Advances in femtosecond micromachining and inscription of micro and nano photonic devices

This thesis has focused on three key areas of interest for femtosecond micromachining and inscription. The first area is micromachining where the work has focused on the ability to process highly repeatable, high precision machining with often extremely complex geometrical structures with little or no damage. High aspect ratio features have been demonstrated in transparent materials, metals and ceramics. Etch depth control was demonstrated especially in the work on phase mask fabrication. Practical chemical sensing and microfluidic devices were also fabricated to demonstrate the capability of the techniques developed during this work. The second area is femtosecond inscription. Here, the work has utilised the non-linear absorption mechanisms associated with femtosecond pulse-material interactions to create highly localised refractive index changes in transparent materials to create complex 3D structures. The techniques employed were then utilised in the fabrication of Phase masks and Optical Coherence Tomography (OCT) phantom calibration artefacts both of which show the potential to fill voids in the development of the fields. This especially the case for the OCT phantoms where there exists no previous artefacts of known shape, allowing for the initial specification of parameters associated with the quality of OCT machines that are being taken up across the world in industry and research. Finally the third area of focus was the combination of all of the techniques developed through work in planar samples to create a range of artefacts in optical fibres. The development of techniques and methods for compensating for the geometrical complexities associated with working with the cylindrical samples with varying refractive indices allowed for fundamental inscription parameters to be examined, structures for use as power monitors and polarisers with the optical fibres and finally the combination of femtosecond inscription and ablation techniques to create a magnetic field sensor with an optical fibre coated in Terfenol-D with directional capability. Through the development of understanding, practical techniques and equipment the work presented here demonstrates several novel pieces of research in the field of femtosecond micromachining and inscription that has provided a broad range of related fields with practical devices that were previously unavailable or that would take great cost and time to facilitate.

Organizing the innovation process:complementarities in innovation networking

This paper contributes to the developing literature on complementarities in organizational design. We test for the existence of complementarities in the use of external networking between stages of the innovation process in a sample of UK and German manufacturing plants. Our evidence suggests some differences between the UK and Germany in terms of the optimal combination of innovation activities in which to implement external networking. Broadly, there is more evidence of complementarities in the case of Germany, with the exception of the product engineering stage. By contrast, the UK exhibits generally strong evidence of substitutability in external networking in different stages, except between the identification of new products and product design and development stages. These findings suggest that previous studies indicating strong complementarity between internal and external knowledge sources have provided only part of the picture of the strategic dilemmas facing firms.

Organising the innovation process:complementarities in innovation networking

This paper contributes to the developing literature on complementarities in organisational design. We test for the existence of complementarities in the use of external networking between phases of the innovation process in a sample of UK and German manufacturing plants. Our evidence suggests some differences between the UK and Germany in terms of the optimal combination of innovation activities in which to implement external networking. Broadly, there is more evidence of complementarities in the case of Germany, with the exception of the product engineering phase. By contrast, the UK exhibits generally strong evidence of substitutability in external networking in different phases, except between the identification of new products and product design and development phases.

Systemic analysis of concurrent engineering practice

This paper discusses three major areas of knowledge; business process reengineering (BPR), soft systems methodology (SSM) and concurrent engineering (CE) to demonstrate that their philosophies are complementary. An example is given depicting how a manufacturing resource planning system is set up and how improvements can be achieved by applying CE best practice.

Process integration and improvement using systemic diagrams and a human-centred approach

If product cycle time reduction is the mission, and the multifunctional team is the means of achieving the mission, what then is the modus operandi by which this means is to accomplish its mission? This paper asserts that a preferred modus operandi for the multifunctional team is to adopt a process-oriented view of the manufacturing enterprise, and for this it needs the medium of a process map [16] The substance of this paper is a methodology which enables the creation of such maps Specific examples of process models drawn from the product develop ment life cycle are presented and described in order to support the methodology's integrity and value The specific deliverables we have so far obtained are a methodology for process capture and analysis, a collection of process models spanning the product development cycle, and, an engineering handbook which hosts these models and presents a computer-based means of navigating through these processes in order to allow users a better understanding of the nature of the business, their role in it, and why the job that they do benefits the work of the company We assert that this kind of thinking is the essence of concurrent engineering implementation, and further that the systemigram process models uniquely stim ulate and organise such thinking.

