10,599 research outputs found
Experimental study of the compaction dynamics for 2D anisotropic granular materials
We present an experimental study of the compaction dynamics for
two-dimensional anisotropic granular systems. Compaction dynamics is measured
at three different scales : (i) the macroscopic scale through the packing
fraction , (ii) the mesoscopic scale through both fractions of aligned
grains and ideally ordered grains , and (iii) the
microscopic scale through both rotational and translational grain mobilities
. The effect of the grain rotations on the compaction dynamics has
been measured. At the macroscopic scale, we have observed a discontinuity in
the late stages of the compaction curve. At the mesoscopic scale, we have
observed the formation and the growth of domains made of aligned grains. From a
microscopic point of view, measurements reveal that the beginning of the
compaction process is essentially related to translational motion of the
grains. The grains rotations drive mainly the process during the latest stages
of compaction.Comment: 8pages, 11 figure
Influencia de los parámetros fundamentales de rotura frágil sobre el ensayo Niblink y su comparación con el ensayo Charpy - V.
Se trata del estudio experimental de un nuevo ensayo de rotura frágil, cuyas peculiares características suponen un avance en las técnicas de estudio de ese tipo de roturas. La investigación se lleva a cabo sobre chapas soldadas de construcción naval, de 28mm de espesor, para los procedimientos de soldeo por arco eléctrico manual, soldeo semiautomático bajo CO2 y arco sumergido por una sola cara. El artículo comienza con una revisión general de los fundamentos de los numerosos ensayos de rotura frágil existentes, describiendo y comentando después el ensayo Niblink. A continuación, se exponen los objetivos de la investigación y los datos de base y normas comunes a los diversos ensayos, para pasar después a la parte experimental, donde se estudia la influencia sobre el ensayo Niblink de la velocidad y la energía de impacto en función de la temperatura, así como las posibilidades de reducción del tamaño de la probeta. Paralelamente se hace una comparación con el ensayo Charpy - V, comentando, por último, los resultados y sacando unas conclusiones finales sobre el ensayo en cuestión. 
Hexaaquazinc(II) dinitrate bis[5-(pyridinium-3-yl)tetrazol-1-ide]
Indexación: Scopus.Funding for this research was provided by: Fondecyt Regular (award No. 1151527); Proyecto REDES ETAPA INICIAL, Convocatoria 2017 (award No. REDI170423); Millennium Institute for Research in Optics (MIRO); Basal USA (award No. 1799).Hexaaquazinc(II) dinitrate 5-(pyridinium-3-yl)tetrazol-1-ide, [Zn(H2 O)6](NO 3)2 ·2C6H5 N 5, crystallizes in the space group P. The asymmetric unit contains one zwitterionic 5-(pyridinium-3-yl)tetrazol-1-ide molecule, one NO3-anion and one half of a [Zn(H2 O)6]2+ cation (symmetry). The pyridinium and tetrazolide rings in the zwitterion are nearly coplanar, with a dihedral angle of 5.4 (2)°. Several O-H..N and N-H..O hydrogen-bonding interactions exist between the [Zn(H2 O)6]2+ cation and the N atoms of the tetrazolide ring, and between the nitrate anions and the N-H groups of the pyridinium ring, respectively, giving rise to a three-dimensional network. The 5-(pyridinium-3-yl)tetrazol-1-ide molecules show parallel-displaced π-π stacking interactions; the centroid-centroid distance between adjacent tetrazolide rings is 3.6298 (6) Å and that between the pyridinium and tetrazolide rings is 3.6120 (5) Å. © 2018 Chi-Duran et al.http://journals.iucr.org/e/issues/2018/09/00/cq2025/index.htm
Dynamics of shallow impact cratering
We present data for the time-dependence of wooden spheres penetrating into a
loose non-cohesive packing of glass beads. The stopping time is a factor of
three longer than the time needed to travel the total penetration
distance at the impact speed . The acceleration decreases
monotonically throughout the impact. These kinematics are modelled by a
position- and velocity-dependent stopping force that is constrained to
reproduce prior observations for the scaling of the penetration depth with the
total drop distance.Comment: 4 pages, experimen
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