47 research outputs found
Statistics of a Family of Piecewise Linear Maps
We study statistical properties of the truncated flat spot map . In
particular, we investigate whether for large , the deviations
upon rescaling satisfy a
-Gaussian distribution if and are both independently and uniformly
distributed on the unit circle. This was motivated by the fact that if is
the rotation by , then it has been shown that in this case the rescaled
deviations are distributed as a -Gaussian with (a Cauchy
distribution). This is the only case where a non-trivial (i.e. )
-Gaussian has been analytically established in a conservative dynamical
system.
In this note, however, we prove that for the family considered here, converges to a random variable with a curious distribution which is
clearly not a -Gaussian or any other standard smooth distribution
One-Sided Derivative of Distance to a Compact Set
We give a complete and self-contained proof of a folklore theorem which says
that in an Alexandrov space the distance between a point on a
geodesic and a compact set is a right-differentiable function of
. Moreover, the value of this right-derivative is given by the negative
cosine of the minimal angle between the geodesic and any shortest path to the
compact set (Theorem 4.3). Our treatment serves as a general introduction to
metric geometry and relies only on the basic elements, such as comparison
triangles and upper angles.Comment: 22 pages, 8 figure
Thermal Diffusion and Quench Propagation in YBCO Pancake Coils Wound with ZnO-and Mylar Insulations
The thermal diffusion properties of several different kinds of YBCO
insulations and the quench properties of pancake coils made using these
insulations were studied. Insulations investigated include Nomex, Kapton, and
Mylar, as well as insulations based on ZnO, Zn2GeO4, and ZnO-Cu. Initially,
short stacks of YBCO conductors with interlayer insulation, epoxy, and a
central heater strip were made and later measured for thermal conductivity in
liquid nitrogen. Subsequently, three different pancake coils were made. The
first two were smaller, each using one meter total of YBCO tape present as four
turns around a G-10 former. One of these smaller coils used Mylar insulation
co-wound with the YBCO tape, the other used YBCO tape onto which ZnO based
insulation had been deposited. One larger coil was made which used 12 total
meters of ZnO-insulated tape and had 45 turns. The results for all short sample
and coil thermal conductivities were ~1-3 Wm-1K-1. Finally, quench propagation
velocity measurements were performed on the coils (77 K, self field) by
applying a DC current and then using a heater pulse to initiate a quench.
Normal zone propagation velocity (NZP) values were obtained for the coils both
in the radial direction and in the azimuthal direction. Radial NZP values
(0.05-0.7 mm/s) were two orders of magnitude lower than axial values (~14-17
mm/s). Nevertheless, the quenches were generally seen to propagate radially
within the coils, in the sense that any given layer in the coil is driven
normal by the layer underneath it.Comment: 58 pages, 5 tables, 16 fig
Statistics of a Family of Piecewise Linear Maps
We study statistical properties of a family of piecewise linear monotone circle maps ft (x) related to the Σ angle doubling map x → 2x mod 1. In particular, we investigate whether for large n, the deviations n−1 i=0 (f it (x0) − 12) upon rescaling satisfies a Q-Gaussian distribution if x0 and t are both independently and uniformly distributed on the unit circle. This was motivated by the fact that if ft is the rotation by t, then it was recently found that in this case the rescaled deviations are distributed as a Q-Gaussian with Q = 2 (a Cauchy distribution). This is the only case where a non-trivial (i.e. Q ̸= 1) Q-Gaussian has been analytically established in a conservative dynamical system. In this note, however, we prove that for the family considered here, limn Sn/n converges to a random variable with a curious distribution which is clearly not a Q-Gaussian or any other standard smooth distribution
Influence of nickel substrate grain structure on YBa2Cu3O7-x supercurrent connectivity in deformation-textured coated conductors
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