1,729 research outputs found
A Turbine Based Combined Cycle Engine Inlet Model and Mode Transition Simulation Based on HiTECC Tool
An inlet system is being tested to evaluate methodologies for a turbine based combined cycle propulsion system to perform a controlled inlet mode transition. Prior to wind tunnel based hardware testing of controlled mode transitions, simulation models are used to test, debug, and validate potential control algorithms. One candidate simulation package for this purpose is the High Mach Transient Engine Cycle Code (HiTECC). The HiTECC simulation package models the inlet system, propulsion systems, thermal energy, geometry, nozzle, and fuel systems. This paper discusses the modification and redesign of the simulation package and control system to represent the NASA large-scale inlet model for Combined Cycle Engine mode transition studies, mounted in NASA Glenn s 10- by 10-Foot Supersonic Wind Tunnel. This model will be used for designing and testing candidate control algorithms before implementation
The influence of the frontal surface area and swim velocity variation in front crawl active drag
Purpose The aims of this study were to 1) compare active drag (D-a) calculation between a single land-based measurement of frontal surface area (FSA) and in-water FSA measures obtained at key events of the arm pull (1, right upper-limb catch; 2, right upper-limb insweep; 3, right upper-limb exit and left upper-limb catch; 4, left upper-limb insweep; and 5, left upper-limb exit and right upper-limb catch) at front crawl swimming, and 2) compare mechanical power variables computed based on these two approaches. Methods Seventeen swimmers (11, male; 6, female; 16.15 +/- 0.94 yr old) were recruited. The FSA was measured based on two approaches: (i) nonvariation, that is, assuming a constant value, and (ii) variation, that is, calculated in each key event of the front crawl swim. Active drag based on a nonvariation of the FSA was measured using the Velocity Perturbation method. Active drag based on a variation approach was measured in each key event of the front crawl according to the law of linear motion. Pairedt-test (P <= 0.05), simple linear regression models, and Bland-Altman plots between assessment methods (variation vs nonvariation) were computed. Results The FSA (variation) was higher than when assuming a nonvariation (0.1110 +/- 0.010 vs 0.0968 +/- 0.010 m(2), Delta = 15.69%,t= 4.40,P< 0.001,d= 0.95). Active drag (variation) was also significantly higher than when assuming a nonvariation (88.44 +/- 25.92 vs 75.41 +/- 15.11 N, Delta = 16.09%,t= 3.66,P= 0.002,d= 0.61). Conclusions Besides the FSA, swim velocity also changes during the front crawl arm pull. The variation of both variables had a significant effect on the active drag measurement and consequently on mechanical power and total power input variables.This work is supported by national funds (FCT-Portuguese Foundation for Science and Technology) under the project UIDB/04045/2020. There were no conflicts of interests.
The results of this study do not constitute endorsement by the American College of Sports Medicine. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.info:eu-repo/semantics/publishedVersio
Environmental Effects on Glass Fiber Reinforced Polyester and Vinylester Composites
The effects of environment on glass fiber reinforced polyester and vinylester composites immersed in liquids and in humid air were investi gated. Tests were performed at temperatures 23 C and 93 C with the materials exposed to humid air at 50 and 100 percent relative humidities, and to five different liquids: saturated salt water, No. 2 diesel fuel, lubrica ting oil, antifreeze, and indolene. Changes in weight, ultimate tensile strength, tensile modulus, short beam shear strength, and shear modulus were measured over a six month period, and the effects of the environment on these parameters were assessed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66642/2/10.1177_002199838001400304.pd
Quantum Walks driven by many coins
Quantum random walks have been much studied recently, largely due to their
highly nonclassical behavior. In this paper, we study one possible route to
classical behavior for the discrete quantum random walk on the line: the use of
multiple quantum ``coins'' in order to diminish the effects of interference
between paths. We find solutions to this system in terms of the single coin
random walk, and compare the asymptotic limit of these solutions to numerical
simulations. We find exact analytical expressions for the time-dependence of
the first two moments, and show that in the long time limit the ``quantum
mechanical'' behavior of the one-coin walk persists. We further show that this
is generic for a very broad class of possible walks, and that this behavior
disappears only in the limit of a new coin for every step of the walk.Comment: 36 pages RevTeX 4.0 + 5 figures (encapsulated Postscript). Submitted
to Physical Review
Fluence Dependence of Charge Collection of irradiated Pixel Sensors
The barrel region of the CMS pixel detector will be equipped with ``n-in-n''
type silicon sensors. They are processed on DOFZ material, use the moderated
p-spray technique and feature a bias grid. The latter leads to a small fraction
of the pixel area to be less sensitive to particles. In order to quantify this
inefficiency prototype pixel sensors irradiated to particle fluences between
and 2.6\times 10^{15} \Neq have been bump bonded to
un-irradiated readout chips and tested using high energy pions at the H2 beam
line of the CERN SPS. The readout chip allows a non zero suppressed analogue
readout and is therefore well suited to measure the charge collection
properties of the sensors.
