The study of non-Newtonian nanofluid with hall and ion slip effects on peristaltically induced motion in a non-uniform channel

In this study, we considered the unsteady peristaltic motion of a non-Newtonian nanofluid under the influence of a magnetic field and Hall currents. The simultaneous effects of ion slip and chemical reaction were also taken into consideration. The flow problem was suggested on the basis of the continuity, thermal energy, linear momentum, and nanoparticle concentration, which were further reduced with the help of Ohm's law. Mathematical modelling was executed using the lubrication approach. The resulting highly nonlinear partial differential equations were solved semi-analytically using the homotopy perturbation technique. The impacts of all the pertinent parameters were investigated mathematically and graphically. Numerical calculations have been used to calculate the expressions for the pressure increase and friction forces along the whole length of the channel. The results depict that for a relatively large value of the Brownian parameter, the chemical reaction has a dual behaviour on the concentration profile. Moreover, there is a critical point of the magnetic parameter at which the behaviours of the pressure increase and friction forces are reversed for progressive values of the power law index. The present investigation provides a theoretical model that estimates the impact of a wide range of parameters on the characteristics of blood-like fluid flows

Electro-absorption of silicene and bilayer graphene quantum dots

We study numerically the optical properties of low-buckled silicene and AB-stacked bilayer graphene quantum dots subjected to an external electric field, which is normal to their surface. Within the tight-binding model, the optical absorption is calculated for quantum dots, of triangular and hexagonal shapes, with zigzag and armchair edge terminations. We show that in triangular silicene clusters with zigzag edges a rich and widely tunable infrared absorption peak structure originates from transitions involving zero energy states. The edge of absorption in silicene quantum dots undergoes red shift in the external electric field for triangular clusters, whereas blue shift takes place for hexagonal ones. In small clusters of bilayer graphene with zigzag edges the edge of absorption undergoes blue/red shift for triangular/hexagonal geometry. In armchair clusters of silicene blue shift of the absorption edge takes place for both cluster shapes, while red shift is inherent for both shapes of the bilayer graphene quantum dots.Comment: 7 pages, 7 figure

Causal Relationship Modeling of the Implicit Theories of Emotion and Emotion Regulation in View of the Cognitive Reappraisal Strategy and Happiness

The purpose of this study was to unveil the causal relationship modeling of the implicit theories of emotion and emotion regulation in view of cognitive reappraisal strategy and happiness for the students of the Jordanian University of Science and Technology (JUST). Based on scientific foundations, the study has constructed a proposed causal relationship model using path analysis for interpreting happiness. To achieve this goal, the emotion regulation, by Gross and John (2003), the implicit theories of emotion Scale of Livingstone, (2012), and the Oxford Happiness Inventory were employed. The sample consisted of 350 students who were chosen on availability grounds. The results of the study showed no statistically significant differences between the proposed and the optimal causal relationship models due to high matches on: AGFI=0.90, NFI=0.98, GFI=0.99, TLI =0.933, CFI=0.99, RMR=0.022. Thus, the model explained the relationships proposed and represented the optimal causal relationship model for the variables of the study

Current source back to back converter for wind energy conversion systems

This paper proposes a new back-to-back current source converter (BTB-CSC) suitable for mediumvoltage high power wind energy conversion systems (WECS). It employs a dual three-phase permanent magnet synchronous generator and two current source inverters with a phase-shift transformer at the grid side. The proposed BTB-CSC has the following advantages: reduced power circuit and control complexity; low switching losses (zero switching losses at the inverter side); and independent control of active and reactive power. PSCAD/EMTDC simulations are used as to assess the steady-state and dynamic behaviour of the proposed system under different operating conditions. It is shown that the proposed WECS can ride-through ac faults. Experimental results from scaled prototype of the proposed WECS are used to validate the simulations

Solitary and blow-up electrostatic excitations in rotating magnetized electron-positron-ion plasmas

The nonlinear dynamics of a rotating magnetoplasma consisting of electrons, positrons and stationary positive ions is considered. The basic set of hydrodynamic and Poisson equations are reduced to a Zakharov-Kuznetsov (ZK) equation for the electric potential. The ZK equation is solved by applying an improved modified extended tanh-function method (2008 Phys. Lett. A 372 5691) and its characteristics are investigated. A set of new solutions are derived, including localized solitary waves, periodic nonlinear waveforms and divergent (explosive) pulses. The characteristics of these nonlinear excitations are investigated in detail

The study of non-Newtonian nanofluid with hall and ion slip effects on peristaltically induced motion in a non-uniform channel

