2,292 research outputs found
Risk for chronic kidney disease in high school students: Italian report for World Kidney Day 2008-2009
No full textWorld Kidney Day (WKD) was conceived in 2003 to inform the general population of the fact that chronic kidney dis- ease is a global, public health threat that frequently occurs with no symptoms, and which can be treated with early detection using simple and inexpensive methods (1). The need for a WKD devoted to kidney diseases arises also from the knowledge that most people are unaware of their blood pressure and the potential presence of abnormalities in their urine. Indeed, some surveys have shown that less than 5% of the general population know where the kidneys are lo- cated and what they d
Frequency Diverse Array for Signal Geofencing in Wireless Communications: Does It Work ?
No full textFrequency Diverse Array is an advanced antenna technology for clustering received power spatial distribution in specific areas, which has shown significant potential in many applications, including radar or wireless power transfer. In wireless communications, signal geofencing might be beneficial in increasing communication secrecy or reduce interference issues, but system communications through frequency diverse arrays require careful consideration about several design parameters. In this paper, a detailed analysis of the sensitivity of the geofencing effectiveness to the main array parameters is carried out. The analysis covers many aspects of the design, including the selection of the geometrical layout and the number of elements of the array, the frequency increase policy and the frequency offset across the elements and their spacing. The study also discusses the trade-offs between different design choices and provides insights into the performance in terms of focus efficiency and size of the focus area. Results show that bidimensional layouts, e.g. circular or planar, often represent effective solutions, whereas the linear arrangement can be a viable option only in case the frequencies are spread across the elements in a random-like fashion. Frequencies are usually increased according to either a logarithmic or a linear policy. The linear solution in general yields lower performance, but also lower complexity. Frequency offset, number of elements and their spacing represent further project parameters. Finally, a preliminary assessment of the multipath effect on the focus task shows that the performance of frequency diverse arrays can be affected by complex propagation conditions and deserve further investigations
Automatically switchable two-way rectifier
No full textThis work proposes a novel design of a modular rectifier for seamless operation in a wide range of RF received power (PRX). The solution adopts a set of rectifiers, each one optimized for a specific power range, connected in such a way that, for any incoming RF power, the most suitable one is activated, with no need for external biases to activate switches or complex control logic. Thus, the operation is fully energy-autonomous. In this work the idea is demonstrated with two rectifiers: a low-power one (RECTLOW), for the range -15 to 0 dBm and a high power one (RECTHIGH), for the range 0 to 15 dBm. Two P-HEMT-based switching circuits are located along the rectifiers RF and dc paths, respectively, and are normally OFF over the power range of -15 to 0 dBm. In such conditions the isolation between RECTLOW and RECTHIGH is about 10 dB, which allows RECTLOW to operate in its high efficiency conditions. When PRX exceeds 0 dBm, a small amount of power is leaked into RECTHIGH so that a reduced dc-voltage is available at its dc output. This voltage, by means of a limiter, controls the P-HEMPT gates, thus creating a feedback system: if PRX further increases, the P-HEMPTs are turned ON and RECTHIGH starts operating, while the path to RECTLOW is inhibited. The whole system has been tested over the entire power range and shows an RF-to-dc efficiency equivalent to the one obtained by the standalone rectifiers
Multi-Frequency SAR Data for an Effective Maritime Domain Awareness
No full textThis paper presents the findings of the COAST project, an innovative investigation into maritime surveillance using Synthetic Aperture Radar (SAR) technology, funded by the Italian Space Agency. The research specifically delves into the synergistic potential of a multi-frequency/multi-mission (MFMM) approach to detect and identify vessels, a facet relatively unexplored in previous studies. Four technical objectives drive the study, including the detection of both visible and non-visible non-cooperating ships and their classification using SAR tomography techniques, as well as AIS/SAR data matching with velocity estimation. This research promises to enhance maritime domain awareness and security by furthering our understanding of SAR-based vessel detection and classification methodologies
A NEW DATASET OF MULTI-MISSION/MULTI-FREQUENCY SAR DATA FOR MARITIME MONITORING: FIRST RESULTS AND CRITICAL ANALYSIS
No full textThis paper evaluates the capabilities offered by the synergic exploitation of multi-frequency and multimission Synthetic Aperture Radar (SAR) images for the enhancement of Maritime Situational Awareness (MSA). Nowadays, SAR-based ship detection methodologies have proven their effectiveness in overpassing current limitations of existing monitoring systems based on Automatic Identification System (AIS). However, SAR potential for maritime surveillance is still underutilized, e.g., the fusion among data gathered by different SAR missions. A new database of multi-mission/multi-frequency SAR data has been recently developed by the authors in the framework of the COAST project, funded by the Italian Space Agency. The dataset includes COSMO-SkyMed, SAOCOM, and Sentinel-1 images collected over the same areas with less than 15 minutes time lag between consecutive acquisitions. The preliminary analysis of the data set has been just completed revealing the value of multi-mission/multi-frequency SAR data for MSA
- …
