112,035 research outputs found
Planar slow wave structures for millimeter-wave vacuum electron devices
No full text<p>Underlying data corresponding to the conference paper: G. Ulisse, V. Krozer, "Planar slow wave structures for millimeter-wave vacuum electron devices", 47th European Microwave Conference (EuMC), Nuremberg, Germany, October 2017</p>
Interaction of guided electromagnetic waves with defects emerging in metallic plates
No full textUltra-wideband guided electromagnetic waves have been recently adopted to detect damage in structures. Transmission and reflection coefficients are indeed sensitive to any defect within the waveguide and can potentially warn the presence of hidden failures. Within this context, the paper shows a detection and localization approach for a structural health monitoring system based on elctromagnetic sensors permanently integrated with the structure to be monitored. A metallic plate is equipped with a dielectric waveguide patch attached to the structure's surface and a multi-input multi-output approach is adopted to interrogate the host component characterized by a reversible defect in different position. The findings show the sensitivity of transmission and reflection loss to the defect presence in between 3-20 GHz. Furthermore, an optimal frequency band beyond 12-15 GHz can be generally found. Based on wave spectrum changes, damage indicators result reliable means of detection. On top of that, they can be further elaborated to reconstruct and localize the defect. Both the amplitude and the phase of the signals are worth being investigated as detection and localization features
Elliptical monopole antenna design for the early breast cancer imaging at high frequencies
No full textThis paper presents a design of an ultra-wideband, slotted, elliptical monopole antenna for breast cancer imaging. The antenna has a compact size of 9 mm × 7 mm to cover the frequency range from 16 to 24 GHz. Its operation is optimized to direct contact with the patient breast's skin without any coupling medium. On top of that, the antenna also features as an electrode for the electrical impedance tomography (EIT) applications. Experimental results on a female volunteer's breast verify the excellent microwave performance of the antenna. In addition, the results also indicate the reliability of the breast tissues models, which were used in the simulation. Finally, a simple EIT measurement setup also demonstrates the multi- functional detection capabilities from the antenna element
ASSESSMENT OF DAMAGE IN METALLIC PLATES BY ULTRA-WIDEBAND GUIDED ELECTROMAGNETIC WAVES
No full textGuided electromagnetic wave propagation using ultrawideband signals is a barely new approach for damage detection. However, still many challenges are present, including the way to deal with the GHz domain signals and the physics behind the interaction phenomena enabled by any type of flaw. The present work proposes a feasibility analysis for a structural health monitoring system employing permanently integrated microwave sensors. This setup allows to interrogate the structure continuously using multiple transmitters and multiple receivers when the electromagnetic waveguide is established. To this end, a metallic plate is equipped with a dielectric waveguide patch attached to the structures' surface. To validate the detectability of damage, a reversible defect is modeled through removable bolts accessible from the other surface of the plate. The experiments are carried out considering different bottom holes at different spatial locations of the plate. In addition, concurrent measurements are adopted to characterize the noise level within the signal. The characteristic changes of electromagnetic wave signals are caught using a damage index approach returning whether the defect can be detected sensitively or not. Different coupling conditions are used to let the guided electromagnetic waves propagate and interact with underlaying structure. The results show that this approach can be adopted for damage detection with a reasonable signal to noise ratio, especially when the waveguide is well coupled. In addition, both transmission and reflection loss can be monitored reliably
Ultra-wideband microwave leakage monitoring for stringer debonding detection in carbon composite fuselage structures
No full textUltra-wideband guided electromagnetic waves have been proposed recently for non-destructive testing and structural health monitoring applications. However, many possibilities are still unexplored given by the multitude of possible microwave waveguides. The present work introduces the concept of microwave leakage monitoring to detect stringer debondings in hollow carbon composite structures. The principle is to monitor the wave propagation characteristics within the cavity formed by the stringer and the airframe skin using transmission measurements. Changes in the transmission path, e.g. occurring from microwave leakage in the debonded region, can be assessed through a damage indicator approach.
To proof this concept, an experimental campaign was carried out according to the building block approach typically used in aeronautics. First, a small-scale specimen with a debonded stringer was investigated in the laboratory. Then, a large-scale fuselage structure was used for technology demonstration enabling stringer debonding with increasing severity through static and fatigue loading. The paper shows that the microwave characteristics in the waveguide (stringer tunnel) is affected by the debonding conditions according to its severity and depth. This allows designing a structural health monitoring system based on guided electromagnetic waves trapped in the tunnel
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Breast Cancer Imaging using a 24 GHz Ultra-Wideband MIMO FMCW Radar: System Considerations and First Imaging Results
No full textMicrowave imaging for breast cancer detection has been widely studied as an alternative technique to the conventional X-ray mammography. The systems developed until now operate at frequencies of a few gigahertz. This limits the achievable image quality. Higher operational frequencies are advantageous for achieving a better resolution, at the expense of a lower penetration depth. The downscaling of components together with an integrated radar transceiver would lead to the development of a compact and cost-effective radar imaging system. This paper investigates the possibility of using an integrated ultra-wideband frequency-modulated continuous-wave (FMCW) radar system operating at a center frequency of 20 GHz and bandwidth of 8 GHz for breast cancer imaging. System considerations are developed to assess the tumor detectability based on the signal attenuation within the breast and the radar sensitivity. A numerical simulation is conducted and first imaging results are presented
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Folded wave guide TWT for 92 – 95 GHz band outdoor wireless frontend
No full text<p>Underlying data from the conference paper: C. Paoloni, F. André, V. Krozer, R. Zimmermann, Q.T. Le, R. Letizia, S. Kohler, A. Sabaawi, G. Ulisse, “Folded wave guide TWT for 92 – 95 GHz band outdoor wireless frontend”, Workshop on Microwave Technology and Techniques (MTT), ESA/ESTEC, The Netherlands, April 2017.</p>
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