Suspended sediment yield estimation using genetic algorithm-based artificial intelligence models: case study of Mahanadi River,India

The estimation of sediment yield is important in design, planning and management of river systems. Unfortunately, its accurate estimation using traditional methods is difficult as it involves various complex processes and variables. This investigation deals with a hybrid approach which comprises genetic algorithm-based artificial intelligence (GA-AI) models for the prediction of sediment yield in the Mahanadi River basin, India. Artificial neural network (ANN) and support vector machine (SVM) models are developed for sediment yield prediction, where all parameters associated with the models are optimized using genetic algorithms simultaneously. Water discharge, rainfall and temperature are used as input to develop the GA-AI models. The performance of the GA-AI models is compared to that of traditional AI models (ANN and SVM), multiple linear regression (MLR) and sediment rating curve (SRC) method for evaluating the predictive capability of the models. The results suggest that GA-AI models exhibit better performance than other models.     

Role of reservoirs in sustained seismicity of Koyna-Warna region—a statistical analysis

Koyna-Warna region in western India is a globally recognized site of reservoir-triggered seismicity near the Koyna and Warna reservoirs. The region has been reported with several M?>?5 earthquakes in the last five decades including M6.3 Koyna earthquake which is considered as the largest triggered earthquake worldwide. In the present study, a detailed statistical analysis has been done for long period earthquake catalogues during 1968–2004 of MERI and 2005–2012 of CSIR-NGRI to find out the spatio-temporal influence of the Koyna and Warna reservoirs impoundment on the seismicity of the region. Depending upon the earthquake clusters, we divided the region into three different zones and performed power spectrum and singular spectrum analysis (SSA) on them. For the time period 1983–1995, the earthquake zone near the Warna reservoir; for 1996–2004, the earthquake zone near the Koyna reservoir; and for 2005–2012, the earthquake zone near the Warna reservoir found to be influenced by the annual water level variations in the reservoirs that confirm the continuous role of both the reservoirs in the seismicity of the Koyna-Warna region.     

Rock-physics forward modelling to predict seismic behaviour: A case study for exploration target in Mahanadi basin,East Coast of India

One of the major aspects of rock-physics forward modelling is to predict seismic behaviour at an undrilled location using drilled well data. It is important to model the rock and fluid properties away from drilled wells to characterize the reservoir and investigate the root causes of different seismic responses. Using the forward modelling technique, it is possible to explain the amplitude responses of present seismic data in terms of probable rock and reservoir properties. In this context, rock-physics modelling adds significant values in the prospect maturation process by reducing the risk of reservoir presence in exploration and appraisal phases. The synthetic amplitude variation with offset gathers from the forward model is compared with real seismic gathers to ensure the fidelity of the existing geological model. ‘Prospect A’ in the study area has been identified from seismic interpretation, which was deposited as slope fan sediments in Mahanadi basin, East Coast of India. The mapped prospect has shown class-I amplitude variation with offset response in seismic without any direct hydrocarbon indicator support. The existing geological model suggests the presence of an excellent gas reservoir with proven charge access from the fetch area, moderate porosity and type of lithology within this fan prospect. But, whether the seismic response from this geological model will exhibit a class-I amplitude variation with offset behaviour or ‘dim spot’ will be visible; the objective of the present study is to investigate these queries. A rock-physics depth trend analysis has been done to envisage the possibilities of class-I reservoir in ‘Prospect A’. Forward modelling, using a combination of mechanical and chemical compaction, shows the synthetic gas gathers at ‘Prospect A’, which are class I in nature. The study has also depicted 2D forward modelling using lithology and fluid properties of discovery well within similar stratigraphy to predict whether ‘dim spot’ will be seen in seismic. The estimated change in synthetic amplitude response has been observed as ∼5% at contact, which suggests that the changes will not be visible in seismic. The study connects the existing geological model with a top-down seismic interpretation using rock-physics forward modelling technique to mature a deep-water exploratory prospect.     

