A multiscale modeling methodology was developed for continuous fiber composites that incorporates a statistical distribution of fiber strengths into coupled multiscale micromechanics/ finite element ...(FE) analyses. A modified twoparameter Weibull cumulative distribution function, which accounts for the effect of fiber length on the probability of failure, was used to characterize the statistical distribution of fiber strengths. A parametric study using the NASA Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC) was performed to assess the effect of variable fiber strengths on local composite failure within a repeating unit cell (RUC) and subsequent global failure. The NASA code FEAMAC and the ABAQUS finite element solver were used to analyze the progressive failure of a unidirectional SCS-6/ TIMETAL 21S metal matrix composite tensile dogbone specimen at 650°C. Multiscale progressive failure analyses were performed to quantify the effect of spatially varying fiber strengths on the RUCaveraged and global stress-strain responses and failure. The ultimate composite strengths and distribution of failure locations (predominately within the gage section) reasonably matched the experimentally observed failure behavior. The predicted composite failure behavior suggests that use of macroscale models that exploit global geometric symmetries are inappropriate for cases where the actual distribution of local fiber strengths displays no such symmetries. This issue has not received much attention in the literature. Moreover, the model discretization at a specific length scale can have a profound effect on the computational costs associated with multiscale simulations.
Despite the higher operating pressure, carbon dioxide has attracted many researchers' attention because of its higher density, favorable heat transfer characteristics, and environmental friendliness. ...In order to design components and systems for carbon dioxide, a performance database should be established. As part of the efforts for developing such a performance database, a set of tests were conducted for a fin-and-tube type heat exchanger serving as a gas cooler in the transcritical cycle by using a specially designed test facility. Furthermore, to provide a better understanding of the performance of a carbon dioxide gas cooler, a set ofparametric measurements at various inlet air temperatures and velocities, refrigerant mass flow rates, and operating pressures were conducted. The test results of one CO2 gas cooler are reported in the current paper. In the secondphase of the study, fin-and-tube type heat exchangers (as a condenser and an evaporator) and microchannel heat exchangers (as a gas cooler, a condenser, and an evaporator) will be constructed and tested. Then experimental results ofthose studies will serve as our design database for the CO 2heat exchangers.
Victor H. Yngve Hutchins, W. John
Computational linguistics - Association for Computational Linguistics,
09/2012, Letnik:
38, Številka:
3
Journal Article
RÉSUMÉ : Cet article propose une histoire de la traduction automatique depuis ses débuts dans les années 40 jusqu'à nos jours. Dans les premières années, les chercheurs concentraient leurs efforts ...sur la confection de systèmes immédiatement utilisables, bien que fournissant des traductions grossières, ou bien sur des recherches portant sur des systèmes de traduction dé très grande qualité. Après le rapport de l'ALPAC, paru en 1966, qui mit virtuellement fin à la recherche en TA aux États-Unis pendant plus d'une dizaine d'années, les travaux se focalisèrent sur le développement de systèmes assistés par des humains et destinés à traduire des documents techniques, ou sur des outils de traduction directement utilisables par les traducteurs eux-mêmes. Récemment, on développe des systèmes de traduction des messages électroniques, des pages Web ou autres documents sur Internet, pour lesquels la rapidité des résultats est supposée compenser la médiocrité de la traduction.
abstract : The history of machine translation is described from its beginnings in the 1940s to the present day. In the earliest years, efforts were concentrated either on developing immediately useful systems, however crude in their translation quality, or on fundamental research for high quality translation systems. After the ALPAC report in 1966, which virtually ended MT research in the US for more than a decade, research focussed on the development of systems requiring human assistance for producing translations of technical documentation, on translation tools for direct use by translators themselves, and, in recent years, on systems for translating email, Web pages and other Internet documentation, where poor quality is acceptable in the interest of rapid results.
The history of machine translation is described from its beginnings in the 1940s to the present day. In the earliest years, efforts were concentrated either on developing immediately useful systems, ...however crude in their translation quality, or on fundamental research for high quality translation systems. After the ALPAC report in 1966, which virtually ended machine translation research in the US for more than a decade, research focused on the development of systems requiring human assistance for producing translations of technical documentation, on translation tools for direct use by translators themselves, &, in recent years, on systems for translating e-mail, Web pages & other Internet documentation where poor quality is acceptable in the interest of rapid results. 24 References. Adapted from the source document
A multiscale modeling methodology was developed for continuous fiber composites that incorporates a statistical distribution of fiber strengths into coupled multiscale micromechanics/finite element ...(FE) analyses. A modified two-parameter Weibull cumulative distribution function, which accounts for the effect of fiber length on the probability of failure, was used to characterize the statistical distribution of fiber strengths. A parametric study using the NASA Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC) was performed to assess the effect of variable fiber strengths on local composite failure within a repeating unit cell (RUC) and subsequent global failure. The NASA code FEAMAC and the ABAQUS finite element solver were used to analyze the progressive failure of a unidirectional SCS-6/TIMETAL 21S metal matrix composite tensile dogbone specimen at 650 degC. Multiscale progressive failure analyses were performed to quantify the effect of spatially varying fiber strengths on the RUC-averaged and global stress-strain responses and failure. The ultimate composite strengths and distribution of failure locations (predominately within the gage section) reasonably matched the experimentally observed failure behavior. The predicted composite failure behavior suggests that use of macroscale models that exploit global geometric symmetries are inappropriate for cases where the actual distribution of local fiber strengths displays no such symmetries. This issue has not received much attention in the literature. Moreover, the model discretization at a specific length scale can have a profound effect on the computational costs associated with multiscale simulations.models that yield accurate yet tractable results.
An Introduction to Machine Translation Magnusdottir, Gudrun (Review of: Hutchins, W John; Somers, Harold L)
Computational Linguistics,
06/1993, Letnik:
19, Številka:
2
Book Review
