1,721,127 research outputs found
THE TIME-DELAY ROUTE TO REACTIVE SCATTERING RESONACES: THE CASE OF THE F + H2 --> HF + D REACTION
No full text"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
Comparison of Three Different Methods for Correction of HIV-Associated Facial Lipodystrophy
No full textHIV-1-infected patients can have peripheral fat loss or lipoatrophy of the face, limbs, and buttocks and central fat accumulation within the abdomen, breast, and the dorso-cervical spine both of which may be present in the same individual. Lipoatrophy causes negative psychosocial impact and an impairment of quality of life because of erosion of self-image and self-esteem, demoralization and depression, problems in social and sexual relations, and threats to locus of control.
Surgical treatments for facial lipoatrophy include autologous fat transplant (AFT) from a subcutaneous abdominal graft or injections of biodegradable or nonbiodegradable fillers into the lipoatrophic areas of the face. The authors discuss how to choose from the different surgical procedures to treat HIV-related facial lipoatrophy
Circular cutting strategy for drilling of carbon fiber-reinforced plastics (CFRPs)
No full textThe drilling process of carbon fiber-reinforced plastics (CFRPs) is the most commonly employed machining operation due to the necessity of joining these materials. However, these materials are prone to delaminate during the process, and the presence of this defect is the most cause of rejection for CFRP products, especially those produced for the aeronautic industry. Therefore, this article aims to study a drilling strategy (named circular drilling strategy) by using dedicated tools with different diameters, in order to reduce the extension of delaminations. Holes with different diameters (6, 8, and 10 mm) were obtained both with the conventional and with the proposed drilling strategy under distinct cutting conditions that mainly differ in the feed rates (62, 125, and 250 mm/min) and cutting velocities (50, 75, and 100 m/min). The effect of the cutting parameters and tool diameter on the cutting forces and delamination factor was studied for both the conventional and circular drilling process. The results proved that the proposed technique produces better hole quality and lower thrust forces than the conventional one under the same cutting conditions
On the origin of the forward peak and backward oscillations in the F + H2(v=0) --> HF(v'=2)+H reaction
No full textFacial fat hypertrophy in patients who receive autologous fat tissue transfer
No full textHIV-1-infected patients may develop lipodystrophy characterized by peripheral fat loss or lipoatrophy of the face, limbs, and buttocks and central fat accumulation within the abdomen, breast, and the dorso-cervical spine both of which may be present in the same individual. Facial lipoatrophy is undoubtedly the most frequent and distressing sign of this clinical syndrome. The authors believe that autologous fat transplant should be the preferred option for the treatment of facial lipoatrophy when an appropriate graft site is available. Nevertheless, this major surgery technique may have minor and major complications. Minor complications include pain, edema, and superficial bleeding. Major complications may be represented by disfiguring facial fat graft hypertrophy. Four patients who had fat transferred from the dorsocervical fat pad or from subcutaneous abdominal tissue developed a disfiguring fat graft hypertrophy of the face that occurred at the same time as recurrent fat accumulation in the tissue harvest site. A clinical implication is that when autologous fat transplant is chosen for face atrophy treatment, the preferred subcutaneous adipose graft site should be abdomen or groin. © 2010 Springer-Verlag Berlin Heidelberg
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