262 research outputs found
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface
A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance
Advanced experimental techniques for SiPM characterization at cryogenic temperatures
The main topic of this thesis is the characterization of silicon photomultipliers (SiPM) detectors for the DUNE experiment, in particular for the ProtoDUNE-HD and DUNE-FD1 modules, and the development of novel experimental setups and techniques to perform this task.
The initial overview of DUNE outlines the main features of the experiment (underlying physics, scientific program and current design for single components), giving particular attention to the first of the four DUNE far detector modules (DUNE-FD1). This includes the general working principles of a LArTPC, the current plan for the DUNE-FD1 design and lastly the role of SiPMs in this design (i.e. fundamental units of the photon detection system PDS). A brief description of the ProtoDUNE2-HD detector is also reported, since it shares the same PDS design with the DUNE-FD1 detector. A detailed description of the SiPM fundamental properties and working principles is also reported, discussing the most important parameters involved in their characterization (in the context of the DUNE experiment).
The presented work falls in the context of the SiPM test campaign engaged by the DUNE PDS consortium to down-select and test SiPMs for both the ProtoDUNE-HD and DUNE-FD1 detectors.
The Ferrara group took active participation on both the first test phase, that consisted in the full characterization of single sensors to down-select two SiPM models as most promising devices, and the second phase, which is a quality assurance test campaign for a large number of SiPMs of the selected models.
The Ferrara group, together with the Bologna group, developed a custom apparatus (CACTUS) to perform fast and automatized characterizations in order to leverage the time involved in the aforementioned massive SiPM test campaign. This apparatus was used for test the ProtoDUNE2-HD SiPM production (6000 units), which resulted in all the sensors being within the DUNE specifications (failure rate around 0.05%), and it is currently operating for the DUNEFD1-HD SiPM characterization campaign (288000 units).
The CACTUS system permits to characterize automatically up to 120 SiPMs in parallel, both at room temperature and at LN2 temperature, in a single measurement session, and it is planned to be installed in other 3 sites to join the DUNEFD1-HD SiPM characterization campaign in 2023.Il tema principale di questo trattato è lo sviluppo di apparati di misura e procedure sperimentali per la caratterizzazione delle proprietà optoelettroniche di fotomoltiplicatori al Silicio (SiPMs) nel contesto dell’esperimento DUNE (Deep Underground Neutrino Experiment), al fine di predisporre
il loro utilizzo nei rivelatori ProtoDUNE-HD e DUNE-FD1.
Inizialmente viene fornita una visione generale dell’esperimento DUNE, in cui vengono descritti i punti salienti del programma scientifico, la teoria fisica sottostante, e il design attualmente previsto per le singole componenti. La descrizione diventa più dettagliata per quanto riguarda il primo modulo del far detector (DUNE-FD1), dato che i SiPM in questione verranno utilizzati come unità fondamentale del sistema di foto-rivelazione (PDS) della camera a proiezione temporale ad argon liquido (LArTPC). Per completare la contestualizzazione del tema principale, il trattato contiene anche una descrizione dettagliata delle proprietà elettriche e optoelettroniche dei SiPM, dei modelli teorici adottati per descrivere il loro funzionamento e delle procedure comunemente adottate per caratterizzarli.
La caratterizzazione dei SiPM per ProtoDUNE-HD e DUNE-FD1 svolta dalla divisione di Ferrara del Consorzio DUNE-PDS è l’argomento centrale di questo trattato. Questo contributo è consistito nella caratterizzazione di singoli sensori SiPM, a temperatura ambiente e alla temperatura di azoto liquido, che ha permesso la selezione dei modelli più promettenti per applicazioni nel contesto dell’esperimento DUNE, assieme alla definizione delle migliori condizioni di lavoro per
massimizzare le loro performance.
Il gruppo DUNE-PDS Ferrara sta contribuendo anche alla seconda fase della campagna di test, che prevede lo svolgimento di test di garanzia per un grande numero di SiPM. In particolare, il gruppo DUNE-PDS Ferrara, in collaborazione con il gruppo DUNE-PDS Bologna, hanno sviluppato un setup sperimentale per velocizzare questa procedura. Il sistema, denominato CACTUS, permette la caratterizzazione automatizzata di 120 sensori in parallelo a livello di caratteristica IV e conteggi di buio (DCR), sia a temperatura ambiente che in azoto liquido, in una singola sessione di misura.
L’apparato CACTUS è stato già utilizzato per testare la produzione di SiPM per ProtoDUNE-HD, un prototipo in scala ridotta di DUNE-FD1 che condivide con esso lo stesso design a livello di singole componenti. Le 6000 unit`a testate con CACTUS per ProtoDUNE-HD non hanno riportato anomalie (failure rate circa 0.05%).
Il sistema CACTUS verrà replicato anche nelle università di Milano Bicocca, Granada e Praga, queste si aggiungeranno ai siti di Ferrara e Bologna nella campagna di caratterizzazione di SiPM per la produzione DUNEFD1-HD, che conta 288000 sensor
INTER-ENG 2020
These proceedings contain research papers that were accepted for presentation at the 14th International Conference Inter-Eng 2020 ,Interdisciplinarity in Engineering, which was held on 8–9 October 2020, in Târgu Mureș, Romania. It is a leading international professional and scientific forum for engineers and scientists to present research works, contributions, and recent developments, as well as current practices in engineering, which is falling into a tradition of important scientific events occurring at Faculty of Engineering and Information Technology in the George Emil Palade University of Medicine, Pharmacy Science, and Technology of Târgu Mures, Romania. The Inter-Eng conference started from the observation that in the 21st century, the era of high technology, without new approaches in research, we cannot speak of a harmonious society. The theme of the conference, proposing a new approach related to Industry 4.0, was the development of a new generation of smart factories based on the manufacturing and assembly process digitalization, related to advanced manufacturing technology, lean manufacturing, sustainable manufacturing, additive manufacturing, and manufacturing tools and equipment. The conference slogan was “Europe’s future is digital: a broad vision of the Industry 4.0 concept beyond direct manufacturing in the company”
Optical Gas Sensing: Media, Mechanisms and Applications
Optical gas sensing is one of the fastest developing research areas in laser spectroscopy. Continuous development of new coherent light sources operating especially in the Mid-IR spectral band (QCL—Quantum Cascade Lasers, ICL—Interband Cascade Lasers, OPO—Optical Parametric Oscillator, DFG—Difference Frequency Generation, optical frequency combs, etc.) stimulates new, sophisticated methods and technological solutions in this area. The development of clever techniques in gas detection based on new mechanisms of sensing (photoacoustic, photothermal, dispersion, etc.) supported by advanced applied electronics and huge progress in signal processing allows us to introduce more sensitive, broader-band and miniaturized optical sensors. Additionally, the substantial development of fast and sensitive photodetectors in MIR and FIR is of great support to progress in gas sensing. Recent material and technological progress in the development of hollow-core optical fibers allowing low-loss transmission of light in both Near- and Mid-IR has opened a new route for obtaining the low-volume, long optical paths that are so strongly required in laser-based gas sensors, leading to the development of a novel branch of laser-based gas detectors. This Special Issue summarizes the most recent progress in the development of optical sensors utilizing novel materials and laser-based gas sensing techniques
Advances in Sensors and Sensing for Technical Condition Assessment and NDT
The adequate assessment of key apparatus conditions is a hot topic in all branches of industry. Various online and offline diagnostic methods are widely applied to provide early detections of any abnormality in exploitation. Furthermore, different sensors may also be applied to capture selected physical quantities that may be used to indicate the type of potential fault. The essential steps of the signal analysis regarding the technical condition assessment process may be listed as: signal measurement (using relevant sensors), processing, modelling, and classification. In the Special Issue entitled “Advances in Sensors and Sensing for Technical Condition Assessment and NDT”, we present the latest research in various areas of technology
Synergistic optical and microwave remote sensing approaches for soil moisture mapping at high resolution
Aplicat embargament des de la data de defensa fins al dia 1 d'octubre de 2022Soil moisture is an essential climate variable that plays a crucial role linking the Earth’s water, energy, and carbon cycles. It is responsible for the water exchange between the Earth’s surface and the atmosphere, and provides key information about soil evaporation, plant transpiration, and the allocation of precipitation into runoff, surface flow and infiltration. Therefore, an accurate estimation of soil moisture is needed to enhance our current climate and meteorological forecasting skills, and to improve our current understanding of the hydrological cycle and its extremes (e.g., droughts and floods). L-band Microwave passive and active sensors have been used during the last decades to estimate soil moisture, since there is a strong relationship between this variable and the soil dielectric properties.
