具有体膨胀和剪切效应的结构陶瓷相变塑性细观本构模型:Ⅰ.非比例加载历史

本文在对结构陶瓷的四方至单斜(t→m)马氏体相变进行细观力学、热力学和微观机制分析的基础上,导出了在非比例加载条件下考虑材料的体膨胀和剪切效应的相变塑性细观本构模型。作者首次采用 Mori-Tanaka 方法以自洽的方式导出了材料构元的 Helmho-ltz 自由能及余能函数的解析表达式,它是外加宏观应力(或应变)、温度、相变夹杂体积分数以及夹杂内平均相变应变的函数,其中夹杂体积分数和平均相变应变为描述材料构元微结构变化的内变量。最后按 Hill-Rice 本构理论框架导出相变塑性屈服面方程及增量本构关系。     

Final-state interactions and single-spin asymmetries in semi-inclusive deep inelastic scattering

Recent measurements from the HERMES and SMC Collaborations show a remarkably large azimuthal single-spin asymmetries A_UL and A_UT of the proton in semi-inclusive pion leptoproduction γ^*(q)p→πX. We show that final-state interactions from gluon exchange between the outgoing quark and the target spectator system lead to single-spin asymmetries in deep inelastic lepton–proton scattering at leading twist in perturbative QCD; i.e., the rescattering corrections are not power-law suppressed at large photon virtuality Q² at fixed x_bj. The existence of such single-spin asymmetries requires a phase difference between two amplitudes coupling the proton target with J^z_p=±1/2 to the same final-state, the same amplitudes which are necessary to produce a nonzero proton anomalous magnetic moment. We show that the exchange of gauge particles between the outgoing quark and the proton spectators produces a Coulomb-like complex phase which depends on the angular momentum L^z of the proton's constituents and is thus distinct for different proton spin amplitudes. The single-spin asymmetry which arises from such final-state interactions does not factorize into a product of distribution function and fragmentation function, and it is not related to the transversity distribution δq(x,Q) which correlates transversely polarized quarks with the spin of the transversely polarized target nucleon.     

Catalytic formation of hydrogen peroxide from H2 and O2 over hydrogen transfer agent-anchored Pd°/beta zeolites

Hydrogen transfer agents (HTAs) have been successfully anchored on Pd°/H-beta zeolite and exhibit enhanced catalytic activity in the formation of H₂O₂ from H₂ and O₂ at atmospheric pressure compared with that of the Pd°/H-beta and the HTA included catalysts.     

93Nb knight shift and quadrupole coupling parameters in the orthorhombic β phase hydride and deuteride of niobium

The Knight shift tensor components and quadrupole coupling parameters of the ⁹³Nb NMR have been measured for the first time in the orthorhombic β phase hydride and deuteride of niobium. The isotropic component of the Knight shift tensor has the same value in the hydride phase as in the solid solution (α') phase at the same composition, indicating that no significant change in band structure details occurs as a consequence of the structural phase transition. Comparison of the measured asymmetry parameter of the quadrupole interaction with calculated values indicates that the probable Nb environment is that of the ordered NbH structure. Estimates of the activation energy for hydrogen (deuterium) diffusion are obtained from the temperature dependence of the linewidths of the spectrum features.     

Recoil corrections to magnetic moments of octet baryons in the MIT bag model

The presence of certain recoil corrections in the determination of baryon magnetic moments is described and taken into account for the octet members. Inclusion of these recoil corrections makes the MIT bag model, even in its zeroth-order version, very appealing, if the sum of many other corrections is not important by comparison.     

The temperature dependence of the elastic constants for highly oriented pyrolytic graphite determined by ultrasonic techniques

Sound velocities along the c-axis of highly oriented pyrolytic graphite between 4 and 325 K were measured with an ultrasonic pulse-echo phase-comparison method. The echo delay times were determined with an accuracy of 0.05 and 0.15%, respectively, for the longitudinal and transverse modes. The temperature dependence of the c-axis elastic constants C₃₃ and C₄₄ was deduced with the correction of thermal expansion. C₃₃ was found to decrease by 5.8% from 4 to 300 K and can be interpreted by a model based on the simple Lennard-Jones interlayer interaction. C₄₄ and its temperature variation are found to be strongly sample dependent.     

拟定曲率空间上的几个定理

The present paper is devoted to determining the metric g for an n-dimension-al (n≥4) Riemannian manifold (M, g) of quasi-constant curvature [1]. By the way, we have identified the space of quasi-constant curvature with the κ-special conformally flat space of K.Yano & B.Y.Chen [8]. Based upon the results so obtained, we have completely determined the canonical metric for such a space to admit the relevant field X as geodesic field, and the geometric structure for (M, g) to be a recurrent space of quasi-constant curvature. Also we have examined the validity of our results just obtained for a 3-dimensional conformally flat space of quasi-constant cvrvature. Besides, we have deduced some global properties of a complete manifold of quasi-constant curvature, which may be useful in applications.     

A short proof of a result of Pollak on Steiner minimal trees

The long-standing conjecture of Gilbert and Pollak states that for any set of n given points in the euclidean plane, the ratio of the length of a Steiner minimal tree and the length of a minimal (spanning) tree is at least $\text{3}\text{2}$. This conjecture was shown to be true for n = 3 by Gilbert and Pollak, and for n = 4 by Pollak. However, the proof for n = 4 by Pollak is sufficiently complicated that no generalization to any other value of n has been found. We use a different approach to give a very short proof for the n = 4 case. This approach also allows us to attack the n = 5 case, though the proof is no longer short (to be reported in a subsequent paper).     

Complete balanced Howell rotations for 8k+5 teams

Complete balanced Howell rotations are mathematical designs for highly structured paired-comparison experiments. They have been widely used in bridge tournaments, and many special cases are applicable to round-robin tournaments for all kinds of sports. In this paper we construct complete balanced Howell rotations of 8k + 5 teams, for 8k + 5 a prime power greater than 5. We also show that “table balanced” complete balanced Howell rotations for 8k + 5 teams do not exist unless 8k + 5 is the sum of two squares of integers.