bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral and magnetic properties of the jet base in NGC 315
Authors: Ricci L. , Boccardi B. , Röder J. , Perucho M. , Mattia G. , Kadler M. , Benke P. , Bartolini V. , Krichbaum T. P. , Madika E.
Published: December 2024

Aims. The dynamics of relativistic jets in inner parsec regions are deeply affected by the nature of magnetic fields. The level of magnetization of the plasma as well as the geometry of these fields on compact scales have not yet been fully constrained.

Methods. In this paper, we employ multi-frequency and multi-epoch very long baseline interferometry observations of the nearby radio galaxy NGC 315. We aim to derive insights into the magnetic field properties on sub-parsec and parsec scales by examining observational signatures such as the spectral index, synchrotron turnover frequency, and brightness temperature profiles. This analysis was performed by considering the properties of the jet acceleration and collimation zone, which can be probed thanks to the source vicinity as well as the inner part of the jet conical region.

Results. We observed remarkably steep values for the spectral index on sub-parsec scales (α ∼ −2, Sν ∝ να), which flatten around α ∼ −0.8 on parsec scales. We suggest that the observed steep values may result from particles being accelerated via diffusive shock acceleration mechanisms in magnetized plasma and subsequently experiencing cooling through synchrotron losses. The brightness temperature of the 43 GHz cores indicates a dominance of the magnetic energy at the jet base, while the cores at progressively lower frequencies reveal a gradual transition toward equipartition. Based on the spectral index and brightness temperature along the incoming jet and by employing theoretical models, we derived that the magnetic field strength has a close-to-linear dependence with distance going from parsec scales up to the jet apex. Overall, our findings are consistent with a toroidal-dominated magnetic field on all the analyzed scales.
Design and additive manufacturing of Ti-6Al-4V test-piece for use in aeronautical turboshaft engine heat exchanger
Authors: Bester Paul. , Aggenbacht F. C. , Adam Imdaadulah
Published: December 2024

While post-compression intercooling is commonly used to modify the performance characteristics of traditional turbocharged internal combustion engine layouts, there may be benefits to installing similar modifications in aeronautical turboshaft engines. The rise of Additive Manufacturing (AM) techniques offers the potential for lighter and more compact heat exchanger designs to be manufactured. To this end, a heat exchanger was designed to cool the charge air supplied by the compressor stages of a turboshaft engine. Using dimensional analysis techniques, a model was manufactured to assess the suitability of a heat exchanger produced using AM for aeronautical turboshaft engines.
The development of platinum alloys for jewellery applications by considering both the conventional and the advanced manufacturing techniques-review paper
Authors: Lekganyane Kedibone , Khodja-Moller Malika , Mkhonto Donald , Mostert Roelof , Phasha Maje
Published: December 2024

The thermophysical properties of platinum (Pt) and its alloys are key when deciding on jewellery fabrication or manufacturing techniques. They include the platinum alloys’ density, viscosity, melting point, thermal conductivity, reflectivity and surface tension as they directly impact traditional manufacturing practices compared to gold (Au) and silver (Ag). This review aims to assess the thermophysical properties of Pt and its alloys by considering their castability, printability and resulting physical and mechanical properties during jewellery platinum alloy development. The alloying elements of interest include copper (Cu), iron (Fe), germanium (Ge), tungsten (W), manganese (Mn), vanadium (V), ruthenium (Ru), rhodium (Rh), iridium (Ir), tantalum (Ta), and titanium (Ti) and their influence on the Pt properties will also be evaluated. The review attempts to define which Pt alloys should perform best, particularly concerning the production methods such as the investment casting technique and 3D metal printing i.e. additive manufacturing technique typical of Laser Beam Powder Bed Fusion (LB-PBF).
Investigating the effect of titanium substitution on the stability and performance of lithium-rich Li1.2Mn0.8O2 cathode material
Authors: Kgoedi Moloko Emmanuel , Ledwaba Raesibe Sylvia , Masedi Malang Cliffton , Ngoepe Noko , Ngoepe Phuti
Published: December 2024

Doping with titanium (Ti) is a potent technique for enhancing the performance of lithium-rich cathode materials due to strong Ti-O bonds and stable valence Ti-based modifications which have been used to improve the electrochemical performance of layered cathodes. Despite the large benefits of Li-rich oxides, several issues such as voltage decay and poor cycling stability still hinder their practical application. In recent years, many studies have focused on improving the electrochemical properties via various strategies such as regulating oxygen redox reactions and enhancing structure. In this study, the molecular dynamics simulation technique was utilized, and the influence of Ti doping on Li1.2Mn0.8O2 was investigated, revealing crystal disordering at 1500 K and Mn atom migration into tetrahedral sites. Notably, titanium doping was observed to increase structural stability, reduce cationic mixing, and hold promise for enhancing electrode capacity and strength. This research highlights the significance of comprehending the impact of ion doping on material properties through advanced simulations, offering a pathway toward the advancement of more effective energy storage solutions. By mitigating crystal disordering and bolstering structural integrity, titanium doping emerges as a valuable strategy for optimizing the performance of lithium-rich cathode materials, showcasing the potential for significant improvements in energy storage technologies.
Computational study of water adsorption on the TiNi (110) surface
Authors: Chauke Vukosi , Tshwane David , Ngoepe Phuti , Chauke Hasani
Published: December 2024

