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31.
Kumar Gulshan Bhadwal Reetika Kumar Mukesh Kumari Punam Kumar Arvind Walia Vivek Mehra Rohit Goyal Ayush 《Natural Hazards》2022,111(3):2219-2240
Natural Hazards - This work reports radon-thoron monitoring at two depths (60 and 90 cm) and at 82 sites around Jawalamukhi thrust of NW Himalaya, India using Solid State Nuclear Track... 相似文献
32.
Dipesh Rupakheti Maheswar Rupakheti Xiufeng Yin Julian Hofer Mukesh Rai Yuling Hu Sabur F.Abdullaev Shichang Kang 《地学前缘(英文版)》2021,12(6):299-312
The location of Central Asia,almost at the center of the global dust belt region,makes it susceptible for dust events.The studies on atmospheric impact of dust over the region are very limited despite the large area occupied by the region and its proximity to the mountain regions(Tianshan,Hindu Kush-Karakoram-Himalayas,and Tibetan Plateau).In this study,we analyse and explain the modification in aerosols'phys-ical,optical and radiative properties during various levels of aerosol loading observed over Central Asia utilizing the data collected during 2010-2018 at the AERONET station in Dushanbe,Tajikistan.Aerosol epi-sodes were classified as strong anthropogenic,strong dust and extreme dust.The mean aerosol optical depth(AOD)during these three types of events was observed a factor of～3,3.5 and 6.6,respectively,higher than the mean AOD for the period 2010-2018.The corresponding mean fine-mode fraction was 0.94,0.20 and 0.16,respectively,clearly indicating the dominance of fine-mode anthropogenic aerosol during the first type of events,whereas coarse-mode dust aerosol dominated during the other two types of events.This was corroborated by the relationships among various aerosol parameters(AOD vs.AE,and EAE vs.AAE,SSA and RRI).The mean aerosol radiative forcing(ARF)at the top of the atmosphere(ARFTOA),the bottom of the atmosphere(ARFBOA),and in the atmosphere(ARFATM)were-35±7,-73±16,and 38±17 Wm-2 during strong anthropogenic events,-48±12,-85±24,and 37±15 Wm-2 during strong dust event,and-68±19,-117±38,and 49±21 Wm-2 during extreme dust events.Increase in aerosol loading enhanced the aerosol-induced atmospheric heating rate to 0.5-1.6 K day-1(strong anthropogenic events),0.4-1.9 K day-1(strong dust events)and 0.8-2.7 K day 1(extreme dust events).The source regions of air masses to Dushanbe during the onset of such events are also identified.Our study con-tributes to the understanding of dust and anthropogenic aerosols,in particular the extreme events and their disproportionally high radiative impacts over Central Asia. 相似文献
33.
Forecasting effective drought index using a wavelet extreme learning machine (W-ELM) model 总被引：3，自引：1，他引：2
Ravinesh?C.?DeoEmail author Mukesh?K.?Tiwari Jan?F.?Adamowski John M.?Quilty 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(5):1211-1240
A drought forecasting model is a practical tool for drought-risk management. Drought models are used to forecast drought indices (DIs) that quantify drought by its onset, termination, and subsequent properties such as the severity, duration, and peak intensity in order to monitor and evaluate the impacts of future drought. In this study, a wavelet-based drought model using the extreme learning machine (W-ELM) algorithm where the input data are first screened through the wavelet pre-processing technique for better accuracy is developed to forecast the monthly effective DI (EDI). The EDI is an intensive index that considers water accumulation with a weighting function applied to rainfall data with the passage of time in order to analyze the drought-risk. Determined by the autocorrelation function (ACF) and partial ACFs, the lagged EDI signals for the current and past months are used as significant inputs for 1 month lead-time EDI forecasting. For drought model development, 97 years of data for three hydrological stations (Bathurst Agricultural, Wilsons Promontory and Merredin in Australia) are partitioned in approximately 90:5:5 ratios for training, cross-validation and test purposes, respectively. The discrete wavelet transformation (DWT) is applied to the predictor datasets to decompose inputs into their time–frequency components that capture important information on periodicities. DWT sub-series are used to develop new EDI sub-series as inputs for the W-ELM model. The forecasting capability of W-ELM is benchmarked with ELM, artificial neural network (ANN), least squares support vector regression (LSSVR) and their wavelet-equivalent (W-ANN, W-LSSVR) models. Statistical metrics based on agreement between the forecasted and observed EDI, including the coefficient of determination, Willmott’s index, Nash–Sutcliffe coefficient, percentage peak deviation, root-mean-square error, mean absolute error, and model execution time are used to assess the effectiveness of the models. The results demonstrate enhanced forecast skill of the drought models that use wavelet pre-processing of the predictor dataset. Based on statistical measures, W-ELM outperformed traditional ELM, LSSVR, ANN and their wavelet-equivalent counterparts (W-ANN, W-LSSVR). It is found that the W-ELM model is computationally efficient as shown by a faster running time with the majority of forecasting errors in lower frequency bands. The results demonstrate the usefulness of W-ELM over W-ANN and W-LSSVR models and the benefits of wavelet transformation of input data to improve the performance of drought forecasting models. 相似文献
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Climatic Change - Anthropogenic climate warming has increased the likelihood of extreme hot summers. To facilitate mitigation and adaptation planning, it is essential to quantify and synthesize... 相似文献
35.
