A conductimetric investigation of phenomena in extremely dilute aqueous solutions
- Authors: Faure, Pierre Knobel
- Date: 1957
- Subjects: Adsorption , Solution (Chemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4524 , http://hdl.handle.net/10962/d1014891
- Description: 1. The apparatus used in this investigation is fully described, and a new method is outlined for the calibration of bridge resistances "in situ". 2. A chart is given for the accurate correction of weights in air to weights in vacuum for a range of temperatures extending from 10° to 28°C, and for pressures from 690 to 730 mm. 3. An automatic recycling still has been designed for the continuous production of "ultra-pure" water. This still is capable of delivering daily, in routine operation, 16 l. of water of conductivity less than 100 nm/cm after aeration with "C0₂- and NH₃-free" air. 4. A very soluble layer appears to form on the surface of' glass when it is dried; this layer is readily removed on contact with water. 5. The removal of carbon dioxide and of ammonia from aqueous solution by aeration with an indifferent gas has been fully investigated, and it has been shown that these gases can be completely eliminated by such a process. Whereas the carbon dioxide is removed fairly rapidly, however, the ammonia, whether present alone or together with carbon dioxide, only goes out of solution rather slowly. 6. It has been shown that ammonia is adsorbed from aqueous solution on the glass walls of the cell. 7. There does not appear to be any ammonium bicarbonate in the residual impurity left in the "ultra-pure" water obtained from the still; the impurity can, in fact, be regarded as neutral salt with sufficient accuracy for most purposes. 8. The resistance change which accompanies any variation in the rate of bubbling of the stirring gas through the water has been investigated, but no solution has been found as to the cause of this change. 9. A comparison has been made of the efficiency of different gases for stirring purposes, and it seems that, for general work, nitrogen is by far the most suitable of the common gases. 10. The extrapolation to be used for converting resistances to their values at infinite frequency appears ...
- Full Text:
- Date Issued: 1957
- Authors: Faure, Pierre Knobel
- Date: 1957
- Subjects: Adsorption , Solution (Chemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4524 , http://hdl.handle.net/10962/d1014891
- Description: 1. The apparatus used in this investigation is fully described, and a new method is outlined for the calibration of bridge resistances "in situ". 2. A chart is given for the accurate correction of weights in air to weights in vacuum for a range of temperatures extending from 10° to 28°C, and for pressures from 690 to 730 mm. 3. An automatic recycling still has been designed for the continuous production of "ultra-pure" water. This still is capable of delivering daily, in routine operation, 16 l. of water of conductivity less than 100 nm/cm after aeration with "C0₂- and NH₃-free" air. 4. A very soluble layer appears to form on the surface of' glass when it is dried; this layer is readily removed on contact with water. 5. The removal of carbon dioxide and of ammonia from aqueous solution by aeration with an indifferent gas has been fully investigated, and it has been shown that these gases can be completely eliminated by such a process. Whereas the carbon dioxide is removed fairly rapidly, however, the ammonia, whether present alone or together with carbon dioxide, only goes out of solution rather slowly. 6. It has been shown that ammonia is adsorbed from aqueous solution on the glass walls of the cell. 7. There does not appear to be any ammonium bicarbonate in the residual impurity left in the "ultra-pure" water obtained from the still; the impurity can, in fact, be regarded as neutral salt with sufficient accuracy for most purposes. 8. The resistance change which accompanies any variation in the rate of bubbling of the stirring gas through the water has been investigated, but no solution has been found as to the cause of this change. 9. A comparison has been made of the efficiency of different gases for stirring purposes, and it seems that, for general work, nitrogen is by far the most suitable of the common gases. 10. The extrapolation to be used for converting resistances to their values at infinite frequency appears ...
- Full Text:
- Date Issued: 1957
The British organ and its music during the nineteenth century
- Authors: Wise, James Patrick Gerald
- Date: 1957
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2694 , http://hdl.handle.net/10962/d1013429
- Description: It is a curious fact that, although the literature of the organ is a reasonably large one, no attempt has been made to study the history of the instrument in Britain in any detail. Hopkins and Rimbault covered a certain amount of ground up to 1800, but even they could not deal very extensively with the subject in a volume that was tracing the history of the organ not only in Britain, but throughout Europe, and not only its history but its construction also. For similar reasons Dr. Sumner? (name unclear), in his recent book, could paint little more than an outline picture. However, the British organ's development prior to 1800 was one that does not admit of very discursive treatment. Progress was lamentably slow in comparison with that of Continental organs; and consequently the nineteenth century dawned with British organ-building literally hundreds of years behind that of France, Germany, Belgium and Holland. Yet, a century later, the position was redeemed, and even before the present era opened, the products of British organ-builders were not merely equal to, but, in general superior to those of the Continent in tonal design, mechanism, in artistic finish, and in ordinary maintenance and preservation. The nineteenth century, then, must clearly be regarded as a remarkable, indeed glorious, period in British organ-building, in fact one is tempted to enquire, whether there exists, in the entire artistic and scientific history of any country a similar example of accelerated development; in which one country has made up three hundred years' leeway in one third of that time. This thesis therefore, sets out to examine and describe the events of the century, and the men who were responsible for those events, to trace the growth of the organ in its various departments, and as the instrument itself is only a means to an end, to say something about the way in which it was used, the music that was played on it, and the men who played and composed this music. The thesis is divided into two volumes, the first deals entirely with the history of the instrument and its builders during the nineteenth century, with an introduction briefly recounting the story from the Restoration up to the year 1800; and the second volume is concerned with the music and the musicians as well as the several detailed indexes which are so necessary if a work of this kind is to be of any value at all. A full bibliography is given in Volume Two, but supreme acknowledgement must be paid here to the quarterly periodical "The Organ" - still thriving after an active career that began in July 1921. Its scholarly articles range over the whole field of international organ-building and organ-history, and without its help this thesis would have been far less comprehensive in its scope and far lesss authorative in its source-material.
- Full Text:
- Date Issued: 1957
- Authors: Wise, James Patrick Gerald
- Date: 1957
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2694 , http://hdl.handle.net/10962/d1013429
- Description: It is a curious fact that, although the literature of the organ is a reasonably large one, no attempt has been made to study the history of the instrument in Britain in any detail. Hopkins and Rimbault covered a certain amount of ground up to 1800, but even they could not deal very extensively with the subject in a volume that was tracing the history of the organ not only in Britain, but throughout Europe, and not only its history but its construction also. For similar reasons Dr. Sumner? (name unclear), in his recent book, could paint little more than an outline picture. However, the British organ's development prior to 1800 was one that does not admit of very discursive treatment. Progress was lamentably slow in comparison with that of Continental organs; and consequently the nineteenth century dawned with British organ-building literally hundreds of years behind that of France, Germany, Belgium and Holland. Yet, a century later, the position was redeemed, and even before the present era opened, the products of British organ-builders were not merely equal to, but, in general superior to those of the Continent in tonal design, mechanism, in artistic finish, and in ordinary maintenance and preservation. The nineteenth century, then, must clearly be regarded as a remarkable, indeed glorious, period in British organ-building, in fact one is tempted to enquire, whether there exists, in the entire artistic and scientific history of any country a similar example of accelerated development; in which one country has made up three hundred years' leeway in one third of that time. This thesis therefore, sets out to examine and describe the events of the century, and the men who were responsible for those events, to trace the growth of the organ in its various departments, and as the instrument itself is only a means to an end, to say something about the way in which it was used, the music that was played on it, and the men who played and composed this music. The thesis is divided into two volumes, the first deals entirely with the history of the instrument and its builders during the nineteenth century, with an introduction briefly recounting the story from the Restoration up to the year 1800; and the second volume is concerned with the music and the musicians as well as the several detailed indexes which are so necessary if a work of this kind is to be of any value at all. A full bibliography is given in Volume Two, but supreme acknowledgement must be paid here to the quarterly periodical "The Organ" - still thriving after an active career that began in July 1921. Its scholarly articles range over the whole field of international organ-building and organ-history, and without its help this thesis would have been far less comprehensive in its scope and far lesss authorative in its source-material.
