Chapter 113: Kill with Ease (2-in-1 Chapter) Wenfeng and Yu Chenxi discussed for a long time last night and vowed to finish Paper A, which was not about civil engineering at all, but about signals. It is about modeling multi-source opportunity signals. Neither of them is a student majoring in communications. Although Wenfeng is a science student, his knowledge of the basic principles of communication signals is still at the high school level. He will definitely not be able to solve this problem. Well, two people gave up the A roll and saw what the B roll was. As a result, the B volume also left the two of them confused. Paper B is actually a combination of physics and chemistry. It is a study on the co-pyrolysis of biomass and coal. Yu Chenxi was a liberal arts student and couldn’t even understand the questions. She looked at Wenfeng and placed all her hopes on him.
But Wenfeng was also confused. Wenfeng said very embarrassedly: "Look, I'm useless. I don't understand this question either." "The peak of a person's life is in the third year of high school. I'm a sophomore now, and I don't know where I threw all my previous knowledge of biochemistry. I can't solve this problem." Yu Chenxi didn't know whether to laugh or cry. She felt that the special training her group had conducted more than a week in advance was completely in vain. I discussed the problem for a long time yesterday, but it was all in vain how to choose the topic. No matter which test paper you choose, abc, you still won’t be able to do it. Wenfeng was a little embarrassed, touched his nose and said: "Let's take a look at the C paper. The C paper should be more relevant to life, and we both should know it." When Wen Feng said this, he also complained, "What's going on with that Lu Shan?" "Fan Bing said she would definitely attend on the way. It's almost 9:00 now, why hasn't she come yet?" "Are you standing us up?" Yu Chenxi was also a little worried. They placed all their hopes on Lu Shan. If Lu Sheng stood them up and didn't come, then there would be no need for him to participate in the Mathematical Modeling Competition. Yu Chenxi clicked on paper C (question). As expected, they could understand question C. The title of question C is that a certain place suffered a severe earthquake, communication signals were completely interrupted, and transportation was also blocked. The disaster relief command center sent several teams to the disaster relief area to determine the exact location of the trapped people, to develop new routes for the rescue workers, and to formulate models of time, personnel and equipment deployment under different external conditions. Okay, the problem now is that I can understand the question, but I don’t know where to start.
The two of them spent a long time working on the draft paper, but still had no idea what to do. There are actually some techniques to take the College Students Mathematical Modeling Competition exam. That is, don't waste too much time on choosing a topic. Because no matter how hard you try, you may not be able to solve the problem you choose. You have to do it even if you don't know how. As long as you build this model according to your ideas, the grader can also give you a score based on it. After all, not all models are correct. Correctness is important, but the modeling mindset is even more important. Time passed by minute by minute, and it was already 9:30. Although there was air conditioning in the study room, the two of them were already sweating profusely and had used up a lot of draft paper. I still don't know how to do question C. If you don't know how to do question C, then there is no difference between question C and questions A and B. On the contrary, more students chose question C. The two people began to argue again. It was at this time that Lu Shan came slowly. His daily routine is the same as usual and will not change at all because of participating in the Mathematical Modeling Competition. After getting up in the morning and running, I washed up, had breakfast, and then checked my email. Zheng Kaige had already sent the perfected addition program to Lu Shan. Zheng Kaige's skills are pretty good and his attitude is also very positive. His polished JAVA application barely passed muster. Lu Shan spent some time optimizing the code and sent the email to Zheng Kaige again before coming to the library. After seeing Lu Shan, Wenfeng and Yu Chenxi felt more at ease. But Wenfeng is a senior after all, and is also the leader of the three-person team in this mathematical modeling competition. He still has to show his posture and attitude. "People should have a little team spirit. We agreed to meet in the study room at 8:30. How come you only got here at 10 o'clock?" "If you have something and cannot attend the competition, you can tell us in advance. There is no need for us two to wait here for you." It was indeed that he was late, but Lu Shan still said sorry embarrassedly. Maybe it was because Lu Shan’s lateness annoyed Wen Feng. It may also be that when the questions were drawn, Wenfeng found all three papers, ABC, very difficult, which made him feel very upset, so he took his anger out on Lu Shan.
