1,720,957 research outputs found
Static/quasi-static thermomechanical analysis of 3D thin-walled beam structures based on CUF considering radiation dissipation condition
No full textThin-walled structures are widely applied in spacecraft as structural components due to their lightweight property. Extreme thermal environment in space may cause highly unfavorable thermal responses in thin-walled structures. Therefore, accurately predicting the thermal-coupling responses of thin-walled structures is of great engineering significance. In order to avoid the disadvantages of 3D finite element model caused by an abundance of computational degrees of freedom, the present paper proposes a thermo-mechanical coupling model based on Carrera Unified Formulation (CUF) for the static and quasi-static thermal response of space thin-walled structures. The longitudinal direction of the structures is discretized by one-dimensional linear and cubic finite elements (B2 and B4), whereas Lagrange expansion functions are used for the description of temperature fields and displacement fields within the cross-section. The governing differential equations of thermal-coupling problems are derived in a unified form according to the principle of virtual displacement and the weighted residual method. In order to demonstrate the accuracy of the numerical results, a convergence analysis is conducted on both beam elements and expansion forms. The results reveal that piece-wise quadratic beam theories approximated with B4 elements are accurate enough for the prediction of thermally-induced displacements, while the high-order cubic cross-sectional expansion is required for the description of stresses. Finally, influences of factors like angle of solar radiation, local shadows, emissivity and thermal conductivity on static and quasi-static displacement distributions are discussed. This research may pave a high-efficiency computational method for solving static/quasi-static thermally induced response of space thin-walled structures
Transient Thermal Analysis of Space Rectangular Thin-Walled Structures by Carrera Unified Formulation
Full text linkThe accurate prediction of transient thermal fields of space structures is of paramount significance for the analysis of geometrical stability and thermal management systems. This paper proposes a novel method to solve the transient thermal field of the thin-walled cross section of beams in outer space. High-order beam elements are derived by means of the Carrera unified formulation (CUF), where the longitudinal direction of the beam is discretized by one-dimensional two-node and four-node elements, whereas arbitrary high-order expansion functions are used for the description of the temperature expansion within the cross section. The governing differential equations of the transient temperature field are derived according to the transient thermal conduction theory and the weighted residual method. The solution of the initial value problem for ordinary differential equations is obtained through the application of the Adams-Bashforth method, leading to the determination of the transient thermal field. In order to demonstrate the accuracy of the temperature results, a convergence analysis is conducted. Finally, temperature distributions within the cross section and along the longitudinal direction of the model are discussed to show the effects of several factors, including material properties, angle of solar radiation, and shadows induced by the shelter of other components
High-order multiscale modeling for the thermo-elastic analysis of large-scale phased array antennas
No full textMulti-scale analysis of thermal conductivity of graphene foam/PDMS composites
No full textIn this paper, multiscale modeling of polymer composites consisting of Graphene Foam (GF) and Polydimethylsiloxane (PDMS) is conducted, and their Thermal Conductivity (TC) is investigated through the use of nano-to-microscale analyses. The TC of the PDMS matrix and GF is calculated using the Molecular Dynamics (MD) method. The effective properties of the composites are computed utilizing the Mechanics of Structure Genome (MSG) coupled with Carrera Unified Formulation (CUF) as a novel micromechanical method, which allows an accurate description of the problem resulting in a high-fidelity analysis. Due to the unique interconnected structure of GF, the TC of GF/PDMS composite reaches 0.406 Wm-1 K-1 for GF with 63% porosity, which is about 69% & PLUSMN; 2% higher than that of neat PDMS
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
- …
