Prior Knowledge Optimum Understanding by Means of Oblique Projectors and Their First Order Derivatives

International audienceRecently, an optimal Prior-knowledge method for DOA estimation has been proposed. This method solely estimates a subset of DOA's accounting known ones. The global idea is to maximize the orthogonal-ity between an estimated signal subspace and noise subspace by constraining the orthogonal noise-made projector to only project onto the desired unknown signal subspace. As it could be surprising, no deflation process is used for. Understanding how it is made possible needs to derive the variance for the DOA estimates. During the derivation, oblique projection operators and their first order derivatives appear and are needed. Those operators show in consequence how the optimal Prior-knowledge criterion can focus only on DOA's of interest and how the optimality is reached

Review of Recent Trends

This work was partially supported by the European Regional Development Fund (FEDER), through the Regional Operational Programme of Centre (CENTRO 2020) of the Portugal 2020 framework, through projects SOCA (CENTRO-01-0145-FEDER-000010) and ORCIP (CENTRO-01-0145-FEDER-022141). Fernando P. Guiomar acknowledges a fellowship from “la Caixa” Foundation (ID100010434), code LCF/BQ/PR20/11770015. Houda Harkat acknowledges the financial support of the Programmatic Financing of the CTS R&D Unit (UIDP/00066/2020).MIMO-OFDM is a key technology and a strong candidate for 5G telecommunication systems. In the literature, there is no convenient survey study that rounds up all the necessary points to be investigated concerning such systems. The current deeper review paper inspects and interprets the state of the art and addresses several research axes related to MIMO-OFDM systems. Two topics have received special attention: MIMO waveforms and MIMO-OFDM channel estimation. The existing MIMO hardware and software innovations, in addition to the MIMO-OFDM equalization techniques, are discussed concisely. In the literature, only a few authors have discussed the MIMO channel estimation and modeling problems for a variety of MIMO systems. However, to the best of our knowledge, there has been until now no review paper specifically discussing the recent works concerning channel estimation and the equalization process for MIMO-OFDM systems. Hence, the current work focuses on analyzing the recently used algorithms in the field, which could be a rich reference for researchers. Moreover, some research perspectives are identified.publishersversionpublishe

Did the September 2010 (Darfield) earthquake trigger the February 2011 (Christchurch) event?

We have investigated the possible cause-and-effect relationship due to stress transfer between two earthquakes that occurred near Christchurch, New Zealand, in September 2010 and in February 2011. The Mw 7.1 Darfield (Canterbury) event took place along a previously unrecognized fault. The Mw 6.3 Christchurch earthquake, generated by a thrust fault, occurred approximately five months later, 6 km south-east of Christchurch's city center. We have first measured the surface displacement field to retrieve the geometries of the two seismic sources and the slip distribution. In order to assess whether the first earthquake increased the likelihood of occurrence of a second earthquake, we compute the Coulomb Failure Function (CFF). We find that the maximum CFF increase over the second fault plane is reached exactly around the hypocenter of the second earthquake. In this respect, we may conclude that the Darfield earthquake contributed to promote the rupture of the Christchurch fault

Gaze-stabilizing central vestibular neurons project asymmetrically to extraocular motoneuron pools.

Within reflex circuits, specific anatomical projections allow central neurons to relay sensations to effectors that generate movements. A major challenge is to relate anatomical features of central neural populations -- such as asymmetric connectivity -- to the computations the populations perform. To address this problem, we mapped the anatomy, modeled the function, and discovered a new behavioral role for a genetically-defined population of central vestibular neurons in rhombomeres 5-7 of larval zebrafish. First, we found that neurons within this central population project preferentially to motoneurons that move the eyes downward. Concordantly, when the entire population of asymmetrically-projecting neurons was stimulated collectively, only downward eye rotations were observed, demonstrating a functional correlate of the anatomical bias. When these neurons are ablated, fish failed to rotate their eyes following either nose-up or nose-down body tilts. This asymmetrically-projecting central population thus participates in both up and downward gaze stabilization. In addition to projecting to motoneurons, central vestibular neurons also receive direct sensory input from peripheral afferents. To infer whether asymmetric projections can facilitate sensory encoding or motor output, we modeled differentially-projecting sets of central vestibular neurons. Whereas motor command strength was independent of projection allocation, asymmetric projections enabled more accurate representation of nose-up stimuli. The model shows how asymmetric connectivity could enhance the representation of imbalance during nose-up postures while preserving gaze-stabilization performance. Finally, we found that central vestibular neurons were necessary for a vital behavior requiring maintenance of a nose-up posture: swim bladder inflation. These observations suggest that asymmetric connectivity in the vestibular system facilitates representation of ethologically-relevant stimuli without compromising reflexive behavior.SIGNIFICANCE STATEMENTInterneuron populations use specific anatomical projections to transform sensations into reflexive actions. Here we examined how the anatomical composition of a genetically-defined population of balance interneurons in the larval zebrafish relates to the computations it performs. First, we found that the population of interneurons that stabilize gaze preferentially project to motoneurons that move the eyes downward. Next, we discovered through modeling that such projection patterns can enhance the encoding of nose-up sensations without compromising gaze stabilization. Finally we found that loss of these interneurons impairs a vital behavior, swim bladder inflation, that relies on maintaining a nose-up posture. These observations suggest that anatomical specialization permits neural circuits to represent relevant features of the environment without compromising behavior

