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Sample records for granular materials obtained

  1. Thermal conductivity of granular materials

    Buyevich, Yu A

    1974-01-01

    Stationary heat transfer in a granular material consisting of a continuous medium containing spherical granules of other substances is considered under the assumption that the spatial distribution of granules is random. The effective thermal conductivity characterizing macroscopic heat transfer in such a material is expressed as a certain function of the conductivities and volume fractions of the medium and dispersed substances. For reasons of mathematical analogy, all the results obtained for the thermal conductivity are valid while computing the effective diffusivity of some admixture in granular materials as well as for evaluation of the effective electric conductivity or the mean dielectric and magnetic permeabilities of granular conductors and dielectrics. (23 refs.)

  2. Acoustic waves in granular materials

    Mouraille, O.J.P.; Luding, Stefan

    2008-01-01

    Dynamic simulations with discrete elements are used to obtain more insight into the wave propagation in dense granular media. A small perturbation is created on one side of a dense, static packing and examined during its propagation until it arrives at the opposite side. The influence of

  3. HYPERELASTIC MODELS FOR GRANULAR MATERIALS

    Humrickhouse, Paul W; Corradini, Michael L

    2009-01-29

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

  4. Impact Compaction of a Granular Material

    Fenton, Gregg; Asay, Blaine; Todd, Steve; Grady, Dennis

    2017-06-01

    The dynamic behavior of granular materials has importance to a variety of engineering applications. Although, the mechanical behavior of granular materials have been studied extensively for several decades, the dynamic behavior of these materials remains poorly understood. High-quality experimental data are needed to improve our general understanding of granular material compaction physics. This paper describes how an instrumented plunger impact system can be used to measure the compaction process for granular materials at high and controlled strain rates and subsequently used for computational modelling. The experimental technique relies on a gas-gun driven plunger system to generate a compaction wave through a volume of granular material. This volume of material has been redundantly instrumented along the bed length to track the progression of the compaction wave, and the piston displacement is measured with Photon Doppler Velocimetry (PDV). Using the gathered experimental data along with the initial material tap density, a granular material equation of state can be determined.

  5. Characterization of Unbound Granular Materials for Pavements

    Araya, A.A.

    2011-01-01

    This research is focused on the characterization of the mechanical behavior of unbound granular road base materials (UGMs). An extensive laboratory investigation is described, in which various methods for determination of the mechanical properties of granular materials are examined for their

  6. Shear failure of granular materials

    Degiuli, Eric; Balmforth, Neil; McElwaine, Jim; Schoof, Christian; Hewitt, Ian

    2012-02-01

    Connecting the macroscopic behavior of granular materials with the microstructure remains a great challenge. Recent work connects these scales with a discrete calculus [1]. In this work we generalize this formalism from monodisperse packings of disks to 2D assemblies of arbitrarily shaped grains. In particular, we derive Airy's expression for a symmetric, divergence-free stress tensor. Using these tools, we derive, from first-principles and in a mean-field approximation, the entropy of frictional force configurations in the Force Network Ensemble. As a macroscopic consequence of the Coulomb friction condition at contacts, we predict shear failure at a critical shear stress, in accordance with the Mohr-Coulomb failure condition well known in engineering. Results are compared with numerical simulations, and the dependence on the microscopic geometric configuration is discussed. [4pt] [1] E. DeGiuli & J. McElwaine, PRE 2011. doi: 10.1103/PhysRevE.84.041310

  7. Granular materials flow like complex fluids

    Kou, Binquan; Cao, Yixin; Li, Jindong; Xia, Chengjie; Li, Zhifeng; Dong, Haipeng; Zhang, Ang; Zhang, Jie; Kob, Walter; Wang, Yujie

    2017-11-01

    Granular materials such as sand, powders and foams are ubiquitous in daily life and in industrial and geotechnical applications. These disordered systems form stable structures when unperturbed, but in the presence of external influences such as tapping or shear they `relax', becoming fluid in nature. It is often assumed that the relaxation dynamics of granular systems is similar to that of thermal glass-forming systems. However, so far it has not been possible to determine experimentally the dynamic properties of three-dimensional granular systems at the particle level. This lack of experimental data, combined with the fact that the motion of granular particles involves friction (whereas the motion of particles in thermal glass-forming systems does not), means that an accurate description of the relaxation dynamics of granular materials is lacking. Here we use X-ray tomography to determine the microscale relaxation dynamics of hard granular ellipsoids subject to an oscillatory shear. We find that the distribution of the displacements of the ellipsoids is well described by a Gumbel law (which is similar to a Gaussian distribution for small displacements but has a heavier tail for larger displacements), with a shape parameter that is independent of the amplitude of the shear strain and of the time. Despite this universality, the mean squared displacement of an individual ellipsoid follows a power law as a function of time, with an exponent that does depend on the strain amplitude and time. We argue that these results are related to microscale relaxation mechanisms that involve friction and memory effects (whereby the motion of an ellipsoid at a given point in time depends on its previous motion). Our observations demonstrate that, at the particle level, the dynamic behaviour of granular systems is qualitatively different from that of thermal glass-forming systems, and is instead more similar to that of complex fluids. We conclude that granular materials can relax

  8. Granular Materials and Risks In ISRU

    Behringer, Robert P.; Wilkinson, R. Allen

    2004-01-01

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

  9. Mathematics and Mechanics of Granular Materials

    Hill, James M

    2005-01-01

    Granular or particulate materials arise in almost every aspect of our lives, including many familiar materials such as tea, coffee, sugar, sand, cement and powders. At some stage almost every industrial process involves a particulate material, and it is usually the cause of the disruption to the smooth running of the process. In the natural environment, understanding the behaviour of particulate materials is vital in many geophysical processes such as earthquakes, landslides and avalanches. This book is a collection of current research from some of the major contributors in the topic of modelling the behaviour of granular materials. Papers from every area of current activity are included, such as theoretical, numerical, engineering and computational approaches. This book illustrates the numerous diverse approaches to one of the outstanding problems of modern continuum mechanics.

  10. Fuzzy batch controller for granular materials

    Zamyatin Nikolaj; Smirnov Gennadij; Fedorchuk Yuri; Rusina Olga

    2018-01-01

    The paper focuses on batch control of granular materials in production of building materials from fluorine anhydrite. Batching equipment is intended for smooth operation and timely feeding of supply hoppers at a required level. Level sensors and a controller of an asynchronous screw drive motor are used to control filling of the hopper with industrial anhydrite binders. The controller generates a required frequency and ensures required productivity of a feed conveyor. Mamdani-type fuzzy infer...

  11. Electrostatics effects in granular materials

    Sarkar, Saurabh; Chaudhuri, Bodhisattwa

    2013-06-01

    This purpose of this study is to investigate the role of physiochemical properties and operational conditions in determining the electrostatic interactions between two species on a surface under typical industrial conditions. The variables considered for the study were particle type, particle size and shape, loading mass, surface type, angle of inclination of chute, nature and concentration of additive. Triboelectrification of simple and binary mixtures in a simple hopper and chute geometry was observed to be strongly linked to work function and moisture content of the powdered material.

  12. Fuzzy batch controller for granular materials

    Zamyatin Nikolaj

    2018-01-01

    Full Text Available The paper focuses on batch control of granular materials in production of building materials from fluorine anhydrite. Batching equipment is intended for smooth operation and timely feeding of supply hoppers at a required level. Level sensors and a controller of an asynchronous screw drive motor are used to control filling of the hopper with industrial anhydrite binders. The controller generates a required frequency and ensures required productivity of a feed conveyor. Mamdani-type fuzzy inference is proposed for controlling the speed of the screw that feeds mixture components. As related to production of building materials based on fluoride anhydrite, this method is used for the first time. A fuzzy controller is proven to be effective in controlling the filling level of the supply hopper. In addition, the authors determined optimal parameters of the batching process to ensure smooth operation and production of fluorine anhydrite materials of specified properties that can compete with gypsum-based products.

  13. Resilient Modulus Characterization of Alaskan Granular Base Materials

    2010-08-01

    Resilient modulus (MR) of base course material is an important material input for : pavement design. In Alaska, due to distinctiveness of local climate, material source, : fines content and groundwater level, resilient properties of D-1 granular base...

  14. A hydrodynamic model for granular material flows including segregation effects

    Gilberg, Dominik; Klar, Axel; Steiner, Konrad

    2017-06-01

    The simulation of granular flows including segregation effects in large industrial processes using particle methods is accurate, but very time-consuming. To overcome the long computation times a macroscopic model is a natural choice. Therefore, we couple a mixture theory based segregation model to a hydrodynamic model of Navier-Stokes-type, describing the flow behavior of the granular material. The granular flow model is a hybrid model derived from kinetic theory and a soil mechanical approach to cover the regime of fast dilute flow, as well as slow dense flow, where the density of the granular material is close to the maximum packing density. Originally, the segregation model has been formulated by Thornton and Gray for idealized avalanches. It is modified and adapted to be in the preferred form for the coupling. In the final coupled model the segregation process depends on the local state of the granular system. On the other hand, the granular system changes as differently mixed regions of the granular material differ i.e. in the packing density. For the modeling process the focus lies on dry granular material flows of two particle types differing only in size but can be easily extended to arbitrary granular mixtures of different particle size and density. To solve the coupled system a finite volume approach is used. To test the model the rotational mixing of small and large particles in a tumbler is simulated.

  15. Friction law and hysteresis in granular materials

    DeGiuli, E.; Wyart, M.

    2017-08-01

    The macroscopic friction of particulate materials often weakens as the flow rate is increased, leading to potentially disastrous intermittent phenomena including earthquakes and landslides. We theoretically and numerically study this phenomenon in simple granular materials. We show that velocity weakening, corresponding to a nonmonotonic behavior in the friction law, μ(I), is present even if the dynamic and static microscopic friction coefficients are identical, but disappears for softer particles. We argue that this instability is induced by endogenous acoustic noise, which tends to make contacts slide, leading to faster flow and increased noise. We show that soft spots, or excitable regions in the materials, correspond to rolling contacts that are about to slide, whose density is described by a nontrivial exponent θs. We build a microscopic theory for the nonmonotonicity of μ(I), which also predicts the scaling behavior of acoustic noise, the fraction of sliding contacts χ, and the sliding velocity, in terms of θs. Surprisingly, these quantities have no limit when particles become infinitely hard, as confirmed numerically. Our analysis rationalizes previously unexplained observations and makes experimentally testable predictions.

  16. Friction law and hysteresis in granular materials.

    DeGiuli, E; Wyart, M

    2017-08-29

    The macroscopic friction of particulate materials often weakens as the flow rate is increased, leading to potentially disastrous intermittent phenomena including earthquakes and landslides. We theoretically and numerically study this phenomenon in simple granular materials. We show that velocity weakening, corresponding to a nonmonotonic behavior in the friction law, [Formula: see text], is present even if the dynamic and static microscopic friction coefficients are identical, but disappears for softer particles. We argue that this instability is induced by endogenous acoustic noise, which tends to make contacts slide, leading to faster flow and increased noise. We show that soft spots, or excitable regions in the materials, correspond to rolling contacts that are about to slide, whose density is described by a nontrivial exponent [Formula: see text] We build a microscopic theory for the nonmonotonicity of [Formula: see text], which also predicts the scaling behavior of acoustic noise, the fraction of sliding contacts [Formula: see text], and the sliding velocity, in terms of [Formula: see text] Surprisingly, these quantities have no limit when particles become infinitely hard, as confirmed numerically. Our analysis rationalizes previously unexplained observations and makes experimentally testable predictions.

  17. Jetting and flooding of granular backfill materials : [summary].

    2015-03-01

    Granular backfill materials on highway projects are often compacted by mechanical methods. : This requires the contractor to place backfill material into loose lifts of varying thickness : and use compaction equipment to reduce air voids and increase...

  18. Penetration in bimodal, polydisperse granular material

    Kouraytem, Nadia; Thoroddsen, Sigurdur T; Marston, J. O.

    2016-01-01

    We investigate the impact penetration of spheres into granular media which are compositions of two discrete size ranges, thus creating a polydisperse bimodal material. We examine the penetration depth as a function of the composition (volume fractions of the respective sizes) and impact speed. Penetration depths were found to vary between delta = 0.5D(0) and delta = 7D(0), which, for mono-modal media only, could be correlated in terms of the total drop height, H = h + delta, as in previous studies, by incorporating correction factors for the packing fraction. Bimodal data can only be collapsed by deriving a critical packing fraction for each mass fraction. The data for the mixed grains exhibit a surprising lubricating effect, which was most significant when the finest grains [d(s) similar to O(30) mu m] were added to the larger particles [d(l) similar to O(200 - 500) mu m], with a size ratio, epsilon = d(l)/d(s), larger than 3 and mass fractions over 25%, despite the increased packing fraction. We postulate that the small grains get between the large grains and reduce their intergrain friction, only when their mass fraction is sufficiently large to prevent them from simply rattling in the voids between the large particles. This is supported by our experimental observations of the largest lubrication effect produced by adding small glass beads to a bed of large sand particles with rough surfaces.

  19. Penetration in bimodal, polydisperse granular material

    Kouraytem, N.

    2016-11-07

    We investigate the impact penetration of spheres into granular media which are compositions of two discrete size ranges, thus creating a polydisperse bimodal material. We examine the penetration depth as a function of the composition (volume fractions of the respective sizes) and impact speed. Penetration depths were found to vary between delta = 0.5D(0) and delta = 7D(0), which, for mono-modal media only, could be correlated in terms of the total drop height, H = h + delta, as in previous studies, by incorporating correction factors for the packing fraction. Bimodal data can only be collapsed by deriving a critical packing fraction for each mass fraction. The data for the mixed grains exhibit a surprising lubricating effect, which was most significant when the finest grains [d(s) similar to O(30) mu m] were added to the larger particles [d(l) similar to O(200 - 500) mu m], with a size ratio, epsilon = d(l)/d(s), larger than 3 and mass fractions over 25%, despite the increased packing fraction. We postulate that the small grains get between the large grains and reduce their intergrain friction, only when their mass fraction is sufficiently large to prevent them from simply rattling in the voids between the large particles. This is supported by our experimental observations of the largest lubrication effect produced by adding small glass beads to a bed of large sand particles with rough surfaces.

  20. Temperature scaling in a dense vibrofluidized granular material.

    Sunthar, P; Kumaran, V

    1999-08-01

    The leading order "temperature" of a dense two-dimensional granular material fluidized by external vibrations is determined. The grain interactions are characterized by inelastic collisions, but the coefficient of restitution is considered to be close to 1, so that the dissipation of energy during a collision is small compared to the average energy of a particle. An asymptotic solution is obtained where the particles are considered to be elastic in the leading approximation. The velocity distribution is a Maxwell-Boltzmann distribution in the leading approximation. The density profile is determined by solving the momentum balance equation in the vertical direction, where the relation between the pressure and density is provided by the virial equation of state. The temperature is determined by relating the source of energy due to the vibrating surface and the energy dissipation due to inelastic collisions. The predictions of the present analysis show good agreement with simulation results at higher densities where theories for a dilute vibrated granular material, with the pressure-density relation provided by the ideal gas law, are in error.

  1. Editorial: Modelling and computational challenges in granular materials

    Weinhart, Thomas; Thornton, Anthony Richard; Einav, Itai

    2015-01-01

    This is the editorial for the special issue on “Modelling and computational challenges in granular materials” in the journal on Computational Particle Mechanics (CPM). The issue aims to provide an opportunity for physicists, engineers, applied mathematicians and computational scientists to discuss the current progress and latest advancements in the field of advanced numerical methods and modelling of granular materials. The focus will be on computational methods, improved algorithms and the m...

  2. An automata model of granular materials

    Gutt, G.M.; Haff, P.K.

    1990-01-01

    In this paper a new modeling technique (the Lattice Grain Model) is presented for the simulation of two-dimensional granular systems involving large numbers of grains. These granular systems may include both high shear rate regions as well as static plugs of grains and cannot easily be handled within the framework of existing continuum theories such as soil mechanics. The Lattice Grain Model (LGrM) is similar to the Lattice Gas Model (LBM). This allows large simulations to be programmed onto a hypercube concurrent processor in a straightforward manner. However, it differs from LBM in that it includes the inelastic collisions and volume-filling properties of macroscopic grains. Examples to be presented will include Couette flow, flow through an hourglass, and gravity-driven flows around obstacles

  3. Flowability of granular materials with industrial applications - An experimental approach

    Torres-Serra, Joel; Romero, Enrique; Rodríguez-Ferran, Antonio; Caba, Joan; Arderiu, Xavier; Padullés, Josep-Manel; González, Juanjo

    2017-06-01

    Designing bulk material handling equipment requires a thorough understanding of the mechanical behaviour of powders and grains. Experimental characterization of granular materials is introduced focusing on flowability. A new prototype is presented which performs granular column collapse tests. The device consists of a channel whose design accounts for test inspection using visualization techniques and load measurements. A reservoir is attached where packing state of the granular material can be adjusted before run-off to simulate actual handling conditions by fluidisation and deaeration of the pile. Bulk materials on the market, with a wide range of particle sizes, can be tested with the prototype and the results used for classification in terms of flowability to improve industrial equipment selection processes.

  4. Modelling of Granular Materials Using the Discrete Element Method

    Ullidtz, Per

    1997-01-01

    With the Discrete Element Method it is possible to model materials that consists of individual particles where a particle may role or slide on other particles. This is interesting because most of the deformation in granular materials is due to rolling or sliding rather that compression of the gra...

  5. Frost susceptibility of granular subbase materials contaminated by deicing chemicals

    Jørgensen, Anders Stuhr; Orlander, Tobias; Doré, Guy

    2013-01-01

    The increase in urban population in arctic areas leads to an increased demand for transportation infrastructures (such as roads and airfields) in the regions. This challenges the road constructions in terms of condition, bearing capacity and maintenance. It is believed that deicing agents used...... on roads and airfields enter the granular subbase materials and thereby makes the soil more frost-susceptible. In this project a series of isothermal frost heave tests has been carried out on granular subbase material from the runway at Kuujjuaq Airport, Québec, Canada. The tests have been carried out...

  6. Sealing of boreholes using natural, compatible materials: Granular salt

    Finley, R.E.; Zeuch, D.H.; Stormont, J.C.; Daemen, J.J.K.

    1994-01-01

    Granular salt can be used to construct high performance permanent seals in boreholes which penetrate rock salt formations. These seals are described as seal systems comprised of the host rock, the seal material, and the seal rock interface. The performance of these seal systems is defined by the complex interactions between these seal system components through time. The interactions are largely driven by the creep of the host formation applying boundary stress on the seal forcing host rock permeability with time. The immediate permeability of these seals is dependent on the emplaced density. Laboratory test results suggest that careful emplacement techniques could results in immediate seal system permeability on the order of 10 -16 m 2 to 10 -18 m 2 (10 -4 darcy to 10 -6 ). The visco-plastic behavior of the host rock coupled with the granular salts ability to ''heal'' or consolidate make granular salt an ideal sealing material for boreholes whose permanent sealing is required

  7. Mechanics of Granular Materials : Constitutive Behavior and Pattern Transformation

    Göncü, F.

    2012-01-01

    From pharmaceutical to mining or traveling desert dunes to earthquakes, granular materials are at the heart of many industries and natural phenomena. Improving the efficiency of the machines handling them or, constructing safer buildings requires a critical understanding of their behavior. However,

  8. Statics and kinematics of discrete Cosserat-type granular materials

    Kruyt, Nicolaas P.

    2003-01-01

    A theoretical framework is presented for the statics and kinematics of discrete Cosserat-type granular materials. In analogy to the force and moment equilibrium equations for particles, compatibility equations for closed loops are formulated in the two-dimensional case for relative displacements and

  9. Martian gullies: possible formation mechanism by dry granular material..

    Cedillo-Flores, Y.; Durand-Manterola, H. J.

    section Some of the geomorphological features in Mars are the gullies Some theories developed tried explain its origin either by liquid water liquid carbon dioxide or flows of dry granular material We made a comparative analysis of the Martian gullies with the terrestrial ones We propose that the mechanism of formation of the gullies is as follows In winter CO 2 snow mixed with sand falls in the terrain In spring the CO 2 snow sublimate and gaseous CO 2 make fluid the sand which flows like liquid eroding the terrain and forming the gullies By experimental work with dry granular material we simulated the development of the Martian gullies injecting air in the granular material section We present the characteristics of some terrestrial gullies forms at cold environment sited at Nevado de Toluca Volcano near Toluca City M e xico We compare them with Martian gullies choose from four different areas to target goal recognize or to distinguish to identify possible processes evolved in its formation Also we measured the lengths of those Martian gullies and the range was from 24 m to 1775 meters Finally we present results of our experimental work at laboratory with dry granular material

  10. Non-Steady Oscillatory Flow in Coarse Granular Materials

    Andersen, O. H.; Gent, M. R. A. van; Meer, J. W. van der

    1992-01-01

    Stationary and oscillatory flow through coarse granular materials have been investigated experimentally at Delft Hydraulics in their oscillating water tunnel with the objective of determining the coefficients of the extended Forchheimer equation. Cylinders, spheres and different types of rock have....... Further, for the non-stationary term, the virtual mass coefficient will be derived....

  11. Rheological Behavior of Dense Assemblies of Granular Materials

    Sundaresan, Sankaran; Tardos, Gabriel I.; Subramaniam, Shankar

    2011-01-01

    Assemblies of granular materials behave differently when they are owing rapidly, from when they are slowly deforming. The behavior of rapidly owing granular materials, where the particle-particle interactions occur largely through binary collisions, is commonly related to the properties of the constituent particles through the kinetic theory of granular materials. The same cannot be said for slowly moving or static assemblies of granular materials, where enduring contacts between particles are prevalent. For instance, a continuum description of the yield characteristics of dense assemblies of particles in the quasistatic ow regime cannot be written explicitly on the basis of particle properties, even for cohesionless particles. Continuum models for this regime have been proposed and applied, but these models typically assume that the assembly is at incipient yield and they are expressed in terms of the yield function, which we do not yet know how to express in terms of particle-level properties. The description of the continuum rheology in the intermediate regime is even less understood. Yet, many practically important flows in nature and in a wide range of technological applications occur in the dense flow regime and at the transition between dilute and dense regimes; the lack of validated continuum rheological models for particle assemblies in these regimes limits predictive modeling of such flows. This research project is aimed at developing such rheological models.

  12. Discrete Element study of granular material - Bumpy wall interface behavior

    El Cheikh, Khadija; Rémond, Sébastien; Pizette, Patrick; Vanhove, Yannick; Djelal, Chafika

    2016-09-01

    This paper presents a DEM study of a confined granular material sheared between two parallel bumpy walls. The granular material consists of packed dry spherical particles. The bumpiness is modeled by spheres of a given diameter glued on horizontal planes. Different bumpy surfaces are modeled by varying diameter or concentration of glued spheres. The material is sheared by moving the two bumpy walls at fixed velocity. During shear, the confining pressure applied on each bumpy wall is controlled. The effect of wall bumpiness on the effective friction coefficient and on the granular material behavior at the bumpy walls is reported for various shearing conditions. For given bumpiness and confining pressure that we have studied, it is found that the shear velocity does not affect the shear stress. However, the effective friction coefficient and the behavior of the granular material depend on the bumpiness. When the diameter of the glued spheres is larger than about the average grains diameter of the medium, the latter is uniformly sheared and the effective friction coefficient remains constant. For smaller diameters of the glued spheres, the effective friction coefficient increases with the diameter of glued spheres. The influence of glued spheres concentration is significant only for small glued spheres diameters, typically half of average particle diameter of the granular material. In this case, increasing the concentration of glued spheres leads to a decrease in effective friction coefficient and to shear localization at the interface. For different diameters and concentrations of glued spheres, we show that the effect of bumpiness on the effective friction coefficient can be characterized by the depth of interlocking.

  13. Consideration of reinforcement mechanism in the short fiber mixing granular materials by granular element simulations

    Mori, Kentaro; Kaneko, Kenji; Hashizume, Yutaka

    2017-06-01

    The short fiber mixing method is well known as one of the method to improve the strength of gran- ular soils in geotechnical engineering. Mechanical properties of the short fiber mixing granular materials are influenced by many factors, such as the mixture ratio of the short fiber, the material of short fiber, the length, and the orientation. In particular, the mixture ratio of the short fibers is very important in mixture design. In the past study, we understood that the strength is reduced by too much short fiber mixing by a series of tri-axial compression experiments. Namely, there is "optimum mixture ratio" in the short fiber mixing granular soils. In this study, to consider the mechanism of occurrence of the optimum mixture ratio, we carried out the numerical experiments by granular element method. As the results, we can understand that the strength decrease when too much grain-fiber contact points exist, because a friction coefficient is smaller than the grain-grain contact points.

  14. Suitability of granular carbon as an anode material for sediment microbial fuel cells

    Arends, Jan B.A.; Blondeel, Evelyne; Boon, Nico; Verstraete, Willy [Ghent Univ. (Belgium). Faculty of Bioscience Engineering; Tennison, Steve R. [Mast Carbon International Ltd., Basingstoke, Hampshire (United Kingdom)

    2012-08-15

    Purpose: Sediment microbial fuel cells (S-MFCs) are bio-electrochemical devices that are able to oxidize organic matter directly into harvestable electrical power. The flux of organic matter into the sediment is rather low; therefore, other researchers have introduced plants for a continuous supply of organic matter to the anode electrode. Until now only interconnected materials have been considered as anode materials in S-MFCs. Here, granular carbon materials were investigated for their suitability as an anode material in S-MFCs. Materials and methods: Laboratory microcosms with eight different electrode materials (granules, felts and cloths) were examined with controlled organic matter addition under brackish conditions. Current density, organic matter removal and microbial community composition were monitored using 16S rRNA gene PCR followed by denaturing gradient gel electrophoresis (DGGE). The main parameters investigated were the influence of the amount of electrode material applied to the sediment, the size of the granular material and the electrode configuration. Results and discussion: Felt material had an overall superior performance in terms of current density per amount of applied electrode material; felt and granular anode obtained similar current densities (approx. 50-60 mA m{sup -2}), but felt materials required 29 % less material to be applied. Yet, when growing plants, granular carbon is more suited because it is considered to restore, upon disturbance, the electrical connectivity within the anode compartment. Small granules (0.25-0.5 mm) gave the highest current density compared to larger granules (1-5 mm) of the same material. Granules with a rough surface had a better performance compared to smooth granules of the same size. The different granular materials lead to a selection of distinct microbial communities for each material, as shown by DGGE. Conclusions: Granular carbon is suitable as an anode material for S-MFCs. This opens the possibility

  15. Dynamics of crater formations in immersed granular materials

    Varas, G.; Vidal, V.; Géminard, J.

    2009-12-01

    Craters are part of the widespread phenomena observed in nature. Among the main applications to natural phenomena, aside from meteorite impact craters, are the formation and growth of volcanic edifices, by successive ejecta emplacement and/or erosion. The time evolution and dynamics play a crucial role here, as the competition between volcanic-jet mass-flux (degassing and ejecta) and crater-size evolution may control directly the eruptive regime. Crater morphology in dry granular material has been extensively studied, both experimentally and theoretically. Most of these studies investigate the final, steady crater shape resulting from the collision of solid bodies with the material surface and scaling laws are derived. In immersed granular material, craters generated by an underwater vortex ring, or underwater impact craters generated by landslide, have been reported. In a previous experimental study, Gostiaux et al. [Gran. Matt., 2002] have investigated the dynamics of air flowing through an immersed granular layer. They reported that, depending on the flow rate, the system exhibits two qualitatively different regimes: At small flow rate, the bubbling regime during which bubbles escape the granular layer independently one from another; At large flow rate, the open-channel regime which corresponds to the formation of a channel crossing the whole thickness of the granular bed through which air escapes almost continuously. At intermediate flow rate, a spontaneous alternation between these two regimes is observed. Here, we report the dynamics of crater formations at the free surface of an immersed granular bed, locally crossed by an ascending gas flow. We reproduce the experimental conditions of Gostiaux et al. (2002) in two dimensions: In a vertical Hele-Shaw cell, the crater consists of two sand piles which develop around the location of the gas emission. We observe that the typical size of the crater increases logarithmically with time, independently of the gas

  16. Breakage mechanics for granular materials in surface-reactive environments

    Zhang, Yida; Buscarnera, Giuseppe

    2018-03-01

    It is known that the crushing behaviour of granular materials is sensitive to the state of the fluids occupying the pore space. Here, a thermomechanical theory is developed to link such macroscopic observations with the physico-chemical processes operating at the microcracks of individual grains. The theory relies on the hypothesis that subcritical fracture propagation at intra-particle scale is the controlling mechanism for the rate-dependent, water-sensitive compression of granular specimens. First, the fracture of uniaxially compressed particles in surface-reactive environments is studied in light of irreversible thermodynamics. Such analysis recovers the Gibbs adsorption isotherm as a central component linking the reduction of the fracture toughness of a solid to the increase of vapour concentration. The same methodology is then extended to assemblies immersed in wet air, for which solid-fluid interfaces have been treated as a separate phase. It is shown that this choice brings the solid surface energy into the dissipation equations of the granular matrix, thus providing a pathway to (i) integrate the Gibbs isotherm with the continuum description of particle assemblies and (ii) reproduce the reduction of their yield strength in presence of high relative humidity. The rate-effects involved in the propagation of cracks and the evolution of breakage have been recovered by considering non-homogenous dissipation potentials associated with the creation of surface area at both scales. It is shown that the proposed model captures satisfactorily the compression response of different types of granular materials subjected to varying relative humidity. This result was achieved simply by using parameters based on the actual adsorption characteristics of the constituting minerals. The theory therefore provides a physically sound and thermodynamically consistent framework to study the behaviour of granular solids in surface-reactive environments.

  17. The nature of quasistatic deformation in granular materials

    ROUX, JN

    2005-01-01

    Strain in granular materials in quasistatic conditions under varying stress originate in (I) contact deformation and (II) rearrangements of the contact network. Depending on sample history and applied load, eiter mechanism might dominate. One may thus define rheological regimes I and II accordingly. Their porperties are presented and illustrated here with discrete numerical simulatiion results in 2 and 3 dimensions. This discussion of the microscopic physical origin of strain is shown to clar...

  18. Compaction dynamics of crunchy granular material

    Guillard François

    2017-01-01

    Full Text Available Compaction of brittle porous material leads to a wide variety of densification patterns. Static compaction bands occurs naturally in rocks or bones, and have important consequences in industry for the manufacturing of powder tablets or metallic foams for example. Recently, oscillatory compaction bands have been observed in brittle porous media like snow or cereals. We will discuss the great variety of densification patterns arising during the compaction of puffed rice, including erratic compaction at low velocity, one or several travelling compaction bands at medium velocity and homogeneous compaction at larger velocity. The conditions of existence of each pattern are studied thanks to a numerical spring lattice model undergoing breakage and is mapped to the phase diagram of the patterns based on dimensionless characteristic quantities. This also allows to rationalise the evolution of the compaction behaviour during a single test. Finally, the localisation of compaction bands is linked to the strain rate sensitivity of the material.

  19. Compaction dynamics of crunchy granular material

    Guillard, François; Golshan, Pouya; Shen, Luming; Valdès, Julio R.; Einav, Itai

    2017-06-01

    Compaction of brittle porous material leads to a wide variety of densification patterns. Static compaction bands occurs naturally in rocks or bones, and have important consequences in industry for the manufacturing of powder tablets or metallic foams for example. Recently, oscillatory compaction bands have been observed in brittle porous media like snow or cereals. We will discuss the great variety of densification patterns arising during the compaction of puffed rice, including erratic compaction at low velocity, one or several travelling compaction bands at medium velocity and homogeneous compaction at larger velocity. The conditions of existence of each pattern are studied thanks to a numerical spring lattice model undergoing breakage and is mapped to the phase diagram of the patterns based on dimensionless characteristic quantities. This also allows to rationalise the evolution of the compaction behaviour during a single test. Finally, the localisation of compaction bands is linked to the strain rate sensitivity of the material.

  20. Analysis of Cylindrical Granular Material Silos under Seismic Excitation

    Christoph Butenweg

    2017-07-01

    Full Text Available Silos generally work as storage structures between supply and demand for various goods, and their structural safety has long been of interest to the civil engineering profession. This is especially true for dynamically loaded silos, e.g., in case of seismic excitation. Particularly thin-walled cylindrical silos are highly vulnerable to seismic induced pressures, which can cause critical buckling phenomena of the silo shell. The analysis of silos can be carried out in two different ways. In the first, the seismic loading is modeled through statically equivalent loads acting on the shell. Alternatively, a time history analysis might be carried out, in which nonlinear phenomena due to the filling as well as the interaction between the shell and the granular material are taken into account. The paper presents a comparison of these approaches. The model used for the nonlinear time history analysis considers the granular material by means of the intergranular strain approach for hypoplasticity theory. The interaction effects between the granular material and the shell is represented by contact elements. Additionally, soil–structure interaction effects are taken into account.

  1. Granular flow

    Mitarai, Namiko; Nakanishi, Hiizu

    2012-01-01

    Granular material is a collection of macroscopic particles that are visible with naked eyes. The non-equilibrium nature of the granular materials makes their rheology quite different from that of molecular systems. In this minireview, we present the unique features of granular materials focusing...... on the shear flow of dry granular materials and granule-liquid mixture....

  2. Leaching models for multiple immersed materials and for granular materials flushed in a column

    Brouwers, H.J.H.

    1997-01-01

    The present paper addresses the leaching of hazardous contaminants from immersed and replenished materials and from granular materials flushed in a column. First, the leaching of an immersed material in contact with a limited volume of leachant is studied. The mass transfer from material to leachant

  3. Mechanical properties of granular materials: A variational approach to grain-scale simulations

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

    2009-01-15

    The mechanical properties of cohesionless granular materials are evaluated from grain-scale simulations. A three-dimensional pack of spherical grains is loaded by incremental displacements of its boundaries. The deformation is described as a sequence of equilibrium configurations. Each configuration is characterized by a minimum of the total potential energy. This minimum is computed using a modification of the conjugate gradient algorithm. Our simulations capture the nonlinear, path-dependent behavior of granular materials observed in experiments. Micromechanical analysis provides valuable insight into phenomena such as hysteresis, strain hardening and stress-induced anisotropy. Estimates of the effective bulk modulus, obtained with no adjustment of material parameters, are in agreement with published experimental data. The model is applied to evaluate the effects of hydrate dissociation in marine sediments. Weakening of the sediment is quantified as a reduction in the effective elastic moduli.

  4. A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part II - Validation and localization analysis

    Das, Arghya; Tengattini, Alessandro; Nguyen, Giang D.; Viggiani, Gioacchino; Hall, Stephen A.; Einav, Itai

    2014-10-01

    We study the mechanical failure of cemented granular materials (e.g., sandstones) using a constitutive model based on breakage mechanics for grain crushing and damage mechanics for cement fracture. The theoretical aspects of this model are presented in Part I: Tengattini et al. (2014), A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables, Part I - Theory (Journal of the Mechanics and Physics of Solids, 10.1016/j.jmps.2014.05.021). In this Part II we investigate the constitutive and structural responses of cemented granular materials through analyses of Boundary Value Problems (BVPs). The multiple failure mechanisms captured by the proposed model enable the behavior of cemented granular rocks to be well reproduced for a wide range of confining pressures. Furthermore, through comparison of the model predictions and experimental data, the micromechanical basis of the model provides improved understanding of failure mechanisms of cemented granular materials. In particular, we show that grain crushing is the predominant inelastic deformation mechanism under high pressures while cement failure is the relevant mechanism at low pressures. Over an intermediate pressure regime a mixed mode of failure mechanisms is observed. Furthermore, the micromechanical roots of the model allow the effects on localized deformation modes of various initial microstructures to be studied. The results obtained from both the constitutive responses and BVP solutions indicate that the proposed approach and model provide a promising basis for future theoretical studies on cemented granular materials.

  5. Numerical Simulation on Dense Packing of Granular Materials by Container Oscillation

    Jun Liu; Dongxu You

    2013-01-01

    The packing of granular materials is a basic and important problem in geomechanics. An approach, which generates dense packing of spheres confined in cylindrical and cuboidal containers in three steps, is introduced in this work. A loose packing structure is first generated by means of a reference lattice method. Then a dense packing structure is obtained in a container by simulating dropping of particles under gravitational forces. Furthermore, a scheme that makes the bottom boundary fluctua...

  6. Implicit integration of plasticity models for granular materials

    Ahadi, A.; Krenk, Steen

    2003-01-01

    A stress integration algorithm for granular materials based on fully implicit integration with explicit updating is presented. In the implicit method the solution makes use of the gradient to the potential surface at the final stress state which is unknown. The final stress and hardening parameters...... stresses are not supported the functions and their derivatives are not representative outside the compressive octant of the principal stress space. The elastic predictor is therefore preconditioned in order to ensure that the first predictor is within the valid region. Capability and robustness...

  7. Relating water and air flow characteristics in coarse granular materials

    Andreasen, Rune Røjgaard; Canga, Eriona; Poulsen, Tjalfe Gorm

    2013-01-01

    Water pressure drop as a function of velocity controls w 1 ater cleaning biofilter operation 2 cost. At present this relationship in biofilter materials must be determined experimentally as no 3 universal link between pressure drop, velocity and filter material properties have been established. 4...... Pressure drop - velocity in porous media is much simpler and faster to measure for air than for water. 5 For soils and similar materials, observations show a strong connection between pressure drop – 6 velocity relations for air and water, indicating that water pressure drop – velocity may be estimated 7...... from air flow data. The objective of this study was, therefore, to investigate if this approach is valid 8 also for coarse granular biofilter media which usually consists of much larger particles than soils. In 9 this paper the connection between the pressure drop – velocity relationships for air...

  8. Superconducting materials fabrication process and materials obtained

    Lafon, M.O.; Magnier, C.

    1989-01-01

    The preparation process of a fine powder of YBaCuO type superconductors of easy sintering comprises: mixing in presence of alcohol an aqueous solution of rare earth nitrate or acetate, alkaline earth nitrate or acetate and copper nitrate or acetate and an oxalic acid solution, the pH value of the mixture is comprised between 2 and 4, the obtained precipitate is separated, dried, calcined and eventually crushed [fr

  9. Failure evolution in granular material retained by rigid wall in active mode

    Pietrzak, Magdalena; Leśniewska, Danuta

    2012-10-01

    This paper presents a detailed study of a selected small scale model test, performed on a sample of surrogate granular material, retained by a rigid wall (typical geotechnical problem of earth thrust on a retaining wall). The experimental data presented in this paper show that the deformation of granular sample behind retaining wall can undergo some cyclic changes. The nature of these cycles is not clear - it is probably related to some micromechanical features of granular materials, which are recently extensively studied in many research centers in the world. Employing very precise DIC (PIV) method can help to relate micro and macro-scale behavior of granular materials.

  10. Micromechanical definition of an entropy for quasi-static deformation of granular materials

    Rothenburg, L.; Kruyt, Nicolaas P.

    2009-01-01

    A micromechanical theory is formulated for quasi-static deformation of granular materials, which is based on information theory. A reasoning is presented that leads to the definition of an information entropy that is appropriate for quasi-static deformation of granular materials. This definition is

  11. Experimental study of shear bands formation in a granular material

    Nguyen Thai Binh

    2017-01-01

    Full Text Available We present an experimental investigation of the formation of shear bands in a granular sample submitted to a biaxial test. Our principal result is the direct observation of the bifurcation at the origin of the localization process in the material. At the bifurcation, the shear band is spatially extended: we observe a breaking of symmetry without any sudden localization of the deformation in a narrow band. Our work thus allows to clearly distinguish different phenomena: bifurcation which is a ponctual event which occurs before the peak, localization which is a process that covers a range of deformation of several percents during which the peak occurs and finally stationary shear bands which are well-defined permanent structures that can be observed at the end of the localization process, after the peak.

  12. Thermodynamical aspects of modeling the mechanical response of granular materials

    Elata, D.

    1995-01-01

    In many applications in rock physics, the material is treated as a continuum. By supplementing the related conservation laws with constitutive equations such as stress-strain relations, a well-posed problem can be formulated and solved. The stress-strain relations may be based on a combination of experimental data and a phenomenological or micromechanical model. If the model is physically sound and its parameters have a physical meaning, it can serve to predict the stress response of the material to unmeasured deformations, predict the stress response of other materials, and perhaps predict other categories of the mechanical response such as failure, permeability, and conductivity. However, it is essential that the model be consistent with all conservation laws and consistent with the second law of thermodynamics. Specifically, some models of the mechanical response of granular materials proposed in literature, are based on intergranular contact force-displacement laws that violate the second law of thermodynamics by permitting energy generation at no cost. This diminishes the usefulness of these models as it invalidates their predictive capabilities. [This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.

  13. A Comparison of Streaming and Microelectrophoresis Methods for Obtaining the zeta Potential of Granular Porous Media Surfaces.

    Johnson

    1999-01-01

    The electrokinetic behavior of granular quartz sand in aqueous solution is investigated by both microelectrophoresis and streaming potential methods. zeta potentials of surfaces composed of granular quartz obtained via streaming potential methods are compared to electrophoretic mobility zeta potential values of colloid-sized quartz fragments. The zeta values generated by these alternate methods are in close agreement over a wide pH range and electrolyte concentrations spanning several orders of magnitude. Streaming measurements performed on chemically heterogeneous mixtures of physically homogeneous sand are shown to obey a simple mixing model based on the surface area-weighted average of the streaming potentials associated with the individual end members. These experimental results support the applicability of the streaming potential method as a means of determining the zeta potential of granular porous media surfaces. Copyright 1999 Academic Press.

  14. Shear test on viscoelastic granular material using Contact Dynamics simulations

    Quezada, Juan Carlos; Sagnol, Loba; Chazallon, Cyrille

    2017-06-01

    By means of 3D contact dynamic simulations, the behavior of a viscoelastic granular material under shear loading is investigated. A viscoelastic fluid phase surrounding the solid particles is simulated by a contact model acting between them. This contact law was implemented in the LMGC90 software, based on the Burgers model. This model is able to simulate also the effect of creep relaxation. To validate the proposed contact model, several direct shear tests were performed, experimentally and numerically using the Leutner device. The numerical samples were created using spheres with two particle size distribution, each one identified for two layers from a road structure. Our results show a reasonable agreement between experimental and numerical data regarding the strain-stress evolution curves and the stress levels measured at failure. The proposed model can be used to simulate the mechanical behavior of multi-layer road structure and to study the influence of traffic on road deformation, cracking and particles pull-out induced by traffic loading.

  15. The influence of the fractal particle size distribution on the mobility of dry granular materials

    Vallejo Luis E.

    2017-01-01

    Full Text Available This study presents an experimental analysis on the influence of the particle size distribution (psd on the mobility of dry granular materials. The psd obeys a power law of the form: N(L>d=kd-Df, where N is the number of particles with diameter L greater than a given diameter d, k is a proportionality constant, and Df is the fractal dimension of the psd. No laboratory or numerical study has been conducted to date analysing how a fractal psd influences the mobility of granular flows as in the case of rock avalanches. In this study, the flow characteristics of poly-dispersed granular materials that have a fractal psd were investigated in the laboratory. Granular mixtures having different fractal psd values were placed in a hollow cylinder. The cylinder was lifted and the distance of flow of the mixture was measured with respect to the original position of the cylinder. It was determined that the distance of flow of the mixtures was directly related to their fractal psd values. That is, the larger the distance of flow of the mixture, the larger is the fractal psd of the granular mixture tested. Thus, the fractal psd in dry granular mixtures seems to have a large influence on the easiness by which dry granular mixtures move in the field.

  16. Elaboration of building materials from industrial waste from solid granular diatomaceous earth; Elaboracion de material de construccion a partir de residuos industriales solidos granulares procedentes de tierras diatomaceas

    Del Angel S, A.

    2015-07-01

    In this work the initial characterization of granular solid industrial waste from diatomaceous earth was carried out using techniques of Scanning Electron Microscopy and X-ray Diffraction. In a second stage leaching of the material was undertaken to the US Patent Number 5, 376,000 and 5, 356,601 obtaining the samples M1-S ph 2, M1-L ph, M1-S ph 10 and M1-L ph 10. In the third stage a new characterization of the samples obtained with the techniques of Scanning Electron Microscopy, X-ray Diffraction and Atomic Absorption Spectrometry was performed, the latter in order to determine the efficiency percentage of the leaching process. In the fourth stage the specimens for performing mechanical, physical and chemical tests were manufactured, using molds as PVC pipes of 1 inch in diameter and 2 inches in length, with a composition of 50% of diatomaceous earth and 50% of cement produced in each. Finally, in the fifth stage mechanical testing (compression resistance), physical (moisture absorption rate) and chemical (composition and structure of the material) are performed. In the last stage, when conducting mechanical testing with the test specimens, the presence of bubbles enclosed in each obtaining erroneous results noted, so it was necessary to develop the specimens again, obtaining in this occasion concentrations of 20:80, 40:60, 60:40 and 80:20 of diatomaceous earth with the cement. These results were analyzed to determine if the used material is suitable for the production of building materials such as bricks or partitions, being demonstrated by the tests carried out if they are eligible. (Author)

  17. DEM Simulation of Biaxial Compression Experiments of Inherently Anisotropic Granular Materials and the Boundary Effects

    Zhao-Xia Tong

    2013-01-01

    Full Text Available The reliability of discrete element method (DEM numerical simulations is significantly dependent on the particle-scale parameters and boundary conditions. To verify the DEM models, two series of biaxial compression tests on ellipse-shaped steel rods are used. The comparisons on the stress-strain relationship, strength, and deformation pattern of experiments and simulations indicate that the DEM models are able to capture the key macro- and micromechanical behavior of inherently anisotropic granular materials with high fidelity. By using the validated DEM models, the boundary effects on the macrodeformation, strain localization, and nonuniformity of stress distribution inside the specimens are investigated using two rigid boundaries and one flexible boundary. The results demonstrate that the boundary condition plays a significant role on the stress-strain relationship and strength of granular materials with inherent fabric anisotropy if the stresses are calculated by the force applied on the wall. However, the responses of the particle assembly measured inside the specimens are almost the same with little influence from the boundary conditions. The peak friction angle obtained from the compression tests with flexible boundary represents the real friction angle of particle assembly. Due to the weak lateral constraints, the degree of stress nonuniformity under flexible boundary is higher than that under rigid boundary.

  18. Computational domain discretization in numerical analysis of flow within granular materials

    Sosnowski, Marcin

    2018-06-01

    The discretization of computational domain is a crucial step in Computational Fluid Dynamics (CFD) because it influences not only the numerical stability of the analysed model but also the agreement of obtained results and real data. Modelling flow in packed beds of granular materials is a very challenging task in terms of discretization due to the existence of narrow spaces between spherical granules contacting tangentially in a single point. Standard approach to this issue results in a low quality mesh and unreliable results in consequence. Therefore the common method is to reduce the diameter of the modelled granules in order to eliminate the single-point contact between the individual granules. The drawback of such method is the adulteration of flow and contact heat resistance among others. Therefore an innovative method is proposed in the paper: single-point contact is extended to a cylinder-shaped volume contact. Such approach eliminates the low quality mesh elements and simultaneously introduces only slight distortion to the flow as well as contact heat transfer. The performed analysis of numerous test cases prove the great potential of the proposed method of meshing the packed beds of granular materials.

  19. Editorial: Modelling and computational challenges in granular materials

    Weinhart, Thomas; Thornton, Anthony Richard; Einav, Itai

    2015-01-01

    This is the editorial for the special issue on “Modelling and computational challenges in granular materials” in the journal on Computational Particle Mechanics (CPM). The issue aims to provide an opportunity for physicists, engineers, applied mathematicians and computational scientists to discuss

  20. "Coulombic Viscosity" In Granular Materials: Planetary and Astrophysical Implications

    Marshall, J. R.

    1999-01-01

    The term "Coulombic viscosity" is introduced here to define an empirically observed phenomenon from experiments conducted in both microgravity, and in ground-based 1-g conditions. In the latter case, a sand attrition device was employed to test the longevity of aeolian materials by creating two intersecting grain-circulation paths or cells that would lead to most of the grain energy being expended on grain-to-grain collisions (simulating dune systems). In the areas in the device where gravitationally-driven grain-slurries recycled the sand, the slurries moved with a boundary-layer impeded motion down the chamber walls. Excessive electrostatic charging of the grains during these experiments was prevented by the use of an a.c. corona (created by a Tesla coil) through which the grains passed on every cycle. This created both positive and negative ions which neutralized the triboelectrically-generated grain charges. When the corona was switched on, the velocity of the wall-attached slurries increased by a factor of two as approximately determined by direct observation. What appeared to be a freely-flowing slurry of grains impeded only by intergranular mechanical friction, had obviously been significantly retarded in its motion by electrostatic forces between the grains; with the charging reduced, the grains were able to move past one another without a flow "viscosity" imposed by the Coulombic intergranular forces. A similar phenomenon was observed during microgravity experiments aboard Space Shuttle in USML-1 & USML-2 spacelabs where freely-suspended clouds of sand were being investigated for their potential to for-m aggregates. In this environment, the grains were also charged electrostatically (by natural processes prior to flight), but were free from the intervention of gravity in their interactions. The grains were dispersed into dense clouds by bursts of air turbulence and allowed to form aggregates as the ballistic and turbulent motions damped out. During this

  1. "Coulombic Viscosity" In Granular Materials: Planetary and Astrophysical Implications

    Marshall, J. R.

    1999-09-01

    The term "Coulombic viscosity" is introduced here to define an empirically observed phenomenon from experiments conducted in both microgravity, and in ground-based 1-g conditions. In the latter case, a sand attrition device was employed to test the longevity of aeolian materials by creating two intersecting grain-circulation paths or cells that would lead to most of the grain energy being expended on grain-to-grain collisions (simulating dune systems). In the areas in the device where gravitationally-driven grain-slurries recycled the sand, the slurries moved with a boundary-layer impeded motion down the chamber walls. Excessive electrostatic charging of the grains during these experiments was prevented by the use of an a.c. corona (created by a Tesla coil) through which the grains passed on every cycle. This created both positive and negative ions which neutralized the triboelectrically-generated grain charges. When the corona was switched on, the velocity of the wall-attached slurries increased by a factor of two as approximately determined by direct observation. What appeared to be a freely-flowing slurry of grains impeded only by intergranular mechanical friction, had obviously been significantly retarded in its motion by electrostatic forces between the grains; with the charging reduced, the grains were able to move past one another without a flow "viscosity" imposed by the Coulombic intergranular forces. A similar phenomenon was observed during microgravity experiments aboard Space Shuttle in USML-1 & USML-2 spacelabs where freely-suspended clouds of sand were being investigated for their potential to for-m aggregates. In this environment, the grains were also charged electrostatically (by natural processes prior to flight), but were free from the intervention of gravity in their interactions. The grains were dispersed into dense clouds by bursts of air turbulence and allowed to form aggregates as the ballistic and turbulent motions damped out. During this

  2. Numerical Simulation on Dense Packing of Granular Materials by Container Oscillation

    Jun Liu

    2013-01-01

    Full Text Available The packing of granular materials is a basic and important problem in geomechanics. An approach, which generates dense packing of spheres confined in cylindrical and cuboidal containers in three steps, is introduced in this work. A loose packing structure is first generated by means of a reference lattice method. Then a dense packing structure is obtained in a container by simulating dropping of particles under gravitational forces. Furthermore, a scheme that makes the bottom boundary fluctuate up and down was applied to obtain more denser packing. The discrete element method (DEM was employed to simulate the interactions between particle-particle and particle-boundary during the particles' motions. Finally, two cases were presented to indicate the validity of the method proposed in this work.

  3. Experimental and analytical investigations of granular materials: Shear flow and convective heat transfer

    Ahn, Hojin

    1989-12-01

    Granular materials flowing down an inclined chute were studied experimentally and analytically. Characteristics of convective heat transfer to granular flows were also investigated experimentally and numerically. Experiments on continuous, steady flows of granular materials in an inclined chute were conducted with the objectives of understanding the characteristics of chute flows and of acquiring information on the rheological behavior of granular material flow. Existing constitutive equations and governing equations were used to solve for fully developed chute flows of granular materials, and thus the boundary value problem was formulated with two parameters (the coefficient of restitution between particles, and the chute inclination) and three boundary values at the chute base wall (the values of solid fraction, granular temperature, and mean velocity at the wall). The boundary value problem was numerically solved by the shooting method. These analytical results were also compared with the present experimental values and with the computer simulations by other investigators in their literature. Experiments on heat transfer to granular flows over a flat heating plate were conducted with three sizes of glass beads, polystyrene beads, and mustard seeds. A modification on the existing model for the convective heat transfer was made using the effective Nusselt number and the effective Peclet number, which include the effects of solid fraction variations. The slightly modified model could describe the heat transfer characteristics of both fast and slow flows (supercritical and subcritical). A numerical analysis of the transfer to granular flows was also performed. The results were compared with the present experimental data, and reasonable agreement was found in the comparison.

  4. Subglacial sediment mechanics investigated by computer simulation of granular material

    Damsgaard, Anders; Egholm, David Lundbek; Tulaczyk, Slawek

    The mechanical properties of subglacial sediments are known to directly influence the stability of ice streams and fast-moving glaciers, but existing models of granular sediment deformation are poorly constrained. In addition, upscaling to generalized mathematical models is difficult due to the m......The mechanical properties of subglacial sediments are known to directly influence the stability of ice streams and fast-moving glaciers, but existing models of granular sediment deformation are poorly constrained. In addition, upscaling to generalized mathematical models is difficult due....... The numerical method is applied to better understand the mechanical properties of the subglacial sediment and its interaction with meltwater. The computational approach allows full experimental control and offers insights into the internal kinematics, stress distribution, and mechanical stability. During...

  5. Numerical investigations on flow dynamics of prismatic granular materials using the discrete element method

    Hancock, W.; Weatherley, D.; Wruck, B.; Chitombo, G. P.

    2012-04-01

    The flow dynamics of granular materials is of broad interest in both the geosciences (e.g. landslides, fault zone evolution, and brecchia pipe formation) and many engineering disciplines (e.g chemical engineering, food sciences, pharmaceuticals and materials science). At the interface between natural and human-induced granular media flow, current underground mass-mining methods are trending towards the induced failure and subsequent gravitational flow of large volumes of broken rock, a method known as cave mining. Cave mining relies upon the undercutting of a large ore body, inducement of fragmentation of the rock and subsequent extraction of ore from below, via hopper-like outlets. Design of such mines currently relies upon a simplified kinematic theory of granular flow in hoppers, known as the ellipsoid theory of mass movement. This theory assumes that the zone of moving material grows as an ellipsoid above the outlet of the silo. The boundary of the movement zone is a shear band and internal to the movement zone, the granular material is assumed to have a uniformly high bulk porosity compared with surrounding stagnant regions. There is however, increasing anecdotal evidence and field measurements suggesting this theory fails to capture the full complexity of granular material flow within cave mines. Given the practical challenges obstructing direct measurement of movement both in laboratory experiments and in-situ, the Discrete Element Method (DEM [1]) is a popular alternative to investigate granular media flow. Small-scale DEM studies (c.f. [3] and references therein) have confirmed that movement within DEM silo flow models matches that predicted by ellipsoid theory, at least for mono-disperse granular material freely outflowing at a constant rate. A major draw-back of these small-scale DEM studies is that the initial bulk porosity of the simulated granular material is significantly higher than that of broken, prismatic rock. In this investigation, more

  6. Jamming of three-dimensional prolate granular materials.

    Desmond, K; Franklin, Scott V

    2006-03-01

    We have found that the ability of long thin rods to jam into a solidlike state in response to a local perturbation depends upon both the particle aspect ratio and the container size. The dynamic phase diagram in this parameter space reveals a broad transition region separating granular stick-slip and solidlike behavior. In this transition region the pile displays both solid and stick-slip behavior. We measure the force on a small object pulled through the pile, and find the fluctuation spectra to have power law tails with an exponent characteristic of the region. The exponent varies from beta=-2 in the stick-slip region to beta=-1 in the solid region. These values reflect the different origins--granular rearrangements vs dry friction--of the fluctuations. Finally, the packing fraction shows only a slight dependence on container size, but depends on aspect ratio in a manner predicted by mean-field theory and implies an aspect-ratio-independent contact number of =5.25 +/- 0.03.

  7. STUDY OF HYDRODYNAMICS IN FIXED BED OF COMPOSITE GRANULAR MATERIALS

    Stelian Petrescu

    2010-12-01

    Full Text Available This study aims at the experimental determination of pressure drop and friction factor at gas flow through fixed beds of granular silica gel, alumina and activated carbon, and establishment of an equation containing a modified friction factor Fm to calculate pressure drop. In order to calculate the modified friction factor, an equation was suggested.The experimental values for pressure drop and friction factor were determined using spherical grains of silica gel, cylindrical grains of alumina and silica gel, alumina and activated carbon impregnated with calcium chloride. By means of the suggested equation, the values of pressure drop in fixed bed were calculated and compared with the experimental values. A good agreement between the predicted and experimental data is noticed.

  8. Elaboration of building materials from industrial waste from solid granular diatomaceous earth

    Del Angel S, A.

    2015-01-01

    In this work the initial characterization of granular solid industrial waste from diatomaceous earth was carried out using techniques of Scanning Electron Microscopy and X-ray Diffraction. In a second stage leaching of the material was undertaken to the US Patent Number 5, 376,000 and 5, 356,601 obtaining the samples M1-S ph 2, M1-L ph, M1-S ph 10 and M1-L ph 10. In the third stage a new characterization of the samples obtained with the techniques of Scanning Electron Microscopy, X-ray Diffraction and Atomic Absorption Spectrometry was performed, the latter in order to determine the efficiency percentage of the leaching process. In the fourth stage the specimens for performing mechanical, physical and chemical tests were manufactured, using molds as PVC pipes of 1 inch in diameter and 2 inches in length, with a composition of 50% of diatomaceous earth and 50% of cement produced in each. Finally, in the fifth stage mechanical testing (compression resistance), physical (moisture absorption rate) and chemical (composition and structure of the material) are performed. In the last stage, when conducting mechanical testing with the test specimens, the presence of bubbles enclosed in each obtaining erroneous results noted, so it was necessary to develop the specimens again, obtaining in this occasion concentrations of 20:80, 40:60, 60:40 and 80:20 of diatomaceous earth with the cement. These results were analyzed to determine if the used material is suitable for the production of building materials such as bricks or partitions, being demonstrated by the tests carried out if they are eligible. (Author)

  9. Effect of Anisotropy on the Resilient Behaviour of a Granular Material in Low Traffic Pavement.

    Jing, Peng; Nowamooz, Hossein; Chazallon, Cyrille

    2017-12-03

    Granular materials are often used in pavement structures. The influence of anisotropy on the mechanical behaviour of granular materials is very important. The coupled effects of water content and fine content usually lead to more complex anisotropic behaviour. With a repeated load triaxial test (RLTT), it is possible to measure the anisotropic deformation behaviour of granular materials. This article initially presents an experimental study of the resilient repeated load response of a compacted clayey natural sand with three fine contents and different water contents. Based on anisotropic behaviour, the non-linear resilient model (Boyce model) is improved by the radial anisotropy coefficient γ ₃ instead of the axial anisotropy coefficient γ ₁. The results from both approaches ( γ ₁ and γ ₃) are compared with the measured volumetric and deviatoric responses. These results confirm the capacity of the improved model to capture the general trend of the experiments. Finally, finite element calculations are performed with CAST3M in order to validate the improvement of the modified Boyce model (from γ ₁ to γ ₃). The modelling results indicate that the modified Boyce model with γ ₃ is more widely available in different water contents and different fine contents for this granular material. Besides, based on the results, the coupled effects of water content and fine content on the deflection of the structures can also be observed.

