Chapter 22 third quarter

In the decades since he entered Tsinghua University for the second time, Ye Qisun, in addition to playing many social roles, has spent more time in preaching and teaching. He has been a teacher as his job and is deeply loved by students. Please listen to what his students praised him in the book "A Generation of Teacher Ye Qisun"—— Qian Sanqiang (a graduate of the eighth grade of the Department of Physics, Tsinghua University): Mr. Ye taught thermodynamics to our class in 1933.Thermodynamics is a relatively difficult course to understand. In addition, he has a Shanghai accent and has a bit of a stutter, but these did not prevent him from teaching thermodynamics well.He explained the basic concepts very clearly, and in those important and critical places, he took the trouble to repeat the explanation until the students figured it out.He has reference books in class, but he never reads according to the contents of the books. He lectures on thermodynamics for different classes between two and three years, and the examples he gives are almost never repeated each year, so sometimes he asks us to borrow the books from the previous class. notes. In 1948, I returned to China to teach at Tsinghua University. I stayed at Mr. Ye’s home, and I discovered that he prepared his lectures very carefully. Almost all of his lectures were based on examples from recent developments in thermodynamics, which was somewhat similar to the lectures given by foreign high-level professors.Although he has not published many research papers after returning to China, the process of his teaching is the process of absorbing the latest foreign research results and developing his own insights.We old students still feel that Mr. Ye's original education has left a deep impression on us when we talk about it.

Wang Daheng (8th grade graduate of Department of Physics, Tsinghua University): I listened to Mr. Ye Qisun personally teach in the third and fourth grades.He lectures us on thermodynamics, kinetic theory of gases and statistical physics.Mr. Ye speaks very slowly due to stuttering, but his words are concise. He focuses on guiding students to understand physics concepts and proceeds step by step. He is really persuasive.He is knowledgeable and chooses his lectures calmly. The same course, the same principle, different content and examples in the previous grades, but the same approach but the same effect, can enable students to have a correct understanding of the laws of physics and inspire them in application.From learning the concept of physics and dialectically understanding the laws of physics, I benefited a lot from Master Ye, so that when I was engaged in teaching and scientific research later, I imitated Master Ye’s way of thinking connotatively, which also enabled me to learn from Chairman Mao in New China. The theory of practice and the theory of contradiction are easy to understand as scientific viewpoints and methods, and are connected with reality.

Qian Weichang (a graduate of the seventh grade of the Department of Physics, Tsinghua University): Teacher Ye is not good at eloquence, stutters, and has a Shanghai accent, but the logic of the lectures is very strong and clear, and the development and formation of physics concepts are particularly in-depth and fascinating.No matter how busy Mr. Ye is with the school's administrative work, he still has to teach a class every semester. I have listened to Mr. Ye's lectures on heat and thermodynamics, optics, acoustics and modern physics in four years.He also lectured on physics, quantum theory, atomic spectroscopy, etc. in other shifts.When I arrived at Kunming Southwest Associated University from Beijing in the spring of 1939, because Mr. Ye was going to Chongqing to take over as the director-general of the Academia Sinica, he gave me the task of teaching thermodynamics in the second year of the Department of Physics. I heard Mr. Ye in 1933. He thought he had done a good job in his thermodynamics class, so he agreed. At the same time, he also gave me the notes of the five lectures (Ye already gave two lectures) for the convenience of taking the class.But after Master Ye left Yunnan, when I carefully prepared the lesson according to Master Ye's notes, I found that although the basic principles taught were still the first and second laws of thermodynamics that I was familiar with, the examples cited were entirely related to the thermodynamic properties of metallurgy. I didn't expect it.When I was studying thermodynamics in 1933, all the examples were related to gas law, such as ideal gas law, van der Waals equation, critical state and thermodynamic function of gas, etc. This reflects the problem of gas state in the early 1930s. 1. The issue of steam power was a hot topic in the industry at that time. Therefore, no matter in the thermodynamics of the physics department, the thermal engineering of the mechanical department, or the physical chemistry of the chemistry department, the gas issue was emphasized.However, in the late 1930s, due to the advent of the Second World War, metallurgy developed rapidly, and the thermodynamic properties of metals made great progress. Although thermodynamics, as a basic physical law, did not change much, its application focus has shifted to Metallurgy went.Teacher Ye is well read, and he incorporates into his lectures fruitful parts of the latest developments in the academic journals of metallurgy that utilize the laws of thermodynamics.Master Ye’s less than ten-page lectures taught me deeply, and made me realize that it is not easy to be a university professor. Although I teach the same course every year, I should change the scope of application of the basic theory with the times, so that A basic course must keep up with the pace of scientific development, often read a large number of international journals related to science and technology, digest and absorb them into the textbooks, and only then can the professor's lecturing responsibility be fulfilled.This has given me a lifetime of guiding principles for lecturing...

