Combined Effects of Sequential Velocity and Variable Magnetic Field on the Phase Change Process in a 3D Cylinder Having a Conic-Shaped PCM-Packed Bed System

Effects of sequential velocity and variable magnetic field on the phase change during hybrid nanofluid convection through a 3D cylinder containing a phase-change material packed bed (PCM-PB) system is analyzed with the finite element method. As the heat transfer fluid, 40% ethylene glycol with hybrid TiO2-Al2O3 nanoparticles is considered. Impacts of the sequential velocity parameter (K, between 0.5 and 1.5), geometric factor of the conic-shaped PCM-PB (M, between 0.2 and 0.9), magnetic field strength (Ha number between 0 and 50) and solid volume fraction of hybrid nanoparticles (vol.% between 0.02% and 0.1%) on the phase change dynamics are explored. Effects of both constant and varying magnetic fields on the phase change process were considered. Due to the increased fluid velocity at the walls, the phase change becomes higher with higher values of the sequential velocity parameter (K). There is a 21.6% reduction in phase transition time (tF) between the smallest and highest values of K both in the absence and presence of a constant magnetic field. The value of tF is reduced with higher magnetic field strength and the amount of reduction depends upon the sequential velocity parameter. At K = 1.5, the reduction amount with the highest Ha number is 14.7%, while it is 26% at K = 0.5. When nanoparticle is loaded in the base fluid, the value of tF is further reduced. In the absence of a magnetic field, the amount of phase-transition time reduction is 6.9%, while at Ha = 50, it is 11.7%. The phase change process can be controlled with varying magnetic field parameters as well. As the wave number and amplitude of the varying magnetic field are considered, significant changes in the tF are observed.

Near-occlusion is difficult to diagnose with common carotid ultrasound methods

Purpose To assess the sensitivity and specificity of common carotid ultrasound method for carotid near-occlusion diagnosis. Methods Five hundred forty-eight patients examined with both ultrasound and CTA within 30 days of each other were analyzed. CTA graded by near-occlusion experts was used as reference standard. Low flow velocity, unusual findings, and commonly used flow velocity parameters were analyzed. Results One hundred three near-occlusions, 272 conventional ≥50% stenosis, 162 <50% stenosis, and 11 occlusions were included. Carotid ultrasound was 22% (95%CI 14–30%; 23/103) sensitive and 99% (95%CI 99–100%; 442/445) specific for near-occlusion diagnosis. Near-occlusions overlooked on ultrasound were found misdiagnosed as occlusions (n = 13, 13%), conventional ≥50% stenosis (n = 65, 63%) and < 50% stenosis (n = 2, 2%). No velocity parameter or combination of parameters could identify the 65 near-occlusions mistaken for conventional ≥50% stenoses with >75% sensitivity and specificity. Conclusion Near-occlusion is difficult to diagnose with commonly used carotid ultrasound methods. Improved carotid ultrasound methods are needed if ultrasound is to retain its position as sole preoperative modality.

A REVIEW OF PENETRATION TUNGSTEN BASED PROJECTILE ON DEPTH OF PENETRATION AT ARMOR OF CERAMIC BASED

<p>Nowadays, tungsten-based material is used for the core of projectile, while ceramic-based is used for the main material of armor. Tungsten-based material is chosen because it has density and hardness superior to steel based-material. Meanwhile, the ceramic-based can enhance mobility and resistance penetration of armor. Penetration of projectile on target generates an impact velocity parameter. This velocity has resulted when the projectile hits the target. Therefore, the value of impact velocity affects the quantity of depth of penetration (DoP) result. This paper reviews some papers regarding the penetration of tungsten-based projectile on ceramic-based armor. Furthermore, the content of these papers is reviewed by the narrative review method, and the impact velocity and DoP are the main data to analyze. Through this paper, impact velocity has a linear correlation with the DoP, the big of impact velocity produced bigger of DoP, and vice versa. Based on the data in this review, for the same impact velocity, material, and (almost) dimension of a projectile, SiC has better penetration resistance than B4C, TiB2, and Al2O3. Furthermore, the parameter of projectile dimension, projectile material type, target design, and material composition of the target also affects the DoP result.</p>

Perturbation Analysis of Rivlin-Ericksen Fluid on Heat Transfer in the Presence of Heat Absorption

The problem of visco-elastic Rivlin-Ericksen fluid flow past a semi- infinite vertical plate embedded in a porous medium with variable temperature and suction in the presence of a uniform transverse magnetic field and thermal buoyancy effect is considered. The plate is assumed to move with a constant velocity in the direction of fluid flow while the free stream velocity is assumed to follow the exponentially increasing small perturbation law. Time-dependent wall suction is assumed to occur at the permeable surface. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and non-harmonic functions. Numerical evaluation of the analytical results is performed and some graphical results such as visco-elastic parameter Rm, heat absorption parameter Q, Grashof number Gr, Prandtl number Pr, time t, suction velocity parameter A, moving velocity parameter Up and an exponential parameter ε, for the velocity and temperature profiles within the boundary layer are presented. Skin-friction coefficient, Nusselt numbers are also discussed with the help of the tables.

