A comprehensive and quantitative assessment of Raunthi Gad flash flood,Rishi Ganga catchment,central Himalaya,Uttarakhand, India     

Nainwal  Harish Chandra  Shankar  R.  Mishra  Aditya  Mishra  Sumit  Pandey  Ankit  Shah  Sunil Singh  Chauhan  Gambhir Singh  Kumar  Deepak 《Natural Hazards》2022,113(1):157-184

Natural Hazards - Drought severity is increasing in Southern Africa which is affecting rain-fed agriculture, the main source of livelihood in most countries in this region. The study assessed the...  相似文献   

Geochemical assessment of fluoride enrichment and nitrate contamination in groundwater in hard-rock aquifer by using graphical and statistical methods     

Sunil Kumar Srivastava  A L Ramanathan 《Journal of Earth System Science》2018,127(7):104

This systematic study was carried out with objective to delineate the various sources responsible for \(\hbox {NO}_{3}^{-}\) contamination and \(\hbox {F}^{-}\) enrichment by utilizing statistical and graphical methods. Since Central Ground Water Board, India, indicated susceptibility of \(\hbox {NO}_{3}^{-}\) contamination and \(\hbox {F}^{-}\) enrichment, in most of the groundwater, \(\hbox {NO}_{3}^{-}\) and \(\hbox {F}^{-}\) concentration primarily observed \({>}45\) and \({>}1.5~\hbox {mg/L}\), respectively, i.e., higher than the permissible limit for drinking water. Water Quality Index (WQI) indicates \({\sim }22.81\%\) groundwater are good-water, \({\sim }71.14\%\) groundwater poor-water, \({\sim }5.37\%\) very poor-water and 0.67% unsuitable for drinking purpose. Piper diagram indicates \({\sim }59.73\%\) groundwater hydrogeochemical facies are Ca–Mg–\(\hbox {HCO}_{3 }\) water-types, \({\sim }28.19\%\) Ca–Mg–\(\hbox {SO}_{4}\)–Cl water-types, \({\sim }8.72\%\) Na–K–\(\hbox {SO}_{4}\)–Cl water-types and 3.36% Na–K–\(\hbox {HCO}_{3 }\) water-types. This classification indicates dissolution and mixing are mainly controlling groundwater chemistry. Salinity diagram indicate \({\sim }44.30\%\) groundwater under in low sodium and medium salinity hazard, \({\sim }49.66\%\) groundwater fall under low sodium and high salinity hazard, \({\sim }3.36\%\) groundwater fall under very-high salinity hazard. Sodium adsorption ratio indicates \({\sim }97\%\) groundwater are in excellent condition for irrigation. The spatial distribution of \(\hbox {NO}_{3}^{-}\) indicates significant contribution of fertilizer from agriculture lands. Fluoride enrichment occurs in groundwater through the dissolution of fluoride-rich minerals. By reducing the consumption of fertilizer and stress over groundwater, the water quality can be improved.  相似文献   

Estimation of Pullout Capacity of Vertical Plate Anchors in Cohesionless Soil Using MARS     

R. Ganesh  Sunil Khuntia 《Geotechnical and Geological Engineering》2018,36(1):223-233

Vertical plate anchors provide an economical solution to safely resist the large horizontal forces experienced by the foundation of different structures such as bulkheads, sheet piles, retaining walls and so forth. This paper develops a multivariate adaptive regression spline (MARS) model-based approach for the determination of horizontal pullout capacity (P _u ) of vertical plate anchors buried in cohesionless soil by utilizing experimental results reported by different researchers. Based on the collection of forty different pullout experimental test results reported in the literature for anchors buried in loose to dense cohesionless soil with an embedment ratio ranges from 1 to 5, a predictive approach for P _u of vertical plate anchors has been developed in terms of non-dimensional pullout coefficient (M _γq ). The capability of the proposed MARS model for estimating the values of M _γq is examined by comparing the results obtained in the present study with those methods available in the literature. Using different statistical error measure criteria, this study indicates that the present approach is efficient in estimating the horizontal pullout capacity of vertical plate anchors as compared to other methods. The sensitivity analysis indicates that the embedment ratio (H/h, where H = embedment depth of anchor, and h = height of anchor) and internal friction angle (?) of soil mass are the two most important parameters for the evaluation of non-dimensional pullout coefficient (M _γq ) using the proposed MARS model.  相似文献   

Lower bound solutions for uplift capacity of strip anchors adjacent to sloping ground in clay     

Jagdish Prasad Sahoo  Sunil Khuntia 《Marine Georesources & Geotechnology》2018,36(4):405-416

Numerical solutions have been obtained for the vertical uplift capacity of strip plate anchors embedded adjacent to sloping ground in fully cohesive soil under undrained condition. The analysis was performed using finite element lower bound limit analysis with second-order conic optimization technique. The effect of anchor edge distance from the crest of slope, angle and height of slope, normalized overburden pressure due to soil self-weight, and embedded depth of anchor on the uplift capacity has been examined. A nondimensional uplift factor defined as F_cγ owing to the combined contribution of soil cohesion (c_u), and soil unit weight (γ) is used for expressing the uplift capacity. For an anchor buried near to a sloping ground, the ultimate uplift capacity is dependent on either pullout failure of anchor or overall slope failure. The magnitude of F_cγ has been found to increase with an increase in the normalized overburden pressure up to a certain maximum value, beyond which either the behavior of anchor transfers from shallow to deep anchor or overall slope failure occurs.  相似文献   

