Comparison of experimental ponds for the treatment of dye wastewater under controlled and semi-natural conditions
- Yaseen, Dina A., Scholz, Miklas
- Authors: Yaseen, Dina A. , Scholz, Miklas
- Date: 2017
- Subjects: Basic Red 46 , Biological treatment , Environmental conditions
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/256743 , uj:26956 , Citation: Yaseen, D.A. & Scholz, M. 2017. Comparison of experimental ponds for the treatment of dye wastewater under controlled and semi-natural conditions. Environ Sci Pollut Res (2017) 24:16031–16040 DOI 10.1007/s11356-017-9245-5
- Description: Abstract: This study compares the performance of simulated shallow ponds vegetated with Lemna minor L. under controlled and semi-natural conditions for the treatment of simulated wastewater containing textile dyes. The objectives were to assess the water quality outflow parameters, the potential of L. minor concerning the removal of chemical oxygen demand (COD) and four azo dyes (Acid blue 113, reactive blue 198, Direct Orange 46 and Basic Red 46) and the plants’ growth rate. Findings show that all mean outflow values of COD, total dissolved solids (TDS) and electrical conductivity (EC) were significantly (p < 0.05) lower within the outdoor compared to the indoor experiment except the dissolved oxygen (DO). The COD removal was low for both experiments. The outflow TDS values were acceptable for all ponds. The pond systems were able to reduce only BR46 significantly (p < 0.05) for the tested boundary conditions. Removals under laboratory conditions were better than those for semi-natural environments, indicating the suitability of operating the pond system as a polishing step in warmer regions. The mean outflow values of zinc and copper were below the thresholds set for drinking and irrigation waters and acceptable for L. minor. The dyes inhibited the growth of the L. minor.
- Full Text:
- Authors: Yaseen, Dina A. , Scholz, Miklas
- Date: 2017
- Subjects: Basic Red 46 , Biological treatment , Environmental conditions
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/256743 , uj:26956 , Citation: Yaseen, D.A. & Scholz, M. 2017. Comparison of experimental ponds for the treatment of dye wastewater under controlled and semi-natural conditions. Environ Sci Pollut Res (2017) 24:16031–16040 DOI 10.1007/s11356-017-9245-5
- Description: Abstract: This study compares the performance of simulated shallow ponds vegetated with Lemna minor L. under controlled and semi-natural conditions for the treatment of simulated wastewater containing textile dyes. The objectives were to assess the water quality outflow parameters, the potential of L. minor concerning the removal of chemical oxygen demand (COD) and four azo dyes (Acid blue 113, reactive blue 198, Direct Orange 46 and Basic Red 46) and the plants’ growth rate. Findings show that all mean outflow values of COD, total dissolved solids (TDS) and electrical conductivity (EC) were significantly (p < 0.05) lower within the outdoor compared to the indoor experiment except the dissolved oxygen (DO). The COD removal was low for both experiments. The outflow TDS values were acceptable for all ponds. The pond systems were able to reduce only BR46 significantly (p < 0.05) for the tested boundary conditions. Removals under laboratory conditions were better than those for semi-natural environments, indicating the suitability of operating the pond system as a polishing step in warmer regions. The mean outflow values of zinc and copper were below the thresholds set for drinking and irrigation waters and acceptable for L. minor. The dyes inhibited the growth of the L. minor.
- Full Text:
A new multi-swarm multi-objective particle swarm optimization based power and supply voltage unbalance optimization of three-phase submerged arc furnace
- Authors: Sun, Yanxia , Wang, Zenghui
- Date: 2015
- Subjects: Multi-objective optimization , Particle swarm optimization , Submerged arc furnace , Power optimization , Supply voltage unbalances
- Language: English
- Type: Conference proceedings
- Identifier: http://ujcontent.uj.ac.za8080/10210/390077 , http://hdl.handle.net/10210/20559 , uj:16112 , Citation: Sun, Y. & Wang, Z. 2015. A new multi-swarm multi-objective particle swarm optimization based power and supply voltage unbalance optimization of three-phase submerged arc furnace. Proceedings of the Sixth International Conference on Swarm Intelligence (ICSI 2015), Beijing, China, 25-29, June 2015.
- Description: Abstract: To improve the production ability of a three-phase submerged arc furnace (SAF), it is necessary to maximize the power input; minimize the supply voltage unbalances to reduce the side effect of the power grids. In this paper, maximizing the power input and minimum the supply voltage unbalances based on a proposed multi-swarm multi-objective particle swarm optimization algorithm are focused on. It is necessary to have objective functions when an optimization algorithm is applied. However, it is difficult to get the mathematic model of a three-phase submerged arc furnace according to its mechanisms because the system is complex and there are many disturbances. The neural networks (NN) have been applied since its ability can be used as an arbitrary function approximation mechanism based on the observed data. Based on the Pareto front, a multi-swarm multi-objective particle swarm optimization is pro-posed, which can be used to optimize the NN model of the three-phase SAF. The optimization results showed the efficiency of the proposed method.
- Full Text:
- Authors: Sun, Yanxia , Wang, Zenghui
- Date: 2015
- Subjects: Multi-objective optimization , Particle swarm optimization , Submerged arc furnace , Power optimization , Supply voltage unbalances
- Language: English
- Type: Conference proceedings
- Identifier: http://ujcontent.uj.ac.za8080/10210/390077 , http://hdl.handle.net/10210/20559 , uj:16112 , Citation: Sun, Y. & Wang, Z. 2015. A new multi-swarm multi-objective particle swarm optimization based power and supply voltage unbalance optimization of three-phase submerged arc furnace. Proceedings of the Sixth International Conference on Swarm Intelligence (ICSI 2015), Beijing, China, 25-29, June 2015.
- Description: Abstract: To improve the production ability of a three-phase submerged arc furnace (SAF), it is necessary to maximize the power input; minimize the supply voltage unbalances to reduce the side effect of the power grids. In this paper, maximizing the power input and minimum the supply voltage unbalances based on a proposed multi-swarm multi-objective particle swarm optimization algorithm are focused on. It is necessary to have objective functions when an optimization algorithm is applied. However, it is difficult to get the mathematic model of a three-phase submerged arc furnace according to its mechanisms because the system is complex and there are many disturbances. The neural networks (NN) have been applied since its ability can be used as an arbitrary function approximation mechanism based on the observed data. Based on the Pareto front, a multi-swarm multi-objective particle swarm optimization is pro-posed, which can be used to optimize the NN model of the three-phase SAF. The optimization results showed the efficiency of the proposed method.
- Full Text:
Fully connected multi-objective particle swarm optimizer based on neural network
- Authors: Wang, Zenghui , Sun, Yanxia
- Date: 2011
- Subjects: Multi-objective optimization , Particle swarm optimization , Neural network , Pareto front , Non domination
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22087 , uj:16157 , Citation: Wang, Z. & Sun, Y. 2011. Fully connected multi-objective particle swarm optimizer based on neural network. Lecture notes in computer science 6838:170-177.
