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11.
A new commercially available diode model is described. This unified model is capable of simulating the widest range of diode technologies of any presently available. The emphasis of this paper is on describing the model's extensive features and flexibility in the different domains of operation and is of particular interest in power applications 相似文献
12.
Daniel L. Feldheim Del R. Lawson Charles R. Martin 《Journal of Polymer Science.Polymer Physics》1993,31(8):953-957
We report a strong dependence of the thermal stability of Nafion® perfluorosulfonate ionomer on the nature of the counterion associated with the fixed sulfonate site. These results were obtained using thermal gravimetric analysis on a series of alkali metal and alkyl ammonium cation-exchanged Nafion films. We have found that the temperature of decomposition of Nafion is inversely dependent on the size of the exchanged cation; i.e., Nafion films show improved thermal stability as the size of the counter cation decreases. We attribute this inverse relationship of thermal stability with counterion size to an initial decomposition reaction which is strongly influenced by the strength of the sulfonate-coun-terion interaction. © 1993 John Wiley & Sons, Inc. 相似文献
13.
Shamansky H.T. Dominek A.K. Peters L. Jr. 《Antennas and Propagation, IEEE Transactions on》1989,37(8):1019-1025
The traveling-wave energy, which multiply diffracts on a straight thin wire, is represented as a sum of terms, each with a distinct physical meaning, that can be individually examined in the time domain. Expressions for each scattering mechanism on a straight thin wire are cast in the form of four basic electromagnetic wave concepts: diffraction, attachment, launch, and reflection. Using the basic mechanisms from P.Ya. Ufimtsev (1962), each of the scattering mechanisms is included into the total scattered field for the straight thin wire. Scattering as a function of angle and frequency is then compared to the moment-method solution. These analytic expressions are then extended to a lossy wire with a simple approximate modification using the propagation velocity on the wire as derived from the Sommerfeld wave on a straight lossy wire. Both the perfectly conducting and lossy wire solutions are compared to moment-method results, and excellent agreement is found. As is common with asymptotic solutions, when the electrical length of wire is smaller than 0.2 λ the results lose accuracy. The expressions modified to approximate the scattering for the lossy thin wire yield excellent agreement even for lossy wires where the wire radius is on the order of skin depth 相似文献
14.
Buttari D. Chini A. Meneghesso G. Zanoni E. Moran B. Heikman S. Zhang N.Q. Shen L. Coffie R. DenBaars S.P. Mishra U.K. 《Electron Device Letters, IEEE》2002,23(2):76-78
Pre-metal-deposition reactive ion etching (RIE) was performed on an Al0.3Ga0.7N/AlN/GaN heterostructure in order to improve the metal-to-semiconductor contact resistance. An optimum AlGaN thickness for minimizing contact resistance was determined. An initial decrease in contact resistance with etching time was explained in terms of removal of an oxide surface layer and/or by an increase in tunnelling current with the decrease of the AlGaN thickness. The presence of a dissimilar surface layer was confirmed by an initial nonuniform etch depth rate. An increase in contact resistance for deeper etches was experienced. The increase was related to depletion of the two-dimensional (2-D) electron gas (2-DEG) under the ohmics. Etch depths were measured by atomic force microscopy (AFM). The contact resistance decreased from about 0.45 Ωmm for unetched ohmics to a minimum of 0.27 Ωmm for 70 Å etched ohmics. The initial thickness of the AlGaN layer was 250 Å. The decrease in contact resistance, without excessive complications on device processing, supports RIE etching as a viable solution to improve ohmic contact resistance in AlGaN/GaN HEMTs 相似文献
15.
The dynamic linewidth of 1.5 ?m ridge waveguide DFB lasers is shown to be reduced by shaping the pulse of the laser modulating waveform. Pulse shaping is performed by a second-order network designed to cancel the small-signal laser resonance. Results demonstrate a dynamic linewidth reduction from 1.4 ? to 0.55 ? FWHM for a 500 ps pulse. 相似文献
16.
17.
A. L. Chistov 《Journal of Mathematical Sciences》2006,138(3):5733-5752
Consider a projective algebraic variety W which is an irreducible component of the set of all common zeros of a family of
homogeneous polynomials of degrees less than d in n + 1 variables over a field of zero characteristic. Consider a dominant
rational morphism from W to W′ given by homogeneous polynomials of degree d′. We suggest algorithms for constructing objects
in general position related to this morphism. They generalize some algorithms from the first part of the paper to the case
dim W > dim W′. These algorithms are deterministic and polynomial in (dd′)n and the size of the input. Bibliography: 12 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 325, 2005, pp. 181–224. 相似文献
18.
19.
Jeroen J. L. M. Cornelissen W. Sander Graswinckel Alan E. Rowan Nico A. J. M. Sommerdijk Roeland J. M. Nolte 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1725-1736
The conformational properties of polymers derived from isocyanodipeptides have been investigated with a combination of model calculations, X‐ray diffraction, and circular dichroism spectroscopy. Depending on the configuration of the side chains, defined arrays of hydrogen bonds along the polymeric backbone are formed. This leads to a well‐defined conformation as, for example, expressed in the formation of lyotropic liquid‐crystalline phases and increased helical stability. Upon the disruption of the hydrogen bonds by a strong acid, a less well‐defined macromolecular conformation is observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1725–1736, 2003 相似文献
20.
The results of experimental investigations on thermal nonequilibrium ionization in CO2: N2: He mixtures are presented. Measurements of electron density, ne, in vibrationally excited nitrogen were made in a supersonic flow with different CO2 contents as well as in a CO2: N2: He = 1 : 5 : 4 mixture laser gas. The mixtures were heated in a shock tube and expanded through a supersonic nozzle. Furthermore, supersonic mixing of N2 and CO2 + He was used in some experiments. The measured values of ne in the plenum chamber and in the supersonic nozzle are reported, and the processes responsible for nonequilibrium ionization in a laser-active medium are discussed. 相似文献