Chapter 35: A single sentence of true transmission

A single sentence of true transmission is worth more than ten thousand volumes of books.

If Lin Ran hadn't pointed it out directly, Chen Jingrun might not have realized until many years later that Professor Lin had already stuffed dense mathematical knowledge related to intercontinental missile trajectory optimization into this mathematics seminar.

He also finally understood why he only accepted young students and did not accept professors from the University of Xiangjiang to participate in the seminar.

On the surface, he said it was because he liked dealing with young people and wanted to cultivate the next generation for Xiangjiang mathematics.

In reality, it was because it was difficult for students to keep up, unless they were top geniuses, but in this era when Shing-Tung Yau was still in elementary school, there were no such mathematical geniuses in Xiangjiang.

The possibility of students hearing the true meaning contained in Lin Ran's course from such complex content was not even slim; it was impossible, but professors might be able to understand, especially professors dug back from England.

Who knew the other party's past background, whether they had helped the Allied logistics design missiles during the war?

As long as the other party had a similar background, this possibility would start to rise rapidly.

"If this multivariate differential equation is regarded as the flight trajectory of a ballistic missile, then it will be affected by Earth's gravity, air resistance, etc., among which this constant is undoubtedly Earth's gravity.

This is air resistance, but what do the subsequent terms mean?"

"Here I can understand that it has been simplified into a linear recursive least squares filter, but what is the application scenario?"

"Here, by processing the formula through small parameter expansion, the high-dimensional complex formula is simplified into a low-order equation to reduce the amount of calculation.

These should be factors such as air density changes and Earth's curvature, respectively, so it answers the first-order air resistance approximation equation solution fed back by President Qian!"

Chen Jingrun understood; the cases mentioned in Lin Ran's class were like ore, some of which hid true gold.

Out of dozens of cases in total, after analyzing them one by one, he found that one of them contained the solution to the mathematical problem raised by Qian Xuesen.

More importantly, what the other party gave was not a value, but a model that could be used universally.

Using this model, the originally complex equation could be simplified into a linear recursive least squares filter, and combined with the piecewise stationary error model taught by the other party, an approximate solution could be obtained for this type of problem through manual calculation.

Even in his cognition, the approximate solution obtained in this way would be at least two decimal places ahead of the original accuracy.

Originally, it would take a lot of manpower and might not be calculated, and even if it were calculated, it could only be approximated to one decimal place at most, but now it could be approximated to three decimal places by conventional manpower.

Although he was not doing missile design and didn't know what the significance of this formula was, he knew that this equation was given to him by Qian Xuesen, and it ranked number one in priority among many problems.

Then it was of great significance to the current Cultural Huaguo.

Even if there was only this one equation, it would not be excessive for him to activate Channel 3.

Because in his view, such an ingenious method had never been seen in the most cutting-edge mathematical journals he had seen in the past at the Institute of Mathematics of the Chinese Academy of Sciences.

Although what could be circulated to Cultural Huaguo didn't have much to do with the cutting edge, it was at least two years behind.

But after he came to Xiangjiang, because he was admitted to Lin Ran's seminar, the University of Xiangjiang opened various permissions for them according to student treatment, and he was able to read the most cutting-edge journals in the library of the Department of Mathematics of the University of Xiangjiang.

In these journals, he also didn't find a similar method.

However, what Chen Jingrun had to worry about now was which of the 37 cases in total were valuable.

In short, he didn't sleep all night.

The next day, he went to class with two dark circles under his eyes, and then at 11 o'clock in the evening, he stood in front of the door at No. 08, Zone 3, Kowloon Tong, ate a bowl of ramen, and waited until 11 o'clock in the evening.

All the shops on the street were closed, and a Rover P4 whizzed past, slowed down in front of Chen Jingrun, and then drove away.

In these short three seconds, Chen Jingrun had trained exactly three hundred times in Yangcheng in the past, no more, no less.

When the prepared document bag was accurately thrown into the glass window, Chen Jingrun's hanging heart finally let go; his task had been completed.

It's just that he didn't know that his life trajectory was about to undergo a earth-shaking change; his task was not completed, but had just begun.

"Old Qian, the Science and Technology Commission needs you to go to a meeting urgently.

The car is already ready downstairs!"

Qian Xuesen, who had already fallen asleep, heard a rush of short knocking on the door, and then his wife got up to open the door and woke him up in his ear.

He got up and glanced at the Wu Yi watch on the bedside table; it was 2:30 in the morning.

What important thing could happen at this time? He pondered inwardly, could it be related to Professor Lin Ran on the other side of the river?

Qian Xuesen, with questions, simply tidied up and walked into the night.

When he arrived at the Science and Technology Commission building, he found that the blackboard was already covered with formulas.

"Come, President Qian, please sit down quickly, you look at this material first."

Qian Xuesen took the material from the other party's hand, and after reading only two lines, he couldn't suppress his inner excitement and walked to the blackboard.

"Yes, that's right."

"What is used here is Monte Carlo simulation."

"This is manual sampling, only mechanical computers and manual sampling are needed to simulate randomness."

"But what is this here?"

"No, this must have its significance. Since Lin Ran chose to package the entire algorithm together, this will absolutely not be a meaningless existence."

"No, it could also be noise, noise that exists to cover up the real purpose."

"No, Xiao Zhang! Hurry up and help me find the second notebook in the bottom right drawer of my office!"

"This is reminding us that we can use Monte Carlo simulation, that's right, this should be Monte Carlo simulation!"

Qian Xuesen stood in front of the blackboard, seemingly talking to Lin Ran in Xiangjiang across the air; the middle-aged man next to him saw Qian Xuesen immersed in his own world and didn't interrupt him.

After waiting for a long time, he didn't see Zhang Kewen bring his notebook, so Qian Xuesen couldn't help but walk to the side and light a cigarette.

At this time, the middle-aged man stepped forward at the right time: "President Qian, what is the Monte Carlo simulation you just mentioned?"

Qian Xuesen explained: "This is a numerical simulation method thought of by scientists in the Manhattan Project during World War II who needed to solve complex physical problems such as neutron diffusion, but analytical solutions were difficult to obtain.

John von Neumann and Stanislaw Ulam proposed a systematic Monte Carlo method, performing numerical simulation through random sampling. And

Nicholas Metropolis first used Monte Carlo to name it in 1947.

I have heard of this method; it is to use manual sampling combined with mechanical computers to simulate the nuclear reaction process, but they have never let me understand the specific details of this algorithm."

"In other words, it can be used to build a nuclear bomb?" The middle-aged man's eyes lit up. ===== CHAPTER 36 =====