The causes and effects of water pollution are Listed and the mechanisms of stream self-purification described. The parameters for which mathematical models have been developed are described and the success of the various previous models for predicting them is discussed. The equations governing the concentration of dissolved oxygen in a polluted waterway are developed and a review is made of the various finite difference schemes which available for solving them. Models are developed for predicting dissolved oxygen concentrations in two polluted New Zealand rivers, the Waikate and the Tarawera. It was found that the models used previously in other waterways were not adequate for either of these rivers. The model of the Waikato River uses the well-known Streeter-phelps equation to model the exertion of BOD but includes the effects of the macrophyte and phytoplankton communities on the concentration of dissolved oxygen. The model of the Tarawera River uses the Monod equations to predict the concentrations of active biomass in the porous pumice sediments on the river bed, and successfully accounts for the high rate of oxygen uptake which has been observed. The way in which these models could profitably be developed is also discussed.

The work described in this thesis represents the results of an investigation undertaken with the dual intention of (a) establishing the apparatus and techniques necessary for carrying out investigations into the work-hardening behaviour of metals under-going plastic deformation, and (b) examining the work-hardening behaviour of polycrystalline copper during interrupted tensile testing. The first part of the investigation required the development of the basic apparatus for investigations of the type envisaged. This apparatus included a tensile testing-machine, apparatus for the production of meta1 single crystals, apparatus for the determination of the orientation of metal single crystals and apparatus for the strain-free machining of metal single crystals. Details of the design and construction of this apparatus are presented. The second part of the investigation required the assessing of the existing knowledge of work-hardening and the establishment of a programme aimed at contributing further to this knowledge. A review is presented of information which pertains to the results of interrupted tensile tests such as those where the temperature dependence of the flow stress is examined, or the yield phenomenon produced by unloading is examined. Some omissions and anomalies in this information are noted and a programme of interrupted tests of the types described in the review is outlined for polycrystalline copper. As a result of this programme, the following conclusions are made concerning the work-hardening behaviour of polycrystalline copper during interrupted tensile testing: (a) polycrystalline copper obeys the Cottrell-Stokes law irrespective of the grain size or purity. (b) copper single crystals of polyslip orientations obey the Cottrell-Stokes law. (c) polycrystalline copper exhibits a yield phenomenon produced by unloading at all temperatures and strains. The magnitude of the change in flow stress associated with the yield phenomenon increases with decreasing temperature and is not significantly dependent on grain-size or purity. The magnitude of the change in flow stress increases with increasing strain and passes through a maximum. (d) the magnitude of the change in flow stress associated with the yield phenomenon produced by unloading in polycrystalline copper increases as the amount of unloading increases.

