We establish adaptive joint power control/rate allocation policies which maximize system throughput for multiaccess and broadcast fading channels with random packet arrivals and queueing.
We establish adaptive joint power control/rate allocation policies which maximize system throughput for multiaccess and broadcast fading channels with random packet arrivals and queueing.
We provide methods of computing multivalued solutions to the Euler-Poisson system and test them in the context of a klystron amplifier. An Eulerian formulation capable of computing multivalued solutions is derived fro...
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We provide methods of computing multivalued solutions to the Euler-Poisson system and test them in the context of a klystron amplifier. An Eulerian formulation capable of computing multivalued solutions is derived from a kinetic description of the Euler-Poisson system and a moment closure. The system of the moment equations may be closed due to the special structure of the solution in phase space. The Eulerian moment equations are computed for a velocity modulated electron beam, which has been shown by prior Lagrangian theories to break in a finite time and form multivalued solutions. The results of the Eulerian moment equations are compared to direct computation of the kinetic equations and a Lagrangian method also developed in the paper. We use the Lagrangian formulation for the explicit computation of wave breaking time and location for typical velocity modulation boundary conditions.
We develop a new approach based on the finite-difference time-domain (FDTD) method for simulating dynamics of modelocked VCSELs. Our FDTD model, transcends the limitation of a widely used traveling-wave technique, and...
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The lock-in periodic solutions of the Stuart-Landau equation with a periodic excitation are studied. Using singularity theory, the bifurcation behavior of these solutions with respect to the excitation amplitude and f...
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The lock-in periodic solutions of the Stuart-Landau equation with a periodic excitation are studied. Using singularity theory, the bifurcation behavior of these solutions with respect to the excitation amplitude and frequency are investigated in detail, *** results show that the universal unfolding with respect to the excitation amplitude possesses codimension 3. The transition sets in unfolding parameter plane and the bifurcation diagrams are plotted under some conditions. Additionally, it has also been proved that the bifurcation problem with respect to frequence possesses infinite codimension. Therefore the dynamical bifurcation behavior is very complex in this case. Some new dynamical phenomena are presented, which are the supplement of the results obtained by Sun Liang et al.
A simple model displaying structural-acoustic behavior is considered. The model comprises of two parallel infinitely-long flat membranes lying on elastic foundations and the acoustic medium which separates them. The s...
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A simple model displaying structural-acoustic behavior is considered. The model comprises of two parallel infinitely-long flat membranes lying on elastic foundations and the acoustic medium which separates them. The structural-acoustic coupling is demonstrated by the fact that a vibrational excitation of one of the membranes triggers vibrations in the other. Being two-dimensional and involving a small number of parameters, the proposed model is especially simple - however, at the same time, it also exemplifies some important features associated with structural-acoustic coupling. Hence, it may serve as a benchmark for the evaluation of numerical structural-acoustic schemes and, possibly, as an educational tool for studying structural-acoustic coupling in a simple context.
This paper describes the novel approach of face recognition using the combination principal component analysis (PCA) and independent component analysis (ICA). The results produced, are up to 99.3% accurate on the subj...
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This paper describes the novel approach of face recognition using the combination principal component analysis (PCA) and independent component analysis (ICA). The results produced, are up to 99.3% accurate on the subjects of ORL database. While previously, independent use of either PCA or ICA resulted in lower percentage of accuracy. Also PCA and ICA are considered equivalent. The computational strategy presented in this work yields high accuracy while maintaining efficiency.
We develop a new approach based on the finite-difference time-domain (FDTD) method for simulating dynamics of modelocked VCSELs. Our FDTD model, transcends the limitation of a widely used traveling-wave technique, and...
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We develop a new approach based on the finite-difference time-domain (FDTD) method for simulating dynamics of modelocked VCSELs. Our FDTD model, transcends the limitation of a widely used traveling-wave technique, and can be used to determine both the sub-wavelength spatial features of the optical field, as well as its temporal dynamics on a sub-cycle time-scale. The thermal effects are included through coupled lattice and plasma temperature equations. The material response is incorporated via the effective Bloch equations. A VCSEL with gain and saturable absorber is simulated and stable modelocking obtained. Fine features of the pulses spatial profile are also studied.
It is shown that the high p-type conductivity in GaN:Mg, grown by metal-organic chemical vapor deposition followed by post-growth annealing, is due to non-equilibrium acceptor concentrations. A series of samples cut f...
It is shown that the high p-type conductivity in GaN:Mg, grown by metal-organic chemical vapor deposition followed by post-growth annealing, is due to non-equilibrium acceptor concentrations. A series of samples cut from a single GaN:Mg wafer, which initially had undergone rapid thermal annealing (RTA) after growth, has been investigated. The samples were annealed at various temperatures in nitrogen ambient for over 12 hours, and temperature-dependent Hall effect measurements were performed. For samples annealed at temperatures higher than 850°C, the hole concentrations decrease by at least an order of magnitude, compared with the original sample. This behavior is explained by an Mg acceptor concentration in excess of its equilibrium solubility limit in the original sample; thus, at high enough temperatures, in the absence of hydrogen, Mg acceptors diffuse either to form electrically inactive precipitates or are eliminated. It is worth noting that the acceptor activation energy remains the same for all samples.
A validation study was conducted to assess the accuracy of an algorithm developed for automatic reconstruction of the cerebral cortex from T1-weighted magnetic resonance (MR) brain images. Manually selected landmarks ...
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A simple and novel method for evaluating the partial fraction expansion of proper rational functions is presented. The technique involves simultaneous determination of the partial fraction coefficients associated with...
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A simple and novel method for evaluating the partial fraction expansion of proper rational functions is presented. The technique involves simultaneous determination of the partial fraction coefficients associated with each of the multiple poles in the expansion in turn. Only synthetic division is required, which makes the process very suitable for hand and machine calculation. [ABSTRACT FROM AUTHOR]
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