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Equilibration of quantum Hall edges in symmetry-broken bilayer graphene
No full textEquilibration of quantum Hall edges is studied in a high quality dual gated bilayer graphene device in both unipolar and bipolar regimes when all the degeneracies of the zero energy Landau level are completely lifted. We find that in the unipolar regime when the filling factor under the top gate region is higher than the back gate filling factor, the equilibration is partial based on their spin polarization. However, the mixing of the edge states in the bipolar regime is insensitive to the spin configurations of the Landau levels and the values are very close to the full equilibration prediction. This has been explained by Landau level collapsing at the sharp p-n junction in our thin hBN (similar to 15 nm) encapsulated device, in consistent with the existing theory
Synthesis of phase pure vanadium dioxide (VO2) thin film by reactive pulsed laser deposition
No full textThin films of phase pure VO2 (M1 phase) are deposited on thermally grown oxide (Si/SiO2) substrate by reactive pulsed laser deposition of vanadium metal target. The influence of deposition parameters is studied by varying oxygen partial pressure while keeping other parameters constant. A thin film obtained at 50 mTorr is found to be phase pure by XRD and Raman spectral studies. SEM and AFM studies show smooth morphology with a surface roughness of 3-5 nm. The quality of the thin film was further established by characterizing the 68 degrees C (T-SMT) transition by 2-3 orders of jump in resistance and a 60% change in reflectivity with minimum hysteresis. This single step process of deposition would be a suitable method for fabricating devices for smart window and metamaterial applications. Published by AIP Publishing
Novel Sensor Scheduling Scheme for Intruder Tracking in Energy Efficient Sensor Networks
No full textWe consider the problem of tracking an intruder using a network of wireless sensors. For tracking the intruder at each instant, the optimal number and the right configuration of sensors has to be powered. As powering the sensors consumes energy, there is a trade off between accurately tracking the position of the intruder at each instant and the energy consumption of sensors. This problem has been formulated in the framework of partially observable Markov decision process (POMDP). Even for the state-of-the-art algorithm in the literature, the curse of dimensionality renders the problem intractable. In this letter, we formulate the intrusion detection (ID) problem with a suitable state-action space in the framework of POMDP and develop a reinforcement learning algorithm utilizing the upper confidence tree search method to solve the ID problem. Through simulations, we show that our algorithm performs and scales well with the increasing state and action spaces
Effects of Cu and In Trace Elements on Microstructure and Thermal and Mechanical Properties of Sn-Zn Eutectic Alloy
No full textThe effects of addition of small amounts of copper (Cu) and indium (In) on the microstructure and thermal and mechanical properties of Sn-Zn eutectic alloy have been investigated. Cu and In were added in varying amounts to Sn-14.9at.%Zn alloy by replacing an equal amount of Sn. Addition of Cu changed the eutectic composition, leading to the appearance of primary phases followed by the formation of intermetallic compounds (IMC) CuZn5 and Cu5Zn8. However, addition of indium (In) did not lead to formation of any new IMCs. With addition of Cu or In to the binary eutectic, the eutectic microstructure coarsened (the eutectic spacing increased). Addition of 1.919at.% indium decreased the Sn-Zn eutectic temperature from 198.8 degrees C to 192.0 degrees C. On the other hand, addition of Cu did not affect the eutectic temperature as much as In addition did. The mushy (or pasty) range (the temperature range between the eutectic temperature and the melting temperature of the primary phase) increased with addition of Cu or In. Addition of a small amount of copper increased the yield strength of the binary eutectic alloy. The maximum hardness and yield strength of 24 +/- 2HV and 60 +/- 3MPa, respectively, were found with addition of 0.841at.% Cu; this improvement in strength can be attributed to formation of hard IMCs. In contrast, addition of a small amount of In initially decreased the strength, but the strength increased to 50 MPa at 1.919at.% In. This can be attributed to the effect of solid-solution strengthening due to the In solute in soft beta-Sn
Encoding of quantum stabilizer codes over qudits with d = p(k)
No full textStabilizer codes over qudits have been widely studied but their encoding procedures have not been investigated in detail by many. The encoding procedure proposed previously by Grassi et al. generates the stabilizer codes over qudits for prime d, while it may only generate a subspace of the codespace over qudits where d is a power of a prime. In this paper, we propose an encoding procedure to generate the stabilizer codes over qudits for d being a power of a prime. The procedure involves reducing the problem of encoding over qudits with d = p(k) to a problem similar to encoding over qudits with d = p
THE SOLID FINE PRECIPITATES BEHAVIOUR IN FESICR SOLUTION DURING LADLE RAFINATION
