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1

3D Imaging Of Wet Granular Matter  

E-print Network

3D Imaging Of Wet Granular Matter Leonard Goff Advisor: Dr. Wolfgang Losert With Application to Penetrometer Insertion #12;3D Imaging Of Wet Granular Matter Leonard Goff, Advisor: Dr. Wolfgang Losert Background ·Granular matter: · Interesting Question: How does a stable configuration of granular matter fail

Anlage, Steven

2

Equation of State of Wet Granular Matter  

E-print Network

A theory is derived for the nonequilibrium probability currents of the capillary interaction which determines the pair correlation function near contact. This yields an analytic expression for the equation of state, P = P(N/V,T), of wet granular matter for D=2 dimensions, 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 Tmatter [Phys. Rev. Lett. 97, 078001 (2006)], and extends the effect to higher dimensional systems. Since the limiting case of sticky bonds, E_cb >> 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 s_crit. This result implies that particles that stick at the surface, s_crit=0, form isostatic clusters.

A. Fingerle; S. Herminghaus

2007-08-27

3

Equation of state of wet granular matter  

NASA Astrophysics Data System (ADS)

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.

Fingerle, A.; Herminghaus, S.

2008-01-01

4

Foam-film-stabilized liquid bridge networks in evaporative lithography and wet granular matter.  

PubMed

Evaporative lithography using latex particle templates is a novel approach for the self-assembly of suspension-dispersed nanoparticles into ordered microwire networks. The phenomenon that drives the self-assembly process is the propagation of a network of interconnected liquid bridges between the template particles and the underlying substrate. With the aid of video microscopy, we demonstrate that these liquid bridges are in fact the border zone between the underlying substrate and foam films vertical to the substrate, which are formed during the evaporation of the liquid from the suspension. The stability of the foam films and thus the liquid bridge network stability are due to the presence of a small amount of surfactant in the evaporating solution. We show that the same type of foam-film-stabilized liquid bridge network can also propagate in 3D clusters of spherical particles, which has important implications for the understanding of wet granular matter. PMID:23534699

Vakarelski, Ivan U; Marston, Jeremy O; Thoroddsen, Sigurdur T

2013-04-23

5

Erosion dynamics of a wet granular medium  

NASA Astrophysics Data System (ADS)

Liquid may give strong cohesion properties to a granular medium, and confer a solidlike 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.

Lefebvre, Gautier; Jop, Pierre

2013-09-01

6

Erosion dynamics of a wet granular medium  

E-print Network

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.

Gautier Lefebvre; Pierre Jop

2014-12-08

7

Hierarchical Structures in Granular Matter  

NASA Astrophysics Data System (ADS)

Granular matter, under the proper conditions of vibration, exhibits a behavior that closely resembles that of gases, liquids or solids. In a vibrated mix of glass particles and magnetic steel particles, it is also possible to observe aggregation phenomena, as well as, processes of reconstruction of the generated clusters. In this work we discuss the effects of the so called granular temperature on the evolution of the agglomerates generated by the magnetic interactions. On the basis of a fractal analysis and the measured mass distribution, we analyze experimental results on the static structural aspects of the aggregates originated by two methods we call: granular diffusion limited aggregation (GDLA) and growth limited by concentration (GLC).

Gonzlez-Gutirrez, J.; Carrillo-Estrada, J. L.; Ruiz-Surez, J. C.

2013-12-01

8

Shear strength properties of wet granular materials Vincent Richefeu,  

E-print Network

effects appear only at low confining pressures, e.g. in surface soils. It is a common observation that, when plowing a wet granular soil, large cohesive aggre- gates are formed. The largest capillary]. Although capillary phenomena at the interface be- tween two solid bodies are well understood, it is much

Paris-Sud XI, Université de

9

Collapse of quasi-two-dimensional wet granular columns  

E-print Network

This paper deals with the experimental characterization of the collapse of wet granular columns in the pendular state, with the purpose of collecting data on triggering and jamming phenomena in wet granular media. The final deposit shape and the runout dynamics were studied for samples of glass beads, varying particle diameter, liquid surface tension, and liquid amount. We show how the runout distance decreases with increasing water amount (reaching a plateau for $w>1 \\%$) and increases with increasing Bond number, while the top and toe angles and the final deposit height increase with increasing water amount and decrease with decreasing Bond number. Dimensional analysis allowed to discuss possible scalings for the runout length and the top and toe angles: a satisfying scaling was found, based on the combination of Bond number and liquid amount.

Riccardo Artoni; Andrea C. Santomaso; Fabio Gabrieli; Diego Tono; Simonetta Cola

2014-01-09

10

Friction and dilatancy in immersed granular matter  

E-print Network

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.

Thibaut Divoux; Jean-Christophe Gminard

2008-06-10

11

Penetration depth scaling for impact into wet granular packings  

E-print Network

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.

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

2015-01-25

12

Granular matter: A special buffer for impact load  

NASA Astrophysics Data System (ADS)

As a typical energy dissipation system, granular matter can reduce the impact force effectively via inter-particle friction, viscous force and particle splash. To investigate the impact-absorbing capacity of granular matter, a spherical projectile dropping on a granular layer is studied by physical experiments and numerical simulations with the discrete element method (DEM). Both physical experiments and numerical simulations show that the granular layer reduces the impact load well. The impact load decreases with increasing granular layer thickness, but is not sensitive to the granular thickness when the thickness is larger than a critical thickness, HC. The critical thickness is a function of initial impact velocity. This study can be helpful for understanding the basic mechanical behaviors of granular matter under impact loads, and for the potential engineering applications of the impact absorption of granular matter.

Ji, Shunying; Chen, Xiaodong; Li, Pengfei; Yan, Ying

2013-06-01

13

Pattern formation in vibrated beds of dry and wet granular materials  

NASA Astrophysics Data System (ADS)

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.

Chuan Lim, Eldin Wee

2014-01-01

14

Capillary condensation in wet granular media via meso-scale Monte Carlo simulation  

NASA Astrophysics Data System (ADS)

Partially wet granular systems exhibit a wide variety of interesting phenomena. In particular, the wetting of the system yields a complex liquid network that can play a dominant role in mechanical properties. Moreover, the interplay between the liquid network and the solid grains influences the evolution of the system under deformation. A significant challenge for further understanding is a theoretical description of the statistical geometry and resulting mechanics of this liquid network. We present a meso-scale Monte Carlo simulation approach for modeling partially wet granular systems that treats the liquid phase as a lattice fluid, and demonstrate the approach on systems of two and four grains. We examine the geometry of the liquid phase as a function of liquid volume fraction, which can ultimately be used to determine the resulting constitutive properties of the partially wet granular material.

Zeidman, Benjamin D.; Wu, David T.; Lu, Ning; Lusk, Mark T.

2009-06-01

15

Extraterrestrial sink dynamics in granular matter  

E-print Network

A loosely packed bed of sand sits precariously on the fence between mechanically stable and flowing states. This has especially strong implications for animals or vehicles needing to navigate sandy environments, which can sink and become stuck in a "dry quicksand" if their weight exceeds the yield stress of this fragile matter. While it is known that the contact stresses in these systems are loaded by gravity, very little is known about the sinking dynamics of objects into loose granular systems under gravitational accelerations different from the Earth's (g). A fundamental understanding of how objects sink in different gravitational environments is not only necessary for successful planetary navigation and engineering, but it can also improve our understanding of celestial impact dynamics and crater geomorphology. Here we perform and explain the first systematic experiments of the sink dynamics of objects into granular media in different gravitational accelerations. By using an accelerating experimental apparatus, we explore gravitational conditions ranging from 0.4g to 1.2g. With the aid of discrete element modeling simulations, we reproduce these results and extend this range to include objects as small as asteroids and as large as Jupiter. Surprisingly, we find that the final sink depth is independent of the gravitational acceleration, an observation with immediate relevance to the design of future extraterrestrial structures land-roving spacecraft. Using a phenomenological equation of motion that includes a gravity-loaded frictional term, we are able to quantitatively explain the experimental and simulation results.

E. Altshuler; H. Torres; A. Gonzlez-Pita; G. Snchez-Colina; C. Prez-Penichet; S. Waitukaitis; R. C. Hidalgo

2013-05-29

16

Penetration of spherical projectiles into wet granular media.  

PubMed

We measure experimentally the penetration depth d of spherical particles into a water-saturated granular medium made of much smaller sand-sized grains. We vary the density, size R, and velocity U of the impacting spheres, and the size ? of the grains in the granular medium. We consider velocities between 7 and 107 m/s, a range not previously addressed, but relevant for impacts produced by volcanic eruptions. We find that d?R(1/3)?(1/3)U(2/3). The scaling with velocity is similar to that identified in previous, low-velocity collisions, but it also depends on the size of the grains in the granular medium. We develop a model, consistent with the observed scaling, in which the energy dissipation is dominated by the work required to rearrange grains along a network of force chains in the granular medium. PMID:25314438

Birch, S P D; Manga, M; Delbridge, B; Chamberlain, M

2014-09-01

17

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

E-print Network

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.

Ruediger Schwarze; Anton Gladkyy; Fabian Uhlig; Stefan Luding

2014-09-12

18

Microstructure evolution during impact on granular matter.  

PubMed

We study the impact of an intruder on a dense granular material. The process of impact and interaction between the intruder and the granular particles is modeled using discrete element simulations in two spatial dimensions. In the first part of the paper we discuss how the intruder's dynamics depends on (1) the intruder's properties, including its size, shape and composition, (2) the properties of the grains, including friction, polydispersity, structural order, and elasticity, and (3) the properties of the system, including its size and gravitational field. It is found that polydispersity and related structural order, and frictional properties of the granular particles, play a crucial role in determining impact dynamics. In the second part of the paper we consider the response of the granular system itself. We discuss the force networks that develop, including their topological evolution. The influence of friction and structural order on force propagation, including the transition from hyperbolic-like to elastic-like behavior is discussed, as well as the affine and nonaffine components of the grain dynamics. Several broad observations include the following: tangential forces between granular particles are found to play a crucial role in determining impact dynamics; both force networks and particle dynamics are correlated with the dynamics of the intruder itself. PMID:22400563

Kondic, L; Fang, X; Losert, W; O'Hern, C S; Behringer, R P

2012-01-01

19

Runaway electrification of friable self-replicating granular matter.  

PubMed

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

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

2013-10-15

20

Runaway electrification of friable self-replicating granular matter  

E-print Network

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.

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

2014-11-19

21

Strength and failure of cemented granular matter  

NASA Astrophysics Data System (ADS)

Cemented granular materials (CGMs) consist of densely packed solid particles and a pore-filling solid matrix sticking to the particles. We use a sub-particle lattice discretization method to investigate the particle-scale origins of strength and failure properties of CGMs. We show that jamming of the particles leads to highly inhomogeneous stress fields. The stress probability density functions are increasingly wider for a decreasing matrix volume fraction, the stresses being more and more concentrated in the interparticle contact zones with an exponential distribution as in cohesionless granular media. Under uniaxial loading, pronounced asymmetry can occur between tension and compression both in strength and in the initial stiffness as a result of the presence of bare contacts (with no matrix interposed) between the particles. Damage growth is analyzed by considering the evolution of stiffness degradation and the number of broken bonds in the particle phase. A brutal degradation appears in tension as a consequence of brittle fracture in contrast to the more progressive nature of damage growth in compression. We also carry out a detailed parametric study in order to assess the combined influence of the matrix volume fraction and particle-matrix adherence. Three regimes of crack propagation can be distinguished corresponding to no particle damage, particle abrasion and particle fragmentation, respectively. We find that particle damage scales well with the relative toughness of the particle-matrix interface with respect to the particle toughness. This relative toughness is a function of both matrix volume fraction and particle-matrix adherence and it appears therefore to be the unique control parameter governing transition from soft to hard behavior.

Topin, V.; Delenne, J.-Y.; Radja?, F.; Brendel, L.; Mabille, F.

2007-08-01

22

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

23

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

24

Edwards entropy and compactivity in a model of granular matter.  

PubMed

Formulating a statistical mechanics for granular matter remains a significant challenge, in part due to the difficulty associated with a complete characterization of the systems under study. We present a fully characterized model of a granular material consisting of N two-dimensional, frictionless hard disks, confined between hard walls, including a complete enumeration of all possible jammed structures. We show that the properties of the jammed packings are independent of the distribution of defects within the system and that all the packings are isostatic. This suggests that the assumption of equal probability for states of equal volume, which provides one possible way of constructing the equivalent of a microcanonical ensemble, is likely to be valid for our model. An application of the second law of thermodynamics involving two subsystems in contact shows that the expected spontaneous equilibration of defects between the two is accompanied by an increase in entropy and that the equilibrium, obtained by entropy maximization, is characterized by the equality of compactivities. Finally, we explore the properties of the equivalent to the canonical ensemble for this system. PMID:21517489

Bowles, Richard K; Ashwin, S S

2011-03-01

25

The Flow Of Granular Matter Under Reduced-Gravity Conditions  

E-print Network

To gain a better understanding of the surfaces of planets and small bodies in the solar system, the flow behavior of granular material for various gravity levels is of utmost interest. We performed a set of reduced-gravity measurements to analyze the flow behavior of granular matter with a quasi-2D hourglass under coarse-vacuum conditions and with a tilting avalanche box. We used the Bremen drop tower and a small centrifuge to achieve residual-gravity levels between 0.01 g and 0.3 g. Both experiments were carried out with basalt and glass grains as well as with two kinds of ordinary sand. For the hourglass experiments, the volume flow through the orifice, the repose and friction angles, and the flow behavior of the particles close to the surface were determined. In the avalanche-box experiment, we measured the duration of the avalanche, the maximum slope angle as well as the width of the avalanche as a function of the gravity level.

Hofmeister, Paul Gerke; Heielmann, Daniel

2009-01-01

26

Time-resolved dynamics of granular matter by random laser emission  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

27

Multiple impacts of a planar kinematic chain with a granular matter  

Microsoft Academic Search

The theoretical model of a planar kinematic chain with multiple points impacting with a granular matter is studied. The force acting on the links penetrating the granular media is a linear superposition of a static (depth-dependent) resistance force and a dynamic (velocity-dependent) frictional force. A general algorithm for the m impacts for an n planar kinematic chain is presented. The

S. Lee; Dan B. Marghitu

2009-01-01

28

The glass and jamming transitions in dense granular matter  

NASA Astrophysics Data System (ADS)

Everyday life tells us that matter acquires rigidity either when it cools down, like lava flows which turn into solid rocks, or when it is compacted, like tablets simply formed by powder compression. As suggested by these examples, solidification is not the sole privilege of crystals but also happens for disordered media such as glass formers, granular media, foams, emulsions and colloidal suspensions. Fifteen years ago the "Jamming paradigm" emerged to encompass in a unique framework the glass transition and the emergence of yield stress, two challenging issues in modern condensed matter physics. One must realize how bold this proposal was, given that the glass transition is a finite temperature transition governing the dynamical properties of supercooled liquids, while Jamming is essentially a zero temperature, zero external stress and purely geometric transition which occurs when a given packing of particles reaches the maximum compression state above which particles start to overlap. More recently, the observation of remarkable scaling properties on the approach to jamming led to the conjecture that this zero temperature "critical point" could determine the properties of dense particle systems within a region of the parameter space to be determined, which in principle could include thermal and stressed systems. Fifteen years of intense theoretical and experimental work later, what have we learned about Jamming and glassy dynamics? In this paper, we discuss these issues in the light of the experiments we have been conducting with vibrated grains.

Coulais, Corentin; Candelier, Raphal; Dauchot, Olivier

2013-06-01

29

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

E-print Network

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.

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

2014-10-20

30

Time-resolved dynamics of granular matter by random laser emission  

PubMed Central

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. PMID:23872642

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

2013-01-01

31

Glass transition associated with the jamming of vibrated granular matter.  

PubMed

We investigate a vibrated granular system composed of millimeter-size glass beads. When the system is submitted to a perturbation with decreasing intensity, below the fluidization limit, it evolves in a way similar to glass-forming liquids until it reaches an amorphous jammed state. This jamming transition is observed by the means of an immersed oscillator, either in the free or forced mode, while the granular medium is submitted to an external perturbation at a fixed frequency or within a frequency band. The complex susceptibility of the oscillator is measured as a function of the probe forcing frequency or as a function of the perturbation intensity. Data show that the jamming dynamics is "activated," similarly to thermal systems. The empirical control parameter is found proportional to the square root of the vibration intensity and inversely proportional to the vibration frequency. In the case of broadband external vibration, the average frequency of the power spectrum has to be considered. PMID:21405837

Sellerio, Alessandro Luigi; Mari, Daniele; Gremaud, Grard; D'Anna, Gianfranco

2011-02-01

32

Granular Matter Rolling, sliding & torsion of micron-sized silica particles -Experimental, numerical and  

E-print Network

Granular Matter Rolling, sliding & torsion of micron-sized silica particles - Experimental: Rolling, sliding & torsion of micron-sized silica particles - Experimental, numerical and theoretical a nanoindenter setup that allows normal and lateral displacement control and measurement of the respective forces

Luding, Stefan

33

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

E-print Network

properties and enzyme activities in a lowland tropical forest. We assayed six hydrolytic soil enzymesOrganic 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

Cleveland, Cory

34

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

NASA Astrophysics Data System (ADS)

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.

Navakas, Robertas; Diugys, Algis; Peters, Bernhard

2014-08-01

35

Flocking at a distance in active granular matter  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

36

Flocking at a distance in active granular matter.  

PubMed

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

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

2014-01-01

37

Flocking at a distance in active granular matter  

E-print Network

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.

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

2014-09-22

38

Granular magnetoresistance in cobalt/poly ,,3-hexylthiophene, 2, 5-diyl... hybrid thin films prepared by a wet chemical method  

E-print Network

Granular magnetoresistance in cobalt/poly ,,3-hexylthiophene, 2, 5-diyl... hybrid thin films.9993 to the fluctuation induced tunneling model. Moreover, by applying a magnetic field, a magnetoresistance ratio of 3 materials systems, and morphologies, as demonstrated by the observa- tions of anisotropic magnetoresistance

Krishnan, Kannan M.

39

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

SciTech Connect

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.

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

40

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

PubMed

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

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

2013-06-15

41

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

NASA Astrophysics Data System (ADS)

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.

Snchez-Colina, G.; Alonso-Llanes, L.; Martnez, E.; Batista-Leyva, A. J.; Clement, C.; Fliedner, C.; Toussaint, R.; Altshuler, E.

2014-12-01

42

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

PubMed

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

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

2014-12-01

43

Role and significance of extracellular polymeric substances from granular sludge for simultaneous removal of organic matter and ammonia nitrogen.  

PubMed

This study analyzed the organics and content of metal ions in extracellular polymeric substances (EPSs), tightly (TB-EPSs) and loosely (LB-EPSs) bound EPSs of granular sludge with simultaneous removal of organic matters and ammonia nitrogen, studied the dynamic variation of metal ions in EPSs from granular sludge with different particle sizes and the change of zeta potential before and after cation exchange resin (CER) treatment. Results showed, with particle size increasing, the protein content gradually increased, the content of polysaccharide basically unchanged; the content of Ca, Mg, K, Na and Zn also increased, whereas others did not show a consistent regularity. The existence of metal ions reduced zeta potential of EPSs. The existence of metal ions helped to the adhesion among granules, in order to form a granule with bigger particle size. PMID:25575205

Yan, Lilong; Liu, Yu; Wen, Yan; Ren, Yuan; Hao, Guoxin; Zhang, Ying

2015-03-01

44

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

45

Granular Matter (2012) 14:229234 DOI 10.1007/s10035-012-0339-y  

E-print Network

that the steady flow of granular material down a rough inclined plane has a surface that is not parallel plane inclined at a range of angles, a steady flow develops between static levées down the slope [1­3]. Remarkably, however, the surface of the flowing region is not parallel to the inclined plane, but is curved

Huppert, Herbert

46

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

Microsoft Academic Search

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

L. Beyer; C. Wachendorf; C. Koebbemann

1993-01-01

47

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

48

Crystalline Silica Dust and Respirable Particulate Matter During Indoor Concrete GrindingWet Grinding and Ventilated Grinding Compared with Uncontrolled Conventional Grinding  

Microsoft Academic Search

The effectiveness of wet grinding (wet dust reduction method) and ventilated grinding (local exhaust ventilation method, LEV) in reducing the levels of respirable crystalline silica dust (quartz) and respirable suspended particulate matter (RSP) were compared with that of uncontrolled (no dust reduction method) conventional grinding. A field laboratory was set up to simulate concrete surface grinding using hand-held angle grinders

Farhang Akbar-Khanzadeh; Sheryl Milz; April Ames; Pamela P. Susi; Michael Bisesi; Sadik A. Khuder; Mahboubeh Akbar-Khanzadeh

2007-01-01

49

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

NASA Astrophysics Data System (ADS)

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.

Percier, Baptiste; Divoux, Thibaut; Taberlet, Nicolas

2013-10-01

50

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

PubMed Central

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

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

2012-01-01

51

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

E-print Network

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.

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

2014-12-17

52

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

53

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)

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: 8.1mgL-1), 0.16-40 (average: 1.3mgL-1), and 0.34-6.9mgL-1 (average: 1.4mgL-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 1580ngL-1 with an average of 170ngL-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 (0-4.3mmh-1). The total annual fluxes of wet and dry depositions combined for PM and PAHs in the urban area of Guangzhou were 34gm-2yr-1 and 6.0נ102?gm-2yr-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.

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

2014-02-01

54

Dissolved copper speciation behaviour during estuarine mixing in the San Simon Inlet (wet season, Galicia). Influence of particulate matter  

NASA Astrophysics Data System (ADS)

The speciation trend of dissolved copper (DCu) was studied for the first time in a Galician Ria across the estuarine zone of the Vigo Ria during the wet season and related to the copper levels in suspended particulate matter (PCu) and sediments. In the riverine and ocean end-members DCu concentrations can be defined as pristine (<4 nM in Oitaven River). DCu is not conservative during the estuarine mixing and its concentration increase (5-8 nM) cannot be only associated to PCu (0.5-1.0 nM) variations and the ria sediments may be an important DCu source. DCu speciation was mainly controlled by two types of ligands ( logKL1'=12.9-13.9; and logKL'=10.8-12.1). In all samples the concentration of L 1 ( C =15-34nM) was greater than that of copper, which speciation is so dominated by this strong organic ligand. The transport of copper contamination from the middle Ria to the San Simon Inlet is limited during the wet season; in spite of similar salinities, DCu in the inlet (6 nM) was much lower than at Rande Strait (15 nM).

Santos-Echeandia, Juan; Laglera, Luis M.; Prego, Ricardo; van den Berg, Constant M. G.

2008-01-01

55

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

PubMed

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

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

2014-11-21

56

Permittivity of porous granular matter, in relation with Rosetta cometary mission  

NASA Astrophysics Data System (ADS)

We report measurements in laboratory conditions of the relative complex permittivity (hereafter permittivity) of porous material on a large range of frequencies from 50 MHz to 190 GHz. Such measurements, developed in preparation of the Rosetta mission to comet 67P/Churyumov-Gerasimenko, specifically for the MIRO radiometric experiment, were obtained with different instrumentations in three frequency bands: 50-500 MHz, 2.45 - 12 GHz and 190 GHz (center-band frequency of the millimeter receiver of MIRO, specially developed for our purpose). Considering the expected properties of cometary nuclei, they were carried out with porous granular materials of volcanic origin, with various sizes ranging from a few to 500 ?m, i.e. Etna's ashes and NASA JSC Mars-1 martian soil simulant. The samples were split into several sub-samples with different size ranges and bulk densities. The real part and the imaginary part of the permittivity remain respectively in the 2.1 - 4.0 range and in the 0.05 - 0.31 range. Volume scattering becomes significant for the measurements at 190 GHz when the mean grain size of sub-samples is greater than about 200 ?m and implies an increase of the real part and the imaginary part of the permittivity. Without this effect, for any sub-sample, the results are consistent over the frequency range. From 50 MHz to 190 GHz, evidence is provided for a slight decrease of the real part of the permittivity. Bulk densities of the sub-samples, being in the 800-1300 kg m-3 range, were determined during the measurements at 190 GHz. Taking into account the expected bulk density of the nucleus (100-370 kg m-3), as well as temperature for the surface and subsurface (in the 30-300 K range) and its composition (consisting both of silica-rich dust and ices, mostly of water), these first series of results allow an estimate of the real part and the imaginary part of the permittivity of the near-surface of the cometary nucleus: the real part is likely to be lower than 1.6 for non-icy regions and lower than 1.4 for icy regions; the imaginary part is likely to be below 0.09. These estimates represent upper limits relevant for the interpretation of the future data of MIRO.

Brouet, Y.; Levasseur-Regourd, A. C.; Encrenaz, P.; Gulkis, S.

2014-11-01

57

WET SOLIDS FLOW ENHANCEMENT  

SciTech Connect

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.

Hugo S. Caram; Natalie Foster

1997-03-31

58

WET SOLIDS FLOW ENHANCEMENT  

SciTech Connect

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.

Unknown

2001-03-25

59

PREFACE: Dynamics of wetting Dynamics of wetting  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

60

Granular Materials  

NSDL National Science Digital Library

A granular material can be defined as any loosely interacting collection of (usually) solid particles.1 Depending on the conditions, a granular material can be best described as a solid, or as a fluid, or as a gas, or in some case not adequately as any of these, which makes this both an interesting and difficult field of study. The behavior of granular materials is something that is encountered frequently in all aspects of everyday life. Some of the situations include grain silos, trash piles, sand & salt that is used for building and on winter roads, snow (as in avalanches), and mixing of various food and medical supplies, such as pharmaceuticals. A granular material would be generally defined as consisting of discrete units of a solid material that neither chemically interact, nor otherwise strongly cohere together. Thus, the arrangement and motion of these materials is neither that of a solid (in which the various parts are tightly bound together) nor that of a fluid (in which the parts may easily flow over & around other parts). The size of the particles, per se, is not important -- the phenomenology is similar with very fine grains (such as powders) and with rather large grains (such as cannonballs). The possibility of using various sizes of grains allows for some interesting research proposals covering several length scales. For many experiments the size of the container needs to be large compared to the grain size (typically a factor of 100 could be considered as large), so that end effects are indeed restricted only to the ends. This of course means also a large number of particles easy with things like sand, less so with things like marbles (1003 marbles can be quite massive!)

Dolan, Paul

2012-03-08

61

Distribution and disinfection of bacterial loadings associated with particulate matter fractions transported in urban wet weather flows.  

PubMed

Urban runoff is a resource for reuse water. However, runoff transports indicator and pathogenic organisms which are mobilized from sources of fecal contamination. These organisms are entrained with particulate matter (PM) that can serve as a mobile substrate for these organisms. Within a framework of additional treatment for reuse of treated runoff which requires the management of PM inventories in unit operationsand drainage systems there is a need to characterize organism distributions on PM and the disinfection potential thereof. This study quantifies total coliform, Escherichia coli, fecal streptococcus, and enterococcus generated from 25 runoff events. With the ubiquity and hetero-dispersivity of PM in urban runoff this study examines organism distributions for suspended, settleable and sediment PM fractions differentiated based on PM size and transport functionality. Hypochlorite is applied in batch to elaborate inactivation of PM-associated organisms for each PM fraction. Results indicate that urban runoff bacterial loadings of indicator organisms exceed U.S. wastewater reuse, recreational contact, and Australian runoff reuse criteria as comparative metrics. All monitored events exceeded the Australian runoff reuse criteria for E. coli in non-potable residential and unrestricted access systems. In PM-differentiated events, bacteriological mobilization primarily occurred in the suspended PM fraction. However, sediment PM shielded PM-associated coliforms at all hypochlorite doses, whereas suspended and settleable PM fractions provide less shielding resulting in higher inactivation by hypochlorite. PMID:22244969

Dickenson, Joshua A; Sansalone, John J

2012-12-15

62

J. Phys. A: Math. Gen. 33 (2000) 44014426. Printed in the UK PII: S0305-4470(00)09511-1 Response properties in a model for granular matter  

E-print Network

, ontheroleplayedbythespatialinhomogeneities (structures) spontaneously emerging during the compaction process, the history of the sample of the compaction process and we comment on the validity of our results for the description of granular materials in a thermodynamic framework. (Some figures in this article are in colour only in the electronic version; see www

Barrat, Alain

63

ccsd00000978, Relation between dry granular ow regimes and morphology of deposits: formation of  

E-print Network

granular matter owing down an inclined plane are performed in order to study the dynamics of dense ux and on the inclination of the plane. Each ow regime corresponds to a particular morphology/channel morphology; frictional granular ow regimes on inclined planes PACS numbers: 45.70.Mg Granular ows - 45

64

From liquid to solid bonding in cohesive granular Jean-Yves Delenne  

E-print Network

From liquid to solid bonding in cohesive granular media Jean-Yves Delenne , Fabien Souli´e, Moulay of a granular packing from liquid to solid bonding in the course of drying. The particles are initially wetted of the solute transforms the liquid bonds into partially cemented bonds. This transition is evidenced

Boyer, Edmond

65

Matter  

NSDL National Science Digital Library

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 ...

Mcnees, Mrs.

2010-11-16

66

A review of mesoscale simulations of granular materials  

Microsoft Academic Search

With the advent of increased computing power, mesoscale simulations have been used to explore grain level phenomenology of dynamic compaction events of various heterogenous systems including foams, reactive materials and porous granular materials. This paper presents an overview of several mesoscale studies on a variety of materials include tungsten carbide and epoxy mixtures, wet and dry sand, and reactive materials

John Borg

2009-01-01

67

Self assembly in soft matter  

E-print Network

The term soft matter applies to a variety of physical systems, such as liquids, colloids, polymers, foams, gels, and granular materials. The most fascinating aspect of soft matter lies in the fact that they are not ...

Chremos, Alexandros

2009-01-01

68

Self Assembly in Soft Matter  

E-print Network

The term soft matter applies to a variety of physical systems, such as liquids, colloids, polymers, foams, gels, and granular materials. The most fascinating aspect of soft matter lies in the fact that they are not ...

Chremos, Alexandros

2009-01-01

69

Wet Adhesion and Adhesive Locomotion of Snails on Anti-Adhesive Non-Wetting Surfaces  

PubMed Central

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

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

2012-01-01

70

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

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

Pennycook, Steve

71

Adapting granular materials through artificial evolution  

NASA Astrophysics Data System (ADS)

Over 200 years after Coulombs studies, a general connection between the mechanical response of a granular material and the constituents shape remains unknown. The key difficulty in articulating this relationship is that shape is an inexhaustible parameter, making its systematic exploration infeasible. Here we show that the role of particle shape can, however, be explored efficiently when granular design is viewed in the context of artificial evolution. By introducing a mutable representation for particle shapes, we demonstrate with computer simulation how shapes can be evolved. As proof of principle, we predicted motifs that link shape to packing stiffness, discovered a particle that produces aggregates that stiffenrather than weakenunder compression, and verified the results using three-dimensional printing. More generally, our approach facilitates the exploration of the role of arbitrary particle geometry in jammed systems, and invites the discovery and design of granular matter with optimized properties.