The transformational implementation of JSD process specifications via finite automata representation

Conventional structured methods of software engineering are often based on the use of functional decomposition coupled with the Waterfall development process model. This approach is argued to be inadequate for coping with the evolutionary nature of large software systems. Alternative development paradigms, including the operational paradigm and the transformational paradigm, have been proposed to address the inadequacies of this conventional view of software developement, and these are reviewed. JSD is presented as an example of an operational approach to software engineering, and is contrasted with other well documented examples. The thesis shows how aspects of JSD can be characterised with reference to formal language theory and automata theory. In particular, it is noted that Jackson structure diagrams are equivalent to regular expressions and can be thought of as specifying corresponding finite automata. The thesis discusses the automatic transformation of structure diagrams into finite automata using an algorithm adapted from compiler theory, and then extends the technique to deal with areas of JSD which are not strictly formalisable in terms of regular languages. In particular, an elegant and novel method for dealing with so called recognition (or parsing) difficulties is described,. Various applications of the extended technique are described. They include a new method of automatically implementing the dismemberment transformation; an efficient way of implementing inversion in languages lacking a goto-statement; and a new in-the-large implementation strategy.

Computer interpretation of engineering drawings as solid models

Much of the geometrical data relating to engineering components and assemblies is stored in the form of orthographic views, either on paper or computer files. For various engineering applications, however, it is necessary to describe objects in formal geometric modelling terms. The work reported in this thesis is concerned with the development and implementation of concepts and algorithms for the automatic interpretation of orthographic views as solid models. The various rules and conventions associated with engineering drawings are reviewed and several geometric modelling representations are briefly examined. A review of existing techniques for the automatic, and semi-automatic, interpretation of engineering drawings as solid models is given. A new theoretical approach is then presented and discussed. The author shows how the implementation of such an approach for uniform thickness objects may be extended to more general objects by introducing the concept of `approximation models'. Means by which the quality of the transformations is monitored, are also described. Detailed descriptions of the interpretation algorithms and the software package that were developed for this project are given. The process is then illustrated by a number of practical examples. Finally, the thesis concludes that, using the techniques developed, a substantial percentage of drawings of engineering components could be converted into geometric models with a specific degree of accuracy. This degree is indicative of the suitability of the model for a particular application. Further work on important details is required before a commercially acceptable package is produced.

The application of knowledge based expert systems to mechanical engineering design

Investigation of the different approaches used by Expert Systems researchers to solve problems in the domain of Mechanical Design and Expert Systems was carried out. The techniques used for conventional formal logic programming were compared with those used when applying Expert Systems concepts. A literature survey of design processes was also conducted with a view to adopting a suitable model of the design process. A model, comprising a variation on two established ones, was developed and applied to a problem within what are described as class 3 design tasks. The research explored the application of these concepts to Mechanical Engineering Design problems and their implementation on a microcomputer using an Expert System building tool. It was necessary to explore the use of Expert Systems in this manner so as to bridge the gap between their use as a control structure and for detailed analytical design. The former application is well researched into and this thesis discusses the latter. Some Expert System building tools available to the author at the beginning of his work were evaluated specifically for their suitability for Mechanical Engineering design problems. Microsynics was found to be the most suitable on which to implement a design problem because of its simple but powerful Semantic Net Knowledge Representation structure and the ability to use other types of representation schemes. Two major implementations were carried out. The first involved a design program for a Helical compression spring and the second a gearpair system design. Two concepts were proposed in the thesis for the modelling and implementation of design systems involving many equations. The method proposed enables equation manipulation and analysis using a combination of frames, semantic nets and production rules. The use of semantic nets for purposes other than for psychology and natural language interpretation, is quite new and represents one of the major contributions to knowledge by the author. The development of a purpose built shell program for this type of design problems was recommended as an extension of the research. Microsynics may usefully be used as a platform for this development.

