Memory impairment in flowing suspensions. II. Experimental results

1978 ◽  
Vol 56 (22) ◽  
pp. 2824-2832 ◽  
Author(s):  
G. J. Ennis ◽  
A. Okagawa ◽  
S. G. Mason
Keyword(s):  
Memory Loss ◽  
Orientation Distribution ◽  
Particle Orientation ◽  
Light Transmittance ◽  
Particle Interactions ◽  
Electrical Shock ◽  
Cyclic Shear ◽  
Rigid Rods ◽  
Gradual Loss ◽  
Orientation Distributions

Experiments on the reversibility of particle orientation distributions in suspensions of nearly monodisperse rigid rods and hardened red blood cells (HRBC) subjected to cyclic shearing are described.The orientation distributions of initially aligned rods measured by direct observation exhibited a gradual loss in memory as flow was reversed back and forth which was attributed mainly to non-reversible particle interactions. When an electric field was applied continuously during cyclic shear flow, the rate of memory loss was increased. However, if an electrical shock was applied momentarily between each reversal of flow, the suspension maintained some memory. These results are generally in agreement with the theory presented in the preceding paper.With suspensions of HRBC, the particles were initially randomly oriented and the light transmittance across the planes of shear was used to measure changes in orientation distribution. Since HRBC are small enough to exhibit appreciable rotary Brownian motion, memory loss was inevitable and increased with the duration of each shear cycle and the cell concentration.Memory loss was also observed for rods and HRBC in non-Newtonian media and was attributed to drift in the rotational orbit constants of the particles.

The measurement of orientation distribution and its application to quantitative X-ray diffraction analysis

Clay Minerals ◽  
1966 ◽  
Vol 6 (3) ◽  
pp. 127-142 ◽  
Author(s):  
R.M. Taylor ◽  
K. Norrish
Keyword(s):  
Particle Morphology ◽  
Orientation Distribution ◽  
Particle Orientation ◽  
Small Specimen ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Mathematical Relation ◽  
Degree Of Orientation ◽  
Orientation Distributions

AbstractUsing X-ray techniques, the orientation distributions of crystal planes in laboratory prepared and naturally occurring aggregates were measured. A small specimen was mounted on the axis of a goniometer and the diffracted intensity measured as the specimen was rotated. Mo radiation was used to reduce the absorption effects. A mathematical relation between the distribution of particles and the distribution of crystal planes was derived for platy and fibrous particles in flake-like and rod-shaped specimens.When diffracted intensities of the 001 reflection of several different kaolinites were corrected for the degree of orientation in the respective specimens, a constant value was obtained. This would enable quantitative diffraction analyses to be made without the large errors that can be introduced by orientation effects. The degree of particle orientation achieved appeared to be more dependent on particle morphology than on the method of sample preparation or formation.

scholarly journals Tools for Visualizing and Analyzing Fourier Space Sampling in Cryo-EM

2020 ◽  
Author(s):  
Philip R. Baldwin ◽  
Dmitry Lyumkis
Keyword(s):  
Graphical User Interface ◽  
Signal To Noise Ratio ◽  
Orientation Distribution ◽  
Geometrical Factor ◽  
Fourier Space ◽  
Complete Understanding ◽  
Spherical Surfaces ◽  
Compensation Factor ◽  
Spectral Signal ◽  
Orientation Distributions

AbstractA complete understanding of how an orientation distribution contributes to a cryo-EM reconstruction remains lacking. It is necessary to begin critically assessing the set of views to gain an understanding of its effect on experimental reconstructions. Toward that end, we recently suggested that the type of orientation distribution may alter resolution measures in a systematic manner. We introduced the sampling compensation factor (SCF), which incorporates how the collection geometry might change the spectral signal-to-noise ratio (SSNR), irrespective of the other experimental aspects. We show here that knowledge of the sampling restricted to spherical surfaces of sufficiently large radii in Fourier space is equivalent to knowledge of the set of projection views. Moreover, the SCF geometrical factor may be calculated from one such surface. To aid cryo-EM researchers, we developed a graphical user interface (GUI) tool that evaluates experimental orientation distributions. The GUI returns plots of projection directions, sampling constrained to the surface of a sphere, the SCF value, the fraction of the empty region of Fourier space, and a histogram of the sampling values over the points on a sphere. Finally, a fixed tilt angle may be incorporated to determine how tilting the grid during collection may improve the distribution of views and Fourier space sampling. We advocate this simple conception of sampling and the use of such tools as a complement to the distribution of views to capture the different aspects of the effect of projection directions on cryo-EM reconstructions.

Reliability criteria in quantitative texture analysis with experimental and simulated orientation distributions

2005 ◽  
Vol 38 (4) ◽  
pp. 603-611 ◽  
Author(s):  
Daniel Chateigner
Keyword(s):  
Texture Analysis ◽  
Orientation Distribution ◽  
Point Of View ◽  
Real Sample ◽  
Experimental Point ◽  
Orientation Distributions ◽  
Counting Statistics ◽  
New Criterion

Quantitative texture analysis reliability factors are examined from an experimental point of view, using real-sample and modelled orientation distribution refinements. The classicalRPfactors of texture analysis are shown to depend on the texture strength, and their representation of the various textures is not homogeneous. The surface-weightedRPwhomologues exhibit lower texture strength dependency and better homogeneities, but still do not allow for comparison of refinements operated on samples with different textures. New factors,Rw, weighted by the counting statistics, show the lowest dependency and best homogeneity. FromRw1(Rw0) curves a new criterion is established, which allows the detection of poorly refined orientation distributions. This study highlights a unique entropy-to-texture index relationship, which also gives a new criterion for testing refinement reliability, and proposes two different ranges in which to apply the texture index and the entropy factors.

