VUT DigiResearch
Digiresearch is the VUT electronic open access archive. Its purpose is to collect, distribute and preserve the research performed by the VUT Research community
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Communities in DigiResearch
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- Inaugural addresses, Presentations etc.
Recent Submissions
Formulation of nanocellulosic fibres and particle fillers and their mono and hybrid reinforced polymer composites
(Vaal University of Technology, 2022-03) Webo, Wilson Wachuli; Nziu, P. K., Dr.; Masu, L. M., Prof.
This study aimed to focus on the state of knowledge and practice on natural fibres, extract cellulose, and subsequent formation of nanocellulosic fibres and particles from selected natural fibres. Moreover, both mono and hybrid composites were fabricated and modeled using ABAQUS software. After that, the formulation of the optimal mix ratio of both the fibres and the matrix for different mechanical applications was determined using the Minitab software version 2017. Sisal and rice husk were selected for this purpose due to their ease of availability.
An experimental solution was used to extract cellulose, and, subsequently, nanofibres and nanoparticles were formed. These were then used to fabricate composites. The possibility of using new processing technology for modeling both sisal and rice husk nanocomposites in their mono and hybrid forms through the use of Finite Element Analysis (FEA) is a novel idea that has been explored in this study. Finite Element Analysis (FEA) using ABAQUS/CAE software version 2018 was used to develop novel models of mono and hybrid nanocomposites and to determine their mechanical properties of strength and stiffness. The finite element analysis method incorporates the effects of nonlinearities which are very common in composite fabrication. Furthermore, this study sought to formulate the optimal combination mix ratio of fibres and matrix for different mechanical applications using the Minitab software version 2017.
A total of 198 finite element part models were created and analyzed. The Finite Element Analysis (FEA) models developed predicted correctly the flexural and tensile properties of the nanocellulosic composites that had been modelled. The experimental method was used to validate the FEA results. Moreover, analysis of variance (ANOVA) was performed for each property of the mono and hybrid composites in this study.
The tensile and flexural properties of the mono and hybrid composites were found to gradually increase with an increase in fibre volume fraction up to a certain optimum point, beyond which they gradually began to reduce with more fibre additions. The analysis of variance of properties indicated that, for all the tensile and flexural properties under study, the F statistic > F critical, and the P-value < 0.05, implying that the tests were significant and there was a difference between the means of the groups.
In the thermal analyses, the Thermogravimetric Analysis(TGA) graph exhibited three distinct sections: An initial flat section, then a section with a constant slope and finally a flat section. In the Dynamic Scanning Calorimetry (DSC) graphs, all the samples exhibited a glass transition temperature of between 50ºC and 75ºC. Furthermore, all the samples exhibited a melting temperature of between 350ºC and 400ºC.
Overall, the hybrid nanocomposites had better tensile, flexural and thermal properties than the mono composites.
Regarding the formulation of the optimal combination mix of the fibres and the matrix for use in different mechanical applications, this study established that: a ratio of fibres to a matrix of 4:1 is suitable for mechanical applications where all the flexural and tensile properties of the mono and hybrid composites are maximized. For applications that require the flexural properties of mono and hybrid nanocellulosic composites to be maximized, while the tensile properties of the mono and hybrid nanocellulosic composites are minimized, the ratio was found to be 1:2. A similar ratio was found to be suitable for applications that require the tensile properties of mono and hybrid nanocellulosic composites to be maximized while the flexural properties are minimized. For applications that required a target of 10 MPa for the tensile and flexural strength of mono and hybrid nanocellulosic composites and 10 GPa for the tensile and flexural stiffness of mono and hybrid nanocellulosic composites, this ratio was found to be 2:3.
Supply chain strategy, flexibility and performance in the Gauteng fast-moving consumer goods (FMCG) industry
(Vaal University of Technology, 2023) Ngomane, Sikhulile Rhine; van der Westhuizen, J. P., Dr.; Mafini, C., Prof.
