4,290 research outputs found
Youth Perspectives on Permanency
"What do foster youth think about permanency?" CPYP, in partnership with the California Youth Connection (CYC), held interviews and focus groups with several foster youth to talk about this question. This document explores some of their answers
Nanovoid nucleation by vacancy aggregation and vacancy-cluster coarsening in high-purity metallic single crystals
A numerical model to estimate critical times required for nanovoid nucleation in high-purity aluminum single crystals subjected to shock loading is presented. We regard a nanovoid to be nucleated when it attains a size sufficient for subsequent growth by dislocation-mediated plasticity. Nucleation is assumed to proceed by means of diffusion-mediated vacancy aggregation and subsequent vacancy cluster coarsening. Nucleation times are computed by a combination of lattice kinetic Monte Carlo simulations and simple estimates of nanovoid cavitation pressures and vacancy concentrations. The domain of validity of the model is established by considering rate-limiting physical processes and theoretical strength limits. The computed nucleation times are compared to experiments suggesting that vacancy aggregation and cluster coarsening are feasible mechanisms of nanovoid nucleation in a specific subdomain of the pressure-strain rate-temperature space
Non-equilibrium entanglement in a driven Dicke model
We study the entanglement dynamics in the externally-driven single-mode Dicke
model in the thermodynamic limit, when the field is in resonance with the
atoms. We compute the correlations in the atoms-field ground state by means of
the density operator that represents the pure state of the universe and the
reduced density operator for the atoms, which results from taking the partial
trace over the field coordinates. As a measure of bipartite entanglement, we
calculate the linear entropy, from which we analyze the entanglement dynamics.
In particular, we found a strong relation between the stability of the
dynamical parameters and the reported entanglement.Comment: Contribution to the SLAFES XIX. This version to appear in J. Phys.:
Conference Serie
Scheme Independence of the Effective Hamiltonian for and Decays
We present a calculation of the effective weak Hamiltonian which governs and transitions in two different
renormalization schemes (NDR and HV). In the leading logarithmic approximation,
we show that the coefficients of the effective Hamiltonian are scheme
independent only when one takes correctly into account the scheme dependence of
one- and two- loop diagrams. We demonstrate that in NDR there are contributions
which were missed in previous calculations. These contributions are necessary
to obtain scheme independent coefficients in the final results.Comment: 16 pp + 5 figures not included (available by anonymous ftp at
amisan.iss.infn.it (141.108.15.215), directory /ftp/bsgamma), LaTeX, LPTENS
93/28, ROME 93/958, ULB-TH 93/0
Note on islands in path-length sequences of binary trees
An earlier characterization of topologically ordered (lexicographic)
path-length sequences of binary trees is reformulated in terms of an
integrality condition on a scaled Kraft sum of certain subsequences (full
segments, or islands). The scaled Kraft sum is seen to count the set of
ancestors at a certain level of a set of topologically consecutive leaves is a
binary tree.Comment: 4 page
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