Analysis of the Effects of Dynamic Alloying on the Structure of Aluminium and its Alloys

The dynamic alloying of aluminum and its alloy with a high-speed stream of silicon carbide (SiC) particles simulates the effect of a stream of cosmic dust on spacecraft materials. The study showed a structure change in the volume of aluminum and its alloy and the formation of new structural elements. The transformation of the structure during dynamic alloying leads to a change of the composition and mechanical properties of the matrix material.

Evolution of stream interaction regions from 1 to 1.5 AU

<p>We inspect the evolution of stream interaction regions from Earth to Mars for the declining solar cycle 24. In particular, the opposition phases of the two planets are analyzed in more detail. So far, there is no study comparing the long-term properties of stream interaction regions and accompanying high-speed streams at both planets for the same time period. We build a catalogue covering a dataset of all measured stream interaction regions at Earth and Mars for the time period December 2014 – November 2018. The number of events (>120) allows for a strong statistical basis. To build the catalogue we use near-earth OMNI data as well as measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. For the opposition phase, we additionally use image data from the Solar Dynamics Observatory to complement the in-situ observations. Bulk speed, proton density, temperature, magnetic field magnitude and total perpendicular pressure are statistically evaluated using a superposed epoch analysis. For the opposition phase, coronal holes that are linked to individual streams are identified. The extracted coronal hole areas (using CATCH) and their longitudinal/latitudinal extension are correlated to the duration and maximum bulk speed of the high-speed stream following the passage of a stream interaction region. We find that an expansion of the stream interface from 1 to 1.5 AU is most visible in magnetic field and total perpendicular pressure. The duration of the high-speed stream does not increase significantly from Earth to Mars, however, the stream crest seems to increase. The amplitudes of the SW parameters are found to only slightly increase or stagnate from 1 – 1.5 AU. We arrive at similar correlation coefficients for both planets with the properties of the related coronal holes. There is a stronger linking of maximum bulk speed to latitudinal extent of the coronal hole than to the longitudinal. On average, the occurrence rate of fast forward shocks increases from Earth to Mars.</p>

A statistical study of the long-term evolution of coronal hole properties as observed by SDO

Context. Understanding the evolution of coronal holes is especially important when studying the high-speed solar wind streams that emanate from them. Slow- and high-speed stream interaction regions may deliver large amounts of energy into the Earth’s magnetosphere-ionosphere system, cause geomagnetic storms, and shape interplanetary space. Aims. By statistically investigating the long-term evolution of well-observed coronal holes we aim to reveal processes that drive the observed changes in the coronal hole parameters. By analyzing 16 long-living coronal holes observed by the Solar Dynamic Observatory, we focus on coronal, morphological, and underlying photospheric magnetic field characteristics, and investigate the evolution of the associated high-speed streams. Methods. We use the Collection of Analysis Tools for Coronal Holes to extract and analyze coronal holes using 193 Å EUV observations taken by the Atmospheric Imaging Assembly as well as line–of–sight magnetograms observed by the Helioseismic and Magnetic Imager. We derive changes in the coronal hole properties and look for correlations with coronal hole evolution. Further, we analyze the properties of the high–speed stream signatures near 1AU from OMNI data by manually extracting the peak bulk velocity of the solar wind plasma. Results. We find that the area evolution of coronal holes shows a general trend of growing to a maximum followed by a decay. We did not find any correlation between the area evolution and the evolution of the signed magnetic flux or signed magnetic flux density enclosed in the projected coronal hole area. From this we conclude that the magnetic flux within the extracted coronal hole boundaries is not the main cause for its area evolution. We derive coronal hole area change rates (growth and decay) of (14.2 ± 15.0)×108 km2 per day showing a reasonable anti-correlation (ccPearson = −0.48) to the solar activity, approximated by the sunspot number. The change rates of the signed mean magnetic flux density (27.3 ± 32.2 mG day−1) and the signed magnetic flux (30.3 ± 31.5 1018 Mx day−1) were also found to be dependent on solar activity (ccPearson = 0.50 and ccPearson = 0.69 respectively) rather than on the individual coronal hole evolutions. Further we find that the relation between coronal hole area and high-speed stream peak velocity is valid for each coronal hole over its evolution, but we see significant variations in the slopes of the regression lines.

Design and Fabrication of Abrasive Jet Machine (AJM) & Analyzing its Performance

Abrasive Jet Machining (AJM) is the process of material removal from a work piece by the application of a high speed stream of abrasive particles carried in a gas medium from a nozzle. The material removal process is mainly by erosion. The AJM can principally be wont to cut shapes in arduous and brittle materials like glass, ceramics etc. In this concept, a model of the Abrasive Jet Machine is proposed to design by taking into consideration of commercially available components. Care will be taken to use less fabricated components rather than directly procuring them, because, the lack of accuracy in fabricated components would lead to a diminished performance of the machine. To analyse its performance, Drilling of glass sheets with different abrasives and different nozzles will be carried out by Abrasive Jet Machining process (AJM) in order to determine its machinability.