88,707 research outputs found
Missione archeologica italo-siriana a Arslan Tash
No full textLa seconda campagna sul sito di Arslan Tash della missione congiunta siro-italiana diretta da Mohammed Zerhal per la parte siriana e da Serena Maria Cecchini si è svolta tra il 25 e 30 ottobre 2008. L’indagine si propone di identificare e posizionare i monumenti scavati da F. Thureau-Dangin, nel 1928 nel contesto fortemente urbanizzato del villaggio moderno che attualmente occupa la quasi totalità del tell. Al rilievo topografico effettuato durante la campagna 2007 ha fatto seguito un’analisi georadar delle aree precedentemente rilevate. Nel fitto contesto urbano moderno del sito sono stati così individuati i luoghi dei vecchi scavi, su cui far convergere la prima campagna di scavi. Le indagini perfettamente mirate permetteranno di storicizzare gli straordinari rinvenimenti degli anni '20 nonché di aggiungere nuovi dati alla storia di uno dei siti fondamentali per la storia del Vicino Oriente
DOE analysis of the rheological data of shear-thickening fluids for puncture-resistant composite shells
No full textThe dilatancy (Shear-thickening) is a time-independent rheological behaviour exhibited by some non-Newtonian fluids. These fluids manifest a surge in the apparent viscosity with an increase in the shear rate. If these fluids are encapsulated, they can be used to manufacture high-end stab resistance inserts (Cecchini et al., 2018) [1]. In the first part of this work, a comparison between the rheological performance of different shear-thickening fluids (STFs) based on nanosilica dispersed in glycols is presented. This analysis attempts to investigate the combinations of fillers and carriers with the highest energy-absorbing capabilities, among the various glycol-based colloidal STFs. In the second part, the influence of the composition of the STF on its rheological properties is analyzed statistically. The statistical analysis is performed by evaluating the interaction between the main design variables of the fluids (filler dimension, weight-to-weight ratio and molecular weight of the carrier). Finally, the puncture resistance of a composite system obtained by encapsulating the previously manufactured shear-thickening fluids in a polymeric shell is analyzed by means of a high-speed puncture test. This test is performed on the mockup of a tyre tread containing the best performing STF. The results showed that the use of the STF core increased the resistance to puncture by 20% as compared to the same volume of tyre tread material. Furthermore, the STF hermetically sealed the pierced sample, even when the tyre mockup was inflated at high internal pressures
Explicación funcional en ciencias sociales: del "organicismo" a los equivalentes funcionales
No full textFil: Cecchini, Gabriel F. Universidad Nacional de Córdoba; Argentina.Sí al comienzo del siglo veinte el funcionalismo social concebido análogamente al modelo de explicación funcional de la biología se presentaba como un modo de explicación poderoso y prometedor de los fenómenos sociales, las críticas que le fueron dirigidas con posterioridad tanto desde las ciencias sociales como desde la filosofía de la ciencia demostraron ser lo suficientemente contundentes como para acabar con el optimismo inicial.
Ahora bien, entre otros autores, Niklas Lubmann ha considerado un error equiparar funcionalismo con "organicismo", rescatando el potencial inherente del primero como método comparativo que privilegia las ''equivalencias funcionales".
