Efficient Electromagnetic Modelling of Complex Structures

Part 1. Space vehicles re-entering earth's atmosphere produce a shock wave which in turns results in a bow of plasma around the vehicle body. This plasma signicantly affects all radio links between the vehicle and ground, since the electron plasma frequency reaches beyond several GHz. In this work, a model of the propagation in plasma issue is developed. The radiofrequency propagation from/to antennae installed aboard the vehicle to the ground stations (or Data Relay Satellites) can be predicted, and the position of this antennae improved before a mission launch. Part 2. The Surface Integral Equation is one of the most used methods in the simulation of electromagnetic problems. The method used a discretized description of the surface on which a number of basis functions are needed. In the case of multi-scale structures, the test-object has regions with high details that require a fine mesh, together with flat surfaces where the current can be properly described with a coarser mesh. The goal of this work is to develop an automatic tool that identies the regions to be refined in a initial coarse mesh (dened only by geometry) using electromagnetic characteristics of the problem. It avoid the use of more unknowns that the actually needed (computational cost) and permits use a geometric mesh as base for different problems, adapting to each electromagnetic incidence automatically

Efficient Electromagnetic Modelling of Complex Structures

Part 1. Space vehicles re-entering earth's atmosphere produce a shock wave which in turns results in a bow of plasma around the vehicle body. This plasma signicantly affects all radio links between the vehicle and ground, since the electron plasma frequency reaches beyond several GHz. In this work, a model of the propagation in plasma issue is developed. The radiofrequency propagation from/to antennae installed aboard the vehicle to the ground stations (or Data Relay Satellites) can be predicted, and the position of this antennae improved before a mission launch. Part 2. The Surface Integral Equation is one of the most used methods in the simulation of electromagnetic problems. The method used a discretized description of the surface on which a number of basis functions are needed. In the case of multi-scale structures, the test-object has regions with high details that require a fine mesh, together with flat surfaces where the current can be properly described with a coarser mesh. The goal of this work is to develop an automatic tool that identies the regions to be refined in a initial coarse mesh (dened only by geometry) using electromagnetic characteristics of the problem. It avoid the use of more unknowns that the actually needed (computational cost) and permits use a geometric mesh as base for different problems, adapting to each electromagnetic incidence automaticall

Microwave Sensing for Food Safety: a Neural Network Implementation

Customers’ attention in packaged food quality is arising in the last few years, as physical intrusions can still be found in commercialized products. Frightful newspapers articles attract consideration on this matter, and pose a serious health issue: accidental ingestion of foreign bodies can severely damage the digestive system, or even cause choking, with seniors and children being particularly exposed. Existing devices to monitor food products have lacks, missing certain classes of contaminant, low-density ones in particular, due to intrinsic limitations to their working principle, based on materials density in the case of x-rays inspection. Here, we propose a novel detection principle, based on microwave-sensing and exploiting the dielectric contrast between the potential intrusion and the surrounding matter. The realized microwave-sensing device is, then, combined with a machine-learning approach, with a classification mechanism capable in discerning clean from contaminated samples. The microwave-sensing device is applied to an industrial food production line, showing a remarkable precision in correctly detecting millimetric-sized intrusions made of plastic, glass or wood, which are the classes of materials unlikely to be located by existing inspection devices

Efficient Integral Equation Approach for the Modelling of Glide-Symmetric Structures

For the design of advanced microwave and antenna components, efficient and accurate electromagnetic methods are required. In this work, we present a technique to fast simulate mirror- and glide-symmetric periodic structures. More concretely, a novel Green’s function is proposed which allows to reduce the computational domain to one half of the unit cell. Full dispersion diagrams are computed for metallic glide- and mirror-symmetric structures with three stages of mesh refinement. The results converge with the meshing and agree well with conventional eigenmode analyses

Reentry vehicles: evaluation of plasma effects on RF propagation

In the frame of communication technology relevant to the re-entry vehicles, the communication black-out occurring in the presence of plasma is one of the main challenging issues. The re-entry plasma is a complex physical system, where the ionization derives from a shock-wave and non-equilibrium phenomena. As discussed elsewhere, the time scales of plasma dynamics (including its evolution along mission trajectory) and radio wave propagation are well separated so that radio wave propagation is solved at an appropriate number of time "snapshots" in which plasma dynamics is held unchanged and considered as known. In this activity, a consistent effort has been devoted to model the electromagnetic problem. For the involved range of oprative frequencies and expected densities, the plasma can be considered as an inhomogeneous dielectric. The associated electromagnetic problem is solved in two steps, via use of the field equivalence principle. The vehicle-plasma system is substituted by equivalent (Love's) currents on its boundary, radiating in free space; the fields at the boundary are obtained by solving the propagation problem from the antenna, installed on the spacecraft, up to the plasma boundary, through the Eikonal approximation. Radiation is then obtained without further approximations. Unlike other well-known numerical methods (e.g. FEM), this technique is not intrinsecally limited by the electrical dimension of the vehicle-plasma system. This enables to analyze high frequency problems. Since the formation of the re-entry plasma critically depends on the re-entry vehicle shape and kinematics, the related model has been directly derived from the output data of the Computational Fluid Dynamics simulations. All the results of the above mentioned activities have been collected in a new software, the AIPT (Antenna In Plasma Tool, integrated into ADF-EMS Antenna Design Framework Electromagnetic Satellite) able to predict the electromagnetic propagation in the presence of plasm

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

System and method for spatially detecting any foreign bodies within a product on the basis of dielectric characteristics of said product

The present invention relates to a system (100) for spatially detecting any foreign bodies within a product (135) on the basis of dielectric characteristics of said product (135), said system (100) comprising: conveyor means (150) adapted to convey said product (135) through a scanning region (S) along a crossing direction (L), in a predefined crossing time interval (T) for crossing said scanning region (S); a plurality of antennae (200) arranged transversally to said crossing direction (L), wherein each antenna (210) of said plurality of antennae (200) is adapted to operate in the microwave range, and wherein each antenna (210) is adapted to transmit an electromagnetic scanning signal adapted to propagate in said scanning region (S), so as to diffuse in said product (135); processing means (250) adapted to generate a first set of values indicative of the dielectric characteristics of said product (135) based on at least one diffused electromagnetic signal received by at least one antenna (210) of said plurality of antennae (200), said processing means (250) being adapted to compare said first set of values with a second set of values indicative of the dielectric characteristics of said product (135) in the absence of any foreign bodies,wherein each antenna (210) of said plurality of antennae (200) is adapted to transmit said electromagnetic scanning signal at least once in said crossing time interval (T), according to a predefined transmission frequency