Professor Ju does an excellent job of teaching his material. He made the entire course lecture into a pdf file for you to follow. While the material of 105D may not come as easily as material of other courses, he really does cover all the material in a very concise and organized manner.

He really believes in thinking as opposed to plugging and chugging, and thus is a fan of derivations in his tests. The problems he gives are good. i.e. slightly challenging, but very "core".

In lecture, sitting in your seat, he seems like the nicest guy. When you ask him a question, however, he cam make you feel pretty stupid, and kind of don't feel like asking him any further questions. But thicken your skin, and ask what you need to know. He makes himself very available, despite all that, and will answer your question thoroughly, provided he deems it not too basic and something you should have learned from other classes.

Overall, great professor. You learn a ton from his lectures, he puts a lot of effort into organizing his lectures, and they are effective. His education philosophy is good, and you come out learning something worthwhile.