Reference letter
(Control Theories)

Dear Sir or Madam:

The purpose of this letter is to recommend Mr. Yi, aworthy candidate for admission to your graduate program.

Mr. Yi have ever took my course "Introduction to Control". Iwas deeply impressed with him not only the good score "A" he gotin the class but also the highly active and devout attitude helearn Control Theory. Sometimes, he came to my office to ask mesome interesting questions about the Control and System theoriesnot mensioned in the autobiology of my class and to discuss thedevelopment and application of control theory in Science andIndustry. with me. He imagined this theory is truly an amazingsubject. If people understand and use it very well, this worldwill get better. "Well!" I thought, " This young man is reallylike Control."

Then he took part in my research "Design of Sinusoidal OscillatorsUsing the Theory of Variable Structure Systems" (published in theInt. J. of Electronics, 1992, Vol. 72, No. 1) to design theoscillator circuits. From simulating the circuits he designed withPSPICE to assembling the electronic elements. he shown methe enthusiam and hardily spirit in his work. When getting a newidea or finding some questions, he always shared his opinion abouthow to overcome the error or improve the experiment results to me.After try-and-error and ameliorating the circuit many times, wefinally got a refined but good-performance oscillator.

Mr. Yi also got admirable grades in a couple of courses ofcontrol and systems, I truly believe he has strong learningcapability and enthusism in this field. So I no doubt that he willbecome a good student in your esteemed departmant. Should you needany further information about Mr. Yi, please do not hesitatecontact me.

Sincerely Yours,