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Comparative Assessment of the Leaching Properties of Fly Ash and Phosphogypsum Disposed of in South Africa
Get PDFFly ash (FA) and phosphogypsum (PG) are readily available industrial waste materials commonly disposed of in landfills. Knowledge of the leaching behavior of FA and PG can help us understand how to diminish their adverse effects on the ecosystem. However, there is limited research on the leaching properties of the FA and PG disposed of in South Africa. This study aims to comparatively assess the leaching properties of FA and PG disposed of at Eskom Duvha Power Station in Mpumalanga and Foskor Ltd in Phalaborwa, South Africa. The toxicity characteristic leaching procedure (TCLP) was used to obtain the leachates which were further analyzed by the inductively coupled plasma-mass spectrometer (ICP-MS). An XRF spectrometer was used to find the chemical composition of FA and PG. It was found that both FA and PG are non-hazardous since their leachate concentrations are within the US EPA TC, US EPA land disposal regulation, and EU waste acceptance at landfills. The solubility and mobility of As and Se depend on the alkaline concentration of the solution. The As adsorption rate escalates in Fe oxides and its mobility depends on the waste chemistry and pH. The chemical elements present in FA and PG i.e., Al3+, Si4+, Fe2+, Ca2+, instead of being leached into the ground can be incorporated into cement for construction applications. The present study output contributes knowledge on leaching properties of FA and PG in South Africa and can help policymakers create informed solid waste management frameworks and understand the potential of reusing in construction and recovering the elements of economic interest (e.g., Zn, Cu, Fe, P). The recycling of FA and PG for use as construction materials can help address landfill leaching problems and promote circularity
EFFECT OF WORKPLACE FLEXIBILITY ON EMPLOYEES’ ENGAGEMENT IN PIGGYVEST AND OPAY IN LAGOS STATE, NIGERIA
Get PDFThis research focused on the effect of workplace flexibility on employee engagement: A study of
selected FinTech Companies. Job satisfaction and work-life balance are not achieved because a
non-flexible work environment and less focused employee engagement may stifle creativity and
innovation. Employees may feel constrained within rigid structures, limiting their ability to
experiment with new ideas or approaches. As the main concerns of employee engagement are job
satisfaction and organizational behavior. The purpose of this study is to know how flexible work
environments affects employee engagements. The social exchange theory, work/family theory and
spillover theory provided to the theoretical foundation of the study. A quantitative survey method
was adopted for this study. The population of the study comprised of 762 employees and sample
questionnaire were administered to a sample size of 262 employees using convenience and
stratified sampling techniques. Results showed there is a significant positive relationship between
Compressed workweek, Job sharing, Flextime and employee engagement of selected FinTech
companies and implementing flexible work arrangements at these companies can lead to enhanced
employee engagement, personal development, and a more satisfied workforce. Hence, this study
recommends that Organizations should incorporate workplace flexibility, Compressed workweek,
Job sharing, and part-time work into their recruitment processes to enhance employee engagement
and satisfaction
3D mmWave MIMO Channel Modeling and Reconstruction for Street Canyon and Highrise Scenarios
Get PDFThe use of millimeter-wave (mmWave) and full-dimensional multiple-input multiple-output
(FD-MIMO) antenna systems for 3D wireless communication is being exploited for
enhanced network capacity improvement in the ongoing fifth-generation (5G) deployment.
