13,389 research outputs found
Constructed wetlands: Treatment of concentrated storm water runoff (part A)
The aim of this research was to assess the treatment efficiencies for gully pot liquor of experimental vertical-
flow constructed wetland filters containing Phragmites australis (Cav.) Trin. ex Steud. (common
reed) and filter media of different adsorption capacities. Six out of 12 filters received inflow water spiked
with metals. For 2 years, hydrated nickel and copper nitrate were added to sieved gully pot liquor to simulate
contaminated primary treated storm runoff. For those six constructed wetland filters receiving heavy
metals, an obvious breakthrough of dissolved nickel was recorded after road salting during the first winter.
However, a breakthrough of nickel was not observed, since the inflow pH was raised to eight after
the first year of operation. High pH facilitated the formation of particulate metal compounds such as nickel
hydroxide. During the second year, reduction efficiencies of heavy metal, 5-days at 20°C N-Allylthiourea
biochemical oxygen demand (BOD) and suspended solids (SS) improved considerably. Concentrations of
BOD were frequently �20 mg/L. However, concentrations for SS were frequently �30 mg/L. These are
the two international thresholds for secondary wastewater treatment. The BOD removal increased over
time due to biomass maturation, and the increase of pH. An analysis of the findings with case-based reasoning
can be found in the corresponding follow-up paper (Part B)
Planetary host stars: Evaluating uncertainties in ultra-cool model atmospheres
M-dwarfs are emerging in the literature as promising targets for detecting
low-mass, Earth-like planets. An important step in this process is to determine
the stellar parameters of the M-dwarf host star as accurately as possible.
Different well-tested stellar model atmosphere simulations from different
groups are widely applied to undertake this task. This paper provides a
comparison of different model atmosphere families to allow a better estimate of
systematic errors on host-star stellar parameter introduced by the use of one
specific model atmosphere family only. We present a comparison of the ATLAS9,
MARCS, Phoenix and Drift-Phoenix model atmosphere families including the
M-dwarf parameter space (TK4000K,
log(g)=3.05.0, [M/H]=). We examine the differences in
the (T, p)-structures, in synthetic photometric fluxes
and in colour indices. Model atmospheres results for higher log(g) deviate
considerably less between different models families than those for lower log(g)
for all TK4000K examined. We compiled the broad-band
synthetic photometric fluxes for all available model atmospheres (incl.
M-dwarfs and brown dwarfs) for the UKIRT WFCAM ZYJHK, 2MASS JHKs and Johnson
UBVRI filters, and calculated related colour indices. Synthetic colours in the
IR wavelengths diverge by no more than 0.15 dex amongst all model families. For
all spectral bands considered, model discrepancies in colour diminish for
higher T atmosphere simulations. We notice differences in synthetic
colours between all model families and observed example data (incl. Kepler 42
and GJ1214).Comment: accepted for publication in MNRA
Graphene with time-dependent spin-orbit coupling: Truncated Magnus expansion approach
We analyze the role of ac-driven Rashba spin-orbit coupling in monolayer
graphene including a spin-dependent mass term. Using the Magnus expansion as a
semi-analytical approximation scheme a full account of the quasienergie
spectrum of spin states is given. We discuss the subtleties arising in
correctly applying the Magnus expansion technique in order to determine the
quasienergy spectrum. Comparison to the exact numerical solution gives
appropriate boundaries to the validity of the Magnus expansion solution.Comment: 8 pages, 4 figure
Total and partial cross sections of the Sn()Te reaction measured via in-beam -ray spectroscopy
An extended database of experimental data is needed to address uncertainties
of the nuclear-physics input parameters for Hauser-Feshbach calculations.
Especially +nucleus optical model potentials at low energies are not
well known. The in-beam technique with an array of high-purity germanium (HPGe)
detectors was successfully applied to the measurement of absolute cross
sections of an (,) reaction on a heavy nucleus at sub-Coulomb
energies. The total and partial cross-section values were measured by means of
in-beam -ray spectroscopy. Total and partial cross sections were
measured at four different -particle energies from
MeV to MeV. The measured total cross-section values are in
excellent agreement with previous results obtained with the activation
technique, which proves the validity of the applied method. The experimental
data was compared to Hauser-Feshbach calculations using the nuclear reaction
code TALYS. A modified version of the semi-microscopic +nucleus optical
model potential OMP 3, as well as modified proton and widths, are
needed in order to obtain a good agreement between experimental data and
theory. It is found, that a model using a local modification of the
nuclear-physics input parameters simultaneously reproduces total cross sections
of the Sn(,) and Sn(,p) reactions. The
measurement of partial cross sections turns out to be very important in this
case in order to apply the correct -ray strength function in the
Hauser-Feshbach calculations. The model also reproduces cross-section values of
-induced reactions on Cd, as well as of (,n) reactions
on Sn, hinting at a more global character of the obtained
nuclear-physics input.Comment: 8 pages, 9 figure
The Rotation of Young Low-Mass Stars and Brown Dwarfs
We review the current state of our knowledge concerning the rotation and
angular momentum evolution of young stellar objects and brown dwarfs from a
primarily observational view point. Periods are typically accurate to 1% and
available for about 1700 stars and 30 brown dwarfs in young clusters.
