16,733 research outputs found

    Sistema de bloqueio de computadores

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    Mestrado em Engenharia de Computadores e TelemáticaThe use of multiple computing devices per person is increasing more and more. Nowadays is normal that mobile devices like smartphones, tablets and laptops are present in the everyday life of a single person and in many cases people use these devices to perform important operations related with their professional life. This also presents a problem, as these devices come with the user in everyday life and the fact that often they have a high monetary value means that these devices are susceptible to theft. This thesis introduces a computer locking system that distinguishes itself from existing similar systems because (i) it is designed to work independently of the Operating System(s) installed on the laptop or mobile device, (ii) depends on a firrmware driver that implements the lock operation making it resistant to storage device formats or any other attack that uses software operations. It is also explored the operation of a device that has a firrmware that follows the Unified Extensible Firmware Interface (UEFI) specification as well as the development of drivers for this type of firrmware. It was also developed a security protocol and various cryptographic techniques where explored and implemented.O uso de vários dispositivos computacionais por pessoa está a aumentar cada vez mais. Hoje em dia é normal dispositivos móveis como o smartphone, tablet e computador portátil estarem presentes no quotidiano das pessoas e em muitos casos as pessoas necessitam de realizar tarefas na sua vida profissional nestes dispositivos. Isto apresenta também um problema, como estes dispositivos acompanham o utilizador no dia a dia e pelo facto de muitas vezes terem um valor monetário elevado faz com que estes dispositivos sejam suscetíveis a roubos. Esta tese introduz um sistema de bloqueio de computadores que se distingue dos sistemas similares existentes porque, (i) _e desenhado para funcionar independentemente do(s) sistema(s) operativo(s) instalado(s) no computador portátil ou no dispositivo móvel, (ii) depende de um driver do firrmware que concretiza a operação de bloqueio fazendo com que seja resistente contra formatação do dispositivo de armazenamento ou qualquer outro ataque que tenho por base a utilização de software. É explorado então o funcionamento de um dispositivo que tenha um firmware que respeita a especificação Unfied Extensible Firmware Interface (UEFI) assim como a programação de drivers para este tipo de firmware. Foi também desenvolvido um protocolo de segurança e são exploradas várias técnicas criptográficas passiveis de serem implementadas

    Technical Dimensions of Programming Systems

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    Programming requires much more than just writing code in a programming language. It is usually done in the context of a stateful environment, by interacting with a system through a graphical user interface. Yet, this wide space of possibilities lacks a common structure for navigation. Work on programming systems fails to form a coherent body of research, making it hard to improve on past work and advance the state of the art. In computer science, much has been said and done to allow comparison of programming languages, yet no similar theory exists for programming systems; we believe that programming systems deserve a theory too. We present a framework of technical dimensions which capture the underlying characteristics of programming systems and provide a means for conceptualizing and comparing them. We identify technical dimensions by examining past influential programming systems and reviewing their design principles, technical capabilities, and styles of user interaction. Technical dimensions capture characteristics that may be studied, compared and advanced independently. This makes it possible to talk about programming systems in a way that can be shared and constructively debated rather than relying solely on personal impressions. Our framework is derived using a qualitative analysis of past programming systems. We outline two concrete ways of using our framework. First, we show how it can analyze a recently developed novel programming system. Then, we use it to identify an interesting unexplored point in the design space of programming systems. Much research effort focuses on building programming systems that are easier to use, accessible to non-experts, moldable and/or powerful, but such efforts are disconnected. They are informal, guided by the personal vision of their authors and thus are only evaluable and comparable on the basis of individual experience using them. By providing foundations for more systematic research, we can help programming systems researchers to stand, at last, on the shoulders of giants

