Noura Alsedais, Amal Al-Hanaya and Abdelraheem M. Aly
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…
Abstract
Purpose
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.
Design/methodology/approach
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 Rab (1–100), circular cylinder’s radius Rc (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 NCylinders (1–4), Rayleigh number Ra (103–106) and fusion temperature θf (0.005–0.9).
Findings
The simulations revealed that there is a strong enhancement in the velocity field according to an increase in Rab. The intensity and location of the phase zone change in response to changes in θf. The time-fractional derivative a acting on a nanofluid velocity and flow characteristics in an annulus. The number of embedded cylinders NCylinders is playing a significant role in the cooling processes and as NCylinders increases from 1 to 4, the velocity field’s maximum reduces by almost 33.3%.
Originality/value
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.
Details
Keywords
Investigates urban bias in state policy making in Mexico. Refers to literature claiming that rural poverty in developing nations is a major problem because capitalism reflects an…
Abstract
Investigates urban bias in state policy making in Mexico. Refers to literature claiming that rural poverty in developing nations is a major problem because capitalism reflects an urban bias. Examines social security coverage for the rural poor in Mexico and notes that there are great variations depending on area, suggesting that social security coverage is politically negotiable. Outlines briefly the historical development of Mexico’s welfare state and uses a power resource model to demonstrate how groups with competing interests go about securing benefits from the state. Cites literature on dependency theory, indicating that rural groups have failed to mobilize politically and have therefore not secured the same state resources (such as social security benefits and housing) as urban groups, yet argues that this does not always apply in Mexico, partially due to party politics and bureaucratic paternalism. Explains how data was collected to examine regional variations in social security coverage among the rural poor and how the data was analysed. Reveal that workers in important international export markets (such as cotton and sugar) have greater political leverage in obtaining better social security benefits. Notes also that areas supporting the political party in power obtain better benefits. Concludes, therefore, that rural workers are not powerless in the face of urban capitalism and that urban bias and dependency theories do not reflect the situation in Mexico – rather social security benefits are politically negotiable.
Details
Keywords
Abdelraheem M. Aly, Noura Alsedais and Hakan F. Oztop
The purpose of this study is to use the incompressible smoothed particle hydrodynamics method to examine the influences of a magnetic field on the double-diffusive convection…
Abstract
Purpose
The purpose of this study is to use the incompressible smoothed particle hydrodynamics method to examine the influences of a magnetic field on the double-diffusive convection caused by a rotating circular cylinder with paddles within a square cavity filled by a nanofluid.
Design/methodology/approach
The cavity is saturated by two wavy layers of non-Darcy porous media with a variable amplitude parameter. The embedded circular cylinder with paddles carrying T_h and C_h is rotating around the cavity center by a uniform circular velocity.
Findings
The lineaments of nanofluid velocity and convective flow, as well as the mean of Nusselt and Sherwood numbers, are represented below the variations on the frequency parameter, amplitude parameter of the wavy porous layers, Darcy parameter, nanoparticles parameter, Hartmann number and Ryleigh number. The performed simulations showed the role of paddles mounted on circular cylinders for enhancing the transmission of heat and mass within a cavity. The wavy porous layers at the lower Darcy parameter are playing as a blockage for the nanofluid flow within the porous area. Increasing the concentration of the nanoparticles to 6% reduces the maximum flow speed by 8.97% and maximum streamlines |ψ|max by 10.76%. Increasing Hartmann number to 100 reduces the maximum flow speed by 65.83% and |ψ|max by 75.54%.
Originality/value
The novelty of this work is to examine the effects of an inclined magnetic field and rotating novel shape of a circular cylinder with paddles on the transmission of heat/mass in the interior of a nanofluid-filled cavity saturated by undulating porous medium layers.
Details
Keywords
Zehba Raizah and Abdelraheem M. Aly
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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).
Originality/value
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.
Details
Keywords
This paper aims to adopt incompressible smoothed particle hydrodynamics (ISPH) method to simulate MHD double-diffusive natural convection in a cavity containing an oscillating…
Abstract
Purpose
This paper aims to adopt incompressible smoothed particle hydrodynamics (ISPH) method to simulate MHD double-diffusive natural convection in a cavity containing an oscillating pipe and filled with nanofluid.
Design/methodology/approach
The Lagrangian description of the governing partial differential equations are solved numerically using improved ISPH method. The inner oscillating pipe is divided into two different pipes as an open and a closed pipe. The sidewalls of the cavity are cooled with a lower concentration C_c and the horizontal walls are adiabatic. The inner pipe is heated with higher concentration C_h. The analysis has been conducted for the two different cases of inner oscillating pipes under the effects of wide range of governing parameters.
