The application of artificial neural networks to magnetotelluric time-series analysis   总被引：4，自引：0，他引：4  

C. Manoj  Nandini Nagarajan 《Geophysical Journal International》2003,153(2):409-423

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Development of observation-based parameterizations of standard deviations of wind velocity fluctuations over an Indian region     

Srivastava  Piyush  Sharan  Maithili  Kumar  Manoj 《Theoretical and Applied Climatology》2020,139(3):1057-1077

Theoretical and Applied Climatology - The present study utilizes the turbulence observations over an Indian region, Ranchi, to study the diurnal and seasonal characteristics of mean and turbulent...  相似文献   

Predicting elastic properties of schistose rocks from unconfined strength using intelligent approach   总被引：3，自引：1，他引：2  

Manoj Khandelwal  T. N. Singh 《Arabian Journal of Geosciences》2011,4(3-4):435-442

Elastic properties of rocks play a major and crucial role for the design of any engineering structure. Determination of elastic properties in laboratory is tedious, laborious, very time consuming, as well as expertise is required, whereas determination of uniaxial compressive strength (UCS) and tensile strength in laboratory is simple, easy, and less expertise is required. Here, an attempt has been made to predict the elastic properties (Poisson’s ratio and Young’s modulus) of the schistose rocks from unconfined strength (UCS and tensile strength) using artificial neural network (ANN). A three-layer feed-forward back propagation neural network with 2-5-2 architecture was trained up to 855 epochs to predict the elastic properties of rock mass. The network was trained and tested by 120 data sets, and validation of the network was done by 20 new randomly selected data sets of UCS and tensile strength. The samples were collected from the schistose rocks of Nathpa-Jhakri hydropower project site, SJVNL, Himachal Pradesh, India. To check the validity and suitability of the artificial neural network technique, multivariate regression analysis (MVRA) is also performed, and comparison has been made. It was found that ANN gives closer values of predicted Poisson’s ratio and Young’s modulus as compared to MVRA. The coefficient of determination for Poisson’s ratio was 0.9809 and 0.843 by ANN and MVRA, respectively, whereas 0.9922 and 0.9362 for Young’s modulus by ANN and MVRA, respectively. The mean absolute percentage error (MAPE) for Young’s modulus is 11.13 and 28.21 by ANN and MVRA, respectively; whereas MAPE for Poisson’s ratio is 3.64 and 9.23 by ANN and MVRA, respectively.  相似文献   

Photometric distances to dark clouds: cometary globule CG 12     

G. Maheswar  P. Manoj  H. C. Bhatt 《Monthly notices of the Royal Astronomical Society》2004,355(4):1272-1282

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Non-emission-line young stars of intermediate mass     

P. Manoj  G. Maheswar  H. C. Bhatt 《Monthly notices of the Royal Astronomical Society》2002,334(2):419-425

We present optical spectra of four intermediate-mass candidate young stellar objects that have often been classified as Herbig Ae/Be stars. Typical Herbig Ae/Be emission features are not present in the spectra of these stars. Three of them, HD 36917, HD 36982 and HD 37062, are members of the young Orion nebula cluster (ONC). This association constrains their ages to be ≲1 Myr. The lack of appreciable near-infrared excess in them suggests the absence of hot dust close to the central star. However, they do possess significant amounts of cold and extended dust as revealed by the large excess emission observed at far-infrared wavelengths. The fractional infrared luminosities  ( L _ir/ L _★)  and the dust masses computed from IRAS fluxes are systematically lower than those found for Herbig Ae/Be stars but higher than those for Vega-like stars. These stars may thus represent the youngest examples of the Vega phenomenon known so far. In contrast, the other star in our sample, HD 58647, is more likely to be a classical Be star, as is evident from the low   L _ir/ L _★  , the scarcity of circumstellar dust, the low polarization, the presence of H α emission and near-infrared excess, and the far-infrared spectral energy distribution consistent with free–free emission similar to other well-known classical Be stars.  相似文献   

Daytime boundary layer behavior over eastern region (per-humid climate) and western regions (semi-arid climate) of India: a case study     

Manoj Kumar  Anil Kumar  Chinmay Mallik  N. C. Mahanti  A. M. Shekh 《Meteorology and Atmospheric Physics》2011,111(1-2):55-64

The annual variation in planetary boundary layer (PBL) height is determined from the profiles of conserved thermodynamic variables, i.e., virtual potential temperature ?? _v and equivalent potential temperature ?? _e, using radiosonde data at per-humid climate region, Ranchi (23°42??N, 85°33??E, 610?m asl) and semi-arid region, Anand (23°35??N, 72°55??E, 45.1?m asl), India. Of all the variables, the ?? _v profile seems to provide the most reasonable estimate of the PBL height. This has been supplemented by T-Phi gram analysis for specific days. It has been found that in winter the height of boundary layer is very low due to subsidence and radiational cooling, while pre-monsoon months exhibit the most variable convection. It may be inferred that synoptic conditions accompanied by a variety of weather phenomena such as thunderstorms, onset and withdrawal of monsoons, etc. control the ABL over Ranchi, while daytime solar insolation and nighttime radiative cooling mainly control the ABL over Anand.  相似文献   

Alternative climate data sources for distributed hydrological modelling on a daily time step   总被引：1，自引：0，他引：1  

