Neutral-point Voltage Control of Three-level NPC Inverter for Three-phase APF based on Zero-sequence Voltage Injection

© 2019 IEEE. Active Power Filters (APF) have already adopted the three-level inverter topology in medium-voltage and high-power applications for solving power-quality problems. The Neutral-point voltage clamped (NPC) Inverter because of its robustness has become a matured and broadly used topology. It is necessary to maintain the neutral-point voltage at the DC-side as close to zero as possible. The focus of this paper is on the neutral-point voltage control of the three-level NPC inverter based on multicarrier PWM by manipulating the dwell time of small vectors by injecting a zero-sequence voltage into the modulating signal. The effectiveness of the presented method on a three-level NPC inverter is validated via simulation in MATLAB/Simulink. The results confirm the efficacy of the method in maintaining the neutral-point voltage at a minimum value with the desired overall good APF compensation characteristics

Statistical shape modeling of multi-organ anatomies with shared boundaries

Introduction: Statistical shape modeling (SSM) is a valuable and powerful tool to generate a detailed representation of complex anatomy that enables quantitative analysis of shapes and their variations. SSM applies mathematics, statistics, and computing to parse the shape into some quantitative representation (such as correspondence points or landmarks) which can be used to study the covariance patterns of the shapes and answer various questions about the anatomical variations across the population. Complex anatomical structures have many diverse parts with varying interactions or intricate architecture. For example, the heart is a four-chambered organ with several shared boundaries between chambers. Subtle shape changes within the shared boundaries of the heart can indicate potential pathologic changes such as right ventricular overload. Early detection and robust quantification could provide insight into ideal treatment techniques and intervention timing. However, existing SSM methods do not explicitly handle shared boundaries which aid in a better understanding of the anatomy of interest. If shared boundaries are not explicitly modeled, it restricts the capability of the shape model to identify the pathological shape changes occurring at the shared boundary. Hence, this paper presents a general and flexible data-driven approach for building statistical shape models of multi-organ anatomies with shared boundaries that explicitly model contact surfaces.Methods: This work focuses on particle-based shape modeling (PSM), a state-of-art SSM approach for building shape models by optimizing the position of correspondence particles. The proposed PSM strategy for handling shared boundaries entails (a) detecting and extracting the shared boundary surface and contour (outline of the surface mesh/isoline) of the meshes of the two organs, (b) followed by a formulation for a correspondence-based optimization algorithm to build a multi-organ anatomy statistical shape model that captures morphological and alignment changes of individual organs and their shared boundary surfaces throughout the population.Results: We demonstrate the shared boundary pipeline using a toy dataset of parameterized shapes and a clinical dataset of the biventricular heart models. The shared boundary model for the cardiac biventricular data achieves consistent parameterization of the shared surface (interventricular septum) and identifies the curvature of the interventricular septum as pathological shape differences

Dielectric properties of (CuO,CaO₂, and BaO)y/CuTl-1223 composites

We synthesized (CuO, CaO₂, and BaO)y/Cu₀,₅Tl₀,₅Ba₂Ca₂Cu₃O₁₀–δ (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties such as real and imag-inary part of dielectric constant, dielectric loss, and ac-conductivity of these composites are studied by capacitance and conductance measurement as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). The x-ray diffraction analysis reveals that the characteristic behavior of Cu₀,₅Tl₀,₅Ba₂Ca₂Cu₃O₁₀–δ supercon-ductor phase and its structure is nearly undisturbed by doping of nanoparticles. The scanning electron microsco-py images show the improvement in the intergranular links among the superconducting grains with increasing nanoparticles concentration. Microcracks are healed up with the inclusion of these nanoparticles and superconduct-ing volume fraction is also increased. The dielectric properties of these composites strongly depend upon the fre-quency and temperature. The zero resistivity critical temperature and dielectric properties show opposite trend with the addition of nanoparticles in Cu₀,₅Tl₀,₅Ba₂Ca₂Cu₃O₁₀–δ superconductor matrix

