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991.
992.
In the present study, dynamic differential scanning calorimetry has been used to investigate the effect of an alkali lignin in amounts up to 20% by weight, on the crosslinking kinetics of an epoxy prepolymer cured with an aliphatic polyamine. Lignin presence does not significantly affect the overall reaction order, but the activation energy increases and the slowing of the overall curing process with lignin content could be explained by the interaction between lignin and the polyamine hardener. The possibility of having a “false compensation” in the case of the use of single DSC scans is also discussed. 相似文献
993.
Heinz-E. Albrecht Michael Borys Marcus Wenzel Thomas Wriedt 《Particle & Particle Systems Characterization》1994,11(4):339-344
In phase Doppler anemometry (PDA), phase difference errors are caused by the Gaussian intensity distribution of the laser beam and the curvature of the phase fronts outside of the beam waist. This results in erroneous particle sizes. Based on a physical analysis by geometrical optics [1], this phase difference error is evaluated for reflected mode operation (Part I) and for refracted mode operation (Part II). By varying the particle trajectories statistically, the error in determining the particle size and the mass flow can be simulated. By the method described the error in the measured phase difference can easily be estimated. 相似文献
994.
Marcus Greferath 《Journal of Geometry》1991,42(1-2):100-108
As a completion and extension of a result of A. Day and D. Pickering [5] we obtain the following structure theorem in the conceptual frame of projective lattice geometries: In a Desarguesian projective geometry the subgeometry of every at least one-dimensional hyperplane is module induced.
Ich danke Dr. S. E. Schmidt ganz herzlich für alle kritischen und wertvollen Anregungen während der Entstehung dieser Arbeit.
Prof. Armin Herzer zum 60. Geburtstag gewidmet 相似文献
Ich danke Dr. S. E. Schmidt ganz herzlich für alle kritischen und wertvollen Anregungen während der Entstehung dieser Arbeit.
Prof. Armin Herzer zum 60. Geburtstag gewidmet 相似文献
995.
Yongchang Fan Marcus R. Davidson James A. Cairns Graham J. Berry Alexander G. Fitzgerald 《Mikrochimica acta》2002,139(1-4):49-54
This study examines the thermal decomposition of 1,5-cyclooctadiene platinum (II) chloride organometallic films, deposited
by thermal evaporation. The thin film samples were annealed both in air and hydrogen with well-controlled temperature regimes.
After annealing, the decomposed thin films were examined by AFM and STM scanning probe, XPS and TEM microbeam analytical techniques.
The experimental results confirm that the thermal decomposition products on silicon substrates are composed predominantly
of metallic platinum. Annealing in hydrogen can reduce substantially the decomposition temperature of the material from around
250 to 160 °C but the surface morphology of the decomposed films is significantly different to those annealed in air. The
metallic nature of the thermally decomposed films was confirmed by bonding configuration recognition, electronic property
probing and microstructure analysis. 相似文献
996.
R. Rosentsveig A. Margolin Y. Feldman R. Popovitz-Biro R. Tenne 《Applied Physics A: Materials Science & Processing》2002,74(3):367-369
In this paper, the synthesis of multigram portions of WS2 nanotubes and large foils consisting of aligned nanotubes is described. For this purpose, a fluidized bed reactor, in which
WO3 powder is fed from the top and the reaction gases are blown from below maintaining the powder aloft, is described. The reaction
mechanism is briefly discussed.
Received: 20 August 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002 相似文献
997.
998.
The gauge invariance of relativistic two-particle energy levels in quantum electrodynamics is demonstrated for both covariant and non-covariant gauges, by considering infinitesimal gauge transformations from a fixed gauge. The proof is carried out by expressing the bound-state energies in terms of ratios of contour integrals involving four-point Green functions in the neighborhood of their poles in the energy plane. The generalized Ward-Takahashi identities are then used to help reduce the Green functions which appear into forms which make the singularity structure of the four-point function apparent. The formalism is illustrated for the special cases of one- and two-photon exchange in perturbation theory. 相似文献
999.
Ya. E. Ryabov H. Nuriel G. Marom Yu. Feldman 《Journal of Polymer Science.Polymer Physics》2003,41(3):217-223
The relationship between the parameter of symmetric broadening of the glass‐transition relaxation process and the structure of aramid‐fiber‐reinforced nylon‐66 microcomposites is investigated in this article. The approach is based on a previously derived model that sets a quantitative interrelation between the Cole–Cole parameter α, the relaxation time, and the fractal dimension of a mobile polymer segment. The microcomposite, the dielectric response of which reflects the transcrystallinity effects, indeed exhibits significantly different values, such as higher Kirkwood correlation factor and α exponent values, in comparison with the control materials, and this indicates its different crystalline morphology and perhaps lower order in the amorphous phase. However, at this stage, it is still difficult to establish a quantitative relationship with the polymer chain dynamics. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 217–223, 2003 相似文献
1000.
Three elementary proofs of the positive definiteness of the A-numerical radius, as defined by Goldberg and Straus, are given and a stronger result concerning exterior powers is conjectured 相似文献