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201.
S. S. Nath D. Chakdar G. Gope A. Talukdar D. K. Avasthi 《Journal of Dispersion Science and Technology》2013,34(7):1111-1113
We report synthesis of ZnS quantum dots by chemical method at room temperature. In this technique, ZnS quantum dots are produced by simple chemical reactions where zeolite, acts as matrix, plays the key role in controlling particle growth during synthesis. Quantum dots exhibit luminescence properties such as Zn2+ related emission, efficient low voltage electroluminescence, and super linear voltage-brightness EL characteristics. This study demonstrates the technological importance of semiconductor nanosystems prepared by low cost chemical route. 相似文献
202.
The interaction of the doped holes with lattice vibrations in an antiferromagnetic (AF) background is studied using the -Holstein model on an 8-site cluster with 2-holes by an exact method. The phonon mediated interactions between the holes at nearest-neighbor (NN) sites are considered. We have calculated the effective kinetic energy, hole-phonon and hole–hole correlations, two hole binding energy to study the nature and stability of various quasiparticles. At negligible to very weak hole-phonon () couplings, the holes get dressed by the AF background forming spin-polarons. At weak to intermediate couplings, the holes are dressed by the phonon cloud forming large hole-polarons and/or nearly free hole-polarons. A narrow transition region is observed at intermediate coupling depending on phonon energy, which marks the formation of S1 hole-bipolarons and small-hole-polarons. At strong coupling regime, stable hole-bipolarons are formed which may lead to superconducting condensation. We also argue that these results cannot be completely reproduced by considering pure attraction between holes. Results show the relevance of inter-site coupling in high cuprates. 相似文献
203.
Summary The linear stability of a stratified shear flow of a perfectly conducting bounded fluid in the presence of a magnetic field
aligned with the flow and buoyancy forces has been studied under Boussinesq approximation. A new upper bound has been obtained
for the range of real and imaginary parts of the complex wave velocity for growing perturbations. The upper bound depends
on minimum Richardson number, wave number, Alfvén velocity and basic flow velocity. H?iland's necessary criterion for instability
of hydrodynamic stratified homogeneous shear flow is modified and its analog for nonhomogeneous magnetohydrodynamic cases
is derived. Finally the upper bound for the growth rate ofKC
i and its variants, whereK is the wave number andC
i the imaginary part of complex wave velocity, is derived as the necessary condition of instability. All estimates remain valid
even when the minimum richardson numberJ
1, for some practical problems, exceeds 1/4 for growing perturbations.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
204.
The geometrically non-linear, axisymmetric transient elastic response is determined of cylindrically orthotropic thin annular plates with a rigid central mass subjected to a uniformly distributed load on the plate as well as a central load on the rigid mass. The dynamic analogue of the von Kármán equations in terms of the normal displacement w and the stress function Ψ are employed. The displacement w and stress function Ψ are expanded in finite power series and the orthogonal point collocation method in the space domain and the Newmark β scheme in the time domain are used. The response of isotropic and orthotropic, clamped as well as simply supported, annular plates with a rigid central mass, subjected to step function and sinusoidal pulse loads, has been calculated for two values of the annular ratio. The influence of the mass ratio and the magnitude of the step load on the deflection response has been determined. The effect of mass ratio, amplitude and duration of sinusoidal pulse on the deflection response has also been studied. 相似文献
205.
Kinetics of the oxidation of methanol and mono-deutero-methanol by Cr(VI) over a wide range of temperature (25–40°) have been studied in perchloric acid medium at constant ionic strength (μ = 1.0 M) adjusted with sodium perchlorate. Each reaction is first order with respect to the substrate and dichromate concentrations but the order with respect to [H+] is nearly 3 in each case. Both these reactions take place at almost the same rate under identical experimental conditions. The activation parameters of the reactions are not widely different and the values of ΔH3 and ΔS3 for the oxidation of methanol are 79.5 kJ mole -1 and - 38.1 J deg-1 mole-1 respectively, whereas the corresponding values for the deuterated compound are 83.8 kJ mole-1 and -23.9 J deg-1 mole-1. The probable mechanism of the reactions is discussed. 相似文献
206.
T. -C. Yuan R. Arnowitt A. H. Chamseddine Pran Nath 《Zeitschrift fur Physik C Particles and Fields》1984,26(3):407-413
A model independent analysis of the super-symmetric electroweak contribution tog μ?2 is discussed within the framework ofN=1 Supergravity unified theory. A detailed comparison with existing experiment of two models (R.G. and T.B.) is carried out. The supersymmetric electro-weak contributions are found to be characteristically different and generally larger than the electro-weak contributions of the standard theory, and in many cases significantly larger. Effects of the hidden sector and the photino mass dependence ofg μ?2 are also investigated. Present data already eliminates some choices of parameters. Reduction of existing experimental errors by a factor of 3 will make contact with most R.G. models and by a factor of 10 with most T.B. models. 相似文献
207.
Various criteria for designing high power convective cooled CO2 lasers have been discussed. Considering the saturation intensity, optical damage threshold of the optical resonator components
and the small-signal gain, the scaling laws for designing high power CW CO2 lasers have been established. In transverse flow CO2 lasers having discharge of square cross-section, the discharge lengthL and its widthW for a specific laser powerP (Watt) and gas flow velocityV (cm/s) can be given byL = 1.4 x 104
p
1/2
V
-1 cms andW = 0.04P
1/2 cms.
The optimum transmitivity of the output coupler is found to be almost constant (about 60%), independent of the small signal
gain and laser power. In fast axial flow CO2 lasers the gas flow should be divided into several discharge tubes to maintain the flow velocity within sonic limit. The
discharge length in this type of laser does not depend explicitly on the laser power, instead it depends on the input power
density in the discharge and the gas flow velocity. Various considerations for ensuring better laser beam quality are also
discussed. 相似文献
208.
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210.