Sample records for wet granular matter

  1. Equation of state of wet granular matter

    NASA Astrophysics Data System (ADS)

    Fingerle, A.; Herminghaus, S.

    2008-01-01

    An expression for the near-contact pair correlation function of D -dimensional weakly polydisperse hard spheres is presented, which arises from elementary free-volume arguments. Its derivative at contact agrees very well with our simulations for D=2 . For jammed states, the expression predicts that the number of exact contacts is equal to 2D, in agreement with established simulations. When the particles are wetted, they interact by the formation and rupture of liquid capillary bridges. Since formation and rupture events of capillary bonds are well separated in configuration space, the interaction is hysteretic with a characteristic energy loss Ecb . The pair correlation is strongly affected by this capillary interaction depending on the liquid-bond status of neighboring particles. A theory is derived for the nonequilibrium probability currents of the capillary interaction which determines the pair correlation function near contact. This finally yields an analytic expression for the equation of state, P=P(N/V,T) , of wet granular matter for D=2 , valid in the complete density range from gas to jamming. Driven wet granular matter exhibits a van der Waals-like unstable branch at granular temperatures Tgranular droplets reported for the free cooling of one-dimensional wet granular matter [A. Fingerle and S. Herminghaus, Phys. Rev. Lett. 97, 078001 (2006)], and extends the effect to higher dimensional systems. Since the limiting case of sticky bonds, Ecb?T , is of relevance for aggregation in general, simulations have been performed which show very good agreement with the theoretically predicted coordination K of capillary bonds as a function of the bond length scrit . This result implies that particles that stick at the surface, scrit=0 , form isostatic clusters. An extension of the theory in which the bridge coordination number K plays the role of a self-consistent mean-field is proposed.

  2. Spiral patterns in wet granular matter under vertical vibrations

    NASA Astrophysics Data System (ADS)

    Huang, Kai; Gollwitzer, Frank; Rehberg, Ingo

    2010-03-01

    From the evolution of galaxy to hurricane, from the inner structure of sea shell to the cochlea of our inner ears, spirals are widely existing in nature. In the past decades, spiral patterns have been discovered and extensively studied in model systems such as Rayleigh-B'ernard convection, Belousov-Zhabotinksy reactions and various biological systems. Here we report spiral patterns observed in a thin layer of wet granular matter driven by vertical vibrations. In the phase diagram of driven wet granular matter, spirals appear close to a fluid-gas coexistence phase and show hysteresis. The trajectory and rotation velocity of the three-armed spirals are studied as a function of the driving parameters and compared with other model systems.

  3. Mixing characteristics of wet granular matter in a bladed mixer

    Microsoft Academic Search

    Stefan Radl; Eva Kalvoda; Benjamin J. Glasser; Johannes G. Khinast

    2010-01-01

    We performed numerical simulations of dry and wet granular flow inside a four-bladed mixer using the discrete element method (DEM). A capillary force model was incorporated to mimic the complex effects of pendular liquid bridges on particle flow. The simulations are able to capture the main features of granular flow, which is substantiated by the comparison of our results with

  4. Arrest of three-dimensional gravity-confined shear flow of wet granular matter

    E-print Network

    Klaus Roeller; Johannes Blaschke; Stephan Herminghaus; Jürgen Vollmer

    2012-10-11

    We study the arrest of three-dimensional flow in wet granular matter subject to a sinusoidal external force and a gravitational field confining the flow in the vertical direction. The minimal strength of the external force that is required to keep the system in motion is determined by considering the balance of injected and dissipated power. This provides a prediction whose excellent quality is demonstrated by a data collapse for an extensive set of event-driven molecular dynamics simulations where we varied the system size, particle number, the energy dissipated upon rupturing capillary bridges, and the bridge length where rupture occurs. The three parameters of the theoretical prediction all lie within narrow margins of theoretical estimates.

  5. Chaoticity of the Wet Granular Gas

    E-print Network

    A. Fingerle; S. Herminghaus; V. Yu. Zaburdaev

    2007-05-22

    In this work we derive an analytic expression for the Kolmogorov-Sinai entropy of dilute wet granular matter, valid for any spatial dimension. The grains are modelled as hard spheres and the influence of the wetting liquid is described according to the Capillary Model, in which dissipation is due to the hysteretic cohesion force of capillary bridges. The Kolmogorov-Sinai entropy is expanded in a series with respect to density. We find a rapid increase of the leading term when liquid is added. This demonstrates the sensitivity of the granular dynamics to humidity, and shows that the liquid significantly increases the chaoticity of the granular gas.

  6. Erosion dynamics of a wet granular medium

    E-print Network

    Gautier Lefebvre; Pierre Jop

    2014-12-08

    Liquid may give strong cohesion properties to a granular medium, and confer a solid-like behavior. We study the erosion of a fixed circular aggregate of wet granular matter subjected to a flow of dry grains inside a half-filled rotating drum. During the rotation, the dry grains flow around the fixed obstacle. We show that its diameter decreases linearly with time for low liquid content, as wet grains are pulled-out of the aggregate. This erosion phenomenon is governed by the properties of the liquids. The erosion rate decreases exponentially with the surface tension while it depends on the viscosity to the power -1. We propose a model based on the force fluctuations arising inside the flow, explaining both dependencies: the capillary force acts as a threshold and the viscosity controls the erosion time scale. We also provide experiments using different flowing grains confirming our model.

  7. Wet granular materials in sheared flows

    Microsoft Academic Search

    Wen-Lung Yang; Shu-San Hsiau

    2005-01-01

    The transport properties of wet granular materials in a shear cell apparatus have been studied. If the particles are wet, the flow becomes more viscous forming liquid bridges between particles. The dynamic liquid bridge forces are considered as the cohesive forces between particles to restrict their movements. The cohesive forces make the particles stick tighter with each other and hamper

  8. Compaction Dynamics of Wet Granular Assemblies

    NASA Astrophysics Data System (ADS)

    Fiscina, J. E.; Lumay, G.; Ludewig, F.; Vandewalle, N.

    2010-07-01

    The extremely slow compaction dynamics of wet granular assemblies is studied experimentally. The cohesion, due to capillary bridges between neighboring grains, is tuned using different liquids having specific surface tension values. The compaction dynamics of a cohesive packing obeys an inverse logarithmic law, like most dry random packings. However, the characteristic relaxation time ? grows strongly with cohesion. A model, based on free volume kinetic equations and the presence of a capillary energy barrier, is able to reproduce quantitatively the experimental curves.

  9. Similarity of wet granular packing to gels

    NASA Astrophysics Data System (ADS)

    Li, Jindong; Cao, Yixin; Xia, Chengjie; Kou, Binquan; Xiao, Xianghui; Fezzaa, Kamel; Wang, Yujie

    2014-09-01

    To date, there is still no general consensus on the fundamental principle that governs glass transition. Colloidal suspensions are ordinarily utilized as model systems to study the dynamical arrest mechanisms in glass or gels. Here, we tackle the problem using athermal granular particles. Slow dynamics and structural evolution of granular packing upon tapping are monitored by fast X-ray tomography. When the packing are wet and short-range attractive interactions exist, we find a large amount of locally favoured structures with fivefold symmetry, which bear great structural similarity to colloidal gels. In addition, these structures are almost absent in dry packing with similar packing fractions. The study leads strong support for the geometrical frustration mechanism for dynamic arrest in both thermal and athermal systems with attractive interactions. It also suggests nontrivial structural mechanism, if exists, for dynamic arrest in systems with purely repulsive interactions.

  10. Bond anisotropy and cohesion of wet granular materials

    E-print Network

    Boyer, Edmond

    for its crucial role in flow and mixing properties of granular materials. Wet processing is common to the curvature of the liquid bridge. The pendular state represents both the simplest topology of the liquid phaseBond anisotropy and cohesion of wet granular materials By Farhang Radjai and Vincent Richefeu LMGC

  11. Shear strength properties of wet granular materials Vincent Richefeu,

    E-print Network

    Paris-Sud XI, Université de

    Shear strength properties of wet granular materials Vincent Richefeu, Moulay Sa¨id El Youssoufi shear strength properties of wet granular materials in the pendular state (i.e. the state where of capillary interactions, the major influence of water content over the shear strength stems from

  12. Segregation, avalanching and metastability of dry and wet granular materials

    NASA Astrophysics Data System (ADS)

    Samadani, Azadeh

    Granular materials are ubiquitous, but we lack a fundamental understanding of their properties. The problem is two-fold as quantitative experimental investigations are scarce and a comprehensive theory describing their various properties does not exist. In this dissertation, I present the results of experimental studies of the flow, instability, and segregation of granular materials in order to obtain quantitative data to test and develop theories. First, I investigate the flow of dry granular materials inside a quasi-two dimensional silo that is draining from an orifice at the bottom. The boundary between static and flowing regions and the velocity distribution of the grains are investigated and observed to be consistent with the existing phenomenological models. At low flow rates, the surface is observed to be inclined at the angle of repose. However, a hydraulic jump is observed at the surface at high flow rates. I show that it is a shock, and give an explanation for its occurrence. I also show that size separation occurs at the surface, when multi-sized particles are used. Second, I investigate the stability and segregation properties of wet granular materials by pouring the grains into a silo. In this case, the presence of capillary bridges provides additional forces besides hard-core repulsion and friction. The angle of repose of the resulting pile increases rapidly with the addition of a small amount of liquid and then saturates depending on the viscosity of the liquid. If the particles are bi-disperse, size separation is observed to correspondingly decrease. By using a horizontally rotated drum half-filled with wet granular matter, I also observe that the maximum angle of stability reached just before an avalanche increases with the viscosity of the introduced liquid. Using a series of experiments and estimates, I argue that the creep relaxation and the change of the number of liquid bridges between particles may be the reason for the observed effect.

  13. Shear strength properties of wet granular materials

    NASA Astrophysics Data System (ADS)

    Richefeu, Vincent; El Youssoufi, Moulay Saïd; Radjaï, Farhang

    2006-05-01

    We investigate shear strength properties of wet granular materials in the pendular state (i.e., the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume, and surface tension. We show that, due to the peculiar features of capillary interactions, the major influence of water content over the shear strength stems from the distribution of liquid bonds. This property results in shear strength saturation as a function of water content. We arrive at the same conclusion by a microscopic analysis of the shear strength. We propose a model that accounts for the capillary force, the granular texture, and particle size polydispersity. We find fairly good agreement of the theoretical estimate of the shear strength with both experimental data and simulations. From numerical data, we analyze the connectivity and anisotropy of different classes of liquid bonds according to the sign and level of the normal force as well as the bond direction. We find that weak compressive bonds are almost isotropically distributed whereas strong compressive and tensile bonds have a pronounced anisotropy. The probability distribution function of normal forces is exponentially decreasing for strong compressive bonds, a decreasing power-law function over nearly one decade for weak compressive bonds, and an increasing linear function in the range of tensile bonds. These features suggest that different bond classes do not play the same role with respect to the shear strength.

  14. Maximum angle of stability of a wet granular pile

    NASA Astrophysics Data System (ADS)

    Nowak, Sarah; Samadani, Azadeh; Kudrolli, Arshad

    2005-10-01

    Anyone who has built a sandcastle recognizes that adding liquid to the sand grains increases the overall stability. However, measurements of the stability in wet granular materials often conflict with theory and with each other. The friction-based Mohr-Coulomb model distinguishes between granular friction and interparticle friction, but uses the former without providing a physical mechanism. A frictionless model for the geometric stability of dry particles on the surface of a pile is in excellent agreement with experiment. However, the same model applied to wet grains overestimates the stability and predicts no dependence on system size. Here we take a frictionless liquid-bridge model and perform a stability analysis within the pile. We reproduce our experimentally observed dependence of the stability angle on system size, particle size and surface tension. Furthermore, we account for past discrepancies in experimental reports by showing that sidewalls can significantly increase the stability of granular material.

  15. On liquid migration in sheared granular matter

    NASA Astrophysics Data System (ADS)

    Mani, R.; Kadau, D.; Or, D.; Herrmann, H. J.

    2013-06-01

    Mixing liquids with powders is of great importance, e.g. in process engineering and for pharmaceutical applications. Generally, one might expect that homogeneously shearing or stirring wet granular matter would lead to a homogeneous liquid distribution, however, it is not clear what happens when shear is applied non-homogeneously, e.g. in shear bands. It is commonly accepted that at large liquid contents, liquid flows inside dilating zones as percolating liquid networks prevent air from entering the dilating pores, but it is unknown what happens at low liquid contents. We present experimental measurements showing a decreased liquid concentration inside a shear band where glass beads are sheared in a split bottom shear cell. Furthermore, a microscopic model for liquid transport at low liquid contents is presented, where fluid dynamics between individual liquid structures driven by Laplace pressure differences is taken into account. Our model shows liquid depletion patterns in quantitative agreement with experiments. On the other hand, our model is also applicable to the situation where shear is applied homogeneously, showing diffusive spreading of liquid.

  16. Penetration depth scaling for impact into wet granular packings

    NASA Astrophysics Data System (ADS)

    Brzinski, T. A.; Schug, J.; Mao, K.; Durian, D. J.

    2015-02-01

    We present experimental measurements of penetration depths for the impact of spheres into wetted granular media. We observe that the penetration depth in the liquid saturated case scales with projectile density, size, and drop height in a fashion consistent with the scaling observed in the dry case, but with smaller penetrations. Neither viscous drag nor density effects can explain the enhancement to the stopping force. The penetration depth exhibits a complicated dependence on liquid fraction, accompanied by a change in the drop-height dependence, that must be the consequence of accompanying changes in the conformation of the liquid phase in the interstices.

  17. Dilute wet granular particles: nonequilibrium dynamics and structure formation.

    PubMed

    Ulrich, Stephan; Aspelmeier, Timo; Zippelius, Annette; Roeller, Klaus; Fingerle, Axel; Herminghaus, Stephan

    2009-09-01

    We investigate a gas of wet granular particles covered by a thin liquid film. The dynamic evolution is governed by two-particle interactions, which are mainly due to interfacial forces in contrast to dry granular gases. When two wet grains collide, a capillary bridge is formed and stays intact up to a certain distance of withdrawal when the bridge ruptures, dissipating a fixed amount of energy. A freely cooling system is shown to undergo a nonequilibrium dynamic phase transition from a state with mainly single particles and fast cooling to a state with growing aggregates such that bridge rupture becomes a rare event and cooling is slow. In the early stage of cluster growth, aggregation is a self-similar process with a fractal dimension of the aggregates approximately equal to Df approximately 2 . At later times, a percolating cluster is observed which ultimately absorbs all the particles. The final cluster is compact on large length scales, but fractal with Df approximately 2 on small length scales. PMID:19905109

  18. Friction and dilatancy in immersed granular matter

    E-print Network

    Thibaut Divoux; Jean-Christophe Géminard

    2008-06-10

    The friction of a sliding plate on a thin immersed granular layer obeys Amonton-Coulomb law. We bring to the fore a large set of experimental results which indicate that, over a few decades of values, the effective dynamical friction-coefficient depends neither on the viscosity of the interstitial fluid nor on the size of beads in the sheared layer, which bears out the analogy with the solid-solid friction in a wide range of experimental parameters. We accurately determine the granular-layer dilatancy, which dependance on the grain size and slider velocity can be qualitatively accounted by considering the rheological behaviour of the whole slurry. However, additional results, obtained after modification of the grain surface by a chemical treatment, demonstrate that the theoretical description of the flow properties of granular matter, even immersed, requires the detailed properties of the grain surface to be taken into account.

  19. Penetration depth scaling for impact into wet granular packings

    E-print Network

    Theodore A. Brzinski III; Jorin Schug; Kelly Mao; Douglas J. Durian

    2015-01-25

    We present experimental measurements of penetration depths for the impact of spheres into wetted granular media. We observe that the penetration depth in the liquid saturated case scales with projectile density, size, and drop height in a fashion consistent with the scaling observed in the dry case, but that penetration depths into saturated packings tend to be smaller. This result suggests that, for the range of impact energies observed, the stopping force is set by static contact forces between grains within the bed, and that the presence of liquid serves, primarily, to enhance these contact forces. The enhancement to the stopping force has a complicated dependence on liquid fraction, accompanied by a change in the drop-height dependence, that must be the consequence of accompanying changes in the conformation of the liquid phase in the interstices.

  20. Shear strength and stress distribution in wet granular media

    NASA Astrophysics Data System (ADS)

    Richefeu, Vincent; Radjaï, Farhang; El Youssoufi, Moulay Saïd

    2009-06-01

    We investigate the shear strength and stress distribution properties of wet granular media in the pendular state where the liquid is mainly in the form of capillary bonds between particles. This work is based on a 3D discrete-element approach (molecular dynamics) with spherical particles enriched by a capillary force law. We show that the capillary force can be expressed as an explicit function of the gap and volume of the liquid bridge. The length scales involved in this expression are analyzed by comparing with direct integration of the Laplace-Young equation. In the simulations, we consider a maximum number density of liquid bonds in the bulk in agreement with equilibrium of each liquid bridge. This liquid bond number is a decisive parameter for the overall cohesion of wet granular materials. It is shown that the shear strength can be expressed as a function of liquid bond characteristics. The expression proposed initially by Rumpf is thus generalized to account for size polydispersity We show that this expression is in good agreement with our experimental data that will be briefly described. At low confining stress, the tensile action of capillary bonds induces a self-stressed particle network organized in a bi-percolating structure of positive and negative particle pressures. Various statistical descriptors of the microstructure and bond force network are used to characterize this partition. Two basic properties emerge: (i) The highest particle pressure is located in the bulk of each phase (positive and negative particle pressures); (ii) The lowest pressure level occurs at the interface between the two phases, involving also the largest connectivity of the particles via tensile and compressive bonds.

  1. Pattern formation in vibrated beds of dry and wet granular materials

    NASA Astrophysics Data System (ADS)

    Chuan Lim, Eldin Wee

    2014-01-01

    The Discrete Element Method was coupled with a capillary liquid bridge force model for computational studies of pattern formation in vibrated granular beds containing dry or wet granular materials. Depending on the vibration conditions applied, hexagonal, stripes, or cellular pattern was observed in the dry vibrated granular bed. In each of these cases, the same hexagonal, stripes, or cellular pattern was also observed in the spatial distribution of the magnitudes of particle-particle collision forces prior to the formation of the corresponding actual pattern in physical distributions of the particles. This seemed to suggest that the pattern formation phenomenon of vibrated granular bed systems might be the result of a two-dimensional Newton's cradle effect. In the presence of a small amount of wetness, these patterns were no longer formed in the vibrated granular beds under the same corresponding set of vibration conditions. Despite the relatively much weaker capillary forces arising from the simulated liquid bridges between particles compared with particle-particle collision forces, the spatial distributions of these collision forces, physical distributions of particles, as well as time profiles of average collision forces were altered significantly in comparison with the corresponding distributions and profiles observed for the dry vibrated granular beds. This seemed to suggest the presence of a two-dimensional Stokes' cradle effect in these wet vibrated granular bed systems which disrupted the formation of patterns in the wet granular materials that would have been observed in their dry counterparts.

  2. Segregation, avalanching and metastability of dry and wet granular materials

    Microsoft Academic Search

    Azadeh Samadani

    2002-01-01

    Granular materials are ubiquitous, but we lack a fundamental understanding of their properties. The problem is two-fold as quantitative experimental investigations are scarce and a comprehensive theory describing their various properties does not exist. In this dissertation, I present the results of experimental studies of the flow, instability, and segregation of granular materials in order to obtain quantitative data to

  3. Thermal conductivity of a partially wet granular material

    Microsoft Academic Search

    J.-C. Géminard; H. Gayvallet

    2001-01-01

    We report an experimental study of the thermal conductivity of a granular material when water is added to the system. Because of the formation of liquid bridges at the contacts between grains, the thermal conductivity increases. Below a critical amount of water, the number of bridges increases. Any additional water simply flows by gravity to the bottom of the container.

  4. Thermal conductivity of a partially wet granular material

    NASA Astrophysics Data System (ADS)

    Géminard, J.-C.; Gayvallet, H.

    2001-10-01

    We report an experimental study of the thermal conductivity of a granular material when water is added to the system. Because of the formation of liquid bridges at the contacts between grains, the thermal conductivity increases. Below a critical amount of water, the number of bridges increases. Any additional water simply flows by gravity to the bottom of the container. Simple theoretical models account for both the critical amount of water and the measured thermal conductivity.

  5. On the capillary stress tensor in wet granular materials

    E-print Network

    Luc Scholtès; Pierre-Yves Hicher; François Nicot; Bruno Chareyre; Félix Darve

    2011-05-05

    This paper presents a micromechanical study of unsaturated granular media in the pendular regime, based upon numerical experiments using the discrete element method, compared to a microstructural elastoplastic model. Water effects are taken into account by adding capillary menisci at contacts and their consequences in terms of force and water volume are studied. Simulations of triaxial compression tests are used to investigate both macro and micro-effects of a partial saturation. The results provided by the two methods appear to be in good agreement, reproducing the major trends of a partially saturated granular assembly, such as the increase in the shear strength and the hardening with suction. Moreover, a capillary stress tensor is exhibited from capillary forces by using homogenisation techniques. Both macroscopic and microscopic considerations emphasize an induced anisotropy of the capillary stress tensor in relation with the pore fluid distribution inside the material. In so far as the tensorial nature of this fluid fabric implies shear effects on the solid phase associated with suction, a comparison has been made with the standard equivalent pore pressure assumption. It is shown that water effects induce microstrural phenomena that cannot be considered at the macro level, particularly when dealing with material history. Thus, the study points out that unsaturated soil stress definitions should include, besides the macroscopic stresses such as the total stress, the microscopic interparticle stresses such as the ones resulting from capillary forces, in order to interpret more precisely the implications of the pore fluid on the mechanical behaviour of granular materials.

  6. Mixing and Condensation in a Wet Granular Medium

    NASA Astrophysics Data System (ADS)

    Geromichalos, Dimitrios; Kohonen, Mika M.; Mugele, Frieder; Herminghaus, Stephan

    2003-04-01

    We have studied the effect of small amounts of added liquid on the dynamic behavior of a granular system consisting of a mixture of glass beads of two different sizes. Segregation of the large beads to the top of the sample is found to depend in a nontrivial way on the liquid content. A transition to viscoplastic behavior occurs at a critical liquid content, which depends upon the bead size. We show that this transition can be interpreted as a condensation due to the hysteretic liquid bridge forces connecting the beads, and we provide the corresponding phase diagram.

  7. Maximum angle of stability of a wet granular pile

    E-print Network

    Loss, Daniel

    , the same model applied to wet grains overestimates the stability and predicts no dependence on system size reproduce our experimentally observed dependence of the stability angle on system size, particle size of the liquid was tested by using silicone oil and water, which have = 20±1 and 70±1 dyn cm-1 , respectively

  8. Rheology of weakly wetted granular materials - a comparison of experimental and numerical data

    E-print Network

    Ruediger Schwarze; Anton Gladkyy; Fabian Uhlig; Stefan Luding

    2014-09-12

    Shear cell simulations and experiments of weakly wetted particles (a few volume percent liquid binders) are compared, with the goal to understand their flow rheology. Application examples are cores for metal casting by core shooting made of sand and liquid binding materials. The experiments are carried out with a Couette-like rotating viscometer. The weakly wetted granular materials are made of quartz sand and small amounts of Newtonian liquids. For comparison, experiments on dry sand are also performed with a modified configuration of the viscometer. The numerical model involves spherical, monodisperse particles with contact forces and a simple liquid bridge model for individual capillary bridges between two particles. Different liquid content and properties lead to different flow rheology when measuring the shear stress-strain relations. In the experiments of the weakly wetted granular material, the apparent shear viscosity $\\eta_g$ scales inversely proportional to the inertial number $I$, for all shear rates. On the contrary, in the dry case, an intermediate scaling regime inversely quadratic in $I$ is observed for moderate shear rates. In the simulations, both scaling regimes are found for dry and wet granular material as well.

  9. Granular matter: a tentative view P. G. de Gennes

    E-print Network

    Weeks, Eric R.

    Stress Fields S376 A. The general problem S376 B. The Janssen picture for a silo S376 C. Critique-defined size). If we measure it by tons, the material most manipu- lated by man is water; the second-most-manipulated is granular matter. But in our supposedly sophisticated 20th century, the manipulation of powders still

  10. NEWTON VS STOKES: COMPETING FORCES IN GRANULAR MATTER

    E-print Network

    Twente, Universiteit

    Meer #12;Contents 1 General introduction 1 1.1 Sir Isaac Newton and Sir George Gabriel Stokes#12;NEWTON VS STOKES: COMPETING FORCES IN GRANULAR MATTER #12;Samenstelling promotiecommissie Prof of Twente. Nederlandse titel: Newton vs Stokes -- Concurrerende krachten in granulaire materie Publisher

  11. Runaway Electrification of Friable Self-Replicating Granular Matter

    PubMed Central

    2013-01-01

    We establish that the nonlinear dynamics of collisions between particles favors the charging of an insulating, friable, self-replicating granular material that undergoes nucleation, growth, and fission processes; we demonstrate with a minimal dynamical model that secondary nucleation produces a positive feedback in an electrification mechanism that leads to runaway charging. We discuss ice as an example of such a self-replicating granular material: We confirm with laboratory experiments in which we grow ice from the vapor phase in situ within an environmental scanning electron microscope that charging causes fast-growing and easily breakable palmlike structures to form, which when broken off may form secondary nuclei. We propose that thunderstorms, both terrestrial and on other planets, and lightning in the solar nebula are instances of such runaway charging arising from this nonlinear dynamics in self-replicating granular matter. PMID:24041221

  12. Runaway electrification of friable self-replicating granular matter

    E-print Network

    Julyan H. E. Cartwright; Bruno Escribano; Hinrich Grothe; Oreste Piro; C. Ignacio Sainz Díaz; Idan Tuval

    2014-11-19

    We establish that the nonlinear dynamics of collisions between particles favors the charging of a insulating, friable, self-replicating granular material that undergoes nucleation, growth, and fission processes; we demonstrate with a minimal dynamical model that secondary nucleation produces a positive feedback in an electrification mechanism that leads to runaway charging. We discuss ice as an example of such a self-replicating granular material: We confirm with laboratory experiments in which we grow ice from the vapor phase in situ within an environmental scanning electron microscope that charging causes fast-growing and easily breakable palm-like structures to form, which when broken off may form secondary nuclei. We propose that thunderstorms, both terrestrial and on other planets, and lightning in the solar nebula are instances of such runaway charging arising from this nonlinear dynamics in self-replicating granular matter.

  13. Runaway electrification of friable self-replicating granular matter.

    PubMed

    Cartwright, Julyan H E; Escribano, Bruno; Grothe, Hinrich; Piro, Oreste; Sainz Díaz, C Ignacio; Tuval, Idan

    2013-10-15

    We establish that the nonlinear dynamics of collisions between particles favors the charging of an insulating, friable, self-replicating granular material that undergoes nucleation, growth, and fission processes; we demonstrate with a minimal dynamical model that secondary nucleation produces a positive feedback in an electrification mechanism that leads to runaway charging. We discuss ice as an example of such a self-replicating granular material: We confirm with laboratory experiments in which we grow ice from the vapor phase in situ within an environmental scanning electron microscope that charging causes fast-growing and easily breakable palmlike structures to form, which when broken off may form secondary nuclei. We propose that thunderstorms, both terrestrial and on other planets, and lightning in the solar nebula are instances of such runaway charging arising from this nonlinear dynamics in self-replicating granular matter. PMID:24041221

  14. Numerical investigation of the cylinder movement in granular matter

    NASA Astrophysics Data System (ADS)

    Zhang, Xue; Sheng, Daichao; Kouretzis, George P.; Krabbenhoft, Kristian; Sloan, Scott W.

    2015-02-01

    We investigate numerically the mechanisms governing horizontal dragging of a rigid cylinder buried inside granular matter, with particular emphasis on enumerating drag and lift forces that resist cylinder movement. The recently proposed particle finite element method is employed, which combines the robustness of classical continuum mechanics formulations in terms of representing complex aspects of the material constitutive behavior, with the effectiveness of discrete element methods in simulating ultralarge deformation problems. The investigation focuses on the effect of embedment depth, cylinder roughness, granular matter macromechanical properties, and of the magnitude of the cylinder's horizontal displacement on the amplitude of the resisting forces, which are discussed in light of published experimental data. Interpretation of the results provides insight on how the material flow around the cylinder affects the developing resistance, and a mechanism is proposed to describe the development of a steady-state drag force at large horizontal movements of the cylinder.

  15. Force transmission in dry and wet granular media Vincent Richefeu a,b,, Moulay Said El Youssoufi a

    E-print Network

    Boyer, Edmond

    - lastic experiments [11,12]. The carbon paper tech- nique was used later to record the force printsForce transmission in dry and wet granular media Vincent Richefeu a,b,, Moulay Sa¨id El Youssoufi-34095 Montpellier Cedex 5, France Abstract We compare the probability density functions of normal forces

  16. Segregation and layering in the flow of wet granular matter

    Microsoft Academic Search

    Azadeh Samadani; Arshad Kudrolli

    2000-01-01

    We report the effect of interstitial fluid on the extent of segregation by imaging the pile that results after bidisperse color-coded glass particles are poured into a silo. Segregation is sharply reduced and the angle of repose increases when a small volume fraction of fluid is added. The phase diagram of segregation as a function of volume fraction of the

  17. Segregation and layering in the flow of wet granular matter

    NASA Astrophysics Data System (ADS)

    Samadani, Azadeh; Kudrolli, Arshad

    2000-11-01

    We report the effect of interstitial fluid on the extent of segregation by imaging the pile that results after bidisperse color-coded glass particles are poured into a silo. Segregation is sharply reduced and the angle of repose increases when a small volume fraction of fluid is added. The phase diagram of segregation as a function of volume fraction of the fluid and the size ratio of the particles is obtained. We also find that viscous forces in addition to capillary forces have an important effect on the extent of segregation and the angle of repose. We show that the sharp initial change and the subsequent saturation in the extent of segregation and angle of repose occurs over similar volume fraction of the fluid. Preferential clumping of small particles causes layering to occur when the size of the clumps of small particles exceeds the size of smoother large particles. We calculate the azimuthal correlation function of particle density inside the pile to characterize the layering. Finally the progress of segregation in the limit where particles are completely immersed in a fluid was measured. In this case liquid bridges and capillary forces are absent but viscous forces are present. We find that a transition back to segregation can occur when the particles are completely immersed in a fluid at low viscosities.

  18. Discrete particle simulations and experiments on the collapse of wet granular columns

    NASA Astrophysics Data System (ADS)

    Gabrieli, Fabio; Artoni, Riccardo; Santomaso, Andrea; Cola, Simonetta

    2013-10-01

    Small quantities of liquid in a granular material control the flow dynamics as well as the triggering and jamming phases. In order to study this problem, some experimental collapse tests conducted in a rectangular box were reproduced with a 1:1 scale numerical model using the Discrete Element Method. In simulations the effect of the capillary bridges has been investigated implementing a mid-range attractive force between particles based on the minimum energy approach. Also a bonding-debonding mechanism was incorporated in the algorithm and the volume of each sessile drop on the particle surface was considered during its motion. The influence of some variables was investigated with respect to the final slope profiles and the runout lengths: the initial liquid content, the particle size, the solid density, the liquid surface tension, and the liquid-solid contact angle. Also the crucial effect of the confinement walls on the collapse phenomenon was investigated: wet particles adhere to the lateral walls providing a higher flow resistance in comparison to the same material in dry conditions. It was observed that particles with largest path-lengths are localized near the movable wall at a middle-height of the initial column sample. Other particles at the surface moves in a rigid way especially if they were wet and with a low solid density. The "fidelity" of each particle with respect to the nearest neighbours was evaluated allowing to recognize the emergence of clusters of particles and rigid parts, to extract the failure surface and to localize where debonding mechanisms concentrate in the wet case.

  19. Stress-dependent normal-mode frequencies from the effective mass of granular matter

    NASA Astrophysics Data System (ADS)

    Hu, Yanqing; Johnson, David L.; Valenza, John J.; Santibanez, Francisco; Makse, Hernán A.

    2014-06-01

    A zero-temperature critical point has been invoked to control the anomalous behavior of granular matter as it approaches jamming or mechanical arrest. Criticality manifests itself in an anomalous spectrum of low-frequency normal modes and scaling behavior near the jamming transition. The critical point may explain the peculiar mechanical properties of dissimilar systems such as glasses and granular materials. Here we study the critical scenario via an experimental measurement of the normal modes frequencies of granular matter under stress from a pole decomposition analysis of the effective mass. We extract a complex-valued characteristic frequency which displays scaling |?*(?)|˜??' with vanishing stress ? for a variety of granular systems. The critical exponent is smaller than that predicted by mean-field theory opening new challenges to explain the exponent for frictional and dissipative granular matter. Our results shed light on the anomalous behavior of stress-dependent acoustics and attenuation in granular materials near the jamming transition.

  20. Time-resolved dynamics of granular matter by random laser emission

    NASA Astrophysics Data System (ADS)

    Folli, Viola; Ghofraniha, Neda; Puglisi, Andrea; Leuzzi, Luca; Conti, Claudio

    2013-07-01

    Because of the huge commercial importance of granular systems, the second-most used material in industry after water, intersecting the industry in multiple trades, like pharmacy and agriculture, fundamental research on grain-like materials has received an increasing amount of attention in the last decades. In photonics, the applications of granular materials have been only marginally investigated. We report the first phase-diagram of a granular as obtained by laser emission. The dynamics of vertically-oscillated granular in a liquid solution in a three-dimensional container is investigated by employing its random laser emission. The granular motion is function of the frequency and amplitude of the mechanical solicitation, we show how the laser emission allows to distinguish two phases in the granular and analyze its spectral distribution. This constitutes a fundamental step in the field of granulars and gives a clear evidence of the possible control on light-matter interaction achievable in grain-like system.

  1. Confocal Microscopy of Jammed Matter: From Elasticity to Granular Thermodynamics

    NASA Astrophysics Data System (ADS)

    Jorjadze, Ivane

    Packings of particles are ubiquitous in nature and are of interest not only to the scientific community but also to the food, pharmaceutical, and oil industries. In this thesis we use confocal microscopy to investigate packing geometry and stress transmission in 3D jammed particulate systems. By introducing weak depletion attraction we probe the accessible phase-space and demonstrate that a microscopic approach to jammed matter gives validity to statistical mechanics framework, which is intriguing because our particles are not thermally activated. We show that the fluctuations of the local packing parameters can be successfully captured by the recently proposed 'granocentric' model, which generates packing statistics according to simple stochastic processes. This model enables us to calculate packing entropy and granular temperature, the so-called 'compactivity', therefore, providing a basis for a statistical mechanics of granular matter. At a jamming transition point at which there are formed just enough number of contacts to guarantee the mechanical stability, theoretical arguments suggest a singularity which gives rise to the surprising scaling behavior of the elastic moduli and the microstructure, as observed in numerical simulations. Since the contact network in 3D is typically hidden from view, experimental test of the scaling law between the coordination number and the applied pressure is lacking in the literature. Our data show corrections to the linear scaling of the pressure with density which takes into account the creation of contacts. Numerical studies of vibrational spectra, in turn, reveal sudden features such as excess of low frequency modes, dependence of mode localization and structure on the pressure. Chapter four describes the first calculation of vibrational density of states from the experimental 3D data and is in qualitative agreement with the analogous computer simulations. We study the configurational role of the pressure and demonstrate that low frequency modes become progressively localized as the packing density is increased. Another application of our oil-in-water emulsions serves to mimic cell adhesion in biological tissues. By analyzing the microstructure in 3D we find that a threshold compression force is necessary to overcome electrostatic repulsion and surface elasticity and establish protein-mediated adhesion.

  2. From Granular Matter to Generalized J.D. Goddard

    E-print Network

    Goddard, Joe

    .D. Goddard 1 INTRODUCTION Arguments against new ideas generally pass through distinct stages from: "It, and granular mechanics, a graph-theoretic, energy-based homogenization is proposed for the systematic the overall progress of granular mechanics in the last two decades, a renewed effort to elucidate the above

  3. Continuous shearing of dense and wet granular materials in a torsional rheometer

    E-print Network

    Kannan, Raguraman

    2002-01-01

    -static deformation and exhibit properties of fluid when subjected to rapid deformation in a confined area, it is vital that carefully designed experiments are conducted to characterize the properties of granular materials for different regimes of flow...

  4. Angle of repose and segregation in cohesive granular matter

    NASA Astrophysics Data System (ADS)

    Samadani, Azadeh; Kudrolli, A.

    2001-11-01

    We study the effect of fluids on the angle of repose and the segregation of granular matter poured into a silo. The experiments are conducted in two regimes where: (i) the volume fraction of the fluid (liquid) is small and it forms liquid bridges between particles thus giving rise to cohesive forces, and (ii) the particles are completely immersed in the fluid. The data is obtained by imaging the pile formed inside a quasi-two-dimensional silo through the transparent glass side walls and using color-coded particles. In the first series of experiments, the angle of repose is observed to increase sharply with the volume fraction of the fluid and then saturates at a value that depends on the size of the particles. We systematically study the effect of viscosity by using water-glycerol mixtures to vary it over at least three orders of magnitude while keeping the surface tension almost constant. Besides surface tension, the viscosity of the fluid is observed to have an effect on the angle of repose and the extent of segregation. In case of bidisperse particles, segregation is observed to decrease and finally saturate depending on the size ratio of the particles and the viscosity of the fluid. The sharp initial change and the subsequent saturation in the extent of segregation and angle of repose occurs over similar volume fraction of the fluid. Preferential clumping of small particles causes layering to occur when the size of the clumps of small particles exceeds the size of large particles. We calculate the azimuthal correlation function of particle density inside the pile to characterize the extent of layering. In the second series of experiments, particles are poured into a container filled with a fluid. Although the angle of repose is observed to be unchanged, segregation is observed to decrease with an increase in the viscosity of the fluid. The viscosity at which segregation decreases to zero depends on the size ratio of the particles.

  5. Stress-dependent normal mode frequencies from the effective mass of granular matter

    E-print Network

    Yanqing Hu; David L. Johnson; John J. Valenza; Francisco Santibanez; Hernán A. Makse

    2014-10-20

    A zero-temperature critical point has been invoked to control the anomalous behavior of granular matter as it approaches jamming or mechanical arrest. Criticality manifests itself in an anomalous spectrum of low-frequency normal modes and scaling behavior near the jamming transition. The critical point may explain the peculiar mechanical properties of dissimilar systems such as glasses and granular materials. Here, we study the critical scenario via an experimental measurement of the normal modes frequencies of granular matter under stress from a pole decomposition analysis of the effective mass. We extract a complex-valued characteristic frequency which displays scaling $|\\omega^*(\\sigma)|\\sim\\sigma^{\\Omega'}$ with vanishing stress $\\sigma$ for a variety of granular systems. The critical exponent is smaller than that predicted by mean-field theory opening new challenges to explain the exponent for frictional and dissipative granular matter. Our results shed light on the anomalous behavior of stress-dependent acoustics and attenuation in granular materials near the jamming transition.

  6. Critical Flow of Granular Matter on a Conveyor Belt

    Microsoft Academic Search

    Giorgos Kanellopoulos; Ko van der Weele

    2008-01-01

    We study the flow of granular material on a conveyor belt consisting of a number of connected, vertically vibrated compartments. Flows of this type are notorious for obstructing themselves due to the spontaneous formation of dense particle clusters. We apply a steady inflow Q to the top compartment and our goal is to describe the conditions that ensure a continuous

  7. Granular Matter manuscript No. (will be inserted by the editor)

    E-print Network

    Luding, Stefan

    , for the volumetric and shear strains as well as for the new ingredient, the anisotropy modulus. The non and shear modulus are set to constants, while the shear stress ratio and the anisotropy evolve with differ] and anisotropy [6,13,22­24] ­ among many others. If an isotropic granular packing is subject to isotropic

  8. Experimental observations of structural relaxation in granular matter

    Microsoft Academic Search

    M. Massalska-Arodz-acute; J. Mayer; J. Bran-acutekowski; A. Ostrowicz; E. Lisiecki

    1997-01-01

    The relaxational changes of the electrical capacitance of a system of grains poured abruptly into a vessel capacitor have been observed. Two power-law decays have been found. The faster relaxation at the beginning has been interpreted as being driven by independent-grain motion. The later slower process has been ascribed to the collective reorganization of the granular system. The observations seem

  9. A deductive statistical mechanics approach for granular matter

    E-print Network

    T. Aste; T. Di Matteo

    2007-11-21

    We introduce a deductive statistical mechanics approach for granular materials which is formally built from few realistic physical assumptions. The main finding is an universal behavior for the distribution of the density fluctuations. Such a distribution is the equivalent of the Maxwell-Boltzmann's distribution in the kinetic theory of gasses. The comparison with a very extensive set of experimental and simulation data for packings of monosized spherical grains, reveals a remarkably good quantitative agreement with the theoretical predictions for the density fluctuations both at the grain level and at the global system level. Such agreement is robust over a broad range of packing fractions and it is observed in several distinct systems prepared by using different methods. The equilibrium distributions are characterized by only one parameter ($k$) which is a quantity very sensitive to changes in the structural organization. The thermodynamical equivalent of $k$ and its relation with the `granular temperature' are also discussed.

  10. Mechanisms for Acoustic Absorption in Dry and Weakly Wet Granular Media

    SciTech Connect

    Brunet, Th.; Jia, X.; Mills, P. [Laboratoire de Physique des Milieux Divises et Interfaces, Universite Paris-Est, CNRS UMR 8108, 77454 Marne-La-Vallee (France)

    2008-09-26

    The dissipation of an elastic wave in dry and wet glass bead packings is measured using multiple sound scattering. The interplay of a linear viscoelastic loss and a nonlinear frictional one is observed in dry media. The Mindlin model provides a qualitative description of the experiment, but fails to quantitatively account for the data due to grain roughness. In weakly wet media, we find that the dissipation is dominated by a linear viscous loss due to the liquid films trapped at the grain surface asperities. Adding more liquid enables us to form the capillary menisci but does not increase the energy loss.

  11. Does canopy wetness matter? Evapotranspiration from a subtropical montane cloud forest in Taiwan

    E-print Network

    Chen, Jiquan

    Does canopy wetness matter? Evapotranspiration from a subtropical montane cloud forest in Taiwan, Münster, Germany Abstract: Evapotranspiration (ET) and canopy wetness were measured over a 2-year and formulate adaptive management plans. Copyright © 2012 John Wiley & Sons, Ltd. KEY WORDS evapotranspiration

  12. Compaction creep of wet granular calcite by pressure solution at 28°C to 150°C

    Microsoft Academic Search

    Xiangmin Zhang; Christopher J. Spiers; Colin J. Peach

    2010-01-01

    Uniaxial compaction experiments have been carried out on wet calcite powders prepared from milled limestone, analytical grade calcite, and superpure calcite. The tests were performed at 28°C–150°C, effective stresses of 20–47 MPa, and a pore pressure of 20 MPa, using presaturated CaCO3 solution as the pore fluid. Sample grain sizes ranged from 12 to 86 ?m. The aim was to

  13. Extended event driven molecular dynamics for simulating dense granular matter

    E-print Network

    J. Sebastian Gonzalez; Dino Risso; Rodrigo Soto

    2010-12-21

    A new numerical method is presented to efficiently simulate the inelastic hard sphere (IHS) model for granular media, when fluid and frozen regions coexist in the presence of gravity. The IHS model is extended by allowing particles to change their dynamics into either a frozen state or back to the normal collisional state, while computing the dynamics only for the particles in the normal state. Careful criteria, local in time and space, are designed such that particles become frozen only at mechanically stable positions. The homogeneous deposition over a static surface and the dynamics of a rotating drum are studied as test cases. The simulations agree with previous experimental results. The model is much more efficient than the usual event driven method and allows to overcome some of the difficulties of the standard IHS model, such as the existence of a static limit.

  14. Extended event driven molecular dynamics for simulating dense granular matter

    NASA Astrophysics Data System (ADS)

    González, S.; Risso, D.; Soto, R.

    2009-12-01

    A new numerical method is presented to efficiently simulate the inelastic hard sphere (IHS) model for granular media, when fluid and frozen regions coexist in the presence of gravity. The IHS model is extended by allowing particles to change their dynamics into either a frozen state or back to the normal collisional state, while computing the dynamics only for the particles in the normal state. Careful criteria, local in time and space, are designed such that particles become frozen only at mechanically stable positions. The homogeneous deposition over a static surface and the dynamics of a rotating drum are studied as test cases. The simulations agree with previous experimental results. The model is much more efficient than the usual event driven method and allows to overcome some of the difficulties of the standard IHS model, such as the existence of a static limit.

  15. Organic matter inputs shift soil enzyme activity and allocation patterns in a wet tropical forest

    E-print Network

    Cleveland, Cory

    Organic matter inputs shift soil enzyme activity and allocation patterns in a wet tropical forest enzymes mediate organic matter turnover and nutrient cycling yet remain little studied in one of Earth properties and enzyme activities in a lowland tropical forest. We assayed six hydrolytic soil enzymes

  16. Critical Flow of Granular Matter on a Conveyor Belt

    NASA Astrophysics Data System (ADS)

    Kanellopoulos, Giorgos; van der Weele, Ko

    2008-11-01

    We study the flow of granular material on a conveyor belt consisting of a number of connected, vertically vibrated compartments. Flows of this type are notorious for obstructing themselves due to the spontaneous formation of dense particle clusters. We apply a steady inflow Q to the top compartment and our goal is to describe the conditions that ensure a continuous flow all the way down to the last compartment. Given the vibration strength and the dimensions of the system, we determine the critical flow rate Qcr beyond which cluster formation becomes inevitable. We show that the clusters are announced in advance {before the value Qcr) by the appearance of a wavy density profile along the conveyor belt. This provides a new, potentially very valuable warning signal in industrial applications. The critical flow and the associated wavy profile are explained quantitatively in terms of a dynamical flux model. The appearance of the wavy structure turns out to be closely related to a reverse period doubling bifurcation of the (previously uniform) density profile.

  17. A community-detection based approach to identification of inhomogeneities in granular matter

    NASA Astrophysics Data System (ADS)

    Navakas, Robertas; Džiugys, Algis; Peters, Bernhard

    2014-08-01

    Interparticle interactions in granular matter are commonly represented by appropriate graphs, therefore, inhomogeneities in granular matter can be possibly reflected by community structure in the respective graphs. Approaches and algorithms for community detection are being actively developed and the achievements in this area can be utilized for analysis of granular systems, where bridging the gap from microscopic configuration to macroscopic phenomena is of great interest. Here, we analyse applicability of graph community detection algorithms for identification of inhomogeneities of particle parameter distribution in granular matter, in order to explore the relevance of the selected approach in general. As an example application, we analyse identification of temperature distribution inhomogeneities in a simulated packed bed of fuel particles on a moving grate. We build a graph based on particle parameter similarity from the particle temperature data, available from Discrete Element/Particle Modelling, and the problem of identification of particle temperature inhomogeneities is thereby made equivalent to community detection in graphs. We apply a number of well-known community detection algorithms: Edge Betweenness, Walktrap, Infomap, Label Propagation, Spinglass and compare the resulting partitions. We apply this approach to a number of graphs, corresponding to different particle configurations, in order to identify regularities characteristic of partitions produced by different algorithms. We propose a procedure for additional postprocessing of the partitions in order to improve the quality of clusterization. In addition, we apply two alternative algorithms (not related to community detection in graphs) to identify particle distribution inhomogeneities. We also introduce a parameter to evaluate the cluster structure in particle systems.

  18. Flocking at a distance in active granular matter.

    PubMed

    Kumar, Nitin; Soni, Harsh; Ramaswamy, Sriram; Sood, A K

    2014-01-01

    The self-organized motion of vast numbers of creatures in a single direction is a spectacular example of emergent order. Here, we recreate this phenomenon using actuated nonliving components. We report here that millimetre-sized tapered rods, rendered motile by contact with an underlying vibrated surface and interacting through a medium of spherical beads, undergo a phase transition to a state of spontaneous alignment of velocities and orientations above a threshold bead area fraction. Guided by a detailed simulation model, we construct an analytical theory of this flocking transition, with two ingredients: a moving rod drags beads; neighbouring rods reorient in the resulting flow like a weathercock in the wind. Theory and experiment agree on the structure of our phase diagram in the plane of rod and bead concentrations and power-law spatial correlations near the phase boundary. Our discovery suggests possible new mechanisms for the collective transport of particulate or cellular matter. PMID:25181961

  19. Flocking at a distance in active granular matter

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Soni, Harsh; Ramaswamy, Sriram; Sood, A. K.

    2014-09-01

    The self-organized motion of vast numbers of creatures in a single direction is a spectacular example of emergent order. Here, we recreate this phenomenon using actuated nonliving components. We report here that millimetre-sized tapered rods, rendered motile by contact with an underlying vibrated surface and interacting through a medium of spherical beads, undergo a phase transition to a state of spontaneous alignment of velocities and orientations above a threshold bead area fraction. Guided by a detailed simulation model, we construct an analytical theory of this flocking transition, with two ingredients: a moving rod drags beads; neighbouring rods reorient in the resulting flow like a weathercock in the wind. Theory and experiment agree on the structure of our phase diagram in the plane of rod and bead concentrations and power-law spatial correlations near the phase boundary. Our discovery suggests possible new mechanisms for the collective transport of particulate or cellular matter.

  20. Flocking at a distance in active granular matter

    E-print Network

    Nitin Kumar; Harsh Soni; Sriram Ramaswamy; A. K. Sood

    2014-09-22

    The self-organised motion of vast numbers of creatures in a single direction is a spectacular example of emergent order. We recreate this phenomenon using actuated non-living components. We report here that millimetre-sized tapered rods, rendered motile by contact with an underlying vibrated surface and interacting through a medium of spherical beads, undergo a phase transition to a state of spontaneous alignment of velocities and orientations above a threshold bead area fraction. Guided by a detailed simulation model, we construct an analytical theory of this flocking transition, with two ingredients: a moving rod drags beads; neighbouring rods reorient in the resulting flow like a weathercock in the wind. Theory and experiment agree on the structure of our phase diagram in the plane of rod and bead concentrations and power-law spatial correlations near the phase boundary. Our discovery suggests possible new mechanisms for the collective transport of particulate or cellular matter.

  1. Granular Matter 2, 179187 c Springer-Verlag 2000 Effect of particle size distribution on pile tip resistance

    E-print Network

    Bolton, Malcolm

    Granular Matter 2, 179­187 c Springer-Verlag 2000 Effect of particle size distribution on pile tip the specific boundary problem associated with the penetration of a model pile into two different gradings of fine particles on the pile end bearing resistance. The first grading of sand comprised particles

  2. Granular Matter 3, 113116 c Springer-Verlag 2001 Simulations for dynamics of granular mixtures in a rotating drum

    E-print Network

    Kenkre, V.M.

    Introduction Recently, flows of granular material (GM) have received much attention from many disciplines, the understanding of the behavior of GM is very important to Received: 30 March 2000 R. Monetti Instituto de in the production of several goods such as pharmaceuticals, foods, polymers, semiconductors, etc. However, under

  3. Granular Matter (2012) 14:145149 DOI 10.1007/s10035-011-0299-7

    E-print Network

    Goddard, Joe

    cycle · Granular materials · Coulomb friction · Vibrated granular layers 1 Introduction Vibratory conveyors, routinely employed in industry for transport of granular materials, generally consist of an oscil. The main advantages of such conveyors are their simple construction, their suitability for handling hot

  4. Granular Matter (2011) 13:241245 DOI 10.1007/s10035-011-0248-5

    E-print Network

    Blumenfeld, Rafi

    2011-01-01

    granular materials and indeed such an approach has a long history. The kinetic theory of so-called dense gases, which takes into considerations dissipation during collision between particles, presents a useful attempt of modeling granular flow. Unfortunately, it is only useful for low-concentration granular systems

  5. Simulation of electron-matter interaction during wet-STEM electron tomography

    SciTech Connect

    Septiyanto, Rahmat Firman, E-mail: karine.masenelli-varlot@insa-lyon.fr [MATEIS, INSA-Lyon, CNRS UMR5510, F-69621, France and Physics of Electronic Material, Departement of Physics, Faculty of Mathematic and Natural Sciences, ITB Jalan Ganesha No. 10, Bandung 40132 (Indonesia); Masenelli-Varlot, Karine [MATEIS, INSA-Lyon, CNRS UMR5510, F-69621 (France); Iskandar, Ferry [Physics of Electronic Material, Departement of Physics, Faculty of Mathematic and Natural Sciences, ITB Jalan Ganesha No. 10, Bandung 40132 (Indonesia)

    2014-02-24

    Tomography is an efficient tool to probe the 3 dimensional (3D) structure of materials. In the laboratory, a device has been developed to perform electron tomography in an environmental scanning electron microscopy (ESEM). The configuration of Scanning Transmission Electron Microscopy (STEM) in Environmental Scanning Electron Microscopy (ESEM) provides a novel approach for the characterization of the 3D structure of materials and optimizes a compromise between the resolution level of a few nm and the large tomogram due to the high thickness of transparency. Moreover, STEM allows the observation in 2D of wet samples in an ESEM by finely controlling the sample temperature and the water pressure of the sample environment. It has been recently demonstrated that it was possible to acquire image series of hydrated objects and thus to attain 3D characterization of wet samples. In order to get reliable and quantitative data, the present study deals with the simulation of electron-matter interactions. From such simulation on the MCM-41 material, we determine the minimum quantity of water layer which can be detected on wet materials.

