Bubble size distribution resulting from the breakup of an air cavity injected into a turbulent water jet

We investigated experimentally the shape of the final size PDF(D) resulting from the breakup of an air bubble injected into the fully developed region of a high Reynolds number turbulent water jet. It is shown that the PDF(Dcirc) of the normalized bubble size Dcirc=D/D32, where D32 is the Sauter mean diameter of the distribution, has a universal single shape independent of the value of the turbulent kinetic energy of the water jet at the bubble injection point and of the air void fraction, α. The shape of the exponential tails characterizing each PDF(D) is shown to be only a function of the initial bubble size D0 and the critical bubble size Dc, defined as Dc=(1.46σ/ρ)3/5ɛ-2/5, where ɛ is the value of the dissipation rate of turbulent kinetic energy per unit mass at the air injection point

Statistical description of the bubble cloud resulting from the injection of air into a turbulent water jet

The final bubble size distribution, resulting from the break-up of an air jet injected into the central axis of a fully developed, high Reynolds number turbulent water jet has been measured using a Phase Doppler Particle Analyzer (PDPA). The shape of the final size distribution is shown to depend not only on the dissipation rate of turbulent kinetic energy, ε, but also on the global void fraction, αH. It has been shown that such a dependence can be expressed as a function of two dimensionless numbers, namely the jet Weber number, Wen=ρUJ2DJ/σ, and the ratio between the initial bubble's size and the critical diameter, D0/Dc. The statistical properties of the time and distance separating two bubbles of the same diameter, after the turbulent break process is complete, have also been measured. The probability density function of the inter-arrival time between two consecutive bubbles was found to follow an exponential distribution with intensity factor, λ, depending on the number density of bubbles of a certain diameter and on the velocity of the flow

A control problem arising in the process of waste water purification

AbstractIn this paper we state and solve an optimal control problem arisen from the management of the sewage disposal which is dumped into the sea through submarine outfalls. Firstly, we fix oxygen and amount of organic matter as water quality indicators and we state a partial differential equations model to simulate them in a domain occupied by shallow waters. Constraints about water quality and economic objectives lead us to a pointwise optimal control problem with state and control constraints. (The theoretical analysis of the problem has been developed by the authors in (Martinez et al., C. R. Acad. Sci. Paris, Serie I 328 (1999) 35.) (Martinez et al., Preprint, Dept. Matematica Aplicada, Univ. Santiago de Compostela, Spain, 1998.)). We deal with the problem by using time and space discretizations and we propose two algorithms for the numerical resolution of the discretized problem. Finally, we give numerical results obtained by applying the described techniques for a realistic problem posed in the rı́a of Vigo (Spain)

A review of statistical models for the break-up of an immiscible fluid immersed into a fully developed turbulent flow

We consider the statistical description of the break-up of an immiscible fluid lump immersed into a fully developed turbulent flow. We focus on systems where there is no relative velocity between the continuous and dispersed phases. In this case, particle fragmentation is caused only by turbulent velocity fluctuations. The most relevant models proposed for the particle break-up frequency and for the shape of the daughter particle size distribution are reviewed. Their predictions are compared to recent experimental data, obtained for the break-up of an air cavity immersed into a high Reynolds number, turbulent water jet. Models based on purely kinematic arguments show the best agreement with the experimental data

Electromagnetic Radiation Hardness of Diamond Detectors

The behavior of artificially grown CVD diamond films under intense electromagnetic radiation has been studied. The properties of irradiated diamond samples have been investigated using the method of thermally stimulated current and by studying their charge collection properties. Diamonds have been found to remain unaffected after doses of 6.8 MGy of 10 keV photons and 10 MGy of MeV-range photons. This observation makes diamond an attractive detector material for a calorimeter in the very forward region of the proposed TESLA detector.Comment: 19 pages, 9 figure

Role of toxin activation on binding and pore formation activity of the Bacillus thuringiensis Cry3 toxins in membranes of Leptinotarsa decemlineata (Say)