  10. REFINEMENT AND GRANULATING OF COHERENT-GRANULAR MATERIALS IN MACHINES OF ROLL TYPE

    E. B. Lozhechnikov

    2006-01-01

    Full Text Available The way of selective break of heterogeneous compositions, in particular slags of copper-smelting production and also granular metal-containing powder materials, is based and developed. Calibration of the rolls, providing contrilled granulating of metal-containing powders by rolling.

  11. Obtaining cementitious material from municipal solid waste

    Macías, A.

    2007-06-01

    Full Text Available The primary purpose of the present study was to determine the viability of using incinerator ash and slag from municipal solid waste as a secondary source of cementitious materials. The combustion products used were taken from two types of Spanish MSW incinerators, one located at Valdemingómez, in Madrid, and the other in Melilla, with different incineration systems: one with fluidised bed combustion and other with mass burn waterwall. The effect of temperature (from 800 to 1,200 ºC on washed and unwashed incinerator residue was studied, in particular with regard to phase formation in washed products with a high NaCl and KCl content. The solid phases obtained were characterized by X-ray diffraction and BET-N2 specific surface procedures.El principal objetivo del trabajo ha sido determinar la viabilidad del uso de las cenizas y escorias procedentes de la incineración de residuos sólidos urbanos, como materia prima secundaria para la obtención de fases cementantes. Para ello se han empleado los residuos generados en dos tipos de incineradoras españolas de residuos sólidos urbanos: la incineradora de Valdemingómez y la incineradora de Melilla. Se ha estudiado la transformación de los residuos, sin tratamiento previo, en función de la temperatura de calentamiento (desde 800 ºC hasta 1.200 ºC, así como la influencia del lavado de los residuos con alto contenido en NaCl y KCl en la formación de fases obtenidas a las diferentes temperaturas de calcinación. Las fases obtenidas fueron caracterizadas por difracción de rayos X y área superficial por el método BET-N2.

  12. Granular superconductor in a honeycomb lattice as a realization of bosonic Dirac material

    Banerjee, S.; Fransson, J.; Black-Schaffer, A. M.; Ågren, H.; Balatsky, A. V.

    2016-04-01

    We examine the low-energy effective theory of phase oscillations in a two-dimensional granular superconducting sheet where the grains are arranged in a honeycomb lattice structure. Using the example of graphene, we present evidence for the engineered Dirac nodes in the bosonic excitations: the spectra of the collective bosonic modes cross at the K and K' points in the Brillouin zone and form Dirac nodes. We show how two different types of collective phase oscillations are obtained and that they are analogous to the Leggett and the Bogoliubov-Anderson-Gorkov modes in a two-band superconductor. We show that the Dirac node is preserved in the presence of an intergrain interaction, despite induced changes of the qualitative features of the two collective modes. Finally, breaking the sublattice symmetry by choosing different on-site potentials for the two sublattices leads to a gap opening near the Dirac node, in analogy with fermionic Dirac materials. The Dirac node dispersion of bosonic excitations is thus expanding the discussion of the conventional Dirac cone excitations to the case of bosons. We call this case as a representative of bosonic Dirac materials (BDM), similar to the case of Fermionic Dirac materials extensively discussed in the literature.

  13. Study of an athermal quasi static plastic deformation in a 2D granular material

    Zhang, Jie

    2017-11-01

    In crystalline materials, the plasticity has been well understood in terms of dynamics of dislocation, i.e. flow defects in the crystals where the flow defects can be directly visualized under a microscope. In a contrast, the plasticity in amorphous materials, i.e. glass, is still poorly understood due to the disordered nature of the materials. In this talk, I will discuss the recent results we have obtained in our ongoing research of the plasticity of a 2D glass in the athermal quasi static limit where the 2D glass is made of bi-disperse granular disks with very low friction. Starting from a densely packed homogeneous and isotropic initial state, we apply pure shear deformation to the system. For a sufficiently small strain, the response of the system is linear and elastic like; when the strain is large enough, the plasticity of the system gradually develops and eventually the shear bands are fully developed. In this study, we are particularly interested in how to relate the local plastic deformation to the macroscopic response of the system and also in the development of the shear bands.

  14. Measurements of Acoustic Properties of Porous and Granular Materials and Application to Vibration Control

    Park, Junhong; Palumbo, Daniel L.

    2004-01-01

    For application of porous and granular materials to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic materials. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic materials - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured also. The data were used to extract the damping materials characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.

  15. Granular patterns

    Aranson, Igor S

    2009-01-01

    This title presents a review of experiments and novel theoretical concepts needed to understand the mechanisms of pattern formation in granular materials. An effort is made to connect concepts and ideas developed in granular physics with new emergent fields, especially in biology, such as cytoskeleton dynamics.

  16. Terminal velocity of liquids and granular materials dispersed by a high explosive

    Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

    2018-04-01

    The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass (M/C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/C ratio, with larger M/C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

  17. Terminal velocity of liquids and granular materials dispersed by a high explosive

    Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

    2018-05-01

    The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass ( M/ C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/ C ratio, with larger M/ C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

  18. Polymeric materials obtained by electron beam irradiation

    Dragusin, M.; Moraru, R.; Martin, D.; Radoiu, M.; Marghitu, S.; Oproiu, C.

    1995-01-01

    Research activities in the field of electron beam irradiation of monomer aqueous solution to produce polymeric materials used for waste waters treatment, agriculture and medicine are presented. The technologies and special features of these polymeric materials are also described. The influence of the chemical composition of the solution to ba irradiated, absorbed dose level and absorbed dose rate level are discussed. Two kinds of polyelectrolytes, PA and PV types and three kinds of hydrogels, pAAm, pAAmNa and pNaAc types, the production of which was first developed with IETI-10000 Co-60 source and then adapted to the linacs built in Accelerator Laboratory, are described. (author)

  19. Left-handed materials in metallic magnetic granular composites

    Chui, S.T.; Lin, Z.F.; Hu, L.-B.

    2003-01-01

    There is recently interests in the 'left-handed' materials. In these materials the direction of the wave vector of electromagnetic radiation is opposite to the direction of the energy flow. We present simple arguments that suggests that magnetic composites can also be left-handed materials. However, the physics involved seems to be different from the original argument. In our argument, the imaginary part of the dielectric constant is much larger than the real part, opposite to the original argument

  20. Mechanical and Structural Behavior of Granular Material Packed Beds for Space Life Support System Applications

    Malla, Ramesh B.; Anandakumar, Ganesh

    2005-01-01

    the bed media increased with decrease in initial compaction of the bed media. This effect could be attributed to the greater tendency for inter-particle sliding/rub bing due to smaller internal friction angles, as seen from the shear tests, at lesser initial compacted levels. Upon unloading, it was obse rved that there was no change in displacement (especially rebounding) in the bed media. This effect could be attributed to the fact that th e porous activated alumina particles fracture/break upon increase in applied load (during loading phase) and occupy void spaces in between the material grains; thereby leading to settling of the media. The lo ad-displacement curve becomes more linear with increase in initial compaction of the bed media. It is concluded that compaction considerabl y affects the load-displacement behavior of the bed media. A series of tests were also conducted on the packed bed media to determine the f orce required to mobilize the friction between the bed media and the housing cylinder. The results from these tests showed the existence of significant friction between the bed media and the encasing stainles s steel cylinder. Further, it was found that friction effects were more pronounced for media with higher initial compaction. Internal frict ion of the granular media was measured using direct shear apparatus. It was observed that the internal friction increased with increase in initial compaction of the bed media. In this study, a computational m odel (CM) is also developed using finite element software ANSYS to verify experimental results obtained for the distribution of the axial n ormal stress and axial displacement along the length of the full-scal e activated alumina bed media. In the computational model, the granular material is considered to have appropriate failure and frictional c ontact exists between the wall and the granular media. It is observed that the model predicts results closely with the experimental method. The compational

  1. Static Friction Phenomena in Granular Materials: Coulomb Law vs. Particle Geometry

    Poeschel, T.; Buchholtz, V.

    1993-01-01

    The static as well as the dynamic behaviour of granular material are determined by dynamic {\\it and} static friction. There are well known methods to include static friction in molecular dynamics simulations using scarcely understood forces. We propose an Ansatz based on the geometrical shape of nonspherical particles which does not involve an explicit expression for static friction. It is shown that the simulations based on this model are close to experimental results.

  2. A numerical toolkit to understand the mechanics of partially saturated granular materials

    Roux , Jean-Noël

    2015-01-01

    ``Focus on Fluids'' section; International audience; The mechanisms by which a wetting, non-saturating liquid bestows macroscopic cohesion and strength to a granular material are usually not accessible to micromechanical investigations for saturations exceeding the pendular regime of isolated menisci, easily studied by discrete element models. The " JFM-Rapids " paper (vol. 762, R5, 2015) by Delenne, Richefeu and Radja¨ıRadja¨ı, exploiting a multiphase Lattice Boltzmann approach, pioneers the...

  3. Advances in the simulation and automated measurement of well-sorted granular material: 1. Simulation

    Daniel Buscombe,; Rubin, David M.

    2012-01-01

    1. In this, the first of a pair of papers which address the simulation and automated measurement of well-sorted natural granular material, a method is presented for simulation of two-phase (solid, void) assemblages of discrete non-cohesive particles. The purpose is to have a flexible, yet computationally and theoretically simple, suite of tools with well constrained and well known statistical properties, in order to simulate realistic granular material as a discrete element model with realistic size and shape distributions, for a variety of purposes. The stochastic modeling framework is based on three-dimensional tessellations with variable degrees of order in particle-packing arrangement. Examples of sediments with a variety of particle size distributions and spatial variability in grain size are presented. The relationship between particle shape and porosity conforms to published data. The immediate application is testing new algorithms for automated measurements of particle properties (mean and standard deviation of particle sizes, and apparent porosity) from images of natural sediment, as detailed in the second of this pair of papers. The model could also prove useful for simulating specific depositional structures found in natural sediments, the result of physical alterations to packing and grain fabric, using discrete particle flow models. While the principal focus here is on naturally occurring sediment and sedimentary rock, the methods presented might also be useful for simulations of similar granular or cellular material encountered in engineering, industrial and life sciences.

  4. A new perspective of particle adsorption: Dispersed oil and granular materials interactions in simulated coastal environment.

    Meng, Long; Bao, Mutai; Sun, Peiyan

    2017-09-15

    This study, adsorption behaviors of dispersed oil in seawaters by granular materials were explored in simulation environment. We quantitatively demonstrated the dispersed oil adsorbed by granular materials were both dissolved petroleum hydrocarbons (DPHs) and oil droplets. Furthermore, DPHs were accounted for 42.5%, 63.4%, and 85.2% (35.5% was emulsion adsorption) in the adsorption of dispersed oil by coastal rocks, sediments, and bacterial strain particles respectively. Effects of controlling parameters, such as temperature, particle size and concentration on adsorption of petroleum hydrocarbons were described in detail. Most strikingly, adsorption concentration was followed a decreasing order of bacterial strain (0.5-2μm)>sediments (0.005-0.625mm)>coastal rocks (0.2-1cm). With particle concentration or temperature increased, adsorption concentration increased for coastal rocks particle but decreased for sediments particle. Besides, particle adsorption rate of petroleum hydrocarbons (n-alkanes and PAHs) was different among granular materials during 60 days. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Exact Solutions of the Hierarchical Korteweg-de Vries Equation of Micro structured Granular Materials

    Abourabia, A.M.; El-Danaf, T.S.; Morad, A.M.

    2008-01-01

    The problem under consideration are related to wave propagation in micro structured materials, characterized by higher-order nonlinear and higher-order dispersive effects; particularly, the wave propagation in dilatant granular materials. In the present paper the model equation is solved analytically by exact method called Jacobi elliptic method. The types of solutions are defined and discussed over a wide range of material parameters (two dispersion parameters and one microstructure parameter). The dispersion properties and the relation between group and phase velocities of the model equation are studied. The diagrams are drawn to illustrate the physical properties of the exact solutions

  6. Partitioning of fresh crude oil between floating, dispersed and sediment phases: Effect of exposure order to dispersant and granular materials.

    Boglaienko, Daria; Tansel, Berrin

    2016-06-15

    When three or more high and low energy substrates are mixed, wetting order can significantly affect the behavior of the mixture. We analyzed the phase distribution of fresh floating Louisiana crude oil into dispersed, settled and floating phases depending on the exposure sequence to Corexit 9500A (dispersant) and granular materials. In the experiments artificial sea water at salinity 34‰ was used. Limestone (2.00-0.300 mm) and quartz sand (0.300-0.075 mm) were used as the natural granular materials. Dispersant Corexit 9500A increased the amount of dispersed oil up to 33.76 ± 7.04%. Addition of granular materials after the dispersant increased dispersion of oil to 47.96 ± 1.96%. When solid particles were applied on the floating oil before the dispersant, oil was captured as oil-particle aggregates and removed from the floating layer. However, dispersant addition led to partial release of the captured oil, removing it from the aggregated form to the dispersed and floating phases. There was no visible oil aggregation with the granular materials when quartz or limestone was at the bottom of the flask before the addition of oil and dispersant. The results show that granular materials can be effective when applied from the surface for aggregating or dispersing oil. However, the granular materials in the sediments are not effective neither for aggregating nor dispersing floating oil. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. COMPORTAMIENTO RESILIENTE DE MATERIALES GRANULARES EN PAVIMENTOS FLEXIBLES: ESTADO DEL CONOCIMIENTO RESILIENT BEHAVIOR OF GRANULAR MATERIALS IN FLEXIBLE PAVEMENTS: STATE OF THE ART

    Hugo Alexander Rondón Quintana

    2007-07-01

    Full Text Available Los vehículos que circulan sobre una estructura de pavimento inducen ciclos de carga y descarga que generan dentro de las capas granulares deformaciones recuperables (resilientes y permanentes (plásticas. La ingeniería de pavimentos ha venido desarrollando estudios desde la década de los 60 con el fin de intentar comprender el comportamiento elastoplástico que experimentan materiales granulares cuando conforman capas de base y subbase en estructuras flexibles. La mayor parte de las investigaciones que se han realizado en esta área se han concentrado en estudiar su comportamiento resiliente. El estado del conocimiento de estudios desarrollados para medir la respuesta resiliente y la deformación permanente en materiales granulares es presentado en dos artículos por separado. En este primer artículo se presenta la forma como ha sido estudiado el comportamiento resiliente de materiales granulares y se discuten los factores que influyen en dicho comportamiento. Al final del artículo se presenta la evolución de las ecuaciones matemáticas desarrolladas a partir de resultados de estudios teóricos y experimentales. Un estado del conocimiento sobre el fenómeno de deformación permanente es presentado en un segundo artículo.When vehicles move on a pavement structure, they induce load cycles that generate resilient and permanent strains inside granular layers. Since the 60's, pavement engineering has developed studies in order to understand the elasto-plastic behavior that granular materials experiment on base and sub-base layers of flexible pavements. Most of the researches that have been made in this area have concentrated in studying their resilient behavior. A state of the art about the behavior of granular materials in flexible pavements is presented in two separate papers. This first paper tries on resilient stress-strain characteristics of such materials. The mathematical equations found in the literature to predict the resilient

  8. Modelling transient 3D multi-phase criticality in fluidised granular materials - the FETCH code

    Pain, C.C.; Gomes, J.L.M.A.; Eaton, M.D.; Ziver, A.K.; Umpleby, A.P.; Oliveira, C.R.E. de; Goddard, A.J.H.

    2003-01-01

    The development and application of a generic model for modelling criticality in fluidised granular materials is described within the Finite Element Transient Criticality (FETCH) code - which models criticality transients in spatial and temporal detail from fundamental principles, as far as is currently possible. The neutronics model in FETCH solves the neutron transport in full phase space with a spherical harmonics angle of travel representation, multi-group in neutron energy, Crank Nicholson based in time stepping, and finite elements in space. The fluids representation coupled with the neutronics model is a two-fluid-granular-temperature model, also finite element fased. A separate fluid is used to represent the liquid/vapour gas and the solid fuel particle phases, respectively. Particle-particle, particle-wall interactions are modelled using a kinetic theory approach on an analogy between the motion of gas molecules subject to binary collisions and granular flows. This model has been extensively validated by comparison with fluidised bed experimental results. Gas-fluidised beds involve particles that are often extremely agitated (measured by granular temperature) and can thus be viewed as a particularly demanding application of the two-fluid model. Liquid fluidised systems are of criticality interest, but these can become demanding with the production of gases (e.g. radiolytic and water vapour) and large fluid/particle velocities in energetic transients. We present results from a test transient model in which fissile material ( 239 Pu) is presented as spherical granules subsiding in water, located in a tank initially at constant temperature and at two alternative over-pressures in order to verify the theoretical model implemented in FETCH. (author)

  9. Effect of cohesion on local compaction and granulation of sheared soft granular materials

    Roy Sudeshna

    2017-01-01

    Full Text Available This paper results from an ongoing investigation of the effect of cohesion on the compaction of sheared soft wet granular materials. We compare dry non-cohesive and wet moderately-to-strongly cohesive soft almost frictionless granular materials and report the effect of cohesion between the grains on the local volume fraction. We study this in a three dimensional, unconfined, slowly sheared split-bottom ring shear cell, where materials while sheared are subject to compression under the confining weight of the material above. Our results show that inter-particle cohesion has a considerable impact on the compaction of soft materials. Cohesion causes additional stresses, due to capillary forces between particles, leading to an increase in volume fraction due to higher compaction. This effect is not visible in a system of infinitely stiff particles. In addition, acting oppositely, we observe a general decrease in volume fraction due to increased cohesion for frictional particle, which we attribute to the role of contact friction that enhances dilation.

  10. Deformación permanente de materiales granulares en pavimentos flexibles: estado del conocimiento Permanent strain of granular materials in flexible pavements: state of the art

    Hugo Alexánder Rondón

    2009-01-01

    Full Text Available Diversos estudios han sido desarrollados en el área de los pavimentos para comprender el comportamiento elastoplástico que experimentan materiales granulares bajo carga cíclica. Este es el segundo de dos artículos que presentan el estado del conocimiento de investigaciones desarrolladas en esta área. Basado en una amplia revisión bibliográfica, este artículo da cuenta de la forma como ha sido estudiado el fenómeno de deformación permanente en materiales granulares empleados para conformar capas de base y sub-base de estructuras de pavimentos flexibles. Además, se exponen y se discuten los factores que afectan la resistencia a la deformación permanente y la evolución de las ecuaciones matemáticas desarrolladas para predecir la deformación que experimentan estos materiales bajo carga cíclica. Un estado del conocimiento sobre el comportamiento resiliente de estos materiales es presentado en el primer artículo (Rondón y Reyes, 2007.Several studies have been conducted in pavement field for trying to understand the elastoplastic behavior experienced by granular materials under a cyclic load. This is the second out of two articles which show state-of-the-art of researches conducted in this field. Based on a wide literature review, this article accounts for the way how permanent strain phenomenon has been studied in granular materials used for creating base and sub-base layers of flexible pavement structures. Besides, this article displays and discusses factors which affect resistance to permanent strain and evolution of mathematical equations developed for predicting that strain experienced by these materials under a cyclic load. A state-of-the-art about resilient behavior of these materials has been presented in the first article (Rondón and Reyes, 2007.

  11. Reduction of intergranular exchange coupling and grain size for high Ku CoPt-based granular media: Metal-oxide buffer layer and multiple oxide boundary materials

    Kim Kong Tham

    2018-05-01

    Full Text Available Investigation of magnetic properties and microstructure of granular media with various multiple oxides as the grain boundary material is reported. Saturation magnetization (Ms, uniaxial magnetocrystalline anisotropy (Ku, and magnetic grain diameter (GD of the granular media show linear correlation with volume weighted average for melting point (Tm of each oxides (Tmave. Ku of magnetic grains (Kugrain shows a trade-off relation with GD that it is a big challenge to satisfy both high Kugrain and small GD by only controlling Tmave. To obtain a granular medium with appropriate Kugrain, GD, and low degree of intergranular exchange coupling, the combination of Tmave control of grain boundary material by mixing oxides and employment of a buffer layer are required. Here the degree of intergranular exchange coupling is estimated from the slope of M-H loop at around coercivity (α. By applying this technique, a typical granular medium with Kugrain of 1.0×107 erg/cm3, GD of 5.1 nm, and α of 1.2 is realized.

  12. Reduction of intergranular exchange coupling and grain size for high Ku CoPt-based granular media: Metal-oxide buffer layer and multiple oxide boundary materials

    Tham, Kim Kong; Kushibiki, Ryosuke; Kamada, Tomonari; Hinata, Shintaro; Saito, Shin

    2018-05-01

    Investigation of magnetic properties and microstructure of granular media with various multiple oxides as the grain boundary material is reported. Saturation magnetization (Ms), uniaxial magnetocrystalline anisotropy (Ku), and magnetic grain diameter (GD) of the granular media show linear correlation with volume weighted average for melting point (Tm) of each oxides (Tmave). Ku of magnetic grains (Kugrain) shows a trade-off relation with GD that it is a big challenge to satisfy both high Kugrain and small GD by only controlling Tmave. To obtain a granular medium with appropriate Kugrain, GD, and low degree of intergranular exchange coupling, the combination of Tmave control of grain boundary material by mixing oxides and employment of a buffer layer are required. Here the degree of intergranular exchange coupling is estimated from the slope of M-H loop at around coercivity (α). By applying this technique, a typical granular medium with Kugrain of 1.0×107 erg/cm3, GD of 5.1 nm, and α of 1.2 is realized.

  13. An automatic granular structure generation and finite element analysis of heterogeneous semi-solid materials

    Sharifi, Hamid; Larouche, Daniel

    2015-01-01

    The quality of cast metal products depends on the capacity of the semi-solid metal to sustain the stresses generated during the casting. Predicting the evolution of these stresses with accuracy in the solidification interval should be highly helpful to avoid the formation of defects like hot tearing. This task is however very difficult because of the heterogeneous nature of the material. In this paper, we propose to evaluate the mechanical behaviour of a metal during solidification using a mesh generation technique of the heterogeneous semi-solid material for a finite element analysis at the microscopic level. This task is done on a two-dimensional (2D) domain in which the granular structure of the solid phase is generated surrounded by an intergranular and interdendritc liquid phase. Some basic solid grains are first constructed and projected in the 2D domain with random orientations and scale factors. Depending on their orientation, the basic grains are combined to produce larger grains or separated by a liquid film. Different basic grain shapes can produce different granular structures of the mushy zone. As a result, using this automatic grain generation procedure, we can investigate the effect of grain shapes and sizes on the thermo-mechanical behaviour of the semi-solid material. The granular models are automatically converted to the finite element meshes. The solid grains and the liquid phase are meshed properly using quadrilateral elements. This method has been used to simulate the microstructure of a binary aluminium–copper alloy (Al–5.8 wt% Cu) when the fraction solid is 0.92. Using the finite element method and the Mie–Grüneisen equation of state for the liquid phase, the transient mechanical behaviour of the mushy zone under tensile loading has been investigated. The stress distribution and the bridges, which are formed during the tensile loading, have been detected. (paper)

  14. Granular model, percolation-resistivity, ESR and elastic modulus of carbonaceous materials application to the babassu endocarp heat treated up to 22000C

    Emmerich, F.G.

    1987-01-01

    A microscopic model (granular model) is presented to study heat treated carbons. A granular structure is defined in the carbon matrix, composed of turbostratic graphite-like microcrystallites, cross-linkings and micropores. A general expression is developed to calculate the volume fraction X of the conducting phase of the granular structure as a function of structural parameters obtained from X-ray diffraction small angle X-ray scattering. The granular model and the percolation theory are used to explain the electrical resistivity behaviour with the heat treatment temperature (HTT), where X is the fundamental parameter. An electron spin resonance (ESR) study of the low and high HTT ranges is presented, including the transition range (700-1300 0 C). The elucitation of the spin center nature in this range and the liking with the two adjacent ranges has been pursued. An expression to calculate the elastic modulus (Young's modulus), based on the microscopic granular model with the fundamental participation of the cross-linkings, is derived to account for the behavior of the modulus with the HTT. The granular model with the expression of X, the percolation-resistivity theory, the ESR study, and the expression of the elastic modulus are applied to the babassu endocarp carbon heat treated up to 2200 0 C. This material can be classified as a tipical non-graphitic carbon, being useful to search the validity of the model and the proposed expressions. It is observed that the theoretical expressions describe with reasonable accuracy the respective experimental behaviours. The measurements of physical and chemical parameters of the babassu endocarp treated up to 2200 0 C area also included. (author) [pt

  15. Influence of particle shape on the microstructure evolution and the mechanical properties of granular materials

    Tian, Jianqiu; Liu, Enlong; Jiang, Lian; Jiang, Xiaoqiong; Sun, Yi; Xu, Ran

    2018-06-01

    In order to study the influence of particle shape on the microstructure evolution and the mechanical properties of granular materials, a two-dimensional DEM analysis of samples with three particle shapes, including circular particles, triangular particles, and elongated particles, is proposed here to simulate the direct shear tests of coarse-grained soils. For the numerical test results, analyses are conducted in terms of particle rotations, fabric evolution, and average path length evolution. A modified Rowe's stress-dilatancy equation is also proposed and successfully fitted onto simulation data.

  16. Combined full field stress and strain measurement methods for granular materials

    Broere W.

    2010-06-01

    Full Text Available The current paper re-introduces the photoelastic measurement method in experimental geomechanics. A full-field phase stepping polariscope suitable for geomechanical model tests has been developed. Additional constraints on the measurement and mechanical setup arising from geomechanical test conditions are outlined as well as the opportunity to measure the displacement fields in the sample with digital image correlation. The capability of the current setup in retrieving the stress and strain field in a granular material is demonstrated.

  17. Developing a Magnetic Resonance Imaging measurement of the forces within 3D granular materials under external loads

    Elrington, Stefan; Bertrand, Thibault; Frey, Merideth; Shattuck, Mark; O'Hern, Corey; Barrett, Sean

    2014-03-01

    Granular materials are comprised of an ensemble of discrete macroscopic grains that interact with each other via highly dissipative forces. These materials are ubiquitous in our everyday life ranging in scale from the granular media that forms the Earth's crust to that used in agricultural and pharmaceutical industries. Granular materials exhibit complex behaviors that are poorly understood and cannot be easily described by statistical mechanics. Under external loads individual grains are jammed into place by a network of force chains. These networks have been imaged in quasi two-dimensional and on the outer surface of three-dimensional granular materials. Our goal is to use magnetic resonance imaging (MRI) to detect contact forces deep within three-dimensional granular materials, using hydrogen-1 relaxation times as a reporter for changes in local stress and strain. To this end, we use a novel pulse sequence to narrow the line width of hydrogen-1 in rubber. Here we present our progress to date, and prospects for future improvements.

  18. Understanding creep in sandstone reservoirs - theoretical deformation mechanism maps for pressure solution in granular materials

    Hangx, Suzanne; Spiers, Christopher

    2014-05-01

    Subsurface exploitation of the Earth's natural resources removes the natural system from its chemical and physical equilibrium. As such, groundwater extraction and hydrocarbon production from subsurface reservoirs frequently causes surface subsidence and induces (micro)seismicity. These effects are not only a problem in onshore (e.g. Groningen, the Netherlands) and offshore hydrocarbon fields (e.g. Ekofisk, Norway), but also in urban areas with extensive groundwater pumping (e.g. Venice, Italy). It is known that fluid extraction inevitably leads to (poro)elastic compaction of reservoirs, hence subsidence and occasional fault reactivation, and causes significant technical, economic and ecological impact. However, such effects often exceed what is expected from purely elastic reservoir behaviour and may continue long after exploitation has ceased. This is most likely due to time-dependent compaction, or 'creep deformation', of such reservoirs, driven by the reduction in pore fluid pressure compared with the rock overburden. Given the societal and ecological impact of surface subsidence, as well as the current interest in developing geothermal energy and unconventional gas resources in densely populated areas, there is much need for obtaining better quantitative understanding of creep in sediments to improve the predictability of the impact of geo-energy and groundwater production. The key problem in developing a reliable, quantitative description of the creep behaviour of sediments, such as sands and sandstones, is that the operative deformation mechanisms are poorly known and poorly quantified. While grain-scale brittle fracturing plus intergranular sliding play an important role in the early stages of compaction, these time-independent, brittle-frictional processes give way to compaction creep on longer time-scales. Thermally-activated mass transfer processes, like pressure solution, can cause creep via dissolution of material at stressed grain contacts, grain

  19. Relationship between electrical conductivity anisotropy and fabric anisotropy in granular materials during drained triaxial compressive tests: a numerical approach

    Niu, Qifei; Revil, André; Li, Zhaofeng; Wang, Yu-Hsing

    2017-07-01

    The anisotropy of granular media and its evolution during shearing are important aspects required in developing physics-based constitutive models in Earth sciences. The development of relationships between geoelectrical properties and the deformation of porous media has applications to the monitoring of faulting and landslides. However, such relationships are still poorly understood. In this study, we first investigate the definition of the electrical conductivity anisotropy tensor of granular materials in presence of surface conductivity of the grains. Fabric anisotropy is related to the components of the fabric tensor. We define an electrical anisotropy factor based on the Archie's exponent second-order symmetric tensor m of granular materials. We use numerical simulations to confirm a relationship between the evolution of electrical and fabric anisotropy factors during shearing. To realize the simulations, we build a virtual laboratory in which we can easily perform synthetic experiments. We first simulate drained compressive triaxial tests of loose and dense granular materials (porosity 0.45 and 0.38, respectively) using the discrete element method. Then, the electrical conductivity tensor of a set of deformed synthetic samples is computed using the finite-difference method. The numerical results show that shear strains are responsible for a measurable anisotropy in the bulk conductivity of granular media. The observed electrical anisotropy response, during shearing, is distinct for dense and loose synthetic samples. Electrical and fabric anisotropy factors exhibit however a unique linear correlation, regardless of the shear strain and the initial state (porosity) of the synthetic samples. The practical implication of this finding confirms the usefulness of the electrical conductivity method in studying the fabric tensor of granular media. This result opens the door in using time-lapse electrical resistivity to study non-intrusively the evolution of anisotropy

  20. Shear dilatancy and acoustic emission in dry and saturated granular materials

    Brodsky, E. E.; Siman-Tov, S.

    2017-12-01

    Shearing of granular materials plays a strong role in naturally sheared systems as landslides and faults. Many works on granular flows have concentrated on dry materials, but relatively little work has been done on water saturated sands. Here we experimentally investigate dry versus saturated quartz-rich sand to understand the effect of the fluid medium on the rheology and acoustic waves emission of the sheared sand. The sand was sheared in a rotary shear rheometer under applied constant normal stress boundary at low (100 µm/s) to high (1 m/s) velocities. Mechanical, acoustic data and deformation were continuously recorded and imaged. For dry and water saturated experiments the granular volume remains constant for low shear velocities ( 10-3 m/s) and increases during shearing at higher velocities ( 1 m/s). Continuous imaging of the sheared sand show that the steady state shear band thickness is thicker during the high velocity steps. No significant change observed in the shear band thickness between dry and water saturated experiments. In contrast, the amount of dilation during water saturated experiments is about half the value measured for dry material. The measured decrease cannot be explained by shear band thickness change as such is not exist. However, the reduced dilation is supported by our acoustic measurements. In general, the event rate and acoustic event amplitudes increase with shear velocity. While isolated events are clearly detected during low velocities at higher the events overlap, resulting in a noisy signal. Although detection is better for saturated experiments, during the high velocity steps the acoustic energy measured from the signal is lower compared to that recorded for dry experiments. We suggest that the presence of fluid suppresses grain motion and particles impacts leading to mild increase in the internal pressure and therefore for the reduced dilation. In addition, the viscosity of fluids may influence the internal pressure via

  1. Resilient modulus for unbound granular materials and subgrade soils in Egypt

    Mousa Rabah

    2017-01-01

    Full Text Available Mechanistic Empirical (ME pavement design methods started to gain attention especially the last couple of years in Egypt and the Middle East. One of the challenges facing the spread of these methods in Egypt is lack of advanced properties of local soil and asphalt, which are needed as input data in ME design. Resilient modulus (Mr for example is an important engineering property that expresses the elastic behavior of soil/unbound granular materials (UGMs under cyclic traffic loading for ME design. In order to overcome the scarcity of the resilient modulus data for soil/UGMs in Egypt, a comprehensive laboratory testing program was conducted to measure resilient modulus of typical UGMs and subgrade soils typically used in pavement construction in Egypt. The factors that affect the resilient modulus of soil/UGMs were reviewed, studied and discussed. Finally, the prediction accuracy of the most well-known Mr Prediction models for the locally investigated materials was investigated.

  2. Flow and Jamming of Granular Materials in a Two-dimensional Hopper

    Tang, Junyao

    Flow in a hopper is both a fertile testing ground for understanding fundamental granular flow rheology and industrially highly relevant. Despite increasing research efforts in this area, a comprehensive physical theory is still lacking for both jamming and flow of granular materials in a hopper. In this work, I have designed a two dimensional (2D) hopper experiment using photoelastic particles (particles' shape: disk or ellipse), with the goal to build a bridge between macroscopic phenomenon of hopper flow and microscopic particle-scale dynamics. Through synchronized data of particle tracking and stress distributions in particles, I have shown differences between my data of the time-averaged velocity/stress profile of 2D hopper flow with previous theoretical predictions. I have also demonstrated the importance of a mechanical stable arch near the opening on controlling hopper flow rheology and suggested a heuristic phase diagram for the hopper flow/jamming transition. Another part of this thesis work is focused on studying the impact of particle shape of particles on hopper flow. By comparing particle-tracking and photoelastic data for ellipses and disks at the appropriate length scale, I have demonstrated an important role for the rotational freedom of elliptical particles in controlling flow rheology through particle tracking and stress analysis. This work has been supported by International Fine Particle Research Institute (IFPRI) .

  3. Does modifying the particle size distribution of a granular material (i.e., material scalping alters its shear strength?

    Azéma Emilien

    2017-01-01

    Full Text Available By means of two dimensional contact dynamics simulations, we analyzed the effect of the particle size distribution (PSD on the shear strength of granular materials composed of un-breakable disks. We modelled PSDs with a normalized beta function, which allows for building S-shaped gradation curves, such as those that typically occur in soils. We systematically controlled and varied the size span and the shape of the PSD, and found that the shear strength is independent both characteristics. This implies that PSD modification procedures such as material scalping (i.e., removing the smallest and/or largest particles in the sample should not affect significantly the shear strength of the material composed of unbreakable discs. In order to explore the origins of the invariance of the shear strength with PSD, we analyzed the connectivity, force transmission, and friction mobilization in terms of anisotropies, finding that the constant shear strength is due to a subtle compensation of anisotropies.

  4. Granular Materials and the Risks They Pose for Success on the Moon and Mars

    Wilkinson, R. Allen; Behringer, Robert P.; Jenkins, James T.; Louge, Michel Y.

    2005-02-01

    Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to do it on the Moon and Mars as we do it on Earth. This paper brings to the fore how little these processes are understood and the millennia-long trial-and-error practices that lead to today's massive over-design, high failure rate, and extensive incremental scaling up of industrial processes because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, and what understanding is needed to greatly reduce the risks.

  5. A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part I-Theory

    Tengattini, Alessandro; Das, Arghya; Nguyen, Giang D.; Viggiani, Gioacchino; Hall, Stephen A.; Einav, Itai

    2014-10-01

    This is the first of two papers introducing a novel thermomechanical continuum constitutive model for cemented granular materials. Here, we establish the theoretical foundations of the model, and highlight its novelties. At the limit of no cement, the model is fully consistent with the original Breakage Mechanics model. An essential ingredient of the model is the use of measurable and micro-mechanics based internal variables, describing the evolution of the dominant inelastic processes. This imposes a link between the macroscopic mechanical behavior and the statistically averaged evolution of the microstructure. As a consequence this model requires only a few physically identifiable parameters, including those of the original breakage model and new ones describing the cement: its volume fraction, its critical damage energy and bulk stiffness, and the cohesion.

  6. Leaching behaviour of municipal solid waste incineration bottom ash: From granular material to monolithic concrete.

    Sorlini, Sabrina; Collivignarelli, Maria Cristina; Abbà, Alessandro

    2017-09-01

    The aim of this work was to assess the leaching behaviour of the bottom ash derived from municipal solid waste incineration (MSWI) used in concrete production. In particular, the release of pollutants was evaluated by the application of different leaching tests, both on granular materials and monolithic samples (concrete mixtures cast with bottom ash). The results confirmed that, according to Italian regulations, unwashed bottom ashes present critical issues for the use as alternative aggregates in the construction sector due to the excessive release of pollutants; instead, the leachate from washed bottom ashes was similar to natural aggregates. The concentration of pollutants in the leachate from concrete mixtures was lower than regulation limits for reuse. The crushing process significantly influenced the release of pollutants: this behaviour was due both to the increase in surface area and the release of contaminants from cement. Moreover, the increase in contact time (up to 64 days) involved more heavy metals to be released.

  7. Shear test results for cohesion and friction coefficients for different granular materials : Scaling implications for their usage in analogue modelling

    Schellart, W. P.

    2000-01-01

    Laboratory tests have been carried out on dry granular materials such as quartz sand, glass microspheres and sugar with different grain size, rounding and sphericity. The measurements have been made with a simple shear test machine for different values of normal stress (~ 50-900 Pa). Shear stress

  8. Advances in the simulation and automated measurement of well-sorted granular material: 2. Direct measures of particle properties

    Buscombe, D.; Rubin, D. M.

    2012-06-01

    In this, the second of a pair of papers on the structure of well-sorted natural granular material (sediment), new methods are described for automated measurements from images of sediment, of: 1) particle-size standard deviation (arithmetic sorting) with and without apparent void fraction; and 2) mean particle size in material with void fraction. A variety of simulations of granular material are used for testing purposes, in addition to images of natural sediment. Simulations are also used to establish that the effects on automated particle sizing of grains visible through the interstices of the grains at the very surface of a granular material continue to a depth of approximately 4 grain diameters and that this is independent of mean particle size. Ensemble root-mean squared error between observed and estimated arithmetic sorting coefficients for 262 images of natural silts, sands and gravels (drawn from 8 populations) is 31%, which reduces to 27% if adjusted for bias (slope correction between observed and estimated values). These methods allow non-intrusive and fully automated measurements of surfaces of unconsolidated granular material. With no tunable parameters or empirically derived coefficients, they should be broadly universal in appropriate applications. However, empirical corrections may need to be applied for the most accurate results. Finally, analytical formulas are derived for the one-step pore-particle transition probability matrix, estimated from the image's autocorrelogram, from which void fraction of a section of granular material can be estimated directly. This model gives excellent predictions of bulk void fraction yet imperfect predictions of pore-particle transitions.

  9. Mechanical strength model for plastic bonded granular materials at high strain rates and large strains

    Browning, R.V.; Scammon, R.J.

    1998-01-01

    Modeling impact events on systems containing plastic bonded explosive materials requires accurate models for stress evolution at high strain rates out to large strains. For example, in the Steven test geometry reactions occur after strains of 0.5 or more are reached for PBX-9501. The morphology of this class of materials and properties of the constituents are briefly described. We then review the viscoelastic behavior observed at small strains for this class of material, and evaluate large strain models used for granular materials such as cap models. Dilatation under shearing deformations of the PBX is experimentally observed and is one of the key features modeled in cap style plasticity theories, together with bulk plastic flow at high pressures. We propose a model that combines viscoelastic behavior at small strains but adds intergranular stresses at larger strains. A procedure using numerical simulations and comparisons with results from flyer plate tests and low rate uniaxial stress tests is used to develop a rough set of constants for PBX-9501. Comparisons with the high rate flyer plate tests demonstrate that the observed characteristic behavior is captured by this viscoelastic based model. copyright 1998 American Institute of Physics

  10. Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

    Ross, Pierre-Simon; White, James D. L.; Zimanowski, Bernd; Büttner, Ralf

    2008-10-01

    In diatremes and other volcanic vents, steep bodies of volcaniclastic material having differing properties (particle size distribution, proportion of lithic fragments, etc.) from those of the surrounding vent-filling volcaniclastic material are often found. It has been proposed that cylindrical or cone-shaped bodies result from the passage of “debris jets” generated after phreatomagmatic explosions or other discrete subterranean bursts. To learn more about such phenomena, we model experimentally the injection of gas-particulate dispersions through other particles. Analogue materials (glass beads or sand) and a finite amount of compressed air are used in the laboratory. The gas is made available by rapidly opening a valve—therefore the injection of gas and coloured particles into a granular host is a brief (non-erupting injections produce cylindrical bodies of coloured beads whereas erupting runs produce flaring upward or conical deposits. Changing the particle size of the host glass beads does not have a large effect under the size range investigated (100 200 to 300 400 μm). Doubling the host thickness (injection depth) requires a doubling of the initial gas pressure to produce similar phenomena. Such injections—whether erupting or wholly subterranean—provide a compelling explanation for the origin and characteristics of multiple cross-cutting bodies that have been documented for diatreme and other vent deposits.

  11. Stress distribution retrieval in granular materials: A multi-scale model and digital image correlation measurements

    Bruno, Luigi; Decuzzi, Paolo; Gentile, Francesco

    2016-01-01

    The promise of nanotechnology lies in the possibility of engineering matter on the nanoscale and creating technological interfaces that, because of their small scales, may directly interact with biological objects, creating new strategies for the treatment of pathologies that are otherwise beyond the reach of conventional medicine. Nanotechnology is inherently a multiscale, multiphenomena challenge. Fundamental understanding and highly accurate predictive methods are critical to successful manufacturing of nanostructured materials, bio/mechanical devices and systems. In biomedical engineering, and in the mechanical analysis of biological tissues, classical continuum approaches are routinely utilized, even if these disregard the discrete nature of tissues, that are an interpenetrating network of a matrix (the extra cellular matrix, ECM) and a generally large but finite number of cells with a size falling in the micrometer range. Here, we introduce a nano-mechanical theory that accounts for the-non continuum nature of bio systems and other discrete systems. This discrete field theory, doublet mechanics (DM), is a technique to model the mechanical behavior of materials over multiple scales, ranging from some millimeters down to few nanometers. In the paper, we use this theory to predict the response of a granular material to an external applied load. Such a representation is extremely attractive in modeling biological tissues which may be considered as a spatial set of a large number of particulate (cells) dispersed in an extracellular matrix. Possibly more important of this, using digital image correlation (DIC) optical methods, we provide an experimental verification of the model.

  12. A new methodology to simulate subglacial deformation of water saturated granular material

    Damsgaard, Anders; Egholm, David Lundbek; Piotrowski, Jan A.

    2015-01-01

    The dynamics of glaciers are to a large degree governed by processes operating at the ice-bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglac......The dynamics of glaciers are to a large degree governed by processes operating at the ice-bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response...... or weakening components, depending on the rate of deformation, the material state, clay mineral content, and the hydrological properties of the material. The influence of the fluid phase is negligible when relatively permeable sediment is deformed. However, by reducing the local permeability, fast deformation...... can cause variations in the pore-fluid pressure. The pressure variations weaken or strengthen the granular phase, and in turn influence the distribution of shear strain with depth. In permeable sediments the strain distribution is governed by the grain-size distribution and effective normal stress...

  13. Attachment and Detachment Behavior of Human Adenovirus and Surrogates in Fine Granular Limestone Aquifer Material.

    Stevenson, Margaret E; Sommer, Regina; Lindner, Gerhard; Farnleitner, Andreas H; Toze, Simon; Kirschner, Alexander K T; Blaschke, Alfred P; Sidhu, Jatinder P S

    2015-09-01

    The transport of human adenovirus, nanoparticles, and PRD1 and MS2 bacteriophages was tested in fine granular limestone aquifer material taken from a borehole at a managed aquifer recharge site in Adelaide, South Australia. Comparison of transport and removal of virus surrogates with the pathogenic virus is necessary to understand the differences between the virus and surrogate. Because experiments using pathogenic viruses cannot be done in the field, laboratory tests using flow-through soil columns were used. Results show that PRD1 is the most appropriate surrogate for adenovirus in an aquifer dominated by calcite material but not under high ionic strength or high pH conditions. It was also found that straining due to size and the charge of the colloid were not dominant removal mechanisms in this system. Implications of this study indicate that a certain surrogate may not represent a specific pathogen solely based on similar size, morphology, and/or surface charge. Moreover, if a particular surrogate is representative of a pathogen in one aquifer system, it may not be the most appropriate surrogate in another porous media system. This was apparent in the inferior performance of MS2 as a surrogate, which is commonly used in virus transport studies. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  14. Influence of granular material characteristics in the behaviour of “Bouregreg Valley” soft ground improved with stone columns

    Nehab Noura

    2018-01-01

    Full Text Available The use of finite element analysis has become widespread in geotechnical practice as means of optimizing engineering tasks; it can be easily applied to the treated areas by stone columns, which are a method of improving the soil having low geotechnical properties and likely to deform significantly under load action, by incorporating granular material (commonly called ballast compacted by remounting passes, so they act mainly as inclusions with a higher stiffness, shear strength than the natural soil. Moreover the stone columns are highly permeable and act as vertical drains facilitating consolidation of the soft soil improving the performance of the foundation. However the characteristics of this granular material influence the behavior of soft soils treated by the stone columns technique, especially: the friction angle, the cohesion, the modular ratio and the constitutive model. The choice of the constitutive model depends on many factors but, in general, it is related to the type of analysis that we intend to perform. Numerical modeling must consider the diversity of the materials nature, the complex geometry of structures-land and the behavior of materials generally nonlinear (permanent deformation. It is a simple and effective alternative to approach the real behavior of soils reinforced by stone columns and the influence of materials characteristics, it allows settlement analysis, lateral deformation, vertical and horizontal stresses in order to understand the behavior of columns and soil. It also has the advantage of integrating the settlements of the underlying layers. This paper aims to study the mechanisms of functioning and interactions of stone columns with the surrounding ground, and vis-à-vis the various parameters characterizing the granular material "ballast" and the surrounding soil, which influence the behavior of the improved soil, The paper presents, in the first part, soil conditions and the parameters associated with

  15. Granular and layered ferroelectric–ferromagnetic thin-film nanocomposites as promising materials with high magnetotransmission effect

    Akbashev, A.R. [Department of Materials Science, Moscow State University, 119992 Moscow (Russian Federation); Telegin, A.V., E-mail: telegin@imp.uran.ru [M.N. Miheev Institute of Metal Physics of Ural Branch of RAS, 620990 Ekaterinburg (Russian Federation); Kaul, A.R. [Department of Chemistry, Moscow State University, 119992 Moscow (Russian Federation); Sukhorukov, Yu.P. [M.N. Miheev Institute of Metal Physics of Ural Branch of RAS, 620990 Ekaterinburg (Russian Federation)

    2015-06-15

    Epitaxial thin films of granular and layered nanocomposites consisting of ferromagnetic perovskite Pr{sub 1–x}Sr{sub x}MnO{sub 3} and ferroelectric hexagonal LuMnO{sub 3} were grown on ZrO{sub 2}(Y{sub 2}O{sub 3}) substrates using metal-organic chemical vapor deposition (MOCVD). A self-organized growth of the granular composite took place in situ as a result of phase separation of the Pr–Sr–Lu–Mn–O system into the perovskite and hexagonal phases. Optical transmission measurements revealed a large negative magnetotransmission effect in the layered nanocomposite over a wide spectral and temperature range. The granular nanocomposite unexpectedly showed an even larger, but positive, magnetotransmission effect at room temperature. - Highlights: • Thin-film ferromagnetic–ferroelectric nanocomposites have been prepared by MOCVD. • Giant change of optical transparency of nanocomposites in magnetic field was detected. • Positive magnetotransmission in the granular nanocomposite was discovered in the IR. • Negative magnetotransmission in the layered nanocomposite was revealed in the IR. • Ferroelectric–ferromangetic nanocomposite is a promising material for optoelectronics.

  16. Granular and layered ferroelectric–ferromagnetic thin-film nanocomposites as promising materials with high magnetotransmission effect

    Akbashev, A.R.; Telegin, A.V.; Kaul, A.R.; Sukhorukov, Yu.P.

    2015-01-01

    Epitaxial thin films of granular and layered nanocomposites consisting of ferromagnetic perovskite Pr 1–x Sr x MnO 3 and ferroelectric hexagonal LuMnO 3 were grown on ZrO 2 (Y 2 O 3 ) substrates using metal-organic chemical vapor deposition (MOCVD). A self-organized growth of the granular composite took place in situ as a result of phase separation of the Pr–Sr–Lu–Mn–O system into the perovskite and hexagonal phases. Optical transmission measurements revealed a large negative magnetotransmission effect in the layered nanocomposite over a wide spectral and temperature range. The granular nanocomposite unexpectedly showed an even larger, but positive, magnetotransmission effect at room temperature. - Highlights: • Thin-film ferromagnetic–ferroelectric nanocomposites have been prepared by MOCVD. • Giant change of optical transparency of nanocomposites in magnetic field was detected. • Positive magnetotransmission in the granular nanocomposite was discovered in the IR. • Negative magnetotransmission in the layered nanocomposite was revealed in the IR. • Ferroelectric–ferromangetic nanocomposite is a promising material for optoelectronics

  17. Antimicrobial material obtained from pulping white paper waste

    Angioletto, E.; Fiori, M.A.; Pitch, C.T.; Mendes, E.; Oliveira, C.M.; Melo, C.R.; Riella, H.G.

    2011-01-01

    The paper industry produces white waste, consisting of 45% kaolin, 45% calcium carbonate and 10% cellulose. After calcination at 903K for two hours, the cellulose is burnt and decomposed kaolin in metakaolin. Held treatment of the calcined material with hydrochloric acid to remove calcium carbonate. The metakaolin is treated with sodium hydroxide solution to obtain the type of zeolite 4A. The zeolites were characterized using XRD, XRF and SEM. The zeolite was subjected to ion exchange with zinc sulphate and silver nitrate at room temperature, stirring, for six hours. This material was tested with Staphylococcus aureus and Escherichia coli, to get excellent results with regard to bactericidal properties.(author)

  18. Lithium storage into carbonaceous materials obtained from sugarcane bagasse

    Matsubara, Elaine Y.; Lala, Stella M.; Rosolen, Jose Mauricio

    2010-01-01

    Carbonaceous materials with different structures are prepared by carbonization of sugarcane bagasse. Depending on carbonization conditions, it is possible to obtain soot rich in flakes or in honeycomb-shaped micrometric particles, whose concentration has large influence on lithium storage into electrodes. The soot rich in honeycomb-shaped particles provides the best electrochemical performance, with a reversible specific capacity of 310 mAh g -1 . The results suggest that the sugarcane bagasse can be potentially used in the design of anodic materials for lithium ion batteries. (author)

  19. Numerical insight into the micromechanics of jet erosion of a cohesive granular material

    Cuéllar Pablo

    2017-01-01

    Full Text Available Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet.

  20. Numerical insight into the micromechanics of jet erosion of a cohesive granular material

    Cuéllar, Pablo; Benseghier, Zeyd; Luu, Li-Hua; Bonelli, Stéphane; Delenne, Jean-Yves; Radjaï, Farhang; Philippe, Pierre

    2017-06-01

    Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM) and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet.

  1. Pulling an intruder from a granular material: a novel depinning experiment

    Zhang Yue

    2017-01-01

    Full Text Available Two-dimensional impact experiments by Clark et al. [2] identified the source of inertial drag to be caused by ‘collisions’ with a latent force network, leading to large fluctuations of the force experienced by the impactor. These collisions provided the major drag on an impacting intruder until the intruder was nearly at rest. As a complement, we consider controlled pull-out experiments where a buried intruder is pulled out of a material, starting from rest. This provides a means to better understand the non-inertial part of the drag force, and to explore the mechanisms associated with the force fluctuations. To some extent, the pull out process is a time reversed version of the impact process. In order to visualize this pulling process, we use 2D photoelastic disks from which circular intruders of different radii are pulled out. We present results about the dynamics of the intruder and the structures of the force chains inside the granular system as captured by slow and high speed imaging.

  2. Particle Damping with Granular Materials for Multi Degree of Freedom System

    Masanobu Inoue

    2011-01-01

    Full Text Available A particle damper consists of a bed of granular materials moving in cavities within a multi degree-of-freedom (MDOF structure. This paper deals with the damping effects on forced vibrations of a MDOF structure provided with the vertical particle dampers. In the analysis, the particle bed is assumed to be a single mass, and the collisions between the granules and the cavities are completely inelastic, i.e., all energy dissipation mechanisms are wrapped into zero coefficient of restitution. To predict the particle damping effect, equations of motion are developed in terms of equivalent single degree-of-freedom (SDOF system and damper mass with use made of modal approach. In this report, the periodic vibration model comprising sustained contact on or separation of the damper mass from vibrating structure is developed. A digital model is also formulated to simulate the damped motion of the physical system, taking account of all vibration modes. Numerical and experimental studies are made of the damping performance of plural dampers located at selected positions throughout a 3MDOF system. The experimental results confirm numerical prediction that collision between granules and structures is completely inelastic as the contributing mechanism of damping in the vertical vibration. It is found that particle dampers with properly selected mass ratios and clearances effectively suppress the resonance peaks over a wide frequency range.

  3. Accuracy of stone casts obtained by different impression materials

    Adriana Cláudia Lapria Faria

    2008-12-01

    Full Text Available Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p .05 to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.

  4. Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials

    Perry, J. L.; Agui, J. H.; Vijayakimar, R

    2016-01-01

    Contaminants generated aboard crewed spacecraft by diverse sources consist of both gaseous chemical contaminants and particulate matter. Both HEPA media filters and packed beds of granular material, such as activated carbon, which are both commonly employed for cabin atmosphere purification purposes have efficacy for removing nanoparticulate contaminants from the cabin atmosphere. The phenomena associated with particulate matter removal by HEPA media filters and packed beds of granular material are reviewed relative to their efficacy for removing fine (less than 2.5 micrometers) and ultrafine (less than 0.01 micrometers) sized particulate matter. Considerations are discussed for using these methods in an appropriate configuration to provide the most effective performance for a broad range of particle sizes including nanoparticulates.

  5. A theoretical and numerical study of the flow of granular materials down an inclined plane. [Quarterly progress report, January--March 1995

    Rajagopal, K.R.

    1995-09-01

    The mechanics of the flowing granular materials such as coal, agricultural products, fertilizers, dry chemicals, metal ores, etc. have received a great deal of attention as it has relevance to several important technological problems. Despite wide interest and more than five decades of experimental and theoretical investigations, most aspects of the behavior of flowing granular materials are still not well understood. So Experiments have to be devised which quantify and describe the non-linear behavior of the granular materials, and theories developed which can explain the experimentally observed facts. Here we carry out a systematic numerical study of the flow of granular materials down an inclined plane using the models that stem from both the continuum theory approach and the kinetic theory approach. We also look at the existence of solutions, multiplicity and stability of solutions to the governing equations.

  6. Planning for the Collection and Analysis of Samples of Martian Granular Materials Potentially to be Returned by Mars Sample Return

    Carrier, B. L.; Beaty, D. W.

    2017-12-01

    NASA's Mars 2020 rover is scheduled to land on Mars in 2021 and will be equipped with a sampling system capable of collecting rock cores, as well as a specialized drill bit for collecting unconsolidated granular material. A key mission objective is to collect a set of samples that have enough scientific merit to justify returning to Earth. In the case of granular materials, we would like to catalyze community discussion on what we would do with these samples if they arrived in our laboratories, as input to decision-making related to sampling the regolith. Numerous scientific objectives have been identified which could be achieved or significantly advanced via the analysis of martian rocks, "regolith," and gas samples. The term "regolith" has more than one definition, including one that is general and one that is much more specific. For the purpose of this analysis we use the term "granular materials" to encompass the most general meaning and restrict "regolith" to a subset of that. Our working taxonomy includes the following: 1) globally sourced airfall dust (dust); 2) saltation-sized particles (sand); 3) locally sourced decomposed rock (regolith); 4) crater ejecta (ejecta); and, 5) other. Analysis of martian granular materials could serve to advance our understanding areas including habitability and astrobiology, surface-atmosphere interactions, chemistry, mineralogy, geology and environmental processes. Results of these analyses would also provide input into planning for future human exploration of Mars, elucidating possible health and mechanical hazards caused by the martian surface material, as well as providing valuable information regarding available resources for ISRU and civil engineering purposes. Results would also be relevant to matters of planetary protection and ground-truthing orbital observations. We will present a preliminary analysis of the following, in order to generate community discussion and feedback on all issues relating to: What are the

  7. Porous materials based on foaming solutions obtained from industrial waste

    Starostina, I. V.; Antipova, A. N.; Ovcharova, I. V.; Starostina, Yu L.

    2018-03-01

    This study analyzes foam concrete production efficiency. Research has shown the possibility of using a newly-designed protein-based foaming agent to produce porous materials using gypsum and cement binders. The protein foaming agent is obtained by alkaline hydrolysis of a raw mixture consisting of industrial waste in an electromagnetic field. The mixture consists of spent biomass of the Aspergillus niger fungus and dust from burning furnaces used in cement production. Varying the content of the foaming agent allows obtaining gypsum binder-based foam concretes with the density of 200-500 kg/m3 and compressive strength of 0.1-1.0 MPa, which can be used for thermal and sound insulation of building interiors. Cement binders were used to obtain structural and thermal insulation materials with the density of 300-950 kg/m3 and compressive strength of 0.9-9.0 MPa. The maximum operating temperature of cement-based foam concretes is 500°C because it provides the shrinkage of less than 2%.

  8. Granular MX-80 bentonite as buffer material: a focus on swelling characteristics

    Rizzi, M.; Laloui, L.; Salager, S.; Marschall, P.

    2010-01-01

    Document available in extended abstract form only. The Swiss High Level Waste (HLW) disposal concept envisages the emplacement of the waste canisters in horizontal tunnels excavated at a depth of several hundred meters in an over-consolidated clay-stone formation. After waste emplacement the disposal tunnels are backfilled with MX-80 granular bentonite. Research activities are presented in this paper, aimed at characterising the geomechanical behaviour of the MX-80 granular bentonite and at providing the theoretical framework for modelling its response to thermo-hydro- mechanical (THM) perturbations. From the experimental point of view, a series of tests has been designed in order to extract constitutive data and to assess the temperature and suction effects on the mechanical behaviour of the bentonite, paying particular attention in the investigation to the swelling behaviour of the material. As for the theoretical framework an elasto-plastic constitutive model has been developed to take into account those coupled processes of stress, capillary pressure, and temperature to which the bentonite will be submitted,. Bentonite is mainly composed of the smectite mineral montmorillonite with a high swelling capacity which may provide sufficient sealing properties to seal the tunnel without gaps and to restore the buffer continuity. In fact, as bentonite hydrates in the repositories it will expand in those areas where it is allowed and will exert a swelling pressure where the material is confined. The results of both confined and free swelling tests are presented. Confined tests are aiming at determining the pressure applied by the material during complete saturation under isochoric conditions, whereas in the free swelling tests the strain on hydration is measured. Some results from confined swelling tests at ambient temperature are presented. The specimen is compacted uniaxially directly in the cells, the initial dry density being chosen in the range between 1.6 and 1

  9. Numerical investigation of particle-blast interaction during explosive dispersal of liquids and granular materials

    Pontalier, Q.; Lhoumeau, M.; Milne, A. M.; Longbottom, A. W.; Frost, D. L.

