Productivity Analysis of Draglines Operating in Horizontal and Vertical Tandem Mode of Operation in a Coal Mine—A Case Study     

Piyush Rai  Umakant Yadav  Ashok Kumar 《Geotechnical and Geological Engineering》2011,29(4):493-504

The tandem operation of draglines is in use in some of the major Indian opencast coalmines owing to the favourable geo-mining conditions, technical suitability, efficiency and economic viability. In view of the importance of tandem operation, the present study has been undertaken in a large Indian opencast coalmine in order to critically investigate the horizontal and vertical tandem operation of draglines on moderately strong and high sandstone benches (35–42 m), overlying a 15–18 m thick coal seam. The study has revealed that although the preparation of balancing diagram for planning of dragline operations is the first and the most important step, its actual implementation is equally important. Marked discrepancies in the productivity parameters as envisaged by the balancing diagram and as observed in the field studies, have been investigated and reported. The study also propounds the importance of appraisal of dragline productivity parameters, such as, cycle time, swing angle, seating position, availability, utilization, etc., in the field scale. Irrespective of the mode of operation (horizontal or vertical tandem), the study moots the concept of computation of the weighted cycle time and overall cycle time vis-à-vis swing angle variation for the draglines operating in field. The results drawn from the case study have been discussed in terms of cycle time computations, annual output computation and evaluation of earthmoving efficiency for the horizontal and vertical tandem modes of operation.  相似文献   

X-ray crystallography and mineral chemistry of bastnaesite from Kanigiri granite,Prakasam district,Andhra Pradesh,India     

Yamuna Singh  G. Nagendra Babu  R. Viswanathan  M. Sai Baba  A. K. Rai  P. S. Parihar 《Central European Journal of Geosciences》2014,6(4):492-505

The authors report the results of X-ray diffraction (XRD) and geochemical studies on bastnaesites (lanthanum cerium fluoro-carbonate) hosted in alkali Kanigiri Granite of the Prakasam district in Andhra Pradesh, India. The XRD pattern of the investigated bastnaesite displays sharply-defined reflections. The observed d-spacings of the bastnaesite are in very close agreement with those published for bastnaesite standard in International Centre for Diffraction Data (ICDD) Card No. 11–340. The calculated unit cell parameters (a _o ; c _o ) and unit cell volume (V) of the studied bastnaesite (a _o 7.1301–7.1413 Å, c _o 9.7643–9.7902Å and V 429.8940–432.3875 ų) are almost equal to values published for bastnaesite standard (c _o 7.1290 Å, c _o 9.7744 Å and V 430.19 ų) in the relevant data card. Geochemical data of bastnaesite reveals high content of Ce (mean 27.22%) followed by La (mean 16.82%), Nd (mean 6.12%) and Pr (mean 1.91%). Compared to light REE (LREE) content (mean 437165 ppm), heavy REE (HREE) content (mean 5867 ppm) is drastically low, with unusually high LREE/HREE ratio (mean 80). The chondrite-normalised plot also exhibits drastic enrichment of LREE relative to HREE with pronounced negative Euanomaly (mean Eu/Eu* = 0.15). High (LREE) _N / (HREE) _N , (La/Lu) _N , (La/Yb) _N and (Ce/Yb) _N ratios reveal higher fractionation of LREE relative to HREE. The rare earth element (REE) contents of the studied bastnaesite are very close to REE contents of bastnaesite hosted in alkali syenite from Madagascar. The presence of bastnaesite in Kanigiri Granite and soils derived from it enhances the scope of further exploration for bastnaesite in several bodies of alkaline rocks and alkali granitoids present along the eastern margins of the Cuddapah basin, Andhra Pradesh.  相似文献   

On the out of phase appearance of large-scale diffuse magnetic field of the Sun with respect to sunspots     

Mausumi Dikpati  Arnab Rai Choudhuri 《Astrophysics and Space Science》1996,243(1):169-172

We assume the large-scale diffuse magnetic field of the Sun to originate from the poloidal component of a dynamo operating at the base of the convection zone, whereas the sunspots are due to the toroidal component. The evolution of the poloidal component is studied to model the poleward migration of the diffuse field seen on the solar surface and the polar reversal at the time of sunspots maxima (Dikpati and Choudhuri 1994, 1995).  相似文献   

Distinguishing Mountain Front and Mountain Block Recharge in an Intermontane Basin of the Himalayan Region     