- Description: Abstract: In this paper, a new model for multi-objective particle swarm optimization (MOPSO) is proposed. In this model, each particle’s behavior is influenced by the best experience among its neighbors, its own best experience and all its components. The influence among different components of particles is implemented by the on-line training of a multi-input Multi-output back propagation (BP) neural network. The inputs and outputs of the BP neural network are the particle position and its the ’gradient descent’ direction vector to the less objective value according to the definition of no-domination, respectively. Therefore, the new structured MOPSO model is called a fully connected multi-objective particle swarm optimizer (FCMOPSO). Simulation results and comparisons with exiting MOPSOs demonstrate that the proposed FCMOPSO is more stable and can improve the optimization performance. , Originally presented at Fourth International Conference on Information and Computing (ICIC 2011), Phuket Island, Thailand 25 – 27 April 2011.
- Full Text:
- Authors: Wang, Zenghui , Sun, Yanxia
- Date: 2011
- Subjects: Multi-objective optimization , Particle swarm optimization , Neural network , Pareto front , Non domination
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22087 , uj:16157 , Citation: Wang, Z. & Sun, Y. 2011. Fully connected multi-objective particle swarm optimizer based on neural network. Lecture notes in computer science 6838:170-177.
- Description: Abstract: In this paper, a new model for multi-objective particle swarm optimization (MOPSO) is proposed. In this model, each particle’s behavior is influenced by the best experience among its neighbors, its own best experience and all its components. The influence among different components of particles is implemented by the on-line training of a multi-input Multi-output back propagation (BP) neural network. The inputs and outputs of the BP neural network are the particle position and its the ’gradient descent’ direction vector to the less objective value according to the definition of no-domination, respectively. Therefore, the new structured MOPSO model is called a fully connected multi-objective particle swarm optimizer (FCMOPSO). Simulation results and comparisons with exiting MOPSOs demonstrate that the proposed FCMOPSO is more stable and can improve the optimization performance. , Originally presented at Fourth International Conference on Information and Computing (ICIC 2011), Phuket Island, Thailand 25 – 27 April 2011.
- Full Text:
Experimental analyses to investigate the feasibility and effectiveness in using heat pipe-embedded drills
- Zhu, Lin, Jen, Tien-Chien, Yin, Cheng-Long, Kong, Xiao-Ling, Yen, Yi-Hsin
- Authors: Zhu, Lin , Jen, Tien-Chien , Yin, Cheng-Long , Kong, Xiao-Ling , Yen, Yi-Hsin
- Date: 2012
- Subjects: Heat pipe cooling , Drilling , Heat pipes
- Type: Article
- Identifier: uj:5289 , http://hdl.handle.net/10210/14958
- Description: This paper presents an experimental investigation to verify the feasibility and effectiveness of heat pipe cooling in drilling operations. The basic idea is to insert a heat pipe at the center of the drill tool with the evaporator close to the drill tip and the condenser at the end of the drill. Consequently, the heat generated at the tool–chip interface can be removed by convection heat transfer. Experimental studies were involved in three cases, including solid drill without coolant, solid drill with coolant, and heat pipe drill. Drilling tests were conducted on a CNC machining center with full immersion cutting. The cast iron square block was used as the workpiece, and the high-speed steel was chosen for the drill tool material. Flank wear is considered as the criterion for tool failure, and the wear was measured using a Hisomet II Toolmaker’s microscope. The tests were conducted until the drill was rejected when an average flank wear greater than 0.10 mm was recorded. The results demonstrate that using a heat pipe in the drilling process can effectively perform thermal management comparable to the flooding coolant cooling used pervasively in the manufacturing industry, extending the tool life of the drill.
- Full Text:
- Authors: Zhu, Lin , Jen, Tien-Chien , Yin, Cheng-Long , Kong, Xiao-Ling , Yen, Yi-Hsin
- Date: 2012
- Subjects: Heat pipe cooling , Drilling , Heat pipes
- Type: Article
- Identifier: uj:5289 , http://hdl.handle.net/10210/14958
- Description: This paper presents an experimental investigation to verify the feasibility and effectiveness of heat pipe cooling in drilling operations. The basic idea is to insert a heat pipe at the center of the drill tool with the evaporator close to the drill tip and the condenser at the end of the drill. Consequently, the heat generated at the tool–chip interface can be removed by convection heat transfer. Experimental studies were involved in three cases, including solid drill without coolant, solid drill with coolant, and heat pipe drill. Drilling tests were conducted on a CNC machining center with full immersion cutting. The cast iron square block was used as the workpiece, and the high-speed steel was chosen for the drill tool material. Flank wear is considered as the criterion for tool failure, and the wear was measured using a Hisomet II Toolmaker’s microscope. The tests were conducted until the drill was rejected when an average flank wear greater than 0.10 mm was recorded. The results demonstrate that using a heat pipe in the drilling process can effectively perform thermal management comparable to the flooding coolant cooling used pervasively in the manufacturing industry, extending the tool life of the drill.
- Full Text:
RF IC performance optimization by synthesizing optimum inductors
- Božanić, Mladen, Sinha, Saurabh
- Authors: Božanić, Mladen , Sinha, Saurabh
- Date: 2015
- Subjects: Optimal system design , Optimum inductors , Radio frequency
- Type: Book chapter
- Identifier: uj:5223 , ISBN 978-3-319-19871-2 , http://hdl.handle.net/10210/14509
- Description: Even with optimal system design and careful choice of topology for a particular RF application, large amounts of energy are often wasted due to low-quality passives, especially inductors. Inductors have traditionally been difficult to integrate due to their inherent low quality factors and modelling complexity. Furthermore, although many different inductor configurations are available for an RF designer to explore, support for integrated inductors in electronic design automation tools and process design kits has been very limited in the past. In this chapter, a recent advance in technology-aware integrated inductor design is presented, where drawbacks of the integrated inductor design are addressed by introducing an equation-based inductor synthesis algorithm. The intelligent computation technique aims to allow RF designers to optimize integrated inductors, given the inductor center frequency dictated by the device application, and geometry constraints. This does not only lay down a foundation for system-level RF circuit performance optimization, but, because inductors are often the largest parts of an RF system, it also allows for optimal usage of chip real estate.
- Full Text:
- Authors: Božanić, Mladen , Sinha, Saurabh
- Date: 2015
- Subjects: Optimal system design , Optimum inductors , Radio frequency
- Type: Book chapter
- Identifier: uj:5223 , ISBN 978-3-319-19871-2 , http://hdl.handle.net/10210/14509
- Description: Even with optimal system design and careful choice of topology for a particular RF application, large amounts of energy are often wasted due to low-quality passives, especially inductors. Inductors have traditionally been difficult to integrate due to their inherent low quality factors and modelling complexity. Furthermore, although many different inductor configurations are available for an RF designer to explore, support for integrated inductors in electronic design automation tools and process design kits has been very limited in the past. In this chapter, a recent advance in technology-aware integrated inductor design is presented, where drawbacks of the integrated inductor design are addressed by introducing an equation-based inductor synthesis algorithm. The intelligent computation technique aims to allow RF designers to optimize integrated inductors, given the inductor center frequency dictated by the device application, and geometry constraints. This does not only lay down a foundation for system-level RF circuit performance optimization, but, because inductors are often the largest parts of an RF system, it also allows for optimal usage of chip real estate.