    BRAMAC: Compute-in-BRAM Architectures for Multiply-Accumulate on FPGAs

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    Deep neural network (DNN) inference using reduced integer precision has been shown to achieve significant improvements in memory utilization and compute throughput with little or no accuracy loss compared to full-precision floating-point. Modern FPGA-based DNN inference relies heavily on the on-chip block RAM (BRAM) for model storage and the digital signal processing (DSP) unit for implementing the multiply-accumulate (MAC) operation, a fundamental DNN primitive. In this paper, we enhance the existing BRAM to also compute MAC by proposing BRAMAC (Compute-in-BR‾\underline{\text{BR}}AM A‾\underline{\text{A}}rchitectures for M‾\underline{\text{M}}ultiply-Ac‾\underline{\text{Ac}}cumulate). BRAMAC supports 2's complement 2- to 8-bit MAC in a small dummy BRAM array using a hybrid bit-serial & bit-parallel data flow. Unlike previous compute-in-BRAM architectures, BRAMAC allows read/write access to the main BRAM array while computing in the dummy BRAM array, enabling both persistent and tiling-based DNN inference. We explore two BRAMAC variants: BRAMAC-2SA (with 2 synchronous dummy arrays) and BRAMAC-1DA (with 1 double-pumped dummy array). BRAMAC-2SA/BRAMAC-1DA can boost the peak MAC throughput of a large Arria-10 FPGA by 2.6×\times/2.1×\times, 2.3×\times/2.0×\times, and 1.9×\times/1.7×\times for 2-bit, 4-bit, and 8-bit precisions, respectively at the cost of 6.8%/3.4% increase in the FPGA core area. By adding BRAMAC-2SA/BRAMAC-1DA to a state-of-the-art tiling-based DNN accelerator, an average speedup of 2.05×\times/1.7×\times and 1.33×\times/1.52×\times can be achieved for AlexNet and ResNet-34, respectively across different model precisions.Comment: 11 pages, 13 figures, 3 tables, FCCM conference 202

    ‘Mental fight’ and ‘seeing & writing’ in Virginia Woolf and William Blake

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    This thesis is the first full-length study to assess the writer and publisher Virginia Woolf’s (1882-1941) responses to the radical Romantic poet-painter, and engraver, William Blake (1757-1827). I trace Woolf’s public and private, overt and subtle references to Blake in fiction, essays, notebooks, diaries, letters and drawings. I have examined volumes in Leonard and Virginia Woolf’s library that are pertinent, directly and indirectly, to Woolf’s understanding of Blake. I focus on Woolf’s key phrases about Blake: ‘Mental fight’, and ‘seeing & writing.’ I consider the other phrases Woolf uses to think about Blake in the context of these two categories. Woolf and Blake are both interested in combining visual and verbal aesthetics (‘seeing & writing’). They are both critical of their respective cultures (‘Mental fight’). Woolf mentions ‘seeing & writing’ in connection to Blake in a 1940 notebook. She engages with Blake’s ‘Mental fight’ in ‘Thoughts on Peace in an Air Raid’ (1940). I map late nineteenth and early twentieth-century opinion on Blake and explore Woolf’s engagement with Blake in these wider contexts. I make use of the circumstantial detail of Woolf’s friendship with the great Blake collector and scholar, Geoffrey Keynes (1887-1982), brother of Bloomsbury economist John Maynard Keynes. Woolf was party to the Blake centenary celebrations courtesy of Geoffrey Keynes’s organisation of the centenary exhibition in London in 1927. Chapter One introduces Woolf’s explicit references to Blake and examines the record of Woolf scholarship that unites Woolf and Blake. To see how her predecessors had responded, Chapter Two examines the nineteenth-century interest in Blake and Woolf’s engagement with key nineteenth-century Blakeans. Chapter Three looks at the modernist, early twentieth-century engagement with Blake, to contextualise Woolf’s position on Blake. Chapter Four assesses how Woolf and Blake use ‘Mental fight’ to oppose warmongering and fascist politics. Chapter Five is about what Woolf and Blake write and think about the country and the city. Chapter Six discusses Woolf’s reading of John Milton (1608-1674) in relation to her interest in Blake, drawing on the evidence of Blake’s intense reading of Milton. Chapter Seven examines further miscellaneous continuities between Woolf and Blake. Chapter Eight proposes, in conclusion, that we can only form an impression of Woolf’s Blake. The thesis also has three appendices. First, a chronology of key publications which chart Blake’s reputation as well as Woolf’s allusions to Blake. Second a list all of Blake’s poetry represented in Woolf’s library including contents page. The third lists all the other volumes in Woolf’s library that proved relevant. Although Woolf’s writing is the subject of this thesis, my project necessitates an attempt to recover how Blake was understood and misunderstood by numerous writers in the early twentieth century. The thesis argues Blake is a model radical Romantic who combines the visual and the verbal and that Woolf sees him as a kindred artist