  6. Granular activated carbon adsorption of MIB in the presence of dissolved organic matter.

    PubMed

    Summers, R Scott; Kim, Soo Myung; Shimabuku, Kyle; Chae, Seon-Ha; Corwin, Christopher J

    2013-06-15

    Based on the results of over twenty laboratory granular activated carbon (GAC) column runs, models were developed and utilized for the prediction of 2-methylisoborneol (MIB) breakthrough behavior at parts per trillion levels and verified with pilot-scale data. The influent MIB concentration was found not to impact the concentration normalized breakthrough. Increasing influent background dissolved organic matter (DOM) concentration was found to systematically decrease the GAC adsorption capacity for MIB. A series of empirical models were developed that related the throughput in bed volumes for a range of MIB breakthrough targets to the influent DOM concentration. The proportional diffusivity (PD) designed rapid small-scale column test (RSSCT) could be directly used to scale-up MIB breakthrough performance below 15% breakthrough. The empirical model to predict the throughput to 50% breakthrough based on the influent DOM concentration served as input to the pore diffusion model (PDM) and well-predicted the MIB breakthrough performance below a 50% breakthrough. The PDM predictions of throughput to 10% breakthrough well simulated the PD-RSSCT and pilot-scale 10% MIB breakthrough. PMID:23623469

  7. Note: "Lock-in accelerometry" to follow sink dynamics in shaken granular matter.

    PubMed

    Sánchez-Colina, G; Alonso-Llanes, L; Martínez, E; Batista-Leyva, A J; Clement, C; Fliedner, C; Toussaint, R; Altshuler, E

    2014-12-01

    Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental physics, but also for geophysical processes and construction on sediments or granular soils in areas potentially affected by earthquakes. While the penetration of intruders in two dimensional (2D) laboratory granular beds can be followed using video recording, this is useless in three dimensional (3D) beds of non-transparent materials such as common sand. Here, we propose a method to quantify the sink dynamics of an intruder into laterally shaken granular beds based on the temporal correlations between the signals from a reference accelerometer fixed to the shaken granular bed, and a probe accelerometer deployed inside the intruder. Due to its analogy with the working principle of a lock-in amplifier, we call this technique lock-in accelerometry. PMID:25554337

  8. Efficient numerical simulation of granular matter using the Bottom-To-Top Reconstruction method

    E-print Network

    Thomas Schwager; Thorsten Poeschel

    2006-11-24

    The numerical simulation of granular systems of even moderate size is a challenging computational problem. In most investigations, either Molecular Dynamics or Event-driven Molecular Dynamics is applied. Here we show that in certain cases, mainly (but not exclusively) for static granular packings, the Bottom-to-top Reconstruction method allows for the efficient simulation of very large systems. We apply the method to heap formation, granular flow in a rotating cylinder and to structure formation in nano-powders. We also present an efficient implementation of the algorithm in C++, including a benchmark.

  9. Fiat or Bona Fide Boundary—A Matter of Granular Perspective

    PubMed Central

    Vogt, Lars; Grobe, Peter; Quast, Björn; Bartolomaeus, Thomas

    2012-01-01

    Background Distinguishing bona fide (i.e. natural) and fiat (i.e. artificial) physical boundaries plays a key role for distinguishing natural from artificial material entities and is thus relevant to any scientific formal foundational top-level ontology, as for instance the Basic Formal Ontology (BFO). In BFO, the distinction is essential for demarcating two foundational categories of material entity: object and fiat object part. The commonly used basis for demarcating bona fide from fiat boundary refers to two criteria: (i) intrinsic qualities of the boundary bearers (i.e. spatial/physical discontinuity, qualitative heterogeneity) and (ii) mind-independent existence of the boundary. The resulting distinction of bona fide and fiat boundaries is considered to be categorial and exhaustive. Methodology/Principal Findings By referring to various examples from biology, we demonstrate that the hitherto used distinction of boundaries is not categorial: (i) spatial/physical discontinuity is a matter of scale and the differentiation of bona fide and fiat boundaries is thus granularity-dependent, and (ii) this differentiation is not absolute, but comes in degrees. By reducing the demarcation criteria to mind-independence and by also considering dispositions and historical relations of the bearers of boundaries, instead of only considering their spatio-structural properties, we demonstrate with various examples that spatio-structurally fiat boundaries can nevertheless be mind-independent and in this sense bona fide. Conclusions/Significance We argue that the ontological status of a given boundary is perspective-dependent and that the strictly spatio-structural demarcation criteria follow a static perspective that is ignorant of causality and the dynamics of reality. Based on a distinction of several ontologically independent perspectives, we suggest different types of boundaries and corresponding material entities, including boundaries based on function (locomotion, physiology, ecology, development, reproduction) and common history (development, heredity, evolution). We argue that for each perspective one can differentiate respective bona fide from fiat boundaries. PMID:23251333

  10. Influence of dry–wet cycles on the interrelationship between aggregate, particulate organic matter, and microbial community dynamics

    Microsoft Academic Search

    Karolien Denef; Johan Six; Heleen Bossuyt; Serita D. Frey; Edward T. Elliott; Roel Merckx; Keith Paustian

    2001-01-01

    Aggregate dynamics and their relationship to the microbial community have been suggested as key factors controlling SOM dynamics. Dry–wet (DW) cycles are thought to enhance aggregate turnover and decomposition of soil organic matter (SOM), particularly in tilled soils. The objective of this study was to evaluate the effects of DW cycles on aggregate stability, SOM dynamics, and fungal and bacterial

  11. Grain- and Pore-level Analysis of Drainage in Fractionally-wet Granular Media using Synchrotron X-ray Computed Microtomography

    NASA Astrophysics Data System (ADS)

    Willson, C. S.; Bradley, S.; Thompson, K. E.

    2011-12-01

    Numerous lab- and field-scale experimental studies have shown the strong impact of wettability on multiphase flow constitutive relations and how increased water repellency can lead to preferential flow paths and a heterogeneous water distribution. In conjunction, theoretical and pore-scale modeling work has been performed seeking to improve our understanding of the impact of grain-level wettability properties. Advances in high-resolution X-ray computed tomography (XCT) techniques now make it possible to nondestructively image opaque materials providing previously hard-to-observe qualitative and quantitative data and information. Furthermore, the characteristics of synchrotron X-rays make it possible to monochromatize the incident energy allowing for both k-edge absorption differencing and segmentation of fluids and materials that have even slightly different chemical composition. Concurrent with these advances has been the development of methods to extract granular packing and pore network structure data from XCT images. In this talk, we will present results from a series of experiments designed to obtain grain-, pore- and fluid-scale details during the drainage of water in fractionally-wet glass bead systems. Here, two sets of glass beads were used each having slightly different chemical compositions and thus, different X-ray absorption properties. One set was treated so that the bead surface was water neutral while the other set remained hydrophilic. Three sets of drainage experiments were conducted on three fractionally-wet systems: 100, 90, and 75% hydrophilic by weight. First, traditional lab-scale drainage experiments were performed to obtain a baseline set of characteristic drainage curves for the three systms. Next, a set of tomography-scale (i.e., 5.5 mm inner diameter column) drainage experiments were conducted in the lab to ensure that the drainage curves in the smaller columns were consistent with the lab-scale curves. Finally, tomography-scale drainage experiments were performed at the APS/GSECARS 13-BMD tomography beamline to obtain ~10 micron voxel resolution 3D images at specific capillary suction heads. Results will be presented that show that, at these levels of fractional-wettability, the drainage curves from the tomography-scale columns are consistent with the larger scale data and therefore, the fluid phase distribution imaged at the various drainage steps is also representative. Next, granular packing and pore network structure results will be discussed highlight our ability to characterize and uniquely identify the packing and distribution of different grain types and ensuring consistent pore morphology. Finally, the water phase distribution at different stages of drainage is correlated to the pore network structure and the individual water-wet and water-repellant grains providing valuable insights into the impact of grain- and pore-level wettability variations. These quantitative results show that grain-level differences in wettability captured using this approach have an impact on the connectivity of the water phase during drainage and should provide valuable insights for further development of theoretical and numerical approaches.

  12. Critical Phenomena in Driven Granular Matter: Jamming and Glassy Behavior - Final Report

    SciTech Connect

    Teitel, Stephen

    2013-02-20

    Granular materials, such as powders, seeds, grains, sand, rocks, etc., are ubiquitous both in nature and in industrial processes. At the scale of individual grains, granular systems are particularly simple: particles interact only when they touch. But when viewed in the aggregate, granular systems can display complex behavior. In particular, as the volume packing fraction of the grains increases, the system undergoes a jamming transition from a flowing liquid to a disordered but rigid solid. We study the critical behavior of such systems near the jamming transition using numerical simulations of a simple model of soft-core, bidisperse, frictionless disks in two dimensions. We seek to understand the structural and transport properties of such systems under a variety of physical perturbations such as steady state shear driven flow, and finite thermal fluctuations.

  13. Granular Matter (2014) 16:193201 DOI 10.1007/s10035-014-0482-8

    E-print Network

    Claudin, Philippe

    c. We find that the shear modulus of the system decreases with , but tends to a finite value as c,31,32,37,44]. As the system loses its mechanical rigid- ity at the transition, its shear modulus G is found to van- ish. The properties of frictional granular packings have also been investigated, see e.g. [40], but, in this context

  14. WET SOLIDS FLOW ENHANCEMENT

    SciTech Connect

    Hugo S. Caram; Natalie Foster

    1999-07-01

    The strain-stress behavior of a wet granular media was measured using a split Parfitt tensile tester. In all cases the stress increases linearly with distance until the maximum uniaxial tensile stress is reached. The stress then decreases exponentially with distance after this maximum is reached. The linear region indicates that wet solids behave elastically for stresses below the tensile stresses and can store significant elastic energy. The elastic deformation cannot be explained by analyzing the behavior of individual capillary bridges and requires accounting for the deformation of the solids particles. The elastic modulus of the wet granular material remains unexplained.

  15. WET SOLIDS FLOW ENHANCEMENT

    SciTech Connect

    Hugo S. Caram; Natalie Foster

    1998-03-30

    The strain-stress behavior of a wet granular media was measured using a split Parfitt tensile tester. In all cases the stress increases linearly with distance until the maximum uniaxial tensile stress is reached. The stress then decreases exponentially with distance after this maximum is reached. The linear region indicates that wet solids behave elastically for stresses below the tensile stresses and can store significant elastic energy. The elastic deformation cannot be explained by analyzing the behavior of individual capillary bridges and may require accounting for the deformation of the solids particles. The elastic modulus of the wet granular material remains unexplained.

  16. Production response of lactating cows fed dried versus wet brewers' grain in diets with similar dry matter content.

    PubMed

    Dhiman, T R; Bingham, H R; Radloff, H D

    2003-09-01

    Twenty-four Holstein-Friesian dairy cows (20 intact and 4 fitted with rumen cannula) during early lactation (56 +/- 25.3 d in milk) were assigned to two treatments to determine intake and production responses to feeding dried and wet brewers' grain. There were two cows fitted with a rumen cannula in each treatment. Cows were fed a total mixed ration twice daily containing either dried or wet brewers' grain at 15% of the dietary dry matter (DM). The diet contained 47% forage and 53% concentrate. The experimental design was a replicated 2 x 2 Latin square with two periods of 5 wk each. First 2 wk in each period were considered as adaptation to diets and data from the last 3 wk were used for treatment comparisons. Dried and wet brewers' diets contained 68.0 and 66.5% DM, respectively. Feeding brewers' grain dry or wet to dairy cows had no influence on feed intake (25.6 vs. 25.1 kg/d), fat corrected milk yield (40.1 vs. 40.7 kg/d), milk composition and feed consumption. The pH, ammonia, total volatile fatty acids and molar ratios of volatile fatty acids in the rumen fluid were not different between treatments. Fatty acid composition of milk fat from cows fed diets containing dry or wet brewers' grain was identical, except C18:2 and C18:3 fatty acids were lower in milk fat from cows fed wet brewers' grain compared with dried brewers' grain. The results from the present study suggest that the performance of cows fed either dried or wet brewers' grain at 15% of dietary DM was similar when diets had the same DM. The average price for dried and wet brewers' grain in the United States from July 2001 to June 2002 was dollars 145.3 and dollars 96.9/metric tonne DM, respectively. Using wet instead of dried brewers' grain will save dollars 49/metric tonne minus the difference in storage costs. Wet brewers' grain can be fed to dairy cows in areas that are close to the brewery and provides nutritive value similar to the dried brewers' grain. PMID:14507027

  17. A simple wet chemical extraction procedure to characterize soil organic matter (SOM). I. application and recovery rate

    Microsoft Academic Search

    L. Beyer; C. Wachendorf; C. Koebbemann

    1993-01-01

    The knowledge of soil organic matter (SOM) composition is important for research in soil science. This is why two classical wet chemical extraction procedures were tested and combined to characterize SOM. Twenty?five samples from typical forest and arable soils in Schleswig?Holstein, Northwest Germany, were investigated in the laboratory. Lipids were extracted using a pre?step method. Several polysaccharide fractions were extracted

  18. "EGM" (Electrostatics of Granular Matter): A Space Station Experiment to Examine Natural Particulate Systems

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Sauke, T.; Buehler, M.; Farrell, W.; Green, R.; Birchenough, A.

    1999-01-01

    A granular-materials experiment is being developed for a 2002 launch for Space Station deployment. The experiment is funded by NASA HQ and managed through NASA Lewis Research Center. The experiment will examine electrostatic aggregation of coarse granular materials with the goals of (a) obtaining proof for an electrostatic dipole model of grain interactions, and (b) obtaining knowledge about the way aggregation affects the behavior of natural particulate masses: (1) in unconfined dispersions (clouds such as nebulae, aeolian dust palls, volcanic plumes), (2) in semi-confined, self-loaded masses as in fluidized flows (pyroclastic surges, avalanches) and compacted regolith, or (3) in semi-confined non-loaded masses as in dust layers adhering to solar cells or space suits on Mars. The experiment addresses both planetary/astrophysical issues as well as practical concerns for human exploration of Mars or other solar system bodies. Additional information is contained in the original.

  19. Insights on the local dynamics induced by thermal cycling in granular matter

    E-print Network

    Baptiste Percier; Thibaut Divoux; Nicolas Taberlet

    2013-06-18

    In this letter, we report results on the effect of temperature variations on a granular assembly through Molecular Dynamic simulations of a 2D granular column. Periodic dilation of the grains are shown to perfectly mimic such thermal cycling, and allows to rationalize the link between the compaction process, the local grains dynamics and finite size effects. Here we show that the individual grain properties, namely their roughness and elastic modulus define a minimal cycling amplitude of temperature \\Delta Tc below which the dynamics is intermittent and spatially heterogeneous while confined into localized regions recently coined "hot spot" [Amon et al., Phys. Rev. Lett. 108, 135502 (2012)]. Above \\Delta Tc, the whole column flows while the grains dynamics ranges continuously from cage-like at the bottom of the column to purely diffusive at the top. Our results provide a solid framework for the futur use of thermal cycling as an alternate driving method for soft glassy materials.

  20. Insights on the local dynamics induced by thermal cycling in granular matter

    NASA Astrophysics Data System (ADS)

    Percier, Baptiste; Divoux, Thibaut; Taberlet, Nicolas

    2013-10-01

    In this letter, we report results on the effect of temperature variations on a granular assembly through molecular-dynamic simulations of a 2D granular column. Periodic dilations of the grains are shown to perfectly mimic such thermal cycling, and allow to rationalize the link between the compaction process, the local grains dynamics and finite-size effects. Through extensive simulations, we show quantitatively that the individual disks properties, namely their roughness and elastic modulus, define a critical cycling amplitude of temperature \\Delta T_c . Below \\Delta T_c , the dynamics is intermittent and spatially heterogeneous while confined into localized regions, whereas above \\Delta T_c , the whole column flows and the disks dynamics ranges continuously from cage-like at the bottom of the column to purely diffusive at the top. Our results rationalize a series of experimental results reported in the literature on dry or immersed granular materials and provide a simple simulation method for the study of thermal cycling as an alternate driving method for soft glassy materials.

  1. The jamming surface of granular matter determined from soil mechanics results

    E-print Network

    P. Evesque

    2005-06-17

    Classical soil mechanics results are used to propose the equation of the jamming transition surface in the (stress, specific volume) space. Taking axis-ymmetric conditions, labelling q the deviatoric stress and p' the mean pressure applied on the granular skeleton, and considering normal range of pressure (10 kPa-10MPa) the equation of the surface of jamming transition is v = vo-m ln(p'/p'o)+ md ln(1+q q/(M' M' p' p')); M' is related to the friction angle, m and md are two constants which depend on soil characteristics; p'o is a "unit" pressure.

  2. Wet voice as a sign of penetration/aspiration in Parkinson's disease: does testing material matter?

    PubMed

    Sampaio, Marília; Argolo, Natalie; Melo, Ailton; Nóbrega, Ana Caline

    2014-10-01

    Wet voice is a perceptual vocal quality that is commonly used as an indicator of penetration and/or aspiration in clinical swallowing assessments and bedside screening tests. Our aim was to describe the clinimetric characteristics of this clinical sign using various fluid materials and one solid food in the Parkinson's disease (PD) population. Consecutive PD individuals were submitted for simultaneous fiberoptic endoscopic evaluation of swallowing (FEES) and voice recording. Speech therapists rated the presence or absence of wetness and other voice abnormalities. Two binary endpoints of FEES were selected for comparison with an index test: low penetration (LP) and low penetration and/or aspiration (LP/ASP). The accuracy of wet voice changed according to the testing material in PD patients. Overall, the specificity of this indicator was better than its sensitivity, and the wafer cookie and yogurt drink yielded the best indices. Our data show that wet voice is clearly indicative of LP or LP/ASP in PD patients in case of positive test. However, in the case of a negative result, the wet voice test should be repeated or combined with other clinical tests to include or exclude the risk of LP or LP/ASP. PMID:25001523

  3. Removal of Particulate Matter in a Tubular Wet Electrostatic Precipitator Using a Water Collection Electrode

    PubMed Central

    Kim, Jong-Ho; Yoo, Hee-Jung; Hwang, You-Seong; Kim, Hyeok-Gyu

    2012-01-01

    As one of the effective control devices of air pollutants, the wet electrostatic precipitator (ESP) is an effective technique to eliminate acid mist and fine particles that are re-entrained in a collection electrode. However, its collection efficiency can deteriorate, as its operation is subject to water-induced corrosion of the collection electrode. To overcome this drawback, we modified the wet ESP system with the installation of a PVC dust precipitator wherein water is supplied as a replacement of the collection electrode. With this modification, we were able to construct a compact wet ESP with a small specific collection area (SCA, 0.83?m2/(m3/min)) that can acquire a high collection efficiency of fine particles (99.7%). PMID:22577353

  4. Coherent Transport and Symmetry Breaking - Laser Dynamics of Constrained Granular Matter

    E-print Network

    Andreas Lubatsch; Regine Frank

    2014-08-14

    We present diagrammatic transport theory including self-consistent nonlinear enhancement and dissipation in the multiple scattering regime. Our model of Vollhardt-W\\"olfle transport of photons is fit-parameter-free and raises the claim that the results hold up to the closest packed volume of randomly arranged ZnO Mie scatterers. We find that a symmetry breaking caused by dissipative effects of a lossy underlying substrate leads to qualitatively different physics of coherence and lasing in granular amplifying media. According to our results, confined and extended mode and their laser thresholds can be clearly attributed to unbroken and broken spatial symmetry. The diameters and emission profiles of random laser modes, as well as their thresholds and the positional-dependent degree of coherence can be checked experimentally.

  5. Flow of granular matter in a silo with multiple exit orifices: Jamming to mixing

    NASA Astrophysics Data System (ADS)

    Kamath, Sandesh; Kunte, Amit; Doshi, Pankaj; Orpe, Ashish V.

    2014-12-01

    We investigate the mixing characteristics of dry granular material while draining down a silo with multiple exit orifices. The mixing in the silo, which otherwise consists of noninteracting stagnant and flowing regions, is observed to improve significantly when the flow through specific orifices is stopped intermittently. This momentary stoppage of flow through the orifice is either controlled manually or is chosen by the system itself when the orifice width is small enough to cause spontaneous jamming and unjamming. We observe that the overall mixing behavior shows a systematic dependence on the frequency of closing and opening of specific orifices. In particular, the silo configuration employing random jamming and unjamming of any of the orifices shows early evidence of chaotic mixing. When operated in a multipass mode, the system exhibits a practical and efficient way of mixing particles.

  6. Flow of granular matter in a silo with multiple exit orifices: Jamming to mixing

    E-print Network

    Sandesh Deshmukh; Amit Kunte; Pankaj Doshi; Ashish V. Orpe

    2014-12-17

    We investigate the mixing characteristics of dry granular material while draining down a silo with multiple exit orifices. The mixing in the silo, which otherwise consists of noninteracting stagnant and flow regions, is observed to improve significantly when the flow through specific orifices is stopped intermittently. This momentary stoppage of flow through the orifice is either controlled manually or is chosen by the system itself when the orifice width is small enough to cause spontaneous jamming and unjamming. We observe that the overall mixing behavior shows a systematic dependence on the frequency of closing and opening of specific orifices. In particular, the silo configuration employing random jamming and unjamming of any of the orifices shows early evidence of chaotic mixing. When operated in a multipass mode, the system exhibits a practical and efficient way of mixing particles.

  7. Radial and axial segregation of granular matter in a rotating cylinder: A simulation study

    E-print Network

    D. C. Rapaport

    2007-02-07

    The phenomena of radial and axial segregation in a horizontal rotating cylinder containing a mixture of granular particles of two different species have been modeled using discrete particle simulation. Space-time plots and detailed imagery provide a comprehensive description of what occurs in the system. As is the case experimentally, the nature of the segregation depends on the parameters defining the problem; the radial component of the segregation may be transient or long-lasting, and the axial component may or may not develop. Simulations displaying the different kinds of behavior are described and the particle dynamics associated with the axially segregated state examined. The importance of an appropriate choice of interaction for representing the effective friction force is demonstrated.

  8. Significance of wet deposition to removal of atmospheric particulate matter and polycyclic aromatic hydrocarbons: A case study in Guangzhou, China

    NASA Astrophysics Data System (ADS)

    Guo, Ling-Chuan; Bao, Lian-Jun; She, Jian-Wen; Zeng, Eddy Y.

    2014-02-01

    Rainwater samples were simultaneously collected from three locations in Guangzhou, a mega metropolitan center in South China, during the entire year of 2010, and analyzed for particulate matter (PM), total organic carbon and polycyclic aromatic hydrocarbons (PAHs), with the objectives of assessing the seasonality of washout effects and efficiency for removal of pollutants from the atmosphere by wet deposition. The contents of PM, particulate organic carbon, and dissolved organic carbon were in the ranges of 0.74-420 (average: 8.1 mg L-1), 0.16-40 (average: 1.3 mg L-1), and 0.34-6.9 mg L-1 (average: 1.4 mg L-1), respectively. Concentrations of ?15PAH (sum of the 16 priority PAH compounds defined by the United States Environmental Protection Agency minus naphthalene) in wet deposition samples ranged from 39 to 1580 ng L-1 with an average of 170 ng L-1. The PAH concentration levels were slightly abated compared to those acquired previously in Guangzhou during the year of 2005, probably indicating a favorable change of energy consumption patterns in the region. There were moderately significant negative correlations between washout ratios and rainfall intensities (0-4.3 mm h-1). The total annual fluxes of wet and dry depositions combined for PM and PAHs in the urban area of Guangzhou were 34 g m-2 yr-1 and 6.0 × 102 ?g m-2 yr-1 with 50 and 57% being contributed from wet deposition, respectively. The monthly capacity for removal (CR) of PM and PAHs (calculated as the wet deposition flux dividing the total flux) varied widely with different months, and was lower during the dry weather season (January-March and October-December) than during the wet weather season (April-September). Finally, the air quality index related to PM10 was negatively correlated to CR values of PM and PAHs, indicating the need to control the emissions of anthropogenically derived pollutants during the dry weather season.

  9. Granular matter optics: basic principles, properties and applications of one-dimensional systems

    NASA Astrophysics Data System (ADS)

    Girardeau-Montaut, Jean-Pierre; Girardeau-Montaut, Claire

    2003-01-01

    We propose a study of the optical properties of refractive systems made up of single-dimensional ordered spherical micro-balls, bubbles or grains. The study was initiated within the framework of the paraxial approximation and then extended to a much more general situation in which this approximation does not hold. Such granular materials appear to be appropriate for the transport, focusing and filtering of any radiation from hard x-rays to microwaves, provided that two conditions are satisfied simultaneously: grain diameters must be much larger than the wavelength of radiation, and the difference between the refractive indices of the grains and of their surrounding medium must be small, typically lower than 10-2. Results of calculations are discussed for both x-ray and visible radiation. We report experimental observations from linear and curved guide-lenses, consisting of glass micro-balls plunged in a convenient transparent liquid, irradiated with a 7.5 mW-633 nm He-Ne laser beam, in support of our theoretical results.

  10. The effect of water temperature on the adsorption equilibrium of dissolved organic matter and atrazine on granular activated carbon

    SciTech Connect

    Bernd Schreiber; Viktor Schmalz; Thomas Brinkmann; Eckhard Worch [Dresden University of Technology, Dresden (Germany). Institute of Water Chemistry

    2007-09-15

    The influence of water temperature on the adsorption of natural dissolved organic matter (DOM) on activated carbon has not been investigated intensively yet. In this study, batch experiments with granular activated carbon (GAC) F300, from bituminous coal, have been carried out at three temperatures (5, 20, 35{sup o} C) using a humic acid model water and different types of surface water (lake, river, canal). Furthermore, the adsorption of an anthropogenic contaminant, atrazine, was quantified in the absence and presence of DOM. The results indicate a significant influence of water temperature on the adsorption equilibrium of DOM and atrazine. Contrary to expectations, DOM and atrazine adsorption in surface water tends to be increased with increasing water temperature, whereas the extent of this effect is dependent on the type and concentration of DOM. Furthermore, the temperature effect on atrazine adsorption is controlled by competition of DOM and atrazine on adsorption sites. Some assumptions are proposed and discussed for explaining the temperature effects observed in the batch studies. 39 refs., 4 figs., 2 tabs.

  11. Impact of natural organic matter on monochloramine reduction by granular activated carbon: the role of porosity and electrostatic surface properties

    SciTech Connect

    Julian L. Fairey; Gerald E. Speitel Jr.; Lynn E. Katz [University of Texas at Austin, TX (United States). Department of Civil, Architectural, and Environmental Engineering

    2006-07-01

    Steady-state monochloramine reduction in fixed-bed reactors (FBRs) was quantified on five types of granular activated carbon (GAC) using two background waters - one natural source water (LAW) containing 2.5-3.5 mg/L organic carbon and one synthetic organic-free water (NW). GACs used were coal-based Filtrasorb 400, Filtrasorb 600, Centaur and Medical Grade, and wood-based AquaGuard. While more monochloramine was reduced at steady-state using NW compared to LAW for each GAC and empty-bed contact time studied, the differences in removal varied considerably among the GACs tested. Physical characterization of the GACs suggested that the degree of interference caused by natural organic matter (NOM) increased with increasing GAC surface area contained within pores greater than 2 nm in width. Acid/base and electrostatic properties of the GACs were not found to be significant in terms of NOM uptake, which indicated that size exclusion effects of the GAC pores overwhelmed the impact of the GAC surface chemistry. Therefore, selection of GAC to limit the impact of NOM on monochloramine reduction in FBRs should be based on pore size distribution alone, with the impact of NOM decreasing with decreasing mesoporosity and macroporosity. 23 refs., 4 figs., 3 tabs.

  12. Effects of surface-active organic matter on carbon dioxide nucleation in atmospheric wet aerosols: a molecular dynamics study.

    PubMed

    Daskalakis, Vangelis; Charalambous, Fevronia; Panagiotou, Fostira; Nearchou, Irene

    2014-11-21

    Organic matter (OM) uptake in cloud droplets produces water-soluble secondary organic aerosols (SOA) via aqueous chemistry. These play a significant role in aerosol properties. We report the effects of OM uptake in wet aerosols, in terms of the dissolved-to-gas carbon dioxide nucleation using molecular dynamics (MD) simulations. Carbon dioxide has been implicated in the natural rainwater as well as seawater acidity. Variability of the cloud and raindrop pH is assumed in space and time, as regional emissions, local human activities and geophysical characteristics differ. Rain scavenging of inorganic SOx, NOx and NH3 plays a major role in rain acidity in terms of acid-base activity, however carbon dioxide solubility also remains a key parameter. Based on the MD simulations we propose that the presence of surface-active OM promotes the dissolved-to-gas carbon dioxide nucleation in wet aerosols, even at low temperatures, strongly decreasing carbon dioxide solubility. A discussion is made on the role of OM in controlling the pH of a cloud or raindrop, as a consequence, without involving OM ionization equilibrium. The results are compared with experimental and computational studies in the literature. PMID:25272147

  13. Enzymatic Hydrolysis and Ethanol Fermentation of High Dry Matter Wet-Exploded Wheat Straw at Low Enzyme Loading

    NASA Astrophysics Data System (ADS)

    Georgieva, Tania I.; Hou, Xiaoru; Hilstrøm, Troels; Ahring, Birgitte K.

    Wheat straw was pretreated by wet explosion using three different oxidizing agents (H2O2, O2, and air). The effect of the pretreatment was evaluated based on glucose and xylose liberated during enzymatic hydrolysis. The results showed that pretreatment with the use of O2 as oxidizing agent was the most efficient in enhancing overall convertibility of the raw material to sugars and minimizing generation of furfural as a by-product. For scale-up of the process, high dry matter (DM) concentrations of 15-20% will be necessary. However, high DM hydrolysis and fermentation are limited by high viscosity of the material, higher inhibition of the enzymes, and fermenting microorganism. The wet-explosion pretreatment method enabled relatively high yields from both enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) to be obtained when performed on unwashed slurry with 14% DM and a low enzyme loading of 10 FPU/g cellulose in an industrial acceptable time frame of 96 h. Cellulose and hemicellulose conversion from enzymatic hydrolysis were 70 and 68%, respectively, and an overall ethanol yield from SSF was 68%.

  14. Mapping soil organic matter using the topographic wetness index: A comparative study based on different flow-direction algorithms and kriging methods

    Microsoft Academic Search

    Tao Pei; Cheng-Zhi Qin; A-Xing Zhu; Lin Yang; Ming Luo; Baolin Li; Chenghu Zhou

    2010-01-01

    Terrain attributes derived from digital elevation models have been used widely for mapping soil organic matter (SOM). Among these attributes, the topographic wetness index (TWI), an index for quantitatively indicating the balance between water accumulation and drainage conditions at the local scale, has been shown to correlate with SOM. However, TWIs used in most studies are calculated using a single-flow-direction

  15. WET SOLIDS FLOW ENHANCEMENT

    SciTech Connect

    Hugo S. Caram; Natalie Foster

    1997-03-31

    The objective was to visualize the flow of granular materials in flat bottomed silo. This was done by for dry materials introducing mustard seeds and poppy seeds as tracer particles and imaging them using Nuclear Magnetic Resonance. The region sampled was a cylinder 25 mm in diameter and 40 mm in length. Eight slices containing 128*128 to 256*256 pixels were generated for each image. The size of the silo was limited by the size of the high resolution NMR imager available. Cross-sections of 150mm flat bottomed silos, with the tracer layers immobilized by a gel, showed similar qualitative patterns for both dry and wet granular solids.

  16. Granularity in granular cell ameloblastoma

    PubMed Central

    Yamunadevi, Andamuthu; Madhushankari, G. S.; Selvamani, Manickam; Basandi, Praveen S.; Yoithapprabhunath, Thukanayyakanpalayam Ragunathan; Ganapathy, N.

    2014-01-01

    Granular cell ameloblastoma (GCA) is one of the rare histological variants of ameloblastoma (1.5-3.5%), identified by Krompechner in 1918 and is diagnosed by the characteristic presence of granular cells. These granular cells are seen in several physiological and pathological conditions and the granularity in GCA is due to lysosomal aggregates. This review is about the clinical features, histopathological features and differential diagnosis of GCA and also adds the theories for occurrence of granularity, electron microscopic findings, cell signaling pathways and immunohistochemistry findings related to these granular cells in GCA. PMID:25210361

  17. WET SOLIDS FLOW ENHANCEMENT

    SciTech Connect

    Hugo S. Caram; Natalie Foster

    1999-03-30

    The elastic modulus E of wet granular material was found to be of the order of 0.25 MPa, this value does not compare well with the value predicted for a cubic array of spheres under Hertzian contact were the predicted values were in the order of 250 MPa . The strain-stress behavior of a wet granular media was measured using a split Parfitt tensile tester. In all cases the stress increases linearly with distance until the maximum uniaxial tensile stress is reached. The stress then decreases exponentially with distance after this maximum is reached. The linear region indicates that wet solids behave elastically for stresses below the tensile stresses and can store significant elastic energy. The elastic deformation cannot be explained by analyzing the behavior of individual capillary bridges and requires accounting for the deformation of the solids particles. The elastic modulus of the wet granular material remains unexplained. New information was found to support the experimental finding and a first theory to explain the very small elastic modulus is presented. A new model based on the used of the finite element method is being developed.

  18. COMBINED USE OF ION EXCHANGE RESINS AND GRANULAR ACTIVATED CARBON FOR THE CONTROL OF ORGANIC MATTER AND DISINFECTION BY PRODUCTS

    EPA Science Inventory

    The use of anion exchange resin as a pretreatment step to granular activated carbon is evaluated. erformance is evaluated by DOC, SAC, TOXFP, and THMFP parameters. hio River water and Palm Beach groundwater are used. he results show that resin pretreatment is significant in exten...

  19. Shaken Granular Lasers

    E-print Network

    Folli, Viola; Leuzzi, Luca; Conti, Claudio

    2012-01-01

    Granular materials have been studied for decades, also driven by industrial and technological applications. These very simple systems, composed by agglomerations of mesoscopic particles, are characterized, in specific regimes, by a large number of metastable states and an extreme sensitivity (e.g., in sound transmission) on the arrangement of grains; they are not substantially affected by thermal phenomena, but can be controlled by mechanical solicitations. Laser emission from shaken granular matter is so far unexplored; here we provide experimental evidence that it can be affected and controlled by the status of motion of the granular, we also find that competitive random lasers can be observed. We hence demonstrate the potentialities of gravity affected moving disordered materials for optical applications, and open the road to a variety of novel interdisciplinary investigations, involving modern statistical mechanics and disordered photonics.

  20. The effect of moisture content on the explosively driven fragmentation of wet sand

    NASA Astrophysics Data System (ADS)

    Xue, K.

    2014-05-01

    A comprehensive model is established to account for the instability onset of rapidly expanding granular shells subject to the explosion loadings generated by the detonation of the central explosives. The moisture content strongly influences the shock interactions in the wet particle beds and the ensuing evolvement of the granular compacts. A material model for granular materials which can account for the degree of saturation was incorporated into a nonlinear dynamic simulation program to investigate the moisture effect on the shock responses of wet granular materials. In conjunction with our instability model, the predicted instability diameters of the expanding dry/wet granular shells are in a good agreement with the experimental results. Particularly the postponed instability onset of the wet granular shell found both experimentally and analytically can largely be attributed to the significantly greater kinetic energy obtained by wet particles thanks to less energy of shock wave consumed in compacting the granular material.

  1. Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon.

    PubMed

    Kupryianchyk, D; Noori, A; Rakowska, M I; Grotenhuis, J T C; Koelmans, A A

    2013-05-21

    Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we report polychlorobiphenyl (PCB) pore water concentrations, fluxes, mass transfer coefficients, and survival data of two benthic species, for four treatments: no AC addition (control), powdered AC addition, granular AC addition and addition and subsequent removal of GAC (sediment stripping). AC addition decreased mass fluxes but increased apparent mass transfer coefficients because of dissolved organic carbon (DOC) facilitated transport across the benthic boundary layer (BBL). In turn, DOC concentrations depended on bioturbator activity which was high for the PAC tolerant species Asellus aquaticus and low for AC sensitive species Lumbriculus variegatus. A dual BBL resistance model combining AC effects on gradients, DOC facilitated transport and biodiffusion was evaluated against the data and showed how the type of resistance differs with treatment and chemical hydrophobicity. Data and simulations illustrate the complex interplay between AC and contaminant toxicity to benthic organisms and how differences in species tolerance affect mass fluxes from sediment to the water column. PMID:23590290

  2. WET SOLIDS FLOW ENHANCEMENT

    SciTech Connect

    Unknown

    2001-03-25

    The yield locus, tensile strength and fracture mechanisms of wet granular materials were studied. The yield locus of a wet material was shifted to the left of that of the dry specimen by a constant value equal to the compressive isostatic stress due to pendular bridges. for materials with straight yield loci, the shift was computed from the uniaxial tensile strength, either measured in a tensile strength tester or calculated from the correlation, and the angle of internal friction of the material. The predicted shift in the yield loci due to different moisture contents compare well with the measured shift in the yield loci of glass beads, crushed limestone, super D catalyst and Leslie coal. Measurement of the void fraction during the shear testing was critical to obtain the correct tensile strength theoretically or experimentally.

  3. Granular Plumes

    NASA Astrophysics Data System (ADS)

    Shinbrot, Troy; Alexander, Albert; Muzzio, Fernando J.

    1998-11-01

    We report on apparently fractal patterns seen in cross sections of granular tumblers. These patterns are found in fine grains tumbled at moderate speed, in both cylindrical and 'double-cone' tumblers, driven in the cascading regime. A model, in which the cascading layer alternates between steady flow and periodic slip events, duplicates some of the features of these patterns.

  4. Continuum modelling of granular flows

    NASA Astrophysics Data System (ADS)

    Staron, L.; Lagrée, P.-Y.

    2011-10-01

    The continuum modelling of transient granular flows is of primary importance in the context of predicting the behaviour of many natural systems involving granular matter. In this perspective, the granular column collapse experiment provides an interesting benchmark due to its challenging complexity (Lajeunesse et al 2004, Lube et al 2004), and form a trying test for candidate rheological models. In this contribution, we present 2D continuum simulations of granular column collapse using Navier-Stokes solver Gerris (Popinet 2003). The rheology implemented to model the granular media is the so-called ?(I)-rheology, relating the frictional properties and the viscosity of the material to the pressure and shear rate. In addition, discrete simulations using the Contact Dynamics method are performed for systematic comparison between the granular flow dynamics and its continuum counterpart (Staron & Hinch 2005). We find a good agreement, recovering the shape of the flow in the course of time as well as experimental scaling laws for the run-out. A systematic underestimation of the latter is nevertheless observed, and discussed in terms of physical and numerical modeling.

  5. Harnessing the instabilities of soft matter: Dynamically tuning of wetting, assembly and pattern transformation in polymer microstructures

    NASA Astrophysics Data System (ADS)

    Zhang, Ying

    2008-10-01

    In this dissertation, we have investigated the fabrication, mechanical instability and applications of two kinds of polymer micro/nano-structures: high-aspect-ratio (HAR) polymer pillar arrays, and periodic porous elastomer membranes. For HAR polymer pillar arrays, we demonstrated the fabrication of high-aspect-ratio (up to 18) polymer micropillars with different shapes and dimensions by replica molding. Capillary force lithography (CFL) is also demonstrated as a simple and flexible method to fabricate microstructures with controlled aspect ratios. Meanwhile, by introducing conventional photoresist SU-8, CFL is successfully coupled with photolithography and used to create hierarchical 2D or 3D structures, which greatly expand the capability of current capillary force lithography. The mechanical stability of HAR structures with varied materials and different aspect ratio, density and shape were also studied and the results show that the adhesive forces from environment are the major cause of structure collapsing. When HAR polymer pillars are subjected to different solvents treatment, both capillary force and solvent swelling need to be considered to completely understand the structure instability. On HAR micropillar array, thermoresponsive polymer brushes, poly ( N-isopropylacrylamide) (PNIPAAm), were selectively grafted at different locations for dynamically tuning surface wetting or pattern assembly. When the temperature changed from 40°C to 20°, depending on the location of polymer brushes, different wetting transitions, either from a composite solid/air state (Cassie state) to a composite solid/liquid state (Hemi-wicking state) or a transition between two Cassie states were observed. Meanwhile, the dynamically tuning of water contact angle enables us to control capillary drying force and thus harness pattern collapse to create superlattice micropatterns. For periodic porous elastomer membrane, a novel pattern transformation effect is discovered due to the mechanical instability of membrane under solvent swelling. To harness this elastic instability, we convectively assemble nanoparticles onto a swollen membrane and capture this dynamic pattern transformation process. By using the nanoparticle film that imprinted with deformed pattern as a master mold, the complex pattern formed by elastic deformation can be transferred into other materials through replica molding, capillary imprinting & selective etching. The unique 3D morphology of the elastic deformation pattern allows us to perform gradient etching, allowing more flexibility to control pattern morphology.

  6. PREFACE: Dynamics of wetting Dynamics of wetting

    NASA Astrophysics Data System (ADS)

    Grest, Gary S.; Oshanin, Gleb; Webb, Edmund B., III

    2009-11-01

    Capillary phenomena associated with fluids wetting other condensed matter phases have drawn great scientific interest for hundreds of years; consider the recent bicentennial celebration of Thomas Young's paper on equilibrium contact angles, describing the geometric shape assumed near a three phase contact line in terms of the relevant surface energies of the constituent phases [1]. Indeed, nearly a century has passed since the seminal papers of Lucas and Washburn, describing dynamics of capillary imbibition [2, 3]. While it is generally appreciated that dynamics of fluid wetting processes are determined by the degree to which a system is out of capillary equilibrium, myriad complications exist that challenge the fundamental understanding of dynamic capillary phenomena. The topic has gathered much interest from recent Nobel laureate Pierre-Gilles de Gennes, who provided a seminal review of relevant dissipation mechanisms for fluid droplets spreading on solid surfaces [4] Although much about the dynamics of wetting has been revealed, much remains to be learned and intrinsic technological and fundamental interest in the topic drives continuing high levels of research activity. This is enabled partly by improved experimental capabilities for resolving wetting processes at increasingly finer temporal, spatial, and chemical resolution. Additionally, dynamic wetting research advances via higher fidelity computational modeling capabilities, which drive more highly refined theory development. The significance of this topic both fundamentally and technologically has resulted in a number of reviews of research activity in wetting dynamics. One recent example addresses the evaluation of existing wetting dynamics theories from an experimentalist's perspective [5]. A Current Opinion issue was recently dedicated to high temperature capillarity, including dynamics of high temperature spreading [6]. New educational tools have recently emerged for providing instruction in wetting dynamics and the broader field of fluid dynamics [7-9]. Such an active field requires an occasional collective examination of current research to highlight both recent successes and remaining challenges. Herein, we have collected a range of articles to illustrate the broad nature of research associated with understanding dynamics of moving condensed matter three phase contact lines. Despite the breadth of topics examined, certain unifying themes emerge. The role of the substrate surface is critical in determining kinetics of wetting; this is evidenced by the attention given to this in articles herein. McHale et al investigate the role of surface topography on wetting kinetics and how its effect can be incorporated in existing theories describing contact line dynamics. Moosavi et al examine surface topography effects via a mesoscopic hydrodynamics approach. The capillary driven motion of fluid through structures on a surface bears tremendous importance for microfluidics studies and the emerging field of nanofluidics. Blow et al examine this phenomena for liquid imbibition into a geometric array of structures on a solid surface, while Shen et al analyze the effects of surface temperature during boiling and non-boiling conditionson droplet impingement dynamics. Finally, Pesika et al discover a wonderful world of smart surfaces, like gecko adhesion pads. A number of papers utilize computational modeling to explore phenomena underlying wetting dynamics and to consider relevant mechanisms in terms of existing theory for contact line dynamics. Winter et al utilize Monte Carlo simulation techniques and thermodynamic integration methods to test classical theory describing heterogeneous nucleation at a wall near a wetting transition. Qian et al briefly review the Onsager principle of minimum energy dissipation underlying many descriptions of dissipative systems; they then provide a variational approach description of hydrodynamics of moving contact lines and demonstrate the validity of their continuum model via comparison with molecular dynamics simulations.Bertrand et al

  7. The Effect of Slowly Biodegradable Carbon on the Morphology, Integrity and Performance of Aerobic Granular Sludge

    E-print Network

    Faraj, Rasha Attwan

    2014-08-31

    of this study was to investigate the influence of slowly biodegradable organic matters, including particulate compounds, on the morphology, integrity and performance of aerobic granular sludge. Three identical lab-scale aerobic granular reactors (AGRs) were...

  8. Dilatancy in slow granular flows.

    PubMed

    Kabla, Alexandre J; Senden, Tim J

    2009-06-01

    When walking on wet sand, each footstep leaves behind a temporarily dry impression. This counterintuitive observation is the most common illustration of the Reynolds principle of dilatancy: that is, a granular packing tends to expand as it is deformed, therefore increasing the amount of porous space. Although widely called upon in areas such as soil mechanics and geotechnics, a deeper understanding of this principle is constrained by the lack of analytical tools to study this behavior. Using x-ray radiography, we track a broad variety of granular flow profiles and quantify their intrinsic dilatancy behavior. These measurements frame Reynolds dilatancy as a kinematic process. Closer inspection demonstrates, however, the practical importance of flow induced compaction which competes with dilatancy, leading more complex flow properties than expected. PMID:19658906

  9. Wet solids flow enhancemant

    SciTech Connect

    Caram, H.S.; Foster, N.; Wildman, D.J. [USDOE Pittsburgh Energy Technology Center, PA (United States)

    1996-12-31

    WE used glass beads of different sizes as.a model system to study the flow enhancing properties of Octadecyltrichlorosilane (OTS). 0TS provides Si(CH{sub 2}){sub 17}CH{sub 3} groups that bind with the surface hydrox groups to make it hydrophobic. Experimental data showed, indeed, that surface hydrophobicity promotes the flow of wet granular materials. Mixtures of different percentage of silanized/unsilanized particles were prepared for tensile strength measurements. The tensile strength decreased as more silanized particles were added to the samples. The relationship between dimensionless tensile strength and void fraction followed the correlation found by Pierrat (1994). Contact angles were larger for the silanized particles, as compared with unsilanized ones.

  10. Critical Scaling of Granular Rheology

    NASA Astrophysics Data System (ADS)

    Hatano, T.

    Rheology of dense granular matter in the vicinity of the jamming transition is investigated. Critical scaling laws that describe shear stress, pressure, and kinetic temperature are investigated. The scaling exponents are modified from those previously estimated by the present author [T. Hatano, J. Phys. Soc. Jpn. 77 (2008), 123002]. and also compared with those proposed by Otsuki and Hayakawa [M. Otsuki and H. Hayakawa, Prog. Theor. Phys. 121 (2009), 647].

  11. Wet Adhesion and Adhesive Locomotion of Snails on AntiAdhesive Non-Wetting Surfaces

    Microsoft Academic Search

    Neil J. Shirtcliffe; Glen McHale; Michael I. Newton

    2012-01-01

    Creating surfaces capable of resisting liquid-mediated adhesion is extremely difficult due to the strong capillary forces that exist between surfaces. Land snails use this to adhere to and traverse across almost any type of solid surface of any orientation (horizontal, vertical or inverted), texture (smooth, rough or granular) or wetting property (hydrophilic or hydrophobic) via a layer of mucus. However,

  12. PREFACE: Wetting: introductory note

    NASA Astrophysics Data System (ADS)

    Herminghaus, S.

    2005-03-01

    The discovery of wetting as a topic of physical science dates back two hundred years, to one of the many achievements of the eminent British scholar Thomas Young. He suggested a simple equation relating the contact angle between a liquid surface and a solid substrate to the interfacial tensions involved [1], ?lg cos ? = ?sg - ?sl (1) In modern terms, ? denotes the excess free energy per unit area of the interface indicated by its indices, with l, g and s corresponding to the liquid, gas and solid, respectively [2]. After that, wetting seems to have been largely ignored by physicists for a long time. The discovery by Gabriel Lippmann that ? may be tuned over a wide range by electrochemical means [3], and some important papers about modifications of equation~(1) due to substrate inhomogeneities [4,5] are among the rare exceptions. This changed completely during the seventies, when condensed matter physics had become enthusiastic about critical phenomena, and was vividly inspired by the development of the renormalization group by Kenneth Wilson [6]. This had solved the long standing problem of how to treat fluctuations, and to understand the universal values of bulk critical exponents. By inspection of the critical exponents of the quantities involved in equation~(1), John W Cahn discovered what he called critical point wetting: for any liquid, there should be a well-defined transition to complete wetting (i.e., ? = 0) as the critical point of the liquid is approached along the coexistence curve [7]. His paper inspired an enormous amount of further work, and may be legitimately viewed as the entrance of wetting into the realm of modern physics. Most of the publications directly following Cahn's work were theoretical papers which elaborated on wetting in relation to critical phenomena. A vast amount of interesting, and in part quite unexpected, ramifications were discovered, such as the breakdown of universality in thin film systems [8]. Simultaneously, a number of very specific and quantitative predictions were put forward which were aimed at direct experimental tests of the developed concepts [9]. Experimentally, wetting phenomena proved to be a rather difficult field of research. While contact angles seem quite easy to measure, deeper insight can only be gained by assessing the physical properties of minute amounts of material, as provided by the molecularly thin wetting layers. At the same time, the variations in the chemical potential relevant for studying wetting transitions are very small, such that system stability sometimes poses hard to solve practical problems. As a consequence, layering transitions in cryogenic systems were among the first to be thoroughly studied [10] experimentally, since they require comparably moderate stability. First-order wetting transitions were not observed experimentally before the early nineties, either in (cryogenic) quantum systems [11,12] or in binary liquid mixtures [13,14]. The first observation of critical wetting, a continuous wetting transition, in 1996 [15] was a major breakthrough [16]. In the meantime, a detailed seminal paper by Pierre Gilles de Gennes published in 1985 [17] had spurred a large number of new research projects which were directed to wetting phenomena other than those related to phase transitions. More attention was paid to non-equilibrium physics, as it is at work when oil spreads over a surface, or a liquid coating beads off (`dewets') from its support and forms a pattern of many individual droplets. This turned out to be an extremely fruitful field of research, and was more readily complemented by experimental efforts than was the case with wetting transitions. It was encouraging to find effects analogous to layering (as mentioned above) in more common systems such as oil films spreading on a solid support [18,19]. Long standing riddles such as the divergence of dissipation at a moving contact line were now addressed both theoretically and experimentally [20,21]. However, the requirements concerning resolution of the measurements, as well as the sta

  13. SOILS, SEC 1 SOIL ORGANIC MATTER DYNAMICS AND NUTRIENT CYCLING RESEARCH ARTICLE Soil carbon and nitrogen storage in alluvial wet meadows

    E-print Network

    Norton, Jay B.

    and nitrogen storage in alluvial wet meadows of the Southern Sierra Nevada Mountains, USA Jay B. Norton and many other ecosystem services (Norton et al. 2011). Wet meadows provide crucial habitats for many: Zucong Cai J. B. Norton (*) :H. R. Olsen :D. E. Legg Department of Ecosystem Science and Management

  14. Dynamics of Excited Granular Systems

    NASA Astrophysics Data System (ADS)

    Cordero, Patricio; Risso, Dino

    2002-08-01

    Getting a hydrodynamic sort of behavior for excited granular systems is a delicate matter. In the case of ordinary (conservative) fluid systems the hydrodynamic limit is the limit of small Knudsen number. For granular systems such limit may lead to inconsistencies unless carefully performed. We present quite general gas-dynamic equations---derived from kinetic theory---which correctly describe highly excited granular systems. The theory describes a system of hard spheres (disks really) with normal restitution coefficient r and it requires no constitutive equations (dynamic equations take their place) [R. Ramirez, D. Risso, R. Soto, and P. Cordero, Phys. Rev. E 62, 2521 (2000); D. Risso, P. Cordero, Phys. Rev. E. 65 021304 (2002)]. Well known analytic results such as the presence of a fourth cumulant in the velocity distribution function are reproduced exactly. The formalism also predicts Bénard's type of convection triggerd by the granular temperature gradient that is dynamically created because of the inelastic nature of the collisons [R. Ramirez, D. Risso, and P. Cordero, Phys. Rev. Letters 85 1230 (2000); X. He, B. Meerson and G. Doolen, Phys. Rev. E 65 030301 (2002)]. A quasi-homogenoeus solution is also described in detail.

