Overdense Threads in the Solar Corona Induced by Torsional Alfvén Waves

High-resolution and high-cadence observations have shown that Alfvén waves are ubiquitous in the solar atmosphere. Theoretical works suggest their ability to transfer large energy fluxes from the photosphere to the corona and solar wind. In this proof-of-concept Letter we show that torsional Alfvén waves can induce the formation of filamentary plasma structures in the solar corona. We perform high-resolution 3D ideal MHD simulations in an initially uniform coronal plasma permeated by a line-tied twisted magnetic field. We find that torsional Alfvén waves develop Kelvin–Helmholtz instabilities as a result of the phase mixing process. The Kelvin–Helmholtz instability drives plasma compression that breaks the uniformity of density, creating elongated overdense threads aligned with the direction of the magnetic field. With synthetic modeling of SDO/AIA imaging we show that the overdense filaments could be seen in observations as fine strands that illuminate the underlying magnetic structure.

Measurement of volume fraction of air in water: experimental Study

In multi phase mixing of flow streams, the measurement of fraction of individual components with consideration of proportion of volume need to be analyzed considering the serious issues in many chemical and other processing industries. Even though, quantifiable measurements technique are exist for the calculation of solubility, partial pressure, molar fraction and VOF, the VOF measurement is the meaningful measure of percentage fraction of air in water. In this experimental procedure, the method to resolve the Volume fraction (VOF) is discussed and the same is achieved by impedance probe method.

Aluminum Composite Materials Providing Extended Service Life

Hardness and tribotechnical characteristics were investigated under conditions of dry sliding friction on steel obtained by liquid-phase mixing of Aluminum-Matrix Composite (AMC) materials based on aluminum alloys AK12, D16, V124, AL9, AL25, reinforced with silicon carbide SiC particles with a size of 28 μm with a content of 5, 10 or 15% by volume. AMC performed better than matrix alloys and the commonly used antifriction aluminum alloy AOM 2-1. The dry friction coefficient was 1.5-3 times lower on average, and the volumetric wear rate was 5-9 times lower. An increase in the content of SiC particles in the composite from 5 to 20 vol.%. As a rule, leads to an improvement in the tribotechnical characteristics. The composites obtained have shown a sufficiently high operational suitability for work in friction units with steels both in dry friction and in friction with lubrication.

Formation of Ultramylonites in an Upper Mantle Shear Zone, Erro-Tobbio, Italy

Deformation in the upper mantle is localized in shear zones. In order to localize strain, weakening has to occur, which can be achieved by a reduction in grain size. In order for grains to remain small and preserve shear zones, phases have to mix. Phase mixing leads to dragging or pinning of grain boundaries which slows down or halts grain growth. Multiple phase mixing processes have been suggested to be important during shear zone evolution. The importance of a phase mixing process depends on the geodynamic setting. This study presents detailed microstructural analysis of spinel bearing shear zones from the Erro-Tobbio peridotite (Italy) that formed during pre-alpine rifting. The first stage of deformation occurred under melt-free conditions, during which clinopyroxene and olivine porphyroclasts dynamically recrystallized. With ongoing extension, silica-undersaturated melt percolated through the shear zones and reacted with the clinopyroxene neoblasts, forming olivine–clinopyroxene layers. Furthermore, the melt reacted with orthopyroxene porphyroclasts, forming fine-grained polymineralic layers (ultramylonites) adjacent to the porphyroclasts. Strain rates in these layers are estimated to be about an order of magnitude faster than within the olivine-rich matrix. This study demonstrates the importance of melt-rock reactions for grain size reduction, phase mixing and strain localization in these shear zones.

Study on Two-Phase Mixing inside Flow Focusing/Blurring Nozzle by Gray Distribution Analysis Method

The application prospect of a flow focusing/blurring nozzle is broad but research on gas-liquid flow inside the nozzle is not comprehensive. The gas-liquid mixing inside the nozzle is difficult to study by visualization experiment, so this paper proposes to study the gas-liquid flow or mixing inside the nozzle by the gray scale level distribution of the experimental images. The results show that the increase of air flow rate is beneficial to two-phase mixing inside the nozzle, while the influence of water flow rate, tube hole distance (the distance between inner tube and nozzle outlet) and orifice diameter increase is opposite. The influence of air inertia force on two-phase mixing is weaker than the water inertia force under different parameters, the effect of the air inertia force on two-phase mixing is similar to tube hole distance under a small flow rate, the effect of the orifice diameter on two-phase mixing is relatively weak. In addition, the analysis of the gas-liquid flow field in the mixing zone shows that the gas-liquid flow in the nozzle is stable in the flow focusing mode. In the flow blurring mode, the gas-liquid flow inside the nozzle has radial stability but axial pulsation. In the transition mode, the gas-liquid flow inside the nozzle is unstable, but the gas-liquid flow is close to the flow blurring mode.

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure–property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.

On the method for the analysis of compulsive phase mixing and its application in cosmogony

In this paper, we study the strong non-stationary stochastic processes that take place in the phase space of self-gravitating systems at the earlier non-stationary stage of their evolution. The numerical calculations of the compulsive phase mixing process were carried out according to the model of chaotic impacts, where the initially selected phase volume experiences random pushes that are of a diverse and complex nature. The application of the method for studying random impacts on a volume element in the case of three-dimensional space is carried out.

Phonon Scattering and Suppression of Bipolar Effect in MgO/VO2 Nanoparticle Dispersed p-Type Bi0.5Sb1.5Te3 Composites

Bismuth-Telluride-based compounds are unique materials for thermoelectric cooling applications. Because Bi2Te3 is a narrow gap semiconductor, the bipolar diffusion effect is a critical issue to enhance thermoelectric performance. Here, we report the significant reduction of thermal conductivity by decreasing lattice and bipolar thermal conductivity in extrinsic phase mixing of MgO and VO2 nanoparticles in Bi0.5Sb1.5Te3 (BST) bulk matrix. When we separate the thermal conductivity by electronic κel, lattice κlat, and bipolar κbi thermal conductivities, all the contributions in thermal conductivities are decreased with increasing the concentration of oxide particle distribution, indicating the effective phonon scattering with an asymmetric scattering of carriers. The reduction of thermal conductivity affects the improvement of the ZT values. Even though significant carrier filtering effect is not observed in the oxide bulk composites due to micro-meter size agglomeration of particles, the interface between oxide and bulk matrix scatters carriers giving rise to the increase of the Seebeck coefficient and electrical resistivity. Therefore, we suggest the extrinsic phase mixing of nanoparticles decreases lattice and bipolar thermal conductivity, resulting in the enhancement of thermoelectric performance over a wide temperature range.