9,983 research outputs found

    Towards A Practical High-Assurance Systems Programming Language

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    Writing correct and performant low-level systems code is a notoriously demanding job, even for experienced developers. To make the matter worse, formally reasoning about their correctness properties introduces yet another level of complexity to the task. It requires considerable expertise in both systems programming and formal verification. The development can be extremely costly due to the sheer complexity of the systems and the nuances in them, if not assisted with appropriate tools that provide abstraction and automation. Cogent is designed to alleviate the burden on developers when writing and verifying systems code. It is a high-level functional language with a certifying compiler, which automatically proves the correctness of the compiled code and also provides a purely functional abstraction of the low-level program to the developer. Equational reasoning techniques can then be used to prove functional correctness properties of the program on top of this abstract semantics, which is notably less laborious than directly verifying the C code. To make Cogent a more approachable and effective tool for developing real-world systems, we further strengthen the framework by extending the core language and its ecosystem. Specifically, we enrich the language to allow users to control the memory representation of algebraic data types, while retaining the automatic proof with a data layout refinement calculus. We repurpose existing tools in a novel way and develop an intuitive foreign function interface, which provides users a seamless experience when using Cogent in conjunction with native C. We augment the Cogent ecosystem with a property-based testing framework, which helps developers better understand the impact formal verification has on their programs and enables a progressive approach to producing high-assurance systems. Finally we explore refinement type systems, which we plan to incorporate into Cogent for more expressiveness and better integration of systems programmers with the verification process

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Executable Models and Instance Tracking for Decentralized Applications on Blockchains and Cloud Platforms -- Metamodel and Implementation

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    Decentralized applications rely on non-centralized technical infrastructures and coordination principles. Without trusted third parties, their execution is not controlled by entities exercising centralized coordination but is instead realized through technologies supporting distribution such as blockchains and serverless computing. Executing decentralized applications with these technologies, however, is challenging due to the limited transparency and insight in the execution, especially when involving centralized cloud platforms. This paper extends an approach for execution and instance tracking on blockchains and cloud platforms permitting distributed parties to observe the instances and states of executable models. The approach is extended with (1.) a metamodel describing the concepts for instance tracking on cloud platforms independent of concrete models or implementation, (2.) a multidimensional data model realizing the concepts accordingly, permitting the verifiable storage, tracking, and analysis of execution states for distributed parties, and (3.) an implementation on the Ethereum blockchain and Amazon Web Services (AWS) using state machine models. Towards supporting decentralized applications with high scalability and distribution requirements, the approach establishes a consistent view on instances for distributed parties to track and analyze the execution along multiple dimensions such as specific clients and execution engines.Comment: This is an unpublished preprint; both versions archived on arXiv.org have not been published. Although initially intended for publication, the preprint has undergone further improvements and has been utilized as input for new publications. (see also: https://www.unifr.ch/inf/digits/en/group/team/haerer.html

    An empirical investigation of the relationship between integration, dynamic capabilities and performance in supply chains

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    This research aimed to develop an empirical understanding of the relationships between integration, dynamic capabilities and performance in the supply chain domain, based on which, two conceptual frameworks were constructed to advance the field. The core motivation for the research was that, at the stage of writing the thesis, the combined relationship between the three concepts had not yet been examined, although their interrelationships have been studied individually. To achieve this aim, deductive and inductive reasoning logics were utilised to guide the qualitative study, which was undertaken via multiple case studies to investigate lines of enquiry that would address the research questions formulated. This is consistent with the author’s philosophical adoption of the ontology of relativism and the epistemology of constructionism, which was considered appropriate to address the research questions. Empirical data and evidence were collected, and various triangulation techniques were employed to ensure their credibility. Some key features of grounded theory coding techniques were drawn upon for data coding and analysis, generating two levels of findings. These revealed that whilst integration and dynamic capabilities were crucial in improving performance, the performance also informed the former. This reflects a cyclical and iterative approach rather than one purely based on linearity. Adopting a holistic approach towards the relationship was key in producing complementary strategies that can deliver sustainable supply chain performance. The research makes theoretical, methodological and practical contributions to the field of supply chain management. The theoretical contribution includes the development of two emerging conceptual frameworks at the micro and macro levels. The former provides greater specificity, as it allows meta-analytic evaluation of the three concepts and their dimensions, providing a detailed insight into their correlations. The latter gives a holistic view of their relationships and how they are connected, reflecting a middle-range theory that bridges theory and practice. The methodological contribution lies in presenting models that address gaps associated with the inconsistent use of terminologies in philosophical assumptions, and lack of rigor in deploying case study research methods. In terms of its practical contribution, this research offers insights that practitioners could adopt to enhance their performance. They can do so without necessarily having to forgo certain desired outcomes using targeted integrative strategies and drawing on their dynamic capabilities

    Learn, Teach, Heal: Articulations of Indigeneity and Spirituality in Indigenous Tourism in British Columbia, Canada

