An Zhusheng listened carefully to Shen Yiyi's explanation of Luo Yu one by one. Obviously, the two are discussing the derivation of a formula. However, when I think about the formula derivation in the textbook, it should not be as complicated as the formula discussed by the two students now. Just by glancing at it, An Zhusheng found that there seemed to be a lot of steps in the derivation of this formula. When he heard what Shen Yi said to Luo Yu at the beginning about the concept of "equivalent infinitesimal amount", An Zhusheng really couldn't sit still.

Have you ever heard of calculus in the derivation of formulas in high school textbooks? It's a course that even college students are afraid of. You only have to go to various universities and see the look of the students who grit their teeth and want to ask the teacher to give a good score when they mention "advanced mathematics", and you can imagine how profound the knowledge points of such a course are. What kind of formula can be derived using calculus, and then it can be obtained through so many steps of derivation?

An Zhusheng couldn't sit still. He couldn't help but stand up and slowly paced behind Shen Yiyi and Luo Yu, wanting to see the form of this formula with his own eyes. And Shen Yiyi and Luo Yu were still immersed in their own world of knowledge, and they never noticed that such a stranger had stood behind them.

When Shen Yiyi deduced step by step, she reproduced the whole process of the formula she explained to Xiao Yizhan for Luo Yu at that time. Of course, this time the process is more detailed, and there are even a lot of additional explanations, just to let Luo Yu, who is still deficient in knowledge accumulation, understand the source of each step of the proof. Therefore, when she was finally able to finish writing the formula of the last step, she was secretly relieved in her own heart. To know the Tao and deduce a long formula, it is true that students need to concentrate in the process of listening to the lecture and understand the information conveyed by the teacher's explanation in time; But the teacher who is the narrator. It is also necessary to concentrate on ensuring that every step of your derivation is not wrong, which is also a mental pressure for the teacher. Now that it's finally done, there is no fork after pushing this formula, and Shen Yiyi's heart can be put down.

She was about to ask Luo Yu if she already had a feeling for the derivation of the formula just now, and there was nothing she couldn't understand. But before he could speak, a voice suddenly came from above his head.

"You deduced this formula yourself? Are you sure this is accurate? ”

Shen Yiyi was startled for a moment, raised his head, and saw a person's upside-down face. She turned to the side and didn't answer the man's question, just asked, "Are you———? ”

She found that this was an old man, about sixty or seventy years old, but he was goosebump-haired, and he looked very "stylish". For the elderly who like to soak in the library. Shen Yiyi has always dared not despise it. She always felt that a place like the library would hide dragons and crouching tigers, and maybe she would run into the sweeping monk of Shaolin Temple written by Master Jin Yong. Of course, the sweeping monk is a legend, but I can't guarantee that there will be some old expert, old scholar or old cadre here, so I can't ignore it.

An Zhusheng also did not answer the questions raised by Shen Yiyi. He just repeated his question: "Are you so confident in the formula you pushed yourself?" How did you start teaching and teaching to others? ”

At this time, Luo Yu, who was sitting next to Shen Yiyi, also stood up. He had already recognized the identity of this old man, who was his grandfather's good friend, An Zhusheng, the former chief engineer of the 606 Institute. After seeing him stand up, he saluted the old man in a proper manner. Greeted and said, "Hello Grandpa An, I'm Luo Yu." Do you remember me? ”

Old man An didn't expect that there was a boy who still knew him. So when he looked in the direction of the voice, and saw a face that he still had a little impression of, he looked at it a little and recalled the identity of this young man.

"Aren't you the grandson of Old Man Xiao? What's the matter, this female classmate is your classmate? ”

"It's not. Grandpa Ann. This is Shen Yiyi, a classmate from the city's No. 11 Middle School. Luo Yu hurriedly explained to An Zhusheng, and then turned back to Shen Yiyi and said: "Yiyi, this is the chief engineer of the 606 Research Institute, An Zhusheng is an old man, and he is also a good friend of my grandfather. ”

Shen Yiyi heard that this old man was the chief engineer of the 606 Institute. I remembered the news that Mr. Xiao brought a few days ago, that the drawings of his engine had been sent to others to see, and it seemed to be 606. And the manufacture of that prototype will also be placed in the 606 Institute, could it be that Old Man Xiao went to find the old man in front of him at that time?

An Zhusheng now heard Luo Yu introduce that the classmate in front of him was named Shen Yiyi, and suddenly remembered that two days ago, Xiao Yizhan, an old man, came to him and took out a set of engine drawings, which made his backward colleagues greatly admired, and also introduced that the author of this set of drawings was a high school girl. At that time, he also introduced that this girl also came up with a few formulas that amazed him, could it be that the girl in front of him?

