THE SOLOW¡¯S MODEL WITH ENDOGENOUS POPULATION: A NEOCLASSICAL GROWTH CYCLE MODEL

It is shown here that the Solow (1956) neo-classical growth paradigm not only explains the ¡°first¡± stylised fact of economic growth, namely the existence of a globally stable state of balanced growth, but, once endowed with a demographically founded formulation of the labour supply, is also capable to endogenously explain a second main stylised fact of growth, i.e., the generation of globally stable oscillations around the path of balanced growth.Solow¡¯s Balanced Growth Model, Endogenous Population, Neoclassical Growth-Cycle Model

Lyapunov stability of an SIRS epidemic model with varying population

In this paper we consider an SIRS epidemic model under a general assumption of density-dependent mortality. We prove the global stability of the disease-free equilibrium and propose a Lyapunov function that allows to demonstrate the global stability of the (unique) endemic state under broad conditions.Comment: 7 page

Lyapunov Stability of an SIRS epidemic model with varying population: ecological VS physical approaches

We consider a general SIRS epidemiological transmission model for an endemic infection with variable population including a general assumption of density-dependent mortality and vertical transmission. We analyse global stability by the Lyapunov approach, proposing two alternative Lyapunov functions. The first one is based on traditional ecological arguments, while the second one is a 'physical' Lyapunov function based on the energy of an appropriate second order equation. Both functions allow to prove the global stability of the (unique) endemic state under broad - not equivalent - parametric conditions. This suggests that using different Lyapunov functions provide useful complementary information on the parametric regions where global stability prevails

Simplified Modeling of Rectangular Concrete Cross-Sections Confined by External FRP Wrapping

The goal of this research project is to model the effect of confinement by means of fiber reinforced polymer (FRP) externally bonded wrapping, hence to provide a simplified closed form solution to determine directly the ultimate confined concrete strength. Common cross-section shapes for reinforced concrete (RC) columns are considered herein, namely square and rectangular. The simplified model is derived from a more refined iterative confinement model proposed by the same authors to evaluate the entire stress-strain relationship of confined concrete. Based on a detailed analysis of the stress state through Mohr's circle, a simplified closed form solution is proposed to account for the non-uniformly confined concrete performance exhibited in non-axisymmetric sections. The non-uniform confining stress field exhibited in such cross-sections is explicitly considered by means of the mean value integral of the pointwise variable stress state over the cross-section. The key aspect of the proposed methodology is the evaluation of the effective equivalent pressure to be inserted in any triaxial confinement model, to account for the peculiarities of square and rectangular cross-sections. Experimental data, available in the literature and representative of a wide stock of applications, were compared to the results of the theoretical simplified model to validate the proposed approach, and satisfactory results were found

Effects of the gg-factor in semi-classical kinetic plasma theory

A kinetic theory for spin plasmas is put forward, generalizing those of previous authors. In the model, the ordinary phase space is extended to include the spin degrees of freedom. Together with Maxwell's equations, the system is shown to be energy conserving. Analysing the linear properties, it is found that new types of wave-particle resonances are possible, that depend directly on the anomalous magnetic moment of the electron. As a result new wave modes, not present in the absence of spin, appear. The implications of our results are discussed.Comment: 4 pages, two figures, version to appear in Physical Review Letter

Heterogeneity in regional notification patterns and its impact on aggregate national case notification data: the example of measles in Italy

BACKGROUND: A monthly time series of measles case notifications exists for Italy from 1949 onwards, although its usefulness is seriously undermined by extensive under-reporting which varies strikingly between regions, giving rise to the possibility of significant distortions in epidemic patterns seen in aggregated national data. RESULTS: A corrected national time series is calculated using an algorithm based upon the approximate equality between births and measles cases; under-reporting estimates are presented for each Italian region, and poor levels of reporting in Southern Italy are confirmed. CONCLUSION: Although an order of magnitude larger, despite great heterogeneity between regions in under-reporting and in epidemic patterns, the shape of the corrected national time series remains close to that of the aggregated uncorrected data. This suggests such aggregate data may be quite robust to great heterogeneity in reporting and epidemic patterns at the regional level. The corrected data set maintains an epidemic pattern distinct from that of England and Wales

Accuracy of a markerless acquisition technique for studying speech articulators. In Interspeech 2015

International audienceThe main disadvantages of the existing methods for studying speech articulators (such as electromagnetic and optoelectronic systems) are the high cost and the discomfort to participants or patients. The aim of this work is to introduce a completely markerless low-cost 3D tracking technique in the context of speech articulation, and then compare it with a well-established marker-based one to evaluate the performances. A Kinect-like device was used in conjunction with an existing face tracking algorithm to track lips movements in 3D without markers. The method was tested on two subjects uttering 200 words and 100 sentences. For most of points of the lips the RMSE ranged between 1 and 3 mm. Although the image resolution used in this experiment was low, these results are very promising. Nevertheless, further studies should consider higher video resolutions in order to obtain better results

Tiered social distancing policies and epidemic control

International audienceTiered social distancing policies have been adopted by many governments to mitigate the harmful consequences of COVID-19. Such policies have a number of well-established features i.e., they are short-term, adaptive (to the changing epidemiological conditions), and based on a multiplicity of indicators of the prevailing epidemic activity. Here, we use ideas from Behavioural Epidemiology to represent tiered policies in an SEIRS model by using a composite information index including multiple indicators of current and past epidemic activity mimicking those used by governments during the COVID-19 pandemic, such as transmission intensity, infection incidence and hospitals' occupancy. In its turn, the dynamics of the information index is assumed to endogenously inform the governmental social distancing interventions. The resulting model is described by a hereditary system showing a noteworthy property i.e., a dependency of the endemic levels of epidemiological variables from initial conditions. This is a consequence of the need to normalise the different indicators to pool them into a single index. Simulations suggest a rich spectrum of possible results. These include policy suggestions and identify pitfalls and undesired outcomes, such as a worsening of epidemic control, that can arise following such types of approaches to epidemic responses