1,355,488 research outputs found
The investigation of inclined aft wall cavities in a circular scramjet combustor
No full textAchieving good mixing with high combustion efficiency, stable flame holding, and low stagnation pressure losses are still open issues in supersonic reacting flows. Mixing and vorticity in supersonic flows are mainly driven by the baroclinic term that is correlated to the density and pressure gradients. An increase of the baroclinic term has been observed to strongly depend on shock waves arising within the combustion chamber. This work numerically investigated the interaction between the fuel jet and the air stream as a function of the aft wall angle inclination. In fact, this parameter has a primary impact on the shock wave inclination arising from the cavity leading edge and therefore on the baroclinic term. Four different combustor geometries have been investigated: without cavity and with three different aft wall inclinations (90°–15°, 60°–15°, 30°–15°). 3D RANS numerical simulations showed that the primary ramp angle has a critical impact on the fuel-air mixing and consequently on the combustion efficiency. A correlation between the combustor geometry and the shock angle inclination has been proposed. Greater combustion efficiency, homogeneous H2O, and temperature distribution across the combustor are found with the 30–15 aft wall cavity configuration. Lowering the primary aft wall of the cavity from 90° to 30°, resulted in the rising of a stronger bow shock, extended recirculation volume within the cavity, and increased fuel-air mixing
The implication of injection locations in an axisymmetric cavity-based scramjet combustor
No full textThis paper presents the effect of cavity-based injection in an axisymmetric supersonic combustor using numerical investigation. An axisymmetric cavity-based angled and transverse injections in a circular scramjet combustor are studied. A three-dimensional Reynolds-averaged Navier–Stokes (RANS) equation along with the k-ω shear-stress transport (SST) turbulence model and species transport equations are considered for the reacting flow studies. The numerical results of the non-reacting flow studies are validated with the available experimental data and are in good agreement with it. The performance of the injection system is analyzed based on the parameters like wall pressures, combustion efficiency, and total pressure loss of the scramjet combustor. The transverse injection upstream of the cavity and at the bottom wall of the cavity in a supersonic flow field creates a strong shock train in the cavity region that enhances complete combustion of hydrogen-air in the cavity region compared to the cavity fore wall injection schemes. Eventually, the shock train in the flow field enhances the total pressure loss across the combustor. However, a marginal variation in the total pressure loss is observed between the injection schemes
Asymptotic conditions for weak and proper optimality in infinite dimensional convex vector optimization
No full textWe establish necessary and sufficient dual conditions for weak and proper minimality of infinite dimensional vector convex programming problems without any regularity conditions. The optimality conditions are given in asymptotic form using epigraphs of conjugate function and subdifferentials. It is shown how these asymptotic conditions yield standard Lagrangian conditions under appropriate regularity conditions.The main tool used to obtain these results is a new solvability result of Motzkin type for cone convex systems. We also provide local Lagrangian conditions for certain nonconvex problems using convex approximations
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Sufficient conditions for global optimality of bivalent nonconvex quadratic programs with inequality constraints
No full textWe present sufficient conditions for the global optimality of bivalent nonconvex quadratic programs involving quadratic inequality constraints as well as equality constraints. By employing the Lagrangian function, we extend the global subdifferential approach, developed recently in Jeyakumar et al. (J. Glob. Optim., 2007, to appear; Math. Program. Ser. A, 2007, to appear) for studying bivalent quadratic programs without quadratic constraints, and derive global optimality conditions. © 2007 Springer Science+Business Media, LLC.C
Supplemental_tables - Water, sanitation and hygiene (WaSH) practices and diarrhoea prevalence among children under five years in a tribal setting in Palghar, Maharashtra, India
No full textSupplemental_tables for Water, sanitation and hygiene (WaSH) practices and diarrhoea prevalence among children under five years in a tribal setting in Palghar, Maharashtra, India by Angeline Jeyakumar, Swapnil Rajendra Godbharle and Bibek Raj Giri in Journal of Child Health Care</p
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
No full textThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
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