A model to improve the effectiveness of the Occupational Health and Safety Inspectorate function relative to South African construction
- Authors: Geminiani, Franco Luciano
- Date: 2008
- Subjects: Construction industry -- Safety measures
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9695 , http://hdl.handle.net/10948/719 , Construction industry -- Safety measures
- Description: Irrespective of all the efforts made by the Department of Labour (DoL) and other relevant stakeholders to improve the performance of Occupational Health and Safety (OH&S) in construction. In the Construction Industry, there is still a very high level of accidents and fatalities in South Africa. Injuries and accidents to workers do not help a community in any nation. The construction industry in South Africa is generally known to be one of the most hazardous and has one of the most dismal OH&S records among all industrial segments with an unacceptably high level of injuries and fatalities resulting in considerable human suffering. A doctoral study was recently conducted with the aim of investigating the effectiveness and performance of the DoL OH&S Inspectorate in South Africa. The empirical study was conducted among a range of stakeholders: civil engineering and building contractors; OH&S consultants; project managers; DoL inspectors; and designers by means of a questionnaire survey. The methodology adopted in this study included the exploratory and descriptive methods, which entails the technique of observation including the use of questionnaires and data analysis. The salient findings of the study are presented and elucidate that the DoL OH&S Inspectorate is not effective in terms of OH&S relative to the construction industry in South Africa. Conclusions and recommendations included expound that the DoL OH&S Inspectorate is not effectively conducting their duties reinforcing the need for a reviewed OH&S Inspectorate model framework. The proposed structured normative model consists of fundamental elements which would improve the effectiveness of the DoL OH&S Inspectorate. The findings of the study with recommendations are included.
- Full Text:
- Date Issued: 2008
- Authors: Geminiani, Franco Luciano
- Date: 2008
- Subjects: Construction industry -- Safety measures
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9695 , http://hdl.handle.net/10948/719 , Construction industry -- Safety measures
- Description: Irrespective of all the efforts made by the Department of Labour (DoL) and other relevant stakeholders to improve the performance of Occupational Health and Safety (OH&S) in construction. In the Construction Industry, there is still a very high level of accidents and fatalities in South Africa. Injuries and accidents to workers do not help a community in any nation. The construction industry in South Africa is generally known to be one of the most hazardous and has one of the most dismal OH&S records among all industrial segments with an unacceptably high level of injuries and fatalities resulting in considerable human suffering. A doctoral study was recently conducted with the aim of investigating the effectiveness and performance of the DoL OH&S Inspectorate in South Africa. The empirical study was conducted among a range of stakeholders: civil engineering and building contractors; OH&S consultants; project managers; DoL inspectors; and designers by means of a questionnaire survey. The methodology adopted in this study included the exploratory and descriptive methods, which entails the technique of observation including the use of questionnaires and data analysis. The salient findings of the study are presented and elucidate that the DoL OH&S Inspectorate is not effective in terms of OH&S relative to the construction industry in South Africa. Conclusions and recommendations included expound that the DoL OH&S Inspectorate is not effectively conducting their duties reinforcing the need for a reviewed OH&S Inspectorate model framework. The proposed structured normative model consists of fundamental elements which would improve the effectiveness of the DoL OH&S Inspectorate. The findings of the study with recommendations are included.
- Full Text:
- Date Issued: 2008
Development of a reciprocating aerofoil wind energy harvester
- Authors: Phillips, Russell Leslie
- Date: 2008
- Subjects: Windmills , Wind power , Wind turbines
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9622 , http://hdl.handle.net/10948/899 , Windmills , Wind power , Wind turbines
- Description: Cross flow wind turbines are not unique. The performance of Savonius and Darrieus turbines is well documented. Both share the advantage of being able to accept fluid flow from any direction. The Savonius is drag based and hence has poor power output while the Darrieus is lift based. Due to the fact that the Darrieus has fixed blades the fluid flow through the rotor does not result in optimal lift being generated at all points in the rotation circle. A drawback of the Darrieus system is that it has to operate at a high tip-to wind-speed ratio to obtain reasonable performance with the fixed blades. Deviation from a small optimal range of tip speed ratios results in poor performance. The Darrieus also has poor starting torque. The research conducted in this project focused on overcoming the shortcomings of other turbines and developing an effective cross flow turbine capable of good performance. A number of different concepts were experimented with, however all were based on a symmetrical aerofoil presented to the actual relative airflow at an angle that would produce the highest lift force at all times. The lift force was then utilized to generate movement and to do work on an electrical generator. All concepts contemplated were researched to ascertain their appropriateness for the intended application. During development of the final experimental platform and after lodging of a provisional patent (RSA 2007/00927) it was ascertained that the design shared some similarities with an American patent 5503525 dated 28/4/1994. This patent employed complex electronic sensing and control equipment for control of blade angle. This was thought to be overly complex and costly, particularly for small scale wind energy generation applications and a simpler mechanical solution was sought in the design of the final experimental platform used in this project. The design of the mechanical control system was refined in an attempt to make it simpler, more durable and employ the least number of moving parts. Literature studies and patent searches conducted, suggested that the mechanical control system as developed for the final experimental platform was unique. The enormous variation in the power available from the wind at the different wind speeds likely to be encountered by the device necessitated some means of control. In high wind conditions control of the amount of wind power into the device was deemed to be the preferable means of control. A number of different concepts to achieve this were devised and tested. The final concept employed limited the tail angle deflection and hence the lift produced by the aerofoils. This resulted in a seamless “throttle” control allowing the device to be used in any wind strength by adjusting the control to a position that resulted in the device receiving a suitable amount of power from the wind. The outcome of performance tests conducted indicated that the device has the potential to be developed into a viable wind turbine for both small and large scale applications. The ability to control the power input from the wind to the machine from zero to a maximum is considered to be one of the most beneficial outcomes of this project and together with the quiet operation and low speed, are considered the main advantages of the device over existing wind turbine designs. The possibilities of using the device to compress air for energy storage are exciting avenues that warrant further research.
