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81.
Radio pulses from extensive air showers (EAS) at 30, 44, and 60 MHz frequencies have been studied, using wide band broad-side
arrays of half-wave dipole antenna systems. The experimental results support the theoretical prediction that the field strength
of radio emission depends on the shower size. An asymmetry has been noticed in the pulse height distributions of radio pulses
detected by North-South and East-West directed arrays. These observations are in agreement with the theory that the charge
separation mechanism is predominant in generating radio pulses from EAS and radio emission is polarised in the East-West direction.
Experimental data are compared with those of earlier workers. 相似文献
82.
83.
This paper presents the influence of magnetic field on heat due to viscous and electrical dissipations for an incompressible, viscous, electrically conducting fluid through a circular pipe in the presence of an applied (transverse) uniform magnetic field. The walls of the pipe are assumed to be non-conducting and kept at uniform temperature gradient in one case and at a constant temperature gradient in another case. The heat equation governing the present problem is solved exactly in hypergeometric series. The temperature at the centre of the pipe Te, unweighted mean temperature Tm and weight mean temperature TM are calculated. The temperature profiles are shown graphically for different values of Hartmann number M, Brinkman number Br and a non-dimensional number S. Numerical calculations are made for the Nusselt number and are entered in the table. 相似文献
84.
A. P. Pathak 《physica status solidi b》1971,46(1):83-87
Using a modified Hubbard approximation for the static dielectric function, numerical calculations of the screening charge density around a fixed foreign charge in an electron liquid are presented for values of rs corresponding to the metallic density range. The screening parameter has been taken to reproduce the compressibility limit properly. The results are compared with those based on the original Hubbard approximation as calculated by Langer and Vosko, and it is found that the difference is small but not negligible. 相似文献
85.
An expression for the coefficient of linear expansion of a linear lattice is obtained by using the thermodynamic Green's function method. 相似文献
86.
Results of calculation of channeling potentials in crystals using the local density theory are given. The linear muffin-tin orbitals method is used in the atomic spheres approximation (LMTO-ASA) to calculate the planar-averaged potential seen by MeV electrons and positrons channeled along (110) planes of diamond, Si, and Ge. The calculations thus include the spherical charge relaxation effects (“solid state effects”) in the solid but omits the non-spherical part. The calculated potentials are in excellent agreement with the empirical potentials derived from channeling radiation experiments, but are significantly different near the atomic planes from the potentials obtained from superposition of the atomic Thomas-Fermi statistical (Molière) potentials. Agreement of the potentials with the ones obtained from superposition of atomic Doyle-Turner potentials is reasonably good. Frequencies of emitted radiation from the channeled electrons and positrons are also calculated and compared to experiments. For the crystals considered, it is concluded that the solid state effects on the planar-averaged potential are moderate to small. It is expected that these effects should be more important for channeling in ionic solids. The deviation of the observed positron channeling radiation from the calculated values for Si and C indicates that the non-spherical part of the charge relaxation might be relatively important for these solids. 相似文献
87.
The spectral features of the electromagnetic radiation emitted from relativistically fast positrons and electrons channeled along major crystallographic directions and planes are very sensitive to the interatomic potential assumed between theprojectile and the target crystal. The effects are investigated of platelets present in diamond type Ia on the channeling radiation by assuming a imple model for these defects, as seen from (100),(110), and (111) planar directions. The results arequalitatively correct and for (110) planar channel, quantitative agreement with the experimental results is also satisfactory. 相似文献
88.
Debye-Waller factors of zinc, cadmium, and magnesium are determined from room temperature up to about their melting points by X-ray diffraction using a diffractometer, scintillation counter, chart recorder, and a specially designed furnace having a large volume of uniform temperature. For all the three metals the Debye-Waller factor B is found to rise rapidly at higher temperatures. It is shown for the first time that the deviations AB from the initial part of the curves varies exponentially with 1/T. When reduced values of B are plotted against reduced temperature, the points corresponding to all the three metals are found to fall approximately on the same curve. Thus the metals obey a “law of corresponding states”. A common relation, applicable to all the three metals, between the total anharmonic contribution to B and the melting temperature is established. 相似文献
89.
A. A. Pathak 《physica status solidi b》1984,122(1):171-174
The position dependence of energy loss rates of MeV α-particles along (110) and (111) planar channels of silicon single crystals is calculated. The effective electron density responsible for stopping power is estimated by averaging the spherically symmetric radial charge densities corresponding to individual shells of atoms along the relevant planes. This averaging procedure is similar to that adopted in finding the continuum potential, using superposition of interatomic potentials; except that here each individual shell is considered and the contribution is added after planar averaging. The results thus obtained are compared with the recent experimental results of Moak et al. 相似文献
90.
The longitudinal phonon—plasmon interactions in semiconducting plasmas having piezoelectrixc or deformation potential coupling or both (viz. n-InSb) is investigated when the electrons drift in the direction ofthe acoustic wave propagation, in presence of an magnetic field of arbitrary orientation. Using the hydrodynamic approach, the dispersion relation D(Ω, k ) is derived. The conditions for excitation and the gain per radian of the acoustic wave in the collision dominated regime are studied in detail in the quasi-static approximation. The analysis takes into account hot carrier effects and the temperature dependence of the momentum collision frequency. The variation of the gain per radian wih the system parameters is investigated. It is shown that the heating of the carrier decreases the gain. 相似文献