排序方式： 共有11条查询结果，搜索用时 0 毫秒
1.
We present a new event-driven approach that combines a shallow water flow model with a practical sedimentation technique to simulate the formation of turbidite depositional systems at a stratigraphic scale. The equations that govern turbidity currents dynamics are solved using a new finite element flux-corrected transport scheme. In this sense, the low-order formulation is built by adding a novel Rusanov-like scalar dissipation scaled by a shock-capturing operator to standard Galerkin equations. From it, the high-order system is obtained by including antidiffusive fluxes linearized around the low-order solution and limited with the Zalesak's algorithm, following a minmod prelimiter. Implicit time integration with adaptive time steps is performed with an iterative nonlinear scheme that linearizes source terms. Sedimentation is implemented by carrying five granulometric fractions (clay, silt, and fine, medium, and coarse sands) along evolved streaklines and radially scattering sediments that deposit filling the available depositional space and compacting the underneath sediment layers. The flow is computed while an event discharge into an area of interest is active, or the inflow current has not reached an equilibrium state. Afterward, the event deposition step is executed. Numerical results of our flow solver presented a good agreement with available exact and literature solutions, and the simulated sediment deposits suggest that our approach is well suited for stratigraphic scale simulations. 相似文献
2.
Paz Arjonilla Ana Domínguez-Vidal Ramn Rubio Domene Elena Correa Gmez María Jos de la Torre-Lpez María Jos Ayora-Caada 《Molecules (Basel, Switzerland)》2022,27(5)
Non-invasive techniques (X-ray fluorescence, XRF, and Raman spectroscopy) were used for the study of the Hispano Muslim wall paintings. Principal component analysis (PCA) was performed on the semi-quantitative XRF results directly provided by the in-built factory calibrations with minimum user manipulation. The results obtained were satisfactory and highlighted differences and similarities among the measurement points. In this way, it was possible to differentiate the decorations carried out on gypsum plasterwork and the wall paintings over lime plaster. The color palette, revealed by combining the results from XRF and Raman spectroscopies, comprised the pigments hematite, lapis lazuli, cinnabar (in poor conservation state), and possibly, carbon. Evidence of past interventions was also provided by PCA on XRF data, which detected the presence of Pb, Ba, and Zn in some areas. Furthermore, the preparation layers have been studied in detail on cross-sections of two microsamples. Several layers of lime plaster with a compact microstructure have been observed. The characteristic of the pictorial layer and the identification of calcium oxalate point to the use of a secco-technique. The main alteration identified was a gypsum surface layer covering the painting and signs of plaster deterioration due to gypsum migration to more internal areas. Finally, the comparison with the observations made by restorers in previous interventions on these paintings revealed the importance of the representativeness gained with the in situ study, which enabled the analysis of a high number of areas. 相似文献
3.
The character of the definition of the Permian-Triassic boundary is discussed in detail. Based on the research on conodonts and other fossils, graphic correlation is used to determine the relationship between the Shangsi, Maoertang, Chaotian, Huaying, Hechuan, Liangfenya, Xixiang, Selong and Changxing sections, in which the Changxing section is selected as a Standard Reference Section. The reason of rational definition (the base of Ophiceras bed) is expounded. 相似文献
4.
Paytan A Gray ET Ma Z Erhardt A Faul K 《Isotopes in environmental and health studies》2012,48(1):195-206
The sulphur isotopic composition of dissolved sulphate in seawater has varied considerably through time. Certain time intervals are characterised by distinct variations and a relatively high rate of change. These relatively rapid fluctuations allow for correlation of sediment sections using sulphur isotopes. Sulphur isotope reconstructions based on the analysis of carbonate associated sulphate or marine barite result in sulphur isotope records with an age resolution of 1–5 million years (Ma), and for some age intervals the resolution is<0.25 Ma. At these specific time intervals, where higher resolution records exist and excursions in the record are identified, the trends could be used for stratigraphic correlations. Such records are particularly useful in sections from deep marine sites that lack biostratigraphic controls or where biozones do not provide sufficient resolution. 相似文献
5.
