Diagnóstico de falhas num conversor de energias das ondas

Trabalho final de mestrado para obtenção do grau de mestre em Engenharia MecânicaAtualmente as energias renováveis são uma alternativa aos recursos petrolíferos, sendo a exploração dos recursos marítimos uma área de maior interesse científico na obtenção de energia elétrica. Deste modo, muitas são as instituições que estudam a melhor alternativa para a transformação de energia mecânica (de qualquer tipo de natureza) numa resposta elétrica favorável, que seja ilimitada e estável. De forma a entender as diferentes formas de conversão da energia das ondas, no presente estudo foi efetuada uma revisão de todas as tecnologias desenvolvidas a nível mundial, para identificar os níveis mais relevantes de manutenção, de fiabilidade e de custo para cada tecnologia existente e com isso obter uma matriz de comparação fidigna. Foi igualmente estudado, com base na literatura atual, um sistema de conversão de potência das ondas usando um sistema hidráulico para a conversão da energia existente offshore. Neste sistema foi feita a identificação de todas as falhas existentes, evidenciando algumas técnicas possíveis de projeto tolerante a falhas de forma a construir um sistema capaz de diagnosticar o estado dos componentes. As técnicas utilizadas neste trabalho foram: análise por árvore de falhas, diagrama de blocos de fiabilidade (utilizando um software Blocksim da empresa ReliaSoft®) e cálculo da criticidade dos componentes dos diversos subsistemas. A simulação do sistema estudado revelou uma probabilidade de falha elevada para a sua exequibilidade e, como tal, foi necessário desenvolver uma alternativa viável de forma a maximizar a fiabilidade do sistema.Currently, renewable energy is an alternative to petroleum resources, and the exploitation of marine resources is an area of greater scientific interest in obtaining electricity. In this way, many institutions are studying the best alternative for the transformation of mechanical energy (of any kind of nature) into a favorable electric response, which is unlimited and stable. To understand the different ways of converting wave energy, in the present study a review was made of all the technologies developed worldwide to identify the most relevant levels of maintenance, reliability and cost for each existing technology and with this gives a trustworthy comparison matrix. It was also studied, based on the current literature, a wave power conversion system using a hydraulic system for the conversion of existing offshore energy. In this system it was made the identification of all the existing faults, evidencing some possible techniques of fault tolerant design to build a system capable of diagnosing the state of the components. The techniques used in this work were: fault tree analysis, reliability block diagram (using Blocksim software from ReliaSoft®) and calculation of the criticality of the components of the various subsystems. The simulation of the studied system revealed a high probability of failure for its feasibility and, as such, it was necessary to develop a viable alternative to maximize the reliability of the system.N/

High-Resolution Hard X-Ray and Gamma-Ray Spectrometers Based on Superconducting Absorbers Coupled to Superconducting Transition Edge Sensors

We are developing detectors based on bulk superconducting absorbers coupled to superconducting transition edge sensors (TES) for high-resolution spectroscopy of hard X-rays and soft gamma-rays. We have achieved an energy resolution of 70 eV FWHM at 60 keV using a 1 x 1 x 0.25 mm{sup 3} Sn absorber coupled to a Mo/Cu multilayer TES with a transition temperature of 100 mK. The response of the detector is compared with a simple model using only material properties data and characteristics derived from IV-measurements. We have also manufactured detectors using superconducting absorbers with a higher stopping power, such as Pb and Ta. We present our first measurements of these detectors, including the thermalization characteristics of the bulk superconducting absorbers. The differences in performance between the detectors are discussed and an outline of the future direction of our detector development efforts is given

Arnold diffusion for a complete family of perturbations

In this work we illustrate the Arnold diffusion in a concrete example — the a priori unstable Hamiltonian system of 2 + 1/2 degrees of freedom H(p, q, I, f, s) = p2/2+ cos q - 1 + I2/2 + h(q, f, s; e) — proving that for any small periodic perturbation of the form h(q, f, s; e) = e cos q (a00 + a10 cosf + a01 cos s) (a10a01 ¿ 0) there is global instability for the action. For the proof we apply a geometrical mechanism based on the so-called scattering map. This work has the following structure: In the first stage, for a more restricted case (I* ~ p/2µ, µ = a10/a01), we use only one scattering map, with a special property: the existence of simple paths of diffusion called highways. Later, in the general case we combine a scattering map with the inner map (inner dynamics) to prove the more general result (the existence of instability for any µ). The bifurcations of the scattering map are also studied as a function of µ. Finally, we give an estimate for the time of diffusion, and we show that this time is primarily the time spent under the scattering map.Peer ReviewedPostprint (published version

A Monte Carlo Model for Interrogation of Thick Cargos for Clandestine Fissionable Materials; Tests with 14-MeV Neutrons

A Monte Carlo model has been developed for interrogation of fissionable material embedded in thick cargos when high-energy {beta}-delayed {gamma} rays are detected following neutron-induced fission. The model includes the principal structural components of the laboratory, the neutron source and collimator assembly in which it resides, the assembly that represents cargo of given characteristics, a target of highly-enriched uranium (HEU) and large external plastic scintillators for photon detection. The ability of this model to reproduce experimental measurements was tested by comparing simulations with measurements of the number of induced fissions and the number of detected photons when the HUE target was irradiated with 14.25-MeV neutrons in the absence of any cargo and while embedded in assemblies of plywood and iron pipes. The simulations agreed with experimental measurements within a factor of about 2 for irradiation of the bare target and when the areal density of intervening cargo was 33 g cm{sup -2} (wood) and 61 g cm{sup -2} (steel pipes). This suggests that the model can permit exploration of a large range in parameter space with reasonable fidelity

High-Resolution Gamma-Ray Spectrometers using Bulk Absorbers Coupled to Mo/Cu Multilayer Superconducting Transition-Edge Sensors

In x-ray and gamma-ray spectroscopy, it is desirable to have detectors with high energy resolution and high absorption efficiency. At LLNL, we have developed superconducting tunnel junction-based single photon x-ray detectors with thin film absorbers that have achieved these goals for photon energies up to 1 keV. However, for energies above 1 keV, the absorption efficiency of these thin-film detectors decreases drastically. We are developing the use of high-purity superconducting bulk materials as microcalorimeter absorbers for high-energy x-rays and gamma rays. The increase in absorber temperature due to incident photons is sensed by a superconducting transition-edge sensor (TES) composed of a Mo/Cu multilayer thin film. Films of Mo and Cu are mutually insoluble and therefore very stable and can be annealed. The multilayer structure allows scaling in thickness to optimize heat capacity and normal state resistance. We measured an energy resolution of 70 eV for 60 keV incident gamma-rays with a 1 x 1 x 0.25 mm{sup 3} Sn absorber. We present x-ray and gamma-ray results from this detector design with a Sn absorber. We also propose the use of an active negative feedback voltage bias to improve the performance of our detector and show preliminary results