Baqar M.,Case Western Reserve University |
Baqar M.,Azzaytuna University |
Agag T.,Case Western Reserve University |
Agag T.,Tanta University |
And 4 more authors.
Macromolecules | Year: 2012
The polymerization mechanism of methylol-functional benzoxazine monomers is reported using a series of monofunctional benzoxazine monomers synthesized via a condensation reaction of ortho-, meta-, or para-methylol-phenol, aniline, and paraformaldehyde following the traditional route of benzoxazine synthesis. A phenol/aniline-type monofunctional benzoxazine monomer has been synthesized as a control. The structures of the synthesized monomers have been confirmed by 1H NMR and FT-IR. The polymerization behavior of methylol monomers is studied by DSC and shows an exothermic peak associated with condensation reaction of methylol groups and ring-opening polymerization of benzoxazine at a lower temperature range than the control monomer. The presence of methylol group accelerates the ring-opening polymerization to give the ascending order of para-, meta-, and ortho-positions in comparison to the unfunctionalized monomer. Furthermore, rheological measurements show that the position of methylol group relative to benzoxazine structure plays a significant role in accelerating the polymerization. © 2012 American Chemical Society.
Elmehdi A.,Azzaytuna University |
Momen A.,University of Idaho |
Johnson B.K.,University of Idaho
2014 North American Power Symposium, NAPS 2014 | Year: 2014
Line commutated current source converter-based (LCC) HVDC systems are being considered for the transfer of power from remote wind resources to existing ac transmission systems. The rectifier terminals of these systems are connected to weak ac systems. A modified CIGRE HVDC benchmark model implemented in the PSCAD/EMTDC program is used to study the impact of varying amounts of dynamic reactive compensation on performance during rectifier operation. Determination of the amount of dynamic reactive compensation needed at the rectifier terminal is based on the following dynamic parameters: the magnitude of the first peak of the temporary overvoltages (TOVs) of the rectifier ac voltage following disturbance and time for the dc system to reach 80% of pre-disturbance dc power transfer after the clearing an ac fault. An effective short circuit ratio (ESCR) for best operation will be calculated based on the selected value of the dynamic reactive power compensation rating. © 2014 IEEE.
Maher A.M.D.,National University of Ireland |
Asaiyah M.A.M.,National University of Ireland |
Asaiyah M.A.M.,Azzaytuna University |
Brophy C.,National University of Ireland |
Griffin C.T.,National University of Ireland
Microbial Ecology | Year: 2016
Bacterial symbionts are increasingly recognised as mediators of ecologically important traits of their animal hosts, with acquisition of new traits possible by uptake of novel symbionts. The entomopathogenic nematode Heterorhabditis downesi associates with two bacterial symbionts, Photorhabdus temperata subsp. temperata and P. temperata subsp. cinerea. At one intensively studied coastal dune site, P. temperata subsp. cinerea is consistently more frequently isolated than P. temperata subsp. temperata in H. downesi recovered from under the bare sand/Ammophila arrenaria of the front dunes (where harsh conditions, including drought, prevail). This is not the case in the more permissive closed dune grassland further from the sea. No differences were detected in ITS1 (internal transcribed spacer) sequence between nematode lines carrying either of the two symbiont subspecies, nor did they differ in their ability to utilise insects from three orders. The two symbionts could be readily swapped between lines, and both were carried in equal numbers within infective juveniles. In laboratory experiments, we tested whether the symbionts differentially affected nematode survival in insect cadavers that were allowed to dry. We assessed numbers of nematode infective juveniles emerging from insects that had been infected with H. downesi carrying either symbiont subspecies and then allowed to desiccate for up to 62 days. In moist conditions, cadavers produced similar numbers of nematodes, irrespective of the symbiont subspecies present, while under desiccating conditions, P. temperata subsp. cinerea cadavers yielded more nematode progeny than P. temperata subsp. temperata cadavers. Desiccating cadavers with the same nematode isolates, carrying either one or the other symbiont subspecies, confirmed that the symbiont was responsible for differences in nematode survival. Moreover, cadavers harbouring P. temperata subsp. cinerea had a reduced rate of drying relative to cadavers harbouring P. temperata subsp. temperata. Our experiments support the hypothesis that H. downesi can extend its niche into harsher conditions by associating with P. temperata subsp. cinerea. © 2016 Springer Science+Business Media New York
Al-Habashi R.,Azzaytuna University |
Abbas Z.,University Putra Malaysia
Key Engineering Materials | Year: 2013
A new developed formula named the Habashi-Zul formula, based on the Maxwell-Garnett (MG) formula was fabricated and used to calculate the complex permittivity of the Sm-YIG in PVDF composite samples in the frequency range of 10 MHz to 1 GHz. The calculated permittivities results were compared with the measured values of each sample of Sm-YIG in PVDF composite samples and, with calculated results from various theoretical models including the MG, Looyenga, Bruggeman and, Sen Scala and Cohen. The Habashi-Zule formula presented higher accuracy as compared to other models. © (2013) Trans Tech Publications, Switzerland.
