1,721,069 research outputs found
Numerical quantitative evaluation of the skin impact in breast cancer imaging at mm-waves
No full textIn this paper, a quantitative evaluation of the skin impact on mm-wave imaging systems for breast cancer detection is presented. Different scenarios, considering both homogeneous (skin + fat) and heterogeneous (skin + fat + fibro glandular) breast, were evaluated in a frequency range from 26.5 to 40 GHz. To take into account the dielectric and propagation losses, together with the reflection at the interfaces, the simulated results for both planar and full-wave scenarios were compared. All simulations were performed by using the software Ansys HFSS. The link budget was evaluated considering several constraints (i.e., the maximum transmitting power, the noise-floor of the Vector Network Analyzer, the maximum scan time), together with the possible improving factor due to the expected utilization of a multi-static radar configuration in the final system. Results show that a target up to 4 cm in fat under a 2-mm skin is reachable with a standard VNA, while a dedicated electronic is required in presence of fibro-glandular tissue
A novel approach for calculating the internal layers of snowpacks using a S-band radar
No full textIn the last years, the development of new ground-based techniques for studying the snowpack has tried to fill the gap between satellite and manual techniques. In particular, ground-based radars are considered a very useful technology for their ability to sound relatively deep snowpacks in a non-destructive way. Obtaining the bulk physical parameters of the snowpack (density, liquid water content...) has been successfully done using ground-based radars by several research groups, however, estimating the internal structure of the snowpack remains as a challenge due, mainly, to technological limitations. This work presents a novel quasi-automatic approach to estimate the internal structure of the snowpack, in terms of density and liquid water content (LWC), based in a double receiver S-band radar. The approach is validated with numerical simulations and the very first field results
Mixed Analytical-Numerical Modeling of Radar Backscattering for Seasonal Snowpacks
No full textThe intensity of the backscattered signal collected by active radars over wet, seasonal snowpacks depends on numerous variables related to the snowpack, which are often difficult to determine accurately. In recent years, thanks to the increased availability of spaceborne synthetic aperture radars (SARs), a temporal relationship between wet-snow metamorphism and microwave backscattering has been demonstrated. However, a precise quantitative description of this phenomenon has yet to be fully determined. In this article, we propose a new mixed analytical-numerical model to describe the effect of the physical parameters related to the wet snowpack metamorphism on the intensity of the backscattering at L, C, and X bands, with a focus on high alpine snowpacks. Particular attention was paid to integrate the effects of the snow superficial roughness and the snow scattering. The model is first applied to several simulated snowpacks and then validated against a real multitemporal SAR signature acquired by Sentinel-1 over the snow station of Malga Fadner (South Tyrol, Italy) and of Torgnon (Aosta Valley, Italy). The comparison between the model outcomes and the satellite data were in good agreement, leading to the possibility of using such method for operational identification of the run-off phase from remote locations
A Novel PIFA Antennas Design With Capacitive Load for Glacier Monitoring Applications
No full textIn glaciology, Ground Penetrating Radar (GPR) are frequently used to characterize electrical and physical properties of glaciers and snow coverages. An application is the estimation of the snow water equivalent of glaciers, coming from the knowledge of internal features of the glacier itself, such as its depth and density. For glacier monitoring, the usual frequencies space from few MHz to hundreds of MHz. Depending on the compromise between the penetration depth and the spatial resolution, the working frequency was determined. In this work, we designed, developed and measured a 300 MHz antenna used for this purpose. The shape and size were modeled in order to be used in portable systems; therefore, it was important to have light and small radiators. For this reason, we implement a novel planar inverted-F antenna (PIFA) design with capacitive load, reaching small dimensions compared to the wavelength
Glacier Monitoring with Dual-Receiver Radar Architecture: Preliminary Experimental Results
No full textGlaciers are nowadays becoming a more and more important topic to investigate, due to their close relationship with the climate change and impact on people living in mountainous areas. For this reason, the researches on new, faster, non-destructive and valuable techniques to monitor such natural bodies became necessary. In this framework, an already-existed radar dual-receiver architecture, used in recent years for snowpack monitoring, has been tailored to be used for the first time for glacier monitoring. After some improvements of the system, the radar architecture was tested in the Italian Alps, more precisely at the Cherillon glacier (Valle d'Aosta). The preliminary results show a good agreement with the traces collected by a Ground Penetrating Radar (GPR) in 2019 for what concerns glacier depth, when a speed for the wave in the ice is assumed. However, the dual-receiver architecture demonstrated that it was capable of estimating independently not only the glacier depth, but also the wave speed, opening in addition the analysis to further possibilities
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On the effects of struts diameter and shape on the European Space Agency deep space antenna directivity and first side lobe
No full textLarge reflector antennas, such as the European Space Agency deep space antennas (DSAs), practically always require struts to support the sub-reflector. While inevitable, they deteriorate the antenna performance. To minimize this deterioration, it is pivotal to understand the role played by different features, including struts diameter and shape. This paper proposes a detailed numerical investigation on the impact of these features on antenna efficiency and side lobes, for a test case comprising both DSA3 and DSA4. It is demonstrated, for the first time in a comprehensive and quantitative way that includes different permutations for the strut design, that both features are significant to define the deterioration, thus providing a significant feedback for struts design
Comparative Study on the Design of Dichroic Mirrors for the Upgrade to the K-band uplink channel for the ESA Deep Space Antennas
No full textDielectric Characterization of Snow at 24 GHZ: Insights from a Low-Cost Radar in Sodankyla, Finland
No full textMonitoring the internal structure of the snowpack is imperative for managing snow-related hazards like avalanches and snowmelt floods. The surge in availability of cost-effective, low-power, and low-profile 24 GHz frequency-modulated continuous-wave (FMCW) radars, originally designed for the automotive sector, has opened new possibilities. This paper illustrates the application of a compact and economical FMCW radar to enhance snowpack studies by swiftly providing the dielectric properties of snow and potentially assessing density and liquid water content (LWC). The radar functions as a snowpit instrument, creating expedited snow profiles of dielectric properties, aiming to overcome the drawbacks of slower, operator-dependent traditional density cutters. Initial results showcase the real part of the relative dielectric permittivity in actual snow conditions. Results are compared with manual measurements directly taken in the snowpit and with the bulk measurements taken with a well-established multi-band radar
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