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51.
Spinodal decomposition during continuous cooling of the PbOB2O3Al2O3 quasi-binary glass system was analysed by numerical integration of Cook's differential equation (which includes the contribution of random density fluctuations) for small angle X-ray scattering (SAXS) intensity. The SAXS curves derived from the calculations have a wide range of k-Fourier components (0 < k < kc) for which a positive amplification factor occurs and they show a “crossover” point at . The wavenumber which receives maximal amplification, km, increases with the cooling rate, Q, as , with n = 10.9. This Q dependence of km is similar to that predicted by Huston et al., however our results show a higher value of n. The dependence on Q and km of the SAXS intensity I(km) was also deduced. The measurements of SAXS curves were performed on glass samples prepared by the splat-cooling technique. Because of the difficulties which arise in the determination of the cooling rate of the samples, the only experimental results that could be compared with the theory are the km dependence of I and the value of kc. These results are satisfactorily understood in terms of the present analysis. 相似文献
52.
The rate of a standard gradedK-algebraR is a measure of the growth of the shifts in a minimal free resolution ofK as anR-module. It is known that rate(R)=1 if and only ifR is Koszul and that rate(R) ≥m(I)−1 wherem(I) denotes the highest degree of a generator of the defining idealI ofR. We show that the rate of the coordinate ring of certain sets of pointsX of the projective space P
n
is equal tom(I)−1. This extends a theorem of Kempf. We study also the rate of algebras defined by a space of forms of some fixed degreed and of small codimension. 相似文献
53.
Umberto Costantino Maria Antonietta Massucci Aldo La Ginestra Anna Maria Tarola Laura Zampa 《Journal of inclusion phenomena and macrocyclic chemistry》1986,4(2):147-162
The intercalation of imidazole and some organic species containing the imidazole ring, between the layers of crystalline zirconium phosphate has been investigated. Fourteen new, well-ordered intercalation compounds are obtained with the batch procedure at r.t. and/or 60°C. A mechanism of formation of the various compounds is proposed on the basis of the interaction between the guest molecules (with their dimensions and geometries) and the free PO3OH groups available between the layers of the host. The new phases have been characterized by TG and X-ray methods. 相似文献
54.
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56.
57.
Aldo Banfi Alberto Sala P. Angelo Soresinetti Giovanni Russo 《Journal of heterocyclic chemistry》1990,27(2):215-219
The preparation of new imidazole derivatives containing a carboxylic moiety such as succinic, adipic or benzoic into the side chain, is reported starting from the suitable imidazole intermediates. 相似文献
58.
Aldo Belleni Morante 《Meccanica》1973,8(1):11-15
Summary We prove existence and uniqueness of the solution of a linearized version of the kinetic equation of vehicular traffic on a highway by using the theory of semigroups of linear bounded operators.We assume that a perturbation is introduced at the entrance of the highway, i. e., at x=0 and that it continues for a given time interval [0,
].We then study the behaviour of such a perturvation at values of x close to zero by using perturbation theory for linear operators.Finally, we prove that the perturbation attenuates and approaches zero as x+, i. e. at a large distance from the entrance of the highway.
Work performed under the auspices of the National Research Council (C.N.R., Gruppo Nazionale per la Fisica Matematica). 相似文献
Sommario Si prova l'esistenza e l'unicità della soluzione dell'equazione linearizzata del traffico automobilistico su un'autostrada con un'entrata in corrispondenza di x=0.Si studia poi il comportamento di una perturbazione, dovuta per esempio all'uscita da una partita di calcio, e si mostra come tale perturbazione si attenui al crescere della distanza dall'ingresso dell'autostrada.
Work performed under the auspices of the National Research Council (C.N.R., Gruppo Nazionale per la Fisica Matematica). 相似文献
59.
Summary An ionized gas whose dynamics is dominated by charge exchange is considered. The following two problems are studied: the time
behaviour of sinusoidal waves in a uniform equilibrium; the propagation in a bounded equilibrium of sinusoidal oscillations
forced to the wall. It is shown, in particular, that the equilibria considered, not necessarily thermal equilibria, are stable
for any form of the distribution function.
Research supported in part by C.N.R., G.N.F.M. 相似文献
Sommario Si considera un gas ionizzato, non necessariamente in equilibrio termico, la cui dinamica sia dominata dal processo di scambio di carica, e si studiano i seguenti due problemi: evoluzione temporale di onde sinusoidali su un equilibrio uniforme; propagazione di oscillazioni sinusoidali forzate alla parete in un equilibrio spazialmente limitato. Si mostra in particolare la stabilitá degli equilibri per qualunque forma della funzione di distribuzione.
Research supported in part by C.N.R., G.N.F.M. 相似文献
60.
The merits and limitations of gas-phase electron diffraction as a technique for determining accurately the structures of small
organic molecules are demonstrated by comparing the molecular structures of five benzene derivatives studied in two different
laboratories. The existence of many possible representations of the structure of a molecule (r
a, r
g, r
α, r
α0, r
e, …), implying differences in the physical meaning of geometrical parameters, is discussed in some detail as it may cause
difficulties in a comparison. Also illustrated are different ways of estimating and expressing uncertainties in the geometrical
parameters from a gas-phase electron diffraction study. 相似文献