Random porosity fields and their influence on the stability of granular media

2008 ◽  
Vol 32 (10) ◽  
pp. 1147-1172 ◽  
Author(s):  
José E. Andrade ◽  
Jack W. Baker ◽  
Kirk C. Ellison
Keyword(s):  
Granular Media ◽  
The Stability ◽  
Random Porosity

The role of solution chemistry in the stability and detachment of cohesive kaolinite particles

2001 ◽  
Vol 1 (1) ◽  
pp. 25-32 ◽  
Author(s):  
V. Ravisangar ◽  
B.M. Brouckaert ◽  
A. Amirtharajah ◽  
T.W. Sturm
Keyword(s):  
Granular Media ◽  
Interaction Force ◽  
Solution Chemistry ◽  
Force Model ◽  
Concentrated Suspensions ◽  
Sediment Deposits ◽  
The Stability ◽  
Relationship Of ◽  
Filter Backwashing

The effect of solution chemistry on the behavior of kaolinite in three different situations was investigated: (1) the detachment of kaolinite from glass beads in a fluidized bed, (2) the erosion of kaolinite deposits in a laboratory flume and (3) the determination of the stress-strain rate relationship of concentrated suspensions in a rheometer. The experimental results from these three different approaches could be explained in terms of changes in mode of particle associations which in turn could be characterized in terms of a micromechanical force model which predicts the effect of solution chemistry on the interaction force between adjacent particle surfaces. Understanding the relationship between solution and surface chemistry on the structure, mechanical strength and mechanism of erosion of cohesive sediment deposits is an important step towards developing predictive models of a number of processes including erosion of cohesive sediments in streams and estuaries, and detachment of particles from granular media during filtration and filter backwashing.

Physical bases of packing of frozen clods of soil in ground massifs in transport and hydraulic structures

2021 ◽  
pp. 127-135
Author(s):  
A. N. Shuvaev ◽  
M. V. Panova ◽  
Ya. A. Pronozin
Keyword(s):  
Granular Media ◽  
Frozen Soil ◽  
The Arctic ◽  
Hydraulic Structures ◽  
Winter Period ◽  
Frozen Soils ◽  
Main Layer ◽  
Soil Skeleton ◽  
The Stability ◽  
Selection Of

The current regulatory documents for infrastructure construction indicate the use of only thawed, mainly sandy soils. When erecting embankments during the winter period, a limited number of applied frozen soils are allowed. In this case, the stability and strength of the soil massif decrease. The absence of thawed soils in the regions of Siberia and the Arctic requires an expansion of the types of soils used, one of which is frozen soils. We have developed the designs of the subgrade that allow using frozen soils, enclosed in geosynthetic cages or without them. Increasing the stability and strength of the embankment by creating a dense soil skeleton is one of the scientific issues, which is solved in this article by applying the theory of granular media. In practice, the formation of dense systems from frozen soils is based on two principles: the method of dense mixtures and the method of impregnation, where the main layer of frozen soil is impregnated from above with dry frozen soils. Almost by selection of the composition, you can achieve the maximum density.

Bifurcations of Periodic Orbits of a One-Dimensional Pre-Compressed Granular Array

2018 ◽  
Author(s):  
Gizem Dilber Acar ◽  
Balakumar Balachandran
Keyword(s):  
Periodic Orbit ◽  
Periodic Orbits ◽  
Bifurcation Point ◽  
Granular Media ◽  
Period Doubling ◽  
Initial Step ◽  
Hertzian Contact ◽  
One Dimensional ◽  
The Stability ◽  
External Forces

Bifurcations of periodic orbits of a one-dimensional granular array are numerically investigated in this study. A conservative two-bead system is considered without any damping or external forces. By using the Hertzian contact model, and confining the system’s total energy to a certain level, changes in in-phase periodic orbit are studied for various pre-compression levels. At a certain pre-compression level, symmetry breaking and period doubling occur, and an asymmetric period-two orbit emerges from the in-phase periodic orbit. Floquet analysis is conducted to study the stability of the in-phase periodic solution, and to detect the bifurcation location. Although the trajectory of period-two orbit is close to the in-phase orbit at the bifurcation point, the asymmetry of the period-two orbit becomes more pronounced as one moves away from the bifurcation point. This work is meant to serve as an initial step towards understanding how pre-compression may introduce qualitative changes in system dynamics of granular media.