AbstractBinding and pore formation constitute key steps in the mode of action of Bacillus thuringiensis δ-endotoxins.In this work, we present a comparative analysis of toxin-binding capacities of proteolytically processed Cry3A, Cry3B and Cry3C toxins to brush border membranes (BBMV) of the Colorado potato beetle Leptinotarsa decemlineata (CPB), a major potato coleopteran-insect pest. Competition experiments showed that the three Cry3 proteolytically activated toxins share a common binding site. Also heterologous competition experiments showed that Cry3Aa and Cry3Ca toxins have an extra binding site that is not shared with Cry3Ba toxin. The pore formation activity of the three different Cry3 toxins is analysed. High pore-formation activities were observed in Cry3 toxins obtained by proteolytical activation with CPB BBMV in contrast to toxins activated with either trypsin or chymotrypsin proteases. The pore-formation activity correlated with the formation of soluble oligomeric structures. Our data support that, similarly to the Cry1A toxins, the Cry3 oligomer is formed after receptor binding and before membrane insertion, forming a pre-pore structure that is insertion-competent

Residual strain effects on the two-dimensional electron gas concentration of AlGaN/GaN heterostructures

Ga-face AlGaN/GaN heterostructures with different sheet carrier concentrations have been studied by photoluminescence and Raman spectroscopy. Compared to bulk GaN, an energy shift of the excitonic emission lines towards higher energies was observed, indicating the presence of residual compressive strain in the GaN layer. This strain was confirmed by the shift of the E2 Raman line, from which biaxial compressive stresses ranging between 0.34 and 1.7 GPa were deduced. The spontaneous and piezoelectric polarizations for each layer of the heterostructures have been also calculated. The analysis of these quantities clarified the influence of the residual stress on the sheet electron concentration (ns). Possible causes for the discrepancies between the calculated and experimentally determined sheet carrier densities are briefly [email protected] ; [email protected]

Optical and photovoltaic properties of indium selenide thin films prepared by van der Waals epitaxy

Indium selenide thin films have been grown on p-type gallium selenide single crystal substrates by van der Waals epitaxy. The use of two crucibles in the growth process has resulted in indium selenide films with physical properties closer to these of bulk indium selenide than those prepared by other techniques. The optical properties of the films have been studied by electroabsorption measurements. The band gap and its temperature dependence are very close to those of indium selenide single crystals. The width of the fundamental transition, even if larger than that of the pure single crystal material, decreases monotonously with temperature. Exciton peaks are not observed even at low temperature, which reveals that these layers still contain a large defect concentration. The current–voltage characteristic of indium selenide thin film devices was measured under simulated AM2 conditions. The solar conversion efficiency of these devices is lower than 0.6%. The high concentration of defects reduces the diffusion length of minority carriers down to values round to 0.2 μ[email protected] ; [email protected]

Calcium and temperature effect on structural damage of hot air dried apple slices: Nonlinear irreversible thermodynamic approach and rehydration analysis

Mathematical models traditionally employed in fitting convective drying data do not use to report information about chemical and other physical changes different from the simple decrease in moisture content. In the present study, structural damage undergone by fresh and vacuum impregnated apple slices with different calcium lactate concentrations during convective drying at 30, 40 and 50 °C was analysed by applying equations derived from nonlinear irreversible thermodynamics to experimental data. According to the results obtained, vacuum impregnation with isotonic sucrose solution before drying at 30 °C provided maximum protection to cellular structure by promoting reversible deformations against irreversible breakages. On the contrary, cell walls strengthen with calcium had severe damaged during drying. Regarding air temperature, it was directly related both to the molar energy employed in deforming structures and the drying rate. These results were confirmed by analysing dried samples behaviour during further rehydration.Barrera Puigdollers, C.; Betoret Valls, N.; Betoret Valls, ME.; Fito Maupoey, P. (2016). Calcium and temperature effect on structural damage of hot air dried apple slices: Nonlinear irreversible thermodynamic approach and rehydration analysis. Journal of Food Engineering. 189:106-114. doi:10.1016/j.jfoodeng.2016.05.024S10611418