-the-art YBCO thin films as similar as possible,
prepared by pulsed laser deposition on LaAlO3 substrates: a surface impedance measurement on 4000 ? thick films using a parallel plate resonator (10 GHz), and a far infrared
transmission (100-400 GHz) measurement which requires thinner (1000 ?) samples. The former measurement yields the temperature
variation of the penetration depth λ(T) and the real part of the conductivity, provided the absolute value of λ(T) is known. The latter yields the imaginary part of the conductivity, hence the absolute value of the penetration depth, as
well as its temperature dependence at the measuring frequency. Combining these two experiments, we establish a quasi-linear
temperature variation of λ(T), with a 2 ? K-1 low temperature slope, and a fairly large zero temperature value λ(T = 0)=(1800±200) ? . The scattering rate of the quasi-particles calculated from a two-fluids model shows that the films compare
to good quality single crystals, where twice a larger slope has been found. This surprising behavior is described in detail,
including an in-depth structural analysis of the samples in order to evaluate their similarities. We find that the 10 GHz
data obtained in the thickest films can be fitted to the dirty d-wave mode in the unitarity limit, with an extrapolated slope of 3 ? K-1, but yield a scattering rate that is difficult to reconcile with the high T
c (92 K) of the films.
Received 7 May 2001 and Received in final form 18 October 2001 相似文献
999.
Based on theab initio calculation results, the hydrogen atom transfer has been investigated. In order to explain the experimental results, a new
mechanism is proposed, that is, hydrogen transfer occurs before but not after CI atom eliminates from aromatic ring. The calculation
result strongly supports this mechanism. 相似文献
1000.
The new bioaffinity membranes comprise mammalian blood and tissue cells immobilized in the polymer matrix. The method of immobilization does not assume the retention of physiological and enzymatic activity of immobilized cells, but it ensures the safety of cellular membrane receptors that are used as specific ligands. Macroporous polymer carriers based on polyacrylonitrile maintain the accessibility of the cellular receptors for all blood plasma components including immunoglobulins and viral particles. The sorption capacity of membranes with respect to model substances in a batchwise technique is evaluated. Although the results are of a preliminary nature, the membranes may be used in crossflow modules for selective blood plasma correction of endogenous substances. 相似文献