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
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
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
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.
- Full Text:
- 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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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.
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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.
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Primeness in near-rings of continuous maps
- Authors: Mogae, Kabelo
- Subjects: Near-rings , Topological algebras
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10512 , http://hdl.handle.net/10948/d1020597
- Description: The prototype of a near-ring is the set of all self-maps of an additively written (but not necessarily abelian) group under pointwise addition and composition of maps. Moreover, any near-ring with unity can be embedded in a near-ring (with unity) of self-maps of some group. For this reason, a lot of research has been done on near-rings of maps. In 1979, Hofer [16] gave the study of near-rings of maps a topological avour by considering the near- ring of all continuous self-maps of a topological group. In this dissertation we consider some standard constructions of near-rings of maps on a group G and investigate these when G is a topological group and our near-ring consists of continuous maps.
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- Authors: Mogae, Kabelo
- Subjects: Near-rings , Topological algebras
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10512 , http://hdl.handle.net/10948/d1020597
- Description: The prototype of a near-ring is the set of all self-maps of an additively written (but not necessarily abelian) group under pointwise addition and composition of maps. Moreover, any near-ring with unity can be embedded in a near-ring (with unity) of self-maps of some group. For this reason, a lot of research has been done on near-rings of maps. In 1979, Hofer [16] gave the study of near-rings of maps a topological avour by considering the near- ring of all continuous self-maps of a topological group. In this dissertation we consider some standard constructions of near-rings of maps on a group G and investigate these when G is a topological group and our near-ring consists of continuous maps.
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Resource utilization and reproduction of the hermit crab Clibanarius virescens (Crustacea: Decapoda : Anomura)
- Authors: Wait, Michelle
- Subjects: Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10599 , http://hdl.handle.net/10948/1553 , Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Description: Clibanarius virescens (Krauss) is a common and abundant hermit crab along the East coast of South Africa. Despite this, its biology is poorly known, both in South Africa and throughout the rest of its range in the West Indo-Pacific region. This study focuses on the descriptive analysis of the shell resource used by C. virescens and of the effects of this resource on crab populations. The underlying hypothesis of the study is that biogeographically imposed gradients in the morphology of intertidal gastropod shells used by hermit crabs affect hermit crab population parameters. The gradient of potential change in the shell resource was captured by sampling at 12 localities, encompassing the range of C. virescens in South Africa. Seasonal changes in shell use, population structure and reproduction at a single locality (Cape Recife) were recorded over a period of 13 months. The breeding season of C. virescens at the southern extreme of its range extended from December to June. The population structure shows some seasonal change, but no clear trends emerge. The shell resource changed substantially in nature over the region studied. Based on shell use, localities clustered into separate southern and northern groups with a break occurring between Dwesa and Coffee Bay. Southern localities were characterised by use of Burnupena cincta, B. lagenaria and B. pubescens. Northern localities were characterised by the use of Morula granulata, M. nodosa and Peristernia forskalii. Intertidal shells used by C. virescens show fewer adaptations to predation in southern localities than shells from northern localities. Southern shells ii are relatively large, light and have wider apertures than those from northern localities which are generally smaller, heavier and have decreased aperture widths. Shell parameters affect population size-distributions as southern crabs were larger and heavier than northern crabs. C. virescens show sexual size dimorphism in which male crabs uniformly dominate the larger size classes at all localities. Differences in the sex ratio between males and females show more variable patterns. Most southern localities show no difference in the number of male and female crabs, but most northern localities show a skewed sex ratio in favour of females. Shell use and population size distributions of females affect reproductive output. Southern females produced significantly larger clutches than northern females. Reproductive output was related to crab mass and shell volume. Shell use patterns conform to the biogeographical regions in the range of the study and have a clear effect on both the population size distributions and reproductive output of Clibanarius virescens.
