Coating thickness and elastic modulus measurement using ultrasonic bulk wave resonance

Measurement of the resonant through thickness ultrasonic modes of a homogeneous plate using a fast Fourier transform of the temporal data can be used to calculate plate thickness very accurately. We describe an extension of this principle to two-layer systems, examining a thin coating on a substrate of known properties. The resonant behavior of these systems is predicted and we explain how this approach is used to measure coating thickness and elastic modulus. Noncontact electromagnetic acoustic transducers are used for ultrasonic measurement, as they do not significantly affect the resonant response of the system, unlike alternative contact transducers

Investigation of the nonlocal coherent-potential approximation

Recently the nonlocal coherent-potential approximation (NLCPA) has been introduced by Jarrell and Krishnamurthy for describing the electronic structure of substitutionally disordered systems. The NLCPA provides systematic corrections to the widely used coherent-potential approximation (CPA) whilst preserving the full symmetry of the underlying lattice. Here an analytical and systematic numerical study of the NLCPA is presented for a one-dimensional tight-binding model Hamiltonian, and comparisons with the embedded cluster method (ECM) and molecular coherent potential approximation (MCPA) are made.Comment: 18 pages, 5 figure

The flow of equatorial Kelvin waves and the equatorial undercurrent around islands

A linear theory is presented for the flow of equatorial Kelvin waves and of the equatorial undercurrent around islands situated on or near the equator. The island is modelled as an infinitesimally thin meridional barrier. It is shown that small islands affect the flow very little, while large islands effectively block the flow...

Scaling collapse and structure functions: identifying self-affinity in finite length time series

Empirical determination of the scaling properties and exponents of time series presents a formidable challenge in testing, and developing, a theoretical understanding of turbulence and other out-of-equilibrium phenomena. We discuss the special case of self affine time series in the context of a stochastic process. We highlight two complementary approaches to the differenced variable of the data: i) attempting a scaling collapse of the Probability Density Functions which should then be well described by the solution of the corresponding Fokker-Planck equation and ii) using structure functions to determine the scaling properties of the higher order moments. We consider a method of conditioning that recovers the underlying self affine scaling in a finite length time series, and illustrate it using a Lévy flight

Transduodenal Sphincteroplasty and Transampullary Septectomy for Papillary Stenosis

Twenty patients received transduodenal sphincteroplasty and transampullary septectomy between 1987 and 1993. Seven patients had post-cholecystectomy pain which was much improved or abolished in 5 of 7 patients at a mean follow-up of 4 years and 5 months. Four of five patients with chronic pancreatitis were improved at 3 years and 2 months. Three of five patients with recurrent acute pancreatitis were improved at 4 years and 5 months. One of three patients with chronic abdominal pain of hepatobiliary origin was improved at 3 years. Transduodenal sphincteroplasty and transampullary septectomy can relieve pain in patients with post-cholecystectomy pain, recurrent acute pancreatitis, chronic pancreatitis, and chronic abdominal pain of hepatobiliary origin, presumably by improving drainage of the obstructed ducts

Effects of short-range order on the electronic structure of disordered metallic systems

For many years the Korringa-Kohn-Rostoker coherent-potential approximation (KKR-CPA) has been widely used to describe the electronic structure of disordered systems based upon a first-principles description of the crystal potential. However, as a single-site theory the KKR-CPA is unable to account for important environmental effects such as short-range order (SRO) in alloys and spin fluctuations in magnets, amongst others. Using the recently devised KKR-NLCPA (where NL stands for nonlocal), we show how to remedy this by presenting explicit calculations for the effects of SRO on the electronic structure of the bcc Cu_{50}Zn_{50} solid solution.Comment: 8 pages, 6 figures, Revised versio

The role of inertia-gravity and planetary waves in the response of a tropical ocean to the incidence of an equatorial Kelvin wave on a meridional boundary

The problem of an equatorial Kelvin wave of step-function form incident on an eastern meridional boundary is solved on an equatorial beta-plane. The nature of the transient planetary and inertia-gravity waves is examined and the way in which they combine to produce a coastally trapped Kelvin wave evaluated...

The Somali Current response to the Southwest Monsoon: The relative importance of local and remote forcing

A simple model of the Somali current is formul ated which allows both local longshore forcing and remote east-west forcing. Asymptotic solutions for the pressure perturbation and velocity fields are obtained for both cases and the sensitivity of the boundary response to changes in the shape and position of the forcing is examined. The local forcing drives a flow whose north-south velocity increases linearly with time and the remote forcing , a flow in which the north-south velocity increases quadratically...