Elliptic Flow from a Transversally Thermalized Fireball

The agreement of elliptic flow data at RHIC at central rapidity with the hydrodynamic model has led to the conclusion of very rapid thermalization. This conclusion is based on the intuitive argument that hydrodynamics, which assumes instantaneous local thermalization, produces the largest possible elliptic flow values and that the data seem to saturate this limit. We here investigate the question whether incompletely thermalized viscous systems may actually produce more elliptic flow than ideal hydrodynamics. Motivated by the extremely fast primordial longitudinal expansion of the reaction zone, we investigate a toy model which exhibits thermalization only in the transverse directions but undergoes collisionless free-streaming expansion in the longitudinal direction. For collisions at RHIC energies, elliptic flow results from the model are compared with those from hydrodynamics. With the final particle yield and \kt-distribution fixed, the transversally thermalized model is shown not to be able to produce the measured amount of elliptic flow. This investigation provides further support for very rapid local kinetic equilibration at RHIC. It also yields interesting novel results for the elliptic flow of massless particles such as direct photons.Comment: revtex4, 15 pages + 10 embedded EPS figure

Large amplitude MHD waves upstream of the Jovian bow shock: Reinterpretation

Observations of large amplitude magnetohydrodynamic (MHD) waves upstream of the Jovian bow shock were previously interpreted as arising from a resonant electromagnetic ion beam instability. That interpretation was based on the conclusion that the observed fluctuations were predominantly right elliptically polarized in the solar wind rest frame. Because it was noted that the fluctuations are, in fact, left elliptically polarized, a reanalysis of the observations was necessary. Several mechanisms for producing left hand polarized MHD waves in the observed frequency range were investigated. Instabilities excited by protons appear unlikely to account for the observations. A resonant instability excited by relativistic electrons escaping from the Jovian magnetosphere is a likely source of free energy consistent with the observations. Evidence for the existence of such a population of electrons was found in both the Low Energy Charged Particle experiments and Cosmic Ray experiments on Voyager 2

A Simple Low-Profile Coaxially-Fed Magneto-Electric Dipole Antenna Without Slot-Cavity

A simple coaxially-fed magneto-electric dipole (ME dipole) antenna is designed and experimentally evaluated. The proposed antenna does not require the conventional quarter-wavelength slot cavity for generating the magnetic dipole mode, and only consists of two simple rectangular horizontal patches, a vertical semi-rigid coaxial cable and a square ground plane. It makes the fabrication easier and can reduce the production cost. Also, as the quarter-wavelength slot cavity is removed in the proposed design, the thickness of the antenna can be reduced to 21 mm, i.e., 16.4% of the free space wavelength at the center frequency. The low-profile antenna shows comparable wide impedance bandwidth of 41.03% (S11 ≤ −10 dB), and a more stable and higher realized gain from 7.90 - 9.74 dBi (± 0.92 dB variation) over the operating frequency band from 1.86 GHz to 2.82 GHz (centered at 2.34 GHz). The maximum gain has increased around 9.4% when compare with that of the highest reported. While the gain variation in the passband of the proposed antenna is about 58% lower than that of those ME dipole antennas reported in the literature. The radiation mechanism and the effects of the critical parameters of the antenna are also explained with the assistance of the parametric study presented

The control parametrization enhancing transform for constrained time--delayed optimal control problems

The Control Parametrization Enhancing Technique (CPET), is extended to a general class of constrained time-delayed optimal control problems. A model transformation approach is used to convert the time-delayed problem to an optimal control problem involving mixed boundary conditions, but without time-delayed arguments. The CPET is then used to solve this non delayed problem. Two test examples have been solved to illustrate the efficiencies of the CPET for time delayed problems

J/Psi Propagation in Hadronic Matter

We study J/$\psi$ propagation in hot hadronic matter using a four-flavor chiral Lagrangian to model the dynamics and using QCD sum rules to model the finite size effects manifested in vertex interactions through form factors. Charmonium breakup due to scattering with light mesons is the primary impediment to continued propagation. Breakup rates introduce nontrivial temperature and momentum dependence into the J/$\psi$ spectral function.Comment: 6 Pages LaTeX, 3 postscript figures. Proceedings for Strangeness in Quark Matter 2003, Atlantic Beach, NC, March 12-17, 2003; minor corrections in version 2, to appear in J. Phys.

Wireless Information and Power Transfer Design for Energy Cooperation Distributed Antenna Systems

Distributed antenna systems (DASs) have been widely implemented in the state-of-the-art cellular communication systems to cover dead spots. Recent studies have also indicated that DAS has advantages in wireless energy transfer (WET). In this paper, we study simultaneous wireless information and power transfer for a multiple-input single-output DAS in the downlink, which consists of arbitrarily distributed remote antenna units (RAUs). In order to save the energy cost, we adopt the energy cooperation of energy harvesting (EH) and two-way energy flows to let the RAUs trade their harvested energy through the smart grid network. Under individual EH constraints, per-RAU power constraints, and various smart grid considerations, we investigate a power management strategy that determines how to utilize the stochastically spatially distributed harvested energy at the RAUs and how to trade the energy with the smart grid simultaneously to supply maximum wireless information transfer (WIT) with a minimum WET constraint for a receiver adopting power splitting. Our analysis shows that the optimal design can be achieved in two steps. The first step is to maximize a new objective that can simultaneously maximize both WET and WIT, considering both the smart grid profitable and smart grid neutral cases. For the grid-profitable case, we derive the optimal full power strategy and provide a closed-form result to see under what condition this strategy is used. On the other hand, for the grid-neutral case, we illustrate that the optimal power policy has a double-threshold structure and present an optimal allocation strategy. The second step is then to solve the whole problem by obtaining the splitting power ratio based on the minimum WET constraint. Simulation results are provided to evaluate the performance under various settings and characterize the double-threshold structure

Epidemiology of tobacco smoking in patients undergoing elective vascular surgery in the UK

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