Several people looked at Lin Yuan intently, and Lin Yuan said: "I saw the book "Introduction to Naval Weapons" on your desk, who will tell me what this book is about?" ”

Liu Guang raised his hand, Lin Yuan nodded, and Liu Guang said: "This book talks about the weapon system of warships, including naval guns, torpedoes, propellants, shells, and so on. ”

Lin Yuan said: "Then I believe everyone is no stranger to all kinds of shells in naval battles, so who will tell me what shells are in naval battles?" ”

Liu Guang raised his hand again, Lin Yuan motioned for him to answer, Liu Guang said: "There are armor-piercing shells, high-explosive shells, and armor-piercing blasting shells." ”

Lin Yuan asked again: "Okay, you can explain to me the purpose of these shells." ”

Liu Guang said: "Let's talk about armor-piercing shells first, because the warships of the navies of various countries in the world use relatively thick armor, so if you want to damage the enemy's warships, you must penetrate their armor, and in this case, high-speed armor-piercing shells are required; From the point of view of the structure of the warship, because the ballistics of the shells are relatively straight, the probability of the warship being hit on the broadside is the greatest, so the armor of the warship is generally laid on the broadside. ”

"There are three elements of a battleship: firepower, armor, and mobility, these three elements restrain each other, the armor is thicker, the mass of the warship will become larger, so the mobility will decrease, in order to maintain the balance of the three, so the weight of the armor can not be too large, in this case, the navies of various countries have arranged the heavy armor on the broadside, and the deck, bridge, these places are not equipped with armor or only a small amount of armor."

"High-explosive bombs are specially designed to deal with the superstructure of enemy warships, when high-explosive bombs explode, although the fragments produced are not enough to penetrate the armor of the hull, but they can cause great damage to the personnel on the deck, and the lethality does not only come from shrapnel, it will produce a strong shock wave when it explodes, and after the shock wave hits the human body, it can cause the vibration of the internal organs, so that the internal organs will burst."

"And the armor-piercing blasting projectile is more powerful, this kind of bullet can explode after penetrating the opponent's armor, and the inside of the enemy's hull is a very critical component, and if these parts are damaged, the battleship is not only a matter of losing combat effectiveness, but more importantly, losing vitality."

"However, the production design of this armor-piercing blasting bomb is also very difficult, one of which is the design of the fuze, the fuse must control the timing of the explosion, not to explode too early, otherwise there will be no effect, and the fuse must ensure that the explosive does not explode in the process of armor-piercing.

Lin Yuan nodded and smiled: "What you said is very good, then my problem will come." ”

When everyone heard Lin Yuan want to ask a question, they all looked at Lin Yuan, wanting to show their skills, Lin Yuan said: "You will all be the commanders of warships in the future, although it is impossible to be the captain and chief of staff from the beginning, but you will also start from the staff officers, so my question is related to formulating operational plans." ”

Lin Yuan continued: "In order to describe the convenience of the problem, we introduce a concept of lethality index, we don't need to consider how this index came about, we just need to simply understand that the higher the lethality index, the greater the lethality, and now we set the lethality index of armor-piercing shells at 2, high-explosive shells at 1.5, and armor-piercing blasting shells at 3. ”

"We now think of such a tactical environment, you need to lead your warship to attack the enemy's fleet, assuming that your warship can only carry a hundred kilograms of shells, here we do not consider the authenticity, the weight of each armor-piercing explosive projectile is five kilograms, the weight of the armor-piercing projectile is four kilograms, and the high-explosive shell is two kilograms, now you can only use two kinds of shells, may I ask, how do you choose, can make the lethality index the maximum?"

After everyone listened, they all thought intently, and Lin Yuan said: "You can also discuss and discuss, it's okay, tell me when you're done thinking about it." ”

Several people immediately began to discuss: "How should this be calculated?" "I think it's more similar to the linear programming I talked about, is it solved by linear programming?" "Yes, that's right, it should be done with linear programming."

Several people discussed for a while, and then began to write on the paper, Lin Yuan smiled: "The specific calculation process is not needed, just tell me the idea." ”

Liu Guang said: "This should be abstracted into a linear programming problem, in this problem, the objective function is the lethality index, and the constraint is the sum of masses, so we express the number of two kinds of bullets as unknowns, we can list an equation and an inequality, and when solving, draw the straight line represented by the equation and inequality in the coordinate system that uses these two unknowns as the horizontal and vertical axes." ”

"On the graph, these two lines will have an intersection point, and the intersection point may be the point you want to select, choose two of the three bullets to combine, there are three in total, calculate these three cases separately, and then compare them to see which group makes the objective function the largest can take which group."

Lin Yuan nodded and said, "Very good, the idea is good, but I haven't calculated the numbers in it, there may be problems, but your thinking is very correct, and now the real difficulty is coming-" Lin Yuan looked at them and said: "Now that we have improved the technique, these three shells can be equipped together, tell me how to choose this time?" ”

Liu Guang said: "It used to be two variables, but now it has become just three variables. ”

Lin Yuan smiled: "That's right, it's become three variables, but how do you solve it this time?" ”

Everyone frowned when they heard Lin Yuan's question, indeed, the linear programming problem of two variables can be calculated using the graphical method, but there is no way to draw three variables, Lin Yuan looked at their silent appearance and said: "Now we only have three kinds of shells, but we still have torpedoes in actual combat?" Four variables! If we use other weapons, there will be more variables, what should we do then? ”

Everyone shook their heads, Lin Yuan turned around and took the linear algebra book from the shelf, and said: "The solution is inside, but looking at the way you linear algebra looks, even if I tell you how to solve it, you won't be able to, study hard, the answer is inside." ”

Lin Yuan continued: "You will encounter a lot of such situations in actual combat in the future, there is a special discipline, called military operations research, this discipline will guide you, how to choose the most optimal parameters in actual combat, do you say this discipline is very useful?" ”

When everyone heard that the selection of optimization parameters was also a science, they couldn't help but nod their heads, and Lin Yuan said: "Although this course is useful, its foundation is what you are learning now, so you should learn what you are learning now." ”

After Lin Yuan finished speaking, he said to everyone: "Actually, the courses you are learning now can be used in the future, many people feel that those things are not used, because they have not learned them well, and when you reach a certain level, you will find that in fact, everything is useful, but you don't know how to use it and where to use it." ”

A few people nodded, Lin Yuan looked at Liu Guang and asked, "What do you think of geometry?" ”