Low temperature in-stream solute acquisition in a glacial environment with very high suspended sediment is critical for downstream evolution of water chemistry. Present work is carried out on 18 km headwater reach from Gomukh (snout of the Gangotri glacier) to Gangotri along River Bhagirathi, India for understanding the hydrological processes controlling the solute acquisition in the glacial environment. This is the first attempt to conduct dissolution experiments with river bed sediments and meltwater considering different operating variables namely; contact time, seasonality, different sediment particle sizes, different sediment dose, effect of pH, wetting and crushing of bed sediments of the glacial stream. The role of sediment in low temperature solute acquisition process is characterized by sudden release of ions from the sediment in initial few seconds. Equilibrium time was observed to be 600 s (10 min). Further progressive increase in EC was observed from Gomukh to Gangotri, suggesting change in sediment surface characteristics/or source. Higher dissolution was observed from the bed sediments collected in June. It is found that the dissolution increases with increase in sediment doses but decreases with an increase in sediment particle size fraction. Higher solute acquisition was observed from crushed sediment because of an abundance of very fine particles having fresh, aggressive/reactive mineral surfaces which are capable of dissolution. The solute released from wetted sediment is significantly lower than the fresh sediment, which may be attributed to the destruction of microparticles adhering to mineral grains, the removal of fresh reactive surface sites, dissolution of rapidly weathered minerals such as calcite and evolution towards to equilibrium of the solution. Further, higher dissolution was observed with decrease in pH, which may be attributed to the availability of more hydrogen ion concentration of the solution, which favours more solute acquisition from sediment into meltwater. 相似文献
36.
We use moment formalism of relativistic radiation hydrodynamics to obtain equations of motion of radial jets and solve them using polytropic equation of state of the relativistic gas. We consider curved space-time around black holes and obtain jets with moderately relativistic terminal speeds. In addition, the radiation field from the accretion disc, is able to induce internal shocks in the jet close to the horizon. Under combined effect of thermal as well as radiative driving, terminal speeds up to 0.75 (units of light speed) are obtained. 相似文献
37.
Prabal Shankar Das Rima Chatterjee Sumangal Dasgupta Ranajit Das Debjani Bakshi Mukesh Gupta 《Geophysical Prospecting》2019,67(1):150-166
Sands belonging to Kamalapuram Formation of Paleocene-Eocene age are deposited in Cauvery basin as incised valley fill during a regressive cycle. Here we attempt to quantify the influence of diagenesis on pore-filling materials using rock physics template constrained by geohistory modelling. Primarily, porosity–velocity and acoustic impedance – the ratio of P-wave and S-wave velocity (VP/Vs) cross-plots are used as rock physics templates. Rock physics template has efficiently quantified pore-filling materials namely; contact cement and non-contact cement. The estimated contact cement and non-contact cement are correlated with conventional petrophysical logs within the selected depth interval. Further, this correlation is used to interpret the composition of pore-filling materials. Shallower depth intervals (I and II) exhibit moderate non-contact cement (4–5%) and insignificant contact cement (1–2% approx.) depositions. However, deeper interval (III) records a significant amount of pore-filling materials amounting average of 12% non-contact cement and 4% contact cement. Pore-filling materials demonstrate a positive correlation with the depth of burial. The fluid response is substantially affected by the degree of diagenesis, composition and spatial distribution of pore-filling materials. Shallower depth intervals (1770–1786 m and 1858–1878 m) are relatively more sensitive to fluid changes as it is affected by insignificant contact cement. The depth interval 1770–1786 m shows class II (oil) and class III (gas) amplitude variation with offset anomalies. The sand occurring in depth interval 1858–1878 m demonstrates class IIP (oil) and II (gas) anomaly. The deeper interval (2118–2170 m) is comparatively stiffer and demonstrates class I amplitude variation with offset (oil and gas sand) anomaly. 相似文献
38.
Eleftherios-Stamatios Telis George Besseris Constantinos Stergiou Mukesh Limbachiya 《Geotechnical and Geological Engineering》2013,31(4):1275-1289
The aim of this paper is to present a method for simultaneous optimization of the design characteristics of an earth retaining structure design using quality tools. The design characteristics examined in this paper are safety factor, total displacements and cost. The methodology for the multi-response optimization used is the desirability analysis which gives the appropriate combinations for the design variables. Through standard experimental runs, we process the results for this optimization. The experimental measurements are calculated via finite elements analysis. The designs used are taken from two real-life case studies. This methodology is intended as a guide tool for civil and geotechnical engineers to predict the values of the design variables as long as they can be named and take discrete values. The uniqueness in this study is that approved experimental methodology can simultaneously optimize the design characteristics of an earth retaining structural design, which were until now calculated empirically. 相似文献
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40.
Long-and short-term variations in shore morphology of Van Island in gulf of Mannar using remote sensing images and DSAS analysis 总被引：1，自引：0，他引：1
T. Immanuvel David M. V. Mukesh S. Kumaravel H. M. Sabeen 《Arabian Journal of Geosciences》2016,9(20):756
Trends of shoreline changes need a scientific study as erosion affects the coastal ecosystem and environment. This study focuses on the trends of shoreline changes along the Van Island, Gulf of Mannar, during the period from 2000 to 2016 using the Digital Shoreline Analysis System model of a tool in Arc Map. Shorelines were extracted from the Landsat OLI and ETM+ satellite data from the years 2000, 2005, 2010 and 2015 and short-term changes obtained by TSS with the help of GPS. The rates of changes were calculated by the standard method of end point rate based on 157 transects lines and baseline. The average value of EPR observed was ?5.03 m/year during the study period. Statistics of EPR further calculated the average long-time intervals during the period of 15 years and also short-term changes. It is noted that the study area of Van Island’s degradation is very rapid. The analysis shows that the surveyed years from 2015 to 2016 record the highest erosion and retreat of shoreline changes in December 2014 to May2015 than in May2015 to December 2015. Based on the predicted EPR value of ?125 m/year of erosion in the next 25 years, it is concluded that the Van Island will vanish. 相似文献