Numerical Simulation of Electroosmotic Flow with Step Change in Zeta Potential

Electroosmotic flow is a convenient mechanism for transporting polar fluid in a microfluidic device. The flow is generated through the application of an external electric field that acts on the free charges that exists in a thin Debye layer at the channel walls. The charge on the wall is due to the chemistry of the solid-fluid interface, and it can vary along the channel, e.g. due to modification of the wall. This investigation focuses on the simulation of the electroosmotic flow (EOF) profile in a cylindrical microchannel with step change in zeta potential. The modified Navier-Stoke equation governing the velocity field and a non-linear two-dimensional Poisson-Boltzmann equation governing the electrical double-layer (EDL) field distribution are solved numerically using finite control-volume method. Continuities of flow rate and electric current are enforced resulting in a non-uniform electrical field and pressure gradient distribution along the channel. The resulting parabolic velocity distribution at the junction of the step change in zeta potential, which is more typical of a pressure-driven velocity flow profile, is obtained.

Study on Granular Dynamics in Vertically Vibrated Beds using Tracking Technique

The study of granular material is of great interest to many researchers in both engineering and science communities. The importance of such a study derives from its complex rheological character and also its significant role in a wide range of industrial applications, such as coal, food, plastics, pharmaceutical, powder metallurgy and mineral processing. A number of recent reports have been focused on the physics of non-cohesive granular material submitted to vertical vibration in either experimental or theoretical approaches. Such a kind of system can be used to separate, mix and dry granular materials in industries. It exhibits different instability behaviour on its surface when under vertical vibration, for example, avalanching, surface fluidization and surface wave, and these phenomena have attracted particular interest of many researchers. However, its fundamental understanding of the instability mechanism is not yet well-understood. This paper is therefore to study the dynamics of granular motion in such a kind of system using Positron Emission Particle Tracking (PEPT), which allows the motion of a single tracer particle to be followed in a non-invasive way. Features of the solids motion such as cycle frequency and dispersion index were investigated via means of authors��� specially-written programmes. Regardless of the surface behaviour, particles are found to travel in rotational movement in horizontal plane. Particle cycle frequency is found to increase strongly with increasing vibration amplitude. Particle dispersion also increased strongly with vibration amplitude. Horizontal dispersion is observed to always exceed vertical dispersion.

The Inertio-Elastic Planar Entry Flow of Low-Viscosity Elastic Fluids in Micro-fabricated Geometries

The non-Newtonian flow of dilute aqueous polyethylene oxide (PEO) solutions through microfabricated planar abrupt contraction-expansions is investigated. The contraction geometries are fabricated from a high-resolution chrome mask and cross-linked PDMS gels using the tools of soft-lithography. The small length scales and high deformation rates in the contraction throat lead to significant extensional flow effects even with dilute polymer solutions having time constants on the order of milliseconds. The dimensionless extra pressure drop across the contraction increases by more than 200% and is accompanied by significant upstream vortex growth. Streak photography and videomicroscopy using epifluorescent particles shows that the flow ultimately becomes unstable and three-dimensional. The moderate Reynolds numbers (0.03 ������ Re ������ 44) associated with these high Deborah number (0 ������ De ������ 600) microfluidic flows results in the exploration of new regions of the Re-De parameter space in which the effects of both elasticity and inertia can be observed. Understanding such interactions will be increasingly important in microfluidic applications involving complex fluids and can best be interpreted in terms of the elasticity number, El = De/Re, which is independent of the flow kinematics and depends only on the fluid rheology and the characteristic size of the device.

Viscous Flow and Fluid Dynamics

Exam questions and solutions for a third year maths course. Diagrams for the questions are all together in the support.zip file, as .eps files

On the Foundations of Quantitative Information Flow

The paper introduces vulnerability and quantitative privacy. Optional reading

Open Equipment data flow

Short set of slides explaining the workflow from a university website to equipment.data.ac.uk

Genome-wide evidence for speciation with gene flow in Heliconius butterflies

Most speciation events probably occur gradually, without complete and immediate reproductive isolation, but the full extent of gene flow between diverging species has rarely been characterized on a genome-wide scale. Documenting the extent and timing of admixture between diverging species can clarify the role of geographic isolation in speciation. Here we use new methodology to quantify admixture at different stages of divergence in Heliconius butterflies, based on whole-genome sequences of 31 individuals. Comparisons between sympatric and allopatric populations of H. melpomene, H. cydno, and H. timareta revealed a genome-wide trend of increased shared variation in sympatry, indicative of pervasive interspecific gene flow. Up to 40% of 100-kb genomic windows clustered by geography rather than by species, demonstrating that a very substantial fraction of the genome has been shared between sympatric species. Analyses of genetic variation shared over different time intervals suggested that admixture between these species has continued since early in speciation. Alleles shared between species during recent time intervals displayed higher levels of linkage disequilibrium than those shared over longer time intervals, suggesting that this admixture took place at multiple points during divergence and is probably ongoing. The signal of admixture was significantly reduced around loci controlling divergent wing patterns, as well as throughout the Z chromosome, consistent with strong selection for M��llerian mimicry and with known Z-linked hybrid incompatibility. Overall these results show that species divergence can occur in the face of persistent and genome-wide admixture over long periods of time.

