Symplectic Mappings of Co-orbital Motion in the Restricted Problem of Three Bodies     

Zsolt Sándor  Bálint Érdi  Carl D. Murray 《Celestial Mechanics and Dynamical Astronomy》2002,84(4):355-368

The dynamics of co-orbital motion in the restricted three-body problem are investigated by symplectic mappings. Analytical and semi-numerical mappings have been developed and studied in detail. The mappings have been tested by numerical integration of the equations of motion. These mappings have been proved to be useful for a quick determination of the phase space structure reflecting the main characteristics of the dynamics of the co-orbital problem.  相似文献   

Optimum merger time-scales and binary evolution     

Tapan K. Chatterjee 《Astrophysics and Space Science》1993,199(1):35-44

A study of galaxy mergers, on the basis of the collisional theory, using galaxy models without halos and considering the evolution of the proginator galaxies only from a time when the gravitational interaction between them is physically significant, indicates that most of the mergers are affected in 2 to 3 orbital periods for progenitors of comparable mass: shorter and longer time-scales being underabundant. These results have a bearing on the evolution of binary galaxies; indicating that once the relative orbit of a binary is circularized, the components will merge during the subsequent orbit or the next one (in a time-scale ~ 10⁸ years). These results are also indicative of the fact that binary evolution is very likely to cause a gradual evolution of the fundamental plane occupied by paired ellipticals from that of isolated ellipticals. After the merger, the remnant is very likely to define a fundamental plane with a slightly different slope.  相似文献   

Hα Photometry of Two Contact Binaries     

Szilárd Csizmadia  Zsolt Kővári  Péter Klagyivik 《Astrophysics and Space Science》2006,304(1-4):355-357

We carried out optical and Hα photometry of two contact binaries (V861 Herculis, EQ Tauri). The light curve modeling revealed stellar spots in both contact systems and strong Hα excess in the position of the observed stellar spots. A correlation was found between the V−R and R−H_α colour indices of V861 Her.  相似文献   

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco     

Haydon P. Mort  Thierry Adatte  Gerta Keller  David Bartels  Karl B. Fllmi  Philipp Steinmann  Zsolt Berner  E.H. Chellai 《Cretaceous Research》2008,29(5-6):1008

With a multi-proxy approach, an attempt was made to constrain productivity and bottom-water redox conditions and their effects on the phosphorus accumulation rate at the Mohammed Plage section on the Tarfaya coast, Morocco, during the Cenomanian-Turonian Anoxic Event (OAE 2). A distinct δ¹³C_org isotope excursion of +2.5‰ occurs close to the top of the section. The unusually abrupt shift of the isotope excursion and disappearance of several planktonic foraminiferal species (e.g. Rotalipora cushmani and Rotalipora greenhornensis) in this level suggests a hiatus of between 40–60 kyrs at the excursion onset. Nevertheless, it was possible to determine both the long-term environmental history as well as the processes that took place immediately prior to and during OAE 2. TOC% values increase gradually from the base of the section to the top (from 2.5% to 10%). This is interpreted as the consequence of a long-term eustatic sea-level rise and subsidence causing the encroachment of less oxic waters into the Tarfaya Basin. Similarly a reduction in the mineralogically constructed ‘detrital index’ can be explained by the decrease in the continental flux of terrigenous material due to a relative sea-level rise. A speciation of phosphorus in the upper part of the section, which spans the start and mid-stages of OAE 2, shows overall higher abundances of P_reactive mass accumulation rates before the isotope excursion onset and lower values during the plateau. Due to the probable short hiatus, the onset of the decrease in phosphorus content relative to the isotope excursion is uncertain, although the excursion plateau already contains lower concentrations. The C_org/P_total and V/Al ratios suggest that this reduction was mostly likely caused by a decrease in the available bottom oxygen content (probably as a result of higher productivity) and a corresponding fall in the phosphorus retention ability of the sediment. Productivity appears to have remained high during the isotope plateau possibly due to a combination of ocean-surface fertilisation via increased aridity (increased K/Al and Ti/Al ratios) and/or higher dissolved inorganic phosphorus content in the water column as a result of the decrease in sediment P retention. The evidence for decreased P-burial has been observed in many other palaeoenvironments during OAE 2. Tarfaya's unique upwelling paleosituation provides strong evidence that the nutrient recycling was a global phenomenon and therefore a critical factor in starting and sustaining OAE 2.  相似文献   

