Nanostructured ferromagnetic materials have gained considerable attention recently for use in novel devices in the areas of data storage, microwave signal processing and propagation of electromagnetic waves. Structural modifications allow a control over the internal magnetic properties of the system down to the nanoscale. Lateral confinement gives rise to a distribution of demagnetisation fields in the plane of the thin film which can create interesting effects on static and dynamic magnetic properties. In the context of this dissertation, nanostructuring is used as a means to engineer the static and dynamic response of magnetic systems. In particular, periodic arrays of holes embedded in continuous films are studied. With patterning one observes the emergence of an anisotropic field dependence as well as the emergence of non-uniform spin precession modes due to the dipole distribution at the film interfaces. These properties were probed primarily using a technique called broadband ferromagnetic resonance, whereby a microwave field drives the local spin dynamics of the magnetic system. A way to further modify the magnetic properties induced due to the symmetry of the periodic structuring is by introducing an unidirectional field contribution which is characteristic of an exchange biased system. It was found that the magnetic pole distribution in antidots is particularly sensitive to the effects of exchange bias, giving rise to an asymmetric frequency response with respect to the applied field. The asymmetric microwave properties of an exchange biased FeMn/NiFe system with antidot structuring, obtained using electron beam lithography, are investigated. The ferromagnetic resonance (FMR) spectra exhibited several magnetostatic spin wave modes with 8-fold and 4-fold anisotropy components. Moreover, it was observed that large frequency asymmetries are obtained along the directions 10 degrees off the main antidot lattice axes, as result of the competing anisotropies. Brillouin light scattering measurements showed the presence of a magnonic band gap as expected for this type of structure. To interpret these observations, the spin precessional modes obtained experimentally are correlated with localised mode profiles obtained by micromagnetic simulations. This hybrid structure is a good candidate for applications such as selective microwave filtering and for use in multi-state magnetic logic. The prospects of using patterned exchange biased systems to engineer microwave properties is greatly increased if one goes beyond the 2-dimensional perspective. In multilayered structures, one can modify the magnetic properties layer-by-layer to achieve the desired response. This concept is demonstrated here by using a three dimensional structure in which an exchange biased and a free magnetic layer are stacked upon one another and patterned with an antidot configuration. The exchange bias acts as a pinning field for one layer, while the free layer reverses, promoting a zero net moment state. Interlayer dipole interactions are found to result in the partial cancellation of the microwave response. Micromagnetic simulations support the existence of a diminished microwave response which was confirmed by FMR measurements of an equivalent structure. The net moment cancellation, indicative of the antiparallel alignment, was observed on a Lorentz differential phase contrast scanning transmission electron microscope equipped with an FMR probe, which was designed and built for the purpose. This unique tool allows access to complex microwave response while the ground state of a nanostructured film is imaged via Lorentz microscopy. From the magnetostatic viewpoint, our results differ greatly from previous studies in a way that this sample shows distinct magnetic history and the near remanence states exhibit unique magnetic textures: magnetic vortices. The applicability of the TEM in-situ FMR probe was extended to the mapping of radio frequency electromagnetic (EM) fields using low angle diffraction (LAD) imaging. The electron beam, propagating in a sample free environment, experiences the field distribution generated by the microstrip waveguide, which alters the electron amplitude and phase, as described by the Aharonov-Bohm effect, and results in different intensity profiles at the detector. As the microwave frequencies were varied, the different polarisation states are imaged directly. Microwave simulations allowed the EM field distribution to be calculated, which was used to reproduce the LAD results. A knowledge of the near field distribution in antennas is often a challenging task so this technique opens up new opportunities for planar devices operating in high vacuum conditions.

