1,043 research outputs found
Intermediate Fidelity Closed Brayton Cycle Power Conversion Model
This paper describes the implementation of an intermediate fidelity model of a closed Brayton Cycle power conversion system (Closed Cycle System Simulation). The simulation is developed within the Numerical Propulsion Simulation System architecture using component elements from earlier models. Of particular interest, and power, is the ability of this new simulation system to initiate a more detailed analysis of compressor and turbine components automatically and to incorporate the overall results into the general system simulation
Ambient Temperature Growth and Superconducting Properties of Ti-V Alloy Thin Films
A study on the optimization of ambient temperature growth and superconducting
properties of Ti-V alloy thin films grown on SiO2-coated Si substrate is
reported here. These films have been synthesized by co-sputtering of Ti and V
targets, and films having different Ti concentrations were deposited to get the
optimized critical temperature (TC) of thin films close to the bulk value. The
maximum TC of 5.2 K has been obtained in the Ti40V60 composition, which is
further increased to 6.2 K when a 10 nm thick Ti underlayer is added below the
Ti-V film. GIXRD measurements confirm the formation of Ti-V alloys in the
desired crystal structure. The upper critical field (HC2) of the thin films has
been estimated with the help of magnetotransport measurements. The utility of
Ti-V alloy thin films in superconducting radiation detection applications is
ascertained.Comment: 4 pages, 6 figure
Stability prediction of residual soil and rock slope using artificial neural network
A sudden downward movement of the geomaterial, either composed of soil, rock, or a mixture of both, along the mountain slopes due to various natural or anthropogenic factors is known as a landslide. The Himalayan Mountain slopes are either made up of residual soil or rocks. Residual soil is formed from weathering of the bedrock and mainly occurs in gentle-to-moderate slope inclinations. In contrast, steep slopes are mostly devoid of soil cover and are primarily rocky. A stability prediction system that can analyse the slope under both the condition of the soil or rock surface is missing. In this study, artificial neural network technology has been utilised to predict the stability of jointed rock and residual soil slope of the Himalayan region. The database for the artificial neural network was obtained from numerical simulation of several residual soils and rock slope models. Nonlinear equations have been formulated by coding the artificial neural network algorithm. An android application has also been developed to predict the stability of residual soil and rock slope instantly. It was observed that the developed android app provides promising results in predicting the factor of safety and stability state of the slopes. © 2022 Mahesh Paliwal et al. This is an open access article distributed under the Creative Commons Attribution License
Cytotoxic Effect of Poly-Dispersed Single Walled Carbon Nanotubes on Erythrocytes In Vitro and In Vivo
Single wall Carbon Nanotubes (SWCNTs) are hydrophobic and do not disperse in aqueous solvents. Acid functionalization of SWCNTs results in attachment of carboxy and sulfonate groups to carbon atoms and the resulting acid functionalized product (AF-SWCNTs) is negatively charged and disperses easily in water and buffers. In the present study, effect of AF-SWCNTs on blood erythrocytes was examined. Incubation of mouse erythrocytes with AF-SWCNTs and not with control SWCNTs, resulted in a dose and time dependent lysis of erythrocyte. Using fluorescence tagged AF-SWCNTs, binding of AF-SWCNTs with erythrocytes could be demonstrated. Confocal microscopy results indicated that AF-SWCNTs could enter the erythrocytes. Treatment with AF-SWCNTs resulted in exposure of hydrophobic patches on erythrocyte membrane that is indicative of membrane damage. A time and dose dependent increase in externalization of phosphatidylserine on erythrocyte membrane bilayer was also found. Administration of AF-SWCNTs through intravenous route resulted in a transient anemia as seen by a sharp decline in blood erythrocyte count accompanied with a significant drop in blood haemoglobin level. Administration of AF-SWCNTs through intratracheal administration also showed significant decline in RBC count while administration through other routes (gavage and intra-peritoneal) was not effective. By using a recently developed technique of a two step in vivo biotinylation of erythrocytes that enables simultaneous enumeration of young (age <10 days) and old (age>40 days) erythrocytes in mouse blood, it was found that the in vivo toxic effect of AF-SWCNTs was more pronounced on older subpopulation of erythrocytes. Subpopulation of old erythrocytes fell after treatment with AF-SWCNTs but recovered by third day after the intravenous administration of AF-SWCNTs. Taken together our results indicate that treatment with AF-SWCNTs results in acute membrane damage and eventual lysis of erythrocytes. Intravenous administration of AF-SWCNTs resulted in a transient anemia in which older erythrocytes are preferably lysed
