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This document is a guide to Valgrind, the malloc debugger.* NEW entry
This article explains some of the difficulties and biases women face in the Linux community and examines various strategies for addressing those difficulties in order to encourage more participation by women.* NEW entry
We introduce an approach in which results from atomistic simulations are combined with discrete dislocation dynamics simulations of crack-tip plasticity. The method is used to study the effects of dislocation pinning due to grain boundaries or secondary particles on the fracture behavior of aluminum. We find that the fracture resistance is reduced with decreasing pinning distance. The results show that the pinning of the dislocations causes a net decrease in the shear stress projected on the slip plane, preventing further dislocation emission. Semibrittle cleavage occurs after a certain number of dislocations is emitted.
The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250-673 K. The concentration of [Li]0 centers (substitutional Li+ ions each with a trapped hole) resulting from oxidation was monitored by optical absorption measurements. At low electric fields, dc measurements reveal blocking contacts. At high fields, the I-V characteristic is similar to that of a diode connected in series with the bulk resistance of the sample. Low-voltage ac measurements show that the equivalent circuit for the sample consists of the bulk resistance in series with the junction capacitance connected in parallel with a capacitance, which represents the dielectric constant of the sample. Both dc and ac experiments provide consistent values for the bulk resistance. The electrical conductivity of oxidized MgO:Li crystals increases linearly with the concentration of [Li]0 centers. The conductivity is thermally activated with an activation energy of (0.70±0.02) eV, which is independent of the [Li]0 content. The standard semiconducting mechanism satisfactorily explains these results. Free holes are the main contribution to band conduction as they are released from the [Li]0-acceptor centers. In as-grown MgO:Li crystals (without [Li]0 centers) the electrical current increases with time as [Li]0 centers are being formed. When ample [Li]0 centers are formed, an activation energy of 0.7 eV was observed. At sufficiently high current, Joule heating thermally destroys the [Li]0 centers.