A survey of visual preprocessing and shape representation techniques

Many recent theories and methods proposed for visual preprocessing and shape representation are summarized. The survey brings together research from the fields of biology, psychology, computer science, electrical engineering, and most recently, neural networks. It was motivated by the need to preprocess images for a sparse distributed memory (SDM), but the techniques presented may also prove useful for applying other associative memories to visual pattern recognition. The material of this survey is divided into three sections: an overview of biological visual processing; methods of preprocessing (extracting parts of shape, texture, motion, and depth); and shape representation and recognition (form invariance, primitives and structural descriptions, and theories of attention)

Optical Quantum Computation

We review the field of Optical Quantum Computation, considering the various implementations that have been proposed and the experimental progress that has been made toward realizing them. We examine both linear and nonlinear approaches and both particle and field encodings. In particular we discuss the prospects for large scale optical quantum computing in terms of the most promising physical architectures and the technical requirements for realizing them

The drivers and timescales of solar wind-magnetosphere-Ionosphere coupling in global MHD simulations

The interaction between the solar wind and the terrestrial magnetosphere-ionosphere system is highly dynamic and non-linear, strongly influencing conditions in near-Earth space. Understanding the coupling between each component of the system is crucial to mitigating societal effects, known as space weather. Global magnetohydrodynamic (MHD) simulations are an invaluable tool in studying this interaction. This thesis entails the use of the Gorgon MHD code for simulating the Earth’s magnetosphere. An updated version of the code is presented, including a newly developed ionosphere module which is tested and benchmarked to validate its proper coupling to the magnetosphere. The model is applied to study the effect of the geomagnetic dipole tilt angle on magnetopause reconnection and ionospheric current systems. The location of the reconnection line is identified for tilt angles up to 90°, with reconnection found to be weaker and more unsteady at large tilt angles. The tilt introduces a North-South asymmetry driving more FAC in the sunward-facing hemisphere, highlighting the sensitivity to onset time in the potential impact of a severe space weather event. An idealised example of such an event is then simulated by impacting the magnetosphere with an interplanetary shock. The location and intensity of dayside reconnection is found to be highly time-dependent following impact, with reconnection enhanced in the vicinity of the shock. These results suggest that steady models of reconnection may not be reliable immediately after onset. Finally, an extended version of the code is implemented to simulate a real geomagnetic storm. The key response timescales of the magnetosphere-ionosphere system to the varying solar wind are investigated, and found to be consistent with those of global convection, being sensitive to the particular mode of driving. It is shown that Gorgon is a capable space weather modelling tool, forming a crucial step towards future operational forecasting purposes.Open Acces

Ferroelectric field effect at ionically conducting oxide interfaces

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 17-01-2019En este trabajo, realizamos un análisis de la interacción entre la ferroelectricidad, las paredes de dominio ferroeléctrico cargadas y el memristor en las dimensiones reducidas de una unión túnel. Para alcanzar este objetivo, crecemos bicapas de heteroestructuras epitaxiales de manganitas ferromagnéticas.The main findings of this dissertation are summarized here. We performed an analysis of the interplay between ferroelectricity, ferromagnetism, domain structure and memristive response inmagnetic tunnel junctions. In order to reach this objective, we grew epitaxial heterostructures combining ferromagnetic manganites.Fac. de Ciencias FísicasTRUEunpu

A low power engine test stand

The engine test stand is a set of systems needed to identify, map, or optimize an engine. The complex task of the integration of those system requires many areas of expertise. This work tries to tackle that, aiming on three main points. One is provide a list of the set of transducers and measurements needed to test an engine. Second is to provide basic knowledge of the techniques needed to put to practice to achieve a data acquisition. And third the development of a dynamometer controller based on renewable energies, to be more precise, on wind energy harvesting. To conclude this work a transient analysis of the controller is listed.O banco de ensaios de motores alternativos é constituído por um conjunto de sistemas necessários para efetuar identificação, mapeamento ou otimização de um dado motor. A integração dos vários sistemas requer um vasto conjunto disciplinas. Este trabalho, tenta resolver isto, apontando para três pontos importantes do banco de ensaios. Um é listar os vários sensores e medições necessárias para testar um motor. Segundo é prever o conhecimento básico das técnicas necessárias para por em prática um sistema de adquisição de dados. Terceiro é desenvolver um dinamómetro baseado em energias renováveis, mais precisamente, energia eólica. Para concluir este trabalho é efetuada ao controlador uma análise de transição

A study of multiplex data bus techniques for the space shuttle

A comprehensive technology base for the design of a multiplexed data bus subsystem is provided. Extensive analyses, both analytical and empirical, were performed. Subjects covered are classified under the following headings: requirements identification and analysis; transmission media studies; signal design and detection studies; synchronization, timing, and control studies; user-subsystem interface studies; operational reliability analyses; design of candidate data bus configurations; and evaluation of candidate data bus designs