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An alternative to dark matter and dark energy : scale-dependent gravity in superfluid vacuum theory
No full textWe derive an effective gravitational potential, induced by the quantum wavefunction of a physical vacuum of a self-gravitating configuration, while the vacuum itself is viewed as the superfluid described by the logarithmic quantum wave equation. We determine that gravity has a multiple-scale pattern, to such an extent that one can distinguish sub-Newtonian, Newtonian, galactic, extragalactic and cosmological terms. The last of these dominates at the largest length scale of the model, where superfluid vacuum induces an asymptotically Friedmann–Lemaître–Robertson–Walker-type spacetime, which provides an explanation for the accelerating expansion of the Universe. The model describes different types of expansion mechanisms, which could explain the discrepancy between measurements of the Hubble constant using different methods. On a galactic scale, our model explains the non-Keplerian behaviour of galactic rotation curves, and also why their profiles can vary depending on the galaxy. It also makes a number of predictions about the behaviour of gravity at larger galactic and extragalactic scales. We demonstrate how the behaviour of rotation curves varies with distance from a gravitating center, growing from an inner galactic scale towards a metagalactic scale: A squared orbital velocity’s profile crosses over from Keplerian to flat, and then to non-flat. The asymptotic non-flat regime is thus expected to be seen in the outer regions of large spiral galaxies
Kinks in the relativistic model with logarithmic nonlinearity
No full textAbstract
We study the properties of a relativistic model with logarithmic nonlinearity. We show that such model allows two types of solutions: topologically trivial (gaussons) and topologically non-trivial (kinks), depending on a sign of the nonlinear coupling. We focus primarily on the kinks' case and study their scattering properties. For the kink-antikink scattering, we have found a critical value of the initial velocity, which separates two different scenarios of scattering. For the initial velocities below this critical value, the kinks form a bound state, which then decays slowly. If the initial velocities are above the critical value, the kinks collide, bounce and eventually escape to infinities. During this process, the higher initial velocity is, the greater is the elasticity of the collision. We also study excitation spectrum of the kink solution.</jats:p
Matrix logarithmic wave equation and multi-channel systems in fluid mechanics
No full textWe formulate the mapping between a large class of nonlinear wave equations
and flow equations for barotropic fluid with internal surface tension and
capillary effects. Motivated by statistical mechanics and multi-channel physics
arguments, we focus on wave equations with logarithmic nonlinearity, and
further generalize them to matrix equations. We map the resulting equation to
flow equations of multi-channel or multi-component Korteweg-type materials. For
some special cases, we analytically derive Gaussian-type matrix solutions and
study them in the context of fluid mechanics
Strengthening teamwork and respect (STAR) in maternity units : developing a health system intervention in South Africa
No full textDisrespect and abuse in maternity services in South Africa has been described over several decades and are rooted in the country's complex socio-political landscape and unequal health system which places strain on public sector health professionals. Strategies to improve the quality of health care typically involve once-off didactic teaching or outside technical consultants focused on improving specific health programmes. These approaches fail to encourage self-reflection or to establish learning cultures. Participatory learning processes, embedded in routine service delivery, are a potentially powerful way to improve ownership and accountability for health system performance. We describe the process followed to develop the Strengthening Teamwork and Respect (STAR) intervention which is being implemented in nine district hospitals in two rural districts of KwaZulu-Natal. The intervention approach draws on a conceptual framework for learning health systems, with intervention strategies informed by participatory learning and action theory. The intervention design was an iterative process informed by literature reviews, formative data collection, consultation with provincial, district and hospital management stakeholders, expert reviewer inputs and piloting of proposed activities. This process produced the STAR intervention approach and toolkit, consisting of: identification and training of champions, creation of STAR teams, convening of learning sessions to work through STAR toolkit activities, identification, implementation and monitoring of change projects, and onsite and virtual mentorship from the STAR development team. Endline cross-sectional surveys and a parallel process evaluation will advance the evidence base for interventions to improve respectful care and cultures of teamwork and learning within maternity units in rural low- and middle-income settings
The perceptions of Zimbabwean SMEs on the relevance of risk management in their businesses
No full textSMEs are faced with different types of risks while running their businesses and RM could play a vital role in