Tanveer Dar  Nachiketa Rai  Sudhir Kumar 《Ground water》2022,60(4):488-495

Intermontane basin aquifers worldwide, particularly in the Himalayan region, are recharged largely by the adjoining mountains. Recharge in these basins can occur either by water infiltrating from streams near mountain fronts (MFs) as mountain front recharge (MFR) or by sub-surface mountain block infiltration as mountain block recharge (MBR). MFR and MBR recharge are challenging to distinguish and are least quantified, considering the lack of extensive understanding of the hydrological processes in the mountains. This study used oxygen and hydrogen isotopes (δ¹⁸O and δ²H), electrical conductivity (EC) data, hydraulic head, and groundwater level data to differentiate MFR and MBR. Groundwater level data provide information about the groundwater-surface water interactions and groundwater flow directions, whereas isotopes and EC data are used to distinguish and quantify different recharge sources. The present methodology is tested in an intermontane basin of the Himalayan region. The results suggest that karst springs (KS) and deep groundwater (DGW) recharge are dominated by snowmelt (47% ± 10% and 46% ± 9%) as MBR from adjacent mountains, insignificantly affected by evaporation. The hydraulic head data and isotopes indicate Quaternary shallow groundwater (SGW) aquifer system recharge as MFR of local meteoric water with significant evaporation. The results indicate several flow paths in the aquifer system, a local flow for KS, intermediate flow for SGW, and regional flow for DGW. The findings will significantly impact water resource management in the area and provide vital baseline knowledge for sustainable groundwater management in other Himalayan intermontane basins.  相似文献   

Groundwater Quality assessment using Water Quality Index (WQI) in parts of Varanasi District,Uttar Pradesh,India     

Abhishek Kumar Chaurasia  H. K. Pandey  S. K. Tiwari  Ram Prakash  Prashant Pandey  Arjun Ram 《Journal of the Geological Society of India》2018,91(1):76-80

Either naturally occurring process or human activities may have a significant impact on the quality of sub-surface waters which further limit its use. Multivariate statistical techniques such as factor analysis (FA), cluster analysis (CA) were applied for the evaluation of spatial variations and the interpretation of ground water quality data around Bacheli and Kirandul area. The major anions, cations and heavy metals were determined for each of 20 samples collected in pre-monsoon seasons. Hydrochemical parameters like EC, pH, TDS, TH, TA, Na⁺, K⁺, Ca²⁺, Cl^-, F^-, SO₄^2-, As, Sb, Se, Pb, Cd, Zn, Cu were estimated in pre monsoon and post monsoon seasons. Different geochemical controls of the investigated parameters were also assessed. Factor 1 explains 33.47% of the total variance and indicates atmospheric controls and silicate mineral weathering process. Factor 2 explains 13.83% of total variance, indicating silicate mineral weathering process resulting in elevated pH. Generally, water types tend towards magnesium-bicarbonate-chloride.  相似文献   

Delineation of groundwater resources using electrical resistivity tomography     

S. Thiagarajan  S. N. Rai  Dewashish Kumar  A. Manglik 《Arabian Journal of Geosciences》2018,11(9):212

Chandrabhaga basin of the Nagpur district is a part of the drought prone Vidarbha region of Maharashtra, India. This region is facing acute shortage of water for drinking and irrigation purposes. The basin is located at the eastern fringe of the Deccan traps consisting of volcanic rocks. Presently, dug wells penetrating composite layers of the weathered mantle and highly fractured rocks overlying stratified basaltic lava flows are the main source of water supply. However, water available in the dug wells is inadequate to meet the ever increasing demand for water causing considerable economic losses to the farming community. In this work, we present the results of an electrical resistivity tomography (ERT) survey carried out in the basin for the delineation of groundwater potential zones. Validity of the hydrogeological setup obtained from the ERT results has been confirmed by bore well drillings at two investigated sites. The study demonstrates the efficacy of the ERT technique in delineation of groundwater potential zones in the hydrogeologically complex basaltic terrain of the Deccan traps.  相似文献   

Solar activity forecast with a dynamo model     

Jie Jiang  Piyali Chatterjee  Arnab Rai Choudhuri 《Monthly notices of the Royal Astronomical Society》2007,381(4):1527-1542