- Full Text:
- Date Issued: 1957
The struggle for national independence in its international setting : its economic and political background and its manifestation in the Fourth Committee of the United Nations General Assembly
- Authors: Lumsden, Geoffrey S
- Date: 1957
- Subjects: United Nations. General Assembly Self-determination, National Sovereignty Economics -- Political aspects Economic policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1091 , http://hdl.handle.net/10962/d1012790
- Description: The decade following the close of the Second World War has been dominated throughout by the clash of political power of the United States and the Soviet Union. Their wartime alliance has crumbled. New, antagonistic alliances have come into existence. The so-called 'EastWest' split, polar in its effect, has forced the admission that prospects of stable peace depend on how successfully bridges can be made to span the gulf. This over-riding and pervading reality has blinded us to the importance of another struggle, which is everywhere mounting in force and intensity and which history may well record as a dominant theme of the twentieth century -- the world-wide struggle for independence. In some cases it has produced revolution and violence: full-scale wars have been fought in its cause in Indonesia and Indo-China; military engagements have taken place in Kenya and Tunisia; Cypriots and British garrison forces have exchanged fire; Malayans have rioted; and 'incidents' too numerous to detail have been reported from a great variety of countries where political dependence exists. Intro., p. 1.
- Full Text:
- Date Issued: 1957
- Authors: Lumsden, Geoffrey S
- Date: 1957
- Subjects: United Nations. General Assembly Self-determination, National Sovereignty Economics -- Political aspects Economic policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1091 , http://hdl.handle.net/10962/d1012790
- Description: The decade following the close of the Second World War has been dominated throughout by the clash of political power of the United States and the Soviet Union. Their wartime alliance has crumbled. New, antagonistic alliances have come into existence. The so-called 'EastWest' split, polar in its effect, has forced the admission that prospects of stable peace depend on how successfully bridges can be made to span the gulf. This over-riding and pervading reality has blinded us to the importance of another struggle, which is everywhere mounting in force and intensity and which history may well record as a dominant theme of the twentieth century -- the world-wide struggle for independence. In some cases it has produced revolution and violence: full-scale wars have been fought in its cause in Indonesia and Indo-China; military engagements have taken place in Kenya and Tunisia; Cypriots and British garrison forces have exchanged fire; Malayans have rioted; and 'incidents' too numerous to detail have been reported from a great variety of countries where political dependence exists. Intro., p. 1.
- Full Text:
- Date Issued: 1957
The voluntary welfare organisations of the Border and Transkei: a contribution to the sociology of social work
- Authors: Bettison, D G
- Date: 1956
- Subjects: Social service -- South Africa -- Transkei Social service -- South Africa -- Eastern Cape Volunteer workers in social service
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3314 , http://hdl.handle.net/10962/d1003102
- Description: This research is intended to examine the internal organisational structure of the existing [voluntary welfare] organisations to ascertain what relationship may prove effective between themselves and the [Border Local Welfare] Board. This aim introduced the need to ascertain whether a) the organisations in any town were connected with organisations in other towns or to a central administrative office either in the area of investigation or outside it; or b) the organisations of any town were simply ad hoc units unrelated to any other organisation or similar organisations elsewhere. If the latter were the case then the difficulty of co-ordination and representation on the Board could probably be no better arranged than an ad hoc system as at present. If, however, the former was the predominant pattern, then it would suggest other and more convenient means to the end in view. Fourthly, it was hoped to gain some knowledge of the fund raising methods of welfare organisations, the nature of the people controlling them, the attitudes of managing committees to social work, and what they thought a case work agency should do; and, lastly, some indication of the history of social work as practised by the voluntary agencies in the area of investigation. These latter topics were not intended to form the principal subject matter of the work. They have not been treated fully in the text, but the information gathered has been included in appropriate places throughout.
- Full Text:
- Date Issued: 1956
- Authors: Bettison, D G
- Date: 1956
- Subjects: Social service -- South Africa -- Transkei Social service -- South Africa -- Eastern Cape Volunteer workers in social service
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3314 , http://hdl.handle.net/10962/d1003102
- Description: This research is intended to examine the internal organisational structure of the existing [voluntary welfare] organisations to ascertain what relationship may prove effective between themselves and the [Border Local Welfare] Board. This aim introduced the need to ascertain whether a) the organisations in any town were connected with organisations in other towns or to a central administrative office either in the area of investigation or outside it; or b) the organisations of any town were simply ad hoc units unrelated to any other organisation or similar organisations elsewhere. If the latter were the case then the difficulty of co-ordination and representation on the Board could probably be no better arranged than an ad hoc system as at present. If, however, the former was the predominant pattern, then it would suggest other and more convenient means to the end in view. Fourthly, it was hoped to gain some knowledge of the fund raising methods of welfare organisations, the nature of the people controlling them, the attitudes of managing committees to social work, and what they thought a case work agency should do; and, lastly, some indication of the history of social work as practised by the voluntary agencies in the area of investigation. These latter topics were not intended to form the principal subject matter of the work. They have not been treated fully in the text, but the information gathered has been included in appropriate places throughout.
- Full Text:
- Date Issued: 1956
An investigation of the spectra and decay times of some organic phosphors under ultraviolet and ionising radiation
- Authors: Little, W A
- Date: 1955
- Subjects: Phosphors -- Spectra
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5530 , http://hdl.handle.net/10962/d1012733
- Description: In this thesis I have given an account of the work carried out by me on the measurement of the spectra and decay times of a few selected organic phosphors under ultraviolet and ionising radiation. The purpose of the investigation has been to attempt to throw more light on the mechanism by which energy migrates within the crystalline lattice. A general introduction is given to the process of fluorescence and the various proposed theories by which the excitation energy, which eventually appears as fluorescence light, is able to move about in the crystalline lattice. Preface, p. 1.
- Full Text:
- Date Issued: 1955
- Authors: Little, W A
- Date: 1955
- Subjects: Phosphors -- Spectra
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5530 , http://hdl.handle.net/10962/d1012733
- Description: In this thesis I have given an account of the work carried out by me on the measurement of the spectra and decay times of a few selected organic phosphors under ultraviolet and ionising radiation. The purpose of the investigation has been to attempt to throw more light on the mechanism by which energy migrates within the crystalline lattice. A general introduction is given to the process of fluorescence and the various proposed theories by which the excitation energy, which eventually appears as fluorescence light, is able to move about in the crystalline lattice. Preface, p. 1.
- Full Text:
- Date Issued: 1955
Measurements of the solubilities of some silver halides in water by electrical methods
- Authors: Malan, George McPherson
- Date: 1955
- Subjects: Silver halides -- Solubility , Silver halides -- Analysis , Conductometric analysis , Potentiometry , Silver halides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4515 , http://hdl.handle.net/10962/d1013502
- Description: [Introduction, p. 3] The solubilities of the silver halides cannot be determined by the conventional methods of analytical chemistry because they are too sparingly soluble (of the order 1 x 10⁻⁵ to 1 x 10⁻⁶ g . equiv./1. at 25°C.) However, electrical, and to a lesser extent optical methods, are admirably suited because of their greater sensitivity. The conductometric and potentiometric methods are the two most important electrical techniques for the measurement of the solubilities of sparingly soluble salts, and are the ones employed in this research. There are large discrepancies between the published values for the solubility of silver chloride. Results obtained by the conductometric and potentiometric methods disagree. In addition, figures quoted by independent authors using the same method differ by as much as 15%.