The successful implementation of supply chain strategy has received significant attention among literature and practitioners, due to its importance in contributing to company success. The success of the FMCG industry in South Africa has also been attributed to the effectiveness of its supply chain strategies. However, the industry faces numerous challenges such as miscellaneous risks that include the potential loss of key suppliers, innovation, and risk, planning and forecasting, power outages in manufacturing plants and the fact that only a limited amount of safety stock can be held to offset uncertainty. It also faces difficulties in improving supply and demand, which further extends to transforming supplier relationships into effective collaboration. Thus, this study applies supply chain strategy to the FMCG industry in South Africa, and seeks to establish the connection between supply chain strategies, flexibility (SCF) and performance (SCP) in the sector.
The methodological procedure in this study was guided by the positivist paradigm which is embedded in quantitative and causal designs. A sample of 228 respondents purposively drawn from the FMCG industry in Gauteng province participated in the survey. The collected data were tested using descriptive and inferential statistics. The specific statistical techniques applied included the analysis of frequency distributions, percentages, mean scores, exploratory factor analysis (EFA), confirmatory factor analysis (CFA) and hypotheses tests using partial least squares-based structural equation modelling.
The empirical results showed that two supply chain strategies, namely, organisational learning and supplier integration contribute significantly to SCF. In turn, SCF contributes positively to financial and non-financial performance. Supply chain strategies such as innovation, risk management and customer orientation were statistically insignificant in predicting SCP. The study is significant because it identifies that supply chain strategies are important in developing flexible FMCG supply chains in South Africa. It also confirms the importance of SCF in improving the performance of FMCG supply chains. The study may therefore be used as a reference source for information on the improvement of SCP in FMCG supply chains.
Design and implementation of personal health data monitoring and retrieval system for health providers
(Vaal University of Technology, 2020-08-17) Ojo-Seriki, D. F.; Mathaba, Tebello N. D., Dr.; Ohanga, M. O., Prof.
Personal health record system (PHRS) is a tool that is used in maintaining the health and wellness of an individual as well as helping with illness of an individual. PHRS gives the individual access to a wide range of credible health information, data, and knowledge. Individuals can use that access to improve their health and manage their diseases. Patients with chronic illness can track and manage their health in conjunction with their health provider, this will promote early intervention when they encounter an abnormality or complications. Continuous monitoring and storing of health information has been a challenge for patients and health providers. Personal health data monitoring and retrieval system for health providers was designed and implemented. The main aim of this study was to develop an accurate, secure and flexible personal health data monitoring and retrieval system for health providers (PHRS). This was achieved. The research showed that when a patient health information (Electrocardiogram (ECG) and temperature) was monitored, the heartbeat (ECG) sensor output the value as an analog value to the signal processing (NodeMCU) which was then converted to a digital value.
The temperature sensor used in this research is a digital sensor which lowers the amount of ADC conversion that was done. The digital values are displayed on LCD, its send to a personal health data storage system which was designed for health information storage purposes. It also sends the value to a retrieval system which is an android application that is connected to the data storage system to display health information to the health providers from a remote location. Personal health data storage and the retrieval system are secure due to the Message queuing telemetry transport (MQTT) protocol used in the application layer. The MQTT protocol is secure due to the secure socket layer (SSL) which is an encryption based on presentation layer embedded inside the MQTT protocol. After the comparison of the software simulation and the prototype test, the differences in the value for the heartbeat and temperature sensor indicate 0.04 BPM and 0.04 oC which shows the accuracy of the sensing circuit.
Personal health data monitoring and retrieval system developed is applicable and useful to multiple entities in and around South Africa such as; Ministry of health, hospitals, sport and recreations.
Optimal geometric configuration of a cross bore in thick compound cylinders
(Vaal University of Technology, 2021-09) Kiplagat, N.; Nziu, P. K., Dr.; Masu, L. M., Prof.
The purpose of this research was to develop optimal numerical solutions that can be employed during the design of cross bored thick-walled compound cylinders. The geometric design parameters of a cross bored compound cylinder that were optimized include shrinkage pressure, cross bore size, shape, location, and obliquity.