Ashraf El‐Sadek  Max Bleiweiss  Manoj Shukla  Steve Guldan  Alexander Fernald 《水文研究》2011,25(10):1542-1557

Two major criteria in choosing climate data for use in hydrological modelling are the period of record of the data set and the proximity of the collection platform(s) to the basin under study. Conventional data sets are derived from weather stations; however, in many cases there are no weather stations sufficiently close to a basin to be representative of climate conditions in that basin. In addition, it is often the case either that the period of record for the weather station(s) does not cover the period of the proposed simulation or that there are gaps in the data. Therefore, the objectives of this study are to investigate alternative climate data sources for use in hydrological modelling and to develop a protocol for creating hydrological data sets that are spatially and temporally harmonized. The methods we used for constructing daily, spatially distributed, climatic data sets of precipitation, maximum and minimum temperature, wind speed, solar radiation, potential evapotranspiration, and relative humidity are described. The model used in this study was the Soil and Water Assessment Tool implemented on the Mimbres River Basin located in southwestern New Mexico, USA, for the period 2003–2006. Our hydrological simulations showed that two events in January and February 2005 were missed, while an event in August 2006 was well simulated. We have also investigated the usefulness of several other precipitation data sets and compared the simulation results. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Modelling the pore fluid diffusion process in aftershock initiation for 2004 Sumatra earthquake: implications for marine geohazard estimation in the Andaman region     

Basab Mukhopadhyay  Sujit Dasgupta  M. Fnais  Manoj Mukhopadhyay 《Natural Hazards》2011,57(1):39-49

The role of fluid injection on the occurrence and migration path for the aftershocks of 2004 Sumatra earthquake (Mw 9.3) and January 2005 Andaman earthquake swarm within the aftershock sequence is investigated here from the viewpoint of pore fluid diffusion process. The Sumatra earthquake created a regionally extensive crustal rupture plane exceeding 1,200 km length below the Andaman Sea. The r–t plots (Shapiro et al. 1997) are constructed for these aftershocks in order to examine the role of poroelastic effects as rupturing progressed with time. Their main results are as follows: the r–t plot corresponding to first 3 h of aftershock activity (when only 44 events of mb ≥ 4.5 originated) reveals that 95% of the data points occurred below the modelled parabola with relatively high D value of 20 m²/s, whereas a significantly low D value of 3.5 m²/s characterises the aftershock activity for the first 24 h (when 420 events of mb ≥ 4.0 occurred). Here, the Coulomb stress was transferred from the main shock with a rapid imposition of normal stress, thus inducing the pore-pressure change that started diminishing almost immediately by fluid diffusion, at a rate, defined by the diminishing D value. The modelling results for fault seismicity at far off distances from the main epicentre are interpreted here as potential indicators for large-scale sub-seabed rupturing—consequent to stress changes induced by bending of the Indian Ocean plate. Bathymetric slopes under the Andaman subduction zone are particularly amenable to sub-marine slides where crustal E–W hinge faults inferred seismically cut across the N–S trending regional thrust and strike-slip faults. Seabed rupturing appears to allow deep-slab hydration in these areas, producing pressure gradients along the normal faults. These features are important since they can herald marine geohazards in the Andaman region.  相似文献   

Role of transverse tectonics in the Himalayan collision: Further evidences from two contemporary earthquakes     

Sujit Dasgupta  Basab Mukhopadhyay  Manoj Mukhopadhyay  D. R. Nandy 《Journal of the Geological Society of India》2013,81(2):241-247

Two contemporary earthquakes originating in the central Himalayan arc and its foredeep (Sikkim earthquake of 18.09.2011, M_w 6.9, h: 10–60 (?) km and Bihar-Nepal earthquake of 20.08.1988, Mw 6.8, h: 57 km) are commonly associated with transverse lineaments/faults traversing the region. Such lineaments/faults form active seismic blocks defining promontories for the advancing Indian Craton. These actually produce conjugate shear faulting pattern suggestive of pervasive crustal interplay deep inside the mountains. Focal mechanism solutions allow inferring that large part of the current convergence across the central Himalayan arc is accommodated by lateral slip. Similar slip also continues unabated in the densely populated foredeep for distances up to several tens of kilometers south of the Main Boundary Thrust (MBT).  相似文献   

Application of an Expert System to Predict Maximum Explosive Charge Used Per Delay in Surface Mining     

Manoj Khandelwal  T. N. Singh 《Rock Mechanics and Rock Engineering》2013,46(6):1551-1558

The present paper mainly deals with the prediction of maximum explosive charge used per delay (Q _MAX) using an artificial neural network (ANN) incorporating peak particle velocity (PPV) and distance between blast face to monitoring point (D). One hundred and fifty blast vibration data sets were monitored at different vulnerable and strategic locations in and around major coal producing opencast coal mines in India. One hundred and twenty-four blast vibrations records were used for the training of the ANN model vis-à-vis to determine site constants of various conventional vibration predictors. The other 26 new randomly selected data sets were used to test, evaluate and compare the ANN prediction results with widely used conventional predictors. Results were compared based on coefficient of correlation (R), mean absolute error and mean squared between measured and predicted values of Q _MAX. It was found that coefficient of correlation between measured and predicted Q _MAX by ANN was 0.985, whereas it ranged from 0.316 to 0.762 by different conventional predictor equations. Mean absolute error and mean squared error was also very small by ANN, whereas it was very high for different conventional predictor equations.  相似文献