Chapter 253 The absorbing efficiency is increased by 15%?!
Chapter 253: Wave absorption efficiency increased by 15%?!
Let’s start with doctoral students.
Some of these doctoral students are exempt from Ph.D. candidates, and some are direct Ph.D. students.
The first person is Bai Hongyuan, a direct PhD student who studied in their School of Mathematics at Beijing University as an undergraduate, with a four-year grade point average of 4.2.
Peking University has a 4-grade point system, which means that even if you score 90 or above in all subjects for four years of university, the highest grade point can only be 4.0.
Therefore, a grade point of 4.2 means that he has made some achievements that comply with the grade point bonus policy, and for mathematics undergraduates, they have basically published papers.
Lin Xiao looked at his resume and found that he had published SCI papers, and he had published papers in the third area.
This is very good for an undergraduate, and at least shows that he has certain scientific research capabilities.
Of course, Lin Xiao did not let it go easily. Instead, he directly found the paper published by this student based on the DOI number attached to his resume.
"Conjugate Gradient Method in Random Variables" studies the conjugate gradient method for solving linear equations whose coefficients are measurable functions, and determines the convergence speed of this method.
It seemed pretty good, but when Lin Xiao downloaded the paper and read it, he shook his head.
This paper did not satisfy him very much.
Although the method used is good, it just lacks innovation, and innovation is very important in Lin Xiao's opinion.
Of course, considering that this is a paper published by this undergraduate named Bai Hongyuan, the lack of innovation is not actually a particularly important thing.
As for other things such as what student positions Bai Hongyuan has held, or what activities he has participated in, they are not within the scope of Lin Xiao's consideration, because these are all social skills or work abilities.
It has nothing to do with academic ability. For Lin Xiao, academic ability is the most important. Their mathematics is not social science. Social science requires doing social surveys and other things, so social ability is also a manifestation of ability, and mathematics
You just need to be smart enough and take academics seriously enough.
Then he stopped paying attention, put Bai Hongyuan aside as a candidate, and then looked at the second person.
The second one is also a direct doctoral student, named Xue Wanqing, who is also a postgraduate student of the school. What makes Lin Xiao's eyes bright is that this student has participated in the Qiu Chengtong Undergraduate Mathematics Competition, and also won the individual gold medal in the number theory group. Qiu Chengtong Undergraduate Mathematics Competition is a
The most important thing about this valuable mathematics competition is that it is different from the ordinary national college mathematics competition. The latter tests problem-solving skills, while the former tests mathematical knowledge reserves.
Although the two have different focuses, Lin Xiao prefers the one with more mathematical knowledge, because it means that he likes mathematics and has accumulated enough. If he does not accumulate much, he will definitely not get the gold medal.
.
In addition, this Xue Wanqing has other achievements and has also published mathematics papers. Although he is not in the third area of SCI like the previous one, the fact that he can publish papers shows his ability.
After writing down the name, Lin Xiao continued to look at the third person. The third student was also very good and had won the CMO gold medal, but he did not enter the national team to participate in the IMO. Of course, he was also very good.
I also participated in many competitions in college.
Next is the fourth, fifth...
Among them, nine are PhD students, and the rest are master's students.
All in all, these people who have been admitted to the School of Mathematical Sciences at Peking University are all very good. There are even two students from foreign countries. One of them is a master of mathematics from the Paris Normal University and wants to apply for his PhD.
The other one is a mathematics undergraduate at Princeton University and wants to apply for his master's degree.
Naturally, he just passed it by. He was not in the mood to teach foreigners.
After final selection, four doctoral students and six master's students were left, and then an interview was conducted to select the final students.
The time for the interview needed to be coordinated by the college. After he registered the students he selected, he stopped taking care of them and continued to study the crystal structure that could amplify and reduce X-rays.
…
Huaguo Aviation Industry Group, Chengdu Aircraft Research Institute.
The Chengdu Aircraft Research Institute is the place where China's fifth-generation fighter jet J-20 was born. Yang Wei, the chief engineer of the J-20, once served as the director of the Chengdu Aircraft Research Institute.
Today, the Chengdu Aircraft Research Institute welcomed a person, Ma Gaoliang.
Ma Gaoliang came here in person carrying the information Lin Xiao gave him.
Fighter stealth coating material!
Such an important thing was certainly worth a visit in person.
Soon, he found Shen Zhi, the current director of the Chengdu Aircraft Research Institute.
Seeing Ma Gaoliang, Shen Zhi smiled and said, "Director Ma always goes to the Three Treasures Hall for no reason. What is the purpose of coming here in person?"
"Haha, there is something important." Ma Gaoliang said without any nonsense: "In your research institute, who is the expert who knows the most about invisible absorbing materials?"
"Absorbing material?" Shen Zhi was stunned, then thought for a while and said: "It should be...Professor Zhang Heng from the Third Research Department. He is responsible for studying the overall layout of the absorbing coating on the surface of our fighter aircraft.
There’s a lot of material research.”
