Searching for galactic sources in the Swift GRB catalog

Since the early 1990s Gamma Ray Bursts have been accepted to be of extra-galactic origin due to the isotropic distribution observed by BATSE and the redshifts observed via absorption line spectroscopy. Nevertheless, upon further examination at least one case turned out to be of galactic origin. This particular event presented a Fast Rise, Exponential Decay (FRED) structure which leads us to believe that other FRED sources might also be Galactic. This study was set out to estimate the most probable degree of contamination by galactic sources that certain samples of FREDs have. In order to quantify the degree of anisotropy the average dipolar and quadripolar moments of each sample of GRBs with respect to the galactic plane were calculated. This was then compared to the probability distribution of simulated samples comprised of a combination of isotropically generated sources and galactic sources. We observe that the dipolar and quadripolar moments of the selected subsamples of FREDs are found more than two standard deviations outside those of random isotropically generated samples.The most probable degree of contamination by galactic sources for the FRED GRBs of the Swift catalog detected until February 2011 that do not have a known redshift is about 21 out of 77 sources which is roughly equal to 27%. Furthermore we observe, that by removing from this sample those bursts that may have any type of indirect redshift indicator and multiple peaks gives the most probable contamination increases up to 34% (17 out of 49 sources). It is probable that a high degree of contamination by galactic sources occurs among the single peak FREDs observed by Swift.Comment: Published to A&A, 4 pages, 5 figures, this arXiv version includes appended table with all the bursts considered in this stud

Control of a DC motor using algebraic derivative estimation with real time experiments

This paper presents an experimental control scheme for DC motors which combines an overlapping implementation of the algebraic derivative estimation method and a disturbance estimator based on the aforementioned algebraic derivative method. The methodology only requires the measurement of the angular position of the motor and the voltage input to the motor. The main advantages of the proposed approach are: it is independent of the motor’s initial conditions, the methodology is robust to Coulomb friction effects, it does not require any statistical knowledge of the noises that corrupt the data, the derivative estimation process does not require initial conditions or dependence between the system input and output, and the algorithm is computed on-line and in real time. The effectiveness of the proposed controller has been verified by means of computer simulations and it has also been experimentally implemented on a laboratory prototype with excellent results in both, stabilization and trajectory tracking tasks

Linear active disturbance rejection control of the hovercraft vessel model

A linearizing robust dynamic output feedback control scheme is proposed for earth coordinate position variables trajectory tracking tasks in a hovercraft vessel model. The controller design is carried out using only position and orientation measurements. A highly simplified model obtained from flatness considerations is proposed which vastly simplifies the controller design task. Only the order of integration of the input-to-flat output subsystems, along with the associated input matrix gain, is retained in the simplified model. All the unknown additive nonlinearities and exogenous perturbations are lumped into an absolutely bounded, unstructured, vector of time signals whose components may be locally on-line estimated by means of a high gain Generalized Proportional Integral (GPI) observer. GPI observers are the dual counterpart of GPI controllers providing accurate simultaneous estimation of each flat output associated phase variables and of the exogenous and endogenous perturbation inputs. These observers exhibit remarkably convenient self-updating internal models of the unknown disturbance input vector components. These two key pieces of on-line information are used in the proposed feedback controller to conform an active disturbance rejection, or disturbance accommodation, control scheme. Simulation results validate the effectiveness of the proposed design method

Frecuencia de comportamientos anormales y estereotipados en caballos de patrullaje policial urbano : estudio de 48 horas continuas

ABSTRACT: Abnormal and stereotypic behaviors in horses have been widely studied around the world and different epidemiological situations have been described for behavioral disturbances. Objective: To determine the frequency of abnormal and stereotypic behaviors in a population of police patrolling horses. Additionally, to establish chronic stress levels in the population of interest. Methods: Twenty police horses were evaluated. The animals went through 48 hours of continuous observation to record the frequency of normal, abnormal, and stereotypic behaviors. Cortisol index (CI) was calculated for all the subjects. Results: A 65% of the horses expressed behavioral disturbances, with 55% corresponding to stereotypies. The abnormal behaviors consisted on wood chewing, pawing, and bed eating. Stereotypic behaviors were weaving, stall walking, and aerophagia (crib-biting or wind sucking). According to the CI, 13 horses were under chronic stress (CI<0.30). Conclusion: High level of chronic stress, expressed as abnormal and stereotypic behaviors, was observed in the horses.RESUMEN: los comportamientos anormales y estereotipados en caballos han sido ampliamente estudiados en el mundo, así como también diversas situaciones epidemiológicas relacionadas con estos disturbios. Objetivo: determinar la frecuencia de los comportamientos anormales y estereotipados en una población de caballos de patrullaje de la policía y establecer su nivel de estrés crónico. Métodos: se evaluaron 20 caballos. Los animales fueron observados durante 48 horas continuas para recopilar los comportamientos anormales y estereotipados. El índice del cortisol (CI) fue calculado para todos los animales. Resultados: el 65% de la población estudiada expresó disturbios del comportamiento, y el 55% de dichos disturbios se clasificó como estereotipias. Los comportamientos anormales observados consistieron en lignofagia, patear y comer cama. Los comportamientos estereotipados fueron balanceo, caminar en círculos y aerofagia. El CI mostró presencia de estrés crónico en 13 caballos (CI<0.30). Conclusión: se encontró un alto porcentaje de estrés crónico en los caballos de la policía, expresado como comportamientos anormales y estereotipados

