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Digital Encoding Of Television Signals Using The Pulse Width Modulator, John Graham Wade Jan 1975

Digital Encoding Of Television Signals Using The Pulse Width Modulator, John Graham Wade

School of Engineering, Computing and Mathematics Theses

An attempt is made to quantify the circuit complexity and mean circuit speed of linearly quantized straight PCM video encoding techniques. Any significant reduction in circuit complexity (i.e. the number of active and passive devices to be integrated) is considered important since this determines: chip area and yield if the encoder is to be fully integrated. Analysis indicates that the complexity of the more highly developed straight PCM video encoders can be reduced by typically a factor 3 using either non-programmed sequential encoding, pulse width modulator encoding or programmed sequential encoding (closed loop successive approximation). The encoder studied in this …

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Aspects Of Sterol Metabolism In Crustacea, D.N. Parsons Jan 1974

Aspects Of Sterol Metabolism In Crustacea, D.N. Parsons

School of Biological and Marine Sciences Theses

The sterol content of various species of Crustacea has been subject to comparatively few investigations. Previous work has been mainly confined to members of the Decapoda. To date, few studies have been made to determine the capacity of crustaceans to synthesise and metabolise sterols. In the present work, an initial survey of representative members of the main crustacean orders was made. The results obtained were similar to already published work, with the exception that two previously unreported classes of sterols, the 4-methyl and 4,4¹ -dimethyl sterols, were identified in certain organisms.

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Electron Spin Resonance And Morphology Of Doped Synthetic Kaolinites, J.P.E. Jones Jan 1974

Electron Spin Resonance And Morphology Of Doped Synthetic Kaolinites, J.P.E. Jones

School of Engineering, Computing and Mathematics Theses

This thesis is divided into nine chapters. The first three chapters describe previous E.S.R. and Mossbauer studies of kaolinite together with the properties of the ferric ion and defect centres. The structure, properties, morphology and synthesis of kaolinite are outlined in chapters four and five. The experimental results are presented in the three chapters following. Chapter six describes the various methods of synthesis attempted and the nature of the kaolinite formed together with their morphology.

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Oxidation Of Zinc Sulphide, Bodhisattwa Basak Jan 1973

Oxidation Of Zinc Sulphide, Bodhisattwa Basak

School of Geography, Earth and Environmental Sciences Theses

A physicochemical study has been made of roasting and sintering processes for zinc sulphide ores. The sulphides are oxidised to metal oxides or sulphates according to conditions, e.g. temperature and time of heating, composition of surrounding gases, whether under static or dynamic conditions. The mechanisms and kinetics of oxidation depend also on surface area, crystallite and aggregate sizes of the materials and the presence of any impurities. Thus, for basic oxidation studies, finely-divided zinc sulphide samples have been precipitated from solution at various pH levels and in the presence of different concentrations of eletrolytes. These experimental conditions have been correlated …

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The Formation And Reactivity Of Some Nonmetal Silicides, Bertram John Brockington Jan 1973

The Formation And Reactivity Of Some Nonmetal Silicides, Bertram John Brockington

School of Geography, Earth and Environmental Sciences Theses

Boron silicides, B₄Si and B₆Si, have been produced by calcining mixtures of finely-divided boron and silicon at different temperatures and information obtained regarding the process mechanism. There are optimum reaction times for the formation of B₄Si, before it disproportionates into B₆Si and Si. The atmospheric oxidation of boron silicides is retarded by the product layers of boric oxide, B₂O₃, and silica, SiO₂, and also by their mineralising action promoting sintering of the material. Boron silicides may be used only in an oxidising environment at lower temperatures (500 - 800°C) without severe degradation occurring if they have been first subjected to …

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The Crystal Structures Of Some Transition Metal Complexes, Andrew Quick Jan 1973

The Crystal Structures Of Some Transition Metal Complexes, Andrew Quick

School of Geography, Earth and Environmental Sciences Theses

A brief theoretical background to crystal structure analysis is given in Chapter 1. The remaining chapters describe the determination of five crystal structures, one using photographic data, and four using diffractometer data.