TiNi (Nitinol) alloys exhibit unique properties such as low density, high strength, superelasticity and shape memory effector various applications in medical devices, and aerospace industry. Understanding their surface water interactions is crucial. This work employs the density functional theory to examine water adsorption on the TiNi (110) surface. The results indicated an exothermic adsorption process favouring the bridge site energetically. Electronic structure analysis revealed the dominance of d- orbitals and the presence of states at the Fermi level. The charge density difference suggested covalent bonding between water and the TiNi surface. Insights into TiNi's surface chemistry and reactivity, which are essential for the reduction of corrosion in aqueous environments, were investigated.
First-principle study of Ti50Ni50-xNbx shape memory alloys for biomedical applications
Authors: Mathews Thabiso , Madigoe Mandy , Modiba Rosinah , Sithole Enoch
Published: December 2024

The excellent shape memory effect and biocompatibility of TiNi alloys have revolutionized the scientific and industrial communities, particularly in biomedical applications. These materials can undergo major or quasi-plastic deformation before returning to their original form when subjected to external stimuli like stress or temperature. However, nickel has been shown to be carcinogenic, it may lead to cytotoxicity which can result in infections, follow-up issues, or implant failure. The aim of this study is to improve the biocompatibility of TiNi by substituting Ni with Nb employing the first principle approach. The structural and elastic properties of the TiNi- Nb alloy were investigated using the CASTEP code embedded in Materials Studio. The findings indicated that Ti8Ni4Nb4's formation energy had increased. The poisons ratio decreased slightly, reaching a value of 0.32 in line with the G/B findings. Increasing Nb content also lowered the density of states at the Fermi levels. It was found that Ti8Ni4Nb4 was the most suitable substitute for TiNi alloys.
Influence of cooling medium on the microstructure and hardness of metastable Ti-15Mo-8Fe alloy
Authors: Moshokoa Nthabiseng , Makhatha Elizabeth , Raganya Lerato , Makoana Nkutwane Washington , Chauke Hasani , Diale Ramogohlo , Phasha Maje
Published: December 2024

Mechanical properties of metastable β-titanium (Ti) alloys are affected by factors such as the composition of the alloying elements, the process technique and phases formed due to different cooling medium after heat treatment. The effect of high iron (Fe) content in Ti-15Mo alloy under different cooling medium on the microstructural characteristics and hardness are investigated in this study. The alloy with a composition of Ti-15Mo-8Fe (wt%) was fabricated by melting in a commercially arc melting furnace and they were heat treated in a muffle furnace at 1100°C with 1hr holding time. The heat treated samples were subjected to various cooling medium such as water quench (WQ), Air cooling (AC) and furnace cooling (FC). Different characterization techniques such as the X-ray diffractometer (XRD) was used to analyse the presence of the phases, the Optical Microscope (OM) was used to analyse the microstructure and the Micro-Vickers hardness tester was used to measure the hardness. The XRD peaks revealed Fe·Ti·O2 oxides and β phase only in WQ condition, peaks in AC illustrated only β phase, FC samples showed both the β and the α phases only and B2 peaks in As-cast. The OM of WQ sample demonstrated large equiaxed β grains with pores around the grain boundaries, whereas the AC and FC illustrated medium grains with substructures and small grains with precipitates around the grain boundaries respectively and the OM micrographs of As-cast displayed dendritic structure only. The AC sample showed the highest hardness followed by the As-cast, then the WQ and the lowest hardness was seen in FC sample.
Nanomechanical, tribological and electrochemical characterization of Co-Cr-Mo ternary alloys fabricated via spark plasma sintering
Authors: Abe John Olorunfemi , Phasani Martha , Popoola Patricia Abimbola , Dada Modupeola , Popoola Olawale Muhammed
Published: December 2024

This research investigated the nanomechanical properties, tribological performance, and electrochemical behavior of Co-Cr-Mo ternary alloys. The ternary alloys were fabricated using spark plasma sintering and characterized using a nanoindenter, tribometer, and galvanostat/potentiostat to evaluate their properties accordingly. The findings indicated that the concentrations of Cr and Mo promoted the development of the FCC phase (γ-Co) and the HCP phase (ε-Co). As Mo content increased, the alloys showed better densification and improved nanomechanical characteristics (hardness and modulus of elasticity). Wear resistance was enhanced, with mean COF values and specific wear rates decreasing with Mo increasing content. Electrochemical tests showed that Mo content influenced the Co-Cr alloy's electrochemical behavior, with the Co-Cr-7Mo alloy showing the best electrochemical characteristics for biomedical application. The study elucidates the fabrication and performance of Co-Cr-Mo alloys, widely utilized in biomedical sector.
Computational high entropy alloy design
Authors: Simelane Khombisile , Becker Thorsten Hermann
Published: December 2024