  15. Vibration-induced Liquefaction of Granular Suspensions

    NASA Astrophysics Data System (ADS)

    Hanotin, C.; Kiesgen de Richter, S.; Marchal, P.; Michot, L. J.; Baravian, C.

    2012-05-01

    We investigate the mechanical behavior of granular suspensions subjected to coupled vibrations and shear. At high shear stress, whatever the mechanical vibration energy and bead size, the system behaves like a homogeneous suspension of hard spheres. At low shear stress, in addition to a dependence on bead size, vibration energy drastically influences the viscosity of the material that can decrease by more than 2 orders of magnitude. All experiments can be rationalized by introducing a hydrodynamical Peclet number defined as the ratio between the lubrication stress induced by vibrations and granular pressure. The behavior of vibrated wet and dry granular materials can then be unified by assimilating the Hookean stress in dry media to the lubrication stress in suspensions.

  16. Transport in granular systems

    E-print Network

    Wendell, Dawn M. (Dawn Marie), 1983-

    2011-01-01

    There are many situations in which a continuum view of granular systems does not fully capture the relevant mechanics. In order for engineers to be able to design systems for transporting granular materials, there needs ...

  17. A constitutive law for dense granular flows.

    PubMed

    Jop, Pierre; Forterre, Yoël; Pouliquen, Olivier

    2006-06-01

    A continuum description of granular flows would be of considerable help in predicting natural geophysical hazards or in designing industrial processes. However, the constitutive equations for dry granular flows, which govern how the material moves under shear, are still a matter of debate. One difficulty is that grains can behave like a solid (in a sand pile), a liquid (when poured from a silo) or a gas (when strongly agitated). For the two extreme regimes, constitutive equations have been proposed based on kinetic theory for collisional rapid flows, and soil mechanics for slow plastic flows. However, the intermediate dense regime, where the granular material flows like a liquid, still lacks a unified view and has motivated many studies over the past decade. The main characteristics of granular liquids are: a yield criterion (a critical shear stress below which flow is not possible) and a complex dependence on shear rate when flowing. In this sense, granular matter shares similarities with classical visco-plastic fluids such as Bingham fluids. Here we propose a new constitutive relation for dense granular flows, inspired by this analogy and recent numerical and experimental work. We then test our three-dimensional (3D) model through experiments on granular flows on a pile between rough sidewalls, in which a complex 3D flow pattern develops. We show that, without any fitting parameter, the model gives quantitative predictions for the flow shape and velocity profiles. Our results support the idea that a simple visco-plastic approach can quantitatively capture granular flow properties, and could serve as a basic tool for modelling more complex flows in geophysical or industrial applications. PMID:16760972

  18. Predictability and granular materials

    Microsoft Academic Search

    R. P. Behringer; Daniel Howell; Lou Kondic; Sarath Tennakoon; Christian Veje

    1999-01-01

    Granular materials present a number of challenges to predictability. The classical description of a dense granular material is based on Coulomb friction. For a static array of grains, the Coulomb friction forces are typically underdetermined. If we are to make useful statements about such arrays, we must develop new approaches, including the development of statistical descriptions. Granular materials also show

  19. Under consideration for publication in J. Fluid Mech. 1 Dense flows of cohesive granular materials

    E-print Network

    Paris-Sud XI, Université de

    Under consideration for publication in J. Fluid Mech. 1 Dense flows of cohesive granular materials soils or wet snow, and solid bridges in sintered powders (Miclea et al. 2005) or when liquid menisci freeze (Hatzes et al. 1991). How do these cohesive forces affect dense granular flows ? Up to now

  20. Granular statistical mechanics - a personal perspective

    NASA Astrophysics Data System (ADS)

    Blumenfeld, R.; Edwards, S. F.

    2014-10-01

    The science of granular matter has expanded from an activity for specialised engineering applications to a fundamental field in its own right. This has been accompanied by an explosion of research and literature, which cannot be reviewed in one paper. A key to progress in this field is the formulation of a statistical mechanical formalism that could help develop equations of state and constitutive relations. This paper aims at reviewing some milestones in this direction. An essential basic step toward the development of any static and quasi-static theory of granular matter is a systematic and useful method to quantify the grain-scale structure and we start with a review of such a method. We then review and discuss the ongoing attempt to construct a statistical mechanical theory of granular systems. Along the way, we will clarify a number of misconceptions in the field, as well as highlight several outstanding problems.

  1. Matter

    NSDL National Science Digital Library

    Mrs. McNees

    2010-11-16

    What is matter? All matter we see and can not see is made of atoms. Matter is affected by heat. What is an atom? Molecules? Zoom! All about atoms. Zoom! Atoms arranged in solids. Atomic Arrangements in Solids Atoms and electrons. Atoms and electrons Smaller than electrons are Quarks. Quarks: Inside the Atom What holds a molecule together? What Holds a Molecule Together? The Periodic table Periodic Table What is matter? What is Matter? Methods of heat transfer. Methods of Heat Transfer ...

  2. Granular Volcano Group

    NSDL National Science Digital Library

    S'bastien Dartevelle, a Ph.D. student at Michigan Tech, created this Web site devoted to the understanding of "granular flows, granular processes, fluid dynamic, supercomputer modeling, and grain-size analysis of Volcanology, Geophysics, and Physics." Providing challenging materials in an accurate and simple manner, students can easily learn about topics including granular theory and granular medium. Users will find essential facts about viscous phenomenon in the newly added link, All I Wanna Know 'bout Viscous Stress. Educators and students can view the Plinian Cloud simulations. The author also provides mathematical equations, atmospheric profiles, and much more.

  3. Granular Volcano Group

    NSDL National Science Digital Library

    Dartevelle, Sébastien

    Sébastien Dartevelle, a Ph.D. student at Michigan Tech, created this Web site devoted to the understanding of "granular flows, granular processes, fluid dynamic, supercomputer modeling, and grain-size analysis of Volcanology, Geophysics, and Physics." Providing challenging materials in an accurate and simple manner, students can easily learn about topics including granular theory and granular medium. Users will find essential facts about viscous phenomenon in the newly added link, All I Wanna Know 'bout Viscous Stress. Educators and students can view the Plinian Cloud simulations. The author also provides mathematical equations, atmospheric profiles, and much more.

  4. Wet adhesion and adhesive locomotion of snails on anti-adhesive non-wetting surfaces.

    PubMed

    Shirtcliffe, Neil J; McHale, Glen; Newton, Michael I

    2012-01-01

    Creating surfaces capable of resisting liquid-mediated adhesion is extremely difficult due to the strong capillary forces that exist between surfaces. Land snails use this to adhere to and traverse across almost any type of solid surface of any orientation (horizontal, vertical or inverted), texture (smooth, rough or granular) or wetting property (hydrophilic or hydrophobic) via a layer of mucus. However, the wetting properties that enable snails to generate strong temporary attachment and the effectiveness of this adhesive locomotion on modern super-slippy superhydrophobic surfaces are unclear. Here we report that snail adhesion overcomes a wide range of these microscale and nanoscale topographically structured non-stick surfaces. For the one surface which we found to be snail resistant, we show that the effect is correlated with the wetting response of the surface to a weak surfactant. Our results elucidate some critical wetting factors for the design of anti-adhesive and bio-adhesion resistant surfaces. PMID:22693563

  5. Photoluminescence and local structure of Ge nanoclusters on Si without a wetting layer Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

    E-print Network

    Pennycook, Steve

    Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA F. Flack Ridge, Tennessee 37831, USA Zhenyu Zhang and H. H. Weitering Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Department of Physics and Astronomy

  6. EVALUATION OF WET AND DRY DISTILLERS GRAINS AND WET AND DRY CORN GLUTEN FEEDS FOR RUMINANTS

    Microsoft Academic Search

    J. L. Firkins; L. L. Berger; G. C. Fahey

    2010-01-01

    Summary Eight trials were conducted to evaluate wet and dry distillers grains (WDG and DDG) and wet and dry corn gluten feeds (WCGF and DCGF) as feed sources for cattle and sheep. Data from in situ trial 1 indicated that dry matter (DM) of WCGF and DCGF disappeared at .a faster rate (P<.05) than that of WDG or DDG. In

  7. Matter

    NSDL National Science Digital Library

    Houghton Mifflin Science

    This self-contained module on matter includes a range of fun activities that students can perform in the classroom and at home with family members. They impart important concepts such as observation, identification, measurement, and differentiation.

  8. Dynamics of Granular Materials

    NASA Technical Reports Server (NTRS)

    Behringer, Robert P.

    1996-01-01

    Granular materials exhibit a rich variety of dynamical behavior, much of which is poorly understood. Fractal-like stress chains, convection, a variety of wave dynamics, including waves which resemble capillary waves, l/f noise, and fractional Brownian motion provide examples. Work beginning at Duke will focus on gravity driven convection, mixing and gravitational collapse. Although granular materials consist of collections of interacting particles, there are important differences between the dynamics of a collections of grains and the dynamics of a collections of molecules. In particular, the ergodic hypothesis is generally invalid for granular materials, so that ordinary statistical physics does not apply. In the absence of a steady energy input, granular materials undergo a rapid collapse which is strongly influenced by the presence of gravity. Fluctuations on laboratory scales in such quantities as the stress can be very large-as much as an order of magnitude greater than the mean.

  9. Coarsening in granular systems

    E-print Network

    Andrea Baldassarri; Andrea Puglisi; Alessandro Sarracino

    2015-02-04

    We review a few representative examples of granular experiments or models where phase separation, accompanied by domain coarsening, is a relevant phenomenon. We first elucidate the intrinsic non-equilibrium, or athermal, nature of granular media. Thereafter, dilute systems, the so-called "granular gases" are discussed: idealized kinetic models, such as the gas of inelastic hard spheres in the cooling regime, are the optimal playground to study the slow growth of correlated structures, e.g. shear patterns, vortices and clusters. In fluidized experiments, liquid-gas or solid-gas separations have been observed. In the case of monolayers of particles, phase coexistence and coarsening appear in several different setups, with mechanical or electrostatic energy input. Phenomenological models describe, even quantitatively, several experimental measures, both for the coarsening dynamics and for the dynamic transition between different granular phases. The origin of the underlying bistability is in general related to negative compressibility from granular hydrodynamics computations, even if the understanding of the mechanism is far from complete. A relevant problem, with important industrial applications, is related to the demixing or segregation of mixtures, for instance in rotating tumblers or on horizontally vibrated plates. Finally, the problem of compaction of highly dense granular materials, which has many important applications, is usually described in terms of coarsening dynamics: there, bubbles of mis-aligned grains evaporate, allowing the coalescence of optimally arranged islands and a progressive reduction of total occupied volume.

  10. Wet Sand flows better than dry sand

    E-print Network

    Jorge E. Fiscina; Christian Wagner

    2007-11-19

    We investigated the yield stress and the apparent viscosity of sand with and without small amounts of liquid. By pushing the sand through a tube with an enforced Poiseuille like profile we minimize the effect of avalanches and shear localization. We find that the system starts to flow when a critical shear of the order of one particle diameter is exceeded. In contrast to common believe, we observe that the resistance against the flow of wet sand is much smaller than that of dry sand. For the dissipative flow we propose a non-equilibrium state equation for granular fluids.

  11. Microfiltration of gluten processing streams from corn wet milling C.I. Thompson a

    E-print Network

    Microfiltration of gluten processing streams from corn wet milling C.I. Thompson a , K.D. Rausch b 2005; accepted 6 February 2005 Available online 12 April 2005 Abstract In corn wet milling, dry matter composition; Corn processing; Membrane filtration; Corn gluten meal; Wet milling 1. Introduction Wet milling

  12. Flow of wet granular materials: a numerical study

    E-print Network

    Saeed Khamseh; Jean-Noël Roux; François Chevoir

    2015-04-15

    We simulate dense assemblies of frictional spherical grains in steady shear flow under controlled normal stress $P$ in the presence of a small amount of an interstitial liquid, which gives rise to capillary menisci, assumed isolated (pendular regime), and to attractive forces. The system behavior depends on two dimensionless control parameters: inertial number $I$ and reduced pressure $P^*=aP/(\\pi\\Gamma)$, comparing confining forces $\\sim a^2P$ to meniscus tensile strength $F_0=\\pi\\Gamma a$, for grains of diameter $a$ joined by menisci with surface tension $\\Gamma$. We pay special attention to the quasi-static limit of slow flow and observe systematic, enduring strain localization in some of the cohesion-dominated ($P^*\\sim 0.1$) systems. Homogeneous steady flows are characterized by the dependence of internal friction coefficient $\\mu^*$ and solid fraction $\\Phi$ on $I$ and $P^*$. We record fairly small but not negligible normal stress differences and the moderate sensitivity of the system to saturation within the pendular regime. Capillary forces have a significant effect on the macroscopic behavior of the system, up to $P^*$ values of several units. The concept of effective pressure may be used to predict an order of magnitude for the strong increase of $\\mu^*$ as $P^*$ decreases but such a crude approach is unable to account for the complex structural changes induced by capillary cohesion. Likewise, the Mohr-Coulomb criterion for pressure-dependent critical states is, at best, an approximation valid within a restricted range of pressures, with $P^*\\ge 1$. At small enough $P^*$, large clusters of interacting grains form in slow flows, in which liquid bonds survive shear strains of several units. This affects the anisotropies associated to different interactions, and the shape of function $\\mu^*(I)$, which departs more slowly from its quasistatic limit than in cohesionless systems.

  13. Flow of wet granular materials: a numerical study

    E-print Network

    Khamseh, Saeed; Chevoir, François

    2015-01-01

    We simulate dense assemblies of frictional spherical grains in steady shear flow under controlled normal stress $P$ in the presence of a small amount of an interstitial liquid, which gives rise to capillary menisci, assumed isolated (pendular regime), and to attractive forces. The system behavior depends on two dimensionless control parameters: inertial number $I$ and reduced pressure $P^*=aP/(\\pi\\Gamma)$, comparing confining forces $\\sim a^2P$ to meniscus tensile strength $F_0=\\pi\\Gamma a$, for grains of diameter $a$ joined by menisci with surface tension $\\Gamma$. We pay special attention to the quasi-static limit of slow flow and observe systematic, enduring strain localization in some of the cohesion-dominated ($P^*\\sim 0.1$) systems. Homogeneous steady flows are characterized by the dependence of internal friction coefficient $\\mu^*$ and solid fraction $\\Phi$ on $I$ and $P^*$. We record fairly small but not negligible normal stress differences and the moderate sensitivity of the system to saturation with...

  14. Lubrication effects on the flow of wet granular materials

    E-print Network

    Qing Xu; Ashish V. Orpe; Arshad Kudrolli

    2007-06-25

    We investigate the dynamics of a partially saturated grain-liquid mixture with a rotating drum apparatus. The drum is partially filled with the mixture and then rotated about its horizontal axis. We focus on the continous avalanching regime and measure the impact of volume fraction and viscosity of the liquid on the dynamic surface angle. The inclination angle of the surface is observed to increase sharply to a peak and then decrease as a function of liquid volume fraction. The height of the peak is observed to increase with rotation rate. For higher liquid volume fractions, the inclination angle of the surface can decrease with viscosity before increasing. The viscosity where the minima occurs decreases with the rotation rate of the drum. Limited measurements of the flow depth were made, and these were observed to show only fractional changes with volume fraction and rotation speeds. We show that the qualitative features of our observations can be understood by analyzing the effect of lubrication forces on the timescale over which particles come in contact.

  15. JOURNAL OF MATHEMATICAL PHYSICS 51, 113302 (2010) Random close packing in a granular model

    E-print Network

    Aristoff, David

    2010-01-01

    -dimensional lattice model of granular matter. Using a combination of proof and simulation we demonstrate an order of Physics. [doi:10.1063/1.3511359] I. INTRODUCTION Granular materials, such as a static pile of sand sedimented in a fluid such as air or water, exhibit interesting characteristic behavior near certain volume

  16. Hydrodynamics of soft active matter

    NASA Astrophysics Data System (ADS)

    Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S.; Liverpool, T. B.; Prost, J.; Rao, Madan; Simha, R. Aditi

    2013-07-01

    This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are “dry” systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or “wet” systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.

  17. Bifurcation and nonlinear behavior of compartmentalized granular gases

    NASA Astrophysics Data System (ADS)

    Hou, Meiying; Liu, Rui; Li, Yinchang; Zhang, Yin; Shah, Sajjad Hussain

    2014-12-01

    Different from the molecular gas, clustering is a most commonly observed feature of the granular gas. A review is given of our previous work on the clustering, especially the oscillatory clustering for shaken fluidized granular matter in connected compartments, as examples for pattern formation and bifurcations in far from equilibrium systems. Flux model is presented and discussed for mono-disperse and bi-disperse granular systems. Comparison of the flux model with simulation results is given. They show reasonably well agreements. Besides the homogeneous (HOM), segregation (SEG), and oscillatory (OSC) states, two new stationary states (d-OSC and s-HOM) in the bi-disperse granular system are predicted by our simulation. In our recent work these two new states are observed experimentally, and their flow diagrams are obtained based on the flux model. The transition from degenerate oscillation state to oscillation state demonstrates a homoclinic gluing bifurcation.

  18. Enuresis (Bed-Wetting)

    MedlinePLUS

    ... their development. Bed-wetting is more common among boys than girls. What causes bed-wetting? A number of things ... valves in boys or in the ureter in girls or boys Abnormalities in the spinal cord A small bladder ...

  19. Geophysical granular and particle-laden flows: review of the field.

    PubMed

    Hutter, Kolumban

    2005-07-15

    An introduction is given to the title theme, in general, and the specific topics treated in detail in the articles of this theme issue of the Philosophical Transactions. They fit into the following broader subjects: (i) dense, dry and wet granular flows as avalanche and debris flow events, (ii) air-borne particle-laden turbulent flows in air over a granular base as exemplified in gravity currents, aeolian transport of sand, dust and snow and (iii) transport of a granular mass on a two-dimensional surface in ripple formations of estuaries and rivers and the motion of sea ice. PMID:16011930

  20. Multiscale modeling in granular flow

    E-print Network

    Rycroft, Christopher Harley

    2007-01-01

    Granular materials are common in everyday experience, but have long-resisted a complete theoretical description. Here, we consider the regime of slow, dense granular flow, for which there is no general model, representing ...

  1. Electrokinetic Copper and Iron Migration in Anaerobic Granular Sludge

    Microsoft Academic Search

    Jurate Virkutyte; Mika Sillanpää; Piet Lens

    2006-01-01

    The application of low-level direct electric current (0.15 mA cm?2) as an electrokinetic technique to treat copper-contaminated mesophilic anaerobic granular sludge was investigated. The sludge was obtained from a full scale UASB reactor treating paper-mill wastewater and was artificially contaminated by Cu(NO3)2 or CuEDTA2? with initial copper concentrations of 1000 mg . kg?1 wet sludge. The effect of different electrokinetic

  2. Anaerobic Granular Sludge Bioreactor Technology

    Microsoft Academic Search

    Sharon McHugh; Caroline O'Reilly; Thérèse Mahony; Emer Colleran; Vincent O'Flaherty

    2003-01-01

    Anaerobic digestion is a mature wastewater treatment technology, with worldwide application. The predominantly applied bioreactor designs, such as the upflow anaerobic sludge blanket and expanded granular sludge bed, are based on the spontaneous formation of granular sludge. Despite the exploitation of granular reactors at full-scale for more than two decades, the mechanisms of granulation are not completely understood and numerous

  3. Performance of aerobic granular sludge in different bioreactors.

    PubMed

    Zhao, Xia; Chen, Zhonglin; Shen, Jimin; Wang, Xiaochun

    2014-01-01

    Inoculated sludge from the Brewery wastewater treatment plant was cultured in a sequencing batch reactor (SBR). The granular sludge was then used to process the artificial simulation wastewater to compare the performance and efficiency of the granular sludge in organic matter removal by using SBR and granular membrane bioreactor (GMBR). Results showed that the granular sludge in the SBR exhibited desirable characteristics and good removal efficiency. The mixed liquor suspended solids (MLSS) and the sludge volume index (SVI) were approximately 2.56 g/L and 78.13 mL/g, respectively, and it exhibited a satisfactory settling ability. The removal efficiency of the resulting chemical oxygen demand (COD), NH3-N and total phosphorus (TP) reached 89.35%, 96.49% and 83.76%, respectively. The removal efficiency of both nitrate nitrogen and total nitrogen (TN) reached 90%. The performance of the granular sludge as well as the removal efficiency of the organic matter in the GMBR was subsequently observed. Results showed that the process influenced the characteristics and microbial biomass of the granular sludge. The SVI and the MLSS were about 175.82 mL/g and 1.14 g/L, respectively. The removal efficiency of COD and TP increased to 93.17% and 90.42%, respectively. The removal efficiency of NH3-N was slightly affected, whereas that of both nitrate nitrogen and TN increased to 95%. In this study, the physical properties and the removal efficiency of granular sludge in different bioreactors were compared. The comparison demonstrated that granulation membrane bioreactors perform more efficiently compared with SBR in wastewater treatment for organic matter removal. PMID:24645477

  4. Granular Convection in Microgravity

    E-print Network

    N. Murdoch; B. Rozitis; K. Nordstrom; S. F. Green; P. Michel; T. -L. de Lophem; W. Losert

    2013-06-07

    We investigate the role of gravity on convection in a dense granular shear flow. Using a microgravity modified Taylor-Couette shear cell under the conditions of parabolic flight microgravity, we demonstrate experimentally that secondary, convective-like flows in a sheared granular material are close to zero in microgravity and enhanced under high-gravity conditions, though the primary flow fields are unaffected by gravity. We suggest that gravity tunes the frictional particle-particle and particle-wall interactions, which have been proposed to drive the secondary flow. In addition, the degree of plastic deformation increases with increasing gravitational forces, supporting the notion that friction is the ultimate cause.

  5. GRANULAR ACTIVATED CARBON INSTALLATIONS

    EPA Science Inventory

    This paper presents a compilation and summary of design criteria, performance, and cost data from 22 operating municipal and industrial granular activated carbon (GAC) installations that treat water and wastewater or process food and beverage products. Guidance for using this inf...

  6. Wetting in electrolyte solutions

    E-print Network

    Ingrid Ibagon; Markus Bier; S. Dietrich

    2013-03-08

    Wetting of a charged substrate by an electrolyte solution is investigated by means of classical density functional theory applied to a lattice model. Within the present model the pure, i.e., salt-free solvent, for which all interactions are of the nearest-neighbor type only, exhibits a second-order wetting transition for all strengths of the substrate-particle and the particle-particle interactions for which the wetting transition temperature is nonzero. The influences of the substrate charge density and of the ionic strength on the wetting transition temperature and on the order of the wetting transition are studied. If the substrate is neutral, the addition of salt to the solvent changes neither the order nor the transition temperature of the wetting transition of the system. If the surface charge is nonzero, upon adding salt this continuous wetting transition changes to first-order within the wide range of substrate surface charge densities and ionic strengths studied here. As the substrate surface charge density is increased, at fixed ionic strength, the wetting transition temperature decreases and the prewetting line associated with the first-order wetting transition becomes longer. This decrease of the wetting transition temperature upon increasing the surface charge density becomes more pronounced by decreasing the ionic strength.

  7. Effect of cohesion on granular-fluid flows in spouted beds: PIV measurement and DEM simulations

    NASA Astrophysics Data System (ADS)

    Zhu, Runru; LI, Shuiqing; Yao, Qiang

    2013-06-01

    In contrast to wet granular flows, the effect of cohesion on complex granular-fluid flows is intriguing but much challenging. The liquid bridges, forming between binary particles with the addition of a small amount of liquids, might significantly change the granular-fluid system due to both cohesion and lubrication effects. In this paper, a spouted bed, among various fluidization technologies, is particularly selected as a prototypical system for studying granular-fluid flows, since it can provide a quasi-steady flow pattern of granular particles, i.e., a core of upward granular-fluid flow called the "spout" and a surrounding region of downward quasi-static granular flow called the "annulus". Firstly, using self-developed particle image velocimetery (PIV) technique, the effects of cohesion on the spout-annulus interface (namely the spout width) and on the particle velocity profiles in distinct zones are examined. Further, the discrete element method (DEM), by incorporating liquid bridge adhesion into soft-sphere model, is established and used to predict the microdynamic behavior of particles in spouted beds. Finally, based on both experiments and DEM validation, the effects on the granular patterns in these two zones are comparatively discussed.

  8. Stresses in two-dimensional isostatic granular systems: exact solutions

    E-print Network

    Blumenfeld, Rafi

    in closed form and give rise to force chains that propagate along straight characteristic lines that they play in everyday life. Examples are soil, gravel, beans, agricultural grain and seeds, pharmaceutical range of industries. From a theoretical point of view, granular matter exhibits a wide range of complex

  9. Surface wave acoustics of granular packing under gravity

    Microsoft Academic Search

    Eric Clement; Lenaic Bonneau; Bruno Andreotti

    2009-01-01

    Due to the non-linearity of Hertzian contacts, the speed of sound in granular matter increases with pressure. For a packing under gravity and in the presence of a free surface, bulk acoustic waves cannot propagate due to the inherent refraction toward the surface (the mirage effect). Thus, only modes corresponding to surface waves (Raleigh-Hertz modes) are able to propagate the

  10. Granular flow over inclined channels with constrictions

    NASA Astrophysics Data System (ADS)

    Tunuguntla, Deepak; Weinhart, Thomas; Thornton, Anthony; Bokhove, Onno

    2013-04-01

    Study of granular flows down inclined channels is essential in understanding the dynamics of natural grain flows like landslides and snow avalanches. As a stepping stone, dry granular flow over an inclined channel with a localised constriction is investigated using both continuum methods and particle simulations. Initially, depth-averaged equations of motion (Savage & Hutter 1989) containing an unknown friction law are considered. The shallow-layer model for granular flows is closed with a friction law obtained from particle simulations of steady flows (Weinhart et al. 2012) undertaken in the open source package Mercury DPM (Mercury 2010). The closed two-dimensional (2D) shallow-layer model is then width-averaged to obtain a novel one-dimensional (1D) model which is an extension of the one for water flows through contraction (Akers & Bokhove 2008). Different flow states are predicted by this novel one-dimensional theory. Flow regimes with distinct flow states are determined as a function of upstream channel Froude number, F, and channel width ratio, Bc. The latter being the ratio of the channel exit width and upstream channel width. Existence of multiple steady states is predicted in a certain regime of F - Bc parameter plane which is in agreement with experiments previously undertaken by (Akers & Bokhove 2008) and for granular flows (Vreman et al. 2007). Furthermore, the 1D model is verified by solving the 2D shallow granular equations using an open source discontinuous Galerkin finite element package hpGEM (Pesch et al. 2007). For supercritical flows i.e. F > 1 the 1D asymptotics holds although the two-dimensional oblique granular jumps largely vary across the converging channel. This computationally efficient closed 1D model is validated by comparing it to the computationally more expensiveaa three-dimensional particle simulations. Finally, we aim to present a quasi-steady particle simulation of inclined flow through two rectangular blocks separated by a gap, investigate the channel formed by the dead zones and compare it with our analytical calculations. REFERENCES 1. Akers, B. & Bokhove, O. 2008 Hydraulic flow through a channel contraction: Multiple steady states. Physics of fluids 20 (056601), 056601. 2. Mercury 2010 http://www2.msm.ctw.utwente.nl/athornton/md/ . 3. Pesch, L., Bell, A., Sollie, H., Ambati, V.R., Bokhove, O. & Van der Vegt, J.J.W. 2007 hpGEM—a software framework for discontinuous Galerkin finite element methods. ACM Transactions on Mathematical Software (TOMS) 33 (4), 23. 4. Savage, SB & Hutter, K. 1989 The motion of a finite mass of granular material down a rough incline. Journal of Fluid Mechanics 199 (1), 177-215. 5. Vreman, AW, Al-Tarazi, M., Kuipers, JAM, van Sint Annaland, M. & Bokhove, O. 2007 Supercritical shallow granular flow through a contraction: experiment, theory and simulation. Journal of Fluid Mechanics 578 (1), 233-269. 6. Weinhart, T., Thornton, A.R., Luding, S. & Bokhove, O. 2012 Closure relations for shallow granular flows from particle simulations. Granular Matter 14 (4), 531-552.

  11. Wet type plasma reactor for incinerator

    Microsoft Academic Search

    I. Yamamoto; K. Yamamoto; K. Shimizu; Y. Fujiyama; K. Tsunoda; A. Mizuno

    1998-01-01

    The wet type plasma reactor is a new facility developed to control the emission of dioxin. Flue gases from coal-fired power plants, waste incinerator etc. contain harmful pollutants such as dioxin, NOx , SO2 and particle matter. Many processes have been developed for the removal of such pollutants from the flue gas before release to the atmosphere. For example, a

  12. Spreading of triboelectrically charged granular matter

    PubMed Central

    Kumar, Deepak; Sane, A.; Gohil, Smita.; Bandaru, P. R.; Bhattacharya, S.; Ghosh, Shankar

    2014-01-01

    We report on the spreading of triboelectrically charged glass particles on an oppositely charged surface of a plastic cylindrical container in the presence of a constant mechanical agitation. The particles spread via sticking, as a monolayer on the cylinder's surface. Continued agitation initiates a sequence of instabilities of this monolayer, which first forms periodic wavy-stripe-shaped transverse density modulation in the monolayer and then ejects narrow and long particle-jets from the tips of these stripes. These jets finally coalesce laterally to form a homogeneous spreading front that is layered along the spreading direction. These remarkable growth patterns are related to a time evolving frictional drag between the moving charged glass particles and the countercharges on the plastic container. The results provide insight into the multiscale time-dependent tribolelectric processes and motivates further investigation into the microscopic causes of these macroscopic dynamical instabilities and spatial structures. PMID:24919483

  13. Spreading of triboelectrically charged granular matter

    E-print Network

    Deepak Kumar; A. Sane; Smita Gohil; P. R. Bandaru; S. Bhattacharya; Shankar Ghosh

    2014-06-10

    We report on the spreading of triboelectrically charged glass particles on an oppositely charged surface of a plastic cylindrical container in the presence of a constant mechanical agitation. The particles spread via sticking, as a monolayer on the cylinder's surface. Continued agitation initiates a sequence of instabilities of this monolayer, which first forms periodic wavy-stripe-shaped transverse density modulation in the monolayer and then ejects narrow and long particle-jets from the tips of these stripes. These jets finally coalesce laterally to form a homogeneous spreading front that is layered along the spreading direction. These remarkable growth patterns are related to a time evolving frictional drag between the moving charged glass particles and the countercharges on the plastic container. The results provide insight into the multiscale time-dependent tribolelectric processes and motivates further investigation into the microscopic causes of these macroscopic dynamical instabilities and spatial structures.

  14. Spreading of triboelectrically charged granular matter

    NASA Astrophysics Data System (ADS)

    Kumar, Deepak; Sane, A.; Gohil, Smita.; Bandaru, P. R.; Bhattacharya, S.; Ghosh, Shankar

    2014-06-01

    We report on the spreading of triboelectrically charged glass particles on an oppositely charged surface of a plastic cylindrical container in the presence of a constant mechanical agitation. The particles spread via sticking, as a monolayer on the cylinder's surface. Continued agitation initiates a sequence of instabilities of this monolayer, which first forms periodic wavy-stripe-shaped transverse density modulation in the monolayer and then ejects narrow and long particle-jets from the tips of these stripes. These jets finally coalesce laterally to form a homogeneous spreading front that is layered along the spreading direction. These remarkable growth patterns are related to a time evolving frictional drag between the moving charged glass particles and the countercharges on the plastic container. The results provide insight into the multiscale time-dependent tribolelectric processes and motivates further investigation into the microscopic causes of these macroscopic dynamical instabilities and spatial structures.

  15. Stationary Shear Flow of Granular Matter,

    E-print Network

    Lagrée, Pierre-Yves

    is only part of the stress D2 ( Vx z )2 zz xz xz = µ()zz present model: at incipient motion #12;normal shear stress xz z +gsin() = 0 zz z -gcos() = 0 Equations of motion for given F,µ,µN,µT,we obtain (z

  16. Unified force law for granular impact cratering

    E-print Network

    H. Katsuragi; D. J. Durian

    2007-03-02

    Experiments on the low-speed impact of solid objects into granular media have been used both to mimic geophysical events and to probe the unusual nature of the granular state of matter. Observations have been interpreted in terms of conflicting stopping forces: product of powers of projectile depth and speed; linear in speed; constant, proportional to the initial impact speed; and proportional to depth. This is reminiscent of high-speed ballistics impact in the 19th and 20th centuries, when a plethora of empirical rules were proposed. To make progress, we developed a means to measure projectile dynamics with 100 nm and 20 us precision. For a 1-inch diameter steel sphere dropped from a wide range of heights into non-cohesive glass beads, we reproduce prior observations either as reasonable approximations or as limiting behaviours. Furthermore, we demonstrate that the interaction between projectile and medium can be decomposed into the sum of velocity-dependent inertial drag plus depth-dependent friction. Thus we achieve a unified description of low-speed impact phenomena and show that the complex response of granular materials to impact, while fundamentally different from that of liquids and solids, can be simply understood.

  17. Equilibration of granular subsystems

    E-print Network

    F. Lechenault; Karen E. Daniels

    2010-01-29

    We experimentally investigate the steady states of two granular assemblies differing in their material properties and allowed to exchange volume with each other under external agitation in the vicinity of their jamming transition. We extract the statistics of various static and dynamic quantities, and uncover a materials-independent relationship between the average packing fraction and its fluctuations. This relationship defines an intensive parameter which decouples from the volume statistics, and remarkably takes the same value in both subsystems. We also observe that an effective diffusion coefficient also takes the same value in each subsystem, even as the structural relaxation time increases over several orders of magnitude. These observations provide strong constraints on the eventual establishment of a granular equation of state.

  18. Stresses in Granular Materials

    Microsoft Academic Search

    R. Behringer; J. Geng; E. Longhi; D. Howell; E. Clement; G. Reydellet

    2000-01-01

    Forces are carried in a granular materials along tenuous complex structures--force\\/stress chains, whose properties depend on the sample preparation. Several models of force propagation have been proposed recently, a) the q-model of Coppersmith et al. and b) the three-leg model of Claudin et al. The first predicts a parabolic PDE for stresses in the continuum limit, and the second predicts

  19. Constitutive relations for steady, dense granular flows

    NASA Astrophysics Data System (ADS)

    Vescovi, D.; Berzi, D.; di Prisco, C. G.

    2011-12-01

    In the recent past, the flow of dense granular materials has been the subject of many scientific works; this is due to the large number of natural phenomena involving solid particles flowing at high concentration (e.g., debris flows and landslides). In contrast with the flow of dilute granular media, where the energy is essentially dissipated in binary collisions, the flow of dense granular materials is characterized by multiple, long-lasting and frictional contacts among the particles. The work focuses on the mechanical response of dry granular materials under steady, simple shear conditions. In particular, the goal is to obtain a complete rheology able to describe the material behavior within the entire range of concentrations for which the flow can be considered dense. The total stress is assumed to be the linear sum of a frictional and a kinetic component. The frictional and the kinetic contribution are modeled in the context of the critical state theory [8, 10] and the kinetic theory of dense granular gases [1, 3, 7], respectively. In the critical state theory, the granular material approaches a certain attractor state, independent on the initial arrangement, characterized by the capability of developing unlimited shear strains without any change in the concentration. Given that a disordered granular packing exists only for a range of concentration between the random loose and close packing [11], a form for the concentration dependence of the frictional normal stress that makes the latter vanish at the random loose packing is defined. In the kinetic theory, the particles are assumed to interact through instantaneous, binary and uncorrelated collisions. A new state variable of the problem is introduced, the granular temperature, which accounts for the velocity fluctuations. The model has been extended to account for the decrease in the energy dissipation due to the existence of correlated motion among the particles [5, 6] and to deal with non-instantaneous collisions [4]. We have shown that the present theory is capable of reproducing, qualitatively and quantitatively, the numerical simulations on disks [2] and the experiments on incline flows of glass spere [9]. [1] C. S. Campbell, Annual Review of Fluid Mechanics 22, 57 (1990) [2] F. da Cruz, S. Emam, M. Prochnow, J. Roux, and F. Chevoir, Physical Review E 72, 021309 (2005) [3] I. Goldhirsch, Annual Review of Fluid Mechanics 35, 267 (2003). [4] H. Hwang and K. Hutter, Continuum Mechanics and Thermodynamics 7, 357 (1995) [5] J. T. Jenkins, Granular Matter 10, 47 (2007) [6] J. T. Jenkins, Physics of Fluids 18, 103307 (2006) [7] J. T. Jenkins and M. W. Richman, Archive for Rational Mechanics and Analysis 87, 355 (1985) [8] D. Muir Wood, Geotechnical modelling (Spon Press, New York, 2004) [9] O. Pouliquen, Physics of Fluids 11, 542 (1999) [10] A. N. Schofield and C. P. Wroth, Critical state soil mechanics (McGraw-Hill, London, U.K., 1968) [11] C. Song, P. Wang, and H. A. Makse, Nature 453, 629 (2008)

  20. Adsorption and wetting

    Microsoft Academic Search

    L. J. M. Schlangen

    1995-01-01

    Adsorption and wetting are related phenomena. In order to improve knowledge of both and their relations, experiments, thermodynamics and a theoretical interpretation have been connected, starring n-alkanes.Starting from the Gibbs adsorption equation thermodynamic relations between vapour adsorption and wetting are derived. The surface pressure of a film, formed by vapour adsorption on a solid surface, is calculated by integrating the

  1. Corn Wet Milling Lab

    NSDL National Science Digital Library

    Olson, Eric

    Description: Wet Corn Milling is an industrial process that that converts corn to a wide variety of by-products. The wet milling industry is the largest non-feed user of corn, using approximately 1 billion bushels annually. This lab looks at the separation steps in the industrial processing of corn.

  2. Very, Very Fast Wetting

    NASA Technical Reports Server (NTRS)

    Jacqmin, David; Lee, Chi-Ming (Technical Monitor); Salzman, Jack (Technical Monitor)

    2001-01-01

    Just after formation, optical fibers are wetted stably with acrylate at capillary numbers routinely exceeding 1000. It is hypothesized that this is possible because of dissolution of air into the liquid coating. A lubrication/boundary integral analysis that includes gas diffusion and solubility is developed. It is applied using conservatively estimated solubility and diffusivity coefficients and solutions are found that are consistent with industry practice and with the hypothesis. The results also agree with the claim of Deneka, Kar & Mensah (1988) that the use of high solubility gases to bathe a wetting line allows significantly greater wetting speeds. The solutions indicate a maximum speed of wetting which increases with gas solubility and with reduction in wetting-channel diameter.

  3. Dynamic wetting on superhydrophobic surfaces: Droplet impact and wetting hysteresis

    E-print Network

    Smyth, Katherine M.

    We study the wetting energetics and wetting hysteresis of sessile and impacting water droplets on superhydrophobic surfaces as a function of surface texture and surface energy. For sessile drops, we find three wetting ...

  4. Wet solids flow enhancement

    SciTech Connect

    Caram, H.S.; Agrawal, D.K.; Foster, N.

    1997-07-01

    The objective was to visualize the flow of granular materials in the silo using Nuclear Magnetic Resonance. This was done by introducing traces. Mustard seeds and poppy seeds were used as trace particles. The region sampled was a cylinder 25 mm in diameter and 40 mm in length. Eight slices containing 128 by 128 to 256 by 256 pixels were generated for each image.

  5. The Big Wet

    NSDL National Science Digital Library

    This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on a particular climate found in Northern Australia, known as the tropical wet and dry. This lesson goes over the 12 categories of climates, and looks at the specifics of the 'big wet', or tropical wet and dry climate. It includes objectives, materials, procedures, discussion questions, evaluation ideas, performing extensions, suggested readings, and vocabulary. There are videos available to order which complement this lesson, audio vocabulary, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

  6. Wet Oxidation Process

    NSDL National Science Digital Library

    In this YouTube video, created by Southwest Center for Microsystems Education (SCME), viewers can watch an animation on the wet oxidation process. This animation "illustrates the chemistry of a wet thermal oxidation process that is used to grow silicon dioxide (SiO2) on a silicon (Si) wafer. In a wet oxidation process, water vapor (H2O) interacts with the silicon atoms at the SiO2-Si interface to form SiO2. This process is discussed in more detail in the Deposition Overview for MEMS Learning Module" found on the SCME website.

  7. Triboelectric separation of granular materials

    Microsoft Academic Search

    K. B. Tennal; M. K. Mazumder; D. Lindquist; J. Zhang; F. Tendeku

    1997-01-01

    Triboelectric separation of granular materials is based on either the difference in electrical resistivity of the materials or on the difference in their effective work functions. We discuss here triboelectric separation based on different work functions of the materials. In this case, two granular materials to be separated from each other must acquire electrostatic charges of opposite polarity when tribocharged

  8. Shock Waves in Granular Gases

    Microsoft Academic Search

    Alexander Goldshtein; Alexander Alexeev; Michael Shapiro

    2003-01-01

    This review is the first attempt to systematize the results on shock waves in granular gases. We present experimental and computational evidences of shock and expansion waves propagating within granular gases. The analysis of model flows with shock and expansion waves shows that even smallest kinetic energy dissipations crucially affects such flows. We discuss the role of these waves for

  9. What is soil organic matter worth?

    PubMed

    Sparling, G P; Wheeler, D; Vesely, E-T; Schipper, L A

    2006-01-01

    The conservation and restoration of soil organic matter are often advocated because of the generally beneficial effects on soil attributes for plant growth and crop production. More recently, organic matter has become important as a terrestrial sink and store for C and N. We have attempted to derive a monetary value of soil organic matter for crop production and storage functions in three contrasting New Zealand soil orders (Gley, Melanic, and Granular Soils). Soil chemical and physical characteristics of real-life examples of three pairs of matched soils with low organic matter contents (after long-term continuous cropping for vegetables or maize) or high organic matter content (continuous pasture) were used as input data for a pasture (grass-clover) production model. The differences in pasture dry matter yields (non-irrigated) were calculated for three climate scenarios (wet, dry, and average years) and the yields converted to an equivalent weight and financial value of milk solids. We also estimated the hypothetical value of the C and N sequestered during the recovery phase of the low organic matter content soils assuming trading with C and N credits. For all three soil orders, and for the three climate scenarios, pasture dry matter yields were decreased in the soils with lower organic matter contents. The extra organic matter in the high C soils was estimated to be worth NZ$27 to NZ$150 ha(-1) yr(-1) in terms of increased milk solids production. The decreased yields from the previously cropped soils were predicted to persist for 36 to 125 yr, but with declining effect as organic matter gradually recovered, giving an accumulated loss in pastoral production worth around NZ$518 to NZ$1239 ha(-1). This was 42 to 73 times lower than the hypothetical value of the organic matter as a sequestering agent for C and N, which varied between NZ$22,963 to NZ$90,849 depending on the soil, region, discount rates, and values used for carbon and nitrogen credits. PMID:16510699

  10. Bulldozing of granular material

    E-print Network

    A. Sauret; N. J. Balmforth; C. P. Caulfield; J. N. McElwaine

    2014-05-01

    We investigate the bulldozing motion of a granular sandpile driven forwards by a vertical plate. The problem is set up in the laboratory by emplacing the pile on a table rotating underneath a stationary plate; the continual circulation of the bulldozed material allows the dynamics to be explored over relatively long times, and the variation of the velocity with radius permits one to explore the dependence on bulldozing speed within a single experiment. We measure the time-dependent surface shape of the dune for a range of rotation rates, initial volumes and radial positions, for four granular materials, ranging from glass spheres to irregularly shaped sand. The evolution of the dune can be separated into two phases: a rapid initial adjustment to a state of quasi-steady avalanching perpendicular to the blade, followed by a much slower phase of lateral spreading and radial migration. The quasi-steady avalanching sets up a well-defined perpendicular profile with a nearly constant slope. This profile can be scaled by the depth against the bulldozer to collapse data from different times, radial positions and experiments onto common master curves that are characteristic of the granular material and depend on the local Froude number. The lateral profile of the dune along the face of the bulldozer varies more gradually with radial position, and evolves by slow lateral spreading. The spreading is asymmetrical, with the inward progress of the dune eventually arrested and its bulk migrating to larger radii. A one-dimensional depth-averaged model recovers the nearly linear perpendicular profile of the dune, but does not capture the finer nonlinear details of the master curves. A two-dimensional version of the model leads to an advection-diffusion equation that reproduces the lateral spreading and radial migration.

  11. Wetting and Contact Angle

    NSDL National Science Digital Library

    NSF CAREER Award and RET Program, Mechanical Engineering and Material Science,

    Students are presented with the concepts of wetting and contact angle. They are also introduced to the distinction between hydrophobic and hydrophilic surfaces. Students observe how different surfaces are used to maintain visibility under different conditions.

  12. Granular mechanics and rifting

    NASA Astrophysics Data System (ADS)

    Reber, Jacqueline E.; Hayman, Nicholas W.; Lavier, Luc L.

    2013-04-01

    Numerical models have proved useful in the interpretation of seismic-scale images of rifted margins. In an effort to both test and further illuminate predictions of numerical models, workers have made some strides using map-scale field relations, microstructures, and strain analyses. Yet, fundamental predictions of modeling and tectonic restorations are not able to capture critical observations. For example, many models and interpretations call on continuous faults with restorable kinematic histories. In contrast, s-reflectors and other interpreted shear fabrics in the middle crust tend to be discontinuous and non-planar across a margin. Additionally, most rift-evolution models and interpretations call on end-member ductile flow laws over a range of mechanical and thermal conditions. In contrast, field observations have found that a range of "brittle" fault rocks (e.g., cataclasites and breccias) form in the deeper crust. Similarly, upper crustal materials in deep basins and fault zones can deform through both distributed and localized deformation. Altogether, there appears to be reason to bring a new perspective to aspects of the structural evolution of rifted margins. A granular mechanics approach to crustal deformation studies has several important strengths. Granular materials efficiently localize shear and exhibit a range of stick-slip behaviors, including quasi-viscous rheological responses. These behaviors emerge in discrete element models, analog-materials experiments, and natural and engineered systems regardless of the specific micromechanical flow law. Yet, strictly speaking, granular deformation occurs via failure of frictional contacts between elastic grains. Here, we explore how to relate granular-mechanics models to mesoscale (outcrop) structural evolution, in turn providing insight into basin- and margin- scale evolution. At this stage we are focusing on analog-materials experiments and micro-to-mesoscale observations linking theoretical predictions to structural geological observations. With this combined approach we seek to establish characteristic length scales such as grain sizes and shear zone thicknesses, and time-scales such as stick-slip event dynamics. This would allow us to define a flow law at the mesoscale from comparing the experimental results and the field observations. This rheology could eventually be used to model the strain localization history of rifted margins

  13. Granular Avalanches in Fluids

    E-print Network

    S. Courrech du Pont; P. Gondret; B. Perrin; M. Rabaud

    2002-09-03

    Three regimes of granular avalanches in fluids are put in light depending on the Stokes number St which prescribes the relative importance of grain inertia and fluid viscous effects, and on the grain/fluid density ratio r. In gas (r >> 1 and St > 1, e.g., the dry case), the amplitude and time duration of avalanches do not depend on any fluid effect. In liquids (r ~ 1), for decreasing St, the amplitude decreases and the time duration increases, exploring an inertial regime and a viscous regime. These regimes are described by the analysis of the elementary motion of one grain.

  14. WetNet operations

    NASA Technical Reports Server (NTRS)

    Goodman, H. Michael; Smith, Matt; Lafontaine, Vada; Lafontaine, Frank; Moss, Don

    1991-01-01

    WetNet is an interdisciplinary Earth science data analysis and research project with an emphasis on the study of the global hydrological cycle. The project goals are to facilitate scientific discussion, collaboration, and interaction among a selected group of investigators by providing data access and data analysis software on a personal computer. The WetNet system fulfills some of the functionality of a prototype Product Generation System (PGS), Data Archive and Distribution System (DADS), and Information Management System for the Distributed Active Archive Center. The PGS functionality is satisfied in WetNet by processing the Special Sensor Microwave/Imager (SSM/I) data into a standard format (McIDAS) data sets and generating geophysical parameter Level II browse data sets. The DADS functionality is fulfilled when the data sets are archived on magneto optical cartridges and distributed to the WetNet investigators. The WetNet data sets on the magneto optical cartridges contain the complete WetNet processing, catalogue, and menu software in addition to SSM/I orbit data for the respective two week time period.

  15. Effects of cohesion on the flow patterns of granular materials in spouted beds

    NASA Astrophysics Data System (ADS)

    Zhu, Runru; Li, Shuiqing; Yao, Qiang

    2013-02-01

    Two-dimensional spouted bed, capable to provide both dilute granular gas and dense granular solid flow patterns in one system, was selected as a prototypical system for studying granular materials. Effects of liquid cohesion on such kind of complex granular patterns were studied using particle image velocimetry. It is seen that the addition of liquid oils by a small fraction of 10-3-10-2 causes a remarkable narrowing (about 15%) of the spout area. In the dense annulus, as the liquid fraction increases, the downward particle velocity gradually decreases and approaches a minimum where, at a microscopic grain scale, the liquid bridge reaches spherical regimes with a maximum capillarity. Viscous lubrication effect is observed at a much higher fraction but is really weak with respect to the capillary effect. In the dilute spout, in contrast to the dry grains, the wet grains have a lightly smaller acceleration in the initial 1/3 of the spout, but have a dramatically higher acceleration in the rest of the spout. We attribute the former to the additional work needed to overcome interparticle cohesion during particle entrainment at the spout-annulus interface. Then, using mass and momentum balances, the latter is explained by the relative higher drag force resulting from both higher gas velocities and higher voidages due to spout narrowing in the wet system. The experimental findings will provide useful data for the validation of discrete element simulation of cohesive granular-fluid flows.

  16. Effects of cohesion on the flow patterns of granular materials in spouted beds.

    PubMed

    Zhu, Runru; Li, Shuiqing; Yao, Qiang

    2013-02-01

    Two-dimensional spouted bed, capable to provide both dilute granular gas and dense granular solid flow patterns in one system, was selected as a prototypical system for studying granular materials. Effects of liquid cohesion on such kind of complex granular patterns were studied using particle image velocimetry. It is seen that the addition of liquid oils by a small fraction of 10(-3)-10(-2) causes a remarkable narrowing (about 15%) of the spout area. In the dense annulus, as the liquid fraction increases, the downward particle velocity gradually decreases and approaches a minimum where, at a microscopic grain scale, the liquid bridge reaches spherical regimes with a maximum capillarity. Viscous lubrication effect is observed at a much higher fraction but is really weak with respect to the capillary effect. In the dilute spout, in contrast to the dry grains, the wet grains have a lightly smaller acceleration in the initial 1/3 of the spout, but have a dramatically higher acceleration in the rest of the spout. We attribute the former to the additional work needed to overcome interparticle cohesion during particle entrainment at the spout-annulus interface. Then, using mass and momentum balances, the latter is explained by the relative higher drag force resulting from both higher gas velocities and higher voidages due to spout narrowing in the wet system. The experimental findings will provide useful data for the validation of discrete element simulation of cohesive granular-fluid flows. PMID:23496504

  17. Membrane-based wet electrostatic precipitation

    SciTech Connect

    David J. Bayless; Liming Shi; Gregory Kremer; Ben J. Stuart; James Reynolds; John Caine [Ohio University, Athens, OH (US). Ohio Coal Research Center

    2005-06-01

    Emissions of fine particulate matter, PM2.5, in both primary and secondary form, are difficult to capture in typical dry electrostatic precipitators (ESPs). Wet (or waterbased) ESPs are well suited for collection of acid aerosols and fine particulates because of greater corona power and virtually no re-entrainment. However, field disruptions because of spraying (misting) of water, formation of dry spots (channeling), and collector surface corrosion limit the applicability of current wet ESPs in the control of secondary PM2.5. Researchers at Ohio University have patented novel membrane collection surfaces to address these problems. Water-based cleaning in membrane collectors made of corrosion-resistant fibers is facilitated by capillary action between the fibers, maintaining an even distribution of water. This paper presents collection efficiency results of lab-scale and pilot-scale testing at First Energy's Bruce Mansfield Plant for the membrane-based wet ESP. The data indicate that a membrane wet ESP was more effective at collecting fine particulates, acid aerosols, and oxidized mercury than the metal-plate wet ESP, even with {approximately}15% less collecting area. 15 refs., 7 figs., 6 tabs.

