Indirect rotor field orientation vector control for induction motor drives in the absence of current sensors

Author name used in this publication: S. L. HoVersion of RecordPublishe

Aharonov-Bohm effect induced by mutual inductance for an array of mesoscopic rings

The effect of mutual inductance on the persistent currents in N mesoscopic rings placed periodically on a plane is investigated. The persistent currents for the situations with mutual inductance between the nearest-neighbor rings are calculaed in detail. We find that while the self-inductance suppresses the persistent current, the effect of the mutual inductance is to enhance it. For example, for a metal ring (Au or Cu) of length L0=1 μm and cross-section A=0.02×0.02 μm2, the persistent current due to the self-inductance is IL=0.2I0 where I0 is the persistent current without the self-inductance. For a pair of rings, the contribution of the persistent current due to the mutual inductance is about 10%. The results can be understood as entirely due to self-consistency of the equilibrium properties in the nanostructure.published_or_final_versio

Influence of ferromagnetic spin waves on persistent currents in one-dimensional mesoscopic rings

The influence of the electron-magnon and the electron-phonon interactions on the persistent current in a one-dimensional mesoscopic ring is studied. We show that, due to the electron-magnon interaction, the amplitude of the persistent current is exponentially reduced compared to the free case. Two features occur in the presence of an electron-phonon interaction. For the normal state of electrons, the persistent current is weakened by the Debye-Waller factor. Considering the so-called Peierls distortions, we show that the effect of the Peierls instability on the amplitude of the persistent current (i.e., the oscillation with respect to the flux) is suppressed significantly and the persistent current will be practically undetectable in the case of a wide-gap Peierls material. © 1996 The American Physical Society.published_or_final_versio

Gender differences in anthropometric data and in blood pressure values after a 10 weeks training program

Purpose: The prevalence of overweight and obesity and the and incidence of non-communicable diseases increased dramatically over the past 20 years in GCC countries includes Qatar (1,2). The early screening and the propagation of the regular physical activity is essen- tial in the country. The aims of the study were: 1. to map the body composition and blood pressure of young Qatari adults (18-30yr), 2. to determine changes in it after a 10 weeks training program. Methods: 158 Qataris were involved to the study [men (n=89), women (n=69)] from Qatar University (QU). We measured systolic (BPS) and diastolic (BPD) blood pressure body high, body weight, % body fat and the regular physical activity (PA) was assessed by IPAQ. Pre-hypertensive/hypertensive and overweight/obese subjects (20 males and 20 females) were selected and involved into the 10 weeks training program (3-5 times/week, 30-60 minutes/session, 55-60% of the HRmax). The training sessions on 3 times/week were guided by an instructor, the other 2 trainings were individually performed by the subjects followed by a written training schedule. Results: 28.3% of males were overweight and 34.8% were obese; where females were 23.2% and 17.4%, respectively. Male subjects had significantly higher BMI values than females (27.38±6.24 vs. 23.24±5.57 p<.001). IPAQ results shown that vigorous, and moderate type activity didn’t differ between genders, but in low intensity PA (walking) females were more active than males 111min/week vs. 88 min/week, p<.001. Males attended frequently on the face-to-face training sessions than females (2.3 vs. 1.45 hours/week, p<0.05). The 10 weeks training program induced significant reduction in BDP (78.00±6.06 vs. 74.81±10.2 mmHg, p<0.05), BW (91.12±16.31 vs. 85.2±15.28 kg, p<0.01), %BF (31.15±9.0 vs. 21.19±4.38 p<0.01), in male subjects but we couldn’t established these differences in females. Discussion: The used intervention induced substantial changes in most of the meas- ured parameters in males. The total PA in both genders was far away from the recommendation so it is crucial to pay attention its benefi- cial effects. Because the PA social image is differ in Qatar than in other Western countries to maintain the motivation, the suitable duration and the intensity of the PA, continuous control by a sports expert seems to be effective.This study was made possible by a UREP award [UREP 12-048-3-009] from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors

Solar influenced late Holocene temperature changes on the northern Tibetan Plateau

