Airglow atmospheric imager on board the ‘IK-Bulgaria-1300’ satellite

This paper shows the possibilities of the optical scanning imager for investigation of the structure of the auroral, SAR and tropical arcs and in this way to study the particle precipitation, neutral winds across the magnetic equator, drifts, electric fields and the current systems in the ionosphere.     

The Flight 2000 avionics suite: paving the way to free flight

The FAA's Flight 2000 project is an innovative initiative to implement and validate selected operational improvements leading to Free Flight. It integrates new avionics, new ground systems, new procedures, avionics certification, and operational approval. Approximately 2000 aircraft operating in Alaska, Hawaii, and Oceanic airspace will be equipped with new capabilities enabling benefits such as improved situational awareness, increased flexibility, and efficiency gains. By developing and fielding these operational improvements, the actual benefits of new procedures and capabilities will be validated and risks associated with national implementation will be reduced     

Estimation of Correlation Functions by Stochastic Approximation

Two techniques for estimating the correlation function of a stationary random process using the method of stochastic approximation are developed. Both provide updated estimates as successive T-second observations are processed. Both assume a functional form for the correlation function that depends on a number of parameters that are estimated. One technique is based on the mean-square error; the other maximizes a likelihood function. Examples are included.     

Spectres auroraux

Summary The paper presents a review of the main spectroscopic studies of polar aurora accomplished during the past eight years.In a first part, the few new results concerning knowledge of the spectrum itself are examined. They concern detailed spectrum analysis, a few spectral features (sodium doublet, helium lines) and the extension of spectral observations to very low wavelengths (3000 to 1000 Å). The main features discovered in this region are the Vegard-Kaplan and Lyman-Birge-Hopfield systems as well as the 1304 oxygen line. A comparison of observed and theoretical intensities shows serious discrepancies, not all of which may be attributed to difficulties of observation. Next is given classification, from a spectral point of view, of the various kinds of auroral phenomena, with respect to altitude and latitude. Particular attention is given to high altitude and sunlit aurorae, and to low intensity, non discrete aurorae observed around the 70th degree (geomagnetic) and around the polar cap.A second part underlines the influence of two important parameters, time and location, mainly as a possible means of detection of different mechanisms.As far as the time parameter is concerned, a few pages are devoted to statistical analysis of the great wealth of observational data accumulated over twenty or thirty years.It is shown that important conclusions emerge from such studies. Very small scale time variations are mainly concerned with the study of metastable states, their lifetimes and de-excitation due to shocks between particles. Differences of spectra with the location of the observed emitting volume is a much more recent subject, which has, however, produced important results. These concern mainly observations made from rockets, although a few results have been obtained from the ground. All these indicate significant differences that may shed some light on the difficult problem of mechanisms. The latter has not been developed, since a recent review has been written on the subject. The same is true for the very important problem of hydrogen emissions.The last pages are concerned with the latest developments of experimental methods, with some stress on image tubes, which will probably be one of the main detecting devices for observing auroral spectra in the near future.     

A technique for presentation and application of the propeller fan multidimensional characteristics in semi-full-scale simulation of a gas turbine engine and its automatic control system

A technique for linear interpolation of the multidimensional characteristics of a coaxial propeller fan with opposite rotation propellers is proposed; the technique makes it possible to simulate the turbofan engine operation in the entire range of flight conditions and reduce expenses for fullscale tests. The mathematical models obtained meet the requirements imposed in the semi-full-scale simulation.     

Pareto-optimal solution of a two-objective problem in choosing conditions of monoimpeller milling

A problem of optimization of cutting parameters with respect to the criteria of maximum efficiency and maximum tool resistance is formulated. To solve the problem, a method is developed and applied for determining the Pareto-optimal values of machining conditions in milling the present-day GTE monoimpeller blade passages with a circular milling cutter.     

Gasodynamic characteristics of a combustion chamber in the integrated power plant with an asymmetric air intake

The results of experimental investigations of gasodynamic characteristics of a combustion chamber model in the integrated power plant (IPP) with an asymmetric air intake are presented. The influence of an angle of air supply into the chamber model on hydraulic losses and the flow structure is shown at different air flowrates, relative values of the minimal flow section area of the feeding air intake pipes, under changes of the flowrate of gas simulating gas generation products and geometric model parameters. A technique for measuring the concentration of carbon dioxide simulating IPP gas generation products in the combustion chamber air flow and the results of experimental investigations of a mixture formation process in the combustion chamber model are described.     

Analysis of structural elements made of composite materials with defects

The paper presents an improved technique and the results of strength analysis for the aircraft structural elements with a structural defect like an arbitrary shape delamination.