Predicci��n del flow disposicional seg��n clima motivacional y el trato generado por el profesor en clase de Educaci��n F��sica.

Resumen tomado de la publicaci��n

An��lisis de las relaciones entre orientaciones de meta, clima motivacional, valoraci��n de la Educaci��n F��sica y flow disposicional en estudiantes de Educaci��n F��sica en secundaria.

Resumen tomado de la publicaci��n

Motivaci��n, comportamientos de disciplina, trato de igualdad y flow disposicional en estudiantes de educaci��n f��sica.

Analizar las relaciones existentes dentro del entorno marcado por la educaci��n f��sica entre cuatro factores claramente diferenciados: la motivaci��n del alumno hacia las clases, la que genera el profesor, los comportamientos disciplinados e indisciplinados, la percepci��n de la igualdad en el trato entre chicos y chicas y el flow disposicional mostrado en la mejor experiencia sentida por el alumno en sus clases. . Poblaci��n de estudiantes de primer ciclo de ESO de la Comunidad Valenciana. Muestra compuesta por un total de 1103 alumnos pertenecientes al segundo curso de ESO de centros p��blicos y privados de la provincia de Alicante. Los instrumentos empleados para recoger la informaci��n son: Cuestionario de Percepci��n del ��xito (Cervell��, Escart�� y Balagu��, 1999); Instrumento de Medici��n del Clima Motivacional en las Clases de Educaci��n F��sica (Cervell��, Moreno, Del Villar y Reina, 2006); Cuestionario de Conductas de Disciplina-Indisciplina en Educaci��n F��sica (Cervell��, Jim��nez, Nerea, Ramos, Del Villar y Santos-Rosa, 2002); Cuestionario de Percepci��n de Igualdad-Discriminaci��n en Educaci��n F��sica (Cervell��, Jim��nez, Del Villar, Ramos y Santos-Rosa, 2004); Escala de Flow Dispocicional (Jackson, 2000. Traducida por Cervell��, Nerea, Jim��nez, Garc��a-Calvo y santos-Rosa, 2001). Se utiliz�� el an��lisis factorial de componentes principales con rotaci��n varimax para todos los cuestionarios con el fin de determinar su estructura. Se aplica el an��lisis de correlaci��n para descubrir las relaciones entre variables del estudio. El an��lisis jer��rquico de cluster para identificar los perfiles motivacionales de los alumnos que componen la muestra de estudio atendiendo a las variables de orientaci��n disposicional, clima motivacional percibido, disciplina, coeducaci��n y flow disposicional y el an��lisis de ecuaciones estructurales para testar los modelos te��ricos de la investigaci��n.. Es de vital importancia que el profesor de educaci��n f��sica cree un adecuado clima motivacional implicante en la tarea porque ser�� as�� facilitador de un trato justo y ecu��nime hacia todos sus alumnos, generador de un buen ambiente de clase debido al buen comportamiento de sus discentes ocasionado por la preocupaci��n de ��stos hacia el aprendizaje de la materia impartida y fomentador de un estado psicol��gico ��ptimo que le ayude a concentrar su atenci��n sobre la actividad a realizar obteniendo como resultado una experiencia enriquecedora y satisfactoria..

Biological nutrient removal in SBR technology: from floccular to granular sludge

Biological nutrient removal has been studied and applied for decades in order to remove nitrogen and phosphorus from wastewater. However, more anthropogenic uses and the continued demand for water have forced the facilities to operate at their maximum capacity. Therefore, the goal of this thesis is to obtain more compact systems for nutrient removal from domestic wastewater. In this sense, optimization and long-term stabilization of high volume exchange ratios reactors, treating higher volumes of wastewater, have been investigated. With the same target, aerobic granular sludge was proposed as a reliable alternative to reduce space and increase loading rates in treatment plants. However, the low organic loading rate from low-strength influents (less than 1 Kg COD���m-3d-1) results in slower granular formation and a longer time to reach a steady state. Because of that, different methodologies and operational conditions were investigated in order to enhance granulation and nutrient removal from domestic wastewater.

Flow e os fen��menos de mentoria e lideran��a em ind��strias de inje����o de pl��sticos da Marinha Grande

Este estudo procura investigar poss��veis associa����es entre as experi��ncias de flow e os fen��menos de mentoria e lideran��a. Procura-se identificar as caracter��sticas e benef��cios de experi��ncias de flow e de rela����es de mentoria e lideran��a, percebidos pelos colaboradores de quatro empresas de Inje����o de Pl��sticos da Marinha Grande. Identificam-se as fun����es de mentoria, os estilos de lideran��a transacional, transformacional e servidora e os componentes de flow entre estes colaboradores. Para a medi����o dos estilos de lideran��a foram utilizados os instrumentos desenvolvidos por Avolio e Bass (2004) e Dennis (2004). Para as fun����es das rela����es de mentoria, definidas por Ragins e Kram (2007), o instrumento desenvolvido por Noe (1988). Para os componentes observados em experi��ncias de flow, o instrumento desenvolvido por Jackson e Ecklund (2002). Apoiado nos instrumentos referidos foi aplicado um question��rio na recolha dos dados para este estudo. Foram encontradas influ��ncias moderadas e fortes entre os estilos de lideran��a, as fun����es de mentoria e os componentes de uma experi��ncia de flow.

