Digitala Vetenskapliga Arkivet - Academic Archive On-line
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A Suitcase of Algae: Using PCRPresence-Absence to Determine MultipleTrebouxia Lineages in Thamnolia Lichen
No full textCharacteristics of bark and wood of Norway spruce infested by spruce bark beetle and blue-stain fungi : relevance for biomass utilization
No full textRecent droughts have accentuated problems with attacks of the European spruce bark beetle (SBB) (Ips typographus) on Norway spruce (Picea abies), one of the most important tree species in European forestry. SBB attacks are typically accompanied by infestation with Ophiostomatoid fungi causing blue stain. The chemical composition of sapwood and bark from spruce trees infested by SBB, or by both SBB and blue-stain fungi (BSF), was investigated and compared to corresponding fractions from non-infested reference (REF) trees. While sapwood from infested trees showed higher carbohydrate:lignin (C:L) ratios (SBB, 2.21; BSF, 2.47) than sapwood from non-infested trees (REF, 2.17), BSF bark showed lower C:L ratio (0.81) than REF bark (1.23). For BSF sapwood and bark, and SBB bark, the fractions of extractives were half or less than half of that of the corresponding REF materials. Group analysis using GC-FID showed significantly (p ≤ 0.01) lower levels of resin acids, fatty acids, steryl esters, and triglycerides in BSF materials than in REF materials, a phenomenon that was, however, not observed for sterols. Analysis of subgroups and individual fatty acids, resin acids, and sterols identified using GC-MS revealed complex patterns, in which many, but not all, substances exhibited lower values in BSF and SBB materials than in REF materials. Overall, the results point towards the possibility to utilize a larger portion of wood logs from trees infested by beetles and fungi for value-added applications, such as pulping, rather than as fuel wood
Education and Traffic Safety Among Young Drivers with A-Tractors in Sweden
No full textIn the new proposal of the Driving Licence Directive in the EU, a new B1 driving licence category are discussed, where Member States can extend driving rights of young driving licence holders (from 16 years of age), to drive vehicles with a maximum speed of up to 45 km/h. Sweden have had A-tractors (a slow-moving vehicle) for many years, which is a standard vehicle and originally built and used by farmers. However, after the Swedish authorities introduced new rules, the A-tractors have become very popular among young people. The purpose of the study was to gain better knowledge into the use of these vehicles and the drivers’ perceptions of road safety. A survey and interviews were carried out with young drivers. Unique knowledge has been gained about where, how and why young people use A-tractors. Especially noticeable was the low rate of belt use in A-tractors, speeding (i.e. vehicle tuning) and the high number of passengers travelling in the vehicles. As the vehicles have increased significantly, new regulations are needed to find possible changes that can improve the driving education and increase traffic safety for drivers with A-tractors. Furthermore, driver training has an important preventive role and to be allowed to drive an A-tractor a certificate of competence obtained through driving practice should be required
Metal and dust exposure in workers from the metal recycling industry in Sweden : cross-sectional GreenMetalWaste study
No full textThe green transition relies on metals, requiring increased metal recovery from waste. However, exposure risks among metal recycling workers are poorly understood. We conducted a cross-sectional study to assess dust and metal exposure among 139 recycling workers from 13 Swedish metal recycling companies and 90 controls. We documented work practices through observations and questionnaires and assessed dust and metal exposures using a combination of individual air sampling (inhalable (ID) and respirable dust) and biomonitoring (blood and pre-/post-shift urine). ICP-MS was used to measure 39 metals in air, 47 in blood, and 42 in urine. Thirty-two % of the workers were involved in the recycling of e-waste. At most workplaces, dust control was insufficient, respiratory protective equipment was rarely or incorrectly used, and hygienic routines were inadequate. This was reflected in 6.2 times higher ID levels in recycling workers; 14 % exceeded the 5 mg/m3 exposure limit for ID, and some also exceeded limits for Pb, Cu, As, Cd, and Sb. Workers had elevated blood and/or urine levels of Pb, Hg, Al, Sb, Fe and Mn with known human toxicity, and of Y, Lu, In, Ga, W, and Te with limited or unknown toxicity. Furthermore, observed were also co-exposure patterns for those metals. Inhalation was the likely primary exposure route for Pb, Sb, Y, In, and Te. In conclusion, Swedish recycling workers were exposed to elevated levels of dust and metals, highlighting the need for ongoing monitoring of both known and emerging metals
