Effect of PDOP on performance of Kalman Filters for GNSS-based space vehicle position estimation

GPS Solutions - A theoretical performance analysis of Kalman Filters for Global Navigation Satellite System GNSS-based space vehicle position estimation in varying Position Dilution of Precision...     

Consolidation and Drainage Characteristics of Expansive Soil Stabilized with Fly Ash and Dolochar

Expansive soils undergo alternate swelling and shrinkage due to cyclic wetting and drying when left to nature. This property of Expansive soil affects its strength and stiffness characteristics thereby causing damage and distress to structures built on them. Industrial wastes can be added scientifically to these soils in modifying and reducing their swelling and shrinkage behaviour and increasing their strength and stiffness. In this technical article, an attempt has been made to study the compressibility and drainage characteristics of these soils using economic and ecofriendly industrial wastes such as Fly Ash and Dolochar as stabilizers. This paper also focuses on many other improved engineering properties of base soil like liquid limit, plasticity index, differential free swell, compaction and consolidation characteristics of Expansive (BC) soil stabilized with Fly Ash and Dolochar in different proportions. The virgin Expansive soil has been collected from eastern part of India (Odisha) and different percentages of Fly Ash (5, 10, 15, 20, 25 and 30 %) and Dolochar (5, 10, 15, 20, 25 and 30 %) were added to it, to predict the influence of these additives on compaction and consolidation characteristics of Expansive soil. Addition of both Fly Ash and Dolochar were found to decrease the index properties such as liquid limit, plastic limit, plasticity index, swelling index and enhancing the consolidation as well as drainage characteristics of Expansive soil. However, the maximum dry density of soil was found to decrease with addition of Fly Ash and increase with addition of Dolochar.     

Recent seismicity in Northeast India and its adjoining region

Recent seismicity in the northeast India and its adjoining region exhibits different earthquake mechanisms – predominantly thrust faulting on the eastern boundary, normal faulting in the upper Himalaya, and strike slip in the remaining areas. A homogenized catalogue in moment magnitude, M _W, covering a period from 1906 to 2006 is derived from International Seismological Center (ISC) catalogue, and Global Centroid Moment Tensor (GCMT) database. Owing to significant and stable earthquake recordings as seen from 1964 onwards, the seismicity in the region is analyzed for the period with spatial distribution of magnitude of completeness m _t, b value, a value, and correlation fractal dimension D _C. The estimated value of m _t is found to vary between 4.0 and 4.8. The a value is seen to vary from 4.47 to 8.59 while b value ranges from 0.61 to 1.36. Thrust zones are seen to exhibit predominantly lower b value distribution while strike-slip and normal faulting regimes are associated with moderate to higher b value distribution. D _C is found to vary from 0.70 to 1.66. Although the correlation between spatial distribution of b value and D _C is seen predominantly negative, positive correlations can also be observed in some parts of this territory. A major observation is the strikingly negative correlation with low b value in the eastern boundary thrust region implying a possible case of extending asperity. Incidentally, application of box counting method on fault segments of the study region indicates comparatively higher fractal dimension, D, suggesting an inclination towards a planar geometrical coverage in the 2D spatial extent. Finally, four broad seismic source zones are demarcated based on the estimated spatial seismicity patterns in collaboration with the underlying active fault networks. The present work appraises the seismicity scenario in fulfillment of a basic groundwork for seismic hazard assessment in this earthquake province of the country.     

Mapping of shear zones in the Western Ghats,Southwestern part of Dharwar Craton

A new map of structural architecture has been compiled involving modern mapping techniques at the cratonmobile belt interface in the Western Ghats around the Coorg granulite massif revealing the occurrence of important shear zones. The shear zones are linked to the Moyar-Bhavani Shear Zone in Southern India. The nature, geometry and kinematics of the shear zones in the granulitic crust and the cratonic part are distinctly different.     

http://www.sciencedirect.com/science/article/pii/S1674987111001289

The disastrous M_w 9.3(seismic moment 1.0×10³⁰ dyn/cm) earthquake that struck northwest Sumatra on 26 December 2004 and triggered～30 m high tsunami has rejuvenated the quest for identifying the forcing behind subduction related earthquakes around the world.Studies reveal that the strongest part（elastic core） of the oceanic lithosphere lie between 20 and 60 km depth beneath the upper （～7 km thick） crustal layer,and compressive stress of GPa order is required to fail the rock-layers within the core zone.Here we present evidences in favor of an intraplate origin of mega-earthquakes right within the strong core part（at the interface of semi-brittle and brittle zone）,and propose an alternate model exploring the flexing zone of the descending lithosphere as the nodal area for major stress accumulation. We believe that at high confining pressure and elevated temperature,unidirectional cyclic compressive stress loading in the flexing zone results in an increase of material yield strength through strain hardening, which transforms the rheology of the layer from semi-brittle to near-brittle state.The increased compressive stress field coupled with upward migration of the neutral surface（of zero stress fields） under noncoaxial deformation triggers shear crack.The growth of the shear crack is initially confined in the near-brittle domain,and propagates later through the more brittle crustal part of the descending oceanic lithosphere in the form of cataclastic failure.     

