Statistical Classification of Different Petrographic Varieties of Aggregates by Means of Near and Mid Infrared Spectra   总被引：1，自引：0，他引：1  

Vera Hofer  Juergen Pilz  Thorgeir S. Helgason 《Mathematical Geology》2006,38(7):851-870

The increasing interest of the construction aggregates industry in reducing production costs and the costs resulting from improper use of construction materials leads to the question whether it is possible to statistically identify some rock variants by their reflectivity of near-infrared and mid-infrared light. Infrared spectroscopy allows quantitative and qualitative analysis of minerals in a reliable manner, whereas the classification of rocks is complicated by the fact that the optic behavior of minerals forming the rock often appears muted. In addition, minor constituents may dominate the spectrum. Furthermore the relevant spectra form high dimensional data, which are extremely difficult to analyse statistically, especially when curves are very similar. Common methods of multivariate statistics for this type of data, used in chemometric studies, followed by linear discriminant analysis, do not lead to acceptable classification error rates. In this paper wavelets are used in order to reduce dimensionality. As wavelets are better able to mirror local behavior of curves, they are more suitable for selecting characteristic features. The approximation is analyzed in terms of its classification properties using Mahalanobis distance or flexible discriminant analysis.  相似文献   

R. W. Battarbee, F. Gasse and C. E. Stickley (eds), Past Climate Variability through Europe and Africa, volume 6     

Vera Markgraf 《Journal of Paleolimnology》2006,36(3):319-321

  相似文献   

Stability of Titanium Dioxide Nanoparticle Agglomerates in Transitional Waters and Their Effects Towards Plankton from Lagoon of Venice (Italy)     

Clémentine Perstrimaux  Séverine Le Faucheur  Monika Mortimer  Serge Stoll  Fabrizio Bernardi Aubry  Margherita Botter  Roberto Zonta  Vera I. Slaveykova 《Aquatic Geochemistry》2015,21(2-4):343-362

The present study explores the effect of salinity and dissolved organic carbon (DOC) gradients on the stability and reactivity of titanium dioxide nanoparticle (TiO₂-NP) agglomerates in ambient water from the Lagoon of Venice and their possible effect on nauplii sampled at the same locations. In all ambient water samples, TiO₂-NPs formed rapidly micrometre-sized agglomerates. The increase in the salinity and concomitant decrease in DOC content induced the formation of larger agglomerates, with z-average hydrodynamic diameter increasing with TiO₂-NP concentration and exposure duration. Under the studied conditions, ζ-potential exhibited negative values. In line with agglomeration results, enhancement of the salinity and lower DOC resulted in less negative ζ-potential with close to 0 values in the dispersions of 100 mg L^?1 TiO₂-NPs in sea water. Two-hour exposure to micrometre-sized agglomerates of TiO₂-NPs resulted in an increase in the fluorescence of propidium iodide (PI) stained nauplii in comparison with unexposed controls, but had no effect at 24-h exposure. The increase in nauplii-associated PI fluorescence was more noticeable in dispersions containing 100 mg L^?1 than those containing 10 mg L^?1 TiO₂-NPs, suggesting membrane permeability alteration in a concentration-dependent manner. However, the PI staining results have to be interpreted with caution because of the possible dye binding to the nauplii surface without penetration of cellular membrane. The effect of TiO₂-NPs on nauplii was more pronounced at higher salinity and decreased with increasing DOC concentrations at 2 h, while no trends were found at 24-h exposure, as well as exposure to 100 mg L^?1 TiO₂-NPs.  相似文献   

Modification of the Natural Slake Test and Assessment of Slaking Behavior of a Shale from Malaysia Under Rainfall     

Lai  Teck Yew  Loo  Vera Hui  Wong  Vun Ket  Wong  Kwong Soon 《Geotechnical and Geological Engineering》2022,40(6):3169-3190

Geotechnical and Geological Engineering - The durability of clay-bearing rocks has been a concern to the construction industry. Extensive research have been conducted to determine the durability of...  相似文献   

Seafloor change detection using multibeam echosounder backscatter: case study on the Belgian part of the North Sea   总被引：1，自引：0，他引：1  

Giacomo Montereale-Gavazzi  Marc Roche  Xavier Lurton  Koen Degrendele  Nathan Terseleer  Vera Van Lancker 《Marine Geophysical Researches》2018,39(1-2):229-247

