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201.
Bartolo A. Clymer B.D. Burgess R.C. Turnbull J.P. 《Signal Processing, IEEE Transactions on》1998,46(8):2243-2248
A new method of implementing efficient FIR filters is presented. It involves approximation of an equiripple FIR by a rounding operation and application of the derived impulse response by a simple recursive equation. The technique is extremely efficient for lowpass, highpass, bandpass, and bandstop filters with sharp transitions and low edge frequencies 相似文献
202.
Sarkar T.K. Su C. Adve R. Salazar-Palma M. Garcia-Castillo L. Boix R.R. 《Antennas and Propagation Magazine, IEEE》1998,40(5):49-68
The objective of this paper is to present the subject of wavelets from a filter-theory perspective, which is quite familiar to electrical engineers. Such a presentation provides both physical and mathematical insights into the problem. It is shown that taking the discrete wavelet transform of a function is equivalent to filtering it by a bank of constant-Q filters, the non-overlapping bandwidths of which differ by an octave. The discrete wavelets are presented, and a recipe is provided for generating such entities. One of the goals of this tutorial is to illustrate how the wavelet decomposition is carried out, starting from the fundamentals, and how the scaling functions and wavelets are generated from the filter-theory perspective. Examples (including image compression) are presented to illustrate the class of problems for which the discrete wavelet techniques are ideally suited. It is interesting to note that it is not necessary to generate the wavelets or the scaling functions in order to implement the discrete wavelet transform. Finally, it is shown how wavelet techniques can be used to solve operator/matrix equations. It is shown that the “orthogonal-transform property” of the discrete wavelet techniques does not hold in numerical computations 相似文献
203.
Double-diffusive convection due to a cylindrical source submerged in a salt-stratified solution is numerically investigated
in this study. For proper simulation of the vortex generated around the cylinder, a computational domain with irregular shape
is employed. Flow conditions depend strongly on the thermal Rayleigh number, Ra
T
, and the buoyancy ratio, R
ρ. There are two types of onset of instability existing in the flow field. Both types are due to either the interaction of
the upward temperature gradient and downward salinity gradient or the interaction of the lateral temperature gradient and
downward salinity gradient. The onset of layer instability due to plume convection is due to the former, whereas, the onset
of layer instability of layers around the cylinder is due to the latter. Both types can be found in the flow field. The transport
mechanism of layers at the top of the basic plume belongs to former while that due to basic plume and layer around the cylinder
are the latter. The increase in Ra
T
reinforces the plume convection and reduces the layer numbers generated around the cylinder for the same buoyancy ratio.
For the same Ra
T
, the increase of R
ρ suppresses the plume convection but reinforces the layers generated around the cylinder. The profiles of local Nusselt number
reflects the heat transfer characteristics of plume convection and layered structure. The profiles of averaged Nusselt number
are between the pure conduction and natural convection modes and the variation is due to the evolution of layers.
Received on 13 September 1996 相似文献
204.
This paper studies a particular single-stage power-factor-correction (PFC) switching regulator employing a discontinuous-conduction-mode (DCM) boost-input cell and a continuous-current-mode (CCM) forward output cell. Although this single-stage PFC regulator can provide a reasonably high power factor when its PFC stage is operating in discontinuous mode, substantial reduction in line-current harmonics is possible by applying a suitable frequency-modulation scheme. This paper derives a frequency-modulation scheme and proposes a practical implementation using a simple translinear analog circuit. A quantitative analysis on the total harmonic distortion (THD) of the line current when the circuit is subject to a limited range of frequency variations is presented along with some considerations for practical design. Experimental data obtained from a prototype confirms the effectiveness of the proposed frequency-modulation scheme. The proposed analog translinear circuit allows custom integrated circuit implementation, making it a viable low-cost solution to the elimination of line-current harmonics in switching regulators 相似文献
205.
206.
