Chapter 159 Damn!

In late December, Huizhou was hit by wave after wave of cold air.

The laboratory on the second basement floor of the USTC Institute of Applied Physics has no windows, and several rows of cold white fluorescent tubes are lit.

In the very center of the laboratory stands an expensive vacuum chamber testing device.

The complex pipelines, the robust load-bearing alloy brackets, and the densely packed sensor lines resemble a giant metal spider web, firmly encasing this core instrument in the center.

Two movable whiteboards stood against the wall, covered with partial differential equations, matrix derivations, and Fourier transform expansions written in black marker. Some parts were erased and rewritten, leaving behind clusters of dark marks.

Doctoral student Zhao Peng held half a whiteboard marker in his hand, his brows furrowed, staring intently at the last line of formula on the whiteboard, remaining motionless for a long time.

Beside him, another doctoral student, Zheng Nan, walked over carrying two disposable paper cups filled with freshly brewed instant coffee.

He handed one of the cups to Zhao Peng, took a big gulp himself, and gasped for breath from the heat.

"Old Zhao, take a break."

Zheng Nan glanced at the whiteboard.

"We checked the boundary conditions of this set of partial differential equations three times last night, and we didn't find any flaws in the mathematical derivation." Zhao Peng took the paper cup but didn't drink it. He irritably threw the whiteboard marker on the table and rubbed his hair vigorously.

"If the derivation has no flaws, then what's going on with the data on the computer screen?"

Zhao Peng turned around and pointed to the monitor on the control panel not far away.

On the monitor, a green real-time data curve is slowly scrolling to the left.

That's the noise monitoring data inside the vacuum chamber. According to theoretical calculations, this line should be a smooth straight line, with fluctuations not exceeding five per thousand.

But now, at fixed intervals along that green line, there are very noticeable jagged burrs.

Zhao Peng walked to the monitor and tapped the few glaring jagged edges on the screen with his finger.

"The noise floor drift is too regular, 50 Hz, a very stable 50 Hz periodic low-frequency interference peak. It's like a leech, sticking to our effective signal, and software filtering can't remove it no matter what."

Zheng Nan followed, stared at the screen for a while, sighed, and tentatively guessed.

"Power supply ripple? Or is the grounding not done properly? 50 Hz is exactly the AC frequency of our country's mains power. Could it be that the electromagnetic shielding layer of one of the power lines is aging, causing leakage magnetic interference?"

"Yesterday afternoon, I took a gaussmeter and measured the magnetic field around this device inch by inch."

Zhao Peng took a big gulp of coffee.

"The magnetic shielding layer is intact, the grounding resistance of the outer shell is far below the standard value, and a top-of-the-line active filter has been added to the power supply end. All physical electromagnetic interference paths have been cut off."

"That's unbelievable."

Zheng Nan put down the paper cup and put his hands on his hips.

"If electromagnetic interference is ruled out, then what could it be? Quantum fluctuations on this macroscopic scale simply cannot exhibit such a large amplitude, especially at a fixed frequency."

Two doctoral students in theoretical physics from top universities in China fell into deep self-doubt.

They've been working tirelessly through several sleepless nights trying to find answers to this noise floor problem, drawing from electromagnetic field theory, quantum mechanical wave equations, and even complex signal processing algorithms, all in the hopes of writing a filtering code to remove this 50Hz ghost. "It must be that the algorithm's weights are misplaced."

Zhao Peng gritted his teeth, turned around, and walked back towards the whiteboard.

"Let's modify the window function of the Fourier transform and try using a Hamming window to further tighten the cutoff frequency in the low-frequency range." The two gathered around the whiteboard again, picked up their pens, and began a new round of formula derivation.

Less than five meters away from them, Wang Dayong was sitting in a chair at an iron table.

Because it was a bit stuffy in the underground laboratory, he casually pushed his sleeves up to his arms.

On the table lay a book titled "Materials Physics," next to a stack of draft paper. The top page was covered with various rough but clearly marked mechanical force analysis diagrams and several scattered calculation formulas drawn in pencil.

Da Yong twirled a ballpoint pen in his hand, silently listening to the conversation between Zhao Peng and Zheng Nan.