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- Authors: Wait, Michelle
- Subjects: Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10599 , http://hdl.handle.net/10948/1553 , Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Description: Clibanarius virescens (Krauss) is a common and abundant hermit crab along the East coast of South Africa. Despite this, its biology is poorly known, both in South Africa and throughout the rest of its range in the West Indo-Pacific region. This study focuses on the descriptive analysis of the shell resource used by C. virescens and of the effects of this resource on crab populations. The underlying hypothesis of the study is that biogeographically imposed gradients in the morphology of intertidal gastropod shells used by hermit crabs affect hermit crab population parameters. The gradient of potential change in the shell resource was captured by sampling at 12 localities, encompassing the range of C. virescens in South Africa. Seasonal changes in shell use, population structure and reproduction at a single locality (Cape Recife) were recorded over a period of 13 months. The breeding season of C. virescens at the southern extreme of its range extended from December to June. The population structure shows some seasonal change, but no clear trends emerge. The shell resource changed substantially in nature over the region studied. Based on shell use, localities clustered into separate southern and northern groups with a break occurring between Dwesa and Coffee Bay. Southern localities were characterised by use of Burnupena cincta, B. lagenaria and B. pubescens. Northern localities were characterised by the use of Morula granulata, M. nodosa and Peristernia forskalii. Intertidal shells used by C. virescens show fewer adaptations to predation in southern localities than shells from northern localities. Southern shells ii are relatively large, light and have wider apertures than those from northern localities which are generally smaller, heavier and have decreased aperture widths. Shell parameters affect population size-distributions as southern crabs were larger and heavier than northern crabs. C. virescens show sexual size dimorphism in which male crabs uniformly dominate the larger size classes at all localities. Differences in the sex ratio between males and females show more variable patterns. Most southern localities show no difference in the number of male and female crabs, but most northern localities show a skewed sex ratio in favour of females. Shell use and population size distributions of females affect reproductive output. Southern females produced significantly larger clutches than northern females. Reproductive output was related to crab mass and shell volume. Shell use patterns conform to the biogeographical regions in the range of the study and have a clear effect on both the population size distributions and reproductive output of Clibanarius virescens.
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Social media reviews to investigate restaurant dinning experiences
- Authors: Van Achterbergh, Leon
- Subjects: Hospitality industry -- Social aspects , Restaurants -- Social aspects , Social media -- Economic aspects , Consumers -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9349 , http://hdl.handle.net/10948/d1021126
- Description: Restaurateurs often assume that customers' online reviews of their dining experiences are a reflection of their dining preferences. This study finds this assumption not to be true. Online written reviews do not explain diners’ preferred dining experiences. In this study post-experience reactions captured in reviews are shown to be contextually different to established dining preferences. Results show online reviews to be most important in facilitating customer dining expectations, but not influencing customers’ preferences in dining experiences. Evidence gathered during the secondary research shows that in general, social media has become the great marketing equaliser in commerce. In the dining industry, restaurants cannot solely rely on traditional media in the initial attraction and retention of dining customers. Continuous interaction between the business and customers is increasingly necessary for restaurateurs to remain competitive and in-touch with customers’ needs. This study concentrates its research area on the post-experience evaluation phase as found on review websites, like TripAdvisor. TripAdvisor has especially become a popular means to perpetuate word-of-mouth opinions of dining experiences among prospective customers. Research shows clear evidence of the importance of other's online opinions in the consumer decision-making process. The main variables of the study, namely customer experiences, restaurant dining and social media, are theoretically explored within the disciplines of service management and customer behaviour. These theories have laid a sound foundation for the subsequent research methods followed. The main purpose of the study was using social media reviews from TripAdvisor to investigate dining experiences in the restaurant industry. The outcomes desired were: firstly to advise the restaurant industry about superior customer practices, secondly emphasising the importance for industry of social media use in the dining experience, and thirdly rendering clarification on the experience perceptions of customers about factors that might lead to ‘delight’ and ‘frustration’. This research centralises the constructs of delight and frustration factors, which are typically extremely emotional dining experiences for the customer, that have the common element of surprise. Methodologically, the research required two phases: firstly, the qualitative analysis of online user-generated content by content analysis. The global sample consisted of seven international cities, which included the best, worst and average-rated TripAdvisor restaurant reviews. The content analysis produced the theoretical base for the dining perception variables used in the empirical survey. In the second phase of the study, the global surveys administered resulted in measuring the general public’s perceptions of the delight and frustration factors of dining experiences. Subsequently, the research process required various quantitative data analyses to reach substantial results with inferences. The results and interpreted findings achieved were twofold: Firstly, from the content analysis: customers regard service quality as relatively unimportant in relation to the holistic dining experience. Customers regarded food and beverage quality as crucial in the dining experience. Value for money increasingly becomes an issue as customers become more frustrated, more so than when the dining was generally experienced as pleasant. Secondly, from the empirical data: mood and aesthetics are essential, especially when diners chose between their favourite restaurants. Further results show managing the service basics for restaurants is essential; this included welcoming, professional, attentive and friendly service. Service consistency has also proven to be imperative in customers’ perceptions. Results further show that different nationalities could perceive food quality and service reliability differently. In addition, men and women could perceive food quality, mood and aesthetics, and value for money differently. This study recommends various findings to the restaurant industry: most importantly that the post-experience reviews are contextually different to customers’ dining preferences. The factor determining the reputation of a restaurant is food quality and not so much service quality. Value for money should be associated with a specific service or product feature for it to be of meaningful consequence to the restaurateur.