Reducing traffic with “carrots” : A review of the evidence
No full textReducing traffic volumes is one way to reduce carbon emissions from the transport sector. Since increasing driving costs is often met with public resistance, high hopes are often pinned on the possibility to reduce traffic volumes by non-coercive policy measures, or “carrots”. Such measures include improvements of alternative modes, strategies that affect urban forms, and “soft measures” that aim to affect behaviour by providing information or changing norms and attitudes. This paper reviews the empirical evidence regarding such measures, focusing on their potential to reduce aggregate road traffic volumes in a national perspective. While such measures can yield significant other benefits, and may also reduce traffic volumes locally, our general conclusion is that their effects on aggregate traffic volumes appear small, especially from a climate policy perspective where emissions need to be cut radically and rapidly. While they are often motivated for several other reasons, overestimating their effects on aggregate traffic volumes may cause complacency, misallocations of scarce public resources and backlashes against climate policy.
Digital Twins for Asset Management of Civil Structures : Perceived Potential and Practical Applications
No full textThe Engineering and Construction (E&C) industry has vast potential to leverage technology for solving current asset management issues, with significant environmental and financial benefits. This study investigates the use of Digital Twins (DTs) for asset management of civil structures, identifying a gap between the perceived potential of DTs and practical applications due to misconceptions, industry fragmentation, and lack of standardizations. To address this, a literature review and experimental programs were conducted, leading to the development and validation of a proof-of-concept DT platform applied to two case studies. The study concludes with a purpose-driven DT roadmap to address the gap between potential and practical applications in the E&C industry. Background: the integration of Building Information Modeling (BIM) and DTs for asset management in construction offers a promising solution to improve current processes, which are often time-consuming or inefficient. With technology rapidly advancing and the advent of Industry 4.0, there is a growing belief in the transformative potential of DTs to address longstanding challenges within the industry. By leveraging these innovative tools, stakeholders aim to enhance operational efficiency, optimize maintenance practices, and ultimately revolutionize infrastructure asset management. Aims and objectives: this study aims to investigate the use of DTs to improve asset management processes within the E&C industry. The objectives include a thorough investigation of DTs, establishing their purpose within the industry, proposing a replicable DT methodology, demonstrating the methodology through case studies, and addressing the gap between potential and practical applications to promote DT dissemination. Methodological approach: i. Identify problem: thorough literature review and DT investigation (Paper I). ii. Define solution: understand the purpose of DT applications in E&C (Paper II). iii. Methodology and Demonstration: propose and demonstrate a replicable DT methodology through experimental work, digital modelling, and case studies (Papers III, IV, and V). iv. Evaluation: propose a purpose-driven DT roadmap to evaluate the impact of applications, address the gap between potential and applications, and promote widespread DT adoption (Paper VI). Results: the main results include a deep DT investigation, experimental work with a reinforced concrete beam, snow galleries and a trough bridge, digital models using BIM and finite elements, a scalable DT platform methodology demonstrated in two case studies, and a roadmap from conclusions and lessons learned to promote DT adoption in the industry. Conclusions: given the particularities of the E&C industry and its assets, DTs can primarily benefit asset management and maintenance processes by enabling real-time monitoring, predictive maintenance, and data integration for improved safety and efficiency. To address the gap between potential and practical applications, two paradigm shifts are proposed: shifting the perception of DTs from a digital model to integrated technology tools, and adopting a generalizable, purpose-focused approach instead of context-specific frameworks
Potential för organosolv lignin nanopartiklar som en hållbar flotations reagens : ett steg mot en gruvindustri med ett lågt koldioxidavtryck
