Hellinger Distance Trees for Imbalanced Streams

Classifiers trained on data sets possessing an imbalanced class distribution are known to exhibit poor generalisation performance. This is known as the imbalanced learning problem. The problem becomes particularly acute when we consider incremental classifiers operating on imbalanced data streams, especially when the learning objective is rare class identification. As accuracy may provide a misleading impression of performance on imbalanced data, existing stream classifiers based on accuracy can suffer poor minority class performance on imbalanced streams, with the result being low minority class recall rates. In this paper we address this deficiency by proposing the use of the Hellinger distance measure, as a very fast decision tree split criterion. We demonstrate that by using Hellinger a statistically significant improvement in recall rates on imbalanced data streams can be achieved, with an acceptable increase in the false positive rate.Comment: 6 Pages, 2 figures, to be published in Proceedings 22nd International Conference on Pattern Recognition (ICPR) 201

Flow field prediction and analysis study for project RAM B3 Final report

Flow field properties in shock layer surrounding Ram B3 vehicl

Sea-Level and Crustal Movements along the New England-Acadian Shore, 4,500-3,000 B.P

Remains of three drowned forests have been investigated at Odiorne Point, New Hampshire, and Fort Lawrence and Grand Pre, west-central Nova Scotia. Carbon-14 ages and altitudes below mean tide levels were determined for four in-place stumps of white pine at each locality. Assuming that each dated stump was killed by rising salt water, and that its C14 age represented its true age at death, it was possible to construct curves showing the sequence of submergence and emergence at each site. A continuous transgression of the sea, approximating 0.31 foot per century, is indicated for the period 4,500-3,200 B.P. This rate corresponds well with Shepard\u27s (1960) estimate of eustatic sea-level rise along the stable Texas coast for this time interval. Interpretation of the submergence-emergence curves in terms of crustal movements yields the following history: 4,500-3,800 B.P.: crustal stability at all three sites; 3,800-3,400 B.P.: crustal downwarping of west- central Nova Scotia at the approximate rate of 2.6 feet per century; slightly greater downwarping at Grand Pre possible, indicating a hinge for the warping lying to the north of Fort Lawrence; slight crustal depression of the New Hampshire coast may have taken place; 3,400-3,250 B.P.: upwarping of west-central Nova Scotia at the approximate rate of 4 feet per century; crustal stability of New Hampshire shore; 3,250-3,000 B.P.: renewed downwarping in west-central Nova Scotia at the approximate rate of 0.88 foot per century; crustal stability of New Hampshire shore

Nitrogen fertility in semiarid dryland wheat production is challenging for beginning organic farmers

Organic farming systems use green and animal manures to supply nitrogen (N) to their fields for crop production. The objective of this study was to evaluate the effect of green manure and composted cattle manure on the subsequent winter wheat (Triticum aestivum L.) crop in a semiarid environment. Dry pea (Pisum sativum L.) was seeded in early April and terminated at first flower in late June. Composted cattle manure was applied at 0, 11.2 or 22.5Mgha−1 just prior to pea termination. Winter wheat was planted in mid September following the green manure or tilled summer fallow. No positive wheat response to green manure or composted cattle manure was observed in any of the 3 years of the study. In 2 of the 3 years, wheat yields and grain test weight were reduced following green manure. Green manure reduced grain yields compared with summer fallow by 220 and 1190 kgha−1 in 2009 and 2010, respectively. This may partially be explained by 40 and 47mm less soil water at wheat planting following peas compared with tilled summer fallow in 2008 and 2009, respectively. Also, in 2008 and 2009, soil nitrate level averaged 45kgha−1 higher for black fallow compared with green manure fallow when no compost was added. Organic growers in the semiarid Central Great Plains will be challenged to supply N fertility to their winter wheat crop in a rapid and consistent manner as a result of the inherently variable precipitation. Growers may need to allow several years to pass before seeing the benefits of fertility practices in their winter wheat cropping systems

Coherence of Spin Qubits in Silicon

Given the effectiveness of semiconductor devices for classical computation one is naturally led to consider semiconductor systems for solid state quantum information processing. Semiconductors are particularly suitable where local control of electric fields and charge transport are required. Conventional semiconductor electronics is built upon these capabilities and has demonstrated scaling to large complicated arrays of interconnected devices. However, the requirements for a quantum computer are very different from those for classical computation, and it is not immediately obvious how best to build one in a semiconductor. One possible approach is to use spins as qubits: of nuclei, of electrons, or both in combination. Long qubit coherence times are a prerequisite for quantum computing, and in this paper we will discuss measurements of spin coherence in silicon. The results are encouraging - both electrons bound to donors and the donor nuclei exhibit low decoherence under the right circumstances. Doped silicon thus appears to pass the first test on the road to a quantum computer.Comment: Submitted to J Cond Matter on Nov 15th, 200

