Modeling of flowing film concentrators: Part 1. Water split behaviour

A large number of mineral processing equipment employs the basic principles of gravity concentration in a flowing fluid of a few millimetres thick in small open channels where the particles are distributed along the flow height based on their physical properties and the fluid flow characteristics. Fluid flow behaviour and slurry transportation characteristics in open channels have been the research topic for many years in many engineering disciplines. However, the open channels used in the mineral processing industries are different in terms of the size of the channel and the flow velocity used. Understanding of water split behaviour is, therefore, essential in modeling flowing film concentrators. In this paper, an attempt has been made to model the water split behaviour in an inclined open rectangular channel, resembling the actual size and the flow velocity used by the mineral processing industries, based on the Prandtl's mixing length approach.     

Studies on flow characteristics of coal–oil–water slurry system

Experiments were carried out to investigate the rheological properties of coal–oil–water suspension containing solids of different sizes. Two different coal samples with mean particle sizes of 120 mesh, 175 mesh and 220 mesh were used. The coal concentration was varied from 5% to 25% by weight. Sodium silicate has been used as an additive to study the behavior of the variation of average viscosity of the suspension. A generalized correlation has been developed to predict the average viscosity of suspension in terms of particle diameter of the coal, concentration of coal, viscosity of the suspending medium and the concentration of water. Experimental investigations revealed that coal–oil–water suspensions show an increase in the viscosity with decrease in coal size but with the addition of an additive, the average viscosity tends to decrease initially up to a certain optimum dosages and thereafter it increases with further addition of additives. Two empirical correlations are proposed for average viscosity of the coal–oil–water suspension, μ_sL in terms of physical properties of the solid and viscosity of the suspending medium with and without additives.     

Cenozoic geodynamic evolution of the Andaman–Sumatra subduction margin: Current understanding

The Andaman–Sumatra margin displays a unique set‐up of extensional subduction–accretion complexes, which are the Java Trench, a tectonic (outer arc) prism, a sliver plate, a forearc, oceanic rises, inner‐arc volcanoes, and an extensional back‐arc with active spreading. Existing knowledge is reviewed in this paper, and some new data on the surface and subsurface signatures for operative geotectonics of this margin is analyzed. Subduction‐related deformation along the trench has been operating either continuously or intermittently since the Cretaceous. The oblique subduction has initiated strike–slip motion in the northern Sumatra–Andaman sector, and has formed a sliver plate between the subduction zone and a complex, right‐lateral fault system. The sliver fault, initiated in the Eocene, extended through the outer‐arc ridge offshore from Sumatra, and continued through the Andaman Sea connecting the Sagaing Fault in the north. Dominance of regional plate dynamics over simple subduction‐related accretionary processes led to the development and evolution of sedimentary basins of widely varied tectonic character along this margin. A number of north–south‐trending dismembered ophiolite slices of Cretaceous age, occurring at different structural levels with Eocene trench‐slope sediments, were uplifted and emplaced by a series of east‐dipping thrusts to shape the outer‐arc prism. North–south and east–west strike–slip faults controlled the subsidence, resulting in the development of a forearc basins and record Oligocene to Miocene–Pliocene sedimentation within mixed siliciclastic–carbonate systems. The opening of the Andaman Sea back‐arc occurred in two phases: an early (～11 Ma) stretching and rifting, followed by spreading since 4–5 Ma. The history of inner‐arc volcanic activity in the Andaman region extends to the early Miocene, and since the Miocene arc volcanism has been associated with an evolution from felsic to basaltic composition.     

