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31.
Anand Sivaramakrishnan 《Celestial Mechanics and Dynamical Astronomy》1989,46(1):35-48
Linked twist maps of ergodic theory are modified to provide a model for chaotic orbits in ‘double bowl’ potentials in conservative
systems, e.g. direct ‘exchange’ orbits in the planar restricted problem of three bodies. The maps are typically ergodic (and
mixing), and provide a clue to the nature of relaxation or diffusion in chaotic Hamiltonian systems. 相似文献
32.
The study of uniformly polytropes with axial symmetry is extended to include all rotational terms of order 4, where is the angular velocity, consistently within the first post-Newtonian approximation to general relativity. The equilibrium structure is determined by treating the effects of rotation and post-Newtonian gravitation as independent perturbations on the classical polytropic structure. The perturbation effects are characterized by a rotation parameter = 2/2G
c
and a relativity parameter, =p
c
/
c
C
2
, wherep
c
and c are the central pressure and density respectively. The solution to the structural problem is obtained by following Chandrasekhar's series expansion technique and is complete to the post-Newtonian rotation terms of order
2. The critical rotation parameterv
c
, which characterizes the configuration with maximum uniform rotation, is accurately evaluated as a function of . Numerical values for all the structural parameters needed to determine the equilibrium configurations are presented for polytropes with indicesn=1, 1.5, 2, 2 5, 3, and 3.5. 相似文献
33.
Geospatial Information Integration for Authoritative and Crowd Sourced Road Vector Data 总被引:1,自引:0,他引:1
Heshan Du Suchith Anand Natasha Alechina Jeremy Morley Glen Hart Didier Leibovici Mike Jackson Mark Ware 《Transactions in GIS》2012,16(4):455-476
This article describes results from a research project undertaken to explore the technical issues associated with integrating unstructured crowd sourced data with authoritative national mapping data. The ultimate objective is to develop methodologies to ensure the feature enrichment of authoritative data, using crowd sourced data. Users increasingly find that they wish to use data from both kinds of geographic data sources. Different techniques and methodologies can be developed to solve this problem. In our previous research, a position map matching algorithm was developed for integrating authoritative and crowd sourced road vector data, and showed promising results ( Anand et al. 2010 ). However, especially when integrating different forms of data at the feature level, these techniques are often time consuming and are more computationally intensive than other techniques available. To tackle these problems, this project aims at developing a methodology for automated conflict resolution, linking and merging of geographical information from disparate authoritative and crowd‐sourced data sources. This article describes research undertaken by the authors on the design, implementation, and evaluation of algorithms and procedures for producing a coherent ontology from disparate geospatial data sources. To integrate road vector data from disparate sources, the method presented in this article first converts input data sets to ontologies, and then merges these ontologies into a new ontology. This new ontology is then checked and modified to ensure that it is consistent. The developed methodology can deal with topological and geometry inconsistency and provide more flexibility for geospatial information merging. 相似文献
34.
Extreme weather events, such as storms and cyclones, pose dire occupational hazards in marine fishing. Thus, warnings against such events can reduce risks to the life and property of fishing communities. This study is an attempt to assess the factors driving fishermen’s decision to respond to weather warnings. Mixed methods, such as exploratory fieldwork, literature review, and focus group discussions, helped in identifying the available weather warnings and hypothesizing the probable factors influencing response to the warnings in the marine fishing community in Maharashtra, India. The plausible drivers of response include perceived potential risk, credibility of the warning and its disseminators, community social capital, and other demographic characteristics. Data from a household survey, comprising 601 fishermen, is used to empirically test the hypotheses. The results suggest that trust in the source and disseminator of the warning is related to higher response rates. There is heterogeneity in the role of community social capital as a motivator to respond. Further, fishermen perceiving traditional information to be more reliable are less likely to respond frequently to the warnings. The findings of the study are relevant for designing interventions which can prompt high response rates to weather warnings from fishermen. 相似文献
35.
