Theory and applications of multi-dimensional stationary stochastic processes

The theory of stationary stochastic processes in several dimensions has been investigated to provide a general model which may be applied to various problems which involve unknown functions of several variables. In particular, when values of the function are known only at a finite set of points, treating the unknown function as a realisation of a stationary stochastic process leads to an interpolating function which reproduces the values exactly at the given points. With suitable choice of auto-correlation for the model, the interpolating function may also he shown to be continuous in all its derivatives everywhere. A few parameters only need to be found for the interpolator, and these may be estimated from the given data. One problem tackled using such an interpolator is that of automatic contouring of functions of two variables from arbitrarily scattered data points. A "two-stage" model was developed, which incorporates a long-range "trend" component as well as a shorter-range "residual" term. This leads to a contouring algorithm which gives good results with difficult data. The second area of application is that of optimisation, particularly of objective functions which are expensive to compute. Since the interpolator gives an estimate of the derivatives with little work, it is simple to optimise it using conventional techniques, and to re-evaluate the true function at the apparent optimum point. An iterative algorithm along these lines gives good results with test functions, especially with fuactions of more than two variables. A program has been developed whicj incorporates both the optimisation and contouring applications into a single peckage. Finally, the theory of excursions of a stationary process above a fixed level has been applied to the problem of modelling the occurrence of oilfields, with special reference to their spatial distribution and tendency to cluster. An intuitively reasonable model with few parameters has been developed and applied to North Sea data, with interesting results

Improvement in inspection methods for aero-engine components using computer-linked electro-optical techniques

An improved technique for inspecting aero-engine turbine blades was developed. The technique increased the area of the blade that was examined and presented the difference information in an easily assimilated form without increasing the overall inspection time above that of present methods. To achieve this an optical contouring technique was used to measure the blade shape and this was linked to a computer to enable the dimensional information to be processed quickly. [Continues.

Investigation related to multispectral imaging systems

A summary of technical progress made during a five year research program directed toward the development of operational information systems based on multispectral sensing and the use of these systems in earth-resource survey applications is presented. Efforts were undertaken during this program to: (1) improve the basic understanding of the many facets of multispectral remote sensing, (2) develop methods for improving the accuracy of information generated by remote sensing systems, (3) improve the efficiency of data processing and information extraction techniques to enhance the cost-effectiveness of remote sensing systems, (4) investigate additional problems having potential remote sensing solutions, and (5) apply the existing and developing technology for specific users and document and transfer that technology to the remote sensing community

Fluids mobilization in Arabia Terra, Mars: depth of pressurized reservoir from mounds self-similar clustering

Arabia Terra is a region of Mars where signs of past-water occurrence are recorded in several landforms. Broad and local scale geomorphological, compositional and hydrological analyses point towards pervasive fluid circulation through time. In this work we focus on mound fields located in the interior of three casters larger than 40 km (Firsoff, Kotido and unnamed crater 20 km to the east) and showing strong morphological and textural resemblance to terrestrial mud volcanoes and spring-related features. We infer that these landforms likely testify the presence of a pressurized fluid reservoir at depth and past fluid upwelling. We have performed morphometric analyses to characterize the mound morphologies and consequently retrieve an accurate automated mapping of the mounds within the craters for spatial distribution and fractal clustering analysis. The outcome of the fractal clustering yields information about the possible extent of the percolating fracture network at depth below the craters. We have been able to constrain the depth of the pressurized fluid reservoir between ~2.5 and 3.2 km of depth and hence, we propose that mounds and mounds alignments are most likely associated to the presence of fissure ridges and fluid outflow. Their process of formation is genetically linked to the formation of large intra-crater bulges previously interpreted as large scale spring deposits. The overburden removal caused by the impact crater formation is the inferred triggering mechanism for fluid pressurization and upwelling, that through time led to the formation of the intra-crater bulges and, after compaction and sealing, to the widespread mound fields in their surroundings

Laser interferometric measurement of ion electrode shape and charge exchange erosion

A projected fringe profilometry system was applied to surface contour measurements of an accelerator electrode from an ion thrustor. The system permitted noncontact, nondestructive evaluation of the fine and gross structure of the electrode. A 3-D surface map of a dished electrode was generated without altering the electrode surface. The same system was used to examine charge exchange erosion pits near the periphery of the electrode to determine the depth, location, and volume of material lost. This electro-optical measurement system allowed rapid, nondestructive, digital data acquisition coupled with automated computer data processing. In addition, variable sensitivity allowed both coarse and fine measurements of objects having various surface finishes

New measuring techniques using holographic and speckle interferometric recording

Electronic and photographic interferometric recording, and their combination, result in several novel optical measuring techniques. The interferometric properties of holographic and speckle processes in these techniques encompass fields such as lapse time, real time and time average holographic interferometry, two-wavelength and multiple-index speckle contouring, figure (moire) interference, photographic bleach processes and electronic processing. Each of these fields is analysed and conclusions are drawn in their interaction with the proposed techniques. A clear and simple approach to optical wave theory is intended with emphasis in scalar wave theory. [Continues.

Bathymetric Artifacts in Sea Beam Data: How to Recognize Them and What Causes Them

Sea Beam multibeam bathymetric data have greatly advanced understanding of the deep seafloor. However, several types of bathymetric artifacts have been identified in Sea Beam\u27s contoured output. Surveys with many overlapping swaths and digital recording on magnetic tape of Sea Beam\u27s 16 acoustic returns made it possible to evaluate actual system performance. The artifacts are not due to the contouring algorithm used. Rather, they result from errors in echo detection and processing. These errors are due to internal factors such as side lobe interference, bottom-tracking gate malfunctions, or external interference from other sound sources (e.g., 3.5 kHz echo sounders or seismic sound sources). Although many artifacts are obviously spurious and would be disregarded, some (particularly the omega effects described in this paper) are more subtle and could mislead the unwary observer. Artifacts observed could be mistaken for volcanic constructs, abyssal hill trends, hydrothermal mounds, slump blocks, or channels and could seriously affect volcanic, tectonic, or sedimentological interpretations. Misinterpretation of these artifacts may result in positioning errors when seafloor bathymetry is used to navigate the ship. Considering these possible geological misinterpretations, a clear understanding of the Sea Beam system\u27s capabilities and limitations is deemed essential