Texas A & iversity at Qatar

Doha, United States

Texas A & iversity at Qatar

Doha, United States
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Anoop K.,Thermo Fluids | Sadr R.,Thermo Fluids | Yrac R.,Texas A & iversity at Qatar | Amani M.,Texas A & iversity at Qatar
Powder Technology | Year: 2016

The effect of high-pressure on the rheological characteristics of alumina-silicone oil nanofluids at room temperature is investigated in this paper. Nanofluids are engineered colloidal suspensions of nano-sized particles dispersed in a basefluid. The rheological characteristics of nanofluids are studied with pressures up to 100 MPa and particle concentrations up to 8% by mass using a high-pressure viscometer. The addition of nanoparticles is observed to increase the apparent viscosity of the nanofluids. A non-Newtonian, shear-thinning behavior is observed for both the basefluid and the nanofluids at all pressures at the higher shear rates. The critical shear rate at which shear thinning occurs is observed to be strongly influenced by particle addition. An increase in the pressure is observed to have an equal effect on the basefluid and on the nanofluids, which results in an average pressure-viscosity coefficient for both to be approximately 0.015 mm2/N. The relative increase in the viscosity of the nanofluid to that of the basefluid was not affected by the pressure and was several orders higher than that predicted by the classical effective medium theory. © 2016

Koizumi H.,University of Tsukuba | Okazaki A.,University of Tsukuba | Ghantous M.A.,Texas A & iversity at Qatar | Tachiki M.,Tohoku University
Journal of Superconductivity and Novel Magnetism | Year: 2014

We propose a novel supercurrent generation mechanism in the cuprate. The supercurrent is generated as a collection of the spin-vortex-induced loop currents created with the doped holes at their centers. A quartet of the spin-vortices with width 4a (a is the lattice constant of the CuO2 plane) is the stable unit of the spin-vortices, and an assembly of them creates a network channel for the supercurrent flow. A macroscopic supercurrent flows when they cover the whole CuO2 plane. The Ginzburg-Landau macroscopic wave function formalism is also derived from the present supercurrent generation mechanism. © 2014, Springer Science+Business Media New York.

Wang X.,Southwest University | Wang H.,Chongqing Normal University | Li C.,Southwest University | Huang T.,Texas A & iversity at Qatar
Nonlinear Dynamics | Year: 2016

Synchronization of coupled delayed switched neural networks (DSNNs) with impulsive time window is one of the most challenging problems in the field of complex networks. In this paper, some sufficient conditions ensuring the synchronization of coupled DSNNs with all subsystems self-synchronizing are presented. Then this results are extended to the following two cases: all subsystems are desynchronizing and some of subsystems are self-synchronizing. By applying switching Lyapunov function method, some general criteria which characterize the impulse and switching effects in aggregated form are given. Moreover, from our results, one can easily observes that the impulsive time window control strategy is more general and more applicable than the fixed impulses controllers. Finally, numerical simulations are presented to further demonstrate the effectiveness of the proposed results. © 2016 Springer Science+Business Media Dordrecht

Wang X.,Chongqing University | Li C.,Chongqing University | Huang T.,Texas A & iversity at Qatar | Pan X.,Liuzhou Teachers College
Nonlinear Dynamics | Year: 2014

In this paper, the issue on impulsive control and synchronization of nonlinear system with impulse time window are investigated. The considered impulsive effects can be stochastically occurred at a determined time window. Hence, the impulses here can be more general and more applicable than the fixed impulses. Some novel and easy-to-check criteria with impulse time window are obtained to guarantee the impulsive control and synchronization global asymptotical stable. Especially, on the basis of the our analysis, we only choose an efficient impulse time window instead of choosing fixed-impulse sequences. Finally, the simulation results further demonstrate the effectiveness of our theoretical results. © 2014, Springer Science+Business Media Dordrecht.