Analysis of the 2003 Varunawat Landslide,Uttarkashi, India using Earth Observation data     

K. Vinod kumar  R. C. Lakhera  Tapas R. Martha  R. S. Chatterjee  A. Bhattacharya 《Environmental Geology》2008,55(4):789-799

Mass movements such as landslides in mountainous terrains are natural degradation processes and one of the most important landscape-building factors. Varunawat Parbat overlooking Uttarkashi town witnessed a series of landslides on 23 September 2003 and the debris slides and rock falls continued for 2 weeks. This landslide complex was triggered due to the incessant rainfall prior to the event, and its occurrence led to the blockage of the pilgrim route to Gangotri (source of the Ganges river) and evacuation of thousands of people to safer places. Though there was no loss of lives due to timely evacuation, heavy losses to the property were reported. High-resolution stereoscopic earth observation data were acquired after the incidence to study the landslide in detail with emphasis on the cause of the landslide and mode of failure. Areas along the road and below the Varunawat foothill region are mapped for landslide risk. It was found that the foothill region of the Varunawat Parbat was highly disturbed by man-made activities and houses are dangerously located below steep slopes. The potential zones for landslides along with the existing active and old landslides are mapped. These areas are critical and their treatment with priority is required in order to minimise further landslide occurrences.  相似文献   

Bayes estimation: A novel approach to derivation of internally consistent thermodynamic data for minerals,their uncertainties,and correlations. Part II: Application     

Niranjan D. Chatterjee  Klaus Miller  Walter Olbricht 《Physics and Chemistry of Minerals》1994,21(1-2):50-62

Internally consistent thermodynamic data, including their uncertainties and correlations, are reported for 22 phases of the quaternary system CaO-Al₂O₃-SiO₂-H₂O. These data have been derived by simultaneous evaluation of the appropriate phase properties (PP) and reaction properties (RP) by the novel technique of Bayes estimation (BE). The thermodynamic model used and the theory of BE was expounded in Part I of this paper. Part II is the follow-up study illustrating an application of BE. The input for BE comprised, among others, the a priori values for standard enthalpy of formation of the i-th phase, Δ_f H _i ⁰ , and its standard entropy, S _i ⁰ , in addition to the reaction reversal constraints for 33 equilibria involving the relevant phases. A total of 269 RP restrictions have been processed, of which 107 turned out to be non-redundant. The refined values for Δ_f H _i ⁰ and S _i ⁰ obtained by BE, including their 2σ-uncertainties, appear in Table 4; the Appendix reproduces the corresponding correlation matrix. These data permit generation of computed phase diagrams with 2σ-uncertainty envelopes based on conventional error propagation; Fig. 3 depicts such a phase diagram for the system CaO-Al₂O₃-SiO₂. It shows that the refined dataset is capable of yielding phase diagrams with uncertainty envelopes narrow enough to be geologically useful. The results in Table 4 demonstrate that the uncertainties of the prior values for Δ_f H _i ^Emphasis>0 , given in Table 1, have decreased by up to an order of magnitude, while those for S _i ⁰ improved by a factor of up to two. For comparison, Table 4 also lists the refined Δ_f H _i ⁰ and S _i ⁰ data obtained by mathematical programming (MAP), minimizing a quadratic objective function used earlier by Berman (1988). Examples of calculated phase diagrams are given to demonstrate the advantages of BE for deriving internally consistent thermodynamic data. Although P-T curves generated from both MAP and BE databases will pass through the reversal restrictions, BE datasets appear to be better suited for extrapolations beyond the P-T range explored experimentally and for predicting equilibria not constrained by reversals.  相似文献   