No full textThe green transition is driving a steep increase in the demand for minerals, which has put the focus on more responsible and sustainable mining practices as there is a growing pressure on mining operations to minimise their environmental footprint, mitigate risks in neighbouring communities, and decrease the consumption of natural resources. In 2022, mineral froth flotation was used to recover 18 million tonnes of copper from copper ore, accounting for 80% of total copper mine output. The mineral froth flotation process can be made more sustainable through the use of bio-based and biodegradable flotation reagents. Currently, xanthates are used as collectors for the recovery of copper-bearing sulfide minerals from sulfide ores. However, xanthates are fossil-based and pose significant risks, particularly to aquatic life and ecosystems. Additionally, a significant part of xanthates is currently obtained from production sites in Asia, which can lead to supply dependency and delays, as evident during the global pandemic. The aim of this thesis was to develop an efficient, sustainable, and environmentally friendly mineral froth flotation process based on total or partial replacement of xanthates with bio-based, biodegradable, and low-carbon footprint organosolv lignin particles (OLP). The lignin was obtained through organosolv fractionation of residual forest biomass, i.e. spruce and birch. The particles were produced via solvent exchange method from the homogenized lignin solution. As a result, 4 different particle types were produced: birch nanoparticles (BN), birch microparticles (BM), spruce nanoparticles (SN), and spruce microparticles (SM). At first, the characterization and surface chemistry study of the OLP was carried out to deepen the understanding of interaction mechanism between the OLP and mineral surfaces. The lignin was characterized by gel permeation chromatography and nuclear magnetic resonance for its molecular size and content of functional groups. While morphology, surface charge and stability in dispersion of the particles was determined using scanning electron microscopy, ζ-potential, and Turbiscan. All 4 particles were spherical with the diameter around 100 nm for nanoparticles and 1μm for microparticles. The ζ-potential measurement showed the surface variation caused by the difference in size and content of functional groups. Spruce particles, SN and SM, had higher negative charge due to higher content of carboxylic and total phenolic groups. Under alkali conditions, the ζ-potential below -20mV for all particles, with the lowest at −55.1 mV for SM. Finaly, the interaction of OLP with mineral surfaces was examined using quartz crystal microbalance. While the attachment of all OLP was very rigid for both, chalcopyrite and pyrite surfaces, the affinity for attachment was notably greater in the case of pyrite compared to chalcopyrite. The OLP was tested in proof-of-concept study on three different ore samples, and improvements in the flotation performance was observed, including better selectivity and increased recovery. The further evaluation of the OLP as flotation reagent was conducted with copper ore samples. The flotation trials were carried out with 600 g of ore sample in laboratory flotation cell. Starting with the dosage study, the results were confirmed in rougher-cleaner flotation tests. However, the OLP could not be used as a sole collector, it was shown that significant part of xanthate in the flotation mix could be replaced by OLP resulting in improved copper recovery and selectivity. Additionally, a synergy was observed when the OLP and xanthate mixture was used as combined reagents performed better than each of them separately at the same dosage. The copper recovery was increased from 82.2% to 88.7% in a semi-pilot rougher flotation when 50% of xanthate was replaced by OLP compared to the xanthate alone. Significant depression of iron recovery was observed when the OLP was utilized, even in absence of lime. Thus, the OLP reagents eliminated the need for lime, which is required on an industrial scale. Further positive effect of OLP application was indicated recovery of other valuable elements in the concentrates, such as cobalt and molybdenum, while there was no increase in penalty elements. The amount of OLP needed was up to 10 g/ton of ore, which is very small amount, and it is roughly 10 times less compared to any other modifier used in such a process. Therefore, this thesis demonstrates the potential of OLP as flotation reagent. If implemented, the proposed flotation system would lead to better resource efficiency and lower environmental impact
Enabling mixed-precision in spectral element codes