To characterize seafloor substrate type, seabed mapping and particularly multibeam echosounding are increasingly used. Yet, the utilisation of repetitive MBES-borne backscatter surveys to monitor the environmental status of the seafloor remains limited. Often methodological frameworks are missing, and should comprise of a suite of change detection procedures, similarly to those developed in the terrestrial sciences. In this study, pre-, ensemble and post-classification approaches were tested on an eight km² study site within a Habitat Directive Area in the Belgian part of the North Sea. In this area, gravel beds with epifaunal assemblages were observed. Flourishing of the fauna is constrained by overtopping with sand or increased turbidity levels, which could result from anthropogenic activities. Monitoring of the gravel to sand ratio was hence put forward as an indicator of good environmental status. Seven acoustic surveys were undertaken from 2004 to 2015. The methods allowed quantifying temporal trends and patterns of change of the main substrate classes identified in the study area; namely fine to medium homogenous sand, medium sand with bioclastic detritus and medium to coarse sand with gravel. Results indicated that by considering the entire study area and the entire time series, the gravel to sand ratio fluctuated, but was overall stable. Nonetheless, when only the biodiversity hotspots were considered, net losses and a gradual trend, indicative of potential smothering, was captured by ensemble and post-classification approaches respectively. Additionally, a two-dimensional morphological analysis, based on the bathymetric data, suggested a loss of profile complexity from 2004 to 2015. Causal relationships with natural and anthropogenic stressors are yet to be established. The methodologies presented and discussed are repeatable and can be applied to broad-scale geographical extents given that broad-scale time series datasets become available.  相似文献   

Empirical prediction of the ground shaking scenario for the Catania area     

Vera Pessina 《Journal of Seismology》1999,3(3):265-277

Simplified approaches for prediction of strong ground shaking, that can be efficiently implemented through a Geographical Information System (GIS), are applied to constructing earthquake scenarios for the Catania municipal area. Ground shaking maps in terms of peak ground acceleration and response spectral ordinates are developed both for a repetition of the catastrophic 1693 earthquake (M7.3), and for a lower energy event, like that which occurred in 1818 (M6.2). The maps account for amplification due to local site conditions. According to the commonly used attenuation relations, the local amplification is taken into account either in a simpler way or in a more detailed approach, derived from an extensive geotechnical zonation. The approximation introduced by the simpler methodology, to be used whenever accurate data are not available, is estimated by a comparison with damage distribution.  相似文献   

Tephrochronological dating of paleoearthquakes in active volcanic arcs: A case of the Eastern Volcanic Front on the Kamchatka Peninsula (northwest Pacific)     

Egor Zelenin  Andrey Kozhurin  Vera Ponomareva  Maxim Portnyagin 《第四纪科学杂志》2020,35(1-2):349-361

Investigation of active faults is crucial for the seismic hazard assessment and, in the case of volcanic belts, it provides a deeper understanding of the interactions between volcanism and tectonic faulting. In this study, we report the results of the first paleoseismological and tephrochronological investigation undertaken on Holocene faulting in Kamchatka's volcanic belts. The studied trenches and additional excavations are located along the axial fault zone of the Eastern Volcanic Front, where the earlier dated tephra layers provide a robust age control of the faulting events. Electron microprobe analysis of glass from 22 tephra samples permitted correlations among the disparate tephra profiles for constructing a summary tephra sequence. The latter, together with published geochronological data, allowed the construction of a Bayesian age model. Detailed examination of the tephra layers deformed by faulting allowed us to reconstruct and date six faulting events with the offsets of 1 to 20 cm indicating paleoearthquakes with magnitudes of M_w < 5.4. Holocene crustal seismicity of the Eastern Volcanic Front manifests temporal clustering rather than a uniform flux of events. However, no correlation between dated seismic events and the largest Holocene eruptions of proximal volcanoes was observed.  相似文献   

Identification of Icelandic tephras from the last two millennia in the White Sea region (Vodoprovodnoe peat bog,northwestern Russia)     

Polina Vakhrameeva  Maxim Portnyagin  Vera Ponomareva  Peter M. Abbott  Tatiana Repkina  Anna Novikova  Andreas Koutsodendris  Jörg Pross 《第四纪科学杂志》2020,35(4):493-504

