35,774 research outputs found
Delivering light-weight online geographic information analysis using ArcIMS
As of July 9, 2002, more than 300 websites, which provide automated mapping and facilities
management over the internet, are registered in the ESRI Internet Map Server (IMS) user
registry [1]. But it won’t be an exaggeration to assume that this is only a tiny fraction of the
actual number of IMS sold and used over the world. In fact, realising the potential scope and
issues of this new form of geographic information delivery, the International Cartographic
Association has formed a Commission dedicated to Maps and the Internet [2]. The IMS
software has also kept pace with the growing demand and progress in technology. IMS has
evolved from the simple HTML image maps to sophisticated servelet-driven mapping
services. During this period, a very significant event happened with the arrival of ArcIMS.
With the ArcIMS the use of IMS changed from merely an interactive visualisation and query
of the spatial databases to a platform for sharing remote spatial databases. In other words, the
ArcIMS made the scale of operation of IMS global.
While the accessibility and usability of the IMS have certainly increased in the past 5-
6 years, the functionalities provided by IMS however remained fairly static. A widely felt but
unreported criticism of IMS has been that the lack of a broader range of spatial analysis
functions (except the usual buffering) in the off-the-shelf IMS installation. Therefore a couple
of eyebrows always tend to rise if the word “Internet GIS” is used for IMS. Oddly enough, the
ArcIMS 3.x and the older versions carry this limitation as well. Essentially, IMS suffer from
the limitation for not being able to allow simultaneous update and dynamic manipulation of
the thematic content of the online maps. For example, in the case of ArcIMS while there are
provisions for complex scale-dependent rendering, it is not easily possible to manipulate (for
example add layers or delete layers) the crucial axl file of a mapping service on the fly. The
recent launch of ArcIMS 4 promises to bridge this gap by allowing an enhanced integration
with the ArcGIS. The aim of this article is to propose a generic framework, which makes the
link between an IMS and a standard GIS, to provide geographic analysis in online maps. We
will take the example of such a framework developed for ArcIMS
Coherent information analysis of quantum channels in simple quantum systems
The coherent information concept is used to analyze a variety of simple
quantum systems. Coherent information was calculated for the information decay
in a two-level atom in the presence of an external resonant field, for the
information exchange between two coupled two-level atoms, and for the
information transfer from a two-level atom to another atom and to a photon
field. The coherent information is shown to be equal to zero for all
full-measurement procedures, but it completely retains its original value for
quantum duplication. Transmission of information from one open subsystem to
another one in the entire closed system is analyzed to learn quantum
information about the forbidden atomic transition via a dipole active
transition of the same atom. It is argued that coherent information can be used
effectively to quantify the information channels in physical systems where
quantum coherence plays an important role.Comment: 24 pages, 7 figs; Final versiob after minor changes, title changed;
to be published in Phys. Rev. A, September 200
Transit Light Curves with Finite Integration Time: Fisher Information Analysis
Kepler has revolutionized the study of transiting planets with its
unprecedented photometric precision on more than 150,000 target stars. Most of
the transiting planet candidates detected by Kepler have been observed as
long-cadence targets with 30 minute integration times, and the upcoming
Transiting Exoplanet Survey Satellite (TESS) will record full frame images with
a similar integration time. Integrations of 30 minutes affect the transit
shape, particularly for small planets and in cases of low signal-to-noise.
Using the Fisher information matrix technique, we derive analytic
approximations for the variances and covariances on the transit parameters
obtained from fitting light curve photometry collected with a finite
integration time. We find that binning the light curve can significantly
increase the uncertainties and covariances on the inferred parameters when
comparing scenarios with constant total signal-to-noise (constant total
integration time in the absence of read noise). Uncertainties on the transit
ingress/egress time increase by a factor of 34 for Earth-size planets and 3.4
for Jupiter-size planets around Sun-like stars for integration times of 30
minutes compared to instantaneously-sampled light curves. Similarly,
uncertainties on the mid-transit time for Earth and Jupiter-size planets
increase by factors of 3.9 and 1.4. Uncertainties on the transit depth are
largely unaffected by finite integration times. While correlations among the
transit depth, ingress duration, and transit duration all increase in magnitude
with longer integration times, the mid-transit time remains uncorrelated with
the other parameters. We provide code in Python and Mathematica for predicting
the variances and covariances at www.its.caltech.edu/~eprice
Quantum information analysis of electronic states at different molecular structures
We have studied transition metal clusters from a quantum information theory
perspective using the density-matrix renormalization group (DMRG) method. We
demonstrate the competition between entanglement and interaction localization.
We also discuss the application of the configuration interaction based
dynamically extended active space procedure which significantly reduces the
effective system size and accelerates the speed of convergence for complicated
molecular electronic structures to a great extent. Our results indicate the
importance of taking entanglement among molecular orbitals into account in
order to devise an optimal orbital ordering and carry out efficient
calculations on transition metal clusters. We propose a recipe to perform DMRG
calculations in a black-box fashion and we point out the connections of our
work to other tensor network state approaches
Coherent and compatible information: a basis to information analysis of quantum systems
Relevance of key quantum information measures for analysis of quantum systems
is discussed. It is argued that possible ways of measuring quantum information
are based on compatibility/incompatibility of the quantum states of a quantum
system, resulting in the coherent information and introduced here the
compatible information measures, respectively. A sketch of an information
optimization of a quantum experimental setup is proposed.Comment: 10 pages, 5 figures, submitted to the Procs of 17th Int'l Conf. on
Coherent and Nonlinear Optics (ICONO-2001), June 26-July 1, 2001, Minsk,
Belaru
Quantum information analysis of the phase diagram of the half-filled extended Hubbard model
We examine the phase diagram of the half-filled one-dimensional extended
Hubbard model using quantum information entropies within the density-matrix
renormalization group. It is well known that there is a charge-density-wave
phase at large nearest-neighbor and small on-site Coloumb repulsion and a
spin-density-wave at small nearest-neighbor and large on-site Coloumb
repulsion. At intermediate Coulomb interaction strength, we find an additional
narrow region of a bond-order phase between these two phases. The phase
transition line for the transition out of the charge-density-wave phase changes
from first-order at strong coupling to second-order in a parameter regime where
all three phases are present. We present evidence that the additional
phase-transition line between the spin-density-wave and bond-order phases is
infinite order. While these results are in agreement with recent numerical
work, our study provides an independent, unbiased means of determining the
phase boundaries by using quantum information analysis, yields values for the
location of some of the phase boundaries that differ from those previously
found, and provides insight into the limitations of numerical methods in
determining phase boundaries, especially those of infinite-order transitions.Comment: 8 pages, 7 figure
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