8,303 research outputs found
Mapping urbanized area expansion through digital image processing of LANDSAT and conventional data
There are no author-identified significant results in this report
Urban solar photovoltaics potential: An inventory and modelling study applied to the San Fernando Valley region of Los Angeles
Procedures for analyzing the potential of solar photovoltaic collectors to meet energy requirements in a metropolitan region are described and a modeling effort is applied to the San Fernando Valley region of Los Angeles. The procedure involves a series of steps designed to produce maps and tabulations revealing the amount of rooftop area available for establishing solar collectors and the proportion of energy requirement that could be potentially supplied by solar photovoltaics within each of the 533 mainline feeder service areas in the study area. For the sixty five square mile study area, the results showed that, with half the available flat and south facing roofs used and assuming the availability of energy storage, 52.7 percent of the actual kWh energy requirements could have been met in 1978 using photovoltaic collectors. Hourly, daily, weekly, and monthly fluctuations in potential supply and actual loads and recommendations of avenues for further research are discussed. Some further potential applications of the modeling technique are suggested
Cost-sensitive Bayesian network learning using sampling
A significant advance in recent years has been the development of cost-sensitive decision tree learners, recognising that real world classification problems need to take account of costs of misclassification and not just focus on accuracy. The literature contains well over 50 cost-sensitive decision tree induction algorithms, each with varying performance profiles. Obtaining good Bayesian networks can be challenging and hence several algorithms have been proposed for learning their structure and parameters from data. However, most of these algorithms focus on learning Bayesian networks that aim to maximise the accuracy of classifications. Hence an obvious question that arises is whether it is possible to develop cost-sensitive Bayesian networks and whether they would perform better than cost-sensitive decision trees for minimising classification cost? This paper explores this question by developing a new Bayesian network learning algorithm based on changing the data distribution to reflect the costs of misclassification. The proposed method is explored by conducting experiments on over 20 data sets. The results show that this approach produces good results in comparison to more complex cost-sensitive decision tree algorithms
Geometric-Phase-Effect Tunnel-Splitting Oscillations in Single-Molecule Magnets with Fourth-Order Anisotropy Induced by Orthorhombic Distortion
We analyze the interference between tunneling paths that occurs for a spin
system with both fourth-order and second-order transverse anisotropy. Using an
instanton approach, we find that as the strength of the second-order transverse
anisotropy is increased, the tunnel splitting is modulated, with zeros
occurring periodically. This effect results from the interference of four
tunneling paths connecting easy-axis spin orientations and occurs in the
absence of any magnetic field.Comment: 6 pages, 5 eps figures. Version published in EPL. Expanded from v1:
Appendix added, references added, 1 figure added, others modified
cosmeticall
What is the Geometry of Superspace ?
We investigate certain properties of the Wheeler-DeWitt metric (for constant
lapse) in canonical General Relativity associated with its non-definite nature.
Contribution to the conference on Mach's principle: "From Newtons Bucket to
Quantum Gravity", July 26-30 1993, Tuebingen, GermanyComment: 10 pages, Plain Te
Regularity of Ornstein-Uhlenbeck processes driven by a L{\'e}vy white noise
The paper is concerned with spatial and time regularity of solutions to
linear stochastic evolution equation perturbed by L\'evy white noise "obtained
by subordination of a Gaussian white noise". Sufficient conditions for spatial
continuity are derived. It is also shown that solutions do not have in general
\cadlag modifications. General results are applied to equations with fractional
Laplacian. Applications to Burgers stochastic equations are considered as well.Comment: This is an updated version of the same paper. In fact, it has already
been publishe
Cancer incidence in the Falkland Islands
Cancer incidence in the Falkland Islands, 1989–2000, was compared with rates in England and Wales, from which most Islanders originate. Colon and rectum cancer incidence was significantly raised 1989–93 but greatly reduced after 1994, when colonoscopic screening in high-risk families and sigmoidoscopic screening in the general population were introduced. http://www.bjcancer.com © 2001 Cancer Research Campaig
Stochastic Reaction-diffusion Equations Driven by Jump Processes
We establish the existence of weak martingale solutions to a class of second
order parabolic stochastic partial differential equations. The equations are
driven by multiplicative jump type noise, with a non-Lipschitz multiplicative
functional. The drift in the equations contains a dissipative nonlinearity of
polynomial growth.Comment: See journal reference for teh final published versio
Observations of Overturning in the Upper Mesosphere and Lower Thermosphere
A number of observations of the sodium density primarily in the mesosphere and lower thermosphere (but also of the electron density structure) have shown what appears to be overturning or convective roll cells near the transition from the mesosphere to the lower thermosphere. The cells are found in the region between 95 and 105 km and occur near the boundary between the region of lower stability in the mesosphere and the region of higher stability in the lower thermosphere. The vertical scale for the rolls is ~5–6 km, and the timescale is ~1–3 hours. The rolls occur in a region characterized by large shear in the neutral winds, but the timescales are too long to be explained by simple Kelvin-Helmholtz instability. We present observations from the University of Illinois lidar facility located at the Starfire Optical Range near Albuquerque, New Mexico, from the Arecibo Observatory in Puerto Rico, and from the Maui/MALT Lidar Facility located on Maui in Hawaii that show the overturning structure. Possible mechanisms for generating the convective rolls are discussed, including the relationship of the observed features to the characteristics expected for an inflection point instability
Optical absorption spectra in fullerenes C60 and C70: Effects of Coulomb interactions, lattice fluctuations, and anisotropy
Effects of Coulomb interactions and lattice fluctuations in the optical
absorption spectra of C60 and C70 are theoretically investigated by using a
tight binding model with long-range Coulomb interaction and bond disorder.
Anisotropy effects in C70 are also considered. Optical spectra are calculated
by using the Hartree-Fock approximation followed by the configuration
interaction method. The main conclusions are as follows: (1) The broad peaks at
excitation energies, 3.7eV, 4.7eV, and 5.7eV, observed in experiments of C60
molecules in a solution are reasonably described by the present theory. Peak
positions and relative oscillator strengths are in overall agreement with the
experiments. The broadening of peaks by lattice fluctuations is well simulated
by the bond disorder model. (2) The optical gap of C70 is larger when the
electric field of light is parallel to the long axis of the molecule. The shape
of the frequency dispersion also depends on the orientation of the molecule.
These properties are common in the free electron model and the model with
Coulomb interactions. (3) The spectrum of C70 averaged over bond disorder and
random orientations is compared with experiments in a solution. There is an
overall agreement about the spectral shape. Differences in the spectra of C60
and C70 are discussed in connection with the symmetry reduction from a
soccerball to a rugbyball.Comment: PACS numbers: 78.66.Qn, 78.20.Dj, 71.35.+z, 31.20.Tz; LaTeX, 15
pages, 5 figures (Physical Review B); Note: Please request figures to
Authors. They will be sent via snail mai
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