Findings
It is found that a suitable oscillating pipe makes a well convective transport inside a cavity. Presence of the oscillating pipe has effects on the heat and mass transfer and fluid intensity inside a cavity. Hartman parameter suppresses the velocity and weakens the maximum values of the stream function. An increase on Hartman, Lewis and solid volume fraction parameters leads to an increase on average Nusselt number on an oscillating pipe and left cavity wall. Average Sherwood number on an oscillating pipe and left cavity wall decreases as Hartman parameter increases.
Originality/value
The main objective of this work is to study the MHD double-diffusive natural convection of a nanofluid in a square cavity containing an oscillating pipe using improved ISPH method.
Details
Keywords
Saleh Aly Saleh Aly, Ahmed Diab and Samir Ibrahim Abdelazim
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
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.
Details
Keywords
Abdelraheem M. Aly and Ehab Mahmoud Mohamed
The purpose of this study is to use an incompressible smoothed particle hydrodynamics (ISPH) method for simulating buoyancy ratio and magnetic field effects on double diffusive…
Abstract
Purpose
The purpose of this study is to use an incompressible smoothed particle hydrodynamics (ISPH) method for simulating buoyancy ratio and magnetic field effects on double diffusive natural convection of a cooper-water nanofluid in a cavity. An open pipe is embedded inside the center of a cavity, and it is occupied by solid particles.
Design/methodology/approach
The dimensionless governing equations in Lagrangian form were solved by ISPH method. Two different thermal conditions were considered for the solid particles. The actions of the solid particles were tracked inside a cavity. The effects of Hartman parameter, Rayleigh number, nanoparticles volume fraction and Lewis number on features of heat and mass transfer and flow field were tested.
Findings
The results showed that the buoyancy ratio changes the directions of the solid particles diffusion in a cavity. The hot solid particles were raised upwards at aiding mode (N > 0) and downwards at an opposing mode (N < 0). A comparison is made with experimental and numerical simulation results, and it showed a well agreement.
Originality/value
Novel studies for the impacts of buoyancy ratio on the diffusion of solid particles embedded in an open pipe during double-diffusive flow were conducted.
Details
Keywords
The purpose of this paper is to investigate the main organizational factors that contribute to the successful implementation of business process reengineering (BPR) in the…
Abstract
Purpose
The purpose of this paper is to investigate the main organizational factors that contribute to the successful implementation of business process reengineering (BPR) in the Egyptian banking sector. These factors include management commitment, information technology (IT) infrastructure, people management, change readiness, centralization and formalization.
Design/methodology/approach
The key organizational enablers were identified through an extensive literature review. Then, statistical analysis was carried out based on data collected, using a questionnaire instrument, from 184 managers employed in 38 banks operating in Egypt.
Findings
The results of the study indicate that management commitment, IT infrastructure, people management, change readiness and organizational structure with a low degree of formalization are critical enablers for implementing a successful BPR program within the Egyptian banking sector.
Practical implications
The results may support managers of banks in identifying and assessing the influence of integrating organizational factors that facilitate or hinder the successful implementation of BPR.
Originality/value
Since 2004, the Egyptian banking system has involved in major reform programs and many BPR efforts. Much research effort is required to investigate the BPR projects within the Egyptian banks in order to develop a concrete base of knowledge and understanding of the nature of BPR and factors that support its successful implementation. Moreover, there is an insufficiency of empirical studies regarding the implementation of BPR within the Egyptian service sector. The current study fills this gap by exploring and examining the main organizational factors affecting BPR implementation in a developing country.
Details
Keywords
In the context of lifelong learning society, education experts pay more and more attention to online assessment (OLA) correlated with the concept of e-learning environment. This…
Abstract
In the context of lifelong learning society, education experts pay more and more attention to online assessment (OLA) correlated with the concept of e-learning environment. This chapter builds upon these issues concerning the e-learning environment and the inevitable move to using OLA which is a natural outcome of the increasing use of information and communication technologies (ICTs) assisting in enhancing flexible learning and assessment.
The main purpose of this research is to (a) analyze the postgraduates’ perceptions toward OLA they had taken part in, and (b) identify if there are significant differences in these perceptions based on the variables of gender and skills of using ICTs. Subjects were postgraduate students of master third level enrolled in “Advanced seminar in Islamic Education” syllabus in Faculty of Education, Umm Al Qura University, K.S.A. The study used an e-questionnaire and semi-structured interviews to investigate postgraduate students’ attitudes and opinions about OLA.
The results of the study indicated highly positive perceptions of OLA. In addition, the study concluded that gender and ICTs familiarity significantly affect postgraduate students’ responses in most of the areas studied. The study recommended the necessity of implementing OLA culture as a way to the formation of the knowledge-based society.
Details
Keywords
A.A. Aboukhashaba, M.A. Rabah and M.S. Aly
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…
Abstract
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.