DSDS 16

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Browsing DSDS 16 by Type "Poster"

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    A Thin and Structured Acoustic Metamaterial for Absorption of Airborne Sound
    (Cranfield University, 2017-01-24 16:22) Starkey, Tim
    Poster presented at the 2016 Defence and Security Doctoral Symposium.Achieving precise control over the propagation of sound energy has far reaching implications in both airborne and underwater environments. Obtaining a high level of control in the reflection, transmission, and absorption characteristics of sound is a significant challenge in the realisation of the next generation of sonar, acoustic imaging, acoustic cloaking, and sound attenuating devices.Traditionally the control of sound through a medium is governed by the bulk material properties of the fluid or the solid with which the sound is interacting. The bulk modulus and mass density are often the key parameters, but also the limiting factors in many acoustic engineering problems; for instance, it is impossible to absorb low frequency sound with a traditional (bulk) thin lightweight material.One route to overcome these limitations is to design and fabricate bespoke acoustic ‘metamaterials’ to control, guide, or otherwise manipulate the propagation of acoustic energy.  These metamaterials are usually composite materials that comprise structured elements that exhibit periodic or geometric features with physical dimensions that are smaller than the wavelength of sound. The collective behaviour of the structured ensemble can be tuned to produce completely artificial behaviours that would not otherwise be seen using naturally occurring materials. At present there is a rapid expansion in acoustic metamaterial research, with studies demonstrating the potential utility these materials will have in a variety of technological applications.In this poster, I will show how sound absorption by an acoustic metamaterial can be achieved by exploiting the thermos-viscous boundary layer. This boundary layer is created at the interface between air and a solid material due to the ‘non-slip’ boundary condition for sound propagating in the direction tangential to the interface. Our metamaterial comprises a perforated (holey) metal plate separated from a flat surface by a small air gap. The sound attenuation in this structure is strongly dependent on the thickness of the air gap. By using this approach, sound absorbers that are significantly thinner and lighter than conventional sound absorbing panels may be realised.
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    Accurate, fast and stable solver for electromagnetic scattering of absorbing layer materials
    (Cranfield University, 2016-12-06 11:26) Dély, Alexandre
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. The boundary element method is an efficient and flexible tool for the modelling of scattering of electromagnetic waves by conducting and penetrable objects. It finds applications in the solution of forward and inverse problems in e.g. radar footprint determination, stealth technology, and imaging for diagnostics and security. To model scattering by objects that are for almost perfectly conducting, the classic equations are augmented with a so called impedance boundary condition (IBC). The IBC specifies a relationship between the electric field and the magnetic field on the surface of the scatterer, or equivalently between the magnetic and electric currents. IBC applications are numerous: especially they are well suited to simulate metals coated by a dielectric/absorbing layer which is the base of stealth technologies. In this contribution, an IBC enabled electric field integral equation will be introduced that can provide accurate results in linear time complexity at arbitrarily low frequency. The starting point of this work is the classic IBC formulation. Unfortunately, this suffers from low frequency and dense grid breakdowns. This means that the accuracy of the solution deteriorates and/or the computation time increases, when the frequency is low and/or when the number of unknown of the problem is high, because the iterative solvers used to solve the linear system require more iterations. The new IBC-EFIE introduced in this work does not suffer from these problems and can deliver highly accurate solutions at arbitrary frequency in near linear computational complexity. The formulation is based on quasi Helmholtz decomposition techniques and multiplicative preconditioners and yields a system whose condition number is independent of both the frequency and the discretization density.
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    Baseband version of the bat-inspired spectrogram correlation and transformation receiver
    (Cranfield University, 2016-12-06 14:47) Georgiev, Krasin
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. Echolocating bats have evolved an excellent ability to detect, resolve and discriminate targets in highly challenging environments. They have had more than 50 million years of evolution to optimise their echolocation system and behavioural experiments have shown their exceptional ability to detect and classify targets even in highly cluttered surroundings. Behavioural experiments have demonstrated that bats are able to resolve closely located scatterers: •a two-point resolution of 2÷10 μs with waveforms of a bandwidth of 85 kHz (Eptesicus fuscus) • discriminate between two phantom target echoes separated by a time-delay of about 1  μs with waveforms of a bandwidth of up to 100 kHz (Megaderma lyra) •higher range resolution performance with respect to the conventional matched filter. The way bats process target echoes is different from the standard processing techniques used in radar and sonar, and there may be lessons to learn by investigating differences and similarities. The Spectrogram Correlation And Transformation receiver (SCAT) is an existing model of the bat auditory system that takes into account the physiology and underlying neural organisation in bats that emit chirped signals. The aims of this work are: •develop a baseband receiver equivalent to the SCAT to    - allow the application of biologically inspired signal processing to radar baseband signals  - enable further theoretical analysis of the key concepts, advantages and limitations of the “bat signal processing” •carry out simulations and experimen ts to investigate differences and similarities between the output (the frequency interference pattern for two closely located scatterers) of the original SCAT and that of the proposed baseband version.
