Crystallization of metal alloys in microgravity and uniform compression conditions

This is an analysis of the experimental results to study the metastable phase formation while crystallization of binary metal melts in microgravity and quasi-isostatic (uniform) compression takes place. The alloy system PbSn serves as an illustration     

Thermal and thermosolutal convective effects in bridgman solidification: Effect of orientation relative to gravity

A concentrated binary system (Ge-Si) and a dilute one (Ge-Ga) have been solidified at 1 g, in a new vertical Bridgman furnace where radial thermal gradients have been minimized. Very different solutal boundary layer extents (δ_Ge-Si = 3 cm, δ_Ge-Ga = 2.5 mm) obtained for both systems solidified in the same thermal conditions are explained by simple analytical hydrodynamic models. It is demonstrated that :1. The convective transport of Ga in the Ge-Ga system is due to the unavoidable residual horizontal thermal gradients associated with discontinuity of thermal properties at the solid-liquid interface.2. The larger boundary layer extent observed for Ge-Si and the corresponding pure diffusive transport is the result of the stabilizing effect of the longitudinal solutal gradient in this system.Thus, in the case of dilute systems, convective effects can only be cancelled through a reduction of the gravity level. On the opposite, pure diffusive solute transport can be achieved in the vertical configuration a 1 g in the case of concentrated systems where a stabilizing solutal effect is operating.     

The GYROLITE: Is it Unstable?

A new derivation of the GYROLITE stability criterion is presented. It is confirmed that, for the satellite to have a stable attitude, the spinning part must have a favorable inertia ratio.     

Effects due to an artificial earth satellite in rapid motion through the ionosphere or the interplanetary medium

Conclusion In this paper we have been concerned with the results of theoretical calculations of the interaction between a fast moving body and a tenuous plasma. Particular attention was paid to the case where the velocity of the body is much smaller than the velocity of neutral particles and ions, while the dimensions of the body are sufficiently large in comparison with the Debye radius. Such conditions are realized during the motion of artificial satellites or space rockets through the ionosphere, or through the interplanetary medium in the immediate neighborhood of the earth. Although this case has, on the whole, been investigated quite extensively, there are still a number of problems which require further analysis. Firstly, it is necessary to take into account the effect of the electric field on the motion of ions in the near zone at the rear of the body. Another important problem is that of magnetic disturbances. In the case of scattering of radio waves by the trail of the body, it would be interesting indeed to know the increase in the effective cross-section in the resonance region in which 0. A number of other research problems which arise in the analysis of phenomena in the neighborhood of a moving body have been noted in the Introduction.In the lower layers of the ionosphere it is important to allow for the fact that the dimensions of the body are comparable with the mean free path. Under these conditions there is the further interesting problem of the heating and additional ionization of the plasma, the disintegration of the surface, and the emission of waves. At large distances from the surface of the earth, the dimensions of the body may become comparable with the Debye radius, and the velocity of the body in the given region may become smaller than the thermal velocity of the particles. The character of the various disturbances introduced by the body under these conditions will also require a special investigation.Thus, the interaction of a moving body with plasma leads to special and exceptionally varied effects. Disturbances due to the body are very considerable, so that the physical state of the region surrounding the body is very different from the state of the undisturbed medium.The above results indicate that the phenomena in the neighborhood of satellites and space rockets in the ionosphere, or the interplanetary medium, must be taken into account, in the processing of experimental data when it is required to deduce information about the state of the undisturbed medium. This is particularly important in the analysis of the results of measurements obtained with various types of probes. Considerable errors may be introduced if these effects are not allowed for.Further extensive experimental and theoretical studies of the structure of the disturbed region in the neighborhood of moving bodies in plasma are clearly necessary. Such investigations will, in particular, lead to the development of the most effective methods of studying the properties of the media through which satellites and space rockets travel.Translated from the Russian: Ob effektah vyzyvaemyh iskusstvennym sputnikom bystro dviimsja v ionosfere ili meplanetnoj srede (Uspehi fizieskih nauk 79, 23–80) by Express Translation Service.     