Absence of pair breaking effect in Cu

We have investigated the existence of any possible pair breaking mechanism in Cu0.5Tl0.5Ba2Ca2Cu0.35Zn2.65O10−δ superconductor by carrying out post-annealing experiments in nitrogen, oxygen and air atmospheres. This material is grown in tetragonal structure with a and c-axes lengths 3.879 Å and 14.581 Å; the c-axis length is found to decrease with the increased concentration of Zn in the final compound. The substitution of Zn at CuO2 planar sites in formula unit Cu0.5Tl0.5Ba2Ca2Cu3−yZnyO10−δ has given superconductivity for all the Zn doping concentration of y = 0.75, 1.5, 2.25, 2.5, 2.65. The zero resistivity critical temperature [Tc(R = 0)], the quantity of diamagnetism and critical current [Ic(H = 0)] are found to increase with increased Zn doping. In Zn doped samples, post-annealing in air has given a maximum increase in superconducting properties, which showed that final material is optimally doped with carriers in ZnO2 planes. Since the superconducting properties are marginally suppressed in Zn doped samples by post annealing in O2 and N2 atmospheres, it has lead to a definite conclusion that pair breaking mechanism, suggested in previous studies, are absent altogether in our Cu0.5Tl0.5Ba2Ca2Cu0.35Zn2.65O10−δ superconductor. The synthesis of Cu0.5Tl0.5Ba2Ca2Zn3O10−δ superconductor by this method is extremely reproducible

Excess conductivity of Cu₀.₅Tl₀.₅Ba₂Ca₃Cu₄₋yZnyO₁₂₋δ superconductors

Oxide high-Tc superconductors (HTSC) are anisotropic in character since the charge carriers have free moment in the conducting CuO₂ planes [1] whereas their motion is impeded by insulating/partially insulating MBa₂O₄₋δ (M = Y, Bi, Hg, Tl, CuTl, etc.) charge reservoir layers. In the transport process the charge carriers have to tunnel across insulating/partially insulating barriers along the c-axis and across the grain boundaries, which promote a fluctuation in the order parameter and in turn to the conductivity of the carriers. The studies of such fluctuation conductivity (FIC) may help in understanding the intrinsic mechanism of superconductivity. Here the electrical resistivity ρ(T) versus temperature data of as-prepared and oxygen post-annealed Cu₀.₅Tl₀.₅Ba₂Ca₃Cu₄₋yZnyO₁₂₋δ (y = 0, 0.5, 1.5, 2.5) samples is studied for FIC analyses in the temperature regime well above the critical temperature; such analyses have been carried out by employing Lawrence and Doniach (LD) and Maki–Thompson (MT) models. The coherence length, inter-plane coupling, exponent, dimensionality of fluctuations and the phase relaxation time of the carriers are determined from such analyses. It is observed that the crossover temperature associated with two distinct exponents fits very well with the two-dimensional (2D) and three-dimensional (3D) LD equations. The crossover temperature T0 is shifted to higher temperatures with enhanced Zn doping. The 3D LD region is shifted to higher temperature with the increased Zn doping. We have elucidated from these analyses that lower Tl content in the final compound may increase the charge carrier’s doping efficiency of MBa2O4–δ charge reservoir layer, resulting into an increase in the coherence length along the c-axis and superconductivity parameters. A small decrease in the coherence length along the c-axis ξc(0) is observed in the samples with Zn doping of y = 1.5 whereas ξc(0) increases in the samples y = 0.5, 2.5. In comparison with as-prepared samples, the ξc(0) decreases after post-annealing in oxygen atmosphere. It is most likely that a decrease in the density of charge carrier’s is promoted by oxygen diffusion in the unit cell may suppress the ξc(0). The increase oxygen diffusion is evidenced from the softening of phonon modes after postannealing in oxygen atmosphere. The decreased population of small spins of Cu atoms induced by doping of Zn is viewed in the terms of suppression of spin gap and hence the pseudo-gap in Cu₀.₅Tl₀.₅Ba₂Ca₃Cu₄₋yZnyO₁₂₋δ (y = 0, 0.5, 1.5, 2.5) samples

