Modelling Fluid-Structure Interaction Problems with Coupled DEM-LBM

When studying the properties and behaviour of particulate systems, a multi-scale approach is an efficient way to describe interactions at different levels or dimensions; this means that phenomena taking place at one scale will inherently impact the properties and behaviour of the same system in a different scale. Numerical representation and simulation of fluid-structure interaction (FSI) systems is of particular interest in the present work. Conventional computational fluid dynamics (CFD) methods involve a top-down approach based on the discretisation of the macroscopic continuum Navier-Stokes equations; cells are typically much larger than individual particles and the hydrodynamic force is calculated for all the solid particles contained in singular a cell. Unlike traditional CFD solvers, the lattice Boltzmann method (LBM) is an alternative approach to simulate fluid flows in complex geometries in a mesoscale level. In LBM the fluid is deemed as a collection of cells, each one containing a particle that represents a density distribution function with a velocity field. The distinct element method (DEM) is in charge of handling the motion of particles and calculating the interparticle contact forces. The two methodologies LBM and DEM were selected among the available approaches to be combined in a single computational code to represent FSI systems. The key task to undertake was the implementation of a coupling code to exchange information between the two solvers LBM and DEM in a correct and efficient manner. The calculation of hydrodynamic forces exerted by the fluid on the particles is the major challenge in coupled FSI simulations. This was addressed by including the momentum exchange method, based on the link bounce-back technique, together with the immersed boundary method to deal with moving particles immersed in a fluid. In addition, in order to better understand the dynamics of FSI systems in a mesoscale level, the present work paid special attention to the accurate representation of individual particles displaying irregular geometries instead of the preferred spherical particles. This goal was achieved by means of X-ray microtomography digitisation of particles, allowing the capture of complex micro-structural features such as particle shape, texture and porosity. In this way a more realistic particle representation was achieved, extending its use to the implementation into computational simulations. The DEM-LBM coupling implementation carried out was tested quantitatively and qualitatively based on theoretical models and experimental data. Different cases were selected to simulate the dynamic process of packing particles, particle fluidisation and segregation, particles sedimentation, fluid permeability calculations and fluid flow through porous media. Results and predictions from simulations for a number of configurations showed good agreement when compared with analytical and experimental data. For instance, the relative error in terminal velocity of a non-spherical particle settling down in a column of water was 4.2%, showing an asymptotic convergence to the reference value. In different tests like the drag on two interacting particles and the flow past a circular cylinder at Re = 100, the corresponding deviations from the references published were 20% and 8.23% respectively. The extended Re range for the latter case followed closely the reference curve for the case of a rough cylinder, indicating the effects of the inherent staircase-like boundary in digital particles. Three dimensional simulations of applications such as fluidisation and sedimentation showed the expected behaviour, not only for spherical particles but also considering complex geometries such as sand grains. A symmetric array of spheres and randomly mixed particles were simulated successfully. Segregation was observed in a case configured with particles with different size and density. Hindered settling was also observed causing the slow settling of the small particles. Incipient fluidisation of spherical and irregular geometries was observed in relatively large computational domains. However, the minimum fluidisation velocity configured at the inlet was commonly 10 times larger than the calculated from the Ergun equation