For adequate assessment of competing air interface, random access channelization, and
beam alignment procedures in mmWave systems, channel models for different use
scenarios are necessary. A ray-tracing study was conducted with the use of a Wireless
Insite ray tracing algorithm to characterize the mmWave channel in urban areas, using
Lagos Island, Nigeria databases to predict measured statistics. These statistics include path
loss, rms delay spread, angular spread of arrival, and departure in the azimuth and
elevation domain. A 3GPP-style 3D mmWave channel is modeled and reconstructed,
emphasizing the use of a ray tracer to determine elevation model parameters. Line of sight
(LOS) and non-line of sight (NLOS) 3D models were developed for street canyon and highrise
scenario
Homomorphic Encryption for Genomics Data Storage on a Federated Cloud: A Mini Review
Get PDFThis paper provides an analysis and review of the fundamental aspects of securing
genomics data on a federated cloud. It highlights the concept of cloud computing and the
security issues associated with it. Furthermore, the concept of genomics, ethical and
privacy concerns relating to genomics data, and existing attacks on genomics data. Various
cryptographic approaches to data breach the importance of employing homomorphic
encryption schemes to safeguard genomics data. It discusses security issues in cloud
computing, the concept of federation in cloud computing, the genomics concept and
cryptographic approaches for protecting genomics data
Intra-Datacenter Load Balancing in a Federated Cloud with Throttled Algorithm
Get PDFThe emergence of cloud computing technology has motivated a very high number of users
in different organizations to access its services in running and delivering their various
operations and services. However, this surge of cloud users has led to the problem of
uneven load sharing among the cloud computing infrastructures. As a result, federated
cloud infrastructure was initiated to provide more cloud computing resources to
accommodate more cloud users’ requests and also to provide equal requests mapping with
the available cloud resources. Nevertheless, the issue of unequal allocation of requests
within the datacenter(s) that makes up the federated cloud environment still persists. This
research work presents an intra-datacenter load balancing algorithm in a federated cloud
environment named; the intra-balancer adapted throttled algorithm to evenly distribute
requests in each datacenter that formulate the federated cloud infrastructures. The
simulation of the intra-balancer was carried out in CloudAnalyst, the results of the
implementation showed that the intra-balancer outperformed the Round-Robin and ESCE
with 98.93ms and 2.26ms for the response and processing time respectively. The results
assert that the intra-balancer algorithm provides a better load balancing solution in a
federated cloud environment
A model predictive control-based STATCOM for weak grid voltage enhancement
Get PDFThis paper presents a model predictive control (MPC) technique for the control of reactive power flow from a static synchronous compensator (STATCOM) into a weak power system network. The MPC strategy enables the STATCOM to mitigate weak phase voltage magnitudes in a distribution grid. The weak voltage magnitudes usually emanate from large inductive loads connected to the grid’s point of common coupling (PCC). The MPC utilizes a finite control set of voltage vectors to minimize a cost function, which reduces the errors between set references and the corresponding predicted variables. The references in the cost function are set by two outer loop controllers. A time delay compensation strategy is introduced and proposed for selecting the gains of the outer loop controllers. An LC filter was also designed at the STATCOM’s output terminals to confine the harmonics in the injected compensation current to permissible limits. A robust all high pass filter dual second order generalized integrator (AHPF-DSOGI) based phase locked loop (PLL) is developed and proposed for synchronization of the STATCOM into the weak grid. The overall MPC strategy on the STATCOM enables shunt injection of compensation currents at the PCC while mitigating harmonics and consequently improving power quality. The STATCOM effectively regulated the bus voltage when required by switching between the capacitive and inductive modes. Results showing the efficacy of integration of the STATCOM to the grid and robust capabilities of the STATCOM in mitigating voltage swell and dip, as well as harmonics, are presented
A comparative analysis on the effects of sodium nitrate and hexamine on the corrosion of aluminium alloy in an acidic environment
Get PDFDespite aluminium and its alloys being relatively resistant to corrosion reaction as a
result of their passivating tendencies, aluminium alloys usually succumb to acidic
attacks resulting in mostly pitting corrosion. This study is focused on comparing the
efficiency of sodium nitrate with that of hexamine on the acid
corrosion of aluminium when used individually as inhibitors in 1 M Hydrochloric acid.