Miskin, Marc Z.; Jaeger, Heinrich M.

2013-04-01

72

Matter  

NSDL National Science Digital Library

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.

Houghton Mifflin Science

73

Capillary cohesion and mechanical strength of polydisperse granular materials.  

PubMed

We investigate the macroscopic mechanical behaviour of wet polydisperse granular media. Capillary bonding between two grains of unequal diameters is described by a realistic force law implemented in a molecular-dynamics algorithm together with a protocol for the distribution of water in the bulk. Axial-compression tests are simulated for granular samples at different levels of water content, and compared to experiments performed in similar conditions. We find good agreement between numerical and experimental data in terms of the rupture strength as a function of water content. Our results show the importance of the distribution of water for the mechanical behaviour. PMID:17294088

Souli, F; El Youssoufi, M S; Cherblanc, F; Saix, C

2006-12-01

74

Gravity and Granular Materials  

NASA Technical Reports Server (NTRS)

We describe experiments that probe a number of different types of granular flow where either gravity is effectively eliminated or it is modulated in time. These experiments include the shaking of granular materials both vertically and horizontally, and the shearing of a 2D granular material. For the shaken system, we identify interesting dynamical phenomena and relate them to standard simple friction models. An interesting application of this set of experiments is to the mixing of dissimilar materials. For the sheared system we identify a new kind of dynamical phase transition.

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

1999-01-01

75

Dynamics of Granular Materials  

NASA Technical Reports Server (NTRS)

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.

Behringer, Robert P.

1996-01-01

76

Forced Granular Orifice Flow  

E-print Network

The flow of granular material through an orifice is studied experimentally as a function of force $F$ pushing the flow. It is found that the flow rate increases linearly with $F$ -- a new, unexpected result that is in contrast to the usual view that $F$, completely screened by an arch formed around the orifice, has no way of altering the rate. Employing energy balance, we show that this behavior results mainly from dissipation in the granular material.

Zheng Peng; Hepeng Zheng; Yimin Jiang

2009-08-03

77

Numerical calculation of granular entropy  

E-print Network

We present numerical simulations that allow us to compute the number of ways in which $N$ particles can pack into a given volume $V$. Our technique modifies the method of Xu et al. (Phys. Rev. Lett. 106, 245502 (2011)) and outperforms existing direct enumeration methods by more than 200 orders of magnitude. We use our approach to study the system size dependence of the number of distinct packings of a system of up to 128 poly-disperse soft disks. We show that, even though granular particles are distinguishable, we have to include a factor $1/N!$ to ensure that the entropy does not change when exchanging particles between systems in the same macroscopic state. Our simulations provide strong evidence that the packing entropy, when properly defined, is extensive. As different packings are created with unequal probabilities, it is natural to express the packing entropy as $S=-\\sum_i p_i\\ln p_i -\\ln N!$, where $p_i$ denotes the probability to generate the $i$-th packing. We can compute this quantity reliably and it is also extensive. The granular entropy thus (re)defined, whilst distinct from the one proposed by Edwards assumed (J. Phys.: Condens.Matter 2, SA63(1990)), does have all the properties Edwards assumed.

Daniel Asenjo; Fabien Paillusson; Daan Frenkel

2014-03-24

78

Numerical Calculation of Granular Entropy  

NASA Astrophysics Data System (ADS)

We present numerical simulations that allow us to compute the number of ways in which N particles can pack into a given volume V. Our technique modifies the method of Xu, Frenkel, and Liu [Phys. Rev. Lett. 106, 245502 (2011)] and outperforms existing direct enumeration methods by more than 200 orders of magnitude. We use our approach to study the system size dependence of the number of distinct packings of a system of up to 128 polydisperse soft disks. We show that, even though granular particles are distinguishable, we have to include a factor 1/N! to ensure that the entropy does not change when exchanging particles between systems in the same macroscopic state. Our simulations provide strong evidence that the packing entropy, when properly defined, is extensive. As different packings are created with unequal probabilities, it is natural to express the packing entropy as S=-?ipilnpi-lnN!, where pi denotes the probability to generate the ith packing. We can compute this quantity reliably and it is also extensive. The granular entropy thus (re)defined, while distinct from the one proposed by Edwards [J. Phys. Condens. Matter 2, SA63 (1990)], does have all the properties Edwards assumed.

Asenjo, Daniel; Paillusson, Fabien; Frenkel, Daan

2014-03-01

79

Flow of dry and wet granular materials: Numerical simulation results  

NASA Astrophysics Data System (ADS)

We use a DEM method to simulate dense assemblies of frictional spherical grains in 3D steady shear flow under controlled normal stress P, either dry or in the presence of a small amount of an interstitial liquid, which gives rise to capillary menisci and attractive forces. We pay special attention to the quasi-static limit of slow flow. The system behavior is characterized by the dependence of internal friction coefficient and solid fraction on two dimensionless control parameters: the inertial number, I and the reduced pressure, P*, comparing confining forces to contact tensile strength. Capillary forces have a significant effect on the macroscopic behavior of the system, up to P* values of several unities, especially for longer force ranges associated with larger menisci. We relate this effect to fabric anisotropy parameters of contact and distant interactions.

Khamseh, Saeed; Roux, Jean-Nol; Chevoir, Franois

2013-06-01

80

Hydrodynamics of soft active matter  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

81

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 ...

82

Granular gases under extreme driving  

NASA Astrophysics Data System (ADS)

We study inelastic gases in two dimensions using event-driven molecular-dynamics simulations. Our focus is the nature of the stationary state attained by rare injection of large amounts of energy to balance the dissipation due to collisions. We find that under such extreme driving, with the injection rate much smaller than the collision rate, the velocity distribution has a power-law high-energy tail. The numerically measured exponent characterizing this tail is in excellent agreement with predictions of kinetic theory over a wide range of system parameters. We conclude that driving by rare but powerful energy injection leads to a well-mixed gas and constitutes an alternative mechanism for agitating granular matter. In this distinct nonequilibrium steady state, energy cascades from large to small scales. Our simulations also show that when the injection rate is comparable with the collision rate, the velocity distribution has a stretched exponential tail.

Kang, W.; Machta, J.; Ben-Naim, E.

2010-08-01

83

Bifurcation and nonlinear behavior of compartmentalized granular gases  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

84

a Review of Mesoscale Simulations of Granular Materials  

Microsoft Academic Search

With the advent of increased computing power, mesoscale simulations have been used to explore grain level phenomenology of dynamic compaction events of various heterogenous systems including foams, reactive materials and porous granular materials. This paper presents an overview of several mesoscale studies on a variety of materials including tungsten carbide, wet and dry sand, and an inert mixture of Al-MnO2-Epoxy.

J. P. Borg; T. J. Vogler; A. Fraser

2009-01-01

85

A REVIEW OF MESOSCALE SIMULATIONS OF GRANULAR MATERIALS  

Microsoft Academic Search

With the advent of increased computing power, mesoscale simulations have been used to explore grain level phenomenology of dynamic compaction events of various heterogenous systems including foams, reactive materials and porous granular materials. This paper presents an overview of several mesoscale studies on a variety of materials including tungsten carbide, wet and dry sand, and an inert mixture of Al-MnO2-Epoxy.

J. P. Borg; T. J. Vogler; A. Fraser

2009-01-01

86

Multiscale modeling in granular flow  

E-print Network

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 ...

Rycroft, Christopher Harley

2007-01-01

87

Strain Effects on Granular Impact  

E-print Network

Strain Effects on Granular Impact Emily Lim, Kerstin Nordstrom, Matt Harrington, Steven Slotterback, Wolfgang Losert #12;Impacts into Granular Materials Tunguska Crater June 1908 - Leveled more than 2,000 sq km Foot-Ground Interaction How does preparation of the granular material affect impact dynamics

Anlage, Steven

88

Granular Convection in Microgravity  

E-print Network

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.

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

2013-06-07

89

Granular Convection in Microgravity  

E-print Network

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.

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

2013-01-01

90

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...

91

Granular flow over inclined channels with constrictions  

NASA Astrophysics Data System (ADS)

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 hpGEMa 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.

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

2013-04-01

92

Matter on granular space-time  

E-print Network

We develop further the formalism of the non-Abelian gauge field theory on a cell complex space-time and show how the gauge-invariant action and the equations of motion for gauge fields interacting with spinors can be written without a reference to the geometrical nature of the cells of the cell complex. The general results are illustrated with examples of solutions of equations of motion for U(N) and SU(N) gauge groups.

Alexander N. Jourjine

2008-04-28

93

Spreading of triboelectrically charged granular matter  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

94

Prestress stability Session on Granular Matter  

E-print Network

,...) is a proper self stress for the tensegrity G(p). Our goal is to determine when the configuration p is a local-by-e diagonal matrix whose ij, ij diagonal entry is cij, where e is the number of members in the tensegrity. #12 of global information about the tensegrity, although it can have negative eigenvalues. Define the matrix H

Connelly, Robert

95

Corn Wet Milling Lab  

NSDL National Science Digital Library

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.

Olson, Eric; Warren, Noreen

2008-10-27

96

Adsorption and wetting  

Microsoft Academic Search

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

L. J. M. Schlangen

1995-01-01

97

Wet storage integrity update  

Microsoft Academic Search

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

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

1983-01-01

98

Very, Very Fast Wetting  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

99

Unified force law for granular impact cratering  

E-print Network

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.

H. Katsuragi; D. J. Durian

2007-03-02

100

Wet solids flow enhancement  

SciTech Connect

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.

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

1997-07-01

101

Artificial Intelligence Perspectives on Granular Computing  

E-print Network

Artificial Intelligence Perspectives on Granular Computing Yiyu Yao Department of Computer Science, 2008) offer artificial intelligence perspectives on granular computing (Yao, 2008a). Specifically- ing; this classes is characterized by multiple levels of granularity. Regarding human intelligence

Yao, Yiyu

102

Granular Dynamics during Impact  

NASA Astrophysics Data System (ADS)

In this work, we study the impact of a projectile onto a bed of 3 mm grains immersed in an index-matched fluid. Using a laser sheet scanning technique, a high speed camera, and particle tracking, we can measure the trajectory of each grain throughout an impact event. We characterize the bulk and microscopic dynamics within the granular material as a function of initial sample preparation, specifically applying a uniaxial prestrain to the sample. We find that small changes in sample preparation lead to drastic departures from the universal depth scaling seen in previous studies of shallow granular impacts. By examining the nonaffine motion within the system, we propose the effect is due to different loading and buckling of force chains within the system.

Nordstrom, Kerstin; Lim, Emily; Harrington, Matt; Losert, Wolfgang

2013-03-01

103

Spatiotemporally resolved granular acoustics  

NASA Astrophysics Data System (ADS)

Acoustic techniques provide a non-invasive method of characterizing granular material properties; however, there are many challenges in formulating accurate models of sound propagation due to the inherently heterogeneous nature of granular materials. In order to quantify acoustic responses in space and time, we perform experiments in a photoelastic granular material in which the internal stress pattern (in the form of force chains) is visible. We utilize two complementary methods, high-speed imaging and piezoelectric transduction, to provide particle-scale measurements of the amplitude of the acoustic wave. We observe that the average wave amplitude is largest within particles experiencing the largest forces. The force-dependence of this amplitude is in qualitative agreement with a simple Hertzian-like model for contact area. In addition, we investigate the power spectrum of the propagating signal using the piezoelectric sensors. For a Gaussian wave packet input, we observe a broad spectrum of transmitted frequencies below the driving frequency, and we quantify the characteristic frequencies and corresponding length scales of our material as the system pressure is varied.

Owens, Eli; Daniels, Karen

2011-03-01

104

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.

2014-07-07

105

Wetting transition in water.  

PubMed

Optical images were used to study the wetting behavior of water on graphite, sapphire, and quartz along the liquid vapor coexistence curve from room temperature to 300 C. Wetting transitions were identified by the temperature at which the contact angle decreased to zero and also by the disappearance of dropwise condensation. These two methods yielded consistent values for the wetting temperatures, which were 185 C, 234 C, and 271 C for water on quartz, sapphire, and graphite, respectively. We compare our results with the theoretical predictions based on a simplified model of the water-substrate potential and sharp interfaces. PMID:24329458

Friedman, S R; Khalil, M; Taborek, P

2013-11-27

106

Vibrated granular media as experimentally realizable Granular Gases  

E-print Network

of the granular temperature, collision frequency, impulse and pressure with the vibrating piston velocity. As the system changes from a homogeneous gas state at low density to a clustered state at high density wall can be replaced by a thermal boundary. The vibrated granular gas thus attains a steady state

Falcon, Eric

107

Wetting and Contact Angle  

NSDL National Science Digital Library

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.

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

108

Shocks in rapid granular flows  

Microsoft Academic Search

The speed of a pressure wave (the speed of sound) in rapid granular flows is typically only a few centimeters per second while the collective streaming motion of the particles is on the order of meters per second. In this supersonic regime, shocks form when a granular flow encounters an obstacles. This work examines the shocks formed in three geometries:

Erin Colleen Rericha

2004-01-01

109

Spreading of a granular droplet.  

SciTech Connect

The influence of controlled vibrations on the granular rheology is investigated in a specifically designed experiment in which a granular film spreads under the action of horizontal vibrations. A nonlinear diffusion equation is derived theoretically that describes the evolution of the deposit shape. A self-similar parabolic shape (the granular droplet) and a spreading dynamics are predicted that both agree quantitatively with the experimental results. The theoretical analysis is used to extract effective friction coefficients between the base and the granular layer under sustained and controlled vibrations. A shear thickening regime characteristic of dense granular flows is evidenced at low vibration energy, both for glass beads and natural sand. Conversely, shear thinning is observed at high agitation.

Sanchez, I.; Raynaud, F.; Lanuza, J.; Andreotti, B.; Clement, E.; Aranson, I. S.; Materials Science Division; Univ. Simon; CNRS-ESPCI-Univ.

2007-01-01

110

Nonlinear granular breathing  

NASA Astrophysics Data System (ADS)

A numerical study of the problem of driven horizontal alignments of solid, elastic spheres that are placed between two rigid walls is presented. The studies are confined to cases where the initial loading between the spheres is zero. The driving force is applied on the left outer sphere and directed into the chain. The spheres are considered to interact via the repulsive and strongly nonlinear Hertz potential. Three systems are analyzed, the monodispersed chain, the tapered chain and the decorated chain. A Hertzian chain over-compressed will respond via a dilation phase leading the system to a pulsatory mode which we call nonlinear breathing. Exhaustive studies show that the dynamics of monodispersed and tapered granular chains acted upon by a constant/time dependent force presents surprising features such as the breathing period (frequency) and the anomalous nonlinear resonance frequency. The breathing period characterizes the response of the system which is dependent upon the external force and is strongly influenced by the geometry of chain. Approximate relations for the breathing period and the anomalous nonlinear resonance frequency as functions of the magnitude of the driving force and of the chain's parameters are developed. Then the ratios of the analyzed quantities are compared to ratios obtained from simulations. Inertial mismatches introduced in granular chains enrich the dynamics of monodispersed chains leading to the discussion of continuing our work beyond this dissertation. Converting the ocean wave's energy and of small scale wind energy via granular chains into mechanical and electrical energies is discussed as possible application of the breathing phenomenon.

Simion, Robert Paul

111

Bulldozing of granular material  

E-print Network

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.

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

2014-05-01

112

Granular Avalanches in Fluids  

E-print Network

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.

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

2002-09-03

113

Granular mechanics and rifting  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

114

Membrane-based wet electrostatic precipitation  

SciTech Connect

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.

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

115

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

NASA Astrophysics Data System (ADS)

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.

Zhu, Runru; Li, Shuiqing; Yao, Qiang

2013-02-01

116

Granular Materials Research at NASA-Glenn  

NASA Technical Reports Server (NTRS)

This paper presents viewgraphs of granular materials research at NASA-Glenn. The topics include: 1) Impulse dispersion of a tapered granular chain; 2) High Speed Digital Images of Tapered Chain Dynamics; 3) Impulse Dispersion; 4) Three Dimensional Granular Bed Experimental Setup; 5) Magnetic Resonance Imaging of Fluid Flow in Porous Media; and 6) Net Charge on Granular Materials (NCharG).

Agui, Juan H.; Daidzic, Nihad; Green, Robert D.; Nakagawa, Masami; Nayagam, Vedha; Rame, Enrique; Wilkinson, Allen

2002-01-01

117

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...

118

a Review of Mesoscale Simulations of Granular Materials  

NASA Astrophysics Data System (ADS)

With the advent of increased computing power, mesoscale simulations have been used to explore grain level phenomenology of dynamic compaction events of various heterogenous systems including foams, reactive materials and porous granular materials. This paper presents an overview of several mesoscale studies on a variety of materials including tungsten carbide, wet and dry sand, and an inert mixture of Al-MnO2-Epoxy. This paper focuses on relating bulk and compaction wave phenomenology from the mesoscale modeling to experimental results and exploring the nature of the compaction wave. In addition, lessons learned during these explorations, modeling techniques, strengths and weaknesses of hydrodynamic mesoscale simulations are also discussed.

Borg, J. P.; Vogler, T. J.; Fraser, A.

2009-12-01

119

Wet gas metering performance  

SciTech Connect

This paper presents laboratory and field test data for orifice and turbine meters in wet gas flow measurement. Laboratory testing has revealed that orifice meter measurement of natural gas with only small amounts of entrained liquid will have large errors. The data also indicates that commonly used correlations for two phase orifice metering are unacceptable for the low liquid loading at mass ratio below 2%. Controlled laboratory turbine meter tests using an air-water system at moderate pressure have shown that turbine meters are more accurate than orifice meters in a wet gas flow. Field data on orifice meter and turbine meter performance are also presented and results are compared to laboratory tests. The comparison indicates that the field performance of orifice meters have higher metering errors than laboratory results. The possible causes of the discrepancy are discussed. The authors concluded that the two most commonly used natural gas meters contributed higher measurement errors for long-term wet gas service.

Jones, E.H. Jr.; Ting, V.C. [Chevron Petroleum Technology Co., La Habra, CA (United States)

1996-12-01

120

Wet and Wild Water.  

ERIC Educational Resources Information Center

This guide uses a thematic approach to show the integration of subjects (reading, mathematics, language arts, science/fine arts) and skills to create a context for learning. The contents of this guide are presented in a holistic format. There are six major topics in the guide, each with subtopics: (1) "Getting Your Feet Wet--An Introduction to

Indiana State Dept. of Education, Indianapolis. Center for School Improvement and Performance.

121

Granular Dynamics during Impact  

E-print Network

We study the impact of a projectile onto a bed of 3 mm grains immersed in an index-matched fluid. Specifically, we vary the amount of prestrain on the sample, strengthening the force chains within the system. We find this affects only the prefactor of linear depth-dependent term in the stopping force. We therefore attribute this term to pressure within the material, and not the grain-intruder friction as is sometimes suggested. Using a laser sheet scanning technique to visualize internal grain motion, a high-speed camera, and particle tracking, we can measure the trajectory of each grain throughout an impact event. Microscopically, our results indicate that weaker initial force chains result in more irreversible, plastic rearrangements during impact, suggesting static friction between grains does play a substantial role in the energy dissipation within the granular material.

Kerstin Nordstrom; Emily Lim; Matthew Harrington; Wolfgang Losert

2014-04-04

122

Intradural spinal granular cell tumor  

PubMed Central

Granular cell tumor is a rare, usually benign tumor with classical histomorphology. Location of tumor varies widely within body, but spine is distinctly a rare location for this tumor. We report a rare case of granular cell tumor involving intradural extramedullary portion of lumbar region of spinal cord. Knowledge of which is important as subsequent prognosis differs from other tumor at same location. PMID:25126126

Vaghasiya, Viren L.; Nasit, Jitendra G.; Parikh, Pinki A.; Trivedi, Priti P.

2014-01-01

123

Intradural spinal granular cell tumor.  

PubMed

Granular cell tumor is a rare, usually benign tumor with classical histomorphology. Location of tumor varies widely within body, but spine is distinctly a rare location for this tumor. We report a rare case of granular cell tumor involving intradural extramedullary portion of lumbar region of spinal cord. Knowledge of which is important as subsequent prognosis differs from other tumor at same location. PMID:25126126

Vaghasiya, Viren L; Nasit, Jitendra G; Parikh, Pinki A; Trivedi, Priti P

2014-04-01

124

Arrested coarsening of granular roll waves  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

125

Self-diffusion of wet particles in rotating drums  

NASA Astrophysics Data System (ADS)

Axial mixing of wet particles in rotating drums was investigated by the discrete element method with the capillary force explicitly considered. Different flow regimes were observed by varying the surface tension of liquid and keeping other conditions unchanged. The analysis of the concentration and mean square displacement of particles indicated that the axial motion of wet particles was a diffusive process characterised by Fick's law. Particle diffusivity decreased with increasing inter-particle cohesion and drum filling level but increased with increasing drum rotation speed. Two competing mechanisms were proposed to explain these effects. A theoretical model based on the relation between local diffusivity and shear rate was developed to predict particle diffusivity as a function of drum operation conditions. It was also observed that despite the high inhomogeneity of particle flow in rotating drums, the mean diffusivity of flow exhibited a strong correlation with granular temperature, defined as the mean square fluctuating velocity of particles.

Liu, P. Y.; Yang, R. Y.; Yu, A. B.

2013-06-01

126

Different Effects of Roughness (Granularity) and Hydrophobicity  

NASA Astrophysics Data System (ADS)

With thanks to Stefan Doerr and Jorge Mataix-Solera for their invitation Superhydrophobicity is an interesting effect that appears to be simple on the outset; increased surface area from roughness increases interfacial area and therefore energy loss or gain. More extreme roughness prevents total wetting, resulting in gas pockets present at the surface and a drastic change in the properties of the system. Increases in complexity of the system, by adding porosity (granularity), allowing the structures to move, varying the shape of the roughness or the composition of the liquid used often has unexpected effects. Here we will consider a few of these related to complex topography. Overhanging features are commonly used in test samples as they perform better in some tests than simple roughness. It has been shown to be a prerequisite for superoleophobic surfaces as it allows liquids to be suspended for contact angles considerably below 90. It also allows trapping of gas in lower layers even if the first layer is flooded. This is important in soils as a fixed bed of granules behaves just like a surface with overhanging roughness. Using simple geometry it is possible to predict at what contact angle penetration will occur. Plants have some structured superhydrophobic surfaces and we have shown that some use them in conjunction with other structured surfaces to control water flows. This allows some plants to survive in difficult environments and shows us how subtly different structures interact completely differently with water. Long fibres can either cause water droplets to roll over a plant surface or halt it in its tracks. Implications of this in soils include predicting when particles will adhere more strongly to water drops and why organic fibrous material may play a greater role in the behaviour of water in soils than may be expected from the amount present. The garden snail uses a biosurfactant that is very effective at wetting surfaces and can crawl over most superhydrophobic surfaces. There are some, however, that defeat even the snail's complex slime. Looking at these surfaces in more detail reveals that some superhydrophobic surfaces are much more resistant to the effects of surfactants than others. As mentioned above, overhanging structures, such as those found in granular materials are particularly effective at suspending liquids. This does not, however, always translate to them being more effective against surfactants, unfortunately, however, surfactants are not always as effective as we would like them to be, although drops do not skate across superhydrophobic surfaces they often do not penetrate into them fully either.

Shirtcliffe, Neil; McHale, Glen; Hamlett, Christopher; Newton, Michael

2010-05-01

127

Achtergrond De Wet van Moore  

E-print Network

Achtergrond De Wet van Moore In 1965 deed Gordon E. Moore zijn beroemde voorspelling dat het aantal van Moore, en met recht. Want al een dikke veertig jaar gaat de wet prima op. De transistoren worden van de wet van Moore biedt voor de chips-fabrikanten, zorgt ervoor dat de exponentiële groei steeds

Emmerich, Michael

128

Underwater wet welding of steel  

Microsoft Academic Search

Underwater wet welding is conducted directly in water with the shielded metal arc (SMA) and flux cored arc (FCA) welding processes. Underwater wet welding has been demonstrated as an acceptable repair technique down to 100 meters (325 ft.) in depth, but wet welds have been attempted on carbon steel structures down to 200 meters (650 ft.). The primary purpose of

S. Ibarra; S. Liu; D. L. Olson

1995-01-01

129

Adsorption of Methyl Tertiary Butyl Ether on Granular Zeolites: Batch and Column Studies  

PubMed Central

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

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

2010-01-01

130

Active microrheology of driven granular particles.  

PubMed

When pulling a particle in a driven granular fluid with constant force Fex, the probe particle approaches a steady-state average velocity v. This velocity and the corresponding friction coefficient of the probe ?=Fex/v are obtained within a schematic model of mode-coupling theory and compared to results from event-driven simulations. For small and moderate drag forces, the model describes the simulation results successfully for both the linear as well as the nonlinear region: The linear response regime (constant friction) for small drag forces is followed by shear thinning (decreasing friction) for moderate forces. For large forces, the model demonstrates a subsequent increasing friction in qualitative agreement with the data. The square-root increase of the friction with force found in [Fiege et al., Granul. Matter 14, 247 (2012)] is explained by a simple kinetic theory. PMID:24827243

Wang, Ting; Grob, Matthias; Zippelius, Annette; Sperl, Matthias

2014-04-01

131

Active microrheology of driven granular particles  

NASA Astrophysics Data System (ADS)

When pulling a particle in a driven granular fluid with constant force Fex, the probe particle approaches a steady-state average velocity v. This velocity and the corresponding friction coefficient of the probe ? =Fex/v are obtained within a schematic model of mode-coupling theory and compared to results from event-driven simulations. For small and moderate drag forces, the model describes the simulation results successfully for both the linear as well as the nonlinear region: The linear response regime (constant friction) for small drag forces is followed by shear thinning (decreasing friction) for moderate forces. For large forces, the model demonstrates a subsequent increasing friction in qualitative agreement with the data. The square-root increase of the friction with force found in [Fiege et al., Granul. Matter 14, 247 (2012), 10.1007/s10035-011-0309-9] is explained by a simple kinetic theory.

Wang, Ting; Grob, Matthias; Zippelius, Annette; Sperl, Matthias

2014-04-01

132

Granular structure determined by terahertz scattering  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

133

Granular Superconductors and Gravity  

NASA Technical Reports Server (NTRS)

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.

Noever, David; Koczor, Ron

1999-01-01

134

Silo Collapse under Granular Discharge.  

PubMed

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[Rt]. 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. PMID:25615503

Gutirrez, G; Colonnello, C; Boltenhagen, P; Darias, J R; Peralta-Fabi, R; Brau, F; Clment, E

2015-01-01

135

Silo collapse under granular discharge  

E-print Network

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.

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

2014-12-05

136

Silo Collapse under Granular Discharge  

NASA Astrophysics Data System (ADS)

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 /?{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.

Gutirrez, G.; Colonnello, C.; Boltenhagen, P.; Darias, J. R.; Peralta-Fabi, R.; Brau, F.; Clment, E.

2015-01-01

137

A Comparison of Mssbauer Spectroscopy and Wet Analytical Chemistry Determination of Iron Cations in Biotite  

NASA Astrophysics Data System (ADS)

Iron content in true trioctahedral mica granules and powders were determined by wet-chemical method. Powdered mica dissolves more readily during acid attack than the granular micas and thus yields higher precision and accuracy. International powdered whole-rock standards were analyzed simultaneously with micas to evaluate the accuracy of the method. High precision Mssbauer spectroscopic Fe3+/Fe2+ ratios coupled with the electron microprobe iron determinations were then compared with the wet-chemical data. The results of Fe total determinations through EPMA and UV-visible spectrophotometry show both techniques have same precision (?=0.2).

Tabbakh Shabani, Amir Ali

2010-05-01

138

Optical wet steam monitor  

DOEpatents

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.

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

1995-01-17

139

Wet coastal plain tundra  

SciTech Connect

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).

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

1980-01-01

140

Optical wet steam monitor  

DOEpatents

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.

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

1995-01-01

141

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, andTeacher guide.

142

Phoenix's Wet Chemistry Lab  

NASA Technical Reports Server (NTRS)

This is an illustration of soil analysis on NASA's Phoenix Mars Lander's Wet Chemistry Lab (WCL) on board the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) instrument. By dissolving small amounts of soil in water, WCL will attempt to determine the pH, the abundance of minerals such as magnesium and sodium cations or chloride, bromide and sulfate anions, as well as the conductivity and redox potential.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

143

Phoenix's Wet Chemistry Lab  

NASA Technical Reports Server (NTRS)

This is an illustration of the analytical procedure of NASA's Phoenix Mars Lander's Wet Chemistry Lab (WCL) on board the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) instrument. By dissolving small amounts of soil in water, WCL can determine the pH, the abundance of minerals such as magnesium and sodium cations or chloride, bromide and sulfate anions, as well as the conductivity and redox potential.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

144

Wetting in Color  

NASA Astrophysics Data System (ADS)

Colorimetric litmus tests such as pH paper have enjoyed wide commercial success due to their inexpensive production and exceptional ease of use. However, expansion of colorimetry to new sensing paradigms is challenging because macroscopic color changes are seldom coupled to arbitrary differences in the physical/chemical properties of a system. In this thesis I present in detail the development of Wetting in Color Technology, focusing primarily on its application as an inexpensive and highly selective colorimetric indicator for organic liquids. The technology exploits chemically-encoded inverse-opal photonic crystals to control the infiltration of fluids to liquid-specific spatial patterns, projecting minute differences in liquids' wettability to macroscopically distinct, easy-to-visualize structural color patterns. It is shown experimentally and corroborated with theoretical modeling using percolation theory that the high selectivity of wetting, upon-which the sensitivity of the indicator relies, is caused by the highly symmetric structure of our large-area, defect-free SiO2 inverse-opals. The regular structure also produces a bright iridescent color, which disappears when infiltrated with liquid - naturally coupling the optical and fluidic responses. Surface modification protocols are developed, requiring only silanization and selective oxidation, to facilitate the deterministic design of an indicator that differentiates a broad range of liquids. The resulting tunable, built-in horizontal and vertical chemistry gradients allow the wettability threshold to be tailored to specific liquids across a continuous range, and make the readout rely only on countable color differences. As wetting is a generic fluidic phenomenon, Wetting in Color technology could be suitable for applications in authentication or identification of unknown liquids across a broad range of industries. However, the generic nature of the response also ensures chemical non-specificity. It is shown that combinatorial measurements from an array of indicators add a degree of chemical specificity to the platform, which can be further improved by monitoring the drying of the inverse-opal films. While colorimetry is the central focus of this thesis, applications of this platform in encryption, fluidics and nanofabrication are also briefly explored.