Modelling Fluid-Structure Interaction Problems with Coupled DEM-LBM

When studying the properties and behaviour of particulate systems, a multi-scale approach is an efficient way to describe interactions at different levels or dimensions; this means that phenomena taking place at one scale will inherently impact the properties and behaviour of the same system in a different scale. Numerical representation and simulation of fluid-structure interaction (FSI) systems is of particular interest in the present work. Conventional computational fluid dynamics (CFD) methods involve a top-down approach based on the discretisation of the macroscopic continuum Navier-Stokes equations; cells are typically much larger than individual particles and the hydrodynamic force is calculated for all the solid particles contained in singular a cell. Unlike traditional CFD solvers, the lattice Boltzmann method (LBM) is an alternative approach to simulate fluid flows in complex geometries in a mesoscale level. In LBM the fluid is deemed as a collection of cells, each one containing a particle that represents a density distribution function with a velocity field. The distinct element method (DEM) is in charge of handling the motion of particles and calculating the interparticle contact forces. The two methodologies LBM and DEM were selected among the available approaches to be combined in a single computational code to represent FSI systems. The key task to undertake was the implementation of a coupling code to exchange information between the two solvers LBM and DEM in a correct and efficient manner. The calculation of hydrodynamic forces exerted by the fluid on the particles is the major challenge in coupled FSI simulations. This was addressed by including the momentum exchange method, based on the link bounce-back technique, together with the immersed boundary method to deal with moving particles immersed in a fluid. In addition, in order to better understand the dynamics of FSI systems in a mesoscale level, the present work paid special attention to the accurate representation of individual particles displaying irregular geometries instead of the preferred spherical particles. This goal was achieved by means of X-ray microtomography digitisation of particles, allowing the capture of complex micro-structural features such as particle shape, texture and porosity. In this way a more realistic particle representation was achieved, extending its use to the implementation into computational simulations. The DEM-LBM coupling implementation carried out was tested quantitatively and qualitatively based on theoretical models and experimental data. Different cases were selected to simulate the dynamic process of packing particles, particle fluidisation and segregation, particles sedimentation, fluid permeability calculations and fluid flow through porous media. Results and predictions from simulations for a number of configurations showed good agreement when compared with analytical and experimental data. For instance, the relative error in terminal velocity of a non-spherical particle settling down in a column of water was 4.2%, showing an asymptotic convergence to the reference value. In different tests like the drag on two interacting particles and the flow past a circular cylinder at Re = 100, the corresponding deviations from the references published were 20% and 8.23% respectively. The extended Re range for the latter case followed closely the reference curve for the case of a rough cylinder, indicating the effects of the inherent staircase-like boundary in digital particles. Three dimensional simulations of applications such as fluidisation and sedimentation showed the expected behaviour, not only for spherical particles but also considering complex geometries such as sand grains. A symmetric array of spheres and randomly mixed particles were simulated successfully. Segregation was observed in a case configured with particles with different size and density. Hindered settling was also observed causing the slow settling of the small particles. Incipient fluidisation of spherical and irregular geometries was observed in relatively large computational domains. However, the minimum fluidisation velocity configured at the inlet was commonly 10 times larger than the calculated from the Ergun equation

The influence of accretion bursts on methanol and water in massive young stellar objects

The effect of accretion bursts on massive young stellar objects (MYSOs) represents a new research field in the study of young stars and their environment. We aim to investigate the impact of an accretion burst on massive disks with different types of envelopes and to study the effects of an accretion burst on the temperature structure and the chemistry of the disk. We focus on water and methanol as chemical species for this paper. The thermochemical code of PRODIMO (PROtoplanetary DIsk MOdel) is used to perform simulation of high mass protoplanetary disk models with different types of envelopes under the presence of an accretion burst. The models in question represent different evolutionary stages of protostellar objects. We calculate and show the chemical abundances in three phases of the simulation (pre-burst, burst, and post-burst). More heavily embedded disks show higher temperatures. The impact of the accretion burst is mainly characterized by the desorption of chemical species present in the disk and envelope from the dust grains to the gas phase. When the post-burst phase starts, the sublimated species freeze out again. The degree of sublimation depends strongly on the type of envelope the disk is embedded in. An accretion burst in more massive envelopes produces stronger desorption of the chemical species. However, our models show that the timescale for the chemistry to reach the pre-burst state is independent of the type of envelope. The study shows that the disk's temperature increases with a more massive envelope enclosing it. Thus, the chemistry of MYSOs in earlier stages of their evolution reacts stronger to an accretion burst than at later stages where the envelope has lost most of its mass or has been dissipated. The study of the impact of accretion bursts could also provide helpful theoretical context to the observation of methanol masers in massive disks.Comment: 16 pages, 14 figure

Vecinos y redes sociales: Comunicación e interacción, el caso de la @vecinodeteca

Las relaciones de negocios y las empresas han comenzado a utilizar estas redes sociales electrónicas para impulsar sus marcas, sus productos y sus vínculos personales. Este artículo es parte de una línea de investigación que monitorea una red de vecinos que utiliza la plataforma Twitter para enviar mensajes y organizarse. Mediante una investigación longitudinal que comenzó en 2010 hasta 2015, se ha analizado su impacto en las comunicaciones entre vecinos y el gobierno municipal. Se presentan resultados de una investigación mixta: cuantitativo y cualitativa con la que se ha podido determinar la forma de interacción con el municipio.Las relaciones de negocios y las empresas han comenzado a utilizar estas redes sociales electrónicas para impulsar sus marcas, sus productos y sus vínculos personales. Este artículo es parte de una línea de investigación que monitorea una red de vecinos que utiliza la plataforma Twitter para enviar mensajes y organizarse. Mediante una investigación longitudinal que comenzó en 2010 hasta 2015, se ha analizado su impacto en las comunicaciones entre vecinos y el gobierno municipal. Se presentan resultados de una investigación mixta: cuantitativo y cualitativa con la que se ha podido determinar la forma de interacción con el municipio

