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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 105 (2000), S. 295-309 
    ISSN: 1573-2673
    Keywords: J-integral ; fracture criterion ; welded joint.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Based on the existed results of stress field solutions, in the present work a modified dual parameter J∼Q fracture criterion is proposed for plane strain state, and the criterion may be suitable to both homogeneous material and welded joint. Center cracked welded plate in plane strain condition is selected as a research object. Combined with finite element analysis, discussions are made on the engineering estimate and measurement of the various parameters. The engineering algorithm on the various factors in the fracture criterion is also proposed. Referring to the HRR results, it is indicated that the new criterion can describe stress field nature of homogeneous material and welded joint in plane strain state well. The availability of the new proposed criterion to the homogeneous material and welded joint is discussed. Thereafter, the difficulty of the single parameter J-integral can be overcome, when the modified J-integral parameter is used to describe the stress field intensity of plane strain and weld joint. Thus, the new criterion may be a good basis for engineering evaluation of fracture of welded structures.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Vegetation history and archaeobotany 9 (2000), S. 161-168 
    ISSN: 1617-6278
    Keywords: Phytolith analysis ; Pollen analysis ; Rice cultivation ; Neolithic ; Southern China
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract Phytolith and pollen analyses were carried out at the archaeological site at Longqiuzhuang in Gaoyou, Jiangsu, southern China. The results indicate that the key morphological phytolith types associated with cultivated rice (Oryza) are common in the Neolithic cultural layers at this site. The evidence strongly suggests that cultivated rice (mainlyO. japonica) was grown locally during the Neolithic. The archaeopalynological record provides information about the impact of human activity and, in particular, farming on the natural vegetation. The evergreen and deciduous broad-leaved forest was substantially altered, and herbaceous taxa, including ruderals, expanded. Based on the results from the phytolith and pollen analyses, two distinct phases of human activity have been recognized, namely (1) phase A (7000-6300 B.P., i.e. early Neolithic) a warm and humid period when arable farming, including rice cultivation, was pursued but the variation in the size of the carbonized rice grains was low, and (2) phase B (6300-5500 B.P., late Neolithic age), a period of relatively cold and/or arid climate when cultivated rice was of major importance and was morphologically similar to present-day rice. Environment, and in particular climate change in the late Neolithic, were important factors affecting the development of rice as a cultivated crop. It was mainly during this period that artificial selection favoured the emergence of forms similar to those of today.
    Type of Medium: Electronic Resource
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