Floating oscillating bodies constitute a large class of wave energy converters, especially for offshore deployment. Usually the Power-Take-Off（PTO） system is a directly linear electric generator or a hydraulic motor...Floating oscillating bodies constitute a large class of wave energy converters, especially for offshore deployment. Usually the Power-Take-Off（PTO） system is a directly linear electric generator or a hydraulic motor that drives an electric generator. The PTO system is simplified as a linear spring and a linear damper. However the conversion is less powerful with wave periods off resonance. Thus, a nonlinear snap-through mechanism with two symmetrically oblique springs and a linear damper is applied in the PTO system. The nonlinear snap-through mechanism is characteristics of negative stiffness and double-well potential. An important nonlinear parameter γ is defined as the ratio of half of the horizontal distance between the two springs to the original length of both springs. Time domain method is applied to the dynamics of wave energy converter in regular waves. And the state space model is used to replace the convolution terms in the time domain equation. The results show that the energy harvested by the nonlinear PTO system is larger than that by linear system for low frequency input. While the power captured by nonlinear converters is slightly smaller than that by linear converters for high frequency input. The wave amplitude, damping coefficient of PTO systems and the nonlinear parameter γ affect power capture performance of nonlinear converters. The oscillation of nonlinear wave energy converters may be local or periodically inter well for certain values of the incident wave frequency and the nonlinear parameter γ, which is different from linear converters characteristics of sinusoidal response in regular waves.展开更多
设计了一款采用硅基板作为载体的毫米波上变频微系统系统级封装(System in Package,SiP)模块。该模块利用类同轴硅通孔(Through-Silicon-Via,TSV)结构解决了毫米波频段信号在转接板层间低损耗垂直传输的问题。该结构整体采用四层硅基板...设计了一款采用硅基板作为载体的毫米波上变频微系统系统级封装(System in Package,SiP)模块。该模块利用类同轴硅通孔(Through-Silicon-Via,TSV)结构解决了毫米波频段信号在转接板层间低损耗垂直传输的问题。该结构整体采用四层硅基板封装,并在封装完成后对硅基射频SiP模块进行了测试。测试结果显示,在工作频段29~31 GHz之间,其增益大于27 dB,端口驻波小于1.4,且带外杂散抑制大于55 dB。该毫米波硅基SiP模块具有结构简单、集成度高、射频性能良好等优点,其体积不到传统二维集成结构的5%,实现了毫米波频段模块的微系统化,可广泛运用于射频微系统。展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51239007)the Independent Research Project of State Key Laboratory of Ocean Engineering in Shanghai Jiao Tong University(Grant No.GKZD010023)
文摘Floating oscillating bodies constitute a large class of wave energy converters, especially for offshore deployment. Usually the Power-Take-Off（PTO） system is a directly linear electric generator or a hydraulic motor that drives an electric generator. The PTO system is simplified as a linear spring and a linear damper. However the conversion is less powerful with wave periods off resonance. Thus, a nonlinear snap-through mechanism with two symmetrically oblique springs and a linear damper is applied in the PTO system. The nonlinear snap-through mechanism is characteristics of negative stiffness and double-well potential. An important nonlinear parameter γ is defined as the ratio of half of the horizontal distance between the two springs to the original length of both springs. Time domain method is applied to the dynamics of wave energy converter in regular waves. And the state space model is used to replace the convolution terms in the time domain equation. The results show that the energy harvested by the nonlinear PTO system is larger than that by linear system for low frequency input. While the power captured by nonlinear converters is slightly smaller than that by linear converters for high frequency input. The wave amplitude, damping coefficient of PTO systems and the nonlinear parameter γ affect power capture performance of nonlinear converters. The oscillation of nonlinear wave energy converters may be local or periodically inter well for certain values of the incident wave frequency and the nonlinear parameter γ, which is different from linear converters characteristics of sinusoidal response in regular waves.
文摘针对隔墙探测雷达的实际应用需求,研究了三种常见墙体对1~2 GHz电磁波的衰减特性.利用电磁波理论,仿真分析了这三种常见墙体的穿墙衰减特性;在微波暗室和隔墙情况下分别测试了电磁波的衰减,得到电磁波穿墙后的衰减值.实测结果表明,仿真结果和实测结果的衰减趋势基本一致;蒸压灰砂砖墙的电磁波衰减能力在三种常见墙体中最强,达到每厘米厚度衰减0.510~1.081d B.