An Zhusheng's eyes were different when he looked at Shen Yiyi again this time. He changed the question to this girl with great interest: "It turns out that you are Shen Yiyi." Is the formula you deduced for Luo Yu now one of the few formulas you gave Xiao Yizhan last time? ”

When Shen Yiyi heard An Zhusheng's question, he guessed that it was estimated that this old-timer had already heard about himself from elsewhere, so he nodded: "Yes, An Lao, I am Shen Yiyi." This formula is also one of the several formulas given to Xiao Lao last time. ”

An Zhusheng nodded. Since he knew that the two students in front of him had some relationship with Xiao Yizhan, and also confirmed the identities of these two people, they could be regarded as his juniors, so he began to rely on the old and sell the old land. He simply picked up the piece of paper that Shen Yi had just written and drawn a bunch of formulas from the table, put it in his hand and looked at it.

Just now, I just listened to some sporadically in my ears, but now when I hold it in my hand, An Zhusheng is really an eye-opener. When the most basic one of the formulas she handed over last time that Shen Yiyi deduced was completely displayed in front of An Zhusheng's eyes, it still made him feel like a treasure.

One of the biggest differences between the old intellectuals of their generation and the new generation of college graduates is that their basic skills are quite solid. While today's college students have relied heavily on modern computing tools such as computers, most of these older generation of college students have the ability to take out a blank piece of paper and a pen to complete a calculation task completely. Today's college students can't do anything without the computer at all, and they suffer from severe computer dependence. Sometimes it's a joke that once China goes to war with a foreign country, as long as the foreign country cuts off China's electricity, then all China's R&D activities will stop. Of course, in Shen Yiyi's view, this problem is not only in China, but also in the United States, which can only be deeper than China's, not less than China's. This may be the price that the progress of technology has made for mankind.

An Zhusheng's own profound theoretical foundation and solid calculation skills made it effortless for him to look at Shen Yiyi's set of derivation formulas. What's more, the formula written by Shen Yiyi this time was specially explained in more detail in order to take care of Luo Yu's degree. Every step in the derivation of the formula, in An Zhusheng's eyes, is so unexpected, but it is reasonable, and it is also a perfect fit in mathematical logic. An Zhusheng applauded from time to time when he saw it. He was quite satisfied to see that the logic of the derivation of this set of formulas was still very rigorous, and this was a guarantee for the correctness of the formulas at the very least.

When he saw the results later, An Zhusheng raised his head, looked at the girl in front of him who had been waiting quietly since he began to study the paper in his hand, and asked, "Shen Yiyi, I have read your formula, it seems that there should be no problem with this formula for gas flow." In this way, in fact, Xiao Yizhan has preliminarily verified this formula. ”

"Yes, Elder An, Elder Xiao has verified this formula with some data in his hand, and it has reached a good correct rate." Shen Yiyi replied calmly. She thought to herself, just kidding, not only did Mr. Xiao verify it, but I also checked the data on the materials I found from everywhere on my computer workstation more than ten years later in order to write a thesis, of course there would be no problem.

Luo Yu also became energetic at this time, and he also said to An Zhusheng: "Yes, Grandpa An, my grandfather and I have calculated several models together, and they are all correct." My grandfather took this formula very seriously. In fact, he wanted to emphasize that he was the first one to discover Shen Yiyi's formula, and his credit is not small.

An Zhusheng nodded, didn't speak, and muttered for a while before he spoke: "So, this formula can also be used on our engines?" "Theoretically, the working fluid of the engine is also a gas, so it is naturally easy to apply the formula that applies to the airfoil shape of an aircraft to the engine.

But Shen Yiyi shook his head as An Zhusheng expected: "You can't apply it directly." As you have just seen, this formula is derived in part using the assumption of an ideal fluid. However, the temperature of the working fluid of the engine is quite high, and I am afraid that the assumption of the ideal fluid cannot be directly used. So if you want to use it, you have to fix it. ”

An Zhusheng nodded, this little girl is still clear-headed. It is true that many formulas at room temperature are not suitable for high-temperature gases. He didn't have much hope either. I asked this question just to see if there was any problem with this little girl's understanding of the formula. But his next unintentional question, Shen Yiyi's answer brought him a huge impact. (To be continued......)

PS: One more sends, and then go to the code word.

Everyone is very supportive.