One of the most important process operations in the pulp and paper industry is the transport of pulp in pipe lines. Because pipe friction losses are much higher than with water under comparable conditions, accurate design correlations for each pulp are important to the industry. The purpose of this investigation was to design and build a flow rig suitable for investigating a wide range of pulp conditions, to obtain pipe friction loss data for New Zealand pulps, and to produce design correlations and procedures for the industry. This thesis is therefore concerned primarily with describing the experimental equipment and procedures, presenting pipe friction loss data for a variety of New Zealand pulps, including a design correlation for them, and developing design methods for computing friction losses. It includes, in addition, data on drag reduction observed at high velocities of flow, and a discussion of flow mechanisms in each regime of flow. The equipment was designed to produce friction loss data from three pipe diameters simultaneously for each consistency of pulp. Flow rate was controlled without throttling the flow. Pipe friction loss data are presented for five Kraft pulps and one neutral sulphite semi-chemical pulp. Data were obtained from 1,2,3 and 4 in. diameter PVC pipes for a wide range of consistencies and flow rates up to 0.8 ft3/sec. Standard Lampen mill evaluations on hand sheets made from the pulps are presented, as well as data on the characteristics of the fibres. The Kraft pulps exhibited the characteristic maxima and minima but the semi-chemical pulp did not exhibit these turning points. For Kraft pulps head losses before the respective maxima were increased by refining the pulp and using rough pipe; and decreased by adding short-fibre Tawa and by drying and reslushing the pulp. In comparison with maxima for the unbeaten Kraft Pulp, the maxima of the head loss curves for all Kraft pulps were shifted to lower velocities by the above-mentioned operations. This would reduce the friction loss in many practical cases. In particular, rough pipe lowers the magnitude of friction loss in this regime, and can therefore yield a considerable economic advantage. A single design correlation for Kraft pulps is presented for the regime of flow before the maxima in the head loss curves. The limits of the correlation are given. Friction losses of New Zealand pulps were found to be lower than those previously reported in the literature. Two methods of design are presented for the regimes at velocities above the maxima in the head loss curves. A procedure is suggested for pulp and paper mills to obtain their own limits for the design correlation and to verify the correlation proposed in this investigation for their own pulps. A design correlation for the Tawa NSSC pulp is also presented. Mechanisms of flow are discussed for Kraft pulps and a semi-chemical pulp. Visual observations in an artificially roughened pipe for the regime of flow before the maxima of the head loss curves have confirmed fibre-wall contact in this regime. Data obtained at the first sign of permanent plug disruption have been correlated with data at the onset of drag reduction. Fully developed turbulence was found to occur at the maximum level of drag reduction. Some velocity profiles are reported for the transition regime using a modified annular-purge probe. In addition the disruptive shear stress of fibre networks has been correlated by three different methods. Data for the onset of drag reduction are presented and compared with data previously obtained from large diameter pipes from other investigations. This correlation is used as a method for designing piping systems at high flow rates.

This thesis presents a report of an analytical investigation of the characteristic features of the transient response of fully yielding structures to a dynamic exciting force. The study was concerned with an estimation of the maximum possible peak-to-peak amplitude of simple idealised models subjected to pulses of a sinusoidal nature. The study was mainly centred around the maximum response of the single degree of freedom elastoplastic system and the effect upon it of viscous damping and a transition region between the elastic and plastic states. The extension of the approach to the two degree of freedom elastoplastic system was also investigated. The study was undertaken within the context of the earthquake engineering field. The investigation shows up certain basic characteristics of the transient response of fully yielding structures which appear to be common for widely varying types of exciting function. It also shows that the response of fully yielding structures to earthquake motions is probably a function of the characteristics of the largest pulses of an earthquake. A brief review of the study of the inelastic response of structures in the earthquake engineering context is also presented.

The relationship between heat treatment, microstructure, fracture topography and room temperature fracture toughness has been determined for a high strength low-alloy steel, En 25. 0ptical, transmission and scanning electron microscopy were used to characterize the structure and morphology while fracture toughness, notched impact and tensile tests were used to determine the mechanical properties. The as-quenched microstructure was predominantly autotempered lath martensite. A little retained austenite was observed in all as-quenched martensite. Austenitizing at 1200°C instead of the conventional 850°C resulted in a 30 percent increase in as-quenched fracture toughness with no loss in tensile strength. Step quenching from 1200 to 850°C for 15 minutes before oil quenching resulted in embrittlement of the austenite grain boundaries and consequently a loss of fracture toughness. The superior fracture toughness of the coarse grain l200°C material was maintained for tempers up to 200°C. Severe intergranular embrittlement and a considerable reduction in toughness were observed when the coarse grain 1200°C material was tempered in the 300-400°C tempered martensite embrittlement range. The fine grain 850°C material also exhibited a drop in toughness in the 300-400°C tempering range but in this case the fracture mode was mainly transgranular cleavage. Transgranular cleavage fracture was tentatively associated with the precipitation of lath boundary cementite, Fe3C. Tempering the fine grain material above 400°C eliminated cleavage and brittle intergranular fracture and resulted in a significant increase in toughness. A little brittle intergranular fracture was observed in the coarse grain material tempered at 500°C. The transverse fracture toughness for material of yield strength less than 1200 MPa was controlled by the major MnS stringer population. The fracture profile was zig-zag, each peak or trough terminating at a MnS stringer. A shear fracture mechanism has been proposed to account for the observed zig-zag fracture mode. The longitudinal fracture toughness was significantly greater than the transverse fracture toughness for tempers of 400°C and above. Mixed microstructures containing lower bainite and martensite did not have inferior relative toughness to wholly martensitic structures. Relationships were found between relative toughness and yield strength and relative toughness and shear lip thickness. There was no meaningful relationship between notched bar impact and fracture toughness data.

