Energy partition and segregation for an intruder in a vibrated granular system under gravity

The difference of temperatures between an impurity and the surrounding gas in an open vibrated granular system is studied. It is shown that, in spite of the high inhomogeneity of the state, the temperature ratio remains constant in the bulk of the system. The lack of energy equipartition is associated to the change of sign of the pressure diffusion coefficient for the impurity at certain values of the parameters of the system, leading to a segregation criterium. The theoretical predictions are consistent with previous experimental results, and also in agreement with molecular dynamics simulation results reported in this paper.Comment: To appear in Phys. Rev. Let

Symmetry breaking and clustering in a vibrated granular gas with several macroscopically connected compartments

The spontaneous symmetry breaking in a vibro-fluidized low-density granular gas in three connected compartments is investigated. When the total number of particles in the system becomes large enough, particles distribute themselves unequally among the three compartments. Particles tend to concentrate in one of the compartments, the other two having the (relatively small) same average number of particles. A hydrodynamical model that accurately predicts the bifurcation diagram of the system is presented. The theory can be easily extended to the case of an arbitrary number of connected compartments

Broadening of H2_2O rotational lines by collision with He atoms at low temperature

We report pressure broadening coefficients for the 21 electric-dipole transitions between the eight lowest rotational levels of ortho-H$_2$O and para-H$_2$O molecules by collisions with He at temperatures from 20 to 120 K. These coefficients are derived from recently published experimental state-to-state rate coefficients for H$_2$O:He inelastic collisions, plus an elastic contribution from close coupling calculations. The resulting coefficients are compared to the available experimental data. Mostly due to the elastic contribution, the pressure broadening coefficients differ much from line to line, and increase markedly at low temperature. The present results are meant as a guide for future experiments and astrophysical observations.Comment: 2 figures, 2 table

Hydrodynamic profiles for an impurity in a open vibrated granular gas

The hydrodynamic state of an impurity immersed in a low density granular gas is analyzed. Explicit expressions for the temperature and density fields of the impurity in terms of the hydrodynamic fields of the gas are derived. It is shown that the ratio between the temperatures of the two components, measuring the departure from energy equipartition, only depends on the mechanical properties of the particles, being therefore constant in the bulk of the system. This ratio plays an important role in determining the density profile of the intruder and its position with respect to the gas, since it determines the sign of the pressure diffusion coefficient. The theoretical predictions are compared with molecular dynamics simulation results for the particular case of the steady state of an open vibrated granular system in absence of macroscopic fluxes, and a satisfactory agreement is found

Mixing Effects in the Crystallization of Supercooled Quantum Binary Liquids

By means of Raman spectroscopy of liquid microjets we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH$_2$) diluted with small amounts of up to 5\% of either neon or orthodeuterium (oD$_2$), and of oD$_2$ diluted with either Ne or pH$_2$. We show that the introduction of Ne impurities affects the crystallization kinetics in both the pH$_2$-Ne and oD$_2$-Ne mixtures in terms of a significant reduction of the crystal growth rate, similarly to what found in our previous work on supercooled pH$_2$-oD$_2$ liquid mixtures [M. K\"uhnel et {\it al.}, Phys. Rev. B \textbf{89}, 180506(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixture is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne crystallites.Comment: 19 pages, 7 figures, submitted to J. Chem. Phy

Steady state representation of the homogeneous cooling state of a granular gas

The properties of a dilute granular gas in the homogeneous cooling state are mapped to those of a stationary state by means of a change in the time scale that does not involve any internal property of the system. The new representation is closely related with a general property of the granular temperature in the long time limit. The physical and practical implications of the mapping are discussed. In particular, simulation results obtained by the direct simulation Monte Carlo method applied to the scaled dynamics are reported. This includes ensemble averages and also the velocity autocorrelation function, as well as the self-diffusion coefficient obtained from the latter by means of the Green-Kubo representation. In all cases, the obtained results are compared with theoretical predictions

Europatitan eastwoodi, a new sauropod from the lower Cretaceous of Iberia in the initial radiation of somphospondylans in Laurasia

The sauropod of El Oterillo II is a specimen that was excavated from the Castrillo de la Reina Formation (Burgos, Spain), late Barremian-early Aptian, in the 2000s but initially remained undescribed. A tooth and elements of the axial skeleton, and the scapular and pelvic girdle, represent it. It is one of the most complete titanosauriform sauropods from the Early Cretaceous of Europe and presents an opportunity to deepen our understanding of the radiation of this clade in the Early Cretaceous and study the paleobiogeographical relationships of Iberia with Gondwana and with other parts of Laurasia. The late Barremian-early Aptian is the time interval in the Cretaceous with the greatest diversity of sauropod taxa described in Iberia: two titanosauriforms, Tastavinsaurus and Europatitan; and a rebbachisaurid, Demandasaurus. The new sauropod Europatitan eastwoodi n. gen. n. sp. presents a series of autapomorphic characters in the presacral vertebrae and scapula that distinguish it from the other sauropods of the Early Cretaceous of Iberia. Our phylogenetic study locates Europatitan as the basalmost member of the Somphospondyli, clearly differentiated from other clades such as Brachiosauridae and Titanosauria, and distantly related to the contemporaneous Tastavinsaurus. Europatitan could be a representative of a Eurogondwanan fauna like Demandasaurus, the other sauropod described from the Castrillo de la Reina Formation. The presence of a sauropod fauna with marked Gondwananan affinities in the Aptian of Iberia reinforces the idea of faunal exchanges between this continental masses during the Early Cretaceous. Further specimens and more detailed analysis are needed to elucidate if this Aptian fauna is caused by the presence of previously unnoticed Aptian land bridges, or it represents a relict fauna from an earlier dispersal event

