1,359,382 research outputs found
76. Ara a Saturno; 77. ara sacra di Titus Titienus Florus: 78. Ara sacra alle Giunoni Matrone; 79. Ara sacra alle Giunoni; 80. Ara sacra a Giove Lustrale; 81. Ara sacra a Silvano
No full textSi studiano alcuni rilievi di età romana con iscrizioni votiv
Livella a bolla
No full textLa livella a bolla fu inventata dal francese M. Thévenot, che la descrisse nel 1666. E\u27 composta da un tubo di vetro chiuso ermeticamente e parzialmente riempito da un liquido come alcol o etere, mentre la bolla è costituita da aria e vapore del liquido stesso. La bolla, avendo una densità minore del liquido, tende a galleggiare portandosi quindi nella parte più alta. Il tubo di vetro è inserito in una custodia metallica dotata di una finestrella. Questo tipo di livella viene anche definito “torica”. Lo strumento serviva per verificare la perfetta orizzontalità di una superficie ma, in questo caso, poteva essere utilizzato anche per misurare l’inclinazione di un asse. Infatti, posizionando la livella sull’asse, si leggeva la graduazione segnata dai due estremi della bolla; la differenza tra il vertice e la media delle letture moltiplicata per il valore angolare della particella, forniva l’inclinazione della superficie. Lo strumento faceva parte della tavoletta pretoriana costruita da Montan.La livella a bolla fu inventata dal francese M. Thévenot, che la descrisse nel 1666. E\u27 composta da un tubo di vetro chiuso ermeticamente e parzialmente riempito da un liquido come alcol o etere, mentre la bolla è costituita da aria e vapore del liquido stesso. La bolla, avendo una densità minore del liquido, tende a galleggiare portandosi quindi nella parte più alta. Il tubo di vetro è inserito in una custodia metallica dotata di una finestrella. Questo tipo di livella viene anche definito “torica”. Lo strumento serviva per verificare la perfetta orizzontalità di una superficie ma, in questo caso, poteva essere utilizzato anche per misurare l’inclinazione di un asse. Infatti, posizionando la livella sull’asse, si leggeva la graduazione segnata dai due estremi della bolla; la differenza tra il vertice e la media delle letture moltiplicata per il valore angolare della particella, forniva l’inclinazione della superficie. Lo strumento faceva parte della tavoletta pretoriana costruita da Montan
The IP Lookup Mechanism in a Linux Software Router: Performance Evaluation and Optimizations
No full text2007 IEEE Workshop on High Performance Switching and Routing, HPSR
2007, Article number 4281242, Pages 82-87
2007 IEEE Workshop on High Performance Switching and Routing, HPSR; Brooklyn, NY; United States; 30 May 2007 through 1 June 2007; Category number07EX1775C; Code 72703
The IP lookup mechanism in a Linux software router: Performance evaluation and optimizations (Conference Paper)
Bolla, R. , Bruschi, R.
DIST - Department of Communications, Computer and Systems Science, University of Genoa, Via Opera Pia 13, 16145 Genova, Italy
View references (23)
Abstract
In the last years, networking device architectures based on Open Source Software, like Linux, have aroused lively interest from both Scientific and Industrial Communities. The key to this success can probably be found in the flexibility and fast development time of the Software approach, and the reliability level guaranteed by large communities of users and developers. In this contest, our aim is to customize, to analyze and to optimize a Linux based architecture for an exclusive networking use. In particular, the objective of this work is to study, to evaluate the performance and to optimize the IP lookup mechanism included in the Linux kernel. With this aim we have released a set of kernel patches to enhance the performance of the system by optimizing the IP lookup mechanism. We present a complete set of benchmarking results with both internal and external measurements
Livella a bolla
No full textLa livella a bolla fu inventata dal francese M. Thévenot, che la descrisse nel 1666. Essa è composta da un tubo di vetro chiuso ermeticamente e parzialmente riempito da un liquido come alcol o etere, mentre la bolla è costituita da aria e vapore del liquido stesso. La bolla, avendo una densità minore del liquido, tende a galleggiare portandosi quindi nella parte più alta. Il tubo di vetro è inserito in una custodia metallica dotata di una finestrella. Sul vetro del tubo, in corrispondenza della finestrella, sono incise delle tacche che distano tra loro circa 2 mm. Questo tipo di livella viene anche definito “torica”. Lo strumento serviva per verificare la perfetta orizzontalità di una superficie ma, in questo caso, esso poteva essere utilizzato anche per misurare l’inclinazione di un asse. Infatti, posizionando la livella sull’asse, si leggeva la graduazione segnata dai due estremi della bolla; la differenza tra il vertice C e la media delle letture moltiplicata per il valore angolare della particella, forniva l’inclinazione della superficie. Lo strumento faceva parte della tavoletta pretoriana costruita da Giuseppe Stefani (?