Developing a Grid within High Energy Physics for the Large Hadron Collider particle accelerator is characterised as a highly collaborative, distributed and dynamic systems development effort. This research examines the way this distributed Grid is developed, deployed and provided as a service to the thousands of physicists analysing data from the Large Hadron Collider. The particle physics community has always been at the forefront of computing with a tradition of working in large distributed collaborations, therefore providing a "distinctive" case of distributed systems development practice. The focus of concern is the collaborative systems development practices employed by particle physicists in their attempt to develop a usable Grid. The research aims to offer lessons and practical recommendations to those involved in globally distributed systems development and to inform the information systems development literature. Global software development presents unaddressed challenges to organisations and it is argued that there is an urgent need for new systems development practices and strategies to be created that can facilitate and embrace the rapid changes of the environment and the complexities involved in such projects. The contribution of the study, therefore, is a framework of guidance towards engendering what the author defines as "Hybrid Experimental Agile Distributed Systems Development Communities" revealing a set of dynamic collaborative practices for those organisational contexts engaged in distributed systems development. The framework will allow them to reflect on their own practice and perhaps foster a similarly dynamic flexible community in order to manage their global software development effort. The research is in the form of an interpretative qualitative exploratory case study, which draws upon Activity Theory, and frames the Grid's distributed development activity as a complex overarching networked activity system influenced by the context, the community's tools, rules, norms, culture, history, past experiences, shared visions and collaborative way of working. Tensions and contradictions throughout the development of this Grid are explored and surfaced, with the research focusing on how these are resolved in order for the activity system to achieve stability. Such stability leads to the construction of new knowledge and learning and the formation of new systems development practices. In studying this, practices are considered as an emergent property linked to improvisation, bricolage and dynamic competences that unfold as large-scale projects evolve.

No description available.

SILVA FILHO, E. M. Uma Proposta de Aplicação de Webquests No Processo de Ensino e Aprendizagem de Física. 2016. 89 f. Dissertação (Mestrado Nacional Profissional em Ensino de Física) - Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2016. / Submitted by francisco lima (admir@ufc.br) on 2017-06-29T13:49:21Z No. of bitstreams: 1 2016_dis_emsf.pdf: 3707083 bytes, checksum: 2df242365bbc55245c388ea213c6f5a2 (MD5) / Approved for entry into archive by Amélia Barrocas (barrocas.amelia@gmail.com) on 2017-06-29T14:37:13Z (GMT) No. of bitstreams: 1 2016_dis_emsf.pdf: 3707083 bytes, checksum: 2df242365bbc55245c388ea213c6f5a2 (MD5) / Made available in DSpace on 2017-06-29T14:37:13Z (GMT). No. of bitstreams: 1 2016_dis_emsf.pdf: 3707083 bytes, checksum: 2df242365bbc55245c388ea213c6f5a2 (MD5) Previous issue date: 2016 / This work aims to analyze the use of technological resources WebQuest in physics classes, in order to verify their behavior as a facilitating tool in the learning process. Given the presence of technological resources, such as computer and Internet in the daily lives of all, it is proposed a teaching method based on this exchange between the classroom of physics and the use of virtual tools. To develop this proposal, a survey was conducted among 131 students of College of the Military Police of Ceará, one of the most prestigious schools in the state public network of Ceará; this research addressed the demand for the inclusion of new technologies in the daily physics classes for high school and primary school. The interviewed students showed interest and excitement in the activities carried out with the WebQuest methodology, because until then, these resources were not used in physics classes. The proposed solution led to the use of dynamic and interactive technology tools in class. / Este trabalho acadêmico tem como objetivo analisar a utilização do recurso tecnológico WebQuest em aulas de Física, com o desígnio de verificar o seu comportamento como ferramenta facilitadora no processo de aprendizagem. Tendo em vista a abarcante presença de recursos tecnológicos, como computador e Internet, no cotidiano de todos, é proposta uma metodologia de ensino baseada nesse intercâmbio entre a Física da sala de aula e o uso de ferramentas virtuais. Para desenvolver essa proposta, foi realizado um levantamento entre 131 alunos do Colégio da Polícia militar do Ceará, uma das mais conceituadas escolas da rede pública estadual do Ceará; nesse levantamento foi abordada a demanda da inclusão das novas tecnologias no cotidiano escolar das aulas de Física para algumas turmas de ensino médio e fundamental. Os alunos entrevistados mostraram interesse e empolgação pela atividade realizada na metodologia com a WebQuest, pois, até então, não havia a praxe da utilização deste recurso nas aulas de Física, mas, para esse problema, a solução proposta levava a uma modificação na metodologia a ser utilizada durante as aulas, as quais passariam a ser contempladas pelo uso de ferramentas tecnológicas dinâmicas e interativas.

