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In this study, the dual solutions for mixed convection flow of an Oldroyd-B fluid containing alumina nanoparticles over a shrinking sheet are investigated taking into account the effects of magnetic field and heat source/sink. By utilizing the similarity transformations, the governing equations are reduced to ordinary differential equations which have been solved by the well-known shooting method. The present investigation reveals that some published results are not realistic. It is remarkable that for higher Deborah numbers for relaxation and retardation times, suction parameter and magnetic field parameter, the domain of the occurrence of dual solutions becomes wider and the local skin friction coefficient and local Nusselt number are found to increase. On the other hand, dual solutions exist in a broader domain as long as the volume fraction of alumina nanoparticles is less than or equal to 0.05 and after that it decreases. The critical values of the shrinking parameter relating to the existence of dual solutions are rendered in approximate functions. These characteristics of an Oldroyd-B nanofluid are not reported yet and might be useful in the development of the existing technology.

The magnetohydrodynamic (MHD) radiative flow of a hybrid alumina-copper/water nanofluid past a permeable vertical plate with mixed convection is the focal interest in this present work. Dissimilar to the traditional nanofluid model that considers only one type of nanoparticles, we consider the hybridization of two types of nanoparticles in this work which are alumina and copper. The governing flow and heat transfer equations are simplified to the ordinary differential equations (ODEs) with the adaptation of conventional similarity transformations which are then evaluated by the bvp4c solver (MATLAB) to generate the numerical solutions. The solutions are generated and illustrated in the form of graph to be easily observed. Although dual solutions are obtained in this study, only one solution is determined to be stable. By reducing the concentration volume of copper and increasing the magnetic and radiation parameters, the boundary layer separation can be hindered. With the occurrence of opposing flow due to the mixed convection parameter, the heat transfer can be enhanced when the concentration volume of copper is being reduced and when the magnetic and radiation parameters are being proliferated.

The proficiency of hybrid nanoparticles in augmenting the heat transfer has fascinated many researchers to further analysing the working fluid. The present paper is focused on the MHD hybrid nanofluid flow with heat transfer on a moving plate with Joule heating. The combination of metal (Cu) and metal oxide (Al2O3) nanoparticles with water (H2O) as the base fluid is used for the analysis. Similarity transformation reduces the complexity of the PDEs into a system of ODEs, which is then solved numerically using the function bvp4c from MATLAB for different values of the governing parameters. Two solutions are obtained when the plate is moved oppositely from the free stream flow. Analysis of flow stability unveils the first solution as the real physical solution, which is realizable in practice. From physical perspective, the real solution must be available for all cases of λ which affirms the finding from stability analysis. An upsurge of suction’s strength and magnetic parameter enhances the heat transfer operation and extends the critical value λ c . Meanwhile, there is no change on the critical value when the Eckert number is added. This study is important in determining the thermal behavior of Cu-Al2O3/H2O when the physical parameters like magnetic field and Joule heating are embedded. The results are new and original with many practical applications in the modern industry.

The ferrofluid transport phenomena have a considerable interest in the boundary layer flow due to its versatility in advancing emerging industrial applications, such as printing. In this concern, the current theoretical model examines the particulate suspension's transport phenomena in the magnetite ferrofluid past a permeable non-isothermal moving surface with the viscous dissipation effect. Self-similarity quantities are applied to ease the solving process in the built-in collocation method, bvp4c function in the MATLAB software. The kerosene-based ferrofluid showed a better convective heat transfer rate than the water-based ferrofluid as the governing parameters vary. The dust particles’ increment in the ferrofluid increases the frictional drag force exerted on the shrinking sheet significantly. Dual solutions are obtainable only when the sheet shrinks to some extent. However, stability analysis confirmed that one of the numerical solutions is not stable.

Looking for multifunctional materials, an assessment of the performances both as fire retardant and generator of electrically conductive surfaces for a three component mixture of graphene oxide, phosphoric acid and melamine applied on wood chipboard was performed. A simple approach was used to investigate the intumescent char formation and quantify the loss mass during vertical burning tests, in which the prepared samples were exposed for a certain time interval to a flame generated by an ethanol lamp in ambient conditions. Moreover, mass loss evolution and structural changes that occur during the burning process were more comprehensive investigated by differential thermal and thermogravimetric (DTA/TGA) techniques. By comparing the performances between the wood chipboard samples without any coverage and those covered with one or multiple component mixture, an increase of protection against the fire action was noticed when the three component mixture was used. Also, an improvement of the electrical properties was observed, after flame exposure of the samples covered with multiple layers (i.e., two and three), when the three component mixture was used. Morphological and structural investigations by microscopy (optical and electronic-SEMEDX), X-ray diffraction (XRD) and spectral (Raman, FTIR) methods are described. An assessment of market potential is also discussed.

Here, continuous two-dimensional boundary layer flow of a Fe2O3 CuO/water hybrid nanofluid over a porous stretching/shrinking wedge with radiation and MHD effects has been investigated semi–analytically. The dual solutions of the problem and also its stability analysis are taken into account. Moreover, the mass-based procedure for hybrid nanofluid modeling has been used. According to this procedure, the volume fraction of first and second nanoparticles is written in terms of both nanoparticles as well as base fluid masses. The Tiwari-Das model joined with mass-based hybrid nanofluid procedure is applied to find the governing partial differential equations which are then transferred to a set of dimensionless ordinary differential equations with help of the similarity transform method. The numerical method of solution has been chosen based on a famous finite difference scheme (bvp4c) from MATLAB software. The results demonstrate that dual solutions exist for a certain domain of the wedge stretching/shrinking parameter. Also it is observed that always the first solutions have thinner boundary layer thickness than the second ones. Moreover, the critical value in which the solution is in existence increase with the enhancement of magnetic parameter and suction parameter. The magnetic parameter and the mass suction at the wedge's surface also leads to the increase in the local Nusselt number. Further, it is inferred that the second nanoparticle's mass enhancement results in the amplification of the skin friction coefficient and the local Nusselt number for the first solutions. In addition, the rise in radiation parameter tends to enhance the thermal boundary layer thickness.