dealing with these risks. Therefore, it is crucial to examine the SMEs perceptions on the relevance of risk management in the success of their businesses as it might influence SMEs owner-manager to adopt or ignore RM practice. This study was conducted to establish the perception of SMEs on the relevance of risk management in the success of their businesses. The study was conducted among SMEs who reside in two provinces of Zimbabwe namely Harare Province and Mashonaland Central province. In order to achieve the main purpose of the study, a mixed method research design was used. The target population of the study include Small to Medium Enterprises from all sectors in Zimbabwe’s ten provinces. The study’s target population was around 780 684 and the sample was 278 respondents. The study used a combination of cluster sampling and simple random sampling methods to select the sample. Data was collected using structured-questionnaire and semi-structured interviews to SMEs in Harare and Mashonaland Central provinces. The findings of the study show that the SMEs have a negative perception on the relevance of risk management in the success of their businesses. Thus, risk management is not relevant for SMEs due to their size and is viewed as more relevant to big businesses who have the resources and have much at stake. The researcher concluded that the perception on the relevance of risk management is negative in Small to Medium enterprises in Zimbabwe and recommended SMEs capacity building on risk management, transformation of SMEs business norms, review of SMEs policy framework and SMEs networking in order for them to obtain risk management skills and knowledge
In situ synthesis and AC conductivity studies of polypyrrole–cobalt nanocomposites
No full textThrough in situ pyrrole chemical polymerization with various concentrations of CoCl2, conducting polypyrrole-cobalt composites were synthesized using ammonium persulfate as the oxidizing agent. These composites were synthesized using different molarities (0.01, 0.02, 0.03, and 0.05 M) of CoCl2 in polypyrrole. The PPy-Co nanocomposites and their AC conductivity studies were evaluated in this study. The formation of anocomposites and the structural properties of PPy/PVA/Co were confirmed using FTIR analysis and X-ray
crystallography. Scanning electron microscopy (SEM) was used to analyze the morphology of the composites, and thermogravimetric analysis (TGA) was used to investigate their thermal behavior. The room-temperature AC conductivity and dielectric response of the composites were investigated, and frequency-dependent AC conductivity investigations were conducted in the frequency range of 100 Hz–1 MHz
Application of DMAIC technique to improve supply chain efficiency
No full textSubmitted in fulfilment of the requirements for the Master of Engineering: Industrial Engineering, Durban University of Technology, Durban, South Africa, 2025.This study presents a detailed analysis of the use of Lean manufacturing approaches
to improve operational efficiency and minimize waste in the production processes of a
sugar packaging company situated in South Africa. Faced with obstacles in fulfilling
waste reduction targets and improving operational efficiency, the study attempted to
carefully identify underlying sources of waste and implement Lean concepts, notably
the DMAIC technique.
The study used a range of Lean problem-solving approaches, beginning with an ABC
analysis to identify Stock Keeping Units (SKU) with the greatest waste levels, followed
by a mix of the 5- Whys probing methodology and Ishikawa diagrams to go deeper
into waste reduction initiatives. Matrix prioritization was then used to prioritize actions
and implementations that address identified inefficiencies and issues, leading to the
creation and execution of an implementation strategy.
During the improvement phase, waste was significantly reduced, notably in the 500g
stock-keeping unit. Despite encountering obstacles associated with 1 kg SKUs, due
to variances in the Bill of Materials (BOM), significant progress was accomplished. The
DMAIC framework offered an organized method that included problem identification,
process evaluation, data analysis, improvement implementation, and control
installation.
The study indicated significant waste levels, which were above weekly targets,
resulting in a 70% production efficiency, (or 30% inefficiency), emphasizing the need
for process improvements. Among other recommendations, the study suggests
improving supervisor handover methods and introducing non-conformance reports
(NCRs) to increase supplier responsibility and raw material quality. Supplier
participation in performance reviews emerged as a crucial driver in dramatically
decreasing waste and increasing production efficiency, resulting in a remarkable 20%
improvement in production efficiency, thus raising the production efficiency levels to
90%.
In essence, this study sheds light on the efficacy of the DMAIC methodology within the
sugar company, offering practical insights into enhancing supply chain efficiency and
minimizing waste. By targeting significant process inefficiencies, the research
contributes to enhancing sugar production operations, benefiting stakeholders, and
bolstering industry competitiveness. The results advocate for the adoption of Lean
methodologies to optimize production processes and enhance profitability.