Hu Ning (a graduate of the tenth grade of the Department of Physics, Tsinghua University): When I was studying at Tsinghua University in 1935, I heard him give a lecture on thermodynamics, and he left a deep impression on me.He didn't bring his lecture notes, he didn't write many words or formulas on the blackboard, and he spoke very slowly, partly because he had a slight stutter.He explained the content of the lecture slowly, carefully considering every word in every sentence, and constantly analyzed and deliberated carefully on the physics problems he talked about during the lecture, as if he was also exposed to this problem for the first time like us , The classmates who attended the class were naturally infected by him and thought together with him.Every time Mr. Ye draws an important conclusion or derives an important formula, we feel as if we discovered these results together for the first time. His explanations are always very clear and focused, and sometimes he stands in front of the window After thinking silently for a while, the students also waited silently.Mr. Ye taught a lot of courses for our "tenth grade" students. These courses are intermediate heat, thermodynamics, theoretical mechanics and gas molecular motion theory in order of priority. Partial differential equations are the most used mathematics in thermodynamics. But listen to Mr. Ye Lectures on thermodynamics do not make people feel that I have taught a lot of mathematics. On the contrary, my main concepts on partial differential equations are derived from Mr. Yeh's lectures on thermodynamics. The content is still deeply in my mind.In the theoretical mechanics class, Mr. Ye once talked about how to deal with the problem of doing exercises. He said that after reading the exercises, he said that he should first understand the problem to be solved, and then know how to solve it after thinking about it. There is no need to do a lot of exercises. .My understanding is the same. The function of the exercises is only to help us understand the content of the class more deeply. Attending the lectures is not for doing exercises, and it is even more unnecessary to do difficult problems.The real problems encountered in life are the problems encountered in actual scientific research, and these problems may take a month or half a year to be solved.In contrast, the so-called difficult problems in the usual textbooks are nothing more than a calculation game.A person who can take exams or do exercises is not necessarily a good physicist. This is what I heard Mr. Ye and other teachers often emphasize when I was studying in college.Practice has also proved that this statement is completely correct.The "Molecular Kinematic Theory" taught by Mr. Ye is an important achievement of Newtonian mechanics applied to molecular motion in gas. The British have made a lot of contributions in this area. They proudly call the Kinematic Theory of Gas Molecules the colorful clouds over Britain in the 19th century.This kind of class is generally taught by theoretical physics teachers now, but Mr. Ye, as an experimental physics teacher, shows a deep knowledge of theory in his lectures, and his lectures are both vivid and inspiring.He always pointed out relevant references to us after he finished speaking on a topic, which made us feel as if we were introduced into a wonderful place by Mr. Ye, and we saw many beautiful things inside, but even more beautiful things are still inside.Mr. Ye just pointed out that we should go in and explore by ourselves. This kind of teaching and guidance that inspires us to further pursue the truth is the most precious part of Mr. Ye's teaching thinking.

Tang Zhengyin (graduated from the twelfth class of the Department of Physics, Tsinghua University): In the autumn of 1936, when I was admitted to the Department of Physics of Tsinghua University, Mr. Ye’s reputation was already well-known. I heard that he insisted on principles, did not show favoritism, and was very powerful. In the first class of thermodynamics in 1936, I finally met this great man. He was of medium build, with a square face, articulate, occasionally stuttering, and always had a smile on his face, but he looked very kind.His lectures have several characteristics: 1. Focus on the difficult to understand, discuss repeatedly or write relevant reference materials; mention the easy to understand or let the students study by themselves; 3. Connect with reality and improve students' hands-on ability. For example, when it comes to thermometers, he mentioned the glass tube of the thermometer. The aging process must be carried out in advance, and how to age it; 4. Be very careful when correcting homework and test papers. When some formulas do not use the usual method and the operation is concise, more points will be added, and the name of the student will be recorded. In the future, we will often meet with the student for conversation and encouragement, and give individual guidance.

Hu Yuhe (Graduate of the twelfth class of the Department of Physics, Tsinghua University): Mr. Ye has experience in lecturing. For some abstract concepts, he explained them in a simple way and explained them in detail, so that students can understand them correctly.He selected textbooks in an orderly manner, and he finished the courses of heat and thermodynamics, which are quite complicated, in two semesters.His writing on the blackboard is neat and easy to take notes.Mr. Ye attaches great importance to the ability to inspire students to think about problems; the exercises or test questions he gives are not necessarily very difficult, but they require hard thinking, correct concepts, and quick calculations to obtain satisfactory results.