Fabrication Materials for a Closed Cycle Brayton Turbine Wheel
A multidisciplinary analysis of a radial inflow turbine rotor is presented. This work couples high-fidelity fluid, structural, and thermal simulations in a seamless multidisciplinary analysis to investigate the consequences of material selection. This analysis extends multidisciplinary techniques previously demonstrated on rocket turbopumps and hypersonic engines. Since no design information is available for the anticipated Brayton rotating machinery, an existing rotor design (the Brayton Rotating Unit (BRU)) was used in the analysis. Steady state analysis results of a notional turbine rotor indicate that stress levels are easily manageable at the turbine inlet temperature, and stress levels anticipated using either superalloys or ceramics
Temperature and terahertz frequency dependence of the dielectric properties of Fe3O4 thin films deposited on Si substrate
The FeO/Si films are considered to be promising materials for THz
spintronic applications due to their high temperature magnetic transition and
semiconducting properties. In this article, we present the real part of the
dielectric constant () and the optical conductivity () of
FeO films of different thicknesses deposited on Si substrate
(FeO/Si) in the THz range at temperatures 2- 300 K. Although the
magnetization of the films with thickness 115 nm shows a clear change at
the Verwey transition temperature T = 121 K, their optical properties in
the THz frequency range are drastically different from each other. We have
shown that is maximum and is minimum when the
Fe/Fe ratio is equal to 0.54 which is the ratio of Fe+2/Fe+3 for
pure FeO. The reduces and increases at all
temperatures when the Fe/Fe ratio deviates from 0.54. We have
shown that a slight change in the Fe/Fe ratio can induce large
changes in the optical properties which shall have implications in the
application of the Fe3O4 films in THz spintronics.Comment: 18 pages, 6 figure
Spectroscopic Evidence for the Localization of Skyrmions near Nu=1 as T->0
Optically pumped nuclear magnetic resonance measurements of Ga-71 spectra
were carried out in an n-doped GaAs/Al0.1Ga0.9As multiple quantum well sample
near the integer quantum Hall ground state Nu=1. As the temperature is lowered
(down to T~0.3 K), a ``tilted plateau'' emerges in the Knight shift data, which
is a novel experimental signature of quasiparticle localization. The dependence
of the spectra on both T and Nu suggests that the localization is a collective
process. The frozen limit spectra appear to rule out a 2D lattice of
conventional skyrmions.Comment: 4 pages (REVTEX), 5 eps figures embedded in text, published versio
Skyrmion Dynamics and NMR Line Shapes in QHE Ferromagnets
The low energy charged excitations in quantum Hall ferromagnets are
topological defects in the spin orientation known as skyrmions. Recent
experimental studies on nuclear magnetic resonance spectral line shapes in
quantum well heterostructures show a transition from a motionally narrowed to a
broader `frozen' line shape as the temperature is lowered at fixed filling
factor. We present a skyrmion diffusion model that describes the experimental
observations qualitatively and shows a time scale of for
the transport relaxation time of the skyrmions. The transition is characterized
by an intermediate time regime that we demonstrate is weakly sensitive to the
dynamics of the charged spin texture excitations and the sub-band electronic
wave functions within our model. We also show that the spectral line shape is
very sensitive to the nuclear polarization profile along the z-axis obtained
through the optical pumping technique.Comment: 6 pages, 4 figure
Electrically-Controlled Nuclear Spin Polarization and Relaxation by Quantum-Hall states
We investigate interactions between electrons and nuclear spins by using the
resistance (Rxx) peak which develops near filling factor n = 2/3 as a probe. By
temporarily tuning n to a different value, ntemp, with a gate, the Rxx peak is
shown to relax quickly on both sides of ntemp = 1. This is due to enhanced
nuclear spin relaxation by Skyrmions, and demonstrates the dominant role of
nuclear spin in the transport anomaly near n = 2/3. We also observe an
additional enhancement in the nuclear spin relaxation around n = 1/2 and 3/2,
which suggests a Fermi sea of partially-polarized composite fermions.Comment: 6 pages, 3 figure
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