… we have a radioactive substance that emits, on the average, a particle, an alpha particle, once every second on the average. Now, here I have a counter, and I close that counter, so it won’t count, except that I open it for half a second. If, in that half a second, a particle arrives, …
Author Archives: saemiller
On Large Language Models (AI) and Aerospace Education
Artificial intelligence (AI) is changing all aspects of our lives, much like the internet did when it became widely available to consumers in the mid-1990s. There are many discussions about how the AI revolution has affected different areas, including the workplace, art, culture, writing, and academics. Recently, the “ChatGPT: Optimizing Language Models for Dialogue” has …
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Codex Arundel
While reading Leonardo da Vinci’s Codex Arundel last evening, I noticed that the Codex had less scholars examining it relative to others. The fluid dynamics of da Vinci have been extensively studied, with entire dissertations dedicated to the subject. I came across a curious drawing that exhibited turbulent flow. The text is written backward in …
Additional Thoughts on Pressure
I am obsessed with pressure, particularly the internal pressure of fluids. Unlike viscosity, it is absent of frictional forces, and it is a key driving force in both human behavior and aerospace flows. Pressure is an essential component of a perfect fluid and appears on the right-hand side of the Navier-Stokes equations. Without pressure, fluid …
A simplified semi-empirical model for long-range low-frequency noise propagation in the turbulent atmosphere
My student, Dr. Tianshu Zhang, and myself recently published a modified long range acoustic propagation model that handles turbulence in the atmosphere. The abstract is We present a semi-empirical long-range low-frequency acoustic propagation model, which accounts for atmospheric turbulence. Ostashev and Wilson’s scattering model is combined with a ray-theory based refraction model to account for …
NASA Langley Feb. 2023
Caverns of the Wind
Silent are the caverns of the wind, But within them, a secret lies pinned Like Pandora’s box, locked up tight Holding within, a glimmer of light For in these tunnels, dreams did reside And hope for the future, they did provide But like Pandora’s box, they were lost Their secrets stolen, at a great cost …
The Tempest
In the skies above, a tempest swirls,Its winds, a cascade of power unfurled. Turbulence, a beast with might so true, Its roars, a symphony in shades of blue. The winds, the rain, the lightning’s bright gleam, A show of strength, a testament supreme. Turbulence, cascade, and acoustics play, A performance, unmatched, in skies so grey. …
A Note on Critical Thinking
Miller, S. A. E., “Note on Critical Thinking,” NASA Alumni Association Magazine, Dec., 2022. pp 5. (one-page) One might visit any leading university campus in the United States and ask the graduate faculty training future researchers one question, “what is the purpose of educating students?” One of the most frequent answers is to create critical …
Viscosity Coefficients
Often viscosity is isotropic, meaning that it is the same in all directions. In such a case, only two of the six components of the strain rate tensor are independent, so two coefficients of viscosity can be used to describe the viscous behavior of the fluid. These two coefficients are related by -2/3. This relationship …