- Full Text:
The effects of microstructural evolution and mechanical behaviour of unalloyed medium carbon steel (EN8 Steel) after subsequent heat treatment
- Sanusi, Kazeem O., Moleejane, Cullen M., Ayodele, Olukayode L., Oliverm Graeme J.
- Authors: Sanusi, Kazeem O. , Moleejane, Cullen M. , Ayodele, Olukayode L. , Oliverm Graeme J.
- Date: 2015
- Subjects: Carbon steel - Mechanical properties , Carbon steel - Heat treatment , Steel - Testing
- Language: English
- Type: Journal article
- Identifier: http://hdl.handle.net/10210/55746 , uj:16307 , Sanusi, K.O. et al. 2015. The effects of microstructural evolution and mechanical behaviour of unalloyed medium carbon steel (EN8 Steel) after subsequent heat treatment. Transactions on Engineering Technologies. DOI: 10.1007/978-94-017-7236-5_37
- Description: Abstract: The effect of microstructural evolution on mechanical properties of unalloyed medium carbon (EN8) steel with emphasis on the effects of grain size within solid phase mixtures and the mechanical response of the material is investigated and reported. Specimens with a range of microstructures (grain size and phase) were prepared by heat treatment. The microstructures were carefully characterized using both optical electronic microscope (OEM) and scanning electron microscope (SEM) and the mechanical properties were studied using tensile and hardness tests. The results indicated that structural parameter that directly controls the yield strength, the ultimate tensile strength and elongation at failure have some influence (direct or indirect) on the stress flow and formability of the material.
- Full Text: false
- Authors: Sanusi, Kazeem O. , Moleejane, Cullen M. , Ayodele, Olukayode L. , Oliverm Graeme J.
- Date: 2015
- Subjects: Carbon steel - Mechanical properties , Carbon steel - Heat treatment , Steel - Testing
- Language: English
- Type: Journal article
- Identifier: http://hdl.handle.net/10210/55746 , uj:16307 , Sanusi, K.O. et al. 2015. The effects of microstructural evolution and mechanical behaviour of unalloyed medium carbon steel (EN8 Steel) after subsequent heat treatment. Transactions on Engineering Technologies. DOI: 10.1007/978-94-017-7236-5_37
- Description: Abstract: The effect of microstructural evolution on mechanical properties of unalloyed medium carbon (EN8) steel with emphasis on the effects of grain size within solid phase mixtures and the mechanical response of the material is investigated and reported. Specimens with a range of microstructures (grain size and phase) were prepared by heat treatment. The microstructures were carefully characterized using both optical electronic microscope (OEM) and scanning electron microscope (SEM) and the mechanical properties were studied using tensile and hardness tests. The results indicated that structural parameter that directly controls the yield strength, the ultimate tensile strength and elongation at failure have some influence (direct or indirect) on the stress flow and formability of the material.
- Full Text: false
Numerical investigation of the structure of a silicon six-wafer micro-combustor under the effect of hydrogen/air ratio
- Zhu, Lin, Jen, Tien-Chien, Ji, Ying-Feng, Yin, Cheng-Long, Zhu, Mei
- Authors: Zhu, Lin , Jen, Tien-Chien , Ji, Ying-Feng , Yin, Cheng-Long , Zhu, Mei
- Date: 2010
- Subjects: Micro-combustors
- Type: Article
- Identifier: uj:5266 , http://hdl.handle.net/10210/14935
- Description: Research reports indicate that sufficiently high equivalence ratio of the hydrogen/air mixture leads to the upstream burning in the recirculation jacket, possibly damaging the micro- combustor due to the high wall temperature. This work investigates the influences of the equivalence ratio of the mixture on the structure of a micro-combustor device. Numerical simulation approaches focused on the structural design of the micro-combustor with the flame burning in the recirculation jacket. Combustion characteristics of the combustor were first analysed based on 2D computational Fluid Dynamics (CFD), and then thermo-mechanical analysis on the combustor was carried out by means of 3D Finite Element Analysis (FEA) method. The results showed that the most dangerous locations where the critical failure could possibly occur lay at the burning areas in the recirculation jacket due to the poor bonding, the high temperature and the residual stress. The results of this study can be used for the design and improvement of the micro-combustors.
- Full Text:
- Authors: Zhu, Lin , Jen, Tien-Chien , Ji, Ying-Feng , Yin, Cheng-Long , Zhu, Mei
- Date: 2010
- Subjects: Micro-combustors
- Type: Article
- Identifier: uj:5266 , http://hdl.handle.net/10210/14935
- Description: Research reports indicate that sufficiently high equivalence ratio of the hydrogen/air mixture leads to the upstream burning in the recirculation jacket, possibly damaging the micro- combustor due to the high wall temperature. This work investigates the influences of the equivalence ratio of the mixture on the structure of a micro-combustor device. Numerical simulation approaches focused on the structural design of the micro-combustor with the flame burning in the recirculation jacket. Combustion characteristics of the combustor were first analysed based on 2D computational Fluid Dynamics (CFD), and then thermo-mechanical analysis on the combustor was carried out by means of 3D Finite Element Analysis (FEA) method. The results showed that the most dangerous locations where the critical failure could possibly occur lay at the burning areas in the recirculation jacket due to the poor bonding, the high temperature and the residual stress. The results of this study can be used for the design and improvement of the micro-combustors.
- Full Text:
Lexicographic multi-objective optimization of thermoacoustic refrigerator’s stack
- Tartibu, L.K., Sun, B., Kaunda, M.A.E.
- Authors: Tartibu, L.K. , Sun, B. , Kaunda, M.A.E.
- Date: 2015
- Subjects: Thermoacoustic , Stack , Cooling Load , Coefficient of performance , Multi-objective optimization , GAMS
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/17624 , uj:15907 , ISSN: 0947-7411 , Citation: Tartibu, L.K., Sun, B. & Kaunda M.A.E. 2015. Lexicographic multi-objective optimisation of thermoacoustic refrigerator’s stack. Journal of Heat and Mass Transfer. 51(5): 649-660. DOI: 10.1007/s00231-014-1440-z. , DOI: 10.1007/s00231-014-1440-z
- Description: Abstract: This work develops a novel mathematical programming model to optimize the performance of a simple thermoacoustic refrigerator (TAR). This study aims to optimize the geometric parameters namely the stack position, the stack length, the blockage ratio and the plate spacing involved in designing TARs. System parameters and constraints that capture the underlying thermoacoustic dynamics have been used to define the models. The cooling load, the coefficient of performance and the acoustic power loss have been used to measure the performance of the device. The optimization task is formulated as a three-criterion nonlinear programming problem with discontinuous derivatives (DNLP). Since we optimize multiple objectives simultaneously, each objective component has been given a weighting factor to provide appropriate user-defined emphasis. A practical example is given to illustrate the approach. We have determined a design statement of a stack describing how the geometrical parameters describing would change if emphasis is given to one objective in particular. We also considered optimization of multiple objectives components simultaneously and identify global optimal solutions describing the stack geometry using a lexicographic multiobjective optimization scheme. Additionally, this approach illustrates the difference between a design for maximum cooling and best coefficient of performance of a simple TAR.