Burgess, Ian Bruce

145

Initiation of immersed granular avalanches  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

146

Initiation of immersed granular avalanches.  

PubMed

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

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

2014-05-01

147

Wet steam wetness measurement in a 10 MW steam turbine  

NASA Astrophysics Data System (ADS)

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 koda Power s.r.o.

Kolovratnk, Michal; Barto, Ond?ej

2014-03-01

148

Momentum Transport in Granular Flows  

E-print Network

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.

Gregg Lois; Anael Lemaitre; Jean M. Carlson

2006-02-10

149

DUNE - a granular flow code  

SciTech Connect

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.

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

2004-11-23

150

Wetting Characteristics of Immiscibles  

NASA Technical Reports Server (NTRS)

Early microgravity experiments with immiscible alloys were usually carried out with the intent of forming dispersed microstructures. By processing under microgravity conditions, the main mechanism leading to gross phase separation could be eliminated. However, analysis of flight samples revealed a separated structure where the minor phase was present along the outer surface, while the major phase was present in the center. The Wetting Characteristics of Immiscibles (WCI) project, which flew aboard the USMP-4 (United States Microgravity Payload) mission in November of 1997, was designed to gain insight into the mechanisms causing segregation of these alloys. This investigation utilized an immiscible transparent organic alloy system and a transparent container in order to facilitate direct observation of the separation process. A range of immiscible alloy compositions was utilized in order to obtain variations in the minor and major phases present and observe the influence on the segregation processes. A small composition range was found where the minor liquid phase perfectly wet the cell gasket. Unexplained observations were made at the extremes of the composition range.

Andrews, J. B.; Little, L. J.

1999-01-01

151

Marginal Matter  

NASA Astrophysics Data System (ADS)

All around us, things are falling apart. The foam on our cappuccinos appears solid, but gentle stirring irreversibly changes its shape. Skin, a biological fiber network, is firm when you pinch it, but soft under light touch. Sand mimics a solid when we walk on the beach but a liquid when we pour it out of our shoes. Crucially, a marginal point separates the rigid or jammed state from the mechanical vacuum (freely flowing) state - at their marginal points, soft materials are neither solid nor liquid. Here I will show how the marginal point gives birth to a third sector of soft matter physics: intrinsically nonlinear mechanics. I will illustrate this with shock waves in weakly compressed granular media, the nonlinear rheology of foams, and the nonlinear mechanics of weakly connected elastic networks.

van Hecke, Martin

2013-03-01

152

Friction and the oscillatory motion of granular flows  

E-print Network

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.

Lydie Staron

2012-11-26

153

Wave mitigation in ordered networks of granular chains  

NASA Astrophysics Data System (ADS)

We study the propagation of stress waves through ordered 2D networks of granular chains. The quasi-particle continuum theory employed captures the acoustic pulse splitting, bending, and recombination through the network and is used to derive its effective acoustic properties. The strong wave mitigation properties of the network predicted theoretically are confirmed through both numerical simulations and experimental tests. In particular, the leading pulse amplitude propagating through the system is shown to decay exponentially with the propagation distance and the spatial structure of the transmitted wave shows an exponential localization along the direction of the incident wave. The length scales that characterized these exponential decays are studied and determined as a function of the geometrical properties of the network. These results open avenues for the design of efficient impact mitigating structures and provide new insights into the mechanisms of wave propagation in granular matter.

Leonard, Andrea; Ponson, Laurent; Daraio, Chiara

2014-12-01

154

Stress fluctuations and macroscopic stick-slip in granular materials.  

PubMed

This paper deals with the quasi-static regime of deformation of granular matter. It investigates the size of the Representative Elementary Volume (REV), which is the minimum packing size above which the macroscopic mechanical behaviour of granular materials can be defined from averaging. The first part uses typical results from recent literature and finds that the minimum REV contains in general 10 grains; this result holds true either for most experiments or for Discrete Element Method (DEM) simulation. This appears to be quite small. However, the second part gives a counterexample, which has been found when investigating uniaxial compression of glass spheres which exhibit stick-slip; we show in this case that the minimum REV becomes 10(7) grains. This makes the system not computable by DEM. Moreover, similarity between the Richter law of seism and the exponential statistics of stick-slip is stressed. PMID:15010916

Evesque, P; Adjmian, F

2002-11-01

155

Armoring a droplet: soft jamming of a dense granular interface.  

PubMed

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. PMID:25314379

Lagubeau, Guillaume; Rescaglio, Antonella; Melo, Francisco

2014-09-01

156

Armoring a droplet: Soft jamming of a dense granular interface  

NASA Astrophysics Data System (ADS)

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.

Lagubeau, Guillaume; Rescaglio, Antonella; Melo, Francisco

2014-09-01

157

Origin of the Velocity-Strengthening Nature of Granular Friction  

NASA Astrophysics Data System (ADS)

A simple theory for a constitutive law for steady state dynamic friction in granular matter is presented. Starting from the energy balance equation together with the kinetics of grains, the energy dissipation rate is estimated, which directly leads to a constitutive law. The result indicates that a system of lower density is stronger than a system of higher density, albeit somewhat counterintuitive. This is a consequence of the fact that the grain rearrangement, which causes energy dissipation, is more frequent in a system of lower density. Thus, the velocity-strengthening nature of granular friction is naturally explained by the negative shear-rate dependence of the density. The present theory also qualitatively explains the experimental observation that a system of smaller layer thickness tends to be velocity-weakening.

Hatano, Takahiro; Kuwano, Osamu

2013-01-01

158

Nanoparticle induced wetting of polymer films and self-assembled multilayers of nanocomponents  

Microsoft Academic Search

The control of dewetting for thin polymer films is a technical challenge and of significant academic interest. Although studies have been published on the wetting of polymer films in the presence of nanoparticles, the underlying physics is still a matter of debate. In this work, we report a systematic study of improved wetting behavior of thin polymer films containing nanoparticles,

R. S. Krishnan

2006-01-01

159

Shocks in rapid granular flows  

NASA Astrophysics Data System (ADS)

The speed of a pressure wave (the speed of sound) in rapid granular flows is typically only a few centimeters per second while the collective streaming motion of the particles is on the order of meters per second. In this supersonic regime, shocks form when a granular flow encounters an obstacles. This work examines the shocks formed in three geometries: the surface wake behind a cylinder, the oblique shock formed at a wedge and a normal shock propagating through a funnel. In each case we evaluate the applicability of a hydrodynamic description to shocks in rapid granular flows. We study the V-shaped wake formed by a cylindrical rod moving through a vertically vibrated granular layer. The wake appears for rod velocities vR greater than a critical velocity c. We measure the half-angle theta of the wake as a function of v R and layer depth h. We find that c and theta can be described by a hydrodynamic description applied to shallow fluids, where c = gh is the speed of a gravitational wave on a shallow fluid and sintheta = c/vR is the Mach relation. We find the decrease in the height of the wake h max as it propagates away from the rod agrees with Landau's theory for the decay of shock waves far from their origin. We measure the time-averaged velocity, density and temperature fields for a gravity driven granular flow past a wedge. The flow is supersonic with a sound speed less than 10% of the flow speed. We find the shock formed at the wedge tip is nearly identical to oblique shocks found in a supersonic, elastic gas. Molecular dynamics simulations of Newton's laws yield fields in quantitative agreement with experiment. A numerical solution of granular hydrodynamic equations is only in qualitatively accord with experiment. We show that hydrodynamic theory fails because it does not include friction. We use molecular dynamics simulations to examine the effect of friction on the dissipation of energy and scattering angles in collisions. We examine the propagation of a normal shock formed in a quasi-two dimensional funnel. For shocks propagating without, change in a fluid, one can use the Rankine-Hugoniot approximation to predict the velocity of the shock and the difference in flow values across the shock. We show that inelastic collisions between particles cause the shock to continuously evolve, hence the Rankine-Hugoniot predictions are inadequate for describing the evolution of granular shocks.

Rericha, Erin Colleen

160

Wetting transitions of Ne  

NASA Astrophysics Data System (ADS)

We report studies of the wetting behavior of Ne on very weakly attractive surfaces, carried out with the grand canonical Monte Carlo method. The Ne-Ne interaction was taken to be of Lennard-Jones form, while the Ne-surface interaction was derived from an ab initio calculation of Chizmeshya et al. [J. Low Temp. Phys. 110, 677 (1998)]. Nonwetting behavior was found for Li, Rb, and Cs in the temperature regime explored (i.e., T<42 K). Drying behavior was manifested in a depleted fluid density near the Cs surface. In contrast, for the case of Mg (a more attractive potential) a prewetting transition was found near T=28 K. This temperature was found to shift slightly when a corrugated potential was used instead of a uniform potential. The isotherm shape and the density profiles did not differ qualitatively between these cases.

Bojan, M. J.; Stan, G.; Curtarolo, S.; Steele, W. A.; Cole, M. W.

1999-01-01

161

Reduction of bromate by granular activated carbon  

SciTech Connect

Ozonation of waters containing bromide can lead to the formation of bromate, a probable human carcinogen. Since bromate will be regulated at 10 {micro}g/L by the Stage 1 Disinfectants/Disinfection By-Products Rule, there is considerable interest in finding a suitable method of bromate reduction. Granular activated carbon (GAC) can be used to chemically reduce bromate to bromide, but interference from organic matter and anions present in natural water render this process inefficient. In an effort to improve bromate reduction by GAC, several modifications were made to the GAC filtration process. The use of a biologically active carbon (BAC) filter ahead of a fresh GAC filter with and without preozonation, to remove the biodegradable organic matter, did not substantially improve the bromate removal of the GAC filter. The use of the BAC filter for biological bromate reduction proved to be the most encouraging experiment. By lowering the dissolved oxygen in the influent to the BAC from 8.0 mg/L to 2.0 mg/L, the percent bromate removal increased from 42% to 61%.

Kirisits, M.J.; Snoeyink, V.L.; Kruithof, J.C.

1998-07-01

162

Wet Winding Improves Coil Encapsulation  

NASA Technical Reports Server (NTRS)

Wet-winding process encapsulates electrical coils more uniformily than conventional processes. Process requires no vacuum pump and adapts easily to existing winding machines. Encapsulant applied to each layer of wire as soon as added to coil. Wet-winding process eliminates voids, giving more uniformly encapsulated coil.

Hill, A. J.

1987-01-01

163

Capturing nonlocal effects in 2D granular flows  

NASA Astrophysics Data System (ADS)

There is an industrial need, and a scientific desire, to produce a continuum model that can predict the flow of dense granular matter in an arbitrary geometry. A viscoplastic continuum approach, developed over recent years, has shown some ability to approximate steady flow and stress profiles in multiple inhomogeneous flow environments. However, the model incorrectly represents phenomena observed in the slow, creeping flow regime. As normalized flow-rate decreases, granular stresses are observed to become largely rate-independent and a dominating length-scale emerges in the mechanics. This talk attempts to account for these effects, in the simplified case of 2D, using the notion of nonlocal fluidity, which has proven successful in treating nonlocal effects in emulsions. The idea is to augment the local granular fluidity law with a diffusive second-order term scaled by the particle size, which spreads flowing zones accordingly. Below the yield stress, the local contribution vanishes and the fluidity becomes rate-independent, as we require. We implement the modified law in multiple geometries and validate its flow and stress predictions in multiple geometries compared against discrete particle simulations. In so doing, we demonstrate that the nonlocal relation proposed is satisfied universally in a seemingly geometry-independent fashion.

Kamrin, Ken; Koval, Georg

2013-03-01

164

A review of mesoscale simulations of granular materials  

NASA Astrophysics Data System (ADS)

With the advent of increased computing power, mesoscale simulations have been used to explore grain level phenomenology of dynamic compaction events of various heterogenous systems including foams, reactive materials and porous granular materials. This paper presents an overview of several mesoscale studies on a variety of materials include tungsten carbide and epoxy mixtures, wet and dry sand, and reactive materials (Al-MnO2-Epoxy mixtures). The simulations encompass a variety of geometries including one-dimensional planar and spherical shock configurations. This talk will focus on relating mesoscale modeling to experimental data and the role of material constitutive relations in this effort. In addition, lessons learning during these explorations, modeling techniques, strengths and weaknesses of hydrodynamic mesoscale simulations will also be presented.

Borg, John

2009-06-01

165

76 FR 39896 - Granular Polytetrafluoroethylene Resin From Italy  

Federal Register 2010, 2011, 2012, 2013

...731-TA-385 (Third Review)] Granular Polytetrafluoroethylene Resin From Italy Determination...antidumping duty order on granular polytetrafluoroethylene resin from Italy would be likely...June 2011), entitled Granular Polytetrafluoroethylene Resin from Italy:...

2011-07-07

166

76 FR 4936 - Granular Polytetrafluoroethylene Resin From Italy  

Federal Register 2010, 2011, 2012, 2013

...Granular Polytetrafluoroethylene Resin From Italy AGENCY: United States International Trade...resin (``granular PTFE resin'') from Italy...duty orders on granular PTFE resin from Italy and Japan (75 FR 67082-67083 and...

2011-01-27

167

77 FR 59979 - Pure Magnesium (Granular) From China  

Federal Register 2010, 2011, 2012, 2013

...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:...

2012-10-01

168

Granular Character of Particle Rafts  

NASA Astrophysics Data System (ADS)

We consider a monolayer of particles floating at a horizontal liquid-gas interfacea particle raft. Upon compressing the monolayer in a Langmuir trough, the particles at first pack but ultimately the monolayer buckles out of the plane. We measure the stress profile within the raft at the onset of buckling and show for the first time that such systems exhibit a Janssen effect: the stress decays exponentially away from the compressing barriers over a length scale that depends on the width of the trough. We find quantitative agreement between the rate of decay and the simple theory presented by Janssen and others. This demonstrates that particle rafts have a granular, as well as elastic, character, which is neglected by current models. Finally, we suggest that our experimental setup may be suitable for exploring granular effects in two dimensions without the complications of gravity and basal friction.

Cicuta, Pietro; Vella, Dominic

2009-04-01

169

Energy Cascades in Granular Gases  

NASA Astrophysics Data System (ADS)

A new class of stationary states in granular gases where energy is transfered from large velocity scales to small velocity scales is found. These steady-states exist for arbitrary collision rules and arbitrary dimension. Their signature is a velocity distribution f(v) with an algebraic high-energy tail, f(v)v^-?. The exponent ? is obtained analytically and it varies continuously with the spatial dimension, the homogeneity index characterizing the collision rate, and the restitution coefficient. These stationary states are realized in numerical simulations in which energy is injected into the system by infrequently boosting particles to high velocities. It is proposed that these states may be realized experimentally in driven granular systems.

Ben-Naim, Eli

2005-03-01

170

Toward Rough-Granular Computing  

Microsoft Academic Search

Developing methods for approximation of compound concepts expressing the result of perception belongs to the main challenges\\u000a of Perception Based Computing (PBC) [70]. The perceived concepts are expressed in natural language. We discuss the rough-granular\\u000a approach to approximation of such concepts from sensory data and domain knowledge. This additional knowledge, represented\\u000a by ontology of concepts, is used to make it

Andrzej Jankowski; Andrzej Skowron

2007-01-01

171

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. 

2014-07-09

172

FNA of thyroid granular cell tumor.  

PubMed

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

Harp, Eric; Caraway, Nancy P

2013-09-01

173

Thorsten Poschel, Stefan Luding (Eds.) Granular Gases  

E-print Network

4. The rings around the outer planets of the Solar system have been intensively studied { and continue to do so. In a strict de#12;nition, \\Granular Gases" are dilute granular systems, i.e., many as a many particle system requires comprehensive understanding of the details of collisions of only two

Luding, Stefan

174

Shallow granular flows O. Bokhove1  

E-print Network

will not be required to model these shallow flows. From a macro-scale viewpoint, the dynamics of fast granular flows are then akin to the fluid mechanics of shallow layers of #12;2 water with a free surface. A notable difference1 Shallow granular flows O. Bokhove1 and A.R. Thornton2 1. Department of Applied Mathematics 2

Al Hanbali, Ahmad

175

Unified force law for granular impact cratering  

E-print Network

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

Loss, Daniel

176

Shear viscosity of a model for confined granular media  

NASA Astrophysics Data System (ADS)

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.

Soto, Rodrigo; Risso, Dino; Brito, Ricardo

2014-12-01

177

Dynamics of Sheared Granular Materials  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

178

Theoretical model of granular compaction  

SciTech Connect

Experimental studies show that the density of a vibrated granular material evolves from a low density initial state into a higher density final steady state. The relaxation towards the final density follows an inverse logarithmic law. As the system approaches its final state, a growing number of beads have to be rearranged to enable a local density increase. A free volume argument shows that this number grows as N = {rho}/(1 {minus} {rho}). The time scale associated with such events increases exponentially e{sup {minus}N}, and as a result a logarithmically slow approach to the final state is found {rho} {infinity} {minus}{rho}(t) {approx_equal} 1/lnt.

Ben-Naim, E. [Los Alamos National Lab., NM (United States); Knight, J.B. [Princeton Univ., NJ (United States). Dept. of Physics; Nowak, E.R. [Univ. of Illinois, Urbana, IL (United States). Dept. of Physics]|[Univ. of Chicago, IL (United States). James Franck Inst.; Jaeger, H.M.; Nagel, S.R. [Univ. of Chicago, IL (United States). James Franck Inst.

1997-11-01

179

Tetris Model for Granular Drag  

E-print Network

Motivated by recent experiments on objects moved vertically through a bed a glass beads, a simple model to study granular drag is proposed. The model consists of dimers on a slanted two-dimensional lattice through which objects are dragged very slowly to obtain full relaxation between moves. Such an approach avoids complications due to static friction in more realistic off-lattice models, and provides for fast simulations at large system sizes. The upward motion of objects of various diameters embedded in the lattice is simulated and close resemblance with the experiments is found.

Tomasz M. Kott; Stefan Boettcher

2005-10-16

180

Rheology of confined granular flows  

SciTech Connect

The properties of confined granular flows on a heap are studied through numerical simulations and experiments. We address how such system can be simulated with period boundaries in the flow direction. The packing fraction and velocity profiles are found to be described by one length scale. The dependence of the kinematic properties on the number of grains and on micromechanical parameters (coefficient of restitution and coefficient of friction) is described. Our results show that the friction at the sidewalls gradually decreases and that this decrease can be explained by the intermittent motion of the grains in the quasistatic part of the flow.

Richard, Patrick; Valance, Alexandre; Metayer, Jean-Francois; Crassous, Jerome; Delannay, Renaud [Universite Rennes 1, Institut de Physique de Rennes, UMR CNRS 6251, 263 av. General Leclerc, 35042 Rennes cedex FRANCE (France); Louge, Michel [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 (United States)

2010-05-05

181

Thermoelectric performance of granular semiconductors  

NASA Astrophysics Data System (ADS)

We study the effects of doping and confinement on the thermoelectric properties of nanocrystalline semiconductors. We calculate the thermopower and figure of merit for temperatures less than the charging energy. For weakly coupled semiconducting grains it is shown that the figure of merit is optimized for grain sizes of order 5 nm for typical materials, and that its value can be larger than one. Using the similarities between granular semiconductors and electron or Coulomb glasses allows for a quantitative description of inhomogeneous semiconducting thermoelectrics.

Glatz, Andreas; Beloborodov, I. S.

2009-12-01

182

WHERE THE GRANULAR FLOWS BEND  

SciTech Connect

Based on IMaX/SUNRISE data, we report on a previously undetected phenomenon in solar granulation. We show that in a very narrow region separating granules and intergranular lanes, the spectral line width of the Fe I 5250.2 A line becomes extremely small. We offer an explanation of this observation with the help of magneto-convection simulations. These regions with extremely small line widths correspond to the places where the granular flows bend from upflow in granules to downflow in intergranular lanes. We show that the resolution and image stability achieved by IMaX/SUNRISE are important requisites to detect this interesting phenomenon.

Khomenko, E.; Martinez Pillet, V.; Bonet, J. A. [Instituto de Astrofisica de Canarias, 38205 C/VIa Lactea, s/n, La Laguna, Tenerife (Spain); Solanki, S. K.; Gandorfer, A.; Barthol, P. [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany); Del Toro Iniesta, J. C. [Instituto de Astrofisica de Andalucia (CSIC), Apdo. de Correos 3004, E-18080 Granada (Spain); Domingo, V. [Grupo de AstronomIa y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain); Schmidt, W. [Kiepenheuer-Institut fuer Sonnenphysik, 79104 Freiburg (Germany); Knoelker, M., E-mail: khomenko@iac.e [High Altitude Observatory (NCAR), Boulder, CO 80307-3000 (United States)

2010-11-10

183

Nonlinear Sound during Granular Impact  

E-print Network

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.

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

2014-08-08

184

Extensional Rheology of Granular Staples  

NASA Astrophysics Data System (ADS)

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.

Franklin, Scott

2013-03-01

185

Spectral responses in granular compaction  

NASA Astrophysics Data System (ADS)

I study the compaction of a granular pack under periodic tapping. The magnitude of acceleration ? at each tap is modulated with frequency ? and amplitude ??: ?(t) = ?DC + ??(?t), where t is time measured by the number of taps. From the temporal modulation ?v in packing volume v, frequency- locked to the modulated tapping input, we can define the real and imaginary volume susceptibilities ?v' = (?v/??) ? and ?v'' = (?v/??) ?; here ? is the phase lag between ?(t) and v(t). As a function of ?DC, ?v', ?v'' are peaked at low ?DC, a behavior reminiscent of the temperature-dependent susceptibilities in dielectric and spin glasses. For the packing of small particles (d = 0.5 mm) in ambient pressure, ?v' exhibits memory and rejuvenation effects under ?DC cycling, similar to that seen in the magnetic susceptibility of spin glasses when subjected to thermal cycling [1]. However this memory effect is suppressed for the packing of larger particles and in vacuum. The measurement of volume susceptibilities shows promise as a new way to study the packing of granular materials, and as an avenue to explore analogies between jammed grains and molecular and spin glasses. [3pt] [1] K. Jonason et al., Phys. Rev. Lett. 81, 3243 (1998).

Zou, Ling-Nan

2009-03-01

186

Squeezing wetting and nonwetting liquids  

NASA Astrophysics Data System (ADS)

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.

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

2004-01-01

187

Movers and shakers: Granular damping in microgravity  

E-print Network

The response of an oscillating granular damper to an initial perturbation is studied using experiments performed in microgravity and granular dynamics mulations. High-speed video and image processing techniques are used to extract experimental data. An inelastic hard sphere model is developed to perform simulations and the results are in excellent agreement with the experiments. The granular damper behaves like a frictional damper and a linear decay of the amplitude is bserved. This is true even for the simulation model, where friction forces are absent. A simple expression is developed which predicts the optimal damping conditions for a given amplitude and is independent of the oscillation frequency and particle inelasticities.

Marcus N. Bannerman; Jonathan E. Kollmer; Achim Sack; Michael Heckel; Patric Mueller; Thorsten Poeschel

2010-10-12

188

Continuum description of avalanches in granular media.  

SciTech Connect

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.

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

2000-12-05

189

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

190

European Journal of Mechanics A/Solids 25 (2006) 358369 An elastoplastic framework for granular materials becoming  

E-print Network

of this paper. 2005 Elsevier SAS. All rights reserved. Keywords: Elastoplasticity; Large strains; Granular matter 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.euromechsol.2005.10.002 #12;A. Piccolroaz; accepted 10 October 2005 Available online 22 November 2005 Abstract The two key phenomena occurring

Bigoni, Davide

191

Numerical Simulations of Granular Processes  

NASA Astrophysics Data System (ADS)

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 Commissions 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.

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

2014-11-01

192

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...

193

Properties of wet welded joints  

Microsoft Academic Search

The increasing interest taken by the international diving industry in wet welding plays an important part in determining research activities to improve the process and consumables for offshore applications, particularly for higher strength steels at greater water depths. On the basis of an investigation comparing the properties of existing electrodes for underwater applications, specially modified electrodes have been tested by

P. Szelagowski; H. Stuhff; H. G. Schafstall; J. Blight; I. Pachniuk

1993-01-01

194

Surface wave acoustics of granular packing under gravity  

SciTech Connect

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.

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

195

Surface wave acoustics of granular packing under gravity  

NASA Astrophysics Data System (ADS)

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.

Clement, Eric; Bonneau, Lenaic; Andreotti, Bruno

2009-06-01

196

Granular Matter 3, 5761 c Springer-Verlag 2001 Glassy models for granular systems  

E-print Network

.sellitto@enslapp.ens-lyon.fr Work partially supported by the brazilian agency CNPq. to wander through the many microscopic, indeed behave in a similar fashion. For the gran- ulars, the increase in the bulk density as the system

Arenzon, Jeferson J.

197

Deformation patterns in granular materials  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

198

Stability of Granular Materials under Vertical Vibrations  

E-print Network

The influence of periodic vibrations on the granular flow of materials is of great interests to scientists and engineers due to both theoretical and practical reasons. In this paper, the stability of a vertically vibrated ...

Deng, Rensheng

199

Oculomotor disturbances due to granular cell tumor.  

PubMed

Primary granular cell tumor of the orbit is a rare type of neoplasm. The tumor is frequently associated with extraocular muscles, and eye motility limitation is an unavoidable complication after its surgical removal. The objective of the present article is to review the literature on primary granular cell tumors of the orbit and to report a case of this uncommon neoplasia. Granular cell tumor is a benign lesion encountered in most cases (58.3%) in the inferior aspect of the orbit. Extraocular muscle involvement occurs in 72.2% of the patients, and diplopia is present in 77.1% of the cases. The inferior and medial recti are the most affected muscles (38.5% and 26.9%, respectively). Surgical excision is the only modality of treatment, but diplopia persists in 73.3% of the cases. In conclusion, granular cell tumor is a benign lesion but involves a high rate of extraocular muscle morbidity. PMID:21464781

Ribeiro, Sara F T; Chahud, Fernando; Cruz, Antonio A V

2012-01-01

200

Numerical-linguistic knowledge discovery using granular neural networks  

NASA Astrophysics Data System (ADS)

In this paper, a granular-neural-network-based Knowledge Discovery and Data Mining (KDDM) method based on granular computing, neural computing, fuzzy computing, linguistic computing and pattern recognition is presented. The major issues include (1) how to use neural networks to discover granular knowledge from numerical-linguistic databases, and (2) how to use discovered granular knowledge to predict missing data. A Granular Neural Network (GNN) is designed to deal with numerical-linguistic data fusion and granular knowledge discovery in numerical-linguistic databases. From a data granulation point of view, the GNN can process granular data in a database. From a data fusion point of view, the GNN makes decisions based on different kinds of granular data. From a KDDM point of view, the GNN is able to learn internal granular relations between numerical-linguistic inputs and outputs, and predict new relations in a database.

Zhang, Yanqing

2000-04-01

201

Endobronchial granular cell tumor: a case report  

PubMed Central

Granular cell tumors (GCTs) are benign neoplasms that are most commonly found in the head and neck region. We present a case of endobronchial granular cell tumor presenting as hemoptysis in a 22-year-old African American female. Patient subsequently underwent a right upper and middle lobectomy, and upon histologic analysis was found to have GCT with borders impinging upon cartilage and adjacent peribronchial lymph nodes. PMID:22470750

Meyer, Monique Anne; Becker, Joseph M.; Quinones, William

2010-01-01

202

Medications to Treat Bed-Wetting  

MedlinePLUS

... Us You are here Home Medications to Treat Bed-wetting: Desmopressin Acetate (DDAVP) Imipramine Anticholinergics Summary Desmopressin ... DDAVP is a drug to treat children with bed-wetting. Although DDAVP does not cure the condition, ...

203

7 CFR 51.491 - Wet slip.  

Code of Federal Regulations, 2011 CFR

...Wet slip means a condition present at time of packing in which the stem scar is abnormally large, excessively wet and slippery, yields...frequently accompanied by fresh radial growth cracks at the edge of the stem...

2011-01-01

204

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

E-print Network

formation of shear band, inherent inhomogeneous nature of the material, velocity fluctuations etc. Phosphorescent paint can be used to measure shear band thickness at the lateral surface of the cup at different rotation speeds. The cup should be made...

Kannan, Raguraman

2012-06-07

205

Free-volume kinetic models of granular matter Mauro Sellitto  

E-print Network

by means of simple models of fragile-glass-forming liquid Kob and Andersen, Phys. Rev. E 48, 4364 1993 and segregation phenomena can be reproduced within a simple microscopic model of fragile-glass-forming liquid 9 at the mesoscopic level. The model we consider was introduced by Kob and Andersen as a lattice-gas model of fragile

Arenzon, Jeferson J.

206

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

E-print Network

'' are an important part of a commercial detergent: they are based on inorganic particles such as calcium carbonate, or prilling (prilling is based on a molten thread of material, which breaks into droplets via the Ray- leigh

Weeks, Eric R.

207

Characterizing shear-flow-driven erosion of granular beds  

NASA Astrophysics Data System (ADS)

The complex interactions between granular media and flowing fluid play a principal role in shaping landscapes via erosion. Despite a large body of work in granular materials and large scale topographical changes in granular beds due to fluid flow, the detailed physical mechanisms that underlie particle entrainment into a fluid flow from an erodible bed and the coupling between hydrodynamic shear and internal rearrangement remain poorly understood. To address these questions, we perform experimental studies of pulsed shear flow across granular beds. We characterize the fluid flow using particle tracking techniques and monitor changes in the structural properties of the granular packing and contour of the granular bed.

Salevan, Julia; Shattuck, Mark; O'Hern, Corey; Ouellette, Nicholas

2013-03-01

208

Constraining Mercury Oxidation Using Wet Deposition  

E-print Network

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

Selin, Noelle Eckley

209

Physicochemical properties of granular and non-granular cationic starches prepared under ultra high pressure.  

