The Hydroson system is a novel cleaning system which has recently been adopted to solve cleaning problems in many industries, particularly in metal finishing. Although effective the fundamental principles and mode of action of the process are not fully understood. In this work, the Hydros on system was quantitatively evalued and compared with other methods of cleaning. Further, the mechanism of cleaning was studied and was shown to be due to the scouring action produced by the impingement of the high pressure jets on the contaminated surface. The rate of cleaning was comparable with ultrasonic cleaning at a frequency of 13 KHz and intensity of 520 Wm[-2]. The effect of Hydroson agitation was studied on the electrodeposition process using an alkali zinc electrolyte with and without addition agents. Hydroson agitation reduced the diffusion layer thickness at the cathode to a similar value compared with ultrasonic agitation, and gave many beneficial effects on the properties of both the electrolyte and the deposit. It reduced cathodic and anodic polarization, increased the cathodic current efficiency and maximum current density, thus allowing good quality deposits to be obtained even at higher current densities. The deposit from the zincate bath without addition agents was less porous, had a finer crystallite structure and was harder than those formed from solutions with no agitation, with magnetic stirring to give a flow rate of 20 cm s[-1], or with ultrasonic agitation. In the zincate bath with addition agents, Hydroson and ultrasonic agitation increased the hardness, but reduced the brightness of the deposit. Hydroson agitation was also shown to increase the rate of electrolytic recovery of zinc metal from dilute zincate solutions by 3-4 fold compared with magnetic stirring. The flow velocity of solution across a surface in the centre of the Hydroson tank was determined by a theoretical and experimental approach and was found to be approximately 1.2 ms[-1].

The main achievement of this research is the development of a genetic algorithm model as a solution approach to the single model assembly line balancing problem (SMALBP), considered a difficult combinatorial optimisation problem. This is accomplished by developing a genetic algorithm with a new fitness function and genetic operators. The novel fitness function is based on a new front-loading concept capable of yielding substantially improved and sometimes optimum solutions for the SMALBP. The new genetic operators include a modified selection technique, moving crossover point technique, rank positional weight based repair method and dynamic mutation technique. The moving crossover point technique addressed the issue of propagating best attributes from parents to offspring and also supports the forward loading process. The new selection technique was developed by modifying the original rank-based selection scheme. This eliminates the high selective pressure associate with the original rank-based technique. Furthermore, the modified selection technique allows the algorithm to run long enough, if required, without premature convergence and this feature is very useful for balancing more complex real world problems. The repair technique included in this model repairs a higher proportion of distorted chromosomes after crossover than previous methods. Moreover, a third innovative feature, a moving adjacent mutation technique, strengthens the forward loading procedure and accelerates convergence. The performance of the front-loading fitness function currently outperforms the published fitness functions and fifty-four published test cases generated from sixteen precedence networks are used to assess the overall performance of the model. Encompassing the new genetic algorithm concepts, forty-four test problems (81%) achieved the best solutions obtained by published techniques and twenty-four problems (44%) produced better results than the benchmark Hoffmann precedence procedure, the closest non-genetic algorithm method. The superiority of the genetic model over other heuristics is identified in this research and future developments of this genetic algorithm application for assembly line balancing problems is evident.

Brazing may be described as more of an art than a science , there is little comprehension of the basic mechanisms governing brazing in air or vacuum. Consequently the behaviour of the Gold 18% Nickel brazing alloy in vacuum was studied using the novel techniques of hot-stage scanning electron microscopy with simultaneous bulk and surface analysis. The work demonstrates that careful control of experimental conditions allows both Auger electron and X-Ray spectroscopies (AES and EDXA) to be carried out at high spatial and energy resolutions , with good signal to noise in a realistic analyical time. Combining post-brazing examination of samples heated in a UHV oven , with real-time studies of braze powder/substrate combinations on a heating stage in an Auger microprobe , revealed several important mechanisms. Vacuum brazing is a two-stage process; oxide penetration followed by wetting and spreading via a suboxide route. AES analysis showed that oxide penetration is achieved by reduction as a result of low oxygen partial pressures and high carbon activities , in the system as a whole , or locally (for example under or around a molten braze droplet) , leaving an oxide-free surface , or a discontinuous , penetrable oxide. After penetration has occurred wetting and spreading continues along the metal/metal-oxide interface. Flow may be impeded by residual oxide resisting the advancing liquid which is trying to disbond it. Alternatively , interdiffusion of the braze metal and substrate allows pick-up of elements which raise the melting temperature of the braze alloy and causes solidification. EDX analysis and digital element mapping during interdiffusion and solidification illustrates that the periphery of the braze pools are most affected , and that further elevating the temperature initially caused remelting , but eventually resulted in second phase formation in accord with the Au/Ni/Fe equilibrium diagram.

