157 research outputs found

    Advanced signal processing tools for ballistic missile defence and space situational awareness

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    The research presented in this Thesis deals with signal processing algorithms for the classification of sensitive targets for defence applications and with novel solutions for the detection of space objects. These novel tools include classification algorithms for Ballistic Targets (BTs) from both micro-Doppler (mD) and High Resolution Range Profiles (HRRPs) of a target, and a space-borne Passive Bistatic Radar (PBR) designed for exploiting the advantages guaranteed by the Forward Scattering (FS) configuration for the detection and identification of targets orbiting around the Earth.;Nowadays the challenge of the identification of Ballistic Missile (BM) warheads in a cloud of decoys and debris is essential in order to optimize the use of ammunition resources. In this Thesis, two different and efficient robust frameworks are presented. Both the frameworks exploit in different fashions the effect in the radar return of micro-motions exhibited by the target during its flight.;The first algorithm analyses the radar echo from the target in the time-frequency domain, with the aim to extract the mD information. Specifically, the Cadence Velocity Diagram (CVD) from the received signal is evaluated as mD profile of the target, where the mD components composing the radar echo and their repetition rates are shown.;Different feature extraction approaches are proposed based on the estimation of statistical indices from the 1-Dimensional (1D) Averaged CVD (ACVD), on the evaluation of pseudo-Zerike (pZ) and Krawtchouk (Kr) image moments and on the use of 2-Dimensional (2D) Gabor filter, considering the CVD as 2D image. The reliability of the proposed feature extraction approaches is tested on both simulated and real data, demonstrating the adaptivity of the framework to different radar scenarios and to different amount of available resources.;The real data are realized in laboratory, conducting an experiment for simulating the mD signature of a BT by using scaled replicas of the targets, a robotic manipulator for the micro-motions simulation and a Continuous Waveform (CW) radar for the radar measurements.;The second algorithm is based on the computation of the Inverse Radon Transform (IRT) of the target signature, represented by a HRRP frame acquired within an entire period of the main rotating motion of the target, which are precession for warheads and tumbling for decoys. Following, pZ moments of the resulting transformation are evaluated as final feature vector for the classifier. The features guarantee robustness against the target dimensions and the initial phase and the angular velocity of its motion.;The classification results on simulated data are shown for different polarization of the ElectroMagnetic (EM) radar waveform and for various operational conditions, confirming the the validity of the algorithm.The knowledge of space debris population is of fundamental importance for the safety of both the existing and new space missions. In this Thesis, a low budget solution to detect and possibly track space debris and satellites in Low Earth Orbit (LEO) is proposed.;The concept consists in a space-borne PBR installed on a CubeSaT flying at low altitude and detecting the occultations of radio signals coming from existing satellites flying at higher altitudes. The feasibility of such a PBR system is conducted, with key performance such as metrics the minimumsize of detectable objects, taking into account visibility and frequency constraints on existing radio sources, the receiver size and the compatibility with current CubeSaT's technology.;Different illuminator types and receiver altitudes are considered under the assumption that all illuminators and receivers are on circular orbits. Finally, the designed system can represent a possible solution to the the demand for Ballistic Missile Defence (BMD) systems able to provide early warning and classification and its potential has been assessed also for this purpose.The research presented in this Thesis deals with signal processing algorithms for the classification of sensitive targets for defence applications and with novel solutions for the detection of space objects. These novel tools include classification algorithms for Ballistic Targets (BTs) from both micro-Doppler (mD) and High Resolution Range Profiles (HRRPs) of a target, and a space-borne Passive Bistatic Radar (PBR) designed for exploiting the advantages guaranteed by the Forward Scattering (FS) configuration for the detection and identification of targets orbiting around the Earth.;Nowadays the challenge of the identification of Ballistic Missile (BM) warheads in a cloud of decoys and debris is essential in order to optimize the use of ammunition resources. In this Thesis, two different and efficient robust frameworks are presented. Both the frameworks exploit in different fashions the effect in the radar return of micro-motions exhibited by the target during its flight.;The first algorithm analyses the radar echo from the target in the time-frequency domain, with the aim to extract the mD information. Specifically, the Cadence Velocity Diagram (CVD) from the received signal is evaluated as mD profile of the target, where the mD components composing the radar echo and their repetition rates are shown.;Different feature extraction approaches are proposed based on the estimation of statistical indices from the 1-Dimensional (1D) Averaged CVD (ACVD), on the evaluation of pseudo-Zerike (pZ) and Krawtchouk (Kr) image moments and on the use of 2-Dimensional (2D) Gabor filter, considering the CVD as 2D image. The reliability of the proposed feature extraction approaches is tested on both simulated and real data, demonstrating the adaptivity of the framework to different radar scenarios and to different amount of available resources.;The real data are realized in laboratory, conducting an experiment for simulating the mD signature of a BT by using scaled replicas of the targets, a robotic manipulator for the micro-motions simulation and a Continuous Waveform (CW) radar for the radar measurements.;The second algorithm is based on the computation of the Inverse Radon Transform (IRT) of the target signature, represented by a HRRP frame acquired within an entire period of the main rotating motion of the target, which are precession for warheads and tumbling for decoys. Following, pZ moments of the resulting transformation are evaluated as final feature vector for the classifier. The features guarantee robustness against the target dimensions and the initial phase and the angular velocity of its motion.;The classification results on simulated data are shown for different polarization of the ElectroMagnetic (EM) radar waveform and for various operational conditions, confirming the the validity of the algorithm.The knowledge of space debris population is of fundamental importance for the safety of both the existing and new space missions. In this Thesis, a low budget solution to detect and possibly track space debris and satellites in Low Earth Orbit (LEO) is proposed.;The concept consists in a space-borne PBR installed on a CubeSaT flying at low altitude and detecting the occultations of radio signals coming from existing satellites flying at higher altitudes. The feasibility of such a PBR system is conducted, with key performance such as metrics the minimumsize of detectable objects, taking into account visibility and frequency constraints on existing radio sources, the receiver size and the compatibility with current CubeSaT's technology.;Different illuminator types and receiver altitudes are considered under the assumption that all illuminators and receivers are on circular orbits. Finally, the designed system can represent a possible solution to the the demand for Ballistic Missile Defence (BMD) systems able to provide early warning and classification and its potential has been assessed also for this purpose

