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Work is not enough! : Addressing mid-career professionals' needs for leadership development
No full textBusiness schools face growing pressure to develop socially responsible and effective leaders, particularly among mid-career professionals. This study explores a reversed work-integrated learning (WIL) model, with a starting point in participants’ real-world leadership practices, integrating theory and continuous structured reflection. This contrasts with traditional WIL models that start with academic theory and rely on formal partnerships between academia and industry for work placements. Drawing on five years of qualitative data from 99 participants in a master's level leadership program, the study explores how this contract-free, practice-first approach supports leadership development by leveraging participants' ongoing professional experience. The pedagogical design emphasizes contextualized, lifelong learning through continuous individual and peer reflection. Reflexive thematic analysis reveals that the reversed WIL model effectively addresses leadership development gaps, enhances workplace impact, and offers a strong return on investment for individual participants and organizations. The study contributes a novel framework for leadership development education tailored to experienced professionals based on five key design principles: learner adaptation, contextualization, self-efficacy building, flexible structure, and peer-based learning.CC BY 4.0</p
Graphene-PVDF composite membrane for piezoelectric nanogenerators and lithium-ion batteries
No full textHerein, we introduce a composite membrane comprising polyvinylidene fluoride/graphene nanosheets (PVDF/graphene) for applications in piezoelectric nanogenerators (PENGs) and lithium-ion batteries (LIBs), where the graphene nanosheets play a vital role in enhancing the piezoelectric properties, surface energy, and porosity. A comparative analysis of the pure PVDF and the PVDF/graphene is conducted to evaluate their piezoelectric performance and suitability as separators in LIBs. The PVDF/graphene composite membrane produced a significantly improved piezoelectric output of ∼10.8 V under a force of 75 N, while the pure PVDF membrane exhibited only ∼3.7 V under the same conditions. Additionally, the Li//PVDF/graphene//graphite half-cell retained ∼81.3% of its specific capacity and maintained a coulombic efficiency of over 99.2% after 100 cycles at a 0.2 C rate. In contrast, the Li//pure PVDF//graphite half-cell retained only ∼48.6% specific capacity. Furthermore, in a full-cell configuration, the graphite//PVDF/graphene//LCO cell demonstrated excellent stability, retaining ∼88% of its specific capacity after 50 cycles, whereas the cell with pure PVDF membrane retained only 38%. Therefore, the PVDF/graphene nanosheet composite membrane has the potential to be used as a piezoelectric membrane in PENGs and as a separator in LIBs.Funder: National Centre for Photovoltaic Research and Education (NCPRE); J. Gust. Richert Foundation (2023-00824);Fulltext license: CC BY-NC</p
Wire arc additive manufacturing : A review on quality enhancement using nano-particle reinforcement
No full textWire Arc Additive Manufacturing (WAAM) has emerged as a promising metal additive manufacturing technique due to its high deposition rate, cost-effectiveness, and ability to build large-scale components. However, challenges such as porosity, poor mechanical properties, limited microstructural control, and residual stress hinder its full potential. Incorporating nanoparticles into the WAAM process has recently gained significant attention as a strategy to enhance material performance. This review provides a detailed and systematic analysis of the various types of nanoparticles used in WAAM, their methods of incorporation, effects on microstructure, mechanical performance, and functional properties of the built components. This review provides the first comprehensive classification and quantitative analysis of nanoparticle incorporation strategies in WAAM, systematically categorising 72 research articles across four distinct deposition strategies, including feedstock modification, interlayer application, direct melt pool injection, and ultrasonic dispersion. This work presents a comparative framework analysing the relative efficacy of different nanoparticle types (carbides, nitrides, and oxides) across multiple alloy systems, revealing that TiC emerges as the most extensively studied reinforcement. The review establishes that nanoparticle addition demonstrates positive influence on yield strength and ultimate tensile strength up to optimal concentrations, beyond which agglomeration-induced property deterioration occurs. Furthermore, the review identifies future perspectives for the optimized integration of nanoparticles in WAAM for high-performance manufacturing, design of multifunctional and hybrid reinforcement strategies, and adoption of AI-driven predictive modeling. The review discusses the industrial adoption barriers of the process. This systematic framework provides practical guidance for nanoparticle selection and process optimization, accelerating the industrial deployment of nanoparticle-reinforced WAAM technology.CC-BY 4.0</p