A new forward-scatter visibility sensor based on a universal frequency-to-digital converter

Traffic delays attributable to weather conditions may cause an increase in fuel consumption and then an increase in CO2 emissions to the environment. Visibility reduction in roads due to dense fog is a main cause of traffic accidents and possible environmental pollution, hence the importance of deploying fog warning systems. In this article, we present a forward-scatter visibility sensor that uses a quasi-digital photodetector and a universal frequency-to-digital converter instead of a conventional analog-to-digital converter as data acquisition system. This feature has allowed the design of a low-cost, robust, and simple sensor-to-microcontroller interface as demanded by Intelligent Transportation Systems (ITS) applications. An optical system to limit light interference is proposed. The visibilimeter was calibrated from a self-calibrated transmissometer using the same frequency-to-digital technique. This new instrument is capable of a 41 662.5m visibility range detection and to transmit the information wirelessly to a 100m distance.The authors would like to thank the Universidad Autonoma Metropolitana-Azcapotzalco and the Universidad Politecnica de Valencia for their support.Barrales Guadarrama, R.; Mocholí Salcedo, A.; Rodríguez Rodríguez, M.; Barrales Guadarrame, VR.; Vázquez Cerón, ER. (2013). A new forward-scatter visibility sensor based on a universal frequency-to-digital converter. Instrumentation Science and Technology. 41:445-462. doi:10.1080/10739149.2013.780250S44546241News Section, p. 8, (April-March 2009), ITS International Electronic Magazine [Online]. Available: www.itsinternational.comBandivadekar , A. ; Bodek , K. ; Cheah , L. ; Evans , C. ; Groode , T. ; Heywood , J. ; Kasseris , E. ; Kromer , M. ; Weiss , M. On the Road in 2035: Reducing Transportation's Petroleum Consumption and GHG Emissions. Report No. LFEE 2008–05 RP, MIT Laboratory for Energy and the Environment, Cambridge, Massachusetts, 2008.Schrank , D. ; Lomax , T. ; Turner , S. TTI's Urban Mobility Report 2010 [Online]. Avalaible: http://tti.tamu.edu/publications/catalog/record/?id=36580.Bradley , J. T. ; Kraus , K. ; Townshend , T. Federal Citing Criteria for Automated Surface Weather Observations. 7th Symp. On Meteorological Observations and Instrumentation, New Orleans, LA, 1991, 207–210.Winstanley, J. V., & Adams, M. J. (1975). Point Visibility Meter: a forward scatter instrument for the measurement of aerosol extinction coefficient. Applied Optics, 14(9), 2151. doi:10.1364/ao.14.002151Horner, J. L. (1976). Analog visibility computer. Applied Optics, 15(4), 999. doi:10.1364/ao.15.000999Twomey, S., & Howell, H. B. (1965). The Relative Merit of White and Monochromatic Light for the Determination of Visibility by Backscattering Measurements. Applied Optics, 4(4), 501. doi:10.1364/ao.4.000501Vogt, H. (1968). Visibility Measurement Using Backscattered Light. Journal of the Atmospheric Sciences, 25(5), 912-918. doi:10.1175/1520-0469(1968)0252.0.co;2Tjugum, S. A., Vaagen, J. S., Jakobsen, T., & Hamre, B. (2005). Use of optical scatter sensors for measurement of visibility. Journal of Environmental Monitoring, 7(6), 608. doi:10.1039/b414327bNebuloni, R. (2005). Empirical relationships between extinction coefficient and visibility in fog. Applied Optics, 44(18), 3795. doi:10.1364/ao.44.003795Kirianaki, N. V., Yurish, S. Y., Shpak, N. O., & Deynega, V. P. (2002). Data Acquisition and Signal Processing for Smart Sensors. doi:10.1002/0470846100Hlupic, N., Butorac, J., & Kresic, M. (2005). Improved Frequency Measurement by Means of DMM and Verification of its Specifications. IEEE Transactions on Instrumentation and Measurement, 54(5), 1957-1963. doi:10.1109/tim.2005.853561Prokin, M. (1991). Double buffered wide-range frequency measurement method for digital tachometers. IEEE Transactions on Instrumentation and Measurement, 40(3), 606-610. doi:10.1109/19.87027Yurish, S. Y., Reverter, F., & Pallàs-Areny, R. (2005). Measurement error analysis and uncertainty reduction for period- and time-interval-to-digital converters based on microcontrollers. Measurement Science and Technology, 16(8), 1660-1666. doi:10.1088/0957-0233/16/8/018Kirianaki, N. V., Yurish, S. Y., & Shpak, N. O. (2001). Methods of dependent count for frequency measurements. Measurement, 29(1), 31-50. doi:10.1016/s0263-2241(00)00026-9Barrales-Guadarrama , R. ; Mocholí-Salcedo , A. ; Vázquez-Cerón , E. R. ; Rodríguez-Rodríguez , M. E. ; Barrales-Guadarrama , V. R. A Technique for Adapting a Quasi-digital Photodetector to a Frequency-to-digital Converter. Proceedings 2012 IEEE Electronics, Robotics and Automotive Mechanics Conference, CERMA 2012, Cuernavaca, Morelos, México, Nov. 20–23, 2012.(2011) 700–999 nm Bandpass Interference Filters, [Online]. Available: http://www.edmundoptics.com/products/displayproduct.cfm?productid=3198&PageNum=6&Sort=displayOrder&Order=asc#products.AeroGrapher's Mate, Module 05—Basic Meteorology, Ch. 5, Atmospheric Phenomena, Radiation Fog, [Online]. Available: http://www.tpub.com/content/aerographer/14312/css/14312_143.htm

