Table of Content

01 September 2020, Volume 41 Issue 9

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Articles

Improving control effects of absence seizures using single-pulse alternately resetting stimulation (SARS) of corticothalamic circuit

Denggui FAN, Yanhong ZHENG, Zecheng YANG, Qingyun WANG

2020, 41(9):  1287-1302.  doi:10.1007/s10483-020-2644-8

Abstract ( 677 )   HTML ( 23)   PDF (2538KB) ( 166 )  

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Presently, we develop a simplified corticothalamic (SCT) model and propose a single-pulse alternately resetting stimulation (SARS) with sequentially applying anodic (A, “+”) or cathodic (C, “-”) phase pulses to the thalamic reticular (RE) nuclei, thalamus-cortex (TC) relay nuclei, and cortical excitatory (EX) neurons, respectively. Abatement effects of ACC-SARS of RE, TC, and EX for the 2 Hz–4 Hz spike and wave discharges (SWD) of absence seizures are then concerned. The m:n on-off ACC-SARS protocol is shown to effectively reduce the SWD with the least current consumption. In particular, when its frequency is out of the 2 Hz–4 Hz SWD dominant rhythm, the desired seizure abatements can be obtained, which can be further improved by our proposed directional steering (DS) stimulation. The dynamical explanations for the SARS induced seizure abatements are lastly given by calculating the averaged mean firing rate (AMFR) of neurons and triggering averaged mean firing rates (TAMFRs) of 2 Hz–4 Hz SWD.

Transverse shear and normal deformation effects on vibration behaviors of functionally graded micro-beams

Zhu SU, Lifeng WANG, Kaipeng SUN, Jie SUN

2020, 41(9):  1303-1320.  doi:10.1007/s10483-020-2662-6

Abstract ( 648 )   HTML ( 11)   PDF (357KB) ( 85 )  

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A quasi-three dimensional model is proposed for the vibration analysis of functionally graded (FG) micro-beams with general boundary conditions based on the modified strain gradient theory. To consider the effects of transverse shear and normal deformations, a general displacement field is achieved by relaxing the assumption of the constant transverse displacement through the thickness. The conventional beam theories including the classical beam theory, the first-order beam theory, and the higherorder beam theory are regarded as the special cases of this model. The material properties changing gradually along the thickness direction are calculated by the Mori-Tanaka scheme. The energy-based formulation is derived by a variational method integrated with the penalty function method, where the Chebyshev orthogonal polynomials are used as the basis function of the displacement variables. The formulation is validated by some comparative examples, and then the parametric studies are conducted to investigate the effects of transverse shear and normal deformations on vibration behaviors.

Dynamic analysis of a deployable/retractable damped cantilever beam

Ming LIU, Zhi LI, Xiaodong YANG, Wei ZHANG, C. W. LIM

2020, 41(9):  1321-1332.  doi:10.1007/s10483-020-2650-6

Abstract ( 696 )   HTML ( 6)   PDF (2429KB) ( 145 )  

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Deployable/retractable damped cantilever beams are a class of time-varying parametric structures which have attracted considerable research interest due to their many potential applications in the intelligent robot field and aerospace. In the present work, the dynamic characteristics of a deployable/retractable damped cantilever beam are investigated experimentally and theoretically. The time-varying damping, as a function of the beam length, is obtained by both the enveloped fitting method and the period decrement method. Furthermore, the governing equation of the deployable/retractable damped cantilever beam is derived by introducing the time-varying damping parameter, and the corresponding closed-form solution and vibration principles are investigated based on the averaged method. The theoretical predictions for transient dynamic responses are in good agreement with the experimental results. The dynamic mechanism analysis on time-varying damping offers flexible technology in mechanical and aerospace fields.

Dynamics of bioconvection flow of micropolar nanoparticles with Cattaneo-Christov expressions

S. A. SHEHZAD, T. MUSHTAQ, Z. ABBAS, A. RAUF, S. U. KHAN, I. TLILI

2020, 41(9):  1333-1344.  doi:10.1007/s10483-020-2645-9

Abstract ( 660 )   HTML ( 4)   PDF (195KB) ( 33 )  

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A numerical analysis is performed to analyze the bioconvective double diffusive micropolar non-Newtonian nanofluid flow caused by stationary porous disks. The consequences of the current flow problem are further extended by incorporating the Brownian and thermophoresis aspects. The energy and mass species equations are developed by utilizing the Cattaneo and Christov model of heat-mass fluxes. The flow equations are converted into an ordinary differential model by employing the appropriate variables. The numerical solution is reported by using the MATLAB builtin bvp4c method. The consequences of engineering parameters on the flow velocity, the concentration, the microorganisms, and the temperature profiles are evaluated graphically. The numerical data for fascinating physical quantities, namely, the motile density number, the local Sherwood number, and the local Nusselt number, are calculated and executed against various parametric values. The microrotation magnitude reduces for increasing magnetic parameters. The intensity of the applied magnetic field may be utilized to reduce the angular rotation which occurs in the lubrication processes, especially in the suspension of flows. On the account of industrial applications, the constituted output can be useful to enhance the energy transport efficacy and microbial fuel cells.

