When our students come into contact with Professor Liang, he always looks younger than his actual age, full of energy, flushed and has no traces of years on his face. He can even be said to have tender skin, which is "small fresh meat" in the current network language. Less than fifty years old, he became the youngest principal of Xidian at that time. In my impression, it seems that he has never been old, or he will never be old at all. The photos of his youth are always so high-spirited, revealing the unique youth and handsomeness of that era.
Professor Liang is from Shanghai. He still speaks Mandarin with a southern accent. He sometimes likes to speak in Shaanxi dialect or xi dialect in class. He is still the kind with a southern accent, very approachable, or "very cute" in online language. My wife, Mr Zhang, is also my teacher. She is from Yangzhou. She is modest, easy-going and gentle. She is the kind of person who can't bear to hurt. At that time, we didn't quite understand why the couple wanted to stay and work in the northwest, separated by a red and professional historical era. We don't have to delve into it, and we may never understand it. With these thoughts, I can only say that I am narrow-minded.
However, more than 30 years have passed, and the photos on the Internet have clearly shown that he is white-haired on the podium and can't help but have mixed feelings.
When I was an undergraduate, Professor Liang was already a vice principal, busy with school affairs. This year, we were just lucky enough to hear the course of field theory and complex variable function.
Field Theory and Complex Variable Function is a basic theoretical course of engineering, which further expands solid coordinates into high-dimensional vectors. The introduction of the concept of complex number makes it possible to operate and transform plane coordinates in a complicated way, paving the way for the unification of amplitude and phase in electromagnetic applications. So this course is actually a stepping stone from advanced mathematics to applied mathematics.
Of course, such an important basic course is not only the course of field theory and complex variable function, but also other courses are hard to impress. If the class number is small, we can still vaguely remember who the teacher is. In most other classes, we rely on the support of our classmates and argue with each other to determine who the teacher is when talking about the past. Of course, the memory of the lecture content is naturally proportional to the memory of the teacher's name-almost all of them are returned to the teacher.
Obviously, in the memory of many students, everyone has a deep impression on complex variable function, and most of them think it is the best course. This is obviously related to teaching factors.
For example, in the preface of Field Theory and Complex Variable Function, he said:
"On the premise of the speech, I have a question (under tension). Why did you come to the lecture? -there are already textbooks, so why give lectures? In fact, this question is for Professor Liang himself. ) This is a problem! (starts whispering at the bottom) This is really a problem. I think of two answers. First, teaching materials are different from lectures. I have a lecture outside, so you can watch my lecture later. The handout says how I learned this textbook. It's different.
"For example, Water Margin is a classic, and many people have read it. People are interested, and I don't know what medicine is sold in the gourd. But everyone didn't see the tricks. There is a fifteen-year-old boy, Jin Shengtan, (Jin Shengtan? I haven't heard of it. I'm an engineering student, not a liberal arts student, right? Up to now, no one has recognized Water Margin. His criticism of the Water Margin is how he studied and viewed the Water Margin, in which there are many innovations and discoveries. He first discovered that Pan Jinlian's name was Song Wu, the first 72 times it was Song Wu Song Wu, and the 73rd time it became, your relationship has changed. Students smile and gain knowledge! )
"Second, mainly through the teacher to see the spirit. You are talking again. I'm talking about something big. I said, I never talk big: what is spirit? How the spirit plays. (The audience is unexpectedly quiet) Really, have fun when you should play, and work hard when you should work. This is our current young college students in China, which is far from the students in developed countries abroad. We all saw it clearly. I can't ask you not to play. This is wrong, isn't it? However, the students in China are all sloppy in their work and have not played well. Of course, I said the bad parts, but they are still very good. Work, like work, is the way you play when you play, and that is spirit. The students are very thoughtful. )
"Well, get to the point. What is the focus of the course Field Theory and Complex Variable Function? Grasp three: grasp the concept, grasp the idea, grasp the application ... "
This first contact is unusual, because Professor Liang's teaching style really gives students a refreshing feeling. Unlike other professors, he either paints a gourd ladle, or follows the book, or is a cliche. His lectures are very vivid, and they often inspire people to reflect on philosophical thoughts and values outside the classroom or teaching content. This prologue can easily arouse students' interest and attention, and challenge their knowledge and acceptance. This kind of frankness brings only earth-shaking shock!
To say that Professor Liang is different, his blackboard writing is impressive.
Anyone who has seen Professor Liang's calligraphy knows that although he does not have the beauty of traditional calligraphy, he is really unique and intriguing, which others can't learn. His blackboard writing is even more unique, which has been reported by CCTV radio. I remember that when he taught us, he didn't put many vivid portraits of Einstein and Newton, but we know that his painting skills are also quite tough. It is not difficult to find from many of his notes that his paintings are printed.
