scholarly journals Large-Scale Shape Transformations of a Sphere Made of a Magnetoactive Elastomer

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2933
Author(s):  
Oleg Stolbov ◽  
Yuriy Raikher
Keyword(s):  
Aspect Ratio ◽  
Numerical Modelling ◽  
Carbonyl Iron ◽  
Applied Field ◽  
Large Scale ◽  
Ellipsoidal Approximation ◽  
Spherical Sample ◽  
Micron Size ◽  
Ellipsoid Of Revolution ◽  
Magnetoactive Elastomer

Magnetostriction effect, i.e., deformation under the action of a uniform applied field, is analyzed to detail for a spherical sample of a magnetoactive elastomer (MAE). A close analogy with the field-induced elongation of spherical ferrofluid droplets implies that similar characteristic effects viz. hysteresis stretching and transfiguration into a distinctively nonellipsoidal bodies, should be inherent to MAE objects as well. The absence until now of such studies seems to be due to very unfavorable conclusions which follow from the theoretical estimates, all of which are based on the assumption that a deformed sphere always retains the geometry of ellipsoid of revolution just changing its aspect ratio under field. Building up an adequate numerical modelling tool, we show that the ‘ellipsoidal’ approximation is misleading beginning right from the case of infinitesimal field strengths and strain increments. The results obtained show that the above-mentioned magnetodeformational effect should distinctively manifest itself in the objects made of quite ordinary MAEs, e.g., composites on the base of silicone cautchouc filled with micron-size carbonyl iron powder.

Preferential dissolution along misoriented boundaries in heterogenite

2000 ◽  
Vol 620 ◽  
Author(s):  
R. Lee Penn ◽  
Alan T. Stone ◽  
David R. Veblen
Keyword(s):  
Electron Microscopy ◽  
Aspect Ratio ◽  
Reductive Dissolution ◽  
Morphology Evolution ◽  
Crystal Chemical ◽  
Transmission Electron ◽  
Micron Size ◽  
Primary Particles ◽  
Size And Morphology ◽  
Preferential Dissolution

ABSTRACTHigh-Resolution Transmission Electron Microscopy (HRTEM) results show a strong crystal-chemical and defect dependence on the mode of dissolution of synthetic heterogenite (CoOOH) particles. As-synthesized heterogenite particles are micron-size plates (aspect ratio ∼ 1/30) constructed of crystallographically oriented ∼ 3-nm primary particles or are single ∼ 21-nm unattached heterogenite platelets (aspect ratio ∼1/7). Reductive dissolution, using hydroquinone, was examined in order to evaluate morphology evolution as a function of reductant concentration. Two end-member modes of dissolution were observed: 1) non-specific dissolution of macroparticles and 2) preferential dissolution along misoriented boundaries. In the case of non-specific dissolution, average macrocrystal size and morphology are not altered as building block crystals are consumed. The result is web-like particles with similar breadth and shape as undissolved particles. Preferential dissolution involves the formation of channels or holes along boundaries of angular misorientation. Such boundaries involve only a few degrees of tilt, but dissolution occurs almost exclusively at such sites. Energy-Filtered TEM thickness maps show that the thickness of surrounding material is not significantly different from that of undissolved particles. Finally, natural heterogenite from Goodsprings, Nevada, shows morphology and microstructure similar to those of this synthetic heterogenite.

Carbonyl-Iron Electrodes for Rechargeable-Iron Batteries

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
A. Sundar Rajan ◽  
M. K. Ravikumar ◽  
K. R. Priolkar ◽  
S. Sampath ◽  
A. K. Shukla
Keyword(s):  
Carbonyl Iron ◽  
Large Scale ◽  
Low Cost ◽  
Specific Capacity ◽  
Electrical Energy ◽  
Slow Increase ◽  
Faradaic Efficiency ◽  
Nickel Iron ◽  
In Situ Xrd ◽  
Iron Electrodes

AbstractNickel-iron and iron-air batteries are attractive for large-scale-electrical-energy storage because iron is abundant, low-cost and non-toxic. However, these batteries suffer from poor charge acceptance due to hydrogen evolution during charging. In this study, we have demonstrated iron electrodes prepared from carbonyl iron powder (CIP) that are capable of delivering a specific discharge capacity of about 400 mAh g−1 at a current density of 100 mA g−1 with a faradaic efficiency of about 80%. The specific capacity of the electrodes increases gradually during formation cycles and reaches a maximum in the 180th cycle. The slow increase in the specific capacity is attributed to the low surface area and limited porosity of the pristine CIP. Evolution of charge potential profiles is investigated to understand the extent of charge acceptance during formation cycles. In situ XRD pattern for the electrodes subsequent to 300 charge/discharge cycles confirms the presence of Fe with Fe(OH)2 as dominant phase.

Gas Source Silicon Molecular Beam Epitaxy

1991 ◽  
Vol 220 ◽  
Author(s):  
H. Hirayama ◽  
M. Hiroi ◽  
K. Koyama ◽  
T. Tatsumi ◽  
M. Sato
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Molecular Beam ◽  
Hydrogen Desorption ◽  
Dissociative Adsorption ◽  
Molecular Beam Epitaxial ◽  
Gas Source ◽  
Surface Migration ◽  
Micron Size ◽  
Silicon Hydrides

ABSTRACTGas source silicon molecular beam epitaxial (Si-MBE) growth is microscopically governed by a disociative adsorption of silicon hydrides, such as Si2H6 source gas molecules on Si surface. The dissociative adsorption generates SiH species on the surface. From this hydride phase, hydrogen desorbs thermaly. The temperature dependence of the growth rate indicated that the hydrogen desorption from the SiH is the rate limiting step. In HBO2 Knudsen cell doping, B adsorbates block the surface migration. Such a blocking effect can be avoided by B2H6 gas dopant, because of the similar incorpration mechanism of B2H6 to that of Si2H6. However, in PH3 gas doping, a crystal quality degradation was observed at a high doping range due to the preferentially high sticking coefficient of PH3 and the resulting surface dangling bond termination. The selective epitaxial growth of a B doped layer using Si2H6 and B2H6 was applied to a novel structured base fabrication for super self-aligned selectively grown base transistor (SSSBT). A successful achievement of the SSSBT fabrication indicates the high potentiality of gas source Si-MBE to the sub-micron size ultra-high speed bipolar large scale integrated (LSI) circuits.