  18. Creep of wet gypsum aggregates under hydrostatic loading conditions

    NASA Astrophysics Data System (ADS)

    de Meer, Siese; Spiers, Christopher J.

    1995-05-01

    Gypsum-dominated evaporite sequences are known to play an important role in controlling the mechanics of foreland thrust and nappe tectonics, as well as occasionally forming large-scale halokinetic structures associated with oil and gas accumulations. However, relatively little is known regarding the relevant deformation mechanisms and mechanical behaviour of gypsum. In this study, attention is focused on determining the compaction creep behaviour of wet granular gypsum aggregates with the aim of assessing the importance of pressure solution. Hydrostatic compaction experiments were performed at room temperature and applied effective pressures in the range 0.4-3.9 MPa, using grain sizes ranging from 15 to 125 ?m. The microstructure of the wet-tested samples showed that compaction occurred by a process of dissolution within grain contacts and precipitation on pore walls. In addition, for most of the range of conditions investigated, the mechanical data were found to be broadly consistent with models for interface-reaction-controlled grain boundary diffusional pressure solution. Combining the mechanical data with kinetic data taken from the crystal growth / dissolution literature it is suggested that for the bulk of conditions studied, creep of our wet granular gypsum aggregates was probably rate-limited by precipitation on the pore walls. This is in sharp contrast to the diffusion-controlled pressure solution creep behaviour recently reported for highly soluble salts, such as NaCl and NaNO 3, under similar conditions.

  19. Pattern formation in granular and granular-fluid flows

    NASA Astrophysics Data System (ADS)

    Duong, Nhat-Hang P.

    Particles and suspensions of particles in fluids are regularly used in many engineering disciplines such as catalysis and reaction engineering, environmental engineering, pharmaceutical engineering, etc. A few issues that are commonly encountered include ensuring homogeneity in pharmaceutical suspensions, predicting particle transport in atmospheric and effluent streams, and manufacturing uniform composite materials. Yet the fundamental study of particle motions in granular media or in highly concentrated granular suspensions has received little attention. Relevant issues of research interest include development of adaptive models that permit wide ranges of particle concentrations, improvement of analyses that allow physical interpretation of particle motions in any medium, of scales ranging from particle size to system size, and accurate validation of theoretical with experimental data. Given the above shortcomings, this dissertation will focus on investigating basic transport behavior of particles in fluids and developing predictive models for granular media and granular suspensions. Emphasis will be given to combining experiments with computations through examples of pattern forming phenomena in a granular medium and a dense granular-fluid system. The background motivation and the objectives of this dissertation are stated in the opening chapter 1. The next three chapters address these objectives in detail. First, chapter 2 presents experimental evidence, descriptions, and characteristics of novel patterns in a dense granular suspension. This is followed by chapter 3 in which a mean-field continuum model is derived to further elucidate the reported patterning phenomena. Chapter 4 uncovers several novel granular patterns experimentally and is concluded with a coarse-grained phenomenological model for granular surface flows. Lastly, chapter 5 closes the dissertation with conclusions and possible future directions. This work provides additional understanding and prediction of coexisting static (solid-like) and flowing (liquid-like) regions that are ubiquitous in granular flows. The mechanism of how the solid-like region differs from the fluid-like region will provide guidance for predicting related issues such as segregation and mixing of granular media, sedimentation and surface morphologies in multiphase flows and in nature.

  20. WET AND DRY SCRUBBERS FOR EMISSION CONTROL

    EPA Science Inventory

    Generally speaking, absorption equipment includes two major categories: Wet adsorption scrubbers (or wet scrubbers); Dry absorption scrubbers (or dry scrubbers). Wet scrubbers: As the name implies, wet scrubbers (also known as wet collectors) are devices which use a liquid fo...

  1. The Underlying Physics in Wetted Particle Collisions

    NASA Astrophysics Data System (ADS)

    Donahue, Carly; Hrenya, Christine; Davis, Robert

    2008-11-01

    Wetted granular particles are relevant in many industries including the pharmaceutical and chemical industries and has applications to granulation, filtration, coagulation, spray coating, drying and pneumatic transport. In our current focus, we investigate the dynamics of a three-body normal wetted particle collision. In order to conduct collisions we use an apparatus called a ``Stokes Cradle,'' similar to the Newton's Cradle (desktop toy) except that the target particles are covered with oil. Here, we are able to vary the oil thickness, oil viscosity, and material properties. With a three particle collision there are four possible outcomes: fully agglomerated (FA); Newton's Cradle (NC), the striker and the first target ball are agglomerated and the last target ball is separated; Reverse Newton's Cradle (RNC), the striker is separated and the two targets are agglomerated; and fully separated (FS). Varying the properties of the collisions, we have observed all four outcomes. We use elastohydrodynamics as a theoretical basis for modeling the system. We also have considered the glass transition of the oil as the pressure increases upon impact and the cavitation of the oil as the pressure drops below the vapor pressure upon rebound. A toy model has been developed where the collision is modeled as a series of two-body collisions. A qualitative agreement between the toy model and experiments gives insight into the underlying physics.

  2. Rapid wetting dynamics

    NASA Astrophysics Data System (ADS)

    Carlson, Andreas; Bellani, Gabriele; Amberg, Gustav

    2010-11-01

    Contact lines between solids and liquid or gas interfaces appear in very many instances of fluid flows. This could be coffee stains, water-oil mixtures in oil recovery, hydrophobic feet of insects or leaves in nature. In the present work we elucidate some of the wetting physics governing the very rapid wetting. Experimental and numerical results of spontaneously spreading droplets are presented, where focus is directed towards understanding the very rapid flow regime and highly dynamic initial wetting phase, where the contact line speed is limited by dissipative processes on a molecular scale occurring at the contact line. In particular we show the influence of the surface wettability and the liquid viscosity on the spreading dynamics, such as the contact line motion and dynamic contact angle in time.

  3. Wet storage integrity update

    SciTech Connect

    Bailey, W.J.; Johnson, A.B. Jr.

    1983-09-01

    This report includes information from various studies performed under the Wet Storage Task of the Spent Fuel Integrity Project of the Commercial Spent Fuel Management (CSFM) Program at Pacific Northwest Laboratory. An overview of recent developments in the technology of wet storage of spent water reactor fuel is presented. Licensee Event Reports pertaining to spent fuel pools and the associated performance of spent fuel and storage components during wet storage are discussed. The current status of fuel that was examined under the CSFM Program is described. Assessments of the effect of boric acid in spent fuel pool water on the corrosion and stress corrosion cracking of stainless steel and the stress corrosion cracking of stainless steel piping containing stagnant water at spent fuel pools are discussed. A list of pertinent publications is included. 84 references, 21 figures, 11 tables.

  4. Influence of cohesive forces on the macroscopic properties of granular assemblies

    NASA Astrophysics Data System (ADS)

    Lumay, Geoffroy; Fiscina, Jorge; Ludewig, Francois; Vandewalle, Nicolas

    2013-06-01

    The influence of cohesive forces inside a granular material is analyzed with compaction experiments. To begin, a model cohesive granular material is considered. This granular material is made of millimetric grains with a cohesion induced by an external magnetic field. Therefore, the cohesion between the grains is adjusted through the intensity of the applied magnetic field. Afterward, the cohesion induced by capillary bridges are considered. In the first study concerning capillary forces, the cohesion between neighboring grains is induced by liquid bridges in a wet granular material. The cohesiveness is tuned using different liquids having specific surface tension values. The second study performed with capillary forces concerns initially dry granular materials surrounded by a well controlled air humidity. Then, the cohesion inside the packing is controlled through the relative humidity which influence both triboelectric and capillary effects. The evolution of the parameters extracted from the compaction curves have been analyzed as a function of the cohesiveness. All the results show that the packing fraction of a pile and the compaction dynamics is strongly sensitive to cohesive forces. Therefore, the compaction measurement is a good way to characterize a powder or a granular material for R&D and quality control in industrial applications. Finally, we show that the cohesive forces play an important role when the grain size is typically below 50?m.

  5. The Physics of Granular Mechanics

    E-print Network

    Yimin Jiang; Mario Liu

    2012-06-13

    The {\\em hydrodynamic} approach to a continuum mechanical description of granular behavior is reviewed and elucidated. By considering energy and momentum conservation simultaneously, the general formalism of {\\em hydrodynamics} provides a systematic method to {derive} the structure of constitutive relations, including all gradient terms needed for nonuniform systems. An important input to arrive at different relations (say, for Newtonian fluid, solid and granular medium) is the energy, especially the number and types of its variables. Starting from a careful examination of the physics underlying granular behavior, we identify the independent variables and suggest a simple and qualitatively appropriate expression for the granular energy. The resultant hydrodynamic theory, especially the constitutive relation, is presented and given preliminary validation.

  6. Capillary Fracturing in Granular Media

    E-print Network

    Holtzman, Ran

    We study the displacement of immiscible fluids in deformable, noncohesive granular media. Experimentally, we inject air into a thin bed of water-saturated glass beads and observe the invasion morphology. The control ...

  7. Arrested coarsening of granular roll waves

    NASA Astrophysics Data System (ADS)

    Razis, D.; Edwards, A. N.; Gray, J. M. N. T.; van der Weele, Ko

    2014-12-01

    We study a system in which granular matter, flowing down an inclined chute with periodic boundary conditions, organizes itself in a train of roll waves of varying size. Since large waves travel faster than small ones, the waves merge, and their number gradually diminishes. This coarsening process, however, does not generally proceed to the ultimate one-wave state: Numerical simulations of the dynamical equations (being the granular analogue of the shallow water equations) reveal that the process is arrested at some intermediate stage. This is confirmed by a theoretical analysis, in which we show that the roll waves cannot grow beyond a certain limiting size (which is fully determined by the system parameters), meaning that on long chutes the material necessarily remains distributed over more waves. We determine the average lifetime ?N of the successive N-wave states, from the initial state with typically N = 50 waves (depending on the length of the periodic domain) down to the final state consisting of only a handful of waves (N = Narr). At the latter value of N, the lifetime ?N goes to infinity. At this point the roll waves all have become equal in size and are traveling with the same speed. Our theoretical predictions for the successive lifetimes ?N and the value for Narr show good agreement with the numerical observations.

  8. Optimized Simulation of Granular Materials

    NASA Astrophysics Data System (ADS)

    Holladay, Seth

    Visual effects for film and animation often require simulated granular materials, such as sand, wheat, or dirt, to meet a director's needs. Simulating granular materials can be time consuming, in both computation and labor, as these particulate materials have complex behavior and an enormous amount of small-scale detail. Furthermore, a single cubic meter of granular material, where each grain is a cubic millimeter, would contain a billion granules, and simulating all such interacting granules would take an impractical amount of time for productions. This calls for a simplified model for granular materials that retains high surface detail and granular behavior yet requires significantly less computational time. Our proposed method simulates a minimal number of individual granules while retaining particulate detail on the surface by supporting surface particles with simplified interior granular models. We introduce a multi-state model where, depending on the material state of the interior granules, we replace interior granules with a simplified simulation model for the state they are in and automate the transitions between those states. The majority of simulation time can thus be focused on visible portions of the material, reducing the time spent on non-visible portions, while maintaining the appearance and behavior of the mass as a whole.

  9. Uniaxial compaction creep of wet gypsum aggregates

    NASA Astrophysics Data System (ADS)

    de Meer, Siese; Spiers, Christopher J.

    1997-01-01

    The uniaxial compaction creep behavior of wet, granular gypsum is investigated under both chemically closed (i.e., drained) and open (i.e., flow through) conditions known to favor pressure solution. The experiments were performed using applied stresses of 0.5 to 2.5 MPa and grain sizes of 32-280 ?m, at room temperature, using pore fluids saturated with respect to unstressed sample material. All wet-tested samples crept rapidly. In contrast, control experiments using dry and oil-saturated samples showed no measurable creep. The microstructures developed in the wet tests provide classical evidence for the operation of grain boundary diffusional pressure solution. To enable detailed comparison with theory, it is demonstrated that despite minor effects of the water of crystallization, conventional pressure solution creep models, for closed systems, are applicable to gypsum. However, the mechanical behavior observed in the closed-system experiments does not fully match these models for either dissolution, diffusion, or precipitation control. Nonetheless, independent crystal growth data suggest that precipitation is most likely to be rate controlling. Additional evidence for this was provided by the experiments with through-flowing solution. In such experiments, precipitation can no longer control the rate of deformation, so that dissolution or diffusion are expected to take over as the rate-limiting process, thus enhancing the creep rate. Indeed, a 10 to 30 times increase in compaction creep rate was observed in the flow-through tests, confirming that creep in the closed-system case probably occurred by precipitation-controlled grain boundary diffusional pressure solution.

  10. Granular structure determined by terahertz scattering

    NASA Astrophysics Data System (ADS)

    Born, Philip; Rothbart, Nick; Sperl, Matthias; Hübers, Heinz-Wilhelm

    2014-05-01

    Light scattering from particles reveals static and dynamical information about the particles and their correlations. Such methods are particularly powerful when the wavelength of the light is chosen similar to the sizes and distances of the particles. To apply scattering to investigate granular matter in particular —or other objects of similar submillimeter size— light of suitable wavelength in the terahertz regime needs to be chosen. By using a quantum cascade laser in a benchtop setup we determine the angle-dependent scattering of spherical particles as well as coffee powder and sugar grains. The scattering from single particles can be interpreted by form factors derived within the Mie theory. In addition, collective correlations can be extracted as static structure factors and compared to recent computer simulations.

  11. Adsorption of methyl tertiary butyl ether on granular zeolites: Batch and column studies.

    PubMed

    Abu-Lail, Laila; Bergendahl, John A; Thompson, Robert W

    2010-06-15

    Methyl tertiary butyl ether (MTBE) has been shown to be readily removed from water with powdered zeolites, but the passage of water through fixed-beds of very small powdered zeolites produces high friction losses not encountered in flow through larger sized granular materials. In this study, equilibrium and kinetic adsorption of MTBE onto granular zeolites, a coconut shell granular activated carbon (CS-1240), and a commercial carbon adsorbent (CCA) sample was evaluated. In addition, the effect of natural organic matter (NOM) on MTBE adsorption was evaluated. Batch adsorption experiments determined that ZSM-5 was the most effective granular zeolite for MTBE adsorption. Further equilibrium and kinetic experiments verified that granular ZSM-5 is superior to CS-1240 and CCA in removing MTBE from water. No competitive adsorption effects between NOM and MTBE were observed for adsorption to granular ZSM-5 or CS-1240, however there was competition between NOM and MTBE for adsorption onto the CCA granules. Fixed-bed adsorption experiments for longer run times were performed using granular ZSM-5. The bed depth service time model (BDST) was used to analyze the breakthrough data. PMID:20153106

  12. Experimental Investigation of Plastic Deformations Before Granular Avalanche

    E-print Network

    Axelle Amon; Roman Bertoni; Jérôme Crassous

    2012-11-23

    We present an experimental study of the deformation inside a granular material that is progressively tilted. We investigate the deformation before the avalanche with a spatially resolved Diffusive Wave Spectroscopy setup. At the beginning of the inclination process, we first observe localized and isolated events in the bulk, with a density which decreases with the depth. As the angle of inclination increases, series of micro-failures occur periodically in the bulk, and finally a granular avalanche takes place. The micro-failures are observed only when the tilt angles are larger than a threshold angle much smaller than the granular avalanche angle. We have characterized the density of reorganizations and the localization of micro-failures. We have also explored the effect of the nature of the grains, the relative humidity conditions and the packing fraction of the sample. We discuss those observations in the framework of the plasticity of granular matter. Micro-failures may then be viewed as the result of the accumulation of numerous plastic events.

  13. Direct observation of medium-range crystalline order in granular liquids near the glass transition.

    PubMed

    Watanabe, Keiji; Tanaka, Hajime

    2008-04-18

    Collective behavior of driven granular matter is often strikingly analogous to that of thermal systems. Here we use a vibrated quasi-two-dimensional granular matter as a model system and investigate the mechanism of the liquid-glass transition. We demonstrate by direct observation the existence of long-lived medium-range crystalline order, which is found to be closely related to both dynamic heterogeneity and slow dynamics. Our findings are remarkably similar to recent numerical results on model thermal liquids and thus open an intriguing possibility of understanding the dynamic arrest in both thermal and athermal systems in a unified manner. PMID:18518153

  14. Predicting discharge dynamics of wet cohesive particles from a rectangular hopper using the discrete element method (DEM)

    Microsoft Academic Search

    Anshu Anand; Jennifer S. Curtis; Carl R. Wassgren; Bruno C. Hancock; William R. Ketterhagen

    2009-01-01

    Accurate prediction of the discharge rate from hoppers is important in many industrial processes involving the handling of granular materials. The present work investigates the parameters affecting the discharge rate of a wet cohesive system from a quasi-3-D, rectangular hopper using the discrete element method (DEM). The cohesion between the particles is described by a pendular liquid bridge force model

  15. Granular Superconductors and Gravity

    NASA Technical Reports Server (NTRS)

    Noever, David; Koczor, Ron

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with a relatively high percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 104 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field and exposed without levitation to low-field strength AC magnetic fields. Changes in observed gravity signals were measured to be less than 2 parts in 108 of the normal gravitational acceleration. Given the high sensitivity of the test, future work will examine variants on the basic magnetic behavior of granular superconductors, with particular focus on quantifying their proposed importance to gravity.

  16. Process improvement: wet reads.

    PubMed

    Tobey, Mary Ellen; Yamamoto, Alvin; Robertson, Dawn

    2014-01-01

    Through a four month Clinical Process Improvement Leadership Program, professionals at North Shore Medical Center in Massachusetts developed a process improvement to gain efficiency in communicating urgently requested x-ray results, or "wet reads." The initial steps included summoning a diverse team, mapping the process in detail, and clearly defining the problem. Once the problem was defined, the team brainstormed potential solutions and constructed a priority/pay-off matrix. By using the Plan Do Study Act (PDSA) system, a repeating cycle of activity that tests the new experimental work flow by tracking, adjusting, tweaking, and tracking again, efforts were built upon until the goal was met.The average wet read turnaround time went from 44 minutes to 15 minutes, a reduction of 66%. PMID:24605443

  17. Wetting on Nanorough Surfaces

    E-print Network

    Thierry Biben; Laurent Joly

    2009-12-07

    We present in this Letter a free-energy approach to the dynamics of a fluid near a nanostructured surface. The model accounts both for the static phase equilibrium in the vicinity of the surface (wetting angles, Cassie-Wenzel transition) and the dynamical properties like liquid slippage at the boundary. This method bridges the gap between phenomenological phase-field approaches and more macroscopic lattice-Boltzmann models.

  18. Wets, drys, and damps.

    PubMed

    Phipps, W E

    1987-09-01

    The real issues pertaining to beverage alcohol have been obscured by propaganda from America's "drys" and "wets." The Judeo-Christian culture has, throughout its history, usually advocated moderation. A similar position has been supported by Plato and by some modern researchers concerned with the prevention of alcoholism. Problem drinkers are more likely to come from a family tradition of abstinence than from moderate imbibers. PMID:24302036

  19. Wet chemistry instrument prototype

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A wet chemistry instrument prototype for detecting amino acids in planetary soil samples was developed. The importance of amino acids and their condensation products to the development of life forms is explained. The characteristics of the instrument and the tests which were conducted to determine the materials compatibility are described. Diagrams are provided to show the construction of the instrument. Data obtained from the performance tests are reported.

  20. Silo collapse under granular discharge

    E-print Network

    G. Gutiérrez; C. Colonnello; P. Boltenhagen; J. R. Darias; R. Peralta-Fabi; F. Brau; E. Clément

    2014-12-05

    We investigate, at a laboratory scale, the collapse of cylindrical shells of radius $R$ and thickness $t$ induced by a granular discharge. We measure the critical filling height for which the structure fails upon discharge. We observe that the silos sustain filling heights significantly above an estimation obtained by coupling standard shell-buckling and granular stress distribution theories. Two effects contribute to stabilize the structure: (i) below the critical filling height, a dynamical stabilization due to granular wall friction prevents the localized shell-buckling modes to grow irreversibly; (ii) above the critical filling height, collapse occurs before the downward sliding motion of the whole granular column sets in, such that only a partial friction mobilization is at play. However, we notice also that the critical filling height is reduced as the grain size, $d$, increases. The importance of grain size contribution is controlled by the ratio $d/\\sqrt{R t}$. We rationalize these antagonist effects with a novel fluid/structure theory both accounting for the actual status of granular friction at the wall and the inherent shell imperfections mediated by the grains. This theory yields new scaling predictions which are compared with the experimental results.

  1. Wetting of porous solids.

    PubMed

    Patkar, Saket; Chaudhuri, Parag

    2013-09-01

    This paper presents a simple, three stage method to simulate the mechanics of wetting of porous solid objects, like sponges and cloth, when they interact with a fluid. In the first stage, we model the absorption of fluid by the object when it comes in contact with the fluid. In the second stage, we model the transport of absorbed fluid inside the object, due to diffusion, as a flow in a deforming, unstructured mesh. The fluid diffuses within the object depending on saturation of its various parts and other body forces. Finally, in the third stage, oversaturated parts of the object shed extra fluid by dripping. The simulation model is motivated by the physics of imbibition of fluids into porous solids in the presence of gravity. It is phenomenologically capable of simulating wicking and imbibition, dripping, surface flows over wet media, material weakening, and volume expansion due to wetting. The model is inherently mass conserving and works for both thin 2D objects like cloth and for 3D volumetric objects like sponges. It is also designed to be computationally efficient and can be easily added to existing cloth, soft body, and fluid simulation pipelines. PMID:23846102

  2. Hydrodynamics of vibrated granular monolayer.

    SciTech Connect

    Khain, E.; Aranson, I. S. (Materials Science Division); (Oakland Univ.)

    2011-01-01

    We investigate the long-standing puzzle of phase separation in a granular monolayer vibrated from below. Although this system is three dimensional, an interesting dynamics occurs mostly in the horizontal plane, perpendicular to the direction of vibration. Experiments [Olafsen and Urbach, Phys. Rev. Lett. 81 4369 (1998)] demonstrated that for a high amplitude of vibration the system is in the gaslike phase, but when the amplitude becomes smaller than a certain threshold, a phase separation occurs: A solidlike dense condensate of particles forms in the center of the system, surrounded by particles in the gaslike phase. We explain theoretically the experimentally observed coexistence of dilute and dense phases, employing Navier-Stokes granular hydrodynamics. We show that the phase separation is associated with a negative compressibility of granular gas.

  3. Granular Rayleigh-Taylor instability

    NASA Astrophysics Data System (ADS)

    Vinningland, Jan Ludvig; Johnsen, Øistein; Flekkøy, Eirik G.; Toussaint, Renaud; Ma?Løy, Knut Jørgen

    2009-06-01

    A granular instability driven by gravity is studied experimentally and numerically. The instability arises as grains fall in a closed Hele-Shaw cell where a layer of dense granular material is positioned above a layer of air. The initially flat front defined by the grains subsequently develops into a pattern of falling granular fingers separated by rising bubbles of air. A transient coarsening of the front is observed right from the start by a finger merging process. The coarsening is later stabilized by new fingers growing from the center of the rising bubbles. The structures are quantified by means of Fourier analysis and quantitative agreement between experiment and computation is shown. This analysis also reveals scale invariance of the flow structures under overall change of spatial scale.

  4. Granular Rayleigh-Taylor instability

    SciTech Connect

    Vinningland, Jan Ludvig; Johnsen, Oistein; Flekkoey, Eirik G.; Maaloey, Knut Joergen [Department of Physics, University of Oslo, P.O.Box 1048, N-0316 Oslo (Norway); Toussaint, Renaud [Institut de Physique du Globe de Strasbourg, CNRS, Universite Louis Pasteur, 5 rue Descartes, 67084 Strasbourg Cedex (France)

    2009-06-18

    A granular instability driven by gravity is studied experimentally and numerically. The instability arises as grains fall in a closed Hele-Shaw cell where a layer of dense granular material is positioned above a layer of air. The initially flat front defined by the grains subsequently develops into a pattern of falling granular fingers separated by rising bubbles of air. A transient coarsening of the front is observed right from the start by a finger merging process. The coarsening is later stabilized by new fingers growing from the center of the rising bubbles. The structures are quantified by means of Fourier analysis and quantitative agreement between experiment and computation is shown. This analysis also reveals scale invariance of the flow structures under overall change of spatial scale.

  5. Recent bright gully deposits on Mars: Wet or dry flow?

    USGS Publications Warehouse

    Pelletier, J.D.; Kolb, K.J.; McEwen, A.S.; Kirk, R.L.

    2008-01-01

    Bright gully sediments attributed to liquid water flow have been deposited on Mars within the past several years. To test the liquid water flow hypothesis, we constructed a high-resolution (1 m/pixel) photogrammetric digital elevation model of a crater in the Centauri Montes region, where a bright gully deposit formed between 2001 and 2005. We conducted one-dimensional (1-D) and 2-D numerical flow modeling to test whether the deposit morphology is most consistent with liquid water or dry granular How. Liquid water flow models that incorporate freezing can match the runout distance of the flow for certain freezing rates but fail to reconstruct the distributary lobe morphology of the distal end of the deposit. Dry granular flow models can match both the observed runout distance and the distal morphology. Wet debris flows with high sediment concentrations are also consistent with the observed morphology because their rheologies are often similar to that of dry granular flows. As such, the presence of liquid water in this flow event cannot be ruled out, but the available evidence is consistent with dry landsliding. ?? 2008 The Geological Society of America.

  6. HYPERELASTIC MODELS FOR GRANULAR MATERIALS

    SciTech Connect

    Humrickhouse, Paul W; Corradini, Michael L

    2009-01-29

    A continuum framework for modeling of dust mobilization and transport, and the behavior of granular systems in general, has been reviewed, developed and evaluated for reactor design applications. The large quantities of micron-sized particles expected in the international fusion reactor design, ITER, will accumulate into piles and layers on surfaces, which are large relative to the individual particle size; thus, particle-particle, rather than particle-surface, interactions will determine the behavior of the material in bulk, and a continuum approach is necessary and justified in treating the phenomena of interest; e.g., particle resuspension and transport. The various constitutive relations that characterize these solid particle interactions in dense granular flows have been discussed previously, but prior to mobilization their behavior is not even fluid. Even in the absence of adhesive forces between particles, dust or sand piles can exist in static equilibrium under gravity and other forces, e.g., fluid shear. Their behavior is understood to be elastic, though not linear. The recent “granular elasticity” theory proposes a non-linear elastic model based on “Hertz contacts” between particles; the theory identifies the Coulomb yield condition as a requirement for thermodynamic stability, and has successfully reproduced experimental results for stress distributions in sand piles. The granular elasticity theory is developed and implemented in a stand- alone model and then implemented as part of a finite element model, ABAQUS, to determine the stress distributions in dust piles subjected to shear by a fluid flow. We identify yield with the onset of mobilization, and establish, for a given dust pile and flow geometry, the threshold pressure (force) conditions on the surface due to flow required to initiate it. While the granular elasticity theory applies strictly to cohesionless granular materials, attractive forces are clearly important in the interaction of micron-sized particles; extension of the theory to account for these effects is also considered. A set of continuum models are proposed for use in the future dust transport modeling.

  7. Initiation of immersed granular avalanches.

    PubMed

    Mutabaruka, Patrick; Delenne, Jean-Yves; Soga, Kenichi; Radjai, Farhang

    2014-05-01

    By means of coupled molecular dynamics-computational fluid dynamics simulations, we analyze the initiation of avalanches in a granular bed of spherical particles immersed in a viscous fluid and inclined above its angle of repose. In quantitative agreement with experiments, we find that the bed is unstable for a packing fraction below 0.59 but is stabilized above this packing fraction by negative excess pore pressure induced by the effect of dilatancy. From detailed numerical data, we explore the time evolution of shear strain, packing fraction, excess pore pressures, and granular microstructure in this creeplike pressure redistribution regime, and we show that they scale excellently with a characteristic time extracted from a model based on the balance of granular stresses in the presence of a negative excess pressure and its interplay with dilatancy. The cumulative shear strain at failure is found to be ? 0.2, in close agreement with the experiments, irrespective of the initial packing fraction and inclination angle. Remarkably, the avalanche is triggered when dilatancy vanishes instantly as a result of fluctuations while the average dilatancy is still positive (expanding bed) with a packing fraction that declines with the initial packing fraction. Another nontrivial feature of this creeplike regime is that, in contrast to dry granular materials, the internal friction angle of the bed at failure is independent of dilatancy but depends on the inclination angle, leading therefore to a nonlinear dependence of the excess pore pressure on the inclination angle. We show that this behavior may be described in terms of the contact network anisotropy, which increases with a nearly constant connectivity and levels off at a value (critical state) that increases with the inclination angle. These features suggest that the behavior of immersed granular materials is controlled not only directly by hydrodynamic forces acting on the particles but also by the influence of the fluid on the granular microstructure. PMID:25353783

  8. Unifying Suspension and Granular Rheology

    NASA Astrophysics Data System (ADS)

    Boyer, François; Guazzelli, Élisabeth; Pouliquen, Olivier

    2011-10-01

    Using an original pressure-imposed shear cell, we study the rheology of dense suspensions. We show that they exhibit a viscoplastic behavior similarly to granular media successfully described by a frictional rheology and fully characterized by the evolution of the friction coefficient ? and the volume fraction ? with a dimensionless viscous number Iv. Dense suspension and granular media are thus unified under a common framework. These results are shown to be compatible with classical empirical models of suspension rheology and provide a clear determination of constitutive laws close to the jamming transition.

  9. Mott transition in granular aluminum

    NASA Astrophysics Data System (ADS)

    Bachar, N.; Lerer, S.; Levy, A.; Hacohen-Gourgy, S.; Almog, B.; Saadaoui, H.; Salman, Z.; Morenzoni, E.; Deutscher, G.

    2015-01-01

    A Mott transition in granular Al films is observed by probing the increase of the spin-flip scattering rate of conduction electrons as the nanosize metallic grains are being progressively decoupled. The presence of free spins in granular Al films is directly demonstrated by ? SR measurements. Analysis of the magnetoresistance in terms of an effective Fermi energy shows that it becomes of the order of the grains electrostatic charging energy at a room temperature resistivity ?300 K?50000 ? ? cm , at which a metal to insulator transition is known to exist. As this transition is approached the magnetoresistance exhibits a heavy-fermion-like behavior, consistent with an increased electron effective mass.

  10. DUNE - a granular flow code

    SciTech Connect

    Slone, D M; Cottom, T L; Bateson, W B

    2004-11-23

    DUNE was designed to accurately model the spectrum of granular. Granular flow encompasses the motions of discrete particles. The particles are macroscopic in that there is no Brownian motion. The flow can be thought of as a dispersed phase (the particles) interacting with a fluid phase (air or water). Validation of the physical models proceeds in tandem with simple experimental confirmation. The current development team is working toward the goal of building a flexible architecture where existing technologies can easily be integrated to further the capability of the simulation. We describe the DUNE architecture in some detail using physics models appropriate for an imploding liner experiment.

  11. Momentum Transport in Granular Flows

    E-print Network

    Gregg Lois; Anael Lemaitre; Jean M. Carlson

    2006-02-10

    We investigate the error induced by only considering binary collisions in the momentum transport of hard-sphere granular materials, as is done in kinetic theories. In this process, we first present a general microscopic derivation of the momentum transport equation and compare it to the kinetic theory derivation, which relies on the binary collision assumption. These two derivations yield different microscopic expressions for the stress tensor, which we compare using simulations. This provides a quantitative bound on the regime where binary collisions dominate momentum transport and reveals that most realistic granular flows occur in the region of phase space where the binary collision assumption does not apply.

  12. Armoring a droplet: Soft jamming of a dense granular interface

    NASA Astrophysics Data System (ADS)

    Lagubeau, Guillaume; Rescaglio, Antonella; Melo, Francisco

    2014-09-01

    Droplets and bubbles protected by armors of particles have found vast applications in encapsulation, stabilization of emulsions and foams, or flotation processes. The liquid phase stores capillary energy, while concurrently the solid contacts of the granular network induce friction and energy dissipation, leading to hybrid interfaces of combined properties. By means of nonintrusive tensiometric methods and structural measurements, we distinguish three surface phases of increasing rigidity during the evaporation of armored droplets. The emergence of surface rigidity is reminiscent of jamming of granular matter, but it occurs differently since it is marked by a step by step hardening under surface compression. These results show that the concept of the effective surface tension remains useful only below the first jamming transition. Beyond this point, the surface stresses become anisotropic.

  13. Friction and the oscillatory motion of granular flows

    E-print Network

    Lydie Staron

    2012-11-26

    This contribution reports on numerical simulations of 2D granular flows on erodible beds. The broad aim is to investigate whether simple flows of model granular matter exhibits spontaneous oscillatory motion in generic flow conditions, and in this case, whether the frictional properties of the contacts between grains may affect the existence or the characteristics of this oscillatory motion. The analysis of different series of simulations show that the flow develops an oscillatory motion with a well-defined frequency which increases like the inverse of the velocity's square root. We show that the oscillation is essentially a surface phenomena. The amplitude of the oscillation is higher for lower volume fractions, and can thus be related to the flow velocity and grains friction properties. The study of the influence of the periodic geometry of the simulation cell shows no significant effect. These results are discussed in relation to sonic sands.

  14. Shear strength of vibrated granular\\/granular-fluid mixtures

    Microsoft Academic Search

    Brian Utter; Ralph Herman; Ben Foltz

    2011-01-01

    The behavior of dense granular materials can be characterized by the continuous forming and breaking of a strong force network resisting flow. This jamming\\/unjamming behavior is typical of a variety of systems and is influenced by factors such as grain packing fraction, applied shear stress, and the random kinetic energy of the particles. We present experiments on shear strength of

  15. Pattern formation in granular and granular-fluid flows

    Microsoft Academic Search

    Nhat-Hang P. Duong

    2004-01-01

    Particles and suspensions of particles in fluids are regularly used in many engineering disciplines such as catalysis and reaction engineering, environmental engineering, pharmaceutical engineering, etc. A few issues that are commonly encountered include ensuring homogeneity in pharmaceutical suspensions, predicting particle transport in atmospheric and effluent streams, and manufacturing uniform composite materials. Yet the fundamental study of particle motions in granular

  16. Particle deposition in granular media: Progress report

    SciTech Connect

    Tien, Chi

    1987-01-01

    This paper discusses topics on particle deposition in granular media. The six topics discussed are: experimental determination of initial collection efficiency in granular beds - an assessment of the effect of instrument sensitivity and the extent of particle bounce-off; deposition of polydispersed aerosols in granular media; in situ observation of aerosol deposition in a two-dimensional model filter; solid velocity in cross-flow granular moving bed; aerosol deposition in granular moving bed; and aerosol deposition in a magnetically stabilized fluidized bed. (LSP)

  17. Pattern Transitions in a Granular Fluid System

    NASA Astrophysics Data System (ADS)

    Sandnes, Bjørnar; Knudsen, Henning Arendt; Flekkøy, Eirik Grude; Ma?Løy, Knut Jørgen

    2009-06-01

    A branching labyrinth of granular material emerges when a confined granular fluid system is slowly drained. From a series of experiments, simulations and theoretical modeling, we explain the mechanism for the pattern formation in terms of the forces involved. We further show that the granular fluid system undergoes a series of transitions whereby new types of patterns develop as the volume fraction of granular material is increased. A balloon pattern is demonstrated, generated by the sudden inflation of air through narrow necks in the densely packed granular front.

  18. Wet Etching in Nanofabrication

    NSDL National Science Digital Library

    This lab, presented by the National Nanotechnology Infrastructure Network, students will "help students understand how chemical reactions are used to create the specific shapes on surfaces of crystalline materials, which make up functional components within electronics." The wet etching process is used to create computer chips, and through this simulated lab, students will have a chance to explore the same process using different materials. Included in this lab are: Student Worksheet #1, Student Worksheet #2, Student worksheet 1 with answers, Student worksheet 2 with answers, and Teacher guide.

  19. Wet coastal plain tundra

    SciTech Connect

    Myers, J.P.; McCaffery, B.J.; Pitelka, F.A.

    1980-01-01

    This years's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSW of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 43'W; Barrow Quadrangle, USGS, reflect an increase in breeding species of 31% over the 5-year average, while breeding density was up 22%. Ten species increased and only 4 decreased. There was a total of 17 species; 61.5 territorial males or females (171/km/sup 2/, 69/100 acres).

  20. Wet-dog shake

    NASA Astrophysics Data System (ADS)

    Dickerson, Andrew; Mills, Zack; Hu, David

    2010-11-01

    The drying of wet fur is a critical to mammalian heat regulation. We investigate experimentally the ability of hirsute animals to rapidly oscillate their bodies to shed water droplets, nature's analogy to the spin cycle of a washing machine. High-speed videography and fur-particle tracking is employed to determine the angular position of the animal's shoulder skin as a function of time. We determine conditions for drop ejection by considering the balance of surface tension and centripetal forces on drops adhering to the animal. Particular attention is paid to rationalizing the relationship between animal size and oscillation frequency required to self-dry.

  1. Optical wet steam monitor

    DOEpatents

    Maxey, Lonnie C. (Powell, TN); Simpson, Marc L. (Knoxville, TN)

    1995-01-01

    A wet steam monitor determines steam particle size by using laser doppler velocimeter (LDV) device to produce backscatter light. The backscatter light signal is processed with a spectrum analyzer to produce a visibility waveform in the frequency domain. The visibility waveform includes a primary peak and a plurality of sidebands. The bandwidth of at least the primary frequency peak is correlated to particle size by either visually comparing the bandwidth to those of known particle sizes, or by digitizing the waveform and comparing the waveforms electronically.

  2. Optical wet steam monitor

    DOEpatents

    Maxey, L.C.; Simpson, M.L.

    1995-01-17

    A wet steam monitor determines steam particle size by using laser doppler velocimeter (LDV) device to produce backscatter light. The backscatter light signal is processed with a spectrum analyzer to produce a visibility waveform in the frequency domain. The visibility waveform includes a primary peak and a plurality of sidebands. The bandwidth of at least the primary frequency peak is correlated to particle size by either visually comparing the bandwidth to those of known particle sizes, or by digitizing the waveform and comparing the waveforms electronically. 4 figures.

  3. Wet steam wetness measurement in a 10 MW steam turbine

    NASA Astrophysics Data System (ADS)

    Kolovratník, Michal; Bartoš, Ond?ej

    2014-03-01

    The aim of this paper is to introduce a new design of the extinction probes developed for wet steam wetness measurement in steam turbines. This new generation of small sized extinction probes was developed at CTU in Prague. A data processing technique is presented together with yielded examples of the wetness distribution along the last blade of a 10MW steam turbine. The experimental measurement was done in cooperation with Doosan Škoda Power s.r.o.

  4. Mechanics of Granular Materials (MGM)

    NASA Technical Reports Server (NTRS)

    Alshibli, Khalid A.; Costes, Nicholas C.; Porter, Ronald F.

    1996-01-01

    The constitutive behavior of uncemented granular materials such as strength, stiffness, and localization of deformations are to a large extend derived from interparticle friction transmitted between solid particles and particle groups. Interparticle forces are highly dependent on gravitational body forces. At very low effective confining pressures, the true nature of the Mohr envelope, which defines the Mohr-Coulomb failure criterion for soils, as well as the relative contribution of each of non-frictional components to soil's shear strength cannot be evaluated in terrestrial laboratories. Because of the impossibility of eliminating gravitational body forces on earth, the weight of soil grains develops interparticle compressive stresses which mask true soil constitutive behavior even in the smallest samples of models. Therefore the microgravity environment induced by near-earth orbits of spacecraft provides unique experimental opportunities for testing theories related to the mechanical behavior of terrestrial granular materials. Such materials may include cohesionless soils, industrial powders, crushed coal, etc. This paper will describe the microgravity experiment, 'Mechanics of Granular Materials (MGM)', scheduled to be flown on Space Shuttle-MIR missions. The paper will describe the experiment's hardware, instrumentation, specimen preparation procedures, testing procedures in flight, as well as a brief summary of the post-mission analysis. It is expected that the experimental results will significantly improve the understanding of the behavior of granular materials under very low effective stress levels.

  5. Wet start for 1982

    NASA Astrophysics Data System (ADS)

    The first half of the 1982 water year (October 1, 1981-March 31, 1982) saw streamflow conditions across the country get off to a generally wet start, with almost 90% of the key index gaging stations reporting normal to above normal flows, according to the U.S. Geological Survey, Department of the Interior.USGS hydrologists said that the overall wet water picture was reflected in the nation's Big Five rivers—Mississippi, Missouri, St. Lawrence, Ohio, and Columbia—which averaged above normal for 4 of the first 6 months of the new water year. The water year used by hydrologists runs from October 1 to September 1 of the following calendar year and is designed to roughly follow the growing season and to begin and end during a period of generally low streamflow. Hydrologists use the Big Five, which together drain more than half of the conterminous United States, as a quick check on the status of the nation's water resources. Combined flow of the Big Five averaged 787 billion gallons a day (bgd) during the first half of the 1982 water year, 14% above normal.

  6. Wetting of Nanopatterned Grooved Surfaces

    SciTech Connect

    T Hofmann; M Tasinkevych; A Checco; L Dobisz; S Dietrich; B Ocko

    2011-12-31

    The wetting by perfluoromethylcyclohexane of a well-defined silicon grating with a channel width of 16 nm has been studied using transmission small angle x-ray scattering. Prefilling, capillary filling, and postfilling wetting regimes have been identified. A detailed comparison of the data with theory reveals the importance of long-ranged substrate-fluid and fluid-fluid interactions for determining the wetting behavior on these length scales, especially at the onset of capillary condensation and in the prefilling regime.

  7. Fluctuations in granular media

    NASA Astrophysics Data System (ADS)

    Howell, Daniel W.; Behringer, R. P.; Veje, C. T.

    1999-09-01

    Dense slowly evolving or static granular materials exhibit strong force fluctuations even though the spatial disorder of the grains is relatively weak. Typically, forces are carried preferentially along a network of "force chains." These consist of linearly aligned grains with larger-than-average force. A growing body of work has explored the nature of these fluctuations. We first briefly review recent work concerning stress fluctuations. We then focus on a series of experiments in both two- and three-dimension [(2D) and (3D)] to characterize force fluctuations in slowly sheared systems. Both sets of experiments show strong temporal fluctuations in the local stress/force; the length scales of these fluctuations extend up to 102 grains. In 2D, we use photoelastic disks that permit visualization of the internal force structure. From this we can make comparisons to recent models and calculations that predict the distributions of forces. Typically, these models indicate that the distributions should fall off exponentially at large force. We find in the experiments that the force distributions change systematically as we change the mean packing fraction, ?. For ?'s typical of dense packings of nondeformable grains, we see distributions that are consistent with an exponential decrease at large forces. For both lower and higher ?, the observed force distributions appear to differ from this prediction, with a more Gaussian distribution at larger ? and perhaps a power law at lower ?. For high ?, the distributions differ from this prediction because the grains begin to deform, allowing more grains to carry the applied force, and causing the distributions to have a local maximum at nonzero force. It is less clear why the distributions differ from the models at lower ?. An exploration in ? has led to the discovery of an interesting continuous or "critical" transition (the strengthening/softening transition) in which the mean stress is the order parameter, and the mean packing fraction, ?, must be adjusted to a value ?c to reach the "critical point." We also follow the motion of individual disks and obtain detailed statistical information on the kinematics, including velocities and particle rotations or spin. Distributions for the azimuthal velocity, V?, and spin, S, of the particles are nearly rate invariant, which is consistent with conventional wisdom. Near ?c, the grain motion becomes intermittent causing the mean velocity of grains to slow down. Also, the length of stress chains grows as ???c. The 3D experiments show statistical rate invariance for the stress in the sense that when the power spectra and spectral frequencies of the stress time series are appropriately scaled by the shear rate, ?, all spectra collapse onto a single curve for given particle and sample sizes. The frequency dependence of the spectra can be characterized by two different power laws, P??-?, in the high and low frequency regimes: ?˜2 at high ?; ?<2 at low ?. The force distributions computed from the 3D stress time series are at least qualitatively consistent with exponential fall-off at large stresses.

  8. On the equations of fully fluidized granular materials

    Microsoft Academic Search

    Satoru Ogawa; Akira Umemura; Nobunori Oshima

    1980-01-01

    Equations for fully fluidized granular materials are proposed and are solved in a simple case. In fully fluidized granular materials, the granular particles slip or collide with each other and energy is dissipated. In describing the energy dissipation process characteristic to granular materials, a measure of random motion of granular particles is introduced as a new internal variable. We derive

  9. MODELING THE WET MILLING PROCESS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Process engineering and cost models for a conventional corn wet milling process have been developed to aid research being conducted by the USDA, Agricultural Research Service, Eastern Regional Research Center. Information on the corn wet milling process was obtained from various technical sources i...

  10. Wetting in Soldering and Microelectronics

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.; Nogi, K.

    2008-08-01

    Wettability of solid metals by molten solders is reviewed. The contact angle and wetting force are tabulated for various combinations of solid metals and molten solders such as Sn-Pb base alloys, Sn-Ag base alloys, Sn-Zn base alloys, Sn-Cu base alloys, and Sn-Bi base alloys. Studies on the wetting rate are also discussed.

  11. Wet and Dry Bulb Thermometers

    Microsoft Academic Search

    T. H. Tizard

    1890-01-01

    IT may, perhaps, interest you to know that on Friday last the difference between the wet and dry bulb thermometers, on board this ship in Grimsby roads, amounted to 12½° the dry bulb showing 66°, and the wet bulb 53°.5. Wind west; force, 7 to 8 by Beaufort's scale. This is the greatest difference I have recorded in this country

  12. SCHEDULE OF FEES Wet Milling

    E-print Network

    Illinois at Urbana-Champaign, University of

    be characterized by Rapid Visco Analysis (RVA). 100 gram Wet Milling Wet milling at 100 g scale is used by seed, that are used in a variety of breakfast cereals, snack foods and bakery products. The prime product from dry accurately yields of prime flaking and smaller grits for cereal and snack food processors, as well as flour

  13. Scale-up of catalytic wet oxidation under moderate conditions

    SciTech Connect

    Harf, J.; Hug, A.; Vogel, F.; Rohr, P.R. von [Swiss Federal Inst. of Tech., Zuerich (Switzerland). Inst. of Process Engineering] [Swiss Federal Inst. of Tech., Zuerich (Switzerland). Inst. of Process Engineering

    1999-05-01

    The Catalytic Wet Oxidation with pure oxygen is a suitable treatment process for the degradation of organic matter in wastewaters and sludges. The applied moderate reaction conditions lead only to a partial oxidation of the organics. Therefore the resulting process water has to be purified in a biological treatment plant. In this study, experimental data collected during the wet oxidation of phenol and sewage sludge in a laboratory batch reactor as well as in a pilot plant are presented. A generalized kinetic model combined with a residence time analysis allows to predict accurately the degradation of organic matter in the pilot plant. The wet oxidation of wastewaters and sewage sludge was realized in one single plant concept. Treating suspended or diluted organic wastes produces a highly biodegradable process water containing low molecular oxidation products. The investigated Catalytic Wet Oxidation of sewage sludge generates a residual solid complying with the European quality standards of disposal concerning leachability and organic content. Due to its low capital and operating costs, the Catalytic Wet Oxidation process constitutes an acceptable alternative to incineration for the disposal of sludges.

  14. 77 FR 59979 - Pure Magnesium (Granular) From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-01

    ...731-TA-895 (Second Review)] Pure Magnesium (Granular) From China Determination...of the antidumping duty order on pure magnesium (granular) from China would be likely...4350 (September 2012), entitled Pure Magnesium (Granular) from China:...

  15. Observation of anisotropic diffusion of light in compacted granular porous materials

    E-print Network

    Alerstam, Erik

    2011-01-01

    Employing spatially resolved photon time-of-flight spectroscopy, we reveal anisotropic diffusion of light in compressed granular media. Findings correlate well with recent reports of pore structural anisotropy and its pressure dependence, and significantly reshape our understanding of the optics of compacted granular matter. New routes to material characterization and investigations of compression-induced anisotropy are opened, and an urgent need for better understanding of the relation between compression, microstructure and light scattering is disclosed. Important implications for quantitative spectroscopy of powder compacts in general, and pharmaceutical tablets in particular, are also discussed.

  16. Three-dimensional (3D) experimental realization and observation of a granular gas in microgravity

    NASA Astrophysics Data System (ADS)

    Harth, Kirsten; Trittel, Torsten; May, Kathrin; Wegner, Sandra; Stannarius, Ralf

    2015-04-01

    Experiments with granular gases do not only provide statistical information on multi-particle systems undergoing random dissipative interactions, they may also help to test predictions of numerical simulations and to gain understanding of the self-organization of dilute granular matter to clusters and stable assemblies. We shortly review an experiment under zero gravity conditions on different platforms. Implementations on a sounding rocket flight, parabolic flights and drop tower shots are analyzed. We evaluate general experimental requirements, judge the appropriateness of the different platforms, and present quantitative results.

  17. BRIDGES IN VIBRATED GRANULAR MEDIA

    Microsoft Academic Search

    Anita Mehta

    We study a particular consequence of the dynamics of vibrated granular media, which is the spontaneous formation of stable\\u000a bridges. Here we examine their geometrical characteristics, and compare the results of a simple theory with those of independent\\u000a simulations of three-dimensional hard spheres. Our conclusion is that bridges are the signatures of spatiotemporal inhomogeneities,\\u000a the carriers of the so-called ‘force

  18. On Classifying Mappings Induced by Granular Structures

    Microsoft Academic Search

    Lech Polkowski; Piotr Artiemjew

    2008-01-01

    In this work the subject of granular computing is pursued beyond the content of the previous paper [21]. We study here voting\\u000a on a decision by granules of training objects, granules of decision rules, granules of granular reflections of training data,\\u000a and granules of decision rules induced from granular reflections of training data. This approach can be perceived as a

  19. Anisotropy of Weakly Vibrated Granular Flows

    E-print Network

    Geert Wortel; Martin van Hecke

    2014-10-16

    We experimentally probe the anisotropy of the fabric of weakly vibrated, flowing granular media. Depending on the driving parameters --- flow rate and vibration strength --- this anisotropy varies significantly. We show how the anisotropy collapses when plotted as function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggests that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a crucial role in determining the rheology of granular flows.

  20. Why Granular Media Are, After All, Thermal

    E-print Network

    Yimin Jiang; Mario Liu

    2014-07-27

    Granular media are considered "athermal", because the grains are too large to display Brownian type thermal fluctuations. Yet being macroscopic, every grain undergoes thermal expansion, possesses a temperature that may be measured with a thermometer, and consists of many, many internal degrees of freedom that in their sum do affect granular dynamics. Therefore, including them in a comprehensive approach to account for granular behavior entails crucial advantages. The pros and cons of thermal versus athermal descriptions are considered.

  1. Shock wave propagation in vibrofluidized granular materials

    E-print Network

    Kai Huang; Guoqing Miao; Peng Zhang; Yi Yun; Rongjue Wei

    2005-11-29

    Shock wave formation and propagation in two-dimensional granular materials under vertical vibration are studied by digital high speed photography. The steepen density and temperature wave fronts form near the plate as granular layer collides with vibrating plate and propagate upward through the layer. The temperature front is always in the transition region between the upward and downward granular flows. The effects of driving parameters and particle number on the shock are also explored.

  2. Dynamic compaction of granular materials.

    PubMed

    Favrie, N; Gavrilyuk, S

    2013-12-01

    An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding 'intergranular stress' coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading-unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model. PMID:24353466

  3. Dynamic compaction of granular materials

    PubMed Central

    Favrie, N.; Gavrilyuk, S.

