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111.
The vectorial nonparaxial four-petal Gaussian beam (FPGB) is introduced. The closed-form propagation expressions for the free-space propagation of FPGBs are derived and their more general applicable advantages are illustrated analytically and numerically. Some special interesting cases, in particular the paraxial one, are discussed. It is found that the parameter f = 1/kwo with the k being the wave number and wo being the waist width plays a crucial role in determining the nonparaxiallity of FPGBs. For small values of the f parameter the paraxial approximation is allowable. In the nonparaxial regime the beam order n additionally affects the vectorial and nonparaxial behaviour of FPGBs. 相似文献
112.
Discrete phase libraries of thermoelectric compounds, MgxSiyGe1−y, were fabricated by a combinatorial pulsed laser deposition followed by annealing as a thin film form on an integrated ceramic substrate. In the substrate are embedded four probe electrical contacts to each sample, lead wires and pads to be accessed by needle probes. Resistivity and Seebeck coefficient were evaluated electrically, while temperature difference was locally given to each sample by a local heater also embedded in the substrate. The sample temperature (300-673 K) was controlled by a heating stage and temperature difference at the two contact points for each sample was evaluated by an infrared camera. The dependences of polarity and absolute values of Seebeck coefficient on the composition agree well with the data in literature. 相似文献
113.
K. Drühl 《Applied physics. B, Lasers and optics》1998,66(6):677-683
I /kP=0.33and0.50. It is found that the ratio of pump depletion to maximal depletion as a function of the ratio of pump power to
threshold power agrees with the plane-wave prediction to within 5%, for a wide range of focusing conditions. The observed
trends are explained as resulting from intensity- and phase-dependent mechanisms.
Received: 19 January 1998/Revised version: 13 March 1998 相似文献
114.
S. Guha 《Applied physics. B, Lasers and optics》1998,66(6):663-675
Received: 15 February 1998/Revised version: 6 April 1998 相似文献
115.
In order to investigate the pressure effect on the magnetism in the layered cobaltites, positive muon spin rotation and relaxation μ+SR experiments have been carried out up to 1.3 GPa using c-aligned polycrystalline samples of [Ca2CoO3]0.62[CoO2] and [Ca2Co4/3Cu2/3O4]0.62[CoO2]. A transverse field μ+SR experiment indicates that the transition temperature to an incommensurate spin density wave IC-SDW state is independent of hydrostatic pressure up to 1.3 GPa for the both compounds. Furthermore, there are no changes in the spontanious muon precession frequency in zero field at 5 K even under 1.3 GPa. These results strongly suggest that the IC-SDW exists not in the rocksalt-type block ([Ca2CoO3] and/or [Ca2Co4/3Cu2/3O4]) but in the CoO2 plane. 相似文献
116.
Based on the Huygens-Fresnel diffraction integral and Fourier transform, propagation expression of a chirped Gaussian pulse passing through a hard-edged aperture is derived. Intensity distributions of the pulse with different frequency chirp in the near-field and far-field are analyzed in detail by numerical calculations. In the near-field, amplitudes of the intensity peaks generated by the modulation of the hard-edged aperture decrease with increasing the frequency chirp, which results in the improving of the beam uniformity. A physical explanation for the smoothing effect brought by increasing the frequency chirp is given. The smoothing effect is achieved not only in the pulse with Gaussian transverse profile but also in the pulse with Hermite-Gaussian transverse profile when the frequency chirp increases. 相似文献
117.
A.M. Ahmed N.M. Megahid M.M. Wakkad A.K. Diab 《Journal of Physics and Chemistry of Solids》2005,66(7):1274-1280
Chalcogenide bulk alloys of Agx (As0.4Se0.6) 100−x (x=5, 7.5, 10, 12.5, 15 and 17.5) system were prepared by the conventional melt-quench technique. The d.c. electrical conductivity (σ) and thermoelectric power (TEP) measurements were carried out in the temperature range from 83 to 373 K and from 253 to 373 K, respectively. Variations of both σ and TEP with ambient temperature proved the p-type semiconducting behaviour of these materials. The current density-electric field characteristics were found to be linear. The activation energies, calculated from both the electrical conductivity Eσ and thermoelectric power Es, were found to be dependent on composition. 相似文献
118.
F. J. Gálvez E. Buendía A. Sarsa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(2):161-167
Explicitly correlated wave functions including a Jastrow factor
to take into account the dynamical correlation effects, and a
multi determinant model wave function to account for the non–dynamical
correlations are used to study some metastable excited states of the
negative ions Li- and Be-.
A detailed analysis of one– and two–body properties has been carried out
for these states. In particular the single–particle density as well as both
the two–body inter electronic and center of mass densities have been obtained.
All the calculations have been performed by using the variational Monte Carlo
method. 相似文献
119.
J. Pierre K. Kaczmarska J. Tobola 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):247-255
The Anderson localisation has been observed in Heusler-type solid solutions where Mn replaces Ti or V in NiTiSb or CoVSb compounds
respectively, due to the atomic and magnetic disorders. The magnetoresistance, Hall effect, thermopower and electron spin
resonance of these solutions are investigated. Strong anomalies appear for the concentration range where a carrier localisation
occurs; the mobility of carriers is strongly reduced, the magnetoresistance scales with the resistivity and the susceptibility
of solid solutions.
Received 31 May 2000 相似文献
120.
Filippus S. Roux 《Optics Communications》2006,268(2):196-202
We consider the symmetry properties of polynomial Gaussian beam profiles (intensity distributions) that remain stable during propagation, apart from being scaled and possibly rotated. These beams are expressed as special linear combinations of the Laguerre-Gaussian modes. Two kinds of symmetries are present: discreet rotational symmetries and mirror symmetries. The symmetry properties are shown to depend on the particular subset of Laguerre-Gaussian modes that is used to construct the stable beam. We demonstrate the symmetry properties of a few examples of stable beams through numerical simulations. 相似文献