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( Attia Sajjad ),( Muhammad Rizwan ),( Ghulam Mujtaba ),( Naim Rashid ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.4
Chitosan is a promising flocculant for microalgae harvesting, but its scale-up application is not economically supported yet. Low solubility of chitosan in microalgae suspension demands high dosage (as a flocculant) to destabilize the cells, and thus, increases the cost of microalgae harvesting. This study identifies efficient solvents for the chitosan, and optimizes the concentration of solvents and chitosan dose to improve the harvesting efficiency. Chitosan was dissolved in different acids, and subsequently used as a flocculant. The flocculant efficacy was measured in terms of harvesting efficiency and reduction in chemical oxygen demand (COD) of the microalgae suspension. It was found that chitosan dissolved in 0.05 M HCl showed the highest harvesting efficiency (89 ± 0.87%) at only 30 mg/L of dosage. In comparison, 270 mg/L of FeCl<sub>3</sub>·6H<sub>2</sub>O was required to attain 86 ± 0.083% of the harvesting efficiency. H<sub>2</sub>SO<sub>4</sub> dissolved chitosan required high flocculant dose (150 mg/L) and resulted in relatively low harvesting efficiency (77±0.11%). It was concluded that the efficacy of chitosan is solvent dependent, and the selection of proper solvent can decrease the dosage requirement for microalgae harvesting.
Ion Slip Effect on the Flow Due to a Rotating Disk with Heat Transfer
Attia Hazem Ali The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.12
The steady hydromagnetic flow due to a rotating disk is studied with heat transfer considering the ion slip. The governing equations are solved numerically using finite differences. The results show that the inclusion of the ion slip has important effects on the velocity distribution as well as the heat transfer.
REGULARITIES OF MULTIFRACTAL HEWITT-STROMBERG MEASURES
Attia, Najmeddine,Selmi, Bilel Korean Mathematical Society 2019 대한수학회논문집 Vol.34 No.1
We construct new metric outer measures (multifractal analogues of the Hewitt-Stromberg measure) $H^{q,t}_{\mu}$ and $P^{q,t}_{\mu}$ lying between the multifractal Hausdorff measure ${\mathcal{H}}^{q,t}_{\mu}$ and the multifractal packing measure ${\mathcal{P}}^{q,t}_{\mu}$. We set up a necessary and sufficient condition for which multifractal Hausdorff and packing measures are equivalent to the new ones. Also, we focus our study on some regularities for these given measures. In particular, we try to formulate a new version of Olsen's density theorem when ${\mu}$ satisfies the doubling condition. As an application, we extend the density theorem given in [3].
Numerical Kinematic Analysis of the Standard Macpherson Motor-Vehicle Suspension System
Attia, Hazem-Ali The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.12
In this paper, an efficient numerical algorithm for the kinematic analysis of the standard MacPherson suspension system is presented. The kinematic analysis of the suspension mechanism is carried out in terms of the rectangular Cartesian coordinates of some defined points in the links and at the kinematic joints. Geometric constraints that fix the distances between the points belonging to the same rigid link are introduced. The nonlinear constraint equations are solved by iterative numerical methods. The corresponding linear equations of the velocity and acceleration are solved to yield the velocities and accelerations of the unknown points. The velocities and accelerations of other points of interest as well as the angular velocity and acceleration of any link in the mechanism can be calculated.
Multi-objective Capacitor Allocations in Distribution Networks using Artificial Bee Colony Algorithm
Attia El-Fergany,A. Y. Abdelaziz 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.2
This article addresses an efficient heuristic-based approach to assign static shunt capacitors along radial distribution networks using the artificial bee colony algorithm. The objective function is adapted to enhance the overall system static voltage stability index and to achieve maximum net yearly savings. Load variations have been considered to optimally scope the fixed and switched capacitors required. The numerical results are compared with those obtained using recent heuristic methods and show that the proposed approach is capable of generating high-grade solutions and validated viability.
Dynamics of the Macpherson Strut Motor-Vehicle Suspension System in Point and Joint Coordinates
Attia, Hazem-Ali The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.9
In this paper the dynamic analysis of the Macpherson strut motor-vehicle suspension system is presented. The equations of motion are formulated using a two-step transformation. Initially, the equations of motion are derived for a dynamically equivalent constrained system of particles that replaces the rigid bodies by applying Newton's second law The equations of motion are then transformed to a reduced set in terms of the relative joint variables. Use of both Cartesian and joint variables produces an efficient set of equations without loss of generality For open chains, this process automatically eliminates all of the non-working constraint forces and leads to an efficient solution and integration of the equations of motion. For closed loops, suitable joints should be cut and few cut-joints constraint equations should be included for each closed chain. The chosen suspension includes open and closed loops with quarter-car model. The results of the simulation indicate the simplicity and generality of the dynamic formulation.
Attia Hazem A. The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.8
The unsteady Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking the Hall effect into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.
Attia, Amina A.,Girgis, Badie S.,Tawfik, Nady A.F. Korean Carbon Society 2005 Carbon Letters Vol.6 No.2
Crushed peach stone shells were impregnated with $H_3PO_4$ of increasing concentrations (30-70%) followed by heat treatment at 773 K for 3 h. Produced carbons (ACs) were characterized by $N_2$ adsorption at 77 K using the BET-equation and the ${\alpha}$-method. High surface area microporous ACs were obtained, with enhanced internal pore volume, as function of % $H_3PO_4$. Adsorption isotherms from aqueous solution were determined for methylene blue (MB) and p-nitrophenol (PNP), as representatives for dye and phenolics pollutant molecules. Application of the Langmuir model proved the high limiting capacity towards both solute molecules, MB was uptaken in increasing amounts as function of $H_3PO_4$ concentration and generated porosity. High removal of PNP was almost the same irrespective of porosity characteristics. Competitive adsorption of $H_2O$ molecules on the hydrophilic carbon surface seems to partially reduce the available area to the PNP molecules. Application of the pseudo-second order law described well the fast adsorption (${\leq}$ 120 min) at two initial dye concentrations.
MHD Hartmann flow of a Dusty Fluid with Exponential Decaying Pressure Gradient
ATTIA HAZEM A. The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.8
In the present study, the unsteady Hartmann flow with heat transfer of a viscous incompressible electrically conducting fluid under the influence of an exponentially decreasing pressure gradient is studied. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below while the fluid is acted upon by an external uniform magnetic field applied perpendicular to the plates. The equations of motion are solved analytically to yield the velocity distributions for both the fluid and dust particles. The energy equations for both the fluid and dust particles including the viscous and Joule dissipation terms, are solved numerically using finite differences to get the temperature distributions.
Kinematic Analysis of the Multi-Link Five-Point Suspension System in Point Coordinates
Attia, Hazem-Ali The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.8
In this paper, a numerical algorithm for the kinematic analysis of a multi-link five-point suspension system is presented. The kinematic analysis is carried out in terms of the rectangular Cartesian coordinates of some defined points in the links and at the joints. Geometric constraints are introduced to fix the relative positions between the points belonging to the same rigid body. Position, velocity and acceleration analyses are carried out. The presented formulation in terms or this system of coordinates is simple and involves only elementary mathematics. The results of the kinematic analysis are presented and discussed.