Biosorptive behaviour of mango leaf powder and rice husk for arsenic(III) from aqueous solutions

The present study deals with the biosorption of As(III) from aqueous solution using mango leaves powder (MLP) and rice husk (RH) in a batch operation. Scanning electron microscopy and Fourier transformation infrared spectrometry analysis shows the surface texture of biosorbents and metal binding of functional groups of before and after biosorption of As(III). The optimum pH was obtained at 7 and 6 with 7 and 6?g/l of dosage of MLP and RH, respectively. The adsorption of As(III) onto MLP and RH was favourably influenced by an increase in temperature. Equilibrium data were well represented by the Freundlich isotherm model. Nitric acid and ethylenediaminetetra acetic acid was found to be a better eluant for the desorption followed by hydrochloric acid and sodium hydroxide of As(III) with a maximum desorption efficiency of 69.5, 48.5 and 79.4, 86.3?%, respectively. The pseudo-second-order kinetic model was found to best fitted of the experimental data over the equilibrium time at 32?h. The positive values of heat of adsorption (23.89?kJ/mol for MLP and 52.26?kJ/mol for RH) indicate the endothermic nature of the adsorption process. The thermodynamic study showed the spontaneous nature of the sorption of As(III) onto MLP and RH.     

Solar modulation of galactic cosmic rays during 19–23 solar cycles

We make a detailed analysis of cross-correlation and time-lag between monthly data of galactic cosmic rays (GCRs) intensity and different solar activity indices (e.g., sunspot number, sunspot area, green coronal Fe line and 10.7 cm solar radio flux) during 19–23 solar cycles. GCRs time-series data from Kiel neutron monitor station and solar data from the last 50 years period, covering five solar cycles (19–23), and alternating solar polarity states (i.e., five A < 0 and four A > 0) have been investigated. We find a clear asymmetry in the cross-correlation between GCRs and solar activity indicators for both odd and even-numbered solar cycles. The time-lags between GCRs and solar parameters are found different in different solar cycles as well as in the opposite polarity states (A < 0 and A > 0) within the same solar cycle. Possible explanations of the observed results are discussed in light of modulation models, including drift effects.     

Evaluation of the intermediate-term periodicities in solar and cosmic ray activities during cycle 23

In this paper we investigate the presence and temporal evolution of galactic cosmic rays (GCRs) time-series and three solar parameters, namely the daily sunspot number, the coronal green line and the 10.7 cm solar radio flux over the period 1996–2003 by the wavelet technique. A number of short- and intermediate-term quasi-periodicities were also detected in both GCR and solar parameters. For the short-term range, we have identified quasi-periods of 16–30 days, 40–55 days, 60–70 days, 80–90 days and 80–100 days. In the case of intermediate range, the significant periods were 120–140 days, 150–170 days, 190–210 days, 240–260 days, ≈1.09 yr. and ≈1.23 yr. The wavelet power spectra show that all the above-mentioned periods are intermittent in nature and occurred in different time-series in different intervals. The result exhibits that the well-known “Rieger period” of (150–160 days) was prominent in both GCR and solar data sets during the ascending phase of cycle 23. Possible reasons behind the observed periods were discussed with the help of previous results and existing numerical models.     

Groundwater flow system in Bengal Delta,Bangladesh revealed by environmental isotopes

A total number of 328 groundwater samples are analysed to evaluate the groundwater flow systems in Bengal Delta aquifers, Bangladesh using environmental isotope (²H, ¹⁸O, ¹³C, ³H, and ¹⁴C) techniques. A well-defined Local Meteoric Water Line (LMWL) δ²H = 7.7 δ¹⁸O + 10.7 ‰ is constructed applying linear correlation analyses to the monthly weighted rainfall isotopic compositions (δ¹⁸O and δ²H). The δ¹⁸O and δ²H concentrations of all groundwater samples in the study area are plotted more or less over the LMWL, which provides compelling evidence that all groundwaters are derived from rainfall and floodwater with a minor localized evaporation effects for the shallow groundwaters. Tritium concentration is observed in 40 samples out of 41 with values varying between 0.3 and 5.0 TU, which represents an evidence of young water recharge to the shallow and intermediate aquifers. A decreasing trend of ¹⁴C activity is associated with the heavier δ¹³C values, which indicates the presence of geochemical reactions affecting the ¹⁴C concentration along the groundwater flow system. Both vertical and lateral decrease of ¹⁴C activity toward down gradient show the presence of regional groundwater flow commencing from the unconfined aquifers, which discharges along the coastal regions. Finally, shallow, intermediate, and deep groundwater flow dynamics has revealed in the Bengal Delta aquifers, Bangladesh.