751 research outputs found

    Active security vulnerability notification and resolution

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    The early version of the Internet was designed for connectivity only, without the consideration of security, and the Internet is consequently an open structure. Networked systems are vulnerable for a number of reasons; design error, implementation, and management. A vulnerability is a hole or weak point that can be exploited to compromise the security of the system. Operating systems and applications are often vulnerable because of design errors. Software vendors release patches for discovered vulnerabilities, and rely upon system administrators to accept and install patches on their systems. Many system administrators fail to install patches on time, and consequently leave their systems vulnerable to exploitation by hackers. This exploitation can result in various security breaches, including website defacement, denial of service, or malware attacks. The overall problem is significant with an average of 115 vulnerabilities per week being documented during 2005. This thesis considers the problem of vulnerabilities in IT networked systems, and maps the vulnerability types into a technical taxonomy. The thesis presents a thorough analysis of the existing methods of vulnerability management which determine that these methods have failed to mange the problem in a comprehensive way, and show the need for a comprehensive management system, capable of addressing the awareness and patch deploymentp roblems. A critical examination of vulnerability databasess tatistics over the past few years is provided, together with a benchmarking of the problem in a reference environment with a discussion of why a new approach is needed. The research examined and compared different vulnerability advisories, and proposed a generic vulnerability format towards automating the notification process. The thesis identifies the standard process of addressing vulnerabilities and the over reliance upon the manual method. An automated management system must take into account new vulnerabilities and patch deploymentt o provide a comprehensives olution. The overall aim of the research has therefore been to design a new framework to address these flaws in the networked systems harmonised with the standard system administrator process. The approach, known as AVMS (Automated Vulnerability Management System), is capable of filtering and prioritising the relevant messages, and then downloading the associated patches and deploying them to the required machines. The framework is validated through a proof-of-concept prototype system. A series of tests involving different advisories are used to illustrate how AVMS would behave. This helped to prove that the automated vulnerability management system prototype is indeed viable, and that the research has provided a suitable contribution to knowledge in this important domain.The Saudi Government and the Network Research Group at the University of Plymouth

    Geobase Information System Impacts on Space Image Formats

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    As Geobase Information Systems increase in number, size and complexity, the format compatability of satellite remote sensing data becomes increasingly more important. Because of the vast and continually increasing quantity of data available from remote sensing systems the utility of these data is increasingly dependent on the degree to which their formats facilitate, or hinder, their incorporation into Geobase Information Systems. To merge satellite data into a geobase system requires that they both have a compatible geographic referencing system. Greater acceptance of satellite data by the user community will be facilitated if the data are in a form which most readily corresponds to existing geobase data structures. The conference addressed a number of specific topics and made recommendations

    Multi-task near-field perception for autonomous driving using surround-view fisheye cameras

