23,435 research outputs found
Cubic Partial Cubes from Simplicial Arrangements
We show how to construct a cubic partial cube from any simplicial arrangement
of lines or pseudolines in the projective plane. As a consequence, we find nine
new infinite families of cubic partial cubes as well as many sporadic examples.Comment: 11 pages, 10 figure
Ferroelectricity in strained CaSrTiO from first principles
We present a density functional theory investigation of strained
CaSrTiO. We have determined the structure and polarization
for a number of arrangements of Ca and Sr in a 222 supercell.
The a and b lattice vectors are strained to match the lattice constants of the
rotated Si(001) face. To set the context for the CSTO study, we also include
simulations of the Si(001) constrained structures for CaTiO and SrTiO.
Our primary findings are that all CaSrTiO structures
examined except one are ferroelectric, exhibiting polarizations ranging from
0.08 C/m for the lowest energy configuration to about 0.26 C/m for the
higher energy configurations. We find that the configurations with larger
polarizations have lower c/a ratios. The net polarization of the cell is the
result of Ti-O ferroelectric displacements regulated by A-site cations.Comment: 13 pages, 4 figure
Mobility of bodies in contact. I. A 2nd-order mobility index formultiple-finger grasps
Using a configuration-space approach, the paper develops a 2nd-order mobility theory for rigid bodies in contact. A major component of this theory is a coordinate invariant 2nd-order mobility index for a body, B, in frictionless contact with finger bodies A1,...A k. The index is an integer that captures the inherent mobility of B in an equilibrium grasp due to second order, or surface curvature, effects. It differentiates between grasps which are deemed equivalent by classical 1st-order theories, but are physically different. We further show that 2nd-order effects can be used to lower the effective mobility of a grasped object, and discuss implications of this result for achieving new lower bounds on the number of contacting finger bodies needed to immobilize an object. Physical interpretation and stability analysis of 2nd-order effects are taken up in the companion pape
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