Currently, there are two operational L-band missions specifically devoted to globally measure soil moisture: the ESA’s Soil Moisture and the Ocean Salinity (SMOS), launched in November 2009; and the NASA’s Soil Moisture Active Passive (SMAP), launched in January 2015. The spatial resolution of the SMOS and SMAP radiometers, in the order of tens of kilometers (~40 km), is adequate for global applications. However, to fulfill the needs of a growing number of applications at local or regional scale, higher spatial detail (< 1 km) is required. To bridge this gap and improve the spatial resolution of the soil moisture maps, a variety of spatial enhancement or spatial (sub-pixel) disaggregation approaches have been proposed.
This Ph.D. Thesis focuses on the study of the Earth’s surface soil moisture from remotely sensed observations. This work includes the implementation of several soil moisture retrieval techniques and the development, implementation, validation and comparison of different spatial enhancement or downscaling techniques, applied at local, regional, and continental scale. To meet these objectives, synergies between several active/passive microwave sensors (SMOS, SMAP and Sentinel-1) and optical/thermal sensors (MODIS) have been explored. The results are presented as follows:
- Spatially consistent downscaling approach for SMOS using an adaptive moving window
A passive microwave/optical downscaling algorithm for SMOS is proposed to obtain fine-scale soil moisture maps (1 km) from the native resolution (~40 km) of the instrument. This algorithm introduces the concept of a shape-adaptive window as a central improvement of the disaggregation technique presented by Piles et al. (2014), allowing its application at continental scales.
- Assessment of multi-scale SMOS and SMAP soil moisture products across the Iberian Peninsula
The temporal and spatial characteristics of SMOS and SMAP soil moisture products at coarse- and fine-scales are assessed in order to learn about their distinct features and the rationale behind them, tracing back to the physical assumptions they are based upon.
- Impact of incidence angle diversity on soil moisture retrievals at coarse and fine scales
An incidence angle (32.5°, 42.5° and 52.5°)-adaptive calibration of radiative transfer effective parameters single scattering albedo and soil roughness has been carried out, highlighting the importance of such parameterization to accurately estimate soil moisture at coarse-resolution. Then, these parameterizations are used to examine the potential application of a physically-based active-passive downscaling approach to upcoming microwave missions, namely CIMR, ROSE-L and Sentinel-1 Next Generation. Soil moisture maps obtained for the Iberian Peninsula at the three different angles, and at coarse and fine scales are inter-compared using in situ measurements and model data as benchmarks.La humedad del suelo es una variable climática esencial que juega un papel crucial en la relación de los ciclos del agua, la energía y el carbono de la Tierra. Es responsable del intercambio de agua entre la superficie de la Tierra y la atmósfera, y proporciona información crucial sobre la evaporación del suelo, la transpiración de las plantas y la distribución de la precipitación en escorrentía, flujo superficial e infiltración. Por lo tanto, es necesaria una estimación precisa de la humedad del suelo para mejorar las predicciones climáticas y meteorológicas, y comprender mejor el ciclo hidrológico y sus extremos (v.g., sequías e inundaciones). Los sensores pasivos y activos en banda L se han usado durante las últimas décadas para estimar la humedad del suelo debido a la relación directa que existe entre esta variable y las propiedades dieléctricas del suelo.
