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本打算在谢教授的原文(http://blog.sciencenet.cn/home.php?mod=space&uid=669170&do=blog&id=634422)中做评论,可惜不知为何,已经不让加评论了,只好在我这里做些评论。 我就是谢教授所提到的Yuguang Fang.
很久之前,谢教授就让我给些补充,可就是找不出时间。最近频频出现亲人,好友离去,让我好不伤心。半夜三更,却不能入眠。借助我出差之机遇,离上次所留博客整整十年之后,再留支言片语,聊作纪念逝去的亲人,好友,以慰我苍老之心。
翔波(Xiangbo)与我皆为Loparo教授之弟子,我去Case似乎也有他功劳。据说是他推荐我给我导师那儿,才争取到TA的。由于种种原因,我赴美晚了两个月,丢掉了那份还不错的奖学金,就荒废了一年。幸好第二年,又争到了奖学金,得以成为翔波的师弟,也曾做过远东(Yuandong)的师弟. 谢教授称我们为三杰,但对我来讲,实在有点过誉。远东硕果累累,大都在系统设计方面,而翔波与我更集中在稳定性分析。虽然远东与翔波文章颇丰,但赶上苏联解体,冷战结束。国防控制工业的美国人开始转入民用或学术界。本来就不多的一些教职,也渐渐被美国人拿去。很想去学术界的翔波与远东,就失去去学术界的机会。翔波毕业时暂留在我们系做访问教授,所以也是我的老师。记得有个老师讲非线性几何控制理论讲得一塌糊涂,后来还是让翔波去上。他不仅讲得清晰透彻,而且是我所上过的最好的课。他的数学功底可以与数学系老师相比。他也是我最佩服的研究者。在他访问期限已到,在试图转成tenure-track的过程中,我们系所有的研究生,组成一个团队,去找工学院院长为他争取,这在当时是少有的事。只可惜,院长很守旧,坚决反对近亲繁殖,不允许他留下任教。他一气之下加入了工业界。第一个是在亚特兰大的一个utility公司。他去了后,把人家原有的优化软件彻底改革,所发展的优化算法快速几倍。研究部门的副总裁打算专门给他成立了一个团队,让他领队开发。只可惜,公司重组,结果那团队还没有成立,就搁浅。后来他去了在休斯顿的Hitachi,做网络优化设计。他去了没有一年,又提出一套更好的算法。公司不能马上让他发展的算法马上上马,所以公司让他在家发展这套软件,只拿工资,不用上班,这是公司职员少有的待遇。这就是天才的翔波!
只可惜,天妒奇才,2004年附近,他被查出癌症。我也是那年差点魂归西天。我俩相互鼓励,与病魔作斗争。只可惜,他抗争了几年,还是没能战胜恶魔,英才早逝。翔波是我的良师益友,我们合作好几篇文章。在我最困难时,是他跟我导师沟通,给我争取到奖学金。在我在postdoc与留校做研究员之间举棋不定之时,是他告诉我,“树挪死,人挪活”,建议我走出去Case, 去做postdoc. 虽然过去了这么久,我依然记得他的音容笑貌,那个抽烟不停,一直笑容可掬的样子。我生存下来,都活到至今,培养了三十多位博士,包括二十多位教授。而我那最佩服的师兄翔波,却永远离我而去。试想,若他被留下做教授,该会是啥样?培养出多少英才?翔波的逝去,世之憾事!
很感谢谢教授为他做了小传,而作为师弟的我,却迟迟不能动笔。每次下笔,总有万分沉重。翔波,你在天国是否还在玩着Lie algebra?到现在,我还是看不懂你用Ito方程做得随机稳定性证明,你的Lyapunov exponent文章也不会有几个人看懂。虽然我现在已离开控制领域,下辈子咱们还做师兄弟!