    2013-01-01

    An Eulerian hyperbolic multiphase flow model for dynamic and irreversible compaction of granular materials is constructed. The reversible model is first constructed on the basis of the classical Hertz theory. The irreversible model is then derived in accordance with the following two basic principles. First, the entropy inequality is satisfied by the model. Second, the corresponding ‘intergranular stress’ coming from elastic energy owing to contact between grains decreases in time (the granular media behave as Maxwell-type materials). The irreversible model admits an equilibrium state corresponding to von Mises-type yield limit. The yield limit depends on the volume fraction of the solid. The sound velocity at the yield surface is smaller than that in the reversible model. The last one is smaller than the sound velocity in the irreversible model. Such an embedded model structure assures a thermodynamically correct formulation of the model of granular materials. The model is validated on quasi-static experiments on loading–unloading cycles. The experimentally observed hysteresis phenomena were numerically confirmed with a good accuracy by the proposed model. PMID:24353466

  4. FNA of thyroid granular cell tumor.

    PubMed

    Harp, Eric; Caraway, Nancy P

    2013-09-01

    Granular cell tumor rarely occurs in the thyroid. This case report describes the cytologic features of a granular cell tumor seen in a fine needle aspirate obtained from a 27-year-old woman with a gradually enlarging thyroid nodule. The aspirate showed single as well as syncytial clusters of cells with abundant granular cytoplasm. The differential diagnosis in this case included granular cell tumor, Hurthle cell lesion/neoplasm, and a histiocytic reparative process. Immunohistochemical studies, including S-100 protein and CD68, performed on a cell block preparation were helpful in supporting the diagnosis. PMID:22508678

  5. Segregation of granular particles in suspension flow

    E-print Network

    Tsay, Jessica, 1983-

    2004-01-01

    An experiment was conducted to investigate the development of longitudinal stripes of granular particles due to instabilities in particle suspension flow. Research was conducted to characterize environmental phenomena ...

  6. Dynamics of wetting revisited.

    PubMed

    Seveno, D; Vaillant, A; Rioboo, R; Adão, H; Conti, J; De Coninck, J

    2009-11-17

    We present new spreading-drop data obtained over four orders of time and apply our new analysis tool G-Dyna to demonstrate the specific range over which the various models of dynamic wetting would seem to apply for our experimental system. We follow the contact angle and radius dynamics of four liquids on the smooth silica surface of silicon wafers or PET from the first milliseconds to several seconds. Analysis of the images allows us to make several hundred contact angle and droplet radius measurements with great accuracy. The G-Dyna software is then used to fit the data to the relevant theory (hydrodynamic, molecular-kinetic theory, Petrov and De Ruijter combined models, and Shikhmurzaev's formula). The distributions, correlations, and average values of the free parameters are analyzed and it is shown that for the systems studied even with very good data and a robust fitting procedure, it may be difficult to make reliable claims as to the model which best describes results for a given system. This conclusions also suggests that claims based on smaller data sets and less stringent fitting procedures should be treated with caution. PMID:19845346

  7. Cellular Automata Models for Complex Matter

    Microsoft Academic Search

    Dominique Désérable; Pascal Dupont; Mustapha Hellou; Siham Kamali-bernard

    2007-01-01

    Complex matter may lie in various forms from granular matter, soft matter, fluid-fluid or solid-fluid mixtures to compact\\u000a heterogeneous material. Cellular automata models make a suitable and powerful tool to catch the influence of the microscopic\\u000a scale onto the macroscopic behaviour of these complex systems. Rather than a survey, this paper will attempt to bring out\\u000a the main concepts underlying

  8. Wet vs. Dry Oxidation Processes

    NSDL National Science Digital Library

    In this YouTube video, created by Southwest Center for Microsystems Education (SCME), viewers can watch an animation on the the difference between wet and dry thermal oxidation processes. This animation "shows a side by side comparison of a wet oxidation process vs. a dry oxidation process. Both processes use an oxygen source to grow silicon dioxide (SiO2) on a silicon wafer heated furnace. Wet thermal oxidation uses water vapor. Dry thermal oxidation uses oxygen gas." Viewers can learn more on this topic in the Deposition Overview for MEMS Learning Module which can be found on the SCME website along with supplementary materials. 

  9. All-Wet Metallization Process for Transparent Polyimide Films

    NASA Astrophysics Data System (ADS)

    Ikeda, S.; Kobayashi, Y.; Fujiwara, Y.; Akamatsu, K.; Nawafune, H.

    2013-03-01

    Electrically conductive Ag thin films were successfully formed onto optically transparent polyimide films via all-wet chemical process. The process involves alkaline-induced surface modification of polyimide films, subsequent incorporation of Ag+ ions through ion exchange reaction followed by reduction of incorporated Ag+ ions. Initial alkaline treatment time determines thickness (depth) of surface-modified layer and amount of Ag+ ions loading consequently. Higher Ag+ ions loading result in forming electrically conductive Ag thin films and its granular interfacial structure. Cu electroplating is able to be conducted on the resulting Ag thin films directly, and adhesive strength between the Cu(/Ag) film and transparent polyimide substrate reached up to 2 kN m-1.

  10. Clinical Trials for Wet AMD

    MedlinePLUS

    ... and potentially more effective than intravitreal anti-VEGF therapy alone in eyes with exudative age-related macular degeneration. Anti-VEGF therapy is the current standard treatment for wet macular ...

  11. Pulse Propagation in Granular Chains Katja Lindenberg

    E-print Network

    Lindenberg, Katja

    sedimentary systems, and also in man-made forms such as shock absorbers and bulletproof vests. Man-made granular materials are frequently used to dampen the effect of a shock or energy pulse (sequence of sizes and masses) would optimize the shock absorption capability of a granular chain? What

  12. Unified force law for granular impact cratering

    E-print Network

    Loss, Daniel

    LETTERS Unified force law for granular impact cratering HIROAKI KATSURAGI* AND DOUGLAS J. DURIAN.1038/nphys583 Experiments on the low-speed impact of solid objects into granular media have been used both depth and speed6 ; linear in speed7 ; constant, proportional to the initial impact speed8

  13. Local Anisotropy In Globally Isotropic Granular Packings

    E-print Network

    Gruner, Daniel S.

    Local Anisotropy In Globally Isotropic Granular Packings Kamran Karimi Craig E Maloney #12;Granular Moduli 17 C( 1 , 2 , 3 ) K C12 C13 C21 1 C23 C31 C32 2 : Bulk Modulus 1, 2: Shear Moduli max min C ( 1,C

  14. Gravity-driven dense granular flows

    Microsoft Academic Search

    Deniz Ertas

    2002-01-01

    Despite their importance in many areas of science and technology, the emergent physics of hard granular systems remain largely obscure, especially when the packing density approaches that of a jammed system. In particular, I will focus on the rheology of gravity-driven dense granular flows on an incline with a ``rough\\

  15. Shear viscosity of a model for confined granular media

    NASA Astrophysics Data System (ADS)

    Soto, Rodrigo; Risso, Dino; Brito, Ricardo

    2014-12-01

    The shear viscosity in the dilute regime of a model for confined granular matter is studied by simulations and kinetic theory. The model consists on projecting into two dimensions the motion of vibrofluidized granular matter in shallow boxes by modifying the collision rule: besides the restitution coefficient that accounts for the energy dissipation, there is a separation velocity that is added in each collision in the normal direction. The two mechanisms balance on average, producing stationary homogeneous states. Molecular dynamics simulations show that in the steady state the distribution function departs from a Maxwellian, with cumulants that remain small in the whole range of inelasticities. The shear viscosity normalized with stationary temperature presents a clear dependence with the inelasticity, taking smaller values compared to the elastic case. A Boltzmann-like equation is built and analyzed using linear response theory. It is found that the predictions show an excellent agreement with the simulations when the correct stationary distribution is used but a Maxwellian approximation fails in predicting the inelasticity dependence of the viscosity. These results confirm that transport coefficients depend strongly on the mechanisms that drive them to stationary states.

  16. Shear viscosity of a model for confined granular media.

    PubMed

    Soto, Rodrigo; Risso, Dino; Brito, Ricardo

    2014-12-01

    The shear viscosity in the dilute regime of a model for confined granular matter is studied by simulations and kinetic theory. The model consists on projecting into two dimensions the motion of vibrofluidized granular matter in shallow boxes by modifying the collision rule: besides the restitution coefficient that accounts for the energy dissipation, there is a separation velocity that is added in each collision in the normal direction. The two mechanisms balance on average, producing stationary homogeneous states. Molecular dynamics simulations show that in the steady state the distribution function departs from a Maxwellian, with cumulants that remain small in the whole range of inelasticities. The shear viscosity normalized with stationary temperature presents a clear dependence with the inelasticity, taking smaller values compared to the elastic case. A Boltzmann-like equation is built and analyzed using linear response theory. It is found that the predictions show an excellent agreement with the simulations when the correct stationary distribution is used but a Maxwellian approximation fails in predicting the inelasticity dependence of the viscosity. These results confirm that transport coefficients depend strongly on the mechanisms that drive them to stationary states. PMID:25615082

  17. Dynamics of Sheared Granular Materials

    NASA Technical Reports Server (NTRS)

    Kondic, Lou; Utter, Brian; Behringer, Robert P.

    2002-01-01

    This work focuses on the properties of sheared granular materials near the jamming transition. The project currently involves two aspects. The first of these is an experiment that is a prototype for a planned ISS (International Space Station) flight. The second is discrete element simulations (DES) that can give insight into the behavior one might expect in a reduced-g environment. The experimental arrangement consists of an annular channel that contains the granular material. One surface, say the upper surface, rotates so as to shear the material contained in the annulus. The lower surface controls the mean density/mean stress on the sample through an actuator or other control system. A novel feature under development is the ability to 'thermalize' the layer, i.e. create a larger amount of random motion in the material, by using the actuating system to provide vibrations as well control the mean volume of the annulus. The stress states of the system are determined by transducers on the non-rotating wall. These measure both shear and normal components of the stress on different size scales. Here, the idea is to characterize the system as the density varies through values spanning dense almost solid to relatively mobile granular states. This transition regime encompasses the regime usually thought of as the glass transition, and/or the jamming transition. Motivation for this experiment springs from ideas of a granular glass transition, a related jamming transition, and from recent experiments. In particular, we note recent experiments carried out by our group to characterize this type of transition and also to demonstrate/ characterize fluctuations in slowly sheared systems. These experiments give key insights into what one might expect in near-zero g. In particular, they show that the compressibility of granular systems diverges at a transition or critical point. It is this divergence, coupled to gravity, that makes it extremely difficult if not impossible to characterize the transition region in an earth-bound experiment. In the DE modeling, we analyze dynamics of a sheared granular system in Couette geometry in two (2D) and three (3D) space dimensions. Here, the idea is to both better understand what we might encounter in a reduced-g environment, and at a deeper level to deduce the physics of sheared systems in a density regime that has not been addressed by past experiments or simulations. One aspect of the simulations addresses sheared 2D system in zero-g environment. For low volume fractions, the expected dynamics of this type of system is relatively well understood. However, as the volume fraction is increased, the system undergoes a phase transition, as explained above. The DES concentrate on the evolution of the system as the solid volume fraction is slowly increased, and in particular on the behavior of very dense systems. For these configurations, the simulations show that polydispersity of the sheared particles is a crucial factor that determines the system response. Figures 1 and 2 below, that present the total force on each grain, show that even relatively small (10 %) nonuniformity of the size of the grains (expected in typical experiments) may lead to significant modifications of the system properties, such as velocity profiles, temperature, force propagation, and formation shear bands. The simulations are extended in a few other directions, in order to provide additional insight to the experimental system analyzed above. In one direction, both gravity, and driving due to vibrations are included. These simulations allow for predictions on the driving regime that is required in the experiments in order to analyze the jamming transition. Furthermore, direct comparison of experiments and DES will allow for verification of the modeling assumptions. We have also extended our modeling efforts to 3D. The (preliminary) results of these simulations of an annular system in zero-g environment will conclude the presentation.

  18. Slow relaxation and compaction of granular systems.

    PubMed

    Richard, Patrick; Nicodemi, Mario; Delannay, Renaud; Ribière, Philippe; Bideau, Daniel

    2005-02-01

    Granular materials are of substantial importance in many industrial and natural processes, yet their complex behaviours, ranging from mechanical properties of static packing to their dynamics, rheology and instabilities, are still poorly understood. Here we focus on the dynamics of compaction and its 'jamming' phenomena, outlining recent statistical mechanics approaches to describe it and their deep correspondence with thermal systems such as glass formers. In fact, granular media are often presented as ideal systems for studying complex relaxation towards equilibrium. Granular compaction is defined as an increase of the bulk density of a granular medium submitted to mechanical perturbation. This phenomenon, relevant in many industrial processes and widely studied by the soil mechanics community, is simple enough to be fully investigated and yet reveals all the complex nature of granular dynamics, attracting considerable attention in a broad range of disciplines ranging from chemical to physical sciences. PMID:15689950

  19. Filamentous bacteria existence in aerobic granular reactors.

    PubMed

    Figueroa, M; Val Del Río, A; Campos, J L; Méndez, R; Mosquera-Corral, A

    2015-05-01

    Filamentous bacteria are associated to biomass settling problems in wastewater treatment plants. In systems based on aerobic granular biomass they have been proposed to contribute to the initial biomass aggregation process. However, their development on mature aerobic granular systems has not been sufficiently studied. In the present research work, filamentous bacteria were studied for the first time after long-term operation (up to 300 days) of aerobic granular systems. Chloroflexi and Sphaerotilus natans have been observed in a reactor fed with synthetic wastewater. These filamentous bacteria could only come from the inoculated sludge. Thiothrix and Chloroflexi bacteria were observed in aerobic granular biomass treating wastewater from a fish canning industry. Meganema perideroedes was detected in a reactor treating wastewater from a plant processing marine products. As a conclusion, the source of filamentous bacteria in these mature aerobic granular systems fed with industrial effluents was the incoming wastewater. PMID:25533039

  20. 022. Granular cell tumor of the lung

    PubMed Central

    Baliaka, Aggeliki; Pastelli, Nikoleta; Tziastoudi, Eirini; Cheva, Angeliki; Papaemmanouil, Styliani; Sakkas, Leonidas

    2015-01-01

    Background Granular cell tumor, also known as granular cell myoblastoma, is an uncommon benign tumor with female predisposition, that involves any part of the oral cavity, but the tongue is the most common site. It is considered to be of mesenchymal origin (myoblastic), but at present, the tumor is believed to derive from Schwann cells, and the granularity of the cytoplasm may be associated with accumulation of lysosomes. Cases of granular cell tumors of the lung/ tracheobronchial tree are extremely rare (6-10% of all the granular cell tumors, 0.2% of the lung neoplasms). Methods Three cases of granular cell tumor of the lung could be retrieved from files of the Department of Pathology of the “G. Papanicolaou” General Hospital, Thessaloniki at the period 1994-2014. Two of the patients were men of the 5th decade of life and the third case was about a woman, 52-year-old, with multiple small bilateral intrabronchial tumors. The patients presented with slight chest pain, shortness of breath and cough. An excision biopsy via bronchoscopy was performed in all of them. Results Microscopically, the lesions were composed of large polygonal eosinophilic cells with highly granular cytoplasm and indistinct cell membranes, with ill-defined growth pattern. Immunohistochemically, the tumor cells were positive for S-100 protein. Ki 67 was practically zero. The lesions were pathologically diagnosed as granular cell tumors. There are no recurrences after removal. Conclusions Lung/tracheobronchial tree is an uncommon site for granular cell tumor, with the tongue being the classical location. In about 10-20% of the patients, the lesions are multiple. Congenital examples have been reported and others have systematic involvement. It is benign, rarely recurs, but occasional lesions with malignant behavior have been described. Granular cell tumor of the tracheobronchial tree usually can be easily excised via bronchoscopy, but when it involves submucosal glands, nerves or peribronchial tissues, should need surgical excision.

  1. BOOK REVIEW: Kinetic Theory of Granular Gases

    NASA Astrophysics Data System (ADS)

    Trizac, Emmanuel

    2005-11-01

    Granular gases are composed of macroscopic bodies kept in motion by an external energy source such as a violent shaking. The behaviour of such systems is quantitatively different from that of ordinary molecular gases: due to the size of the constituents, external fields have a stronger effect on the dynamics and, more importantly, the kinetic energy of the gas is no longer a conserved quantity. The key role of the inelasticity of collisions has been correctly appreciated for about fifteen years, and the ensuing consequences in terms of phase behaviour or transport properties studied in an increasing and now vast body of literature. The purpose of this book is to help the newcomer to the field in acquiring the essential theoretical tools together with some numerical techniques. As emphasized by the authors—who were among the pioneers in the domain— the content could be covered in a one semester course for advanced undergraduates, or it could be incorporated in a more general course dealing with the statistical mechanics of dissipative systems. The book is self-contained, clear, and avoids mathematical complications. In order to elucidate the main physical ideas, heuristic points of views are sometimes preferred to a more rigorous route that would lead to a longer discussion. The 28 chapters are short; they offer exercises and worked examples, solved at the end of the book. Each part is supplemented with a relevant foreword and a useful summary including take-home messages. The editorial work is of good quality, with very few typographical errors. In spite of the title, kinetic theory stricto sensu is not the crux of the matter covered. The authors discuss the consequences of the molecular chaos assumption both at the individual particle level and in terms of collective behaviour. The first part of the book addresses the mechanics of grain collisions. It is emphasized that considering the coefficient of restitution ? —a central quantity governing the inelasticity of inter-grain encounters—as velocity independent is inconsistent with the mechanical point of view. An asymptotic expression for the impact velocity dependence of ? is therefore derived for visco-elastic spheres. The important inelastic Boltzmann equation is introduced in part II and the associated velocity distribution characterized for a force-free medium (so-called free cooling regime). Transport processes can then be analyzed in part III at the single particle level, and part IV from a more macroscopic viewpoint. The corresponding Chapman Enskog-like hydrodynamic approach is worked out in detail, in a clear fashion. Finally, the tendency of granular gases to develop instabilities is illustrated in part V where the hydrodynamic picture plays a pivotal role. This book clearly sets the stage. For the sake of simplicity, the authors have discarded some subtle points, such as the open questions underlying the hydrodynamic description (why include the temperature among the hydrodynamic modes, and what about the separation of space and time scales between kinetic and hydrodynamic excitations?). Such omissions are understandable. To a certain extent however, the scope of the book is centered on previous work by the authors, and I have a few regrets. Special emphasis is put on the (variable ?) visco-elastic model, which enhances the technical difficulty of the presentation. On the other hand, the important physical effects including scaling laws, hydrodynamic behaviour and structure formation, can be understood in two steps, from the results derived within the much simpler constant ? model, allowing subsequently \\varepsilon to depend on the granular temperature. The authors justify their choice with the inconsistency of the constant ? route. The improvements brought by the visco-elastic model remain to be assessed, since the rotational degrees of freedom, discarded in the book, play an important role and require due consideration of both tangential and normal restitution coefficients, that are again velocity dependent. This seems to be the price of a cons

  2. Spatio-structural granularity of biological material entities

    Microsoft Academic Search

    Lars Vogt

    2010-01-01

    BACKGROUND: With the continuously increasing demands on knowledge- and data-management that databases have to meet, ontologies and the theories of granularity they use become more and more important. Unfortunately, currently used theories and schemes of granularity unnecessarily limit the performance of ontologies due to two shortcomings: (i) they do not allow the integration of multiple granularity perspectives into one granularity

  3. Compaction Waves in Granular HMX

    SciTech Connect

    E. Kober; R. Menikoff

    1999-01-01

    Piston driven compaction waves in granular HMX are simulated with a two-dimensional continuum mechanics code in which individual grains are resolved. The constitutive properties of the grains are modeled with a hydrostatic pressure and a simple elastic-plastic model for the shear stress. Parameters are chosen to correspond to inert HMX. For a tightly packed random grain distribution (with initial porosity of 19%) we varied the piston velocity to obtain weak partly compacted waves and stronger fully compacted waves. The average stress and wave speed are compatible with the porous Hugoniot locus for uni- axial strain. However, the heterogeneities give rise to stress concentrations, which lead to localized plastic flow. For weak waves, plastic deformation is the dominant dissipative mechanism and leads to dispersed waves that spread out in time. In addition to dispersion, the granular heterogeneities give rise to subgrain spatial variation in the thermodynamic variables. The peaks in the temperature fluctuations, known as hot spots, are in the range such that they are the critical factor for initiation sensitivity.

  4. Extensional Rheology of Granular Staples

    NASA Astrophysics Data System (ADS)

    Franklin, Scott

    2013-03-01

    Collections of U-shaped granular materials (e.g. staples) show a surprising resistance to being pulled apart. We conduct extensional stress-strain experiments on staple piles with vary arm/spine (barb) ratio. The elongation is not smooth, with the pile growing in bursts, reminiscent of intruder motion through ordinary and rod-like granular materials. The force-distance curve shows a power-law scaling, consistent with previous intruder experiments. Surprisingly, there is significant plastic creep of the pile as particles rearrange slightly in response to the increasing force. There is a broad distribution of yield forces that does not seem to evolve as the pile lengthens, suggesting that each yield event is independent of the pile's history. The distribution of yield forces can be interpreted in the context of a Weibullian weakest-link theory that predicts the maximum pile strength to decrease sharply with increasing pile length. From this interpretation arise length and force scales that may be used to characterize the sample.

  5. Nonlinear Sound during Granular Impact

    E-print Network

    Abram H. Clark; Alec J. Petersen; Lou Kondic; R. P. Behringer

    2014-08-08

    How do dynamic stresses propagate in granular material after a high-speed impact? This occurs often in natural and industrial processes. Stress propagation in a granular material is controlled by the inter-particle force law, $f$, in terms of particle deformation, $\\delta$, often given by $f\\propto\\delta^{\\alpha}$, with $\\alpha>1$. This means that a linear wave description is invalid when dynamic stresses are large compared to the original confining pressure. With high-speed video and photoelastic grains with varying stiffness, we experimentally study how forces propagate following an impact and explain the results in terms of the nonlinear force law (we measure $\\alpha\\approx 1.4$). The spatial structure of the forces and the propagation speed, $v_f$, depend on a dimensionless parameter, $M'=t_cv_0/d$, where $v_0$ is the intruder speed at impact, $d$ is the grain diameter, and $t_c$ is a binary collision time between grains with relative speed $v_0$. For $M'\\ll 1$, propagati ng forces are chain-like, and the measured $v_f \\propto d/t_c\\propto v_b(v_0/v_b)^\\frac{\\alpha-1}{\\alpha+1}$, where $v_b$ is the bulk sound speed. For larger $M'$, the force response has a 2D character, and forces propagate faster than predicted by $d/t_c$ due to collective stiffening of a packing.

  6. Uncertainty quantification and granular thermodynamics

    NASA Astrophysics Data System (ADS)

    Picka, Jeffrey D.

    2013-06-01

    To objectively assess a DEM model for granular flow, the DEM model must be able to randomly sample possible flow histories. Objective assessment is then based on comparing a sample of flows from the model with a sample of experimental flows by means of statistical inference. The practical implementation of this method of model assessment yields a model for the relationships among small collections of macroscopic flow variables. This model of relationships is analogous to models from classical thermodynamics, but is a fully stochastic summarization of bulk flow properties for a physical system that is not at equilibrium. It strongly distinguishes the microscale disorder within the flow from the between-experiment unpredictability of the bulk properties of the flow. It clearly identifies the sources of bulk property uncertainties, and allows ignorance of the detailed dynamics of the flow to be incorporated into the modelling process. This approach to constructing granular thermodynamic models will be compared with approaches to model development arising from modern statistical physics and with the development of the first thermodynamic models.

  7. Mortality of passerines adjacent to a North Carolina corn field treated with granular carbofuran.

    PubMed

    Augspurger, T; Smith, M R; Meteyer, C U; Converse, K A

    1996-01-01

    Red-winged blackbirds (Agelaius phoeniceus) were collected during an epizootic in southeastern North Carolina (USA). Activity of brain cholinesterase (ChE) was inhibited by 14 to 48% in three of five specimens, and returned to normal levels after incubation. Gastrointestinal tracts were analyzed for 30 anti-ChE agents. Carbofuran, the only compound detected, was present in all specimens at levels from 5.44 to 72.7 micrograms/g wet weight. Application of granular carbofuran in an adjacent corn field, results of necropsy examinations, and chemical analyses are consistent with a diagnosis of carbofuran poisoning in these specimens. PMID:8627921

  8. Cohesion, granular solids, granular liquids, and their connection to small near-Earth objects

    NASA Astrophysics Data System (ADS)

    Sánchez, P.; Scheeres, D.

    2014-07-01

    During the last 15 years or so, the Planetary Sciences community has been using Discrete Element Method (DEM) simulation codes to study small near-Earth objects (NEOs). In general, these codes treat gravitational aggregates as conglomerates of spherical particles; a good approximation given that many asteroids are self-gravitating granular media. Unfortunately, the degree of sophistication of these codes, and our own understanding, has not been high enough as to appropriately represent realistic physical properties of granular matter. In particular, angles of friction (?) and cohesive strength (?_c) of the aggregates were rarely taken in consideration and this could have led to unrealistic dynamics, and therefore, unrealistic conclusions about the dynamical evolution of small NEOs. In our research, we explore the failure mechanics of spherical (r=71 m) and ellipsoidal (r_1=92 m) self-gravitating aggregates with different angles of friction and values for their cohesive strength, in order to better understand the geophysics of rubble-pile asteroids. In particular we focused on the deformation and different disruption modes provoked by an always increasing angular velocity (spin rate). Scaling arguments allow us to regard simulations with the same aggregate size and different ?_c as equivalent to simulations of aggregates of different size and the same ?_c. We use a computational code that implements a Soft-Sphere DEM. The aggregates are composed by 3,000 spherical solid spheres (7--10 m) with 6 degrees of freedom. The code calculates normal, as well as, frictional (tangential) contact forces by means of soft potentials and the aggregate as a whole mimics the effect of non- spherical particles through the implementation of rolling friction. Cohesive forces, and a cohesive stress, are calculated as the net effect of the sum of the van der Waals forces between the smaller regolith, sand and dust (powder) that are present in real asteroids [1]. These finer materials form a matrix of sorts that holds the bigger boulders together. The aggregates were slowly spun up to disruption controlling for angle of friction, cohesion and global shape. Systems with no frictional forces had ?? 12° and are in effect granular liquids in the best case scenario. Systems with only surface-surface friction had ?? 25°, which is typical in laboratory experiments with spherical glass beads. Systems that also implemented rolling friction had ?? 35°, which is typical of non-cohesive granular media on the Earth. How much each aggregate deformed before disruption was directly related to the angle of friction. The greater ? allowed for much less deformation before disruption. Cohesive forces on the other hand controlled the mode of disruption and maximum spin rate and showed that the change from shedding to fission is continuous and therefore, they should not be seen as different disruption processes. The figure shows the deformation and disruption of three initially spherical aggregates (left) and three initially ellipsoidal aggregates (right) with increasing cohesive strength from left to right (?? 35°). Through scaling arguments we could also see these aggregates as having the exact same ?_c=25 Pa but different sizes. If we do that, the aggregates measure about 1.6 km, 5 km, and 22 km, and the particles, or groups of particles being detached now have similar sizes. This has now become a problem of resolution, i.e., the number and size of particles used in a simulation. These results start to raise fundamental questions regarding the difference between shedding and fission. Is it shedding when it is dust grain by dust grain ejection from the main body or when it is in groups of 10, 100, or 100,000 dust particles? Is it fission when a 1-m piece of the asteroid detaches or when it splits in the middle? Which values of ? and ?_c are realistic? These and other questions will be explored.

  9. Granular filtration in a fluidized bed

    SciTech Connect

    Mei, J.S.; Yue, P.C.; Halow, J.S.

    1995-12-01

    Successful development of advanced coal-fired power conversion systems often require reliable and efficient cleanup devices which can remove particulate and gaseous pollutants from high-temperature high-pressure gas streams. A novel filtration concept for particulate cleanup has been developed at the Morgantown Energy Technology Center (METC) of the U.S. Department of Energy. The filtration system consists of a fine metal screen filter immersed in a fluidized bed of granular material. As the gas stream passes through the fluidized bed, a layer of the bed granular material is entrained and deposited at the screen surface. This material provides a natural granular filter to separate fine particles from the gas stream passing through the bed. Since the filtering media is the granular material supplied by the fluidized bed, the filter is not subjected to blinding like candle filters. Because only the inflowing gas, not fine particle cohesive forces, maintains the granular layer at the screen surface, once the thickness and permeability of the granular layer is stabilized, it remains unchanged as long as the in-flowing gas flow rate remains constant. The weight of the particles and the turbulent nature of the fluidized bed limits the thickness of the granular layer on the filter leading to a self-cleaning attribute of the filter. This paper presents work since then on a continuous filtration system. The continuous filtration testing system consisted of a filter, a two-dimensional fluidized-bed, a continuous powder feeder, a laser-based in-line particle counting, sizing, and velocimeter (PCSV), and a continuous solids feeding/bed material withdrawal system. The two-dimensional, transparent fluidized-bed allowed clear observation of the general fluidized state of the granular material and the conditions under which fines are captured by the granular layer.

  10. Continuum description of avalanches in granular media.

    SciTech Connect

    Aranson, I. S.; Tsimring, L. S.

    2000-12-05

    A continuum theory of partially fluidized granular flows is proposed. The theory is based on a combination of the mass and momentum conservation equations with the order parameter equation which describes the transition between flowing and static components of the granular system. We apply this model to the dynamics of avalanches in chutes. The theory provides a quantitative description of recent observations of granular flows on rough inclined planes (Daerr and Douady 1999): layer bistability, and the transition from triangular avalanches propagating downhill at small inclination angles to balloon-shaped avalanches also propagating uphill for larger angles.

  11. The data reduction based on granular computing

    NASA Astrophysics Data System (ADS)

    Deng, Shaobo; Guan, Sujie

    2011-12-01

    This paper first defines the elementary granulation and the granulation, and other concepts, then we could convert decision tables to granular graph, and make visual presentation of them .some relevant knowledge of graph theory is applied to granular graph and its computing. In the paper it is shown that it is feasible and effective that granular graph is applied in describing data reduction. The method has the characteristic of simple and visual form and so on. Compared with other analysis methods, its time complexity is decreased to O(n).

  12. Surface structure determines dynamic wetting

    NASA Astrophysics Data System (ADS)

    Wang, Jiayu; Do-Quang, Minh; Cannon, James J.; Yue, Feng; Suzuki, Yuji; Amberg, Gustav; Shiomi, Junichiro

    2015-02-01

    Liquid wetting of a surface is omnipresent in nature and the advance of micro-fabrication and assembly techniques in recent years offers increasing ability to control this phenomenon. Here, we identify how surface roughness influences the initial dynamic spreading of a partially wetting droplet by studying the spreading on a solid substrate patterned with microstructures just a few micrometers in size. We reveal that the roughness influence can be quantified in terms of a line friction coefficient for the energy dissipation rate at the contact line, and that this can be described in a simple formula in terms of the geometrical parameters of the roughness and the line-friction coefficient of the planar surface. We further identify a criterion to predict if the spreading will be controlled by this surface roughness or by liquid inertia. Our results point to the possibility of selectively controlling the wetting behavior by engineering the surface structure.

  13. Surface structure determines dynamic wetting.

    PubMed

    Wang, Jiayu; Do-Quang, Minh; Cannon, James J; Yue, Feng; Suzuki, Yuji; Amberg, Gustav; Shiomi, Junichiro

    2015-01-01

    Liquid wetting of a surface is omnipresent in nature and the advance of micro-fabrication and assembly techniques in recent years offers increasing ability to control this phenomenon. Here, we identify how surface roughness influences the initial dynamic spreading of a partially wetting droplet by studying the spreading on a solid substrate patterned with microstructures just a few micrometers in size. We reveal that the roughness influence can be quantified in terms of a line friction coefficient for the energy dissipation rate at the contact line, and that this can be described in a simple formula in terms of the geometrical parameters of the roughness and the line-friction coefficient of the planar surface. We further identify a criterion to predict if the spreading will be controlled by this surface roughness or by liquid inertia. Our results point to the possibility of selectively controlling the wetting behavior by engineering the surface structure. PMID:25683872

  14. Numerical Simulations of Granular Processes

    NASA Astrophysics Data System (ADS)

    Richardson, Derek C.; Michel, Patrick; Schwartz, Stephen R.; Ballouz, Ronald-Louis; Yu, Yang; Matsumura, Soko

    2014-11-01

    Spacecraft images and indirect observations including thermal inertia measurements indicate most small bodies have surface regolith. Evidence of granular flow is also apparent in the images. This material motion occurs in very low gravity, therefore in a completely different gravitational environment than on the Earth. Understanding and modeling these motions can aid in the interpretation of imaged surface features that may exhibit signatures of constituent material properties. Also, upcoming sample-return missions to small bodies, and possible future manned missions, will involve interaction with the surface regolith, so it is important to develop tools to predict the surface response. We have added new capabilities to the parallelized N-body gravity tree code pkdgrav [1,2] that permit the simulation of granular dynamics, including multi-contact physics and friction forces, using the soft-sphere discrete-element method [3]. The numerical approach has been validated through comparison with laboratory experiments (e.g., [3,4]). Ongoing and recently completed projects include: impacts into granular materials using different projectile shapes [5]; possible tidal resurfacing of asteroid Apophis during its 2029 encounter [6]; the Brazil-nut effect in low gravity [7]; and avalanche modeling.Acknowledgements: DCR acknowledges NASA (grants NNX08AM39G, NNX10AQ01G, NNX12AG29G) and NSF (AST1009579). PM acknowledges the French agency CNES. SRS works on the NEOShield Project funded under the European Commission’s FP7 program agreement No. 282703. SM acknowledges support from the Center for Theory and Computation at U Maryland and the Dundee Fellowship at U Dundee. Most simulations were performed using the YORP cluster in the Dept. of Astronomy at U Maryland and on the Deepthought High-Performance Computing Cluster at U Maryland.References: [1] Richardson, D.C. et al. 2000, Icarus 143, 45; [2] Stadel, J. 2001, Ph.D. Thesis, U Washington; [3] Schwartz, S.R. et al. 2012, Gran. Matt. 14, 363. [4] Schwartz, S.R. et al. 2013, Icarus 226, 67; [5] Schwartz, S.R. et al. 2014, P&SS, 10.1016/j.pss.2014.07.013; [6] Yu, Y. et al. 2014, Icarus, 10.1016/j.icarus.2014.07.027; [7] Matsumura, S. et al. 2014, MNRAS, 10.1093/mnras/stu1388.

  15. Squeezing wetting and nonwetting liquids

    NASA Astrophysics Data System (ADS)

    Samoilov, V. N.; Persson, B. N. J.

    2004-01-01

    We present molecular-dynamics results for the squeezing of octane (C8H18) between two approaching solid elastic walls with different wetting properties. The interaction energy between the octane bead units and the solid walls is varied from a very small value (1 meV), corresponding to a nonwetting surface with a very large contact angle (nearly 180 degrees), to a high value (18.6 meV) corresponding to complete wetting. When at least one of the solid walls is wetted by octane we observe well defined molecular layers develop in the lubricant film when the thickness of the film is of the order of a few atomic diameters. An external squeezing-pressure induces discontinuous, thermally activated changes in the number n of lubricant layers (n?n-1 layering transitions). With increasing interaction energy between the octane bead units and the solid walls, the transitions from n to n-1 layers occur at higher average pressure. This results from the increasing activation barrier to nucleate the squeeze-out with increasing lubricant-wall binding energy (per unit surface area) in the contact zone. Thus, strongly wetting lubricant fluids are better boundary lubricants than the less wetting ones, and this should result in less wear. We analyze in detail the effect of capillary bridge formation (in the wetting case) and droplets formation (in the nonwetting case) on the forces exerted by the lubricant on the walls. For the latter case small liquid droplets may be trapped at the interface, resulting in a repulsive force between the walls during squeezing, until the solid walls come into direct contact, where the wall-wall interaction may be initially attractive. This effect is made use of in some practical applications, and we give one illustration involving conditioners for hair care application.

  16. PPCPs removal by aerobic granular sludge membrane bioreactor.

    PubMed

    Zhao, Xia; Chen, Zhong-Lin; Wang, Xiao-Chun; Shen, Ji-Min; Xu, Hao

    2014-12-01

    An aerobic granular sludge membrane bioreactor (GMBR) was applied to the treatment of pharmaceutical and personal care products (PPCPs) wastewater. The influence of granular sludge on five antibiotic and antiphlogistic PPCPs wastewater and the removal effect of methyl alcohol and conventional organic matter were investigated while constantly reducing the density of inflow organic matter. The results showed that the sludge granulation process in the system was rapid but unstable, and that the system exhibits a dissolution-reunion dynamic equilibrium. The reactor demonstrated varying removal effects of PPCPs on different objects. The use of a GMBR was more effective for the removal of prednisolone, naproxen, and ibuprofen; the first two drugs were lower the average removal rate of which reached 98.46 and 84.02 %, respectively; whereas the average removal rate of ibuprofen was 63.32 %. By contrast, the GMBR has an insignificant degradation effect on antibiotics such as amoxicillin, indicating that such antibiotic medicine is not easily degraded by microorganisms, which plays different roles in system operation. Because of the different chemical structures and characteristics of drugs that result in various degradation behavior. During the GMBR granulation process, the value of mixed liquor volatility suspended solids (MLVSS) gradually increases from 1.5 to 4.1 g/L during the GMBR granulation process, and the removal rate of CODCr reaches up to 87.98 %. After reducing the density of organic matter is reduced, the removal rates of NH3-N and TP both reach more than 90 %, respectively. Moreover, the proposed technique is considerably effective in the removal of methanol. PMID:25038925

  17. Pore-Scale Investigation on Stress-Dependent Characteristics of Granular Packs and Their Impact on Multiphase Fluid Distribution

    NASA Astrophysics Data System (ADS)

    Torrealba, V.; Karpyn, Z.; Yoon, H.; Hart, D. B.; Klise, K. A.

    2013-12-01

    The pore-scale dynamics that govern multiphase flow under variable stress conditions are not well understood. This lack of fundamental understanding limits our ability to quantitatively predict multiphase flow and fluid distributions in natural geologic systems. In this research, we focus on pore-scale, single and multiphase flow properties that impact displacement mechanisms and residual trapping of non-wetting phase under varying stress conditions. X-ray micro-tomography is used to image pore structures and distribution of wetting and non-wetting fluids in water-wet synthetic granular packs, under dynamic load. Micro-tomography images are also used to determine structural features such as medial axis, surface area, and pore body and throat distribution; while the corresponding transport properties are determined from Lattice-Boltzmann simulations performed on lattice replicas of the imaged specimens. Results are used to investigate how inter-granular deformation mechanisms affect fluid displacement and residual trapping at the pore-scale. This will improve our understanding of the dynamic interaction of mechanical deformation and fluid flow during enhanced oil recovery and geologic CO2 sequestration. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  18. Granular activated algae for wastewater treatment.

    PubMed

    Tiron, O; Bumbac, C; Patroescu, I V; Badescu, V R; Postolache, C

    2015-01-01

    The study used activated algae granules for low-strength wastewater treatment in sequential batch mode. Each treatment cycle was conducted within 24 h in a bioreactor exposed to 235 ?mol/m(2)/s light intensity. Wastewater treatment was performed mostly in aerobic conditions, oxygen being provided by microalgae. High removal efficiency of chemical oxygen demand (COD) was achieved (86-98%) in the first hours of the reaction phase, during which the indicator's removal rate was 17.4 ± 3.9 mg O2/g h; NH4(+) was removed during organic matter degradation processes with a rate of 1.8 ± 0.6 mg/g h. After almost complete COD removal, the NH4(+) remaining in the liquor was removed through nitrification processes promoted by the increase of the liquor's oxygen saturation (O2%), the transformation rate of NH4(+) into NO3(-) increasing from 0.14 ± 0.05 to 1.5 ± 0.4 mg NH4(+)/g h, along with an O2% increase. A wide removal efficiency was achieved in the case of PO4(3-) (11-85%), with the indicator's removal rate being 1.3 ± 0.7 mg/g h. In the provided optimum conditions, the occurrence of the denitrifying activity was also noticed. A large pH variation was registered (5-8.5) during treatment cycles. The granular activated algae system proved to be a promising alternative for wastewater treatment as it also sustains cost-efficient microalgae harvesting, with microalgae recovery efficiency ranging between 99.85 and 99.99% after granules settling with a velocity of 19 ± 3.6 m/h. PMID:25812091

  19. Surface wave acoustics of granular packing under gravity

    SciTech Connect

    Clement, Eric; Andreotti, Bruno [PMMH, ESPCI, CNRS (UMR 7636) and Univ. Paris 6 and Paris 7, 10 rue Vauquelin, 75005 Paris (France); Bonneau, Lenaic [PMMH, ESPCI, CNRS (UMR 7636) and Univ. Paris 6 and Paris 7, 10 rue Vauquelin, 75005 Paris (France)

    2009-06-18

    Due to the non-linearity of Hertzian contacts, the speed of sound in granular matter increases with pressure. For a packing under gravity and in the presence of a free surface, bulk acoustic waves cannot propagate due to the inherent refraction toward the surface (the mirage effect). Thus, only modes corresponding to surface waves (Raleigh-Hertz modes) are able to propagate the acoustic signal. First, based on a non-linear elasticity model, we describe the main features associated to these surface waves. We show that under gravity, a granular packing is from the acoustic propagation point of view an index gradient waveguide that selects modes of two distinct families i.e. the sagittal and transverse waves localized in the vicinity of the free surface. A striking feature of these surface waves is the multi-modal propagation: for both transverse and sagittal waves, we show the existence of a infinite but discrete series of propagating modes. In each case, we determine the mode shape and and the corresponding dispersion relation. In the case of a finite size system, a geometric waveguide is superimposed to the index gradient wave guide. In this later case, the dispersion relations are modified by the appearance of a cut-off frequency that scales with depth. The second part is devoted to an experimental study of surface waves propagating in a granular packing confined in a long channel. This set-up allows to tune a monomodal emission by taking advantage of the geometric waveguide features combined with properly designed emitters. For both sagittal and transverses waves, we were able to isolate a single mode (the fundamental one) and to plot the dispersion relation. This measurements agree well with the Hertzian scaling law as predicted by meanfield models. Furthermore, it allows us to determine quantitatively relations on the elastic moduli. However, we observe that our data yield a shear modulus abnormally weak when compared to several meanfield predictions.

  20. Fracture surfaces of granular pastes.

    PubMed

    Mohamed Abdelhaye, Y O; Chaouche, M; Van Damme, H

    2013-11-01

    Granular pastes are dense dispersions of non-colloidal grains in a simple or a complex fluid. Typical examples are the coating, gluing or sealing mortars used in building applications. We study the cohesive rupture of thick mortar layers in a simple pulling test where the paste is initially confined between two flat surfaces. After hardening, the morphology of the fracture surfaces was investigated, using either the box counting method to analyze fracture profiles perpendicular to the mean fracture plane, or the slit-island method to analyze the islands obtained by cutting the fracture surfaces at different heights, parallel to the mean fracture plane. The fracture surfaces were shown to exhibit scaling properties over several decades. However, contrary to what has been observed in the brittle or ductile fracture of solid materials, the islands were shown to be mass fractals. This was related to the extensive plastic flow involved in the fracture process. PMID:24241751

  1. Granular metamaterials for vibration mitigation

    NASA Astrophysics Data System (ADS)

    Gantzounis, G.; Serra-Garcia, M.; Homma, K.; Mendoza, J. M.; Daraio, C.

    2013-09-01

    Acoustic metamaterials that allow low-frequency band gaps are interesting for many practical engineering applications, where vibration control and sound insulation are necessary. In most prior studies, the mechanical response of these structures has been described using linear continuum approximations. In this work, we experimentally and theoretically address the formation of low-frequency band gaps in locally resonant granular crystals, where the dynamics of the system is governed by discrete equations. We investigate the quasi-linear behavior of such structures. The analysis shows that a stopband can be introduced at about one octave lower frequency than in materials without local resonances. Broadband and multi-frequency stopband characteristics can also be achieved by strategically tailoring the non-uniform local resonance parameters.

  2. Deformation patterns in granular materials

    NASA Astrophysics Data System (ADS)

    MacMinn, C. W.; Xue, Q. C.; Dufresne, E. R.; Wettlaufer, J. S.

    2013-12-01

    Motivated by a range of problems in geophysics where fluid injection drives the mechanical deformation of soils or rocks, we perform laboratory experiments in a model system. We inject fluid into a packing of soft particles and measure the dynamic, flow-driven deformation of the packing at high spatial resolution. We find that the mean deformation and relaxation of the packing can be described by continuum poroelastic theory, which also captures the buildup and dissipation of pressure at the injection point. We find, in contrast, that the granular microstructure leads to the spontaneous emergence of mesoscale deformation patterns such as shear bands that are absent from the continuum theory. We show that similar features develop during the simple compaction of such a material. We discuss the implications of these results.

  3. Mechanical characterization of jammable granular systems

    E-print Network

    Hudson, Shaymus William

    2012-01-01

    The mode by which a granular material can transition between fluid-like and solid-like states has been often referred to as jamming. The use of this property (via vacuum pressure) for engineering applications has only ...

  4. Nonlocal Constitutive Relation for Steady Granular Flow

    E-print Network

    Kamrin, Kenneth N.

    Extending recent modeling efforts for emulsions, we propose a nonlocal fluidity relation for flowing granular materials, capturing several known finite-size effects observed in steady flow. We express the local Bagnold-type ...

  5. Adsorption of dissolved natural organic matter by modified activated carbons

    Microsoft Academic Search

    Wei Cheng; Seyed A. Dastgheib; Tanju Karanfil

    2005-01-01

    Adsorption of dissolved natural organic matter (DOM) by virgin and modified granular activated carbons (GACs) was studied. DOM samples were obtained from two water treatment plants before (i.e., raw water) and after coagulation\\/flocculation\\/sedimentation processes (i.e., treated water). A granular activated carbon (GAC) was modified by high temperature helium or ammonia treatment, or iron impregnation followed by high temperature ammonia treatment.

  6. Granular neural web agents for stock prediction

    Microsoft Academic Search

    Yan-qing Zhang; Somasheker Akkaladevi; George J. Vachtsevanos; Tsau Young Lin

    2002-01-01

    A granular neural Web-based stock prediction agent is developed using the granular neural network (GNN) that can discover fuzzy rules. Stock data sets are downloaded from www.yahoo.com website. These data sets are inserted into the database tables using a java program. Then, the GNN is trained using sample data for any stock. After learning from the past stock data, the

  7. Heterogeneities in Aging Models of Granular Compaction

    E-print Network

    Jeferson J. Arenzon

    2006-09-21

    Kinetically constrained models (KCM) are systems with trivial thermodynamics but often complex dynamical behavior due to constraints on the accessible paths followed by the system. Exploring these properties, the Kob-Andersen (KA) model was introduced to study the slow dynamics of glass forming liquids and later extended to granular materials. In this last context, we present new results on the heterogeneous character of both in and out of equilibrium dynamics, further stretching the granular-glass analogy.

  8. Shear dispersion in dense granular flows

    E-print Network

    Christov, Ivan C

    2014-01-01

    We formulate and solve a model problem of dispersion of dense granular materials in rapid shear flow down an incline. The effective dispersivity of the depth-averaged concentration of the dispersing powder is shown to vary as the P\\'eclet number squared, as in classical Taylor--Aris dispersion of molecular solutes. An extensions to generic shear profiles is presented, and possible applications to industrial and geological granular flows are noted.

  9. Signatures of Unconventional Superconductivity in Granular Aluminum

    NASA Astrophysics Data System (ADS)

    Bachar, N.; Pracht, U. S.; Farber, E.; Dressel, M.; Deutscher, G.; Scheffler, M.

    2015-04-01

    We present measurements of the complex transmission of superconducting granular aluminum thin films in the THz optical range. We discuss the dynamical conductivity and temperature-dependent energy gap of two films of different granular coupling. While the film of well-coupled grains follows the predictions for a conventional BCS superconductor, signatures of enhanced absorption are found at sub-gap frequencies when coupling is decreased. We discuss possible explanations which might account for the observed deviations from BCS theory.

  10. Capillary bonding of wet surfaces

    Microsoft Academic Search

    Samuel C. Colbeck

    1996-01-01

    Adhesion of wet surfaces to one another through a water film is common and important for a variety of problems. The nature of this adhesion is explored through a simple model of a grooved polyethylene surface adhering to ice. The effects of contact angle and geometry are included. A set of experiments was performed to show how contact area and

  11. Wetting of textured hydrophobic surfaces

    Microsoft Academic Search

    Matthew Hancock; John Bush

    2008-01-01

    Water repellency in nature and technology typically results from textured hydrophobic surfaces. The roughness elements of such surfaces typically have edges that pin the contact lines of advancing droplets. We present the results of a numerical investigation that relates the contact angle hysteresis and adhesive force to the geometrical, wetting, and elastic properties of the substrate. A number of generic

  12. CEILCOTE IONIZING WET SCRUBBER EVALUATION

    EPA Science Inventory

    The report gives results of an evaluation of a Ceilcote ionizing wet scrubber installed on a refractory brick kiln. Tests involved particulate mass emission, particle size distribution, and opacity. Overall efficiency was 93% with an average outlet opacity determined with a heate...

  13. Dissolutive Wetting: What Controls Spreading?

    E-print Network

    Maryland at College Park, University of

    Boettinger, NIST Modeling the early stages of reactive wetting, Daniel Wheeler, James A. Warren and William J the phase field method No special algorithms Fundamental Based on thermo (not ad-hoc) nano? -- micro with appropriate fluxes) NEED TO ENSURE ENTROPY PRODUCTION IS POSITIVE BY POSTULATING CONSTITUTIVE LAWS

  14. Materials resist wet coal abrasion

    SciTech Connect

    Green, P.

    1983-01-01

    The use of wear-resistant lining materials in coal preparation and coal handling plants to reduce the abrasion caused by wet coal is discussed. Various types of material such as ceramics, polyethylene, polyurethane and epoxies are considered and the ways in which they may be applied are described.

  15. Contact micromechanics in granular media with clay

    SciTech Connect

    Ita, S.L.

    1994-08-01

    Many granular materials, including sedimentary rocks and soils, contain clay particles in the pores, grain contacts, or matrix. The amount and location of the clays and fluids can influence the mechanical and hydraulic properties of the granular material. This research investigated the mechanical effects of clay at grain-to-grain contacts in the presence of different fluids. Laboratory seismic wave propagation tests were conducted at ultrasonic frequencies using spherical glass beads coated with Montmorillonite clay (SWy-1) onto which different fluids were adsorbed. For all bead samples, seismic velocity increased and attenuation decreased as the contact stiffnesses increased with increasing stress demonstrating that grain contacts control seismic transmission in poorly consolidated and unconsolidated granular material. Coating the beads with clay added stiffness and introduced viscosity to the mechanical contact properties that increased the velocity and attenuation of the propagating seismic wave. Clay-fluid interactions were studied by allowing the clay coating to absorb water, ethyl alcohol, and hexadecane. Increasing water amounts initially increased seismic attenuation due to clay swelling at the contacts. Attenuation decreased for higher water amounts where the clay exceeded the plastic limit and was forced from the contact areas into the surrounding open pore space during sample consolidation. This work investigates how clay located at grain contacts affects the micromechanical, particularly seismic, behavior of granular materials. The need for this work is shown by a review of the effects of clays on seismic wave propagation, laboratory measurements of attenuation in granular media, and proposed mechanisms for attenuation in granular media.

  16. Thermodynamics and kinetic theory of granular materials

    NASA Astrophysics Data System (ADS)

    Kremer, Gilberto M.

    2014-03-01

    The aim of this work is two-fold, first a kinetic theory is developed to determine the entropy balance equation for granular gases and second a thermodynamic theory of granular materials is established within the framework of continuum thermodynamics. Unlike to the entropy inequality of a simple fluid, the one obtained from the Boltzmann equation for a granular gas has a term which can be identified as the entropy density rate. For processes closed to equilibrium the entropy density, its flux, the entropy density and production rates are obtained from a non-equilibrium distribution function. A spatially homogeneous problem is also analyzed and it is shown that the entropy decay of a granular gas is associated with its temperature decay. A thermodynamic theory of granular materials is developed where the constitutive laws are restricted by the principle of material frame indifference and by the entropy principle. The results that follow from the exploitation of the entropy principle with the method of Lagrange multipliers are compared with those obtained from the kinetic theory of granular gases.