The alkaline reaction of FEBEX bentonite: a contribution to the study of the performance of bentonite/concrete engineered barrier system

Desde 1997, el desarrollo de dos proyectos de la Unión Europea, Effects of Cement On CLAY barrier performance (ECOCLAY, 1997-2000) y ECOCLAY phase II (2000-2003), ha permitido abordar la investigación del efecto de la pluma alcalina inducida por la lixiviación del hormigón sobre la bentonita. Ambos materiales forman parte de un concepto de barrera compuesta de hormigón y bentonita, en el contexto del almacenamiento de residuos a una profundidad dada. El grupo de geoquímica aplicada a las arcillas de la Universidad Autónoma de Madrid (UAM) ha participado en ambos proyectos, y ha conseguido aportar experiencia y cono¬cimiento al estudio del comportamiento de la bentonita de referencia española (FEBEX) bajo condiciones de elevada alcalinidad. Este artículo ofrece una síntesis del trabajo desarrollado, mencionando las lecciones aprendidas sobre la reactividad alcalina de la bentonita, y su enfoque práctico hacia el análisis del comportamiento de uno de los conceptos de referencia, el almacenamiento de residuos en formaciones arcillosas. Se han seleccionado las principales contribuciones científicas a este respecto, a juicio de los autores: (1) la naturaleza particular de los productos generados en la reacción alcalina de la bentonita FEBEX (zeolitas, arcillas magnésicas y geles de silicato aluminato cálcico hidratado (CASH)); (2) la aproximación mediante mineralogía cuantitativa al ritmo de reacción de la montmorillonita FEBEX a pHs elevados, y (3) la validación experimental de la reactividad alcalina de la bentonita a partir de experimentos en columna

ICONE10-22143 MIXED RELOAD DESIGN USING MOX AND UOX FUEL ASSEMBLIES

ABSTRACT As part of the studies involved in plutonium utilization assessment for a Boiling Water Reactor, a conceptual design of MOX fuel was developed, this design is mechanically the same design of 10X10 BWR fuel assemblies but different fisil material. Several plutonium and gadolinium concentrations were tested to match the 18 months cycle length which is the current cycle length of LVNPP, a reference UO 2 assembly was modeled to have a full cycle length to compare results, an effective value of 0.97 for the multiplication factor was set as target for 470 Effective Full Power days for both cycles, here the gadolinium concentration was a key to find an average fisil plutonium content of 6.55% in the assembly. A reload of 124 fuel assemblies was assumed to simulate the complete core, several load fractions of MOX fuel mixed with UO 2 fresh fuel were tested to verify the shutdown margin, the UO 2 fuel meets the shutdown margin when 124 fuel assemblies are loaded into the core, but it does not happen when those 124 assemblies are replaced with MOX fuel assemblies, so the fraction of MOX was reduced step by step up to find a mixed load that meets both length cycle and shutdown margin. Finally the conclusion is that control rods losses some of their worth in presence of plutonium due to a more hardened neutron spectrum in MOX fuel and this fact limits the load of MOX fuel assemblies in the core, this results are shown in this paper. INTRODUCTION In prior years, the use of MOX fuel in thermal reactors was considered only as an alternative back-end policy option. However the plutonium recycling and MOX fuel technology ha

CLASSICAL SPLITTING OF FUNDAMENTAL STRINGS

We find exact solutions of the string equations of motion and constraints describing the {\em classical}\ splitting of a string into two. We show that for the same Cauchy data, the strings that split have {\bf smaller} action than the string without splitting. This phenomenon is already present in flat space-time. The mass, energy and momentum carried out by the strings are computed. We show that the splitting solution describes a natural decay process of one string of mass $M$ into two strings with a smaller total mass and some kinetic energy. The standard non-splitting solution is contained as a particular case. We also describe the splitting of a closed string in the background of a singular gravitational plane wave, and show how the presence of the strong gravitational field increases (and amplifies by an overall factor) the negative difference between the action of the splitting and non-splitting solutions.Comment: 27 pages, revtex