- Full Text:
- Authors: Tartibu, L.K. , Sun, B. , Kaunda, M.A.E.
- Date: 2015
- Subjects: Thermoacoustic , Stack , Cooling Load , Coefficient of performance , Multi-objective optimization , GAMS
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/17624 , uj:15907 , ISSN: 0947-7411 , Citation: Tartibu, L.K., Sun, B. & Kaunda M.A.E. 2015. Lexicographic multi-objective optimisation of thermoacoustic refrigerator’s stack. Journal of Heat and Mass Transfer. 51(5): 649-660. DOI: 10.1007/s00231-014-1440-z. , DOI: 10.1007/s00231-014-1440-z
- Description: Abstract: This work develops a novel mathematical programming model to optimize the performance of a simple thermoacoustic refrigerator (TAR). This study aims to optimize the geometric parameters namely the stack position, the stack length, the blockage ratio and the plate spacing involved in designing TARs. System parameters and constraints that capture the underlying thermoacoustic dynamics have been used to define the models. The cooling load, the coefficient of performance and the acoustic power loss have been used to measure the performance of the device. The optimization task is formulated as a three-criterion nonlinear programming problem with discontinuous derivatives (DNLP). Since we optimize multiple objectives simultaneously, each objective component has been given a weighting factor to provide appropriate user-defined emphasis. A practical example is given to illustrate the approach. We have determined a design statement of a stack describing how the geometrical parameters describing would change if emphasis is given to one objective in particular. We also considered optimization of multiple objectives components simultaneously and identify global optimal solutions describing the stack geometry using a lexicographic multiobjective optimization scheme. Additionally, this approach illustrates the difference between a design for maximum cooling and best coefficient of performance of a simple TAR.
- Full Text:
The South African industry use of Mössbauer spectroscopy to solve operational problems
- Waanders, Frans B., Mulaba-Bafubiandi, Antoinne F., Lodya, Lonzeche
- Authors: Waanders, Frans B. , Mulaba-Bafubiandi, Antoinne F. , Lodya, Lonzeche
- Date: 2014
- Subjects: Mössbauer spectroscopy , Fischer Tropsch process , Mineralogy - South Africa
- Type: Article
- Identifier: uj:4769 , http://hdl.handle.net/10210/11944
- Description: South Africa is a country that is very rich in mineral resources but the use of Mössbauer spectroscopy to solve operational industrial problems is however very limited. In the Bushveld Igneous Complex the main minerals extracted from the ore are the platinum group metals and chromium, but secondary recovery of base metals such as nickel, copper and cobalt forms an integral part of the process. Losses of nickel in the slag can amount to about 4%and subsequent a slag cleaning furnace is used to reduce the loss to less than 0.5% nickel oxide. The Fe2+/Fe3+ ratio and mineralogy was used to determine the partial oxygen pressure in the furnaces and also the efficiency of the nickel recovery. From the Mössbauer results, augmented with XRD, SEM, EMP-WDX and MLA analyses, optimum conditions were determined to ensure minimum metal losses. The use of Mössbauer spectroscopy in the coal industry, to investigate mineral changes that occur during its use, is also of importance. The main minerals present in coal were determined with the aid of various techniques, such as Mössbauer, XRD, SEM and HR-TEM, with the major iron minerals found to be pyrite, illite, ankerite and jarosite. A large quantity of coal is used to produce syngas via gasification plants for the production of synthetic fuels. The change of the mineral matter during gasification was studied and the changes occurring during the gasification process were followed. The syngas produced, is further treated by means of the Fischer–Tropsch process where an iron catalyst is incorporated in the process. The usefulness and fouling of the catalyst is being studied with the aid of Mössbauer spectroscopy.
- Full Text: false
- Authors: Waanders, Frans B. , Mulaba-Bafubiandi, Antoinne F. , Lodya, Lonzeche
- Date: 2014
- Subjects: Mössbauer spectroscopy , Fischer Tropsch process , Mineralogy - South Africa
- Type: Article
- Identifier: uj:4769 , http://hdl.handle.net/10210/11944
- Description: South Africa is a country that is very rich in mineral resources but the use of Mössbauer spectroscopy to solve operational industrial problems is however very limited. In the Bushveld Igneous Complex the main minerals extracted from the ore are the platinum group metals and chromium, but secondary recovery of base metals such as nickel, copper and cobalt forms an integral part of the process. Losses of nickel in the slag can amount to about 4%and subsequent a slag cleaning furnace is used to reduce the loss to less than 0.5% nickel oxide. The Fe2+/Fe3+ ratio and mineralogy was used to determine the partial oxygen pressure in the furnaces and also the efficiency of the nickel recovery. From the Mössbauer results, augmented with XRD, SEM, EMP-WDX and MLA analyses, optimum conditions were determined to ensure minimum metal losses. The use of Mössbauer spectroscopy in the coal industry, to investigate mineral changes that occur during its use, is also of importance. The main minerals present in coal were determined with the aid of various techniques, such as Mössbauer, XRD, SEM and HR-TEM, with the major iron minerals found to be pyrite, illite, ankerite and jarosite. A large quantity of coal is used to produce syngas via gasification plants for the production of synthetic fuels. The change of the mineral matter during gasification was studied and the changes occurring during the gasification process were followed. The syngas produced, is further treated by means of the Fischer–Tropsch process where an iron catalyst is incorporated in the process. The usefulness and fouling of the catalyst is being studied with the aid of Mössbauer spectroscopy.
- Full Text: false
Adaptation strategy to mitigate the impact of climate change on water resources in arid and semi-arid regions : a case study
- Mohammed, Ruqayah, Scholz, Miklas
- Authors: Mohammed, Ruqayah , Scholz, Miklas
- Date: 2017
- Subjects: Alteration measure , Precipitation , Reservoir operation and reliability
- Type: Article
- Identifier: http://hdl.handle.net/10210/226384 , uj:22888 , Citation: Mohammed, R. & Scholz, M. 2017. Adaptation strategy to mitigate the impact of climate change on water resources in arid and semi-arid regions : a case study. Water Resour Manage, 27. DOI 10.1007/s11269-017-1685-7. , ISSN: 0920-4741
- Description: Abstract: Climate change and drought phenomena impacts have become a growing concern for water resources engineers and policy makers, mainly in arid and semi-arid areas. This study aims to contribute to the development of a decision support tool to prepare water resources managers and planners for climate change adaptation. The Hydrologiska Byråns Vattenbalansavdelning (The Water Balance Department of the Hydrological Bureau) hydrologic model was used to define the boundary conditions for the reservoir capacity yield model comprising daily reservoir inflow from a representative example watershed with the size of 14,924 km2 into a reservoir with the capacity of 6.80 Gm3. The reservoir capacity yield model was used to simulate variability in climate change-induced differences in reservoir capacity needs and performance (operational probability of failure, resilience, and vulnerability). Owing to the future precipitation reduction and potential evapotranspiration increase during the worst case scenario (−40% precipitation and +30% potential evapotranspiration), substantial reductions in streamflow of between −56% and −58% are anticipated for the dry and wet seasons, respectively. Furthermore, model simulations recommend that as a result of future climatic conditions, the reservoir operational probability of failure would generally increase due to declined reservoir inflow. The study developed preparedness plans to combat the consequences of climate change and drought.
