二阶Sturm-Liouville特征值问题解的存在与非存在性

讨论了二阶Sturm-Liouville特征值边值问题解的存在性与非存在性,得到了边值问题至少有一个正解的特征值λ的存在区间的结论.进一步,给出了边值问题没有正解的特征值存在区间.     

非线性算子的歧点

本文研究了Banach空间中非线性全连续算子在不假设Fréchet可微的条件下,歧点的存在性和不存在性.利用齐次算子,获得了这类算子歧点的存在和不存在的充分条件,推广和改进了已有文献中的结果.     

无界区域中半线性椭圆型方程的渐近解

本文讨论一类无界区域中半线性椭圆型方程渐近解的存在性,包括最大解与最小解的存在性。最后讨论了存在最大解的必要条件,并得到了一个存在最大解的充要条件。     

关于曲率的深入研究

本文就曲线上一点处曲率的存在条件做了讨论,提出了曲率存在的一个定理,给出了单侧曲率的概念,从而说明了曲率并非在光滑曲线上的每一点处都存在.     

一般异面直线的相交线问题

讨论了一般异面直线的相交直线存在及唯一存在的充要条件,证明了两者的等价性,并在唯一存在时给出了一般的表达式.     

两类分段对称系统周期的存在性

本文研究了两类分段对系统周期解的存在性,得到了系统相应的周期解存在的充分条件,作用应用,证明了一类具有分段对称性的时滞微分方程的周期解的存在性,推广了现有的相关结果。     

一类具正负系数中立型方程的正解

研究一类具有正负系数的中立型微分方程,得到了这类方程存在正解的充分条件和存在有界正解的充要条件,并据此给出了其存在无界正解的充分条件。     

广义阿贝尔微分方程的周期解

本文讨论了广义阿贝尔微分方程.利用不动点定理,得到了方程存在两个非零周期解的充分条件.同时,我们还讨论了不存在非零周期解和存在唯一非零周期解的情况.     

二阶非线性中立型时滞差分方程的正解

本文研究了一类二阶非线性中立型时滞差分方程的正解,得到了最终正解的存在性判据及存在正解的必要条件,建立了一些正解不存在性定理,所得结论推广并改进了已知的一些结果。     

n阶非线性常微分方程的非线性两点边值问题

本文利用打靶法,给出了ｎ阶非线性常微分方程具有非线性两点边界条件的边值问题存在解与存在唯一解的一般性结果,并将所得结果应用于Ｌｉｐｓｃｈｉｔｚ方程的两点过值问题,给出了存在解与存在唯一解的具体的充分条件。     

Harmonic distrotions under nonlinear periodic deformation of fluid polymers

Conclusions 1. It has been shown for a number of viscoelastic fluid systems that under nonlinear periodic deformation, the contribution of the third harmonic of the stress to the fundamental does not exceed 20% of the amplitude.2. In the case of clay soil and melt of filled polyethylene, the shape of the stress waves is essentially definable by the relative phase angle of the third harmonic of the stress and is practically independent of the deformation amplitude in a growing nonlinear range of deformation.3. In the case of the polyethylene melt, the amplitude dependence of the phase angles of the stress harmonics is in satisfactory agreement with the analysis of model I. With increasing deformation amplitude, the modulus vector of the first harmonic rotates counterclockwise and remains in the first trigonometric quadrant; the modulus vector of the third harmonic passes from the second to the third quadrant, and the modulus vector of the fifth harmonic passes from the second to the fourth quadrant via the third.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 893–898, September–October, 1978.     

An investigation on the influence of slot injection/suction on the spreading of a thin film under gravity on a rotating disk

We investigate the influence of slot injection/suction on the axisymmetric spreading of a thin film under the influence of gravity and rotation. The effects of surface tension are ignored. We allow a very thin film to precede the bulk of the fluid to overcome the singularity which arises as a consequence of applying the no-slip boundary condition. We show how the width of the slot and magnitude of the injection/suction influences the height of ridges and depth of cavities on the profile of the free surface of the thin film. Rotation increases the depth of the cavities and the height of the ridges as compared to the effects of gravity alone. The presence of rotation also results in the formation of a breaking wave.     

Some observations on the performance of balloons from the rate of rotation of the fan in the F-Type radiosonde

If the rate of ascent of the balloon is constant, the rate of rotation of the fan in the F-Type radiosonde should decrease with height, due to the decrease in the density of the air. It was observed from the radiosonde ascents of Minicoy that the rate of rotation of the fan remained almost unchanged up to even 100 mb. It is shown that this is due to the increase in the rate of ascent of the balloon by about 2% of the value near the ground per km. ascent. Positive evidence of turbulence in the stratosphere is provided by the large fluctuations in the rate of rotation of the fan. It is also observed that the balloon whose fabric at the 50 mb. level is about 0·014 mm. thick bursts due to the turbulence.     