Discussion of angular momentum evolution also requires knowledge of stellar
radii, which are poorly known for pre-main sequence stars. It is clear that
rotation rates at a given age depend strongly on mass; higher mass stars
(0.4-1.2 M) have longer periods than lower mass stars and brown dwarfs.
On the other hand, specific angular momentum is approximately independent of
mass for low mass pre-main sequence stars and young brown dwarfs. A spread of
about a factor of 30 is seen at any given mass and age. The evolution of
rotation of solar-like stars during the first 100 Myr is discussed. A broad,
bimodal distribution exists at the earliest observable phases (1 Myr) for
stars more massive than 0.4 M. The rapid rotators (50-60% of the
sample) evolve to the ZAMS with little or no angular momentum loss. The slow
rotators continue to lose substantial amounts of angular momentum for up to 5
Myr, creating the even broader bimodal distribution characteristic of 30-120
Myr old clusters. Accretion disk signatures are more prevalent among slowly
rotating PMS stars, indicating a connection between accretion and rotation.
Disks appear to influence rotation for, at most, 5 Myr, and considerably
less than that for the majority of stars. If the dense clusters studied so far
are an accurate guide, then the typical solar-like star may have only 1
Myr for this task. It appears that both disk interactions and stellar winds are
less efficient at braking these objects.Comment: Review chapter for Protostars and Planets V. 15 page and 8 figure
Comparison of planted soil infiltration systems for treatment of log yard runoff
Treatment of log yard runoff is required to avoid
contamination of receiving watercourses. The research aim was to assess
if infiltration of log yard runoff through planted soil systems is successful
and if different plant species affect the treatment performance at a fieldscale
experimental site in Sweden (2005 to 2007). Contaminated runoff
from the log yard of a sawmill was infiltrated through soil planted with
Alnus glutinosa (L.) Ga¨rtner (common alder), Salix schwerinii3viminalis
(willow variety ‘‘Gudrun’’), Lolium perenne (L.) (rye grass), and Phalaris
arundinacea (L.) (reed canary grass). The study concluded that there were
no treatment differences when comparing the four different plants with
each other, and there also were no differences between the tree and the
grass species. Furthermore, the infiltration treatment was effective in
reducing total organic carbon (55%) and total phosphorus (45%)
concentrations in the runoff, even when the loads on the infiltration
system increased from year to year
Constructed wetlands: Prediction of performance with case-based reasoning (part B)
The aim of this research was to assess the treatment efficiencies for gully pot liquor of experimental vertical-
flow constructed wetland filters containing Phragmites australis (Cav.) Trin. ex Steud. (common reed)
and filter media of different adsorption capacities. Six out of 12 filters received inflow water spiked with
metals. For 2 years, hydrated nickel and copper nitrate were added to sieved gully pot liquor to simulate
contaminated primary treated storm runoff. The findings were analyzed and discussed in a previous paper
(Part A). Case-based reasoning (CBR) methods were applied to predict 5 days at 20°C N-Allylthiourea biochemical
oxygen demand (BOD) and suspended solids (SS), and to demonstrate an alternative method of
analyzing water quality performance indicators. The CBR method was successful in predicting if outflow
concentrations were either above or below the thresholds set for water-quality variables. Relatively small
case bases of approximately 60 entries are sufficient to yield relatively high predictions of compliance of
at least 90% for BOD. Biochemical oxygen demand and SS are expensive to estimate, and can be cost-effectively
controlled by applying CBR with the input variables turbidity and conductivity
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
Wavelength dependence of angular diameters of M giants: an observational perspective
We discuss the wavelength dependence of angular diameters of M giants from an
observational perspective. Observers cannot directly measure an optical-depth
radius for a star, despite this being a common theoretical definition. Instead,
they can use an interferometer to measure the square of the fringe visibility.
We present new plots of the wavelength-dependent centre-to-limb variation (CLV)
of intensity of the stellar disk as well as visibility for Mira and non-Mira M
giant models. We use the terms ``CLV spectra'' and ``visibility spectra'' for
these plots. We discuss a model-predicted extreme limb-darkening effect (also
called the narrow-bright-core effect) in very strong TiO bands which can lead
to a misinterpretation of the size of a star in these bands. We find no
evidence as yet that this effect occurs in real stars. Our CLV spectra can
explain the similarity in visibilities of R Dor (M8IIIe) that have been
observed recently despite the use of two different passbands. We compare
several observations with models and find the models generally under-estimate
the observed variation in visibility with wavelength. We present CLV and
visibility spectra for a model that is applicable to the M supergiant alpha
Ori.Comment: 16 pages with figures. Accepted by MNRA
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