MEDIDOR DE PH, ELECTRO-CONDUCTIVIDAD Y TEMPERATURA PARA CULTIVOS HIDROPÓNICOS

Se propone un instrumento que permita monitorizar los niveles de pH, temperatura y conductividad eléctrica en cultivos hidropónicos de raíz flotante para que un agricultor pueda controlar los niveles de estas variables en la solución nutritiva del cultivo, los cuales han de mantenerse dentro de rangos específicos para evitar la muerte de la planta. Esta monitorización se hace de forma inalámbrica, haciendo uso de un iPhone. El instrumento mide con fiabilidad los niveles de pH en el rango de 5.5 a 6.5 y los niveles de conductividad eléctrica de 1.5 a 3 mS/cm con incertidumbres del 10% para cada mesurando y que son los indicados para cultivos hidropónicos. Se llevó a cabo una investigación para reducir las pérdidas de señal de la sonda pH y la reducción de la polarización y la dependencia de componentes capacitivas en la sonda de conducción eléctrica. Además, la selección juiciosa de los materiales y la capacidad de comunicación inalámbrica del instrumento han resultado en características con ventajas sobre los modelos comerciales como la miniaturización, el bajo costo, la fiabilidad y la capacidad de medición simultánea

A meso-scale model for fluid-microstructure interactions

Particle-fluid and fluid-structure interactions are important areas in particle technology. Typical processes where such interactions are prevalent include fluidized beds, filtration and sedimentation. In addition, fluid-structure interactions are significant in applications such as nuclear waste management, for example in the cementation process used to store radioactive materials, as well as in carbon capture and storage applications where the leakage of gas injected in underground geological reservoirs must be considered in hazard and risk assessments. Given the difficulties in directly measuring the propagation of cracks in solid structures, their permeability or the internal build-up of any gases, for example, numerical techniques in conjunction with non-destructive measurements are important tools of value in assessing and predicting the behavior of fluid-structure interactions. In this work, coupling between the lattice Boltzmann method and a digital packing algorithm based on the discrete element method is used to provide a basis for predicting such coupled interactions. The development of the coupled algorithm is described, with the calculations performed on a regular lattice grid and based on the momentum exchange method to evaluate the force exerted by the fluid on a solid boundary. A number of test cases are reported to allow assessment of the coupled model’s capabilities. Overall, these test cases demonstrate reasonable quantitative agreement with available analytical and experimental results for the case of a sphere settling in a liquid, and the expected qualitative behavior for the case of different orientation cylinders settling in a fluid, and for three dynamic packing processes

Engineered rHDL Nanoparticles as a Suitable Platform for Theranostic Applications