Considerable efforts have been made to extend temperature records beyond the instrumental period through proxy reconstructions, in order to further understand the mechanisms of past climate variability. Yet, the global coverage of existing temperature records is still limited, especially for some key regions like the Tibetan Plateau and for earlier times including the Medieval Warm Period (MWP). Here we present decadally-resolved, alkenone-based, temperature records from two lakes on the northern Tibetan Plateau. Characterized by marked temperature variability, our records provide evidence that temperatures during the MWP were slightly higher than the modern period in this region. Further, our temperature reconstructions, within age uncertainty, can be well correlated with solar irradiance changes, suggesting a possible link between solar forcing and natural climate variability, at least on the northern Tibetan Plateau. © 2013 The Author(s).published_or_final_versio

Collectivity evolution in the neutron-rich Pd isotopes towards the N=82 shell closure

The neutron-rich, even-even 122,124,126Pd isotopes has been studied via in-beam gamma-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory. Excited states at 499(9), 590(11), and 686(17) keV were found in the three isotopes, which we assign to the respective 2+ -> 0+ decays. In addition, a candidate for the 4+ state at 1164(20) keV was observed in 122Pd. The resulting Ex(2+) systematics are essentially similar to those of the Xe (Z=54) isotopic chain and theoretical prediction by IBM-2, suggesting no serious shell quenching in the Pd isotopes in the vicinity of N=82

Ising-like dynamical signatures and the end-point of the QCD transition line

An increase in the size of coherent domains in the one component $\Phi^4$ field theory under the influence of a uniformly changing external magnetic field near the critical end-point $T_{\Phi}=T_c, h_{\Phi}=0$ was proposed recently as an estimate also for the variation of the chiral correlation length of QCD near its respective hypothetical end point in the $T_{QCD}-\mu_{QCD}$ plane. The present detailed numerical investigation of the effective model suggests that passing by the critical QCD end point with realistic rate of temperature change will trigger large amplitude oscillations in the temporal variation of the chiral correlation length. A simple mechanism for producing this phenomenon is suggested.Comment: 10 pages, RevTeX, 5 figures. Version accepted for publication in PR

Facile Synthesis of High Quality Graphene Nanoribbons

Graphene nanoribbons have attracted attention for their novel electronic and spin transport properties1-6, and because nanoribbons less than 10 nm wide have a band gap that can be used to make field effect transistors. However, producing nanoribbons of very high quality, or in high volumes, remains a challenge. Here, we show that pristine few-layer nanoribbons can be produced by unzipping mildly gas-phase oxidized multiwalled carbon nanotube using mechanical sonication in an organic solvent. The nanoribbons exhibit very high quality, with smooth edges (as seen by high-resolution transmission electron microscopy), low ratios of disorder to graphitic Raman bands, and the highest electrical conductance and mobility reported to date (up to 5e2/h and 1500 cm2/Vs for ribbons 10-20 nm in width). Further, at low temperature, the nanoribbons exhibit phase coherent transport and Fabry-Perot interference, suggesting minimal defects and edge roughness. The yield of nanoribbons was ~2% of the starting raw nanotube soot material, which was significantly higher than previous methods capable of producing high quality narrow nanoribbons1. The relatively high yield synthesis of pristine graphene nanoribbons will make these materials easily accessible for a wide range of fundamental and practical applications.Comment: Nature Nanotechnology in pres

High power picosecond lasers mode locked with carbon based absorbers

2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

SG-VAE: Scene Grammar Variational Autoencoder to generate new indoor scenes

Deep generative models have been used in recent years to learn coherent latent representations in order to synthesize high-quality images. In this work, we propose a neural network to learn a generative model for sampling consistent indoor scene layouts. Our method learns the co-occurrences, and appearance parameters such as shape and pose, for different objects categories through a grammar-based auto-encoder, resulting in a compact and accurate representation for scene layouts. In contrast to existing grammar-based methods with a user-specified grammar, we construct the grammar automatically by extracting a set of production rules on reasoning about object co-occurrences in training data. The extracted grammar is able to represent a scene by an augmented parse tree. The proposed auto-encoder encodes these parse trees to a latent code, and decodes the latent code to a parse tree, thereby ensuring the generated scene is always valid. We experimentally demonstrate that the proposed auto-encoder learns not only to generate valid scenes (i.e. the arrangements and appearances of objects), but it also learns coherent latent representations where nearby latent samples decode to similar scene outputs. The obtained generative model is applicable to several computer vision tasks such as 3D pose and layout estimation from RGB-D data