Actualmente, hay dos misiones operativas en banda L específicamente dedicadas a medir la
humedad del suelo a escala global: la misión Soil Moisture and Ocean Salinity (SMOS) de la ESA,
lanzada en noviembre de 2009; y la misión Soil Moisture Active Passive (SMAP) de la NASA,
lanzada en enero de 2015. La resolución espacial de los radiómetros SMOS y SMAP, del orden de unas decenas de kilómetros (~40 km), es adecuada para aplicaciones a escala global. Sin embargo, para satisfacer las necesidades de un número creciente de aplicaciones a escala local o regional, se requiere más detalle espacial (<1 km). Para solventar esta limitación y mejorar la resolución espacial de los mapas de humedad, se han propuesto diferentes técnicas de mejora o desagregación espacial.
Esta Tesis se centra en el estudio de la humedad de la superficie terrestre a partir de datos
obtenidos a través de teledetección. Este trabajo incluye la implementación de distintos
algoritmos de recuperación de la humedad del suelo y el desarrollo, implementación, validación y comparación de distintas técnicas de desagregación, aplicadas a escala local, regional y continental. Para cumplir estos objetivos, se han explorado sinergias entre diferentes sensores de microondas activos/pasivos (SMOS, SMAP y Sentinel-1) y sensores ópticos/térmicos. Los resultados se presentan de la siguiente manera:
- Técnica de desagregación espacialmente consistente, basada en una ventana móvil
adaptativa, aplicada a los datos SMOS
Se propone un algoritmo de desagregación del píxel basado en datos obtenidos de medidas
radiométricas de microondas en banda L y datos ópticos, para mejorar la resolución espacial de
los mapas de humedad del suelo desde la resolución nativa del instrumento (~40 km) hasta
resoluciones de 1 km. El algoritmo introduce el concepto de una ventana de contorno
adaptativo, como mejora principal sobre la técnica de desagregación presentada en Piles et al. (2014), permitiendo su implementación a escala continental.
- Análisis multiescalar de productos de humedad del suelo SMAP y SMOS sobre la
Península Ibérica Se han evaluado las características temporales y espaciales de distintos productos de humedad del suelo SMOS y SMAP, a baja y a alta resolución, para conocer sus características distintivas y comprender las razones de sus diferencias. Para ello, ha sido necesario rastrear los supuestos físicos en los que se basan.
- Impacto del ángulo de incidencia en la recuperación de la humedad del suelo a baja y a
alta resolución
Se ha llevado a cabo una calibración adaptada al ángulo de incidencia (32.5°, 42.5° y 52.5°)
de los parámetros efectivos, albedo de dispersión simple y rugosidad del suelo, descritos en el modelo de transferencia radiativa � − �, incidiendo en la importancia de esta parametrización para estimar la humedad del suelo de forma precisa a baja resolución. El resultado de las mismas se ha utilizado para estudiar la potencial aplicación de un algoritmo activo/pasivo de desagregación basado en la física para las próximas misiones de microondas, llamadas CIMR, ROSE-L y Sentinel-1 Next Generation. Los mapas de humedad recuperados a los tres ángulos de incidencia, tanto a baja como a alta resolución, se han obtenido para la Península Ibérica y se han comparado entre ellos usando como referencia mediciones de humedad in situ.Postprint (published version
Machine Learning in Sensors and Imaging
Machine learning is extending its applications in various fields, such as image processing, the Internet of Things, user interface, big data, manufacturing, management, etc. As data are required to build machine learning networks, sensors are one of the most important technologies. In addition, machine learning networks can contribute to the improvement in sensor performance and the creation of new sensor applications. This Special Issue addresses all types of machine learning applications related to sensors and imaging. It covers computer vision-based control, activity recognition, fuzzy label classification, failure classification, motor temperature estimation, the camera calibration of intelligent vehicles, error detection, color prior model, compressive sensing, wildfire risk assessment, shelf auditing, forest-growing stem volume estimation, road management, image denoising, and touchscreens
Human reproduction in space. Late results
Objectius de Desenvolupament Sostenible::3 - Salut i BenestarPostprint (published version
Investigative Development of an UWB Radar for UAS-borne Applications
The engineering ethos of the last decade has been miniaturization. Progress in various industries like material design, semiconductor technology, and digital signal processing has resulted in low-profile electrical systems. This has facilitated the means of integration onto platforms. Sensors such as radars are typically large, heavy, and consume a lot of power. Miniaturization of radars can enable important applications like remote sensing the various aspects of the Earth System from Unmanned Aerial Systems (UAS). Information about natural topography like ice sheets, vegetation cover, and ocean currents can improve our understanding of the natural processes and continued measurements offer insight into the changes over time. Soil plays a vital role in the Earth’s hydrological cycle. The moisture in soil influences the weather, vegetation, and human endeavors like construction. Models are built using an extensive set of temporal soil moisture data to predict natural disasters like droughts, floods, and landslides. It plays a central role in the areas of agriculture and water resource management and hence can influence policy making and economic decisions.