Radio aurora magnetic and streaming aspect sensitivities on 6 simultaneous links at 50 MHz

During August 1981, a 50 MHz c.w. radar system was operated in central Canada to measure auroral scatter amplitudes and Doppler spectra from a scattering region centered near 66° magnetic invariant latitude (L ≈ 6.0). Narrow beams from 3 transmitters, differing in frequency by 1 KHz, were directed to cover a common volume of the ionosphere over a ground location at 56.3°N, 103.5°W. The scattered signals were received on narrow beam antennas at two receiving sites, and recorded in analog form on magnetic tape under the control of an AIM65 microcomputer. The analog tapes were digitized later and FFT-processed to obtain Doppler spectra and amplitudes.The 6 transmission paths were designed to provide several magnetic aspect angles varying by 1.5°-7° from perpendicularity with the earth's field B and two streaming aspect angles differing by ～38°. The objective was to employ controlled geometric factors to study the functional dependency of signal amplitudes and Doppler shifts on magnetic and streaming aspect angles. Several hundred hours of excellent data were obtained in continuous operation during the month of August 1981. Preliminary results will be reported.     

America's Abundant Electricity and the ASME Boiler Code

The building of great steam power plants with utmost consideration for public safety has created today's American miracle of abundant electricity. Behind this great achievement stand the mechanical engineers who have designed and built these power plants under their ethical responsibilities for public safety, in full compliance with the American Society of Mechanical Engineers (ASME) Boiler Code and under the strict disciplines imposed by a specialist insurance company willing to write 100 percent insurance coverage against boiler explosions. The historical origin of this great achievement dates back to the days of the Civil War and a small group of men with exceptional vision and a profound concern for public safety. They saw the opportunity to apply their talents and sense of responsibility to solving the problem of steam boiler explosions and the terrible losses of human lives. These early leaders have earned the esteem and honor of our present and future generations, but who remembers them? Today, in the scientific revolution of this century, there is a critical need for similar new leaders of exceptional integrity, responsibility, and initiative, both in engineering and in industry.     

Analysis of gravity-wave induced instabilities and turbulence viscosity parameters from optical emissions

The effects of gravity waves on OH and 5577 0I emissions have been used to investigate (1) the possible production of “secondary” waves or “ripples” by a “primary” wave; (2) the possible application of such observed optical emissions for computing atmospheric parameters such as turbulence viscosity in the mesospheric regions.     

Supernova remnants

Optical observations of young supernova remnants can give information on the abundance structure of the supernova ejecta, from which properties of the supernova explosion can be deduced. Young remnants also act as laboratories for fast shock wave phenomena. Observations of X-ray and optical line emission show that while a collisionless shock wave does form, it is far from thermal equilibrium. Some young remnants are promising candidates for particle acceleration in shock waves, while in other remnants a central compact object is probably responsible for particle acceleration.     

Sea surface temperature measurement from satellites: Validation and accuracy

A review of the latest published results concerning the accuracy of satellite derived sea surface temperature (SST) estimation is presented. Two types of platforms are considered : orbiting satellites and geosynchronous satellites and the accuracies that may now be expected from such systems are reported. This review emphasizes the impressive improvement in global mapping of SST obtained from the Advanced Very High Resolution Radiometer (AVHRR) on NOAA's operational polar satellites. Tests of the AVHRR SST's against a high reliability data set consisting of buoys, bathythermographs and research ship reports indicate biases of < 0.1°C and RMS differences of < 0.75°C (McClain [1]). Particular attention is also paid to a method adding along track scanning capability to the present multichannel AVHRR technique. This method is demonstrated owing to the coupling of an orbiting satellite (TIROS-N) and a geosynchronous satellite (METEOSAT). Another type of coupling of two such platforms is also presented in connection with the advent of geostationary satellites equipped with a vertical sounding capability, such as GOES-4.