Kinematics of large scale asymmetric folds and associated smaller scale brittle — Ductile structures in the proterozoic somnur formation, pranhita — Godavari Valley, South India     

Gautam Ghosh  Dilip Saha 《Journal of Earth System Science》2005,114(2):125-142

The development of structural elements and finite strain data are analysed to constrain kinematics of folds and faults at various scales within a Proterozoic fold-and-thrust belt in Pranhita-Godavari basin, south India. The first order structures in this belt are interpreted as large scale buckle folds above a subsurface decollement emphasizing the importance of detachment folding in thin skinned deformation of a sedimentary prism lying above a gneissic basement. That the folds have developed through fixed-hinge buckling is constrained by the nature of variation of mesoscopic fabric over large folds and finite strain data. Relatively low, irrotational flattening strain (X:Z-3.1-4.8, k<1) are associated with zones of near upright early mesoscopic folds and cleavage, whereas large flattening strain (X:Z-3.9-7.3, k<1) involving noncoaxiality are linked to domains of asymmetric, later inclined folds, faults and intense cleavage on the hanging wall of thrusts on the flanks of large folds. In the latter case, the bulk strain can be factorized to components of pure shear and simple shear with a maximum shearing strain of 3. The present work reiterates the importance of analysis of minor structures in conjunction with strain data to unravel the kinematic history of fold-and-thrust belts developed at shallow crustal level.  相似文献   

Effect of Mothers' Exposure to Electronic Mass Media on Knowledge and Use of Prenatal Care Services: A Comparative Analysis of Indian States*     

Debarchana Ghosh 《The Professional geographer》2006,58(3):278-293

The Government of India considers prenatal care programs as a priority activity for promoting safe motherhood and child survival. It relies heavily on electronic mass media, including radio, television, and cinema to educate mothers—two‐thirds of whom are illiterate—about prenatal check‐ups and timing, iron prophylaxis, and tetanus toxoid injections. This study evaluated the effect of mothers' exposure to electronic mass media on knowledge and use of prenatal care services, using data from India's 1998–1999 National Family Health Survey. Multivariate logistic regressions were used to estimate the effects of media exposure by calculating odds ratios of each of the four response variables (complete prenatal care services, prenatal check‐ups, tetanus toxoid injections, and iron prophylaxes) for exposure to mass media. The results indicated that exposure to mass media is related to the use of prenatal care services even when other likely causes of the relationships are statistically controlled at their mean. The effect also showed a north‐south divide among the Indian States, being stronger in northern states as compared with southern states.  相似文献   

Risk minimization in water quality control problems of a river system     

Subimal Ghosh  P.P. Mujumdar 《Advances in water resources》2006

Methodologies are presented for minimization of risk in a river water quality management problem. A risk minimization model is developed to minimize the risk of low water quality along a river in the face of conflict among various stake holders. The model consists of three parts: a water quality simulation model, a risk evaluation model with uncertainty analysis and an optimization model. Sensitivity analysis, First Order Reliability Analysis (FORA) and Monte–Carlo simulations are performed to evaluate the fuzzy risk of low water quality. Fuzzy multiobjective programming is used to formulate the multiobjective model. Probabilistic Global Search Laussane (PGSL), a global search algorithm developed recently, is used for solving the resulting non-linear optimization problem. The algorithm is based on the assumption that better sets of points are more likely to be found in the neighborhood of good sets of points, therefore intensifying the search in the regions that contain good solutions. Another model is developed for risk minimization, which deals with only the moments of the generated probability density functions of the water quality indicators. Suitable skewness values of water quality indicators, which lead to low fuzzy risk are identified. Results of the models are compared with the results of a deterministic fuzzy waste load allocation model (FWLAM), when methodologies are applied to the case study of Tunga–Bhadra river system in southern India, with a steady state BOD–DO model. The fractional removal levels resulting from the risk minimization model are slightly higher, but result in a significant reduction in risk of low water quality.  相似文献   

On the application of the classic Kessler and Berry schemes in Large Eddy Simulation models with a particular emphasis on cloud autoconversion, the onset time of precipitation and droplet evaporation     

S. Ghosh  P. R. Jonas 《Annales Geophysicae》1998,16(5):628-637

Many Large Eddy Simulation (LES) models use the classic Kessler parameterisation either as it is or in a modified form to model the process of cloud water autoconversion into precipitation. The Kessler scheme, being linear, is particularly useful and is computationally straightforward to implement. However, a major limitation with this scheme lies in its inability to predict different autoconversion rates for maritime and continental clouds. In contrast, the Berry formulation overcomes this difficulty, although it is cubic. Due to their different forms, it is difficult to match the two solutions to each other. In this paper we single out the processes of cloud conversion and accretion operating in a deep model cloud and neglect the advection terms for simplicity. This facilitates exact analytical integration and we are able to derive new expressions for the time of onset of precipitation using both the Kessler and Berry formulations. We then discuss the conditions when the two schemes are equivalent. Finally, we also critically examine the process of droplet evaporation within the framework of the classic Kessler scheme. We improve the existing parameterisation with an accurate estimation of the diffusional mass transport of water vapour. We then demonstrate the overall robustness of our calculations by comparing our results with the experimental observations of Beard and Pruppacher, and find excellent agreement.  相似文献   

Application of GIS for land-use/land-cover change analysis in a mountainous terrain     

S Ghosh  K K Sen  U Rana  K S Rao  K G Saxena 《Journal of the Indian Society of Remote Sensing》1996,24(3):193-202

Integration of remote sensing data with other spatial/non-spatial data was carried out using ARC/INFO software package. A simple classification technique was adopted for land cover/land-use change analyses in relation to elevation, slope, aspect and bio-climatic classes. Suitability assessment of land where agricultural extension occurred between 1963 and 1993 was made using GIS software package. Expansion of agriculture and was found to be maximum in 2200-2400 m elevation zone and 20–30° slope classes. When topographic aspects were considered expansion was maximum on south east and west facing slopes. The loss of vegetal cover is estimated to be 15 per cent between 1963–1993. However regeneration of forest was found to be maximum in elevation ranges of 1600–2000 metre and mostly having 20–30° average slope, Land deterioration over the two mapping periods was identified and strategies were suggested to mitigate the problem.  相似文献   

Use of a Lennard-Jones calculation for molecular diffusivity of pollutant gases in the PBL and its bearing on scavenging models     

S. Ghosh  M. P. Singh  U. C. Mohanty 《Boundary-Layer Meteorology》1986,34(3):311-316

Use of a Lennard-Jones calculation for estimation of molecular diffusivity of gases like SO₂ for use in scavenging models is recommended. A profile of molecular diffusivity of SO₂ in air through the PBL is obtained. Results indicate a change of about 17.5% between the diffusivity values at the surface and at the top of the PBL. The possible changes that could result in scavenging model calculations due to this change are also discussed.  相似文献   

Lateritisation of gabbro-granophyre rock units of the Ezhimala Complex of north Kerala, India     

Narayanaswamy  Swapan K. Ghosh 《Chemical Geology》1987,60(1-4):251-257

Laterites are ubiquitous in Kerala and are developed over different rock types. The laterite profiles developed over gabbro, granophyre of the Ezhimala Complex are discussed here.

The principal mineral assemblages of the laterites are kaolinite, gibbsite, goethite, hematite and quartz with minor amounts of zircon. Amorphous ferric hydroxide, Al-hydroxide and Al-silicate are also present. Samples from various units of the weathering profile have been analysed for major and trace elements. Major-element data show a steady depletion of Si and enrichment of sesquioxides and TiO₂ during weathering. It is also observed that the more the content of the mobile elements (Si, Mg, Ca, K, Na) in the parent rock, the greater is its depletion during lateritisation. The trace elements Co, Cr, V, Cu and Ni show an enrichment while Zn and Ba show depletion over both the rock types. Pb shows almost a consistent behaviour.  相似文献   

Electron delocalization and magnetic behavior in a single crystal of ilvaite,a mixed valence iron silicate     