- Full Text:
- Date Issued: 1955
- Authors: Malan, George McPherson
- Date: 1955
- Subjects: Silver halides -- Solubility , Silver halides -- Analysis , Conductometric analysis , Potentiometry , Silver halides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4515 , http://hdl.handle.net/10962/d1013502
- Description: [Introduction, p. 3] The solubilities of the silver halides cannot be determined by the conventional methods of analytical chemistry because they are too sparingly soluble (of the order 1 x 10⁻⁵ to 1 x 10⁻⁶ g . equiv./1. at 25°C.) However, electrical, and to a lesser extent optical methods, are admirably suited because of their greater sensitivity. The conductometric and potentiometric methods are the two most important electrical techniques for the measurement of the solubilities of sparingly soluble salts, and are the ones employed in this research. There are large discrepancies between the published values for the solubility of silver chloride. Results obtained by the conductometric and potentiometric methods disagree. In addition, figures quoted by independent authors using the same method differ by as much as 15%.
- Full Text:
- Date Issued: 1955
Some problems and methods of measuring the growth of African negroid populations
- Myburgh, Corneles Albert Lloyd
- Authors: Myburgh, Corneles Albert Lloyd
- Date: 1955
- Subjects: Africa -- Population -- Statistics , Demography -- Africa , Population forecasting -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3388 , http://hdl.handle.net/10962/d1013560
- Description: A dissertation ... giving details of problems and methods of obtaining statistics of the more important demographic aspects of the African Negroid populations, that is the size of a population, its sex and age distribution, migration movements, deaths and rates of increase.
- Full Text:
- Date Issued: 1955
- Authors: Myburgh, Corneles Albert Lloyd
- Date: 1955
- Subjects: Africa -- Population -- Statistics , Demography -- Africa , Population forecasting -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3388 , http://hdl.handle.net/10962/d1013560
- Description: A dissertation ... giving details of problems and methods of obtaining statistics of the more important demographic aspects of the African Negroid populations, that is the size of a population, its sex and age distribution, migration movements, deaths and rates of increase.
- Full Text:
- Date Issued: 1955
Boerdery in die Suid-Afrikaanse Republiek 1858-1899
- Authors: Naudé, Petrus
- Date: 1954
- Subjects: Agriculture -- South Africa -- History -- 19th century , Agricultural laborers -- South Africa -- History , Agriculture -- Economic aspects -- South Africa -- History , Farmers -- South Africa -- History -- 19th century
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1092 , http://hdl.handle.net/10962/d1012946
- Description: In Suid-Afrika het die opkoms van die sosialistiese gedagte teen die einde van die negentiende eeu ook merkbare invloed op die staatshuishouding gehad. In die negentiende eeu was die ekonomiese wetgewing, hoofsaaklik onder invloed van die indiwidualisme volgens die leer van "Laissez- faire", daarop gerig om die maksimum welvaart te verkry deur vrye mededinging aan te moedig en te beskerm, en om privaat inisiatief sy gang te laat gaan. Daar het egter geleidelik 'n verandering in hierdie houding en beleid ingetree. Deur 'n verandering in die beskouing omtrent die einddoel van die menslike arbeid en sy ekonomiese bedrywigheid moes die staat uit sosiaal-ekonomiese oorwegings sekere seksies van die samelewing deur spesiale en beskermende wetgewing te hulp kom. Die ontwikkeling van die aandeel wat die staat geneem het in die beheer en bevordering van die welvaart van die boere in die Suid-Afrikaanse Republiek is ' n voorbeeld van die voorgenoemde omwenteling in die ekonomiese en bedryfslewe teen die einde van die vorige eeu. Die staat het aanvanklik weinig gedoen vir die bevordering en beheer van die onderhoudsboerdery. Later, met die veranderde boerderyekonomie, het staatshulp, staatsvoorligting en -beheer egter noodsaaklik geword. Gedurende die laaste jare van die Suid- Afrikaanse Republiek het die owerheid meer en meer verpligtings teenoor die boeregemeenskap aanvaar. Namate die staat groter hulp en diens verskaf het, na dié mate moes hy ook groter beheer uitoefen.
- Full Text:
- Date Issued: 1954
- Authors: Naudé, Petrus
- Date: 1954
- Subjects: Agriculture -- South Africa -- History -- 19th century , Agricultural laborers -- South Africa -- History , Agriculture -- Economic aspects -- South Africa -- History , Farmers -- South Africa -- History -- 19th century
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1092 , http://hdl.handle.net/10962/d1012946
- Description: In Suid-Afrika het die opkoms van die sosialistiese gedagte teen die einde van die negentiende eeu ook merkbare invloed op die staatshuishouding gehad. In die negentiende eeu was die ekonomiese wetgewing, hoofsaaklik onder invloed van die indiwidualisme volgens die leer van "Laissez- faire", daarop gerig om die maksimum welvaart te verkry deur vrye mededinging aan te moedig en te beskerm, en om privaat inisiatief sy gang te laat gaan. Daar het egter geleidelik 'n verandering in hierdie houding en beleid ingetree. Deur 'n verandering in die beskouing omtrent die einddoel van die menslike arbeid en sy ekonomiese bedrywigheid moes die staat uit sosiaal-ekonomiese oorwegings sekere seksies van die samelewing deur spesiale en beskermende wetgewing te hulp kom. Die ontwikkeling van die aandeel wat die staat geneem het in die beheer en bevordering van die welvaart van die boere in die Suid-Afrikaanse Republiek is ' n voorbeeld van die voorgenoemde omwenteling in die ekonomiese en bedryfslewe teen die einde van die vorige eeu. Die staat het aanvanklik weinig gedoen vir die bevordering en beheer van die onderhoudsboerdery. Later, met die veranderde boerderyekonomie, het staatshulp, staatsvoorligting en -beheer egter noodsaaklik geword. Gedurende die laaste jare van die Suid- Afrikaanse Republiek het die owerheid meer en meer verpligtings teenoor die boeregemeenskap aanvaar. Namate die staat groter hulp en diens verskaf het, na dié mate moes hy ook groter beheer uitoefen.
- Full Text:
- Date Issued: 1954
Some measurements of the conductivities of dilute potassium chloride solutions
- Authors: Faure, Abraham
- Date: 1954
- Subjects: Potassium chloride
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4471 , http://hdl.handle.net/10962/d1011787
- Description: A constant temperature room has been constructed in which the thermoregulator is controlled by a temperature-sensitive resistance. A thermostat has been constructed in which the 0 temperature is controlled to within 0.001°C. A precision conductance bridge has been built in a very convenient form. Improvements include the replacement of the telephone as null detector by a cathode ray oscilloscope, and the use of a resistance-capacity phase-shift oscillator, which gives a good wave-form. An automatic recycling conductance water still has been built which regularly gives water with a conductivity less than 0.09 micromhos per cm. The conductivities of dilute KCl solutions have been measured, taking special care to prevent errors due to the adsorption of KCl on the surface of glass. Two cells were used for these measurements : a modified Jones cell, and a special conductimetric titration cell. The modified Jones cell has given results in good agreement with the generally-accepted values. The results of the conductimetric titration cell do not agree well with the generally-accepted values; the greatest difference (for the most dilute solution) is 0.4%. The reason for this is not known.
- Full Text:
- Date Issued: 1954
- Authors: Faure, Abraham
- Date: 1954
- Subjects: Potassium chloride
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4471 , http://hdl.handle.net/10962/d1011787
- Description: A constant temperature room has been constructed in which the thermoregulator is controlled by a temperature-sensitive resistance. A thermostat has been constructed in which the 0 temperature is controlled to within 0.001°C. A precision conductance bridge has been built in a very convenient form. Improvements include the replacement of the telephone as null detector by a cathode ray oscilloscope, and the use of a resistance-capacity phase-shift oscillator, which gives a good wave-form. An automatic recycling conductance water still has been built which regularly gives water with a conductivity less than 0.09 micromhos per cm. The conductivities of dilute KCl solutions have been measured, taking special care to prevent errors due to the adsorption of KCl on the surface of glass. Two cells were used for these measurements : a modified Jones cell, and a special conductimetric titration cell. The modified Jones cell has given results in good agreement with the generally-accepted values. The results of the conductimetric titration cell do not agree well with the generally-accepted values; the greatest difference (for the most dilute solution) is 0.4%. The reason for this is not known.