  17. Production of granular ammonium polyphosphate from wet-process phosphoric acid

    SciTech Connect

    Parker, B.R.

    1984-01-01

    Although solid ammonium orthophosphates, such as MAP and DAP, are excellent fertilizer materials, the advantages of solid materials containing polyphosphate have been shown, particularly in connection with their use to make fluid fertilizers. The demonstration-scale pipe reactor/pug mill process at TVA has produced an excellent product; however, a suitable APP product also can be made with the pipe/drum granulator process, which is simpler, more economical, and readily adaptable to granulation plants in which pipe-cross reactors have been installed. This APP product is comparable to MAP for direct application and bulk blending, and it produces superior suspensions. The cost of production of APP should be no more than about 1% higher than that for MAP. APP also can be produced from sludge acid. So, it appears that production of APP containing 10% of the P/sub 2/O/sub 5/ as polyphosphate, instead of producing MAP, would be beneficial. TVA is in the process of modifying a TVA demonstration-scale plant to demonstrate the production of APP with the pipe reactor/drum granulator process. This 20-ton-per-hour unit is scheduled to start up in July 1985.

  18. Granular Matter, Foams, and Beyond: Applications of the Granocentric Model

    NASA Astrophysics Data System (ADS)

    Newhall, Katherine

    2012-02-01

    We present a local stochastic model that predicts the statistical fluctuations in jammed packings of monodisperse and polydisperse spheres revealed by confocal microscopy. Moreover, we find that this model can account for the properties of looser and denser random packings that result from depletion attraction between the particles or compression by an applied load, respectively. Finally, we extend the model to space-filling packings of cells in tissues and biliquid foams by testing analytic predictions for the dependence of the number of neighbors of a given cell on its volume. Interestingly, the model distinguishes between scenarios in which size or positional disorder in the packing dominate, in good agreement with experimental data. This versatile model can be put into the statistical mechanics framework proposed by Edwards in order to compute the entropy and compactivity of each packing.

  19. Micro-Macro and Rheology in sheared Granular Matter

    E-print Network

    Luding, Stefan

    , but did not cave in Made me think soil is solid ! Growing older one day, I read about the Leaning Tower of Pisa and I saw a horrible landslide The same soil That lies beneath my foot looked different than

  20. Granular Matter manuscript No. (will be inserted by the editor)

    E-print Network

    Luding, Stefan

    -tests. As an example, as the basis for silo-design, the Jenike procedure to measure the so-called "incipient yield lo of Newton's equations of motion [4; 5] of all particles. Finding the connection between the micro

  1. Uncertainty Management in Seismic Vulnerability Assessment Using Granular Computing Based on Covering of Universe

    NASA Astrophysics Data System (ADS)

    Khamespanah, F.; Delavar, M. R.; Zare, M.

    2013-05-01

    Earthquake is an abrupt displacement of the earth's crust caused by the discharge of strain collected along faults or by volcanic eruptions. Earthquake as a recurring natural cataclysm has always been a matter of concern in Tehran, capital of Iran, as a laying city on a number of known and unknown faults. Earthquakes can cause severe physical, psychological and financial damages. Consequently, some procedures should be developed to assist modelling the potential casualties and its spatial uncertainty. One of these procedures is production of seismic vulnerability maps to take preventive measures to mitigate corporeal and financial losses of future earthquakes. Since vulnerability assessment is a multi-criteria decision making problem depending on some parameters and expert's judgments, it undoubtedly is characterized by intrinsic uncertainties. In this study, it is attempted to use Granular computing (GrC) model based on covering of universe to handle the spatial uncertainty. Granular computing model concentrates on a general theory and methodology for problem solving as well as information processing by assuming multiple levels of granularity. Basic elements in granular computing are subsets, classes, and clusters of a universe called elements. In this research GrC is used for extracting classification rules based on seismic vulnerability with minimum entropy to handle uncertainty related to earthquake data. Tehran was selected as the study area. In our previous research, Granular computing model based on a partition model of universe was employed. The model has some kinds of limitations in defining similarity between elements of the universe and defining granules. In the model similarity between elements is defined based on an equivalence relation. According to this relation, two objects are similar based on some attributes, provided for each attribute the values of these objects are equal. In this research a general relation for defining similarity between elements of universe is proposed. The general relation is used for defining similarity and instead of partitioning the universe, granulation is done based on covering of universe. As a result of the study, a physical seismic vulnerability map of Tehran has been produced based on granular computing model. The accuracy of the seismic vulnerability map is evaluated using granular computing model based on covering of universe. The comparison between this model and granular computing model based on partition model of universe is undertaken which verified the superiority of the GrC based on covering of the universe in terms of the match between the achieved results with those confirmed by the related experts' judgments.

  2. Nonlinear effects for coda-type elastic waves in stressed granular media

    NASA Astrophysics Data System (ADS)

    Tournat, V.; Gusev, V. E.

    2009-07-01

    Experimental results and their interpretations are presented on the nonlinear acoustic effects of multiple scattered elastic waves in unconsolidated granular media. Short wave packets with a central frequency higher than the so-called cutoff frequency of the medium are emitted at one side of the statically stressed slab of glass beads, and received at the other side after multiple-scattering and nonlinear elastic effects. Typical signals are strongly distorted compared to their initially radiated shape both due to nonlinearity and scattering. It is shown that acoustic waves with a deformation amplitude much lower than the mean static deformation of the contacts in the medium can modify the elastic properties of the medium. This addresses the problem of acoustic wave action on granular matter during and after acoustic excitation, which is necessary to understand in the nondestructive testing of the elastic properties of granular media by acoustic methods. Coda signal analysis is shown to be a powerful time-resolved tool in monitoring slight modifications in the elastic response of an unconsolidated granular structure.

  3. Numerical analysis of granular soil fabrics

    NASA Astrophysics Data System (ADS)

    Torbahn, L.; Huhn, K.

    2012-04-01

    Soil stability strongly depends on the material strength that is in general influenced by deformation processes and vice versa. Hence, investigation of material strength is of great interest in many geoscientific studies where soil deformations occur, e.g. the destabilization of slopes or the evolution of fault gouges. Particularly in the former case, slope failure occurs if the applied forces exceed the shear strength of slope material. Hence, the soil resistance or respectively the material strength acts contrary to deformation processes. Besides, geotechnical experiments, e.g. direct shear or ring shear tests, suggest that shear resistance mainly depends on properties of soil structure, texture and fabric. Although laboratory tests enable investigations of soil structure and texture during shear, detailed observations inside the sheared specimen during the failure processes as well as fabric effects are very limited. So, high-resolution information in space and time regarding texture evolution and/or grain behavior during shear is refused. However, such data is essential to gain a deeper insight into the key role of soil structure, texture, etc. on material strength and the physical processes occurring during material deformation on a micro-scaled level. Additionally, laboratory tests are not completely reproducible enabling a detailed statistical investigation of fabric during shear. So, almost identical setups to run methodical tests investigating the impact of fabric on soil resistance are hard to archive under laboratory conditions. Hence, we used numerical shear test experiments utilizing the Discrete Element Method to quantify the impact of different material fabrics on the shear resistance of soil as this granular model approach enables to investigate failure processes on a grain-scaled level. Our numerical setup adapts general settings from laboratory tests while the model characteristics are fixed except for the soil structure particularly the used grain shapes. So, ideal round or stick- and plate-shaped grains were utilized to represent natural silts or clays to test two end-members. To quantify texture influences on soil strength, physical parameters, e.g. soil resistance, were calculated during deformation process. Furthermore, fabric analysis during shear reveals new information on detailed pore space regarding distribution and shape of voids. For this, a three-dimensional visualization of pore space is realized with the Visualization Toolkit (VTK) that allows the volume calculation and hence a quantification of single voids with progressive deformation. As a result, imaging of particle contact distribution and particle orientations within samples show significant changes with ongoing strain such as strong variations in material fabric and particle re-organization and therewith significant structural changes. These findings confirm that in general grain shape and its factor of soil fabric is not negligible for soil resistance and hence soil strength. This is notably affected by the deformation behavior of granular matter. With the broad investigation of the three most important factors that specify fabric behavior, this study attains a comprehensive view evaluating the impact of fabric on soil strength.

  4. WET LOOSE SNOW AVALANCHING IN SOUTHWESTERN MONTANA Simon August Trautman

    E-print Network

    Lawrence, Rick L.

    WET LOOSE SNOW AVALANCHING IN SOUTHWESTERN MONTANA by Simon August Trautman A thesis submitted ..........................................................................................................1 2. WET SNOW...................................................................................................................3 Metamorphism of Wet Snow

  5. 7 CFR 51.897 - Wet.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...United States Standards for Grades of Table Grapes (European or Vinifera Type) 1 Definitions...51.897 Wet. Wet means that the grapes are wet from moisture from crushed, leaking, or decayed berries or from rain. Grapes which are moist from dew or other...

  6. 7 CFR 51.897 - Wet.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...United States Standards for Grades of Table Grapes (European or Vinifera Type) 1 Definitions...51.897 Wet. Wet means that the grapes are wet from moisture from crushed, leaking, or decayed berries or from rain. Grapes which are moist from dew or other...

  7. 7 CFR 51.897 - Wet.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...United States Standards for Grades of Table Grapes (European or Vinifera Type) 1 Definitions...51.897 Wet. Wet means that the grapes are wet from moisture from crushed, leaking, or decayed berries or from rain. Grapes which are moist from dew or other...

  8. 7 CFR 51.897 - Wet.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...United States Standards for Grades of Table Grapes (European or Vinifera Type) 1 Definitions...51.897 Wet. Wet means that the grapes are wet from moisture from crushed, leaking, or decayed berries or from rain. Grapes which are moist from dew or other...

  9. 7 CFR 51.897 - Wet.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...United States Standards for Grades of Table Grapes (European or Vinifera Type) 1 Definitions...51.897 Wet. Wet means that the grapes are wet from moisture from crushed, leaking, or decayed berries or from rain. Grapes which are moist from dew or other...

  10. Constraining Mercury Oxidation Using Wet Deposition

    E-print Network

    Selin, Noelle Eckley

    Constraining Mercury Oxidation Using Wet Deposition Noelle E. Selin and Christopher D. Holmes mercury oxidation [Selin & Jacob, Atmos. Env. 2008] 30 60 90 120 150 30 60 90 120 150 30 60 90 120 150 30 Influences on Mercury Wet Deposition · Hg wet dep = f(precipitation, [Hg(II)+Hg(P)]) Correlation (r2) between

  11. Uniform and mixed wetting in square capillaries

    Microsoft Academic Search

    Kristine Spildo; Jill S. Buckley

    1999-01-01

    Square capillaries provide a better model of the pore space in rocks than do capillary tubes of circular cross-section because they have corners where wetting fluid can be retained. We report experimental observations of imbibition of an aqueous phase into square capillary tubes with uniform and mixed wetting. Each capillary had an oil-wet end to ensure that water imbibed in

  12. Driven fragmentation of granular gases

    NASA Astrophysics Data System (ADS)

    Cruz Hidalgo, Raúl; Pagonabarraga, Ignacio

    2008-06-01

    The dynamics of homogeneously heated granular gases which fragment due to particle collisions is analyzed. We introduce a kinetic model which accounts for correlations induced at the grain collisions and analyze both the kinetics and relevant distribution functions these systems develop. The work combines analytical and numerical studies based on direct simulation Monte Carlo calculations. A broad family of fragmentation probabilities is considered, and its implications for the system kinetics are discussed. We show that generically these driven materials evolve asymptotically into a dynamical scaling regime. If the fragmentation probability tends to a constant, the grain number diverges at a finite time, leading to a shattering singularity. If the fragmentation probability vanishes, then the number of grains grows monotonously as a power law. We consider different homogeneous thermostats and show that the kinetics of these systems depends weakly on both the grain inelasticity and driving. We observe that fragmentation plays a relevant role in the shape of the velocity distribution of the particles. When the fragmentation is driven by local stochastic events, the long velocity tail is essentially exponential independently of the heating frequency and the breaking rule. However, for a Lowe-Andersen thermostat, numerical evidence strongly supports the conjecture that the scaled velocity distribution follows a generalized exponential behavior f(c)˜exp(-cn) , with n?1.2 , regarding less the fragmentation mechanisms.

  13. Mechanics of Granular Materials (MGM)

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The packing of particles can change radically during cyclic loading such as in an earthquake or when shaking a container to compact a powder. A large hole (1) is maintained by the particles sticking to each other. A small, counterclockwise strain (2) collapses the hole, and another large strain (3) forms more new holes which collapse when the strain reverses (4). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (after T.L. Youd, Packing Changes and Liquefaction Susceptibility, Journal of the Geotechnical Engieering Division, 103: GT8,918-922, 1977)(Credit: NASA/Marshall Space Flight Center.)(Credit: University of Colorado at Boulder).

  14. Traffic equations and granular convection

    NASA Astrophysics Data System (ADS)

    Hong, Daniel C.; Yue, Su

    1998-10-01

    We investigate both numerically and analytically the convective instability of granular materials by two-dimensional traffic equations. In the absence of vibrations traffic equations assume two distinctive classes of fixed bed solutions with either a spatially uniform or nonuniform density profile. The former one exists only when the function V(?) that monitors the relaxation of grains assumes a cutoff at the closed packed density, ?c, with V(?c)=0, while the latter one exists for any form of V. Since there is little difference between the uniform and nonuniform solution deep inside the bed, the convective instability of the bulk may be studied by focusing on the stability of the uniform solution. In the presence of vibrations, we find that the uniform solution bifurcates into a bouncing solution, which then undergoes a supercritical bifurcation to the convective instability. We determine the onset of convection as a function of control parameters and confirm this picture by solving the traffic equations numerically, which reveals bouncing solutions, two convective rolls, and four convective rolls. Further, convective patterns change as the aspect ratio changes: in a vertically long container, the rolls move toward the surface, and in a horizontally long container, the rolls move toward the side walls. We compare these results with the those reported previously with a different continuum model by Hayakawa, Yue, and Hong [Phys. Rev. Lett. 75, 2328 (1995)]. Finally, we also present a derivation of the traffic equations from Enskoq equation.

  15. Continuum Modeling of Secondary Rheology in Dense Granular Materials

    E-print Network

    Henann, David L.

    Recent dense granular flow experiments have shown that shear deformation in one region of a granular medium fluidizes its entirety, including regions far from the sheared zone, effectively erasing the yield condition ...

  16. Stochastic and deterministic models for dense granular flow

    E-print Network

    Kamrin, Kenneth Norman

    2008-01-01

    Granular materials such as sand or gravel surround us everyday and yet remain poorly understood. In this thesis, two models are developed for dense granular flow, each capable of predicting flows with accuracy in multiple ...

  17. Jamming transition in emulsions and granular materials.

    PubMed

    Zhang, H P; Makse, H A

    2005-07-01

    We investigate the jamming transition in packings of emulsions and granular materials via molecular dynamics simulations. The emulsion model is composed of frictionless droplets interacting via nonlinear normal forces obtained using experimental data acquired by confocal microscopy of compressed emulsions systems. Granular materials are modeled by Hertz-Mindlin deformable spherical grains with Coulomb friction. In both cases, we find power-law scaling for the vanishing of pressure and excess number of contacts as the system approaches the jamming transition from high volume fractions. We find that the construction history parametrized by the compression rate during the preparation protocol has a strong effect on the micromechanical properties of granular materials but not on emulsions. This leads the granular system to jam at different volume fractions depending on the histories. Isostaticity is found in the packings close to the jamming transition in emulsions and in granular materials at slow compression rates and infinite friction. Heterogeneity of interparticle forces increases as the packings approach the jamming transition which is demonstrated by the exponential tail in force distributions and the small values of the participation number measuring spatial localization of the forces. However, no signatures of the jamming transition are observed in structural properties, like the radial distribution functions and the distributions of contacts. PMID:16089950

  18. Granular Materials and Risks In ISRU

    NASA Technical Reports Server (NTRS)

    Behringer, Robert P.; Wilkinson, R. Allen

    2004-01-01

    Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to execute these operations on the Moon and Mars as we do on Earth. We discuss how little these processes are understood and point out the nature of trial-and-error practices that are used in today's massive over-design. Nevertheless, such designs have a high failure rate. Implementation and extensive incremental scaling up of industrial processes are routine because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, what some of the basic issues are, and what understanding is needed to greatly reduce the risks. This talk will focus on a particular class of granular flow issues, those that pertain to dense materials, their physics, and the failure problems associated with them. In particular, key issues where basic predictability is lacking include stability of soils for the support of vehicles and facilities, ability to control the flow of dense materials (jamming and flooding/unjamming at the wrong time), the ability to predict stress profiles (hence create reliable designs) for containers such as bunkers or silos. In particular, stress fluctuations, which are not accounted for in standard granular design models, can be very large as granular materials flows, and one result is frequent catastrophic failure of granular devices.

  19. Granular Materials and Risks in ISRU

    NASA Technical Reports Server (NTRS)

    Behringer, Robert P.; Wilki8nson, R. Allen

    2004-01-01

    Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to execute these operations on the Moon and Mars as we do on Earth. We discuss how little these processes are understood and point out the nature of trial-and-error practices that are used in today s massive over-design. Nevertheless, such designs have a high failure rate. Implementation and extensive incremental scaling up of industrial processes are routine because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, what some of the basic issues are, and what understanding is needed to greatly reduce the risks. This talk will focus on a particular class of granular flow issues, those that pertain to dense materials, their physics, and the failure problems associated with them. In particular, key issues where basic predictability is lacking include stability of soils for the support of vehicles and facilities, ability to control the flow of dense materials (jamming and flooding/unjamming at the wrong time), the ability to predict stress profiles (hence create reliable designs) for containers such as bunkers or silos. In particular, stress fluctuations, which are not accounted for in standard granular design models, can be very large as granular materials flows, and one result is frequent catastrophic failure of granular devices.

  20. Granular Solid Hydrodynamics: Dense Flow, Fluidization and Jamming

    E-print Network

    Stefan Mahle; Yimin Jiang; Mario Liu

    2010-10-26

    Granular solid hydrodynamics, constructed to describe quasi-elastic and plastic motion of granular solid, is shown also capable of accounting for the rheology of granular dense flow. This makes it a unified, though still qualitative, hydrodynamic description, enabling one to tackle fluidization and jamming, the hysteretic transition between elasto-plastic motion and uniform dense flow.

  1. From elasticity to hypoplasticity: dynamics of granular solids.

    PubMed

    Jiang, Yimin; Liu, Mario

    2007-09-01

    "Granular elasticity," useful for calculating static stress distributions in granular media, is generalized by including the effects of slowly moving, deformed grains. The result is a hydrodynamic theory for granular solids that agrees well with models from soil mechanics. PMID:17930395

  2. 76 FR 4936 - Granular Polytetrafluoroethylene Resin From Italy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-27

    ...identified a review on granular PTFE resin from Japan, it did not...review of the order on granular PTFE resin from Italy. Instead...cut-to-length carbon quality steel plate...antidumping duty orders on granular PTFE from Italy and Japan, and...

  3. EXTENDING KAMP THEOREM WITH BINARY OPERATORS TO MODEL TIME GRANULARITY

    E-print Network

    Peron, Adriano

    EXTENDING KAMP THEOREM WITH BINARY OPERATORS TO MODEL TIME GRANULARITY ANGELO MONTANARI, ADRIANO PERON, AND ALBERTO POLICRITI Abstract. In this paper, a generalization of Kamp theorem relative granularity in !­layered temporal structures. Keywords: Kamp theorem, linear temporal logic, time granularity

  4. Physica D 133 (1999) 117 Predictability and granular materials

    E-print Network

    Kondic, Lou

    Physica D 133 (1999) 1­17 Predictability and granular materials R.P. Behringer a, , Daniel Howell Abstract Granular materials present a number of challenges to predictability. The classical description of a dense granular material is based on Coulomb friction. For a static array of grains, the Coulomb friction

  5. From liquid to solid bonding in cohesive granular media

    E-print Network

    Jean-Yves Delenne; Fabien Soulié; Moulay Saïd El Youssoufi; Farhang Radjaï

    2010-02-26

    We study the transition of a granular packing from liquid to solid bonding in the course of drying. The particles are initially wetted by a liquid brine and the cohesion of the packing is ensured by capillary forces, but the crystallization of the solute transforms the liquid bonds into partially cemented bonds. This transition is evidenced experimentally by measuring the compressive strength of the samples at regular intervals of times. Our experimental data reveal three regimes: 1) Up to a critical degree of saturation, no solid bonds are formed and the cohesion remains practically constant; 2) The onset of cementation occurs at the surface and a front spreads towards the center of the sample with a nonlinear increase of the cohesion; 3) All bonds are partially cemented when the cementation front reaches the center of the sample, but the cohesion increases rapidly due to the consolidation of cemented bonds. We introduce a model based on a parametric cohesion law at the bonds and a bond crystallization parameter. This model predicts correctly the phase transition and the relation between microscopic and macroscopic cohesion.

  6. Degradation of phenylamine by catalytic wet air oxidation using metal catalysts with modified supports.

    PubMed

    Torrellas, Silvia A; Escudero, Gabriel O; Rodriguez, Araceli R; Rodriguez, Juan G

    2015-03-21

    The effect of acid treatments with HCl and HNO3 on the surface area and surface chemistry of three granular activated carbons was studied. These supports were characterized and the hydrochloric acid treatment leads to the best activated carbon support (AC2-C). The catalytic behavior of Pt, Ru and Fe (1 wt.%) supported on granular activated carbon treated with HCl was tested in the phenylamine continuous catalytic wet air oxidation in a three-phase, high-pressure catalytic reactor over a range of reaction temperatures 130-170ºC and total pressure of 1.0-3.0 MPa at LHSV = 0.4-1 h(-1), whereas the phenylamine concentration range and the catalyst loading were 5-16 mol.m(-3) and 0.5-1.5 g, respectively. Activity as well as conversion varied as a function of the metal, the catalyst preparation method and operation conditions. Higher activities were obtained with Pt incorporated on hydrochloric acid -treated activated carbon by the ion exchange method. In steady state, approximately 98% phenylamine conversion, 77% of TOC and 94% of COD removal, was recorded at 150ºC, 11 mol m(-3) of phenylamine concentration and 1.5 g of catalyst, and the selectivity to non-organic compounds was 78%. Several reaction intermediaries were detected. A Langmuir-Hinshelwood model gave an excellent fit of the kinetic data of phenylamine continuous catalytic wet air oxidation over the catalysts of this work. PMID:25723063

  7. Flow and jamming of sheared granular media

    NASA Astrophysics Data System (ADS)

    Ciamarra, M. Pica; Nicodemi, M.; Coniglio, A.

    2009-06-01

    Granular materials, such as athermal suspensions, can either be jammed and rigid, or yield and flow. Recent experiments on granular suspensions in a annular shear cell (vibrated and/or sheared) show a hysteretic freezing and melting transition [1, 2]: a crystallised state is found, which can be melted by sufficient shear. The question is open on what are the mechanisms underlying these phenomena and which are the control parameters. Via Molecular Dynamics simulations, we study the rheology of vibrated and sheared granular materials [3]. In particular, we aim to understand the nature of a critical line separating crystallised and melted states and the "jammed" region in the phase diagram, as well as the connections with thermal glass formers and colloidal suspensions.

  8. Granular cell tumor of the suprasternal space.

    PubMed

    Ihara, Koji; Ito, Hiroshi; Nakajima, Yumiko; Fukaya, Eri; Nakazawa, Hiroaki; Nozaki, Motohiro

    2010-10-01

    A case of granular cell tumor (GCT) was reported. We encountered a 33-year-old woman with a painless, elastic, hard mass in the soft tissue of the suprasternal space. The tumor was excised with several millimeters margin of normal tissue above the deep cervical fascia and the wound was closed primarily. Histological examination on hematoxylin-eosin stain showed a tumor growth in the mid- to deep dermis and eosinophilic small granules that were consistent with granular cell tumors. Immunohistochemical studies showed positive staining for S-100 protein. We experienced a case of a granular cell tumor occurring in the suprasternal space and report the importance of including it in the differential diagnosis of subcutaneous soft tissue tumors. PMID:20860741

  9. Shock waves in a dilute granular gas

    NASA Astrophysics Data System (ADS)

    Reddy, M. H. Lakshminarayana; Ansumali, Santosh; Alam, Meheboob

    2014-12-01

    We study the evolution of shock waves in a dilute granular gas which is modelled using three variants of hydrodynamic equations: Euler, 10-moment and 14-moment models. The one-dimensional shock-wave problem is formulated and the resulting equations are solved numerically using a relaxation-type scheme. Focusing on the specific case of blast waves, the results on the density, the granular temperature, the skew temperature, the heat flux and the fourth moment are compared among three models. We find that the shock profiles are smoother for the 14-moment model compared to those predicted by the standard Euler equations. A shock-splitting phenomenon is observed in the skew granular temperature profiles for a blast wave.

  10. Image Superresolution Reconstruction via Granular Computing Clustering

    PubMed Central

    Liu, Hongbing; Zhang, Fan; Wu, Chang-an; Huang, Jun

    2014-01-01

    The problem of generating a superresolution (SR) image from a single low-resolution (LR) input image is addressed via granular computing clustering in the paper. Firstly, and the training images are regarded as SR image and partitioned into some SR patches, which are resized into LS patches, the training set is composed of the SR patches and the corresponding LR patches. Secondly, the granular computing (GrC) clustering is proposed by the hypersphere representation of granule and the fuzzy inclusion measure compounded by the operation between two granules. Thirdly, the granule set (GS) including hypersphere granules with different granularities is induced by GrC and used to form the relation between the LR image and the SR image by lasso. Experimental results showed that GrC achieved the least root mean square errors between the reconstructed SR image and the original image compared with bicubic interpolation, sparse representation, and NNLasso. PMID:25610456

  11. A simple lattice model for the effect of voids on slip avalanches in sheared granular materials

    NASA Astrophysics Data System (ADS)

    Dahmen, K.; Ben-Zion, Y.; Uhl, J. T.

    2009-12-01

    It is well known that densely packed granular materials respond to slow shear with slip avalanches. Experiments and simulations show that the avalanche statistics depend strongly on the granular volume fraction v and grain shape related properties [1]. Previous studies have focused on force chain properties [2-6]. Here we use a mean field technique to construct an analytic model of the universal (i.e. detail-independent) slip avalanche statistics. For large v, and small frictional weakening ?, the model predicts solid-like behavior, with power-law avalanche size distributions and universal exponents and scaling functions. For large v and large ? it predicts mode switching between stick slip behavior and power law avalanche size distributions. For small v it predicts fluid-like flow. The results are presented in a (v, ?) phase diagram. They agree with published experiments [6-10] and simulations [2-4]. They complement recent studies on static properties, such as the shear modulus as a function of v near the jamming transition [2-4,7-10]. References: [1] V. Frette et al., “Avalanche Dynamics in a Pile of Rice”, Nature 379, 49-52 (1996). [2] E. Aharonov and D. Sparks, “Rigidity phase transition in granular packings”, Phys. Rev E, 60, 6890-6896 (1999). [3] E. Aharonov and D. Sparks, “Stick-slip motion in simulated granular layers”, J. Geophys. Res, 109, B09306 (2004). [4] E. Aharonov and D. Sparks, “Shear profiles and localization in simulations of granular materials”, Phys. Rev. E 65, 051302/1-12 (2002). [5] M.E. Cates, J.P. Wittmer, J.-P. Bouchaud, and P. Claudin, “Jamming, Force Chains, and Fragile Matter”, Phys. Rev. Lett., 81, 1841 (1998) and references therein. [6

  12. How granularity issues concern biomedical ontology integration.

    PubMed

    Schulz, Stefan; Boeker, Martin; Stenzhorn, Holger

    2008-01-01

    The application of upper ontologies has been repeatedly advocated for supporting interoperability between domain ontologies in order to facilitate shared data use both within and across disciplines. We have developed BioTop as a top-domain ontology to integrate more specialized ontologies in the biomolecular and biomedical domain. In this paper, we report on concrete integration problems of this ontology with the domain-independent Basic Formal Ontology (BFO) concerning the issue of fiat and aggregated objects in the context of different granularity levels. We conclude that the third BFO level must be ignored in order not to obviate cross-granularity integration. PMID:18487840

  13. Challenges in Predicting Planetary Granular Mechanics

    NASA Technical Reports Server (NTRS)

    Metzger, Philip T.

    2005-01-01

    Through the course of human history, our needs in agriculture, habitat construction, and resource extraction have driven us to gain more experience working with the granular materials of planet Earth than with any other type of substance in nature, with the possible exception being water. Furthermore, throughout the past two centuries we have seen a dramatic and ever growing interest among scientists and engineers to understand and predict both its static and rheological properties. Ironically, however, despite this wealth of experience we still do not have a fundamental understanding of the complex physical phenomena that emerge even as just ordinary sand is shaken, squeezed or poured. As humanity is now reaching outward through the solar system, not only robotic ally but also with our immediate human presence, the need to understand and predict granular mechanics has taken on a new dimension. We must learn to farm, build and mine the regoliths of other planets where the environmental conditions are different than on Earth, and we are rapidly discovering that the effects of these environmental conditions are not trivial. Some of the relevant environmental features include the regolith formation processes throughout a planet's geologic and hydrologic history, the unknown mixtures of volatiles residing within the soil, the relative strength of gravitation, d the atm9spheric pressure and its seasonal variations. The need to work with soils outside our terrestrial experience base provides us with both a challenge and an opportunity. The challenge is to learn how to extrapolate our experience into these new planetary conditions, enabling the engineering decisions that are needed right now as we take the next few steps in solar system exploration. The opportunity is to use these new planetary environments as laboratories that will help us to see granular mechanics in new ways, to challenge our assumptions, and to help us finally unravel the elusive physics that lie behind complex granular phenomena. Toward these goals, a workshop was held recently at NASA's John F. Kennedy Space Center, attracting over a hundred scientists and engineers from around the world and from a broad crosssection of scientific and engineering disciplines. This talk will provide an out-briefing from that workshop, communicating some of its early findings in regard to lunar and Martian exploration: (1) the requirements for working with granular materials, (2) the challenges that granular materials will pose, (3) the environmental conditions that affect granular mechanics, (4) instruments and measurements that are needed on the Moon and Mars to support granular material research, and (5) some of the possible research avenues that should be pursued.

  14. Melting a granular glass by cooling

    E-print Network

    Jan Plagge; Claus Heussinger

    2013-02-05

    Driven granular systems readily form glassy phases at high particle volume fractions and low driving amplitudes. We use computer simulations of a driven granular glass to evidence a re-entrance melting transition into a fluid state, which, contrary to intuition, occurs by \\emph{reducing} the amplitude of the driving. This transition is accompanied by anomalous particle dynamics and super-diffusive behavior on intermediate time-scales. We highlight the special role played by frictional interactions, which help particles to escape their glassy cages. Such an effect is in striking contrast to what friction is expected to do: reduce particle mobility by making them stick.

  15. Granular Impact Dynamics: Acoustics and Fluctuations

    E-print Network

    Abram H. Clark; R. P. Behringer

    2012-10-12

    In the corresponding fluid dynamics video, created for the APS DFD 2012 Gallery of Fluid Motion, we show high-speed videos of 2D granular impact experiments, where an intruder strikes a collection of bidisperse photoelastic disks from above. We discuss the force beneath the intruder, which is strongly fluctuating in space and time. These fluctuations correspond to acoustic pulses which propagate into the medium. Analysis shows that this process, in our experiments, is dominated by collisions with grain clusters. The energy from these collisions is carried into the granular medium along networks of grains, where is it dissipated.

  16. Internal Avalanches in a Granular Medium

    E-print Network

    S. S. Manna; D. V. Khakhar

    1998-08-04

    Avalanches of grain displacements can be generated by creating local voids within the interior of a granular material at rest in a bin. Modeling such a two-dimensional granular system by a collection of mono-disperse discs, the system on repeated perturbations, shows all signatures of Self-Organized Criticality. During the propagation of avalanches the competition among grains creates arches and in the critical state a distribution of arches of different sizes is obtained. Using a cellular automata model we demonstrate that the existence of arches determines the universal behaviour of the model system.

  17. Rheology of Dense Granular Mixtures: Boundary Pressures

    NASA Astrophysics Data System (ADS)

    Hill, K. M.; Yohannes, B.

    2011-02-01

    Models for dense sheared granular materials indicate that their rheological properties depend on particle size, but the representative size for mixtures is not obvious. Here, we computationally study pressure on a boundary due to sheared granular mixtures to determine its dependence on particle size distribution. We find that the pressure does not depend monotonically on average particle size. Instead it has an additional dependence on a measure of the effective free volume per particle we adapt from an expression for packing of monosized particles near the jammed state.

  18. Wetting of flexible fibre arrays.

    PubMed

    Duprat, C; Protière, S; Beebe, A Y; Stone, H A

    2012-02-23

    Fibrous media are functional and versatile materials, as demonstrated by their ubiquity both in natural systems such as feathers and adhesive pads and in engineered systems from nanotextured surfaces to textile products, where they offer benefits in filtration, insulation, wetting and colouring. The elasticity and high aspect ratios of the fibres allow deformation under capillary forces, which cause mechanical damage, matting self-assembly or colour changes, with many industrial and ecological consequences. Attempts to understand these systems have mostly focused on the wetting of rigid fibres or on elastocapillary effects in planar geometries and on a fibre brush withdrawn from an infinite bath. Here we consider the frequently encountered case of a liquid drop deposited on a flexible fibre array and show that flexibility, fibre geometry and drop volume are the crucial parameters that are necessary to understand the various observations referred to above. We identify the conditions required for a drop to remain compact with minimal spreading or to cause a pair of elastic fibres to coalesce. We find that there is a critical volume of liquid, and, hence, a critical drop size, above which this coalescence does not occur. We also identify a drop size that maximizes liquid capture. For both wetting and deformation of the substrates, we present rules that are deduced from the geometric and material properties of the fibres and the volume of the drop. These ideas are applicable to a wide range of fibrous materials, as we illustrate with examples for feathers, beetle tarsi, sprays and microfabricated systems. PMID:22358841

  19. Mold management of wetted carpet.

    PubMed

    Ong, Kee-Hean; Dixit, Anupma; Lewis, Roger D; MacDonald Perkins, Maureen; Backer, Denis; Condoor, Sridhar; Emo, Brett; Yang, Mingan

    2014-01-01

    This study evaluated the growth and removal of fungi on wetted carpet using newly designed technologies that rely on physical principles of steam, heat, and fluid flow. Sixty samples of carpet were embedded with heat-treated house dust, followed by embedding, wearing with a hexapod, and wetting. Samples were inoculated using a liquid suspension of Cladosporium sphaerospermum prior to placement over a water-saturated foam pad. Incubation times were 24 hr, 7 days, and 30 days. Cleaning was performed using three methods; high-flow hot water extraction, hot water and detergent, and steam. Fungal loading increased from approximately 1500 colony forming units per area (CFU/cm(2)) in 24 hr to a maximum of approximately 10,200 CFU/cm(2) after 7 days with a slight decline to 9700 CFU/cm(2) after 30 days incubation. Statistically significant differences were found among all three methods for removal of fungi for all three time periods (p < 0.05). Steam-vapor was significantly better than the alternative methods (p <0.001) with over 99% efficiency in mold spore decline from wetted carpet after 24 hr and 30 days, and over 92% efficiency after 7 days. The alternative methods exhibited lower efficiencies with a decline over time, from a maximum of 82% and 81% at 24 hr down to 60% and 43% at 30 days for detergent-hot water and high-flow, hot water extraction, respectively. The net effect of the mold management study demonstrates that while steam has a consistent fungal removal rate, the detergent and high-flow, hot water methods decline in efficiency with increasing incubation time. PMID:24856911

  20. Coal combustion by wet oxidation

    SciTech Connect

    Bettinger, J.A.; Lamparter, R.A.; McDowell, D.C.

    1980-11-15

    The combustion of coal by wet oxidation was studied by the Center for Waste Management Programs, of Michigan Technological University. In wet oxidation a combustible material, such as coal, is reacted with oxygen in the presence of liquid water. The reaction is typically carried out in the range of 204/sup 0/C (400/sup 0/F) to 353/sup 0/C (650/sup 0/F) with sufficient pressure to maintain the water present in the liquid state, and provide the partial pressure of oxygen in the gas phase necessary to carry out the reaction. Experimental studies to explore the key reaction parameters of temperature, time, oxidant, catalyst, coal type, and mesh size were conducted by running batch tests in a one-gallon stirred autoclave. The factors exhibiting the greatest effect on the extent of reaction were temperature and residence time. The effect of temperature was studied from 204/sup 0/C (400/sup 0/F) to 260/sup 0/C (500/sup 0/F) with a residence time from 600 to 3600 seconds. From this data, the reaction activation energy of 2.7 x 10/sup 4/ calories per mole was determined for a high-volatile-A-Bituminous type coal. The reaction rate constant may be determined at any temperature from the activation energy using the Arrhenius equation. Additional data were generated on the effect of mesh size and different coal types. A sample of peat was also tested. Two catalysts were evaluated, and their effects on reaction rate presented in the report. In addition to the high temperature combustion, low temperature desulfurization is discussed. Desulfurization can improve low grade coal to be used in conventional combustion methods. It was found that 90% of the sulfur can be removed from the coal by wet oxidation with the carbon untouched. Further desulfurization studies are indicated.

  1. Wet coastal plain tundra III

    SciTech Connect

    Myers, J.P.; Gellman, S.T.; Pitelka, F.A.

    1980-01-01

    This year's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSE of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 38'W; Barrow Quadrangle, USGS reflect a decrease in the total number of species breeding. However, total breeding density rose by 82%. Lapland Longspurs (up 105%) accounted for half of this increase while the rest was spread among many species. There was a total of 8 species; 40.5 territorial males or females (162/km/sup 2/, 66/100 acres).

  2. Elucidating the mysteries of wetting.

    SciTech Connect

    Webb, Edmund Blackburn, III (,; ); Bourdon, Christopher Jay; Grillet, Anne Mary; Sackinger, Philip A.; Grest, Gary Stephen; Emerson, John Allen; Ash, Benjamin Jesse; Heine, David R.; Brooks, Carlton, F.; Gorby, Allen D.

    2005-11-01

    Nearly every manufacturing and many technologies central to Sandia's business involve physical processes controlled by interfacial wetting. Interfacial forces, e.g. conjoining/disjoining pressure, electrostatics, and capillary condensation, are ubiquitous and can surpass and even dominate bulk inertial or viscous effects on a continuum level. Moreover, the statics and dynamics of three-phase contact lines exhibit a wide range of complex behavior, such as contact angle hysteresis due to surface roughness, surface reaction, or compositional heterogeneities. These thermodynamically and kinetically driven interactions are essential to the development of new materials and processes. A detailed understanding was developed for the factors controlling wettability in multicomponent systems from computational modeling tools, and experimental diagnostics for systems, and processes dominated by interfacial effects. Wettability probed by dynamic advancing and receding contact angle measurements, ellipsometry, and direct determination of the capillary and disjoining forces. Molecular scale experiments determined the relationships between the fundamental interactions between molecular species and with the substrate. Atomistic simulations studied the equilibrium concentration profiles near the solid and vapor interfaces and tested the basic assumptions used in the continuum approaches. These simulations provide guidance in developing constitutive equations, which more accurately take into account the effects of surface induced phase separation and concentration gradients near the three-phase contact line. The development of these accurate models for dynamic multicomponent wetting allows improvement in science based engineering of manufacturing processes previously developed through costly trial and error by varying material formulation and geometry modification.

  3. Mars: Always Cold, Sometimes Wet?

    NASA Technical Reports Server (NTRS)

    Lee, Pascal; McKay, Christoper P.

    2003-01-01

    A synthesis of a diverse suite of observations of H2O-related landforms that are possible Mars analogs from terrestrial polar regions (Devon Island in the Arctic; the Dry Valleys of Antarctica) put into question any requirement for extended episode(s) of warm and wet climate in Mars past. Geologically transient episodes of localized H2O cycling, forced by exogenic impacts, enhanced endogenic heat flow, and/or orbit-driven short-term local environmental change under an otherwise cold, low pressure (=10(exp 2) mbar) global climate, may be sufficient to account for the martian surface's exposed record of aqueous activity. A Mars that was only sometimes locally warm and wet while remaining climatically cold throughout its history is consistent with results (difficulties) encountered in modeling efforts attempting to support warm martian climate hypotheses. Possible analogs from terrestrial cold climate regions for the recent gully features on Mars also illustrate how transient localized aqueous activity might, under specific circumstances, also occur on Mars under the present frigid global climatic regime.

  4. Granular Elasticity’ and the loss of elastic stability in granular materials

    SciTech Connect

    P. W. Humrickhouse

    2009-07-01

    A recently proposed hyperelastic model for granular materials, called "granular elasticity", identifies a yield angle as a result of thermodynamic instability. GE gives yield angles that are smaller than those found in real materials; a generalization of the theory is considered here that includes dependence on the third strain invariant. This generalization proves unsuccessful, as it gives smaller, not larger, yield angles. Fully convex hyperelastic models are identified as a point for future investigation.

  5. Scaling of convective velocity in a vertically vibrated granular bed

    NASA Astrophysics Data System (ADS)

    Yamada, Tomoya M.; Katsuragi, Hiroaki

    2014-10-01

    We experimentally study the velocity scaling of granular convection which is a possible mechanism of the regolith migration on the surface of small asteroids. In order to evaluate the contribution of granular convection to the regolith migration, the velocity of granular convection under the microgravity condition has to be revealed. Although it is hard to control the gravitational acceleration in laboratory experiments, scaling relations involving the gravitational effect can be evaluated by systematic experiments. Therefore, we perform such a systematic experiment of the vibration-induced granular convection. From the experimental data, a scaling form for the granular convective velocity is obtained. The obtained scaling form implies that the granular convective velocity can be decomposed into two characteristic velocity components: vibrational and gravitational velocities. In addition, the system size dependence is also scaled. According to the scaling form, the granular convective velocity v depends on the gravitational acceleration g as v?g0.97 when the normalized vibrational acceleration is fixed.

  6. Geomorphology, disturbance, and the soil and vegetation of two subtropical wet steepland watersheds of Puerto Rico

    Microsoft Academic Search

    F. N. Scatena; Ariel E. Lugo

    1995-01-01

    Relationships between landforms, soil nutrients, forest structure, and the relative importance of different disturbances were quantified in two subtropical wet steepland watersheds in Puerto Rico. Ridges had fewer landslides and treefall gaps, more above-ground biomass, older aged stands, and greater species richness than other landscape positions. Ridge soils had relatively low quantities of exchangeable bases but high soil organic matter,

  7. COMPUTER SIMULATION OF GRANULAR MATERIAL: VIBRATING FEEDERS

    Microsoft Academic Search

    Guillermo Rein Soto-Yarritu; Ángel de Andrés Martínez

    2001-01-01

    This paper presents a numerical model for simulation of granular material movement. The proposed computer model is based on Discontinuous Deformation Analysis, a numerical method recently adapted for simulation of particles motion. Gravity, impacts between particles, impacts with the boundaries, friction and cohesion are considered. The motion of particles is induced by the vibration of the deck on which they

  8. DOWNFLOW GRANULAR FILTRATION OF ACTIVATED SLUDGE EFFLUENTS

    EPA Science Inventory

    The performance of downflow granular filters subjected to effluents from activated sludge processes was investigated at the EPA-DC Pilot Plant in Washington, D.C. Several media combinations were investigated, including both single anthracite and dual anthracite-sand configuration...

  9. Sound wave acceleration in granular materials

    Microsoft Academic Search

    O Mouraillea

    The goal of this study is a better understanding of the numerous sound propagation mechanisms in granular materials. In a static, regular (crystal), 3D packing, a small perturbation is created on one side and examined during its propagation through frictionless and frictional packings. The perturbation can be applied in longitudinal and shear direction in order to excite dieren t modes

  10. Sound wave acceleration in granular materials

    Microsoft Academic Search

    O. Mouraille; W. A. Mulder; S. Luding

    2006-01-01

    The goal of this study is a better understanding of the numerous sound propagation mechanisms in granular materials. In a static, regular (crystal), three-dimensional packing, a small perturbation is created on one side and examined during its propagation through frictionless and frictional packings. The perturbation can be applied in longitudinal and shear directions in order to excite different modes of

  11. Structure and stability of methanogenic granular sludge

    Microsoft Academic Search

    J. T. C. Grotenhuis

    1992-01-01

    Immobilization of anaerobic bacteria was essential for the development of high rate anaerobic systems for the treatment of waste waters. The most widely applied anaerobic reactor type in which solids retention time is uncoupled from the hydraulic retention time is the Upflow Anaerobic Sludge Blanket (UASB) reactor. In this reactor type methanogenic granular sludge is formed by self-immobilization of methanogenic

  12. REGIONAL REACTIVATION OF GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    A major portion of the cost of using Granular Activated Carbon (GAC) as a water treatment unit process is associated with spent carbon replacement or reactivation. Regional reactivation or sharing a reactivation furnace among several users, has been proposed as a means of minimiz...

  13. Testing ergodicity in dense granular systems

    NASA Astrophysics Data System (ADS)

    Gao, Guo-Jie; Blawzdziewicz, Jerzy; O'Hern, Corey

    2008-03-01

    The Edwards' entropy formalism provides a statistical mechanical framework for describing dense granular systems. Experiments on vibrated granular columns and numerical simulations of quasi- static shear flow of dense granular systems have provided indirect evidence that the Edwards' theory may accurately describe certain aspects of these systems. However, a fundamental assumption of the Edwards' description---that all mechanically stable (MS) granular packings at a given packing fraction and externally imposed stress are equally accessible---has not been explicitly tested. We investigate this assumption by generating all mechanically stable hard disk packings in small bidisperse systems using a protocol where we successively compress or decompress the system followed by energy minimization. We then apply quasi-static shear flow at zero pressure to these MS packings and record the MS packings that occur during the shear flow. We generate a complete library of the allowed MS packings at each value of shear strain and determine the frequency with which each MS packing occurs. We find that the MS packings do not occur with equal probability at any value of shear strain. In fact, in small systems we find that the evolution becomes periodic with a period that grows with system-size. Our studies show that ergodicity can be improved by either adding random fluctuations to the system or increasing the system size.

  14. A Multi-granular Linguistic Promethee Model

    Microsoft Academic Search

    Nesrin Halouani; Luis Martínez; Habib Chabchoub; Jean-marc Martel; Jun Liu

    2009-01-01

    In Multi-criteria Decision Making (MCDM) problems dealing with qualitative criteria and uncertain information the use of linguistic values is suitable for the experts in order to express their judgments. It is common that the group of experts involved in such problems have different degrees of knowledge about the criteria, so we propose a multi-granular linguistic framework such that each expert

  15. Shallow granular flows O. Bokhove1

    E-print Network

    Al Hanbali, Ahmad

    and their positions updated via the integration of Newton's equations of motion. In DPMs, the deformation, in the granular case, is that the constitutive or closure laws for the bottom stress relations are generally channel, into the blast furnace for iron-ore melting, at Corus #12;3 Hoogovens, IJmuiden, The Netherlands

  16. Trajectory entanglement in dense granular materials

    E-print Network

    James G. Puckett; Frédéric Lechenault; Karen E. Daniels; Jean-Luc Thiffeault

    2012-02-23

    The particle-scale dynamics of granular materials have commonly been characterized by the self-diffusion coefficient $D$. However, this measure discards the collective and topological information known to be an important characteristic of particle trajectories in dense systems. Direct measurement of the entanglement of particle space-time trajectories can be obtained via the topological braid entropy $\\Sbraid$, which has previously been used to quantify mixing efficiency in fluid systems. Here, we investigate the utility of $\\Sbraid$ in characterizing the dynamics of a dense, driven granular material at packing densities near the static jamming point $\\phi_J$. From particle trajectories measured within a two-dimensional granular material, we typically observe that $\\Sbraid$ is well-defined and extensive. However, for systems where $\\phi \\gtrsim 0.79$, we find that $\\Sbraid$ (like $D$) is not well-defined, signifying that these systems are not ergodic on the experimental timescale. Both $\\Sbraid$ and $D$ decrease with either increasing packing density or confining pressure, independent of the applied boundary condition. The related braiding factor provides a means to identify multi-particle phenomena such as collective rearrangements. We discuss possible uses for this measure in characterizing granular systems.

  17. Granular Gas in a Periodic Lattice

    ERIC Educational Resources Information Center

    Dorbolo, S.; Brandenbourger, M.; Damanet, F.; Dister, H.; Ludewig, F.; Terwagne, D.; Lumay, G.; Vandewalle, N.

    2011-01-01

    Glass beads are placed in the compartments of a horizontal square grid. This grid is then vertically shaken. According to the reduced acceleration [image omitted] of the system, the granular material exhibits various behaviours. By counting the number of beads in each compartment after shaking, it is possible to define three regimes. At low…

  18. Design and analysis of jammable granular systems

    E-print Network

    Cheng, Nadia G. (Nadia Gen San)

    2013-01-01

    Jamming--the mechanism by which granular media can transition between liquid-like and solid-like states-has recently been demonstrated as a variable strength and stiffness mechanism in a range of applications. As a low-cost ...

  19. Localized fluidization in a granular medium.

    PubMed

    Philippe, P; Badiane, M

    2013-04-01

    We present here experimental results on the progressive development of a fluidized zone in a bed of grains, immersed in a liquid, under the effect of a localized upward flow injected through a small orifice at the bottom of the bed. Visualization inside the model granular medium consisting of glass beads is made possible by the combined use of two optical techniques: refractive index matching between the liquid and the beads and planar laser-induced fluorescence. Gradually increasing the injection rate, three regimes are successively observed: static bed, fluidized cavity that does not open to the upper surface of the granular bed, and finally fluidization over the entire height of the granular bed inside a fluidized chimney. The phase diagram is plotted and partially interpreted using a model previously developed by Zoueshtiagh and Merlen [F. Zoueshtiagh and A. Merlen, Phys. Rev. E 75, 053613 (2007)]. A typical sequence, where the flow rate is first increased and then decreased back to zero, reveals a strong hysteretic behavior since the stability of the fluidized cavity is considerably strengthened during the defluidization phase. This effect can be explained by the formation of force arches within the granular packing when the chimney closes up at the top of the bed. A study of the expansion rate of the fluidized cavity was also conducted as well as the analysis of the interaction between two injection orifices with respect to their spacing. PMID:23679406

  20. Dynamical behaviour of rotated granular mixtures

    NASA Astrophysics Data System (ADS)

    Puri, Sanjay; Hayakawa, Hisao

    1999-08-01

    We present a phenomenological model for the dynamics of granular mixtures in a rotating drum. We demonstrate that our model successfully captures many of the experimental features known in the context of this problem. The results presented here are supplementary to those presented in a detailed paper (S. Puri, H. Hayakawa, cond-mat/9901260).

