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131.
Extensive experimental results are presented to reveal the relaxations of polystyrene surface deformed by rubbing with a velvet
cloth. We found that surface topographic features, such as ditches and ridges created by rubbing, relax at temperatures at
about 20°
C below the bulk glass transition temperature of the polystyrene for a molecular weight of 442 kg/mol, even though we estimate
the Laplace Pressure driving the relaxation to be 1/500 of the yield limit. The relaxation is independent of the thermal history
before the rubbing process, and post rubbing thermal history below 55°
C . In other words, physical-aging processes at 23°
C for up to 7 days and at 50°
C for 2 days, which would have drastic effects on the relaxations of bulk polymers, have little effects on the relaxations
of rubbed surfaces. This is consistent with the mobility enhancement in the surface layer previously reported in the literature. 相似文献
132.
This paper presents the analytical and simulation responses of the closed orbit distortion in the SSRF storage ring to random and plane wave like magnet vibrations respectively. It is shown that the use of girder is very beneficial in the view of suppressing this response function. Effect of the independently supported gradient bending magnets to the closed orbit response is given. An analytic formula is written to give a rough estimate of the closed orbit distortion due to ground motion, taking into account the closed orbit response function and girder transfer function. As an example, the result of SSRF case is given. 相似文献
133.
I. Kh. Abdukadyrova 《Journal of Applied Spectroscopy》2008,75(3):374-378
The influence of radiation damage on a number of lattice vibration parameters in two SiO2 modifications was investigated using IR reflectance spectroscopy. The radiation kinetics of changes in spectral characteristics
of SiO2 fundamental vibrations in crystalline and glassy states were determined. The reflectivity coefficient and the frequency of
degenerate vibrations as functions of dose showed minima, the locations of which were governed by the type of sample. At high
neutron irradiation doses (1021 cm−2), certain characteristics of the bands had the same values for both modified materials. Features of the radiation kinetics
of sample dynamic parameters were determined. It was deduced that the specific character of the observed radiation-induced
changes in spectral and dynamic parameters of vibrations near degenerate modes was due to both the accumulation of radiation
damage and a change in the force field surrounding bridging bonds, which is related to a change in the SiO2 structure.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 354–358, May–June, 2008. 相似文献
134.
Sidney F. A. Kettle Eliano Diana Edoardo M. C. Marchese Enrico Boccaleri Pier Luigi Stanghellini 《Journal of Raman spectroscopy : JRS》2011,42(11):2006-2014
A careful analysis of the Raman spectra of the M′x[M(CN)6]y Prussian blue species has enabled a general model for the interpretation of the ν(CN) vibrational spectra. The spectral patterns are derived from those of the metal ions with local Oh symmetry. Two limiting models are discussed. A ‘localized mode’ model, involving matrix‐isolated species, is in much better accord with the observations than a ‘factor group’ model. The use of the infrared feature as fingerprint of specific M CN M′ units arises from the axis‐specific nature of individual T1u modes. The interpretation of the A1g and Eg Raman features is done in terms of localized vibrations, with involvement of additional energy terms from the lattice motions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
135.
Torsional states caused by vibrations of hydroxyl groups in the methanediol molecule and its two deuterated analogues – DO(CH2)OH and DO(CH2)OD were analysed at MP2/cc-pVTZ and CCSD(T)/cc-pVQZ levels of theory. In the first case, 2D PES and 2D surfaces of kinematic coefficients were calculated with geometry optimisation for all other geometric parameters, and in the second case, only the energy of optimised configurations at the MP2/cc-pVTZ level of theory was determined. Then 2D PES was recounted to the complete basis set (CBS) limit by extrapolating the results of calculations at the MP2/cc-pVTZ and MP2/cc-pVQZ levels of theory The calculated values were then averaged over four equivalent points on the coordinate plane. Hamiltonian matrices were constructed using DVR and Fourier methods. After their subsequent diagonalization, the energies of the stationary torsional states were computed. Their classification by C2V(M) and CS(M) molecular symmetry groups has been performed. The splitting values due to the tunnelling of the thirty most deeply located torsional states in the three studied molecules were also determined. The torsional states, internal rotation barriers, and tunnelling frequencies in the molecules of methanediol and hydrogen trioxide were compared. 相似文献
136.