CHEMICAL SPECIES OF IRIDIUM AND OTHER TRACE ELEMENTS AT K-T BOUNDARY CLAY LAYER, STEVNS KLINT, DENMARK, AND ITS IMPLICATION 总被引：2，自引：0，他引：2
The chemical species of anomalous Ir in the Fish Clay K-T boundary at Stevns Klint, Denmark, was studied by using a newly-developed chemical stepwise dissolution procedure and neutron activation analysis. The experimental results indicate that the anomalous Ir mostly exists in the acid-insoluble residue phase. The Ir pattern of the K-T boundary resembles that of the Ningqiang carbonaceous chondrite, while remarkably different from those of the ultrabasic rock and volcanic lava. Thus, we deduce that the Ir anomaly at K-T boundary is mainly extraterrestrial, instead of volcanogenic or geochemical enrichment origin. The patterns of other trace elements in various phases also confirm the above conclusion. 相似文献
6.
一种适用于高分辨分子地层学研究的有机质分离及定量方法 总被引：2，自引：0，他引：2
研究全球变化的手段多种多样,高分辨分子地层学是最有力的工具之一,进行此项研究工作要分析的样品大且溶量小,因此建立一种合适的有机质分离及定量方法十分重要。本文采用冷抽提法的方法抽提出这类样品的有机质,衍生化合利用ＧＣ／ＭＳ对化合物进行定性、定量分析。利用本方法分析的空白加标（地质体中最常见化合物）回收率结果为：烷烃９５．８％,脂肪酸９２．３％,胆甾醇９９．７％;脂肪醇９３．７％;基质加标加收率结果为 相似文献
7.
Leonardo Brizi Villiam Bortolotti Giulia Marmotti Mara Camaiti 《Magnetic resonance in chemistry : MRC》2020,58(9):889-901
Paintings on canvas are complex structures created by superimposing layers of different composition. Investigations on the structure of these artworks can provide essential information on their state of conservation, pictorial technique, possible overpaintings, and in planning a proper conservation plan. Standard methods of investigation consist in sampling a limited number of fragments for stratigraphic analyses. Despite the recognized validity of these methods, they are affected by evident limitations. Nuclear magnetic resonance (NMR) profiling, often named NMR stratigraphy, is an NMR relaxometry technique applied by single-sided portable devices developed to overcome the disadvantages of microinvasive stratigraphic analyses. The potential of this approach on artworks, including wall paintings and a few examples of painted canvas, is described in the literature. In this study, NMR profiles of painting on canvas were examined by analyzing transverse relaxation time data by T2 quasi-continuous distributions and the results compared with standard stratigraphic cross-sections analysis. Combining signal intensity and T2 quasi-continuous distributions, the identification of textile, preparatory, and paint layers was enhanced. The diction “NMR stratigraphy” for these inhomogeneous layered artworks is also discussed. Indeed, unlike the stratigraphic cross-sections, NMR profiles provide information on a volume (flat slice), rather than on a surface, and the collected signal can derive from nonuniform and partially overlapping layers. This study paves the way for extensive investigations on relaxation time quasi-continuous distributions in various binder/pigment mixtures in order to improve the reliability of NMR profile as an innovative, non–invasive, and nondestructive method for analyzing paintings on canvas. 相似文献
8.
9.
Alessandra Botteon Chiara Colombo Marco Realini Chiara Castiglioni Anna Piccirillo Pavel Matousek Claudia Conti 《Journal of Raman spectroscopy : JRS》2020,51(10):2016-2021
Nowadays, the research in conservation science is focused on developing advanced portable analytical techniques able to achieve subsurface data in situ and in a non-invasive way. Micro-spatially offset Raman spectroscopy (micro-SORS) is an emerging analytical technique developed to address the need of non-invasively retrieving the molecular composition of the subsurface compounds; however, so far, micro-SORS studies of artworks have been carried out only with benchtop Raman microscopes, precluding the non-invasive analysis of large objects and artworks in situ. Here, for the first time, portable micro-SORS was used for non-invasive and in situ investigation of art objects. The potential of portable micro-SORS is demonstrated through the reconstruction of the layer sequences in selected areas of two 16th century panel paintings, providing unequivocal information about the preparation layer spread over the panels and the pigments used in the painted layers and supplying essential information on the artist's technique. 相似文献
10.
Depositing ages of sediment in core CK6 of Qarhan Salt Lake were determined by usingmethods of ~(14)C, ~(230)Th and paleo-terrestrial-magnetism. Based on synthetic analyses for thevariation of the content of organic carbon, sporo-pollen composition and lithofacies, the fluc-tuating model of paleo-climate since 750 ka B.P. was set up. It is divided into 21 fluctua-ting epochs of climate, among them, 11 are warm and humid epochs, and 10 are dry andcold epochs. 相似文献