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- Authors: Van Achterbergh, Leon
- Subjects: Hospitality industry -- Social aspects , Restaurants -- Social aspects , Social media -- Economic aspects , Consumers -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9349 , http://hdl.handle.net/10948/d1021126
- Description: Restaurateurs often assume that customers' online reviews of their dining experiences are a reflection of their dining preferences. This study finds this assumption not to be true. Online written reviews do not explain diners’ preferred dining experiences. In this study post-experience reactions captured in reviews are shown to be contextually different to established dining preferences. Results show online reviews to be most important in facilitating customer dining expectations, but not influencing customers’ preferences in dining experiences. Evidence gathered during the secondary research shows that in general, social media has become the great marketing equaliser in commerce. In the dining industry, restaurants cannot solely rely on traditional media in the initial attraction and retention of dining customers. Continuous interaction between the business and customers is increasingly necessary for restaurateurs to remain competitive and in-touch with customers’ needs. This study concentrates its research area on the post-experience evaluation phase as found on review websites, like TripAdvisor. TripAdvisor has especially become a popular means to perpetuate word-of-mouth opinions of dining experiences among prospective customers. Research shows clear evidence of the importance of other's online opinions in the consumer decision-making process. The main variables of the study, namely customer experiences, restaurant dining and social media, are theoretically explored within the disciplines of service management and customer behaviour. These theories have laid a sound foundation for the subsequent research methods followed. The main purpose of the study was using social media reviews from TripAdvisor to investigate dining experiences in the restaurant industry. The outcomes desired were: firstly to advise the restaurant industry about superior customer practices, secondly emphasising the importance for industry of social media use in the dining experience, and thirdly rendering clarification on the experience perceptions of customers about factors that might lead to ‘delight’ and ‘frustration’. This research centralises the constructs of delight and frustration factors, which are typically extremely emotional dining experiences for the customer, that have the common element of surprise. Methodologically, the research required two phases: firstly, the qualitative analysis of online user-generated content by content analysis. The global sample consisted of seven international cities, which included the best, worst and average-rated TripAdvisor restaurant reviews. The content analysis produced the theoretical base for the dining perception variables used in the empirical survey. In the second phase of the study, the global surveys administered resulted in measuring the general public’s perceptions of the delight and frustration factors of dining experiences. Subsequently, the research process required various quantitative data analyses to reach substantial results with inferences. The results and interpreted findings achieved were twofold: Firstly, from the content analysis: customers regard service quality as relatively unimportant in relation to the holistic dining experience. Customers regarded food and beverage quality as crucial in the dining experience. Value for money increasingly becomes an issue as customers become more frustrated, more so than when the dining was generally experienced as pleasant. Secondly, from the empirical data: mood and aesthetics are essential, especially when diners chose between their favourite restaurants. Further results show managing the service basics for restaurants is essential; this included welcoming, professional, attentive and friendly service. Service consistency has also proven to be imperative in customers’ perceptions. Results further show that different nationalities could perceive food quality and service reliability differently. In addition, men and women could perceive food quality, mood and aesthetics, and value for money differently. This study recommends various findings to the restaurant industry: most importantly that the post-experience reviews are contextually different to customers’ dining preferences. The factor determining the reputation of a restaurant is food quality and not so much service quality. Value for money should be associated with a specific service or product feature for it to be of meaningful consequence to the restaurateur.
- Full Text: