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941.
Modeling synchronization and suppression of spontaneous otoacoustic emissions using Van der Pol oscillators: effects of aspirin administration 总被引:1,自引:0,他引:1
Many of the aspects of the interaction of spontaneous otoacoustic emissions with external tones (suppression and synchronization) can be qualitatively simulated by the behavior of a single driven Van der Pol oscillator. Analytical and numerical investigations of a model of spontaneous otoacoustic emissions based on such an oscillator (with appropriate parametric changes in the nonlinear and negative damping components) lead to predictions of the nature of the changes in suppression and synchronization (frequency-locking) tuning curves when the levels of spontaneous otoacoustic emissions are modified. Observations of the suppression and synchronization of spontaneous otoacoustic emissions by external tones of different frequencies and levels were obtained while the levels of spontaneous emissions were altered by aspirin administration. Modeling an emission as a single Van der Pol oscillator qualitatively accounts for: (1) the reduction of the level of an external tone required to suppress the emission by a decibel amount equivalent to the level reduction induced by aspirin administration; (2) the broadening of the frequency-locking tuning curve of an emission whose level is reduced; and (3) the pulling of the emission frequency by an external tone. It does not account for: (1) the observed asymmetry in the slopes of the external-tone suppression curves (more gradual for frequencies of the suppressor tone higher, rather than lower, than that of the emission); and (2) the frequency pushing of the emission by an external tone. 相似文献
942.
943.
We give an almost complete classification of ergodicity and transience conditions for a general multi-queue system with the
following features: arrivals form Poisson streams and there are various routing schemes for allocating arrivals to queues;
the servers can be configured in a variety of ways; completed jobs can feed back into the system; the exponential service
times and feedback probabilities depend upon the configuration of the servers (this model includes some types of multi-class
queueing system); switching between service regimes is instantaneous. Several different levels of control of the service regimes
are considered. Our results for the N-queue system require randomisation of service configurations but we have studied the two queue system in situations where
there is less control. We use the semi-martingale methods described in Fayolle, Malyshev and Menshikov [3] and our results
generalise Kurkova [8] and complement Foley and McDonald [4] and [5].
AMS 2000 subject classification: Primary: 90B22; Secondary: 60J10 90B15 相似文献
944.
M. Yu. Kulikov A. M. Feigin G. R. Sonnemann 《Radiophysics and Quantum Electronics》2006,49(9):683-691
We propose a method for retrieval of directly unmeasurable concentrations of minor gas constituents of the mesosphere from
available experimental data using simplified models of atmospheric photochemical systems. The method is used for processing
of the results of simultaneous measurements of ozone and hydroxyl concentrations within the framework of the CRISTA-MAHRSI
satellite experiments. As a result, vertical distributions of concentrations of three more key chemical components of the
mesosphere, namely, atomic oxygen, atomic hydrogen, and hydroperoxide, were retrieved. It is shown that a limiting altitude-dependent
ratio between OH and O3 concentrations is valid in the mesosphere and lower thermosphere. It is found that CRISTA-MAHRSI data satisfy this ratio
up to an altitude of 87 km, but a strong discrepancy between theory and experiment arises in the upper region.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 9, pp. 760–769, September 2006. 相似文献
945.
946.
947.
948.
V. Shatokhin T. Wellens C. A. Müller A. Buchleitner 《The European physical journal. Special topics》2007,151(1):51-57
We survey recent progress achieved in understanding the
impact of inelastic processes on coherent backscattering of light
from cold atoms that are saturated by a powerful laser field. 相似文献
949.
Transverse flow transversely excited (TFTE) CO2 lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas flow
and discharge volume. It was observed in a TFTE CW CO2 laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge
volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant.
The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity.
This necessitated revision of the scaling laws for designing this type of high power CO2 laser. Experimental results of laser performance for different electrode separations are discussed and the modifications
in the scaling laws are presented. 相似文献
950.
T. V. Ramakrishnan H. R. Krishnamurthy S. R. Hassan G. Venketeswara Pai 《Journal of Chemical Sciences》2003,115(5-6):767-774
Manganites of the LA1−x
Ca
x
MnO3 family show a variety of new and poorly understood electronic, magnetic and structural effects. Here we outline a new approach
recently proposed by us, where we argue that due to strong Jahn-Teller (JT) coupling with phonons the twofold degeneratee
g
states at the Mn sites dynamically reorganize themselves into localised, JT polaronsl with exponentially small inter-site hopping, and band-like, nonpolaronic statesb, leading to anew 2-band model for manganites which includes strong Coulomb and Hund’s couplings. We also discuss some results from a dynamical mean-field theory treatment
of the model which explains quantitatively a wide variety of experimental results, including insulator-metal transitions and
CMR, in terms of the influence of physical conditions on the relative energies and occupation of thel andb states. We argue that this microscopic coexistence of the two types of electronic states, and their relative occupation and
spatial correlation is the key to manganite physics.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献