1,720,978 research outputs found
Aerodynamic and Aerothermodynamic Trade-off Analysis of the Italian USV2 Flying Test Bed in the Framework of an Hypersonic Flight Test
No full text“Thermo-Structural Behaviour of an UHTC Made Nose Cap of a Re-entry Vehicle
No full textIn the frame of the technology project sharp hot structures (SHS), focused on the assessment of the applicability of ultra-high temperature ceramics (UHTCs) to the fabrication of high performance and SHS for reusable launch vehicles, the nose cap demonstrator named Nose_2 has been tested in the plasma wind tunnel (PWT) facility. In this paper, the FEM based thermo-structural analyses, carried out for the rebuilding of this PWT test are presented. Comparisons with experimental data measured in the PWT have been introduced to validate the FEM model and to help in interpreting the experimental test itself. Synergies between numerical and experimental activities have been finalized to the improvement of knowledge on the physical phenomenon under investigation. The effects on the thermal response due to the assumption of the catalytic condition of the wall, due to the uncertainties related to heat flux and pressure measurements on the probe (which influence the heat flux computation) and due to uncertainties in the determination of some UHTC thermal properties, have been investigated. The experimental temperatures curves falls very close to the numerical envelope (taking in account several sources of error) for all the test duration and the NCW model was found more reliable in reproducing thermal behaviour of the nose cap
A University Space Technology Program to Design and Validate New and Potentially Cost-Effective Hardware
No full textNumerical/Experimental Correlation of a Plasma Wind Tunnel Test on a UHTC-Made Nose Cap of a Reentry Vehicle
No full textThe nose cap demonstrator named Nose-2 has been tested for the second time in the plasma wind tunnel (PWT) facility which is part of the sharp hot structure (SHS) technology project, focused on the assessment of the applicability of ultrahigh temperature ceramics (UHTC) to the fabrication of high performance vehicles and SHS for reusable launch vehicles. In this paper the FEM based thermal analyses, carried out for the rebuilding of this PWT test, are presented. Experimental data measured in the PWT have been compared with numerical ones in order to validate the FEM model and to help in interpreting the experimental test itself. The knowledge on the physical phenomenon under investigation has been greatly improved, thanks to the synergy between numerical and experimental activities. In particular, a qualitative study of the modeling of the tip-dome interface has been performed in order to estimate the thermal contact resistance that heat flux encounters in passing through the demonstrator. The correlation between numerical and experimental temperature curves has been found to be satisfactory for both internal and surface temperature distribution, and the FEM model was found reliable in reproducing the thermal behavior of the nose cap
Contact Sensitivity Analysis of a Coupling Pin For the Nose Cap of a Launch Re-entry Vehicle
No full textThe present work has been developed within CIRA Unmanned Space Vehicle-Sharp Hot Structures (USV-SHS) activities. The Sharp Hot Structures Project (SHS) is focused on the applicability of modified diboride compounds to the manufacturing of high performance and slender shaped hot structures. The final products of the research are, in the short term, an innovative nose cap and a wing leading edge. The aim of the work is to size the coupling pin and the corresponding contact area with massive ZrB2-SiC and C/SiC-Graphite dome, ensuring structural integrity of the components connected. The use of a coupling pin is necessary since adhesive ceramics present several attaching difficulties. The design variables considered in the thermal-structural design of the coupling pin are: pin length, hole length, pin and hole shapes and diameters. The coupling pin is made of the same material of the massive cone to avoid thermal stresses caused by the mismatch between coefficients of thermal expansion; however, metallic coupling pin will be analysed because of the reduced manufacturing costs. The results of this work will be useful to prepare a prototype of the Nose cap concept that will be on-ground tested in the arc-jet Plasma Wind Tunnel, available at CIRA. Ansys commercial code, employing finite element modelling, has been adopted in order to perform non-linear contact analyses
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
Contact Sensitivity Analysis of a Coupling For the Nose Cap of a Launch Re-entry Vehicle
No full textThe present work has been developed within CIRA USV-SHS activities. The Sharp Hot Structures Project (SHS) is focused on the applicability of modified diboride compounds to the manufacturing of high performance and slender shaped hot structures. The final products of the research are, on the short term, an innovative nose cap and a wing leading edge. The aim of the work is to size the coupling pin and the corresponding contact area with massive ZrB2-SiC and C/SiC-Graphite dome, ensuring structural integrity of the components connected. The use of a coupling pin is necessary since adhesive ceramics present several attaching difficulties. The design variables considered in the thermal-structural design of the coupling pin are: pin length, hole length, pin and hole shapes and diameters. The coupling pin is made of the same material of the massive cone to avoid the coming up of thermal stresses caused by the mismatch between coefficients of thermal expansion; however, metallic coupling pin will be analysed because of the reduced manufacturing costs. The results of this work will be useful to prepare a prototype of the Nose cap concept that will be on-ground tested into the arcjet Plasma Wind Tunnel, available at CIRA. Ansys commercial code, employing finite element modelling, has been adopted in order to perform non-linear contact analyses
- …