As a student in the gifted youth program, he naturally recognized the long partial differential equations on the whiteboard and could fully understand the mathematical logic behind Zhao Peng and his team's attempt to cut off specific frequency signals at the software level.

But he felt that his senior brothers might have become a little confused from staying up too long.

He just caught a word.

50 Hz.

Da Yong stopped twirling the pen in his hand.

50 Hz—this number was so intuitive to him that he didn't need to analyze it at all; the standard operating frequency of all AC motors in China was 50 Hz.

He closed the book "Materials Physics," stood up, and instead of disturbing his two senior classmates who were engaged in a heated debate, he bypassed the operation and walked to the public storage shelf against the wall in the laboratory.

The shelves were cluttered with various spare parts, wires, and utility tools.

Da Yong rummaged through a pile of junk and found a palm-sized piece of discarded high-density shock-absorbing rubber sheet, along with a wrench. Holding these two items, Da Yong walked to the massive vacuum chamber.

The equipment made a lot of noise while it was running, including the whooshing sound of the ventilation ducts and the humming sound of the instrument's cooling fan.

Dayong stretched out a hand and gently placed it on the load-bearing alloy support on the outside of the vacuum chamber, quietly feeling the vibration transmitted from inside the metal.

In his perception, this machine, weighing several tons, was not an inanimate object.

Countless tiny shockwaves crisscrossed the metal frame, and soon, he caught a regular and subtle low-frequency vibration within this complex network of vibrations.

Da Yong's palm followed the trembling veins, slowly exploring upwards.

From the main load-bearing column to the horizontal connectors, Dayong's gaze finally settled on a black rigid water pipe.

That's the inlet pipe that supplies cooling circulating water to the vacuum pump.

One end of the water pipe was connected to a high-powered industrial water-cooled pump in the corner of the laboratory, and the other end was connected to the heat dissipation layer of the vacuum chamber. To keep the wiring neat, this rigid cooling water pipe was tightly bound to the main load-bearing bracket of the vacuum chamber with several thick metal cable ties. Da Yong looked at the water-cooled pump, and then at the metal cable ties.

The water-cooled pump motor was running, and the tiny vibrations it generated were transmitted along the rigid water pipes. Because the pipes were tied too tightly, there was no buffer between the pipes and the metal support, and the vibrations were transmitted to the main structure of the vacuum chamber without any reservation.

The operating frequency of the water-cooled pump motor is exactly 50 Hz.

Da Yong turned his head and glanced at the scene not far away, where Zhao Peng and Zheng Nan were still arguing heatedly in front of the whiteboard about how to modify the parameters of the Hanming window. He didn't say anything, but picked up a wrench and wrenched it into the nut of the metal cable tie.

crunch~

With a flick of his wrist, the nut loosened, creating a gap between the tightly fitted water pipe and the metal bracket. Da Yong deftly folded the shock-absorbing rubber piece in half, fitting it snugly into the gap, and then tightened the nut again with a wrench. The rubber piece, deformed and stretched across the gap between the water pipe and the bracket, severed the path of physical transmission.

Dayong placed his hand on the main load-bearing bracket again. The annoying low-frequency pulsating vibration disappeared, and the bracket returned to silence. He dusted off his hands and casually tossed the wrench onto the metal workbench next to him.

There was a loud bang.

Zhao Peng and Zheng Nan, who were standing in front of the whiteboard, stopped writing and looked over.

"Dayong, be careful with the tools, we're running a real-time data test."

Zhao Peng casually gave a word of advice, then turned around to continue writing the formula.

Zheng Nan sighed and walked towards the computer he was operating.

"Old Zhao, let me try inputting these new parameters first."

He pulled out a chair and sat down, placing his hands on the keyboard and habitually scanning the real-time curves on the screen.

His hand suddenly stopped in mid-air.

Zheng Nan blinked hard, leaned forward abruptly, and stared intently at the screen.

On the screen, the green curve that used to have jagged edges at regular intervals had now become smooth.

Those annoying 50Hz jagged edges disappeared completely, and the data stabilized within a perfectly narrow range, as straight as a line drawn with a ruler.

"Old...Old Zhao."

Zheng Nan's voice trembled slightly as he dared not speak loudly, fearing that the vibration of his voice might scare away the perfect curve.

"What's wrong? Did the parameters work?"

