VTT Research System
Not a member yet
161399 research outputs found
Sort by
Extreme fitness: Applying ecophysics to reduce human stress in everyday extreme environments
No full textIt has been proposed that ergonomics and human factors (EHF) can be advanced by moving beyond old methodologies, by strengthening theoretical basis, and by making more use of artificial intelligence. Here, with the example of human remote operation of robots, i.e., teleoperation, it is argued that progress towards realising proposals for advancing EHF can be made by increasing reference to ecophysics. That is by increasing reference to science concerned with interactions between ecological systems and physical laws. In this document, human stress associated with remote operations work is situated in the broader context of extreme work environments. Those being environments that many people experience every workday, such as typical factories and offices, which are far from the natural environments in which humans evolved. With reference to ecological fitness, morphological fitness, and tripartite entropy, it is explained how application of ecophysics in EHF has potential to reduce human work stress
Transition of dominating roles from dislocations to stacking faults enables superior mechanical properties of CoCrNi alloys
No full textGenerally, balanced strength and ductility can be achieved by tailoring crystal defects for face-centered cubic (FCC) alloys, in which dislocations play a critical role. This study investigates the deformation mechanisms and strain-hardening behavior of CoCrNi alloys (45Ni, 33Ni, 24Ni) with different stacking fault energies (SFEs). The 45Ni and 33Ni exhibit a dislocation-dominated deformation mechanism. In contrast, stacking faults (SFs) dominate in the 24Ni alloy, which is closely related to the very low SFE. SFs not only strengthen the FCC matrix but also promote the hexagonal close-packed (HCP) phase nucleation. The overall effect of the nanoscale thickness and the significant volume fraction of the HCP phase leads to a sustained high strain-hardening rate. In addition, the product of ductility and strength of 24Ni is significantly higher than that of equiatomic CoCrNi alloy and 316 L stainless steel at the critical grain size of ∼0.7 μm. These findings provide new insights for further improving the mechanical properties of FCC alloys.</p
Unexpected low temperature crack propagation in nuclear post-shutdown water chemistry of Alloy 52 with potential effects of hydrogen
Get PDFConstant-displacement bolt-loaded compact tension specimens of Nickel-based Alloy 52 were exposed to boiling water reactor environment for 12 years, followed by an additional 3 years in post-shutdown cold water conditions in a Swedish nuclear power plant test loop, under a stress intensity factor of 20 MPa√m. After outer surface decontamination and specimen opening, unexpected crack extensions of 3–4.5 mm were observed. The fracture surface and the cross-sectional deformation microstructure were examined by electron microscopies techniques down to the nanoscale. The oxide layer in the region exhibiting unexpected crack growth was notably thin, suggesting that it formed after exposure to elevated operating temperatures. The dominant fracture mode is transgranular, propagating along close-packed {111} planes. The grains contained heterogeneous microstructures with regions enriched in nanometer-sized Ti(N,C) and the zigzag crack paths did not traverse these regions strengthened areas. Extensive shear bands were present near the crack tips, indicating pronounced localized plasticity. Hydrogen reduces stacking fault energy, results in localized plasticity and enhances shear bands formation. Low temperature crack propagation with evident effects of hydrogen was considered as the potential cause of crack propagation in Alloy 52 in the absence of external dynamic loading under post-shutdown cold water chemistry
A Framework for Road Authorities to Assess Their Readiness to Support Connected and Automated Driving
No full textConnected and Automated Driving (CAD) will bring disruption to individuals, economies, and society. Most forms of CAD require some level of support from the infrastructure for their safe operation, in particular communications. However, additional infrastructure services to support CAD could improve safety and robustness and bring further benefits such as increased capacity. However, the infrastructure requirements of vehicle Original Equipment Manufacturers (OEMs) are not always clear, and it is therefore difficult for National Road Authorities (NRA) to prepare future levels of support for CAD, given rapidly evolving technology and uncertain projections of future CAD demand. There is a need to articulate those requirements, bringing stakeholders together to formulate a structured approach, and a roadmap that will advance safe and smart roads that support CAD. This paper presents the DiREC project (consortium partners: TRL, ARUP, TU Delft, VTT, VTI and FEHRL) funded by the CEDR Transnational Road Research Programme Call 2020 with funding provided by CEDR members of Belgium (Flanders), Denmark, Ireland, Israel, Netherlands, Norway, Sweden, Switzerland and the United Kingdom. DiREC is seeking to address the above challenge. The project has established a CAV-Readiness Framework (CRF) based on a level of service approach to understand the needs of CAD, and to define the infrastructure and services that NRAs could provide to support these needs.</p
