347 research outputs found
Modelling of multiscale nonlinear interaction of elastic waves with three-dimensional cracks
No full textThis paper presents a nonlinear elastic material model able to simulate the nonlinear effects generated by the interaction of acoustic/ultrasonic waves with damage precursors and micro-cracks in a variety of materials. Such a constitutive model is implemented in an in-house finite element code and exhibits a multiscale nature where the macroscopic behavior of damaged structures can be represented through a contribution of a number of mesoscopic elements, which are composed by a statistical collection of microscopic units. By means of the semi-analytical Landau formulation and Preisach-Mayergoyz space representation, this multiscale model allows the description of the structural response under continuous harmonic excitation of micro-damaged materials showing both anharmonic and dissipative hysteretic effects. In this manner, nonlinear effects observed experimentally, such as the generation of both even and odd harmonics, can be reproduced. In addition, by using Kelvin eigentensors and eigenelastic constants, the wave propagation problem in both isotropic and orthotropic solids was extended to the three-dimensional Cartesian space. The developed model has been verified for a number of different geometrical and material configurations. Particularly, the influence of a small region with classical and non-classical elasticity and the variations of the input amplitudes on the harmonics generation were analyzed
Investment, autonomous demand and long run capacity utilization. An empirical test for the euro area
No full textThis paper reviews and empirically tests the validity of the Sraffian Supermultiplier model (SSM) and the modified Neo-Kaleckian model after the inclusion of autonomous components of aggregate demand. First, we theoretically assess whether the SSM may constitute a complex variant of the Neo-Kaleckian model. In this sense, it is shown that results compatible with the SSM can be obtained by implementing a set of mechanisms in a modified Neo-Kaleckian model. Second, the paper empirically tests the main implications of the models in the Euro Area, based on Eurostat data. In particular, the discussion outlines the short and long-run relation between autonomous demand and output, by testing cointegration and causality with a VECM model. Moreover, the role accounted by both theories to the rate of capacity utilization is empirically assessed, through a time-series estimation of the Sraffian and Neo-Kaleckian investment functions. While confirming the theoretical relation between autonomous demand and output in the long run, the results also show that capacity utilization still plays a key role in the short-run adjustment mechanism
Infection is the cycle. Unemployment, output and economic policies in the COVID-19 pandemic
No full textThis paper seeks to capture the dynamic interaction between the epidemiological evolution of COVID-19 and its effect on the macroeconomy, in absence of widespread vaccination. We do that by building a stylized two-equations dynamical system in the COVID-19 positivity rate and the unemployment rate. The solution of the system makes the case for an endemic equilibrium of COVID-19 infections, thus producing waves in the two variables in the absence of widespread immunity through vaccination. Furthermore, we model the impact of the pandemic-driven unemployment shock on output, showing how the emergence of cyclical downswings could determine a L-shaped recession in the medium run, in absence of adequate stimulus policies. Moreover, we simulate the model, calibrating it for the US. The simulation highlights the effects on unemployment and on overall economic activity produced by recurrent waves of COVID-19, which risk to jeopardize the coming back to the pre-crisis trend in the medium run
Teaching heterodox macroeconomics
No full textThis contribution examines recent developments in post-Keynesian macroeconomics teaching through an analysis of five textbooks: Blecker and Setterfield (2019), Hein (2014; 2023), and Lavoie (2014; 2022). The focus is on Hein’s latest book, Macroeconomics after Kalecki and Keynes (2023), which aims to provide a comprehensive and teachable post-Keynesian macroeconomic model, by covering topics such as effective demand, policy coordination, distribution and growth, finance-dominated capitalism, and ecological constraints. The review discusses Hein’s textbook in a comparative way, highlighting points of strength and aspects that should be explored further, particularly (but not related to) the field of climate change and environmental constraints to growth. Overall, it is argued that Hein's book contributes to the literature on post-Keynesian economics and provides a valuable resource for undergraduate and graduate students in the field
A Predator-Prey Model of Unemployment and W-shaped Recession in the COVID-19 Pandemic
