Search results

International audience In the upper crust, the chemical infuence of pore water promotes time dependent brittle deformation through sub-critical crack growth. Sub-critical crack growth allows rocks to deform and fail at stresses well below their short-term failure strength, and even at constant applied stress (\brittle creep"). Here we provide a micromechanical model describing time dependent brittle creep of water-saturated rocks under triaxial stress conditions. Macroscopic brittle creep is modeled on the basis of microcrack extension under compressive stresses due to sub-critical crack growth. The incremental strains due to the growth of cracks in compression are derived from the sliding wing crack model of Ashby and Sammis [1990], and the crack length evolution is computed from Charles' law. The macroscopic strains and strain rates computed from the model are non linear, and compare well with experimental results obtained on granite, low porosity sandstone and basalt rock samples. Primary creep (decelerating strain) corresponds to decelerating crack growth, due to an initial decrease in stress intensity factor with increasing crack length in compression. Tertiary creep (accelerating strain as failure is approached) corresponds to an increase in crack growth rate due to crack interactions. Secondary creep with apparently constant strain rate arises as an inflexion between those two end-member phases. The minimum strain rate at the inflexion point can be estimated analytically as a function of model parameters, e ective con ning pressure and temperature, which provides an approximate creep law for the process. The creep law is used to infer the long term strain rate as a function of depth in the upper crust due to the action of the applied stresses: in this way, sub-critical cracking reduces the failure stress in a manner equivalent to a decrease in cohesion. We also investigate the competition with pressure solution in porous rocks, and show that the transition from sub-critical cracking to pressure solution ...

"The role of physics in our culture is examined from the time of Newton to the present day. It has three parts: an introduction to physics and two parts covering the roles of Newtonian and Modern/Postmodern physics. It is shown how popularization enabled physics to become part of our culture, while the topics discussed include religion, philosophy, politics, literature, the visual arts, and music. An underlying theme is that physics is an intimate part of our culture which, together with the other sciences, has had a wide general influence that cannot be ignored. The book has been written for all that are genuinely interested in culture. It is well referenced and illustrated, and suitable for the general public, students and academics who are interested in bridging the sciences and humanities in today's era of specialization"--

1 Classical atomic, theory and interatomic binding -- 2 Quantum mechanics and band theory -- 3 Statistical mechanics -- 4 Semiconductors in thermodynamic equilibrium -- 5 Current flow in semiconductors -- 6 Semiconductors in non-equilibrium conditions -- 7 Current flow across semiconductor junctions -- 8 Minority carrier transistors -- 9 Space-charge-limited currents in semiconductors and insulators Majority carrier transistors -- Appendices -- II Common-emitter characteristics -- III The transistor as a charge controlled device. Circuit problems.

Chapter 1 - Introduction -- Chapter 2 - Concepts of finance -- Chapter 3 - Portfolio theory and CAPM -- Chapter 4 - Stochastic processes -- Chapter 5 - Black-Scholes differential equation -- Chapter 6 - The Greeks and risk management -- Chapter 7 - Regression models and hypothesis testing -- Chapter 8 - Time series -- Chapter 9 - Bubbles, crashes, fat tails and Levy-stable distributions -- Chapter 10 - Quantum finance and path integrals -- Chapter 11 - Optimal control theory.