Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

IL DRAGAGGIO NEL DIVENIRE. LE MIGLIORI TECNICHE DISPONIBILI PER IL DRAGAGGIO IN SIN - SIR.

Il presente lavoro intende delineare un quadro generale delle problematiche legate alla progettazione ed esecuzione degli interventi di bonifica in ambito marino, alla luce delle vigenti disposizioni normative in ambito nazionale. Purtroppo l’attività di dragaggio attualmente è affetta da dubbi ed incertezze interpretative, disorganicità dell’attuale sistema normativo in materia ambientale, che non sono state superate neanche dopo l’emanazione del nuovo Testo Unico per l’Ambiente. Il problema ambientale, aggravatosi a causa della crescente evoluzione industriale, è ad oggi una complicata e pesante eredità da affrontare, in cui decenni di incuria e mancata vigilanza hanno consegnato alle nuove generazioni siti industriali dismessi, vecchi siti di centrali nucleari inattive, discariche abusive e rifiuti pericolosi mal gestiti, con conseguente alterazione delle caratteristiche qualitative dei terreni, delle acque superficiali e sotterranee. I siti inquinati possono essere un enorme risorsa se solo si riuscisse a promuovere la loro bonifica, assicurando la continuità delle attività produttive oppure per farne occasione di rilancio e riutilizzo del territorio. Affinché ciò possa accadere è necessario un grande sforzo pubblico e privato ed un cambiamento nell’approccio in tale disciplina. In particolare tale elaborato, vuole cercare di porre attenzione sull’azione di risanamento dei siti contaminati, che non deve limitarsi ad utilizzare esclusivamente tecnologie invadenti rapide ed onerose, ma deve perseguire come obiettivo principale l’impiego e la sperimentazione di nuove tecnologie che rispettino il naturale equilibrio dell’ambiente e la salute dell’uomo, e che conducano comunque a risultati efficienti e sostenibili. Tutto ciò dovrà passare attraverso un miglioramento dell’efficienza e della qualità dei processi produttivi, mediante il ricorso a nuove tecnologie, nuovi materiali e nuovi sistemi operativi, compatibili con la sicurezza e la salvaguardia dell’ambiente. L'Unione Europea ha emanato la Direttiva 96/61 CE con lo scopo di ottenere una prevenzione ed un controllo integrati dell'inquinamento proveniente dai diversi settori produttivi, attraverso interventi alla fonte delle attività inquinanti, con l'obiettivo di conseguire un elevato livello di protezione dell'ambiente nel suo complesso, attraverso l’utilizzo delle Migliori Tecnologie Disponibili (BAT, Best Available Techniques). Durante lo svolgimento della tesi verrà posto un confronto, su cui avanzeremo delle riflessioni, con l’attuale politica sui rifiuti. Nello specifico analizzeremo quanto affrontato dalla Commissione per le Migliori Tecnologie di gestione e smaltimento dei rifiuti, consapevole che le giuste modalità di intervento sono con tecnologie appropriate e con opportune iniziative di tipo gestionale in ogni sua fase. L’approccio con cui si attua una corretta politica di smaltimento dei rifiuti è basato sull’adozione di un preciso ordine gerarchico,che tenga conto dell’intera filiera partendo dalla loro produzione industriale, passando attraverso la raccolta, il recupero o riciclaggio, e terminando con lo smaltimento. A partire da ciò, cercheremo di comprendere perché quanto dettato dalla Direttiva Europea non venga recepito dalla normativa nazionale in campo di bonifica dei siti contaminati, analizzando in particolar modo casi pratici di bonifica di SIN presenti sul territorio italiano. Concluderemo l’elaborato con la presentazione di una valida alternativa, già esistente in campo industriale, che rappresenta come sia possibile operare con tecnologie e metodologie innovative tali da rispondere ai principi normativi da un lato e, dall’altro, conferire pregi operativi ed economici per i dragaggi in ambito portuale e per bonifiche in ambito SIN

Propagation of perturbations and meandering in a free surface shallow water jet

A shallow water free-surface turbulent jet is investigated at Froude numbers variable between about 0.15 and 0.6 and a Reynolds number equal to 5000, with a jet height-to-width aspect ratio variable from 0.5 to 1.1. In these experimental conditions, the flow is unstable and develops local transverse instabilities, which are amplified to a global meandering motion, forcing the jet to oscillate orthogonally to its axis. Instantaneous and averaged velocity fields are obtained by means of high-density, correlation-based time-resolved Particle Tracking Velocimetry. From the average point of view, the present jet configuration resembles a confined jet condition similar to that of wall jets, but with additional relevant three-dimensional effects, retaining self-similar properties, with a net co-flow and some ambient fluid entrainment. For increasing Froude numbers, such configuration is moved downstream and the jet spreading is delayed. The high resolution in space and time of present measurements allows to locally detect and following perturbed patterns and to derive amplitude and frequency of oscillation of the global meandering motion, the former increasing with axial distance and decreasing with Froude number, the latter doing just the opposite. The velocity of propagation of perturbed patterns is also investigated in comparison to the jet mean velocity, the local celerity of propagation of fluctuating velocity fields being derived. Results indicate that axial fluctuations propagate downstream similarly to transverse fluctuations along the orthogonal direction, thus showing a close coupling among the two motions and the onset of a self-sustained mechanism driven by the mean flow, responsible for the generation of the macroscopic meandering motion. This effect is in agreement with numerical predictions and is emphasised as the Froude number increases

