Dynamic response of cylindrical structures considering coupled soil-structure interaction under seismic loading

This paper attempts to develop a mathematical model for estimating the seismic response of a cylindrical shaped nuclear reactor building resting in an elastic halfspace considering foundation compliance. Most of the research carried out on this topic has either been carried out by resorting to finite element method (FEM) which makes the computational cost expensive or based on the simplifying assumption of assuming the cylindrical structure as a multi degree lumped mass stick model with soil coupled as boundary springs. In the present paper an analytical model has been developed in which the deformation of the cylindrical body (including its shear deformation characteristics) has been taken into cognizance and then coupling with foundation stiffness a comprehensive solution has been sought based on Galerkin’s weighted residual technique. The results are finally compared with FEM to check the reliability of the same. The results are found to be in good agreement with the detailed finite element analysis.     

Examining the Effect of Ancillary and Derived Geographical Data on Improvement of Per-Pixel Classification Accuracy of Different Landscapes

Effective conservation and management of natural resources requires up-to-date information of the land cover (LC) types and their dynamics. Multi-resolution remote sensing (RS) data coupled with additional ancillary topographical layers (both remotely acquired or derived from ground measurements) with appropriate classification strategies would be more effective in capturing LC dynamics and changes associated with the natural resources. Ancillary information would make the decision boundaries between the LC classes more widely separable, enabling classification with higher accuracy compared to conventional methods of RS data classification. In this work, we ascertain the possibility of improvement in classification accuracy of RS data with the addition of ancillary and derived geographical layers such as vegetation indices, temperature, digital elevation model, aspect, slope and texture, implemented in three different terrains of varying topography—urbanised landscape (Greater Bangalore), forested landscape (Western Ghats) and rugged terrain (Western Himalaya). The study showed that use of additional spatial ancillary and derived information significantly improved the classification accuracy compared to the classification of only original spectral bands. The analysis revealed that in a highly urbanised area with less vegetation cover and contrasting features, inclusion of elevation and texture increased the overall accuracy of IKONOS data classification to 88.72% (3.5% improvement), and inclusion of temperature, NDVI, EVI, elevation, slope, aspect, Panchromatic band along with texture measures, significantly increased the overall accuracy of Landsat ETM+ data classification to 83.15% (7.6% improvement). In a forested landscape with moderate elevation, temperature was useful in improving the overall accuracy by 6.7 to 88.26%, and in a rugged terrain with temperate climate, temperature, EVI, elevation, slope, aspect and Panchromatic band significantly improved the classification accuracy to 89.97% (10.84% improvement) compared to the classification of only original spectral bands, suggesting selection of appropriate ancillary data depending on the terrain.     

The relationship between volatile halocarbons and phytoplankton pigments during a Trichodesmium bloom in the coastal eastern Arabian Sea

Eukaryotic phytoplankton such as diatoms and prymnesiophytes produce biogenic halocarbons in the ocean that serve as important sources of chlorine and bromine to the atmosphere, but the role of cyanobacteria in halocarbon production is not well established. We studied distributions of chloroform (CHCl₃), carbon tetrachloride (CCl₄), methylene bromide (CH₂Br₂) and bromoform (CHBr₃) in relation to phytoplankton composition, determined from pigment analysis complemented by microscopic examination, for one month in coastal waters of the eastern Arabian that experienced a Trichodesmium bloom that typically occurs during the Spring Intermonsoon season. High concentrations of zeaxanthin (23 μg l⁻¹), alpha beta betacarotene (6 μg l⁻¹) and chlorophyll a (67 μg l⁻¹) were found within the bloom whereas the marker pigment concentrations were low outside the bloom. CHCl₃ and CCl₄ occurred in relatively high concentrations in surface waters whereas CH₂Br₂ and CHBr₃ were restricted to the subsurface layer. Chlorinated halocarbons were positively inter-correlated and with CHBr₃. The observed spatial and temporal trends in brominated compounds appear to be related to the abundance of Trichodesmium although correlations between concentrations of brominated compounds with various marker pigments were poor and statistically non-significant. The results support the existence of multiple sources and sinks of halogenated compounds, which might obscure the relationship between halocarbons and phytoplankton composition.     

