The methods of impedance tomography may be employed to obtain images of subsurface electrical and conductivity variations. For practical reasons, voltages and currents are usually applied at locations on the ground surface or down a limited number of boreholes, but almost never over the entire surface of the region being investigated. The geophysical inversion process can be facilitated by constructing algorithms adopted to these particular geometries and to the lack of complete surface data. In this paper we assume that the fluctuations in conductivity are small compared to the background value. The imaging of these fluctuations is carried out exactly within the constraints imposed by the problem geometry. Several possible arrangements of injection and monitoring electrodes are considered. In two dimensions include: Cross-line geometry, current input along one line (borehole) and measurements along a separate parallel line. Single-line geometry, injection and monitoring using the same borehole. Surface reflection geometry, all input and measurement along the ground surface. Theoretical and practical limitations on the image quality produced by the algorithms are discussed. They are applied to several sets of simulated data, and the images produced are displayed and analyzed.

This paper describes some recent developments in adaptive contact algorithms for the transient analysis of penetration and material failure. A failure criterion is defined for volumes of potentially failing material on each side of a contact surface. As material within an element fails, the element is removed from the calculation and the contact surface is adaptively redefined to include the newly exposed outer material boundary. This contact algorithm admits arbitrary combinations of shell and solid elements to facilitate the representation of composite or honeycomb structures. The algorithms and their application are illustrated with several large-scale simulations using the explicit transient analysis code DYNA3D.

This paper discusses the technical progress of a US Department of Energy Innovative Clean Coal Technology project demonstrating advanced wall-fired combustion techniques for the reduction of nitrogen oxide(NO{sub x}) emissions from coal-fired boilers. The primary objective of the demonstration is to determine the performance of two low NO{sub x} combustion technologies applied in a stepwise fashion to a 500 MW boiler. A target of achieving 50 percent NO{sub x} reductions has been established for the project. The main focus of this paper is the presentation of the low NO{sub x} burner (LNB) short and long-term tests results.