We present an efficient way to incorporate the Maxwell-Stefan approach (Krishna, 1990) for modeling gas separation processes, i.e., adsorbent particles and membranes. Ideal Adsorbed Solution Theory ...(Myers and Prausnitz, 1965) is applied for the description of competitive equilibria. The proposed calculation method introduces analytical expressions for the partial derivatives of the loadings w.r.t. fluid-phase concentrations, developed by Rubiera Landa et al. (2013), in the calculation of the thermodynamic correction factors, as required by Maxwell-Stefan flux equations. These expressions are solved simultaneously with transient mass balances that describe the gas separation processes in a differential-algebraic equation formulation. Robustness and advantages of the proposed solution approach are demonstrated with several examples adapted from the literature.
•Computationally-efficient solution of M-S approach applying IAST is developed.•Analytical Jacobian formula under the frame of IAST is exploited in differential-algebraic equation formulation.•Applications of this approach are provided, including adsorbent particle dynamics and thin-layered membranes.
•When the BST particles are mixed with PVDF polymer, hydrogen bond will form between the F atoms on the PVDF and the –OH groups on the surface of the BST particles.•The permittivity of PVDF+40vol% ...BST composites is 190 at 1 kHz at 160°C and the tunability amounts to 7.2% under the bias voltage of 1.0kV/mm at 10kHz.•The breakdown strength decreased with BST fillers increasing and the energy storage density of PVDF+40vol% BST composites was about 0.36J/cm3.
The poly(vinylidene fluoride) (PVDF)/barium strontium titanate (BST) composites were fabricated by solution casting method. The microstructure and dielectric properties of composites comprising polyvinylidene fluoride (PVDF) and barium strontium titanate (BST) particles have been investigated. It was found that the permittivity of the BST/PVDF composites increases from 16 to 40 while loss tangent decreases from 0.27 to 0.19 with BST fillers increasing from 10vol% to 40vol%. The tunability of PVDF+40vol% BST composites was 7.2% under the bias voltage of 1.0kV/mm and the energy density was 0.36J/cm3, making it suitable for embedded capacitor applications. The dielectric properties of PVDF were improved by increasing BST fillers and studying the mechanism of interface reaction.
Ferroelectric ceramic materials are receiving increasing attention due to their extensive applications in electrical systems. In this work, three-layer BaTiO3/SrTiO3 ceramic composites consisting of ...one Ba1-xTiO3-SrxTiO3 (at x = 5, 10, 20 and 30) composite interlayer sandwiched by two BaTiO3 outer layers were fabricated. And the effects of SrTiO3 modification on their phase structures, microstructures and dielectric performance were studied in detail. A pure perovskite phase was observed in the Ba1-xTiO3-SrxTiO3 ceramic composites. The BaTiO3 ceramic doping by SrTiO3 exhibited refined grain size. With increased SrTiO3 content, both the permittivity and dielectric loss have increased. Furthermore, a layered structure was designed to enhance the dielectric properties. Consequently, a high permittivity of 7118 and low loss of 0.028 were achieved at 10 kHz in BaTiO3-30 w% SrTiO3–BaTiO3 three-layer ceramic composites. In summary, the introduction of SrTiO3 is believed to reduce the BaTiO3 Curie temperature and greatly improve its permittivity at room temperature. Furthermore, the accumulation of charge carriers at the interface significantly increases the permittivity, while preventing the transport of the charge carriers and reducing the loss. The ultrahigh permittivity and low loss make these composites promising candidates for microwave antennas, field effect transistors and dielectric capacitors.
Graphic stability of generalised motions Millar, Cameron G.; McRobie, Allan
International journal of solids and structures,
12/2022, Letnik:
256
Journal Article
Recenzirano
This paper presents a graphical method for determining the stability and stiffness of generalised motions of a pin-jointed framework. Previous work has focused on mechanisms; this paper offers an ...extension to nodal motions which induce a first order change in member length. The Williot diagram is used to decompose nodal motions into their rotational and extensional components. From here, a weighted Maxwell–Minkowski diagram and spring equations are used to determine the stiffness of the motion. The Maxwell–Minkowski diagram combines the form and force diagram in graphic statics and provides a TL term which is the rotational stiffness of the member. This method is generalised to 3D and allows for the study of mechanism buckling. This methodology is also extended to cover the analysis of multiple nodal motions simultaneously. This paper also extends the work of Pellegrino who introduced the concept of product forces.