    Physics opportunities with the Advanced Gamma Tracking Array : AGATA

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    New physics opportunities are opening up by the Advanced Gamma Tracking Array, AGATA, as it evolves to the full 4 pi instrument. AGATA is a high-resolution gamma -ray spectrometer, solely built from highly segmented high-purity Ge detectors, capable of measuring gamma rays from a few tens of keV to beyond 10 MeV, with unprecedented efficiency, excellent position resolution for individual gamma -ray interactions, and very high count-rate capability. As a travelling detector AGATA will be employed at all major current and near-future European research facilities delivering stable and radioactive ion beams.Peer reviewe

    Novel classification algorithm for ballistic target based on HRRP frame

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    Nowadays the identification of ballistic missile warheads in a cloud of decoys and debris is essential for defence systems in order to optimize the use of ammunition resources, avoiding to run out of all the available interceptors in vain. This paper introduces a novel solution for the classification of ballistic targets based on the computation of the inverse Radon transform of the target signatures, represented by a high resolution range profile frame acquired within an entire period of the main rotation of the target. Namely, the precession for warheads and the tumbling for decoys are taken into account. Following, the pseudo-Zernike moments of the resulting transformation are evaluated as the final feature vector for the classifier. The extracted features guarantee robustness against target's dimensions and rotation velocity, and the initial phase of the target's motion. The classification results on simulated data are shown for different polarizations of the electromagnetic radar waveform and for various operational conditions, confirming the validity of the algorithm

    Structural Organization and Chemical Activity Revealed by New Developments in Single-Molecule Fluorescence and Orientation Imaging

