Diffraction by a perfectly conducting rectangular cylinder which is illuminated by an array of line sources

The geometrical theory of diffraction (GTD) is employed to analyze the radiation from a perfectly-conducting rectangular cylinder illuminated by an array of line sources. The excitation of the cylinder by a single electric or magnetic current line source is considered first, and a solution which includes contributions from the geometrical optics rays and all singly- and doubly-diffracted rays is obtained. A new diffraction coefficient valid in the transition regions of the shadow and reflection boundaries is employed to obtain a continuous total field, except for negligible discontinuities in the doubly-diffracted field at its shadow boundaries. Patterns calculated by the GTD method are found to be in excellent agreement with those calculated from an integral equation formulation. Using superposition the solution for array or aperture excitation of the rectangular cylinder is obtained. A computer program for this solution is included

Correlation Functions of Multisite Interaction Spin-S models on the Bethe-like Lattices

Multisite interaction spin-S models in an external magnetic field are studied recursively on the Bethe-like lattices. The transfer-matrix method is extended to calculate exactly the two-spin correlation functions. The exact expressions for the correlation length and magnetic susceptibility are derived for spin-1/2 models. The singularity of the correlation length with critical index $\nu =1$ and the proportionality of magnetic susceptibility to correlation length in the second order phase transition region of spin-1/2 ferromagnetic models on the Bethe-like lattices are established analytically.Comment: 13 pages, In Press Int. J. Mod. Phys.

The puzzles in B→ππB\to \pi\pi and πK \pi K decays: possible implications for R-parity violating supersymmetry

Recent experiments suggest that certain data of $B \to \pi\pi,\pi K$ decays are inconsistent with the standard model expectations. We try to explain the discrepancies with R-parity violating suppersymmetry. By employing the QCD factorization approach, we study these decays in the minimal supersymmetric standard model with R-parity violation. We show that R-parity violation can resolve the discrepancies in both $B \to \pi\pi$ and $B \to \pi K$ decays, and find that in some regions of parameter spaces all these requirements, including the CP averaged branching ratios and the direct CP asymmetries, can be satisfied. Furthermore, we have derived stringent bounds on relevant R-parity violating couplings from the latest experimental data, and some of these constraints are stronger than the existing bounds.Comment: 24 pages, 6 figures and 5 tables. Text revised. Final version to appear in PR

Space Alignment Based on Regularized Inversion Precoding in Cognitive Transmission

For a two-tier Multiple-Input Multiple-Output (MIMO) cognitive network with common receiver, the precoding matrix has a compact relationship with the capacity performance in the unlicensed secondary system. To increase the capacity of secondary system, an improved precoder based on the idea of regularized inversion for secondary transmitter is proposed. An iterative space alignment algorithm is also presented to ensure the Quality of Service (QoS) for primary system. The simulations reveal that, on the premise of achieving QoS for primary system, our proposed algorithm can get larger capacity in secondary system at low Signal-to-Noise Ratio (SNR), which proves the effectiveness of the algorithm