Hybrid nanofluid has become one of the major interest topics among researchers nowadays due to its significant impact in myriad applications. This paper modeled and explored the properties of flow and heat transfer of mixed convection stagnation point flow for hybrid nanofluid (alumina-copper/water) on a vertical plate with slips and suction. By using the method of similarity transformation, the governing set of partial differential equations (PDEs) are transformed into ordinary differential equations (ODEs). These derived equations are then evaluated numerically by adopting the bvp4c function that is available in Matlab software. In the presence of slips together with the opposing flow of mixed convection, the local Nusselt number (heat transfer rate) can be augmented by increasing the solid volume fraction of copper. The surge of 0.5% of copper volume fraction can accelerate the heat transfer rate by approximately 1.3% in this present analysis within the specified value of slips, mixed convection, and suction. The stability analysis is conducted due to the existence of dual solutions and only the first solution is stable for practical application.

"The origin of resistance and its relation to the superconducting mechanism remain a profound, unsolved mystery. Currently, model parameters used to fit normal state properties are specific and vary arbitrarily from one doping. This short review illustrates the electrical resistivity of ceramic high temperature superconductors copper oxides. The article gives a summary of the prevailing arguments of researchers to relate the material to ceramic HTS compounds. Keywords: superconductivity, HTC ceramic compounds, resistivity. "

Single-crystal X-ray diffraction studies on Halogen-Bonded Organic Frameworks (XBOF) formed by N---I contacts of 2,2′,7,7′-tetrapyridyl-9,9′-spirobifluorene with pentafluoroiodobenzene or the isome...

To fill the existing literature gap, the numerical solutions for the oblique stagnation-point flow of Cu-Al2O3/H2O hybrid nanofluid past a shrinking surface are computed and analyzed. The computation, using similarity transformation and bvp4c solver, results in dual solutions. Stability analysis then shows that the first solution is stable with positive smallest eigenvalues. Besides that, the addition of Al2O3 nanoparticles into the Cu-H2O nanofluid is found to reduce the skin friction coefficient by 37.753% while enhances the local Nusselt number by 4.798%. The increase in the shrinking parameter reduces the velocity profile but increases the temperature profile of the hybrid nanofluid. Meanwhile, the increase in the free parameter related to the shear flow reduces the oblique flow skin friction.

Purpose The boundary-layer analysis is required to reveal the fluid flow behavior in several industrial processes and enhance the products’ effectiveness. Therefore, this research aims to investigate the buoyancy or mixed convective stagnation-point flow (SPF) and heat transfer of a micropolar fluid filled with hybrid nanoparticles over a vertical plate. The nanoparticles silver (Ag) and titanium dioxide (TiO2) are scattered into various base fluids to form a new-fangled class of (Ag-TiO2/various base fluid) hybrid nanofluid along with different shape factors. Design/methodology/approach The self-similarity transformations are used to reformulate the leading requisite partial differential equations into renovated non-linear dimensionless ordinary differential equations. The numerical dual solutions are gained for the transmuted requisite equations with the help of the bvp4c built-in package in MATLAB software. The results are validated by comparing them with previously available published data for a particular case of the present study. Findings The impact of various pertaining parameters such as nanoparticle volume fraction, material parameter, shape factor and mixed convective on temperature, heat transfer, fluid motion, micro-rotation and drag force are visualized and scrutinized through tables and graphs. It is observed that dual or non-uniqueness outcomes are found for the case of buoyancy assisting flow, whereas the solution is unique in the buoyancy opposing flow case. Additionally, the fluid motion and micro-rotation profiles decelerate in the presence of nanoparticle volume fraction, while the temperature augments. Originality/value The mixed convective stagnation point flow conveying TiO2/Ag hybrid nanofluid with micropolar fluid with various shape factors is the significant originality of the current investigation where multiple outcomes are obtained for the assisting flow. The various base fluids such as glycerin, water and water–ethylene glycol (50%:50%) are considered in the present problem. The bifurcation values of the considered problem do not exist, probably because of various base fluids. To the best of the authors’ knowledge, this work is new and original which were not previously reported.

This paper aims at analyzing the effect of heat treatment using Concentrated Solar Energy (CSE) on the martensitic microstructure evolution of Ti-6Al-4V alloy manufactured by Selective Laser Melting (SLM) technology. The application of CSE, a renewable energy sources, in post-processing of SLMed Ti-6Al-4V alloy is discussed based on heat treatments performed at Plataforma Solar de Almeria, Spain, using solar furnace SF40. In SLM process of Ti-6Al-4V powder because of local high heating followed by a rapid cooling the microstructure consists of an acicular martensite (α′ phase). Decomposition of α′ martensite of SLMed Ti-6Al-4V after heat treatment in solar furnace, using CSE, by SEM, EDX, TEM, SAED, and XRD analyses, was investigated. It has been found that for treatment below β-transus at 705 °C, because of low temperature, the α′ martensite was not fully converted into α + β and the β phase was not identified by XRD analysis. Heat treatments below (940 °C followed by 650 °C) and above (1050 °C) β-transus have revealed that α′ martensite was converted into a lamellar α + β mixture and also β phase was identified by XRD and TEM analysis. In the analyzed areas, middle areas of the samples contain an area fraction of β phase greater than the top areas. Area fraction of β phase, after heat treatment above β-transus, at 1050 °C, is greater than that obtained after treatment below β-transus.

