1,721,197 research outputs found
On residuation in paraorthomodular lattices
No full textParaorthomodular lattices are quantum structures of prominent importance within the framework of the logico-algebraic approach to (unsharp) quantum theory. However, at the present time it is not clear whether the above algebras may be regarded as the algebraic semantic of a logic in its own right. In this paper, we start the investigation of material implications in paraorthomodular lattices by showing that any bounded modular lattice with antitone involution A can be converted into a left-residuated groupoid if it satisfies a strengthened form of regularity. Moreover, the above condition turns out to be also necessary whenever A is distributive
On residuation in paraorthomodular lattices
No full textParaorthomodular lattices are quantum structures of prominent importance within the framework of the logico-algebraic approach to (unsharp) quantum theory. However, at the present time it is not clear whether the above algebras may be regarded as the algebraic semantic of a logic in its own right. In this paper, we start the investigation of material implications in paraorthomodular lattices by showing that any bounded modular lattice with antitone involution A can be converted into a left-residuated groupoid if it satisfies a strengthened form of regularity. Moreover, the above condition turns out to be also necessary whenever A is distributive
THE TIME-DELAY ROUTE TO REACTIVE SCATTERING RESONACES: THE CASE OF THE F + H2 --> HF + D REACTION
No full text
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
"L'Italia nacque divisa". La lingua politica nella stampa cattolica (anti)risorgimentale: Il caso de La Frusta - giornale politico morale
No full textAngular and hyperangular momentum coupling coefficients as Hahn polynomials
No full textThe relationship is investigated between Hahn coefficients, i.e,, normalized Hahn polynomials of a discrete variable, and generalized 3j coefficients. Their role is outlined as matrix elements for the overlap of alternative hyperspherical harmonics (timber coefficients). The semiclassical limit is also investigated, with reference to their use as discrete analogs of hyperspherical harmonics
Production of PP composites reinforced with flax and hemp woven mesh fabrics via compression molding
No full textHemp and flax fibers are among the most interesting vegetable fibers that can be used to reinforce polymeric matrices. In line with the global environmental requests, the use of these fibers especially coupled with thermoforming polymers are increasing more and more in order to expand their applications and replace synthetic fibers and thermosetting plastics. However, one of the major limitations of vegetable fibers is their poor adhesion with polymeric matrices that is often overcome by fibers chemical treatments or by using coupling agents within the matrix. Aiming to produce polypropylene (PP) bio composite laminates reinforced by hemp and flax fibers without additional process steps, this paper deals on the study of their production via the compression molding technique by using woven fabrics characterized by a large mesh size able to ensure a mechanical anchoring between fibers and matrix. Two different forming strategies that differ in the time required for reaching the maximum values of compression pressure and in the dwelling time at this value were used in order to investigate how the yarn impregnation was affected by them. To expand the applications of composites under investigation, tensile, bending, Izod, heat deflection temperature (HDT) and bearing tests were carried out. The results highlighted how the use of a waiting time before the reaching of the maximum moulding pressure allowed a better matrix flow within the vegetable yarn leading to higher mechanical performances
Tribological Behaviour of Hemp, Glass and Carbon Fibre Composites
No full textLightweight composite materials are frequently used for transportation, or the interiors of furniture and boxes. Wear of the surfaces of these materials is a potential health risk affecting the respiratory system or skin. The latter can frequently occur due to human touch of uncovered synthetic fibres after wear causing dermatitis, or inflammation of the skin. Therefore, composite materials made of natural fibres as reinforcement are an interesting alternative to synthetic fibres, because they are usually less dangerous to human health. Therefore, the goal of this research is to highlight the wear resistance of hemp fibres and compare it with glass and carbon fibre composites. In this work, hemp, glass and carbon fibres in form of woven fabrics were impregnated with epoxy resin through vacuum infusion process. In order to compare the tribological behaviour of the manufactured composites, a detailed experimental campaign, including tribological tests, microgeometrical measurements and indentation tests, was carried out. The tribological behaviour was studied through the pin-on-disk tests under different conditions that mainly differ in the applied load and both the composite and the single un-impregnated fabrics were tested. The results demonstrate good wear behaviour of the laminates reinforced by hemp fibres emphasising a better wear resistance at prolonged time and under high load conditions
Comparison of tribological behaviour between natural and synthetic fibres composites
No full textThis work aims to study the wear resistance of composite materials that mainly differ in the fibre typologies used as reinforcement. In detail hemp, glass and carbon fibres in form of woven fabric were used. For the production of the composite materials, an epoxy resin was used as matrix, and the vacuum infusion process was adopted. In order to compare the tribological behaviour of the manufactured composites, a detailed experimental campaign, including tribological tests and microgeometrical measurements, was carried out. In particular, the tribological behaviour was studied through the pin-on-disk tests conducted at 210 mm/s as peripheral speed under 50 N as applied load testing both the composite and the single un-impregnated fabrics. These tests were followed by microgeometrical measurements in order to critically observe the wear tracks, evaluate their depth, width and volume and then to calculate the final less of volume. The tests results showed a good and interesting behaviour of composite materials reinforced with hemp fibres
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