Materials scientists are developing new materials to meet increasing demands by employing a systematic approach linking material performance to composition, processing, and microstructure. Computational techniques, such as Calculation of Phase Diagrams and Integrated Computational Materials Engineering, play a crucial role in this process, enabling fast and efficient material design. This study focuses on developing a high damage-tolerant high entropy alloy for hydrogen service, using the two computational techniques to identify optimal composition, predict mechanical properties, and elucidate strengthening mechanisms.
Characterization of the solution heat-treated binary β-type Ti-Mo alloy for bio-implant applications
Authors: Netshia Mukhethwa , Phasha Maje , Ngobe Bongani , Olubambi Peter
Published: December 2024

There is currently a high demand for biomedical implant materials due to the rapidly growing population of aged people in many countries. Ti-Mo alloys belong to a class of promising examples of beta (β)- type Ti materials containing non-toxic and non-allergic alloying elements that can be used for bio-implant applications. This study focuses on characterizing the solution heat-treated binary β Ti-14Mo alloy manufactured using the vacuum arc melting technique. All heat-treated samples resulted in dual phase structure comprised of β and α″ phases. As detected from XRD analysis, the intensity of the orthorhombic (α″) martensite phase increased with a decrease in heat-treated temperature. However, the samples heat-treated at 1100℃ yielded the highest hardness compared to those at 1000 and 900℃, respectively. Evidenced by micrographs, this high hardness is attributed to the degree of fineness of the α″ sub-structures that nucleated within the large β grains. The results show that the different solution heat treatments influence the structure of materials and mechanical properties.
Itaconic acid as an effective biobased platform molecule for vat photopolymerisation additive manufacturing
Authors: Dicks James , Masela Susan
Published: December 2024

The successful development of renewable feedstocks for monomer and oligomer synthesis has remained limited in its achievable biobased content, and often still rely on toxic compounds for functionalisation (e.g., acrylates). As such, the viability of itaconic acid as an abundant, cheap, and highly sustainable source of functionalisation for free radical polymerisation was explored to overcome these issues. Itaconic acid presented itself as a versatile α,β-unsaturated carbonyl diacid with the ability to be incorporated into monomers via several facile and sustainable synthesis pathways. Owing to these attributes, a novel monomer system composed of an unsaturated polyester oligomer and a castor oil derived monomer were developed and used alongside isobornyl methacrylate as a commercially available biobased reactive diluent for additive manufacturing. This system was demonstrated as an effective combination to achieve tailorable resins for masked stereolithography additive manufacturing with desirable mechanical properties, whilst maintaining a high sustainability.
Microstructural characterisation and hardness of Fe-Mn alloys compared to commercial 9%Nickel alloy
Authors: Mampuru Lebedike , Phasha Maje , Bodunrin Michael , Klenam Desmond , Moema Joseph
Published: December 2024

Increased energy demand globally due to population growth opens opportunities for alternative energy sources. Liquefied natural gas is gaining traction as an alternative to diversifying energy supply. 9%Nickel steel is used in the construction of tanks for storage and transportation of liquefied natural gas because of its high toughness and tensile strength properties. This alloy is not readily available because of its complex production process and high cost. In this research, cast Fe-Mn-based alloys are explored as an alternative to 9%Nickel steel. Computer-simulated binary compositions are cast and subjected to a thermomechanical process. Thermomechanically processed alloys are microstructurally assessed and harness tested as the initial evaluation step in selecting high-performing base alloy for further alloying. Alloy.
Foot placement optimisation for a hexapod robot on uneven terrain using heightmaps
Authors: Lotriet Andries Phillipus , Engelbrecht Jacobus Adriaan Albertus
Published: December 2024

This paper presents a method for selecting the optimal foot placement for a hexapod robot to facilitate travel over uneven terrain. This is achieved by using an RGB-D (Red Green Blue - Depth) camera to generate a heightmap in real time as the robot walks. The heightmap is then analysed using a convolution matrix to identify areas suitable for foot placement, where the slope of terrain, proximity to steep edges, and distance from the robot are considered. Based on these factors, the foot placement positions for the hexapod are optimised for each step.
Autonomous oil containment system for oil spill recovery
Authors: Benjamin Ra-Ees , Welgemoed Jacques , van Niekerk Theo , Young Andrew
Published: December 2024

The release of petroleum hydrocarbons in marine environments is harmful to aquatic and human life, necessitating efficient oil spill recovery processes. This paper presents an autonomous oil spill containment system designed to enhance response times. The system features a floating oil boom and two autonomous surface vehicles (ASVs) controlled by a ground control station (GCS) for coordinated manoeuvring. Due to their scalable and adaptable nature, the system can be configured for various oil spill scenarios. Simulations using a GCS and Software-in-the-loop demonstrated the autonomous potential, while real-world tests focused on ASV manual tuning and water condition analysis. Simulation results indicate the system's effectiveness in containing oil spills using GPS-guided ASV navigation. This prototype offers a foundation for future work in oil spill recovery technology.
Design of a remotely accessible satellite tracking system
Authors: Kisoon Rushil , Gumede Khehla , Fernandes J. , Stopforth Riaan
Published: December 2024

