On September 12th, the competition went on as scheduled!

The day before the competition, Lu Zhou and others took a school bus from the new campus to the old campus and lived in a temporary dormitory arranged by the school.

Mattresses and pillows are prepared, just bring a set of sheets, and people who are not particular about it can even go directly to the individual, after all, although the game time is 72 hours, but the average bedtime for each person may not even be ten hours.

This is the case with Lu Zhou, for example.

He had the heaviest task and the most work to complete, and he could only take a nap the next day, so he didn't even bring a change of clothes and went empty-handed. And the first thing I did when I arrived at the new dormitory was to lie down and sleep.

If you can't sleep, you have to force yourself to fall asleep.

The next morning, I woke up at five o'clock, closed my eyes on the bed until seven o'clock, went to the cafeteria for breakfast, and Lu Zhou met with Wang Xiaodong and Lin Yuxiang, and went to the special computer room prepared by the school for the mathematical modeling competition.

According to the official registration information, the competition has more than 70,000 college students from 25,347 teams from 1,338 colleges and universities in 33 provinces, municipalities and autonomous regions (including Hong Kong and Macao), the United States and Singapore.

The competition is co-sponsored by the Department of Higher Education of the Ministry of Education and the Chinese Society of Industrial and Applied Mathematics.

At half past seven in the morning, the computer room was already full of ten teams.

Although many people choose to use their own laptops to answer questions, they usually bring their computers to the computer room. After all, only the wifi in the computer room and the library can download papers from CNKI for free. This kind of competition is expected to be won by those unverified materials on Baidu, and it is better to burn a stick of incense and other papers to complete automatically.

Teacher Liu came over for a turn, said hello to Lu Zhou and the three of them with a smile, and didn't talk about the competition, so he greeted "How was your rest last night?" "Are you used to the dormitory in the old campus? Then he wandered outside the computer room and drove back to the new campus to work on his own projects.

At eight o'clock, the bell rang.

Everyone quickly logged on to the official website and downloaded the questions.

According to the rules, the questions are divided into four major questions of ABCD, of which AB belongs to the undergraduate group and CD belongs to the junior college group. Each team chooses a question as the goal, completes and uploads the MD5 code generated by the official website software within 72 hours, and uploads the PDF format paper corresponding to the MD5 code on the day of the end of the competition.

Generally speaking, the topic must be controlled within half an hour, and everyone is racing against time to read the question.

However, the moment they saw the title, everyone was dumbfounded.

"Question A: Design and Control Strategy of Chang'e-3 Soft Landing Orbit...... Question B Creative Flat Folding Table?! Hold the grass? What the hell is this year's topic? ”

"MMP, it's completely different from the training we do!"

"I seem to have done something similar a few days ago, as if I was designing the launch plan of the Shenzhou rocket...... But I think such a mysterious theme will definitely not come out, I didn't expect it...... Careless! ”

"Hold the grass, big guy, aren't you ninety-five points high? Think of a way! ”

"I studied advanced mathematics, and I didn't learn how to go to heaven!"

"Design the table...... What is there to design for a table, isn't it just four legs? Foldable ...... Do we put a spring behind the leg of the stool? ”

The computer room was quite lively, and it could be seen that the students were all confused by this topic and didn't know what to do.

But there are also masters in it.

For example, Luo Rundong, the second student in Lu Zhou's class, was communicating with his teammates in a calm voice at this time.

and Liu Rui...... The kid seems to have a very reliable thigh on his team, and now he has finished reading the questions and is starting to assign work to his two teammates.

Looking at the two questions downloaded from the official website, Wang Xiaodong frowned.

The sky collapsed to the beginning.

Both questions are related to physics.

The previous one involves orbit calculation in aerospace physics, and it is certainly not enough to rely on high school physics knowledge, and question B is very simple on the surface, but it is not much easier than the first question, which involves the dynamic motion analysis of table legs, material force analysis and a series of problems, involving not only mathematical modeling knowledge, but also requires a certain amount of knowledge in structural mechanics and materials science and even ergonomics.

However......

The "math genius" in the team has just entered his sophomore year, and he has even just started physics class.

There's no way, avoid the important and light.

The first one is not enough physics knowledge to do at all, and the second one can also collect data through the Internet and find ways to transform it into mathematical problem solving.