- Full Text:
- Date Issued: 1954
Studies in the comparative anatomy and systematic importance of the hexapod tentorium
- Authors: Hudson, Gerda Bland
- Date: 1954
- Subjects: Insects -- Anatomy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5858 , http://hdl.handle.net/10962/d1012457
- Description: During a study of the morphology of the orthopteroid Hexapoda between the years 1939-1941, it appeareded to the writer that further investigation into the structure of the insect tentorium was necessary. The early entomologists laid the foundation or our knowledge or the tentorium but during the latter half of the last century little was added in this particulart field. Comstock and Kochi (1902), as far as the writer is aware are the only workers who have published a paper devoted entirely to the skeleton of the bead of insects, and they did much to clarify both nomenclature and existing knowledge of this structure at that time. Berlese (1909) described a typical tentorlum as observed in orthopteroid Hexapoda and then considered the variations of the tentorium which occur in other groups of insects. Some confusion then appears to have arisen amongst workers, over the origin of the dorsal arms which were erroneously considered by some to be cuticular invaginations and not secondary outgrowths of the anterior tentorial arms. Certain morphologists amongst them, Hoke (1924) Denis (1928), Snodgrass (1928, 1935), Hansen (1930), Walker (1933) Imms (1934), and Symmons (1952), have done much towards improving our knowledge of the tentorium, but all too frequently workers offer brief and inadequate descriptions of this structure in otherwise comprehensive investigations of the insect head. Themain objects in this study are threefold, vlz. (1) The claification of nomenclature (2) The examination and the interpretation ot the tentorium in certain groups of insects. (3) The deliberation as to whether the tentorium is of phylogenetic significance, and thus of use in assessing various schemes of insect classification which have been presented. Introduction, p. 1-2.
- Full Text:
- Date Issued: 1954
- Authors: Hudson, Gerda Bland
- Date: 1954
- Subjects: Insects -- Anatomy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5858 , http://hdl.handle.net/10962/d1012457
- Description: During a study of the morphology of the orthopteroid Hexapoda between the years 1939-1941, it appeareded to the writer that further investigation into the structure of the insect tentorium was necessary. The early entomologists laid the foundation or our knowledge or the tentorium but during the latter half of the last century little was added in this particulart field. Comstock and Kochi (1902), as far as the writer is aware are the only workers who have published a paper devoted entirely to the skeleton of the bead of insects, and they did much to clarify both nomenclature and existing knowledge of this structure at that time. Berlese (1909) described a typical tentorlum as observed in orthopteroid Hexapoda and then considered the variations of the tentorium which occur in other groups of insects. Some confusion then appears to have arisen amongst workers, over the origin of the dorsal arms which were erroneously considered by some to be cuticular invaginations and not secondary outgrowths of the anterior tentorial arms. Certain morphologists amongst them, Hoke (1924) Denis (1928), Snodgrass (1928, 1935), Hansen (1930), Walker (1933) Imms (1934), and Symmons (1952), have done much towards improving our knowledge of the tentorium, but all too frequently workers offer brief and inadequate descriptions of this structure in otherwise comprehensive investigations of the insect head. Themain objects in this study are threefold, vlz. (1) The claification of nomenclature (2) The examination and the interpretation ot the tentorium in certain groups of insects. (3) The deliberation as to whether the tentorium is of phylogenetic significance, and thus of use in assessing various schemes of insect classification which have been presented. Introduction, p. 1-2.
- Full Text:
- Date Issued: 1954
The chemistry of naturally occurring long chain unsaturated compounds
- Authors: Silk, M H
- Date: 1954
- Subjects: Compounds, Unsaturated
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4518 , http://hdl.handle.net/10962/d1014332
- Description: [From Introduction, p. 3] Raw marine oils are subject to considerable variation in composition with season and are moreover very unbalanced oils for direct use in the paint industry. Further refining is undertaken chiefly by Messrs Marine Oil Refiners of Africa Ltd., whose factory is situated at Simonstown. In their plant marine oils and others are treated by the Solexol process involving counter current extraction of the oil with liquid propane in a tower over which a temperature gradient is maintained. The process achieves the removal of a large proportion of the relatively saturated glycerides, the natural antitioxidants, and the relatively highly unsaturated components, all of which are detrimental to the eventual formation of good paint films. The segregated marine oil from the Solexol process is then bodied or polymerised at high temperatures to yield a "drying oil" which is used as a substitute for bodied linseed oil in paints. The chemical reactions taking place during the polymerisation and drying of these oils are of an exemely complex nature, and for their understanding it is necessary to have an accurate knowledge of the chemical nature of the component fatty acids in the natural glycerides ... The term "marine oils" in this work should be understood to mean marine fish body oils, marine mammal oils being excluded from consideration.
- Full Text:
- Date Issued: 1954
- Authors: Silk, M H
- Date: 1954
- Subjects: Compounds, Unsaturated
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4518 , http://hdl.handle.net/10962/d1014332
- Description: [From Introduction, p. 3] Raw marine oils are subject to considerable variation in composition with season and are moreover very unbalanced oils for direct use in the paint industry. Further refining is undertaken chiefly by Messrs Marine Oil Refiners of Africa Ltd., whose factory is situated at Simonstown. In their plant marine oils and others are treated by the Solexol process involving counter current extraction of the oil with liquid propane in a tower over which a temperature gradient is maintained. The process achieves the removal of a large proportion of the relatively saturated glycerides, the natural antitioxidants, and the relatively highly unsaturated components, all of which are detrimental to the eventual formation of good paint films. The segregated marine oil from the Solexol process is then bodied or polymerised at high temperatures to yield a "drying oil" which is used as a substitute for bodied linseed oil in paints. The chemical reactions taking place during the polymerisation and drying of these oils are of an exemely complex nature, and for their understanding it is necessary to have an accurate knowledge of the chemical nature of the component fatty acids in the natural glycerides ... The term "marine oils" in this work should be understood to mean marine fish body oils, marine mammal oils being excluded from consideration.
- Full Text:
- Date Issued: 1954
The rehabilitative value of sub-economic housing as illustrated by Schauder Township, Port Elizabeth, Cape Province, Union of South Africa, 1938-1948
- Authors: Stoker, F M L
- Date: 1954
- Subjects: Housing rehabilitation -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3389 , http://hdl.handle.net/10962/d1014554
- Description: [From Introductory discussion]. The modern approach to any sociological problem is characterised by the attempt to analyse the contributory factors in such a way that their inter-active association is clearly discernible. The simple concept of "single cause and effect" is now recognised to be a traversity of social fact. Social Pathology, therefore, may be said to attempt to isolate the multiple factors involved in a given situation, and to endeavour to determine thelr mode of inter-action in order that remedial techniques may be applied effectively. Slum conditions are obviously pathologic, by which it is understood that the environment imposes strains upon the individual to which there is ineffective adjustment. The rehabilitation of such a population would involve the converse process, restoring individuals to a condition where they are able to cope in every respect with the demands of life at their respective class levels. It is very rare indeed that only a single factor is involved in a social pathological condition and for this reason it is quite possible that one- sided efforts at rehabilitation - such as the attempt to re-house ALL slum dwellers in sub-economic houses - have a tendency to increase the pathology in another direction. Rehabilitation must therefore be based on multi-factorial analysis in which allowance is, as far as possible, made for the inter-connection of each of the individual deviations from the normal. The aim of this thesis is to evaluate the effect of good housing conditions on the 2335 Coloured slum families re-housed in sub-economic houses at Schauder Township, Port Elizabeth, from the time that these houses were first available for occupancy.
