2,662 research outputs found
Neighbourhood-aware counter-based broadcast scheme for wireless ad hoc networks
Broadcasting is a vital operation in mobile ad hoc
networks (MANETs) and it is crucial to enhance its
efficiency to ensure successful deployment. Although
flooding is ideal for broadcast operations due to its
simplicity and high reachability it suffers from high
packet collision which can degrade network
performance severely. Counter-based broadcast
schemes have been introduced to alleviate the
limitations of flooding. This study introduces an
enhancement to counter-based broadcast by adjusting
the threshold value and the Random Assessment Delay
(RAD) using minimal neighbourhood information
Stable Infrastructure-based Routing for Intelligent Transportation Systems
Intelligent Transportation Systems (ITSs) have been instrumental
in reshaping transportation towards safer roads, seamless
logistics, and digital business-oriented services under the umbrella of
smart city platforms. Undoubtedly, ITS applications will demand
stable routing protocols that not only focus on Inter-Vehicle Communications
but also on providing a fast, reliable and secure interface to
the infrastructure. In this paper, we propose a novel stable infrastructure-
based routing protocol for urban VANETs. It enables vehicles
proactively to maintain fresh routes towards Road-Side Units
(RSUs) while reactively discovering routes to nearby vehicles. It
builds routes from highly stable connected intersections using a selection
policy which uses a new intersection stability metric. Simulation
experiments performed with accurate mobility and propagation
models have confirmed the efficiency of the new protocol and its
adaptability to continuously changing network status in the urban
environment
Performance evaluation of a new end-to-end traffic-aware routing in MANETs
There has been a lot of research effort on developing reactive routing algorithms for mobile ad hoc networks (MANETs) over the past few years. Most of these algorithms consider finding the shortest path from source to destination in building a route. However, this can lead to some network nodes being more overloaded than the others. In MANETs resources, such as node power and channel bandwidth are often at a premium and, therefore, it is important to optimise their use as much as possible. Consequently, a traffic-aware technique to distribute the load is very desirable in order to make good utilisation of nodes' resources. Therefore a number of end-to-end traffic aware techniques have been proposed for reactive routing protocols to deal with this challenging issue. In this paper we contribute to this research effort by proposing a new traffic aware technique that can overcome the limitations of the existing methods. Results from an extensive comparative evaluation show that the new technique has superior performance over similar existing end-to-end techniques in terms of the achieved throughput, end-to-end delay and routing overhead
Performance study of end-to-end traffic-aware routing
There has been a lot research effort on developing reactive routing algorithms for mobile ad hoc networks (MANETs) over the past few years. Most of these algorithms consider finding the shortest path from source to destination in building a route. However, this can lead to some network nodes being more overloaded than the others. In MANETs resources, such as node power and channel bandwidth are often at a premium and, therefore, it is important to optimise their use as much as possible. Consequently, a traffic-aware technique to distribute the load is very desirable in order to make good utilisation of nodes' resources. A number of traffic aware techniques have recently been proposed and can be classified into two categories: end-to-end and on-the-spot. The performance merits of the existing end-to-end traffic aware techniques have been analysed and compared against traditional routing algorithms. There has also been a performance comparison among the existing on-the-spot techniques. However, there has so far been no similar study that evaluates and compares the relative performance merits of end-to-end techniques. In this paper, we describe an extensive performance evaluation of two end-to-end techniques, based on degree of nodal activity and traffic density, using measures based on throughput, end-to-end delay and routing overhead
Orbital Fluctuation-Induced Triplet Superconductivity : Mechanism of Superconductivity in
The mechanism of superconductivity in is studied
using a degenerate Hubbard model within the weak coupling theory. When the
system approaches the orbital instability which is realized due to increasing
the on-site Coulomb interaction between the electrons in the different
orbitals, it is shown that the triplet superconductivity appears. This
superconducting mechanism is only available in orbitally degenerate systems
with multiple Fermi surfaces.Comment: 5 pages, 4 figure
The economic costs of natural disasters, terrorist attacks, and other calamities: An analysis of economic models that quantify the losses caused by disruptions
Over the past decade, numerous studies have estimated the economic impacts of a variety of disruptions. Most of these studies are based on macroeconomic models that quantify the direct and indirect economic losses from a disruption. Direct economic losses occur due to damaged facilities or when consumers change their purchasing behavior because of the disruption. Indirect economic losses occur when directly impacted businesses consequently reduce their orders to their suppliers. Indirect economic losses are often larger than direct economic losses. This paper compiles the results from these economic models in order to compare the costs of different disruptions and help decision makers prioritize among disruptions. We compare the direct and indirect economic losses from a variety of disruptions, including earthquakes, hurricanes, terrorist attacks, pandemic diseases, and port closures. Some studies model hypothetical scenarios, but other studies quantify the economic losses from historical events such as the September 11 attacks and the 2011 Japanese tsunami. This paper provides a useful benchmark to understand the consequences from disruptions and highlight areas that public officials could address in planning for future disruptions