- Full Text:
- Authors: Mohammed, Ruqayah , Scholz, Miklas
- Date: 2017
- Subjects: Alteration measure , Precipitation , Reservoir operation and reliability
- Type: Article
- Identifier: http://hdl.handle.net/10210/226384 , uj:22888 , Citation: Mohammed, R. & Scholz, M. 2017. Adaptation strategy to mitigate the impact of climate change on water resources in arid and semi-arid regions : a case study. Water Resour Manage, 27. DOI 10.1007/s11269-017-1685-7. , ISSN: 0920-4741
- Description: Abstract: Climate change and drought phenomena impacts have become a growing concern for water resources engineers and policy makers, mainly in arid and semi-arid areas. This study aims to contribute to the development of a decision support tool to prepare water resources managers and planners for climate change adaptation. The Hydrologiska Byråns Vattenbalansavdelning (The Water Balance Department of the Hydrological Bureau) hydrologic model was used to define the boundary conditions for the reservoir capacity yield model comprising daily reservoir inflow from a representative example watershed with the size of 14,924 km2 into a reservoir with the capacity of 6.80 Gm3. The reservoir capacity yield model was used to simulate variability in climate change-induced differences in reservoir capacity needs and performance (operational probability of failure, resilience, and vulnerability). Owing to the future precipitation reduction and potential evapotranspiration increase during the worst case scenario (−40% precipitation and +30% potential evapotranspiration), substantial reductions in streamflow of between −56% and −58% are anticipated for the dry and wet seasons, respectively. Furthermore, model simulations recommend that as a result of future climatic conditions, the reservoir operational probability of failure would generally increase due to declined reservoir inflow. The study developed preparedness plans to combat the consequences of climate change and drought.
- Full Text:
Binary permutation sequences as subsets of Levenshtein codes, spectral null codes, run-length limited codes and constant weight codes
- Ouahada, Khmaies, Swart, Theo G., Ferreira, Hendrik C., Cheng, Ling
- Authors: Ouahada, Khmaies , Swart, Theo G. , Ferreira, Hendrik C. , Cheng, Ling
- Date: 2008
- Subjects: Permutation codes , Insertion/deletion correcting codes , Constant weight codes , Spectral null codes , Run-length limited codes
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/18337 , uj:15986 , Citation: Ouahada, K. et al. 2008. Binary permutation sequences as subsets of Levenshtein codes, spectral null codes, run-length limited codes and constant weight codes. Designs, Codes and Cryptography, 48(2): 141-154. DOI: 10.1007s10623-007-9161-7. , DOI: 10.1007s10623-007-9161-7.
- Description: Abstract: We investigate binary sequences which can be obtained by concatenating the columns of (0,1)-matrices derived from permutation sequences. We then prove that these binary sequences are subsets of a surprisingly diverse ensemble of codes, namely the Levenshtein codes, capable of correcting insertion/deletion errors; spectral null codes, with spectral nulls at certain frequencies; as well as being subsets of run-length limited codes, Nyquist null codes and constant weight codes.
- Full Text:
- Authors: Ouahada, Khmaies , Swart, Theo G. , Ferreira, Hendrik C. , Cheng, Ling
- Date: 2008
- Subjects: Permutation codes , Insertion/deletion correcting codes , Constant weight codes , Spectral null codes , Run-length limited codes
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/18337 , uj:15986 , Citation: Ouahada, K. et al. 2008. Binary permutation sequences as subsets of Levenshtein codes, spectral null codes, run-length limited codes and constant weight codes. Designs, Codes and Cryptography, 48(2): 141-154. DOI: 10.1007s10623-007-9161-7. , DOI: 10.1007s10623-007-9161-7.
- Description: Abstract: We investigate binary sequences which can be obtained by concatenating the columns of (0,1)-matrices derived from permutation sequences. We then prove that these binary sequences are subsets of a surprisingly diverse ensemble of codes, namely the Levenshtein codes, capable of correcting insertion/deletion errors; spectral null codes, with spectral nulls at certain frequencies; as well as being subsets of run-length limited codes, Nyquist null codes and constant weight codes.
- Full Text:
Simulation of wireless sensor node transmission over a multiple access channel
- Ouahada, Khmaies, Rimer, Suvendi, Paul, Babu Sean, Kanyane, Katleho
- Authors: Ouahada, Khmaies , Rimer, Suvendi , Paul, Babu Sean , Kanyane, Katleho
- Date: 2014
- Subjects: Smart grids , Wireless sensor networks , Wireless communication
- Type: Article
- Identifier: uj:5047 , ISSN 1867-8211 , http://hdl.handle.net/10210/13586
- Description: Smart Grids are emerging as a sustainable technology that can greatly improve the quality, cost and efficiency of electrical power distribution. Wireless communication technology, in particular wireless sensor networks, are being considered as a viable solution to Smart Grid communication requirements. Homes have multiple electrical appliances that may communicate concurrently. In addition, electrical appliances induce white noise that can interfere with the wireless signal. In this paper an indoor wireless sensor multiple access communication environ- ment is simulated based on the IEEE 802.15.4 wireless communication standard. An indoor wireless propagation model is implemented and the effects of signal interference on the wireless signal are examined.
- Full Text:
- Authors: Ouahada, Khmaies , Rimer, Suvendi , Paul, Babu Sean , Kanyane, Katleho
- Date: 2014
- Subjects: Smart grids , Wireless sensor networks , Wireless communication
- Type: Article
- Identifier: uj:5047 , ISSN 1867-8211 , http://hdl.handle.net/10210/13586
- Description: Smart Grids are emerging as a sustainable technology that can greatly improve the quality, cost and efficiency of electrical power distribution. Wireless communication technology, in particular wireless sensor networks, are being considered as a viable solution to Smart Grid communication requirements. Homes have multiple electrical appliances that may communicate concurrently. In addition, electrical appliances induce white noise that can interfere with the wireless signal. In this paper an indoor wireless sensor multiple access communication environ- ment is simulated based on the IEEE 802.15.4 wireless communication standard. An indoor wireless propagation model is implemented and the effects of signal interference on the wireless signal are examined.
