133,518 research outputs found
‘Doing research’ with gypsy-travellers in England: reflections on experience and practice
In order to bring the lives of Gypsy–Travellers in line with the sustainable communities’ agenda, there is now a duty for local planning authorities in England to assess the accommodation and related needs of Gypsy–Travellers. As such, there has been an increase in research, which aims to ‘find out’ more about these communities. This article explores some of the issues that researchers should consider when carrying out research with Gypsy–
Travellers. It focuses specifically on issues around identifying and engaging with members of the Gypsy and Traveller communities, offering some strategies and solutions based on the experiences of the authors and other researchers
Independent Orbiter Assessment (IOA): Assessment of the electrical power generation/fuel cell powerplant subsystem FMEA/CIL
Results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Electrical Power Generation/Fuel Cell Powerplant (EPG/FCP) hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. A resolution of each discrepancy from the comparison was provided through additional analysis as required. This report documents the results of that comparison for the Orbiter EPG/FCP hardware
An experimental documentation of a separated trailing-edge flow at a transonic Mach number
A detailed experiment on the separated flow field at a sharp trailing edge is described and documented. The separated flow is a result of sustained adverse pressure gradients. The experiment was conducted using an elongated airfoil-like model at a transonic Mach number and at a high Reynolds number of practical interest. Measurements made include surface pressures and detailed mean and turbulence flow quantities in the region just upstream of separation to downstream into the near-wake, following wake closure. The data obtained are presented mostly in tabular form. These data are of sufficient quality and detail to be useful as a test case for evaluating turbulence models and calculation methods
Exploring the vs relation with flux transport dynamo models of solar-like stars
Aims: To understand stellar magnetism and to test the validity of the
Babcock-Leighton flux transport mean field dynamo models with stellar activity
observations Methods: 2-D mean field dynamo models at various rotation rates
are computed with the STELEM code to study the sensitivity of the activity
cycle period and butterfly diagram to parameter changes and are compared to
observational data. The novelty is that these 2-D mean field dynamo models
incorporate scaling laws deduced from 3-D hydrodynamical simulations for the
influence of rotation rate on the amplitude and profile of the meridional
circulation. These models make also use of observational scaling laws for the
variation of differential rotation with rotation rate. Results: We find that
Babcock-Leighton flux transport dynamo models are able to reproduce the change
in topology of the magnetic field (i.e. toward being more toroidal with
increasing rotation rate) but seem to have difficulty reproducing the cycle
period vs activity period correlation observed in solar-like stars if a
monolithic single cell meridional flow is assumed. It may however be possible
to recover the vs relation with more complex meridional
flows, if the profile changes in a particular assumed manner with rotation
rate. Conclusions: The Babcock-Leighton flux transport dynamo model based on
single cell meridional circulation does not reproduce the vs
relation unless the amplitude of the meridional circulation is
assumed to increase with rotation rate which seems to be in contradiction with
recent results obtained with 3-D global simulations.Comment: 12 pages, 8 figures, accepted for publication by A&A 1: AIM,
CEA/DSM-CNRS-Univ. Paris 7, IRFU/SAp, France, 2: D.A.M.T.P., Centre for
Mathematical Sciences, Univ. of Cambridge, UK, 3: JILA and Department of
Astrophysical and Planetary Sciences, Univ. of Colorado, US
Independent Orbiter Assessment (IOA): Analysis of the electrical power generation/fuel cell powerplant subsystem
Results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Electrical Power Generation (EPG)/Fuel Cell Powerplant (FCP) hardware. The EPG/FCP hardware is required for performing functions of electrical power generation and product water distribution in the Orbiter. Specifically, the EPG/FCP hardware consists of the following divisions: (1) Power Section Assembly (PSA); (2) Reactant Control Subsystem (RCS); (3) Thermal Control Subsystem (TCS); and (4) Water Removal Subsystem (WRS). The IOA analysis process utilized available EPG/FCP hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode
Monogroove heat pipe design: Insulated liquid channel with bridging wick
A screen mesh artery supported concentrically within the evaporator section of a heat pipe liquid channel retains liquid in the channel. Continued and uniform liquid feed to the heat pipe evaporation section (20) during periods of excessive heat transfer is assured. The overall design provides high evaporation and condensation film coefficients for the working fluid by means of the circumferential grooves in the walls of the vapor channel, while not interfering with the overall heat transport capability of the axial groove. The design has particular utility in zero-g environments
Attitudes in Physics Education: An Alternative Approach to Teaching Physics to Non-Science College Students
In this article, we present an alternative way of teaching conceptual physics for non-science majors by depicting the role of physics in today\u27s technology. The goal of this approach is to increase in the minds of non-science students the acceptance of physics as a useful component in general education, and as a major tool in comprehending the present-day technological world experienced by students outside the classroom
A retrospective segmentation analysis of placental volume by magnetic resonance imaging from first trimester to term gestation
Background
Abnormalities of the placenta affect 5–7% of pregnancies. Because disturbances in fetal growth are often preceded by dysfunction of the placenta or attenuation of its normal expansion, placental health warrants careful surveillance. There are limited normative data available for placental volume by MRI.
Objective
To determine normative ranges of placental volume by MRI throughout gestation.
Materials and methods
In this cross-sectional retrospective analysis, we reviewed MRI examinations of pregnant females obtained between 2002 and 2017 at a single institution. We performed semi-automated segmentation of the placenta in images obtained in patients with no radiologic evidence of maternal or fetal pathology, using the Philips Intellispace Tumor Tracking Tool.
Results
Placental segmentation was performed in 112 women and had a high degree of interrater reliability (single-measure intraclass correlation coefficient =0.978 with 95% confidence interval [CI] 0.956, 0.989; P<0.001). Normative data on placental volume by MRI increased nonlinearly from 6 weeks to 39 weeks of gestation, with wider variability of placental volume at higher gestational age (GA). We fit placental volumetric data to a polynomial curve of third order described as placental volume = –0.02*GA3 + 1.6*GA2 – 13.3*GA + 8.3. Placental volume showed positive correlation with estimated fetal weight (P=0.03) and birth weight (P=0.05).
Conclusion
This study provides normative placental volume by MRI from early first trimester to term gestation. Deviations in placental volume from normal might prove to be an imaging biomarker of adverse fetal health and neonatal outcome, and further studies are needed to more fully understand this metric. Assessment of placental volume should be considered in all routine fetal MRI examinations
Temperature equilibration in a fully ionized plasma: electron-ion mass ratio effects
Brown, Preston, and Singleton (BPS) produced an analytic calculation for
energy exchange processes for a weakly to moderately coupled plasma: the
electron-ion temperature equilibration rate and the charged particle stopping
power. These precise calculations are accurate to leading and next-to-leading
order in the plasma coupling parameter, and to all orders for two-body quantum
scattering within the plasma. Classical molecular dynamics can provide another
approach that can be rigorously implemented. It is therefore useful to compare
the predictions from these two methods, particularly since the former is
theoretically based and the latter numerically. An agreement would provide both
confidence in our theoretical machinery and in the reliability of the computer
simulations. The comparisons can be made cleanly in the purely classical
regime, thereby avoiding the arbitrariness associated with constructing
effective potentials to mock up quantum effects. We present here the classical
limit of the general result for the temperature equilibration rate presented in
BPS. We examine the validity of the m_electron/m_ion --> 0 limit used in BPS to
obtain a very simple analytic evaluation of the long-distance, collective
effects in the background plasma.Comment: 14 pages, 4 figures, small change in titl
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