Markov random field-based method for super-resolution mapping of forest encroachment from remotely sensed ASTER image     

L.K. Tiwari  S.K. Sinha  S. Saran  V.A. Tolpekin  P.L.N. Raju 《国际地球制图》2016,31(4):428-445

Forest encroachment (FE) is a problem in Andaman and Nicobar Islands (ANI) in India for environment and planning. Small gaps created in the forest slowly expand its periphery disturbing the biodiversity. Therefore, intrusion of poachers, slash and burn and other factors causing FE must be carefully detected and monitored. Remote sensing offers a great opportunity to accomplish this task because of its synoptic view. Conventional classification methods with remotely sensed images are problematic because of small size of FE and mixed landcover composition. This study presents an application of super-resolution mapping (SRM) based on Markov random field for detection of FE using ASTER (15 m) images. The SRM results were validated using multispectral IRS LISS-IV (5.8 m) image. Non-contiguous FE patches of various sizes and shapes are characterized using the spatial contextual information. The novelty of this approach lies in the identification and separability of small FE pockets which could not be achieved with pixel-based maximum likelihood classifier (MLC). The SRM parameters were optimized and found comparable to previous studies. Classification accuracy obtained with SRM at scale factor 3 is κ = 0.62 that is superior to accuracy of MLC (κ = 0.51). SRM is a promising tool for detection and monitoring of FE at Rutland Island in ANI, India.  相似文献   

Bridging the gap or broadening the problem?     

Harinarayan Tiwari  Subash Pd. Rai  Kumari Shivangi 《Natural Hazards》2016,80(1):351-365

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Hydrogeochemical evaluation of groundwater quality and seasonal variation in East Bokaro coalfield region,Jharkhand     

Mukesh Kumar Mahato  Prasoon Kumar Singh  Ashwani Kumar Tiwari 《Journal of the Geological Society of India》2016,88(2):173-184

Groundwater samples collected from the East Bokaro coalfield of Jharkhand state, India during the dry and rainy seasons of the year 2012. Samples were analyzed for the assessment of groundwater quality in the study area. The results of the chemical analysis indicate that the pH values were found alkaline in nature during both the season. The major cations in groundwater was in the order of Na⁺>Ca²⁺>Mg²⁺>K⁺ during the dry season while Ca²⁺>Na⁺>Mg²⁺>K⁺ during the rainy season. The abundance of the major anions was of HCO₃^->SO₄^2->Cl^->NO₃^->F^- did not change on the seasonal basis. The average NO₃^-concentration was exceeded the desirable limit for drinking water as per Indian standard in the rainy season. Silicate weathering was inferred to be a dominant process, controlling the groundwater chemistry in both seasons, with lesser contributions by carbonate weathering and ion exchange. Leaching of salts from the unsaturated zone also has a major impact on groundwater quality during the rainy season. The water quality data indicate that groundwater is generally suitable for irrigation. However, higher salinity and residual sodium carbonate values at some sites may limit groundwater use and therefore an adequate drainage and water management plan for the study area is required.  相似文献   

Stabilization of fuel oil contaminated soil—A case study   总被引：1，自引：0，他引：1  

Sanjay J. Shah  A. V. Shroff  Jignesh V. Patel  K. C. Tiwari  D. Ramakrishnan 《Geotechnical and Geological Engineering》2003,21(4):415-427

Fuel oil contamination brings adverse effect on basic geotechnical properties of foundation soil. The present study pertains to one such case, from the petrochemical complex near Vadodara City in Gujarat State, India. Here, the fuel oil contaminated soil samples exhibit drastic changes in their geotechnical parameters. Noteworthy among such deleterious changes are: decrease in maximum dry density (–4%), cohesion (–66%), angle of internal friction (–23%) and unconfined compressive strength (UCS) (–35%) and increase in liquid limit (+11%). An attempt has been made to stabilize the contaminated soil using various additives viz., lime, fly ash and cement independently as well as an admixture of different combinations. It is apparent from the test results that the stabilization agents improved the geo-technical properties of the soil by way of cation exchange, agglomeration, and pozzuolanic actions. The best results were observed when a combination of 10% lime, 5% fly ash and 5% cement was added to the contaminated soil. The improvement in unconfined compressive strength (UCS), cohesion and angle of internal friction can be attributed to neo-formations such as Calcium Silicate Hydrates (CSH, CSH-1) that coats and binds the soil particles. Formation of stable complex between oil and metallic cations, results in reduction of leachableoil.  相似文献   

Prioritization of watersheds using morphometric parameters and assessment of surface water potential using remote sensing   总被引：3，自引：0，他引：3  

M. Suresh  S. Sudhakar  K. N. Tiwari  V. M. Chowdary 《Journal of the Indian Society of Remote Sensing》2004,32(3):249-259

In the present study, prioritization of sub-watersheds was carried out on the basis of sediment production rate. Further, basic hydrologic information such as peak rate of runoff and annual surface water potential were also assessed for the study watersheds and these are essential requisites for effective watershed management. The 10 sub watersheds of Tarai development project area are selected for the present study. Morphometric parameters pertaining to study area are used in the estimation of sediment production rate. The sediment production rate in the study area varies between 2.45 to 11.0 ha-m/100 km²/year. The remote sensing data has been utilized for generating land use/land cover data which is an essential prerequisite for land and water resource planning and development. The remote sensing data can especially play significant role in collection of real time information from remote areas of river basins for generation of parameters required for hydrologic modeling.  相似文献   

Gravitational sources of purely electromagnetic origin     

R. N. Tiwari  J. R. Rao  Saibal Ray 《Astrophysics and Space Science》1991,178(1):119-132

The Einstein-Maxwell field equations for charged dust corresponding to static axially-symmetric metric of Levi-Civita have been studied. It has been shown that when the metric potentialsg _ij are functions of only one of the coordinates, viz.,r, the interior charged dust becomes purely of electromagnetic origin, in the sense that the physical quantities like the energy density, the effective gravitational mass, etc., are dependent only on the charge density and vanish when this charge density vanishes. Such models are known as electromagnetic mass models in the classical electrodynamics. An interior charged dust solution corresponding to this case has been obtained which, in a sense, represents an infinite dust distribution of electromagnetic origin. In the second case, viz., when the metric potentials are functions of the coordinatesr andz both, it has been shown that some of the situations correspond to electromagnetic mass models. An example to illustrate this case has been obtained. This represents the source of the Reissner-Nordström-Curzon field (an analogue of the Reissner-Nordström solution obtained by Curzon) which according to Curzon describes the exterior field of an electron.  相似文献   

Assessment of surface water potential using morphometry and curve number-based approaches     

K. Nidhi  K. N. Tiwari  V. Shinde  V. K. Dadhwal 《国际地球制图》2017,32(11):1206-1228

Geomorphic and curve number-based run-off estimation approaches are proposed in this study for Olidih watershed, India. Cartosat Digital Elevation Model derived morphometry parameters were used for the computation of run-off. The observed and predicted run-off are uniformly scattered around 1:1 line and coefficient of correlation (R²) is found to be around 0.94 in case of NRCS-CN method. Run-off assessment computed using geomorphological parameters and NRCS-CN approach has improved with the introduction of rainfall correction factor. The improved R² from 0.3 to 0.86 in this case was attributed to rainfall correction factor computed based on the long-term rainfall average of the study area. Run-off assessment made using composite parameter approach shows R² values of 0.98 and 0.82 for different initial abstraction losses 0.2 and 0.3, respectively, and has indicated better prediction. Therefore, proposed morphometry-based approaches can be explored as an alternative for simulating the hydrological response of the watersheds.  相似文献   

A new look on Imperial Porphyry: a famous ancient dimension stone from the Eastern Desert of Egypt—petrogenesis and cultural relevance     

Abu El-Enen  Mahrous M.  Lorenz  Joachim  Ali  Kamal A.  von Seckendorff  Volker  Okrusch  Martin  Schüssler  Ulrich  Brätz  Helene  Schmitt  Ralf-Thomas 《International Journal of Earth Sciences》2018,107(7):2393-2408

International Journal of Earth Sciences - Imperial Porphyry, a famous dimension stone of spectacular purple color, was quarried in the Mons Porphyrites area north of Jabal Dokhan in the Eastern...  相似文献   

Gorkha earthquake (MW7.8) and aftershock sequence: A fractal approach          下载免费PDF全文

Ram Krishna Tiwari  Harihar Paudyal 《地震科学（英文版）》2022,35(3):193-204

On April 25, 2015, Nepal was struck by the M_W7.8 Gorkha earthquake followed by an intense aftershock sequence. It was one of the most destructive earthquakes in the Himalayan arc, causing more than 8900 fatalities. In this study, we analyzed the dataset (429 events, magnitude of completeness (M_c) ≥ 4.2 local magnitude) of the first 45 days after the Gorkha earthquake to estimate the seismicity parameters b-value, D-value, and p-value. We used the maximum likelihood method to estimate the b-value and Omori-Utsu parameters, whereas the correlation integral method was applied to estimate the fractal dimension (D-value). The analysis was carried out using running and sliding window techniques. The lowest b-value (0.57 ± 0.04) and the highest D-value (1.65 ± 0.02) were computed at the time of the Gorkha earthquake, after which the b-value significantly increased to a maximum of 1.57. It again dropped to 0.93 at the time of the major aftershock on May 12, 2015. The D-value showed an initial quick drop and then decreased in a wavy pattern until the end of the study period, indicating the clustering and scattering of earthquakes in a fault region. The b-value contour map identified the eastern part of the study area as a high stress region (b = ～0.8), implying that the stress shifted to that region. The D-value contour map reveals that the seismogenic structure shifted from linear to planar in the region. The rate of aftershock decay (p = 0.86 ± 0.04) for a short period reflects that the level of stress decreased rapidly. This study helps to understand the level of stress and seismicity pattern of a region, which could be useful for aftershock studies.  相似文献   

Liquefaction resistance evaluation of soils using artificial neural network for Dhaka City,Bangladesh     

Fahim  Abul Kashem Faruki  Rahman  Md. Zillur  Hossain  Md. Shakhawat  Kamal  A. S. M. Maksud 《Natural Hazards》2022,113(2):933-963

Natural Hazards - Soil liquefaction resistance evaluation is an important site investigation for seismically active areas. To minimize the loss of life and property, liquefaction hazard analysis is...  相似文献