Low frequency Raman spectra of(Pb_(0.97)La_(0.02)T(Zr_(0.864)Sn_(0.04)Ti_(0.096))O_(3)ceramic samples have been studied near cubic to antiferroelectric phase transition at about 200℃.A set of low frequency soft modes...Low frequency Raman spectra of(Pb_(0.97)La_(0.02)T(Zr_(0.864)Sn_(0.04)Ti_(0.096))O_(3)ceramic samples have been studied near cubic to antiferroelectric phase transition at about 200℃.A set of low frequency soft modes were observed restoring below the transition point,in addition to the known one above 100 cm^(-1).These modes show strong damping anomalies at the transition point that supposes considerable intermode interactions via dampings.展开更多
1 Introduction In 1962, Subbarao’s thermal expansion and the dielectric measurement indicated a phase transition occurring at 250℃ in Bi<sub>2</sub>Ti<sub>4</sub>O<sub>11</sub>. T...1 Introduction In 1962, Subbarao’s thermal expansion and the dielectric measurement indicated a phase transition occurring at 250℃ in Bi<sub>2</sub>Ti<sub>4</sub>O<sub>11</sub>. The conclusion was firstly confirmed by Raman experiment at high temperature. The phase transition is connected with the softening of the mode with temperature. In our previous study, we reported its Raman spectra under high pressure. The experimental results reveal that a pressure-induced phase transition occurs at 3.7 GPa. It has also been found that the intensity, half-width,展开更多
Self-sensing and –actuating probes optimized for conventional tapping mode atomic force microscopy (AFM) are described. 32-kHz quartz tuning forks with a chemically etched and focus ion beam (FIB) sharpened (curvatur...Self-sensing and –actuating probes optimized for conventional tapping mode atomic force microscopy (AFM) are described. 32-kHz quartz tuning forks with a chemically etched and focus ion beam (FIB) sharpened (curvature radii are 5-10 nm) tungsten tip are stable at air and liquid nitrogen atmosphere and at a wide range of temperatures. If driven at constant frequency, the scan speed of such sensors can be up to 3 Hz. AFM was performed on polymer samples in order to study the stability and applicability of these sensor for investigation of soft materials with high dynamical tendencies.展开更多
With the development of high-speed railway in China, composite foundation with rigid piles has become a stamdard solution of meeting the high requirements of stability and post-construction settlement of embankment on...With the development of high-speed railway in China, composite foundation with rigid piles has become a stamdard solution of meeting the high requirements of stability and post-construction settlement of embankment on soft subgrade. Among several im- provement pattems, plain concrete piles have been extensively used to treat soft ground supported embankment. To investigate the deformation and failure modes of unimproved soft ground and soft ground reinforced by sub-embankment plain concrete piles, and to learn the influences of track and vehicle load, the effect of pile spacing, as well as the compression moduli of soil layers and upper load condition on the failure modes, a series of centrifuge model tests were performed. Test results indicate that the dis- placement of unimproved soft ground under the embankment increases continuously as embankment, track and train loading, and slip circle failure takes place. The deformation law of soft ground reinforced by sub-embankment plain concrete piles depends on pile spacing, compression modulus of the soft ground, and loading conditions. It was also found that plain concrete piles show displacement and failure patterns depending on its location, compression modulus of soft soil around the pile, and loading condi- tions. Furthermore, the evaluation of improved ground stability as well as the model test procedure is also presented.展开更多
文摘Low frequency Raman spectra of(Pb_(0.97)La_(0.02)T(Zr_(0.864)Sn_(0.04)Ti_(0.096))O_(3)ceramic samples have been studied near cubic to antiferroelectric phase transition at about 200℃.A set of low frequency soft modes were observed restoring below the transition point,in addition to the known one above 100 cm^(-1).These modes show strong damping anomalies at the transition point that supposes considerable intermode interactions via dampings.
文摘1 Introduction In 1962, Subbarao’s thermal expansion and the dielectric measurement indicated a phase transition occurring at 250℃ in Bi<sub>2</sub>Ti<sub>4</sub>O<sub>11</sub>. The conclusion was firstly confirmed by Raman experiment at high temperature. The phase transition is connected with the softening of the mode with temperature. In our previous study, we reported its Raman spectra under high pressure. The experimental results reveal that a pressure-induced phase transition occurs at 3.7 GPa. It has also been found that the intensity, half-width,
文摘Self-sensing and –actuating probes optimized for conventional tapping mode atomic force microscopy (AFM) are described. 32-kHz quartz tuning forks with a chemically etched and focus ion beam (FIB) sharpened (curvature radii are 5-10 nm) tungsten tip are stable at air and liquid nitrogen atmosphere and at a wide range of temperatures. If driven at constant frequency, the scan speed of such sensors can be up to 3 Hz. AFM was performed on polymer samples in order to study the stability and applicability of these sensor for investigation of soft materials with high dynamical tendencies.
基金supported by Program for New Century Excellent Talents in University of China (Grant No.NCET-12-0941)the Fundamental Research Funds for the Central Universities of China (Grant No.A0920502051206-3)
文摘With the development of high-speed railway in China, composite foundation with rigid piles has become a stamdard solution of meeting the high requirements of stability and post-construction settlement of embankment on soft subgrade. Among several im- provement pattems, plain concrete piles have been extensively used to treat soft ground supported embankment. To investigate the deformation and failure modes of unimproved soft ground and soft ground reinforced by sub-embankment plain concrete piles, and to learn the influences of track and vehicle load, the effect of pile spacing, as well as the compression moduli of soil layers and upper load condition on the failure modes, a series of centrifuge model tests were performed. Test results indicate that the dis- placement of unimproved soft ground under the embankment increases continuously as embankment, track and train loading, and slip circle failure takes place. The deformation law of soft ground reinforced by sub-embankment plain concrete piles depends on pile spacing, compression modulus of the soft ground, and loading conditions. It was also found that plain concrete piles show displacement and failure patterns depending on its location, compression modulus of soft soil around the pile, and loading condi- tions. Furthermore, the evaluation of improved ground stability as well as the model test procedure is also presented.
