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101.
In this paper, we study the exact controllability and boundary stabilization of the torsional vibrations of a flexible space structure (such as a solar cell array) modeled by a rectangular panel, incorporating the material damping of the structure. The panel is hoisted at one end by a rigid hub and the other end is totally free. For the attachment of this hub on one side of the panel, the hub dynamics leads to a nonstandard boundary condition. To incorporate internal damping of the material, we assume Voigt-type viscoelasticity of the structure. Exact controllability theory is established using the Hilbert uniqueness method by means of a control torque applied only on the rigid hub of the panel. At the same time, uniform exponential energy decay rate is obtained directly for the solution of this problem. 相似文献
102.
103.
Temperature-dependent surface X-ray diffraction experiments have been performed on the K/Ag(001)-(2 × 1) adsorption system. The structure is characterized by a missing-row geometry in which alternate Ag rows along [1
0] are missing. The K atoms reside within the large grooves coordinated by six Ag atoms at a distance of 3.44(5) Å, corresponding to an effective K-radius of 2.00(5) Å. Large anisotropic disorder is observed for both the K-atoms and the top-layer (“ridge”) Ag atoms. The K-atom displacements are largest in the direction along the grooves, whereas for the Ag atoms the vibrations along [110] are significantly larger. The temperature dependence of the Ag vibrations is in accordance with Debye theory for the [110] direction, but deviates from it for the [1
0] vibrations at high temperature. In contrast to the K-atoms, the out-of-plane vibrations of the top-layer Ag atoms are larger than the in-plane vibrations. The inclusion of anharmonic contributions to describe the Ag disorder significantly improves the fits. It is shown that if anharmonicity is neglected the interlayer contraction is overestimated (Δd12/d12 only −3.2%, instead of −12.7% if anharmonicity is neglected). Due to the anharmonicity, different definitions of the atomic position arise (mean, mode and equilibrium position), which are discussed on the basis of the results. 相似文献
104.
In this paper, a model equation is presented for the study of rain-wind-induced vibrations of a simple oscillator. As will be shown the presence of raindrops in the wind-field may have an essential influence on the dynamic stability of the oscillator. In this model equation the influence of the variation of the mass of the oscillator due to an incoming flow of raindrops hitting the oscillator and a mass flow which is blown and shaken off is investigated. The time-varying mass is modeled by a time harmonic function whereas simultaneously also time-varying lift and drag forces are considered. 相似文献
105.
Treating the symmetry operations as transformations in higher dimensional space, it is shown that Wigner’s method can be straightaway
extended to study the vibrations of nonrigid molecules exhibiting free or nearly free internal rotations. The molecule B(CH3)3 is illustrated. 相似文献
106.
The effect of liquid on the propagation of waves in a micropolar elastic layer with stretch has been investigated. The frequency
and wave velocity equations for symmetric and antisymmetric vibrations are derived. Propagation of monochromatic waves in
a micropolar elastic layer with stretch is discussed. Results of this analysis reduce to those without stretch. 相似文献
107.
The suitability of ormosils as photonic materials was investigated. Vinyl and phenyl silicates were synthesised below 100°C. A detailed assignment of mid-infrared vibrational absorption bands is given. This allowed assignment of overtone and combination bands in the near-infrared region and an assessment of residual water contamination, which is low and can be expelled by evacuation. These ormosils have low intrinsic and extrinsic optical absorption in the visible spectral region and at useful wavelengths in the near-infrared. 相似文献
108.
Jan Philipp Hofmann 《Journal of Molecular Spectroscopy》2010,262(2):75-81
The emission spectrum of H13CN at 1370 K has been recorded with a hot gas high resolution FT-IR emission apparatus [1] in the wavenumber region of with a resolution of . This work reports the analysis of 50 subbands for the H13CN isotopologue of hydrogen cyanide in the 2ν1 wavenumber region. 23 rovibronic states of H13CN including the rovibronic states at have been characterized for the first time and for seven other states it was possible to improve the existing spectroscopic constants substantially. The dense emission spectrum was analyzed with the spectrum analysis software SyMath™ implemented in the Mathematica™ computer algebra system [1]. 相似文献
109.
Jacqueline Krim 《物理学进展》2013,62(3):155-323
This review provides an overview of recent advances that have been achieved in understanding the basic physics of friction and energy dissipation in molecularly thin adsorbed films and the associated impact on friction at microscopic and macroscopic length scales. Topics covered include a historical overview of the fundamental understanding of macroscopic friction, theoretical treatments of phononic and electronic energy dissipation mechanisms in thin films, and current experimental methods capable of probing such phenomena. Measurements performed on adsorbates sliding in unconfined geometries with the quartz crystal microbalance technique receive particular attention. The final sections review the experimental literature of how measurements of sliding friction in thin films reveal energy dissipation mechanisms and how the results can be linked to film-spreading behavior, lubrication, film phase transitions, superconductivity-dependent friction, and microelectromechanical systems applications. Materials systems reported on include adsorbed films comprised of helium, neon, argon, krypton, xenon, water, oxygen, nitrogen, carbon monoxide, ethane, ethanol, trifluoroethanol, methanol, cyclohexane, ethylene, pentanol, toluene, tricresylphosphate, t-butylphenyl phosphate, benzene, and iodobenzene. Substrates reported on include silver, gold, aluminum, copper, nickel, lead, silicon, graphite, graphene, fullerenes, C60, diamond, carbon, diamond-like carbon, and YBa2Cu3O7, and self-assembled monolayers consisting of tethered polymeric molecules. 相似文献
110.
Periodic variations in the Z 1 dependence of the interatomic potential has recently bevlen revealed by a channeling technique. To search for oscillations of similar kind in a target of randomly arranged atoms we have made systematic measurements on the scattering distributions of energetic (32–56 keV) ions in amorphous carbon. Our technique was to transmit light mass ions through carbon foils with a thickness of 2–4 μg/cm2. The atomic number of the ions, Z, ranged from 3 to 18. The scattering distribution of the transmitted particles was recorded. From these curves the angular halfwidth,ψ 1/2, and the relative intensity at a scattering angle 2.5 times ψ 1/2 was determined. The experimental values are in good agreement with theoretical calculations based on the Thomas-Fermi and Lenz- Jensen potentials. Furthermore, the saturation value of the mean nuclear stopping cross sections for ions scattered in the straight forward direction with a mean energy of 50 keV are given. No evidence for a Z 1 oscillatory behaviour could be found in any of the three parameters investigated. 相似文献