Exponential Modular Multilevel Converter for Low Voltage Applications

This paper presents the structure and control of a single phase Exponential Modular Multilevel Converter (EMMC), which works as a bidirectional AC/DC converter. In addition to the main H-bridge converter, it uses series connected H-bridges with DC link capacitors. The nominal voltage rating of the capacitors is increased with each module by factor of two. In this manner, the number of output voltage levels exponentially increases with the number of series connected H-bridges. By using low-voltage MOSFETs it is possible to achieve a very high efficiency, especially at partial loading. The high number of voltage levels reduces the output voltage THD, while using a low switching frequency. Thus, the required grid filter size can be substantially reduced. Furthermore, the additional capacitor modules increase the nominal output voltage at the AC side, so that the flow of the active and reactive power can be dynamically adjusted. Therefore, the EMMC could be used, for instance, as a vehicle charger directly connected to the grid

Quantification of myocardial deformation in children by cardiovascular magnetic resonance feature tracking: determination of reference values for left ventricular strain and strain rate

Background: The objective assessment of global and regional cardiac function in children has shown to be clinically relevant but is challenging to conduct. Cardiovascular magnetic resonance (CMR) has emerged as a valuable diagnostic modality especially in patients with cardiomyopathy or congenital heart disease. However, data on the normal cardiac deformation in children assessed by CMR is lacking at present. Thus, the aim of this study was to provide reference values for cardiac strain and strain rate in children and adolescents derived from CMR feature tracking (FT) measurements. Methods: In this binational study, eighty children and adolescents (age 0.4–18.0 years, 41 male, 39 female) free from cardiac diseases from two centers underwent CMR in 1.5 T whole-body scanners in supine position. Global peak radial, circumferential and longitudinal systolic strains as well as the corresponding early peak diastolic strain rates were assessed applying FT on short axis as well as 3- and 4-chamber views of standard cine steady-state free precession images. Results: The difference between genders yielded no significance for all assessed strains. Yet, all strains showed a significant parabolic relation to age and an even stronger one to body surface area (BSA). Therefore, BSA-specific reference values were determined using a polynomial regression model. The apical cardiac segments featured significant higher peak circumferential but lower peak radial systolic strains than the midventricular and basal segments (all p < 0.001). Conclusions: The assessment of cardiac deformation by CMR-FT is feasible in children. This is the first CMR study providing specific reference values for FT-derived strain and strain rate in the pediatric age range

Atomization of Borosilicate Glass Melts for the Fabrication of Hollow Glass Microspheres

Direct atomization of a free-flowing glass melt was carried out using a high-speed flame with the aim of producing tiny, self-expanding glass melt droplets to form hollow glass microspheres. Atomization experiments were carried out using a specially adapted free-fall atomizer in combination with a high-power gas burner to achieve sufficient temperatures to atomize the melt droplets and to directly expand them into hollow glass spheres. In addition, numerical simulations were carried out to investigate non-measurable parameters such as hot gas velocities and temperatures in the flame region by the finite volume-based software Star CCM+® (v. 2022.1.1), using the Reynolds-Averaged Navier–Stokes (RANS) turbulence and the segregated flow model. To calculate the combustion process, the laminar flamelet method was used. The experiments and simulations indicated that a maximum gas velocity of about 170 m/s was achieved at the point of atomization in the flame. The particle size distribution of the atomized glass droplets, either solid or hollow, ranged from 2 µm to 4 mm. Mean particle sizes in the range of 370 µm to 650 µm were highly dependent on process parameters such as gas velocity. They were in good agreement with theoretically calculated median diameters. The formation of hollow glass microspheres with the proposed concept could be demonstrated. However, only a small fraction of hollow glass spheres was found to be formed. These hollow spheres had diameters up to 50 µm and, as expected, a thin wall thickness

Quantification of myocardial deformation in children by cardiovascular magnetic resonance feature tracking: determination of reference values for left ventricular strain and strain rate

