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@openstem · Joined Jul 2026
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Note~321 words · 2 min
Reynolds decomposition Split every field into a time-mean and a fluctuation about it. The mean is what you want to predict; the fluctuation is what makes it hard. Substitute into incompressible Navier-Stokes and time-average. Everything lin
Engineering

Engineering · L5 · Turbulence: Reynolds Decomposition & Energy Cascade

@openstem
Engineering · L5 · Turbulence: Reynolds Decomposition & Energy Cascade
Note~447 words · 2 min
No sensor gives you the state you actually care about. GPS is noisy, accelerometers drift, temperature probes lag. The Kalman filter fuses an imperfect model with imperfect measurements and beats either one alone. The model it assumes Predi
Engineering

Engineering · L5 · The Kalman filter: optimal recursive state estimation

@openstem
Engineering · L5 · The Kalman filter: optimal recursive state estimation
Note~478 words · 2 min
LQR gives you one fixed gain, computed offline from an unconstrained quadratic problem. Real actuators saturate and real states have safety limits, and LQR has no way to express either. MPC solves the optimisation online instead, with the c
Engineering

Engineering · L5 · Model predictive control: optimizing a receding horizon under constraints

@openstem
Engineering · L5 · Model predictive control: optimizing a receding horizon under constraints
Note~475 words · 2 min
A manipulator is a chain of rigid links joined by joints. Two questions drive everything: given the joint angles, where is the tool? And given a desired motion, what torques do the motors need? Forward and inverse kinematics Denavit-Hartenb
Engineering

Engineering · L5 · Robot kinematics and dynamics: from joint angles to end-effector motion

@openstem
Engineering · L5 · Robot kinematics and dynamics: from joint angles to end-effector motion
Plot1 plot · 1 param
Engineering

RC Charging: V(t) = 1 − e^(−t/τ)

@openstem
RC Charging: V(t) = 1 − e^(−t/τ)
Plot1 plot · 1 param
Engineering

RC Discharging: V(t) = e^(−t/τ)

@openstem
RC Discharging: V(t) = e^(−t/τ)
Plot1 plot · 1 param
Engineering

Step Response with Overshoot: 1 − e^(−x)·cos(b·x)

@openstem
Step Response with Overshoot: 1 − e^(−x)·cos(b·x)
Plot1 plot · 2 params
Engineering

Stress–Strain Curve

@openstem
Stress–Strain Curve
Plot1 plot · 1 param
Engineering

Low-Pass Filter Magnitude: H(ω) = 1/√(1 + (ω/ω_c)²)

@openstem
Low-Pass Filter Magnitude: H(ω) = 1/√(1 + (ω/ω_c)²)
Plot1 plot · 1 param
Engineering

Power Dissipated vs. Current: P = R·I²

@openstem
Power Dissipated vs. Current: P = R·I²
Plot1 plot · 1 param
Engineering

Charge Stored vs. Voltage: Q = C·V

@openstem
Charge Stored vs. Voltage: Q = C·V
Plot1 plot · 2 params
Engineering

Instantaneous Voltage vs. Time: v(t) = Vpk·sin(ωt)

@openstem
Instantaneous Voltage vs. Time: v(t) = Vpk·sin(ωt)
Plot1 plot · 2 params
Engineering

Engineering · L5 · Damped Oscillatory Response

@openstem
Engineering · L5 · Damped Oscillatory Response
Flowchart5 objects
Engineering

Engineering · L1 · Light Bulbs Quiz · flowchart

@openstem
Engineering · L1 · Light Bulbs Quiz · flowchart
Flowchart5 objects
Engineering

Engineering · L1 · Sound Makers Quiz · flowchart

@openstem
Engineering · L1 · Sound Makers Quiz · flowchart
Flowchart6 objects
Engineering

Engineering · L1 · Building Simple Circuits · flowchart

@openstem
Engineering · L1 · Building Simple Circuits · flowchart
Flowchart5 objects
Engineering

Engineering · L1 · Air Takes Up Space · flowchart

@openstem
Engineering · L1 · Air Takes Up Space · flowchart
Flowchart5 objects
Engineering

Engineering · L2 · Matching Tools to Lever Classes · flowchart

@openstem
Engineering · L2 · Matching Tools to Lever Classes · flowchart
Flowchart9 objects
Engineering

Engineering · L2 · Batteries in Series vs Parallel · flowchart

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Engineering · L2 · Batteries in Series vs Parallel · flowchart
Flowchart7 objects
Engineering

Engineering · L2 · Pulleys & Mechanical Advantage — Worked Numbers · flowchart

@openstem
Engineering · L2 · Pulleys & Mechanical Advantage — Worked Numbers · flowchart
Flowchart8 objects
Engineering

Engineering · L2 · How Heat Travels · flowchart

@openstem
Engineering · L2 · How Heat Travels · flowchart
Flowchart5 objects
Engineering

Engineering · L2 · Hydraulics — Force Multiplication by the Numbers · flowchart

@openstem
Engineering · L2 · Hydraulics — Force Multiplication by the Numbers · flowchart
Flowchart9 objects
Engineering

Engineering · L2 · Standards & Codes · flowchart

@openstem
Engineering · L2 · Standards & Codes · flowchart
Flowchart5 objects
Engineering

Engineering · L2 · What Does a Capacitor Do? · flowchart

@openstem
Engineering · L2 · What Does a Capacitor Do? · flowchart
Flowchart9 objects
Engineering

Engineering · L2 · Engineering Evaporative Cooling · flowchart

@openstem
Engineering · L2 · Engineering Evaporative Cooling · flowchart
Flowchart12 objects
Engineering

Engineering · L2 · Requirements Gathering · flowchart

@openstem
Engineering · L2 · Requirements Gathering · flowchart
Flowchart7 objects
Engineering

Engineering · L2 · Choosing the Right Prototyping Method · flowchart

@openstem
Engineering · L2 · Choosing the Right Prototyping Method · flowchart
Flowchart9 objects
Engineering

Engineering · L3 · Specific Heat Capacity · flowchart

@openstem
Engineering · L3 · Specific Heat Capacity · flowchart
Flowchart7 objects
Engineering

Engineering · L3 · AC Circuits — Numeric Problems · flowchart

@openstem
Engineering · L3 · AC Circuits — Numeric Problems · flowchart
Flowchart10 objects
Engineering

Engineering · L3 · Viscosity in Engineering Practice · flowchart

@openstem
Engineering · L3 · Viscosity in Engineering Practice · flowchart

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