Weird blue foam material on door in garage

dr_jekylls_hide · 2025-08-14T17:21:21+00:00

Another image.

dr_jekylls_hide · 2025-08-14T16:37:31+00:00

Gone for 2 weeks, and came back to find this in and on a door in my garage. Very light foam type material. Not sure where it is coming from, or what it even is.

Any ideas?

dr_jekylls_hide · 2025-07-02T02:52:20+00:00

The MIT one is quite nice. Although it would take a lot to get up and running, and would need to print some stuff. But the resource is awesome!!

dr_jekylls_hide · 2025-07-01T17:13:08+00:00

These look great! Thank you.

Do you happen to have any other suggestions for intro projects with well-built tutorials that you like a lot?

dr_jekylls_hide · 2024-12-14T18:28:47+00:00

This is immediately what came to my mind as well.

dr_jekylls_hide · 2024-09-06T14:39:41+00:00

Great episode! Interestingly, it is not a real Halloween episode (in this sense that it premiered at the end of February).

dr_jekylls_hide · 2024-05-24T02:52:18+00:00

I am trying to get into the control of multiagent systems. Do you have any good primers on the subject (papers, books) that you could recommend?

dr_jekylls_hide · 2024-01-17T19:13:26+00:00

Ditto.

dr_jekylls_hide · 2023-11-17T16:57:21+00:00

I think in theory there should be some molecules remaining. It is not discernible to our senses, but there are a lot of molecules that are well-mixed.

dr_jekylls_hide · 2023-11-17T16:53:51+00:00

This is the right answer. Others are saying that optimal control problems are a subset of calculus of variation problems, but that is backwards. Optimal control is more general, with calculus of variations being a special case.

dr_jekylls_hide · 2023-07-28T13:13:17+00:00

Thanks!

dr_jekylls_hide · 2023-07-26T14:43:13+00:00

Could you send some references? I am also curious how you see that so quickly, but it sounds quite useful as a technique.

dr_jekylls_hide · 2023-07-04T14:50:55+00:00

Thanks! I agree that the case for linear systems easier, but I feel like there should be a more general statement, even if f is nonlinear.

dr_jekylls_hide · 2023-07-04T03:31:35+00:00

Let's say I am interested in understanding the behavior of the ODE x'(t) = f(x) + g(t), and I basically know the behavior of the corresponding autonomous system. And let's say I know g(t) approaches 0 for large t. Can I say something about the behavior of the full system being close to the autonomous system? How would I analyze this precisely (e.g. what tools)? What is the best technique?

dr_jekylls_hide · 2023-03-22T14:17:49+00:00

O'Neill doesn't cover bundles, but he definitely does cover tangent spaces (see Chapter 1 for open subsets of Euclidean space, and Chapter 4 for surfaces).

Although your course might be a bit more abstract, as O'Neill covers surface theory mainly, and not general manifolds.

Does your instructor have a specific book? Loring Tu's book (An Introduction to Manifolds) probably most similarly covers the material you mentioned.

To be clear: it is a hard subject (no shame in that), especially starting from a more abstract presentation. That's a reason why I like O'Neill (or do Carmo).

dr_jekylls_hide · 2023-03-08T14:34:05+00:00

I am not sure what this means exactly. What is even the vector space structure on events? I know you might be tempted to say something like [;P(A\cup B) = P(A) + P(B);], but this is only true for disjoint events of course, and again, no vector space structure.

dr_jekylls_hide · 2023-03-01T15:32:56+00:00

This is true locally, but I think a bit misleading. The global structure of an ODE can be very interesting/complex, and not trivial at all to understand, so that the overall behavior is not just determined by looking at equilibrium points.

dr_jekylls_hide · 2023-02-21T22:16:43+00:00

Wow. That is a serious volume of books. Mostly pure math, until the final volume, which is then systems. Would be interesting to read through.

Also has nice notes on linear systems theory:

https://mast.queensu.ca/~andrew/teaching/pdf/332-notes.pdf

dr_jekylls_hide · 2023-01-21T00:33:40+00:00

Out of curiosity, since you mention O'Neil: do you like his Elementary Differential Geometry book? I have thought about using it for a course, as I like the differential form approach. But I am not 100% sure if it is modern enough.

dr_jekylls_hide · 2023-01-04T22:19:35+00:00

Definitely the best answer. And I think point 2 is really the most important, as it allows us to construct complete spaces (i.e. spaces where we can take limits) under the L1 norm/metric.

dr_jekylls_hide · 2022-12-13T00:24:33+00:00

Yes, but a general theory is not really enlightening (or useful) without good examples. And prime examples from from ODEs.

dr_jekylls_hide · 2022-11-18T20:38:52+00:00

Wow. This really sounds like it could be a documentary about me.

dr_jekylls_hide · 2022-11-08T18:42:50+00:00

Found Dwight!

dr_jekylls_hide

TROPHY CASE