Chapter 18 After studying separately for a period of time, dormitory 310 held a second seminar. They unanimously agreed that achieving a "zero gravity" effect on a chair was more feasible and less technically difficult than using a cushion.

Lin Lang has been working intensely on ergonomics lately, analyzing the comfort of various body parts from millions of data points. He opened his laptop and showed the other two the diagrams and data he had compiled:

"The human spine has an S-shaped curve, and the normal sitting posture concentrates pressure on the buttocks and groin. Therefore, if the chair can provide strong support for the shoulders, mid-back, and lower lumbar spine, it can reduce the load on the body to the greatest extent..."

Of course, this can only be considered as reducing pressure, and is far from reaching the standard of zero gravity, so he further studied the resonant frequencies of various parts of the human body.

"The average natural frequency of the human body is 4-5Hz, the major internal organs are 3-6Hz, the trunk is 3-6Hz, the spine is 4-6Hz, the pelvis is 1-3Hz... If we can use a magnetic levitation unit to make the seat contact surface emit a frequency close to that of the human body, it may be possible to counteract the reaction force brought by the pressure."

“But according to Enshaw’s Last Theorem and Maxwell’s equations, magnetic field lines do not diverge,” Ji Zhixing said. This was something they would learn in the second semester of their sophomore year, and he had finished reading all the sophomore books during the summer vacation.

"Huh?" Lin Lang slapped his forehead in frustration. "I spent so much time thinking about how to make static magnetic separation stable!"

Xu Dongyang laughed and said, "I remember you said last semester that your grandfather was overly addicted to magnetic therapy health products. How could you forget?"

Lin Lang held his head and remembered that his grandfather had been a huge believer in magnetic therapy. He bought a whole bunch of things, from small magnetic patches to magnetic therapy beds, from magnetic underwear to magnetic therapy pendants. He didn't trust hospitals, but believed that these things could cure all diseases.

His father was afraid that his grandfather would go astray and become unwell, so he called him, a science student, overnight, hoping that he could persuade his grandfather from a scientific perspective. He even did a lot of research at the time.

As a result, the grandfather agreed readily to his beloved grandson's request to his face, but secretly took the magnetic therapy business underground.

When it came to him, he couldn't escape the limitations of being blinded by his own involvement. Lin Lang irritably ruffled his hair into a bird's nest.

"Ah—" he let out a long howl, "All this research has been for nothing!"

“How could that be?” Ji Zhixing comforted him. “I think the idea of ​​focusing on resonant frequencies has great potential.”

Lin Lang's eyes lit up: "Really?" This was the first time he had conducted independent research, and the first time in his life he had felt so unconfident.

Ji Zhixing nodded and offered a suggestion: "A hybrid of electromagnetic and permanent magnet might be feasible."

"Is it just an electromagnetic levitation structure and a magnetic buffer structure based on the principle of permanent magnet repulsion?" Lin Lang thought for a moment and felt that it was very feasible.

"Lin Lang, remember to copy the data for me later," Xu Dongyang said. "I'll see if I can import the memory chip into the transmission path." He wanted to try using the memory chip to remember the sitting posture data of different people, so that the chair might be able to automatically adjust to the optimal position according to different individuals.

After speaking, he looked at Ji Zhixing and said, "I tried several built-in sensors, and the miniature cantilever beam sensor might be more suitable. It has a fast response speed and can collect position or pressure signals of the human body in contact with the seat in real time, output them to the ECU, and then the ECU outputs control commands to the actuator..."

Ji Zhixing also felt that Xu Dongyang's research direction was quite suitable, but they needed to communicate with Lin Lang about the data to see the actual implementation effect.

Seeing that neither of them had anything else to say, Ji Zhixing began to recount what he had gained during this period.

His biggest task was to study how to achieve dynamic and uniform distribution of body pressure and release of pressure points. At the beginning, he divided the seat contact surface into 8 support areas with a total of 74 parameters based on the U-shaped concave shape that best fits the human body.

However, he eventually discovered that no matter whether he used a miniature air compressor, a height valve elastic element, or other components, he could not avoid one problem: how to respond promptly to changes in the human body's contact surface.

"If the positive angle between the torso and legs can be adjusted to within the range of 122°±7°, so that the heart and knees are on the same horizontal line, the pressure on the body and internal organs can be greatly reduced..."

“But it’s impossible to expect everyone to sit properly,” Lin Lang said, with one leg on the ground and the other bent on the chair.

"Yes, that's the most troublesome part."

Human sitting postures are incredibly diverse, ranging from crossing legs to the relaxed, slouching posture, to sitting cross-legged... the possibilities are endless. If they can only achieve the ideal zero-gravity effect by forcibly regulating their posture, then this project is only half successful, and its chances of winning a national championship are probably not very secure.

The diversity and complexity of sitting postures made it impossible for them to transfer the theory of deformation mechanics to the theory of particle system mechanics in a one-to-one correspondence. Fortunately, he later found an analytical tool that matched the changes in the human body—the Navier-Stokes equations.

The Navier-Stokes equations, or NS equations for short, are arguably the most difficult equations in physics.

The existence problem of smooth solutions to the Navier-Stokes equations in three-dimensional space was designated as one of the seven Millennium Prize Problems by the Clay Mathematics Institute in the United States. Because it has not been fully solved to date, mathematicians have always questioned the mathematical validity of this equation.