Numerical simulation of MHD natural convection flow in a wavy cavity filled by a hybrid Cu-Al₂O₃-water nanofluid with discrete heating

C. REVNIC, T. GROŞAN, M. SHEREMET, I. POP

2020, 41(9):  1345-1358.  doi:10.1007/s10483-020-2652-8

Abstract ( 810 )   HTML ( 2)   PDF (4102KB) ( 138 )  

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We consider the combined effect of the magnetic field and heat transfer inside a square cavity containing a hybrid nanofluid (Cu-Al₂O₃-water). The upper and bottom walls of the cavity have a wavy shape. The temperature of the vertical walls is lower, the third part in the middle of the bottom wall is kept at a constant higher temperature, and the remaining parts of the bottom wall and the upper wall are thermally insulated. The magnetic field is applied under the angle γ, an opposite clockwise direction. For the numerical simulation, the finite element technique is employed. The ranges of the characteristics are as follows: the Rayleigh number (10³ ≤ Ra ≤ 10⁵), the Hartmann number (0 ≤ Ha ≤ 100), the nanoparticle hybrid concentration (φ_Al2O3, φ_Cu = 0, 0.025, 0.05), the magnetic field orientation (0 ≤ γ ≤ 2π), and the Prandtl number Pr, the amplitude of wavy cavity A, and the number of waviness n are fixed at Pr = 7, A = 0.1, and n = 3, respectively. The comparison with a reported finding in the open literature is done, and the data are observed to be in very good agreement. The effects of the governing parameters on the energy transport and fluid flow parameters are studied. The results prove that the increment of the magnetic influence determines the decrease of the energy transference because the conduction motion dominates the fluid movement. When the Rayleigh number is raised, the Nusselt number is increased, too. For moderate Rayleigh numbers, the maximum ratio of the heat transfer takes place for the hybrid nanofluid and then the Cu-nanofluid, followed by the Al₂O₃-nanofluid. The nature of motion and energy transport parameters has been scrutinized.

Hygroelasticity analysis of an elastically restrained functionally graded porous metamaterial circular plate resting on an auxetic material circular plate

A. BEHRAVAN-RAD, M. JAFARI

2020, 41(9):  1359-1380.  doi:10.1007/s10483-020-2651-7

Abstract ( 590 )   HTML ( 4)   PDF (1976KB) ( 147 )  

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The main objective of this research is to investigate the hygroelastic behavior of a non-homogeneous circular plate made up of porous metamaterial resting on an auxetic material plate. The mechanical properties of the main plate, as well as moisture concentration, vary as an exponential function in the transverse direction. Poisson's ratio is constant. The elastic supporting medium is developed by considering the structurestructure coupling. Based on the linear hygroelasticity theory, the governing state equations in terms of displacements and moisture concentration are acquired. At first, the Fickian equation is solved to compute the nonlinear distribution of moisture through the plate thickness, and then the state equations are semi-analytically solved using the statespace (SS) method and the differential quadrature (DQ) rule to predict the elastic field quantities. A comprehensive parametric analysis is accomplished to elucidate the effects of key parameters on the steady-state response of the plate under the mechanical and hygral loads.

Extremely large-amplitude oscillation of soft pipes conveying fluid under gravity

Wei CHEN, Ziyang HU, Huliang DAI, Lin WANG

2020, 41(9):  1381-1400.  doi:10.1007/s10483-020-2646-6

Abstract ( 733 )   HTML ( 2)   PDF (1966KB) ( 58 )  

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In this work, the nonlinear behaviors of soft cantilevered pipes containing internal fluid flow are studied based on a geometrically exact model, with particular focus on the mechanism of large-amplitude oscillations of the pipe under gravity. Four key parameters, including the flow velocity, the mass ratio, the gravity parameter, and the inclination angle between the pipe length and the gravity direction, are considered to affect the static and dynamic behaviors of the soft pipe. The stability analyses show that, provided that the inclination angle is not equal to π, the soft pipe is stable at a low flow velocity and becomes unstable via flutter once the flow velocity is beyond a critical value. As the inclination angle is equal to π, the pipe experiences, in turn, buckling instability, regaining stability, and flutter instability with the increase in the flow velocity. Interestingly, the stability of the pipe can be either enhanced or weakened by varying the gravity parameter, mainly dependent on the value of the inclination angle. In the nonlinear dynamic analysis, it is demonstrated that the post-flutter amplitude of the soft pipe can be extremely large in the form of limit-cycle oscillations. Besides, the oscillating shapes for various inclination angles are provided to display interesting dynamical behaviors of the inclined soft pipe conveying fluid.

