Pre-monsoon and post-monsoon surface waterlogged areas were delineated using satellite remote sensing data for Muzaffarpur,
Vaishali and Saran districts of North Bihar. Digital data of IRS-1C LISS-III sensor acquired on December 7, 1998 and April
6, 1999 were analyzed using digital image processing software-ERDAS Imagine 8.3.1. The surface waterlogged areas were delineated
using modeling technique which is the most advanced and accurate method. Using the modeling technique, a pixel is classified
as water if the digital number (DN) value of its Near Infra Red (NIR) band is less than the DN value of the Red band and the
Green band, and the Normalized Difference Water Index (NDWI) is greater than or equal to 0.32. The pre-monsoon surface waterlogged
areas are found to be 14.02, 23.61 and 9.61 km2 while the post-monsoon surface waterlogged areas are found to be 231.83, 118.19 and 176.06 km2 for Muzaffarpur, Vaishali and Saran districts, respectively. Also, land use/land cover maps were prepared. 相似文献
Sulfur and O isotope analyses of dissolved SO4 were used to constrain a hydrogeological model for the area overlying the Gorleben–Rambow Salt Structure, Northern Germany. Samples were collected from 80 wells screened at different depth-intervals. The study area consists of a set of two vertically stacked aquifer systems. Generally, the isotope data show a good spatial correlation, outlining well-defined groundwater zones containing SO4 of characteristic isotopic composition. Highly saline waters from deeper parts of the lower aquifer system are characterized by rather constant SO4 isotopic compositions, which are typical of Permian Zechstein evaporites (δ34S=9.6–11.9‰; δ18O=9.5–12.1‰). Above this is a transition zone containing ground waters of intermediate salinity and slightly higher isotopic values (average δ34S=16.6‰; δ18O=15.3‰). The confined groundwater horizon on the top of the lower aquifer system below the low permeable Hamburg Clays is low in total dissolved solids and is characterized by an extreme 34S enrichment (average δ34S=39.1‰; δ18O=18.4‰), suggesting that bacterially mediated SO4 reduction is a dominant geochemical process in this zone. Two areas of distinct isotopic composition can be identified in the shallow ground water horizons of the upper hydrogeological system. Sulfate in groundwaters adjacent to the river Elbe and Löcknitz has a typical meteoric isotopic signature (δ34S=5.2‰; δ18O=8.2‰), whereas the central part of the area is characterized by more elevated isotopic ratios (δ34S=12.7‰; δ18O=15.6‰). The two major SO4 pools in the area are represented by Permian seawater SO4 and a SO4 of meteoric origin that has been mixed with SO4 resulting from the oxidation of pyrite. It is suggested that the S-isotope compositions observed reflect the nature of the SO4 source that have been modified to various extent by bacterial SO4 reduction. Groundwaters with transitional salinity have resulted from mixing between brines and low-mineralized waters affected by bacterial SO4 reduction. 相似文献
Triassic strata of the Dockum Group in Texas comprise two major upward-fining alluvial-lacustrine depositional sequences.
The two sequences are represented by the (1) Santa Rosa-Tecovas, and (2) Trujillo-Cooper Canyon Formations. The second sequence
is much thicker than the first, and occupies a greater geographic part of the Dockum basin. Each sequence of alluvial and
lacustrine sediment accumulation is characterized by sediment derivation from a different source terrain. The unconformable
relationship between the two depositional sequences, the change in mineralogical composition and presumed source areas between
these units, differences in paleocurrent orientation between units, and evidence for intervening episodes of local deformation
indicate that the sequences are of tectonic origin. These strata are not the product of a single sediment dispersal system,
such as the centripetally-drained lacustrine delta complex previously envisioned for the Dockum basin. Both Dockum sequences
are comprised largely of two typical alluvial facies associations; stream channel facies, and overbank flood-plain facies,
that are similar to those described in nearly all fluvial deposits. In addition, the Dockum Group contains a peculiar lacustrine
facies that accumulated in local flood-plain depressions, and probably resulted from subsidence over areas of subsurface salt
dissolution. Vertebrate fossil assemblages are found in all three Dockum facies associations. Five fossiliferous sites in
the Dockum are discussed in the context of these three depositional settings. The Dockum tetrapod diversity is reviewed in
a hierarchical phylogeny with remarks on the history of collection, stratigraphic distribution of genera, and their taxonomic
status. The stratigraphic ranges of tetrapod taxa do not support the recently proposed successive Otischalkian, Adamanian,
Revueltian, and Apachean biochrons within the Dockum Group. Instead, a few index fossils provide a broad framework for correlation
of Late Triassic nonmarine strata of the Dockum with the Carnian and Norian Alpine marine stages. 相似文献
