16,217 research outputs found
Link stability estimation based on link connectivity changes in mobile ad-hoc networks
No full textDear Wang,
Re: Link Stability Estimation Based on Link Connectivity Changes in Mobile Ad-hoc Networks
I have not been able to assess if this is an author version peer-reviewed or is it an author version non peer reviewed. Could you please clarify this so I can proceed to add your paper to Spiral. Spiral digital repository only accept peer-reviewed papers.
30/11/12 author has confirmed peer reviewe
Mobile Ad Hoc Networks: the DHT paradigm
No full textIn this thesis, the adoption of the hierarchical routing paradigm to achieve a scalable network layer for ad hoc networks has been proposed. The main concept of hierarchical routing is to keep, at any node, complete routing information about nodes which are close to it and lesser information about nodes located further away.
The Augmented Tree-based Routing protocol, a routing protocol for ad hoc networks exploiting both a location-aware addressing schema and a distribute hash table (DHT) system, has been proposed. The adopted addressing schema allows nodes to adopt hierarchical routing, limiting so the overhead introduced in the network, while the DHT system provides the mapping between transient identifiers and node identities.
Since the Augmented Tree-based Routing protocol adopts a multi-path strategy and since most studies in the area of multi-path routing focus on heuristic methods and the performances of these strategies are commonly evaluated by numerical simulations, an analytical framework to evaluate the performance gain achieved by multi-path routing has been proposed. The framework
is based on on graph theory and on terminal-pair routing reliability (TPRR) as performance measure.
Moreover, some features of the proposed protocol has been exploited design a peer-to-peer (P2P) system over a mobile ad hoc network (MANET) resorting to a cross-layer approach. It has been proved that simply deploying P2P systems over MANETs may cause poor performances. By coupling both the direct and the indirect key-based routing at the network layer and by resorting to the same hierarchical address space structure of ATR, we are able to build a P2P overlay network in which the logical proximity agrees with the physical one, limiting so the message overhead and avoiding the redundancy.
Finally, by extending the proposed location-aware addressing to match with the opportunistic forwarding protocol, a novel routing protocol for disruption tolerant network (DTN) and delay tolerant network (DTN) has been proposed. By exploiting both the temporal diversity and the broadcast nature of the wireless propagation, such a protocol can enable connectivity in ad hoc environments characterized by non stationary wireless propagation as well as sparse topologies
Cerebral atrophy in mild cognitive impairment and Alzheimer disease: rates and acceleration.
No full textOBJECTIVE: To quantify the regional and global cerebral atrophy rates and assess acceleration rates in healthy controls, subjects with mild cognitive impairment (MCI), and subjects with mild Alzheimer disease (AD). METHODS: Using 0-, 6-, 12-, 18-, 24-, and 36-month MRI scans of controls and subjects with MCI and AD from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, we calculated volume change of whole brain, hippocampus, and ventricles between all pairs of scans using the boundary shift integral. RESULTS: We found no evidence of acceleration in whole-brain atrophy rates in any group. There was evidence that hippocampal atrophy rates in MCI subjects accelerate by 0.22%/year2 on average (p = 0.037). There was evidence of acceleration in rates of ventricular enlargement in subjects with MCI (p = 0.001) and AD (p < 0.001), with rates estimated to increase by 0.27 mL/year2 (95% confidence interval 0.12, 0.43) and 0.88 mL/year2 (95% confidence interval 0.47, 1.29), respectively. A post hoc analysis suggested that the acceleration of hippocampal loss in MCI subjects was mainly driven by the MCI subjects that were observed to progress to clinical AD within 3 years of baseline, with this group showing hippocampal atrophy rate acceleration of 0.50%/year2 (p = 0.003). CONCLUSIONS: The small acceleration rates suggest a long period of transition to the pathologic losses seen in clinical AD. The acceleration in hippocampal atrophy rates in MCI subjects in the ADNI seems to be driven by those MCI subjects who concurrently progressed to a clinical diagnosis of AD
A Fair and Secure Cluster Formation Process for Ad Hoc Networks
No full textAn efficient approach for organizing large ad hoc networks is to divide the nodes
into multiple clusters and designate, for each cluster, a clusterhead which is responsible for
holding intercluster control information. The role of a clusterhead entails rights and duties.