Memory impairment in flowing suspensions. I. Some theoretical considerations

1978 ◽  
Vol 56 (22) ◽  
pp. 2815-2823 ◽  
Author(s):  
A. Okagawa ◽  
G. J. Ennis ◽  
S. G. Mason
Keyword(s):  
Numerical Calculation ◽  
Experimental Verification ◽  
Memory Impairment ◽  
Orientation Distribution ◽  
Newtonian Liquid ◽  
Initial Orientation ◽  
Initial State ◽  
Damped Oscillations ◽  
Orientation Distributions ◽  
Theoretical Considerations

When a suspension of nearly monodisperse rigid axisymmetric particles in a Newtonian liquid is sheared, the orientation distributions of the particle undergo damped oscillations of frequency twice that of the rotating particles. If the flow is stopped and then reversed, the oscillations regrow under certain restricted conditions until the initial state is fully restored: the system has perfect memory. Removing some of the restrictions causes imperfect recovery of the initial orientation distribution, so that when the flow is reversed cyclically back and forth, the orientation distribution eventually becomes time-independent: the system has lost all of its memory. A number of sources of memory impairment are considered theoretically, several of which are amenable to experimental verification and are illustrated by numerical calculation.

scholarly journals Texture, Piezoelectricity and Ferroelectricity

1995 ◽  
Vol 23 (4) ◽  
pp. 221-236 ◽  
Author(s):  
L. Fuentes ◽  
O. Raymond
Keyword(s):  
Distribution Function ◽  
Barium Titanate ◽  
Texture Analysis ◽  
Technological Process ◽  
Orientation Distribution Function ◽  
Orientation Distribution ◽  
Odd Order ◽  
Order Expansion ◽  
Orientation Distributions ◽  
Expansion Coefficients

A Quantitative Texture Analysis approach to polycrystal piezoelectric and ferroelectric phenomena is given. Monocrystal longitudinal piezoelectric moduli are expanded in Bunge's symmetry- adapted functional bases. Suitable expansion coefficients are given. Orientation Distribution Function based algorithms for polycrystal piezo-moduli prediction are presented. Significant odd-order expansion terms are calculated and their relation to ghost phenomena is commented. Polycrystal ferroelectricity is characterized. Quantitative describers associated to crystallographic and electric orientation distributions are presented and related. Their evolution during heat and poling processes is discussed. Two computer-simulated examples are analyzed: (a) Texture-modulated longitudinal piezo-modulus is calculated for an ideal quartz single-component texture. (b) Barium titanate fibre texture transformation during a hypothetical technological process is investigated.

scholarly journals Calculation of Texture Volume Fractions by Integration and Gaussian Fitting

1997 ◽  
Vol 29 (3-4) ◽  
pp. 155-183 ◽  
Author(s):  
M. B. Cortie
Keyword(s):  
Distribution Function ◽  
Harmonic Function ◽  
Texture Component ◽  
Volume Fraction ◽  
Orientation Distribution ◽  
Volume Fractions ◽  
Gaussian Fitting ◽  
Orientation Distributions ◽  
Function Integration ◽  
The Ideal

The concept of texture volume fractions has proved useful in the assessment of the orientation distributions of polycrystalline samples. Unfortunately, there is more than one method of calculating volume fractions, and the different techniques may give rather different answers. The three most commonly used methods appear to be calculation from the coefficients of the harmonic function, integration over a selected portion of an orientation distribution function (ODF), or decomposition of an ODF into component Gaussian ideal textures by a least squares fitting. The integration and Gaussian fitting methods are examined further here. In particular, the nature of the errors or differences arising from the method of integration or fitting chosen, the differing interpretations of the shape and ‘spread’ of the ideal texture, and the effect of neglecting texture components lying outside of the H0 subspace are considered. Integration of a volume enclosed by one or more cylinders defined in Eulerian space seems the most robust technique. It is usually, but not always, acceptable to neglect the effect of texture components lying outside of H0. However, it is vital that the ‘spread’ of the ideal texture component be precisely defined, and the texture volume fraction is very sensitive to the magnitude of the spread as well as to the geometric shape assumed for it.

scholarly journals Numerical Investigation into the Influence of Grain Orientation Distribution on the Local and Global Elastic-Plastic Behaviour of Polycrystalline Nickel-Based Superalloy INC-738 LC

Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 100
Author(s):  
Benedikt Engel ◽  
Mark Huth ◽  
Christopher Hyde
Keyword(s):  
Orientation Distribution ◽  
Cooling Process ◽  
Polycrystalline Nickel ◽  
Source Codes ◽  
Plastic Behaviour ◽  
Nickel Based Superalloy ◽  
Young’S Moduli ◽  
Schmid Factor ◽  
Orientation Distributions ◽  
Elastic Strains

Polycrystalline nickel-based superalloys tend to have large grains within component areas where high loads are dominant during operation. Due to these large grains, caused by the manufacturing and cooling process, the orientation of each grain becomes highly important, since it influences the elastic and plastic behaviour of the material. With the usage of the open source codes NEPER and FEPX, polycrystalline models of Inconel 738 LC were generated and their elastic and crystal plasticity behaviour simulated in dependence of different orientation distributions under uniaxial loading. Orientation distributions close to the [100] direction showed the lowest Young’s moduli as well as the highest elastic strains before yielding, as expected. Orientations close to the [5¯89] direction, showed the lowest elastic strains and therefore first plastic deformation under strain loading due to the highest shear stress in the slip systems caused by the interaction of Young’s modulus and the Schmid factor.

Sign in / Sign up

Export Citation Format

Share Document