Chapter 34: A True Disciple’s Word
One true sentence from a master is worth ten thousand volumes of false books.
If Lin Ran had not directly pointed it out, Chen Jingrun might not have realized for many years that Professor Lin had stuffed dense mathematical knowledge related to intercontinental missile trajectory optimization into this mathematics seminar.
He finally understood why he only accepted young students and not professors from Hong Kong University to attend the seminar.
On the surface, it was said to be because he liked interacting with young people and wanted to cultivate the next generation for Hong Kong mathematics.
In reality, it was because even students found it difficult to keep up, unless they were top-tier geniuses, but in this era when Shing-Tung Yau was still in elementary school, Hong Kong had no such mathematics geniuses.
The possibility that students could discern the true intent contained in Lin Ran’s courses from such complex content was not negligible—it was impossible—but professors might understand, especially professors dug back from England.
Who knew what the other’s background was, whether they had helped the Allies with missile logistics design during the war?
If the other party had a similar background, this possibility would start to rise rapidly.
“If we view this multivariable differential equation as the flight trajectory of a ballistic missile, it would be affected by Earth’s gravity, air resistance, and other factors, where this constant is undoubtedly Earth’s gravity.
This is air resistance, but what do the subsequent terms represent?”
“Here I can understand that it has been simplified into linear recursive least squares filtering, but what is the application scenario?”
“Here, by handling the formula with small parameter expansion, the high-dimensional complex formula is simplified into a low-order equation to reduce computation.
These should respectively be factors like air density changes and Earth’s curvature, so it directly answers the first-order air resistance approximate equation solution fed back by Dean Qian!”
Chen Jingrun understood that the cases mentioned in Lin Ran’s class were like ore, some of which contained true gold.
Among a total of dozens of cases, after analyzing them one by one, he discovered that one contained the solution to the mathematical problem posed by Qian Xuesen.
More importantly, what the other party gave was not a single value, but a general model.
Using this model, the originally complex equation can be simplified into linear recursive least squares filtering, and combined with the piecewise constant error model taught by the other party, approximate solutions for this class of problems can be obtained through manual calculation.
Even in his cognition, such an approximate solution would advance the precision by at least two decimal places compared to the original.
Originally, it required massive manpower and might not even be calculable; even if calculated, it could at most approximate to one decimal place, but now with conventional manpower, it can approximate to three decimal places.
Although he was not involved in missile design and did not know the significance of this formula, he knew that this equation was given to him by Qian Xuesen and ranked first in priority among numerous problems.
So it was of great significance to contemporary China.
Even if only this one equation, activating channel 3 would not be excessive.
Because in his view, such an ingenious method had not appeared in the most cutting-edge mathematics journals at the Mathematics Research Institute of the Chinese Academy of Sciences in the past.
Although what could circulate to China was already not closely related to the forefront, at least two years behind.
But after coming to Hong Kong, due to being admitted to Lin Ran’s seminar, Hong Kong University granted them various permissions according to student treatment, so he could access the most cutting-edge journals in the library of the Hong Kong University Mathematics Department.
In these journals, he also did not find similar methods.
However, what Chen Jingrun now had to worry about was which ones among the total of 37 cases were valuable.
In short, he didn’t sleep all night.
The next day, with two black eye circles, he went to class, then at ten o’clock at night stood in front of No. 08, Zone 3, Kowloon, ate a bowl of ramen, and waited until eleven o’clock.
All the shops on the street had already closed, a Luo Fu P4 roared past, slowed down in front of Chen Jingrun, and then sped away.
In these short three seconds, Chen Jingrun had trained exactly three hundred times in total in Yangcheng in the past.
After the prepared document bag was precisely thrown into the glass window, Chen Jingrun’s suspended heart finally relaxed; his task was completed.
But he didn’t know that his life trajectory was about to undergo earth-shattering changes; his task was not completed, but had just begun.
“Old Qian, the Science and Technology Committee needs you to come urgently for a meeting.
The car is already prepared downstairs!”
Qian Xuesen, who had already fallen asleep, heard a rapid and brief knock at the door, then his wife got up to open it, and woke him up in his ear.
He got up and looked at the May 1st wristwatch on the bedside table: 2:30 a.m.
At this time, what important matter could there be? He pondered inwardly, could it be related to Professor Lin Ran across the river?
Qian Xuesen simply packed up with questions and walked into the night.
When he arrived at the Science and Technology Committee building, he found the blackboard already densely covered with formulas.
“Come, Dean Qian, please sit quickly, you first look at this material.”
Qian Xuesen took the material from the other’s hand, and after reading just two lines, he could no longer contain his inner excitement and walked to the blackboard.
“Yes, that’s right.”
“Here it uses Monte Carlo simulation.”
“Here it uses manual sampling; only a mechanical computer and manual sampling are needed to simulate randomness.”
“But what is this?”
“No, there must be some significance here; since Lin Ran chose to package the entire algorithm together, this absolutely would not be a meaningless existence.”
“No, it could also be noise, noise existing to cover the true purpose.”
“No, Little Zhang! Hurry and get me the second notebook from the bottom right drawer of my office!”
“Here it reminds us that Monte Carlo simulation can be used, yes, this should be Monte Carlo simulation!”
Qian Xuesen stood in front of the blackboard, seemingly engaging in a dialogue across the air with Lin Ran in Hong Kong; the middle-aged man beside him saw Qian Xuesen immersed in his own world and did not interrupt him.
After waiting a long time without seeing Zhang Kewen bring his notebook, Qian Xuesen couldn’t hold back and walked to the side to light a cigarette.
At this time, the middle-aged man finally stepped forward appropriately: “Dean Qian, what is the Monte Carlo simulation you just mentioned?”
Qian Xuesen explained: “This is a numerical simulation method that scientists in the Manhattan Project during World War II needed to solve complex physics problems like neutron diffusion, but analytical solutions were hard to obtain.
Von Neumann and Stanislaw Ulam proposed a systematic Monte Carlo method, using random sampling for numerical simulation. Nicholas Metropolis first used ‘Monte Carlo’ to name it in 1947.
I have heard of this method; it uses manual sampling combined with mechanical computers to simulate nuclear reaction processes, but they never let me know the specific details of this algorithm.”
“So it can be used for making nuclear bombs?” The middle-aged man’s eyes lit up.
em don’t rush ya, new book stage two chapters daily unwavering okay!