-1842), meccanico della Specola di Padova dal 1834 al 1842 e allievo prediletto di Giovanni Battista Rodella (1749-1834), del quale fu il successore.La livella a bolla fu inventata dal francese M. Thévenot, che la descrisse nel 1666. Essa è composta da un tubo di vetro chiuso ermeticamente e parzialmente riempito da un liquido come alcol o etere, mentre la bolla è costituita da aria e vapore del liquido stesso. La bolla, avendo una densità minore del liquido, tende a galleggiare portandosi quindi nella parte più alta. Il tubo di vetro è inserito in una custodia metallica dotata di una finestrella. Sul vetro del tubo, in corrispondenza della finestrella, sono incise delle tacche che distano tra loro circa 2 mm. Questo tipo di livella viene anche definito “torica”. Lo strumento serviva per verificare la perfetta orizzontalità di una superficie ma, in questo caso, esso poteva essere utilizzato anche per misurare l’inclinazione di un asse. Infatti, posizionando la livella sull’asse, si leggeva la graduazione segnata dai due estremi della bolla; la differenza tra il vertice C e la media delle letture moltiplicata per il valore angolare della particella, forniva l’inclinazione della superficie. Lo strumento faceva parte della tavoletta pretoriana costruita da Giuseppe Stefani (?-1842), meccanico della Specola di Padova dal 1834 al 1842 e allievo prediletto di Giovanni Battista Rodella (1749-1834), del quale fu il successore
On the convective nature of bar instability: the effect of suspended load.
No full textFederici & Seminara (2003) have recently shown that the nature of bar instability if the sediment is transported mainly as bed load is convective. In the present paper, we extend the above work to the case when a significant portion of the sediment load is carried in suspension. We employ a depth averaged approach suitable to slowly varying flows which leads to the analytical form for the flux of suspended sediment recently derived by Bolla Pittaluga & Seminara (2003)
Archives orales de la Convention du patrimoine mondial : entrevue menée avec Gérard Bolla par Christina Cameron et Mechtild Rössler
No full text1. La Convention du patrimoine mondial ; 1a. Implication et participation de Gérard Bolla au patrimoine mondial ; 1b. La liste du patrimoine mondial ; 1c. La Convention comme outil de conservation et de coopération internationale ; 1d. Échecs et réussites de la Convention ; 2. Le Comité du patrimoine mondial ; 3. Les organes consultatifs : UICN, ICOMOS et ICCROMGérard Bolla a étudié l’économie et le droit en Suisse avant d’entrer à l’UNESCO en 1955. Il devient directeur du cabinet du Directeur général René Maheu en 1969, fonction qu’il occupera pendant deux ans avant d’être nommé Sous-Directeur général pour la culture. C’est à ce titre qu’il sera impliqué dans les négociations pour la rédaction du texte de la Convention du patrimoine mondial et son adoption à la Conférence générale de l’UNESCO en 1972. Il participera ensuite aux réunions statutaires pour le patrimoine mondial jusqu’en 1981. En 1992, son importante contribution est soulignée à l’occasion du vingtième anniversaire de la Convention, lors de la session du Comité à Santa Fe, aux États-Unis. Avec Michel Batisse, Gérard Bolla a consigné son expérience dans L’Invention du patrimoine mondial en 2003 (Cahiers d’Histoire de l’Association des anciens fonctionnaires de l’UNESCO). Il est également co-auteur de Le patrimoine à l’UNESCO : le défi de la sauvegarde, paru en 2009 dans la même série. Les extraits audio suivants sont issus d’une entrevue menée avec Gérard Bolla par Christina Cameron et Mechtild Rössler en octobre 2007 au siège social de l’UNESCO à Paris, France. Ces capsules révèlent, grâce à la perspective «de l’intérieur» de Gérard Bolla, les coulisses des négociations ayant mené à l’adoption de la Convention du patrimoine mondial. Elles replacent également la Convention dans le cercle plus vaste des interventions de l’UNESCO en matière de culture et de patrimoine
Seismic Analysis of a Limestone Rock Slope through Numerical Modelling: Pseudo-Static vs. Non-Linear Dynamic Approach
No full textIn the present work, a seismic analysis was performed in advance on a limestone rock slope (height = 150 m) outcropping along the Tagliamento River valley, in the Friuli Venezia Giulia Region, north-eastern Italy. The analysed slope is characterised by strong rock mass damage, thus resulting in a critical stability condition (unstable volume = 110,000-200,000 m3). The seismic analysis was performed adopting the 2D finite difference method (FDM) and employing both a pseudo-static approach and a non-linear dynamic approach. Model outcomes demonstrate that the seismic motion induces internal, localised ruptures within the rock mass. Some important differences in the mechanical behaviour of the rock slope were highlighted, depending on the specific modelling approach assumed. When adopting a pseudo-static approach, the slope failure occurs for PGA values ranging between 0.056 g and 0.124 g, depending on the different initial static stability condition assumed for the slope (Strength Reduction Factor SRF = 1.00-1.15). According to the non-linear dynamic approach, the slope failure is achieved for PGA values varying between 0.056 g and 0.213 g. Pre-collapse slope displacements calculated with the pseudo-static approach (12-15 cm) are much more greater than those obtained through the non-linear dynamic approach (0.5-3 mm). The modelling results obtained through the non-linear dynamic analysis also testify that the seismic topographic amplification is 1.5 times the target acceleration at the slope face and 2.5 times the target acceleration at the slope toe