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    Single-molecule (SM) fluorescence and its localization are important and versatile tools for understanding and quantifying dynamical nanoscale behavior of nanoparticles and biological systems. By actively controlling the concentration of fluorescent molecules and precisely localizing individual single molecules, it is possible to overcome the classical diffraction limit and achieve \u27super-resolution\u27 with image resolution on the order of 10 nanometers. Single molecules also can be considered as nanoscale sensors since their fluorescence changes in response to their local nanoenvironment. This dissertation discusses extending this SM approach to resolve heterogeneity and dynamics of nanoscale materials and biophysical structures by using positions and orientations of single fluorescent molecules. I first present an SM approach for resolving spatial variations in the catalytic activity of individual photocatalysts. Quantitative colocalization of chemically triggered molecular probes reveals the role of structural defects on the activity of catalytic nanoparticles. Next, I demonstrate a new engineered optical point spread function (PSF), called the Duo-spot PSF, for SM orientation measurements. This PSF exhibits high sensitivity for estimating orientations of dim fluorescent molecules. This dissertation also discusses a new amyloid imaging method, transient amyloid binding (TAB) microscopy, for studying heterogeneous organization of amyloid structures, which are associated with various aging-related neurodegenerative diseases. Continuous transient binding of dye molecules to amyloid structures generates photon bursts for SM localization over hours to days with minimal photobleaching, yielding about 40% more localizations than standard immunolabeling. Finally, I augment TAB imaging to simultaneously measure positions and orientations of fluorescent molecules bound to amyloid surfaces. This new method, termed single-molecule orientation localization microscopy (SMOLM), robustly and sensitively measures the in-plane (xy) orientations of fluorophores (approximately 9 degree precision in azimuthal angle) near a refractive index interface and reveals structural heterogeneities along amyloid fibrillar networks that cannot be resolved by SM localization alone

    Statistical analysis of bacteria locomotion

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    Many bacteria swim by employing their helical appendages, the flagella. We studied the statistics of this locomotion. To obtain more natural and especially long trajectories compared to two-dimensional tracking strategies, we developed a measurement-setup suitable to track bacteria in three-dimensions.The main component of this setup is an electrically focus tunable lens (ETL), able to adapt it’s shape via an applied electrical current, resulting in a change of the current focal plane. This setup has no mechanical interaction with the sample to avoid adulteration of the measured trajectories. We found that for times smaller than the average running-time, the slope of the mean-squared displacement MSD of the tracked bacteria obeys a ballistic behavior, whereas for longer times we saw a clear diffusive behavior. To allow for a more efficient evaluation of the measured trajectories we introduce the Kalman-Filter. By using simulated trajectories we could show that the Kalman-Filter allows a more accurate determination of the rotational-diffusion coefficient than conventional methods. Furthermore we could show that evaluation of three-dimensional trajectories obeys slightly different statistics than the evaluation of projected two-dimensional trajectories due to missing information.Through the qualitative simulation of bacteria locomotion we could show that the flagella-positioning has a crucial impact on the tumbling dynamics.Viele Bakterien schwimmen durch Nutzung ihrer spiralförmigen Anhänge,den Flagellen. Wir untersuchten die Statistik dieser Bewegung. Um natürlichere und vor allem längere Trajektorien - verglichen mit konventionellen zweidimensionalen Trackingmethoden - zu erhalten, haben wir einen Messaufbau zum dreidimensionalen tracken von Bakterien entwickelt. Die Hauptkomponente dieses Setups ist eine elektrische, fokusanpassbare Linse (ETL),welche ihre Form durch Anlegen eines elektrischen Stroms ändern kann,was zu einer Änderung der Fokusebene führt. Dieser Messaufbau hat keine mechanischen Wechselwirkungen mit der Probe, wodurch Verfälschungender gemessenen Trajektorien verhindert werden. Wir konnten zeigen dassfür Zeiten kleiner als die durchschnittlicherunning-Zeit (dt.Renn-Zeit), die mittlere quadratische Verschiebung (MSD) der getrackten Bakterien ein ballistisches Verhalten zeigt, wohingegen für längere Zeiten ein diffusives Verhalten vorliegt. Um eine effizientere Auswertung der gemessenen Trajektorien zu erlauben, führten wir den Kalman-Filter ein. Durch Nutzung simulierterTrajektorien konnten wir zeigen dass der Kalman-Filter eine genauere Bestimmung des Rotations-Diffusionskoeffizienten - verglichen mit konventionellen Methoden - erlaubt.Weiterhin konnten wir zeigen, dass die Auswertung dreidimensionaler Trajektorien leicht andere Statistiken als die Auswertung zweidimensionaler Trajektorien liefert, was durch den Verlust an Information zu erklären ist. Durch die qualitative Simulation der Bewegung von Bakterien konnten wir zeigen, dass die Position der Flagellen einen wesentlichen Einfluss auf die Tumbling-Dynamik (dt.Taumel-Dynamik) hat