The Pleiades apex and its kinematical structure

A study of cluster characteristics and internal kinematical structure of the middle-aged Pleiades open star cluster is presented. The individual star apexes and various cluster kinematical parameters including the velocity ellipsoid parameters are determined using both Hipparcos and Gaia data. Modern astrometric parameters were taken from the Gaia Data Release 1 (DR1) in combination with the Radial Velocity Experiment Fifth Data Release (DR5). The necessary set of parameters including parallaxes, proper motions and radial velocities are used for \(n=17\) stars from Gaia DR1+RAVE DR5 and for \(n=19\) stars from the Hipparcos catalog using SIMBAD data base. Single stars are used to improve accuracy by eliminating orbital movements. RAVE DR5 measurements were taken only for the stars with the radial velocity errors not exceeding \(2~\mbox{km}/\mbox{s}\). For the Pleiades stars taken from Gaia, we found mean heliocentric distance as \(136.8 \pm 6.4\) pc, and the apex position is calculated as: \(A_{CP}=92^{\circ }.52\pm 1^{\circ }.72\), \(D_{CP}=-42^{\circ }.28\pm 2^{\circ }.56\) by the convergent point method and \(A_{0}=95^{\circ }.59\pm 2^{\circ }.30\) and \(D_{0}=-50^{\circ }.90\pm 2^{\circ }.04\) using AD-diagram method (\(n=17\) in both cases). The results are compared with those obtained historically before the Gaia mission era.     

Physical Properties of Umbral Dots Observed in Sunspots: A <Emphasis Type="Italic">Hinode</Emphasis> Observation

Umbral dots (UDs) are small-scale bright features observed in the umbral part of sunspots and pores. It is well established that they are manifestations of magnetoconvection phenomena inside umbrae. We study the physical properties of UDs in different sunspots and their dependence on decay rate and filling factor. We have selected high-resolution, G-band continuum filtergrams of seven sunspots from Hinode to study their physical properties. We have also used Michelson Doppler Imager (MDI) continuum images to estimate the decay rate of selected sunspots. An identification and tracking algorithm was developed to identify the UDs in time sequences. The statistical analysis of UDs exhibits an averaged maximum intensity and effective diameter of 0.26 \(I_{\mathrm{QS}}\) and 270 km. Furthermore, the lifetime, horizontal speed, trajectory length, and displacement length (birth–death distance) of UDs are 8.19 minutes, 0.5 km?s^?1, 284 km, and 155 km, respectively. We also find a positive correlation between intensity–diameter, intensity–lifetime, and diameter–lifetime of UDs. However, UD properties do not show any significant relation with the decay rate or filling factor.     

Lissajous motion near Lagrangian point $$ L_{2} $$ in radial solar sail

An attempt was made to study the dynamics close to the collinear libration point \( L_{2} \) of the radial solar sail circular-restricted three-body problem (RSCRTBP) in the Sun–Jupiter System, where the third massless body is a solar sail. We analyse the qausi-periodic (Lissajous solutions) orbits about the libration point \( L_{2} \). The Lindstedt–Poincaré approximation for the qausi-periodic orbits was used for numerical simulations. We utilized linear quadratic regulator (LQR) to stabilize the full nonlinear model, and linear state-feedback controller was designed to stabilize the trajectory.     

Large Area X-Ray Proportional Counter (LAXPC) Instrument on AstroSat and Some Preliminary Results from its Performance in the Orbit

Large area X-ray propositional counter (LAXPC) instrument on AstroSat is aimed at providing high time resolution X-ray observations in 3–80 keV energy band with moderate energy resolution. To achieve large collecting area, a cluster of three co-aligned identical LAXPC detectors, is used to realize an effective area in access of \({\sim }6000\,\hbox {cm}^{2}\) at 15 keV. The large detection volume of the LAXPC detectors, filled with xenon gas at \({\sim }\)2 atmosphere pressure, results in detection efficiency greater than 50%, above 30 keV. In this article, we present salient features of the LAXPC detectors, their testing and characterization in the laboratory prior to launch and calibration in the orbit. Some preliminary results on timing and spectral characteristics of a few X-ray binaries and other type of sources, are briefly discussed to demonstrate that the LAXPC instrument is performing as planned in the orbit.     