The ability to measure tiny variations in the local gravitational acceleration allows – amongst other applications – the detection of hidden hydrocarbon reserves, magma build-up before volcanic eruptions, and subterranean tunnels. Several technologies are available that achieve the sensitivities required (tens of μGal/√Hz), and stabilities required (periods of days to weeks) for such applications: free-fall gravimeters, spring-based gravimeters, superconducting gravimeters, and atom interferometers. All of these devices can observe the Earth tides; the elastic deformation of the Earth’s crust as a result of tidal forces. This is a universally predictable gravitational signal that requires both high sensitivity and high stability over timescales of several days to measure. All present gravimeters, however, have limitations of excessive cost (£70 k) and high mass (<8 kg). In this thesis, the building of a microelectromechanical system (MEMS) gravimeter with a sensitivity of 40 μGal/√Hz in a package size of only a few cubic centimetres is discussed. MEMS accelerometers – found in most smart phones – can be mass-produced remarkably cheaply, but most are not sensitive enough, and none have been stable enough to be called a ‘gravimeter’. The remarkable stability and sensitivity of the device is demonstrated with a measurement of the Earth tides. Such a measurement has never been undertaken with a MEMS device, and proves the long term stability of the instrument compared to any other MEMS device, making it the first MEMS accelerometer that can be classed as a gravimeter. This heralds a transformative step in MEMS accelerometer technology. Due to their small size and low cost, MEMS gravimeters could create a new paradigm in gravity mapping: exploration surveys could be carried out with drones instead of low-flying aircraft; they could be used for distributed land surveys in exploration settings, for the monitoring of volcanoes; or built into multi-pixel density contrast imaging arrays.

En del didaktisk forskning handlar om hur elever lär sig kunskaper effektivt och praktiskt. Ett effektivtsätt att lära ut fysikkunskaper är med hjälp av representationer som text, språk, matematik, grafer ochtekniska verktyg som simulering. Det finns många forskare och elever som hävdar att PhET-simuleringar är ett grundläggande verktyg för att hjälpa till att förbättra och utveckla fysikaliskkonceptuell förståelse.”Rörelse och krafter” är ett centralt innehåll i fysikundervisningen. I detta arbete undersöks därför hursimulering och särskilt PhET-simulering kan bidra till djupare förståelse av det fysikaliska begreppetfjäderkraft (Hooks lag). I den här studien genomfördes kort enskild undervisning för femgymnasieelever och sen användande de PhET-simuleringen för att lösa några problem samtidigt somde berättade hur de tänkte. Datan samlades in genom metoden ”think aloud protocols” ochanalyserades senare med en kvalitativ metod (tematisk analys). I studien undersöktes också vilkainställningar i PhET-simuleringen som var mest och mist hjälpsamma.Resultatet visar att PhET-simuleringen hjälpte eleverna på i huvudsak tre sätt; att ge visualisering avdet fysikaliska begreppet (fjäderkraft), att vara interaktivt (få direkt feedback) och att fokusera på denkonceptuella förståelsen. Eftersom eleverna svarade olika på vilka inställningar som var mest ochminst hjälpsamma, visade detta att eleverna lär sig på olika sätt, beroende på deras tidigare kunskaperoch förutsättningar. Alla deltagarna tyckte att PhET-simuleringen var ett bra sätt att utforskafjäderkraften på egen hand.Elever behöver få vissa förkunskaper från lärare eller pedagoger innan användning av simuleringenannars lär de sig inte effektivt. Lärare måste också förtydliga vilka skillnader det är mellansimuleringen, som är en modell av verkligheten, och verkligheten. Lärare måste lyfta fram skillnadermellan karaktärsdrag för naturvetenskapliga arbetssättet och användning av simulering, annars missar elever detta.

