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The owl of Minerva spreads its wing only with the falling of the dusk. The aim of this work is to provide some new trends in the observation for linear systems. In the general framework of designing linear functional observers for linear systems the necessary and sufficient existence conditions are well known. Whether in the O’Reilly textbook or in the recently published ones on this topic, and, roughly speaking, the design methods can be categorized in two kinds. The first one is based on the solution of a Sylvester equation and a projection of the observed linear functional. The second one, based on the recent notion of functional observability, starts from the Darouach criterion which is an Popov-Belevitch-Hautus type one. Nevertheless, the main drawback of the deduced methods is that they cannot be used for linear time-varying systems. These models are of primary importance, for instance with linearization about a trajectory. Consequently, we cope with this problem by considering a new point of view for the design of linear functional observers. We see also that Darouach observers or Cumming-Gopinath observers are particular cases of the proposed methodology. For simplicity sake we suppose the system has no unknown inputs and is not described by a distributed parameters model as well. Nevertheless, these cases can be thought as possible extensions of the presented standpoints.

We have used neutron diffraction on polycrystalline samples of AnF4 (An=Th, U, and Np) to examine the structures. All are isostructural with monoclinic space group C2/c. The structure of UF4 has been examined in some detail as a function of temperature. The volume of the unit cell has a minimum not at lowest temperature (15 K) examined, but rather at ∼350 K. ThF4 also has a larger volume at low rather than room temperature; suggesting that this effect is caused by structural rather than electronic (as ThF4 has no 5f electrons) interactions. An examination of the coordination around the two independent An sites in UF4 shows that the fluorine configuration changes appreciably around An2 as a function of temperature. At low temperatures the distorted cubic antiprism structure is considerably more ‘‘puckered’’ than at higher temperatures. This puckering requires more volume for the molecule, thus causing the volume to expand as the temperature is lowered. The temperature factors and the interatomic distances vary smoothly with temperature and show no unusual behavior. © 1994 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This paper describes how device simulation may be used for the modeling, analysis, and design of radio-frequency (RF) laterally diffused metal-oxide-semiconducotr (LDMOS) transistors. Improvements to device analysis needed to meet the requirements of RF devices are discussed. Key modeling regions of the LDMOS device are explored and important physical effects are characterized. The LDMOS model is compared to dc and small-signal ac measurements for calibration purposes. Using the calibrated model, large-signal accuracy is verified using harmonic distortion simulation, and intermodulation analysis. Predictive analysis and a study of the structure's parasitic components are also presented. Load-pull simulation is used to analyze matching network effects to determine the best choices for device impedance matching.