Investigation on Ageing Behaviour of Bio-Extended Bituminous Binders and Asphalt Mixtures for Sustainable Road Infrastructure
No full textThis paper investigates the use of a plant-based bio-oil in bituminous binders as a partial replacement of petroleum-based bitumen for asphalt mixtures. Its effects on the ageing behaviour of bituminous binders and asphalt mixtures are studied. A total of six bituminous binders and their asphalt mixtures were prepared and analysed in laboratory, including three different binder formulations with varying percentages of bio-oil and their respective reference binders. Both the bituminous binders and asphalt mixtures were subjected to ageing protocols in laboratory. Softening point test, rheological and dynamic mechanical analyses were conducted to evaluate the changes in properties of the materials before and after ageing. The results indicate that the mechanical properties of aged binders and mixtures show very similar relationships as between the fresh materials, but the relationships after ageing are at changed levels due to the laboratory conditioning. This supports further studies to verify their functional performance in asphalt pavements.10th Transport Research Arena (TRA) Conference, Dublin, Ireland, April 15-18, 2024.</p
Tempering of press hardening steels PHS1500 and PHS2000: characterization and influence on fracture toughness
No full textWith the continuous development of the automobile industry, the use of advanced high-strength steel in vehicles has become increasingly prevalent. Press hardening steels, known for their ultra-high strength, are gaining significant traction in this domain. Components manufactured using press hardening exhibit high dimensional accuracy and minimal spring back. The press hardening components are produced by heating the steel blank at the austenitization temperature, followed by hot forming and rapid cooling using pressing dies. However, despite the advancement in press hardening technologies and the widespread adoption of ultra-high-strength steels, certain challenges remain in further improving the performance of these materials, particularly in understanding the effect of processing treatments. This work studies the behavior of two ultra-high strength press hardening steels (PHS2000 and PHS1500) after undergoing heat treatment methods, specifically focusing on low-temperature tempering and press hardening. The objective is to increase the understanding of microstructure evolution and its influence on mechanical performance. The first method involved quenching the steels in oil followed by tempering at four temperatures in the range of 180-300 °C, while the second utilized die quenching to targeted temperatures, followed by air cooling to induce auto-tempering. Tensile properties, hardness, and microstructure changes were tested to understand how these treatments affect the steels' mechanical properties. The tensile properties of the steels investigated are influenced by the auto-tempering of martensite that occurs during the processes of oil quenching and die cooling. This phenomenon allows the steel to attain an optimal balance, demonstrating ultra-high strength exceeding 1900 MPa and good elongation at fracture, reaching around 8% or slightly higher. The tensile tests and microstructure analysis implied that low-temperature tempering (180-200 °C) could improve the yield strength of the steel as well as the elongation with a small reduction in the strength of the steel, in which the tempering effect caused precipitation strengthening and reducing of residual stresses in the microstructure. It was found that tempering at 300 °C promotes the formation and coarsening of cementite carbide, which led to a deterioration in the tensile elongation of the steels. The fracture toughness and bending properties of the steels were evaluated following oil quenching, press hardening, and a combination of press hardening with subsequent bake hardening. PHS2000 displayed brittle fracture characteristics and lower fracture toughness, while PHS1500 exhibited ductile fracture behavior and higher fracture toughness, with similar trends observed in three-point bending results. STEM and EDS analyses identified precipitates of varying compositions and morphologies, with coarse precipitates acting as key factors that limit grain refinement and contribute to stress concentration, thereby influencing fracture toughness and bending properties
Numerical study of mixing dynamics in controlled coaxial jets