- Full Text:
- Date Issued: 1954
- Authors: Stoker, F M L
- Date: 1954
- Subjects: Housing rehabilitation -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3389 , http://hdl.handle.net/10962/d1014554
- Description: [From Introductory discussion]. The modern approach to any sociological problem is characterised by the attempt to analyse the contributory factors in such a way that their inter-active association is clearly discernible. The simple concept of "single cause and effect" is now recognised to be a traversity of social fact. Social Pathology, therefore, may be said to attempt to isolate the multiple factors involved in a given situation, and to endeavour to determine thelr mode of inter-action in order that remedial techniques may be applied effectively. Slum conditions are obviously pathologic, by which it is understood that the environment imposes strains upon the individual to which there is ineffective adjustment. The rehabilitation of such a population would involve the converse process, restoring individuals to a condition where they are able to cope in every respect with the demands of life at their respective class levels. It is very rare indeed that only a single factor is involved in a social pathological condition and for this reason it is quite possible that one- sided efforts at rehabilitation - such as the attempt to re-house ALL slum dwellers in sub-economic houses - have a tendency to increase the pathology in another direction. Rehabilitation must therefore be based on multi-factorial analysis in which allowance is, as far as possible, made for the inter-connection of each of the individual deviations from the normal. The aim of this thesis is to evaluate the effect of good housing conditions on the 2335 Coloured slum families re-housed in sub-economic houses at Schauder Township, Port Elizabeth, from the time that these houses were first available for occupancy.
- Full Text:
- Date Issued: 1954
Die evolusie van nedersetting in die Sondagsriviervallei
- Authors: Potgieter, J M
- Date: 1953
- Subjects: Land settlement -- South Africa -- Sundays River Valley , Agriculture -- South Africa -- Sundays River Valley , Irrigation -- South Africa -- Eastern Cape -- Sundays River Valley
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4875 , http://hdl.handle.net/10962/d1013041
- Description: Soos die titel aandui is hierdie verhandeling 'n volledige en noukeurige oorsig van die evolusie (ontwikkeling) van blanke nedersetting in die Sondagsriviervallei. Dis die eerste poging wat aangewend is om die ontwikkeling op alle gebiede van die grondlegging af tot op die huidige datum teen 'n geskiedkundige agtergrond te skilder. Maar dwarsdaur is daar getrag om 'n duidelike begrip van die interaksie van natuur en mens te handhaaf.
- Full Text:
- Date Issued: 1953
- Authors: Potgieter, J M
- Date: 1953
- Subjects: Land settlement -- South Africa -- Sundays River Valley , Agriculture -- South Africa -- Sundays River Valley , Irrigation -- South Africa -- Eastern Cape -- Sundays River Valley
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4875 , http://hdl.handle.net/10962/d1013041
- Description: Soos die titel aandui is hierdie verhandeling 'n volledige en noukeurige oorsig van die evolusie (ontwikkeling) van blanke nedersetting in die Sondagsriviervallei. Dis die eerste poging wat aangewend is om die ontwikkeling op alle gebiede van die grondlegging af tot op die huidige datum teen 'n geskiedkundige agtergrond te skilder. Maar dwarsdaur is daar getrag om 'n duidelike begrip van die interaksie van natuur en mens te handhaaf.
- Full Text:
- Date Issued: 1953
The chemistry of the wattle tannins
- Authors: Roux, David Gerhardus
- Date: 1953
- Subjects: Tannin plants , Tannins , Wattles (Plants)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: vital:4492 , http://hdl.handle.net/10962/d1013098
- Description: Four species of acacia of Auatralian origin are associated with the wattle industry in South Africa. Black wattle, Acacia mollissima willd., is the most important of these and is today almost exclusively cultivated. The tree grows successfully only in a limited area of rich soil and high rainfall and is easily affected by adverse conditions caused by insect pests, frost damage and drought. Expansion of the area under cultivation is therefore, not feasible, although the world demand for vegetable extracts far exceeds the available supply. The remaining species such as green (Acacia decurrrens willd.) and silver wattles (Acacia dealbata Link.) possess many desirable characteristics which resist such adverse factors. Their barks, however, give reddish extracts, which are considered unsuitable for tannery usage because of the red colour they impart to the leather. Hybridisation studies, involving the crossing of green and silver wattle with the black, and aimed at produc1ng progenies containing many of the desirable characterlstics of the parent plants, are thus a natural result and have been in progress for a considerable period. Summary, p. i.
- Full Text:
- Date Issued: 1953
- Authors: Roux, David Gerhardus
- Date: 1953
- Subjects: Tannin plants , Tannins , Wattles (Plants)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: vital:4492 , http://hdl.handle.net/10962/d1013098
- Description: Four species of acacia of Auatralian origin are associated with the wattle industry in South Africa. Black wattle, Acacia mollissima willd., is the most important of these and is today almost exclusively cultivated. The tree grows successfully only in a limited area of rich soil and high rainfall and is easily affected by adverse conditions caused by insect pests, frost damage and drought. Expansion of the area under cultivation is therefore, not feasible, although the world demand for vegetable extracts far exceeds the available supply. The remaining species such as green (Acacia decurrrens willd.) and silver wattles (Acacia dealbata Link.) possess many desirable characteristics which resist such adverse factors. Their barks, however, give reddish extracts, which are considered unsuitable for tannery usage because of the red colour they impart to the leather. Hybridisation studies, involving the crossing of green and silver wattle with the black, and aimed at produc1ng progenies containing many of the desirable characterlstics of the parent plants, are thus a natural result and have been in progress for a considerable period. Summary, p. i.
- Full Text:
- Date Issued: 1953
German immigration to the Cape, with special reference to (a) the German military settlers of 1857; and (b) the German immigrants of 1858
- Authors: Schnell, E L G
- Date: 1952
- Subjects: Germans -- South Africa -- Cape of Good Hope , Immigrants -- South Africa -- Cape of Good Hope , Cape of Good Hope (South Africa) -- History , Eastern Cape (South Africa) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2613 , http://hdl.handle.net/10962/d1013168
- Description: South Africa is a multi-racial society in more than one sense. There are the broad divisions of Colour, but in addition there are further divisions within each group. The European section is mostly of Dutch and British origin, but there are important other strains, notably the French and the German. The history of the Dutch and British sections has been written, and that of the French too, but the story of the German element is still incomplete. Preface.
- Full Text:
- Date Issued: 1952
- Authors: Schnell, E L G
- Date: 1952
- Subjects: Germans -- South Africa -- Cape of Good Hope , Immigrants -- South Africa -- Cape of Good Hope , Cape of Good Hope (South Africa) -- History , Eastern Cape (South Africa) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2613 , http://hdl.handle.net/10962/d1013168
- Description: South Africa is a multi-racial society in more than one sense. There are the broad divisions of Colour, but in addition there are further divisions within each group. The European section is mostly of Dutch and British origin, but there are important other strains, notably the French and the German. The history of the Dutch and British sections has been written, and that of the French too, but the story of the German element is still incomplete. Preface.
- Full Text:
- Date Issued: 1952
A study of conditions in the upper atmosphere and their deduction from radio measurements
- Gledhill, J A, Szendrei, M E
- Authors: Gledhill, J A , Szendrei, M E
- Date: 1948
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21181 , http://hdl.handle.net/10962/6795
- Description: Summary: In part 1 (a), after a brief historical outline of methods of ionospheric investigation and their development, the construction in this laboratory of manually operated equipment for sounding the ionosphere is described. Photographic records of good definition were taken at regular intervals over a period of four months during the summer of 1945-6. These were fully sealed for critical frequencies, true heights and thicknesses of all the layers present, and mean monthly values of these quantities for each hour are tabulated. An extensive correlation with magnetic data from Hermanus indicated good correlation between magnetic activity and disturbed ionospheric conditions. On these grounds some disturbed days were rejected, and others were eliminated on ionospheric grounds. Smoothed mean values are tabulated and graphs drawn. These are presented in concise form on "electron density maps", which are graphs showing lines of constant electron density plotted as functions of time and height. In part 1 (b), a new theory of layer-formation is developed, in which the temperature is assumed to vary linearly with height. The equations are compared at each step with those obtained by Chapman in his theory of layer-formation in an isothermal atmosphere. The equations for the maximum of electron density and its height are also given. The effect of the parameters on the shape of the layer is shown in graphical form. The equations are somewhat complex in form, but an ingenious graphical method has been devised suitable for the application of the theory to results given in the form of those in section 1 (a). From this application values are obtained for the temperature gradient, the temperature at 200 km. and its variation over the middle part of the day. The results obtained are in accordance with previous estimates, and offer numerical confirmation of the theory that the atmosphere expands bodily upwards during the middle part of a summer day.