In this paper we discuss the fluence dependence of the collected signal and
the particle detection efficiency. Further the position dependence of the
efficiency is investigated.Comment: 11 Pages, Presented at the 5th Int. Conf. on Radiation Effects on
Semiconductor Materials Detectors and Devices, October 10-13, 2004 in
Florence, Italy, v3: more typos corrected, minor changes required by the
refere
He Scattering from Compact Clusters and from Diffusion-Limited Aggregates on Surfaces: Observable Signatures of Structure
The angular intensity distribution of He beams scattered from compact
clusters and from diffusion limited aggregates, epitaxially grown on metal
surfaces, is investigated theoretically. The purpose is twofold: to distinguish
compact cluster structures from diffusion limited aggregates, and to find
observable {\em signatures} that can characterize the compact clusters at the
atomic level of detail. To simplify the collision dynamics, the study is
carried out in the framework of the sudden approximation, which assumes that
momentum changes perpendicular to the surface are large compared with momentum
transfer due to surface corrugation. The diffusion limited aggregates on which
the scattering calculations were done, were generated by kinetic Monte Carlo
simulations. It is demonstrated, by focusing on the example of compact Pt
Heptamers, that signatures of structure of compact clusters may indeed be
extracted from the scattering distribution. These signatures enable both an
experimental distinction between diffusion limited aggregates and compact
clusters, and a determination of the cluster structure. The characteristics
comprising the signatures are, to varying degrees, the Rainbow, Fraunhofer,
specular and constructive interference peaks, all seen in the intensity
distribution. It is also shown, how the distribution of adsorbate heights above
the metal surface can be obtained by an analysis of the specular peak
attenuation. The results contribute to establishing He scattering as a powerful
tool in the investigation of surface disorder and epitaxial growth on surfaces,
alongside with STM.Comment: 41 pages, 16 postscript figures. For more details see
http://www.fh.huji.ac.il/~dan
Efficiency of the dynamical mechanism
The most extreme starbursts occur in galaxy mergers, and it is now
acknowledged that dynamical triggering has a primary importance in star
formation. This triggering is due partly to the enhanced velocity dispersion
provided by gravitational instabilities, such as density waves and bars, but
mainly to the radial gas flows they drive, allowing large amounts of gas to
condense towards nuclear regions in a small time scale. Numerical simulations
with several gas phases, taking into account the feedback to regulate star
formation, have explored the various processes, using recipes like the Schmidt
law, moderated by the gas instability criterion. May be the most fundamental
parameter in starbursts is the availability of gas: this sheds light on the
amount of external gas accretion in galaxy evolution. The detailed mechanisms
governing gas infall in the inner parts of galaxy disks are discussed.Comment: 6 pages, 3 figures, to be published in "Starbursts - From 30 Doradus
to Lyman break galaxies", ed. R. de Grijs and R. Gonzalez-Delgad
Vanishing spin alignment : experimental indication of triaxial nuclear molecule
Fragment-fragment- coincidences have been measured for at an energy corresponding to the population of a conjectured
resonance in Ni. Fragment angular distributions as well as -ray
angular correlations indicate that the spin orientations of the outgoing
fragments are perpendicular to the orbital angular momentum. This differs from
the and the resonances, and
suggests two oblate nuclei interacting in an equator-to-equator
molecular configuration.Comment: 14 pages standard REVTeX file, 3 ps Figures -- Accepted for
publication in Physical Review C (Rapid Communication
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