Cost models for engineering services

This thesis describes the procedure and results from four years research undertaken through the IHD (Interdisciplinary Higher Degrees) Scheme at Aston University in Birmingham, sponsored by the SERC (Science and Engineering Research Council) and Monk Dunstone Associates, Chartered Quantity Surveyors. A stochastic networking technique VERT (Venture Evaluation and Review Technique) was used to model the pre-tender costs of public health, heating ventilating, air-conditioning, fire protection, lifts and electrical installations within office developments. The model enabled the quantity surveyor to analyse, manipulate and explore complex scenarios which previously had defied ready mathematical analysis. The process involved the examination of historical material costs, labour factors and design performance data. Components and installation types were defined and formatted. Data was updated and adjusted using mechanical and electrical pre-tender cost indices and location, selection of contractor, contract sum, height and site condition factors. Ranges of cost, time and performance data were represented by probability density functions and defined by constant, uniform, normal and beta distributions. These variables and a network of the interrelationships between services components provided the framework for analysis. The VERT program, in this particular study, relied upon Monte Carlo simulation to model the uncertainties associated with pre-tender estimates of all possible installations. The computer generated output in the form of relative and cumulative frequency distributions of current element and total services costs, critical path analyses and details of statistical parameters. From this data alternative design solutions were compared, the degree of risk associated with estimates was determined, heuristics were tested and redeveloped, and cost significant items were isolated for closer examination. The resultant models successfully combined cost, time and performance factors and provided the quantity surveyor with an appreciation of the cost ranges associated with the various engineering services design options.

The pore system and engineering properties of hardened cement paste

The work described in this thesis is an attempt to elucidate the relationships between the pore system and a number of engineering properties of hardened cement paste, particularly tensile strength and resistances to carbonation and ionic penetration. By examining aspects such as the rate of carbonisation, the pore size distribution, the concentration of ions in the pore solution and the phase composition of cement pastes, relationships between the pore system (pores and pore solution) and the resistance to carbonation were investigated. The study was carried out in two parts. First, cement pastes with different pore systems were compared, whilst secondly comparisons were made between the pore systems of cement pastes with different degrees of carbonation. Relationships between the pore structure and ionic penetration were studied by comparing kinetic data relating to the diffusion of various ions in cement pastes with different pore systems. Diffusion coefficients and activation energies for the diffusion process of Cl- and Na+ ions in carbonated and non-carbonated cement pastes were determined by a quasi-steady state technique. The effect of the geometry of pores on ionic diffusion was studied by comparing the mechanisms of ionic diffusion for ions with different radii. In order to investigate the possible relationship between tensile strength and macroporosity, cement paste specimens with cross sectional areas less than 1mm2 were produced so that the chance of a macropore existing within them was low. The tensile strengths of such specimens were then compared with those of larger specimens.

The role of micro computers on the construction site

The control needed in the management of a project was analysed with particular reference to the unique needs of the construction industry within the context of site management. This was explored further by analysing the various problems facing managers within the overall system and determining to what extent the organisation would benefit from an integrated mangement information system. Integration and management of information within the organisational units and the cycles of events that make up the main sub-system was suggested as the means of achieving this objective. A conceptual model of the flow of information was constructed within the whole process of project management by examining the type of information and documents which are generated for the production cycle of a project. This model was analysed with respect to the site managers' needs and the minimum requirements for an overall integrated system. The most tedious and time-consuming task facing the site manager is the determination of weekly production costs, calculation and preparation of interim certificates and valuation of variations occurring during the production stage and finally the settlement and preparation of supplier and sub-contractors' accounts. These areas where microcomputers could be of most help were identified and a number of packages were designed and implemented for various contractors. The gradual integration of stand-alone packages within the whole of the construction industry is a logical sequence to achieve integration of management system. The methods of doing this were analysed together with the resulting advantages and disadvantages.