- Full Text:
Local and global search based PSO algorithm
- Sun, Yanxia, Wang, Zenghui, Van Wyk, Barend Jacobus
- Authors: Sun, Yanxia , Wang, Zenghui , Van Wyk, Barend Jacobus
- Date: 2013
- Subjects: Local search , Global search , Particle swarm optimisation
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/21240 , uj:16129 , Citation: Sun,Y., Wang, Z. & Van Wyk, B. 2013. Local and global search based PSO algorithm. Lecture Notes in Computer Sciences (LNCS) 7928: 129-136. ISSN: 0302-9743
- Description: Abstract: In this paper, a new algorithm for particle swarm optimisation (PSO) is proposed. In this algorithm, the particles are divided into two groups. The two groups have different focuses when all the particles are searching the problem space. The first group of particles will search the area around the best experience of their neighbours. The particles in the second group are influenced by the best experience of their neighbors and the individual best experience, which is the same as the standard PSO. Simulation results and comparisons with the standard PSO 2007 demonstrate that the proposed algorithm effectively enhances searching efficiency and improves the quality of searching. , Originally presented at Fourth International Conference on Swarm Intelligence (ICSI 2013), Harbin, China, 12-15, June, 2013.
- Full Text:
- Authors: Sun, Yanxia , Wang, Zenghui , Van Wyk, Barend Jacobus
- Date: 2013
- Subjects: Local search , Global search , Particle swarm optimisation
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/21240 , uj:16129 , Citation: Sun,Y., Wang, Z. & Van Wyk, B. 2013. Local and global search based PSO algorithm. Lecture Notes in Computer Sciences (LNCS) 7928: 129-136. ISSN: 0302-9743
- Description: Abstract: In this paper, a new algorithm for particle swarm optimisation (PSO) is proposed. In this algorithm, the particles are divided into two groups. The two groups have different focuses when all the particles are searching the problem space. The first group of particles will search the area around the best experience of their neighbours. The particles in the second group are influenced by the best experience of their neighbors and the individual best experience, which is the same as the standard PSO. Simulation results and comparisons with the standard PSO 2007 demonstrate that the proposed algorithm effectively enhances searching efficiency and improves the quality of searching. , Originally presented at Fourth International Conference on Swarm Intelligence (ICSI 2013), Harbin, China, 12-15, June, 2013.
- Full Text:
Corporate social responsibility forays in Southern Africa : perspectives from South Africa and Zambia
- Authors: Noyoo, Ndangwa
- Date: 2016
- Subjects: Social responsibility of business - Africa, Sub-Saharan , Corporate social responsibility , Business planning
- Language: English
- Type: Book chapter
- Identifier: http://hdl.handle.net/10210/55950 , uj:16327 , ISBN: 9783319266671 (Print) , ISBN: 9783319266688 (e-book) , ISSN: 2196-7075 (Print) , ISSN: 2196-7083 (electronic) , Citation: Noyoo, N. 2016. Corporate social responsibility forays in Southern Africa : perspectives from South Africa and Zambia. In: Corporate social responsibility in Sub-Saharan Africa, edited by S. Vertigans, S.O. Idowu & Schmidpeter, R. DOI:10.1007/978-3-319-26668-8-83.
- Description: Abstract: Please refer to full text to view the abstract
- Full Text: false
- Authors: Noyoo, Ndangwa
- Date: 2016
- Subjects: Social responsibility of business - Africa, Sub-Saharan , Corporate social responsibility , Business planning
- Language: English
- Type: Book chapter
- Identifier: http://hdl.handle.net/10210/55950 , uj:16327 , ISBN: 9783319266671 (Print) , ISBN: 9783319266688 (e-book) , ISSN: 2196-7075 (Print) , ISSN: 2196-7083 (electronic) , Citation: Noyoo, N. 2016. Corporate social responsibility forays in Southern Africa : perspectives from South Africa and Zambia. In: Corporate social responsibility in Sub-Saharan Africa, edited by S. Vertigans, S.O. Idowu & Schmidpeter, R. DOI:10.1007/978-3-319-26668-8-83.
- Description: Abstract: Please refer to full text to view the abstract
- Full Text: false
Convergence opportunities and factors influencing the use of internet and telephony by rural women in South Africa and India towards empowerment
- Joseph, Meera K., Andrew, Theo N.
- Authors: Joseph, Meera K. , Andrew, Theo N.
- Date: 2007
- Subjects: Mobile technology , Rural development , Women in development
- Language: English
- Type: Journal article
- Identifier: http://hdl.handle.net/10210/18741 , uj:16037 , Citation: Joseph, M.K. & Andrew, T.N. 2007. Convergence opportunities and factors influencing the use of internet and telephony by rural women in South Africa and India towards empowerment. IFIP International Federation for Information Processing, Volume 241 (Venkatesh, A. et al. (Eds.) Home Informatics and Telematics: ICT for the Next Billion), pp. 1-20. ISBN: 978-0-387-73696-9
- Description: Abstract: Access to Information and Communication Technologies (ICTs) can have dramatic impact on poverty alleviation for rural women and for achieving socio economic development goals. Rural women need to treat ICTs as an empowerment tool and a means to a living. The use of mobile communication devices and internet are changing the way agricultural activities are managed by farmers nowadays. Rural women's lack of mobility and less hands-on computer experience might hinder women's welfare and empowerment. This paper analyses how use of the telephony (both cellular and land line), internet and other ICTs can benefit rural women in educational, business and economic sector. Women in rural India and rural South Africa were marginalized partly due to their lack of ability in being vocal when it comes to empowering themselves using ICTs due to cultural norms in India, and apartheid in South Africa. Over the years, unlike other developing countries, the above-mentioned countries have its unique ICT projects meant for empowering rural women. This paper is driven from the authors' commitment for rural development and rural women empowerment. It highlights different low-cost ICT initiatives and strategies taken by women's organizations, various companies and other non-governmental organizations (NGOs) for rural women empowerment. The paper also highlights various factors influencing use of internet and mobile phone adoption by rural women. Various bottlenecks for the community projects, factors de-motivating the use of mobile phones and internet by rural women and possible solutions for these are also mentioned.
- Full Text:
- Authors: Joseph, Meera K. , Andrew, Theo N.
- Date: 2007
- Subjects: Mobile technology , Rural development , Women in development
- Language: English
- Type: Journal article
- Identifier: http://hdl.handle.net/10210/18741 , uj:16037 , Citation: Joseph, M.K. & Andrew, T.N. 2007. Convergence opportunities and factors influencing the use of internet and telephony by rural women in South Africa and India towards empowerment. IFIP International Federation for Information Processing, Volume 241 (Venkatesh, A. et al. (Eds.) Home Informatics and Telematics: ICT for the Next Billion), pp. 1-20. ISBN: 978-0-387-73696-9
- Description: Abstract: Access to Information and Communication Technologies (ICTs) can have dramatic impact on poverty alleviation for rural women and for achieving socio economic development goals. Rural women need to treat ICTs as an empowerment tool and a means to a living. The use of mobile communication devices and internet are changing the way agricultural activities are managed by farmers nowadays. Rural women's lack of mobility and less hands-on computer experience might hinder women's welfare and empowerment. This paper analyses how use of the telephony (both cellular and land line), internet and other ICTs can benefit rural women in educational, business and economic sector. Women in rural India and rural South Africa were marginalized partly due to their lack of ability in being vocal when it comes to empowering themselves using ICTs due to cultural norms in India, and apartheid in South Africa. Over the years, unlike other developing countries, the above-mentioned countries have its unique ICT projects meant for empowering rural women. This paper is driven from the authors' commitment for rural development and rural women empowerment. It highlights different low-cost ICT initiatives and strategies taken by women's organizations, various companies and other non-governmental organizations (NGOs) for rural women empowerment. The paper also highlights various factors influencing use of internet and mobile phone adoption by rural women. Various bottlenecks for the community projects, factors de-motivating the use of mobile phones and internet by rural women and possible solutions for these are also mentioned.
