OKREŚLENIE OPTYMALNEGO KROKU SKANOWANIA DO OCENY JAKOŚCI REKONSTRUKCJI OBRAZU W TOMOGRAFII MAGNETOAKUSTYCZNEJ ZE WZBUDZENIEM INDUKCYJNYM

Magnetoacoustic Tomography with Magnetic Induction (MAT-MI) is a new hybrid imaging modality especially dedicated for non-invasive electrical conductivity imaging of low-conductivity objects such as e.g. biological tissues. The purpose of the present paper is to determine the optimal scanning step assuring the best quality of image reconstruction. In order to resolve this problem a special image reconstruction quality indicator based on binarization has been applied. Taking into account different numbers of measuring points and various image processing algorithms, the conditions allowing successful image reconstruction have been provided in the paper. Finally, the image reconstruction examples for objects’ complex shapes have been analyzed.Tomografia magnetoakustyczna ze wzbudzeniem indukcyjnym (MAT-MI) to nowa hybrydowa technika obrazowania dedykowana szczególnie do nieinwazyjnego obrazowania obiektów o niskiej konduktywności elektrycznej, takich jak na przykład tkanki biologiczne. Celem niniejszej pracy jest określenie optymalnego kroku skanowania zapewniającego najlepszą jakość rekonstrukcji obrazu. W celu rozwiązania tego problemu zastosowano specjalny wskaźnik jakości rekonstrukcji obrazu bazujący na binaryzacji. W artykule przedstawiono warunki umożliwiające pomyślne zrekonstruowanie obrazu biorąc pod uwagę różną liczbę punktów pomiarowych oraz różne algorytmy przetwarzania obrazu. W końcowym etapie pracy przeanalizowano przykłady rekonstrukcji obrazu dla obiektów o bardziej złożonych kształtach

NUMERYCZNE ASPEKTY ODWZOROWANIA WTÓRNEGO POLA MAGNETYCZNEGO W MAGNETYCZNEJ TOMOGRAFII INDUKCYJNEJ

Magnetic Induction Tomography (MIT) belongs to the noncontact electromagnetic imaging techniques. This paper focuses on determination of a secondary magnetic field map calculated with the help of the Biot-Savart law around the low-conductivity object. The inclusions of various shapes and different electrical conductivities values and two measurement planes are considered. In each case the objects’ single maximal cell volume with assumed uniform eddy current density has been determined. In order to keep the relative error below 1% the object should be divided in most cases into elements with maximal cell volume equal to 0.244 mm3 for yz − plane, and 0.03 mm3 for xy − plane.Magnetyczna Tomografia Indukcyjna (MIT) należy do bezkontaktowych, elektromagnetycznych technik obrazowania. Artykuł skupia się na wyznaczeniu mapy wtórnego pola magnetycznego obliczonego za pomocą prawa Biota-Savarta wokół obiektu słaboprzewodzącego. Przeanalizowano wtrącenia o różnym kształcie i różnej wartości konduktywności elektrycznej oraz dwie płaszczyzny pomiarowe. W każdym przypadku została wyznaczona maksymalna objętość pojedynczej komórki obiektu z założoną stałą wartością gęstości prądu. W celu uzyskania błędu względnego poniżej 1% obiekt powinien zostać podzielony w większości przypadków na elementy z maksymalną objętością równą 0,244 mm3 dla płaszczyzny yz oraz 0,03 mm3 dla płaszczyzny xy

Synthetic Image Data for Deep Learning

Realistic synthetic image data rendered from 3D models can be used to augment image sets and train image classification semantic segmentation models. In this work, we explore how high quality physically-based rendering and domain randomization can efficiently create a large synthetic dataset based on production 3D CAD models of a real vehicle. We use this dataset to quantify the effectiveness of synthetic augmentation using U-net and Double-U-net models. We found that, for this domain, synthetic images were an effective technique for augmenting limited sets of real training data. We observed that models trained on purely synthetic images had a very low mean prediction IoU on real validation images. We also observed that adding even very small amounts of real images to a synthetic dataset greatly improved accuracy, and that models trained on datasets augmented with synthetic images were more accurate than those trained on real images alone. Finally, we found that in use cases that benefit from incremental training or model specialization, pretraining a base model on synthetic images provided a sizeable reduction in the training cost of transfer learning, allowing up to 90\% of the model training to be front-loaded

Multilayer metamaterial absorbers inspired by perfectly matched layers

We derive periodic multilayer absorbers with effective uniaxial properties similar to perfectly matched layers (PML). This approximate representation of PML is based on the effective medium theory and we call it an effective medium PML (EM-PML). We compare the spatial reflection spectrum of the layered absorbers to that of a PML material and demonstrate that after neglecting gain and magnetic properties, the absorber remains functional. This opens a route to create electromagnetic absorbers for real and not only numerical applications and as an example we introduce a layered absorber for the wavelength of $8$~$\mu$m made of SiO$_2$ and NaCl. We also show that similar cylindrical core-shell nanostructures derived from flat multilayers also exhibit very good absorptive and reflective properties despite the different geometry

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