    2018-04-01

    Experiments show that when a high-explosive charge with embedded particles or a charge surrounded by a layer of liquid or granular material is detonated, the flow generated is perturbed by the motion of the particles and the blast wave profile differs from that of an ideal Friedlander form. Initially, the blast wave overpressure is reduced due to the energy dissipation resulting from compaction, fragmentation, and heating of the particle bed, and acceleration of the material. However, as the blast wave propagates, particle-flow interactions collectively serve to reduce the rate of decay of the peak blast wave overpressure. Computations carried out with a multiphase hydrocode reproduce the general trends observed experimentally and highlight the transition between the particle acceleration/deceleration phases, which is not accessible experimentally, since the particles are obscured by the detonation products. The dependence of the particle-blast interaction and the blast mitigation effectiveness on the mitigant to explosive mass ratio, the particle size, and the initial solid volume fraction is investigated systematically. The reduction in peak blast overpressure is, as in experiments, primarily dependent on the mass ratio of material to explosive, with the particle size, density, and initial porosity of the particle bed playing secondary roles. In the near field, the blast overpressure decreases sharply with distance as the particles are accelerated by the flow. When the particles decelerate due to drag, energy is returned to the flow and the peak blast overpressure recovers and reaches values similar to that of a bare explosive charge for low mass ratios. Time-distance trajectory plots of the particle and blast wave motion with the pressure field superimposed, illustrate the weak pressure waves generated by the motion of the particle layer which travel upstream and perturb the blast wave motion. Computation of the particle and gas momentum flux in the multiphase

  10. Numerical investigation of particle-blast interaction during explosive dispersal of liquids and granular materials

    Pontalier, Q.; Lhoumeau, M.; Milne, A. M.; Longbottom, A. W.; Frost, D. L.

    2018-05-01

    Experiments show that when a high-explosive charge with embedded particles or a charge surrounded by a layer of liquid or granular material is detonated, the flow generated is perturbed by the motion of the particles and the blast wave profile differs from that of an ideal Friedlander form. Initially, the blast wave overpressure is reduced due to the energy dissipation resulting from compaction, fragmentation, and heating of the particle bed, and acceleration of the material. However, as the blast wave propagates, particle-flow interactions collectively serve to reduce the rate of decay of the peak blast wave overpressure. Computations carried out with a multiphase hydrocode reproduce the general trends observed experimentally and highlight the transition between the particle acceleration/deceleration phases, which is not accessible experimentally, since the particles are obscured by the detonation products. The dependence of the particle-blast interaction and the blast mitigation effectiveness on the mitigant to explosive mass ratio, the particle size, and the initial solid volume fraction is investigated systematically. The reduction in peak blast overpressure is, as in experiments, primarily dependent on the mass ratio of material to explosive, with the particle size, density, and initial porosity of the particle bed playing secondary roles. In the near field, the blast overpressure decreases sharply with distance as the particles are accelerated by the flow. When the particles decelerate due to drag, energy is returned to the flow and the peak blast overpressure recovers and reaches values similar to that of a bare explosive charge for low mass ratios. Time-distance trajectory plots of the particle and blast wave motion with the pressure field superimposed, illustrate the weak pressure waves generated by the motion of the particle layer which travel upstream and perturb the blast wave motion. Computation of the particle and gas momentum flux in the multiphase

  11. Strain localisation in granular media

    Desrues , Jacques

    1984-01-01

    This study is devoted to strain localisation in Granular materials. Both experimental and theoretical results have been obtained.The first part of the thesis is a review of the methods and theories about rupture in sols mechanics and more generally, in solid mechanics. The classical framework of Shear Band analysis is presented, and the main results available for different classes of materials are discussed.The second part describes an experimental study of strain localisation in sand specime...

  12. Effective elasticity coefficients of native rocks and consolidated granular matter

    Schulz, Beatrix M.; Schulz, Michael

    2008-01-01

    The elastic coefficients of binary heterogeneous materials, such as several native rock materials or consolidated granular matter will be determined in terms of a perturbation expansion. Furthermore, in order to check the validity of the obtained results, these are compared with numerical investigations using Boole's model of randomly distributed spheres. Finally, we apply the results on several classes of native rocks and consolidated granular materials

  13. A theoretical and numerical study of the flow of granular materials down an inclined plane. Final report

    Rajagopal, K.R.

    1995-12-31

    The mechanics of the flowing granular materials such as coal, agricultural products, at deal of attention as it has fertilizers, dry chemicals, metal ores, etc. have received a great deal of attention as it has relevance to several important technological problems. Despite wide interest and more than five decades of experimental and theoretical investigations, most aspects of the behavior of flowing granular materials are still not well understood. So Experiments have to be devised which quantify and describe the non-linear behavior of the modular materials, and theories developed which can explain the experimentally observed facts. As many models have been suggested for describing the behavior of granular materials, from both continuum and kinetic theory viewpoints, we proposed to investigate the validity and usefulness of representative models from both the continuum and kinetic theory points of view, by determining the prediction of such a theory, in a representative flow, with respect to existence, non-existence, multiplicity and stability of solutions. The continuum model to be investigated is an outgrowth of a model due to Goodman and Cowin (1971, 1972) and the kinetic theory models being those due to Jenkins and Richman (1985) and Boyle and Massoudi (1989). In this report we present detailed results regarding the same. Interestingly, we find that the predictions of all the theories, in certain parameter space associated with these models, are qualitatively similar. This ofcourse depends on the values assumed for various material parameters in the models, which as yet are unknown, as reliable experiments have not been carried out as yet for their determination.

  14. Sound propagation in dry granular materials : discrete element simulations, theory, and experiments

    Mouraille, O.J.P.

    2009-01-01

    In this study sound wave propagation through different types of dry confined granular systems is studied. With three-dimensional discrete element simulations, theory and experiments, the influence of several micro-scale properties: friction, dissipation, particle rotation, and contact disorder, on

  15. Thermal transport in lithium ion batteries: An experimental investigation of interfaces and granular materials

    Gaitonde, Aalok Jaisheela Uday

    Increasing usage and recent accidents due to lithium-ion (Li-ion) batteries exploding or catching on fire has inspired research on the characterization and thermal management of these batteries. In cylindrical 18650 cells, heat generated during the battery's charge/discharge cycle is poorly dissipated to the surrounding through its metallic case due to the poor thermal conductivity of the jelly roll, which is spirally wound with many interfaces between electrodes and the polymeric separator. This work presents a technique to measure the thermal conduction across the metallic case-plastic separator interface, which ultimately limits heat transfer out of the jelly roll. The polymeric separator and metallic case are harvested from discharged commercial 18650 battery cells for thermal testing. A miniaturized version of the reference bar method enables measurements of the interface resistance between the case and the separator by establishing a temperature gradient across a multilayer stack consisting of two reference layers of known thermal conductivity and the case-separator sample. The case-separator interfacial conductance is reported for a range of case temperatures and interface pressures. The mean thermal conductance across the case-separator interface is 670 +/- 275 W/(m2K) and no significant temperature or pressure dependence is observed. The effective thermal conductivity of the battery stack is measured to be 0.27 W/m/K and 0.32 W/m/K in linear and radial configurations, respectively. Many techniques for fabricating battery electrodes involve coating particles of the active materials on metallic current collectors. The impact of mechanical shearing on the resultant thermal properties of these packed particle beds during the fabrication process has not yet been studied. Thus, the final portion of this thesis designs and validates a measurement system to measure the effects of mechanical shearing on the thermal conductivity of packed granular beds. This system

  16. Analysis and Modeling of Process of Residual Deformations Accumulation in Soils and Granular Materials

    Aleksandrov, A. S.; Dolgih, G. V.; Kalinin, A. L.

    2017-11-01

    It is established that under the influence of repeated loads the process of plastic deformation in soils and discrete materials is hereditary. To perform the mathematical modeling of plastic deformation, the authors applied the integral equation by solution of which they manage to obtain the power and logarithmic dependencies connecting plastic deformation with the number of repeated loads, the parameters of the material and components of the stress tensor in the principal axes. It is shown that these dependences generalize a number of models proposed earlier in Russia and abroad. Based on the analysis of the experimental data obtained during material testing in the dynamic devices of triaxial compression at different values of the stress deviator, the coefficients in the proposed models of deformation are determined. The authors determined the application domain for logarithmic and degree dependences.

  17. A thermodynamic approach to obtain materials properties for engineering applications

    Chang, Y. Austin

    1993-01-01

    With the ever increases in the capabilities of computers for numerical computations, we are on the verge of using these tools to model manufacturing processes for improving the efficiency of these processes as well as the quality of the products. One such process is casting for the production of metals. However, in order to model metal casting processes in a meaningful way it is essential to have the basic properties of these materials in their molten state, solid state as well as in the mixed state of solid and liquid. Some of the properties needed may be considered as intrinsic such as the density, heat capacity or enthalpy of freezing of a pure metal, while others are not. For instance, the enthalpy of solidification of an alloy is not a defined thermodynamic quantity. Its value depends on the micro-segregation of the phases during the course of solidification. The objective of the present study is to present a thermodynamic approach to obtain some of the intrinsic properties and combining thermodynamics with kinetic models to estimate such quantities as the enthalpy of solidification of an alloy.

  18. Computational study on the behaviors of granular materials under mechanical cycling

    Wang, Xiaoliang; Ye, Minyou; Chen, Hongli

    2015-01-01

    Considering that fusion pebble beds are probably subjected to the cyclic compression excitation in their future applications, we presented a computational study to report the effect of mechanical cycling on the behaviors of granular matter. The correctness of our numerical experiments was confirmed by a comparison with the effective medium theory. Under the cyclic loads, the fast granular compaction was observed to evolve in a stretched exponential law. Besides, the increasing stiffening in packing structure, especially the decreasing moduli pressure dependence due to granular consolidation, was also observed. For the force chains inside the pebble beds, both the internal force distribution and the spatial distribution of force chains would become increasingly uniform as the external force perturbation proceeded and therefore produced the stress relief on grains. In this case, the originally proposed 3-parameter Mueth function was found to fail to describe the internal force distribution. Thereby, its improved functional form with 4 parameters was proposed here and proved to better fit the data. These findings will provide more detailed information on the pebble beds for the relevant fusion design and analysis

  19. The contact heat transfer between the heating plate and granular materials in rotary heat exchanger under overloaded condition

    Luanfang Duan

    2018-03-01

    Full Text Available In the present work, the contact heat transfer between the granular materials and heating plates inside plate rotary heat exchanger (PRHE was investigated. The heat transfer coefficient is dominated by the contact heat transfer coefficient at hot wall surface of the heating plates and the heat penetration inside the solid bed. A plot scale PRHE with a diameter of Do = 273 mm and a length of L = 1000 mm has been established. Quartz sand with dp = 2 mm was employed as the experimental material. The operational parameters were in the range of ω = 1 – 8 rpm, and F = 15, 20, 25, 30%, and the effect of these parameters on the time-average contact heat transfer coefficient was analyzed. The time-average contact heat transfer coefficient increases with the increase of rotary speed, but decreases with the increase of the filling degree. The measured data of time-average heat transfer coefficients were compared with theoretical calculations from Schlünder’s model, a good agreement between the measurements and the model could be achieved, especially at a lower rotary speed and filling degree level. The maximum deviation between the calculated data and the experimental data is approximate 10%. Keywords: Rotary heat exchanger, Contact heat transfer, Granular material, Heating plate, Overloaded

  20. Granular gas dynamics

    Brilliantov, Nikolai

    2003-01-01

    While there is not yet any general theory for granular materials, significant progress has been achieved for dilute systems, also called granular gases. The contributions in this book address both the kinetic approach one using the Boltzmann equation for dissipative gases as well as the less established hydrodynamic description. The last part of the book is devoted to driven granular gases and their analogy with molecular fluids. Care has been taken so as to present the material in a pedagogical and self-contained way and this volume will thus be particularly useful to nonspecialists and newcomers to the field.

  1. Modeling of light dynamic cone penetration test - Panda 3 ® in granular material by using 3D Discrete element method

    Tran, Quoc Anh; Chevalier, Bastien; Benz, Miguel; Breul, Pierre; Gourvès, Roland

    2017-06-01

    The recent technological developments made on the light dynamic penetration test Panda 3 ® provide a dynamic load-penetration curve σp - sp for each impact. This curve is influenced by the mechanical and physical properties of the investigated granular media. In order to analyze and exploit the load-penetration curve, a numerical model of penetration test using 3D Discrete Element Method is proposed for reproducing tests in dynamic conditions in granular media. All parameters of impact used in this model have at first been calibrated by respecting mechanical and geometrical properties of the hammer and the rod. There is a good agreement between experimental results and the ones obtained from simulations in 2D or 3D. After creating a sample, we will simulate the Panda 3 ®. It is possible to measure directly the dynamic load-penetration curve occurring at the tip for each impact. Using the force and acceleration measured in the top part of the rod, it is possible to separate the incident and reflected waves and then calculate the tip's load-penetration curve. The load-penetration curve obtained is qualitatively similar with that obtained by experimental tests. In addition, the frequency analysis of the measured signals present also a good compliance with that measured in reality when the tip resistance is qualitatively similar.

  2. What Actually Happens When Granular Materials Deform Under Shear: A Look Within

    Viggiani, C.

    2012-12-01

    depends on the quality of the physics one injects: ideally, this comes directly from experiments. In Grenoble, this is what we do, combining various advanced experimental techniques. We are able to image, in three dimensions and at small scales, the deformation processes accompanying failure in geomaterials. This allows us to understand these processes and subsequently to define models at a pertinently small scale. I will present a few examples of the kind of experimental results which could inform a micro scale model. X-ray micro tomography imaging is the key measurement tool. This is used during loading, providing complete 3D images of a sand specimen at several stages throughout a triaxial compression test. Images from x-rays are then analyzed either in a continuum sense (using 3D Digital Image Correlation) or looking at the individual particle kinematics (Particle Tracking). I will show some of our most recent results, in which individual sand grains are followed with a technique combining very recent developments in image correlation and particle tracking. These advanced techniques offer us a look at what actually happens when a granular material deforms and eventually fails.

  3. Characteristic analysis on moderating material for obtaining epithermal neutron beam

    Jiang Xinbiao; Chen Da; Zhang Ying

    2000-01-01

    The one dimension discrete coordinates transport code ANISN was used to calculate three-group constants of 11 elements which could be used to consist moderating epithermal neutron material of beam. Moderating character of simple substances, compounds and mixtures consisted of the optimized elements analyzed three kinds of moderating materials were optimized for epithermal neutron beam

  4. Stagnation, circulation, and erosion of granular materials through belt conveyor sluice gate

    Pohlman, Nicholas; Moralda, Michael; Dunne, Ryan

    2013-11-01

    Control of flow rates in conversion reactors for discrete materials like biomass can be achieved in belt conveyors through a combination of belt speed, hopper size, and aperture opening. As material is extracted from the bottom of the storage hopper, other material cannot achieve plug flow and therefore is restricted from exiting through a sluice-gate type opening. The excess material moves vertically from the opening causing a pile up and recirculation back along the free surface of the hopper. Experimental results obtained through high speed imaging show the position of the stagnation point as well as the rate of circulation is dependent on the mass flow rate achieved and instantaneous fill level. The movement of material into the plug flow along the belt allows verification of deposition models on erodible beds rather than rigid surfaces with artificial roughness of glued particles. Similarly, the pile-up at the exit influences the efficiency of the transport affecting the narrow energy return on investment of biomass resources. The laboratory-scale behavior can therefore be translated into industrial performance metrics for increased operational efficiency. This work is supported by the NSF REU Site Operation E-Tank under award number 1156789.

  5. An approach to discriminatively determine thoron and radon emanation rates for a granular material with a scintillation cell

    Sakoda, Akihiro; Meisenberg, Oliver; Tschiersch, Jochen

    2016-01-01

    A powder sandwich technique was applied to determine thoron ("2"2"0Rn) and radon ("2"2"2Rn) emanation rates for a granular material. The feature of this technique is the sample preparation, in which a granular material is put and fixed between two membrane filters. Airflow is directly given to this sandwich sample, will include thoron and radon emanated from the material, and then is transferred to the detector. This method makes sure that thoron and radon emanated are not retained in pore space within the sample volume, which is crucial for the appropriate emanation test. This technique was first introduced by Kanse et al. (2013) with the intention to measure the emanation of thoron - but not of radon - from materials having much higher "2"2"4Ra activity than "2"2"6Ra. In the present study, the methodology for the discriminative determination of thoron and radon emanation rates from a granular material has been examined using a flow-through scintillation cell and sandwich sample. The mathematical model was developed to differentiate total alpha counts into thoron- and radon-associated counts. With a sample of uranium ore, this model was experimentally validated by comparison between the scintillation cell and a reference detector that can discriminatively measure thoron and radon concentrations. Furthermore, the detection limits and uncertainties were evaluated to discuss the characteristics of this method. Key parameters for improving the determination of thoron and radon emanations were found to be the background radon concentration and the leakage of radon from the measurement system, respectively. It was concluded that the present method is advantageous to a sample that has much higher "2"2"6Ra activity than "2"2"4Ra. - Highlights: • The methodology of appropriate and discriminative measurement of thoron and radon emanation is presented. • Measurement of thoron and radon emanated from a sample was made using a scintillation cell. • Detection limits and

  6. The response of dense dry granular material to the shear reversal

    Zhang, Jie; Ren, Jie; Farhadi, Somayeh; Behringer, Robert

    2008-11-01

    We have performed two dimensional granular experiments under pure shear using bidisperse photo-elastic disks. Starting from a stress free state, a square box filled with granular particles is subject to shear. The forward shears involved various number of steps, leading to maximum strains between 0.1 and 0.3. The area is kept constant during the shear. The network of force chains gradually built up as the strain increased, leading to increased pressure and shear stress. Reverse shear was then applied to the system. Depending on the initial packing fraction and the strain at which the shear is reversed, the force chain network built prior to the shear reversal may be destroyed completely or partially destroyed. Following the force chain weakening, when the reserve shear is continuously applied to the system, there is a force chain strengthening. Following each change of the system, contact forces of individual disks were measured by applying an inverse algorithm. We also kept track of the displacement and angle of rotation of every particle from frame to frame. We present the results for the structure failure and reconstruction during shear reversals. We also present data for stresses, contact force distributions and other statistical measures.

  7. Physical Explanation of Archie's Porosity Exponent in Granular Materials: A Process-Based, Pore-Scale Numerical Study

    Niu, Qifei; Zhang, Chi

    2018-02-01

    The empirical Archie's law has been widely used in geosciences and engineering to explain the measured electrical resistivity of many geological materials, but its physical basis has not been fully understood yet. In this study, we use a pore-scale numerical approach combining discrete element-finite difference methods to study Archie's porosity exponent m of granular materials over a wide porosity range. Numerical results reveal that at dilute states (e.g., porosity ϕ > 65%), m is exclusively related to the particle shape and orientation. As the porosity decreases, the electric flow in pore space concentrates progressively near particle contacts and m increases continuously in response to the intensified nonuniformity of the local electrical field. It is also found that the increase in m is universally correlated with the volume fraction of pore throats for all the samples regardless of their particle shapes, particle size range, and porosities.

  8. COMPORTAMIENTO DE UN MATERIAL GRANULAR NO TRATADO EN ENSAYOS TRIAXIALES CÍCLICOS CON PRESIÓN DE CONFINAMIENTO CONSTANTE Y VARIABLE BEHAVIOR OF AN UNBOUND GRANULAR MATERIAL IN CYCLIC TRIAXIAL TESTS WITH CONSTANT AND VARIABLE CONFINING PRESSURE

    Hugo Alexander Rondón Quintana

    2008-12-01

    Full Text Available En un pavimento, cada una de las capas de la estructura experimenta bajo una carga vehicular ciclos de esfuerzo con componentes vertical, horizontal y de corte. Para el estudio de materiales granulares no tratados (utilizados para conformar capas de base y subbase, la mayor parte de las investigaciones se realizan empleando equipos triaxiales cíclicos en donde sólo la carga vertical es cíclica y la presión de confinamiento permanece constante durante el ensayo. Un ensayo que reproduce mejor la forma como se distribuyen los esfuerzos en estas capas es el ensayo triaxial cíclico con presión de confinamiento variable. En este ensayo se pueden modelar las componentes cíclicas tanto en el sentido vertical como horizontal. A pesar que son ensayos distintos, la ingeniería de pavimentos supone que la respuesta que experimentan estos materiales en estos ensayos es similar, lo anterior basado en algunos estudios realizados en la década de los setenta. En la presente investigación se diseña y desarrolla un programa experimental más detallado, para comparar el comportamiento que desarrolla un material granular no tratado en estos ensayos. De los resultados se evidencia que sólo para algunas trayectorias de esfuerzo, la dirección y la acumulación de la deformación vertical y volumétrica es similar.In a pavement structure, passing wheel loads impose cyclic stresses consisting of vertical, horizontal and shear components. Studies of the behavior of unbound granular materials (UGM, used for base and sub-base layers under cyclic loading are mostly performed using the axisymmetric triaxial test with constant confining pressure (CCP test and a cyclic variation of the axial stress. However, in this type of test only the vertical component of the cyclic stress path is considered. The oscillation of the horizontal stress can be reproduced by an additional cyclic variation of the confining pressure (VCP test. CCP and VCP tests are sometimes assumed to

  9. Size-induced axial band structure and directional flow of a ternary-size granular material in a 3-D horizontal rotating drum

    Yang, Shiliang; Sun, Yuhao; Ma, Honghe; Chew, Jia Wei

    2018-05-01

    Differences in the material property of the granular material induce segregation which inevitably influences both natural and industrial processes. To understand the dynamical segregation behavior, the band structure, and also the spatial redistribution of particles induced by the size differences of the particles, a ternary-size granular mixture in a three-dimensional rotating drum operating in the rolling flow regime is numerically simulated using the discrete element method. The results demonstrate that (i) the axial bands of the medium particles are spatially sandwiched in between those of the large and small ones; (ii) the total mass in the active and passive regions is a global parameter independent of segregation; (iii) nearly one-third of all the particles are in the active region, with the small particles having the highest mass fraction; (iv) the axial bands initially appear near the end wall, then become wider and purer in the particular species with time as more axial bands form toward the axial center; and (v) the medium particle type exhibits segregation later and has the narrowest axial bandwidth and least purity in the bands. Compared to the binary-size system, the presence of the medium particle type slightly increases the total mass in the active region, leads to larger mass fractions of the small and large particle types in the active region, and enhances the axial segregation in the system. The results obtained in the current work provide valuable insights regarding size segregation, and band structure and formation in the rotating drum with polydisperse particles.

  10. Quasi-static incremental behavior of granular materials: Elastic-plastic coupling and micro-scale dissipation

    Kuhn, Matthew R.; Daouadji, Ali

    2018-05-01

    The paper addresses a common assumption of elastoplastic modeling: that the recoverable, elastic strain increment is unaffected by alterations of the elastic moduli that accompany loading. This assumption is found to be false for a granular material, and discrete element (DEM) simulations demonstrate that granular materials are coupled materials at both micro- and macro-scales. Elasto-plastic coupling at the macro-scale is placed in the context of thermomechanics framework of Tomasz Hueckel and Hans Ziegler, in which the elastic moduli are altered by irreversible processes during loading. This complex behavior is explored for multi-directional loading probes that follow an initial monotonic loading. An advanced DEM model is used in the study, with non-convex non-spherical particles and two different contact models: a conventional linear-frictional model and an exact implementation of the Hertz-like Cattaneo-Mindlin model. Orthotropic true-triaxial probes were used in the study (i.e., no direct shear strain), with tiny strain increments of 2 ×10-6 . At the micro-scale, contact movements were monitored during small increments of loading and load-reversal, and results show that these movements are not reversed by a reversal of strain direction, and some contacts that were sliding during a loading increment continue to slide during reversal. The probes show that the coupled part of a strain increment, the difference between the recoverable (elastic) increment and its reversible part, must be considered when partitioning strain increments into elastic and plastic parts. Small increments of irreversible (and plastic) strain and contact slipping and frictional dissipation occur for all directions of loading, and an elastic domain, if it exists at all, is smaller than the strain increment used in the simulations.

  11. Comparisons of physical experiment and discrete element simulations of sheared granular materials in an annular shear cell

    Ji, S.; Hanes, D.M.; Shen, H.H.

    2009-01-01

    In this study, we report a direct comparison between a physical test and a computer simulation of rapidly sheared granular materials. An annular shear cell experiment was conducted. All parameters were kept the same between the physical and the computational systems to the extent possible. Artificially softened particles were used in the simulation to reduce the computational time to a manageable level. Sensitivity study on the particle stiffness ensured such artificial modification was acceptable. In the experiment, a range of normal stress was applied to a given amount of particles sheared in an annular trough with a range of controlled shear speed. Two types of particles, glass and Delrin, were used in the experiment. Qualitatively, the required torque to shear the materials under different rotational speed compared well with those in the physical experiments for both the glass and the Delrin particles. However, the quantitative discrepancies between the measured and simulated shear stresses were nearly a factor of two. Boundary conditions, particle size distribution, particle damping and friction, including a sliding and rolling, contact force model, were examined to determine their effects on the computational results. It was found that of the above, the rolling friction between particles had the most significant effect on the macro stress level. This study shows that discrete element simulation is a viable method for engineering design for granular material systems. Particle level information is needed to properly conduct these simulations. However, not all particle level information is equally important in the study regime. Rolling friction, which is not commonly considered in many discrete element models, appears to play an important role. ?? 2009 Elsevier Ltd.

  12. Discrete Element Method for Modeling the Mechanical Behavior of Unsaturated Granular Material

    K. Tourani

    2016-09-01

    Full Text Available Although a significant portion of conditions encountered in geotechnical engineering, for investigating engineering behavior of soil, involves unsaturated soils; the traditional analysis and design approach has been to assume the limiting conditions of soils being either completely dry or completely saturated. In unsaturated soils the capillary force produce attractive forces between particles. Discrete Element Method (DEM is an appropriate tool to consider the capillary effects. The calculations performed in DEM is based on iterative application of Newton’s second law to the particles and force-displacement law at the contacts. In the present study, the behavior of unsaturated soils in pendular regime is simulated utilizing DEM. Triaxial  compression tests were modeled as two-dimensional, considering capillary force effects. Finally, capillary effects on Macro parameters of a simulated granular soil (stress, axial strain, volumetric strain and void ratio and Mohr Coulomb failure criteria parameters were studied.

  13. Torsional shear flow of granular materials: shear localization and minimum energy principle

    Artoni, Riccardo; Richard, Patrick

    2018-01-01

    The rheological properties of granular matter submitted to torsional shear are investigated numerically by means of discrete element method. The shear cell is made of a cylinder filled by grains which are sheared by a bumpy bottom and submitted to a vertical pressure which is applied at the top. Regimes differing by their strain localization features are observed. They originate from the competition between dissipation at the sidewalls and dissipation in the bulk of the system. The effects of the (i) the applied pressure, (ii) sidewall friction, and (iii) angular velocity are investigated. A model, based on the purely local μ (I)-rheology and a minimum energy principle is able to capture the effect of the two former quantities but unable to account the effect of the latter. Although, an ad hoc modification of the model allows to reproduce all the numerical results, our results point out the need for an alternative rheology.

  14. Percolation-induced plasmonic state and double negative electromagnetic properties of Ni-Zn Ferrite/Cu granular composite materials

    Massango, Herieta; Kono, Koji; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2018-05-01

    Complex permeability and permittivity spectra of Ni-Zn Ferrite/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. The electrical conductivity σ shows insulating properties in the volume fraction of Cu particles below φ = 0.14. A large jump in conductivity was observed between φ = 0.14 and 0.24 indicating that the Cu particles make metallic conduction between this interval. Hence, the percolation threshold φC, was estimated to be 0.14. A percolation-induced low frequency plasmonic state with negative permittivity spectrum was observed from φ = 0.14-0.24. Meanwhile the negative permeability was observed at φ = 0.16, 0.19 and 0.24. Hence the DNG characteristic was realized in these Cu volume content in the frequency range from 105 MHz to 2 GHz.

  15. On the submerging of a spherical intruder into granular beds

    Wu Chuan-Yu

    2017-01-01

    Full Text Available Granular materials are complex systems and their mechanical behaviours are determined by the material properties of individual particles, the interaction between particles and the surrounding media, which are still incompletely understood. Using an advanced discrete element method (DEM, we simulate the submerging process of a spherical projectile (an intruder into granular materials of various properties with a zero penetration velocity (i.e. the intruder is touching the top surface of the granular bed and released from stationary and examine its settling behaviour. By systematically changing the density and size of the intruder and the particle density (i.e. the density of the particles in the granular bed, we find that the intruder can sink deep into the granular bed even with a zero penetration velocity. Furthermore, we confirm that under certain conditions the granular bed can behave like a Newtonian liquid and the submerging intruder can reach a constant velocity, i.e. the terminal velocity, identical to the settling of a sphere in a liquid, as observed experimentally. A mathematical model is also developed to predict the maximum penetration depth of the intruder. The model predictions are compared with experimental data reported in the literature,good agreement was obtained, demonstrating the model can accurately predict the submerging behaviour of the intruder in the granular media.

  16. Capillary pressure-saturation relationships for porous granular materials: Pore morphology method vs. pore unit assembly method

    Sweijen, Thomas; Aslannejad, Hamed; Hassanizadeh, S. Majid

    2017-09-01

    In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure-saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary pressure-saturation curves. To do so, we have generated 12 packings of spheres that are representative of four different glass-bead packings and eight different sand packings, for which we have found experimental data on the capillary pressure-saturation curve in the literature. In generating the packings, we matched the particle size distributions and porosity values of the granular materials. We have used three different pore-scale approaches for generating the capillary pressure-saturation curves of each packing: i) the Pore Unit Assembly (PUA) method in combination with the Mayer and Stowe-Princen (MS-P) approximation for estimating the entry pressures of pore throats, ii) the PUA method in combination with the hemisphere approximation, and iii) the Pore Morphology Method (PMM) in combination with the hemisphere approximation. The three approaches were also used to produce capillary pressure-saturation curves for the coating layer of paper, used in inkjet printing. Curves for such layers are extremely difficult to determine experimentally, due to their very small thickness and the presence of extremely small pores (less than one micrometer in size). Results indicate that the PMM and PUA-hemisphere method give similar capillary pressure-saturation curves, because both methods rely on a hemisphere to represent the air-water interface. The ability of the hemisphere approximation and the MS-P approximation to reproduce correct capillary pressure seems to depend on the type of particle size distribution, with the hemisphere approximation working well for narrowly distributed granular materials.

  17. MICROCT AND PREPARATION OF ß-TCP GRANULAR MATERIAL BY THE POLYURETHANE FOAM METHOD

    Robert Filmon

    2011-05-01

    Full Text Available Commercial ß-tricalcium phosphate (ß-TCP is commercialy available in granules manufactured by sintering of powders. We have evaluated the different steps of the manufacturing process of ß-TCP ceramics granules prepared from blocks obtained with the polyurethane foam technology. Three types of slurry were prepared with 10, 15 and 25 g of ß-TCP per gram of polyurethane foam. Analysis was done by scanning electron microscopy, EDX, Raman spectroscopy and microcomputed tomography combined with image analysis. A special algorithm was used to identify the internal microporosity (created by the calcination of the foam from the internal macroporosity due to the spatial repartition of the material. The low ß-TCP dosages readily infiltrated the foam and the slurry was deposited along the polymer rods. On the contrary, the highest concentration produced inhomogeneous infiltrated blocks and foam cavities appeared completely filled in some areas. 2D microcomputed sections and reconstructed 3D models evidenced this phenomenon and the frequency distribution of the thickness and separation of material trabeculae confirmed the heterogeneity of the distribution. When crushed, blocks prepared with the 25 g slurry provided the largest and irregular granulates.

  18. Obtaining of Grafted Planting Material at Some Romanian Tomatoes

    Madalina Doltu

    2016-11-01

    Full Text Available The tomatoes have highest share in Romanian crops from protected spaces (greenhouses, solariums. The grafting is an agronomical technique that induces or improves some qualities of the tomato cultivars (resistance to soil diseases and pests, resistance to abiotic factors, quantity and quality of fruit production. The research was aimed the establishing of the technological stages for producing of scion and rootstock seedlings from L. esculentum species, to obtain compatible phenotype when is grafted. The observations of this research were conducted on Department of Horticultural Cultures in Protected Spaces from Horting Institute Bucharest. The experience was carry out on a cultivar collection consisting from L. esculentum plants: scions (‘Siriana’–F1 hybrid and ‘Buzău 1600’– variety, creations from the germplasm bank of Research and Development Station for Vegetable Growing Buzău Romania (VDRS Buzău and rootstock (‘Groundforce’–F1 hybrid. The plant diameters were correlated for a grafting by the annexation method, cutting at 45 degrees. The grafting was performed successfully. The technological steps have achieved phenotypic compatibility of the symbiotes when was the grafting by annexation. The technology for producing of scion and rootstock seedlings at these Romanian tomatoes (‘Siriana’ and ‘Buzău’ 1600 was established for the crops in protected spaces in south area of Romania.

  19. Dynamic induced softening in frictional granular materials investigated by discrete-element-method simulation

    Lemrich, Laure; Carmeliet, Jan; Johnson, Paul A.; Guyer, Robert; Jia, Xiaoping

    2017-12-01

    A granular system composed of frictional glass beads is simulated using the discrete element method. The intergrain forces are based on the Hertz contact law in the normal direction with frictional tangential force. The damping due to collision is also accounted for. Systems are loaded at various stresses and their quasistatic elastic moduli are characterized. Each system is subjected to an extensive dynamic testing protocol by measuring the resonant response to a broad range of ac drive amplitudes and frequencies via a set of diagnostic strains. The system, linear at small ac drive amplitudes, has resonance frequencies that shift downward (i.e., modulus softening) with increased ac drive amplitude. Detailed testing shows that the slipping contact ratio does not contribute significantly to this dynamic modulus softening, but the coordination number is strongly correlated to this reduction. This suggests that the softening arises from the extended structural change via break and remake of contacts during the rearrangement of bead positions driven by the ac amplitude.

  20. The Grading Entropy-based Criteria for Structural Stability of Granular Materials and Filters

    Janos Lőrincz

    2015-05-01

    Full Text Available This paper deals with three grading entropy-based rules that describe different soil structure stability phenomena: an internal stability rule, a filtering rule and a segregation rule. These rules are elaborated on the basis of a large amount of laboratory testing and from existing knowledge in the field. Use is made of the theory of grading entropy to derive parameters which incorporate all of the information of the grading curve into a pair of entropy-based parameters that allow soils with common behaviours to be grouped into domains on an entropy diagram. Applications of the derived entropy-based rules are presented by examining the reason of a dam failure, by testing against the existing filter rules from the literature, and by giving some examples for the design of non-segregating grading curves (discrete particle size distributions by dry weight. A physical basis for the internal stability rule is established, wherein the higher values of base entropy required for granular stability are shown to reflect the closeness between the mean and maximum grain diameters, which explains how there are sufficient coarser grains to achieve a stable grain skeleton.

  1. The Quantified Characterization Method of the Micro-Macro Contacts of Three-Dimensional Granular Materials on the Basis of Graph Theory.

    Guan, Yanpeng; Wang, Enzhi; Liu, Xiaoli; Wang, Sijing; Luan, Hebing

    2017-08-03

    We have attempted a multiscale and quantified characterization method of the contact in three-dimensional granular material made of spherical particles, particularly in cemented granular material. Particle contact is defined as a type of surface contact with voids in its surroundings, rather than a point contact. Macro contact is a particle contact set satisfying the restrictive condition of a two-dimensional manifold with a boundary. On the basis of graph theory, two dual geometrical systems are abstracted from the granular pack. The face and the face set, which satisfies the two-dimensional manifold with a boundary in the solid cell system, are extracted to characterize the particle contact and the macro contact, respectively. This characterization method is utilized to improve the post-processing in DEM (Discrete Element Method) from a micro perspective to describe the macro effect of the cemented granular material made of spherical particles. Since the crack has the same shape as its corresponding contact, this method is adopted to characterize the crack and realize its visualization. The integral failure route of the sample can be determined by a graph theory algorithm. The contact force is assigned to the weight value of the face characterizing the particle contact. Since the force vectors can be added, the macro contact force can be solved by adding the weight of its corresponding faces.

  2. Obtaining of granular fertilizers based on ashes from combustion of waste residues and ground bones using phosphorous solubilization by bacteria Bacillus megaterium.

    Rolewicz, M; Rusek, P; Borowik, K

    2018-06-15

    The article presents research results on obtaining phosphorus granulated fertilizers on the basis of microbiologically activated sewage sludge ashes, ground bones and dried blood from meat industry. Granulation tests were carried out using a laboratory pan granulator as well as on an experimental pilot plant. The aim of the studies was to select the proper composition of the mixture of raw materials and binding agents to obtain granulated fertilizers from waste materials such as MSSA and MBM and bacteria lyophilisate. Obtained fertilizer samples were subjected to physical tests (granulation tests etc.) and quality assessment. The tests confirmed that it was possible to produce granulated phosphate fertilizers using the Bacillus megaterium for solubilization of phosphorus in a simple process. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Frequency Methods Applied to the Characterization of the Thermophysical Properties of a Granular Material with a Cylindrical Probe

    Carpentier, Olivier; Defer, Didier; Antczak, Emmanuel; Chartier, Thierry

    2012-01-01

    In many fields, such as in the agri-food industry or in the building industry, it is important to be able to monitor the thermophysical properties of granular materials. Regular thermal probes allow for the determination of one or several thermophysical factors. The success of the method used depends in part on the nature of the signal sent, on the type of physical model applied and eventually on the type of probe used and its implantation in the material. Although efficacious for most applications, regular thermal probes do present some limitations. It is the case, for example, when one has to know precisely the thermal contact resistance or the nature of the signal sent. In this article is presented a characterization method based on thermal impedance formalism. This method allows for the determination of the thermal conductivity, the thermal diffusivity, and the contact thermal resistance in one single test. The application of this method requires the use of a specific probe developed to enable measurement of heat flux and temperature at the interface of the probe and the studied material. Its practical application is presented for dry sand.

  4. Relationship between dilatancy, stresses and plastic dissipation in a granular material with rigid grains

    Evesque, Pierre; Stefani, Christian

    1991-11-01

    By considering a drained cohesionless granular sample made up of rigid grains and submitted to a triaxial test, we derive an equation relating the dilatancy K, the deviatoric stress q and the confining pressure p to the energy losses D_plastic due to plastic yielding. We demonstrate that the system is contracting (K le 0) at q = 0, when q is increasing and that spontaneous uncontrolled yielding begins occurring when dilatancy K is maximum. We also demonstrate the existence of the characteristic state introduced by Luong and Habib and the existence of the critical state of Schofield and Wroth. Finally, we give a method to determine the plastic losses during a triaxial cell test using the experimental data. En utilisant un postulat de reproductibilité des essais triaxiaux et une relation liant l'énergie dissipée, la dilatance K et les contraintes imposées à un échantillon, on démontre qu'un matériau granulaire ne peut que se contracter après avoir subi une contrainte de confinement isotrope (i.e. q = 0), que la rupture spontanée a lieu après un maximum de dilatance, qu'il existe un état caractéristique (au sens de Luong et Habib) et qu'il existe un état “ critique ” (au sens de Schofield et Wroth). Nous donnons de plus une méthode pour estimer la dissipation-plastique durant un essai triaxial à partir des résultats expérimentaux.

  5. Granular boycott effect: How to mix granulates

    Duran, J.; Mazozi, T.

    1999-11-01

    Granular material can display the basic features of the Boycott effect in sedimentation. A simple experiment shows that granular material falls faster in an inclined tube than in a vertical tube, in analogy with the Boycott effect. As long as the inclination of the tube is above the avalanche threshold, descent of granular material in the tube causes internal convection which in turn results in an efficient mixture of the granular components. By contrast, as in analogous experiments in two dimensions, a vertical fall of granular material occurs via successive block fragmentation, resulting in poor mixing.

  6. Electromagnetic properties of Fe-Co granular composite materials containing acicular nanoparticles

    Kasagi, Teruhiro; Massango, Herieta; Tsutaoka, Takanori; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2018-03-01

    Electromagnetic properties of acicular (needle-like) Fe76Co24 nanoparticle composite materials have been studied in microwave frequency range up to 20 GHz. The Fe76Co24 particles are commercially available acicular Fe76Co24 nanoparticles with an approximate length and diameter of 100 and 25 nm, respectively. The Fe76Co24 nanocomposites were prepared by embedding the Fe76Co24 nanoparticle in an appropriate resin. Since the metallic Fe76Co24 nanoparticles have an oxidized surface, even high particle content composites at 78 vol.%, which is in the percolated state, does not show metallic conduction; a low frequency plasmonic state with the negative permittivity spectrum was not observed. Meanwhile, the negative permeability spectrum caused by the magnetic resonance in Fe76Co24 alloy was obtained in the high particle content composites. From the measurement of the complex permeability spectra under the external dc magnetic field, it was clarified that the gyromagnetic spin rotation mainly contributes to the permeability spectrum of nanocomposites due to extremely small quantity of domain walls in the acicular nanoparticles. This result suggests that the negative permeability spectrum was caused by the gyromagnetic spin resonance. By the comparison of the complex permeability spectrum between the acicular Fe76Co24 nanocomposite and the spherical Fe50Co50 microcomposite, the gyromagnetic spin resonance frequency of the acicular nanocomposite tends to locate higher than that of the spherical microcomposite owing to the demagnetizing field effect. Therefore, it can be concluded that the negative permeability frequency band of the acicular nanocomposite is higher than that of the spherical microcomposite at the same particle content.

  7. An Evaluation of the Resilient Modulus and Permanent Deformation of Unbound Mixtures of Granular Materials and Rubber Particles from Scrap Tyres to Be Used in Subballast Layers

    Hidalgo Sgnes, C.

    2016-07-01

    Over the last years rubber from scrap tyres has been reused in different civil works such as road embankments and railway platforms due to its resilient properties, low degradation and vibration attenuation. Unfortunately, this issue is still scarce. For instance, in Spain about 175.000 tonnes of scrap tyres were collected in 2014, of which only 0.6% were reused in civil works. Aiming to contribute to the reutilisation of large quantities of this waste material, this paper focuses on the analysis of unbound mixtures of granular materials with different percentages of rubber particles to be used as subballast layers. Mixtures are tested under cyclic triaxial tests so as to obtain their resilient modulus and evaluate their permanent deformations. It is found that as the rubber content increases, the resilient modulus decreases and the permanent deformation increases. Taking into account the usual loads transmitted to the subballast layer, the optimum rubber content that does not compromise the behaviour of the mixture is set in a range between 2.5% and 5% in terms of weight. (Author)

  8. Aplicação da alvenaria estrutural em sistemas de armazenamento de produtos agrícolas a granel Applying structural masonry for granular material storage systems

    José F. de A Marques Neto

    2011-02-01

    Full Text Available O armazenamento de produtos agrícolas cumpre um papel importante no agronegócio. Observa-se uma tendência cada vez maior em se trabalhar com produtos a granel, em grandes volumes. Visando a uma concepção construtiva racional e econômica, o presente trabalho propõe um sistema misto em concreto armado e alvenaria estrutural aplicado a silos para armazenagem de produto agrícola a granel. No projeto proposto, o silo é composto de células em alvenaria estrutural, geminadas duas a duas na largura e com um número variável de células no comprimento, em função do volume desejado de armazenagem. Esse sistema simétrico favorece a racionalidade operacional, garantindo a continuidade entre os fluxos de recebimento e de expedição. O fundo da célula é em forma de tremonha dupla troncopiramidal, com saída central, construída em painéis treliçados pré-moldados. A sustentação das células e das tremonhas é feita através de vigas e de pilares de concreto armado. O isolamento térmico necessário para que a qualidade do produto armazenado seja garantida é estabelecido pela utilização de telhas trapezoidais de aço galvanizado, tanto na cobertura como nos fechamentos laterais. A fim de ilustrar o presente trabalho, um exemplo de silo utilizando o sistema proposto é apresentado, e a viabilidade da concepção construtiva adotada é analisada.The storage of granular materials has had an important role in the agribusiness. Storing granular materials in silos, instead of in bags or big-bags, has been an increase tendency. Aiming at an economic and rational solution for storing granular materials this paper presents an alternative design: a multi-cell silo group composed of reinforced masonry rectangular cells coupled two by two in width, and a variable number of cells in length according to the volume of desired storage. Such symmetrical system benefits the loading and the unloading operations, and guarantees the continuity between the

  9. Localization and Instability in Sheared Granular Materials: Role of Pore Fluids and Non-monotonic Rate Dependent Rheology

    Ma, X.; Elbanna, A. E.; Kothari, K.

    2017-12-01

    Fault zone dynamics hold the key to resolving many outstanding geophysical problems including the heat flow paradox, discrepancy between fault static and dynamic strength, and energy partitioning. Most fault zones that generate tectonic events are gouge filled and fluid saturated posing the need for formulating gouge-specific constitutive models that capture spatially heterogeneous compaction and dilation, non-monotonic rate dependence, and transition between localized and distributed deformation. In this presentation, we focus primarily on elucidating microscopic underpinnings for shear banding and stick-slip instabilities in sheared saturated granular materials and explore their implications for earthquake dynamics. We use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in the presence and absence of pore fluids. We also consider the possible influence of self-induced mechanical vibrations as well as the role of external acoustic vibrations as analogue for triggering by a distant event. For the dry case, our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the granular network and de-localize slip at these rates. Stick-slip is only observed for rough grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of application alters the system response and may cause long-lasting rheological changes. The presence of pore fluids modifies the stick slip pattern and may lead to both loss and development of slip instability depending on the value of the confining pressure, imposed strain rate and hydraulic parameters. We analyze these observations in terms of possible transitions between rate

  10. Micro-mechanical investigation of the effect of fine content on mechanical behavior of gap graded granular materials using DEM

    Taha Habib

    2017-01-01

    Full Text Available In this paper, we present a micro-mechanical study of the effect of fine content on the behavior of gap graded granular samples by using numerical simulations performed with the Discrete Element Method. Different samples with fine content varied from 0% to 30% are simulated. The role of fine content in reinforcing the granular skeleton and in supporting the external deviatoric stress is then brought into the light.

  11. Influence of Fines Content on Consolidation and Compressibility Characteristics of Granular Materials

    Lipiński, Mirosław J.; Wdowska, Małgorzata K.; Jaroń, Łukasz

    2017-10-01

    Various behaviour of soil under loading results to large extent from kind of soil considered. There is a lot of literature concerning pure sand or plastic clays, while little is known about materials, which are from classification point of view, between those soils. These materials can be considered as cohesionless soils with various fines content. The paper present results of tests carried out in large consolidometer on three kinds of soil, containing 10, 36 and 97% of fines content. Consolidation, permeability and compressibility characteristics were determined. Analysis of the test results allowed to formulate conclusion concerning change in soil behaviour resulting from fines content.

  12. Normal Stresses in a Granular Material Under Falling Weight Deflectometer loading

    Ullidtz, Per; Askegaar, Vagn; Sjølin, Finn Ole

    1996-01-01

    The vertical normal stress under a falling weight deflectometer (FWD) was measured in a sand. The material had more than 90 percent falling within the sand fraction from 60 micrometer to 2 mm. The stress was measured with three different transducers. All transducers were installed at a depth of 2...

  13. Comparison of the release of constituents from granular materials under batch and column testing.

    Lopez Meza, Sarynna; Garrabrants, Andrew C; van der Sloot, Hans; Kosson, David S

    2008-01-01

    Column leaching testing can be considered a better basis for assessing field impact data than any other available batch test method and thus provides a fundamental basis from which to estimate constituent release under a variety of field conditions. However, column testing is time-intensive compared to the more simplified batch testing, and may not always be a viable option when making decisions for material reuse. Batch tests are used most frequently as a simple tool for compliance or quality control reasons. Therefore, it is important to compare the release that occurs under batch and column testing, and establish conservative interpretation protocols for extrapolation from batch data when column data are not available. Five different materials (concrete, construction debris, aluminum recycling residue, coal fly ash and bottom ash) were evaluated via batch and column testing, including different column flow regimes (continuously saturated and intermittent unsaturated flow). Constituent release data from batch and column tests were compared. Results showed no significant difference between the column flow regimes when constituent release data from batch and column tests were compared. In most cases batch and column testing agreed when presented in the form of cumulative release. For arsenic in carbonated materials, however, batch testing underestimates the column constituent release for most LS ratios and also on a cumulative basis. For cases when As is a constituent of concern, column testing may be required.

  14. Column studies of strontium and cesium migration in a granular geologic material

    Reynolds, W.D.; Gilham, R.W.; Cherry, J.A.

    1981-06-01

    Infinite-pulse, miscible-displacement experiments were conducted to investigate the applicability of batch Ksub(d) values in the prediction of reactive solute transport during dynamic flow through porous media. Non-reactive tracers (chloride, tritium and oxygen-18), and the reactive tracers (strontium-85 and cesium-137) were passed through a column 5.0 cm long and 6.5 cm in diameter packed with a medium to fine sand. The effluent concentrations of the nonreactive solutes were accurately predicted using the advection-dispersion equation; however, there were large discrepancies between the measured and predicted effluent concentrations for both reactive species. Good agreement was obtained between the measured and computed results by incorporating an empirical isotherm into the advection-dispersion model

  15. A numerical study of granular dam-break flow

    Pophet, N.; Rébillout, L.; Ozeren, Y.; Altinakar, M.

    2017-12-01

    Accurate prediction of granular flow behavior is essential to optimize mitigation measures for hazardous natural granular flows such as landslides, debris flows and tailings-dam break flows. So far, most successful models for these types of flows focus on either pure granular flows or flows of saturated grain-fluid mixtures by employing a constant friction model or more complex rheological models. These saturated models often produce non-physical result when they are applied to simulate flows of partially saturated mixtures. Therefore, more advanced models are needed. A numerical model was developed for granular flow employing a constant friction and μ(I) rheology (Jop et al., J. Fluid Mech. 2005) coupled with a groundwater flow model for seepage flow. The granular flow is simulated by solving a mixture model using Finite Volume Method (FVM). The Volume-of-Fluid (VOF) technique is used to capture the free surface motion. The constant friction and μ(I) rheological models are incorporated in the mixture model. The seepage flow is modeled by solving Richards equation. A framework is developed to couple these two solvers in OpenFOAM. The model was validated and tested by reproducing laboratory experiments of partially and fully channelized dam-break flows of dry and initially saturated granular material. To obtain appropriate parameters for rheological models, a series of simulations with different sets of rheological parameters is performed. The simulation results obtained from constant friction and μ(I) rheological models are compared with laboratory experiments for granular free surface interface, front position and velocity field during the flows. The numerical predictions indicate that the proposed model is promising in predicting dynamics of the flow and deposition process. The proposed model may provide more reliable insight than the previous assumed saturated mixture model, when saturated and partially saturated portions of granular mixture co-exist.

  16. 22 CFR 212.25 - Procedures for obtaining materials under this subpart.

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Procedures for obtaining materials under this subpart. 212.25 Section 212.25 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT PUBLIC INFORMATION Availability of Information for Public Inspection and Copying § 212.25 Procedures for obtaining materials under...

  17. New technology for production of granular adding material with nanomodifying additives for steel arc welding

    BOLDYREV Alexander Mikhaylovich

    2016-12-01

    Full Text Available The chemical analysis of metal seam showed that introduction of titanium dioxide with MCA intensifies transition of Al2O3 from slag into metal pool and provides double concentration of titanium in the seam compared to the one which appears in the interaction of bathtub with melted flux AH-47 without TiO2 additives. The presence of oxides of titanium and aluminium of endogenous origin in the melt leads to formation of refractory particles with the center of TiO2 and Al2O3 in it. These particles are the centers of crystallization in the tail part of the molten pool and they remain in seam metal in the form of evenly distributed fine nonmetallic inclusions, which have crystallographic affinity with a matrix (α-iron. That provides the fine-grained seam structure with the raised and stable strength characteristics. This article compares the existing and developed technologies for production of MCA. The granulometric analysis of the powder TiO2 has demonstrated that when MCA is processed in the planetary mill, particles of titanium dioxide are crushed to a nanodimensional order. It is shown that the preparation of MCA in high-energy planetary mill (due to double increase of durability in coupling of the modifier with granulate provides its stable structure, increases the cold resistance (20–25% and stability of strength characteristics along the length of welded seam. Metalgraphic researches determined that the fine-grained structure which linear size of grain is twice smaller than the one obtained in the old technology welding is formed in a seam. However the direct introduction of nanomodifiers in a molten pool through the flux or an electrode wire is not efficient because of their deactivation and high temperature in welding zone. Therefore it was offered to use modifiers in the mix with the cooling macroparticles in case of automatic welding of a bridge metalware under flux using metalchemical additive (MCA. The MCA consists of a chopped

  18. Contribution to an understanding of the action of gamma radiation on granular starch - interpretation of results obtained using the enzymatic and chromatographic method

    Robin, J.P.; Tollier, M.Th.; Guilbot, A.

    1978-01-01

    Besides compounds of low molecular mass, the gamma irradiation of granular starch produces radiodextrins with a mass lying between that of the low-molecular-mass compounds and that of the amylose and amylopectin macromolecules from which they derive. The authors present the main results relating to characterization of the radiodextrins of strongly irradiated relating to characterization of the radiodextrins of strongly irradiated normal and waxy maize starches. The method of study - both enzymatic and chromatographic - is the one that has been in use for some ten years for studying the fine structure of α-1.4-1.6 glucanes. An attempt is made to interpret and integrate the results in the light of new data derived from a study of the controlled acid hydrolysis of starch. In particular, the following hypothesis is advanced: the 'hydrolytic' effect of irradiation is, at the qualitative level, independent of the nature of the starch and similar to the effect produced by acid hydrolysis; as with acid hydrolysis, the breaking of the covalent bonds is a function of the internal strucutre of the grain and especially of its amorphous/crystalline organization; the zones of an amorphous character are more easily degraded; on the other hand, the 'crystalline' zones are better protected; in fact, the 'hydrolytic' effect of irradiation is not homogeneous and does not conform to a statistical pattern. (author)

  19. A dehydration process for ovine hide to obtain a new collagenous material

    Ollé Otero, Lluís; Sorolla, Silvia; Casas Solé, Concepció; Bacardit Dalmases, Anna

    2014-01-01

    The aim of the present work is to develop a dehydration process for ovine hide to obtain a new collagenous material for use in the leather industry. What is obtained through this new process is a dry and very porous collagenous substrate which allows the application of tanning chemicals by immersion in aqueous solutions. When compared to existing, traditional processes, economic and environmental advantages are obtained from the use of this new material. More specifically, the new process ...

  20. Behavior of pressure and viscosity at high densities for two-dimensional hard and soft granular materials

    Otsuki, Michio; Hayakawa, Hisao; Luding, Stefan

    2010-01-01

    The pressure and the viscosity in two-dimensional sheared granular assemblies are investigated numerically. The behavior of both pressure and viscosity is smoothly changing qualitatively when starting from a mono-disperse hard-disk system without dissipation and moving towards a system of (i)

  1. The additive technology for obtaining thermal storages based on nanomodified materials

    Shchegolkov Alexander

    2017-01-01

    Full Text Available The approaches for the implementation of an additive technology for obtaining heat accumulators are considered. The implementation of the provided technology can be realized on the standard 3D printers, which are aimed to obtain plastic materials. However, the software of the printers has to include adjusting analytical expressions, which take into account thermophysical properties of the heat-retaining materials. The analytical expressions have been derived by solving a mathematical model. The mathematical model contains the main data on thermophysical and mechanical and physical properties of the nanomodified material. These properties of the nanomodified material are defined during the experimental studies.

  2. Procedures for EPA Libraries to Obtain Materials through Interlibrary Loan/Document Delivery

    The purpose of this document is to establish Agency-wide procedures by which EPA libraries obtain materials for Agency employees and authorized EPA contractors through interlibrary loan (ILL) and other document delivery methods.

  3. The Effect of Binder and Waste Granular Materials (WGM on the Shear Strength and Shear Resistance of Dredged Marine Soils (DMS

    Rosman Mohammad Zawawi

    2017-01-01

    Full Text Available Dredged marine soil (DMS is considered as weak and soft problematic soil. It is possible to give this type of soil a second life if only its geotechnical properties are improved. Infusing soil with solidification agent is the common practice of soil improvement. This study uses binder and waste granular material (WGM such as cement, bottom ash (BA and palm oil clinker (POC. The aforementioned materials are capable to fortify the poor features of the soil. Series numbers of soil bed samples were tested for its shear strength and shear resistance. Test results show that the mentioned soil parameters were corresponded with each other. In short, geo-waste and biomass materials are possible to be reused instead of being discarded.

  4. Seismic wave propagation in granular media

    Tancredi, Gonzalo; López, Francisco; Gallot, Thomas; Ginares, Alejandro; Ortega, Henry; Sanchís, Johnny; Agriela, Adrián; Weatherley, Dion

    2016-10-01

    Asteroids and small bodies of the Solar System are thought to be agglomerates of irregular boulders, therefore cataloged as granular media. It is a consensus that many asteroids might be considered as rubble or gravel piles.Impacts on their surface could produce seismic waves which propagate in the interior of these bodies, thus causing modifications in the internal distribution of rocks and ejections of particles and dust, resulting in a cometary-type comma.We present experimental and numerical results on the study of propagation of impact-induced seismic waves in granular media, with special focus on behavior changes by increasing compression.For the experiment, we use an acrylic box filled with granular materials such as sand, gravel and glass spheres. Pressure inside the box is controlled by a movable side wall and measured with sensors. Impacts are created on the upper face of the box through a hole, ranging from free-falling spheres to gunshots. We put high-speed cameras outside the box to record the impact as well as piezoelectic sensors and accelerometers placed at several depths in the granular material to detect the seismic wave.Numerical simulations are performed with ESyS-Particle, a software that implements the Discrete Element Method. The experimental setting is reproduced in the numerical simulations using both individual spherical particles and agglomerates of spherical particles shaped as irregular boulders, according to rock models obtained with a 3D scanner. The numerical experiments also reproduces the force loading on one of the wall to vary the pressure inside the box.We are interested in the velocity, attenuation and energy transmission of the waves. These quantities are measured in the experiments and in the simulations. We study the dependance of these three parameters with characteristics like: impact speed, properties of the target material and the pressure in the media.These results are relevant to understand the outcomes of impacts in

  5. Granular packing as model glass formers

    Wang Yujie

    2017-01-01

    Static granular packings are model hard-sphere glass formers. The nature of glass transition has remained a hotly debated issue. We review recent experimental progresses in using granular materials to study glass transitions. We focus on the growth of glass order with five-fold symmetry in granular packings and relate the findings to both geometric frustration and random first-order phase transition theories. (paper)

  6. Distrofia corneal granular

    Alexeide de la C Castillo Pérez

    Full Text Available Las distrofias corneales constituyen un conjunto de enfermedades que presentan, en su mayoría, una baja incidencia y se caracterizan por acúmulo de material hialino o amiloide que disminuyen la transparencia corneal. La distrofia granular es una enfermedad autosómica dominante que presenta opacidades grises en el estroma superficial central de la córnea y se hacen visibles en la primera y segunda décadas de la vida, lo que provoca disminución de la visión más significativa cerca de los 40 años de edad. Presentamos dos casos clínicos de distrofia granular en pacientes hermanos de diferentes sexos, quienes acudieron a la consulta y refirieron visión nublada. El estudio de la historia familiar nos ayuda en el correcto diagnóstico y la biomicroscopia constituye el elemento más importante.

  7. Fracture surfaces of granular pastes.

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

    2013-11-01

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

  8. Fine defective structure of silicon carbide powders obtained from different starting materials

    Tomila T.V.

