V. Yu. Demin  S. A. Yurgenson 《Russian Aeronautics (Iz VUZ)》2012,55(2):113-119

The basic principles of selecting some design parameters of a lightweight airplane for the contemporary Russian market are presented. Recommendations for selecting these parameters with the service requirements specified are given based on the study performed.  相似文献   

    

E. R. Muslimov  E. Hugot  M. Ferrari  T. Behaghel  N. K. Pavlycheva 《Russian Aeronautics (Iz VUZ)》2018,61(1):1-7

The possibility of constructing an optical scheme of a telescope for a small satellite based on mirrors with freeform surfaces and a curved photodetector is considered. It is shown that the use of a new element base allows the effective area of the main mirror to be maximized and the field of view up to 9.4 times to be increased in comparison with the classical scheme of the Ritchey–Chretien scheme in ensuring the high image quality.  相似文献   

    

V. Biffi  F. Mernier  P. Medvedev 《Space Science Reviews》2018,214(8):123

The distribution of chemical elements in the hot intracluster medium (ICM) retains valuable information about the enrichment and star formation histories of galaxy clusters, and on the feedback and dynamical processes driving the evolution of the cosmic baryons. In the present study we review the progresses made so far in the modelling of the ICM chemical enrichment in a cosmological context, focusing in particular on cosmological hydrodynamical simulations. We will review the key aspects of embedding chemical evolution models into hydrodynamical simulations, with special attention to the crucial assumptions on the initial stellar mass function, stellar lifetimes and metal yields, and to the numerical limitations of the modelling. At a second stage, we will overview the main simulation results obtained in the last decades and compare them to X-ray observations of the ICM enrichment patterns. In particular, we will discuss how state-of-the-art simulations are able to reproduce the observed radial distribution of metals in the ICM, from the core to the outskirts, the chemical diversity depending on cluster thermo-dynamical properties, the evolution of ICM metallicity and its dependency on the system mass from group to cluster scales. Finally, we will discuss the limitations still present in modern cosmological, chemical, hydrodynamical simulations and the perspectives for improving the theoretical modelling of the ICM enrichment in galaxy clusters in the future.  相似文献   

    

S. A. Mikhailov  L. V. Korotkov  D. V. Nedel’ko 《Russian Aeronautics (Iz VUZ)》2010,53(4):369-374

A three-dimensional design model of a helicopter tubular skid landing gear based on the application of the large beam displacement theory is presented. The design model takes into account special features of constructive, physical and geometrical deformation nonlinearity. The analysis of a real helicopter structure is given that confirms sufficient validity of calculation results obtained using the model developed by comparing with the results of the finite element analysis.  相似文献   

    

Possehl SR 《Aerospace America》1995,33(3):32-34

Teams of chronobiologists from the U.S., Russia, and Japan are working toward a remote computerized health care system which, once tested in space, may change how doctors diagnose and treat cardiovascular diseases, including hypertension and conditions predisposing stroke. The system is based on ongoing research indicating that swings in blood pressure charted over a span of 24 hr or longer, rather than a single systolic and diastolic reading, can reveal a new major risk factor for heart disease.  相似文献   

    

S. R. Cranmer  G. B. Field  J. L. Kohl 《Space Science Reviews》1999,87(1-2):149-152

Using empirical velocity distributions derived from UVCS and SUMER ultraviolet spectroscopy, we construct theoretical models of anisotropic ion temperatures in the polar solar corona. The primary energy deposition mechanism we investigate is the dissipation of high frequency (10-10000 Hz) ion-cyclotron resonant Alfvén waves which can heat and accelerate ions differently depending on their charge and mass. We find that it is possible to explain the observed high perpendicular temperatures and strong anisotropies with relatively small amplitudes for the resonant waves. There is suggestive evidence for steepening of the Alfvén wave spectrum between the coronal base and the largest heights observed spectroscopically. Because the ion-cyclotron wave dissipation is rapid, even for minor ions like O⁵⁺, the observed extended heating seems to demand a constantly replenished population of waves over several solar radii. This indicates that the waves are generated gradually throughout the wind rather than propagated up from the base of the corona. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

    

Ferens  D.V. 《Aerospace and Electronic Systems Magazine, IEEE》1999,14(3):23-29

There are many sophisticated models and methods for estimating the size, cost, and schedule of software projects. However, the ability to accurately estimate software cost, size, or schedule is still dubious. In general, the predictive accuracy of models for estimating software development cost and schedule has not been shown to be better than “within 25 percent of actual cost or schedule, about one half of the time”, especially for Department of Defense software efforts. The same is true for software size estimating models and methods, although there are some studies that have shown superior results. For software support (or maintenance) cost estimation, no model has been demonstrated to be accurate. This paper presents a summary of efforts performed to date which demonstrate the accuracy (or lack thereof) of software models. The results of several studies in the areas of software development cost and schedule estimation, size estimation, and support cost estimation are presented to show what these models can and cannot do. Some ideas for improvement are also presented, including the results of some studies which may lead to a resolution of the accuracy conundrum which currently exists  相似文献   

    

Vladimir V. Zheleznyakov  A. V. Serber 《Space Science Reviews》1994,68(1-4):275-289

The current status of the theory of a new astrophysical phenomenon, aradiation-driven diskon, is outlined.The cyclotron radiation pressure around sufficiently hot, strongly magnetized white dwarfs and neutron stars is shown to be able to drive a wind from the photosphere and support a plasma envelope in the closed part of the magnetosphere. The magnetohydrostatic configuration of an optically thin, radiatively supported plasma envelope is determined. It consists of an equatorial disk in the region where the cyclotron radiation force exceeds the local force of gravity and a closed shell near the equilibrium surface where the radiation pressure equals gravity. The effects of finite optical depth on the behaviour of the magnetospheric plasma and the influence of the envelope on the observed radiation are discussed.Classes of magnetic degenerate stars are pointed out in which radiation-driven diskons may be found. The best candidates are two individual stars, the strongly magnetized white dwarfs GD 229 and PG 1031+234. Both exhibit broad and deep depressions in the ultraviolet which are explained as a result of cyclotron scattering by an optically thick radiation-driven envelope in the inhomogeneous magnetic field of the star. We predict a temporal and spectral variability of these features due to non-stationary plasma motions in the envelope.  相似文献   

    

T. V. Stepanova  A. G. Kosovichev 《Space Science Reviews》1994,70(1-2):171-174

Parameters of expanding magnetic loops and arches and of mass flows generated by them in the corona have been computed in a 1D two-fluid approximation. Two possible trigger mechanisms of the coronal transients have been considered: (i) sudden increase of the background magnetic field strength, and (ii) heating and compression plasma inside these magnetic structures. We discuss the formation of shock waves and their dependence on dynamics and geometry of the magnetic structures.  相似文献   

    

Hurd  W.J. Statman  J.I. Vilnrotter  V.A. 《IEEE transactions on aerospace and electronic systems》1987,(4):425-437

A new high dynamic global positioning system (GPS) receiver ispresented and its performance characterized by analysis,simulation, and demonstration. The demonstration receiver is abreadboard model capable of tracking a single simulated satellitesignal in pseudorange and range rate. Pseudorange and range rateestimates are made once every 20 ms, using a maximum likelihoodestimator, and are tracked by means of a third-order fadingmemory filter in a feedback configuration. The receiver trackspseudorange with rms errors of under 1 m when subjected tosimulated 50 g, 40 g/s circular trajectories. The tracking thresholdis approximately 28 dB·Hz, which provides 12 dB margin relativethe the minimum specified signal strength, assuming 3.5 dB systemnoise figure and 0 dB antenna gain.  相似文献