SPIN: An Inversion Code for the Photospheric Spectral Line

Inversion codes are the most useful tools to infer the physical properties of the solar atmosphere from the interpretation of Stokes profiles. In this paper, we present the details of a new Stokes Profile INversion code (SPIN) developed specifically to invert the spectro-polarimetric data of the Multi-Application Solar Telescope (MAST) at Udaipur Solar Observatory. The SPIN code has adopted Milne–Eddington approximations to solve the polarized radiative transfer equation (RTE) and for the purpose of fitting a modified Levenberg–Marquardt algorithm has been employed. We describe the details and utilization of the SPIN code to invert the spectro-polarimetric data. We also present the details of tests performed to validate the inversion code by comparing the results from the other widely used inversion codes (VFISV and SIR). The inverted results of the SPIN code after its application to Hinode/SP data have been compared with the inverted results from other inversion codes.     

Potential environmental pollution hazards by coal based power plant at Jhansi (UP) India

Coal, a fossil fuel, is the largest source of energy for the generation of electricity in India. In order to study the potential environmental hazards by coal based power plants, particulate matters were collected using Stack Monitoring Kit and gaseous pollutants by Automatic Flue Gas Analyzer. The morphological and chemical properties, mineralogical composition and particle size distributions have been determined by SEM–EDX, XRD and CILAS. The data revealed the presence of particulate matters, SO₂, NOx in the range of 236–315, 162–238, 173–222 mg/Nm³ respectively. The emission of CO₂ was in the range of 43,004–60,115 Nm³/h with an average of 52,830 Nm³/h. Among the elements, Fe > Mn > Al > Zn > B > Ni > Cr > Cu were present in substantially higher proportion than Pb > Mo > Cd > Se > As > Hg. It was found that most of the elements were concentrated on fly ash surface rather than coal, bottom ash and pond ash. This variation may be attributed to the fineness of fly ash particles with large surface ratio to mass. Mineralogical studies of coal and fly ash by X-ray diffraction revealed the presence of mullite, quartz, cristobalite and maghemite. Presence of mullite and quartz found in fly ash indicate the conversion of complex minerals to mullite and quartz at high temperature. Transfer Coefficient was calculated to determine the ratio of the enrichment of trace elements in fly or bottom ash with respect to coal and pond ash.     

Geochemistry of aerosols of northwestern part of India adjoining the Thar desert

The northwestern part of India, which includes the Thar desert on its western side, is a hot and arid region with intense aeolian activity and transport of aerosols by the prevailing SW-W summer winds. Different size fractions of aerosols (free fall = FF, suspended particulate matter = SPM, PM₁₀ = <10 μm, and >10 μm) from air were sampled simultaneously at four locations along the dominant wind trajectory for ∼600 km. These aerosols and deposited surface sediments were characterized for their texture, mineralogy and geochemistry including REE and Sr isotopes. Within each size fraction, a bimodal distribution of grain size was observed. Quartz is the dominant mineral followed by K-feldspar, mica, calcite, chlorite and plagioclase. Garnet, amphibole, titanite and zircon are some of the identified heavy minerals. All samples, particularly those collected during summer, are compositionally homogeneous, including in their REE geochemistry, and are similar to average upper continental crust (UCC). However, in the winter aerosol samples, large deviations from the UCC composition are observed. This is attributed to meteorological parameters such as low wind velocity and temperature inversions in the winter season. During winter, secondary non-silicate and anthropogenic materials become important sources to Ca, Na, Mg, K, Ba and Ni budget; also reduction in the uptake and transport of heavy minerals lowered the concentration of Ti, Zr, Y, Cr, and REE in the aerosols. Geochemical coherence among aerosols, deposited surface sediments and the Thar sands, and the limited Sr isotopic data indicate that the Thar sediments and certain lithotectonic units of the Himalayan orogen are the proximal and distal crustal sources, respectively, for the aerosols in this region. Prevailing aridity and strong summer winds, and the presence of river alluvium in the Thar act together to transport silt rich dust, the removal of which could be a possible mechanism of ongoing desertification.