Different intermittency for longitudinal and transversal turbulent fluctuations

Scaling exponents of the longitudinal and transversal velocity structure functions in numerical Navier-Stokes turbulence simulations with Taylor-Reynolds numbers up to \rel = 110 are determined by the extended self similarity method. We find significant differences in the degree of intermittency: For the sixth moments the scaling corrections to the classical Kolmogorov expectations are $\delta\xi_6^L= -0.21 \pm 0.01$ and \dx_6^T= -0.43 \pm 0.01, respectively, independent of \rel. Also the generalized extended self similarity exponents \rho_{p,q} = \dx_p/\dx_q differ significantly for the longitudinal and transversal structure functions. Within the She-Leveque model this means that longitudinal and transversal fluctuations obey different types of hierarchies of the moments. Moreover, the She-Leveque model hierarchy parameters $\beta^L$ and $\beta^T$ show small but significant dependences on the order of the moment.Comment: 20 pages, 10 eps-figures, to appear in Physics of Fluids, December 199

Generalized scaling in fully developed turbulence

In this paper we report numerical and experimental results on the scaling properties of the velocity turbulent fields in several flows. The limits of a new form of scaling, named Extended Self Similarity(ESS), are discussed. We show that, when a mean shear is absent, the self scaling exponents are universal and they do not depend on the specific flow (3D homogeneous turbulence, thermal convection , MHD). In contrast, ESS is not observed when a strong shear is present. We propose a generalized version of self scaling which extends down to the smallest resolvable scales even in cases where ESS is not present. This new scaling is checked in several laboratory and numerical experiment. A possible theoretical interpretation is also proposed. A synthetic turbulent signal having most of the properties of a real one has been generated.Comment: 25 pages, plain Latex, figures are available upon request to the authors ([email protected], [email protected]

Multiscale velocity correlation in turbulence: experiments, numerical simulations, synthetic signals

Multiscale correlation functions in high Reynolds number experimental turbulence, numerical simulations and synthetic signals are investigated. Fusion Rules predictions as they arise from multiplicative, almost uncorrelated, random processes for the energy cascade are tested. Leading and sub-leading contribution, in the inertial range, can be explained as arising from a multiplicative random process for the energy transfer mechanisms. Two different predictions for correlations involving dissipative observable are also briefly discussed

Brand Communities: another way to generate conversations and Public Relations

En este trabajo se exploran las ventajas de cultivar las llamadas comunidades de marca, término que proviene de la mercadotecnia pero que está en íntima relación con la comunicación, las relaciones públicas, el diálogo, y en general, las conversaciones y los lazos generados entre las personas a través de internet. El estudio se centra en Universidades por el estrecho vínculo que se crea entre éstas y sus egresados, y analiza el caso de las asociaciones Exatec (grupos de egresados del Tecnológico de Monterrey) para revisar los beneficios que estas agrupaciones brindan a la institución, así como las estrategias que la universidad desarrolla para mantener vivo el lazo con estas comunidades. A través de una metodología cualitativa (entrevistas) se explora este exitoso caso mexicano.Instituto de Investigación en Relaciones Pública

A new scaling property of turbulent flows

We discuss a possible theoretical interpretation of the self scaling property of turbulent flows (Extended Self Similarity). Our interpretation predicts that, even in cases when ESS is not observed, a generalized self scaling, must be observed. This prediction is checked on a number of laboratory experiments and direct numerical simulations.Comment: Plain Latex, 1 figure available upon request to [email protected]

Surrogate model for carbon dioxide equilibrium absorption using aqueous monoethanolamine

A novel surrogate model useful for designing CO2 absorption columns is provided to describe the vapour-liquid equilibrium of CO2 in a flue gas or biogas and aqueous monoethanolamine (MEA). The surrogate model is adjusted with experimental data and compared with dedicated software for electrolyte mixtures, i.e. OLI®. The assessment of CO2 partial pressure is conducted at different MEA concentrations, temperatures and loading of CO2/ MEA in the liquid phase. The OLI® model is in good agreement with the experimental data when MEA concentration is between 15 to 30 % wt, as well as for high MEA concentrations (between 45 and 60 % wt) at 60 °C. However, for temperatures above 80 °C, the model is in agreement with experimental data only when the load of CO2 in the liquid phase exceeds the range from 0.25 to 0.30 (usual industrial operating range is from 0.2 to 0.4). A point not addressed in experimental data in literature is the presence of MEA in the vapour phase, which overcomes the recommended values from health safety point of view at 100 °C. The presence of MEA in biogas could produce NOx. The influence of inert gas (CH4) on the equilibrium is considered to check the model suitability for biogas enrichment. The novel surrogate model provides a good regression of all the experimental data in the operating region and it is validated using Pareto diagrams

