Jayanta Kumar Ghosh

Knowledge-Based Landslide Susceptibility Zonation System

The landslide susceptibility of a region is important for socioeconomic considerations and engineering applications. Thus, an automated system for mapping of landslide susceptibility could be of significant benefit for society. In this paper, a knowledge-based landslide susceptibility zonation (LSZ) system has been proposed. The system consists of input, understanding, expert, and output modules. The input module accepts thematic images of contributing factors for landslides. The understanding module interprets input images to extract relevant information as required by the expert module. The expert module consists of knowledge base and inference strategy to categorize a region into different landslide intensities. Finally the output module provides a LSZ map. It is a pixel-based system and provides output having the scale same as that of the input maps. The system has been tested to prepare a landslide susceptibility map for the Tehri-Garhwal region in Indias lower Himalayas, and further validated with studies for two other different regions. The proposed system provides output commensurate with that provided by experts. The categories of hazard zones have a discrepancy as little as 6.2% in high hazard zones and near to 1.5% and 4% in moderate and low hazard zones, respectively. The high hazard zones in the LSZ maps from the proposed system are supersets of that obtained by experts (i.e., the proposed system provides safer LSZ map). Thus, it can be concluded that the proposed system can be used for preparation of LSZ maps. In the future, the methodology may be extended for real time assessment and prediction of landslide hazards.

Median change vector analysis algorithm for land-use land-cover change detection from remote-sensing data

Improved change vector analysis (ICVA) has recently been promoted as an effective algorithm for multi-class change detection. Unlike the conventional change vector analysis (CVA) that works on two-dimensional data, the ICVA works on multidimensional data. However, ICVA has limitations when the change vector is fraught with similar direction cosine values. In this article, a new algorithm, named median change vector analysis (MCVA) has been proposed for multi-class change detection. The algorithm is based on an enhanced 2n-dimensional feature space comprising direction cosine values of both the change vector and the median vector, which allows for more accurate detection of change classes than those obtained from ICVA. As a case study, the proposed algorithm has been implemented on Landsat-7 Enhanced Thematic Mapper Plus (ETM+) images of a typical Indian city and surrounding areas for land-cover change detection.

A linear helicon plasma device with controllable magnetic field gradient

Current free double layers (CFDLs) are localized potential structures having spatial dimensions - Debye lengths and potential drops of more than local electron temperature across them. CFDLs do not need a current for them to be sustained and hence they differ from the current driven double layers. Helicon antenna produced plasmas in an expanded chamber along with an expanding magnetic field have shown the existence of CFDL near the expansion region. A helicon plasma device has been designed, fabricated, and installed in the Institute for Plasma Research, India to study the role of maximum magnetic field gradient as well as its location with respect to the geometrical expansion region of the chamber in CFDL formation. The special feature of this machine consisting of two chambers of different radii is its capability of producing different magnetic field gradients near the physical boundary between the two chambers either by changing current in one particular coil in the direction opposite to that in other coils and/or by varying the position of this particular coil. Although, the machine is primarily designed for CFDL experiments, it is also capable of carrying out many basic plasma physics experiments such as wave propagation, wave coupling, and plasma instabilities in a varying magnetic field topology. In this paper, we will present the details of the machine construction, its specialties, and some preliminary results about the production and characterization of helicon plasma in this machine.

Wireless hazard communication system

Purpose – Communication of an impending hazard to people in near real time is critical. The purpose of this paper is to develop an internet‐SMS based geo‐hazard warning communication system.Design/methodology/approach – A warning system based on an internet‐resident concept and the available cellular mobile infrastructure is proposed in this study. The functionality of the system is modular in architecture.Findings – The messages have been transmitted in a set of 20 SMSs six times, to locally‐owned mobile numbers, resulting in a total number of 120. It has been found that 58 messages got delivered within ten seconds, the rest within 40 more seconds. The threat messages reached the impending threat areas within acceptable time delay.Originality/value – The paper describes the implementation of a novel and stand‐alone system for dynamic hazard warning. Cellular or mobile phone, a gadget used by common man, is expected to be the best proposition to effectively warn people individually and to propagate hazard...

Generation of multiple toroidal dust vortices by a non-monotonic density gradient in a direct current glow discharge plasma

Observation of two well-separated dust vortices in an unmagnetized parallel plate DC glow discharge plasma is reported in this paper. A non-monotonic radial density profile, achieved by an especially designed cathode structure using a concentric metallic disk and ring of different radii, is observed to produce double dust tori between cathode and anode. PIV analysis of the still images of the double tori shows oppositely rotating dust structures between the central disk and the ring. Langmuir probe measurements of background plasma shows a non-uniform plasma density profile between the disk and the ring. Location and sense of rotation of the dust vortices coincides with the location and direction of the radial gradient in the ion drag force caused by the radial density gradient. The experimentally observed dust vorticity matches well with the calculated one using hydrodynamic formulations with shear in ion drag dominating over the dust charge gradient. These results corroborate that a radial gradient in the ion drag force directed towards cathode is the principal cause of dust rotation.

Fuzzy Knowledge Based GIS for Zonation of Landslide Susceptibility

Natural phenomena do not evolve linearly. The rapidly changing dynamics of eco-processes require modeling through non-linear concepts such as non-discreet fuzzy theory. The classification of data has been done using maximum likelihood classifier and Gaussian distribution. To better capture an event such as landslide it is imperative that the inherent continuity of the causative factors of the phenomenon are well represented. And that the uncertainties involved in assigning the probabilities of occurrences are taken care of. Decision making depends upon multiple parameters and their collective evaluation. Hence multi-criteria evaluation (MCE) of fuzzy variables has been implemented. A fuzzy knowledge-based geographical information system to categorize a given region into five levels of landslide susceptibility very high, high, moderate, low, and very low, has been presented in this chapter. The approach has used membership function for causative factors of landslide. This makes the system take into account uncertainty of the contributory factors of landslide. Due weightage has been assigned to the different spatial variations of these causative factors stored in the knowledge base. The input to the system consists of satellite data and topographic maps, as layers of information for the causative factors. The system carries out decision making by using multi-criteria evaluation of each input layer for adjusting its suitability, defined by the membership values and weights towards landslide susceptibility. The test conducted shows that the highly susceptible region extends along the zone of high rock mass thrust and slope failure and occupies 20-25% of the total study area. The very high threat occupies around 9-12% of the study area also falling on the higher slopes. On comparison of the susceptibility map with ground data, it has been found that three existing slides appear in the very high and high threat susceptible zones delineated by the system.

Space- and time-resolved visible-emission spectroscopy of Aditya-tokamak discharges using multi-track spectrometer

A diagnostic system based on a multi-fiber input high resolution spectrograph has been set up on the Aditya tokamak (Bhatt et al 1989 Ind. J. Pure Appl. Phys. 27 710) for utilizing the passive light emission to measure different kinds of plasma flow and to identify the location of emissions of hydrogen and impurities along with their temperatures. Eight simultaneous vertically collimated lines-of-sight from a top port view a poloidal cross-section of the plasma. This arrangement simplifies the analysis of spectra in terms of making the Zeeman splitting easier to account for, since each chord passes through a region of nearly constant toroidal magnetic field (BT). This paper describes the complete set-up, the wavelength and intensity calibrations performed and the initial results including the impurity emissivity profiles and simultaneous flow measurements in the inboard and outboard regions of the Aditya tokamak.

Investigation of oxygen impurity transport using the O4+ visible spectral line in the Aditya tokamak

Intense visible lines from Be-like oxygen impurity are routinely observed in the Aditya tokamak. The spatial profile of brightness of a Be-like oxygen spectral line (2p3p 3D3?2p3d 3F4) at 650.024?nm is used to investigate oxygen impurity transport in typical discharges of the Aditya tokamak. A 1.0?m multi-track spectrometer (Czerny?Turner) capable of simultaneous measurements from eight lines of sight is used to obtain the radial profile of brightness of O4+ spectral emission. The emissivity profile of O4+ spectral emission is obtained from the spatial profile of brightness using an Abel-like matrix inversion. The oxygen transport coefficients are determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional empirical impurity transport code, STRAHL. Much higher values of the diffusion coefficient compared with the neo-classical values are observed in both the high magnetic field edge region and the low magnetic field edge region of typical Aditya ohmic plasmas, which seems to be due to fluctuation-induced transport. The diffusion coefficient at the limiter radius in the low-field (outboard) region is typically ? twice as high as that at the limiter radius in the high-field (inboard) region.

Observation of dust torus with poloidal rotation in direct current glow discharge plasma

Observation of dust cloud rotation in parallel-plate DC glow discharge plasma is reported here. The experiments are carried out at high pressures (∼130 Pa) with a metallic ring placed on the lower electrode (cathode). The dust cloud rotates poloidally in the vertical plane near the cathode surface. This structure is continuous toroidally. Absence of magnetic field rules out the possibility of E × B induced ion flow as the cause of dust rotation. The dust rotational structures exist even with water cooled cathode. Therefore, temperature gradient driven mechanisms, such as thermophoretic force, thermal creep flow, and free convection cannot be causing the observed dust rotation. Langmuir probe measurement reveals the existence of a sharp density gradient near the location of the rotating dust cloud. The gradient in the density, giving rise to a gradient in the ion drag force, has been identified as the principal cause behind the rotation of dust particles.

Observation of low magnetic field density peaks in helicon plasma

Single density peak has been commonly observed in low magnetic field (<100 G) helicon discharges. In this paper, we report the observations of multiple density peaks in low magnetic field (<100 G) helicon discharges produced in the linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. Experiments are carried out using argon gas with m = +1 right helical antenna operating at 13.56 MHz by varying the magnetic field from 0 G to 100 G. The plasma density varies with varying the magnetic field at constant input power and gas pressure and reaches to its peak value at a magnetic field value of ∼25 G. Another peak of smaller magnitude in density has been observed near 50 G. Measurement of amplitude and phase of the axial component of the wave using magnetic probes for two magnetic field values corresponding to the observed density peaks indicated the existence of radial modes. Measured parallel wave number together with the estimated perpendicular wave number suggests oblique mode pr...