Review of Cuttability Indices and A New Rockmass Classification Approach for Selection of Surface Miners     

Kaushik Dey  A. K. Ghose 《Rock Mechanics and Rock Engineering》2011,44(5):601-611

Rock excavation is carried out either by drilling and blasting or using rock-cutting machines like rippers, bucket wheel excavators, surface miners, road headers etc. Economics of mechanised rock excavation by rock-cutting machines largely depends on the achieved production rates. Thus, assessment of the performance (productivity) is important prior to deploying a rock-cutting machine. In doing so, several researchers have classified rockmass in different ways and have developed cuttability indices to correlate machine performance directly. However, most of these indices were developed to assess the performance of road headers/tunnel-boring machines apart from a few that were developed in the earlier days when the ripper was a popular excavating equipment. Presently, around 400 surface miners are in operation around the world amongst which, 105 are in India. Until now, no rockmass classification system is available to assess the performance of surface miners. Surface miners are being deployed largely on trial and error basis or based on the performance charts provided by the manufacturer. In this context, it is logical to establish a suitable cuttability index to predict the performance of surface miners. In this present paper, the existing cuttability indices are reviewed and a new cuttability indexes proposed. A new relationship is also developed to predict the output from surface miners using the proposed cuttability index.  相似文献   

Possible Effect of the Earth’s Inertial Induction on the Orbital Decay of LAGEOS     

Ujjal Dey  Samanwita Kar  Amitabha Ghosh 《Journal of Astrophysics and Astronomy》2016,37(3):17

The theory of velocity dependent inertial induction, based upon extended Mach’s principle, has been able to generate many interesting results related to celestial mechanics and cosmological problems. Because of the extremely minute magnitude of the effect its presence can be detected through the motion of accurately observed bodies like Earth satellites. LAGEOS I and II are medium altitude satellites with nearly circular orbits. The motions of these satellites are accurately recorded and the past data of a few decades help to test many theories including the general theory of relativity. Therefore, it is hoped that the effect of the Earth’s inertial induction can have any detectable effect on the motion of these satellites. It is established that the semi-major axis of LAGEOS I is decreasing at the rate of 1.3 mm/d. As the atmospheric drag is negligible at that altitude, a proper explanation of the secular change has been wanting, and, therefore, this paper examines the effect of the Earth’s inertial induction effect on LAGEOS I. Past researches have established that Yarkovsky thermal drag, charged and neutral particle drag might be the possible mechanisms for this orbital decay. Inertial induction is found to generate a perturbing force that results in 0.33 mm/d decay of the semi major axis. Some other changes are also predicted and the phenomenon also helps to explain the observed changes in the orbits of a few other satellites. The results indicate the feasibility of the theory of inertial induction i.e. the dynamic gravitation phenomenon of the Earth on its satellites as a possible partial cause for orbital decay.  相似文献   

kHz QPOs in LMXBs, relations between different frequencies and compactness of stars     

Taparati GangopadhyayXiang-Dong Li  Subharthi RayMira Dey  Jishnu Dey 《New Astronomy》2012,17(1):43-45

We suggest that the mass of four compact stars SAX J1808.4-3658, KS 1731-260, SAX J1750.8-2900 and IGR J17191-2821 can be determined from the difference in the observed kiloHertz quasi periodic oscillations (kHz QPO-s) of these stars. The stellar radius is very close to the marginally stable orbit R_ms as predicted by Einstein’s general relativity. It may be noted that the first of these stars was suggested to be a strange star more than a decade back by Li et al. (1999a) from the unique millisecond X-ray pulsations with an accurate determination of its rotation period. It showed kHz QPO-s eight years back and so far it is the only set that has been observed. This is the first time we give an estimate of the mass of the star and of three other compact stars in low-mass X-ray binaries using their observed kHz QPO-s.  相似文献   

Vegetation covers as indicator of seismo-tectonic environment: an integrated geophysical study in north Baromura hill, India     

