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  • 1
    Electronic Resource
    Electronic Resource
    An empirical comparison of distance matrix techniques for estimating codon usage divergence (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 533-536 
    Details
    ISSN: 1432-1432
    Keywords: Codon usage ; Phylogeny ; Distance matrices ; Ordination ; Clustering ; Apicomplexa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The quantitative description of codon usage divergence among taxa is a two-step process involving first the calculation of a standardized measure of intertaxon divergence for each possible pair of taxa followed by a summary and visual display of the patterns among the taxa inherent in these measures. Three different measures have been proposed in the literature, and three different summaries have been used. These different techniques are empirically compared using a data set consisting of gene sequences from seven species of Apicomplexa. The results suggest that the manhattan distance measure may be preferable to the use of the chisquare measure, although the separation of amino acid usage and codon usage by the genetic distance produces theoretical advantages. The multidimensional scaling ordination and unweighted pair-group clustering are both successful in displaying the patterns, while the eigenanalysis ordination is not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173423
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    Paper (German National Licenses)
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  • 2
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    Verification of Experimental Techniques for Flow Surface Determination (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The concept of a yield surface is central to the mathematical formulation of a classical plasticity theory. However, at elevated temperatures, material response can be highly time-dependent, which is beyond the realm of classical plasticity. Viscoplastic theories have been developed for just such conditions. In viscoplastic theories, the flow law is given in terms of inelastic strain rate rather than the inelastic strain increment used in time-independent plasticity. Thus, surfaces of constant inelastic strain rate or flow surfaces are to viscoplastic theories what yield surfaces are to classical plasticity. The purpose of the work reported herein was to validate experimental procedures for determining flow surfaces at elevated temperatures. Since experimental procedures for determining yield surfaces in axial/torsional stress space are well established, they were employed -- except inelastic strain rates were used rather than total inelastic strains. In yield-surface determinations, the use of small-offset definitions of yield minimizes the change of material state and allows multiple loadings to be applied to a single specimen. The key to the experiments reported here was precise, decoupled measurement of axial and torsional strain. With this requirement in mind, the performance of a high-temperature multi-axial extensometer was evaluated by comparing its results with strain gauge results at room temperature. Both the extensometer and strain gauges gave nearly identical yield surfaces (both initial and subsequent) for type 316 stainless steel (316 SS). The extensometer also successfully determined flow surfaces for 316 SS at 650 C. Furthermore, to judge the applicability of the technique for composite materials, yield surfaces were determined for unidirectional tungsten/Kanthal (Fe-Cr-Al).
    Keywords: Composite Materials
    Type: NASA-TM-107053 , E-9900 , NAS 1.15:107053
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Ceramic Matrix Composites (CMC) Life Prediction Development (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Advanced launch systems will very likely incorporate fiber reinforced ceramic matrix composites (CMC) in critical propulsion and airframe components. The use of CMC will save weight, increase operating margin, safety and performance, and improve reuse capability. For reusable and single mission use, accurate life prediction is critical to success. The tools to accomplish this are immature and not oriented toward the behavior of carbon fiber reinforced silicon carbide (C/SiC), the primary system of interest for many applications. This paper describes an approach and progress made to satisfy the need to develop an integrated life prediction system that addresses mechanical durability and environmental degradation.
    Keywords: Composite Materials
    Type: 26th Annual Conference on Composites, Materials and Structures; Jan 28, 2002 - Jan 31, 2002; Cape Caneveral, FL; United States
    Format: text
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  • 4
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    Ceramic Matrix Composites (CMC) Life Prediction Development - 2003 (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Accurate life prediction is critical to successful use of ceramic matrix composites (CMCs). The tools to accomplish this are immature and not oriented toward the behavior of carbon fiber reinforced silicon carbide (C/SiC), the primary system of interest for many reusable and single mission launch vehicle propulsion and airframe applications. This paper describes an approach and progress made to satisfy the need to develop an integrated life prediction system that addresses mechanical durability and environmental degradation of C/SiC.
    Keywords: Composite Materials
    Type: NASA/TM-2003-212493 , NAS 1.15.212493 , E-14042 , 27th Annual Conference on Composites, Materials and Structures; Jan 27, 2003 - Jan 31, 2003; Cape Canaveral, FL; United States
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  • 5
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    Ceramic Matrix Composites (CMC) Life Prediction Method Development (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Advanced launch systems (e.g., Reusable Launch Vehicle and other Shuttle Class concepts, Rocket-Based Combine Cycle, etc.), and interplanetary vehicles will very likely incorporate fiber reinforced ceramic matrix composites (CMC) in critical propulsion components. The use of CMC is highly desirable to save weight, to improve reuse capability, and to increase performance. CMC candidate applications are mission and cycle dependent and may include turbopump rotors, housings, combustors, nozzle injectors, exit cones or ramps, and throats. For reusable and single mission uses, accurate prediction of life is critical to mission success. The tools to accomplish life prediction are very immature and not oriented toward the behavior of carbon fiber reinforced silicon carbide (C/SiC), the primary system of interest for a variety of space propulsion applications. This paper describes an approach to satisfy the need to develop an integrated life prediction system for CMC that addresses mechanical durability due to cyclic and steady thermomechanical loads, and takes into account the impact of environmental degradation.
    Keywords: Composite Materials
    Type: NASA/TM-2000-210052 , E-12253 , NAS 1.15:210052 , Composites, Materials and Structures; Jan 24, 2000 - Jan 28, 2000; Cape Canaveral, FL; United States
    Format: application/pdf
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