Book Review
“Sand: The Never-Ending Story”, by Michael Welland, University of California Press, 2009; ISBN: 978-0-520-26597-4, USD 17.95     

Sujit S. Datta 《Pure and Applied Geophysics》2011,168(10):1883-1884

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Study of the motions of fishing vessels by a time domain panel method     

R. Datta  J.M. Rodrigues  C. Guedes Soares 《Ocean Engineering》2011,38(5-6):782-792

In this paper, a wide variety of computed motion results is presented for three existing fishing vessels. In order to do that, time domain computations of 3D ship motions are performed with a time domain Green's function. The computational method adopted is based on a previously developed one, whose numerical scheme here is subjected to modifications that increase its robustness and overall efficiency, so that it can be applied to calculate the motions of fishing vessels. The results are then compared with simulations using WAMIT for the zero speed case, and a strip theory method is used to determine the effect of forward speed. Results are presented for head seas, quartering head waves and following waves with three distinct Froude numbers.  相似文献   

Geochemical modelling, ionic ratio and GIS based mapping of groundwater salinity and assessment of governing processes in Northern Gujarat, India   总被引：1，自引：0，他引：1  

Kumari Rina  Chander Kumar Singh  P. S. Datta  Neha Singh  S. Mukherjee 《Environmental Earth Sciences》2013,69(7):2377-2391

In semi-arid/arid regions, groundwater is the major source of irrigation, drinking and industrial requirements, water salinity and shortage are major problems of concern. North Gujarat, India, is one such area where highly saline groundwater is generally ascribed to rapid increase of population, agriculture and industries induced decline in water table by unplanned abstraction of groundwater. However, no effort has been made to discriminate the natural and anthropogenic influences on groundwater salinity. In this brief background, the present study attempts to identify the factors and processes controlling the groundwater salinity in the area, based on ionic ratios in integration with various graphical methods, saturation indices and geographical information system. Na⁺/Ca²⁺ > 1 indicates the deficiency of Ca²⁺ possibly due to CaCO₃ precipitation or ion exchange process. Na⁺/Cl^? > 1 and $ {\text{SO}}_{4}{}^{2 - } /{\text{Cl}}^{ - } \gg 0.05 $ suggest salinization is mainly due to wastewater infiltration and/or due to irrigation water return flow. Sea water intrusion in coastal parts, vertical and lateral mixing of water and anthropogenic inputs are also responsible for salinization of groundwater. USSL diagram, Na%, sodium adsorption ratio, residual sodium carbonate and magnesium hazard indicate unsuitability of groundwater for irrigation purposes. To prevent groundwater salinization, appropriate measures need to be taken to control further indiscriminate exploitation of groundwater for irrigation.  相似文献   

Reionization and the Cosmic Dawn with the Square Kilometre Array     

Garrelt Mellema  Léon V. E. Koopmans  Filipe A. Abdalla  Gianni Bernardi  Benedetta Ciardi  Soobash Daiboo  A. G. de Bruyn  Kanan K. Datta  Heino Falcke  Andrea Ferrara  Ilian T. Iliev  Fabio Iocco  Vibor Jelić  Hannes Jensen  Ronniy Joseph  Panos Labroupoulos  Avery Meiksin  Andrei Mesinger  André R. Offringa  V. N. Pandey  Jonathan R. Pritchard  Mario G. Santos  Dominik J. Schwarz  Benoit Semelin  Harish Vedantham  Sarod Yatawatta  Saleem Zaroubi 《Experimental Astronomy》2013,36(1-2):235-318

The Square Kilometre Array (SKA) will have a low frequency component (SKA-low) which has as one of its main science goals the study of the redshifted 21 cm line from the earliest phases of star and galaxy formation in the Universe. This 21 cm signal provides a new and unique window both on the time of the formation of the first stars and accreting black holes and the subsequent period of substantial ionization of the intergalactic medium. The signal will teach us fundamental new things about the earliest phases of structure formation, cosmology and even has the potential to lead to the discovery of new physical phenomena. Here we present a white paper with an overview of the science questions that SKA-low can address, how we plan to tackle these questions and what this implies for the basic design of the telescope.  相似文献   

Neutral fermions as the missing mass matter in galactic halos     

B. Datta  C. Sivaram  S. K. Ghosh 《Astrophysics and Space Science》1985,111(2):413-417

We point out that several independent considerations rule out the hypothesis that the missing mass in galactic halos is dominated by massive neutral fermions such as neutrinos, gravitinos or photinos.  相似文献   