Prediction of the deformation properties of a polymeric composite with a granular-fibrous filler

Conclusion A variant of calculation of the characteristics of the deformation properties of a hybrid composite containing a complex disperse filler in the form of granular particles and short fibers was proposed. The effect of aggregation of the granular filler, the statistical distributions of the fibers by lengths and orientation in the material, and the anisotropy of the fibers are taken into consideration in the calculation. The statistical distribution of the orientation of the fibers is given by a function proportional to the distance from the center to the surface of a triaxial ellipsoid in the corresponding direction. The uniform random distribution of the fibers in bulk and in the plane is a special case of this distribution. The results of the analysis of the effect of the parameters of the statistical distributions of the length and orientation of short fibers on the elasticity characteristics of a composite are reported. The dependence of the creep of the composite on the ratio of the concentration of the components of the complex filler was determined, and the efficiency of partial replacement of a granular filler by a short-fiber filler to inhibit creep of the composite was demonstrated. The possibilities of predicting the long-term creep were experimentally confirmed on the example of LDPE filled with ground limestone and short glass fibers.Presented at the Sixth All-Union Conference on the Mechanics of Polymer and Composite Materials (Riga, November, 1986).Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 898–909, September–October, 1987.     

The thermodynamically consistent equations of a thermoelastic saturated porous medium

A phenomenological model of a porous medium saturated with fluid is considered with in the framework of the hypothesis of interpenetrating continua. Assuming that there are no phase transitions, that the contribution of pulsations to the stress tensor and kinetic energy is small, and the components of the medium are in thermal equilibrium, mass, momentum and energy equations and a law of conservation of compatibility of the deformations and velocities are formulated. Using a representation of the force of interaction of the components in the form of the sum of equilibrium and dissipative components, a new form of inequality is obtained for the rate of entropy production. A definition of a thermoelastic saturated porous medium is given. The symmetry group of such a medium is considered as a set of two groups, corresponding to the symmetry of the skeleton and the fluid. It is shown that, in the class of thermoelastic porous media with an arbitrary type of symmetry of the skeleton, the saturating fluid can only be an ideal fluid, while the thermodynamic potentials and the porosity, stresses and entropies determined by them do not depend on the temperature gradient and the relative fluid velocity. It is found that the condition of incompressibility of only one of the components of the medium leads to the elimination of the porosity from the governing relations, rather than to kinematic limitations. The limitations imposed on the governing relations by the principle of thermodynamic consistency and the requirement of independence of the choice of the frame of reference are investigated. A form of the governing relations, necessary and sufficient to satisfy these principles, is obtained. It is shown that the Biot equations are one of the forms of thermodynamically consistent governing relations. A thermodynamic validation of the effective-stress tensor is given.     

Identification and orbit determination of a tethered satellite system

Orbital motion of a tethered satellite system, composed of two satellites and an inextensible tether, is considered by using a perturbed two-body model. This approach is adopted so that the determination of the orbit of one of the satellites can be attempted without using observations of the motion of the other satellite in the system. The identification of the tethered condition of the system using observations of only one of the satellites in the tethered satellite system is considered. The characteristics of the `tether perturbed' motion of the observed satellite are investigated. Estimation of the state of the system using near perfect data is also illustrated. Observations of one satellite provide the entire state of the system and a parameter involving the ratio of the masses of satellites and the tether length.     

State of stress and strain of brake-class parachutes

The article describes the special features of the operation of brake-class parachutes. It substantiates the possibility of replacing the solution of the dynamic problem of opening of a brake parachute by the static calculation of its state of stress and strain (SSS). The derivation of the equation of motion of a soft carcassed shell is based on the finite element method. The steady-state solution is obtained by the method of adjustment. As an example the results of calculation of the characteristics of the SSS of a cross-shaped brake parachute are presented. It is shown that in the zone of its lower edge considerable concentrations of tension arise in the tissue, the tissue gradually joins the operation of the carcass; the transverse carcass is unsubstantially loaded. The results of the calculations agree with the experimental data.Translated from Dinamicheskie Sistemy, No. 5, pp. 32–36, 1986.     

On the “genetic memory” of chaotic attractor of the barotropic ocean model

The structure of attractor of barotropic ocean model is studied in this paper. Theorems of the existence of the attractor for the finite dimensional approximation of this model are proved as well as its convergence to the attractor of the model itself. Some properties of stationary solutions of this model and their stability are discussed.The structure of the attractor is partially explained by the sequence of bifurcations the system is subjected to by variations of leading parameters. The principal feature of the studied system is the existence of two “almost invariant” basins of chaotic attractor with very rare transitions between them. This is related to the rise of a couple of non-symmetric stable stationary solutions in the model with symmetric forcing.The “memory” of chaos appears also in the presence of maxima in the spectrum of energy. These maxima correspond either to the principal frequency of the limit cycle which arose in the Hopf bifurcation, or to the frequencies of the Feigenbaum phenomenon.     

Free vibrations of a cantilevered plate with a polymer coating

The article considers some of the special characteristics of the free vibrations of a steel cantilevered plate, with the formation of a polymer coating on the plate. It compares the results of an experimental investigation of the effect of internal stresses in the coating on the vibrations and on the static bending of the plate. It demonstrates the possibility of determining the internal stresses in the coating from the change in the frequency of the natural vibrations of a plate with a coating.Institute for the Mechanics of Metal-Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel'. Translated from Mehanika Polimerov, No. 3, pp. 541–544, May–June, 1970.