Gradient of Residual Stress and Lattice Parameter in Mechanically Polished Tungsten Measured Using Classical X rays and Synchrotron Radiation

In this work, the stress gradient in mechanically polished tungsten sample was studied using X ray diffraction methods. To determine in depth stress evolution in the very shallow subsurface region up to 10 amp; 956;m , special methods based on reflection geometry were applied. The subsurface stresses depth up to 1 amp; 956;m were measured using the multiple reflection grazing incidence X ray diffraction method with classical characteristic X rays, while the deeper volumes depth up to 10 amp; 956;m were investigated using energy dispersive diffraction with white high energy synchrotron beam. Both complementary methods allowed for determining in depth stress profile and the evolution of stress free lattice parameter. It was confirmed that the crystals of tungsten are elastically isotropic, which simplifies the stress analysis and makes tungsten a suitable material for testing stress measurement methods. Furthermore, it was found that an important compressive stress of about amp; 8722; 1000 MPa was generated on the surface of the mechanically polished sample, and this stress decreases to zero value at the depth of about 9 amp; 956;m. On the other hand, the strain free lattice parameter does not change significantly in the examined subsurface regio

Saccadic reaction times in infants and adults: spatiotemporal factors, gender, and inter-laboratory variation

Saccade latency is widely used across infant psychology to investigate infants’understanding of events. Interpreting particular latency values requires knowledge of standard saccadic reaction times, but there is no consensus as to typical values. This study provides standard estimates of infants’ (n=194, ages 9 to 15 months) saccadic reaction times under a range of different spatiotemporal conditions. To investigate the reliability of such standard estimates, data is collected at four laboratories in three countries. Results indicate that reactions to the appearance of a new object are much faster than reactions to the deflection of a currently fixated moving object; upward saccades are slower than downward or horizontal saccades; reactions to more peripheral stimuli are much slower; and this slowdown is greater for boys than girls. There was little decrease in saccadic reaction times between 9 and 15 month, indicating that the period of slow development which is protracted into adolescence begins in late infancy. Except for appearance and deflection differences, infant effects were weak or absent in adults (n=40). Latency estimates and spatiotemporal effects on latency were generally consistent across laboratories, but a number of lab differences in factors such as individual variation were found. Some but not all differences were attributed to minor procedural differences, highlighting the importance of replication. Confidence intervals (95%) for infants’ median reaction latencies for appearance stimuli were 242 – 250 ms and for deflection stimuli 350 – 367 ms

Action Prediction Allows Hypothesis Testing via Internal Forward Models at 6 Months of Age

We propose that action prediction provides a cornerstone in a learning process known as internal forward models. According to this suggestion infants’ predictions (looking to the mouth of someone moving a spoon upward) will moments later be validated or proven false (spoon was in fact directed toward a bowl), information that is directly perceived as the distance between the predicted and actual goal. Using an individual difference approach we demonstrate that action prediction correlates with the tendency to react with surprise when social interactions are not acted out as expected (action evaluation). This association is demonstrated across tasks and in a large sample (n = 118) at 6 months of age. These results provide the first indication that infants might rely on internal forward models to structure their social world. Additional analysis, consistent with prior work and assumptions from embodied cognition, demonstrates that the latency of infants’ action predictions correlate with the infant’s own manual proficiency

A novel approach for nondestructive depth resolved analysis of residual stress and grain interaction in the near surface zone applied to an austenitic stainless steel sample subjected to mechanical polishing

The choice of the grain interaction model is a critical element of residual stress analysis using diffraction methods. For the near surface region of a mechanically polished austenitic steel, it is shown that the application of the widely used Eshelby Kröner model does not lead to a satisfactory agreement with experimental observations. Therefore, a new grain interaction model called tunable free surface is proposed, allowing for the determination of the in depth evolution of the elastic interaction between grains. It has a strong physical justification and is adjusted to experimental data using three complementary verification methods. It is shown that a significant relaxation of the intergranular stresses perpendicular to the sample surface occurs in the subsurface layer having a thickness comparable with the average size of the grain. Using the new type of X ray Stress Factors, the in depth evolution up to the depth of 45 amp; 956;m of residual stresses and of the strain free lattice parameter is determine