Short video spoiler history: The beginning of modern warfare

Chapter 158 Electromagnetic Waves

[Now I know that most foreigners are allergic to milk, peanuts, grains, pineapples, mangoes, etc. There is even a rumor that a five-nut mooncake can knock down half of the Europeans]

[Netizens shared that we have been planting and eating peanuts since the Ming Dynasty, and many people at that time had allergic reactions after eating them. Symptoms included rashes, itchy skin, diarrhea, abdominal pain, nausea, swollen throat, etc. In severe cases, breathing difficulties may occur.]

[But at that time people would not say it was a problem with the food, but rather that the person had a bad fate and died at a young age. There are still many people abroad who are allergic to peanuts. They will develop large red rashes after eating a little bit. It is quite amazing.]

[Some people say that the Chinese were originally 100% allergic to mangoes, but the Chinese do not believe in superstition and insist on eating until they have a low allergy and no symptoms at all. Drinking coffee and having diarrhea and a fast heartbeat are all signs of being allergic to caffeine.]

[It is also quite appropriate for allergic symptoms. Diarrhea is uniformly interpreted as laxative, and drowsiness is interpreted as a sleep aid.]

[Another netizen shared that when he was a child, he would have diarrhea after drinking milk. His family coaxed him and said that after drinking a box of milk, he could play games for half a day. Who knew that he couldn’t play at all because he vomited and had diarrhea after drinking it, so he was sent to the hospital. Then his parents liked to coax and force him to drink, and said that if he drank more in the morning and evening, he would get used to it. They also told embarrassing stories about him in front of relatives during festivals until I threw the test report in their faces.]

[I have to say, this is too real. Chinese people are like this. They would rather doubt themselves than suspect that they are allergic. Peanuts, milk, mangoes, kiwis, seafood, etc. may cause allergies.]

[Continuously eating repeatedly is like a long-lasting desensitization training. If you eat too much, you will naturally become desensitized. But you still have to pay attention that real desensitization training is to eat small amounts and multiple times, so that the body can slowly adapt, rather than taking in a large amount at the beginning.]

[The terms allergy and desensitization have a theoretical basis. Allergy is essentially the body's rejection of proteins in food. Because it is the first time to see it, the cells in the body will call on antibodies to attack. Later, as the number of intakes increases, the cells also realize that these proteins are harmless to the human body, and gradually become desensitized.]

Jinling City, Hexing Tea and Snack Shop.

Mr. Su, Shopkeeper Wan and other people who have already started a family are a little embarrassed.
As parents, we naturally want to save all the delicious food for our children, and they are no exception.

I just didn't expect that there is such a thing as an allergy to food, which in severe cases can even be life-threatening.

"So after my son ate mango, he said his lips were numb and he got a rash, which was also an allergy?" Shopkeeper Wan was also a little confused. He thought it was just nonsense from the child, but he didn't expect it was an allergy. Fortunately, the symptoms were not serious. Thinking of this, he patted his chest in fear and said, "Ancestors bless you!"

With the tacit abolition of the "sea ban policy" last year, a wave of trade with Southeast Asia has emerged among the people. A large number of rare and precious goods, vegetables, fruits, etc. from Southeast Asia have poured into the country, and mango is one of them.

Because the price was high, he couldn't bear to eat any of them himself. He bought nearly a pound of mangoes and shared them with his three children.
"You're still okay." Mr. Su smiled bitterly and shook his head, remembering that his youngest child was allergic to coriander. Every time he ate it, he complained of itchy eyes and irregular heartbeats. No one in the family had this problem, except him.

If Tianmu hadn’t mentioned it, I wouldn’t have known this was the case.

Inside the store, everyone was at a loss whether to laugh or cry. It turned out that it wasn't because their children were spoiled, but because many things that adults could eat might not be suitable for children.
But when you think about the fact that foreigners are allergic to so many things, and we have accidentally found the path of desensitization, everyone is very happy.

Inside Fengtian Hall.

Zhu Yuanzhang was also happy. All the food in the palace was tasted by servants, so this problem rarely occurred, no matter whether it was tribute.

It seems that it is right not to allow local specialties to be tributed. It not only avoids the waste of money and labor, but also avoids food allergies.