    Radio observations of active galactic nuclei with mm-VLBI

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    Over the past few decades, our knowledge of jets produced by active galactic nuclei (AGN) has greatly progressed thanks to the development of very-long-baseline interferometry (VLBI). Nevertheless, the crucial mechanisms involved in the formation of the plasma flow, as well as those driving its exceptional radiative output up to TeV energies, remain to be clarified. Most likely, these physical processes take place at short separations from the supermassive black hole, on scales which are inaccessible to VLBI observations at centimeter wavelengths. Due to their high synchrotron opacity, the dense and highly magnetized regions in the vicinity of the central engine can only be penetrated when observing at shorter wavelengths, in the millimeter and sub-millimeter regimes. While this was recognized already in the early days of VLBI, it was not until the very recent years that sensitive VLBI imaging at high frequencies has become possible. Ongoing technical development and wide band observing now provide adequate imaging fidelity to carry out more detailed analyses. In this article we overview some open questions concerning the physics of AGN jets, and we discuss the impact of mm-VLBI studies. Among the rich set of results produced so far in this frequency regime, we particularly focus on studies performed at 43 GHz (7 mm) and at 86 GHz (3 mm). Some of the first findings at 230 GHz (1 mm) obtained with the Event Horizon Telescope are also presented.Comment: Published in The Astronomy & Astrophysics Review. Open access: https://link.springer.com/article/10.1007/s00159-017-0105-

    Cilia motility studies in zebrafish embryos

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    A thesis submitted in fulfilment of the requirements for the degree of Masters in Molecular Genetics and BiomedicineMotile ciliary dysfunctions cause specific Ciliopathies that affect mainly the respiratory tract, fertilization and left-right body establishment. The embryonic organ where left-right decisions are first taken is called the organizer, a ciliated organ where a leftward cilia driven fluid-flow is generated. The organizer is named node in the mouse and Kupffer’s vesicle (KV) in zebrafish. The correct left-right axis formation is highly dependent on signaling pathways downstream of such directional fluid-flow. Motile cilia need to be coordinated and Ciliary Beat Frequency (CBF) is characteristic of different types of cilia depending on their function. Using zebrafish as a model, our group has been studying cilia length regulation and motility in wild-type and deltaD-/- mutant embryos. Recently, we showed that Notch signalling was directly involved in the control of cilia length in the KV cells given that the deltaD-/- mutant present shorter KV cilia. The goal of this project was to characterize the CBF of deltaD-/- KV cilia vs. wild-type cilia and reveal how potential differences in CBF impact on KV fluid flow, using spectral analysis associated with highspeed videomicroscopy. By decomposing and comparing the obtained CBF with Fast Fourier Transform, we identified two major populations of motile cilia in wild-type as well as in deltaD-/- mutant embryos. However, we found the CBF populations had differential relative contributions and different distributions between wild-type and mutant embryos. Furthermore, by measuring the velocity of native particles we studied the KV fluid-flow and concluded that the dispersion of the flow velocity was much wider in the deltaD-/- mutants. On the other hand, based on a gene expression study of motility genes downstream of DeltaD, we concluded that motility related genes (dnah7, rsph3 and foxj1a) were deregulated in the mutants. During this project we generated data that led to new hypotheses that will allow us to test the causality between the described correlations

    Performance of multiphase packed-bed reactors and scrubbers on offshore floating platforms: hydrodynamics, chemical reaction, CFD modeling and simulation

