Feng Yan quickly returned to the United States during this period.Daily flights from Bingcheng to Beijing have been opened, making going abroad much more convenient.

She has graduated with a Ph.D. There are not many things to deal with, and she will return soon.

She came back this time with Li Dan.

Although Li Danren came back, he did not plan to join Optoelectronics, but continued to study and study as a graduate student at the University of Technology.This caused the students to drop their glasses.

Li Dan's mentality is very good.Holding the stocks of Optoelectronics, the annual dividend is enough to make her food worry-free.She is now learning purely for learning.Not everyone has the ambition and ambition to change the day.

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The colorful development is very good, but the challenges are not small.

The brightness of the LED has increased, and when the brightness reaches a certain level, some new obstacles have been encountered.

Sapphire is an insulator, so devices with a vertical structure cannot be fabricated, and n-type and p-type electrodes can only be fabricated on the upper surface of the epitaxial layer. This is the so-called lateral structure.

The lateral structure has several disadvantages: high current density in the material, current crowding, poor reliability, and short life; in addition, the light loss through sapphire is large.

In order to overcome this problem, Feng Yan and Cheng Yongxing discussed a sapphire substrate stripping plan.

After adopting this kind of scheme, vertical structure LED becomes possible.It can provide greater current, eliminate current congestion problems and bottlenecks in the device structure, and significantly improve the maximum output optical power and maximum efficiency of the LED.

But this process method requires brand-new laser stripping equipment and procedures. These days, Feng Yan has been cooperating with "Technical University Laser" and is busy with this issue.

If this process can be realized, LED will formally have the strength to enter the ordinary light source market.

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Feng Yan has officially joined the Optoelectronics and he can enjoy many benefits, such as housing.

After getting a set of 100-meter high-rise buildings, she moved out and lived by herself.

In addition to the house, there are also cars.She didn't lack money, the company's Jetta had a square head and a square brain. She didn't like it, so she simply paid for an imported Accord.

After the new car arrived, she deliberately took a few classmates to the new home to have a meal, which was regarded as a celebration of the housewarming.

These small high-rise buildings of 100 meters are very close to the high-end residences of later generations, and the parking lots are all underground.After the meal came out, Feng Yan sent the guests out.

"what happened?"

"Just such a few cars?"

Cheng Yongxing looked at the unusually empty underground parking lot in a daze.

"This community drives by itself, I'm afraid I will be the only one."

In this era, few people drive themselves.Some leaders of enterprises and institutions have cars, but they all have full-time drivers.After the driver sends the leader home, he will drive away, and will pick him up the next morning.

Like Feng Yan and Cheng Yongxing, there are only a few who drive by themselves.

"What's wrong with you, what are you thinking about? Isn't you afraid to drive after drinking some alcohol? How about going upstairs and sitting for a while?"

The traffic laws of this era are not strictly controlled.Drivers are all public drivers, and most of the penalties, public to public, are nothing.Cheng Yongxing drove without a license for half a year, and nothing happened.

Although his car is only a Jetta, his car number is probably remembered by all the traffic police.

"This bit of wine is nothing. But the parking lot, it won't work."

"Why not?"

"Not safe. It's not safe."

The empty parking lot feels cold even in the hot summer.

The underground parking lot is entirely the product of Cheng Yongxing's advanced thinking.Logically, each household can be allocated a parking space, and some users simply surround the parking space as a warehouse or pile up garbage.

How can this be?

As a result, the parking spaces were collectively recovered and left empty here.Since it is a welfare housing distribution, there are no disputes over property rights.If this batch of parking spaces were taken back, they were taken back.

"There are security guards in the community, what are you afraid of?"

The optoelectronics department is rich in wealth. These newly-built communities have copied the model of later generations of private apartments. They are managed in a closed manner and have some sports facilities inside. In this era, the grades are quite high.

Cheng Yongxing didn't explain anything. He simply drove the Jetta around the parking lot twice and drove away.

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At Feng Yan's family dinner, he saw Li Dan's boyfriend, Zhang Tianhang.

This person Cheng Yongxing had a bit of an impression. He did not expect that after so many changes, Li Dan's home would return to its original history.She has a reason to return to study in China.

Li Dan went back to the original history, so what about Feng Yan?

Feng Yan's incident was to walk from the parking lot back to the apartment.

Now she drives to and from get off work every day, and this risk is inevitable.

But Cheng Yongxing couldn't do much, because it was still early, more than ten years before the incident, and Feng Yan's place had changed.The place where her accident occurred has been designated as the South Campus and will no longer be transformed into a commercial residential area.

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Back at the company, he brought in Zhang Yan and Secretary Lin to arrange to strengthen the security forces of small high-rise residential buildings.The gates of the community must be censored. In addition, security posts must be placed in the parking lot, which must be guarded 24 hours a day.

Cheng Yongxing didn't know what to do and could only do what he could.

This order made several people in the office a little baffling.

In this community, the people who live in this area are either rich or expensive, not company executives, or school professors, and some are also city officials.Therefore, the security forces in the community are already very strong.

In addition, arrange security in the unused underground parking lot. What are they doing there?

There are not a few cars in the community at all.With the exception of Feng Yan, the few other cars have their family members as drivers, and they drove back to the unit and parked there temporarily.

But Cheng Yongxing is stubborn.His reason is also considered sufficient.The vehicle is now an out-and-out valuable item. No matter how common a Jetta is, it is worth starting with ten houses.

After receiving the order, a series of tasks were arranged, security guards were also set up in the parking lot, and a closed-circuit surveillance system was installed.

The current monitoring system is not cheap, but Cheng Yongxing still insisted on spending it.Even if security is installed, people can easily lose their alertness if no one moves in the parking lot for a long time.

In order to solve the problem that the underground parking lot is too deserted and not popular, we simply set aside a space in the parking lot and open a community-selected supermarket to increase popularity.Let the security guards protect the supermarket at the same time, it is considered to have something to do.

As a result, this supermarket is very popular.

The residential areas of the photovoltaic system generally do not have commercial parts, and the residents are all high-income groups. There is a great demand in this regard.

Since then, building a supermarket in the underground parking lot in the photovoltaic residential area has become a standard feature.

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A meeting room.

A group of people are in a meeting.

"These days, the whereabouts of the protected objects are all normal, but Zhang Yan has reflected a new situation. After he attended a classmate’s house dinner, he arranged security work for the Mulan Street community. Not only the community’s guards were It has been strengthened, and monitoring facilities for the entire community have been installed. In addition, security guards have been arranged even in the underground parking lot."

Captain Lin is doing routine reporting.

"Is it only this community or all residential communities?"

"Only this community."

"Well, interesting. He feels danger again, right."

The fainting incident has not yet been closed.Because of the lack of clues, things have been hanging here.

But one detail that everyone is very vigilant about is that Cheng Yongxing has confirmed that it is dangerous.

"Yeah. But what kind of danger is it? Why do you need to strengthen the security of this community? What is special about this community? And even the parking lot where no one moves around?"

A group of people in the room are also talking about it.

Cheng Yongxing's non-cooperation is the biggest difficulty.What is it that scares him?

Who is in danger?

The inconclusive meeting soon ended, and the next topic began again.

More than half of Deputy Director Zhang's daily work consists of non-stop meetings.

Cheng Yongxing's security is only a small topic.