914 research outputs found
Fabrication of an in-plane SU-8 cantilever with integrated strain gauge for wall shear stress measurements in fluid flows.
We present a cantilever fabricated from the polymer SU-8 for the measurement of wall shear stress in fluid flows. The pressure induced deflection of the cantilever, measured using a calibrated and integrated nichrome strain gauge, can be related to the wall shear stress on the surface. The initial degree of curvature of the cantilever can be controlled via the exposure dose, which allows a small positive deflection to be achieved, and so minimises the intrusion into the flow. Wind tunnel testing results show a sensitivity greater than 2.5 mV/Pa, with a shear stress of 0.38 Pa and excitation of 1 V
Characterising Deadlines in Temporal Modal Defeasible Logic
We provide a conceptual analysis of several kinds of deadlines, represented in Temporal Modal Defeasible Logic. The paper presents a typology of deadlines, based on the following parameters: deontic operator, maintenance or achievement, presence or absence of sanctions, and persistence after the deadline. The deadline types are illustrated by a set of examples
Data Analysis Challenges for the Einstein Telescope
The Einstein Telescope is a proposed third generation gravitational wave
detector that will operate in the region of 1 Hz to a few kHz. As well as the
inspiral of compact binaries composed of neutron stars or black holes, the
lower frequency cut-off of the detector will open the window to a number of new
sources. These will include the end stage of inspirals, plus merger and
ringdown of intermediate mass black holes, where the masses of the component
bodies are on the order of a few hundred solar masses. There is also the
possibility of observing intermediate mass ratio inspirals, where a stellar
mass compact object inspirals into a black hole which is a few hundred to a few
thousand times more massive. In this article, we investigate some of the data
analysis challenges for the Einstein Telescope such as the effects of increased
source number, the need for more accurate waveform models and the some of the
computational issues that a data analysis strategy might face.Comment: 18 pages, Invited review for Einstein Telescope special edition of
GR
From Molecular Cores to Planet-forming Disks: An SIRTF Legacy Program
Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe
Methods to Determine Neutrino Flux at Low Energies:Investigation of the Low Method
We investigate the "low-" method (developed by the CCFR/NUTEV
collaborations) to determine the neutrino flux in a wide band neutrino beam at
very low energies, a region of interest to neutrino oscillations experiments.
Events with low hadronic final state energy (of 1, 2 and 5 GeV)
were used by the MINOS collaboration to determine the neutrino flux in their
measurements of neutrino () and antineutrino (\nub_\mu) total cross
sections. The lowest energy for which the method was used in MINOS is
3.5 GeV, and the lowest \nub_\mu energy is 6 GeV. At these energies, the
cross sections are dominated by inelastic processes. We investigate the
application of the method to determine the neutrino flux for ,
\nub_\mu energies as low as 0.7 GeV where the cross sections are dominated by
quasielastic scattering and (1232) resonance production. We find that
the method can be extended to low energies by using values of 0.25
and 0.50 GeV, which is feasible in fully active neutrino detectors such as
MINERvA.Comment: 25 pages, 32 figures, to be published in European Physics Journal
Iodopentafluorobenzene: Electronic state spectroscopy by high resolution vacuum ultraviolet photoabsorption and photoelectron spectroscopy
The electronic transitions of iodopentafluorobenzene (C6F5I) have been investigated experimentally for the first time by high-resolution photoabsorption spectroscopy in the energy range 3.6 – 10.7 eV. The character of the valence excited states has been discussed taking into account calculations available in the literature. The ionisation energies of the molecule in its electronic ground state have been measured by high-resolution He(I) photoelectron spectroscopy. The energies of the ionic bands are shifted by about 0.5 eV compared to the earliest literature values but they agree with the most recently published measurements. All the spectra presented in this paper represent highest resolution measurements of their kind for iodopentafluorobenzene. The absolute photoabsorption cross sections have been used to model photolysis rates and residence times in the terrestrial atmosphere
Crop coefficient approaches based on fixed estimates of leaf resistance are not appropriate for estimating water use of citrus
The estimation of crop water use is critical for accurate irrigation scheduling and
water licenses. However, the direct measurement of crop water use is too expensive
and time consuming to be performed under all possible conditions, which
necessitates the use of water use models. The FAO-56 procedure is a simple,
convenient and reproducible method, but as canopy cover and height vary greatly
among different orchards, crop coefficients may not be readily transferrable from one
orchard to another. Allen and Pereira (2009) therefore incorporated a procedure into
the FAO-56 approach which estimates crop coefficients based on a physical
description of the vegetation and an adjustment for relative crop stomatal control