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    Les systèmes flottants de production, stockage et de déchargement (FPSO) ont été introduits dans les secteurs d'exploitation des hydrocarbures offshore en tant qu'outils facilement déplaçables pour l’exploitation de champs de pétrole et de gaz de petites ‘a moyenne tailles ou lorsque ceux-ci sont éloignés des côtes ou en eaux profondes. Ces systèmes sont de plus en plus envisagés pour les opérations de traitement et de raffinage des hydrocarbures à proximité des sites d'extraction des réservoirs sous-marins en utilisant des laveurs et des réacteurs à lit fixe embarqués. De nombreuses études dans la littérature pour découvrir l'hydrodynamique de l'écoulement polyphasiques dans des lits garnis ont révélé que la maîtrise de tels réacteurs continue d’être un défi quant à leur conception /mise à l'échelle ou à leur fonctionnement. De plus, lorsque de tels réacteurs sont soumis à des conditions fluctuantes propres au contexte marin, l'interaction des phases devient encore plus complexe, ce qui entraîne encore plus de défis dans leur conception. Les travaux de recherche proposés visent à fournir des informations cruciales sur les performances des réacteurs à lit fixes à deux phases dans le cadre d'applications industrielles flottantes. Pour atteindre cet objectif, un simulateur de mouvement de navire de type hexapode avec des mouvements à six degrés de liberté a été utilisé pour simuler les mouvements des FPSO tandis que des capteurs à maillage capacitif (WMS) et un tomographe à capacitance électrique (ECT) couplés avec le lit garni ont permis de suivre en ligne les caractéristiques dynamiques locales des écoulements diphasiques. L'effet des inclinaisons et des oscillations de la colonne sur le comportement hydrodynamique des lits garnis biphasiques a été étudié, puis les résultats ont été comparés à leurs analogues terrestres correspondants (colonne verticale immobile). De plus, des stratégies opérationnelles potentielles ont été proposées pour atténuer la maldistribution des fluides résultant des oscillations du lit ainsi que pour intensifier le processus de réactions dans les réacteurs à lit fixe. Parallèlement aux études expérimentales, un modèle Eulérien CFD transitoire 3D a été développé pour simuler le comportement hydrodynamique de lits garnis polyphasiques sous des inclinaisons et des oscillations de colonnes. Enfin, pour compléter le travail expérimental, une étude systématique a été réalisée pour étudier les performances de capture de CO2 à base d'amines d’un laveur à garnissage (en vrac et structuré) émulant une colonne à bord des ...Floating production storage and offloading (FPSO) systems have been introduced to offshore hydrocarbon exploitation sectors as readily movable tools for development of small or remote oil and gas fields in deeper water. These systems are increasingly contemplated for onboard treatment and refining operations of hydrocarbons extracted from undersea reservoirs near extraction sites using embarked packed-bed scrubbers and reactors. Numerous efforts in the literature to uncover the hydrodynamics of multiphase flow in packed beds have disclosed that such reactors continue to challenge us either in their design/scale-up or their operation. Furthermore, when such reactors are subjected to marine conditions, the interaction of phases becomes even more complex, resulting in further challenges for design and scale-up. The proposed research aims at providing important insights into the performance of two-phase flow packed-bed reactors in the context of floating industrial applications. To achieve this aim, a hexapod ship motion simulator with six-degree-of-freedom motions was employed to emulate FPSO movements while capacitance wire mesh sensors (WMS) and electrical capacitance tomography (ECT) coupled with the packed bed scrutinized on-line and locally the two-phase flow dynamic features. The effect of column tilts and oscillations on the hydrodynamic behavior of multiphase packed beds was investigated and then the results were compared with their corresponding onshore analogs. Moreover, potential operational strategies were proposed to diminish fluid maldistribution resulting from bed oscillations as well as for process intensification of heterogeneous catalytic reactions in packed-bed reactors. In parallel with the experiment studies, a 3D transient Eulerian CFD model was developed to simulate the hydrodynamic behavior of multiphase packed beds under column tilts and oscillations. Ultimately, a systematic experimental study was performed to address the amine-based CO2 capture performance of packed-bed scrubbers on board offshore floating vessels/platforms. Apart from gaining a comprehensive knowledge on the influence of translational and rotational movements on multiphase flows in porous media, oil and gas sectors and ship industry would benefit from the results of this work for design and scale-up of industrial reactors and scrubbers.Unité flottante de production, de stockage et de déchargemen
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