A Double Myers-Perry Black Hole in Five Dimensions

Using the inverse scattering method we construct a six-parameter family of exact, stationary, asymptotically flat solutions of the 4+1 dimensional vacuum Einstein equations, with U(1)^2 rotational symmetry. It describes the superposition of two Myers-Perry black holes, each with a single angular momentum parameter, both in the same plane. The black holes live in a background geometry which is the Euclidean C-metric with an extra flat time direction. This background possesses conical singularities in two adjacent compact regions, each corresponding to a set of fixed points of one of the U(1) actions in the Cartan sub-algebra of SO(4). We discuss several aspects of the black holes geometry, including the conical singularities arising from force imbalance, and the torsion singularity arising from torque imbalance. The double Myers-Perry solution presented herein is considerably simpler than the four dimensional double Kerr solution and might be of interest in studying spin-spin interactions in five dimensional general relativity.Comment: 23 pages, 7 figures, LaTeX. v2: minor changes, references added; version published in JHE

Numerical simulation of blast effects on fibre grout RC panels

The main purpose of the present dissertation is the simulation of the response of fibre grout strengthened RC panels when subjected to blast effects using the Applied Element Method, in order to validate and verify its applicability. Therefore, four experimental models, three of which were strengthened with a cement-based grout, each reinforced by one type of steel reinforcement, were tested against blast effects. After the calibration of the experimental set-up, it was possible to obtain and compare the response to the blast effects of the model without strengthening (reference model), and a fibre grout strengthened RC panel (strengthened model). Afterwards, a numerical model of the reference model was created in the commercial software Extreme Loading for Structures, which is based on the Applied Element Method, and calibrated to the obtained experimental results, namely to the residual displacement obtained by the experimental monitoring system. With the calibration verified, it is possible to assume that the numerical model correctly predicts the response of fibre grout RC panels when subjected to blast effects. In order to verify this assumption, the strengthened model was modelled and subjected to the blast effects of the corresponding experimental set-up. The comparison between the residual and maximum displacements and the bottom surface’s cracking obtained in the experimental and the numerical tests yields a difference of 4 % for the maximum displacements of the reference model, and a difference of 4 and 10 % for the residual and maximum displacements of the strengthened model, respectively. Additionally, the cracking on the bottom surface of the models was similar in both methods. Therefore, one can conclude that the Applied ElementMethod can correctly predict and simulate the response of fibre grout strengthened RC panels when subjected to blast effects

Lattice computation of the Kugo-Ojima correlation function

As of today, color confinement in Quantum Chromodynamics remains a mystery from the theoretical point of view. So far, no analytical proof of color confinement has been found and the mechanism that confines colored states from the space of physical states is still unknown. Taichiro Kugo and Izumi Ojima proposed such confinement mechanism, using as basis the BRST-symmetry and derived the requirements for the realization of this mechanism. One such requirement, which happens to be the non-trivial one, is that a special correlation function, the Kugo-Ojima correlation function $u(p^2)$, approaches $-1$ at the origin ($p^2=0)$. This correlation function can be obtained on the lattice within the lattice formulation of gauge theories. The present work consists on lattice results for this correlation function on the Landau gauge. We present results obtained from 4 symmetric large volume lattices $(32^{4}, 48^{4}, 64^{4}, 80^{4})$ with $\beta = 6.0$ on the Landau gauge. A test on the transversality of the Kugo-Ojima correlation function is also performed, along with some statistical considerations of the results. The results present further evidence that the Kugo-Ojima confinement scenario is not realized on the lattice and that the Kugo-Ojima correlation function, in the Landau gauge, is transverse. Our findings align qualitatively with existing literature.Comment: Master's Degree Dissertation, 72 Pages, 10 Figure

Development of an Efficient Propulsion System for a Battery Electric Shell Eco Marathon Prototype Vehicle

For the participation of the Aero@UBI team in Shell Eco-Marathon competition an in-wheel electric, ironless brushless permanent magnet motor was designed and build, this type of motors is characterized by very inductance and a very low resistance between phases which leads to current ripple, to solve this problem, and also, as Shell Eco-marathon competition requirements, a controller must be developed. In this case a controller with a 60-degree commutation was implemented and tested

Development and study of a high performance protective solution against blast loads

