[article-cris] Insinööritieteiden korkeakoulu / ENG

Permanent URI for this collectionhttps://aaltodoc.aalto.fi/handle/123456789/21533

Browse

Recent Submissions

Now showing 1 - 20 of 4220
  • Mechanical Properties and Microstructural Analysis of Concrete Designed for Low and Intermediate Level Nuclear Waste Repositories
    (2025-12-01) Al-Neshawy, Fahim; Ragaa, Abobaker Ba
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This study investigates the mechanical properties and microstructural characteristics of five concrete mixtures specifically designed for application in low and intermediate-level nuclear waste repositories. These repositories necessitate construction materials that not only offer durability and strength but also maintain a long service-life under the underground environmental conditions over extended period. The concrete mix design was formulated with a focus on optimizing durability and sustainability, incorporating supplementary cementitious materials such as silica fume and slag to enhance the concrete durability. Comprehensive microstructural analyses using petrographic analysis and Micro x-ray fluorescence (mu-XRF) provided insights into the hydrate phases and pore structure evolution, revealing that the concrete exhibits dense microstructures and low permeability, essential for reducing leaching and sulfate attack risks. Mechanical testing demonstrated high compressive strength and modulus of elasticity, showing the suitability of concrete mixtures for structural components in repository environment. Overall, the findings highlight the potential of this designed concrete mixture in meeting the demands of low and intermediate level nuclear waste storage, ensuring safety and stability while also supporting environmental sustainability using eco-friendly materials.
  • Groups on the Micromove: Analysis of Emerging E-Scooter Flock-Riding in Helsinki
    (2025-01-06) Dibaj, Samira; Mladenović, Miloš; Vosough, Shaghayegh
    A4 Artikkeli konferenssijulkaisussa
    Shared electric scooters (e-scooters) have caused significant changes in the urban landscape and people’s daily travel choices across Europe. While providing a fast, pleasant, and flexible mobility option for users, there have been some emerging behaviors among their users. Therefore, there is a need to understand specific e-scooter riding behaviors, one of which is group riding. Group riding or flock-riding has been investigated in rather limited previous studies, mostly focusing on the objective and subjective safety aspects. This research examines the scale of this phenomenon, age, and gender distribution among flock-riders, the reasons behind flock-riding while considering its frequency, and the perceptions of both e-scooter users and non-users regarding this riding behavior. To this aim, a mixed method approach using a video recording observation as well as an online questionnaire survey has been utilized. The results revealed that the scale of flock-riders in Helsinki is considerably higher than in the previous studies. In addition, the majority of group-riders are male teenagers and young adults. Flock-riders engage in this behavior for having fun and as a more flexible option compared to scheduled public transportation. The study highlights the importance of further understanding emerging riding behavior with micromobility vehicles, all in order to develop effective policy actions.
  • Our Best Friends : How Dogs Alter Indoor Air Quality
    (2026-02-02) Yang, Shen; Wang, Nijing; Arnoldi-Meadows, Tatjana; Bekö, Gabriel; Zhang, Meixia; Merizak, Marouane; Wargocki, Pawel; Williams, Jonathan; Taubel, Martin; Licina, Dusan
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Dogs are dynamic contributors to the indoor environment, yet their impact on air quality remains largely unexplored, warranting a comprehensive assessment of their pollutant emissions. This study characterized chemical, particulate, and microbial emissions from small and big dogs. Big dogs emitted CO2, NH3, fungi, and bacteria at considerably higher rates than small dogs, whereas their emissions of 1-10 mu m particles were similar. With ozone present, all dogs contributed to the formation of nanocluster aerosols (1-3 nm) and ozonized volatile organic compound (VOC) products, likely from human skin oil transfer through petting. With ozone present, nanocluster aerosols (1-3 nm) were observed during dog experiments, likely reflecting ozone reactions with human-derived skin lipids transferred onto dog fur. Relative to a seated adult, big dogs emitted less ozonized products, comparable CO2 and NH3, more >5 mu m coarse particles (fewer 2-5 mu m particles), 2-4x more bacteria and fungi, and showed compound-specific differences in VOCs: while some species exhibited a strongly elevated dog-to-human ratio (with one up to 15x), others were not pronounced when dogs were present. Our findings highlight dogs as significant indoor emission sources and contributors to indoor air chemistry and microbial transport, with implications for air quality and exposure assessment.
