Choice of optimal subset of numbers using a learning automaton

Some methods are proposed for employing a stochastic learning automaton in selectingM largest numbers out ofN numbers which are given via realizations of Bernoulli random variables. The different methods are compared by simulation.     

Variational problems on multiply connected thin strips III: Integration of the Ginzburg-Landau equations over graphs

We analyze the one-dimensional Ginzburg-Landau functional of superconductivity on a planar graph. In the Euler-Lagrange equations, the equation for the phase can be integrated, provided that the order parameter does not vanish at the vertices; in this case, the minimization of the Ginzburg-Landau functional is equivalent to the minimization of another functional, whose unknowns are a real-valued function on the graph and a finite set of integers.

     

Thawing in saturated porous media

A mathematical model for thawing in a saturated porous medium is considered. The well-posedness of the corresponding mathematical problem is proved and similarity solutions are found.

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Sommario Si considera un modello matematico per to scongelamento in un mezzo poroso saturo. Viene dimostrata la buona posizione del corrispondente problema matematico e si trovano soluzioni di similarità.

     

A relaxation approximation for time-dependent second-order effects in shear turbulence

The Crow constraint on time-dependent turbulence models is generalized to effects of second order in the strain rate. For simple shear flow, this generalization requires agreement of the time-dependent normal stress deviators with the short-time rapid distortion limit and with long-time equilibrium data. A model consistent with these requirements is proposed based on a perturbative solution of the equations of the direct interaction approximation for shear flow. It requires a decomposition of the Reynolds stress into tensor components which satisfy coupled linear relaxation equations. This approach to time-dependent turbulence modeling based on analytical theories offers an alternative to the standard ones, in which various hypotheses are introduced to close correlations in the exact transport equation for second-order single-point moments.Partial financial support provided by ONR Contract N00014-94-1-0124 is gratefully acknowledged.     

Structure and stability of the negative hydrogen molecular ion

We present the results of a Coulomb explosion experiment that allows for the imaging of the rovibrational wave function of the metastable H2- ion. Our measurements confirm the predicted large internuclear separation of 6 a.u., and they show that the ion decays by autodetachment rather than by spontaneous dissociation. Imaging of the resulting H2 products reveals a large angular momentum of J = 25 ± 2, quantifying the rotation that leads to the metastability of this most fundamental molecular anion.     

Copolymerization of Metal Nanoparticles: A Route to Colloidal Plasmonic Copolymers

The resemblance between colloidal and molecular polymerization reactions is very useful in fundamental studies of polymerization reactions, as well as in the development of new nanoscale systems with desired properties. Future applications of colloidal polymers will require nanoparticle ensembles with a high degree of complexity that can be realized by hetero‐assembly of NPs with different dimensions, shapes, and compositions. A method has been developed to apply strategies from molecular copolymerization to the co‐assembly of gold nanorods with different dimensions into random and block copolymer structures (plasmonic copolymers). The approach was extended to the co‐assembly of random copolymers of gold and palladium nanorods. A kinetic model validated and further expanded the kinetic theories developed for molecular copolymerization reactions.     

Generation of Bernoulli processes

We consider five different algorithms for generating Bernoulli processes and discuss their efficiency. Simulation results are presented as well.