Abstract Background The objective assessment of global and regional cardiac function in children has shown to be clinically relevant but is challenging to conduct. Cardiovascular magnetic resonance (CMR) has emerged as a valuable diagnostic modality especially in patients with cardiomyopathy or congenital heart disease. However, data on the normal cardiac deformation in children assessed by CMR is lacking at present. Thus, the aim of this study was to provide reference values for cardiac strain and strain rate in children and adolescents derived from CMR feature tracking (FT) measurements. Methods In this binational study, eighty children and adolescents (age 0.4\u201318.0\ua0years, 41 male, 39 female) free from cardiac diseases from two centers underwent CMR in 1.5\ua0T whole-body scanners in supine position. Global peak radial, circumferential and longitudinal systolic strains as well as the corresponding early peak diastolic strain rates were assessed applying FT on short axis as well as 3- and 4-chamber views of standard cine steady-state free precession images. Results The difference between genders yielded no significance for all assessed strains. Yet, all strains showed a significant parabolic relation to age and an even stronger one to body surface area (BSA). Therefore, BSA-specific reference values were determined using a polynomial regression model. The apical cardiac segments featured significant higher peak circumferential but lower peak radial systolic strains than the midventricular and basal segments (all p \u2009<\u20090.001). Conclusions The assessment of cardiac deformation by CMR-FT is feasible in children. This is the first CMR study providing specific reference values for FT-derived strain and strain rate in the pediatric age range

Additional file 1: Table S1. of Quantification of myocardial deformation in children by cardiovascular magnetic resonance feature tracking: determination of reference values for left ventricular strain and strain rate

Centiles of the global peak longitudinal endocardial systolic strain derived only from 4-chamber views. Table S2. Centiles of the global peak longitudinal epicardial systolic strain derived only from 4-chamber views. Table S3. Centiles of the early peak longitudinal endocardial diastolic strain rate derived only from 4-chamber views. Table S4. Centiles of the early peak longitudinal epicardial diastolic strain rate derived only from 4-chamber views. (PDF 654 kb

Search for dark matter in association with an energetic photon in pp collisions at s = 13 TeV with the ATLAS detector

Abstract: A search for dark matter is conducted in final states containing a photon and missing transverse momentum in proton-proton collisions at s = 13 TeV. The data, collected during 2015–2018 by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 fb−1. No deviations from the predictions of the Standard Model are observed and 95% confidence-level upper limits between 2.45 fb and 0.5 fb are set on the visible cross section for contributions from physics beyond the Standard Model, in different ranges of the missing transverse momentum. The results are interpreted as 95% confidence-level limits in models where weakly interacting dark-matter candidates are pair-produced via an s-channel axial-vector or vector mediator. Dark-matter candidates with masses up to 415 (580) GeV are excluded for axial-vector (vector) mediators, while the maximum excluded mass of the mediator is 1460 (1470) GeV. In addition, the results are expressed in terms of 95% confidence-level limits on the parameters of a model with an axion-like particle produced in association with a photon, and are used to constrain the coupling gaZγ of an axion-like particle to the electroweak gauge bosons

Search for doubly and singly charged Higgs bosons decaying into vector bosons in multi-lepton final states with the ATLAS detector using proton-proton collisions at s\sqrt{\mathrm{s}} = 13 TeV

A search for charged Higgs bosons decaying into W$^±$W$^±$ or W$^±$Z bosons is performed, involving experimental signatures with two leptons of the same charge, or three or four leptons with a variety of charge combinations, missing transverse momentum and jets. A data sample of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb$^{−1}$. The search is guided by a type-II seesaw model that extends the scalar sector of the Standard Model with a scalar triplet, leading to a phenomenology that includes doubly and singly charged Higgs bosons. Two scenarios are explored, corresponding to the pair production of doubly charged H$^±$$^±$ bosons, or the associated production of a doubly charged H$^±$$^±$ boson and a singly charged H$^±$ boson. No significant deviations from the Standard Model predictions are observed. H$^±$$^±$ bosons are excluded at 95% confidence level up to 350 GeV and 230 GeV for the pair and associated production modes, respectively