No full textMixed-precision computing has the potential to significantly reduce the cost of exascale computations, but determining when and how to implement it in programs can be challenging. In this article, we propose a methodology for enabling mixed-precision with the help of computer arithmetic tools, roofline model, and computer arithmetic techniques. As case studies, we consider Nekbone (Nek5000 developers), a mini-application for the Computational Fluid Dynamics (CFD) solver Nek5000 (Fischer et al.), and a modern Neko (Jansson et al., 2024) CFD application. With the help of the Verificarlo (Denis et al., 2016) tool and computer arithmetic techniques, we introduce a strategy to address stagnation issues in the preconditioned Conjugate Gradient method in Nekbone and apply these insights to implement a mixed-precision version of Neko. We evaluate the derived mixed-precision versions of these codes by combining metrics in three dimensions: accuracy, time-to-solution, and energy-to-solution. Notably, mixed-precision in Nekbone reduces time-to-solution by roughly 1.62x and energy-to-solution by 2.43x on MareNostrum 5, while in the real-world Neko application, the gain is up to 1.3x in both time and energy, with the accuracy that matches double-precision results
Mechanical Characterization and Modeling of Heterogeneous Brittle Materials in Comminution Processes
No full textThe steel industry has been an asset in society’s development; therefore, the worldwide production of crude steel has shown a growing trend. Following the sustainability principles reflected by the World Steel Association, incorporating pyrometallurgical by-products into a circular economy framework is of great interest to maximize the efficient use of resources throughout the life cycle of steel products and to help reduce CO2 emissions. Thus, research to optimize the supply chain of raw materials has increased, and there is a need to address the energy consumption of the highly demanding mechanical processes related to it, such as crushing. This PhD research focuses on the development of a framework that facilitates the optimization of comminution processes for secondary raw materials and enhances the value of material data for modeling breakage processes in the upscaling and evaluation of crushing at an industrial scale. This investigation was divided into two primary components. First, an experimental framework was developed and implemented to characterize the tensile and compressive responses of electric arc furnace (EAF) manganese slag under both quasi-static and dynamic conditions. In the first study, manganese slag, a highly heterogeneous material, was examined, providing insights into the methodologies and challenges associated with sample manufacturing, quasi-static testing using simple loading schemes, and processing of mechanical and optical data. In the second study, the macro-response of slag under dynamic conditions was investigated, providing pertinent information regarding processing and crushing in relation to rate-dependent behavior, as well as energy expenditure during the fragmentation processes. The second part of this research focused on evaluating a numerical framework to upscale the fracture processes in crushing applications. Simulations of the fracture process of quasi-brittle materials employing finite element methods (FEM) were implemented and evaluated for mineral and secondary raw materials, enhancing the knowledge regarding the calibration of material models to simulate complex geometries with a high level of detail in the crack patterns and the accuracy of the failure loads. Finally, a fourth research article demonstrated the viability of employing an established material model to simulate slag from a macroscopic perspective.
Greater increase in surface albedo following clear-cutting than wildfire in pine dominated northern Swedish boreal forests
No full textThere is a public debate on how boreal forests can deliver climate change mitigation benefits. While most debates regarding Fennoscandian forests have centered on the contrasting effects of actively managed and old-growth unmanaged forests on carbon uptake and storage, the impact of surface albedo has often been overlooked. According to the new EU forest strategy for 2030, with aim of improving quantity and quality of forests by promoting primary old-growth forests and avoiding clear-cutting, among others, we examined how albedo across a wide age range of boreal Pinus-dominated forests develops over time after wildfire (defined as unmanaged) and clear-cutting (defined as managed). We find that albedo decreases over time after disturbance, but mainly in managed forests. Annual mean albedo in young (<30 years) managed forests (0.36±0.04) is markedly larger than in young unmanaged forests (0.18±0.04). This difference is particularly prominent during winter, when snow-covered ground is present. The mean albedo over the entire unmanaged forest-age gradient (0.17±0.05) is significantly lower (p < 0.05) than that of the managed forest-age gradient (0.23±0.10). Considering the typically higher frequency of clear-cuts compared to wildfires in Fennoscandian forests, these albedo differences would be even larger over long time scales. Our findings reveal the importance of considering the climatic cooling potential of albedo when making decisions on how to optimize future forest management in northern boreal forests to mitigate climate change