The plane strain fracture toughness of a high strength low alloy steel, En 25, tempered from the as-quenched state to 650°C, and a high strength aluminium alloy, 7075-T6, have been determined using compact tension specimens of varying thicknesses from 4 to 25mm. The size of the shear lips, BSL, measured at the free surfaces of the specimens was found to be independent of the specimen thickness and to be related to the true plane strain fracture toughness, KIC, through the expression BSL = 0.41(KIC/σ ys)2.02, where σys is the 0.2% proof stress of the material. A rationale for this behaviour is that BSL is approximately equal to the size of the plane stress plastic zone, ry, at the surfaces of a plate specimen, which from theoretical analysis, has been shown to be rY = Π/8(KIC/σYS)2. The ASTM standard plane strain fracture toughness test method has been proven to be insensitive to detect excess yielding in the specimens tempered at temperatures higher than 450°C. At high tempers, yielding fracture mechanics approaches were used to determine the true KIC values. The fracture toughness versus shear lip size relationship is believed to have considerable importance in the analysis of service failures and in the preliminary study of specimen size effect in plane strain fracture toughness determination.

The investigation reported in this thesis was the initial phase of an experimental programme initiated in 1969 at Auckland University to study the application of hydrometallurgical techniques to the recovery of base-metals from New Zealand sulphide ores. The principal aim was to design and build a suitable autoclave for conducting pressure leaching experiments and with this to evaluate the sulphuric acid leaching kinetics of a bulk lead-zinc-copper-iron concentrate, under a range of experimental conditions that might have process potential. The effects of temperature, oxygen partial pressure, initial acid concentration, excess or deficiency of acid, initial particulate surface area, agitation, catalyst additions (cupric and ferric sulphate) and time on the rate of leaching of sphalerite, galena, chalcopyrite and pyrite were investigated. Galena was found to dissolve with the formation of hydrogen sulphide and lead sulphate. The hydrogen sulphide inhibited the dissolution of both sphalerite and chalcopyrite but not galena. The effect of experimental variables on the rate of oxidation of hydrogen sulphide to sulphur are reported. This reaction was found to take place on the surface of sulphide particles between adsorbed species and the rate determining step was the oxidation of adsorbed ferrous ions by dissolved oxygen. Scanning electron micrographs are presented which show that the lead sulphate forms as a non-coherent crystalline layer on the galena surface. Conversion reaction kinetics were consistent with rate control by liquid phase diffusion in the pores of this layer. The rate of conversion was independent of oxygen partial pressure, initial acid concentration and hydrodynamics but was directly proportional to the initial particulate surface area. A very low temperature dependence was exhibited. Sphalerite was found to exhibit linear leaching kinetics up to extractions of eighty percent after reaction inhibiting hydrogen sulphide had been removed by oxidation. The rate of linear leaching was directly proportional to oxygen partial pressure and surface area but independent of acid concentration and hydrodynamics. The ultimate sulphide oxidation products were elemental sulphur and sulphate ions with the former usually accounting for over ninety percent of the reacted sulphide sulphur. The dissolution reaction producing sulphur was electrochemical in nature and the cathodic reaction involving the discharge of oxygen was found to be rate controlling. Soluble iron catalysed this reaction and a mechanism is proposed that involves the chemisorption of ferrous ions and dissolved oxygen at the mineral surface. Scanning electron micrographs are presented which show that certain crystal faces are preferentially attacked and that dissolution occurs by a pitting action. They also explain why sphalerite dissolution is severely curtailed at temperatures exceeding the meltinq point of sulphur. For extractions exceeding eighty percent the dissolution rate decreased rapidly due to a decrease in cathodic area and to the agglomeration of residues. Chalcopyrite and pyrite dissolved much more slowly than sphalerite and were extensively coated by elemental sulphur because the oxidation of hydrogen sulphide was catalysed on their surfaces. Some practical implications of the leaching results are discussed.