A class of regular and well behaved charge analogue of?Kuchowicz’s relativistic super-dense star model     

Y. K. Gupta  Sunil Kumar Maurya 《Astrophysics and Space Science》2011,332(2):415-421

We obtain a well behaved class of charge analogues of neutral superdense star model due to Kuchowicz, by using a particular electric field, which involves a parameter K and vanishes when K=0. The members of this class are seen to satisfy the various physical conditions e.g. c ² ρ≥3p≥0, dp/dr<0, dρ/dr<0, along with the velocity of sound, dp/c ² dρ<1 and the adiabatic index ((p+c ² ρ)/p)(dp/(c ² dρ))>1, for the interval 0<K<1 with the maximum mass 6.8374M _Θ and the radius 23.4679 km with the central red shift Z _c =0.75364. In the interval, 0<K≤0.1179, the velocity of sound and the ratio p/c ² ρ are found monotonically decreasing towards the pressure free interface, which presents a relevant model for massive star like Neutron star or pulsar with the maximum mass as 4.1474M _Θ and the radius 20.5481 km with the central red shift Z _c =0.6654.  相似文献   

A class of charged analogues of Durgapal and Fuloria superdense star     

Y. K. Gupta  Sunil Kumar Maurya 《Astrophysics and Space Science》2011,331(1):135-144

We obtain a new class of charged super-dense star models after prescribing particular forms of the metric potential g ₄₄ and electric intensity. The metric describing the superdense stars joins smoothly with the Reissner-Nordstrom metric at the pressure free boundary. The interior of the stars possess there energy density, pressure, pressure-density ratio and velocity of sound to be monotonically decreasing towards the pressure free interface. In view of the surface density 2×10¹⁴ g/cm³, the heaviest star occupies a mass 5.6996 M _⊙ with its radius 17.0960 km. The red shift at the centre and boundary are found to be 3.5120 and 1.1268 respectively. In absence of the charge we are left behind with the regular and well behaved fifth model of Durgapal (J. Phys. A 15:2637, 1982).  相似文献   

IAG/AIG Newsletter No. 28 (3/2012)     

Sunil Kumar De 《地球表面变化过程与地形》2013,38(7):767-770

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Rule-based classification of high-resolution imagery over urban areas in New York City     

Sunil Bhaskaran  Eric Nez  Karolyn Jimenez  Sanjiv K. Bhatia 《国际地球制图》2013,28(6):527-545

This paper describes the integration of results from different feature extraction algorithms using spectral and spatial attributes to detect specific urban features. Methodology includes segmentation of IKONOS data, computing attributes for creating image objects and classifying the objects with fuzzy logic and rule-based algorithms. Previous research reported low class accuracies for two specific classes – dark and grey roofs. A modified per-field approach was employed to extract urban features. New rule-sets were used on image objects having similar or near-similar spectral and spatial characteristics. Different algorithms using spectral and spatial attributes were developed to extract specific urban features from a time-series of Multi-Spectral Scanner (MSS) (4 m × 4 m) IKONOS data. The modified approach resulted in a remarkable improvement in the accuracy of classes that registered low spectral seperability and therefore low accuracy. The spectral and spatial based classification model may be useful in mapping heterogeneous and spectrally similar urban features.  相似文献   

Enhanced velocity mixed finite element methods for modeling coupled flow and transport on non-matching multiblock grids     

Sunil G. Thomas  Mary F. Wheeler 《Computational Geosciences》2011,15(4):605-625

The enhanced velocity mixed finite element method, due to Wheeler et al. (Comput Geosci 6(3–4):315–332, 2002), is analyzed and extended to the problem of modeling slightly compressible flow coupled to the transport of chemical species through porous media, on non-matching multiblock grids. Applications include modeling bio-remediation of heavy oil spills and many other subsurface hazardous wastes, angiogenesis in transition of tumors from dormant to malignant states, transport of contaminants in ground water flow, and acid injection from well bores to increase permeability of surrounding rock. The analysis and numerical examples presented here demonstrate convergence and computational efficiency of this method.  相似文献   

Charged anisotropic models for quark stars     

Jefta M. Sunzu  Sunil D. Maharaj  Subharthi Ray 《Astrophysics and Space Science》2014,352(2):719-727

We perform a detailed physical analysis for a class of exact solutions for the Einstein–Maxwell equations. The linear equation of state consistent with quark stars has been incorporated in the model. The physical analysis of the exact solutions is performed by considering the charged anisotropic stars for the particular nonsingular exact model obtained by Maharaj, Sunzu and Ray. In performing such an analysis we regain masses obtained by previous researchers for isotropic and anisotropic matter. It is also indicated that other masses and radii may be generated which are in acceptable ranges consistent with observed values of stellar objects. A study of the mass-radius relation indicates the effect of the electromagnetic field and anisotropy on the mass of the relativistic star.  相似文献