Although the history of Virtual Reality (VR) is only about half a century old, all kinds of technologies in the VR field are developing rapidly. VR is a computer generated simulation that replaces or augments the real world by various media. In a VR environment, participants have a perception of “presence”, which can be described by the sense of immersion and intuitive interaction. One of the major VR applications is in the field of sports, in which a life-like sports environment is simulated, and the body actions of players can be tracked and represented by using VR tracking and visualisation technology. In the entertainment field, exergaming that merges video game with physical exercise activities by employing tracking or even 3D display technology can be considered as a small scale VR. For the research presented in this thesis, a novel realistic real-time table tennis game combining immersive, interactive and competitive features is developed. The implemented system integrates the InterSense tracking system, SwissRanger 3D camera and a three-wall rear projection stereoscopic screen. The Intersense tracking system is based on ultrasonic and inertia sensing techniques which provide fast and accurate 6-DOF (i.e. six degrees of freedom) tracking information of four trackers. Two trackers are placed on the two players’ heads to provide the players’ viewing positions. The other two trackers are held by players as the racquets. The SwissRanger 3D camera is mounted on top of the screen to capture the player’s

This research work developed an innovative computational approach to the preliminary design of low-thrust trajectories optimising multiple mission criteria. Low-Thrust (LT) propulsion has become the propulsion system of choice for a number of near Earth and interplanetary missions. Consequently, in the last two decades a good wealth of research has been devoted to the development of computational method to design low-thrust trajectories. Most of the techniques, however, minimise or maximise a single figure of merit under a set of design constraints. Less effort has been devoted to the development of efficient methods for the minimisation (or maximisation) of two or more figures of merit. On the other hand, in the preliminary mission design phase, the decision maker is interested in analysing as many design solutions as possible against different trade-off criteria. Therefore, in this PhD work, an innovative Multi-Objective (MO), memetic optimisation algorithm, called Multi-Agent Collaborative Search (MACS2), has been implemented to tackle low-thrust trajectory design problems with multiple figures of merit. Tests on both academic and real-world problems showed that the proposed MACS2 paradigm performs better than or as well as other state-of-the-art Multi-Objective optimisation algorithms. Concurrently, a set of novel approximated, first-order, analytical formulae has been developed, to obtain a fast but reliable estimation of the main trade-off criteria. These formulae allow for a fast propagation of the orbital motion under a constant perturbing acceleration. These formulae have been shown to allow for the fast and relatively accurate propagation of long LT trajectories under the typical acceleration level delivered by current engine technology. Various applications are presented to demonstrate the validity of the combination of the analytical formulae with MACS2. Among them, the preliminary design of the JAXA low-cost DESTINY mission to L2, a novel approach to the optimisation under uncertainty of deflection actions for Near Earth Objects (NEO), and the de-orbiting of space debris with low-thrust and with a combination of low-thrust and solar radiation pressure.

The Cold-Electron Bolometer (CEB) is a sensitive detector of millimeter-wave radiation, in which tunnel junctions are used as temperature sensors of a nanoscale normal metal strip absorber. The absorber is fed by an antenna via two Superconductor-Insulator-Normal metal (SIN) tunnel junctions, fabricated at both ends of the absorber. Incoming photons excite electrons, heating the whole electron system. The incoming RF power is determined by measuring the tunneling current through the SIN junctions. Since electrons at highest energy levels escape the absorber through the tunnel junctions, it causes cooling of the absorber. This electron cooling provides electro-thermal feedback that makes the saturation power of a CEB well above that of other types of millimeter-wave receivers. The key features of CEB detectors are high sensitivity, large dynamic range, fast response, easy integration in arrays on planar substrates, and simple readout. The high dynamic range allows the detector to operate under relatively high background levels. In this thesis, we present the development and successful operation of CEB, focusing on the fabrication technology and different implementations of the CEB for efficient detection of electromagnetic signals. We present the CEB detector integrated across a unilateral finline deposited on a planar substrate. We have measured the finline-integrated CEB performance at 280-315 mK using a calibrated black-body source mounted inside the cryostat. The results have demonstrated strong response to the incoming RF power and reasonable sensitivity. We also present CEB devices fabricated with advanced technologies and integrated in log-periodic, double-dipole and cross-slot antennas. The measured CEB performance satisfied the requirements of the balloon-borne experiment BOOMERANG and could be considered for future balloon-borne and ground-based instruments. In this thesis we also investigated a planar phase switch integrated in a back-to-back finline for modulating the polarization of weak electromagnetic signals. We examine the switching characteristics and demonstrate that the switching speed of the device is well above the speed required for phase modulation in astronomical instruments. We also investigated the combination of a detector and a superconducting phase switch for modulating the polarization of electromagnetic radiation.