A Novel Insertion Mutation on Exon 20 of Epidermal Growth Factor Receptor, Conferring Resistance to Erlotinib

The epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein tyrosine kinase receptor. The small-molecule tyrosine kinase receptor inhibitors (TKIs) are in clinical use to treat non-small cell lung cancer with EGFR mutations. Variable tumor responses to erlotinib and gefitinib have been observed. The response to these TKIs varies by the type of EGFR mutations found in the tumor. The deletion on exon 19 and the L858R substitution on exon 21 constitute the most frequent mutations and are known to show good response to TKIs. However, mutations on exon 20 are less common and seem to respond poorly to TKIs. In clinical settings, the reported response of exon 20 mutations to reversible TKIs (both gefitinib and erlotinib) remains inconstant. The type of coexisting mutation seems to affect the response of these insertions to TKIs. We herein present a case of disease progression despite the use of erlotinib in a female patient who had a novel insertion mutation on exon 20. Our patient was a never-smoker and was identified to have a Pro772_His773insGlnCysPro mutation on exon 20. She had previously been treated with cisplatin and gemcitabine and then with carboplatin and pemetrexed. She was treated with erlotinib upon intolerance to second-line chemotherapy and did not respond. Our patient had a novel insertion mutation on exon 20, which was found to be resistant to erlotinib

Excess conductivity analysis and infrared absorption spectroscopy of Mg-doped TlBa₂Ca₂Cu₃O₁₀−δ superconductor

Fluctuation induced conductivity (FIC) analysis on dc resistivity versus temperature data of as-prepared and oxygen post-annealed TlBa₂(Ca₂–yMgy)Cu₃O₁₀–δ (y = 0, 0.25, 0.5, 0.75, 1.0) superconductor samples are carried out by using Aslamazov–Larkin model for excess conductivity. The microscopic parameters such as zero temperature coherence length along c axis {ξc(0)}, interlayer coupling (J), intergrain coupling (α), critical exponent (λ) and dimensionality of superconducting fluctuations are calculated with the help of aforementioned model. The crossover temperature (T₀) is shifted towards higher temperature values with the increase of Mg contents up to y = 0.5 and then start to decrease but still remains greater than those values of undoped samples. The increase in ξc(0) and J after Mg-doping at Ca sites shows the improvement of interplane coupling in TlBa₂(Ca₂–yMgy)Cu₃O₁₀–δ samples. The appreciable change in all the microscopic parameters extracted from the FIC analysis indicates the optimization of oxygen in all the oxygen post-annealed samples. The increase in relative intensity of almost all the oxygen modes indicates the oxygen diffusion in the unit cell after oxygen post-annealing. The diffusion of oxygen can take place at intergranular sites along with intragranular sites, which increases the grains size, intergrain connectivity and carrier density in CuO₂ planes

Infield superconductivity of carbon nanotubes-Cu0.5Tl0.5Ba2Ca2Cu3O10−δ superconductor composites

We investigated the infield superconducting properties of carbon nanotubes-Cu0.5Tl0.5Ba2Ca2Cu3O10−δ superconductor {(CNTs)x-(CuTl-1223)}; x = 0∼7 wt.% composites. The zero resistivity critical temperature {Tc(0)}, critical superconducting onset transition temperature {Tconset(K)} and glass transition temperature (Tg) have been shifted towards lower values after the addition of carbon nanotubes (CNTs). The double transitions for all concentration of CNTs have indicated the existence of vortex-glass phase. The significant resistive broadening {ΔT = Tconset(K)-Tc(0)} has been observed with increasing values of external applied magnetic field. The more increasing trend in resistive broadening has also been observed after the addition of CNTs in CuTl-1223 matrix. The magnetic field dependent activation energy Uo (H) has been calculated according to thermally activated flux flow (TAFF) model. The overall decreasing rate in pinning energy could be due to diffusion of carbon across the grain-boundaries