Zhao Peng was tidying up draft paper with his back to him.

"...I haven't even touched the keyboard yet." Zheng Nan pointed to the screen. "Come and take a look."

Hearing that Zheng Nan's tone was off, Zhao Peng quickly put down what he was holding and walked briskly to the computer.

He froze when he saw the smooth, silky data curve on the screen.

"What's going on?"

Zhao Peng shoved Zheng Nan aside and rushed to the keyboard, quickly checking the parameter settings of the running program and the filtering algorithm. Everything was the same; it was still the old code that couldn't filter out background noise.

"Old Zheng, what did you just do?"

Zhao Peng turned his head, his face full of confusion.

"I didn't touch the keyboard with a single finger."

Zheng Nan raised his hands, equally bewildered.

"I just sat down, and it suddenly became like this; the background noise disappeared out of nowhere."

The two looked at each other in bewilderment.

Just as Dayong strolled back to his desk to continue reading, he heard a noise and turned to glance at the screen.

"Hey, this line looks pretty straight, it's not shaking anymore?"

Da Yong casually replied.

Zhao Peng looked at him anxiously.

"Dayong, did you just do something?"

"I didn't do anything."

Da Yong stood by the table, his hand resting on a thick book, and laughed. He pointed towards the vacuum chamber.

"Isn't that the water-cooled pipe? When the water pump starts, the rated frequency of the AC motor is 50 Hz, right? You've strapped it tightly to the load-bearing frame. When the water pump shakes, how can this big iron frame not shake along with it? That's the most basic mechanical resonance."

Zhao Peng and Zheng Nan looked in the direction Da Yong pointed and saw the black rubber pad stuffed between the tube and the support.

Da Yong looked at his two senior brothers and continued speaking.

"I've seen you guys spend days calculating Fourier transforms on the whiteboard, and your calculations are indeed impressive, but when you were doing the calculations, you must have been treating this big iron frame as an absolutely rigid body, right?"

He walked over to the machine and patted the sturdy alloy frame.

"Anything made of metal will deform during transmission, even if it's only a fraction of a millimeter. The sensors inside can detect that. It's physically connected, so no matter how hard you filter it in the computer, can you completely eliminate the background noise?"

Da Yong walked back and grinned sheepishly.

"I just loosened the cable ties with a wrench, put in a piece of shock-absorbing rubber, and broke the physical transmission chain. Isn't that better than you guys typing on the keyboard?" After hearing Da Yong's words, Zhao Peng and Zheng Nan were completely dumbfounded, and the laboratory fell into silence.

Two seconds later.

"Damn it!"

Zheng Nan slapped his thigh and let out a miserable howl.

Zhao Peng held his head in his hands, turning his already messy hair into a bird's nest, looking utterly hopeless.

"Three days! Old Zheng, we've been working on partial differential equations here for three days and three nights! I even took quantum fluctuations into account, and it's still just physical resonance!"

He looked up at the fluorescent light on the ceiling.

"I should have checked that broken iron frame first! All that studying has been for nothing!"

Seeing his two senior brothers devastated and questioning their existence, Da Yong felt a little embarrassed.

He pulled out a chair, sat down, and casually waved his hand to comfort them.

"Senior brothers, don't take it to heart. You guys spend all day staring at the computer solving partial differential equations, and your minds get so complicated that you tend to overcomplicate simple things."

"It's just like how we use that old twin-tub washing machine in the dorm to spin dry. When it starts spinning, it bounces around on the floor. You guys insist on calculating its contact area and centrifugal force theoretically, but it's useless. Just put a piece of cardboard under its feet to flatten it out, and it'll immediately behave. It's the same principle with the metal frame and water-cooling pipes!"

Just then, the soundproof door to the laboratory was pushed open.

Professor Liu walked in, holding a newly printed optical path test report in his hand.

"Zhao Peng, Zheng Nan."

Professor Liu asked questions as he walked inside.

"Has the background noise issue been resolved? The testing schedule can't be delayed any longer."

Zhao Peng and Zheng Nan exchanged a glance, their faces turning bright red.

Zhao Peng steeled himself and stepped forward.

"Teacher, the background noise... is resolved."

"Oh?"