No full textThe paper presents a predator-prey model which captures the interactions between unemployment rate and COVID-19 infection rate. The model shows that lockdown measures can effectively reduce the infection rate, but at the cost of higher unemployment rate. The solution of the system makes the case for an endemic equilibrium of COVID-19 infections, hence producing waves in the unemployment rate in the absence of widespread immunity and/or vaccination. Furthermore, we simulate the model, calibrating it for the US. The simulation shows the dramatic effects on unemployment and on overall economic activity produced by potential recurrent waves of COVID-19, leading to a series of W-shaped recessions that - in absence of adequate policy response - jeopardize the coming back to the normal trend in the medium run. ; COVID-19, unemployment rate, jobless recovery, W-shaped recessio
A Predator-Prey Model of Unemployment and W-shaped Recession in the COVID-19 Pandemic
No full textThe paper presents a predator-prey model which captures the interactions between unemployment rate and COVID-19 infection rate. The model shows that lockdown measures can effectively reduce the infection rate, but at the cost of higher unemployment rate. The solution of the system makes the case for an endemic equilibrium of COVID-19 infections, hence producing waves in the unemployment rate in the absence of widespread immunity and/or vaccination. Furthermore, we simulate the model, calibrating it for the US. The simulation shows the dramatic effects on unemployment and on overall economic activity produced by potential recurrent waves of COVID-19, leading to a series of W-shaped recessions that - in absence of adequate policy response - jeopardize the coming back to the normal trend in the medium run. ; COVID-19, unemployment rate, jobless recovery, W-shaped recessio
Le carte del monastero di San Pietro in Ciel d'Oro di Pavla. II : 1165-1190, a cura di Ezio Barbieri, Maria Antonietta Casagrande Mazzoli, Ettore Cau. Pavia-Milano : Fontes, 1984. In-8°, XXX-542 pages. (Fonti storicogiuridiche, Documenti, 1.)
No full textGuyotjeannin Olivier. Le carte del monastero di San Pietro in Ciel d'Oro di Pavla. II : 1165-1190, a cura di Ezio Barbieri, Maria Antonietta Casagrande Mazzoli, Ettore Cau. Pavia-Milano : Fontes, 1984. In-8°, XXX-542 pages. (Fonti storicogiuridiche, Documenti, 1.). In: Bibliothèque de l'école des chartes. 1986, tome 144, livraison 2. pp. 398-402
Impact localization in composite structures of arbitrary cross section
No full textThis article proposes an in situ structural health monitoring method able to locate the impact source and to determine the flexural Lamb mode A0 velocity in composite structures with unknown lay-up and cross section. The algorithm is based on the differences of the stress waves measured by six surface-attached acoustic emission piezoelectric (lead zirconate titanate) sensors and is branched off into two steps. In the first step, the magnitude of the squared modulus of continuous wavelet transform, which guarantees high accuracy in the time-frequency analysis of the acoustic waves, was used to identify the time of arrival of the flexural Lamb wave. Then, the coordinates of the impact location and the group speed values are obtained by solving a set of non-linear equations through a combination of local Newton's iterative method associated with line search and polynomial backtracking techniques. The proposed method, in contrast to the current impact localization algorithms, does not require a priori knowledge of the anisotropy angular-group velocity pattern of the measured waveforms as well as the mechanical properties of the structure. To validate this method, experimental location testing was conducted on two different composite structures: a quasi-isotropic carbon fibre-reinforced plastic laminate and a sandwich panel. The results showed that source location was achieved with satisfactory accuracy (maximum error in estimation of the impact location was approximately 3 mm for quasi-isotropic carbon fibre-reinforced plastic panel and nearly 2 mm for sandwich plate), requiring little computational time (nearly 1 s). In addition, the values of the fundamental flexural Lamb mode A0 obtained from the optimization algorithm were compared with those determined by a numerical spectral finite element method
Sellers' Inflation and Distributive Conflict: Lessons from the Post-COVID Recovery
No full textThe paper offers a post-Keynesian explanation of the soaring inflation experienced during the post-COVID recovery, coherent both at the microeconomic and macroeconomic levels. The microeconomic argument is rooted on the premise that price-making firms consider both their costs and their desired share of profits when setting prices. To defend profit margins in the aftermath of the pandemic, the initial cost-push shock was passed to consumers through higher prices; in a second phase, some firms, particularly in more highly concentrated and systemically significant sectors, benefited from the post-pandemic permissive pricing environment to increase their price mark-ups, leading to temporary profit-fueled inflation following the cost-push shock. This microeconomic explanation is compatible with the macroeconomic notion of a stable inflation barrier. For a given quantity of real output, it is shown that if profit earners defend their share of income following a cost-push, this will produce a one-time price increase, with inflation becoming more persistent if the target adapts endogenously — i.e., if the aggregate mark-up changes. The paper contrasts the notion of a wage-price spiral with that of a profit-price sink, arguing that sellers’ inflation is a real — albeit temporary phenomenon
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