Preflare heating of filaments

Disappearances of preflare filaments have been observed on June 22, 1980 (S07,W13) (flare at 13.04 U.T.) and September 3, 1980 (flare at 7.52 U.T.). The analysis of MSDP data (MEUDON) leads to the followings conclusions : - Disappearances begin a few minutes before the Hα impulsive phase. - The filaments can be seen again after the flares. - Upwards motions occur in several points, without disturbing significantly preëxisting downflows.Velocity maps suggest shears or velocity loops.The filament disappearance seems to be due to a heating mechanism beginning before the flare maximum.     

Informational need of emotional stress.

According to the informational theory of emotions, emotions in humans depend on the power of some need (motivation) and the estimation by the subject of the probability (possibility) of the need satisfaction (the goal achievement). Low probability of need satisfaction leads to negative emotions, actively minimized by the subject. Increased probability of satisfaction, as compared to earlier forecast, generates positive emotions, which the subject tries to maximize, i.e. to enhance, to prolong, to repeat. The informational theory of emotions encompasses their reflective function, the laws of their appearance, the regulatory significance of emotions, and their role in organization of behavior. The level of emotional stress influences the operator's performance. A decrease in the emotional tonus leads to drowsiness, lack of vigilance, missing of significant signals and to slower reactions. An extremely high stress level disorganizes the activity, complicates it with a trend toward incorrect actions and reactions to insignificant signals (false alarms). The neurophysiological mechanisms of the influence of emotions on perceptual activity and operator performance as well as the significance of individuality are discussed.     

The Magellan project

Magellan is one of the future space projects being studied by the European Space Agency. The aim is to provide high resolution (λ/Δλ ≥ 2.5 × 10⁴) spectra in the far and extreme UV (between 500 and 1550 Å) of faint galactic and extragalactic objects (V ≤ 16^m). The instrument consists of a mechanical collimator, a concave holographic grating and a bidimensional photon-counting detector. A low resolution mode (λ/Δλ ≥ 10³) will provide spectra of objects as faint as 18^m.5. Magellan is planned as an observatory, operated in real time, and allowing interaction with the observer.     

Transient processes and stability in an LC chopper

The analysis of the transient and steady-state processes in LC choppers is presented. The method, used previously for the analysis of processes in grid-connected and self-commutated converters, is adjusted for analysis of LC chopper's processes. The difference equations describing these processes, are obtained and solved. The analytical solution of the problem and the conditions of the transient, steady-state, and stability existence in the chopper are found. Theoretical and experimental results are compared and satisfactory agreement is obtained     

Impact linear polarization observed in a UV chromospheric line during a solar flare

Linear polarization was observed in the S I 1437Å line in bright flaring points during the soft X-ray emission. The degree of polarization is about 25% and is detected at a signal to noise ratio of 2.9. The polarized electric vector is directed towards disk center to within 3°.This polarization could be due to collisional excitationm of S I by energetic electrons beamed in the vertical direction. We suggest that the heat flux in the region interconnecting the transition zone to the high chromosphere during the gradual phase of a flare could lead to an anisotropic excitation. Then the observed polarization would be due to vertical motions of the transition zone sweeping the preexisting chromosphere.     

Beamspace ML bearing estimation incorporating low-angle geometry

A problem in low-angle radar tracking, namely, bearing estimation in the presence of a strong specular multipath component that arrives within the beamwidth of the direct path signal, is studied. Three-dimensional beamspace domain maximum likelihood (3D-BDML) is a computationally simple ML bearing estimation algorithm applicable in this scenario which operates in a 3-D beamspace. A variation of 3D-BDML incorporating the multipath geometry as a priori information is presented. In symmetric 3D-BDML the pointing angle of the center beam is equal to the bisector angle between the direct path ray and the image ray, which may be estimated a priori given only the radar height and the target range. The effect of the inclusion of a priori information on the performance of 3D-BDML is analyzed in terms of the dependence on the relative phase difference between the direct and specular path signals, the sensitivity to error in the bisector angle estimate, and the results of operation when no specular multipath component is present in the data. In addition, computationally simple schemes for coherently incorporating multifrequency data into 3D-BDML are investigated     

Chaotic zero dynamics in kinematically redundant robots

The authors attempt to integrate two areas in robotics that are maturing rapidly: the control of kinematically redundant rigid robots and feedback linearization. Kinematically redundant robots have several advantages over nonredundant robot arms. The extra degrees of freedom are used to reach around or between obstacles. Unlike nonredundant rigid link robots that do not exhibit zero dynamics, the self motions of kinematically redundant robots can be used for torque optimization or avoiding obstacles. It is shown that induced self motions can be chaotic. The main contribution is to demonstrate chaos in cases of feedback linearization when the decoupling matrix is nonsquare and there are less outputs than inputs     

Direct integration methods in dynamic problems of structural mechanics

A method of direct integration with respect to time is proposed to solve dynamic problems of structural mechanics and comparison with the well-known methods is presented.