1,412 research outputs found
“Boundary Work for Water Sustainability and Urban Climate Adaptation: Lessons from the Decision Center for a Desert City”
地域環境知プロジェクト第1回国際シンポジウム,総合地球環境学研究所 講演室,2014-09-13,総合地球環境学研究所 地域環境知プロジェク
Verifying timestamps of occultation observation systems
We describe an image timestamp verification system to determine the exposure
timing characteristics and continuity of images made by an imaging camera and
recorder, with reference to Coordinated Universal Time (UTC). The original use
was to verify the timestamps of stellar occultation recording systems, but the
system is applicable to lunar flashes, planetary transits, sprite recording, or
any area where reliable timestamps are required. The system offers good
temporal resolution (down to 2 msec, referred to UTC) and provides exposure
duration and interframe dead time information. The system uses inexpensive,
off-the- shelf components, requires minimal assembly and requires no
high-voltage components or connections. We also describe an application to load
FITS (and other format) image files, which can decode the verification image
timestamp. Source code, wiring diagrams and built applications are provided to
aid the construction and use of the device.Comment: 10 pages, 7 figures, accepted to Publications of the Astronomical
Society of Australia (PASA
Cooling Radiation and the Lyman-alpha Luminosity of Forming Galaxies
We examine the cooling radiation from forming galaxies in hydrodynamic
simulations of the LCDM model (cold dark matter with a cosmological constant),
focusing on the Ly-alpha line luminosities of high-redshift systems. Primordial
composition gas condenses within dark matter potential wells, forming objects
with masses and sizes comparable to the luminous regions of observed galaxies.
As expected, the energy radiated in this process is comparable to the
gravitational binding energy of the baryons, and the total cooling luminosity
of the galaxy population peaks at z ~= 2. However, in contrast to the classical
picture of gas cooling from the \sim 10^6 K virial temperature of a typical
dark matter halo, we find that most of the cooling radiation is emitted by gas
with T < 20,000 K. As a consequence, roughly 50% of this cooling radiation
emerges in the Ly-alpha line. While a galaxy's cooling luminosity is usually
smaller than the ionizing continuum luminosity of its young stars, the two are
comparable in the most massive systems, and the cooling radiation is produced
at larger radii, where the Ly-alpha photons are less likely to be extinguished
by dust. We suggest, in particular, that cooling radiation could explain the
two large (\sim 100 kpc), luminous (L_{Ly-alpha} \sim 10^{44} erg s^{-1})
``blobs'' of Ly-alpha emission found in Steidel et al.'s (1999) narrow band
survey of a z = 3 proto-cluster. Our simulations predict objects of the
observed luminosity at about the right space density, and radiative transfer
effects can account for the observed sizes and line widths. We discuss
observable tests of this hypothesis for the nature of the Ly-alpha blobs, and
we present predictions for the contribution of cooling radiation to the
Ly-alpha luminosity function of galaxies as a function of redshift.Comment: Submitted to ApJ. 28 pages including 9 PS figures. Version with color
figures available at
http://donald.astro.umass.edu/~fardal/papers/cooling/cooling.htm
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Antecedents of Effective Environmental Management in a Hotel Setting: A Test of the Value-Belief-Norm Theory
The purpose of this quantitative study is to test the validity of a behavioral theory in the context of environmental hotel management. The lack of theoretical consideration in previous studies on environmental attitudes of hotel/resort managers warrants an investigation of a theory with the potential to better explain behaviors that support the goals of environment management systems. The goal of this research was to document the values, beliefs, personal norms, and environmental management support behaviors of managers in a hospitality setting to test the behavioral theory. Data were collected from a sample of hotel and resort managers in the Phoenix metropolitan area by using a survey of well-documented items from previous research on the theory. Results suggest the theory is successful in explaining environmental management support behaviors. Implications for practitioners as well as researchers are discusse
Voigt-Profile Analysis of the Lyman-alpha Forest in a Cold Dark Matter Universe
We use an automated Voigt-profile fitting procedure to extract statistical
properties of the Ly forest in a numerical simulation of an ,
cold dark matter (CDM) universe. Our analysis method is similar to that used in
most observational studies of the forest, and we compare the simulations to
recently published results derived from Keck HIRES spectra. With the
Voigt-profile decomposition analysis, the simulation reproduces the large
number of weak lines (N_{\rm HI}\la 10^{13}\cdunits) found in the HIRES
spectra. The column density distribution evolves significantly between
and , with the number of lines at fixed column density dropping by a
factor in the range where line blending is not severe. At , the
-parameter distribution has a median of 35 \kms and a dispersion of 20
\kms, in reasonable agreement with the observed values. The comparison between
our new analysis and recent data strengthens earlier claims that the \lya
forest arises naturally in hierarchical structure formation as photoionized gas
falls into dark matter potential wells. However, there are two statistically
signficant discrepancies between the simulated forest and the HIRES results:
the model produces too many lines at by a factor , and it
produces more narrow lines (b<20 \kms) than are seen in the data. The first
result is sensitive to our adopted normalization of the mean \lya optical
depth, and the second is sensitive to our assumption that helium reionization
has not significantly raised gas temperatures at . It is therefore too
early to say whether these discrepancies indicate a fundamental problem with
the high-redshift structure of the CDM model or reflect errors of
