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Attia, Hazem-Ali The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.4
In this paper, a recursive formulation for generating the equations of motion of spatial mechanical systems is presented. The rigid bodies are replaced by a dynamically equivalent constrained system of particles which avoids introducing any rotational coordinates. For the open-chain system, the equations of motion are generated recursively along the serial chains using the concepts of linear and angular momenta Closed-chain systems are transformed to open-chain systems by cutting suitable kinematic joints and introducing cut-joint constraints. The formulation is used to carry out the dynamic analysis of multi-link five-point suspension. The results of the simulation demonstrate the generality and simplicity of the proposed dynamic formulation.
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.
RELATIVE MULTIFRACTAL SPECTRUM
Attia, Najmeddine Korean Mathematical Society 2018 대한수학회논문집 Vol.33 No.2
We obtain a relation between generalized Hausdorff and packing multifractal premeasures and generalized Hausdorff and packing multifractal measures. As an application, we study a general formalism for the multifractal analysis of one probability measure with respect to an other.
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.
Attia Hazem A. The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4
In the present study, the unsteady Couette flow with heat transfer of a dusty viscous incompressible electrically conducting fluid under the influence of an exponential decaying pressure gradient is studied without neglecting the Hall effect. 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 is applied perpendicular to the plates. The governing equations are solved numerically using finite differences to yield the velocity and temperature distributions for both the fluid and dust particles.
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.
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.
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.
Attia Hazem Ali The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.5
In the present study, the unsteady Hartmann flow of a dusty viscous incompressible electrically conducting fluid under the influence of an exponentially decreasing pressure gradient is studied without neglecting the ion slip. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below. The fluid is acted upon by an external uniform magnetic field which is applied perpendicular to the plates. An analytical solution for the governing equations of motion is obtained to yield the velocity distributions for both the fluid and dust particles.