The main objective was to reduce the consumption of material when obtaining 3D printed parts (different empty shapes inside) and the secondary one was to maintain the mechanical properties closer to the full printed version. In order to achieve these objectives, two internal configurations were designed - a configuration with hexagonal gaps (material reduction was 30%) and a configuration with sinuous gaps (material reduction was 15%). The specimens thus obtained were tested for traction, three-point bending and shock (resilience). Hexagonal hollow configuration has a resistance values close to those of solid specimens but with the advantage of consuming with 30% less material.

Boundary layer flow in the industrial applications such as extrusion processes is attributable to impulsive movement of an extensible moving surface. However, the velocity of the extruded surface may not necessarily be linear. Hence, this study proposes a unique model to investigate the unsteady stagnation point flow in hybrid nanofluid (Al2O3-Cu/H2O) induced by exponentially permeable stretching/shrinking sheet with the magnetic field. The system of ordinary differential equations is attained through a simplification of governing partial differential equations by employing appropriate similarity transformation. The numerical computation is determined by utilising the bvp4c procedure in the MATLAB program, which is proficient in generating non-uniqueness solutions. The noteworthy findings revealed that the skin friction coefficient intensifies in conjunction with the local Nusselt number by enhancing the suction/injection parameter and the nanoparticles volume fraction past an exponentially stretching/shrinking sheet. The results also signified that the increment in the unsteady parameter conclusively increases the skin friction coefficient, and the heat transfer rate shows an upsurge attribution resulting from the inclusion of the magnetic parameter towards an exponentially shrinking sheet. Also, the results are evidenced by having dual solutions, which ultimately lead to an investigation of the analysis of the solution stability, thereby validating the feasibility of the first solution. This crucial contribution will help to enhance industrial growth, especially in the manufacturing and processing sectors.

The operational performance of small-scale refrigeration systems is mainly decided by their capillary tubes outlet parameters, wherein an accurate determination of the pressure and vapour quality is a prerequisite. Experiments have been performed for a capillary tube (CT) with specified geometry consisting of a straight, a helical and a suction line heat exchanger (SLHX) section. The capillary tube is incorporated in a small refrigeration system operated with R600a. In addition, a model was developed to determine the steady-state operation of the capillary tubes (activated with R134a, R1234yf, R1234ze(E), R600, R600a, R152a and R513A refrigerants) and validated. The highest and lowest value of the vapour quality was discerned to be 0.3132 (for R1234yf) and 0.2124 (for R600), respectively. The relative errors between the experimental and model results for the CT outlet pressure and temperature were ranged from 1.16 to 5.35% and 0.12–0.81%, respectively. It is asserted that the present strategy may contribute towards the precise estimation of the pressure and vapour quality to customize the working performance of small scale refrigeration systems.

The problem of steady laminar three-dimensional stagnation-point flow on a permeable stretching/shrinking sheet with second order slip flow model is studied numerically. Similarity transformation has been used to reduce the governing system of nonlinear partial differential equations into the system of ordinary (similarity) differential equations. The transformed equations are then solved numerically using the \texttt{bvp4c} function in MATLAB. Multiple solutions are found for a certain range of the governing parameters. The effects of the governing parameters on the skin friction coefficients and the velocity profiles are presented and discussed. It is found that the second order slip flow model is necessary to predict the flow characteristics accurately.

An analysis is carried out to theoretically investigate the unsteady three dimensional stagnation-point of a viscous flow over a permeable stretching/shrinking sheet. A similarity transformation is used to reduce the governing system of nonlinear partial differential equations to a set of nonlinear ordinary (similarity) differential equations, which are then solved numerically using the \texttt{bvp4c} function in MATLAB. Results show that multiple solutions exist for a certain range of unsteadiness and stretching/shrinking parameters. The effects of the governing parameters on the skin friction coefficients and the velocity profiles are presented and discussed.

The non-Newtonian fluid model reflects the behavior of the fluid flow in global manufacturing progress and increases product performance. Therefore, the present work strives to analyze the unsteady Maxwell hybrid nanofluid toward a stretching/shrinking surface with thermal radiation effect and heat transfer. The partial derivatives of the multivariable differential equations are transformed into ordinary differential equations in a specified form by applying appropriate transformations. The resulting mathematical model is clarified by utilizing the bvp4c technique. Different control parameters are investigated to see how they affect the outcomes. The results reveal that the skin friction coefficient increases by adding nanoparticles and suction parameters. The inclusion of the Maxwell parameter and thermal radiation effect both show a declining tendency in the local Nusselt number, and as a result, the thermal flow efficacy is reduced. The reduction of the unsteadiness characteristic, on the other hand, considerably promotes the improvement of heat transfer performance. The existence of more than one solution is proven, and this invariably leads to an analysis of solution stability, which validates the first solution viability.

