Stable rank of Leavitt path algebras

We characterize the values of the stable rank for Leavitt path algebras by giving concrete criteria in terms of properties of the underlying graph

Refinement monoids with weak comparability and applications to regular rings and C*-algebras

We prove a cancellation theorem for simple re nement monoids satisfying the weak comparability condition, rst introduced by K.C. O'Meara in the context of von Neumann regular rings. This result is then applied to von Neumann regular rings and C -algebras of real rank zero via the monoid of isomorphism classes of nitely generated projective modules

Representing finitely generated refinement monoids as graph monoids

Graph monoids arise naturally in the study of non-stable K-theory of graph C*-algebras and Leavitt path algebras. They play also an important role in the current approaches to the realization problem for von Neumann regular rings. In this paper, we characterize when a finitely generated conical refinement monoid can be represented as a graph monoid. The characterization is expressed in terms of the behavior of the structural maps of the associated I-system at the free primes of the monoid.Both authors are partially supported by the DGI-MINECO and European Regional Development Fund, jointly, through Project MTM2014-53644-P. The second author was partially supported by PAI III grant FQM-298 of the Junta de Andalucía

Kullback-leibler entropy analysis of the electroencephalogram background activity in alzheimer's disease patients

Alzheimer's disease (AD) is the most frequent form of dementia in western countries. An early detection would be beneficial, but currently diagnostic accuracy is relatively poor. In this study, differences in information content between cortical areas in 12 AD patients and 11 control subjects were assessed with Kullback-Leibler (KL) entropy. KL entropy measures the degree of similarity between two probability distributions. EEGs were recorded from 19 scalp electrodes and KL entropy values of the EEGs in both groups were estimated for the local, distant and interhemispheric electrodes. KL entropy values were lower in AD patients than in age-matched control subjects, with significant effects for diagnosis and brain region (p < 0.05, two-way ANOVA). No significant interaction for diagnosis X region was found (p = 0.7671). Additionally a one-way ANOVA showed that KL entropy values were significantly lower in AD patients (p < 0.05) for the distant electrodes on the right hemisphere. These results suggest that KL entropy highlights information content changes in the EEG due to AD. However, further studies are needed to address the possible usefulness of KL entropy in the characterisation and early detection of AD

Microwave Spectroscopy

Contains research objectives, reports on work completed and one research project.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E

K0 of purely infinite simple regular rings

We extend the notion of a purely in nite simple C*-algebra to the context of unital rings, and we study its basic properties, specially those related to K-Theory. For instance, if R is a purely in nite simple ring, then K0(R)+ = K0(R), the monoid of isomorphism classes of nitely generated projective R-modules is isomorphic to the monoid obtained from K0(R) by adjoining a new zero element, and K1(R) is the abelianization of the group of units of R. We develop techniques of construction, obtaining new examples in this class in the case of von Neumann regular rings, and we compute the Grothendieck groups of these examples. In particular, we prove that every countable abelian group is isomorphic to K0 of some purely in nite simple regular ring. Finally, some known examples are analyzed within this framework

Modeling and Simulation of Rotating Machine Windings Fed by High-Power Frequency Converters for Insulation Design

Modern power systems include a considerable amount of power electronic converters related to the introduction of renewable energy sources, high-voltage direct current (HVDC) systems, adjustable speed drives, and so on. These components introduce repetitive pulses generated by the commutation of semiconductor switches, resulting in overvoltages with very steep fronts and high dielectric stresses. This phenomenon is one of the main causes of accelerated insulation aging of motors in power electronic-based systems. This chapter presents state-of-the-art computational tools for the analysis of motor windings excited by fast-front pulses related to the use of frequency converters based on pulse-width modulation (PWM). These tools can be applied for the accurate prediction of overvoltages and dielectric stresses required to propose insulation design improvements. In the case of the stress-grading system used in medium-voltage (MV) motors, transient finite-element method (FEM) is used to study the effect of fast pulses. It is shown how, by controlling the material properties and the design of the stress-grading systems, solutions to reduce the adverse effects of fast pulses from PWM-type inverters can be proposed

Electroencephalogram background activity characterization with Detrended Moving Average in Alzheimer's disease patients

The aim of this study was to analyse the electroencephalogram (EEG) background activity in Alzheimer's disease (AD) with the Detrended Moving Average (DMA) method, a new approach to quantify correlation properties in non-stationary signals with underlying trends. EEGs were recorded from the 19 scalp loci of the international 10-20 system in 11 AD patients and 11 age-matched controls. Our results showed two scaling regions in all subjects' channels, with a clear bend when their corresponding slopes (alpha(1) and alpha(2)) were distinctly different. With the exception of electrode T4, the alpha(1) values were lower in control subjects than in AD patients, with significant differences at TS, P3, P4 and O1 (p < 0.01, Student's t-test). On the other hand, alpha(2) values were higher in control subjects than in AD patients, with significant differences only at F4. Furthermore, we evaluated the ability of alpha(2) to discriminate AD patients from control subjects at these electrodes using ROC plots. We obtained a maximum accuracy of 81.82% at O1 with alpha(1) and at F4 with alpha(2). These findings suggest that the scaling behaviour of the EEG is sensitive to AD and that the DMA method could help to increase our insight into brain dysfunction in AD