887 research outputs found
Helping Communities Build: A review of the Community Land Trust Funds and lessons for future support
MINIMO: A Search for Mini Proper Motion Stars in the Southern Sky
I report 1684 new proper motion systems in the southern sky (declinations -90 degrees to -47 degrees) with 0.50 arcsec/yr \u3e mu \u3e= 0.18 arcsec/yr. This effort is a continuation of the SuperCOSMOS-RECONS (SCR) proper motion search to lower proper motions than reported in Hambly et al. (2004); Henry et al. (2004); Subasavage et al. (2005a,b). Distance estimates are presented for the new systems, assuming that all stars are on the main sequence. I find that 34 systems are within 25 pc, including three systems --- SCR 0838-5855, SCR 1826-6542, and SCR 0630-7643AB --- anticipated to be within 10 pc. These mini-motion (MINIMO) discoveries constitute a more than ten-fold increase in new systems found in the same region of sky searched for systems with mu \u3e= 0.50 arcsec/yr, suggesting a happy hunting ground for new nearby slower proper motion systems in the region just north (declinations -47 degrees to 0 degrees), much of which has not been rigorously searched during previous efforts
Soil Moisture Estimation for landslide monitoring: A new approach using multi-temporal Synthetic Aperture RADAR data
This study explores the utility of the Spotlight2 X-band Synthetic Aperture Radar product developed by the Italian Space Agency for use in multi-temporal estimation of soil moisture in a landslide monitoring context, using a time series of monthly images of the Hollin Hill Landslide Observatory – North Yorkshire, UK. The study shows the complexity of surface soil moisture at an active landslide, using high resolution in situ soil moisture data. This in situ data is also used for ground truthing the soil moisture estimations from the SAR data. The study shows the limitations of inter-and intra-sensor calibration within the Cosmo-SkyMed array and contextualises this problem within the current research climate where SAR imagery is increasingly being created using multi-satellite constellation, while being used, increasingly, by environmental scientists rather than remote sensing specialists
Cuyahoga County’s Tax-Base Challenge: Renewing and Redeveloping Core Communities
Two major factors threaten the well-being of Cuyahoga County: the approaching build-out of its outer suburbs, which will severely limit tax-base growth through new construction, and the aged condition of inner suburbs, which jeopardizes property values. The situation calls for unprecedented cooperative action among elected officials to secure the county’s future.
Recent changes in the value of real estate in Cuyahoga County compared with adjacent counties shows the seriousness of the situation and the criticality of the primary course of action: redevelopment and renewal in Cleveland and inner suburbs
Bias in Zipf's Law Estimators
The prevailing maximum likelihood estimators for inferring power law models
from rank-frequency data are biased. The source of this bias is an
inappropriate likelihood function. The correct likelihood function is derived
and shown to be computationally intractable. A more computationally efficient
method of approximate Bayesian computation (ABC) is explored. This method is
shown to have less bias for data generated from idealised rank-frequency
Zipfian distributions. However, the existing estimators and the ABC estimator
described here assume that words are drawn from a simple probability
distribution, while language is a much more complex process. We show that this
false assumption leads to continued biases when applying any of these methods
to natural language to estimate Zipf exponents. We recommend that researchers
be aware of these biases when investigating power laws in rank-frequency data.Comment: 15 pages, 11 figure
Manipulating type-I and type-II Dirac polaritons in cavity-embedded honeycomb metasurfaces
Pseudorelativistic Dirac quasiparticles have emerged in a plethora of
artificial graphene systems that mimic the underlying honeycomb symmetry of
graphene. However, it is notoriously difficult to manipulate their properties
without modifying the lattice structure. Here we theoretically investigate
polaritons supported by honeycomb metasurfaces and, despite the trivial nature
of the resonant elements, we unveil rich Dirac physics stemming from a
non-trivial winding in the light-matter interaction. The metasurfaces
simultaneously exhibit two distinct species of massless Dirac polaritons,
namely type-I and type-II. By modifying only the photonic environment via an
enclosing cavity, one can manipulate the location of the type-II Dirac points,
leading to qualitatively different polariton phases. This enables one to alter
the fundamental properties of the emergent Dirac polaritons while preserving
the lattice structure - a unique scenario which has no analog in real or
artificial graphene systems. Exploiting the photonic environment will thus give
rise to unexplored Dirac physics at the subwavelength scale
- …