  • Impinging jet duct diffuser ventilation effectiveness benchmarking with mixing ventilation in a mock-up classroom
    (2026-01-21) Jaanus, Renate; Teresk, Sten Marc; Kiil, Martin; Võsa, Karl Villem; Simson, Raimo; Mikola, Alo; Kurnitski, Jarek
    A4 Artikkeli konferenssijulkaisussa
    The benefits of effective classroom ventilation for health and learning outcomes are well known. However, studies continue to report inadequate air quality, insufficient air change rates, and too high air velocities. This study investigated classroom air distribution solutions in the ventilation air distribution laboratory at Tallinn University of Technology. Nozzle diffusers and duct diffusers mounted in the ceiling were compared with two impinging duct diffuser configurations installed on the shorter sides or the single longer wall of the mock-up classroom. Draught risk was assessed using air velocity probes in a mock-up classroom setup with a dedicated room-based air handling unit and thermal dummies simulating student heat loads. Contaminant removal effectiveness was evaluated using the continuous tracer gas injection method with multiple point source locations. Results showed that close to fully mixed ventilation effectiveness was achieved both with ceiling and perimeter impinging ventilation. Measured contaminant removal effectiveness varied across 0.85 to 1.16. The 10° nozzle duct diffuser configuration demonstrated the best performance of impinging ventilation in terms of ventilation effectiveness and draught control. When positioned to the longer side of the room with the extract close to the opposite wall, this configuration further improved overall performance, though it resulted in elevated air velocities at floor level. To avoid draught, the airflow rate needed to be reduced with these perimeter nozzle duct diffusers to 3.3 L/s m2 while the ceiling nozzle and ceiling duct diffusers were capable of 4.5 L/s m2 without draught. The results demonstrate the potential and also a challenge of floor level air velocity of perimeter impinging jet ventilation worth to be further studied for practical applications.
  • A methodological framework for microscale mapping of carbon emissions from daily multimodal travel: Application to the Helsinki Metropolitan Area
    (2026-04-01) Dey, Subhrasankha; Marín-Flores, Cesar; Tenkanen, Henrikki
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Urban transportation is a key challenge for achieving climate neutrality. However, effective intervention is hindered by a lack of granular data to identify spatially heterogeneous emission hotspots, as scalable approaches for jointly estimating private car and public transport (PT) emissions at high resolution remain scarce. This study introduces a hybrid bottom-up framework to address this issue. By integrating mobile phone-based travel demand data, unified multimodal routing and Life Cycle Assessment (LCA) emission factors, daily travel related CO emissions is mapped at high spatial resolution in the Helsinki Metropolitan Area. The results reveal pronounced spatial disparities: while the inner-city core exhibits high emission intensity across all modes, car emissions in the suburban periphery are found to exceed public transport emissions by over 50 times. Inspecting the emission patterns against underlying urban structures, the key findings show that high-emission clusters align with areas of high income and low job density, with the highest total emissions occurring in a suburban zone 10–20 km from the Helsinki city centre. The emission estimates were validated against municipal inventories, showing an overall agreement with the annual totals. The presented approach offers a diagnostic tool that can be beneficial for transport planning and policy to target decarbonization interventions and efforts to areas where they have the most impact.
  • The socio-cultural values of ecosystem services in managed, semi-managed and low-managed urban blue spaces and their surroundings. A case study of Warsaw, Poland
    (2026-06) Wilczyńska, Anna; Karasov, Oleksandr; Myszka, Izabela; Nevzati, Fiona; Bell, Simon; Candiago, Sebastian; Järv, Olle; Gawryszewska, Beata
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Urban blue spaces provide important ecosystem services (ES), that support health and well-being of city residents. This study examined residents' perceptions of ES provided by managed, semi-managed and low-managed blue spaces and their surroundings in Warsaw, a city dominated by the River Vistula which flows through its centre and is partially unregulated. We conducted a geo-questionnaire, asking respondents to mark their favourite blue spaces and evaluate them for different ES benefits. The data were analysed using cluster, correlation and spatial analysis to identify patterns and synergies among perceived ES. The results revealed five distinct ES clusters, showing synergies among aesthetic, recreational and nature appreciation related values. Managed blue spaces, such as urban parks or promenades, were primarily associated with social bonding, while historical and neighbourhood parks are valued for providing an everyday connection to nature and biodiversity. Low- and semi-managed areas, including vast informal riversides, play an important role in recreation, relaxation, connection to nature, and social bonding. These areas provide similar benefits with minimal interventions, highlighting their potential as Informal Blue Spaces, integral part of urban blue-green infrastructure. The results add to the increasing evidence of the social value of blue spaces and demonstrate how diverse management and investment approaches can support complementary socio-cultural benefits in cities.
  • Enhancing social resilience : the role of social infrastructure in crisis management within the built environment
    (2026-03) Rashidfarokhi, Anahita; Pelsmakers, Sofie; Maununaho, Katja; Rosa, Raul Castano De La; Järventausta, Heini; Toivonen, Saija; Tarpio, Jyrki; Tähtinen, Lassi
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Resilient solutions in the built environment primarily focus on technical aspects, with implementation processes often based on a top-down approach that overlooks people's perspectives. However, social resilience plays a crucial role in addressing polycrises, and social infrastructure is critical for building such resilience. This study aims to enhance understanding of how social infrastructures can improve social resilience. Through analysis of 58 Futures-Wheel workshops with 179 multidisciplinary experts investigating 128 crises,seven groups of social impacts were developed. Subsequently, three Finnish social infrastructure cases were selected to explore how and to what extent they address the identified social impacts. The findings indicate that social infrastructure fosters resilience by generating two specific forms of social capital: bonding capital (essential for immediate response) and bridging capital (critical for prevention and adaptation). However, the analysis also identifies critical trade-offs, including risks of green gentrification, exclusionary group dynamics, and resource fatigue in volunteer-led initiatives. Consequently, policymakers, urban planners, and community organisations should adopt a context-specific approach that balances these networks and integrates both bottom-up and top-down perspectives. By doing so, they can ensure that social infrastructure not only supports everyday life but also strengthens communities' ability to cope with crises.
  • Exploring Emerging Battery-Electric Micromobility Vehicles: A Perspective from Helsinki
    (2025-01-06) Mladenović, Miloš; Dibaj, Samira; Lopatnikov, Daniel; Vosough, Shaghayegh
    A4 Artikkeli konferenssijulkaisussa
    This study delves into the emergence of battery-electric micro-vehicles within the urban context, with a particular focus on atypical vehicles such as fat-tire e-scooters and e-unicycles. Addressing a conspicuous gap in the existing literature, this empirical investigation, located in Helsinki, Finland, involves an in-depth analysis of 64 hours of video recordings from four strategically chosen sites. The findings reveal a tangible presence of emerging e-micromobility vehicles (EMV) at the street level, contrasting it to the prevailing emphasis on more conventional options such as e-bikes and e-scooters. In addition to assessing the scale of EMV diffusion in comparison to their mainstream counterparts, the study examines the diverse types and proportions of these unconventional devices. Furthermore, it offers insights into the profiles and riding practices of the observed riders. Despite lagging in societal diffusion when compared to e-scooters, EMVs have already achieved noteworthy popularity in Helsinki. The identified riders exhibit notable skill and experience, with discernible differences in profiles based on whether they are engaged in delivery services. The study’s preliminary conclusion suggests that the use of EMV is spearheaded by a cohort of riders demonstrating both playful and utilitarian motivations. However, acknowledging the exploratory nature of this study and its limited sample size, further research is warranted to comprehensively ascertain the further diffusion and integration of EMV into the urban transportation system.
  • Roadmap for Low-Carbon Concrete in Finland
    (2025-12-01) Punkki, Jouni
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A roadmap for low-carbon concrete was prepared in Finland. The aim of the roadmap was to identify possible options for CO2-emission reductions in concrete production. The calculations were made to correspond the situations in 2030, 2040 and 2050. The calculations were based on the maximum saving potential and the degree of utilization of the options. The roadmap covers the whole Finnish concrete industry and individual companies in different product segments. It is well known that cement has the largest potential for CO2 saving, but the roadmap reveals several other potential options as well. The most potential options vary between the product segments. The roadmap also confirms that concrete can reach very low CO2-emission level in the future.
  • Effects of carbonation and ageing of slag concrete on salt freeze-thaw scaling, porosity, and portlandite consumption
    (2026-03-28) Iqbal, Ahsan; Antonova, Anna; Kuva, Jukka; Punkki, Jouni
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This study investigated the combined effects of ground granulated blast furnace slag (GGBFS) content (0 – 46%) and carbonation conditions on salt freeze-thaw scaling resistance of concrete. Standard 7 days curing resulted in minimal scaling (' 1.0 kg/m2), while accelerated carbonation for similar duration amplified scaling values to 1 kg/m2, 3.3 kg/m2, and 4.5 kg/m2 in 0%, 15%, and 46% GGBFS concretes, respectively. Extended carbonation (30 days) further increased scaling to 1.2, 5.7, and 7.4 kg/m2 for these mixtures, with 70% of total scaling occurring within the first 14 freeze-thaw cycles. The strong correlation (R2 = 0.873) between carbonation depth and scaling depth confirmed that approximately 50% of the carbonated layer was removed during the slab test. Specimens with 0% and 46% GGBFS showed 56% and 8% reduction in large capillary pores at paste level (2 µm/voxel), respectively. While concrete specimens with 46% GGBFS exhibited 22% increase in macropores (≥15 µm), indicating carbonation-induced microcracking. Despite these porosity changes, capillary sorptivity remained unchanged across all concretes, while total water absorption decreased between 12 – 16%, suggesting that carbonation fills pore bodies without blocking connecting throats. Cement paste with 46% GGBFS contained 47% less portlandite than paste with 0% GGBFS. Thermogravimetric analysis showed the formation of calcium carbonate (27% in paste with 46% GGBFS after 30 days carbonation) greater than the amount attributable to portlandite alone, confirming decomposition of calcium silicate hydrate. This decalcification combined with carbonation induced microcracking and deterioration of air-void system, might weakened the binding matrix and explained the severe salt freeze-thaw scaling in carbonated slag concretes.
  • Creating Safer Learning Environments Through Universal Design for Learning Framework
    (2025) Savolainen, Timo; Kärpänen, Terhi
    A3 Kirjan tai muun kokoomateoksen osa
    Ensuring the safety and security (S&S) of learning environments remains a critical challenge, even in the Nordic countries such as Finland, ranked the world’s happiest nation for the seventh consecutive year in 2024. Research identifies a poor psychosocial climate as a major factor contributing to unsafe school environments. This paper examines how the Universal Design for Learning (UDL) framework can enhance school S&S by improving the psychosocial environment. Drawing on existing literature with snowball approach, the study analyzes key risk factors—such as negative social atmosphere, inadequate physical space design, security deficiencies, and cognitive challenges—that compromise safety. Findings suggest that integrating UDL principles, including technology adoption, flexibility, accessibility, and thoughtful spatial design, can help create safer and more inclusive educational settings. By linking UDL to school S&S, this paper offers a novel perspective on how universal design strategies can address diverse student needs and foster more supportive, secure learning environments.
  • Performance of demand-controlled heat recovery ventilation systems with central and zonal control in a single-family house
    (2026-01-21) Onemar, Kätriin; Simson, Raimo; Kurnitski, Jarek
    A4 Artikkeli konferenssijulkaisussa
    Improving ventilation efficiency in residential buildings is crucial to reducing energy consumption while maintaining indoor air quality. This study investigates three demand-controlled ventilation (DCV) strategies compared to a traditional constant airflow (CAV) system in a single-family house. The DCV strategies evaluated include central CO2 control using a sensor in the exhaust duct, central CO2 control using the highest reading from individual rooms, zonal CO2 control with two zones prioritized by the highest CO2 level in each, and constant airflow as the baseline system. Dynamic energy simulations were performed using a calibrated model based on Estonian climate conditions and a typical residential occupancy profile. Each control strategy was simulated in combination with three types of heat recovery ventilation units: rotary heat exchanger (RHE), energy recovery ventilator (ERV), and heat recovery ventilator (HRV). Results show that energy saving of demand-controlled system with dual-zone control was 33% while maintaining indoor air quality, but central control with exhaust sensor resulted in negligible saving. Notably, the dual-zone strategy with enthalpy recovery plate achieved the lowest overall energy consumption, reducing both space heating and fan electricity demand. The findings highlight the importance of sensor placement, control logic, and heat recovery selection in optimizing ventilation energy performance in residential buildings.
  • Does size matter? Assessing the role of lentic system area on diatom diversity in subarctic Finland
    (2026) Heikkinen, Janne M.; Granqvist, Sonja K.J.; Laksela, Paula; Soininen, Janne; Pajunen, Virpi
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Lentic systems are often small, experiencing a wide range of consequences of climate change through shifts in chemistry and community assembly processes. Such vulnerable systems support most of the regional freshwater biodiversity in the Finnish subarctic, highlighting their conservation value. Despite increasing research of subarctic freshwater diatoms focusing on the relationship between biodiversity and various factors, the effect of habitat size on benthic diatoms remains understudied. This study compared diatom diversity and water chemistry between and within subarctic lentic systems. Significant differences in species richness, water pH, conductivity, Ca, Cl, and Na were found between lakes and ponds, but the variation within systems was insignificant. Our results suggest that there were size-dependent differences in community composition, assembly processes, and local contributions towards beta diversity, and that differences in water chemistry between ponds and lakes help shape the benthic diatom communities. Thus, surface area may be used as a proxy for water chemistry. Microhabitat abundance and environmental harshness likely cause such area effects, but further investigation is required on isolation, dispersal limitations, and water depth. Studying the benthic communities of these vulnerable systems will provide insight into the effects of climate change.
  • The role of residential urban form and built environment in supporting social interaction, health, and well-being: a focus on forming and maintaining ties
    (2026-12) Ishikawa, Taiyo; Kyttä, Marketta; Rinne, Tiina
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Background Social interaction is essential for health and well-being, given the growing public health concern of social isolation and loneliness. The role of the built environment in supporting social interaction has been widely studied. However, previous research has often treated social interaction as a single, undifferentiated category, although different types of interaction may serve distinct social functions and be influenced by different environmental factors. Moreover, most studies have focused primarily on residential neighborhood contexts. This study addresses these key gaps by distinguishing between two types of social interaction—tie formation and tie maintenance—and by examining built environment characteristics across broader, individualized multidimensional activity space models. Method Using data from a Public Participatory GIS (PPGIS) survey (n = 386) in Turku, Finland, this study analyzed how residential urban form and built environment features relate to tie formation and tie maintenance. Built environment features were assessed using three activity space models: 500-meter home buffer, combined buffer around home and daily destinations, and individualized activity range spanning between home and destinations. Structural Equation Modeling was used to examine how these factors influence each type of social interaction and associated psychosocial outcomes. Results Residing in urban areas was significantly associated with tie maintenance but not with tie formation. Walkability around the home supported both types of interaction, whereas parks and green spaces near daily destinations were positively associated with tie formation. A similar pattern was observed within individualized activity ranges, where park ratio predicted tie formation. These two types of social interaction influenced psychosocial outcomes through distinct pathways: tie formation had direct positive effects on health and well-being, while tie maintenance contributed indirectly through increased relationship satisfaction. Conclusion The findings emphasize the importance of distinguishing between different types of social interaction and accounting for their unique spatial and functional drivers. Urban planning and public health efforts should consider how different aspects of the built environment foster both the formation and maintenance of social ties. Promoting environments that support diverse forms of social interaction is essential not only for enhancing health and well-being but also for reducing the risk of loneliness.
  • Lean Construction 4.0: enhancing situational awareness for autonomous decision-making through digital visual management
    (2026-02-18) Görsch, Christopher; Tezel, Algan; Lappalainen, Eelon; Seppänen, Olli; Koskela, Lauri
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Purpose This paper aims to address the need for a comprehensive management framework that supports decentralised and autonomous decision-making to reduce waste and improve flow in construction. Design/methodology/approach Following a design science research approach, an integrative literature review was conducted to build the framework, which was then comparatively assessed against existing visual-management and situation-awareness systems to identify functional gaps and potential applications. Findings The resulting framework links the physical, informational and socio-psychological dimensions of construction to deliver continuously accessible, task-relevant information that supports real-time decision-making and coordination across trades. Research limitations/implications Implementation of the DVM framework remains limited by economic, organisational and technological barriers. This calls for future research on scalable adoption, interoperability and digital skills development. Practical implications The framework strengthens operational decision-making and cross-trade coordination by integrating automated data capture, analysis, and visual information delivery. In practice, it supports proactive constraint management, increases safety and resource efficiency and minimises waste arising from fragmented information flow. Social implications The framework advances human-centric construction management by strengthening workers' autonomy and situational awareness while integrating digital systems that support, rather than replace, human judgement. It highlights management as a socio-technical process built on awareness, trust and informed decision-making. Originality/value The study introduces a digital visual management framework that unites physical, digital and cognitive perspectives, extending lean construction theory and offering a practical foundation for developing and implementing next-generation, human-centric decision-support systems in construction projects.
  • Cost-effective renovation of Nordic old apartment heating systems with hydrogen-production-based low-temperature district heating
    (2026-04-15) Liu, Jiayi; Ju, Yuchen; Kosonen, Risto; Jokisalo, Juha; Meriläinen, Altti; Kosonen, Antti
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Integrating waste heat from hydrogen production into low-temperature district heating (LTDH) can improve hydrogen production profitability and the renewable energy usage of building heating. However, cost-effectiveness evidence for such applications on the demand side of old buildings remains limited. This study evaluates the potential of hydrogen-production-based waste heat in an LTDH context for two old Finnish apartment buildings with commonly used high-temperature radiators (80/50 °C and 70/40 °C). Based on these buildings, LTDH solutions are proposed to address the temperature mismatch between LTDH supply and existing space heating systems: retaining the existing radiators with the backup heater (an electric heater or a heat pump), and retrofitting low-temperature radiators (60/30 °C) compatible with LTDH. IDA ICE was used for energy simulations for representative weather years and a future climate scenario of 2050, and indoor temperature simulation during the cold event. The economic feasibility of each solution is evaluated. The findings indicate that LTDH meets at least 93% of total heat demand with 80/50 °C radiators and about 99% with 70/40 °C radiators. Backup electric heaters and heat pumps raise peak electricity demand by up to 169% and 38%, respectively, relative to the references. Resilience analysis indicates that backup heating is required to maintain indoor temperatures for the old building with 80/50 °C radiators. Economically, all proposed LTDH solutions are feasible with lower life-cycle costs (LCC) than the reference cases. Electric heater yields the shortest discounted payback period, whereas the heat pump solution offers the lowest cost over the full life cycle.
  • Eco-friendly synthesis of metal oxide nanoparticles (ZnO, MgO and CuO) for efficient water purification : A review
    (2026-02) Alhamdany, Sarah R.; Alsalhy, Qusay F.; Hassan, Ahmed K.; Al-Saadi, Saad; Meskher, Hicham; Al-Juboori, Raed A.
    A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Escalating water pollution and scarcity necessitate the development of advanced, sustainable water treatment technologies. This review presents a critical and comprehensive analysis of the green synthesis of ZnO, MgO, and CuO nanoparticles (NPs), as well as their integration into membrane technologies for effective water remediation. Green synthesis harnesses biological resources such as plant extracts, offering a low-cost, energy-efficient, and environmentally friendly alternative to conventional methods while producing nanoparticles with superior catalytic and antimicrobial properties. We elucidate how the physicochemical characteristics of these green-synthesized nanoparticles enhance membrane hydrophilicity, antifouling behavior, and photocatalytic degradation of contaminants, thereby improving water purification efficiency. Additionally, this review addresses current challenges in controlling particle size, morphology, and scalability, emphasizing the need for advanced synthesis strategies such as microwave-assisted, supercritical CO₂, and hybrid green synthesis methods to optimize nanoparticle production for industrial applications. By bridging the gap between sustainable nanoparticle synthesis and practical membrane modification, this review emphasizes the potential of green nanotechnology to transform water treatment processes, aligning with sustainability.
  • Scale Effects of Patch Configuration and Density on Vegetation Drag in Floodplain Flows
    (2026-01-01) Jafari Mohammadi, Seyed Mahdi; Järvelä, Juha; Västilä, Kaisa
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Vegetated floodplains modulate river hydraulics through drag forces that affect flow conveyance, sediment transport and floodplain ecosystems. Non-uniform vegetation patches are widespread in natural floodplains and challenge drag prediction models, as the scale-dependent effects of patch configuration, canopy density and submergence remain inadequately quantified. Here, we directly measured drag forces on nature-like flexible woody vegetation across individual plant, isolated patch and reach-scale patch set-ups using a novel multi-scale drag measurement system in a recirculating flume. Investigations span emergent (H/hd ≈ 1) and submerged (H/hd ≈ 2) regimes, with patches varying in planform configuration and density. Results show that drag increased non-linearly with spatial scale. For instance, reach-scale patches having the same number of plants and canopy density (LAI) as the isolated ones exerted 1.1–2.2 times greater drag than isolated patches due to canopy continuity and wake interactions. Normalization of drag by one-sided leaf area revealed strong dependence on patch configuration and flow velocity, whereas normalization by newly defined configuration–density parameter (DW) reduced inter-configuration variability, providing a scaling framework from emergent to submerged conditions. For patches submerged to twice the deflected canopy height, the total drag was reduced by roughly half compared with emergent condition. These findings show that vegetation-induced drag depends jointly on spatial scale, configuration, plant density and submergence. Overall, the results establish a physical basis for linking vegetation-induced drag to flow resistance and flow distribution, which together determine key ecohydrological functions such as flow partitioning, sediment retention and hydraulic connectivity across vegetated floodplains.
  • Keeping it Real: The Role of Real-World Problems in Students' Engineering Competence Development in Interdisciplinary Project-Based Learning
    (2025) Feng, Xiaoqi; Sundman, Julia
    A4 Artikkeli konferenssijulkaisussa
    Engineering education increasingly adopts problem- and project-based learning (PBL) to engage students with real-world challenges. Even when working with hypothetical cases, they are often designed to simulate authentic professional contexts, encouraging students to collaborate, make responsible decisions, and take their work seriously. This study investigates how characteristics of interdisciplinary PBL relate to students' perceived development of engineering competences. Survey responses were collected from 33 students enrolled in interdisciplinary PBL courses, measuring their perceptions of task authenticity, team climate, team composition, and self-assessed engineering competences. Additionally, 29 student interviews were included to complement and contextualize the survey findings. Regression analysis revealed that task authenticity is significantly associated with students' perceived engineering competences. Qualitative analysis also showed how students are driven by real-life projects, especially to collaborate with real clients, gain futurerelevant skills, and engage with topics related to future career aspirations. However, barriers such as limited client communication, vague project briefs, and uneven team engagement were perceived to undermine authenticity. These findings suggest the need to scaffold students in dissecting project brief, support effective teamwork, and strengthen student-stakeholder communication. Such support can better prepare students to navigate ambiguity and complexity, and, at the same time, leveraging these complexities as productive learning dilemmas to foster deep learning.
  • Mechanical performance of reinforced concrete sandwich shells with different boundary conditions
    (2026-04) Shi, Jiaxu; Chen, An; Yossef, Mostafa; Li, Zhi; Tang, Haifeng; Sun, Jing
    A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Concrete sandwich panels have been extensively used due to their cost-effective and multi-functional capacities. Building on this concept, concrete sandwich shells were developed, which extends their applications to curved structures. The objective of this paper is to study the mechanical performance of prototype concrete sandwich shells. First, full-size concrete sandwich and solid shells with the same dimensions were manufactured and tested using four-point bending test, considering both simple support and axially restrained support boundary conditions. Next, Finite Element (FE) models are constructed, and good correlations can be observed between experimental and FE results. It can be concluded that, before concrete cracks, the degree of composite action between the sandwich shell and the solid shell is similar. Under the simply-supported boundary condition, the existence of the connectors in the sandwich shell leads to an increased reinforcement ratio, resulting in a higher ultimate load (936 kN) compared with that of the solid shell (580 kN). Under axially restrained support boundary condition, the ultimate load of the sandwich shell (1847 kN) is lower than that of the solid shell (3505 kN), due to the significant axial force. The solid shell, which has a thicker concrete wythe, exhibits higher bending capacity. Finally, the FE model is used to conduct a parametric study on the sandwich shell. It is found that, as the number of the rows of connectors increases, the ultimate load of the shells increases. The load-bearing capacity of the sandwich shell with the thickness from 130 mm to 140 mm is similar, which tends to be stable when the thickness of the insulation is less than 120 mm. Based on this study, it can be shown that, when properly designed, the sandwich shells have enough capacities to be used as structure members, but with lower weight compared with that of solid shells.