IoT Service Orchestration in Edge-Cloud Continuum with 6G:A Review
No full textThe development of 6th-generation (6G) mobile networks brings advancements in wireless communications, including lower latency, higher data rates, and improved spectral efficiency, as well as enhanced facilitation for the use of Artificial Intelligence (AI) technologies, integrated communications, sensing, and renewable energy sources. To harness this potential, a scalable framework integrating edge and cloud computing is needed to provide a robust computing continuum for various IoT applications and services. This paper analyses the strengths and weaknesses of existing and emerging distributed computing frameworks—ranging from traditional centralized IoT architectures, through fog, edge, and local-edge architectures, to the full three-tier edge–cloud continuum—in terms of IoT service orchestration and diverse application requirements. We emphasize the latest evolutionary step, three-tier edge-cloud continuum, which aims to resolve the most significant limitations of the previous frameworks, recognized in the literature. It enables efficient IoT service orchestration by utilizing distributed resources and computation closer to end users, while taking full advantage of the centralized resources at data centers. We evaluate the maturity of these frameworks, considering factors such as scalability, resource efficiency, adaptability to changes, resource availability, security and privacy, as well as robustness and resilience. Overall, this study aims to serve as a roadmap for researchers, network architects, and industry stakeholders to make informed decisions on implementing the computing continuum in 6G networks.</p
Efficient debromination of tetrabromobisphenol A in protic solvents by supported nickel catalysts:Effect of metal-support interactions
No full textToxic and environmentally hazardous brominated flame retardants (BFR) hinder the recycling of plastic waste, which has led to the development of various extraction processes to remove them. These processes can be further advanced by debrominating BFRs into less harmful compounds with potential commercial value, thus supporting the principles of a circular economy. Herein, Ni/Al2O3 was employed for the catalytic debromination of tetrabromobisphenol A flame retardant in mixtures of H2O, isopropanol and NaOH at modest reaction temperatures. Activity experiments conducted in an autoclave indicated that studied catalyst exhibits impressive debromination activity and complete selectivity towards C−Br bond scission. The catalyst reduction temperature was found to correlate with debromination activity, with higher temperatures yielding improved performance. Debromination proceeded under H2 and also under N2 in protic solvents via transfer hydrogenation. Catalyst characterization, coupled with high-resolution mass-spectrometry product analytics and deuterium labelling, suggested that the enhanced catalytic activity can be attributed to the activation of the metal-support interface and subsequent interactions with adsorbed solvent molecules and associated dissociation products on the alumina support. Used experimental conditions also provided high tolerance against bromine poisoning of the catalyst, in contrast to reference debromination experiments conducted in toluene. The study demonstrates the capability of Ni/Al2O3 as an efficient and affordable debromination catalyst in solvents of low environmental impact. Furthermore, the results provide additional insights into structure-activity relationships of supported nickel catalysts in protic solvents, which can be leveraged for the development of more efficient and sustainable dehalogenation and heteroatom removal processes for environmental applications.</p
Preparing a social impact bond in a Nordic welfare state: governance challenges and hybrid responses
No full textPurposeThis study aims to examine the preparation of a complex Social Impact Bond (SIB) project in Finland, exploring how challenges and solutions reflect the interplay between new public management (NPM) and new public governance (NPG) logics. It contributes to debates on the institutional adaptability of SIBs beyond Anglo-American contexts.Design/methodology/approachThe authors conduct a longitudinal case study of the Children’s SIB II in Finland, analysing data from 21 stakeholder interviews. Five preparation phases are identified and examined for governance dynamics and challenge-response logics.FindingsThe findings show how SIB preparation involved hybrid governance, combining NPM tools, such as performance-based incentives, with NPG principles like trust-building and cross-sector collaboration. While many challenges were initially framed through NPM logics, their resolution often leaned towards