- Full Text:
- Date Issued: 1948
- Authors: Gledhill, J A , Szendrei, M E
- Date: 1948
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21181 , http://hdl.handle.net/10962/6795
- Description: Summary: In part 1 (a), after a brief historical outline of methods of ionospheric investigation and their development, the construction in this laboratory of manually operated equipment for sounding the ionosphere is described. Photographic records of good definition were taken at regular intervals over a period of four months during the summer of 1945-6. These were fully sealed for critical frequencies, true heights and thicknesses of all the layers present, and mean monthly values of these quantities for each hour are tabulated. An extensive correlation with magnetic data from Hermanus indicated good correlation between magnetic activity and disturbed ionospheric conditions. On these grounds some disturbed days were rejected, and others were eliminated on ionospheric grounds. Smoothed mean values are tabulated and graphs drawn. These are presented in concise form on "electron density maps", which are graphs showing lines of constant electron density plotted as functions of time and height. In part 1 (b), a new theory of layer-formation is developed, in which the temperature is assumed to vary linearly with height. The equations are compared at each step with those obtained by Chapman in his theory of layer-formation in an isothermal atmosphere. The equations for the maximum of electron density and its height are also given. The effect of the parameters on the shape of the layer is shown in graphical form. The equations are somewhat complex in form, but an ingenious graphical method has been devised suitable for the application of the theory to results given in the form of those in section 1 (a). From this application values are obtained for the temperature gradient, the temperature at 200 km. and its variation over the middle part of the day. The results obtained are in accordance with previous estimates, and offer numerical confirmation of the theory that the atmosphere expands bodily upwards during the middle part of a summer day.
- Full Text:
- Date Issued: 1948
The preservation and standardisation of South African hides and skins
- Authors: Kritzinger, Carl Cronje
- Date: 1946
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21052 , http://hdl.handle.net/10962/6157
- Description: During the past fifty years the problems of the leather industry have been tackled from various aspects by scientific research workers all over the world, and "works control" today forms one of .the important foundation stones of efficiently run tanneries and footwear factories. The raw materials of the tanning industry, hides and skins, constitute the largest proportion of the cost of production, and it is ' only natural that the improvement of these valuable raw materials should be given primary attention by any leather scientist. Until only a few years ago, however, the South African hide and skin industry was at a serious ·disadvantage in that it had to base recommendations for improved production methods almost exclusively on overseas experience and practice. The importance of the differences existing between South Africa and European or American countries with regard to climate, slaughtering, hide and skin production in general, transport and sale, however, necessitates a different approach to our specific problems. The overseas hide and skin industry has had, since the beginning of this century, the support and particularly the guidance of scientific research; but it was not until 1935, when, through the support of the Hide and Skin advisory Board, Prof. W. F. Barker founded the original Tanning, Hides and Skins Research Department at Rhodes University College, Grahamstown, that science actively entered the field of hide and skin production in this country. Much of the work done had of course to be based on the results obtained by overseas research institutions, and the adaptation of such results to suit our own problems for some time formed a considerable part of the investigations undertaken. This thesis embodies the results of work undertaken by the writer since 1943 on specific problems of the South African hide and skin industry. Much of the work has already received publication through the Circulars and Journals of this Institute, but it is embodied here again in order to maintain the continuity. The attitude throughout has been to evolve methods of production suited to our own conditions, and the adoption of the recommendations contained in this thesis should lead to improvement in the quality of our hides and skins. Much still remains to be done, and it is the sincere hope of the writer that this work will stimulate and form the basis for subsequent investigations. For that reason more or less detailed descriptions are given of all experiments conducted, and the theory of curing in its relation to tanning is briefly discussed . The literature in each of the four Parts has been attached at the end of that Part to facilitate reference work. At the same time, however, the writer kept in mind the requirements of the trade itself, therefore much of the work is discussed in popular terms. It is hoped that the correct balance between the two extremes has been arrived at.
- Full Text:
- Date Issued: 1946
- Authors: Kritzinger, Carl Cronje
- Date: 1946
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21052 , http://hdl.handle.net/10962/6157
- Description: During the past fifty years the problems of the leather industry have been tackled from various aspects by scientific research workers all over the world, and "works control" today forms one of .the important foundation stones of efficiently run tanneries and footwear factories. The raw materials of the tanning industry, hides and skins, constitute the largest proportion of the cost of production, and it is ' only natural that the improvement of these valuable raw materials should be given primary attention by any leather scientist. Until only a few years ago, however, the South African hide and skin industry was at a serious ·disadvantage in that it had to base recommendations for improved production methods almost exclusively on overseas experience and practice. The importance of the differences existing between South Africa and European or American countries with regard to climate, slaughtering, hide and skin production in general, transport and sale, however, necessitates a different approach to our specific problems. The overseas hide and skin industry has had, since the beginning of this century, the support and particularly the guidance of scientific research; but it was not until 1935, when, through the support of the Hide and Skin advisory Board, Prof. W. F. Barker founded the original Tanning, Hides and Skins Research Department at Rhodes University College, Grahamstown, that science actively entered the field of hide and skin production in this country. Much of the work done had of course to be based on the results obtained by overseas research institutions, and the adaptation of such results to suit our own problems for some time formed a considerable part of the investigations undertaken. This thesis embodies the results of work undertaken by the writer since 1943 on specific problems of the South African hide and skin industry. Much of the work has already received publication through the Circulars and Journals of this Institute, but it is embodied here again in order to maintain the continuity. The attitude throughout has been to evolve methods of production suited to our own conditions, and the adoption of the recommendations contained in this thesis should lead to improvement in the quality of our hides and skins. Much still remains to be done, and it is the sincere hope of the writer that this work will stimulate and form the basis for subsequent investigations. For that reason more or less detailed descriptions are given of all experiments conducted, and the theory of curing in its relation to tanning is briefly discussed . The literature in each of the four Parts has been attached at the end of that Part to facilitate reference work. At the same time, however, the writer kept in mind the requirements of the trade itself, therefore much of the work is discussed in popular terms. It is hoped that the correct balance between the two extremes has been arrived at.
- Full Text:
- Date Issued: 1946
Analysis of decision making in smallholder irrigation practice: a case study of Shiloh and Zanyokwe irrigation schemes in Central Eastern Cape, South Africa
- Authors: Isaac, Agholor Azikiwe
- Subjects: Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11215 , http://hdl.handle.net/10353/d1019766 , Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Description: The study was conducted in Zanyokwe and Shiloh smallholder irrigation schemes located in Eastern Cape Province at Amathole and Chris Hani districts respectively. The choice of Zanyokwe and Shiloh smallholder irrigation scheme for this study is mainly supported by the fact that it had a substantial level of crop farming activity taking place especially at Zanyokwe while the Shiloh smallholder irrigation specialises dairy farming. The study examined decision making in smallholder irrigation practice with particular reference to Shiloh and Zanyokwe irrigation schemes. The general objective of the thesis was to analyse and model the determinants of SIS farmer‟s decision making. The specific objectives of the study are as follows: to investigate the determinants of decision making among smallholder irrigation farmers; to examine the relationship between household and farm characteristics and institutional factors that explain decision making in smallholder irrigation scheme; assess the contribution of smallholder irrigation farming to household food security; and determine the production and marketing constraints of smallholder farmers‟ in both schemes. The theoretical and conceptual framework of the study gave a detailed discussion on the determinants of decision making of households. The theories used to understand household behaviour under different assumptions were variously discussed. Comprehensive illustrations of analytical framework of the study were also conceptualised. This study used a survey design, quantitative and qualitative research methodologies involving the use of questionnaires and focus group discussions. The data was coded and analysed using the Statistical Package for Social Science (SPSS). However, frequencies, percentages, bar and pie chart was also computed to describe the data. In consideration of the conceptual framework of the study, the agricultural household model was adopted to analyse smallholder farmer‟s household decision making. Twenty one explanatory variables identified in the conceptual framework of the study were discussed and some of these identified variables were incorporated into the model. The logistic regression model was used as a method of analysis because it can estimate the probability of a certain event occurring and it accommodates a lot of variables which can be ranked in order to illustrate which variables are significant. In the binary logistic model used, seven variables (farm experience, size of farmland, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant effect on influencing household decision making in Shiloh smallholder irrigation scheme, while five variables (gender, age, education, road distance and extension access) were not significant. Of the seven significant variables, four had positive signs (land rights/PTO, water sufficiency and market information); which means that an increase in either of these variables may be associated with an increase in household decision making in Shiloh. The other three predictor variables (farm experience, farm asset and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. In Zanyokwe, six variables (farm experience, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant impact on influencing household decision making, while six variables (gender, age, education, size of farm land, road distance and extension access) were not significant. Of the six significant variables, two had positive signs (water sufficiency and farm asset); which means that an increase in either of these variables may be associated with an increase in household decision making in Zanyokwe. The other four predictor variables (farm experience, land rights/PTO, market information and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. The study concludes that smallholder agriculture is essential for employment generation and food security of households. It is apparent that household food security will not be achieved without giving attention to the role played by smallholders‟ farmers in South Africa. It is pertinent to promulgate an efficient policy programme to address the diversity of smallholders‟ situations and identify the main constraints on investment. Therefore, all spheres of government, the private sector and NGOs should consider investment in smallholder agriculture through coordinated strategies and political support. This study also recommends that government should develop a strategic Smallholder Investment Plan which would improve investments in smallholder agriculture.