2D and 3D seismic reflection and well log data from Andaman deep water basin are analyzed to investigate geophysical evidence related to gas hydrate accumulation and saturation. Analysis of seismic data reveals the presence of a bottom simulating reflector (BSR) in the area showing all the characteristics of a classical BSR associated with gas hydrate accumulation. Double BSRs are also observed on some seismic sections of area (Area B) that suggest substantial changes in pressure–temperature (P–T) conditions in the past. The manifestation of changes in P–T conditions can also be marked by the varying gas hydrate stability zone thickness (200–650 m) in the area. The 3D seismic data of Area B located in the ponded fill, west of Alcock Rise has been pre-stack depth migrated. A significant velocity inversion across the BSR (1,950–1,650 m/s) has been observed on the velocity model obtained from pre-stack depth migration. The areas with low velocity of the order of 1,450 m/s below the BSR and high amplitudes indicate presence of dissociated or free gas beneath the hydrate layer. The amplitude variation with offset analysis of BSR depicts increase in amplitude with offset, a similar trend as observed for the BSR associated with the gas hydrate accumulations. The presence of gas hydrate shown by logging results from a drilled well for hydrocarbon exploration in Area B, where gas hydrate deposit was predicted from seismic evidence, validate our findings. The base of the hydrate layer derived from the resistivity and acoustic transit-time logs is in agreement with the depth of hydrate layer interpreted from the pre-stack depth migrated seismic section. The resistivity and acoustic transit-time logs indicate 30-m-thick hydrate layer at the depth interval of 1,865–1,895 m with 30 % hydrate saturation. The total hydrate bound gas in Area B is estimated to be 1.8 × 1010 m3, which is comparable (by volume) to the reserves in major conventional gas fields. 相似文献
36.
Response surface methodology (RSM) was applied to study the combined effects of the various parameters namely, pH, biosorbent dosage, cadmium concentration and temperature, and to optimize the process conditions for the maximum removal of cadmium using Psidium guvajava L. leaf powder. In order to obtain the mutual interactions between the variables and to optimize these variables, a 24 full factorial central composite design using RSM was employed. The analysis of variance (ANOVA) of the quadratic model demonstrates that the model was highly significant. The model was statistically tested and verified by experimentation. A maximum cadmium removal of 93.2% was obtained under the following optimum conditions: aqueous cadmium concentration 40.15 mg/L, adsorbent dosage 0.5 g/50 mL solution, pH 5.0, and temperature (35°C). The value of desirability factor obtained was 1. 相似文献
37.
Hydrogeochemistry of the Koyna River basin,India 总被引:1,自引:1,他引:0
Pradeep Kumar Naik A. K. Awasthi A. V. S. S. Anand P. N. Behera 《Environmental Earth Sciences》2009,59(3):613-629
Hydrogeochemistry of the Koyna River basin, famous for the Koyna earthquake (magnitude 7) of 1967, has been studied. Basalt
is the primary aquifer; laterites, alluvium, and talus deposits form aquifers of secondary importance. Groundwater generally
occurs under water table conditions in shallow aquifers. Deeper aquifers are associated only with basalts. One hundred and
87 water samples were collected from various sources, such as dugwells, borewells, springs, and surface water, including 40
samples for analysis of iron. Only major constituents were analyzed. Analyses show that the concentrations of Ca2+ exceed that of Mg2+ in almost all water samples; the concentrations of Na+ are generally next to Ca2+ and are always higher than that of K+; and CO3
2– and SO4
2– are very low and are often negligible. Groundwater in borewells tapping deeper aquifers has higher mineralization compared
to that in dugwells representing shallow aquifers. Majority of the water samples are dominated by alkaline earths (Ca2+, Mg2+) and weak acids (HCO3
−, CO3
2–). Groundwater from shallow aquifers is generally calcium-bicarbonate type (53%) and calcium-magnesium-bicarbonate type (27%).
In case of deeper aquifer, it is mostly calcium-magnesium-bicarbonate type (29%), sodium-bicarbonate type (24%), calcium-bicarbonate
type (19%), calcium-magnesium-sodium-bicarbonate type (19%) and sodium-calcium-bicarbonate type (9%). Groundwater water is
generally fit for drinking and irrigation purposes, except in the lower reaches of the Koyna River basin, which is affected
by near water logging conditions. 相似文献
38.
