| 1. |
- Fang, Xing, et al.
(författare)
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Impact of rapid-hardening cements on mechanical properties of cement bitumen emulsion asphalt
- 2016
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Ingår i: Materials and Structures. - : Springer. - 1359-5997 .- 1871-6873. ; 49:1-2, s. 487-498
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Tidskriftsartikel (refereegranskat)abstract
- Cement bitumen emulsion asphalt (CBEA) is obtained by mixing bitumen emulsion, cement, aggregates and filler at ambient temperature. CBEA is thought to be a promising substitute for hot mix asphalt because of its low environmental impact and cost-effectiveness. Disadvantages of this material are the long time required to reach its full strength and the inadequate understanding of the hardening mechanisms. This study aims at accelerating the development of mechanical properties of CBEA by using rapid-hardening cements while at the same time gaining a deeper understanding of the role of cement in CBEA. With this purpose, cold mix asphalt mixtures with cationic and anionic emulsions and different types of cement (ordinary Portland, calcium sulfoaluminate and calcium aluminate cement) were studied by means of isothermal calorimetry, measurements of water evaporation and Marshall tests. The results indicate that both anionic and cationic bitumen emulsions may affect the initial hydration rates of the cements used but have no significant influence on their degree of hydration after a few days. The addition of calcium sulfoaluminate and calcium aluminate cement to CBEA leads to mechanical properties after 1-day curing similar to those obtained with Portland cement after 1-week curing. Cement hydration dominates the strength gain, especially for rapid-hardening cements, and the type of cement influences both the amount of bound water and the rate of water evaporation from the CBEA.
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| 2. |
- Fang, Xing, et al.
(författare)
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Microstructure and mechanical properties of the laser welded air-hardening steel joint
- 2024
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Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 213
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Tidskriftsartikel (refereegranskat)abstract
- The decrease in mechanical properties of high-strength steel after welding is an important issue affecting the wide application of high-strength steel. Air-hardening steel is a high-strength steel suitable for lower body structural parts such as subframes. Its application process involves welding, hot forming and other processes. The present work investigates the microstructure and mechanical properties of the air-hardening steel laser welded joint that is air-cooled after hot forming in the two-phase zone (800 °C). The microstructure was characterized by electron backscattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that during hot forming, the welded joint transforms from martensite to ferrite and acicular martensite, and the base metal transforms from ferrite to polygonal martensite and ferrite. The difference in martensite morphology between the welded joint and the base metal is attributed to the nucleation positions of austenite. The structural evolution of the welded joint and the base metal is accompanied with the annihilation and reproduction of dislocations, which results in significant changes in hardness. The hardness value dropped from the highest 430 HV to 271 HV in the welded joint, while increased from the lowest 184 HV to 203 HV in the base metal. After hot forming, the tensile strength of the welded sample is reduced by only 36 MPa, and the total elongation is slightly decreased by about 1.5% compared with the unwelded sample. The welded joint and the base metal have similar plastic deformation capabilities, since the acicular martensite in the welded joint displays good plastic deformation ability, and the dislocation density of the welded joint and the base metal is similar. Overall, the microstructure and dislocation density of the air-hardening steel welded joint after hot forming are similar to those of the base metal, which is responsible for the good mechanical properties of air-hardening steel welded joint.
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| 3. |
- Johansson, Magnus, 1970-, et al.
(författare)
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Social learning in education – an important step in practical integration of preventive risk reduction and adaptation to climate change
- 2012
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Konferensbidrag (refereegranskat)abstract
- The potential of linking the preventive phase of Disaster Risk Reduction (DRR) with the adaptation in human society to forecasted consequences from climate change, has received growing acceptance internationally, but the integration of both fields is still at an embryonic stage. Integration in this case implies transdisciplinary approaches in complex fields where liabilities and stakeholders normally are found in different sectors and levels in society. For integration to be successful, a first step is to create platforms and contexts where participants may generate raised awareness about each other’s roles and evolve a shared problem identification. Social learning is a concept that has been used in many different contexts where uncertainty and change are crucial and challenging. It has earlier been linked as a suitable approach to issues such as public participation, governance or natural resource management. Here it is used in education, gathering among others stakeholders working within the fields of Flood Risk Management, DRR and Climate Change Adaptation at local or regional level around the two Swedish lakes Vänern and Mälaren. Teaching arrangements and didactic elements are described for the two pilot-courses that were held 2009-2010. The academic institutional arrangements favoured an open exchange and knowledge building, with local examples of management and strategies repeatedly in focus during several study visits in different cities along the shoreline. The elements of social learning facilitated the build-up of shared holistic perspectives, identified areas in need of development or research efforts and contributed to informal as well as formal relationships among participants.
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| 4. |
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| 5. |
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"Theme Section 2: Specfic 2021: Time and History"
- 2022
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- A theme section in Fafnir based on four contributions from the conference "SpecFic2021: Time and History", Karlstad University December 1-3 2021, edited by Godhe, Oakes & Varis.
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