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81.
Influence of annealing and chain defects on the melting behaviour of poly(vinylidene fluoride) 总被引:2,自引:0,他引:2
C. Marega 《European Polymer Journal》2003,39(8):1713-1720
The melting behaviour of poly(vinylidene fluoride) (PVDF) was investigated by differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering in order to study the influence of the chain defects content and of the temperature of annealing on the crystallization and melting behaviour.All the DSC scans show a double endotherm and the analysis of the data suggests that the low temperature endotherm is due to the melting of a population of thin lamellae, whose thickness increases during the annealing, but a high content of chain defects prevents the lamellar thickening and the main effect in this case is the crystallization of thin lamellae from a portion of polymer which did not crystallize during the quenching from the melt. Furthermore, the two melting endotherms, which are observed, can be partially ascribed to a melting-recrystallization process.Furthermore, stepwise isothermal cooling was performed in a differential scanning calorimeter followed by melting scans of fractionated PVDF samples to point out the possible presence of a series of endothermic peaks. 相似文献
82.
We consider some types of packet discretization for continuous spectra in quantum scattering problems. As we previously showed, this discretization leads to a convenient finite-dimensional (i.e., matrix) approximation for integral operators in the scattering theory and allows reducing the solution of singular integral equations connected with the scattering theory to some suitable purely algebraic equations on an analytic basis. All singularities are explicitly singled out. Our primary emphasis is on realizing the method practically. 相似文献
83.
Usually, numerical self-consistent calculations predict a much larger intrinsic bistability region than actually is measured in resonant tunneling diodes (RTDs). In addition, numerical calculations have shown that scattering in the well reduces bistability. We used a unified treatment of current flowing from continuum states and emitter quasi-bound states to show numerically and analytically that not only the scattering in the quantum well but also the scattering in the emitter reduces bistability. Moreover, within the Hartree approximation, bistability occurs by tunneling resonantly between emitter quasi-bound state and well quasi-bound state as a pitchfork bifurcation. 相似文献
84.
Werner Kaller 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,87(2):107-117
The angular dependence of light scattered by aerosol particles in the atmosphere—the aerosol phase function—is one of the key properties of every radiative transfer and climate model. Side-scattering in the atmosphere is currently believed to be underestimated by most of the radiative transfer models in certain cases. The aerosol phase function can be measured with polar nephelometers.An innovative polar nephelometer able to measure the phase function of ambient aerosol directly is presented in this publication. The performance of the device was simulated completely using ray-tracing techniques. The results of these simulations are used to interpret the measurement data precisely. The measurements with the new polar nephelometer are fully automated. The quality of the measurement results was verified using different approaches. The values of the statistical and systematic error in measuring atmospheric aerosol are about 4% each. Scattering angles from 10° to 160° were measured and it is shown that with the same design this range can be extended to 3-177° in steps of 0.16° with an aperture of less than 1.8°.Measurements of the aerosol phase function are presented and compared with data taken with an integrating nephelometer and measurements of the particulate matter concentration. All data correlate very well. The described polar nephelometer can measure the phase function and the scattering coefficient of atmospheric aerosol with high accuracy and can be used for continuous monitoring measurements as well as in field campaigns. 相似文献
85.
86.
Yang Ruike Wu Zhensen You Jinguang 《International Journal of Infrared and Millimeter Waves》2003,24(8):1383-1392
The influence of sand and dust storms on modern MMW and satellite communication systems reliability have been paid more attention to. The attenuations induced by sand and dust storms are estimated by means of Mie-theory and Rayleigh approximation, in the case of the tenuous distribution of particles. With the particle density increasing, however, these method become inadequate, the multiple scattering effects then become dominant for attenuation estimation. The attenuations considering multiple scattering effects are estimated by Monte-Carlo and four fluxes method at horizontal paths. At slant paths, based on multi-layer media model, the attenuations considering multiple scattering effects are calculated by layered Monte-Carlo method at 100, 37, 24, and 14GHz. It is shown that the multiple scattering effects should be considered at the attenuation prediction in the sand and dust storm, which the visibility is about 0.5km and smaller than 0.5km and frequency is about 20GHz. Above 30GHz, the multiple scattering effects due to sand and dust particles should be considered, as visibility is about 1km and smaller than 1km at slant paths. 相似文献
87.
单壁碳纳米管的SERS研究 总被引:2,自引:2,他引:0
本文通过改进实验方法,将单壁碳纳米管的乙醇溶液与金胶混合并制作成固体薄膜,使单壁碳纳米管夹裹在金纳米粒子之间,保证了吸附的紧密性,获得了高质量的单壁碳纳米管SERS光谱。不但观测到文献中报道的径向呼吸振动模(RBM)和C-C正切拉伸模(GM)的增强,还在1100-1500cm-1区域观测到一组新峰,其峰形完整并有相当的强度。这些峰在现有的文献中几乎没有报导。文章对这组新峰的出现进行了初步的分析。 相似文献
88.
89.
Fabiano Severo Rodembusch Ndya Pesce da Silveira Dimitrios Samios Leandra Franciscato Campo Valter Stefani 《Journal of Polymer Science.Polymer Physics》2003,41(4):341-350
The solution behavior of new copolymers of methyl methacrylate and benzazole dyes emitting fluorescence because of an intramolecular proton‐transfer mechanism in the electronically excited state has been investigated by static light scattering, fluorescence spectroscopy, ultraviolet–visible, and gel permeation chromatography. In the dilute regime, with tetrahydrofuran (THF) and chloroform as solvents, the copolymers behave as typical polydisperse linear chains in good solvents. The analysis of the osmotic modulus for concentrated solutions in THF (c ≥ 60 g L?1) indicates the existence of an interchain association mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 341–350, 2003 相似文献
90.
Two structure functions W1(x,Q2) and W2(x,Q2) are determined by using the cross sections measured in the deep inelastic electron-proton scattering experiments at Stanford Linac in the energy range of 5 to 20 GeV. In this paper an alternative mathematical approach have been used in such determination, resulting in a larger number of points in the graphs of the structure functions. 相似文献