Knudsen cell mass spectrometry has been applied to obtain activity (ai) vs composition (Xi) data for 18 synthetic roedderites. (K, Na)2Mg5Si12O30, at temperatures between 900° and 1100° C. The samples were synthesized at 800° C and 1 kbar PH2O and characterized by X-ray powder diffractometry (XRD) and electron probe microanalysis (EPMA) prior to mass spectrometric activity measurement. The experimental ai-Xi data have been smoothed, assuming for now the simplest possible model of a two-site K-Na mixing for this binary crystalline solution. Using the Margules formalism, and expressing the results in terms of one atom of K-Na mixing, the tentative equation of state is: WG [J/mol] =-8704 -0.0067 · P, with P given in bar. The temperature-dependence of WG could not be resolved due to its large uncertainty on the order of 2.8 kJ/mol. A more rigorous thermodynamic model for roedderites will have to be deferred until information on temperature-dependent K-Na disordering becomes available. Besides roedderites, single-phase eifelite-roedderite crystalline solutions have also been snythesized for the first time. They show a symmetric positive excess volume of mixing, with WV [J/bar·mol]=0.1064±0.0021. 相似文献
Geotectonics - The tectonic activity in the Himalayan region is reflected through major and minor lineaments associated with the major fault and thrust systems. In the present study, we used... 相似文献
A 22-member ensemble from CMIP6 is used to analyze the projected changes and seasonal behavior in surface air temperature over South America during the twenty-first century. In the future projections, CMIP6 models shown a high dependency to the socioeconomic pathway over each country of South America. The multimodel ensemble projects a continuous increase in the annual mean temperature over South America during the twenty-first century under the three future scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5). Besides, it was possible to identify consistent positive trends across all the models, with values between 0.45 ± 0.05 and 2.05 ± 0.31 °C cy−1 under the historical experiment, however largest trends occurs for the projection periods (near, mid and far future), with values between − 0.87 ± 0.84 to 2.88 ± 0.60 °C cy−1 (SSP1-2.6), 1.41 ± 0.88 to 5.32 ± 0.81 °C cy−1 (SSP2-4.5) and 4.75 ± 0.58 to 8.76 ± 0.74 °C cy−1 (SSP5-8.5) with maximum values at Bolivia, Brasil, Paraguay and Venezuela whilst minimum values for Argentina and Uruguay, regardless of the SSP scenario used. From the seasonal behavior analysis was possible to identify maximum values between January and March whilst minimum between June and July, except in Brasil, Venezuela and Guyana–Surinam–French Guayana, with annual range decreasing as the latidude decreases. By the end of the twenty-first century the annual mean temperature over South america is projected to increase between 0.92–2.11 °C, 0.97–3.37 °C and 1.27–6.14 °C under SSP1-2.6, SSP2-4.5 and SSP5-8.5 projection scenarios respectively. This projected increase of temperature across the continent will produce negative repercussions in the social, economic and political spheres. The results obtained in this study provide insights about the CMIP6 performance over this region, which can be used to develop adaptation strategies and might be useful for the adaptation to the climate change.
Interaction of nonplanar ion acoustic solitary waves is an important source of information to study the nature and characteristics of ion acoustic solitary waves (IASWs) structures. The head-on collision between two cylindrical/spherical IASWs in un-magnetized plasmas comprising with inertial ions, superthermal electrons and positrons is investigated by using the extended version of Poincaré-Lighthill-Kuo (PLK) perturbation method. It has been shown numerically that how the interactions are taking place in cylindrical and spherical geometry. The nonplanar geometry modified analytical phase shifts following the head-on collision are derived. The effects of the superthermal electrons and positrons on the phase shift are studied. It is shown that the properties of the interaction IASWs in different geometry are very different. 相似文献
The nonlinearity of the soil affects soil–structure interaction to a considerable extent. For a reliable and safe analysis of soil interaction effects on the dynamic response of structures, a more realistic and relatively straightforward method incorporating the nonlinear hysteretic nature of the underlying soil–foundation system needs to be developed. The present paper models the soil–foundation system as a single degree of freedom spring–dashpot system with nonlinear hysteresis in form of elasto-perfectly plastic behavior. Analytical results for the lateral dynamic stiffness on footing have been presented. An example study has been carried out in case of circular footings. It is shown how the analytical results can be used to get a preliminary idea of the lateral dynamic stiffness of footings on a soil medium prior to a detailed computational geo-mechanics analysis provided the static nonlinear load–deformation characteristic of the soil medium is known and can be modeled by a hysteretic elasto-plastic behavior. The corresponding results are presented in a graphical form. The results have been computed showing parametric variations with the change in the amplitude and dimensionless frequency of the non-dimensional excitation force. Analytical results are also presented for the asymptotic cases at low and very high values of dimensionless frequency parameter. 相似文献