Design and construction of a VLF monitoring station for solar flare detection

Entender la actividad solar es ahora más importante que nunca. Tanto fulguraciones como eyecciones de masa coronal (CMEs) pueden producir efectos devastadores sobre nuestra tecnología además de interrumpir las telecomunicaciones. A pesar de que ya existen equipos dedicados a su monitorización, estos son extremadamente complejos y costosos. Desde 1939 se ha podido utilizar la monitorización de transmisiones de muy baja frecuencia (VLF) distantes para la detección de fulguraciones solares, a través de las perturbaciones ionosféricas súbitas (SIDs) producidas por el cambio en el flujo de rayos X duros en la ionosfera; un método mucho más sencillo y accesible. Este proyecto tiene como objetivo desarrollar los fundamentos teóricos y proponer un diseño de una de estas estaciones de monitorización junto con su construcción y prueba.Understanding solar activity is now more important than ever. Flares and coronal mass ejections (CMEs) can produce devastating e ects in our technology and disrupt telecommunications. Ways of monitoring it have been developed, but rely on extremely complex and expensive equipment. Since 1936, very low frequency (VLF) monitoring is known to allow are detection through events called sudden ionospheric disturbances (SIDs) produced by the change on hard X-ray ux in the Earth's ionosphere, which is a much more simpler and accessible method. This project aims to provide the theoretical background and design for one of this monitoring stations, along with its construction and a demonstration.Grado en Ingeniería en Sistemas de Telecomunicació

A Literature Review on the Application of Acoustic Emission to Machine Condition Monitoring

Acoustic emission (AE) is a common physical phenomenon, in which the strain energy is released in the form of elastic wave when a material is deformed or cracked during the stress process. The condition monitoring based on AE is a relatively new method that aims to use noise/vibration anomalies to detect machine failures. However, some challenges lie ahead of its application. This thesis aims to analyze the literature in the field of AE applications to machine condition monitoring. The principles of AE technology, relevant instruments, machine monitoring and AE signal analysis, and practical examples of AE monitoring applications will be presented. More specifically, challenges, solutions and future direction in solving signal noise and attenuation challenges will be discussed. Through the example of rotating machinery, the characteristics of AE will be explained in detail. This thesis lays the foundation for the actual use of AE to monitor and analyze the state of machinery and provides guideline for future data collection and analysis of AE signals

Hydroacoustic Channel Emulator - HACE

Kongsberg Maritime wanted a channel emulator for testing their hydroacoustic equipment before deploying it at sea. The benefits of such a system are that it detects problems in an earlier phase of development, thus conveniently reducing the number of expensive sea trials necessary. This master thesis describes how a channel emulator with hydroacoustic properties can be made. The emulator will replace the transducers and water with a computer simulating the acoustics, an audio interface and voltage attenuation. Our approach has been to develop a stable and user-friendly channel emulator with a basis in acoustic wave theory. The hydroacoustic channel emulator, HACE, includes acoustic simulation models where the user is allowed to change acoustic parameters and place the positions of transducers for both point-to-point and network communication. This thesis has focused on advanced acoustic models such as Doppler spread, surface scatter, varying seabed and surface in 3D, sound speed profile with ray tracing, and network communication, together with the fundamental models such as, propagation loss and delay, and reflections. In order to meet the requirements of this master s thesis, with respect to latency and jitter, a good programming platform is important. MATLAB was chosen due to the huge library of built-in-functions, especially with respect to digital signal processing. To control the system a user interface was created with the focus on simplicity, where the interface allows the user to control the system and adjust parameters. The real-time requirement for the system was a latency with a maximum of 100 ms. Since the latency is dependent on both software and hardware, and varies from setup to setup, a calibration function was developed to ensure the best performance for each individual system. HACE has full control over the system latency and exploits it when adding the propagation delay. The minimum latency was measured as 34.2 ms, which resulted in a minimum distance between two nodes using a sound speed of 1500 m/s, being 51.3 meters. For the system to model other distances correctly, this latency must be taken into account when adding propagation delay. Ideally, zero latency would have been preferred so that all distances could be simulated. Two tests were performed to determine the performance of the total system, one that compared the real world impulse response with the simulated impulse response, and secondly to verify the propagation delay in HACE against the measured distance from APOS. The results showed that the simulated ranges corresponded well with the ranges measured in APOS, with an offset of around 20 cm throughout all the results. Impulse response measurements were performed at a sea trial in Horten (Breiangen) measuring at horizontal ranges from 0 to 3000 meters between two nodes. Results from the sea trial compared with those of HACE showed very good similarities between the two, with time deviations between the first and second arrival being from 0 - 3 ms (0 to 15 %), where the largest deviations were found at the shortest ranges

Nondestructive testing of metals and composite materials using ultrasound thermography : comparison with pulse-echo ultrasonics

La thermographie stimulée par ultrasons (TU) est une méthode de contrôle non destructif qui a été inventée en 1979 mais qui a s'est répandue à la fin des années 90. L'idée de cette méthode est d'exciter le matériau à inspecter avec des ondes mécaniques à des fréquences allant de 20kHz à 40kHz et d'observer ensuite leur température de surface avec une caméra infrarouge. TU est une méthode de thermographie active; les autres méthodes les plus connues sont la thermographie optique et celle stimulée par courants de Foucault. Son habilité à révéler des défauts dans des cas où les autres techniques échouent, fait d'elle une méthode pertinente ou complémentaire. L'inconvénient de la TU est que beaucoup de conditions expérimentales doivent être respectées pour obtenir des résultats adéquats incluant quelques paramètres qui doivent être bien choisis. Le but de ce projet est d'explorer les capacités, les avantages et les limites de la TU. Pour comparer la performance de la TU à celle des ultrasons conventionnels, des tests ultrasons de type C-Scan ont été réalisés pour quelques échantillons. Quatre matériaux différents avec quatre types de défauts ont été investigués afin de mieux définir les conditions optimales pour améliorer la détection des défauts. Les résultats bruts obtenus étaient traités dans chaque cas afin de mieux visualiser les contrastes thermiques causés par les discontinuités cachées

Advanced sensors technology survey

This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed

Optical sensors for mechanomyography and tissue chromophores

The mechanomyogram (MMG) is a mechanical oscillations observable on the surface of the skin as a muscle contracts. Measurement of the MMG utilizing contact sensors with a weight greater than 6 g has proved to interfere with the measurement. Use of optical displacement sensors without direct contact to the skin would remove this deficiency. A Michelson interferometer, an intensity shift set-up and a configuration able of measuring both MMG and tissue oxygenation dynamics simultaneously were all evaluated in regard to their precision, easy of use and efficacy. The results were analysed using the fast Fourier transform (FFT) and the continuous wavelet transform (CWT) A regular Michelson interferometer proved to be unsuited for measuring oscillations with an amplitude greater than =4. Demodulation of signals exceeding this limit requires cumbersome analysis methods that would not be practically feasible in a clinical set-up. By measuring the light reflected from an oscillating target, a second simpler set-up was able to measure the frequency and amplitude of a tuning fork with high precision. Measurements on biceps bracii was performed but no clear results were found. A set-up combining MMG and tissue chromophores was realised with three optical fibres attached to the skin. The haemoglobin oxygenation dynamics was successfully measured during contraction and relaxation of the biceps brachii but no MMG signal could be deduced. The outcome of this thesis suggest that further research is required to investigate the possibility of designing a set-up able to measure both MMG and haemoglobin oxygenation dynamics with high precision. This would enable a detailed study of muscle dynamics which have not been done before