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791.
Geomagnetic Core Field Secular Variation Models 总被引:1,自引:0,他引:1
We analyse models describing time changes of the Earth’s core magnetic field (secular variation) covering the historical period (several centuries) and the more recent satellite era (previous decade), and we illustrate how both the information contained in the data and the a priori information (regularisation) affect the result of the ill-posed geomagnetic inverse problem. We show how data quality, frequency and selection procedures govern part of the temporal changes in the secular variation norms and spectra, which are sometimes difficult to dissociate from true changes of the core state. We highlight the difficulty of resolving the time variability of the high degree secular variation coefficients (i.e. the secular acceleration), arising for instance from the challenge to properly separate sources of internal and of external origin. In addition, the regularisation process may also result in artificial changes in the model norms and spectra. Model users should keep in mind that such features can be mis-interpreted as the signature of physical mechanisms (e.g. diffusion). Finally, we present perspectives concerning core field modelling: imposing dynamical constraints (e.g. by means of data assimilation) reduces the non-uniqueness of the geomagnetic inverse problem. 相似文献
792.
Basic principles of a mathematical model for disk-wing aircraft balancing and evaluation of power expenditure for flight as
compared with a helicopter are presented. 相似文献
793.
Methodology of constructing a stationary multichannel flow aerometric receiver using the effects of deceleration and throttling
of an incoming airflow and their circular transformation in the yaw plane is considered. The mathematical models and algorithms
for processing primary informative signals entering along the channels of speed, altitude, angles of attack and slip of the
helicopter air data system constructed on the basis of the aerometric receiver being proposed are obtained. 相似文献
794.
E. N. Bogomolov S. M. Piotukh I. A. Simonov V. A. Uglov 《Russian Aeronautics (Iz VUZ)》2010,53(4):416-420
A method for calculating the flowrate of the gas flowing through the cellular insert cells over the labyrinth seal strip is
proposed. The gas density is taken to be average with respect to the decisive section. It is assumed that jets flowing out
of cells disrupt the direct flow of the labyrinth seal. A practical implementation of the method is confirmed by the known
experimental data. 相似文献
795.
We reveal a functional diagram, design features of a receiver electrode system, a principle of forming primary informative
signals, a technique for synthesizing angular characteristics and estimating indicated errors, channel realization and algorithms
of forming output signals of an ionmarking aerodynamic angle and airspeed sensor with logometric informative signals and interpolation
processing scheme. 相似文献
796.
Using the results of numerical modeling of nonstationary gas hydrodynamic working processes in the gas conduit variable section
channel when removing and cooling hot gases of different purpose technical plants, an engineering technique has been developed
to provide the gas conduit operation under limitations on the flow temperature in the outlet plant section. A multiparametric
area of permissible gas conduit operation connecting the characteristics of technical plants, gas conduit and water feeding
system is presented. 相似文献
797.
In this paper, a simple technique for calculating the ideal ejector thrust augmenter of a jet engine is presented. It is based on the well-known method for averaging the parameters of a nonuniform gas flow with the entropy of the initial flow being unchanged. Making use of the technique presented, we compare the calculated data on the pressure ratio in the gas being ejected as well as the thrust boost coefficient with those obtained by the other authors. Also shown is the existence of the thrust boost maximum in the ideal and real thrust augmenters when the value of the ejection coefficient is approximately equal to 100. 相似文献
798.
R. Modzelewska M.V. Alania 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
We show that the higher range of the heliolongitudinal asymmetry of the solar wind speed in the positive polarity period (A > 0) than in the negative polarity period (A < 0) is one of the important reasons of the larger amplitudes of the 27-day variation of the galactic cosmic ray (GCR) intensity in the period of 1995–1997 (A > 0) than in 1985–1987 (A < 0). Subsequently, different ranges of the heliolongitudinal asymmetry of the solar wind speed jointly with equally important corresponding drift effect are general causes of the polarity dependence of the amplitudes of the 27-day variation of the GCR intensity. At the same time, we show that the polarity dependence is feeble for the last unusual minimum epoch of solar activity 2007–2009 (A < 0); the amplitude of the 27-day variation of the GCR intensity shows only a tendency of the polarity dependence. We present a three dimensional (3-D) model of the 27-day variation of GCR based on the Parker’s transport equation. In the 3-D model is implemented a longitudinal variation of the solar wind speed reproducing in situ measurements and corresponding divergence-free interplanetary magnetic field (IMF) derived from the Maxwell’s equations. We show that results of the proposed 3-D modeling of the 27-day variation of GCR intensity for different polarities of the solar magnetic cycle are in good agreement with the neutron monitors experimental data. To reach a compatibility of the theoretical modeling with observations for the last minimum epoch of solar activity 2007–2009 (A < 0) a parallel diffusion coefficient was increased by ∼40%. 相似文献
799.
V.V. Lyahov V.M. Neshchadim 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
A procedure for investigating the stability of a current sheath, taking into account the effect of plasma polarization, is offered. The kinetic equation with a self-consistent electromagnetic field for perturbation of the distribution function is solved. On the basis of this solution, the tensor of dielectric permeability for a non-electroneutral current sheath plasma is calculated, and the dispersion equation for the study of possible instability modes of this current sheath is obtained. The instability of the current sheath of the magnetospheric tail with respect to tearing perturbations, and the influence of the effect of plasma polarization on the development of tearing instability, are investigated. 相似文献
800.
V. S. Moiseev D. S. Gushchina A. N. Kozar G. E. Borzov 《Russian Aeronautics (Iz VUZ)》2009,52(2):221-227
Using formalism of the queueing theory, we propose two-objective models for optimizing the number of unmanned aerial vehicles (UAV) designed for remote monitoring (reconnaissance) of certain regions. A model that takes into account the UAV failure in performing a flight mission is considered. The numerical method and examples of solving problems stated are presented. 相似文献