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181.
The static dielectric properties of (001)(GaAs)(p)/(AlAs)(p) superlattices have been calculated as a function of their period p for 1< or = p < or =12, starting from density-functional theory. The interplay between quantum confinement and local field effects is shown to be crucial. For light polarized in the growth direction it leads to the otherwise surprising justification of the use of a classical effective medium theory, even for the smallest periods. Only the inclusion of both contributions allows in ab initio and in semiempirical calculations to reproduce the experimentally observed birefringence. 相似文献
182.
We implement a dynamic model that describes the polarization behavior in vertical-cavity surface-emitting lasers that contain an absorbing region surrounding the active zone. We find four regions of qualitatively different behavior: stable linearly polarized operation, intensity pulsations of a linearly polarized component, pulsations of both total-intensity and polarization components, and polarization self-pulsation with constant total intensity. We characterize the four regions by computing the polarization-resolved optical and power spectra. The predicted behavior agrees with recent experimental results. 相似文献
183.
Pioger P Couderc V Lefort L Barthelemy A Baronio F De Angelis C Min Y Quiring V Sohler W 《Optics letters》2002,27(24):2182-2184
We show numerically and experimentally that spatial trapping can be induced in quadratic media even if the pump pulse's duration is shorter than the group-delay mismatch between fundamental wave and second-harmonic components. The influence of phase mismatch and pulse power on the trapping effect is discussed. Spatial, temporal, and spectral behaviors that accompany self-trapped propagation are highlighted. 相似文献
184.
Claudio Baiocchi 《Annali di Matematica Pura ed Applicata》1966,72(1):395-417
Sunto Si studia la regolarità (del tipo diGevrey) per le soluzioni delle equazioni differenziali astratte del tipo (*) e (**) dell'introduzione.
Lavoro eseguito nell'ambito delle attività svolte nei Gruppi Matematici di Ricerca del C. N. R. 相似文献
185.
Salvatore Pignataro Giovanni Marletta Orazio Puglisi Umberto Costantino Giulio Alberti 《Journal of Electron Spectroscopy and Related Phenomena》1982,25(1):49-57
Mg Kα ESCA spectra of several α-Zr(PO4)2M2 compounds (M = Li+, Na+, K+, Cs+) have been obtained. Satellite structure is observed at ~7–8 eV from the main P 2s peak (corresponding to ~15–16 eV from the main Zr 3d peak). The intensity of the satellite depends on the counter-ion intercalated. For a given counter-ion it is strongly increased by sputtering, the rate of increase being also dependent on the counter-ion. This observation is interpreted mainly in terms of electron-defect formation similar to that involved in the formation of colour centres by radiation damage, and subsequent charge-transfer shake-up of the trapped electrons to the electron-deficient phosphorus or Zr(IV) centres. 相似文献
186.
Claudio Rea 《Annali di Matematica Pura ed Applicata》1976,110(1):161-175
Sunto Si dimostra l'esistenza della soluzione per l'operatore di Cauchy-Riemann parametrizzato, nel caso continuo per varietà fortemente
pseudoconvesse e nel caso differenziabile per varietà di Stein.
Entrata in Redazione il 20 maggio 1975.
Supported by C.N.R. research groups. 相似文献
Entrata in Redazione il 20 maggio 1975.
Supported by C.N.R. research groups. 相似文献
187.
V. Vitagliano R. Sartorio A. Acampora L. Costantino S. Wurzburger 《European Polymer Journal》1973,9(9):909-918
The moving boundary technique has been used to measure independently the transference numbers of macroion and counterions in water solutions of sodium polyacrylate at 25° and in the concentration range 0·050-0·8 eq/l. The experimental results allow us to compute, without any arbitrary assumption, the fraction of counterions which contribute to the transport of current towards the cathode and which may be called the “fraction of free ions”. 相似文献
188.
Claudio Teitelboim 《Physics letters. [Part B]》1977,69(2):240-244
It is shown that in asymptotically flat space the weakly vanishing Hamiltonian of supergravity theory has to be modified by adding to it certain surface integrals. The numerical value of the surface integrals yields the total energy-momentum, angular momentum and supercharge of the system. The surface integrals have well defined (Dirac) brackets only after the coordinates and supergauge are fixed. In that case they close according to the flat space supersymmetry algebra. If an internal symmetry is included, new surface integrals appear corresponding to the additional gauge charges. 相似文献
189.
Canevali C Mari CM Mattoni M Morazzoni F Nodari L Ruffo R Russo U Scotti R 《The journal of physical chemistry. B》2005,109(15):7195-7202
The mechanism of NO interaction with nanosized Ru(Pd,Pt)-doped SnO(2) was studied by electron paramagnetic resonance, M?ssbauer, and electric resistance measurements. Three steps were proposed for the reaction between the semiconductor oxide and the gaseous component: (i) the formation of bielectronic oxygen vacancies (V(o)) in SnO(2); (ii) their single-ionization (V(o)(*)) with injection of electrons into the SnO(2) conduction band; (iii) the subsequent transfer of electrons from V(o)(*) to [Ru(Pd,Pt)](4+). The last process induces the formation of further oxygen vacancies which reduce the transition metal centers to lower oxidation states; the redox processes is enhanced and the electrical resistance in transition metal-doped SnO(2) is stronger modified with respect to the undoped material. 相似文献
190.
Light propagation in uniform arrays of photonic crystal waveguides is studied. We demonstrate that, in stark contrast to the case of conventional waveguide arrays, diffraction can be tailored both in magnitude and sign by varying only the spacing between adjacent waveguides. Diffraction management in ultracompact arrays of straight photonic crystal waveguides is demonstrated by solving Maxwell's equations through the time-domain finite-element method. 相似文献