scholarly journals WAVE ENERGY DISSIPATION IK ROCKFILL

1972 ◽  
Vol 1 (13) ◽  
pp. 103
Author(s):  
John A. McCorquodale
Keyword(s):  
Wave Energy ◽  
Granular Media ◽  
Present Report ◽  
Internal Flow ◽  
Wave Action ◽  
Darcy Flow ◽  
Water Level Fluctuations ◽  
Wave Energy Dissipation ◽  
The Stability ◽  
External Wave

Very little literature exists on the subject of unsteady non-Darcy flow in coarse granular media. However, unsteady non-Darcy flow is encountered in a few important hydraulic problems, for example, (a) Wave absorption and transmission in rubble-mound break-waters; (b) Water level fluctuations in the rockfill and filter zones of a dam subjected to wave action; (c) Transmission of floods or tides through rockfill dams and causeways, A mathematical model, to simulate the internal Darcy and/or non-Darcy flow in an embankment subjected to wave action, would permit an improved analysis of: the stability of the embankment; the stability of the armour layer; and the absorption and dissipation of wave energy by the rockfill. Since the internal flow in the embankment and the external wave action are interdependent, a complete model requires the simulation of both of these flows. Such a model would permit the computation of wave run-up and reflection. The present report is limited to the simulation of the unsteady internal flow. Heitner and Housner (4), using a finite element method, have developed an external wave action simulation for Tsunamis. The author is presently attempting to couple the internal and external models.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

Uniformity of Magnification from Different Electron Microscopes

1967 ◽  
Vol 25 ◽  
pp. 32-33
Author(s):  
Godfrey C. Hoskins ◽  
V. Williams ◽  
V. Allison
Keyword(s):  
Diffraction Grating ◽  
The Other ◽  
Carbon Replica ◽  
Electron Microscopes ◽  
The Stability

The method demonstrated is an adaptation of a proven procedure for accurately determining the magnification of light photomicrographs. Because of the stability of modern electrical lenses, the method is shown to be directly applicable for providing precise reproducibility of magnification in various models of electron microscopes.A readily recognizable area of a carbon replica of a crossed-line diffraction grating is used as a standard. The same area of the standard was photographed in Phillips EM 200, Hitachi HU-11B2, and RCA EMU 3F electron microscopes at taps representative of the range of magnification of each. Negatives from one microscope were selected as guides and printed at convenient magnifications; then negatives from each of the other microscopes were projected to register with these prints. By deferring measurement to the print rather than comparing negatives, correspondence of magnification of the specimen in the three microscopes could be brought to within 2%.

Effect of Improved ThO2 Particle Dispersion in Nickel on High-Temperature Strength

1970 ◽  
Vol 28 ◽  
pp. 444-445
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
High Temperature ◽  
Metal Matrix ◽  
Oxide Particle ◽  
Oxide Phase ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Particles ◽  
The Stability

The strengthening effect at high temperature produced by a dispersed oxide phase in a metal matrix is seemingly dependent on at least two major contributors: oxide particle size and spatial distribution, and stability of the worked microstructure. These two are strongly interrelated. The stability of the microstructure is produced by polygonization of the worked structure forming low angle cell boundaries which become anchored by the dispersed oxide particles. The effect of the particles on strength is therefore twofold, in that they stabilize the worked microstructure and also hinder dislocation motion during loading.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Formation and Structure of Casein Micelles in Lactating Mammary Tissue

1970 ◽  
Vol 28 ◽  
pp. 150-151
Author(s):  
Robert J. Carroll ◽  
Marvin P. Thompson ◽  
Harold M. Farrell
Keyword(s):  
Size Distribution ◽  
G Protein ◽  
Milk Proteins ◽  
Mammary Tissue ◽  
Colloidal System ◽  
Casein Micelles ◽  
The Stability

Milk is an unusually stable colloidal system; the stability of this system is due primarily to the formation of micelles by the major milk proteins, the caseins. Numerous models for the structure of casein micelles have been proposed; these models have been formulated on the basis of in vitro studies. Synthetic casein micelles (i.e., those formed by mixing the purified αsl- and k-caseins with Ca2+ in appropriate ratios) are dissimilar to those from freshly-drawn milks in (i) size distribution, (ii) ratio of Ca/P, and (iii) solvation (g. water/g. protein). Evidently, in vivo organization of the caseins into the micellar form occurs in-a manner which is not identical to the in vitro mode of formation.

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