Purpose The purpose of this article is to study the steady laminar magnetohydrodynamics mixed convection stagnation-point flow of an alumina-graphene/water hybrid nanofluid with spherical nanoparticles over a vertical permeable plate with focus on dual similarity solutions. Design/methodology/approach The single-phase hybrid nanofluid modeling is based on nanoparticles and base fluid masses instead of volume fraction of first and second nanoparticles as inputs. After substituting pertinent similarity variables into the basic partial differential equations governing on the problem, the authors obtain a complicated system of nondimensional ordinary differential equations, which has non-unique solution in a certain range of the buoyancy parameter. It is worth mentioning that, the stability analysis of the solutions is also presented and it is shown that always the first solutions are stable and physically realizable. Findings It is proved that the magnetic parameter and the wall permeability parameter widen the range of the buoyancy parameter for which the solution exists; however, the opposite trend is valid for second nanoparticle mass. Besides, mass suction at the surface of the plate as well as magnetic parameter leads to reduce both hydrodynamic and thermal boundary layer thicknesses. Moreover, the assisting flow regime always has higher values of similarity skin friction and Nusselt number relative to opposing flow regime. Originality/value A novel mass-based model of the hybridity in nanofluids has been used to study the foregoing problem with focus on dual similarity solutions. The results of this paper are completely original and, to the best of the authors’ knowledge, the numerical results of the present paper were never published by any researcher.

We present vibrational properties of Franckeite, which is a naturally occurring van der Waals heterostructure consisting of two different semiconducting layers. Franckeite is a complex layered crystal composed of alternating SnS$_2$ like pseudohexagonal and PbS-like pseudotetragonal layers stacked on top of each other, providing a unique platform to study vibrational properties and thermal transport across layers with mass density and phonon mismatches. By using micro-Raman spectroscopy and first-principles Raman simulations, we found that the PbS-like pseudotetragonal structure is mostly composed of Pb$_3$SbS$_4$. We also discovered several low-frequency Raman modes that originate from the intralayer vibrations of the pseudotetragonal layer. Using density functional theory, we determined all vibrational patterns of Franckeite, whose signatures are observed in the Raman spectrum. By studying temperature dependent Raman spectroscopy (300 K - 500 K), we have found different temperature coefficients for both pseudotetragonal and pseudohexagonal layers. We believe that our study will help understand the vibration modes of its complex heterostructure and the thermal properties at the nanoscale., Comment: 15 pages, 10 figures

Purpose This paper aims to accentuate the behavior of second-grade hybrid Al2O3–Cu nanofluid flow and its thermal characteristics driven by a stretching/shrinking Riga plate. Design/methodology/approach The second-grade fluid is considered with the combination of Cu and Al2O3 nanoparticles. Three base fluids namely water, ethylene glycol (EG) and methanol with different Prandtl number are also examined. The formulation of the mathematical model of second-grade hybrid nanofluid complies with the boundary layer approximations. The complexity of the governing model is reduced into a simpler differential equations using the similarity transformation. The bvp4c solver is fully used to solve the reduced equations. The observation of multiple solutions is conducted for the assisting (stretching) and opposing (shrinking) cases. Findings The impact of suction parameter, second-grade parameter, electromagnetohydrodynamics (EMHD) parameter, velocity ratio parameter and the volumetric concentration of the alumina and copper nanoparticles are numerically analyzed on the velocity and temperature profiles, skin friction coefficient and local Nusselt number (thermal rate) of the second-grade Al2O3–Cu/water. The solution is unique when (static and stretching cases) while dual for a specific range of negative in the presence of suction effect. Based on the appearance of the first solution in all cases of, it is physically showed that the first solution is stable. Further examination reveals that the EMHD and suction parameters are the contributing factors for the thermal enhancement of this non-Newtonian working fluid. Meanwhile, the viscosity of the non-Newtonian fluid also plays a significant role in the fluid motion and heat transfer rate based on the finding that the EG base fluid produces the maximum heat transfer rate but the lowest critical value and skin friction coefficient. Originality/value The results are novel and contribute to the discovery of the hybrid nanoparticles’ performance in the non-Newtonian second-grade fluid. Besides, this study is beneficial to the researchers in this field and general audience from industries regarding the factors, which contributing to the thermal enhancement of the working fluid.

Phase-change memory (PCM) is a promising candidate for data storage in flexible electronics, but its high switching current and power are often drawbacks. In this study, we demonstrate a switching current density of ~0.1 mega-ampere per square centimeter in flexible superlattice PCM, a value that is one to two orders of magnitude lower than in conventional PCM on flexible or silicon substrates. This reduced switching current density is enabled by heat confinement in the superlattice material, assisted by current confinement in a pore-type device and the thermally insulating flexible substrate. Our devices also show multilevel operation with low resistance drift. The low switching current and good resistance on/off ratio are retained before, during, and after repeated bending and cycling. These results pave the way to low-power memory for flexible electronics and also provide key insights for PCM optimization on conventional silicon substrates.

A key bottleneck in using phase change memory (PCM) for training artificial neural networks is the abrupt nature of the melt-quench process (amorphization), which does not allow gradual reset. Here we demonstrate analog reset (partial amorphization) in PCM by applying sub-nanosecond programming pulses. Intermediate-level reset states are enabled by reducing the pulse width below the dominant thermal time constant of the PCM, which is on the order of a few nanoseconds. We show gradual change in PCM resistance as a function of number of (sub-ns) reset pulses with 50 intermediate states. Our unique scheme allows fine-tuning the resistance with sub-ns pulses of constant amplitude, which can significantly reduce the programming complexity in training neuromorphic hardware.

This paper examines the wall jet flow and heat transfer of the Glauert problem with the effect of the hybrid nanoparticles. Also, the influence of the magnetic field and the variable surface temperature are taken into consideration. Here, we consider copper (Cu) and alumina (Al2O3) as the hybrid nanoparticles while water is the base fluid. The governing equations are reduced to the similarity equations using similarity transformations. Then, the numerical solutions are obtained by using the bvp4c function in MATLAB software. The findings reveal that hybrid nanofluid provides a higher heat transfer rate compared to regular nanofluid. Besides, the heat transfer rate and the skin friction coefficient increase in the presence of nanoparticles. Moreover, the rise of the temperature index parameter contributes to the enhancement of the heat transfer rate, but it does not affect the skin friction coefficient. The stronger magnetic strength led to the reduction of the heat transfer rate and the skin friction coefficient.