Sudip Dey  Prasamita Sarkar 《Environmental Earth Sciences》2012,67(8):2469-2481

Spatial distributions of vegetation cover are closely related to topographical characters like slope, steepness, soil types, elevations, etc. In seismo-tectonic regions fault lines or tectonic lineaments are the most prominent surface signatures that can be reflected by vegetation distribution as tectonic displacement causes the change of topographical parameters. In the present study a part of northern Baromura hill (between 23º 42′ N to 23º49 N latitudes and 91º30 E to 91º36 E longitudes), which is considered as an active seismo-tectonic region of Tripura as well as northeast India, was selected for assessing the relationship between spatial variation of plant cover and topography. Geologically, Baromura hill is a north–south extended fold belt and formed by late Tertiary to Quaternary depositions. Evidences show that tectonic events played very important role in landform evolution of this area during the geological past. In this research an extensive fieldwork was conducted in the study area to understand the geomorphic and vegetation signatures and their environmental relationships. Various spectral resolutions of Landsat ETM+ were used for digital analysis. To analyse the vegetation character of this area digital operation was done within the spectral range 0.63–1.75 μm. Band 4 and band 3 were used for NDVI operation. Band 5 or mid-wave infrared band was classified in unsupervised mode to understand the range of plant water in the study area. Overlay operation with those operated images shows the spatial distribution pattern of vegetation cover indicates the landform condition. Three clear tectonic lineaments (faults) were detected from the digital study in on the northern part Baromura hill. Structural conditions of those fault lines were verified by geo-electrical survey during fieldwork. GPS tool was used for fixing the ground control points. Resistivity characters of the study area assessed from VES profile strongly supports that vegetation cover analysis from remotely sensed data within 0.63–1.75 μm spectral ranges can be a very useful tool for detecting surface tectonic signatures of the landform.  相似文献   

Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin,Sonbhadra district,Uttar Pradesh,India     

N. Janardhana Raju  Sangita Dey  Wolfgang Gossel  Peter Wycisk 《水文科学杂志》2013,58(7):1433-1452

Abstract

Around 9000 inhabitants in the Panda River basin, Sonbhadhra District, Uttar Pradesh, India, are vulnerable to a “silent” dental and skeletal fluorosis from groundwater consumption. The fluoride source and seasonal groundwater quality variation were studied by collecting 65 groundwater samples in the Upper Panda River basin. Major rock types are phyllites and granite gneissic rocks. Fluoride concentrations are in the range 0.4–5.6 mg/L in the pre-monsoon season and 0.1–6.7 mg/L in the post-monsoon season. Fluor-apatite and biotite mica in the granite gneissic rock were identified as the main provenance of fluoride in the groundwater through water–rock interactions. Due to precipitation of calcium, soils become alkaline with high contents of sodium; these conditions allow fluoride to accumulate in water. According to risk index calculations, the fluoride-affected villages were shown to fall in the fluoride risk zone (with a risk index of around 1.7). On the basis of mineral stability diagrams, groundwater from the weathered and fractured aquifers appears to be stable within the kaolinite field, suggesting weathering of silicate minerals. The groundwater is chemically potable and suitable for domestic and agricultural purposes, except for a few wells in the southern region that are contaminated with high amounts of fluoride.

Editor D. Koutsoyiannis

Citation Raju, N.J., Dey, S., Gossel, W., and Wycisk, P., 2012. Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin, Sonbhadra District, Uttar Pradesh, India. Hydrological Sciences Journal, 57 (7), 1433–1452.  相似文献   

Wide-angle linear forward modelling of synthetic seismograms     

A. Dey  A. Gisolf 《Geophysical Prospecting》2007,55(5):707-718

We address the issue of linearity and scale dependence in forward modelling of seismic data from well logs, for large ray parameters, wide angles or large offsets. We present a forward model, within the context of seismic‐to‐well matching, that is linearized in the elastic properties of the earth. This model preserves linearity at large ray parameters and can handle fine‐layering effects such as induced anisotropy. Starting from a low‐contrast small‐ray‐parameter model, we extend it to a large‐ray‐parameter model by fully linearizing the elastic‐property contrasts. Overall linearity of the forward model is extended by partitioning the compressional‐wave and shear‐wave velocity fields into two fundamental scales: a kinematic scale that governs wavefield propagation effects and a dynamic scale that governs wavefield scattering effects. This analysis reveals that the standard practice in forward modelling of strongly filtering the ratio of compressional‐wave velocity to shear‐wave velocity is well founded in the underlying physics. The partitioning of the velocity fields also leads naturally to forward modelling that accounts fully for stretch effects, to resolution of the angle‐of‐incidence versus ray‐parameter dichotomy in seismic‐amplitude analysis, and to full accounting for induced anisotropy and dispersion effects due to fine‐layering of isotropic media. With the onset of routine long‐offset acquisition and the compelling need to optimize asset management in order to maximize reserve recovery, this forward model recognizes the physics of seismic wave propagation and enables a more complete exploitation of amplitude information in pre‐critical seismic data.  相似文献   

A new incompatible mode element with selective mass scaling for saturated soil dynamics     

