Ahmed A. Abdelhafez

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Dissolved organic matter (DOM) plays an important role in biogeochemical cycles in aquatic ecosystem. To investigate the characteristics of DOM in Huangpu River (the last tributary of the Yangtze River), surface water samples were collected along the river from December 2011 to June, 2013. The concentrations of dissolved organic carbon (DOC), the absorbance(More)
For the reason that grid resources are valuable, access is usually limited, based on the requested resource and the requesting user’s identity. Authentication in distributed systems like grid computing environment is the first defense line before other security aspects; authorization, confidentiality, integrity and auditing. The main grid authentication(More)
Voting is a fundamental decision making instrument in any consensus-based society and democracy depends on the proper administration of popular elections. In any election, there exists a set of requirements among which voters should receive assurance that their intent was correctly captured and that all eligible votes were correctly tallied. On the other(More)
The More-Electric Aircraft (MEA) underlines the utilization of the electrical power to power the non-propulsive aircraft systems. Adopting the MEA achieves numerous advantages such as optimizing the aircraft performance and decreasing operating and maintenance costs. Moreover, the MEA reduces the emission of the air pollutant gases from the aircraft, which(More)
The predominant grid authentication mechanisms use public key infrastructure (PKI). Nonetheless, certificate-less public key cryptography (CL-PKC) has several advantages that seem to well align with the demands of grid computing. Security and efficiency are the main objectives of grid authentication protocols. Unfortunately, certificate-less authenticated(More)
Cognition is a high level mental faculty of the brain that includes functions like adaptation, learning, deciding, and others. Accordingly, a Cognitive Radio must have capabilities that mimic such Cognitive functions. As one of the fundamental cognitive abilities of the radio, this paper proposes a novel adaptation method; which uses Real-coded Genetic(More)
EDTA amendments are widely used for micronutrient fertilization in arid soils, besides their effectiveness in the remediation process of heavy metal from contaminated soils. However, the persistence of EDTA in arsenic contaminated soil may have further negative effects on the grown plants. To investigate the influences of EDTA on soil As, a pot experiment(More)
The most prevalent grid security standard, grid security infrastructure uses an authentication protocol based on public key infrastructure (PKI). Certificateless public key cryptography (CL-PKC) overcomes PKI certificate management problems and is well aligned with grid computing demands. Security and efficiency are the main grid authentication protocol(More)
The grid computing coordinates resource sharing between different administrative domains in large scale, dynamic, and heterogeneous environment. Efficient and secure certificateless public key cryptography (CLPKC) based authentication protocol for multi-domain grid environment is widely acknowledged as a challenging issue. Trust relationships management(More)
The main objectives of the current study were to evaluate the potential effects of biochar derived from sugar cane bagasse (SC-BC) and orange peel (OP-BC) on improving the physicochemical properties of a metal smelter contaminated soil, and determining its potentiality for stabilizing Pb and As in soil. To achieve these goals, biochar was produced in a(More)