Observations, analysis and interpretation with non-LTE of chromospheric structures of the Sun

This thesis is based on observations performed at the Vacuum Tower Telescope (Tenerife). We have used an infrared spectropolarimeter (TIP) and a Fabry-Perot spectrometer (G-FPI) from years 2004 to 2006. We have applied several imaging speckle reconstruction techniques, and compared them. We have studied chromospheric dynamics inside the solar disc and at the limb using H\alpha with very high spatial, spectral and temporal resolution. Keywords (see full abstract for details): fibrils, surge, MHD waves, speckle, blind deconvolution, Fabry-Perot, mini-flares, cloud model, spicules in Halpha, spicules continuing on the disc) Using He I 10830 we studied the offlimb spicular spectral I profiles with height over the limb. The analysis shows the variation of the off-limb emission profiles as a function of the distance to the visible solar limb. The intensity ratio of the multiplet (which is related to the optical thickness and coronal irradiation) is studied and compared with standard atmospheric models. We report observational properties from high-resolution filtergrams in the H$\alpha$ spectral line taken with the G-FPI. We find that spicules can reach heights of 8 Mm above the limb. We show that spicules outside the limb continue as dark fibrils inside the disc.Comment: PhD thesis. 107 pages. Source .tex files and images available at http://www.brunosan.e

Astigmatism and Pseudoaccommodation in Pseudophakic Eyes

noAdvanced IOLs with circumferential zones of different power provide pseudoaccommodation. We investigated the potential for power variation with meridian, namely astigmatism, to provide pseudo-accommodation. With appropriate power and axis orientations, acceptable pseudo-accommodation can be achieved