"Okay, then I need to meet with Professor Zhang Heng now. I have an important matter that I need to entrust him with," Ma Gaoliang said.
Hearing Ma Gaoliang's serious look, Shen Zhi was a little curious, but he didn't say much. He stood up and said: "Then you come with me, but if Professor Zhang Heng is doing research and disturbs him, we may have to fight each other."
Got scolded."
Director Ma couldn't help but smile: "You are the director, and this Professor Zhang still scolds you?"
"The problem of the absorbing coating on the surface of our J-20 was solved by Professor Zhang Heng. If the old man wants to scold me, what can I do?" Shen Zhi spread his hands and said: "If you, Director Ma, hadn't come here in person, otherwise I wouldn't have
Dare to go find Professor Zhang at this time."
Director Ma smiled and said, "That's true."
He respected Lin Xiao, and naturally he also respected scientists like Professor Zhang Heng.
In the past, foreign countries believed that China could not build a fifth-generation fighter jet, because the standards for a fifth-generation fighter jet have four S's, namely four supers: ultra-low detectability (stealth), supersonic cruise capability, super maneuverability, and super information superiority.
In 2011, China released photos of the J-20. Some people abroad and even at home expressed disbelief and even ridicule, believing that China would not be able to build a fifth-generation fighter jet within 20 years, because at that time foreign countries believed that China could not build a fifth-generation fighter jet at all.
There is no fifth-generation fighter that can meet the 4S standard.
The test of supersonic cruise capability is the engine. At that time, we used a Russian engine instead, because our turbofan 15 engine had not yet been built at that time, but no matter what, this S has achieved it, and then it has super maneuverability.
This also tests the engine, followed by the overall structural strength of the fuselage. The super information advantage is the combination of various sensors to achieve various advantages from radar, infrared, electronic warfare, etc., and finally it is stealth.
Each one is crucial, and the stealth problem solved by Professor Zhang Heng is also the key among the keys. After all, the fifth-generation fighter is known as a stealth fighter because of the importance of its stealth ability.
Therefore, Professor Zhang Heng’s contribution is considerable.
And it was precisely because experts like him worked hard to solve various problems that the J-20 officially took off. The loud sound caused by the sonic boom over Chengdu declared that China's fifth-generation fighter aircraft
The official birth of.
Soon, under the leadership of Shen Zhi, Ma Gaoliang and he came to the Third Research Department. After asking people, they came to the door of one of the laboratories.
"Bang bang."
knocking.
"Is Professor Zhang here? I am Shen Zhi."
But no one responded. Shen Zhi knocked a few more times. Finally, the door of the laboratory opened. A dark-faced man who looked about fifty years old stood behind the door and said, "Director Shen, I said it."
How many times have you asked me not to come to me when I am researching something?"
Shen Zhi shrugged towards Ma Gaoliang, not paying attention to Shen Zhi's tone, but first introduced Ma Gaoliang next to him.
"Professor Zhang, I know, I know. Director Ma Gaoliang of our Science and Technology Bureau came to see you for something."
"Director Ma?" Zhang Heng glanced at Ma Gaoliang and snorted: "What's wrong with the Science and Technology Bureau? Can the director of the Science and Technology Bureau disturb people's research? Do you know how important it is to design the J-35 stealth layout?"
J-35 is the fifth-generation carrier-based aircraft currently being developed by China. Carrier-based aircraft are different from fighter jets. Carrier-based aircraft are aircraft that can take off and land on aircraft carriers. China has never built a fifth-generation carrier-based aircraft before.
There is a big gap between China and some foreign countries in terms of naval combat capabilities.
Ma Gaoliang smiled and was not angry either. Instead, he said: "That's why I came to you today just to provide you with a helping hand."
"Help?" Zhang Heng wondered, "Director Ma also studies invisible materials? Is the threshold for the director of the government so high?"
"...Uh, no." Ma Gaoliang was helpless, is there something in your words?
He waved his hand and said: "I want to show you a new theory. This theory will play a very important role in your development of absorbing materials and their layout..."
After his explanation, Zhang Heng finally became interested: "Can you understand the coherent superposition of waves? Master the laws of interference and diffraction?"
If this is true, it would be really useful for his research.
So Professor Zhang Heng didn't waste any time. He got this theory from Director Ma and started to verify whether it was really useful.
For people like him who engage in applied research, pragmatism is the most important, so he doesn't care how important the proof process of this theory is. He only cares about whether the final results can be applied to his research.
And this is very simple. Since the final result is a partial differential equation, he can directly substitute various numerical values into this equation, and then perform simulation calculations through the computer.
Soon, he completed this step, and then made modifications to the surface of the absorbing material, mainly using this partial differential equation for optimization. After a while, the simulation began.
The calculations of the computer drive the internal fan to rotate rapidly.
After a while, the results appeared.
Zhang Heng's eyes suddenly widened.
After the surface of the absorbing material optimized by this partial differential equation, the absorbing efficiency actually increased by 15%!
"This... is incredible!"
Zhang Heng, whose expression had remained unchanged, looked so surprised for the first time.