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- Stephens, Lucas, et al.
(författare)
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Archaeological assessment reveals Earth’s early transformation through land use
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 365:6456, s. 897-902
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Tidskriftsartikel (refereegranskat)abstract
- Humans began to leave lasting impacts on Earth’s surface starting 10,000 to 8000 years ago. Through a synthetic collaboration with archaeologists around the globe, Stephens et al. compiled a comprehensive picture of the trajectory of human land use worldwide during the Holocene (see the Perspective by Roberts). Hunter-gatherers, farmers, and pastoralists transformed the face of Earth earlier and to a greater extent than has been widely appreciated, a transformation that was essentially global by 3000 years before the present.Science, this issue p. 897; see also p. 865Environmentally transformative human use of land accelerated with the emergence of agriculture, but the extent, trajectory, and implications of these early changes are not well understood. An empirical global assessment of land use from 10,000 years before the present (yr B.P.) to 1850 CE reveals a planet largely transformed by hunter-gatherers, farmers, and pastoralists by 3000 years ago, considerably earlier than the dates in the land-use reconstructions commonly used by Earth scientists. Synthesis of knowledge contributed by more than 250 archaeologists highlighted gaps in archaeological expertise and data quality, which peaked for 2000 yr B.P. and in traditionally studied and wealthier regions. Archaeological reconstruction of global land-use history illuminates the deep roots of Earth’s transformation and challenges the emerging Anthropocene paradigm that large-scale anthropogenic global environmental change is mostly a recent phenomenon.
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- Sisodia, Sanjay M., et al.
(författare)
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High-resolution computed tomography in resin infused woven carbon fibre composites with voids
- 2016
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 131, s. 12-21
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Tidskriftsartikel (refereegranskat)abstract
- Tomographic imaging using both microfocus radiation and synchrotron radiation was performed to assess the void defects in resin transfer moulded woven carbon fibre composites. The focus of this study is on characterising the void homology (e.g. local void size and spatial distribution) in relation to weave orientation, infusion direction and potential effects on damage formation in tensile loading. As the orientation angle between the fibre direction of unidirectional layer in the laminate and the direction of the global resin flow increases, from parallel to perpendicular, larger voids and a greater volume fraction of voids were observed, which led to increased damage formation upon loading. Significant accumulation of voids around both the layer interfaces and yarn fibres were also observed. With regard to yarn design, it is recommended to balance the benefits (e.g. fabric handling, structural integrity of preform) and drawbacks (e.g. lower fibre content, more voids) of the supporting yarn. Also, sensible placement of resin inlets and outlets could reduce the amount of deleterious voids, i.e. by promoting resin flow along the fibre direction in the most defect-sensitive off-axis layers.
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