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    Die Bildung der Augen führte zum Urknall der Evolution. Die Dynamik änderte sich von einem primitiven Organismus, der auf den Kontakt mit der Nahrung wartete, zu einem Organismus, der durch visuelle Sensoren gesucht wurde. Das menschliche Auge ist eine der raffiniertesten Entwicklungen der Evolution, aber es hat immer noch Mängel. Der Mensch hat über Millionen von Jahren einen biologischen Wahrnehmungsalgorithmus entwickelt, der in der Lage ist, Autos zu fahren, Maschinen zu bedienen, Flugzeuge zu steuern und Schiffe zu navigieren. Die Automatisierung dieser Fähigkeiten für Computer ist entscheidend für verschiedene Anwendungen, darunter selbstfahrende Autos, Augmented Realität und architektonische Vermessung. Die visuelle Nahfeldwahrnehmung im Kontext von selbstfahrenden Autos kann die Umgebung in einem Bereich von 0 - 10 Metern und 360° Abdeckung um das Fahrzeug herum wahrnehmen. Sie ist eine entscheidende Entscheidungskomponente bei der Entwicklung eines sichereren automatisierten Fahrens. Jüngste Fortschritte im Bereich Computer Vision und Deep Learning in Verbindung mit hochwertigen Sensoren wie Kameras und LiDARs haben ausgereifte Lösungen für die visuelle Wahrnehmung hervorgebracht. Bisher stand die Fernfeldwahrnehmung im Vordergrund. Ein weiteres wichtiges Problem ist die begrenzte Rechenleistung, die für die Entwicklung von Echtzeit-Anwendungen zur Verfügung steht. Aufgrund dieses Engpasses kommt es häufig zu einem Kompromiss zwischen Leistung und Laufzeiteffizienz. Wir konzentrieren uns auf die folgenden Themen, um diese anzugehen: 1) Entwicklung von Nahfeld-Wahrnehmungsalgorithmen mit hoher Leistung und geringer Rechenkomplexität für verschiedene visuelle Wahrnehmungsaufgaben wie geometrische und semantische Aufgaben unter Verwendung von faltbaren neuronalen Netzen. 2) Verwendung von Multi-Task-Learning zur Überwindung von Rechenengpässen durch die gemeinsame Nutzung von initialen Faltungsschichten zwischen den Aufgaben und die Entwicklung von Optimierungsstrategien, die die Aufgaben ausbalancieren.The formation of eyes led to the big bang of evolution. The dynamics changed from a primitive organism waiting for the food to come into contact for eating food being sought after by visual sensors. The human eye is one of the most sophisticated developments of evolution, but it still has defects. Humans have evolved a biological perception algorithm capable of driving cars, operating machinery, piloting aircraft, and navigating ships over millions of years. Automating these capabilities for computers is critical for various applications, including self-driving cars, augmented reality, and architectural surveying. Near-field visual perception in the context of self-driving cars can perceive the environment in a range of 0 - 10 meters and 360° coverage around the vehicle. It is a critical decision-making component in the development of safer automated driving. Recent advances in computer vision and deep learning, in conjunction with high-quality sensors such as cameras and LiDARs, have fueled mature visual perception solutions. Until now, far-field perception has been the primary focus. Another significant issue is the limited processing power available for developing real-time applications. Because of this bottleneck, there is frequently a trade-off between performance and run-time efficiency. We concentrate on the following issues in order to address them: 1) Developing near-field perception algorithms with high performance and low computational complexity for various visual perception tasks such as geometric and semantic tasks using convolutional neural networks. 2) Using Multi-Task Learning to overcome computational bottlenecks by sharing initial convolutional layers between tasks and developing optimization strategies that balance tasks

    Study of Computational Image Matching Techniques: Improving Our View of Biomedical Image Data

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    Image matching techniques are proven to be necessary in various fields of science and engineering, with many new methods and applications introduced over the years. In this PhD thesis, several computational image matching methods are introduced and investigated for improving the analysis of various biomedical image data. These improvements include the use of matching techniques for enhancing visualization of cross-sectional imaging modalities such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), denoising of retinal Optical Coherence Tomography (OCT), and high quality 3D reconstruction of surfaces from Scanning Electron Microscope (SEM) images. This work greatly improves the process of data interpretation of image data with far reaching consequences for basic sciences research. The thesis starts with a general notion of the problem of image matching followed by an overview of the topics covered in the thesis. This is followed by introduction and investigation of several applications of image matching/registration in biomdecial image processing: a) registration-based slice interpolation, b) fast mesh-based deformable image registration and c) use of simultaneous rigid registration and Robust Principal Component Analysis (RPCA) for speckle noise reduction of retinal OCT images. Moving towards a different notion of image matching/correspondence, the problem of view synthesis and 3D reconstruction, with a focus on 3D reconstruction of microscopic samples from 2D images captured by SEM, is considered next. Starting from sparse feature-based matching techniques, an extensive analysis is provided for using several well-known feature detector/descriptor techniques, namely ORB, BRIEF, SURF and SIFT, for the problem of multi-view 3D reconstruction. This chapter contains qualitative and quantitative comparisons in order to reveal the shortcomings of the sparse feature-based techniques. This is followed by introduction of a novel framework using sparse-dense matching/correspondence for high quality 3D reconstruction of SEM images. As will be shown, the proposed framework results in better reconstructions when compared with state-of-the-art sparse-feature based techniques. Even though the proposed framework produces satisfactory results, there is room for improvements. These improvements become more necessary when dealing with higher complexity microscopic samples imaged by SEM as well as in cases with large displacements between corresponding points in micrographs. Therefore, based on the proposed framework, a new approach is proposed for high quality 3D reconstruction of microscopic samples. While in case of having simpler microscopic samples the performance of the two proposed techniques are comparable, the new technique results in more truthful reconstruction of highly complex samples. The thesis is concluded with an overview of the thesis and also pointers regarding future directions of the research using both multi-view and photometric techniques for 3D reconstruction of SEM images

