272 research outputs found
Endogenous age structure in descriptive macroeconomic growth models: a general framework and some steady states analysis
No full textInnovation Diffusion Processes: Concepts, Models, and Predictions
No full textInnovation diffusion processes have attracted considerable research attention for their interdisciplinary character, which combines theories and concepts from disciplines such as mathematics, physics, statistics, social sciences, marketing, economics, and technological forecasting. The formal representation of innovation diffusion processes historically used epidemic models borrowed from biology, departing from the logistic equation, under the hypothesis that an innovation spreads in a social system through communication between people like an epidemic through contagion. This review integrates basic innovation diffusion models built upon the Bass model, primarily from the marketing literature, with a number of ideas from the epidemiological literature in order to offer a different perspective on innovation diffusion by focusing on critical diffusions, which are key for the progress of human communities. The article analyzes three key issues: barriers to diffusion, centrality of word-of-mouth, and the management of policy interventions to assist beneficial diffusions and to prevent harmful ones. We focus on deterministic innovation diffusion models described by ordinary differential equations
Damage assessment and design of structural interventions for Monte di Pietà in Naples, Italy
No full textSeveral signs of damage???such as cracks passing through the wall and surface deterioration appearing on the façade of the monumental building of Monte di Pietà in Naples, Italy???suggested the need to carry out on-site investigations to check the safety of this monumental structure. The investigations concerned several aspects: i) geometric survey, ii) survey of the crack patterns and of the deterioration distribution on the internal and external surfaces of the walls, iii) in situ measurements of the state of stress, and iv) georadar investigations to detect the geometry and conditions of the external pilasters in piperno stone (a sort of structural frame), which was suspected of being detached from the rest of the wall and therefore susceptible to possible local failures. An advanced numerical finite element method (FEM) analysis was conducted for the evaluation of the static conditions of the structure. A methodological and interdisciplinary experience to analyze and assess the stability of monumental buildings is discussed. The knowledge of historical reparative interventions and, moreover, an accurate knowledge of the geometry and the structural assessment of the façade suggested the need to design some strengthening and reparative interventions and each type of these interventions has been described in detail
Coordination games vs prisoner's dilemma in sustainability games: A critique of recent contributions and a discussion of policy implications
No full textRecent works have suggested that most games arising in climate change diplomacy and sustainability choices, should have a coordinative nature rather than that of a prisoners' dilemma, as typically suggested. In this note, after having proposed a definition of sustainability game, we critically review the merits and shortcomings of these contributions and use a simple, yet sufficiently general, model to recall the difficulties for coordination to emerge in such games. Indeed, as far as the players' short-term interest is involved, at least in some degree, these games will most often generate a prisoner's dilemma, thereby allowing coordination only upon long-term interactions possibly under the pressure of a continuing environmental deterioration. A counter- intuitive result is proved, showing the circumstances when the deterioration of the environment can hinder cooperation in repeated games. We conclude by highlighting a number of factors forcing “brown” behaviour and therefore threatening coordination, first of all poverty and inequality, and pinpointing that, though ability to enact coordination will be key for a successful battle for climate, undue emphasis on coordination might be the deleterious in view of its optimistic message
A combination of NDT methods for the restoration of monumental façades: the case study of Monte di Pietà (Naples, Italy)
No full textThe paper focuses on an interdisciplinary research project concerning the preservation of the XVII century monumental building of Monte di Pietà in Naples, Italy. The building underwent a series of restorations being the structural walls affected by humidity and cracks. The importance of this monumental building in the historical city center of Naples led to design an extensive surveying program to provide the designers of strengthening with a detailed investigation of the geometry of the entire structure, and particularly of the entrance façade, with great details on several materials, thicknesses and restraints. A preliminary investigation was performed on the historical phases of this monumental building to have a clear knowledge of its vicissitudes, and then in situ structural assessment included 3D laser scanner techniques probing radar, in situ stress measures. This surveying phase was crucial especially for the subsequent Finite Elements modeling (F.E.M.) of the façade. The scope of the numerical refined analyses was to evaluate the state of stress in the structural elements of the façade putting in evidence structural ???weak points??? and finally to design a retrofit intervention having a detailed map of the ???intervention areas???. The theoretical damage assessment has been compared with on-site assessment and in situ stress measures. The damage primarily concerned the entrance façade and its valuable decorations. Furthermore, the basic principles for the design of the strengthening have been discussed
Diffusion of Renewable Energy for Electricity: An Analysis for Leading Countries
No full textMany countries are undertaking their energy transition process, by investing in renewable energy technologies, in order to face climate change and energy security problems. This paper investigates the temporal trends of the diffusion process of renewable energies, namely, wind and solar, in leading countries for their consumption. In doing so, a bivariate diffusion model is employed to investigate the possibly competitive dynamics between renewables and the top source for electricity production in each country. The obtained results confirm a significant competitive pressure enacted by renewables on the top source. A notable exception is represented by the USA, where renewables appear to reinforce the dominant position of gas
The Impact of Current Demographic Trends on the Dynamics and Control of Vaccine Preventable Childhood Infection.
