‘Ayn al ‘Arab, Syria
‘Ayn al ‘Arab, Syria

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Almradi A.,Azzaytuna University | Almradi A.,University of Manchester
2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings | Year: 2016

This paper studies the deployment of multiple- input multiple-output (MIMO) full-duplex (FD) relaying systems in a multi-cell environment, where a multi-antenna amplify-and-forward (AF) FD relay station serves multiple half-duplex (HD) multi-antenna users. The fundamental challenges of loopback self-interference (LI) and multiple co-channel interferers (CCI) at the relay and destination when incorporating FD relaying in cellular systems are addressed. Due to the higher frequency reuse in FD relaying compared to its HD relaying counterpart, the number of CCI is expected to double as the FD relay station simultaneously schedule uplink and downlink transmission on the same channel. In this paper, the optimal design of transmit/receive precoding/decoding weight vectors which maximizes the overall signal-to- interefernce-plus-noise ratio (SINR) is formulated by a proper optimization problem, then a closed-form sub-optimal solution is proposed. The proposed hop-by-hop zero-forcing (ZF) beamforming vectors are based on added ZF constraints used to suppress the LI and CCI channels at the relay and destination. To this end, new exact expressions for the outage probability and ergodic capacity are derived in closed-form. Numerical results sustained by Monte-Carlo simulations show the exactness of the proposed analytical expressions. In addition, our results show that while multi- antenna terminals improve the system performance, the detrimental effect of the number of interferers on FD relaying is clearly seen. Furthermore, our findings reveal that MIMO FD relaying could substantially boost the system performance compared to its conventional MIMO HD relaying counterpart. © 2016 IEEE.

Almradi A.,Azzaytuna University | Almradi A.,University of Manchester
2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings | Year: 2016

This paper analyzes the performance of information and energy beamforming in multiple-input multiple- output (MIMO) wireless communications systems, where a self-powered multi-antenna hybrid access point (AP) coordinates wireless information and power transfer (WIPT) with an energy-constrained multi-antenna user terminal (UT). The wirelessly powered UT scavenge energy from the hybrid AP radio-frequency (RF) signal in the downlink (DL) using the harvest-then-transmit protocol, then uses the harvested energy to send its information to the hybrid AP in the uplink (UL). To maximize the overall signal-to-noise ratio (SNR) as well as the harvested energy so as to mitigate the severe effects of fading and enable long-distance wireless power transfer, information and energy beamforming is investigated by steering the transmitted information and energy signals along the strongest eigenmode. To this end, exact and lower-bound expressions for the outage probability and ergodic capacity are presented in closed-form, through which the throughput of the delay- constrained and delay-tolerant transmission modes are analyzed, respectively. Numerical results sustained by Monte Carlo simulations show the exactness and tightness of the proposed analytical expressions. The impact of various parameters such as energy harvesting time, hybrid AP transmit power and the number of antennas on the system throughput is also considered. © 2016 IEEE.

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.

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.

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