Huang Zuqia (Graduate of Tsinghua University in 1948): Mr. Ye taught us electromagnetism in my sophomore year, and taught physics theory and kinetic theory of gas molecules in my third year.In his lectures, he pays attention to explaining the basic concepts of physics and inspiring students to think for themselves. Questions to students can often make the questions deeper and more meaningful. At the same time, he always introduces suitable reference books for students to read. Remember that he is talking about gas molecules When discussing motion theory, he introduced me to carefully read the original works of Boltzman because I often raised some questions. His guidance benefited me a lot in my future work.

Long Qiwei (graduated from Tsinghua University in 1949): Our class is very lucky. During the school period, we had the opportunity to listen to Mr. Ye's lectures three times.The first time was in the second semester of the first year at Southwest Associated University in Kunming in 1946.Since Professor Zheng Huachi was going north to prepare for the resumption of the school, Mr. Ye taught the general physics class he left behind.If there is no one to teach him in any class, he will teach it.Mr. Ye has rich experience in lecturing, and adopts heuristics. He constantly asks us questions in the lectures, inspires us to think, attracts our attention, and then explains each question one by one, which impresses us deeply.The next two lectures were the "Theory of Physical Properties" and "Theory of Molecular Kinematics" respectively in the second and third grades.

Continuum mechanics should belong to the scope of physics, and it can be well connected with material technology and engineering.This is the content of the fifth volume of "A Course in Theoretical Physics" by Landau and Sofschitz.There was no such course in the formal curriculum plan of our physics department at that time.Students in our physics department must learn from scratch if they want to involve elastic theory or fluid mechanics in their later work.The "Physical Property Theory" given to us by Mr. Ye just supplemented the above-mentioned deficiencies, and enabled us to gain initial knowledge in the work on the mechanical properties of metal dislocations and fractures.For example, Mr. Ye told us about the girder problem.In 1976, we applied the dislocation theory to calculate the stress intensity factor of the cantilever beam crack.Later, it was further developed to discuss the distribution of dislocations in the crack top domain.

The old physics department did not offer statistical physics courses.This course was a postgraduate subject at the time.Considering the long-term needs, Mr. Ye taught us the course "Molecular Kinetic Theory".This course also gives us the foundation for studying statistical physics after we leave school.The knowledge of statistical physics is very useful to those of us in the metal industry, whether it is alloys, phase transitions, defects, diffusion, and mechanical and physical properties, it is needed. Liu Guangjun (graduated in 1952 from the Department of Physics, Tsinghua University):

