| 1. |
- Ardi, Shanai, et al.
(författare)
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A Case Study of Introducing Security Risk Assessment in Requirements Engineering in a Large Organization
- 2023
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Ingår i: SN Computer Science. - : Springer. - 2661-8907. ; 4:5
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Tidskriftsartikel (refereegranskat)abstract
- Software products are increasingly used in critical infrastructures, and verifying the security of these products has become a necessary part of every software development project. Effective and practical methods and processes are needed by software vendors and infrastructure operators to meet the existing extensive demand for security. This article describes a lightweight security risk assessment method that flags security issues as early as possible in the software project, namely during requirements analysis. The method requires minimal training effort, adds low overhead, and makes it possible to show immediate results to affected stakeholders. We present a longitudinal case study of how a large enterprise developing complex telecom products adopted this method all the way from pilot studies to full-scale regular use. Lessons learned from the case study provide knowledge about the impact that upskilling and training of requirements engineers have on reducing the risk of malfunctions or security vulnerabilities in situations where it is not possible to have security experts go through all requirements. The case study highlights the challenges of process changes in large organizations as well as the pros and cons of having centralized, distributed, or semi-distributed workforce for security assurance in requirements engineering.
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| 2. |
- Blomqvist, Göran, 1963-, et al.
(författare)
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Microplastics in snow in urban traffic environments
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Microplastics from road traffic, mainly from tyre wear, are globally considered to be one of the largest sources of microplastic contamination in the environment. Plastics can either be deposited in the road vicinity, at the roadside and in ditches or spread via stormwater and air to the environment and receiving water bodies. In cold climates, microplastics, as well as other traffic-related pollutants, can be temporarily stored in snow and ice on and around roads and streets. The location and concentration of these pollutants is influenced by winter operations, where ploughing and skid control contribute to redistribution, and by melting and compaction of ice and snow. This creates reservoirs of microplastics and other pollutants, which are released into stormwater or surrounding soil during thaws, but also provides an opportunity to reduce the spread of microplastics by managing snow and ice appropriately. In the present report, a case study of microplastics in snow has been carried out in the municipality of Karlstad in Sweden, to get an idea of the potential variation, both in terms of concentration and total amounts in relation to traffic and the location of the sampling in the street environment. Microplastics have been analysed by pyrolysis GC/MS to identify tyre-specific polymers in combination with eight commonly occurring plastic types. In addition, six municipalities in different parts of the country responded to a questionnaire on microplastics in snow and urban snowmelt management. The results show that microplastics related to tyre wear (rubber polymers) tend to be present in higher concentrations on and near the carriageway. Other plastics show a less clear link to traffic. Along a salted bicycle lane, an elevated level of polypropylene, from which the brush of the sweep-salting machine is made, could be detected in the surface layer of the snow. In general, knowledge about microplastics in urban snow is low in the municipalities that responded to the survey.
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| 3. |
- Brännvall, Rickard, 1975-, et al.
(författare)
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Cost Optimization for the Edge-Cloud Continuum by Energy-Aware Workload Placement
- 2023
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Ingår i: Companion Proceedings of the 14th ACM International Conference on Future Energy Systems. - : Association for Computing Machinery. ; , s. 79-84
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Konferensbidrag (refereegranskat)abstract
- This article investigates the problem of where to place the computation workload in an edge-cloud network topology considering the trade-off between the location-specific cost of computation and data communication. For this purpose, a Monte Carlo simulation model is defined that accounts for different workload types, their distribution across time and location, as well as correlation structure. Results confirm and quantify the intuition that optimization can be achieved by distributing a part of cloud computation to make efficient use of resources in an edge data center network, with operational energy savings of 4–6% and up to 50% reduction in its claim for cloud capacity.
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| 4. |
- Capek, Miloslav, et al.
(författare)
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Characteristic Mode Decomposition Using the Scattering Dyadic in Arbitrary Full-Wave Solvers
- 2023
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 71:1, s. 830-839
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Tidskriftsartikel (refereegranskat)abstract
- Characteristic modes are formulated using the scattering dyadic, which maps incident plane waves to scattered far fields generated by an object of arbitrary material composition. Numerical construction of the scattering dyadic using arbitrary full-wave electromagnetic solvers is demonstrated in examples involving a variety of dielectric and magnetic materials. Wrapper functions for computing characteristic modes in method-of-moments, finite-difference time domain, and finite element solvers are provided as supplementary material.
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| 5. |
- Capek, Miloslav, et al.
