369 research outputs found
Band Positions Used for On-Line Crystallographic Orientation Determination from Electron Back Scattering Patterns
A computer procedure for on-line analysis of electron back scattering patterns (EBSP) has been developed. An experimental EBSP is computer recorded and displayed on a computer monitor. The user identifies the positions of at least two bands in the EBSP with a cursor. Based on this input the computer calculates possible crystallographic orientations. The corresponding EBSPs are simulated and superimposed on the experimental EBSP. The correct crystallographic orientation is determined from a comparison between the experimental and simulated EBSPs. Typically, the analysis takes a 10-30 seconds per pattern. Advantages with the present procedure are that it can be applied for any crystal symmetry, that it requires no knowledge about electron diffraction maps, that it can be used for EBSPs with relatively low contrast, and that the indexing is very precise. For relative orientation measurements the accuracy is found to be within range 0.05°-0.20°, whereas, for repeated measurements of a given grain after complete remounting of sample and EBSP equipment, it was determined to be 0.5°. Furthermore, the procedure facilitates fully automatic pattern recognition
Recovery and recrystallization in commercial purity aluminum cold rolled to an ultrahigh strain
A phase-field simulation study of irregular grain boundary migration during recrystallization
We present simulation results based on a phase-field model that describes the
migration of recrystallization boundaries into spatially varying deformation energy fields.
Energy fields with 2-dimensional variations representing 2 sets of dislocation boundaries lying at
equal, but opposite, angles to the moving boundary are considered. The simulations show that
the shape and overall migration rate of the recrystallization front is considerably affected by
spatial variations in the deformation microstructure. It is seen that, depending on characteristics
of the variations in the deformation microstructure, highly asymmetrical protrusions and
retrusions can develop on the migrating recrystallization front resulting in a migration velocity
considerably larger than that expected from standard recrystallization models. It is also seen
that, when the wavelength of the variations in a deformation microstructure along the grain
boundary is larger than the wavelength of the variations in the direction of migration, parts
of the boundary show a stop-and-go type of migration, resulting in a lower overall migration
rate. These simulations thus reproduce and explain many of the typical features observed in
recrystallization experiments. They give new insights in the way deformation microstructures
can affect the migration behavior of recrystallization boundaries and can lead to a stop-and-go
type of migration of the recrystallization boundary even in pure materials.status: publishe
Thermal stability of a highly-deformed warm-rolled tungsten plate in the temperature range 1100 °C to 1250 °C
Development of Deformation Textures in Polycrystalline Copper Experiments and Model Predictions
Adverse trends in male reproductive health: we may have reached a crucial ‘tipping point’
Healthy men produce an enormous number of sperms, far more than necessary for conception. However, several studies suggest that semen samples where the concentration of sperms is below 40 mill/mL may be associated with longer time to pregnancy or even subfertility, and specimens where the concentration of sperms is below 15 mill/mL may carry a high risk of infertility. Historic data from the 1940s show that the bulk of young men at that time had sperm counts far above 40 mill/mL with averages higher than 100 mill/mL. However, recent surveillance studies of young men from the general populations of young men in Northern Europe show that semen quality is much poorer. In Denmark approximately 40 percent of the men have now sperm counts below 40 mill/mL. A simulation assuming that average sperm count had declined from 100 mill/mL in ‘old times’ to a current level close to 40 mill/mL indicated that the first decline in average sperm number of 20–40 mill/mL might not have had much effect on pregnancy rates, as the majority of men would still have had counts far above the threshold value. However, due to the assumed decline in semen quality, the sperm counts of the majority of 20 year old European men are now so low that we may be close to the crucial tipping point of 40 mill/mL spermatozoa. Consequently, we must face the possibility of more infertile couples and lower fertility rates in the future
Fecundability among newly married couples in agricultural villages in Palestine: a prospective study
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