11,427 research outputs found
Design comparison of experimental storm water detention systems treating concentrated road runoff
The aim was to assess the treatment efficiencies of experimental storm water detention (extended
storage) systems based on the Atlantis Water Management Limited detention cells receiving concentrated
runoff that has been primary treated by filtration with different inert aggregates. Randomly collected gully
pot liquor was used in stead of road runoff. To test for a 'worst case scenario', the experimental system
received higher volumes and pollutant concentrations in comparison to real detention systems under real
(frequently longer but diluted) runoff events. Gravel (6 and 20 mm), sand (1.5 mm), Ecosoil (inert 2 mm
aggregate provided by Atlantis Water Management Limited), block paving and turf were tested in terms of
their influence on the water quality. Concentrations of five-day @ 20� C ATU biochemical oxygen demand
(BOD) in contrast to suspended solids (SS) were frequently reduced to below international secondary
wastewater treatment standards. The denitrification process was not completed. This resulted in higher
outflow than inflow nitrate-nitrogen concentrations. An analysis of variance indicated that some systems
were similar in terms of most of their treatment performance variables including BOD and SS. It follows that
there is no advantage in using additional aggregates with high adsorption capacities in the primary treatment
stage
Taxes and the poor: A microsimulation study of implicit and explicit taxes
The authors measure the cumulative burden on low-income households resulting from explicit taxes (state and federal income, and payroll taxes) and implicit taxes (reductions of program benefits as earnings rise). With monthly data from the 1990 Survey of Income and Program Participation, a simulation model calculates the benefits and taxes households receive and pay in 1990. A household's marginal tax rate is established by simulating the benefits and taxes the household would receive and pay if each member aged 15 or more received additional earnings of $10 per month. The changes in income that would result if all household members age 15 or older took a half-time, minimum-wage job are also calculated. Typical cumulative marginal tax rates on poor households are found to be about 27 percent, but this masks considerable variation across states as a result of differences in program eligibility rules, state income taxes, and state AFDC policies. The tax burdens resulting from taking a half-time minimum-wage job also vary greatly across states, and participants in AFDC and food stamps face median marginal tax rates significantly above the rates for all poor households. A consistent result, however, is that typical tax rates on the poor rarely exceed 60 percent when income changes resulting from incremental changes in monthly earnings are calculated. The authors conclude that for most poor households, tax rates are not so high as to diminish the possible effectiveness of such policies as the Earned Income Tax Credit, which try to make work more attractive than welfare.
Theory of time-dependent rupture in the Earth
Fracture mechanics is used to develop a theory of earthquake mechanism which includes the phenomenon of subcritical crack growth. The following phenomena are predicted: slow earthquakes, multiple events, delayed multiple events (doublets), postseismic rupture growth and afterslip, foreshocks, and aftershocks. The theory predicts a nucleation stage prior to an earthquake, and suggests a physical mechanism by which one earthquake may 'trigger' another
An Introduction to Slice-Based Cohesion and Coupling Metrics
This report provides an overview of slice-based software metrics. It brings together information about the development of the metrics from Weiser’s original idea that program slices may be used in the measurement of program complexity, with alternative slice-based measures proposed by other researchers. In particular, it details two aspects of slice-based metric calculation not covered elsewhere in the literature: output variables and worked examples of the calculations. First, output variables are explained, their use explored and standard reference terms and usage proposed. Calculating slice-based metrics requires a clear understanding of ‘output variables’ because they form the basis for extracting the program slices on which the calculations depend. This report includes a survey of the variation in the definition of output variables used by different research groups and suggests standard terms of reference for these variables. Our study identifies four elements which are combined in the definition of output variables. These are the function return value, modified global variables, modified reference parameters and variables printed or otherwise output by the module. Second, slice-based metric calculations are explained with the aid of worked examples, to assist newcomers to the field. Step-by-step calculations of slice-based cohesion and coupling metrics based on the vertices output by the static analysis tool CodeSurfer (R) are presented and compared with line-based calculations
A cycling state that can lead to glassy dynamics in intracellular transport
Power-law dwell times have been observed for molecular motors in living
cells, but the origins of these trapped states are not known. We introduce a
minimal model of motors moving on a two-dimensional network of filaments, and
simulations of its dynamics exhibit statistics comparable to those observed
experimentally. Analysis of the model trajectories, as well as experimental
particle tracking data, reveals a state in which motors cycle unproductively at
junctions of three or more filaments. We formulate a master equation for these
junction dynamics and show that the time required to escape from this
vortex-like state can account for the power-law dwell times. We identify trends
in the dynamics with the motor valency for further experimental validation. We
demonstrate that these trends exist in individual trajectories of myosin II on
an actin network. We discuss how cells could regulate intracellular transport
and, in turn, biological function, by controlling their cytoskeletal network
structures locally
Angular momentum evolution of young low-mass stars and brown dwarfs: observations and theory
This chapter aims at providing the most complete review of both the emerging
concepts and the latest observational results regarding the angular momentum
evolution of young low-mass stars and brown dwarfs. In the time since
Protostars & Planets V, there have been major developments in the availability
of rotation period measurements at multiple ages and in different star-forming
environments that are essential for testing theory. In parallel, substantial
theoretical developments have been carried out in the last few years, including
the physics of the star-disk interaction, numerical simulations of stellar
winds, and the investigation of angular momentum transport processes in stellar
interiors. This chapter reviews both the recent observational and theoretical
advances that prompted the development of renewed angular momentum evolution
models for cool stars and brown dwarfs. While the main observational trends of
the rotational history of low mass objects seem to be accounted for by these
new models, a number of critical open issues remain that are outlined in this
review.Comment: 22 pages, 8 figures, accepted for publication in Protostars & Planets
VI, 2014, University of Arizona Press, eds. H. Beuther, R. Klessen, K.
Dullemond, Th. Hennin
Lattice simulations with improved Wilson fermions at a fixed strange quark mass
The explicit breaking of chiral symmetry of the Wilson fermion action results
in additive quark mass renormalization. Moreover, flavour singlet and
non-singlet scalar currents acquire different renormalization constants with
respect to continuum regularization schemes. This complicates keeping the
renormalized strange quark mass fixed when varying the light quark mass in
simulations with sea quark flavours. Here we present and validate our
strategy within the CLS (Coordinated Lattice Simulations) effort to achieve
this in simulations with non-perturbatively order- improved Wilson fermions.
We also determine various combinations of renormalization constants and
improvement coefficients.Comment: 18 pages, 11 Figures, V2: References added/updated, all fits rerun
with improved statistics for ensemble N204, also using the final values for
the improvement coefficients A and b_P-b_A (very minor impact), The figures
have been replotted accordingly. (The differences with respect to V1 are
invisible to the human eye). Minor change
Global survey of star clusters in the Milky Way II. The catalogue of basic parameters
Although they are the main constituents of the Galactic disk population, for
half of the open clusters in the Milky Way reported in the literature nothing
is known except the raw position and an approximate size. The main goal of this
study is to determine a full set of uniform spatial, structural, kinematic, and
astrophysical parameters for as many known open clusters as possible. On the
basis of stellar data from PPMXL and 2MASS, we used a dedicated data-processing
pipeline to determine kinematic and photometric membership probabilities for
stars in a cluster region. For an input list of 3784 targets from the
literature, we confirm that 3006 are real objects, the vast majority of them
are open clusters, but associations and globular clusters are also present. For
each confirmed object we determined the exact position of the cluster centre,
the apparent size, proper motion, distance, colour excess, and age. For about
1500 clusters, these basic astrophysical parameters have been determined for
the first time. For the bulk of the clusters we also derived the tidal radius.
We estimated additionally average radial velocities for more than 30% of the
confirmed clusters. The present sample (called MWSC) reaches both the central
parts of the Milky Way and its outer regions. It is almost complete up to 1.8
kpc from the Sun and also covers neighbouring spiral arms. However, for a small
subset of the oldest open clusters () we found some evidence
of incompleteness within about 1 kpc from the Sun.Comment: 8 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Global survey of star clusters in the Milky Way IV. 63 new open clusters detected by proper motions
AIMS: In their 1st extension to the Milky Way Star Clusters (MWSC) survey,
Schmeja et al. applied photometric filters to the 2MASS to find new cluster
candidates that were subsequently confirmed or rejected by the MWSC pipeline.
To further extend the MWSC census, we aimed at discovering new clusters by
conducting an almost global search in proper motion catalogues as a starting
point. METHODS: We first selected high-quality samples from the PPMXL and UCAC4
for comparison and verification of the proper motions. For 441 circular proper
motion bins (radius 15 mas/yr) within 50 mas/yr, the sky outside a thin
Galactic plane zone (5) was binned in small areas ('sky
pixels') of 0.250.25 deg. Sky pixels with enhanced numbers of stars
with a certain common proper motion in both catalogues were considered as
cluster candidates. After visual inspection of the sky images, we built an
automated procedure that combined these representations of the sky for
neighbouring proper motion subsamples after a background correction. RESULTS:
About half of our 692 candidates overlapped with known clusters (46 globular
and 68 open clusters in the Galaxy, about 150 known clusters of galaxies) or
the Magellanic Clouds. About 10% of our candidates turned out to be 63 new open
clusters confirmed by the MWSC pipeline. They occupy predominantly the two
inner Galactic quadrants and have apparent sizes and numbers of high-probable
members slightly larger than those of the typically small MWSC clusters,
whereas their other parameters (ages, distances, tidal radii) fall in the
typical ranges. As our search aimed at finding compact clusters, we did not
find new very nearby (extended) clusters. (abridged)Comment: 14 pages, 14 figures, accepted for publication in Astronomy and
Astrophysic
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