No full textProducing iron ore pellets in grate-kiln plants involves several steps in order to obtain the final product. During the induration, the pellets are fired inside a rotary kiln; a large rotating oven, with two channels through which secondary process air enters. The secondary air channels are divided by the so-called back plate, causing an area of reduced velocity to form as the air flows past it. Current plants use coal to produce a flame inside the rotary kiln which heats the pellets. The coal flame is long and stable, and gives an even temperature profile inside the rotary kiln, something that is important for the quality of the pellets. As industries are transitioning towards more environmentally friendly processes and solutions, there is a desire to eliminate the use of fossil fuels such as coal. One alternative fuel of interest is hydrogen, since it can be produced and used without CO2 emissions. The issue with replacing the coal with hydrogen directly in the rotary kiln is that mixing with the surrounding secondary process air, necessary for combustion, occurs too quickly. This results in a flame that is short and intense, negatively impacting the pellet quality. Hence, different methods of injecting the hydrogen into the rotary kiln need to be investigated. This thesis investigates the use of a so-called coaxial jet to control the mixing of fuel and secondary air. The coaxial jet consists of a central round jet mounted in the back plate, through which hydrogen is issued. Surrounding the inner jet is an annular outer jet, issuing either hydrogen or a different fluid. By altering the parameters of the coaxial jet, mixing of the hydrogen fuel and the surrounding secondary air can be controlled, making it possible to tune the resulting flame. To investigate the effect of different parameter values, Computational Fluid Dynamics (CFD) simulations are used. As a first step a simplified, axisymmetric model of the rotary kiln is modeled in 2D. This approach reduces the computational effort, enabling large amounts of parameter values to be evaluated. The so-called momentum flow ratio of the outer jet to the inner jet, Mjet, is used to compare different configurations of the coaxial jet. By increasing or decreasing the outer jet velocity, the value of Mjet is increased or decreased, respectively. Two scenarios for the coaxial jet are considered; the first is using hydrogen through both the inner and the outer jet, and the second is using air instead of hydrogen through the outer jet. In Paper A, it is found that when using hydrogen through both the inner and outer jet, the potential core can be extended by decreasing the value of Mjet. This is achieved by decreasing the velocity of the outer jet, and thus providing a more gradual change in velocity between the high velocity inner jet, and the relatively slow secondary air. As a result the shear is reduced and the mixing is delayed. Among the values considered, Mjet = 0.25 produces the longest jet core and least mixing. This configuration, however, experiences recirculation and accumulation of hydrogen in a wake behind the back plate. If the outer jet fluid is substituted for air (Paper B) a different trend is seen, in which an increase of Mjet is beneficial for the jet length. The increased outer jet velocity, and thus momentum, enables the inner jet to be protected over a greater distance. Mjet = 2, the highest considered value, provides the longest hydrogen jet potential core and the most contained jet close to the jet exit. This is an indication that mixing with the secondary air is delayed. Further downstream, on the other hand, the increased shear that comes with higher Mjet -values contributes to increased mixing and spread. Lastly, a three-dimensional model is simulated in Paper C, offering insights into a more complete view of the flow field inside the rotary kiln. Three-dimensional as well as transient characteristics of the flow are scrutinized, showing that there are effects not captured by the simplified steady-state 2D model. Unsteadiness along the jet core boundary, as well as a difference in the prediction of the flow behind the back plate, contribute to a difference in the jet evolution between the 3D model and the 2D model. The main conclusion from this investigation is that the simplified axisymmetric model of the rotary kiln fails to capture important features of the flow field, making it unsuitable to use for predicting accurate details about the coaxial jet evolution. The findings from this thesis will be used as a basis for the continued work, which includes investigating the influence of additional parameters on the mixing and flow field, as well as conducting experiments to enable validation of the numerical simulations.Funder: Swedish Mining Innovation</p
Analysis of Production Area Layouts in Sublevel Caving Mines Using Discrete Event Simulation
No full textA traditional production layout is typically adopted in sublevel caving mines. However, as mining operations progress to deeper levels, increasing stresses necessitate exploring alternatives for production layouts. Other aspects of traditional production layouts that need to be improved are productivity, development distance, safety, and automation. Possible alternatives to the traditional layout are the fork and the heart layouts which might potentially be used in production areas. To evaluate and compare the production capacity of these layouts, this study analyzed the productivity and energy consumption of Load-Haul-Dump (LHD)vehicles using discrete event simulation (DES) method. Productivity of diesel-powered LHDs was analyzed in the traditional, the fork, and the heart layouts; productivity and energy consumption of battery-powered LHDs were analyzed in the traditional and the fork layouts. Findings showed productivity was 9-10% and 38% higher in the traditional layout than in the fork and the heart layouts, respectively, when diesel-powered LHD operations were simulated. Energy consumption per tonne of battery-powered LHDs was 10-11% lower in the traditional layout than in the fork layout, and the productivity of battery-powered LHDs was 9% higher in the traditional layout than the fork layout. Although the production capacities of these alternative layouts are lower than the capacity of the traditional layout, alternative layouts can be preferred if the perimeter drive or ore passes are positioned farther away from the production drifts to mitigate instability in the structures near the orebody boundary. When designing a production area layout, several aspects need to be considered in addition to productivity to balance the potential trade-offs between productivity and other factors such as safety and stability