We even know that when he knits at home, he can weave many patterns that even ordinary knitters can't. If you are still joking at this time, can the professor still knit sweaters? Allow me to despise your connotation. Don't underestimate wool On each knitting yarn, local accurate calculation and overall layout are beyond the ability of ordinary people.
Professor Liang has a doctoral student disciple who is our teacher. He studied as a doctoral student on the job and practiced good calligraphy. He also tried to write on the blackboard in Professor Liang's style, but he looked like a ghost and could not surpass it. The reason is that his books are so beautiful that he ignores the balance consideration in the layout of blackboard writing. Professor Liang's blackboard writing is not so beautiful, but the whole style and layout are unique, and almost every stroke is carefully designed. It is conceivable that Professor Liang's blackboard writing is also an important part of preparing lessons. After a class, he never used an eraser again, and the layout was very clean, which was a masterpiece.
After class, the students take turns to clean the blackboard to prepare for the next class. Whenever Professor Liang's blackboard is to be erased, almost everyone will hesitate for a while, as if what is about to be destroyed and erased is a respected work of art, and no one wants to be such a "sinner". Almost everyone will do the same thing: go to the blackboard, pick up the eraser, step back and take a last look at the blackboard, as if to remember this final freeze.
Another thing that others can't learn is Professor Liang's sharpness and keenness in class.
At that time, the big class was a lecture hall, and the whole lecture hall was very large, which could accommodate two or three hundred people. The number of stairs is also high. Generally speaking, we are afraid of being called by the teacher, so we all take seats in advance and sit at the back, but we don't know that from the teacher's point of view, the person sitting at the back can look straight effortlessly, while the person sitting next to us has to look down. Generally, teachers don't ask too many questions in class, mainly because they don't want to embarrass students.
But Professor Liang always asks questions in class to attract everyone's attention and interaction, no matter how affectionate he is. Among the students he called up were class cadres, ordinary students, those who studied well and those who didn't study well, which seemed very casual and irregular. However, what students hear most after class is this description, "I was called as soon as I deserted!" " ""Me too, I just want to doze off! "Almost everyone has the same experience, that is, once they are distracted, they will be called up by Professor Liang to ask questions or go to the stage to do problems.
I was summoned, too.
Once, I listened carefully in front of the whole class, and the result may be that I didn't eat enough breakfast in the morning, and my head was very tired, either lack of oxygen or sugar, and I began to wander. When I talked about the concept of complex multiplication, it was already in the middle. At this time, Professor Liang suddenly called the roll and asked him to do an exercise on the blackboard. To be honest, I don't even know what the topic is. After being called up, a tingle began to wake up and then began to think about what the problem was. It took me about twenty or thirty seconds to walk from the middle seat of a row of stairs to the next corridor, and then to the front of the stage. I feel the air is frozen, only my brain is spinning fast, but it is idling, because my brain is still blank. No wonder the students who have been called in the past can't answer the questions!
When I walked to the blackboard, Professor Liang saw that I was at a loss, so he reminded me what this problem was, which was a graph obtained by multiplying a sector by j (yes, I will never forget this problem again! )。 At this time, my brain seems to be hung with files. In the fierce search process, the concept began to emerge, and finally I caught a lifeline-multiplying J is equivalent to rotating 90 degrees-and I already know what the answer is! I made a gesture on the blackboard on purpose, as if I were rotating this sector, and then I drew this figure accurately. I guess all the performances were seen by Professor Liang, and I am grateful-let me go back to my seat completely and let me go!
Among our classmates, I have been in contact with Professor Liang for the longest time, because I was his only master student that year. As for why I want to go to graduate school, I didn't understand it at that time, but the only thing that is clear is that if I want to go to graduate school, I will go to Professor Liang. Although I had the only postgraduate degree in my class at that time, I made the choice of postgraduate entrance examination. As a result, the postgraduate entrance examination went smoothly, and finally an interview with the tutor was needed. This is the first time in my life that I have experienced such an interview. I have no experience and don't know how to prepare. I recited a lot of formulas and went.
Professor Liang asked me a very simple question: after the inner diameter of coaxial line increases, does its capacitance increase or decrease?
I remember the calculation formula of coaxial line capacitance at that time, which is the reciprocal of the ratio of outer diameter to inner diameter after taking the natural logarithm. Therefore, after the inner diameter increases, the ratio of outer diameter to inner diameter decreases, the natural logarithm decreases and the reciprocal increases. According to this formula, it is easy to get the increase of capacitance. I hesitated for a few seconds, mainly to reconfirm the order of inner diameter and outer diameter in the formula. This order is reversed, the result is reversed, and the correct answer is given.
But unexpectedly, Professor Liang did not continue to ask other questions, but suddenly asked, why?
I was speechless at that time, thinking, why, according to the formula. So I faltered and said, what is this capacitance formula and how does it work according to it?
But the professor continued to ask, why?