"What's the use of apologizing? Can it make up for time?" These words made Lu Shan unhappy. Lu Shan said to Wen Feng with a smile: "Our team should still be a little more efficient." "I just joined the team last night, and you have been preparing for two weeks in advance." "Did you guys divide up the work in these two weeks? Did you decide on the topic? It seems like you haven't done anything." "It's 10 o'clock now. It's been an hour and a half since the start of the competition. Have you chosen the question type?" "Your efficiency is almost zero, so what's the difference between me coming and me not coming?" Wen Feng was speechless. He wanted to get angry but was persuaded by Yu Chenxi. Through the contact with Wenfeng in the past two weeks, Yu Chenxi also realized that apart from his love of bragging, Wenfeng actually had no leadership ability. Not to mention leadership skills, he doesn't even have the ability to solve problems. I didn't even come up with an idea for how to solve the problem. Yu Chenxi felt a little regretful that he had seen Wen Feng’s recruitment post through the campus BBS and joined Wen Feng’s team. Yu Chenxi said quickly: "We don't have much time now, let's quickly decide on the topic." Wenfeng deliberately said: "Let's choose C. Let's proceed according to question C and the ideas just now." Lu Shan's opinion is opposite to Wen Feng's. Among these three questions, question A is obviously the most difficult. It is very likely that many people will get question C right, so the competition for question C will be greater. Of course, the most important thing is that Lu Shan felt that question C was too simple. He is unwilling to waste his precious time on simple things. Lu Shan said, "Choose question A. Question A is not that difficult, so not many people will choose it." Wenfeng couldn't help but sarcastically said, "Do you know how to answer question A? You majored in mathematics, not communications." Lu Shan didn't want to talk to Wen Feng at all. The follow-up work was arranged directly. "I will build the model, the mathematical ideas and methods, and you will write the paper, the literature major, so I would like to trouble you to help me look up the references." There are three most important things in the Mathematical Modeling Competition. The first thing is to find ideas, the second thing is to build a model, and the third thing is to write a paper. If the first two things are done right, then the paper is actually very easy to write, so the difficulty is not particularly great. That is, Lu Shan arranged the work, assigning the two most difficult tasks to himself, and the slightly more difficult tasks to Yu Chenxi. The simplest job can be said to be a miscellaneous job, and checking papers was assigned to Wenfeng.
This made Wenfeng really embarrassed. He was the leader of a team of three, but he ended up doing odd jobs. How ridiculous. Wenfeng said: "I don't agree with this division of labor. I object. I am the team leader, so I will divide the work." Lu Shan smiled and looked at Wen Feng. But Wenfeng realized the difficulty of the questions was so great. I was suddenly speechless. If you ask him to use mathematical methods or develop models, he doesn't know any of them. Wouldn't that be a complete disgrace to yourself? Wenfeng compromised. In order to get a ranking, he had no choice but to compromise. But no matter how much we compromise, we must not lose face. Wen Feng said seriously: "I am responsible for the overall coordination of the work, and I will also help check the papers." "Lu Shan will be responsible for mathematical thinking and model building, and Yu Chenxi will be responsible for writing the paper. Okay, it's settled." Yu Chenqian and Lu Shan looked at each other, speechless. In order to ensure the unity and stability of the team, Yu Chenxi took the initiative to say: "I taught myself some SPSS some time ago, and I can come to help when we are modeling." Lu Shan declined and said, "I want to use MATLAB. It will be faster and easier to model." Yu Chenxi has heard of MATLAB and has tried using it. But the operation was too complicated and too professional, so she gave up learning the software. Wenfeng said, "Okay, let's get started. You guys do it first, and I'll pour you some hot water." Since Wenfeng doesn’t know how to do it, he wants to see if Lu Shan can do it. Lu Shan quickly got into the state. Question A is about the signals received by an aircraft while it is in continuous flight. Lu Shan, who was able to work out the distribution of base stations together with Poincare, did not have to think about this kind of question at all; he could answer it effortlessly. The first question is: combine the information in the topic with the data to establish a mathematical expression for the opportunity signal. At the same time, for each type of opportunity signal, discuss the minimum number of opportunity signals that can uniquely determine the position of the aircraft. Lu Shan quickly wrote down the answer: "Assume that the number of types of opportunity signals received by the aircraft at time t is N. , the number of each opportunity signal ni..." "The mathematical expression of each signal is as follows: (1) Time of arrival information TOA(j) = t(rj)…." This problem is actually very easy to answer. You just need to figure out the relationship between the time difference between the aircraft receiving the signal and the time difference between the signal transmitting. After completing Question 1, Lu Shan also obtained some model conclusions.
