Search results for "Shocks"
showing 10 items of 31 documents
Simultaneous seismic wave clustering and registration
2012
In this paper we introduce a simple procedure to identify clusters of multivariate waveforms based on a simultaneous assignation and alignment procedure. This approach is aimed at the identification of clusters of earthquakes, assuming that similarities between seismic events with respect to hypocentral parameters and focal mechanism correspond to similarities between waveforms of events. Therefore we define a distance measure between seismic curves in R^d d>=1, in order to interpret and better understand the main features of the generating seismic process.
Laboratory unraveling of matter accretion in young stars
2017
When matter accretes onto a young star, a shell of dense material can form around the impact, reducing its x-ray emission.
Shipping Costs and Inflation
2023
The Covid-19 pandemic has disrupted global supply chains, leading to shipment delays and soaring shipping costs. We study the impact of global shipping costs-measured by the Baltic Dry Index (BDI)-on domestic prices for a large panel of countries during the period 1992-2021. We find that spikes in the BDI are followed by sizable and statistically signif-icant increases in import prices, PPI, headline, and core inflation, as well as inflation expec-tations. The impact is similar in magnitude but more persistent than for shocks to global oil and food prices. The effects are more muted in countries where imports make up a smaller share of domestic consumption, and those with inflation targetin…
The effects of monetary policy shocks on inequality
2018
Abstract This paper provides new evidence of the effect of conventional monetary policy shocks on income inequality. We construct a measure of unanticipated changes in policy rates—changes in short-term interest rates that are orthogonal to unexpected changes in growth and inflation news—for a panel of 32 advanced and emerging market countries over the period 1990–2013. Our main finding is that contractionary monetary policy shocks increase income inequality, on average. The effect is asymmetric—tightening of policy raises inequality more than easing lowers it—and depends on the state of the business cycle. We find some evidence that the effect increases with the share of labor income and i…
Bank-specific shocks and aggregate leverage: Empirical evidence from a panel of developed countries
2020
International audience; This paper investigates the link between shocks in the banking sector and aggregate leverage measured by the credit-to-GDP gap. Using a balanced panel of 15 countries for the period 1989–2016, we exploit the approach due to Gabaix (2011) and consider banking granular shocks as an indicator of banking distress. Using methods that account for potential endogeneity, we find that banking shocks Granger-cause aggregate leverage. In particular, banking shocks tend to increase the level of leverage and cause departures of the credit-to-GDP ratio from its long-term trend.
Modelling systemic price cojumps with Hawkes factor models
2015
Instabilities in the price dynamics of a large number of financial assets are a clear sign of systemic events. By investigating a set of 20 high cap stocks traded at the Italian Stock Exchange, we find that there is a large number of high frequency cojumps. We show that the dynamics of these jumps is described neither by a multivariate Poisson nor by a multivariate Hawkes model. We introduce a Hawkes one factor model which is able to capture simultaneously the time clustering of jumps and the high synchronization of jumps across assets.
3D numerical modeling of YSO accretion shocks
2013
International audience; The dynamics of YSO accretion shocks is determined by radiative processes as well as the strength and structure of the magnetic field. A quasi-periodic emission signature is theoretically expected to be observed, but observations do not confirm any such pattern. In this work, we assume a uniform background field, in the regime of optically thin energy losses, and we study the multi-dimensional shock evolution in the presence of perturbations, i.e. clumps in the stream and an acoustic energy flux flowing at the base of the chromosphere. We perform 3D MHD simulations using the PLUTO code, modeling locally the impact of the infalling gas onto the chromosphere. We find t…
Role of local absorption on the X-ray emission from MHD accretion shocks in classical T Tauri stars
2014
Accretion processes onto classical T Tauri stars (CTTSs) are believed to generate shocks at the stellar surface due to the impact of supersonic downflowing plasma. Although current models of accretion streams provide a plausible global picture of this process, several aspects are still unclear. For example, the observed X-ray luminosity in accretion shocks is, in general, well below the predicted value. A possible explanation discussed in the literature is in terms of significant absorption of the emission due to the thick surrounding medium. Here we consider a 2D MHD model describing an accretion stream propagating through the atmosphere of a CTTS and impacting onto its chromosphere. The m…
A numerical study of postshock oscillations in slowly moving shock waves
2003
Abstract Godunov-type methods and other shock capturing schemes can display pathological behavior in certain flow situations. This paper discusses the numerical anomaly associated to slowly moving shocks. We present a series of numerical experiments that illustrate the formation and propagation of this pathology, and allows us to establish some conclusions and question some previous conjectures for the source of the numerical noise. A simple diagnosis on an explicit Steger-Warming scheme shows that some intermediate states in the first time steps deviate from the true direction and contaminate the flow structure. A remedy is presented in the form of a new flux split method with an entropy i…
Crushing of Interstellar Gas Clouds in Supernova Remnants: the Role of Thermal Conduction and Radiative Losses
2004
We model hydrodynamic interactions of an old supernova remnant shock wave with a small interstellar gas cloud, taking into account the effects of thermal conduction and radiative losses. In particular, we consider a representative case of a Mach 30 shock impacting on an isolated cloud with density contrast χ = 10 with respect to the ambient medium. Thermal conduction appears to be effective in suppressing the Kelvin-Helmholtz and Rayleigh-Taylor instabilities which would develop at the cloud boundaries. We demonstrate that the radiative losses play a crucial role in the dynamics of the shock-cloud interaction, dominating evolution of the shocked cloud medium.