Lu Jia frowned, his mind quickly starting to build a model.
"A fixed 50-Hertz spike?"
Lu Jia’s fingers tapped unconsciously on the desktop.
"Electromagnetic interference? Or frequency leakage from the power supply ripple? This would definitely require a Fourier transform for windowed filtering. If I use a Hamming window, the cutoff frequency should be set at..."
"Cutoff, my ass."
Dayong bluntly interrupted Lu Jia’s line of reasoning.
Lu Jia froze.
Dayong looked at Lu Jia’s serious, pondering expression and thought he looked exactly like those two senior students from the lab this afternoon.
"Lu Jia, stop the calculations."
Dayong patted Lu Jia’s shoulder.
"You don’t need to calculate any of that. The water pump was right there. An AC motor’s frequency is 50 Hertz. The cooling pipe was lashed tightly to the load-bearing iron frame, so when the pump turned on, the frame started shaking right along with it."
Dayong spread his hands.
"It’s just basic mechanical resonance. I found a shim, used a wrench to loosen the nut, and stuffed it in there. The spike vanished. The curve was as straight as if it were drawn with a ruler."
Dorm Room 216 fell silent.
Lu Jia’s fingers were still tapping the desk, his mouth hanging slightly open.
"Mechanical... resonance?"
Lu Jia muttered to himself.
"Yeah."
Dayong nodded matter-of-factly.
"My seniors had been calculating for days. They even factored in quantum fluctuations, but it never occurred to them that the water pipe was rattling against the iron frame."
Chu Ge snapped out of his stupor, slapped his thigh, and doubled over with laughter.
"HAHAHA! Lu Jia, listen to this! You spend all day building models on paper, and those PhD students build models on paper, too. And for what? Our boy Dayong here, with one little shim, completely shattered their partial differential equations!"
Chu Ge pointed at Lu Jia.
"Your model got shattered by Brother Zhuo’s bowl of instant noodles, and this afternoon their algorithm got shattered by a shim. Are you theory guys having a string of bad luck or what?"
Lu Jia’s expression soured. He pushed up his glasses, trying to salvage a shred of dignity for students of theoretical physics.
"That’s... that’s because they didn’t define enough boundary conditions when they built the model."
Lu Jia mumbled under his breath.
"They treated the support frame as a perfectly rigid body and failed to account for deformation..."
"Sure, sure. You’re absolutely right."
Dayong grinned and picked up his canvas bag.
"That’s why Professor Liu is having me get the machine’s structural blueprints tomorrow morning. The base’s center of gravity was designed poorly. I have to draw up a new set of plans, find some channel steel and jacks, and build it a new chassis to disperse the stress points. This kind of work is way more interesting than calculating partial differential equations."
With that, Dayong waved goodbye to them.
"Alright, you guys go on back to your data and practice problems. I’m heading back to my room to wash up. I stink."
Dayong turned and left Room 216, pulling the door closed behind him and shutting in Chu Ge’s uninhibited laughter and the dejected sight of Lu Jia, who had already buried his head back in his advanced math problems.
Chen Zhuo sat at his desk, an English-language edition of *Topology and Geometric Analysis* open before him. He held a freshly washed Red Fuji apple and was taking a bite.
"You’re back."
Hearing the sound, Chen Zhuo turned to look at Dayong.
"Yeah. The snow’s coming down pretty hard out there. The wind blows right down your collar."
Dayong placed his canvas bag on his chair.
He didn’t sit down right away. Instead, he walked directly to the washstand behind the door, grabbed a bar of soap, and began to scrub his hands.
The soap quickly worked into a lather.
"Xiaozhuo, did you see the state Lu Jia was in across the hall?"
Dayong asked with a smile, chatting with Chen Zhuo as he scrubbed the grime from his hands.
"What happened?"
Chen Zhuo asked, chewing his apple.
"He’s still over there, sulking and grinding practice problems. Chu Ge even hacked the dining hall’s card system to pull up the records of that senior girl he likes, but Lu Jia refused to even look."
Dayong turned the faucet to the hot water setting, and a cloud of steam rose up.
"He said that bowl of instant noodles of yours really messed with him. Now he’s all bummed out, thinking human behavior is too unpredictable."
When Chen Zhuo heard this, the corners of his mouth turned up in a slight smile.
He swiveled in his chair to face Dayong, leaning back against it.
"Lu Jia’s just too rigid in his thinking."
Chen Zhuo swallowed the bite of apple.
"Mathematical models are used to approximate reality, not to confine it. He’s just a little stubborn."
Dayong rinsed the soap suds off his hands and pulled a towel from the rack to dry them.
"Definitely. My two seniors in the lab tonight, the PhD candidates, were the exact same way."
Dayong hung the towel back up, walked back to the middle of the dorm room, pulled out the chair from his desk, and sat down.
"I spent the whole afternoon reading over there."
Dayong pointed to his canvas bag.
"I’d planned on reading some *Materials Physics*, but the two seniors next to me had been stuck on a background noise spike for days. They’d filled two entire whiteboards with Fourier transforms."
Chen Zhuo didn’t say anything, listening quietly, his fingers unconsciously turning the half-eaten apple in his hand.
"I overheard them talking about 50 Hertz and electromagnetic interference."
Dayong leaned back casually in his chair.
"I took one look, and there was this huge water-cooling pump running right next to it. The pipe was tied fast to the iron frame, solid against solid. How could it not shake along with it?"
Dayong picked up the cup on his desk and took a sip of water.
"I just found a shim, used a wrench to loosen the clamp, slipped the shim in, and the line went flat instantly."
"They didn’t notice?" Chen Zhuo asked.
"It never occurred to them."
Dayong put down his cup and sighed.
"When they were doing their calculations, they must have treated that big iron frame as a perfectly rigid body in their heads. They thought it was a solid plate that wouldn’t deform or conduct vibrations."
Dayong shook his head.
"There’s no such thing as a perfectly rigid body in this world. As long as it’s metal, even a one or two-degree temperature difference will make it strain."

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