For time of arrival information (TOA), time difference of arrival information (TDOA), Doppler frequency difference information (DFD) and received strength indicator information (RSSI), at least two different signals must be received to determine the position of the aircraft. Therefore, at least 6 different signals need to be received to determine the position of the aircraft. For angle of arrival information (AOA), at least three different signals of each type need to be received to determine the position of the aircraft. Therefore, at least 15 different signals need to be received to determine the position of the aircraft. In summary, at least 21 different opportunity signals need to be received to determine the position of the aircraft. Later, Lu Shan felt that using MATLAB would be an overkill for this kind of problem, and that it could be modeled using C language. After Wenfeng took the water. Lu Shan has finished answering questions 1 and 2 and is currently answering question 3. While Lu Shan was answering the questions, ideas for modeling came to his mind. He can think about which data he will encounter when writing the paper and which data will require references. So he dictated to Yu Chenxi to write down the information he requested. Then let Wenfeng search for literature based on the required information. At the same time, Lu Shan also told Yu Chenxi how to write a paper and asked Yu Chenxi to start writing the paper immediately. This is Yu Chenxi's first time writing a paper. She thought writing a paper was a very difficult task, but she didn't expect that with Lu Shan's guidance, the paper would be so easy. She just sorted out the framework and ideas of the paper. When you need to use mathematical logic and mathematical formulas, just copy and paste what Lu Shan wrote. Wenfeng and Yu Chenxi also quickly got down to work. The Mathematical Modeling Competition lasts for three days, or a full 72 hours. The school also provided excellent basic services for the competition. For example, the library's study room was provided free of charge to the participating teams, and the air conditioner was generously turned on. All three of them were very dedicated. From 10 am to 2 pm. They were indeed hungry, so the three of them went to the cafeteria to have a simple meal. Of course, at this point the teacher's window and the regular student window were closed. I can only eat some noodles, dumplings or rice noodles. Yu Chenxi saw that Lu Shan was indeed very dedicated and professional all morning. Take the initiative to invite Lu Shan and Wen Feng to have lunch.
While eating, Wenfeng was still talking a lot, talking about some of his experiences in mathematical modeling that morning. It turns out that what was said had nothing to do with the technical knowledge of modeling and was all just bragging. Lu Shan was too lazy to pay attention to him. After dinner, everyone took a break and worked from 3pm to 8pm. Wenfeng pretended to be generous and said that he would treat everyone to coffee, and he was prepared to stay up late. For many college students, the Mathematical Modeling Competition is actually a competition that requires a huge workload and is extremely time-sensitive. Sometimes 72 hours is simply not enough. This resulted in many teams only having 4 to 5 hours of rest a day, and spending the rest of the time brainstorming. Yu Chenxi thought Wenfeng was going to treat everyone to some coffee, but he ended up buying three packs of Nestle instant coffee. A pack of coffee costs 7 cents, three packs cost 2 yuan. Yu Chenxi was really speechless. 10 pm. After Lu Shan sorted out all the data, he stretched lazily. Yu Chenxi saw that Lu Shan was fully committed throughout the day, and it seemed that he was indeed a little overdrawn. She still felt very sorry for this junior. To put it nicely, the Mathematical Modeling Competition is about three people collaborating and working together. To put it bluntly, it was actually only Lu Shan who was doing the work, and Yu Chenxi was just doing odd jobs when she was writing the thesis. Yu Chenqian said uncomfortably, "We've worked hard all day today, why don't you go back and rest first, and come back tomorrow. Let's meet early tomorrow morning at 7:30." Wenfeng quickly refused and said, "No, time is very tight, let's stay up all night tonight." Lu Shan packed up his things and said, "I have solved all the questions, built the model, and put the files in a folder on the desktop. I also wrote down the ideas for writing the paper and put it on the desktop. Senior Sister Yu can take a look." "I have something else to do tomorrow so I won't be here. You guys can take your time with your work. I'm going to go back and rest first." Everyone: “What??!!” (End of this chapter)