1,721,217 research outputs found
Seismic Behavior of Precast Buildings With Dissipative Connections
Full text linkRecent earthquakes in southern Europe highlighted that the connections of cladding panels to R.C. frames in precast buildings had a major role in the structural collapse. For this reason, there is an urgent need for a review of the design methods for these connections as well as for an improvement in the manufacturing technology. This article aimed to assess the efficiency of dissipative panel-to-structure and roof connections in R.C. precast buildings. A parametric study consisting of linear and non-linear analyses on one case-study building is performed. Different sensitivity analyses are performed varying their mechanical properties (i.e., stiffness, strength, and ductility) to analyze the behavior of the CP/frame connections. The study focuses on dissipative connections with an elastic–plastic behavior, placed between cladding panels (CPs) and frames in precast buildings with stacked horizontal cladding panels. The introduction of dissipative CP/frame connections implies the inclusion of panels in the global seismic resisting system. The “panels + frame” system highlights a high stiffness until the yield strength of the CP/frame connections is reached. The results, obtained from non-linear dynamic analyses (NLDAs), clearly show how the proposed connection improves the structural seismic performance. By contrast, this is no longer true for R.C. precast structures with flexible diaphragms, especially for intermediate columns, far from panels aligned to seismic action. In this case, significant and unexpected axial forces arise on out-of-plane connections between panels and columns. The integration of an efficient diaphragm is essential to prevent these critical issues both on intermediate columns and CP/column connections; it enables the dissipative capacity of the “panels + frame” system, and it significantly limits the forces and displacements of intermediate alignments. Unfortunately, the achievement of a rigid diaphragm is not always feasible in precast buildings. A possible alternative to activate dissipative capacities of the roof diaphragm with limited in-plane stiffness is the use of dissipative connections linking roof beams and main beams. The solutions described in this article can be applied both in the design of new buildings and for the seismic upgrading of existing ones with easy-to-install and low-impact applications
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
Applicazione delle metodologie geo-topografiche satellitari per lo studio di modelli matematici del geoide in ambito locale.
No full textUniversità di Padova, Dipartimento di Architettura, Urbanistica e Rilevamento
Variation of the mechanical and radiometric properties of LDPE greenhouse films exposed to agrochemicals and solar radiation
No full textAgrochemical substances used in protected cultivation, especially those based on sulphur, iron and chlorine, generate by-products that lead to a degradation of greenhouse plastic films evidenced by the variation of their mechanical and radiometric properties. A research was carried out to evaluate how agrochemicals contamination and solar radiation influence the mechanical and radiometric properties of low density polyethylene (LDPE) films. The LDPE films, manufactured on purpose adding different anti-UV stabilizer systems, were exposed to natural outdoor weathering at the University of Bari (Italy; 41° 05' N) during 2009. Each film was tested as covering of two low tunnels: one was sprayed from inside with commercial agrochemicals containing iron, chlorine and sulphur while the other one was not sprayed and used as control. Mechanical and radiometric tests were carried out on the new films and on film samples taken at the end of the trial. Analyses on absorption of the selected contaminants were carried out in laboratory on the samples taken at the end of the exposure in the field in order to compare the relative effectiveness of the stabilizing systems under evaluation. Additional accelerated aging tests were performed in laboratory on samples taken at the end of the film in-field exposure in order to better differentiate the film tensile properties. The experimental tests showed that at the end of the field exposure the stress at break and the strain at break decreased slightly for the control and sprayed stabilised films while the artificial weathering induced a sharp decrease of their mechanical properties. Radiometric tests showed that the natural weathering together with the agrochemicals did not modify significantly the radiometric properties of the films in the solar and PAR wavelength range. Variations were recorded for the stabilised films in the LWIR wavelength range
Effect of the pesticides on the degradation of EVA plastic films for greenhouse covering
No full textObject of the research is the study of the effects of the pesticides, generally used in protected cultivation, on greenhouse plastic films.
Two different EVA innovative plastic films, EVA and EVA-IR, were produced by PATI each of them realized in three versions using different anti-UV additives.
Experimental tests were carried out using six different little tunnels covered with the EVA films, in which a system for spraying the pesticides was realised. The pesticides were applied for 16 weeks and contained sulphur, chlorine and copper in order to evaluate the effects of these components on the materials. Samples of the tested plastic materials were taken at fixed time intervals from the tunnels, and their physical and mechanical properties were measured. Particularly the tensile strength and the elongation at break were measured as mechanical properties, solar and long wave infrared transmissivity as physical properties. Tests showed a marked decrease of the transmittance in all the wavelength ranges after 16 weeks of exposure to the atmospheric elements and to the pesticides. Less marked decreases were pointed out concerning the mechanical properties
Interaction between agrochemical contaminants and UV stabilizers for greenhouse EVA plastic films
No full textResearch was conducted to evaluate how solar radiation, agrochemical contamination, and different light
stabilizer systems influence the mechanical properties of ethylene-vinyl acetate copolymer (EVA/C) based films suitable
for crop protection. Three independent outdoor trials were performed at the experimental field of the University of Bari
(Italy) in 2006, 2007, and 2008. During each trial each film type was installed in the field as new covering of two low
tunnels: one of the tunnels was periodically sprayed inside with agrochemicals containing sulfur, chlorine and iron, while
the other one, not sprayed, was used as control. Besides, artificial photoaging tests were carried out on the films in
laboratory. The research showed that the different light stabilizer systems influenced the mechanical behavior of the films
in the presence of the progressively absorbed agrochemicals. An improved resistance to the agrochemicals was recorded
for the EVA/C films stabilized with aminoether type hindered amine light stabilizer (NOR-HALS) and ultra violet filter
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
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