He X.,Southwest University | Li C.,Southwest University | Huang T.,Texas A & iversity at Qatar | Yu J.,CAS Institute of Automation
Science China Technological Sciences | Year: 2016

This paper presents an Euler discretized inertial delayed neuron model, and its bifurcation dynamical behaviors are discussed. By using the associated characteristic model, center manifold theorem and the normal form method, it is shown that the model not only undergoes codimension one (flip, Neimark-Sacker) bifurcation, but also undergoes cusp and resonance bifurcation (1:1 and 1:2) of codimension two. Further, it is found that the parity of delay has some effect on bifurcation behaviors. Finally, some numerical simulations are given to support the analytic results and explore complex dynamics, such as periodic orbits near homoclinic orbits, quasiperiodic orbits, and chaotic orbits. © 2016 Science China Press and Springer-Verlag Berlin Heidelberg

Lee E.,Worcester Polytechnic Institute | Ryu J.,Pusan National University | Jeon S.,Pusan National University | Mishra B.,Worcester Polytechnic Institute | Palmer B.R.,Texas A & iversity at Qatar
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2016

The mechanical and corrosion properties of air/water-quenched CN66 (0.28/0.38 wt pct, C/N) and CN71 (0.27/0.44 wt pct, C/N) steels after heat treatment were investigated. The carbon condensed area of the water-quenched alloys decreased compared with the air-cooled alloys, and lattice expansions occurred, resulting in a strained region. The values of UTS and elongation of water-quenched CN71 were increased as 105 MPa and 25.2 pct compared with the air-cooled CN71, and decreased sour corrosion resistance (1.8 × 10−4 mm/year). © 2016 The Minerals, Metals & Materials Society and ASM International

PubMed | Hubei Normal University, Texas A & iversity at Qatar and Huazhong University of Science and Technology
Type: | Journal: Neural networks : the official journal of the International Neural Network Society | Year: 2016

Neurodynamic system is an emerging research field. To understand the essential motivational representations of neural activity, neurodynamics is an important question in cognitive system research. This paper is to investigate Mittag-Leffler stability of a class of fractional-order neural networks in the presence of generalized piecewise constant arguments. To identify neural types of computational principles in mathematical and computational analysis, the existence and uniqueness of the solution of neurodynamic system is the first prerequisite. We prove that the existence and uniqueness of the solution of the network holds when some conditions are satisfied. In addition, self-active neurodynamic system demands stable internal dynamical states (equilibria). The main emphasis will be then on several sufficient conditions to guarantee a unique equilibrium point. Furthermore, to provide deeper explanations of neurodynamic process, Mittag-Leffler stability is studied in detail. The established results are based on the theories of fractional differential equation and differential equation with generalized piecewise constant arguments. The derived criteria improve and extend the existing related results.

PubMed | University of Hong Kong, Texas A & iversity at Qatar and Huazhong University of Science and Technology
Type: | Journal: Neural networks : the official journal of the International Neural Network Society | Year: 2016

This paper investigates the problem of global exponential anti-synchronization of a class of switched neural networks with time-varying delays and lag signals. Considering the packed circuits, the controller is dependent on the output of the system as the inner states are very hard to measure. Therefore, it is necessary to investigate the controller based on the output of the neuron cell. Through theoretical analysis, it is obvious that the obtained ones improve and generalize the results derived in the previous literature. To illustrate the effectiveness, a simulation example with applications in image encryptions is also presented in the paper.

PubMed | University of Sydney, King Abdulaziz University, University of the Southwest, Texas A & iversity at Qatar and Southwest University
Type: | Journal: Neural networks : the official journal of the International Neural Network Society | Year: 2015

In this paper, we present an asynchronous algorithm to estimate the unknown parameter under an unreliable network which allows new sensors to join and old sensors to leave, and can tolerate link failures. Each sensor has access to partially informative measurements when it is awakened. In addition, the proposed algorithm can avoid the interference among messages and effectively reduce the accumulated measurement and quantization errors. Based on the theory of stochastic approximation, we prove that our proposed algorithm almost surely converges to the unknown parameter. Finally, we present a numerical example to assess the performance and the communication cost of the algorithm.

PubMed | University of Belgrade, University of New Orleans, Texas A & iversity at Qatar and Studentski trg 12 16
Type: Journal Article | Journal: Chemphyschem : a European journal of chemical physics and physical chemistry | Year: 2016

The hydrogen bonding of noncoordinated water molecules to each other and to water molecules that are coordinated to metal-ion complexes has been investigated by means of a search of the Cambridge Structural Database (CSD) and through quantum chemical calculations. Tetrahedral and octahedral complexes that were both charged and neutral were studied. A general conclusion is that hydrogen bonds between noncoordinated water and coordinated water are much stronger than those between noncoordinated waters, whereas hydrogen bonds of water molecule in tetrahedral complexes are stronger than in octahedral complexes. We examined the possibility of correlating the computed interaction energies with the most positive electrostatic potentials on the interacting hydrogen atoms prior to interaction and obtained very good correlation. This study illustrates the fact that electrostatic potentials computed for ground-state molecules, prior to interaction, can provide considerable insight into the interactions.

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