(författare)
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Optimal Inverse Design Based on Memetic Algorithms - Part 1 : Theory and Implementation
- 2023
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 71:11, s. 8806-8816
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Tidskriftsartikel (refereegranskat)abstract
- A memetic framework for optimal inverse design is proposed by combining a local gradient-based procedure and a robust global scheme. The procedure is based on method-of-moments matrices and does not demand full inversion of a system matrix. Fundamental bounds are evaluated for all optimized metrics in the same manner, providing natural stopping criteria and quality measures for realized devices. Compared to density-based topology optimization, the proposed routine does not require filtering or thresholding. Compared to commonly used heuristics, the technique is significantly faster, still preserving a high level of versatility and robustness. This is a two-part paper in which the first part is devoted to the theoretical background and properties, and the second part applies the method to examples of varying complexity.
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| 6. |
- Capek, Miloslav, et al.
(författare)
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Optimal Inverse Design Based on Memetic Algorithms - Part II : Examples and Properties
- 2023
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 71:11, s. 8817-8829
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Tidskriftsartikel (refereegranskat)abstract
- Optimal inverse design, including topology optimization and evaluation of fundamental bounds on performance, which was introduced in Part 1, is applied to various antenna design problems. A memetic scheme for topology optimization combines local and global techniques to accelerate convergence and maintain robustness. Method-of-moments (MoMs) matrices are used to evaluate objective functions and allow determination of fundamental bounds on performance. By applying the Shermann-Morrison-Woodbury identity, the repetitively performed structural update is inversion-free yet full-wave. The technique can easily be combined with additional features often required in practice, e.g., only a part of the structure is controllable, or evaluation of an objective function is required in a subdomain only. The memetic framework supports multifrequency and multiport optimization and offers many other advantages, such as an actual shape being known at every moment of the optimization. The performance of the method is assessed, including its convergence and computational cost.
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| 7. |
- Cordova, Stephanie S., 1988-
(författare)
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Utilizing CO2 from biomethane production : Sustainability and climate performance
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biogas solutions offer many benefits for the environment and society, including organic waste treatment as well as being an enabler for energy and nutrient recovery. The products of anaerobic digestion are a biogas, which contains a share of 30 to 50% carbon dioxide (CO2) and 50 to 70% methane, and a liquid remanent, rich in nutrients. The biogas can be upgraded by removing the CO2 to increase the energy content, producing biomethane. At present, CO2 is considered a waste in biomethane production systems, and hence it is emitted into the atmosphere. Nevertheless, biogas upgrading technologies separate a pure-grade CO2 and, likewise, carbon capture processes, providing a pure CO2 flow that can be stored or utilized. Compared to storage, carbon capture and utilization (CCU) technologies deliver valuable carbon-based products required to sustain human activities. The valorization of green CO2 could aid the transition towards defossilization of the economy. Indeed, several CO2 utilization technologies could be incorporated into biomethane production systems, but there is still a limited understanding of the available alternatives and their potential impacts on biomethane systems.This thesis aims to investigate the integration of CO2 utilization technologies in biomethane production systems by revealing its potential, identifying alternatives, and assessing the impacts of the integration. Using Sweden as an example, scenarios of future biomethane production were employed to estimate the potential CO2 available for utilization. To complement the analysis, a qualitative approach made possible the identification of aspects that could affect CO2 utilization in biomethane production. Moreover, a multi-criteria analysis (MCA) framework was developed to identify relevant indicators for assessment and available alternatives for CO2 utilization. The research also includes a life cycle assessment (LCA) to evaluate the climate performance of relevant CCU alternatives in the biomethane production system.Results show that 160 kt of CO2 could be obtained from biomethane production in Sweden, which could potentially increase threefold from 2020 to 2030. The evaluation of alternatives for CO2 utilization includes environmental, technical, economic, and social criteria with sound indicators within an MCA framework. Indicators to evaluate each criterion provide valuable information to identify feasible and sustainable alternatives that can be integrated into biomethane plants. The identified alternatives with a high readiness level are additional methane through methanation, horticulture, mineral carbonates, fuels, pH control, bulk chemicals, and liquefied CO2 for direct use. The results provide information to decision-makers in relation to considerations to take before implementation, like energy requirements, the existence of regulations and standards, and uncertainty. In terms of the climate performance of biomethane with the inclusion of CCU alternatives, the results show a possible reduction of CO2 emissions that depends on the possibility of substituting fossil-based products. The investigated alternatives all result in lower emissions, but concrete curing and methanation using renewable hydrogen produce the best results.To conclude, the potential future increase of green CO2 from biomethane in Sweden creates opportunities to substitute fossil carbon in current applications and mature conversion pathways. Moreover, the inclusion of CCU in biomethane production contributes to reducing biomethane system emissions and diversifying its products. Possible alternatives of CCU that can be integrated into biomethane production systems in the short term include methanation and concrete curing. Other alternatives could be possible but present lower performance and higher uncertainties at the moment.
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| 8. |
- Cordova, Stephanie, 1988-, et al.
(författare)
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What should we do with CO₂ from biogas upgrading?
- 2023
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Ingår i: Journal of CO2 Utilization. - : Elsevier. - 2212-9820 .- 2212-9839. ; 77
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Tidskriftsartikel (refereegranskat)abstract
- Carbon capture and utilization has been proposed as an essential climate change mitigation strategy, but only a few implemented cases exist. During biomethane production from anaerobic digestion, CO₂ is commonly separated and emitted into the atmosphere, which can be utilized as raw material for various products. This research aims to identify and assess CO₂ utilization alternatives for possible integration with biogas upgrading from anaerobic digestion by developing a soft multi-criteria analysis (MCA). A literature review complemented with stakeholder participation enabled the identification of relevant alternatives and criteria for assessment. Potential alternatives for CO₂ utilization include methane, mineral carbonates, biomass production, fuels, chemicals, pH control, and liquefied CO₂. Results show that although no alternative performs well in all indicators, there is an opportunity for short-term implementation for methane, biomass production, mineral carbonates, liquefied CO₂, and pH control. Moreover, the uncertainty analysis reveals that even though the technologies have a high technological development, more information on critical aspects is still required. The soft MCA provides information to decision-makers, practitioners, and the academic community on learning opportunities of the alternatives and indicators to step from development into implementation. For instance, the method can be used to assess more specific systems with different locations and scales or to direct efforts to ease the implementation of CCU.
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| 9. |
- Gustafsson, Mats, et al.
(författare)
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Degrees of Freedom and Characteristic Modes
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The number of degrees of freedom is a crucial parameter in many electromagnetic problems. In for example modern communication systems spatial diversity is often employed through multiple beams to enhance capacity and reliability. However, while the degrees of freedom can be computed, their connection to physical quantities is not as easily understood. To address this issue, this paper proposes a scattering-based formulation of characteristic mode analysis that can estimate the degrees of freedom of arbitrarily-shaped objects. The relation between the number of dominant characteristic modes and physical characteristics differs for electrically large and small objects. Specifically, for large objects, it is linked to the average shadow area, while for small objects, it is linked to their average polarizability through the forward scattering sum rule. Therefore, the average shadow area and polarizability are fundamental parameters that provide insight into the number of degrees of freedom for any object. These basic parameters also provide straightforward estimates of the minimum size of a device region required to support a desired number of electromagnetic degrees of freedom across a given spectral response.
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| 10. |
- Gustafsson, Mats, 1966-, et al.
(författare)
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Indikativ metod för bedömning av partikelemission från dubbdäcksslitage av vägbeläggning : modifiering och utvärdering av Tröger-metoden
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Att testa partikelemissionen från dubbdäcksslitage av vägbeläggningar på ett kontrollerat sätt är oftast förknippat med verklighetsnära, men storskaliga tester med storskalig och avancerad laboratorie[1]utrustning och därmed förhållandevis höga kostnader. Det finns därför ett angeläget behov av en enklare metod som kan användas för att ge en rimlig och god skattning av hur skillnader i beläggningsrecept påverkar partikelbildningen, som kan användas till val av beläggningsrecept som ska användas i senare storskaliga tester. En möjlighet är att använda en befintlig slitagetestmetod för provkroppar av slitlager. Tröger är en sådan metod där ett knippe stålnålar hamrar mot en roterande provkropp i ett klimatskåp som bedömds lämplig för att mäta och studera partikelemissioner till luft. VTI:s Tröger-utrustning modifierades för partikelemissionsmätningar genom att installera partikelinsugsmunstycke i kylluftflödet som passerar över provkroppen. Initiala tester tydde på acceptabel/tillräcklig god repeterbarhet och ett antal provkroppar från några befintliga material med olika slitstyrka valdes ut för vidare tester. En statistiskt optimerad försökplan och provhantering togs fram. En testomgång var planerad initialt men senare utökades det till två omgångar. En andra omgång krävdes dels på grund av att ett material i första omgången misstagits för enhetligt, men bestod av tre olika material, dels då försöksuppställningen kunnat förbättras något. De bildade partiklarna (PM10) har en bimodal fördelning med en primär topp vid 2–3 µm och en sekundär vid ca 8–10 µm. Den statistiska analysen visade på signifikanta skillnader mellan de tre ingående materialen i provkropparna i den andra testomgången och att metoden i sin nuvarande form kan användas för att skilja partikelemissionen från olika vägbeläggningar. Förslag för att utveckla metoden är bland annat att förhindra uppbyggnad av damm i kylsystemet och säkerställa jämn kvalitet hos nålarna.
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