Weak dissipation of electrostatic solitary structures in warm collisional pair-ion plasmas with non-Maxwellian electron population

The localized electrostatic structures with dissipation due to ion-neutral collisions in a symmetric warm pair-ion plasma in the presence of non-Maxwellian population of electrons are studied. The analytical model for ion dynamics is based on fluid equations and the evolution equation is derived by using the reductive perturbation scheme in the form of a damped Korteweg-de Vries equation. The parameter regime relevant to space-based observations and laboratory plasmas is considered and time evolution of the propagating ion-acoustic soliton is discussed. The energetic-particles-driven properties of soliton for various spectral indices, dissipation, ion temperature, and density are illustrated with comparison to the thermal mode for Boltzmann distribution of electrons.     

The noncommutative values of quantum observables

We discuss the notion of representing the values of physical quantities by the real numbers, and its limits to describe the nature to be understood in the relation to our appreciation that the quantum theory is a better theory of natural phenomena than its classical analog. Getting from the algebra of physical observables to their values for a fixed state is, at least for classical physics, really a homomorphic map from the algebra into the real number algebra. The limitation of the latter to represent the values of quantum observables with noncommutative algebraic relation is obvious. We introduce and discuss the idea of the noncommutative values of quantum observables and its feasibility, arguing that at least in terms of the representation of such a value as an infinite set of complex numbers, the idea makes reasonable sense theoretically as well as practically.     

Impact of anisotropic slip on the stagnation-point flow past a stretching/shrinking surface of the Al_2O_3-Cu/H_2O hybrid nanofluid

The characteristics of heat transfer in the three-dimensional stagnationpoint flow past a stretching/shrinking surface of the Al_2O_3-Cu/H_2O 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.     

Hybrid nanofluid flow induced by an exponentially shrinking sheet

The flow and heat transfer induced by an exponentially shrinking sheet with hybrid nanoparticles is investigated in this paper. The alumina (Al₂O₃) and copper (Cu) nanoparticles are suspended in water to form Al₂O₃–Cu/water hybrid nanofluid. In addition, the effects of magnetohydrodynamic (MHD) and radiation are also taken into account. The similarity equations are gained from the governing equations using similarity transformation, and their solutions are obtained by the aid of the bvp4c solver available in Matlab software. Results elucidate that dual solutions exist for suction strength S > S_c and shrinking strength λ > λ_c. The critical values S_c and λ_c for the existence of the dual solutions decrease with the rising of the solid volume fractions of Cu, φ₂ and the magnetic parameter, M. Besides, the skin friction and the heat transfer rate increase with the increasing of φ₂ and M for the upper branch solutions. The increasing of radiation, R leads to reduce the surface temperature gradient which implies to the reduction of the heat transfer rate for both branches when λ < 0 (shrinking sheet). The stability of the dual solutions is determined by the temporal stability analysis, and it is discovered that only one of them is stable and physically applicable.     

Magnetohydrodynamics (MHD) axisymmetric flow and heat transfer of a hybrid nanofluid past a radially permeable stretching/shrinking sheet with Joule heating

The main interest of the present work is to fundamentally investigate the flow characteristics and heat transfer of a hybrid Cu-Al₂O₃/water nanofluid due to a radially stretching/shrinking surface with the mutual effects of MHD, suction and Joule heating. The surface is permeable to physically allow the wall mass fluid suction. Tiwari and Das model of nanofluid is used with the new thermophysical properties of hybrid nanofluid to represent the problem. A similarity transformation is adopted to convert the governing model (PDEs) into a nonlinear set of ordinary differential equations (ODEs). A bvp4c solver in MATLAB software is employed to numerically compute the transformed system. The numerical results are discussed and graphically manifested in velocity and temperature profiles, as well as the skin friction coefficient and heat transfer rate with the pertinent values of the dimensionless parameters namely magnetic, Cu volume fraction, suction and Eckert number. The Eckert number has no impact on the boundary layer separation while the higher value of the suction parameter may affect the heat transfer performance. The presence of dual solutions (first and second) is seen on all the profiles within a limited range of the physical parameters. The stability analysis is executed, and it is validated that the first solution is the real solution.     

Flat sheet direct contact membrane distillation desalination system using temperature-dependent correlations: thermal efficiency via a multi-parameter sensitivity analysis based on Monte Carlo method

Journal of Thermal Analysis and Calorimetry - In this paper, a 1D model of direct contact membrane distillation is presented in which all fluid properties are temperature-dependent. In addition, a...     

Bioremediation strategies of palm oil mill effluent and landfill leachate using microalgae cultivation: An approach contributing towards environmental sustainability

Palm oil mill effluent (POME) is defined as the wastewater that contains high concentrations of organics, nutrients and oil and grease generated from the production process of palm oil. Therefore, proper discharge and management of POME is important to avoid deleterious impact on the environment. In fact, solid waste generation is a precursor for its disposal issues as most of the solid waste generated in developing nations is dumped into landfills. This has led to the threat posed by the generation of landfill leachate (LL). LL is a complex dark coloured liquid consisting of organic matter, inorganic substances, trace elements and xenobiotics. Hence, it is essential to effectively treat the landfill leachate before discharging it to avoid contamination of soil, surface & groundwater bodies. Conventional treatment methods comprises of physical, biological and chemical treatment, however, microalgal-based treatment could also be incorporated. Furthermore, with the benefits offered by microalgae in valorisation, the application of microalgae in POME and leachate treatment as well as biofuel production, is considerably viable. This paper provides an acumen of the microalgae-based treatment of POME and LL, integrated with biofuel production in a systematic and critical manner. The pollutants assimilation from wastewater and CO₂ biosequestration are discussed for environmental protection. Cultivation systems for wastewater treatment with simultaneous biomass production and its valorisation, are summarised. The study aims to provide insight to industrial stakeholders on economically viable and environmentally sustainable treatment of wastewaters using microalgae, and eventually contributing to the circular bioeconomy and environmental sustainability.     

An overview of techniques and strategies for isolation of flavonoids from the genus Erythrina

Plants in the genus Erythrina is a potential source of chemical constituents, one of which is flavonoids, which have diverse bioactivities. To date, literature on the flavonoids from the genus Erythrina has only highlighted the phytochemical aspects, so this review article will discuss isolation techniques and strategies for the first time. More than 420 flavonoids have been reported in the Erythrina genus, which are grouped into 17 categories. These flavonoid compounds were obtained through isolation techniques and strategies using polar, semi-polar, and non-polar solvents. Various chromatographic techniques have been developed to isolate flavonoids using column flash chromatography, quick column chromatography, centrifugally accelerated thin-layer chromatography, radial chromatography, medium-pressure column chromatography, semi-preparative high-performance liquid chromatography, and preparative high-performance liquid chromatography. Chromatographic processes for isolating flavonoids can be optimized using multivariate statistical applications such as response surface methodology with central composite design, Box–Behnken design, Doehlert design, and mixture design.     

Characterization of Laves phase in Crofer 22 H stainless steel

This study investigated the effect of annealing temperature on the precipitation behavior of Crofer^® 22 H at 600 °C, 700 °C, and 800 °C. The grain size distribution, precipitate phase identification, and microstructure were analyzed using electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS). The morphology of Laves phase (Fe,Cr,Si)₂(Nb,W) precipitates having the Cr₂Nb structure changed from strip-like to needle-shaped as the annealing temperature was increased. The precipitates of the Laves phase also shifted from the grain boundaries to the grain interiors when the temperature was increased. However, the average grain size (150 μm) of the ferritic matrix did not significantly change at 600 °C, 700 °C, and 800 °C for 10 h.