Experimental Characterization and Numerical Investigation on the Azzone Visconti Bridge in Lecco (Italy)

AbstractThe paper presents the results of a numerical investigation on the Azzone Visconti Bridge in Lecco (Italy). Starting from the historical data and from an extensive mechanical characterization of both the soil constituting the riverbed and of the masonry constituting the piers, the aim of the analyses is to predict the behaviour of the structure under the testing loading scheme prescribed by the current Italian Code. A finite element structural model has been conceived, and three different models describing the mechanical behaviour of the foundation have been implemented. Limited differences are observed in terms of absolute vertical settlement of the bridge, but important effects are highlighted in terms of stress redistribution within the piers

On Usage Control for GRID Systems

This paper introduces a formal model, an architecture and a prototype implementation for usage control on GRID systems. The usage control model (UCON) is a new access control paradigm proposed by Park and Sandhu that encompasses and extends several existing models (e.g. MAC, DAC, Bell-Lapadula, RBAC, etc). Its main novelty is based on continuity of the access monitoring and mutability of attributes of subjects and objects. We identified this model as a perfect candidate for managing access/usage control in GRID systems due to their peculiarities, where continuity of control is a central issue. Here we adapt the original UCON model to develop a full model for usage control in GRID systems. We use as policy specification language a process description language and show how this is suitable to model the usage policy models of the original UCON model. We also describe a possible architecture to implement the usage control model. Moreover, we describe a prototype implementation for usage control of GRID computational services, and we show how our language can be used to define a security policy that regulates the usage of network communications to protect the local computational service from the applications that are executed on behalf of remote GRID users

Usage control in SIP-based multimedia delivery

The Session Initiation Protocol (SIP) is an application layer signaling protocol for the creation, modification and termination of multimedia sessions and VoIP calls with one or more participants.SIP is widely accepted as the protocol that will dominate multimedia communications in the future and one of the reasons is that it can inherently support multidomain heterogeneous networks.While SIP operates in highly dynamic environments, in the current version its authorization support is based on traditional access control models.The main problem these models face is that they were designed many years ago, and under some circumstances tend to be inadequate in modern highly dynamic environments.Usage Control (UCON), instead, is a model that supports the same operations as traditional access control models do, but it further enhances them with novel ones.In previous work, an architecture supporting continuous authorizations on SIP, based on the UCON model, was presented.In this paper, an authorization support implementing the whole UCON model, including authorizations, obligations and conditions, has been integrated in a SIP system.Moreover, a testbed has been set up to experimentally evaluate the performance of the proposed security mechanism

Formula to Predict Transmission for pi-Type Floating Breakwaters

n/

"Pre-Earthquake" Micro-Structural Effects Induced by Shear Stress on α-Quartz in Laboratory Experiments

This paper presents the results of measurements performed on α-quartz subjected to shear stress in dry conditions, to understand the relationship between the shear intensity and the resulting physical and chemical effects. If a shear stress of intensity higher than 100 MPa is applied continuously to alpha quartz crystals, they will tend to lose their crystallinity, progressively reduce their friction coefficient (Cof) and change into a low-order material, apparently amorphous under X-ray diffraction, but with a structure different from silica glass. Raman and Pair Distribution Function analyses suggested a structure like cristobalite, a silica polymorph well-known for its auxetic behavior, i.e., having a negative Poisson ratio. This elastic parameter pre-eminently controls the friction coefficient of the material and, if it is negative, the Cof lowering. As a result, the increase in low crystallinity cristobalite is sufficientto explain the lowering of the quartz friction coefficient up to values able to contribute, in principle, to the triggering processes of active faults. This allows hypothesizing a slip induction mechanism that does not include the need to have the interposition of layers of hydrated silica, as invoked by many authors, to justify the low friction coefficients that are achieved in shear stress tests on rocks abundant in quartz

Investigating the Privacy vs. Forwarding Accuracy Tradeoff in Opportunistic Interest-Casting

Many mobile social networking applications are based on a ``friend proximity detection" step, according to which two mobile users try to jointly estimate whether they have friends in common, or share similar interests, etc. Performing ``friend proximity detection" in a privacy-preserving way is fundamental to achieve widespread acceptance of mobile social networking applications. However, the need of privacy preservation is often at odds with application-level performance of the mobile social networking application, since only obfuscated information about the other user\u27s profile is available for optimizing performance. noindent In this paper, we study for the first time the fundamental tradeoff between privacy preservation and application-level performance in mobile social networks. More specifically, we consider a mobile social networking application for opportunistic networks called interest-casting. In the interest-casting model, a user wants to deliver a piece of information to other users sharing similar interests (``friends"), possibly through multi-hop forwarding. In this paper, we propose a privacy-preserving friend proximity detection scheme based on a protocol for solving the Yao\u27s ``Millionaire\u27s Problem", and we introduce three interest-casting protocols achieving different tradeoffs between privacy and accuracy of the information forwarding process. The privacy vs. accuracy tradeoff is analyzed both theoretically, and through simulations based on a real-world mobility trace. The results of our study demonstrate for the first time that privacy preservation is at odds with forwarding accuracy, and that the best tradeoff between these two conflicting goals should be identified based on the application-level requirements

Hybrid Strategy to Achieve 3D Base Isolation of Structures

Some aspects, related to the 3D base isolation of structures to control the effects of both the horizontal and vertical components of ground motion, are presented in this paper. A massive structure (a Nuclear Power Plant building) equipped with a traditional horizontal base isolation system is numerically studied. The base isolation system uses rubber bearings (low and high damping) coupled with a tuned mass damper (TMD) in the vertical direction. Possible positive and negative aspects from the implementation of the proposed hybrid strategy are investigated. Numerical analyses show that the presence of the TMD mitigate the vertical effects of the three-dimensional ground motion coupled with the elastomeric bearings, reducing both the vertical and the horizontal absolute acceleration in the superstructure under certain conditions. Vertical acceleration in the superstructure appears related to the horizontal motion, due to the building’s centroid position that induces rocking

Fine Grained Access Control for Computational Services

Grid environment concerns the sharing of a large set of resources among entities that belong to Virtual Organizations. To this aim, the environment instantiates interactions among entities that belong to distinct administrative domains, that are potentially unknown, and among which no trust relationships exist a priori. For instance, a grid user that provides a computational service, executes unknown applications on its local computational resources on behalf on unknown grid users. In this context, the environment must provide an adequate support to guarantee security in these interactions. To improve the security of the grid environment, this paper proposes to adopt a continuous usage control model to monitor accesses to grid computational services, i.e. to monitor the behaviour of the applications executed on these services on behalf of grid users. This approach requires the definition of a security policy that describes the admitted application behaviour, and the integration in the grid security infrastructure of a component that monitors the application behaviour and that enforces this security policy. This paper also presents the architecture of the prototype of computational service monitor we have developed, along with some performance figures and its integration into the Globus framework

Robustness of RC girder bridges: The case of half-joint bridges

Considerable research efforts have been made on the progressive collapse resistance of buildings. This effort is much more limited in the case of bridges, where robustness criteria are just as, or even more important than in buildings. Existing studies dealing with the robustness of bridges, although appreciable, often are limited to qualitative considerations that can provide designers with valuable pointers when designing new bridges. It is equally important to assess not only the safety but also the robustness of existing bridges through reliable metrics that can be used in the prioritization of interventions by the managing authority. According to this aim, this paper applies a selected measure of robustness to a particular type of reinforced concrete (RC) girder bridge, namely half-joint bridges. The Annone viaduct, which collapsed in 2016 after the passage of a heavy truck, is used as a case study