现代酸性矿山废水环境中的真核微生物:生物多样性、生理学、生物地球化学特征及其对古环境和早期生命演化的指示

现代酸性矿山废水(AMD)环境被认为是地球早期环境的理想对应物。AMD的水环境具有金属含量高、pH低的特点,这与太古代-早元古代时期海洋的某些环境条件十分类似。然而,尽管AMD的环境条件恶劣,但仍然栖息着非常丰富的原核和真核微生物,在这其中那些嗜酸的、营光合作用的真核微生物类群(特别是Euglena mutabilis)更是引起众多科学家极大的研究兴趣。本文全面概述了在AMD环境中发现的真核微生物Euglenids种群的生物化学、生理学和生物地球化学特征,以及这些特征对于理解生命演化和早期地球环境条件等方面的指示性作用。Euglenids的细胞具备区域化功能,因而具备需氧和厌氧的蜡酯和甾醇的双生物合成途径,同时它们还可以形成生物膜,所有这些均使得Euglenids能够在早期地球极端恶劣的环境条件下生存并持续演化。在AMD酸性环境中发育的富铁叠层石、嗜酸微生物的脂类化合物及其碳同位素比值以及它们独特的生理和生化特征可用于阐述真核生物的演化、地球早期大气中氧气的产生、条带状富铁建造的形成以及地球早期的环境演化等。     

Intergalactic suprathermal grains

The physical conditions under which suprathermal grains may loose energy and the processes involving the grains (a3×10^–6 cm) destruction are investigated. It is found that the dust grain once attaining the velocityU (10⁵ cm s^–1) may attain suprathermal energy (v _g3×10⁸ cm s^–1) and subsequently may also attain relativistic energy are almost indestructible in the accelerating phase.     

A modified iterative sandwich method for determination of near-solidus partial melt compositions. II. Application to determination of near-solidus melt compositions of carbonated peridotite

We performed modified iterative sandwich experiments (MISE) to determine the composition of carbonatitic melt generated near the solidus of natural, fertile peridotite + CO₂ at 1,200–1,245°C and 6.6 GPa. Six iterations were performed with natural peridotite (MixKLB-1: Mg# = 89.7) and ∼10 wt% added carbonate to achieve the equilibrium carbonatite composition. Compositions of melts and coexisting minerals converged to a constant composition after the fourth iteration, with the silicate mineral compositions matching those expected at the solidus of carbonated peridotite at 6.6 GPa and 1,230°C, as determined from a sub-solidus experiment with MixKLB-1 peridotite. Partial melts expected from a carbonated lherzolite at a melt fraction of 0.01–0.05% at 6.6 GPa have the composition of sodic iron-bearing dolomitic carbonatite, with molar Ca/(Ca + Mg) of 0.413 ± 0.001, Ca# [100 × molar Ca/(Ca + Mg + Fe*)] of 37.1 ± 0.1, and Mg# of 83.7 ± 0.6. SiO₂, TiO₂ and Al₂O₃ concentrations are 4.1 ± 0.1, 1.0 ± 0.1, and 0.30 ± 0.02 wt%, whereas the Na₂O concentration is 4.0 ± 0.2 wt%. Comparison of our results with other iterative sandwich experiments at lower pressures indicate that near-solidus carbonatite derived from mantle lherzolite become less calcic with increasing pressure. Thus carbonatitic melt percolating through the deep mantle must dissolve cpx from surrounding peridotite and precipitate opx. Significant FeO* and Na₂O concentrations in near solidus carbonatitic partial melt likely account for the ∼150°C lower solidus temperature of natural carbonated peridotite compared to the solidus of synthetic peridotite in the system CMAS + CO₂. The experiments demonstrate that the MISE method can determine the composition of partial melts at very low melt fraction after a small number of iterations.     

Nonstoichiometry and growth of some Fe carbides

Iron carbides containing from 31 to 17 atomic % carbon, with cohenite XRD structure and optical properties, were grown in experiments in Fe–Ni–S–C, Fe–Ni–C, and in Fe–C at 1, 6, and 7 GPa. X-ray cell volumes increase with C content. Compositions listed above vary considerably outside the nominal (Fe,Ni)₃C stoichiometry of cohenite/cementite. Cohenites coexisting with Fe–C liquid are carbon poor. The Eckstrom-Adcock carbide, nominally Fe₇C₃, was found to show compositions from 29 to 36 atomic % C at 7 GPa in Fe–C. Both these materials are better regarded as solutions than as stoichiometric compounds, and their properties such as volume have compositional dependencies, as do the iron oxides, sulfides, silicides, and hydrides. The fraction of C dissolved in cohenite-saturated alloy is found to become smaller between 1 and 7 GPa. If this trend continues at higher pressures, the deep mantle should be easier to saturate with carbide than the shallow mantle, whether or not carbide is metastable as at ambient pressure. At temperatures below the cohenite-graphite peritectic, cohenite may grow as a compositionally zoned layer between Fe and graphite. The Eckstrom-Adcock carbide joins the assemblage at 7 GPa. Phases appear between Fe and C in an order consistent with metasomatic interface growth between chemically incompatible feed stocks. Diffusion across the carbide layer is not the growth rate limiting step. Carbon transport along the grain boundaries of solid Fe source stock at 1 GPa, to form C-saturated Fe alloy, is observed to be orders of magnitude faster than the cohenite layer growth. Growth stagnates too rapidly to be consistent with diffusion control. Furthermore, lateral variations in carbide layer thickness, convoluted inert marker horizons, and variable compositional profiles within the layers suggest that there are local transport complexities not covered by one-dimensional diffusive metasomatic growth. In contrast to many transport phenomena which slow with pressure, at 7 GPa and 1,162 °C, carbide growth without open grain boundaries is faster than at 1 GPa with fast grain boundary channels, again suggesting C transport is less of a constraint on growth than C supply. C supply at 7 GPa is enhanced by graphite metastability and the absence of fast grain boundary channels to divert C into the Fe instead of growing carbide. At both 1 and 7 GPa, the growth rate of carbide is found to systematically vary depending on which of two stock pieces of graphite are used to form the growth couple, suggesting that some property of each specific graphite, like C release rate, possibly from amorphous binder material, may influence the cohenite growth process. At temperatures near and above the cohenite-graphite peritectic at 1–1.5 GPa, complex intergrowths involving Fe–C liquids and extensive thermal migration transport were encountered, eroding the organized spatial resolution, and the range of cohenite compositions found grown below this peritectic from growth couples of crystalline Fe and graphite. The migration of graphite to a position in the metasomatic sequence between liquid and cohenite demonstrates that the solubility of graphite in liquid increases with temperature above the peritectic, whereas the solubility of graphite in cohenite below the peritectic decreases with temperature. The variable solubility of graphite in cohenite, shown by thermal migration, emphasizes that cohenite does have compositional variations.     

Determination of the fractal dimension of a shore platform profile

Morphological studies of shore platforms have focused on elements like width, gradient and elevation, while mostly ignoring the surface roughness as a morphometric attribute. This paper uses the Roughness-length method to show how the Fractal Dimension of a shore platform profile can be obtained. The higher the value of the fractal dimension, the higher is the roughness of the platform. The studied profile is situated in Houghton Bay on the south coast of Wellington, New Zealand. The fractal dimension of the profile under consideration was found to be 1.314. However, one profile is not sufficient to provide information about the surface roughness of a shore platform. Therefore, a number of profiles should be taken to have an idea about surface roughness.     

