1,721,174 research outputs found
Effect of elevated triaxial cyclic and constant loads on the mechanical properties of plain concrete
No full textAn experimental programme was carried out to investigate the effect of elevated cyclic or constant triaxial stresses on the change in mechanical properties of plain concrete. Triaxial cyclic tests on cylinders, with confining pressure and axial load varying in phase opposition at 1 Hz, were performed in three different deviatoric planes. The maximum stress deviator was 90% of the deviator at failure in a given deviatoric plane; the minimum deviator was 80% of the maximum one. In constant-load tests, the applied stresses were equal to the stresses at the maximum deviator applied in cyclic tests. At the cycle amplitudes selected, the creep effects under constant load are usually larger than the dynamic effects. The results obtained show that: the residual strength is increased with respect to the strength of companion virgin specimens, for any test condition; the increase in residual strength is much more important in triaxial tests than in uniaxial tests and increases with the test duration; the decrease in elastic modulus increases with the isotropic pressure at which tests are performed; and the test duration has a less pronounced effect on the decrease in elastic modulus
Fatigue life and change in mechanical properties of plain concrete under triaxial deviatoric cyclic stresses
No full textThe effects of a lateral confinement on the fatigue behaviour of plain concrete are experimentally investigated. Triaxial cyclic tests on cylinders, with confining pressure and axial load varying in phase opposition at 1 Hz, were performed in different deviatoric planes. The maximum stress deviator was 90% of the deviator at failure in a given deviatoric plane; the minimum deviator ranged between 70% and 95% of the maximum one. The residual strength and stiffness properties of those specimens that did not fail within a prescribed number of cycles were also assessed. For tests with cycles of equal amplitude (normalized to the triaxial static strength), fatigue life and residual strength seem to be positively affected by an increase in hydrostatic stress only up to a certain level. With the maximum deviator equal, in a given deviatoric plane fatigue life usually increases with decreasing cycle amplitude. In one of the deviatoric planes, cycle amplitude and mean stress were found to have opposite effects upon damage and residual strength
Preschool Physical Education and Care in Italy – National Literature Review
No full textThis chapter presents selected papers focused on preschool physical education and care in Italy. It is divided into the following four parts: (a) a brief overview of Italian policies and curriculum documents; (b) a review of research focusing on the implementation of programs to develop pre-school children’s physical activity; (c) a review of research on preschoolers’ physical activity; and (d) a review of some resources in Italian language, such as books and manuals for teachers and parents
Experimental investigation on the triaxial fatigue behaviour of plain concrete
No full textAn experimental research program was carried out with the aim of investigating the effects of a cyclic triaxial loading upon the mechanical behaviour of concrete. A triaxial press was used, capable of applying on cylindrical specimens an axial load and a confining pressure cyclically varying in time according to independent programs. Cycles (at 1 Hz) were characterized by different (a) mean stress, (b) amplitude, (c) ratio r of the mean confining pressure to the mean axial stress and (d) phase angle between loads. Some uniaxial cyclic tests were also performed. Those specimens that did not fail within about 400,000 cycles were monotonically tested to failure in uniaxial compression. Despite their scatter, the obtained results qualitatively show that: (a) at equal other tests parameters, fatigue life is usually shorter in tests in phase opposition rather than in phase coincidence; (b) as the cycle amplitude increases, fatigue life decreases (mainly in tests in phase opposition); (c) fatigue life increases as the mean confinement increases; (d) a strong correlation exists between 'secondary creep rate' and fatigue life, irrespective of the ratio between mean stresses; (e) all specimens submitted to post-cyclic failure tests exhibited a decrease in elastic modulus as greater as higher r was during cycles; the specimens submitted to uniaxial cycles experienced an increased in static strength in comparison with the virgin ones
Play fighting to cope with children aggression: a study in primary school
Full text linkAggressive behaviours among young people represent a universal concern and many children and adolescents report having been victimized or having bullied others. Cost-effective strategies are required to cope with this problem. The present study investigated the effect of play fighting on self-perceived aggression in
primary school pupils. Using a crossover longitudinal design, 42 fourth and fifth-grade pupils (21 boys, mean age = 9.8 ± 0.5 years) took part in a controlled play fighting school-based intervention 2 days/week for 4 consecutive weeks, replicating the program adopted in a previous study with 13-year old junior high school
students. Participants filled in the 12-item short version of the Aggression Questionnaire three times: baseline period (T0 and T1), and after the play fighting intervention (T2). A RM-ANOVA showed significant withinsubject differences among the three evaluation times (F = 2.95, p = .004). At T1 Verbal Aggression, Anger, and Hostility significantly decreased, while at the post-intervention, only Physical Aggression was significantly lower in comparison with T1 (T1 =5.5 ± 2.7; T2 = 5.0 ± 2.4; F = 5.22, p = .007). Results provide some preliminary insight on the role that play fighting can have as a part of a physical education curriculum to cope with children antisocial and aggressive behaviours, confirming the encouraging conclusions of previous research in young adolescents
Preschool Physical Education and Care in Italy – National Literature Review
No full textThis chapter presents selected papers focused on preschool physical education and care in Italy. It is divided into the following four parts: (a) a brief overview of Italian policies and curriculum documents; (b) a review of research focusing on the implementation of programs to develop pre-school children’s physical activity; (c) a review of research on preschoolers’ physical activity; and (d) a review of some resources in Italian language, such as books and manuals for teachers and parents
Sportunterricht in Italien ursprünge, problem, zukunftperspektiven
No full textIm vorliegenden Übersichtsartikel werden die historischen Wurzeln des Sportunterrichts in Italien dargestellt, die aktuelle Struktur des Unterrichts in den verschiedenen Schulstufen erläutert und einige aktuelle Problemlagen und Herausforderungen für das Unterrichtsfach Sport diskutiert. Hierbei wird deutlich, dass für die Legitimation des Sportunterrichts in verschiedenen historischen Epochen medizinische, militärische, ästhetische sowie pädagogische Argumente angeführt wurden. Auch wird ein knapper Blick auf die Sportlehrerbildung gerichtet, die in Italien erst seit gut einem Jahrzehnt an universitären Einrichtungen stattfindet.
In the presented overview the author refers to the historic roots of physical education in Italy, explains today’s instructional structure of different school levels and discusses some current problem areas and challenges for the subject of physical education at Italian schools. Thereby it becomes obvious that medical, military, aesthetic as well as educational arguments were used to legitimize physical education during diffe-rent historic periods. In addition, the author sketches physical educators’ university education, which just became established in Italy about a decade ago
Crotti P., Fiorini L., Ferraboli S., Baroncelli R., Sarrocco S., Vannacci G., Gobbi E. (2016) Velvet Complex and Gliotoxin Biosynthesis in Trichoderma afro-harzianum T6776.
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