Dynamic viscoplastic granular flows: A persistent challenge in gas-solid fluidization

Fluidization is a prime example of complex granular flows driven by fluid-solid interactions. The interplay of gravity, particle-particle and fluid-particle forces leads to a rich spectrum of hydrodynamic behavior. A number of complex mathematical formulations exist to describe granular flows. At a macroscopic scale, Eulerian models based on the Kinetic Theory of Granular Flow (KTGF) have been successfully employed to simulate dilute and moderately dense systems, such as circulating fluidized bed reactors. However, their applications to dense flows are challenging, because sustained particle contacts are important. As solid fraction rises, the behavior of granular media responds dramatically to particle properties and changes in concentration. Lacking a coherent transition between formulations of dilute, dense and quasi-static flow behavior, kinetic models are incapable of describing how microstructure emerges and affects the rheology. The behavior of transitional granular flows, such as pulsed fluidized beds, for which the particulate phase transitions between the viscous and plastic regimes, are good reminders of this limitation. In recent years, tremendous effort has been devoted to finding new ways to describe the effects of sustained solids friction and dense flow rheology. This article provides a perspective on this matter from the viewpoint of gas-solid fluidization and discusses advances in describing the dilute-to-dense transition in a continuum framework. Four innovative approaches prevail to extend or supersede the existing kinetic theory: (i) including effective restitution coefficients, (ii) coupling local granular rheological correlations, (iii) introducing rotational granular energy, and (iv) combining non-local laws. While their reliability is still far from that of a Eulerian-Lagrangian approach, they lay a promising foundation for developing a rigorous description of granular media that merges the classical frameworks of continuous fluid and soil mechanics. The progress of continuum formulations does not compete with multi-scale modeling platforms with an applied focus. Ultimately, combining both is a prerequisite to developing new solid stress models that will improve not only the performance of macroscopic models, but also our understanding of granular physics

Spray drying of detergents in counter current towers: a study of turbulent swirling flows, fouling and agglomeration

This thesis is concerned with the manufacture of granular laundry detergents in counter-current spray dryers making use of turbulent swirling flows. It contributes to a comprehensive description of this process by providing a) an experimental study of the swirling fluid dynamics in various scales and designs, introducing the use of sonic anemometry to this context, b) the description of a complex fouling dynamics at the walls, quantified by rates of deposition and re-entrainment of material, and c) the analysis of the sources of particle-droplet agglomeration in different sections of the dryer, under the operation of one or multiple sprays. This thesis demonstrates that the interaction with the walls is a central part of the process. In the one hand, friction affects the structure of the flow: it reduces its angular momentum and destabilizes the swirl, which causes recirculation in the dryer and the production of turbulence. In the other, particles deposit at the walls forming a multi-layer that continuously builds and breaks up. A tracer experiment has revealed that this equilibrium in part governs the product residence time, and ultimately how particles dry and aggregate. The data provided here constitute the first evidence of such a behavior in spray dryers

Una investigación intra-cultural de liderazgo en México: igualdad en las PYMES de Hidalgo, Colima y Tamaulipas

This research evidences leadership practices in 301 SMEs distributed in three Mexican states as follows: 121 in Hidalgo; 87 in Colima; and 93 in Tamaulipas. Also, this research concludes that such SMEs share the same managerial behavior based on Kouzes and Posner ́s five-dimension model, i.e., managerial behavior is independent from business and economic regional context. Such conclusions are obtained through leadership framework – mainly from Kouzes and Posner ́s; SMEs context in the three states by establishing three regional samples, validating the IPL test in Spanish, and proving the hypothesis using the test for equality of average sampling.La presente investigación expone las prácticas de liderazgo en 301 Pequeñas y Medianas Empresas (PyMEs). 121 del estado de Hidalgo, 87 de Colima y 93 de Tamaulipas, del país, México. Este estudio se basa en el Inventario de las Prácticas de Liderazgo (IPL) de Kouzes y Posner en sus cinco dimensiones, desafiar los procesos, inspirar una visión compartida, habilitar a los demás para que actúen, modelar el camino y dar aliento al corazón, demuestra concluyentemente, una igualdad de comportamiento gerencial entre las PyMEs de tres estados, objetivo de la presente investigación. Esto es, una independencia en el comportamiento gerencial con relación al contexto empresarial y económico regional. Se siguió el marco teórico de liderazgo, fundamentalmente el de Kouzes y Posner, el Contexto de las PyMEs de los tres estados, se estableció tres muestras regionales, validando el test del IPL en español. Finalmente, se realizó la prueba sobre la bondad de ajuste de muestras y comprobando la hipótesis a través de la prueba de igualdad de promedio entre muestras

