Statistical Time Series Models of Pilot Control with Applications to Instrument Discrimination

A general description of the methodology used in obtaining the transfer function models and verification of model fidelity, frequency domain plots of the modeled transfer functions, numerical results obtained from an analysis of poles and zeroes obtained from z plane to s-plane conversions of the transfer functions, and the results of a study on the sequential introduction of other variables, both exogenous and endogenous into the loop are contained

Kepler super-flare stars: what are they?

The Kepler mission has led to the serendipitous discovery of a significant number of `super flares' - white light flares with energies between 10^33 erg and 10^36 erg - on solar-type stars. It has been speculated that these could be `freak' events that might happen on the Sun, too. We have started a programme to study the nature of the stars on which these super flares have been observed. Here we present high-resolution spectroscopy of 11 of these stars and discuss our results. We find that several of these stars are very young, fast-rotating stars where high levels of stellar activity can be expected, but for some other stars we do not find a straightforward explanation for the occurrence of super flares.Comment: Accepted for publication in A&A, 9 pages, 4 figure

Vibrations and diverging length scales near the unjamming transition

We numerically study the vibrations of jammed packings of particles interacting with finite-range, repulsive potentials at zero temperature. As the packing fraction $\phi$ is lowered towards the onset of unjamming at $\phi_{c}$, the density of vibrational states approaches a non-zero value in the limit of zero frequency. For $\phi>\phi_{c}$, there is a crossover frequency, $\omega^{*}$ below which the density of states drops towards zero. This crossover frequency obeys power-law scaling with $\phi-\phi_{c}$. Characteristic length scales, determined from the dominant wavevector contributing to the eigenmode at $\omega^{*}$, diverge as power-laws at the unjamming transition.Comment: Submitted to PRL, 4 pages + 7 .eps figure

Structural signatures of the unjamming transition at zero temperature

We study the pair correlation function $g(r)$ for zero-temperature, disordered, soft-sphere packings just above the onset of jamming. We find distinct signatures of the transition in both the first and split second peaks of this function. As the transition is approached from the jammed side (at higher packing fraction) the first peak diverges and narrows on the small-$r$ side to a delta-function. On the high-$r$ side of this peak, $g(r)$ decays as a power-law. In the split second peak, the two subpeaks are both singular at the transition, with power-law behavior on their low-$r$ sides and step-function drop-offs on their high-$r$ sides. These singularities at the transition are reminiscent of empirical criteria that have previously been used to distinguish glassy structures from liquid ones.Comment: 8 pages, 13 figure

Reply to "Comment on `Jamming at zero temperature and zero applied stress: The epitome of disorder' "

We answer the questions raised by Donev, Torquato, Stillinger, and Connelly in their "Comment on "Jamming at zero temperature and zero applied stress: The epitome of disorder.' " We emphasize that we follow a fundamentally different approach than they have done to reinterpret random close packing in terms of the "maximally random jammed" framework. We define the "maximally random jammed packing fraction" to be where the largest number of initial states, chosen completely randomly, have relaxed final states at the jamming threshold in the thermodynamic limit. Thus, we focus on an ensemble of states at the jamming threshold, while DTSC are interested in determining the amount of order and degree of jamming for a particular configuration. We also argue that soft-particle systems are as "clean" as those using hard spheres for studying jammed packings and point out the benefits of using soft potentials