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661.
A. V. Bogatyi R. V. El’nikov I. P. Nazarenko G. A. Popov S. A. Semenikhin 《Russian Aeronautics (Iz VUZ)》2018,61(3):445-451
The paper presents the research results of the effect of a capacitor energy storage device configuration on the specific characteristics of advanced modern propulsion systems based on the ablative pulsed plasma thrusters (APPT). These thrusters are designed to perform specific tasks within the small spacecrafts with the onboard power capacity up to 200 W. 相似文献
662.
Messenger S. Stadermann F.J. Floss C. Nittler L.R. Mukhopadhyay S. 《Space Science Reviews》2003,106(1-4):155-172
Interplanetary dust particles collected in the stratosphere frequently exhibit enrichments in deuterium (D) and 15N relative to terrestrial materials. These effects are most likely due to the preservation of presolar interstellar materials.
While the elevated D/H ratios probably resulted from mass fractionation during chemical reactions at very low < 100 K temperatures,
the origin of the N isotopic anomalies remains unresolved. The bulk of the N-bearing material may have obtained its isotopic
signatures from low temperature chemistry, but a nucleosynthetic origin is also possible.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
663.
Haines K. Hipkin R. Beggan C. Bingley R. Hernandez F. Holt J. Baker T. Bingham R.J. 《Space Science Reviews》2003,108(1-2):205-216
Accurate local geoids derived from in situ gravity data will be valuable in the validation of GOCE results. In addition it will be a challenge to use GOCE data in an
optimal way, in combination with in situ gravity, to produce better local geoid solutions. This paper discusses the derivation of a new geoid over the NW European
shelf, and its comparison with both tide gauge and altimetric sea level data, and with data from ocean models. It is hoped
that over the next few years local geoid methods such as these can be extended to cover larger areas and to incorporate both
in situ and satellite measured gravity data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
664.
665.
F.B. Rizzato A.C.-L. Chian M.V. Alves R. Erichsen S.R. Lopes G.I. de Oliveira R. Pakter E.L. Rempel 《Space Science Reviews》2003,107(1-2):507-514
Langmuir waves and turbulence resulting from an electron beam-plasma instability play a fundamental role in the generation
of solar radio bursts. We report recent theoretical advances in nonlinear dynamics of Langmuir waves. First, starting from
the generalized Zakharov equations, we study the parametric excitation of solar radio bursts at the fundamental plasma frequency
driven by a pair of oppositely propagating Langmuir waves with different wave amplitudes. Next, we briefly discuss the emergence
of chaos in the Zakharov equations. We point out that chaos can lead to turbulence in the source regions of solar radio emissions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
666.
Kamide Y. Kihn E.A. Ridley A.J. Cliver E.W. Kadowaki Y. 《Space Science Reviews》2003,107(1-2):307-316
We report the recent progress in our joint program of real-time mapping of ionospheric electric fields and currents and field-aligned
currents through the Geospace Environment Data Analysis System (GEDAS) at the Solar-Terrestrial Environment Laboratory and
similar computer systems in the world. Data from individual ground magnetometers as well as from the solar wind are collected
by these systems and are used as input for the KRM and AMIE magnetogram-inversion algorithms, which calculate the two-dimensional
distribution of the ionospheric parameters. One of the goals of this program is to specify the solar-terrestrial environment
in terms of ionospheric processes, providing the scientific community with more than what geomagnetic activity indices and
statistical models provide.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
667.
Blind adaptive decision fusion for distributed detection 总被引:3,自引:0,他引:3
Mirjalily G. Zhi-Quan Luo Davidson T.N. Bosse E. 《IEEE transactions on aerospace and electronic systems》2003,39(1):34-52
We consider the problem of decision fusion in a distributed detection system. In this system, each detector makes a binary decision based on its own observation, and then communicates its binary decision to a fusion center. The objective of the fusion center is to optimally fuse the local decisions in order to minimize the final error probability. To implement such an optimal fusion center, the performance parameters of each detector (i.e., its probabilities of false alarm and missed detection) as well as the a priori probabilities of the hypotheses must be known. However, in practical applications these statistics may be unknown or may vary with time. We develop a recursive algorithm that approximates these unknown values on-line. We then use these approximations to adapt the fusion center. Our algorithm is based on an explicit analytic relation between the unknown probabilities and the joint probabilities of the local decisions. Under the assumption that the local observations are conditionally independent, the estimates given by our algorithm are shown to be asymptotically unbiased and converge to their true values at the rate of O(1/k/sup 1/2/) in the rms error sense, where k is the number of iterations. Simulation results indicate that our algorithm is substantially more reliable than two existing (asymptotically biased) algorithms, and performs at least as well as those algorithms when they work. 相似文献
668.
Savkin A.V. Pathirana P.N. Faruqi F.A. 《IEEE transactions on aerospace and electronic systems》2003,39(3):901-910
Addressed here is the precision missile guidance problem where the successful intercept criterion has been defined in terms of both minimizing the miss distance and controlling the missile body attitude with respect to the target at the terminal point. We show that the H/sup /spl infin// control theory, when suitably modified, provides an effective framework for the precision missile guidance problem. The existence of feedback controllers (guidance laws) is investigated for the case of finite horizon and non-zero initial conditions. Both state feedback and output feedback implementations are explored. 相似文献
669.
The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research 总被引:2,自引:0,他引:2
Pollock C.J. C:son-Brandt P. Burch J.L. Henderson M.G. Jahn J.-M. McComas D.J. Mende S.B. Mitchell D.G. Reeves G.D. Scime E.E. Skoug R.M. Thomsen M. Valek P. 《Space Science Reviews》2003,109(1-4):155-182
Energetic Neutral Atom (ENA) imaging has contributed substantially to substorm research. This technique has allowed significant advances in areas such as observation and quantification of injected particle drift as a function of energy, observation of dynamics in the tail that are directly related to the effects of imposed (growth phase) and induced (expansion phase) electric fields on the plasma, the prompt extraction of oxygen from the ionosphere during substorms, the relationship between storms and substorms, and the timing of substorm ENA signatures. We present discussion of the advantages and shortcomings of the ENA technique for studying space plasmas. Although the technique is in its infancy, it is yielding results that enrich our understanding of the substorm process and its effects. 相似文献
670.
Tracking multiple objects with particle filtering 总被引:8,自引:0,他引:8
Hue C. Le Cadre J.-P. Perez P. 《IEEE transactions on aerospace and electronic systems》2002,38(3):791-812
We address the problem of multitarget tracking (MTT) encountered in many situations in signal or image processing. We consider stochastic dynamic systems detected by observation processes. The difficulty lies in the fact that the estimation of the states requires the assignment of the observations to the multiple targets. We propose an extension of the classical particle filter where the stochastic vector of assignment is estimated by a Gibbs sampler. This algorithm is used to estimate the trajectories of multiple targets from their noisy bearings, thus showing its ability to solve the data association problem. Moreover this algorithm is easily extended to multireceiver observations where the receivers can produce measurements of various nature with different frequencies. 相似文献