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This paper aims to investigate magnetic impacts on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders. The annulus is filled by oxytactic microorganisms and nano-encapsulated phase change materials.

The modified ISPH method based on the time-fractional derivative is applied to solve the regulating equations in Lagrangian dimensionless forms. The pertinent factors are bioconvection Rayleigh number Ra_b (1–100), circular cylinder’s radius R_c (0.1–0.3), fractional time derivative α (0.95–1), Darcy parameter Da (10⁻⁵–10⁻²), nanoparticle parameter ϕ (0–0.1), Hartmann number Ha (0–50), Lewis number Le (1–20), Peclet number Pe (0.1–0.75), s (0.1–0.9), number of cylinders N_Cylinders (1–4), Rayleigh number Ra (10³–10⁶) and fusion temperature θ_f (0.005–0.9).

The simulations revealed that there is a strong enhancement in the velocity field according to an increase in Ra_b. The intensity and location of the phase zone change in response to changes in θ_f. The time-fractional derivative a acting on a nanofluid velocity and flow characteristics in an annulus. The number of embedded cylinders N_Cylinders is playing a significant role in the cooling processes and as N_Cylinders increases from 1 to 4, the velocity field’s maximum reduces by almost 33.3%.

The novelty of this study is examining the impacts of the magnetic field and the presence of several numbers of embedded cylinders on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders.

The purpose of this paper is to perform numerical simulations based on the incompressible smoothed particle hydrodynamics (ISPH) method for thermo-diffusion convection in a hexagonal-shaped cavity saturated by a porous medium and suspended by a nano-encapsulated phase change material (NEPCM). Here, the solid particles are inserted into a phase change material to enhance its thermal performance.

Superellipse rotated shapes with variable lengths are embedded inside a hexagonal-shaped cavity. These inner shapes are rotated around their center by a uniform circular velocity and their conditions are positioned at high temperature and concentration. The controlling equations in a non-dimensional form were analyzed by using the ISPH method. At first, the validation of the ISPH results is performed. Afterward, the implications of a fusion temperature, lengths/types of the superellipse shapes, nanoparticles parameter and time parameter on the phase change heat transfer, isotherms, isoconcentration and streamlines were addressed.

The achieved simulations indicated that the excess in the length of an inner superellipse shape augments the temperature, concentration and maximum of the streamlines in a hexagonal-shaped cavity. The largest values of mean Nusselt number are attained at the inner rhombus shape with convex (n = 1.5) and the largest values of mean Sherwood number are attained at the inner rectangle shape with rounded corners (n = 4).

The ISPH method is developed to emulate the influences of the uniform rotation of the novel geometry shapes on heat/mass transport inside a hexagonal-shaped cavity suspended by NEPCM and saturated by porous media.

The purpose of this paper is to work out the magnetic forces on heat/mass transmission in a cavity filled with a nanofluid and wavy porous medium by applying the incompressible smoothed particle hydrodynamics (ISPH) method.

The cavity is filled by a nanofluid and an undulating layer of a porous medium. The inserted two circular cylinders are rotated around the cavity’s center by a uniform circular velocity. The outer circular cylinder has four gates, and it carries two different boundary conditions. The inner circular cylinder is carrying Th and Ch. The Lagrangian description of the dimensionless regulating equations is solved numerically by the ISPH method.

The major outcomes of the completed numerical simulations illustrated the significance of the wavy porous layer in declining the nanofluid movements, temperature and concentration in a cavity. The nanofluid movements are declining by an increase in nanoparticle parameter and Hartmann number. The variations on the boundary conditions of an outer circular cylinder are changing the lineaments of heat/mass transfer in a cavity.

The originality of this study is investigating the dual rotations of the cylinders on magnetohydrodynamics thermosolutal convection of a nanofluid in a cavity saturated by two wavy horizontal porous layers.

This study aims to investigate the impact of audit fees on audit quality, the impact of audit quality on firm value and whether these effects are conditional on audit tenure by bringing evidence from an emerging market.

Different regression techniques are used, such as logistic regression, probit regression, ordinary least squares regression and fixed effects regression. The authors used panel data of 80 nonfinancial Egyptian-listed firms over 2016–2020.

The authors found a significant positive relationship between audit fees and audit quality and a significant positive relationship between audit quality and firm value. Furthermore, the authors found that the positive relationship between audit fees and audit quality is less pronounced for higher audit tenure firms. Finally, the authors also found that the positive relationship between audit quality and firm value is stronger for lower audit tenure firms.

