Effect of some operating variables on the efficiency index of a coal flotation operation

Coal cleaning performance can be evaluated by a simple index called the efficiency index. The effect of operating parameters on the efficiency index has been qualitatively discussed. Maximization of the efficiency index implies process optimization and a method is indicated to optimize the process variables for maximization of the efficiency index.     

Seismic microzonation of a nuclear power plant site with detailed geotechnical,geophysical and site effect studies

This paper highlights the seismic microzonation carried out for a nuclear power plant site. Nuclear power plants are considered to be one of the most important and critical structures designed to withstand all natural disasters. Seismic microzonation is a process of demarcating a region into individual areas having different levels of various seismic hazards. This will help in identifying regions having high seismic hazard which is vital for engineering design and land-use planning. The main objective of this paper is to carry out the seismic microzonation of a nuclear power plant site situated in the east coast of South India, based on the spatial distribution of the hazard index value. The hazard index represents the consolidated effect of all major earthquake hazards and hazard influencing parameters. The present work will provide new directions for assessing the seismic hazards of new power plant sites in the country. Major seismic hazards considered for the evaluation of the hazard index are (1) intensity of ground shaking at bedrock, (2) site amplification, (3) liquefaction potential and (4) the predominant frequency of the earthquake motion at the surface. The intensity of ground shaking in terms of peak horizontal acceleration (PHA) was estimated for the study area using both deterministic and probabilistic approaches with logic tree methodology. The site characterization of the study area has been carried out using the multichannel analysis of surface waves test and available borehole data. One-dimensional ground response analysis was carried out at major locations within the study area for evaluating PHA and spectral accelerations at the ground surface. Based on the standard penetration test data, deterministic as well as probabilistic liquefaction hazard analysis has been carried out for the entire study area. Finally, all the major earthquake hazards estimated above, and other significant parameters representing local geology were integrated using the analytic hierarchy process and hazard index map for the study area was prepared. Maps showing the spatial variation of seismic hazards (intensity of ground shaking, liquefaction potential and predominant frequency) and hazard index are presented in this work.     

Foundation Floor Geological Mapping of a Nuclear Reactor

Foundation floor mapping is essential for very important structures to provide permanent data set for geological interpretations. Prototype fast breeder reactor (PFBR) is being constructing at Kalpakkam, India. Nuclear Island Connected Building (NICB) is the main nuclear safety related structure of (PFBR), and is resting on a raft of 101.5 m × 93 m size at about 20 m below the existing ground level. Geological floor mapping was prepared after the excavation. 2 m × 2 m grids were used for sampling study and mapping of the walls and floor. The floor region of this raft foundation was seen to contain certain weathered zone with fractures of thickness of in the order of 2 m. No evidences of faulting/shearing were observed on the surface of the floor area. The entire floor area was made up of compact and sound rock mass. However, there were some isolated patches of soft weathered/altered rock and small fractures in the rock. The structural features observed during the mapping exercise indicated the need for consolidation grouting so that the entire floor area function as single rock mass. This foundation geological map will assist in making better interpretation of post-construction foundation instrumentation data.     

Significance of the turbulent sheath following the interplanetary shocks in producing forbush decreases

The physical processes responsible for transient cosmic-ray decreases have been investigated for two types of interplanetary shock events associated with helium enhancement (He-shocks) and those not associated with helium enhancement (non-He-shocks). The Calgary cosmic-ray neutron monitor data and the interplanetary field data have been subjected to a superposed-epoch Chree analysis. The difference in the profiles of the cosmic-ray intensity have been compared with the interplanetary field data and its variance. It is suggested that the turbulence sheath following the shock front is very effective and of major importance for producing cosmic-ray decreases. A simple model has been proposed to explain the observations which show that a Forbush decrease modulating region consists of a shock front associated with a plasma sheath in which the magnetic field is turbulent and the sheath, in turn, is followed by an ejected plasma cloud having ordered structure and high magnetic field strength.     

An assessment of the merits of remote sensing techniques for environmental mapping: A case study from Kerala

For a proper analysis of any ecosystem and the assessment of environment impact on it, the bearing of data on distribution properties and characteristics of land-form, water, vegetation, soil and rock and even of the typology of cultural pattern are to be evaluated on the basis of the everchanging anthropogenic involvement. The extent to which the techniques of Remote Sensing alone could attain this is yet to be ascertained. The direct method for this would be to conduct the resource surveys of specific regions exclusively and separately by remote sensing as well as by field-studies and then compare the results. An extract of a major study pursued in this line in the Coastal Zone of Kerala, India has indicated an authenticity of about seventy percent through remote sensing. Weighing on the comparative time factor involved, the procedure of mapping through remore sensing alone may be advocated.     

Enhanced subsurface mixing due to near-inertial waves: observation from Seychelles-Chagos Thermocline Ridge

Ocean Dynamics - The Seychelles-Chagos Thermocline Ridge (SCTR) is a key region which plays a major role in various regional climatic processes at all time scales. The vertical mixing at the base...     

An Overview of the Land Surface Processes Experiment (Laspex) over a Semi-Arid Region of India

To understand and quantify the land-surface-vegetation interactionwith the atmospheric boundary layer, and validate or improve upon the existing surfaceflux parameterization schemes in various weather forecast models, a LAnd SurfaceProcesses EXperiment (LASPEX), was designed and executed in the semi-arid regionof Gujarat, India during January 1997–December 1998. Micrometeorological tower observations,soil and vegetation parameters, radiation, turbulence and upper airobservations were taken continuously for two years at five sites, separated by about60–100 km from each other. Towers of 9 m height with instruments at four levels wereinstalled at sites that are agricultural fields and characterized with a variety of soilproperties, vegetation and diverse crops. An overview of the experiment is presented.Some results, such as the seasonal variation of surface energy balance and turbulence statistics,are discussed.