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521.
A novel engine health management (EHM) scheme is introduced. It uses flight-level, instead of thermodynamic, data to cost-effectively augment the onboard EHM redundancy. For a nominal healthy aircraft, fault-sensitive interrelations among flight data are globally modelled inside a flight regime via Constant-Coefficient Pooled Nonlinear AutoRegressive with eXogenous (CCP-NARX) excitation representations. Single or sequential engine faults perturb these interrelations. Statistically evaluating the perturbation-induced effects draws reliable conclusions on the engine?s health. Validation and comparisons with Kalman filter-based alternatives are made throughout the regime under various operational conditions. 相似文献
522.
A computational viewpoint on the problems of design and numerical simulation for the nozzles of modern aircraft turbofan engines is presented. Modern concepts of noise-suppressing nozzles for civil aircraft are reviewed. Examples of application of CFD (computational fluid dynamics) methods to the analysis of nozzle flow structure and assessment of nozzle thrust characteristics are given. Errors of turbulence models in simulation of jets are analyzed. The authors’ experience in simulation of noise-suppressing nozzles for supersonic civil aircrafts is demonstrated. Insufficient accuracy of acoustic analogies for this class of tasks is shown, but a possible area of acoustic analogies application is noted. The essential elements of computational aeroacoustics (CAA) approach and numerical methods characteristic of CAA are reviewed. Numerical methodology for the simulation of nozzle acoustic performance is described in detail, including methods for simulation of near and far field of a nozzle, for generation of input perturbations and for the processing the far-field noise. Results of verification and methodical analysis of this acoustic methodology are presented. 相似文献
523.
S. Yu. Mikheev I. I. Shkarban Y. A. Ryzhov S. A. Khartov M. M. Gorshkov R. P. Markov 《Russian Aeronautics (Iz VUZ)》2012,55(1):108-112
A process of manufacture of porous membranes made of aluminum foil (Al 99.99%) by the method of electrochemical anodic oxidation followed by a continuous barrier layer removal with ion-plasma irradiation is described. The membranes having a 8 mm diameter made from AL2O3 with a thickness from 2 to 5 microns thick with a regular channel arrangement are obtained. A possibility to change the channel diameter in the range of 20?C100 nm by adjusting voltage and temperature during the oxidation is shown. We present the experimental dependencies of aluminum and aluminum oxide sputtering coefficients on the energy and incidence angle of xenon ions within the energy range of 100??400 eV. 相似文献
524.
S. Ibadov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Problems connected with mechanisms for comet brightness outbursts as well as for gamma-ray bursts remain open. Meantime, calculations show that irradiation of a certain class of comet nuclei, having high specific electric resistance, by intense fluxes of energetic protons and positively charged ions with kinetic energies more than 1 MeV/nucleon, ejected from the Sun during strong solar flares, can produce a macroscopic high-voltage electric double layer with positive charge in the subsurface zone of the nucleus, during irradiation times of the order of 10–100 h at heliocentric distances around 1–10 AU. The maximum electric energy accumulated in such layer will be restricted by the electric discharge potential of the layer material. For comet nuclei with typical radii of the order of 1–10 km the accumulated energy of such natural electric capacitor is comparable to the energy of large comet outbursts that are estimated on the basis of ground based optical observations. The impulse gamma and X-ray radiation together with optical burst from the comet nucleus during solar flares, anticipated due to high-voltage electric discharge, may serve as an indicator of realization of the processes above considered. Multi-wavelength observations of comets and pseudo-asteroids of cometary origin, having brightness correlation with solar activity, using ground based optical telescopes as well as space gamma and X-ray observatories, during strong solar flares, are very interesting for the physics of comets as well as for high energy astrophysics. 相似文献
525.