O Segredo como Base Da Camarilla: Um Estudo Etnográfico Secreto em uma Organização Hospitalar

The purpose of the present study was to identify the secrets between cliques of a hospital establishment. The findings of the present study highlight the importance of covert ethnography,showing the secrets of these groups. Two related cases are reported, one on septic shock andthe other on unspecialized surgery, which affected the health of the respective patients. It wasshown that shared secrecy and mutual trust between cliques form full cohesive groups in anorganization, since they mutually protect their secrets, safeguarding substantial information andeven endangering the lives of other individuals.El propósito del presente estudio fue identificar los secretos entre camarillas de un establecimiento hospitalario. Los hallazgos del presente estudio resaltan la importancia de la etnografía encubierta, mostrando los secretos de estos grupos. Se reportan dos casos relacionados, uno sobre choque séptico y otro sobre una cirugía no especializada, que afectaron la salud de los respectivos pacientes. Se demostró que el secreto compartido y la confianza mutua entre camarillas, conforman plenas agrupaciones cohesionadas en una organización, pues ellas protegen mutuamente sus secretos, resguardando información substancial y poniendo en peligro, incluso, la vida de otros individuos.O objetivo do presente estudo foi identificar os segredos entre panelinhas de um estabelecimento hospitalar. Os achados do presente estudo destacam a importância da etnografia encoberta,mostrando os segredos desses grupos. São relatados dois casos relacionados, um em choqueséptico e outro em cirurgia não especializada, que afetou a saúde dos respectivos pacientes. Foidemonstrado que o segredo compartilhado e a confiança mútua entre as panelinhas formam grupos coesos completos em uma organização, uma vez que protegem mutuamente seus segredos, salvaguardando informações substanciais e até colocando em risco a vida de outras pessoas

Sistema web basado en Robotic Process Automation para el Proceso de Conocimiento en la empresa T-ID Solutions S.A.C

La presente tesis puntualiza el desarrollo del sistema web basado en robotic process automation para el proceso de conocimiento en la empresa T-ID SOLUTIONS S.A.C., empresa que se encuentra en el rubro de Consultores, Programación y Suministros Informáticos, siendo el giro del negocio gestionar proyectos nacionales e internacionales, desde la recepción de requerimientos hasta el mantenimiento de los mismos, incluyendo el soporte o Mesa de Ayuda (Nivel 1 y 2) con el fin de atender los incidentes reportados por los usuarios finales, todo lo mencionado pertenece a la gestión operativa, así mismo gestiona procesos administrativos internos de desarrollo, calidad, infraestructura y consultorías, estando ausente el proceso de conocimiento, siendo este no explotado en la empresa. Tenemos como propósito en esta tesis el establecer la influencia del Sistema Web Basado en Robotic Process Automation en el proceso del Conocimiento en La Empresa T-ID Solutions SAC, en Miraflores 2019. El tipo de investigación es aplicada, el diseño es pre-experimental y tiene un enfoque cuantitativo. La técnica de recolección de datos ha sido el fichaje y el instrumento fue la ficha de registro, siendo estos validados por expertos. Luego de realizadas las pruebas de pre-test y post-test, se obtuvo con el indicador aprovechamiento de los tickets generados un incremento de 79,3%, teniendo inicialmente 6,10% y posteriormente 85,40%, mientras que de los miembros involucrados fue 33,7 teniendo inicialmente una media de 5,0 y posteriormente 38,7. Por último, se determina que el producto web influyo positivamente en el proceso del Conocimiento de La Empresa T-ID Solutions SAC

Influence of wall friction on flow regimes and scale-up of counter-current swirl spray dryers

The structure of the vortex flow in swirl spray dryers is investigated after having fouled the walls with deposits typical of detergent manufacture. The range of Re and swirl intensity Ω characteristic of industry are studied using three counter-current units of varying scale and design. The friction with the deposits increases the flow turbulence kinetic energy and causes a drastic attenuation of the swirl and as a result, the vortex breaks down in the chamber forming recirculation regions (i.e. areas of reverse flow). Three flow regimes (1) no recirculation, (2) central and (3) annular recirculation have been identified depending on the swirl intensity. New control and scale up strategies are proposed for swirl dryers based in predicting the decay and the flow regime using the unit geometry (i.e. initial swirl intensity Ωi) and experimental decay rates function of the coverage and thickness of deposits. The impact in design and numerical modelling must be stressed. Adequate prediction of the swirl is vital to study fouling and recirculation, which surely play an important part in the dispersion and aggregation of the solid phase. Current models have no means to replicate these phenomena, and yet, in this case neglecting the deposits and assuming smooth walls would result in (a) over-prediction of swirl velocity up to 40-186% (b) under-prediction of turbulent kinetic energy up to 67-85% and (c) failure to recognise recirculation areas

Las ventajas y desventajas de una posible regulaci?n en el uso de las criptomonedas en el Per?

