In the following days, Liu Feng returned to the life of the dormitory, canteen, library and laboratory.

The physics exam was easily passed by him, and Professor Qi Xin did not deliberately embarrass him like Boss Duan, a very simple small topic - conservation of angular momentum and its application as a graduation thesis, and did not ask Liu Feng to publish SCI or anything.

Of course, almost all domestic universities will not make it difficult for undergraduates' graduation projects, which is also the biggest difference between Chinese universities and foreign universities.

China has always adhered to the principle of strict entry and wide exit, while Europe and the United States have just the opposite, with wide entry and strict exit! These are two completely different practices caused by different national conditions, and Liu Feng can not question which educational method is better.

However, in terms of basic education, China is indeed a big step ahead of Europe and the United States, and even the mathematics level of primary school students is higher than that of European and American junior high school students, while in higher education, China is a big step behind Europe and the United States, which can also be seen in fact.

At a time when Europe and the United States are gradually learning from China's basic education, some people in China want to study the quality education of Europe and the United States in an all-round way, so as to 'reduce the burden' on primary and secondary school students, and they do not know what kind of peace they have.

In short, Liu Feng didn't even have more than two days to discuss this topic, and a small paper was freshly released.

【Conservation of Angular Momentum and Its Applications】

Angular momentum and its laws are another important result derived from Newton's laws. The angular momentum theorem holds true for both the mass and the mass system. Conservation of angular momentum is used in some sports, cat falls, and meteorologically-related natural phenomena......]

Theoretical Basis......

The theorem of angular momentum of the particle is......

Application of angular momentum theorem:

The flip of the cat in free fall is conserved with angular momentum.

Let a cat fall on all fours, and it will always roll over 180 degrees before landing, and land in a safe position on all fours.

In the process of free fall, the only external force received by the cat is gravity, and gravity has no moment on the center of mass of the cat, so the moment of the cat in the process of falling and the external force is 0, so how did the cat obtain the angular displacement of 180 degrees?

The answer is that the cat bends down first, so that the front half and the back half of the body are almost at a 90-degree angle, and then its front and back half rotate respectively, but the direction of rotation of the front and rear bodies is opposite, so the angular momentum of the front and rear parts can be the same, but the sign is opposite, so its angular momentum can still be 0 as if it began to fall.

Therefore, for the cat as a whole, its angular momentum is conserved.

Writing this, Liu Feng couldn't help but think that those guys who like to pet cats can blow again, at least, this ability, the legendary teddy dog that can live every day can't do it.

That's really an interesting little study.

At that time, he actually captured a cat for experiments, and used a high-speed camera in the laboratory to film the cat's fall from the second floor, which directly confirmed his research.

But the results of the study showed that Liu Feng never touched the big white cat that was not afraid of people who often ran to the classroom to rub in class, even if he used its favorite fried fish for the elderly.

In order to make up for the wounded heart of your old man, let's simply change the title of this little essay to "On the Best Posture of Cats Jumping Off the Building", what do you think?

Hehe, next, continue to write.

…… In figure skating, an athlete uses the expansion and contraction of the body to change the moment of inertia of his or her to change the angular velocity around his vertical axis...... Meteorologically, the shift of the surface winds ...... Formation of the four seasons...... And so on can be explained by the angular momentum theorem.

Summary: Angular momentum and its laws are another important result derived from Newton's laws...... In modern physical theories, for example, the angular momentum of the atomic nucleus, also known as the spin of the atomic nucleus, is the quantity that describes the characteristics of the atomic nucleus. In the field of microscopic particles, where Newton's laws of motion do not apply, this conservation law is still used.

References: ......

happily submitted the thesis to Professor Qi Xin, and then happily approved it, informing Liu Feng to wait directly until the graduation season to do a graduation defense, a bachelor's degree in physics, you can easily get it.

The graduation project on the physics side is indeed simple, but Liu Feng's new topic, he is in trouble.

As a university tyrant who can control the particles of the microscopic world, Liu Feng is indeed arrogant.

Boss Duan recommended to him the research direction of three membrane materials, and he directly chose the research of semi-permeable membrane materials that can be applied to water treatment, especially seawater desalination.

And the reason why Liu Feng chose this direction is very simple, two words - Qian Jing!

