Scholar’s Advanced Technological System

Three days in the Mathematical Modeling Competition, it will just wash away two big lessons.

Although it was a dedication, but it was not very good to take the leave in consideration of the first class. Lu Zhou decided to send the fake article personally, so that he would not bother the squad leader to do it.

Looking at the class information given by the Academic Affairs Office, the name of the teacher is Li Rongen, an old professor with high qualifications. After asking the phone number in the school group, Lu Zhou made a phone call and confirmed that the teacher was in the office before taking the fake article.

After knocking on the door, Lu Zhou walked in and placed the fake strip on the desk, explaining his intentions.

“Walk?” Looked at the fake note, Professor Li took off the reading glasses and raised his head and smiled. “Your name is Lu Zhou?”

"Yes." Lu Zhou nodded.

Professor Li smiled and said: "That line, I will test you two questions. If you solve it, I will approve your fake article."

Is there such an operation? !

Lu Zhou is dumbfounded.

"How? Fear?" Li Rongen asked with a smile.

"No," Lu Zhou fixed his mind and shook his head. "Teacher, let's ask."

"The first question, take it," put an A4 paper on Lu Zhou's hand. Li Rongen smiled and looked at Lu Zhou. The old **** was saying, "How much can be written, I want to see the process."

Even the questions are ready? !

Lu Zhou always feels that this guy is premeditated, otherwise how to explain, why is this question already printed on A4 paper?

However, even if he guessed a point, Lu Zhou did not say anything, picked up the A4 paper and started reading the questions.

[The half-life of the U238 core in a nuclear submarine is 4.5×10^9 years, and the probability of a decay of 0.7% becomes the U234 core, while releasing a high-energy photon, 93% of these photons are absorbed by the submarine steel plate. In 1981, the high-energy photons transmitted by the nuclear submarine of the former Soviet Union number U137 to the outside of the boat were measured by a detector at a distance of 1.5 m from the nuclear source (processed as a dot). The instrument has a normal incident area of ​​22 cm^2, an efficiency of 0.25% (a pulse signal is generated for every 400 incident photons), and 125 signals are measured every hour.

1 Find the average life of the U238 core (ln2=0.693).

2 Find the mass of U238 in the nuclear submarine (unit kg, take 2 digits)

】

After reading the topic, Lu Zhou whispered softly.

It is worthy of Professor Li, who was named "Four Devils of the Court" by previous predecessors. Is this a problem?

In other words, the next big thing class will be opened next Monday. It is really no problem to take this nuclear physics knowledge of the super-level ball.

“Would you like to find a place to sit and count?”

"No, just here."

After receiving the pen and draft paper handed by Prof. Li, Lu Zhou stood beside the desk, frowning and thinking for a moment.

Physics is not really an area he is good at.

However, after a summer of explosive liver learning, standing here is invulnerable!

About five minutes later, Lu Zhou’s brow was loose and his pen tip moved.

[The decay law of radionuclide: N=N0e^(-λt)

The relationship between the decay constant and the half-life is: N0/2=N0e^(-λT1/2), from which T1/2=ln2/λ

】

Write these two lines of calculations, Lu Zhou's eyes flashed slightly.

He has successfully turned physics into a high number problem.

Next, it is to break through one by one!

First question!

The nib swam on the A4 paper.

[(1) Average lifetime of radionuclide t=∫λNtdt/N0=...=1.1443T1/2

Substituting data is available, t=6.49*10^9 years.

】

After sweeping the A4 paper, Professor Li Rongen picked up his eyebrows and showed an interesting look in his eyes.

Did not notice the change of Professor Li's expression, the attention is highly concentrated on the paper on the boat, began to continue to answer the next question.

[The problem can be solved by the dry information, the number of high-energy photons generated by decaying to U234 at dt time is -dN·n0=n0λNdt

The efficiency of photons passing through the steel plate is n1, and the number of photons passing through the steel plate in the dt time is calculated as dN1=n0λNdt·n1

The number of photons entering the detector...

The number of signals generated in the detector...

Calculate the number of U238s in the submarine and calculate the number of U238 cores from this.

】

Lu Zhou substituted all the data and calculated the number of U238 cores in the submarine N=7.456*10^25.