In this study, we considered the unsteady peristaltic motion of a non-Newtonian nanofluid under the influence of a magnetic field and Hall currents. The simultaneous effects of ion slip and chemical reaction were also taken into consideration. The flow problem was suggested on the basis of the continuity, thermal energy, linear momentum, and nanoparticle concentration, which were further reduced with the help of Ohm's law. Mathematical modelling was executed using the lubrication approach. The resulting highly nonlinear partial differential equations were solved semi-analytically using the homotopy perturbation technique. The impacts of all the pertinent parameters were investigated mathematically and graphically. Numerical calculations have been used to calculate the expressions for the pressure increase and friction forces along the whole length of the channel. The results depict that for a relatively large value of the Brownian parameter, the chemical reaction has a dual behaviour on the concentration profile. Moreover, there is a critical point of the magnetic parameter at which the behaviours of the pressure increase and friction forces are reversed for progressive values of the power law index. The present investigation provides a theoretical model that estimates the impact of a wide range of parameters on the characteristics of blood-like fluid flows

Electronic and magnetic properties of graphite quantum dots

We study the electronic and magnetic properties of multilayer quantum dots (MQDs) of graphite in the nearest-neighbor approximation of tight-binding model. We calculate the electronic density of states and orbital susceptibility of the system as function of the Fermi level location. We demonstrate that properties of MQD depend strongly on the shape of the system, on the parity of the layer number and on the form of the cluster edge. The special emphasis is given to reveal the new properties with respect to the monolayer graphene quantum dots. The most interesting results are obtained for the triangular MQD with zig-zag edge at near-zero energies. The asymmetrically smeared multipeak feature is observed at Dirac point within the size-quantized energy gap region, where monolayer graphene flakes demonstrate the highly-degenerate zero-energy state. This feature, provided by the edge-localized electronic states results in the splash-wavelet behavior in diamagnetic orbital susceptibility as function of energy

Structural, Magnetic and Electrical Properties of Co-Doped Barium Monoferrite BaFe2O4

Cobalt-substituted barium monoferrite with theformula BaCoxFe2-xO4 (x = 0.0 – 0.4, step 0.1) has been preparedthrough the sol-gel autocombustion method. Phase purity forprepared samples sintered at 700 and 1050 ̊C was analyzed byX-ray diffraction (XRD) patterns that indicated the formationof the typical orthorhombic phase for the samples. Fouriertransforminfrared (FTIR) spectroscopy was used to investigatethe effect of cobalt doping on the vibrational modes of thestudied samples. Scherrer and Williamson-Hall formulae wereused to define the microstrian and the crystallite size being inthe range of 44.1 to 59.7 nm, which was further confirmed withtransmission electron microscopy (TEM) images. Magneticcharacteristics including magnetic saturation and coercivitywere obtained from hysteresis loops traced using vibratingsample magnetometry (VSM). Magnetic properties werecorrelated with the composition of the prepared samples.Finally, dielectric measurements were operated to furtherconfirm the structural and magnetic analysis

Análisis de la interacción ventrículo-valvulo-arterial en pacientes con estenosis aórtica

La estenosis aórtica es probablemente la valvulopatía más importante en el mundo occidental, debido a su alta prevalencia y al grave impacto que tiene sobre la calidad y esperanza de vida de las personas que la padecen, de modo que la supervivencia en los pacientes sintomáticos es de aproximadamente un 50% a dos años. Durante décadas, la sustitución valvular quirúrgica ha sido la única opción de tratamiento con capacidad para modificar el pronóstico de la estenosis aórtica, y sin embargo, un 30% de los pacientes con estenosis aórtica severa sintomática no son operados por diversos motivos. En los últimos años, la sustitución valvular aórtica con catéter (TAVI) ha surgido como una opción de tratamiento para pacientes inoperables y de alto riesgo quirúrgico. La TAVI es superior al tratamiento farmacológico, reduciendo la mortalidad y mejorando los síntomas; además, en pacientes de alto riesgo quirúrgico, la TAVI tiene resultados al menos tan buenos como la cirugía. En la última década se ha producido un gran avance en los dispositivos y técnicas disponibles para TAVI, lo que ha contribuido a mejorar los resultados y reducir las complicaciones. La oposición al flujo sistólico en la estenosis aórtica viene determinada por la suma de la obstrucción valvular y la carga vascular. Esta última a menudo se encuentra anormalmente alta en la estenosis aórtica, debido a la hipertensión arterial y a la alta prevalencia de enfermedad vascular sistémica que presentan estos pacientes, lo que contribuye de forma importante a la postcarga total del ventrículo izquierdo. Además, entre la obstrucción valvular y la carga vascular existe un fenómeno de interdependencia, de forma que al reducir uno de los componentes aumenta el otro, y a la inversa..