I'm sweating again, and I really don't know how to answer.
I can't remember if there was a pause, maybe a few seconds or dozens of seconds. It feels like a long time for me. The professor explained that if the inner and outer conductors are unfolded, it is equivalent to two planes, that is, the plate capacitor. When your inner diameter becomes larger, the area of the polar plate expands, so the capacitance expands. This is a method to qualitatively analyze the problem from the concept. Although there is a formula, it may be wrong.
Yes! If the formula is backwards, the conclusion is completely wrong, but I can't judge the rationality of the conclusion. Obviously, in our learning process, we ignore too many concepts and the application of concepts. In fact, the concepts and methods have not really been mastered.
This interview gave me great inspiration and saw the shortcomings in my study, so that in my later study, I started with concepts more purposefully, not just remembering them, but using them. This is an advanced method, which plays a great role in my future study.
I went to Professor Liang's house several times when I was a graduate student. At that time, he was already the principal, but his salary didn't improve much. Every time I feel that his family is a very ordinary family, and there is no special treatment from the principal and professor. The building at that time, that is, the early tube-shaped building, may be two bedrooms and one living room, or three bedrooms and one living room or something. There isn't even a drawing room at home. As soon as I enter the door, I can only talk about work in a public room that is both a restaurant and a living room. I remember Professor Liang's home has a unique taste, not the legendary scholarly family, but the taste of cooked food. At that time, he was curious about what the professor's family usually ate, and he was afraid to ask, so he never got the answer, just like a question he didn't understand when he was studying, and he had regrets all his life.
Undergraduates after the principal leaves office should be luckier, and they can listen to Professor Liang's more direct and professional lectures. This is his opening remarks in Fundamentals of Microwave Technology:
"What is microwave technology? It depends on Maxwell's equation to eat. If you don't understand, you don't know how to use it. What's the problem? The Maxwell equation we just emphasized reflects the mutual transformation between electricity and magnetism, space and time, and the transformation conditions must be proportional to the frequency. It reflects the contradiction between frequency and medium: non-conducting means medium, conducting means conductor when conducting, and semiconductor in the middle. This is our definition of media.
(Subjective objectivity of blackboard writing fluctuation)
"Electromagnetic wave, objective existence, there are many things in the world, are objective existence, can you know? Not necessarily. Why can't we know the objective existence? Let's take an example, the earth that people know. Chinese civilization has lasted for five thousand years. China people are very clever, but they dare not compliment their knowledge of the earth. Our ancestors told us:' The sky is round and the earth is square'. Up to now,' there is a beautiful place' is still called' place', which can't be changed-no one can understand it. Until Magellan discovered the new world. When did he find out? Why hasn't everyone discovered that the earth is round for so long? The earth is too big! Just like an ant crawling on a big ball, it thinks the ball is flat and climbs comfortably; The Monkey King urinated in Tathagata's palm, thinking that he had reached the horizon. Why? Tathagata's hands are too big! So we all know that compared with us, something too big is difficult to study, and this is the universe. On the contrary, things that are too small are difficult to study, such as molecular atoms and neutrinos as we know them. What is the easiest thing for people to learn? As long as it is about the size of human beings, I will talk about the characteristic dimensions of human beings.
(blackboard writing: the characteristic dimension of human beings)
"Height, human characteristic size, one meter five to two meters, such as Yao Ming is two meters tall and Wu Dalang is one meter three seven. This is a small probability event. Human hair, 0. 1 mm, is about half a hair. This maximum size and minimum size are just the size of our microwave band, so the microwave band has a very close relationship with people.
"Let's give another example ..."
If I had listened to Professor Liang's "Fundamentals of Microwave Technology", I wouldn't have answered the question of coaxial capacitance so stutteringly!
Now Professor Liang's students still have a happy place, that is, they are lucky enough to get a hand-painted New Year card designed by Professor Liang every year. As we all know, this kind of effort, this pure sincerity, can't be bought by money.
An unknown teacher and sister professor has worked abroad for more than twenty years. When she returned to China to visit Professor Liang and Teacher Zhang, she felt deeply:
"Visiting a teacher, Liang Changhong, touched my life several times and reflected on my own smallness several times. In those days, I learned from him because I admired his knowledge, wisdom and talent. I admire him now because of his personality, his sincerity and responsibility to his family and students. His classes are always so vivid and his blackboard writing is always so artistic. His pen drawing is very fast and realistic; He attends classes with nearly 100 master students and doctoral students; He writes books and has published five or six books in recent years. The hardest thing is that he has to take care of his wife who can't take care of herself. He takes his wife with him in class and on business trips. Under his careful care, his wife's condition did not improve quickly and remained stable for a long time. Although Jenny can't express herself in words, we know from her bright smile that she is the happiest woman in the world. Teacher Liang is flexible and is the best person I have ever met. "