Femtosecond time-resolved spectrocopy has been used to investigate electronic excitations contributing to the superconducting gap function $\Delta (\omega ,T)$ in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$. The optical response is strongly peaked at 1.5 eV, and contains two distinct components: one with a characteristic relaxation time of $\sim 5\mathrm{ps}$, whose amplitude displays a two-fluid-like temperature dependence, and a long-lived component $(>10\mathrm{}\mathrm{ns})$ which is consistent with localized quasiparticle states at the Fermi energy. The latter shows activated behavior below $T_c$ with an activation energy $2{\Delta }_0\approx {3.5kT}_c$.

We report on the development and use of a highly anisotropic magnetic metamaterial for near-field imaging. The material consists of an array of Swiss Roll structures, resonant near 21.3 MHz, with a peak value of relative permeability ~35. At this peak, the material transfers an input magnetic field pattern to the output face without loss of intensity and with a spatial resolution equal to the roll diameter. It behaves as a near-field imaging device consisting of a bundle of magnetic wires.

This is a review article of the latest advances in 3D printing for enabling new materials and new geometries for radio-frequency (RF) devices, antennas, and metamaterials. The article discusses the achievable material properties and various optimized applications that are achievable by creating new shapes in either dielectric or metal. This article demonstrates what is currently possible with additive manufacturing and the current limitations. Various additively manufactured RF devices are reviewed.

Orthogonal netted radar transmitter signals require a very low aperiodic autocorrelation peak sidelobe level (PSL), low aperiodic cross-correlation, and a good resilience to small Doppler shifts. A new set of polyphase sequences is presented with good correlation properties as well as resilience to Doppler shifts. These sequences are built using numerical optimization based on correlation properties. A structural constraint is imposed on the optimized polyphase sequences, which maintains Doppler tolerance. Cross entropy (CE) technique is used to optimize the sequences. Correlation and Doppler results are compared with best-known sequences on various merit factors and shown to be superior

Recent research in wireless power transfer has highlighted the potential benefits for relaying power from source to receiver by a number of resonating relay coils coupled via mutual inductance. A number of researchers have reported experimental systems based on relay coils and have noted that power transfer efficiency to loads located at different points on the structure can vary widely. Such structures, often known as magnetoinductive waveguides are well known to carry signals known as magnetoinductive waves (MIW) when excited with a frequency in their passband. This paper presents an investigation into their impact on wireless power systems and methods by which negative effects may be minimized. Using the physics of magnetoinductive waves it becomes possible to understand the behavior of relay coil systems and to model them in a closed form. The effects of reflections and standing waves on a one-dimensional system are considered and their effect on the input impedance and the variation of matching conditions determined. An optimum receiver load is proposed based on the results and tested experimentally. A simple experimental demonstrator is used as a model for study, which achieves 58% efficient power transfer to a single load at any point on its length.