Effect of Coriolis and buoyancy forces on three-dimensional flow of chemically reactive tangent hyperbolic fluid subject to variable viscosity

Thermophoresis effect has wide range of applications in electro-static precipitators and in biology for calculating single biological macro molecules, such as genomic-length DNA and HIV virus in the micro channels. Current study deal with effects of Coriolis and buoyancy forces on the three-dimensional boundary layer flow of tangent hyperbolic fluid with thermo-migration and haphazard motion of nano-sized particles. Arrhenius kind of chemical reaction is taken along an exponentially stretchable surface. The main focus of current exploration is to execute shear thinning nano-liquid flow past an exponentially rotating stretchable surface under the influence of variable viscosity, mixed convection and activation energy. We are motivated to explore the features of three-dimensional shear thinning model combined under the features of mixed convention, variable viscosity, and activation energy. The mathematical model is designed to generate PDEs and converted them into ODEs by employing fractious transformation. The numerical outcomes are exhibited via graphs by employing Bvp4c numerical technique whereas the values of skin friction coefficient are calculated by monopolizing shooting method. Characteristics of the parameters appearing in modeling like the viscosity parameter, power-law index, local Weissenberg number, mix convection parameter, rotation parameter, Prandtl number and chemical reaction parameter are comprehensively analyzed through graphical behavior. The impact of governing parameters on skin friction, heat and mass transfer rates is illustrated through tables. The detail analysis anticipates that the elevation in Weissenberg number and porosity caused decline in velocity. Further, the temperature behaves doppositely analogous to development Prandtl besides the thermophoresis parameter.     

Variable chemical species and thermo-diffusion Darcy–Forchheimer squeezed flow of Jeffrey nanofluid in horizontal channel with viscous dissipation effects

This research communicates the applications of thermos-diffusion effect associated to the squeezing flow of Jeffrey nanofluid due to horizontal channel. The problem presents the applications of inertial effects by following the Darcy–Forchheimer flow. Moreover, the effects of viscous dissipation and activation energy phenomenon has been discussed. The dimensionless attention of problem is retained. The shooting technique is implemented to present the numerical computations. The numerical validation of results is reported. The essential assessment of physical flow parameters is studied. The numerical outcomes are presented for heat and mass transfer phenomenon. It is observed that presence of inertial forces control to velocity flow in the regime. The enhancing contribution of thermal and concentration rate is noted for inertial constant.     

Peeling of polydimethylsiloxane adhesives: The case of adhesive failure

The adhesion properties of high molecular weight polydimethylsiloxane adhesives are measured using 90°‐peel adhesion tests, in the high velocity range. Such adhesives undergo mainly adhesive failure in this regime. The influence of viscosity (non‐Newtonian), adhesive thickness, peeling velocity, and backing properties are studied, and new unexpected behaviors are shown. The role of rheology and peeling velocity can be explained by an extension of a model already presented for cohesive failure, by using a power‐law fluid for the adhesive. On the other hand, the influence of the backing rigidity reveals to be coupled with the adhesive elastic properties, this effect being correlated to the introduction of a new parameter in the model, the Weissenberg number for viscoelasticity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2113–2122, 2007     

Effects of binary chemical reaction and Arrhenius activation energy in Darcy–Forchheimer three-dimensional flow of nanofluid subject to rotating frame

Darcy–Forchheimer three-dimensional rotating flow of nanoliquid in the presence of activation energy and heat generation/absorption is examined. Heat and mass transport via convective process is considered. Buongiorno model has been employed to illustrate thermophoresis and Brownian diffusion effects. Adequate transformation procedure gives rise to system in terms of nonlinear ODE’s. An efficient numerical technique namely NDsolve is used to tackle the governing nonlinear system. The graphical illustrations examine the outcomes of various sundry variables. Heat and mass transfer rates are also computed and examined. Our results indicate that the temperature and concentration distributions are enhanced for larger values of porosity parameter and Forchheimer number.