DC microgrid energy optimization
No full textThis dissertation is submitted in the fulfilment of the requirements for the degree of Master of Engineering in Electronic & Computer Engineering, Durban University of Technology, Durban, South Africa, 2024.Microgrids that generate electricity using photovoltaic panels or wind turbines and batteries,
provide a viable solution to meet low to moderate energy needs in rural, remote and informal
settlements. However, these solutions are limited because they depend on the availability of
sunlight or wind. To solve these limitations, researchers have proposed hybrid systems that
combine multiple energy sources and can be more efficient than battery-powered photovoltaic
or wind systems. These hybrid systems use dynamic dispatching to optimize the overall cost
and performance of the microgrid. Energy management systems are widely used to achieve this
dynamic energy distribution, including load profiling and intelligent decision-making for
energy distribution. While many energy management systems focusing on automated demand
side management have been deployed worldwide to optimize microgrids, less work has been
done in South Africa.
This research is focused on designing a hybrid PV-driven battery and fuel cell backup system,
initially concentrating on sizing the PV, battery, and fuel cell. The focus then shifts to
developing an energy management system. The proposed system follows a low-power
provision in a 48 VDC format, offering electricity for lighting, computing, entertainment
devices, and communication modules. Seven rural households were chosen for the study,
collectively consuming 8.64 kWh/day. The efficacy of the microgrid is examined with and
without demand-side management and considering the impact of load scheduling. The findings
revealed that reducing energy demand by the demand side led to an increase in current and
output power due to the proportional relationship between current and power, while the bus
voltage remained constant at 48V DC. Furthermore, an increase in loads resulted in a decrease
in output power. The simulation was carried out using the MATLAB® Simulink™
environment.
Fostering civic engagement on “Ghana X”: an analysis of data-driven journalistic practices of mainstream and peripheral media actors
No full textThis study employed qualitative content analysis to explore data-driven journalistic practices employed by mainstream and citizen journalists on X (formerly known as Twitter) and how these practices foster civic engagement among Ghanaian X users. The study was grounded in the materiality, performativity, and reflexivity framework of data journalism and the civic engagement model. The findings were that the main themes of data-driven narratives on X were politics, socioeconomic discourse, and particularly economic metrics. Materiality and performativity showed up in the human agency of journalists and in the skills and expertise of those who contextualise and interpret the data. Data journalists liaise with allied data production specialists to convert raw data into data artifacts to tell stories. Ghanaian X users actively used the offered data stories to participate in civic arguments and discussions on social media. They back data stories with personal anecdotes. Through the proactive deployment of surveys, the creation of X polls, and other cooperative efforts, the examined narratives illustrated the performativity of data journalism as a technique that subverts power structures. The study provides evidence for the important role of peripheral actors in data journalism and how their efforts drive civic discourse to potentially drive tangible societal transformations
Using optical metrology in injection moulding
No full textSubmitted in fulfilment of requirements of the Degree Master of Management Sciences Specialising in Quality Management at Durban University of Technology, Durban, South Africa, 2025.Quality control (QC) is integral to monitoring and controlling defective or poor-quality
products from reaching the customer. Developments in optical metrology promise more
accurate measurements and faster turnaround times to QC than current tactile measurements.
With the rising demand and complexity of injection moulded products, manufacturers are
pressured to produce quality products faster, notwithstanding that the current metrological
methods may not meet the output demand.
This study investigates the efficacy of optical metrological devices (3-D scanner) as a QC tool
for injection moulding.
The study followed a quantitative and experimental methodology. This study adopted a
probability, simple random type of sampling technique. A sample size of four was used.
Measurements of four different products (closures and tubs) were undertaken, including eight
attributes of the closures and five different attributes of the tubs. Tests were conducted on two
samples of each product, utilising a 3-D scanner and contact measuring devices. The statistical
conclusion validity method was used to determine the validity of the data obtained.
Repeatability and reproducibility methods were used to determine the reliability of the data
obtained from the tests conducted in the study.
The results indicated that optical metrology provided insufficient measurements for plastic
injection-moulded products. The results also provided an understanding of optical
measurements compared to tactile measurements.
Based on the study conducted, it can be concluded that even though there are established and
emerging optical metrological technologies, such as 3-D scanners, which are versatile and fit
for industries such as automotive and aeronautical manufacturing, they are currently not
effective or adequate for routine quality control testing in injection-moulded plastic products.
Although the 3-D scanner proved to be an inappropriate quality control measuring device for
plastic injection moulded products in this study, it is recommended that further investigation is
required. The importance of considering aspects such as product size, material composition,
and colour of the products in future studies cannot be overstated, as these factors could
significantly impact the effectiveness of the 3-D scanner.