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Organizational Analysis And Change In Merchant Shipping, David Henry Moreby Jan 1973

Organizational Analysis And Change In Merchant Shipping, David Henry Moreby

Other Faculty of Science and Engineering Theses

This research was conducted during a period of rapid change within marine technology and within society ashore. The ships used for the field work were relatively highly mechanized and specialized. Two were owned by a large, old tanker company which had a stable labour force while the remaining two were owned by a small and very young company employing highly mobile officers recruited from other shipping companies. The focus of the research lay within the officer groups, their relationships with each other and with their managers ashore. Attention was paid to the manner in which both officers and shore managers …

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Electron Spin Resonance Studies Of Aluminosilicate Minerals And Associated Organic Substances, Peter L. Hall Jan 1972

Electron Spin Resonance Studies Of Aluminosilicate Minerals And Associated Organic Substances, Peter L. Hall

School of Geography, Earth and Environmental Sciences Theses

This thesis is divided into seven chapters. The first chapter describes the basic principles of electron spin resonance (ESR) spectroscopy. In the second chapter, relevant previous studies of clay minerals are reviewed, including a summary of previous studies by optical, Mössbauer and ESR spectroscopy of iron and other transition metal impurities in clay minerals. The third chapter reviews previous ESR studies of Fe³˖ ions in aluminosilicate minerals and other materials. The fourth chapter reviews the nature and properties of organic substances associated with natural clays and carbonaceous materials, emphasis being placed on the occurrence of organic free radicals and transition …

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The Formation And Reactivity Of Aluminum Nitride And Related Materials, N.G. Coles Jan 1970

The Formation And Reactivity Of Aluminum Nitride And Related Materials, N.G. Coles

School of Geography, Earth and Environmental Sciences Theses

The preparation and properties of aluminium nitride are reviewed with special reference to the newer production methods and fabrication techniques. Information so far available on the sintering of materials is summarised. For nitrides the sintering is influenced by additives or impurities such as oxides formed by partial hydrolysis and oxidation. Resistance to oxidation is increased by sintering and hot-pressing the refractories. The kinetics and products of oxidation of nitrides so far studied depend mainly on the intrinsic reactivity of the material and available surface at which oxidation can occur. In the present research conditions are investigated for preparing aluminium nitride …

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The Formation And Reactivity Of Boron Carbide And Related Materials, James Alfred Jones Jan 1970

The Formation And Reactivity Of Boron Carbide And Related Materials, James Alfred Jones

School of Geography, Earth and Environmental Sciences Theses

The formation of boron carbide, (CBC)+B110C;(B4C) is re-viewed with special reference to newer production methods and fabrication techniques. Its crystal structure and the nature of its bonding are discussed in relation to those of other borides and carbides. Information so far available on the sintering of this material is summarised in relation to its reactivity. Sintering into monolithic components can only be achieved by hot pressing at pressures between 200 and 300 Kgcm-2 and at temperatures above 2000°C preferably at about 2,300°C for the most rapid achievement of theoretical density, i.e. pore free.

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The Formation And Reactivity Of Some Nitrides, Shanath Anarasiri Aruabada Jayawaera Jan 1969

The Formation And Reactivity Of Some Nitrides, Shanath Anarasiri Aruabada Jayawaera

School of Geography, Earth and Environmental Sciences Theses

Nitrides are reviewed generally with respect to their bonding, production (including thermodynamics and kinetics of formation) and reactivity. This is followed by a summary of the studies by previous workers on the formation and reactivity of the particular nitrides, which are the subject of the present investigation. This thesis embodies further studies on various aspects of the formation and reactivity of nitrides of some Group II-IV elements. They include nitrides of more active metals such as calcium and magnesium, and of less active ones such as titanium and zirconium.