J. B. Blake P. A. Carranza S. G. Claudepierre J. H. Clemmons W. R. Crain Jr. Y. Dotan J. F. Fennell F. H. Fuentes R. M. Galvan J. S. George M. G. Henderson M. Lalic A. Y. Lin M. D. Looper D. J. Mabry J. E. Mazur B. McCarthy C. Q. Nguyen T. P. O’Brien M. A. Perez M. T. Redding J. L. Roeder D. J. Salvaggio G. A. Sorensen H. E. Spence S. Yi M. P. Zakrzewski 《Space Science Reviews》2013,179(1-4):383-421
This paper describes the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the RBSP spacecraft from an instrumentation and engineering point of view. There are four magnetic spectrometers aboard each of the two spacecraft, one low-energy unit (20–240 keV), two medium-energy units (80–1200 keV), and a high-energy unit (800–4800 keV). The high unit also contains a proton telescope (55 keV–20 MeV). The magnetic spectrometers focus electrons within a selected energy pass band upon a focal plane of several silicon detectors where pulse-height analysis is used to determine if the energy of the incident electron is appropriate for the electron momentum selected by the magnet. Thus each event is a two-parameter analysis, an approach leading to a greatly reduced background. The physics of these instruments are described in detail followed by the engineering implementation. The data outputs are described, and examples of the calibration results and early flight data presented. 相似文献
526.
M. P. Danilaev S. A. Mikhailov Yu. E. Pol’skii K. V. Faizullin 《Russian Aeronautics (Iz VUZ)》2012,55(2):208-211
In this paper, we formulated the criteria for evaluating the effectiveness of mixing chambers, needed in obtaining polymeric materials with reproducible properties. The results of comparative analysis of organizing the methods for mixing two multiphase flows of oppositely charged particles are presented. This analysis, carried out using CFD programs, shows that the mixing chamber construction in which the flows being mixed are directed at an angle to each other, and additional gas flow inlets are provided in the lateral wall, is the most efficient. 相似文献
527.
A new technique is developed to compensate multiple-wavelength distortion in airborne antenna arrays. This approach exploits the phase information in microwave reflections from arbitrary terrain. To handle reflections incident over a broad angle, a range-Doppler preprocessor is used in each element channel to resolve wavefronts incident simultaneously from different directions. The phase information for each direction of arrival is compared between elements and processed by optimal estimators to determine the phase corrections needed to compensate the distortion. To develop the estimators, a statistical model of the complex baseband terrain reflections is developed. This is in turn used to generate conditional probability densities involving the range Doppler observations and the parameters to be estimated. These densities are subsequently used to develop minimum variance and maximum likelihood estimators. The new estimators use additional information that has not been exploited by previous techniques and therefore provide enhanced performance 相似文献
528.
529.
The mean and covariance of a Kalman filter residual are computed for specific cases in which the Kalman filter model differs from a linear model that accurately represents the true system (the truth model). Multiple model adaptive estimation (MMAE) uses a bank of Kalman filters, each with a different internal model, and a hypothesis testing algorithm that uses the residuals from this bank of Kalman filters to estimate the true system model. At most, only one Kalman filter model will exactly match the truth model and will produce a residual whose mean and standard deviation have already been analyzed. All of the other filters use internal models that mismodel the true system. We compute the effects of a mismodeled input matrix, output matrix, and state transition matrix on these residuals. The computed mean and covariance are compared with simulation results of flight control failures that correspond to mismodeled input matrices and output matrices 相似文献
530.
N S Pechurkin I M Shirobokova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(9):1497-1504
Closed Artificial ecosystems (CAES) have good prospects for wide use as new means for quantitative studies of different types of both natural ecosystems and man-made ones. The paper deals with the discussion of three points of CAES applications. The first one is of importance for theoretical ecology development and is connected with bringing together "holistic" and "merological" approaches in ecosystems studies. Using CAES, we can combine both approaches, taking into account the biotic turnover of limiting substrates which few in number even for complicated natural ecosystems. The second CAES use concerns the development of "ecosystems health" concept and application of a key-factor-approach for the indication and measurement of healthy unhealthy state and functioning of ecosystems or their links. The third use is more of an applied nature, oriented to the intensification of bioremediation or biodepollution processes in different types of ecosystems, including the global biosphere. Grant numbers: N 99-04-96017, N25. 相似文献