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91.
Hall mobilities in high purity epitaxial layers of n-type Ga1?xAxAs alloys with room-temperature electron concentrations in the range (5–10) × 1015 cm?3 have been measured at 300 K for alloy compositions in the range 0? x ? 0.78. Models for the variation of various material parameters with composition are developed. The acoustic deformation potentials for the Π and X conduction band minima, the intervalley coupling constants for electron scattering among the X-X and L-X minima and the longitudinal optical phonon temperature for these scatterings and the polar optical scattering in the X minima have been determined from a theoretical fit to the experimental data. The electron mobilities in the Π, L and X minima are found to decrease with the composition in the range 0≦ x ? 0.45, show a minimum at x ? 0.50 and then increase again with composition. These mobility variations are reflected in the minimum in the Hall mobility at x ? 0.5 due to intense non-equivalent electron scattering involving the L and x minima. The minimum in the electron mobilities in the Π and X minima have been identified to occur mainly due to the space charge and intervalley scattering among the L and X minima, respectively. The number of equivalent x minima in Ga1?x Alx As alloys are estimated to be three and are, thus, situated at the zone edge. 相似文献
92.
Two uncoupled two-level atoms cannot be jointly excited by classical light under general circumstances, due to destructive interference of excitation pathways in two-photon absorption. However, with temporally entangled light, two-atom excitation is shown possible. Photons arising from three-level cascade decay are intrinsically ordered in time of emission. This field correlation induces a joint resonance in the two-atom excitation probability via suppression of one of the time-ordered excitation pathways. The relative gain in two-photon absorption increases with the time-frequency entanglement. 相似文献
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96.
N.S. Venkata Narayanan B.V. Ashok Raj S. Sampath 《Electrochemistry communications》2009,11(10):2027-2031
Room temperature, magnesium ion conducting binary molten electrolyte consisting of acetamide and magnesium perchlorate has been prepared and characterized. The molten liquid is very stable and shows high ionic conductivity, of the order of several mS cm−1 at 25 °C with other favourable physicochemical properties. Vibrational spectroscopic studies reveal that the free ion concentration is higher than that of ion pairs and aggregates in the melt. The electrochemical reversibility of magnesium deposition and dissolution is demonstrated using voltammetry and impedance studies. Preliminary studies on rechargeable batteries assembled using γ-MnO2 and Mg metal as the electrodes together with the molten electrolyte show high discharge capacity. 相似文献
97.
H. R. Khajuria S. K. Mehta Ashok K. Gupta 《Journal of Thermal Analysis and Calorimetry》1986,31(1):15-20
Clay from the Purmandal area of J&K State was separated into its different size fractions by the method of sedimentation and with Sharple's super centrifuge process. Dilatometric studies were performed on each clay fraction; the results obtained from the dilatation curves are discussed in detail. The results revealed that the finer fraction of clay is bentonitic in nature, whereas the other fractions are felsphatic and micaceous in nature. 相似文献
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99.
Subhash P. Chavan Mahesh Thakkar Ashok B. Pathak Mohan M. Bhadbhade 《Tetrahedron》2005,61(15):3873-3879
The first enantiospecific synthesis of (+)-β-herbertenol, from naturally occurring R-(+)-citronellal, employing Taber's diazo decomposition protocol as the key step, is described. 相似文献
100.
J. Barcelos-Neto Ashok Das J. Maharana 《Zeitschrift fur Physik C Particles and Fields》1986,30(3):401-405
We examine the algebra of the nonlocal charges in the supersymmetric nonlinear σ model and show that they satisfy a nonlinear algebra at the tree-level. We also discuss other interesting questions like the transformation of these charges under a supersymmetry transformation and speculate that this algebra possibly continues to hold in the full quantum theory. 相似文献