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D. E. NELSON G. CHALOUPKA C. CHIPPINDALE M. S. ALDERSON J. R. SOUTHON 《Archaeometry》1995,37(1):151-156
Accelerator mass spectrometry radiocarbon ages have been taken for a test suite of small samples of material removed from some of the ‘beeswax’art figures found in rock shelters in northern Australia. The results indicate that we can reliably date this unique form of rock art with no noticeable damage. We had not expected to find figures of any great antiquity, and so we were surprised to find that the ages obtained spanned the time period from the recent past to about 4000 BP. 相似文献
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This paper describes the numerical simulation of the seismic behaviour of a mock-up of a six-floor building, constituted by two parallel R/C walls and experimentally tested on a shaking table. Within the scope of an international benchmark the mock-up was submitted to three earthquakes with intensities up to 0.71 g, which induced nonlinear behaviour in the concrete and reinforcement. For the numerical simulations concrete is discretised with 2D finite elements, and its behaviour reproduced via a constitutive model with two scalar damage variables. Steel rebars are discretised with 2-noded truss elements, and their constitutive behaviour under cyclic conditions reproduced by the Menegottb-Pinto model. Specific attention is devoted to Rayleigh damping, focusing on two different strategies: (i) disregarding the damping contribution, or (ii) adopting a damping matrix that takes into account the stiffness changes during the nonlinear analyses. Main results and strategies for simulating the benchmark axe presented, with emphasis on the comparison between the numerical and the experimental results, which show good agreement when the damping contribution is neglected. 相似文献
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We have developed a simple field kit for identifying C4 plants, the use of which requires little technical training. The system has proven very useful for surveying plants in areas for which carbon isotopic dating and dietary studies are to be undertaken. 相似文献
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Several geological sources of obsidian in the Pacific Northwest have been characterized by means of their trace element concentrations, as measured by X-ray fluorescence analysis. The technique is fast and completely non-destructive, making it well-suited for identifying the sources of obsidian from which artifacts were fabricated. 相似文献
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A stochastically based seismological model is described in this paper and used to generate synthetic accelerograms that are considered representative of intraplate earthquake events recorded on rock. The model, whilst well publicised in the seismological literature, is discussed and reviewed in this paper from an engineering perspective. The key factors influencing the frequency properties of the Fourier spectrum of the earthquake ground motion are presented and the differences observed between regions such as between eastern and western USA axe discussed. A procedure to generate representative artificial accelerograms from the Fourier spectrum is described. Average response spectra derived from these synthetic accelerograms are then compared with a selection of response spectra derived from recorded accelerograms to test and substantiate the model. The application of the seismological modelling approach to regions outside North America and the implications of the Displacement Based prinicples on the future development of seismological modelling have been addressed and discussed in the paper. 相似文献