The growing number of objects in orbits has led to an increase in space monitoring. While large-scale tracking system exist, enthusiasts often use basic methods for satellite monitoring. To eliminate the need for physical access to tracking stations, the remote accessible satellite tracking system is proposed and implemented in this paper. The proposed system will track satellites and receive transmissions. A Raspberry Pi was used for control of the device, and a satellite tracking software – Gpredict – was used for calculating coordinates for rotation. Test results showed that the system could operate within 5 degrees of the intended target. Radio transmissions and slow-scan images could be received and recorded.
Material selection and optimisation of a 3D-printed indoor aerial robotics platform
Authors: de Ronde Willis , Botha Natasha , van Eden Beatrice , Tshabalala Lerato
Published: December 2024

Both aerial robotic platforms and additive manufacturing (AM) have become more affordable to consumers. Indoor aerial robotic platforms are typically small and lightweight, while AM is renowned for creating small, high-strength prototypes and components. This paper discusses the material selection and structural optimisation of a 3D-printed indoor aerial robotic platform. Three commonly used AM materials were compared using finite element analysis (FEA): acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol (PETG), and Nylon. It was found that Nylon offered the best performance in terms of the strength-to-weight ratio. The aerial robotic frame was optimised using an iterative design approach and previous knowledge with regards to the breaks observed during flight crashes. A dynamic FEA was performed to simulate a drop test from a height of one meter to compare the optimised design with the previous frame design. It was found that the improvements in the redesign have led to a 13.67 % decrease in weight and a 11.78 % decrease stress of the aerial robotic frame. This not only demonstrates the effectiveness of design optimisation, but also highlights the commitment to producing more efficient, reliable and sustainable designs.
Using additively manufactured compression moulds to produce polymer heart valves with variable leaflet thickness
Authors: Masheane Ronald , Combrinck Jacques , Masheane Lebohang
Published: December 2024

The durability of polymer valve lifespan can be impacted by fatigue-induced leaflet deterioration. One effective way to reduce the risk of fatigue failure is by increasing the thickness of the leaflets along the belly curve. A study indicates that valves manufactured using the dip moulding method, displayed thinner thickness at the belly of the valve and experienced a higher stress concentration in that area. This implies that a carefully regulated varying thickness could play a crucial role in optimizing the valve hemodynamic performance and enhancing its longevity. The additive manufacturing process was utilized to manufacture the complex and intricated Ti6Al4V (ELI) static and dynamic assemblies of the compression mould. The process and moulding parameters that facilitated the fabrication of an experimental valve prototype were ascertained. Scanning electron microscopy studies were performed to confirm the obtained wall thickness using thickness measuring instruments and to evaluate the surface topography of the leaflet’s surfaces. The valves were subjected to tensile testing to examine the fundamental mechanical properties of the valve and compared with natural valves.
Parameter development for near-fully dense LPBF-produced stainless steel 316 using a design of experiment approach
Authors: van Niekerk Marné , Dicks James , Kloppers C.P. , Becker Thorsten Hermann
Published: December 2024

This study aims to develop parameters that minimize porosity in SS316 using a Design of Experiments approach (DOE). Employing the D- Optimal (D-Optimal) method and ANOVA, we determined a quadratic model for predicting porosity. The model was validated through three-point predictions, demonstrating high accuracy. The study utilised the bootstrapping method to identify the minimum sample size required for reliable predictions, establishing that 15 samples are sufficient. This was verified by plotting three sets of 15 random samples, where actual vs. predicted values showed strong agreement. The study achieved the highest density of 7.94 g/cm³, corresponding to 99.6% relative density. These findings offer a robust framework for optimising material properties to reduce porosity effectively.
Digital intellectual property and privacy right in achieving the sustainable development goals using South Africa as a case study
Authors: Aroba Oluwasegun Julius , Ramchander Manduth
Published: December 2024

A key barrier to achieving the Sustainable Development Goals (SDGs) is the intersection of intellectual property (IP) rights and privacy concerns, especially as reliance on digital technologies grows for economic and social progress. One of the critical ethical trade-offs in IP rights in IT in South Africa is the tension between protecting the interests of creators and promoting access to Information and knowledge, particularly in the context of the digital divide. This article, with a focus on South Africa, examines how digital IP and privacy rights impact SDG 9, 16 (Peace, Justice, and Strong Institutions). Loopholes, copyright protection is not always compatible with I.T. technology. Through legal analysis, policy evaluation, and case studies, it explores how IP protection can spur economic growth, ensure fair competition, and promote innovation while addressing privacy threats. The study also assesses existing policies' effectiveness in advancing SDG 9, 16, protecting privacy, and fostering innovation across vital industries. The study's conclusions advance knowledge of the intricate relationships between digital intellectual property, private property rights, and sustainable development. Particularly in the context of South Africa, the analysis provides insights into policy recommendations and best practices for practitioners, stakeholders, and policy makers to effectively exploit digital technologies while protecting individual rights and achieving the 9th and 16th SDGs.
Ionic diffusivity of manganese-based spinel-layered composite nanoarchitectures: An analysis of morphological dependence
Authors: Ledwaba Raesibe , Ngoepe Phuti
Published: December 2024

The electrochemical performance of spinel LiMn2O4 has been demonstrated to vary depending on the morphology of the electrode material. Lithium-ion battery development and optimization require a thorough understanding of the diffusion of lithium ions in electrode materials. Modifying the microstructure of the LiMn2O4 by controlling the distribution and compactness of particles can improve electrochemical properties. This interest in spinel is driven by its enormous appeal as a cathode material due to its robust structure with a three-dimensional ion transport channel, high operating voltage (~4.7 V versus Li+/Li), and its use in high-energy lithium-ion batteries. The Mn-rich chemical composition renders it more economically benign considering the abundance of Mn-raw materials. In this study, we elucidate the impact of morphology on electrochemical ionic kinetics of the simulated nanoarchitecture materials by utilizing molecular dynamics simulations from 300K to 2000K. Analysis of the diffusion coefficients demonstrates that the nanospherical particles display dominant ionic diffusivity compared to 2D-nanosheets and 3D- nanoporous morphology. Ultimately, the volumetric and surface analysis demonstrates the robustness of nanoporous morphology as they are reported as 5% and 1%, respectively. These findings demonstrate that the nanoporous morphology has a robust structural integrity.
Phase and mechanical property prediction of intermetallic-strengthening Ti-Al-Cr-Nb-Ni-Cu-Co high entropy alloys by thermo-physical parametric calculation and CALPHAD-based technique
Authors: Anamu Ufoma Silas , Ayodele Olusoji Oluremi , Olorundaisi Emmanuel , Babalola Bukola Joseph , Odetola Peter Ifeolu , Ogunmefun Anthony , Ukoba Kingsley , Jen Tien-Chien , Olubambi Peter Apata
Published: December 2024

Non-conventional alloy developmental approach targeted at incorporating intermetallics as strengtheners using thermo-physical parametric calculation and CALPHAD-based tool (ThermoCalc software) were adopted in the design of septenary non-equiatomic [Ti20Al20Cr5Nb5Ni19Cu12Co19] HEAs. Thermo-physical properties indicated a lightweight and dual-phase HEA having density of 6.22gcm-3 and 6.88 VEC value. At room temperature conditions, computation using ThermoCalc of version 2021b (TCHEA4) encrypted database shows the presence of 6 phases, where BCC_B2, FCC_L12, Sigma, Heusler and C1_Laves are pronounced at varied volume fractions with BCC_B2 occupying 69.8 vol% of the predicted HEA. Traces of O_Phase were observed, and 144.096HV was computed as the maximum predicted total hardness.
Investigation of hydrogen storage properties for high entropy alloys (Ti30V30Cr30Fe10 and Ti40V30Cr10Fe10Al10)
Authors: Tau Jacuquline , Siyasiya Charles , Modiba Rosinah , Mathe Ntombi , Arthur Nana , Pityana Sisa
Published: December 2024

The broad compositional space of high entropy alloys (HEAs) presents an opportunity to research new hydrogen storage materials, with improved hydrogen storage properties under ambient temperature and pressure. The properties of these materials are influenced by several factors including composition, operating pressure, and temperature, as well as the fabrication techniques employed. As such this study investigated two HEAs, namely Ti30V30Cr30Fe10 and Ti40V30Cr10Fe10Al10 using empirical and thermodynamic modelling methods, where Ti30V30Cr30Fe10 was successfully synthesized using LENS. The phase prediction criterion showed formation of a single solid BCC structure with VEC ≤ 5.4 and XRD confirmed formation of BCC and Laves phase structure. The investigated HEAs demonstrated excellent performance for hydrogen storage with maximum hydrogen storage capacities of about 3.8 and 4 wt% respectively at 25 and 100 0C, exceeding the previously reported HEAs for hydrogen storage.
Mechanical and thermal properties of monazite LaPO4 under pressure
Authors: Motsomone Lebogang , Diale Ramogohlo , Ngoepe Phuti , Bissett Hertzog , Chauke Hasani
Published: December 2024

Monazite-La (LaPO4) is considered the first constituent of the rare-earth orthophosphate group and has received a considerable scientific interest owing to its notable physical characteristics, such as its optical emissivity and its ability to withstand radiation damage and corrosion when exposed to molten glass. This material is deemed suitable for the extended- term containment of radioactive nuclear waste. This study investigates the influence of pressure on the mechanical and thermal properties of Monazite- La within the pressure range of 0 to 100 gigapascals (GPa) through the utilization of the density functional theory (DFT) approach. At 0 GPa, it was shown that the lattice parameters exhibited a significant level of concurrence with experimental findings to within 3%. Furthermore, it has been observed that the structure exhibits mechanical stability up to a pressure of 100 GPa. Additionally, this paper will also address the concepts of heat capacity, and thermal expansion. The findings provide enhanced insights into the mechanical and thermal properties of Monazite-La when subjected to pressure.
Thermal aging of additively manufactured maraging steel
Authors: Davids Micaela , Johnston Charmaine , Tshabalala Lerato
Published: December 2024

The mechanical properties of Additively Manufactured M300 Maraging Steel were tested after two thermal treatments. It was found that the stress-relief process resulted in tensile strength comparable to the powder specification, but low ductility compared to the specifications, whilst the addition of an aging process resulted in substandard tensile strength and extreme brittleness. The results of a hardness test and the tensile properties achieved suggest that the material was embrittled by both thermal processes. The samples were inspected using an Optical Microscope (OM) after testing.
Towards the design qualification of removable partial dentures produced through laser powder bed fusion of cobalt-chrome – a case study
Authors: Adam Imdaadulah , Combrinck Jacques , du Preez Willie
Published: December 2024

Part qualification, a component of quality assurance, is a critical requirement for components produced through additive manufacturing (AM) and intended to replace traditionally manufactured qualified industrial components. The part qualification process is broad and can cover requirements which are linked to individual additive manufactured parts, machines, materials and process parameters based on overall risk. This paper reviews the design qualification process for removable partial dentures (RPDs) fabricated through laser powder bed fusion (LPBF) using cobalt- chromium (Co-Cr) alloys. Key considerations during the manufacturing process which ensure the reliability and efficacy of LPBF-produced RPDs are discussed. With reference to the dental industry, one such consideration is the need for patient comfort which is derived from the fit of the RPD. This paper further demonstrates the use of design qualification (DQ) to define the fit of LPBF RPDs according to dental requirements. The DQ was instrumental in defining a suitable material fit for RPD produced using the LPBF of Co-Cr.
Analysis of the influence of belly thickness and free edge curves on the hemodynamic performance of a polymer heart valve
Authors: Masheane Lebohang , du Preez Willie , Combrinck Jacques
Published: December 2024

Polymer heart valves are emerging as a viable attractive substitute for mechanical and biological valves because of recent developments in material and manufacturing production. This study focuses on key aspect of design optimization in addressing challenges associated with the fatigue and hemodynamic performance of polymer heart valves. Numerical simulations were conducted to investigate the effects of belly and free edge curves on the mechanical stress and hemodynamic performance of the leaflets. Results showed that increasing leaflet thickness reduced stress and uncontrolled thickness could result in stiffer valves affecting valve natural functioning. Curved free edges of the leaflets also necessitated more effort to unfold them fully. Optimizing leaflet curvature and thickness could significantly improve valve performance.
Wearable productivity measurement IoT system development
Authors: Heppell Reevan , van der Merwe André
Published: December 2024

This project develops a system that captures and stores acceleration and rotation data from an operator’s hand and tests said data’s compatibility with a machine-learning algorithm. Tracking the productivity of operations is a goal a follow-up project aims to achieve, and this system is a necessary part of a possible solution. An IoT system was developed and tested by presenting the data to a machine learning algorithm to ensure that an algorithm can identify certain movements from the data. The results are valid since the system itself was tested in a case study with 24 participants and performed as expected. the data that the system provides as output was presented to two machine learning algorithms and both were able to identify movements with more than 80% accuracy.
Overcoming the challenges of developing CubeSat flight software with limited access to satellite hardware
Authors: Slabber Dirk , Fisher Callen , Jordaan Willem
Published: December 2024

The drastic rise of CubeSat missions in recent years has forced satellite developers to deliver satellites at high speeds. The complexity of flight software for missions, however, leaves it susceptible to programmatic failure. To develop the DockSat mission in an acceptable timeframe, this article proposes to utilize digital twins of satellite components to allow software development and complex testing at earlier stages of the mission development cycle where hardware and experimental setups are not available.
An optical gas imaging technique based on strobed illumination
Authors: Chirindo Mathews , Cox Ettienne , Duness Kahesh
Published: December 2024

Gas leakage from equipment poses undesirable safety, environmental and operational impacts. Many optimal gas imaging techniques exist which detect and visualize gas plumes. However, most of these techniques struggle to produce clear images when the temperature gradient between the scene background and the gas plume is small. This paper presents an optical gas imaging technique that is based on strobed illumination, wherein the strobing frequency of the illuminating device is associated with the camera frame rate. Experimental test results are presented to show the improved detection of volatile organic compound gases during strobed illumination under dark room laboratory conditions where the percentage contrast value of the illuminated gas relative to its background varies by 50.8% The test results for the detection of sulphur hexafluoride gas and liquid petroleum gas under an outside environment are also presented.
Microstructural evolution of heat-treated 316L stainless steel using various etchants
Authors: Moumakwe Molebogeng , Arthur Nana K.K , Poopola Abimbola P.I , Raji Sadiq A.
Published: December 2024

The rapid heating and cooling cycles inherent to laser additive manufacturing result in the accumulation of high residual stress magnitudes that may have an adverse effect on the material's mechanical properties. Post-processing heat treatment has been suggested to mitigate the problems associated with residual stress build-up and heterogeneous microstructure that results from localized heating and rapid solidification. This study investigates the effect of post-processing heat treatment of additively manufactured 316L stainless steel impellers to customize the treatment for optimal microstructure and mechanical performance. The samples were stress-relieved and solution-treated to homogenize the microstructure. From the results, it was observed that heat treatment substantially decreased the microhardness of the as-built specimen. The microhardness was reduced by 10% when stress relief was applied at 600ºC while showing a reduction of 28% at an annealing temperature of 1150ºC. Furthermore, the potassium in water etchant revealed carbide precipitates more pronounced and visible in the solution-treated specimens than in stress-relieved specimens. Similarly, Kallings etchant revealed a heterogeneous microstructure with a laser- generated pattern more visible in the stress-relieved specimen while no apparent pattern was observed in the homogenized specimen.
Dry electropolishing of Ti6Al4V samples produced by laser powder bed fusion for bone
Authors: Mhlanga Moses , Masheane Lebohang R. , Yadroitsava Ina , Yadroitsev Igor
Published: December 2024

This study describes the DLyte dry electropolishing of heat- treated Ti6Al4V samples (vertical, horizontal and semi-sphere samples) produced by laser powder bed fusion technology. The Ti6Al4V samples were divided and build-in zones according to the Argon inlet and outlet as well as the start and end areas of the powder distribution within the building plate. The as-build Ti6Al4V samples were investigated for their suitability in medical bone implant applications and were found to have a surface roughness that exceeds the standards of a bone implant irrespective of the zone in which they are built. This necessitates additional post surface finishing procedures to achieve the desired surface finish for bone implants. DLyte dry electropolishing was employed for surface finishing to enhance the surface condition of Ti6Al4V as-build samples. The Ti6Al4V as-build samples were polished according to their zones in which they were build. The efficacy of polishing was assessed based on different time intervals (30, 60 and 120 minutes) and the decrease in surface roughness. The results show that after 30 minutes of polishing there was a lower reduction in surface roughness and the higher surface reduction was observed after 120 minutes of polishing. It was noted that as the polishing time increased, the surface become progressively smoother.
Comparison of recycling processes of the used sand produced during the binder-jetting process
Authors: Matjila Makwena Annikie , Nyembwe Kasongo Didier
Published: December 2024

The binder-jetting process, also known as rapid sand casting, generates used sand that researchers have been exploring ways to recycle. Methods such as mixing the used sand with new sand or using thermal and mechanical reclamation processes have been investigated. This paper compares the efficiencies of these recycling methods by examining whether the used-sand test specimens meet the required mechanical properties, and their potential for circularity. The methodology used in the paper is based on Multi-Criteria Decision Analysis (MCDA), which is a decision-making process that evaluates and prioritizes multiple criteria to determine the best option using weighing and scoring. Applying the MCDA approach ranked sand mixing as the most effective recycling method, followed by thermal reclamation and then mechanical reclamation. This study aims to improve the understanding of how to manage waste sand produced by rapid sand casting more efficiently.
Characterizations of Italian graphs and Sicilian graphs
Authors: Ferrari Alberto José , Leoni Valeria , Lopez Pujato María Inés
Published: December 2024

In this work we deal with three variants of domination in graphs, these are Italian domination (or Roman {2}-domination), {2}-domination and 2-domination. We define Sicilian graphs as those graphs for which the Italian domination and the {2}-domination numbers coincide. Sicilian graphs constitute a superclass of Italian graphs (introduced by Klostermeyer and MacGillivray [J. Comb. Math. Comb. Comput. 108 (2019) 125–146]). First, we give a characterization of Italian graphs in terms of the existence of a special Roman {2}-dominating function. Then, we focus on web graphs for which their {2}-domination number was recently found (Cheng et al., Discrete Math. Algorithms App. 12 (2020) 2050055), and we study Sicilian web graphs. We explore also Sicilian co-bipartite graphs. As a by-product, we find the 2-domination number for web graphs and co-bipartite graphs. Finally, we show necessary conditions for non-Italian graphs to be Sicilian as well as characterize Sicilian graphs within some relevant graph classes such as quasi-threshold graphs and cographs.
Pricing and platform coupon decisions of a hybrid channel supply chain under different power structures
Authors: Wan Nana , Fan Jianchang
Published: December 2024

