22,221 research outputs found
Coupled aerodynamic and acoustical predictions for turboprops
To predict the noise fields for proposed turboprop airplanes, an existing turboprop noise code by Farassat has been modified to accept blade pressure inputs from a three-dimensional aerodynamic code. A Euler-type code can handle the nonlinear transonic flow of these high-speed, highly swept blades. This turbofan code was modified to allow the calculation mesh to extend to about twice the blade radius and to apply circumferential periodicity rather than solid-wall boundary conditions on the blade in the region between the blade tip and the outer shroud. Outputs were added for input to the noise prediction program and for color contour plots of various flow variables. The Farassat input subroutines were modified to read files of blade coordinates and predicted surface pressures. Aerodynamic and acoustic results are shown for the SR-3 model blade. Comparison of the acoustic predicted results with measured data show good agreement
Radiation resistance studies of amorphous silicon films
Hydrogenated amorphous silicon thin films were irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15 cm(-2). The films were characterized using photothermal deflection spectroscopy and photoconductivity measurements. The investigations show that the radiation introduces sub-band-gap states 1.35 eV below the conduction band and the states increase supralinearly with fluence. Photoconductivity measurements suggest the density of states above the Fermi energy is not changing drastically with fluence
Introducing a Practitioner-focused Publication in Exercise Science and Kinesiology
The purpose is to introduce Topics in Exercise and Science Kinesiology (TESK) as an outlet for practical information. We searched available journals in the field to determine practitioner-focused options, we also determined the percentage of presented abstracts at a popular meeting compared to the number of published papers in a leading peer-reviewed scientific journal. Point of application 1: Only 2% of publication options in kinesiology or exercise science have a practitioner focus. Point of application 2: A relatively small number of peer-reviewed conference abstracts (less than 10%) are deemed publication-worthy following journal peer-review. Point of application 3: To be more inclusive, we announce the International Community of Scholars in Kinesiology (ICSK); and to provide students with important information on professional development and trending research, we will host a virtual Student Research Week each year
The Full Re-Ionization of Helium
Observations of resolved HeII Lyman alpha absorption in spectra of two QSO's
suggest that the epoch of helium ionization occurred at z~3. Proximity zones in
the spectra of the quasars (z=3.18, 3.285) at 304 A resemble Stromgren spheres,
suggesting that the intergalactic medium is only singly ionized in helium. We
present models of the proximity effect which include the full physics of the
ionization, heating and cooling and an accurately simulated inhomogeneous gas
distribution. In these models the underdense intergalactic medium is heated to
at least 10,000-20,000 K after cooling to as low as a few 1000 K due to
cosmological expansion, with higher temperatures achieved farther away from the
quasar due to absorption-hardened ionizing spectra. The quasars turn on for a
few times 10^7 years with a fairly steady flux output at 228 A comparable to
the 304 A flux output directly observed with HST. The recoveries in the spectra
occur naturally due to voids in the IGM and may provide a fairly
model-independent probe of the baryon density.Comment: 5 pages, 3 figures, to appear in the proceedings of "After the Dark
Ages: When Galaxies were Young (the Universe at 2<z<5)", 9th Annual October
Astrophysics Conference in Marylan
Trade imbalance in international message telephone services
An econometric model is estimated to identify determinants of trade imbalance in international message telephone services markets. Results indicate that asymmetric market structure is important in explaining bilateral market imbalances for high income country pairs. For low and high income country pairs, GDP per capita is the dominant cause of traffic imbalances. The findings suggest that telecommunications liberalization policies are effective in reducing distortions in international traffic flows and settlement payments. However, liberalization should be accompanied by developmental programmes that enhance income per capita and telecommunications network investment in developing countries. Such programmes may be effective in providing a more equitable distribution of the gains from telecommunications reform across countries.Trade imbalance; international message telephone services
Horizontal transmission of Escherichia coli O157:H7 during cattle housing, survival kinetics in feces and water of Escherichia coli O157:H7 and characterisation of E. coli O157:H7 isolates from cattle faeces and a feedlot environment
End of project reportTeagasc acknowledges with gratitude the support of European Union Structural Funds (EAGGF) in financing this research projectEscherichia coli O157:H7 can cause severe illness and in some cases leading to death. Cattle are the main reservoir with transmission to humans occurring through contamination of food or the environment. Improved understanding of the survival and transmission and survival of E. coli O157:H7 on the farm is essential for developing future controls of this pathogen. This study showed that transmission of E. coli O157:H7 can occur rapidly in groups of housed cattle, with contamination of the pens and hides occurring in 24 hrs. The inoculation dose for cattle is lower than previously reported. Ingestion of bacteria from the hide through social grooming is important for pathogen transmission in housed cattle along with faecal contamination of the environment. Sampling hide will improve the estimation of prevalence of E. coli O157:H7 in pens
Predictable hydrodynamic conditions explain temporal variations in the density of benthic foraging seabirds in a tidal stream environment
VC International Council for the Exploration of the Sea 2016. James J. Waggitt was funded by a NERC Case studentship supported by OpenHydro Ltd and Marine Scotland Science (NE/J500148/1). Shore-based surveys were funded by a NERC (NE/J004340/1) and a Scottish National Heritage (SNH) grant. FVCOM was funded by a NERC grant (NE/J004316/1). The bathymetry data used in hydrodynamic models (HI 1122 Sanday Sound to Westray Firth) was collected by the Maritime and Coastguard Agency (MCA) as part of the UK Civil Hydrography Programme. We wish to thank Christina Bristow, Matthew Finn and Jennifer Norris at the European Marine Energy Centre (EMEC); Ian Davies at Marine Scotland Science; Gail Davoren, Shaun Fraser, Pauline Goulet, Alex Robbins and Helen Wade for invaluable discussions; Thomas Cornulier, Alex Douglas, James Grecian and Samantha Patrick for their help with statistical analysis; and Jenny Campbell and the Cockram family for assistance during fieldwork.Peer reviewedPublisher PD
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