- Full Text:
Fossil hyaenidae from cooper’s cave, South Africa, and the palaeoenvironmental implications
- Kuhn, Brian F., Werdelin, Lars, Steininger, Christine
- Authors: Kuhn, Brian F. , Werdelin, Lars , Steininger, Christine
- Date: 2016
- Subjects: Hyaenidae , Cooper’s Cave , Palaeoenvironment
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/225437 , uj:22768 , Citation: Kuhn, B.F., Werdelin, L. & Steininger, C. 2016. Fossil hyaenidae from cooper’s cave, South Africa, and the palaeoenvironmental implications. Palaeobio Palaeoenv. 10:1-11. DOI: 10.1007/s12549-016-0247-y. , ISSN: 1867-1594
- Description: Abstract: We present material of the family Hyaenidae from Cooper’s Cave, an early Pleistocene (ca 1.5 Ma) fossil-bearing site in Gauteng, South Africa. This site is exceptionally rich in Carnivora, including five species of Hyaenidae: Chasmaporthetes nitidula, Crocuta ultra, Parahyaena brunnea, Hyaena hyaena and cf. Proteles sp. This diversity is greater than that of the entire family in the modern fauna and is matched at other sites in the vicinity of Cooper’s Cave. This raises issues about time averaging and the carrying capacity of the palaeoenvironment that require resolution if we are to properly understand the environments in which Paranthropus robustus, present at Cooper’s Cave, and other early hominins evolved. In addition, the presence of several hyaenid species with bone-eating/collecting capabilities raises questions about the identity of the accumulators of fossil bone assemblages that have yet to be fully resolved.
- Full Text:
- Authors: Kuhn, Brian F. , Werdelin, Lars , Steininger, Christine
- Date: 2016
- Subjects: Hyaenidae , Cooper’s Cave , Palaeoenvironment
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/225437 , uj:22768 , Citation: Kuhn, B.F., Werdelin, L. & Steininger, C. 2016. Fossil hyaenidae from cooper’s cave, South Africa, and the palaeoenvironmental implications. Palaeobio Palaeoenv. 10:1-11. DOI: 10.1007/s12549-016-0247-y. , ISSN: 1867-1594
- Description: Abstract: We present material of the family Hyaenidae from Cooper’s Cave, an early Pleistocene (ca 1.5 Ma) fossil-bearing site in Gauteng, South Africa. This site is exceptionally rich in Carnivora, including five species of Hyaenidae: Chasmaporthetes nitidula, Crocuta ultra, Parahyaena brunnea, Hyaena hyaena and cf. Proteles sp. This diversity is greater than that of the entire family in the modern fauna and is matched at other sites in the vicinity of Cooper’s Cave. This raises issues about time averaging and the carrying capacity of the palaeoenvironment that require resolution if we are to properly understand the environments in which Paranthropus robustus, present at Cooper’s Cave, and other early hominins evolved. In addition, the presence of several hyaenid species with bone-eating/collecting capabilities raises questions about the identity of the accumulators of fossil bone assemblages that have yet to be fully resolved.
- Full Text:
A temperature stabilized CMOS VCO
- Sebastian, Johny, Sinha, Saurabh
- Authors: Sebastian, Johny , Sinha, Saurabh
- Date: 2014
- Subjects: Voltage controlled oscillators
- Type: Article
- Identifier: uj:4828 , http://hdl.handle.net/10210/12351
- Description: The established method of frequency drift compensation in voltage controlled oscillators (VCOs) resulting from temperature variance involves modulation of control voltage using a non-linear voltage internally generated. An innovative frequency drift compensation scheme for a VCO, based on amplitude control, is described in this paper. Two peak detectors are used to generate voltages representing positive and negative peaks of the sinusoidal driving an error amplifier. The amplifier output controls the delivery of transconductance accessible to the oscillator, thereby keeping the oscillation amplitude steady. Frequency stability has improved to 16 ppm/ C from an uncompensated value of 189 ppm/ C and is applicable where frequency stability requirements are not stringent, such as HS-USB and S-ATA. The temperature stabilized VCO at 2.4 GHz center frequency is prototyped using CMOS technology from ams AG (formerly austriamicrosystems AG). The result obtained from this study indicates that better frequency stability may be achievable if the traditional compensation scheme is preceded by amplitude control.
- Full Text: false
- Authors: Sebastian, Johny , Sinha, Saurabh
- Date: 2014
- Subjects: Voltage controlled oscillators
- Type: Article
- Identifier: uj:4828 , http://hdl.handle.net/10210/12351
- Description: The established method of frequency drift compensation in voltage controlled oscillators (VCOs) resulting from temperature variance involves modulation of control voltage using a non-linear voltage internally generated. An innovative frequency drift compensation scheme for a VCO, based on amplitude control, is described in this paper. Two peak detectors are used to generate voltages representing positive and negative peaks of the sinusoidal driving an error amplifier. The amplifier output controls the delivery of transconductance accessible to the oscillator, thereby keeping the oscillation amplitude steady. Frequency stability has improved to 16 ppm/ C from an uncompensated value of 189 ppm/ C and is applicable where frequency stability requirements are not stringent, such as HS-USB and S-ATA. The temperature stabilized VCO at 2.4 GHz center frequency is prototyped using CMOS technology from ams AG (formerly austriamicrosystems AG). The result obtained from this study indicates that better frequency stability may be achievable if the traditional compensation scheme is preceded by amplitude control.
- Full Text: false
Designing of sampling programmes for industrial effluent monitoring
- Ntuli, Freeman, Kuipa, P.K., Muzenda, Edison
- Authors: Ntuli, Freeman , Kuipa, P.K. , Muzenda, Edison
- Date: 2011
- Subjects: Effluent monitoring , Sampling strategies , Water pollution control , Sampling (Statistics)
- Type: Article
- Identifier: uj:5313 , ISSN 0944-1344 , http://hdl.handle.net/10210/7736
- Description: Monitoring of effluent discharges from industrial establishments discharging directly into municipality sewers is one of the major water pollution control activities conducted by municipalities. For largely industrialised municipalities the task can be quite expensive and not effective if sampling programmes are not properly designed. In most cases samples are randomly collected without proper knowledge of the discharge patterns of various industries. As a result the information obtained does not give a good reflection of the quality of effluent being discharged. These problems can be resolved by adapting a statistical approach to the design of sampling programmes. This approach is useful in determining the frequency of sampling, the number of samples needed to estimate the average concentration of target pollution indicator parameters and the magnitude of the uncertainty involved. The benefits and applications of this approach are demonstrated by a case study presented in this paper. It was found that the number of samples and cost of sample analysis can be greatly reduced by the use of systematic instead of random sampling. The statistical approach greatly improves the estimate of monthly means of pollution indicator parameters and is an effective approach for pollution control when coupled with the “polluter pays principle”.