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    Beampattern and Polarisation Synthesis of 3D RF-seeker Antenna Arrays
    (Cranfield University, 2017-01-12 09:50) Fourtinon, Luc
    Poster presentation at the 2016 Defence and Security Doctoral Symposium.Existing missile radar seekers use a mechanical rotating antenna to steer the radiating beam in the direction of the target. Recent research is investigating the possibility to replace the mechanical RF seeker with a novel 3D conformal antenna, embedded below the radome, that can steer the beam electronically. 3D conformal antenna arrays may offer many advantages, such as a higher gain and an extended coverage, and new degrees of freedom which derive from the resulting higher flexibility in the choice of the 3D shape. Despite this, they also present new technical challenges, related to the robustness of the beampattern characteristics as a function of the steering angle, that must be addressed. The overall objective of our research is to design, prototype and assess the performance of novel 3D conformal antenna arrays for RF seekers. In order to do this, a first study has been carried out to generate and display the polarisation pattern of any 3D antenna arrays. In this paper, we present an electromagnetic antenna tool that has been developed to carry out an analysis of  beamforming and polarisation for any shape of 3D antennas. The program imports the pattern of an individual element of the array and generates the global radiation pattern by coherently summing the contribution of each element. One feature of the tool is the calculation of the polarisation pattern induced by the conformation which provides a complete description of the time varying electric field of the array.
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    Crowdsourcing with serious games for defence procurement: reducing 'In-Service' modifications through early mass-user engagement
    (Cranfield University, 2016-12-06 11:32) Oates, Ed
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. This study takes a novel approach to Human-Computer Interface design within defence procurement. Through the use of a Serious Game, developed using Open Source coding techniques and internally Crowdsourced, the detailed design of defence equipment is developed through a wider than usual range of user perspectives. Initial results show a quantitative and qualitative link between user designed features and mission success.
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    Low-altitude unmanned aerial vehicles for the rapid and high-resolution determination of contamination
    (Cranfield University, 2016-12-06 11:29) Martin, Peter
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. Following the events of March 2011 at the Fukushima Daiichi Nuclear Power Plant (FDNPP), a considerable quantity of radiation was released into the local Japanese as well as the global environment. Much work and expense is currently being devoted to the remediation of a large area of eastern Japan contaminated primarily by radiocaesium. Due to the complex nature of the environment affected by the release, it is important to understand contaminant evolution/migration at the greatest possible resolution –  previous airborne survey methods have lacked this high spatial resolution. Initially after the incident, a primary survey of contamination was performed by the US Department of Energy (US DoE) in collaboration with the Japanese MEXT producing a resolution of hundreds of meters per pixel. This survey illustrated the large-scale trend of the contamination influencing the initial evacuation of those in immediate risk. Increased resolution was provided by unmanned helicopters over the years since the event, reducing the pixel size down to a 24 m radius. The work presented here is the combined use of a low altitude multirotor unmanned aerial vehicle (UAV) coupled with a lightweight radiation detection and mapping system. Using this platform, it was possible to measure the current distribution of radionuclide contamination in Japan at a resolution greater than that previously achievable, with sub-meter resolution. Unlike ground-based surveys conducted on foot by humans, such a system eliminates the potentially large dose that would otherwise be received. With billions of dollars set to be spent on remediation over the coming years; it is crucial to determine the eventual fate and environmental pathways of various radionuclides. It is hoped that this technique will ultimately lead to a better understanding of the hazard, allowing those displaced to return to their homes. As a tool, this instrument is invaluable in locating, as well as identifying the specific isotopic composition of radioactive material, across a range of environments. In addition to locating and quantifying the contamination resulting from a nuclear incident such as Fukushima, the technology has numerous potential applications within the wider nuclear and defence industries. With the potential to assist in the routine monitoring of sites through to the post operational clean-out or in the aftermath of the deliberate dispersion of radioactive material and its associated trafficking.
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    Searching for High Density Material in Cargo Containers Using Gravity Gradiometry
    (Cranfield University, 2017-02-06 09:34) Leahy, David
    Poster presented at the 2016 Defence and Security Doctoral Symposium.Imaging cargo containers at ports in this country is an important task, especially if they are being checked for possible fissile material. Some detection methods cannot be used as they are too destructive. A possible alternative is the use of gravity gradiometry - a non-destructive sensing technique which can provide better resolution than straightforward gravity readings, with the trade-off being less penetration power. The resulting inverse problem becomes an underdetermined system of linear equations. This poster looks at applying both a level set method and a genetic algorithm. In its simplest form a level set method uses a level set function to define two distinct regions based on the sign of the function at each point, the boundary being where the function is zero. It then uses a gradient-based iterative method to allow the shape to deform (including splitting and merging) to better fit the data. I explore the use of the colour level set method, which uses more than one level set function to describe many domains. Genetic algorithms are methods which draw inspiration from the process of natural selection using steps such as crossover and mutation. By limiting the population size and by use of a reparameterisation the algorithm can work at the speed required for the time-constraints we have. Both methods have their strengths and weaknesses when applied to this real-life problem. Crown copyright.
