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181.
O. N. Vasilenko 《Strength of Materials》1989,21(10):1415-1420
The Malkin method, which was developed to construct a single unique resonance solution of nonlinear equations, is generalized for the case of the derivation of all stationary solutions in the near-resonance zone, and also for transient oscillations.Kiev Polytechnic Institute. Translated from Problemy Prochnosti, No. 10, pp. 108–112, October, 1989. 相似文献
182.
An expression is derived for the power spectral density of a coded mark inversion (CMI) TV signal transmitted through a fibre-optic heterodyne system. An illustrative example is given, and its power spectral density has been computed numerically. 相似文献
183.
C. Y. Liao S. N. Atluri 《International journal for numerical methods in engineering》1991,32(6):1339-1361
An efficient method, based on the Schwarz–Neumann alternating technique, is presented for computing weight functions of a general solid (3-D as well as 2-D), with embedded or surface-flaw configurations. The total rate of change of the crack-opening displacements, due to simple perturbations of crack-dimension characteristics, is conveniently decomposed into the infinite-domain and boundary-correction parts. The former is determined from available analytical solutions of ideal-shaped cracks, whereas the latter is computed numerically by imposing nil boundary-traction requirements for the displacement field corresponding to the weight functions. Numerical examples, with solutions for 3-D weighted-average and local stress intensity factors, indicate that the proposed method is very accurate and efficient. 相似文献
184.
We consider the dynamics of a dark soliton in an elongated harmonically trapped Bose-Einstein condensate. A central question
concerns the behavior at finite temperatures, where dissipation arises due to the presence of a thermal cloud. We study this
problem using coupled Gross-Pitaevskii and N-body simulations, which include the mean field coupling between the condensate and thermal cloud. We find that the soliton
decays relatively quickly even at very low temperatures, with the decay rate increasing with rising temperature. 相似文献
185.
The effect of varying normalising and hardening temperatures on the prior austenite grain size in a low alloy Cr–Mo–Ni–V steel
has been examined. An initial relative insensitivity of grain size to increasing austenitising temperature was observed followed
by a sudden growth of grains at approximately 1000 °C. A detailed study of the precipitates in the steel showed the presence
of a bimodal size distribution of vanadium carbides. The grain size increase is attributed to a decrease in volume fraction
and an increase in size of V4C3 particles with increasing temperature. 相似文献
186.
Dielectric and thermal characteristics of gel grown single crystals of ytterbium tartrate trihydrate
Dielectric and thermal characteristics of gel grown single crystals of ytterbium tartrate trihydrate have been carried out.
The dielectric constant has been measured as a function of frequency in the range 2 kHz–1 MHz and temperature range 30–300 °C.
The dielectric constant increases with temperature, attains a peak near 215 °C, and then decreases as the temperature exceeds
215 °C. The dielectric anomaly at 215 °C is suggested to be due to phase transition brought about in the material. The dielectric
behaviour of the material is correlated with the results on thermal analysis. Thermogravimetric and differential thermal analysis
have been used to study the thermal characteristics of the material. The experimental results show that the material is thermally
stable up to 200 °C. The decomposition process occurs in two stages until ytterbium oxide is formed at 700 °C. The non-isothermal
kinetic parameters e.g., activation energy and the frequency factor have been evaluated for each stage of thermal decomposition
by using the integral method, applying the Coats–Redfern approximation. 相似文献
187.
In this paper we report the results of electrical resistivity (1.5≤ T ≤ 300K) and point contact spectroscopy (PCS) measurements on single crystals of metallic sodium tungsten bronze with varying sodium content. We have shown that the electron-phonon coupling function as measured through PCS can explain quantitatively the large temperature dependence of resistivity ρ seen in these materials over the entire temperature range. The electron-phonon coupling function shows predominately large peaks for phonon frequency range of 30 meV ≤ ω ≤ 100 meV which match well with the calculated optical phonons for WO6 octahedron. The integrated electron-phonon coupling constant λ from this data is ≈ 0.25-0.45, depending on the Na content. PACS numbers: 72.15.-v, 72.80.Ga 相似文献
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