Search

Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show that strain perpendicular to the copper-oxide planes couples directly to the competing interaction between charge stripe order and superconductivity in La1.88Sr0.12CuO4 (LSCO). Compressive c-axis pressure amplifies stripe order within the superconducting state, while having no impact on the normal state. By contrast, strain dramatically diminishes the magnetic field enhancement of stripe order in the superconducting state. These results suggest that c-axis strain acts as tuning parameter of the competing interaction between charge stripe order and superconductivity. This interpretation implies a uniaxial pressure-induced ground state in which the competition between charge order and superconductivity is reduced.

Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show that strain perpendicular to the copper-oxide planes couples directly to the competing interaction between charge stripe order and superconductivity in La$_{1.88}$Sr$_{0.12}$CuO$_{4}$ (LSCO). Compressive c-axis pressure amplifies stripe order within the superconducting state, while having no impact on the normal state. By contrast, strain dramatically diminishes the magnetic field enhancement of stripe order in the superconducting state. These results suggest that c-axis strain acts as tuning parameter of the competing interaction between charge stripe order and superconductivity. This interpretation implies a uniaxial pressure-induced ground state in which the competition between charge order and superconductivity is reduced.

The research team performed measurements in a bounded wave simulator to obtain the radar cross section (RCS) of a scale model of a particular airborne target. Measurements of the airborne target were obtained from two different flying orientations. The transient scattering response data were scaled to allow comparison with the RCS obtained by numerical methods for a full-size target. This document also presents the measurement procedure and data processing techniques that were used by the research team. METHOD A target was placed within the bounded wave simulator (BWS) area and was hit with an electromagnetic impulse, returning the scattered signal through the BWS for measurement in the control room. Measurements were also made of the background signal, as well as the in- cident signal. As the signals return to the control room below the BWS structure, the wave- forms are captured on an oscilloscope, then processed using Tektronix's Signal Processing and Display Package and Radar Cross Section program developed at NRaD. These programs convert the waveforms from time domain representations to frequency through the Fast Fourier Transform process. Further waveform processing allowed the calculation of RCS, which is the basis for target identification efforts using resonant frequencies. The measure- ment procedure and signal processing techniques are discussed in detail in the appendices. (KAR) P. 5

In a communication system one of the primary concerns is maximum efficiency in signal transmission and reception. For maximum power transfer there must be an impedance match between the antenna and transmitter (or receiver). A basic problem is to design a coupling network between a given source and a given load so that the transfer of power from the source to the load is maximized over a given frequency band of interest. The device used to perform this impedance matching is called an antenna matching network. The number of pieces of equipment requiring an antenna connection in some applications may exceed the number of acceptable locations available for antennas. One solution is the use of broadband antennas that have a low VSWR (voltage standing-wave ratio) over the operating band. Broadband antennas are used in conjunction with multicouplers (filters with multiple inputs) to provide a sufficient number of antenna connections. Despite the aid of Smith Charts, the traditional design of an antenna matching network by engineering experience and manual calculation means is an extremely time-consuming task. This paper is intended to relieve the engineer of the tedious numerical calculation involved in the network design.

An interactive BASIC language computer program to aid in the design of a matching network for a broadband antenna is described. Guidelines for the design of a broadband matching network are presented. The Antenna Matching (ANTMAT) program provides a computer-aided design tool for determining network topology and component values of the networks. It improves the speed and accuracy of the broadband matching network design procedures. An optimization algorithm finds that the values of the components that minimize the input reflection coefficient. At first, the optimization algorithm with an exponential weighting function is employed for determining a list of network candidates (either a pi network for a T network) from which a network topology is selected. After a topology is specified, the optimization algorithm with other weighting function is used for finding optimum element values. Keywords include: Interactive computer program, Computer-aided design, Network topology, and Optimization algorithm.

This report describes an EMI evaluation of the effects of off-shore exploratory drilling operations on the SESEF facility at Long Beach Naval Shipyard. This study uses mathematical model simulation techniques to determine interference effects due to electromagnetic scattering (diffraction and multipath reflections). Interference due to radio frequency transmissions and electromagnetic noise is also considered. (Author)