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31.
Grédiac  M.  Blaysat  B.  Sur  F. 《Experimental Mechanics》2019,59(2):219-243
Experimental Mechanics - Digital Image Correlation (DIC) and Localized Spectrum Analysis (LSA) are two techniques available to extract displacement fields from images of deformed surfaces marked...  相似文献   
32.
The ground state and first few excited energy levels of the generalized anharmonic oscillator defined by the HamiltonianH=–d 2/dx 2+x 2+x 2k (k=3, 4,...) have been calculated by employing the method of quantum normal form, which is the quantum mechanical analogue of the classical Birkhoff-Gustavson normal form. The present energy eigenvalues are consistent with other tabulations of the energy levels.  相似文献   
33.
We have studied the orientation and barrier properties of self-assembled monolayers (SAMs) of two alkanedithiols, hexanedithiol, octanedithiol, and an aromatic dithiol, 1,4-benzene dimethanethiol (BDMT), on gold in acetonitrile. From our studies, we conclude that BDMT molecules can form more organized monolayers on gold than aliphatic dithiol SAMs due to extremely strong lateral van der Waals interaction among the phenyl rings in the former. A study of the adsorption kinetics of octanedithiol in ethanol indicates that the adsorption rate law is concentration dependent just as for alkanethiols. However, the rate of adsorption is considerably faster than for simple alkanethiols.  相似文献   
34.
The far-uv photolysis of phosphine sorbed in cancrinite matrix at 77 K has been studied by epr spectroscopy. Cancrinite is demonstrated to stabilise the photolytically generated radicals ·PH2, ·P and ·H. Computer simulation of the entire lineshapes has been employed to assess the spin Hamiltonian parameters for both ·PH2 and ·P. The intensity distribution pattern of the ·PH2 spectrum at 77 K is indicative of a thermally-equilibrated population of rotational states of this radical in its matrix environment. The similarity of the epr data of ·PH2 trapped in cancrinite to that isolated in rare gas matrices, as well as theisotropic nature of the31P and1H hyperfine couplings in the former situation, suggest that ·PH2 is trapped in pseudospherical cavities of cancrinite with minimal matrix perturbations. Marked departures are observed for theg- andA- values of cancrinite-trapped P atoms as compared with the gasphase counterparts.  相似文献   
35.
Grédiac  M.  Blaysat  B.  Sur  F. 《Experimental Mechanics》2020,60(4):509-534
Experimental Mechanics - This paper deals with the optimal pattern that can be used to retrieve displacement fields by minimizing the optical residual calculated over small regions of contrasted...  相似文献   
36.
It is demonstrated that time resolved laser spectroscopy can give atomic lifetime data with an accuracy of better than 0.5%. This is achieved by a single-photon counting delayed coincidence technique, using a mode-locked dye laser for the excitation. Natural radiative lifetimes are measured for the sodium and bismuth atoms.  相似文献   
37.
The ESR spectroscopic investigations on the formation of neutral and anionic radical species from 1,1′-Bi-2-naphthol and 1,1′-Bi-2-phenol at room temperature are reported. The photogeneration of the neutral radicals is accompanied by an unusual kinetic decay in the presence of light. The nature and the structure of the radicals are discussed.  相似文献   
38.
Mesoporous silica was synthesized by hydrolysis of tetraethylorthosilicate (TEOS, formula Si(OCH2CH3)4) at ambient temperature in a basic ethanol-water solution, with cetyltrimethyl ammonium bromide as a template. It had a surface area of approximately 1,400 m2/g, and an average pore diameter of approximately 40 Å. Portions were blended into three samples of poly(ethylene oxide) (PEO) of varying molecular weights, in the hope of making novel composites by penetrating some of the PEO chains into the silica channels. Differential Scanning Calorimetry (DSC) and X-ray diffraction (XRD) were used to characterize the structures of the PEO/mesoporous silica composites after they were held at 100 °C for up to 30 min. In both experiments, the melting temperature of the PEO decreased and ultimately disappeared. These results suggest that the PEO chains did penetrate into the silica pores, and since they were constrained in the pores, their crystallization was suppressed. This provides an interesting parallel to the disappearance of the glass transition temperatures of polymers constrained in the cavities of zeolites or in the galleries of intercalated clays.  相似文献   
39.
The mixed spinel systems CoxFe1−xCr2S4 has been studied using the Mössbauer effect. Spectra have been collected over the temperature range 83–300 K. The isomer shifts indicate that the charge states of Fe ions are ferrous in character throughout the series. Absence of quadrupole splitting above the magnetic ordering temperature Tc suggests that iron ions occupy only tetrahedral sites. It is notable that as the temperature decreases below Tc, both quadrupole shift and asymmetrical line-broadening appear and increase with decreasing temperature, suggesting the presence of electric field gradient and accompanying relaxation effects.  相似文献   
40.
The thermomechanical properties, morphology, and gas permeability of hybrids prepared with three types of organoclays were compared in detail. Hexadecylamine–montmorillonite (C16–MMT), dodecyltrimethyl ammonium bromide–montmorillonite (DTA‐MMT), and Cloisite 25A were used as organoclays in the preparation of nanocomposites. From morphological studies using transmission electron microscopy, most clay layers were found to be dispersed homogeneously in the matrix polymer, although some clusters or agglomerated particles were also detected. The initial degradation temperature (at a 2% weight loss) of the poly(lactic acid) (PLA) hybrid films with C16–MMT and Cloisite 25A decreased linearly with an increasing amount of organoclay. For hybrid films, the tensile properties initially increased but then decreased with the introduction of more of the inorganic phase. The O2 permeability values for all the hybrids for clay loadings up to 10 wt % were less than half the corresponding values for pure PLA, regardless of the organoclay. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 94–103, 2003  相似文献   
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