3,377 research outputs found

    Coupled Fluids-Radiation Analysis of a High-Mass Mars Vehicle

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    The NEQAIR line-by-line radiation code has been incorporated into the DPLR Navier-Stokes flow solver such that the NEQAIR subroutines are now callable functions of DPLR. The coupled DPLR-NEQAIR code was applied to compute the convective and radiative heating rates over high-mass Mars entry vehicles. Two vehicle geometries were considered - a 15 m diameter 70-degree sphere cone configuration and a slender, mid-L/D vehicle with a diameter of 5 m called an Ellipsled. The entry masses ranged from 100 to 165 metric tons. Solutions were generated for entry velocities ranging from 6.5 to 9.1 km/s. The coupled fluids-radiation solutions were performed at the peak heating location along trajectories generated by the Traj trajectory analysis code. The impact of fluids-radiation coupling is a function of the level of radiative heating and the freestream density and velocity. For the high-mass Mars vehicles examined in this study, coupling effects were greatest for entry velocities above 8.5 km/s where the surface radiative heating was reduced by up 17%. Generally speaking, the Ellipsled geometry experiences a lower peak radiative heating rate but a higher peak turbulent convective heating rate than the MSL-based vehicle

    Comparison of Nonequilibrium Solution Algorithms Applied to Chemically Stiff Hypersonic Flows

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    Three solution algorithms, explicit under-relaxation, point implicit, and lower-upper symmetric Gauss-Seidel, are used to compute nonequilibrium flow around the Apollo 4 return capsule at the 62-km altitude point in its descent trajectory. By varying the Mach number, the efficiency and robustness of the solution algorithms were tested for different levels of chemical stiffness.The performance of the solution algorithms degraded as the Mach number and stiffness of the flow increased. At Mach 15 and 30, the lower-upper symmetric Gauss-Seidel method produces an eight order of magnitude drop in the energy residual in one-third to one-half the Cray C-90 computer time as compared to the point implicit and explicit under-relaxation methods. The explicit under-relaxation algorithm experienced convergence difficulties at Mach 30 and above. At Mach 40 the performance of the lower-upper symmetric Gauss-Seidel algorithm deteriorates to the point that it is out performed by the point implicit method. The effects of the viscous terms are investigated. Grid dependency questions are explored

    'Bad teacher? Using films as texts when teaching business ethics: Exploring the issues'

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    The contemporary teaching of business ethics necessarily involves the recognition that texts, materials and modes of assessment ought to be rendered appealing to students, while at the same time ensuring the quality of teaching. Prima facie the use of film can be seen as a way to address this dilemma: Students may be attracted to the ‘delivery’ of course content through the medium of film as opposed to, for example, standard lecture format, participation in online activities or, at a stretch, reading and writing. An alternative scenario can also be envisioned where the use of film in teaching business ethics is bad professional practice, pandering to both the requirement for positive assessments from students and for technological change. This paper discusses these issues by critically examining the films recommended by a contemporary business ethics text, Crane and Matten (2010). We identify significant problems with the use of two films, The Corporation (2005) and Michael Clayton (2007). Against our own criticisms of these two texts, the paper then focuses upon Ken Loach’s (2007) film It’s a Free World, arguing that it is a useful text for the illustration of what students, more often than not, regard as the clichéd issue of unskilled foreign wage labourers being exploited in ‘advanced’ western economies. Despite the considerable virtues of Loach’s particular text, we argue that any recourse to film as an alternative method of examining a range of issues in business ethics has to be treated with caution

    Nectarivory in the Rockwarbler 'Origma solitaria'

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    The Rockwarbler 'Origma solitaria' is restricted to the sedimentary-rock formations around the Sydney region of New South Wales and, like other species in the Acanthizidae, is mainly insectivorous, although its diet is considered poorly known. Here we report on two observations of nectarivory, a food source not previously reported for this species. They involved Rockwarblers feeding at flowers of Heath-leaved Banksia 'Banksia ericifolia' at two locations

    Material Response Analysis of a Titan Entry Heatshield

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    Accurate calculation of thermal protection material response is critical to the vehicle design for missions to the Saturn moon Titan. In this study, Icarus, a three-dimensional, unstructured, finite-volume material response solver under active development at NASA Ames Research Center, is used to compute the in-depth material response of the Huygens spacecraft along its November 11 entry trajectory. The heatshield analyzed in this study consists of a five-layer stack-up of Phenolic Impregnated Carbon Ablator (PICA), aluminum honeycomb, adhesive, and face sheetmaterials. During planetary entry, the PICA outer layer is expected to undergo pyrolysis. A surface energy balance boundary condition that captures both time- and spatial-variance of surface properties during entry is used in the simulation

    Coupled Fluids-Radiation Analysis of a High-Mass Mars Entry Vehicle

    Get PDF
    The NEQAIR line-by-line radiation code has been incorporated into the DPLR Navier-Stokes flow solver such that the NEQAIR subroutines are now callable functions of DPLR. The coupled DPLR-NEQAIR code was applied to compute the convective and radiative heating rates over high-mass Mars entry vehicles. Two vehicle geometries were considered - a 15 m diameter 70-degree sphere cone configuration and a slender, mid-L/D vehicle with a diameter of 5 m called an Ellipsled. The entry masses ranged from 100 to 165 metric tons. Solutions were generated for entry velocities ranging from 6.5 to 9.1 km/s. The coupled fluids-radiation solutions were performed at the peak heating location along trajectories generated by the Traj trajectory analysis code. The impact of fluids-radiation coupling is a function of the level of radiative heating and the freestream density and velocity. For the high-mass Mars vehicles examined in this study, coupling effects were greatest for entry velocities above 8.5 km/s where the surface radiative heating was reduced by up 17%. Generally speaking, the Ellipsled geometry experiences a lower peak radiative heating rate but a higher peak turbulent convective heating rate than the MSL-based vehicle

    Chloroplast DNA and molecular phylogeny

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    The small, relatively constant size and conservative evolution of chloroplast DNA (cpDNA) make it an ideal molecule for tracing the evolutionary history of plant species. At lower taxonomic levels, cpDNA variation is easily and conveniently assayed by comparing restriction patterns and maps, while at higher taxonomic levels, DNA sequencing and inversion analysis are the methods of choice for comparing chloroplast genomes. The study of cpDNA variation has already yielded important new insights into the origin and evolution of many agriculturally important crop plants, and promises to significantly enhance our phylogenetic understanding of the major lines of descent among land plants and algae.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50180/1/950020607_ftp.pd
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