PubMed

Granular and non-granular cationic starches were prepared through the reaction of tapioca and corn starches with 2,3-epoxypropyl trimethyl ammonium chloride (ETMAC) using conventional and ultra high pressure (UHP)-assisted reactions. The cationic starches were characterized with respect to morphology, degree of substitution (DS), FT-IR, (13)C NMR, X-ray diffraction pattern, solubility and swelling power, pasting viscosity, and flocculating activity. Non-granular (relative to granular) cationic starches possessed higher DS values. While DS values of non-granular cationic starches were lower for UHP-assisted (relative to conventional) reaction, granular cationic starches did not differ for both reactions. For flocculation activity, granular cationic starches with lower solubility and higher swelling power were higher than non-granular counterparts with reversed patterns in solubility and swelling power, regardless of conventional and UHP-assisted reactions. Overall results suggested that flocculation activity of cationic starches may be directly associated with their swelling powers (relative to DS values). PMID:24274522

Chang, Yoon-Je; Choi, Hyun-Wook; Kim, Hyun-Seok; Lee, Hyungjae; Kim, Wooki; Kim, Dae-Ok; Kim, Byung-Yong; Baik, Moo-Yeol

2014-01-01

210

Water Movement in Wet Snow  

Microsoft Academic Search

The three phases of water co-exist at the triple-point temperature which is very close to 273.1 K. Wet snow packs are therefore nearly isothermal. Weak temperature gradients result from the dependence of the triple-point on grain size and capillary pressure and these need to be considered if metamorphism of the snow pack is modelled. The bulk energy balance determines the

J. M. N. T. Gray

1996-01-01

211

Discrete Element Modeling of Complex Granular Flows  

NASA Astrophysics Data System (ADS)

Granular materials occur almost everywhere in nature, and are actively studied in many fields of research, from food industry to planetary science. One approach to the study of granular media, the continuum approach, attempts to find a constitutive law that determines the material's flow, or strain, under applied stress. The main difficulty with this approach is that granular systems exhibit different behavior under different conditions, behaving at times as an elastic solid (e.g. pile of sand), at times as a viscous fluid (e.g. when poured), or even as a gas (e.g. when shaken). Even if all these physics are accounted for, numerical implementation is made difficult by the wide and often discontinuous ranges in continuum density and sound speed. A different approach is Discrete Element Modeling (DEM). Here the goal is to directly model every grain in the system as a rigid body subject to various body and surface forces. The advantage of this method is that it treats all of the above regimes in the same way, and can easily deal with a system moving back and forth between regimes. But as a granular system typically contains a multitude of individual grains, the direct integration of the system can be very computationally expensive. For this reason most DEM codes are limited to spherical grains of uniform size. However, spherical grains often cannot replicate the behavior of real world granular systems. A simple pile of spherical grains, for example, relies on static friction alone to keep its shape, while in reality a pile of irregular grains can maintain a much steeper angle by interlocking force chains. In the present study we employ a commercial DEM, nVidia's PhysX Engine, originally designed for the game and animation industry, to simulate complex granular flows with irregular, non-spherical grains. This engine runs as a multi threaded process and can be GPU accelerated. We demonstrate the code's ability to physically model granular materials in the three regimes mentioned above: (1) a static and steep granular pile; (2) granular flow with a complex velocity field; and (3) an agitated granular pile resulting in size based segregation. We compare our simulations to laboratory experiments in the first and third regimes, and to a known empirical constitutive law (Jop et al. 2006) in the second. We discuss application of this code in studies of several planetary systems, including analysis of the tensile strength of comets from evidence of tidal disruption, and bulking and banding on rubble-pile asteroids, as an indication of their seismic history.

Movshovitz, N.; Asphaug, E. I.

2010-12-01

212

Probability analysis of contact forces in quasi-solid-liquid phase transition of granular shear flow  

NASA Astrophysics Data System (ADS)

The quasi-solid-liquid phase transition exists widely in different fields, and attracts more attention due to its instinctive mechanism. The structure of force chains is an important factor to describe the phase transition properties. In this study, the discrete element model (DEM) is adopted to simulate a simple granular shear flow with period boundary condition on micro scale. The quasi-solid-liquid phase transition is obtained under various volume fractions and shear rates. Based on the DEM results, the probability distribution functions of the inter-particle contact force are obtained in different shear flow phases. The normal, tangential and total contact forces have the same distributions. The distribution can be fitted as the exponential function for the liquid-like phase, and as the Weibull function for the solid-like phase. To describe the progressive evolution of the force distribution in phase transition, we use the Weibull function and Corwin-Ngan function, respectively. Both of them can determine the probability distributions in different phases and the Weibull function shows more reasonable results. Finally, the force distributions are discussed to explain the characteristics of the force chain in the phase transition of granular shear flow. The distribution of the contact force is an indicator to determine the flow phase of granular materials. With the discussions on the statistical properties of the force chain, the phase transition of granular matter can be well understood.

Ji, ShunYing

2013-02-01

213

Granular friction in a wide range of shear rates  

NASA Astrophysics Data System (ADS)

We conduct an experiment on the frictional properties of granular matter over a wide range of shear rate that covers both the quasistatic and the inertial regimes. We show that the friction coefficient exhibits negative shear-rate dependence in the quasistatic regime, whereas the shear-rate dependence is positive in the inertial regime. The crossover shear rate is determined in terms of the competition between two physical processes, namely frictional healing and anelasticity. We confirm that these results are independent of the grain shape by using angular sand and spherical beads. We also show that the behavior in the inertial regime is quantitatively the same as that in numerical simulations. As an application, we derive the exponential velocity profiles that are often observed in the quasistatic heap flow.

Kuwano, Osamu; Ando, Ryosuke; Hatano, Takahiro

2013-06-01

214

Persistence of force networks in compressed granular media.  

PubMed

We utilize the tools of persistent homology to analyze features of force networks in dense granular matter, modeled as a collection of circular, inelastic frictional particles. The proposed approach describes these networks in a precise and tractable manner, allowing us to identify features that are difficult or impossible to characterize by other means. In contrast to other techniques that consider each force threshold level separately, persistent homology allows us to consider all threshold levels at once to describe the force network in a complete and insightful manner. We consider continuously compressed system of particles characterized by varied polydispersity and friction in two spatial dimensions. We find significant differences between the force networks in these systems, suggesting that their mechanical response may differ considerably as well. PMID:23679407

Kramar, M; Goullet, A; Kondic, L; Mischaikow, K

2013-04-01

215

Tap density equations of granular powders based on the rate process theory and the free volume concept.  

PubMed

The tap density of a granular powder is often linked to the flowability via the 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 the literature: the inverse logarithmic and the stretched exponential. Using the rate process theory and the free volume concept under the assumption that particles will obey similar thermodynamic laws during the tapping process if the "granular temperature" is defined in a different way, we obtain the tap density equations, and they are 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 environmental temperature are grouped into this parameter that weighs the pace of the 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). PMID:25589375

Hao, Tian

2015-02-11

216

Granular acoustics of polyhedral particles  

NASA Astrophysics Data System (ADS)

Our previous time-of-flight studies with two-dimensional polygonal simulations and one-and three-dimensional experiments showed that the sound-velocity in granular materials in one and two dimensions is of the order of 10% of that of the bulk material, while in three dimensions with spherical beads, it is only of the order of one percent. The conclusion was that the force network in three dimensions leads to a reduction of the sound velocity compared to two dimensions. With our newly completed fully three dimensional discrete element method with polyhedral particles, we investigate the relation between particle shape, size dispersion and sound velocity. The force-law is able to reproduce the sound velocity of the bulk material for space-filling particle packings. We find that the sound velocities in polyhedral assemblies are about 3% to 5% of the bulk sound velocities. This means that the influence of the particle geometry on the contact is significant. Aggregates with particles with many surfaces show higher sound velocities than those with sharp edges. Additionally, solitonic waves were observed which propagated in front of the sound-waves, but only in a relatively short range.

Cheng, Wei Shen; Chen, Jian; Matuttis, Hans-Georg

2013-06-01

217

Survival in granular cell astrocytomas.  

PubMed

Background?Granular cell astrocytomas (GCAs) are rarely encountered aggressive glial neoplasms. Treatment options comprise surgery, radiotherapy, and chemotherapy. Due to the small number of cases, a standard therapeutic regimen for GCA does not exist. Material and Methods?We report on the case of a 64-year-old woman with GCA subjected to tumor biopsy followed by radiochemotherapy with temozolomide. We provide clinical, histopathologic, and magnetic resonance imaging findings as well as a complete follow-up. To assess the relation of age, gender, time of publication, and different treatment options with survival we performed log-rank tests and calculated Cox regression models and hazard ratios in data from all available reports on GCA. Results?A significant difference in survival rates in favor of adjuvant therapy (radiotherapy or radiochemotherapy) at 12 months was found. Age?>?70 years at the time of diagnosis had a significantly unfavorable impact on survival at 12 months. Although not statistically significant, a tendency toward higher probability of survival at 12 months was found in cases reported after 2002. In surgically treated patients, we could not find a significant impact of extent of resection on survival. A significant impact of gender on survival was not found. Conclusion?Adjuvant therapy is significantly related to a higher probability of survival at 12 months and may therefore be recommended for patients with a GCA. Further analysis of these rare neoplasms is warranted. PMID:25072317

Voellger, Benjamin; Tapia-Perez, Jorge Humberto; Rupa, Rosita; Karagiannis, Dimitrios; Mawrin, Christian; Kirches, Elmar; Schneider, Thomas

2015-01-01

218

Aerobic granular sludge: recent advances.  

PubMed

Aerobic granulation, a novel environmental biotechnological process, was increasingly drawing interest of researchers engaging in work in the area of biological wastewater treatment. Developed about one decade ago, it was exciting research work that explored beyond the limits of aerobic wastewater treatment such as treatment of high strength organic wastewaters, bioremediation of toxic aromatic pollutants including phenol, toluene, pyridine and textile dyes, removal of nitrogen, phosphate, sulphate and nuclear waste and adsorption of heavy metals. Despite this intensive research the mechanisms responsible for aerobic granulation and the strategy to expedite the formation of granular sludge, and effects of different operational and environmental factors have not yet been clearly described. This paper provides an up-to-date review on recent research development in aerobic biogranulation technology and applications in treating toxic industrial and municipal wastewaters. Factors affecting granulation, granule characterization, granulation hypotheses, effects of different operational parameters on aerobic granulation, response of aerobic granules to different environmental conditions, their applications in bioremediations, and possible future trends were delineated. The review attempts to shed light on the fundamental understanding in aerobic granulation by newly employed confocal laser scanning microscopic techniques and microscopic observations of granules. PMID:18573633

Adav, Sunil S; Lee, Duu-Jong; Show, Kuan-Yeow; Tay, Joo-Hwa

2008-01-01

219

Mechanics of Granular Materials (MGM)  

NASA Technical Reports Server (NTRS)

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).

2000-01-01

220

Continuum Modeling of Secondary Rheology in Dense Granular Materials  

E-print Network

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 ...

Henann, David L.

221

76 FR 8774 - Granular Polytetrafluoroethylene Resin From Japan  

Federal Register 2010, 2011, 2012, 2013

...731-TA-386 (Third Review)] Granular Polytetrafluoroethylene Resin From Japan AGENCY: United States International...of the antidumping duty order on granular polytetrafluoroethylene resin from Japan would be likely to...

2011-02-15

222

Psychological Resilience and Positive Emotional Granularity: Examining the  

E-print Network

Psychological Resilience and Positive Emotional Granularity: Examining the Benefits of Positive that ex- amine such traits (psychological resilience and positive emotional granularity) and demonstrate be instantiated in Michele M. Tugade, Department of Psychology, Vassar College; Barbara L. Fred- rickson

Barrett, Lisa Feldman

223

Energy Conservation for Granular Coal Injection into a Blast Furnace  

NASA Astrophysics Data System (ADS)

Due to the lack of knowledge regarding the combustion of granular coal injected into a blast furnace, injection characteristics of granular coal were first studied through proximate analysis, element analysis, and research of explosivity, ignition point, meltability of ash, grindability, calorific value, etc. Using a sampling device in the raceway combined with petrographic analysis, during the combustion process of granular coal with high crystal water and volatile in raceway, cracks and bursts were found, leading to a reduction of particle size. Based on a model of mass control and dynamic theory of particle combustion, the transition dynamic model for cracking in combustion of granular coal was found, and the critical value of cracking ratio (?P) for granular coal combustion in the raceway was calculated. Finally, the utilization ratio and energy efficiency of granular coal used in the blast furnace were discussed, offering theoretical foundation and technical support for intensifying granular coal combustion and promoting granular coal injection.

Guo, Hongwei; Su, Buxin; Zhang, Jianliang; Shao, Jiugang; Zuo, Haibin; Ren, Shan

2012-08-01

224

Jamming and Fluidization in Granular Flows  

NASA Astrophysics Data System (ADS)

Granular materials exist all around us, from avalanches in nature to the mixing of pharmaceuticals, yet the behavior of these ``fluids'' is poorly understood. While the interaction of individual particles is simply through friction and inelastic collisions, the non-linear forces and large number of particles leads to an unpredictable, complex system. Flow can be characterized by the continuous forming and breaking of a strong force network resisting flow, leading to jamming, avalanching and shear banding. I'll present recent work on quasi-static shear and free-surface granular flows under the influence of external vibrations as well as related experiments on particle-fluid suspensions. By using photoelastic grains, we are able to measure both particle trajectories and the local force network in 2D flows. We find through particle tracking that dense granular flow is composed of comparable contributions from the mean flow, elastic deformations, and permanent, plastic deformations. Vibration typically weakens granular materials and removes hysteresis, though small vibrations can lead to strengthening of a pile. Flows of particle-fluid suspensions allow another avenue to probe failure of granular piles and additional control parameters, such as the surface chemistry of the particles.

Utter, Brian

2011-10-01

225

Granular Materials and Risks In ISRU  

NASA Technical Reports Server (NTRS)

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.

Behringer, Robert P.; Wilkinson, R. Allen

2004-01-01

226

Granular Materials and Risks in ISRU  

NASA Technical Reports Server (NTRS)

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.

Behringer, Robert P.; Wilki8nson, R. Allen

2004-01-01

227

Mold management of wetted carpet.  

PubMed

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

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

2014-01-01

228

Wetting of flexible fibre arrays.  

PubMed

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

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

2012-02-23

229

Coal combustion by wet oxidation  

SciTech Connect

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.

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

1980-11-15

230

From liquid to solid bonding in cohesive granular media  

E-print Network

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.

Jean-Yves Delenne; Fabien Souli; Moulay Sad El Youssoufi; Farhang Radja

2010-02-26

231

Wetting dynamics of multiscaled structures  

NASA Astrophysics Data System (ADS)

Priming dynamics is one of the critical parameters in designing a capillary-driven thermal management system. We report both an experimental and simulation study of hierarchical structures with silicon pillars and silicon nanowires on the pillar surface. Liquid front velocity covered and uncovered was characterized using capillary wetting experiments and validated by numerical simulation and theoretical prediction. The water under cover moves one order of magnitude faster than the water in the uncovered case. The experimental results and the prediction are in good agreement for flow regimes in both the covered and the uncovered regions.

Chen, Hsiu-Hung; Shi, Junxiang; Chen, Chung-Lung

2013-10-01

232

Wet coastal plain tundra III  

SciTech Connect

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).

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

1980-01-01

233

Frictional effects on pressure in a column of granular material  

NASA Astrophysics Data System (ADS)

Frictional effects in granular materials are not well understood. In Janssen's original paper he ignored internal friction completely. More recent theories that treat the granular materials as a continuum assume a slip condition for the internal friction. We report on measurements of the pressure at the bottom a column of granular material for several different frictional coefficients.

Back, Randy

2010-03-01

234

Fluoride removal from water by granular ceramic adsorption  

Microsoft Academic Search

A new medium, granular ceramic, has been developed for fluoride removal from water. Granular ceramic is a solid-phase medium that produces a stable AlFe surface complex for fluoride adsorption. BET, SEM, and EDS were used to characterize the physical attributes (particle size, pore size and distribution, surface roughness) of the granular ceramic. Fluoride adsorption characteristics were studied in a batch

Nan Chen; Zhenya Zhang; Chuanping Feng; Norio Sugiura; Miao Li; Rongzhi Chen

2010-01-01

235

Image Superresolution Reconstruction via Granular Computing Clustering  

PubMed Central

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

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

2014-01-01

236

Local stresses in the Janssen granular column  

NASA Astrophysics Data System (ADS)

We study experimentally the distribution of local stresses in a granular material confined inside a vertical cylinder. We use an image correlation technique to measure the displacement field of the container induced by the forces exerted by the grains on the inner wall. We describe an optimization procedure based on the linear theory of elastic shells to deduce the distribution of these forces from the measured displacement field. They correspond to the stress field of the granular material close to the container's inner wall. We first confirm the validity of Janssen's description for various experiments, including the influence of the bead diameter and the effect of an additional mass on top of the granular column. We then apply this method to determine the stress field during the gravity-driven discharge of a silo through an aperture.

Cambau, Thomas; Hure, Jrmy; Marthelot, Jol

2013-08-01

237

Mesoscopic approach to granular crystal dynamics.  

PubMed

We present a mesoscopic approach to granular crystal dynamics, which comprises a three-dimensional finite-element model and a one-dimensional regularized contact model. The approach investigates the role of vibrational-energy trapping effects in the dynamic behavior of one-dimensional chains of particles in contact (i.e., granular crystals), under small to moderate impact velocities. The only inputs of the models are the geometry and the elastic material properties of the individual particles that form the system. We present detailed verification results and validate the model comparing its predictions with experimental data. This approach provides a physically sound, first-principles description of dissipative losses in granular systems. PMID:22400692

Gonzalez, Marcial; Yang, Jinkyu; Daraio, Chiara; Ortiz, Michael

2012-01-01

238

Superstable Granular Heap in a Thin Channel  

NASA Astrophysics Data System (ADS)

We observed experimentally a new regime for granular flows in an inclined channel with a flow-rate-controlled system. For high flow rates, the flow occurs atop a static granular heap whose angle is considerably higher than those usually exhibited by granular heaps. The properties of such superstable heaps (SSH) are drastically affected by a change in the channel width W. This indicates that the unusual stability of these heaps can be accounted for by the flowing layer and its friction on the sidewalls. A simple depth-averaged model, assuming Coulomb friction, shows that the SSH angle scales as h/W (W being the channel width), and that grain size plays no part.

Taberlet, Nicolas; Richard, Patrick; Valance, Alexandre; Losert, Wolfgang; Pasini, Jos Miguel; Jenkins, James T.; Delannay, Renaud

2003-12-01

239

Case for diagnosis. Granular cell tumor.  

PubMed

Granular cell tumor is a rare benign neoplasm of neural origin. We report the case of a female patient, 27 years old presenting a brown-red nodule in the right arm, which pathological examination showed to be formed by polygonal cells with eosinophilic granular cytoplasm and immunohistochemistry positive for S100 protein and CD68. Granular cell tumor is usually solitary and in half the cases located in the head and neck areas, 30% of these in the tongue. It is most frequent between the third and fifth decades of life in women and people of African-American ethnicity. Its origination is controversial, including the possible origins in muscle, fibroblasts, neural crest, neural sheath or histiocytes. The positivity for S-100 and CD68 suggest the neural origin. PMID:24474119

Lage, Thaiane Lima; Miranda, Mario Fernando Ribeiro de; Bittencourt, Maraya de Jesus Semblano; Dias, Carolina Moraes; Parijs, Amanda Magno de; Raiol, Theisla Kely Azevedo

2013-01-01

240

Proportional Paths, Barodesy, and Granular Solid Hydrodynamics  

E-print Network

Propotional paths as summed up by the Goldscheider Rule (GR) -- stating that given a constant strain rate, the evolution of the stress maintains the ratios of its components -- is a characteristics of elasto-plastic motion in granular media. Barodesy, a constitutive relation proposed recently by Kolymbas, is a model that, with GR as input, successfully accounts for data from soil mechanical experiments. Granular solid hydrodynamics (GSH), a theory derived from general principles of physics and two assumptions about the basic behavior of granular media, is constructed to qualitatively account for a wide range of observation -- from elastic waves over elasto-plastic motion to rapid dense flow. In this paper, showing the close resemblance of results from Barodesy and GSH, we further validate GSH and provide an understanding for GR.

Yimin Jiang; Mario Liu

2012-12-16

241

Statistical mechanics of dry granular materials: Between fragile solid (jamming) and dry fluid (rheology)  

NASA Astrophysics Data System (ADS)

Dry granular matter, with infinite tangential friction, is modeled as a connected graph of grains linked by purely repulsive contacts. The degrees of freedom of a grain are non-slip rotation on, and disconnection from another. The material stability under shear (jamming) is ensured by odd circuits of grains in contact that prevent the grains from rolling on each other. A dense hard granular material has two possible states: fragile solid, blocked by odd circuits, and dry fluid or bearing, in the absence of odd circuits, that flows under shear by creation and glide of a pair of dislocations as in plasticity of continuous media. We did introduce the notions of blob, a region of the material containing only even circuits, and of critical contact that closes an odd circuit. The granular material is then represented, at low energies and critical applied shear, as a chain of blobs connected by critical contacts. The entropy is the logarithm of the number of spanning trees constrained to go through critical links. For a vanishing tangential friction, the graph description with the frustrating odd circuits is still valid, because the force between grains remains a scalar and repulsive. A granular material inside a cylindrical drum rotating at constant velocity around its horizontal axis alternates intermittently between solid and fluid states. As a fragile solid, it follows a limit cycle of avalanches (slip) and stuck rotations with the drum. This is the stick-slip behavior of a solid subjected to solid friction (to the driving drum) and gravity. In the fluid state, the friction is viscous and the granular material flows to a fixed point with constant slope.

Rivier, Nicolas; Fortin, Jean-Yves

2013-06-01

242

Elucidating the mysteries of wetting.  

SciTech Connect

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.

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

243

Dynamic wetting of Boger fluids.  

PubMed

The impact of fluid elasticity on the dynamic wetting of polymer solutions is important because many polymer solutions in technological use exhibit non-Newtonian behaviors in the high shear environment of the wedge-like flow near a moving contact line. Our former study [G.K. Seevaratnam, Y. Suo, E. Ram, L.M. Walker, Phys. Fluids 19 (2007) Art. No. 012103] showed that shear thinning induced by a semi-flexible high molecular weight polymer reduces the viscous bending near a moving contact line as compared to a Newtonian fluid having the same zero-shear viscosity. This results in a dramatic reduction of the dependence of the effective dynamic contact angle on contact line speed. In this paper, we discuss dynamic wetting of Boger fluids which exhibit elasticity-dominated rheology with minimal shear thinning. These fluids are prepared by dissolving a dilute concentration of high molecular weight polymer in a "solvent" of the oligomer of the polymer. We demonstrate that elasticity in these fluids increases curvature near the contact line but that the enhancement arises mostly from the weakly non-Newtonian behavior already present in the oligomeric solvent. We present evidence of instabilities on the liquid/vapor interface near the moving contact line. PMID:17499759

Wei, Y; Seevaratnam, G K; Garoff, S; Ram, E; Walker, L M

2007-09-01

244

Particle Scale Dynamics in Granular Impact  

NASA Astrophysics Data System (ADS)

We perform an experimental study of granular impact, where intruders strike 2D beds of photoelastic disks from above. High-speed video captures the intruder dynamics and the local granular force response, allowing investigation of grain-scale mechanisms in this process. We observe rich acoustic behavior at the leading edge of the intruder, strongly fluctuating in space and time, and we show that this acoustic activity controls the intruder deceleration, including large force fluctuations at short time scales. The average intruder dynamics match previous studies using empirical force laws, suggesting a new microscopic picture, where acoustic energy is carried away and dissipated.

Clark, Abram H.; Kondic, Lou; Behringer, Robert P.

2012-12-01

245

Particle Scale Dynamics in Granular Impact  

E-print Network

We perform an experimental study of granular impact, where intruders strike 2D beds of photoelastic disks from above. High-speed video captures the intruder dynamics and the local granular force response, allowing investigation of grain-scale mechanisms in this process. We observe rich acoustic behavior at the leading edge of the intruder, strongly fluctuating in space and time, and we show that this acoustic activity controls the intruder deceleration, including large force fluctuations at short time scales. The average intruder dynamics match previous studies using empirical force laws, suggesting a new microscopic picture, where acoustic energy is carried away and dissipated.

Abram. H. Clark; Lou Kondic; Robert P. Behringer

2012-08-28

246

Granular Impact Dynamics: Acoustics and Fluctuations  

E-print Network

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.

Abram H. Clark; R. P. Behringer

2012-10-12

247

Angularly anisotropic correlation in granular packings  

NASA Astrophysics Data System (ADS)

We present an x-ray microtomography study of the three-dimensional structural correlations in monodisperse granular packings. By measuring an orientation-dependent pair correlation function, we find that the local structure shows an angularly anisotropic orientation correlation. The correlation is strongest along the major axis of the local Minkowski tensor of the Voronoi cell. It turns out that this anisotropic correlation is consistent with the existence of some locally favored structures. The study suggests the importance of high-order structural correlations in random granular packings.

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

2014-12-01

248

Internal Avalanches in a Granular Medium  

E-print Network

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.

S. S. Manna; D. V. Khakhar

1998-08-04

249

Spatially modulated kinks in shallow granular layers.  

PubMed

We report on the experimental observation of spatially modulated kinks in a shallow one-dimensional fluidized granular layer subjected to a periodic air flow. We show the appearance of these solutions as the layer undergoes a parametric instability. Due to the inherent fluctuations of the granular layer, the kink profile exhibits an effective wavelength, a precursor, which modulates spatially the homogeneous states and drastically modifies the kink dynamics. We characterize the average and fluctuating properties of this solution. Finally, we show that the temporal evolution of these kinks is dominated by a hopping dynamics, related directly to the underlying spatial structure. PMID:24032762

Macas, J E; Clerc, M G; Falcn, C; Garca-ustes, M A

2013-08-01

250

Axisymmetric granular collapse: a transient 3D flow test of viscoplasticity.  

PubMed

A viscoplastic continuum theory has recently been proposed to model dense, cohesionless granular flows [P. Jop, Nature (London) 441, 727 (2006)10.1038/nature04801]. We confront this theory for the first time with a transient, three-dimensional flow situation--the simple collapse of a cylinder of granular matter onto a horizontal plane--by extracting stress and strain rate tensors directly from soft particle simulations. These simulations faithfully reproduce the different flow regimes and capture the observed scaling laws for the final deposit. Remarkably, the theoretical hypothesis that there is a simple stress-strain rate tensorial relationship does seem to hold across the whole flow even close to the rough boundary provided the flow is dense enough. These encouraging results suggest viscoplastic theory is more generally applicable to transient, multidirectional, dense flows and open the way for quantitative predictions in real applications. PMID:19392169

Lacaze, Laurent; Kerswell, Rich R

2009-03-13

251

Project WET (Water Education for Teachers)  

NSDL National Science Digital Library

Project WET (Water Education for Teachers) is an international, interdisciplinary, water education program for formal and informal educators of students ages 5 to 18. This project site provides opportunities to order high quality educational material, samples of Project WET activities, information on Make a Splash Festivals, education standards, information on events, Project Wet reports and water related links. There is also a link to all of the state coordinators for this project.

252

Carbon nanotube fiber spun from wetted ribbon  

SciTech Connect

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.

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

2014-04-29

253

Directional wetting in anisotropic inverse opals.  

PubMed

Porous materials display interesting transport phenomena due to restricted motion of fluids within the nano- to microscale voids. Here, we investigate how liquid wetting in highly ordered inverse opals is affected by anisotropy in pore geometry. We compare samples with different degrees of pore asphericity and find different wetting patterns depending on the pore shape. Highly anisotropic structures are infiltrated more easily than their isotropic counterparts. Further, the wetting of anisotropic inverse opals is directional, with liquids filling from the side more easily. This effect is supported by percolation simulations as well as direct observations of wetting using time-resolved optical microscopy. PMID:24941308

Phillips, Katherine R; Vogel, Nicolas; Burgess, Ian B; Perry, Carole C; Aizenberg, Joanna

2014-07-01

254

Scaling of convective velocity in a vertically vibrated granular bed  

E-print Network

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 $v \\propto g^{0.97}$ when the normalized vibrational acceleration is fixed.

Tomoya M. Yamada; Hiroaki Katsuragi

2014-04-01

255

Scaling of convective velocity in a vertically vibrated granular bed  

NASA Astrophysics Data System (ADS)

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.

Yamada, Tomoya M.; Katsuragi, Hiroaki

2014-10-01

256

The Wet-Dog Shake  

E-print Network

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.

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

2010-01-01

257

Externally Wetted Ionic Liquid Thruster  

NASA Astrophysics Data System (ADS)

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.

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

2004-10-01

258

Stochastic flow rule for granular materials  

NASA Astrophysics Data System (ADS)

There have been many attempts to derive continuum models for dense granular flow, but a general theory is still lacking. Here, we start with Mohr-Coulomb plasticity for quasi-two-dimensional granular materials to calculate (average) stresses and slip planes, but we propose a stochastic flow rule (SFR) to replace the principle of coaxiality in classical plasticity. The SFR takes into account two crucial features of granular materialsdiscreteness and randomnessvia diffusing spots of local fluidization, which act as carriers of plasticity. We postulate that spots perform random walks biased along slip lines with a drift direction determined by the stress imbalance upon a local switch from static to dynamic friction. In the continuum limit (based on a Fokker-Planck equation for the spot concentration), this simple model is able to predict a variety of granular flow profiles in flat-bottom silos, annular Couette cells, flowing heaps, and plate-dragging experimentswith essentially no fitting parametersalthough it is only expected to function where material is at incipient failure and slip lines are inadmissible. For special cases of admissible slip lines, such as plate dragging under a heavy load or flow down an inclined plane, we postulate a transition to rate-dependent Bagnold rheology, where flow occurs by sliding shear planes. With different yield criteria, the SFR provides a general framework for multiscale modeling of plasticity in amorphous materials, cycling between continuum limit-state stress calculations, mesoscale spot random walks, and microscopic particle relaxation.

Kamrin, Ken; Bazant, Martin Z.

2007-04-01

259

Optimal design of composite granular protectors  

Microsoft Academic Search

We employ an evolutionary algorithm to investigate the optimal design of composite protectors using one-dimensional granular chains composed of beads of various sizes, masses, and stiffnesses. We define a fitness function using the maximum force transmitted from the protector to a \\

Fernando Fraternali; Mason A. Porter; Chiara Daraio

2008-01-01

260

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...

261

Memory effects in vibrated granular systems  

E-print Network

Granular materials present memory effects when submitted to tapping processes. These effects have been observed experimentally and are discussed here in the context of a general kind of model systems for compaction formulated at a mesoscopic level. The theoretical predictions qualitatively agree with the experimental results. As an example, a particular simple model is used for detailed calculations.