Magnetotelluric study of the Mérida Andes and surrounding basins, Venezuela

The Caribbean and South American tectonic plates bound the north-eastwards expulsion of the North Andean Block in western Venezuela. This complicated geodynamic setting resulted in the formation of major strike-slip fault systems and sizeable mountain chains. The 100 km wide Mérida Andes extend from the Colombian/Venezuelan border to the Coastal Cordillera. To the north and south, the Mérida Andes are bound by hydrocarbon-rich sedimentary basins. Knowledge of lithospheric structures, related to the formation of the Mérida Andes, is limited though, due to a lack of deep geophysical data. This thesis presents the results of the first broadband magnetotelluric profile crossing the Mérida Andes and the Maracaibo and Barinas-Apure foreland basins spanning a distance of 240 km. The MT dataset consists of 72 stations installed during March and April 2015 with a minimum recording period of 3 days per station. Geoelectrical strike and dimensionality analyses are consistent with one- or two- dimensional subsurface structures for the sedimentary basins yet also indicate a strong three- dimensional setting for the Mérida Andes. Even more significantly, these analyses showed the presence of off-profile features that influenced the data considerably, particularly at long periods. Therefore, a combination of 2D and 3D modelling was necessary for analysing the geoelectrical structures associated with this dataset. Off-profile structures can significantly affect the outcome of a 2D inversion. Thus, the systematic examination of the influence of 3D structures on 2D inversions was necessary to support the obtained result. Synthetic data sets derived from 3D modelling allowed identification and quantification of spurious off-profile features as well as smoothing artefacts due to limited areal station coverage of data collected along a profile. In general, structures in the 2D inversion are affected by the projection and rotation of the data resulting in sub-horizontal anomalies to reproduce the oblique extent of the fault systems and sedimentary basins. Moreover, a profile distributed dataset can limit the lateral resolution of a 3D inversion considerably. Hence, the effect of data distribution on a 3D inversion was carefully studied to determine the areas of the models that can be confidently explained by the data. To this end, several synthetic datasets were derived from 3D models with varying levels of complexity. The analysis of the synthetic datasets allows determination of the lateral resolution of the 3D models and identification of spurious shallow and deep features considered artefacts related to off-profile features. Furthermore, the inversion of synthetic models provided support to the geological interpretation of the recovered anomalies for the 2D and 3D modelling. The 2D and 3D inversion models were similar above the sedimentary basins and showed marked differences above the Mérida Andes, due to the 3D nature of this section. The inversion models show electrically conductive basins with depths of 2 to 5 km for the Barinas-Apure and 2 to 9 km for the Maracaibo basins. Many resistive bodies within the Maracaibo basin could be related to active deformation causing juxtaposition of older geological formations and younger basin sediments. A conductive zone under the Maracaibo Basin correlates spatially with the location of a Bouguer anomaly low and seem to describe the SE tilt of the Maracaibo Triangular Block under the Mérida Andes. This conductive zone is limited towards the mountain by the north-western thrust system, whose fault plane may function as a detachment surface reaching depth larger than 30 km in the 3D inversion models. The most prominent fault systems of the area, the Boconó and Valera Faults, cross-cut the Mérida Andes in NE-SW direction along its strike with a length 400 km and N-S direction at its centre with a length 60 km, respectively. Both faults are associated with sub-vertical zones of high electrical conductivity and sensitivity tests suggest that the Valera fault reach depths of up to 12 km. The Boconó fault can be considered a crustal structure with a depth up to 35 km. The observed anomalies seem to show a deep connection of the fault planes, possibly related to the formation of the fault systems in a transpressive regime. Conductive anomalies to the south of the Boconó Fault seem to represent a considerable back thrust structure well constrained between 3 and 10 km depth. The high conductivity of these structures is possibly related to weathering water from the surface and the accumulation of clay minerals in the fault gauges. However, fluids related to the flat and shallow subduction of the Caribbean Plate in north-western Venezuela could better explain the low resistivity of the deep structures (> 15 km). A sizeable conductor at 50 km depth, which appears consistently in the 2D sections, could be identified as an inversion artefact caused by a conductor east of the profile. The 3D inversion places this structure 10 km to the east at 15 km deep. This model also shows depth connection (12 km depth) of the anomalies related to the Valera and Boconó faults with the off-profile conductor. The observed anomalies in the 2D and 3D inversion related to these conductors were tested and reproduced employing synthetic datasets, leading to the speculation that the high conductivity associated with the off-profile conductor may be related to the detachment of the Trujillo Block. The models obtained confirm the shape and distribution of the known geological structures related to the complicated geodynamic settings responsible for the formation of the Mérida Andes. These results partially support the "floating orogen hypothesis" developed to explain the geodynamic evolution of western Venezuela, and they highlight the relevance of the Trujillo Block in this process. However, they also show that features of known structures such as the Boconó fault system maximum depth, the back-thrusting in the Mérida Andes, and the relevance of the escape of the Trujillo Block in the tectonic processes need to be adjusted to the current knowledge.Die Karibische und Südamerikanische tektonischen Platten begrenzten die nordöstliche Abschiebung des Nord-Anden-Blocks im Westen Venezuelas. Diese komplizierte geodynamische Umgebung führte zur Bildung großer Blattverschiebungen-Verwerfungssysteme und beträchtlicher Gebirgsketten. Die 100 km breiten Mérida-Andes erstrecken sich von der Grenze zwischen