Increasing interest in renewable energy sources for electricity production complying with stricter environmental policies has greatly contributed to further optimisation of existing devices and the development of novel renewable energy generation systems. The research and development of these advanced systems is tightly bound to the use of reliable design methods, which enable accurate and efficient design. Reynolds-averaged Navier-Stokes Computational Fluid Dynamics is one of the design methods that may be used to accurately analyse complex flows past current and forthcoming renewable energy fluid machinery such as wind turbines and oscillating wings for marine power generation. The use of this simulation technology offers a deeper insight into the complex flow physics of renewable energy machines than the lower-fidelity methods widely used in industry. The complex flows past these devices, which are characterised by highly unsteady and, often, predominantly periodic behaviour, can significantly affect power production and structural loads. Therefore, such flows need to be accurately predicted. The research work presented in this thesis deals with the development of a novel, accurate, scalable, massively parallel CFD research code COSA for general fluid-based renewable energy applications. The research work also demonstrates the capabilities of newly developed solvers of COSA by investigating complex three-dimensional unsteady periodic flows past oscillating wings and horizontal-axis wind turbines. Oscillating wings for the extraction of energy from an oncoming water or air stream, feature highly unsteady hydrodynamics. The flow past oscillating wings may feature dynamic stall and leading edge vortex shedding, and is significantly three-dimensional due to finite-wing effects. Detailed understanding of these phenomena is essential for maximising the power generation efficiency. Most of the knowledge on oscillating wing hydrodynamics is based on two-dimensional low-Reynolds number computational fluid dynamics studies and experimental testing. However, real installations are expected to feature Reynolds numbers of the order of 1 million and strong finite-wing-induced losses. This research investigates the impact of finite wing effects on the hydrodynamics of a realistic aspect ratio 10 oscillating wing device in a stream with Reynolds number of 1.5 million, for two high-energy extraction operating regimes. The benefits of using endplates in order to reduce finite-wing-induced losses are also analyzed. Three-dimensional time-accurate Reynolds-averaged Navier-Stokes simulations using Menter's shear stress transport turbulence model and a 30-million-cell grid are performed. Detailed comparative hydrodynamic analyses of the finite and infinite wings highlight that the power generation efficiency of the finite wing with sharp tips for the considered high energy-extraction regimes decreases by up to 20 %, whereas the maximum power drop is 15 % at most when using the endplates. Horizontal-axis wind turbines may experience strong unsteady periodic flow regimes, such as those associated with the yawed wind condition. Reynolds-averaged Navier-Stokes CFD has been demonstrated to predict horizontal-axis wind turbine unsteady flows with accuracy suitable for reliable turbine design. The major drawback of conventional Reynolds-averaged Navier-Stokes CFD is its high computational cost. A time-step-independent time-domain simulation of horizontal-axis wind turbine periodic flows requires long runtimes, as several rotor revolutions have to be simulated before the periodic state is achieved. Runtimes can be significantly reduced by using the frequency-domain harmonic balance method for solving the unsteady Reynolds-averaged Navier-Stokes equations. This research has demonstrated that this promising technology can be efficiently used for the analyses of complex three-dimensional horizontal-axis wind turbine periodic flows, and has a vast potential for rapid wind turbine design. The three-dimensional simulations of the periodic flow past the blade of the NREL 5-MW baseline horizontal-axis wind turbine in yawed wind have been selected for the demonstration of the effectiveness of the developed technology. The comparative assessment is based on thorough parametric time-domain and harmonic balance analyses. Presented results highlight that horizontal-axis wind turbine periodic flows can be computed by the harmonic balance solver about fifty times more rapidly than by the conventional time-domain analysis, with accuracy comparable to that of the time-domain solver.