Deep shear-wave velocity profiles at eight places in Lima Peru were estimated based on the inversion of dispersion curves. The dispersion curves were calculated from small and large microtremor arrays using two method...Deep shear-wave velocity profiles at eight places in Lima Peru were estimated based on the inversion of dispersion curves. The dispersion curves were calculated from small and large microtremor arrays using two methods： the F-k proposed by Capon （1969） and the CCA proposed by Cho et al. （2004）. For the purpose of large array measurement we introduced a new type of sensor. Important results are the relative shallow depths to the basement rock in the area classified as alluvial gravel that covers most of the area of Lima city; and the relative large depth to the bedrock in places identified as VSV and CMA. It is recommended that this study be complemented with PS loggings in order to verify the estimated profiles.展开更多
相控阵高强度聚焦超声换能器可以通过换能器上不同阵元发射超声波的时间不同来实现变焦、多焦点。该论文应用Westervelt方程的近似式,结合Pennes热传导方程,以人体乳房为例,FDTD(finite difference time domain)仿真对比研究平面阵列相...相控阵高强度聚焦超声换能器可以通过换能器上不同阵元发射超声波的时间不同来实现变焦、多焦点。该论文应用Westervelt方程的近似式,结合Pennes热传导方程,以人体乳房为例,FDTD(finite difference time domain)仿真对比研究平面阵列相控聚焦换能器与曲面阵列相控聚焦换能器形成温度场的特性,同时数值仿真研究不同占空比的正弦激励函数、不同治疗频率、声强对曲面阵列相控聚焦换能器超声温度场的影响。研究结果表明曲面阵列相控聚焦换能器能有效地减少皮肤处的温升,对皮肤的伤害较小;对于曲面阵列相控聚焦换能器,不同占空比的正弦激励函数形成的可治疗区域(60℃以上)大小差别不大,但最高温度不同;随着频率升高,形成的可治疗区域体积减小;随着输入声强的增大,可治疗区域变大,但焦距不变。展开更多
An effective design method of freeform micro lens array is presented for shaping varied laser beams into prescribed rectangular illumination. The variable separation mapping is applied to design concave freeform surfa...An effective design method of freeform micro lens array is presented for shaping varied laser beams into prescribed rectangular illumination. The variable separation mapping is applied to design concave freeform surfaces for constructing a freeform lens array. Several dedicated examples show that the designed freeform optical lens array can achieve a prescribed rectangular illumination pattern, especially without considering the initial states of incident laser beams. Both high collection efficiency and good spatial uniformity can be available simultaneously. Tolerance analysis is also performed to demonstrate that this optical device can well avoid fabricating difficulty in actual applications.展开更多
文摘Deep shear-wave velocity profiles at eight places in Lima Peru were estimated based on the inversion of dispersion curves. The dispersion curves were calculated from small and large microtremor arrays using two methods： the F-k proposed by Capon （1969） and the CCA proposed by Cho et al. （2004）. For the purpose of large array measurement we introduced a new type of sensor. Important results are the relative shallow depths to the basement rock in the area classified as alluvial gravel that covers most of the area of Lima city; and the relative large depth to the bedrock in places identified as VSV and CMA. It is recommended that this study be complemented with PS loggings in order to verify the estimated profiles.
文摘相控阵高强度聚焦超声换能器可以通过换能器上不同阵元发射超声波的时间不同来实现变焦、多焦点。该论文应用Westervelt方程的近似式,结合Pennes热传导方程,以人体乳房为例,FDTD(finite difference time domain)仿真对比研究平面阵列相控聚焦换能器与曲面阵列相控聚焦换能器形成温度场的特性,同时数值仿真研究不同占空比的正弦激励函数、不同治疗频率、声强对曲面阵列相控聚焦换能器超声温度场的影响。研究结果表明曲面阵列相控聚焦换能器能有效地减少皮肤处的温升,对皮肤的伤害较小;对于曲面阵列相控聚焦换能器,不同占空比的正弦激励函数形成的可治疗区域(60℃以上)大小差别不大,但最高温度不同;随着频率升高,形成的可治疗区域体积减小;随着输入声强的增大,可治疗区域变大,但焦距不变。
基金supported by the National Natural Science Foundation of China(No.61405037)the Science and Technology Project of Fujian Province(No.2015H4014)
文摘An effective design method of freeform micro lens array is presented for shaping varied laser beams into prescribed rectangular illumination. The variable separation mapping is applied to design concave freeform surfaces for constructing a freeform lens array. Several dedicated examples show that the designed freeform optical lens array can achieve a prescribed rectangular illumination pattern, especially without considering the initial states of incident laser beams. Both high collection efficiency and good spatial uniformity can be available simultaneously. Tolerance analysis is also performed to demonstrate that this optical device can well avoid fabricating difficulty in actual applications.