Purpose This paper aims to examine the Cu-Al2O3/water hybrid nanofluid flow over a shrinking sheet in the presence of the magnetic field and dust particles. Design/methodology/approach The governing partial differential equations for the two-phase flow of the hybrid nanofluid and the dust particles are reduced to ordinary differential equations using a similarity transformation. Then, these equations are solved using bvp4c in MATLAB software. The bvp4c solver is a finite-difference code that implements the three-stage Lobatto IIIa formula. The numerical results are gained for several values of the physical parameters. The effects of these parameters on the flow and the thermal characteristics of the hybrid nanofluid and the dust particles are analyzed and discussed. Later, the temporal stability analysis is used to determine the stability of the dual solutions obtained as time evolves. Findings The outcome shows that the flow is unlikely to exist unless satisfactory suction strength is imposed on the shrinking sheet. Besides, the heat transfer rate on the shrinking sheet decreases with the increase of . However, the increase in and lead to enhance the heat transfer rate. Two solutions are found, where the domain of the solutions is expanded with the rising of, and. Consequently, the boundary layer separation on the surface is delayed in the presence of these parameters. Implementing the temporal stability analysis, it is found that only one of the solutions is stable as time evolves. Originality/value The dusty fluid problem has been widely studied for the flow over a stretching sheet, but only limited findings can be found for the shrinking counterpart. Therefore, this study considers the problem of the dusty fluid flow over a shrinking sheet containing Cu-Al2O3/water hybrid nanofluid with the effect of the magnetic field. In fact, this is the first study to discover the dual solutions of the dusty hybrid nanofluid flow over a shrinking sheet. Also, further analysis shows that only one of the solutions is stable as time evolves.

The study of boundary layer flow has gained considerable interest owing to its extensive engineering applications. Thus, this numerical study aims to investigate the stability analysis of unsteady flow in the hybrid Al2O3-Cu/H2O nanofluid past a shrinking permeable cylinder. The impacts of suction and unsteadiness parameters are considered in this study. The partial differential equations are converted into a system of nonlinear ordinary differential equations by selecting suitable similarity transformation and solved using the bvp4c code in the MATLAB program. The findings revealed that the existence of dual solutions is visible. The skin friction coefficient and the local Nusselt numbers of Al2O3-Cu/H2O increase with the inclusion of the suction parameter. The presence of the unsteadiness parameter actively promotes heat transfer degradation on the shrinking cylinder. Stability analysis indicates that a stable and physically realizable solution appeared in the first solution, whereas the second solution is unstable.

Purpose The purpose of this paper is to numerically investigate the hybrid nanofluid flow with the imposition of magnetohydrodynamic (MHD) and radiation effects alongside the convective boundary conditions over a permeable stretching/shrinking surface. Design/methodology/approach The mathematical model is formulated in the form of partial differential equations (PDEs) and are then transformed into the form of ordinary differential equations (ODEs) by using the similarity variables. The deriving ODEs are solved numerically by using the bvp4c solver in MATLAB software. Stability analysis also has been performed to determine the stable solution among the dual solutions obtain. For method validation purposes, a comparison of numerical results has been made with the previous studies. Findings The flow and the heat transfer of the fluid at the boundary layer are described through the plot of the velocity profile, temperature profile, skin friction coefficient and local Nusselt number that are presented graphically. Dual solutions are obtained, but only the first solution is stable. For the realizable solution at the shrinking surface, the proliferation of nanoparticle volume fraction (copper) and magnetic (magnetohydrodynamics) parameters can impede the boundary layer separation. Also, Biot number could enhance the temperature profile and the heat transfer rate at the shrinking surface region. The incrementation of 0.1% of Biot number has enhanced the heat transfer rate by approximately 0.1% and the incrementation of 0.5% volume fraction for copper has reduced the heat transfer rate by approximately 0.17%. Originality/value The presented model and numerical results are original and new. It can be used as a future reference for further investigation and related practical application. The main contribution of this investigation includes giving the initial prediction and providing the numerical data for the other researchers for their future reference regarding the impacts of nanoparticles volumetric concentration towards the main physical quantities of interest in the presence of magnetic and radiation parameters with the convective boundary conditions.

Purpose The analysis of boundary layers is needed to reflect the behaviour of fluid flows in current industrial processes and to improve the efficacy of products. Hence, this study aims to analyse the flow and heat transfer performance of hybrid alumina-copper/water (Al2O3-Cu/H2O) nanofluid with the inclusion of activation energy and binary chemical reaction effect towards a moving wedge. Design/methodology/approach The multivariable differential equations with partial derivatives are converted into a specific type of ordinary differential equations by using valid similarity transformations. The reduced mathematical model is elucidated in the MATLAB system by using the bvp4c procedure. This solution method is competent in delivering multiple solutions once appropriate assumptions are supplied. Findings The results of multiple control parameters have been studied, and the findings are verified to provide more than one solution. The coefficient of skin friction was discovered to be increased by adding nanoparticles volume fraction from 0% to 0.5% and 1%, by almost 1.6% and 3.2%. Besides, increasing the nanoparticles volume fraction improves heat transfer efficiency gradually. The inclusion of the activation energy factor displays a downward trend in the mass transfer rates, consequently reducing the concentration profile. In contrast, the increment of the binary reaction rate greatly facilitates the augmentation of mass transfer rates. There is a significant enhancement in the heat transfer rate, approximately 13.2%, when the suction effect dominates about 10% in the boundary layer flow. Additionally, the results revealed that as the activation energy rises, the temperature and concentration profiles rise as well. It is proved that the activation energy parameter boosts the concentration of chemical species in the boundary layer. A similar pattern emerges as the wedge angle parameter increases. The current effort aims to improve the thermal analysis process, particularly in real-world applications such as geothermal reservoirs, chemical engineering and food processing, which often encountered mass transfer phenomenon followed by chemical reactions with activation energy. Originality/value The present results are original and new for the study of flow and heat transfer over a permeable moving wedge in a hybrid nanofluid with activation energy and binary chemical reaction.