The increasing use of improvised explosive devices in terrorist attacks against civil targets has challenged the scientific community to find new strengthening or protective solutions able to mitigate the effects of the blast loads. As a response to this demand, the main purpose of the present thesis is the development and study of a high performance protective solution based on the concept of sacrificial claddings. Due to the high flexibility, precision and relatively low costs, additive manufacturing has been increasingly used in the search of new material disposition patterns that improve the mitigation capabilities of crushable cores. The presentwork assesses the performance of a PLA crushable core manufactured through fused deposition modelling 3D printing. An experimental campaign is conducted to determine the mechanical behaviour of the PLA. These results allow the selection and calibration of an adequate numerical constitutive model, which considers the anisotropy and compressive/tensile asymmetry exhibited in additively manufactured materials. Once the constitutive material calibrated, the results of a second experimental campaign resorting to an explosive driven shock tube are used to validate a numerical model that allows the deterministic design of a sacrificial cladding which successfully improves the blast resistant capabilities of a given structural element. However, when verified taking into account the model’s uncertainties and the probabilistic distribution of the structural element’s properties, the cladding solution might, for certain blast scenarios, negatively impact the performance of the structural element it intends to protect. Therefore, one may conclude that the use of a probabilistic approach in the design of such protective solutions is recommended, as the deterministic approach might yields results against safety

Making Sense Out Of Nothing

When I was a child, fortunately, I used to sleep with the light on. The absence of light was lived through as a phobia, a fear of what can’t be seen, of what can’t be perceived, as an unbearable feeling of nothing, of emptiness. Death existed in that space; it walked and lived in darkness, inhabiting the unknown. Over time, these problematic issues were converted into something new. I do not know exactly what this new thing is, but we can say we have created a familiar relationship. Throughout my existence, this discomfort, and at the same time curiosity, unconsciously generated a primary point of reference of great personal interest. Later, when I began to contemplate some of these powerful emotional feelings, I began to select them, understand them, and name them: space, time, life and death, and light. Dealing with some of the natural facts of life soon started to be an important part of my reality. Later, a sort of tranquility set in. Thus, this thesis comes from an intimate personal perspective, where I do not seek for answers or explanations, but where I simply expose my perspective on some specific fields, pertinent to my personal and artistic motivations, and hopefully creating consistent and deep associations between them. Light comes later, as the central point of reference; a point of concert and harmony, living as the unifying element. Light is the connecting topic that involves all these referents, and is explored between the fields of art and science

Differences in ERP use and value across Iberian Manufacturing and Services SMEs

Enterprise Resource Planning (ERP) system literature reports very little research on post-adoption stages, that is, actual usage and value. Even fewer studies focus on the specificities of an industry analysis. Based on the Technology-Organizational-Environment (TOE) framework and the Resource-Based View (RBV) theory, we develop a research model to measure and examine determinants of ERP use and value and their impact in the Iberian region (Portugal and Spain) across Manufacturing and Services industries in Small and Medium Enterprises (SMEs). The empirical test was conducted through structural equation modelling, using data from 261 firms in the peninsula in the Manufacturing and Service industries. Results show that amongst ERP use determinants, Training is the most important determinant for Service firms and Compatibility for Manufacturing firms. Firm size, Analytics, and Collaboration contribute to ERP Value in both industries, with Analytics being more important for the Service industry. The paper provides insight into which determinants contribute to ERP use and ERP value in Iberian Manufacturing and Services SMEs, offering managerial and academic implications

Development of a Modular Controller to Minimize Current Ripple in Low Inductance Coreless Permanent Magnet Motor

In this paper, a development of a modular controller to minimize current ripple in a low inductance coreless permanent magnet synchronous motor (CPMSM) is described. Based on individual modules, the controller uses a 60 degree commutation scheme instead of the conventional 120 degree. The neutral point of the motor’s windings is connected to an intermediate voltage level provided by a capacitor bank relative to the DC power bus. This feature allows the utilization of a single current sensing point that is used to regulate the motor’s torque by hysteretic current level control. With this simplification of the control strategy it was possible to use a single Programable Logic Device (PLD) to implement all the processing in the controller. The controller was built and tested, and the results showed efficient and smooth operation of the motor. Keywords: Current ripple, Permanent magnet motor, Low inductanc