1,781 research outputs found
Efficient route discovery for reactive routing
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Information on the location of mobile nodes in Mobile Ad-hoc Networks (MANETs) has
the potential to significantly improve network performance. This thesis uses node location information to develop new techniques for route discovery in on-demand routing protocols such as the Ad-hoc On-Demand Distance Vector (AODV), thus making an important contribution to enhancing the experience of using mobile networks.
A Candidate Neighbours to Rebroadcast the Route Request (CNRR) approach has been
proposed to reduce the deleterious impact, known as the broadcast storm, of RREQ packets
flooding in traditional on-demand routing protocols. The main concept behind CNRR is
specifying a set of neighbours which will rebroadcast the received RREQ. This is a departure from the traditional approach of all receiving nodes rebroadcasting RREQs and has the effect of reducing the problem of redundancy from which mobile networks suffer. The proposed protocol has been developed in two phases: Closest-CNRR and Furthest-CNRR. The simulation results show that the proposed algorithms have a significant effect as they reduce the routing overhead of the AODV protocol by up to 28% compared to the C-CNRR, and by up to 17.5% compared to the F-CNRR. Notably, the proposed algorithms simultaneously achieve better throughput and less data dropping.
The Link Stability and Energy Aware protocol (LSEA) has been developed to reduce the
overhead while increasing network lifetimes. The LSEA helps to control the global
dissemination of RREQs in the network by eliminating those nodes that have a residual
energy level below a specific threshold value from participation in end-to-end routes. The proposed LSEA protocol significantly increases network lifetimes by up to 19% compared with other on-demand routing protocols while still managing to obtain the same packet delivery ratio and network throughput levels. Furthermore, merging the LSEA and CNRR concepts has the great advantage of reducing the dissemination of RREQs in the network without loss of reachability among the nodes.
This increases network lifetimes, reduces the overhead and increases the amount of data
sent and received. Accordingly, a Position-based Selective Neighbour (PSN) approach has
been proposed which combines the advantages of zoning and link stability. The results
show that the proposed technique has notable advantages over both the AODV and MAAODV
as it improves delivery ratios by 24.6% and 18.8%, respectively.Funded by National Council for Training -
Sudan and the Sudan Academy of Science
Triazole-Assisted Ruthenium-Catalyzed C-H Arylation of Aromatic Amides
No full textSite-selective ruthenium(II)-catalyzed direct arylation of amides was achieved through C-H cleavages with modular auxiliaries, derived from easily accessible 1,2,3-triazoles. The triazolyldimethylmethyl (TAM) bidentate directing group was prepared in a highly modular fashion through copper(I)-catalyzed 1,3-dipolar cycloaddition and allowed for ruthenium-catalyzed C-H arylations on arenes and heteroarenes, as well as alkenes, by using easy-to-handle aryl bromides as the arylating reagents. The triazole-assisted C-H activation strategy was found to be widely applicable, to occur under mild reaction conditions, and the catalytic system was tolerant of important electrophilic functionalities. Notably, the flexible triazole-based auxiliary proved to be a more potent directing group for the optimized ruthenium(II)-catalyzed direct arylations, compared with pyridylsubstituted amides or substrates derived from 8-aminoquinoline
ChemInform Abstract: Triazole‐Assisted Ruthenium‐Catalyzed C—H Arylation of Aromatic Amides.
No full textIron- Catalyzed C( sp(2))-H and C( sp(3)) -H Arylation by Triazole Assistance
No full textModular 1,2,3-triazoles enabled iron-catalyzed CH arylations with broad scope. The novel triazole-based bidentate auxiliary is easily accessible in a highly modular fashion and allowed for user-friendly iron-catalyzed C(sp(2))H functionalizations of arenes and alkenes with excellent chemo- and diastereoselectivities. The versatile iron catalyst also proved applicable for challenging C(sp(3))H functionalizations, and proceeds by an organometallic mode of action. The triazole-assisted CH activation strategy occurred under remarkably mild reaction conditions, and the auxiliary was easily removed in a traceless fashion. Intriguingly, the triazole group proved superior to previously used auxiliaries
H H honours top 32 achievers; 280 students receive degrees and diplomas from six colleges
No full textThe Emir H H Sheikh Tamim bin Hamad Al Thani graced the men’s graduation ceremony of Qatar University’s (QU) Class of 2014 yesterday at Qatar National Convention Centre
QU President welcomes Al Fadalah
No full textDeputy Emir H H Sheikh Abdullah bin Hamad Al Thani, the Chairman of the Board of Trustees of Qatar University (QU), presided over the second meeting of the Board of Trustees for the academic year 2016/2017
Al Attiyah attends QU seminar
No full textThe Chairman of the Administrative Control and Transparency Authority H E Abdullah bin Hamad Al Attiyah at a seminar held at the Qatar University
Dr Al Derham reappointed as President of QU
No full textThe Board of Trustees of Qatar University (QU), which is chaired by Deputy Amir H H Sheikh Abdullah bin Hamad Al Thani, has renewed its trust on Dr Hassan Rashid Al Derham as President of Qatar University reappointing him for another four years
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