- Full Text:
- Date Issued: 2008
- Authors: Phillips, Russell Leslie
- Date: 2008
- Subjects: Windmills , Wind power , Wind turbines
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9622 , http://hdl.handle.net/10948/899 , Windmills , Wind power , Wind turbines
- Description: Cross flow wind turbines are not unique. The performance of Savonius and Darrieus turbines is well documented. Both share the advantage of being able to accept fluid flow from any direction. The Savonius is drag based and hence has poor power output while the Darrieus is lift based. Due to the fact that the Darrieus has fixed blades the fluid flow through the rotor does not result in optimal lift being generated at all points in the rotation circle. A drawback of the Darrieus system is that it has to operate at a high tip-to wind-speed ratio to obtain reasonable performance with the fixed blades. Deviation from a small optimal range of tip speed ratios results in poor performance. The Darrieus also has poor starting torque. The research conducted in this project focused on overcoming the shortcomings of other turbines and developing an effective cross flow turbine capable of good performance. A number of different concepts were experimented with, however all were based on a symmetrical aerofoil presented to the actual relative airflow at an angle that would produce the highest lift force at all times. The lift force was then utilized to generate movement and to do work on an electrical generator. All concepts contemplated were researched to ascertain their appropriateness for the intended application. During development of the final experimental platform and after lodging of a provisional patent (RSA 2007/00927) it was ascertained that the design shared some similarities with an American patent 5503525 dated 28/4/1994. This patent employed complex electronic sensing and control equipment for control of blade angle. This was thought to be overly complex and costly, particularly for small scale wind energy generation applications and a simpler mechanical solution was sought in the design of the final experimental platform used in this project. The design of the mechanical control system was refined in an attempt to make it simpler, more durable and employ the least number of moving parts. Literature studies and patent searches conducted, suggested that the mechanical control system as developed for the final experimental platform was unique. The enormous variation in the power available from the wind at the different wind speeds likely to be encountered by the device necessitated some means of control. In high wind conditions control of the amount of wind power into the device was deemed to be the preferable means of control. A number of different concepts to achieve this were devised and tested. The final concept employed limited the tail angle deflection and hence the lift produced by the aerofoils. This resulted in a seamless “throttle” control allowing the device to be used in any wind strength by adjusting the control to a position that resulted in the device receiving a suitable amount of power from the wind. The outcome of performance tests conducted indicated that the device has the potential to be developed into a viable wind turbine for both small and large scale applications. The ability to control the power input from the wind to the machine from zero to a maximum is considered to be one of the most beneficial outcomes of this project and together with the quiet operation and low speed, are considered the main advantages of the device over existing wind turbine designs. The possibilities of using the device to compress air for energy storage are exciting avenues that warrant further research.