The steady two-dimensional Homan stagnation point flow and heat transfer of water base hybrid nanofluids (Al2O3 & Cu) over a permeable radially stretching/shrinking sheet have been studied. The similarity variables are introduced to transform the partial differential equations of the model into the ordinary differential equations. Numerical findings and dual solutions have been carried out by implementing the bvp4c code through MATLAB software. The most prominent effect is illustrated in the boundary layer thickness where the velocity profile increases upon the increment of the suction intensity but decreases in the temperature profile. Besides, the reduced Nusselt number also decreases as enlarging the value of copper and alumina nanoparticle volume fraction. The analysis of the first and second solutions are presented graphically with critical values as well as the detail discussions on the effects of the other involving parameters.

The impact of gyrotactic microorganisms in the mixed convection stagnation point flow of Cu-Al2O3/water hybrid nanofluid towards an immovable plate is numerically examined. The boundary layer equation coupled with the energy, nanoparticle volume fraction and conservation equations for microorganisms are simplified into a set of ordinary differential equations by adopting similarity transformation. The validation results are in a good agreement with previous studies approximately by 0% difference relative error. The results imply that the dual solutions only exist in the opposing flow up to a critical value/turning point. Beyond this turning point, the solutions are unavailable which reflects the separation of flow. The hybrid nanofluid is essential in delaying the separation process where the results show that λ c , h n f = − 3.5804 > λ c , C u = − 3.3903 > λ c , A l = − 3.2016 . Moreover, the advantage of this hybrid Cu-Al2O3/water nanofluid is in the augmentation of heat and mass transfer rates including the density of microorganisms which is higher than the Cu- and Al2O3-water nanofluids.

This significant study is designed to analyze the axisymmetric hybrid nanofluid flow with heat transfer on a convectively heated stretching/shrinking disk. The combination of metal (Cu) and metal oxide (Al2O3) nanoparticles with water (H2O) as the base fluid is used for the analysis. Similarity transformation is adopted to reduce the complexity of the PDEs into a system of ODEs. The utilization of suction in maintaining the steady flow solution for the shrinking disk case discloses the presence of dual solutions. Besides, an upsurge of Biot number and suction’s strength enhances the heat transfer operation. The application of Cu-Al2O3/water nanofluid can extend the range of solutions’ existence and consequently, decelerate the separation of laminar flow.

Hybrid nanofluid has been widely used in various heat transfer applications especially as the heat exchanger due to the great thermal conductivity compared to the conventional fluid. However, numerous investigations should still be carried out to properly understand its properties. Hence, in this study, a three-dimensional radiative flow of hybrid Cu-Al2O3/water nanofluid past a permeable shrinking plate is numerically analyzed. The boundary layer including the energy equations are reduced to a system of ordinary differential equations using the similarity transformations and are then solved numerically by using the bvp4c solver in MATLAB. The application of suction through the permeable plate is necessary in aiding the fluid motion past the shrinking surface. Dual solutions are also observable, hence the stability analysis is conducted to mathematically validate the real solution. The enhancement of copper volumetric concentration in the hybrid nanofluid is capable in decelerating the boundary layer separation.

Superlattice-like phase change memory (SL-PCM) promises lower switching current than conventional PCM based on Ge2Sb2Te5 (GST); however, a fundamental understanding of SL-PCM requires detailed characterization of the interfaces within such an SL. Here we explore the electrical and thermal transport of SLs with deposited Sb2Te3 and GeTe alternating layers of various thicknesses. We find up to an approximately four-fold reduction of the effective cross-plane thermal conductivity of the SL stack (as-deposited polycrystalline) compared with polycrystalline GST (as-deposited amorphous and later annealed) due to the thermal interface resistances within the SL. Thermal measurements with varying periods of our SLs show a signature of phonon coherence with a transition from wave-like to particle-like phonon transport, further described by our modeling. Electrical resistivity measurements of such SLs reveal strong anisotropy (∼2000×) between the in-plane and cross-plane directions due to the weakly interacting van der Waals-like gaps. This work uncovers electrothermal transport in SLs based on Sb2Te3 and GeTe for the improved design of low-power PCM.