Partial list of Xiangbo's publications:
@article{feng1992stochastic, title={Stochastic stability properties of jump linear systems}, author={Feng, Xiangbo and Loparo, Kenneth A and Ji, Yuandong and Chizeck, Howard Jay}, journal={IEEE transactions on Automatic Control}, volume={37}, number={1}, pages={38--53}, year={1992}, publisher={IEEE} }
@article{fang1994inequalities, title={Inequalities for the trace of matrix product}, author={Fang, Yuguang and Loparo, Kenneth A and Feng, Xiangbo}, journal={IEEE Transactions on Automatic Control}, volume={39}, number={12}, pages={2489--2490}, year={1994}, publisher={IEEE} }
@article{feng1997optimal, title={Optimal state estimation for stochastic systems: An information theoretic approach}, author={Feng, Xiangbo and Loparo, Kenneth A and Fang, Yuguang}, journal={IEEE Transactions on Automatic Control}, volume={42}, number={6}, pages={771--785}, year={1997}, publisher={IEEE} }
@article{feng1997active, title={Active probing for information in control systems with quantized state measurements: A minimum entropy approach}, author={Feng, Xiangbo and Loparo, Kenneth A}, journal={IEEE Transactions on Automatic Control}, volume={42}, number={2}, pages={216--238}, year={1997}, publisher={IEEE} }
@article{fang1997new, title={New estimates for solutions of Lyapunov equations}, author={Fang, Yuguang and Loparo, Kenneth A and Feng, Xiangbo}, journal={IEEE Transactions on Automatic Control}, volume={42}, number={3}, pages={408--411}, year={1997}, publisher={IEEE} }
@article{feng1990almost, title={Almost sure instability of the random harmonic oscillator}, author={Feng, Xiangbo and Loparo, Kenneth A}, journal={SIAM Journal on Applied Mathematics}, volume={50}, number={3}, pages={744--759}, year={1990}, publisher={SIAM} }
@article{fang1993sufficient, title={Sufficient conditions for the stability of interval matrices}, author={FANG, YUGUANG and Loparo, Kenneth A and FENG, XIANGBO}, journal={International Journal of Control}, volume={58}, number={4}, pages={969--977}, year={1993}, publisher={Taylor \& Francis} }
@inproceedings{feng1990stability, title={Stability of linear Markovian jump systems}, author={Feng, Xiangbo and Loparo, KA}, booktitle={29th IEEE Conference on Decision and Control}, pages={1408--1413}, year={1990}, organization={IEEE} }
@article{fang1994sufficient, title={A sufficient condition for stability of a polytope of matrices}, author={Fang, Yuguang and Loparo, Kenneth A and Feng, Xiangbo}, journal={Systems \& control letters}, volume={23}, number={4}, pages={237--245}, year={1994}, publisher={Elsevier} }
@book{feng1990lyapunov, title={Lyapunov exponents and stability of linear stochastic systems}, author={Feng, Xiangbo}, year={1990}, publisher={Case Western Reserve University} }
@inproceedings{feng1992study, title={A study of chaos in discrete-time linear systems with quantized state feedback}, author={Feng, Xiangbo and Loparo, Kenneth A}, booktitle={[1992] Proceedings of the 31st IEEE Conference on Decision and Control}, pages={2107--2112}, year={1992}, organization={IEEE} }
@article{feng1991nonrandom, title={A nonrandom spectrum for lyapunov exponents of linear stochastic systems}, author={Feng, Xiangbo and Loparo, Kenneth A}, journal={Stochastic Analysis and Applications}, volume={9}, number={1}, pages={25--40}, year={1991}, publisher={Taylor \& Francis} }
@inproceedings{fang1993robust, title={Robust stability and performance analysis: a new approach}, author={Fang, Yuguang and Loparo, Kenneth A and Feng, Xiangbo}, booktitle={Proceedings of 32nd IEEE Conference on Decision and Control}, pages={2006--2007}, year={1993}, organization={IEEE} }
@article{loparo1993lyapunov, title={Lyapunov exponent and rotation number of two-dimensional linear stochastic systems with telegraphic noise}, author={Loparo, Kenneth A and Feng, Xiangbo}, journal={SIAM Journal on Applied Mathematics}, volume={53}, number={1}, pages={283--300}, year={1993}, publisher={SIAM} }
@inproceedings{loparo1991almost, title={Almost sure stability of linear stochastic systems via lyapunov exponents method}, author={Loparo, Kenneth A and Feng, Xiangbo}, booktitle={1991 American Control Conference}, pages={1553--1558}, year={1991}, organization={IEEE} }
@inproceedings{feng1992design, title={On the design of active learning controllers for linear systems with quantized state measurements}, author={Feng, Xiangbo and Loparo, Kenneth A}, booktitle={1992 American Control Conference}, pages={2488--2493}, year={1992}, organization={IEEE} }
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