Hu Weiyong and others suddenly realized that eating mangoes and pineapples would cause itching and rashes on the skin, which was an allergy. The solution was also very simple: take small amounts and multiple times.
Mangoes are so delicious and sweet, but this allergy is really annoying.

[In the 19th century, scientists discovered that there is a close connection between electricity and magnetism, which is the phenomenon of electromagnetic sensation. After summarizing the research of his predecessors, Maxwell proposed the very famous Maxwell equations, which unified electricity and magnetism.]

[A changing electric field will generate a magnetic field, and similarly, a changing magnetic field will also generate an electric field. So he thought, if the magnetic field generated by a changing electric field is also changing, then does it mean that the two can excite each other? This mutually excited magnetic field and electric field will oscillate along a straight line to a distance, which is an electromagnetic wave.]

[In this way, he predicted the existence of electromagnetic waves and calculated the speed of electromagnetic waves through the formula: v = λf, where the speed of v is equal to the speed of light, so v is written as c by default, λ is the wavelength, and f is the frequency. The higher the frequency, the higher the energy and the longer the propagation distance]

[Because the speed of light in a vacuum is exactly the same as the speed of electromagnetic waves, he firmly believed that light is a kind of electromagnetic wave. It must be said that a genius is a genius. We all know what happened later. Light does have the characteristics of waves, which is what we often call wave-particle duality.]

[Electromagnetic waves are generated by the mutual excitation of electric and magnetic fields, so they can propagate without a medium, and the propagation speed is very fast. This is different from sound, which needs to pass through a medium to propagate.]

[What about the actual applications? For example, the smallest wavelength is called gamma rays. Because of its high energy and strong penetrating power, it can be used in industry for metal flaw detection. It can also be used to remove cancer cells because of its cell-killing power. This is the radiotherapy of cancer.]

[Electromagnetic waves are very common in our daily lives. The radio signals used in mobile phones are electromagnetic waves. The light we see from objects is also electromagnetic waves. X-rays taken at the hospital are also electromagnetic waves. The radios we often listened to as children are also electromagnetic waves.]

[So how do you emit an electromagnetic wave? It's very simple. Just put two metal plates facing each other (they have stronger transmission capacity when they are in an outward-facing position) and connect the two ends to alternating current. Because the two poles of alternating current are constantly changing, the corresponding electric field is constantly changing. The positive and negative charges in the two metal plates connected to the positive and negative poles are constantly switching back and forth, thus generating a constantly changing magnetic field.]

[It is also very simple to receive electromagnetic waves, as long as your receiving device is at the same frequency as the transmitting device, that is, by adjusting the capacitor in the LC loop to receive the corresponding signal, and then transferring it to another circuit through mutual inductance, and then demodulating and removing the high-frequency signal, what remains is the low-frequency signal we need. For example, if your transmitting end is sound, you can play the sound by connecting the output end to a speaker.]

In front of Fengtian Hall.

Even the people in the science department felt their scalps tingling because they couldn't understand anything.

"Look at the circuit diagram. On the left is the transmitter. The signal from the signal source is connected to the inductor, induced to the antenna and then transmitted."

"The one on the right is the receiving device, which is a connected circuit of capacitors and inductors. The frequency is adjusted by adjusting the capacitors. Then there is the demodulation part." In the Science Department, Du Ping, Sun Chuanshi and others quickly copied down the circuit diagram in full and continued to analyze it.

Others, such as Zhu Yuanzhang, Hu Weiyong and others, were already confused when they saw the circuit diagram. They could not understand the last few paragraphs at all and just waited quietly.

"No, capacitors and antennas should be the same thing, but what is an inductor?"

"Why can this part of the circuit filter high-frequency signals?" Sun Chuanshi and others were very puzzled. Although they got the so-called circuit diagram from the sky curtain, they only had a vague understanding of many of the contents, and the sky curtain did not explain the reason.

"There's no mention of high-frequency signals on the left?" "Frequency. Signal source." Zhu Biao and others also came over. "Could it be that the frequency of the signal source on the left is very low and can't be transmitted far, so it needs to be converted to high frequency?"

"Maybe this part can be put aside for later study, and first try to see if the transmission and reception can be successful over a short distance." Zhu Yuanzhang said. He didn't quite understand what was said, but he knew that at this time he should try his best to resolve the problem, from small to large.

First reproduce, short-distance wireless transmission, and then slowly expand the distance.