Potencial forrajero y nutritivo de los pastos hibridos: Brachiaria hibrido CIAT BRO2/1752 cv. Cayman, Brachiaria hibrido CIAT BRO2/1794 cv. Cobra y Brachiaria hibrido GP 3025 cv. Camello, periodo lluvioso, Finca Santa Rosa Managua 2019

El objetivo de esta investigación fue evaluar el potencial forrajero y nutritivo de los híbridos de pastos: Brachiaria híbrido CIAT BR02/1752 cv. Cayman, Brachiaria híbrido CIAT BR02/1794 cv. Cobra y Brachiaria híbrido GP 3025 cv. Camello durante el periodo lluvioso en Finca Santa Rosa, Managua 2019. Se utilizó un (DCA) con arreglo de parcelas divididas con 5 repeticiones, utilizando prueba de Tukey (p > 0.05) para el análisis de separación de medias en software estadístico Infostat®, las variables evaluadas fueron: altura de la planta (AP) cm, rendimiento de biomasa fresca (RBF) kg, y biomasa seca (RBS) kg, relación hoja: tallo (RH/T) %, Porcentaje de materia seca (MS), proteína bruta (PB) y Fibra Neutro Detergente (FDN). A los 35 días de rebrote no se encontró diferencia significativa para (AP) de Cobra respecto a Camello y Cayman, pero Cayman y Camello presentaron diferencias altamente significativas. (RBF) no se encontraron diferencias para Cobra con respecto a Cayman y Camello, pero si se encontraron diferencias altamente significativas entre Cayman y Camello. (RMS) no se encontró diferencia para Cobra respecto a Cayman y Camello, pero se encontraron diferencias altamente significativas entre Cayman y Camello. (RH/T) no se encontró diferencias significativas. A los 45 días (AP) no presento diferencias entre Camello, Cobra y Cayman, pero Cayman y Cobra presentaron diferencias significativas. (RBF) no se encontró diferencias de Cobra con Cayman y Camello, pero Camello y Cayman presentaron diferencias altamente significativas. (RBS) no se encontraron diferencias. (RH/T) se encontraron diferencias altamente significativas de Cayman con respecto a Cobra y Camello, pero no entre Cobra y Camello. En cuanto a las variables bromatológicas el hibrido que mejor comportamiento mostró a los 35 días de rebrote fue el hibrido Cayman y los 45 días fue el hibrido Cobra tomando en cuenta el contenido de PC y FDN. Palabras claves: Rebrote, relación hoja-tallo, altura de la planta, pr

Inhomogeneous turbulence in the vicinity of a large scale coherent vortex

We study the statistics of turbulent velocity fluctuations in the neighbourhood of a strong large scale vortex at very large Reynolds number. At each distance from the vortex core, we observe that the velocity spectrum has a power law ``inertial range'' of scales and that intermittency -- defined as the variation of the probability density function (PDF) of velocity increments as the length of the increment is varied -- is also present. We show that the spectrum scaling exponents and intermittency characteristics vary with the distance to the vortex. They are also influenced by the large scale dynamics of the vortex.Comment: submitted to europhys lett, 6 pages, 5 figure

The loss of anisotropy in MgB2 with Sc substitution and its relationship with the critical temperature

The electrical conductivity anisotropy of the sigma-bands is calculated for the (Mg,Sc)B2 system using a virtual crystal model. Our results reveal that anisotropy drops with relatively little scandium content (< 30%); this behaviour coincides with the lowering of Tc and the reduction of the Kohn anomaly. This anisotropy loss is also found in the Al and C doped systems. In this work it is argued that the anisotropy, or 2D character, of the sigma-bands is an important parameter for the understanding of the high Tc found in MgB2