     

黏弹性聚合物溶液在突扩孔道内的流动特性

采用上随体Maxwell本构方程,描述油藏条件下以第一法向应力差为主要特征的聚合物溶液的流变性.利用有限体积法对黏弹性聚合物溶液在突扩孔道内的流动特征进行数值模拟.绘制了流函数和速度的等值线图.研究了黏弹性的变化对微观波及效率的影响.数值模拟结果表明,聚合物溶液的黏弹性是影响波及效率的主要因素.凹角处的流动区域随着弹性的增加在不断增大,因此滞留区域不断减小,微观波及效率不断增大.具有黏弹特性的聚合物溶液相比于纯黏性的牛顿流体更利于提高驱油效率.这一结论有助于驱油工业上聚合物溶液的设计和优选.     

Hydrothermal stagnation point flow of Carreau nanofluid over a moving thin needle with non-linear Navier's slip and cubic autocatalytic chemical reactions in Darcy-Forchheimer medium

The present analysis deals with the hydrothermal and stagnation point flow of non-Newtonian fluid characterized by Carreau model over a moving thin needle. Darcy-Forchheimer medium is introduced. Homogeneous and heterogeneous chemical reactions are involved in the flow model. Non-linear Navier's slip condition is taken into account. Buongiorno model is adopted. The present hydrothermal flow model is useful in many complex industrial processes. The required numerical solution is obtained by 4th order Runge Kutta method along with shooting technique. The some remarkable outcomes of the current study are that axial velocity whittles down with rise in Weissenberg number and exhibits reverse trend in response to increase in non-linear slip parameter. Amplification of homogeneous and heterogeneous reaction parameters leads to diminution of nanoparticles concentration. Surface viscous drag intensify due to increment in Forchheimer number and heat transfer rate ameliorates with hike in Weissenberg number for both power law behavior (shear thinning and shear thickening) of Carreau nanofluid.     

Green,rapid, and highly efficient syntheses of α,α′-bis[(aryl or allyl)idene]cycloalkanones and 2-[(aryl or allyl)idene]-1-indanones as potentially biologic compounds via solvent-free microwave-assisted Claisen–Schmidt condensation catalyzed by MoCl5

A new, green, and highly efficient protocol for the expeditious preparation of some α,α′-bis[(aryl or allyl)idene]cycloalkanones and 2-[(aryl or allyl)idene]-1-indanones via a simple microwave-assisted Claisen–Schmidt condensation reaction catalyzed by MoCl₅ was successfully developed. Outstanding features of the current methodology include the use of solvent-free conditions, simple operation, use of a very inexpensive and available catalyst, low catalyst loading, short reaction times, high yields of the pure products, no harmful by-products, easy workup, and also the applicability of microwave irradiation as a clean source of energy. Furthermore, a gram-scale reaction was successfully conducted, proving the scalability of this current Claisen–Schmidt condensation reaction.     

Bioconvection Due to Gyrotactic Microorganisms in Couple Stress Hybrid Nanofluid Laminar Mixed Convection Incompressible Flow with Magnetic Nanoparticles and Chemical Reaction as Carrier for Targeted Drug Delivery through Porous Stretching Sheet

In this paper, the steady electrically conducting hybrid nanofluid (CuO-Cu/blood) laminar-mixed convection incompressible flow at the stagnation-point with viscous and gyrotactic microorganisms is considered. Additionally, hybrid nanofluid flow over a horizontal porous stretching sheet along with an induced magnetic field and external magnetic field effects that can be used in biomedical fields, such as in drug delivery and the flow dynamics of the microcirculatory system. This investigation can also deliver a perfect view about the mass and heat transfer behavior of blood flow in a circulatory system and various hyperthermia treatments such as the treatment of cancer. The simple partial differential equations (PDEs) are converted into a series of dimensional ordinary differential equations (ODEs), which are determined using appropriate similarities variables (HAM). The influence of the suction or injection parameter, mixed convection, Prandtl number, buoyancy ratio parameter, permeability parameter, magnetic parameter, reciprocal magnetic prandtl number, bioconvection Rayleigh number, coupled stress parameter, thermophoretic parameter, Schmidt number, inertial parameter, heat source parameter, and Brownian motion parameter on the concentration, motile microorganisms, velocity, and temperature is outlined, and we study the physical importance of the present problem graphically.     