Purpose This paper aims to investigate the radiation and magnetohydrodynamic effect on the flow toward a stagnation point of an exponentially shrinking sheet in a hybrid nanofluid. Design/methodology/approach The governing partial differential equations are transformed into a set of similarity equations and are then solved numerically using the boundary value problem solver, bvp4c, available in MATLAB software. The effects of several physical parameters on the flow and the thermal characteristics of the hybrid nanofluid are analyzed and discussed. Findings Numerical results clarify that the dual solutions arise for the shrinking case (λ < 0). The critical values expand for the stronger magnetic field. Besides, the skin friction and the heat transfer coefficients enhance with the rise of the magnetic field and the hybrid nanoparticles. The heat transfer rate increases by 10.11% for the nanofluid and 28.69% for the hybrid nanofluid compared to the regular fluid. In addition, the presence of radiation gives a higher heat transfer rate. Using the stability analysis, it is found that the first solution is stable, and the second solution is unstable, over time. Originality/value The stagnation point flow problem has been widely studied for the flow over a stretching sheet, but only limited findings can be found for the flow over a shrinking sheet. Therefore, the present study considers the problem of the stagnation point flow over a shrinking sheet in a Cu-Al2O3/water hybrid nanofluid with the effects of magnetic field and thermal radiation. The dual solutions of the hybrid nanofluid flow over a shrinking sheet are obtained. Further analysis shows that only one of the solutions is stable and thus physically reliable as time evolves.

The proficiency of hybrid nanofluid from Cu-Al2O3/water formation as the heat transfer coolant is numerically analyzed using the powerful and user-friendly interface bvp4c in the Matlab software. For that purpose, the Cu-Al2O3/water nanofluid flow between two parallel plates is examined where the lower plate can be deformed while the upper plate moves towards/away from the lower plate. Another considerable factor are the wall mass suction/injection and the magnetic field which applied on the lower plate. The reduced ordinary (similarity) differential equations are solved using the bvp4c application. The validation of this novel model is conducted by comparing a few of numerical values for the reduced case of viscous fluid. The results imply the potency of this heat transfer fluid which can enhance the heat transfer performance for both upper and lower plates approximately by 7.10% and 4.11%, respectively. An increase of squeezing parameter deteriorates the heat transfer coefficient by 4.28% (upper) and 5.35% (lower), accordingly. The rise of suction strength inflates the heat transfer at the lower plate while the presence of magnetic field shows reverse result.

In this study, temperature-dependent X-ray diffraction and transmission electron microscopy have been combined to reveal the mechanisms in the first-order phase transitions of ferroelectric K0·5Na0·5NbO3. Hereby, abnormal grain growth has been suppressed in the bulk material since it is a feature known to inhibit measurement reproducibility due to the introduced inhomogeneities. It is shown that phase transitions in this ceramic are multi-step processes, which feature an intermediate twinning stage. As perovskite-type ceramics can be regarded as model systems with respect to displacive transformations, the presented experiments give an insight into nucleation, propagation path and twinning mechanisms in ceramic materials.

Two-dimensional (2D) semiconducting transition metal dichalcogenides could be used to build high-performance flexible electronics. However, flexible field-effect transistors (FETs) based on such materials are typically fabricated with channel lengths on the micrometre scale, not benefitting from the short-channel advantages of 2D materials. Here, we report flexible nanoscale FETs based on 2D semiconductors; these are fabricated by transferring chemical-vapour-deposited transition metal dichalcogenides from rigid growth substrates together with nano-patterned metal contacts, using a polyimide film, which becomes the flexible substrate after release. Transistors based on monolayer molybdenum disulfide (MoS2) are created with channel lengths down to 60 nm and on-state currents up to 470 μA μm−1 at a drain–source voltage of 1 V, which is comparable to the performance of flexible graphene and crystalline silicon FETs. Despite the low thermal conductivity of the flexible substrate, we find that heat spreading through the metal gate and contacts is essential to reach such high current densities. We also show that the approach can be used to create flexible FETs based on molybdenum diselenide (MoSe2) and tungsten diselenide (WSe2). By transferring two-dimensional semiconductors from rigid growth substrates together with nano-patterned metal contacts, flexible field-effect transistors can be fabricated with channel lengths down to 60 nm.

The present work proposes the theoretical model of the mixed convection boundary layer flow and heat transfer in a hybrid nanofluid past an exponentially stretching/shrinking sheet. The transport phenomena occur in a porous medium along with the viscous dissipation and suction/injection effects. The governing equations expressing the current problem were modified into a solvable form of the mathematical model by applying valid similarity transformations. The function bvp4c in MATLAB was used to solve the attained equations. Two different solutions were achieved, and the stability analysis results designated that the upper branch solution promises stable transport phenomena in the flow region. The study also verified the influences of porosity parameter and nanoparticle volume fraction to broaden the existence range of the dual solutions. The heat transfer performance of hybrid nanofluid is enhanced than ordinary nanofluid. The proposed mixed convection hybrid nanofluid model is significant in the extrusion process, which yields desired heat transfer phenomena, and the disrupted flow phenomena are identified and clarified through the unstable solutions and stability analysis.

Purpose The purpose of this paper is to study the effects of thermal radiation and homogeneous-heterogeneous reactions in the three-dimensional hybrid nanofluid flow past a permeable stretching/shrinking sheet. Design/methodology/approach The combination of aluminum oxide (Al2O3) and copper (Cu) nanoparticles with total volumetric concentration is numerically analyzed using the existing correlations of hybrid nanofluid. With the consideration that both homogeneous and heterogeneous reactions are isothermal while the diffusion coefficients of both autocatalyst and reactant are same, the governing model is simplified into a set of differential (similarity) equations. Findings Using the bvp4c solver, dual solutions are presented, and the stability analysis certifies the physical/real solution. The findings show that the suction parameter is requisite to induce the steady solution for shrinking parameter. Besides, the fluid concentration owing to the shrinking sheet is diminished with the addition of surface reaction. Originality/value The present findings are novel and can be a reference point to other researchers to further analyze the heat transfer performance and stability of the working fluids.