    2006-01-01

    Full Text Available The fine defective structure of silicon carbide powders obtained from silicic acid-saccharose, aerosil-saccharose, aerosil-carbon black, and hydrated cellulose-silicic acid gel systems was investigated. The relation between IR absorption characteristics and the microstructure of SiC particles obtained from different starting materials was established. The numerical relationship between the lattice parameter a and the frequency νTO is presented.

  9. Radio Frequencies Emitted by Mobile Granular Materials: A Basis for Remote Sensing of Sand and Dust Activity on Mars and Earth

    Marshall, J.; Farrell, W.; Houser, G.; Bratton, C.

    1999-01-01

    In recent laboratory experiments, measurements were made of microsecond radio-wave (RF) bursts emitted by grains of sand as they energetically circulated in a closed, electrically ungrounded chamber. The bursts appeared to result from nanoscale electrical discharging from grain surfaces. Both the magnitude and wave form of the RF pulses varied with the type of material undergoing motion. The release of RF from electrical discharging is a well-known phenomenon, but it is generally measured on much larger energy scales (e.g., in association with lightning or electrical motors). This phenomenon might be used to detect, on planetary surfaces, the motion and composition of sand moving over dunes, the turbulent motion of fine particles in dust storms, highly-energetic grain and rock collisions in volcanic eruptions, and frictional grinding of granular materials in dry debris flows, landslides, and avalanches. The occurrence of these discharges has been predicted from theoretical considerations Additional information is contained in the original.

  10. Structure and characteristics of functional powder composite materials obtained by spark plasma sintering

    Oglezneva, S. A.; Kachenyuk, M. N.; Kulmeteva, V. B.; Ogleznev, N. B.

    2017-07-01

    The article describes the results of spark plasma sintering of ceramic materials based on titanium carbide, titanium carbosilicide, ceramic composite materials based on zirconium oxide, strengthened by carbon nanostructures and composite materials of electrotechnical purpose based on copper with addition of carbon structures and titanium carbosilicide. The research shows that the spark plasma sintering can achieve relative density of the material up to 98%. The effect of sintering temperature on the phase composition, density and porosity of the final product has been studied. It was found that with addition of carbon nanostructures the relative density and hardness decrease, but the fracture strength of ZrO2 increases up to times 2. The relative erosion resistance of the electrodes made of composite copper-based powder materials, obtained by spark plasma sintering during electroerosion treatment of tool steel exceeds that parameter of pure copper up to times 15.

  11. Recent advances of basic materials to obtain electrospun polymeric nanofibers for medical applications

    Manea, L. R.; Hristian, L.; Leon, A. L.; Popa, A.

    2016-08-01

    The most important applications of electrospun polymeric nanofibers are by far those from biomedical field. From the biological point of view, almost all the human tissues and organs consist of nanofibroas structures. The examples include the bone, dentine, cartilage, tendons and skin. All these are characterized through different fibrous structures, hierarchically organized at nanometer scale. Electrospinning represents one of the nanotechnologies that permit to obtain such structures for cell cultures, besides other technologies, such as selfassembling and phase separation technologies. The basic materials used to produce electrospun nanofibers can be natural or synthetic, having polymeric, ceramic or composite nature. These materials are selected depending of the nature and structure of the tissue meant to be regenerated, namely: for the regeneration of smooth tissues regeneration one needs to process through electrospinning polymeric basic materials, while in order to obtain the supports for the regeneration of hard tissues one must mainly use ceramic materials or composite structures that permit imbedding the bioactive substances in distinctive zones of the matrix. This work presents recent studies concerning basic materials used to obtain electrospun polymeric nanofibers, and real possibilities to produce and implement these nanofibers in medical bioengineering applications.

  12. OBTAINING HYSTERESIS LOOPS AT LOW FREQUENCY FOR CHARACTERIZATION OF MATERIALS TO BE USED IN BIOMEDICAL APPLICATIONS

    Atika Arshad

    2015-05-01

    Full Text Available The promising development of magnetic sensors in biomedical field demands an appropriate level of understanding of the magnetic properties of the materials used in their fabrication. To date only few of the types of magnetic materials are encountered where their magnetic properties, characterization techniques and magnetization behavior are yet to be explored more suitably in the light of their applications. This research work studies the characterization of materials by using a cost effective and simple circuit consisting of inductive transducer and an OP-AMP as a voltage integrator. In this approach the circuit was simulated using PSPICE and experiments have been conducted to achieve the desired results. The simulation and experimental results are obtained for three test materials namely iron, steel and plastic. The novelty lies in applying the simple circuit for material testing and characterization via obtaining simulation results and validating these results through experiment. The magnetic properties in low external magnetic field are studied with materials under test. The magnetization effect of a magneto-inductive sensor is detected in low frequency range for different magnetic core materials. The results have shown magnetization behaviour of magnetic materials due to the variation of permeability and magnetism. The resulted hysteresis loops appeared to have different shapes for different materials. The magnetic hysteresis loop found for iron core demonstrated a bigger coercive force and larger reversals of magnetism than these of steel core, thus obtaining its magnetic saturation at a larger magnetic field strength. The shape of the hysteresis loop itself is found to be varying upon the nature of the material in use. The resulted magnetization behaviors of the materials proved their possible applicability for use in sensing devices. The key concern of this work is found upon selecting the appropriate magnetic materials at the desired

  13. Coating multilayer material with improved tribological properties obtained by magnetron sputtering

    Mateescu, A. O.; Mateescu, G.; Balasoiu, M.; Pompilian, G. O.; Lungu, M.

    2017-02-01

    This work is based on the Patent no. RO 128094 B1, granted by the Romanian State Office for Inventions and Trademarks. The goal of the work is to obtain for investigations tribological coatings with multilayer structure with improved tribological properties, deposited by magnetron sputtering process from three materials (sputtering targets). Starting from compound chemical materials (TiC, TiB2 and WC), as sputtering targets, by deposition in argon atmosphere on polished stainless steel, we have obtained, based on the claims of the above patent, thin films of multilayer design with promising results regarding their hardness, elastic modulus, adherence, coefficient of friction and wear resistance. The sputtering process took place in a special sequence in order to ensure better tribological properties to the coating, comparing to those of the individual component materials. The tribological properties, such as the coefficient of friction, are evaluated using the tribometer test.

  14. Granular flows in constrained geometries

    Murthy, Tejas; Viswanathan, Koushik

    Confined geometries are widespread in granular processing applications. The deformation and flow fields in such a geometry, with non-trivial boundary conditions, determine the resultant mechanical properties of the material (local porosity, density, residual stresses etc.). We present experimental studies of deformation and plastic flow of a prototypical granular medium in different nontrivial geometries- flat-punch compression, Couette-shear flow and a rigid body sliding past a granular half-space. These geometries represent simplified scaled-down versions of common industrial configurations such as compaction and dredging. The corresponding granular flows show a rich variety of flow features, representing the entire gamut of material types, from elastic solids (beam buckling) to fluids (vortex-formation, boundary layers) and even plastically deforming metals (dead material zone, pile-up). The effect of changing particle-level properties (e.g., shape, size, density) on the observed flows is also explicitly demonstrated. Non-smooth contact dynamics particle simulations are shown to reproduce some of the observed flow features quantitatively. These results showcase some central challenges facing continuum-scale constitutive theories for dynamic granular flows.

  15. Plasma Methods of Obtainment of Multifunctional Composite Materials, Dispersion-Hardened by Nanoparticles

    Sizonenko, O. N.; Grigoryev, E. G.; Pristash, N. S.; Zaichenko, A. D.; Torpakov, A. S.; Lypian, Ye. V.; Tregub, V. A.; Zholnin, A. G.; Yudin, A. V.; Kovalenko, A. A.

    2017-09-01

    High voltage electric discharge (HVED) in disperse system "hydrocarbon liquid - powder" due to impact of plasma discharge channel, electromagnetic fields, shock waves mechanical impact, hydro flows and volume microcavitation leads to synthesis of nanocarbon, metal powders dispersion and synthesis of micro- (from 10-6 to 10-7 m) and nanosized (from 10-7 to 10-9 m) composite powders of hardening phases. Spark plasma sintering (SPS) of powder mixtures allows targeted control of grain growth rate and thus allows obtainment of multifunctional composite materials dispersion hardened by nanoparticles. Processes of HVED synthesis of micro- and nanosized powders of new compositions from elemental metal powders and their mixtures with the subsequent application of high-speed SPS of obtained powders create conditions for increase of strength (by 10-20 %), hardness and wear-resistance (by 30-60 %) of obtained materials.

  16. Composite materials obtained by the ion-plasma sputtering of metal compound coatings on polymer films

    Khlebnikov, Nikolai; Polyakov, Evgenii; Borisov, Sergei; Barashev, Nikolai; Biramov, Emir; Maltceva, Anastasia; Vereshchagin, Artem; Khartov, Stas; Voronin, Anton

    2016-01-01

    In this article, the principle and examples composite materials obtained by deposition of metal compound coatings on polymer film substrates by the ion-plasma sputtering method are presented. A synergistic effect is to obtain the materials with structural properties of the polymer substrate and the surface properties of the metal deposited coatings. The technology of sputtering of TiN coatings of various thicknesses on polyethylene terephthalate films is discussed. The obtained composites are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) is shown. The examples of application of this method, such as receiving nanocomposite track membranes and flexible transparent electrodes, are considered.

  17. Semi-conducting material obtained from natural fiber modified with PAni

    Rocha, Eli V. da; Silva Junior, Fernando Gomes; Oliveira, Geiza E.; Pinto, Jose Carlos

    2009-01-01

    The surface of natural Brazilian Amazonic fibers (curaua, Ananas erectifolius) was modified with polyaniline nanoparticles, through in-situ preparation of polyaniline nanoparticles in presence of the curaua fibers. As it was shown here, this modification allowed a very significant increase of the electrical conductivity of the fibers (about 2.500 times). The modified materials were also characterized by FTIR (Fourier Transform Infrared Spectroscopy), AFM (Atomic Force Microscopy) and SAXS (Small Angle X-ray Scattering) and the obtained results were used to explain some of the chemical and morphological aspects of the materials. (author)

  18. Palm oil based polymer materials obtained by ROMP: study by low field NMR

    Fernandes, Henrique; Azevedo, Eduardo R. de; Lima-Neto, Benedito S.

    2015-01-01

    Aiming to study and develop new materials synthesized from sustainable sources, several polymers were prepared using in its monomeric composition, different amounts of NPO (Norbornenyl Palm Oil) monomer. This monomer was developed based on a vegetable oil rather produced in northern Brazil, the Palm Oil. Since this oil have a low content of unsaturation, its use in developing new monomer for ROMP (Ring-Opening Metathesis Polymerization) is not exploited. In this regard, polymeric materials were obtained using the NOP and both the reaction process and the resulting products were analyzed by Nuclear Magnetic Resonance in the time domain (TD-NMR) at low magnetic field. (author)

  19. Application of the final flotation waste for obtaining the glass-ceramic materials

    Cocić Mira

    2017-01-01

    Full Text Available This work describes the investigation of the final flotation waste (FFW, originating from the RTB Bor Company (Serbia, as the main component for the production of glass-ceramic materials. The glass-ceramics was synthesized by the sintering of FFW, mixtures of FFW with basalt (10%, 20%, and 40%, and mixtures of FFW with tuff (20% and 40%. The sintering was conducted at the different temperatures and with the different time duration in order to find the optimal composition and conditions for crystallization. The increase of temperature, from 1100 to 1480°C, and sintering time, from 4 to 6h resulted in a higher content of hematite crystal in the obtained glass-ceramic (up to 44%. The glass-ceramics sintered from pure FFW (1080°C/36h has good mechanical properties, such as high propagation speed (4500 m/s and hardness (10800 MPa, as well as very good thermal stability. The glass-ceramics obtained from mixtures shows weaker mechanical properties compared to that obtained from pure FFW. The mixtures of FFW with tuff have a significantly lower bulk density compared to other obtained glass-ceramics. Our results indicate that FFW can be applied as a basis for obtaining the construction materials. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176010: Composition, genesis, application, and contribution to the environmental sustainability

  20. Obtaining of dense and highly porous ceramic materials from metallurgical slag

    Fidancevska E.; Mangutova B.; Milosevski D.; Milosevski M.; Bossert J.

    2003-01-01

    Glass-ceramics in a dense and highly porous form can be obtained from metallurgical slag and waste glass of TV monitors. Using polyurethane foam as pore creator, a highly porous system with porosity of 65 ± 5 %, E-modulus and flexural strength of 8 ± 3 GPa and 13 ± 3.5 MPa respectively can be obtained. This porous material had durability (mass loss) of 0.03 % in 0.1 M HCl that is identical with the durability of a dense composite.

  1. Obtaining of dense and highly porous ceramic materials from metallurgical slag

    Fidancevska E.

    2003-01-01

    Full Text Available Glass-ceramics in a dense and highly porous form can be obtained from metallurgical slag and waste glass of TV monitors. Using polyurethane foam as pore creator, a highly porous system with porosity of 65 ± 5 %, E-modulus and flexural strength of 8 ± 3 GPa and 13 ± 3.5 MPa respectively can be obtained. This porous material had durability (mass loss of 0.03 % in 0.1 M HCl that is identical with the durability of a dense composite.

  2. MATERIAL BALANCE FOR OBTAINING MUSSEL AND OYSTER CANS IN OWN JUICE AND OIL

    CARMEN NICOLAE

    2007-10-01

    Full Text Available Seafood could be presented as food products with a great nourishing value and aspecial contribution to human nutrition optimization, but also as raw material forthe processing unit. After the end of the Second World War, seafood production andconsumption have followed and increasing trajectory. Thus, their productionincreased from 19 millions tons in 1950 to 39 millions tons in 1961, but 130 millionstons in 2002. The present study proposed itself the analyze of processing 100kg/day mussels andoysters having in view the obtaining of two canned sorts (in own juice and oilestablishing the material balance for each sort. Upon the balance it can concludethat by processing the same amount of seafood it is obtained a larger amount of cansin oil.

  3. Nanocarbon materials obtained of coniferous trees in the composition of black powder

    Zulkhair Mansurov

    2012-03-01

    Full Text Available Obtained black powders from coniferous wood. The carbon content of up to 90% can be used in warfare, pyrotechnics and industries. In the Republic of Kazakhstan does not produce gunpowder. In the energy-intensive materials laboratory, developed industrial black powders (ordinary, composed of components produced in the republic of Kazakhstan. Sulfur, activated carbon, based on apricot seeds and rice husks, softwood sawdust, which have lower costs than their foreign counterparts.

  4. Granular corneal dystrophy

    Castillo Pérez, Alexeide de la C; Vilches Lescaille, Daysi; Noriega, Justo Luis; Martínez Balido, Daneel; León Balbón, Bárbaro Ramón; León Bernal, Danysleidi

    2015-01-01

    Las distrofias corneales constituyen un conjunto de enfermedades que presentan, en su mayoría, una baja incidencia y se caracterizan por acúmulo de material hialino o amiloide que disminuyen la transparencia corneal. La distrofia granular es una enfermedad autosómica dominante que presenta opacidades grises en el estroma superficial central de la córnea y se hacen visibles en la primera y segunda décadas de la vida, lo que provoca disminución de la visión más significativa cerca de los 40 año...

  5. Characterization of mesoporous VOx/MCM-41 composite materials obtained via post-synthesis impregnation

    Bukallah, Saeed B.; Bumajdad, Ali; Khalil, Kamal M.S.; Zaki, Mohamed I.

    2010-01-01

    Spherical-particle MCM-41 was synthesized at room temperature, and, then, impregnated with aqueous solutions of NH 4 VO 3 to produce variously loaded VO x /MCM-41 composite materials. Bulk and surface properties of the materials thus produced were characterized by means of X-ray powder diffractometry (XRD), infrared spectroscopy (FTIR), N 2 sorptiometry and X-ray photoelectron spectroscopy (XPS). Results obtained indicated that subsequent calcination at 550 deg. C (for 2 h) of the blank and impregnated MCM-41 particles, results in materials assuming the same bulk structure of MCM-41, and exposing uniformly mesporous, high area surfaces (P w = 2.0-2.3 nm; 974-829 m 2 /g), except for the material obtained at 20 wt%-V 2 O 5 that was shown to suffer a considerable loss on surface area (down to 503 m 2 /g). XPS results implied that the immobilization of the VO x species occurs via interaction with surface OH/H 2 O groups of MCM-41, leading to the formation of vanadate (VO 3 - ) surface species, as well as minor V-O-Si and V 2 O 5 -like species. However, in all cases, the vanadium sites remained pentavalent and exposed on the surface.

  6. Two-phase modeling of deflagration-to-detonation transition in granular materials: A critical examination of modeling issues

    Bdzil, J.B.; Menikoff, R.; Son, S.F.; Kapila, A.K.; Stewart, D.S.

    1999-01-01

    The two-phase mixture model developed by Baer and Nunziato (BN) to study the deflagration-to-detonation transition (DDT) in granular explosives is critically reviewed. The continuum-mixture theory foundation of the model is examined, with particular attention paid to the manner in which its constitutive functions are formulated. Connections between the mechanical and energetic phenomena occurring at the scales of the grains, and their manifestations on the continuum averaged scale, are explored. The nature and extent of approximations inherent in formulating the constitutive terms, and their domain of applicability, are clarified. Deficiencies and inconsistencies in the derivation are cited, and improvements suggested. It is emphasized that the entropy inequality constrains but does not uniquely determine the phase interaction terms. The resulting flexibility is exploited to suggest improved forms for the phase interactions. These improved forms better treat the energy associated with the dynamic compaction of the bed and the single-phase limits of the model. Companion papers of this study [Kapila et al., Phys. Fluids 9, 3885 (1997); Kapila et al., in preparation; Son et al., in preparation] examine simpler, reduced models, in which the fine scales of velocity and pressure disequilibrium between the phases allow the corresponding relaxation zones to be treated as discontinuities that need not be resolved in a numerical computation. copyright 1999 American Institute of Physics

  7. The fungicidal properties of the carbon materials obtained from chitin and chitosan promoted by copper salts

    Ilnicka, Anna, E-mail: annakucinska@o2.pl; Walczyk, Mariusz; Lukaszewicz, Jerzy P.

    2015-07-01

    Renewable raw materials chitin and chitosan (N-deacetylated derivative of chitin) were subjected to action of different copper modifiers that were carbonized in the atmosphere of the N{sub 2} inert gas. As a result of the novel manufacturing procedure, a series of carbon materials was obtained with developed surface area and containing copper derivatives of differentiated form, size, and dispersion. The copper modifier and manufacturing procedure (concentration, carbonization temperature) influence the physical–chemical and fungicide properties of the carbons. The received carbons were chemically characterized using several methods like low-temperature adsorption of nitrogen, X-ray diffraction analysis, scanning electron microscopy, cyclic voltammetry, elemental analysis, and bioassay. Besides chemical testing, some biological tests were performed and let to select carbons with the highest fungicidal activity. Such carbons were characteristic of the specific form of copper derivatives occurring in them, i.e., nanocrystallites of Cu{sup 0} and/or Cu{sub 2}O of high dispersion on the surface of carbon. The carbons may find an application as effective contact fungistatic agents in cosmetology, medicine, food industry, etc. - Highlights: • The novel manufacturing procedure yields new functional carbon materials. • Two biopolymers chitin and chitosan can undergo copper(II) ion modification. • The Cu-modified carbon materials exhibit high fungicidal activity. • The fungicidal activity results from the presence of Cu{sup 0} and Cu{sub 2}O nano-crystallites.

  8. A non-linear optimal control problem in obtaining homogeneous concentration for semiconductor materials

    Huang, C.-H.; Li, J.-X.

    2006-01-01

    A non-linear optimal control algorithm is examined in this study for the diffusion process of semiconductor materials. The purpose of this algorithm is to estimate an optimal control function such that the homogeneity of the concentration can be controlled during the diffusion process and the diffusion-induced stresses for the semiconductor materials can thus be reduced. The validation of this optimal control analysis utilizing the conjugate gradient method of minimization is analysed by using numerical experiments. Three different diffusion processing times are given and the corresponding optimal control functions are to be determined. Results show that the diffusion time can be shortened significantly by applying the optimal control function at the boundary and the homogeneity of the concentration is also guaranteed. This control function can be obtained within a very short CPU time on a Pentium III 600 MHz PC

  9. Preliminary Results from Duplex Procedure for Obtain of Fe Based Materials for Automotive Applications

    Crăciun, R. C.; Stanciu, S.; Geantă, V.; Voiculescu, I.; Manole, V.; Gârneţ, I. A.; Alexandru, A.; Cimpoesu, N.; Săndulache, F.

    2017-06-01

    Abstract Iron based materials still represent a high percentage from metallic materials used in industry, in general, and in automotive industry, in particular. In this case we used a duplex process in order to obtain the FeMnSiAl experimental alloy for a more efficient use of various units. In the first stage iron, manganese, silicon and aluminum were melted and mixed together using arc melting technology and for the second stage the alloy was re-melt for homogeneity in an induction furnace. Chemical composition, after each melting step, was analyzed using EDS Bruker detector for various areas and microstructural characterization using SEM, VegaTescan LMH II with SE detector, equipment. This alloy is proposed as a metallic approach of mechanical dumpers used in automotive industry for low and medium impact contacts.

  10. SiC-Based Composite Materials Obtained by Siliconizing Carbon Matrices

    Shikunov, S. L.; Kurlov, V. N.

    2017-12-01

    We have developed a method for fabrication of parts of complicated configuration from composite materials based on SiC ceramics, which employs the interaction of silicon melt with the carbon matrix having a certain composition and porosity. For elevating the operating temperatures of ceramic components, we have developed a method for depositing protective silicon-carbide coatings that is based on the interaction of the silicon melt and vapor with carbon obtained during thermal splitting of hydrocarbon molecules. The new structural ceramics are characterized by higher operating temperatures; chemical stability; mechanical strength; thermal shock, wear and radiation resistance; and parameters stability.

  11. New biphasic monocomponent composite material obtained by the partial oxypropylation of bacterial cellulose

    Rosa, Joyce Rover; Silva, Ingrid S.V. da; Pasquini, Daniel; Santos, Daniele B. dos; Barud, Hernane S.; Ribeiro, Sidney J.L.

    2011-01-01

    This study aimed to partial oxypropylation of bacterial cellulose (CB), as well as the characterization of pure CB, oxypropylated CB (CBO) and oxypropylated CB after Soxhlet extraction with hexane (CBOE). The oxypropylation reaction was carried out by propylene oxide polymerization, catalyzed by KOH, in the presence of CB The CB samples, before and after modification, were subjected to analysis of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was possible verify that the partial transformation of bacterial cellulose by inserting a layer of thermoplastic polymer on its surface occurred efficiently, obtaining a biphasic monocomponent composite material. (author)

  12. E-learning Materials Development: Applying and Implementing Software Reuse Principles and Granularity Levels in the Small

    Nabil Arman

    2010-01-01

    E-learning materials development is typically acknowledged as an expensive, complicated, and lengthy process, often producing materials that are of low quality and difficult to adaptand maintain. It has always been a challenge to identify proper e-learning materials that can be reused at a reasonable cost and effort. In this paper, software engineering reuse principlesare applied to e-learning materials development process. These principles are then applied and implemented in a prototype that...

  13. Advanced Granular System Modeling, Phase I

    National Aeronautics and Space Administration — Spaceports of the future will utilize new granular materials in unique applications including insulation for cryogenic tanks and Lunar regolith processing for usable...

  14. Improving the Technology of Obtaining Technical Ethanol from Alternative Raw Materials

    Sergіj Petrov

    2018-05-01

    Full Text Available The purpose of the article is to study the properties of fallen leaves as raw materials for the production of bioethanol; Improvement of the technology of recycling cellulosic raw materials into bioethanol in the most energy-efficient and ecological way. As a result of the study, it has been found out that the production of biofuels from renewable raw materials is characterized by features of innovative technology: the rapid growth of this sector of economy is accompanied by a significant increase in market share. The use of fallen leaves as raw material will eliminate the current conflict of interests associated with the use of food raw materials for the production of bioethanol, will prevent the withdrawal of resources from the sphere of food production. Significant positive factors in the production and use of biofuels are improvement of environmental conditions, reduction of the harmful effects of exhaust gases on the human body, reducing environmental pollution and, consequently, reducing morbidity and associated costs of medical care. The use of bioethanol as an ecobiopilot makes it possible to increase the octane number of fuel, and, accordingly, increase the efficiency of the engine. Thus, the use of bioethanol leads to a qualitative improvement of technical and economic indicators, which is also an indicator of innovation. The threat of reducing (exhausting non-renewable sources of energy is also the factor that necessitates the development and improvement of biofuel production technology. The relatively low profitability of biofuel production is due to the low yield of the target product and the high cost of pre-treatment of cellulose raw materials. The method of obtaining bioethanol from renewable non-demanded raw materials - fallen leaves - was improved. The technique allows to increase the bioethanol yield due to more effective hydrolysis of hard-hydrolysable polysaccharides. Further development of the study of the differences in

  15. Precision Obtained Using an Artificial Neural Network for Predicting the Material Removal Rate in Ultrasonic Machining

    Gaoyan Zhong

    2017-12-01

    Full Text Available The present study proposes a back propagation artificial neural network (BPANN to provide improved precision for predicting the material removal rate (MRR in ultrasonic machining. The BPANN benefits from the advantage of artificial neural networks (ANNs in dealing with complex input-output relationships without explicit mathematical functions. In our previous study, a conventional linear regression model and improved nonlinear regression model were established for modelling the MRR in ultrasonic machining to reflect the influence of machining parameters on process response. In the present work, we quantitatively compare the prediction precision obtained by the previously proposed regression models and the presently proposed BPANN model. The results of detailed analyses indicate that the BPANN model provided the highest prediction precision of the three models considered. The present work makes a positive contribution to expanding the applications of ANNs and can be considered as a guide for modelling complex problems of general machining.

  16. Influence of hydrothermal carbonization and treatment by microwave on morphology of carbonaceous materials obtained from lignin

    Oliveira, I.B.; Barin, G.B.; Barreto, L.S.; Santos, M.C.G.

    2014-01-01

    The conversion of biomass into carbon materials with special morphologies via hydrothermal carbonization presents itself as a potential route for the use of renewable precursors in obtaining carbonaceous structures. In the present study the influence of the hydrothermal carbonization (250 ° C / 4 h) followed by microwave treatment (1-2-4 hours at 25 and 40 mL) in morphology and structure of lignin. The samples were analyzed by X-ray diffraction and scanning electron microscopy. The plaque morphology of lignin was preserved during the hydrothermal process. However, when treated by microwave can be observed partial dissolution of lignin leading to the formation of microspheres on the surface. XRD presence of an amorphous halo 2θ = 23 ° attributed to the (002) network of the amorphous carbon was observed. (author)

  17. Sweet whey as a raw material for the dietary supplements obtaining with immunomodulatory effect

    G. Didukh

    2017-06-01

    Full Text Available This article presents the results of the study of literary sources to prove the viability of the idea of using sweet whey to deep its fractionation, and to obtain biologically active proteins with immunomodulatory effect. We demonstrated methods for fractionation of milk whey (membrane and chromatographic, as well as the technological scheme of concentration of sweet whey. We introduced the composition of sweet whey and protein content of immunomodulatory action. Modern methods of processing whey, which include, basically, only the process of dehydration and concentration of whey and its use in the complete component composition, which limits its use for food purposes are shown. The necessity of processing of secondary resources in a catastrophic ecological situation on the planet and full use of the composite processing of raw materials for food purposes, and also shows properties of proteins immunomodulating actions which are part of the whey are grounded.

  18. A facile method to compare EFTEM maps obtained from materials changing composition over time

    Casu, Alberto

    2015-10-31

    Energy Filtered Transmission Electron Microscopy (EFTEM) is an analytical tool that has been successfully and widely employed in the last two decades for obtaining fast elemental maps in TEM mode. Several studies and efforts have been addressed to investigate limitations and advantages of such technique, as well as to improve the spatial resolution of compositional maps. Usually, EFTEM maps undergo post-acquisition treatments by changing brightness and contrast levels, either via dedicated software or via human elaboration, in order to maximize their signal-to-noise ratio and render them as visible as possible. However, elemental maps forming a single set of EFTEM images are usually subjected to independent map-by-map image treatment. This post-acquisition step becomes crucial when analyzing materials that change composition over time as a consequence of an external stimulus, because the map-by-map approach doesn\\'t take into account how the chemical features of the imaged materials actually progress, in particular when the investigated elements exhibit very low signals. In this article, we present a facile procedure applicable to whole sets of EFTEM maps acquired on a sample that is evolving over time. The main aim is to find a common method to treat the images features, in order to make them as comparable as possible without affecting the information there contained. Microsc. Res. Tech. 78:1090–1097, 2015. © 2015 Wiley Periodicals, Inc.

  19. A facile method to compare EFTEM maps obtained from materials changing composition over time

    Casu, Alberto; Genovese, Alessandro; Di Benedetto, Cristiano; Lentijo Mozo, Sergio; Sogne, Elisa; Zuddas, Efisio; Falqui, Andrea

    2015-01-01

    Energy Filtered Transmission Electron Microscopy (EFTEM) is an analytical tool that has been successfully and widely employed in the last two decades for obtaining fast elemental maps in TEM mode. Several studies and efforts have been addressed to investigate limitations and advantages of such technique, as well as to improve the spatial resolution of compositional maps. Usually, EFTEM maps undergo post-acquisition treatments by changing brightness and contrast levels, either via dedicated software or via human elaboration, in order to maximize their signal-to-noise ratio and render them as visible as possible. However, elemental maps forming a single set of EFTEM images are usually subjected to independent map-by-map image treatment. This post-acquisition step becomes crucial when analyzing materials that change composition over time as a consequence of an external stimulus, because the map-by-map approach doesn't take into account how the chemical features of the imaged materials actually progress, in particular when the investigated elements exhibit very low signals. In this article, we present a facile procedure applicable to whole sets of EFTEM maps acquired on a sample that is evolving over time. The main aim is to find a common method to treat the images features, in order to make them as comparable as possible without affecting the information there contained. Microsc. Res. Tech. 78:1090–1097, 2015. © 2015 Wiley Periodicals, Inc.

  20. Wave propagation of spectral energy content in a granular chain

    Shrivastava Rohit Kumar

    2017-01-01

    Full Text Available A mechanical wave is propagation of vibration with transfer of energy and momentum. Understanding the spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through inhomogeneous materials like soil. The study of these properties is aimed at modeling wave propagation for oil, mineral or gas exploration (seismic prospecting or non-destructive testing of the internal structure of solids. The focus is on the total energy content of a pulse propagating through an idealized one-dimensional discrete particle system like a mass disordered granular chain, which allows understanding the energy attenuation due to disorder since it isolates the longitudinal P-wave from shear or rotational modes. It is observed from the signal that stronger disorder leads to faster attenuation of the signal. An ordered granular chain exhibits ballistic propagation of energy whereas, a disordered granular chain exhibits more diffusive like propagation, which eventually becomes localized at long time periods. For obtaining mean-field macroscopic/continuum properties, ensemble averaging has been used, however, such an ensemble averaged spectral energy response does not resolve multiple scattering, leading to loss of information, indicating the need for a different framework for micro-macro averaging.

  1. Use of municipal solid waste incineration bottom ashes in alkali-activated materials, ceramics and granular applications: A review.

    Silva, R V; de Brito, J; Lynn, C J; Dhir, R K

    2017-10-01

    This paper presents a literature review on the incorporation of municipal solid waste incinerated bottom ash as raw material in several markets, other than those where it is conventionally used, such as geotechnical applications and road pavement construction. The main findings of an ample selection of experimental investigations on the use of the bottom ash as precursor of alkali-activated materials, as an adsorbent material for the removal of hazardous elements from wastewater and landfill gases, as soil replacement in agricultural activities, as partial or complete substitute of raw materials for the manufacture of ceramic-based products, as landfill cover and as biogas production enhancer, were gathered, collated and analysed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. NMR Measurements of Granular Flow and Compaction

    Fukushima, Eiichi

    1998-03-01

    Nuclear magnetic resonance (NMR) can be used to measure statistical distributions of granular flow velocity and fluctuations of velocity, as well as spatial distributions of particulate concentration, flow velocity, its fluctuations, and other parameters that may be derived from these. All measurements have been of protons in liquid-containing particles such as mustard seeds or pharmaceutical pills. Our favorite geometry has been the slowly rotating partially filled rotating drum with granular flow taking place along the free surface of the particles. All the above-mentioned parameters have been studied as well as a spatial distribution of particulate diffusion coefficients, energy dissipation due to collisions, as well as segregation of non-uniform mixtures of granular material. Finally, we describe some motions of granular material under periodic vibrations.

  3. Co-disposal of industrial wastes to obtain an inert material for environmental reclamation

    Polcaro, A.M.; Palams, S.; Mascia, M.; Renoldi, F. [Cagliari Univ., Cagliari (Italy). Dipt. di Ingegneria Chimica e dei Materiali

    2000-02-01

    The present work deals with the treatment of red mud from Eurallumina Bayer plant with gypsum, in order to obtain an inert which might be disposed without risk. The proposed process has particular concern in the local contest in which the Bayer plant is located. The paper compares the characteristics of the effluents obtained leaching with water, beds of either red mud coming from the thickening filters of the Bayer plant (RMF) or from the holding ponds (RMP) or their mixtures with gypsum. The results obtained up to now show that the process is able to lower ph at values near 9, which is stable to further leaching runs. Also the physical characteristics of the resulting material are enhanced, in terms of both particle size distribution and hydraulic permeability. The addition of 10% sandy soil is sufficient to give permeability in the order of 10{sup -4} cm/s, which is typical od sandy soil. [Italian] Il lavoro analizza il trattamento di fango rosso del processo Bayer con gesso allo scopo di ottenere un materiale inerte, che possa essere smaltito senza particolari precauzioni. Il trattamento proposto puo' avere una certa rilevanza nel contesto territoriale in cui l'impianto di produzione e' inserito. In particolare sono state esaminate e confrontate le caratteristiche degli effluenti da prove di liscivazione con acqua di letti costituiti sia da fango prelevato direttamente dai filtri di ispessimento, che da fango prelevato dal bacino di lagunaggio. I risultati mostrano che il processo e' in grado di abbassare il pH del fango ad un valore intorno a 9, che si mantiene stabile alla liscivazione, anche quando la salinita' della massa ha raggiunto valori molto bassi. Il processo consente inoltre di migliorare le caratteristiche fisiche del materiale, sia in termini di granulometria, che si sposta verso le frazioni piu' grosse, che di permeabilita'. Una miscelazione con il 10% di terreno sabbioso e' sufficiente a conferire al

  4. Mechanical and trybological characterization of ceramic materials obtained of mine solid wastes

    Soto T, J.L.

    2003-01-01

    A discussion of the physical, mechanical and tribological characterization of the ceramics Jaar, Jaca and Vijaar is presented in this work. They have been obtained from the industrial residuals, coming from metals and sand of the mining industry in Pachuca Hidalgo, Mexico. The methodology followed for the obtention and characterization of these ceramics consists on eliminating the cyanides from the tailings through columns coupled with a system controlled with thermostats. Then, the chemical composition is analysed with spectrometry emission of plasma and scanning electronic microscopy. Then the ceramics are produced. The base material is agglutinated with clay or kaolin. For this purpose, it was used a sintering processes and isothermal compacting in hot condition. Finally, the physical, chemical, mechanical and tribological properties of these new products are determined. Carbon, oxygen, sodium, magnesium, aluminium, manganese, silicon, potassium, phosphor, calcium, titanium, iron, molybdenum, silver and gold are in the chemical composition or ceramic analysed. Also these are heterogeneous mixture of clay and kaolin. The cyanide was eliminated. The results show that Vijaar has better wear resistances to the waste; this was demonstrated in tribology tests. They were not perforated with the abrasive particles. Also, they have high hardness and they can to support more loads in compression than Jaar and the Jaca. Consequently, they are less fragile and, therefore, they can tolerate bending stresses and bigger impact loading. (Author)

  5. Technological physics and special materials: wood-plastic composites obtained by radiation polymerization

    Peteu, Gh.; Iliescu, V.

    1995-01-01

    General estimates and references are made in connection with the role of technological physics in obtaining materials with specific features. The first part of the paper presents the modification of weak wood essences as well as technological processes at bench-scale and semi industrial scale of wood-plastic composites, under various irradiation conditions. Two technological installations for the fabrication of wood-plastic composites on both scales with technical and practical specifications of their performances are presented. Experimental data for different wood-plastic composite systems using some local wood essences in combination with several polymer and copolymer systems are given. Impregnation and polymerization levels are mentioned for every specific system. The radiation dose rate and integrated dose are given for every experimental polymerization system. The features of the wood-plastic composites are compared with the initial wood essences. Finally, a few technical and economic assessments of wood-plastic composites and their implications in the domestic economy are presented. (author)

  6. Characterization of fly ash, slag and glass hull for the obtaining of vitreous materials

    Ayala Valderrama, D. M.; Gómez Cuaspud, J. A.

    2017-12-01

    This article presents the structural and thermal characterization of fly ash, the waste from blast furnace slag and the glass hull, generated as common residues in industry, which cannot be recycled easily or destroyed in a simple and fast way. In the particular case of fly ash, at present are being used as a lightweight aggregate in the production of cement, concrete and additive in the production of glass and glass ceramics. As far as the slag and hull, are being used as additives for the asphalt and concretes, however its use still is restricted, reason why its use in alternative ways are necessary. Initially the chemical composition of residues was established, determining that the fly ashes contains SiO2, Al2O3 and Fe2O3 oxides; 90% of the total composition, was confirmed by X-ray diffraction analysis. As minor constituents, small percentages of Mg, P, S, K, Na and Ti were found. For the slag case, the phases of Fe3O4, Ca3Mg (SiO2)4 and Ca(MgAl)(Si,Al)2O6 were identified, observing the presence of amorphous phase higher than 94% of the total phase of the system. Meanwhile, the glass hull sample showed a higher percentage of 95% amorphicity, mainly identifying a weak signal associated with silicon oxide SiO2. The thermal analyses of the samples, exhibit a decrease in mass for samples between 25-1000°C was observed, which can be attributed to different physical-chemical events that occur in the materials. The heat flow for each sample is related with the removal of the water retained by the physisorption processes around 92-110°C in all cases. With this previous characterization of the precursors, a sample was composed using 70% fly ash, 10% slag and 20% of glass hull was composed and treated at 1200°C/1.5 hours, obtaining a dense black glassy material for potential applications in field of the glass ceramics.

  7. Granular compaction and stretched exponentials - Experiments and a numerical stochastic model

    Nicolas Maxime

    2017-01-01

    Full Text Available We present a stochastic model to investigate the compaction kinetics of a granular material submitted to vibration. The model is compared to experimental results obtained with glass beads and with a cohesive powder. We also propose a physical interpretation of the characteristic time τ and the exponent β of the stretched exponential function widely used to represent the granular compaction kinetics, and we show that the characteristic time is proportional to the number of grains to move. The exponent β is expressed as a logarithmic compaction rate.

  8. Electromagnetic response of a highly granular hadronic calorimeter

    Adloff, C.; Blaha, J.; Blaising, J.J. [Savoie Univ., CNRS/IN2P3, Annecy-le-Vieux (FR). Lab. d' Annecy-le-Vieux de Physique des Particules] (and others)

    2010-12-15

    The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the hadronic calorimeter, one option is a highly granular sampling calorimeter with steel as absorber and scintillator layers as active material. High granularity is obtained by segmenting the scintillator into small tiles individually read out via silicon photo-multipliers (SiPM). A prototype has been built, consisting of thirty-eight sensitive layers, segmented into about eight thousand channels. In 2007 the prototype was exposed to positrons and hadrons using the CERN SPS beam, covering a wide range of beam energies and incidence angles. The challenge of cell equalization and calibration of such a large number of channels is best validated using electromagnetic processes. The response of the prototype steel-scintillator calorimeter, including linearity and uniformity, to electrons is investigated and described. (orig.)

  9. Electromagnetic response of a highly granular hadronic calorimeter

    Adloff, C.; Blaha, J.; Blaising, J.J.

    2010-12-01

    The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the hadronic calorimeter, one option is a highly granular sampling calorimeter with steel as absorber and scintillator layers as active material. High granularity is obtained by segmenting the scintillator into small tiles individually read out via silicon photo-multipliers (SiPM). A prototype has been built, consisting of thirty-eight sensitive layers, segmented into about eight thousand channels. In 2007 the prototype was exposed to positrons and hadrons using the CERN SPS beam, covering a wide range of beam energies and incidence angles. The challenge of cell equalization and calibration of such a large number of channels is best validated using electromagnetic processes. The response of the prototype steel-scintillator calorimeter, including linearity and uniformity, to electrons is investigated and described. (orig.)

  10. Irradiation devices for fusion reactor materials results obtained from irradiated lithium aluminate at the OSIRIS reactor

    Lefevre, F.; Thevenot, G.; Rasneur, B.; Botter, F.

    1986-06-01

    Studies about controlled fusion reactor of the Tokamak type require the examination of the radiation effects on the behaviour of various potential materials. Thus, in the first part of this paper, are presented the devices adapted to these materials studies and used in the OSIRIS reactor. In a second part, is described an experiment of irradiation ceramics used as candidates for breeding material and are given the first results

  11. Electrochemical treatment of an oxide material, application to superconductors, and obtained superconductors

    Grenier, J.C.; Pouchard, M.; Wattiaux, A.

    1991-01-01

    The present invention describes the electrochemical treatment of a superconductor oxide so as to modify its stoichiometry. These materials comprise in their anionic lattice oxygenated and hydrogenated species. These treated materials are prepared by an electrochemical process in which the oxide is an electrode in a liquid electrolysis. 3 refs., 3 figs

  12. Characterization of raw materials to obtain the mass for white ware, using waste glass

    Cavalcanti, M.S.L.; Porto, V.S.; Meneses, R.L; Albuquerque, A.V.; Guedes, B.F.R.; Morais, C.R.S.; Santana, L.N.L.

    2009-01-01

    A major problem faced in the post modern society is the huge amount of glass, accumulated in landfills cities. The glass material is one hundred percent recyclable and has the property to act as fluxes as well as feldspar. Given this premise, this study aimed to characterize materials - raw materials and waste glass regional plan for development of ceramic bodies with the similar behavior produced industrially, using shards of glass to partially replace the feldspar. The materials - raw materials used were clay, ball clay, kaolin, quartz, feldspar and shard of glass, being characterized by the techniques: chemical analysis, size analysis, differential thermal analysis vibrational spectroscopy in the infrared region, the Ray-Diffraction X and scanning electron microscopy. The results showed that the waste had higher rates of vitreous oxides fluxes and similar. (author)

  13. A constitutive law for dense granular flows.

    Jop, Pierre; Forterre, Yoël; Pouliquen, Olivier

    2006-06-08

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

  14. Reliability of Scores Obtained from Self-, Peer-, and Teacher-Assessments on Teaching Materials Prepared by Teacher Candidates

    Nalbantoglu Yilmaz, Funda

    2017-01-01

    This study aims to determine the reliability of scores obtained from self-, peer-, and teacher-assessments in terms of teaching materials prepared by teacher candidates. The study group of this research constitutes 56 teacher candidates. In the scope of research, teacher candidates were asked to develop teaching material related to their study.…

  15. Detection and Analysis of the Magnetic Field Component of Electromagnetic Radiation Emission from Macroscopic Fracturing of Cement-Bound Granular Material

    Maquiling, J. T.; Ceralde, P. I. B.

    2016-12-01

    Countries most prone to earthquake damage have been in pursuit of a possible earthquake precursor. This study aims to detect and measure the magnetic field component of the Electromagnetic Radiation (EMR) emitted by quasi-brittle materials that undergo macroscopic fracturing. Cement-Bound Granular Materials (CBGM) were prepared by mixing cement, sand and gravel in a beam mold. Additional aggregates in the form of saw dust were added to produce variable CBGM samples. A concrete beam holder was designed and fabricated such that induced cracks from impact loading would form at the center of the beam. Six Vernier software magnetic field sensors were used to detect the magnetic field (MF) component of the EMR emission. Initial calibration was done to minimize noise in the laboratory. The magnetic field sensors were set at a low amplification range (±6.4x10-3 T) setting with 0.0002 mT precision at 20-50 Hz. Sensor locations and orientations were specified and fixed throughout the experiment. The impact loading process was repeated until concrete failure. The time of drop was determined through the occurrence of peak sound levels (dB) induced by the collision noise using a sound level meter at fast time weighting. Magnetic field fluctuations manifesting near the occurrence of sound level impulses were recorded. Peak magnetic field values within ±200ms from the recorded time of impact were considered to be originating from the concrete fracture. Concrete samples consisting of cement, sand and gravel produced magnetic field emissions measuring 0.58-1.07 μT while the same concrete mixture added with dispersed fine sawdust released 0.55-1.28 μT. A more dispersed set of values of magnetic field emissions were observed for concrete with sawdust. Comparison between the average number of drops done before failure occurs between the two concrete mixtures also indicated that the addition of dispersed sawdust resulted to weaker CBGM samples. Upon increasing input energy from

  16. Beyond waste: new sustainable fillers from fly ashes stabilization, obtained by low cost raw materials

    N. Rodella

    2016-09-01

    Full Text Available A sustainable economy can be achieved only by assessing processes finalized to optimize the use of resources. Waste can be a relevant source of energy thanks to energy-from-waste processes. Concerns regarding the toxic fly ashes can be solved by transforming them into resource as recycled materials. The commitment to recycle is driven by the need to conserve natural resources, reduce imports of raw materials, save landfill space and reduce pollution. A new method to stabilize fly ash from Municipal Solid Waste Incinerator (MSWI at room temperature has been developed thanks to COSMOS-RICE LIFE+ project (www.cosmos-rice.csmt.eu. This process is based on a chemical reaction that occurs properly mixing three waste fly ashes with rice husk ash, an agricultural by-product. COSMOS inert can replace critical raw materials (i.e. silica, fluorspar, clays, bentonite, antimony and alumina as filler. Moreover the materials employed in the stabilization procedure may be not available in all areas. This paper investigates the possibility of substituting silica fume with corresponding condensed silica fume and to substitute flue-gas desulfurization (FGD residues with low-cost calcium hydroxide powder. The removal of coal fly ash was also considered. The results will be presented and a possible substitution of the materials to stabilize fly ash will be discussed.

  17. On the possibility of high-dispersed composite material obtaining in impulsive high-enthalpy flow

    Blinkov, I.V.; Brodyagin, A.G.; Ivanov, A.V.

    1987-01-01

    Thermodynamic possibility for the formation of TiC-Mo composite dispersed material in 1200-2800 K temperature interval and effect of H/Cl, C/Ti relation on the composite material composition are demonstrated. Investigation into the plasmo-chemical process of producing high-dispersed composite material in the pulsed regime has pointed out to a possibility of the product chemical composition regulation by changing the energy, flow-rate parameters and by conditions of component introduction into the plasmochemical reactor. Molybdenum-carbide composition powders produced are characterized by the particle size of ∼ 10 nm and high Mo and TiC distribution steadyness which allows one to exclude the stage of a long-term component mixing under the composition production

  18. Ultrathin Hydrophobic Coatings Obtained on Polyethylene Terephthalate Materials in Supercritical Carbon Dioxide with Co-Solvents

    Kumeeva, T. Yu.; Prorokova, N. P.

    2018-02-01

    The surface properties of ultradisperse polytetrafluoroethylene coatings on polyethylene terephthalate materials modified in a supercritical carbon dioxide medium with co-solvent additions (aliphatic alcohols) were analyzed. An atomic force microscopy study revealed the peculiarities of the morphology of the hydrophobic coatings formed in the presence of co-solvents. The contribution of the co-solvents to the formation of the surface layer with a low surface energy was evaluated from the surface energy components of the modified polyester material. The stability of the coatings against dry friction was analyzed.

  19. DISCHARGE VALVE FOR GRANULAR MATERIAL

    Stoughton, L.D.; Robinson, S.T.

    1962-05-15

    A gravity-red dispenser or valve is designed for discharging the fueled spherical elements used in a pebble bed reactor. The dispenser consists of an axially movable tube terminating under a hood having side walls with openings. When the tube is moved so that its top edge is above the tops of the side openings the elements will not flow. As the tube is moved downwardly, the elements flow into the hood through the side openings and over the top edge into the tube at an increasing rate as the tube is lowered further. The tube is spaced at all times from the hood and side walls a distance greater than the diameter of the largest element to prevent damaging of the elements when the dispenser is closed to flow. (AEC)

  20. Granular-front formation in free-surface flow of concentrated suspensions

    Leonardi, Alessandro; Cabrera, Miguel; Wittel, Falk K.; Kaitna, Roland; Mendoza, Miller; Wu, Wei; Herrmann, Hans J.

    2015-11-01

    A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The flowing material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid materials, such as fresh concrete or debris flow. In these materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.

  1. Synthesis and characterization of a ferrous compound material obtained by combustion of ferroboron and ferrotitanium mixtures

    Bejar, M.A; Fuenzalida, J.L

    2008-01-01

    A ferrous compound material was synthesized in this work, by the air auto-combustion of mixtures of powdered ferroboron and ferrotitanium, compacted under pressures of 79 and 93 MPa and preheated to a temperature of about 1000 o C. The synthesized compounds were characterized by XRD analysis, and macro and micro-hardness tests. The formation of titanium diboride was found in all the synthesized test pieces (au)

  2. Raw material from the state of Rio Grande do Norte, Brazil, to obtain sandstone porcelain

    Sousa, Maria Rosimar de

    2009-01-01

    Currently, the production of the ceramic industry of the River Great of the North she is restricted to the manufacture of bricks and roofing tiles. development of new ceramic products of bigger added value, such as gres covering porcelanato, using regional raw materials is of basic importance for the growth of the local ceramic industry and economic development of the region. In this work, they had been studied raw materials as kaolin, sodico feldspato and quartz of the State of the Great River of the North for the attainment of an covering of the gres type porcelanato of base white.The ceramic masses had been prepared by the process saw humid. The body-of-tests they had been conformed by uniaxial prensagem of 40MPa, dried in 110 deg C and burnt between 1160 and 1240 deg, used a cycle of fast burning (approximately 60min.). The qualitative analysis of the formed phases disclosed silica, mullite e sodico feldspato after the sintering. The technological properties of burning evaluated they had been: linear retraction, water absorption, apparent specific mass, porosity and breaking strength to the flexal (shipment of 3 points). Results show that raw materials proceeding from the State of the Great River of North could be used in processes for gres porcelanato, therefore they present characteristics technological, similar chemistry, physics and to the standard of reference and the data of literature. (author)

  3. Modeling granular phosphor screens by Monte Carlo methods

    Liaparinos, Panagiotis F.; Kandarakis, Ioannis S.; Cavouras, Dionisis A.; Delis, Harry B.; Panayiotakis, George S.

    2006-01-01

    The intrinsic phosphor properties are of significant importance for the performance of phosphor screens used in medical imaging systems. In previous analytical-theoretical and Monte Carlo studies on granular phosphor materials, values of optical properties, and light interaction cross sections were found by fitting to experimental data. These values were then employed for the assessment of phosphor screen imaging performance. However, it was found that, depending on the experimental technique and fitting methodology, the optical parameters of a specific phosphor material varied within a wide range of values, i.e., variations of light scattering with respect to light absorption coefficients were often observed for the same phosphor material. In this study, x-ray and light transport within granular phosphor materials was studied by developing a computational model using Monte Carlo methods. The model was based on the intrinsic physical characteristics of the phosphor. Input values required to feed the model can be easily obtained from tabulated data. The complex refractive index was introduced and microscopic probabilities for light interactions were produced, using Mie scattering theory. Model validation was carried out by comparing model results on x-ray and light parameters (x-ray absorption, statistical fluctuations in the x-ray to light conversion process, number of emitted light photons, output light spatial distribution) with previous published experimental data on Gd 2 O 2 S:Tb phosphor material (Kodak Min-R screen). Results showed the dependence of the modulation transfer function (MTF) on phosphor grain size and material packing density. It was predicted that granular Gd 2 O 2 S:Tb screens of high packing density and small grain size may exhibit considerably better resolution and light emission properties than the conventional Gd 2 O 2 S:Tb screens, under similar conditions (x-ray incident energy, screen thickness)

  4. Superconducting materials fabrication process and materials obtained. Procede de preparation de materiaux supraconducteurs et materiaux ainsi obtenus

    Lafon, M O; Magnier, C

    1989-03-24

    The preparation process of a fine powder of YBaCuO type superconductors of easy sintering comprises: mixing in presence of alcohol an aqueous solution of rare earth nitrate or acetate, alkaline earth nitrate or acetate and copper nitrate or acetate and an oxalic acid solution, the pH value of the mixture is comprised between 2 and 4, the obtained precipitate is separated, dried, calcined and eventually crushed.

  5. Anisotropy in cohesive, frictional granular media

    Luding, Stefan

    2005-01-01

    The modelling of cohesive, frictional granular materials with a discrete particle molecular dynamics is reviewed. From the structure of the quasi-static granular solid, the fabric, stress, and stiffness tensors are determined, including both normal and tangential forces. The influence of the material properties on the flow behaviour is also reported, including relations between the microscopic attractive force and the macroscopic cohesion as well as the dependence of the macroscopic friction on the microscopic contact friction coefficient. Related to the dynamics, the anisotropy of both structure and stress are exponentially approaching the maximum

  6. Carbonaceous Materials Obtained from Sewage Sludge for NO2 Removal under Wet Conditions at Room Temperature

    Pietrzak, R.

    2010-01-01

    The effect of the processes of carbonisation and activation on adsorbents obtained from sewage sludge and their sorption properties towards NO 2 were studied. Carbonaceous adsorbents were obtained by carbonisation of sewage sludge at 600 o C for four different times 30, 60, 90 and 120 min followed by activation of the carbonisates by CO 2 at 800 o C for 60 min. Adsorption of NO 2 was carried out in wet air. It has been shown that by appropriate thermal and chemical treatment of sludge, mesoporous adsorbents capable of NO 2 removal can be obtained. The sorption abilities of the carbonised and activated samples to adsorb NO 2 have been shown to increase with increased time of carbonisation and reach maximum for the carbonisation maintained for 90 min. Further increase in this time causes a decrease in the adsorption abilities of the samples. The sorption properties of the carbonisates have been proved to be determined by the chemical character of the surface, while those of the activated samples - by the porous structure. (author)

  7. Dynamic Deformation and Collapse of Granular Columns

    Uenishi, K.; Tsuji, K.; Doi, S.

    2009-12-01

    Large dynamic deformation of granular materials may be found in nature not only in the failure of slopes and cliffs — due to earthquakes, rock avalanches, debris flows and landslides — but also in earthquake faulting itself. Granular surface flows often consist of solid grains and intergranular fluid, but the effect of the fluid may be usually negligible because the volumetric concentration of grains is in many cases high enough for interparticle forces to dominate momentum transport. Therefore, the investigation of dry granular flow of a mass might assist in further understanding of the above mentioned geophysical events. Here, utilizing a high-speed digital video camera system, we perform a simple yet fully-controlled series of laboratory experiments related to the collapse of granular columns. We record, at an interval of some microseconds, the dynamic transient granular mass flow initiated by abrupt release of a tube that contains dry granular materials. The acrylic tube is partially filled with glass beads and has a cross-section of either a fully- or semi-cylindrical shape. Upon sudden removal of the tube, the granular solid may fragment under the action of its own weight and the particles spread on a rigid horizontal plane. This study is essentially the extension of the previous ones by Lajeunesse et al. (Phys. Fluids 2004) and Uenishi and Tsuji (JPGU 2008), but the striped layers of particles in a semi-cylindrical tube, newly introduced in this contribution, allow us to observe the precise particle movement inside the granular column: The development of slip lines inside the column and the movement of particles against each other can be clearly identified. The major controlling parameters of the spreading dynamics are the initial aspect ratio of the granular (semi-)cylindrical column, the frictional properties of the horizontal plane (substrate) and the size of beads. We show the influence of each parameter on the average flow velocity and final radius

  8. Study of phase changing characteristics of granular composites using differential scanning calorimetry

    Rady, Mohamed

    2009-01-01

    Characterization of the phase changing behavior of granular materials is an important issue for design and optimization of latent heat thermal energy storage (LHTES) systems. In the present work, differential scanning calorimetry (DSC) has been used to study the phase changing behavior of granular composites consisting of ceramic encapsulated phase change material (EPCM) with particle diameters of 1-3 mm. The obtained DSC curves characterizing melting and solidification of the composite material are shown to be dependent upon the values of heating and cooling rates. Direct utilization of the measured DSC curves could result in an inexact representation of the sample enthalpy change. A simple procedure has been advised to obtain accurate quantitative results from the DSC measurements based on the estimation of the thermal resistance between the sample and its enclosure. Analysis of the evolution of latent heat of EPCM with temperature at different values of cooling/heating rates is presented.

  9. Application of the Method of Direct Solidification for Obtaining New Materials

    Grankin, S.S.

    2007-01-01

    The influence of the method of direct solidification on the formation of the material structure has been considered. The main methods of single crystal growth have been described. A considerable influence of the crystal growth parameters (temperature gradient at the front of solidification and the speed of moving of the front of solidification) on the type of the structure and morphology of single crystals has been shown. The examples of application of the method of direct solidification in experimental and industrial production are showed: production of directly crystallized blades for turbines of nuclear power plants and gas-turbine engines

  10. Granular motor in the non-Brownian limit

    Oyarte Galvez, Loreto Alejandra; van der Meer, Roger M.

    2016-01-01

    In this work we experimentally study a granular rotor which is similar to the famous Smoluchowski–Feynman device and which consists of a rotor with four vanes immersed in a granular gas. Each side of the vanes can be composed of two different materials, creating a rotational asymmetry and turning

  11. Granular Leidenfrost effect: Experiment and theory of floating particle clusters

    Eshuis, Peter; Eshuis, P.G.; van der Meer, Roger M.; van der Weele, J.P.; Lohse, Detlef

    2005-01-01

    Granular material is vertically vibrated in a 2D container: above a critical shaking strength, and for a sufficient number of beads, a crystalline cluster is elevated and supported by a dilute gaseous layer of fast beads underneath. We call this phenomenon the granular Leidenfrost effect. The

  12. USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

    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...

  13. Surface instabilities in shock loaded granular media

    Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

    2017-12-01

    The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to

  14. Cellulose nanocrystals obtained from office waste paper and their potential application in PET packing materials.

    Lei, Wanqing; Fang, Changqing; Zhou, Xing; Yin, Qian; Pan, Shaofei; Yang, Rong; Liu, Donghong; Ouyang, Yun

    2018-02-01

    Annually a tremendous amount of office waste paper (OWP) is discarded creating environmental pollution. Therefore, how to make this paper from waste to wealth and use it in new approaches have become a meaningful and challenging work. In this work, OWP being a cellulose rich biomass was employed for the production of cellulose nanocrystals (CNCs) by acid hydrolysis with different acid concentrations but without subjecting OWP to alkali and bleaching treatments. The testing results showed that CNCs prepared using sulfuric acid concentration of 59% with respect to OWP had the highest crystallinity and this concentration was the transition concentration for the production of opaque CNCs film with convoluted nanofibers to transparent one with orientated nanofibers. Besides, CNCs prepared using acid concentration of 65% coated on PET sheet not only had a better water vapor barrier property but also was on a par with the transparency of PET, which was hopeful to be used as coating materials in packaging materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Optical spectroscopic characterization of amorphous germanium carbide materials obtained by X-Ray Chemical Vapor Deposition

    Paola Antoniotti

    2015-05-01

    Full Text Available Amorphous germanium carbides have been prepared by X-ray activated Chemical Vapor Deposition from germane/allene systems. The allene percentage and irradiation time (total dose were correlated to the composition, the structural features, and the optical coefficients of the films, as studied by IR and UV-VIS spectroscopic techniques. The materials composition is found to change depending on both the allene percentage in the mixture and the irradiation time. IR spectroscopy results indicate that the solids consist of randomly bound networks of carbon and germanium atoms with hydrogen atoms terminating all the dangling bonds. Moreover, the elemental analysis results, the absence of both unsaturated bonds and CH3 groups into the solids and the absence of allene autocondensation reactions products, indicate that polymerization reactions leading to mixed species, containing Ge-C bonds, are favored. Eopt values around 3.5 eV have been found in most of the cases, and are correlated with C sp3-bonding configuration. The B1/2 value, related to the order degree, has been found to be dependent on solid composition, atoms distribution in the material and hydrogenation degree of carbon atoms.