Nanofluid flow containing carbon nanotubes with quartic autocatalytic chemical reaction and Thompson and Troian slip at the boundary

A mathematical model is envisioned to discourse the impact of Thompson and Troian slip boundary in the carbon nanotubes suspended nanofluid flow near a stagnation point along an expanding/contracting surface. The water is considered as a base fluid and both types of carbon nanotubes i.e., single-wall (SWCNTs) and multi-wall (MWCNTs) are considered. The flow is taken in a Dacry-Forchheimer porous media amalgamated with quartic autocatalysis chemical reaction. Additional impacts added to the novelty of the mathematical model are the heat generation/absorption and buoyancy effect. The dimensionless variables led the envisaged mathematical model to a physical problem. The numerical solution is then found by engaging MATLAB built-in bvp4c function for non-dimensional velocity, temperature, and homogeneous-heterogeneous reactions. The validation of the proposed mathematical model is ascertained by comparing it with a published article in limiting case. An excellent consensus is accomplished in this regard. The behavior of numerous dimensionless flow variables including solid volume fraction, inertia coefficient, velocity ratio parameter, porosity parameter, slip velocity parameter, magnetic parameter, Schmidt number, and strength of homogeneous/heterogeneous reaction parameters are portrayed via graphical illustrations. Computational iterations for surface drag force are tabulated to analyze the impacts at the stretched surface. It is witnessed that the slip velocity parameter enhances the fluid stream velocity and diminishes the surface drag force. Furthermore, the concentration of the nanofluid flow is augmented for higher estimates of quartic autocatalysis chemical.

Effect of magnetized variable thermal conductivity on flow and heat transfer characteristics of unsteady Williamson fluid

A two-dimensional mathematical model of magnetized unsteady incompressible Williamson fluid flow over a sensor surface with variable thermal conductivity and exterior squeezing with viscous dissipation effect is investigated, numerically. Present flow model is developed based on the considered flow geometry. Effect of Lorentz forces on flow behaviour is described in terms of magnetic field and which is accounted in momentum equation. Influence of variable thermal conductivity on heat transfer is considered in the energy equation. Present investigated problem gives the highly complicated nonlinear, unsteady governing flow equations and which are coupled in nature. Owing to the failure of analytical/direct techniques, the considered physical problem is solved by using Runge-Kutta scheme (RK-4) via similarity transformations approach. Graphs and tables are presented to describe the physical behaviour of various control parameters on flow phenomenon. Temperature boundary layer thickens for the amplifying value of Weissenberg parameter and permeable velocity parameter. Velocity profile decreased for the increasing squeezed flow index and permeable velocity parameter. Increasing magnetic number increases the velocity profile. Magnifying squeezed flow index magnifies the magnitude of Nusselt number. Also, RK-4 efficiently solves the highly complicated nonlinear complex equations that are arising in the fluid flow problems. The present results in this article are significantly matching with the published results in the literature.

Construction of Solitary Two-Wave Solutions for a New Two-Mode Version of the Zakharov-Kuznetsov Equation

A new two-mode version of the generalized Zakharov-Kuznetsov equation is derived using Korsunsky’s method. This dynamical model describes the propagation of two-wave solitons moving simultaneously in the same direction with mutual interaction that depends on an embedded phase-velocity parameter. Three different methods are used to obtain exact bell-shaped soliton solutions and singular soliton solutions to the proposed model. Two-dimensional and three-dimensional plots are also provided to illustrate the interaction dynamics of the obtained two-wave exact solutions upon increasing the phase-velocity parameter.

Visual dependence after vestibular rehabilitation by virtual reality in individuals with unilateral peripheral vestibular dysfunction – one year of results

Introduction One of the most common approaches in individuals with unilateral peripheral vestibular dysfunction (UPVD) is vestibular rehabilitation (RV). Many factors can negatively affect the result of RV. Virtual reality based treatment may represent an important tool in the solution of these problems. In individuals with UPVD there is a decrease in the reception of vestibular stimuli and there is an adjustment in the reception of visual and proprioceptive stimuli. They use more visual cues to minimise the decrease in vestibular stimuli – visual dependence (VD). Although the importance and results of virtual reality as a tool in improving balance in individuals with UPVD have already been demonstrated, we intend to demonstrate that virtual reality allows significant improvements in the decrease in VD. Objectives The aim of the study is to compare VD levels in individuals with UPVD after RV program by virtual reality. Methodology For the evaluation of VD, dynamic posturography was performed with the Balance Rehabilition Unit equipment for 39 people with UPVD, before and after the RV program by virtual reality. Ten conditions were tested, with different visual and propriocetive stimuli. The parameters considered were the oscillation area of the pressure centre and the sway velocity. Results In the parameter of the oscillation area of the pressure centre, statistically significant results were found in the 10 conditions tested. In the sway velocity parameter, statistically significant results were found in the condition 1, 2, 3, 4, 5 e 10. Conclusion Virtual reality incorporated in the RV programs presents itself as an important tool in improving VD in individuals with UPVD.