Purpose This paper aims to focus on the analysis of the entropy generation in an inclined square cavity filled with a porous media saturated by a nanofluid with sinusoidal temperature distribution on the side walls, adiabatic conditions on the upper wall and a heat source at the lower wall. Design/methodology/approach The two-phase nanofluid model including the Brownian diffusion and thermophoresis effects has been used for simulation of nanofluid transport inside the porous cavity. The governing equations and the entropy generation owing to fluid friction, heat and mass transfer are transformed in terms of the dimensionless variables, and the results are obtained by using the finite difference method of the second-order accuracy. Findings The numerical results of the model are investigated, and the effect of different important parameters, such as inclination angle of the cavity, amplitude ratio of the sinusoidal temperature or phase deviation, is discussed. The results for no inclination of the cavity is compared and successfully validated with previous reported results of the literature. The important findings of the study are focused mainly on the existence of the irreversibility phenomena which are affected by the conditions of the model and the values of the studied parameters. Originality/value The originality of this work is given by the presented mathematical model, the numerical solution with new results for entropy generation in an inclined porous cavity filled by a nanofluid and the applications for design of electronic or energy devices.

Purpose This paper aims to investigate numerically the free convective heat transfer efficiency inside a rectotrapezoidal enclosure filled with Al2O3–Cu/water hybrid fluid. The bottom wall of the cavity is uniformly heated, the upper horizontal wall is insulated, and the remaining walls are considered cold. A new thermophysical relation determining the thermal conductivity of the hybrid nanofluid has been established, which produced results those match with experimental ones. Design/methodology/approach The governing partial differential equations are solved using the finite element method of Galerkin type. The simulated results in terms of streamlines, heat lines and isotherms are displayed for various values of the model parameters, which govern the flow. Findings The Nusselt number, friction factor and the thermal efficiency index are also determined for the pertinent parameters varying different ratios of the hybrid nanoparticles. The simulated results showed that thermal buoyancy significantly controls the heat transfer, friction factor and thermal efficiency index. The highest thermal efficiency is obtained for the lowest Rayleigh number. Practical implications This theoretical study is significantly relevant to the applications of the hybrid nanofluids electronic devices cooled by fans, manufacturing process, renewable energies, nuclear reactors, electronic cooling, lubrication, refrigeration, combustion, medicine, thermal storage, etc. Originality/value The results showed that nanoparticle loading intensified the rate of heat transfer and thermal efficiency index at the expense of the higher friction factor or higher pumping power. The results further show that the heat transmission in Al2O3–Cu/water hybrid nanofluid at a fixed value of intensified $\phi_{hnf}$ compared to the Al2O3/water nanofluid when an amount of higher conductivity nanoparticles (Cu) added to it. Besides, the rate of heat transfer in Cu/water nanofluid declines when the lower thermal conductivity Al2O3 nanoparticles are added to the mixture.

We report on the experimental characterization of anisotropic supramolecular assemblies by infrared (IR) nanopolarimetry. The presented IR absorption anisotropy imaging method simultaneously provides nanoscale-resolved insights into internal composition, intermolecular interactions, and supramolecular orientation in a label-free and noninvasive fashion. Our study of porphyrin aggregates demonstrates that their morphology can be correlated with stable J-type and metastable H-type stacking-induced anisotropic organization, revealing different oriented attachment growth mechanisms supported by theory. This analysis establishes the broad applicability of IR nanopolarimetric studies to supramolecular polymerization and biomolecular assemblies, opening up new routes in polymer science and macromolecular research.

Layered semiconducting transition metal dichalcogenides (TMDs) are promising materials for high-specific-power photovoltaics due to their excellent optoelectronic properties. However, in practice, contacts to TMDs have poor charge carrier selectivity, while imperfect surfaces cause recombination, leading to a low open-circuit voltage (VOC) and therefore limited power conversion efficiency (PCE) in TMD photovoltaics. Here, we simultaneously address these fundamental issues with a simple MoOx (x ≈ 3) surface charge-transfer doping and passivation method, applying it to multilayer tungsten disulfide (WS2) Schottky-junction solar cells with initially near-zero VOC. Doping and passivation turn these into lateral p-n junction photovoltaic cells with a record VOC of 681 mV under AM 1.5G illumination, the highest among all p-n junction TMD solar cells with a practical design. The enhanced VOC also leads to record PCE in ultrathin (2 photovoltaics. This easily scalable doping and passivation scheme is expected to enable further advances in TMD electronics and optoelectronics.

OBJECTIVE To analyze translucency variations among four different contemporary esthetic ceramic systems having different shades and thicknesses. MATERIAL AND METHODS Ceramic specimens having different shades and translucencies were tested: leucite reinforced glass-ceramic (ECAD), conventional feldspathic ceramic (Noritake), zirconia reinforced lithium silicate glass-ceramic (Suprinity) and hybrid ceramic (Enamic). Specimens of 0.6, 0.9, 1.2, 1.5 and 2.0-mm thickness (n = 3/group, 615 total) were prepared. Translucency (TP) and Relative Translucency (RTP) Parameters were calculated from spectroradiometric color readings. Effects of shade and thickness for a given system were statistically analyzed using MANOVA and Tukey post-hoc multiple comparisons tests. Translucency variations were assessed comparatively with literature-based perceptibility and acceptability thresholds. RESULTS TP/RTP values of all ceramic materials decreased with increasing thickness. The most translucent specimens were 0.6-mm thick ECAD HT-A3.5 (TP = 31.99) and ECAD HT-C2 (RTP = 23.75), while the least translucent was 2-mm thick Enamic T-3 M2 (TP = 7.27; RTP = 4.79). Thickness and material type significantly influenced translucency (p