Asymptotic Theory of Steady Axisymmetrical Needlelike Crystal Growth

The present paper is concerned with the stationary needle crystal growth with arbitrary undercooling. We discuss two classes of asymptotic solutions: (1) the regular-tip solutions; (2) the smooth-root solutions. When the surface tension is nonzero, the regular-tip solutions may not have smooth roots. Among the regular-tip solutions, however, one can identify a “principal regular-tip solution,” which has the best behavior in the far field and is physically acceptable.     

Axisymmetrical marine magnetotelluric models for locally nonhomogeneous layered media

An axisymmetrical model with a plane linearly polarized electromagnetic wave normally incident onto a body of revolution is proposed for magnetotelluric sounding problems in conducting layered media. The electrodynamic boundary-value problem is reduced to a system of one-dimensional integro-differential equations along the contour of the body of revolution. __________ Translated from Prikladnaya Matematika i Informatika, No. 27, pp. 54–64, 2007.     

Axisymmetrical vibrations of shells of revolution under abrupt loading

A frequency method is proposed for solving the problem of the vibrations of shells of revolution taking into account the energy dissipation under arbitrary force loading and on collision with a rigid obstacle. The Laplace transform is taken of the equation of the vibrations of a shell of revolution with non-zero initial conditions. For the inhomogeneous differential equation obtained, a variational method is used to solve the boundary-value problem, which consists of finding the Laplace-transformed boundary transverse and longitudinal forces and bending moments as functions of the boundary displacements. The equations of equilibrium of nodes, i.e. the corresponding equations of the finite-element method, are then compared, using results obtained earlier [1–4]. Amplitude-phase-frequency characteristics (APFCs) for the shell cross-sections selected are plotted. An inverse Laplace transformation is carried out using the clear relationship between the extreme points of the APFCs and the coefficients of the corresponding terms of the series in an expansion vibration modes [3]. In view of the fact that the proposed approach is approximate, numerical testing is used.     

具有非轴对称几何缺陷的双曲旋转壳应力分析

本文探讨了分析具有非轴对称几何缺陷的双曲旋转壳的一种近似方法,在这种方法中,缺陷的影响是由虚构的载荷模拟的.并提出了在非轴对称载荷作用下,使用该方法分析具有鼓包形缺陷壳体时的一种有效的算法.这种方法既分开了各种曲率误差对于内力和力矩的影响,又体现了它们之间的相互作用,避免了在非轴对称载荷下所需的重复运算,并能在一个仅有轴对称分析能力的程序上实现.本文用该方法分析了受自重载荷和风载荷作用的,具有鼓包形缺陷的双曲冷却塔,并同时用一个特殊的有限元程序直分析了缺陷塔.通过数字结果的比较,检查了等效载荷法的精度及适用性.     

Double structures and jets

We show how the double vector bundle structure of the manifold of double velocities, with its submanifolds of holonomic and semiholonomic double velocities, is mirrored by a structure of holonomic and semiholonomic subgroups in the principal prolongation of the first jet group. We use the actions of these groups to construct holonomic and semiholonomic submanifolds in the manifold of double contact elements, and show that these give rise to affine bundles where a semiholonomic element has well-defined holonomic and curvature components.     

On symmetrization of jets

Let F = F ^(A,H,t) and F¹ = F^(A1,H1,t1){F^1} = {F^{({A^1},{H^1},{t^1})}} be fiber product preserving bundle functors on the category FM _m of fibred manifolds Y with m-dimensional bases and fibred maps covering local diffeomorphisms. We define a quasi-morphism (A, H, t) → (A ¹, H ¹, t ¹) to be a GL(m)-invariant algebra homomorphism ν: A → A ¹ with t ¹ = ν ∘ t. The main result is that there exists an FM _m -natural transformation FY → F ¹ Y depending on a classical linear connection on the base of Y if and only if there exists a quasi-morphism (A, H, t) → (A ¹, H ¹, t ¹). As applications, we study existence problems of symmetrization (holonomization) of higher order jets and of holonomic prolongation of general connections.     

Flatness of Bernoulli jets

Level sets of minimizers of a possibly singular or degenerate elliptic variational problem related with fluid jets are shown to possess a Harnack-type inequality. A few flatness and one-dimensional results thence follow. This work has been partially supported by MIUR Variational Methods and Nonlinear Differential Equations. ``...e diedi un volto a quelle mie chimere le navi costruii di forma ardita, concavi navi dalle vele nere...'(Fancesco Guccini, Odysseus.)     

