A New Formulation of Electrodynamics

A new formulation of electromagnetism based on linear differential commutator brackets is developed. Maxwell equations are derived, using these commutator brackets, from the vector potential $\vec{A}$, the scalar potential $\phi$ and the Lorentz gauge connecting them. With the same formalism, the continuity equation is written in terms of these new differential commutator brackets. Keywords: Mathematical formulation, Maxwell's equationsComment: 11 Latex pages, no figure

Performance evaluation of flooding in MANETs in the presence of multi-broadcast traffic

Broadcasting has many important uses and several mobile ad hoc networks (MANETs) protocols assume the availability of an underlying broadcast service. Applications, which make use of broadcasting, include LAN emulation, paging a particular node. However, broadcasting induces what is known as the "broadcast storm problem" which causes severe degradation in network performance, due to excessive redundant retransmission, collision, and contention. Although probabilistic flooding has been one of the earliest suggested approaches to broadcasting. There has not been so far any attempt to analyse its performance behaviour in MANETs. This paper investigates using extensive ns-2 simulations the effects of a number of important parameters in a MANET, including node speed, pause time and, traffic load, on the performance of probabilistic flooding. The results reveal that while these parameters have a critical impact on the reachability achieved by probabilistic flooding, they have relatively a lower effect on the number of saved rebroadcast packets

A Resource Intensive Traffic-Aware Scheme for Cluster-based Energy Conservation in Wireless Devices

Wireless traffic that is destined for a certain device in a network, can be exploited in order to minimize the availability and delay trade-offs, and mitigate the Energy consumption. The Energy Conservation (EC) mechanism can be node-centric by considering the traversed nodal traffic in order to prolong the network lifetime. This work describes a quantitative traffic-based approach where a clustered Sleep-Proxy mechanism takes place in order to enable each node to sleep according to the time duration of the active traffic that each node expects and experiences. Sleep-proxies within the clusters are created according to pairwise active-time comparison, where each node expects during the active periods, a requested traffic. For resource availability and recovery purposes, the caching mechanism takes place in case where the node for which the traffic is destined is not available. The proposed scheme uses Role-based nodes which are assigned to manipulate the traffic in a cluster, through the time-oriented backward difference traffic evaluation scheme. Simulation study is carried out for the proposed backward estimation scheme and the effectiveness of the end-to-end EC mechanism taking into account a number of metrics and measures for the effects while incrementing the sleep time duration under the proposed framework. Comparative simulation results show that the proposed scheme could be applied to infrastructure-less systems, providing energy-efficient resource exchange with significant minimization in the power consumption of each device.Comment: 6 pages, 8 figures, To appear in the proceedings of IEEE 14th International Conference on High Performance Computing and Communications (HPCC-2012) of the Third International Workshop on Wireless Networks and Multimedia (WNM-2012), 25-27 June 2012, Liverpool, U

Performance evaluation of adjusted probabilistic broadcasting in MANETs

Appropriate use of a probabilistic broadcasting method in MANETs can decrease the number of rebroadcasts, and as a result reduce the opportunity of contention and collision among neighbouring nodes. In this paper we evaluate the performance of adjusted probabilistic flooding by comparing it to "simple" flooding as used with the ad hoc on demand distance vector (AODV) routing protocol as well as a fixed probabilistic approach. The results reveal that the adjusted probabilistic flooding exhibits superior performance in terms of both reachability and saved rebroadcast

Improving route discovery in on-demand routing protocols using local topology information in MANETs

Most existing routing protocols proposed for MANETs use flooding as a broadcast technique for the propagation of network control packets; a particular example of this is the dissemination of route requests (RREQs), which facilitate route discovery. In flooding, each mobile node rebroadcasts received packets, which, in this manner, are propagated network-wide with considerable overhead. This paper improves on the performance of existing routing protocols by reducing the communication overhead incurred during the route discovery process by implementing a new broadcast algorithm called the adjusted probabilistic flooding on the Ad-Hoc on Demand Distance Vector (AODV) protocol. AODV [3] is a well-known and widely studied algorithm which has been shown over the past few years to maintain an overall lower routing overhead compared to traditional proactive schemes, even though it uses flooding to propagate RREQs. Our results, as presented in this paper, reveal that equipping AODV with fixed and adjusted probabilistic flooding, instead, helps reduce the overhead of the route discovery process whilst maintaining comparable performance levels in terms of saved rebroadcasts and reachability as achieved by conventional AODV\@. Moreover, the results indicate that the adjusted probabilistic technique results in better performance compared to the fixed one for both of these metrics

Reduced sevoflurane consumption in cirrhotic compared to non-cirrhotic patients undergoing major hepatic surgery During entropy monitored general anesthesia

