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191.
D. J. Hartfiel 《Linear and Multilinear Algebra》1994,36(4):293-304
In this paper we consider the nonnegative matrix system ciA+uiB=ci+1 where the nonnegative matrix A is allowed to vary, within bounds. The cone control problem is to find a nonnegative matrix B such that if Ci is a nonnegative vector in a specified cone, then there is a nonnegative vector ui such that ci+1 is in that cone. We extend this problem to input control by finding a B such that the cone, generated by the rows of B, is as small as possible. Thus, the percent distribution of ∣uiB∣ through the states of the sustem by uiB is either constant or varies little. 相似文献
192.
193.
It is shown that the unique coherence properties of mode-locked lasers can be exploited to provide new opportunities for high-speed data transmission. Using passive Mach-Zehnder optical delay stages, very high bit rate optical data streams constructed from asynchronously combined transmitters can be demultiplexed directly in the optical domain, without imposing restrictions on the source wavelength. Potential implementation and performance of the technique are discussed.<> 相似文献
194.
V. D. Levchenko A. I. Morozov A. S. Sigov 《Journal of Experimental and Theoretical Physics》2002,94(5):985-991
Multilayer ferromagnet-layered antiferromagnet (Fe/Cr) structures frustrated because of roughness of interlayer boundaries were studied by mathematical modeling methods. The phase diagram of a three-layer system (plotted as film thickness versus the degree of roughness of the interfaces) was obtained, and the order parameter distributions in each phase were determined. The character of phase transitions in this system was studied. The applicability range of the Slonczewski magnetic proximity model was determined. 相似文献
195.
196.
The authors present an original analysis of an aperture-coupled microstrip antenna. The theory is based on the segmentation method, which considers the patch as a multiport network whose impedance matrix is deduced from a hybrid matrix, and the use of analytical expressions of the cavity admittance at the slot centre. The theory is presented for the first time, and the theoretical results are in good agreement with previous published measurements 相似文献
197.
The feasibility of using a thick ground plane with an aperture coupled microstrip patch antenna while maintaining reasonable antenna performance is demonstrated using moment method and reciprocity analyses in the spectral domain. The thick ground plane, which may serve as a heatsink for active MMIC circuitry, or as a mechanical support for thin substrates, is particularly advantageous in millimetre wave phased array applications. It is found that the effect of ground plane thickness is to reduce the level of coupling from the feed line to the patch 相似文献
198.
Two layer frequency selective surfaces (FSS) comprised of aperture elements on a single dielectric substrate are used to produce extremely narrow and angularly stable passband transmission responses. Experimental results are compared with predictions to verify a computer model which is based on solving a pair of coupled aperture integral equations. Reductions in bandwidth of up to a factor of seven have been achieved 相似文献
199.
Experiments for the determination of mono-, di and tri-butyltin (MBT, DBT and TBT) by hydride generation/gas chromatography/atomic absorption spectrometry in various matrices (sediment, suspended matter, mussel, algae and water) have revealed that poor butyltin recoveries are obtained in sediments displaying high sulphur and hydrocarbon contents; very poor recoveries were also observed for TBT in sediments with high chlorophyll pigment contents as well as in algal samples. It was however not clear whether the hydride generatin was inhibited by these infering compounds, as was previously assumed in the case of hydrocarbons, or whether interferences affected the atomization rate. Further studies were performed to solve this problem in order to validate this method in the case of analyses of, for example, oil-contaminated sediment and algae. This paper presents the results obtained. It is concluded here that the poor recoveries were due to an inhibition of hydride generation rather than to interference at the atomization stage. 相似文献
200.
Results from a unique analytical and experimental effort to assess low-altitude, short-range, radar detection capabilities in an evaporation ducting environment are presented. Within the horizon, the duct may shift the location of the last interference null several kilometers in range, which may cause nondetection at ranges where detection is expected and detection at ranges where detection is not expected. In addition, the evaporation duct may reduce the signal strength at ranges near the last interference peak so that detection of low-altitude, small-size, targets may not be possible until the target is much closer. At ranges near and beyond the horizon, radar signal strength depends both on the surface layer and on the mixed layer. To accurately model propagation in this region, knowledge of both surface layer and upper air meteorology Is required. An empirical model to merge the surface layer with the mixed layer has been developed. Comparisons of measured to calculated detection range indicate that the assumption of a standard atmosphere minimizes the variance of the difference between the detection ranges whereas ranges calculated using the measured surface meteorological conditions and a modified surface layer model minimizes the median of the difference 相似文献