However, when he was preparing to bring N into M=N*238u and complete the final blow to the enemy's spring, Professor Li Rongen suddenly spoke.

"Okay, count you too."

Lu Zhou:? ? ?

He was not happy at all.

What is it that I have passed?

I have counted here, you can't wait for me to finish talking!

"Professor, I haven't finished yet..."

"Everyone has counted this step, and you can find a junior high school student," Li Rongen said with a smile. "If you want to finish it, just follow it."

The atmosphere of the problem was destroyed, and Lu Zhou was speechless.

Can not stand the entanglement of obsessive-compulsive disorder, he still wrote the results at the end.

The answer is M=29.634kg, take two is about 30kg

The steps are correct, and the result is no suspense.

Lu Zhou gave this title a perfect ending.

“Would you like to listen to the second question?” Li Rongen said with a smile.

Although Lu Zhou wanted to say "do not want to", but thought that the professor had not approved his own fake article, could not help but said: "You say."

Li Rongen smiled and continued: "Don't be nervous, the second question is very simple, you will tell me, Kennan, the second law of thermodynamics."

Upon hearing this question, Lu Zhou breathed a sigh of relief.

Originally, he thought that the second question of this professor would be debuted. He couldn’t write a difficult question and beat him. He told him not to be proud of himself. As a result, he did not expect that Professor Li did not press the routine, so he simply let go. He is.

In general, there are two main expressions of the second law of thermodynamics, one is the famous Kelvin expression, and the other is the expression mentioned by Clausius in the 1850 paper.

As for Kennan's expression, it is a relatively new expression that has recently emerged.

When you look at the materials carefully, you will not miss them.

which is--

"For a system with a given energy, material composition, and parameters, there is such a stable equilibrium state: other states can always be achieved through a reversible process." Like the back text, Lu Zhou retells this expression.

"Not bad." Li Rongen nodded with approval.

The textbooks used by non-physical majors do not mention this more advanced expression in the text, but they will be mentioned in the appendix. Students who are generally not interested in physics will not be able to get there when they graduate.

If Lu Zhoulian is so clear in this secluded knowledge point, it is enough to prove that he has thoroughly immersed in the entire "University Physics" textbook.

After this shallow and deep investigation, Li Rongen can now confirm that he is a course for undergraduate non-physical students, and there is really nothing to teach him.

It seems that Lao Tang did not brag, this kid is a personal talent!

In fact, it is a joke to the young people to say that they have answered the questions correctly.

Since yesterday, he has approved dozens of fakes in the mathematical modeling contest. Will it be such a fake?

Even if Lu Zhou couldn't answer it, he would at most tweeted two sentences, and he would still approve it.

After signing the fake note, Li Rongen pulled out the name list in the drawer and drew two hooks on it, while using the tone of the elder.

"Lu Zhou."

"what happened?"

“Is there any plan to study?”

Lu Zhou thought about it and said in an uncertain tone: "Yes."

Who is good about the future?

However, Professor Li’s intuition is obviously not as sharp as that of Lao Tang. He did not hear the uncertainty in Lu Zhou’s tone. Instead, he nodded his approval and continued.

"The physics department of Nanda is also a top standard in colleges and universities across the country. In terms of modesty, even if Peking University and Pelican are tied for the first place, if it is specific to the research direction, superconducting physics and strong associated electronic systems, and cohesion. In the fields of physics and material design, they are not as good as us. If you are interested in physics, you can come to me when you are studying. Our carbon nanotube laboratory needs top talents in mathematics."

this is……

Is it implied that I will report to his graduate students later?

Lu Zhou was crying and laughing. He is only a sophomore, and he is far from the postgraduate.

But in any case, this is the kindness of the teacher.

Lu Zhou said with sincerity: "Thank you teacher."

Li Rongen nodded with a smile: "Oh, let's go with a fake strip. This kind of game has the opportunity to participate more. If you can't do it, you can pay attention to the opportunity of the next year. Or wait until next year, you will be in the junior year. Ask me, ask you, Teacher Tang, you can."

Lu Zhou smiled and expressed his gratitude. He didn't talk much more. He quickly said goodbye with this hard-won fake note.