Simulation of tornado over Orissa (India) on March 31, 2009, using WRF–NMM model

A severe thunderstorm produced a tornado (F3 on the Fujita-Pearson scale), which affected Rajkanika block of Kendrapara district of Orissa in the afternoon of March 31, 2009. The devastation caused by the tornado consumed 15 lives and left several injured with huge loss of property. The meteorological conditions that led to this tornado have been analyzed. An attempt is also made to simulate this rare event using Non-hydrostatic Mesoscale Model (NMM) core of the Weather Research and Forecasting (WRF) system with a spatial resolution of 4 km for a period of 24 h, starting at 0000 UTC of March 31, 2009. The atmospheric settings resulted from synoptic, surface, upper air, satellite and radar echo studies were favorable for the occurrence of a severe thunderstorm activity over Rajkanika. The model-simulated meteorological parameters are consistent with each other, and all are in good agreement with the observation in terms of the region of occurrence of the intense convective activity. The model has well captured the vertical motion. The core of the strongest winds is shown to be very close to the site of actual occurrence of the event. The wind speed is not in good agreement with the observation as it has shown the strongest wind of only 20 ms⁻¹, against the estimated wind speed of 70 ms⁻¹. The spatial distributions as well as intensity of rainfall rates are in good agreement with the observation as model simulated 35.4 mm against the observed rainfall of 41 mm over Chandbali. The results of these analyses demonstrated the capability of high-resolution WRF–NMM model in simulation of severe thunderstorm events.     

Simulation of very severe cyclone Mala over Bay of Bengal with HWRF modeling system

Tropical cyclone is one of the most devastating weather phenomena all over the world. The Environmental Modeling Center (EMC) of the National Center for Environmental Prediction (NCEP) has developed a sophisticated mesoscale model known as Hurricane Weather Research and Forecasting (HWRF) system for tropical cyclone studies. The state-of-the-art HWRF model (atmospheric component) has been used in simulating most of the features our present study of a very severe tropical cyclone ??Mala??, which developed on April 26 over the Bay of Bengal and crossed the Arakan coast of Myanmar on April 29, 2006. The initial and lateral boundary conditions are obtained from Global Forecast System (GFS) analysis and forecast fields of the NCEP, respectively. The performance of the model is evaluated with simulation of cyclone Mala with six different initial conditions at an interval of 12?h each from 00 UTC 25 April 2006 to 12 UTC 27 April 2006. The best result in terms of track and intensity forecast as obtained from different initial conditions is further investigated for large-scale fields and structure of the cyclone. For this purpose, a number of important predicted fields?? viz. central pressure/pressure drop, winds, precipitation, etc. are verified against observations/verification analysis. Also, some of the simulated diagnostic fields such as relative vorticity, pressure vertical velocity, heat fluxes, precipitation rate, and moisture convergences are investigated for understanding of the characteristics of the cyclone in more detail. The vector displacement errors in track forecasts are calculated with the estimated best track provided by the India Meteorological Department (IMD). The results indicate that the model is able to capture most of the features of cyclone Mala with reasonable accuracy.     

Classification of cyclone hazard prone districts of India

Hazards associated with tropical cyclones are long-duration rotatory high-velocity winds, very heavy rain and storm tide. India has a coastline of about 7,516?km of which 5,400?km is along the mainland. The entire coast is affected by cyclones with varying frequency and intensity. The India Meteorological Department (IMD) is the nodal government agency that provides weather services related to cyclones in India. However, IMD has not identified cyclone-prone districts following any specific definition though the districts for which cyclone warnings are issued have been identified. On the other hand, for the purpose of better cyclone disaster management in the country, it is necessary to define cyclone proneness and identify cyclone-prone coastal districts. It is also necessary to decide degree of hazard proneness of a district by considering cyclone parameters so that mitigation measures are prioritised. In this context, an attempt has been made to prepare a list of cyclone hazard prone districts by adopting hazard criteria. Out of 96 districts under consideration, 12, 45, 31 and 08 districts are in very high, high, moderate and low categories of proneness, respectively. In general, the coastal districts of West Bengal, Orissa, Andhra Pradesh and Tamil Nadu are more prone and are in the high to very high category. The cyclone hazard proneness factor is very high for the districts of Nellore, East Godawari, and Krishna in Andhra Pradesh; Yanam in Puducherry; Balasore, Bhadrak, Kendrapara and Jagatsinghpur in Orissa; and South and North 24 Parganas, Medinipur and Kolkata in West Bengal. The results give a realistic picture of degree of cyclone hazard proneness of districts, as they represent the frequency and intensity of land falling cyclones along with all other hazards like rainfall, wind and storm surge. The categorisation of districts with degree of proneness also tallies with observed pictures. Therefore, this classification of coastal districts based on hazard may be considered for all the required purposes including coastal zone management and planning. However, the vulnerability of the place has not been taken into consideration. Therefore, composite cyclone risk of a district, which is the product of hazard and vulnerability, needs to be assessed separately through detailed study.