Modeling of Magnetorheological Fluids by the Discrete Element Method

Magnetorheological (MR) fluids are fluids whose properties vary in response to an applied magnetic field. Such fluids are typically composed of microscopic iron particles ( 1 20 lm diameter, 20 40% by volume) suspended in a carrier fluid such as mineral oil or water. MR fluids are increasingly proposed for use in various mechanical system applications, many of which fall in the domain of tribology, such as smart dampers and clutches, prosthetic articulations, and controllable polishing fluids. The goal of this study is to present an overview of the topic to the tribology audience, and to develop an MR fluid model from the microscopic point of view using the discrete element method (DEM), with a long range objective to better optimize and understand MR fluid behavior in such tribological applications. As in most DEM studies, inter-particle forces are determined by a force-displacement law and trajectories are calculated using Newton’s second law. In this study, particle magnetization and magnetic interactions between particles have been added to the discrete element code. The global behavior of the MR fluid can be analyzed by examining the time evolution of the ensemble of particles. Microscopically, the known behavior is observed: particles align themselves with the external magnetic field. Macroscopically, averaging over a number of particles and a significant time interval, effective viscosity increases significantly when an external magnetic field is applied. These preliminary results would appear to establish that the DEM is a promising method to study MR fluids at the microscopic and macroscopic scales as an aid to tribological design. [DOI: 10.1115/1.4006021

Modeling of Magnetorheological Fluids by the Discrete Element Method

Magnetorheological (MR) fluids are fluids whose properties vary in response to an applied magnetic field. Such fluids are typically composed of microscopic iron particles ( 1 20 lm diameter, 20 40% by volume) suspended in a carrier fluid such as mineral oil or water. MR fluids are increasingly proposed for use in various mechanical system applications, many of which fall in the domain of tribology, such as smart dampers and clutches, prosthetic articulations, and controllable polishing fluids. The goal of this study is to present an overview of the topic to the tribology audience, and to develop an MR fluid model from the microscopic point of view using the discrete element method (DEM), with a long range objective to better optimize and understand MR fluid behavior in such tribological applications. As in most DEM studies, inter-particle forces are determined by a force-displacement law and trajectories are calculated using Newton’s second law. In this study, particle magnetization and magnetic interactions between particles have been added to the discrete element code. The global behavior of the MR fluid can be analyzed by examining the time evolution of the ensemble of particles. Microscopically, the known behavior is observed: particles align themselves with the external magnetic field. Macroscopically, averaging over a number of particles and a significant time interval, effective viscosity increases significantly when an external magnetic field is applied. These preliminary results would appear to establish that the DEM is a promising method to study MR fluids at the microscopic and macroscopic scales as an aid to tribological design. [DOI: 10.1115/1.4006021

The communication and information process during the La Palma eruption errors, successes, learnings and proposals for improvement

After nearly fifty years without showing obvious signs of volcanic activity on the surface, in 2021 a new eruption occurred in the area called Cabeza de Vaca, on La Palma (Canary Islands, Spain). The eruption lasted eighty-five days and produced numerous losses due to the extensive area affected by continuous lava flows and pyroclastic falls.Although the volcanic dynamics were similar to other eruptions that occurred on the island in historical times, the follow-up it received from the media and social networks was totally different, with an international impact for several weeks. Throughout this coverage process, the volunteers from the Canary Islands Volcanoes Association observed some communication and information practices that could condition the management of the emergency, both positively and negatively. GeoTenerife, for its part, collected numerous testimonies from representatives of all the sectors involved in the volcanic crisis in a thorough audiovisual support work called Volcano Stories and recorded a documentary Lava bombs analyzing the role of communication and its impact. This monitoring was completed with the compilation of numerous communications made at different levels and by different means, where, among others, the "intentionality", techniques used and various problems observed were analyzed.The great capacity of influence that social networks exerted in monitoring the volcanic eruption and even in decision-making was confirmed. With the aim of improving communication in future events involving natural hazards of short or long duration, we also provide a series of key recommendations for the different groups involved in monitoring the emergency

Web: A Wireless Experiment Box for the Dextre Pointing Package ELC Payload

The Wireless Experiment Box (WEB) was proposed to work with the International Space Station (ISS) External Wireless Communication (EWC) system to support high-definition video from the Dextre Pointing Package (DPP). DPP/WEB was a NASA GSFC proposed ExPRESS Logistics Carrier (ELC) payload designed to flight test an integrated suite of Autonomous Rendezvous and Docking (AR&D) technologies to enable a wide spectrum of future missions across NASA and other US Government agencies. The ISS EWC uses COTS Wireless Access Points (WAPs) to provide high-rate bi-directional communications to ISS. In this paper, we discuss WEB s packaging, operation, antenna development, and performance testing

Development of NASA's Next Generation L-Band Digital Beamforming Synthetic Aperture Radar (DBSAR-2)

NASA's Next generation Digital Beamforming SAR (DBSAR-2) is a state-of-the-art airborne L-band radar developed at the NASA Goddard Space Flight Center (GSFC). The instrument builds upon the advanced architectures in NASA's DBSAR-1 and EcoSAR instruments. The new instrument employs a 16-channel radar architecture characterized by multi-mode operation, software defined waveform generation, digital beamforming, and configurable radar parameters. The instrument has been design to support several disciplines in Earth and Planetary sciences. The instrument was recently completed, and tested and calibrated in a anechoic chamber