J. Javier Brey; A. Prados

2001-08-30

262

Granular Gas in a Periodic Lattice  

ERIC Educational Resources Information Center

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

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

2011-01-01

263

Granular Activated Carbon Filter-Adsorber Systems  

Microsoft Academic Search

The design, operation, and performance of granular activated carbon (GAC) filter-adsorbers were documented and potential problems were identified by means of a survey of operating plants and a review of the literature. It was found that GAC as a total or partial replacement for sand is as effective as conventional filtration media for removing turbidity, provided an appropriate medium size

Sandra L. Graese; Vernon L. Snoeyink; Ramon G. Lee

1987-01-01

264

Fragile granular jamming M. M. Bandi,1  

E-print Network

Fragile granular jamming M. M. Bandi,1 M. K. Rivera,2 F. Krzakala,3,4 and R. E. Ecke4, 1 T of a consolidation state, a fragile jammed state, and finally a rigid jammed state. In the consolidation regime chains. In the fragile jammed state, stress chains are visible, the pressure increases exponentially

Weeks, Eric R.

265

Decorated, Tapered, and Highly Nonlinear Granular Chain  

Microsoft Academic Search

It has been seen that inertial mismatches in 1D granular chains lead to remarkable energy absorption which increases with the number of spheres, N, and tapering, q. Short chains, however, are limited in that regard, and we therefore present one solution which greatly improves performance for any size chain. These strongly nonlinear and scalable systems feature surprisingly complicated dynamics and

Robert Doney; Surajit Sen

2006-01-01

266

Design and analysis of jammable granular systems  

E-print Network

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 ...

Cheng, Nadia G. (Nadia Gen San)

2013-01-01

267

A granular description of ECG signals.  

PubMed

In this paper, we develop a general framework of a granular representation of ECG signals. The crux of the approach lies in the development and ongoing processing realized in the setting of information granules-fuzzy sets. They serve as basic conceptual and semantically meaningful entities using which we describe signals and build their models (such as various predictive schemes or classifiers). A comprehensive two-phase scheme of the design of the information granules is proposed and described. At the first phase, we discuss the temporal granulation through a series of temporal windows (granular windows) and an aggregation of the values of signal by means of fuzzy sets. To address this issue, offered is a detailed method of building a fuzzy set based on numeric data and a certain optimization criterion that strikes a balance between the highest experimental relevance of the fuzzy set supported by numeric data and its substantial specificity. At the next phase of the granular design, a collection of information granules is further summarized with the use of fuzzy clustering (Fuzzy C-Means). The resulting prototypes (centroids) formed by this grouping process serve as elements of the granular vocabulary. We discuss ways of using these vocabularies in the knowledge-based representation, modeling, and classification of ECG beats. PMID:17019861

Gacek, Adam; Pedrycz, Witold

2006-10-01

268

Scales and kinetics of granular flows.  

PubMed

When a granular material experiences strong forcing, as may be the case, e.g., for coal or gravel flowing down a chute or snow (or rocks) avalanching down a mountain slope, the individual grains interact by nearly instantaneous collisions, much like in the classical model of a gas. The dissipative nature of the particle collisions renders this analogy incomplete and is the source of a number of phenomena which are peculiar to "granular gases," such as clustering and collapse. In addition, the inelasticity of the collisions is the reason that granular gases, unlike atomic ones, lack temporal and spatial scale separation, a fact manifested by macroscopic mean free paths, scale dependent stresses, "macroscopic measurability" of "microscopic fluctuations" and observability of the effects of the Burnett and super-Burnett "corrections." The latter features may also exist in atomic fluids but they are observable there only under extreme conditions. Clustering, collapse and a kinetic theory for rapid flows of dilute granular systems, including a derivation of boundary conditions, are described alongside the mesoscopic properties of these systems with emphasis on the effects, theoretical conclusions and restrictions imposed by the lack of scale separation. (c) 1999 American Institute of Physics. PMID:12779862

Goldhirsch, I.

1999-09-01

269

Submarine granular flows down inclined planes  

Microsoft Academic Search

Submarine flows of granular material down a rough inclined plane are experimentally investigated. We focus on the dense flow regime when the whole sediment layer is flowing down the slope and when no deposition nor entrainment occurs. In this regime, steady uniform flows are observed for which we systematically measure the depth-averaged velocity, the thickness, and the excess pore pressure

C. Cassar; M. Nicolas; O. Pouliquen

2005-01-01

270

Impulse Propagation in Granular Systems Surajit Sen,*  

E-print Network

Impulse Propagation in Granular Systems Surajit Sen,* Soumya Chakravarti,+ Donald P. Visco, Jr.,¶ Masami Nakagawa, David T. Wu and Juan Agui, Jr. *Department of Physics, State University of New York at Buffalo, Buffalo, NY 14260-1500, USA +Department of Physics, California State Polytechnic University

Sen, Surajit

271

Impulse propagation in granular systems Surajit Sen,*  

E-print Network

Impulse propagation in granular systems Surajit Sen,* Soumya Chakravarti,+ Donald P. Visco, Jr.,¶ Masami Nakagawa, David T. Wu and Juan Agui, Jr. *Department of Physics State University of New York at Buffalo, Buffalo, NY 14260-1500, USA +Department of Physics, California State Polytechnic University

Sen, Surajit

272

Multiscale modeling of multi-component granular avalanches  

NASA Astrophysics Data System (ADS)

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)

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

2014-05-01

273

Wet periods along the East Africa Coast and the extreme wet spell event of October 1997  

E-print Network

1 Wet periods along the East Africa Coast and the extreme wet spell event of October 1997 R. E Meteorological Society 2, 1 (2008) 67-83" #12;2 Abstract Extreme wet spells affect the East Africa Coast (EAC. Introduction The East Africa Coast (EAC, fig.1) is regularly affected by heavy rainfall events. These events

Boyer, Edmond

274

Ensuring message embedding in wet paper steganography  

E-print Network

Ensuring message embedding in wet paper steganography Daniel Augot1, Morgan Barbier1, and Caroline of this new scheme in the case of perfect codes. Keywords: steganography, syndrome coding problem, wet paper codes. 1 Introduction Hiding messages in innocuous-looking cover-media in a stealthy way, steganography

Paris-Sud XI, Université de

275

Wet runways. [aircraft landing and directional control  

NASA Technical Reports Server (NTRS)

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.

Horne, W. B.

1975-01-01

276

Anomalous wetting of helium on cesium  

Microsoft Academic Search

We report studies of the anomalous wetting of a cesium substrate by a liquid helium film by means of the technique of third sound. A hysteretic pre-wetting transition is observed as a function of the amount of helium in the experimental cell.

K. S. Ketola; S. Wang; R. B. Hallock

1992-01-01

277

Anomalous wetting of helium on cesium  

SciTech Connect

The authors report studies of the anomalous wetting of a cesium substrate by a liquid helium film by means of the technique of third sound. A hysteretic pre-wetting transition is observed as a function of the amount of helium in the experimental cell. 10 refs., 2 figs.

Ketola, K.S.; Wang, S.; Hallock, R.B. [Univ. of Massachusetts, Amherst (United States)

1992-11-01

278

Constitutive Relation in Transitional Granular Flows  

NASA Technical Reports Server (NTRS)

To study the constitutive behavior of granular materials, the presence of gravity is detrimental. Although empirical relations have been obtained for engineering designs to control granular flows on Earth, it is not known how well these Earthbound relations can be used in another gravity field. Fundamental understanding must be derived to reliably design for granular flows in space exploration. There are two extremes of granular flows of which significant amount of knowledge is available. One deals with a dense and quasi-static situation where the deformation rate nearly vanishes. The other deals with dilute and rapidly fluctuating grain velocities where particle inertia dominates. This project, funded by the NASA Microgravity Fluid Physics Program, aims to study this transitional regime via physical experiments and computer simulations. A conceptual model has been established as described below. There are two natural time scales in a granular flow. One is the travel time between two consecutive collisions and the other is the duration of a collision contact. At a very low shear-rate, the shear-induced particle velocity is low. Hence the travel time between collisions is longer than the contact time between colliding particles. Binary collisions prevail. As the shear-rate increases, the traveling time between collisions reduces and the probability of multiple collisions goes up. These particle groups disperse shortly after and new groups form. When shear-rate is further increased, clusters grow in size due to an increasing chance for free particles to join before groups have the time to disperse. The maximum cluster size may depend on the global concentration and material properties. As the solid concentration approaches zero, the cluster size goes to one particle diameter. The maximum possible cluster size under any condition is the container size, provided that the shear flow is inside a container. The critical shear-rates that dictate the initiation of the multiple contacts, and the size and lifetime of the collision clusters, are functions of the concentration also. A 'regime' theory has been proposed by Babic et al. This theory suggested that both the solid concentration, C, and the non-dimensional shear-rate, B, are important in determining the regimes of the granular constitutive law. Additional information is included in the original extended abstract.

Shen, Hayley H.; Hanes, Daniel M.; Jenkins, James T.

2002-01-01

279

Thin wetting film lensless imaging  

NASA Astrophysics Data System (ADS)

Lensless imaging has recently attracted a lot of attention as a compact, easy-to-use method to image or detect biological objects like cells, but failed at detecting micron size objects like bacteria that often do not scatter enough light. In order to detect single bacterium, we have developed a method based on a thin wetting film that produces a micro-lens effect. Compared with previously reported results, a large improvement in signal to noise ratio is obtained due to the presence of a micro-lens on top of each bacterium. In these conditions, standard CMOS sensors are able to detect single bacterium, e.g. E.coli, Bacillus subtilis and Bacillus thuringiensis, with a large signal to noise ratio. This paper presents our sensor optimization to enhance the SNR; improve the detection of sub-micron objects; and increase the imaging FOV, from 4.3 mm2 to 12 mm2 to 24 mm2, which allows the detection of bacteria contained in 0.5?l to 4?l to 10?l, respectively.

Allier, C. P.; Poher, V.; Coutard, J. G.; Hiernard, G.; Dinten, J. M.

2011-03-01

280

Precursor films in wetting phenomena  

E-print Network

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 rather 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.

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

2012-05-07

281

Dark Matter  

NASA Astrophysics Data System (ADS)

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.

Einasto, Jaan

2013-12-01

282

Resolving a paradox of anomalous scalings in the diffusion of granular materials  

PubMed Central

Granular materials do not perform Brownian motion, yet diffusion can be observed in such systems when agitation causes inelastic collisions between particles. It has been suggested that axial diffusion of granular matter in a rotating drum might be anomalous in the sense that the mean squared displacement of particles follows a power law in time with exponent less than unity. Further numerical and experimental studies have been unable to definitively confirm or disprove this observation. We show two possible resolutions to this apparent paradox without the need to appeal to anomalous diffusion. First, we consider the evolution of arbitrary (non-point-source) initial data towards the self-similar intermediate asymptotics of diffusion by deriving an analytical expression for the instantaneous collapse exponent of the macroscopic concentration profiles. Second, we account for the concentration-dependent diffusivity in bidisperse mixtures, and we give an asymptotic argument for the self-similar behavior of such a diffusion process, for which an exact self-similar analytical solution does not exist. The theoretical arguments are verified through numerical simulations of the governing partial differential equations, showing that concentration-dependent diffusivity leads to two intermediate asymptotic regimes: one with an anomalous scaling that matches the experimental observations for naturally polydisperse granular materials, and another with a normal diffusive scaling (consistent with a normal random walk) at even longer times. PMID:22992653

Christov, Ivan C.; Stone, Howard A.

2012-01-01

283

Resolving a paradox of anomalous scalings in the diffusion of granular materials.  

PubMed

Granular materials do not perform Brownian motion, yet diffusion can be observed in such systems when agitation causes inelastic collisions between particles. It has been suggested that axial diffusion of granular matter in a rotating drum might be "anomalous" in the sense that the mean squared displacement of particles follows a power law in time with exponent less than unity. Further numerical and experimental studies have been unable to definitively confirm or disprove this observation. We show two possible resolutions to this apparent paradox without the need to appeal to anomalous diffusion. First, we consider the evolution of arbitrary (non-point-source) initial data towards the self-similar intermediate asymptotics of diffusion by deriving an analytical expression for the instantaneous collapse exponent of the macroscopic concentration profiles. Second, we account for the concentration-dependent diffusivity in bidisperse mixtures, and we give an asymptotic argument for the self-similar behavior of such a diffusion process, for which an exact self-similar analytical solution does not exist. The theoretical arguments are verified through numerical simulations of the governing partial differential equations, showing that concentration-dependent diffusivity leads to two intermediate asymptotic regimes: one with an anomalous scaling that matches the experimental observations for naturally polydisperse granular materials, and another with a "normal" diffusive scaling (consistent with a "normal" random walk) at even longer times. PMID:22992653

Christov, Ivan C; Stone, Howard A

2012-10-01

284

Granular hydrodynamics and pattern formation in vertically oscillated granular disk layers  

NASA Astrophysics Data System (ADS)

The goal of this study is to demonstrate numerically that certain hydrodynamic systems, derived from inelastic kinetic theory, give fairly good descriptions of rapid granular flows even if they are way beyond their supposed validity limits. A numerical hydrodynamic solver is presented for a vibrated granular bed in two dimensions. It is based on a highly accurate shock capturing state-of-the-art numerical scheme applied to a compressible Navier-Stokes system for granular flow. The hydrodynamic simulation of granular flows is challenging, particularly in systems where dilute and dense regions occur at the same time and interact with each other. As a benchmark experiment, we investigate the formation of Faraday waves in a two-dimensional thin layer exposed to vertical vibration in the presence of gravity. The results of the hydrodynamic simulations are compared with those of event-driven molecular dynamics and the overall quantitative agreement is good at the level of the formation and structure of periodic patterns. The accurate numerical scheme for the hydrodynamic description improves the reproduction of the primary onset of patterns compared to previous literature. To our knowledge, these are the first hydrodynamic results for Faraday waves in two-dimensional granular beds that accurately predict the wavelengths of the two-dimensional standing waves as a function of the perturbation's amplitude. Movies are available with the online version of the paper.

Carrillo, Jos? A.; P?Schel, Thorsten; Salue?A, Clara

285

EFFECT OF UV IRRADIATION ON ORGANIC MATTER EXTRACTED FROM TREATED OHIO RIVER WATER STUDIED THROUGH THE USE OF ELECTROSPRAY MASS SPECTROMETRY  

EPA Science Inventory

Ohio River water was treated by settling, sand filtration, and granular activated carbon filtration. It was then irradiated by low pressure (monochromatic) and medium pressure (polychromatic) UV lamps to investigate the effects of UV irradiation of natural organic matter (NOM). ...

286

Order of wetting transitions in electrolyte solutions  

SciTech Connect

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.

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

2014-05-07

287

Critical point wetting drop tower experiment  

NASA Technical Reports Server (NTRS)

The 100 m Drop Tower at NASA-Marshall was used to provide the step change in acceleration from 1.0 to 0.0005 g. An inter-fluid meniscus oscillates vertically within a cylindrical container when suddenly released from earth's gravity and taken into a microgravity environment. Oscillations damp out from energy dissipative mechanisms such as viscosity and interfacial friction. Damping of the oscillations by the later mechanism is affected by the nature of the interfacial junction between the fluid-fluid interface and the container wall. In earlier stages of the project, the meniscus shape which developed during microgravity conditions was applied to evaluations of wetting phenomena near the critical temperature. Variations in equilibrium contact angle against the container wall were expected to occur under critical wetting conditions. However, it became apparent that the meaningful phenomenon was the damping of interfacial oscillations. This latter concept makes up the bulk of this report. Perfluoromethyl cyclohexane and isopropanol in glass were the materials used for the experiment. The wetting condition of the fluids against the wall changes at the critical wetting transition temperature. This change in wetting causes a change in the damping characteristics of the interfacial excursions during oscillation and no measurable change in contact angle. The effect of contact line friction measured above and below the wetting transition temperature was to increase the period of vertical oscillation for the vapor-liquid interface when below the wetting transition temperature.

Kaukler, William F.

1990-01-01

288

WET LOOSE SNOW AVALANCHING IN SOUTHWESTERN MONTANA Simon August Trautman  

E-print Network

WET LOOSE SNOW AVALANCHING IN SOUTHWESTERN MONTANA by Simon August Trautman A thesis submitted .......................................................................................................11 Wet Loose Snow Avalanching in Southwestern Montana ...........................................13 3. RELATING SNOWPACK STRATIGRAPHY TO WET LOOSE SNOW AVALANCHING

Lawrence, Rick L.

289

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

Federal Register 2010, 2011, 2012, 2013

...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...

2011-05-12

290

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

Federal Register 2010, 2011, 2012, 2013

...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...

2011-05-17

291

Electrostatics of Granular Material (EGM): Space Station Experiment  

NASA Technical Reports Server (NTRS)

Aggregates were observed to form very suddenly in a lab-contained dust cloud, transforming (within seconds) an opaque monodispersed cloud into a clear volume containing rapidly-settling, long hair-like aggregates. The implications of such a "phase change" led to a series of experiments progressing from the lab, to KC-135, followed by micro-g flights on USML-1 and USML-2, and now EGM slated for Space Station. We attribute the sudden "collapse" of a cloud to the effect of dipoles. This has significant ramifications for all types of cloud systems, and additionally implicates dipoles in the processes of cohesion and adhesion of granular matter. Notably, there is the inference that like-charged grains need not necessarily repel if they are close enough together: attraction or repulsion depends on intergranular distance (the dipole being more powerful at short range), and the D/M ratio for each grain, where D is the dipole moment and M is the net charge. We discovered that these ideas about dipoles, the likely pervasiveness of them in granular material, the significance of the D/M ratio, and the idea of mixed charges on individual grains resulting from tribological processes --are not universally recognized in electrostatics, granular material studies, and aerosol science, despite some early seminal work in the literature, and despite commercial applications of dipoles in such modern uses as "Krazy Glue", housecleaning dust cloths, and photocopying. The overarching goal of EGM is to empirically prove that (triboelectrically) charged dielectric grains of material have dipole moments that provide an "always attractive" intergranular force as a result of both positive and negative charges residing on the surfaces of individual grains. Microgravity is required for this experiment because sand grains can be suspended as a cloud for protracted periods, the grains are free to rotate to express their electrostatic character, and Coulombic forces are unmasked. Suspended grains will be "interrogated" by applied electrical fields. In one module, grains will be immersed in an inhomogeneous electric field and allowed to be attracted towards or repelled from the central electrode of the module: part of the grain's speed will be a function of its net charge (monopole), part will be a function of the dipole. Observed grain position vs. time will provide a curve that can be deconvolved into the dipole and monopole forces responsible, since both have distinctive radial dependencies. In a second approach, the inhomogeneous field will be alternated at low frequency (e.g., every 5-10 seconds) so that the grains are alternately attracted and repelled from the center of the field. The resulting "zigzag" grain motion will gradually drift inwards, then suddenly change to a unidirectional inward path when a critical radial distance is encountered (a sort of "Coulombic event horizon") at which the dipole strength supersedes the monopole strength --thus proving the presence of a dipole, while also quantifying the D/M ratio. In a second module, an homogeneous electric field eliminates dipole effects (both Coulombic and induced) to provide calibration of the monopole and to more readily evaluate net charge statistical variance. In both modules, the e-fields will be exponentially step-ramped in voltage during the experiment, so that the field "nominalizes" grain speed while spreading the response time --effectively forcing each grain to "wait its turn" to be measured. In addition to rigorously quantifying M, D, and the D/M ratio for many hundreds of grains, the experiment will also observe gross electrometric and RF discharge phenomena associated with grain activity. The parameter space will encompass grain charging levels (via intentional triboelectrification), grain size, cloud density, and material type. Results will prove or disprove the dipole hypothesis. In either case, light will be shed on the role of electrostatic forces in governing granular systems. Knowledg

Marshall, J.; Sauke, T.; Farrell, W.

2000-01-01

292

Nonlocal constitutive relation for steady granular flow.  

PubMed

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 granular flow law in terms of a fluidity ratio and then extend it with a particular Laplacian term that is scaled by the grain size. The resulting model is calibrated against a sequence of existing discrete element method data sets for two-dimensional annular shear, where it is shown that the model correctly describes the divergence from a local rheology due to the grain size as well as the rate-independence phenomenon commonly observed in slowly flowing zones. The same law is then applied in two additional inhomogeneous flow geometries, and the predicted velocity profiles are compared against corresponding discrete element method simulations utilizing the same grain composition as before, yielding favorable agreement in each case. PMID:22680912

Kamrin, Ken; Koval, Georg

2012-04-27

293

Heat flux in a granular gas  

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

294

Memory effect in uniformly heated granular gases  

E-print Network

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.

E. Trizac; A. Prados

2014-07-15

295

Granular Brownian motion with dry friction  

NASA Astrophysics Data System (ADS)

The interplay between Coulomb friction and random excitations is studied experimentally by means of a rotating probe in contact with a stationary granular gas. The granular material is independently fluidized by a vertical shaker, acting as a heat bath for the Brownian-like motion of the probe. Two ball bearings supporting the probe exert nonlinear Coulomb friction upon it. The experimental velocity distribution of the probe, autocorrelation function, and power spectra are compared with the predictions of a linear Boltzmann equation with friction, which is known to simplify in two opposite limits: at high collision frequency, it is mapped to a Fokker-Planck equation with nonlinear friction, whereas at low collision frequency, it is described by a sequence of independent random kicks followed by friction-induced relaxations. Comparison between theory and experiment in these two limits shows good agreement. Deviations are observed at very small velocities, where the real bearings are not well modeled by Coulomb friction.

Gnoli, A.; Puglisi, A.; Touchette, H.

2013-04-01

296

Impact of liquid droplets on granular media  

NASA Astrophysics Data System (ADS)

The crater formation due to the impact of a water droplet onto a granular bed has been experimentally investigated. Three parameters have been tuned: the impact velocity, the size of the droplet and the size of the grains. The shape of the crater depends on the Weber number at the moment the droplet starts to impact the bed. From the dynamical point of view, the spreading and the receding of the liquid during the impact have been carefully analyzed using image analysis of high speed video recordings. The different observed regimes are characterized by the balance between the impregnation time of the granular bed by the water contained in the droplet and the capillary time responsible for the receding of the drop.

Delon, Giles; Terwagne, Denis; Dorbolo, Stephane; Vandewalle, Nicolas; Caps, Herve

2012-02-01

297

Impact of liquid droplets on granular media.  

PubMed

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

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

2011-10-01

298

Universal Structural Characteristics of Planar Granular Packs  

NASA Astrophysics Data System (ADS)

The dependence of structural self-organization of granular materials on preparation and grain parameters is key to predictive modeling. We study 60 different mechanically equilibrated polydisperse disc packs, generated numerically by two protocols. We show that, for same-variance disc size distributions (DSDs), (1) the mean coordination number of rattler-free packs versus the packing fraction is a function independent of initial conditions, friction, and the DSD, and (2) all quadron volume and cell order distributions collapse to universal forms, also independent of the above. This apparent universality suggests that, contrary to common wisdom, equilibrated granular structures may be determined mainly by the packing protocol and higher moments of the DSD.

Matsushima, Takashi; Blumenfeld, Raphael

2014-03-01

299

Memory effect in uniformly heated granular gases  

NASA Astrophysics Data System (ADS)

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 nonequilibrium 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 nonmonotonic 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 called anomalous. We find excellent agreement between the analytical predictions and direct Monte Carlo simulations.

Trizac, E.; Prados, A.

2014-07-01

300

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

NASA Astrophysics Data System (ADS)

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.

Langlois, V.; Jia, X.

2014-02-01

301

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

E-print Network

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).

Tian Hao

2014-09-05

302

Swimming in a granular frictional fluid  

NASA Astrophysics Data System (ADS)

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.

Goldman, Daniel

2012-02-01

303

Granular cell breast tumour mimicking infiltrating carcinoma  

PubMed Central

Granular cell tumour (GCT) is a rare, usually benign neoplasm that can mimic carcinoma on breast imaging. GCT can originate anywhere in the body but is most frequently found in the head and neck region, particularly in the tongue. Of the reported cases, 6% have occurred in the breast, most commonly in the upper inner quadrant. We report a case of GCT of the breast presenting as a spiculated mass infiltrating the greater thoracic muscle on breast screening mammogram. PMID:23420726

Gavriilidis, Paschalis; Michalopoulou, Ilektra; Baliaka, Aggeliki; Nikolaidou, Anastasia

2013-01-01

304

Stochastic flow rule for granular materials.  

PubMed

There have been many attempts to derive continuum models for dense granular flow, but a general theory is still lacking. Here, we start with Mohr-Coulomb plasticity for quasi-two-dimensional granular materials to calculate (average) stresses and slip planes, but we propose a "stochastic flow rule" (SFR) to replace the principle of coaxiality in classical plasticity. The SFR takes into account two crucial features of granular materials-discreteness and randomness-via diffusing "spots" of local fluidization, which act as carriers of plasticity. We postulate that spots perform random walks biased along slip lines with a drift direction determined by the stress imbalance upon a local switch from static to dynamic friction. In the continuum limit (based on a Fokker-Planck equation for the spot concentration), this simple model is able to predict a variety of granular flow profiles in flat-bottom silos, annular Couette cells, flowing heaps, and plate-dragging experiments--with essentially no fitting parameters--although it is only expected to function where material is at incipient failure and slip lines are inadmissible. For special cases of admissible slip lines, such as plate dragging under a heavy load or flow down an inclined plane, we postulate a transition to rate-dependent Bagnold rheology, where flow occurs by sliding shear planes. With different yield criteria, the SFR provides a general framework for multiscale modeling of plasticity in amorphous materials, cycling between continuum limit-state stress calculations, mesoscale spot random walks, and microscopic particle relaxation. PMID:17500886

Kamrin, Ken; Bazant, Martin Z

2007-04-01

305

Refraction of shear zones in granular materials  

E-print Network

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.

Tamas Unger

2007-01-08

306

Structural characterization of submerged granular packings  

NASA Astrophysics Data System (ADS)

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 Vorono 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 (Vorono 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.

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

2014-12-01

307

Mechanics of Granular Materials (MGM) Test Cell  

NASA Technical Reports Server (NTRS)

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)

1998-01-01

308

Mechanics of Granular Materials (MGM) Cell  

NASA Technical Reports Server (NTRS)

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

1996-01-01

309

Mechanics of Granular Materials (MGM) Test Cell  

NASA Technical Reports Server (NTRS)

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

2000-01-01

310

Mechanics of Granular Materials (MGM) Test Cell  

NASA Technical Reports Server (NTRS)

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

2000-01-01

311

Mechanics of Granular Materials Test Cell  

NASA Technical Reports Server (NTRS)

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)

1998-01-01

312

Mechanics of Granular Materials (MGM) Flight Hardware  

NASA Technical Reports Server (NTRS)

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)

1997-01-01

313

Effective thermal conductivity of granular porous materials  

SciTech Connect

Various models and formulae have been proposed for the prediction of effective thermal conductivity for two-phase systems, all the models predict the effective thermal conductivity as function of thermal conductivity of each phase and volume content of each phase or porosity which is defined as the ratio of fluid volume to the total volume. Some of the models take further into consideration such parameters as the shape of the solid particles, the orientation and the distribution of the particles, the contact resistance between particles. In this study, various conduction models for two-phase materials are considered and the range of applicability of these models is discussed. Experimental work is carried out on construction sand of various grain size and different porosity in air at atmospheric pressure, and the results are compared with theoretical models. A modified hot-wire method is used in the measurement of effective thermal conductivities. Porous materials may be divided into two main groups: air-cell type and granular-solid type. In the present article only granular-solid type of porous materials, formed of elements of granular solids located in continuous immobile fluid medium (gas or liquid), are considered.

Tavman, I.H. [Dokuz Eylul Univ., Izmir (Turkey). Mechanical Engineering Dept.] [Dokuz Eylul Univ., Izmir (Turkey). Mechanical Engineering Dept.

1996-03-01

314

Visualization of particle interactions in granular media.  

PubMed

Interaction between particles in so-called granular media, such as soil and sand, plays an important role in the context of geomechanical phenomena and numerous industrial applications. A two scale homogenization approach based on a micro and a macro scale level is briefly introduced in this paper. Computation of granular material in such a way gives a deeper insight into the context of discontinuous materials and at the same time reduces the computational costs. However, the description and the understanding of the phenomena in granular materials are not yet satisfactory. A sophisticated problem-specific visualization technique would significantly help to illustrate failure phenomena on the microscopic level. As main contribution, we present a novel 2D approach for the visualization of simulation data, based on the above outlined homogenization technique. Our visualization tool supports visualization on micro scale level as well as on macro scale level. The tool shows both aspects closely arranged in form of multiple coordinated views to give users the possibility to analyze the particle behavior effectively. A novel type of interactive rose diagrams was developed to represent the dynamic contact networks on the micro scale level in a condensed and efficient way. PMID:18599921

Meier, Holger A; Schlemmer, Michael; Wagner, Christian; Kerren, Andreas; Hagen, Hans; Kuhl, Ellen; Steinmann, Paul

2008-01-01

315

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

316

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

PubMed

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

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

2014-04-01

317

Matter may matter  

NASA Astrophysics Data System (ADS)

We propose a gravitational theory in which the effective Lagrangian of the gravitational field is given by an arbitrary function of the Ricci scalar, the trace of the matter energy-momentum tensor, and the contraction of the Ricci tensor with the matter energy-momentum tensor. The matter energy-momentum tensor is generally not conserved, thus leading to the appearance of an extra-force, acting on massive particles in a gravitational field. The stability conditions of the theory with respect to local perturbations are also obtained. The cosmological implications of the theory are investigated, representing an exponential solution. Hence, a Ricci tensor-energy-momentum tensor coupling may explain the recent acceleration of the universe, without resorting to the mysterious dark energy.

Haghani, Zahra; Harko, Tiberiu; Sepangi, Hamid Reza; Shahidi, Shahab

2014-10-01

318

7 CFR 51.491 - Wet slip.  

Code of Federal Regulations, 2010 CFR

...slip means a condition present at time of packing in which the stem scar is abnormally large, excessively wet and slippery, yields to slight...frequently accompanied by fresh radial growth cracks at the edge of the stem...

2010-01-01

319

Wetting on flexible hydrophilic pillar-arrays  

PubMed Central

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

Yuan, Quanzi; Zhao, Ya-Pu

2013-01-01

320

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...

321

Wetting on flexible hydrophilic pillar-arrays  

NASA Astrophysics Data System (ADS)

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.

Yuan, Quanzi; Zhao, Ya-Pu

2013-06-01

322

Breakdown in the Wetting Transparency of Graphene  

E-print Network

We develop a theory to model the van der Waals interactions between liquid and graphene, including quantifying the wetting behavior of a graphene-coated surface. Molecular dynamics simulations and contact angle measurements ...

Shih, Chih-Jen

323

Wetting transparency of graphene in water.  

PubMed

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. PMID:25399182

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

2014-11-14

324

Photoresponsive superhydrophobic surfaces for effective wetting control.  