Wang Xiaodong looked at Lu Zhou, "Do you want to choose question B?" ”

Lu Zhou shook his head: "Choose question A." ”

"Question A?" Wang Xiaodong frowned, "Are you okay?" ”

"As for college physics, I have already finished it, although aerospace physics seems complicated, in the final analysis, it is only the content of the first three chapters," after a pause, Lu Zhou glanced at the team next to him and continued, "Moreover, you can see that there are enough people in this computer room who choose question B." ”

Question AB is selected separately, and in the case of question A is so scary, question B is bound to have many candidates. At this time, it is time to take out the courage of "knowing that there are tigers in the mountains, and preferring to go to the tiger mountains", leave the single-plank bridge to thousands of troops and horses, and walk their own Yangguan Avenue in a chic manner!

Of course, this is also a choice made by Lu Zhou when he was sure of question A in his heart.

Wang Xiaodong nodded expressionlessly, naturally understanding the meaning of Lu Zhou's last sentence.

"Okay, the modeling will be up to you."

"Wrap it up on me."

With eye contact, the two top students have reached a consensus.

Lin Yuxiang looked at the two teammates who had reached a consensus with a confused expression, and couldn't help but ask weakly: "That...... Is there anything I can do to help? ”

Wang Xiaodong showed a smile that he thought was very gentle and said, just about to handsomely say "just leave it to me", but before he could brew feelings on that paralyzed face, Lu Zhou, who was burying his head in the draft on A4 paper, did not raise his head, and said unceremoniously: "Bring food, send water, please." ”

There is no shortage of people for modeling, programming, and papers, but there is a shortage of errands.

Don't think that lying down to win is so easy to lie down, don't let this guy do some work, Lu Zhou's heart is unbalanced.

Wang Xiaodong: "......"

Lin Yuxiang didn't complain, and nodded energetically: "Mmmm, it's on me!" ”

The advantage of mathematical modeling and essay writing being done by one person is that many of the tasks that require two people to communicate can be done by one person, and there are no problems such as teammate cooperation and expression comprehension.

At the same time, in the case of grasping the modeling paper, Lu Zhou, as the captain, can accurately give orders to Wang Xiaodong, who is responsible for the programming link.

As a result, there are almost no differences of opinion between the players!

Beyond the stem information, there are three questions:

(1) Determine the position of the perilunar point and the apogee point of the landing preparation orbit, as well as the magnitude and direction of the corresponding velocity of Chang'e-3.

(2) Determine the landing orbit of Chang'e-3 and the optimal control strategy in six stages.

(3) Error analysis and sensitivity analysis for the landing orbit and control strategy you designed.

The abstract section is a summary of the full text, and this section can be completed after the entire article has been written. The focus is on the problem analysis after the problem restatement, which involves the whole idea of the whole modeling, and the soul of the whole paper is here. Biting the ballpoint pen, Lu Zhou tapped his fingers on the keyboard, wrote out the outline of the paper, and then began to define the most critical soul for his paper based on the draft of the previous pen calculation.

[Question 1: In order to obtain the positions of the perilunar and apogee points of the landing preparation orbit, as well as the magnitude and direction of the corresponding velocity of Chang'e-3, the knowledge of mechanics is first used to calculate the known conditions. Using extreme thinking, the motion of the Chang'e-3 main deceleration stage is divided into infinite linear motion with uniform variable speed. The program was designed using Matlab software to perform iterative calculations on the final deceleration stage......

[Problem 2, in order to ensure the landing orbit of Chang'e-3 and the optimal control strategy in the six stages, it is necessary to minimize fuel consumption as the goal, analyze on this basis, use the parameters obtained in problem 1, use the algorithm of Matlab software to identify obstacles in the digital elevation map, realize the identification of obstacles and the positioning of the landing site, and simulate the optimal landing orbit ...... by establishing a model]

[To analyze the error of the landing track control strategy designed in Problem 2, we should first list all the factors that may cause the error as much as possible, and analyze them......]

Lu Zhou, who had entered the state, was highly focused on the issue at hand.

When he finished analyzing the problem, he only felt that his brain was extremely clear, and even the idea of the entire paper had formed a general framework in his mind.

The rest of the work is to translate this outline into the language of mathematics......

For most teams, the thesis is usually placed after the modeling and programming are completed, but for Lu Zhou, the two can be done simultaneously!

This will be the biggest advantage of their team!