  1. Multiscale modeling of multi-component granular avalanches

    NASA Astrophysics Data System (ADS)

    Weinhart, Thomas; Tunuguntla, Deepak; Luding, Stefan; Thornton, Anthony

    2014-05-01

    Geophysical flows (e.g. snow slab avalanches, debris flows and pyroclastic flows and landslides) often contain particles of different sizes, shapes and materials, which can cause the constituent phases to segregate. Here we will focus of the effects of size and density. Kinetic sieving causes the particles to segregate by size, with small particles sifting downwards, as they have a higher probability than large particles to fit into void spaces [1]. The large particles on the surface are transported sideways to form levees that increase the resistance to lateral motion and thus enhance the run-out. At the same time, particles also segregate by density due to buoyancy, which shifts lighter particles upwards. For bidisperse flows, a mixture-theory continuum model is used that includes the effects of both size and density segregation [2]. We use DEM (DPM) simulations to investigate two key model parameters that are hard to obtain from experiments. A novel coarse-graining expression for the stress tensor of discrete mechanical systems is applied for mixtures to obtain the partial stresses and the interaction drag force [3,4]. The goal is to develop predictive multi-component models of granular avalanches by utilising both continuum and particle simulation approaches. REFERENCES [1] Thornton, A.R., Weinhart, T., Luding, S., Bokhove, O., Modelling of particle size segregation: Calibration using the discrete particle method, Int. J. Mod. Phys. C 23, (2012). [2] Tunuguntla, D., Bokhove, O., Thornton, A.R., Particle segregation in free-surface flows, submitted to JFM rapids (2013) [3] T. Weinhart, A. R. Thornton, S. Luding, O. Bokhove, From discrete particles to continuum fields near a boundary, Granular Matter 14(2), 289-294 (2012). [4] T. Weinhart, S. Luding, A.R. Thornton, From discrete particles to continuum fields in mixtures, AIP Conf. Proc. 1542, 1202-1205 (2013)

  2. From principal curves to granular principal curves.

    PubMed

    Zhang, Hongyun; Pedrycz, Witold; Miao, Duoqian; Wei, Zhihua

    2014-06-01

    Principal curves arising as an essential construct in dimensionality reduction and data analysis have recently attracted much attention from theoretical as well as practical perspective. In many real-world situations, however, the efficiency of existing principal curves algorithms is often arguable, in particular when dealing with massive data owing to the associated high computational complexity. A certain drawback of these constructs stems from the fact that in several applications principal curves cannot fully capture some essential problem-oriented facets of the data dealing with width, aspect ratio, width change, etc. Information granulation is a powerful tool supporting processing and interpreting massive data. In this paper, invoking the underlying ideas of information granulation, we propose a granular principal curves approach, regarded as an extension of principal curves algorithms, to improve efficiency and achieve a sound accuracy-efficiency tradeoff. First, large amounts of numerical data are granulated into C intervals-information granules developed with the use of fuzzy C-means clustering and the two criteria of information granulation, which significantly reduce the amount of data to be processed at the later phase of the overall design. Granular principal curves are then constructed by determining the upper and the lower bounds of the interval data. Finally, we develop an objective function using the criteria of information confidence and specificity to evaluate the granular output formed by the principal curves. We also optimize the granular principal curves by adjusting the level of information granularity (the number of clusters), which is realized with the aid of the particle swarm optimization. A number of numeric studies completed for synthetic and real-world datasets provide a useful quantifiable insight into the effectiveness of the proposed algorithm. PMID:23996588

  3. Wetting by solid helium, a model system

    NASA Astrophysics Data System (ADS)

    Balibar, Sébastien

    2013-08-01

    This is a review of the wetting properties of solid helium on various solid substrates. Due to its extreme purity and to its very fast growth dynamics, solid helium 4 is often considered as a model system in materials science. Several wetting phenomena have been studied with helium 4 crystals, namely contact angles on solid substrates with variable roughness, wetting on graphite where epitaxial growth takes place, the roughening transition as a function of film thickness, the wetting of grain boundaries by the liquid phase.

  4. Carbon nanotube fiber spun from wetted ribbon

    DOEpatents

    Zhu, Yuntian T; Arendt, Paul; Zhang, Xiefei; Li, Qingwen; Fu, Lei; Zheng, Lianxi

    2014-04-29

    A fiber of carbon nanotubes was prepared by a wet-spinning method involving drawing carbon nanotubes away from a substantially aligned, supported array of carbon nanotubes to form a ribbon, wetting the ribbon with a liquid, and spinning a fiber from the wetted ribbon. The liquid can be a polymer solution and after forming the fiber, the polymer can be cured. The resulting fiber has a higher tensile strength and higher conductivity compared to dry-spun fibers and to wet-spun fibers prepared by other methods.

  5. Externally Wetted Ionic Liquid Thruster

    NASA Astrophysics Data System (ADS)

    Lozano, P.; Martinez-Sanchez, M.; Lopez-Urdiales, J. M.

    2004-10-01

    This paper presents initial developments of an electric propulsion system based on ionic liquid ion sources (ILIS). Propellants are ionic liquids, which are organic salts with two important characteristics; they remain in the liquid state at room temperature and have negligible vapor pressure, thus allowing their use in vacuum. The working principles of ILIS are similar to those of liquid metal ion sources (LMIS), in which a Taylor cone is electrostatically formed at the tip of an externally wetted needle while ions are emitted directly from its apex. ILIS have the advantage of being able to produce negative ions that have similar masses than their positive counterparts with similar current levels. This opens up the possibility of achieving plume electrical neutrality without electron emitters. The possible multiplexing of these emitters is discussed in terms of achievable thrust density for applications other than micro-propulsion.

  6. The Wet-Dog Shake

    E-print Network

    Dickerson, Andrew; Bauman, Jay; Chang, Young-Hui; Hu, David

    2010-01-01

    The drying of wet fur is a critical to mammalian heat regulation. In this fluid dynamics video, we show a sequence of films demonstrating how hirsute animals to rapidly oscillate their bodies to shed water droplets, nature's analogy to the spin cycle of a washing machine. High-speed videography and fur-particle tracking is employed to determine the angular position of the animal's shoulder skin as a function of time. X-ray cinematography is used to track the motion of the skeleton. We determine conditions for drop ejection by considering the balance of surface tension and centripetal forces on drops adhering to the animal. Particular attention is paid to rationalizing the relationship between animal size and oscillation frequency required to self-dry.

  7. Dimpling in loose granular sediments

    NASA Astrophysics Data System (ADS)

    Díaz-Hernández, Jose Luis; Yepes, Jorge

    2010-05-01

    Dimpling is the name given to the centimetre-scale collapse of granular deposits covering the interior of alteration shelters in semi-arid badlands. The development of micro-collapses is favoured by the stable conditions found in these shelters, where they are safe from water flows, rain impact, and animal or human traffic. The floor of these shelters is usually covered by several centimetres of sandy sediment resulting from the alteration of the rocky substratum and characterised by apparently very low density and high porosity. We have observed that the dimpling phenomenon does not depend on the mineralogy of the sands and occurs in dry conditions. The dimples are the shapes resulting from this process and are fragile, conical depressions ranging from 1 to 12 cm in diameter. They are generally over 3 cm in depth, depending on the depth of the sandy layer. The dimples can be classified into three groups by diameter (Ø): Ø?1cm, 1cm?Ø?10 cm and Ø?10 cm. These three morphometrical ranges suggest three evolutionary stages of the shapes. The main mechanisms of evolution are the coalescence of neighbouring dimples and the accommodation of the lateral walls towards more open, stable shapes. In this process, the slope of the dimple walls decreases to the angle of equilibrium, or internal friction angle of the sediment, when they acquire a more stable, dense structure. This evolution occurs naturally over several months. The process begins when sufficient sediment with low apparent density accumulates. This takes place by vertical accretion of particles from the shelter walls, which pile up in a stack-of-cards type structure. The increase in weight of the sediment column causes punctual micro-collapses when the limit of the sediment's self-supporting capacity is reached. The process is gravitational. Thermal variations can also condition the structural instability of the sediment due to the dilation-retraction changes undergone by the sediment grains. We can thus establish the following stages of evolution in the dimpling process: 1.Accumulation of deposits detached from the shelter walls by gravity. The sediment has a low apparent density, stack-of-cards inner structure. 2.Punctual micro-collapses of the structure (acicular depressions). Some collapses can be repetitive. 3.Shift to open shapes by lateral widening (conical depressions). This occurs through coalescence of micro-collapses or instability of the lateral walls. 4.Shift to senile shapes (plate-shaped depressions) through instability of the lateral walls. During this stage the shapes would become shallower through accumulation of supply in the bottom of the depression. Throughout this process the angle of the walls of the depression decrease to what we suppose must be the internal friction angle of the sediment.

  8. Wet runways. [aircraft landing and directional control

    NASA Technical Reports Server (NTRS)

    Horne, W. B.

    1975-01-01

    Aircraft stopping and directional control performance on wet runways is discussed. The major elements affecting tire/ground traction developed by jet transport aircraft are identified and described in terms of atmospheric, pavement, tire, aircraft system and pilot performance factors or parameters. Research results are summarized, and means for improving or restoring tire traction/aircraft performance on wet runways are discussed.

  9. Wetting and lubricating film instabilities in microchannels

    E-print Network

    Cubaud, Thomas

    Wetting and lubricating film instabilities in microchannels Thomas Cubaud Department of Mechanical, and silicone oils . Dynamic wetting transitions: a pearl flow thick lubricating film , b spider flow thin lubricating film , c ghost flow metastable dewetting patches . Droplet-decorated streams: d droplets

  10. Spatial variability of characteristics and origins of urban wet weather pollution in combined sewers.

    PubMed

    Kafi-Benyahia, M; Gromaire, M G; Chebbo, G

    2005-01-01

    An experimental on-site observatory of urban pollutant loads in combined sewers was created in the centre of Paris to quantify and characterise the dry and wet weather flow in relation to spatial scale. Eight rainfall events were studied from April 2003 to May 2004. Samples were analysed for suspended solids, organic matter, nitrogen and heavy metals. Results confirm the extent of wet weather pollution. They have shown the relative homogeneity of SS and organic matter characteristics from one urban catchment area to another. Two groups of heavy metals were identified. The first one concerns Cu, which has a higher concentration in wet weather flow (WWF) than in dry weather flow (DWF), and runoff. The second includes Cd, Pb and Zn, where higher concentrations were measured in urban runoff than in WWF and DWF. A first evaluation of contribution of wastewater, urban runoff and sewer deposit erosion sources to wet weather pollution was established and has highlighted the contribution of wastewater and sewer deposits to this pollution. However, it has shown that sewer deposit erosion remains an important source of wet weather pollution at different spatial scales. PMID:16206844

  11. Spiral modes in the diffusion of a granular particle on a vibrating surface

    E-print Network

    R. Klages; I. F. Barna; L. Matyas

    2004-06-22

    We consider a particle that is subject to a constant force and scatters inelastically on a vibrating periodically corrugated floor. At small friction and small radius of the circular scatterers the dynamics is dominated by resonances forming spiral structures in phase space. These spiral modes lead to pronounced maxima and minima in the diffusion coefficient as a function of the vibration frequency, as is shown in computer simulations. Our theoretical predictions may be verified experimentally by studying transport of granular matter on vibratory conveyors.

  12. Microgravity Experiments to Evaluate Electrostatic Forces in Controlling Cohesion and Adhesion of Granular Materials

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Weislogel, M.; Jacobson, T.

    1999-01-01

    The bulk behavior of dispersed, fluidized, or undispersed stationary granular systems cannot be fully understood in terms of adhesive/cohesive properties without understanding the role of electrostatic forces acting at the level of the grains themselves. When grains adhere to a surface, or come in contact with one another in a stationary bulk mass, it is difficult to measure the forces acting on the grains, and the forces themselves that induced the cohesion and adhesion are changed. Even if a single gain were to be scrutinized in the laboratory, it might be difficult, perhaps impossible, to define the distribution and character of surface charging and the three- dimensional relationship that charges (electrons, holes) have to one another. The hypothesis that we propose to test in microgravity (for dielectric materials) is that adhesion and cohesion of granular matter are mediated primarily by dipole forces that do not require the presence of a net charge; in fact, nominally electrically neutral materials should express adhesive and cohesive behavior when the neutrality results from a balance of positive and negative charge carriers. Moreover, the use of net charge alone as a measure of the electrical nature of grain-to-grain relationships within a granular mass may be misleading. We believe that the dipole forces arise from the presence of randomly-distributed positive and negative fixed charge carriers on grains that give rise to a resultant dipole moment. These dipole forces have long-range attraction. Random charges are created whenever there is triboelectrical activity of a granular mass, that is, whenever the grains experience contact/separation sequences or friction. Electrostatic forces are generally under-estimated for their role in causing agglomeration of dispersed grains in particulate clouds, or their role in affecting the internal frictional relationships in packed granular masses. We believe that electrostatic, in particular dipole-mediated processes, are pervasive and probably affect, at some level, everything from astrophysical-scale granular systems such as interstellar nebulae, protoplanetary dust and debris disks, planetary-scale systems such as debris palls from meteorite impact, volcanic eruptions, and aeolian dust storms, all the way to industrial-scale systems in mining, powder and grain processing, pharmaceuticals, and smoke-stack technologies. NASA must concern itself with the electrostatic behavior of dust and sand on Mars because of its potentially critical importance to human exploration. The motion and adhesion of martian surface materials will affect the design and performance of spacesuits, habitats, processing plants, solar panels, and any externally exposed equipment such as surface rovers or communication and weather stations. Additionally, the adhesion of dust and sand could greatly enhance contact with the potentially toxic components of the martian soil.

  13. Collapse and revival of the matter wave field of a Bose-Einstein condensate

    Microsoft Academic Search

    Markus Greiner; Olaf Mandel; Theodor W. Hänsch; Immanuel Bloch

    2002-01-01

    A Bose-Einstein condensate represents the most `classical' form of a matter wave, just as an optical laser emits the most classical form of an electromagnetic wave. Nevertheless, the matter wave field has a quantized structure owing to the granularity of the discrete underlying atoms. Although such a field is usually assumed to be intrinsically stable (apart from incoherent loss processes),

  14. The Dynamics of Granular Shear Flow: Experiments

    NASA Astrophysics Data System (ADS)

    Gollub, J. P.; Losert, W.; Bocquet, L.; Schalk, D.

    2000-11-01

    We have measured quantitatively the velocity and fluctuation profiles, and the internally generated shear forces, for a granular shear flow in a Couette geometry. The tangential velocity V(y) declines approximately exponentially with distance y from the moving wall. The velocity fluctuations ? V(y) decline also, but more slowly with y. We find that ? V(y) varies as a power law of the local velocity gradient. The shear force is approximately independent of shear rate. A levitating air flow is used to reduce the effective pressure within the material. The shear force decreases approximately linearly with increasing air flow and vanishes at the onset of "bubbling". We find excellent agreement between these experimental results and a locally Newtonian continuum model of granular flow.(W. Losert, L. Bocquet, T.C. Lubensky, and J.P. Gollub, Phys. Rev. Lett. 85), (2000), in press; L. Bocquet, W. Losert, T.C. Lubensky, and J.P. Gollub, to be submitted.

  15. Memory effect in uniformly heated granular gases

    E-print Network

    E. Trizac; A. Prados

    2014-07-15

    We evidence a Kovacs-like memory effect in a uniformly driven granular gas. A system of inelastic hard particles, in the low density limit, can reach a non-equilibrium steady state when properly forced. By following a certain protocol for the drive time dependence, we prepare the gas in a state where the granular temperature coincides with its long time value. The temperature subsequently does not remain constant, but exhibits a non-monotonic evolution with either a maximum or a minimum, depending on the dissipation, and on the protocol. We present a theoretical analysis of this memory effect, at Boltzmann-Fokker-Planck equation level, and show that when dissipation exceeds a threshold, the response can be coined anomalous. We find an excellent agreement between the analytical predictions and direct Monte Carlo simulations.

  16. Impact of liquid droplets on granular media.

    PubMed

    Delon, G; Terwagne, D; Dorbolo, S; Vandewalle, N; Caps, H

    2011-10-01

    The crater formation due to the impact of a water droplet onto a granular bed has been experimentally investigated. Three parameters were tuned: the impact velocity, the size of the droplet, and the size of the grains. The aim is to determine the influence of the kinetic energy on the droplet pattern. The shape of the crater depends on the kinetic energy at the moment the droplet starts to impact the bed. The spreading and recession of the liquid during the impact were carefully analyzed from the dynamical point of view, using image analysis of high-speed video recordings. The different observed regimes are characterized by the balance between the impregnation time of the water by the granular bed by the water and the capillary time responsible for the recession of the drop. PMID:22181274

  17. Structural evolution of granular systems: Theory

    E-print Network

    Raphael Blumenfeld

    2014-12-22

    A first-principles theory is developed for the general evolution of a key structural characteristic of planar granular systems - the cell order distribution. The dynamic equations are constructed and solved in closed form for a number of examples: dense systems undergoing progressive compaction; initial dilation of very dense systems; and the approach to steady state of general systems. It is shown that the convergence to steady state is exponential, except when contacts are only broken and no new contacts are made, in which case the approach is algebraic in time. Where no closed form solutions are possible, numerical solutions of the evolution dynamics are shown, which agree with results in the literature. The formalism can be extended to other structural characteristics, making it possible to understand the structural organisation of granular systems in general.

  18. Heat flux in a granular gas

    NASA Astrophysics Data System (ADS)

    Brey, J. J.; Ruiz-Montero, M. J.

    2012-11-01

    A peculiarity of the hydrodynamic Navier-Stokes equations for a granular gas is the modification of the Fourier law, with the presence of an additional contribution to the heat flux that is proportional to the density gradient. Consequently, the constitutive relation involves, in the case of a one-component granular gas, two transport coefficients: the usual (thermal) heat conductivity and a diffusive heat conductivity. A very simple physical interpretation of this effect, in terms of the mean free path and the mean free time is provided. It leads to the modified Fourier law with an expression for the diffusive Fourier coefficient that differs in a factor of the order of unity from the expression obtained by means of the inelastic Boltzmann equation. Also, some aspects of the Chapman-Enskog computation of the new transport coefficients as well as of the comparison between simulation results and theory are discussed.

  19. Rheology of dense sheared granular liquids (Invited)

    NASA Astrophysics Data System (ADS)

    Suzuki, Koshiro; Hayakawa, Hisao

    2014-12-01

    The rheology of dense sheared granular liquids is investigated based on the mode-coupling theory (MCT). This extended MCT includes correlations for the density-current mode as well as the density-density correlation mode, and a self-consistent coupling equation for the energy balance condition. The extended MCT exhibits disappearance of the two-step relaxation of the density-density correlation function, and also successfully reproduces the density dependence of the shear viscosity for volume fractions between 0.50 and 0.60, if we shift the density. However, it predicts unphysical tendency for the granular temperature. The cause of this drawback and the possibilities of its amendment are discussed.

  20. Granular gravitational collapse and chute flow

    E-print Network

    Deniz Ertas; Thomas C. Halsey

    2002-06-04

    Inelastic grains in a flow under gravitation tend to collapse into states in which the relative normal velocities of two neighboring grains is zero. If the time scale for this gravitational collapse is shorter than inverse strain rates in the flow, we propose that this collapse will lead to the formation of ``granular eddies", large scale condensed structures of particles moving coherently with one another. The scale of these eddies is determined by the gradient of the strain rate. Applying these concepts to chute flow of granular media, (gravitationally driven flow down inclined planes) we predict the existence of a bulk flow region whose rheology is determined only by flow density. This theory yields the experimental ``Pouliquen flow rule", correlating different chute flows; it also correctly accounts for the different flow regimes observed.

  1. 76 FR 28455 - Granular Polytetrafluoroethylene Resin From Italy; Scheduling of an Expedited Five-Year Review...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-17

    ...Granular Polytetrafluoroethylene Resin From Italy; Scheduling of an Expedited Five-Year...Granular Polytetrafluoroethylene Resin From Italy AGENCY: United States International Trade...granular polytetrafluoroethylene resin from Italy would be likely to lead to...

  2. 76 FR 27663 - Granular Polytetrafluoroethylene Resin From Italy; Scheduling of an Expedited Five-Year Review...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-12

    ...Granular Polytetrafluoroethylene Resin From Italy; Scheduling of an Expedited Five-Year...Granular Polytetrafluoroethylene Resin From Italy AGENCY: United States International Trade...granular polytetrafluoroethylene resin from Italy would be likely to lead to...

  3. Adsorption of Nonylphenol onto Granular Activated Carbon

    Microsoft Academic Search

    Tom Tanghe; Willy Verstraete

    2001-01-01

    The applicability of granular activated carbon (GAC)filtration for the removal of the xeno-estrogenicmicropollutant nonylphenol (NP) is evaluated using batchadsorption data. From the obtained adsorption data, it wasapparent that with contact times of 4 d and 24 hr and GACdosages of 1 and 0.1 g L-1 no saturationof the GAC could be obtained with NP total contaminantloadings up to 10 000

  4. Transversal inhomogeneities in dilute vibrofluidized granular fluids

    E-print Network

    J. Javier Brey; M. J. Ruiz-Montero; F. Moreno; R. Garcia-Rojo

    2002-01-24

    The spontaneous symmetry breaking taking place in the direction perpendicular to the energy flux in a dilute vibrofluidized granular system is investigated, using both a hydrodynamic description and simulation methods. The latter include molecular dynamics and direct Monte Carlo simulation of the Boltzmann equation. A marginal stability analysis of the hydrodynamic equations, carried out in the WKB approximation, is shown to be in good agreement with the simulation results. The shape of the hydrodynamic profiles beyond the bifurcation is discussed.

  5. Swimming in a granular frictional fluid

    NASA Astrophysics Data System (ADS)

    Goldman, Daniel

    2012-02-01

    X-ray imaging reveals that the sandfish lizard swims within granular media (sand) using axial body undulations to propel itself without the use of limbs. To model the locomotion of the sandfish, we previously developed an empirical resistive force theory (RFT), a numerical sandfish model coupled to an experimentally validated Discrete Element Method (DEM) model of the granular medium, and a physical robot model. The models reveal that only grains close to the swimmer are fluidized, and that the thrust and drag forces are dominated by frictional interactions among grains and the intruder. In this talk I will use these models to discuss principles of swimming within these granular ``frictional fluids". The empirical drag force laws are measured as the steady-state forces on a small cylinder oriented at different angles relative to the displacement direction. Unlike in Newtonian fluids, resistive forces are independent of speed. Drag forces resemble those in viscous fluids while the ratio of thrust to drag forces is always larger in the granular media than in viscous fluids. Using the force laws as inputs, the RFT overestimates swimming speed by approximately 20%. The simulation reveals that this is related to the non-instantaneous increase in force during reversals of body segments. Despite the inaccuracy of the steady-state assumption, we use the force laws and a recently developed geometric mechanics theory to predict optimal gaits for a model system that has been well-studied in Newtonian fluids, the three-link swimmer. The combination of the geometric theory and the force laws allows us to generate a kinematic relationship between the swimmer's shape and position velocities and to construct connection vector field and constraint curvature function visualizations of the system dynamics. From these we predict optimal gaits for forward, lateral and rotational motion. Experiment and simulation are in accord with the theoretical prediction, and demonstrate that swimming in sand can be viewed as movement in a localized frictional fluid.

  6. Fabrication and magnetic properties of granular alloys

    Microsoft Academic Search

    A. Gavrin; C. L. Chien

    1990-01-01

    Granular alloys of iron with other transition metals have been fabricated in both Al2O3 and SiO2 matrices. Both stable (Fe-Ni, Fe-Co) and metastable (Fe-Cu) alloys have been achieved. Under appropriate deposition conditions, the grains are single-phase alloys ranging in size from 15 to 50 A?. Superparamagnetism and enhanced coercivity have been observed, and the effect of grain size on these

  7. Granular Fe in a metallic matrix

    NASA Astrophysics Data System (ADS)

    Childress, J. R.; Chien, C. L.; Nathan, M.

    1990-01-01

    Ultrafine Fe particles with coercivities in excess of 500 Oe have been obtained by rapid annealing of sputtered metastable FexCu1-x alloys. The enhanced magnetic properties of these phase-separated materials are typical of single-domain Fe grains, and can be controlled by the annealing temperature. The Cu matrix, however, is highly conducting, unlike conventional granular materials where the matrix is generally insulating. The evolution of the magnetic properties and microstructure during annealing are described.

  8. Refraction of shear zones in granular materials

    E-print Network

    Tamas Unger

    2007-01-08

    We study strain localization in slow shear flow focusing on layered granular materials. A heretofore unknown effect is presented here. We show that shear zones are refracted at material interfaces in analogy with refraction of light beams in optics. This phenomenon can be obtained as a consequence of a recent variational model of shear zones. The predictions of the model are tested and confirmed by 3D discrete element simulations. We found that shear zones follow Snell's law of light refraction.

  9. On the Definition of Service Granularity and Its Architectural Impact

    Microsoft Academic Search

    Raf Haesen; Monique Snoeck; Wilfried Lemahieu; Stephan Poelmans

    2008-01-01

    Service granularity generally refers to the size of a service. The fact that services should be large-sized or coarse-grained\\u000a is often postulated as a fundamental design principle of service oriented architecture (SOA). However, multiple meanings are\\u000a put on the term granularity and the impact of granularity on architectural qualities is not always clear. In order to structure\\u000a the discussion, we

  10. Tunable wetting of polymer surfaces.

    PubMed

    Yilgor, Iskender; Bilgin, Sevilay; Isik, Mehmet; Yilgor, Emel

    2012-10-16

    A simple method was developed for the preparation of polymeric materials with controlled surface wettability or tunable surface wetting. The method is applicable to a large number of polymers, thermoplastic or thermoset. With this method, it is possible to prepare polymer surfaces with static water contact angles ranging from 0° (superhydrophilic) to greater than 170° (superhydrophobic). The method developed is based on spin-coating of a hydrophilic/hydrophobic silica mixture dispersed in an organic solvent or solvent mixture onto the polymer surface. Depending on the hydrophilic/hydrophobic silica ratio in the coating mixture, it is possible to obtain polymer surfaces displaying gradually changing wettability from superhydrophilic to superhydrophobic. In this article, preparation and surface characteristics of polystyrene (PS) and cross-linked epoxy resin (ER) films are provided as general examples. Polymer surfaces obtained were characterized by scanning electron microscopy, white light interferometry, atomic force microscopy, X-ray photoelectron spectroscopy, and static water contact angle measurements. Effects of the type of polymeric substrate and composition of the silica mixture on the surface behavior of the composite systems were investigated. PMID:22989033

  11. Precursor films in wetting phenomena.

    PubMed

    Popescu, M N; Oshanin, G; Dietrich, S; Cazabat, A-M

    2012-06-20

    The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in the last decade similar films have been reported to occur in solid-on-solid systems. While the situations in which the thickness of such films is of mesoscopic size are fairly well understood, an intriguing and yet to be fully understood aspect is the spreading of microscopic, i.e. molecularly thin, films. Here we review the available experimental observations of such films in various liquid-on-solid and solid-on-solid systems, as well as the corresponding theoretical models and studies aimed at understanding their formation and spreading dynamics. Recent developments and perspectives for future research are discussed. PMID:22627067

  12. Precursor films in wetting phenomena

    NASA Astrophysics Data System (ADS)

    Popescu, M. N.; Oshanin, G.; Dietrich, S.; Cazabat, A.-M.

    2012-06-01

    The spontaneous spreading of non-volatile liquid droplets on solid substrates poses a classic problem in the context of wetting phenomena. It is well known that the spreading of a macroscopic droplet is in many cases accompanied by a thin film of macroscopic lateral extent, the so-called precursor film, which emanates from the three-phase contact line region and spreads ahead of the latter with a much higher speed. Such films have been usually associated with liquid-on-solid systems, but in the last decade similar films have been reported to occur in solid-on-solid systems. While the situations in which the thickness of such films is of mesoscopic size are fairly well understood, an intriguing and yet to be fully understood aspect is the spreading of microscopic, i.e. molecularly thin, films. Here we review the available experimental observations of such films in various liquid-on-solid and solid-on-solid systems, as well as the corresponding theoretical models and studies aimed at understanding their formation and spreading dynamics. Recent developments and perspectives for future research are discussed.

  13. Mechanics of Granular Materials-3 (MGM-3)

    NASA Technical Reports Server (NTRS)

    Sture, Stein; Alshibi, Khalid; Guynes, Buddy (Technical Monitor)

    2002-01-01

    Scientists are going to space to understand how earthquakes and other forces disturb grains of soil and sand. They will examine how the particle arrangement and structure of soils, grains and powders are changed by external forces and gain knowledge about the strength, stiffness and volume changes properties of granular materials at low pressures. The Mechanics of Granular Materials (MGM) experiment uses the microgravity of orbit to test sand columns under conditions that cannot be obtained in experiments on Earth. Research can only go so far on Earth because gravity-induced stresses complicate the analysis and change loads too quickly for detailed analysis. This new knowledge will be applied to improving foundations for buildings, managing undeveloped land, and handling powdered and granular materials in chemical, agricultural, and other industries. NASA wants to understand the way soil behaves under different gravity levels so that crews can safely build habitats on Mars and the Moon. Future MGM experiments will benefit from extended tests aboard the International Space Station, including experiments under simulated lunar and Martian gravity in the science centrifuge.

  14. Structural characterization of submerged granular packings

    NASA Astrophysics Data System (ADS)

    Jakši?, Z. M.; Š?epanovi?, J. R.; Lon?arevi?, I.; Budinski-Petkovi?, Lj.; Vrhovac, S. B.; Beli?, A.

    2014-12-01

    We consider the impact of the effective gravitational acceleration on microstructural properties of granular packings through experimental studies of spherical granular materials saturated within fluids of varying density. We characterize the local organization of spheres in terms of contact connectivity, distribution of the Delaunay free volumes, and the shape factor (parameter of nonsphericity) of the Voronoï polygons. The shape factor gives a clear physical picture of the competition between less and more ordered domains of particles in experimentally obtained packings. As the effective gravity increases, the probability distribution of the shape factor becomes narrower and more localized around the lowest values of the shape factor corresponding to regular hexagon. It is found that curves of the pore distributions are asymmetric with a long tail on the right-hand side, which progressively reduces while the effective gravity gets stronger for lower densities of interstitial fluid. We show that the distribution of local areas (Voronoï cells) broadens with decreasing value of the effective gravity due to the formation of lose structures such as large pores and chainlike structures (arches or bridges). Our results should be particularly helpful in testing the newly developed simulation techniques involving liquid-related forces associated with immersed granular particles.

  15. Energy dissipation in sheared granular flows

    SciTech Connect

    Karion, A.; Hunt, M.L.

    1999-11-01

    Granular material flows describe flows of solid particles in which the interstitial fluid plays a negligible role in the flow mechanics. Examples include the transport of coal, food products, detergents, pharmaceutical tablets, and toner particles in high-speed printers. Using a two-dimensional discrete element computer simulation of a bounded, gravity-free Couette flow of particles, the heat dissipation rate per unit area is calculated as a function of position in the flow as well as overall solid fraction. The computation results compare favorably with the kinetic theory analysis for rough disks. The heat dissipation rate is also measured for binary mixtures of particles for different small to large solid fraction ratios, and for diameter ratios of ten, five, and two. The dissipation rates increase significantly with overall solid fraction as well as local strain rates and granular temperatures. The thermal energy equation is solved for a Couette flow with one adiabatic wall and one at constant temperature. Solutions use the simulation measurements of the heat dissipation rate, solid fraction, and granular temperature to show that the thermodynamic temperature increases with solid fraction and decreases with particle conductivity. In mixtures, both the dissipation rate and the thermodynamic temperature increase with size ratio and with decreasing ratio of small to large particles.

  16. Mechanics of Granular Materials Test Cell

    NASA Technical Reports Server (NTRS)

    1998-01-01

    A test cell for Mechanics of Granular Materials (MGM) experiment is shown from all three sides by its video camera during STS-89. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/Marshall Space Flight Center (MSFC)

  17. Mechanics of Granular Materials (MGM) Cell

    NASA Technical Reports Server (NTRS)

    1996-01-01

    One of three Mechanics of Granular Materials (MGM) test cells after flight on STS-79 and before impregnation with resin. Note that the sand column has bulged in the middle, and that the top of the column is several inches lower than the top of the plastic enclosure. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

  18. Mechanics of Granular Materials (MGM) Test Cell

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A test cell for Mechanics of Granular Materials (MGM) experiment is tested for long-term storage with water in the system as plarned for STS-107. This view shows the compressed sand column with the protective water jacket removed. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

  19. Mechanics of Granular Materials (MGM) Flight Hardware

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A test cell for the Mechanics of Granular Materials (MGM) experiment is shown in its on-orbit configuration in Spacehab during preparations for STS-89. The twin locker to the left contains the hydraulic system to operate the experiment. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Note: Because the image on the screen was muted in the original image, its brightness and contrast are boosted in this rendering to make the test cell more visible. Credit: NASA/Marshall Space Flight Center (MSFC)

  20. Mechanics of Granular Materials (MGM) Test Cell

    NASA Technical Reports Server (NTRS)

    1998-01-01

    A test cell for Mechanics of Granular Materials (MGM) experiment is shown approximately 20 and 60 minutes after the start of an experiment on STS-89. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/Marshall Space Flight Center (MSFC)

  1. Mechanics of Granular Materials (MGM) Test Cell

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A test cell for Mechanics of Granular Materials (MGM) experiment is tested for long-term storage with water in the system as plarned for STS-107. This view shows the top of the sand column with the metal platten removed. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

  2. Vibratory Shock Compaction of Granular Nuclear Waste

    NASA Astrophysics Data System (ADS)

    Amme, Robert C.

    2004-05-01

    Vibratory Shock Compaction (VSC) is a proven means for quickly forming strong, durable solids from a wide variety of granular materials[1]. Calcination of tank and other forms of high level radioactive wastes results in fine granular material that is quite amenable to volume reduction and stabilization. We have employed utilities coal ash as a calcine waste surrogate, blended with a quartz/feldspar-rich sand and 0-20% proportions of a borosilicate glass. The blends were compacted at room temperature and fired so that the glass melt could form an efficient binder. Included in the blend are small quantities of three RCRA metals, chromium, cadmium and lead, to permit testing for heavy metal stability. The VSC process is described and the results presented in terms of the waste form dissolution rates, compressive strengths, elastic moduli as determined from resonant frequency measurements, and heavy metal leach rates from Toxicity Characteristic Leaching Procedure measurements. Vibratory shock compaction employing glass binders appears to be a viable alternative to traditional vitrification processes for granular waste forms. [1] See http://www.resonantshockcompact.com

  3. Structural characterization of submerged granular packings.

    PubMed

    Jakši?, Z M; Š?epanovi?, J R; Lon?arevi?, I; Budinski-Petkovi?, Lj; Vrhovac, S B; Beli?, A

    2014-12-01

    We consider the impact of the effective gravitational acceleration on microstructural properties of granular packings through experimental studies of spherical granular materials saturated within fluids of varying density. We characterize the local organization of spheres in terms of contact connectivity, distribution of the Delaunay free volumes, and the shape factor (parameter of nonsphericity) of the Voronoï polygons. The shape factor gives a clear physical picture of the competition between less and more ordered domains of particles in experimentally obtained packings. As the effective gravity increases, the probability distribution of the shape factor becomes narrower and more localized around the lowest values of the shape factor corresponding to regular hexagon. It is found that curves of the pore distributions are asymmetric with a long tail on the right-hand side, which progressively reduces while the effective gravity gets stronger for lower densities of interstitial fluid. We show that the distribution of local areas (Voronoï cells) broadens with decreasing value of the effective gravity due to the formation of lose structures such as large pores and chainlike structures (arches or bridges). Our results should be particularly helpful in testing the newly developed simulation techniques involving liquid-related forces associated with immersed granular particles. PMID:25615086

  4. A Taylor vortex analogy in granular flows.

    PubMed

    Conway, Stephen L; Shinbrot, Troy; Glasser, Benjamin J

    2004-09-23

    Fluids sheared between concentric rotating cylinders undergo a series of three-dimensional instabilities. Since Taylor's archetypal 1923 study, these have proved pivotal to understanding how fluid flows become unstable and eventually undergo transitions to chaotic or turbulent states. In contrast, predicting the dynamics of granular systems--from nano-sized particles to debris flows--is far less reliable. Under shear these materials resemble fluids, but solid-like responses, non-equilibrium structures and segregation patterns develop unexpectedly. As a result, the analysis of geophysical events and the performance of largely empirical particle technologies might suffer. Here, using gas fluidization to overcome jamming, we show experimentally that granular materials develop vortices consistent with the primary Taylor instability in fluids. However, the vortices observed in our fluidized granular bed are unlike those in fluids in that they are accompanied by novel mixing-segregation transitions. The vortices seem to alleviate increased strain by spawning new vortices, directly modifying the scale of kinetic interactions. Our observations provide insights into the mechanisms of shear transmission by particles and their consequent convective mixing. PMID:15386007

  5. Acoustic probing of elastic behavior and damage in weakly cemented granular media

    NASA Astrophysics Data System (ADS)

    Langlois, V.; Jia, X.

    2014-02-01

    We investigate the elastic behavior and damage of weakly cemented granular media under external load with ultrasound. The cementation controlled experiments are performed by freezing the capillary liquid at the bead contact in a dense glass or polymeric [poly(methyl methacrylate)] bead pack wet by tetradecane of volume fraction ? = 0.1%-4%. When the pendular rings are solidified, an abrupt increase by a factor of 2 in the compressional wave velocity is observed. We interpret the data in terms of effective medium models in which the contact stiffnesses are derived by either a bonded contact model [P. J. Digby, J. Appl. Mech. 48, 803 (1981), 10.1115/1.3157738] or a cemented contact model [J. Dvorkin, A. Nur, and H. Yin, Mech. Mater. 18, 351 (1994), 10.1016/0167-6636(94)90044-2]. The former fails to quantitatively account for the results with a soft cement relative to the grain, whereas the latter considering the mechanical properties of the cement does apply. Moreover, we monitor the irreversible behavior of the cemented granular packs under moderate uniaxial loading (<1.3 MPa) with the correlation method of ultrasound scattering. The damage of the cemented materials is accompanied by a compressional wave velocity decrease up to 60%, likely due to the fractures induced at the grain-cement interfaces.

  6. Acoustic probing of elastic behavior and damage in weakly cemented granular media.

    PubMed

    Langlois, V; Jia, X

    2014-02-01

    We investigate the elastic behavior and damage of weakly cemented granular media under external load with ultrasound. The cementation controlled experiments are performed by freezing the capillary liquid at the bead contact in a dense glass or polymeric [poly(methyl methacrylate)] bead pack wet by tetradecane of volume fraction ? = 0.1%-4%. When the pendular rings are solidified, an abrupt increase by a factor of 2 in the compressional wave velocity is observed. We interpret the data in terms of effective medium models in which the contact stiffnesses are derived by either a bonded contact model [P. J. Digby, J. Appl. Mech. 48, 803 (1981)] or a cemented contact model [J. Dvorkin, A. Nur, and H. Yin, Mech. Mater. 18, 351 (1994)]. The former fails to quantitatively account for the results with a soft cement relative to the grain, whereas the latter considering the mechanical properties of the cement does apply. Moreover, we monitor the irreversible behavior of the cemented granular packs under moderate uniaxial loading (1.3 MPa) with the correlation method of ultrasound scattering. The damage of the cemented materials is accompanied by a compressional wave velocity decrease up to 60%, likely due to the fractures induced at the grain-cement interfaces. PMID:25353594

  7. Microgravity Experiments to Evaluate Electrostatic Forces in Controlling Cohesion and Adhesion of Granular Materials

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Weislogel, M.; Jacobson, T.

    1999-01-01

    The bulk behavior of dispersed, fluidized, or undispersed stationary granular systems cannot be fully understood in terms of adhesive/cohesive properties without understanding the role of electrostatic forces acting at the level of the grains themselves. When grains adhere to a surface, or come in contact with one another in a stationary bulk mass, it is difficult to measure the forces acting on the grains, and the forces themselves that induced the cohesion and adhesion are changed. Even if a single grain were to be scrutinized in the laboratory, it might be difficult, perhaps impossible, to define the distribution and character of surface charging and the three-dimensional relationship that charges (electrons, holes) have to one another. The hypothesis that we propose to test in microgravity (for dielectric materials) is that adhesion and cohesion of granular matter are mediated primarily by dipole forces that do not require the presence of a net charge; in fact, nominally electrically neutral materials should express adhesive and cohesive behavior when the neutrality results from a balance of positive and negative charge carriers. Moreover, the use of net charge alone as a measure of the electrical nature of grain-to-grain relationships within a granular mass may be misleading. We believe that the dipole forces arise from the presence of randomly-distributed positive and negative fixed charge carriers on grains that give rise to a resultant dipole moment. These dipole forces have long-range attraction. Random charges are created whenever there is triboelectrical activity of a granular mass, that is, whenever the grains experience contact/separation sequences or friction.

  8. Regulation of aerobic granular sludge reformulation after granular sludge broken: effect of poly aluminum chloride (PAC).

    PubMed

    Liu, Yongjun; Liu, Zhe; Wang, Fukun; Chen, Yiping; Kuschk, Peter; Wang, Xiaochang

    2014-04-01

    The present study focuses on the effect of poly aluminum chloride (PAC) on the re-formation of aerobic granular sludge after its rupture. The morphological changes, physical characteristics such as SVI, mechanical strength and surface properties of aerobic granular sludge during the re-formation process of broken granules were investigated. Moreover, components (protein (PN), polysaccharides (PS)) and distributions (soluble, loosely-bound (LB), tightly-bound (TB)) of extracellular polymeric substances (EPS) in sludge flocs were taken into consideration. It was found that the effect of charge neutralization and bridging induced by PAC treatment improved the surface properties of sludge, the re-formed granules had a larger size, more compact structure and that the removal performance of pollutants after chemical coagulation had improved. The results of correlation analysis demonstrated that PN in EPS correlated well with the surface characteristics and settling ability of sludge flocs, and PAC treatment strengthened the influence, further accelerated the reformation of granular sludge. PMID:24607455

  9. Tap Density Equations of Granular Powders Based on the Rate Process Theory and the Free Volume Concept

    E-print Network

    Tian Hao

    2014-09-05

    Tap density of a granular powder is often linked to the flowability via Carr Index that measures how tight a powder can be packed, under an assumption that more easily packed powders usually flow poorly. Understanding how particles are packed is important for revealing why a powder flows better than others. There are two types of empirical equations that were proposed to fit the experimental data of packing fractions vs. numbers of taps in literature: The inverse logarithmic and the stretched exponential. Using the rate process theory and the free volume concept, we obtain the tap density equations and they can be reducible to the two empirical equations currently widely used in literature. Our equations could potentially fit experimental data better with an additional adjustable parameter. The tapping amplitude and frequency, the weight of the granular materials, and the environment temperature are grouped into one parameter that weighs the pace of packing process. The current results, in conjunction with our previous findings, may imply that both dry(granular)and wet(colloidal and polymeric) particle systems are governed by the same physical mechanisms in term of the role of the free volume and how particles behave (a rate controlled process).

  10. Dynamic Behaviors of Supersonic Granular Media under Vertical Vibration

    E-print Network

    Kai Huang; Peng Zhang; Guoqing Miao; Rongjue Wei

    2005-11-29

    We present experimental study of vibrofluidized granular materials by high speed photography. Statistical results present the averaged dynamic behaviors of granular materials in one cycle, including the variations of height, velocity and mechanical energy of the center of mass. Furthermore, time-space distribution of granular temperature which corresponds to the random kinetic energy shows that a temperature peak forms in the compression period and propagates upward with a steepened front. The Mach number in the steepened front is found to be greater than unity, indicating a shock propagating in the supersonic granular media.

  11. Nonlinear elasto-plastic model for dense granular flow

    E-print Network

    Ken Kamrin

    2009-05-07

    This work proposes a model for granular deformation that predicts the stress and velocity profiles in well-developed dense granular flows. Recent models for granular elasticity (Jiang and Liu 2003) and rate-sensitive plastic flow (Jop et al. 2006) are reformulated and combined into one universal granular continuum law, capable of predicting flowing regions and stagnant zones simultaneously in any arbitrary 3D flow geometry. The unification is performed by justifying and implementing a Kroner-Lee elasto-plastic decomposition, with care taken to ensure certain continuum physical principles are necessarily upheld. The model is then numerically implemented in multiple geometries and results are compared to experiments and discrete simulations.

  12. Granular Partitions and Vagueness Thomas Bittner and Barry Smith

    E-print Network

    Forbus, Kenneth D.

    Terms -- Theory, Human factors Keywords -- Vagueness, Ontology, Granular Partitions, Semantics 1. Introduction Consider the proper name `Mount Everest'. This refers to some mereological whole, a certain giant

  13. From nanoscale cohesion to macroscale entanglement: Opportunities for designing granular aggregate behavior by tailoring grain shape and interactions

    NASA Astrophysics Data System (ADS)

    Jaeger, Heinrich M.; Miskin, Marc Z.; Waitukaitis, Scott R.

    2013-06-01

    The packing arrangement of individual particles inside a granular material and the resulting response to applied stresses depend critically on particle-particle interactions. One aspect that recently received attention are nanoscale surface features of particles, which play an important role in determining the strength of cohesive van der Waals and capillary interactions and also affect tribo-charging of grains. We describe experiments on freely falling granular streams that can detect the contributions from all three of these forces. We show that it is possible to measure the charge of individual grains and build up distributions that are detailed enough to provide stringent tests of tribo-charging models currently available. A second aspect concerns particle shape. In this case steric interactions become important and new types of aggregate behavior can be expected when non-convex particle shapes are considered that can interlock or entangle. However, a general connection between the mechanical response of a granular material and the constituents' shape remains unknown. This has made it infeasible to tackle the "inverse packing problem", namely to start from a given, desired behavior for the aggregate as a whole and then find the particle shape the produces it. We discuss a new approach, using concepts rooted in artificial evolution that provides a way to solve this inverse problem. This approach facilitates exploring the role of arbitrary particle geometry in jammed systems and invites the discovery and design of granular matter with optimized properties.

  14. Order of wetting transitions in electrolyte solutions.

    PubMed

    Ibagon, Ingrid; Bier, Markus; Dietrich, S

    2014-05-01

    For wetting films in dilute electrolyte solutions close to charged walls we present analytic expressions for their effective interface potentials. The analysis of these expressions renders the conditions under which corresponding wetting transitions can be first- or second-order. Within mean field theory we consider two models, one with short- and one with long-ranged solvent-solvent and solvent-wall interactions. The analytic results reveal in a transparent way that wetting transitions in electrolyte solutions, which occur far away from their critical point (i.e., the bulk correlation length is less than half of the Debye length) are always first-order if the solvent-solvent and solvent-wall interactions are short-ranged. In contrast, wetting transitions close to the bulk critical point of the solvent (i.e., the bulk correlation length is larger than the Debye length) exhibit the same wetting behavior as the pure, i.e., salt-free, solvent. If the salt-free solvent is governed by long-ranged solvent-solvent as well as long-ranged solvent-wall interactions and exhibits critical wetting, adding salt can cause the occurrence of an ion-induced first-order thin-thick transition which precedes the subsequent continuous wetting as for the salt-free solvent. PMID:24811661

  15. Order of wetting transitions in electrolyte solutions

    SciTech Connect

    Ibagon, Ingrid, E-mail: ingrid@is.mpg.de; Bier, Markus, E-mail: bier@is.mpg.de; Dietrich, S. [Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany)] [Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany)

    2014-05-07

    For wetting films in dilute electrolyte solutions close to charged walls we present analytic expressions for their effective interface potentials. The analysis of these expressions renders the conditions under which corresponding wetting transitions can be first- or second-order. Within mean field theory we consider two models, one with short- and one with long-ranged solvent-solvent and solvent-wall interactions. The analytic results reveal in a transparent way that wetting transitions in electrolyte solutions, which occur far away from their critical point (i.e., the bulk correlation length is less than half of the Debye length) are always first-order if the solvent-solvent and solvent-wall interactions are short-ranged. In contrast, wetting transitions close to the bulk critical point of the solvent (i.e., the bulk correlation length is larger than the Debye length) exhibit the same wetting behavior as the pure, i.e., salt-free, solvent. If the salt-free solvent is governed by long-ranged solvent-solvent as well as long-ranged solvent-wall interactions and exhibits critical wetting, adding salt can cause the occurrence of an ion-induced first-order thin-thick transition which precedes the subsequent continuous wetting as for the salt-free solvent.

  16. Dark Matter

    NASA Astrophysics Data System (ADS)

    Einasto, Jaan

    2013-12-01

    I review the development of the concept of dark matter. The dark matter story passed through several stages, from a minor observational puzzle to a major challenge for theory of elementary particles. Modern data suggest that dark matter is the dominant matter component in the Universe and that it consists of some unknown non-baryonic particles. Dark matter is the dominant matter component in the Universe; therefore, properties of dark matter particles determine the structure of the cosmic web.

  17. Mutiscale Modeling of Segregation in Granular Flows

    SciTech Connect

    Jin Sun

    2007-08-03

    Modeling and simulation of segregation phenomena in granular flows are investigated. Computational models at different scales ranging from particle level (microscale) to continuum level (macroscale) are employed in order to determine the important microscale physics relevant to macroscale modeling. The capability of a multi-fluid model to capture segregation caused by density difference is demonstrated by simulating grain-chaff biomass flows in a laboratory-scale air column and in a combine harvester. The multi-fluid model treats gas and solid phases as interpenetrating continua in an Eulerian frame. This model is further improved by incorporating particle rotation using kinetic theory for rapid granular flow of slightly frictional spheres. A simplified model is implemented without changing the current kinetic theory framework by introducing an effective coefficient of restitution to account for additional energy dissipation due to frictional collisions. The accuracy of predicting segregation rate in a gas-fluidized bed is improved by the implementation. This result indicates that particle rotation is important microscopic physics to be incorporated into the hydrodynamic model. Segregation of a large particle in a dense granular bed of small particles under vertical. vibration is studied using molecular dynamics simulations. Wall friction is identified as a necessary condition for the segregation. Large-scale force networks bearing larger-than-average forces are found with the presence of wall friction. The role of force networks in assisting rising of the large particle is analyzed. Single-point force distribution and two-point spatial force correlation are computed. The results show the heterogeneity of forces and a short-range correlation. The short correlation length implies that even dense granular flows may admit local constitutive relations. A modified minimum spanning tree (MST) algorithm is developed to asymptotically recover the force statistics in the force networks. This algorithm provides a possible route to constructing a continuum model with microstructural information supplied from it. Microstructures in gas fluidized beds are also analyzed using a hybrid method, which couples the discrete element method (DEM) for particle dynamics with the averaged two-fluid (TF) equations for the gas phase. Multi-particle contacts are found in defluidized regions away from bubbles in fluidized beds. The multi-particle contacts invalidate the binary-collision assumption made in the kinetic theory of granular flows for the defluidized regions. Large ratios of contact forces to drag forces are found in the same regions, which confirms the relative importance of contact forces in determining particle dynamics in the defluidized regions.

  18. Our experience with wet-wrap treatment.

    PubMed

    Albarrán-Planelles, C; Jiménez-Gallo, D; Linares-Barrios, M; Martínez-Rodríguez, A

    2014-04-01

    A wide range of treatments are currently available for severe atopic dermatitis, including systemic therapies such as ciclosporin, corticosteroids, azathioprine, methotrexate, mofetil mycophenolate, and omalizumab. In patients who can no longer take systemic drugs or who need a dose reduction, wet-wrap treatment can be an excellent option. To date, wet wraps have mostly been used in severe cases of childhood atopic dermatitis. We report our experience with wet-wrap treatment in 5 adults with atopic dermatitis and 2 with nodular prurigo. The results were satisfactory and there were few adverse effects. PMID:24657020

  19. Wetting interaction between Sn-Zn-Ag solders and Cu

    Microsoft Academic Search

    Kwang-Lung Lin; Chia-Ling Shih

    2003-01-01

    The wetting interaction of Sn-(7.1–9)Zn-(0–3)Ag solders with Cu was investigated from 230C to 300C. The wetting time, wetting\\u000a forces, and activation energy of the wetting reaction were studied. The wetting time decreases with increasing temperature\\u000a and increases with Ag content. The wetting force exhibits a disproportional correlation to temperature rise, while no trend\\u000a was observed with respect to Ag content.

  20. Elastic weakening of a dense granular medium by acoustic fluidization

    NASA Astrophysics Data System (ADS)

    Jia, Xiaoping; Laurent, Jerome; Wildenberg, Siet; van Hecke, Martin

    2012-02-01

    Elastic waves propagating through a dense granular pack provide a unique probe of the elastic properties and internal dissipation of the medium [1], and also allow investigating the irreversible rearrangement of the contact network at large vibration amplitude. In this talk, we describe two distinct types of nonlinearity, i.e. hertzian and frictional, at the grain contact by sound amplitude and velocity measurements, respectively, under different confining pressure [2]. Beyond certain wave amplitude, the sound-matter interaction becomes irreversible, leaving the medium in a weakened and slightly compacted state. A slow recovery of the initial elastic modulus is observed after acoustic perturbation, revealing the plastic creep growth of microcontacts. The cross-correlation function of configuration-specific acoustic speckles highlights the relationship between the macroscopic elastic weakening and the local change of the contact networks, induced by strong sound vibration, in the absence of appreciable grain motion. We show that the softening of elastic modulus is much more pronounced with the shear wave (up to 20%) than with the compressional wave (to 10%). [4pt] [1] Th. Brunet, X. Jia and P. Mills, Phys. Rev. Lett 101, 138001 (2008) [0pt] [2] Th. Brunet, X. Jia and P. Johnson, Geophys. Res. Lett 35, L19308 (2008); X. Jia, Th. Brunet and J. Laurent, Phys. Rev. E 00, 000300(R) (2011)

  1. The thermodynamics of dense granular flow and jamming

    NASA Astrophysics Data System (ADS)

    Lu, Shih Yu

    The scope of the thesis is to propose, based on experimental evidence and theoretical validation, a quantifiable connection between systems that exhibit the jamming phenomenon. When jammed, some materials that flow are able to resist deformation so that they appear solid-like on the laboratory scale. But unlike ordinary fusion, which has a critically defined criterion in pressure and temperature, jamming occurs under a wide range of conditions. These condition have been rigorously investigated but at the moment, no self-consistent framework can apply to grains, foam and colloids that may have suddenly ceased to flow. To quantify the jamming behavior, a constitutive model of dense granular flows is deduced from shear-flow experiments. The empirical equations are then generalized, via a thermodynamic approach, into an equation-of-state for jamming. Notably, the unifying theory also predicts the experimental data on the behavior of molecular glassy liquids. This analogy paves a crucial road map for a unifying theoretical framework in condensed matter, for example, ranging from sand to fire retardants to toothpaste.