Kolumbien und Venezuela bis zum Coastal Cordillera. Im Norden und Süden sind die Mérida-Anden von kohlenwasserstoffreichen Sedimentbecken umgeben. Das Wissen über lithosphärische Strukturen im Zusammenhang mit der Bildung der Mérida-Anden ist jedoch aufgrund des Mangels an tiefen geophysikalischen Daten begrenzt. Diese Arbeit präsentiert die Ergebnisse des ersten breitbandigen magnetotellurischen Profils, das die Mérida-Anden und die Vorlandbecken Maracaibo und Barinas-Apure über eine Entfernung von 240 km quert. Der MT-Datensatz besteht aus 72 Stationen, die im März und April 2015 mit einer Mindestaufzeichnungsdauer von 3 Tagen pro Station installiert wurden. Geoelektrische Streich- und Dimensionalitätsanalysen stimmen mit ein- oder zweidimensionalen Untergrundstrukturen für die Sedimentbecken überein, weisen jedoch auch auf eine starke dreidimensionale Strukturen in der Umgebung der Mérida-Andes hin.. Noch wichtiger ist, dass diese Analysen das Vorhandensein von Merkmalen außerhalb des Profils zeigten, die die Daten insbesondere für lange Perioden erheblich beeinflussen. Daher war eine Kombination aus 2D- und 3D-Modellierung erforderlich, um Störungssysteme und Sedimentbecken quer zum Profil zu reproduzieren. Off-Profile-Strukturen können das Ergebnis einer 2D-Inversion erheblich beeinflussen. Daher war die systematische Untersuchung des Einflusses von 3D-Strukturen auf 2D-Inversionen erforderlich, um das erhaltene Ergebnis zu verifizieren. Synthetische Datensätze, die aus der 3D-Modellierung abgeleitet wurden, ermöglichten die Identifizierung und Quantifizierung von störenden Strukturen außerhalb des Profils sowie die Glättung von Artefakten aufgrund der begrenzten Stationsüberdeckung der entlang eines Profils gesammelten Daten. Im Allgemeinen werden Strukturen in der 2D-Inversion durch die Projektion und Rotation der Daten beeinflusst, was zu flach stehenden Anomalien führt, um die schräge Ausdehnung der Verwerfungssysteme und Sedimentbecken zu reproduzieren. Darüber hinaus kann ein Datensatz entlang eines Profils die laterale Auflösung einer 3D-Inversion erheblich einschränken. Daher wurde die Auswirkung der Datenverteilung auf eine 3D-Inversion sorgfältig untersucht, um die Bereiche der Modelle zu bestimmen, die durch die Daten sicher erklärt werden können. Zu diesem Zweck wurden mehrere synthetische Datensätze aus 3D-Modellen mit unterschiedlicher Komplexität abgeleitet. Die Analyse der synthetischen Datensätze ermöglicht die Bestimmung der lateralen Auflösung der 3D-Modelle und die Identifizierung von störenden oberflächennahen und tiefen Merkmalen, die als Artefakte im Zusammenhang mit Strukturen außerhalb des Profils betrachtet werden. Darüber hinaus unterstützte die Inversion synthetischer Modelle die geologische Interpretation der reproduzierten Anomalien für die 2D- und 3D-Modellierung. Die 2D- und 3D-Inversionsmodelle stimmen über den Sedimentbecken überein. Aufgrund der 3D Strukturen über den MA ergaben sich jedoch deutliche unterschiede. Die Inversionsmodelle zeigen elektrisch leitende Becken mit Tiefen von 2 bis 5 km für das Barinas-Apure und 2 bis 9 km für das Maracaibo-Becken. Viele Gebiete höheren Widerstands im Maracaibo-Becken könnten mit einer aktiven Deformation zusammenhängen, die ein Nebeneinander älterer geologischer Formationen und jüngerer Beckensedimente verursacht. Eine besserleitende Zone unter dem Maracaibo-Becken korreliert räumlich mit der Lage einer Bouguer-Anomalie und scheint die SE-Neigung des Maracaibo-Dreiecksblocks unter den Mérida-Anden zu markieren. Diese leitende Zone ist in Richtung des Gebirges durch das nordwestliche Schubsystem begrenzt, dessen Störungsebene als Ablösefläche fungieren kann, die in den 3D-Inversionsmodellen eine Tiefe von mehr als 30 km erreicht. Die bekanntesten Störungssysteme des Gebiets, die Verwerfungen Boconó und Valera, kreuzen die Mérida-Anden in Nordost-Südwest-Richtung entlang ihres Streichens mit einer Länge von 400 km und die N-S-Richtung in ihrer Mitte mit einer Länge von 60 km. Beide Störungen sind durch steil stehende Zonen hoher elektrischer Leitfähigkeit verbunden. Sensitivitätsstudien legen nahe, dass die Valera-Störung Tiefen von bis zu 12 km erreicht. Die Boconó-Verwerfung kann als Krustenstruktur mit einer Tiefe von bis zu 35 km angesehen werden. Die beobachteten Anomalien scheinen eine tiefe Verbindung der Verwerfungsebenen zu zeigen, möglicherweise im Zusammenhang mit der Bildung der Verwerfungssysteme in einem transpressiven Regime. Leitfähige Anomalien südlich der Boconó-Verwerfung scheinen eine beträchtliche Rückschubstruktur darzustellen, die zwischen 3 und 10 km Tiefe gut lokalisiert ist. Die hohe Leitfähigkeit dieser Strukturen hängt möglicherweise mitWasser aus Verwitterungsprozessen nahe der Erdoberfläche und der Ansammlung von Tonmineralien in den Störungszonen zusammen. Alte Fluide im Zusammenhang mit flach stehenden und oberflächenahen Subduktion der Karibikplatte im Nordwesten Venezuelas könnten jedoch den geringen spezifischen Widerstand der tiefen Strukturen (> 15 km) besser erklären. Ein beträchtlicher Leiter in einer Tiefe von 50 km, der in den 2D-Schnitten konsistent erscheint, konnte als Inversionsartefakt identifiziert werden, der durch einen Leiter östlich des Profils verursacht wird. Durch die 3D-Inversion wird diese Struktur 10 km östlich in 15 km Tiefe platziert. Dieses Modell zeigt auch die Tiefenverbindung (12 km Tiefe) der Anomalien im Zusammenhang mit den Störungen von Valera und Boconó mit dem Leiter außerhalb des Profils. Die beobachteten Anomalien in der 2D- und 3D-Inversion in Bezug auf diese Leiter wurden unter Verwendung synthetischer Datensätze getestet und reproduziert. Daher kann man annehmen das die mit dem Leiter abseits des Profils verbundene Leitfähigkeit mit der Ablösung des Trujilo Blocks zusammenhängt. Die erhaltenen Modelle bestätigen die Form und Verteilung der bekannten geologischen Strukturen im Zusammenhang mit dem komplizierten geodynamischen Millieu, welches für die Bildung der Mérida-Andes verantwortlich ist. Diese Ergebnisse stützen teilweise die "schwimmende Orogenhypothese", die entwickelt wurde, um die geodynamische Entwicklung West-Venezuelas zu erklären, und sie unterstreichen die Relevanz des Trujillo-Blocks in diesem Prozess. Sie zeigen jedoch auch, dass Merkmale bekannter Strukturen wie die maximale Tiefe des Boconó-Verwerfungssystems, das Zurückschieben in den Mérida-Anden und die Relevanz des Entweichens des Trujillo-Blocks in den tektonischen Prozessen an den aktuellen Kenntnisstand angepasst werden müssen