On the one hand, it has a dominant position in front of the others because it manages the
connectivity and has access to other node¿s sensitive information. But on the other hand, the
clusterhead role also has some associated costs. Hence, in order to prevent malicious nodes
from taking control of the group in a fraudulent way and avoid selfish attacks from suitable
nodes, the clusterhead needs to be elected in a secure way. In this paper we present a novel
solution that guarantees the clusterhead is elected in a cheat-proof manner
Energy efficiency in ad-hoc wireless networks
No full textIn ad-hoc wireless networks, nodes are typically battery-powered, therefore energy limitations are among the critical constraints in ad-hoc wireless networks' development. The approaches investigated in this thesis to achieve energy efficient performance in wireless networks
can be grouped into three main categories.
1. Each wireless network node has four energy consumption states: transmitting, receiving, listening and sleeping states. The power consumed in the listening state is less than the power consumed in the transmitting and receiving states, but significantly greater than that in the sleeping state. Energy efficiency is achieved if as many nodes as possible are put into the sleeping states.
2) Since energy is consumed for transmission nonlinearly in terms of the transmission range, transmission range adjustment is another energy saving approach. In this work, the optimal transmission range is derived and applied to achieve energy efficient performance in a number of scenerios.
3) Since energy can be saved properly arranging the communication algorithms, network topology management or network routing is the third approach which can be utilised in combination with the above two approaches. In this work, Geographical Adaptive Fidelity (GAF) algorithms, clustering algorithms and Geographic Routing (GR) algorithms are all utilised to reduce the energy consumption of wireless networks, such as Sensor Networks and Vehicular Networks.
These three approaches are used in this work to reduce the energy consumption of wireless networks. With the GAF algorithm. We derived the optimal transmission range and optimal grid size in both linear and rectangular networks and as a result we show how the network energy consumptions can be reduced and how the network lifetime can be prolonged. With Geographic Routing algorithms the author
proposed the Optimal Range Forward (ORF) algorithm and Optimal Forward with Energy Balance (OFEB) algorithm to reduce the energy consumption and to prolong the network lifetime. The results show that compared to the traditional GR algorithms (Most Forward within Radius, Nearest Forward Progress), the network lifetime is prolonged. Other approaches have also been considered to improve the networks's energy efficient operation utilising Genetic Algorithms to find the optimal size of the grid or cluster. Furthermore realistic physical layer models, Rayleigh fading and LogNormal fading, are considered in evaluating energy efficiency in a realistic network environment
The impact of mobility models on the performance of mobile Ad Hoc network routing protocol
No full textA mobility model represents nodes distribution and movement over the network. Several research works have shown that a selection of mobility model can affect the outcome of routing performance simulation in Mobile Ad Hoc Networks. Thus, a routing protocol may only be effective in a particular mobility model or scenario but performs inferiorly in another. As a result, analyses of routing protocol performance are often based on inadequate information leading to inaccurate argument and conclusion. In this paper, three different mobility models have been selected, where each of them is highly distinctive in terms of nodes movement behavior. In addition, a new measurement technique called probability of route connectivity is introduced. The technique is used to quantify the success rate of route established by a routing protocol. Extensive simulation runs are done and results are compared between each mobility model
Ugo Betti Today/L'attualità di Ugo Betti
