Exact Insulating and Conducting Ground States of a Periodic Anderson Model in Three Dimensions

We present a class of exact ground states of a three-dimensional periodic Anderson model at 3/4 filling. Hopping and hybridization of d and f electrons extend over the unit cell of a general Bravais lattice. Employing novel composite operators combined with 55 matching conditions the Hamiltonian is cast into positive semidefinite form. A product wave function in position space allows one to identify stability regions of an insulating and a conducting ground state. The metallic phase is a non-Fermi liquid with one dispersing and one flat band.Comment: 4 pages, 3 figure

Erstellung quantitativer Imaging-Biomarker zur Detektion von fibrosiertem Lungengewebe im HR-CT

Ziel dieser Arbeit war die Erstellung von Imaging-Biomarkern, die robust zwischen fibrosiertem und gesundem Lungengewebe im HR-CT unterscheiden können. Mit Hilfe morphologischer Bildverarbeitungsverfahren sollten die Charakteristika von fibrosiertem Lungengewebe verstärkt und numerisch ausgewertet werden. Hierfür wurden HR-CT-Bilddaten von 78 Patienten mit fibrosiertem Lungengewebe und 23 Patienten mit unauffälligem Lungenparenchym untersucht. Zu Beginn erfolgte eine semiautomatische Segmentierung der Schnittbilder, um anschließend die für fibrosiertes Lungengewebe typischen morphologischen Charakteristika hervorzuheben. Da diese Merkmale bei Lungengesungen nicht vorliegen, führt diese Bearbeitung zu einer Verstärkung der Unterschiede zwischen Patienten mit Lungenfibrose und Lungengesunden. Dazu erfolgte nach der Segmentierung im zweiten Schritt eine Binarisierung durch drei festgelegte Schwellenwertbereiche, um morphologische Charakteristika des Lungengewebes hervorzuheben. Im dritten Schritt wurden diese Merkmale durch vier verschiedene Kombinationen aus Closing- und Opening-Strukturelementen verstärkt. Die Ergebnisse zeigen für alle vier erstellten Parameter statistisch hoch signifikante Gruppenunterschiede. Zur Klassifizierung der insgesamt 39 Datenreihen wurden, auf einer logistischen Regressionsanalyse basierend, die AUC-Werte der ROC-Kurven bestimmt. Eine erste Auswertung erfolgte nach der Binarisierung und eine zweite Auswertung nach der Verstärkung der morphologischen Charakteristika durch Closing- und Opening-Operationen. Schon nach der Binarisierung zeigten sich AUC-Werte bis zu 0,976. Der analysierte Schwellenwertbereich S3-500; -200 HE brachte für die meisten Parameter die prädiktivsten Werte hervor. Der Parameter Cluster-Pixel/CT-Seg-Pixel im Schwellenwertbereich S3 mit einem 5×5 Pixel großem Closing- und einem 3×3 Pixel großem Opening-Strukturelement erreichte einen maximalen AUC-Wert von 0,989. Durch den ersten Arbeitsschritt der Binarisierung konnte im Schwellenwertbereich S3 robust zwischen den Gruppen mit fibrosiertem und gesundem Lungengewebe unterschieden werden. Die Verstärkung der morphologischen Charakteristika konnte eine zusätzliche Verbesserung der AUC-Werte erzielen. Eingebettet in ein Konzept, wie z. B. von Radiomics, stellt dieses Modell einen funktionierenden und robusten Imaging-Biomarker dar.The purpose of this study was the creation of imaging biomarkers to distinguish patients with pulmonary fibrosis and healthy subjects in high-resolution CTs. Intensification of characteristics of pulmonary fibrosis, based on morphological image processing, was performed and evaluated numerically. Datasets of 78 patients with the diagnosis of pulmonary fibrosis and 23 healthy subjects were studied and compared. At first semiautomatic lung parenchyma segmentation was performed. After that, the segmented images were used to isolate and to enhance specif- ic morphological fibrosis characteristics. Next, binary images were created for each of three different Hounsfield unit (HU) threshold ranges. To intensify the morphological fibrosis characteristics, basic image processing methods like morphological opening and closing were applied, leading to different, parameterized image variations of the normal and the fibrotic group. Statistical analysis shows significant differences, between both patient groups, for all parameter settings. In order to find the best parameter settings, a logistic regression analysis was implemented and the values of the area under the receiver operator charac- teristic (ROC) curve (AUC) were computed. A first group comparison was performed after the binarization of the images and a second comparison after the enhancement of the specific fibrosis characteristics by the closing and opening operations. Based on the analysis of binary image, AUC values of up to 0,976 could be found. The threshold range of -500 to -200 HU lead to the highest AUC values. Application of the morpho- logical image processing operations lead to a slight increase up to AUC values being 0,989. These findings suggest that the evaluated image processing operations can serve as a valuable numerical image marker for a reproducible, and observer independent differen- tiation between normal and fibrotic lung parenchyma. The concept fits well into the current radiomics philosophy

Exact Ground States of the Periodic Anderson Model in D=3 Dimensions

We construct a class of exact ground states of three-dimensional periodic Anderson models (PAMs) -- including the conventional PAM -- on regular Bravais lattices at and above 3/4 filling, and discuss their physical properties. In general, the f electrons can have a (weak) dispersion, and the hopping and the non-local hybridization of the d and f electrons extend over the unit cell. The construction is performed in two steps. First the Hamiltonian is cast into positive semi-definite form using composite operators in combination with coupled non-linear matching conditions. This may be achieved in several ways, thus leading to solutions in different regions of the phase diagram. In a second step, a non-local product wave function in position space is constructed which allows one to identify various stability regions corresponding to insulating and conducting states. The compressibility of the insulating state is shown to diverge at the boundary of its stability regime. The metallic phase is a non-Fermi liquid with one dispersing and one flat band. This state is also an exact ground state of the conventional PAM and has the following properties: (i) it is non-magnetic with spin-spin correlations disappearing in the thermodynamic limit, (ii) density-density correlations are short-ranged, and (iii) the momentum distributions of the interacting electrons are analytic functions, i.e., have no discontinuities even in their derivatives. The stability regions of the ground states extend through a large region of parameter space, e.g., from weak to strong on-site interaction U. Exact itinerant, ferromagnetic ground states are found at and below 1/4 filling.Comment: 47 pages, 10 eps figure

Устойчивость процесса зажигания полимерного материала горячей частицей

As a result of the numerical investigation of a typical polymeric material ignition by a local energy source with limited heat content it has been determined three modes: gasification without ignition followed by pyrolysis stop, stable ignition, and unstable ignition. The mathematical model of the process takes in account conductive heat transfer and thermal decomposition in condensed phase, diffusion-convective heat and mass transfer and gaseous pyrolysis products oxidation of polymeric material in air

A new Architecture for High Speed, Low Latency NB-LDPC Check Node Processing

International audience—Non-binary low-density parity-check codes have superior communications performance compared to their binary counterparts. However, to be an option for future standards, efficient hardware architectures must be developed. State-of-the-art decoding algorithms lead to architectures suffering from low throughput and high latency. The check node function accounts for the largest part of the decoders overall complexity. In this paper a new hardware aware check node algorithm and its architecture is proposed. It has state-of-the-art communications performance while reducing the decoding complexity. The presented architecture has a 14 times higher area efficiency, increases the energy efficiency by factor 2.5 and reduces the latency by factor of 3.5 compared to a state-of-the-art architecture