I had Ervin for Numerical Methods as a sophomore in ME and he was by far the best math professor I had. He is extremely intelligent and he knows mathematics a very fundamental level. His education background is pretty remarkable as well. Ervin’s notes are clear and he is a good lecturer. He has a dry sense of humor but he can make you crack a smile every once in a while. One thing to watch out for are the exams. All of his exams were fair however he does not allow an equation sheet or calculator(although it could be different for your class). As a result I had to memorize every single concept, definitions and formulas for the final exam which was difficult for me.