PubMed

Dynamically tuning the surface wettability has long been a scientific challenge, but of great importance in surface science. Robust superhydrophobic surfaces, displaying switchable and tunable extreme wetting behaviors, are successfully developed by spraying photoresponsive hydrophobic nanoparticles onto various substrates. The surface wettability can be intelligently adjusted by applying irradiation with UV or visible light, which is assumed to initiate large conformation changes of azobenzene units at the coating surface, resulting in distinct surface energy change and thus controlled wetting behaviors. The underlying wetting mechanism about the resulting surfaces is systematically investigated and supported by the estimation of water contact angles using newly rewritten Cassie-Baxter and Wenzel relations and also by the evaluation of solid surface free energy adopting the Owens-Wendt approach. The methodology proposed may provide a novel way of tuning surface wettability and investigating the wetting transition mechanism and also promote applications in self-cleaning and smart fluid control. PMID:25322263

Pan, Shuaijun; Guo, Rui; Xu, Weijian

2014-12-01

325

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 ...

326

7 CFR 29.2570 - Wet (W).  

Code of Federal Regulations, 2010 CFR

...REGULATIONS TOBACCO INSPECTION Standards Official Standard Grades for Kentucky and Tennessee Fire-Cured and Foreign-Grown Fire-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) 29.2570 Wet (W). Any sound...

2010-01-01

327

Cavity QED detection of interfering matter waves  

SciTech Connect

We observe the build-up of a matter wave interference pattern from single atom detection events in a double-slit experiment. The interference arises from two overlapping atom laser beams extracted from a rubidium Bose-Einstein condensate. Our detector is a high-finesse optical cavity which realizes a quantum measurement of the presence of an atom and thereby projects delocalized atoms into a state with zero or one atom in the resonator. The experiment reveals simultaneously the granular and the wave nature of matter. We present a setup which is suited for applications in atom interferometry and cavity QED.

Bourdel, T.; Donner, T.; Ritter, S.; Oettl, A.; Koehl, M.; Esslinger, T. [Institute of Quantum Electronics, ETH Zuerich, CH-8093 Zurich (Switzerland)

2006-04-15

328

Mutiscale Modeling of Segregation in Granular Flows  

SciTech Connect

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.

Jin Sun

2007-08-03

329

Drying and passivating wet coals and lignite  

Microsoft Academic Search

This invention discloses a staged process for drying wet carbonaceous materials such as sub-bituminous coal or lignite containing at least about 10 weight percent moisture, usually 15-50 weight percent moisture, by first heating the wet material under low partial pressure of moisture to permit the controlled rapid escape of surface moisture down to a critical moisture content of 8-12 weight

Comolli

1981-01-01

330

Wet/dry cooling tower and method  

DOEpatents

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.

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

1981-01-01

331

Matter: States of Matter  

NSDL National Science Digital Library

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.

Anthony Carpi, Ph.D.

332

Minkowski tensor shape analysis of cellular, granular and porous structures.  

PubMed

Predicting physical properties of materials with spatially complex structures is one of the most challenging problems in material science. One key to a better understanding of such materials is the geometric characterization of their spatial structure. Minkowski tensors are tensorial shape indices that allow quantitative characterization of the anisotropy of complex materials and are particularly well suited for developing structure-property relationships for tensor-valued or orientation-dependent physical properties. They are fundamental shape indices, in some sense being the simplest generalization of the concepts of volume, surface and integral curvatures to tensor-valued quantities. Minkowski tensors are based on a solid mathematical foundation provided by integral and stochastic geometry, and are endowed with strong robustness and completeness theorems. The versatile definition of Minkowski tensors applies widely to different types of morphologies, including ordered and disordered structures. Fast linear-time algorithms are available for their computation. This article provides a practical overview of the different uses of Minkowski tensors to extract quantitative physically-relevant spatial structure information from experimental and simulated data, both in 2D and 3D. Applications are presented that quantify (a) alignment of co-polymer films by an electric field imaged by surface force microscopy; (b) local cell anisotropy of spherical bead pack models for granular matter and of closed-cell liquid foam models; (c) surface orientation in open-cell solid foams studied by X-ray tomography; and (d) defect densities and locations in molecular dynamics simulations of crystalline copper. PMID:21681830

Schrder-Turk, G E; Mickel, W; Kapfer, S C; Klatt, M A; Schaller, F M; Hoffmann, M J F; Kleppmann, N; Armstrong, P; Inayat, A; Hug, D; Reichelsdorfer, M; Peukert, W; Schwieger, W; Mecke, K

2011-06-17

333

The thermodynamics of dense granular flow and jamming  

NASA Astrophysics Data System (ADS)

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.

Lu, Shih Yu

334

The theory of granular packings for coarse soils  

NASA Astrophysics Data System (ADS)

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.

Yanqui, Calixtro

2013-06-01

335

Elastic weakening of a dense granular medium by acoustic fluidization  

NASA Astrophysics Data System (ADS)

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)

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

2012-02-01

336

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

NASA Astrophysics Data System (ADS)

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.

Chen, Yanfeng; Hu, Chaoqun; Ren, Chunhua

2015-02-01

337

INTRODUCTION: Wetting and dewetting in bio-related systems  

NASA Astrophysics Data System (ADS)

Research on such genuinely soft-matter related phenomena as wetting and dewetting would not be complete without reminiscence to biological systems. The recent stir around what has been known as the lotus effect, the amazing ultra-hydrophobic properties of many plants, has highlighted the interconnections of wetting with bio-systems. In the first paper of this section (Mock et al), a `biomimetic' system is conceived which imitates the properties of plant leaves with elastic hairs. The synthesis of such a system turns out to be tricky, but the progress is encouraging. The next three papers deal with surfactant layers, as they occur in many biological systems, such as the plasma membrane. Various experimental techniques, such as fluorescence microscopy (Tanaka et al), neutron reflectivity (Steitz et al), and x-ray scattering (Ahrens et al), are demonstrated as powerful tools for their investigation. The last paper (Heim et al) takes us back to where we started: the morphologies emerging upon dewetting of a liquid. This time, the full diversity of patterns is shown which appears in the deposited solute, once the liquid has evaporated. The motivation of this work is the morphology of deposition of DNA on bio-chips, which may affect the readout results of such devices. It is shown that although much can already be understood, a lot of work has still to be done, and many beautiful mechanisms may still be discovered.

Herminghaus, S.

2005-03-01

338

Scaled experiments to determine the role of density on granular flows behavior: preliminary results  

NASA Astrophysics Data System (ADS)

Geological granular flows are very complex, gravity driven phenomena which can show different behaviors depending on its origin and the characteristics of the constituent material. Due to their dangerous nature, and multiple scientific and technological applications, these phenomena has being studied deeply in order to have a better comprehension, however, after more than one century of scientific research it remains as an open topic with more questions than answers. One of the aspects that still need exhaustive research is the effect of clast density on the flowing granular material, as pointed out by previous laboratory and field studies. There are anyway few studies which have tried to explain the role of bulk density, as well the density of different phases, as it increasing or decreasing on the kinematic and the rheological characteristics of geological granular flows. The content of low density juvenile material seems to condition the processes of transformations of debris flows to more diluted phases, as well the transport and emplacing mechanisms. It is well known that the content of clay in debris flows has great influence on its behavior, physical processes and the deposits characteristics for this reason lahars has being subdivided in base of this parameter. Our hypothesis is that, in like manner, the presence of low density material inside the granular flows (dry and wet) could conditioning its physical characteristics and its behavior. In order to put this to the test, we made some laboratory experiments using a five meter long and 0.3 m wide experimental flume equipped with a wide range of sensors and laser barriers to precisely measure the rheological properties and kinematic of the sliding avalanches. A special effort was devoted to determine a threshold or critical level in the amount of low density material at which the avalanche behavior suffer appreciable changes. The obtained preliminary results confirm our hypothesis and encouraged to perform further experiments. Such studies are important because they could provide useful information for developing analog models that take into account this important physical property.

Rodriguez Sedano, L. A.; Sarocchi, D.; Borselli, L.; Segura, O.

2013-12-01

339

Substrate effects from force chain dynamics in dense granular flows  

NASA Astrophysics Data System (ADS)

Granular materials are composed of solid, discrete particles and exhibit mechanical properties that range from fluid to solid behavior. Some of the complexity exhibited by granular systems arises due to the long-range order that develops due to particle-particle contact. Inter-particle forces in granular materials often form a distributive network of filamentary force-accommodating chains (i.e., force chains), such that a fraction of the total number of particles accommodates the majority of the forces in the system. The force chain network inherent to a system composed of granular materials controls the macroscopic behavior of the granular material. Force transmission by these filamentary chains is focused (or localized) to the grain scale at boundaries such as the granular flow substrate. This investigation addresses the effects of force localization on the substrate by dynamic force chain processes and the implications for bed entrainment in dense, unconfined, two-dimensional, gravity-driven granular flows. Our experimental system employs photoelastic techniques and provides an avenue for quantitative force analysis via image processing and provides a data set that can be used validate discrete element modeling approaches. We show that force chains cause extreme bed-force localization in dynamic granular systems, and that these localized forces can propagate extensively into the substrate, even ahead of the flow front.

Estep, Joe; Dufek, Josef

2012-03-01

340

Geological and mathematical framework for failure modes in granular rock  

E-print Network

Geological and mathematical framework for failure modes in granular rock Atilla Aydina, *, Ronaldo processes in granular rock and provide a geological framework for the corresponding structures. We describe show that sharp structures overlap older narrow tabular structures in the same rock. This switch

Borja, Ronaldo I.

341

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...

342

Longitudinal vortices in granular ows Y. Forterre and O. Pouliquen  

E-print Network

and the opening of the gate hg. This con guration has been widely used to study the rheology of granular ows 16 18 ofgranular ows 4]. One wayto better understand the speci cities of granular ows is to study also been studied numericallyand theoretically 7, 8]. In con- trast, few studies concern the stability

Forterre, Yoël

343

Impact of Virtual Machine Granularity on Cloud Computing Workloads Performance  

E-print Network

the impact of VM granularity on workload performance in cloud computing environments. We use HPL, the performance obtained from utilizing 8VMs is more than 4 times higher than that given by 4 or 16 VMs for HPL for HPL of problem sizes from 256 to 1024. Our results also indicate that the effect of VM granularity

Varela, Carlos

344

Hydrothermal Modification of Granular Steel Slag for Phosphate Removal  

Microsoft Academic Search

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

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

2011-01-01

345

Statistical mechanics for static granular media: open questions  

E-print Network

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

Paris-Sud XI, Université de

346

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...

347

Monodisperse dry granular flows on inclined planes: Role of roughness  

Microsoft Academic Search

Recent studies have pointed out the importance of the basal friction on the dynamics of granular flows. We present experimental results on the influence of the roughness of the inclined plane on the dynamics of a monodisperse dry granular flow. We found experimentally that there exists a maximum of the friction for a given relative roughness. This maximum is shown

Celine GOUJON; Nathalie THOMAS; Blanche DALLOZ-DUBRUJEAUD

2003-01-01

348

Experimental study of collisional granular flows down an inclined plane  

Microsoft Academic Search

The collisional flow of a slightly inelastic granular material down a rough inclined plane is usually described by kinetic theories. We present an experimental study aimed at analysing the assumptions and the quantitative predictions of such theories. A two-dimensional channel coupled to a model granular material and image analysis allow detailed and complete measurement of the kinematics and structure of

Emmanuel Azanza; Franois Chevoir; Pascal Moucheront

1999-01-01

349

Granular Avalanches in Fluids Sylvain Courrech du Pont,1  

E-print Network

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

Weeks, Eric R.

350

Granular lymphocyte proliferative disorders: A multicenter study of 20 cases  

Microsoft Academic Search

Summary A series of 20 patients with granular lymphocyte proliferative disorders (GLPD) is reported. The criterion of inclusion was presence of persistent (=6 months) granular lymphocytosis in the absence of any causative illness. Diagnoses made upon analytical control in half the patients of splenomegaly (25%) and hepatomegaly (25%) were infrequent. Clinical course was nonprogressive in 17\\/20 patients, but two developed

S. Woessner; E. Feliu; N. Villamor; M. A. Zarco; A. Domingo; F. Mill; L. Florensa; M. Rozman; E. Abella; J. Soler; T. Vallesp; M. D. Irriguible; F. Sol

1994-01-01

351

Powdered versus granular carbon for oil refinery wastewater treatment  

Microsoft Academic Search

Pilot studies were conducted on two activated carbon-based systems for meeting the effluent quality requirements of an oil refinery. Upgrading of activated sludge by addition of powdered activated carbon directly into aeration tank mixed liquor and tertiary treatment of activated sludge effluent by granular carbon adsorption were studied. Powdered carbon enhancement was found to be more cost-effective than granular carbon

C. G. Grieves; L. W. Crame; D. G. Venardos; W. Ying

1980-01-01

352

Network model of survival signaling in large granular lymphocyte leukemia  

E-print Network

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

Albert, Réka

353

Modeling of compressible self-organized granular media under static load  

NASA Astrophysics Data System (ADS)

A simple continual model of granular medium, based on original hypotheses, is built. It describes the matter under active quasi-static compression with taking into account the effects of both compaction and self-organization. The analysis of the hypotheses has given the model's constitutive relations. Thus, an exponential dependence for the porosity from the average stress and a linear relationship between the principal stresses are set. The analysis of the constitutive relations at the same time has given need for existence of two new constants. One of them characterizes particular material's compliance to compaction, its value should be determined from experiment. The other new constant is a macroscopic characteristic of the matter's mesoscopic state, its range of values has been determined and ensures for the internal consistency of the model as well as the accord with the mechanics general laws. Such applied questions as compacting granular media under their own weight and the Lam problem for them are solved in the elementary functions. The proposed Lam problem's solution eliminates singularity at the origin. The derived theoretical predictions are in good agreement with available experimental data. The latter include data on a natural carbonates deposit at depth up to 5.5 km, snow drifts at depth up to 10 m, and nano-sized powders in capsules of 10 mm radius under the GPa order pressure.

Skachkov, Mikhail N.

2013-06-01

354

Dark Matter  

NSDL National Science Digital Library

This website introduces dark matter by first explaining Zwicky's discovery of dark matter when he was studying clusters of galaxies about fifty years ago. It then talks about how astronomers detect dark matter today, its relationship to inflation, and the current theories that propose that dark matter may be either WIMPS or MACHOS.

Silk, Joe

2005-06-07

355

A rheological approach to analyze aerobic granular sludge.  

PubMed

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

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

2014-03-01

356

When matter matters  

SciTech Connect

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.

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 fr Theoretische Physik, Ruprecht-Karls-Universitt 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 Genve 23 (Switzerland)

2013-07-01

357

Adsorption of chlorophenols on granular activated carbon  

SciTech Connect

Studies were undertaken of the adsorption of chlorinated phenols from aqueous solution on granular activated carbon (Filtrasorb-400, 30 x 40 mesh). Single-component equilibrium adsorption data on the eight compounds in two concentration ranges at pH 7.0 fit the Langmuir equation better than the Freundlich equation. The adsorptive capacities at pH 7.0 increase from pentachlorophenol to trichlorophenols and are fairly constant from trichlorophenols to monochlorophenols. The adsorption process was found to be exothermic for pentachlorophenol and 2,4,6-trichlorophenol, and endothermic for 2,4-dichlorophenol and 4-chlorophenol. Equilibrium measurements were also conducted for 2,4,5-trichlorophenol, 2,4-dichlorophenol, and 4-chlorophenol over a wide pH range. A surface complexation model was proposed to describe the effect of pH on adsorption equilibria of chlorophenols on activated carbon. The simulations of the model are in excellent agreement with the experimental data. Batch kinetics studies were conducted of the adsorption of chlorinated phenols on granular activated carbon. The results show that the surface reaction model best describes both the short-term and long-term kinetics, while the external film diffusion model describes the short-term kinetics data very well and the linear-driving-force approximation improved its performance for the long-term kinetics. Multicomponent adsorption equilibria of chlorophenols on granular activated carbon was investigated in the micromolar equilibrium concentration range. The Langmuir competitive and Ideal Adsorbed Solution (IAS) models were tested for their performance on the three binary systems of pentachlorophenol/2,4,6-trichlorophenol, 2,4,6-trichlorophenol/2,4-dichlorophenol, and 2,4-dichlorophenol/4-chlorophenol, and the tertiary system of 2,4,6-trichlorophenol/2,4-dichlorophenol/4-chlorophenol, and found to fail to predict the two-component adsorption equilibria of the former two binary systems and the tertiary system.

Yang, M.

1993-12-31

358

Experimental and Computational Techniques in Soft Condensed Matter Physics  

NASA Astrophysics Data System (ADS)

1. Microscopy of soft materials Eric R. Weeks; 2. Computational methods to study jammed Systems Carl F. Schrek and Corey S. O'Hern; 3. Soft random solids: particulate gels, compressed emulsions and hybrid materials Anthony D. Dinsmore; 4. Langmuir monolayers Michael Dennin; 5. Computer modeling of granular rheology Leonardo E. Silbert; 6. Rheological and microrheological measurements of soft condensed matter John R. de Bruyn and Felix K. Oppong; 7. Particle-based measurement techniques for soft matter Nicholas T. Ouellette; 8. Cellular automata models of granular flow G. William Baxter; 9. Photoelastic materials Brian Utter; 10. Image acquisition and analysis in soft condensed matter Jeffrey S. Olafsen; 11. Structure and patterns in bacterial colonies Nicholas C. Darnton.

Olafsen, Jeffrey

2010-09-01

359

Yield loci for an anisotropic granular assembly  

NASA Astrophysics Data System (ADS)

Yield loci of a granular material are derived in case of triaxial compression carried out at constant pressure. The theory is based upon a simple micromechanical model in which particles move according to an average, homogeneous deformation. We show how the presence of an inherent anisotropy in the aggregate (typical of laboratory samples due to depositional processes) produces a deviation of the yield loci in the stress space from the expected Mohr-Coulomb prediction. That is, when the compaction pressure in an anisotropic aggregate is increased, irreversibility associated with sliding between particles occurs and this will influence the yield function in the subsequent triaxial test. Numerical simulations support the theoretical result.

La Ragione, Luigi; Oger, Luc

2012-10-01

360

Drag induced lift in granular media  

E-print Network

Laboratory experiments and numerical simulation reveal that a submerged intruder dragged horizontally at constant velocity within a granular medium experiences a lift force whose sign and magnitude depend on the intruder shape. Comparing the stress on a flat plate at varied inclination angle with the local surface stress on the intruders at regions with the same orientation demonstrates that intruder lift forces are well approximated as the sum of contributions from flat-plate elements. The plate stress is deduced from the force balance on the flowing media near the plate.

Yang Ding; Nick Gravish; Daniel I. Goldman

2011-08-09

361

Prenatal Diagnosis of Granular Cell Tumor  

PubMed Central

Congenital granular cell tumor (GCT) is a relatively rare intraoral benign tumor, approximately 200 cases of which have been reported in the neonatal period worldwide. The newborn infant may have feeding problems and respiratory difficulties due to airway obstruction. This lesion may be diagnosed by prenatal ultrasonography and simple resection is mostly required. We report a case of an adult type of GCT in a newly born infant, who presented with an intraoral protruding mass with a prenatal diagnosis. This article describes the prenatal course, clinical, and pathological characteristics, and management of the GCT. PMID:24644385

Kadivar, Maliheh; Sangsari, Razieh; Alavi, Azin

2014-01-01

362

Granular impact and the critical packing state  

NASA Astrophysics Data System (ADS)

Impact dynamics during collisions of spheres with granular media reveal a pronounced and nontrivial dependence on volume fraction ? . Postimpact crater morphology identifies the critical packing state ?cps , where sheared grains neither dilate nor consolidate, and indicates an associated change in spatial response. Current phenomenological models fail to capture the observed impact force for most ? ; only near ?cps is force separable into additive terms linear in depth and quadratic in velocity. At fixed depth the quadratic drag coefficient decreases (increases) with depth for ??cps) . At fixed low velocity, depth dependence of force shows a Janssen-type exponential response with a length scale that decreases with increasing ? and is nearly constant for ?>?cps .

Umbanhowar, Paul; Goldman, Daniel I.

2010-07-01

363

Contact network topology in tapped granular media.  

PubMed

We analyze the contact network of simulated two-dimensional granular packings in different states of mechanical equilibrium obtained by tapping. We show that topological descriptors of the contact network allow one to distinguish steady states of the same mean density obtained with different tap intensities. These equal-density states were recently proven to be distinguishable through the mean force moment tensor. In contrast, geometrical descriptors, such as radial distribution functions, bond order parameters, and Voronoi cell distributions, can hardly discriminate among these states. We find that small-order loops of contacts-the polygons of the network-are especially sensitive probes for the contact structure. PMID:23496501

Arvalo, Roberto; Pugnaloni, Luis A; Zuriguel, Iker; Maza, Diego

2013-02-01

364

Shear thickening in highly viscous granular suspensions  

NASA Astrophysics Data System (ADS)

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.

Xu, Qin; Majumdar, Sayantan; Brown, Eric; Jaeger, Heinrich M.

2014-09-01

365

Starting to move through a granular medium  

SciTech Connect

We explore the process of initiating motion through a granular medium by measuring the force required to push a flat circular plate upward from underneath the medium. In contrast to previous measurements of the drag and penetration forces, which were conducted during steady state motion, the initiation force has a robust dependence on the diameter of the grains forming the pile. We attribute this dependence to the requirement for local dilation of the grains around the circumference of the plate, as evidenced by an observed linear dependence of the initiation force on the plate diameter.

Costantino, D. J. [Pennsylvania State University; Scheidemantel, T. [Pennsylvania State University; Stone, Matthew B [ORNL; Conger, C. [Pennsylvania State University; Klein, K. [Pennsylvania State University; Lohr, M. [Pennsylvania State University; Modig, Z. [Pennsylvania State University; Schiffer, P. [Pennsylvania State University

2008-01-01

366

DEM simulation of experimental dense granular packing  

SciTech Connect

In this study we present numerical analysis performed on the experimental results of sphere packings of mono-sized hard sphere whose packing fraction spans across a wide range of 0.59<{Phi}<0.72. Using X-ray Computed Tomography (XCT), we have full access to the 3D structure of the granular packings. Numerical analysis performed on thr data provides the first experimental proofs of how densification affects local order parameters. Furthermore by combining Discrete Element Method (DEM) and the experimental results from XCT, we investigate how the intergranular forces change with the onset of crystallization.

Hanifpour, Maryam; Allaei, Mehdi Vaez [Department of Physics, University of Tehran, Tehran (Iran, Islamic Republic of); Francois, Nicolas; Saadatfar, Mohammad [Department of Applied Mathematics, Research School of Physics and Engineering, Australian National University, Canberra (Australia)

2013-06-18

367

Granular jamming transitions for a robotic mechanism  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

368

Interstitial gas effect on vibrated granular columns  

NASA Astrophysics Data System (ADS)

Vibrated granular materials have been intensively used to investigate particle segregation, convection, and heaping. We report on the behavior of a column of heavy grains bouncing on an oscillating solid surface. Measurements indicate that, for weak effects of the interstitial gas, the temporal variations of the pressure at the base of the column are satisfactorily described by considering that the column, despite the observed dilation, behaves like a porous solid. In addition, direct observation of the column dynamics shows that the grains of the upper and lower surfaces are in free fall in the gravitational field and that the dilation is due to a small delay between their takeoff times.

Pastenes, Javier C.; Gminard, Jean-Christophe; Melo, Francisco

2014-06-01

369

Biological and robotic movement through granular media  

NASA Astrophysics Data System (ADS)

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

Goldman, Daniel

2008-03-01

370

Projectile interactions in granular impact cratering  

E-print Network

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.

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

2008-06-04

371

Gravity-driven dense granular flows  

SciTech Connect

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.

ERTAS,DENIZ; GREST,GARY S.; HALSEY,THOMAS C.; DEVINE,DOV; SILBERT,LEONARDO E.

2000-03-29

372

Dark Matter  

E-print Network

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.

Neta Bahcall

1996-11-11

373

1 Molecular Dynamics Simulations of Granular Materials One challenge of todays research is the realistic simulation of granular materials consisting  

E-print Network

1 Molecular Dynamics Simulations of Granular Materials Summary One challenge of todays research, the molecular dynamics method for the simulation of many-particle systems is briefly introduced and some transition. #12;2 1 Molecular Dynamics Simulations of Granular Materials In the following, two versions

Luding, Stefan

374

Epimacular brachytherapy for wet AMD: current perspectives  

PubMed Central

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

Casaroli-Marano, Ricardo P; Alforja, Socorro; Giralt, Joan; Farah, Michel E

2014-01-01

375

Bianchi type VI1 cosmological model with wet dark fluid in scale invariant theory of gravitation  

E-print Network

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.

B. Mishra; P. K. Sahoo

2014-07-29

376

Detoxification of Phenolic Wastewaters by Catalytic Wet Oxidation in Batch and Continuous Mode  

Microsoft Academic Search

Catalytic wet oxidation of simulated olive oil wastewaters has been investigated in batch and trickle-bed reactors. The comparison between two operating reactor systems is presented querying the effect of temperature and pressure. The higher decontamination rates of organic matter were obtained in the batch reactor, which has promoted the complete mineralization of liquid pollutants after 60min at 200C and 30bar.

Rodrigo J. G. Lopes; Rosa M. Quinta-Ferreira

2010-01-01

377

Different Effects of Roughness (Granularity) and Hydrophobicity  

Microsoft Academic Search

With thanks to Stefan Doerr and Jorge Mataix-Solera for their invitation Superhydrophobicity is an interesting effect that appears to be simple on the outset; increased surface area from roughness increases interfacial area and therefore energy loss or gain. More extreme roughness prevents total wetting, resulting in gas pockets present at the surface and a drastic change in the properties of

Neil Shirtcliffe; Glen McHale; Christopher Hamlett; Michael Newton

2010-01-01

378

Wet powder seal for gas containment  

DOEpatents

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.

Stang, Louis G. (Sayville, NY)

1982-01-01

379

Wet powder seal for gas containment  

SciTech Connect

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.

Stang, L.G.

1982-01-19

380

Chimney liners for wet FGD service  

SciTech Connect

In order to meet pollution compliance requirements, many Utilities are adding wet scrubbers to reduce SO{sub 2} emissions. The gas temperatures produced by wet scrubbers also can lead to increased condensation of moisture on interior surfaces of chimney linings and ductwork. This increased condensation can, in turn, increase the risk of corrosion. To protect moist surfaces of chimney liners and ductwork from acid attack, new design and construction methods are required. Materials including high nickel, chrome and titanium alloys are being employed as well as modifications to the widely used acid resistant brick liners which have been conventionally used. This paper explores the experience of chimney manufacturers and builders to address the requirements of operation with wet scrubbers. This includes issues of liner velocities, liquid carryover, the use of new materials and construction techniques.

Sowizal, J. [Industrial Chimney Engineers, Ltd., Hawthorn Woods, IL (United States)

1998-12-31

381

Wet welding qualification trials at 35 MSW  

SciTech Connect

Wet welding is gaining increased attention and attraction for application on marine buildings and offshore structures all over the world because of its versatility, flexibility and mobility in combination with low investment costs. In a common research and development project between PETROBRAS/CENPES, Rio de Janeiro, Brazil and GKSS Research Centre, Geesthacht, Germany wet welding qualification trials have been performed in different water depths up to 35 msw. The tests have been performed with newly developed electrodes in two different wet welding procedures. The experiments have been carried out on SS- as well as on 5F-specimens acc. ANSI/AWS D 3.6-89. Results will be presented in respect to the performance of the two welding procedures especially with regard to the avoidance of hydrogen induced cold cracking and high hardness values.

Dos Santos, V.R.; Teixeira, C.J. [Petrobras/CENPES, Rio de Janeiro (Brazil); Szelagowski, P.J.F. [GKSS Research Center, Geesthacht (Germany)

1993-12-31

382

Hypersaline wet patches in Taylor Valley, Antarctica  

NASA Astrophysics Data System (ADS)

Spatially isolated patches of soil located in Taylor Valley, McMurdo Dry Valleys, Antarctica, are sites of elevated salt content and soil moisture. During Antarctic spring, in the absence of snow melt, visibly wet (reduced albedo) patches of soil are present at the surface. The soil pore fluids are hypersaline and have average water activity of 0.74 (the water activity of a solution determines the equilibrium vapor pressure of that solution), and are an order of magnitude more saline than average soils in the Dry Valleys. These salty soils are 3-5 times more water rich than average soils. Geochemical and meteorological analyses show that these wet patches are sites of direct vapor emplacement into soil pore fluids that may ultimately be sourced by the deliquescence of soil salts. These wet patches represent a non-precipitation, non-groundwater source for water into Antarctic permafrost.

Levy, Joseph S.; Fountain, Andrew G.; Welch, Kathy A.; Lyons, W. Berry

2012-03-01

383

Dynamic effective mass of granular media  

NASA Astrophysics Data System (ADS)

We report an experimental and theoretical investigation of the frequency-dependent effective mass, M(?), of loose granular particles which occupy a rigid cavity to a filling fraction of 48%, the remaining volume being air of differing humidities. We demonstrate that this is a sensitive and direct way to measure those properties of the granular medium that are the cause of the changes in acoustic properties of structures containing grain-filled cavities. Specifically, we apply this understanding to the case of the flexural resonances of a rectangular bar with a grain-filled cavity within it. The dominant features of M(?) are a sharp resonance and a broad background, which we analyze within the context of simple models. We find that: a) These systems may be understood in terms of a height-dependent and diameter-dependent effective sound speed (130 m/s) and an effective viscosity (2x10^4 Poise). b) There is a dynamic Janssen effect in the sense that, at any frequency, and depending on the method of sample preparation, approximately one-half of the effective mass is borne by the side walls of the cavity and one-half by the bottom. c) On a fundamental level, dissipation is dominated by adsorbed films of water at grain-grain contacts in our experiments.

Johnson, David; Ingale, Rohit; Valenza, John; Hsu, Chaur-Jian; Gland, Nicolas; Makse, Hernan

2009-03-01

384

Collisional model for granular impact dynamics  

NASA Astrophysics Data System (ADS)

When an intruder strikes a granular material from above, the grains exert a stopping force which decelerates and stops the intruder. Many previous studies have used a macroscopic force law, including a drag force which is quadratic in velocity, to characterize the decelerating force on the intruder. However, the microscopic origins of the force-law terms are still a subject of debate. Here, drawing from previous experiments with photoelastic particles, we present a model which describes the velocity-squared force in terms of repeated collisions with clusters of grains. From our high speed photoelastic data, we infer that "clusters" correspond to segments of the strong force network that are excited by the advancing intruder. The model predicts a scaling relation for the velocity-squared drag force that accounts for the intruder shape. Additionally, we show that the collisional model predicts an instability to rotations, which depends on the intruder shape. To test this model, we perform a comprehensive experimental study of the dynamics of two-dimensional granular impacts on beds of photoelastic disks, with different profiles for the leading edge of the intruder. We particularly focus on a simple and useful case for testing shape effects by using triangular-nosed intruders. We show that the collisional model effectively captures the dynamics of intruder deceleration and rotation; i.e., these two dynamical effects can be described as two different manifestations of the same grain-scale physical processes.

