Single-Layer Series-Fed Planar Array with Controlled Aperture Distribution for Circularly Polarized Radiation

We propose a compact circularly polarized series-fed patch array with enhanced radiation performance at S -band. To our best knowledge, no similar single-layer structure has been designed, measured, and reported in the literature with equivalent radiation performances in terms of reduced sidelobe level (SLL) and aperture efficiency as well as compactness and simplicity. The planar array consists of a 50- Omega microstrip single feed point, offering uniform and efficient excitation of all its elements that enable a broadside beam with high-gain and low sidelobes. A feeding network for such aperture control is designed and optimized to provide good impedance matching with a two-point excitation per radiating element, which is based on 0° and 90° meander lines to enable circularly polarized radiation. A structure made by a 4!! imes !!1 arrangement of square patches is simulated, optimized, and manufactured, providing a realized gain of about 10 dBic and an SLL below -15 dB. Very good axial ratios and high efficiencies are obtained. The proposed antenna may be of interest for next-generation far-field wireless power transmission systems and other applications including target tracking, radar, and internet of things technologies requiring efficient circularly polarized radiation

Coherence-factor-based rough surface clutter suppression for forward-looking GPR imaging

We present an enhanced imaging procedure for suppression of the rough surface clutter arising in forward-looking ground-penetrating radar (FL-GPR) applications. The procedure is based on a matched filtering formulation of microwave tomographic imaging, and employs coherence factor (CF) for clutter suppression. After tomographic reconstruction, the CF is first applied to generate a "coherence map" of the region in front of the FL-GPR system illuminated by the transmitting antennas. A pixel-by-pixel multiplication of the tomographic image with the coherence map is then performed to generate the clutter-suppressed image. The effectiveness of the CF approach is demonstrated both qualitatively and quantitatively using electromagnetic modeled data of metallic and plastic shallow-buried targets

Monitoring freeze-thaw state by means of GNSS reflectometry. An analysis of TechDemoSat-1 data

The article of the freeze/thaw dynamic of high-latitude Earth surfaces is extremely important and informative for monitoring the carbon cycle, the climate change, and the security of infrastructures. Current methodologies mainly rely on the use of active and passive microwave sensors, while very few efforts have been devoted to the assessment of the potential of observations based on signals of opportunity. This article aims at assessing the performance of spaceborne Global Navigation Satellite System Reflectometry (GNSS-R) for high-spatial and highoral resolution monitoring of the Earth-surface freeze/thaw state. To this aim, reflectivity values derived from the TechDemoSat-1 (TDS-1) data have been collected and elaborated, and thus compared against the soil moisture active passive (SMAP) freeze/thaw information. Shallow subsurface soil temperature values recorded by a network of in situ stations have been considered as well. Even if an extensive and timeliness cross availability of both types of experimental data is limited by the spatial coverage and density of TDS-1 observations, the proposed analysis clearly indicates a significant seasonal cycle in the calibrated reflectivity. This opens new perspectives for the bistatic L-band high-resolution satellite monitoring of the freeze/thaw state, as well as to support the development of next-generation of GNSS-R satellite missions designed to provide enhanced performance and improved temporal and spatial coverage over high latitude areas

The potential mechanism of black crust development on the historic buildings in Cairo and Venice

The development of black crusts on natural stones of historic buildings is mainly related to the surrounded polluted atmosphere. The blackening of surfaces is caused, in fact, by the accumulation of air pollutants produced by human activity, especially carbon particles originating from the incomplete combustion of fossil fuel. Investigations of the chemical composition of such layers in the monuments can be the basis for planning suitable strategies for the protection and conservation of the built cultural heritage. Cairo (Egypt) and Venice (Italy) are two cities with a large amount of cultural heritage buildings; moreover, they suffer high level of air pollution. Black crust with the hosted stones from different sites in Historic Cairo, as well as samples of different archaeological sites in Venice city, were collected and analyzed by using several techniques: polarizing optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS), infrared spectroscopic techniques (FT-IR) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS). The characterization of such samples provided information on the chemical composition of black crusts, the state of conservation of the substrates and the crust-stone interactions. The chemical study highlighted a different pattern of elements within the two cities. Regarding the black crusts of Cairo, results suggest that the air pollution in Cairo is mainly related to vehicular traffic. Indeed, in the city there is high vehicular traffic almost 24 h a day and the direct impact of vehicle emissions is particularly severe. Samples from the Venice show different composition in terms of heavy metals with respect to Cairo that can be explained with the emission from several industries sited in the near industrial center of Porto Marghera and Island of Murano. Moreover, the fuels used for marine transportation, which is abundant into the area, have a slight different fingerprinting in terms of metals with respect to the vehicles

Study of The Corrosion Processes On Roman And Byzantine Glasses From Northern Tunisia

The present investigation focuses on some glass objects among those discovered in an area around the ancient city of Thugga in northern Tunisia, particularly flourishing during the Roman and Byzantine periods (1). The Late Roman-Byzantine time is not characterised by elaborate vessel shapes derived from precious metal prototypes, but rather by simpler multifunctional forms, as beakers, goblets, and dishes with similar features in the whole Mediterranean world. Also the glass composition seems to change between the 4th and the 5th century, turning to a yellowish-green or olive green colouration of the glass instead of the typical Roman blue-greenish colouration of earlier times. This new glass colouration varies further drastically in the 7th century, when a characteristic light blue-turquoise glass becomes the most widespread. A complete chemical characterization of these objects was carried out in a previous study (2) aimed to investigate the production technology including the chromophores responsible for the different shades. In the present work we have investigated the degradation and corrosion processes affecting some of these shards. It is worth to note that to ascertain the composition of the glass surfaces the analyses have been carried out by means of non-destructive techniques such as XPS (X-ray photoelectron spectroscopy), SEM-EDX (scanning electron microscopy coupled with energy dispersive X-ray analysis) and laser-ablation ICP-MS ((Inductively Coupled Plasma \u2013 Mass Spectrometry)

