Quantum Hall to Insulator Transition in the Bilayer Quantum Hall Ferromagnet

We describe a new phase transition of the bilayer quantum Hall ferromagnet at filling fraction $\nu = 1$. In the presence of static disorder (modeled by a periodic potential), bosonic $S=1/2$ spinons can undergo a superfluid-insulator transition while preserving the ferromagnetic order. The Mott insulating phase has an emergent U(1) photon, and the transition is between Higgs and Coulomb phases of this photon. Physical consequences for charge and counterflow conductivity, and for interlayer tunneling conductance in the presence of quenched disorder are discussed.Comment: 4 pages, no figure

A System for Induction of Oblique Decision Trees

This article describes a new system for induction of oblique decision trees. This system, OC1, combines deterministic hill-climbing with two forms of randomization to find a good oblique split (in the form of a hyperplane) at each node of a decision tree. Oblique decision tree methods are tuned especially for domains in which the attributes are numeric, although they can be adapted to symbolic or mixed symbolic/numeric attributes. We present extensive empirical studies, using both real and artificial data, that analyze OC1's ability to construct oblique trees that are smaller and more accurate than their axis-parallel counterparts. We also examine the benefits of randomization for the construction of oblique decision trees.Comment: See http://www.jair.org/ for an online appendix and other files accompanying this articl

The WINCOF-I code: Detailed description

The performance of an axial-flow fan-compressor unit is basically unsteady when there is ingestion of water along with the gas phase. The gas phase is a mixture of air and water vapor in the case of a bypass fan engine that provides thrust power to an aircraft. The liquid water may be in the form of droplets and film at entry to the fan. The unsteadiness is then associated with the relative motion between the gas phase and water, at entry and within the machine, while the water undergoes impact on material surfaces, centrifuging, heat and mass transfer processes, and reingestion in blade wakes, following peal off from blade surfaces. The unsteadiness may be caused by changes in atmospheric conditions and at entry into and exit from rain storms while the aircraft is in flight. In a multi-stage machine, with an uneven distribution of blade tip clearance, the combined effect of various processes in the presence of steady or time-dependent ingestion is such as to make the performance of a fan and a compressor unit time-dependent from the start of ingestion up to a short time following termination of ingestion. The original WINCOF code was developed without accounting for the relative motion between gas and liquid phases in the ingested fluid. A modification of the WINCOF code was developed and named WINCOF-1. The WINCOF-1 code can provide the transient performance of a fan-compressor unit under a variety of input conditions

Nematic - Isotropic Transition in Porous Media - a Monte Carlo Study

We propose a lattice model to simulate the influence of porous medium on the Nematic - Isotropic transition of liquid crystal confined to the pores. The effects of pore size and pore connectivity are modelled through a disorder parameter. Monte Carlo calculations based on the model leads to results that compare well with experiments.Comment: 11 pages; 4 figure

Development of buried wire gages for measurement of wall shear stress in Blastane experiments

Buried Wire Gages operated from a Constant Temperature Anemometer System are among the special types of instrumentation to be used in the Boundary Layer Apparatus for Subsonic and Transonic flow Affected by Noise Environment (BLASTANE). These Gages are of a new type and need to be adapted for specific applications. Methods were developed to fabricate Gage inserts and mount those in the BLASTANE Instrumentation Plugs. A large number of Gages were prepared and operated from a Constant Temperature Anemometer System to derive some of the calibration constants for application to fluid-flow wall shear-stress measurements. The final stage of the calibration was defined, but could not be accomplished because of non-availability of a suitable flow simulating apparatus. This report provides a description of the Buried Wire Gage technique, an explanation of the method evolved for making proper Gages and the calibration constants, namely Temperature Coefficient of Resistance and Conduction Loss Factor

WINCOF-I code for prediction of fan compressor unit with water ingestion

The PURDUE-WINCOF code, which provides a numerical method of obtaining the performance of a fan-compressor unit of a jet engine with water ingestion into the inlet, was modified to take into account: (1) the scoop factor, (2) the time required for the setting-in of a quasi-steady distribution of water, and (3) the heat and mass transfer processes over the time calculated under 2. The modified code, named WINCOF-I was utilized to obtain the performance of a fan-compressor unit of a generic jet engine. The results illustrate the manner in which quasi-equilibrium conditions become established in the machine and the redistribution of ingested water in various stages in the form of a film out of the casing wall, droplets across the span, and vapor due to mass transfer

Neural Representations of Courtship Song in the Drosophila Brain

Acoustic communication in drosophilid flies is based on the production and perception of courtship songs, which facilitate mating. Despite decades of research on courtship songs and behavior in Drosophila, central auditory responses have remained uncharacterized. In this study, we report on intracellular recordings from central neurons that innervate the Drosophila antennal mechanosensory and motor center (AMMC), the first relay for auditory information in the fly brain. These neurons produce graded-potential (nonspiking) responses to sound; we compare recordings from AMMC neurons to extracellular recordings of the receptor neuron population [Johnston's organ neurons (JONs)]. We discover that, while steady-state response profiles for tonal and broadband stimuli are significantly transformed between the JON population in the antenna and AMMC neurons in the brain, transient responses to pulses present in natural stimuli (courtship song) are not. For pulse stimuli in particular, AMMC neurons simply low-pass filter the receptor population response, thus preserving low-frequency temporal features (such as the spacing of song pulses) for analysis by postsynaptic neurons. We also compare responses in two closely related Drosophila species, Drosophila melanogaster and Drosophila simulans, and find that pulse song responses are largely similar, despite differences in the spectral content of their songs. Our recordings inform how downstream circuits may read out behaviorally relevant information from central neurons in the AMMC

Design of optimized three-dimensional thrust nozzle contours

Design of optimized three-dimensional thrust nozzle contour