The Effect of Inkjet Ink Composition on Rheology And Jetting Behaviour

This work presents recent results on the way linear and non linear viscoelastic properties of the fluids affect the jetting mechanism. Recent progress on quantitative characterising both high frequency linear (LVE) and non-linear (NLVE) viscoelasticity of fluids allows fluids to be assessed for their jettability before using such materials in a DoD print head. In term of linear viscoelastic measurements, the Piezo Axial Vibrator (PAV) was used to probe the rheology of the fluids on a frequency range between 10Hz and 10000Hz. A filament stretching apparatus, called the “Cambridge Trimaster”, was used in combination with high speed cinematography, to characterize the fluids high speed stretching and break-up behaviour. The series of fluids investigated here consist in dilutions of mono disperse polystyrene with different molecular weight (110, 210, 306 and 488 kg/mol respectively) diluted in diethyl phthalate. The choice of polymer weights and concentrations were chosen to match both the complex viscosity and the LVE. However, non linear rheological data experiments exhibit differences in the fluid relaxation time and filament break-up mechanism. Ultra-high speed cinematography of DoD jetting events were correlated with filament break-up experiments and demonstrated that fluid rheology provides valuable information on the jetting quality of the fluids

On the modeling of viscoelastic droplet impact dynamics

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In this paper, a numerical modeling of the impact, spreading, and eventually rebound of a viscoelastic droplet is reported. The numerical model is based on the volume of fluid (VOF) method coupled with the FENE-CR constitutive equations, and accounts for both the surface tension and the substrate wettability. The FENE-CR constitutive equations are used to model the polymer solution, while taking advantage of its rheological characterization. The comparison is performed between droplets of Newtonian solvent and a monodisperse polymer solution. The droplet impact on both hydrophilic and superhydrophobic substrate is analyzed through a detailed analysis of the spreading diameter evolution. It is found that while the droplet kinematic phase seems independent of the substrate and fluids properties, the recoiling phase is highly related to all of them. In addition the model infers a critical polymer concentration above which the droplet rebound from a superhydrophobic substrate is suppressed. The simulation is of particular interest to ink-jet processing, and demonstrates the capability of the model to handle complex non-Newtonian droplet dynamics

Femtosecond time-resolved phase-change microscopy and ablation threshold calculations to understand ultrafast laser ablation

El trabajo recoge experimentos realizados en una configuración sonda-prueba haciendo uso de un láser de femtosegundos, con el objetivo de comprender los fenómenos de ablación de materiales sólidos ras irradiación con láseres de pulso ultracorto.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Estudio de los impactos ambientales de los cruces de gasoductos con ríos vadeables

El río Cigüela y su afluente Valdepineda (Cuenca, España) fueron afectados por el cruce de un gasoducto, en Diciembre de 2001, mediante la técnica convencional "cruce subálveo" que consta de tres fases: instalación de la pista de trabajo, apertura de zanja y rehabilitación. Con el objetivo de evaluar el impacto de las distintas etapas de la obra en el medio acuático, se está llevando a cabo un estudio que se centra en el efecto de los sólidos en suspensión en las comunidades macrobentónicas e ícticas. Se presentan los resultados preliminares obtenidos en la fase de apertura de zanja, donde se observa un valor muy elevado de movilización de sólidos en suspensión (hasta 5000 mg/l), alcanzando las mayores concentraciones en los 100 primeros metros aguas abajo del punto de cruce. Estos sólidos en suspensión podrían ser la causa del aumento significativo de la sedimentación de las partículas de tamaño comprendido entre 50-250 μm y 250-500 μm en los 30 primeros metros aguas abajo del punto de cruce. Por otro lado, no se han observado diferencias en el valor del índice BMWP' en las distintas estaciones de muestreo. Sin embargo, en la fase de rehabilitación, se encuentra una diferencia significativa en la frecuencia de distribución de algunas de las especies de peces presentes en el río, además se observa un claro efecto barrera para la ictiofauna al eliminar la pista de trabajo.The Cigüela River and its tributary, Valdepineda (Cuenca, España) were affected by the crossing of a natural gas pipeline, in December 2001, by means of the conventional technique "open-cut water crossing" that consists of three different works: installation of the right-of-way, excavation and backfill of the pipeline trench, and restoration. In order to assess the impacts of these different activities on the aquatic environment, we are carrying out a study that is focused on the effects of suspended solids in the benthic and fish communities. Preliminary results of this study are presented on the excavation and backfill of the pipeline trench, that indicate that a very high value of suspended solids mobilisation is observed (up to 5000 mg/l), reaching the higher concentrations in the first 100 meters downstream of the crossing site. These suspended solids might be responsible for the significant increase in the sedimentation of the particles of sizes 50-250 μm and 250-500 μm in the 30 first meters downstream of the crossing site. On the other hand, we have not found differences in the values of the BMWP' index at the different sampling sites. Nevertheless, in the restoration phase , there is a significant difference in the distribution frequency of some fish species that appear in the river and also a clear barrier effect is observed for fishes when eliminating the right-of-way

Time-resolved laser-induced phase change microscopy: understanding laser-matter effects at the femtosecond scale

LA comunicación describe el desarrollo instrumental y las aplicaciones con un microscopio de cambio de fase con resolución de femtosegundos que se ha puesto a punto en el LAboratorio LAser de la UMAUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Implantes inmediatos con restauración inmediata en situaciones de alto riesgo estético

Poster en jornada o congres

The matching of polymer solution fast filament stretching, relaxation, and break up experimental results with 1D and 2D numerical viscoelastic simulation

this work was supported by EPSRC grant number RG5560

Catchment soil moisture and rainfall characteristics as determinant factors for discharge/suspended sediment hysteretic loops in a small headwater catchment in the Spanish pyrenees

32 páginas, 7 figuras, 4 tablas.-- El PDF es el artículo en formato pre-print.The concentration of suspended sediment and discharge generated during flood events are not normally homogenous, and the curve representing sediment concentration vs. discharge through time is often a hysteretic loop. Three types of hysteretic loops were found at Arnás, a Mediterranean headwater catchment in the Central Spanish Pyrenees: clockwise (the most frequent), counter-clockwise and eight-shaped. They are associated with different levels of humidity and rainfall and therefore indicators of different processes of runoff and sediment transport. Clockwise loops are generated under ‘normal’ stormflow conditions, when the catchment is very moist and runoff generation and sediment supply is limited to areas next to the channel (i.e. sediments are removed, transported and depleted rapidly). Counter-clockwise curves occur under very high moisture and high antecedent rainfall conditions. In this case, flood propagation occurs as a kinematic wave. Sediment sources are incorporated all over the catchment. In both cases, saturation excess overland flow generates the superficial runoff. The eight-shaped loop (partial clockwise followed by counter-clockwise) occurs with low water content. Here, the runoff generation process is supposed to be infiltration excess overland flow, which causes a rapid extension of the contributing areas both near the channel and over the whole catchment.This paper has been supported by the following projects: ‘Water resources management in a changing environment: the impact of sediment on sustainability’ (WARMICE, ENV4-CT98-0789) funded by the European Comission, and ‘Assessment of sediment sources and runoff generation areas in relation to land use changes’ (HIDROESCALA, REN2000-1709-C04-01/GLO) and ‘Hydrological processes in semi-natural Mediterranean areas’ (PROHISEM, REN 2001-2268-C02-01/HID), both funded by CICYT. Monitoring of the catchment has been supported by the agreement between CSIC and the Spanish Ministry of Environment (RESEL).Peer reviewe