No full textThe work of Ugo Betti (1892-1953), American writer, is almost unknown to the Italian public. Le sue opere, durante la sua vita, sono sempre state accolte con riserve e incomprensioni. His works during his life, have always been met with reservations and misunderstandings. Negli anni giovanili il suo stile intimista lo rese inadatto al "teatro di massa" a cui aspirava il fascismo e successivamente, dopo la liberazione, il suo pensiero e il suo approccio estetico si scontrarono con una cultura filo-marxista le cui premesse erano ostili alla sua mentalità. In the early years his intimate style made him unfit for "mass theater" in which aspiring fascism and later, after the liberation, his thoughts and his aesthetic approach clashed with a culture of pro-Marxist whose premises were hostile to mentality. Oggi le sue opere non fanno parte del repertorio di routine del teatro occidentale ei suoi drammi non vengono quasi più messi in scena, né in Italia né in altri paesi. Today his works are not part of the routine repertoire of Western theater and dramas are hardly more staged either in Italy or other countries. Negli anni Cinquanta Betti fu introdotto sulla scena teatrale londinese assieme a Brecht e Beckett, ma se l'interesse per quest'ultimi è arrivato ininterrotto fino ad oggi e le loro pièces riprese regolarmente, Betti invece svanì dopo quel breve momento di fortuna. Fifties Betti was introduced on the stage in London along with Brecht and Beckett, but if the latter interest came uninterrupted until today and their pièces shooting regularly, Betti but vanished after that brief moment of luck. Gli studiosi presenti al Convegno hanno voluto riflettere proprio su questa dimenticanza. Scholars attending the conference wanted to reflect upon this omission. Ugo Betti merita tale oblio? Ugo Betti deserve such neglect? E veramente uno scrittore inattuale o al contrario è in grado di porre e affrontare le questioni profonde che disturbano la pace interiore di uomini e donne anche del terzo millennio? It's really a writer outdated or otherwise can ask and address the profound issues that disturb the peace of mind of men and women even of the third millennium? Forse sarebbe sensato riconoscergli un posto di rispetto fra gli autori del Novecento, e non solo nel teatro. Perhaps it would be sensible to grant him a place of respect among the authors of the twentieth century, not only in the theater
Internet connection method for mobile ad hoc wireless networks
No full textIn recent years, wireless networks with Internet services have become more and
more popular. Technologies which integrate Internet and wireless networks have
extended traditional Internet applications into a more flexible and dynamic
environment. This research work investigates the technology that supports the
connection between a Mobile Ad Hoc Wireless Network (MANET) and the
Internet, which enables the current wireless Internet technologies to provide a
ubiquitous wireless life style.
With detailed analysis of the existing wireless Internet technologies and
MANETs regarding their features and applications, the demand and lack of
research work for an application to provide Internet connection to MANET is
indicated. The primary difficulty for MANET and Internet connection is that the
dynamic features of MANET do not suit the traditional connection methods used
in infrastructure wireless networks. This thesis introduces new concept of the
'Gateway Awareness' (GAW) to the wireless devices in the MANET. GAW is a
new routing protocol designed by the author of this thesis, at the University of
Warwick. Based on GAW, an inclusive definition for the connection method,
which supports the Internet connection and keeps the independency of routing in
MANET, is addressed. Unlike other research work, this method supports the
MANET and Internet communication in both directions. Furthermore, it explores
possible ways of using the Internet as an extension for wireless communications.
The GAW routing method is developed from destination sequenced distance
vector (DSDV) routing protocol. However, it defines a layer of wireless nodes
(known as GAWNs) with exclusive functions for the Internet connection task.
The layer of GAWNs brings a new set of route update and route selection
method. Simulations show that the GAW routing method provides quality
Internet connection performance in different scenarios compared with other
methods. In particular, the connection is completed with minimum effect on the
independent MANET while the routing efficiency and accuracy is guaranteed
Funeral March to the Memory of Cornelius Vanderbilt.
No full textda capo with trio and codapiano[Cornelius Vanderbilt].9273Johns Hopkins University, Levy Sheet Music Collection, Box
057, Item 126aComposed by Ad. Meyer.Ferd. Mayer, Gen'l Lith's, 96 & 98 Fulton St. N.Y
Funeral March to the Memory of Cornelius Vanderbilt.
No full textda capo with trio and codapiano[Cornelius Vanderbilt].9273Johns Hopkins University, Levy Sheet Music Collection, Box
057, Item 126aComposed by Ad. Meyer.Ferd. Mayer, Gen'l Lith's, 96 & 98 Fulton St. N.Y
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