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Mar
17
accepted Is it possible to increase refractive index at lower densities?
Mar
14
awarded  Popular Question
Feb
18
comment Historical costs of nuclear magnetic resonance experiments
@dmckee I think it belongs in history of science (a lot of historical research concerns the price of things)
Feb
18
comment Historical costs of nuclear magnetic resonance experiments
@CarlWitthoft I'd like to get my hands on some data. Anyone can predict that they would have got cheaper, but I would like to know empirically, and by how much.
Feb
18
comment Historical costs of nuclear magnetic resonance experiments
@PeterDiehr Sure. I was kind of hoping that, along the lines of (b), there might be some MR experts who would know where to look, or how to make the question easier to answer. Expert input would make answering the question much easier. For example, they might have had to justify the running costs to their department, or, perhaps they've read around the topic enough to know where some esoterically conceived but relevant data is.
Feb
18
comment Historical costs of nuclear magnetic resonance experiments
@AccidentalFourierTransform I didn't know that existed, that does sound more appropriate.
Feb
18
asked Historical costs of nuclear magnetic resonance experiments
Sep
28
awarded  Notable Question
Aug
10
accepted Calculating the resistance of a 3D shape between two points
Aug
10
comment Calculating the resistance of a 3D shape between two points
yes, this is what I was looking for. I'd figured it talking with RossMillikan below, but it never made it to a proper answer.
Jun
30
awarded  Curious
Jun
29
comment Rules of thumb for estimating visual angles
Luckily, it's dark ;)
Jun
29
comment Rules of thumb for estimating visual angles
That's a creative suggestion. Not sure I can execute it (and then move my arms to the right position) even remotely accurately. One can rule out the 46 degree halo with only one halving, or see if the diameter is 92 without any halving at all.
Jun
29
asked Rules of thumb for estimating visual angles
Jun
21
awarded  Yearling
Jun
21
comment Calculating the resistance of a 3D shape between two points
My model above has about 10,000 nodes. It took about 100,000 iterations to converge. I hope I've done it right, some reverse engineering implies what I've been doing is solving Laplace's equation $\nabla^2 \phi = 0$ with boundary conditions $(\hat{n} \cdot \nabla) \phi = 0$ for non-contacts and $\phi = const$ for the contacts. This seems very plausible to me now. You've been very helpful, thanks.
Jun
21
comment Calculating the resistance of a 3D shape between two points
OK, I'm convinced, and I have a much better understanding now, thanks. See question for some plots.
Jun
21
revised Calculating the resistance of a 3D shape between two points
added some simulations based on an answer below
Jun
21
comment Calculating the resistance of a 3D shape between two points
I've just about coded a basic relaxation procedure in 2D. I'll put some results in the OP when I've got some.
Jun
20
comment Calculating the resistance of a 3D shape between two points
I'm not 100% convinced, but you've persuaded me to code something up and see. Assuming this is correct though, doesn't it suggest an equation expressed in terms of the minimisation of some function?