After Li Kangping finished writing the letter, he was about to leave the laboratory when he suddenly saw two people visiting.

One of the visitors was a tall and burly old man, and the other was a short, sturdy middle-aged man.

Speaking of this bespectacled white old man, he is Michael Idvorsky Pupin, a well-known figure in the physics world.

Michael Pupin was born in the Austro-Hungarian Empire and is of Serbian ethnicity. At the age of twenty, Michael Popin came to the United States on his own to study at Columbia University, where he majored in humanities education.

After graduating from Columbia, he went to Germany to study for a Ph.D., where he studied under the famous German physicists Helmholtz and Kirchhoff. After returning to the United States from Germany, Michael Popin was hired as a professor of physics at Columbia University and became an American citizen.

Michael Puppin's most important academic achievement was the invention of the fluorometer through which X-rays could be directly observed and easily photographed.

Michael Poppin's most important industrial application was the invention of the Popping coil, which he sold to AT Ann T in 1901.

The Pop coil is actually an additive technology. Thanks to the Plain coil, long-distance telephone calls are possible.

On January 25, 1915, the first long-distance telephone line between New York on the East Coast of the United States and San Francisco on the West Coast was opened, a 4,000-kilometer line that used 2,600 tons of copper wire, more than 130,000 telephone poles, and countless plain coils.

Michael Pupin is both an academic physicist, an inventor with a passion for industrial applications, and not only that, but he also has a background in the liberal arts, so he's a real all-rounder.

"Professor Pupin, how are you doing?" Of course, Li Kangping knows Professor Popping, and who on the campus of Columbia University doesn't know Professor Popping?

"I'm fine, and so are you. I heard that Professor Woodgate went to the Solvay conference? Michael Pupin asked.

"Yes, Professor Woodgate arrived in Brussels at the end of September, and I think Professor Woodgate should be speaking at the Solvay meeting at this time."

"Lee, so you're in charge of your lab for the time being?"

Li Kangping already has a certain reputation, and Professor Puping knows him and can accurately say his name.

"That's right, I'm in charge, can I do anything for you?" Li Kangping said warmly and friendly.

"Let's talk about your homeostatic separation technology for atomic and molecular beams, I want to know about this technology and related experimental equipment." Professor Pupin looked at the device not far away, and he said, "I have read your paper, but I want to hear you tell me, can I?" By the way, this is my assistant coach, Edwin. ”

"Edwin, it's a pleasure to meet you. Professor, Edwin, I'm more than happy to be of service to you. Li Kangping smiled slightly, and introduced their atomic and molecular beam steady-state separation technology and experimental details without reservation as a host.

"Three magnetizations, a high degree of vacuum, and then rapid cooling, where the silver atomic beams bombarded...... Clever, very ingenious. Professor Putin is full of praise for his research on X-rays, which belongs to atomic physics, and he is an expert in this field.

"Edwin, have you learned?" Professor Pupin asked his teaching assistant.

Edwin nodded, "Yes, Professor, I think I totally got it." ”

"I'm retiring, and when I retire, my chair will be taken over by Edwin--- if nothing else."

The number of new chairs at Columbia has grown at a slow rate, which means that the number of chairs at Columbia has been fixed for a period of time.

Professors with chairs at Columbia University retire or move to other universities, and the vacant chairs are replaced by others.

It is clear that Professor Popin likes his assistant professor Edwin and is willing to let Edwin take over his chair, and hopes that Edwin will make a difference in atomic physics.

"I'm old, and our world will eventually be taken over by young people, you two talk, talk about it." Professor Pupin took his leave.

Edwin seemed interested in talking to Li Kangping, so Li Kangping chatted with him.

Edwin's full name is Edwin Howard Armstrong and he is 31 years old.

Armstrong studied at Columbia University's School of Engineering, and during the European War, he enlisted in the U.S. Army to fight in Europe.

Armstrong, a World War I veteran, is a teaching assistant at Columbia. Combined with the content of the "American Patent News", Li Kangping knew very well who the war-experienced Armstrong was.

In fact, Armstrong did not kill anyone in World War I, and he served in the U.S. Army Communications Corps Laboratory in Paris, mainly engaged in military radio research.

In 1914, before Armstrong joined the army, he invented and registered the regenerative circuit in the United States.

In 1918, Armstrong used the Eiffel Tower in Paris as a launch pad, and he invented the superheterodyne circuit in Paris.

Not long after the invention of the superheterodyne circuit, it was not used in the war, and the First World War ended. Armstrong returned to the United States, and he registered a patent for superheterodyne circuits in the United States at the end of 1918.

In Li Kangping's memory, the super-regenerative circuit seems to have also been invented by Armstrong. In 1922? In 1923? It won't be 1921 anyway.

But now, excuse me, Mr. Armstrong, I have registered a patent for a super-regenerative circuit in 1921.

In any case, we should give Mr. Armstrong enough respect.

Mr. Armstrong invented the superheterodyne circuit, and until the 21st century, 99% of the world's radio radios, televisions, satellite ground stations, etc. used superheterodyne circuits to work.

Not only that, but the wideband FM circuit was also invented by Armstrong (it seems to have been in 1933), and this World War I veteran was really good at engineering.

"Edwin, you know, the atom and molecular beam method is actually not that mysterious, this technique is so ingenious that if you get the hang of it, it loses its veil of mystery. When you get back to your lab, you can try it out with X-rays or whatever. ”

"Lee, let's talk about your super regenerative circuit."

"Excuse me?"

"Hey, man, don't do that. You know, I subscribe to every issue of American Patent News, Science, and Bridge. ”

"Oh, yes."

Li Kangping looked at the old signal soldier with interest.

Professor Popping is a scientist and inventor in various fields such as atomic physics, electronic engineering, and radio communications.

As a teaching assistant and successor to Professor Puppin, Armstrong is a natural all-rounder in both academic research and industrial applications.

Professor Popping wanted Armstrong to focus on academic research in atomic physics.

However, the Armstrong brothers seem to be more passionate and enthusiastic about radio applications.

Making money, everyone wants to.

But don't be so red-fruited.