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881.
Fluorescence spectroscopic studies of acenaphthylene dimers in saturated hydrocarbon solution have revealed that the dimer (A2) photodissociates to 相似文献
882.
Noise effects on the phase lockings and bifurcations in the sinusoidally forced van der Pol relaxation oscillator are investigated. Deterministic (noise-free) one-dimensional Poincaré mapping is extended to the iteration of the operator defined by a stochastic kernel function. Stochastic phase lockings and bifurcations are analyzed in terms of the density evolution by the operator. In particular, a new method which uses spectra (eigenvalues and eigenfunctions) of the operator to analyze stochastic bifurcations intensively is proposed. 相似文献
883.
A kinetic and mechanistic study of the autoxidation of liquid pentaerythrityl tetraheptanoate (PETH) at 180–220°C has been carried out utilizing a stirred-flow reactor. The results are consistent with the occurrence of a chain reaction scheme similar to that proposed for n-hexadecane autoxidation, namely, the formation of monohydroperoxides by the intermolecular abstraction reaction (3), the formation of α,γ- and α,δ-dihydroperoxides and α,γ- and α,δ-hydroperoxyketones by intramolecular peroxy radical abstraction reactions (4) and (4*), the bimolecular termination of peroxy radicals, reaction (6), and the rapid conversion of α,γ-hydroperoxyketones to the corresponding cleavage acids and methyl ketones, reaction (7). Comparisons of various rate parameters for the n-hexadecane and PETH systems reveal that the values of k7 and (k3/H atom)/(2 k6)1/2 are within experimental uncertainties identical for the two systems at 180°C. The proposed reaction scheme includes the concurrent formation of hydroxy radicals and hydroperoxyketone species. The results of kinetic analysis and the experimentally observed isomer distributions of primary and secondary monohydroperoxide products at high and low oxygen pressures suggest that ≈60% of the hydrogen abstractions from PETH at high oxygen pressures occur by hydroxy radicals. 相似文献
884.
Synthesis of pyrochlore tungsten trioxide thin film and electrochemical lithium intercalation 总被引:2,自引:0,他引:2
The pyrochlore tungstate thin film has been prepared by an autoclave hydrothermal method at a temperature of 200 °C. The film was characterized by X-ray diffractometry, X-ray photoelectron spectroscopy and scanning electron micrograph measurements, showing that pure pyrochlore phase of sodium tungstate containing a small amount of water was formed by heating the film at a temperature of 350 °C. The cyclic voltammetric and galvanostic measurements revealed that a reversible electrochemical lithium intercalation into the crystal lattice of pyrochlore tungstate film takes place with charge-discharge cycling. Furthermore, the thermodynamics and kinetics of electrochemical lithium intercalation into the pyrochlore sodium tungstate film were also studied. 相似文献
885.
Low-temperature elastic moduli and internal dilational and shear friction of polymethyl methacrylate
Longitudinal and transverse wave velocity, five kinds of elastic parameters (young, shear and bulk moduli, Lamér; parameter. Poisson's ratio) and dilational and shear internal friction of polymethyl methacrylate were simultaneously measured over a temperature range 68–400K, using the ultrasonic pulse method. All elastic moduli decrease with increasing temperature, suggesting lowering of molecular bonding strength. From dilational and shear internal frictions, the 139, 382, and 385K peaks are interpreted as rotation of x-methyl estel groups, micro Brownian motion of main chains and stress relaxation, and abrupt increases from 242 and 395K are regarded as free motion of side chains and glass transition, respectively. ©1995 John Wiley & Sons, Inc. 相似文献
886.
887.
K. N. Mikhalev I. E. Litvinov Z. N. Nigamatyanova A. Yu. Yakubovskii A. R. Kaul O. Yu. Gorbenko K. Kumagai Y. Furukawa 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(5):703-706
139La nuclear magnetic resonance spectra have been recorded and the spin-spin relaxation times in the paramagnetic region in
external magnetic fields of 5 and 9.4 T have been measured for two types of manganites: initial (La0.25Pr0.75)0.7Ca0.3Mn16O3 and enriched with the 18O isotope ((La0.25Pr0.75)0.7Ca0.3Mn18O3). The manganite enriched with the heavier oxygen isotope exhibits disappearance of a signal in the charge-ordering region
(T < T
co) in an external field of 5 T. This effect is related to the anomalous increase in the spin-spin relaxation rate. With an
increase in the external magnetic field to 9.4 T, the difference in the behavior of the relaxation rate for the two samples
in the charge-ordering region remains pronounced, although the magnitude of this effect becomes much smaller. The observed
giant isotope effect is a bright evidence of the important role of oxygen motion in the formation of long-range magnetic order
in the manganites under consideration.
Original Russian Text ? K.N. Mikhalev, I.E. Litvinov, Z.N. Nigamat’yanova, A.Yu. Yakubovskii, A.R. Kaul’, O.Yu. Gorbenko,
K. Kumagai, Y. Furukawa, 2007, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2007, Vol. 71, No. 5,
pp. 726–729. 相似文献
888.
889.
890.
D.A. Croydon B.M. Hambly T. Kumagai 《Stochastic Processes and their Applications》2019,129(9):2991-3017
Quenched and annealed heat kernel estimates are established for Fontes–Isopi–Newman (FIN) processes on spaces equipped with a resistance form. These results are new even in the case of the one-dimensional FIN diffusion, and also apply to fractals such as the Sierpinski gasket and carpet. 相似文献