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71.
Structural hydroxyl and deuteroxyl groups within the K4[SiW12O40]/Al2O3 and K6[SiW11PdO39]/Al2O3 systems were studied by diffuse-reflectance FTIR spectroscopy in a spectral range of fundamental stretching vibrations, first
overtones, and combination bands of stretching and bending vibrations. For hydroxyl groups, the region of combination vibrations
is the most informative. The calculated frequencies of bending vibrations of hydroxyl groups (865 and 730 cm−1) are characteristic of acidic OH groups.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2017–2020, October, 1999. 相似文献
72.
An Approximate Analysis of Dry-Friction-Induced Stick-Slip Vibrations by a Smoothing Procedure 总被引:6,自引:0,他引:6
This paper deals with a systematic procedure to find both stable and unstable periodic stick-slip vibrations of autonomous dynamic systems with dry friction. In this procedure, the discontinuous friction forces are approximated by smooth functions. Using the simple shooting method with a stiff-ODE solver, in combination with a path following algorithm, branches of periodic solutions are computed for a changing design variable. For testing purposes, both 1 and 2-DOF autonomous block-on-belt models and a 1-DOF autonomous drill string model from literature are investigated. Comparison of the results shows that the smoothing procedure accurately describes the behavior of the discontinuous systems. The proposed procedure can also easily be applied to more complex MDOF models, as well as to nonautonomous dynamic systems. 相似文献
73.
João C. André 《Nonlinear dynamics》1996,11(3):275-293
In the study of nonlinear vibrations of planar frames and beams with infinitesimal displacements and strains, the influence of the static displacements resulting from gravity effect and other conservative loads is usually disregarded. This paper discusses the effect of the deformed equilibrium configuration on the nonlinear vibrations through the analysis of two planar structures. Both structures present a two-to-one internal resonance and a primary response of the second mode. The equations of motion are reduced to two degrees of freedom and contain all geometrical and inertial nonlinear terms. These equations are derived by modal superposition with additional subsidiary conditions. In the two cases analyzed, the deformed equilibrium configuration virtually coincides with the undeformed configuration. Also, 2% is the maximum difference presented by the first two lower frequencies. The modes are practically coincident for the deformed and undeformed configurations. Nevertheless, the analysis of the frequency response curves clearly shows that the effect of the deformed equilibrium configuration produces a significant translation along the detuning factor axis. Such effect is even more important in the amplitude response curves. The phenomena represented by these curves may be distinct for the same excitation amplitude. 相似文献
74.
N. V. Gnevanov B. L. Smorodin 《Journal of Applied Mechanics and Technical Physics》2006,47(2):214-220
Stability of a plane-parallel flow of a nonuniformly heated binary mixture filling a vertical layer located in a field of
gravity and in a high-frequency vibrational field is studied. The axis of vibrations is directed along the layer. The case
of rigid and isothermal boundaries of the layer impermeable for the mixture is considered. The influence of thermal diffusion
on the evolution of the admixture and the thresholds of flow stability is taken into account. The study is performed on the
basis of equations for averaged fields. An asymptotic method with the use of the perturbation wavenumber as a small parameter
is applied in the long-wave limit. For arbitrary values of the wavenumber, the limit of stability was determined by numerical
integration. Charts of stability of gaseous and liquid binary mixtures are plotted.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 77–84, March–April, 2006. 相似文献
75.
E. K. Ankyanets 《International Applied Mechanics》2005,41(10):1177-1181
The vibrations of a cylindrical shell reinforced with circular ribs attached to it by means of discrete elastic elements are
studied. The problem is solved by the finite-element method. The shell and ribs are modeled by a plane four-node finite element,
which is a combination of a four-node plane stress element and a four-node flexural element. The effect of the stiffness of
the elastic elements on the natural frequencies and modes is examined
__________
Translated from Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 108–113, October 2005. 相似文献
76.
On Free Nonlinear Vibrations of Fluid-Filled Cylindrical Shells with Multiple Natural Frequencies 总被引:1,自引:0,他引:1
Nonlinear free vibrations of a cylindrical shell fully filled with a perfect incompressible fluid are studied. The case is
examined where two natural frequencies of the shell are close
__________
Published in Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 127–138, October 2005 相似文献
77.
L. A. Tkacheva 《Fluid Dynamics》2005,40(2):282-296
The problem of the behavior of an elastic floating plate in the form of a strip under the action of a periodic surface load is solved using the Wiener-Hopf technique. The shortwave approximation is found in explicit form. The effect of the frequency and nature of the acting load on the vibration amplitudes of the fluid and the plate is investigated numerically. It is found that for certain loads no waves propagate in the fluid and the vibrations of the plate are localized in the neighborhood of the acting load. Conditions under which local vibration can be realized are found.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, 2005, pp. 132–146.Original Russian Text Copyright © 2005 by Tkacheva. 相似文献
78.
The equations of nonaxisymmetric vibrations of sandwich cylindrical shells with discrete core under nonstationary loading are presented. The components of the elastic structure are analyzed using a refined Timoshenko theory of shells and rods. The numerical method used to solve the dynamic equations is based on the integro-interpolation method of constructing finite-difference schemes for equations with discontinuous coefficients. The dynamic problem for a sandwich cylindrical shell under distributed nonstationary loading is solved with regard for the discreteness of the core__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 2, pp. 60–67, February 2005. 相似文献
79.
V. D. Lakiza 《International Applied Mechanics》2005,41(1):85-89
The results from an experimental study into the dynamic behavior of a gas-liquid medium and solid particles in a compound shell (sphere-truncated cone) are reported on. The following processes are studied: formation of gas bubbles and their clusters, strong macroflows, and intensive chaotic motion of the medium in the truncated cone as a nonlinear vibrating liquid-gas system__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 1, pp. 112–118, January 2005. 相似文献
80.
Mehmet Çevik 《International Journal of Non》2005,40(6):901-923
Non-linear coupled vertical and torsional vibrations of suspension bridges are investigated. Method of Multiple Scales, a perturbation technique, is applied to the equations to find approximate analytical solutions. The equations are not discretized as usually done, rather the perturbation method is applied directly to the partial differential equations. Free and forced vibrations with damping are investigated in detail. Amplitude and phase modulation equations are obtained. The dependence of non-linear frequency on amplitude is described. Steady-state solutions are analyzed. Frequency-response equation is derived and the jump phenomenon in the frequency-response curves resulting from non-linearity is considered. Effects of initial amplitude and phase values, amplitude of excitation, and damping coefficient on modal amplitudes, are determined. 相似文献