摄动有限元法解一般轴对称壳几何非线性问题

本文在处理几何非线性问题时,利用在变分方程中引入振动过程,得到各级变分摄动方程,并通过有限元法求解.由于有限元法能成功地处理各种复杂边界条件、几何形状的力学问题,摄动法又可将非线性问题转化为线性问题求解.若结合这两种方法的优点,将能够解决大量复杂的非线性力学问题.并能够消除单独使用有限元法或摄动法求解复杂非线性问题所出现的困难. 本文应用摄动有限元法求解了一般轴对称壳的几何非线性问题.     

变厚度圆柱形薄壳轴对称问题的渐近解

本文给出了变厚度圆柱形薄壳轴对称问题的一致有效渐近解.     

三重介质轴对称二维不定常渗流的精确解

本文求得了三重介质轴对称二维不定常渗流的线源解和有限封闭地层的面源解.它们不仅概括和发展了已有的均质和双重介质的主要结果,而且给出多重介质弹性渗流的基本特征.     

Spaces of germs and jets

Summary In this paper we present some results on the theory of jets and germs concerning the paralel transport and the linear structure. Entrata in Redazione l'11 febbraio 1970.     

摄动初参数法解轴对称壳几何非线性问题

作者在文[7]中提出轴对称壳任意大挠度问题的一阶微分方程组和以载荷变量为尺度的变特征无量纲化方法。在此基础上,本文选取挠角非线性偏差的加权均方根作摄动参数,给出该问题的无量纲摄动微分方程组。从而把非线性问题转化为n个线性问题来解决。本文采用数值积分的初参数方法对摄动后的各阶线性问题进行了计算。摄动结果与实验[4]相符合。     

夹层圆板轴对称非线性弯曲和屈曲的样条函数解法

以三次B样条函数为试函数,用配点法计算夹层圆板的非线性弯曲．支座可以是弹性的．夹层板采用Reissner模型．荷载可为多项式型的分布荷载、均布边缘力矩、均布径向压力或均布径向预应力及它们的组合．首次用非线性理论计算了夹层圆板的压曲临界荷载．在均布荷载作用下的结果同幂级数解的结果作了比较,说明样条配点法具有收敛范围大、精度高、编写程序通用的优点．     

饱和粘弹性土层中端承桩纵向振动的轴对称解析解

基于弹性和饱和多孔介质理论,将桩和饱和土层分别视为单相弹性介质和饱和粘弹性介质,利用Helmholtz分解和变量分离法,在频率域研究了饱和粘弹性土层中端承桩纵向振动的动力特性,给出了饱和粘弹性土层中桩纵向振动时动力响应的轴对称解析解及桩头复刚度的解析表达式．通过数值计算,给出了桩头动刚度因子和等效阻尼随激励频率的响应,考察了饱和土物性参数、桩土模量比、桩长径比、桩Poisson比等参数对桩头刚度因子和阻尼的影响．研究表明:由于考虑了桩的径向变形效应以及饱和粘弹性土层对桩的径向力作用,轴对称精确解的桩头动刚度因子和阻尼分别与经典Euler-Bernoulli杆模型桩的桩头动刚度因子和阻尼有较大的区别,特别是在若干激励频率处．因此,经典Euler-Bernoulli杆模型桩的适用性具有一定的局限,更加精确的分析应采用三维精确模型．     

严格求解夹层圆柱壳在轴压下的轴对称失稳问题

本文在文献[1]的基础上,用严格的方法求解两端简支的夹层圆柱壳在均匀轴压下的轴对称失稳问题.内、外表层很薄弹性模量又大,按薄壳理论处理;夹心较厚弹性模量又相当小,横向剪切变形的影响必须考虑,在研究夹层壳的整体失稳尤其是局部失稳时,横向的拉伸和压缩变形也不可忽略,用数学弹性力学的方法处理.本文导得了可求解轴对称整体失稳和局部失稳临界载荷的超越方程,用数值计算的方法可算得临界载荷的最小值.对于整体失稳的情况,给出算例,与夹层壳理论的解作了比较.     

Annular liquid jets in zero gravity

The equations describing the steady-state behavior of long annular liquid jets and liquid membranes in zero gravity are solved analytically as a function of the pressure difference across the jet or membrane, Weber number, and nozzle exit angle. The ranges of the parameters for which the analytical solutions are valid are determined, and analytical solutions of the mass absorption rate are obtained as a function of the Peclet and Weber numbers, nozzle exit angle, pressure difference, and thickness of the annular liquid jet. It is shown that the convergence length of annular liquid jets and liquid membranes increases as the Weber number, nozzle exit angle, and pressure coefficient are increased. It is also shown that the mass absoption rate increases as the nozzle exit angle, pressure coefficient, and Weber number are increased; however, the mass absorption rate decreases as the Peclet number and annular jet initial thickness-to-radius ratio are increased.