over transpiration. Transpiration crop coefficients derived using this procedure and
fixed values for citrus, did not provide good estimates of water use in three citrus
orchards. However, when mean monthly leaf resistance was taken into account, good agreement was found with measured values. A relationship between monthly
reference evapotranspiration and mean leaf resistance provided a means of
estimating mean leaf resistance which estimated transpiration crop coefficients with
a reasonable degree of accuracy. The use of a dynamic estimate of mean leaf
resistance therefore provided reasonable estimates of transpiration in citrus.South Africa‟s Water Research Commission (Project K5/1770, Water use of fruit tree orchards), with cofounding from the South African National Department of Agriculture, Forestry and Fisheries.http://link.springer.com/journal/2712016-12-30hb201
The luminosities of protostars in the spitzer c2d and gould belt legacy clouds
Journal ArticlePublished version available online at the Astronomical Journal, Volume 145, Number 4, Article 94; doi: doi: 10.1088/0004-6256/145/4/94Motivated by the long-standing "luminosity problem" in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 protostars in 18 molecular clouds observed by two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate L bol for each source, and study the protostellar luminosity distribution. This distribution extends over three orders of magnitude, from 0.01 L ȯ to 69 L ȯ, and has a mean and median of 4.3 L ȯ and 1.3 L ȯ, respectively. The distributions are very similar for Class 0 and Class I sources except for an excess of low luminosity (L bol ≲ 0.5 L) Class I sources compared to Class 0. 100 out of the 230 protostars (43%) lack any available data in the far-infrared and submillimeter (70 μm <λ < 850 μm) and have L bol underestimated by factors of 2.5 on average, and up to factors of 8-10 in extreme cases. Correcting these underestimates for each source individually once additional data becomes available will likely increase both the mean and median of the sample by 35%-40%. We discuss and compare our results to several recent theoretical studies of protostellar luminosities and show that our new results do not invalidate the conclusions of any of these studies. As these studies demonstrate that there is more than one plausible accretion scenario that can match observations, future attention is clearly needed. The better statistics provided by our increased data set should aid such future work. © 2013. The American Astronomical Society. All rights reserved..National Science FoundationNational Aeronautics and Space AdministrationJet Propulsion Laboratory, California Institute of Technolog
Modelling water use of subtropical fruit crops : the challenges
Subtropical fruit crops form an important part of the fruit industry in many countries. Many of these crops are grown in semi-arid regions or subtropical regions where rainfall is seasonal and as a result the vast majority of these perennial, evergreen orchards are under irrigation. This represents a significant irrigation requirement and with more emphasis being placed on the conservation of water and orchard profitability, it is becoming increasingly important to accurately estimate water use of these crops and schedule irrigation accordingly. The FAO-56 procedure is a simple, convenient and reproducible method for estimating water use. However, the transferability of crop coefficients between different orchards and growing regions is not always readily achieved, due largely to differences in canopy size and management practices. In addition, as subtropical crops tend to exhibit a higher degree of stomatal control over transpiration than most other agricultural crops, some measure of canopy or leaf resistance must be taken into account when using models based on atmospheric demand. The challenge is therefore to provide reliable and dynamic estimates of canopy resistance from relatively simple parameters which can be of use to irrigation consultants and farmers for determining the water requirements of these crops. The challenge remains to ensure that these dynamic estimates are realistic and readily applicable to a number of growing regions. The derivation of transpiration crop coefficients, based on canopy cover and height and a dynamic estimate of leaf resistance, provided reasonable estimates of transpiration in three orchards in contrasting climates, suggesting that this approach could prove useful in future for subtropical crops.http://www.actahort.org2018-05-10hj2017Plant Production and Soil Scienc
Energy Conditions in Modified Gravity with Non-minimal Coupling to Matter
In this paper we study a model of modified gravity with non-minimal coupling
between a general function of the Gauss-Bonnet invariant, , and matter
Lagrangian from the point of view of the energy conditions. Such model has been
introduced in Ref. [21] for description of early inflation and late-time cosmic
acceleration. We present the suitable energy conditions for the above mentioned
model and then, we use the estimated values of the Hubble, deceleration and
jerk parameters to apply the obtained energy conditions to the specific class
of modified Gauss-Bonnet models.Comment: 12 pages, no figur, Accepted for publication in Astrophysics and
Space Scienc
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