Performance of PIV and PTV for granular flow measurements

As tools and techniques to measure experimental granular flows become increasingly sophisticated, there is a need to rigorously assess the validity of the approaches used. This paper critically assesses the performance of Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) for the measurement of granular flow properties. After a brief review of the PIV and PTV techniques, we describe the most common sources of error arising from the applications of these two methods. For PTV, a series of controlled experiments of a circular motion is used to illustrate the errors associated with the particle centroid uncertainties and the linear approximation of particle trajectories. The influence of these errors is then examined in experiments on dry monodisperse granular flows down an inclined chute geometry. The results are compared to those from PIV analysis in which errors are influenced by the size of the interrogation region. While velocity profiles estimated by the two techniques show strong agreement, second order statistics, e.g. the granular temperature, display very different profiles. We show how the choice of the sampling interval, or frame rate, affects both the magnitude of granular temperature and the profile shape determined in the case of PTV. In addition, the determined magnitudes of granular temperature from PIV tends to be considerably lower when directly measured or largely overestimated when theoretically scaled than those of PTV for the same tests, though the shape of the profiles is less sensitive to frame rate. We finally present solid concentration profiles obtained at the sidewalls and and examine their relationship to the determined shear rate and granular temperature profiles

Virtually Moving Base Stations for Energy Efficiency in Wireless Sensor Networks

Energy efficiency of wireless sensor networks (WSNs) can be improved by moving base stations (BSs), as this scheme evenly distributes the communication load in the network. However, physically moving BSs is complicated and costly. In this paper, we propose a new scheme: virtually moving the BSs. We deploy an excessive number of BSs and adaptively re-select a subset of active BSs so as to emulate the physical movement. Beyond achieving high energy-efficiency, this scheme obviates the difficulties associated with physically moving the BSs. The challenges are (i) that the energy efficiency of BSs should be considered as well, in addition to that of the sensor nodes and (ii) that the number of candidate subset of active BSs is exponential with the number of BSs. We show that scheduling the virtual movement of BSs is NP-hard. Then, we propose a polynomial-time algorithm that is guaranteed under mild conditions to achieve a lifetime longer than 62% of the optimal one. In practice, as verified through extensive numerical simulations, the lifetime achieved by the proposed algorithm is always very close to the optimum

Omnidirectional flat bands in chiral magnonic crystals

The magnonic band structure of two-dimensional chiral magnonic crystals is theoretically investigated. The proposed metamaterial involves a three-dimensional architecture, where a thin ferromagnetic layer is in contact with a two-dimensional periodic array of heavy-metal square islands. When these two materials are in contact, an anti-symmetric exchange coupling known as the Dzyaloshinskii–Moriya interaction (DMI) arises, which generates nonreciprocal spin waves and chiral magnetic order. The Landau–Lifshitz equation and the plane-wave method are employed to study the dynamic magnetic behavior. A systematic variation of geometric parameters, the DMI constant, and the filling fraction allows the examination of spin-wave propagation features, such as the spatial profiles of the dynamic magnetization, the isofrequency contours, and group velocities. In this study, it is found that omnidirectional flat magnonic bands are induced by a sufficiently strong Dzyaloshinskii–Moriya interaction underneath the heavy-metal islands, where the spin excitations are active. The theoretical results were substantiated by micromagnetic simulations. These findings are relevant for envisioning applications associated with spin-wave-based logic devices, where the nonreciprocity and channeling of the spin waves are of fundamental and practical scientific interest

Determinacion de proteina A en cepas de Staphylococcus aureus mediante la tecnica de coaglutinacion

58 p.El presente estudio se basa en la cuantificación de Proteína A de Staphylococcus aureus por la técnica de coaglutinacion. Esta proteína constituye aproximadamente el 5% de la pared celular de S. aureus, y posee la propiedad de unirse a la fracción Fc de la Ig G. La investigación se realizo con 64 cepas de S.aureus obtenidas del cepario del Laboratorio de Microbiología de la U. de Talca y 60 cepas de S. aureus de reciente aislamiento obtenidas del Hospital Regional de Talca, observando se variaciones en el hallazgo de P.A de acuerdo al origen y tiempo de mantención de las cepas. La fagotipificación de las cepas indica que el mayor numero de cepas productoras de P.A corresponden al fago grupo I y misceláneo. Se investigo la producción de bacteriocina en las cepas de reciente aislamiento encontrándose que no existe relación entre producción de P.A y producción de bacteriocinas, el mayor numero de cepas productoras de bacteriocinas corresponden al grupo no tipificado