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    ‘Learn, Teach, Heal’ encapsulates what seems to be occurring in Indigenous Tourism on Vancouver Island and the Haida Gwaii in British Columbia, Canada. Operating as a ‘Tourist-researcher’ in 2017 and 2018, I was there at a time when Indigenous Tourism was booming, partly facilitated by the political movement of Truth & Reconciliation. Tourism is often seen as a shallow, commercial and artificial activity, yet such a view risks speaking over the various reasons why hosts choose to engage in the industry. This dissertation offers a case study based on tours, performances and interviews with six people. The research foregrounds the voices and experiences of: Andy Everson, Tana Thomas, Roy Henry Vickers, Tsimka Martin, K’odi Nelson and Alix Goetzinger. In listening to how they present their work, I study how indigeneity and spirituality were being articulated in ways that relate to processes of decolonisation. Whilst they were all engaged in tourism for their own different reasons, a common theme that emerged was the goal to use tourism to learn, teach and heal, both for themselves and for their guests. Learning how to be guides and performers, their languages, traditional practices, histories and politics, they were able to explore with tourists aspects of their indigeneity and spirituality, illustrate diversity of peoples and practices, and teach about their values and hopes for the future. Healing is gained through having a space to learn and to teach, and to restore pride to the communities by taking control of the narratives. It is my contention that Indigenous Tourism is offering these six people sites of ‘becoming’ and ‘reclaiming’ in a way that puts decolonisation into practice

    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

    Leveraging Ambidexterity in a Digital Platform Ecosystem: Insights from a Complementor’s Perspective

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    This case study explores ambidextrous practices of a complementor firm within a Microsoft-owned digital platform ecosystem (DPE). We draw on organizational ambidexterity and social mechanisms as lenses to analyze how a complementor deals with paradoxical practices of exploration and exploitation in the context of a DPE. By identifying deep structures and surface structures and their related social mechanisms we shed light on the role of ambidextrous complementors in a DPE. Our analysis implies that the identified social mechanisms illustrate how the complementor creates new ideas with other DPE actors to nurture capability development (exploration) and how these ideas are transformed into practice (exploitation). In addition, our findings imply that the complementor’s support of a platform contributes to an increased commitment to the platform owner

    Nutrient Intake and Physical Exercise as Modulators of Healthy Women

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    Cumulative evidence demonstrates that healthy nutrient intake and regular physical exercise are both powerful lifestyle strategies that modulate lifelong health through their ability to improve body composition, musculoskeletal health, sex steroid hormones, sleep quality, and physical and cognitive performance, as well as to prevent chronic diseases across the lifespan, especially in women. While the benefits of nutrition and physical exercise are commonly studied separately, the integration of nutrition and physical exercise has the potential to produce greater benefits in women than strategies focusing only on one or the other. Studying the specificities of women in response to interventions is of the utmost importance for providing optimal healthcare and aids the design of guidelines that are better suited for women. A better knowledge regarding nutrient intake and physical exercise and their interaction in women is therefore needed. This Special Issue entitled “nutrient intake and physical exercise as modulators of healthy women” will comprise manuscripts that highlight this integrational approach as a potential modulator of lifelong outcomes in women

    Analysis of ChatGPT on Source Code

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    This paper explores the use of Large Language Models (LLMs) and in particular ChatGPT in programming, source code analysis, and code generation. LLMs and ChatGPT are built using machine learning and artificial intelligence techniques, and they offer several benefits to developers and programmers. While these models can save time and provide highly accurate results, they are not yet advanced enough to replace human programmers entirely. The paper investigates the potential applications of LLMs and ChatGPT in various areas, such as code creation, code documentation, bug detection, refactoring, and more. The paper also suggests that the usage of LLMs and ChatGPT is expected to increase in the future as they offer unparalleled benefits to the programming community.Comment: 40 pages, examples provided for each experimen

    Binaural virtual auditory display for music discovery and recommendation

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    Emerging patterns in audio consumption present renewed opportunity for searching or navigating music via spatial audio interfaces. This thesis examines the potential benefits and considerations for using binaural audio as the sole or principal output interface in a music browsing system. Three areas of enquiry are addressed. Specific advantages and constraints in spatial display of music tracks are explored in preliminary work. A voice-led binaural music discovery prototype is shown to offer a contrasting interactive experience compared to a mono smartspeaker. Results suggest that touch or gestural interaction may be more conducive input modes in the former case. The limit of three binaurally spatialised streams is identified from separate data as a usability threshold for simultaneous presentation of tracks, with no evident advantages derived from visual prompts to aid source discrimination or localisation. The challenge of implementing personalised binaural rendering for end-users of a mobile system is addressed in detail. A custom framework for assessing head-related transfer function (HRTF) selection is applied to data from an approach using 2D rendering on a personal computer. That HRTF selection method is developed to encompass 3D rendering on a mobile device. Evaluation against the same criteria shows encouraging results in reliability, validity, usability and efficiency. Computational analysis of a novel approach for low-cost, real-time, head-tracked binaural rendering demonstrates measurable advantages compared to first order virtual Ambisonics. Further perceptual evaluation establishes working parameters for interactive auditory display use cases. In summation, the renderer and identified tolerances are deployed with a method for synthesised, parametric 3D reverberation (developed through related research) in a final prototype for mobile immersive playlist editing. Task-oriented comparison with a graphical interface reveals high levels of usability and engagement, plus some evidence of enhanced flow state when using the eyes-free binaural system
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