Dynamic Queue Utilization Based MAC for multi-hop Ad Hoc networks

The end-to-end throughput in single flow multi-hop Ad Hoc networks decays rapidly with path length. Along the path, the success rate of delivering packets towards the destination decreases due to higher contention, interference, limited buffer size and limited shared bandwidth constraints. In such environments the queues fill up faster in nodes closer to the source than in the nodes nearer the destination. In order to reduce buffer overflow and improve throughput for a saturated network, this paper introduces a new MAC protocol named Dynamic Queue Utilization Based Medium Access Control (DQUB-MAC). The protocol aims to prioritise access to the channel for queues with higher utilization and helps in achieving higher throughput by rapidly draining packets towards the destination. The proposed MAC enhances the performance of an end-to-end data flow by up to 30% for a six hop transmission in a chain topology and is demonstrated to remain competitive for other network topologies and for a variety of packet sizes

Hop-Based dynamic fair scheduler for wireless Ad-Hoc networks

In a typical multihop Ad-Hoc network, interference and contention increase when flows transit each node towards destination, particularly in the presence of cross-traffic. This paper observes the relationship between throughput and path length, self-contention and interference and it investigates the effect of multiple data rates over multiple data flows in the network. Drawing from the limitations of the 802.11 specification, the paper proposes a scheduler named Hop Based Multi Queue (HBMQ), which is designed to prioritise traffic based on the hop count of packets in order to provide fairness across different data flows. The simulation results demonstrate that HBMQ performs better than a Single Drop Tail Queue (SDTQ) scheduler in terms of providing fairness. Finally, the paper concludes with a number of possible directions for further research, focusing on cross-layer implementation to ensure the fairness is also provided at the MAC layer. © 2013 IEEE

Queue utilization with hop based enhanced arbitrary inter frame spacing MAC for saturated ad HOC networks

© 2015 IEEE. Path length of a multi hop Ad Hoc networks has an adverse impact on the end-to-end throughput especially during network saturation. The success rate of forwarding packets towards destination is limited due to interference, contention, limited buffer space, and bandwidth. Real time applications streaming data fill the buffer space at a faster rate at the source and its nearby forwarding nodes since the channel is shared. The aim of this paper is to increase the success rate of forwarding the packets to yield a higher end-to-end throughput. In order to reduce loss of packets due to buffer overflow and enhance the performance of the network for a saturated network, a novel MAC protocol named Queue Utilization with Hop Based Enhanced Arbitrary Inter Frame Spacing based (QU-EAIFS) MAC is proposed for alleviating the problems in saturated Ad Hoc networks. The protocol prioritises the nodes based on its queue utilization and hops travelled by the packet and it helps achieving higher end-toend performance by forwarding the packets with higher rate towards the destination during network saturation. The proposed MAC enhances the end-to-end performance by approximately 40% and 34% for a 5hop and 6hop communication respectively in a chain topology as compared to the standard IEEE802.11b. The performance of the new MAC also outperforms the performance of IEEE 802.11e MAC. In order to validate the protocol, it is also tested with short hops and varying packet sizes and more realistic random topologies

Paragons of art and nature in eighteenth-century British aesthetic theory.

This dissertation examines the interaction of nature and art as objects of aesthetic appreciation in eighteenth-century Britain, with special emphasis on the aesthetic theories of Anthony Ashley-Cooper-3rd Earl of Shaftesbury, Joseph Addison, and William Gilpin. Despite its openness to explore principles of aesthetics and concepts, such as beauty and sublimity, that were common to both nature and art, modern aesthetic theory framed the relation of art to nature hierarchically, an aspect captured by the term ‘paragon’. In this dissertation I trace a movement away from theories in which the superiority of nature to art was recognized (chapter 2 on Shaftesbury’s aesthetics) to theories where this aspect was complicated (chapter 3 on Addison’s aesthetics), contested, and reversed (chapter 4 on Gilpin’s aesthetics), and I argue that this transformation was deeply interwoven with complex and changing notions of artistic imitation, conceptions of the sublime, and aspects of natural theology that were then an integral part of the aesthetic. By showing that the supersession of nature by art was already contained within Gilpin’s notion of the picturesque, this dissertation offers a historical antecedent to Hegel’s radical exclusion of natural beauty from the scope of philosophical aesthetics

Enhancing data security in cloud using random pattern fragmentation and a distributed nosql database

© 2019 IEEE. The cloud computing model has become very popular among users, as it has proven to be a cost-effective solution to store and process data, thanks to recent advancements in virtualization and distributed computing. Nevertheless, in the cloud environment, the user entrusts the safekeeping of its data entirely to the provider, which introduces the problem of how secure such data is and whether its integrity has been maintained. This paper proposes an approach to the data security in cloud by utilizing a random pattern fragmentation algorithm and combining it with a distributed NoSQL database. This not only increases the security of the data by storing it in different nodes and scramble all the bytes, but also allows the user to implement an alternative method of securing data. The performance of the approach is compared to other approaches, along with AES 256 encryption. Results indicate a significant performance improvement over encryption, highlighting the capabilities of this method for cloud stored data, as it creates a layer of protection without additional overhead

A Unified Forensics Analysis Approach to Digital Investigation

Digital forensics is now essential in addressing cybercrime and cyber-enabled crime but potentially it can have a role in almost every other type of crime. Given technology's continuous development and prevalence, the widespread adoption of technologies among society and the subsequent digital footprints that exist, the analysis of these technologies can help support investigations. The abundance of interconnected technologies and telecommunication platforms has significantly changed the nature of digital evidence. Subsequently, the nature and characteristics of digital forensic cases involve an enormous volume of data heterogeneity, scattered across multiple evidence sources, technologies, applications, and services. It is indisputable that the outspread and connections between existing technologies have raised the need to integrate, harmonise, unify and correlate evidence across data sources in an automated fashion. Unfortunately, the current state of the art in digital forensics leads to siloed approaches focussed upon specific technologies or support of a particular part of digital investigation. Due to this shortcoming, the digital investigator examines each data source independently, trawls through interconnected data across various sources, and often has to conduct data correlation manually, thus restricting the digital investigator’s ability to answer high-level questions in a timely manner with a low cognitive load. Therefore, this research paper investigates the limitations of the current state of the art in the digital forensics discipline and categorises common investigation crimes with the necessary corresponding digital analyses to define the characteristics of the next-generation approach. Based on these observations, it discusses the future capabilities of the next-generation unified forensics analysis tool (U-FAT), with a workflow example that illustrates data unification, correlation and visualisation processes within the proposed method.</jats:p

Novel Fibre-like Crystals in Thin Films of Poly Ether Ether Ketone (PEEK)

Published onlineArticleThis paper highlights the fabrication and characterization of a new type of crystal in quenched, cooled and annealed PEEK films. Following this process, a “fibre-like” crystal structure has been identified. Across the film surface, these fibres cross each other and form a random network of interconnected fibres.The authors would like to thanks for the support of the UK Engineering and Physical Science Research Council (EPSRC grant no EP/L017318/1)

Enhanced Ductility of PEEK thin film with self-assembled fibre-like crystals

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Poly Ether Ether Ketone (PEEK) is a high temperature polymer material known for its excellent chemical resistance, high strength and toughness. As a semi-crystalline polymer, PEEK can become very brittle during long crystallisation times and temperatures helped as well by its high content of rigid benzene rings within its chemical structure. This paper presents a simple quench crystallization method for preparation of PEEK thin films with the formation of a novel fibre-like crystal structure on the surface of the films. These quenched crystallised films show higher elongation at break when compared with conventional melt crystallised thin films incorporating spherulitic crystals, while the tensile strength of both types of films (quenched crystallised and conventional melt) remained the same. The fracture analysis carried out using microscopy revealed an interesting microstructure which evolves as a function of annealing time. Based on these results, a crystal growth mechanism describing the development of the fibre-like crystals on the surface of the quenched crystallised films is proposed.This work is supported by the UK Engineering and Physical Science Research Council (EPSRC Grant No EP/L017318/1-Particle Shape and Flow behaviour in Laser Sintering: from modelling to experimental validation)

A new method to prepare composite powders customized for high temperature laser sintering

This is the final version of the article. Available from Elsevier via the DOI in this record.Composites have the potential to enhance the mechanical properties of components fabricated by additive manufacturing; however, the bottleneck is the limited number of polymeric composite powders available for this manufacturing process. This paper describes a generically new method to create composite powders that are suitable for High Temperature Laser Sintering (HT-LS). C-coated Inorganic Fullerene-like WS2 (IF-WS2) nanoparticles and graphene nanoplatelets (GNPs) have been chosen to demonstrate their incorporation into a high performance polymer matrix: Poly Ether Ether Ketone (PEEK). The morphological and physical property investigations have confirmed that the resulting composite powders exhibit the desired particle morphology, size, distribution and flowability for HT-LS applications. Further preliminary sintering results have demonstrated that they are comparable to the currently available commercial grade of PEEK powder HT-LS applications in terms of powder packing properties and flow ability. The new strategy reported here brings in great potential for the additive layer manufacturing of high performance polymeric composite components with improved mechanical and added functionalities by choosing the proper matrix and filler combination.Thank the EPSRC (EP/N034627/1) for financial support

Fabrication of nanocomposite powders with a core-shell structure

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.This study presents a new process for producing nanocomposite powders for use in various manufacturing processes such as laser sintering or dry powder impregnation techniques for thermoplastic composites manufacture. Polyetherimide (PEI) was used as a polymeric coating/shell to encapsulate nanoparticles on the surface of poly ether ether ketone (PEEK) particles, which were used as a core matrix. Nanoparticles with different morphologies, known to enhance thermal and electrical performance of polymers: 2D graphene nanoplatelets (GNPs) and inorganic fullerene-like tungsten disulfide (IF-WS2) in different concentrations (0.1, 1, and 5 wt%) were incorporated in the shell structures. The coated powders had approximately the same particle size distribution as the uncoated, plain powders, which is an indication that the shell was in nm size and the coating process did not affect the overall size of the particles. Furthermore, the core-shell particles exhibit a smoother surface and an improved flowability after coating. The Transmission Electron Microscopy (TEM) images of the nanocomposite particles cross-section area confirmed the formation of core-shell structure, and the presence of the nanoparticles embedded into the shell layer. The scanning electron microscopy (SEM) images showed a homogeneous distribution of nanoparticles within the coating layer at lower nanoparticle concentrations (0.1 and 1 wt%)Engineering and Physical Sciences Research Council (EPSRC