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An Experimental Study Of Electron Spin Resonance In Synthetic Diamond, Brian R. Angel Jan 1968

An Experimental Study Of Electron Spin Resonance In Synthetic Diamond, Brian R. Angel

School of Geography, Earth and Environmental Sciences Theses

This thesis is divided into five chapters. The first chapter begins with a discussion of the basic principles of electron spin resonance and concludes with a description of the theoretical interpretation of electron spin resonance spectra in terms of the Spin Hamiltonian. The first part of the second chapter is a general discussion of the physical properties of diamond and includes reasons for the classification of diamond into various types. The second part of the chapter is devoted to a brief historical survey of the developments in the production of synthetic diamond. The final part of the chapter is an …

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Applications Of Mass Spectrometry To Organic Geochemistry, Patricia Ann Haug Jan 1967

Applications Of Mass Spectrometry To Organic Geochemistry, Patricia Ann Haug

Other Faculty of Science and Engineering Theses

How did life originate? Modern evolutionary theories postulate a continuum extending from abiotically formed macromolecules to those capable of reproducing themselves and mutating in a manner which can be considered characteristic of the processes of metabolism, growth, reproduction, sensitivity, and evolution. In this sense, life consists of a small segment of possible chemical reactions. The basic element of these reactions, carbon, is unique because of its ability to form four equivalent sp³ bonds. The strength of the s character is essential for the formation of stable polymers, while the ability to form four bonds permits the greatest degree of structural …

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Disruption Of The Aluminosilicate Lattice By Acid Fluoride Solutions, Barrie Semmens Jan 1965

Disruption Of The Aluminosilicate Lattice By Acid Fluoride Solutions, Barrie Semmens

School of Geography, Earth and Environmental Sciences Theses

The disruption of the aluminosilicate crystal lattice by aqueous fluoride solutions has been studied. The effect of reaction time, fluoride concentration, pH, and temperature on the reaction have been investigated. The stoichiometric exchange of hydroxyls by fluoride ions in kaolinite and muscovite at pH 7 and below was extremely doubtful. Disruption of the aluminosilicate crystal lattice was thought to be the predominant reaction over the acid pH range.

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Isolation And Structure Determination Of Certain Acidic Components From California Petroleum, Ahmed Ismail Abdel-Meguid Khodair Jan 1965

Isolation And Structure Determination Of Certain Acidic Components From California Petroleum, Ahmed Ismail Abdel-Meguid Khodair

Other Faculty of Science and Engineering Theses

The acidic constituents of petroleum are called naphthenic acids. The basic process for the isolation of these acids from petroleum involves extraction of the oil with an alkali and acidification of the aqueous extract with a mineral acid to liberate the organic acids. This product contains not only carboxylic acids, but also significant amounts of phenols and hydrocarbons. The name "naphthenic acids" was suggested long ago by Markownikoff (2), because the early investigation of these acids indicated that they are a mixture of alicyclic acids. Subsequent work showed that these acids do not consist entirely of alicyclic acids but also …

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The Structural Relationships Of Some Glycine Polymers, Roy Alan Williams Jan 1964

The Structural Relationships Of Some Glycine Polymers, Roy Alan Williams

School of Geography, Earth and Environmental Sciences Theses

The Polyglycines are of interest because they are related to nylon and the polyamides, and to the proteins. They resemble nylon in having amine, -NH₂, end groups, and the chains are formed through peptide, C0-NH- linkages. The known Polyglycines are not fibre forming, as products with the required degree of polymerisation have not been prepared, they have a low degree of polymerisation, about 10-20 is the usually recorded value for the number average degree of polymerisation. The degree of polymerisation of the fibre forming polyamides is about 200. The polyglycines may be regarded as the simplest proteins, in that they …

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The Settlement Factor In The Rural Problems Of North-East England, John Aruel Edwards Jan 1964

The Settlement Factor In The Rural Problems Of North-East England, John Aruel Edwards

Other Faculty of Science and Engineering Theses

Much attention has been focussed in recent years on the changing distribution of population in North-east England since the Industrial Revolution. In the introduction to his paper on this subject, J. W. House mentions many of the forces which are still in the process of complicating the earlier relatively simple factor of the drift of population from the countryside to the towns. The impacts of international trade systems, the consequences of government economic policies towards both industry and agriculture, the effects of two world wars, and the increased mobility through improved transport are just a few of the elements which …

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