这次presentation真是多灾多难。能出现的问题似乎都遇到了。还好都是有惊无险。

要准备时，突然发现PPT带错了，只带了在许昌报告的中文版本。差别不仅是语言，内容也有改动，增加了我们在JSV上关于内共振新的工作。笔记本和移动硬盘两个版本都错了。开始想请家人从家里从书房的电脑里拷贝，家里还没有人。想到出发前曾拷贝给Lihua，赶紧联系。幸好他还能找到。这个问题算是解决了。

在报告前，发现会议室里没有电脑。Lihua取来他的笔记本，但尝试一阵，无法连上投影仪。后来Brian来，去取他的笔记本，总算连上投影仪了。但等播放时，我的PPT居然打不开了。拷贝到笔记本硬盘中仍打不开。最后用了Lihua带的U盘中的备份。我之前准备时有些修改，多少都算无关宏旨，不改也不要紧。

这次seminar，在个小会议室而不是上次那个电化教室，只有一个圆桌。人比上次少。4位教师，除Brian和Lihua，还有机械系动力学与控制教学组(Teaching Group)的负责人高级讲师Roger Halkyard博士。另有一位教师不认识。研究生有3个。这次报告，主题是能量采集，虽然热门，但比振动控制还是窄些。而且聚焦在我们自己提出的内共振能量采集，就更专门了。人少也在情理之中

虽然由于种种故障，报告晚开始10分钟，就是比惯例晚5分钟又晚了5分钟。我开场比较简单，就这我PPT上的单位，说明上海大学力学学科的构成。然后就是正文，花大约一半时间把问题背景和研究动机阐述清楚，然后讲我们在内共振能量采集方面的结果。

报告后，Brian问两个问题。一个是他先前在工作午餐时就提到的，关注如果在有跳跃现象时把系统响应控制在上面或下面；另一个是双跳跃时接近严格共振处幅频曲线不稳定对应的运动幅值的大小。前面一个问题没有现成的解答，后面一个我已经说过周期运动失稳后出现准周期运动甚至混沌运动，回答时补充说明幅值通常比较大。Lihua提出一系列更技术性的问题，包括与他自己实验结果的比较。毕竟他是长期在这方面研究的专家。

Seminar后，到他办公室继续讨论一小会儿。然后到家泰国小餐馆吃饭。

饭后回宾馆放松一下。一下午通读长篇小说《道士下山》至终卷。并非实体书，只是能找到的网络版本。

附：报告摘要

Recent explorations on internal resonance energy harvesting

A vibration-based energy harvesteris essentially a resonator working in a limited frequency range. To increase the working frequency range is a challenging problem. A promising solution approach is to introduce intentionally nonlinearities into the design of energy harvesters. The bending of amplitude-frequency response curves can be employed to broaden the harvester working frequency bands. Internal resonance may be a possible mechanism to enhance energy harvesting, because, amplitude-frequency response curves will bend to both increasing and decreasing frequency directions in the presence of internal resonance. The presentation summarizes three investigations on internal resonance energy harvesting. Firstly, a prototype of an internal resonance piezoelectric energy harvester is conceptually designed, and the averaged root-mean-square output voltages are calculated under four kinds of noses, namely, the Gaussian whitenoise, the colored noise defined by a second-order filter, the narrow-bandnoise, and exponentially correlated noise. Secondly, an electromagnetic device with snap-through nonlinearity is proposed as an archetype of an internal resonance energy harvester, the amplitude-frequency response curves derived from the method of multiple scales have two peaks bending to the left and the right respectively, and the averaged power is calculated under the four kinds of noises. Finally, an L-shaped cantilevered structure laminated with a piezoelectric patch and augmented with frequency tuning magnets is treated numerically and experimentally. All these works demonstrate that the internal resonance increases the opening bandwidth and the output electricity.