无轭分块电枢轴向磁场永磁电机(Yokeless and Segmented Armature Machine,YASA)是一种高功率密度、高效率的电机,适于电牵引驱动特别是电动车的轮毂和轮边直驱。本文针对基于软磁复合材料(SMC)的YASA电机的齿槽转矩进行研究。首先比较...无轭分块电枢轴向磁场永磁电机(Yokeless and Segmented Armature Machine,YASA)是一种高功率密度、高效率的电机,适于电牵引驱动特别是电动车的轮毂和轮边直驱。本文针对基于软磁复合材料(SMC)的YASA电机的齿槽转矩进行研究。首先比较了基于SMC和叠压硅钢材料的YASA电机齿槽转矩波形,然后分析了永磁体极弧系数、永磁体斜极、定子齿靴宽度系数以及定子齿靴偏移对基于SMC的YASA电机齿槽转矩的影响,在此基础上建立响应面模型并利用遗传算法对齿槽转矩进行优化,最后,通过3-D FEM验证了优化结果的准确性。结果表明,在选取一定极弧系数的前提下,存在最优的永磁体斜极角度、定子齿靴宽度系数和定子齿靴偏移角度组合能够使电机的齿槽转矩降为最小,且优化前后电机的其他性能基本保持不变。展开更多
A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdow...A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdown mechanism in liquids.Inthe range pf the propagation distance, in which the photoacoustic pulses were meas ured, the variation of the amplitude of photoacoustic pulse with the distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront propagating through a certain distance, the parameter B / A of liquid is determined. Comparing with the plane pulsed wave with bounded beam, the effect of diffraction may e avoided by using the spherical pulsed wave. The nonlinearity parameter B / A of water is obtained by the present method. the results are rcasonably good.展开更多
文摘脾脏肿瘤并不多见,但随着现代影像学技术的发展,越来越多的脾脏占位在体检时被偶然发现,而脾脏是人体的“血库”,活检出血风险极大,因此选择安全的技术获得脾脏样本尤为重要。本文报道了3例内镜超声引导下细针抽吸术(endoscopic ultrasoud-guided fine needle aspiration,EUS-FNA)诊断的脾脏恶性肿瘤,EUS-FNA有助于明确诊断、指导临床医师制定治疗方案。
文摘A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdown mechanism in liquids.Inthe range pf the propagation distance, in which the photoacoustic pulses were meas ured, the variation of the amplitude of photoacoustic pulse with the distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront propagating through a certain distance, the parameter B / A of liquid is determined. Comparing with the plane pulsed wave with bounded beam, the effect of diffraction may e avoided by using the spherical pulsed wave. The nonlinearity parameter B / A of water is obtained by the present method. the results are rcasonably good.