Clark, Abram H.; Petersen, Alec J.; Behringer, Robert P.

2014-01-01

385

Collisional model for granular impact dynamics.  

PubMed

When an intruder strikes a granular material from above, the grains exert a stopping force which decelerates and stops the intruder. Many previous studies have used a macroscopic force law, including a drag force which is quadratic in velocity, to characterize the decelerating force on the intruder. However, the microscopic origins of the force-law terms are still a subject of debate. Here, drawing from previous experiments with photoelastic particles, we present a model which describes the velocity-squared force in terms of repeated collisions with clusters of grains. From our high speed photoelastic data, we infer that "clusters" correspond to segments of the strong force network that are excited by the advancing intruder. The model predicts a scaling relation for the velocity-squared drag force that accounts for the intruder shape. Additionally, we show that the collisional model predicts an instability to rotations, which depends on the intruder shape. To test this model, we perform a comprehensive experimental study of the dynamics of two-dimensional granular impacts on beds of photoelastic disks, with different profiles for the leading edge of the intruder. We particularly focus on a simple and useful case for testing shape effects by using triangular-nosed intruders. We show that the collisional model effectively captures the dynamics of intruder deceleration and rotation; i.e., these two dynamical effects can be described as two different manifestations of the same grain-scale physical processes. PMID:24580216

Clark, Abram H; Petersen, Alec J; Behringer, Robert P

2014-01-01

386

Nonlocal modeling of granular flows down inclines.  

PubMed

Flows of granular media down a rough inclined plane demonstrate a number of nonlocal phenomena. We apply the recently proposed nonlocal granular fluidity model to this geometry and find that the model captures many of these effects. Utilizing the model's dynamical form, we obtain a formula for the critical stopping height of a layer of grains on an inclined surface. Using an existing parameter calibration for glass beads, the theoretical result compares quantitatively to existing experimental data for glass beads. This provides a stringent test of the model, whose previous validations focused on driven steady-flow problems. For layers thicker than the stopping height, the theoretical flow profiles display a thickness-dependent shape whose features are in agreement with previous discrete particle simulations. We also address the issue of the Froude number of the flows, which has been shown experimentally to collapse as a function of the ratio of layer thickness to stopping height. While the collapse is not obvious, two explanations emerge leading to a revisiting of the history of inertial rheology, which the nonlocal model references for its homogeneous flow response. PMID:25376561

Kamrin, Ken; Henann, David L

2014-12-01

387

Dynamics of random packings in granular flow.  

PubMed

We present a multiscale simulation algorithm for amorphous materials, which we illustrate and validate in a canonical case of dense granular flow. Our algorithm is based on the recently proposed spot model, where particles in a dense random packing undergo chainlike collective displacements in response to diffusing "spots" of influence, carrying a slight excess of interstitial free volume. We reconstruct the microscopic dynamics of particles from the "coarse grained" dynamics of spots by introducing a localized particle relaxation step after each spot-induced block displacement, simply to enforce packing constraints with a (fairly arbitrary) soft-core repulsion. To test the model, we study to what extent it can describe the dynamics of up to 135,000 frictional, viscoelastic spheres in granular drainage simulated by the discrete-element method (DEM). With only five fitting parameters (the radius, volume, diffusivity, drift velocity, and injection rate of spots), we find that the spot simulations are able to largely reproduce not only the mean flow and diffusion, but also some subtle statistics of the flowing packings, such as spatial velocity correlations and many-body structural correlations. The spot simulations run over 100 times faster than the DEM and demonstrate the possibility of multiscale modeling for amorphous materials, whenever a suitable model can be devised for the coarse-grained spot dynamics. PMID:16802932

Rycroft, Chris H; Bazant, Martin Z; Grest, Gary S; Landry, James W

2006-05-01

388

An Expression for the Granular Elastic Energy  

E-print Network

Granular Solid Hydrodynamics (GSH) is a broad-ranged continual mechanical description of granular media capable of accounting for static stress distributions, yield phenomena, propagation and damping of elastic waves, the critical state, shear band, and fast dense flow. An important input of GSH is an expression for the elastic energy needed to deform the grains. The original expression, though useful and simple, has some draw-backs. Therefore, a slightly more complicated expression is proposed here that eliminates three of them: (1) The maximal angle at which an inclined layer of grains remains stable is increased from $26^\\circ$ to the more realistic value of $30^\\circ$. (2)Depending on direction and polarization, transverse elastic waves are known to propagate at slightly different velocities. The old expression neglects these differences, the new one successfully reproduces them. (3) Most importantly, the old expression contains only the Drucker-Prager yield surface. The new one contains in addition those named after Coulomb, Lade-Duncan and Matsuoka-Nakai -- realizing each, and interpolating between them, by shifting a single scalar parameter.

Yimin Jiang; Hepeng Zheng; Zheng Peng; Liping Fu; Shixiong Song; Qicheng Sun; Michael Mayer; Mario Liu

2012-06-13

389

Force Chains in a Granular Piston  

NASA Astrophysics Data System (ADS)

We present experimental studies of force distributions and PIV analysis of granular particles driven by a 2D piston.(E. Kolb, et. al. Europhys. J. B). 8, 483-491 (1999). The particles, ~ 1/2 cm photoelastic disks, are confined by rigid sidewalls while being pushed against gravity with a piston whose speed is 10-100 ? m/s. The piston is confined to vertical motion by linear bearings but does not otherwise touch the sidewalls. Friction prevents the free rotation and displacement of particles within the bulk of the material and leads to the buildup of stress chains resisting motion. Photoelasticity of the particles allows us to visualize the local stress by observing the experiment through circular polarizers. We describe the buildup and relaxation of global stress in the system, and explain overshoots in the data as the orientation of stress chains changes from largely vertical to largely horizontal, and vice-versa. Pressure profiles as a function of depth are nearly hydrostatic before the piston is raised, but show many peaks and bumps when the piston is set into motion. Lastly, particle tracking gives quantitative information on dilation of the granular layer along the sidewalls when the piston is in motion.

Hartley, R. R.; Behringer, R. P.; Kolb, E.; Ovarlez, G.; Clment, E.

2000-11-01

390

Impulse dispersion of a tapered granular chain  

NASA Astrophysics Data System (ADS)

The capability of a tapered granular chain to absorb and attenuate acoustic impulses is being studied. The theory of the shock absorption of tapered chains is attributed to Sen[1]. An experimental apparatus has been fabricated at NASA Glenn Research Center to test this concept. The apparatus consists of a chain of chrome steel ball particles with a shrinkage factor of 5 shrinkage factor), resting on a steel rail with near mirror surface finish. The actual force of the impulse is measured using a dynamic response load cell which is interfaced through a high resolution data acquisition system. The impact is imparted by a striker brass ball set into motion by a plunger/solenoid mechanism. The experiment has provided quantitative data on the absorption potential of the granular tapered chain. Significant attenuation was achieved with different chain lengths and the dispersion of the wave was also clearly seen from the data. 1. Sen, S.;Manciu, F.S.;Manciu, M., "Themalizing an Impulse," Phys A Stat Mech Appl., v 299, n 3-4, Oct 15 , 2001, p 551-558.

Nakagawa, Masami; Agui, Juan H.; Sen, Surajit; Wu, David

2002-03-01

391

Mechanic of Granular Materials (MGM) Investigator  

NASA Technical Reports Server (NTRS)

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).

2000-01-01

392

Mechanics of Granular Materials labeled hardware  

NASA Technical Reports Server (NTRS)

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).

2000-01-01

393

Machanics of Granular Materials (MGM) Investigator  

NASA Technical Reports Server (NTRS)

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).

2000-01-01

394

Mechanics of Granular Materials (MGM) Investigators  

NASA Technical Reports Server (NTRS)

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).

2000-01-01

395

Wet air oxidation of propellant wastewaters  

SciTech Connect

Wet Air Oxidation studies have been conducted on a number of propellant wastewaters, to assess destruction levels of specific propellant components. OTTO fuel, used as a torpedo propellant, and hydrazine based rocket fuels were propellants of interest. OTTO fuel wastewaters contain substantial amounts of propylene glycol dinitrate. Hydrazine based rocket fuel wastewaters contain hydrazine and unsymmetrical dimethyl hydrazine. Laboratory Wet Air Oxidation studies on OTTO fuel wastewaters indicated that a 99+ percent destruction of propylene glycol dinitrate can be achieved at an oxidation temperature of 280/sup 0/C.

Randall, T.L.; Copa, W.M.; Deitrich, M.J.

1985-01-01

396

Enhanced selection of micro-aerobic pentachlorophenol degrading granular sludge.  

PubMed

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

Lv, Yuancai; Chen, Yuancai; Song, Wenzhe; Hu, Yongyou

2014-09-15

397

Wettability alteration by trimeric cationic surfactant at water-wet/oil-wet mica mineral surfaces  

NASA Astrophysics Data System (ADS)

The wettability of oil reservoir rock affects the efficiency of the oil recovery process by reducing the capillary force. Methyldodecylbis [2-(dimethyldodecylammonio) ethyl] ammonium tribromide is a trimeric cationic surfactant that contains three dodecyl chains and three quaternary ammonium head groups connected by divinyl groups. The surfactant was synthesized, purified and used as a new wetting alteration agent. This paper focuses on the ability of this trimeric cationic surfactant to alter the wettability of water-wet and oil-wet mica mineral surfaces. The contact angle data of the solid-liquid interface in oil/water/solid three-phase system show that the trimeric cationic surfactant, when compared with single- and double-chain cationic surfactant, is a more effective wetting agent for water-wet and oil-wet mica surfaces at lower concentration. Measurements by atomic force microscopy (AFM) show that the surfactant molecules have formed a monolayer to reverse the wetting properties. On the water-wet surface, the surface is suffused with negative charge, which could attract the cationic head of surfactant, and leave the hydrophobic tails exposed. In contrast, on the oil-wet surface, the hydrophobic tails were attracted by hydrophobic interactions to the oil film between the surfactant and the crude oil. The hydrophilic heads were left outside to form a hydrophilic layer, which could explain the wettable to hydrophilic trend. Alteration to the degree of wettability is mainly dependent on the adsorption areas of the surfactant. The data show that the ability of the trimeric cationic surfactant affect the wettability is independent of surface tension.

Zhang, Rui; Qin, Ni; Peng, Lin; Tang, Ke; Ye, Zhongbin

2012-08-01

398

Discrete blasts in granular material yield two-stage process of cavitation and granular fountaining  

NASA Astrophysics Data System (ADS)

A discrete blast within granular material, such as a single subterranean explosion within a debris-filled diatreme structure, is typically considered to produce a single uprush of material. Our experiments demonstrate that apparent "debris jet deposits" can be formed by a two-stage process of cavitation and subsequent granular fountaining. Bench-scale experiments reported here demonstrate that for a range of overpressures and depths, individual, discrete, buried gas blasts open space and expel particles from the blast site in two largely decoupled stages. Expanding gas initially pierces material nearest the blast source to open a cavity above it; then a fountain of grains rises from the source into the cavity. This staged motion dynamically segregates source grains from host-material grains, and the rates of cavity opening vs. fountain rise show a power-law decay relationship with initial pressure. Our experimental analysis has implications for maar-diatreme systems, field-scale detonation experiments, and underground nuclear testing.

Andrews, Robin; White, James; Drig, Tobi; Zimanowski, Bernd

2014-05-01

399

Discrete blasts in granular material yield two-stage process of cavitation and granular fountaining  

NASA Astrophysics Data System (ADS)

discrete blast within granular material, such as a single subterranean explosion within a debris-filled diatreme structure, is typically considered to produce a single uprush of material. Our experiments demonstrate that apparent "debris jet deposits" can be formed by a two-stage process of cavitation and subsequent granular fountaining. Bench-scale experiments reported here demonstrate that for a range of overpressures and depths, individual, discrete, buried gas blasts open space and expel particles from the blast site in two largely decoupled stages. Expanding gas initially pierces material nearest the blast source to open a cavity above it; then a fountain of grains rises from the source into the cavity. This staged motion dynamically segregates source grains from host-material grains, and the rates of cavity opening versus fountain rise show a power law decay relationship with initial pressure. Our experimental analysis has implications for maar-diatreme systems, field-scale detonation experiments, and underground nuclear testing.

Andrews, Robin G.; White, James D. L.; Drig, Tobi; Zimanowski, Bernd

2014-01-01

400

Conductivity of granular superconductors in a strong magnetic field  

NASA Astrophysics Data System (ADS)

We suggest a theory of the negative magnetoresistance in a metallic granular superconductors. Calculations are performed in a strong magnetic field when the superconducting gap inside the grains is already destroyed by orbital mechanism. We found that even without including the effects of weak localization the conductivity of granular system strongly decreases due to reduction of the density of states by superconducting fluctuations. At the same time, it is shown that Aslamazov-Larkin and Maki-Thompson corrections vanish at very low temperaturs. Our results can explain the unusual experimental behaviour of the resistivity of granular system in a strong magnetic field.

Beloborodov, I. S.; Efetov, K. B.

1999-11-01

401

Granular impact dynamics: Fluctuations at short time-scales  

NASA Astrophysics Data System (ADS)

Several recent studies on granular impact have used a macroscopic force law which describes the slow (mean) dynamics. However, these force-law models must be modified to capture large fluctuations at short time-scales. Here, we discuss granular impact experiments using photoelastic particles, where high-speed video captures both the intruder dynamics and the local granular force response. We show how to systematically separate the fluctuations from the mean dynamics. We also show that these fluctuations are multiplicative with the mean force, and otherwise decoupled from the dynamics. These observations are instructive in connecting to microscopic processes which generate the fluctuations.

Clark, Abram H.; Kondic, Lou; Behringer, R. P.

2013-06-01

402

The Nature of Stresses in a Giant Static Granular Column  

NASA Astrophysics Data System (ADS)

We systematically investigate the mean pressure measurements at the bottom of a giant static granular column. If a constant overload is placed on top of the bed, the pressure observed displays linearity in overload and nonmonotonic in column height. This result is in contradiction with the classical Janssen model. However it is in good agreement with the oriented stress linearity (OSL) model which reveals a local, linear relation between stress components. We conclude that the OSL model works well not only in a tiny static granular column but also in a giant static granular column.

Ge, Bao-Liang; Shi, Qing-Fan; Ram, Chand; He, Jian-Feng; Ma, Shao-Peng

2013-04-01

403

Dynamics of electrostatically-driven granular media. Effects of Humidity  

E-print Network

We performed experimental studies of the effect of humidity on the dynamics of electrostatically-driven granular materials. Both conducting and dielectric particles undergo a phase transition from an immobile state (granular solid) to a fluidized state (granular gas) with increasing applied field. Spontaneous precipitation of solid clusters from the gas phase occurs as the external driving is decreased. The clustering dynamics in conducting particles is primarily controlled by screening of the electric field but is aided by cohesion due to humidity. It is shown that humidity effects dominate the clustering process with dielectric particles.

D. W. Howell; I. S. Aranson; G. W. Crabtree

2000-11-03

404

Impact dynamics of granular jets with noncircular cross sections  

NASA Astrophysics Data System (ADS)

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.

Cheng, Xiang; Gordillo, Leonardo; Zhang, Wendy W.; Jaeger, Heinrich M.; Nagel, Sidney R.

2014-04-01

405

Granular Cell Tumor Presenting as a Large Leg Mass  

PubMed Central

Granular cell tumor is a rare benign neoplasm most commonly appears in the head and neck region, especially in the tongue, cheek mucosa, and palate. Occurrence in limbs is even rarer. These tumors account for approximately 0.5% of all soft tissue tumors. Granular cell tumor can also affect other organs including skin, breast, and lungs. Local recurrence and metastasis is potentially higher in malignant forms with poor prognosis in respect to the benign counterparts. The average diameter of the tumor is usually about 2-3 cm. We report a granular cell tumor in the leg with an unusual size.

Andalib, Ali; Heidary, Mohsen; Sajadieh-Khajouei, Sahar

2014-01-01

406

Hydrodynamic modeling of granular flows in a modified Couette cell  

E-print Network

We present simulations of granular flows in a modified Couette cell, using a continuum model recently proposed for dense granular flows. Based on a friction coefficient, which depends on an inertial number, the model captures the positions of the wide shear bands. We show that a smooth transition in velocity-profile shape occurs when increasing the height of the granular material, leading to a differential rotation of the central part close to the surface. The numerical predictions are in qualitative agreement with previous experimental results. The model provides predictions for the increase of the shear bands width when increasing the rotation rate.

Pierre Jop

2007-12-19

407

Perturbed Quantization Steganography with Wet Paper Codes  

E-print Network

Perturbed Quantization Steganography with Wet Paper Codes Jessica Fridrich SUNY Binghamton.edu ABSTRACT In this paper, we introduce a new approach to passive-warden steganography in which the sender, security, steganalysis, steganography 1. MOTIVATION The primary goal of steganography is to build

Fridrich, Jessica

408

Silver Management for Wet Chemistry Photo Processing  

E-print Network

Silver Management for Wet Chemistry Photo Processing Procedure: 8.44 Created: 9/25/2013 Version: 1 silver recovery units in processing the wastewater effluent generated in the processing of films and use "scrap film" collection containers for capturing silver-containing solid waste. All dark rooms and image

Jia, Songtao

409

ESTIMATING URBAN WET WEATHER POLLUTANT LOADING  

EPA Science Inventory

This paper presents procedures for estimating pollutant loads emanating from wet-weather flow discharge in urban watersheds. Equations are presented for: annual volume of litter and floatables; the quantity of sand from highway runoff; the quantity of dust-and-dirt accumulation ...

410

Amoco Trinidad selects wet welding repair option  

SciTech Connect

A recent underwater inspection of Amoco Trinidad Oil Company`s Samaan A Production platform revealed a separated horizontal brace at a water depth of 125 feet (38.1 m). A closer inspection showed that the 16 in (.4 m) diameter horizontal brace had completely separated from the Leg on the member side. A drilling program scheduled to commence from the Samaan A platform was to begin in about two months. A fast track analysis of the structure and a subsequent repair plan was immediately organized. A computer aided structural analysis was completed for the structure with the horizontal brace removed. Structural engineers decided that the brace must be reinstalled before being loaded with a drilling unit. A clamped brace repair assembly was not practical due to a multi member node at one of the legs. Wet welding was selected over dry hyperbaric welding as the best, safest, most cost effective and quickest option. A wet welding procedure and welder divers were qualified at depth according to AWS D3.6. A repair assembly was designed and fabricated. Personnel, wet welding equipment and the fabrication were shipped by air from New Iberia, LA to Galeota Point, Trinidad. This is the first time that wet welding techniques were employed for structural repairs directly to the leg of an offshore structure at any Amoco location.

Ibarra, S.J. [Amoco Corp., Naperville, IL (United States); Reynolds, T.J. [Global Divers and Contractors, Inc., New Iberia, LA (United States); Gabriel, V. [Amoco Trinidad Oil Co., Port of Spain (Trinidad and Tobago); Haymaker, G.A. [Amoco Corp., Houston, TX (United States)

1996-12-01

411

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.

2014-07-30

412

Wetting and lubricating film instabilities in microchannels  

E-print Network

Wetting and lubricating film instabilities in microchannels Thomas Cubaud Department of Mechanical in a planar micro- channel. Upstream, a steady viscous­core-annular flow is produced in a square microchannel1 and surrounding liquid enter the slit microchannel, the thread enlarges and directly contacts the top and bottom

Cubaud, Thomas

413

Diffusive foam wetting process in microgravity  

E-print Network

We report the experimental study of aqueous foam wetting in microgravity. The liquid fraction $\\ell$ along the bubble edges is measured and is found to be a relevant dynamical parameter during the capillary process. The penetration of the liquid in the foam, the foam inflation, and the rigidity loss are shown all to obey strict diffusion processes.

H. Caps; M. -L. Chevalier; H. Decauwer; G. Soyez; M. Ausloos; N. Vandewalle

2001-08-23

414

MULTI-POLLUTANT WET SCRUBBER TECHNOLOGY  

EPA Science Inventory

Implementation of fine PM standards, EPA's Clean Air Interstate Rule, and Clean Air Mercury Rule are leading to a focus on future reductions of nitrogen oxides (NOx), sulfur dioxide (SO2), and mercury emissions from power plants. Wet scrubber-based technologies are capable of pro...

415

WET/DRY COOLING TOWER TEST MODULE  

EPA Science Inventory

The report gives results of an evaluation of the engineering performance of a single-cell wet/dry cooling tower (about 25 MW) in an 18-month field test at San Bernardino, CA. Test objectives included determination of the water conservation and operating characteristics, and verif...

416

Granular coarsening: phase space and evolution analogies.  

PubMed

Various aspects of axial banding of size-varying bidisperse granular mixtures in cylindrical tumblers have been documented repeatedly over a decade or so, but the dependence of surface band formation on the relative concentration of particles and rotation rate has not been thoroughly examined. Coarsening patterns analogous to nucleation and spinodal decomposition occur as the relative concentration of small and large particles and the rotation rate of the tumbler are varied. A phase diagram with a portion analogous to a miscibility gap can be constructed from the space-time plots. A dynamic scaling approach similar to that for reacting lamellae can be applied to the coarsening patterns as a result of large bands growing at the expense of neighboring smaller bands. PMID:20365416

Juarez, Gabriel; Lueptow, Richard M; Ottino, Julio M

2010-01-01

417

Yield loci for an anisotropic granular assembly.  

PubMed

Yield loci of a granular material are derived in case of triaxial compression carried out at constant pressure. The theory is based upon a simple micromechanical model in which particles move according to an average, homogeneous deformation. We show how the presence of an inherent anisotropy in the aggregate (typical of laboratory samples due to depositional processes) produces a deviation of the yield loci in the stress space from the expected Mohr-Coulomb prediction. That is, when the compaction pressure in an anisotropic aggregate is increased, irreversibility associated with sliding between particles occurs and this will influence the yield function in the subsequent triaxial test. Numerical simulations support the theoretical result. PMID:23214582

La Ragione, Luigi; Oger, Luc

2012-10-01

418

Dense annular flows of granular media  

NASA Astrophysics Data System (ADS)

Dense granular flows constitute an important topic for geophysics and process engineering. To describe them, a rheology based on the coaxiality between the stress and strain tensors with a Mohr-Coulomb yield criterion has been proposed. We propose here an analytic study of flows in an annular cell, with this rheology. This geometry is relevant for a series of powder rheometers or mixing devices, but the discussion is focused on the split-bottom geometry, for which the internal flow has been investigated by NMR technique. In this case, the full resolution of the velocity and stress fields allow to localize the shear deformations. The theoretical results obtained for the latter are compared with the torque measurements by Dijksman et al. [Phys. Rev. E, 82 (2010) 060301].

de Ryck, Alain; Louisnard, Olivier

2013-06-01

419

Granular discharge rate for submerged hoppers  

E-print Network

The discharge of spherical grains from a hole in the bottom of a right circular cylinder is measured with the entire system underwater. We find that the discharge rate depends on filling height, in contrast to the well-known case of dry non-cohesive grains. It is further surprising that the rate increases up to about twenty five percent, as the hopper empties and the granular pressure head decreases. For deep filling, where the discharge rate is constant, we measure the behavior as a function of both grain and hole diameters. The discharge rate scale is set by the product of hole area and the terminal falling speed of isolated grains. But there is a small-hole cutoff of about two and half grain diameters, which is larger than the analogous cutoff in the Beverloo equation for dry grains.

T. J. Wilson; C. R. Pfeifer; N. Mesyngier; D. J. Durian

2014-10-28

420

Lightweight robot locomotion on granular media  

NASA Astrophysics Data System (ADS)

We present an experimental and computer simulation study of a small, light-weight, biologically inspired robot running on a model granular medium (GM), 3 mm diameter glass particles. The six-legged RoACH robot (10 cm long, 25 grams) utilizes an alternating tripod gait to run at speeds up to 25 cm/sec. Forward speed increases with increasing limb frequency 0

Zhang, Tingnan; Qian, Feifei; Shen, Jeffrey; Li, Chen; Hoover, Aaron; Birkmeyer, Paul; Fearing, Ronald; Goldman, Daniel

2011-11-01

421

NMRI Measurements of Flow of Granular Mixtures  

NASA Technical Reports Server (NTRS)

We investigate complex 3D behavior of granular mixtures in shaking and shearing devices. NMRI can non-invasively measure concentration, velocity, and velocity fluctuations of flows of suitable particles. We investigate origins of wall-shear induced convection flow of single component particles by measuring the flow and fluctuating motion of particles near rough boundaries. We also investigate if a mixture of different size particles segregate into their own species under the influence of external shaking and shearing disturbances. These non-invasive measurements will reveal true nature of convecting flow properties and wall disturbance. For experiments in a reduced gravity environment, we will design a light weight NMR imager. The proof of principle development will prepare for the construction of a complete spaceborne system to perform experiments in space.

Nakagawa, Masami; Waggoner, R. Allen; Fukushima, Eiichi

1996-01-01

422

High-Speed Granular Chute Flows  

NASA Astrophysics Data System (ADS)

Nearly all granular flow models have a maximum value for the friction and therefore predict that flows on steep slopes will accelerate at a constant rate until the interaction with the ambient fluid becomes important. This prediction has not been tested by previous work, which has focused on relatively low slope angles where steady, fully developed flows occur after short distances. We report on experiments where we investigating flows over a much greater range of slope angles 30-50 degrees and flow depths 4-130 particle diameters with up to 20kg/s of sand flowing steadily. The data suggests that friction can be much larger than the mu(I) rheology or kinetic theories predict and suggest and that there may be constant velocity states above the angle of vanishing hstop.

McElwaine, Jim

2014-05-01

423

Decorated, Tapered, and Highly Nonlinear Granular Chain  

NASA Astrophysics Data System (ADS)

It has been seen that inertial mismatches in 1D granular chains lead to remarkable energy absorption which increases with the number of spheres, N, and tapering, q. Short chains, however, are limited in that regard, and we therefore present one solution which greatly improves performance for any size chain. These strongly nonlinear and scalable systems feature surprisingly complicated dynamics and are inadequately represented by a hard-sphere approximation. Additionally, such systems have shock absorption capacities that vary as a function of position along the chain. In this Letter, we present results in the form of normalized kinetic energy diagrams to illustrate the impressive mitigation capability of both original and improved tapered chains.

Doney, Robert; Sen, Surajit

2006-10-01

424

Breathing Phenomena in Driven, Confined, Granular Chains  

NASA Astrophysics Data System (ADS)

We consider a tapered granular alignment where the spherical grains progressively shrink in radius by a factor q. The system has a hard wall at one end and a piston at the other. We assume that the piston can be used to impart a force F (time- dependent or otherwise) to an edge grain in the system. Extensive particle dynamics simulations and theoretical analysis reveal that such a system could revert back and forth between an oversqueezed state and a dilated state - i.e., ``breathe." The breathing is strongly dependent on the driving. When driven with a constant force, we show that TF^ 1/6 is a constant for fixed q. More complex dynamics including nonlinear-resonance is observed when F=F(t). The talk shall discuss the observed dynamical responses of the system.

Simion, Robert; Sokolow, Adam; Sen, Surajit

2008-03-01

425

Crossover transition in flowing granular chains  

NASA Astrophysics Data System (ADS)

We report on the dynamical and statistical behavior of flowing collections of granular chains confined two-dimensionally (2D) within a rotating tumbler. Experiments are conducted with systems of chains of fixed length, but various lengths are considered. The dynamics are punctuated by cascades of chains along a free-surface cascades, which drive the development of mixed porous/laminar packing arrangements in bulk. We investigate the conformation of the system, as characterized by the porosity of the flow region occupied by the chains and the mean-square end-to-end distance of the chains during flow. Both of these measures show crossover transitions from a 2D self-avoiding walk to a 2D random walk when the chain length becomes long enough to allow self-contact.

Ulrich, Xialing; Fried, Eliot; Shen, Amy Q.

2009-09-01

426

Crossover transition in flowing granular chains.  

PubMed

We report on the dynamical and statistical behavior of flowing collections of granular chains confined two-dimensionally (2D) within a rotating tumbler. Experiments are conducted with systems of chains of fixed length, but various lengths are considered. The dynamics are punctuated by cascades of chains along a free-surface cascades, which drive the development of mixed porous/laminar packing arrangements in bulk. We investigate the conformation of the system, as characterized by the porosity of the flow region occupied by the chains and the mean-square end-to-end distance of the chains during flow. Both of these measures show crossover transitions from a 2D self-avoiding walk to a 2D random walk when the chain length becomes long enough to allow self-contact. PMID:19905048

Ulrich, Xialing; Fried, Eliot; Shen, Amy Q

2009-09-01

427

Clustering and segregation in driven granular fluids.  

PubMed

In microgravity, the successive inelastic collisions in a granular gas can lead to a dynamical clustering of the particles. This transition depends on the filling fraction of the system, the restitution of the used materials and on the size of the particles. We report simulations of driven bi-disperse gas made of small and large spheres. The size as well as the mass difference imply a strong modification in the kinematic chain of collisions and therefore alter significantly the formation of a cluster. Moreover, the different dynamical behaviors can also lead to a demixing of the system, adding a few small particles in a gas of large ones can lead to a partial clustering of the taller type. We realized a detailed phase diagram recovering the encountered regimes and developed a theoretical model predicting the possibility of dynamical clustering in binary systems. PMID:25412823

Opsomer, E; Vandewalle, N; Noirhomme, M; Ludewig, F

2014-11-01

428

Granular acoustic switches and logic elements.  

PubMed

Electrical flow control devices are fundamental components in electrical appliances and computers; similarly, optical switches are essential in a number of communication, computation and quantum information-processing applications. An acoustic counterpart would use an acoustic (mechanical) signal to control the mechanical energy flow through a solid material. Although earlier research has demonstrated acoustic diodes or circulators, no acoustic switches with wide operational frequency ranges and controllability have been realized. Here we propose and demonstrate an acoustic switch based on a driven chain of spherical particles with a nonlinear contact force. We experimentally and numerically verify that this switching mechanism stems from a combination of nonlinearity and bandgap effects. We also realize the OR and AND acoustic logic elements by exploiting the nonlinear dynamical effects of the granular chain. We anticipate these results to enable the creation of novel acoustic devices for the control of mechanical energy flow in high-performance ultrasonic devices. PMID:25354587

Li, Feng; Anzel, Paul; Yang, Jinkyu; Kevrekidis, Panayotis G; Daraio, Chiara

2014-01-01

429

Frictional granular mechanics: A variational approach  

SciTech Connect

The mechanical properties of a cohesionless granular material are evaluated from grain-scale simulations. Intergranular interactions, including friction and sliding, are modeled by a set of contact rules based on the theories of Hertz, Mindlin, and Deresiewicz. A computer generated, three-dimensional, irregular pack of spherical grains is loaded by incremental displacement of its boundaries. Deformation is described by a sequence of static equilibrium configurations of the pack. A variational approach is employed to find the equilibrium configurations by minimizing the total work against the intergranular loads. Effective elastic moduli are evaluated from the intergranular forces and the deformation of the pack. Good agreement between the computed and measured moduli, achieved with no adjustment of material parameters, establishes the physical soundness of the proposed model.

