1,721,341 research outputs found
Giardia and Cryptosporidium and public health: the epidemiological scenario from the Italian perspective
Full text linkGiardia and Cryptosporidium spp. are protozoa
that cause human and animal disease worldwide and often
exhibit zoonotic transmission. This review gives ample
information concerning the epidemiology of these parasites in
Italy, i.e. prevalence data in humans, farm and pet animals,
shellfish and aquatic environment. Moreover, it reports
genotyping results obtained from different isolates, with
particular emphasis on the spread of host-specific and
zoonotic species/genotypes of various origin, and on molecular
data that make the Italian situation different from that of
other countries. Finally, possible explanations are given for
the infrequent reports of Giardia and Cryptosporidium spp.
outbreaks, despite widespread faecal contamination by these
parasites
Basilica churches under seismic actions: Classification and non-linear behaviour of masonry macro-elements
No full textThe paper provides a contribution for the evaluation of seismic capacity of typical macro-elements of basilica type churches through non-linear static analyses. Previous studies conducted by the authors on the behaviour of masonry churches under the earthquake actions showed how these structures are particularly vulnerable to the horizontal loads due to their specific geometrical configuration, characterized by open plan, slender walls, lack of effective connections between transversal walls, thrusting structures. In this paper, fourteen basilica churches located in Central and Southern Italy are analysed by sub-structuring the whole building in its constituting macro-elements. Each macro-element is then analysed by using pushover analysis with the aim of determining its horizontal capacity and the corresponding failure mechanism. The comparison among the results of the seismic analysis allow for defining eight classes of macro-elements, each one characterized by peculiarity in geometric characteristics, in architectural function and seismic response
Influence of geometry on seismic capacity of circular buttressed arches
No full textThe effect of geometry on the seismic capacity of masonry buttressed arches with circular shape is addressed in this paper. In particular, in the contest of the limit analysis approach for masonry structures, a numerical procedure developed by the authors in previous studies is here used to perform an extensive parametric analysis of 320 circular buttressed arches, obtained by varying the geometrical configuration, namely the angle of embrace, the arch thickness and the buttress aspect ratio. The aim of the parametric analysis is studying the effect of both arch configuration (angle of embrace and arch thickness) and buttress geometry (height and width) on the horizontal strength of buttressed arches. To this end, the results of this study are presented in terms of collapse multiplier and failure mechanism aimed to provide reference values to be used for straightforward assessment of the horizontal strength of arched masonry structures, and for checking the results of more complex structural analyses performed by using "advanced" structural engineering software
Validation of numerical results of complex seismic analysis through simple analytics
No full textThe paper analyzes the application of the numerical findings of the program, which is becoming increasingly difficult for civil and structural design. Since, as in many other countries, the verification of design using a software model is now required by current Italian codes as well. Given this, the structural engineer must provide a technical report using a licensed software tool, attached to other project documents to get the Seismic Authorization at the local Civil Engineering Department offices. Following a brief explanation of structural analysis methodologies, this study presents a criterion for assessing the applicability of numerical findings obtained using any structural software. Three case studies of this criterion are shown to demonstrate how to check them using simple manual calculations: (i) the normal stress in RC columns subjected to gravity loads; (ii) the periods of vibration, participating masses, and seismic base shear derived from dynamic modal analysis; and (iii) the main parameters characterizing the pushover curves of existing buildings. Finally, this work underlines the significance of confirming the application of numerical results obtained by software in civil and structural design. The offered criteria and scenarios exhibit realistic techniques to ensure accuracy and reliability in structural performance assessment, according to the structural requirements imposed by current codes in Italy and similar countries
Analytical modelling for the seismic assessment of pointed arches supported by buttresses
No full textThe seismic behaviour of arches is investigated to provide a contribution to the stability of arches with a pointed shape supported by buttresses. The limit analysis (LA) for masonry structures has been herein implemented in analytical modelling based on the use of nonlinear programming techniques for investigating the potential failure mechanisms associated with pointed arches under horizontal forces. A critical assessment of the positioning of hinges over the arch embrace is conducted here. This will allow for a better prediction of the capacity of these structures under seismic actions. The lateral action, which activates the investigated failure mechanisms, is also computed by implementing this new analytical model. This is assessed both in terms of horizontal loading multiplier and associated ground accelerations. Furthermore, by comparing numerical results derived from scientific literature, it was possible to validate the reliability of the here presented analytical model
Sensitivity Analysis of Adaptive Guidance via Deep Reinforcement Learning for Uncooperative Space Objects Imaging
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