Supervised framework for COVID-19 classification and lesion localization from chest CT

Abstract Background: Quick and precise identification of people suspected of having COVID-19 plays a key function in imposing quarantine at the right time and providing medical treatment, and results not only in societal benefits but also helps in the development of an improved health system. Building a deep-learning framework for automated identification of COVID-19 using chest computed tomography (CT) is beneficial in tackling the epidemic. Aim: To outline a novel deep-learning model created using 3D CT volumes for COVID-19 classification and localization of swellings. Methods: In all cases, subjects’ chest areas were segmented by means of a pre-trained U-Net; the segmented 3D chest areas were submitted as inputs to a 3D deep neural network to forecast the likelihood of infection with COVID-19; the swellings were restricted by joining the initiation areas within the classification system and the unsupervised linked elements. A total of 499 3D CT scans were utilized for training worldwide and 131 3D CTscans were utilized for verification. Results: The algorithm took only 1.93 seconds to process the CT amount of a single affected person using a special graphics processing unit (GPU). Interesting results were obtained in terms of the development of societal challenges and better health policy. Conclusions: The deep-learning model can precisely forecast COVID-19 infectious probabilities and detect swelling areas in chest CT, with no requirement for training swellings. The easy-to-train and high-functioning deep-learning algorithm offers a fast method to classify people affected by COVID-19, which is useful to monitor the SARS-CoV-2 epidemic. [Ethiop. J. Health Dev. 2020; 34(4):235-242] Key words: COVID-19, CT scan, deep learning, neural network, DeCoVNet, RT-PCR, computed tomograph

Rolling Bearing Failure Feature Extraction Based on Large Parameters Stochastic Resonance ⋆

Based on rolling bearing fault signal modulation model in the process of spreading, an improved method that combining Hilbert envelop extraction algorithm and large parameter setting rules in stochastic resonance (SR) is proposed for features extraction. Firstly, Hilbert transform can effectively eliminate the interference of high frequency carrier signal. Secondly, parameters setting rules in a certain frequency range are summarized based on the simulation research on the realization of stochastic resonance under the condition of big parameters. Then, the improved method is used to deal with the experimental data of rolling bearing with typical faults. The experimental results show that the improved method can extract the fault feature and identify the fault type effectively

Hot Spine Loops and the Nature of a Late-Phase Solar Flare

The fan-spine magnetic topology is believed to be responsible for many curious features in solar explosive events. A spine field line links distinct flux domains, but direct observation of such feature has been rare. Here we report a unique event observed by the Solar Dynamic Observatory where a set of hot coronal loops (over 10 MK) connected to a quasi-circular chromospheric ribbon at one end and a remote brightening at the other. Magnetic field extrapolation suggests these loops are partly tracer of the evolving spine field line. Continuous slipping- and null-point-type reconnections were likely at work, energizing the loop plasma and transferring magnetic flux within and across the fan quasi-separatrix layer. We argue that the initial reconnection is of the "breakout" type, which then transitioned to a more violent flare reconnection with an eruption from the fan dome. Significant magnetic field changes are expected and indeed ensued. This event also features an extreme-ultraviolet (EUV) late phase, i.e. a delayed secondary emission peak in warm EUV lines (about 2-7 MK). We show that this peak comes from the cooling of large post-reconnection loops beside and above the compact fan, a direct product of eruption in such topological settings. The long cooling time of the large arcades contributes to the long delay; additional heating may also be required. Our result demonstrates the critical nature of cross-scale magnetic coupling - topological change in a sub-system may lead to explosions on a much larger scale.Comment: Accepted for publication in ApJ. Animations linked from pd

Determinants of Finnish High Technology Exports : An Application of Gravity Model

This paper places its focus on the largest 10 high-tech importers of Finland with the objective to investigate the determinants of Finnish high-tech exports during the period of 1996 and 2010. The Gravity Theory acts as the theoretical foundation of the study and panel data will be adopted to carry out OLS regression and fixed effects regression models. Six clusters of determinant have been introduced to the basic gravity empirical model respectively, seeking to identify categories which have the greatest effects on Finnish high-tech exports. The research finds that the variables related to information cost, labour market and high technological level are more impactful than other factors. An adjusted gravity empirical model with more than 70 per cent explanatory power is subsequently presented. The empirical results manifest that a 1 per cent increase in GDP of Finland’s major trading partners contributes to 0.35 per cent growth in Finnish high-tech exports while a 1 per cent rise in bilateral distance between Finland and its exporting destinations leads to a decline of 0.8 per cent in Finnish high-tech exports. Other independent variables included in this empirical equation are estimated to be statistically significant as well. A case study has been introduced to illustrate certain aspects of the paper as well. The adjusted gravity model together with the Reveal Comparative Advantage (RCA) index are employed to analyse the export potentials of high-tech commodities of China for Finland. The study shows that the high technology export potential is not great, and has the requisites for Finland to develop export potential of products that have comparative advantages over China’s and explore new high-tech commodities

Modelling and observations : a comparison of the magnetic field properties in a prominence

Funding: UK STFC, ERC, and Leverhulme Trust (DHM).Context. Direct magnetic field measurements in solar prominences occur infrequently and are difficult to make and interpret. As a consequence, alternative methods are needed to derive the main properties of the magnetic field that supports the prominence mass. This is important for our understanding of solar prominences, but also for understanding how eruptive prominences may affect space weather. Aims. We present the first direct comparison of the magnetic field strength derived from spectro-polarimetric observations of a solar prominence, with corresponding results from a theoretical flux rope model constructed from on-disc normal component magnetograms. Methods. We first used spectro-polarimetric observations of a prominence obtained with the magnetograph THEMIS operating in the Canary Islands to derive the magnetic field of the observed prominence by inverting the Stokes parameters measured in the He D3 line. Next, we constructed two data-constrained non-linear force-free field (NLFFF) models of the same prominence. In one model we assumed a strongly twisted flux rope solution, and in the other a weakly twisted flux rope solution. Results. The physical extent of the prominence at the limb (height and length) is best reproduced with the strongly twisted flux rope solution. The line-of-sight average of the magnetic field for the strongly twisted solution results in a magnetic field that has a magnitude of within a factor of 1−2 of the observed magnetic field strength. For the peak field strength along the line of sight, an agreement to within 20% of the observations is obtained for the strongly twisted solution. The weakly twisted solution produces significantly lower magnetic field strengths and gives a poor agreement with the observations. Conclusions. The results of this first comparison are promising. We found that the flux rope insertion method of producing a NLFFF is able to deduce the overall properties of the magnetic field in an observed prominence.Publisher PDFPeer reviewe