Class-based target identification with multiaspect scattering data

In underwater sensing applications, it is often difficult to train a classifier in advance for all targets that may be seen during testing, due to the large number of targets that may be encountered. We therefore partition the training data into target classes, with each class characteristic of multiple targets that share similar scattering physics. In some cases, one may have a priori insight into which targets should constitute a given class, while in other cases this segmentation must be done autonomously based on the scattering data. For the latter case, we constitute the classes using an information-theoretic mapping criterion. Having defined the target classes, the second phase of our identification procedure involves determining those features that enhance the similarity between the targets in a given class. This is achieved by using a genetic algorithm (GA)-based feature-selection algorithm with a Kullback-Leibler (KL) cost function. The classifier employed is appropriate for multiaspect scattering data and is based on a hidden Markov model (HMM). The performance of the class-based classification algorithm is examined using both measured and computed acoustic scattering data from submerged elastic targets.     

Petrology of a non-classical Barrovian inverted metamorphic sequence from the western Arunachal Himalaya, India

In this study, we reconstruct the inverted metamorphic sequence in the western Arunachal Himalaya using combined structural and metamorphic analyses of rocks of the Lesser and Greater Himalayan Sequences. Four thrust-bounded stratigraphic units, which from the lower to higher structural heights are (a) the Gondwana rocks and relatively weakly deformed metasediments of the Bomdila Group, (b) the tectonically interleaved sequence of Bomdila gneiss and Bomdila Group, (c) the Dirang Formation and (d) the Se La Group are exposed along the transect, Jira–Rupa–Bomdila–Dirang–Se La Pass. The Main Central thrust, which coincides with intense strain localization and the first appearance of kyanite-grade partial melt is placed at the base of the Se La Group.Five metamorphic zones from garnet through kyanite, kyanite migmatite, kyanite-sillimanite migmatite to K-feldspar-kyanite-sillimanite migmatites are sequentially developed in the metamorphosed low-alumina pelites of Dirang and Se La Group, with increasing structural heights. Three phases of deformation, D₁–D₂–D₃ and two groups of planar structures, S₁ and S₂ are recognized, and S₂ is the most pervasive one. Mineral growths in all these zones are dominantly late-to post-D₂, excepting in some garnet-zone rocks, where syn-D₁ garnet growths are documented. Metamorphic isograds, which are aligned parallel to S₂ were subsequently folded during D₃. The deformation produced plane-non-cylindrical fold along NW–SE axis.In the garnet-zone, peak metamorphism is marked by garnet growth through the reaction biotite + plagioclase → garnet + muscovite. An even earlier phase of syn-D₁ garnet growth occurred in the chlorite stability field with or without epidote. In the kyanite-zone metapelites, kyanite appeared via the pressure-sensitive reaction, garnet + muscovite → kyanite + biotite + quartz. Staurolite was produced in the same rock by retrograde replacement of kyanite following the reaction, garnet + kyanite + H₂O → staurolite + quartz. These reactions depart from the classical kyanite- and staurolite-isograd reactions in low-alumina pelites, encountered in other segments of eastern Himalaya. In the metapelites, just above the kyanite-zone, melting begins in the kyanite field, through water-saturated and water-undersaturated melting of paragonite component in white mica. Leucosomes formed through these reactions are characteristically free of K-feldspar, with sodic plagioclase and quartz as the dominant constituents. With increasing structural height, the melting shifts to water-undersaturated melting of muscovite component of white mica, producing an early K-feldspar + kyanite and later K-feldspar + sillimanite assemblages and granitic leucosomes.Applications of conventional geothermobarometry and average P–T method reveal near isobaric (at P  8 kbar) increase in peak metamorphic temperatures from 550 °C in the garnet-zone to >700 °C for K-feldspar-kyanite-sillimanite-zone rocks. The findings of near isobaric metamorphic field gradient and by the reconstruction of the reaction history, reveal that the described inverted metamorphic sequence in the western Arunachal Himalaya, deviates from the classical Barrovian-type metamorphism. The tectonic implication of such a metamorphic evolution is discussed.