With the rapid development of e-commerce and the increasing popularity of coupons, we investigate the issuing problem of platform coupons in a hybrid channel supply chain with a manufacturer, a physical retailer and an online platform. Based on game models, we derive the optimal pricing and platform coupon decisions under different power structures. We find that without platform coupons the manufacturer and the retailer obtain more profit if they have more power, while the platform and the system attain the same profit regardless of power structure. With platform coupons, three members obtain more profit if they have more power, while the system obtains more profit if the retailer has more power. If the manufacturer obtains more (less) power than the platform, issuing the platform coupons cannot (can) always attract more online purchase. Moreover, issuing the platform coupons cannot result in the “all-win” outcomes for the members under any power structure. Finally, if the manufacturer obtains more (less) power than the platform, issuing the platform coupons cannot (can) always optimize the chain-wide performance. This paper provides advice for the enterprises to properly use the coupon tool to maximize profit under different power structures.
Evaluation of the effect of digital game applications on “speaking and writing skills in teaching Turkish to Foreigners” course
Authors: Tekman Tülay Kaya , Piro Aslı
Published: December 2024

Digital materials are used as an important tool to teach Turkish more effectively. Since digital materials are more interactive and visual, they help to attract students’ attention and help them understand the topics better. The study aims to evaluate the effect of digital game applications on speaking and writing skills in teaching Turkish to foreigners. The main research question of the study has been determined as “Does the use of digital game applications in teaching Turkish to foreigners have an impact on speaking and writing skills?” The study was conducted with a total of 20 students learning Turkish as a foreign language at a private university in TRNC in the fall semester of the 2023-2024 academic year. A mixedmethod approach was preferred in the research. The findings obtained from the quantitative and qualitative data of the study revealed that digital games provide significant improvements in speaking and writing skills, especially in foreign language learning. Student opinions also support that this method is motivating and effective in language learning. These results provide important clues on how digital games can be used effectively in language teaching.
Exploring the link between digital literacy and readiness towards mobile learning among future teachers
Authors: Akpınarlı Sena Seçil , Köseoğlu Pınar
Published: December 2024

This study investigates the relationship between digital literacy and mobile learning readiness among 250 prospective teachers at a state university in Ankara, Türkiye. Data were collected using the “Readiness Scale towards Mobile Learning,” developed by Lin, Lin, Yeh, and Wang (2016) and adapted to Turkish by Gökçearslan, Solmaz, and Kulkul (2017), alongside the “Digital Literacy Scale” by Ng (2012), adapted by Hamutoğlu, Güngören, Kaya Uyanık, and Erdoğan (2017). Results indicated that prospective teachers possessed high digital literacy levels. Their attitudes and technical skills significantly predicted their readiness towards mobile learning. A Pearson Correlation analysis revealed a strong, significant linear relationship between digital literacy and mobile learning readiness (r=.815, p=.000). This suggests that higher digital literacy is closely associated with greater readiness towards mobile learning among prospective teachers.
Investigation of attitudes towards sport and internet addiction levels of faculty of sport sciences students in terms of various demographic variables
Authors: Tosun Seçil , Soyer Alptuğ
Published: December 2024

This study examined the relationship between the attitudes toward sport and internet addiction levels of sport science faculty students according to various demographic variables. In the study, data were collected using the Attitude Toward Sport Scale and Internet Addiction Scale, and the study group of the research consisted of a total of 588 people, 320 of whom were female (54.4%) and 268 of whom were male (45.6%), who were studying at the Faculty of Sport Sciences. The data collected with the Attitude Toward Sport Scale and Internet Addiction Scale were analyzed at the end of the study, considering their normal distribution. When the data were examined because of the analyses, the data were normally distributed and parametric tests; Pearson Correlation Test, and independent samples Ttest were applied. As a result of the tests performed; a positive significant relationship was reached between the Attitude Scale towards Sports and the Internet Addiction Scale. In addition, when examined in the context of gender, marital status, department, and class, it was seen that there was no statistically significant difference. In the context of the variables of participation in sports, being an athlete, spending enough time on sports, opportunity to do sports close to residence, and time allocated to daily social media, a statistically significant difference was found.
The relationship between physical fitness levels, motivation to participate in physical education and physical activity attitudes of middle school students
Authors: Arslan Kabasakal Sema , Geri Serdar
Published: December 2024

This study investigates the relationship between physical fitness levels, motivation to participate in physical education lessons, and physical activity attitudes in middle school students. A total of 106 middle school students with an average age of 12.02±1.16 from Yalova province were included in the study. Physical fitness tests were performed on the participants, and they filled out the Physical Education Motivation Scale (PEMS) and the Physical Activity Attitude Scale for Children and Adolescents (PAASCA). Within the scope of the findings, significant differences were found in right and left flexibility, PEMS total score, intrinsic motivation sub-dimension score, and PAASCA total score according to gender (p<0.05). In contrast, no significant differences were found in other variables (p>0.05). No significant relationship was found between the physical fitness parameters of the participants and PAASCA scores and PEMS total and sub-dimension scores (p>0.05). A significant relationship was found between the PAASCA scores of the participants and the PEMS sub-dimension scores. As a result, as the intrinsic and extrinsic motivation to participate in physical education classes increases, the physical activity attitudes of middle school students improve. The level of physical fitness does not affect the motivation to participate in physical education lessons and the attitude to participate in physical activity of middle school students.*