P. Mira  A. S. Benítez  M. Pastor  J. A. Fernández Merodo 《Acta Geotechnica》2018,13(2):267-282

It is a well-known fact that addressing hydromechanical problems in saturated soils with the finite element method and equal-order interpolation formulations in displacements and pore pressures produces unstable results. Classically, stabilization has been achieved by increasing the interpolation degree of displacement with respect to pore pressure, hence fulfilling the Babuska–Brezzi condition. However, the use of quadratic elements involves high computational costs. From that point of view, the use of stabilized low-order elements is a more desirable option. Much research has been carried out in different directions in the stabilization of low-order formulations for saturated soils in quasistatic conditions, among others with the technique based on strain field enhancement through internal degrees of freedom. This article presents an alternative displacement–pore pressure formulation for saturated soil dynamics based on the enhancement of the displacement field through incompatible modes.  相似文献   

Nagaur — tertiary interface under Punjab-Haryana semi-desertic plains in western India     

R. C. Dey 《Journal of the Geological Society of India》2009,74(1):131-137

The subsurface Nagaur Basin in northwest Haryana and southwest Punjab hosts evaporite sequence, conformably overlain by Nagaur red beds and grey beds. A polymictic conglomerate intervenes the Nagaur sequence and the overlying Tertiary sequence. The focus is on the new finds of (i) distinctive ‘grey beds’ overlying ubiquitous red beds, (ii) ‘Malout conglomerate and grit’ horizon (Palaeocene-Miocene) marking an unconformity over the Nagaur Group (early Cambrian) and (iii) ‘entrapped gas and dried-up leaves/carbonaceous flakes’ in the conglomerate unit and succeeding Tertiary rocks. Palaeoenvironmental significance has been discussed. The Nagaur ‘red beds’ has been likened to ‘continental red beds’ of Schreiber (1978) and ‘reworked red beds’ of Krynine (1949). The ‘grey beds’ are channel fillings, fresh material having been derived from fresh cuttings by streams/rivers following structural grains in the Aravalli landscape where the interfluves provided weathered (oxidised) materials for the red beds. Association of continental red beds and grey beds is known in the Newark Series (Triassic) of the Eastern United States and the Keweenawan ‘late Precambrian’ of the Lake Superior region.  相似文献   

TeV neutrinos and gamma-rays from pulsars     

A. Bhadra  R. K. Dey 《Monthly notices of the Royal Astronomical Society》2009,395(3):1371-1375

Recent studies suggest that pulsars could be strong sources of TeV muon neutrinos provided positive ions are accelerated by pulsar polar caps to PeV energies. In such a situation, muon neutrinos are produced through the Δ-resonance in interactions of pulsar-accelerated ions with its thermal radiation field. High-energy gamma-rays should also be produced simultaneously in pulsar environment as both charged and neutral pions are generated in the interactions of energetic hadrons with the ambient photon fields. Here, we estimate TeV gamma-ray flux at the Earth from a few nearby young pulsars. When compared with the observations, we find that proper consideration of the effect of polar cap geometry in flux calculation is important. Incorporating such an effect, we obtain the (revised) event rates at the Earth due to a few potential nearby pulsars. The results suggest that pulsars are unlikely to be detected by the upcoming neutrino telescopes. We also estimate TeV gamma-ray and neutrino fluxes from pulsar nebulae for the adopted model of particle acceleration.  相似文献   

Constrained simulations of the local universe – II. The nature of the local Hubble flow     

Luis A. Martinez-Vaquero  Gustavo Yepes  Yehuda Hoffman  Stefan Gottlöber  Mira Sivan 《Monthly notices of the Royal Astronomical Society》2009,397(4):2070-2080

Using a suite of N -body simulations in different cold dark matter (CDM) scenarios, with cosmological constant (ΛCDM) and without (OCDM, SCDM), we study the Hubble flow (σ_H) in Local Volumes (LV) around Local Group (LG) like objects found in these simulations, and compare the numerical results with the most recent observations. We show that ΛCDM and OCDM models exhibit the same behaviour of σ_H. Hence, we demonstrate that the observed coldness of the Hubble flow is not likely to be a manifestation of the dark energy, contrary to previous claims. The coldness does not constitute a problem by itself but it poses a problem to the standard ΛCDM model only if the mean density within the LV is greater than twice the mean matter cosmic density. The lack of blueshifted galaxies in the LV, outside of the LG can be considered as another manifestation of the coldness of the flow. Finally, we show that the main dynamical parameter that affects the coldness of the flow is the relative isolation of the LG, and the absence of nearby Milky Way like objects within a distance of about  3 Mpc  .  相似文献