Arbuscular Mycorrhizal Symbiosis Limits Foliar Transcriptional Responses to Viral Infection and Favors Long-Term Virus Accumulation

Tomato (Solanum lycopersicum) can establish symbiotic interactions with arbuscular mycorrhizal (AM) fungi, and can be infected by several pathogenic viruses. Here, we investigated the impact of mycorrhization by the fungus Glomus mosseae on the Tomato spotted wilt virus (TSWV) infection of tomato plants by transcriptomic and hormones level analyses. In TSWV-infected mycorrhizal plants, the AM fungus root colonization limited virus-induced changes in gene expression in the aerial parts. The virus-responsive upregulated genes, no longer induced in infected mycorrhizal plants, were mainly involved in defense responses and hormone signaling, while the virus-responsive downregulated genes, no longer repressed in mycorrhizal plants, were involved in primary metabolism. The presence of the AM fungus limits, in a salicylic acid-independent manner, the accumulation of abscissic acid observed in response to viral infection. At the time of the molecular analysis, no differences in virus concentration or symptom severity were detected between mycorrhizal and nonmycorrhizal plants. However, in a longer period, increase in virus titer and delay in the appearance of recovery were observed in mycorrhizal plants, thus indicating that the plant's reaction to TSWV infection is attenuated by mycorrhization. </jats:p

Vegetation cover analysis using a low budget hyperspectral proximal sensing system

This report describes the implementation of a hyperspectral proximal sensing low-budget acquisition system and its application to the detection of terrestrian vegetation cover anomalies in sites of high environmental quality. Anomalies can be due to stress for lack of water and/or pollution phenomena and weed presence in agricultural fields. The hyperspectral cube (90-bands ranging from 450 to 900 nm) was acquired from the hill near Segni (RM), approximately 500 m far from the target, by means of electronically tunable filters and 8 bit CCD cameras. Spectral libraries were built using both endmember identification method and extraction of centroids of the clusters obtained from a k-means analysis of the image itself. Two classification methods were applied on the hyperspectral cube: Spectral Angle Mapper (hard) and Mixed Tuned Matching Filters (MTMF). Results show the good capability of the system in detecting areas with an arboreal, shrub or leafage cover, distinguishing between zones with different spectral response. Better results were obtained using spectral library originated by the k-means method. The detected anomalies not correlated to seasonal phenomena suggest a ground true analysis to identify their origin

Rocky planet or water world? Observability of low-density lava world atmospheres

Super-Earths span a wide range of bulk densities, indicating a diversity in interior conditions beyond that seen in the solar system. In particular, an emerging population of low-density super-Earths may be explained by volatile-rich interiors. Among these, low-density lava worlds have dayside temperatures high enough to evaporate their surfaces, providing a unique opportunity to probe their interior compositions and test for the presence of volatiles. In this work, we investigate the atmospheric observability of low-density lava worlds. We use a radiative-convective model to explore the atmospheric structures and emission spectra of these planets, focusing on three case studies with high observability metrics and sub-stellar temperatures spanning $\sim$1900-2800 K: HD 86226c, HD 3167b and 55 Cnce. Given the possibility of mixed volatile and silicate interior compositions for these planets, we consider a range of mixed volatile and rock vapor atmospheric compositions. This includes a range of volatile fractions and three volatile compositions: water-rich (100% H$_2$O), water with CO$_2$ (80% H$_2$O+20% CO$_2$), and a desiccated O-rich scenario (67% O$_2$+33%CO$_2$). We find that spectral features due to H$_2$O, CO$_2$, SiO and SiO$_2$ are present in the infrared emission spectra as either emission or absorption features, depending on dayside temperature, volatile fraction and volatile composition. We further simulate JWST secondary eclipse observations for each of the three case studies, finding that H$_2$O and/or CO$_2$ could be detected with as few as $\sim$5 eclipses. Detecting volatiles in these atmospheres would provide crucial independent evidence that volatile-rich interiors exist among the super-Earth population.Comment: Accepted for publication in ApJ. 26 pages, 12 figures, 2 table

Spectroradiometry with sub-microsecond time resolution using multianode photomultiplier tube assemblies

Accurate and precise measurements of spectroradiometric temperature are crucial for many high pressure experiments that use diamond anvil cells or shock waves. In experiments with sub-millisecond timescales, specialized detectors such as streak cameras or photomultiplier tubes are required to measure temperature. High accuracy and precision are difficult to attain, especially at temperatures below 3000 K. Here we present a new spectroradiometry system based on multianode photomultiplier tube technology and passive readout circuitry that yields a 0.24 $\mu$s rise-time for each channel. Temperature is measured using five color spectroradiometry. During high pressure pulsed Joule heating experiments in a diamond anvil cell, we document measurement precision to be $\pm 30$ K at temperatures as low as 2000 K during single-shot heating experiments with $0.6$ $\mu$s time-resolution. Ambient pressure melting tests using pulsed Joule heating indicate that the accuracy is $\pm 80$ K in the temperature range 1800-2700 K.Comment: 17 pages, 18 figure