    Retinal ganglion cells : physiology and prosthesis

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    The retina is responsible for encoding different aspects of the visual world. Light enters the eyes and is converted by the photoreceptors into electrochemical signals. These signals are processed by the retinal network and proceed afferently to the brain via the axons of the retinal ganglion cells (RGCs). The RGCs outputs are in the form of action potentials (spikes), which encrypt the visual information in terms of spike shape, firing frequencies, and the firing patterns. When the photoreceptors are gone due to disease, vision is lost. The idea of a retinal prosthesis is to activate the surviving RGCs by electrical stimulation in order to recreate vision. In this thesis, I have studied the physiological properties of the RGCs, and reconstructed natural RGC spike trains by electrical stimulation. Chapter 1 introduces the anatomy of the retina and the retinal neurons. How the RGCs respond to light. Electrical stimulation is also discussed. A brief historical summary of the receptive field properties and cell physiology is also presented. Chapter 2 characterizes the intrinsic properties of 16 morphologically defined types of rat RGCs. The intrinsic properties include the biophysical properties due to morphology and dendritic stratification, in addition to physiological properties such as firing behaviours. These properties are also compared with the cat RGC intrinsic properties in order to investigate the variations between the morphologically similar RGCs of the two species. The results suggest that the RGCs among species, even with similar morphologies, do not have conservative intrinsic properties. Chapter 3 examines the details of the spiking properties of the different rat RGC types. Spikes are initiated at the axonal initial segment. A 'single' spike recorded at the soma consists of an axonal spike and a somatic spike. The existence of the two spikes can be recognized by two humps in the phase plot, and further revealed in the higher derivatives of the membrane potential. A principal component analysis shows that the parameters extracted from the phase plots are very useful for a model-independent rat RGC classification. Chapter 4 establishes the foundations for electrical stimulation of the retina. The question is to what extent optimum placement of the stimulating and reference electrodes might be affected by anatomical location. Here we placed the stimulating electrode above or below the retinal inner limiting membrane and found no statistical difference between the thresholds. In addition, reflective axonal spikes from the cut end are discussed. Chapter 5 combines the knowledge obtained in the previous chapters for the sole purpose of reproducing natural RGC outputs when using electrical stimulation. The light responses of the eye under saccadic movements were recorded and used to form the stimulus patterns. The reconstructions were performed on the brisk-transient (BT) and the brisk-sustained (BS) RGCs. Our results suggested that BT RGCs are more capable of following the stimulated stimulus patterns over a wide range of frequencies than the BS RGCs. Chapter 6 concludes the whole thesis

    Efficient Rectenna Design for Ambient Microwave Energy Recycling

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    Projecte realitzat en col.laboració amb el Centre Tecnològic de TelecomunicacionsThe work focuses on designing, measuring and testing an antenna and recti er circuit (RECTENNA) optimized for incoming signals of low power density. The rectenna is used to harvest electric energy from the RF signals that have been radiated by communication and broadcasting systems at ISM band centred in 2.45 GHz., This work contains methods to simulate rectennas with Harmonic Balance and electromagnetic full-wave Momemtum by Agilent Advanced Design Software, used of LPKF Milling machine for antenna fabrication , Vector Network Analyzer, spectral analyzer, digital generator, multimeter, and anechoic chamber for antenna and recti er measurements. The work is motivated by two types of applications: powering of low-power sensor and RF energy recycling being aware of the energy consumption and e ect to the natural environment. The goal of this work is to determine the usefulness of low-power recti catio

    On the detectability of multiple input multiple output (MIMO) radar signals using conventional electronic warfare support (ES) receivers