Elastic Solutions can be used to predict stresses and displacements in loaded soil media provided the non-linear stress-strain behaviour of the soil is recognised and allowance made for it in calculating displacements. This thesis examines the methods of elastic analysis suitable for examining problems in Soil Mechanics and the determination of suitable stress-strain parameters. The use of the Finite Element method in Soil Mechanics is reviewed, and a computer program for examining linear elastic plane stress and plane strain problems is presented. The program has been used to examine a range of problems involving infinitely long excavations of rectangular cross-section in the surface of a stratum overlying a rigid base. The excavations were analysed for a uniform vertical loading in the base of the excavation and for lateral wall loads representing the effect of the release of the insitu stresses during excavation. Cases in which the lateral movement of the walls is completely restrained are also considered, and the effect of wall restraint on the vertical displacements due to the vertical base loading is shown to be small. Results obtained by the author suggest that care should be exercised in the use of the Finite Element method to analyse problems involving loaded rigid footings or the stresses behind rigid retaining walls, and that the solutions in these cases may be inaccurate. The solutions available for surface loadings on layered elastic strata are reviewed and results obtained from a Fourier Series approach are presented for a range of problems involving surface loadings on a single rigid base elastic stratum. Uniform vertical and horizontal strip loadings and rigid strip footings with vertical, horizontal and moment loadings are considered. A uniform vertical strip load on the surface of a multilayer stratum overlying a half space or rigid base is also analysed. The computer programs and full mathematical derivations for the strip loading cases are presented, and the extension of the solutions to rectangular loadings is discussed and the basic mathematical derivations outlined. The application of the Fourier Series solutions to the calculation of consolidation settlements is discussed. Work by other investigators suggests that a hyperbolic model may be suitable for approximating soil stress-strain curves and that fundamental stress-strain behaviour should be examined in tests in which the bulk stress remains constant during the application of the shear stress. Equipment designed to carry out slow drained triaxial tests in which the bulk stress is constant during the shearing phase is described, and the results of a short series of tests used to proof test the equipment are presented.

It is generally accepted that some areas of the earth's surface are more prone to earthquake occurrence than others. Furthermore, within these earthquake-prone area the distribution of earthquake epicentres is non-uniform. Ttis has led to a system of regional zoning for earthquake resistant design in most countries. Observations of localised damage resulting from earthquakes has only recently led to the general acceptance of the fact that the degree of damage may be influenced by the characteristics of the soils in the affected area. Where the damage is related to gross instability of the soil resulting in large permanent deformations, association of the damage with local soil conditions is readily apparent. A somewhat less obvious effect of soil conditions on building damage is that subsurface soil layering can influence the intensity of ground shaking, and the frequency content of the surface motion, even though the soils underlying structures may remain perfectly stable during an earthquake. The frequency characteristics of the surface motion are important as the existence of a predominant ground frequency may lead to resonance of structures during prolonged shaking. In Chapter 2 a brief resume of existing knowledge of the occurrence, origin and nature of earthquakes is presented. Basic wave models and wave types are outlined.

A description of the development and design of a two channel solar radiometer is given. Particular attention has been paid, in the choice of receiving system and the design of its components, to the avoidance and reduction of interference. The system used is a two receiver multiplying interferometer with the addition of phase switching. A computer controlled phase cancelling system is used to make the interferometer fringe track the source (i.e the sun), thereby producing a rectified output. An outline of the design of comb-line filters is given. These low loss transmission filters are used at the receiver inputs to attenuate strong out of band interfering signals. Operational amplifiers are used to gain stabilize the RF preamplifiers. Very low sensitivity of gain to temperature change is shown to result from the use of this technique. The system incorporates an analogue magnetic tape recorder so that signals of interest can be replayed for paper strip chart recording at high speed. The recording system has the feature that time of day information is recorded automatically in conjunction with the receiver signals.