From a physics perspective, however, it has consistently performed well in reflecting the mechanical laws governing real fluid flow, demonstrating highly reliable predictive capabilities. It is now widely used to simulate various physical systems, such as water flowing from a tap or airflow over an airplane wing.

Ji Zhixing said, "Although the human body is not a fluid, the fluctuations in sitting posture and the changes in the skin of the buttocks and legs are somewhat similar to those of a fluid. I think the Navier-Stokes equations are very suitable for this scenario."

For their research project, the Navier-Stokes equations fully consider the components of pressure, gravity, and viscous forces, accurately describe the forces and flow behavior of fluids, and allow for the free choice between tracking a pointer or focusing on a spatial point. Moreover, there are already quite mature simulation software programs available to process the data, making it an ideal choice.

But even after spending several days studying in the library, Ji Zhixing still couldn't fully grasp the derivation and application of the equation. He was thinking about it constantly while eating, sleeping, and walking, and then, without paying attention, he bumped into Professor Yan Anjin, who was walking on the road, causing him to stumble.

Professor Yan was very kind. He was quite pleased to learn that the man had been lost in thought because of the Navier-Stokes equation. He took him to his office and spent the entire afternoon explaining the equation to him. He also gave him his personal contact information and told him that he could ask him any questions he might have in the future.

Although they don't have school-assigned instructors like the school team when participating in the CUPT competition, it doesn't mean they can't ask their teachers for advice.

Ji Zhixing was moved and impressed, and later bothered Professor Yan twice more, receiving very patient and detailed answers each time. As a result, his research progressed rapidly, and he could already see the light at the end of the tunnel.

Lin Lang and Xu Dongyang were also very happy. In the end, the key to achieving zero gravity lies in the pressure receiving body. Once this part is solved, everything else is not a problem.

As the days passed, the Guangling University Games, which had been postponed due to the weather, finally took place. Lin Lang, as the sports committee member, was busy from the very first day.

He had to keep track of the contestants' schedules and remind them in a timely manner, provide appropriate logistical support, record and summarize the results, and he also had to prepare for the basketball team's games. He was so busy that he wished he could pluck a hair from a tree and conjure up seventy-two clones.

Having finally made it to the last day, Lin Lang kept thinking about how Ji Zhixing had to run the hellish 3,000 meters today.

Half an hour before the basketball game started, he rushed to the track and field stadium and found Ji Zhixing warming up by the railing. He checked the time and saw that the 3000-meter preliminary and final games were in an hour.

Lin Lang patted Ji Zhixing and asked, "Have you had breakfast yet?"

Last year, someone fainted while running 3,000 meters on an empty stomach and had to be taken to the hospital by ambulance. A few days before the sports meet, the school leaders held a special meeting with the sports committee members to repeatedly emphasize the importance of ensuring supplies were in place.

"I've eaten. Isn't the basketball game about to start? You go ahead, don't worry about me."

Ji Zhixing was very relaxed. He had been training diligently, so running the 3000 meters smoothly would definitely not be a problem. He might even be able to break into the top three.

Lin Lang was still worried, so he rushed to the cafeteria and then took a shortcut back to call Ji Zhixing over through the fence and hand him a takeout bag.

"Let's fill our stomachs a little more."

Looking at the sweat on Lin Lang's forehead and his concerned expression, Ji Zhixing felt for a moment, as if he were in prison, through the bars.

He reached out and took the takeout bag, opened it, and saw two steamed buns inside. Hmm, they looked even more like them.

Lin Lang earnestly instructed, "Try not to drink water or eat anything half an hour before the match. I have another match later and can't take care of you. Zhang Biao will be in charge of bringing you water and acting as your support. You two can contact each other later."

Ji Zhixing interrupted him the moment he took a breath: "Go warm up quickly, don't delay!" Lin Lang is the main player of the Physics Department basketball team, it would be unreasonable if he didn't show up now.

Ji Zhixing, unusually, cleared his mind and leisurely strolled around the sidelines for several tens of minutes until the broadcast informed the athletes to check in at the starting line.

He stood on the starting line, waiting for the referees to check the list one by one.

At the starting line, most of the runners didn't look too happy.

Historically, most students who participate in the 3,000-meter race are forced into it by circumstances, neglecting regular training and only cramming before the race. By the second half of the actual race, they are usually writhing in pain or pale-faced – of course, some are pale-faced even before the race begins.

Among the contestants with solemn or uneasy expressions, Ji Zhixing, who was calm and composed, seemed to have the makings of a champion.

Of course, some people guessed that he planned to run a few laps and then drop out, which was why he felt no pressure at all. Qi Yao thought so too, because that was what he planned to do as well. He secretly calculated that he would drop out after this pretty boy did, so as to avoid attracting attention.

A note from the author:

The human body frequency data in this chapter are referenced from "Natural Frequency of the Human Body and its Response to Vibration". The description of the Navier-Stokes equations is referenced from the books "Solving the Navier-Stokes Equation by Finite Volume Method and Study on the Flow Resistance Problem around Piers (Groups)" and "Mathematical Problems of Viscous Incompressible Fluid Dynamics".