| 1. |
- Eriksson, Emil, 1990, et al.
(författare)
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Dynamic recrystallization during hot compression of Ni-based superalloy Haynes 282
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 960, s. 170837-170837
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the microstructural behaviour of materials during thermomechanical processing is a vital step towards optimizing the mechanical properties. One important aspect during forming processes, such as forging, is dynamic recrystallization (DRX), which sets the starting microstructure for the subsequent manufacturing steps. Here we investigated the DRX behaviour of Ni-base superalloy Haynes 282 during hot compression with a strain rate of 0.05 s−1 at 1080 °C, with care taken to minimize the effects of meta-dynamic recrystallization (mDRX) and adiabatic heating. Small DRX grains could be observed already at ε = 0.1, i.e. before the peak strain εp = 0.15. The DRX process accelerated significantly above ε = 0.2, and the material was fully recrystallized at ε = 1.5. Up to ε = 0.8 DRX occurred through continuous nucleation of new grains, whereas above ε = 0.8 the number density of DRX grains decreased and the increase in recrystallized fraction was due to growth of existing grains. Contrary to common assumptions of DRX nuclei being essentially dislocation free, many of the DRX grains contained pronounced dislocation substructures, even at small strains where they are not expected to have undergone deformation.
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| 2. |
- Eriksson, Emil, 1990, et al.
(författare)
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The Effect of Grain Boundary Carbides on Dynamic Recrystallization During Hot Compression of Ni-Based Superalloy Haynes 282
- 2022
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 53:1, s. 29-38
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Tidskriftsartikel (refereegranskat)abstract
- In alloys where carbides are the main grain boundary phase, the role of carbides during hot working is not known. Here, we address the effect of grain boundary carbides on the dynamic recrystallization during hot compression of Ni-base superalloy Haynes 282. When excluding variations from experimental factors neither stress evolution nor final microstructure indicated that carbides exerted a significant influence on the dynamic recrystallization. The carbide solvus temperature is not a critical limit during thermomechanical processes.
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| 3. |
- Eriksson, Erik, et al.
(författare)
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The Effect of Grain Boundary Carbides on Dynamic Recrystallization During Hot Compression of Ni-Based Superalloy Haynes 282 TM
- 2021
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940.
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Tidskriftsartikel (refereegranskat)abstract
- In alloys where carbides are the main grain boundary phase, the role of carbides during hot working is not known. Here, we address the effect of grain boundary carbides on the dynamic recrystallization during hot compression of Ni-base superalloy Haynes 282. When excluding variations from experimental factors neither stress evolution nor final microstructure indicated that carbides exerted a significant influence on the dynamic recrystallization. The carbide solvus temperature is not a critical limit during thermomechanical processes.
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| 4. |
- Fernandez, Joel, et al.
(författare)
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Linearization of Active Array Transmitters Under Crosstalk via Over-the-Air Observations
- 2023
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Ingår i: European Signal Processing Conference. - 2219-5491. ; , s. 1420-1424
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Konferensbidrag (refereegranskat)abstract
- Finding computationally feasible solutions to linearize active antenna array transmitters is a timely challenge in modern cellular networks, particularly in 5G and the emerging 6G systems. In this paper, we propose a new modeling and parameter estimation approach to characterize the individual power amplifier (PA) units of an active antenna array subject to crosstalk while relying only on over-the-air observations. Additionally, we describe a beam-sweeping based forward model learning procedure and the corresponding closed-loop digital predistortion (DPD) learning algorithm, to efficiently linearize millimeter-wave phased-array transmitters under crosstalk-induced load modulation. The provided numerical results demonstrate excellent parameter estimation and linearization performance, reaching adjacent channel power ratios (ACPRs) as low as -50 to -60 dB with realistic evaluation assumptions.
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| 5. |
- Carlson, Annika, et al.
(författare)
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Fuel cell evaluation of anion exchange membranes based on poly(phenylene oxide) with different cationic group placement
- 2020
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Ingår i: Sustainable Energy & Fuels. - 2398-4902. ; 4:5, s. 2274-2283
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Tidskriftsartikel (refereegranskat)abstract
- Four novel poly(phenylene oxide)-based anion exchange membranes were investigated for electrochemical performance, ionic conductivity and water transport properties in an operating anion exchange membrane fuel cell (AEMFC) , using Pt/C gas diffusion electrodes with Tokuyama ionomer. The poly(phenylene oxide)-membranes have a 1- or 5-carbon alkyl spacer between the backbone and a trimethylalkylammonium (TMA) or piperidinium (Pip) cationic group, and ion-exchange capacities (IECs) between 1.5 and 1.9 mequiv g-1. The polymer with a 5-carbon alkyl spacer, a TMA cationic group, and a higher IEC showed the highest ion conductivity and performance in the AEMFC. The results also show that introducing a 5-carbon alkyl spacer does not improve performance unless the IEC is increased and that exchanging the TMA with a Pip cationic group results in lower fuel cell performance despite a higher IEC. A discrepancy in ion conductivity between fuel cell and ex-situ test was observed for the 5-carbon spacer polymers and is attributed to a higher sensitivity for dehydration. Similar water flux under load, from the anode to the cathode with increased water content at both electrodes, was observed for all membranes and only varied with membrane thickness. The deviation in fuel cell performance observed between the membranes could not be explained by differences in water flux or ionic conduction, suggesting that the electrodes – membrane interaction plays a major role. Nevertheless, the study emphasizes that high membrane conductivity (for the λ-range in a fuel cell) and an efficient water transport (obtained by lower membrane thickness) promote higher electrochemical performance.
