Observation of crack growth in a polycrystalline ferroelectric by synchrotron X-ray diffraction.

Pre-cracked samples of unpoled, polycrystalline, soft ferroelectric lead zirconate titanate were subjected to electrical and mechanical loading whilst using synchrotron X-ray diffraction to map strain-fields. Clear evidence is found of switching around the crack tip and development of a crack-wake. A J-integral estimate based on strain-field data provided a sensitive measure of strain changes during loading. Electrical loading did not cause crack advance or crack-tip switching; this provides evidence for electrically permeable crack models. There was also enhancement of electrically-driven switching in the crack-wake region. The results provide improved understanding and a resource for testing fracture models in ferroelectrics.

Mapping of ferroelectric domain structure using angle-resolved piezoresponse force microscopy.

Angle-resolved piezoresponse force microscopy (AR-PFM) was used in conjunction with electron backscatter diffraction (EBSD) to study ferroelectric domain structure in polycrystalline near-morphotropic lead zirconate titanate (PZT). We introduce the details of AR-PFM including experimental method, the process to generate AR-PFM maps, and the interpretation of AR-PFM map, using domain patterns observed in bulk PZT. The spatial distortion caused by scanner creep and non-linearity in scanning probe microscopy was corrected through image registration, taking advantage of the features present in topography images. Domain structures were mapped using AR-PFM data, and the maps consistently show alternating piezoresponse axes in a lamellar pattern of non-180° domain structure. Comparison of AR-PFM and EBSD data showed a discrepancy between the direction of lateral surface displacement and the in-plane polarization direction. Additionally, using suitable domain patterns, AR-PFM enabled discrimination between the tetragonal and rhombohedral phases at the sub-grain scale.

Formants of children, women, and men: the effects of vocal intensity variation.

The purpose of this study was to investigate the formant frequencies and amplitudes of a wide age range of children and one group of adults at three sound pressure levels (SPLs). Subjects were ten females and ten males in the following age groups (in years): 4, 6, 8, 10, 12, 14, 16, 18, and adults. A sustained /a/ was produced three times by each subject. Formant frequencies were obtained using linear predictive coding analysis. Formant amplitudes were measured from the highest amplitude harmonic in the area of each formant. In addition to following established trends previously published in other studies, it was hypothesized that the first formant frequency would increase with increasing intensity, that females would have higher formant frequencies than same aged males, and that women and children would have reduced formant amplitudes as compared to men. It was found that first formant frequency increased with intensity and changed as a function of age and sex. Second and third formant frequencies changed with age and sex. Formant amplitudes followed the trends set by the SPL differences and did not change as a function of age and sex. Results are discussed in terms of anatomic differences and SPL.

Effects of a circumferentially vented mask on breathing patterns of women as measured by respiratory kinematic techniques.

Since pneumotachograph masks are commonly used in studies of speech breathing, the purpose of this study was to measure the differences in respiratory volumetric and frequency measures during speech under two conditions: with and without a circumferentially vented pneumotachograph mask coupled to the face. Thus we sought to identify whether changes in breathing patterns occur with the use of a specific face mask, because these patterns are accepted as representative of normal speech breathing. Subjects were 10 normal-speaking women, each of whom produced a syllable train and a connected speech task, both at comfortable intensity levels. Respiratory measures were made using linearized magnetometers during speech production. The measurements included lung volume, rib cage volume, and abdominal volume at utterance initiation and termination, volume excursions during the utterance, and the number of breath groups during the speech task. There were no significant differences between the mask-on and mask-off conditions in volumetric and frequency measures. A significant task difference for abdominal initiation was found. It was concluded that the use of a circumferentially vented pneumotachograph mask does not alter the reliability of respiratory volume and frequency measures for studies of voice.