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151.
The effect of an inorganic filler (aerosil) on photopolymerization of an oligoester composition is investigated by means of
IR spectroscopy. It is shown that the filler, depending on its concentration, is capable of enhancing or hindering the main
process, or inducing side reactions.
Institute for Surface Chemistry, National Academy of Sciences of Ukraine, 31, Nauka Ave., Kiev, 252022, Ukraine. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 119–124 January–February, 1999. 相似文献
152.
MgO缺陷和不规则表面吸附Cl2的电子结构研究 总被引:2,自引:0,他引:2
采用从头算程序对MgO表面 3种不同配位位置吸附Cl2 的构型进行优化 ,并用扩展休克尔紧束缚 (EHT)晶体轨道方法对MgO的缺陷和不规则表面吸附Cl2的可能构型进行能带计算 ,讨论了吸附前后能带组成和成键性质的变化。研究表明 :MgO表面吸附Cl2 将更趋向于吸附在O原子上而非Mg原子上 ,而且在 3种配位中MgO表面三配位氧最有利于吸附Cl2 ;吸附时 ,电子从O原子转移到Cl2 分子的反键轨道 ,但是各种吸附构型的MgO表面对Cl2 的吸附作用均比较微弱 ,是典型的物理吸附。 相似文献
153.
A.L. Dobryakov J.L. Prez Lustres S.A. Kovalenko N.P. Ernsting 《Chemical physics》2008,347(1-3):127-138
Femtosecond transient UV/vis absorption spectra of molecules in solution show vibronic structure initially while pump and probe pulses overlap, superimposed on bands which broaden and shift on several time scales. Third-order perturbation theory is used simulate and understand such spectra under experimental conditions, i.e., with chirped pump pulses and 40–80 fs pump/probe correlation time. The electronic system is coupled to a solvent bath whose fluctuations enter through a lineshape function g(t). This approach has two advantages. (i) In the general case when g(t) is modelled realistically it provides a distinction of coherent and sequential contributions to early transient spectra. The time-zero stimulated emission band can be extracted, giving access to the relaxation function for the emission frequency. (ii) For limiting forms of g(t) corresponding to the Bloch approximation and to inhomogeneous broadening the threefold time integrals underlying the theory reduce to a single integral. In such cases the lineshape formulation of transient absorption spectra can be used for data fitting. 相似文献
154.
M. Schocker 《Journal of Algebraic Combinatorics》2008,28(1):231-234
We define the notion of weakly ordered semigroups. For this class of semigroups, we compute the radical of the semigroup algebras.
This generalizes some results on left regular bands and on 0- Hecke algebras. 相似文献
155.
A new type of crisis is shown to exist in a broad class of systems (including the Lorenz model) which leads to an anomalous band splitting or to a symmetry-breaking bifurcation of the strange attractor, depending on the actual values of the control parameters. A piecewise linear model is used to understand the mechanism of this crisis and to obtain exact results. 相似文献
156.
SrBi2Nb2O9 (SBN) thin films were prepared on fused quartz substrates at room temperature by pulsed laser deposition. The influence of deposition parameters such as target-to-substrate distance, oxygen pressure and annealing temperature on film crystallization behavior was investigated by X-ray diffraction. Results indicated that the films grown at the optimum processing conditions have polycrystalline structure with a single layered perovskite phase. The optical transmittance of the films prepared at various oxygen pressures was measured in the wavelength range 200–900 nm using UV–vis spectrophotometer. The results showed that there is a red shift in the optical absorption edge with a rise in the oxygen pressure. Refractive index as a function of wavelength and optical band gap of the films were determined from the optical transmittance spectra. The results indicated that the refractive index increases with increasing oxygen pressure at the same incident light wavelength, while the band gap reduces from 4.13 to 3.88 eV. It may be attributed to an increase in packing density and grain size, and decrease in oxygen defects. 相似文献
157.
158.
159.
A. Šimůnek J. Vackář K. Kunc J. Hutter 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):245-249
A soft, norm-conserving pseudopotential for carbon is presented and its performance tested by calculations on atomic states
and on diamond: electronic energy levels of different atomic configurations, equilibrium lattice constant, bulk modulus, and
the TA(X) frozen-phonon frequency are accurately reproduced. Convergence of the total energy of diamond with the size of the
plane-wave basis set is compared for several frequently used pseudopotentials, and it is shown that calculations with the
reported pseudopotential can be performed at considerably lower cost than with the other norm-conserving pseudopotentials,
without loosing the accuracy of the latter in predicting structural and dynamical properties. The rapid convergence of the
results with the plane-wave cutoff is comparable to the performance of the Vanderbilt's ultrasoft pseudopotentials. The transferability
of the pseudopotential to other electronic configurations is discussed.
Received 8 September 1999 相似文献
160.
A. Chatterjee A. Sarkar Sourav Bhattacharya P. Mukherjee N. Gayathri P. Barat 《Physics letters. A》2008,372(22):4016-4020
Tensile tests were carried out by deforming polycrystalline samples of substitutional Al–2.5%Mg alloy at room temperature for a range of strain rates. The Portevin–Le Chatelier (PLC) effect was observed throughout the strain rate regime. The deformation bands in this region are found to be of type A in nature. From the analysis of the experimental stress time series data we could infer that the dynamics of type A dislocation band propagation is a Markov process. 相似文献