Through-The-Wall Detection Using Ultra Wide Band Frequency Modulated Interrupted Continuous Wave Signals

Through-The-Wall-Detection (TTWD) techniques can improve the situational awareness of police and soldiers, and support first responders in search and rescue operations. A variety of systems for TTWD based on different waveforms have been developed and presented in the literature, e.g. radar systems based on pulses, noise or pseudo-noise waveforms, and frequency modulated continuous wave (FMCW) or stepped frequency continuous wave (SFCW) waveforms. Ultra wide band signals are normally used as they provide suitable resolution to discriminate different targets. A common problem for active radar systems for TTWD is the strong backscattered signal from the air-wall interface. This undesired signal can overshadow the reflections from actual targets, especially those with low radar cross section like human beings, and limit the dynamic range at the receiver, which could be saturated and blocked. Although several techniques have been developed to address this problem, frequency modulated interrupted continuous wave (FMICW) waveforms represent an interesting further approach to wall removal, which can be used as an alternative technique or combined with the existing ones. FMICW waveforms have been used in the past for ionospheric and ocean sensing radar systems, but their application to the wall removal problem in TTWD scenarios is novel. The validation of the effectiveness of the proposed FMICW waveforms as wall removal technique is therefore the primary objective of this thesis, focusing on comparing simulated and experimental results using normal FMCW waveforms and using the proposed FMICW waveforms. Initially, numerical simulations of realistic scenarios for TTWD have been run and FMICW waveforms have been successfully tested for different materials and internal structure of the wall separating the radar system and the targets. Then a radar system capable of generating FMICW waveforms has been designed and built to perform a measurement campaign in environments of the School of Engineering and Computing Sciences, Durham University. These tests aimed at the localization of stationary targets and at the detection of people behind walls. FMICW waveforms prove to be effective in removing/mitigating the undesired return caused by antenna cross-talk and wall reflections, thus enhancing the detection of targets

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion