1,730,808 research outputs found
Numerical characterization of imperfection sensitive composite structures
No full textThe need to take the imperfection sensitivity of thin-walled unstiffened cylinders into account during the early design phases motivated the development of the NASA SP-8007 guideline, which brings an empirically based lower-bound curve that gives the knock-down factor (KDF) as a function of the cylinder’s radius and thickness. This guideline is still used also for composites, using correction. The conservativeness of these guidelines has been proved both stochastically by Arbocz, Starnes Jr., Hilburger, et al.; and deterministically by Geier, Hühne, Degenhardt, et al. A deterministic method: single perturbation load approach; developed by Hühne, showed that after some radial load (called P1) the imperfection sensitivity decreases, i.e. the buckling load remains nearly constant even increasing the radial load. Such physical benefit is not taken into account by the NASA SP-8007 guideline. This study, in the context of DESICOS, investigates the buckling mechanism of composite benchmark cylinder, developed by Zimmermann, being extreme-case laminates with high and low imperfection sensitivity. The explanation why the buckling load is constant after P1 is given and a physical meaning for the P1 value is proposed. These findings pave the way for the development of semi-analytical approaches for calculating P1. By applying the P1 value in the analysis, one can obtain less conservative KDFs which have shown to be closer to test results, allowing cost savings for the space industry
[International Agricultural Corporation, Engine Drawing Card, Sketch No. 8007]
No full textThis engine drawing card was created for International Agricultural Corporation, Class 6-20D. Section H-6D. Sketch 8007. Copy Spec. 28-D-38
Comparison of new Design Guidelines for Composite Cylindrical Shells prone to Buckling
No full textCurrently, imperfection sensitive shell structures prone to buckling are designed according to the NASA SP-8007 guideline, from 1968, using its conservative lower-bound curve. In this guideline the structural behavior of composite materials is not appropriately considered, since the imperfection sensitivity and the buckling load of shells made of such materials depend on the lay-up design. Due to the fact that this approach is outdated for preliminary design purposes, several authors are investigating less conservative methodologies. Some authors propose a new lower-bound curve approach based only on statistical analysis of experimental test on composite cylinders. The problem with this approach is that the range of applicability is limited to the database extension. Finite element models are also used by many researchers to characterize the behavior of cylindrical shell considering different types of material and geometrical imperfections. A representative finite element model allows studying a widespread area of possibilities from the design point of view. In this context a numerical investigation about the different methodologies to characterize the behavior of imperfection sensitive composite structures subjected to compressive loads up to buckling is presented in this paper. A comparative study is addressed between new deterministic methodologies, such as the “Single Perturbation Load Approach” proposed by the European project DESICOS and new statistical approaches based on experimental test on composite cylinders. The aim of this work is to define the range of applicability of these methodologies for unstiffened composite cylinders, advantage and disadvantage to use as a design tool, to provide means to calculate less conservative knock-down factors than the obtained with the NASA SP-8007 guideline
Linked collectors and determiners for: New species of Lepidodactylus (Squamata: Gekkonidae) from New Guinea and adjacent islands.
No full textNatural history specimen data linked to collectors and determiners held within, "New species of Lepidodactylus (Squamata: Gekkonidae) from New Guinea and adjacent islands". Claims or attributions were made on Bionomia by volunteer Scribes, <a href="http://bionomia.net/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8">https://bionomia.net/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8</a> using specimen data from the dataset aggregated by the Global Biodiversity Information Facility, <a href="https://gbif.org/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8">https://gbif.org/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8</a>. Formatted as a Frictionless Data package
Linked collectors and determiners for: Royal Ontario Museum - Entomology Collection.
No full textNatural history specimen data linked to collectors and determiners held within, "Royal Ontario Museum - Entomology Collection". Claims or attributions were made on Bionomia by volunteer Scribes, <a href="http://bionomia.net/dataset/cde844c1-a43e-41b3-8007-dea00fec7d87">https://bionomia.net/dataset/cde844c1-a43e-41b3-8007-dea00fec7d87</a> using specimen data from the dataset aggregated by the Global Biodiversity Information Facility, <a href="https://gbif.org/dataset/cde844c1-a43e-41b3-8007-dea00fec7d87">https://gbif.org/dataset/cde844c1-a43e-41b3-8007-dea00fec7d87</a>. Formatted as a Frictionless Data package
Linked collectors and determiners for: New species of Lepidodactylus (Squamata: Gekkonidae) from New Guinea and adjacent islands.
No full textNatural history specimen data linked to collectors and determiners held within, "New species of Lepidodactylus (Squamata: Gekkonidae) from New Guinea and adjacent islands". Claims or attributions were made on Bionomia by volunteer Scribes, <a href="http://bionomia.net/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8">https://bionomia.net/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8</a> using specimen data from the dataset aggregated by the Global Biodiversity Information Facility, <a href="https://gbif.org/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8">https://gbif.org/dataset/00ad1537-4dda-475f-8007-991dc1f0eac8</a>. Formatted as a Frictionless Data package
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
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