瞬态热传导方程的子结构精细积分方法

对线性定常结构动力系统提出的精细积分方法,在数值精度等方面表现出极大优越性,但是当矩阵尺度很大时在数值计算与存储中将产生困难,对此,本文对瞬态热传导方程,根据结构的概念,将结构分为若干个子结构,对各子结构分别进行指数矩阵运算并通过了结构间界面的物理量相联系,从而提高精细积分方法的计算效率。     

计算力学中的静力衰减

本文在计算力学范围内证明了,平衡力系的影响,由近及远按矩阵连分式的规律衰减.该衰减往往不慢于,但并非总是不慢于指数衰减或幂次衰减.本文结果可用于估计某些简化假定在计算中引入的误差.     

Influence of simultaneous doping of Tl and Bi on microstructure and critical current density of HgBa2Ca2Cu3O8+δ

It has been found that simultaneous doping of Tl and Bi at Hg site of HgBa₂Ca₂Cu₃O_8+δ HTSC phase induces interesting microstructural variants in the form of long period polytypoid (LPP) like structure embodying native defect substructures. It has been observed that the as synthesized (HgTl_0.2−xBi_x)Ba₂Ca₂Cu₃O_8+δ (with x = 0.05, 0.10, 0.15) phases have superconducting onset transition temperature (T_c) of about ∼133 K. However, the intragrain critical current density (J_c) for the various materials with different compositions varies significantly. It varies from 6.2 × 10⁶ A/cm² to 2.9 × 10⁶ A/cm² at 5 K and 1 T for (HgTl_0.10Bi₁₀)Ba₂Ca₂Cu₃O_8+δ and (HgTl_0.15Bi_0.05)Ba₂Ca₂Cu₃O_8+δ HTSC phase respectively. A correlation between the intragrain J_c and the defect substructures has been found to be present. This correlation has been described and disscussed. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Orientation-dependent recovery in strongly deformed Al–0.1% Mn crystals

Single crystals of Al–0.1% Mn were channel-die compressed to a true strain of 2.3 and their recovery behaviour at 240–320°C investigated by microhardness measurements, electron backscatter diffraction (EBSD) microtexture mapping and X-ray line broadening analysis. The crystal orientations were the nominally stable Goss {110}?001?, brass {110}?112? and S {123}?634?. For all three orientations the microhardness decreases with a logarithmic time dependence but the instantaneous recovery rates of the brass oriented crystals are systematically lower than those of the other two orientations by a factor of about 2. The dislocation densities decrease rapidly in the first stages of recovery (<1?min) by dislocation dipole annihilation and more slowly thereafter. In the Goss and S orientations the later stage of recovery is due to sub-grain growth. The orientation dependence is ascribed to the relatively low misorientations developed by plastic straining in the brass crystals (average about 4°) compared with the Goss and S orientations (about 7–8°).     

Substructure lattices and almost minimal end extensions of models of Peano arithmetic

This paper concerns intermediate structure lattices Lt(??/??), where ?? is an almost minimal elementary end extension of the model ?? of Peano Arithmetic. For the purposes of this abstract only, let us say that ?? attains L if L ? Lt(??/??) for some almost minimal elementary end extension of ??. If T is a completion of PA and L is a finite lattice, then: (A) If some model of T attains L, then every countable model of T does. (B) If some rather classless, ?₁‐saturated model of T attains L, then every model of T does. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A crystal plasticity model of a formation of a deformation band structure

The formation of deformation bands with the typically alternating sign of the misorientation across their boundaries is interpreted as spontaneous deformation instability caused by anisotropy of hardening. To analyse the nature of the fragmentation, a model of a rigid-plastic crystal domain deformed by symmetric double slip in a plane-strain compression is considered. The basic reason for the deformation band existence is that a local decrease in number of active slip systems in the bands is energetically less costly than a homogeneous deformation by multislip. However, such model of the bands predicts their extreme orientation and their width tends to zero. This trend is modified by hardening caused by a build up of the band boundaries and by a dislocation bowing (Orowan) stress. The model provides an explanation of observed orientation of the bands, their width and the significant change in the structural morphology seen as the band reorientation occurs at large strains. The predictions are in a favourable agreement with the available observations.     

一类结构的（n－3）重根及其非退化性

基于陀螺模态综合法，从总装阵的块式结构出发，构造性地证明了具有ｎ片桨叶的旋翼型结构陀螺特征值问题存在一系列的（ｎ－３）重特征根，得到了对应的（ｎ－３）个完备的振型．结论进而推广到有阻尼的旋翼型结构．继续研究证明过程表明：结论适用于更广泛的一类具有重复子结构的结构系统，结果表明这类结构几何上的重复性或对称性导致的重根不会引入退化性．不同类型的算例验证了所得到的解析结果．本文还试图说明动力子结构法的定性性质保持特性是值得继续探讨的课题     

无限元与相同子结构串的一致性及其算法

讨论了无限元方法￣［１］与相同子结构串分析￣［２］的一致性，综合文［１］和［２］得到一种通用算法，依据文［３］尚可应用于ＬＱ控制问题，且提出一种直接求出转移矩阵的算法，具有简便和较高精度的优点．     

A note on stability spectrum of generic structures

We show that if a class K of finite relational structures is closed under quasi‐substructures, then there is no saturated K ‐generic structure that is superstable but not ω ‐stable (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Peculiarities and thermal stability of microstructure and strength properties of Ti–Al–Si–O–C–N films

Peculiar relationship between the composition and fine structure and the variations in strength properties of nanostructured and nanocomposite, high-carbon, high-oxygen Ti–Al–Si–N films are investigated using Auger spectroscopy, electron microscopy, X-ray structural analysis and hardness measurements. It is shown that a TiN-based phase can form in these films, which exhibits nanocrystalline or two-level grain structure distributed in the x-ray amorphous phase whose volume fraction is 20–50%. The grain-structure character can be deliberately changed by incorporating aluminum or silicon into the films. It is found out that irrespective of their structural state and composition the films demonstrate high thermal stability of superhardness and microstructure up to the temperatures Т ≈ 1173 K. Hardness is seen to decrease at Т ≥ 1273 K as a result of dislocation recovery, stress relaxation and early recrystallization. It is suggested that the high strength properties demonstrated by these films are due to the presence of dislocation substructure and high shear resistance of the x-ray amorphous phases along nanocrystallite boundaries. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 57–65, November, 2008.