Effect of an underdamped vibration with both diagonal and off-diagonal exciton–phonon interactions on excitation energy transfer

A numerically exact approach, named as the hierarchical stochastic Schrödinger equation, is employed to investigate the resonant vibration-assisted excitation energy transfer in a dimer system, where an underdamped vibration with both diagonal and off-diagonal exciton–phonon interactions is incorporated. From a large parameter space over the site-energy difference, excitonic coupling, and reorganization energy, it is found that the promotion effect of the underdamped vibration is significant only when the excitonic coupling is smaller than the site-energy difference. Under the circumstance, there is an optimal strength ratio between diagonal and off-diagonal exciton–phonon interactions for the resonant vibration-assisted excitation energy transfer as the site-energy difference is greater than the reorganization energy, whereas in the opposite situation the most efficient energy transfer occurs as the exciton–phonon interaction is totally off-diagonal. © 2018 Wiley Periodicals, Inc.     

The kinetics of nucleophilic substitution processes in the alkyl halides. Part B—analysis of experimental data

Nucleophilic substitution reactions in the alkyl halides, RX + Y^? → RY + X^?, proceeding in polar media are considered on the basis of the theory presented in Part A. It is shown that the solvent reorganization energy is the main part of the activation energy for this processes. According to calculations performed, the values of the solvent reorganization energy equal ～2.5–3 eV for H₂O and ～ 1.8–2.3 eV for acetone. From experimental data on the kinetic isotope effect, an estimate for the splitting of nonadiabatic terms and for the slope of the potential curve v′ of the intermolecular interaction between halide ion and methyl halide near transition configuration is made. Further, the parameter v′ is used for calculating the activation entropy of substitution reactions in the methyl halides. Theoretical activation energies and activation entropies agree with experimental values. In the framework of theory presented an interpretation of change of E_a and the preexponential factor with the type of alkyl halide is given.     

Definitive thermochemistry and kinetics of the interconversions among conformers of n‐butane and n‐pentane

The focal‐point analysis (FPA) technique is used for the definitive characterization of conformational interconversion parameters, including activation energy barriers, activation free energies, and kinetic rate coefficients at 298 K, of two n‐alkanes, n‐butane, and n‐pentane, yielding the first complete analysis of their interconversion kinetics. The FPA implementation developed in this study is based on geometry optimizations and harmonic frequency computations carried out with density functional theory methods and single‐point energy computations up to the CCSD(T) level of electronic structure theory using atom‐centered Gaussian basis sets as large as cc‐pV5Z. The anharmonic vibrational computations are carried out, at the MP2/6‐31G* level of theory. Reflecting the convergence behavior of the Gibbs free‐energy terms and the interconversion parameters, well‐defined uncertainties, mostly neglected in previous theoretical studies, are provided. Finally, the effect of these uncertainties on the concentrations of the conformers of n‐butane and n‐pentane is examined via a global Monte–Carlo uncertainty analysis. © 2017 Wiley Periodicals, Inc.     

The reduced Redlich–Kister excess molar Gibbs energy of activation of viscous flow and derived properties in 1,4-dioxane + water binary mixtures from 293.15 to 309.15 K

The excess molar volume, viscosity deviation and excess Gibbs free energy of activation of viscous flow have been investigated from the density and shear viscosity measurements of water–dioxane mixtures over the entire range of mole fractions from 293.15 to 309.15?K. The results were fitted by the Redlich–Kister equation. Partial molar volume and Gibbs energy at infinite dilution were deduced from four methods, activation parameters and partial molar Gibbs energy of activation of viscous flow against compositions were investigated. The water–dioxane interactions have principally an H-bound character and there are two principal types’ structures limited by 0.08?mole fraction in dioxane. The reduced Redlich–Kister excess properties provide an indication of the intermolecular interactions and for dioxane–water cluster formation as suggested in the literature.     