  16. The Enhancement of 3D Scans Depth Resolution Obtained by Confocal Scanning of Porous Materials

    Martisek, Dalibor; Prochazkova, Jana

    2017-12-01

    The 3D reconstruction of simple structured materials using a confocal microscope is widely used in many different areas including civil engineering. Nonetheless, scans of porous materials such as concrete or cement paste are highly problematic. The well-known problem of these scans is low depth resolution in comparison to the horizontal and vertical resolution. The degradation of the image depth resolution is caused by systematic errors and especially by different random events. Our method is focused on the elimination of such random events, mainly the additive noise. We use an averaging method based on the Lindeberg-Lévy theorem that improves the final depth resolution to a level comparable with horizontal and vertical resolution. Moreover, using the least square method, we also precisely determine the limit value of a depth resolution. Therefore, we can continuously evaluate the difference between current resolution and the optimal one. This substantially simplifies the scanning process because the operator can easily determine the required number of scans.

  17. The Enhancement of 3D Scans Depth Resolution Obtained by Confocal Scanning of Porous Materials

    Martisek Dalibor

    2017-12-01

    Full Text Available The 3D reconstruction of simple structured materials using a confocal microscope is widely used in many different areas including civil engineering. Nonetheless, scans of porous materials such as concrete or cement paste are highly problematic. The well-known problem of these scans is low depth resolution in comparison to the horizontal and vertical resolution. The degradation of the image depth resolution is caused by systematic errors and especially by different random events. Our method is focused on the elimination of such random events, mainly the additive noise. We use an averaging method based on the Lindeberg-Lévy theorem that improves the final depth resolution to a level comparable with horizontal and vertical resolution. Moreover, using the least square method, we also precisely determine the limit value of a depth resolution. Therefore, we can continuously evaluate the difference between current resolution and the optimal one. This substantially simplifies the scanning process because the operator can easily determine the required number of scans.

  18. Directly obtained τ-phase MnAl, a high performance magnetic material for permanent magnets

    Fang, Hailiang, E-mail: hailiang.fang@kemi.uu.se [Inorganic Chemistry, Department of Chemistry – Ångström Laboratory, Uppsala University (Sweden); Kontos, Sofia [Solid State Physics, Department of Engineering Sciences, Uppsala University (Sweden); Ångström, Jonas; Cedervall, Johan [Inorganic Chemistry, Department of Chemistry – Ångström Laboratory, Uppsala University (Sweden); Svedlindh, Peter; Gunnarsson, Klas [Solid State Physics, Department of Engineering Sciences, Uppsala University (Sweden); Sahlberg, Martin [Inorganic Chemistry, Department of Chemistry – Ångström Laboratory, Uppsala University (Sweden)

    2016-05-15

    The metastable tetragonal τ-phase has been directly obtained from casting Mn{sub 0.54}Al{sub 0.46} and (Mn{sub 0.55}Al{sub 0.45}){sub 100}C{sub 2} using the drop synthesis method. The as-casted samples were ball milled to decrease the particle size and relaxed at 500 °C for 1 h. The phase composition, crystallographic parameters, magnetic properties and microstructure were systematically studied. The results reveal that the τ-phase could be directly obtained from drop synthesis. The highest M{sub s} of 117 emu/g was achieved in the (Mn{sub 0.55}Al{sub 0.45}){sub 100}C{sub 2} where the τ-phase was stabilized by doping with carbon. Carbon doping increased the c/a ratio of the τ-phase as it occupies specific interstitial positions (½, ½, 0) in the structure. Furthermore, ball milling increases the coercivity (H{sub c}) at the expense of a decrease in magnetic saturation (M{sub s}). The increase in coercivity is explained by a decrease of grain size in conjunction with domain wall pinning due to defects introduced during the ball milling process. - Graphical abstract: The tetragonal τ-phase has been directly obtained from casting Mn{sub 0.54}Al{sub 0.46} and (Mn{sub 0.55}Al{sub 0.45}){sub 100}C{sub 2} using the drop synthesis method. The phase composition, crystallographic parameters, magnetic properties and microstructure were systematically studied. The highest M{sub s} of 117 emu/g was achieved for (Mn{sub 0.55}Al{sub 0.45}){sub 100}C{sub 2} ball milling increases the coercivity (H{sub c}) at the expense of a decrease in magnetic saturation (M{sub s}). - Highlights: • The ferromagnetic τ-phase has been directly obtained from casting. • The highest M{sub s} of 117 emu/g was achieved for (Mn{sub 0.55}Al{sub 0.45}){sub 100}C{sub 2}. • Ball milling increases the coercivity but decreases the magnetic saturation.

  19. Use of modern methods of fibre surface modification to obtain the multifunctional properties of textile materials

    Jocić Dragan

    2003-01-01

    Full Text Available The modern textile fibre treatments aim to obtain the required level of beneficial effect while attempting to confine the modification to the fibre surface. Recently, much attention has been focused on different physical methods of fibre surface modification, cold plasma treatment being considered as very useful. Moreover, there are efficient chemical methods available, such as peroxide, biopolymer and enzyme treatment. Some interesting combinations of these physical and chemical surface modification methods as means to modify fibre surface topography and thus controlling the surface-related properties of the fibre are presented in this paper. The properties obtained are discussed on the basis of the physico-chemical changes in the surface layer of the fibre, being assessed by wettability and contact angle measurements, as well as by FTIR-ATR and XPS analysis. The SEM and AFM technique are used to assess the changes in the fibre surface topography and to correlate these changes to the effectiveness, uniformity and severity of the textile fibre surface modification treatments.

  20. Impact of material thicknesses on fission observables obtained with the FALSTAFF experimental setup

    Thulliez L.

    2017-01-01

    Full Text Available In the past years, the fission studies have been mainly focused on thermal fission because most of the current nuclear reactors work in this energy domain. With the development of GEN-IV reactor concepts, mainly working in the fast energy domain, new nuclear data are needed. The FALSTAFF spectrometer under development at CEA-Saclay, France, is a two-arm spectrometer which will provide mass yields before (2V method and after (EV method neutron evaporation and consequently will have access to the neutron multiplicity as a function of mass. The axial ionization chamber, in addition to the kinetic energy value, will measure the energy loss profile of the fragment along its track. This energy loss profile will give information about the fragment nuclear charge. This paper will focus on recent developments on the FALSTAFF design. A special attention will be paid to the impact of the detector material thickness on the uncertainty of different observables.

  1. Introduction. Physicochemical aspects of uranium concentrates obtaining from the wastes and raw materials

    Mirsaidov, I.U.

    2014-01-01

    The uranium deposits of Tajikistan played an immensely significant role in the practical solution of a radioactive raw materials problem which appeared during the post-World War II years in the USSR. The pioneer in this field became complex №6 (currently known as 'Vostokredmet'). The first soviet uranium was produced from the ores extracted from the republic's deposits. For 50 years (1945-1995 y.), uranium bearing raw materials from all over the former USSR were delivered to Tajikistan, and uranium oxide was produced, which was later delivered back to Russia for further production of enriched uranium. The total volume of uranium produced in Tajikistan plants was approximately 100 thousands tons. In Sughd region, during that period, more than 55 million tons of uranium waste was accumulated. The total activity of the waste, according to different calculations, is approximately 240-285 TBq. The total amount of waste in dumps and tailings piles is estimated to be more than 170 million tons, most of which are located in the neighborhoods of hydrometallurgical plants and heap leaching locations. Uranium industry wastes in Northern Tajikistan have become attractive for different investors and commercial companies, from secondary reprocessing of mines and tailings' point of view, since the uranium price is increasing. In this regard, research on developing uranium extraction methods from wastes is broadening. The study of the possibility and economic reasonability of reprocessing former year's dumps requires comprehensive examination, and relates not only to uranium extraction but to safe extraction of dumps from tailings as well.

  2. Microstructure study of a material on the basis of YSZ obtained be freeze-drying

    Rizea, A.; Abrudeanu, M.; Petot, C.; Petot Ervas, G.

    2001-01-01

    Freeze-drying is a dehydration proceeding of the products in a frozen state, which is based on the ice sublimation process. It is a method, which leads to a very good homogeneity of the products and it allows obtaining very fine powders, which directs to reducing the sintering temperature. Freeze drying always supposes three stages: - freezing, sublimation and absorption of the residual water. The preparation of ZrO 20.91 Y 2 O 30.09 samples proceeds through the following stages: - a. solution preparation; b. solution spraying (into small droplets in liquid nitrogen); c. freeze drying processing; d. calcination of the freeze dried powder; e. powder compacting; f. sintering at four different temperature. The different structure of samples with different density are characterized on basis of micrographs. The results of these analyses are presented, discussed and explained through the chemical composition of the samples

  3. Obtaining Material Data for Heat Treatment Simulation of Casr Alloy Parts with Unified Models

    Bellini, Anna; Thorborg, Jesper; Hattel, Jesper

    2004-01-01

    subjected to high temperature. In this paper a two-state variables unified model is applied in order to simulate creep behavior and time-dependent metallurgical changes. The fundamental assumption of the unified theory is that creep and viscoplasticity, which are both irreversible strains developed because...... study. The results obtained for the simulation of tensile tests and of creep tests are compared with experimental curves, showing a good agreement.......The objective of this work, which is part of the IDEAL (Integrated Development Routes for Optimized Cast Aluminium Components) project, financed by the EU in frame work 6 and born in collaboration with the automobile and foundry industries, is to simulate creep behavior of aluminum cast samples...

  4. New magnetic materials obtained by ion-exchange reactions from non-magnetic layered perovskites

    Kageyama, H; Viciu, L; Caruntu, G; Ueda, Y; Wiley, J B

    2004-01-01

    New layered magnetic materials (MCl)Ca 2 Ta 3 O 10 (M = Cu, Fe), have been prepared by ion-exchange reactions of non-magnetic perovskite derivatives, ACa 2 Ta 3 O 10 (A = Rb, Li), in corresponding anhydrous molten salts. Powder x-ray diffraction patterns of the products are successfully indexed assuming tetragonal symmetry with cell dimensions a = 3.829 A and c = 15.533 A for Cu, and a = 3.822 A and c = 15.672 A for Fe. Being separated by the Ca 2 Ta 3 O 10 triple-layer perovskite slabs, the transition-metal chloride (MCl) network provides a two-dimensional magnetic lattice. Magnetic susceptibility measurements show that (CuCl)Ca 2 Ta 3 O 10 is in an antiferromagnetic state below 8 K, while (FeCl)Ca 2 Ta 3 O 10 has two anomalies at 91 and 125 K, suggesting successive phase transitions due to geometrical spin frustration

  5. Tribological properties of ternary nanolayers, obtained from simple/compound materials

    Jinga, V.; Cristea, D.; Samoilă, C.; Ursuţiu, D.; Mateescu, A. O.; Mateescu, G.; Munteanu, D.

    2016-06-01

    Numerous recently investigations are oriented towards the development of new classes of thin films, having dry-lubrication properties. These efforts were determined by the enormous energy losses generated by friction, and due to technical complications determined by the systems used for classic lubrication. This paper presents our results concerning a new class of nanomaterials, with ternary composition deposited from simple/compound materials (Ti/TixNy, TiB2/TixBiyNz, WC/WxCyNz). The films were deposited by magnetron sputtering, with varying sputtering parameters (sputtering power, reactive gas) on stainless steel substrates - ultrasonically and glow discharge cleaned before the deposition process. The influence of the deposition parameters on the mechanical and wear properties was assessed by nanoindentation, scratch resistance (to quantify the adhesion of the films to the steel substrate) and by pin-on- disk wear tests. The general conclusion was that the sample deposited at 5500 C, with N2 as reactive gas and 0.5 kV for substrate polarization, has the best mechanical characteristics (hardness and elastic modulus) and lubricant properties (represented by μ average), when compared to the remaining samples.

  6. Theoretical model of granular compaction

    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

    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.

  7. Selenium incorporated in vegetable material for the obtaining of worm flour and compost

    Ulbio Alcivar Cedeño

    2015-02-01

    Full Text Available A study was done to evaluate the quality of the earthworm flour fed with the addition of selenium. Two groups with three replicates were used; a food made of sterilized vegetable waste and other with the addition of soya (5% as a source of selenium. Temperature, humidity, and pH were controlled to ensure the optimal growth of earthworms. A 0.5 g sample of both groups replicates was weighed in order to determine the amount of Na, K, Fe, Ca, Zn, Mg, Mn, Cu, Li, Se, Hg and Pb. The humus quality provided by the samples was also qualitatively analyzed, and the amount of moisture, protein, dry matter, fat, ash, crude fiber and soluble carbohydrates were determined. The amount of the elements Ca, Fe, Mg, Zn, Cu, Mn and Li was satisfactory because the flour had concentrations similar to the conventional worm flour, which is first achieved for this type of product. The amount of protein and lipid was also high similar to the conventional foods derived from animals. No heavy metals were found. Remarkably, the use of Eisenia foetida Savigny extracts can be used as a dietary supplement in amounts less than 1 g per person, which minimizes the risk of heavy metals. The application of humus from earthworms that were fed with a diet that contained selenium, corn plants obtained were significantly different from the untreated ones.

  8. Obtaining the Bidirectional Transfer Distribution Function ofIsotropically Scattering Materials Using an Integrating Sphere

    Jonsson, Jacob C.; Branden, Henrik

    2006-10-19

    This paper demonstrates a method to determine thebidirectional transfer distribution function (BTDF) using an integratingsphere. Information about the sample's angle dependent scattering isobtained by making transmittance measurements with the sample atdifferent distances from the integrating sphere. Knowledge about theilluminated area of the sample and the geometry of the sphere port incombination with the measured data combines to an system of equationsthat includes the angle dependent transmittance. The resulting system ofequations is an ill-posed problem which rarely gives a physical solution.A solvable system is obtained by using Tikhonov regularization on theill-posed problem. The solution to this system can then be used to obtainthe BTDF. Four bulk-scattering samples were characterised using both twogoniophotometers and the described method to verify the validity of thenew method. The agreement shown is great for the more diffuse samples.The solution to the low-scattering samples contains unphysicaloscillations, butstill gives the correct shape of the solution. Theorigin of the oscillations and why they are more prominent inlow-scattering samples are discussed.

  9. The profile of Brazilian agriculture as source of raw material to obtain organic cosmetics

    Neila de Paula Pereira

    2017-05-01

    Full Text Available With one of the most notable floras in the world for sustainable research, the Brazilian Amazon region currently counts on financial incentives from the Brazilian Government for private national and foreign businesses. The ongoing implantation of a Biocosmetics Research and Development Network (REDEBIO aims to stimulate research involving natural resources from the Brazilian states that make up the zone defined as “Amazônia Legal”. The objective of this region, still under development in Brazil, is principally to aggregate value to products manufactured in small local industries through the use of sustainable technology currently being established. Certain certified raw materials already included in the country’s sustainability program, have also begun to be cultivated according to the requirements of organic cultivation (Neves, 2009. The majority are species of Amazonian vegetation: Euterpe oleracea (Açai, Orbignya martiana (Babaçu, Theobroma grandi-florum (Cupuaçu, Carapas guianensis (Andiroba, Pentaclethra macroloba (Pracaxi, Copaifera landesdorffi (Copaiba, Platonia insignis (Bacuri, Theobroma cacao (Cacao, Virola surinamensis (Ucuuba and Bertholletia excelsa (Brazil nut. These generate phytopreparations, such as oils, extracts, and dyes that are widely used in the manufacture of Brazilian organic cosmetics with scientifically proven topical and capillary benefits. In the final balance, Brazilian organic cosmetics should continue to gain force over the next few years, especially with the regulation of the organic cosmetics market that is being drafted by the Brazilian Ministry of Agriculture. Moreover, lines of ecologically aware products that provide quality of life for both for rural and metropolitan communities show a tendency to occupy greater space in the market.

  10. Dynamical Heterogeneity in Granular Fluids and Structural Glasses

    Avila, Karina E.

    Our current understanding of the dynamics of supercooled liquids and other similar slowly evolving (glassy) systems is rather limited. One aspect that is particularly poorly understood is the origin and behavior of the strong non trivial fluctuations that appear in the relaxation process toward equilibrium. Glassy systems and granular systems both present regions of particles moving cooperatively and at different rates from other regions. This phenomenon is known as spatially heterogeneous dynamics. A detailed explanation of this phenomenon may lead to a better understanding of the slow relaxation process, and perhaps it could even help to explain the presence of the glass transition. This dissertation concentrates on studying dynamical heterogeneity by analyzing simulation data for models of granular materials and structural glasses. For dissipative granular fluids, the growing behavior of dynamical heterogeneities is studied for different densities and different degrees of inelasticity in the particle collisions. The correlated regions are found to grow rapidly as the system approaches dynamical arrest. Their geometry is conserved even when probing at different cutoff length in the correlation function or when the energy dissipation in the system is increased. For structural glasses, I test a theoretical framework that models dynamical heterogeneity as originated in the presence of Goldstone modes, which emerge from a broken continuous time reparametrization symmetry. This analysis is based on quantifying the size and the spatial correlations of fluctuations in the time variable and of other kinds of fluctuations. The results obtained here agree with the predictions of the hypothesis. In particular, the fluctuations associated to the time reparametrization invariance become stronger for low temperatures, long timescales, and large coarse graining lengths. Overall, this research points to dynamical heterogeneity to be described for granular systems similarly than

  11. Granular computing: perspectives and challenges.

    Yao, JingTao; Vasilakos, Athanasios V; Pedrycz, Witold

    2013-12-01

    Granular computing, as a new and rapidly growing paradigm of information processing, has attracted many researchers and practitioners. Granular computing is an umbrella term to cover any theories, methodologies, techniques, and tools that make use of information granules in complex problem solving. The aim of this paper is to review foundations and schools of research and to elaborate on current developments in granular computing research. We first review some basic notions of granular computing. Classification and descriptions of various schools of research in granular computing are given. We also present and identify some research directions in granular computing.

  12. Study of parameters of heat treatment in obtaining glass ceramic materials with addition of the industrial waste

    Kniess, C.T.; Prates, P.B.; Martins, G.J.M.; Riella, H.G.; Matsinhe, Jonas; Kuhnen, N.C.

    2012-01-01

    The production of materials from crystallization of glass, called glass ceramic, have proved interesting by the possibility of development of different microstructures, with reduced grain size and the presence of residual amorphous phase in different quantities. The method that uses the differential thermal analysis (DTA) provides research on the material properties over a wide temperature range, it's widely applied to crystallization processes of glass ceramic materials. Within this context, this paper aims to study the kinetics of nucleation and crystal growth in glass ceramic materials in the system SiO 2 - Al 2 O 3 -Li 2 O, obtained with the addition of mineral coal bottom ash as source of aluminosilicates, through the technique of differential thermal analysis. (author)

  13. Concentration profiles in the wake of a sphere buried in a granular bed through which fluid flows

    Guedes de Carvalho, J.R.F.; Delgado, J.M.P.Q.; Alves, M.A.

    2005-01-01

    The concentration distribution in the wake of a soluble sphere immersed in a granular bed of inerts has been obtained numerically, for transport by both advection and diffusion/dispersion. Fluid flow in the granular bed around the sphere was assumed to follow Darcy's law and, at each point, dispersion of solute was considered in both the cross-stream and stream-wise directions. The elliptic PDE equation, resulting from a differential material balance on the solute, has been solved numerically over a wide range of values of the relevant parameters. (authors)

  14. Concentration profiles in the wake of a sphere buried in a granular bed through which fluid flows

    Guedes de Carvalho, J.R.F.; Delgado, J.M.P.Q.; Alves, M.A. [Porto Univ., Dpet. de Engenharia Quimica, Faculdade de Engenharia (Portugal)

    2005-07-01

    The concentration distribution in the wake of a soluble sphere immersed in a granular bed of inerts has been obtained numerically, for transport by both advection and diffusion/dispersion. Fluid flow in the granular bed around the sphere was assumed to follow Darcy's law and, at each point, dispersion of solute was considered in both the cross-stream and stream-wise directions. The elliptic PDE equation, resulting from a differential material balance on the solute, has been solved numerically over a wide range of values of the relevant parameters. (authors)

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

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

    1999-09-01

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

  16. International Workshop on Traffic and Granular Flow

    Herrmann, Hans; Schreckenberg, Michael; Wolf, Dietrich; Social, Traffic and Granular Dynamics

    2000-01-01

    "Are there common phenomena and laws in the dynamic behavior of granular materials, traffic, and socio-economic systems?" The answers given at the international workshop "Traffic and Granular Flow '99" are presented in this volume. From a physical standpoint, all these systems can be treated as (self)-driven many-particle systems with strong fluctuations, showing multistability, phase transitions, non-linear waves, etc. The great interest in these systems is due to several unexpected new discoveries and their practical relevance for solving some fundamental problems of today's societies. This includes intelligent measures for traffic flow optimization and methods from "econophysics" for stabilizing (stock) markets.

  17. Granular Gas in a Periodic Lattice

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

    2011-01-01

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

  18. Anomalous infrared absorption in granular superconductors

    Carr, G.L.; Garland, J.C.; Tanner, D.B.

    1983-01-01

    Granular superconductors are shown to have a far-infrared absorption that is larger when the samples are superconducting than when they are normal. By constrast, theoretical models for these materials predict that when the samples become superconducting, the absorption should decrease

  19. Random packing of colloids and granular matter

    Wouterse, A.

    2008-01-01

    This thesis deals with the random packing of colloids and granular matter. A random packing is a stable disordered collection of touching particles, without long-range positional and orientational order. Experimental random packings of particles with the same shape but made of different materials

  20. Deposition and shaking of dry granular piles

    Hasan, M.

    2003-01-01

    A friction force model describing reversible stick-slip transition during contact has been developed with the special purpose to simulate the deposition of granular material. A test with a mass on a conveyor belt kept in position by a spring shows that a numerical simulation of the dynamics of such

  1. Collapse of tall granular columns in fluid

    Kumar, Krishna; Soga, Kenichi; Delenne, Jean-Yves

    2017-06-01

    Avalanches, landslides, and debris flows are geophysical hazards, which involve rapid mass movement of granular solids, water, and air as a multi-phase system. In order to describe the mechanism of immersed granular flows, it is important to consider both the dynamics of the solid phase and the role of the ambient fluid. In the present study, the collapse of a granular column in fluid is studied using 2D LBM - DEM. The flow kinematics are compared with the dry and buoyant granular collapse to understand the influence of hydrodynamic forces and lubrication on the run-out. In the case of tall columns, the amount of material destabilised above the failure plane is larger than that of short columns. Therefore, the surface area of the mobilised mass that interacts with the surrounding fluid in tall columns is significantly higher than the short columns. This increase in the area of soil - fluid interaction results in an increase in the formation of turbulent vortices thereby altering the deposit morphology. It is observed that the vortices result in the formation of heaps that significantly affects the distribution of mass in the flow. In order to understand the behaviour of tall columns, the run-out behaviour of a dense granular column with an initial aspect ratio of 6 is studied. The collapse behaviour is analysed for different slope angles: 0°, 2.5°, 5° and 7.5°.

  2. Impact of granular drops

    Marston, J. O.

    2013-07-15

    We investigate the spreading and splashing of granular drops during impact with a solid target. The granular drops are formed from roughly spherical balls of sand mixed with water, which is used as a binder to hold the ball together during free-fall. We measure the instantaneous spread diameter for different impact speeds and find that the normalized spread diameter d/D grows as (tV/D)1/2. The speeds of the grains ejected during the “splash” are measured and they rarely exceed twice that of the impact speed.

  3. Impact of granular drops

    Marston, J. O.; Mansoor, Mohammad M.; Thoroddsen, Sigurdur T

    2013-01-01

    We investigate the spreading and splashing of granular drops during impact with a solid target. The granular drops are formed from roughly spherical balls of sand mixed with water, which is used as a binder to hold the ball together during free-fall. We measure the instantaneous spread diameter for different impact speeds and find that the normalized spread diameter d/D grows as (tV/D)1/2. The speeds of the grains ejected during the “splash” are measured and they rarely exceed twice that of the impact speed.

  4. Carbothermic reduction of pyrolusite for obtaining carbon bearing ferromanganese and slags, adequated to the development of welding materials

    Cruz-Crespo, A.; Garcia-Sanchez, L. L.; Quintana-Puchol, R.; Perdomo Gonzalez, L.; Gomez-Perez, C. R.; Jimenez-Vielsa, G. E.; Cores-Sanchez, A.

    2004-01-01

    The high carbon ferromanganese obtained by means of carbothermic reduction in an electric arc furnace of direct current is proposed. the ideal composition of slag oxides to achieve a flux to be used in the submerged arc welding (SAW) is established. Calculation for charge components (pyrolusite, coke, steel wool, lime, rutile and fluorite) for no fluxes technology for FeMn is carried out taking into account the welding fluxes characteristics of the SiO 2 -MnO-CaO system. Change materials reduction experiments to obtain FeMn and slag are used to develop a SAW flux. (Author) 21 refs

  5. Development of a technology for obtaining flotation reagent oxane-3 for carbon mineral raw materials of Kazakhstan

    Sergey Kalugin

    2014-12-01

    Full Text Available The paper represents the results of development of a technology for obtaining oxane-3 and its application for enrichment of carbon mineral raw materials. Studies on enrichment of a shungite rock showed that the increase of a pulp temperature to 30°C significantly improves the characteristics and rate of the flotation process. Measured indicators of a shungite rock enrichment using Flotol B were lower in comparison with an enrichment by oxane-3. For schungite mineral, it was established that the obtained heterocyclic compound can replace existing industrial flotation reagents in enrichment processes.

  6. Granular Silo collapse: an experimental study

    Clement, Eric; Gutierriez, Gustavo; Boltenhagen, Philippe; Lanuza, Jose

    2008-03-01

    We present an experimental work that develop some basic insight into the pre-buckling behavior and the buckling transition toward plastic collapse of a granular silo. We study different patterns of deformation generated on thin paper cylindrical shells during granular discharge. We study the collapse threshold for different bed height, flow rates and grain sizes. We compare the patterns that appear during the discharge of spherical beads, with those obtained in the axially compressed cylindrical shells. When the height of the granular column is close to the collapse threshold, we describe a ladder like pattern that rises around the cylinder surface in a spiral path of diamond shaped localizations, and develops into a plastic collapsing fold that grows around the collapsing silo.

  7. Nitrate adsorption from aqueous solution using granular chitosan-Fe{sup 3+} complex

    Hu, Qili [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083 (China); Key Laboratory of Groundwater Cycle and Environment Evolution,China University of Geosciences (Beijing), Ministry of Education, Beijing, 100083 (China); Chen, Nan, E-mail: chennan@cugb.edu.cn [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083 (China); Key Laboratory of Groundwater Cycle and Environment Evolution, China University of Geosciences (Beijing), Ministry of Education, Beijing, 100083 (China); Feng, Chuanping [School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083 (China); Key Laboratory of Groundwater Cycle and Environment Evolution, China University of Geosciences (Beijing), Ministry of Education, Beijing, 100083 (China); Hu, WeiWu [The Journal Center, China University of Geosciences (Beijing), Beijing, 100083 (China)

    2015-08-30

    Highlights: • Granular chitosan-Fe{sup 3+} complex had high performance for nitrate adsorption. • Granular chitosan-Fe{sup 3+} complex had shorter equilibrium time (1.5 h). • Nitrate adsorption was ascribed to ion exchange and electrostatic attraction. • Granular chitosan-Fe{sup 3+} complex could be regenerated using NaCl solution. - Abstract: In the present study, In order to efficiently remove nitrate, granular chitosan-Fe{sup 3+} complex with high chemical stability and good environmental adaptation was synthesized through precipitation method and characterized using SEM, XRD, BET and FTIR. The nitrate adsorption performance was evaluated by batch experiments. The results indicated that granular chitosan-Fe{sup 3+} complex was an amorphous and mesoporous material. The BET specific surface area and average pore size were 8.98 m{sup 2} g{sup −1} and 56.94 Å, respectively. The point of zero charge was obtained at pH 5. The maximum adsorption capacity reached 8.35 mg NO{sub 3}{sup −}-N g{sup −1} based on Langmuir–Freundlich model. Moreover, no significant change in the nitrate removal efficiency was observed in the pH range of 3.0–10.0. The adverse influence of sulphate on nitrate removal was the most significant, followed by bicarbonate and fluoride, whereas chloride had slightly adverse effect. Adsorption process followed the pseudo-second-order kinetic model, and the experimental equilibrium data were fitted well with the Langmuir–Freundlich and D–R isotherm models. Thermodynamic parameters revealed that nitrate adsorption was a spontaneous and exothermic process. Granular chitosan-Fe{sup 3+} complex could be effectively regenerated by NaCl solution.

  8. Wave propagation of spectral energy content in a granular chain

    Shrivastava, Rohit Kumar; Luding, Stefan

    2017-01-01

    A mechanical wave is propagation of vibration with transfer of energy and momentum. Understanding the spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through inhomogeneous materials like

  9. Mechanical Behavior of Granular/Particulate Media Reinforced with Fibers

    Michalowski, Radoslw

    1999-01-01

    ... out. This investigation was built on the results of a previous study. Fiber-reinforced granular material was considered as a composite, and a mathematical homogenization scheme was used to arrive at its macroscopic properties...

  10. Quantified Differentiation of Surface Topography for Nano-materials As-Obtained from Atomic Force Microscopy Images

    Gupta, Mousumi; Chatterjee, Somenath

    2018-04-01

    Surface texture is an important issue to realize the nature (crest and trough) of surfaces. Atomic force microscopy (AFM) image is a key analysis for surface topography. However, in nano-scale, the nature (i.e., deflection or crack) as well as quantification (i.e., height or depth) of deposited layers is essential information for material scientist. In this paper, a gradient-based K-means algorithm is used to differentiate the layered surfaces depending on their color contrast of as-obtained from AFM images. A transformation using wavelet decomposition is initiated to extract the information about deflection or crack on the material surfaces from the same images. Z-axis depth analysis from wavelet coefficients provides information about the crack present in the material. Using the above method corresponding surface information for the material is obtained. In addition, the Gaussian filter is applied to remove the unwanted lines, which occurred during AFM scanning. Few known samples are taken as input, and validity of the above approaches is shown.

  11. Granular Cell Tumor

    1). Her packed cell volume was 40%, she was system, gastro-intestinal tract, brain, heart, and negative to human immunodeficiency virus. 2 female reproductive . ... histocytes and neurons at various times. They granules. The granules are probably of lysosmal were consequently termed granular cell origin and contain ...

  12. Mechanics of a granular skin

    Karmakar, Somnath; Sane, Anit; Bhattacharya, S.; Ghosh, Shankar

    2017-04-01

    Magic sand, a hydrophobic toy granular material, is widely used in popular science instructions because of its nonintuitive mechanical properties. A detailed study of the failure of an underwater column of magic sand shows that these properties can be traced to a single phenomenon: the system self-generates a cohesive skin that encapsulates the material inside. The skin, consisting of pinned air-water-grain interfaces, shows multiscale mechanical properties: they range from contact-line dynamics in the intragrain roughness scale, to plastic flow at the grain scale, all the way to sample-scale mechanical responses. With decreasing rigidity of the skin, the failure mode transforms from brittle to ductile (both of which are collective in nature) to a complete disintegration at the single-grain scale.

  13. Traffic and Granular Flow’05

    Pöschel, Thorsten; Kühne, Reinhart; Schreckenberg, Michael; Wolf, Dietrich

    2007-01-01

    The conference series Tra?c and Granular Flow has been established in 1995 and has since then been held biannually. At that time, the investigation of granular materials and tra?c was still somewhat exotic and was just starting to become popular among physicists. Originally the idea behind this conference series was to facilitate the c- vergence of the two ?elds, inspired by the similarities of certain phenomena and the use of similar theoretical methods. However, in recent years it has become clear that probably the di?erences between the two systems are much more interesting than the similarities. Nevertheless, the importance of various interrelations among these ?elds is still growing. The workshop continues to o?er an opportunity to stimulate this interdisciplinary research. Over the years the spectrum of topics has become much broader and has included also problems related to topics ranging from social dynamics to - ology. The conference manages to bring together people with rather di?erent background, r...

  14. Nonlinear coherent structures in granular crystals

    Chong, C.; Porter, Mason A.; Kevrekidis, P. G.; Daraio, C.

    2017-10-01

    The study of granular crystals, which are nonlinear metamaterials that consist of closely packed arrays of particles that interact elastically, is a vibrant area of research that combines ideas from disciplines such as materials science, nonlinear dynamics, and condensed-matter physics. Granular crystals exploit geometrical nonlinearities in their constitutive microstructure to produce properties (such as tunability and energy localization) that are not conventional to engineering materials and linear devices. In this topical review, we focus on recent experimental, computational, and theoretical results on nonlinear coherent structures in granular crystals. Such structures—which include traveling solitary waves, dispersive shock waves, and discrete breathers—have fascinating dynamics, including a diversity of both transient features and robust, long-lived patterns that emerge from broad classes of initial data. In our review, we primarily discuss phenomena in one-dimensional crystals, as most research to date has focused on such scenarios, but we also present some extensions to two-dimensional settings. Throughout the review, we highlight open problems and discuss a variety of potential engineering applications that arise from the rich dynamic response of granular crystals.

  15. Controlling wave propagation through nonlinear engineered granular systems

    Leonard, Andrea

    We study the fundamental dynamic behavior of a special class of ordered granular systems in order to design new, structured materials with unique physical properties. The dynamic properties of granular systems are dictated by the nonlinear, Hertzian, potential in compression and zero tensile strength resulting from the discrete material structure. Engineering the underlying particle arrangement of granular systems allows for unique dynamic properties, not observed in natural, disordered granular media. While extensive studies on 1D granular crystals have suggested their usefulness for a variety of engineering applications, considerably less attention has been given to higher-dimensional systems. The extension of these studies in higher dimensions could enable the discovery of richer physical phenomena not possible in 1D, such as spatial redirection and anisotropic energy trapping. We present experiments, numerical simulation (based on a discrete particle model), and in some cases theoretical predictions for several engineered granular systems, studying the effects of particle arrangement on the highly nonlinear transient wave propagation to develop means for controlling the wave propagation pathways. The first component of this thesis studies the stress wave propagation resulting from a localized impulsive loading for three different 2D particle lattice structures: square, centered square, and hexagonal granular crystals. By varying the lattice structure, we observe a wide range of properties for the propagating stress waves: quasi-1D solitary wave propagation, fully 2D wave propagation with tunable wave front shapes, and 2D pulsed wave propagation. Additionally the effects of weak disorder, inevitably present in real granular systems, are investigated. The second half of this thesis studies the solitary wave propagation through 2D and 3D ordered networks of granular chains, reducing the effective density compared to granular crystals by selectively placing wave

  16. Nonlocal rheological properties of granular flows near a jamming limit.

    Aranson, Igor S; Tsimring, Lev S; Malloggi, Florent; Clément, Eric

    2008-09-01

    We study the rheology of sheared granular flows close to a jamming transition. We use the approach of partially fluidized theory (PFT) with a full set of equations extending the thin layer approximation derived previously for the description of the granular avalanches phenomenology. This theory provides a picture compatible with a local rheology at large shear rates [G. D. R. Midi, Eur. Phys. J. E 14, 341 (2004)] and it works in the vicinity of the jamming transition, where a description in terms of a simple local rheology comes short. We investigate two situations displaying important deviations from local rheology. The first one is based on a set of numerical simulations of sheared soft two-dimensional circular grains. The next case describes previous experimental results obtained on avalanches of sandy material flowing down an incline. Both cases display, close to jamming, significant deviations from the now standard Pouliquen's flow rule [O. Pouliquen, Phys. Fluids 11, 542 (1999); 11, 1956 (1999)]. This discrepancy is the hallmark of a strongly nonlocal rheology and in both cases, we relate the empirical results and the outcomes of PFT. The numerical simulations show a characteristic constitutive structure for the fluid part of the stress involving the confining pressure and the material stiffness that appear in the form of an additional dimensionless parameter. This constitutive relation is then used to describe the case of sandy flows. We show a quantitative agreement as far as the effective flow rules are concerned. A fundamental feature is identified in PFT as the existence of a jammed layer developing in the vicinity of the flow arrest that corroborates the experimental findings. Finally, we study the case of solitary erosive granular avalanches and relate the outcome with the PFT analysis.

  17. Analysis of synthetic profile of CZTS as photovoltaic material obtained with variations of titanium and TiN

    Muñoz, M.; Vera, E.; Gómez, J.; Pineda, Y.

    2017-12-01

    Semiconductor type Cu2ZnTiS4 (CZTiS) and Cu2ZnSnS4 (CZTS),were synthetized starting from a hydrothermal route from precursor powders such as copper, zinc, tin, titanium isopropoxide and tiocarbammide metal nitrates dissolved in deionized water in concentrations of 1molL-1. Dosed and placed in a steel autoclave equipped with a Teflon jacket under magnetic stirring (150rpm) and at a temperature of 300°C for 24 hours in order to promote the formation of the respective ceramic phases. Segregates have been repeatedly washed with ethanol at all times until obtaining crystalline-looking solids. Subsequently, in order to promote the production of pure crystalline phases, the materials were subjected to a second reaction stage in a tubular furnace at 400°C in flow (50mLmin-1) for the purpose of Reduce the concentration of secondary phases of sulphides. The characterization of the CZTiS and CZTS materials was performed by X-ray Diffraction (XRD) and Raman spectroscopy where the presence of Kesterite type crystalline structures was confirmed in the two materials revealing that the effect of titanium with a higher ionic radius than tin produces a distortion in the cell of the CZTiS material compared to the report for the CZTS system. The results of Scanning Electron Microscopy (SEM), confirm the regular aggregates obtained with composition consistent with the proposal theoretically and validated by Energy-Dispersion X-ray Spectroscopy (EDX) techniques and comparison between secondary emission spectra and Retro-dispersed.

  18. Transport measurements in superconductors: critical current of granular high TC ceramic superconductor samples; Medidas de transporte em supercondutores: corrente critica de supercondutores granulares de alta temperatura critica

    Passos, W.A.C., E-mail: wagner.passos@univasf.edu.br [Universidade Federal do Vale do Sao Francisco (IPCM/UNIVASF), Juazeiro do Norte, BA (Brazil). Instituto de Pesquisas em Ciencia dos Materiais; Silva, E.B. [Companhia Energetica do Sao Francisco (CHESF), Recife, PE (Brazil)

    2016-07-01

    This work presents a method to obtain critical current of granular superconductors. We have carried out transport measurements (ρxT curves and VxI curves) in a YBa{sub 2}Cu{sub 3}O{sub 7-δ} sample to determine critical current density of it. Some specimens reveal a 'semiconductor-like' behavior (electrical resistivity decreases with increasing temperatures above critical temperature T{sub c} of material) competing with superconductor behavior. Due to high granular fraction of the sample, these competition is clearly noted in ρxT curves. Measurements carried out from 0 to 8500 Oe of applied field show the same behavior, and the critical current density of the samples is shown. (author)

  19. Role of hydraulic retention time and granular medium in microbial removal in tertiary treatment reed beds.

    García, Joan; Vivar, Joan; Aromir, Maria; Mujeriego, Rafael

    2003-06-01

    The main objective of this paper is to evaluate the role of hydraulic retention time (HRT) and granular medium in faecal coliform (FC) and somatic coliphage (SC) removal in tertiary reed beds. Experiments were carried out in a pilot plant with four parallel reed beds (horizontal subsurface flow constructed wetlands), each one containing a different type of granular medium. This pilot plant is located in a wastewater treatment plant in Montcada i Reixac, near Barcelona, in northeastern Spain. The microbial inactivation ratios obtained in the different beds are compared as a function of three selected HRTs. Secondary effluent from the wastewater treatment plant was used as the influent of the pilot system. The microbial inactivation ratio ranged between 0.1 and 2.7 log-units for FC and from 0.5 to 1.7 log-units for SC in beds with coarser granular material (5-25mm), while it ranged between 0.7 and 3.4 log-units for FC and from 0.9 to 2.6 log-units for SC in the bed with finer material (2-13mm). HRT and granular medium are both key factors in microbial removal in the tertiary reed beds. The microbial inactivation ratio rises as the HRT increases until it reaches a saturation value (in general at an HRT of 3 days). The value of the microbial inactivation ratio at the saturation level depends on the granular medium contained in the bed. The specific surface area necessary to reach 2-3 log-units of FC and SC is approximately 3m(2)/person-equivalent.

  20. Dynamics of electrostatically driven granular media: Effects of humidity

    Howell, D. W.; Aronson, Igor S.; Crabtree, G. W.

    2001-01-01

    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

  1. Fluorescent silica hybrid materials containing benzimidazole dyes obtained by sol-gel method and high pressure processing

    Hoffmann, Helena Sofia; Stefani, Valter; Benvenutti, Edilson Valmir; Costa, Tania Maria Haas; Gallas, Marcia Russman

    2011-01-01

    Research highlights: → Sol-gel technique was used to obtain silica based hybrid materials containing benzimidazole dyes. → The sol-gel catalysts, HF and NaF, produce xerogels with different optical and textural characteristics. → High pressure technique (6.0 GPa) was used to produce fluorescent and transparent silica compacts with the dyes entrapped in closed pores, maintaining their optical properties. → The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. - Abstract: New silica hybrid materials were obtained by incorporation of two benzimidazole dyes in the silica network by sol-gel technique, using tetraethylorthosilicate (TEOS) as inorganic precursor. Several syntheses were performed with two catalysts (HF and NaF) producing powders and monoliths with different characteristics. The dye 2-(2'-hydroxy-5'-aminophenyl)benzimidazole was dispersed and physically adsorbed in the matrix, and the dye 2'(5'-N-(3-triethoxysilyl)propylurea-2'-hydroxyphenyl)benzimidazole was silylated, becoming chemically bonded to the silica network. High pressure technique was used to produce fluorescent and transparent silica compacts with the silylated and incorporated dye, at 6.0 GPa and room temperature. The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. The influence of the syntheses conditions was investigated by textural analysis using nitrogen adsorption isotherms.

  2. Microservices: Granularity vs. Performance

    Shadija, Dharmendra; Rezai, Mo; Hill, Richard

    2017-01-01

    Microservice Architectures (MA) have the potential to increase the agility of software development. In an era where businesses require software applications to evolve to support emerging software requirements, particularly for Internet of Things (IoT) applications, we examine the issue of microservice granularity and explore its effect upon application latency. Two approaches to microservice deployment are simulated; the first with microservices in a single container, and the second with micr...

  3. Analysis of the possibility for obtaining oil from the spend coffee grounds as potential raw material for biodiesel production

    Iličković Zoran

    2012-01-01

    Full Text Available The aim of this paper was to investigate the possibility of obtaining oil from spent coffee grounds, which are left behind after the coffee is prepared, as the potential feedstock for biodiesel production. The effect of process parameters, such as are the type of solvent, the ratio of spent coffee grounds/solvent and the extraction time on oil yielded from coffee grounds was examined. The oil was obtained by maceration and extraction in the Soxhlet apparatus. The obtain results show that the spent coffee grounds could be used as an alternative raw material for biodiesel production, because it contains a significant amount of oil that can be extracted. The oil yield depends on the extraction (maceration process parameters. The maximum oil yield obtained by the Soxhlet extraction with the n-hexane for the period of 5 h was 11.85% (the weight percentage of oil on dry mater, whereas with petroleum ether the oil yield was slightly lower and amounted to 10.44%. The yield of the oil extracted by maceration increases with the decrease of spent coffee grounds/solvent ratio from 1/3 to 1/7 g/cm3, and other parameters being constant. The oil yield increases with the duration of the maceration. Greater oil yield, ranging from 3 to 8.5%, can be obtained with n-hexane compared to the extraction with petroleum ether. Furthermore, n-hexane is less volatile and flammable, compared to petroleum ether, so it is more convenient to use.

  4. Granular metamaterials for vibration mitigation

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

    2013-09-01

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

  5. Vortex jamming in superconductors and granular rheology

    Yoshino, Hajime; Nogawa, Tomoaki; Kim, Bongsoo

    2009-01-01

    We demonstrate that a highly frustrated anisotropic Josephson junction array (JJA) on a square lattice exhibits a zero-temperature jamming transition, which shares much in common with those in granular systems. Anisotropy of the Josephson couplings along the horizontal and vertical directions plays roles similar to normal load or density in granular systems. We studied numerically static and dynamic response of the system against shear, i.e. injection of external electric current at zero temperature. Current-voltage curves at various strength of the anisotropy exhibit universal scaling features around the jamming point much as do the flow curves in granular rheology, shear-stress versus shear-rate. It turns out that at zero temperature the jamming transition occurs right at the isotropic coupling and anisotropic JJA behaves as exotic fragile vortex matter: it behaves as a superconductor (vortex glass) in one direction, whereas it is a normal conductor (vortex liquid) in the other direction even at zero temperature. Furthermore, we find a variant of the theoretical model for the anisotropic JJA quantitatively reproduces universal master flow-curves of the granular systems. Our results suggest an unexpected common paradigm stretching over seemingly unrelated fields-the rheology of soft materials and superconductivity.

  6. A particle-based method for granular flow simulation

    Chang, Yuanzhang; Bao, Kai; Zhu, Jian; Wu, Enhua

    2012-01-01

    We present a new particle-based method for granular flow simulation. In the method, a new elastic stress term, which is derived from a modified form of the Hooke's law, is included in the momentum governing equation to handle the friction of granular materials. Viscosity force is also added to simulate the dynamic friction for the purpose of smoothing the velocity field and further maintaining the simulation stability. Benefiting from the Lagrangian nature of the SPH method, large flow deformation can be well handled easily and naturally. In addition, a signed distance field is also employed to enforce the solid boundary condition. The experimental results show that the proposed method is effective and efficient for handling the flow of granular materials, and different kinds of granular behaviors can be well simulated by adjusting just one parameter. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

  7. A particle-based method for granular flow simulation

    Chang, Yuanzhang

    2012-03-16

    We present a new particle-based method for granular flow simulation. In the method, a new elastic stress term, which is derived from a modified form of the Hooke\\'s law, is included in the momentum governing equation to handle the friction of granular materials. Viscosity force is also added to simulate the dynamic friction for the purpose of smoothing the velocity field and further maintaining the simulation stability. Benefiting from the Lagrangian nature of the SPH method, large flow deformation can be well handled easily and naturally. In addition, a signed distance field is also employed to enforce the solid boundary condition. The experimental results show that the proposed method is effective and efficient for handling the flow of granular materials, and different kinds of granular behaviors can be well simulated by adjusting just one parameter. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

  8. Granular flow through an aperture: influence of the packing fraction

    Alejandra Aguirre , Maria; De Schant , Rosario; Géminard , Jean-Christophe

    2014-01-01

    For the last 50 years, the flow of a granular material through an aperture has been intensely studied in gravity-driven vertical systems (e.g. silos and hoppers). Nevertheless, in many industrial applications, grains are horizontally transported at constant velocity, lying on conveyor belts or floating on the surface of flowing liquids. Unlike fluid flows, that are controlled by the pressure, granular flow is not sensitive to the local pressure but rather to the local velocity of the grains a...

  9. Controlling mixing and segregation in time periodic granular flows

    Bhattacharya, Tathagata

    Segregation is a major problem for many solids processing industries. Differences in particle size or density can lead to flow-induced segregation. In the present work, we employ the discrete element method (DEM)---one type of particle dynamics (PD) technique---to investigate the mixing and segregation of granular material in some prototypical solid handling devices, such as a rotating drum and chute. In DEM, one calculates the trajectories of individual particles based on Newton's laws of motion by employing suitable contact force models and a collision detection algorithm. Recently, it has been suggested that segregation in particle mixers can be thwarted if the particle flow is inverted at a rate above a critical forcing frequency. Further, it has been hypothesized that, for a rotating drum, the effectiveness of this technique can be linked to the probability distribution of the number of times a particle passes through the flowing layer per rotation of the drum. In the first portion of this work, various configurations of solid mixers are numerically and experimentally studied to investigate the conditions for improved mixing in light of these hypotheses. Besides rotating drums, many studies of granular flow have focused on gravity driven chute flows owing to its practical importance in granular transportation and to the fact that the relative simplicity of this type of flow allows for development and testing of new theories. In this part of the work, we observe the deposition behavior of both mono-sized and polydisperse dry granular materials in an inclined chute flow. The effects of different parameters such as chute angle, particle size, falling height and charge amount on the mass fraction distribution of granular materials after deposition are investigated. The simulation results obtained using DEM are compared with the experimental findings and a high degree of agreement is observed. Tuning of the underlying contact force parameters allows the achievement

  10. Functionalization of nanoparticle titanium dioxide with different bifunctional organic molecules and trimers of transition compounds for obtaining new materials

    Rivera Martinez, Maria Cinthya

    2012-01-01

    Functionalization of titanium dioxide in nanoporous anatase phase is investigated for obtaining new nanomaterials. Functionalizations were performed using two heating methods: the conventional of refluxing heating method and microwave irradiation with bifunctional organic molecules is used to study how to anchor molecules and the change in the wettability of the material. Besides, reactions with organic molecules were performed as the derived from nanoproxene. The growth layer by layer is performed using the bifunctional molecules previous for the immobilization of cobalt trimers. Functionalized molecules were characterized by infrared spectroscopy, X-ray diffraction, contact angle, scanning electron microscopy, x-ray elemental analysis, plasma atomic emission spectroscopy coupled inductively, x-ray photoelectron spectroscopy and thermogravimetric analysis. This type of functionalizations on nanoporous titanium dioxide could potentially improve optical sensitivity and activity of this nanomaterial in the visible region. (author) [es

  11. Type-2 fuzzy granular models

    Sanchez, Mauricio A; Castro, Juan R

    2017-01-01

    In this book, a series of granular algorithms are proposed. A nature inspired granular algorithm based on Newtonian gravitational forces is proposed. A series of methods for the formation of higher-type information granules represented by Interval Type-2 Fuzzy Sets are also shown, via multiple approaches, such as Coefficient of Variation, principle of justifiable granularity, uncertainty-based information concept, and numerical evidence based. And a fuzzy granular application comparison is given as to demonstrate the differences in how uncertainty affects the performance of fuzzy information granules.

  12. Mathematical models of granular matter

    Mariano, Paolo; Giovine, Pasquale

    2008-01-01

    Granular matter displays a variety of peculiarities that distinguish it from other appearances studied in condensed matter physics and renders its overall mathematical modelling somewhat arduous. Prominent directions in the modelling granular flows are analyzed from various points of view. Foundational issues, numerical schemes and experimental results are discussed. The volume furnishes a rather complete overview of the current research trends in the mechanics of granular matter. Various chapters introduce the reader to different points of view and related techniques. New models describing granular bodies as complex bodies are presented. Results on the analysis of the inelastic Boltzmann equations are collected in different chapters. Gallavotti-Cohen symmetry is also discussed.

  13. Characterization and thermal behavior of PrMO{sub 3} (M = Co or Ni) ceramic materials obtained from gelatin

    Aquino, F.M., E-mail: flavyma@hotmail.com [Federal University of Rio Grande of Norte, Laboratory of Catalysis and Refining – NUPRAR, Av. Senador Salgado Filho, 3000, CEP 59078-970, Natal-RN (Brazil); Melo, D.M.A. [Federal University of Rio Grande of Norte, Laboratory of Catalysis and Refining – NUPRAR, Av. Senador Salgado Filho, 3000, CEP 59078-970, Natal-RN (Brazil); Pimentel, P.M. [Universidade Federal Rural do Semi-Árido, Campus Angicos, CEP 59515-000, Angicos-RN (Brazil); Braga, R.M.; Melo, M.A.F.; Martinelli, A.E.; Costa, A.F. [Federal University of Rio Grande of Norte, Laboratory of Catalysis and Refining – NUPRAR, Av. Senador Salgado Filho, 3000, CEP 59078-970, Natal-RN (Brazil)

    2012-09-15

    Graphical abstract: The micrograph in figure shows sample calcined at temperature 900 °C. The sample exhibits morphology with considerable porosity and the formation of agglomerated nanometric particles. Gelatin provides the system with a large amount of organic matter, which is then removed during calcinations, favoring the appearance of pores in the material. Highlights: ► Oxides with PrNiO{sub 3} and PrCoO{sub 3} were prepared by new method synthesis. ► The gelatin, through its carboxylate groups and amine, is an efficient director. ► The obtained materials have magnetic properties and application in catalysis. ► The decomposition kinetic study of bonding groups of gelatin with metallic ions that takes part in the synthesis of PrMO{sub 3}. -- Abstract: Metal oxides with perovskite-type structure have attracted considerable interest in recent years due to their magnetic and electrical properties, as well as their catalytic activity. In this study, oxides with PrNiO{sub 3} and PrCoO{sub 3} composition were prepared by using gelatin powder as a precursor agent for its use as a catalyst. The powders obtained were calcined at 700 °C and 900 °C and characterized using the X-ray diffraction, thermal analysis (thermogravimetry and differential thermal analysis), infrared spectroscopy, temperature programed reduction and scanning electron microscopy techniques. Thermogravimetric data using the non-isothermal kinetic models of Flynn and Wall and “Model-free Kinetics” were used to determine the activation energy to study the decomposition kinetics of the ligand groups with system's metallic ions that takes part in the synthesis of PrMO{sub 3} (M = Ni or Co).

  14. Using a Time Granularity Table for Gradual Granular Data Aggregation

    Iftikhar, Nadeem; Pedersen, Torben Bach

    2010-01-01

    solution for data reduction based on gradual granular data aggregation. With the gradual granular data aggregation mechanism, older data can be made coarse-grained while keeping the newest data fine-grained. For instance, when data is 3 months old aggregate to 1 minute level from 1 second level, when data...... and improve query performance, especially on resource-constrained systems with limited storage and query processing capabilities. A number of data reduction solutions have been developed, however an effective solution particularly based on gradual data reduction is missing. This paper presents an effective...... is 6 months old aggregate to 2 minutes level from 1 minute level and so on. The proposed solution introduces a time granularity based data structure, namely a relational time granularity table that enables long term storage of old data by maintaining it at different levels of granularity and effective...

  15. Sinking a Granular Raft

    Protière, Suzie; Josserand, Christophe; Aristoff, Jeffrey M.; Stone, Howard A.; Abkarian, Manouk

    2017-03-01

    We report experiments that yield new insights on the behavior of granular rafts at an oil-water interface. We show that these particle aggregates can float or sink depending on dimensionless parameters taking into account the particle densities and size and the densities of the two fluids. We characterize the raft shape and stability and propose a model to predict its shape and maximum length to remain afloat. Finally we find that wrinkles and folds appear along the raft due to compression by its own weight, which can trigger destabilization. These features are characteristics of an elastic instability, which we discuss, including the limitations of our model.

  16. Transport measurements in superconductors: critical current of granular high TC ceramic superconductor samples

    Passos, W.A.C.

    2016-01-01

    This work presents a method to obtain critical current of granular superconductors. We have carried out transport measurements (ρxT curves and VxI curves) in a YBa_2Cu_3O_7_-_δ sample to determine critical current density of it. Some specimens reveal a 'semiconductor-like' behavior (electrical resistivity decreases with increasing temperatures above critical temperature T_c of material) competing with superconductor behavior. Due to high granular fraction of the sample, these competition is clearly noted in ρxT curves. Measurements carried out from 0 to 8500 Oe of applied field show the same behavior, and the critical current density of the samples is shown. (author)

  17. Granular rheology: measuring boundary forces with laser-cut leaf springs

    Tang, Zhu; Brzinski, Theodore A.; Daniels, Karen E.

    2017-06-01

    In granular physics experiments, it is a persistent challenge to obtain the boundary stress measurements necessary to provide full a rheological characterization of the dynamics. Here, we describe a new technique by which the outer boundary of a 2D Couette cell both confines the granular material and provides spatially- and temporally- resolved stress measurements. This key advance is enabled by desktop laser-cutting technology, which allows us to design and cut linearly-deformable walls with a specified spring constant. By tracking the position of each segment of the wall, we measure both the normal and tangential stress throughout the experiment. This permits us to calculate the amount of shear stress provided by basal friction, and thereby determine accurate values of μ(I).

  18. Granular flow considerations in the design of a cascade solid breeder reaction chamber

    Walton, O.R.

    1983-10-01

    Both horizontally and vertically oriented rotating chambers with granular material held on the inner surface by centrifugal action are examined. Modifications to the condition for controlled quasi-static flow on an incline plane, phi/sub w/ 0 +- 10 0 for ceramic particles and metal surfaces. For vertical orientations the maximum half-angle of the top cone is slightly less than the wall friction angle phi/sub w/ while the lower portion can have a half angle as large as (90 0 - phi/sub w). Percolation of fines through shearing granular solids is briefly discussed and recommended experimental and calculational studies to obtain a better understanding of this behavior are described

  19. Granular shear flows of flexible rod-like particles

    Guo, Y.; Curtis, J.; Wassgren, C.; Ketterhagen, W.; Hancock, B.

    2013-06-01

    Flexible particles are widely encountered in nature, e.g., stalks of plants, fiberglass particles, and ceramic nanofibers. Early studies indicated that the deformability of particles has a significant impact on the properties of granular materials and fiber suspensions. In this study, shear flows of flexible particles are simulated using the Discrete Element Method (DEM) to explore the effect of particle flexibility on the flow behavior and constitutive laws. A flexible particle is formed by connecting a number of constituent spheres in a straight line using elastic bonds. The forces/moments due to the normal, tangential, bending, and torsional deformation of a bond resist the relative movement between two bonded constituent spheres. The bond stiffness determines how difficult it is to make a particle deform, and the bond damping accounts for the energy dissipation in the particle vibration process. The simulation results show that elastically bonded particles have smaller coefficients of restitution compared to rigidly connected particles, due to the fact that kinetic energy is partially converted to potential energy in a contact between flexible particles. The coefficient of restitution decreases as the bond stiffness decreases and the bond damping coefficient increases. As a result, smaller stresses are obtained for granular flows of the flexible particles with smaller bond stiffness and larger bond damping coefficient.

  20. Oblique shock waves in granular flows over bluff bodies

    Gopan Nandu

    2017-01-01

    Full Text Available Granular flows around an object have been the focus of numerous analytical, experimental and simulation studies. The structure and nature of the oblique shock wave developed when a quasi-two dimensional flow of spherical granular particles streams past an immersed, fixed cylindrical obstacle forms the focus of this study. The binary granular mixture, consisting of particles of the same diameter but different material properties, is investigated by using a modified LIGGGHTS package as the simulation engine. Variations in the solid fraction and granular temperature within the resulting flow are studied. The Mach number is calculated and is used to distinguish between the subsonic and the supersonic regions of the bow shock.