Envejecimiento de la población

•Actividades básicas de la vida diaria en personas mayores y factores asociados •Asociación entre depresión y posesión de mascotas en personas mayores •Calidad de vida en adultos mayores de Santiago aplicando el instrumento WHOQOL-BREF •Calidad de vida en usuarios con enfermedad de Parkinson, demencia y sus cuidadores, comuna de Vitacura •Caracterización de egresos hospitalarios de adultos mayores en Puerto Natales (2007-2009) •Comportamiento de las patologías incluidas como GES para el adulto mayor atendido en un Cesfam •Contribución de vitaminas y minerales a las ingestas recomendadas diarias en ancianos institucionalizados de Madrid •Estado de salud oral del paciente inscrito en el Programa de Visita Domiciliaria •Evaluación del programa de discapacidad severa en Casablanca con la matriz de marco lógico •Factores asociados a satisfacción vital en una cohorte de adultos mayores de Santiago, Chile •Pauta instrumental para la identificación de riesgos para el adulto mayor autovalente, en su vivienda •Perfil farmacológico del paciente geriátrico institucionalizado y posibles consecuencias en el deterioro cognitivo •Programa de cuidados paliativos y alivio del dolor en Puerto Natales •Rehabilitación mandibular implantoprotésica: efecto en calidad de vida relacionada con salud bucal en adultos mayores •Salud bucodental en adultos mayores autovalentes de la Región de Valparaíso •Transición epidemiológica y el estudio de carga de enfermedad en Brasi

Large-scale optimization with the primal-dual column generation method

The primal-dual column generation method (PDCGM) is a general-purpose column generation technique that relies on the primal-dual interior point method to solve the restricted master problems. The use of this interior point method variant allows to obtain suboptimal and well-centered dual solutions which naturally stabilizes the column generation. As recently presented in the literature, reductions in the number of calls to the oracle and in the CPU times are typically observed when compared to the standard column generation, which relies on extreme optimal dual solutions. However, these results are based on relatively small problems obtained from linear relaxations of combinatorial applications. In this paper, we investigate the behaviour of the PDCGM in a broader context, namely when solving large-scale convex optimization problems. We have selected applications that arise in important real-life contexts such as data analysis (multiple kernel learning problem), decision-making under uncertainty (two-stage stochastic programming problems) and telecommunication and transportation networks (multicommodity network flow problem). In the numerical experiments, we use publicly available benchmark instances to compare the performance of the PDCGM against recent results for different methods presented in the literature, which were the best available results to date. The analysis of these results suggests that the PDCGM offers an attractive alternative over specialized methods since it remains competitive in terms of number of iterations and CPU times even for large-scale optimization problems.Comment: 28 pages, 1 figure, minor revision, scaled CPU time

Nocturnal: kebahagiaanku ada di kamu

287 hlm. ; 19 cm

Inhibition of the growth of enteropathogenic bacilli by bacteriocins produced by micro-organisms from the sediment of wells

C. Padilla; P. Brevis; A. Said; R. Molina. Area of Microbiology, Department of Biological Sciences, University of Talca,Chile.The bacterial flora of the sediment of 20 wells of water for human consumption in the rural area of the VII Region in Chile was examined. Fourteen strains of bacteria, from different wells, produced bacteriocins which inhibited the growth of Salmonella typhi, Salm. typhimurium, Shigella sonnei and enterotoxigenic Escherichia coli. About 50% of these strains contained plasmids of different molecular weight and a large number of these codified for bacteriocins. The results suggest what is required to implement an efficient, simple and economical biological system for the purification or control of the number of enteropathogenic bacilli of well water in the rural area. and accepted 28 June 198