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891.
Eigenstructure Assignment for Linear Systems 总被引:2,自引:0,他引:2
Andry A.N. Shapiro E.Y. Chung J.C. 《IEEE transactions on aerospace and electronic systems》1983,(5):711-729
The use of feedback (full state, output, and constrained output) is considered as a means of shaping the transient response of linear time invariant systems. The underlying importance of the eigenstructure (eigenvalues/eigenvectors) is highlighted. Also, the important results and techniques are presented along with a brief literature review. An extensive flight control example is presented which should give direction to the application of eigenstructure assignment in diverse areas. 相似文献
892.
The practical implementation of the ESPRIT algorithm into direction-finding system architecture is considered. In particular, the problems of phase ambiguity resolution for extended array separations and multidimensional azimuth/elevation estimation are addressed. Generalized solutions for these problems are proposed, and a bearing quality indicator that provides a measure of credibility associated with each angle-of-arrival estimate is developed. Plots of computer simulated performance are presented in order to assess the probability of detection, of failure to alarm, and of false alarm as a function of azimuthal separation and period of signal observation 相似文献
893.
Ion-induced nucleation has been suggested to be a potentially important mechanism for atmospheric aerosol formation. Ions
are formed in the background atmosphere by galactic cosmic rays. A possible connection between galactic cosmic rays and cloudiness
has been However, the predictions of current atmospheric nucleation models are highly uncertain because the models are usually
based on the liquid drop model that estimates cluster thermodynamics based on bulk properties (e.g., liquid drop density and
surface tension). Sulfuric acid (H2SO4) and water are assumed to be the most important nucleating agents in the free troposphere. Measurements of the molecular
thermodynamics for the growth and evaporation of cluster ions containing H2SO4 and H2O were performed using a temperature-controlled laminar flow reactor coupled to a linear quadrupole mass spectrometer as well
as a temperature-controlled ion trap mass spectrometer. The measurements were complemented by quantum chemical calculations
of the cluster ion structures. The analysis yielded a complete set of H2SO4 and H2O binding thermodynamics extending from molecular cluster ions to the bulk, based on experimental thermodynamics for the small
clusters. The data were incorporated into a kinetic aerosol model to yield quantitative predictions of the rate of ion-induced
nucleation for atmospheric conditions. The model predicts that the negative ion-H2SO4-H2O nucleation mechanism is an efficient source of new particles in the middle and upper troposphere. 相似文献
894.
Urkowitz [1]has discussed the detection of a deterministic signal of unknown structure in the presence of flat, band-limited, Gaussian noise of known power density. That analysis is extended here to the case where jamming or other conditions preclude knowledge of the noise power density. The chi-square statistic of Urkowitz is replaced with Fisher's variance-ratio statistic, using a separate set of noise samples to estimate the unknown noise power density. Curves are given to show the additional degradation of perform over that due to ignorance of the signal structure, caused by ignorance of the noise power density. 相似文献
895.
Deborah L. Domingue Patrick L. Koehn Rosemary M. Killen Ann L. Sprague Menelaos Sarantos Andrew F. Cheng Eric T. Bradley William E. McClintock 《Space Science Reviews》2007,131(1-4):161-186
The existence of a surface-bounded exosphere about Mercury was discovered through the Mariner 10 airglow and occultation experiments.
Most of what is currently known or understood about this very tenuous atmosphere, however, comes from ground-based telescopic
observations. It is likely that only a subset of the exospheric constituents have been identified, but their variable abundance
with location, time, and space weather events demonstrate that Mercury’s exosphere is part of a complex system involving the
planet’s surface, magnetosphere, and the surrounding space environment (the solar wind and interplanetary magnetic field).
This paper reviews the current hypotheses and supporting observations concerning the processes that form and support the exosphere.
The outstanding questions and issues regarding Mercury’s exosphere stem from our current lack of knowledge concerning the
surface composition, the magnetic field behavior within the local space environment, and the character of the local space
environment. 相似文献
896.
G. Gloeckler E. C. Roelof K. W. Ogilvie D. B. Berdichevsky 《Space Science Reviews》1995,72(1-2):321-326
Proton phase space densities in the solar wind frame from suprathermal velocities 10 km s–1 to 30,000 km s–1 (0.5 eV–5 MeV) were derived from combined SWICS and HISCALE measurements when Ulysses was at 5 AU and –24° heliolatitude. The period (19–23 January 1993) encompasses a forward/reverse shock pair (20 January, 0500 UT and 22 January, 0300 UT). Strong evidence is found for shock acceleration of pickup protons from interstellar hydrogen at all energies measured. 相似文献
897.
