Considerations on bubble fragmentation models

n this paper we describe the restrictions that the probability density function (p.d.f.) of the size of particles resulting from the rupture of a drop or bubble must satisfy. Using conservation of volume, we show that when a particle of diameter, D0, breaks into exactly two fragments of sizes D and D2 = (D30−D3)1/3 respectively, the resulting p.d.f., f(D; D0), must satisfy a symmetry relation given by D22 f(D; D0) = D2 f(D2; D0), which does not depend on the nature of the underlying fragmentation process. In general, for an arbitrary number of resulting particles, m(D0), we determine that the daughter p.d.f. should satisfy the conservation of volume condition given by m(D0) ∫0D0 (D/D0)3 f(D; D0) dD = 1. A detailed analysis of some contemporary fragmentation models shows that they may not exhibit the required conservation of volume condition if they are not adequately formulated. Furthermore, we also analyse several models proposed in the literature for the breakup frequency of drops or bubbles based on different principles, g(ϵ, D0). Although, most of the models are formulated in terms of the particle size D0 and the dissipation rate of turbulent kinetic energy, ϵ, and apparently provide different results, we show here that they are nearly identical when expressed in dimensionless form in terms of the Weber number, g*(Wet) = g(ϵ, D0) D2/30 ϵ−1/3, with Wet ~ ρ ϵ2/3 D05/3/σ, where ρ is the density of the continuous phase and σ the surface tension

Corales tabulados del Ordovícico (Caradoc) de la Precordillera Argentina.

En este estudio se describen por primera vez dos corales tabulados del Ordovícico de la Precordillera Argentina. Se trata de un ejemplar asignado a aff. Paleofavosites sp., procedente de la formación Las Aguaditas y otro clasificado como ?Billingsaria sp., procedente de la Formación Las Plantas, ambos del Caradoc. La escasez del material y detalles problemáticos de su microestructura en el primero de los casos y la mala preservación en el segundo impiden llegar a determinaciones taxonómicas más precisas. [ABSTRACT] This study deals with the description of two Ordovician tabulate corals from Argentine Precordillera. This is the first description of Ordovician tabulate corals in Argentina. They are one specimen of aff. Paleofavosites sp., from the Las Aguaditas Formation and another specimen of ?Billingsaria sp., from the Las Plantas Formation, both Caradoc in age. The scarcity of the material and problematic microstructural details in the first case and the bad preservation of the specimen in the second case impede more precise identifications

Disorder-Induced First Order Transition and Curie Temperature Lowering in Ferromagnatic Manganites

We study the effect that size disorder in the cations surrounding manganese ions has on the magnetic properties of manganites. This disorder is mimic with a proper distribution of spatially disordered Manganese energies. Both, the Curie temperature and the order of the transition are strongly affected by disorder. For moderate disorder the Curie temperature decreases linearly with the the variance of the distribution of the manganese site energies, and for a disorder comparable to that present in real materials the transition becomes first order. Our results provide a theoretical framework to understand disorder effects on the magnetic behavior of manganites.Comment: 4 pages, three figures include

Proposals of a procedure to asses Pollutographs. Application to Murcia's Combined Sewer Overflows (CSOs). Póster

Directives 91/271/EEC and 93/481/EEC set norms regarding the management of Combined Sewer Overflows. European Commission monitors the implementation status and implementation programmes. In fact, during the year 2019 all the utilities should be able to quantify the pollution spilled during storm events. And afterwards, plans have to be developed in order to reduce the impact of such events. In this paper, we proposed a method to estimate the transported pollution during events as well as to serve as a tool for developing plans to lessen the corresponding pollution. The procedure is divided into three steps: A. Periodical measurements of all relevant pollutants, e.g. total suspended solids and chemical oxygen demand, in wet and dry weather. Such pollutant “concentrations” are correlated with the turbidity, updating the relation among them [1]. B. Continuous measures of the turbidity. Turbidity is continously register in the sewer areas near overflow spillways. Turbidimeters are a very convenient equipment for this purpose [2]. Actually, it is reliable, its measures are very correlated with the total suspended solid concentration and its maintenance is easy. In this way, combining A. and B. turbidity measures provide us a real-time estimation of the pollutant concentration. on real time. C. Assesment of each catchment hydrograph. Depending on the available data, this step could be based on a design, a measured or a simulated hydrograph. In order to apply this methodology to Murcia’s Combined Sewer System, we have used simulated hydrographs based on real measured rainfall. Murcia’s utility has developed a calibrated SWMM model, and therefore, using the rainfall data, it is possible to estimate hydrographs for all the relevant points of the system. D. Estimation of each catchment pollutograph. Combining the pollutant concentration, estimated in the previous steps, with the hydrographs, we can asses how the mass of pollutants are transported. This information allows us to comply with EU Directives, but it will also be useful to design Murcia’s strategy to minimize environmental impacts

Evaluating energy recovery potential in Murcia's water supply system

Murcia is the 7th most populated city in Spain. Its water supply system is extensively monitored through a large number of pressure gauges and flow meters. Murcia’s water supply network is fed from distribution reservoirs at enough elevation to avoid needing pumping stations for most of the city districts. Hydraulic resources have been evaluated throughout the water supply system. Besides the pressure reducing valves, where the assessment is quite straight forward [1], District Metered Areas (DMA) inlets have been evaluated. In these areas despite the hydraulic resources are not as great as in pressure reducing valves locations, their location is quite convenient. Actually, these positions are located inside the city, therefore making easy to use the produced energy in municipal self consumption or to provide facilities to the citizens. In order to perform such evaluation, a detailed model of the water supply network has been implemented in EPANET parting from a GIS model. The first step of the evaluation has consisted in the optimizing and validation of the model. Initially, the model was reviewed by comparing pressure and flow rate measurements in the main pipes. Then, an extensive experimental campaign was designed. In that campaign valves were switched so that each day a set of District Metered Areas (DMA) have just one metered inlet or at the most a very short number of metered inlets, whereas having a set of pressure measurements within the DMA. The obtained data was used to minimize errors in pressure time series, optimising roughness of the main pipes through Levenberg/Marquardt BFGS algorithm using EPANET ToolKit through Epanet-Octave [2]. Important roughness proposed changes tended to be located surrounding particular points, where errors in the GIS were located (mainly wrong diameter assignement). After patching all the errors the algorithm eased to localise, model errors were mostly below measures uncertainty, and therefore, the model was considered validated. Then, the hydraulic potential at the DMAs inlets has been evaluated by tracking the “instantaneous” minimum pressure and head within each DMA, as well as the flow rate entering the DMA. So that, the maximum head and the range of flow rates is established for the turbine. At the moment, once that all of these potentials have been assessed, a turbine prototype is being designed

GRB 051221A and Tests of Lorentz Symmetry

Various approaches to quantum gravity suggest the possibility of violation of Lorentz symmetry at very high energies. In these cases we expect a modification at low energies of the dispersion relation of photons that contains extra powers of the momentum suppressed by a high energy scale. These terms break boost invariance and can be tested even at relatively low energies. We use the light curves of the very bright short Gamma-Ray Burst GRB 051221A and compare the arrival times of photons at different energies with the expected time delay due to a modified dispersion relation. As no time delay was observed, we set a lower bound of 0.0066 E_{pl} \sim 0.66 10^{17} GeV on the scale of Lorentz invariance violation.Comment: 9 pages, 2 figure

Caza, recolección y pesca como estrategia de explotación de recursos en forestas tropicales lluviosas: los nukak de la Amazonía colombiana.

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