An electromagnetic simulator for sentinel-3 sar altimeter waveforms over land part ii: forests

Forests play a crucial role in the climate change mitigation by acting as sinks for carbon and, consequently, reducing the CO2 concentration in the atmosphere and slowing global warming. For this reason, above ground biomass (AGB) estimation is essential for effectively monitoring forest health around the globe. Although remote sensing–based forest AGB quantification can be pursued in different ways, in this work we discuss a new technique for vegetation observation through the use of altimetry data that has been introduced by the ESA-funded ALtimetry for BIOMass (ALBIOM) project. ALBIOM investigates the possibility of retrieving forest biomass through Copernicus Sentinel-3 Synthetic Aperture Radar Altimeter (SRAL) measurements at Ku- and C-bands in low- and high-resolution mode. To reach this goal, a simulator able to reproduce the altimeter acquisition system and the scattering phenomena that occur in the interaction of the radar altimeter pulse with vegetated surfaces has been developed. The Tor Vergata Vegetation Scattering Model (TOVSM) developed at Tor Vergata University has been exploited to simulate the contribution from the vegetation volume via the modelling of the backscattering of forest canopy through a discrete scatterer representation. A modification of the SAVERS (Soil And Vegetation Reflection Simulator) simulator developed by the team for Global Navigation Satellite System Reflectometry over land has also been taken into account to simulate the soil contribution

The lady vanishes: what's missing from the stem cell debate

Most opponents of somatic cell nuclear transfer and embryonic stem cell technologies base their arguments on the twin assertions that the embryo is either a human being or a potential human being, and that it is wrong to destroy a human being or potential human being in order to produce stem cell lines. Proponents’ justifications of stem cell research are more varied, but not enough to escape the charge of obsession with the status of the embryo. What unites the two warring sides in ‘the stem cell wars’ is that women are equally invisible to both: ‘the lady vanishes’. Yet the only legitimate property in the body is that which women possess in their reproductive tissue and the products of their reproductive labour. By drawing on the accepted characterisation in law of property as a bundle of rights, and on a Hegelian model of contract as mutual recognition, we can lessen the impact of the tendency to regard women and their eggs as merely receptacles and women’s reproductive labour as unimportant

Archaeometric approach for the study of mortars from the underwater archaeological site of Baia (Naples) Italy: Preliminary results

This work was aimed to evaluate the features of mortar samples taken from the underwater archaeological area of Baia (Naples, Italy), an important site, where the remains of the ancient Roman city of Baiae and Portus Iulius are submerged after bradyseism events, started from 4th century AD. Several architectural structures are still preserved into the submerged environment, such as: luxurious maritime villas, imperial buildings, private houses, thermae, tabernae and warehouses. In particular, some samples were collected from the masonry walls belonging to a building of the underwater area called Villa a Protiro. A first archaeometric approach has been applied to analyse twelve archaeological mortars samples in order to define: textural features, chemical composition and raw materials used for their production. For this purpose different analytical methods were used, such as, polarizing optical microscope (POM) and scanning electron microscopy (SEM-EDS).This work was financially supported by national national research project “COMAS” (Planned COnservation, “in situ”, of underwater archaeological artifacts), funded by the Italian Ministry of Education, Universities and Research (MIUR).Peer reviewe

An indoor air quality study at the Ambrosiana Art Gallery (Milan)

Indoor air quality in historical buildings and museums is receiving increasing concern nowadays among the scientific community. Many sources of pollutants, both gases and particles, are responsible for the accelerated decay of the works of art. Knowing the levels of indoor pollutants is of critical importance to apply conservation and preservation strategies of cultural heritage [1, 2]. Air quality at the Ambrosiana Art Gallery in Milan has been monitored (in the two periods October-November 2017 and March 2018) inside the room where the preparatory cardboard of the School of Athens (1509-1511), one of most important masterpieces by Raffaello Sanzio, is stored. The cardboard is currently undergoing restoration and will be exposed in a new showcase that will be realized according to the specific environmental and microclimatic conditions of the room. The objective of this study was to monitor the concentration and chemical composition of the aerosol particulate matter (PM) up to the nano fraction, which represents the most dangerous fraction for the works of art surfaces. The monitoring campaigns have been carried out in parallel in the Raffaello room (at present not accessible to visitors) and in a nearby room open to visitors. The set of instuments employed included: a TSP sampler (total suspended particles) (Tecora, Pollution Check, Bravo M2); a DustMonit (Contec) analyzer that measures the concentration of dust up to PM1 and provides 13 granulometric classes (up to 300 nm); a NanoScan Nanoparticle sizer 3910 (TSI) instrument that measures particles concentration up to 10 nm; two instruments for the determination of black carbon (BC) in continuous and in particular a SILIIS instrument (Sphere-Integrated Laser Induced Incandescence Spectroscopy) and a micro aethalometer (AE51 Magee Scientific). Quartz fiber filters have been employed to collect TSP samples to be submitted to chemical analysis. The filters have been fully chemically characterized: main ionic constituents and the carbonaceous fraction (i.e organic carbon, OC and elemental carbon, EC) have been analyzed by IC (ion chromatography) and TOT (thermal optical transmittance) respectively. A particles morphological characterization has been carried out on PM collected on polycarbonate filters by means of SEM-EDX (scanning electron microscopy coupled with energy dispersive X-ray spectroscopy). Outdoor PM concentrations, obtained for the two seasons (autumn 2017 and spring 2018) from ARPA monitoring stations placed in the city center, have been correlated with indoor data