1,748 research outputs found
Non-Isothermal Mercury Pipe Flow Turbulent Characteristics
The turbulence structure of fully-developed mercury pipe flow, with and without heat transfer, was studied using hot-film anemometry at Reynolds number of approximately 50,000. Single sensors and slanted multiple sensors were used to obtain the radial distribution of axial fluctuating velocity and temperature quantities. Isothermal data were generally in good agreement with comparable air data indicating similar velocity structure. Temperature intensity data agreed with other data in liquid metals.
Axial and radial turbulent heat flux results were somewhat inconclusive. Spectra and turbulence scales were developed providing a picture of the structure
Scaling of heat transfer augmentation due to mechanical distortions in hypervelocity boundary layers
Surveys of Southern Flying Squirrel Activity Following Timber Harvest in Southern Indiana
Southern flying squirrels (Glaucomys volans) are gliding small mammals that are ecologically important seed dispersers and prey species across their wide range, which extends from southern Canada to Central America. Because of their reliance on forest structure for efficient movement and on forest composition for hard mast production to provide winter food items, habitat use by G. volans may be impacted by timber harvest. Responses of G. volans to timber harvests remains understudied throughout their range, and studies are especially lacking within the Central Hardwoods Region that includes Indiana. Our study in the Hardwood Ecosystem Experiment (HEE) in southern Indiana examined responses in G. volans activity to even- and uneven-aged forestry using passive acoustic sampling. We examined data from Anabat II recorders positioned within and around harvested areas for ultrasonic G. volans vocalizations to determine activity levels in uneven-aged, even-aged, and no harvest treatments in the year following treatment. We identified G. volans calls via comparison to a library of known calls. We used the mean number of calls per night as an estimate of G. volans activity. Our preliminary results found G. volans activity in the treatment area edge and surrounding forest for all treatment types. We found the greatest activity in the interior of uneven-aged patch cuts, whereas even-aged clearcuts and no harvest treatment interiors had lower levels of activity. We found no activity in the interior of even-aged shelterwoods. These results suggest that uneven-aged harvests have less impact on G. volans activity than even-aged forest management
Expansion Tube Investigation of Shock Stand-Off Distances in High-Enthalpy CO_2 Flow Over Blunt Bodies
The shock standoff distance in front of a blunt body is sensitive to the thermochemical
state of the free stream. Recently, experimental and numerical studies
have reported significantly different bow shock profiles in high-enthalpy carbon
dioxide flows, a discrepancy that may result from non-equilibrium processes during
flow acceleration in ground-based facilities. In this work, an expansion tube is used
to create a Mach 5.7 carbon dioxide flow, matching the stagnation enthalpy and
the velocity of previous studies. Images of shock layers are obtained for spherical
geometries and a scaled model of the Mars Science Lander. Different sphere
diameters are used in order to access non-equilibrium and equilibrium stagnation
line shock profiles predicted by theory. Mars Science Lander profiles at zero angle
of attack are in good agreement with available data from the LENS X expansion
tunnel facility, confirming results are facility-independent for the same type of flow
acceleration, and indicating the flow velocity is a suitable first-order matching parameter
for comparative testing. Heat transfer measurements on the Mars Science
Lander are also presented for the three different angle of attacks, and the results
are consistent with previous studies. Initial results from a proposed organo-metallic
based emission spectroscopy technique for bow shock layer interrogation are also
presented
Effectiveness of Gaming in Creating Cultural Awareness
Despite the emphasis on cultural competency education in the United States for the past three decades, inequities and disparities in healthcare continue to persist, particularly among minority populations. With the current growing gap in provider and patient cultural congruence, how effectively we train students to work with diverse populations in healthcare settings warrants attention. This article presents the results of a qualitative study on the effectiveness of experiential learning, in the form of the game BaFa’ BaFa,’ in raising cultural awareness among students of health professions. Using thematic analysis, the authors analyzed written reflections from student participants. The findings support earlier studies, conducted mainly outside of healthcare, on the effectiveness of gaming in nurturing cultural awareness
Evaluation of Hypervelocity Carbon Dioxide Blunt Body Experiments in an Expansion Tube Facility
This work represents efforts to study high-enthalpy carbon dioxide flows in anticipation
of the upcoming Mars Science Laboratory (MSL) and future missions. The
current study extends the previous presentation of experimental results by the comparison
now with axisymmetric simulations incorporating detailed thermochemical
modeling. The work is motivated by observed anomalies between experimental