UCS field estimation of intact rock using the Schmidt hammer: A new empirical approach
No full textIn the present work we discuss the results of a number of Schmidt hammer tests (total number of impacts N > 2,400) that were performed in situ on rock outcrops of different lithology (marl, calcareous marl, limestone, sandstone, quartz sandstone and rhyolite) that occur in Italy. Firstly, a specific field procedure to choose the reference value of the rebound index adopted to calculate UCS of intact rock is suggested. A relationship between L and N hammer rebound index values (RL and RN, respectively) is subsequently assessed. Considering the experimental datasets provided by a Schmidt hammer construction company and other research available in literature, a new exponential equation for the correlation between RL and UCS of intact rock has been derived. Considering the here-proposed RL-RN relationship, a new exponential correlation between RN and UCS has also been defined. The newly proposed procedure and relationships were successfully utilised to determine the intact rock strength of different rocks. The calculated UCS values are very similar when using both types of Schmidt hammer (L and N) and are generally in line with previous determinations from experimental data available in literature
On the migration of tidal free bars
No full textWe derive and employ a depth-averaged model for the formation of free bars in infinitely long tidal channels in order to investigate the mechanism whereby tidal bars may experience a net migration over a tidal cycle. The flux of the suspended sediment is modeled by means of an analytical relationship derived by Bolla Pittaluga and Seminara [ M. Bolla Pittaluga and G. Seminara, Water Resour. Res. 39, 5 (2003) ] for slowly varying flows. The model is validated by performing a linear stability analysis of flow and bed topography in a rectangular channel with an erodible bed, subject to the propagation of a symmetric tidal wave of small amplitude. The results of the present depth averaged model show a fairly satisfactory agreement with previous results based on a three-dimensional model [ G. Seminara and M. Tubino, J. Fluid Mech. 440, 49 (2001) ]. We then investigate the role of overtides, showing that a flood or ebb asymmetry of the basic flow gives rise to a net migration of bars. The mechanism is due to the nonlinearity of the dependence of sediment flux on bottom stress. This phenomenon is somewhat similar to processes occurring in various fields of fluid mechanics, such as steady streaming in an oscillatory boundary layer [ N. Riley, Annu. Rev. Fluid Mech. 33, 43 (2001) ] or acoustic streaming. The present investigation also bears some relevance to the problem of nonlinear development of tidal bars, as it suggests that a depth averaged approach may be adequate to its treatment, while definitely requiring a computational effort much smaller than treatments based on 3D formulations
3D NUMERICAL INVESTIGATION OF TIDAL FORCING ON THE STABILITY OF BIFURCATIONS
No full textRiver bifurcations are ubiquitous features of both gravel-bed and sand-bed fluvial systems, including braiding networks, anabranches and deltas. As such, their morphology and development shape fluvial plains and deltas dictating flood risk areas as well as land loss and land gain. The morphodynamic equilibrium of bifurcations is strongly affected by the characteristics of the upstream channel, such as width-to-depth ratio (Bolla Pittaluga et al., 2003), curvature (Kleinhans et al., 2008), bar presence (Bertoldi et al., 2009; Redolfi et al., 2019), and related sediment transport mechanisms (Bolla Pittaluga et al., 2015; Redolfi et al., 2016), which regulate water and sediment partitioning into the two downstream branches.
Interestingly, in nature the downstream boundary conditions may also influence the bifurcation dynamics due to their oscillatory behaviour with significant backwater effects. It has been observed that tide‐influenced deltas tend to exhibit more stable branches keeping all channels active. Factors such as the length of the downstream channels or tidal ranges strongly affect the evolution of the bifurcations. On the basis of an analytical 1D model developed under the hypothesis of small monochromatic tidal oscillations, Ragno et al. (2020) proved that even small-amplitude tides have a stabilizing effect on the bifurcation due to the erosive character of weak tidal ebb flows. These flows keep both branches morphodynamically active, preventing the development of unbalanced solutions.
The present work aims to corroborate Ragno et al. (2020) findings by means of fully 3D numerical simulations performed through Delft3D and to extend the analysis to the case of strongly tide influenced bifurcations. Moreover, the full description of the flow field along the vertical direction allows for a more thorough evaluation of sediment and flow partitions at the bifurcation and to quantify 3D effects at the node on the evolution and the equilibrium configuration of the system
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