Holtzman, R.; Silin, D.B.; Patzek, T.W.

2009-10-16

430

Flexural fracturing of a cohesive granular layer  

NASA Astrophysics Data System (ADS)

We report on the fracturing of cohesive granular materials subjected to a flexural deformation. A thin layer of glass beads or of flour is deposited on an unstretchable membrane to which flexion is imposed. We observe the formation of a periodic fracturing pattern whose characteristics are discussed in comparison with results previously obtained for an in-plane stretching [Alarcon, Ramos, Vanel, Vittoz, Melo, and Gminard, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.208001 105, 208001 (2010)]. In particular, at a given relative humidity, the wavelength is observed to depend linearly on the layer thickness but to be independent of the grain size, although the smallest grains are clearly more cohesive.

Gminard, Jean-Christophe; Champougny, Lorne; Lidon, Pierre; Melo, Francisco

2012-01-01

431

Thermal conductivity of a granular metal.  

PubMed

Using the Kubo formula approach, we study the effect of electron interaction on thermal transport in the vicinity of a metal-insulator transition, with a granular metal as our model. For small values of dimensionless intergrain tunneling conductance, g<1, we find that the thermal conductivity surprisingly shows a phononlike algebraic decrease, kappa(T) approximately g2T3/E2c even though the electrical conductivity obeys an Arrhenius law, sigma(T) approximately ge-Ec/T ; therefore the Wiedemann-Franz (WF) law is seriously violated. We explicitly show that this violation arises from nonmagnetic bosonic excitations of low energy that transport heat but not charge. At large values of intergrain tunneling, we find it plausible that the WF law weakly deviates from the free-electron theory due to potential fluctuations. Implications for experiment are discussed. PMID:16486870

Tripathi, V; Loh, Y L

2006-02-01

432

Granular cell leiomyosarcoma of the skin  

SciTech Connect

A case is presented of a multifocal malignant neoplasm involving the skin of the upper back in a 10-year-old boy following radiation therapy to the head and neck for a cerebellar medulloblastoma. Histologically, the neoplastic cells were remarkable for the presence of abundant periodic acid-Schiff (PAS)-positive diastase-resistant intracytoplasmic eosinophilic granules. Immunoperoxidase procedures revealed strong positive staining of the tumor cells with desmin, vimentin, and smooth muscle myosin antibodies, and negative staining for myoglobin, S-100 protein and keratin, thus supporting a smooth muscle line of differentiation for this neoplasm. Electronmicroscopy demonstrated numerous intracytoplasmic autophagic vacuoles that corresponded to the granules observed under the light microscope. Leiomyosarcoma should be entertained in the differential diagnosis of poorly differentiated cutaneous neoplasms histologically characterized by a proliferation of cells containing abundant granular eosinophilic cytoplasm.

Suster, S.; Rosen, L.B.; Sanchez, J.L.

1988-06-01

433

Traffic jams, granular flow, and soliton selection  

SciTech Connect

The flow of traffic on a long section of road without entrances or exits can be modeled by continuum equations similar to those describing fluid flow. In a certain range of traffic density, steady flow becomes unstable against the growth of a cluster, or ``phantom`` traffic jam, which moves at a slower speed than the otherwise homogeneous flow. We show that near the onset of this instability, traffic flow is described by a perturbed Korteweg--de Vries (KdV) equation. The traffic jam can be identified with a soliton solution of the KdV equation. The perturbation terms select a unique member of the continuous family of KdV solitons. These results may also apply to the dynamics of granular relaxation.

Kurtze, D.A. [Department of Physics, North Dakota State University, Fargo, North Dakota 58105-5566 (United States)] [Department of Physics, North Dakota State University, Fargo, North Dakota 58105-5566 (United States); Hong, D.C. [Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)] [Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)

1995-07-01

434

Shape of impact craters in granular media.  

PubMed

We present the results of experiments studying the shape of craters formed by the normal impact of a solid spherical projectile into a deep noncohesive granular bed at low energies. The resultant impact crater surfaces are accurately digitized using laser profilometry, allowing for the detailed investigation of the crater shape. We find that these impact craters are very nearly hyperbolic in profile. Crater radii and depths are dependent on impact energy, as well as the projectile density and size. The precise crater shape is a function of the crater aspect ratio. While the dimensions of the crater are highly dependent on the impact energy, we show that the energy required to excavate the crater is only a tiny fraction (0.1%-0.5%) of the kinetic energy of the projectile. PMID:17994980

de Vet, Simon J; de Bruyn, John R

2007-10-01

435

Experimental characterization of vibrated granular rings  

NASA Astrophysics Data System (ADS)

We report an experimental study of the statistical properties of vibrated granular rings. In this system, a linked rod and bead metallic chain in the form of a ring is collisionally excited by a vertically oscillating plate. The dynamics are driven primarily by inelastic bead-plate collisions and are simultaneously constrained by the rings' physical connectedness. By imaging many instances of the ring configurations, we measure the ensemble averages and distributions of several physical characteristics on the scale of individual beads and composite ring. We study local properties such as inter-bead separation and inter-bonds angles, and global properties such as the radius of gyration and center-of-mass motion. We characterize scaling with respect to the size of the chain.

Daya, Z. A.; Ben-Naim, E.; Ecke, R. E.

2006-09-01

436

Singular Energy Distributions in Granular Media  

NASA Astrophysics Data System (ADS)

We study the kinetic theory of driven and undriven granular gases, taking into account both translational and rotational degrees of freedom. We obtain the high-energy tail of the stationary bivariate energy distribution, depending on the total energy E and the ratio x=?Ew/E of rotational energy Ew to total energy. Extremely energetic particles have a unique and well-defined distribution f(x) which has several remarkable features: x is not uniformly distributed as in molecular gases; f(x) is not smooth but has multiple singularities. The latter behavior is sensitive to material properties such as the collision parameters, the moment of inertia and the collision rate. Interestingly, there are preferred ratios of rotational-to-total energy. In general, f(x) is strongly correlated with energy and the deviations from a uniform distribution grow with energy. We also solve for the energy distribution of freely cooling Maxwell Molecules and find qualitatively similar behavior.

Ben-Naim, Eli; Zippelius, Annette

2008-03-01

437

Laws of granular solids: Geometry and topology  

NASA Astrophysics Data System (ADS)

In a granular solid, mechanical equilibrium requires a delicate balance of forces at the disordered grain scale. To understand how macroscopic rigidity can emerge in this amorphous solid, it is crucial that we understand how Newtons laws pass from the disordered grain scale to the laboratory scale. In this work, we introduce an exact discrete calculus, in which Newtons laws appear as differential relations at the scale of a single grain. Using this calculus, we introduce gauge variables that describe identically force- and torque-balanced configurations. In a first, intrinsic formulation, we use the topology of the contact network, but not its geometry. In a second, extrinsic formulation, we introduce geometry with the Delaunay triangulation. These formulations show, with exact methods, how topology and geometry in a disordered medium are related by constraints. In particular, we derive Airys expression for a divergence-free, symmetric stress tensor in two and three dimensions.

Degiuli, Eric; McElwaine, Jim

2011-10-01

438

Sand transport, erosion and granular electrification  

NASA Astrophysics Data System (ADS)

The transport of granular materials by wind has a major impact on our environment through sand/soil erosion and the generation and transport of atmospheric dust aerosols. Terrestrially the transport of dust involves billions of tons of material every year, influencing the global climate and impacting directly upon human health. Research in aeolian transport involves the inter-related fields of fluid dynamics, granular materials and electrification/electrostatics which are in themselves diverse and complex. This review only touches upon this intricacy, but aims to overview the latest work which is expanding our current understanding and outline the areas of advancement needed in the future. Presentation is made of current models for wind driven detachment/entrainment and the transport rates of sand and dust, including the effects of contact induced grain electrification. This ubiquitous phenomenon can affect grain transport through the generation of intense electric fields and processes of electrostatic assembly. Importantly the transport of sand is characterized by saltation, which is known to be an active process for erosion and therefore a source for dust and sand formation. Using novel erosion simulation techniques the link between grain transport rates and erosion rates has been quantified. Furthermore this can be linked to production rates for dust and has been associated with chemical and mineral alteration through a process of mechanical activation of fractured surfaces. This work has implications for the evolution of all terrestrial-like planetary surfaces. Studies in non-terrestrial environments force researchers to be less empirical, ultimately leading to a deeper understanding of these processes.

Merrison, J. P.

2012-06-01

439

Stress, strain rate, and free volume in dense granular flow  

NASA Astrophysics Data System (ADS)

There have been many attempts to describe dense granular flow with continuum models, but a complete theory is still lacking. Often, these models make assumptions about microscopic quantities (such as shear stress, strain rate, and local density) and here we present Discrete Element Method (DEM) simulations to directly measure these in a variety of different non-homogeneous granular flows. Motivated by previous work, we compute these quantities on a mesoscopic length scale of several particle diameters, and examine both spatial distributions, and correlations between the variables. We investigate the validity of the commonly-used Mohr-Coulomb incipient yield hypothesis, which states that the ratio of shear stress to normal stress should be everywhere constant in a flowing granular material. Our results also show some striking correlations between strain rate and local density, which suggest a phase transition between static and flowing granular materials.

Rycroft, Chris; Kamrin, Ken; Bazant, Martin

2007-03-01

440

GRANULAR ACTIVATED CARBON ADSORPTION AND INFRARED REACTIVATION: A CASE STUDY  

EPA Science Inventory

A study evaluated the effectiveness and cost of removing trace organic contaminants and surrogates from drinking water by granular activated carbon (GAC) adsorption. The effect of multiple reactivations of spent GAC was also evaluated. Results indicated that reactivated GAC eff...

441

A Theory of Stochastic Plasticity in Dense Granular Flow  

NASA Astrophysics Data System (ADS)

There have been many attempts to derive continuum models for dense granular flow, but a general theory is still lacking, which can describe different flow conditions, such as gravity-driven silo drainage and forced shear cells. Here, we start with Mohr-Coulomb plasticity for quasi-2d granular materials to calculate stresses and slip planes, but we propose a simple ``stochastic flow rule'' to replace the principle of co-axiality in classical plasticity. This formulation takes into account two crucial features of granular materials -- discreteness and randomness at the scale of a continuum element -- via diffusing ``spots'' which cause chain-like cooperative particle displacements, as in recent simulations of silo drainage. We postulate that spots perform random walks along slip lines, biased by body forces (gravity) and local fluidization (switch from static to dynamic friction). Stochastic plasticity allows a natural description of dense granular flows in silos and shear cells within a single theory, rooted in classical mechanics.

Kamrin, Ken; Bazant, Martin

2006-03-01

442

On the Electrostatics of Pneumatic Conveying of Granular Materials  

E-print Network

In this work the electrostatics of the pneumatic conveying of granular materials in a non-conducting (PVC) vertical pipe is studied using Electrical Capacitance Tomography (ECT) system. The non-conducting wall in general ...

Zhu, Kewu

443

Drag coefficients on razor clams in slightly fluidized granular media  

E-print Network

Razor clams are able to burrow deeply into granular media with only a small fraction of force required by traditional anchoring devices. It is hypothesized that the collapse of their shell and subsequent localized fluidization ...

Becker, Christopher R. (Christopher Ryan)

2008-01-01

444

Small-amplitude acoustics in bulk granular media  

E-print Network

We propose and validate a three-dimensional continuum modeling approach that predicts small-amplitude acoustic behavior of dense-packed granular media. The model is obtained through a joint experimental and finite-element ...

Valenza, John J.

445

DISINFECTION OF BACTERIA ATTACHED TO GRANULAR ACTIVATED CARBON  

EPA Science Inventory

Heterotrophic plate count bacteria, coliform organisms, and pathogenic microorganisms attached to granular activated carbon (GAC) particles were examined for their susceptibility to chlorine disinfection. When these bacteria were grown on carbon particles and then disinfected wit...

446

Stick-slip motion in simulated granular layers Einat Aharonov  

E-print Network

Seismology: Theory and modeling; 3220 Mathematical Geophysics: Nonlinear dynamics; KEYWORDS: granular media. Friction is a measure of the resistance experienced by surfaces to sliding past each other. This resistance

Einat, Aharonov

447

Wave Energy Test Site (WETS) Marine Corps Base Hawaii (MCBH)  

E-print Network

Wave Energy Test Site (WETS) Marine Corps Base Hawaii (MCBH) Alexandra DeVisser, NAVFAC-EXWC Brian/ocean engineering. 2 #12;Commercial Sites: Deploy/Retrieve May to Sep Only WETS: Deploy/Retrieve Year Round 3 Why

448

INNOVATIVE URBAN WET-WEATHER FLOW MANAGEMENT SYSTEMS  

EPA Science Inventory

This report describes innovative methods to improve wet weather flow (WWF) management systems, that provide drainage services at the same time as decreasing stormwater pollutant discharges, for urban developments of the 21st century. Traditionally, wet-weather collection systems...

449

Fast Granular Analysis Based on Watershed in Microscopic Mineral Images  

Microsoft Academic Search

\\u000a The process detecting and measuring granule named granular analysis is very important in mineral analysis. Classical methods\\u000a for granular analysis are based on Matherons sieving method. However, these methods are not adequate for mineral microscope\\u000a image analysis. First, it is not an easy job to choose proper element structure for sieving process. Second, these traditional\\u000a methods cannot exactly locate the

Danping Zou; Desheng Hu; Qizhen Liu

2005-01-01

450

Novel experimental apparatus for granular experiments on basal friction  

NASA Astrophysics Data System (ADS)

We have designed a novel experimental apparatus to probe the mechanics of sheared quasi two-dimensional frictional granular materials with tunable friction from the supporting base of the apparatus. The experiment consists of a floating layer of photoelastic disks, which is subject to deformation. Forces on the particles are measured at the particle scale, using their photoelastic properties. This novel setup makes the study of the role of basal friction on sheared granular media possible.

Zheng, Hu; Dijksman, Joshua A.; Behringer, Robert P.

2013-06-01

451

Stress Transmission in a Multi-Phase Granular Packing  

Microsoft Academic Search

\\u000a We analyze stress transmission in granular media involving an interstitial cementing matrix of variable volume fraction. We\\u000a rely on a lattice-type discretization of both the particles and cemented matrix. We show that the stress chains are essentially\\u000a guided by the cementing matrix in tension and by the particulate backbone in compression. The signature of granular structure\\u000a appears clearly on the

Vincent Topin; Jean-Yves Delenne; Farhang Radja; Frdric Mabille

452

Granular cell tumour of the bronchus: bronchoscopic and clinical features.  

PubMed Central

Granular cell tumours are uncommon, generally benign neoplasms of uncertain origin that occasionally affect the tracheobronchial tree. Their incidence seems to be increasing, despite the fact that such tumours are rarely suspected on clinical grounds or bronchoscopic appearance. Here we describe three cases of endobronchial granular cell tumours, one of which regressed spontaneously after biopsy, and review previous accounts of their bronchoscopic and clinical features. Images PMID:3590055

Hernandez, O G; Haponik, E F; Summer, W R

1986-01-01

453

Stability of a granular layer on an inclined "fakir plane"  

E-print Network

We present here experimental results on the effect of a forest of cylinder obstacles (nails) on the stability of a granular layer over a rough incline, in a so-called "fakir plane" configuration. The nail forest is found to increase the stability of the layer, the more for the densest array, and such an effect is recovered by a simple model taking into account the additional friction force exerted by the pillar forest onto the granular layer.

Jesica Benito; Yann Bertho; Irene Ippolito; Philippe Gondret

2012-12-19

454

Dynamics of Granular Materials and Particle-Laden Flows  

SciTech Connect

Rapid granular flows and particle-laden flows were studied in laboratory experiments, molecular dynamics simulations, and simulations of continuum equations. The research demonstrated that the inclusion of friction is crucial in realistic modeling of granular flows; hence extensive previous analyses and simulations by many researchers for frictionless particles must be reconsidered in the light of our work. We also made the first detailed comparison between experiment and the predictions of continuum theory for granular media (hydrodynamic equations). We found that shock waves easily form in granular flows since the speed of sound waves (pressure fluctuations) in a granular gas is small, typically 10 cm, while flow velocities are easily an order of magnitude larger. Our measurements on vertically oscillating granular layers led to the development of a novel technique for continuously separating particles of different sizes. Our study of craters formed by the impact of a projectile in a granular medium showed, surprisingly, that the time taken for a projectile to come to a rest in the granular layer is independent of the projectiles impact energy. Another study supported by this grant examined a vertically oscillating layer of a mixture of cornstarch and water. The discovery of stable holes in the mixture was reported widely in the popular press, e.g., Science News [15 May 2004], Imaging poking a liquid to create holes that persist like the holes in Swiss cheese. Incredible as that might sound, a group of scientists has done it. Further experiments on glass spheres in an aqueous solution yielded the same holey fluid phenomenon, supporting our conjecture that such holes may occur in dense concentrations of particles in solution in industrial applications.

Swinney, Harry L.

2007-07-11

455

Propagation of elastic waves in granular solid hydrodynamics  

NASA Astrophysics Data System (ADS)

The anisotropic stress-dependent velocity of elastic waves in glass beadsas observed by Khidas and Jia [Phys. Rev. E 81, 021303 (2010)]10.1103/PhysRevE.81.021303is shown to be well accounted for by granular solid hydrodynamics, a broad-range macroscopic theory of granular behavior. As the theory makes no reference to fabric anisotropy, the influence of which on sound is in doubt.

Mayer, Michael; Liu, Mario

2010-10-01

456

Comparison of alkaline- and fungi-assisted wet-storage of corn stover.  

PubMed

Storage of lignocellulosic biomass is critical for a year-round supply of feedstock for a biorefinery. Compared with dry storage, wet storage is a promising alternative technology, providing several advantages including reduced dry matter loss and fire risk and improved feedstock digestibility after storage. This study investigated the concurrent pretreatment and wet-storage of corn stover with the assistance of NaOH or a lignin-degrading fungus, Ceriporiopsis subvermispora, during a 90-d period. Compared with ensilage, adding NaOH or inoculation with C. subvermispora significantly enhanced the enzymatic degradability of corn stover by 2-3-fold after 90-d wet storage. Lignin and xylan removal during NaOH pretreatment and wet-storage were influenced by NaOH loading and moisture. NaOH pretreatment retarded the production of organic acids during storage and the acetate release correlated with lignin and xylan removal. Further study is needed to reduce cellulose degradation during the late stage of fungal treatment. PMID:22306079

Cui, Zhifang; Shi, Jian; Wan, Caixia; Li, Yebo

2012-04-01

457

Substrate Erosion and Force Chain Dynamics in Dense Granular Flows  

NASA Astrophysics Data System (ADS)

Granular materials are composed of solid, discrete particles and exhibit mechanical behavior that differs from those of fluids and solids. The rheology of granular flows is principal to a suite of natural hazards. Laboratory experiments and numerical models have adequately reproduced several features observed in terrestrial gravity driven geophysical flows; however, quantitative comparison to field observations exposes a failure to explain the high mobility and duration of many of these flows. The ability of a granular material to resist deformation is a function of the force chain network inherent to the material. This investigation addresses the evolutionary character of force chains in two-dimensional granular flows. Our particular emphasis concerns the effects of substrate or bed erosion on force chain dynamics in dense granular flows. Experimental systems employing photoelastic techniques provide an avenue for quantitative stress analysis via image processing. Numerical simulations utilizing discrete element methods coupled with interstitial fluid modeling compliment and validate empirical data. Our work highlights the dominant physical parameters responsible for force propagation in granular flows, and elucidates the role of substrate erosion on force chain dynamics.

Estep, J.; Dufek, J.

2010-12-01

458

Fluctuation-dissipation relations for granular snow avalanches  

NASA Astrophysics Data System (ADS)

A fundamental problem in avalanche science is understanding the interaction between frictional processes taking place at the basal running surface and dissipative mechanisms within the avalanche body. In this paper, we address this question by studying how kinetic energy is dissipated into heat in snow avalanches. In doing so we consider the effect of random granular fluctuations and collisions in depth-averaged snow avalanche models. We show that relationships between the size of the granular fluctuations and the energy dissipated by granular collisions can be obtained by studying the energy input required to maintain steady-state flows. The energy input for granular fluctuations comes from mechanisms operating in the basal layer. The kinetic energy of the flow at the basal layer is converted to granular agitation energy, a random kinetic energy, which in turn is dissipated as heat by both viscous shearing and inelastic collisions at higher levels in the avalanche profile. Thus granular fluctuations play a crucial role in understanding the total dissipation process. We apply our theoretical considerations to develop a constitutive model for dense snow avalanches and are able to accurately model steady-state velocity profiles of both snow-chute experiments and field measurements.

Bartelt, Perry; Buser, Othmar; Platzer, Katharina

459

The effectiveness of resistive force theory in granular locomotiona)  

NASA Astrophysics Data System (ADS)

Resistive force theory (RFT) is often used to analyze the movement of microscopic organisms swimming in fluids. In RFT, a body is partitioned into infinitesimal segments, each of which generates thrust and experiences drag. Linear superposition of forces from elements over the body allows prediction of swimming velocities and efficiencies. We show that RFT quantitatively describes the movement of animals and robots that move on and within dry granular media (GM), collections of particles that display solid, fluid, and gas-like features. RFT works well when the GM is slightly polydisperse, and in the "frictional fluid" regime such that frictional forces dominate material inertial forces, and when locomotion can be approximated as confined to a plane. Within a given plane (horizontal or vertical) relationships that govern the force versus orientation of an elemental intruder are functionally independent of the granular medium. We use the RFT to explain features of locomotion on and within granular media including kinematic and muscle activation patterns during sand-swimming by a sandfish lizard and a shovel-nosed snake, optimal movement patterns of a Purcell 3-link sand-swimming robot revealed by a geometric mechanics approach, and legged locomotion of small robots on the surface of GM. We close by discussing situations to which granular RFT has not yet been applied (such as inclined granular surfaces), and the advances in the physics of granular media needed to apply RFT in such situations.

Zhang, Tingnan; Goldman, Daniel I.

2014-10-01

460

Precipitation of suspended particles in wet-film cyclones  

SciTech Connect

The fact that wet and dry mechanical centrifugal dust collectors operate on the same principle allowed the authors to make the calculations for wet cyclones with an equation similar to one used previously. A figure shows that the efficiency of wet cyclones is much higher (20% higher on the average) than that of dry cyclones under the same operating conditions. This improvement is due to a decrease in the secondary discharge of dust particles from the wet wall of the device.

Val'dberg, A.Y.; Kirsanova, N.S.

1986-07-01

461

7 CFR 51.1563 - Soft rot or wet breakdown.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Soft rot or wet breakdown. 51.1563 Section 51.1563 Agriculture... Definitions 51.1563 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky...

2010-01-01

462

7 CFR 51.1582 - Soft rot or wet breakdown.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Soft rot or wet breakdown. 51.1582 Section 51.1582 Agriculture... Definitions 51.1582 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky...

2010-01-01

463

Wetting behavior of dialkylimidazolium chloroaluminate, a room temperature molten salt  

Microsoft Academic Search

Eberhart (1979) has found that the wetting behavior of a battery electrolyte can have a dramatic effect on the internal resistance of the battery as well as its cycle life. Good wetting of battery separators by electrolyte is essential for the easy passage of ions through the separator pores, while porous, gas diffusion electrodes require a lesser degree of wetting.

J. G. Eberhart

1985-01-01

464

76 FR 1404 - Pure Magnesium in Granular Form From the People's Republic of China: Rescission of Changed...  

Federal Register 2010, 2011, 2012, 2013

...Administration [A-570-864] Pure Magnesium in Granular Form From the People's...antidumping duty order \\1\\ on pure magnesium in granular form from the People's...1\\ See Antidumping Duty Order: Pure Magnesium in Granular Form From the...

2011-01-10

465

Drying and passivating wet coals and lignite  

SciTech Connect

This invention discloses a staged process for drying wet carbonaceous materials such as sub-bituminous coal or lignite containing at least about 10 weight percent moisture, usually 15-50 weight percent moisture, by first heating the wet material under low partial pressure of moisture to permit the controlled rapid escape of surface moisture down to a critical moisture content of 8-12 weight percent. In a second step, the material is further heated at lower differential vapor pressure to provide for further moisture evolution at a slower controlled rate. This staged drying procedure permits wicking up of hydrocarbons contained in the coal to seal the surface of the dried coal product sufficient to prevent appreciable reabsorption of moisture and consequent heating and spontaneous ignition.

Comolli, A.G.

1981-02-10

466

Trapping of drops by wetting defects  

NASA Astrophysics Data System (ADS)

Controlling the motion of drops on solid surfaces is crucial in many natural phenomena and technological processes including the collection and removal of rain drops, cleaning technology and heat exchangers. Topographic and chemical heterogeneities on solid surfaces give rise to pinning forces that can capture and steer drops in desired directions. Here we determine general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects. By mapping the drop dynamics on the one-dimensional motion of a point mass, we demonstrate that the trapping process is controlled by two dimensionless parameters, the trapping strength measured in units of the driving force and the ratio between a viscous and an inertial time scale. Complementary experiments involving superhydrophobic surfaces with wetting defects demonstrate the general applicability of the concept. Moreover, we show that electrically tunable defects can be used to guide sliding drops along actively switchable trackswith potential applications in microfluidics.

't Mannetje, Dieter; Ghosh, Somnath; Lagraauw, Rudy; Otten, Simon; Pit, Arjen; Berendsen, Christian; Zeegers, Jos; van den Ende, Dirk; Mugele, Frieder

2014-04-01

467

Trapping of drops by wetting defects.  

PubMed

Controlling the motion of drops on solid surfaces is crucial in many natural phenomena and technological processes including the collection and removal of rain drops, cleaning technology and heat exchangers. Topographic and chemical heterogeneities on solid surfaces give rise to pinning forces that can capture and steer drops in desired directions. Here we determine general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects. By mapping the drop dynamics on the one-dimensional motion of a point mass, we demonstrate that the trapping process is controlled by two dimensionless parameters, the trapping strength measured in units of the driving force and the ratio between a viscous and an inertial time scale. Complementary experiments involving superhydrophobic surfaces with wetting defects demonstrate the general applicability of the concept. Moreover, we show that electrically tunable defects can be used to guide sliding drops along actively switchable tracks-with potential applications in microfluidics. PMID:24721935

't Mannetje, Dieter; Ghosh, Somnath; Lagraauw, Rudy; Otten, Simon; Pit, Arjen; Berendsen, Christian; Zeegers, Jos; van den Ende, Dirk; Mugele, Frieder

2014-01-01

468

A wetting and drying scheme for POM  

NASA Astrophysics Data System (ADS)

In shallow-water models, wetting and drying (WAD) are determined by the total water depth D=0 for `dry' and >0 for `wet'. Checks are applied to decide the fate of each cell during model integration. It is shown that with bottom friction values commonly used in coastal models, the shallow-water system may be cast into a Burger's type equation for D. For flows dominated by D (i.e. |? D|?|? H|, where H( x, y) defines topography) a non-linear diffusion equation results, with an effective diffusivity that varies like D2, so that `dry' cells are regions where `diffusion' is very small. In this case, the system admits D=0 as part of its continuous solution and no checks are necessary. For general topography, and/or in the case of strong momentum advection, `wave-breaking' solution (i.e. hydraulic jumps and/or bores) can develop. A WAD scheme is proposed and applied to the Princeton Ocean Model (POM). The scheme defines `dry' cells as regions with a thin film of fluid O (cm). The primitive equations are solved in the thin film as well as in other regular wet cells. The scheme requires only flux-blocking conditions across cells' interfaces when wet cells become dry, while `dry' cells are temporarily dormant and are dynamically activated through mass and momentum conservation. The scheme is verified against the above-mentioned diffusion and Burger's type equations, and tested also for one and two-dimensional channel flows that contain hydraulic jumps, including a laboratory dam-break problem.

Oey, Lie-Yauw

469

Significance of wet autoclave pretreatment in immunohistochemistry  

Microsoft Academic Search

Until recently the only way to rescue masked epitopes in routinely processed surgical pathological material was enzymatic\\u000a digestion. The use of heat for antigen retrieval, first by microwave irradiation, represents an important breakthrough in\\u000a immunohistochemistry. With the acceptance of microwave oven pretreatment, various modified techniques and alternative heating\\u000a methods have also been proposed. Wet autoclave pretreatment for tissue proteolysis is

gnes Bnkfalvi; Jzsef Piffk; Dietmar fner; Rita Dreier; Werner Bcker; Kurt Werner Schmid

1996-01-01

470

Anomalous wetting of helium on cesium  

Microsoft Academic Search

We report studies of the anomalous wetting of a cesium substrate by a liquid-helium film by means of the technique of third sound. In an apparatus which incorporates both glass and cesium substrates, we observe third sound to propagate across cesium for helium films such that the film thickness on glass is {ital d}{sub {ital g}}11.5 layers. For {ital d}{sub

K. S. Ketola; S. Wang; R. B. Hallock

1992-01-01

471

Evaporation from a partially wet forest canopy  

NASA Technical Reports Server (NTRS)

The results of experimental studies of water storage in a Sitka-spruce canopy are presented and analyzed in terms of model simulations of evaporation. Wet-branch cantilever deflection was measured along with meteorological data on three days in August, 1976, to determine the relationship of canopy evaporation to wind speed and (hence) aerodynamic resistance. Two versions of a simple unilayer model of sensible and latent heat transport from a partially wet canopy were tested in the data analysis: model F1 forbids the exchange of heat between wet and dry foliage surfaces; model F2 assumes that this exchange is highly efficient. Model F1 is found to give results consistent with the rainfall-interception model of Rutter et al. (1971, 1975, 1977), but model F2 gives results which are more plausible and correspond to the multilayer simulations of Sellers and Lockwood (1981) and the experimental findings of Hancock and Crowther (1979). It is inferred that the role of eddy diffusivity for water vapor is enhanced relative to momentum transport, and that the similarity hypothesis used in conventional models may fail in the near vicinity of a forest canopy.

Hancock, N. H.; Sellers, P. J.; Crowther, J. M.

1983-01-01

472