23,262 research outputs found

    A recursive-faulting model of distributed damage in confined brittle materials

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    We develop a model of distributed damage in brittle materials deforming in triaxial compression based on the explicit construction of special microstructures obtained by recursive faulting. The model aims to predict the effective or macroscopic behavior of the material from its elastic and fracture properties; and to predict the microstructures underlying the microscopic behavior. The model accounts for the elasticity of the matrix, fault nucleation and the cohesive and frictional behavior of the faults. We analyze the resulting quasistatic boundary value problem and determine the relaxation of the potential energy, which describes the macroscopic material behavior averaged over all possible fine-scale structures. Finally, we present numerical calculations of the dynamic multi-axial compression experiments on sintered aluminum nitride of Chen and Ravichandran [1994. Dynamic compressive behavior of ceramics under lateral confinement. J. Phys. IV 4, 177–182; 1996a. Static and dynamic compressive behavior of aluminum nitride under moderate confinement. J. Am. Soc. Ceramics 79(3), 579–584; 1996b. An experimental technique for imposing dynamic multiaxial compression with mechanical confinement. Exp. Mech. 36(2), 155–158; 2000. Failure mode transition in ceramics under dynamic multiaxial compression. Int. J. Fracture 101, 141–159]. The model correctly predicts the general trends regarding the observed damage patterns; and the brittle-to-ductile transition resulting under increasing confinement

    Educational Attainment and Risk Preference

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    We explore the relationship between risk preference and educational attainment for a sample of adults drawn from the 1996 U.S. Panel Study of Income Dynamics (PSID). Using a sequence of questions from the 1996 PSID, we construct measures of an individual´s risk aversion and risk tolerance allowing us to explore the implications of interpersonal differences in risk preference for educational attainment. Our empirical findings suggest that an individual´s degree of risk aversion (tolerance) is inversely (positively) associated with their educational attainment. In addition, using the 1997 and 2002 Child Development Supplements of the PSID, we explore the relationship between the risk preference of parents and the academic achievements of their children. Our findings suggest that a parent´s degree of risk aversion (tolerance) is negatively (positively) related to the academic achievements of their children

    Educational loans and attitudes towards risk

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    We explore the relationship between willingness to take financial risk and the probability of taking out a loan for educational purposes as well as the influence of risk attitudes on the size of the loan using data drawn from the U.S. Survey of Consumer Finances. The findings suggest a positive relationship between individuals’ willingness to take financial risk and the probability of taking out a loan for educational purposes. Similarly, individuals’ willingness to take financial risk appears to be an important determinant of the size of the educational loan. The findings suggest that non-white individuals and individuals from less wealthy backgrounds are less likely to finance education through loans which could potentially increase inequalities in education and income if such individuals are deterred from investing in human capital

    A direct primitive variable recovery scheme for hyperbolic conservative equations: the case of relativistic hydrodynamics

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    In this article we develop a Primitive Variable Recovery Scheme (PVRS) to solve any system of coupled differential conservative equations. This method obtains directly the primitive variables applying the chain rule to the time term of the conservative equations. With this, a traditional finite volume method for the flux is applied in order avoid violation of both, the entropy and "Rankine-Hugoniot" jump conditions. The time evolution is then computed using a forward finite difference scheme. This numerical technique evades the recovery of the primitive vector by solving an algebraic system of equations as it is often used and so, it generalises standard techniques to solve these kind of coupled systems. The article is presented bearing in mind special relativistic hydrodynamic numerical schemes with an added pedagogical view in the appendix section in order to easily comprehend the PVRS. We present the convergence of the method for standard shock-tube problems of special relativistic hydrodynamics and a graphical visualisation of the errors using the fluctuations of the numerical values with respect to exact analytic solutions. The PVRS circumvents the sometimes arduous computation that arises from standard numerical methods techniques, which obtain the desired primitive vector solution through an algebraic polynomial of the charges.Comment: 19 pages, 6 figures, 2 tables. Accepted for publication in PLOS ON

    Anomalous non-ergodic scaling in adiabatic multicritical quantum quenches

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    We investigate non-equilibrium dynamical scaling in adiabatic quench processes across quantum multicritical points. Our analysis shows that the resulting power-law scaling depends sensitively on the control path, and that anomalous critical exponents may emerge depending on the universality class. We argue that the observed anomalous behavior originates in the fact that the dynamical excitation process takes place asymmetrically with respect to the static multicritical point, and that non-critical energy modes may play a dominant role. As a consequence, dynamical scaling requires introducing new non-static exponents.Comment: 4 pages, 4 figures, minor change in figure

    Occurrence and mineral chemistry of high pressure phases, Portrillo basalt, southcentral New Mexico

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    Inclusions of clinopyroxenite, kaersutiteclinopyroxenite, kaersutite-rich inclusions, wehrlite and olivine-clinopyroxenite together with megacrysts of feldspar, kaersutite and spinel are found loose on the flanks of cinder cones, as inclusions within lava flows and within the cores of volcanic bombs in the Quaternary alkali-olivine basalt of the West Potrillo Mountains, southcentral New Mexico. Based on petrological and geochemical evidence the megacysts are interpreted to be phenocrysts which formed at great depth rather that xenocrysts of larger crystal aggregates. These large crystals are believed to have formed as stable phases at high temperature and pressure and have partially reacted with the basalt to produce subhedral to anhedral crystal boundaries. It can be demonstrated that the mafic and ultramafic crystal aggregates were derived from an alkali-basalt source rock generated in the mantle. The inclusions are believed to represent a cumulus body or bodies injected within the lower crust or upper mantle
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