The thermodynamics course I took in college was taught by Mr. Ye. Mr. Ye's lectures are very incisive and profound, which benefited me all my life.Mr. Ye is approachable, kind and amiable. He cares about his classmates just as he cares about his own children, which makes us unforgettable all our lives.The following things particularly impressed me. At that time, most of the reference books used in various courses were in foreign languages, and the scientific inventions and creations of my country were not mentioned in the books. The one that impressed me most was the first class of thermodynamics. What Mr. Ye talked about was Chinese scientific inventions. create.It was the first time I heard the names of ancient scientists such as Zhang Heng and Shen Kuo, and knew that there were ancient scientific works such as "Mengxi Bi Tan".This opened my eyes, and I felt that I knew too little about the science of my motherland. Later, I bought a copy of "Heavenly Creation".Mr. Ye's lectures are profound and simple.Thermodynamics is relatively abstract, especially the concept of entropy, which is not easy to grasp.It was 1950 at that time, and the concept of thermodynamics of irreversible processes had just emerged, so it was not popular to divide the change of entropy into two parts: the entropy generation inside the system and the entropy exchange with the surrounding environment.However, Mr. Ye's lectures at that time made us clearly realize that we must distinguish between "inside the system" and "surrounding environment", so that we can have a deeper understanding of entropy.I remember that this question aroused great interest among the students at that time, and many students had a heated discussion on the wall poster in the study corner of the class. Ji Yingnan (enrolled in the Physics Department of Tsinghua University in 1950): I was admitted to the Department of Physics of Tsinghua University in 1950. Due to the adjustment of departments, I transferred to the Department of Physics of Peking University in 1952. Although I was lucky enough to listen to Mr. Ye’s class in 1953, I had very little contact with him. Perhaps I had the least contact with Mr. Ye. one of the students.But despite this, Mr.'s rigorous style of study and his strict and friendly attitude towards students are something I will never forget in my life. ... It was only in the third grade that I was lucky enough to listen to the teacher's lecture.I remember that year, long robes suddenly disappeared among students and ordinary people, and everyone began to wear short clothes, but Mr. Ye still wore long robes, and he always had a smile on his face, adding to Xun Xun's elegant demeanor.To the students, he is a kind elder. He is so kind and kind in giving lectures and answering questions, making everyone feel like a spring breeze.At that time, my husband was in charge of geometric optics, and I only had 2 class hours a week. I used Drude's book, which was concise and thin. Of course, it was easy for my husband to explain it.But Mr. always prepares carefully every time. He highlights the main content and quotes extensively. Sometimes he also introduces some relevant history of physics. Everyone feels that this course is not difficult because they digest well.At that time, I had an idea that physics was different from engineering, mainly to grasp the "principle" of "things" and not to pay much attention to calculation. I am afraid that I am not the only one who has this idea.In this exam, I feel that I can do all the questions. At most, there are some calculation errors here and there, which are harmless, so I am quite satisfied.As a result, when the test papers came out, I was taken aback. The result was more than 20 points lower than I estimated, and the grades of the whole class were not high.After looking at the carefully corrected examination paper, I realized that many points were deducted for calculation errors.At this time, Mr. Ye told everyone that the content of geometric optics is the principle and calculation formula of optical system design. The requirements of optical system are very precise. If the calculation is wrong, will the design be in vain?If it is actual work, it will cause a lot of damage, so digital calculations should also be taken seriously.It is further pointed out that it is necessary to be able to analyze where the error has a great influence. For example, in some formulas, the denominator is a number with a small number of effective digits obtained by subtracting two similar numbers. Therefore, special care should be taken in the calculation process and effective figures.Everyone didn't pay enough attention to this, so they deducted a little points for calculation errors, so that you have a deep impression of this.This incident really left a deep impression on me. In the years of teaching and other work after graduation, whether it was for my own work or the requirements for students, I often thought of Mr. Ye's teachings.So this incident has benefited me far more than dealing with geometric optics itself. In fact, it educates us to have a rigorous scientific attitude towards work and study, and teaches us useful learning methods. For me, it is a lifelong benefit. Chen Peiyun (graduated in 1964 from the Department of Physics, Peking University): Mr. is very knowledgeable.In addition to the profound knowledge of physics, especially magnetism, the knowledge of other aspects is also quite extensive.His English level is very high. During our contact with him, he has never consulted a dictionary when reading English literature.He stutters a bit, but he speaks English fluently and never stutters.Once I came across a new English word and searched the dictionary of the department library but couldn't find it, so I asked him for advice.He said: "This is a new term in physics, and it doesn't exist in the dictionary." He pointed to the one-foot-thick "English-Chinese Dictionary" on the table: "This is the most complete dictionary, and it doesn't exist. "Then he guessed the meaning of the word from the context, and encouraged me to find relevant information to discuss.When we asked him how many languages ​​he knew, he said modestly: "Not many, three. I don't know Russian yet, but there are many Russian literature, and I will learn it in the future." He taught himself German and French.He said: "I learned French from a classmate from the French department. When we were in college, we were free to choose roommates. I lived in the same room with that classmate from the French department. You should also make some liberal arts friends." Qian Weichang (a graduate of the seventh grade of the Department of Physics, Tsinghua University): The first time I met Teacher Ye was at Ye's house.Unexpectedly, Teacher Ye was not a professor in a suit and leather shoes as I imagined, but a kind and gentle elder in a gray robe and a pair of cloth shoes on his feet.I stutter a bit, and when I hear my complaints, I comfort me and say, don’t worry, you can study your request slowly, and when you hear that my math and physics exams are not good, you encourage me to say, I heard your You do well in literature and history exams. If you can learn literature and history well, as long as you have the determination, you can also learn mathematics and physics well.He also gave an example of studying "Historical Records" to find out why Sima Qian used the framework of "Zhi", "Benji" and "Biographies" to describe the development of this period of social history. Sima Qian used the way of describing representative figures to reflect The connotation of the rise and fall of society in this period, using "Taishi Gongyue" to summarize and comment on the role of a certain character in the development of social history, reading history is important to master it, and to understand it does not lie in memorizing certain details.The same is true for studying physics. The key is to understand. Don’t memorize the formulas, memorize the laws. If you understand it, you will remember it naturally.Therefore, if you can learn history well, you can also learn physics well.His conversation doubled my confidence in learning physics, and since then, I have learned the guidelines of various sciences. This is a praise that lasted half a century.From 1924 to 1965, Ye Qisun, as a teacher, fulfilled the promise he signed with the motherland to save the country through science and education, and he never slacked off from beginning to end.In the past fifty years, no matter whether he is in an important position or a commoner, he has always been conscientious in front of students and podiums. He has never eroded his aspirations due to power, nor has his fighting spirit been worn down by suffering.All the students he has taught, whether they are scientific and technological heroes of the Republic or ordinary technicians who are unknown, will echo in their hearts the cry of saving the country through science and education left by Master Ye, and they will serve the motherland like Master Ye for the rest of their lives. Serve and do our best for the early arrival of the scientific spring of the motherland.