"The signal source, is it like a telephone, causing a change in the current through the medium?"

"It's very likely." Sun Chuanshi replied and quickly wrote down the idea.

"If this is the case, and the filtered current on the right is changing, then the speaker at the output end may really be able to produce sound." Du Ping and others said happily. In fact, everyone knew that Tianmu was right, but he just omitted too many things.

"The problem now is this inductor. By the way, do you think this symbol looks familiar? Like..." Liu Ji frowned and recalled carefully. He seemed to have seen a similar symbol before, but he couldn't remember it.

"Like what?" Zhu Yuanzhang's heart was pounding as he looked at Liu Ji expectantly.

The same was true for everyone else. It was so quiet in front of the hall that one could hear the heartbeat. Marquis Chengyi frowned and closed his eyes, as if he was reminiscing.

Time passed slowly. Everyone became anxious.

"Like the windings on both sides of a transformer," a young clerk bit his lip and struggled with his conscience for a long time before he bravely said it. He helped copy the circuit diagram of that issue, so naturally he had an impression of it.

"Ah?" Zhu Yuanzhang and the others were stunned for a moment, and then their eyes shone with a fascinating light: "What did you just say? What did it look like?"

"Like the windings on both sides of a transformer." The young man was stunned by Zhu Yuanzhang's gaze and spoke haltingly, but fortunately everyone understood him.

"Your Majesty!" The official in charge of the documents immediately took out the documents. He did not read them but presented them directly. For a moment, everyone's heart was raised and they were worried about the reckless clerk.

If something goes wrong, you will probably be punished by dozens of strokes of the pen.

Liu Ji had also opened his eyes. He really couldn't remember where he had seen it, but if the clerk could say it was a transformer, it was probably not far off the mark.

Zhu Yuanzhang read ten lines at a glance and finally stopped at the circuit diagram. "It really is the winding of the transformer!"

The information was passed down one by one, and everyone felt it was a little unreal after reading it. The transmission and reception of radio broadcasts... Could it be cracked so easily?
What’s important is that the sky curtain only provides a circuit diagram. If there are so many components in it and there are no records of them from the beginning, no one will be able to understand the meaning of these components, let alone make them.

This is truly high-tech.
Of course, more importantly, it serves as a means of communication.

"Am I dreaming?"

Without a second thought, Zhu Yuanzhang ordered the clerk named He Yang to join the Ministry of Science. Although everyone would probably be able to find the transformer by comparing the previous information one by one afterwards, he would not let go of such a good opportunity to win people's hearts.

One is Sun Chuanshi and the other is He Yang, both are role models and can better inspire the work enthusiasm of their subordinates.

Tang Dynasty, Chang'an City.

"That's all?" Cheng Yaojin said in bewilderment, "Why did you stop halfway through? I, Old Cheng, still don't understand!"

Wei Zheng, Chu Suiliang and others twitched their lips. You are a rough guy, when did you learn about electromagnetic waves?
"What do you, a rough fellow, know about electromagnetic waves?" Yuchi Gong said disdainfully. If you don't understand, then you don't understand. Why are you showing off?

"Hey, how can you talk like that? We are all human beings. Do you think you understand electromagnetic waves as well as I, Old Cheng?" Cheng Yaojin didn't take his disdainful expression seriously. He had gotten used to it over the years.

"Yes, yes, you understand best!"

Li Shimin looked helplessly at the two people who were bickering, and smiled helplessly. It would be great if they were all as heartless as them.

"Write down the circuit diagram first, and then check previous records to see if there are any clues about what you don't understand." Li Shimin said as he looked at the comment section. He looked through the comments here but didn't see any useful information.

I learned from the comments that radio and radio are gradually being phased out, so most people don’t understand this principle.

"If the signal source is transmitted directly, it will not be transmitted far, so it must be loaded onto a high-frequency signal, also known as signal modulation. Generally speaking, it is frequency modulation and amplitude modulation, which are often referred to as AM and FM in radio."

"Why is there no SM? Sincerely eager to learn.jpg"

"Same Want to Listen"

"Since we are talking about frequency, let's also talk about Fourier transform, Laplace transform, digital signal processing, DSP technology and application, and random signal processing [狗头]"

"As soon as I heard these words, I knew that I had an innate science and engineering body, and the pressure was terrifying [dog head]"

(End of this chapter)