The Effect of a Downstream Rotor on the Measured Performance of a Transonic Turbine Nozzle

1986 ◽  
Vol 108 (2) ◽  
pp. 269-274
Author(s):  
R. G. Williamson ◽  
S. H. Moustapha ◽  
J. P. Huot
Keyword(s):  
Performance Evaluation ◽  
Aspect Ratio ◽  
Flow Field ◽  
Large Scale ◽  
Outer Wall ◽  
Nozzle Flow ◽  
Turning Angle ◽  
Low Aspect Ratio ◽  
Transonic Turbine ◽  
Mach Numbers

Two nozzle designs, involving the same low aspect ratio, high turning angle vanes, and differing in outer wall contour, were tested over a range of exit Mach numbers up to supersonic values. The experiments were conducted on a large-scale, full annular configuration with and without a representative rotor downstream. Nozzle performance was found to be significantly affected by rotor operation, the influence depending on the detailed characteristics of the nozzle flow field, as well as on the design and operation of the rotor itself. It is suggested that performance evaluation of low aspect ratio nozzles of high turning angle may require appropriate testing with a rotor.

Assessing the Multiple Pressure Source Hypothesis for the Sakurajima Volcano and Aira Caldera Magmatic System

2021 ◽  
Author(s):  
Robert Backhurst
Keyword(s):  
Numerical Modelling ◽  
Large Scale ◽  
Numerical Study ◽  
Deformation Source ◽  
Geodetic Data ◽  
Analytical Models ◽  
Magmatic System ◽  
Sakurajima Volcano ◽  
Subsurface Heterogeneity ◽  
Increased Risk

<p>Sakurajima, located on the southern rim of Aira caldera, is one of the most active volcanoes in Japan. From long term deformation trends, the volcano is showing an increased risk of large-scale eruption, emphasizing the need to better understand the magmatic system.</p><p>Deformation modelling, primarily using the Mogi method, has dominated the geodetic assessment history of Sakurajima. These methods, however, contain limitations, such as the assumption of a homogeneous crust, and have therefore not accurately depicted the magmatic system. Numerical modelling techniques have reduced this limitation by accounting for subsurface heterogeneity.</p><p>Analytical modelling studies have suggested multiple magmatic sources beneath Aira caldera and Sakurajima volcano, whilst the only numerical study undertaken so far indicated a single source. Here, we test the multiple deformation source hypothesis, whilst also incorporating subsurface heterogeneity and topography, using Finite Element (FE) numerical modelling, and geodetic data from Sakurajima.</p><p>Using a full 3D model geometry for Sakurajima and Aira caldera, preliminary forward modelling suggests a second deformation source produces our best fit to the measured geodetic data. Optimum results indicate a shallow prolate source 7-10 km below sea level (bsl), in addition to a deeper oblate source at ~13 km bsl. These preliminary findings produce greater shallow storage depths than the previous analytical models (3-6 km) and ties in with the trans-crustal magmatic system hypothesis.</p><p>Increasing our understanding of the Sakurajima magmatic system will enable improved interpretations of geodetic data prior to eruptions and will inform models for a range of similar volcanoes world-wide.</p>

Large‐scale Micropillar 3D Patterning with High‐aspect Ratio Using a Theta‐pipette

2021 ◽  
Author(s):  
Xiaobo Liao ◽  
Jian Zhuang ◽  
Jiulin Yang ◽  
Lei Cheng ◽  
Qiangqiang Zheng ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Large Scale

scholarly journals High resolution parameter study of the vertical shear instability

2020 ◽  
Vol 499 (2) ◽  
pp. 1841-1853
Author(s):  
Natascha Manger ◽  
Hubert Klahr ◽  
Wilhelm Kley ◽  
Mario Flock
Keyword(s):  
Aspect Ratio ◽  
Large Scale ◽  
Dead Zone ◽  
Pressure Ratio ◽  
Theoretical Models ◽  
Shear Instability ◽  
Vertical Shear ◽  
Parameter Study ◽  
Aspect Ratios ◽  
Strong Scaling

ABSTRACT Theoretical models of protoplanetary discs have shown the vertical shear instability (VSI) to be a prime candidate to explain turbulence in the dead zone of the disc. However, simulations of the VSI have yet to show consistent levels of key disc turbulence parameters like the stress-to-pressure ratio α. We aim to reconcile these different values by performing a parameter study on the VSI with focus on the disc density gradient p and aspect ratio h = H/R. We use full 2π 3D simulations of the disc for chosen set of both parameters. All simulations are evolved for 1000 reference orbits, at a resolution of 18 cells per h. We find that the saturated stress-to-pressure ratio in our simulations is dependent on the disc aspect ratio with a strong scaling of α∝h2.6, in contrast to the traditional α model, where viscosity scales as ν∝αh2 with a constant α. We also observe consistent formation of large scale vortices across all investigated parameters. The vortices show uniformly aspect ratios of χ ≈ 10 and radial widths of approximately 1.5H. With our findings we can reconcile the different values reported for the stress-to-pressure ratio from both isothermal and full radiation hydrodynamics models, and show long-term evolution effects of the VSI that could aide in the formation of planetesimals.

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