The gravimetric method was used for the corrosion study. Sodium nitrate was found to
have higher inhibitor efficiency of 94% compared to that of hexamine (44%), positioning
the former as a better inhibitor for aluminium alloy in 1 M HCl. ΔGadso was evaluated
and the obtained Standard free energy of adsorption were in the range of −13 to
−17 kJ/mol for NaNO3 and −6 to −12 kJ/mol for hexamine, signifying
the physisorption mode of adsorptio
Biofuel as an alternative for Sub-Saharan Africa’s transition to cleaner energy
Get PDFEnergy plays a vital role in the social and economic development of any nation. Compared to other regions of the world, Sub-Saharan
Africa lags behind in energy access. About half of the population lacks access to electricity and other cleaner fuels. With vast arable
land and good climatic and soil conditions, Sub-Saharan Africa could address its energy supply challenges through bioenergy. This
article reviews the biofuel potential of some Sub-Saharan African countries, the reasons why biofuel is suitable for the region, and the
barriers hindering its expansion and development. Findings from the review indicate that some progress has been made in bioethanol
and biogas production; however, biodiesel production is still in its infancy stage in the region. Most of the feedstocks for biofuel
production are from agricultural waste. Among the countries in Sub-Saharan Africa, South Africa and Kenya have shown great
prospects in the development and utilization of biomass resources for the production of cleaner fuels. Biofuel adoption in the energy
mix of Sub-Saharan African countries will reduce overdependence on the importation of crude oil, thereby saving huge foreign
exchange. It will also provide employment to millions of people in the agricultural value chain through the cultivation of bioenergy
crops. In terms of climate change mitigation, biofuel holds great potential in reducing carbon emission associated with fossil fuels
Correlative evaluation of the corrosion resilience and passivation properties of zinc and aluminum alloys in neutral chloride and acid-chloride solutions
Get PDFComparative analysis of the corrosion resilience
and passivation characteristics of pure zinc (Zn) and aluminum
(Al) alloys in neutral chloride and acid-chloride
solutions at 0.5–3% NaCl concentrations was done with potentiodynamic
polarization, potentiostatic evaluation, optical characterization,
and open circuit potential measurement. Results
show Al alloy was more resistant to general corrosion in both
solutions with values ranging from 0.031 to 0.082 mm/year, and
0.037 to 0.389 mm/year compared to Zn alloys with values
of 0.432–0.691 mm/year and 0.465–5.016 mm/year. Corrosion
potential values of Zn alloy were significantly more electronegative
than the values for Al alloy. The passivated region of the
polarization plots for Al was thermodynamically unstable with
visible current transients compared to that of Zn. Passivation of
Al occurred at the early onset of anodic polarization in the
neutral chloride solution. Zn alloy passivated at specific potentials,
coupled with stable passivation behavior. The passivation
range values of Al were generally greater than the values for
Zn due to delayed stable pitting activity. Optical images for Al
showed extensive localized degradation along specific regions
and grain boundaries, whereas Zn morphology indicates general
surface degradation. Open circuit potential plots indicate
significant growth of Al2O3 oxide on Al coupled with active–
passive transition behavior of the oxide. This contrasts the
observation for Zn where the plot configuration indicates limited
oxide formation and growth but significant thermodynamic
stability
Exploring the role of green hydrogen for distributed energy access planning towards net‑zero emissions in Nigeria
Get PDFProviding sustainable, affordable, and reliable electricity through low-carbon energy development in the Nigerian
energy sector is fundamental to ensuring energy security. Currently, efforts to harness the potential of renewable
energy, to provide universal electricity access for all have not translated into significant economic development
in Nigeria. Investment in green hydrogen could strengthen Nigeria’s net-zero transition plan (NETP) and achieve
sustainable energy access. The study explored the role of green hydrogen among five Electricity Distribution Companies
(DisCos), from three geopolitical zones in Nigeria—North West, North Central, and North East. A bottom-up
optimization linear programming methodology based on an open energy modelling framework (OEMOF) was used
as the modelling paradigm. Secondary data mined from the Nigeria Energy Commission, Nigeria Electricity Regulatory
Commission, NECAL 2050 report and international reports, and 2020 was used as a reference year to benchmark
the model. The basic characteristics of the generation of electricity from green hydrogen, fuel cells, electrolyzers,
and hydrogen storage, among other existing generation plants, were modelled till 2060 using modelled daily data
obtained from Toktarova et al. (Electrical Power and Energy Systems 111:160–181, 2019). Outcomes from benchmarking
led to two planning scenarios; these investigated possible insights that explored green hydrogen in Nigeria.
Results showed that an integrated distributed approach would enhance harnessing green hydrogen in Nigeria,
that is, electricity distribution among the DisCos. The study also revealed the following (1) the levelized cost of electricity
could drop by about 8%, so also the cost of the investment; (2) access to electricity showed an improvement
compared to the base year; and (3) emissions were cut in the power sector. To attain sustainable NETP with green
hydrogen, the study recommends that a distributed generation approach among DisCos would support the national
net-zero transition plan