Reinforced thermoplastics for engineering applications

The effect of mechano-chemically bound polypropylene modifiers on the mechanical performance and thermal-oxidative stability of polypropylene composites has been studied. The mechanical performance of unmodified polypropylene containing silane coupled glass and Rockwool (mineral) fibre was poor by comparison with a similar commercially produced glass reinforced composite; this was attributed to poor fibre-matrix adhesion. Mechano-chemical binding with unsaturated additives was obtained in the presence of a free radical initiator (di-cumyl peroxide). This process was inhibited by stabilisers present in commercial grades of polypropylene composites by chemical bond formation between the chemically bound modifier and the silane coupling agent on the fibre surface, resulting in a dramatic improvement in the mechanical properties, dimensional stability and retention of mechanical performance after immersion in fluids typically found in under-bonnet environments.A feature unique to some of these modifiers was their ability not only to enhance the mechanical properties of polypropylene composites to levels substantially in excess of currently available commercial materials, but their ability to act as effective thermal-oxidative polypropylene stabilisers. The mode of action was shown to be a chain-breaking mechanism and as a result of the high binding levels achieved during melt processing, these modifiers were able to efficiently stabilise polypropylene in the most severe volatilising and solvent-extracting environments, thus giving much better protection to the polymer than currently available commercially stabilised grades of polypropylene.

Rationalisation and improvement of a company's engineering design procedures

There is a great deal of literature about the initial stages of innovative design. This is the process whereby a completely new product is conceived, invented and developed. In industry, however, the continuing success of a company is more often achieved by improving or developing existing designs to maintain their marketability. Unfortunately, this process of design by evolution is less well documented. This thesis reports the way in which this process was improved for the sponsoring company. The improvements were achieved by implementing a new form of computer aided design (C.A.D.) system. The advent of this system enabled the company to both shorten the design and development time and also to review the principles underlying the existing design procedures. C.A.D. was a new venture for the company and care had to be taken to ensure that the new procedures were compatible with the existing design office environment. In particular, they had to be acceptable to the design office staff. The C.A.D. system produced guides the designer from the draft specification to the first prototype layout. The computer presents the consequences of the designer's decisions clearly and fully, often by producing charts and sketches. The C.A.D. system and the necessary peripheral facilities were implemented, monitored and maintained. The system structure was left sufficiently flexible for maintenance to be undertaken quickly and effectively. The problems encountered during implementation are well documented in this thesis.

Improvements to the arc-spraying process

After a brief review of the various forms of thermal spraying equipment and processes, descriptions of the basic principles involved and the general functions for which thermally sprayed coatings are used are given. The background of the collaborating company, Metallisation, is described and their position in the overall market discussed, providing a backdrop against which the appropriateness of various project options might be judged. Current arc-spraying equipment is then examined, firstly in terms of the workings of their constituent parts and subsequently by examining the effects of changes in design and in operating parameters both upon equipment operation and the coatings produced. Published literature relating to these matters is reviewed. Literature relating to the production, comminution and propulsion of the particles which form the spray is discussed as are the mechanisms involved at impact with the substrate. Literature on the use of rockets for thermal spraying and induction heating as a process for feedstock melting are also reviewed. Three distinct options for further study are derived and preliminary tests and costings made to allow one option alone, the use of rocket acceleration, to go forward to the experimental phase. A suitable rocket burner was developed, tested and incorporated into an arc-spray system so that the sprayability of the whole could be assessed. Coatings were made using various parameters and these are compared with coatings produced by a standard system. Coatings were examined for macro and micro hardness, cohesive strength, porosity and by microstructural examination. The results indicate a high degree of similarity between the coatings produced by the standard system and the high velocity system. This was surprising in view of the very different atomising media and velocities. Possible causes for this similarity and the general behaviour of this new system and the standard system are discussed before the study reaches its conclusions in not proving the hypothesis that an increase in particle velocity would improve the mechanical properties of arc-sprayed steel coatings. KEY WORDS: Sprayed metal coatings, Electric arc spraying, High velocity flame spraying, Sprayed coating properties