A study of ion implanted zinc in GaAs has been made using four annealing techniques: e-beam, graphite strip heating, furnace annealing in an arsine ambient and laser annealing. The highest hole concentrations, 7-8 x 10[19]cm[-3] were obtained using electron beam annealing. Graphite strip heating and electron beam annealing were able to electrically activate 100% of the implanted dose. Laser annealing produced surface decomposition during irradiation which was reduced by using a diffuser. The effect of strain on the activation of the zinc has been demonstrated by comparing chemical vapour deposited Si[3]N[4] with reactively evaporated AIN encapsulants. A model for the activation of zinc in GaAs has been formulated to take into account the different annealing techniques used for solid phase recrystallisation. The electrical and structural properties of 1 x 10[14] Se[+]cm[-2], 100-400 kV and 5 x 10[12] Se[++]cm[-2], 350 kV implants into (100) semi-insulating GaAs have been studied. Peak carrier concentrations of 5 x 10[18] cm[-3] have been measured and mobilities of 4000 cm[2]V[-1]s[-1] obtained for low dose implants (n = 1-2 x 10[17]cm[-3]) by annealing samples on a graphite strip heater. Si[3]N[4] and AIN have been used as encapsulants. Comparisons are made with capless annealing in an arsine ambient. A model for the activation of selenium in GaAs relates the activation energy of diffusion with the rate of electrical activation of selenium.

No description available.

The purpose of this project is to make a detailed technological and economic analysis of the current UK situation regarding the use of scrap rubber in order to identify the most effective processes and products. The scope of the investigation is restricted to the re-use of scrap rubber as a primary raw material for rubber product manufacture. The thesis emphasises the following aspects : (i) the structure of the rubber processing industry and the role of the rubber recycling sectors; (ii) property relationships in rubber compounds incorporating scrap rubber crumb, with particular attention to material mechanics; (iii) the estimation of curing agent distribution in a crumb incorporated rubber vulcanizate; and (iv) the economics of the cryogenic grinding of scrap rubber tyres. The property relationships of vulcanizates incorporating recycled rubber have been studied using several mathematical models : Gent, simple law of mixtures, Mooney-Rivlin models, and a non-Gaussian model based on a simplified form of inversed Langevin function. It was found that; (i) for some compounds the elastic modulus and strength could be described well by the law of mixtures for composites, (ii) the reduction in strength caused by the incorporation of crumb decreased with decreasing particle size but there is little advantage to be gained by reducing the size below 20 pm, (iii) different modes of failure may be operative, i.e. adhesive and cohesive, according to the strength of the matrix rubber. The redistribution of curing agent in our whole tyre crumb-rubber vulcanizates has been studied using the SEM and EDAX techniques. Although qualitative and quantitative evidence for the migration of cure agent from matrix to crumb is given, no evidence was found for an interfacial layer between the two phases which is depleted of cure agent. Little detailed information on the economics of the majority of commercially operated processes is available. Data has been obtained for the cryogenic grinding of scrap rubber, a technology which seems to show potential for commercial exploitation, and a thorough economic analysis performed. The result showed that, under currently depressed crumb prices and low demand, the most feasible of the plants considered is just marginally economically viable. It was found that the most important cost input to the cryogrinding process is the cost of cryogenic material (liquid nitrogen) and that the most important factor which governs the economic viability of the process is the price of the rubber crumb output. Socio-environmental and resource conservation factors indicate the desirability of Government support.

The problems encountered in attempting to determine the rate controlling step in the reduction of magnetite end sinters to iron are revealed by a survey of the pertinent literature. On the basis of previous work supplemented by the investigations reported in this thesis the probable sequence of rate controlling steps has been determined. Exhaustive metallographic and mathematical studies have been carried out on the hydrogen reduction of magnetite and lean magnetite sinter samples reduced in thermal balances. The existence of rate minima at 650°C and 900°C in the reduction of magnetite has been shown by metallographic techniques. Additionally the extent of chemical reaction and mass transport control has been shown by mathematical studies. Similarly the extent of chemical and transport control in sinter reduction has been shown metallographically and mathematically. The effect of thermal treatment in oxidising and inert atmosphere has been shown. The improvement in reaction rates as a result of particular thermal treatments has been displayed.