Upper-secondary school segregation in Stockholm metropolitan area : the relationship between commuting distance and school characteristics
No full textAlthough free school choice policies are often proposed as strategies to decouple residential and school segregation, research has found that they may actually increase segregation. This study investigates an underexplored aspect of these policies: the role of commuting in influencing school segregation patterns. Using Swedish register data from Stockholm Metropolitan Area, we analyse ethnic and socioeconomic segregation across residential neighbourhoods and upper-secondary schools. We examine students' distances to the nearest schools offering their chosen programs and their actual commuting distances in relation to the schools' characteristics. Our findings reveal that students with immigrant backgrounds, despite living closer to the nearest schools offering their chosen programs than native peers, tend to travel longer distances to attend their chosen schools. For native students, choosing nearby schools is associated with selecting more privileged institutions that have higher proportions of native students and higher average income levels. In contrast, students with immigrant backgrounds often travel longer distances to reach schools with characteristics similar to those attended by native students. These results challenge simplistic assumptions about the segregation-reducing effects of free school choice policies and highlight the complex interplay among the uneven distribution of educational opportunities, home-to-school mobility, and school selection strategies
Validation of the use of ToF-SIMS for analysis of glycosaminoglycans
No full textGlycosaminoglycans (GAGs) have a range of biological roles and are of particular interest for their pharmaceutical efficacy and their potential as biomarkers or drug targets. Heparin, used globally as an anticoagulant and an antithrombotic, is predominantly derived from porcine sources but bovine and ovine sources are increasingly being considered to reduce the substantial risk of reliance on a single animal species. However, high sensitivity chemical discrimination of heparins from different species is a significant analytical challenge. In this study ToF-SIMS analysis of GAGs is investigated as a methodology to achieve specific chemical discrimination between GAGs of different types and heparins from different animal sources. The ToF-SIMS data acquisition is relatively fast (ti1 min per sample) and requires minimal sample amounts (75 pg of sample analysed). Multivariate analysis (MVA) models enabled high selectivity between GAG type and animal source of heparin, and for the high sensitivity detection of GAG-contaminants within porcine derived heparin. Contaminants are detected down to 0.001 wt%, with the exception of ovine derived heparin where differences could be detected to 0.01 wt%. Assessments of specificity, precision, robustness and quantification limits are conducted to validate the approach for heparin analysis
Early versus adult onset of schizophrenia : an examination of premorbid and current IQ
No full textBACKGROUND: Cognitive deficits are core findings in schizophrenia, but whether the severity of impairments is related to the age of onset remains unclear. We hypothesized that early onset schizophrenia (EOS; onset before age 19) is associated with lower IQ compared to adult-onset schizophrenia (AOS; onset from age 19). METHODS: We included 99 adult patients with EOS (age of onset: 15.3 ± 2.8 years), 282 adult patients with AOS (age of onset: 26.5 ± 7.4 years), and 863 adult healthy controls (HC). We assessed current IQ with Wechsler Abbreviated Scale of Intelligence (WASI) and estimated premorbid IQ with National Adult Reading Test (NART). RESULTS: Both patient groups had lower current IQ than HC (p < 0.001). Full-scale (p = 0.004), performance (p = 0.003) and verbal (p = 0.011) current IQ were significantly lower in EOS than in AOS, with 5 IQ units difference for all three measures. EOS and AOS did not differ in premorbid IQ, but EOS showed a steeper IQ decline from premorbid levels than AOS (11.4 vs. 8 IQ units, respectively, p = 0.013). CONCLUSION: EOS had lower current IQ than AOS, but did not differ in premorbid IQ, suggesting a larger decline from premorbid IQ levels. This could imply different neurodevelopmental processes underlying cognitive dysfunction related to age of onset in schizophrenia, underscoring the necessity for further inquiry into the mechanisms driving this decline and strategies for its prevention