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981.
The emerging Gallium Arsenide digital integrated circuit technology is rapidly becoming well enough established that designers of signal and data processors are planning its incorporation into advanced computational engines of all types. An examination of the characteristics of present and future generation GaAs integrated circuits indicates that they will emphasize moderate on-chip gate counts and high gate speeds. Complete advantage can be taken of GaAs digital technology only if traditional signal processor architectures are completely recast at the memory layout, logic design, arithmetic implementation, and system architecture levels, and if these issues are considered in combination with system, logic board, and chip layout and packaging constraints in a single integrated approach. 相似文献
982.
V.K. Golev I.M. Yancoulova G.T. Petrov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
Based on the spectrophotometric data, by decomposition of the observed continuum, the power - law continuum characteristics of the central source are obtained. The behaviour of both electron temperature Te and density ne in the Narrow - Line Region (NLR) of NGC 7469 is discussed on the thermal and ionization equilibria calculations. Te in NLR of the Sy1 galaxies are higher than the Sy2 ones, and the possible explanation is the lack of the dense (ne 1010 cm−3) zone close to the central source in the Sy2 galaxies. 相似文献
983.
K. -I. Oyama 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(12):105-113
Electron temperature data obtained aboard two satellites are compared with the IRI model. Our comparison may serve as an input to a future version of IRI. HINOTORI data show IRI90 to predict night time Te quite well with the exception of a few peculiar phenomena, in particular a morning overshoot at height around 600 km and anomalous Te observations of AKEBONO for the first time allowed to extend reliably the temperature profile up to − 8000km. This profile clearly depends on local time at all invariant latitudes. The data suggest strong influence of solar activity on electron temperature. 相似文献
984.
985.
Optimum Linear Estimation of Stochastic Signals in the Presence of Multiplicative Noise 总被引:1,自引:0,他引:1
Rajasekaran P.K. Satyanarayana N. Srinath M.D. 《IEEE transactions on aerospace and electronic systems》1971,(3):462-468
This paper considers optimum (MMSE) linear recursive estimation of stochastic signals in the presence of multiplicative noise in addition to measurement noise. Often problems associated with phenomena such as fading or reflection of the transmitted signal at an ionospheric layer, and also situations involving sampling, gating, or amplitude modulation, can be cast into such formulation. The different kinds of estimation problems treated include one-stage prediction, filtering, and smoothing. Algorithms are presented for discrete time as well as for continuous time estimation. 相似文献
986.
Quantitative and robust speed control for a switched reluctance motor (SRM) drive is considered to be rather difficult and challenging owing to its highly nonlinear dynamic behavior. A speed control scheme having two-degree-of-freedom (2DOF) structure is developed here to improve the speed dynamic response of an SRM drive. In the proposed control scheme, the feedback controller is quantitatively designed to meet the desired regulation control requirements first. Then a reference model and a command feedforward controller based on an inverse plant model are employed to yield the desired tracking response at nominal case. As the variations of system parameters and operating conditions occur, the prescribed control specifications may not be satisfied any more. To improve this, the inverse model is adaptively tuned by a fuzzy control scheme so that the model-following tracking error is significantly reduced. In addition, a simple disturbance cancellation robust controller is added to improve the tracking and regulation control performances further. 相似文献
987.
An approach to high-resolution multiple-target-angle tracking that uses the output of an array of sensors is presented. The results of direction-of-arrival estimation by eigenstructure analysis are extended to derive a recursive procedure for tracking moving sources. This procedure involves recursive eigenvalue decomposition and a zero-tracking algorithm, using the coefficient derived from the minimum-norm criterion. The algorithm has superresolution capability in that a pair of closely spaced target angles can be resolved and tracked even though the angular separation between them is less than the reciprocal of the aperture size. Simulation results verify that the algorithm works well in tracking multiple-target sources 相似文献
988.
After testing an early, simplified mass-driver (35 gravity acceleration) a second, designated MD2, was designed and is now operating. MD2 is of axial geometry, with individually powered drive coils of 13.1 cm diameter. Timing is derived through the interruption of light beams by the moving armature (bucket). Electric power is provided by the resonant discharge of sector capacitor banks through silicon-controlled rectifiers in a two-phase, quadrature circuit. The bucket flies in vacuum, guided by passive dynamic eddy-current magnetic forces, those currents flowing in strip conductors lining the inside of a nonconducting vacuum pipe. The initial length of MD2 is 2.5 m, divided equally into acceleration and deceleration. Nominal acceleration is 5000 m/sec2. For routine testing an ohmic bucket is used. Quantitative measurements are obtained with a solid bucket carrying two superconducting coils with a current density of 25 kA/cm2. A cryogenic station for cooling the bucket to liquid helium temperature is connected to the vacuum pipe. The test program, now begun, will concentrate on guidance and acceleration forces, measurement of drive shielding losses, and possible couplings of drive forces into modes of oscillation. 相似文献
989.
R Facius M Schafer K Baltschukat H Bucker 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(8):85-94
The understanding of the radiobiological action of heavy ions requires the knowledge of the dependence of the inactivation probability on the distance between the particle's trajectory and the biological test organism (the impact parameter). Spores of Bacillus subtilis with a cytoplasmic core of about 0.22 micrometer cross section are suitable test objects for the study of this radial inactivation probability in its microscopic details. The spores are irradiated at low fluences of some 10(6) ions/cm2 with very heavy ions at different specific energies up to 10 MeV per atomic mass unit u while in fixed contact with visual nuclear track detectors. The methods are described by which the biological response of individual cells can be evaluated and the impact parameter be determined with an accuracy typically better than 0.2 micrometer. The results demonstrate that the common characteristics of inactivation, e.g., an effective range of inactivation extending to at least 3 micrometers, a nonmonotonic dependence of the inactivation probabilities on the radial distance, and the fact that the inactivation probability even for direct central hits on the cytoplasmic core is substantially below one, are nearly independent of the particle energy and type. The results are incompatible with the assumption that the radiobiological effectiveness can be attributed to the dose of secondary electrons as currently understood. They also demonstrate that the widely held notion of an "overkill" at low impact parameters does not apply for the spores even with the most densely ionizing ions. 相似文献
990.
Sobel K. Kaufman H. Mabius L. 《IEEE transactions on aerospace and electronic systems》1982,(5):576-590
Two implicit model reference adaptive control algorithms for multi-input multi-output systems are developed. These algorithms do not require either satisfaction of the perfect model following conditions or explicit parameter identification. The first algorithm ensures asymptotic stability of the output error provided that the output stabilized plant transfer matrix is strictly positive real. The second algorithm guarantees a bounded error under less restrictive conditions. The algorithms are applied to the lateral axis of an F-8 aircraft. 相似文献