Interpretation of the hydrogen anomaly in neutron and electron compton scattering

In Compton scattering with neutrons in the energy range 20–120 eV, it has been observed that the relative H/M cross sections in a variety of H‐containing materials are 20–40% lower than expected from the composition ratio H/M (M being a heavier element in the same compound). The same phenomenon has also been observed in Compton scattering with electrons of 2 and 20 keV energy. There is, at present, no consensus about the reason for these anomalies. In this theory, they are explained as a result of interference when the scattering particle interacts with more than one hydrogen nucleus. The coherence volume of the actual setup, which limits the number of interfering particles, is therefore an important parameter. It is shown here that the large zero‐point motion of the hydrogen nuclei leads to reductions in the scattering intensity from interfering pairs. Coherence is preserved over the sub‐fs scattering times relevant for this process, even in the condensed systems studied. It is gradually lost when the scattering time is increased, which happens when the neutron energy is reduced (as reflected in lower anomalies for smaller scattering angles). Explicit expressions for the decoherence effect are presented and compared with experimental observation for a selection of observed H‐ and D‐containing systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

WavePacket: A Matlab package for numerical quantum dynamics. III. Quantum-classical simulations and surface hopping trajectories

WavePacket is an open-source program package for numerical simulations in quantum dynamics. Building on the previous Part I (Schmidt and Lorenz, Comput. Phys. Commun. 2017, 213, 223] and Part II (Schmidt and Hartmann, Comput. Phys. Commun. 2018, 228, 229] which dealt with quantum dynamics of closed and open systems, respectively, the present Part III adds fully classical and mixed quantum-classical propagation techniques to WavePacket. There classical phase-space densities are sampled by trajectories which follow (diabatic or adiabatic) potential energy surfaces. In the vicinity of (genuine or avoided) intersections of those surfaces, trajectories may switch between them. To model these transitions, two classes of stochastic algorithms have been implemented: (1) Tully's fewest switches surface hopping and (2) Landau–Zener-based single switch surface hopping. The latter one offers the advantage of being based on adiabatic energy gaps only, thus not requiring nonadiabatic coupling information any more. The present work describes the MATLAB version of WavePacket 6.1.0, which is essentially an object-oriented rewrite of previous versions, allowing to perform fully classical, quantum-classical and quantum-mechanical simulations on an equal footing, that is, for the same physical system described by the same WavePacket input. The software package is hosted and further developed at the Sourceforge platform, where also extensive Wiki-documentation as well as numerous worked-out demonstration examples with animated graphics are available. © 2019 Wiley Periodicals, Inc.     

Berry pseudorotation mechanism for the interpretation of the 19F NMR spectrum in PF5 by ab initio molecular dynamics simulations.

For the first time, theoretical evidence that confirms the importance of the Berry pseudorotation process in the interpretation of the 19F NMR spectrum of phosphorus pentafluoride (PF5) is presented. Ab initio molecular dynamics simulations have been performed to generate a large number of configurations used for NMR parameter computations at the density functional theory level. Two different temperatures were set to highlight the effect of pseudorotation process on the NMR spectrum. Average 19F chemical shifts and spin-spin coupling constants calculated for the five fluorine atoms converge towards the NMR equivalence of the five atoms when the Berry pseudorotation mechanism is accounted for.     

