A cavity-backed spiral antenna with ultra-wide band width is presented. By using a parabolic reflector, the radiation of the antenna becomes uni-directional, and the gain is promoted. The antenna is fed by a coaxial cut-away balun with fan-shaped patch which keeps a wideband impedance matching. The simulated bandwidth for VSWR < 2 covers 0.36 ~ 6.83GHz or bandwidth ratio of 19:1, and the gain a...

In the last years, the Synthetic Aperture Radar (SAR) systems evolution migrates toward the use of multi-channel systems based on Digital Beam Forming (DBF) techniques [1]. This tendendy allows fulfilling stringent SAR requirements, providing high spatial resolution within a wide swath. Moreover, the combination of DBF techniques with parabolic reflector antennas merges both flexibility and hig...

Existence and uniqueness results are given for secondorder parabolic and elliptic equations with variable coefficients in C domains in Sobolev spaces with weights allowing the derivatives of solutions to blow up near the boundary. The “number” of derivatives can be negative and fractional. The coefficients of parabolic equations are only assumed to be measurable in time.

A complex ruled surface admits an iterated blow-up encoded by a parabolic structure with rational weights. Under a condition of parabolic stability, one can construct a Kähler metric of constant scalar curvature on the blow-up according to [18]. We present a generalization of this construction to the case of parabolically polystable ruled surfaces. Thus we can produce numerous examples of Kähle...

We discuss the relationships between the notion of intrinsic ultracontractivity, parabolic Harnack principle, compactness of the 1-resolvent of the Neumann Laplacian, and non-trap property for Euclidean domains with finite Lebesgue measure. In particular, we give an answer to an open problem raised by Davies and Simon in 1984 about the possible relationship between intrinsic ultracontractivity ...

We establish weighted L2−estimates for dissipative wave equations with variable coefficients that exhibit a dissipative term with a space dependent potential. These results yield decay estimates for the energy and the L2−norm of solutions. The proof is based on the multiplier method where multipliers are specially engineered from asymptotic profiles of related parabolic equations.

By restricting to a special class of smooth functions, the local action of the symmetry group is globalized. This special class of functions is constructed using parabolic induction.

We prove that certain parabolic Kazhdan-Lusztig polynomials calculate the graded decomposition matrices of v-Schur algebras given by the Jantzen filtration of Weyl modules, confirming a conjecture of Leclerc and Thibon.

We investigate the conditions under which the solution of the initial-boundary value problem of the non-local equation ut = u + λ f (u)/( ∫ Ω f (u) dx) p , where Ω is a bounded domain of RN and f (u) is a positive, increasing, convex function, performs blow-up. c © 2005 Elsevier Ltd. All rights reserved.