  1. Microfluidics of soft granular gels

    Nixon, Ryan; Bhattacharjee, Tapomoy; Sawyer, W. Gregory; Angelini, Thomas E.

    Microfluidic methods for encapsulating cells and particles typically involve drop making with two immiscible fluids. The main materials constraint in this approach is surface tension, creating inherent instability between the two fluids. We can eliminate this instability by using miscible inner and outer phases. This is achieved by using granular micro gels which are chemically miscible but physically do not mix. These microgels are yield stress materials, so they flow as solid plugs far from shear gradients, and fluidize where gradients are generated - near an injection nozzle for example. We have found that tuning the yield stress of the material by varying polymer concentration, device performance can be controlled. The solid like behavior of the gel allows us to produces infinitely stable jets that maintain their integrity and configuration over long distances and times. These properties can be combined and manipulated to produce discrete particulate bunches of an inner phase, flowing inside of an outer phase, well enough even to print a Morse code message suspended within flow chambers about a millimeter in diameter moving at millimeters a second.

  2. Nonlocal approach to the analysis of the stress distribution in granular systems. I. Theoretical framework

    Kenkre, V. M.; Scott, J. E.; Pease, E. A.; Hurd, A. J.

    1998-05-01

    A theoretical framework for the analysis of the stress distribution in granular materials is presented. It makes use of a transformation of the vertical spatial coordinate into a formal time variable and the subsequent study of a generally non-Markoffian, i.e., memory-possessing (nonlocal) propagation equation. Previous treatments are obtained as particular cases corresponding to, respectively, wavelike and diffusive limits of the general evolution. Calculations are presented for stress propagation in bounded and unbounded media. They can be used to obtain desired features such as a prescribed stress distribution within the compact.

  3. Aerofractures in Confined Granular Media

    Eriksen, Fredrik K.; Turkaya, Semih; Toussaint, Renaud; Måløy, Knut J.; Flekkøy, Eirik G.

    2015-04-01

    processing techniques, we segment out and study the aerofractures over time looking at growth dynamics, fractal dimension and characteristics such as average finger thickness as function of depth into the solid. Also, by performing image correlation on two subsequent frames we estimate displacement fields and investigate the surrounding stress and strain fields in the solid around the fractures. Several experiments are performed with various overpressures and packing densities, and we compare the results. In a directly related project, acoustic emissions are recorded on a cell plate during experiments, and one of our goals is to correlate acoustic events and observations. We will also compare the dependence of the patterns on the saturation of the initial deformable porous material, by comparing experiments performed by air injection in air saturated granular media, to some in liquid saturated granular media. References: MJ Niebling, R Toussaint, EG Flekkøy, KJ Måløy, 2012, Dynamic aerofracture of dense granular packings, 2012, Physical Review E 86 (6), 061315 M Niebling, R Toussaint, EG Flekkøy, KJ Måløy, 2012, Numerical studies of aerofractures in porous media, Revista Cubana de Fisica 29 (1E), pp. 1E66-1E70

  4. Spreading of a granular droplet

    Clement, Eric; Sanchez, Ivan; Raynaud, Franck; Lanuza, Jose; Andreotti, Bruno; Aranson, Igor

    2008-03-01

    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.

  5. Mesostructured Au/C materials obtained by replication of functionalized SBA-15 silica containing highly dispersed gold nanoparticles

    Kerdi, Fatmé

    2011-04-01

    The preparation and characterization of highly dispersed gold nanoparticles in ordered mesoporous carbons CMK-3 are reported. These carbons were obtained using gold-containing functionalized SBA-15 silicas as hard templates. Two series of Au/SiO2 templates were prepared, depending on the nature of the functionalization molecule. While ammonium-functionalized silicas gave gold particles with a size determined by the pores of the silica support, the use of mercaptopropyltrimethoxysilane as grafting molecule afforded the possibility to control the particle size inside the mesopores. Both series gave highly ordered mesoporous carbons with gold particles incorporated in the carbon nanorods. However, the gold particle size in mesoporous carbons was the same for both series and apparently did not depend on the nature of the silica template. Both Au/SiO2 templates and their corresponding Au/CMK-3 materials have been characterized by X-ray diffraction, nitrogen adsorption/desorption, chemical analysis, solid-state nuclear magnetic resonance and transmission electron microscopy. They were also used as catalysts in the aerobic oxidation of cyclohexene and trans-stilbene in the liquid phase. © 2010 Elsevier Inc. All rights reserved.

  6. Large granular lymphocyte leukemia

    Terra, Bruno; Maia, Amanda M.

    2010-01-01

    O presente estudo tem como objetivo o estabelecimento de fundamentação teórica atualizada baseada em revisão bibliográfica sobre a leucemia de grandes linfócitos granulares (LGLG), doença onco-hematológica, que, devido à sua relativa raridade, é pouco conhecida e subdiagnosticada. A LGLG é caracterizada pela proliferação clonal de linfócitos T ou NK na medula óssea e/ou no sangue periférico. Dentre as manifestações clínico-laboratoriais, podem ocorrer citopenias (anemia e/ou neutropenia e/ou ...

  7. Can one ``Hear'' the aggregation state of a granular system?

    Kruelle, Christof A.; Sánchez, Almudena García

    2013-06-01

    If an ensemble of macroscopic particles is mechanically agitated the constant energy input is dissipated into the system by multiple inelastic collisions. As a result, the granular material can exhibit, depending on the magnitude of agitation, several physical states - like a gaseous phase for high energy input or a condensed state for low agitation. Here we introduce a new method for quantifying the acoustical response of the granular system. Our experimental system consists of a monodisperse packing of glass beads with a free upper surface, which is confined inside a cylindrical container. An electro-mechanical shaker exerts a sinusoidal vertical vibration at normalized accelerations well above the fluidization threshold for a monolayer of particles. By increasing the number of beads the granular gas suddenly collapses if a critical threshold is exceeded. The transition can be detected easily with a microphone connected to the soundcard of a PC. From the recorded audio track a FFT is calculated in real-time. Depending on either the number of particles at a fixed acceleration or the amount of energy input for a given number of particles, the resulting rattling noise exhibits a power spectrum with either the dominating (shaker) frequency plus higher harmonics for a granular crystal or a high-frequency broad-band noise for a granular gas, respectively. Our new method demonstrates that it is possible to quantify analytically the subjective audio impressions of a careful listener and thus to distinguish easily between different aggregation states of an excited granular system.

  8. Elastic Nonlinear Response in Granular Media Under Resonance Conditions

    Jia, X.; Johnson, P. A.

    2004-12-01

    We are studying the elastic linear and nonlinear behavior of granular media using dynamic wave methods. In the work presented here, our goal is to quantify the elastic nonlinear response by applying wave resonance. Resonance studies are desirable because they provide the means to easily study amplitude dependencies of elastic nonlinear behavior and thus to characterize the physical nature of the elastic nonlinearity. This work has implications for a variety of topics, in particular, the in situ nonlinear response of surface sediments. For this work we constructed an experimental cell in which high sensitivity dynamic resonance studies were conducted using granular media under controlled effective pressure. We limit our studies here to bulk modes but have the capability to employ shear waves as well. The granular media are composed of glass beads held under pressure by a piston, while applying resonance waves from transducers as both the excitation and the material probe. The container is closed with two fitted pistons and a normal load is applied to the granular sample across the top piston. Force and displacement are measured directly. Resonant frequency sweeps with frequencies corresponding to the fundamental bulk mode are applied to the longitudinal source transducer. The pore pressure in the system is 1 atm. The glass beads used in our experiments are of diameter 0.5 mm, randomly deposited in a duralumin cylinder of diameter 30 mm and height of 15 mm. This corresponds to a granular skeleton acoustic wave velocity of v ª 750m/s under 50 N of force [0.07 Mpa]. The loaded system gives fundamental mode resonances in the audio frequency band at half a wavelength where resonance frequency is effective-pressure dependent. The volume fraction of glass beads thus obtained is found to be 0.63 ± 0.01. Plane-wave generating and detecting transducers of diameter 30 mm are placed on axis at the top and bottom of the cylindrical container in direct contact with the glass

  9. Some exact velocity profiles for granular flow in converging hoppers

    Cox, Grant M.; Hill, James M.

    2005-01-01

    Gravity flow of granular materials through hoppers occurs in many industrial processes. For an ideal cohesionless granular material, which satisfies the Coulomb-Mohr yield condition, the number of known analytical solutions is limited. However, for the special case of the angle of internal friction δ equal to ninety degrees, there exist exact parametric solutions for the governing coupled ordinary differential equations for both two-dimensional wedges and three-dimensional cones, both of which involve two arbitrary constants of integration. These solutions are the only known analytical solutions of this generality. Here, we utilize the double-shearing theory of granular materials to determine the velocity field corresponding to these exact parametric solutions for the two problems of gravity flow through converging wedge and conical hoppers. An independent numerical solution for other angles of internal friction is shown to coincide with the analytical solution.

  10. Tsunamis generated by long and thin granular landslides in a large flume

    Miller, Garrett S.; Andy Take, W.; Mulligan, Ryan P.; McDougall, Scott

    2017-01-01

    In this experimental study, granular material is released down slope to investigate landslide-generated waves. Starting with a known volume and initial position of the landslide source, detailed data are obtained on the velocity and thickness of the granular flow, the shape and location of the submarine landslide deposit, the amplitude and shape of the near-field wave, the far-field wave evolution, and the wave runup elevation on a smooth impermeable slope. The experiments are performed on a 6.7 m long 30° slope on which gravity accelerates the landslides into a 2.1 m wide and 33.0 m long wave flume that terminates with a 27° runup ramp. For a fixed landslide volume of 0.34 m3, tests are conducted in a range of still water depths from 0.05 to 0.50 m. Observations from high-speed cameras and measurements from wave probes indicate that the granular landslide moves as a long and thin train of material, and that only a portion of the landslide (termed the "effective mass") is engaged in activating the leading wave. The wave behavior is highly dependent on the water depth relative to the size of the landslide. In deeper water, the near-field wave behaves as a stable solitary-like wave, while in shallower water, the wave behaves as a breaking dissipative bore. Overall, the physical model observations are in good agreement with the results of existing empirical equations when the effective mass is used to predict the maximum near-field wave amplitude, the far-field amplitude, and the runup of tsunamis generated by granular landslides.

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

    Hao, Tian

    2015-02-28

    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).

  12. Propulsion via flexible flapping in granular media

    Peng, Zhiwei; Ding, Yang; Pietrzyk, Kyle; Elfring, Gwynn; Pak, On Shun

    2017-11-01

    Biological locomotion in nature is often achieved by the interaction between a flexible body and its surrounding medium. The interaction of a flexible body with granular media is less understood compared with viscous fluids partially due to its complex rheological properties. In this work, we explore the effect of flexibility on granular propulsion by considering a simple mechanical model in which a rigid rod is connected to a torsional spring that is under a displacement actuation using a granular resistive force theory. Through a combined numerical and asymptotic investigation, we characterize the propulsive dynamics of such a flexible flapper in relation to the actuation amplitude and spring stiffness, and we compare these dynamics with those observed in a viscous fluid. In addition, we demonstrate that the maximum possible propulsive force can be obtained in the steady propulsion limit with a finite spring stiffness and large actuation amplitude. These results may apply to the development of synthetic locomotive systems that exploit flexibility to move through complex terrestrial media. Funding for Z.P. and Y.D. was partially provided by NSFC 394 Grant No. 11672029 and NSAF-NSFC Grant No. U1530401.

  13. Permeability of granular beds emplaced in vertical drill holes

    Griffiths, S.K.; Morrison, F.A. Jr.

    1979-01-01

    To determine the permeabilities of granular materials emplaced in vertical drill holes used for underground nuclear tests, an experiment at the USDOE Nevada Test Site (NTS) was conducted. As the hole is being filled, falling material increases pressure above and within the granular beds beneath. When the filling operation starts or stops, a transient pressure response occurs within the beds; measurements of this response in beds of various compositions were made. The permeabilities after emplacement were found by matching analytical predictions of the response to these data. This information is useful in assuring the containment of nuclear tests conducted in such drill holes

  14. Granular flows: fundamentals and applications

    Cleary, Paul W.

    DEM allows the prediction of complex industrial and geophysical particle flows. The importance of particle shape is demonstrated through a series of simple examples. Shape controls resistance to shear, the magnitude of collision stress, dilation and the angle of repose. We use a periodic flow of a bed of particles to demonstrate the different states of granular matter, the generation of dilute granular flow when granular temperature is high and the flow dependent nature of the granular thermodynamic boundary conditions. A series of industrial case studies examines how DEM can be used to understand and improve processes such as separation, mixing, grinding, excavation, hopper discharge, metering and conveyor interchange. Finally, an example of landslide motion over real topography is presented.

  15. Effect of Wetting and Contamination of Granular Beds During Sphere Impact

    Kouraytem, Nadia

    2013-01-01

    This thesis presents results from an experimental study of the impact of dense solid spheres onto granular beds. The overall aim is to further our understanding of the dynamical response of granular materials to impact. In order to do this, we

  16. Superconductivity in inhomogeneous granular metals

    McLean, W.L.

    1980-01-01

    A model of elongated metal ellipsoids imbedded in a granular metal is treated by an effective medium approach to explain the observed temperature dependence of the normal-state conductivity of superconducting granular aluminum. Josephson tunneling is thus still required to account for the superconductivity. The model predicts the same kind of contrasting behavior on opposite sides of the metal-insulator transition as is found in the recent scaling treatment of Anderson localization

  17. Effect of dynamic and static friction on an asymmetric granular piston.

    Talbot, Julian; Viot, Pascal

    2012-02-01

    We investigate the influence of dry friction on an asymmetric, granular piston of mass M, composed of two materials, undergoing inelastic collisions with bath particles of mass m. Numerical simulations of the Boltzmann-Lorentz equation reveal the existence of two scaling regimes depending on the friction strength. In the large friction limit, we introduce an exact model giving the asymptotic behavior of the Boltzmann-Lorentz equation. For small friction and for large mass ratio M/m, we derive a Fokker-Planck equation for which the exact solution is also obtained. Static friction attenuates the motor effect and results in a discontinuous velocity distribution. © 2012 American Physical Society

  18. An Evaluation of the Resilient Modulus and Permanent Deformation of Unbound Mixtures of Granular Materials and Rubber Particles from Scrap Tyres to be Used in Subballast Layers

    Signes, Carlos Hidalgo; Fernández, Pablo Martínez; Garzón-Roca, Julio; de la Torre, María Elvira Garrido; Franco, Ricardo Insa

    2016-01-01

    [EN] Over the last years rubber from scrap tyres has been reused in different civil works such as road embankments and railway platforms due to its resilient properties, low degradation and vibration attenuation. Unfortunately, this issue is still scarce. For instance, in Spain about 175.000 tonnes of scrap tyres were collected in 2014, of which only 0.6% were reused in civil works. Aiming to contribute to the reutilisation of large quantities of this waste material, this paper focuses on the...

  19. An Evaluation of the Resilient Modulus and Permanent Deformation of Unbound Mixtures of Granular Materials and Rubber Particles from Scrap Tyres to Be Used in Subballast Layers

    Hidalgo Sgnes, Carlos; Martínez Fernández, Pablo; Garzón Roca, Julio; Garrido De La Torre, Mª Elvira; Insa Franco, Ricardo

    2016-01-01

    [EN] Over the last years rubber from scrap tyres has been reused in different civil works such as road embankments and railway platforms due to its resilient properties, low degradation and vibration attenuation. Unfortunately, this issue is still scarce. For instance, in Spain about 175.000 tonnes of scrap tyres were collected in 2014, of which only 0.6% were reused in civil works. Aiming to contribute to the reutilisation of large quantities of this waste material, this paper focuses on the...

  20. Assessing continuum postulates in simulations of granular flow

    Rycroft, Chris; Kamrin, Ken; Bazant, Martin

    2008-08-26

    Continuum mechanics relies on the fundamental notion of a mesoscopic volume"element" in which properties averaged over discrete particles obey deterministic relationships. Recent work on granular materials suggests a continuum law may be inapplicable, revealing inhomogeneities at the particle level, such as force chains and slow cage breaking. Here, we analyze large-scale three-dimensional Discrete-Element Method (DEM) simulations of different granular flows and show that an approximate"granular element" defined at the scale of observed dynamical correlations (roughly three to five particle diameters) has a reasonable continuum interpretation. By viewing all the simulations as an ensemble of granular elements which deform and move with the flow, we can track material evolution at a local level. Our results confirm some of the hypotheses of classical plasticity theory while contradicting others and suggest a subtle physical picture of granular failure, combining liquid-like dependence on deformation rate and solid-like dependence on strain. Our computational methods and results can be used to guide the development of more realistic continuum models, based on observed local relationships betweenaverage variables.

  1. Granular Superconductors and Gravity

    Noever, David; Koczor, Ron

    1999-01-01

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

  2. Research into material behaviour of the polymeric samples obtained after 3D-printing and subjected to compression test

    Petrov, Mikhail A.; Kosatchyov, Nikolay V.; Petrov, Pavel A.

    2016-10-01

    The paper represents the results of the study concerning the investigation of the influence of the filling grade (material density) on the force characteristic during the uniaxial compression test of the cylindrical polymer probes produced by additive technology based on FDM. The authors have shown that increasing of the filling grate follows to the increase of the deformation forces. However, the dependency is not a linear function and characterized by soft-elastic model of material behaviour, which is typical for polymers partly crystallized structure.

  3. Sensors for the CMS High Granularity Calorimeter

    Maier, Andreas Alexander

    2017-01-01

    The CMS experiment is currently developing high granularity calorimeter endcapsfor its HL-LHC upgrade. The design foresees silicon sensors as the active material for the high radiation region close to the beampipe. Regions of lower radiation are additionally equipped with plastic scintillator tiles. This technology is similar to the calorimeter prototypes developed in the framework of the Linear Collider by the CALICE collaboration. The current status of the silicon sensor development is presented. Results of single diode measurements are shown as well as tests of full 6-inch hexagonal sensor wafers. A short summary of test beam results concludes the article.

  4. Modelling of dc characteristics for granular semiconductors

    Varpula, Aapo; Sinkkonen, Juha; Novikov, Sergey

    2010-01-01

    The dc characteristics of granular n-type semiconductors are calculated analytically with the drift-diffusion theory. Electronic trapping at the grain boundaries (GBs) is taken into account. The use of quadratic and linear GB potential profiles in the calculation is compared. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is excellent in a large voltage range. The results show that electronic trapping at the GBs has a remarkable effect on the highly nonlinear I-V characteristics of the material.

  5. Modelling of dc characteristics for granular semiconductors

    Varpula, Aapo; Sinkkonen, Juha; Novikov, Sergey, E-mail: aapo.varpula@tkk.f [Department of Micro and Nanosciences, Aalto University, PO Box 13500, FI-00076 Aalto, Espoo (Finland)

    2010-11-01

    The dc characteristics of granular n-type semiconductors are calculated analytically with the drift-diffusion theory. Electronic trapping at the grain boundaries (GBs) is taken into account. The use of quadratic and linear GB potential profiles in the calculation is compared. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is excellent in a large voltage range. The results show that electronic trapping at the GBs has a remarkable effect on the highly nonlinear I-V characteristics of the material.

  6. Amorphous and nanocrystalline titanium nitride and carbonitride materials obtained by solution phase ammonolysis of Ti(NMe2)4

    Jackson, Andrew W.; Shebanova, Olga; Hector, Andrew L.; McMillan, Paul F.

    2006-01-01

    Solution phase reactions between tetrakisdimethylamidotitanium (Ti(NMe 2 ) 4 ) and ammonia yield precipitates with composition TiC 0.5 N 1.1 H 2.3 . Thermogravimetric analysis (TGA) indicates that decomposition of these precursor materials proceeds in two steps to yield rocksalt-structured TiN or Ti(C,N), depending upon the gas atmosphere. Heating to above 700 deg. C in NH 3 yields nearly stoichiometric TiN. However, heating in N 2 atmosphere leads to isostructural carbonitrides, approximately TiC 0.2 N 0.8 in composition. The particle sizes of these materials range between 4-12 nm. Heating to a temperature that corresponds to the intermediate plateau in the TGA curve (450 deg. C) results in a black powder that is X-ray amorphous and is electrically conducting. The bulk chemical composition of this material is found to be TiC 0.22 N 1.01 H 0.07 , or Ti 3 (C 0.17 N 0.78 H 0.05 ) 3.96 , close to Ti 3 (C,N) 4 . Previous workers have suggested that the intermediate compound was an amorphous form of Ti 3 N 4 . TEM investigation of the material indicates the presence of nanocrystalline regions x (C,N) y crystalline phases

  7. Novel hierarchically porous carbon materials obtained from natural biopolymer as host matrixes for lithium-sulfur battery applications.

    Zhang, Bin; Xiao, Min; Wang, Shuanjin; Han, Dongmei; Song, Shuqin; Chen, Guohua; Meng, Yuezhong

    2014-08-13

    Novel hierarchically porous carbon materials with very high surface areas, large pore volumes and high electron conductivities were prepared from silk cocoon by carbonization with KOH activation. The prepared novel porous carbon-encapsulated sulfur composites were fabricated by a simple melting process and used as cathodes for lithium sulfur batteries. Because of the large surface area and hierarchically porous structure of the carbon material, soluble polysulfide intermediates can be trapped within the cathode and the volume expansion can be alleviated effectively. Moreover, the electron transport properties of the carbon materials can provide an electron conductive network and promote the utilization rate of sulfur in cathode. The prepared carbon-sulfur composite exhibited a high specific capacity and excellent cycle stability. The results show a high initial discharge capacity of 1443 mAh g(-1) and retain 804 mAh g(-1) after 80 discharge/charge cycles at a rate of 0.5 C. A Coulombic efficiency retained up to 92% after 80 cycles. The prepared hierarchically porous carbon materials were proven to be an effective host matrix for sulfur encapsulation to improve the sulfur utilization rate and restrain the dissolution of polysulfides into lithium-sulfur battery electrolytes.

  8. Superconducting materials fabrication process and products obtained. Procede de fabrication de materiaux supraconducteurs et produits ainsi obtenus

    Dubois, B; Odier, P

    1989-09-15

    A fabrication process of a fine superconducting powder easy to sinter is claimed. It consists in thermal treatment of an aerosol containing an organic and/or inorganic salt and/or a hydroxide of a rare earth, an alkaline earth metal and a transition metal in a ratio corresponding to the stoichiometry of the superconducting materials.

  9. Mesostructured Au/C materials obtained by replication of functionalized SBA-15 silica containing highly dispersed gold nanoparticles

    Kerdi, Fatmé ; Caps, Valerie; Tuel, Alain

    2011-01-01

    was the same for both series and apparently did not depend on the nature of the silica template. Both Au/SiO2 templates and their corresponding Au/CMK-3 materials have been characterized by X-ray diffraction, nitrogen adsorption/desorption, chemical analysis

  10. Results of environmental radiation monitoring and meteorology measurements (material prepared for obtaining the licence for RA reactor experimental operation)

    1980-10-01

    According to the demands for obtaining the licence for restarting the Ra reactor and the experimental operation this document includes the radiation monitoring measured data in the working space and environment of the RA reactor, i.e. Boris Kidric Institute. The meteorology measured data are included as well. All the measurements are performed according to the radiation protection program applied actually from the first reactor start-up at the end of 1959 [sr

  11. Mass Spectrometry-Based Proteomic Profiling of Thrombotic Material Obtained by Endovascular Thrombectomy in Patients with Ischemic Stroke

    Roberto Muñoz

    2018-02-01

    Full Text Available Thrombotic material retrieved from acute ischemic stroke (AIS patients represents a valuable source of biological information. In this study, we have developed a clinical proteomics workflow to characterize the protein cargo of thrombi derived from AIS patients. To analyze the thrombus proteome in a large-scale format, we developed a workflow that combines the isolation of thrombus by endovascular thrombectomy and peptide chromatographic fractionation coupled to mass-spectrometry. Using this workflow, we have characterized a specific proteomic expression profile derived from four AIS patients included in this study. Around 1600 protein species were unambiguously identified in the analyzed material. Functional bioinformatics analyses were performed, emphasizing a clustering of proteins with immunological functions as well as cardiopathy-related proteins with blood-cell dependent functions and peripheral vascular processes. In addition, we established a reference proteomic fingerprint of 341 proteins commonly detected in all patients. Protein interactome network of this subproteome revealed protein clusters involved in the interaction of fibronectin with 14-3-3 proteins, TGFβ signaling, and TCP complex network. Taken together, our data contributes to the repertoire of the human thrombus proteome, serving as a reference library to increase our knowledge about the molecular basis of thrombus derived from AIS patients, paving the way toward the establishment of a quantitative approach necessary to detect and characterize potential novel biomarkers in the stroke field.

  12. Composition characteristics and regularities of dissolving of hydroxyapatite materials obtained in water solutions with varied content of silicate ions

    Solonenko, A. P.

    2018-01-01

    Research aimed at developing new bioactive materials for the repair of defects in bone tissues, do not lose relevance due to the strengthening of the regenerative approach in medicine. From this point of view, materials based on calcium phosphates, including silicate ions, consider as one of the most promising group of substances. Methods of synthesis and properties of hydroxyapatite doped with various amounts of SiO4 4- ions are described in literature. In the present work synthesis of a solid phase in the systems Ca(NO3)2 - (NH4)2HPO4 - Na2SiO3 - NH4OH - H2O (Cca/CP = 1.70) performed with a wide range of sodium silicate additive concentration (y = CSi/CP = 0 ÷ 5). It is established that under the studied conditions at y ≥ 0.3 highly dispersed poorly crystallized apatite containing isomorphic impurities of CO3 2- and SiO4 4- precipitates in a mixture with calcium hydrosilicate and SiO2. It is shown that the resulting composites can gradually dissolve in physiological solution and initiate passive formation of the mineral component of hard tissues.

  13. Measurements of granular flow dynamics with high speed digital images

    Lee, Jingeol [Univ. of Florida, Gainesville, FL (United States)

    1994-01-01

    The flow of granular materials is common to many industrial processes. This dissertation suggests and validates image processing algorithms applied to high speed digital images to measure the dynamics (velocity, temperature and volume fraction) of dry granular solids flowing down an inclined chute under the action of gravity. Glass and acrylic particles have been used as granular solids in the experiment. One technique utilizes block matching for spatially averaged velocity measurements of the glass particles. This technique is compared with the velocity measurement using an optic probe which is a conventional granular flow velocity measurement device. The other technique for measuring the velocities of individual acrylic particles is developed with correspondence using a Hopfield network. This technique first locates the positions of particles with pattern recognition techniques, followed by a clustering technique, which produces point patterns. Also, several techniques are compared for particle recognition: synthetic discriminant function (SDF), minimum average correlation energy (MACE) filter, modified minimum average correlation energy (MMACE) filter and variance normalized correlation. The author proposes an MMACE filter which improves generalization of the MACE filter by adjusting the amount of averaged spectrum of training images in the spectrum whitening stages of the MACE filter. Variance normalized correlation is applied to measure the velocity and temperature of flowing glass particles down the inclined chute. The measurements are taken for the steady and wavy flow and qualitatively compared with a theoretical model of granular flow.

  14. Method to obtain molybdenum 99 from a matrix containing neutron-irradiated, fissionable materials and fission products

    Ali, S.A.H.; Knapp, J.; Reinhardt, J.

    1977-01-01

    A method to obtain a highly pure Mo 99 compound is suggested which is easy to perform even with remote handling. The matrix irradiated by neutrons is rendered soluble with aqueous alkali hydroxide solution, the Mo 99 being dissolved. The Mo rhodanide complex is collected on an organic ion exchanger. The individual process steps are described. A suitable iodine reducing agent (e.g. Na or Ka sulphite, hydroxyl ammonium sulphate) is already added to the first step and to the washing of the ion exchanger. Where necessary Tc 99 is eluated from the fixed Mo 99 mother nuclide for use in nuclear medicine. (UWI) [de

  15. The behaviour of free-flowing granular intruders

    Wyburn Edward

    2017-01-01

    Full Text Available Particle shape affects both the quasi-static and dynamic behaviour of granular media. There has been significant research devoted to the flowability of systems of irregularly shaped particles, as well as the flow of grains around fixed intruders, however the behaviour of free flowing intruders within granular flows remains comparatively unexplored. Here, the effect of the shape of these intruder particles is studied, looking at the kinematic behaviour of the intruders and in particular their tendency of orientation. Experiments are carried out within the Stadium Shear Device, which is a novel apparatus able to continuously apply simple shear conditions to two-dimensional grain analogues. It is found that the intruder shows different behaviour to that of the bulk flow, and that this behaviour is strongly shape dependent. These insights could lead to the development of admixtures that alter the flowability of granular materials.

  16. Quantitative X-ray mapping, scatter diagrams and the generation of correction maps to obtain more information about your material

    Wuhrer, R.; Moran, K.

    2014-03-01

    Quantitative X-ray mapping with silicon drift detectors and multi-EDS detector systems have become an invaluable analysis technique and one of the most useful methods of X-ray microanalysis today. The time to perform an X-ray map has reduced considerably with the ability to map minor and trace elements very accurately due to the larger detector area and higher count rate detectors. Live X-ray imaging can now be performed with a significant amount of data collected in a matter of minutes. A great deal of information can be obtained from X-ray maps. This includes; elemental relationship or scatter diagram creation, elemental ratio mapping, chemical phase mapping (CPM) and quantitative X-ray maps. In obtaining quantitative x-ray maps, we are able to easily generate atomic number (Z), absorption (A), fluorescence (F), theoretical back scatter coefficient (η), and quantitative total maps from each pixel in the image. This allows us to generate an image corresponding to each factor (for each element present). These images allow the user to predict and verify where they are likely to have problems in our images, and are especially helpful to look at possible interface artefacts. The post-processing techniques to improve the quantitation of X-ray map data and the development of post processing techniques for improved characterisation are covered in this paper.

  17. Quantitative X-ray mapping, scatter diagrams and the generation of correction maps to obtain more information about your material

    Wuhrer, R; Moran, K

    2014-01-01

    Quantitative X-ray mapping with silicon drift detectors and multi-EDS detector systems have become an invaluable analysis technique and one of the most useful methods of X-ray microanalysis today. The time to perform an X-ray map has reduced considerably with the ability to map minor and trace elements very accurately due to the larger detector area and higher count rate detectors. Live X-ray imaging can now be performed with a significant amount of data collected in a matter of minutes. A great deal of information can be obtained from X-ray maps. This includes; elemental relationship or scatter diagram creation, elemental ratio mapping, chemical phase mapping (CPM) and quantitative X-ray maps. In obtaining quantitative x-ray maps, we are able to easily generate atomic number (Z), absorption (A), fluorescence (F), theoretical back scatter coefficient (η), and quantitative total maps from each pixel in the image. This allows us to generate an image corresponding to each factor (for each element present). These images allow the user to predict and verify where they are likely to have problems in our images, and are especially helpful to look at possible interface artefacts. The post-processing techniques to improve the quantitation of X-ray map data and the development of post processing techniques for improved characterisation are covered in this paper

  18. Study of electrochemical properties of thin film materials obtained using plasma technologies for production of electrodes for pacemakers

    Obrezkov, O I; Vinogradov, V P; Krauz, V I; Mozgrin, D V; Guseva, I A; Andreev, E S; Zverev, A A; Starostin, A L

    2016-01-01

    Studies of thin film materials (TFM) as coatings of tips of pacemaker electrodes implanted into the human heart have been performed. TFM coatings were deposited in vacuum by arc magnetron discharge plasma, by pulsed discharge of “Plasma Focus”, and by electron beam evaporation. Simulation of electric charge transfer to the heart in physiological blood- imitator solution and determination of electrochemical properties of the coatings were carried out. TFM of highly developed surface of contact with tissue was produced by argon plasma spraying of titanium powder with subsequent coating by titanium nitride in vacuum arc assisted by Ti ion implantation. The TFM coatings of pacemaker electrode have passed necessary clinical tests and were used in medical practice. They provide low voltage myocardium stimulation thresholds within the required operating time. (paper)

  19. Why granular media are thermal after all

    Liu, Mario; Jiang, Yimin

    2017-06-01

    Two approaches exist to account for granular behavior. The thermal one considers the total entropy, which includes microscopic degrees of freedom such as phonons; the athermal one (as with the Edward entropy) takes grains as elementary. Granular solid hydrodynamics (GSH) belongs to the first, DEM, granular kinetic theory and athermal statistical mechanics (ASM) to the second. A careful discussion of their conceptual differences is given here. Three noteworthy insights or results are: (1) While DEM and granular kinetic theory are well justified to take grains as elementary, any athermal entropic consideration is bound to run into trouble. (2) Many general principles are taken as invalid in granular media. Yet within the thermal approach, energy conservation and fluctuation-dissipation theorem remain valid, granular temperatures equilibrate, and phase space is well explored in a grain at rest. Hence these are abnormalities of the athermal approximation, not of granular media as such. (3) GSH is a wide-ranged continuum mechanical description of granular dynamics.

  20. Aspects of simulating the dynamic compaction of a granular ceramic

    Borg, John P; Vogler, Tracy J

    2009-01-01

    Mesoscale hydrodynamic calculations have been conducted in order to gain further insight into the dynamic compaction characteristics of granular ceramics. With a mesoscale approach each individual grain, as well as the porosity, is modeled explicitly; the bulk behavior of the porous material can be resolved as a result. From these calculations bulk material characteristics such as shock speed, stress and density have been obtained and compared with experimental results. A parametric study has been conducted in order to explore the variation and sensitivity of the computationally derived dynamic response characteristics to micro-scale material properties such as Poisson's ratio, dynamic yield and tensile failure strength; macro-scale parameters such as volume fraction, particle morphology and size distribution were explored as well. The results indicate that the baseline bulk Hugoniot response under-predicts the experimentally measured response. These results are sensitive to the volume fraction, dynamic yield strength and particle arrangement, somewhat sensitive to failure strength and insensitive to the micro-scale Hugoniot and grain morphology. A discussion as to the shortcomings in the mesoscale modeling technique, as well as future considerations, is included

  1. Voltage fluctuations in granular superconductors in the perpendicular configuration

    Gerashchenko, O V

    2003-01-01

    The spectral density of voltage fluctuations in granular YBa 2 Cu 3 O 7-δ superconductors in the perpendicular configuration has been studied in the flux flow mode. It has been found that, in this case, the 1/f-voltage noise observed depends weakly on temperature and is associated with motion of a magnetic flux in the superconductor. A comparison of the data obtained with the results of previous measurements in parallel configuration has shown that voltage noise is produced by a single common source, which is presumably associated with self-organization of the critical state in granular superconductors

  2. Effect of cervical relining of acrylic resin copings on the accuracy of stone dies obtained using a polyether impression material

    André Tomazini Gomes de Sá

    2008-02-01

    Full Text Available The purpose of this study was to evaluate the accuracy of the respective dies after polyether elastomeric procedure in the presence or absence of cervical contact of the acrylic resin shell with the cervical region, establishing a comparison to dies obtained with stock trays. This study consisted of three groups with 10 specimens each: 1 acrylic copings without cervical contact, (cn; 2 acrylic copings with cervical contact (cc; 3 perforated stock tray, (st. The accuracy of the resulting dies was verified with the aid of a master crown, precisely fit to the master steel die. ANOVA test found statistically significant differences among groups (p<0.001. Tukey's test found that the smallest discrepancy occurred in group cn, followed by cc, while the st group presented the highest difference (cc x cn: p=0.007; st x cn: p<0.001; st x cc: p<0.001.

  3. First In-Core Measurement Results Obtained with the Innovative Mobile Calorimeter CALMOS inside the OSIRIS Material Testing Reactor

    Carcreff, Hubert; Salmon, Laurent; Courtaux, Cedric

    2013-06-01

    Nuclear heating rate inside an MTR has to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. This measurement is usually carried out by calorimetry [1, 2]. An innovative calorimetric system, CALMOS, has been studied and built in 2011 for the 70 MWth OSIRIS reactor operated by CEA. Thanks to a new calorimetric probe, associated to a specific displacement system, it provides measurements along the fissile height and above the core. The development of the calorimetric probe required the manufacturing and the irradiation of mock-ups in the ex-core area, where nuclear heating rate does not exceed 2 W.g -1 . The calorimeter working mode, the different measurement procedures allowed with such a new probe and main modeling and experimental results have been already presented [3, 4]. In this paper, we present the first results obtained during several measurement campaigns carried out in 2012 and 2013 inside the OSIRIS core with the final device. For the first time, this new experimental measurement system was operated in nominal in-core thermo hydraulic conditions with nominal neutron and gamma fluxes (up to 6 W.g -1 ) in several experimental locations. After a brief presentation of the displacement system specificities, first nuclear heating distributions are presented and discussed. Experimental data were also used to upgrade the Finite Element model of the calorimeter in order to match measured temperatures with calculated ones. This model allowed to estimate a Kc correction factor which takes into account small nonlinearities when the heating rate is deduced from the calibration method. A comparison is made between nuclear heating rates determined from the probe calibration and from the zero method. In addition, an evaluation of the global uncertainty associated to the measurements is detailed. Finally, a global comparison is made with available measurements obtained from previous calorimeters. (authors)

  4. First in-core measurement results obtained with the innovative mobile calorimeter CALMOS inside the OSIRIS material testing reactor

    Carcreff, Hubert; Salmon, Laurent; Courtaux, Cedric

    2014-01-01

    Nuclear heating rate inside an MTR has to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. This measurement is usually carried out by calorimetry. An innovative calorimetric system, CALMOS, has been studied and built in 2011 for the 70 MWth OSIRIS reactor operated by CEA. Thanks to a new calorimetric probe, associated to a specific displacement system, it provides measurements along the fissile height and above the core. Development of the calorimetric probe required manufacturing and irradiation of mock-ups in the ex-core area, where nuclear heating rate does not exceed 2 W.g -1 . The calorimeter working mode, the different measurement procedures, main modeling and ex-core experimental results have been already presented in previous papers. In this paper, we present in-core results obtained from 2011 to 2013 with the final device. For the first time, this new experimental measurement system was operated in several experimental locations, with nominal in-core thermal hydraulic conditions, nominal neutron flux and nuclear heating rate up to 6 W.g -1 (in graphite). After a brief presentation of the displacement system specificities, first nuclear heating distributions are presented and discussed. The Finite Element model of the calorimeter was upgraded in order to match calculated temperatures with measured ones. This 'validated' model allowed to estimate a Kc factor which tends to correct small nonlinearities when heating rate is calculated from the 'calibration method'. A comparison is made between nuclear heating rates determined from 'calibration' and 'zero methods'. In addition, an evaluation of the global uncertainty associated to the measurements is detailed. Finally, a comparison is made with available measurements obtained from previous calorimeters. (authors)

  5. Traffic and Granular Flow '11

    Buslaev, Alexander; Bugaev, Alexander; Yashina, Marina; Schadschneider, Andreas; Schreckenberg, Michael; TGF11

    2013-01-01

    This book continues the biannual series of conference proceedings, which has become a classical reference resource in traffic and granular research alike. It addresses new developments at the interface between physics, engineering and computational science. Complex systems, where many simple agents, be they vehicles or particles, give rise to surprising and fascinating phenomena.   The contributions collected in these proceedings cover several research fields, all of which deal with transport. Topics include highway, pedestrian and internet traffic, granular matter, biological transport, transport networks, data acquisition, data analysis and technological applications. Different perspectives, i.e. modeling, simulations, experiments and phenomenological observations, are considered.

  6. Hierarchical modular granular neural networks with fuzzy aggregation

    Sanchez, Daniela

    2016-01-01

    In this book, a new method for hybrid intelligent systems is proposed. The proposed method is based on a granular computing approach applied in two levels. The techniques used and combined in the proposed method are modular neural networks (MNNs) with a Granular Computing (GrC) approach, thus resulting in a new concept of MNNs; modular granular neural networks (MGNNs). In addition fuzzy logic (FL) and hierarchical genetic algorithms (HGAs) are techniques used in this research work to improve results. These techniques are chosen because in other works have demonstrated to be a good option, and in the case of MNNs and HGAs, these techniques allow to improve the results obtained than with their conventional versions; respectively artificial neural networks and genetic algorithms.

  7. Friction dependence of shallow granular flows from discrete particle simulations

    Thornton, Anthony Richard; Weinhart, Thomas; Luding, Stefan; Bokhove, Onno

    2011-01-01

    A shallow-layer model for granular flows is completed with a closure relation for the macroscopic bed friction or basal roughness obtained from micro-scale discrete particle simulations of steady flows. We systematically vary the bed friction by changing the contact friction coefficient between

  8. Electrokinetic copper and iron migration in anaerobic granular sludge

    Virkutyte, J.; Sillanpää, M.J.; Lens, P.N.L.

    2006-01-01

    The application of low-level direct electric current (0.15 mA cm¿2) as an electrokinetic technique to treat copper-contaminated mesophilic anaerobic granular sludge was investigated. The sludge was obtained from a full scale UASB reactor treating paper-mill wastewater and was artificially

  9. Cantilever beam test in Zr-2.5%Nb: Comparative study between pipe material obtained by laminating and wire drawing

    Gomez, A G; Szieber, W C; Vizcaino, P; Loureiro, N; Bianchi, D R; Banchik, A D

    2012-01-01

    The Zr-2.5Nb alloy is used in the manufacture of pressure tubes for the CANDU nuclear power reactors. These tubes are subjected to severe service conditions: one o f them, the heavy water corrosion due to the coolant generates release of hydrogen, part of which ingress in the material raising its initial concentration and exposing them to a phenomena referred as delay hydrogen cracking. The results presented in this paper show the performance of a pressure tube of domestic manufacture under conditions of tension and hydrogen content in order to be compared with the behavior of a standard pressure tube in operation in the nuclear power plant. To do this is, cantilever notched and pre cracked samples were hydrided from both kinds of tubes. Each one of these samples was subjected to the cantilever beam test, which consists in a bending test performed in a furnace at 250 o C. Starting from a stress intensity factor Ki which determines the propagation start of the crack, the growth is followed by the acoustic emission technique up to the arrest of the crack by controlling the bending load. This work presents the comparative data such as critical voltages, behavior of hydrides, and DHC parameters from both trials. Although the number of tests is reduced; results show a good performance of the tubes of domestic manufacture (author)

  10. IR and NMR studies of hierarchical material obtained by the treatment of zeolite Y by ammonia solution

    Gackowski, Mariusz; Kuterasiński, Łukasz; Podobiński, Jerzy; Sulikowski, Bogdan; Datka, Jerzy

    2018-03-01

    Ammonia treatment of ultrastable zeolite Y has a great impact on its features. XRD showed a partial loss of crystallinity coupled with a loss of long-distance zeolite ordering. However, a typical short-range zeolite ordering, in the light of 29Si NMR studies, was largely preserved. 27Al MAS NMR spectra evidenced that most of Al was located in zeolitic tetrahedral positions, but some of them adopted a distorted configuration. Evolution of zeolites acidity was followed quantitatively by using IR. In particular, such studies revealed the presence of strongly acidic Sisbnd OHsbnd Al groups. IR studies suggest also heterogeneity of these OH groups. The heterogeneity of Sisbnd OHsbnd Al groups was a consequence of the less ordered structure of zeolites treated with ammonia solutions. It was also found that the treatment with ammonia solutions yields hierarchical material. The samples revealed promising catalytic properties in the liquid phase isomerization of α-pinene. Zeolites desilicated with ammonia may constitute an inexpensive route yielding viable hierarchical catalysts.

  11. Uniform shock waves in disordered granular matter

    Gómez, L.R.; Turner, A.M.; Vitelli, V.

    2012-01-01

    The confining pressure P is perhaps the most important parameter controlling the properties of granular matter. Strongly compressed granular media are, in many respects, simple solids in which elastic perturbations travel as ordinary phonons. However, the speed of sound in granular aggregates

  12. Characterization and performance of carbonaceous materials obtained from exhausted sludges for the anaerobic biodecolorization of the azo dye Acid Orange II

    Athalathil, S.; Stüber, F.; Bengoa, C.; Font, J. [Departament d’Enginyeria Quimica, ETSEQ, Universitat Rovira i Virgili, Av. Paisos Catalans 26, 43007 Tarragona, Catalunya (Spain); Fortuny, A. [Departament d’Enginyeria Quimica, EPSEVG, Universitat Politecnica de Catalunya, Av. Victor Balaguer s/n, 08800 Vilanova i la Geltru, Catalunya (Spain); Fabregat, A., E-mail: azael.fabregat@urv.cat [Departament d’Enginyeria Quimica, ETSEQ, Universitat Rovira i Virgili, Av. Paisos Catalans 26, 43007 Tarragona, Catalunya (Spain)

    2014-02-01

    Graphical abstract: - Highlights: • Carbonaceous materials were prepared from exhausted sludge materials. • High surface area and good physicochemical properties were achieved. • Utilization of waste sludge materials and mixed anaerobic cultures were used in a continuous anaerobic UPBR system (upflow packed bed biological reactor). • Effective treatment of dye contaminated wastewater in a cheapest and environmental friendly method was demonstrated. - Abstract: This work presents the preliminary study of new carbonaceous materials (CMs) obtained from exhausted sludge, their use in the heterogeneous anaerobic process of biodecolorization of azo dyes and the comparison of their performance with one commercial active carbon. The preparation of carbonaceous materials was conducted through chemical activation and carbonization. Chemical activation was carried out through impregnation of sludge-exhausted materials with ZnCl{sub 2} and the activation by means of carbonization at different temperatures (400, 600 and 800 °C). Their physicochemical and surface characteristics were also investigated. Sludge based carbonaceous (SBC) materials SBC400, SBC600 and SBC800 present values of 13.0, 111.3 and 202.0 m{sup 2}/g of surface area. Biodecolorization levels of 76% were achieved for SBC600 and 86% for SBC800 at space time (τ) of 1.0 min, similar to that obtained with commercial activated carbons in the continuous anaerobic up-flow packed bed reactor (UPBR). The experimental data fit well to the first order kinetic model and equilibrium data are well represented by the Langmuir isotherm model. Carbonaceous materials show high level of biodecolorization even at very short space times. Results indicate that carbonaceous materials prepared from sludge-exhausted materials have outstanding textural properties and significant degradation capacity for treating textile effluents.

  13. Enhanced selection of micro-aerobic pentachlorophenol degrading granular sludge

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

    2014-01-01

    Graphical abstract: In this work, an aerobic column reactor was placed before the USB to maintain micro-oxygen condition in the reactor and the micro-aerobic pentachlorophenol (PCP) degrading granular sludge under oxygen-limited conditions (0.1–0.2 mg L −1 ) was successfully obtained. PCP degradation by the micro-aerobic system was studied and the variance of microbial community was also discussed by using PCR-DGGE analysis. - Highlights: • Micro-aerobic granular sludge was cultivated in column-type combined reactors. • PCP biodegradation, VFA accumulation and biogas production were studied. • The function of Methanogenic archaeon in the system was investigated. • Fluctuation and diversity of microbial community were discussed by DGGE analysis. • The dominated microorganisms were identified by 16S rDNA sequences. - Abstract: Column-type combined reactors were designed to cultivate micro-aerobic pentachlorophenol (PCP) degrading granular sludge under oxygen-limited conditions (0.1–0.2 mg L −1 ) over 39-day experimental period. Micro-aerobic granular had both anaerobic activity (SMA: 2.34 mMCH 4 /h g VSS) and aerobic activity (SOUR: 2.21 mMO 2 /h g 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

  14. Enhanced selection of micro-aerobic pentachlorophenol degrading granular sludge

    Lv, Yuancai, E-mail: donkey1204@hotmail.com [State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640 (China); Chen, Yuancai, E-mail: chenyc@scut.edu.cn [State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640 (China); Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, College of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); Song, Wenzhe, E-mail: songwenzhe007@126.com [Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, College of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); Hu, Yongyou, E-mail: ppyyhu@scut.edu.cn [State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640 (China); Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, College of Environment and Energy, South China University of Technology, Guangzhou 510006 (China)

    2014-09-15

    Graphical abstract: In this work, an aerobic column reactor was placed before the USB to maintain micro-oxygen condition in the reactor and the micro-aerobic pentachlorophenol (PCP) degrading granular sludge under oxygen-limited conditions (0.1–0.2 mg L{sup −1}) was successfully obtained. PCP degradation by the micro-aerobic system was studied and the variance of microbial community was also discussed by using PCR-DGGE analysis. - Highlights: • Micro-aerobic granular sludge was cultivated in column-type combined reactors. • PCP biodegradation, VFA accumulation and biogas production were studied. • The function of Methanogenic archaeon in the system was investigated. • Fluctuation and diversity of microbial community were discussed by DGGE analysis. • The dominated microorganisms were identified by 16S rDNA sequences. - Abstract: Column-type combined reactors were designed to cultivate micro-aerobic pentachlorophenol (PCP) degrading granular sludge under oxygen-limited conditions (0.1–0.2 mg L{sup −1}) over 39-day experimental period. Micro-aerobic granular had both anaerobic activity (SMA: 2.34 mMCH{sub 4}/h g VSS) and aerobic activity (SOUR: 2.21 mMO{sub 2}/h g 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

  15. Pressure dependence of the magneto-transport properties in Fe/MgO granular systems

    García-García, A.; Algarabel, P.A.; Pardo, J.A.; Arnold, Zdeněk; Kamarád, Jiří

    2013-01-01

    Roč. 62, č. 10 (2013), s. 1458-1460 ISSN 0374-4884 Institutional support: RVO:68378271 Keywords : granular materials * tunneling magnetoresistance * hydrostatic pressure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.425, year: 2013

  16. Computer modelling of granular material microfracturing

    Malan, DF

    1995-08-15

    Full Text Available Interaction and Growth Simulation). Grains were represented by straight-sided polygons generated with a Voronoi generator. Experiments were carried out to simulate experimental micro fracture studies of quartzite in triaxial extension tests. The results...

  17. Signal transmissibility in marginal granular materials

    Pinson, Matthew B.; Witten, Thomas A.

    2016-12-01

    We examine the ‘transmissibility’ of a simulated two-dimensional pack of frictionless disks formed by confining dilute disks in a shrinking, periodic box to the point of mechanical stability. Two opposite boundaries are then removed, thus allowing a set of free motions. Small free displacements on one boundary then induce proportional displacements on the opposite boundary. Transmissibility is the ability to distinguish different perturbations by their distant responses. We assess transmissibility by successively identifying free orthonormal modes of motion that have the smallest distant responses. The last modes to be identified in this ‘pessimistic’ basis are the most transmissive. The transmitted amplitudes of these most transmissive modes fall off exponentially with mode number. Similar exponential falloff is seen in a simple elastic medium, though the responsible modes differ greatly in structure in the two systems. Thus the marginal pack’s transmissibility is qualitatively similar to that of a simple elastic medium. We compare our results with recent findings based on the projection of the space of free motion onto interior sites.

  18. Signal transmissibility in marginal granular materials

    Pinson, Matthew B; Witten, Thomas A

    2016-01-01

    We examine the ‘transmissibility’ of a simulated two-dimensional pack of frictionless disks formed by confining dilute disks in a shrinking, periodic box to the point of mechanical stability. Two opposite boundaries are then removed, thus allowing a set of free motions. Small free displacements on one boundary then induce proportional displacements on the opposite boundary. Transmissibility is the ability to distinguish different perturbations by their distant responses. We assess transmissibility by successively identifying free orthonormal modes of motion that have the smallest distant responses. The last modes to be identified in this ‘pessimistic’ basis are the most transmissive. The transmitted amplitudes of these most transmissive modes fall off exponentially with mode number. Similar exponential falloff is seen in a simple elastic medium, though the responsible modes differ greatly in structure in the two systems. Thus the marginal pack’s transmissibility is qualitatively similar to that of a simple elastic medium. We compare our results with recent findings based on the projection of the space of free motion onto interior sites. (paper)

  19. Thermal diffusion segregation of an impurity in a driven granular fluid

    Reyes, Francisco Vega; Garzó, Vicente [Departamento de Física, Universidad de Extremadura, E-06071 Badajoz, Spain and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, E-06071 Badajoz (Spain)

    2014-12-09

    We study segregation of an impurity in a driven granular fluid under two types of steady states. In the first state, the granular gas is driven by a stochastic volume force field with a Fourier-type profile while in the second state, the granular gas is sheared in such a way that inelastic cooling is balanced by viscous heating. We compare theoretical results derived from a solution of the (inelastic) Boltzmann equation at Navier-Stokes (NS) order with those obtained from the Direct Monte Carlo simulation (DSMC) method and molecular dynamics (MD) simulations. Good agreement is found between theory and simulation, which provides strong evidence of the reliability of NS granular hydrodynamics for these steady states (including the dynamics of the impurity), even at high inelasticity. In addition, preliminary results for thermal diffusion in granular fluids at moderate densities are also presented. As for dilute gases, excellent agreement is also found in this more general case.

  20. Studies of elasticity, sound propagation and attenuation of acoustic modes in granular media: final report

    Makse, Hernan A. [City College of New York, NY (United States). Levich Inst., Dept. of Physcis; Johnson, David L. [Schlumberger-Doll Research, Cambridge, MA (United States)

    2014-09-03

    This is the final report describing the results of DOE Grant # DE-FG02-03ER15458 with original termination date of April 31, 2013, which has been extended to April 31, 2014. The goal of this project is to develop a theoretical and experimental understanding of sound propagation, elasticity and dissipation in granular materials. The topic is relevant for the efficient production of hydrocarbon and for identifying and characterizing the underground formation for storage of either CO2 or nuclear waste material. Furthermore, understanding the basic properties of acoustic propagation in granular media is of importance not only to the energy industry, but also to the pharmaceutical, chemical and agricultural industries. We employ a set of experimental, theoretical and computational tools to develop a study of acoustics and dissipation in granular media. These include the concept effective mass of granular media, normal modes analysis, statistical mechanics frameworks and numerical simulations based on Discrete Element Methods. Effective mass measurements allow us to study the mechanisms of the elastic response and attenuation of acoustic modes in granular media. We perform experiments and simulations under varying conditions, including humidity and vacuum, and different interparticle force-laws to develop a fundamental understanding of the mechanisms of damping and acoustic propagation in granular media. A theoretical statistical approach studies the necessary phase space of configurations in pressure, volume fraction to classify granular materials.

  1. Swelling pressure and water absorption property of compacted granular bentonite during water absorption

    Oyamada, T.; Komine, H.; Murakami, S.; Sekiguchi, T.; Sekine, I.

    2012-01-01

    Document available in extended abstract form only. Bentonite is currently planned to be used as buffer materials in engineered barrier of radioactive waste disposal. Granular bentonites are expected as the materials used in constructions as buffer materials by in-situ compaction methods. After applying these buffer materials, it is expected that the condition of the buffer area changes in long-term by the seepage of groundwater into buffer area. Therefore, it is important to understand water movement and swelling behavior of the buffer materials for evaluating the performance of engineered barrier. In this study, we investigated water absorption property and swelling pressure of compacted granular bentonite. Specifically, the process of swelling pressure and amount of water absorption of granular bentonite-GX (Kunigel-GX, produced at the Tsukinuno mine in Japan) were observed by laboratory tests. To discuss the influence of maximum grain size of bentonite particle on swelling pressure and water absorption property, two types of samples were used. One is granular sample which is Bentonite-GX controlled under 2 mm the maximum grain size, the other is milled sample which is Bentonite-GX with the maximum grain size under 0.18 mm by milling with the agate mortar. In addition, the mechanism on the swelling pressure of compacted granular bentonite was considered and discussed. In the cases of granular sample, swelling pressure increases rapidly, then gradually continues to increase up to maximum value. In the cases of milled sample, swelling pressure also increases rapidly at first. However, then its value decreases before progressing of gradual increase continues. Especially, this trend was clearly observed at a relatively low dry density. At the peaks of these curves, the swelling pressure of granular samples is lower than that of milled samples. In addition, the increasing of swelling pressure by the time the peak observed during the process of swelling pressure from

  2. Capturing gas in soft granular media

    MacMinn, Chris; Lee, Jeremy; Xu, Feng; Lee, Sungyon

    2017-11-01

    Bubble migration through soft granular materials involves a strong coupling between the bubble dynamics and the deformation of the material. This process is relevant to a variety of natural and industrial systems, from fluidized-bed reactors to the migration and venting of biogenic gas in sediments. Here, we study this process experimentally by injecting air into a quasi-2D, liquid-saturated packing of soft particles and measuring the morphology of the bubbles as they invade and then rise due to buoyancy. By systematically varying the confining stress, we show that the competition between buoyancy, capillarity, and elasticity leads to complex bubble-migration dynamics that transition from fluidization to pathway opening to pore invasion, with a strong and surprising impact on the amount of air trapped in the system. The authors are grateful for support from the Royal Society (IE150885), the John Fell Oxford University Press Research Fund, and the Maurice Lubbock Memorial Fund.

  3. Frictional granular mechanics: A variational approach

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

    2009-10-16

    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.

  4. Wrinkles, folds, and plasticity in granular rafts

    Jambon-Puillet, Etienne; Josserand, Christophe; Protière, Suzie

    2017-09-01

    We investigate the mechanical response of a compressed monolayer of large and dense particles at a liquid-fluid interface: a granular raft. Upon compression, rafts first wrinkle; then, as the confinement increases, the deformation localizes in a unique fold. This characteristic buckling pattern is usually associated with floating elastic sheets, and as a result, particle laden interfaces are often modeled as such. Here, we push this analogy to its limits by comparing quantitative measurements of the raft morphology to a theoretical continuous elastic model of the interface. We show that, although powerful to describe the wrinkle wavelength, the wrinkle-to-fold transition, and the fold shape, this elastic description does not capture the finer details of the experiment. We describe an unpredicted secondary wavelength, a compression discrepancy with the model, and a hysteretic behavior during compression cycles, all of which are a signature of the intrinsic discrete and frictional nature of granular rafts. It suggests also that these composite materials exhibit both plastic transition and jamming dynamics.

  5. Collisional model for granular impact dynamics.

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

    2014-01-01

    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.

  6. Characteristics and performance of aerobic algae-bacteria granular consortia in a photo-sequencing batch reactor.

    Liu, Lin; Zeng, Zhichao; Bee, Mingyang; Gibson, Valerie; Wei, Lili; Huang, Xu; Liu, Chaoxiang

    2018-05-05

    The characteristics and performance of algae-bacteria granular consortia which cultivated with aerobic granules and targeted algae (Chlorella and Scenedesmus), and the essential difference between granular consortia and aerobic granules were investigated in this experiment. The result indicated that algae-bacteria granular consortia could be successfully developed, and the algae present in the granular consortia were mainly Chlorella and Scenedesmus. Although the change of chlorophyll composition revealed the occurrence of light limitation for algal growth, the granular consortia could maintain stable granular structure, and even showed better settling property than aerobic granules. Total nitrogen and phosphate in the algal-bacterial granular system showed better removal efficiencies (50.2% and 35.7%) than those in the aerobic granular system (32.8% and 25.6%) within one cycle (6 h). The biodiesel yield of aerobic granules could be significantly improved by algal coupled process, yet methyl linolenate and methyl palmitoleate were the dominant composition of biodiesel obtained from granular consortia and aerobic granules, respectively. Meanwhile, the difference of dominant bacterial communities in the both granules was found at the order level and family level, and alpha diversity indexes revealed the granular consortia had a higher microbial diversity. Copyright © 2018. Published by Elsevier B.V.

  7. Technological effect of vibroprocessing by flows of organic granular media

    Lebedev, V. A.; Shishkina, A. P.; Davydova, I. V.; Morozova, A. V.

