Chaotic mixing by oscillating a Stokeslet in a circular Hele-Shaw microfluidic device

Chaotic mixing by oscillating a Stokeslet in a circular Hele-Shaw microffluidic device is presented in this article. Mathematical modeling for the induced flow motions by moving a Stokeslet along the x-axis is derived using Fourier expansion method. The solution is formulated in terms of the velocity stream function. The model is then used to explore different stirring dynamics as function of the Stokeslet parameters. For instance, the effects of using various oscillation amplitudes and force strengths are investigated. Mixing patterns using Poincaré maps are obtained numerically and have been used to characterize the mixing efficiency. Results have shown that, for a given Stokeslet’s strength, efficient mixing can be obtained when small oscillation amplitudes are used. The present mixing platform is expected to be useful for many of biomicrofluidic applications.

Modelling and Validation of Transmittance from Nanocrystalline Titania film for Photoanodic Action in Dye-Sensitized Solar Cells

A four phase model air/glass/indium doped tin oxide/TiO2 has been studied by modifying Rouard’s model to calculate the final transmittance from TiO2 layer to be used as photoanode in dye-sensitized solar cells. An optical simulation for the reflectance and transmittance has been executed for the constructed nanocrystalline TiO2 films. To validate the theoretical results TiO2 film has been deposited onto indium doped tin oxide (ITO) layer by sol-gel dip coating technique. It has been found that the incident light suffers losses by 5-15% on passage through TiO2 coated ITO layer. Experimentally it has been observed on the basis of efficiency value that meso-nano combination is the best candidate to be used as photoanode in a dye-sensitize solar cell.

Acoustomagnetoelectric Effect in Graphene Nanoribbon in the Presence of External Electric and Magnetic Fields

Acoustomagnetoelectric Effect (AME) in Graphene Nanoribbon (GNR) in the presence of an external electric and magnetic fields was studied using the Boltzmann kinetic equation. On open circuit, the Surface Acoustomagnetoelectric field (ESAME) in GNR was obtained in the region ql >> 1, for energy dispersion "(p) near the Fermi level. The dependence of ESAME on the dimensional factor (ɳ), the sub-band index (pi), and the width (N) of GNR were analyzed numerically. For ESAME versus ɳ, a non-linear graph was obtained. From the graph, at ɳ < 0.62, the obtained graph qualitatively agreed with that experimentally observed in graphite. However at ɳ > 0.62, the ⃗ESAME falls rapidly to a minimum value. We observed that in GNR, the maximum ⃗ESAME was obtained at magnetic field H = 3.2Am−1. The graphs obtainedwere modulated by varying the subband index pi with an inversion observed when pi = 6. The dependence of ESAME on the width N for various pi was also studied where, ⃗ESAME decreases for increase in pi. To enhanced the understanding of ESAME on the N and ɳ, a 3D graph was plotted. This study is relevant for investigating the properties of GNR.

Hybrid fluid-quantum coupling for the simulation of the transport of partially quantized particles in a DG-MOSFET

This paper is devoted to numerical simulations of electronic transport in nanoscale semiconductor devices forwhich charged carriers are extremely confined in one direction. In such devices, like DG-MOSFETs, the subband decomposition method is used to reduce the dimensionality of the problem. In the transversal direction electrons are confined and described by a statistical mixture of eigenstates of the Schrödinger operator. In the longitudinal direction, the device is decomposed into a quantum zone (where quantum effects are expected to be large) and a classical zone (where they are negligible). In the largely doped source and drain regions of a DG-MOSFET, the transport is expected to be highly collisional; then a classical transport equation in diffusive regime coupled with the subband decomposition method is used for the modeling, as proposed in N. Ben Abdallah et al. (2006, Proc. Edind. Math. Soc. [7]). In the quantum region, the purely ballistic model presented in Polizzi et al. (2005, J. Comp. Phys. [25]) is used. This work is devoted to the hybrid coupling between these two regions through connection conditions at the interfaces. These conditions have been obtained in order to verify the continuity of the current. A numerical simulation for a DG-MOSFET, with comparison with the classical and quantum model, is provided to illustrate our approach.

Cross-Kerr nonlinearity: a stability analysis

We analyse the combined effect of the radiation-pressure and cross-Kerr nonlinearity on the stationary solution of the dynamics of a nanomechanical resonator interacting with an electromagnetic cavity. Within this setup,we show how the optical bistability picture induced by the radiation-pressure force is modi fied by the presence of the cross-Kerr interaction term. More specifically, we show how the optically bistable region, characterising the pure radiation-pressure case, is reduced by the presence of a cross-Kerr coupling term. At the same time, the upper unstable branch is extended by the presence of a moderate cross-Kerr term, while it is reduced for larger values of the cross-Kerr coupling.

