Textbooks on phonology and on teaching ESL （English as a Second Language） often present the place of articulation of the sibilant/s/and its voiced counterpart/z/as a settled matter. The/s/and/z/are described and lis...Textbooks on phonology and on teaching ESL （English as a Second Language） often present the place of articulation of the sibilant/s/and its voiced counterpart/z/as a settled matter. The/s/and/z/are described and listed in phonological charts as ＂alveolar fricatives＂, meaning that the tongue is raised and the apex approaches the alveolar ridge. Those teaching pronunciation or remediating speech problems often use these descriptions by the IPA （International Phonetic Association） as models for teaching these phonemes. A number of linguists and instructors, however, have suggested that an acceptable/s/and/z/sound can be produced in English by other means This study attempted to determine the prevalence of the acceptable alternative placements for the/s/and/z/sounds in a sample of 50 English-speaking university students. Results revealed that 64% of participants used alternate tongue positions to that described in the literature as standard. Implications for speech pathology and ESL instruction are discussed.展开更多
对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transfo...对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。展开更多
针对传统电缆舞动检测器在面对电磁干扰和持续供电时灵敏度低、信噪比差、安装复杂和需额外供电等问题,提出一种新型双端Mach-Zehnder(M-Z)电缆扰动监测系统.该系统采用双端光纤M-Z光路结构,可实现长距离、大尺度、多维度的在线监测和...针对传统电缆舞动检测器在面对电磁干扰和持续供电时灵敏度低、信噪比差、安装复杂和需额外供电等问题,提出一种新型双端Mach-Zehnder(M-Z)电缆扰动监测系统.该系统采用双端光纤M-Z光路结构,可实现长距离、大尺度、多维度的在线监测和结构安全预警,从而实时定位舞动位置.该系统的检波器力学单元采用硅胶弹性体和黄铜质量块推挽式结构,经ANSYS软件进行参数化建模和有限元分析后,得出其固有频率为106.77 Hz,与实验所测数据的相对误差仅为1.65%.实验结果表明,该检测器在0~140 Hz内的相对灵敏度为41.25~66.78 dB (rad/Pa),对舞动信号具有较高灵敏度的检测能力.展开更多
文摘Textbooks on phonology and on teaching ESL （English as a Second Language） often present the place of articulation of the sibilant/s/and its voiced counterpart/z/as a settled matter. The/s/and/z/are described and listed in phonological charts as ＂alveolar fricatives＂, meaning that the tongue is raised and the apex approaches the alveolar ridge. Those teaching pronunciation or remediating speech problems often use these descriptions by the IPA （International Phonetic Association） as models for teaching these phonemes. A number of linguists and instructors, however, have suggested that an acceptable/s/and/z/sound can be produced in English by other means This study attempted to determine the prevalence of the acceptable alternative placements for the/s/and/z/sounds in a sample of 50 English-speaking university students. Results revealed that 64% of participants used alternate tongue positions to that described in the literature as standard. Implications for speech pathology and ESL instruction are discussed.
文摘对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。
文摘针对传统电缆舞动检测器在面对电磁干扰和持续供电时灵敏度低、信噪比差、安装复杂和需额外供电等问题,提出一种新型双端Mach-Zehnder(M-Z)电缆扰动监测系统.该系统采用双端光纤M-Z光路结构,可实现长距离、大尺度、多维度的在线监测和结构安全预警,从而实时定位舞动位置.该系统的检波器力学单元采用硅胶弹性体和黄铜质量块推挽式结构,经ANSYS软件进行参数化建模和有限元分析后,得出其固有频率为106.77 Hz,与实验所测数据的相对误差仅为1.65%.实验结果表明,该检测器在0~140 Hz内的相对灵敏度为41.25~66.78 dB (rad/Pa),对舞动信号具有较高灵敏度的检测能力.