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    A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016Multiple-Input Multiple-Output (MIMO) radar is a more general form of phased array radar, where each antenna in the array transmits linearly independent or mutually orthogonal signals. Sustained growth in computational power as well as the decline in the cost of integrated radio frequency (RF) components has made MIMO more viable than in the past. The potential emergence of practical MIMO radar has prompted an investigation into the detectability of MIMO radar signals using existing conventional Electronic warfare Support (ES) receivers such as the Crystal Video Receiver (CVR) and a specific type of superheterodyne receiver (superhet) known as the Zero IF Receiver (ZIFR). Literature on the detectability of MIMO radar signals is extremely scarce and this investigation aims to offer insights into the detectability of MIMO radar signals by means of computer simulations. The fundamental theory necessary for this research includes phased array radar theory, MIMO array radar theory and ES receiver signal detection theory. The detection of MIMO radar signals is compared to a reference phased array case to provide relative context. This investigation focusses on co-located Uniform Linear Arrays (ULA) based radar systems. The result of interest is the relative Signal-to-Noise Ratio (SNR) at which each type of radar can be detected by the ES receiver. Therefore, a lossless transmission, without loss of generality, is assumed. Constraints such as the equal transmit power over all antenna elements in the arrays, are used for a fair comparison. Many different array simulation setups are simulated. These setups are achieved by varying the number of elements in the array and the inter-element spacing. The phased array radar transmitted complex linear chirp signals, and the MIMO radar transmitted Hadamard sequences, interpolated using a Constant Envelope Linear-Route-of-Unity (CE-LRU) technique. The CVR and ZIFR detection thresholds were determined for a Probability of False Alarm (PFA) of 10-4. For all of the setups, the phased array radar was found to be more detectable than the MIMO radar at values of Probability of Detection (PD) below 0.6. The in phase coherent combination of phased array radar signals in its main beam resulted in a signal gain caused by the constructive addition of the signals. This gain thus increases with the number of antenna elements. In contrast, the MIMO signals also add coherently, but the instantaneous phase for each signal is a function of the transmitted signal as well as the direction of propagation relative to the array face. The set of orthogonal signals thus add constructively and destructively, resulting in the average signal power remaining approximately constant despite the number of antenna elements increasing. The difference in detectability of the phased array radar over MIMO radar therefore increases as the number of antenna elements is increased, due to the fact that each element is constrained to transmit a fixed power. Comparing the performance of the ZIFR and CVR, the ZIFR outperforms the CVR. This is due to the fact that the ZIFR implements a quadrature ES receiver, and was able to detect both types of radar signals at a lower SNR than the CVR. However, both ES receivers struggle to detect MIMO radar signals in comparison to detecting phased array radar signals and this performance margin widens as the number of transmitting elements is increased. This result suggests that research into dedicated techniques for the detection of MIMO radar signals using ES receivers may be necessary should the need arise to detect MIMO radar signals in future. This is the first quantitative analysis of the detectability of MIMO radar signals using conventional ES receivers that the author is aware of.MT201

    Ambient RF energy harvesting and efficient DC-load inductive power transfer

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    This thesis analyses in detail the technology required for wireless power transfer via radio frequency (RF) ambient energy harvesting and an inductive power transfer system (IPT). Radio frequency harvesting circuits have been demonstrated for more than fifty years, but only a few have been able to harvest energy from freely available ambient (i.e. non-dedicated) RF sources. To explore the potential for ambient RF energy harvesting, a city-wide RF spectral survey was undertaken in London. Using the results from this survey, various harvesters were designed to cover four frequency bands from the largest RF contributors within the ultra-high frequency (0.3 to 3 GHz) part of the frequency spectrum. Prototypes were designed, fabricated and tested for each band and proved that approximately half of the London Underground stations were found to be suitable locations for harvesting ambient RF energy using the prototypes. Inductive Power Transfer systems for transmitting tens to hundreds of watts have been reported for almost a decade. Most of the work has concentrated on the optimization of the link efficiency and have not taken into account the efficiency of the driver and rectifier. Class-E amplifiers and rectifiers have been identified as ideal drivers for IPT applications, but their power handling capability at tens of MHz has been a crucial limiting factor, since the load and inductor characteristics are set by the requirements of the resonant inductive system. The frequency limitation of the driver restricts the unloaded Q-factor of the coils and thus the link efficiency. The system presented in this work alleviates the use of heavy and expensive field-shaping techniques by presenting an efficient IPT system capable of transmitting energy with high dc-to-load efficiencies at 6 MHz across a distance of 30 cm.Open Acces

    Recent Progress in Image Deblurring

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    This paper comprehensively reviews the recent development of image deblurring, including non-blind/blind, spatially invariant/variant deblurring techniques. Indeed, these techniques share the same objective of inferring a latent sharp image from one or several corresponding blurry images, while the blind deblurring techniques are also required to derive an accurate blur kernel. Considering the critical role of image restoration in modern imaging systems to provide high-quality images under complex environments such as motion, undesirable lighting conditions, and imperfect system components, image deblurring has attracted growing attention in recent years. From the viewpoint of how to handle the ill-posedness which is a crucial issue in deblurring tasks, existing methods can be grouped into five categories: Bayesian inference framework, variational methods, sparse representation-based methods, homography-based modeling, and region-based methods. In spite of achieving a certain level of development, image deblurring, especially the blind case, is limited in its success by complex application conditions which make the blur kernel hard to obtain and be spatially variant. We provide a holistic understanding and deep insight into image deblurring in this review. An analysis of the empirical evidence for representative methods, practical issues, as well as a discussion of promising future directions are also presented.Comment: 53 pages, 17 figure
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