Impact of anisotropic slip on the stagnation-point flow past a stretching/shrinking surface of the Al₂O₃-Cu/H₂O hybrid nanofluid

N. A. ZAINAL, R. NAZAR, K. NAGANTHRAN, I. POP

2020, 41(9):  1401-1416.  doi:10.1007/s10483-020-2642-6

Abstract ( 649 )   HTML ( 2)   PDF (1066KB) ( 85 )  

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The characteristics of heat transfer in the three-dimensional stagnationpoint flow past a stretching/shrinking surface of the Al₂O₃-Cu/H₂O hybrid nanofluid with anisotropic slip are investigated. The partial differential equations are converted into a system of ordinary differential equations by valid similarity transformations. The simplified mathematical model is solved computationally by the bvp4c approach in the MATLAB operating system. This solving method is capable of generating more than one solutions when suitable initial guesses are proposed. The results are proven to have dual solutions, which consequently lead to the application of a stability analysis that verifies the achievability of the first solution. The findings reveal infinite values of the dual solutions at several measured parameters causing the non-appearance of the turning points and the critical values. The skin friction increases with the addition of nanoparticles, while the escalation of the anisotropic slip effect causes a reduction in the heat transfer rate.

Thermal analysis in swirl motion of Maxwell nanofluid over a rotating circular cylinder

A. AHMED, M. KHAN, J. AHMED

2020, 41(9):  1417-1430.  doi:10.1007/s10483-020-2643-7

Abstract ( 728 )   HTML ( 4)   PDF (628KB) ( 127 )  

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In this paper, the mechanism of thermal energy transport in swirling flow of the Maxwell nanofluid induced by a stretchable rotating cylinder is studied. The rotation of the cylinder is kept constant in order to avoid the induced axially secondary flow. Further, the novel features of heat generation/absorption, thermal radiation, and Joule heating are studied to control the rate of heat transfer. The effects of Brownian and thermophoretic forces exerted by the Maxwell nanofluid to the transport of thermal energy are investigated by utilizing an effective model for the nanofluid proposed by Buongiorno. The whole physical problem of fluid flow and thermal energy transport is modelled in the form of partial differential equations (PDEs) and transformed into nonlinear ordinary differential equations (ODEs) with the help of the suitable flow ansatz. Numerically acquired results through the technique bvp4c are reported graphically with physical explanation. Graphical analysis reveals that there is higher transport of heat energy in the Maxwell nanoliquid for a constant wall temperature (CWT) as compared with the prescribed surface temperature (PST). Both thermophoretic and Brownian forces enhance the thermal energy transport in the flowing Maxwell nanofluid. Moreover, the temperature distribution increases with increasing values of the radiation parameter and the Eckert number. It is also noted that an increase in Reynolds number reduces the penetration depth, and as a result the flow and transport of energy occur only near the surface of the cylinder.

Electromagnetohydrodynamic flows and mass transport in curved rectangular microchannels

Yongbo LIU, Yongjun JIAN

2020, 41(9):  1431-1446.  doi:10.1007/s10483-020-2649-9

Abstract ( 722 )   HTML ( 11)   PDF (217KB) ( 144 )  

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Curved microchannels are often encountered in lab-on-chip systems because the effective axial channel lengths of such channels are often larger than those of straight microchannels for a given per unit chip length. In this paper, the effective diffusivity of a neutral solute in an oscillating electromagnetohydrodynamic (EMHD) flow through a curved rectangular microchannel is investigated theoretically. The flow is assumed as a creeping flow due to the extremely low Reynolds number in such microflow systems. Through the theoretical analysis, we find that the effective diffusivity primarily depends on five dimensionless parameters, i.e., the curvature ratio of the curved channel, the Schmidt number, the tidal displacement, the angular Reynolds number, and the dimensionless electric field strength parameter. Based on the obtained results, we can precisely control the mass transfer characteristics of the EMHD flow in a curved rectangular microchannel by appropriately altering the corresponding parameter values.