No full textPossibility of FeSiCr alloys production, with low content of carbon, in industrial conditions depends upon various factors like temperature of the solution, refining time, chemical compositions and others. In order to identify the evolution and behavior of solid inclusions in the solution, laboratory tests for alloys at high temperatures of 1400-1500 degrees C have been carried out. For identifying the trajectory of inclusions, numerical simulations, in industrial conditions, have been performed for velocity and temperature distribution in a ladle furnace. Microscopy identification of selected inclusions, important from industrial refining viewpoint, has also been performed. The paper summarizes results of theoretical calculations and laboratory tests for ultra low carbon (ULC) FeSiCr alloys
A Mixed E-B Finite Element Formulation for the analysis of Periodic Structures
No full textThe analysis of periodic structures with the Finite Element Method (FEM) has received a lot of attention in recent years. FEM formulates Maxwell's curl equations as either a second-order wave equation or two dual first-order (mixed) equations. Up until now the analysis of the periodic structures was primarily restricted to using the second-order wave equation. In this work, a new mixed vector finite element method for solving the coupled Maxwell's equations for the periodic boundary condition is presented. The mixed-order formulation gives a higher accuracy compared to the second-order for the same number of mesh elements. Numerical experiments are performed to validate the new formulation with analytical and commercial methods
Subband Weighting for Binaural Speech Source Localization
No full textWe consider the task of speech source localization from a binaural recording using interaural time difference (ITD). A typical approach is to process binaural speech using gammatone filters and calculate frame-level ITD in each subband. The ITDs in each gammatone subband are statistically modelled using Gaussian mixture models (GMMs) for every direction during training. Given a binaural test-speech, the source is localized using maximum likelihood (ML) criterion. In this work, we propose a subband weighting scheme where subband likelihoods are weighted based on their reliability. We measure the reliability of a subband using the average frame level localization error obtained for the respective subbands. These reliability values are used as the weights for each subband likelihood prior to combining the likelihoods for ML estimation. We also introduce non-linear warping of these weights to accommodate and analyse a larger space of possible subband weights. Experiments on Subject_003 from the CIPIC database reveal that weighting the subbands is better than the unweighted scheme of combining likelihoods
Impact of Undercompensation and Overcompensation of Dead-Time Effect on Small-Signal Stability of Induction Motor Drive
No full textInverter dead-time is known to make open-loop induction motor drives oscillatory, while operating at light-loads in particular. While dead-time compensation schemes exist, precise compensation of the same is often challenging as it involves factors such as device and driver delays and switching transition times, which are difficult to be quantified accurately. Hence, the effect of dead-time could be under or overcompensated. This paper presents a comprehensive analysis of the impact of such undercompensation and overcompensation on the stability of a 100-kW induction motor drive, along with experimental investigations of the same. The effects of undercompensation and overcompensation on the inverter output voltage are analyzed on a switching-cycle average basis. Further, small-signal models are proposed for an open-loop drive, when it is undercompensated and overcompensated. Stability analysis of the above motor drive is reported, which predicts oscillatory behavior with both under and overcompensation, over certain fundamental frequency ranges, respectively. Further, two different types of oscillatory behavior, characterized by different oscillating frequencies, are observed for the cases of under and overcompensation. The analyses are supported by simulations. Experimental investigations carried out also support the analyses and simulation results
Borocarbonitride, (BN)(x)(C)(1-x,) nanosheet-reinforced polymer nanocomposites for high mechanical performance
No full textThe enhancement in mechanical and thermal properties of polymer matrices upon reinforcing with nanoparticles strongly depends on the extent of molecular-level interactions and interfacial adhesion between the nanofiller and the matrix material, which are, in turn, governed by the surface functionalities on the nanofiller. Herein, we examine the reinforcing effect of nanosheets of borocarbonitide, (BN)(x)(C)(1-x) , which are analogues to graphene (x = 0) and boron nitride sheets (x = 1), whose surface functional groups vary with the composition, on the mechanical and thermal properties of poly(vinyl alcohol), PVA. Results show that substantial improvement in hardness and elastic modulus of PVA is achieved by adding just 0.2 wt% of BCN. A significant enhancement in the thermal stability was also noted. These results are rationalized by recourse to detailed structural characterization, which shows a substantial enhancement in the degree of crystallinity in PVA upon BCN addition, and improved interfacial adhesion between the nanofiller and the polymer matrix via strong intermolecular interactions. Overall, our results show that it is possible to engineer polymer matrix nanocomposites with exceptional mechanical and thermal properties via the addition of a small amount of BCN. (C) 2018 Elsevier Ltd. All rights reserved