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111.
112.
We analyze the physical limits of sensitivity of bispectral receivers (bispectral analyzers) due to the background level of
the bispectrum of their own thermal noise. The potential sensitivity of a bispectral receiver, compared with the spectral
analog, is characterized by a parameter introduced in this paper: the effective bispectral temperature. It is shown that for
receivers with a quasilinear input amplifier this temperature is much lower than the actual temperature that determines the
spectral background.
N. I. Lobachevsky State University, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 40, No. 12, pp. 1526–1530, December, 1997. 相似文献
113.
Bochkov G. N. Gorokhov K. V. Ermakov S. A. Konnov I. R. Shchegol'kov Yu. B. 《Radiophysics and Quantum Electronics》2002,45(7):534-553
We perform a laboratory study of the nonlinear phase relation between short gravity waves with wavelengths of the order of 10 cm and their higher harmonics including spurious capillary ripple. The presence of higher harmonics of the basic low-frequency component in the spectrum of gravity capillary waves (GCWs) is confirmed on the basis of the methods of bispectral analysis. To determine the quantitative relations between the contributions of free and forced components in the GCW spectrum, we use the normalized bicoherence function. We show that it is correctly defined for both broadband random processes and polyharmonic random signals. The quantitative relation between the contributions from free and forced waves in the GCW spectrum at the frequency of the second harmonic is obtained. 相似文献
114.
D. M. Bochkov V. V. Kharton A. V. Kovalevsky A. P. Viskup E. N. Naumovich 《Solid State Ionics》1999,120(1-4):281-288
Formation of the La2Cu1−xCoxO4+δ solid solutions with orthorhombic K2NiF4-type structure was found to be in the range of 0≤x≤0.30 at temperatures above 1270 K. Incorporating cobalt into the copper sublattice of lanthanum cuprate leads to increasing oxygen hyperstoichiometry and decreasing electrical conductivity. Thermal expansion coefficients of the La2Cu1−xCoxO4+δ (x=0.02–0.30) ceramics at 470–1100 K were calculated from the dilatometric data to vary in the range (12.2–13.2)×10−6 K−1. Studying the dependence of oxygen permeation fluxes through La2Cu(Co)O4+δ on the membrane thickness demonstrated that the oxygen transport at the thickness values below 1 mm is limited by both surface exchange rate and bulk ionic conductivity. Oxygen permeability of the La2Cu1−xCoxO4+δ solid solutions was ascertained to increase with cobalt concentration at x=0.02–0.10 and to decrease with further dopant additions, indicating a participation of interstitial oxygen in the ionic transport. 相似文献
115.
116.
The electron and phonon temperature distributions in a semiconductor sample with finite dimensions, placed in a thermostat with an arbitrary, fixed temperature profile, were studied. Heat transfer between the thermostat and the electrons and phonons through the wall is assumed to be arbitrary, while the magnetic field is assumed to be weak.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 73–78, August, 1987. 相似文献
117.
118.
119.
On the basis of a complete system of fluctuation-dissipation relations, considered in the first part of this series, a variational principle for nonlinear irreversible processes is derived. According to this principle the virtual entropy production functional (analogous to the action in mechanics) has an absolute minimum meaning on the real trajectory of a system. The universal structure of the “kinetic potential” and the “lagrangian” of a system, each contain complete information about fluctuations of macrovariables. The connection of the lagrangian with the markovian kinetic operator of macrovariables is stated. Fundamental properties of dissipative potentials, reflecting microscopic reversibility, are considered. The derived variational principle can be applied to closed systems (the steady state of which is equilibrium) as well as to open ones (when external dynamic forces cause entropy flux through the system and put it into a steady non-equilibrium state). Canonical transformations of macrovariables are considered. 相似文献
120.