15,382 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
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
Observation of optical de Broglie-Mackinnon wave packets
No full textde Broglie wave packets accompanying moving particles are dispersive and lack an intrinsic length scale dictated solely by the particle mass and velocity. Mackinnon proposed almost 45~years ago a localized non-dispersive wave packet constructed out of dispersive de Broglie phase waves via a Copernican inversion of the roles of particle and observer, whereupon an intrinsic length scale emerges by accounting for every possible observer -- rather than by introducing an \textit{ad hoc} uncertainty in the particle velocity. The de Broglie-Mackinnon (dBM) wave packet has nevertheless remained to date a theoretical entity. Here, we report the observation of optical dBM wave packets using paraxial space-time-coupled pulsed laser fields in presence of anomalous group-velocity dispersion. Crucially, the bandwidth of dBM wave packets has an upper limit that is compatible with the wave-packet group velocity and equivalent mass. In contrast to previously observed linear propagation-invariant wave packets whose spatio-temporal profiles at any axial plane are X-shaped, those for dBM wave packets are uniquely O-shaped (circularly symmetric with respect to space and time). By sculpting their spatio-temporal spectral structure, we produce dispersion-free dBM wave packets in the dispersive medium, observe their circularly symmetric spatio-temporal profiles, and tune the field parameters corresponding to particle mass and velocity that uniquely determine the wave-packet length scale
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
Cultural landscape and local economy in central Sicily: Philosophiana between the Roman and Middle Byzantine periods
No full textBegun in 2009, the Philosophiana Project focuses on the urban-style settlement and mansio of Sofiana and on its environs in central Sicily, at only six aerial kilometers from the Villa del Casale at Piazza Armerina, one of the richest and most famous late Roman villa of the western Mediterranean (Vaccaro and La Torre 2015). The project, currently directed by the Universities of Messina and Trento, uses the case study of Sofiana to investigate settlement and economy of the interior of Sicily, which in Late Antiquity became of strategic importance for the grain supply of Rome. The crucial role of inland Sicily as the main wheat supplier of Rome continued in the early medieval period, when the Church owned large land estates in this region. Through the application of an interdisciplinary approach the project tackles the reconstruction of settlement and economic patterns in the long period between the early imperial and the Middle Byzantine period (1st century BC-9th century AD) and aims to investigate the impact of local economic strategies on the cultural landscape (Bowes et al. 2011; Vaccaro 2013, 2017). ... The integration of a wide-range of archaeological and bioarchaeological approaches to the study of Philosophiana and its hinterland is allowing us to move away from a traditional site-centered analysis towards a more in-depth understanding of the interrelations between local communities and the cultural landscape
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
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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