In a 3D bounded and C1,α-smooth domain Ω, α∈(0,1), we distribute a cluster of nanoparticles enjoying moderately contrasting relative permittivity and permeability which can be anisotropic. We show ...that the effective permittivity and permeability generated by such cluster is explicitly characterized by the corresponding electric and magnetic polarization tensors of the fixed shape. The error of the approximation of the scattered fields corresponding to the cluster and the effective medium is inversely proportional to the dilution parameter cr:=δa, where a is the maximum diameter of the nanoparticles and δ is the minimum distance between them. The constant of the proportionality is given in terms of a-priori bounds on the cluster of nanoparticles (i.e. upper and lower bounds on their permittivity and permeability parameters, upper bound on the dilution parameter cr, the used incident frequency and the domain Ω).
A key point of the analysis is to show that the Foldy-Lax field appearing in the meso-scale approximation, derived in 17, is a discrete form of a (continuous) system of Lippmann-Schwinger equations with a related effective permittivity and permeability contrasts. To derive this, we prove that the Lippmann-Schwinger operator, for the Maxwell system, is invertible in the Hölder spaces. As a by-product, this shows a Hölder regularity property of the electromagnetic fields up to the boundary of the inhomogeneity.
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•Effective medium theory is modified for multicomponent transport.•An optimum network coordination number exists at which species flux is maximum.•A uniform pore size is ...optimal.•Selectivity is very sensitive to temperature and undergoes a cross-over at a certain temperature.•The theory is in excellent agreement with detailed simulations.
We present a new theory to estimate fluxes and effective transport conductances of binary mixtures through a membrane comprising a nonuniform porous medium with both pore size and pore length distributions, using the Onsager formulation at the single pore level. The theory defines a conductance of each species that is dependent on the concentration gradients of the various species, and on using effective medium theory determines the fluxes and concentration profiles self-consistently in the porous medium. The transport of CH4/H2 mixtures in a silica membrane having a known pore size distribution is examined using this theory, and the results compared with those from rigorous simulations, showing good agreement. It is found that an optimal network coordination number exists at which species fluxes are a maximum, due to the opposing effects of increasing porosity and mean pore length with increase in coordination number. Further, network fluxes decrease with increase in pore dispersion, indicating that uniform pore size is optimal. A species and pressure-dependent optimal temperature is also predicted, due to the competing effects of increase in diffusivity and decrease in adsorption on increasing temperature. It is seen that the CH4 selectivity is very sensitive to temperature, and undergoes a cross-over, with the membrane being more selective to CH4 at low temperature and to H2 at high temperature. In general, the selectivity is very sensitive to the distribution of pore volume, and for bimodal pore networks, undergoes a sharp transition at the percolation threshold, when the smaller pore size is impermeable to the larger species, CH4. The approach offers a convenient adaption of effective medium theory to multicomponent systems with nonlinear isotherms, overcoming drawbacks of existing theory.
In this paper, we consider the self-dual O(3) Maxwell-Chern-Simons-Higgs equations on a two-dimensional flat torus arising from the O(3) sigma gauge field model. Our main goal is to obtain the ...existence and uniqueness of topological solutions with vortices and antivortices. In order to achieve this goal, we show that the nondegeneracy of linearized operator for entire solution holds even when the symmetry is broken. Moreover, we also obtain the uniform bound of L1 norm of nonlinearities with respect to large charge of electron. We expect that these results would play an significant role to get the asymptotic behavior of all possible solutions and count the total number of solutions.
This research work explores the thermal and mass transport phenomena for a time-dependent Maxwell fluid flow in the presence of Cattaneo–Christov concept. The Maxwell fluid flow is analyzed through a ...stretching cylinder and sheet. Brownian motion, non-uniform heat source/sink, thermophoresis, and variable thermal conductivity are operated in this study. A theoretical analysis of the modeled system of equations is explored with the help of HAM. Impacts of fixed constraints on velocity, thermal, and concentration functions are offered graphically. It is concluded that the velocity profile heightens quickly for Newtonian fluid equated to non-Newtonian fluid (Maxwell) via curvature parameter while the temperature and concentration distributions increase quickly for non-Newtonian fluid as equated to the Newtonian fluid via curvature parameter. The presence of Maxwell and magnetic parameters increases the size of the trapping bolus.
In this article we have studied the unsteady oscillatory flow of incompressible fluid with heat transfer in a horizontal channel. Maxwell fluid is flowing through a space filled by Forchheimer ...medium. The Caputo time derivative has been used in the formulation of governing flow problem. A numerical solution has been obtained using Finite Element Method for space variables and Finite Difference Method for fractional time derivatives. A small increase in α gives increase in velocity gradient and also thickness of the momentum boundary layer increases with the increase of α values. For α = 1 velocity boundary layer has a maximum peak. It means fractional parameter controls momentum boundary layer. A smooth profile of temperature gradient decreases with rise of temperature distribution and thickness of the thermal boundary layer rises when increase β values. It observe that β play an important rule in thermal boundary layer. The effects of pertinent physical parameters like Forchheimer parameter, Grashof number and Reynolds number on velocity and temperature distribution are considered and demonstrated through graphs.
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