Static current-sheet models of quiescent prominences

A particular class of theoretical models idealize the prominence to be a discrete flat electric-current sheet suspended vertically in a potential magnetic field. The weight of the prominence is supported by the Lorentz force in the current sheet. These models can be extended to have curved electric-current sheets and to vary three-dimensionally. The equation for force balance is 1 over 4 pi (del times B) times Bdel p- p9 z=zero. Using Cartesian coordinates we take, for simplicity, a uniform gravity with constant acceleration g in the direction -z. If we are interested not in the detailed internal structure of the prominence, but in the global magnetic configuration around the prominence, we may take prominence plasma to be cold. Consideration is given to how such equilibrium states can be constructed. To simplify the mathematical problem, suppose there is no electric current in the atmosphere except for the discrete currents in the cold prominence sheet. Let us take the plane z =0 to be the base of the atmosphere and restrict our attention to the domain z greater than 0. The task we have is to solve for a magnetic field which is everywhere potential except on some free surface S, subject to suit able to boundary conditions. The surface S is determined by requiring that it possesses a discrete electric current density such that the Lorentz force on it is everywhere vertically upward to balance the weight of the material m(S). Since the magnetic field is potential in the external atmosphere, the latter is decoupled from the magnetic field and its plane parallel hydrostatic pressure and density can be prescribed

Novelty and Collective Attention

The subject of collective attention is central to an information age where millions of people are inundated with daily messages. It is thus of interest to understand how attention to novel items propagates and eventually fades among large populations. We have analyzed the dynamics of collective attention among one million users of an interactive website -- \texttt{digg.com} -- devoted to thousands of novel news stories. The observations can be described by a dynamical model characterized by a single novelty factor. Our measurements indicate that novelty within groups decays with a stretched-exponential law, suggesting the existence of a natural time scale over which attention fades

Acoustical analysis of gear housing vibration

The modal and acoustical analysis of the NASA gear-noise rig is described. Experimental modal analysis techniques were used to determine the modes of vibration of the transmission housing. The resulting modal data were then used in a boundary element method (BEM) analysis to calculate the sound pressure and sound intensity on the surface of the housing as well as the radiation efficiency of each mode. The radiation efficiencies of the transmission housing modes are compared with theoretical results for finite, baffled plates. A method that uses the measured mode shapes and the BEM to predict the effect of simple structural changes on the sound radiation efficiency of the modes of vibration is also described

Internal Energy of the Potts model on the Triangular Lattice with Two- and Three-body Interactions

We calculate the internal energy of the Potts model on the triangular lattice with two- and three-body interactions at the transition point satisfying certain conditions for coupling constants. The method is a duality transformation. Therefore we have to make assumptions on uniqueness of the transition point and that the transition is of second order. These assumptions have been verified to hold by numerical simulations for q=2, 3 and 4, and our results for the internal energy are expected to be exact in these cases.Comment: 9 pages, 4 figure

Subthreshold rho contribution in J/psi decay to omega pion pion and Kaon anti-Kaon pion

We carry out a theoretical and Monte Carlo study on the $J/\psi$ decays into $\omega\pi\pi$ and $K\bar{K}\pi$ through intermediate subthreshold $\rho$ meson by using SU(3)-symmetric Lagrangian approach. It is found that the subthreshold $\rho$ contribution is not negligible and may have significant influence on partial wave analysis of resonances in these channels, especially near the $\omega \pi$ and $K \bar{K}$ thresholds.Comment: 12 pages, 5 figure

Validation of finite element and boundary element methods for predicting structural vibration and radiated noise

Analytical and experimental validation of methods to predict structural vibration and radiated noise are presented. A rectangular box excited by a mechanical shaker was used as a vibrating structure. Combined finite element method (FEM) and boundary element method (BEM) models of the apparatus were used to predict the noise radiated from the box. The FEM was used to predict the vibration, and the surface vibration was used as input to the BEM to predict the sound intensity and sound power. Vibration predicted by the FEM model was validated by experimental modal analysis. Noise predicted by the BEM was validated by sound intensity measurements. Three types of results are presented for the total radiated sound power: (1) sound power predicted by the BEM modeling using vibration data measured on the surface of the box; (2) sound power predicted by the FEM/BEM model; and (3) sound power measured by a sound intensity scan. The sound power predicted from the BEM model using measured vibration data yields an excellent prediction of radiated noise. The sound power predicted by the combined FEM/BEM model also gives a good prediction of radiated noise except for a shift of the natural frequencies that are due to limitations in the FEM model

Design of Compact BPF and Planar Diplexer for UMTS using Embedded-scheme Resonator

A compact planar diplexer utilizing embedded-scheme resonator (ESR) is designed for universal mobile telecommunications system (UMTS). The ESR is formed by embedding interdigital resonators into an open loop resonator. Based on the proposed ESR, a narrowband bandpass filter suitable for diplexer design is proposed, fabricated and measured. The measured results demonstrate that the filter exhibits good transmission properties within band and high frequency selectivity. The rectangular area occupied by the filter has overall dimensions only 0.086λg by 0.105λg, promises good potential in wireless communication systems that require compact size and high encapsulation quality. Then, a compact planar diplexer operating at the TX-band of 1920-1980MHz and the RX-band of 2110-2170MHz, which is composed of a meander T-junction and two filters initially separately designed, is synthesized, simulated and measured. Both the simulated and measured results indicate that satisfied impedance matching and good isolation between two paths have been achieved