[Paper Review] The Tetrahedron That Led With One Sphere Never Broke Apart — A Bluntness Index for Mach 20 Fragment Clusters
Four spheres at Mach 20 separate by tetrahedron attitude. Bluntness B and asymmetry A on 40,000 orientations show which number sets the split.
[Paper Review] Two Fragments Flew Together Instead of Pushing Apart — The 144° Equilibrium of a Mach 20 Sphere Pair
At Mach 20 two touching spheres align at one angle and generate lift together instead of repelling. A Newtonian approximation pins that angle down.
A 30° rigid rotation read -13% strain — conjugate stress-strain pairs in large-strain shells
Rotation alone fabricates strain in the engineering measure, and a wrong stress-strain pairing shifts the internal work rate by 5% or 54%.
The Weight Sits on Top and She Still Rights Herself — Metacentric Height and the Free Surface Effect
Capsizing is not decided by whether the centre of gravity sits above the buoyancy centre. The second moment of the waterplane, through GM, decides it.
Thinner Means Stiffer — Shear Locking in Shell Elements and the MITC Tying Fix
A linear shell element gets stiffer, not weaker, as it thins out. The cause is one line: shear strain obtained by differentiating displacements.
When a Bullet Passes Straight Through a Wall — Continuous Collision Detection by Inclusion Bisection
An endpoint test says MISS when the crossing sits at t*=0.50000. Inclusion bisection brackets that root in 53 boxes at δ=1e-4 and does not skip the hit.
A Heart Valve Without a Body-Fitted Mesh — Peskin's Immersed Boundary Method and the Discrete Delta
Peskin's four-point delta sums to one on the grid. The listing's 24 markers on a radius-8 cylinder sit more than two cells apart, so the wall stays gappy.