171,173 research outputs found

    Modelling Multiphase Flow Using a Dynamic Pore Network Model for Imbibition

    Get PDF
    Imperial Users onl

    Fast and Tiny Structural Self-Indexes for XML

    Full text link
    XML document markup is highly repetitive and therefore well compressible using dictionary-based methods such as DAGs or grammars. In the context of selectivity estimation, grammar-compressed trees were used before as synopsis for structural XPath queries. Here a fully-fledged index over such grammars is presented. The index allows to execute arbitrary tree algorithms with a slow-down that is comparable to the space improvement. More interestingly, certain algorithms execute much faster over the index (because no decompression occurs). E.g., for structural XPath count queries, evaluating over the index is faster than previous XPath implementations, often by two orders of magnitude. The index also allows to serialize XML results (including texts) faster than previous systems, by a factor of ca. 2-3. This is due to efficient copy handling of grammar repetitions, and because materialization is totally avoided. In order to compare with twig join implementations, we implemented a materializer which writes out pre-order numbers of result nodes, and show its competitiveness.Comment: 13 page

    Financial Development and Income Inequality: A Panel Data Approach

    Get PDF
    We analyze the link between financial development and income inequality for a broad unbalanced dataset of up to 138 developed and developing countries over the years 1960 to 2008. Using credit-to-GDP as a measure of financial development, our results reject theoretical models predicting a negative impact of financial development on income inequality measured by the Gini coefficient. Controlling for country fixed effects and GDP per capita, we find that financial development has a positive effect on income inequality. These results are robust to different measures of financial development, econometric specifications, and control variables.financial development, income inequality, global, panel analysis

    Financial Contagion and the European Debt Crisis

    Get PDF
    Since the beginning of 2010, the Euro Area faces a severe sovereign debt crisis, now generally known as the Euro Crisis. While the Euro Crisis has its origin in Greece, problems have now spread to several other European countries as well. Dynamic conditional correlation models (DCC) are estimated in order to assess if contagious effects are identifiable during the Euro Crisis, or if the countries’ problems are instead due to fundamental problems in the affected economies. Our findings show that there is contagion within the Euro Area. Additionally, contagious effects generated by rating announcements are documented. These results are crucial when it comes to choosing the correct measure and timing of policy intervention.contagion, DCC, Euro Crisis

    Cooling in the shade of warped transition disks

    Full text link
    The mass of the gaseous reservoir in young circumstellar disks is a crucial initial condition for the formation of planetary systems, but estimates vary by orders of magnitude. In some disks with resolvable cavities, sharp inner disk warps cast two-sided shadows on the outer rings; can the cooling of the gas as it crosses the shadows bring constraints on its mass? The finite cooling timescale should result in dust temperature decrements shifted ahead of the optical/IR shadows in the direction of rotation. However, some systems show temperature drops, while others do not. The depth of the drops and the amplitude of the shift depend on the outer disk surface density Sigma through the extent of cooling during the shadow crossing time, and also on the efficiency of radiative diffusion. These phenomena may bear observational counterparts, which we describe with a simple one-dimensional model. An application to the HD142527 disk suggests an asymmetry in its shadows, and predicts a >~10deg shift for a massive gaseous disk, with peak Sigma > 8.3 g/cm2. Another application to the DoAr44 disk limits the peak surface density to Sigma < 13g/cm2Comment: accepted to MNRAS Letter

    Time integration for diffuse interface models for two-phase flow

    Full text link
    We propose a variant of the θ\theta-scheme for diffuse interface models for two-phase flow, together with three new linearization techniques for the surface tension. These involve either additional stabilizing force terms, or a fully implicit coupling of the Navier-Stokes and Cahn-Hilliard equation. In the common case that the equations for interface and flow are coupled explicitly, we find a time step restriction which is very different to other two-phase flow models and in particular is independent of the grid size. We also show that the proposed stabilization techniques can lift this time step restriction. Even more pronounced is the performance of the proposed fully implicit scheme which is stable for arbitrarily large time steps. We demonstrate in a Taylor flow application that this superior coupling between flow and interface equation can render diffuse interface models even computationally cheaper and faster than sharp interface models
    • …