- Full Text:
- Date Issued: 2008
Practical and scalable synthesis of N-Alkyl-N,N'Diacylhydrazines
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
Selective para-funtionalization of phenol
- Authors: Indurkar, Jayant R
- Date: 2008
- Subjects: Phenol
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10402 , http://hdl.handle.net/10948/710 , Phenol
- Description: In previous work done in our laboratories, a method was discovered to produce phenolic mono-ethers from 4-hydroxyacetophenone and other 4-hydroxyketones by treating with ammonium peroxy-disulfate in an alcohol as a reaction solvent and in the presence of concentrated sulphuric acid or other strong protonic acids. Since this method of producing 4-alkoxyphenol ethers provides a very convenient way to modify hydroquinone and substituted hydroquinones to produce a variety of phenol mono-ethers, it was of interest to study the general scope of this reaction, including a more detailed investigation of the reaction mechanism. In previous studies, it was suggested that interaction between the aromatic pi-system of hydroquinone and the cyclohexa-2,5-diene structure of benzoquinone plays a significant role during the reaction. It was therefore of interest to investigate whether other compounds that are also capable of forming the cyclohexa-2,5-diene structure, will interact in a manner analogous to the hydroquinone/benzoquinone couple. Two specific compounds were selected for this purpose, namely 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one . The scope of etherification reactions of hydroquinone-benzoquinone or hydroquinone/benzoquinone like substrates such as 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one in the presence of acid catalyst and alcohols was investigated. These studies showed that hydroquinone, 4- nitrosophenol and 4-(diphenylmethylene)cyclohexa-2,5-dien-1-one successfully affords the phenolic ethers in good to excellent yield. For example, quantitative yield of 4-methoxyphenol could be obtained from a 1:1 mixture of hydroquinone and benzoquinone at the reflux temperature of methanol. In order to study the reaction mechanism, the cross-over reaction between tertbutylhydroquinone and benzoquinone (or hydroquinone and tertbutylbenzoquinone) was studied in detail. The results of these cross-over reactions were used to propose a mechanistic pathway that could explain the requirement for pi-interaction between the hydroquinone and benzoquinone molecules, the role of the acid catalyst, as well as the relative rates of hydroquinone and benzoquinone consumption during these reactions. The mechanism was also capable of explaining all the reaction products observed during these reactions. The work was then extended to reactions of 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one with methanol in the presence of either hydroquinone or benzoquinone. The results of these investigations strongly suggest the presence of similar interactions between these molecules that also influence the outcome of the reactions. The exploitation of pi-interactions between two molecules of these types investigated during this work opens an interesting field of chemistry. Clearly, the level of understanding developed during this work is only beginning to address this interesting field of chemistry and much work will need to be done to gain a fuller understanding of the chemistry involved as well as the potential synthetic value of these interactions.
- Full Text:
- Date Issued: 2008
- Authors: Indurkar, Jayant R
- Date: 2008
- Subjects: Phenol
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10402 , http://hdl.handle.net/10948/710 , Phenol
- Description: In previous work done in our laboratories, a method was discovered to produce phenolic mono-ethers from 4-hydroxyacetophenone and other 4-hydroxyketones by treating with ammonium peroxy-disulfate in an alcohol as a reaction solvent and in the presence of concentrated sulphuric acid or other strong protonic acids. Since this method of producing 4-alkoxyphenol ethers provides a very convenient way to modify hydroquinone and substituted hydroquinones to produce a variety of phenol mono-ethers, it was of interest to study the general scope of this reaction, including a more detailed investigation of the reaction mechanism. In previous studies, it was suggested that interaction between the aromatic pi-system of hydroquinone and the cyclohexa-2,5-diene structure of benzoquinone plays a significant role during the reaction. It was therefore of interest to investigate whether other compounds that are also capable of forming the cyclohexa-2,5-diene structure, will interact in a manner analogous to the hydroquinone/benzoquinone couple. Two specific compounds were selected for this purpose, namely 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one . The scope of etherification reactions of hydroquinone-benzoquinone or hydroquinone/benzoquinone like substrates such as 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one in the presence of acid catalyst and alcohols was investigated. These studies showed that hydroquinone, 4- nitrosophenol and 4-(diphenylmethylene)cyclohexa-2,5-dien-1-one successfully affords the phenolic ethers in good to excellent yield. For example, quantitative yield of 4-methoxyphenol could be obtained from a 1:1 mixture of hydroquinone and benzoquinone at the reflux temperature of methanol. In order to study the reaction mechanism, the cross-over reaction between tertbutylhydroquinone and benzoquinone (or hydroquinone and tertbutylbenzoquinone) was studied in detail. The results of these cross-over reactions were used to propose a mechanistic pathway that could explain the requirement for pi-interaction between the hydroquinone and benzoquinone molecules, the role of the acid catalyst, as well as the relative rates of hydroquinone and benzoquinone consumption during these reactions. The mechanism was also capable of explaining all the reaction products observed during these reactions. The work was then extended to reactions of 4-nitrosophenol and 4- (diphenylmethylene)cyclohexa-2,5-dien-1-one with methanol in the presence of either hydroquinone or benzoquinone. The results of these investigations strongly suggest the presence of similar interactions between these molecules that also influence the outcome of the reactions. The exploitation of pi-interactions between two molecules of these types investigated during this work opens an interesting field of chemistry. Clearly, the level of understanding developed during this work is only beginning to address this interesting field of chemistry and much work will need to be done to gain a fuller understanding of the chemistry involved as well as the potential synthetic value of these interactions.
- Full Text:
- Date Issued: 2008
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