The generation of reliable age models for palaeoenvironmental and archaeological records in the Eurasian Arctic is often problematic when using conventional dating techniques. Tephrochronology can potentially improve the chronologies of such records and synchronise disparate sedimentary archives. However, to date, systematic tephra studies are lacking for this region. This paper presents the first cryptotephra data from the White Sea region (northwestern Russia) based on a peat core spanning the past ~1800 years. We identify seven geochemical glass populations that derive from six Icelandic volcanoes and correlate four of them to north European tephra isochrons; these include Askja ad 1875, the basaltic component of the ad 877 Landnám tephra, and tephras BTD-15 (c. ad 1750–1650) and SL-2/SB-2 (ad 803–767) from unknown eruptions of Katla and Snæfellsjökull, respectively. The remaining three populations originate from Grímsvötn, Hekla and Katla; however, their attribution to individual eruptions remains ambiguous. These findings highlight the potential to extend the Late Holocene tephrochronological framework of northern Europe to the west Eurasian Arctic. The detection of at least three basaltic tephras in the core suggests that basaltic shards can be transported over larger distances than previously known and that peatlands are well suited to preserve such components.  相似文献   

Changes in ostracod assemblages and morphologies during lake‐level variations of Lago Cardiel (49°S), Patagonia,Argentina, over the last 15.6 ka     

Lorena Ramos  Marta Alperin  Antje Schwalb  Vera Markgraf  Daniel Ariztegui  Gabriela Cusminsky 《Boreas: An International Journal of Quaternary Research》2019,48(3):746-760

Changes in the ostracod assemblages from two sediment cores collected from Lago Cardiel in southeastern Patagonia (49°S) reflect the main regional abrupt climatic changes over the last 15.6 cal. ka BP. Shifts in species abundance and switches in dominances suggest that these were mainly driven by variable salinity. During the Late Pleistocene, Limnocythere rionegroensis was abundant and dominant, indicating waters with high salinity and prevalence of evaporative processes. Between 12.6 and 10.8 cal. ka BP, Lago Cardiel expanded markedly and reached an Early Holocene highstand of +55 m above present lake level. A major change in ostracod assemblage in which Limnocythere patagonica appears as the dominant species in parallel with the disappearance of L. rionegroensis and Eucypris aff. cecryphalium mirrored this transitional period between the cold and dry Late Pleistocene and the humid and warm Early Holocene. Over the last 4 cal. ka BP, L. rionegroensis returned to the species assemblage and Riocypris whatleyi increased its abundance pointing towards increasing salinities. The variations in size, shape and ornamentation of L. rionegroensis and R. whatleyi fossil valves were examined using geometric morphometric techniques and further compared to those of modern Patagonian sites. Limnocythere rionegroensis specimens displayed high morphological variability during the evolution of Lago Cardiel. More specifically, the switch in reproductive mode – from sexual to parthenogenetic– and the increase in valve ornamentation around 12.7 cal. ka BP suggest that these changes were promoted by the hydrological alteration that occurred in the Late Pleistocene. This exercise provides a robust range of morphological variation for these proxies, which will be useful in further taxonomic and palaeoenvironmental studies adding more information about different factors influencing the observed morphological trends.  相似文献   

BaMn[CO3]2 – a previously unrecognized double carbonate in low-temperature environments: Structural,spectroscopic, and textural tools for future identification     

Michael E. Böttcher  Herta S. Effenberger  Peer-Lennart Gehlken  Georg H. Grathoff  Burkhard C. Schmidt  Patrizia Geprägs  Rainer Bahlo  Olaf Dellwig  Thomas Leipe  Vera Winde  André Deutschmann  Alexander Stark  David Gallego-Torres  Francisca Martinez-Ruiz 《Chemie der Erde / Geochemistry》2012,72(1):85-89

Following a tentative evidence for the occurrence of low-temperature barium manganese(II) carbonates in brackish sediments of the Baltic Sea, a stoichiometric double carbonate, BaMn[CO₃]₂, was synthesized from aqueous solutions at ambient temperature for the first time. Here we report the results of a multi-method approach, including scanning electron microscopy (SEM–EDX) investigations, the chemical composition, and, in particular, the diagnostic powder X-ray diffraction pattern, as well as diagnostic parts of the FT infrared absorption and Raman spectra for future identification of this new carbonate in low-temperature environments, like brackish sediments.  相似文献