Three model-free methods for calculation of activation energy in TG

Two well-known isoconversion methods, the first one developed by Ozawa-Flynn-Wall and the second one developed by Friedman, are confronted with calculations made using modulated thermogravimetry (MTG). The latter variant is free from a number of assumptions and restrictions made in the isoconversion computations. In particular, it allows the use of a single decomposition curve and it remains in force even in the case of multistage decomposition with conjugated processes.To obtain the model-fitting methods from the model-free methods one should replace some functions averaged over isoconversion levels by the functions calculated on the basis of kinetic models. In the Ozawa-Flynn-Wall method it is the averaged reduced time (integral of Arrhenius exponential over time). In the method of Friedman it is the averaged differential conversion function.In MTG, the perturbations caused by the sinusoidal temperature modulation are connected with derivatives of mass loss by simple scaling, where activation energy plays a role of a scaling parameter. The ratio of the experimentally measured perturbations to the experimental derivative is used for the model-free computation of activation energy. If a theoretical derivative replaces the experimental one, this procedure leads to the model-fitting method. Even a rough approximation of the experimental derivative should not lead to an excessive error in activation energy. If in a vicinity of peaks maxima in derivatives of mass loss the decomposition is controlled by single rate-limiting processes, modulated thermogravimetry should give realistic activation energies for these processes. Inasmuch as the results of MTG are weakly sensitive to selection of kinetic models, this method should have a high predictive force.     

Review: active homogeneous reagents and catalysts in n-alkane activation

The development of selective, efficient, and direct routes for activation and functionalization of naturally abundant n-alkanes could lead to a new paradigm in materials and energy technologies. In this context, the use of homogeneous catalysts to functionalize C–H bonds of unactivated hydrocarbons is of particular interest from a scientific as well as an economic viewpoint. Despite the large body of work on stoichiometric C–H activation reactions produced over the last three decades, relatively few systems have been developed to allow catalytic functionalization of hydrocarbons. This review deals with homogeneous catalytic processes available in the literature for paraffin activation and functionalization. The key intermediates involved in catalytic systems are highlighted, providing important information in the design of new and efficient catalysts. Also, some of the key challenges and approaches to rational development of the next generation of organometallic catalysts will be highlighted.     

A new variational Monte Carlo trial wavefunction with directional Jastrow functions

The addition of a directional term to standard Jastrow functions was investigated in variational quantum Monte Carlo calculations for the LiH molecule using wavefunctions composed of Slater determinants combined with Padé and with Schmidt–Moskowitz functions. The recovery of correlation energy was improved significantly by the added term: from 52% to 71% for the Padé function and from 61% to 78% for the Schmidt–Moskowitz function.     

Hydrodynamic interaction in polymer solutions simulated with dissipative particle dynamics

The authors analyzed extensively the dynamics of polymer chains in solutions simulated with dissipative particle dynamics (DPD), with a special focus on the potential influence of a low Schmidt number of a typical DPD fluid on the simulated polymer dynamics. It has been argued that a low Schmidt number in a DPD fluid can lead to underdevelopment of the hydrodynamic interaction in polymer solutions. The authors' analyses reveal that equilibrium polymer dynamics in dilute solution, under typical DPD simulation conditions, obey the Zimm [J. Chem. Phys. 24, 269 (1956)] model very well. With a further reduction in the Schmidt number, a deviation from the Zimm model to the Rouse model is observed. This implies that the hydrodynamic interaction between monomers is reasonably developed under typical conditions of a DPD simulation. Only when the Schmidt number is further reduced, the hydrodynamic interaction within the chains becomes underdeveloped. The screening of the hydrodynamic interaction and the excluded volume interaction as the polymer volume fraction is increased are well reproduced by the DPD simulations. The use of soft interaction between polymer beads and a low Schmidt number do not produce noticeable problems for the simulated dynamics at high concentrations, except for the entanglement effect which is not captured in the simulations.     

Atom-Efficient,Solvent-Free,Green Synthesis of Chalcones by Grinding

An improved Claisen–Schmidt condensation reaction of methyl ketones and aromatic aldehydes can be achieved by grinding at room temperature in the absence of solvents. This process is simple, efficient, economical, and environmentally benign compared to classical reactions.