D. Ghosh  T. Kundu  S. Dasgupta  Subralā Ghose 《Physics and Chemistry of Minerals》1987,14(2):151-155

Ilvaite, Ca(Fe²⁺, Fe³⁺)Fe²⁺Si₂O₈(OH), a black mixed valence iron silicate shows considerable Fe²⁺?Fe³⁺ electron delocalization above 400 K, reminiscent of magnetite. A crystallographic phase transition from orthorhombic (Pnam) to monoclinic (P2 ₁/a) symmetry takes place on cooling at 343 K induced by electron ordering. In both phases, Fe²⁺ and Fe³⁺ occur in double octahedral chains parallel to the c axis. The thermal characteristics of the magnetic susceptibilities and their anisotropies in different crystallographic planes have been measured in the temperature range 400?21 K. Below 343±1K, a continuous rotation of the molar susceptibility K _∥ in the ab plane down to 90±2 K is observed, where the symmetry of the magnetic ellipsoid remains unchanged. X _a, X _b and X _c increase abruptly below 123±0.5 K, although antiferromagnetic ordering of Fe²⁺ and Fe³⁺ spins on A sites was suggested in previous Mössbauer and neutron powder diffraction studies. In addition, 1/X _a shows an antiferromagnetic maximum at 50±3 K, whereas 1/X _b and 1/X _c at first increase sharply below 123 K, followed by antiferromagnetic curvatures in the lowest temperature region. This behavior is consistent with the antiferromagnetic ordering of Fe²⁺ spins in the B sites. The observed magnetic phenomena suggest charge delocatization effects between adjacent Fe²⁺(A)-Fe³⁺(A) pairs not only along c, but also along a and b directions. The negative sign of the molar anisotropy (K _∥-K_⊥) suggests a singlet ground State ⁵A₁ for the Fe²⁺ ions, in agreement with previous Mössbauer studies.  相似文献   

Study of drainage profiles in Jharia Coalfield,eastern India from aerial photographs: Implication for land use planning     

Rekha Ghosh 《Journal of the Indian Society of Remote Sensing》1989,17(1):55-62

Drainage analysis of an area through aerial photographs helps a lot in knowing its soil textrue, mainly its porosity, permeability, grainsize and compactness. These observations may be used as a guide for land use planning over the area. Studies have been conducted in Jharia Coalfield through scanning of acrial photographs to know the textural characters of soil/rock cover over the area. Nature of valley profiles have been studied in detail. The overall drainage pattern and drainage texture have also been studied. The observation have been used to infer about the textue of the materials (rock/soil) traversed by the drainage lines in the region. The observations suggest that the major part of the field is covered by materials of moderate cohesiveness with good porosity, permeability and recharge capacity. These informations have been used as critical inputs for future land use planning in the area.  相似文献   

Depositional Record of Tidal-Flat Sedimentation in the Permian Coal Measures of Central India: Barakar Formation, Mohpani Coalfield, Satpura Gondwana Basin   总被引：1，自引：0，他引：1  

Chandan Chakraborty  Sanjoy Kumar  Ghosh  Tapan Chakraborty 《Gondwana Research》2003,6(4):817-827

The Permian Barakar Formation in the Mohpani coalfield, Satpura Gondwana basin, is composed of three broad lithologies that occur repetitively and are iterdigitated: (1) several metres thick coarse- to medium-grained sandstone bodies with scoured bases, (2) 5-20 m thick medium- to fine-grained sandstone bodies and (3) 5-20 m thick mudstone-dominated packages with variable proportions of centimetre- to decimetre-scale, fine- to medium-grained sandstone, carbonaceous shale and coal. The Barakar strata were previously interpreted as deposits of braided rivers and associated inter-channel flood basin in a continental setting. However, this study recognizes signatures of tidal current from the mudstone-dominated packages implying marine influence during Barakar sedimentation.

The mudstone-dominated sediment bodies are the focus of this paper and comprise of three lithofacies that bear imprints of tidal processes during Barakar sedimentation: (1) heterolith, (2) sandstone, and (3) coal-carbonaceous shale, which alternate with one another within individual bodies. The heterolithic facies show interlayering of sandstone and claystone resembling flaser, wavy and lenticular bedding, as well as pinstripe stratification. Successive sandstone-mudstone couplets indicate periodic waxing and waning of flows. Within individual heterolithic packages, the sandstone:claystone ratio along with the bedding style, varies cyclically upwards giving rise to alternate sandstone-dominated and claystone-dominated intervals suggesting tidal velocity fluctuation reflective of spring-neap lunar cycle. Thickness plots of successive sand-mud couplets also reveal cyclic variation with a conspicuous periodicity of around 12 couplets per cycle, which corroborates the spring-neap-spring (or neap-spring-neap) lunar cycle. Presence of abundant desiccation cracks indicates periodic emergence and points towards an intertidal setting. The sandstone facies is characterized by a variety of wave-generated features such as bundled and chevron upbuilding of lamina, bi-directional foreset orientations, offshooting and draping laminae, scour-and-drape feature, swollen lens-like geometries suggesting their emplacement under storm-induced combined-flow on the tidal-flat. The coal-carbonaceous shale facies represent supratidal marsh environment.  相似文献