Digitala Vetenskapliga Arkivet - Academic Archive On-line
Not a member yet
734120 research outputs found
Sort by
DesignWise : Design Principles for Smart Applications targeting Internet of Things Services
No full textAs Internet of Things (IoT) has developed, the number of connected entities has increased, allowing systems to interact with users and their environments in smart ways. For example, presence and environmental sensors enable the system to be aware of the user's state and environment, allowing it to provide helpful information for users. The connected entities include not only IoT devices for data acquisition and actuation but also interaction modalities for communication between users and systems. Multimodal interaction (MI) and augmented reality (AR) are enablers for enhanced user experience (UX) for IoT services. However, combining an IoT-enabled system with MI and AR without careful consideration may hinder the benefits of these technologies. Thus, understanding the technologies and target user group's characteristics depending on the application's context is essential. Design principles allow people—who are interested in UX and user interface (UI) development of IoT-enabled mobile AR applications—to gain knowledge about UX/UI design that considers both the technology and user aspects.This thesis aims to identify, propose, and validate design principles for mobile applications within IoT-enabled smart city domains, especially healthcare and energy management services. We identified the requirements and needs of MI and AR through a systematic literature review. We also found that studies of design principles for IoT-enabled mobile AR applications are limited. We designed, developed, and analyzed three IoT-enabled mobile AR applications along with their UX. From the state-of-the-art research, we compiled and categorized 26 existing design principles into seven categories. We derived and evaluated five new design principles based on the analysis of our developed applications. As a practical realization of the identified design principles, we provided examples of design principles through user interface mockups, which represent the re-designed interfaces of the applications. We expect that our findings will give insight into the UX/UI design of IoT-enabled mobile AR applications for researchers, educators, and practitioners interested in UX/UI development
Designing Pavements with Waste and Recycled Materials
No full textRecycled and waste materials from four different sources were investigated as alternatives for crushed rock aggregates in pavement constructions. Two of the materials were coarse fractions of the bottom ash from two incineration plants. The other two materials were crushed concrete from demolished constructions and reclaimed asphalt from road scalpings. Full-scale accelerated tests were conducted on test road-sections constructed with these materials, employing a heavy vehicle simulator (HVS). The materials were also tested in the laboratory e.g., by means of repeated load triaxial (RLT) tests. In both cases, results indicated that the crushed concrete performed the best, followed by the two bottom ash materials and then the reclaimed asphalt. The results from the RLT tests were used to evaluate the model parameters required for simulating the performances of the test-road sections in HVS tests, adopting a mechanistic-empirical pavement analysis tool ERAPave. With this method, good agreements between the measurements and simulations were obtained. Hence, this approach forms the basis for designing pavement sections using these alternative materials for different traffic loading and climatic conditions. With further testing and modelling, it will be possible to create guidelines and design tables for pavement constructions with alternative materials
Utilizing GPR and FWD for Pavement Structural Assessment and Moisture Detection
No full textAsphalt pavement performance is profoundly impacted by the presence of water and moisture in the road, resulting in substantial costs to society. Research showed that significant portion of the road sections need early maintenance measures regardless of traffic volume due to moisture-related damages. Monitoring moisture conditions, preferably using a non-destructive continuous method, is thus vital to the decision-making and selecting appropriate maintenance intervention. Furthermore, understanding moisture conditions is critical for accurately interpreting automatic road condition measurements, especially during the spring (thawing) when the roads exhibit the lowest load bearing capacity due to increased levels of moisture. This study employed a multi-receiver Ground penetrating radar (GPR) and a Falling weight deflectometer (FWD) measurements to assess moisture levels and structural condition of an indoor full-scale test road. The groundwater level of the test road was varied by introducing water to the system. The results revealed a good correlation between the FWD and the average GPR velocity measurements. The GPR measurements provided a relative water content of the test roads. Further exploration of other GPR parameters, such as frequency, magnitude, and amplitude of the GPR signal is recommended, as these may offer an even better correlation to moisture content
Digitized utopias : Public service delivery in smart Stockholm
No full textDigitization, often performed under the heading of becoming "smart,” has been acknowledged as an approach to transform the public sector in terms of efficiency and effectiveness. But what are the specific ideals for future urban government in cities aiming to boost digitization of the public sector? This paper reports the results of an exploration of the smart city initiative in Stockholm. Using utopianism as a lens, the paper reveals the ageing population as a crucial driver of the smart city agenda. Data from interviews, document analyses and observations demonstrate the overall ambition to reduce public sector workload by digitizing and automating tasks, thereby cutting public resource use. This corresponds to findings within the broader digital government scholarship. However, the analysis also shows that becoming smart might create new, complex tasks for the public sector. The paper discusses how these developments might encourage widespread privatization of services currently performed by the public sector. Applying a utopian perspective allows for debate on the ambitions for future improvements embedded in smart city initiatives. Ultimately, such a lens can be applied to a vast range of urban issues, opening avenues for speculative insights into how future cities are envisioned
Optimization of interfacial bonding between graphene-enhanced polyethylene liners and CFRP composites using plasma treatment for hydrogen storage applications
No full textAs the need for sustainable hydrogen storage solutions increases, enhancing the bonding interface between polymer liners and carbon fiber-reinforced polymer (CFRP) in Type IV hydrogen tanks is essential to ensure tank integrity and safety. This study investigates the effect of plasma treatment on polyethylene (PE) and PE/graphene nanoplatelets (GNP) composites to optimize bonding with CFRP, simulating the liner-CFRP interface in hydrogen tanks. Initially, plasma treatment effects on PE surfaces were assessed, focusing on plasma energy and exposure time, with key surface modifications characterized and bonding performance being evaluated. Plasma treatment on PE/GNP composites, with increasing GNP content, was then examined, comparing the bonding effectiveness of untreated and plasma-treated samples. Wedge peel tests revealed that plasma treatment significantly enhanced PE-CFRP bonding, with optimal conditions at 510 W and 180 s resulting in 212 % and 165 % increases in the wedge peel strength and fracture energy, respectively. Plasma-treated PE/GNP composites with 0.75 wt.% GNP achieved a notable bonding enhancement with CFRP, showing 528 % and 269 % improvements in strength and fracture energy over untreated neat PE-CFRP samples. These findings offer practical implications for improving the mechanical performance of hydrogen storage tanks, contributing to safer and more efficient hydrogen storage systems for a sustainable energy future.Funding Agencies|Directed Research Projects Program of the Research and Innovation Center for Graphene and 2D Materials (RIC2D) , Khalifa University [8434000546]</p
Enhancing photocurrent collection in wide-gap ACIGS solar cells
No full textChalcopyrite solar cells utilising (Ag,Cu)(In,Ga)Se2 (ACIGS) absorbers have demonstrated cell efficiencies approaching 24% and adjustable band gaps between 1.0 and 1.7 eV, rendering them a promising material for tandem solar cells. The increased band gap obtained by increasing the compositional [Ga]/([Ga] + [In]) ratio has a detrimental impact on the absorber quality, resulting in open circuit voltage, fill factor and short-circuit current below expectations. The latter is due to a poor photocurrent collection, which is particularly evident in reduced external quantum efficiency (EQE), accompanied by substantial losses in the near infrared. This study identifies a previously unrecognised mechanism reducing the photocurrent collection in wide-gap ACIGS solar cells processed on transparent back contact. Manipulations at the ACIGS/CdS interface, particularly KCN etching and variations in ammonia rinsing duration of the absorber, effectively restores both the EQE maximum and the near-infrared response. The observed inverse correlation between doping density and EQE maximum suggests an electron barrier caused by a highly doped p+ layer near the ACIGS/CdS interface, a trend reproduced by drift-diffusion simulations. Raman spectroscopy and x-ray diffraction analyses demonstrate no correlation between ordered vacancy compounds and the photocurrent collection issue. Mitigation strategies significantly improve photocurrent collection and device performance, notably reduced post deposition treatment associated with reduced doping level, thicker CdS buffer layer through extended chemical bath deposition, and absorber annealing after rinsing. The resulting devices with efficiency reaching 12.9% are close to the most efficient semi-transparent wide-gap ACIGS solar cells to date
Biogeochemical response to drying-rewetting in riparian soils influences carbon mobilization
No full textOrganic-rich riparian soils in northern boreal landscapes are often the primary source of organic and inorganic carbon (C) to headwater streams. During extreme hydro-climatic events, such as droughts, the production and mobilization of C in these soils may be sensitive to changes in groundwater levels. Yet, the biogeochemical effects of drying and rewetting have been under-investigated in boreal riparian zones, particularly when compared to peat soils in discrete landscape components (i.e., mires). Here, we experimentally assess the response of riparian soil cores to simulated drought and rewetting and test whether mobilization of dissolved organic matter (DOM), carbon dioxide (CO2), and methane (CH4) are altered by geochemical and biological drivers over a two-month rewetting period. Drought oxidized the soil profile, upregulated activities of oxidative enzymes, and replenished terminal electron acceptors (TEAs), most notably sulfate (SO42−), which likely suppressed DOM concentrations over the short term. However, over the longer term, soil DOM mobilization increased in response to rewetting, unrelated to the intensity of experimental drought. Enzyme activity during the rewetting phase indicates that the persistent increases in DOM may be linked to microbially-mediated decomposition of organic matter following drought. By contrast, CO2 production was sensitive to drought intensity, with concentrations suppressed in soils subjected to the most extreme drying treatment. Elevated SO42− concentrations also delayed the recovery of CH4 production in soils by creating a pool of more favorable TEAs. Our results collectively show that mobilization of different C forms in riparian soils is influenced by drying-rewetting events through multiple biogeochemical mechanisms operating at different time scales. These findings have broader implications for the lateral transfer of organic and inorganic C from riparian zones to streams in response to predicted increases in climate variability
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
Blue-green infrastructure for climate resilience - quantifying stormwater hydrology impacts
No full textBlue Green Infrastructure (BGI) has emerged as robust measures for managing stormwater, offering benefits such as reducing urban flooding, promoting groundwater recharge etc. However, recent studies highlight that these facilities often underperform during climate-induced intense rainfall events in urban areas. In addition, implementation of BGI in urban catchments is often challenging because many there are many different options and design considerations for BGI and commonly a lack of space. Therefore, there is greater need that 1) a more structured approach is applied during the selection, distribution and design of different BGI alternatives in urban catchments, and 2) facilities like bioretention are adapted to handle these intense events more effectively. The licentiate titled “Blue-green infrastructure for climate resilience - quantifying stormwater hydrology impact” focuses on advancing the understanding of design and implementation of Blue-Green Infrastructure (BGI) in catchment scale, with the explicit focus on design improvement of bioretention facilities by using modelling tools. The licentiate has an overall 3 scientific articles. Paper 1 develops different BGI alternatives by considering spatial scale and design complexity in urban environments having diverse land use characteristics. The study quantifies to what extent hydrological outcomes such as surface runoff, infiltration, and pre-development flow varies with different BGI alternatives in these catchments. One of the results obtained from this study showed that in residential areas, which offer more spaces for planned integration of stormwater control measures, engineered BGI alternatives showed the highest potential to reduce flooding while in densely built inner city catchments the more natural BGIs showed higher potential. Paper 2 evaluates the reliability of the SWMM model used in Paper 1 for bioretention modeling by comparing calibrated and uncalibrated models with observed data. The findings confirm that SWMM is a reliable tool for modeling bioretention systems, accurately capturing key hydrologic processes, especially after calibration. While first study is about how different BGIs can be combined to achieve various hydrologic benefits at catchments, the third study is about effect of different bioretention design variable in managing stormwater hydrology at local scale. Paper 3, by using the calibrated model in Paper 2, explores 54 different biofilter design options, to assess the impact of key design factors—ponding depth, hydraulic conductivity, filter media fraction and storage connection —on different stormwater performance indicators. In general, this study showed that a balanced approach is required while designing bioretention as there are trade-offs between optimizing for volume reduction during daily events (e.g. higher filter media fraction) and reducing overflow occurrences during high-intensity events (e.g. lower filter media fraction, high hydraulic conductivity). Overall, this thesis provides valuable insights and practical recommendations for enhancing the effectiveness of BGI in urban catchments for climate adaptive stormwater management solutions, and with explicit focus on designing bioretention systems.
Evaluation of Crashworthiness and Fracture Toughness at High Deformation Rates for Advanced High Strength Steel sheets
No full textGradually more stringent environmental and safety regulations in the transport sector have made third generation Advanced High Strength Steel (3rd-gen AHSS) grades and new generations of press hardening steels (PHS) cost-effective and natural substitutes in the automotive industry. Increasing the strength of steel allows for potentially downgauging the sheet thickness while maintaining or improving structural performance, and thus reducing the weight of the vehicle. 3rd-gen AHSS and PHS grades have been continuously adapted by the automotive industry for body-in-white parts and energy-absorbing safety components. However, the limited ductility of these higher-strength materials can make them more prone to cracking, which in turn has a negative impact on the folding behaviour of safety structures in a crash. For further introduction of new high-strength steel grades in the design and production of safety parts, proper calibrated material models are needed, and their crash behaviour must be investigated and quantified. Plane stress fracture toughness measured with the Essential Work of Fracture (EWF) method has recently emerged as a viable material parameter to rationalise edge crack resistance and crashworthiness. EWF offers a small-scale laboratory methodology capable of characterising important fracture characteristics of modern automotive steel grades. Hence, EWF together with well-instrumented crash tests in the laboratory are powerful tools for estimating the crashworthiness and quantifying energy absorption. However, much of the published fracture toughness data is based on quasi-static conditions, which do not reflect the conditions in a crash typically involving high deformation rates. To characterise the material for crash scenarios and validate simulation models, further investigation is necessary at higher deformation rates. In this PhD thesis, the crashworthiness and fracture characteristics of 3rd-gen AHSS and PHS grades at higher deformation rates were investigated. The crashworthiness and energy absorbing capacity were evaluated by studying dynamically loaded axially crushed crash boxes both experimentally using full-field deformation measurements and numerically by finite element analysis using a commercially available damage model. Stereo high-speed imaging allowed for more efficient evaluation of crash performance with fewer components and aided in model validation. Furthermore, the rate dependence of fracture toughness and the underlying mechanisms were explored, revealing that crack propagation resistance after crack initiation significantly influences fracture toughness at higher loading rates. It was also experimentally shown that there is significant adiabatic heating in the fracture process zone using the EWF methodology at higher loading rates, which can influence the value of fracture toughness