To the best of the authors’ knowledge, this is the first study to bring evidence from an emerging African market about the joint association between audit tenure, audit fees, audit quality and firm value. It provides beneficial insights to regulators regarding the possibility and the benefits of improving audit quality, which is critically needed in contexts with weak governance systems.

The entropy and thermal behavior analyses of non-Newtonian nanofluid double-diffusive natural convection inside complex domains may captivate a bunch of scholars’ attention because of the potential utilizations that they possess in modern industries, for example, heat exchangers, solar energy collectors and cooling of electronic apparatuses. This study aims to investigate the second law and thermal behavior of non-Newtonian double-diffusive natural convection (DDNC) of Al₂O₃-H₂O nanofluid within a C-shaped cavity emplacing two hot baffles and impacted by a magnetic field.

For the governing equations of the complicated and practical system with all considered parameters to be solved via a formidable numerical approach, the finite element method acts as an approach to achieving the desired solution. This method allows us to gain a detailed solution to the studied geometry.

This investigation has been executed for the considered parameters of range, such as power-law index, baffle length, Lewis number, buoyancy ratio, Hartmann number and Rayleigh number. The main results reveal that isothermal and concentration lines are significantly more distorted, indicating intensified concentration and temperature distributions because of the growth of baffle length (L). Nu_ave decreases by 8.4% and 0.8% while it enhances by 49.86% and 33.87%, respectively, because of growth in the L from 0.1 to 0.2 and 0.2 to 0.3.

Such a comprehensive study on the second law and thermal behavior of DDNC of Al₂O₃-H₂O nanofluid within a C-shaped cavity emplacing two hot baffles and impacted by magnetic field has not yet been carried out.

Tar‐impregnated paper strips, 2m long and 20cm width were painted with 1–1.25mm thick yellow traffic paint. Sand gravel having a grain size 2.0 + 1.5 mm was uniformly screened over the wet paint film. The dry painted samples were fixed on pavements of Jeddah‐Taif highway during the summer [42 ± 2°C]. The mechanical wear rate was determined and compared with that of sand‐free paint.

This study aims to provide an efficient nanocomposite that might be used to protect deteriorated archaeological stucco.

The current experimental study evaluates the effectiveness of the hydroxyapatite nanoparticles (HA NPs) added to graphite carbon nitride (g-C₃N₄) and mixed with Paraloid (B-72) (B-44) in acetone in consolidating samples. The physicochemical properties of the as-prepared nanopowders have been investigated using Fourier transform infrared (FT-IR). This study involves monitoring the transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform changes in consolidated samples after exposure to various conditions by using the digital microscope and scanning electron microscopy to identify the appearance of the consolidated stucco samples after applying the selected nanocomposites and after their artificial aging procedures. Color change is measured using a colorimeter, and comparisons are made between samples before and after aging. Physical and mechanical properties are determined, and the contact angle is measured to measure hydrophobicity rate.

The obtained results indicate that HA/g-C₃N₄ hybrid nanocomposites with a composition of HA 0.5%/g-C₃N₄ 1%/B-72 3% and HA 0.5%/g-C3N4 1%/B-44 3% achieved the best consolidating results among the proposed mixtures for stucco samples, where the percentage of weight loss was 0.77 with B-72, 0.53 with B-44. Surface identification and characterization of hydroxyapatite HA NPs/g-C₃N₄ hybrid nanocomposites embedded in B72/B44matrix were carried out using Scanning Electron Microscopy coupled with energy-dispersive x-ray spectroscopy (SEM–EDX).

This study provides important findings from the analytical procedures used to evaluate the consolidation materials used in this study. The findings are beneficial for the preservation of archaeological stucco. The investigation findings revealed that the most favorable outcomes were obtained from HA/g-C₃N₄ hybrid nanocomposites containing HA 0.5%, g-C₃N₄ 1% and B-72 3%, as well as HA 0.5%, g-C₃N₄ 1% and B-44 3%. Consequently, it is advised to use this nanocomposite to consolidate archaeological stucco, thus establishing a promising initial stride toward conserving archaeological stucco for future research endeavors. This study introduces a new nanocomposite material (HA NPs/G-C₃N₄) that can be used to protect and improve archaeological plaster. This is very important for preserving cultural heritage. The incorporation of nanotechnology improves the material’s physical and mechanical qualities. The research uses various characterization techniques (including TEM, XRD and FT-IR) to meticulously analyze the physicochemical properties of the nanocomposite material and assess its efficacy in practical applications through artificial aging experiments, offering novel insights and methodologies for future cultural relic preservation studies.