No full textBIOLOGICAL COMPLEXITY: PAST COMMITMENTS AND FUTURE CHALLENGES, Arcidosso, Italy September 19-21 2013 [oral presentation
The Epidemiology of Herpes Zoster after Varicella Immunization under Different Biological Hypotheses: Perspectives from Mathematical Modeling
No full textThe impact of varicella vaccination on the epidemiology of herpes zoster (HZ) critically depends on the mechanism of immunological boosting, through which reexposures to varicella-zoster virus are thought to reduce the individual risk of HZ development. However, the qualitative and quantitative dynamics of this process are largely unknown. Consequently, mathematical models evaluating immunization strategies need to rely on theoretical assumptions. Available varicella-zoster virus models can be classified in 3 main families according to the postulated effect of exogenous boosting: 1) progressive accumulation of immunity following repeated reexposures; 2) partial protection that wanes over time; or 3) full but temporary immunity against HZ. In this work, we review and compare quantitative predictions from the 3 modeling approaches regarding the effect of varicella immunization on HZ. All models predict a qualitatively similar, but quantitatively heterogeneous, transient increase of HZ incidence. In particular, novel estimates from the progressive immunity model predict the largest increase in natural HZ and the largest incidence of HZ cases from reactivation of the vaccine strain, which in the long term will likely outnumber prevaccination numbers. Our results reinforce the idea that a better understanding of HZ pathogenesis is required before further mass varicella immunization programs are set out
Simple method for the design of jet grouted umbrellas in tunneling
No full textTunnel excavation in cohesionless soils implies the use of a temporary supporting structure prior to lining installation. This temporary structure has to couple safety and economy, and can be conveniently realized using ground improvement techniques (for instance, by creating an arch of partially overlapped sub-horizontal jet grouted columns). The adoption of ground improvement techniques results into structures far from having a perfect shape because intrinsically affected by defects (in both geometrical and mechanical characteristics), and therefore their design may hide unforeseen risks. As a consequence, this is the typical case in which sophisticated numerical analyses may just give the illusion of being refined, if possible defects are not correctly taken into account.
In this paper a simple yet rational analytical method for the design of non-closed tunnel supporting structure that may be of some help to this aim is presented. It is done with reference to a simple 2D scheme. In the first part of the paper, a design chart to design an optimal shape and minimum structural thickness of the cross section of the supporting structure is shown. In the second part, an iterative procedure to verify the stability or to design the minimum structural thickness of an existing supporting structure with a predefined shape is described.
This method, coupled with the analysis of structural demand, allows in principle to plot design charts. This approach can easily take into account structural defects with a semi probabilistic approach and therefore with a chosen risk level, being of great help for the designer at least in a preliminary design stage. The proposed semi probabilistic procedure is applied to the case of a temporary supporting structure realized by partially overlapped sub horizontal jet grouted columns, intrinsically affected by defects in diameter and position. The variability of these geometrical parameters was considered based on the large experimental evidence collected in field trials by the authors and published elsewhere.
CE Database Subject Headings: Arches, Jet Grouting, Limit Analysis, Probabilistic Methods, Structural Design, Tunnel Supports, Thrust lin
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