Big news for CAD: SMLIB, NVIDIA's NURBS based kernel is finally open source today 🍻🎉
We have been working with SMLIB and its dev team for more than 20 years. It enables all our products: classcad.ch headless CAD, GUI, AI/MCP, PDM, etc
github.com/NVIDIA-Omniverse/…
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i18u retweeted
In 1855, Adolf Fick showed that the diffusion flux depends on the concentration gradient:
J = −D ∂C/∂x
The minus sign matters: particles diffuse down the concentration gradient, from high concentration toward low concentration. The steeper the gradient, the larger the flux.
A simple rule with enormous reach: concentration differences drive diffusion
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i18u retweeted
Can The Sun's Heat Produce Cold? ☀️❄️🤔
How to build your own 100% solar-powered DIY freezer (that reaches -48°C 🥶), with basic hardware store parts, in a single afternoon 👇
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i18u retweeted
A student built a real anti-gravity machine…
using an Arduino.
How to Make an Acoustic Levitator:
Arduino Nano + motor driver + about 60 ultrasonic transducers.
They all emit ~40 kHz sound.
The sound waves meet and form fixed pockets in the air.
Tiny bits of styrofoam get stuck in those pockets and just hang there.
If you put your hand in, the pattern breaks and they fall.
Same principle labs use to move droplets or samples without touching them.
Credit: u/williamlk5341 on r/arduino
Based on an “Acoustic Levitator” Instructable guide:
instructables.com/Making-an-…
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Weekly robotics and AI insights.
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粒子的同一性导致对调两个粒子就等价于翻转360度，翻转的自由度（顺时针/逆时针）牵扯出的奇偶函数波产生了费米子和波色子。
旋量对应的是同一性下的那个两粒子对调，那是矢量的底层操作（平方根），旋量是基础操作。
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i18u retweeted
An electron in a hydrogen atom does not follow a little orbit around the nucleus. Quantum mechanics gives us something stranger: a wavefunction, with |ψ|² telling us the probability density of finding it at a point.
For s orbitals, the radial structure gets more interesting as n increases. The number of radial nodes is
n − l − 1
So 1s has 0, 2s has 1, and 3s has 2. These nodes are not empty shells where the electron “stops”. They are regions where the wavefunction itself is exactly zero.
The deeper lesson is that an electron is described by a spatial probability distribution, not a classical path.
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及时雨，正好有这样的烦恼
You start noticing Greek letters everywhere once you learn physics.
α is the fine structure constant, roughly 1/137. λ is wavelength. ρ is density. ψ represents a quantum state, while ω commonly describes angular frequency.
What makes this interesting is that these symbols are not a universal code. Their meaning depends on context. The same Greek letter can describe completely different ideas in different parts of physics.
That is part of what makes equations so powerful: a few symbols can carry an entire physical idea.
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这两天才知道原子的电子轨道也是波震荡的结果，不是在固定的轨道上旋转，而是在大概率在波动的球节内的电子云团。
期间还经历了在一个首位相接的波动弦上运动的过程。
波/震荡真实无处不在啊。音乐和弦是简单对比关系的谐波的组合。电路是电流的波动。模拟流体流动的核心也是波动方程。
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正在了解这个问题
What does an electron actually look like inside an atom?
Not a tiny particle tracing a neat path around the nucleus. An orbital is a region of space where the electron has a high probability of being found, described by its wavefunction.
That’s why orbitals have distinct shapes: s is spherical, p is dumbbell shaped, and d and f become more complex.
The surprising part is that these shapes are not paths. They are maps of where quantum mechanics says the electron is likely to be.
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散度就是三维空间中x y z 三个方向上空间变化率/速度之和，其结果是正数这点就是向内汇聚的，其结果是复数这点就是向外发散的源。
旋度就是三个方向上各分量的旋转速度组成的代表旋转中心点和方向的向量
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i18u retweeted
Ever wondered how two devices talk to each other without a shared clock?
That’s where UART (Universal Asynchronous Receiver/Transmitter) comes in.
UART is a simple, reliable serial communication protocol widely used in embedded systems. No clock line needed — just two wires and a matching speed.
🔧 Key Features
✅ Asynchronous – no clock signal
✅ Full‑duplex – send & receive simultaneously
✅ Only 2 lines: TX (transmit) and RX (receive)
✅ Predefined baud rate required (e.g., 9600, 115200)
⚙️ How it works (frame format)
➡️ Start bit (LOW)
➡️ Data bits (5–9 bits, LSB first)
➡️ Parity bit (optional – error detection)
➡️ Stop bit(s) (HIGH)
🔄 Basic flow
Microcontroller sends parallel data
UART converts to serial
Bits transmitted one by one via TX
Receiver UART reads via RX
Serial converted back to parallel
Data delivered to receiving device
📊 Example
Transmitting 0xA5 (10100101) at 9600 baud:
Start → 1 0 1 0 0 1 0 1 → Stop
📍 Real‑world applications
MCU ↔ PC communication
GPS modules
Bluetooth modules (HC‑05, HC‑06)
Serial debugging
⚠️ Critical note
Both sides must use the same baud rate — otherwise, no communication.
💡 Why UART matters
It’s simple, cost‑effective, and still the backbone of embedded communication.
👉 Found this useful? Repost to help others debug their serial connections.
♻️ Follow me for more embedded systems & electronics insights.
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