Mass and frequency renormalization for quadratic electron-phonon coupling

The effect of an electron-phonon coupling quadratic in the phonon operators upon the effective electronic mass and the phonon frequency is calculated to second order in perturbation theory. The renormalization effects increase linearly with the temperature, but, for extended molecules, that of the electronic mass might be considerably larger than that of the phonon frequency. The results are discussed in the context of organic metals.     

Modified MM2 scheme for computation of O?C?N-containing systems

A modification of Allinger's MM2 force field for the anomeric effect in O? C? N systems is presented. For optimal consistency, it was parameterized by alternate use of ab initio (3-21G level) and X-ray results to account for the energetic and structural manifestations of the effect in the gas or condensed phase, respectively. The results obtained with the modified force field are in good agreement with those from both theoretical and experimental methods. The parameterization scheme explicitly treats all structural parameters of the C? O? C? N? C moiety as well as C? N bond lengths in tertiary amines contained within an anomeric unit. In addition, it includes directional H-bond type interactions. A limited number of parameters is put forward, in accord with the general MM2 force-field approach. © 1993 John Wiley & Sons, Inc.     

Dominance relations in polling systems

In this paper we compare several service disciplines commonly used in polling systems. We present a sample path comparison which allows us to evaluate the efficiency of the different policies based on thetotal amount of work found in the systemat any time. The analysis is carried out for a large variety of polling schemes under fairly general conditions and can be used to construct a hierarchy of the different service schemes.     

Pseudo-cyclic policies for multi-queue single server systems

In this paper we evaluate the waiting time performance of cycle-time guided algorithms in semi-dynamic polling models. In these models knowledge of the system state is used by the server in the process of on-line determination of the visit pattern. Our main focus is on pseudo-cyclic algorithms which achievefairness by visiting every station exactly once in each cycle.It is shown that in fully symmetric systems the performance ofevery pseudocyclic policy is bounded between the performance of the cycle maximization and the cycle minimization strategies. In particular, stochastic dominance is shown with regard to system workload, implying dominance of mean waiting times. In a fluid approximation model the performance ratio between the two bounding policies is derived and shown to be always between 1 and 3/4 under the gated service regime and between 1 and 1/2 under the exhaustive service regime. Under both regimes, the ratio approaches 3/4 when the number of stations grows to infinity. Simulation results suggest that a similar performance ratio holds for the general (non-symmetric) stochastic model.Further, we study strategies which are guided by the cycle maximization (minimization) criteria, but which do not constrain themselves to pseudo-cyclic orders. It is shown that depending on the switch-over parameters these more dynamic policies may perform much worse than the pseudo-cyclic schemes.     

Locality of reference and the use of sojourn time variance for measuring queue unfairness

Sojourn time variance is widely used as an indication of queue unfairness. We demonstrate that this quantity has a disadvantage, since it is not local to the busy period in which it is measured. We show that RAQFM, a recently proposed queue fairness metric, does possess such a locality property.     

Superconducting state in strong coupling

We consider the behavior of the critical temperature in the limit of strong electron-phonon coupling. The peculiar behavior of the order parameter in this limit allows one to evaluate T_c analytically and directly from Eliashberg's equation. We also consider the effect of Coulomb interaction and the contribution of low phonon modes, the role of lattice instabilities and the relative contribution of phonon and non-phonon interactions.     

OPTIMAL AUSTRALIAN AND JAPANESE HARVESTING OF SOUTHERN BLUEFIN TUNA

A 19-cohort bioeconomic model is developed for the southern bluefin tuna fishery. The fish are long-lived and highly migratory. They are harvested as juveniles by Australia and Japan in Australian waters, and as adults by Japan on the high seas. The potential for conflict between Australian and Japanese fleets therefore exists in the exploitation of the fishery. The model is used to compare Japanese and Australian social rents and harvest levels through time under joint maximization, and under duopoly.