High fidelity quantum memory via dynamical decoupling: theory and experiment

Quantum information processing requires overcoming decoherence---the loss of "quantumness" due to the inevitable interaction between the quantum system and its environment. One approach towards a solution is quantum dynamical decoupling---a method employing strong and frequent pulses applied to the qubits. Here we report on the first experimental test of the concatenated dynamical decoupling (CDD) scheme, which invokes recursively constructed pulse sequences. Using nuclear magnetic resonance, we demonstrate a near order of magnitude improvement in the decay time of stored quantum states. In conjunction with recent results on high fidelity quantum gates using CDD, our results suggest that quantum dynamical decoupling should be used as a first layer of defense against decoherence in quantum information processing implementations, and can be a stand-alone solution in the right parameter regime.Comment: 6 pages, 3 figures. Published version. This paper was initially entitled "Quantum gates via concatenated dynamical decoupling: theory and experiment", by Jacob R. West, Daniel A. Lidar, Bryan H. Fong, Mark F. Gyure, Xinhua Peng, and Dieter Suter. That original version split into two papers: http://arxiv.org/abs/1012.3433 (theory only) and the current pape

Effects of electrojet turbulence on a magnetosphere-ionosphere simulation of a geomagnetic storm

Ionospheric conductance plays an important role in regulating the response of the magnetosphere‐ionosphere system to solar wind driving. Typically, models of magnetosphere‐ionosphere coupling include changes to ionospheric conductance driven by extreme ultraviolet ionization and electron precipitation. This paper shows that effects driven by the Farley‐Buneman instability can also create significant enhancements in the ionospheric conductance, with substantial impacts on geospace. We have implemented a method of including electrojet turbulence (ET) effects into the ionospheric conductance model utilized within geospace simulations. Our particular implementation is tested with simulations of the Lyon‐Fedder‐Mobarry global magnetosphere model coupled with the Rice Convection Model of the inner magnetosphere. We examine the impact of including ET‐modified conductances in a case study of the geomagnetic storm of 17 March 2013. Simulations with ET show a 13% reduction in the cross polar cap potential at the beginning of the storm and up to 20% increases in the Pedersen and Hall conductance. These simulation results show better agreement with Defense Meteorological Satellite Program observations, including capturing features of subauroral polarization streams. The field‐aligned current (FAC) patterns show little differences during the peak of storm and agree well with Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) reconstructions. Typically, the simulated FAC densities are stronger and at slightly higher latitudes than shown by AMPERE. The inner magnetospheric pressures derived from Tsyganenko‐Sitnov empirical magnetic field model show that the inclusion of the ET effects increases the peak pressure and brings the results into better agreement with the empirical model.This material is based upon work supported by NASA grants NNX14AI13G, NNX13AF92G, and NNX16AB80G. The National Center for Atmospheric Research is sponsored by the National Science Foundation. This work used the XSEDE and TACC computational facilities, supported by National Science Foundation grant ACI-1053575. We would like to acknowledge high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation. We thank the AMPERE team and the AMPERE Science Center for providing the Iridium derived data products. All model output, simulation codes, and analysis routines are being preserved on the NCAR High-Performance Storage System and will be made available upon written request to the lead author of this publication. (NNX14AI13G - NASA; NNX13AF92G - NASA; NNX16AB80G - NASA; National Science Foundation; ACI-1053575 - National Science Foundation

Valley splitting of Si/SiGe heterostructures in tilted magnetic fields

We have investigated the valley splitting of two-dimensional electrons in high quality Si/Si$_{1-x}$Ge$_x$ heterostructures under tilted magnetic fields. For all the samples in our study, the valley splitting at filling factor $\nu=3$ ($\Delta_3$) is significantly different before and after the coincidence angle, at which energy levels cross at the Fermi level. On both sides of the coincidence, a linear density dependence of $\Delta_3$ on the electron density was observed, while the slope of these two configurations differs by more than a factor of two. We argue that screening of the Coulomb interaction from the low-lying filled levels, which also explains the observed spin-dependent resistivity, is responsible for the large difference of $\Delta_3$ before and after the coincidence.Comment: REVTEX 4 pages, 4 figure