and numerical studies in hypervelocity impulse facilities. In this work, experiments
are conducted in the Hypervelocity Expansion Tube (HET) which, by virtue of its
flow acceleration process, exhibits minimal freestream dissociation in comparison
to reflected shock tunnels. This simplifies the comparison with computational result
as freestream dissociation and considerable thermochemical excitation can be
neglected. Shock shapes of the Laboratory aeroshell and spherical geometries are
compared with numerical simulations. In an effort to address surface chemistry
issues arising from high-enthalpy carbon dioxide ground-test based experiments,
spherical stagnation point and aeroshell heat transfer distributions are also compared
with simulation. The shock stand-off distance has been identified in the
past as sensitive to the thermochemical state and as such, is used here as an experimental
measureable for comparison with CFD and two different theoretical
models. For low-density, small-scale experiments it is seen that models based upon
assumptions of large binary scaling values are unable to match the experimental
and numerical results. Very good agreement between experiment and CFD is seen
for all shock shapes and heat transfer distributions fall within the non-catalytic and
super-catalytic solutions
Experimental and Numerical Investigation of Hypervelocity Carbon Dioxide Flow over Blunt Bodies
This paper represents ongoing efforts to study high-enthalpy carbon dioxide flows in anticipation of the upcoming
Mars Science Laboratory and future missions. The work is motivated by observed anomalies between experimental
and numerical studies in hypervelocity impulse facilities. In this study, experiments are conducted in the
hypervelocity expansion tube that, by virtue of its flow acceleration process, exhibits minimal freestream dissociation
in comparison with reflected shock tunnels, simplifying comparison with simulations. Shock shapes of the laboratory
aeroshell at angles of attack of 0, 11, and 16 deg and spherical geometries are in very good agreement with simulations
incorporating detailed thermochemical modeling. Laboratory shock shapes at a 0 deg of attack are also in good
agreement with data from the LENS X expansion tunnel facility, confirming results are facility-independent for the
same type of flow acceleration. The shock standoff distance is sensitive to the thermochemical state and is used as an
experimental measurable for comparison with simulations and two different theoretical models. For low-density
small-scale experiments, it is seen that models based upon assumptions of large binary scaling values do not match the
experimental and numerical results. In an effort to address surface chemistry issues arising in high-enthalpy groundtest
experiments, spherical stagnation point and aeroshell heat transfer distributions are also compared with the
simulation. Heat transfer distributions over the aeroshell at the three angles of attack are in reasonable agreement
with simulations, and the data fall within the noncatalytic and supercatalytic solutions
Are Causality Violations Undesirable?
Causality violations are typically seen as unrealistic and undesirable
features of a physical model. The following points out three reasons why
causality violations, which Bonnor and Steadman identified even in solutions to
the Einstein equation referring to ordinary laboratory situations, are not
necessarily undesirable. First, a space-time in which every causal curve can be
extended into a closed causal curve is singularity free--a necessary property
of a globally applicable physical theory. Second, a causality-violating
space-time exhibits a nontrivial topology--no closed timelike curve (CTC) can
be homotopic among CTCs to a point, or that point would not be causally well
behaved--and nontrivial topology has been explored as a model of particles.
Finally, if every causal curve in a given space-time passes through an event
horizon, a property which can be called "causal censorship", then that
space-time with event horizons excised would still be causally well behaved.Comment: Accepted in October 2008 by Foundations of Physics. Latex2e, 6 pages,
no figures. Presented at a seminar at the Universidad Nacional Autonoma de
Mexico. Version 2 was co-winner of the QMUL CTC Essay Priz
From a certain point of view: sensory phenomenological envisionings of running space and place
The precise ways in which we go about the mundane, repetitive, social actions of everyday life are central concerns of ethnographers and theorists working within the traditions of the sociology of the mundane and sociological phenomenology. In this article, we utilize insights derived from sociological phenomenology and the newly developing field of sensory sociology to investigate a particular, mundane, and embodied social practice, that of training for distance running in specific places: our favored running routes. For, despite a growing body of ethnographic studies of particular sports, little analytic attention has been devoted to the actual, concrete practices of “doing” or “producing” sporting activity, particularly from a sensory ethnographic perspective. Drawing upon data from a 2-year joint autoethnographic research project, here we explore the visual dimension, focusing upon three key themes in relation to our runners’ visualization of, respectively, (1) hazardous places, (2) performance places, (3) the time–space–place nexus
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