- Full Text:
- Authors: Isaac, Agholor Azikiwe
- Subjects: Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11215 , http://hdl.handle.net/10353/d1019766 , Irrigation farming -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agricultural extension work -- South Africa -- Eastern Cape , Crops -- Irrigation -- South Africa -- Eastern Cape
- Description: The study was conducted in Zanyokwe and Shiloh smallholder irrigation schemes located in Eastern Cape Province at Amathole and Chris Hani districts respectively. The choice of Zanyokwe and Shiloh smallholder irrigation scheme for this study is mainly supported by the fact that it had a substantial level of crop farming activity taking place especially at Zanyokwe while the Shiloh smallholder irrigation specialises dairy farming. The study examined decision making in smallholder irrigation practice with particular reference to Shiloh and Zanyokwe irrigation schemes. The general objective of the thesis was to analyse and model the determinants of SIS farmer‟s decision making. The specific objectives of the study are as follows: to investigate the determinants of decision making among smallholder irrigation farmers; to examine the relationship between household and farm characteristics and institutional factors that explain decision making in smallholder irrigation scheme; assess the contribution of smallholder irrigation farming to household food security; and determine the production and marketing constraints of smallholder farmers‟ in both schemes. The theoretical and conceptual framework of the study gave a detailed discussion on the determinants of decision making of households. The theories used to understand household behaviour under different assumptions were variously discussed. Comprehensive illustrations of analytical framework of the study were also conceptualised. This study used a survey design, quantitative and qualitative research methodologies involving the use of questionnaires and focus group discussions. The data was coded and analysed using the Statistical Package for Social Science (SPSS). However, frequencies, percentages, bar and pie chart was also computed to describe the data. In consideration of the conceptual framework of the study, the agricultural household model was adopted to analyse smallholder farmer‟s household decision making. Twenty one explanatory variables identified in the conceptual framework of the study were discussed and some of these identified variables were incorporated into the model. The logistic regression model was used as a method of analysis because it can estimate the probability of a certain event occurring and it accommodates a lot of variables which can be ranked in order to illustrate which variables are significant. In the binary logistic model used, seven variables (farm experience, size of farmland, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant effect on influencing household decision making in Shiloh smallholder irrigation scheme, while five variables (gender, age, education, road distance and extension access) were not significant. Of the seven significant variables, four had positive signs (land rights/PTO, water sufficiency and market information); which means that an increase in either of these variables may be associated with an increase in household decision making in Shiloh. The other three predictor variables (farm experience, farm asset and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. In Zanyokwe, six variables (farm experience, land rights/PTO, water sufficiency, farm asset, market information and production variation) out of the twelve predictor variables were found to have significant impact on influencing household decision making, while six variables (gender, age, education, size of farm land, road distance and extension access) were not significant. Of the six significant variables, two had positive signs (water sufficiency and farm asset); which means that an increase in either of these variables may be associated with an increase in household decision making in Zanyokwe. The other four predictor variables (farm experience, land rights/PTO, market information and product variation) had negative signs; this means an increase in either of these variables may be associated with a decrease in decision making. The study concludes that smallholder agriculture is essential for employment generation and food security of households. It is apparent that household food security will not be achieved without giving attention to the role played by smallholders‟ farmers in South Africa. It is pertinent to promulgate an efficient policy programme to address the diversity of smallholders‟ situations and identify the main constraints on investment. Therefore, all spheres of government, the private sector and NGOs should consider investment in smallholder agriculture through coordinated strategies and political support. This study also recommends that government should develop a strategic Smallholder Investment Plan which would improve investments in smallholder agriculture.
- Full Text:
Characterization of friction hydro pillar process weld properties as applied to 10CrMo910 creep resistant steel for application in the power generation Industry
- Authors: Bulbring, Daniel Louis Hans
- Subjects: Materials -- Creep , Friction welding
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9636 , http://hdl.handle.net/10948/d1020586
- Description: Creep degradation of steam carrying vessels in the power generation industry is a concern that needs to be constantly monitored. The Weldcore® process has been earmarked as a potential method of creep sampling which will allow for thick-walled sections to be analysed. A component of the process involves plugging the resultant hole after removing a creep sample using a novel welding technique called friction hydro pillar processing. At the commencement of this study, insufficient data was available to warrant safe industrial application of the process. This research was conducted to evaluate the performance of 10CrMo910 friction hydro pillar process welds. The effects of downward force, stud taper angle, hole taper angle and hole base diameter on process response, defect population, static properties and dynamic performance were evaluated. The variation of downward force showed that higher forces produce significantly smaller defects and higher fatigue life. The occurrence of defects was linked to process parameters and geometry thereby identifying the correct parameters for safe use in the power generation industry. Flash formation was identified as an early indicator of weld defects and can assist with quality control in industrial applications. Methods of standardising the plunge depth and forge force were developed to identify the correct magnitudes for different geometries, without the need for testing. Defects were shown to populate specific regions of the weld and produce variations in fatigue life. Crack initiation sites were detected which will aid in identifying areas of focus in further research and development. Temperature measurements were linked to the occurrence of defects and crack initiation sites and have been identified as a method of identifying defective welds. The effects of process parameters and stud and hole taper angles on energy inputs and near interface temperatures were statistically evaluated. Downward force was shown to have the largest effect on energy input rates, total energy input and temperatures at the 11.5mm and 20.5mm positions. Smaller hole and stud taper angles produced lower energy inputs and were identified as more energy efficient than the larger taper angles. A regression model was also developed to predict the fatigue life of welds and can assist with critical process related decision making. A range of hole base diameters were identified which produced welds with low defect populations and fatigue performance similar to that of the parent plate. Larger hole base diameters were shown to produce significant defects along the hole bottom fillet, in the weld nugget and along the bond line. Temperature measurements of the larger diameter welds showed a delay in response and are attributed to a delayed contact of plasticised stud material with the sidewall. Welds with hole base diameters larger than 11mm produced unrepeatable and defective welds, and also required higher energy inputs making smaller diameters more desirable. Analysis of all welds in this study revealed that clearance and interfacial pressures characterise the quality of friction hydro pillar process welds, therefore models were developed to aid in critical decision making with respect to downward force and geometry. This study has successfully evaluated the effects of process parameters and geometry on the properties of friction hydro pillar process welds and thereby has increased understanding of the process.