    2018-03-01

    The analysis of approaches to modeling of vibrational processing by granulated media is carried out. The vibroprocessing model which provides effective finishing of the surfaces of the parts due to the stone fruit organic media granules is developed. The model is based on the granule flow energy impact on the surface being treated. As the main characteristic of the organic media processing, a specific volumetric metal scrap is used, the physical meaning of which is the increase rate in the thickness of the material removed from the surface at a given velocity and pressure of the medium. It is shown that the metal scrap depends on the medium flow velocity, the height of the loading column of the granular medium, and the conditions for the formation of a medium stationary circulation motion. Based on the analysis of the results of experimental studies of the influence of amplitude-frequency characteristics on the removal of metal in the process of vibroprocessing with abrasive granules, the dependence of the specific volume metal removal is proposed for organic media processing, taking into account the threshold amplitude and frequency of oscillations of the working chamber, at which the effect of surface treatment is observed. The established set of relationships describing the effective conditions for vibroprocessing with stone organic media was obtained using experimental data, which allows us to assume that the model obtained is valid.

  8. 2D transient granular flows over obstacles: experimental and numerical work

    Juez, Carmelo; Caviedes-Voullième, Daniel; Murillo, Javier; García-Navarro, Pilar

    2016-04-01

    Landslides are an ubiquitous natural hazard, and therefore human infrastructure and settlements are often at risk in mountainous regions. In order to better understand and predict landslides, systematic studies of the phenomena need to be undertaken. In particular, computational tools which allow for analysis of field problems require to be thoroughly tested, calibrated and validated under controlled conditions. And to do so, it is necessary for such controlled experiments to be fully characterized in the same terms as the numerical model requires. This work presents an experimental study of dry granular flow over a rough bed with topography which resembles a mountain valley. It has an upper region with a very high slope. The geometry of the bed describes a fourth order polynomial curve, with a low point with zero slope, and afterwards a short region with adverse slope. Obstacles are present in the lower regions which are used as model geometries of human structures. The experiments consisted of a sudden release a mass of sand on the upper region, and allowing it to flow downslope. Furthermore, it has been frequent in previous studies to measure final states of the granular mass at rest, but seldom has transient data being provided, and never for the entire field. In this work we present transient measurements of the moving granular surfaces, obtained with a consumer-grade RGB-D sensor. The sensor, developed for the videogame industry, allows to measure the moving surface of the sand, thus obtaining elevation fields. The experimental results are very consistent and repeatable. The measured surfaces clearly show the distinctive features of the granular flow around the obstacles and allow to qualitatively describe the different flow patterns. More importantly, the quantitative description of the granular surface allows for benchmarking and calibration of predictive numerical models, key in scaling the small-scale experimental knowledge into the field. In addition, as

  9. Bubbling in vibrated granular films.

    Zamankhan, Piroz

    2011-02-01

    With the help of experiments, computer simulations, and a theoretical investigation, a general model is developed of the flow dynamics of dense granular media immersed in air in an intermediate regime where both collisional and frictional interactions may affect the flow behavior. The model is tested using the example of a system in which bubbles and solid structures are produced in granular films shaken vertically. Both experiments and large-scale, three-dimensional simulations of this system are performed. The experimental results are compared with the results of the simulation to verify the validity of the model. The data indicate evidence of formation of bubbles when peak acceleration relative to gravity exceeds a critical value Γ(b). The air-grain interfaces of bubblelike structures are found to exhibit fractal structure with dimension D=1.7±0.05.

  10. Paediatric laryngeal granular cell tumour

    Dauda Ayuba

    2009-01-01

    Full Text Available Granular cell tumour (GCT affecting the larynx is not common, especially in children. Most cases are apt to be confused with respiratory papilloma and may even be mistaken for a malignant neoplasia. We present a case of laryngeal GCT in a 12-year-old child to emphasize that the tumour should be regarded in the differential of growths affecting the larynx in children.

  11. Textural analyses of carbon fiber materials by 2D-FFT of complex images obtained by high frequency eddy current imaging (HF-ECI)

    Schulze, Martin H.; Heuer, Henning

    2012-04-01

    Carbon fiber based materials are used in many lightweight applications in aeronautical, automotive, machine and civil engineering application. By the increasing automation in the production process of CFRP laminates a manual optical inspection of each resin transfer molding (RTM) layer is not practicable. Due to the limitation to surface inspection, the quality parameters of multilayer 3 dimensional materials cannot be observed by optical systems. The Imaging Eddy- Current (EC) NDT is the only suitable inspection method for non-resin materials in the textile state that allows an inspection of surface and hidden layers in parallel. The HF-ECI method has the capability to measure layer displacements (misaligned angle orientations) and gap sizes in a multilayer carbon fiber structure. EC technique uses the variation of the electrical conductivity of carbon based materials to obtain material properties. Beside the determination of textural parameters like layer orientation and gap sizes between rovings, the detection of foreign polymer particles, fuzzy balls or visualization of undulations can be done by the method. For all of these typical parameters an imaging classification process chain based on a high resolving directional ECimaging device named EddyCus® MPECS and a 2D-FFT with adapted preprocessing algorithms are developed.

  12. Extraction of topographic and material contrasts on surfaces from SEM images obtained by energy filtering detection with low-energy primary electrons

    Nagoshi, Masayasu; Aoyama, Tomohiro; Sato, Kaoru

    2013-01-01

    Secondary electron microscope (SEM) images have been obtained for practical materials using low primary electron energies and an in-lens type annular detector with changing negative bias voltage supplied to a grid placed in front of the detector. The kinetic-energy distribution of the detected electrons was evaluated by the gradient of the bias-energy dependence of the brightness of the images. This is divided into mainly two parts at about 500 V, high and low brightness in the low- and high-energy regions, respectively and shows difference among the surface regions having different composition and topography. The combination of the negative grid bias and the pixel-by-pixel image subtraction provides the band-pass filtered images and extracts the material and topographic information of the specimen surfaces. -- Highlights: ► Scanning electron (SE) images contain many kind of information on material surfaces. ► We investigate energy-filtered SE images for practical materials. ► The brightness of the images is divided into two parts by the bias voltage. ► Topographic and material contrasts are extracted by subtracting the filtered images.

  13. Information granularity, big data, and computational intelligence

    Chen, Shyi-Ming

    2015-01-01

    The recent pursuits emerging in the realm of big data processing, interpretation, collection and organization have emerged in numerous sectors including business, industry, and government organizations. Data sets such as customer transactions for a mega-retailer, weather monitoring, intelligence gathering, quickly outpace the capacities of traditional techniques and tools of data analysis. The 3V (volume, variability and velocity) challenges led to the emergence of new techniques and tools in data visualization, acquisition, and serialization. Soft Computing being regarded as a plethora of technologies of fuzzy sets (or Granular Computing), neurocomputing and evolutionary optimization brings forward a number of unique features that might be instrumental to the development of concepts and algorithms to deal with big data. This carefully edited volume provides the reader with an updated, in-depth material on the emerging principles, conceptual underpinnings, algorithms and practice of Computational Intelligenc...

  14. Multiple impacts in dissipative granular chains

    Nguyen, Ngoc Son

    2014-01-01

    The extension of collision models for single impacts between two bodies, to the case of multiple impacts (which take place when several collisions occur at the same time in a multibody system) is a challenge in Solid Mechanics, due to the complexity of such phenomena, even in the frictionless case. This monograph aims at presenting the main multiple collision rules proposed in the literature. Such collisions typically occur in granular materials, the simplest of which are made of chains of aligned balls. These chains are used throughout the book to analyze various multiple impact rules which extend the classical Newton (kinematic restitution), Poisson (kinetic restitution) and Darboux-Keller (energetic or kinetic restitution) approaches for impact modelling. The shock dynamics in various types of chains of aligned balls (monodisperse, tapered, decorated, stepped chains) is carefully studied and shown to depend on several parameters: restitution coefficients, contact stiffness ratios, elasticity coefficients (...

  15. Thermal energy storage in granular deposits

    Ratuszny, Paweł

    2017-10-01

    Energy storage technology is crucial for the development of the use of renewable energy sources. This is a substantial constraint, however it can, to some extent, be solved by storing energy in its various forms: electrical, mechanical, chemical and thermal. This article presents the results of research in thermal properties of granular deposits. Correlation between temperature changes in the stores over a period of time and their physical properties has been studied. The results of the research have practical application in designing thermal stores based on bulk materials and ground deposits. Furthermore, the research results are significant for regeneration of the lower ground sources for heat pumps and provide data for designing ground heat exchangers for ventilation systems.

  16. Effect of Wetting and Contamination of Granular Beds During Sphere Impact

    Kouraytem, Nadia

    2013-03-01

    This thesis presents results from an experimental study of the impact of dense solid spheres onto granular beds. The overall aim is to further our understanding of the dynamical response of granular materials to impact. In order to do this, we will study both the initial penetration stages and peak acceleration exerted on the sphere by using high-speed imaging. Another critical part is to measure the penetration depth of the sphere and calculate the corresponding depth-averaged stopping force. Both of these main focal points will be assessed for not only dry, but wet and “contaminated” grains, whereby the granular bed will be comprised of two distinct size ranges of base grains. In doing so, we aim to broadly determine whether contaminated grains or wet grains are more effective at increasing the tensile strength of granular materials.

  17. Effects of Noise and Vibration on the Solid to Liquid Fluidization Transition in Small Dense Granular Systems Under Shear

    Melhus, Martin Frederic

    2011-07-01

    Granular materials exhibit bulk properties that are distinct from conventional solids, liq- uids, and gases, due to the dissipative nature of the inter-granular forces. Understanding the fundamentals of granular materials draws upon and gives insight into many fields at the current frontiers of physics, such as plasticity of solids, fracture and friction, com- plex systems such as colloids, foams and suspensions, and a variety of biological systems. Particulate flows are widespread in geophysics, and are also essential to many industries. Despite the importance of these phenomena, we lack a theoretical model that explains most behaviors of granular materials. Since granular assemblies are highly dissipative, they are often far from mechanical equilibrium, making most classical analyses inappli- cable. A theory for dilute granular systems exists, but for dense granular systems (by far the majority of granular systems in the real world) no comparable theory is accepted. We approach this problem by examining the fluidization, or transition from solid to liquid, in dense granular systems. In this study, the separate effects of random noise and vibration on the static to flowing transition of a dense granular assembly under planar shear is studied numerically using soft contact particle dynamics simulations in two dimensions. We focus on small systems in a thin planar Couette cell, examining the bistable region while increasing shear, with varying amounts of random noise or vibration, and determine the statistics of the shear required for the onset of flow. We find that the applied power is the key parameter in determining the magnitude of the effects of the noise or vibration, with vibration frequency also having an influence. Similarities and differences between noise and vibration are determined, and the results compare favorably with a two phase model for dense granular flow.

  18. Gravity-driven granular flow in a silo: Characterizing local forces and rearrangements

    Thackray Emma

    2017-01-01

    Full Text Available While the gravity-driven flow of a granular material in a silo geometry can be modeled by the Beverloo equation, the mesoscale-level particle rearrangements and interactions that drive this flow are not wellunderstood. We have constructed a quasi-two-dimensional system of bidisperse, millimeter-scale disks with photoelastic properties that make force networks within the material visible. The system is contained in an acrylic box with an adjustable bottom opening. We can approach the clogging transition by adjusting this opening. By placing the system between cross-polarizers, we can obtain high-speed video of this system during flow, and extract intensity signals that can be used to identify and quantify localized, otherwise indeterminate forces. We can simultaneously track individual particle motions, which can be used to identify shear transformation zones in the system. In this paper, we present our results thus far.

  19. Granular computing in decision approximation an application of rough mereology

    Polkowski, Lech

    2015-01-01

    This book presents a study in knowledge discovery in data with knowledge understood as a set of relations among objects and their properties. Relations in this case are implicative decision rules and the paradigm in which they are induced is that of computing with granules defined by rough inclusions, the latter introduced and studied  within rough mereology, the fuzzified version of mereology. In this book basic classes of rough inclusions are defined and based on them methods for inducing granular structures from data are highlighted. The resulting granular structures are subjected to classifying algorithms, notably k—nearest  neighbors and bayesian classifiers. Experimental results are given in detail both in tabular and visualized form for fourteen data sets from UCI data repository. A striking feature of granular classifiers obtained by this approach is that preserving the accuracy of them on original data, they reduce  substantially the size of the granulated data set as well as the set of granular...

  20. Steady state of tapped granular polygons

    Carlevaro, Carlos M; Pugnaloni, Luis A

    2011-01-01

    The steady state packing fraction of a tapped granular bed is studied for different grain shapes via a discrete element method. Grains are monosized regular polygons, from triangles to icosagons. Comparisons with disc packings show that the steady state packing fraction as a function of the tapping intensity presents the same general trends in polygon packings. However, better packing fractions are obtained, as expected, for shapes that can tessellate the plane (triangles, squares and hexagons). In addition, we find a sharp transition for packings of polygons with more than 13 vertices signaled by a discontinuity in the packing fraction at a particular tapping intensity. Density fluctuations for most shapes are consistent with recent experimental findings in disc packing; however, a peculiar behavior is found for triangles and squares

  1. Erosion of a wet/dry granular interface

    Jop, Pierre; Lefebvre, Gautier

    2013-04-01

    To model the dynamic of landslides, the evolution of the interface between the erodible ground and the flowing material is still studied experimentally or numerically (ie. Mangeney et al. 2010, Iverson 2012). In some cases, the basal material is more cohesive than the flowing one. Such situation arises for example due to cementation or humidity. What are the exchange rates between these phases? What is the coupling between the evolution of the interface and the flow? We studied the erosion phenomenon and performed laboratory experiments to focus on the interaction between a cohesive unsaturated granular material and a dry granular flow. Both materials were spherical grains, the cohesion being induced by adding a given mass of liquid to the grains. Two configurations were explored: a circular aggregate submitted to a dry flow in a rotating drum, and a granular flow eroding a wet granular pile. First, we focused on the influence of the cohesion, controlled by the liquid properties, such as the surface tension and the viscosity. Then the flow characteristics were modified by varying the grain size and density. These results allowed us to present a model for the erosion mechanisms, based on the flow and fluid properties. The main results are the need to take into account the whole probability distribution the stress applied on the wet grains and that both the surface tension and the viscosity are important since they play a different roles. The latter is mainly responsible of the time scale of the dynamic of a wet grain, while the former acts as a threshold on the force distribution. In the second configuration, we could also control the inclination of the slope. This system supported the previous model and moreover revealed an interface instability, leading the formation of steep steps, which is a reminiscence of the cyclic-steps observed during river-channel incision (Parker and Izumi 2000). We will present the dynamics of such granular steps. [1] Mangeney, A., O

  2. Modeling compaction-induced energy dissipation of granular HMX

    Gonthier, K.A. [Lamar Univ., Beaumont, TX (US). Dept. of Mechanical Engineering; Menikoff, R.; Son, S.F.; Asay, B.W. [Los Alamos National Lab., NM (US)

    1998-12-31

    A thermodynamically consistent model is developed for the compaction of granular solids. The model is an extension of the single phase limit of two-phase continuum models used to describe Deflagration-to-Detonation Transition (DDT) experiments. The focus is on the energetics and dissipation of the compaction process. Changes in volume fraction are partitioned into reversible and irreversible components. Unlike conventional DDT models, the model is applicable from the quasi-static to dynamic compaction regimes for elastic, plastic, or brittle materials. When applied to the compaction of granular HMX (a brittle material), the model predicts results commensurate with experiments including stress relaxation, hysteresis, and energy dissipation. The model provides a suitable starting point for the development of thermal energy localization sub-scale models based on compaction-induced dissipation.

  3. Dynamic aerofracture or hydrofracture of dense granular packing: pressure and viscosity control of the fracture patterns

    Niebling, Michael J.; Toussaint, Renaud; Flekkøy, Eirik G.; Jørgen Måløy, Knut

    2013-04-01

    Stress induced by fluid or gases can cause diverse materials to break and fracture. Such hydraulic fractures are a natural and common phenomenon in the field of volcanism and are artificially initiated to enhance the recovery of natural gas and mineral oil by fracturing the reservoir rock with pressurized fluids. A procedure also known as fracking. Recently a new perspective on hydrofractures was added with the storage of supercritical CO2. In this respect two scenarios are considered. First it is one option to inject CO2 into existing hydrofractures, and second the injection of the CO2 can create additional fractures. The typical components for such fractures are a porous material and a compressible gas. The dynamics of such fractures and displacement patterns are simulated and studied in a rectangular Hele-Shaw cell filled with a dense but permeable two-dimensional granular layer. The model used, mixing highly deformable solid and fluid components, can simulate sedimentation problems [1,2], as well as hydrofracture or aerofracture ones. The emerging displacement patterns and fractures variate according to the properties of the injected fluid or gas and the characteristics of the granular phase [3]. The physics behind these variations is discussed and explained. The role of the fluid viscosity and system size shows to lead to a transition from fracturing to compaction, depending on the dynamics of convection versus diffusion of overpressure. The dependence of the obtained patterns on the injection pressure is also explored [4]. References: [1] Niebling, M.J., E.G. Flekkøy, K.J. Måløy, R. Toussaint, Sedimentation instabilities: impact of the fluid compressibility and viscosity, Phys. Rev. E 82, 051302, 2010. doi: 10.1103/PhysRevE.82.051302 [2] Niebling, M.J., E.G. Flekkøy, K.J. Måløy, R. Toussaint, Mixing of a granular layer falling through a fluid, Phys. Rev. E 82, 011301 (2010) doi: 10.1103/PhysRevE.82.011301 [3] Niebling, M., R. Toussaint, E.G. Flekk

  4. Production of high purity granular metals: cadmium, zinc, lead

    Shcherban A. P.

    2017-04-01

    Full Text Available Cadmium, zinc and lead are constituent components of many semiconductor compounds. The obtained high purity distillates and ingots are large-size elements, which is not always convenient to use, and thus require additional grinding, which does not always allow maintaining the purity of the original materials. For the growth of semiconductor and scintillation single crystals it is advisable to use "friable" granular high-purity distillates, which can be processed without the risk of contamination. For example, the European low-background experiment LUCIFER required more than 20 kg of high-purity granulated zinc, which was agreed to be supplied by NSC KIPT. This task was then extended to cadmium and lead. Motivated by these tasks, the authors of this paper propose complex processes of deep refining of cadmium, zinc and lead by vacuum distillation. A device producing granules has been developed. The process of granulation of high-purity metals is explored. The purity of produced granules for cadmium and zinc is >99,9999, and >99,9995% for lead granules. To prevent oxidation of metal granules during exposition to air, chemical methods of surface passivation were used. Organic solvent based on dimethylformamide used as a coolant improves the resistance of granules to atmospheric corrosion during the granulation of high purity Cd, Zn and Pb.

  5. Determination of the attrition resistance of granular charcoals

    Dietz, V.R.

    1979-01-01

    A laboratory procedure has been developed to evaluate the attrition of granular adsorbent charcoals on passing an air flow through the bed. Two factors observed in plant operations were selected as relevant: (1) the characteristic structural vibrations in plant scale equipment (motors, fans, etc.) that are transmitted to charcoal particles and cause the particles to move and rub each other, and (2) the rapid air flow that results in the movement of the attrited dust. In the test a container for charcoal [50 mm diameter and 50 mm high] was vibrated at a frequency of 60 Hz and at a constant energy input manually controlled using a vibration meter in the acceleration mode. Simultaneously, air was applied and exited through glass fiber filter paper. The quantity of dust trapped on the exit filter was then determined, either optically or gravimetrically. The dust formed per minute (attrition coefficient) was found to approach a constant value. The plateau-values from sequential determinations varied with the source of the charcoal; a 5-fold difference was found among a large variety of commercial products. The first testing of a sample released the excess dust accumulated in previous handling of the charcoal. The plateau values were then attained in the succeeding tests and these were characteristic of the material. The results were compared with those obtained for the same charcoals using older test methods such as the Ball and Pan Hardness Test described in RDTM16-1T

  6. Digestion of Alumina from Non-Magnetic Material Obtained from Magnetic Separation of Reduced Iron-Rich Diasporic Bauxite with Sodium Salts

    Guanghui Li

    2016-11-01

    Full Text Available Recovery of iron from iron-rich diasporic bauxite ore via reductive roasting followed by magnetic separation has been explored recently. However, the efficiency of alumina extraction in the non-magnetic materials is absent. In this paper, a further study on the digestion of alumina by the Bayer process from non-magnetic material obtained after magnetic separation of reduced iron-rich diasporic bauxite with sodium salts was investigated. The results indicate that the addition of sodium salts can destroy the original occurrences of iron-, aluminum- and silicon-containing minerals of bauxite ore during reductive roasting. Meanwhile, the reactions of sodium salts with complex aluminum- and silicon-bearing phases generate diaoyudaoite and sodium aluminosilicate. The separation of iron via reductive roasting of bauxite ore with sodium salts followed by magnetic separation improves alumina digestion in the Bayer process. When the alumina-bearing material in bauxite ore is converted into non-magnetic material, the digestion temperature decreases significantly from 280 °C to 240 °C with a nearly 99% relative digestion ratio of alumina.

  7. Extraction of topographic and material contrasts on surfaces from SEM images obtained by energy filtering detection with low-energy primary electrons.

    Nagoshi, Masayasu; Aoyama, Tomohiro; Sato, Kaoru

    2013-01-01

    Secondary electron microscope (SEM) images have been obtained for practical materials using low primary electron energies and an in-lens type annular detector with changing negative bias voltage supplied to a grid placed in front of the detector. The kinetic-energy distribution of the detected electrons was evaluated by the gradient of the bias-energy dependence of the brightness of the images. This is divided into mainly two parts at about 500 V, high and low brightness in the low- and high-energy regions, respectively and shows difference among the surface regions having different composition and topography. The combination of the negative grid bias and the pixel-by-pixel image subtraction provides the band-pass filtered images and extracts the material and topographic information of the specimen surfaces. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. New chemical approach to obtain dense layer phosphate-based ionic conductor coating on negative electrode material surface: Synthesis way, outgassing and improvement of C-rate capability

    Fleutot, Benoit, E-mail: benoit.fleutot@u-picardie.fr [Laboratoire de Réactivité et Chimie des Solides, Université de Picardie Jules Verne, CNRS UMR 7314, 33 rue Saint Leu, 80039 Amiens (France); Réseau sur le Stockage Electrochimique de l’Energie (RS2E), CNRS FR3459 (France); Davoisne, Carine; Gachot, Grégory; Cavalaglio, Sébastien; Grugeon, Sylvie; Viallet, Virginie [Laboratoire de Réactivité et Chimie des Solides, Université de Picardie Jules Verne, CNRS UMR 7314, 33 rue Saint Leu, 80039 Amiens (France); Réseau sur le Stockage Electrochimique de l’Energie (RS2E), CNRS FR3459 (France)

    2017-04-01

    Highlights: • Dense layer coating of based-phosphate ionic conductor obtained by spray-drying. • Influence of dense ionic conductor at the negative surface material on performances. • Impact of dense ionic conductor coating on outgassing phenomena. - Abstract: Li{sub 4}Ti{sub 5}O{sub 12} (LTO) based batteries have severe gassing behavior during charge/discharge and storage process, due to interfacial reactions between active material and electrolyte solution. In the same time, the electronic and ionic conductivity of pristine LTO is very poor and induces the use of nanoparticles which increase the outgassing phenomena. The coating of LTO particles could be a solution. For this the LTO spinel particles are modified with ionic conductor Li{sub 3}PO{sub 4} coating using a spray-drying method. For the first time a homogeneous thin dense layer phosphate based conductor is obtained without nanoparticles, as a thin film material. It is so possible to study the influence of ionic conductor deposited on the negative electrode material on performances by the controlled layer thickness. This coating was characterized by XRD, SEM, XPS and TEM. The electrochemical performance of Li{sub 3}PO{sub 4} coated Li{sub 4}Ti{sub 5}O{sub 12} is improved at high C-rate by the surface modification (improvement of 30 mAh g{sup −1} at 5 C-rate compared to pristine LTO for 5 nm of coating), inducing by a modification of surface energy. An optimum coating thickness was studied. This type of coating allows a significant decrease of outgassing phenomena due the conformal coating and opens the way to a great number of studies and new technologies.

  9. New chemical approach to obtain dense layer phosphate-based ionic conductor coating on negative electrode material surface: Synthesis way, outgassing and improvement of C-rate capability

    Fleutot, Benoit; Davoisne, Carine; Gachot, Grégory; Cavalaglio, Sébastien; Grugeon, Sylvie; Viallet, Virginie

    2017-01-01

    Highlights: • Dense layer coating of based-phosphate ionic conductor obtained by spray-drying. • Influence of dense ionic conductor at the negative surface material on performances. • Impact of dense ionic conductor coating on outgassing phenomena. - Abstract: Li_4Ti_5O_1_2 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process, due to interfacial reactions between active material and electrolyte solution. In the same time, the electronic and ionic conductivity of pristine LTO is very poor and induces the use of nanoparticles which increase the outgassing phenomena. The coating of LTO particles could be a solution. For this the LTO spinel particles are modified with ionic conductor Li_3PO_4 coating using a spray-drying method. For the first time a homogeneous thin dense layer phosphate based conductor is obtained without nanoparticles, as a thin film material. It is so possible to study the influence of ionic conductor deposited on the negative electrode material on performances by the controlled layer thickness. This coating was characterized by XRD, SEM, XPS and TEM. The electrochemical performance of Li_3PO_4 coated Li_4Ti_5O_1_2 is improved at high C-rate by the surface modification (improvement of 30 mAh g"−"1 at 5 C-rate compared to pristine LTO for 5 nm of coating), inducing by a modification of surface energy. An optimum coating thickness was studied. This type of coating allows a significant decrease of outgassing phenomena due the conformal coating and opens the way to a great number of studies and new technologies.

  10. Porous structure and morphology of granular chars from flash and conventional pyrolysis of grape seeds

    Jimenez-Cordero, Diana; Heras, Francisco; Alonso-Morales, Noelia; Gilarranz, Miguel A.; Rodriguez, Juan J.

    2013-01-01

    This work studies the influence of the operating conditions used in the pyrolysis of grape seeds on the morphology and textural properties of the chars resulting. Flash and conventional (283 K min −1 heating rate) pyrolysis have been used within a wide range of temperature (300–1000 °C). The effect of a pretreatment for oil extraction has also been studied. The porous structure of the chars was characterized by adsorption of N 2 at 77 K, Ar at 77 K and 87 K, and CO 2 at 273 K and mercury intrusion porosimetry. The morphology was analyzed by scanning electron microscopy. All the materials prepared revealed an essentially microporous structure, with a poor or even negligible contribution of mesopores. Increasing pyrolysis temperature led to higher specific surface areas and lower pore size. The highest specific surface area values occurred within 700–800 °C, reaching up to 500 m 2 g −1 with pore sizes in the 0.4–1.1 nm range. No significant morphological changes were observed upon carbonization so that the resulting chars were granular materials of similar size than the starting grape seeds. The hollow core structure of the chars, with most of the material allocated at the periphery of the granules can help to overcome the mass transfer limitations of most common (solid or massive) granular activated carbons. The chars showed a good mechanical strength during attrition tests. These chars can be potential candidates for the preparation of granular carbons molecular sieve or activated carbons raw materials. -- Highlights: •We use a raw material that has a very low price and a high availability. •Not very much attention has been paid to this waste for carbonaceous materials preparation. •The chars obtained have high specific surface area that is an interesting starting point for later activation processes. •The chars show a micro-macro porous bimodal distribution. •Pyrolysis does not affect to morphology or initial seed, leading a carbonized

  11. ACTIVATED CARBON (CHARCOAL OBTAINING . APPLICATION

    Florin CIOFU

    2015-05-01

    Full Text Available The activated carbon is a microporous sorbent with a very large adsorption area that can reach in some cases even 1500sqm / gram. Activated carbon is produced from any organic material with high carbon content: coal, wood, peat or moor coal, coconut shells. The granular activated charcoal is most commonly produced by grinding the raw material, adding a suitable binder to provide the desired hardness and shape. Enabling coal is a complete process through which the raw material is fully exposed to temperatures between 600-900 degrees C, in the absence of oxygen, usually in a domestic atmosphere as gases such as nitrogen or argon; as material that results from this process is exposed in an atmosphere of oxygen and steam at a temperature in the interval from 600 - 1200 degrees C.

  12. The Granular Blasius Problem: High inertial number granular flows

    Tsang, Jonathan; Dalziel, Stuart; Vriend, Nathalie

    2017-11-01

    The classical Blasius problem considers the formation of a boundary layer through the change at x = 0 from a free-slip to a no-slip boundary beneath an otherwise steady uniform flow. Discrete particle model (DPM) simulations of granular gravity currents show that a similar phenomenon exists for a steady flow over a uniformly sloped surface that is smooth upstream (allowing slip) but rough downstream (imposing a no-slip condition). The boundary layer is a region of high shear rate and therefore high inertial number I; its dynamics are governed by the asymptotic behaviour of the granular rheology as I -> ∞ . The μ(I) rheology asserts that dμ / dI = O(1 /I2) as I -> ∞ , but current experimental evidence is insufficient to confirm this. We show that `generalised μ(I) rheologies', with different behaviours as I -> ∞ , all permit the formation of a boundary layer. We give approximate solutions for the velocity profile under each rheology. The change in boundary condition considered here mimics more complex topography in which shear stress increases in the streamwise direction (e.g. a curved slope). Such a system would be of interest in avalanche modelling. EPSRC studentship (Tsang) and Royal Society Dorothy Hodgkin Fellowship (Vriend).

  13. New multifunctional materials obtained by the intercalation of anionic dyes into layered zinc hydroxide nitrate followed by dispersion into poly(vinyl alcohol) (PVA).

    Marangoni, Rafael; Ramos, Luiz Pereira; Wypych, Fernando

    2009-02-15

    Different anionic blue and orange dyes have been immobilized on a zinc hydroxide nitrate (Zn(5)(OH)(8)(NO(3))(2)nH(2)O--Zn-OH-NO(3)) by anion exchange with interlayer and/or outer surface nitrate ions of the layered matrix. Orange G (OG) was totally intercalated, orange II (OII) was partially intercalated, while Niagara blue 3B (NB) and Evans blue (EV) were only adsorbed at the outer surface. Several composite films of poly(vinyl alcohol)--PVA were prepared by casting through the dispersion of the hybrid material (Zn-OH-OG) into a PVA aqueous solution and evaporation of water in a vacuum oven. The obtained composite films were transparent, colored, and capable of absorbing UV radiation. Improved mechanical properties were also obtained in relation to the nonfilled PVA films. These results demonstrate the onset of a new range of potential applications for layered hydroxide salts in the preparation of polymer composite multifunctional materials.

  14. Experimental observations of granular debris flows

    Ghilardi, P.

    2003-04-01

    Various tests are run using two different laboratory flumes with rectangular cross section and transparent walls. The grains used in a single experiment have an almost constant grain sizes; mean diameter ranges from 5 mm to 20 mm. In each test various measurements are taken: hydrograms, velocity distribution near the transparent walls and on the free surface, average flow concentration. Concentration values are measured taking samples. Velocity distributions are obtained from movies recorded by high speed video cameras capable of 350 frames per second; flow rates and depth hydrograms are computed from the same velocity distributions. A gate is installed at the beginning of one of the flumes; this gate slides normally to the bed and opens very quickly, reproducing a dam-break. Several tests are run using this device, varying channel slope, sediment concentration, initial mixture thickness before the gate. Velocity distribution in the flume is almost constant from left to right, except for the flow sections near the front. The observed discharges and velocities are less than those given by a classic dam break formula, and depend on sediment concentration. The other flume is fed by a mixture with constant discharge and concentration, and is mainly used for measuring velocity distributions when the flow is uniform, with both rigid and granular bed, and to study erosion/deposition processes near debris flow dams or other mitigation devices. The equilibrium slope of the granular bed is very close to that given by the classical equilibrium formulas for debris flow. Different deposition processes are observed depending on mixture concentration and channel geometry.

  15. Multi-scale mechanics of granular solids from grain-resolved X-ray measurements

    Hurley, R. C.; Hall, S. A.; Wright, J. P.

    2017-11-01

    This work discusses an experimental technique for studying the mechanics of three-dimensional (3D) granular solids. The approach combines 3D X-ray diffraction and X-ray computed tomography to measure grain-resolved strains, kinematics and contact fabric in the bulk of a granular solid, from which continuum strains, grain stresses, interparticle forces and coarse-grained elasto-plastic moduli can be determined. We demonstrate the experimental approach and analysis of selected results on a sample of 1099 stiff, frictional grains undergoing multiple uniaxial compression cycles. We investigate the inter-particle force network, elasto-plastic moduli and associated length scales, reversibility of mechanical responses during cyclic loading, the statistics of microscopic responses and microstructure-property relationships. This work serves to highlight both the fundamental insight into granular mechanics that is furnished by combined X-ray measurements and describes future directions in the field of granular materials that can be pursued with such approaches.

  16. Storage and discharge of a granular fluid

    Pacheco-Martinez, Hector; van Gerner, H.J.; Ruiz-Suarez, J.C.

    2008-01-01

    Experiments and computational simulations are carried out to study the behavior of a granular column in a silo whose walls are able to vibrate horizontally. The column is brought to a steady fluidized state and it behaves similar to a hydrostatic system. We study the dynamics of the granular

  17. Periurethral granular cell tumor: a case report

    Kim, Jeong Kon; Choi, Hyo Gyeong; Cho, Kyoung Sik

    1998-01-01

    Granular cell tumors are uncommon soft tissue tumors which arise as solitary or multiple masses. Lesions commonly arise in the head, neck, and chest wall, but can occur in any part of the body. To our knowledge, periurethral granular cell tumor has not been previously reported. We report one such case

  18. Viscosity evolution of anaerobic granular sludge

    Pevere, A.; Guibaud, G.; Hullebusch, van E.D.; Lens, P.N.L.; Baudu, M.

    2006-01-01

    The evolution of the apparent viscosity at steady shear rate of sieved anaerobic granular sludge (20¿315 ¿m diameter) sampled from different full-scale anaerobic reactors was recorded using rotation tests. The ¿limit viscosity¿ of sieved anaerobic granular sludge was determined from the apparent

  19. Comparative Investigation on the Performance of Modified System Poles and Traditional System Poles Obtained from PDC Data for Diagnosing the Ageing Condition of Transformer Polymer Insulation Materials

    Jiefeng Liu

    2018-02-01

    Full Text Available The life expectancy of a transformer is largely depended on the service life of transformer polymer insulation materials. Nowadays, several papers have reported that the traditional system poles obtained from polarization and depolarization current (PDC data can be used to assess the condition of transformer insulation systems. However, the traditional system poles technique only provides limited ageing information for transformer polymer insulation. In this paper, the modified system poles obtained from PDC data are proposed to assess the ageing condition of transformer polymer insulation. The aim of the work is to focus on reporting a comparative investigation on the performance of modified system poles and traditional system poles for assessing the ageing condition of a transformer polymer insulation system. In the present work, a series of experiments have been performed under controlled laboratory conditions. The PDC measurement data, degree of polymerization (DP and moisture content of the oil-immersed polymer pressboard specimens were carefully monitored. It is observed that, compared to the relationships between traditional system poles and DP values, there are better correlations between the modified system poles and DP values, because the modified system poles can obtain much more ageing information on transformer polymer insulation. Therefore, the modified system poles proposed in the paper are more suitable for the diagnosis of the ageing condition of transformer polymer insulation.

  20. Experimental investigation of the Rowe's dilatancy law on an atypical granular medium from a municipal solid waste incineration bottom ash

    Becquart, Frédéric; Abriak, Nor Edine

    2013-06-01

    Municipal Solid Waste Incineration (MSWI) bottom ashes are irregular granular media because of their origin and are very heterogeneous with a large quantity of angular particles of different chemical species. MSWI bottom ash is a renewable granular resource alternative to the use of non-renewable standard granular materials. Beneficial use of these alternative granular materials mainly lies in road engineering. However, the studies about mechanical properties of such granular media still remain little developed, those being mainly based on empirical considerations. In this paper, a study of mechanical behaviour of a MSWI bottom ash under axisymmetric triaxial loadings conditions is presented. Samples are initially dense after Proctor compaction, are saturated and tested in drained conditions, under different effective confining pressures ranging from 100 to 600 kPa. The evolutions of volumetric strains show an initial contracting phase followed by a dilatancy phase, more pronounced when the confining pressure is low. The stresses ratios at the characteristic state and at the critical state appear in good agreement and with a null rate of volume variation. The angles of internal friction and dilatancy of the studied MSWI bottom ash are estimated and are similar to conventional granular materials used especially in road engineering. The dilatancy law of Rowe is well experimentally verified on this irregular recycled granular material.

  1. Pneumatic fractures in Confined Granular Media

    Eriksen, Fredrik K.; Toussaint, Renaud; Jørgen Måløy, Knut; Grude Flekkøy, Eirik; Turkaya, Semih

    2016-04-01

    We will present our ongoing study of the patterns formed when air flows into a dry, non-cohesive porous medium confined in a horizontal Hele-Shaw cell. This is an optically transparent system consisting of two glass plates separated by 0.5 to 1 mm, containing a packing of dry 80 micron beads in between. The cell is rectangular and has an air-permeable boundary (blocking beads) at one short edge, while the other three edges are completely sealed. The granular medium is loosely packed against the semi-permeable boundary and fills about 80 % of the cell volume. This leaves an empty region at the sealed side, where an inlet allows us to set and maintain the air at a constant overpressure (0.1 - 2 bar). For the air trapped inside the cell to relax its overpressure it has to move through the deformable granular medium. Depending on the applied overpressure and initial density of the medium, we observe a range of different behaviors such as seepage through the pore-network with or without an initial compaction of the solid, formation of low density bubbles with rearrangement of particles, granular fingering/fracturing, and erosion inside formed channels/fractures. The experiments are recorded with a high-speed camera at a framerate of 1000 images/s and a resolution of 1024x1024 pixels. We use various image processing techniques to characterize the evolution of the air invasion patterns and the deformations in the surrounding material. The experiments are similar to deformation processes in porous media which are driven by pore fluid overpressure, such as mud volcanoes and hydraulic or pneumatic (gas-induced) fracturing, and the motivation is to increase the understanding of such processes by optical observations. In addition, this setup is an experimental version of the numerical models analyzed by Niebling et al. [1,2], and is useful for comparison with their results. In a directly related project [3], acoustic emissions from the cell plate are recorded during

  2. Traffic and Granular Flow ’03

    Luding, Stefan; Bovy, Piet; Schreckenberg, Michael; Wolf, Dietrich

    2005-01-01

    These proceedings are the fifth in the series Traffic and Granular Flow, and we hope they will be as useful a reference as their predecessors. Both the realistic modelling of granular media and traffic flow present important challenges at the borderline between physics and engineering, and enormous progress has been made since 1995, when this series started. Still the research on these topics is thriving, so that this book again contains many new results. Some highlights addressed at this conference were the influence of long range electric and magnetic forces and ambient fluids on granular media, new precise traffic measurements, and experiments on the complex decision making of drivers. No doubt the “hot topics” addressed in granular matter research have diverged from those in traffic since the days when the obvious analogies between traffic jams on highways and dissipative clustering in granular flow intrigued both c- munities alike. However, now just this diversity became a stimulating feature of the ...

  3. Centrifuge modelling of granular flows

    Cabrera, Miguel Angel; Wu, Wei

    2015-04-01

    A common characteristic of mass flows like debris flows, rock avalanches and mudflows is that gravity is their main driving force. Gravity defines the intensity and duration of the main interactions between particles and their surrounding media (particle-particle, particle-fluid, fluid-fluid). At the same time, gravity delimits the occurrence of phase separation, inverse segregation, and mass consolidation, among other phenomena. Therefore, in the understanding of the flow physics it is important to account for the scaling of gravity in scaled models. In this research, a centrifuge model is developed to model free surface granular flows down an incline at controlled gravity conditions. Gravity is controlled by the action of an induced inertial acceleration field resulting from the rotation of the model in a geotechnical centrifuge. The characteristics of the induced inertial acceleration field during flow are discussed and validated via experimental data. Flow heights, velocity fields, basal pressure and impact forces are measured for a range of channel inclinations and gravity conditions. Preliminary results enlighten the flow characteristics at variable gravity conditions and open a discussion on the simulation of large scale processes at a laboratory scale. Further analysis on the flow physics brings valuable information for the validation of granular flows rheology.

  4. Blurring the boundary between rapid granular flow and dense granular flow regimes: Evidence from DEM simulations

    Tripathi, Anurag; Prasad, Mahesh; Kumar, Puneet

    2017-11-01

    The saturation of the effective friction coefficient for granular flows at high inertial numbers has been assumed widely by researchers, despite little simulation/experimental evidence. In contrast, a recent simulation study of plane shear flows by Mandal and Khakhar, suggests that the effective friction coefficient becomes maximum and then starts to decrease with increase in the inertial number for I > 0.5 . In order to investigate whether such a dip at higher inertial numbers is indeed a feature of granular rheology, we perform DEM simulations of chute flow of highly inelastic disks. We show that steady, fully developed flows are possible at inclinations much higher than those normally reported in literature. At such high inclinations, the flow is characterised by a significant slip at the base; the height of the layer increases by more than 300 % and kinetic energy of the layer increases by nearly 5 orders of magnitude. We observe, for the first time, steady chute flows at inertial number I 2 and show that the dip at higher inertial numbers can be observed in case of chute flow as well. The predictions of modified μ - I rheology, however, seem to remain valid in the bulk of the layer for packing fractions as low as 0.2. AT acknowledges the funding obtained from IIT Kanpur through the initiation Grant for this study.

  5. On creating macroscopically identical granular systems with different numbers of particles

    van der Meer, Devaraj; Rivas, Nicolas

    2015-11-01

    One of the fundamental differences between granular and molecular hydrodynamics is the enormous difference in the total number of constituents. The small number of particles implies that the role of fluctuations in granular dynamics is of paramount importance. To obtain more insight in these fluctuations, we investigate to what extent it is possible to create identical granular hydrodynamic states with different number of particles. A definition is given of macroscopically equivalent systems, and the dependency of the conservation equations on the particle size is studied. We show that, in certain cases, and by appropriately scaling the microscopic variables, we are able to compare systems with significantly different number of particles that present the same macroscopic phenomenology. We apply these scalings in simulations of a vertically vibrated system, namely the density inverted granular Leidenfrost state and its transition to a buoyancy-driven convective state.

  6. Fuel micro-mechanics: homogenization, cracking, granular media

    Monerie, Yann

    2010-01-01

    This work summarizes about fifteen years of research in the field of micro-mechanics of materials. Emphasis is placed on the most recent work carried out in the context of nuclear safety. Micro-mechanics finds a natural place there, aiming to predict the behavior of heterogeneous materials with an evolving microstructure. The applications concerned mainly involve the nuclear fuel and its tubular cladding. The uranium dioxide fuel is modeled, according to the scales under consideration, as a porous ceramic or a granular medium. The strongly irradiated Zircaloy claddings are identified with a composite medium with a metal matrix and a gradient of properties. The analysis of these classes of material is rich in problems of a more fundamental nature. Three main themes are discussed: 1/ Homogenization, 2/ cracking, rupture and fragmentation, 3/ discrete media and fluid-grain couplings. Homogenization: The analytical scale change methods proposed aim to estimate or limit the linear and equivalent nonlinear behaviors of isotropic porous media and anisotropic composites with a metal matrix. The porous media under consideration are saturated or drained, with a compressible or incompressible matrix, and have one or two scales of spherical or ellipsoid pores, or cracks. The composites studied have a macroscopic anisotropy related to that of the matrix, and to the shape and spatial distribution of the inclusions. Thermoelastic, elastoplastic, and viscoplastic behaviors and ductile damage of these media are examined using different techniques: extensions of classic approaches, linear in particular, variational approaches and approaches using elliptical potentials with thermally activated elementary mechanisms. The models developed are validated on numerical finite element simulations, and their functional relevance is illustrated in comparison to experimental data obtained from the literature. The significant results obtained include a plasticity criterion for Gurson matrix

  7. Granular starch hydrolysis for fuel ethanol production

    Wang, Ping

    addition were evaluated in the dry grind process using GSHE (GSH process). Addition of proteases resulted in higher ethanol concentrations (15.2 to 18.0% v/v) and lower (DDGS) yields (32.9 to 45.8% db) compared to the control (no protease addition). As level of proteases and GSHE increased, ethanol concentrations increased and DDGS yields decreased. Proteases addition reduced required GSHE dose. Ethanol concentrations with protease addition alone were higher than with urea or with addition of both protease and urea. Corn endosperm consists of soft and hard endosperm. More exposed starch granules and rough surfaces produced from soft endosperm compared to hard endosperm will create more surface area which will benefit the solid phase hydrolysis as used in GSH process. In this study, the effects of protease, urea, endosperm hardness and GSHE levels on the GSH process were evaluated. Soft and hard endosperm materials were obtained by grinding and sifting flaking grits from dry milling pilot plant. Soft endosperm resulted in higher ethanol concentrations (at 72 hr) compared to ground corn or hard endosperm. Addition of urea increased ethanol concentrations (at 72 hr) for soft and hard endosperm. The effect of protease addition on increasing ethanol concentrations and fermentation rates was more predominant for soft endosperm, less for hard endosperm and least for ground corn. The GSH process with protease resulted in higher ethanol concentration than that with urea. For fermentation of soft endosperm, GSHE dose can be reduced. Ground corn fermented faster at the beginning than hard and soft endosperm due to the presence of inherent nutrients which enhanced yeast growth.

  8. Ceramic Materials in a Ti–C–Co–Ca3(PO42–Ag–Mg System Obtained by MA SHS for the Deposition of Biomedical Coatings

    Artem Potanin

    2017-09-01

    Full Text Available This study aimed to obtain biocompatible ceramic materials in a Ti–C–Co–Ca3(PO42–Ag–Mg system by the combustion mode of mechanically activated (MA reaction mixtures. The influence of the MA time on the reaction ability capability of the mixtures, on their structural and chemical homogeneity, on the combustion parameters and structural-phase conversions in the combustion wave, as well as on the structure and phase composition of the electrode materials has been researched. It was found that the intense treatment of powder mixtures causes plastic deformation of components, the formation of lamellar composite granules, a reduction in the sizes of coherent scattering regions, and also the formation of minor amounts of products. The influence of the activation duration of the ignition temperature and heat release during the combustion of the reaction mixtures was studied. By the method of quenching the combustion front, it was demonstrated that in a combustion wave, chemical transformations occur within the lamellar structures formed during the process of mechanoactivation. It was shown that in the combustion wave, parallel chemical reactions of Ti with C as well as Ti with Co and Ca3(PO42 occur, with a Ti–Co-based melt forming the reaction surface. Ceramic electrodes with different contents of Ag and Mg were synthesized by force self-propagating high-temperature synthesis (SHS-pressing technology using the MA mixtures. The microstructure of the materials consisted of round-shaped grains of nonstoichiometric titanium carbide TiCx grains, intermetallic matrix (TiCo, TiCo2, CoTiP, inclusions of Ca and Mg oxides, and grains of the Ag-based solid solution. An increased content of Ag and Mg in the composition of the electrodes, as well as an increased MA duration, leads to an enlargement of the inclusions of the Ag-containing phase size and deterioration in the uniformity of their distribution.

  9. Efficient blue-green and green electroluminescent devices obtained by doping iridium complexes into hole-block material as supplementary light-emitting layer

    Zhou, Liang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zheng, Youxuan, E-mail: yxzheng@mail.nju.edu.cn [State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Deng, Ruiping; Feng, Jing; Song, Mingxing; Hao, Zhaomin [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhang, Hongjie, E-mail: hongjie@ciac.jl.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zuo, Jinglin; You, Xiaozeng [State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

    2014-04-15

    In this work, organic electroluminescent (EL) devices with dominant and supplementary light-emitting layers (EMLs) were designed to further improve the EL performances of two iridium{sup III}-based phosphorescent complexes, which have been reported to provide EL devices with slow EL efficiency roll-off. The widely used hole-block material 2,2′,2''-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) was selected as host material to construct the supplementary EML. Compared with single-EML devices, double-EMLs devices showed higher EL efficiencies, higher brightness, and lower operation voltage attributed to wider recombination zone and better balance of carriers. In addition, the insertion of supplementary EML is instrumental in facilitating carriers trapping, thus improving the color purity. Finally, high performance blue-green and green EL devices with maximum current efficiencies of 35.22 and 90.68 cd/A, maximum power efficiencies of 26.36 and 98.18 lm/W, and maximum brightness of 56,678 and 112,352 cd/m{sup 2}, respectively, were obtained by optimizing the doping concentrations. Such a device design strategy extends the application of a double EML device structure and provides a chance to simplify device fabrication processes. -- Highlights: • Electroluminescent devices with supplementary light-emitting layer were fabricated. • Doping concentrations and thicknesses were optimized. • Better balance of holes and electrons causes the enhanced efficiency. • Improved carrier trapping suppresses the emission of host material.

  10. Freely cooling granular gases with short-ranged attractive potentials

    Murphy, Eric; Subramaniam, Shankar, E-mail: shankar@iastate.edu [Department of Mechanical Engineering, Center for Multiphase Flow Research, Iowa State University, Ames, Iowa 50011 (United States)

    2015-04-15

    We treat the case of an undriven gas of inelastic hard-spheres with short-ranged attractive potentials via an extension of the pseudo-Liouville operator formalism. New evolution equations for the granular temperature and coordination number are obtained. The granular temperature exhibits deviation from both Haff’s law and the case of long-ranged potentials. We verify this departure using soft-sphere discrete element method simulations. Excellent agreement is found for the duration of the simulation even beyond where exclusively binary collisions are expected. Simulations show the emergence of strong spatial-velocity correlations on the length scale of the last peak in the pair-correlation function but do not show strong correlations beyond this length scale. We argue that molecular chaos may remain an adequate approximation if the system is modelled as a Smoluchowski type equation with aggregation and break-up processes.

  11. Effect of powder sample granularity on fluorescent intensity and on thermal parameters in x-ray diffraction Rietveld analysis

    Sparks, C.J.; Specht, E.D.; Ice, G.E.; Kumar, R.; Zschack, P.; Shiraishi, T.; Hisatsune, K.

    1991-01-01

    The effect of sample granularity on diffracted x-ray intensity was evaluated by measuring the 2θ dependence of x-ray fluorescence from various samples. Measurements were made in the symmetric geometry on samples ranging from single crystals to highly absorbing coarse powders. A characteristic shape for the absorption correction was observed. A demonstration of the sensitivity of Rietveld refined site occupation parameters is made on CuAu and Cu 50 Au 44 Ni 6 alloys refined with and without granularity corrections. These alloys provide a good example of the effect of granularity due to their large linear x-ray absorption coefficients. Sample granularity and refined thermal parameters obtained from the Rietveld analysis were found to be correlated. Without a granularity correction, the refined thermal parameters are too low and can actually become negative in an attempt to compensate for granularity. A general shape for granularity correction can be included in refinement procedures. If no granularity correction is included, data should be restricted to above 30 degrees 2θ, and thermal parameters should be ignored unless extreme precautions are taken to produce >5 μm particles and high packing densities

  12. The Stability Analysis Method of the Cohesive Granular Slope on the Basis of Graph Theory.

    Guan, Yanpeng; Liu, Xiaoli; Wang, Enzhi; Wang, Sijing

    2017-02-27

    This paper attempted to provide a method to calculate progressive failure of the cohesivefrictional granular geomaterial and the spatial distribution of the stability of the cohesive granular slope. The methodology can be divided into two parts: the characterization method of macro-contact and the analysis of the slope stability. Based on the graph theory, the vertexes, the edges and the edge sequences are abstracted out to characterize the voids, the particle contact and the macro-contact, respectively, bridging the gap between the mesoscopic and macro scales of granular materials. This paper adopts this characterization method to extract a graph from a granular slope and characterize the macro sliding surface, then the weighted graph is analyzed to calculate the slope safety factor. Each edge has three weights representing the sliding moment, the anti-sliding moment and the braking index of contact-bond, respectively, . The safety factor of the slope is calculated by presupposing a certain number of sliding routes and reducing Weight repeatedly and counting the mesoscopic failure of the edge. It is a kind of slope analysis method from mesoscopic perspective so it can present more detail of the mesoscopic property of the granular slope. In the respect of macro scale, the spatial distribution of the stability of the granular slope is in agreement with the theoretical solution.

  13. Analytical and Computational Modeling of Mechanical Waves in Microscale Granular Crystals: Nonlinearity and Rotational Dynamics

    Wallen, Samuel P.

    Granular media are one of the most common, yet least understood forms of matter on earth. The difficulties in understanding the physics of granular media stem from the fact that they are typically heterogeneous and highly disordered, and the grains interact via nonlinear contact forces. Historically, one approach to reducing these complexities and gaining new insight has been the study of granular crystals, which are ordered arrays of similarly-shaped particles (typically spheres) in Hertzian contact. Using this setting, past works explored the rich nonlinear dynamics stemming from contact forces, and proposed avenues where such granular crystals could form designer, dynamically responsive materials, which yield beneficial functionality in dynamic regimes. In recent years, the combination of self-assembly fabrication methods and laser ultrasonic experimental characterization have enabled the study of granular crystals at microscale. While our intuition may suggest that these microscale granular crystals are simply scaled-down versions of their macroscale counterparts, in fact, the relevant physics change drastically; for example, short-range adhesive forces between particles, which are negligible at macroscale, are several orders of magnitude stronger than gravity at microscale. In this thesis, we present recent advances in analytical and computational modeling of microscale granular crystals, in particular concerning the interplay of nonlinearity, shear interactions, and particle rotations, which have previously been either absent, or included separately at macroscale. Drawing inspiration from past works on phononic crystals and nonlinear lattices, we explore problems involving locally-resonant metamaterials, nonlinear localized modes, amplitude-dependent energy partition, and other rich dynamical phenomena. This work enhances our understanding of microscale granular media, which may find applicability in fields such as ultrasonic wave tailoring, signal processing

  14. Storage and discharge of a granular fluid.

    Pacheco-Martinez, Hector; van Gerner, Henk Jan; Ruiz-Suárez, J C

    2008-02-01

    Experiments and computational simulations are carried out to study the behavior of a granular column in a silo whose walls are able to vibrate horizontally. The column is brought to a steady fluidized state and it behaves similar to a hydrostatic system. We study the dynamics of the granular discharge through openings at the bottom of the silo in order to search for a Torricelli-like behavior. We show that the flow rate scales with the wall induced shear rate, and at high rates, the granular bed indeed discharges similar to a viscous fluid.

  15. Energy decay in a granular gas collapse

    Almazán, Lidia; Serero, Dan; Pöschel, Thorsten; Salueña, Clara

    2017-01-01

    An inelastic hard ball bouncing repeatedly off the ground comes to rest in finite time by performing an infinite number of collisions. Similarly, a granular gas under the influence of external gravity, condenses at the bottom of the confinement due to inelastic collisions. By means of hydrodynamical simulations, we find that the condensation process of a granular gas reveals a similar dynamics as the bouncing ball. Our result is in agreement with both experiments and particle simulations, but disagrees with earlier simplified hydrodynamical description. Analyzing the result in detail, we find that the adequate modeling of pressure plays a key role in continuum modeling of granular matter. (paper)

  16. On inconsistency in frictional granular systems

    Alart, Pierre; Renouf, Mathieu

    2018-04-01

    Numerical simulation of granular systems is often based on a discrete element method. The nonsmooth contact dynamics approach can be used to solve a broad range of granular problems, especially involving rigid bodies. However, difficulties could be encountered and hamper successful completion of some simulations. The slow convergence of the nonsmooth solver may sometimes be attributed to an ill-conditioned system, but the convergence may also fail. The prime aim of the present study was to identify situations that hamper the consistency of the mathematical problem to solve. Some simple granular systems were investigated in detail while reviewing and applying the related theoretical results. A practical alternative is briefly analyzed and tested.

  17. Shock waves in weakly compressed granular media.

    van den Wildenberg, Siet; van Loo, Rogier; van Hecke, Martin

    2013-11-22

    We experimentally probe nonlinear wave propagation in weakly compressed granular media and observe a crossover from quasilinear sound waves at low impact to shock waves at high impact. We show that this crossover impact grows with the confining pressure P0, whereas the shock wave speed is independent of P0-two hallmarks of granular shocks predicted recently. The shocks exhibit surprising power law attenuation, which we model with a logarithmic law implying that shock dissipation is weak and qualitatively different from other granular dissipation mechanisms. We show that elastic and potential energy balance in the leading part of the shocks.

  18. Granular-relational data mining how to mine relational data in the paradigm of granular computing ?

    Hońko, Piotr

    2017-01-01

    This book provides two general granular computing approaches to mining relational data, the first of which uses abstract descriptions of relational objects to build their granular representation, while the second extends existing granular data mining solutions to a relational case. Both approaches make it possible to perform and improve popular data mining tasks such as classification, clustering, and association discovery. How can different relational data mining tasks best be unified? How can the construction process of relational patterns be simplified? How can richer knowledge from relational data be discovered? All these questions can be answered in the same way: by mining relational data in the paradigm of granular computing! This book will allow readers with previous experience in the field of relational data mining to discover the many benefits of its granular perspective. In turn, those readers familiar with the paradigm of granular computing will find valuable insights on its application to mining r...

  19. Adsorption of Volatile Organic Compounds from Aqueous Solution by Granular Activated Carbon in Batch System

    Zeinali, F.; Ghoreyshi, A. A.; Najafpour, G.

    2011-01-01

    Chlorinated hydrocarbons and aromatics are the major volatile organic compounds that contaminate the ground water and industrial waste waters. The best way to overcome this problem is to recover the dissolved compounds in water. In order to evaluate the potential ability of granular activated carbon for recovery of volatile organic compounds from water, the equilibrium adsorption was investigated. This study deals with the adsorption of dichloromethane as a typical chlorinated volatile organic compound and toluene as the representative of aromatic volatile organic compounds on a commercial granular activated carbon. The adsorption isotherms of these two volatile organic compounds on granular activated carbon were measured at three different temperatures, toluene at 293, 303 and 313 K and dichloromethane at 298, 303 and 313 K within their solubility concentration range in water. The maximum adsorption capacity of dichloromethane and toluene adsorption by granular activated carbon was 4 and 0.2 mol/Kg-1, respectively. The experimental data obtained were correlated with different adsorption isotherm models. The Langmuir model was well adapted to the description of dichloromethane adsorption on granular activated carbon at all three temperatures, while the adsorption of toluene on granular activated carbon was found to be well described by the Langmuir-BET hybrid model at all three temperatures. The heat of adsorption was also calculated based on the thermodynamic equation of Clausius Clapeyron, which indicates the adsorption process is endothermic for both compounds.

  20. Sidewall-friction-driven ordering transition in granular channel flows: Implications for granular rheology

    Mandal, Sandip; Khakhar, D. V.

    2017-11-01

    We report a transition from a disordered state to an ordered state in the flow of nearly monodisperse granular matter flowing in an inclined channel with planar slide walls and a bumpy base, using discrete element method simulations. For low particle-sidewall friction coefficients, the flowing particles are disordered, however, for high sidewall friction, an ordered state is obtained, characterized by a layering of the particles and hexagonal packing of the particles in each layer. The extent of ordering, quantified by the local bond-orientational order parameter, varies in the cross section of the channel, with the highest ordering near the sidewalls. The flow transition significantly affects the local rheology—the effective friction coefficient is lower, and the packing fraction is higher, in the ordered state compared to the disordered state. A simple model, incorporating the extent of local ordering, is shown to describe the rheology of the system.