Habashi R.A.,Azzaytuna University |
Abbas Z.,University Putra Malaysia
Journal of Nano Research | Year: 2014
This work is concerned with the preparation of samarium iron garnet (Sm3Fe5O12) nanoparticles via an improved technique named: Modified Conventional Mixing Oxides (MCMO) method. This material was characterized by XRD, FESEM, EDX and TEM. Metal oxides and ethanol solution were used as raw materials to prepare Sm3Fe5O12 (SmIG) material. Single-phase SmIG nanoparticles with an average particle value of 25 nm and average crystallite size value of 44 nm have been synthesized at 1350 oC via the MCMO method. SmIG powders with grain sizes below 1 μm and high purity have been presented by FESEM and EDX results, respectively. Lattice constant value of 12.535 A° and density value of 6.221 g.cm-3, were calculated for the SmIG sample. The latter has reached around 99% of its theoretical density. The MCMO method appears to be an attractive route due to the enhancement of structural properties of the interested sample with high yield in the nano-scale product as compared to other preparation techniques. © (2014) Trans Tech Publications, Switzerland.
Salem Ahmed N.A.,Azzaytuna University |
Emhemmed A.,University of Tripoli |
Elgaid K.,University of Glasgow
International Conference on Information Networking | Year: 2013
Recently, multi-radio mesh technology in wireless networks has been put under extensive research. This is because of its potential to overcome the inherent wireless multi-hop throughput, scalability and latency problems caused by the half-duplex nature of the IEEE 802.11. This paper introduces a design and modelling of different elements on a distinct type of multicomputer networks, the dual-radio wireless hypermesh (DIWH), based on SystemC methodology. The hepermesh is a well-known topology that belongs to the hypergraph family of networks. Hypermeshes have been proposed as potential alternatives to the graph networks for the future System Area Networks (SAN). In this work, we consider a two dimensional DIWH network, where each router node is equipped with two radio interfaces and two non-overlapping channels are available for each node. we address the problem of assigning channels to communication links in the network with the objective of keeping overall network latency low and provide a relatively high throughput. The simulations and analysis have shown that our design achieves a significant increase in network throughput with less average network latency for large number of communication nodes, compared with the CSMA shared channel model, which is currently the de facto MAC protocol for most wireless networks. Our simulations have been validated analytically to show the accuracy of the developed model. In addition, simulation results have shown that the wireless hypermesh outperforms shared medium wireless networks under the constant total bandwidth argument, especially in large networks. © 2013 IEEE.