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- Authors: Bulbring, Daniel Louis Hans
- Subjects: Materials -- Creep , Friction welding
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9636 , http://hdl.handle.net/10948/d1020586
- Description: Creep degradation of steam carrying vessels in the power generation industry is a concern that needs to be constantly monitored. The Weldcore® process has been earmarked as a potential method of creep sampling which will allow for thick-walled sections to be analysed. A component of the process involves plugging the resultant hole after removing a creep sample using a novel welding technique called friction hydro pillar processing. At the commencement of this study, insufficient data was available to warrant safe industrial application of the process. This research was conducted to evaluate the performance of 10CrMo910 friction hydro pillar process welds. The effects of downward force, stud taper angle, hole taper angle and hole base diameter on process response, defect population, static properties and dynamic performance were evaluated. The variation of downward force showed that higher forces produce significantly smaller defects and higher fatigue life. The occurrence of defects was linked to process parameters and geometry thereby identifying the correct parameters for safe use in the power generation industry. Flash formation was identified as an early indicator of weld defects and can assist with quality control in industrial applications. Methods of standardising the plunge depth and forge force were developed to identify the correct magnitudes for different geometries, without the need for testing. Defects were shown to populate specific regions of the weld and produce variations in fatigue life. Crack initiation sites were detected which will aid in identifying areas of focus in further research and development. Temperature measurements were linked to the occurrence of defects and crack initiation sites and have been identified as a method of identifying defective welds. The effects of process parameters and stud and hole taper angles on energy inputs and near interface temperatures were statistically evaluated. Downward force was shown to have the largest effect on energy input rates, total energy input and temperatures at the 11.5mm and 20.5mm positions. Smaller hole and stud taper angles produced lower energy inputs and were identified as more energy efficient than the larger taper angles. A regression model was also developed to predict the fatigue life of welds and can assist with critical process related decision making. A range of hole base diameters were identified which produced welds with low defect populations and fatigue performance similar to that of the parent plate. Larger hole base diameters were shown to produce significant defects along the hole bottom fillet, in the weld nugget and along the bond line. Temperature measurements of the larger diameter welds showed a delay in response and are attributed to a delayed contact of plasticised stud material with the sidewall. Welds with hole base diameters larger than 11mm produced unrepeatable and defective welds, and also required higher energy inputs making smaller diameters more desirable. Analysis of all welds in this study revealed that clearance and interfacial pressures characterise the quality of friction hydro pillar process welds, therefore models were developed to aid in critical decision making with respect to downward force and geometry. This study has successfully evaluated the effects of process parameters and geometry on the properties of friction hydro pillar process welds and thereby has increased understanding of the process.
- Full Text:
Designing adaptaptive user interfaces for enterprise resource planning systems for small enterprises
- Authors: Singh, Akash
- Subjects: User interfaces (Computer systems)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10458 , http://hdl.handle.net/10948/2073 , User interfaces (Computer systems)
- Description: It is widely acknowledged that enterprise resource planning (ERP) systems suffer from complex user interfaces. The complexity of these user interfaces negatively affects the usability of these systems. Current research has shown that a need exists to improve the overall usability of ERP systems. This research proposes the use of adaptive user interfaces (AUIs) as a means of improving the overall usability of ERP systems. Research has shown that AUIs are capable of improving system usability by reducing user interface complexity and improving the overall user experience. The primary objective of this research was to determine how AUIs could be designed to improve the usability of ERP systems. An adaptation taxonomy, ERP system architecture (incorporating an AUI), a set of AUI components and a set of usability heuristics for ERP systems were proposed to support the design, development and evaluation of AUIs for ERP systems. The proposed adaptation taxonomy provides support for three types of adaptation: content adaptation, presentation adaptation and navigation adaptation. The proposed ERP system architecture is a three-tiered system architecture, consisting of a Presentation Layer (incorporating an AUI), an Application Layer and a Database Layer. The proposed set of AUI components comprise a user model, a task model and a dialog model. The set of proposed usability heuristics aims to identify usability issues of ERP systems within the areas of Navigation, Presentation, Task Support, Learnability and Customisation. An AUI prototype was developed based on selected adaptive techniques from the proposed adaptation taxonomy and selected components from the proposed system architecture. All of the proposed AUI components were implemented. The AUI prototype was developed for an existing ERP system, namely SAP Business One (SBO). This prototype was designed, in order to resolve the usability issues of SBO identified through the use of the proposed set of heuristics. The development of the AUI prototype was made possible through the use of a software development kit (SDK) provided with SBO. The AUI prototype made use of content adaptation, presentation adaptation and navigation adaptation in order to address the identified usability issues. An empirical evaluation was conducted on the AUI prototype to determine whether it provided any usability benefits over the standard SBO system. The results from the empirical evaluation revealed that the AUI presented usability benefits with regard to learnability and satisfaction. Users who used the AUI prototype were able to learn how to use the ERP system a lot quicker and were more satisfied than users of the standard SBO system. The successful implementation of the AUI prototype provided practical evidence that the proposed adaptation taxonomy and the proposed system architecture can be implemented. This research has provided empirical evidence that the use of AUIs can improve the usability of ERP systems. Future research has outlined several possibilities to utilise and enhance the proposed adaptation taxonomy, the ERP system architecture and ERP heuristics, for the purpose of furthering research within the area of AUIs for ERP systems.
- Full Text:
Designing adaptaptive user interfaces for enterprise resource planning systems for small enterprises
- Authors: Singh, Akash
- Subjects: User interfaces (Computer systems)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10458 , http://hdl.handle.net/10948/2073 , User interfaces (Computer systems)
- Description: It is widely acknowledged that enterprise resource planning (ERP) systems suffer from complex user interfaces. The complexity of these user interfaces negatively affects the usability of these systems. Current research has shown that a need exists to improve the overall usability of ERP systems. This research proposes the use of adaptive user interfaces (AUIs) as a means of improving the overall usability of ERP systems. Research has shown that AUIs are capable of improving system usability by reducing user interface complexity and improving the overall user experience. The primary objective of this research was to determine how AUIs could be designed to improve the usability of ERP systems. An adaptation taxonomy, ERP system architecture (incorporating an AUI), a set of AUI components and a set of usability heuristics for ERP systems were proposed to support the design, development and evaluation of AUIs for ERP systems. The proposed adaptation taxonomy provides support for three types of adaptation: content adaptation, presentation adaptation and navigation adaptation. The proposed ERP system architecture is a three-tiered system architecture, consisting of a Presentation Layer (incorporating an AUI), an Application Layer and a Database Layer. The proposed set of AUI components comprise a user model, a task model and a dialog model. The set of proposed usability heuristics aims to identify usability issues of ERP systems within the areas of Navigation, Presentation, Task Support, Learnability and Customisation. An AUI prototype was developed based on selected adaptive techniques from the proposed adaptation taxonomy and selected components from the proposed system architecture. All of the proposed AUI components were implemented. The AUI prototype was developed for an existing ERP system, namely SAP Business One (SBO). This prototype was designed, in order to resolve the usability issues of SBO identified through the use of the proposed set of heuristics. The development of the AUI prototype was made possible through the use of a software development kit (SDK) provided with SBO. The AUI prototype made use of content adaptation, presentation adaptation and navigation adaptation in order to address the identified usability issues. An empirical evaluation was conducted on the AUI prototype to determine whether it provided any usability benefits over the standard SBO system. The results from the empirical evaluation revealed that the AUI presented usability benefits with regard to learnability and satisfaction. Users who used the AUI prototype were able to learn how to use the ERP system a lot quicker and were more satisfied than users of the standard SBO system. The successful implementation of the AUI prototype provided practical evidence that the proposed adaptation taxonomy and the proposed system architecture can be implemented. This research has provided empirical evidence that the use of AUIs can improve the usability of ERP systems. Future research has outlined several possibilities to utilise and enhance the proposed adaptation taxonomy, the ERP system architecture and ERP heuristics, for the purpose of furthering research within the area of AUIs for ERP systems.
- Full Text: