Evaluation of NDWI and MNDWI for assessment of waterlogging by integrating digital elevation model and groundwater level   总被引：1，自引：0，他引：1  

Kanwar Vivek Singh  Shashikanta Sahoo  Avinash Prasad  Brijendra Pateriya 《国际地球制图》2015,30(6):650-661

Accurate information on the extent of waterlogging is required for flood prediction, monitoring, relief and preventive measures. The rule-based classification algorithms were used for differentiating waterlogged areas from other ground features using Resourcesat-2 AWiFS satellite imagery (Indian Remote Sensing Satellite with spatial resolution of 56 m). Two spectral indices normalized difference water index (NDWI) and modified normalized difference water index (MNDWI) were used for extracting waterlogged areas in Sri Muktsar Sahib district of Punjab, India. These indices extracted the waterlogged areas (cropped areas inundated with water) but the water features were less enhanced in the NDWI-derived image (when compared with MNDWI-derived image) due to negative values of NDWI and, mixing of water with built up features. The water features were more enhanced with MNDWI and the values of MNDWI were positive for water features mixed with vegetation. The overall accuracy of waterlogged areas extracted from the MNDWI image was 96.9% with the Kappa coefficient of 0.89. The digital elevation model (DEM) was extracted from ASTER-GDEM. The relationships among depth to the water table recorded before the incessant rain in the region, DEM and classified MNDWI images explained the differences in the extent of waterlogging in various directions of the study area. These results suggest that MNDWI can be used to better delineate water features mixed with vegetation compared to NDWI.  相似文献   

Impact of Local Groundwater Flow Model Errors on Transport and a Practical Solution for the Issue          下载免费PDF全文

Sorab Panday  Vivek Bedekar  Christian D. Langevin 《Ground water》2018,56(4):667-672

A groundwater flow model is typically used to provide the flow field for conducting groundwater solute transport simulations. The advection term of the mass conserved formulation for groundwater transport assumes that the flow field is perfectly balanced and that all water flowing into a numerical grid cell is exactly balanced by outflows after accounting for sources/sinks or internal storage. However, in many complicated regional or site‐scale models, there may be localized flow balance errors that may be difficult to eliminate through tighter flow convergence tolerances due to simulation time constraints or numerical limits on convergence tolerances. Thus, if water is erroneously gained or lost within a grid cell during the flow computation, the solutes within it will also be numerically affected in the associated transport simulation. Transport solutions neglect this error in groundwater flow as the transport equations that are solved assume no error in flow. This flow imbalance error can however have consequences on the transport solution ranging from unnoticeable errors in the resulting concentrations to spurious oscillations that can grow in time and hinder further solution. An approach has been suggested here, to explicitly handle these flow imbalances during mass conserved advective transport computations and report them in the corresponding transport mass balance output, as corrections that are needed to handle errors originating in the flow solution. Example problems are provided to explain the concepts and demonstrate the impacts.  相似文献   

Mineralogical Study of Beneficiated and Carbonized Indian Coking Coal for Better Utilization: A Case Study     

Chakravarty  K.  Mishra  Vivek  Chakravarty  S.  Chakladar  S.  Saxena  V. K.  Bhattacharya  S. 《Natural Resources Research》2020,29(4):2431-2450

Coking/metallurgical coal is one of the essential raw materials for steel industries. The metallurgical coal in India contains high ash content (mineral matters), is rich in inertinite, and requires optimization before its proper utilization. Distribution of mineral matter in coking coal plays a significant role in achieving the desired product for blast furnace and coke-making operations. The present paper reports a case study on the distribution and nature of mineral matter in Indian coking coals at varying densities with respect to the coal’s beneficiation behavior. The maceral analysis indicated the maximum liberation of reactives at the relative density (RD) of 1.2–1.3 g/cm³ while maximum inerts concentrated at the highest density (RD?>?1.8 g/cm³). The most dominating mineral matter found in the coal is argillaceous minerals containing substantial amounts of quartz followed by carbonate and sulfides existing as cavity fillings or in disseminated form. X-ray diffraction (XRD), X-ray fluorescence (XRF), and electron-probe microanalysis (EPMA) techniques were used to study the mineral distribution and transformation behavior of coke produced from the coking coal during carbonization process. A case study on the reactivity of dispersed mineral matter in coke and the implication of mineral transformation behavior on coke is also discussed in this paper.

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Radon-thoron monitoring in Tatun volcanic areas of northern Taiwan using LR-115 alpha track detector technique: Pre-calibration and installation   总被引：1，自引：0，他引：1  

Arvind Kumar  Vivek Walia  Tsanyao Frank Yang  Hsiao-Hsien Chang  Shih-Jung Lin  Karumpil Philips Eappen  Baldev Raj Arora 《Acta Geophysica》2013,61(4):958-976

In the present study, experiments have been carried out to calibrate LR-115 alpha detector films in bare and cup-mode exposure for the measurement of radon and thoron concentrations in soil gas. Results showed non-uniformity in track formation on the films in bare-mode exposure. However, in cup-mode exposure the non-uniformity was reduced to a greater extent. The calibration factors obtained for radon in bare- and cup-mode exposures are 0.049 and 0.034 tr. cm^?2 per Bq m^?3 d, respectively. An attempt has been made to calibrate the radon-thoron discriminative cup with LR-115 films for simultaneous measurements of radon and thoron. This paper also presents the preliminary results of radonthoron monitoring in Tatun volcanic areas of northern Taiwan for the first time using radon-thoron discriminators with LR-115 films. The results show that the safe temperature to install the LR-115 films in volcanic areas is ≤ 65°C and thoron concentration in the study area is low.  相似文献   

Impact of Vortex Initialization in Prediction of Tropical Cyclones over Bay of Bengal with NCUM Model     

Ashish Routray  Vivek Singh  Ankur Gupta  Devajyoti Dutta  John P. George 《Marine Geodesy》2019,42(2):201-226

The present study evaluates the impact of vortex initialization (VI) scheme within the NCMRWF Global Unified model (NCUM-G) for prediction of tropical cyclones (TCs) formed over Bay of Bengal (BoB). For this purpose, two numerical experiments such as control simulation (CNTL) without using VI scheme and VOTX simulation using the VI scheme in the NCUM-G are performed by considering four landfalling TCs formed over BoB basin during the year 2016–17. The results suggest that even though TCs are large synoptic systems, the introduction of VI scheme has a positive impact on the prediction of the location, movement, intensity and development of rain bands associated with the TCs. The initial vortex position and landfall position errors are reduced by ～64% and ～39% in VOTX simulations over CNTL, respectively. The mean track errors of all the four TCs are reasonably improved by ～58% in VOTX over CNTL. The equitable threat score (ETS) and frequency bias are significantly improved in the VOTX for all the TC cases as compared to CNTL. Study results provide a positive proof of concept that the VI scheme within the NCUM-G can help to improve the simulation of track and intensity of TCs over BoB.  相似文献   

A numerical study of mineral alteration and self-sealing efficiency of a caprock for CO2 geological storage     

Hailong Tian  Tianfu Xu  Fugang Wang  Vivek V. Patil  Yuan Sun  Gaofan Yue 《Acta Geotechnica》2014,9(1):87-100

Geochemical interactions of brine–rock–gas have a significant impact on the stability and integrity of the caprock for long-term CO₂ geological storage. Invasion of CO₂ into the caprock from the storage reservoir by (1) molecular diffusion of dissolved CO₂, (2) CO₂-water two-phase flow after capillary breakthrough, and (3) CO₂ flow through existing open fractures may alter the mineralogy, porosity, and mechanical strength of the caprock due to the mineral dissolution or precipitation. This determines the self-enhancement or self-sealing efficiency of the caprock. In this paper, two types of caprock, a clay-rich shale and a mudstone, are considered for the modeling analyses of the self-sealing and self-enhancement phenomena. The clay-rich shale taken from the Jianghan Basin of China is used as the base-case model. The results are compared with a mudstone caprock which is compositionally very different than the clay-rich shale. We focus on mineral alterations induced by the invasion of CO₂, feedback on medium properties such as porosity, and the self-sealing efficiency of the caprock. A number of sensitivity simulations are performed using the multiphase reactive transport code TOUGHREACT to identify the major minerals that have an impact on the caprock’s self-sealing efficiency. Our model results indicate that under the same hydrogeological conditions, the mudstone is more suitable to be used as a caprock. The sealing distances are barely different in the two types of caprock, both being about 0.6 m far from the interface between the reservoir and caprock. However, the times of occurrence of sealing are considerably different. For the mudstone model, the self-sealing occurs at the beginning of simulation, while for the clay-rich shale model, the porosity begins to decline only after 100 years. At the bottom of the clay-rich shale column, the porosity declines to 0.034, while that of mudstone declines to 0.02. The sensitive minerals in the clay-rich shale model are calcite, magnesite, and smectite-Ca. Anhydrite and illite provide Ca²⁺ and Mg²⁺ to the sensitive minerals for their precipitation. The mudstone model simulation is divided into three stages. There are different governing minerals in different stages, and the effect of the reservoir formation water on the alteration of sensitive minerals is significant.  相似文献   

Compressed History Matching: Exploiting Transform-Domain Sparsity for Regularization of Nonlinear Dynamic Data Integration Problems   总被引：1，自引：1，他引：0  

Behnam?JafarpourEmail author  Vivek?K.?Goyal  Dennis?B.?McLaughlin  William?T.?Freeman 《Mathematical Geosciences》2010,42(1):1-27

In this paper, we present a new approach for estimating spatially-distributed reservoir properties from scattered nonlinear dynamic well measurements by promoting sparsity in an appropriate transform domain where the unknown properties are believed to have a sparse approximation. The method is inspired by recent advances in sparse signal reconstruction that is formalized under the celebrated compressed sensing paradigm. Here, we use a truncated low-frequency discrete cosine transform (DCT) is redundant to approximate the spatial parameters with a sparse set of coefficients that are identified and estimated using available observations while imposing sparsity on the solution. The intrinsic continuity in geological features lends itself to sparse representations using selected low frequency DCT basis elements. By recasting the inversion in the DCT domain, the problem is transformed into identification of significant basis elements and estimation of the values of their corresponding coefficients. To find these significant DCT coefficients, a relatively large number of DCT basis vectors (without any preferred orientation) are initially included in the approximation. Available measurements are combined with a sparsity-promoting penalty on the DCT coefficients to identify coefficients with significant contribution and eliminate the insignificant ones. Specifically, minimization of a least-squares objective function augmented by an l ₁-norm of DCT coefficients is used to implement this scheme. The sparsity regularization approach using the l ₁-norm minimization leads to a better-posed inverse problem that improves the non-uniqueness of the history matching solutions and promotes solutions that are, according to the prior belief, sparse in the transform domain. The approach is related to basis pursuit (BP) and least absolute selection and shrinkage operator (LASSO) methods, and it extends the application of compressed sensing to inverse modeling with nonlinear dynamic observations. While the method appears to be generally applicable for solving dynamic inverse problems involving spatially-distributed parameters with sparse representation in any linear complementary basis, in this paper its suitability is demonstrated using low frequency DCT basis and synthetic waterflooding experiments.  相似文献   

A Comparative Investigation of Image Fusion in the Context of Classification     

Anshu Gupta  Vivek Dey 《Journal of the Indian Society of Remote Sensing》2012,40(2):167-178

Image fusion assists in visual interpretation, mapping, change detection and many other applications. Multispectral and Panchromatic images are fused to produce images having enhanced spatial and spectral properties. These properties are generally distorted from original images. The aim of this paper is to identify the effectiveness of the several fusion techniques based on the distortions and applications. This paper employs seven image fusion techniques namely, Brovey transform, intensity hue saturation, high pass filter, principle component analysis, UNB Pansharpening, wavelet transform and multiplicative, available in various commercial image processing software. The data for this study are panchromatic image of Cartosat-1 and multispectral image of IRS - P6 LISS 4 sensor of study area, Bhopal Municipal Corporation area, M.P. State, India. The effectiveness of image fusion techniques is determined by quantitative and qualitative assessments. Quantitative assessment is divided into two parts: 1) assessment of fusion techniques by statistical parameters and 2) accuracy assessment of land use maps generated from the fused images. For part 1, three parameters namely, mean bias, correlation coefficient and Q4 quality index, have been used. Based on the results of part 1, UNB Pansharpening and wavelet transform are the best among seven fusion techniques. For part 2, Gaussian and Artificial Neural Network classifiers have been used to generate land cover maps. However, the accuracy results are inconclusive to identify a single best method. Nevertheless, image fusion by wavelet transform has provided best results in both the sector. Hence, wavelet transform is concluded as the best among selected fusion techniques.  相似文献   

Bearing capacity of square footings on reinforced layered soil     

Arvind Kumar  B. S. Walia 《Geotechnical and Geological Engineering》2006,24(4):1001-1008

In the present study, an approximate method has been suggested to calculate the ultimate bearing capacity of a square footing resting on reinforced layered soil. The soil is reinforced with horizontal layers of reinforcement in the top layer of soil only. The pre requisite to the method is the ultimate bearing capacity of unreinforced layered soil, which can be determined from the methods already available in literature. The results have been validated with the model tests conducted on two layered soil compacted at different densities and the top layer reinforced with horizontal layers of geogrid reinforcement.  相似文献   

Seismo-Geochemical Variations in SW Taiwan: Multi-Parameter Automatic Gas Monitoring Results   总被引：1，自引：0，他引：1  

T. F. Yang  C.-C. Fu  V. Walia  C.-H. Chen  L. L. Chyi  T.-K. Liu  S.-R. Song  M. Lee  C.-W. Lin  C.-C. Lin 《Pure and Applied Geophysics》2006,163(4):693-709

Gas variations of many mud volcanoes and hot springs distributed along the tectonic sutures in southwestern Taiwan are considered to be sensitive to the earthquake activity. Therefore, a multi-parameter automatic gas station was built on the bank of one of the largest mud-pools at an active fault zone of southwestern Taiwan, for continuous monitoring of CO₂, CH₄, N₂ and H₂O, the major constituents of its bubbling gases. During the year round monitoring from October 2001 to October 2002, the gas composition, especially, CH₄ and CO₂, of the mud pool showed significant variations. Taking the CO₂/CH₄ ratio as the main indicator, anomalous variations can be recognized from a few days to a few weeks before earthquakes and correlated well with those with a local magnitude >4.0 and local intensities >2. It is concluded that the gas composition in the area is sensitive to the local crustal stress/strain and is worthy to conduct real-time monitoring for the seismo-geochemical precursors.  相似文献