In this work, an investigative approach to the design, build, and test of a 2 – 18 GHz Frequency Modulated Continuous Wave radar for snow and soil measurements is reported. The radar system is designed to be integrated to the Vapor 55 rotorcraft, which is a Group 1 UAS. The radar can operate as a scatterometer to measure backscatter signatures in all four combinations of vertical and horizontal polarizations; or as a nadir-looking sounder for fine-resolution snow thickness measurements.
One of the primary contributions of this work is the exploration of a single-module that integrates the radar’s RF transmitter, RF receiver, receiver’s IF section, wideband sweep generator, and the DC bias circuitry for the active components. The sweep generator is based on a phase-locked loop and frequency multiplication/translation stage. The compact assembly is in the form of two multilayer Printed Circuit Boards (PCB) merged together and it occupies an area of nearly 170 cm2. This thesis describes the design, construction, and testing of the module, along with recommendations for future revisions.
A commercially off-the-shelf module (Arena series by Tomorrow.io, formerly Remote Sensing Solutions) is the digital backend and it consists of an Arbitrary Waveform Generator (AWG) and a data acquisition system capable of sampling up to 250 MSPS. The module is low-profile with dimensions of 7.6 cm x 19.3 cm x 2.3 cm and weighs less than 400 g including the separate aluminum enclosure intended to be integrated with the radar’s RF and mixed-signal sections.
A second contribution of this work is the design of a prototype antenna front-end, which consists of four four-element antenna arrays housed in a Delrin plastic fixture and are fed using custom-designed microstrip power dividers. The dimensions of the fixture are 13.7 cm x 5.9 cm x 5.5 cm and the uniform elemental distance is 2.5 cm. The arrays are fastened to a metal sheet and a custom-designed four-layer fiberglass composite fairing protects the arrays. The entire front-end is integrated on the rotorcraft and measured in an anechoic chamber. The measured, fully integrated return loss of each array covers 2 – 18 GHz and the highest value is -7.22 dB at 5.23 GHz. The radiation pattern shows a distinct nadir-pointing main lobe for nearly the entire bandwidth, however the effects of the platform increase the average side-lobe levels to less than 10 dB for 12 – 18 GHz. The measured maximum nadir gain is 15.88 dB at 10 GHz and there is a greater than 6 dB variation in magnitude within the bandwidth. This variation is compensated by processing the backscatter data over distinct sub-bands that have a maximum nadir gain variation of 6 dB.
Lastly, the thesis describes two system tests conducted to evaluate the effectiveness of a prototype radar with soil as the target. These are proof-of-concept measurements to detect differences in backscatter signatures between dry and wet soil. Gravimetric measurements of collected soil samples indicate an average change of 9.5% between the two moisture states. The antenna front-end is exclusively characterized using a Vector Network Analyzer and measurements are recorded for both co- and cross-polarization at three look angles of nadir, 15°, and 30°. The relative measurements are repeated on the same patch of land with a 1U version of the miniaturized radar. There are distinct differences in relative received power and backscatter profile for all four polarizations and at each look angle. It is observed that vertical polarization indicates a change in moisture content by an increase in the relative received power over an extended range beyond the primary backscatter signal. The horizontal polarization results in a greater peak received power for the primary backscatter signal, relative to the vertical polarization. The degradation in backscatter profile for vertical polarization is higher than horizontal polarization as a function of angle and this is observed for both dry and wet soil.The ETD Release form has been added to this record as a License bitstrea
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