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1.
Summary A simply supported beam with fixed ends and an attached strongly nonlinear spring is considered. As the forced bending vibrations
of the beam have moderate amplitudes, the stretching force is a nonlinear function of the deflection. The vibrations are presented
as a series with respect to the modes of the beam without attachment. Applying the Bubnov-Galerkin procedure, an infinite
system of ordinary differential equations is derived. Using the multiple scales method, the quasiperiodic vibrations in the
region of the combination resonance are analyzed in the paper. The system vibrations, when the nonlinear spring is attached
in different points, are analyzed. Applicability of the nonlinear spring for mitigation of a combination resonance is discussed. 相似文献
2.
Strashilov Vesseline L. Alexieva Gergana E. Velichkov Velitchko N. Avramov Ivan D. Evans Stephen D. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(5):1018-1023
A 1 GHz surface transverse wave resonator on 36° Y-cut quartz plate coated with organothiol-functionalized gold nanoparticle film has been studied as a chemical gas sensor. Considerable sensitivity of the resonant frequency to vapors of ethanol, methanol, chloroform, and acetic acid has been found. Owing to the high short-term stability of the oscillator built, the detection limit is in the low ppm range. The results qualitatively confirm previous results on the same film type obtained by conductivity measurements. In the present case, the conductivity effect resulting from variable separation of nanoparticles is accompanied with surface-attached mass of the absorbed gas. The film matrix exhibits considerable capacity to absorb large amounts of molecules at high gas concentrations. 相似文献
3.
The vibrations of the shallow shell with geometrical nonlinearity submerged in a fluid are considered. Interaction of the shell with a fluid is described by linear hypersingular integral equation, which is solved by the boundary element method. The vibrations of the shell are described by the nonlinear finite-degree-of-freedom system. The vibrations are studied by the Shaw–Pierre nonlinear modes. 相似文献
4.
K. V. Avramov 《Acta Mechanica》2003,164(3-4):115-138
Summary. Nonlinear curvature and nonlinear inertia are taken into account in the beam model. The constant part of the parametric force is proposed to be greater than the buckling one, therefore the beam has three equilibria. One-mode approximation of the beam oscillations is used. Bifurcations of the beam oscillations are analyzed by Melnikov's method. Moreover, beam oscillations close to the stable equilibriums are studied by the multiple scales method. 相似文献
5.
6.
D. M. Petrović M. I. Avramov S. R. Lukić V. V. Khiminets M. V. Dobosh 《Journal of Materials Science》1990,25(8):3557-3560
Investigations of five-component glasses of the Ge20As14(Se
x
S1-x
)52I14 type are reviewed for the temperature interval from room temperature to 1273 K. Thermogravimetric analyses enable the determination of the mechanism of thermal decomposition, as well as the range of amorphous phase existence. Electroconductivity was followed by the method of four points under a direct current regime. Semiconductive character was evaluated, as well as the energies of the corresponding energy gaps. The effect of sulphur (i.e. selen) concentrations on the electrical characteristics was also discussed, along with some of the elements significant for determining the mechanisms of electrical conductivity. Results on optical energy gaps were also redetermined. 相似文献
7.
Strashilov V.L. Djordjev K.D. Boyanov B.I. Avramov I.D. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1997,44(3):652-657
The dispersion characteristics of surface transverse waves (STW) on 36° rotated Y-cut quartz have been analyzed numerically. A closed form dispersion relation has been derived and introduced in the equations of the coupling-of-modes (COM) theory to account for the variation of energy trapping with frequency. The transmission and reflection coefficients at the finger edges have been determined from the stopband characteristics. Through the introduction of an electromechanical coupling which varies linearly with the electrode mass loading, quantitative agreement with experimental results on two different types of two-port STW resonators has been achieved, and characteristic features have been explained 相似文献
8.
V Vukobratov D Damjanov S Avramov J Pfau L Hadnadev J Pasternak 《Canadian Metallurgical Quarterly》1998,51(9-10):441-444
Aortoenteric fistula represents a communication between aortic and duodenal lumen. It is a very rare complication of aortic aneurysmal disease as well as aortic prosthetic surgery. There are only few surgeons who have seen more than one case of aortoenteric fistula. At the Institute of Surgery one case of aortoenteric fistula was treated. It was well diagnosed at the Institute for Internal Medicine, and then presented to the vascular surgeon who operated immediately. The whole diagnostic and therapeutic procedure was well done, but stenosing carcinoma of ascendent colon was found during the operation. Resection were done leading to the dehiscence of bowel anastomosis and fatal outcome for the patient. This case is instructive in a diagnostic and surgical manner. 相似文献
9.
An electron microprobe technique is described for determining the thickness of SiO2 and Si3N4 in wafers and devices. The technique is based on the measurement of oxygen and silicon X-ray intensities at 2.5 kV and 10 kV through the nitride overlay. At the lower accelerating voltage, both intensities decrease with increasing nitride thickness owing to absorption and silicon distribution in depth. The SiO2 thickness, however, is obtained by measuring the oxygen X-ray intensity at the higher voltage (10 kV), because at this voltage the oxygen intensity is not dependent on the nitride thickness.Empirical relationships expressing Si3N4 thickness in terms of Si and O X-ray intensities and SiO2 thickness are derived. 相似文献
10.
Degtyarev M. A. Shapoval A. V. Gusev V. V. Avramov K. V. Sirenko V. N. 《Strength of Materials》2019,51(2):223-230
Strength of Materials - A new approach to optimizing the waffle shell sections of the launch vehicle is proposed. The waffle cantilever cylindrical shells are considered under the action of the... 相似文献