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921.
A. C. Sharma 《Solid State Communications》1989,70(12):1171-1174
We present a model calculation of the effective interaction between the charge carriers in YBa2Cu3O7−δ and other related copper oxide superconductors. Our calculation shows that the plasmons (electronic excitations) play a dominant role in producing high superconducting transition temperatures in these materials. 相似文献
922.
Summary The kinetics of oxidation of 1,4-butanediol by chromium(VI) was studied in acid perchlorate medium and the oxidation product of the diol was identified as 4-hydroxybutanal. The kinetic rate law observed accounted for the complex dependence of the hydrogen ion k=(k2K1[H+]+k3K1K2[H+]2)/(1+K1[H]+) where k is the observed second-order rate constant. 相似文献
923.
Efficient and high-power intracavity frequency doubled diode-side-pumped Nd:YAG/KTP continuous wave (CW) green laser 总被引:1,自引:0,他引:1
Highly efficient continuous wave (CW) green beam generation by intracavity frequency doubling of a diode side-pumped Nd:YAG laser using a single pump head based on a copper-coated flow tube in a V-shaped cavity geometry has been demonstrated. A maximum 30.5 W of CW green power was obtained at a total diode pumping power of 260 W corresponding to 11.7% conversion efficiency of diode pump power to CW green power and 4.7% conversion efficiency of electrical power to CW green power. The performance of the laser by considering the pump power induced thermal lensing effect and the M2-parameter at the fundamental wavelength has been analyzed. 相似文献
924.
High-resolution spectra of VO have been reinvestigated in the 12 000-31 000 cm−1 region. VO was produced in a vanadium hollow cathode lamp by discharging 1.5 Torr of Ar and the spectra were recorded using a Fourier transform spectrometer. The oxygen needed to produce VO was present in the system as an impurity. Three new bands observed in the 21 000-22 100 cm−1 region have been attributed to a new 2Δ-12Δ electronic transition of VO. Two bands, with origins near 21 044 and 22 038 cm−1, have been assigned as the 0-1 and 0-0 bands of the 2Δ3/2-12Δ3/2 sub-band while a weak band with an origin near 21 975 cm−1 has been assigned as the 0-0 band of the corresponding 2Δ5/2-12Δ5/2 sub-band. A rotational analysis of these sub-bands has been obtained and spectroscopic constants have been extracted. The 12Δ state is known from the previous analyses of the doublet transitions of VO in the near infrared. The present observation has allowed the determination of the vibrational interval ΔG1/2 and the equilibrium rotational constants for the 12Δ3/2 state. 相似文献
925.
The thermosolutal convection in a layer of Maxwellian viscoelastic fluid heated and soluted from below in porous medium is considered. The effects of uniform magnetic field and uniform rotation on the thermosolutal convection are also considered. For stationary convection, the Maxwellian viscoelastic fluid behaves like a Newtonian fluid. The sufficient conditions for the nonexistence of overstability are obtained. The critical Rayleigh number is found to increase with the increase in magnetic field, rotation and stable solute gradient. 相似文献
926.
S.N. Sharma S. Kohli A.C. Rastogi 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):554-561
Thin films of TiO2 with high volume fraction (40–55%) and crystallite size (6–40 nm) of CdTe nanoparticles had been prepared by rf magnetron sputtering from a composite TiO2:CdTe target at room temperature and 373 K. A detailed optical properties of nanocrystalline CdTe:TiO2 films as-deposited and after thermal treatment (300 °C) are studied. The absorbance of the TiO2 films with CdTe nanocrystallite dispersions depends both on the nanocrystallite size and volume fraction. The blue-shifts of the optical absorption edge concurrent with the CdTe nanocystal size reduction for as-deposited and after thermal treatment of nanocrystalline CdTe:TiO2 thin films with respect to the bulk semiconductor agrees quite well with the strong quantum confinement theory. A slight deviation in absorption edge values than the predicted values from the strong quantum confinement model can be attributed to change in interplanar distance due to oxygen incorporation and inhomogeneous size distribution of CdTe nanocrystallites in these films. 相似文献
927.
Superconductivity in ternary metallic glasses has been investigated using the model pseudopotential approach, which has been
found quite successful in explaining superconductivity in metals, binary alloys and binary glasses. It is observed that this
simple methodology successfully explains superconducting behaviour of ternary glasses without requiring the solution of Dirac
equation for a many body problem or estimation of various interactions as required in ab-initio pseudopotential theory. In
the present work superconducting state parameters of fourteen metallic glasses of (Ni-Zr)-M system (M=Ti, V, Co, Cu) have
been determined in the BCS-Eliashberg-McMillan framework. It is observed that addition of V, Co, and Cu as the third element
(M) to a binary metallic glass (Ni33 Zr67) causes the parameters λ,T
c, α, andN
0
V to decrease, and Coulomb pseudopotential (μ*) to increase with concentration of M, showing that the presence of third element (M) causes suppression of superconducting
behaviour of the alloy. The decrease inT
c with increasing concentration of third element (M) may be attributed to the modifications in density of states at the Fermi
levelN(E
F), and probable changes in the band structure of the alloy due to addition of the third element (M). Slight difference is
noticed when Ti is added to the Ni33 Zr67 alloy. In this caseT
c rises initially and then decreases with concentration of M, showing a peak at aboutx=0.05. This indicates that on addition of Ti, 3d states grow near the Fermi level and hence contribute substantially toN(E
F), favouring superconducting behaviour in this case. The present results forT
c show an excellent agreement with the experimental data. QuadraticT
c equations have been proposed, which provide successfully theT
c values of ternary metallic glasses under consideration.
Paper presented at National Conference on Current Trends in Condensed Matter Research, Warangal, India, September 20–22, 2004. 相似文献
928.
929.
Summary. The splitting of separatrices for the standard-like maps
is measured. For even entire perturbative potentials such that , where is the Borel transform of V(y) , the following asymptotic formula for the area A of the lobes between the perturbed separatrices is established:
This formula agrees with the one provided by the Melnikov theory, which cannot be applied directly, due to the exponentially
small size of A with respect to h .
Received April 8, 1997; revised August 25, 1997, and accepted August 27, 1997 相似文献
930.
The lead salts and their alloys are extremely interesting semiconductors due to their technological importance. The fabrication of devices with alloys of these compounds possessing detecting and lasing capabilities has been an important recent technological development. The high quality polycrystalline thin films of PbSe1−xTex with variable composition (0≤x≤1) have been deposited onto ultra clean glass substrates by vacuum evaporation technique. As deposited films were annealed in vacuum at 350 K. The optical, electrical and structural properties of PbSe1−xTex thin films have been examined. The optical constants (absorption coefficient and bandgap) of the films were determined by absorbance measurements in the wavelength range 2500-5000 nm using Fourier transform infrared spectrophotometer. The dc conductivity and activation energy of the films were measured in the temperature range 300-380 K. The X-ray diffraction patterns were used to determine the sample quality, crystal structure and lattice parameter of the films. 相似文献