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121.
Paddison F.C. Shipley C.A. Maffett A.L. Dawson M.H. 《IEEE transactions on aerospace and electronic systems》1978,(1):27-34
A laboratory method to determine the magnitude and position of radar reflection sources on complex targets is described. In addition the method provides a way to measure the modification of the radar cross section (RCS) due to multipath. The method has application in modeling RCS for radar and electronic countermeasure (ECM) system performance analysis and in the study of the extent to which the signature of the target could be altered. The equipment described, termed MACROSCOPE, was developed for RCS studies by the U.S. Army and is described in limited distribution bution literature. The application to marine targets is new with this paper, as is the technique of measuring the RCS of parts of the target and analytically combining them to represent the whole. An illustration of the need for this type of laboratory equipment was illustrated by the extensive search for full scale data which could be compared to scale model data to validate the technique. 相似文献
122.
T. Sbarrato L. Foschini G. Ghisellini F. Tavecchio 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The γ-ray emission of blazar jets shows a pronounced variability and this feature provides limits to the size and to the speed of the emitting region. We study the γ-ray variability of bright blazars using data from the first 18 months of activity of the Large Area Telescope on the Fermi Gamma-Ray Space Telescope. From the daily light-curves of the blazars characterized by a remarkable activity, we firstly determine the minimum variability time-scale, giving an upper limit for the size of the emitting region of the sources, assumed to be spheroidal blobs in relativistic motion. These regions must be smaller than ∼10−3 parsec. Another interesting time-scale is the duration of the outbursts. We conclude that they cannot correspond to radiation produced by a single blob moving relativistically along the jet, but they are either the signature of emission from a standing shock extracting energy from a modulated jet, or the superposition of a number of flares occurring on a shorter time-scale. We also derive lower limits on the bulk Lorentz factor needed to make the emitting region transparent for gamma-rays interacting through photon–photon collisions. 相似文献
123.
The paper highlights significance of the interturbine transition duct as part of the high pressure and low pressure turbine spool. The correlations have been suggested allowing us to estimate variation of the average cross section flow swirl while its passing the interturbine transition duct. 相似文献
124.
O. M. Alifanov Yu. G. Egorov V. M. Kul’kov V. V. Terent’ev S. O. Firsyuk 《Russian Aeronautics (Iz VUZ)》2015,58(4):376-382
The elements for various types of attitude control systems used in a number of small spacecraft are considered. An approach for assessment of such system effectiveness based on design requirements for spacecraft purpose and restriction in accuracy, mass and energy is proposed. 相似文献
125.
N. I. Akishev I. I. Zakirov V. A. Ivanov V. N. Paimushin M. A. Shishov 《Russian Aeronautics (Iz VUZ)》2011,54(2):115-124
The known analytical solutions of the linearized stability problems for rectangular hinged plates under the combined loading
are generalized to the similar problems for skew plates, the deformation mechanics of which is described by the equations
of the classical theory formed in the oblique Cartesian coordinates. 相似文献
126.
In this paper, we examine experimentally some devices the principle of action of which is based on using the dynamic pressure
of air extracted to engine cooling and which are meant for reducing the radial temperature gradient in GTE rotor disks. We
established that the devices equipped with the ejector channels make it possible to accelerate the process of the disk hub
heating by hot air suction from the cavity periphery towards the rotor axis of rotation. Using the data of visualization studies,
we show the possibility for efficient operation of ejector devices in the conditions of real GTE rotor circumferential velocities. 相似文献
127.
A technique of optimizing the electrode system of the differential recorder for the aircraft time-of-flight ion-marking airspeed
and aircraft angle of attack sensor by the criterion of ion-marking recording error variance minimum is considered. The technique
is based on analyzing the function of spatial distribution for the ion-marking and recorder electrode interaction field potential
and determining a point for which this function reaches the maximum slope. The relations making it possible to synthesize
the sensor electrode system by the complex criterion as a ratio of error variance to transformation channel response are obtained. 相似文献
128.
The basic steps of an algorithm are given for calculating the parameters of the limiting state of a helicopter main rotor
blade. To estimate the static strength, a technique of elastic constants variation is used; it is based on the limit equilibrium
theory and enables us to obtain the upper and lower bounds for the critical load simultaneously. An iterative technique is
proposed to determine the lower bound of the allowable load on the root section of the composite blade depending on the azimuthal
angle of its turn in the helicopter hovering mode. 相似文献
129.
A technique of analyzing the flutter initiation in flat plate compressor cascades was developed. The viscous and inviscid
flow study was carried out using the COBRA solver based on the modified implicit Godunov method and unsteady implicit method
updated for using. The flutter conditions were revealed and the effect of taking into account viscosity, angles of attack
and time steps was investigated. 相似文献
130.
V. A. Futin 《Russian Aeronautics (Iz VUZ)》2011,54(2):165-169
The influence of the clearance between the case and blade ends of the semi-open impeller on the centrifugal stage characteristics
is considered using the experimental data and numerical calculation results. 相似文献