Purpose – The purpose of this paper is to deal with unsteady double diffusive natural convection in a square enclosure filled with a porous medium with various boundary condition effects in the presence of heat source or sink. Design/methodology/approach – Finite difference method was employed to solve the dimensionless governing equations of the problem. The effects of governing parameters, namely, amplitude wave length ratio, dimensionless time parameter, Darcy number, buoyancy parameter and heat generation/absorption parameter on the streamlines, temperature and concentration contours, as well as Nusselt number and Sherwood number, were considered. Findings – The sinusoidal variations of the temperature and concentration remove the singularities which appear in the case of fixed temperature and concentration. Originality/value – The paper's results are validated by favorable comparisons with previously published results. The results of the problem are presented in graphical and tabular forms and discussed.

This paper presents a numerical investigation of laminar mixed convection cooling of heat source embedded on the bottom wall of an enclosure filled with nanofluids. The transport equations for a Newtonian fluid are solved numerically with finite difference method. The influences of governing parameters, namely, Rayleigh number, Reynolds number, location and geometry of the heat source, the type of nanofluid and solid volume fraction of nanoparticles on the cooling performance is studied. The present results are validated by favorable comparisons with previously published results. The results of the problem are presented in graphical and tabular forms and discussed.

A numerical study of laminar magnetohydrodynamic mixed convection in an inclined lid-driven squarecavity with opposing temperature gradients is presented. The vertical sidewalls are assumed to havenon-uniform temperature variation while the top and bottom walls are kept insulated with the topsurface moving at a constant speed. The transport equations are given in terms of the stream functions-vorticity formulation and are non-dimensionalized and then solved numerically by an accurate finite-volume method. The computation is carried out for wide ranges of the inclination angle (0 ≤  ≤ /2), theRichardson number (0.01 ≤ Ri ≤ 100), the Hartmann number (0 ≤ Ha ≤ 100), the amplitude ratio (0 ≤ ε ≤ 1)and the phase deviation (0 ≤  ≤ ). The results indicate that the rate of heat transfer along the heatedwalls is enhanced on increasing either Hartmann number or inclination angle. Average Nusselt numberis also, increased with increasing of the amplitude ratio for all values of the phase deviation. The non-uniform heating on both walls provides higher heat transfer rate than non-uniform heating of one wall.

A numerical investigation is performed into the natural convection heat transfer characteristics within an enclosed cavity filled with nanofluid. The left and right walls of the cavity have a complex-wavy geometry and are maintained at a low and high temperature, respectively. Meanwhile, the upper and lower walls of the cavity are both flat and insulated. The nanofluid is composed of Al2O3 nanoparticles suspended in pure water. In performing the analysis, the governing equations are formulated using the Smoothed Particle Hydrodynamics and the complex-wavy-surface is modeled as the superimposition of two sinusoidal functions. The simulations examine the effects of the volume fraction of nanoparticles, the Rayleigh number and the complex-wavy-surface geometry parameters on the flowstreamlines, isotherm distribution and Nusselt number within the cavity. The results show that for all values of the Rayleigh number, the Nusselt number, increases as the volume fraction of nanoparticles increases. In addition, it is shown that the heat transfer performance can be optimized by tuning the wavy-surface geometry parameters in accordance with the Rayleigh number. Overall, the results presented in this study provide a useful insight into potential strategies for enhancing the convection heat transfer performance within enclosed cavities with complex-wavy-wall surfaces.

A numerical investigation is performed into the natural convection heat transfer characteristics within an enclosed cavity filled with nanofluid. The left and right walls of the cavity have a complex-wavy geometry and are maintained at a low and high temperature, respectively. Meanwhile, the upper and lower walls of the cavity are both flat and insulated. The nanofluid is composed of Al2O3 nanoparticles suspended in pure water. In performing the analysis, the governing equations are formulated using the Smoothed Particle Hydrodynamics and the complex-wavy-surface is modeled as the superimposition of two sinusoidal functions. The simulations examine the effects of the volume fraction of nanoparticles, the Rayleigh number and the complex-wavy-surface geometry parameters on the flowstreamlines, isotherm distribution and Nusselt number within the cavity. The results show that for all values of the Rayleigh number, the Nusselt number, increases as the volume fraction of nanoparticles increases. In addition, it is shown that the heat transfer performance can be optimized by tuning the wavy-surface geometry parameters in accordance with the Rayleigh number. Overall, the results presented in this study provide a useful insight into potential strategies for enhancing the convection heat transfer performance within enclosed cavities with complex-wavy-wall surfaces.