Abhay M. Varade Y. D. Khare N. C. Mondal Sarang Muley Pawan Wankawar Priti Raut 《Journal of the Indian Society of Remote Sensing》2013,41(3):619-630
The paper deals with the application of Remote Sensing and Geographical Information System (GIS) technique for a watershed development program. For this study, the WRJ-2 watershed falling under Narkhed and Katol Tahsils of Nagpur district, Maharashtra, India is investigated. Various thematic maps (i.e. drainage, geology, soil, geomorphology and land use/ land cover) have been prepared using the remote sensing and GIS techniques. Initially, differential weightage values are assigned to all the thematic maps as per their runoff characteristics. Subsequently, the maps are integrated in GIS environment to identify potential sites for water conservation measures like gully plugs, earthen check dams, continuous contour trenches, percolation tanks, cement bandhara, afforestration and farm ponds, etc. The study depicts that the GIS technique facilitates integration of thematic maps and thereby helps in an identification of micro-zones each with unique characters in-terms of hydrogeology, thus amenable to specific water conservation techniques. It is therefore concluded that, the GIS technique is suitable for an identification of water conservation structures. 相似文献
39.
T. L. Krylova M. S. Pandian N. S. Bortnikov Vijay Anand S N. V. Gorelikova V. G. Gonevchuk P. G. Korostelev 《Geology of Ore Deposits》2012,54(4):276-294
Formation conditions of orebodies and conditions of wolframite deposition at the Degana tungsten deposits in Rajasthan, India and the Tigrinoe tin-tungsten deposit in the Russian Far East were studied. Differences in the composition and state of fluid systems were established by microthermometric study of fluid inclusions (FI) and thorough petrographic examination of FI. At the Degana deposit, the ore veins in granite were formed from K-Na-Ca-(Mg, Fe, etc.) chloride solutions with a salinity up to 36 wt % NaCl equiv at a temperature of >420 to 120°C and under a pressure reaching 1550 bar. The formation temperature of the orebodies hosted in breccia reached 450°C and pressure was below 400 bar. The salinity of mainly Nachloride aqueous solutions was no higher than 18 wt % NaCl equiv. At the Tigrinoe deposit, the temperature during formation of quartz-wolframite-cassiterite veins varied from 420 to 240°C and the pressure was no higher than 300 bar. The salt concentration of Na-chloride solutions was 7-3 wt %. Wolframite crystallized at the very beginning of ore deposition. Probable sources of fluids are discussed. It is suggested that the factors controlling wolframite deposition could have been different even at the same deposit. 相似文献
40.
F. A. J. Abernethy A. B. Verchovsky N. A. Starkey M. Anand I. A. Franchi Monica M. Grady 《Meteoritics & planetary science》2013,48(9):1590-1606
Angrites are a small group of ancient basaltic achondrites, notable for their unusual chemistry and extreme volatile depletion. No comprehensive study of indigenous light elements currently exists for the group. Measurement of the abundances and isotopic composition of carbon and nitrogen could provide information pertaining to the evolution of the angrite parent body. Bulk‐sample stepped combustion analyses of five angrites and a glass separate from D'Orbigny were combined with earlier data and acid dissolution experiments of carbonates found in D'Orbigny to compile an inventory of indigenous carbon and nitrogen. Indigenous carbon combusted between 700 °C and 1200 °C, with abundances of 10–140 ppm and a mass‐weighted δ13C of ?25 to ?20‰ with the exception of D'Orbigny (δ13C approximately ?5‰). Nitrogen was released at 850–1200 ºC, 1–20 ppm with a δ15N ?3‰ to +4‰; again, D'Orbigny (δ15N approximately +20 to +25‰) was an exception. We interpret these components as largely indigenous and decoupled; the carbon in graphitic or amorphous form, while the nitrogen is present as a dissolved component in the silicates. No relationship with the textural sub‐classification of angrites is apparent. We suggest that the angrite parent body contains a reservoir of reduced carbon and thus may have undergone a change in redox conditions, although the timing and mechanism for this remain unclear. 相似文献