Many technologies based on fluid–structure interaction mechanisms are being developed to harvest energy from geophysical flows. The velocity of such flows is low, and so is their energy density. Large systems are therefore required to extract a significant amount of energy. The question of the efficiency of energy harvesting using vortex-induced vibrations (VIV) of cables is addressed in this paper, through two reference configurations: (i) a long tensioned cable with periodically-distributed harvesters and (ii) a hanging cable with a single harvester at its upper extremity. After validation against either direct numerical simulations or experiments, an appropriate reduced-order wake-oscillator model is used to perform parametric studies of the impact of the harvesting parameters on the efficiency. For both configurations, an optimal set of parameters is identified and it is shown that the maximum efficiency is close to the value reached with an elastically-mounted rigid cylinder. The variability of the efficiency is studied in light of the fundamental properties of each configuration, i.e. body flexibility and gravity-induced spatial variation of the tension. In the periodically-distributed harvester configuration, it is found that the standing-wave nature of the vibration and structural mode selection plays a central role in energy extraction. In contrast, the efficiency of the hanging cable is essentially driven by the occurrence of traveling wave vibrations. 相似文献
137.
138.
《International journal of quantum chemistry》2018,118(11)
Perturbed structures for QTAIM dual functional analysis (QTAIM‐DFA) are proposed to generate using the coordinates corresponding to the compliance force constants in internal vibrations (CIV). In QTAIM‐DFA, total electron energy densities Hb( r c) are plotted versus Hb( r c) – Vb( r c)/2 at bond critical points (BCPs) of interactions in question, where Vb( r c) are potential energy densities at BCPs. Each plot of an interaction based on the data from both perturbed structures and fully optimized one takes the form (θp, κp), where θp corresponds to the tangent line of the plot and κp is the curvature. The θp values evaluated with CIV are equal to those obtained by partial optimizations with the interaction distance in question being fixed suitably, within the calculation errors. Very high applicability of CIV is demonstrated to generate the perturbed structures for QTAIM‐DFA. Dynamic nature of interactions based on (θp, κp) with CIV is called “intrinsic dynamic nature of interactions.” 相似文献
139.
This paper deals with -periodicity and regularity of solutions to the one dimensional nonlinear wave equation with -dependent coefficients
140.
A quasi-isochronous vibroimpact system is considered, i.e. a linear system with a rigid one-sided barrier, which is slightly offset from the system's static equilibrium position. The system is excited by a sinusoidal force with disorder, or random phase modulation. The mean excitation frequency corresponds to a simple or subharmonic resonance, i.e. the value of its ratio to the natural frequency of the system without a barrier is close to some even integer. Influence of white-noise fluctuations of the instantaneous excitation frequency around its mean on the response is studied in this paper. The analysis is based on a special Zhuravlev transformation, which reduces the system to one without impacts, or velocity jumps, thereby permitting the application of asymptotic averaging over the period for slowly varying inphase and quadrature responses. The averaged stochastic equations are solved exactly by the method of moments for the mean square response amplitude for the case of zero offset. A perturbation-based moment closure scheme is proposed for the case of nonzero offset and small random variations of amplitude. Therefore, the analytical results may be expected to be adequate for small values of excitation/system bandwidth ratio or for small intensities of the excitation frequency variations. However, at very large values of the parameter the results are approaching those predicted by a stochastic averaging method. Moreover, Monte-Carlo simulation has shown the moment closure results to be sufficiently accurate in general for any arbitrary bandwidth ratio. The basic conclusion, both of analytical and numerical simulation studies, is a sort of smearing of the amplitude frequency response curves owing to disorder, or random phase modulation: peak amplitudes may be strongly reduced, whereas somewhat increased response may be expected at large detunings, where response amplitudes to perfectly periodic excitation are relatively small. 相似文献