Hulfachor R.B. Ellis-Monaghan J.J. Kim K.W. Littlejohn M.A. 《Electron Devices, IEEE Transactions on》1996,43(4):661-663
A comprehensive Monte Carlo simulator is employed to investigate nonlocal carrier transport in 0.1 μm n-MOSFET's under low-voltage stress. Specifically, the role of electron-electron (e-e) interactions on hot electron injection is explored for two emerging device designs biased at a drain voltage Vd considerably less than the Si/SiO2 injection barrier height φb. Simulation of both devices reveal that 1) although qVd<φb, carriers can obtain energies greater than φb, and 2) the peak for electron injection is displaced approximately 20 nm beyond the peak in the parallel channel electric field. These phenomena constitute a spatial retardation of carrier heating that is strongly influenced by e-e interactions near the drain edge. (Virtually no injection is observed in our simulations when e-e scattering is not considered.) Simulations also show that an aggressive design based on larger dopant atoms, steeper doping gradients, and a self-aligned junction counter-doping process produces a higher peak in the channel electric field, a hotter carrier energy distribution, and a greater total electron injection rate into the oxide when compared to a more conventionally-doped design. The impact of spatially retarded carrier heating on hot-electron-induced device degradation is further examined by coupling an interface state distribution obtained from Monte Carlo simulations with a drift-diffusion simulator. Because of retarded carrier heating, the interface states are mainly generated further over the drain region where interface charge produces minimal degradation. Thus, surprisingly, both 0.1 μm n-MOSFET designs exhibit comparable drain current degradation rates 相似文献
207.
J. S. Kim D. G. Seiler R. A. Lancaster M. B. Reine 《Journal of Electronic Materials》1996,25(8):1215-1220
Variable-magnetic-field Hall measurements (0 to 1.5 T) are performed on very-narrow-gap bulk-grown Hg1−xCdxTe single crystals (0.165 ≤ x ≤ 0.2) at various temperatures (10 to 300K). The electron densities and mobilities are obtained
within the one-carrier (electrons) approximation of the reduced-con-ductivity-tensor scheme. The present data together with
the selected data set reported by other workers exhibit a pronounced peak when the electron mobility is plotted against the
alloy composition x-value which has been predicted to be due to the effective-mass minimum at the bandgap-crossing (Eg ≈ 0). The observed position (x ≈ 0.165), height (≈4 x 102 m2Vs), and width (≈0.01 in x) of the mobility-peak can be explained by a simple simulation involving only ionized-impurity scattering.
A lower bound of the effective mass is introduced as a fitting parameter to be consistent with the finiteness of the observed
electron mobility and is found to be of the order of 10−4 of the mass of a free electron. 相似文献
208.
Wideband chirp measurement technique for high bit rate sources 总被引:1,自引:0,他引:1
A Mach Zehnder (MZ) interferometer has been used as an optical discriminator to measure the time-resolved frequency chirp of an optical source 相似文献
209.
Punt J.B. Sparreboom D. Brouwer F. Prasad R. 《Vehicular Technology, IEEE Transactions on》1998,47(4):1302-1313
Dynamic channel selection (DCS) is an algorithm for flexible resource sharing in mobile radio systems. The digital enhanced cordless telecommunications (DECT) standard implements a version of DCS based on time as well as frequency multiplexing. In this paper, mathematical models are developed to evaluate the probabilities of channel availability, desired carrier power, and the carrier-to-interference ratio (CIR) for a constant traffic load. These results can be used to compute the call setup blocking probability. The models reported in this study are based on a decentralized DCS according to the DECT standard specifications. The results show that blocking due to availability of a channel (resource blocking), not interference blocking, generally is the most important factor in overall call blocking. Furthermore, it is seen that resource blocking is sensitive to the implementation of portable sets. Also, with homogeneous static traffic, this type of DCS ran be as good as fixed channel allocation (FCA) with respect to resource blocking 相似文献
210.
Pantic-Tanner Z. Scott Savage J. Tanner D.R. Peterson A.F. 《Microwave Theory and Techniques》1998,46(2):178-184
The finite-element method (FEM) exhibits a reduced convergence rate when used for the analysis of geometries containing sharp edges where the electromagnetic field is singular. The convergence of the method can be-improved by introducing singular elements that model analytically predicted singular behavior. A number of authors have developed singular elements that are compatible with the scalar FEM. In this paper, we propose a new singular element that is compatible with edge-based vector finite elements and can cope with any order of singularity while preserving the sparsity of the FEM equations. Edge-based singular elements more correctly model singular fields and thus require fewer unknowns, while avoiding the introduction of spurious modes in the numerical solution. Numerical results verify that the convergence of the FEM is significantly improved 相似文献