La técnica de inyección por solvent-flush en el análisis cuantitativo de ácidos grasos de muy elevada masa molecular por Cromatografía Gaseosa

Se considera que la introducción de la muestra es la mayor fuente de error en el análisis cuantitativo por Cromatografía Gaseosa (CG). Ello es debido a diversos fenómenos (entre ellos, la discriminación en la aguja de la jeringuilla), los cuales provocan cambios sustanciales en la composición de la muestra. Estos cambios resultan más apreciables al ser mayor la diferencia de volatilidades entre los componentes de la mezcla a analizar y se revelan en el factor másico de respuesta relativa (fim). Para analizar la influencia de la técnica de inyección sobre el comportamiento cromatográfico de los ácidos grasos en forma de ésteres metílicos se prepararon varias mezclas con patrones de ácidos comúnmente presentes en las ceras vegetales (C24:0, C26:0, C28:0 y C30:0). A estas mezclas se les añadió C19:0 como patrón interno, se metilaron por catálisis ácida con una disolución de HCl-metanol y se analizaron por CG con detección de ionización por llama. En los análisis se utilizó una columna de vidrio silanizada (3,1 m x 3,0 mm di), rellena con Chromosorb W (HP) de 80 a 100 mallas, impregnado al 3 % con OV-101, y se encontró que existe influencia de la velocidad y del tipo de inyección sobre el fim. Al utilizar la técnica de inyección convencional se observó que ocurre un aumento considerable del fim con la disminución de la velocidad de inyección y con el aumento en la longitud de la cadena

Fourier Analysis for Harmonic Signals in Electrical Power Systems

The harmonic content in electrical power systems is an increasingly worrying issue since the proliferation of nonlinear loads results in power quality problems as the harmonics is more apparent. In this paper, we analyze the behavior of the harmonics in the electrical power systems such as cables, transmission lines, capacitors, transformers, and rotating machines, the induction machine being the object of our study when it is excited to nonsinusoidal operating conditions in the stator winding. For this, a model is proposed for the harmonic analysis of the induction machine in steady‐state regimen applying the Fourier transform. The results of the proposed model are validated by experimental tests which gave good results for each case study concluding in a model proper for harmonic and nonharmonic analysis of the induction machine and for “harmonic” analysis in an electrical power system

HIV-1 envelope glycoproteins isolated from viremic non-progressor individuals are fully functional and cytopathic

International audienc

Efecto del bioproducto CBQ-AgroG® sobre la respuesta morfofisiológica y agronómica de frijol común cultivar ‘CIAP 7247'

The lack of chemical fertilizers has stimulated the use of alternatives to increase plant growth and production such as the use of bioproducts. The objective of the work was to evaluate the effect of microbial origin CBQ-AgroG® bioproduct on the physiological and agronomic response of Phaseolus vulgaris L. cultivar 'CIAP-7247'. Seeds with basic category were used and three doses of the CBQ-AgroG® bioproduct (10.0, 20.0 and 30.0 l ha-1) were used and compared with an absolute control and a relative control (Fitomas E, 2.0%). The height, number of leaves per plant, fresh mass, dry mass and leaf area were evaluated. In addition, the agricultural yield and its components were estimated. Plants increased height up to 45 days after sowing. The maximum values of the morphophysiological variables number of leaves, leaf area, fresh and dry mass were reached 45 days after sowing. Subsequently, they decreased until reaching physiological maturity. With the doses of 20.0 and 30.0 l ha-1, all the morphophysiological and agronomic indicators reached significantly higher values with respect to the rest of the treatments. The first dose is recommended as it is cheaper.La carencia de fertilizantes químicos ha estimulado el uso de alternativas para incrementar el crecimiento vegetal y la producción como el uso de bioproductos. El trabajo tuvo como objetivo evaluar el efecto del bioproducto de origen microbiano CBQ-AgroG® sobre la respuesta fisiológica y agronómica de Phaseolus vulgaris L. cultivar ‘CIAP-7247´. Se utilizaron semillas con categoría básica y se emplearon tres dosis del bioproducto CBQ-AgroG® (10.0, 20.0 y 30.0 l ha-1) y se compararon con un control absoluto y un control relativo (Fitomas E, 2.0%). Se evaluó la altura, número de hojas por planta, masa fresca, masa seca y área foliar. Además, se estimó el rendimiento agrícola y sus componentes. Las plantas incrementaron la altura hasta los 45 días después de la siembra. Los máximos valores de la variables morfofisiológicas número de hojas, área foliar, masa fresca y seca se alcanzaron a los 45 días después de la siembra. Posteriormente decrecieron hasta alcanzar la madurez fisiológica. Con las dosis de 20.0 y 30.0 l ha-1 todos los indicadores morfofisiológicos y agronómicos alcanzaron valores significativamente superiores con respecto al resto de los tratamientos. Se recomienda la primera dosis por ser más económica