THE CLUSTER ION SPECTROMETRY (CIS) EXPERIMENT 总被引:5,自引:0,他引:5
H. RÈME J. M. Bosqued J. A. Sauvaud A. Cros J. Dandouras C. Aoustin J. Bouyssou Th. Camus J. Cuvilo C. Martz J. L. MÉDALE H. Perrier D. Romefort J. Rouzaud C. D'Uston E. MÖBIUS K. Crocker M. Granoff L. M. Kistler M. Popecki D. Hovestadt B. Klecker G. Paschmann M. Scholer C. W. Carlson D. W. Curtis R. P. Lin J. P. Mcfadden V. Formisano E. Amata M. B. Bavassano-CATTANEO P. Baldetti G. Belluci R. Bruno G. Chionchio A. Di Lellis E. G. Shelley A. G. Ghielmetti W. Lennartsson A. Korth H. Rosenbauer R. Lundin S. Olsen G. K. Parks M. Mccarthy H. Balsiger 《Space Science Reviews》1997,79(1-2):303-350
The Cluster Ion Spectrometry (CIS) experiment is a comprehensive ionic plasma spectrometry package on-board the four Cluster spacecraft capable of obtaining full three-dimensional ion distributions with good time resolution (one spacecraft spin) with mass per charge composition determination. The requirements to cover the scientific objectives cannot be met with a single instrument. The CIS package therefore consists of two different instruments, a Hot Ion Analyser (HIA) and a time-of-flight ion COmposition and DIstribution Function analyser (CODIF), plus a sophisticated dual-processor-based instrument-control and Data-Processing System (DPS), which permits extensive on-board data-processing. Both analysers use symmetric optics resulting in continuous, uniform, and well-characterised phase space coverage. CODIF measures the distributions of the major ions (H+, He+, He++, and O+) with energies from ~0 to 40 keV/e with medium (22.5°) angular resolution and two different sensitivities. HIA does not offer mass resolution but, also having two different sensitivities, increases the dynamic range, and has an angular resolution capability (5.6° × 5.6°) adequate for ion-beam and solar-wind measurements. 相似文献
898.
Global ena Image Simulations 总被引:2,自引:0,他引:2
Fok M.-C. Moore T.E. Wilson G.R. Perez J.D. Zhang X.X. Brandt P. C:Son Mitchell D.G. Roelof E.C. Jahn J.-M. Pollock C.J. Wolf R.A. 《Space Science Reviews》2003,109(1-4):77-103
The energetic neutral atom (ENA) images obtained by the ISEE and POLAR satellites pointed the way toward global imaging of the magnetospheric plasmas. The Imager for Magnetopause to Aurora Global Exploration (IMAGE) is the first mission to dedicate multiple neutral atom imagers: HENA, MENA and LENA, to monitor the ion distributions in high-, medium- and low-energy ranges, respectively. Since the start of science operation, HENA, MENA and LENA have been continuously sending down images of the ring current, ionospheric outflow, and magnetosheath enhancements from high pressure solar wind. To unfold multiple-dimensional (equal or greater than 3) plasma distributions from 2-dimensional images is not a trivial task. Comparison with simulated ENA images from a modeled ion distribution provides an important basis for interpretation of features in the observed images. Another approach is to develop image inversion methods to extract ion information from ENA images. Simulation studies have successfully reproduced and explained energetic ion drift dynamics, the transition from open to closed drift paths, and the magnetosheath response to extreme solar wind conditions. On the other hand, HENA has observed storm-time ion enhancement on the nightside toward dawn that differs from simple concepts but can be explained using more sophisticated models. LENA images from perigee passes reveal unexpected characteristics that now can be interpreted as evidence for a transient superthermal exospheric component that is gravitationally-influenced if not bound. In this paper, we will report ENA simulations performed during several IMAGE observed events. These simulations provide insight and explanations to the ENA features that were not readily understandable previously. 相似文献
899.
本文利用边界层动量积分方程和平均流动能积分方程兼容计算了翼面的层流和湍流边界层流动。文中采用一种e~9型转捩判别公式预测翼面存在层流分离气泡情况的转捩位置。并引入对剪应力系数C_r的滞后方程以体现湍流中雷诺应力的历程效应。为避免在翼面流动分离时边界层方程的奇异,采用反解法计算。算例表明,计算与测量结果吻合良好。 相似文献
900.
Vonbun F.O. Argentiero P.D. Schmid P.E. 《IEEE transactions on aerospace and electronic systems》1978,(6):834-842
The results are reported of the ATS-6/GEOS-3 and the ATS-6 NIMBUS-6 satellite-to-satellite orbit determination experiments. NASA intends to use the tracking data relay satellite system for operational orbit determination of NASA satellites. Hence, in the near future, satellite-to-satellite tracking data will be routinely processed to obtain orbits. The satellite-to-satellite tracking system used in the ATS-6/NIMBUS-6 and ATS-6/GEOS-3 experiments performed with a resolution of 1 to 2 m in range and less than 1 mm/s in range rate for a 10-s averaging. A Bayesian least squares estimation technique utilizing independent ranging to the synchronous relay satellite was determined to be the most effective procedure for estimating orbits from satellite-to-satellite tracking data. The use of this technique yields estimates of user satellite orbits which are comparable in accuracy to what is usually obtained from ground based systems. 相似文献