detail in our modeling of the gas distribution or the observational procedure.Comment: 13 pages, 3 figures, AAS LaTex, accepted to Ap
Towards distribution-based control of social networks
Background: Complex networks are found in many domains and the control of these networks is a research topic that continues to draw increasing attention. This paper proposes a method of network control that attempts to maintain a specified target distribution of the network state. In contrast to many existing network control research works, which focus exclusively on structural analysis of the network, this paper also accounts for user actions/behaviours within the network control problem. Methods: This paper proposes and makes use of a novel distribution-based control method. The control approach is applied within a simulation of the real-valued voter model, which could have applications in problems such as the avoidance of consensus or extremism. The network control problem under consideration is investigated using various theoretical network types, including scale free, random, and small world. Results: It is argued that a distribution-based control approach may be more appropriate for several types of social control problems, in which the exact state of the system is of less interest than the overall system behaviour. The preliminary results presented in this paper demonstrate that a standard reinforcement learning approach is capable of learning a control signal selection policy to prevent the network state distribution from straying far from a specified target distribution. Conclusions: In summary, the results presented in this paper demonstrate the feasibility of a distribution-based control solution within the simulated problem. Additionally, several interesting questions arise from these results and are discussed as potential future work
From Galaxy-Galaxy Lensing to Cosmological Parameters
Galaxy-galaxy lensing measures the mean excess surface density DS(r) around a
sample of lensing galaxies. We develop a method for combining DS(r) with the
galaxy correlation function xi_gg(r) to constrain Omega_m and sigma_8, going
beyond the linear bias model to reach the level of accuracy demanded by current
and future measurements. We adopt the halo occupation distribution (HOD)
framework, and we test its applicability to this problem by examining the
effects of replacing satellite galaxies in the halos of an SPH simulation with
randomly selected dark matter particles from the same halos. The difference
between dark matter and satellite galaxy radial profiles has a ~10% effect on
DS(r) at r<1 Mpc/h. However, if radial profiles are matched, the remaining
impact of individual subhalos around satellite galaxies and environmental
dependence of the HOD at fixed halo mass is <5% in DS(r) for 0.1<r<15 Mpc/h. We
develop an analytic approximation for DS(r) that incorporates halo exclusion
and scale-dependent halo bias, and we demonstrate its accuracy with tests
against a suite of populated N-body simulations. We use the analytic model to
investigate the dependence of DS(r) and the galaxy-matter correlation function
xi_gm(r) on Omega_m and sigma_8, once HOD parameters for a given cosmological
model are pinned down by matching xi_gg(r). The linear bias prediction is
accurate for r>2 Mpc/h, but it fails at the 30-50% level on smaller scales. The
scaling of DS(r) ~ Omega_m^a(r) sigma_8^b(r) approaches the linear bias
expectation a=b=1 at r>10 Mpc/h, but a(r) and b(r) vary from 0.8 to 1.6 at
smaller r. We calculate a fiducial DS(r) and scaling indices a(r) and b(r) for
two SDSS galaxy samples; galaxy-galaxy lensing measurements for these samples
can be combined with our predictions to constrain Omega_m and sigma_8.Comment: 18 pages, 10 figures, accepted for publication in The Astrophysical
Journa
DEVELOPING METHODS TO ASSESS THE RELATIONSHIP BETWEEN ERGOMETER AND ON-WATER ROWING PERFORMANCE FROM INDEPENDENT DATASETS
Rowing ergometers are often used by internationally competitive athletes alongside on-water rowing. This study proposes methods to develop a generalisable relationship between maximal effort 2000 m ergometer and on-water rowing performance using independent datasets. Ergometer times for 2000 m tests (n = 153) and 2000 m on-water times from international races (n = 139) were collated. Percentiles from the raw data and fitted probability density functions were mapped to develop a generalisable performance relationship. Bootstrapping was utilised to estimate the uncertainty in the percentile mappings. When built on a larger sample of athletes, this approach could be useful to identify athletes who under or overperform on water compared to ergometers, and this could provide valuable context for future biomechanical investigations of rowing technique
Substructure in the Coma Cluster: Giants vs Dwarfs
The processes that form and shape galaxy clusters, such as infall, mergers
and dynamical relaxation, tend to generate distinguishable differences between
the distributions of a cluster's giant and dwarf galaxies. Thus the dynamics of
dwarf galaxies in a cluster can provide valuable insights into its dynamical
history. With this in mind, we look for differences between the spatial and
velocity distributions of giant (b18) galaxies in the Coma
cluster. Our redshift sample contains new measurements from the 2dF and WYFFOS
spectrographs, making it more complete at faint magnitudes than any previously
studied sample of Coma galaxies. It includes 745 cluster members - 452 giants
and 293 dwarfs. We find that the line-of-sight velocity distribution of the
giants is significantly non-Gaussian, but not that for the dwarfs. A battery of
statistical tests of both the spatial and localised velocity distributions of
the galaxies in our sample finds no strong evidence for differences between the
giant and dwarf populations. These results rule out the cluster as a whole
having moved significantly towards equipartition, and they are consistent with
the cluster having formed via mergers between dynamically-relaxed subclusters.Comment: 23 pages, 6 figures, to appear in Ap
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