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Riyadh, Saudi Arabia

Zenkour A.M.,King Abdulaziz University | Alghamdi N.A.,Riyadh Girls College of Education
Mechanics of Advanced Materials and Structures | Year: 2010

The bending response of sandwich plates subjected to thermo-mechanical loads is studied. The sandwich plate faces are assumed to have isotropic, two-constituent (metal-ceramic) material distribution through the thickness, and the modulus of elasticity, Poisson's ratio, and thermal expansion coefficient of the faces are assumed to vary according to a power law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic ceramic material. Several kinds of sandwich plates are used, taking into account the symmetry of the plate and the thickness of each layer. Field equations for functionally graded sandwich plates whose deformations are governed by either the shear deformation theories or the classical theory are derived. Displacement functions that identically satisfy boundary conditions are used to reduce the governing equations to a set of coupled ordinary differential equations with variable coefficients. Exact solutions for functionally graded materials (FGMs) sandwich plates are presented. Numerical results of the sinusoidal, third-order, first-order, and classical theories are presented to show the effect of material distribution on the deflections and stresses. A wide variety of results is presented for the static response of sandwich plates under thermo-mechanical loads. The effects of thermo-mechanical loads and other parameters on the dimensionless deflections and axial and transverse shear stresses of an FGM sandwich plate are studied. Copyright © Taylor & Francis Group, LLC. Source


Fahmy M.M.,Cairo University | Al-Ghamdi R.F.,Riyadh Girls College of Education | Mohamed N.A.,Cairo University
Polymer Bulletin | Year: 2011

Four novel wholly para-oriented aromatic poly(ether-amide-hydrazide)s containing various pendant groups on their aromatic rings were synthesized from p-aminosalicylic acid hydrazide (PASH) with an equimolar amount of either 4,4′-(1,4-phenylenedioxy)dibenzoyl chloride (1a), 4,4′-(2,5- tolylenedioxy)dibenzoyl chloride (1b), 4,4′-(2-tert-butyl-1,4- phenylenedioxy)dibenzoyl chloride (1c), or 4,4′-(2,5-biphenylenedioxy) dibenzoyl chloride (1d) via a low temperature solution polycondensation reaction. A polyamide-hydrazide without the ether and pendant groups, poly[4-(terephthaloylamino)salicylic acid hydrazide, PTASH, is also investigated for comparison. It was synthesized from PASH and terephthaloyl chloride by the same synthetic route. The polymer intrinsic viscosities ranged from 4.5 to 2.47 dlg-1 in N,N-dimethyl acetamide (DMAc) at 30 °C and decreased with the introduction of the ether and pendant groups into the polymer. All the polymers were soluble in DMAc, N,N-dimethyl formamide (DMF), and N-methyl-2-pyrrolidone (NMP) and their solutions could be cast into flexible films with good mechanical strengths. Further, they exhibited a great affinity to water sorption. Their solubility and hydrophilicity increased with introduction of the ether and pendant groups into the polymer. The prepared polymers could be thermally cyclodehydrated under nitrogen atmosphere into the corresponding poly(ether-amide-1,3,4-oxadiazole)s approximately in the region of 300-450 °C. The introduction of the flexibilizing ether linkages and the pendant groups into the polymer improves the solubility of the resulting poly(ether-amide-1,3,4-oxadiazole)s compared to poly(amide-1,3,4-oxadiazole) free from these groups. © 2010 Springer-Verlag. Source


Aboushady A.M.,Cairo University | El-Sawy S.A.R.,Riyadh Girls College of Education
WIT Transactions on Information and Communication Technologies | Year: 2014

This paper presents a Fuzzy Consensus Qualitative Risk Analysis framework to identify and prioritize risks encountered in real estate projects, which is applied to developing countries. The framework incorporates the consensus and quality of experts in the process of evaluating risk events and is composed of (1) a Fuzzy Expert System (FES)to determine qualification of experts;(2) Fuzzy Similarity Aggregation Algorithms to aggregate experts' opinions; and (3) a threedimensional prioritization approach to rank the risks, qualitatively. Risks are identified through a literature review and interviews with experts who rank the risks in terms of their probability of occurrence, impact and level of detection; each is described using five linguistic terms that are defined by membership functions (MFs) on a 5-point rating scale. The FES determines an importance weight factor for each expert, based on a set of predetermined qualification attributes. Experts' opinions are aggregated in a linguistic framework, based on the proximity of their opinions on the scale to ensure that their aggregated decision is a result of common agreement. The importance weight factor is combined with the consensus weight factor of each expert in the aggregation process using a scalar modifier and the Euclidean Distance Measure Function is used to determine the linguistic criticality of every risk event. A threedimensional prioritization approach applies a set of ranking rules to every risk that enables experts to rank and visualize the priority of the risks in a three-dimensional space. The framework contributes to the Real estate industry by solving a major problem for project teams in developing countries to qualitatively evaluate risks in a fully supported linguistic framework, using fuzzy logic, which addresses the vagueness and imprecision that exist in the decision-making process. © 2014 WIT Press. Source


Al-Jebreen D.H.,Riyadh Girls College of Education
Pakistan Journal of Biological Sciences | Year: 2010

A survey was conducted during 2008 to assess the attitudes and perceptions of the Riyadh University students towards genetically modified crops and foods. Using descriptive analysis, it was found that the majority of surveyed students had good knowledge of genetic modifications, but lack knowledge about Genetically Modified Organisms (GMO) values. Most respondents would not purchase clearly labelled GMO products, though considerable number of the respondents was ready to taste or try the products. It is evident from these results that majority of university students who participated in this survey, in general had very little information or didn't know the genetic engineering technology e.g., gene therapy, fingerprinting, role in reducing pesticide application etc., as appeared in the results, therefore, most of the participants did not know or thought GM foods are harmful and could not be easily detected. The implication of this result is that majority will not support GM products. © 2010 Asian Network for Scientific Information. Source


Zayed M.A.,Cairo University | El-Habeeb A.A.,Riyadh Girls College of Education
Drug Testing and Analysis | Year: 2010

The reactions between diphrenhydramine drug (diphen) in the base form and the iodine amphoteric reagent (n-donor and/or σ-acceptor) and tetracyanoethylene as a π-acceptor reagent (TCNE) have been spectrophotometrically studied at different conditions of reactant concentrations, time intervals, temperatures, solvents, and differentwavelengths aiming to shed light on the nature of these reactions. Consequently, it is possible to select the proper conditions for spectrophotometric determination of this biologically active drug in its formulations. The reaction mechanism between iodine and diphen involves the formation of diphen-I 2 outer-and inner-sphere complexes, whereas diphen-TCNE reaction involves the formation of charge transfer (CT) complex. The analytical parameters of the suggested spectrphometric procedures have been calculated. The values of the Sandell sensitivity, standard deviation (SD), relative standard deviation (RSD) and recovery % refer to the high sensitivity of these procedures applied in analysis of diphen in its formulations. This research also presents a new diphen-I2 promising drug derivative that can be used for the same purpose as its parent. Both diphen-drug and diphen-I 2 separated solid product are critically investigated by elemental analyses, FT-IR, 1HNMR, electron ionizationmass spectrometry (EI-MS) and thermal analyses (TA). Practical investigation (TA and MS) data of diphen-drug and its reaction product are confirmed by MO calculations. This research gives a clear idea about the possible metabolites andmetabolic pathways of diphen and its derivative in vitro system thatmay occur in vivo system. The importance of this drug stems from its use as an antihistamine with anticholinergic (drying) and sedative side effects. Copyright © 2010 John Wiley & Sons, Ltd. Source

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