Almradi A.M.,Azzaytuna University |
Dianat S.A.,Rochester Institute of Technology
International Journal of Business Data Communications and Networking | Year: 2012
This paper discusses the problem of Non Data Aided (NDA) Signal to Noise Ratio (SNR) estimation of Binary Phase Shift keying (BPSK) modulated signals using the Expectation Maximization (EM) Algorithm. In addition, the Cramer-Rao Lower Bounds (CRLB) for the estimation of Data Aided (DA) and Non Data Aided (NDA) Signal to Noise Ratio (SNR) estimation is derived. Multiple Input Single Output (MISO) channels with Space Time Block Codes (STBC) is used. The EM algorithm is a method that finds the Maximum Likelihood (ML) solution iteratively when there are unobserved (hidden or missing) data. Extension of the proposed approach to other types of linearly modulated signals in estimating SNR is straight forward. The performance of the estimator is assessed using the NDA CRLBs. Alamouti coding technique is used in this paper with two transmit antennas and one receive antenna. The authors' assumption is that the received signal is corrupted by additive white Gaussian noise (AWGN) with unknown variance, and scaled by fixed unknown complex channel gain. Monte Carlo simulations are used to show that the proposed estimator offers a substantial improvement over the conventional Single Input Single Output (SISO) NDA SNR estimator due to the use of the statistical dependences in space and time. Moreover, the proposed NDA SNR estimator works close to the NDA SNR estimator over Single Input Multiple Output (SIMO) channels. Copyright © 2012, IGI Global.
Adeka M.,University of Bradford |
Shepherd S.,University of Bradford |
Abd-Alhameed R.,University of Bradford |
Ahmed N.A.S.,Azzaytuna University
2015 Internet Technologies and Applications, ITA 2015 - Proceedings of the 6th International Conference | Year: 2015
The Versatile and Ubiquitous Secret Sharing System, a cloud data repository secure access and a web based authentication scheme. It is designed to implement the sharing, distribution and reconstruction of sensitive secret data that could compromise the functioning of an organisation, if leaked to unauthorised persons. This is carried out in a secure web environment, globally. It is a threshold secret sharing scheme, designed to extend the human trust security perimeter. The system could be adapted to serve as a cloud data repository and secure data communication scheme. A secret sharing scheme is a method by which a dealer distributes shares of a secret data to trustees, such that only authorised subsets of the trustees can reconstruct the secret. This paper gives a brief summary of the layout and functions of a 15-page secure server-based website prototype; the main focus of a PhD research effort titled 'Cryptography and Computer Communications Security: Extending the Human Security Perimeter through a Web of Trust'. The prototype, which has been successfully tested, has globalised the distribution and reconstruction processes. © 2015 IEEE.
Yakhlef S.,Azzaytuna University |
Hamdan M.A.,Azzaytuna University
2013 The International Conference on Technological Advances in Electrical, Electronics and Computer Engineering, TAEECE 2013 | Year: 2013
This paper studies the problems related to the location management strategies, i.e., Location Area Based, Movement Based, and Timer Based for Wireless networks. The simulation models are based on user motion and call arrival is based on Poisson arrival process. The Timer-based Location Management strategy is one in which the user updates its location periodically after an interval of time. This time is based upon the user's mobility. The scheme seeks to minimize the average signaling cost for individual mobile users for both paging and registration. In the adaptive Location Area Based strategy, the user updates its location on each Location Area (LA) call boundary crossing. In this case the LA size is adaptive changing according to the user's mobility characteristics. In the Movement Based Location strategy, the user keeps track of the number of LA calls boundary and updates when the number exceeds a predefined value. © 2013 IEEE.
Elfallagh F.A.,Azzaytuna University
Advanced Structured Materials | Year: 2014
The stresses around the Vickers indents in alumina [surface orientation ð11 _ 0 2Þ] were investigated by Cr3+ fluorescence spectroscopy, measuring the shifts in the Cr3+ R1 and R2 luminescence lines. Changes in R1 peak position can be related directly to changes in residual stress of the alumina in the sampled volume, and changes in R1 peak width arise from local stress variations due to microstructural defects such as cracks and dislocations. The intensity of the R1 and R2 fluorescence peaks was observed to decrease with increasing proximity to the indent centre due to increased scattering from residual surface and microstructural damage such as dislocations, cracks and surface debris. © Springer International Publishing Switzerland 2014.