- Full Text:
- Authors: Ntuli, Freeman , Kuipa, P.K. , Muzenda, Edison
- Date: 2011
- Subjects: Effluent monitoring , Sampling strategies , Water pollution control , Sampling (Statistics)
- Type: Article
- Identifier: uj:5313 , ISSN 0944-1344 , http://hdl.handle.net/10210/7736
- Description: Monitoring of effluent discharges from industrial establishments discharging directly into municipality sewers is one of the major water pollution control activities conducted by municipalities. For largely industrialised municipalities the task can be quite expensive and not effective if sampling programmes are not properly designed. In most cases samples are randomly collected without proper knowledge of the discharge patterns of various industries. As a result the information obtained does not give a good reflection of the quality of effluent being discharged. These problems can be resolved by adapting a statistical approach to the design of sampling programmes. This approach is useful in determining the frequency of sampling, the number of samples needed to estimate the average concentration of target pollution indicator parameters and the magnitude of the uncertainty involved. The benefits and applications of this approach are demonstrated by a case study presented in this paper. It was found that the number of samples and cost of sample analysis can be greatly reduced by the use of systematic instead of random sampling. The statistical approach greatly improves the estimate of monthly means of pollution indicator parameters and is an effective approach for pollution control when coupled with the “polluter pays principle”.
- Full Text:
Microstructure and mechanical properties of ultra-fine grained copper processed by equal channel angular pressing technique
- Sanusi, Kazeem Oladele., Afolabi, Ayo Samuel, Muzenda, Edison
- Authors: Sanusi, Kazeem Oladele. , Afolabi, Ayo Samuel , Muzenda, Edison
- Date: 2015
- Subjects: Copper - Testing , Nanostructured materials , Equal channel angular pressing technique
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/55067 , uj:16268 , Citation: Oladale, S.K., Edison, M. & Samuel, A.A. 2015. Microstructure and mechanical properties of ultra-fine grained copper processed by equal channel angular pressing technique. Transactions on Engineering Technologies. DOI: 10.1007/978-94-017-7236-5_36.
- Description: Abstract: The equal channel angular pressing (ECAP) technique is now recognised for achieving very significant grain refinement of ultra-fine grained materials which, at present produce unique mechanical properties. This study reports the results of the tensile tests and the microstructural analysis carried out on the specimens of ultra-fine grained (UFG) copper processed by ECAP technique at room temperature using a die with a 126o between the die channels. The copper samples used in this work were subjected to six and twelve passes during the ECAP processing. Tensile tests were conducted for samples cut out in two different directions; in the parallel and perpendicular direction at room temperature to evaluate the mechanical properties after the ECAP at these two directions. The microstructural characterization was carried out using optical electron microscope (OEM) and scanning electronic microscope (SEM). The results show ECAP technique introducing significant grain refinement and produced ultrafine grains in copper and there is a potential for achieving high ductility in the copper alloy after processing. The tested sample is characterized by significant differences of strength properties depending on the direction.
- Full Text:
- Authors: Sanusi, Kazeem Oladele. , Afolabi, Ayo Samuel , Muzenda, Edison
- Date: 2015
- Subjects: Copper - Testing , Nanostructured materials , Equal channel angular pressing technique
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/55067 , uj:16268 , Citation: Oladale, S.K., Edison, M. & Samuel, A.A. 2015. Microstructure and mechanical properties of ultra-fine grained copper processed by equal channel angular pressing technique. Transactions on Engineering Technologies. DOI: 10.1007/978-94-017-7236-5_36.
- Description: Abstract: The equal channel angular pressing (ECAP) technique is now recognised for achieving very significant grain refinement of ultra-fine grained materials which, at present produce unique mechanical properties. This study reports the results of the tensile tests and the microstructural analysis carried out on the specimens of ultra-fine grained (UFG) copper processed by ECAP technique at room temperature using a die with a 126o between the die channels. The copper samples used in this work were subjected to six and twelve passes during the ECAP processing. Tensile tests were conducted for samples cut out in two different directions; in the parallel and perpendicular direction at room temperature to evaluate the mechanical properties after the ECAP at these two directions. The microstructural characterization was carried out using optical electron microscope (OEM) and scanning electronic microscope (SEM). The results show ECAP technique introducing significant grain refinement and produced ultrafine grains in copper and there is a potential for achieving high ductility in the copper alloy after processing. The tested sample is characterized by significant differences of strength properties depending on the direction.
- Full Text:
A hyperchaotic system without equilibrium
- Wang, Zenghui, Cang, Shijian, Ochola, Elisha Oketch, Sun, Yanxia
- Authors: Wang, Zenghui , Cang, Shijian , Ochola, Elisha Oketch , Sun, Yanxia
- Date: 2012
- Subjects: Hyperchaos , Chaos , Lyapunov exponents , Poincare map , Equilibrium
- Type: Journal article
- Identifier: http://hdl.handle.net/10210/20529 , uj:16109 , Citation: Wang, Z. et al. 2012. A hyperchaotic system without equilibrium. Nonlinear Dynamics 69(2012):531–537. DOI: 10.1007/s11071-011-0284-z
- Description: Abstract: This article introduces a new chaotic system of 4-D autonomous ordinary differential equations, which has no equilibrium. This system shows a hyper-chaotic attractor. There is no sink in this system as there is no equilibrium. The proposed system is investigated through numerical simulations and analyses including time phase portraits, Lyapunov exponents, and Poincaré maps. There is little difference between this chaotic system and other chaotic systems with one or several equilibria shown by phase portraits, Lyapunov exponents and time series methods, but the Poincaré maps show this system is a chaotic system with more complicated dynamics. Moreover, the circuit realization is also presented.
- Full Text:
- Authors: Wang, Zenghui , Cang, Shijian , Ochola, Elisha Oketch , Sun, Yanxia
- Date: 2012
- Subjects: Hyperchaos , Chaos , Lyapunov exponents , Poincare map , Equilibrium
- Type: Journal article
- Identifier: http://hdl.handle.net/10210/20529 , uj:16109 , Citation: Wang, Z. et al. 2012. A hyperchaotic system without equilibrium. Nonlinear Dynamics 69(2012):531–537. DOI: 10.1007/s11071-011-0284-z
- Description: Abstract: This article introduces a new chaotic system of 4-D autonomous ordinary differential equations, which has no equilibrium. This system shows a hyper-chaotic attractor. There is no sink in this system as there is no equilibrium. The proposed system is investigated through numerical simulations and analyses including time phase portraits, Lyapunov exponents, and Poincaré maps. There is little difference between this chaotic system and other chaotic systems with one or several equilibria shown by phase portraits, Lyapunov exponents and time series methods, but the Poincaré maps show this system is a chaotic system with more complicated dynamics. Moreover, the circuit realization is also presented.
- Full Text: