Mapping of wastelands of Kolar district using false colour composites of thematic mapper (TM) data     

C. R. Shiva Prasad  R. S. Reddy  T. R. Srinivasan  Prabhakara 《Journal of the Indian Society of Remote Sensing》1988,16(4):37-42

This study deals with the technique of remote sensing for identifying and deliniating wastelands in Kolar district of Karnataka. False colour composites of thematic mapper (TM) data supplemented by aerial photographs and toposheets wrere utiliesd for mapping wastelands. A map showing the geographic distribution of the wastelands in the districts was prepared on 1∶250,000 scales by compiling the individual wasteland sheets of 1∶50,000 scale. The seven different catagories of wastelands identified and mapped cover about 11.7% of the area in the district. A procedure for mapping wastelands has been worked out based on the experience gained in Kolar district which is a three phase system comprising image intrepretation of false colour composite of TM data, aerial photo interpretation and limited ground truth verification in the selected doubtful areas. This procedure was found to be adequate enough for mapping wastelands accurately in the shortest possible time with least expense and as such are recommended for mapping wastelands in other districts of the country.  相似文献   

Impact of Climate Change on Indian Agriculture: A Review     

R. K. Mall  Ranjeet Singh  Akhilesh Gupta  G. Srinivasan  L. S. Rathore 《Climatic change》2006,78(2-4):445-478

During the recent decade, with the growing recognition of the possibility of climate change and clear evidence of observed changes in climate during 20^th century, an increasing emphasis on food security and its regional impacts has come to forefront of the scientific community. In recent times, the crop simulation models have been used extensively to study the impact of climate change on agricultural production and food security. The output provided by the simulation models can be used to make appropriate crop management decisions and to provide farmers and others with alternative options for their farming system. It is expected that in the coming decades with the increased use of computers, the use of simulation models by farmers and professionals as well as policy and decision makers will increase. In India, substantial work has been done in last decade aimed at understanding the nature and magnitude of change in yield of different crops due to projected climate change. This paper presents an overview of the state of the knowledge of possible effect of the climate variability and change on food grain production in India. An erratum to this article can be found at  相似文献   

Hydrolysis of neptunium(V) at variable temperatures (10-85°C)     

Linfeng Rao  Thandankorai G. Srinivasan  PierLuigi Zanonato  Arturo Bismondo 《Geochimica et cosmochimica acta》2004,68(23):4821-4830

Neptunium is one of the few radioactive elements that are of great concern in the disposal of nuclear wastes in the geological repository, due to its hazards and the long half-life of the isotope, ²³⁷Np (t_1/2 = 2.14 × 10⁶ years). To understand and predict the migration behavior of neptunium in the geological media, it is of importance to study its hydrolysis at elevated temperatures, because the temperature in the waste package and the vicinity of the repository could be high. Moreover, the chemical analogy between neptunium(V) and plutonium(V) adds even greater value to this investigation, because the latter could exist at tracer levels in neutral and slightly oxidizing waters but is difficult to study due to its rather labile redox behavior.In this work, the hydrolysis of neptunium(V) was studied at variable temperatures (10 to 85°C) in tetramethylammonium chloride (1.12 mol kg⁻¹). Two hydrolyzed species of neptunium(V), NpO₂OH(aq) and NpO₂(OH)₂⁻, were identified by potentiometry and Near-IR absorption spectroscopy. The hydrolysis constants (*β_n) and enthalpy of hydrolysis (ΔH_n) for the reaction NpO₂⁺ + nH₂O = NpO₂(OH)_n⁽¹⁻ⁿ⁾⁺ + nH⁺ (n = 1 and 2) were determined by titration potentiometry and microcalorimetry. The hydrolysis constants, *β₁ and *β₂, increased by 0.8 and 3.4 orders of magnitude, respectively, as the temperature was increased from 10 to 85°C. The enhancement of hydrolysis at elevated temperatures is mainly due to the significant increase of the degree of ionization of water as the temperature is increased. The hydrolysis reactions are endothermic but become less endothermic as the temperature is increased. The heat capacities of hydrolysis, ΔC_p1 and ΔC_p2, are calculated to be −(71 ± 17) J K⁻¹ mol⁻¹ and −(127 ± 17) J K⁻¹ mol⁻¹, respectively. Approximation approaches to predict the effect of temperature, including the constant enthalpy approach, the constant heat capacity approach and the DQUANT equation, have been tested with the data.  相似文献   

Flood basalts from dharwars of Mysore,India     

R. Srinivasan  B. L. Sreenivas 《Bulletin of Volcanology》1971,35(4):824-840

The term flood basalt is redefined emphasizing the importance of the subaerial environment. Using the well established physical criteria of aerial extent, internal structures, time of extrusion and associations, flood basalt activity is distinguished in the Archeans (Dharwars) of Mysore from the geosynclinal volcanics. Study of chemical composition of the Dharwar and other Archean volcanics in the light ofSugimura’s (1968) SWS index, and plotting of the chemical analyses on theMacdonald andKatsura’s (1964) alkali-silica diagram,Kuno’s (1968) alkali-alumina-silica diagram and Scheynamann’s silica-Niggli qz diagram shows both geosynclinal and subaerial volcanics are mainly tholeiitic. Therefore in deciphering the environment of volcanism, it is suggested that the physical criteria take precedence over chemical composition.  相似文献   

Tibetan anticyclone and tropical easterly jet   总被引：2，自引：0，他引：2  

K. Raghavan 《Pure and Applied Geophysics》1973,110(1):2130-2142

Summary During the summer monsoon the upper tropospheric subtropical anticyclone of Asia is centred over SE Tibet (when it is called the Tibetan anticyclone). Further, the equatorward outflow from this anticyclone gains easterly angular momentum and therefore it appears as an easterly jet stream over SE Asia south of 20N between 150 mb and 100 mb. On finding these current concepts questionable, this study offers an alternative explanation for the migration of the upper tropospheric anticyclone to the Tibetan Plateau and also for the development of the tropical easterly jet. In summer the Bay of Bengal is cold compared to its adjoining continental plains in the north. Therefore in the beginning of summer the lower levels of the anticyclone migrate from their winter position in the Bay of Bengal to the warm plains in the north. As they reach the plains by about June, the upper levels of the anticyclone above 150 mb extend north over the Tibetan Plateau irrespective of whether the Plateau is a warm source or cold source because the upper levels of the subtropical anticyclone have a characteristic poleward slope in all seasons. By about July, when the lower levels of the anticyclone migrate from the plains to still warmer areas in the north over the Plateau, the upper levels which are already over the Plateau continue to remain there throughout the season. The zonal component of the equatorward outflow from the Tibetan anticyclone computed from the law of conservation of angular momentum does not bear any comparison with the observed winds in the upper troposphere over India. On the other hand the winds computed from a thermal gradient show a reasonable agreement with the observed winds indicating thereby that the upper tropospheric high winds are thermally generated. These high winds have been found as a unique phenomenon distinct from a jet stream and therefore it is considered appropriate to call them Tropical Strong Easterlies (TSE) rather than as a tropical easterly jet stream. Some of the characteristic features of the TSE are discussed and they are ascribed to the peculiar temperature distribution in the atmosphere between 200 mb and 60 mb mainly brought about by the vertical motion associated with the summer monsoon.  相似文献   

Isotopic analysis of early solar system objects by an ion microprobe: Parametric studies and initial results     

J N Goswami  G Srinivasan 《Journal of Earth System Science》1994,103(1):57-82

Magnesium, potassium and calcium isotope compositions in terrestrial samples and refractory phases from primitive meteorites are determined using an ion microprobe. A thorough investigation of the different instrument parameters is carried out to ensure that conditions necessary for high mass resolution and high precision isotopic studies are adequately satisfied. The instrument can be tuned to achieve mass resolution (M/ΔM) of up to 10,000 (M≤60); it has a very good dynamic stability (ΔB/B≤10 ppm over durations of ≤40 minutes) and the counting system has an effective dead-time of ≤25 nsec and a dynamic background of ≤0·01 c/s. Reproducibility and precision of isotopic measurements are checked by analyzing magnesium and titanium isotopic compositions in terrestrial standards and isotopically doped silicate glasses. A precision of 2‰ (2σ _m ) was achieved during magnesium isotopic analysis in samples with low Mg content (200 ppm). Results from studies of magnesium and potassium isotopic compositions in several Ca−Al-rich refractory inclusions (CAIs) from the primitive meteorites Efremovka and Grosnaja, representing some of the early solar system objects, are presented. The well-behaved Mg−Al isotopic systematics confirm the pristine nature of the Efremovka CAIs inferred earlier from petrographic and trace element studies. The Grosnaja CAIs that have experienced secondary alterations show disturbed magnesium isotopic systematics. Observation of excess²⁶Mg in several of the analyzed CAIs confirms the presence of the now extinct²⁶Al (t _1/2=7×10⁵ years) in the solar nebula at the time of CAI formation. Our data also suggest a relatively uniform distribution of²⁶Al in the solar nebula. Several Efremovka CAIs with excess²⁶Mg also have excess⁴¹K resulting from the decay of⁴¹Ca (t _1/2≃10⁵ years). This observation constrains the time interval between cessation of nucleosynthetic input to the solar nebula and the formation of some of the first solar system solids (CAIs) to less than a million years.  相似文献   

Automatic extraction of lineament information from satellite images using digital elevation data   总被引：1，自引：0，他引：1  

Venkatesh Raghavan  Kiyoshi Wadatsumi  Shinji Masumoto 《Natural Resources Research》1993,2(2):148-155

Using conventional visual interpretation in lineament analysis presents two main problems. The first is subjectivity, introduced because of the bias of various interpreters. The second problem is that lineaments detected from satellite images are constrained by the direction of the illumination source. Since lineament identification mainly involves recognition of diagnostic morphological features, the use of digital elevation can contribute significant information about these features. Further, in generating images using digital elevation data, the direction of illumination can easily be controlled. Thus, the use of digital elevation data offers the possibility of revealing features not apparent in regular satellite images.We discuss a sequential line detection method for extraction of linear features from digital elevation data. In this method, raw elevation data is used for generating shaded relief images using the Lambertian reflection model, wherein the illumination direction is controlled by the user. The Directional Segment Detection Algorithm (DSDA) is used for detecting linear topographic features in user-defined trends. Locational information about these linear features is stored in the computer as coordinate pairs amenable to editing and subsequent analysis. Finally, three-dimensional terrain models are generated by combining the digital elevation data and satellite images. The experiments were carried out using digital elevation data of southwest Japan and Landsat MSS data.  相似文献   

Correction to: Multilevel Graph Partitioning for Three-Dimensional Discrete Fracture Network Flow Simulations     

Ushijima-Mwesigwa  Hayato  Hyman  Jeffrey D.  Hagberg  Aric  Safro  Ilya  Karra  Satish  Gable  Carl W.  Sweeney  Matthew R.  Srinivasan  Gowri 《Mathematical Geosciences》2021,53(8):1977-1978

Mathematical Geosciences - The publication of this article unfortunately contained a mistake. The assignment to the affiliations of author Satish Karra was not correct  相似文献   

Ensemble-Based Assimilation of Nonlinearly Related Dynamic Data in Reservoir Models Exhibiting Non-Gaussian Characteristics     

Kumar  Devesh  Srinivasan  Sanjay 《Mathematical Geosciences》2019,51(1):75-107

Mathematical Geosciences - Inverse modeling techniques for estimating reservoir parameters (e.g., transmissivity, permeability) utilize some dynamic (secondary) information (e.g., hydraulic head or...  相似文献   

Evaluation of global optimization algorithms for parameter calibration of a computationally intensive hydrologic model   总被引：1，自引：0，他引：1  

Xuesong Zhang  Raghavan Srinivasan  Kaiguang Zhao  Mike Van Liew 《水文研究》2009,23(3):430-441

With the popularity of complex hydrologic models, the time taken to run these models is increasing substantially. Comparing and evaluating the efficacy of different optimization algorithms for calibrating computationally intensive hydrologic models is becoming a nontrivial issue. In this study, five global optimization algorithms (genetic algorithms, shuffled complex evolution, particle swarm optimization, differential evolution, and artificial immune system) were tested for automatic parameter calibration of a complex hydrologic model, Soil and Water Assessment Tool (SWAT), in four watersheds. The results show that genetic algorithms (GA) outperform the other four algorithms given model evaluation numbers larger than 2000, while particle swarm optimization (PSO) can obtain better parameter solutions than other algorithms given fewer number of model runs (less than 2000). Given limited computational time, the PSO algorithm is preferred, while GA should be chosen given plenty of computational resources. When applying GA and PSO for parameter optimization of SWAT, small population size should be chosen. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献