Simulation of electrostatic field in electrospinning of polymer nanofibers

Electrospinning is a popular process for fabricating submicron diameter gibers. The process applies a strong electric gield to launch a polymer jet that elongates to create the gine gibers. The jet dries as the solvent evaporates and the dried giber collects on a grounded surface. Most of electrospinning literatures focus the polymer solution compositions and the properties of the produced gibers. Less attention is applied to the electrostatic gield geometries and operating conditions. Through computer simulations and laboratory experiments thiswork shows that by applying the grounded voltage to different regions of the collector surface, the electric gield can be moved spatially to direct the electrospinning jets towards select locations of the grounded surface.

A numerically efficient approach to the modelling of double-Qdot channels

We consider the electronic properties of a system consisting of two quantum dots in physical proximity, which we will refer to as the double-Qdot. Double-Qdots are attractive in light of their potential application to spin-based quantum computing and other electronic applications, e.g. as specialized sensors. Our main goal is to derive the essential properties of the double-Qdot from a model that is rigorous yet numerically tractable, and largely circumvents the complexities of an ab initio simulation. To this end we propose a novel Hamiltonian that captures the dynamics of a bi-partite quantum system, wherein the interaction is described via a Wiener-Hopf type operator. We subsequently describe the density of states function and derive the electronic properties of the underlying system. The analysis seems to capture a plethora of electronic profiles, and reveals the versatility of the proposed framework for double-Qdot channel modelling.

Efficient simulation of unidirectional pulse propagation in high-contrast nonlinear nanowaveguides

This work demonstrates an improved method to simulate long-distance femtosecond pulse propagation in highcontrast nanowaveguides. Different from typical beam propagation methods, the foundational tool here is capable of simulating strong spatiotemporal waveform reshaping and extreme spectral dynamics. Meanwhile, the ability to fully capture effects due to index contrast in the transverse direction is retained, without requiring a decomposition of the electric field in terms of waveguide modes. These simulations can be computationally expensive, however, so cost is reduced in the improved method by considering only the waveguide core. Fields in the cladding are then properly accounted for through a boundary condition suitable for the case of total internal reflection.

Theory of space-time dissipative elasticity and scale effects

In this article a model of irreversible dynamic thermoelasticity of an ideal continuua is constructed from an elasticity theory of asymmetrical, transversely isotropic in time direction, dissipative defectless 4D-continuum. In the model the fourth component of the 4D-displacement vector is locally irregular time R. The kinematic model comprises 3D-tensor of distortion, 3Dvector of velocity, 3D-gradient vector of local irregular time and entropy in unified tensor object which is an asymmetrical 4D-tensor of distortion of second rank. Consequently, the force model comprises 3D-tensor of stress, 3D-vector of impulses, 3D-vector of heat flow and temperature in unified tensor object which is an asymmetrical 4D-stress tensor of second rank. Hooke’s law equations have been formulated which connect components of asymmetrical 4D-tensors of stress and distortion. Physical interpretations have been given to the tensors’ components of thermomechanical properties of formulated continuum. Therefore, the article formulate an irreversible dynamic thermoelasticity covariant model of ideal (defectless) continua in which basic kinematic and force variables are components of unified tensor objects and theory is represented by 4D-vector equation. Sedov’s equation has been derived and resulted into Euler’s equations, space projections of which determine motion equations, and time projection determines heat conductivity equation as well as the whole spectrum of the space-time boundary value problems. The proposed theory allows one to describe the scale effects in the thermal processes and opens prospects for studying the scale effects of the coupled dynamic thermoelasticity and its nanoscience applications. A temperature-scale refinement can also broaden the range of applicability of the law of heat conduction in solids to allow for design of small-sized components, devices and nano-systems.

Modeling the tip-sample interaction in atomic force microscopy with Timoshenko beam theory

A matrix framework is developed for single and multispan micro-cantilevers Timoshenko beam models of use in atomic force microscopy (AFM). They are considered subject to general forcing loads and boundary conditions for modeling tipsample interaction. Surface effects are considered in the frequency analysis of supported and cantilever microbeams. Extensive use is made of a distributed matrix fundamental response that allows to determine forced responses through convolution and to absorb non-homogeneous boundary conditions. Transients are identified from intial values of permanent responses. Eigenanalysis for determining frequencies and matrix mode shapes is done with the use of a fundamental matrix response that characterizes solutions of a damped second-order matrix differential equation. It is observed that surface effects are influential for the natural frequency at the nanoscale. Simulations are performed for a bi-segmented free-free beam and with a micro-cantilever beam actuated by a piezoelectric layer laminated in one side.