Although systematic measurements of the Sun's polar magnetic field exist only from mid-1970s, other proxies can be used to infer the polar field at earlier times. The observational data indicate a strong correlation between the polar field at a sunspot minimum and the strength of the next cycle, although the strength of the cycle is not correlated well with the polar field produced at its end. This suggests that the Babcock–Leighton mechanism of poloidal field generation from decaying sunspots involves randomness, whereas the other aspects of the dynamo process must be reasonably ordered and deterministic. Only if the magnetic diffusivity within the convection zone is assumed to be high (of order  10¹² cm² s⁻¹  ), we can explain the correlation between the polar field at a minimum and the next cycle. We give several independent arguments that the diffusivity must be of this order. In a dynamo model with diffusivity like this, the poloidal field generated at the mid-latitudes is advected toward the poles by the meridional circulation and simultaneously diffuses towards the tachocline, where the toroidal field for the next cycle is produced. To model actual solar cycles with a dynamo model having such high diffusivity, we have to feed the observational data of the poloidal field at the minimum into the theoretical model. We develop a method of doing this in a systematic way. Our model predicts that cycle 24 will be a very weak cycle. Hemispheric asymmetry of solar activity is also calculated with our model and compared with observational data.  相似文献   

Weak waves in radiating gases     

Arisudan Rai  J. P. Vishwakarma  Sudhir Kumar 《Astrophysics and Space Science》1990,167(2):245-252

The propagation of weak waves has been studied by taking into account the influence of thermal radiative field. The singular surface theory is used to determine the modes of wave propagation and to evaluate the behaviour at the wave head. The effects of thermal radiation, conduction and the initial wave front curvature on the nonlinear breaking of weak waves are discussed. It is concluded that, under the thermal radiation effects, the shock wave formation is either disallowed or delayed. On the other hand, the thermal conduction effects destabilize the waves.  相似文献   

Systematic precipitation redistribution following a strong hurricane landfall     

Paul W. Miller  Thomas L. Mote  Abhishek Kumar  Deepak R. Mishra 《Theoretical and Applied Climatology》2020,139(3):861-872

The 2017 and 2018 Atlantic hurricane seasons poignantly illustrated the dangers tropical cyclones pose to US, Central American, and Caribbean coastlines. In particular, Hurricane Maria inflicted widespread damage, including catastrophic defoliation, to Puerto Rico, altering surface heat fluxes and possibly modifying precipitation patterns. This study assesses whether defoliation-driven changes to surface energy fluxes redistribute precipitation in the months following a powerful hurricane landfall. Remote sensing analyses of Maria-related vegetation reduction and recovery from Puerto Rico were adapted to the Georgia coastline. In this novel methodology, the resulting landscape evolution, characterized by an instantaneous vegetation reduction with a gradual recovery, was assimilated into the Weather Research and Forecasting model at a convection-allowing a 3-km grid spacing for the 1 June–1 August 2017 period. The experiment revealed that Maria-scale defoliation reduced precipitation by 14% during the month following landfall within a 50 × 50 km zone containing the hypothetical landfall location. A maximum deficit of 20.0% was reached 4 weeks after landfall. For June 2017, the modeled 14% deficit would have shifted the precipitation total from the 61st to the 47th percentile for years 1981–2016. Meanwhile, precipitation totals were unchanged on the domain scale. The near-landfall drying was also evident in three less-severe defoliation simulations, suggesting that systematic precipitation redistribution near the landfall location is possible following storms considerably weaker than Hurricane Maria. Analyses of the temperature and wind fields suggest that coastal kinematic flow is altered by the introduction of a thermally driven pressure gradient in the defoliated zone.  相似文献   

Era-interim Forced Simulation of the Indian Summer Monsoon     

Lav Kumar  Nishtha Agrawal  Abhishek K. Rai  Shailendra K. Mishra  Vinay S. Pandey 《Marine Geodesy》2013,36(6):558-574

Abstract

In the present study, mean rainfall for the months of June-July-August-September (JJAS) during summer monsoon is simulated over India and its adjoining regions for a period between 1982 and 2006. The study was carried out using Regional Climate Model (RegCM) version 4.6 at a resolution of 25?km. The simulated mean JJAS monsoon rainfall was validated against the observational IMD data. Comparison of JJAS seasonal mean summer rainfall for the first decade 1982–1991, with the later decade 1997–2006 indicate that the intensity of rainfall increases over Indian land-mass during the later decade under the forced conditions of Era-Interim. The observed JJAS mean rainfall indicates two maximum rainfall areas i.e. the Western Ghats and the Himalayan region. A significant bias is observed in the central and Jammu and Kashmir (J&K) region. The JJAS mean seasonal surface air temperature distribution at 0.25?×?0.25-degree grids resolution shows a decreasing trend of temperature over the Indian landmass.  相似文献