In this paper, the buoyancy-driven fluid flow and heat transfer in a square cavity with partially active side walls are investigated numerically. The top and vertical walls of the cavity are maintained at the relatively low temperature. The governing partial differential equations have been described in smoothed particle hydrodynamics formulations. The transport equations for a Newtonian fluid are solved numerically using smoothed particle hydrodynamics (SPH) method. The results indicate the relation among changes taking part in the heat source length, heat source location, Rayleigh number, maximum temperature and maximum value of stream function and velocities.

Three interesting thermoresponsive branched oligoethylene glycol dendrimers based on tetrabromohydroquinone were efficiently synthesized from tetrabromohydroquinone and three different oligoethylene glycol derivatives. By visual inspection, all these dendrimers are water-soluble at room temperature. The thermoresponsive behaviors were investigated by using UV/vis turbidity measurement at different temperatures for 0.25 wt% of aqueous solutions from D1, D2 and D3. The cytotoxicity of the prepared dendrimers was tested against MCF-7 breast cancer cells. All tested dendrimers showed considerable results, where D2 dendrimer gave the best result; it showed cytotoxicity against MCF-7 cell line with IC50 of 1.07 mg/mL and resistant fraction equals 1.97%, the other two dendrimers showed a modest cytotoxic profile.

Nanoparticles exhibit unique physical properties that are not found in their bulk counterpart. The synthesis structure which contains Au or Ag core metallic particles and a shell of CdSe semiconductor has the combined properties of quantum dots and the metallic particles. A new method has been developed to grow plasmonic semiconductor nanocomposites of Au/CdSe and Ag/CdSe nanostructure. The method based on preparing seed of metal nanoparticles which used as a seed using organometllic pyrolysis followed by adding the semiconductor precursors. Their chemical composition crystal structure is determined via X-Ray Diffraction. The collective optical properties of the plasmonic semiconductor nanohybrid has been measured using spectrophotometer techniques and compared to those individual components. The main features which observed in the hybrid nanostructure is broodning of Plasmonic band and decrease in its amplitude in addition to shifting excitonic energy band to higher wave length.The quenching of the emission of Au/CdSe has been observed due to photoinduced electron injection into metallic seed. The electron transfer processes from CdSe to the gold is more faster than that of the silver. For this reason, we can consider the CdSe/Au is strong plasmonic - exitonic coupling but CdSe/Ag is week plasmonic-excitonic coupling.

Nanoparticles exhibit unique physical properties that are not found in their bulk counterpart. The synthesis structure which contains Au or Ag core metallic particles and a shell of CdSe semiconductor has the combined properties of quantum dots and the metallic particles. A new method has been developed to grow plasmonic semiconductor nanocomposites of Au/CdSe and Ag/CdSe nanostructure. The method based on preparing seed of metal nanoparticles which used as a seed using organometllic pyrolysis followed by adding the semiconductor precursors. Their chemical composition crystal structure is determined via X-Ray Diffraction. The collective optical properties of the plasmonic semiconductor nanohybrid has been measured using spectrophotometer techniques and compared to those individual components. The main features which observed in the hybrid nanostructure is broodning of Plasmonic band and decrease in its amplitude in addition to shifting excitonic energy band to higher wave length.The quenching of the emission of Au/CdSe has been observed due to photoinduced electron injection into metallic seed. The electron transfer processes from CdSe to the gold is more faster than that of the silver. For this reason, we can consider the CdSe/Au is strong plasmonic - exitonic coupling but CdSe/Ag is week plasmonic-excitonic coupling.