Professor Liu strode to the computer, glanced at the perfectly smooth curve on the screen, and nodded in satisfaction.

"It's quite clean. Which parameters were adjusted? What filtering function was used in the end?"

Zheng Nan coughed and pointed to the water pipe at the base of the vacuum chamber.

"Teacher, the parameters weren't adjusted. It's Dayong... Dayong put a piece of rubber under the water pump pipe. It's mechanical resonance."

Professor Liu was taken aback.

He walked in the direction Zheng Nan pointed, bent down, and carefully examined the rubber pad that was slightly deformed by the nut. Then he turned around, glanced at the two movable whiteboards on the wall covered with complex mathematical derivations, and finally focused his gaze on Wang Dayong, who was sitting at the table flipping through "Materials Physics".

Professor Liu didn't say much, he just reached out and tapped the desktop.

"There is no friction in the theoretical model."

Professor Liu looked at Zhao Peng and Zheng Nan, his tone very ordinary.

No matter how precise your calculations are, you can't predict whether this cable tie is tied too tightly or too loosely today.

He turned around and gave them instructions.

"From now on, when the lab is running core data, the supercomputer will have to stop for a while. Da Yong should go through the underlying physical baseline first to make sure there is no mechanical interference before you add algorithms on top of it."

"Understood, teacher."

Zhao Peng responded.

Da Yong, who was sitting at the table, nodded.

"Okay, from now on I'll check it out before turning it on, and smooth out any tight parts. Then you guys can get back to work."

Professor Liu pulled up a folding chair and sat down, continuing to stare at the data on the screen and arranging the next steps.

"Now that the noise has been filtered out, go to the warehouse tomorrow morning to replace it with that high-precision probe. Now that there is no interference from the hardware, try to reduce the absolute accuracy of this equipment to five decimal places tomorrow."

Da Yong was about to put the draft paper on the table into his book when he heard this, and he paused for a moment.

"It can't be suppressed anymore, Teacher Liu."

Da Yong didn't look up, but replied directly.

The lab fell silent for a moment.

Professor Liu turned to look at Dayong.

Why?

Da Yong stood up, walked to the vacuum chamber that was more than two meters high, and kicked the metal auxiliary frame that was suspended on one side of the base. "You see, the core chamber weighs several tons, and the weight is all on these four main load-bearing points in the middle, while the auxiliary frames on both sides are suspended in the air and basically not under any load. It's like the kind of four-legged wooden stool we sit on, where one leg is shorter than the other."

He squatted down and ran his finger along the metal texture of the base.

"Although I just put rubber pads on the water pipes so they don't vibrate with the water pump anymore, the internal stress of this big iron frame itself is not evenly distributed."

Da Yong stood up and dusted off his hands.

"If the temperature in the laboratory changes by just one or two degrees, the metal will expand and contract with the temperature, and the key load-bearing points will undergo slight deformation. Even the best probe can only measure this deformation more accurately. The hardware is the bottleneck here, and the accuracy cannot be improved."

Zhao Peng and Zheng Nan exchanged a glance.

Professor Liu did not speak immediately after listening.

He stepped forward, bent down and looked at the main load-bearing points that Dayong had just pointed out, and then reached out and tapped the two auxiliary frames that Dayong said were suspended and not under load.

After a while, Professor Liu stood up straight.

"You're right, the original cast iron base does indeed have a structural problem of stress concentration."

He looked at Da Yong, his tone as if he were assigning a matter that should be taken for granted.

"Now that you can see where it's struggling, can you help you straighten it out?"

Dayong looked at the machine, and his eyes slowly lit up.

"Here's what we'll do: come to my office tomorrow morning to pick up the original mechanical structure drawings for this equipment."

Professor Liu stared at the boy.

"Give me a modification plan to redistribute the base support points and alleviate stress concentration. What kind of channel steel, jacks, or dampers do you need? Make a list and ask the finance department for reimbursement. If you can uncover the hardware physical limits of this machine and reduce its precision, then the underlying physical architecture of this equipment will be entirely your responsibility from now on."

Wang Dayong nodded excitedly. He might not be too interested in studying those complex calculations, but he was very interested in working on hardware.

"Okay, Teacher Liu, I'll go look at the blueprints tomorrow morning."

Professor Liu nodded in satisfaction.