76,819 research outputs found
Improved Heterogeneous Distance Functions
Instance-based learning techniques typically handle continuous and linear
input values well, but often do not handle nominal input attributes
appropriately. The Value Difference Metric (VDM) was designed to find
reasonable distance values between nominal attribute values, but it largely
ignores continuous attributes, requiring discretization to map continuous
values into nominal values. This paper proposes three new heterogeneous
distance functions, called the Heterogeneous Value Difference Metric (HVDM),
the Interpolated Value Difference Metric (IVDM), and the Windowed Value
Difference Metric (WVDM). These new distance functions are designed to handle
applications with nominal attributes, continuous attributes, or both. In
experiments on 48 applications the new distance metrics achieve higher
classification accuracy on average than three previous distance functions on
those datasets that have both nominal and continuous attributes.Comment: See http://www.jair.org/ for an online appendix and other files
accompanying this articl
Study of high-speed angular-contact ball bearings under dynamic load
Research program studies behavior of specific high-speed, angular-contact ball bearings. Program is aimed at detailed investigation of ball-separator behavior and lubrication surface-finish effects in a specific gyro wheel
Evidence for bimodal orbital separations of white dwarf-red dwarf binary stars
We present the results of a radial velocity survey of 20 white dwarf plus M
dwarf binaries selected as a follow up to a \textit{Hubble Space Telescope}
study that aimed to spatially resolve suspected binaries. Our candidates are
taken from the list of targets that were spatially unresolved with
\textit{Hubble}. We have determined the orbital periods for 16 of these compact
binary candidates. The period distribution ranges from 0.14 to 9.16\,d and
peaks near 0.6\,d. The original sample therefore contains two sets of binaries,
wide orbits (\,au) and close orbits (\,au), with
no systems found in the \,au range. This observational evidence
confirms the bimodal distribution predicted by population models and is also
similar to results obtained in previous studies. We find no binary periods in
the months to years range, supporting the post common envelope evolution
scenario. One of our targets, WD\,1504+546, was discovered to be an eclipsing
binary with a period of 0.93\,d
Binary Induced Neutron-Star Compression, Heating, and Collapse
We analyze several aspects of the recently noted neutron star collapse
instability in close binary systems. We utilize (3+1) dimensional and spherical
numerical general relativistic hydrodynamics to study the origin, evolution,
and parametric sensitivity of this instability. We derive the modified
conditions of hydrostatic equilibrium for the stars in the curved space of
quasi-static orbits. We examine the sensitivity of the instability to the
neutron star mass and equation of state. We also estimate limits to the
possible interior heating and associated neutrino luminosity which could be
generated as the stars gradually compress prior to collapse. We show that the
radiative loss in neutrinos from this heating could exceed the power radiated
in gravity waves for several hours prior to collapse. The possibility that the
radiation neutrinos could produce gamma-ray (or other electromagnetic) burst
phenomena is also discussed.Comment: 17 pages, 7 figure
Studies of high latitude current systems using MAGSAT vector data
The magnetic disturbance fields caused by global external current systems are considered with particular emphasis on improving the understanding of the physical processes which control high latitude current systems. Following processing the MAGSAT data were routinely plotted in the Universal Time (UT) format as well as in a polar plot format. The H'D'U' coordinate system, was adopted as the standard for representing the MAGSAT residual magnetic field vectors. A data file was generated and the TPOLAR computer code was developed to determine from the orbital elements, the time, latitude, and MLT of the extremum latitude of each transpolar segment of orbit. The precision of the vector data set from MAGSAT prompted an extended exploratory phase for data analysis procedures, modeling techniques and phenomenology
Granular discharge rate for submerged hoppers
The discharge of spherical grains from a hole in the bottom of a right
circular cylinder is measured with the entire system underwater. We find that
the discharge rate depends on filling height, in contrast to the well-known
case of dry non-cohesive grains. It is further surprising that the rate
increases up to about twenty five percent, as the hopper empties and the
granular pressure head decreases. For deep filling, where the discharge rate is
constant, we measure the behavior as a function of both grain and hole
diameters. The discharge rate scale is set by the product of hole area and the
terminal falling speed of isolated grains. But there is a small-hole cutoff of
about two and half grain diameters, which is larger than the analogous cutoff
in the Beverloo equation for dry grains
Studies of high latitude current systems using Magsat vector data
Disturbance fields caused by global external current systems are analyzed in order to gain an improved understanding of the phydical processes which control high latitude current systems and to increase the confidence level in the identification of internal field levels. The basic approach is to: (1) categorize the vector data by those physical parameters important for investigation of external current systems; (2) map the disturbances for appropriate conditions; (3) model the currents which might cause the mapped disturbances; and (4) correlate results with data from other sources. It is concluded that the Magsat data set appears to have remarkably high precision and quality and should permit major advances to be made in modeling current distribution at high latitudes in the ionosphere and magnetosphere
Stability Analysis of Asynchronous States in Neuronal Networks with Conductance-Based Inhibition
Oscillations in networks of inhibitory interneurons have been reported at various sites of the brain and are thought to play a fundamental role in neuronal processing. This Letter provides a self-contained analytical framework that allows numerically efficient calculations of the population activity of a network of conductance-based integrate-and-fire neurons that are coupled through inhibitory synapses. Based on a normalization equation this Letter introduces a novel stability criterion for a network state of asynchronous activity and discusses its perturbations. The analysis shows that, although often neglected, the reversal potential of synaptic inhibition has a strong influence on the stability as well as the frequency of network oscillations
Wave Energy Amplification in a Metamaterial based Traveling Wave Structure
We consider the interaction between a particle beam and a propagating
electromagnetic wave in the presence of a metamaterial. We show that the
introduction of a metamaterial gives rise to a novel dispersion curve which
determines a unique wave particle relationship, via the frequency dependence of
the metamaterial and the novel ability of metamaterials to exhibit simultaneous
negative permittivity and permeability. Using a modified form of Madey's
theorem we find that the novel dispersion of the metamaterial leads to a
amplification of the EM wave power
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