    Defining Service Level Agreements in Serverless Computing

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    The emergence of serverless computing has brought significant advancements to the delivery of computing resources to cloud users. With the abstraction of infrastructure, ecosystem, and execution environments, users could focus on their code while relying on the cloud provider to manage the abstracted layers. In addition, desirable features such as autoscaling and high availability became a provider’s responsibility and can be adopted by the user\u27s application at no extra overhead. Despite such advancements, significant challenges must be overcome as applications transition from monolithic stand-alone deployments to the ephemeral and stateless microservice model of serverless computing. These challenges pertain to the uniqueness of the conceptual and implementation models of serverless computing. One of the notable challenges is the complexity of defining Service Level Agreements (SLA) for serverless functions. As the serverless model shifts the administration of resources, ecosystem, and execution layers to the provider, users become mere consumers of the provider’s abstracted platform with no insight into its performance. Suboptimal conditions of the abstracted layers are not visible to the end-user who has no means to assess their performance. Thus, SLA in serverless computing must take into consideration the unique abstraction of its model. This work investigates the Service Level Agreement (SLA) modeling of serverless functions\u27 and serverless chains’ executions. We highlight how serverless SLA fundamentally differs from earlier cloud delivery models. We then propose an approach to define SLA for serverless functions by utilizing resource utilization fingerprints for functions\u27 executions and a method to assess if executions adhere to that SLA. We evaluate the approach’s accuracy in detecting SLA violations for a broad range of serverless application categories. Our validation results illustrate a high accuracy in detecting SLA violations resulting from resource contentions and provider’s ecosystem degradations. We conclude by presenting the empirical validation of our proposed approach, which could detect Execution-SLA violations with accuracy up to 99%

    Full stack development toward a trapped ion logical qubit

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    Quantum error correction is a key step toward the construction of a large-scale quantum computer, by preventing small infidelities in quantum gates from accumulating over the course of an algorithm. Detecting and correcting errors is achieved by using multiple physical qubits to form a smaller number of robust logical qubits. The physical implementation of a logical qubit requires multiple qubits, on which high fidelity gates can be performed. The project aims to realize a logical qubit based on ions confined on a microfabricated surface trap. Each physical qubit will be a microwave dressed state qubit based on 171Yb+ ions. Gates are intended to be realized through RF and microwave radiation in combination with magnetic field gradients. The project vertically integrates software down to hardware compilation layers in order to deliver, in the near future, a fully functional small device demonstrator. This thesis presents novel results on multiple layers of a full stack quantum computer model. On the hardware level a robust quantum gate is studied and ion displacement over the X-junction geometry is demonstrated. The experimental organization is optimized through automation and compressed waveform data transmission. A new quantum assembly language purely dedicated to trapped ion quantum computers is introduced. The demonstrator is aimed at testing implementation of quantum error correction codes while preparing for larger scale iterations.Open Acces

    Effect of Pulse Width Modulation Current Control on Shape Memory Alloy Actuators

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    This paper proposes the design, construction and performance of a single element based tactile display. The technology employed utilizes a 100μm diameter heat actuated wire of Nickel-Titanium (NiTi) shape-memory alloy (SMA) which contracts when pulsed with an electrical current (in effect heating the metal) under pre-stress. The display can produce a maximum pin deflection of 5mm which can be raised and lowered to approximate the desired output signal. In other words, SMA materials can directly convert thermal energy to mechanical work. This phenomenon, which provides a unique mechanism for actuation, is associated with the unique interaction between the martensite and austenite crystal structures of the SMA material. The paper discusses the design and evaluation leading to the dynamic performance of the system via step responses as well as the control of tactile sensor length and displacement using pulse width modulated current control technique

    How to Be a God

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    When it comes to questions concerning the nature of Reality, Philosophers and Theologians have the answers. Philosophers have the answers that can’t be proven right. Theologians have the answers that can’t be proven wrong. Today’s designers of Massively-Multiplayer Online Role-Playing Games create realities for a living. They can’t spend centuries mulling over the issues: they have to face them head-on. Their practical experiences can indicate which theoretical proposals actually work in practice. That’s today’s designers. Tomorrow’s will have a whole new set of questions to answer. The designers of virtual worlds are the literal gods of those realities. Suppose Artificial Intelligence comes through and allows us to create non-player characters as smart as us. What are our responsibilities as gods? How should we, as gods, conduct ourselves? How should we be gods
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