NPG-style responses, highlighting the adaptive use of relational governance practices. A key insight is the critical role of a publicly funded intermediary in framing the SIB, mobilizing networks and embedding the instrument within national welfare discourses.Social implicationsHybrid governance tools like SIBs can reinforce trust-based public-private cooperation and support developing responses to complex social issues, but they also require significant institutional capacity.Originality/valueThis study extends the literature on SIBs by examining their preparation in a Nordic welfare state context, distinct from the Anglo-American settings where SIBs have been most studied. It contributes novel insights into how hybrid governance unfolds in such contexts, particularly how NPG-style solutions emerge even when problems are framed through NPM logics. It also highlights the overlooked role of public institutional intermediaries in shaping SIB development beyond technical and financial coordination.<br/
Modeling Thermal Effects in Atomic Layer Deposition for Trench-Shaped Structures
No full textAn atomic layer deposition (ALD) simulation approach is presented for transient diffusion of heat and mass at low Knudsen numbers (Kn < 0.1), focusing on thermal effects in trench-shaped structures. Two boundary conditions (BCs) are analyzed: the ‘thin wall’ BC incorporates exothermic reactions with a derived wall heat flux term, and the ‘thick wall’ BC maintains constant wall temperature ranging between 500 K and 800 K. For both BCs, we examine aspect ratios from 1 to 100. The chosen BC significantly impacts reaction kinetics/peak temperatures, with local temperature variations up to 200 K under ‘thin wall’ conditions. The coating time ratio between ‘thin wall’ and ‘thick wall’ ranges from 0.9 to 1.7. Two ‘universal’ functional forms are proposed to explain how surface coverage depends on time and how coating time relates to aspect ratio and diffusion timescale. Results emphasize the crucial role of temperature distribution in ALD, impacting growth per cycle, reactant decomposition/desorption, and potential substrate damage
Thermoelectric and electronic transport properties of thermal and plasma-enhanced ALD grown titanium nitride thin films
No full textTitanium nitride (TiN) thin films demonstrate high electrical conductivity and thermal stability up to 400 °C in ambient conditions, with stability extending to 600–800 °C under inert or vacuum environments. Unlike many metals and transition metal nitrides, TiN combines high carrier mobility with moderate carrier concentration, making it ideal for thermal management and power-efficient applications in nanoelectronics and energy harvesting. This study systematically investigates the thermoelectric and electronic transport properties of TiN films grown by plasma-enhanced atomic layer deposition (PEALD), comparing them to those produced using traditional thermal atomic layer deposition (thermal ALD). These properties are studied as a function of growth temperature and the number of growth cycles. In particular, TiN films deposited by PEALD at 400 °C for 2000 ALD cycles exhibited a remarkable power factor of 512 µW m−1K−2at room temperature compared to a power factor of 4.95 µW m−1K−2measured for thermal ALD films fabricated under the same deposition conditions. Additionally, thermal conductivity was also measured for thicker TiN films (86 nm), yielding values of 26.96 W m−1K−1for PEALD and 7.01 W m−1K−1for thermal ALD, marking the first such report for ALD-grown TiN. These values offer an upper estimate of the thermal behavior in thinner films. Based on these measured properties, the thermoelectric figure of merit (zT) at room temperature was calculated to be 0.0056 for PEALD TiN films which is significantly higher than the value of 0.0002 obtained for thermal ALD TiN films. Our findings provide critical insights into transport properties of TiN, offering guidance for the development of conductive nanolayers in thermoelectric, nanoelectronic, and on-chip cooling applications, where precise control over thermal and electronic behavior is vital, thereby expanding the relevance of ALD TiN in high-performance applications.</p
A novel real-time noise-resilient zeroing neural network and its applications to matrix problem solving
No full textGiven the critical role of zeroing neural networks (ZNN) in various fields and the practical demand for models in effectively resisting real-time noise, this study introduces a novel anti-noise integral zeroing neural network (AN-IZNN) model alongside its enhanced counterpart (EAN-IZNN), for the applications of matrix problem solving. Theoretical analysis demonstrates their ability to achieve convergence even under different noise conditions. Both theoretical analyses and simulation validations highlight the superior performance of the proposed models over existing neural network models. Notably, the root mean square error of the proposed AN-IZNN and EAN-IZNN models is reduced by 92.6249% and 91.4178%, respectively, compared to scenarios without the proposed method, demonstrating the effectiveness of the solution.</p