A statistical procedure for the analysis of seismotectonically induced hydrochemical signals: A case study from the Eastern Carpathians, Romania   总被引：3，自引：0，他引：3  

Jens Hartmann  Zsolt Berner  Doris Stüben  Norbert Henze   《Tectonophysics》2005,405(1-4):77-98

Changes in the stress field of an aquifer system induced by seismotectonic activity may change the mixing ratio of groundwaters with different compositions in a well, leading to hydrochemical signals which in principle could be related to discrete earthquake events. Due to the complexity of the interactions and the multitude of involved factors the identification of such relationships is a difficult task. In this study we present an empiric statistical approach suitable to analyse if there is an interdependency between changes in the chemical composition of monitoring wells and the regional seismotectonic activity of a considered area. To allow a rigorous comparison with hydrochemistry the regional earthquake time series was aggregated into an univariate time series. This was realized by expressing each earthquake in form of a parameter “e”, taking into consideration both energetic (magnitude of a seismic event) and spatial parameters (position of epi/hypocentrum relative to the monitoring site). The earthquake and the hydrochemical time-series were synchronised aggregating the e-parameters into “earthquake activity” functions E, which takes into account the time of sampling relative to the earthquakes which occurred in the considered area. For the definition of the aggregation functions a variety of different “e” parameters were considered. The set of earthquake functions E was grouped by means of factor analysis to select a limited number of significant and representative earthquake functions E to be used further on in the relation analysis with the multivariate hydrochemical data set. From the hydrochemical data a restricted number of hydrochemical factors were extracted. Factor scores allow to represent and analyse the variation of the hydrochemical factors as a function of time. Finally, regression analysis was used to detect those hydrochemical factors which significantly correlate with the aggregated earthquake functions.This methodological approach was tested with a hydrochemical data set collected from a deep well monitored for two years in the seismically active Vrancea region, Romania. Three of the hydrochemical factors were found to correlate significantly with the considered earthquake activities. A screening with different time combinations revealed that correlations are strongest when the cumulative seismicity over several weeks was considered. The case study also showed that the character of the interdependency depends sometimes on the geometrical distribution of the earthquake foci. By using aggregated earthquake information it was possible to detect interrelationships which couldn't have been identified by analysing only relations between single geochemical signals and single earthquake events. Further on, the approach allows to determine the influence of different seismotectonic patterns on the hydrochemical composition of the sampled well. The method is suitable to be used as a decision instrument in assessing if a monitoring site is suitable or not to be included in a monitoring net within a complex earthquake prediction strategy.  相似文献   

Riddle of arsenic in groundwater of Bengal Delta Plain—role of non-inland source and redox traps     