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| 6. |
- Eriksson, Emil, 1990, et al.
(författare)
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Meta-Dynamic Recrystallization in the Ni-Based Superalloy Haynes 282
- 2023
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- Forging on an industrial scale often involves slow, size-limited cooling rates or high temperature hold times between, or after, deformation. This enables the dynamic recrystallization (DRX) initiated during forging to further progress under static conditions, a phenomenon called meta-dynamic recrystallization (mDRX). As mDRX will influence the final grain size, and thus properties, it is critical to understand and control it during processing. Here, we study the mDRX evolution in Ni-based superalloy Haynes 282 during post-deformation hold times of up to 120 s at 1080 °C after partial DRX. We find that mDRX is the dominating mechanisms responsible for the microstructure evolution the hold time. The very rapid mDRX kinetics in the initial stages suggest that quench delays (the time between the end of the deformation and the onset of the quenching intended to arrest the microstructure evolution) must be kept well below 1 s in order to allow reliable conclusions to be drawn from post-deformation microstructure investigations. A larger prior strain (larger DRX fraction) leads to faster mDRX kinetics and a larger final grain size. Larger strains leads to earlier impingement of the growing grains, which, in combination with smaller remaining deformed regions into which the grains can grow, limits the maximum size of the mDRX grains. We also note a close correlation between static recovery and stress relaxation during the hold time, whereas no such correlation between mDRX and stress relaxation can be observed.
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| 7. |
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| 8. |
- Leander, John, et al.
(författare)
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Smart condition assessment, surveillance and management of critical bridges
- 2018
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Konferensbidrag (refereegranskat)abstract
- Bridges with critical roles in heavily loaded transport infrastructures often need to be kept in service despiteknown damage and deficiencies. Closing or limiting the traffic on a bridge, leading to traffic diversions, issometimes not a feasible option. The current paper describes an approach for securing the functionalityand the safety of critical bridges by using an innovative smart system for monitoring and conditionassessment. It builds on the use of wireless sensor networks, advanced assessment methods, and cloudbased services for storage and distribution of results. This is an ongoing research project and the progressso far is presented in this paper. A case study of the Old Lidingö Bridge in Stockholm, Sweden, is used todemonstrate the approach. The monitoring system installed, devices for energy harvesting, and methodsfor condition assessment are presented. Some preliminary results on the condition of the bridge are alsopresented.
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| 9. |
- Lindgren, Joel, et al.
(författare)
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N-terminal engineering of amyloid-beta-binding Affibody molecules yields improved chemical synthesis and higher binding affinity
- 2010
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Ingår i: Protein Science. - : Wiley. - 0961-8368 .- 1469-896X. ; 19:12, s. 2319-2329
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation of amyloid-beta (A beta) peptides is believed to be a major factor in the onset and progression of Alzheimer's disease Molecules binding with high affinity and selectivity to A beta-peptides are important tools for investigating the aggregation process An A beta-binding Affibody molecule, Z(A beta 3), has earlier been selected by phage display and shown to bind A beta(1-40) with nanomolar affinity and to inhibit A beta-peptide aggregation In this study, we create truncated functional versions of the Z(A beta 3) Affibody molecule better suited for chemical synthesis production Engineered Affibody molecules of different length were produced by solid phase peptide synthesis and allowed to form covalently linked homodimers by S-S-bridges The N-terminally truncated Affibody molecules Z(A beta 3)(12-58), Z(A beta 3)(15-58), and Z(A beta 3)(18-58) were produced in considerably higher synthetic yield than the corresponding full-length molecule Z(A beta 3)(1-58) Circular dichroism spectroscopy and surface plasmon resonance-based biosensor analysis showed that the shortest Affibody molecule, Z(A beta 3)(18-58), exhibited complete loss of binding to the A beta(1-40)-peptide, while the Z(A beta 3)(12-58) and Z(A beta 3)(15-58) Affibody molecules both displayed approximately one order of magnitude higher binding affinity to the A beta(1-40)-peptide compared to the full-length Affibody molecule Nuclear magnetic resonance spectroscopy showed that the structure of A beta(1-40) in complex with the truncated Affibody dimers is very similar to the previously published solution structure of the A beta(1-40)-peptide in complex with the full-length Z(A beta 3) Affibody molecule This indicates that the N-terminally truncated Affibody molecules Z(A beta 3)(12-58) and Z(A beta 3)(15-58) are highly promising for further engineering and future use as binding agents to monomeric A beta(1-40)
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| 10. |
- Shitahun, Alachew, et al.
(författare)
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Model-Based Dynamic Optimization with OpenModelica and CasADi
- 2013
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Ingår i: IFAC-AAC 2013. - 9783902823434 ; , s. 446-451
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Konferensbidrag (refereegranskat)abstract
- This paper demonstrates model-based dynamic optimization through the coupling of two open source tools: OpenModelica, which is a Modelica-based modeling and simulation platform, and CasADi, a framework for numerical optimization. The coupling uses a standardized XML format for exchange of differential-algebraic equations (DAE) models. OpenModelica supports export of models written in Modelica and the optimization language extension using this XML format, while CasADi supports import of models represented in this format. This allows users to define optimal control problems (OCP) using Modelica and optimization language specification, and solve the underlying model formulation using a range of optimization methods, including direct collocation and direct multiple shooting. The proposed solution has been tested on several industrially relevant optimal control problems, including a diesel-electric power train.
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