Finite Element Analysis (FEA) modeling software called Abaqus version 2019 was used to
generate numerical solutions. A total of 48 different part models were created and analyzed in this work. The generated FEA results from these models were validated using analytical
solutions developed from Lame’s theory. The effects of shrinkage pressure on hoop stresses and Stress Concentration Factor (SCF) were studied to determine the optimal conditions. The optimum shrinkage pressure obtained was henceforth used for further analysis in this work. In addition, using one factor at time optimization technique, an optimization process was carried out to determine the optimal combination of the cross bore configuration geometry that gives minimum SCF. These parameters of cross bore configuration geometry include different sizes of either circular or elliptical-shaped cross bore, positioned at radial, offset, and/or inclined. The analyses of the effects of shrinkage pressure ranging from 4.4733 to 223.662 MPa on 11 different part models, established that the shrinkage pressure of 89.464 MPa generated the minimum SCF magnitude of 3.02.
After analyzing 8 different circular cross bore size ratios ranging from 0.1 to 0.8, at the radial position, it was established that the hoop stress increases with an increase in a cross bore size. The smallest cross bore size ratio of 0.1 gave the lowest hoop stress and minimum SCF of 3.02. Whereas the highest stress was developed at the cross-size ratio of 0.8 with an SCF magnitude of 6.75. The minimum magnitude of SCF translates to a reduction of the pressure carrying capacity of the compound cylinder by 67% than a similar plain compound cylinder. Generally, offsetting of the circularly shaped cross bore from the radial position, led to a reduction of the magnitude of SCFs. For instance, from the 8 offset positions analyzed, the minimum SCF occurred at the offset position of 0.006 m with a magnitude of 2.50. This SCF magnitude indicated a reduction of pressure carrying capacity of 60% in comparison to a similar plain compound cylinder.
Evaluation of 12 different diameter ratios of elliptical-shaped cross bore ranging from 0.5 to
10, at the radial position, established the lowest SCF magnitude of 1.33 that occurred at a
diameter ratio of 5. Henceforth, this optimum diameter ratio was used for further analysis. This aforesaid SCF magnitude translated to a reduction of the pressure carrying capacity of the compound cylinder by 24.81% when compared to a similar plain compound cylinder. Besides, offsetting of elliptically shaped cross bore generally decreased the magnitudes of SCFs. Therefore, for elliptically shaped cross bore, the lowest SCF occurred at radial position with magnitude of 1.33. A general comparison between the effects of circular and elliptical cross bore, established that the elliptical-shaped cross bores generated both lower hoop stresses and SCFs than those of circularly shaped cross bores. On the other hand, oblique elliptical offset cross bores along the Z-axis of the compound cylinder led to an increase in SCFs. As the oblique angle increased from 0 0 to 75 0, the SCFs also increased progressively, however, there was a significant increase in SCF when the inclination angle increased from 60 0 to 75 0. The lowest and highest SCF magnitude was 1.52 and 1.92 at 15 0 and 6.19 at 75 0, respectively.
Overall, the optimum geometric configuration of a cross bore in a thick compound cylinder
was found to be elliptically shaped, offset at radial position which is an obliquity angle of 0 0
having a diameter ratio a/b of 5.
Design and implementation of the telecommunication and utility cable tamper monitoring system
(Vaal University of Technology, 2019-04-11) Mabadie, Patrick; Ohanga, M. O., Prof.
The telecommunication and utility cable monitoring system was implemented to protect the cable tampering. Cable tampering occurs despite the fact that methods have been developed, to solve and decrease cable tampering cases such as cable tampering prevention campaigns at the national and international level, organizing security patrols, replacing existing cable with fiber cables and I-Watch system installation. The objective of the research was to design and implement a cable tampering monitoring system which is able to monitor, detect, pinpoint the location and give the distance from the sensor at which the cable tampering took place. The system is an improvement on the traditional cable anti-theft monitoring system, the method of tracking resonance signal frequency was implemented. The system incorporates a sensing circuit which detects a change on the capacitance value of the cable and converts it into an equivalent frequency value, Field-Programable Gate Array (FPGA) board is utilized to convert the frequency into the cable length (the distance from sensor of cable which was taken away), after detecting an anomaly on the cable (tampered with) the output of the system is divided into two parts which are display mode and messaging mode. For display mode, the system uses a Liquid Crystal Display (LCD) which displays the GPS Coordinates of the location where the cable tampering took place and the distance from sensor of the cable which has been tampered with. In the messaging mode, the FPGA activates the GSM module and the module sends alert flag message to the user when the cable is tampered with.