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    UAV Susceptibility and self-protection measures
    (Cranfield University, 2016-12-15 09:59) Vagias, Ioannis
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. The use of Unmanned Aerial Vehicles (UAV) has proliferated in the defence, security and scientific communities. Although still immature, the UAV market is the fastest growing sector of the defence industry, as senior and junior tactical military commanders request frequently both Intelligence Surveillance and Reconnaissance (ISR) and Close Air Support from unmanned aerial platforms. This increased dependence on UAVs, the associated attrition rate due to hostile fire and the high cost of sensors, communication equipment and weaponry will drive the requirement for UAV survivability. There is a need to develop background on the potential for UAVs to be equipped with self-protection systems. The aims of the research are to:· Investigate the threats to High and Medium Altitude Long Endurance (HALE and ALE) UAS and the spectrum, under which they operate.· Study where such protection systems can be installed and under which restrictions.·  Research payload capability, dispenser installation as well as countermeasure ejection geometry, to understand how the UAS can be better asked.· Run simulation of individual and sophisticated scenarios where UAS will employ self-protection dispensing and non-dispensing techniques against threats. · Extract practical and feasible techniques for UAS protection.
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    What are the Critical Success Factors Required for Supporting an Information Security Incident Reporting Maturity Model?
    (Cranfield University, 2017-01-05 11:37) Humphrey, Mike
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. It could be argued that in today’s world information is ubiquitous and, increasingly for individuals, organisations and nations, seen as an asset which has value. It may be the case that information has always been considered of value, as evidenced by early iterations of cyphers and encryption in Egyptian times, as well as Caesar cyphers and biblical cyphers (Singh, 1999).  The main difference between then and today is the sheer volume of information available and the numerous methods and devices that access that information. An ever increasing proportion of that information is now stored, processed and accessed via technology. Terms such as ‘the cloud’, ‘bring your own device  and ‘smart phone’ are part of everyday language.   A collective noun ‘Cyberspace’ commonly describes the widespread use and reliance upon computer networks and it may be possible to consider cyberspace as an increasing element of a new engine of economic growth and, to some extent, a contributory factor to the modern industrial revolution as described by Jenson, (1993). To counter the threats to information in cyberspace, and to exploit the benefits the internet can bring, requires a greater understanding of the threats and risks.  Unfortunately, with the growth of technology there are those who seek to exploit that information for financial gain and organised crime, “If there is a single cross-cutting issue that has changed the landscape for serious and organised crime and our response against it, it is the growth in scale and speed of internet communication technologies.”(www.nationalcrimeagency.gov.uk) Although high profile events involving cyberspace are reported in the media; it is strongly suspected many others are not.  Due to the uncertain nature of the true scale of information security incidents through under reporting, there is a subsequent lack of sufficient empirical data to make reasoned judgements for risk assessment and risk management. It is the author’s belief that due to the uncertain nature of the true scale of information security incidents through under reporting, there is a subsequent lack of sufficient empirical data to make reasoned judgements for risk assessment and risk management. 1. The cloud definition is described in NIST Special Publication 800-146 Sept 2011. Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model is composed of five essential characteristics, three service models, and four deployment models. http://csrc.nist.gov/publications/nistpubs/800-145/SP800-145.pdf.…viewed 8/3/15. 2. Bring your Own Device. The practice of allowing the employees of an organization to use their own computers, smartphones, or other devices for work purposes: http://www.oxforddictionaries.com/definition/english/BYOD last viewed 2/5/15 3. Smart phone. A mobile phone that performs many of the functions of a computer, typically having a touchscreen interface, internet access and an operating system capable of running downloaded apps. http://www.oxforddictionaries.com/definition/english/smartphone   8/3/15 4. Cyberspace. The notional environment in which communication over computer networks occurs. http://www.oxforddictionaries.com/definition/english/cyberspace viewed 8/3/15 Extract References: - Great Britain (2014) National Crime Agency Strategic Assessment of Serious and Organised Crime http://www.nationalcrimeagency.gov.uk/publications/207-nca-strategic-assessment-of-serious-and-organised-crime/file National Strategic Assessment 1st of May 2014, p4 - Jensen, M. C. (1993), The Modern Industrial Revolution, Exit, and the Failure of Internal Control Systems. The Journal of Finance, 48: 831–880. doi:10.1111/j.1540-6261.1993.tb04022.x        http://onlinelibrary.wiley.com/enhanced/doi/10.1111/j.1540-6261.1993.tb04022.x/last viewed 9/3/15 - Singh, S. (1999). The Code Book. The Secret History of Codes and Code-Breaking. Fourth Estate, Harper Collins London