A numerical survey of neutron star crustal density profiles     

B. Datta  A. V. Thampan  D. Bhattacharya 《Journal of Astrophysics and Astronomy》1995,16(3-4):375-391

An accurate numerical survey of the density profiles corresponding to the crusts of neutron stars for representative equation of state models is presented. This will find application in calculations of thermal and magnetic evolution of neutron stars.  相似文献   

A comprehensive study on the surface chemistry of particulate matter collected from Jeddah,Saudi Arabia     

Asim Jilani  Syed Zajif Hussain  Mohd Hafiz Dzarfan Othman  Usama Zulfiqar  Muhammad Bilal Shakoor  Imran Ullah Khan  Javed Iqbal  Attieh A. Al-Ghamdi  Ahmed Alshahrie 《Journal of Atmospheric Chemistry》2018,75(3):271-283

In this work, the X-ray Photoelectron Spectroscopy (XPS) technique is utilized to analyze the surface chemical composition of particulate matter (PM) which was collected from various locations at Jeddah, Saudi Arabia. The main elements found on the surface of PM are carbon (C), oxygen (O) and silicon (Si) with combined percentage of 89.4–94.9 while traces of nitrogen (N), calcium (Ca), aluminum (Al), sodium (Na), chlorine (Cl), manganese (Mg), and sulfur (S) were also present. The analyzed XPS chemical state of C, O and Si was further used to determine their bonding with other elements occurring over the surface of PM. Carbon was found in the form of carbides (18.86%), fluorides (2.39%) and carbonates (78.75%); oxygen was observed as oxides (21.05%) and hydroxides (73.42%) of other metals; and silicon was detected as silicones (12.16%), nitrides (82.53%) and silicates (5.25%). The particle size of a PM is also of great concern for health issues, and thus has been investigated by the Field Emission Scanning Electron Microscope (FESEM). The Energy Dispersive X-ray Spectroscopy (EDS) was employed for cross verification of detected elements by XPS.  相似文献   

Numerical simulation of groundwater flow in the Peshawar intermontane basin, northwest Himalayas     

Asim Yousafzai  Yoram Eckstein  Peter Dahl 《Hydrogeology Journal》2008,16(7):1395-1409

The hypothesis that abnormal fluid pressure is generated in basins under tectonic compression is tested. The study site, between the Main Karakoram Thrust (MKT), Main Mantle Thrust (MMT), Main Central Thrust (MCT), Main Boundary Thrust (MBT) and Salt Range Thrust (SRT) in northwest Pakistan, is experiencing a tectonic compression of 90 MPa. The Peshawar basin is a broad, oval depression comprising a thick sequence of lacustrine, deltaic and fluvial sediments overlain by loess and alluvial deposits dated at 2.8–0.6 Ma. It is surrounded by the Precambrian and Tertiary intrusive and metamorphic rocks on the north and sedimentary rocks of Paleogene and Neogene to the south. The basin was divided into four hydrostratigraphic units for numerical simulations using the three-dimensional finite-element model FEMWATER within groundwater modeling system (GMS) ver. 5.1. Simulated pressure head data have been compared with the field measurements of hydraulic heads. Transient simulations indicate that topography alone is not sufficient to induce the pressure heads observed in the field, generating consistently positive residuals 0.98–2.90 m over the topography-driven flow. The residuals disappeared after inclusion of the elastic properties of the four hydrostratigraphic units in the model, suggesting the effect of tectonic compression.  相似文献   

Effects of patch size,disturbances on diversity and structural traits of tropical semi-evergreen forest in the lowland Indo Burma hotspot: implication on conservation of the threatened tree species     

Koushik Majumdar  Badal Kumar Datta 《山地科学学报》2016,13(8):1397-1410

Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and 10 m wide (0.5 ha) line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.  相似文献   

A B-spline-based method for radiation and diffraction problems     

Ranadev Datta  Debabrata Sen   《Ocean Engineering》2006,33(17-18):2240-2259

An open uniform B-spline-based panel method is developed for solution of potential flow problems. In this method, both geometry as well as the field variables are represented by the same open uniform B-spline basis function. The method is initially applied for the radiation problem in unbounded fluid. Computed results for a spheroid of different aspect ratio are found to be in excellent agreement with analytical results. The method is then applied for diffraction problem formulated based on the transient (time-domain) Green's function. Computed results for a hemisphere and Wigley hull are compared with published results and the comparison shows good agreement.  相似文献