D. Chatterjee  R. K. Roy  B. B. Basu 《Environmental Geology》2005,49(2):188-206

In the Bengal Delta Plain (BDP) the primary arsenic sourcing appears to be different from the global scenario. Here, the Terminal Pleistocene–Holocene depositional platform, the interactive early Holocene depositional morphology with fluvio-estuarine and marine incursions played a crucial role for arsenic sourcing and enrichment. The lenticular silt-fine sand layer between anoxic clay beds favoured entrapment of dissolved organic carbon with decayed phyto-planktons debris. The Terminal Pleistocene–Holocene transgression and regression processes may have acted as major events in the BDP. Interestingly, at the end of the last glacial maxima, the Pleistocene delta had undergone block movements, wherein some parts of the platform were raised above the level of Holocene deposition. Those blocks were found to be free from arsenic in the groundwater. The sea, during re-emerging inundation (10–7 ka BP), has witnessed a monsoon-induced environment in the BDP with the resultant oscillation of sea level leading to higher upsurge towards the north. This might have resulted in the marine incursion and inundation in pre-existing land depressions. Meanwhile arsenic entrapments through marine incursion as well as enrichment in the presence of organic carbon/DOC and/or Fe/Mn/Al catalytic agents could have developed into localised redox traps. It may be of relevance that due to the repetitive transgressive–regressive phases in Holocene, resulting in periodic exposure and weathering of iron-bearing minerals and consequent iron enrichment in the aquifer system. The iron, thus present, had free charge to host arsenic as a sink. It appears that arsenic, wherever found, would likely be of atypical localised exhaustible phenomenon, both in horizontal and vertical context. It also rationalises the cause of the absence of arsenic in the other nearby Pleistocene platform, which has not come across Holocene interaction and marine incursion, as to the likely limiting condition for the search for arsenic in the BDP or beyond.  相似文献   

Estimation of near surface soil moisture in a sloping terrain of a Himalayan watershed using ENVISAT ASAR multi‐incidence angle alternate polarisation data          下载免费PDF全文

Sameer Saran  Geert Sterk  Rajiv Nair  R. S. Chatterjee 《水文研究》2014,28(3):895-904

Soil moisture is one of the important input variables in hydrological and water erosion models. The extraction of information on near surface soil moisture from synthetic aperture radar (SAR) is well established mostly for flat terrain and using low incidence angle single polarisation data. The ENVISAT advanced SAR (ASAR) data available in multiple incidence angles and alternate polarisation modes were investigated in this study for soil moisture estimation in sloping terrain. The test site was Sitla Rao watershed in the Lesser Himalayas of northern India. Empirical models were developed to estimate near surface soil moisture in bare agricultural fields using alternate polarisation ASAR data. Both soil moisture and surface roughness field measurements were performed during the satellite passes. Backscatter from medium incidence angle (IS‐4) and vertical‐vertical (VV) polarisation signal is correlated better with volumetric soil moisture content compared to other incidence angles. The model parameters were further improved, and soil moisture estimation was refined by combining medium incidence angle (IS4) vertical‐horizontal polarisation response as another variable along with VV polarisation response. The effect of slope on the radar backscatter was minimized by incorporating local incidence angles derived from an ASTER DEM. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Changing human-environment interactions in medium mountains: the Apuseni Mts (Romania) as a case study     

Tamás Telbisz  Zoltán Imecs  László Mari  Zsolt Bottlik 《山地科学学报》2016,13(9):1675-1687

The study of human-environment relationships in mountain areas is important for both theoretical and practical reasons, as many mountain areas suffer similar problems, such as depopulation, unemployment and natural hazards. Medium mountains constitute a special case within mountains, because they are more populated but less attractive as tourist destinations than high mountains. In this context, the Apuseni Mts (Romania) are considered as a case study. In this paper, we apply GIS-based, quantitative methods to characterize the strength and dynamics of human-environment interactions, taking into consideration some environmental factors (elevation, relative height, slope, river distance, lithology, land cover, natural attractions) as well as historical population and recent tourism data. We found that population density has strong (r ²>0.8) relationships with all relief factors (elevation, relative height, slope, river distance), and that best-fit functions are nonlinear. We outlined the varying demographic scenarios by elevation zones and interpreted the historically switching sign of population change versus elevation relationship. We demonstrated that lithology also has an impact on the spatial distribution of population, although it is not independent from the relief effect. The land cover of the mainly cultural landscape is very strongly correlated with relief parameters (especially slope), which suggests good adaptation. We pointed out the dominance of karst objects in the natural tourism potential of the Apuseni Mts and also explored further components of real tourism (spas, heritage, towns). Finally, we concluded that the environmental settings investigated do in fact constrain the spatial framework of society, but socio-economic changes in history can be explained from the side of society, which conforms to the theory of cultural possibilism.  相似文献