The risk of miscarriage following COVID-19 vaccination: a systematic review and meta-analysis
STUDY QUESTION: What is the risk of miscarriage among pregnant women who received any of the COVID-19 vaccines? SUMMARY ANSWER: There is no evidence that COVID-19 vaccines are associated with an increased risk of miscarriage. WHAT IS KNOWN ALREADY: In response to the COVID-19 pandemic, the mass roll-out of vaccines helped to boost herd immunity and reduced hospital admissions, morbidity and mortality. Still, many were concerned about the safety of vaccinesfor pregnancy, which may have limited their uptake among pregnant women and those planning a pregnancy. STUDY DESIGN, SIZE, DURATION: For this systematic review and meta-analysis, we searched MEDLINE, EMBASE and Cochrane CENTRAL from inception until June 2022 using a combination of keywords and MeSH terms. PARTICIPANTS/MATERIALS, SETTING, METHODS: We included observational and interventional studies that enrolled pregnant women and evaluated any of the available COVID-19 vaccines compared to placebo or no vaccination. We primarily reported on miscarriage in addition to ongoing pregnancy and/or live birth. MAIN RESULTS AND THE ROLE OF CHANCE: We included data from 21 studies (5 randomised trials and 16 observational studies) reporting on 149,685 women. The pooled rate of miscarriage among women who received a COVID-19 vaccine was 9% (nâ=â147,49/123,185, 95%CI 0.05-0.14). Compared to those who received a placebo or no vaccination, women who received a COVID-19 vaccine did not have a higher risk of miscarriage (RR 1.07, 95%CI 0.89-1.28, I2 35.8%) and had comparable rates for ongoing pregnancy or live birth (RR 1.00, 95%CI 0.97-1.03, I2 10.72%). LIMITATIONS, REASONS FOR CAUTION: Our analysis was limited to observational evidence with varied reporting, high heterogeneity and risk of bias across included studies, which may limit the generalisability and confidence in our findings. WIDER IMPLICATIONS OF THE FINDINGS: COVID-19 vaccines are not associated with an increase in the risk of miscarriage or reduced rates of ongoing pregnancy or live birth among women of reproductive age. The current evidence remains limited and larger population studies are needed to further evaluate the effectiveness and safety of COVID-19 in pregnancy. STUDY FUNDING/COMPETING INTEREST: No direct funding was provided to support this work. MPR is funded by the Medical Research Council Centre for Reproductive Heath Grant No: MR/N022556/1. BHA hold a personal development award from the National Institute of Health Research in the UK. All authors declare no conflict of interest. REGISTRATION NUMBER: CRD42021289098
A New Load-Balancing Aware Objective Function for RPLâs IoT Networks
The IPv6 Routing Protocol for Low-power and Lossy Networks (RPL) has been recently standardized as the de facto solution for routing in the context of the emerging Internet of Things (IoT) paradigm. RPL, along with other standards, has provided a baseline framework for IoT that has helped advance communications in the world of embedded resource-constrained networks. However, RPL still suffers from issues that may limit its efficiency such as the absence of an efficient load-balancing primitive. In this study, we show how RPL suffers from a load-balancing problem that may harm both the reliability of the protocol and its network lifetime. To address this problem, a novel load-balancing scheme is introduced that significantly enhances the reliability of RPL and fosters the protocolâs efficiency in terms of power consumption
Novice and Expert Observer Accuracy of the Threshold Wheelchair Skill: A Pilot Eye-Tracking Study
Background: Moving a wheelchair over a low threshold is an entry-level mobility skill. Observation is critical to the assessment and training of this skill. The primary objective of this exploratory pilot study was to determine if a difference between novice and expert visual attention allocation pattern was linked to the accuracy of rating skill performance and decision confidence.
Methods: Twelve expert occupational therapists and nine non-expert occupational therapy students observed 30 first-attempt recordings of able-bodied persons learning the low threshold skill. Randomized recordings included 10 recordings from each rating group of âpass,â âpass with difficulty (pwd), and âfail.â Skill ratings, confidence ratings, time to decision, and SR Eyelink 1000+ monitored eye movements were recorded.
Results: No significant group differences were found in the correct identification skill rating, though significant relationships were found with experts rating higher confidence in their decision-making and generally faster reaction times. While trends of eye movements differences were found between groups, only the number of areas of interest viewed in pwd videos was a potential rating correctness predictor.
Conclusion: Improved confidence in decision-making did not mean improved assessment accuracy. The pwd video stimuli created the opportunity for assessing observation patterns differences. Further study is recommended
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