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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Model updating of large structures

Shahverdi, Hossein January 2005 (has links)
No description available.

Novel approaches in two-dimensional autoregressive modelling

Lee, Sarah Hung-Hwei January 2005 (has links)
No description available.

Fault location on a distribution feeder using high frequency travelling waves

Hizam, H. January 2004 (has links)
No description available.

Novel developments of Moiré techniques for industrial applications

Heredia Ortiz, Manuel Eduardo January 2004 (has links)
The family of moire and fringe projection techniques can be used to measure the shape, orientation and deformation of arbitrary objects. These experimental techniques are easy to automate, allow remote operation, provide full-field information and are versatile, inexpensive and relatively simple. They have been applied extensively in the past, but mostly in the controlled environment of a laboratory. There is great potential in the use of these techniques for a variety of industrial applications including quality control and process monitoring. However, this implies dealing with the adverse conditions of the factory, hangar or similar environment. In addition, these techniques will only appeal to industry if they are fast, simple, and foolproof. The main goal of this research was to exploit recent technological advances to fulfil the requirements of industry, making these techniques easier to use and more robust, and explore the potential offered by the combination and cross-fertilization of moire methods with techniques from different fields such as experimental stress analysis, non-destructive evaluation, and machine vision. This research resulted in the development of a number of instruments and procedures for industrial applications based in moire and fringe projection techniques, including: • A handheld instrument based in the shadow moire technique designed to assist in the detection of very small surface defects in aircraft parts, during in-service maintenance inspections; • A multi-purpose system to measure remotely (i) the shape and deformation of three dimensional objects by means of the fringe projection technique, and (ii) the location of the object by means of triangulation. The elements were integrated in a portable instrument, and fully automated novel algorithms were implemented to process the data; • Finally, a novel experimental technique is proposed that uses thermal marking to measure deformation in a component, in a combination of concepts from moire and thermography. Experimental results obtained in a range of situations are presented in several industrial applications in the context of the aerospace industry and in bioengineering.

Diagnosis via Qualitative parameter estimation

Al-Ballaa, Hind Rasheed January 2008 (has links)
This thesis presents an approach for qualitative model based fault diagnosis via parameter estimation. Estimating parameters qualitatively in this research is based on the relationships among involved qualitative quantities. To maintain the consistency of ordinal relationships an inequality reasoner is developed. Existing inequality reasoners (or commonly in the AI community referred to as quantity lattices) infer relationships between quantities involved in a system (qualitative or quantitative) based on the real values associated with them. The novel feature of our inequality reasoner is that it infers and maintains relationships among pure qualitative quantities. Inferring ordinal relationships between sign based quantities removes the traditional drawback of qualitative domain, the lack of discriminating power.

A knowledge based approach to inspection qualification

McNab, Douglas January 2007 (has links)
No description available.

Application of a digraph model-based approach to system fault diagnostics

Kelly, Emma Marie January 2007 (has links)
The issue of fault diagnostics is a dominant factor concerning current engineering systems. Information regarding possible failures is required in order to minimise disruption caused to functionality. A method proposed in this research utilises digraphs to model the information flow within an application system. Digraphs are comprised from a set of nodes representing system process variables or component failure modes. The nodes are connected by signed edges thus illustrating the influence, be it positive or negative, one node has on another. System fault diagnostics is conducted through a procedure of back-tracing in the digraph from a known deviating variable. A computational method has been developed to conduct this process. Comparisons are made between retrieved transmitter readings and those expected whilst the system is in a known operating mode. Any noted deviations are assumed to indicate the presence of a failure. The digraph diagnostic method is applied to three systems of increasing complexity; a simple water tank, an industrial based test stand of an aircraft fuel system and the Boeing 777-200 fuel system. This research includes transient system effects; the rate of change of a parameter is taken into consideration as a means of monitoring the system dynamically. The validity of the results achieved are evaluated, along with the development of a 'honing-in' strategy to highlight the most probable fault cause for a given abnormal scenario. Finally, the effectiveness and scalability issues associated with the application of the digraph method in system fault diagnostics are addressed.

Surface strain measurement using pulsed laser shearography with fibre-optic imaging bundles

Francis, Daniel January 2008 (has links)
This thesis describes the development of a shearography instrument for the quantitative measurement of surface strain on dynamic test objects. Shearography is a non-contact, full-field interferometric speckle technique used for the measurement of displacement gradient. It is often used in industry for qualitative inspection of industrial components. To fully characterize the surface strain, a total of six components of displacement gradient are required. These can be measured using shearography instrumentation with at least three measurement channels. Phase measurements from each measurement channel are combined using a matrix transformation to produce the orthogonal displacement gradient measurements. The instrument presented in this thesis possesses four measurement channels consisting of four views of the object under investigation. Images from the four views are transported to the shearing interferometer using coherent fibre-optic imaging bundles. The signals from the four views are then spatially multiplexed onto the four quadrants of a CCD camera. The optical source is a frequency doubled, pulsed Nd:YAG laser which is used to effectively ‘freeze’ the motion of the dynamic object for the duration of the laser pulse. The optical phase difference between images recorded from two laser pulses is determined using the spatial carrier technique. This method involves introducing a carrier frequency into the recorded speckle pattern using a Mach-Zehnder interferometer. A Fourier transform is used to access the phase dependent spectral features, from which the phase distribution is calculated. The instrument is first validated through the measurement of two static test objects. The results of these measurements are compared with modelled data and with results from a multiple-illumination-direction shearography system using a continuous-wave laser. The instrument is then used to investigate two dynamic objects; a plate rotating at 610 rpm and a speaker cone vibrating at frequencies in the range of 1 – 5 kHz.

The use of dry coupling in ultrasonic nondestructive testing

Drinkwater, Bruce Walton January 1995 (has links)
No description available.

The response of intermediate explosives to thermal and shock stimuli

Hutchinson, C. D. January 1985 (has links)
No description available.

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