This thesis studies the operating behaviour of the manual unpaced lines, which are the most important of the flow lines' systems. The lines examined are unbalanced and six types of imbalance are considered, namely, the imbalances of mean service times, coefficients of variation (Covars), buffers'capacities, means and Covars, means and buffers, and Covars and buffers. It is argued that the deep understanding of the behavioural characteristics of such lines, contributes towards the achievement of practical solutions to many of their problems. The lines are simulated under both steady and non-steady states conditions, with positively skewed weibull work times distributions, different values of line length (N), buffer capacity (B), degree of imbalance (DI), and pattern of imbalance, utilizing full factorial designs. The data are subjected to the analysis of variance, multiple regression, multiple comparisons with control, pairwise comparisons, canonical correlation, and utilitv analysis A simple utility approach is also explored briefly. Some of the important conclusions for all the unbalanced lines' investigations are: (1) At least one unbalanced pattern generates superior idle time (I) and/or mean buffer level (ABL), over those of a balanced line. The superiority in I decreases as DI rises, whereas the advantage in ABL reduces as DI is decreased.(2) The DI of the best unbalanced pattern can substantially or moderately be increased and still yields approximately equal I to that of a balanced configuration.(3) If a line is unbalanced in the wrong direction, significantly inferior performance to that of a balanced design will result.(4) The unbalanced patterns' I tends to decrease, when N and DI reduce and B increases, while ABL falls directly with B.(5) The I's transient size increases as N and B become higher and DI increases, while the ABL's transient size rises whenever B reduces.

A detailed investigation is carried out for the novel process of Plasto-hydrodynamically produced wide strip. In this process the conventional die is replaced by a pressure head with a rectangular hole. The internal geometry of the hole is shaped such that a convergent fluid flow is produced. This flow causes the production of hydrodynamic forces within the pressure head, namely hydrodynamic pressure and surface shear stresses. These forces are of sufficient magnitude that plastic deformation is induced within the working material. An in-depth theoretical analysis has been undertaken to establish the relevance of the geometrical parameters of the pressure head for the control of deformation performance. An extensive study of the solution algorithm for this type of plasto-hydrodynamic problem is made and modifications introduced to improve die dynamic response of the model. A new non-Newtonian model of the process has been developed using a power law type constitutive equation for the fluid behaviour. The modifications to the solution algorithm were also included in this new model. The plasto-hydrodynamic models developed during this work were subjected to numerical optimisation. The non-linear pattern search algorithm was utilised for this purpose. Correlations between the optimum geometrical form for the pressure head and process velocity were established. A study was made of the effect of varying the non-Newtonian parameters and the optimum pressure head geometry. A Computational Fluid Dynamic (CFD) analysis was made of the Hydrostatic assumption. This assumption allows major simplifications during the derivation of the models of the process. Its validity is established along with the impact of side leakage on the pressure field. An experimental programme was undertaken to provide data to establish a correlation between the predictions of process performance and an analysis of the output form of the strip produced by the process. The material used for the study was commercially available soft copper strip. The maximum reduction in area produced was 12% approximately.

An understanding of the factors surrounding the achievement of specified quality requirements is imperative and hence a prerequisite for effective management of quality by the construction team. To this end, the research is concerned with identifying, with a high degree of certainty associated with the data, the cause and effect of quality problems directly related-to the site production process and to establish, quantitatively, the relative importance of the factors. Six hypotheses were postulated and their verification was based on balanced and honest conclusions drawn from the data analyses. Five of the six hy 3po thesesa re supported by the data. Therefore, they become explanatory theories for the management of quality in construction. As part of a literature survey, a critical review of the previous works was made and the current state of the art was identified. Based on the knowledge gained from the literature survey, three detailed case studies were made of construction projects in the South East of England, utilising different procurement methods. The case studies, in conjunction with the literature review, were used to develop conceptual models which in turn were used for structuring a detailed questionnaire intended to extend the research throughout England in order to achieve a sufficiently large category proportion'. The responses to the questionnaires were scientifically analysed and statistically validated. The data analysis results in the identification of 30 factors which are expressed as the causes of non-conformance to specified quality requirements. The relative importance of each factor was established. Therefore, a large cloud has been removed and the construction team can now direct their limited resources effectively. The second objective of the research was accomplished with the successful development of a new Quality System entitled "Quality Communication System" (QCS). The implementation of the QCS approach to the management of quality in construction will result in achieving conformance to specified quality requirements at first attempt, lower costs and increased productivity in the construction industry. The research outcome is a significant contribution to the management of quality in the construction process. The outcome is perceived to represent an advance in knowledge associated with construction management.