Oportunidades y perspectivas para PROSISA industria de cintas pl��sticas al aplicar el material flow management (manejo de flujos materiales)

En la presente tesis los prop��sitos principales son la adecuada conceptualizaci��n y presentaci��n del manejo de flujos materiales; nueva tendencia que ha generado expectativas en el exterior principalmente en industrias europeas y de Norte Am��rica. Adem��s se busca dentro del presente trabajo analizar las connotaciones y oportunidades de la aplicaci��n del manejo de flujos materiales en una empresa especifica de nuestro pa��s, ���PROSISA��� Productos sint��ticos S.A., considerando tambi��n las incidencias que esto podr��a tener en la industria general de Pl��sticos. Con el prenombrado an��lisis tambi��n se busca identificar las perspectivas que la empresa de sint��ticos pueda tener al aplicar el manejo de flujos materiales dentro de su proceso productivo principalmente con los desperdicios y posibles soluciones para optimizar los recursos empleados.

The influence of viscous and latent heating on crystal-rich magma flow in a conduit

The flow dynamics of crystal-rich high-viscosity magma is likely to be strongly influenced by viscous and latent heat release. Viscous heating is observed to play an important role in the dynamics of fluids with temperature-dependent viscosities. The growth of microlite crystals and the accompanying release of latent heat should play a similar role in raising fluid temperatures. Earlier models of viscous heating in magmas have shown the potential for unstable (thermal runaway) flow as described by a Gruntfest number, using an Arrhenius temperature dependence for the viscosity, but have not considered crystal growth or latent heating. We present a theoretical model for magma flow in an axisymmetric conduit and consider both heating effects using Finite Element Method techniques. We consider a constant mass flux in a 1-D infinitesimal conduit segment with isothermal and adiabatic boundary conditions and Newtonian and non-Newtonian magma flow properties. We find that the growth of crystals acts to stabilize the flow field and make the magma less likely to experience a thermal runaway. The additional heating influences crystal growth and can counteract supercooling from degassing-induced crystallization and drive the residual melt composition back towards the liquidus temperature. We illustrate the models with results generated using parameters appropriate for the andesite lava dome-forming eruption at Soufriere Hills Volcano, Montserrat. These results emphasize the radial variability of the magma. Both viscous and latent heating effects are shown to be capable of playing a significant role in the eruption dynamics of Soufriere Hills Volcano. Latent heating is a factor in the top two kilometres of the conduit and may be responsible for relatively short-term (days) transients. Viscous heating is less restricted spatially, but because thermal runaway requires periods of hundreds of days to be achieved, the process is likely to be interrupted. Our models show that thermal evolution of the conduit walls could lead to an increase in the effective diameter of flow and an increase in flux at constant magma pressure.

Impact of Tibetan Orography and Heating on the Summer Flow over Asia

The influence on the summer flow over Asia of both the orographic and thermal forcing of the Tibetan Plateau is investigated using a sequence of idealised experiments with a global primitive equation model. The zonally averaged flow is prescribed and both realistic and idealised orography and heating are used. There is some similarity between the responses to the two forcings when applied separately. The upper tropospheric Tibetan anticyclone is predominantly forced by the heating but also weakly by the orography. Below this, both forcings tend to give air descending in an equatorward anticyclonic circulation down the isentropes to the west and rising in a similar poleward circulation to the east. However the heating-only response has a strong ascending southwesterly flow that is guided around the south and south-east of the orography when it is included. On the northern side, the westerly flow over the orography gives ascent on the upslope and descent on the downslope. It is found that heating over the Plateau leads to a potential vorticity (PV) minimum and that if it is sufficiently strong the flow is unstable, producing a quasi-biweekly oscillation. During this oscillation the Tibetan anticyclone changes between a single centre over the southwestern side of the Plateau and a split/double structure with centres over China and the Middle East. These characteristics are similar to observed variability in the region. Associated with this quasi-biweekly oscillation are significant variations in the strength of the ascent over the Plateau and the Rossby wave pattern over the North Pacific. The origin of the variability is instability associated with the zonally extended potential vorticity PV minimum on a ��-surface, as proposed by Hsu and Plumb (2000). This minimum is due to the tendency to reduce the PV above the heating over the Plateau and to advection by the consequent anticyclone of high PV around from the east and low PV to the west. The deep convection to the south and southeast of the Plateau tends to suppress the quasi-biweekly oscillation because the low PV produced above it acts to reduce the meridional PV gradient reversal. The occurrence of the oscillation depends on the relative magnitude of the heating in the two regions.