En la presente investigaci?n analizaremos las ventajas y desventajas de una posible regulaci?n en el uso de criptomonedas en el Per?, utilizando como referencia la evoluci?n del concepto de dinero a lo largo del tiempo y su uso como medio de intercambio legal, a trav?s de los avances tecnol?gicos. El objetivo de esto es mostrar los efectos positivos y negativos ante estos dos escenarios de legislaci?n, lo cual nos permitir? ejemplificar de una forma m?s clara las ventajas y desventajas de la existencia ante una posible legislaci?n en nuestro pa?s. De nuestro an?lisis, y como resultado de nuestra investigaci?n, podemos concluir que una posible regulaci?n representa no solamente una necesidad para el pa?s, adem?s de presentar riesgos y retos que su implementaci?n conllevar?a, al ser el Per? un pa?s con serias deficiencias tecnol?gicas, brechas digitales muy amplias entre distintos. Tambi?n la entendemos como una oportunidad para nuestra naci?n de implementar grandes cambios en infraestructura y comunicaciones, como respuesta a los grandes cambios tecnol?gicos que atraviesa el mundo; de este modo, se ofrecer? soporte a las pol?ticas p?blicas orientadas a mejorar la inclusi?n y cultura financiera, se implementar?n sistemas digitales y llevaremos al Per? en una posici?n de vanguardia de transacciones, medios de pagos y finanzas

An experimental investigation of the swirling flow in a tall-form counter current spray dryer

This work studies the air flow in a large swirl counter-current dryer using sonic anemometry. Air velocity and turbulence fields are reported at isothermal conditions and in the absence of particles. In a tall-form unit the structure of the flow is largely influenced by the design of the exit. A contraction originates a central jet and suppresses the formation of recirculation zones despite the vortex acquires a high swirl intensity Ω (i.e. 1<Ω<2). Access to a full scale tower has permitted to: (a) identify asymmetries owed to the design of inlet and exhaust ducts, (b) present the first detailed turbulence data in production units, characterized by a highly anisotropic field and the axial decay of the turbulence kinetic energy, (c) study the flow stability, identifying the precession of the vortex core and oscillations at a constant Strouhal number and (d) study the impact that a rough wall has in the strength of the swirl. This work presents the first clear evidence of significant friction in spray dryers. The swirl intensity Ω decays exponentially in the dryer at a rate between 0.08 and 0.09, much higher than expected in pipe flow and independent of Re in the range 105-2.2{dot operator}105. Production dryers have a large characteristic wall roughness due the presence of deposits, which explains the stronger friction and the discrepancies found in the past between data at full scale or clean laboratory or pilot scale units. It is essential to address this phenomenon in current numerical models, which are validated on laboratory or pilot scale facilities and ignore the role of deposits, thus causing an overprediction of the tangential velocity above 30-40%

Particle aggregation in large counter-current spray drying towers: Nozzle configuration, vortex momentum and temperature

This work investigates particle growth in a counter-current swirl detergent dryer, operating with a single nozzle, at a range of nozzle heights, air drying temperatures, TA, and superficial air velocities, UA, which were selected to enhance or inhibit particle aggregation in the dryer. The growth kinetics are discussed paying special attention to the impact of the cycle of deposition and re-entrainment of material from the wall deposits. All cases lead to substantial aggregation and mono-modal product size distributions. The operation at low UA and high TA, (i.e. low momentum) does not inhibit growth as one would expect from a lower particle concentration and faster heat and mass transfer, conditions which would lead to less particle collisions resulting in growth. In contrast, generation of aggregated particles > 850 μm is promoted, suggesting that a change in the erosion behavior of particles from the wall due to a reduction in energy of particle impacts. As a result of lower stresses, erosion is suppressed and clusters remain at the wall for longer, what allows them to sinter and be re-entrained at larger sizes. In contrast, increasing the momentum of the continuous phase by operation at low TA and high UA inhibits particle growth, particularly in the production of the largest sizes > 850 μm. In this case the rate and energy of impacts to the wall increases, this leads to higher disruptive stresses on the wall deposits, thus, reducing the size of the clusters re-entrained. In summary, this work describes aggregation mechanisms in swirl detergent dryers operated with single nozzles, suggesting that, contrary to expectations, wearing of deposits rather than air-borne contacts may be a key contributor to the enhancement or inhibition of growth

Salvage stereotactic body radiotherapy for isolated lymph node recurrent prostate cancer : single institution series of 94 consecutive patients and 124 lymph nodes

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