6,817 research outputs found

    A bodner-partom visco-plastic dynamic sphere benchmark problem

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    Developing benchmark analytic solutions for problems in solid and fluid mechanics is very important for the purpose of testing and verifying computational physics codes. Our primary objective in this research is to obtain a benchmark analytic solution to the equation of motion in radially symmetric spherical coordinates. An analytic solution for the dynamic response of a sphere composed of an isotropic visco-plastic material and subjected to spherically symmetric boundary conditions is developed and implemented. The radial displacement u is computed by solving the equation of motion, a linear second-order hyperbolic PDE. The plastic strains εp and εp are computed by solving two non-linear first-order ODEs in time. We obtain a solution for u in terms of the plastic strain components and boundary conditions in the form of an infinite series. Computationally, at each time step, we set up an iteration scheme to solve the PDE-ODE system. The linear momentum equation is solved using the plastic strains from the previous iteration, then the plastic strain equations are solved numerically using the new displacement. We demonstrate the accuracy and convergence of our benchmark solution under spatial mesh, time step, and eigenmode refinement

    Revisiting The Trade Complexity And Economic Growth Nexus: Does Trade Composition Matter?

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    Countries at all stages of economic development desire economic growth. Hausmann et al. (2007) devises a theoretical model and empirical analysis purporting that the type of goods which a country produces, categorized by the wealth level of all countries producing such goods, serves as one determinant of economic growth. Given the importance of this finding, particularly for developing countries, and the broad range of technical capabilities which countries possess, this study seeks to determine if this relationship holds within productive categories, classified by the technological requirements of their production, or simply represents a movement from primary and resource-based products to higher level manufactures. In particular, this study analyzes the sophistication of exports in five categories; primary products, resource based products, as well as low, medium, and high-tech manufactures, correlating each countries level of sophistication in these categories with economic growth using both five and ten year panels over the period 1962-2000. The empirical analysis confirms the importance of sophistication in the low-tech sector, which includes textiles and basic metal manufacturing, as an indicator of economic growth in all countries, while suggesting that sophistication within the high-tech sector, comprised of pharmaceuticals, electronics, and aircraft equipment, plays a significant role in highly developed countries

    Book Review: Fragile States

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    In an era when good governance features prominently on the global development agenda, there seems to be a corollary spotlight on state fragility. In this book - a quick read that covers much ground - the authors wade into the conceptual waters of state fragility with the following aims: (i) sketching more clearly its conceptual parameters, including its core characteristics; (ii) dissecting its connection to violent conflict; (iii) analyzing the role that international society has played in relation to fragile statehood; and (iv) laying out two proposals for tackling its intractability. These analyses are conducted through the prism of three case studies: The Democratic Republic of the Congo (DRC), Afghanistan, and Haiti. [excerpt
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