Interconnection and Competition Among Asymmetric Networks in the Internet Backbone Market

We examine the interrelation between interconnection and competition in the internet backbone market.Networks asymmetric in size choose among different interconnection regimes and compete for end-users.We show that a direct interconnection regime, Peering, softens competition compared to indirect interconnection since asymmetries become less influential when networks peer.If interconnection fees are paid, the smaller network pays the larger one. Sufficiently symmetric networks enter a Peering agreement while others use an intermediary network for exchanging traffic.This is in line with considerations of a non-US policy maker.In contrast, US policy makers prefer Peerings among relatively asymmetric networks.Internet Backbone;Endogenous Network Interconnection;Asymmetric Networks;Two-Way Access Pricing

Initial ionization rates in shock-heated Argon, Krypton, and Xenon

The rate of ionization behind strong shock waves in argon, krypton, and xenon, is observed by a transverse microwave probe, over a range of electron densities low enough that atom-atom inelastic collisions are the rate-determining mechanism. Shocks of Mach number 7.0 to 10.0 propagate down a 2-in. sq. aluminum shock tube into ambient gases at pressures of 3.0 to 17.0 mm. Hg., heating them abruptly to atomic temperatures of 5500°K to 9600°K. The subsequent relaxation toward ionization equilibrium is examined in its early stages by the reflection, transmission, and phase shifts of a 24.0 Gc/sec (1.25 cm) transverse microwave beam propagating between two rectangular horns abreast a glass test section. The data yield effective activation energies of 11.9 ± 0.5 eV for argon, 10.4 ± 0.5 eV for krypton, and 8.6 ± 0.5 eV for xenon. These coincide, within experimental error, with the first excitation potentials, rather than the ionization potentials of the gases, indicating that in this range ionization proceeds via a two-step process involving the first excited electronic states of which the excitation step is rate controlling

Symmetry breaking in the self-consistent Kohn-Sham equations

The Kohn-Sham (KS) equations determine, in a self-consistent way, the particle density of an interacting fermion system at thermal equilibrium. We consider a situation when the KS equations are known to have a unique solution at high temperatures and this solution is a uniform particle density. We show that, at zero temperature, there are stable solutions that are not uniform. We provide the general principles behind this phenomenon, namely the conditions when it can be observed and how to construct these non-uniform solutions. Two concrete examples are provided, including fermions on the sphere which are shown to crystallize in a structure that resembles the C$_{60}$ molecule.Comment: a few typos eliminate

Quasi-exact-solution of the Generalized Exe Jahn-Teller Hamiltonian

We consider the solution of a generalized Exe Jahn-Teller Hamiltonian in the context of quasi-exactly solvable spectral problems. This Hamiltonian is expressed in terms of the generators of the osp(2,2) Lie algebra. Analytical expressions are obtained for eigenstates and eigenvalues. The solutions lead to a number of earlier results discussed in the literature. However, our approach renders a new understanding of ``exact isolated'' solutions

Improvement of numerical wind forecasts at wind turbine height for wind ramp events within the stable boundary layer

Although the forecast capability of numerical weather prediction models has improved significantly over the past decades, there still exists significant issues related to model representation of the complex dynamics of the boundary layer (BL), which impede the realization of turbine-height wind forecast accuracy. This study is an effort to revisit the basic theory of the Mellor, Yamada, Nakanishi, and Niino (MYNN) BL scheme with a focus on its function as posed for the stably stratified environment that supports the onset of a low-level jet (LLJ), a mechanism that can often result in wind ramp events, which are of special concern for the wind power industry. The MYNN BL scheme approximates the turbulence covariance variables, which define turbulence momentum and heat flux as well as turbulent kinetic energy (TKE). These approximations are derived from the Reynolds-averaged Navier-Stokes equations and consist of a system of interdependent diagnostic expressions with terms involving gradients of the mean flow and turbulent fluxes. The influence of each term is affected by a set of weighting factors known as closure parameters (CPs), which have been empirically derived, as well as a diagnosed mixing length. In this study the MYNN scheme is modified in three ways. First, an updated set of CPs are formulated specifically for a stable BL that exhibits LLJ development and associated wind ramps. A large-eddy simulation model with spatial resolution of 3-4m is used to simulate turbulence response and effect for such cases. These data provide the means to generate Reynolds-averaged values for explicit representation of covariance variables and TKE, which in turn, provide the basis for calculating new MYNN closure parameters for mesoscale numerical forecasts of wind ramps. Second, a new means of calculating the turbulent mixing length is formulated, by which vertical mixing is enhanced across the BL above that predicted by Monin-Obukhov theory when wind speeds exceed a given wind threshold. Third, a new approach for calculating turbulent fluxes is implemented within the MYNN framework, which accounts for the effects of anisotropy and turbulent potential energy (TPE). All three modifications are evaluated using a set of 15 wind ramp cases as identified in tall tower data from Iowa in the U.S. and near Hamburg, Germany. The WRF model is used to generate 24-hour wind forecasts, which are evaluated relative to observations at 100m height. It is found that invoking the new set of CPs provides marked forecast improvement only when used in conjunction with the new mixing length formulation and only for cases that are originally under- or over-forecast. For these cases the MAE of wind forecasts at 100m on average is reduced by 17%. Reduction in average MAE by 26% is realized for these same cases when invoking the method that accounts for anisotropy and TPE along with the new mixing length. This last method results in an average reduction in MAE of 13% across all 15 cases

Effects of Static, Countermovement, and Drop Jump Performance on Power and Rate of Force Development in 6 - 16 Year Old Boys

The purpose of this study was to examine the effects of static, counter movement, and drop jump performance on peak power and peak rate of force development (RFD). The secondary purpose of this study was to examine the relationship between vertical jump outcomes, maturity offset, and muscle cress-sectional area (CSA). During a single testing session, twenty-one young males (mean age ± SD = 12.1 ± 2.4 yrs) performed maximal vertical jumps which included: static jump (SJ), counter movement jump (CMJ), and drop jump from 8 (DJ8), 12 (DJ12) and 16 (DJ16) inches in a randomized order. Peak power increased from SJ to CMJ (p ≤ 0.001) but showed no subsequent increases among CMJ, DJ8, DJ12, or DJ16. RFD and force showed no increase from SJ to CMJ (p \u3e 0.05), an increase from CMJ to DJ8 (p ≤ 0.001), but no further increases from DJ8 to DJ12 to DJ16 (p \u3e 0.05). Eccentric impulse increased systematically from SJ to DJ16 (p ≤ 0.001). Concentric impulse increased from SJ to CMJ (p ≤ 0.001), decreased from CMJ to DJ8 (p = 0.003), then showed no change from DJ8 to DJ12 to DJ16 (p \u3e 0.05). Stepwise regression indicated that the increase in power from SJ to CMJ was best explained by height (R2 = 0.517). These findings suggest CMJ is the optimal jump test for maximizing peak power and concentric work, while minimizing eccentric overload in male of a similar age to this study. Additionally, growth and development may influence stretch-shortening cycle (SSC) utilization. Future studies are needed to examine the influence of PHV maturity offset and increased muscle CSA on SSC utilization in this model of incremental eccentric pre-loading during vertical jump tests. Advisor: Joel T. Crame