Determinación de la resistencia a esfuerzo cortante en ensayos de flexión a paneles sándwich PUR: análisis de las dificultades y simulación por elementos finitos

The use of the composite construction elements combining different materials with complementary characteristics, it has spread increasingly. The sandwich panels composed by external metallic sheets that they contributes resistance and core of rigid insulating thermal foam, that provides qualities that improve the thermal comfort inside all kinds of constructions. They are in use in closings and covers that shape the surrounding one of the buildings. Of the different quality controls to which they have to surrender. In this article one proposes an improvement to the indicated one in the procedure for the determination of the resistance to the shear strength, Managing to avoid many anomalous results obtained by the utilization of rigid plates in the supports. Finally, so much the problem observed as the proposed solution, they are modeled and simulate by means of the method of finite elements.La utilización de elementos constructivos compuestos, combinando distintos materiales con características complementarias, se ha extendido cada vez más. Los paneles sándwich, compuestos por capas externas de metal que les aporta resistencia y núcleo de espuma aislante térmica, que proporciona cualidades que mejoran el confort térmico en el interior de todo tipo de construcciones, se utilizan en cerramientos y cubiertas que conforman la envolvente de los edificios. De los distintos controles de calidad a que se han de someter, en este artículo se propone una mejora al indicado en las normas para la determinación de la resistencia al esfuerzo cortante, consiguiendo evitar muchos resultados anómalos obtenidos por la utilización de placas rígidas en los apoyos. Finalmente, tanto el problema observado como la solución propuesta, se modelizan y simulan mediante el método de elementos finitos

Modelo hidráulico para la optimización de subunidades irregulares de riego por goteo

La escasez de los recursos hídricos actuales, especialmente en las zonas con clima árido o semiárido, provocan la necesidad de desarrollar herramientas de ayuda en la toma de decisiones para el diseño y manejo del riego, y más cuando se pretende utilizar energía fotovoltaica. El objetivo del trabajo ha sido desarrollar un modelo hidráulico que pueda acoplarse al modelo fotovoltaico, para el caso más general de subunidades de riego de forma y topografía irregular, constituyendo una herramienta de ayuda en la toma de decisiones para el diseño y manejo del riego con energía fotovoltaica, analizando la calidad del riego en las distintas subunidades con forma y topografía irregular. Para la calibración y validación del modelo, se ha aplicado a una parcela de 90 ha, de un cultivo de almendro regado por goteo, situada en una zona con topografía y forma muy irregular. Los resultados permiten identificar las zonas con problemas en la uniformidad de emisión en función de la presión disponible en la entrada de la subunidad de riego.Nowadays, water resources are limited especially in places with arid and semi-arid conditions. For that reason, it is essential the development of decision support system models (DSS) aiming the design and management of irrigation systems, especially when they are fed with photovoltaic energy. The main objective of this study was the development of a hydraulic model linked with a photovoltaic model, considering the most general case of irrigation subunits with irregular shape and topography. Thus, a decision support system tool (DSS) for the design and management irrigation with photovoltaic power is developed. Analyzing the irrigation quality in different subunit with irregular shape and topography is a main issue in precision irrigation. For model calibration and validation has been applied in an almond field with 90 ha with drip irrigation located in a shape and topography land. The results enabled us to identify the areas with uniformity problems depending on the pressure in the subnit head

The Agilkia boulders/pebbles size-frequency distributions: OSIRIS and ROLIS joint observations of 67P surface

By using the images acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) and ROLIS (ROsetta Lander Imaging System) cameras, we derive the size¿ frequency distribution (SFD) of cometary pebbles and boulders covering the size range 0.05¿ 30.0 m on the Agilkia landing site. The global SFD measured on OSIRIS images, reflects the different properties of the multiple morphological units present on Agilkia, combined with selection effects related to lifting, transport and redeposition. Contrarily, the different ROLIS SFD derived on the smooth and rough units may be related to their different regolith thickness present on Agilkia. In the thicker, smoother layer, ROLIS mainly measures the SFD of the airfall population which almost completely obliterates the signature of underlying boulders up to a size of the order of 1 m. This is well matched by the power-law index derived analysing coma particles identified by the grain analyser Grain Impact Analyser and Dust Accumulator. This result confirms the important blanketing dynamism of Agilkia. The steeper SFD observed in rough terrains from 0.4 to 2 m could point out intrinsic differences between northern and southern dust size distributions, or it may suggest that the underlying boulders `peek through¿ the thinner airfall layer in the rough terrain, thereby producing the observed excess in the decimetre size range. Eventually, the OSIRIS SFD performed on the Philae landing unit may be due to water sublimation from a static population of boulders, affecting smaller boulders before the bigger ones, thus shallowing the original SFD.The support of the national funding agencies of Germany (DLR), France(CNES), Italy(ASI), Spain(MEC), Sweden(SNSB) and the ESA Technical Directorate is gratefully acknowledged.Peer Reviewe