  2. The theory of granular packings for coarse soils

    NASA Astrophysics Data System (ADS)

    Yanqui, Calixtro

    2013-06-01

    Coarse soils are substances made of grains of different shape, size and orientation. In this paper, new massive-measurable grain indexes are defined to develop a simple and systematic theory for the ideal packing of grains. First, a linear relationship between an assemblage of monodisperse spheres and an assemblage of polydisperse grains is deduced. Then, a general formula for the porosity of linearly ordered packings of spheres in contact is settled down by the appropriated choosing of eight neighboring spheres located at the vertices of the unit parallelepiped. The porosity of axisymmetric packings of grains, related to sand piles and axisymmetric compression tests, is proposed to be determined averaging the respective linear parameters. Since they can be tested experimentally, porosities of the densest state and the loosest state of a granular soil can be used to verify the accuracy of the present theory. Diagrams for these extreme quantities show a good agreement between the theoretical lines and the experimental data, no matter the dependency on the protocols and mineral composition.

  3. Wetting transparency of graphene in water

    NASA Astrophysics Data System (ADS)

    Driskill, Joshua; Vanzo, Davide; Bratko, Dusan; Luzar, Alenka

    2014-11-01

    Measurements of contact angle on graphene sheets show a notable dependence on the nature of the underlying substrate, a phenomenon termed wetting transparency. Our molecular modeling studies reveal analogous transparency in case of submerged graphene fragments in water. A combined effect of attractive dispersion forces, angle correlations between aqueous dipoles, and repulsion due to the hydrogen-bond-induced orientation bias in polarized hydration layers acting across graphene sheet, enhances apparent adhesion of water to graphene. We show wetting free energy of a fully wetted graphene platelet to be about 8 mNm-1 lower than for graphene wetted only on one side, which gives close to 10° reduction in contact angle. This difference has potential implications for predictions of water absorption vs. desorption, phase behavior of water in aqueous nanoconfinements, solvent-induced interactions among graphitic nanoparticle and concomitant stability in aqueous dispersions, and can influence permeability of porous materials such as carbon nanotubes by water and aqueous solutions.

  4. ESTIMATING URBAN WET-WEATHER POLLUTANT LOADING

    EPA Science Inventory

    This paper presents procedures for estimating pollutant loads in urban watersheds emanating from wet-weather flow discharge. Equations for pollutant loading estimates will focus on the effects of wastewater characteristics, sewer flow carrying velocity, and sewer-solids depositi...

  5. Chlorine Disinfection of Wet Weather Managed Flows

    EPA Science Inventory

    Blending is a practice used in the wastewater industry to deal with wet weather events when the hydraulic capacity of the treatment facility could be compromised. Blending consists of primary wastewater treatment plant effluent, partially bypassing secondary treatment, and then ...

  6. World Heritage: Welcome to the Wet Tropics

    NSDL National Science Digital Library

    This Web site serves as a visitorâ??s guide to tropical North Queenslandâ??s World Heritage Area -- "the sort of place you could travel to over and over again and still not see everything." The same might be said of this incredibly comprehensive Web site, which provides pages and pages of information about Australiaâ??s wet tropics. Virtual visitors can read up on the flora and fauna of the region, check out some of the sights, learn about Aboriginal culture, and much more. The site also offers a downloadable Cassowary Education Kit (for grades 5-7) and a Wet Tropics Library, providing "a comprehensive and easy to access collection of information related to the Wet Tropics and the Wet Tropics Management Authority."

  7. A WET TALE: TOXICITY OF COMPLEX EFFLUENTS

    EPA Science Inventory

    This course covers standards, regulations, policy, guidance and technical aspects of implementing the whole effluent toxicity program. The curriculum incorporates rationale and information on WET test requirements from USEPA documents, such as the Technical Support Document for W...

  8. Wetting on flexible hydrophilic pillar-arrays

    PubMed Central

    Yuan, Quanzi; Zhao, Ya-Pu

    2013-01-01

    Dynamic wetting on the flexible hydrophilic pillar-arrays is studied using large scale molecular dynamics simulations. For the first time, the combined effect of the surface topology, the intrinsic wettability and the elasticity of a solid on the wetting process is taken into consideration. The direction-dependent dynamics of both liquid and pillars, especially at the moving contact line (MCL), is revealed at atomic level. The flexible pillars accelerate the liquid when the liquid approaches, and pin the liquid when the liquid passes. The liquid deforms the pillars, resulting energy dissipation at the MCL. Scaling analysis is performed based on molecular kinetic theory and validated by our simulations. Our results may expand our knowledge of wetting on pillars and assisting the future design of active control of wetting in practical applications. PMID:23736041

  9. Reducing the atmospheric impact of wet slaking

    SciTech Connect

    B.D. Zubitskii; G.V. Ushakov; B.G. Tryasunov; A.G.Ushakov [Kuznetsk Basin State Technical University, Kemerovo (Russian Federation)

    2009-05-15

    Means of reducing the atmospheric emissions due to the wet slaking of coke are considered. One option, investigated here, is to remove residual active silt and organic compounds from the biologically purified wastewater sent for slaking, by coagulation and flocculation.

  10. Wafer Backside Anisotropic Wet Etching of Silicon

    NSDL National Science Digital Library

    This animation, created by Southwest Center for Microsystems Education (SCME), illustrates how the "wafer backside anisotropic wet etching of silicon is used to form the pressure sensor chamber." Further information and resources can be found on the SCME website.

  11. Skin Rashes Due to Bed-Wetting

    MedlinePLUS

    ... Newsroom Contact Us You are here Home » Skin Rashes Due to Bed-wetting Rashes on the bottom and genital area are a ... long time, these chemicals can be irritating. Skin rashes develop more often in children who wear absorbent ...

  12. 7 CFR 29.3567 - Wet (W).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3567 Wet (W). Any sound tobacco...

  13. 7 CFR 29.3567 - Wet (W).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3567 Wet (W). Any sound tobacco...

  14. Wetting films on chemically heterogeneous substrates

    E-print Network

    C. Bauer; S. Dietrich

    1999-06-11

    Based on a microscopic density functional theory we investigate the morphology of thin liquidlike wetting films adsorbed on substrates endowed with well-defined chemical heterogeneities. As paradigmatic cases we focus on a single chemical step and on a single stripe. In view of applications in microfluidics the accuracy of guiding liquids by chemical microchannels is discussed. Finally we give a general prescription of how to investigate theoretically the wetting properties of substrates with arbitrary chemical structures.

  15. Wet\\/dry cooling tower and method

    Microsoft Academic Search

    Leon R. Glicksman; Warren R. Rohsenow

    1981-01-01

    A wet\\/dry cooling tower wherein a liquid to-be-cooled is flowed along channels of a corrugated open surface or the like, which surface is swept by cooling air. The amount of the surface covered by the liquid is kept small compared to the dry part thereof so that said dry part acts as a fin for the wet part for heat

  16. Wet/dry cooling tower and method

    DOEpatents

    Glicksman, Leon R. (Lynnfield, MA); Rohsenow, Warren R. (Waban, MA)

    1981-01-01

    A wet/dry cooling tower wherein a liquid to-be-cooled is flowed along channels of a corrugated open surface or the like, which surface is swept by cooling air. The amount of the surface covered by the liquid is kept small compared to the dry part thereof so that said dry part acts as a fin for the wet part for heat dissipation.

  17. Wet chemical functionalization of graphene.

    PubMed

    Hirsch, Andreas; Englert, Jan M; Hauke, Frank

    2013-01-15

    The fullerenes, carbon nanotubes, and graphene have enriched the family of carbon allotropes over the last few decades. Synthetic carbon allotropes (SCAs) have attracted chemists, physicists, and materials scientists because of the sheer multitude of their aesthetically pleasing structures and, more so, because of their outstanding and often unprecedented properties. They consist of fully conjugated p-electron systems and are considered topologically confined objects in zero, one, or two dimensions. Among the SCAs, graphene shows the greatest potential for high-performance applications, in the field of nanoelectronics, for example. However, significant fundamental research is still required to develop graphene chemistry. Chemical functionalization of graphene will increase its dispersibility in solvents, improve its processing into new materials, and facilitate the combination of graphene's unprecedented properties with those of other compound classes. On the basis of our experience with fullerenes and carbon nanotubes, we have described a series of covalent and noncovalent approaches to generate graphene derivatives. Using water-soluble perylene surfactants, we could efficiently exfoliate graphite in water and prepare substantial amounts of single-layer-graphene (SLG) and few-layer-graphene (FLG). At the same time, this approach leads to noncovalent graphene derivatives because it establishes efficient ?-?-stacking interactions between graphene and the aromatic perylene chromophors supported by hydrophobic interactions. To gain efficient access to covalently functionalized graphene we employed graphite intercalation compounds (GICs), where positively charged metal cations are located between the negatively charged graphene sheets. The balanced combination of intercalation combined with repulsion driven by Coulombic interactions facilitated efficient exfoliation and wet chemical functionalization of the electronically activated graphene sheets via trapping with reactive electrophilic addends. For example, the treatment of reduced graphite with aryl diazonium salts with the elimination of N(2) led to the formation of arylated graphene. We obtained alkylated graphene via related trapping reactions with alkyl iodides. These new developments have opened the door for combining the unprecedented properties of graphene with those of other compound classes. We expect that further studies of the principles of graphene reactivity, improved characterization methods, and better synthetic control over graphene derivatives will lead to a whole series of new materials with highly specific functionalities and enormous potential for attractive applications. PMID:22946482

  18. Concurrent multiscale computational modeling for dense dry granular materials interfacing

    E-print Network

    Regueiro, Richard A.

    of interfacial mechanics between granular soil and tire, tool, or penetrometer, while properly representing far, agricultural grains (in silo flows), dry soils (sand, silt, gravel), and lunar and martian regolith (soil found computational modeling of interfacial mechanics between granular materials and deformable solid bodies

  19. Granular Media on a Vibrating Plate:. a Molecular Dynamics Simulation

    Microsoft Academic Search

    Jason A. C. Gallas; Hans J. Herrmann; Stefan Sokolowski

    1993-01-01

    When sand or other granular materials are shaken, poured or sheared many intriguing phenomena can be observed. We will model the granular medium by a packing of elastic spheres and simulate it via Molecular Dynamics. Dissipation of energy and shear friction at collisions are included. The onset of fluidization can be determined and is in good agreement with experiments. On

  20. Network model of survival signaling in large granular lymphocyte leukemia

    E-print Network

    Albert, Réka

    Network model of survival signaling in large granular lymphocyte leukemia Ranran Zhang , Mithun granular lymphocyte (T-LGL) leukemia features a clonal expansion of antigen-primed, competent, cytotoxic-LGL leukemia, we constructed a T-LGL survival signaling network by integrating the signaling pathways involved

  1. USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

    EPA Science Inventory

    Granular graphite is a potential electrode material for the electrochemical remediation of refractory chlorinated organic compounds such as trichloroethylene (TCE). However, the use of granular graphite can complicate the experimental results. On one hand, up to 99% of TCE was re...

  2. BACKWASH OF GRANULAR FILTERS USED IN WASTEWATER FILTRATION

    EPA Science Inventory

    The use of deep granular filters in waste treatment is of growing importance. The key to long-term operating success of such filters is proper bed design and adequate bed cleaning during backwashing. Cleaning granular filters by water backwash alone to fluidize the filter bed is ...

  3. Particle shape effects on the stress response of granular packings

    E-print Network

    Haller, Gary L.

    -convex geometries such as hexapods with various arm lengths, dolos, and tetrahedral frames. All particles were 3D-printed that particle shape plays a signicant role in controlling a granular material's microstructure,1­5 most work interactions lead to opportunities to generate granular materials with special properties. Gener- ally, as more

  4. Statistical mechanics for static granular media: open questions

    E-print Network

    Paris-Sud XI, Université de

    Statistical mechanics for static granular media: open questions Massimo Pica Ciamarra Patrick existence of a statistical mechanics of static granular systems, which would permit the description important questions concerning such a statistical mechanics approach. First, we consider how the phase space

  5. A homogenization technique for heat transfer in periodic granular materials

    Microsoft Academic Search

    Q. Zhou; H. W. Zhang; Y. G. Zheng

    A homogenization technique is proposed to simulate the thermal conduction of periodic granular materials in vacuum. The effective thermal conductivity (ETC) and effective volumetric heat capacity (EVHC) can be obtained from the granular represent volume element (RVE) via average techniques: average heat flux and average temperature gradient can be formulated by the positions and heat flows of particles on the

  6. Two innovative devices for depth sampling in granular filtration systems

    Microsoft Academic Search

    Natalia Belkin; Edo Bar-Zeev; Tom Berman; Ilana Berman-Frank

    Appropriate devices for obtaining either interstitial water or grain particle samples or for measuring dissolved oxygen (DO) at depth within the interior of large-scale, industrial granular bed filters are currently lacking. We developed two innovative samplers for studying a Rapid Sand Filter (RSF) at an operational SWRO plant: the first for water and granular material, the second for DO measurements.

  7. Creep Motion of a Granular Pile Induced by Thermal Cycling

    Microsoft Academic Search

    Thibaut Divoux; Hervé Gayvallet; Jean-Christophe Géminard

    2008-01-01

    We report a time-resolved study of the dynamics associated with the slow compaction of a granular column submitted to thermal cycles. The column height displays a complex behavior: for a large amplitude of the temperature cycles, the granular column settles continuously, experiencing a small settling at each cycle. By contrast, for a small-enough amplitude, the column exhibits a discontinuous and

  8. On Granular Rough Computing: Factoring Classifiers Through Granulated Decision Systems

    Microsoft Academic Search

    Lech Polkowski; Piotr Artiemjew

    2007-01-01

    The paradigm of Granular Computing has quite recently emerged as an area of research on its own; in particular, t is pursued within rough set theory initiated by Zdzislaw Pawlak. Granules of knowl- edge consist of entities with a similar in a sense information content. An idea of a granular counterpart to a decision\\/information system has been put forth, along

  9. Shear strength of granular materials Farhang Radjai and Emilien Azma

    E-print Network

    Paris-Sud XI, Université de

    Shear strength of granular materials Farhang Radjai and Emilien Azéma LMGC, CNRS the role of fabric and force anisotropies with respect to the critical-state shear strength. Then, a model. KEYWORDS: granular media, shear strength, fabric anisotropy, weak and strong forces. Revue, Volume X ­ n

  10. BACTERIA ASSOCIATED WITH GRANULAR ACTIVATED CARBON PARTICLES IN DRINKING WATER

    EPA Science Inventory

    A sampling protocol was developed to examine particles released from granular activated carbon filter beds. A gauze filter/Swinnex procedure was used to collect carbon fines from 201 granular activated carbon-treated drinking water samples over 12 months. Application of a homogen...

  11. Green's Function Measurement in a 2D Granular Material

    Microsoft Academic Search

    Junfei Geng; Daniel W. Howell; Emily Longhi; R. P. Behringer; G. Reydellet; L. Vanel; E. Clement; S. Luding

    2001-01-01

    We experimentally determine ensemble-averaged responses of granular packings to point forces. We use 2D granular arrays consisting of photoelastic particles: either disks or pentagons, thus spanning the range from ordered to disordered packings. A key finding is that spatial ordering of the particles is a key factor in the force response. Ordered packings have a propagative component that does not

  12. Physical Properties of Various Materials Relevant to Granular Flow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Because of the ubiquitous nature of granular materials, ranging from natural avalanches to industrial storage and processing operations, interest in quantifying and predicting the dynamics of granular flow continues to increase. The objective of this study was to investigate various physical proper...

  13. Granular Avalanches in Fluids Sylvain Courrech du Pont,1

    E-print Network

    Weeks, Eric R.

    Granular Avalanches in Fluids Sylvain Courrech du Pont,1 Philippe Gondret,1 Bernard Perrin,2 2003) Three regimes of granular avalanches in fluids are put in light depending on the Stokes number St of avalanches do not depend on any fluid effect. In liquids (r 1), for decreasing St, the amplitude decreases

  14. A convex complementarity approach for simulating large granular flows

    Microsoft Academic Search

    Alessandro Tasora; Mihai Anitescu

    2010-01-01

    Aiming at the simulation of dense granular flows, we propose and test a numerical method based on successive convex complementarity problems. This approach originates from a multibody description of the granular flow: all the particles are simulated as rigid bodies with arbitrary shapes and frictional contacts. Unlike the discrete element method (DEM), the proposed approach does not require small integration

  15. Strain-stiffening in random packings of granular chains

    Microsoft Academic Search

    Heinrich Jaeger; Alice Nasto; Dylan Murphy; Eric Brown

    2011-01-01

    We report on triaxial compression experiments performed to characterize the mechanical response of random packings of granular particles. For a wide variety of particle shapes, the packings yield when the shear stress exceeds a value on the order of the confining pressure. In contrast, granular chains consisting of flexibly connected beads exhibit strain stiffening (i.e., the effective modulus increases with

  16. Hydrothermal Modification of Granular Steel Slag for Phosphate Removal

    Microsoft Academic Search

    Guangwei Wang; Liping Qiu; Shoubin Zhang; Xuedong Zhai; Jun Ma

    2011-01-01

    The performance of phosphate removal using hydrothermal modified granular steel slag was evaluated. The effects of steel slag dosage, reaction time, solution pH and initial phosphate concentration of synthesized wastewater on phosphate removal were also investigated. The results show that the modified steel slag is more efficient than raw granular steel slag in phosphate removal. The residual phosphate concentration decreased

  17. Granular phase changing composites for thermal energy storage

    Microsoft Academic Search

    Dong Zhang; Jianming Zhou; Keru Wu; Zongjin Li

    2005-01-01

    Granular phase changing composites for thermal energy storage were made of granular porous materials and organic phase changing materials by means of vacuum impregnation method. Experimental studies on the vacuum impregnation method, phase changing behavior, chemical compatibility between porous materials and phase changing materials, and sealing performance of coating materials arrived in the following conclusions. Firstly, the vacuum impregnation method

  18. Structure of plastically compacting granular packings Lina Uri,1,

    E-print Network

    Dysthe, Dag Kristian

    fractions as low as c=0.125 have been found experi- mentally in three-dimensional 3D systems with high grainStructure of plastically compacting granular packings Lina Uri,1, * Thomas Walmann,1 Luc Alberts,2 proper- ties of granular structures have been studied in dense elastic packings with much focus

  19. Characterization of wet aggregate stability of soils by (1) H-NMR relaxometry.

    PubMed

    Buchmann, C; Meyer, M; Schaumann, G E

    2014-10-10

    For the assessment of soil structural stability against hydraulic stress, wet sieving or constant head permeability tests are typically used but rather limited in their intrinsic information value. The multiple applications of several tests is the only possibility to assess important processes and mechanisms during soil aggregate breakdown, e.g. the influences of soil fragment release or differential swelling on the porous systems of soils or soil aggregate columns. Consequently, the development of new techniques for a faster and more detailed wet aggregate stability assessment is required. (1) H nuclear magnetic resonance relaxometry ((1) H-NMR relaxometry) might provide these requirements because it has already been successfully applied on soils. We evaluated the potential of (1) H-NMR relaxometry for the assessment of wet aggregate stability of soils, with more detailed information on occurring mechanisms at the same time. Therefore, we conducted single wet sieving and constant head permeability tests on untreated and 1% polyacrylic acid-treated soil aggregates of different textures and organic matter contents, subsequently measured by (1) H-NMR relaxometry after percolation. The stability of the soil aggregates were mainly depending on their organic matter contents and the type of aggregate stabilization, whereby additional effects of clay swelling on the measured wet aggregate stability were identified by the transverse relaxation time (T2 ) distributions. Regression analyses showed that only the percentage of water stable aggregates could be determined accurately from percolated soil aggregate columns by (1) H-NMR relaxometry measurements. (1) H-NMR relaxometry seems a promising technique for wet aggregate stability measurements but should be further developed for nonpercolated aggregate columns and real soil samples. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25303035

  20. Application of wet waste from shrimp ( Litopenaeus vannamei) with or without sea mud to feeding sea cucumber ( Stichopus monotuberculatus)

    NASA Astrophysics Data System (ADS)

    Chen, Yanfeng; Hu, Chaoqun; Ren, Chunhua

    2015-02-01

    In the present study, the applicability of the wet waste collected from shrimp ( Litopenaeus vannamei) to the culture of sea cucumber ( Stichopus monotuberculatus) was determined. The effects of dietary wet shrimp waste on the survival, specific growth rate (SGR), fecal production rate (FPR), ammonia- and nitrite-nitrogen productions of sea cucumber were studied. The total organic matter (TOM) level in the feces of sea cucumber was compared with that in corresponding feeds. Diet C (50% wet shrimp waste and 50% sea mud mash) made sea cucumber grow faster than other diets. Sea cucumber fed with either diet D (25% wet shrimp waste and 75% sea mud mash) or sole sea mud exhibited negative growth. The average lowest total FPR of sea cucumber occurred in diet A (wet shrimp waste), and there was no significant difference in total FPR between diet C and diet E (sea mud mash) ( P > 0.05). The average ammonia-nitrogen production of sea cucumber in different diet treatments decreased gradually with the decrease of crude protein content in different diets. The average highest nitrite-nitrogen production occurred in diet E treatment, and there was no significant difference in nitrite-nitrogen production among diet A, diet B (75% wet shrimp waste and 25% sea mud mash) and diet C treatments ( P > 0.05). In each diet treatment, the total organic matter (TOM) level in feces decreased to different extent compared with that in corresponding feeds.

  1. A rheological approach to analyze aerobic granular sludge.

    PubMed

    Ma, Yun-Jie; Xia, Cheng-Wang; Yang, Hai-Yang; Zeng, Raymond J

    2014-03-01

    Aerobic granular sludge is one promising biotechnology in wastewater treatment. Despite intensive researches on granular architecture and strategies to improve treatment efficiency, there are still some elusive material parameters needed to stimulate the granulation process. The main aim of this study was to evaluate aerobic granular sludge innovatively using the universal rheology methodology, in terms of processability or quality and texture. Steady shear and oscillatory measurements were performed. Basic rheological characterization showed that aerobic granular sludge was a shear-thinning Herschel-Bulkley fluid with yield pseudoplasticity. Meanwhile, granular sludge presented characterized viscoelastic behaviors in dynamic sweeps highlighting its superiority to flocculent sludge. Furthermore, a Wagner-type constitutive model incorporating a relaxation and damping function was introduced and able to describe the time-dependent and non-linear viscoelastic behaviors. This study could make a further step on predicting rheological properties, helping improve the actual sludge treatment process and the operation of sludge dewatering. PMID:24374128

  2. Invited review: Effect of temperature on a granular pile

    E-print Network

    Thibaut Divoux

    2010-11-30

    As a fragile construction, a granular pile is very sensitive to minute external perturbations. In particular, it is now well established that a granular assembly is sensitive to variations of temperature. Such variations can produce localized rearrangements as well as global static avalanches inside a pile. In this review, we sum up the various observations that have been made concerning the effect of temperature on a granular assembly. In particular, we dwell on the way controlled variations of temperature have been employed to generate the compaction of a granular pile. After laying emphasis on the key features of this compaction process, we compare it to the classic vibration-induced compaction. Finally, we also review other granular systems in a large sense, from microscopic (jammed multilamellar vesicles) to macroscopic scales (stone heave phenomenon linked to freezing and thawing of soils) for which periodic variations of temperature could play a key role in the dynamics at stake.

  3. Projectile interactions in granular impact cratering

    E-print Network

    E. L. Nelson; H. Katsuragi; P. Mayor; D. J. Durian

    2008-06-04

    We present evidence for the interactions between a ball and the container boundaries, as well as between two balls, that are mediated by the granular medium during impact cratering. The presence of the bottom boundary affects the final penetration depth only for low drop heights with shallow filling, in which case, surprisingly, the penetration becomes deeper. By contrast the presence of the side wall causes less penetration and also an effective repulsion. Repulsion is also found for two balls dropped side-by-side.

  4. Biological and robotic movement through granular media

    NASA Astrophysics Data System (ADS)

    Goldman, Daniel

    2008-03-01

    We discuss laboratory experiments and numerical simulations of locomotion of biological organisms and robots on and within a granular medium. Terrestrial locomotion on granular media (like desert and beach sand) is unlike locomotion on rigid ground because during a step the material begins as a solid, becomes a fluid and then re-solidifies. Subsurface locomotion within granular media is unlike swimming in water for similar reasons. The fluidization and solidification depend on the packing properties of the material and can affect limb penetration depth and propulsive force. Unlike aerial and aquatic locomotion in which the Navier-Stokes equations can be used to model environment interaction, models for limb interaction with granular media do not yet exist. To study how the fluidizing properties affect speed in rapidly running and swimming lizards and crabs, we use a trackway composed of a fluidized bed of of 250 ?m glass spheres. Pulses of air to the bed set the solid volume fraction 0.59

  5. Dissipative solitary waves in granular crystals.

    PubMed

    Carretero-González, R; Khatri, D; Porter, Mason A; Kevrekidis, P G; Daraio, C

    2009-01-16

    We provide a quantitative characterization of dissipative effects in one-dimensional granular crystals. We use the propagation of highly nonlinear solitary waves as a diagnostic tool and develop optimization schemes that allow one to compute the relevant exponents and prefactors of the dissipative terms in the equations of motion. We thereby propose a quantitatively accurate extension of the Hertzian model that encompasses dissipative effects via a discrete Laplacian of the velocities. Experiments and computations with steel, brass, and polytetrafluoroethylene reveal a common dissipation exponent with a material-dependent prefactor. PMID:19257278

  6. Granular instability in a vibrated U tube

    E-print Network

    I. Sánchez; J. R. Darias; R. Paredes; C. J. Lobb; G. Gutiérrez

    2007-05-19

    We study experimentally the collective motion of grains inside a U shaped tube undergoing vertical oscillations, and we develop a very simple quantitative model that captures relevant features of the observed behaviour. The height difference between the granular columns grows with time when the system is shaken at sufficiently low frequencies. The system exhibits two types of growth: exponentially divergent (type I) and exponentially saturating (type II), depending on the size of the grains. The type I growth can be quenched by removing the air whereas the type II behavior can occur in the absence of air. There is a good agreement between the model proposed and our experimental results.

  7. Granular convection observed by magnetic resonance imaging

    SciTech Connect

    Ehrichs, E.E.; Jaeger, H.M.; Knight, J.B.; Nagel, S.R.; Karczmar, G.S.; Kuperman, V.Yu. [Univ. of Chicago, IL (United States)

    1995-03-17

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here. 31 refs., 4 figs.

  8. Granular convection observed by magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ehrichs, E. E.; Jaeger, H. M.; Karczmar, Greg S.; Knight, James B.; Kuperman, Vadim Yu.; Nagel, Sidney R.

    1995-03-01

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.

  9. Granular jamming transitions for a robotic mechanism

    NASA Astrophysics Data System (ADS)

    Jiang, Allen; Aste, Tomaso; Dasgupta, Prokar; Althoefer, Kaspar; Nanayakkara, Thrishantha

    2013-06-01

    The jamming transitions for granules growing field of interest in robotics for use in variable stiffness mechanisms. However, the traditional use of air pressure to control the jamming transition requires heavy vacuums, reducing the mobility of the robot. Thus, we propose the use of water as a hydraulic fluid to control the transition between free and clustered granules. This paper presents comparative studies that show that a hydraulic granular jammed finger joint can both achieve the same stiffness level and maintain the same hysteresis level of a pneumatic system, with only a small volume of fluid.

  10. Rolling friction on a granular medium.

    PubMed

    De Blasio, Fabio Vittorio; Saeter, May-Britt

    2009-02-01

    We present experimental results for the rolling of spheres on a granular bed. We use two sets of glass and steel spheres with varying diameters and a high-speed camera to follow the motion of the spheres. Despite the complex phenomena occurring during the rolling, the results show a friction coefficient nearly independent of the velocity (0.45-0.5 for glass and 0.6-0.65 for steel). It is found that for a given sphere density, the large spheres reach a longer distance, a result that may also help explain the rock sorting along natural stone accumulations at the foot of mountain slopes. PMID:19391789

  11. Shear thickening in highly viscous granular suspensions

    NASA Astrophysics Data System (ADS)

    Xu, Qin; Majumdar, Sayantan; Brown, Eric; Jaeger, Heinrich M.

    2014-09-01

    We experimentally investigate shear thickening in dense granular suspensions under oscillatory shear. Directly imaging the suspension-air interface, we observe dilation beyond a critical strain ?c and the end of shear thickening as the maximum confining stress is reached and the contact line moves. Analyzing the shear profile, we extract the viscosity contributions due to hydrodynamics ?h , dilation ?c and sedimentation ?g . While ?g governs the shear thinning regime, ?h and ?c together determine the shear thickening behavior. As the suspending liquid's viscosity varies from 10 to 1000 cSt, ?h is found to compete with ?c and soften the discontinuous nature of shear thickening.

  12. Mach cone in a shallow granular fluid.

    PubMed

    Heil, Patrick; Rericha, E C; Goldman, Daniel I; Swinney, Harry L

    2004-12-01

    We study the V -shaped wake (Mach cone) formed by a cylindrical rod moving through a thin, vertically vibrated granular layer. The wake, analogous to a shock (hydraulic jump) in shallow water, appears for rod velocities vR greater than a critical velocity c . We measure the half angle theta; of the wake as a function of vR and layer depth h . The angle satisfies the Mach relation, sin theta=c/vR , where c= square root of gh , even for h as small as one-particle diameter. PMID:15697332

  13. Gravity-driven Dense Granular Flows

    E-print Network

    Deniz Ertas; Gary S. Grest; Thomas C. Halsey; Dov Levine; Leonardo E. Silbert

    2000-05-02

    We report and analyze the results of numerical studies of dense granular flows in two and three dimensions, using both linear damped springs and Hertzian force laws between particles. Chute flow generically produces a constant density profile that satisfies scaling relations suggestive of a Bagnold grain inertia regime. The type of force law has little impact on the behavior of the system. Bulk and surface flows differ in their failure criteria and flow rheology, as evidenced by the change in principal stress directions near the surface. Surface-only flows are not observed in this geometry.

  14. Gravity-driven dense granular flows

    SciTech Connect

    ERTAS,DENIZ; GREST,GARY S.; HALSEY,THOMAS C.; DEVINE,DOV; SILBERT,LEONARDO E.

    2000-03-29

    The authors report and analyze the results of numerical studies of dense granular flows in two and three dimensions, using both linear damped springs and Hertzian force laws between particles. Chute flow generically produces a constant density profile that satisfies scaling relations suggestive of a Bagnold grain inertia regime. The type for force law has little impact on the behavior of the system. Failure is not initiated at the surface, consistent with the absence of surface flows and different principal stress directions at vs. below the surface.

  15. Matter: States of Matter

    NSDL National Science Digital Library

    Anthony Carpi, Ph.D.

    The representation is showing the motion of molecules in three states of matter; ice crystals, liquid water, and boiling water/steam. Users can "zoom in" to "view" water's molecular arrangement and motion in each state. The resource includes descriptive text to support the animations.

  16. Nature of stress accommodation in sheared granular material: Insights from 3D numerical modeling

    E-print Network

    Mair, Karen

    Nature of stress accommodation in sheared granular material: Insights from 3D numerical modeling distinct accumulations of granular wear material. During shear, this granular material accommodates stress the nature of contact force distributions during 3D granular shear. Our 3D discrete numerical models consist

  17. Controlling wave propagation through nonlinear engineered granular systems

    NASA Astrophysics Data System (ADS)

    Leonard, Andrea

    We study the fundamental dynamic behavior of a special class of ordered granular systems in order to design new, structured materials with unique physical properties. The dynamic properties of granular systems are dictated by the nonlinear, Hertzian, potential in compression and zero tensile strength resulting from the discrete material structure. Engineering the underlying particle arrangement of granular systems allows for unique dynamic properties, not observed in natural, disordered granular media. While extensive studies on 1D granular crystals have suggested their usefulness for a variety of engineering applications, considerably less attention has been given to higher-dimensional systems. The extension of these studies in higher dimensions could enable the discovery of richer physical phenomena not possible in 1D, such as spatial redirection and anisotropic energy trapping. We present experiments, numerical simulation (based on a discrete particle model), and in some cases theoretical predictions for several engineered granular systems, studying the effects of particle arrangement on the highly nonlinear transient wave propagation to develop means for controlling the wave propagation pathways. The first component of this thesis studies the stress wave propagation resulting from a localized impulsive loading for three different 2D particle lattice structures: square, centered square, and hexagonal granular crystals. By varying the lattice structure, we observe a wide range of properties for the propagating stress waves: quasi-1D solitary wave propagation, fully 2D wave propagation with tunable wave front shapes, and 2D pulsed wave propagation. Additionally the effects of weak disorder, inevitably present in real granular systems, are investigated. The second half of this thesis studies the solitary wave propagation through 2D and 3D ordered networks of granular chains, reducing the effective density compared to granular crystals by selectively placing wave guiding chains to control the acoustic wave transmission. The rapid wave front amplitude decay exhibited by these granular networks makes them highly attractive for impact mitigation applications. The agreement between experiments, numerical simulations, and applicable theoretical predictions validates the wave guiding capabilities of these engineered granular crystals and networks and opens a wide range of possibilities for the realization of increasingly complex granular material design.

  18. Bianchi type VI1 cosmological model with wet dark fluid in scale invariant theory of gravitation

    E-print Network

    B. Mishra; P. K. Sahoo

    2014-07-29

    In this paper, we have investigated Bianchi type VIh, II and III cosmological model with wet dark fluid in scale invariant theory of gravity, where the matter field is in the form of perfect fluid and with a time dependent gauge function (Dirac gauge). A non-singular model for the universe filled with disorder radiation is constructed and some physical behaviors of the model are studied for the feasible VIh (h = 1) space-time.

  19. Settling behaviour of aerobic granular sludge.

    PubMed

    Nor Anuar, A; Ujang, Z; van Loosdrecht, M C M; de Kreuk, M K

    2007-01-01

    Aerobic granular sludge (AGS) technology has been extensively studied recently to improve sludge settling and behaviour in activated sludge systems. The main advantage is that aerobic granular sludge (AGS) can settle very fast in a reactor or clarifier because AGS is compact and has strong structure. It also has good settleability and a high capacity for biomass retention. Several experimental works have been conducted in this study to observe the settling behaviours of AGS. The study thus has two aims: (1) to compare the settling profile of AGS with other sludge flocs and (2) to observe the influence of mechanical mixing and design of the reactor to the settleability of AGS. The first experimental outcome shows that AGS settles after less than 5 min in a depth of 0.4 m compared to other sludge flocs (from sequencing batch reactor, conventional activated sludge and extended aeration) which takes more than 30 min. This study also shows that the turbulence from the mixing mechanism and shear in the reactor provides an insignificant effect on the AGS settling velocity. PMID:17951868

  20. Contact forces in a granular packing.

    PubMed

    Radjai, Farhang; Roux, Stephane; Moreau, Jean Jacques

    1999-09-01

    We present the results of a systematic numerical investigation of force distributions in granular packings. We find that all the main features of force transmission previously established for two-dimensional systems of hard particles hold in three-dimensional systems and for soft particles, too. In particular, the probability distribution of normal forces falls off exponentially for forces above the mean force. For forces below the mean, this distribution is either a decreasing power law when the system is far from static equilibrium, or nearly uniform at static equilibrium, in agreement with recent experiments. Moreover, we show that the forces below the mean do not contribute to the shear stress. The subnetwork of the contacts carrying a force below the mean thus plays a role similar to a fluid surrounding the solid backbone composed of the contacts carrying a force above the mean. We address the issue of the computation of contact forces in a packing at static equilibrium. We introduce a model with no local simplifying force rules, that allows for an exact computation of contact forces for given granular texture and boundary conditions. (c) 1999 American Institute of Physics. PMID:12779850

  1. Machanics of Granular Materials (MGM) Investigator

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Key persornel in the Mechanics of Granular Materials (MGM) experiment include Khalid Alshibli, project scientist at NASA's Marshall Space Flight Center (MSFC). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: MSFC).

  2. Mechanics of Granular Materials (MGM) Investigators

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Key persornel in the Mechanics of Granular Materials (MGM) experiment at the University of Colorado at Boulder include Tawnya Ferbiak (software engineer), Susan Batiste (research assistant), and Christina Winkler (graduate research assistant). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

  3. Mechanic of Granular Materials (MGM) Investigator

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Key persornel in the Mechanics of Granular Materials (MGM) experiment are Mark Lankton (Program Manager at University Colorado at Boulder), Susan Batiste (research assistance, UCB), and Stein Sture (principal investigator). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

  4. Mechanics of Granular Materials labeled hardware

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Mechanics of Granular Materials (MGM) flight hardware takes two twin double locker assemblies in the Space Shuttle middeck or the Spacehab module. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: NASA/MSFC).

  5. Pressure-shear experiments on granular materials.

    SciTech Connect

    Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Thornhill, Tom Finley, III (, Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John; Alexander, C. Scott (Sandia National Laboratories, Albuquerque, NM)

    2011-10-01

    Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.

  6. Impact of wettability on two-phase displacement patterns in granular media

    NASA Astrophysics Data System (ADS)

    Trojer, M.; Szulczewski, M.; Holtzman, R.; Juanes, R.

    2013-12-01

    Two-phase flow in porous media is important in many natural and industrial processes like geologic CO2 sequestration, enhanced oil recovery, water infiltration in soil, and methane venting from organic-rich sediments. While the wetting properties of porous media can vary drastically depending on the type of media and the pore fluids, the effect of wettability on the fluid displacement remains poorly understood. Here, we study experimentally how wettability affects fluid displacement patterns in rigid granular media within the capillary and viscous fingering regimes. The experiments consist of saturating a thin bed of glass beads with a viscous fluid, injecting a less viscous fluid, and imaging the invasion morphology. There are two control parameters: the injection rate of the less viscous fluid and the contact angle, which we control by modifying the surface chemistry of the beads. When the contact angle is fixed at zero (drainage), we recover the well-known transition from capillary fingering to viscous fingering as the injection rate is increased. When the injection rate is fixed, we show that the invasion pattern becomes more stable as the contact angle increases (i.e., as the system transitions from drainage to imbibition), both in the capillary-fingering and viscous-fingering regimes. We quantify the effect of the contact angle on the length scale of the instability, and propose a mechanistic pore-scale model that explains the macroscopic observations. The results demonstrate that wettability can significantly impact multiphase flow in porous media, and highlight the need to better understand the specific effects in many processes such as CO2 sequestration and enhanced oil recovery. Air displacing a water/glycerol mixture within a radial Hele-Shaw cell filled with glass beads. Varying the wetting properties of the solid matrix (horizontal axis) as well as the injection rate (vertical axis) systematically, the invasion pattern stabilizes as the invading phase (air) becomes more wetting.

  7. Observations of mercury wet deposition in Mexico.

    PubMed

    Hansen, Anne M; Gay, David A

    2013-12-01

    We provide a longer-term record of Hg wet deposition at two tropical latitude monitoring sites in Mexico, selected to provide regionally representative data. Weekly wet deposition samples were collected over 2 years, from September 2003 to November 2005. Based on this data set, we discuss the magnitude and seasonal variation of Hg in wet deposition and compare the results to other measurement sites and to several model estimates. With precipitation-weighted mean (PWM) concentrations of 8.2 and 7.9 ng L(-1), respectively, during the sampling period from Sep 30 2003 to Oct 11 2005, and median weekly concentrations of 9.4 ± 1 ng L(-1) for both sites, the wet Hg concentrations and deposition at HD01 were much lower than those observed at the US Gulf Coast MDN sites while the wet Hg deposition at OA02 was much lower than most MDN sites, but somewhat similar to US MDN sites along the Pacific Coast. Based on the limited available data, we conclude that the approximately 30 % higher average precipitation at HD01 and roughly equal PWM concentrations lead to the higher deposition at HD01 versus OA02. We believe that these observations may offer scientists and modelers additional understanding of the depositional fluxes in the lower latitudes of North America. PMID:24062061

  8. Epimacular brachytherapy for wet AMD: current perspectives

    PubMed Central

    Casaroli-Marano, Ricardo P; Alforja, Socorro; Giralt, Joan; Farah, Michel E

    2014-01-01

    Age-related macular degeneration (AMD) is considered the most common cause of blindness in the over-60 age group in developed countries. There are basically two forms of presentation: geographic (dry or atrophic) and wet (neovascular or exudative). Geographic atrophy accounts for approximately 85%–90% of ophthalmic frames and leads to a progressive degeneration of the retinal pigment epithelium and the photoreceptors. Wet AMD causes the highest percentage of central vision loss secondary to disease. This neovascular form involves an angiogenic process in which newly formed choroidal vessels invade the macular area. Today, intravitreal anti-angiogenic drugs attempt to block the angiogenic events and represent a major advance in the treatment of wet AMD. Currently, combination therapy for wet AMD includes different forms of radiation delivery. Epimacular brachytherapy (EMBT) seems to be a useful approach to be associated with current anti-vascular endothelial growth factor agents, presenting an acceptable efficacy and safety profile. However, at the present stage of research, the results of the clinical trials carried out to date are insufficient to justify extending routine use of EMBT for the treatment of wet AMD. PMID:25210436

  9. LIME/LIMESTONE WET-SCRUBBING TEST RESULTS AT THE EPA ALKALI SCRUBBING TEST FACILITY. CAPSULE REPORT

    EPA Science Inventory

    This Capsule Report describes a program conducted by EPA to test prototype lime and limestone wet-scrubbing systems for removing sulfur dioxide and particulate matter from coal-fired boiler flue gases. The program is being carried out in a test facility which is integrated into t...

  10. Experimental investigation of the link between static and dynamic wetting by forced wetting of nylon filament.

    PubMed

    Vega, M J; Gouttière, C; Seveno, D; Blake, T D; Voué, M; De Coninck, J; Clarke, A

    2007-10-01

    Forced wetting experiments with various liquids were conducted to study the dynamic wetting properties of nylon filament. The molecular-kinetic theory of wetting (MKT) was used to interpret the dynamic contact angle data and evaluate the contact-line friction zeta0 at the microscopic scale. By taking account of the viscosity of the liquid, zeta0 could be related exponentially to the reversible work of adhesion. This clearly establishes an experimental link between the static and dynamic wetting properties of the material. Moreover, statistical analysis of the equilibrium molecular displacement frequency K0 and the length of the displacements lambda reveals that these two fundamental parameters of the MKT are strongly correlated, not only in the linearized form of the theory (valid close to equilibrium) but also when the nonlinear form of the equations has to be considered at higher wetting speeds. PMID:17867713

  11. Dispersive behavior and acoustic scaling in granular rocks

    NASA Astrophysics Data System (ADS)

    Carlos, Santos; Vanessa, Urdaneta; Ernesto, Medina; Xavier, García

    2013-06-01

    Handling and making decisions based on data taken at different scales is a critical issue in the design of exploration and production tasks in the oil industry. Acoustic data is the classical example of the integration of dissimilar scales (i.e. seismic, well logs, lab data) where there is a scale dependent velocity. An understanding of the acoustic dispersion phenomenon in granular samples is needed. A detailed numerical work was conducted in order to establish the relationship between frequency and propagation speed for an acoustical pulse induced in simulated granular materials. The granular samples were generated with different grain size distributions while porosity and pressure were targeted and kept invariant using the grain radii expansion method. A sinusoidal burst with frequencies from 10Hz to 1MHz was applied and the corresponding acoustical speeds were estimated for each frequency. A coherent sigmoid dispersion relationship was obtained for each granular sample. The asymptotic boundaries for the dispersion function reflect the limiting cases for the wavelength/heterogeneity ratio in the granular pack. The lower speed asymptote was explained as the mean field value while upper speed asymptote can be understood based on a ray theory approximation scaled by a parameter we defined as the "acoustic tortuosity factor". This factor reflects the intricate acoustical path due to the texture of the stress network developed in the granular samples and can be used together with the sigmoid dispersive relationship to describe and clarify the scale discrepancy between different source acoustic data in granular materials.

  12. Slow drag in granular materials under high pressure

    NASA Astrophysics Data System (ADS)

    Zhou, Fuping; Advani, Suresh G.; Wetzel, Eric D.

    2004-06-01

    The resistance offered by a cylindrical rod to creeping cross flow of granular materials under pressure is investigated. The experimental system consists of a confined bed of granular particles, which are compacted under high pressure to consolidate the granular medium. A cylindrical rod is pulled at a constant and slow rate through the granular medium, and the measured pulling resistance is characterized as a drag force. The influence of various parameters such as the velocity of the cylindrical rod, the rod diameter and length, the granular particle size, and the compaction pressure on the required drag force is investigated experimentally. Nondimensional analysis is performed to simplify the relationships between these variables. The results show that the drag force is independent of the drag velocity, is linearly proportional to compaction pressure and rod diameter, and increases with rod length and particle size. Additional compaction experiments show that the effective density of the granular bed increases linearly with pressure, and similar behavior is noted for all particle sizes. These results should prove useful in the development of constitutive equations that can describe the motion of solid objects through compacted granular media under high pressure, such as during ballistic penetration of soils or ceramic armors.

  13. Enhanced selection of micro-aerobic pentachlorophenol degrading granular sludge.

    PubMed

    Lv, Yuancai; Chen, Yuancai; Song, Wenzhe; Hu, Yongyou

    2014-09-15

    Column-type combined reactors were designed to cultivate micro-aerobic pentachlorophenol (PCP) degrading granular sludge under oxygen-limited conditions (0.1-0.2 mgL(-1)) over 39-day experimental period. Micro-aerobic granular had both anaerobic activity (SMA: 2.34 mMCH4/hg VSS) and aerobic activity (SOUR: 2.21 mMO2/hg VSS). Metabolite analysis results revealed that PCP was sequentially dechlorinated to TCP, DCP, and eventually to MCP. Methanogens were not directly involved in the dechlorination of PCP, but might played a vital role in stabilizing the overall structure of the granule sludge. For Eubacteria, the Shannon Index (2.09 in inoculated granular sludge) increased both in micro-aerobic granular sludge (2.61) and PCP-degradation granular sludge (2.55). However, for Archaea, it decreased from 2.53 to 1.85 and 1.84, respectively. Although the Shannon Index demonstrated slight difference between micro-aerobic granular sludge and PCP-degradation granular sludge, the Principal Component Analysis (PCA) indicated obvious variance of the microbial composition, revealing significant effect of micro-aerobic condition and PCP on microbial community. Furthermore, nucleotide sequencing indicated that the main microorganisms for PCP degradation might be related to Actinobacterium and Sphingomonas. These results provided insights into situ bioremediation of environments contaminated by PCP and had practical implications for the strategies of PCP degradation. PMID:25151236

  14. Dark Matter

    E-print Network

    Neta Bahcall

    1996-11-11

    Observations in the optical, in X-rays, and gravitational lensing of galaxies, clusters of galaxies, and large-scale structure are beginning to provide clues to the dark matter problem. I review the impact of these observations on some of the main questions relating to dark matter: How much dark matter is there? Where is it located? What is the nature of the dark matter? and what is the amount of baryonic dark matter.

  15. Wet powder seal for gas containment

    DOEpatents

    Stang, Louis G. (Sayville, NY)

    1982-01-01

    A gas seal is formed by a compact layer of an insoluble powder and liquid filling the fine interstices of that layer. The smaller the particle size of the selected powder, such as sand or talc, the finer will be the interstices or capillary spaces in the layer and the greater will be the resulting sealing capacity, i.e., the gas pressure differential which the wet powder layer can withstand. Such wet powder seal is useful in constructing underground gas reservoirs or storage cavities for nuclear wastes as well as stopping leaks in gas mains buried under ground or situated under water. The sealing capacity of the wet powder seal can be augmented by the hydrostatic head of a liquid body established over the seal.

  16. When matter matters

    SciTech Connect

    Easson, Damien A. [Department of Physics and School of Earth and Space Exploration and Beyond Center, Arizona State University, Tempe, AZ, 85287-1504 (United States); Sawicki, Ignacy [Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg Philosophenweg 16, 69120 Heidelberg (Germany); Vikman, Alexander, E-mail: easson@asu.edu, E-mail: ignacy.sawicki@uni-heidelberg.de, E-mail: alexander.vikman@cern.ch [CERN, Theory Division, CH-1211 Genève 23 (Switzerland)

    2013-07-01

    We study a recently proposed scenario for the early universe:Subluminal Galilean Genesis. We prove that without any other matter present in the spatially flat Friedmann universe, the perturbations of the Galileon scalar field propagate with a speed at most equal to the speed of light. This proof applies to all cosmological solutions — to the whole phase space. However, in a more realistic situation, when one includes any matter which is not directly coupled to the Galileon, there always exists a region of phase space where these perturbations propagate superluminally, indeed with arbitrarily high speed. We illustrate our analytic proof with numerical computations. We discuss the implications of this result for the possible UV completion of the model.

  17. Impact dynamics of granular jets with noncircular cross sections

    NASA Astrophysics Data System (ADS)

    Cheng, Xiang; Gordillo, Leonardo; Zhang, Wendy W.; Jaeger, Heinrich M.; Nagel, Sidney R.

    2014-04-01

    Using high-speed photography, we investigate two distinct regimes of the impact dynamics of granular jets with noncircular cross sections. In the steady-state regime, we observe the formation of thin granular sheets with anisotropic shapes and show that the degree of anisotropy increases with the aspect ratio of the jet's cross section. Our results illustrate the liquidlike behavior of granular materials during impact and demonstrate that a collective hydrodynamic flow emerges from strongly interacting discrete particles. We discuss the analogy between our experiments and those from the Relativistic Heavy Ion Collider, where similar anisotropic ejecta from a quark-gluon plasma have been observed in heavy-ion impact.

  18. Ageing of a granular pile induced by thermal cycling

    E-print Network

    Thibaut Divoux; Ion Vassilief; Hervé Gayvallet; Jean-Christophe Géminard

    2009-06-02

    Here we show that variations of temperature, even of a few degrees in amplitude, induce the ageing of a granular pile. In particular, we report measurements of physical properties of a granular heap submitted to thermal cycles. Namely, we focus on the evolution of the thermal linear-expansion coefficient and of the thermal conductivity of the pile with the number of cycles. The present contribution nicely supplements a recent article we published elsewhere [Phys. Rev. Lett. \\textbf{101}, 148303 (2008)] and introduces a different and promising method to impose temperature cycles to a granular pile.

  19. Granular flow over inclined channels with linear contraction

    E-print Network

    Tunuguntla, D R; Thornton, A R; Bokhove, O

    2015-01-01

    We consider dry granular flow down an inclined chute with a localised contraction theoretically and numerically. The flow regimes are predicted through a novel extended one-dimensional hydraulic theory. A discrete particle method validated empirical constitutive law is used to close this one-dimensional asymptotic model. The one-dimensional model is verified by solving the two-dimensional shallow granular equations through discontinuous Galerkin finite element method (DGFEM). For supercritical flows, the one-dimensional asymptotic theory surprisingly holds although the two-dimensional oblique granular jumps largely vary across the converging channel.

  20. Slavic *mokr?, Irish ainmech ‘wet, rain’

    E-print Network

    Hamp, Eric P.

    2011-12-08

    — 69 — Slavic *mokr?, Irish ainmech ‘wet, rain’ Er i c P. Ha m P Professor Emeritus, Department of Linguistics, 1010 East 59th Street, Chicago, IL 60637, linguistics@uchicago.edu Avtor prikazuje etimološke povezave med baltš?ino, slovanš?ino... issue Göttingen 1979). I think that this looks less than likely for us. Perhaps we can farther than Vendryes LÉIA M-60 or LEW3 2.30, but that is a discussion perhaps outside the present one. Note that peat goes beyond rain, wet, and urine. Pokorny IEW...