  1. Sidewall-friction-driven ordering transition in granular channel flows: Implications for granular rheology.

    Mandal, Sandip; Khakhar, D V

    2017-11-01

    We report a transition from a disordered state to an ordered state in the flow of nearly monodisperse granular matter flowing in an inclined channel with planar slide walls and a bumpy base, using discrete element method simulations. For low particle-sidewall friction coefficients, the flowing particles are disordered, however, for high sidewall friction, an ordered state is obtained, characterized by a layering of the particles and hexagonal packing of the particles in each layer. The extent of ordering, quantified by the local bond-orientational order parameter, varies in the cross section of the channel, with the highest ordering near the sidewalls. The flow transition significantly affects the local rheology-the effective friction coefficient is lower, and the packing fraction is higher, in the ordered state compared to the disordered state. A simple model, incorporating the extent of local ordering, is shown to describe the rheology of the system.

  2. Recent advances in understanding deformation and flow of granular matter

    Mesarović Siniša Đ.

    2014-01-01

    Full Text Available By means of graph theory, we analyze the changes in topology of a granular assembly during deformation. The elementary mechanism of diffuse deformation consists of intermittent flips. We show that dilatancy is the direct result of: an increasing number of flips, and, elastic relaxation of particles upon flips. Both are dependent on particles' elastic potential energy prior to flip and after the flip. The latter is the result of non uniform distribution of interparticle forces in force chains. Next, we consider shear bands in granular materials. Formation of shear bands is accompanied by accompanied by massive rolling of particle. Since rolling is constrained by neighbors, a characteristic rolling correlation length appears. The transmission of rotations in a particular direction depends on the strength of the force chain branches in the direction of propagation and across. The maximum propagation distance is comparable to observed widths of shear bands. Finally, we turn to the question of vortex formation within shear bands and argue that vortex pattern minimizes the dissipation/resistance in granular fluid.

  3. Fragility and hysteretic creep in frictional granular jamming.

    Bandi, M M; Rivera, M K; Krzakala, F; Ecke, R E

    2013-04-01

    The granular jamming transition is experimentally investigated in a two-dimensional system of frictional, bidispersed disks subject to quasistatic, uniaxial compression without vibrational disturbances (zero granular temperature). Three primary results are presented in this experimental study. First, using disks with different static friction coefficients (μ), we experimentally verify numerical results that predict jamming onset at progressively lower packing fractions with increasing friction. Second, we show that the first compression cycle measurably differs from subsequent cycles. The first cycle is fragile-a metastable configuration with simultaneous jammed and unjammed clusters-over a small packing fraction interval (φ(1)disk displacements over the same packing fraction interval. This fragile behavior is explained through a percolation mechanism of stressed contacts where cluster growth exhibits spatial correlation with disk displacements and contributes to recent results emphasizing fragility in frictional jamming. Control experiments show that the fragile state results from the experimental incompatibility between the requirements for zero friction and zero granular temperature. Measurements with several disk materials of varying elastic moduli E and friction coefficients μ show that friction directly controls the start of the fragile state but indirectly controls the exponential pressure rise. Finally, under repetitive loading (compression) and unloading (decompression), we find the system exhibits pressure hysteresis, and the critical packing fraction φ(c) increases slowly with repetition number. This friction-induced hysteretic creep is interpreted as the granular pack's evolution from a metastable to an eventual structurally stable configuration. It is shown to depend on the quasistatic step size Δφ, which provides the only perturbative mechanism in the experimental protocol, and the friction coefficient μ, which acts to stabilize the pack.

  4. Harmonic response of coupled and uncoupled granular YBCO

    Torralba, Maria Veronica S; Sarmago, Roland V

    2004-01-01

    The harmonic responses of granular YBCO were obtained via mutual inductance measurements. Two samples, one with and another without intergranular coupling, were investigated in terms of the harmonic components of magnetization at various field amplitudes and frequencies. By comparing the behaviour of the features in the harmonics to that of the peaks in the fundamental response, we explicitly identified which features in the harmonics originate from intragranular harmonic generation and which arise due to a contribution of intergranular coupling. Harmonic responses were obtained despite the absence of vortices and even harmonics were detected in a purely AC magnetic field

  5. Obtaining a glass-ceramic material from a steel slag mixed with glass cullet; Obtencion de un material vitroceramico a partir de una escoria de aceria mezclada con vidrio de desecho

    Oziel Mendez Guerrero, D.; Alicia Vazquez Mendez, B.; Alvarez Mendez, A.

    2011-07-01

    In this paper, the qualitative, quantitative and thermal characterization of a steel slag and glass cullet of high generation rate in northern Mexico were made in order to use these wastes as raw materials in the production of glass ceramics. The particle size was controlled at sizes = 75 micrometers and the major components of the slag were located in a phase equilibrium diagram for proposing a reaction temperature that leaded to the starting glass. Later, heat treatments were performed to obtain the glass ceramics. The materials were characterized by powder X-ray diffraction (XRD), differential thermal analysis coupled with thermal gravimetric analysis (DTA-TGA), reflected light optical microscopy (RLOM) and scanning electron microscopy (SEM). Subsequently, Vickers microhardness and chemical resistance tests were performed, which enabled us to propose an application of the glass ceramics. (Author) 18 refs.

  6. Granular filtration for airborne particles : correlation between experiments and models

    Golshahi, L.; Tan, Z. [Calgary Univ., AB (Canada). Schulich School of Engineering, Mechanical and Manufacturing Dept.; Abedi, J. [Calgary Univ., AB (Canada). Schulich School of Engineering, Chemical and Petroleum Engineering Dept.

    2009-10-15

    A new design for a packed bed granular filter was presented. The cylindrical packed bed was designed to filter particles in the range of approximately 10 nm to 15 {mu}m in diameter in different kinetic conditions and configurations. The aim of the study was to develop a precise empirical model to predict the filtration efficiency of the packed beds. A collision-type atomizer was used to generate polydisperse sodium chloride aerosol particles. The effect of flow rates was studied using a thermal mass flow meter. A regression analysis technique was used to determine the correlation between single granule and total packed bed efficiency for the entire granular filter. The experimental data were then compared with results obtained from the theoretical analysis. The least square method was used to correlate experimental data and to develop generalized equations for single granule efficiency. The study showed that the granular filter media has a high filtration efficiency for both micron and submicron particles. It was concluded that the effect of media thickness was more significant at higher flow rates than at lower flow rates. 10 refs., 3 figs.

  7. Investigations on a hybrid positron source with a granular converter

    Artru, X. [Institut de Physique Nucleaire de Lyon, Universite Lyon 1, CNRS/IN2P3, Villeurbanne (France); Chaikovska, I. [Laboratoire de l’Accelerateur Lineaire (LAL), Universite Paris-Sud, Bat. 200, 91898 Orsay (France); Chehab, R., E-mail: chehab@lal.in2p3.fr [Institut de Physique Nucleaire de Lyon, Universite Lyon 1, CNRS/IN2P3, Villeurbanne (France); Chevallier, M. [Institut de Physique Nucleaire de Lyon, Universite Lyon 1, CNRS/IN2P3, Villeurbanne (France); Dadoun, O. [Laboratoire de l’Accelerateur Lineaire (LAL), Universite Paris-Sud, Bat. 200, 91898 Orsay (France); Furukawa, K. [Accelerator Laboratory (KEK), Oho, Tsukuba, Ibaraki 305-0801 (Japan); Guler, H. [Laboratoire de l’Accelerateur Lineaire (LAL), Universite Paris-Sud, Bat. 200, 91898 Orsay (France); Kamitani, T.; Miyahara, F.; Satoh, M. [Accelerator Laboratory (KEK), Oho, Tsukuba, Ibaraki 305-0801 (Japan); Sievers, P. [CERN, Geneva (Switzerland); Suwada, T.; Umemori, K. [Accelerator Laboratory (KEK), Oho, Tsukuba, Ibaraki 305-0801 (Japan); Variola, A. [Laboratoire de l’Accelerateur Lineaire (LAL), Universite Paris-Sud, Bat. 200, 91898 Orsay (France)

    2015-07-15

    Promising results obtained with crystal targets for positron production led to the elaboration of a hybrid source made of an axially oriented tungsten crystal, as a radiator, and an amorphous tungsten converter. If the converter is granular, made of small spheres, the heat dissipation is greatly enhanced and the thermal shocks reduced, allowing the consideration of such device for the future linear colliders. A positron source of this kind is investigated. Previous simulations have shown very promising results for the yield as for the energy deposition and the PEDD (Peak Energy Deposition Density). Here, we present detailed simulations made in this granular converter with emphasis on the energy deposition density, which is a critical parameter as learned from the breakdown of the SLC target. A test on the KEKB linac is foreseen; it will allow a determination of the energy deposited and the PEDD in the converter through temperature measurements. Four granular converters, made of W spheres of mm radius have been built at LAL-Orsay; they will be installed at KEK and compared to compact converters. A description of the experimental layout at KEK is provided. Applications to future linear colliders as CLIC and ILC are considered.

  8. Mechanical and trybological characterization of ceramic materials obtained of mine solid wastes; Caracterizacion mecanica y tribologica de materiales ceramicos obtenidos de residuos solidos mineros

    Soto T, J.L

    2003-07-01

    A discussion of the physical, mechanical and tribological characterization of the ceramics Jaar, Jaca and Vijaar is presented in this work. They have been obtained from the industrial residuals, coming from metals and sand of the mining industry in Pachuca Hidalgo, Mexico. The methodology followed for the obtention and characterization of these ceramics consists on eliminating the cyanides from the tailings through columns coupled with a system controlled with thermostats. Then, the chemical composition is analysed with spectrometry emission of plasma and scanning electronic microscopy. Then the ceramics are produced. The base material is agglutinated with clay or kaolin. For this purpose, it was used a sintering processes and isothermal compacting in hot condition. Finally, the physical, chemical, mechanical and tribological properties of these new products are determined. Carbon, oxygen, sodium, magnesium, aluminium, manganese, silicon, potassium, phosphor, calcium, titanium, iron, molybdenum, silver and gold are in the chemical composition or ceramic analysed. Also these are heterogeneous mixture of clay and kaolin. The cyanide was eliminated. The results show that Vijaar has better wear resistances to the waste; this was demonstrated in tribology tests. They were not perforated with the abrasive particles. Also, they have high hardness and they can to support more loads in compression than Jaar and the Jaca. Consequently, they are less fragile and, therefore, they can tolerate bending stresses and bigger impact loading. (Author)

  9. Stages of destruction and elastic compression of granular nanoporous carbon medium at high pressures

    Neklyudov, I.M.; Ledenyov, O.P.; Bobrova, N.B.; Chupikov, A.A.

    2015-01-01

    The granular nanoporous carbon medium, made of the cylindrical coal granules of the adsorbent of CKT-3, at an influence by the high pressures from 1 MPa to 3 GPa has been researched. The eight consecutive stages of the material's specific volume change, which is characterized by a certain dependence of the volume change on the pressure change, have been registered. It is shown that there is a linear dependence on the double log-log plot of the material's specific volume change on the pressure for an every stage of considered process. The two stages are clearly distinguished: a stage of material's mechanical destruction, and a stage of elastic compression of material without the disintegration of structure at a nano-scale. The hysteresis dependence of the material's specific volume change on the pressure change at the pressure decrease is observed. The small disperse coal dust particles jettisoning between the high pressure cell and the base plate was observed, resulting in the elastic stress reduction in relation to the small disperse coal dust particles volume. The obtained research data can be used to improve the designs of air filters for the radioactive chemical elements absorption at the NPP with the aims to protect the environment

  10. Spatial correlations in compressible granular flows

    van Noije, T.P.C.; Ernst, M.H.; Brito, R.

    The clustering instability in freely evolving granular fluids manifests itself in the density-density correlation function and structure factor. These functions are calculated from fluctuating hydrodynamics. As time increases, the structure factor of density fluctuations develops a maximum, which

  11. Granular Gases: Probing the Boundaries of Hydrodynamics

    Goldhirsch, I.

    1999-01-01

    The dissipative nature of the particle interactions in granular systems renders granular gases mesoscopic and bearing some similarities to regular gases in the ''continuum transition regime'' where shear rates and/or thermal gradients are very large). The following properties of granular gases support the above claim: (i). Mean free times are of the same order as macroscopic time scales (inverse shear rates); (ii). Mean free paths can be macroscopic and comparable to the system's dimensions; (iii). Typical flows are supersonic; (iv). Shear rates are typically ''large''; (v). Stress fields are scale (resolution) dependent; (vi). Burnett and super-Burnett corrections to both the constitutive relations and the boundary conditions are of importance; (vii). Single particle distribution functions can be far from Gaussian. It is concluded that while hydrodynamic descriptions of granular gases are relevant, they are probing the boundaries of applicability of hydrodynamics and perhaps slightly beyond

  12. Resistance capability of microaerobic granular sludge for ...

    enoh

    2012-02-08

    Feb 8, 2012 ... The resistance capability to pH shock of microaerobic granular sludge for pentachlorophenol (PCP) ... process with chlorine gas in pulp and paper, leather and spinning ... nitrifying bacteria in the aerobic zone, and then trans-.

  13. Microbiological aspects of granular methanogenic sludge

    Dolfing, J.

    1987-01-01

    The settling characteristics of anaerobic sludge are enhanced by the formation of microbial conglomerates. Various types of conglomerates having different structures, were distinguished in the present study, viz. granules, pellets and flocs (chapter 1). Granular methanogenic sludge, often

  14. Uniform shock waves in disordered granular matter.

    Gómez, Leopoldo R; Turner, Ari M; Vitelli, Vincenzo

    2012-10-01

    The confining pressure P is perhaps the most important parameter controlling the properties of granular matter. Strongly compressed granular media are, in many respects, simple solids in which elastic perturbations travel as ordinary phonons. However, the speed of sound in granular aggregates continuously decreases as the confining pressure decreases, completely vanishing at the jamming-unjamming transition. This anomalous behavior suggests that the transport of energy at low pressures should not be dominated by phonons. In this work we use simulations and theory to show how the response of granular systems becomes increasingly nonlinear as pressure decreases. In the low-pressure regime the elastic energy is found to be mainly transported through nonlinear waves and shocks. We numerically characterize the propagation speed, shape, and stability of these shocks and model the dependence of the shock speed on pressure and impact intensity by a simple analytical approach.

  15. Kinetic Theory of Granular Gases

    Trizac, Emmanuel [Center of Theoretical Biological Physics, UC San Diego, La Jolla, CA 92093-0374 (United States); Laboratoire de Physique Theorique et Modeles Statistiques, Campus Universitaire, 91405 Orsay (France)

    2005-11-25

    Granular gases are composed of macroscopic bodies kept in motion by an external energy source such as a violent shaking. The behaviour of such systems is quantitatively different from that of ordinary molecular gases: due to the size of the constituents, external fields have a stronger effect on the dynamics and, more importantly, the kinetic energy of the gas is no longer a conserved quantity. The key role of the inelasticity of collisions has been correctly appreciated for about fifteen years, and the ensuing consequences in terms of phase behaviour or transport properties studied in an increasing and now vast body of literature. The purpose of this book is to help the newcomer to the field in acquiring the essential theoretical tools together with some numerical techniques. As emphasized by the authors-who were among the pioneers in the domain- the content could be covered in a one semester course for advanced undergraduates, or it could be incorporated in a more general course dealing with the statistical mechanics of dissipative systems. The book is self-contained, clear, and avoids mathematical complications. In order to elucidate the main physical ideas, heuristic points of views are sometimes preferred to a more rigorous route that would lead to a longer discussion. The 28 chapters are short; they offer exercises and worked examples, solved at the end of the book. Each part is supplemented with a relevant foreword and a useful summary including take-home messages. The editorial work is of good quality, with very few typographical errors. In spite of the title, kinetic theory stricto sensu is not the crux of the matter covered. The authors discuss the consequences of the molecular chaos assumption both at the individual particle level and in terms of collective behaviour. The first part of the book addresses the mechanics of grain collisions. It is emphasized that considering the coefficient of restitution {epsilon} -a central quantity governing the

  16. Kinetic Theory of Granular Gases

    Trizac, Emmanuel

    2005-01-01

    Granular gases are composed of macroscopic bodies kept in motion by an external energy source such as a violent shaking. The behaviour of such systems is quantitatively different from that of ordinary molecular gases: due to the size of the constituents, external fields have a stronger effect on the dynamics and, more importantly, the kinetic energy of the gas is no longer a conserved quantity. The key role of the inelasticity of collisions has been correctly appreciated for about fifteen years, and the ensuing consequences in terms of phase behaviour or transport properties studied in an increasing and now vast body of literature. The purpose of this book is to help the newcomer to the field in acquiring the essential theoretical tools together with some numerical techniques. As emphasized by the authors-who were among the pioneers in the domain- the content could be covered in a one semester course for advanced undergraduates, or it could be incorporated in a more general course dealing with the statistical mechanics of dissipative systems. The book is self-contained, clear, and avoids mathematical complications. In order to elucidate the main physical ideas, heuristic points of views are sometimes preferred to a more rigorous route that would lead to a longer discussion. The 28 chapters are short; they offer exercises and worked examples, solved at the end of the book. Each part is supplemented with a relevant foreword and a useful summary including take-home messages. The editorial work is of good quality, with very few typographical errors. In spite of the title, kinetic theory stricto sensu is not the crux of the matter covered. The authors discuss the consequences of the molecular chaos assumption both at the individual particle level and in terms of collective behaviour. The first part of the book addresses the mechanics of grain collisions. It is emphasized that considering the coefficient of restitution ε -a central quantity governing the inelasticity of

  17. Numerical Simulations of Granular Physics in the Solar System

    Ballouz, Ronald

    2017-08-01

    Granular physics is a sub-discipline of physics that attempts to combine principles that have been developed for both solid-state physics and engineering (such as soil mechanics) with fluid dynamics in order to formulate a coherent theory for the description of granular materials, which are found in both terrestrial (e.g., earthquakes, landslides, and pharmaceuticals) and extra-terrestrial settings (e.g., asteroids surfaces, asteroid interiors, and planetary ring systems). In the case of our solar system, the growth of this sub-discipline has been key in helping to interpret the formation, structure, and evolution of both asteroids and planetary rings. It is difficult to develop a deterministic theory for granular materials due to the fact that granular systems are composed of a large number of elements that interact through a non-linear combination of various forces (mechanical, gravitational, and electrostatic, for example) leading to a high degree of stochasticity. Hence, we study these environments using an N-body code, pkdgrav, that is able to simulate the gravitational, collisional, and cohesive interactions of grains. Using pkdgrav, I have studied the size segregation on asteroid surfaces due to seismic shaking (the Brazil-nut effect), the interaction of the OSIRIS-REx asteroid sample-return mission sampling head, TAGSAM, with the surface of the asteroid Bennu, the collisional disruptions of rubble-pile asteroids, and the formation of structure in Saturn's rings. In all of these scenarios, I have found that the evolution of a granular system depends sensitively on the intrinsic properties of the individual grains (size, shape, sand surface roughness). For example, through our simulations, we have been able to determine relationships between regolith properties and the amount of surface penetration a spacecraft achieves upon landing. Furthermore, we have demonstrated that this relationship also depends on the strength of the local gravity. By comparing our

  18. Emergent Strain Stiffening in Interlocked Granular Chains

    Dumont, Denis; Houze, Maurine; Rambach, Paul; Salez, Thomas; Patinet, Sylvain; Damman, Pascal

    2018-02-01

    Granular chain packings exhibit a striking emergent strain-stiffening behavior despite the individual looseness of the constitutive chains. Using indentation experiments on such assemblies, we measure an exponential increase in the collective resistance force F with the indentation depth z and with the square root of the number N of beads per chain. These two observations are, respectively, reminiscent of the self-amplification of friction in a capstan or in interleaved books, as well as the physics of polymers. The experimental data are well captured by a novel model based on these two ingredients. Specifically, the resistance force is found to vary according to the universal relation log F ˜μ √{N }Φ11 /8z /b , where μ is the friction coefficient between two elementary beads, b is their size, and Φ is the volume fraction of chain beads when semidiluted in a surrounding medium of unconnected beads. Our study suggests that theories normally confined to the realm of polymer physics at a molecular level can be used to explain phenomena at a macroscopic level. This class of systems enables the study of friction in complex assemblies, with practical implications for the design of new materials, the textile industry, and biology.

  19. Granular cell tumors of the urinary bladder

    Kayani Naila

    2007-03-01

    Full Text Available Abstract Background Granular cell tumors (GCTs are extremely rare lesions of the urinary bladder with only nine cases being reported in world literature of which one was malignant. Generally believed to be of neural origin based on histochemical, immunohistochemical, and ultrastructural studies; they mostly follow a clinically benign course but are commonly mistaken for malignant tumors since they are solid looking, ulcerated tumors with ill-defined margins. Materials and methods We herein report two cases of GCTs, one benign and one malignant, presenting with gross hematuria in a 14- and a 47-year-old female, respectively. Results Histopathology revealed characteristic GCTs with positive immunostaining for neural marker (S-100 and negative immunostaining for epithelial (cytokeratin, Cam 5.2, AE/A13, neuroendocrine (neuron specific enolase, chromogranin A, and synaptophysin and sarcoma (desmin, vimentin markers. The benign tumor was successfully managed conservatively with transurethral resection alone while for the malignant tumor, radical cystectomy, hysterectomy with bilateral salpingo-oophorectomy, anterior vaginectomy, plus lymph node dissection was done. Both cases show long-term disease free survival. Conclusion We recommend careful pathologic assessment for establishing the appropriate diagnosis and either a conservative or aggressive surgical treatment for benign or localized malignant GCT of the urinary bladder, respectively.

  20. Small-signal analysis of granular semiconductors

    Varpula, Aapo; Sinkkonen, Juha; Novikov, Sergey, E-mail: aapo.varpula@tkk.f [Department of Micro and Nanosciences, Aalto University, PO Box 13500, FI-00076 Aalto, Espoo (Finland)

    2010-11-01

    The small-signal ac response of granular n-type semiconductors is calculated analytically using the drift-diffusion theory when electronic trapping at grain boundaries is present. An electrical equivalent circuit (EEC) model of a granular n-type semiconductor is presented. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is very good in a broad frequency range at low dc bias voltages.

  1. Small-signal analysis of granular semiconductors

    Varpula, Aapo; Sinkkonen, Juha; Novikov, Sergey

    2010-01-01

    The small-signal ac response of granular n-type semiconductors is calculated analytically using the drift-diffusion theory when electronic trapping at grain boundaries is present. An electrical equivalent circuit (EEC) model of a granular n-type semiconductor is presented. The analytical model is verified with numerical simulation performed by SILVACO ATLAS. The agreement between the analytical and numerical results is very good in a broad frequency range at low dc bias voltages.

  2. Granular cell tumor: An uncommon benign neoplasm

    Tirthankar Gayen

    2015-01-01

    Full Text Available Granular cell tumor is a distinctly rare neoplasm of neural sheath origin. It mainly presents as a solitary asymptomatic swelling in the oral cavity, skin, and rarely internal organs in the middle age. Histopathology is characteristic, showing polyhedral cells containing numerous fine eosinophilic granules with indistinct cell margins. We present a case of granular cell tumor on the back of a 48-year-old woman which was painful, mimicking an adnexal tumor.

  3. Chapter 5. Technological aspects of obtaining of ethynyl-piperidol polymers. 5.1. Elaboration of method of continuous production of bandaging material

    Khalikov, D.Kh.

    2012-01-01

    The elaboration of method of continuous production of styptic and antibacterial material was the purpose of present scientific research. The flowsheet of continuous production of styptic and antibacterial material was elaborated and described. The process of iodine sorption by modified materials was studied. The iodine sorption by modified materials in moment of its formation from the potassium iodide was studied as well. The influence of nature of grafted polymer on sorption of iodide ions was studied as well.

  4. Granular packings with moving side walls

    Landry, James W.; Grest, Gary Stephen

    2004-01-01

    The effects of movement of the side walls of a confined granular packing are studied by discrete element, molecular dynamics simulations. The dynamical evolution of the stress is studied as a function of wall movement both in the direction of gravity as well as opposite to it. For all wall velocities explored, the stress in the final state of the system after wall movement is fundamentally different from the original state obtained by pouring particles into the container and letting them settle under the influence of gravity. The original packing possesses a hydrostaticlike region at the top of the container which crosses over to a depth-independent stress. As the walls are moved in the direction opposite to gravity, the saturation stress first reaches a minimum value independent of the wall velocity, then increases to a steady-state value dependent on the wall velocity. After wall movement ceases and the packing reaches equilibrium, the stress profile fits the classic Janssen form for high wall velocities, while some deviations remain for low wall velocities. The wall movement greatly increases the number of particle-wall and particle-particle forces at the Coulomb criterion. Varying the wall velocity has only small effects on the particle structure of the final packing so long as the walls travel a similar distance.

  5. Modeling of interaction effects in granular systems

    El-Hilo, M.; Shatnawy, M.; Al-Rsheed, A.

    2000-01-01

    Interaction effects on the magnetic behavior of granular solid systems are examined using a numerical model which is capable of predicting the field, temperature and time dependence of magnetization. In this work, interaction effects on the temperature dependence of time viscosity coefficient S(T) and formation of minor hysteresis loops have been studied. The results for the time- and temperature dependence of remanence ratio have showed that the distribution of energy barriers f(ΔE) obtained depend critically on the strength and nature of interactions. These interactions-based changes in f(ΔE) can easily give a temperature-independent behavior of S(T) when these changes give a 1/ΔE behavior to the distribution of energy barriers. Thus, conclusions about macroscopic quantum tunneling must be carefully drawn when the temperature dependence of S(T) is used to probe for MQT effects. For minor hysteresis effects, the result shows that for the non-interacting case, no minor hysteresis loops occur and the loops are only predicted when the interaction field is positive. From these predictions, minor loops will form when the interaction field is strong enough to magnetize some moments during the recoil process back to zero field. Thus, these minor loops are originated from interaction driving irreversible changes along the recoil curve and the irreversible component of magnetization has no direct influence on the formation of these minor loops

  6. Modeling of interaction effects in granular systems

    El-Hilo, M; Al-Rsheed, A

    2000-01-01

    Interaction effects on the magnetic behavior of granular solid systems are examined using a numerical model which is capable of predicting the field, temperature and time dependence of magnetization. In this work, interaction effects on the temperature dependence of time viscosity coefficient S(T) and formation of minor hysteresis loops have been studied. The results for the time- and temperature dependence of remanence ratio have showed that the distribution of energy barriers f(DELTA E) obtained depend critically on the strength and nature of interactions. These interactions-based changes in f(DELTA E) can easily give a temperature-independent behavior of S(T) when these changes give a 1/DELTA E behavior to the distribution of energy barriers. Thus, conclusions about macroscopic quantum tunneling must be carefully drawn when the temperature dependence of S(T) is used to probe for MQT effects. For minor hysteresis effects, the result shows that for the non-interacting case, no minor hysteresis loops occur an...

  7. DEM simulation of granular flows in a centrifugal acceleration field

    Cabrera, Miguel Angel; Peng, Chong; Wu, Wei

    2017-04-01

    The main purpose of mass-flow experimental models is abstracting distinctive features of natural granular flows, and allow its systematic study in the laboratory. In this process, particle size, space, time, and stress scales must be considered for the proper representation of specific phenomena [5]. One of the most challenging tasks in small scale models, is matching the range of stresses and strains among the particle and fluid media observed in a field event. Centrifuge modelling offers an alternative to upscale all gravity-driven processes, and it has been recently employed in the simulation of granular flows [1, 2, 3, 6, 7]. Centrifuge scaling principles are presented in Ref. [4], collecting a wide spectrum of static and dynamic models. However, for the case of kinematic processes, the non-uniformity of the centrifugal acceleration field plays a major role (i.e., Coriolis and inertial effects). In this work, we discuss a general formulation for the centrifugal acceleration field, implemented in a discrete element model framework (DEM), and validated with centrifuge experimental results. Conventional DEM simulations relate the volumetric forces as a function of the gravitational force Gp = mpg. However, in the local coordinate system of a rotating centrifuge model, the cylindrical centrifugal acceleration field needs to be included. In this rotating system, the centrifugal acceleration of a particle depends on the rotating speed of the centrifuge, as well as the position and speed of the particle in the rotating model. Therefore, we obtain the formulation of centrifugal acceleration field by coordinate transformation. The numerical model is validated with a series of centrifuge experiments of monodispersed glass beads, flowing down an inclined plane at different acceleration levels and slope angles. Further discussion leads to the numerical parameterization necessary for simulating equivalent granular flows under an augmented acceleration field. The premise of

  8. EFFECT OF ENDOSPERM HARDNESS ON AN ETHANOL PROCESS USING A GRANULAR STARCH HYDROLYZING ENZYME

    Wang, P; W Liu, D B; Johnston, K D; Rausch, S J; Schmidt, M E; Tumbleson, V Singh

    2010-01-01

    Granular starch hydrolyzing enzymes (GSHE) can hydrolyze starch at low temperature (32°C). The dry grind process using GSHE (GSH process) has fewer unit operations and no changes in process conditions (pH 4.0 and 32°C) compared to the conventional process because it dispenses with the cooking and liquefaction step. In this study, the effects of endosperm hardness, protease, urea, and GSHE levels on GSH process were evaluated. Ground corn, soft endosperm, and hard endosperm were processed using two GSHE levels (0.1 and 0.4 mL per 100 g ground material) and four treatments of protease and urea addition. Soft and hard endosperm materials were obtained by grinding and sifting flaking grits from a dry milling pilot plant; classifications were confirmed using scanning electron microscopy. During 72 h of simultaneous granular starch hydrolysis and fermentation (GSHF), ethanol and glucose profiles were determined using HPLC. Soft endosperm resulted in higher final ethanol concentrations compared to ground corn or hard endosperm. Addition of urea increased final ethanol concentrations for soft and hard endosperm. Protease addition increased ethanol concentrations and fermentation rates for soft endosperm, hard endosperm, and ground corn. The effect of protease addition on ethanol concentrations and fermentation rates was most predominant for soft endosperm, less for hard endosperm, and least for ground corn. Samples (soft endosperm, hard endosperm, or corn) with protease resulted in higher (1.0% to 10.5% v/v) ethanol concentration compared to samples with urea. The GSH process with protease requires little or no urea addition. For fermentation of soft endosperm, GSHE dose can be reduced. Due to nutrients (lipids, minerals, and soluble proteins) present in corn that enhance yeast growth, ground corn fermented faster at the beginning than hard and soft endosperm.

  9. Grain-scale numerical modeling of granular mechanics and fluid dynamics and application in a glacial context

    Damsgaard, Anders; Egholm, David Lundbek; Beem, Lucas H.

    The macroscopic behavior of granular materials is the result of the self-organizing complexity of the constituent grains. Granular materials are known for their ability to change phase, where each phase is characterized by distinct mechanical properties. This rich generic phenomenology has made...... it difficult to constrain generalized and adequate mathematical models for their mechanical behavior. Glaciers and ice streams often move by deformation of underlying melt-water saturated sediments. Glacier flow models including subglacial sediment deformation use simplified a priori assumptions for sediment......, the method imposes intense computational requirements on the computational time step. The majority of steps in the granular dynamics algorithm are massively parallel, which makes the DEM an obvious candidate for exploiting the capabilities of modern GPUs. The granular computations are coupled to a fluid...

  10. In situ grain fracture mechanics during uniaxial compaction of granular solids

    Hurley, R. C.; Lind, J.; Pagan, D. C.; Akin, M. C.; Herbold, E. B.

    2018-03-01

    Grain fracture and crushing are known to influence the macroscopic mechanical behavior of granular materials and be influenced by factors such as grain composition, morphology, and microstructure. In this paper, we investigate grain fracture and crushing by combining synchrotron x-ray computed tomography and three-dimensional x-ray diffraction to study two granular samples undergoing uniaxial compaction. Our measurements provide details of grain kinematics, contacts, average intra-granular stresses, inter-particle forces, and intra-grain crystal and fracture plane orientations. Our analyses elucidate the complex nature of fracture and crushing, showing that: (1) the average stress states of grains prior to fracture vary widely in their relation to global and local trends; (2) fractured grains experience inter-particle forces and stored energies that are statistically higher than intact grains prior to fracture; (3) fracture plane orientations are primarily controlled by average intra-granular stress and contact fabric rather than the orientation of the crystal lattice; (4) the creation of new surfaces during fracture accounts for a very small portion of the energy dissipated during compaction; (5) mixing brittle and ductile grain materials alters the grain-scale fracture response. The results highlight an application of combined x-ray measurements for non-destructive in situ analysis of granular solids and provide details about grain fracture that have important implications for theory and modeling.

  11. Different approaches to analyze the dipolar interaction effects on diluted and concentrated granular superparamagnetic systems

    Moscoso-Londoño, O., E-mail: omoscoso@ifi.unicamp.br [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), CEP13083-859 Campinas, São Paulo (Brazil); Tancredi, P. [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires (UBA), CONICET, C1063ACV Buenos Aires (Argentina); Muraca, D. [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), CEP13083-859 Campinas, São Paulo (Brazil); Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC (UFABC), Av. Dos Estados, 5001, Santo André, SP (Brazil); Mendoza Zélis, P.; Coral, D.; Fernández van Raap, M.B. [Instituto de Física, Universidad Nacional de La Plata (UNLP), CONICET, CC.67, 1900 La Plata, Buenos Aires (Argentina); Wolff, U.; Neu, V.; Damm, C. [IFW Dresden, Leibniz Institute for Solid State and Materials Research, Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany); Oliveira, C.L.P. de [Instituto de Física, Universidade de São Paulo, São Paulo 05314970 (Brazil); Pirota, K.R. [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), CEP13083-859 Campinas, São Paulo (Brazil); and others

    2017-04-15

    Controlled magnetic granular materials with different concentrations of magnetite nanoparticles immersed in a non-conducting polymer matrix were synthesized and, their macroscopic magnetic observables analyzed in order to advance towards a better understanding of the magnetic dipolar interactions and its effects on the obtained magnetic parameters. First, by means of X-ray diffraction, transmission electron microscopy, small angle X-ray scattering and X-ray absorption fine structure an accurate study of the structural properties was carried out. Then, the magnetic properties were analyzed by means of different models, including those that consider the magnetic interactions through long-range dipolar forces as: the Interacting Superparamagnetic Model (ISP) and the Vogel-Fulcher law (V-F). In systems with larger nanoparticle concentrations, magnetic results clearly indicate that the role played by the dipolar interactions affects the magnetic properties, giving rise to obtaining magnetic and structural parameters without physical meaning. Magnetic parameters as the effective anisotropic constant, magnetic moment relaxation time and mean blocking temperature, extracted from the application of the ISP model and V-F Law, were used to simulate the zero-field-cooling (ZFC) and field-cooling curves (FC). A comparative analysis of the simulated, fitted and experimental ZFC/FC curves suggests that the current models depict indeed our dilute granular systems. Notwithstanding, for concentrated samples, the ISP model infers that clustered nanoparticles are being interpreted as single entities of larger magnetic moment and volume, effect that is apparently related to a collective and complex magnetic moment dynamics within the cluster. - Highlights: • Nanoparticle architecture into matrices determines the composite magnetic response. • Magnetically diluted or compacted systems are useful to study magnetism at nanoscale. • Particle aggregation into the matrices was examined

  12. STABILIZATION OF GRANULAR VOLCANIC ASH IN SANA'A AREA

    SUBHI A. ALI

    2014-02-01

    Full Text Available This paper presents the findings of compaction and strength characteristics of a Granular Volcanic Ash from Sana'a city center, which was mixed with various percentages of two binders to form a stabilized material namely; fine soil and Portland cement. The study showed a significant improvement of the Volcanic Ash properties. The maximum dry density and California bearing ration (CBR were considerably increased by addition of stabilizers at different rates for different binder contents. Optimum fine soil content for the maximum dry density and CBR is determined. A relationship between the optimum moisture content and the binder combination content for different fine soil percentages was established.

  13. Statistical and visual probing of evolving granular assemblies

    Smith, Laurence M.

    2002-01-01

    The majority of processes in the chemical and allied industries involve the storage and conveyancing of granular material, the physics of which is still not particularly well understood. Whilst some non-invasive techniques have been developed, much experimental work unfortunately interferes with the fields being investigated. For this reason and in conjunction with increasing computing power, there has been an increase in simulation based studies. Granular dynamics simulations, being based upon inter-particle interaction laws, give the potential to investigate assemblies at the 'micro-level' and have been successful in modelling process conditions in a number of granular flow situations. To date, most analyses of these simulations are essentially static in nature involving 'time snapshots'. However, in a granular dynamics simulation there is a wealth of data available on a time referenced basis which has the potential to allow a quantitative analysis of the dynamics of assembly evolution. This dissertation describes the development and application of a toolkit for post-simulation analysis. However, the utilities within the toolkit would be equally applicable to large experimental data sets should such data sets exist. The application of the toolset focuses largely on the dynamics of heap evolution in both 2D and 3D with some supportive 3D work on hopper discharge. A major part of the work involves the application of time series techniques (including the wavelet transform) in the context of variable coupling during avalanching. Segregation by self-diffusion receives particular attention and a new mechanism is proposed by which segregation by particle size takes place in the boundary layer of a low impact feed heap displaying a clear velocity gradient during discrete avalanching. Periodic lateral surging is shown to enforce mixing for a high impact feed, a phenomenon which appears to switch off below a certain feed impact. Segregation by self-diffusion is also shown

  14. Fine-granularity inference and estimations to network traffic for SDN.

    Dingde Jiang

    Full Text Available An end-to-end network traffic matrix is significantly helpful for network management and for Software Defined Networks (SDN. However, the end-to-end network traffic matrix's inferences and estimations are a challenging problem. Moreover, attaining the traffic matrix in high-speed networks for SDN is a prohibitive challenge. This paper investigates how to estimate and recover the end-to-end network traffic matrix in fine time granularity from the sampled traffic traces, which is a hard inverse problem. Different from previous methods, the fractal interpolation is used to reconstruct the finer-granularity network traffic. Then, the cubic spline interpolation method is used to obtain the smooth reconstruction values. To attain an accurate the end-to-end network traffic in fine time granularity, we perform a weighted-geometric-average process for two interpolation results that are obtained. The simulation results show that our approaches are feasible and effective.

  15. Fine-granularity inference and estimations to network traffic for SDN.

    Jiang, Dingde; Huo, Liuwei; Li, Ya

    2018-01-01

    An end-to-end network traffic matrix is significantly helpful for network management and for Software Defined Networks (SDN). However, the end-to-end network traffic matrix's inferences and estimations are a challenging problem. Moreover, attaining the traffic matrix in high-speed networks for SDN is a prohibitive challenge. This paper investigates how to estimate and recover the end-to-end network traffic matrix in fine time granularity from the sampled traffic traces, which is a hard inverse problem. Different from previous methods, the fractal interpolation is used to reconstruct the finer-granularity network traffic. Then, the cubic spline interpolation method is used to obtain the smooth reconstruction values. To attain an accurate the end-to-end network traffic in fine time granularity, we perform a weighted-geometric-average process for two interpolation results that are obtained. The simulation results show that our approaches are feasible and effective.

  16. Preparation of regenerable granular carbon nanotubes by a simple heating-filtration method for efficient removal of typical pharmaceuticals

    Shan, Danna; Deng, Shubo; Zhao, Tianning; Yu, Gang; Winglee, Judith; Wiesner, Mark R.

    2017-04-01

    A simple and convenient method was used to prepare novel granular carbon nanotubes (CNTs) for enhanced adsorption of pharmaceuticals. By heating CNTs powder at 450 degree centigrade in air, followed by filtration, the obtained granular adsorbent exhibited high surface area and pore volume since the heating process produced some oxygen-containing functional groups on CNT surface, making CNTs more dispersible in the formation of granular cake. The porous granular CNTs not only had more available surfaces for adsorption but also were more easily separated from solution than pristine CNTs (p-CNTs) powder. This adsorbent exhibited relatively fast adsorption for carbamazepine (CBZ), tetracycline (TC) and diclofe- nac sodium (DS), and the maximum adsorption capacity on the granular CNTs was 369.5 μmol/g for CBZ, 284.2 μmol/g for TC and 203.1 μmol/g for DS according to the Langmuir fitting, increasing by 42.4%, 37.8% and 38.0% in comparison with the pristine CNTs powder. Moreover, the spent granular CNTs were successfully regenerated at 400 degree centigrade in air without decreasing the adsorption capacity in five regeneration cycles. The adsorbed CBZ and DS were completely degraded, while the adsorbed TC was partially oxidized and the residual was favorable for the subsequent adsorption. This research develops an easy method to prepare and regenerate granular CNT adsorbent for the enhanced removal of organic pollutants from water or wastewater.

  17. Flux-line cutting in granular high-temperature superconductors

    Perez-Rodriguez, F.; Perez-Gonzalez, A.; Clem, J.R.; Gandolfini, G.; LeBlanc, M.A.

    1997-01-01

    The magnetic response of granular high-temperature superconducting plates subjected to a dc-bias magnetic field and an increasing field perpendicular to it is studied both experimentally and theoretically. The theoretical model is based upon the double critical-state model, which considers not only flux transport but also flux-line cutting effects. Curves of magnetization for the system of grains decoupled by the applied magnetic field in sintered slabs of YBa 2 Cu 3 O 7-x and NdBa 2 Cu 3 O 7-x are analyzed. Good agreement between experimental results and theory is obtained. copyright 1997 The American Physical Society

  18. Scaling of wet granular flows in a rotating drum

    Jarray Ahmed

    2017-01-01

    Full Text Available In this work, we investigate the effect of capillary forces and particle size on wet granular flows and we propose a scaling methodology that ensures the conservation of the bed flow. We validate the scaling law experimentally by using different size glass beads with tunable capillary forces. The latter is obtained using mixtures of ethanol-water as interstitial liquid and by increasing the hydrophobicity of glass beads with an ad-hoc silanization procedure. The scaling methodology in the flow regimes considered (slipping, slumping and rolling yields similar bed flow for different particle sizes including the angle of repose that normally increases when decreasing the particle size.

  19. Comparative potential of black tea leaves waste to granular activated carbon in adsorption of endocrine disrupting compounds from aqueous solution

    A.O. Ifelebuegu; J. E. Ukpebor; C. C. Obidiegwu; B. C. Kwofi

    2015-01-01

    The adsorption properties and mechanics of selected endocrine disrupting compounds; 17 β-estradiol, 17 α – ethinylestradiol and bisphenol A on locally available black tea leaves waste and granular activated carbon were investigated. The results obtained indicated that the kinetics of adsorption were pH, adsorbent dose, contact time and temperature dependent with equilibrium being reached at 20 to 40 minutes for tea leaves waste and 40 to 60 minutes for granular activated compound. Maximum ads...

  20. Rapid penetration into granular media visualizing the fundamental physics of rapid earth penetration

    Iskander, Magued

    2015-01-01

    Rapid Penetration into Granular Media: Visualizing the Fundamental Physics of Rapid Earth Penetration introduces readers to the variety of methods and techniques used to visualize, observe, and model the rapid penetration of natural and man-made projectiles into earth materials. It provides seasoned practitioners with a standard reference that showcases the topic's most recent developments in research and application. The text compiles the findings of new research developments on the subject, outlines the fundamental physics of rapid penetration into granular media, and assembles a com

  1. Role of gravity or confining pressure and contact stiffness in granular rheology

    Singh, A.; Saitoh, K.; Magnanimo, Vanessa; Luding, Stefan

    2015-01-01

    The steady-state shear rheology of granular materials is investigated in slow quasistatic and inertial flows. The effect of gravity (thus the local pressure) and the often-neglected contact stiffness are the focus of this study. A series of particle simulations are performed on a weakly frictional

  2. Nonlocal approach to the analysis of the stress distribution in granular systems. II. Application to experiment

    Scott, J.E.; Kenkre, V.M.; Hurd, A.J.

    1998-01-01

    A theory of stress propagation in granular materials developed recently [Kenkre, Scott, Pease, and Hurd, preceding paper, Phys. Rev. E 57, 5841 (1998)] is applied to the compaction of ceramic and metal powders in pipes with previously unexplained experimental features such as nonmonotonic density and stress variation along the axis of cylindrical compacts. copyright 1998 The American Physical Society

  3. Small-number statistics near the clustering transition in a compartementalized granular gas

    Mikkelsen, René; van der Weele, Ko; van der Meer, Devaraj; van Hecke, Martin; Lohse, Detlef

    2005-01-01

    Statistical fluctuations are observed to profoundly influence the clustering behavior of granular material in a vibrated system consisting of two connected compartments. When the number of particles N is sufficiently large sN<300 is sufficientd, the clustering follows the lines of a standard

  4. Nonlocal approach to the analysis of the stress distribution in granular systems. II. Application to experiment

    Scott, J. E.; Kenkre, V. M.; Hurd, A. J.

    1998-05-01

    A theory of stress propagation in granular materials developed recently [Kenkre, Scott, Pease, and Hurd, preceding paper, Phys. Rev. E 57, 5841 (1998)] is applied to the compaction of ceramic and metal powders in pipes with previously unexplained experimental features such as nonmonotonic density and stress variation along the axis of cylindrical compacts.

  5. Universal scaling of permeability through the granular-to-continuum transition

    Wadsworth, F. B.; Scheu, B.; Heap, M. J.; Kendrick, J. E.; Vasseur, J.; Lavallée, Y.; Dingwell, D. B.

    2015-12-01

    Magmas fragment forming a transiently granular material, which can weld back to a fluid-continuum. This process results in dramatic changes in the gas-volume fraction of the material, which impacts the gas permeability. We collate published data for the gas-volume fraction and permeability of volcanic and synthetic materials which have undergone this process to different amounts and note that in all cases there exists a discontinuity in the relationship between these two properties. By discriminating data for which good microstructural information are provided, we use simple scaling arguments to collapse the data in both the still-granular, high gas-volume fraction regime and the fluid-continuum low gas-volume fraction regime such that a universal description can be achieved. We use this to argue for the microstructural meaning of the well-described discontinuity between gas-permeability and gas-volume fraction and to infer the controls on the position of this transition between dominantly granular and dominantly fluid-continuum material descriptions. As a specific application, we consider the transiently granular magma transported through and deposited in fractures in more-coherent magmas, thought to be a primary degassing pathway in high viscosity systems. We propose that our scaling coupled with constitutive laws for densification can provide insights into the longevity of such degassing channels, informing sub-surface pressure modelling at such volcanoes.

  6. Critical state flow rules for CFD simulations of wet granular flows

    Schwarze, R.; Gladkyy, A.; Luding, Stefan; E. Onate M. Bischoff, E. Ramm; P. Wriggers,

    2013-01-01

    First rheological investigation results of weakly wet granular media are presented. The materials have been examined experimentally and numerically in well- defined shear configurations in steady state, in the intermediate flow regime. For the experiments, a Searl-type ring shear cell with rotating

  7. Real-time magnetic resonance imaging of highly dynamic granular phenomena

    Penn, Alexander; Pruessmann, Klaas P.; Müller, Christoph

    Probing non-intrusively the interior of three-dimensional granular systems is a challenging task for which a number of imaging techniques have been applied including positron emission particle tracking, X-ray tomography and magnetic resonance imaging (MRI). A particular advantage of MRI is its versatility allowing quantitative velocimetry through phase contrast encoding and tagging, arbitrary slice orientations and the flexibility to trade spatial for temporal resolution and vice versa during image reconstruction. However, previous attempts to image granular systems using MRI were often limited to (pseudo-) steady state systems due to the poor temporal resolution of conventional imaging methodology. Here we present an experimental approach that overcomes previous limitations in temporal resolution by implementing a variety of methodological advances, viz. parallel data acquisition through tailored multiple receiver coils, fast gradient readouts for time-efficient data sampling and engineered granular materials that contain signal sources of high proton density. Achieving a spatial and temporal resolution of, respectively, 2 mm x 2 mm and 50 ms, we were able to image highly dynamic phenomena in granular media such as bubble coalescence and granular compaction waves.

  8. Force and flow at the onset of drag in plowed granular media.

    Gravish, Nick; Umbanhowar, Paul B; Goldman, Daniel I

    2014-04-01

    We study the transient drag force FD on a localized intruder in a granular medium composed of spherical glass particles. A flat plate is translated horizontally from rest through the granular medium to observe how FD varies as a function of the medium's initial volume fraction, ϕ. The force response of the granular material differs above and below the granular critical state, ϕc, the volume fraction which corresponds to the onset of grain dilatancy. For ϕϕc, FD rapidly rises to a maximum and then decreases over further displacement. The maximum force for ϕ>ϕc increases with increasing drag velocity. In quasi-two-dimensional drag experiments, we use granular particle image velocimetry (PIV) to measure time resolved strain fields associated with the horizontal motion of a plate started from rest. PIV experiments show that the maxima in FD for ϕ>ϕc are associated with maxima in the spatially averaged shear strain field. For ϕ>ϕc the shear strain occurs in a narrow region in front of the plate, a shear band. For ϕϕc, surface particles move only during the formation of the shear band, coincident with the maxima in FD, after which the particles remain immobile until the sheared region reaches the measurement region.

  9. Wet granular matter a truly complex fluid

    Herminghaus, Stephan

    2013-01-01

    This is a monograph written for the young and advanced researcher who is entering the field of wet granular matter and keen to understand the basic physical principles governing this state of soft matter. It treats wet granulates as an instance of a ternary system, consisting of the grains, a primary, and a secondary fluid. After addressing wetting phenomena in general and outlining the basic facts on dry granular systems, a chapter on basic mechanisms and their effects is dedicated to every region of the ternary phase diagram. Effects of grain shape and roughness are considered as well. Rather than addressing engineering aspects such as existing books on this topic do, the book aims to provide a generalized framework suitable for those who want to understand these systems on a more fundamental basis. Readership: For the young and advanced researcher entering the field of wet granular matter.

  10. 11th Traffic and Granular Flow Conference

    Daamen, Winnie

    2016-01-01

    The Conference on Traffic and Granular Flow brings together international researchers from different fields ranging from physics to computer science and engineering to discuss the latest developments in traffic-related systems. Originally conceived to facilitate new ideas by considering the similarities of traffic and granular flow, TGF'15, organised by Delft University of Technology, now covers a broad range of topics related to driven particle and transport systems. Besides the classical topics of granular flow and highway traffic, its scope includes data transport (Internet traffic), pedestrian and evacuation dynamics, intercellular transport, swarm behaviour and the collective dynamics of other biological systems. Recent advances in modelling, computer simulation and phenomenology are presented, and prospects for applications, for example to traffic control, are discussed. The conference explores the interrelations between the above-mentioned fields and offers the opportunity to stimulate interdisciplinar...

  11. Statistical mechanics of dense granular media

    Coniglio, A; Fierro, A; Nicodemi, M; Ciamarra, M Pica; Tarzia, M

    2005-01-01

    We discuss some recent results on the statistical mechanics approach to dense granular media. In particular, by analytical mean field investigation we derive the phase diagram of monodisperse and bidisperse granular assemblies. We show that 'jamming' corresponds to a phase transition from a 'fluid' to a 'glassy' phase, observed when crystallization is avoided. The nature of such a 'glassy' phase turns out to be the same as found in mean field models for glass formers. This gives quantitative evidence for the idea of a unified description of the 'jamming' transition in granular media and thermal systems, such as glasses. We also discuss mixing/segregation transitions in binary mixtures and their connections to phase separation and 'geometric' effects

  12. Skew scattering dominated anomalous Hall effect in Cox(MgO)100-x granular thin films

    Zhang, Qiang

    2017-07-31

    We investigated the mechanism(s) of the anomalous Hall effect (AHE) in magnetic granular materials by fabricating 100-nm-thick thin films of Cox(MgO)100-x with a Co volume fraction of 34≤x≤100 using co-sputtering at room temperature. We measured the temperature dependence of longitudinal resistivity (ρxx) and anomalous Hall resistivity (ρAHE) from 5 K to 300 K in all samples. We found that when x decreases from 100 to 34, the values of ρxx and ρAHE respectively increased by about four and three orders in magnitude. By linearly fitting the data, obtained at 5 K, of anomalous Hall coefficient (Rs) and of ρxx to log(Rs)~γlog(ρxx), we found that our results perfectly fell on a straight line with a slope of γ= 0.97±0.02. This fitting value of γ in Rsρxxγ clearly suggests that skew scattering dominated the AHE in this granular system. To explore the effect of the scattering on the AHE, we performed the same measurements on annealed samples. We found that although both ρxx and ρAHE significantly reduced after annealing, the correlation between them was almost the same, which was confirmed by the fitted value, γ=0.99±0.03. These data strongly suggest that the AHE originates from the skew scattering in Co-MgO granular thin films no matter how strong the scatterings of electrons by the interfaces and defects is. This observation may be of importance to the development of spintronic devices based on MgO.

  13. Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material

    Valle-Zermeño, R. del; Formosa, J.; Chimenos, J.M.; Martínez, M.; Fernández, A.I.

    2013-01-01

    Highlights: ► A concrete formulation was optimized using Bottom Ash and APC ash. ► 10% of APC ash achieves good compromise between economic and performance aspects. ► The crushed concrete was evaluated as secondary building granular material. ► The environmental behavior allows its use as secondary material. ► The abrasion resistance is not good enough for its use as a road sub-base material. - Abstract: The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incineration (MSWI) bottom ash (BA) and air pollution control (APC) fly ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behavior whilst maximizing the reuse of APC fly ash was considered and assessed. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC fly ash content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured

  14. 76 FR 8774 - Granular Polytetrafluoroethylene Resin From Japan

    2011-02-15

    ... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-386 (Third Review)] Granular Polytetrafluoroethylene Resin From Japan AGENCY: United States International Trade Commission. ACTION: Termination of five... revocation of the antidumping duty order on granular polytetrafluoroethylene resin from Japan would be likely...

  15. Absorbent material for type a radioactive materials packaging containing liquids

    Saunders, G.A.

    1989-11-01

    The application of absorbent materials to the packaging and transport of liquid radioactive materials in Type A packages has not been reported in the literature. However, a significant body of research exists on absorbent materials for personal hygiene products such as diapers. Absorption capacity is dependent on both the absorbent material and the liquid being absorbed. Theoretical principles for capillary absorption in both the horizontal and the vertical plane indicate that small contact angle between the absorbent fibre and the liquid, and a small inter-fibre pore size are important. Some fluid parameters such as viscosity affect the rate of absorption but not the final absorption capacity. There appears to be little comparability between results obtained for the same absorbent and fluid using different test procedures. Test samples of materials from several classes of potential absorbents have been evaluated in this study, and shown to have a wide range of absorbent capacities. Foams, natural fibres, artificial fibres and granular materials are all potentially useful absorbents, with capacities ranging from as little as 0.86 to as much as 40.6 grams of distilled water per gram of absorbent. Two experimental procedures for evaluating the absorbent capacity of these materials have been detailed in this report, and found suitable for evaluating granular, fibrous or foam materials. Compression of the absorbent material reduces its capacity, but parameters such as relative humidity, pH, temperature, and viscosity appear to have little significant influence on capacity. When the materials were loaded to 50% of their one-minute absorbency, subsequent loss of the absorbed liquid was generally minimal. All of the absorbent materials rapidly lost their absorbed water through evaporation within twenty-four hours in still air at 21 degrees C and 50% relative humidity

  16. The dependence of granular plasticity on particle shape

    Murphy, Kieran; Jaeger, Heinrich

    Granular materials plastically deform through reworking an intricate network of particle-particle contacts. Some particle rearrangements have only a fleeting effect before being forgotten while others set in motion global restructuring. How particle shape affects local interactions and how those, in turn, influence the nature of the aggregate's plasticity is far from clear, especially in three dimensions. Here we investigate the remarkably wide range of behaviors in the yielding regime, from quiescent flow to violent jerks, depending on particle shape. We study this complex dependence via uniaxial compression experiments on aggregates of 3D-printed particles, and complement stress-strain data with simultaneous x-ray videos and volumetric strain measurements. We find power law distributions of the slip magnitudes, and discuss their universality. Our data show that the multitude of small slips serves to gradually dilate the packing whereas the fewer large ones accompany significant compaction events. Our findings provide new insights into general features of granular materials during plastic deformation and highlight how small changes in particle shape can give rise to drastic differences in yielding behavior.

  17. Contact force structure and force chains in 3D sheared granular systems

    Mair, Karen; Jettestuen, Espen; Abe, Steffen

    2010-05-01

    Faults often exhibit accumulations of granular debris, ground up to create a layer of rock flour or fault gouge separating the rigid fault walls. Numerical simulations and laboratory experiments of sheared granular materials, suggest that applied loads are preferentially transmitted across such systems by transient force networks that carry enhanced forces. The characterisation of such features is important since their nature and persistence almost certainly influence the macroscopic mechanical stability of these systems and potentially that of natural faults. 3D numerical simulations of granular shear are a valuable investigation tool since they allow us to track individual particle motions, contact forces and their evolution during applied shear, that are difficult to view directly in laboratory experiments or natural fault zones. In characterising contact force distributions, it is important to use global structure measures that allow meaningful comparisons of granular systems having e.g. different grain size distributions, as may be expected at different stages of a fault's evolution. We therefore use a series of simple measures to characterise the structure, such as distributions and correlations of contact forces that can be mapped onto a force network percolation problem as recently proposed by Ostojic and coworkers for 2D granular systems. This allows the use of measures from percolation theory to both define and characterise the force networks. We demonstrate the application of this method to 3D simulations of a sheared granular material. Importantly, we then compare our measure of the contact force structure with macroscopic frictional behaviour measured at the boundaries of our model to determine the influence of the force networks on macroscopic mechanical stability.

  18. Anaerobic granular sludge and biofilm reactors

    Skiadas, Ioannis V.; Gavala, Hariklia N.; Schmidt, Jens Ejbye

    2003-01-01

    by the immobilization of the biomass, which forms static biofilms, particle-supported biofilms, or granules depending on the reactor's operational conditions. The advantages of the high-rate anaerobic digestion over the conventional aerobic wastewater treatment methods has created a clear trend for the change......-rate anaerobic treatment systems based on anaerobic granular sludge and biofilm are described in this chapter. Emphasis is given to a) the Up-flow Anaerobic Sludge Blanket (UASB) systems, b) the main characteristics of the anaerobic granular sludge, and c) the factors that control the granulation process...

  19. Granular contact dynamics using mathematical programming methods

    Krabbenhoft, K.; Lyamin, A. V.; Huang, J.

    2012-01-01

    granular contact dynamics formulation uses an implicit time discretization, thus allowing for large time steps. Moreover, in the limit of an infinite time step, the general dynamic formulation reduces to a static formulation that is useful in simulating common quasi-static problems such as triaxial tests...... is developed and it is concluded that the associated sliding rule, in the context of granular contact dynamics, may be viewed as an artifact of the time discretization and that the use of an associated flow rule at the particle scale level generally is physically acceptable. (C) 2012 Elsevier Ltd. All rights...

  20. Tracing Thermal Creep Through Granular Media

    Steinpilz, Tobias; Teiser, Jens; Koester, Marc; Schywek, Mathias; Wurm, Gerhard

    2017-08-01

    A temperature gradient within a granular medium at low ambient pressure drives a gas flow through the medium by thermal creep. We measured the resulting air flow for a sample of glass beads with particle diameters between 290 μ m and 420 μ m for random close packing. Ambient pressure was varied between 1 Pa and 1000 Pa. The gas flow was quantified by means of tracer particles during parabolic flights. The flow varies systematically with pressure between 0.2 cm/s and 6 cm/s. The measured flow velocities are in quantitative agreement to model calculations that treat the granular medium as a collection of linear capillaries.