15,902 research outputs found

### Generic hypersonic vehicle performance model

An integrated computational model of a generic hypersonic vehicle was developed for the purpose of determining the vehicle's performance characteristics, which include the lift, drag, thrust, and moment acting on the vehicle at specified altitude, flight condition, and vehicular configuration. The lift, drag, thrust, and moment are developed for the body fixed coordinate system. These forces and moments arise from both aerodynamic and propulsive sources. SCRAMjet engine performance characteristics, such as fuel flow rate, can also be determined. The vehicle is assumed to be a lifting body with a single aerodynamic control surface. The body shape and control surface location are arbitrary and must be defined. The aerodynamics are calculated using either 2-dimensional Newtonian or modified Newtonian theory and approximate high-Mach-number Prandtl-Meyer expansion theory. Skin-friction drag was also accounted for. The skin-friction drag coefficient is a function of the freestream Mach number. The data for the skin-friction drag coefficient values were taken from NASA Technical Memorandum 102610. The modeling of the vehicle's SCRAMjet engine is based on quasi 1-dimensional gas dynamics for the engine diffuser, nozzle, and the combustor with heat addition. The engine has three variable inputs for control: the engine inlet diffuser area ratio, the total temperature rise through the combustor due to combustion of the fuel, and the engine internal expansion nozzle area ratio. The pressure distribution over the vehicle's lower aft body surface, which acts as an external nozzle, is calculated using a combination of quasi 1-dimensional gas dynamic theory and Newtonian or modified Newtonian theory. The exhaust plume shape is determined by matching the pressure inside the plume, calculated from the gas dynamic equations, with the freestream pressure, calculated from Newtonian or Modified Newtonian theory. In this manner, the pressure distribution along the vehicle after body expansion surface is then determined. The aerodynamic modeling, the engine modeling, and the exhaust plume analysis are described in more detail. A description of the computer code used to perform the above calculations is given and an input/output example is then given. The computer code is available on a Macintosh floppy disk

### Which point sets admit a k-angulation?

For k >= 3, a k-angulation is a 2-connected plane graph in which every
internal face is a k-gon. We say that a point set P admits a plane graph G if
there is a straight-line drawing of G that maps V(G) onto P and has the same
facial cycles and outer face as G. We investigate the conditions under which a
point set P admits a k-angulation and find that, for sets containing at least
2k^2 points, the only obstructions are those that follow from Euler's formula.Comment: 13 pages, 7 figure

### A Corn Stover Supply Logistics System

Published in Applied Engineering in Agriculture, Vol. 26(3): 455‐461, 2010. American Society of Agricultural and Biological EngineersCorn stover, Economics, GHG emission, Logistics, Roll press compaction, Tub grinding, Agribusiness, Crop Production/Industries,

### High performance forward swept wing aircraft

A high performance aircraft capable of subsonic, transonic and supersonic speeds employs a forward swept wing planform and at least one first and second solution ejector located on the inboard section of the wing. A high degree of flow control on the inboard sections of the wing is achieved along with improved maneuverability and control of pitch, roll and yaw. Lift loss is delayed to higher angles of attack than in conventional aircraft. In one embodiment the ejectors may be advantageously positioned spanwise on the wing while the ductwork is kept to a minimum

### Microbial Biosafety of Pilot-scale Bioreactor Treating MTBE and TBA-contaminated Drinking Water Supply

A pilot-scale sand-based fluidized bed bioreactor (FBBR) was utilized to treat both methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) from a contaminated aquifer. To evaluate the potential for re-use of the treated water, we tested for a panel of water quality indicator microorganisms and potential waterborne pathogens including total coliforms, Escherichia coli, Salmonella and Shigella spp., Campylobacter jejuni, Aeromonas hydrophila, Legionella pneumophila, Vibrio cholerae, Yersinia enterocolytica and Mycobacterium avium in both influent and treated waters from the bioreactor. Total bacteria decreased during FBBR treatment. E. coli, Salmonella and Shigella spp., C. jejuni, V. cholerae, Y. enterocolytica and M. avium were not detected in aquifer water or bioreactor treated water samples. For those pathogens detected, including total coliforms, L. pneumophila and A. hydrophila, numbers were usually lower in treated water than influent samples, suggesting removal during treatment. The detection of particular bacterial species reflected their presence or absence in the influent waters

### Thoughts on Barnette's Conjecture

We prove a new sufficient condition for a cubic 3-connected planar graph to
be Hamiltonian. This condition is most easily described as a property of the
dual graph. Let $G$ be a planar triangulation. Then the dual $G^*$ is a cubic
3-connected planar graph, and $G^*$ is bipartite if and only if $G$ is
Eulerian. We prove that if the vertices of $G$ are (improperly) coloured blue
and red, such that the blue vertices cover the faces of $G$, there is no blue
cycle, and every red cycle contains a vertex of degree at most 4, then $G^*$ is
Hamiltonian.
This result implies the following special case of Barnette's Conjecture: if
$G$ is an Eulerian planar triangulation, whose vertices are properly coloured
blue, red and green, such that every red-green cycle contains a vertex of
degree 4, then $G^*$ is Hamiltonian. Our final result highlights the
limitations of using a proper colouring of $G$ as a starting point for proving
Barnette's Conjecture. We also explain related results on Barnette's Conjecture
that were obtained by Kelmans and for which detailed self-contained proofs have
not been published.Comment: 12 pages, 7 figure

### A simulation study of the flight dynamics of elastic aircraft. Volume 1: Experiment, results and analysis

The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot

### A simulation study of the flight dynamics of elastic aircraft. Volume 2: Data

The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research project. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot

### Correlation Between Student Collaboration Network Centrality and Academic Performance

We compute nodal centrality measures on the collaboration networks of
students enrolled in three upper-division physics courses, usually taken
sequentially, at the Colorado School of Mines. These are complex networks in
which links between students indicate assistance with homework. The courses
included in the study are intermediate Classical Mechanics, introductory
Quantum Mechanics, and intermediate Electromagnetism. By correlating these
nodal centrality measures with students' scores on homework and exams, we find
four centrality measures that correlate significantly with students' homework
scores in all three courses: in-strength, out-strength, closeness centrality,
and harmonic centrality. These correlations suggest that students who not only
collaborate often, but also collaborate significantly with many different
people tend to achieve higher grades. Centrality measures between simultaneous
collaboration networks (analytical vs. numerical homework collaboration)
composed of the same students also correlate with each other, suggesting that
students' collaboration strategies remain relatively stable when presented with
homework assignments targeting different skills. Additionally, we correlate
centrality measures between collaboration networks from different courses and
find that the four centrality measures with the strongest relationship to
students' homework scores are also the most stable measures across networks
involving different courses. Correlations of centrality measures with exam
scores were generally smaller than the correlations with homework scores,
though this finding varied across courses.Comment: 10 pages, 4 figures, submitted to Phys. Rev. PE

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