The European association of pigment and dye manufacturers established a method for the estimation of heat and light fastness of organic pigments. In such method, pigments were dispersed in partially dried linseed oil whereby prints were made on standard writing paper. Degraded prints were visually estimated after comparing with a freshly prepared standard scale of 8 grades. A sample similar to scale 5 or more was considered to be of good or excellent fastness. Practically, it became familiar with controversial personnel estimations, especially in regard to the critical level of 4–5. Furthermore, the specific side effect interference of the linseed oil resin could not be avoided. It becomes reasonable to put forward a method depending on instrumental measurements. In the light of this method, heat and light fastness of organic pigments can be colourimetrically determined. The pigment is pasted in water containing 2–3% weight of sodium silicate as binding agent. Thin film prints are then made on a transparent non‐porous standard paper 80 g/m2. Prints are dried over P2O5 in a desicator placed in a cool and dark place. The dried prints are striped in 2cm width. Some of these stripes are taken for the colourimetric determination of the colour density with the help of a colour densitometer. Other stripes are subjected for 72 hours to daylight (not to direct sun rays) or placed in a drying oven maintained at the required temperature for the same duration. For colour density measurements, prints are underlined with 100 g/m2 white standard paper. Peak heights obtained with certain light wave‐length are computed with reference to the peak of the undergraded sample. It has been shown that a change in heat or light fastness as low as 2% can be determined with an accuracy range of 0.5% compared to 12.5% and 3.5% for the European method respectively.

The purpose of this study is to investigate the interaction between magnetotactic bacteria and Fe₃O₄–water nanofluid (NF) in a wavy enclosure in the presence of 2D natural convection flow.

Uniform magnetic field (MF), Brownian and thermophoresis effects are also contemplated. The dimensionless, time-dependent equations are governed by stream function, vorticity, energy, nanoparticle concentration and number of bacteria. Radial basis function-based finite difference method for the space derivatives and the second-order backward differentiation formula for the time derivatives are performed. Numerical outputs in view of isolines as well as average Nusselt number, average Sherwood number and flux density of microorganisms are presented.

Convective mass transfer rises if any of Lewis number, Peclet number, Rayleigh number, bioconvection Rayleigh number and Brownian motion parameter increases, and the flux density of microorganisms is an increasing function of Rayleigh number, bioconvection Rayleigh number, Peclet number, Brownian and thermophoresis parameters. The rise in buoyancy ratio parameter between 0.1 and 1 and the rise in Hartmann number between 0 and 50 reduce all outputs average Nusselt, average Sherwood numbers and flux density of microorganisms.

This study implies the importance of the presence of magnetotactic bacteria and magnetite nanoparticles inside a host fluid in view of heat transfer and fluid flow. The limitation is to check the efficiency on numerical aspect. Experimental observations would be more effective.

In practical point of view, in a heat transfer and fluid flow system involving magnetite nanoparticles, the inclusion of magnetotactic bacteria and MF effect provide control over fluid flow and heat transfer.

This is a scientific study. However, this idea may be extended to sustainable energy or biofuel studies, too. This means that a better world may create better social environment between people.

The presence of magnetotactic bacteria inside a Fe₃O₄–water NF under the effect of a MF is a good controller on fluid flow and heat transfer. Since the magnetotactic bacteria is fed by nanoparticles Fe₃O₄ which has strong magnetic property, varying nanoparticle concentration and Brownian and thermophoresis effects are first considered.

The purpose of this paper is to provide a summarization and review of the present author's main investigations on failure modes of reticular metal foams under different loadings in engineering applications.

With the octahedral structure model proposed by the present authors themselves, the fundamentally mechanical relations have been systematically studied for reticular metal foams with open cells in their previous works. On this basis, such model theory is continually used to investigate the failure mode of this kind of porous materials under compression, bending, torsion and shearing, which are common loading forms in engineering applications.

The pore-strut of metal foams under different compressive loadings will fail in the tensile breaking mode when it is brittle. While it is ductile, it will tend to the shearing failure mode when the shearing strength is half or nearly half of the tensile strength for the corresponding dense material and to the tensile breaking mode when the shearing strength is higher than half of the tensile strength to a certain value. The failure modes of such porous materials under bending, torsional and shearing loads are also similarly related to their material species.

This paper presents a distinctive method to conveniently analyze and estimate the failure mode of metal foams under different loadings in engineering applications.