ENSO-induced drought hazards and wet spells and related agricultural losses across Anhui province,China     

Sun  Peng  Zhang  Qiang  Cheng  Chen  Singh  Vijay P.  Shi  Peijun 《Natural Hazards》2017,89(2):963-983

Natural Hazards - Using daily precipitation data from 25 meteorological stations for a period of 1961–2014, spatiotemporal features of wet spells and droughts and related impacts on...  相似文献   

General correlation analysis: a new algorithm and application     

Yu Zhou  Qiang Zhang  Vijay P. Singh  Mingzhong Xiao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(3):665-677

Correlation associations have been detected using Pearson’s r which aims to analyze linear correlation between two variables. It should be noted here that associations between hydro-meteorological variables are usually nonlinear. In this sense, the classical correlation analysis method cannot truly reflect the inherent associations between variables characterized by nonlinear associations. In this case, a new algorithm has been proposed by using the ideas of local correlation, detrended cross-correlation analysis and multifractals, and this novel algorithm is called as the general detrended correlation analysis. The newly-proposed algorithm was evaluated for the validity with numerically-generated time series and the real world hydrological series. The results indicate that the newly-proposed algorithm can well reflect the nonlinear and non stationary associations between two hydrological series when compared to the classical relation detection method such as the Pearson correlation analysis method, and it is particularly the case under the condition that hydrological abrupt changes of the hydrological processes occur where the classical association analysis is not appropriate.  相似文献   

Scaling of adsorption reactions: U(VI) experiments and modeling     

Vijay A. Loganathan  Mark O. Barnett  T. Prabhakar Clement  Sushil R. Kanel 《Applied Geochemistry》2009,24(11):2051-2060

Iron-coated sands were prepared via two common protocols, a precipitation method, where Fe was precipitated directly onto the sand in a single step, and an adsorption method, where pure goethite was prepared in the first step and then adsorbed onto the sand in a second step. The coated sands from both the systems were characterized using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and selective Fe extraction. Although neither of the methods produced a completely crystalline Fe coating, the precipitation method produced sands with larger portions of amorphous Fe than the adsorption method, with the fraction of amorphous Fe decreasing with increasing Fe content. Uranium(VI) adsorption isotherms and pH adsorption edges were measured on three coated sands with Fe contents ranging from 0.04% to 0.3%. Experimentally, the adsorption of U(VI) onto the three sands was more comparable when normalized to surface area than when normalized to Fe content. A surface complexation model, although originally developed for U(VI) adsorption onto amorphous Fe oxide, captured the differences in adsorption when adjusted for the surface area of the coated sand. The findings indicate that surface area is a better scaling parameter than Fe content in predicting U(VI) adsorption to Fe-dominated media. These findings are significant because many common surface complexation models are parameterized on the basis of Fe content rather than specific surface area. Although the interactions of U(VI) and Fe-coated sands were used as representative adsorbate and adsorbent, the general principles may be applicable to other adsorbate–adsorbent systems as well.  相似文献   

Transient three-dimensional modeling of riverbank filtration at Grind well field, Germany     

Vijay Shankar  Paul Eckert  Chandra Ojha  Christoph M. König 《Hydrogeology Journal》2009,17(2):321-326

Riverbank filtration (RBF) is a proven treatment step in a multi-barrier method of drinking-water supply at many sites. RBF wells induce a large amount of river water to infiltrate the river base and travel towards the wells, giving the opportunity for mixing of infiltrated surface water and groundwater. Assessment of raw water quality plays an important role in planning and operating a RBF well field. In this context, the determination of the catchment area (and land uses within the catchment) and the ratio of bank filtrate (BF) to raw groundwater (GW) are two prior steps. Transient model simulations were performed in order to study the hydraulic conditions at the RBF well field at Grind near Düsseldorf, Germany. The BF/GW ratio was determined to be 75/25. The flood events in winter, in particular, showed the BF/GW ratio to have high variation. Transient path lines in the well field were used for delineation of the catchment area.  相似文献   

Role of dimensionless numbers in wave analysis     

Surendra Kumar Mishra  Vijay P. Singh 《水文研究》2003,17(3):651-669

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Comments on “Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits”     

Vijay S. Tripathi 《Geochimica et cosmochimica acta》1979,43(12):1989-1990

The necessity of considering protonation and complexation of weak acid ligands, for proper interpretation of their effect on solution equilibria, has been demonstrated. The solubility of uraninite in presence of σF = 2 ppm has been recalculated to be 0.88 ppb at pH 2.  相似文献   

A note on the step error of some finite-difference schemes used to solve kinematic wave equations     

Vijay P. Singh 《Journal of Hydrology》1976,30(3):247-255

An analytical treatment is developed for the step error of some finite-difference schemes that are frequently used to solve the kinematic wave equations. It is shown that for convergent and stable schemes, the production of step error of one scheme may not be the same as that of another. This distinction must be considered in choosing between the schemes. Knowledge of step error is a useful parameter to estimate apriori the step length to be used in a given scheme.  相似文献   

Nighttime enhancements in ionospheric electron content: seasonal and solar cycle variation     

Sudhir Jain  S. K. Vijay  A. K. Gwal  Y. N. Huang 《Annales Geophysicae》1995,13(3):256-261

Various characteristics of anomalous nighttime enhancement in ionospheric electron content (IEC) at Lunping (14.08°N geomagnetic), a station near the crest of the equatorial anomaly, have been presented by considering the IEC data for the 21st solar cycle. Out of a total of 1053 enhancements, 354 occur in pre-midnight and 699 occur in post-midnight hours, which indicates an overall dominance of post-midnight events at Lunping. The occurrence is more frequent during summer, less during the equinox and least during winter months. All the characteristics of the enhancements have seasonal dependencies and they reach their maximum values during summer months. The occurrence of the pre-midnight events show positive and post-midnight events show negative correlation with solar activity. The results have been discussed and compared with those at low-latitude stations in India and Hawaii and at the mid-latitude station, Tokyo.  相似文献   

MMO: An improved estimator for log-Pearson type-3 distribution     

Fang X. Yu  Babak Naghavi  Vijay P. Singh  Guang-Te Wang 《Stochastic Environmental Research and Risk Assessment (SERRA)》1994,8(3):219-231

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On the informative value of the largest sample element of log-Gumbel distribution     

Witold G. Strupczewski  Krzysztof Kochanek  Vijay. P. Singh 《Acta Geophysica》2007,55(4):652-678

Extremes of stream flow and precipitation are commonly modeled by heavytailed distributions. While scrutinizing annual flow maxima or the peaks over threshold, the largest sample elements are quite often suspected to be low quality data, outliers or values corresponding to much longer return periods than the observation period. Since the interest is primarily in the estimation of the right tail (in the case of floods or heavy rainfalls), sensitivity of upper quantiles to largest elements of a series constitutes a problem of special concern. This study investigated the sensitivity problem using the log-Gumbel distribution by generating samples of different sizes (n) and different values of the coefficient of variation by Monte Carlo experiments. Parameters of the log-Gumbel distribution were estimated by the probability weighted moments (PWMs) method, method of moments (MOMs) and maximum likelihood method (MLM), both for complete samples and the samples deprived of their largest elements. In the latter case, the distribution censored by the non-exceedance probability threshold, F _T , was considered. Using F _T instead of the censored threshold T creates possibility of controlling estimator property. The effect of the F _T value on the performance of the quantile estimates was then examined. It is shown that right censoring of data need not reduce an accuracy of large quantile estimates if the method of PWMs or MOMs is employed. Moreover allowing bias of estimates one can get the gain in variance and in mean square error of large quantiles even if ML method is used.  相似文献