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- Johansson, Frank, et al.
(författare)
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Wing shape differences along a migration route of the long-distance migrant Globe Skimmer Dragonfly Pantala flavescens
- 2022
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Ingår i: Journal of Tropical Ecology. - : Cambridge University Press. - 0266-4674 .- 1469-7831. ; 38:1, s. 17-24
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Tidskriftsartikel (refereegranskat)abstract
- Animals which migrate by flying should be subject to selection for optimal wing characteristics that maximize energy efficiency during migration. We investigated wing shape and wing area variation in the Globe Skimmer Dragonfly Pantala flavescens, which has the longest known migration of any insect. Wing shape and wing area differences between individuals in southern Peninsular India, and migrating individuals at a stop-over site on the Maldives, were compared. Results suggest that individuals which successfully reached the Maldives, on their way from India to Africa, had a broader wing base and an overall more slender wing shape than individuals in southern India. Contrary to our expectations, wing area did not differ significantly in most of our comparisons between southern India and the Maldives, suggesting that wing shape is more important than wing area for successful migration in P. flavescens. The results provide indirect evidence of natural selection on wing shape in a migrating dragonfly.
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- Moreno, Maiara, 1993-, et al.
(författare)
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Strain and phase evolution in TiAlN coatings during high-speed metal cutting : An in operando high-energy x-ray diffraction study
- 2024
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- We report on phase and strain changes in Ti1-xAlxN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.
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- Yildiz, Ahmet Bahadir, et al.
(författare)
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Design, synthesis, structure, and stability of novel multi-principal element (Ti,Zr,Hf,W)C ceramic with a miscibility gap
- 2022
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 42:11, s. 4429-4435
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Tidskriftsartikel (refereegranskat)abstract
- Here we design a novel multi-principal element carbide system (Ti,Zr,Hf,W)C with a miscibility gap using computational tools and report on the formation of a single-phase (Ti,Zr,Hf,W)C after spark plasma sintering. The (Ti,Zr,Hf,W)C shows high nanohardness (32.7 GPa) and fracture toughness (5 MPa·m1/2). Aging studies at 1350 °C for 100 h show that the single-phase carbide solid solution is quite stable even though this temperature is within the predicted miscibility gap of the system. Detailed electron microscopy characterization shows that phase separation has initiated with minor decomposition after aging by forming rock-salt (Ti,W)C- and (Zr,Hf)C-rich phases as well as hexagonal WC precipitates. We show that the (Ti,W)C- and (Zr,Hf)C-rich phases form a lamellar structure upon aging and the interlamellar spacing is considerably coarser than what has been previously found for the binary (Ti,Zr)C system. The decomposition kinetics, on the other hand, is sluggish due to the reduced driving force for phase decomposition.
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