Recorrer el camino hasta aquí esbozado será el objetivo de este trabajo.Fil: Cecchini, Gabriel F. Universidad Nacional de Córdoba; Argentina
From gridmap-file to VOMS: managing Authorization in a Grid environment
No full textFrom gridmap-file to VOMS: managing authorization in a Grid environment R. Alfieri, R. Cecchini, V. Ciaschini, L. dell’Agnellod, A. Frohner, K. Lorentey, F. Spataro Future Generation Computer Systems 21 (2005) 549–558 doi:10.1016/j.future.2004.10.006 Abstract Grids are potentially composed of several thousands of users from different institutions sharing their computing resources (or using resources provided by third parties). Controlling access to these resources is a difficult problem, as it depends on the policies of the organizations the users belong to and of the resource owners. Moreover, a simple authorization implementation, based on a direct user registration on the resources, is not applicable to a large scale environment. In this paper, we describe the solution to this problem developed in the framework of the European DataGrid [M. Draoli, G. Mascari, R. Piccinelli, Project Presentation, DataGrid-11-NOT-0103- 1] and DataTAG [http://www.datatag.org/] projects: the Virtual Organization Membership Service (VOMS) [R. Alfieri, et al., Managing Dynamic User Communities in a Grid of Autonomous Resources, TUBT005, in: Proceedings of the CHEP 2003, 2003]. VOMS allows a fine grained control of the use of the resources both to the users’ organizations and to the resource owners
Modelli mono-dimensionali per il calcolo delle concentrazioni nel tempo
No full textPer poter effettuare facilmente previsioni semplificate per l'impianto EVA , attualmente in fase di definizione, vengono proposti alcuni modelli mono-dimensionali per la valutazione delle concentrazioni nel tempo di sostanze immesse in un ambiente provvisto di un impianto di ventilazione. Viene presentata una applicazione su di un caso significativo per l'impianto EV A , allo scopo di verificare l'idoneità dei modelli proposti, attraverso il confronto dei loro risultati
STIMA DELLE CONCENTRAZIONI DELLE EMISSIONI GASSOSE E DI PARTICOLATO NEL TEMPO: MODELLO MONO-DIMENSIONALE
No full textVengono presentati le valutazioni, ottenute utilizzando un modello mono-dimensionale della concentrazione in aria delle principali sostanze emesse da un autobus all'interno della hall tecnologica dell'impianto EVA
Stress Analysis of Bulk Carrier Hatch Corners
No full textOne of the most frequent damage cause for bulk carrier ships is represented by high stress
concentrations occurring in deck plating close to hatch corners in way of coaming stay. In this
area many fractures are found during surveys which are generated mainly by three types of
problems:
• stress concentration in correspondence of deck large openings;
• bad design of stays;
• different thickness between transversal and external deck plates.
The typical approach followed by IACS classification societies consists in a wide range of
qualitative suggestion (transversal stiffening for transversal deck strip, elliptical hatch corner
etc.) and a very simple formula providing the extra thickness of the hatch corner compulsory
insert.
This solution seems to be inadequate to face this phenomenon and a better knowledge is
mandatory to understand which parameters are more influent on stress distribution and
concentration.
The purpose of the analysis herein presented is to identify most important parameters and to
study their influence, in order to develop a more sophisticate procedure to be used in
preliminary design stage.
The investigation has been developed starting from the analysis of five different bulk carriers,
selected on the basis of their geometric and structural properties, and modeled with FEM
software Leonardo hull 3D v. 2.4.1.
The analysis has been divided into two sub-problems:
• study of b/B ratio influence (hatch breadth versus ship breadth);
• study of lw/b ratio influence (cross deck length versus hatch breadt)..
Two different series of FEM models have been realized:
Global models of the hull extended to a portion of three cargo holds;
Simplified models with increasing refinement degree.
All global models have a relatively coarse mesh and are loaded with a wide number of
loading condition (homogeneous, heavy and light ballast, alternate ore) corresponding to
relevant RINA load cases in order to maximize the effects. For what simplified models are concerned four different types of models have been analysed:
a) The first model consists in a simple plate with a rectangular opening and two longitudinal
box structures simulating the wing tanks. All the parts of the model have a constant thickness.
b) A second series of models has then been created, similar to the first one, adding a coaming
around the hatch opening. As in the first case the thickness has been maintained constant.
c) The third series is similar to the first one but the thicknesses of the lateral deck strip and of
the cross deck have different values, according to the real case.
d) The fourth series is similar to the second one. Again deck plates have different thicknesses. For all the models the results have been processed to calculate stress concentration factors “k”
(defined as longitudinal stress close to hatch corner versus theoretical hull girder stress) for all
selected loading conditions.
From the “k” coefficients obtained for every model, a “stress concentration surface”, as a
function of b/B and w/b, has been drawn and expressed by a simplified formula
- …