Since more than 70 percent of the world's population lives in coastal areas, the prospect of seawater desalination technology is undoubtedly very broad, almost comparable to oil, and has been rapidly promoted and applied in the past 20 years.

However, it is a pity that in addition to the transportation cost, compared with the cost of freshwater treatment in inland areas of a few cents a ton, the cost of seawater desalination is as high as 4-5 yuan/ton, so except for water-scarce islands and the Middle East and other tyrant countries, the use of seawater desalination in other regions is not good.

Even so, more than 100 million people in the world today rely on desalination for drinking water.

So, the arrogant Liu Feng set a goal for himself as soon as he came, he wanted to develop this huge market comparable to oil!

So, the trouble came.

The traditional seawater desalination method includes freezing method, electrodialysis method, distillation method and reverse osmosis method, among which reverse osmosis method occupies an absolute cost advantage.

Of course, Liu Feng is also engaged in the research of reverse osmosis method, among which, reverse osmosis membrane and supporting high-pressure facilities occupy an absolute majority of the cost, about more than 90% of the cost of the entire seawater desalination!

Theoretically speaking, as long as the reverse osmosis membrane is good enough, in fact, the supporting high-pressure facilities can be avoided, but it is a pity that today's reverse osmosis desalination membrane is mainly cellulose acetate membrane and polyamide composite reverse osmosis membrane, of which the latter occupies a major position.

The cost of these two membranes remains high due to the fact that they are inherently expensive materials and require high-pressure pressure to treat seawater.

Liu Feng wants to study reverse osmosis membranes, either on the basis of these two materials for in-depth research, or directly look for a new reverse osmosis material.

But either way, it's hellish of difficulty.

The former has been deeply cultivated by countless scientific research teams, and has also achieved a series of results, and the latter has more researchers, but so far has not found a new material that can replace the polyamide composite film.

However, Liu Feng's research plan is carried out by two means at the same time!

"How is it, boy, have you encountered difficulties?" In the office, Boss Duan leisurely soaked a small bag of West Lake Longjing, took a sip gently, and showed an expression of enjoyment.

These days, he is also tired, the research of the subject is quite smooth, and it is time for Q&A once a week, and it is also the time for him to take a vacation to recuperate.

"Yes, boss!" Liu Feng nodded, "I studied the papers of other teams and found that their research on reverse osmosis membrane materials for water treatment is basically based on the research of polyamide composite materials, but there are three problems:

First of all, the operating pressure is high, generally about 50 atmospheres; secondly, the colloids, organic matter, bacteria, etc. in the water are easily deposited on the surface of the membrane to form a polluted layer, which needs to be cleaned regularly; finally, this material is not resistant to active chlorine, and water treatment generally uses active chlorine for disinfection, which reduces the service life of the material. ”

Duan Xue patiently listened to Liu Feng's question, and nodded from time to time: "Well, the problem you said is also the main problem in the research of reverse osmosis membrane materials in the world today, so what is your response to this?"

Boss Duan generally does not answer students' questions directly, but heuristic education, first ask the students if they have any solutions, and then he will check and fill in the gaps, there is really no way, he will give people a lot of relevant information, and then come to him if they don't understand.

Liu Feng didn't want to brush a lot of papers anymore, he was almost throwing up now, so he already had a series of mature plans.

"Yes, the main innovation points of polyamide composites are also in these three aspects, I already have some immature ideas, so I designed these fifteen types of experiments, and I have written the plan, you see. ”

Liu Feng put the printed experimental plan on Duan Xue's table and continued: "Actually, my problem is not here, but, but at the beginning, the experimental content was a bit much, and I couldn't be busy alone, so I hope the boss agrees with me to recruit a few helpers, hehe." ”

The thing touched his head embarrassedly.

Duan Xue looked at the plan and reviewed it word by word.

After a while, seeing him alternately stroking his hands on his baby's blue and white teacup, Liu Feng knew that this was a sign that Boss Duan was in thought.

Finally, Duan Xue nodded and sighed: "These dozen or so methods of yours are not feasible to try, no wonder, no wonder your kid looks sad, it turns out that he is here! Say, you are going to recruit a few people." ”

"Hehe, boss, then, let's recruit 10 part-time students first, well, it won't take long, at most a week, as long as you can do experiments. "Just listen to Liu Feng's weak words.

Duan Xue: "......"

10 people, you kid, shouldn't you go to heaven!