Evaluation of vertical impact factor coefficients for continuous and integral railway bridges under high-speed moving loads

In the railway bridge analysis and design method,dynamic train loads are regarded as static loads enhanced by an impact factor(IF).The IF coefficients for various railway bridges have been reported as a function of span length or frequency of the bridges in Eurocode(2003).However,these IF coefficient values neglect the effects of very high speeds(>200 km/h)and soil-structure interaction(SSI).In this work,a comprehensive study to assess the impact factor coefficients of mid-span vertical displacements for continuous and integral railway bridges subjected to high-speed moving loads is reported.Three different configurations,each for the three-dimensional(3D)continuous and integral bridge,are considered.Also,single-track(1-T)and two-track(2-T)“real train”loading cases for both these bridge types are considered.Subsequently,finite element analysis of the full-scale 3D bridge models,to identify their IF values,considering the effects of SSI for three different soil conditions,is conducted.The IF values obtained from the study for both bridge types are comparable and are greater than the values recommended by Eurocode(2003).The results reveal that with a loss of soil stiffness,the IF value reduces;thus,it confirms the importance of SSI analysis.     

Heating of the solar chromosphere and corona

The generalized inhomogeneous wave equation that governs magnetoacoustic, vortical and thermal motions in compressible fluids and that thus is applicable to the problem of the heating of the solar chromosphere and corona is obtained. The effects of kinematic and bulk viscosity, heat conduction, Joule dissipation and magnetic diffusivity are included. Under the usual assumptions, the generalized wave equation reduces to the well-known equations of Lighthill, Kulsrud, Phillips and others. The major problems encountered in applying Lighthill's mechanism to sound generation in turbulent media are reviewed for both the subsonic and supersonic cases.     

Rapidly rotating supermassive stars in the first post-Newtonian approximation to general relativity

The structure and stability of rapidly uniformly rotating supermassive stars is investigated using the full post-Newtonian equations of hydrodynamics. The standard model of a supermassive star, a polytrope of index three, is adopted. All rotation terms up to and including those of order ⁴, where is the angular velocity, are retained. The effects of rotation and post-Newtonian gravitation on the classical configuration are explicitly evaluated and shown to be very small. The dynamical stability of the model is treated by using the binding energy approach. The most massive objects are found to be dynamically unstable when =1/c ².p _c / _c 2.2 × 10^–3, wherep _c and _c are the central pressure and density, respectively. Hence, the higher-order terms considered in this analysis do not appreciably alter the previously known stability limits.The maximum mass that can be stabilized by uniform rotation in the hydrogen-burning phase is found to be 2.9×10⁶ M , whereM is the solar mass. The corresponding nuclear-generated luminosity of 6×10⁴⁴ erg/sec^–1 is too small for the model to be applicable to the quasi-stellar objects. The maximum kinetic energy of a uniformly rotating supermassive star is found to be 3×10^–5 Mc ², whereM is the mass of the star. Masses in excess of 10¹⁰ M are required if an adequate store of kinetic energy is to be made available to a pulsar like QSO. However such large masses have rotation periods in excess of 100 yr and thus could not account for any short term periodic variability. It is concluded then that the uniformly rotating supermassive star does not provide a suitable base for a model of a QSO.     

The equilibrium and stability of magnetopolytropes

The theory of the oscillations of axisymmetric gaseous configurations with a prevalent magnetic field is presented. The virial tensor method is used to obtain the nine second harmonic modes of oscillations of the system. It is found that out of the nine modes, three are neutral, four are non-radial, and two are coupled. For the Prendergast spherical model it is found that one of the coupled modes is radial and the other non-radial. Both the radial and the non-radial modes obtained in this case agree with the corresponding formulae obtained byChandrasekhar andLimber (1954) andWoltjer (1962).The equilibrium structure of gaseous polytropes with toroidal magnetic fields is also investigated in detail for values of the polytropic indexn=1, 1.5, 2, 3 and 3.5. For this model the components of the moment of intertia and potential energy tensors together with the non-zero components of the supermatrix potential are obtained. The final results in terms of the effect of weak toroidal magnetic fields on the characteristic frequencies of distorted polytropes are presented in the form of tables.     

Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis

Benthic foraminiferal magnesium/calcium ratios were determined on one hundred and forty core-top samples from the Atlantic Ocean, the Norwegian Sea, the Indian Ocean, the Arabian Sea and the Pacific Ocean, mostly at sites with bottom water temperatures below 5 °C. Mg/Ca ratios are consistently lower, by  0.2 mmol/mol, in samples cleaned using oxidative and reductive steps than using oxidative cleaning. Differences between Cibicidoides species have been identified: Mg/Ca of Cibicidoides robertsonianus > Cibicidoides kullenbergi > Cibicidoides wuellerstorfi. Comparison with bottom water temperatures support observations of lowered Mg/Ca of C. wuellerstorfi at temperature below  3 °C compared with values predicted by published calibrations and from other Cibicidoides species. Hydrographic data shows that carbonate ion saturation (Δ[CO₃²⁻]) decreases rapidly below this temperature. An empirical sensitivity of Δ[CO₃²⁻] on Mg/Ca has been established for C. wuellerstorfi of 0.0086 ± 0.0006 mmol/mol/μmol/kg. A novel application using modern temperatures and Last Glacial Maximum temperatures derived via pore fluid modelling supports a carbonate ion saturation state effect on Mg incorporation. This may significantly affect calculated δ¹⁸O_seawater obtained from foraminiferal δ¹⁸O and Mg/Ca temperature.     

3D Subsurface Characterization of Banded Iron Formation Mineralization using Large-Scale Gravity Data: A Case Study in Parts of Bharatpur,Dausa and Karauli Districts of Rajasthan,India

Our study interprets large-scale gravity data to delineate concealed banded iron formation (BIF) iron mineralization in India's Rajasthan province. The study area belongs to the Bharatpur, Dausa, and Karauli districts of Rajasthan. We measured 1462 gravity readings to understand the rock types, depth and geometry of the different rock formations in the proposed study area. We also collected representative lithologies from more than 100 locations in the study area and calculated their density values. The measured gravity datasets are investigated via qualitative (e.g., Bouguer anomaly, first derivative and second derivative) and quantitative (radially averaged power spectrum, 3D Euler deconvolution, and 3D inversion) approach. The qualitative methods suggest a general NE–SW orientation of the BIFs, controlled by the general trend of the study area's structural setting. The lithological contact between the Bhilwara and Vindhyan Supergroups is demarcated by a NE–SW trending steep gravity gradient zone. In this area, representative lithologies yield high densities (about 3.746 gm/cc), and the samples identified as BIF represent exploration targets for iron ore. We have also developed our own in-house 3D gravity inversion code in this study. A model space inversion algorithm is converted into a data space using the identity relationship. It makes inversion algorithm very user-friendly on conventional desktop computers. The outcomes from the 3D inversion suggest that the concealed iron ore thickens to the west. This interpretation is also in good correlation with Euler 3D deconvolution of the gravity data.

     

Evaluation of hydrogeochemical characteristics and the impact of weathering in seepage water collected within the sedimentary formation

A study was conducted by collecting eight seepage water samples that drain through the sedimentary rocks, mainly sandstone and shale, to evaluate the hydrogeochemical characteristics. The collected samples were analyzed for physico-chemical parameters using standard procedures. Three water types were identified in the Piper plot and the hydrogeochemical evolution starts from a Ca–Cl facies (type 1) via mixed Ca–Mg–Cl and Ca–Na–HCO₃ facies (type 2) to Na–Cl facies (type 3). Increasing trend of electrical conductivity (EC) values were observed from type 1 water to type 3 water. Lower ionic concentrations with an average EC value of 35.7 µs/cm in Ca–Cl facies indicate the recharge water by monsoonal rainfall, and ion exchange/weathering process is reflected in the mixing zone. Higher ionic concentration with an average EC value of 399 µs/cm is noted in Na–Cl facies, which indicates the ion exchange during water–rock interaction. Higher log pCO₂ values are also found in this facies, revealing the longer residence time of seepage water in the rock matrix, which release more ions into the water. The relative mobility of elements during weathering suggest that the order of mobility in both sandstone and shale is Na > Ca > Mg > K. It was observed that the hydrogeochemistry of seepage water is mainly controlled by the bedrock geology.     

Prioritization of subwatersheds based on quantitative morphometric analysis in lower Bhavani basin,Tamil Nadu,India using DEM and GIS techniques

Watershed prioritization is one of the most important processes in natural resource management system especially in areas of sustainable watershed development and planning. Morphometric characteristics are the viable entity to understand the hydrological behavior of the subwatershed. For prioritization of subwatershed, morphometric analysis was utilized by using the linear, areal, and relief aspects of the drainage basin. In this context, remote sensing and GIS has been proved to be an efficient tool to identify the morphological features. The Survey of India (SOI) topographical maps, satellite data IRS-LISS III, and Cartosat DEM data were utilized to understand the drainage pattern and also for prioritization of subwatershed areas. The prioritization of subwatershed has been attempted using novel and quantitative approaches based on compound parameter ranking for soil erosion. Lower compound factors were chosen as the most feasible for soil erosion. Based on the observation, eight subwatersheds with a higher degree of the slope were severely prone to soil erosion and remaining 21 subwatersheds occur in low-lying areas that can be developed as sustainable watersheds. The identified subwatershed requires immediate soil remediation and water conservation measures for efficient watershed planning and management. The proposed study might be helpful for resource planners, government agencies, private sectors, and other stake holders to take up soil conservation measures and fixation of water-harvesting structures for better decision making.     

Implication of the Middle Jurassic pholadomyoids of Kachchh in the palaeobiogeography of the Middle East and South Asia: A review

The Kachchh basin is known world over for its rich occurrence of the Middle to Late Jurassic mollusks. The Middle Jurassic sediments in Kachchh range in age from Bajocian (possibly Aalenian) to Callovian. Amongst the Middle Jurassic benthic communities of Kachchh, the pholadomyoid bivalves are one of the dominant groups in both diversity and number. These are represented by 13 genera and 30 constituent species. Distribution of these bivalves was much affected by the evolutionary history of the basin which has been created due to inundation by Tethys sea owing to the opening of Arabian sea sometime in Middle Jurassic. By and large these fauna are typical of the southern Hemisphere and belonged to east African biochore of the Tethyan realm or to the so called Ethiopian faunal province. Analyzing the (palaeo-) autecological behavior of the studied pholadomyoid bivalves and their distribution pattern, an attempt has been made to ascertain the usefulness of these pholadomyoids in evaluating the Middle Jurassic paleobiogeography.     

Models of rapidly rotating white dwarfs

Numerical solutions of the structural equations for rapidly rotating white dwarfs are tabulated for values of the central density parametery ^–2 _o ranging from 0.0001 to 0.80. The physical parameters of white dwarfs rotating at the break-up velocity are also tabulated. Further, the massradius relations for both the equatorial and the polar radii are derived. These two relations are found to differ from other recent theoretical calculations by less than 10 and 4%, respectively. The use of uniformly rotating white dwarf models to account for the observational data on Sirius B is discussed. It is concluded that Sirius B may be rotating rapidly and near its break-up velocity. Further it is suggested that the radius and Einstein red shift for this star are 0.01135 R and 59 km/sec.