AbstractBackgroundThere is evidence in literature that chronic hepatic patients need less anesthesia compared with healthy ones. Liver cirrhosis leads to a reduction in liver mass and hepatic blood flow with an effect on drug clearance and cardiovascular stability.AimTo evaluate sevoflurane consumption during entropy monitored general anesthesia in cirrhotic and non-cirrhotic patients during transition from consciousness to unconsciousness and throughout the procedure of major hepatic surgical procedures.Patients and methodsForty patients scheduled for major hepatic resection at the National Liver Institute, Menofiya University, Egypt, were studied prospectively and randomized into two equal groups. Group I (n. 20) cirrhotic patients (Child Pugh Grade A) with focal lesion, Group II (n. 20) healthy live liver donors undergoing major hepatectomies. Sevoflurane inhalational concentration was adjusted to achieve a state and response entropy of 40–60, and when RE increases 5–10 units above SE; more intravenous analgesics were given.ResultsMean (SD) Sevoflurane consumption in Group II showed higher consumption 23.5 (3.23) ml, compared to Group I 16 (2.19) ml. Mean (SD) sevoflurane consumption after 4 and 6h from induction also showed a lower value in Group I 10.7(1.94), 9(1.22) ml, than in Group II 17.2(1.69), 14.1(2.19) ml, respectively. Mean (SD) end tidal sevoflurane concentration was lower in Group I 1.4(0.12) after 2h from induction than in Group II 1.7(0.11). After 4 and 6h from induction Group I demonstrated a lower value compared to Group II (P<0.05.). Mean blood pressure, heart rate, urine output and CVP showed no significant changes during maintenance between the two groups.ConclusionThis study demonstrated that cirrhotic patients require less sevoflurane consumption and lower end-tidal concentration to maintain general anesthesia with entropy guidance. This could also have an important impact on the economic costs when applied on a larger scale

Enhanced Home Energy Management Scheme (EHEM) in Smart Grids

Wireless Sensor Networks (WSNs) have become one of the most important components that play a major role in home environment applications. It plays a major role in the creation and the development of smart home environments. Smart homes creates home area network (HAN) to be used in different applications including smart grids. In this paper, we propose an enhancement to in-Home Energy Management (iHEM) scheme, namely EHEM, to reduce energy consumption by shifting the residents’ demands to mid-peak or off-peak periods depending on the appliances priorities and delays. The proposed system handles challenging cases by using internal storage battery. The performance of the proposed system is compared against iHEM and the traditional iHEM scheme, based on the total cost of the power consumption. Obtained results show slight improvement over the existing iHEM schem

Toxicity of fipronil and atrazine on Metapenaeus affinis (Milne-Edwards, 1837) and their effects on oxygen consumption

Increasing the use of pesticides has led to declines in crustaceans in aquatic systems. In this study, the effects of acute doses of fipronil insecticides and atrazine herbicides on the toxicity in sublethal concentrations and their effect on oxygen consumption of adult Metapenaeus affinis at 20±1°C and 4 psu salinity were investigated. Series of fipronil (0.05-2 µg.l-1) and atrazine (625-2000 µg.l-1) lethal concentrations were used. Fipronil showed high toxicity to adult shrimp M. affinis compared to the atrazine. The median lethal concentration (LC50) for 96h of fipronil and atrazine were 0.47 and 8280.02 µg.l-1, respectively. A decrease in the rate of oxygen consumption with increasing sublethal concentrations after 24h was observed in fipronil and atrazine exposed shrimps. A significant difference in oxygen consumption was found between the control and the experimental treatments. The oxygen consumption of high concentration of fipronil 0.2 µg.l-1and high concentration of atrazine 6000 µg.l-1were 0.190 and 0.373 µg.l-1/O2/gm/h, respectively, compared to control one (0.540 µg.l-1/O2/gm/h)

On the performance of probabilistic flooding in wireless mobile ad hoc networks

Broadcasting in MANET’s has traditionally been based on flooding, but this can induce broadcast storms that severely degrade network performance due to redundant retransmission, collision and contention. Probabilistic flooding, where a node rebroadcasts a newly arrived one-to-all packet with some probability, p, was an early suggestion to reduce the broadcast storm problem. The first part of this thesis investigates the effects on the performance of probabilistic flooding of a number of important MANET parameters, including node speed, traffic load and node density. It transpires that these parameters have a critical impact both on reachability and on the number of so-called “saved rebroadcast packets” achieved. For instance, across a range of rebroadcast probability values, as network density increases from 25 to 100 nodes, reachability achieved by probabilistic flooding increases from 85% to 100%. Moreover, as node speed increases from 2 to 20 m/sec, reachability increases from 90% to 100%. The second part of this thesis proposes two new probabilistic algorithms that dynamically adjust the rebroadcasting probability contingent on node distribution using only one-hop neighbourhood information, without requiring any assistance of distance measurements or location-determination devices. The performance of the new algorithm is assessed and compared to blind flooding as well as the fixed probabilistic approach. It is demonstrated that the new algorithms have superior performance characteristics in terms of both reachability and saved rebroadcasts. For instance, the suggested algorithms can improve saved rebroadcasts by up to 70% and 47% compared to blind and fixed probabilistic flooding, respectively, even under conditions of high node mobility and high network density without degrading reachability. The final part of the thesis assesses the impact of probabilistic flooding on the performance of routing protocols in MANETs. Our performance results indicate that using our new probabilistic flooding algorithms during route discovery enables AODV to achieve a higher delivery ratio of data packets while keeping a lower routing overhead compared to using blind and fixed probabilistic flooding. For instance, the packet delivery ratio using our algorithm is improved by up to 19% and 12% compared to using blind and fixed probabilistic flooding, respectively. This performance advantage is achieved with a routing overhead that is lower by up to 28% and 19% than in fixed probabilistic and blind flooding, respectively