Reconstituted high-density lipoproteins (rHDLs) can transport and specifically release drugs and imaging agents, mediated by the Scavenger Receptor Type B1 (SR-B1) present in a wide variety of tumor cells, providing convenient platforms for developing theranostic systems. Usually, phospholipids or Apo-A1 lipoproteins on the particle surfaces are the motifs used to conjugate molecules for the multifunctional purposes of the rHDL nanoparticles. Cholesterol has been less addressed as a region to bind molecules or functional groups to the rHDL surface. To maximize the efficacy and improve the radiolabeling of rHDL theranostic systems, we synthesized compounds with bifunctional agents covalently linked to cholesterol. This strategy means that the radionuclide was bound to the surface, while the therapeutic agent was encapsulated in the lipophilic core. In this research, HYNIC-S-(CH2)3-S-Cholesterol and DOTA-benzene-p-SC-NH-(CH2)2-NH-Cholesterol derivatives were synthesized to prepare nanoparticles (NPs) of HYNIC-rHDL and DOTA-rHDL, which can subsequently be linked to radionuclides for SPECT/PET imaging or targeted radiotherapy. HYNIC is used to complexing 99mTc and DOTA for labeling molecules with 111, 113mIn, 67, 68Ga, 177Lu, 161Tb, 225Ac, and 64Cu, among others. In vitro studies showed that the NPs of HYNIC-rHDL and DOTA-rHDL maintain specific recognition by SR-B1 and the ability to internalize and release, in the cytosol of cancer cells, the molecules carried in their core. The biodistribution in mice showed a similar behavior between rHDL (without surface modification) and HYNIC-rHDL, while DOTArHDL exhibited a different biodistribution pattern due to the significant reduction in the lipophilicity of the modified cholesterol molecule. Both systems demonstrated characteristics for the development of suitable theranostic platforms for personalized cancer treatment.Consejo Nacional de Ciencia y Tecnología (CONACyT, Mexico), through Grant SEP-CONACyT-CB-2016-01-287217. the financing program for female scientists EDOMEX, Grant Number FICDTEM-2021-015

Psicología: aspectos fundamentales de la formación y la profesión

El aspecto de la práctica clínica ha sido abordado primeramente por la doctora Córdoba Basulto, desde la experiencia, y de manera muy breve profundiza en el ámbito de la Psicología de la salud, rescata y enfatiza el aspecto de la atención e intervención al paciente de urología, colocándolo en la parte de sujeto y no de enfermedad. Nuevamente señalando el trabajo multidisciplinario donde cada agente contribuye con la atención. Desde una perspectiva meramente clínica y específicamente con la experiencia del psicoanálisis, Márquez, Guadarrama, López y Huitrón nos permiten observar la postura de la adolescencia en el proceso terapéutico, indicando que la mejor forma de tratar a un adolescente no es lo individual, ni lo familiar, sino lo grupal.Este libro es una compilación de aportaciones que permiten observar el estado actual de la psicología en México, permitiendo vislumbrar los retos reales que no solamente tienen los alumnos que asumir en su formación profesional, sino todos aquellos que se encuentran laborando en esta basta disciplina. En este sentido, el mundo globalizado y el empleo exagerado de la tecnología se convierten en nuevas exigencias que propician a su vez nuevas formas, no sólo de atención, sino de estudio e investigación que le permitan la comprensión del comportamiento humano. La Psicología mexicana en los últimos años ha dejado de ser dogmática para convertirse en una ciencia amplia y de visión, lo que le ha permitido incursionar en nuevos campos de conocimiento como el de la psicología de la salud o de la psicología criminal. Es decir ha dejado de ser una psicología de diagnóstico y clínica para convertirse en una ciencia que asume al individuo como un ser social, complejo o bien como algunos ya lo han señalado como un ente psicosociobiológico

Ética profesional en educación superior : finalidades, estrategias y desafíos de la formación

Todo proyecto educativo que no responde a su época se expone a problemas de legitimidad y al duro escrutinio y sanción de los usuarios. Las instituciones de educación superior no son la excepción de esta premisa clásica, incluso más validada por eldinamismos, la versatilidad y ojo crítico en el mundo contemporáneo. La ética se ha convertido en el baremo principal para someter a juicio a las instituciones y a las personas que ahí actuan, como a las finalidades que se pretenden en sus acciones. En esta perspectiva, debe examinarse la función de las instituciones de educación superior.Este libro es el esfuerzo colectivo por acercarnos a esa problemática, en especial a las finalidades, estrategias y relaciones en juego para cumplir la tarea de la formación y sus nexos inevitables con la ética profesional