Validation of Chlorophyll-a Algorithms in the Coastal Waters of Bay of Bengal Initial Validation Results from OCM-2

In this paper we report chlorophyll measurements made during an ocean colour validation cruise in April 2011 of the research vessel, Sagar Paschimi in the coastal waters of Northern Bay of Bengal. The chlorophyll-a concentration in these waters range from 0.2 to 4.0 mg/m³. Chlorophyll-a concentration from OCM-2 was estimated using the global ocean colour algorithms namely, OC2, OC3, OC4 and Chl-a algorithms respectively. OCM data was processed using the global SeaWiFS Data Analysis System (SeaDAS) in which all the above mentioned algorithms are embedded for estimating the chlorophyll-a concentration. A comparative study was made between and in-situ and satellite derived chlorophyll-a concentration. Although the matchups between in-situ and satellite data from OCM-2 were sparse, it indicates that direct application of the standard SeaWiFS algorithm-the OC4-V4 algorithm—in the coastal waters of the Bay of Bengal will underestimate chlorophyll-a by up to 30%. The results show a good correlation with an R value of 0.61 using OC2 algorithm. However, all the other global algorithms over estimate the chlorophyll-a concentration even in low chlorophyll concentration range. The comparison between in-situ and all the existing chlorophyll algorithms shows the efficiency of these algorithms for quantification of chlorophyll in coastal waters and hence the need to develop regional algorithms and fluorescence based algorithms for better quantification.     

One-Dimensional Consolidation of Sedimented Stowed Pond Ash

Use of fly ash locked in the ash ponds in geotechnical applications such as stowing or backfilling of the mines is an attractive alternative to solve the disposal problem. Before it is used as a stowing or backfilling material, the response of the fly ash?to imposed load must be determined in order to assess its load taking ability. The present study examines the effect of time and incremental load on the consolidation characteristics of the sedimented stowed pond ash using a fixed ring consolidometer. The important parameters, viz. rate of settlement, consolidation coefficients and void ratio, etc. of the hydraulically stowed pond ash collected after 7, 14, 21, 28 and 35?days of stowing under step incremental loads are determined. The study revealed that 60.42–84.87% settlement of the sedimented stowed pond ash takes place in the initial 1?min of the loading. In addition, it is observed that the coefficient of consolidation of the sedimented stowed pond ash, which varies in the range of 0.0195–0.1882?cm²/min, is comparatively low and decreases with the increment of applied load and time. This indicates that the structures lying above the stowed pond ash mass will undergo gradual settling and not suffer large deformation.     

Bankline change and the facets of riverine hazards in the floodplain of Subansiri–Ranganadi Doab, Brahmaputra Valley, India

Subansiri?CRanganadi Doab (confluence country), located in Lakhimpur district, Assam, is one of the worst flood-affected areas in Brahmaputra valley. The Doab is well populated, and land around these rivers is extensively used for cultivation. As means of flood protection, embankments were constructed in the 1950s along the banks of both the rivers. On the other hand, these rivers are dynamic in terms of banklines and other forms of channel changes. Progressive migration of bankline, due to erosion, results in loss of cultivable land. Moreover, it causes breaches in the embankments increasing the severity of flood in the Doab. This paper attempts to study the changes in the banklines of two major rivers in the floodplains of the Subansiri?CRanganadi Doab during 1997?C2009 in the context of the riverine hazards it brings to the floodplain dwellers. The shift of the banklines in Subansiri?CRanganadi Doab, downstream of North Lakhimpur, has been estimated using IRS LISS imageries of 1997 and 2009 in GIS environment. The river Subansiri during the study period has migrated westward and has widened substantially resulting in erosion of an area of ~19.137?km². For Ranganadi, the total area that has been eroded due to channel changes is ~0.897?km². The channel changes are mainly due to concave bank erosion associated with high stages of flow. Channel widening in Subansiri and Ranganadi in the study area during the decades of 1990s and 2000 has led to frequent breaches in the embankments. Lateral erosion and inundation due to embankment failure are the most dominant facets of riverine hazards in the study area as these lead to loss of livelihood. Therefore, it is necessary to incorporate geomorphic changes in formulating flood management programmes.     

Spatial Technologies in Deriving the Morphotectonic Characteristics of Tectonically Active Western Tripura Region,Northeast India

Employing integrated remote sensing and GIS technology the western most part of Tripura region (Northeast India) and adjoining Bangladesh region has been investigated in the light of its geomorphological characteristics. Nature of fold ridges, several streams and the respective drainage basins are well depicted in satellite images and digital elevation model providing meaningful information. Quantitative parameters such as stream sinuosity, drainage basin asymmetry, basin elongation ratio have been computed. Main rivers of the study area, namely the Gomti and Khowai follows extremely meandering path and crosses through the transversely faulted anticlinal ridges. Fluvial anomalies viz. shift in stream channel and the abandoned meandering loops have been inferred and mapped. The Haora river in the study area exhibits northward shift in some part. Development of drainage system towards north and south from the drainage divide along the latitude 23°45^′N indicated up arching of the region which is also corroborated by the extracted topographic profiles. It has been observed that several tributary streams have gone dry and agricultural fields are developed along the dried up stream. These derived parameters remained useful to understand the nature of topographical modification attributed to the possible tectonic activity.     

Cleaning of the Ganga

Ganga, the national river of India, is now sadly depleted in flow and utterly polluted due to construction of dams and barrages, discharge of untreated municipal and industrial wastes, floral offerings, cremation of dead bodies on its bank. Kanpur to Trighat is identified as the most polluted section of the river. This critical state of the river has been revealed in the paper based on an analysis of the published accounts and research results by various institutes and individuals. It also sheds light on the strategies and action plans to rejuvenate the Ganga to its pristine quality.     

Enriched finite element procedures for analyzing decoupled bolts installed in rock mass

Numerical procedures are developed to analyze interaction between fully grouted bolts and rock mass using ‘enriched finite element method (EFEM)’. A solid element intersected by a rock bolt along any arbitrary direction is termed as ‘enriched’ element. The nodes of an enriched element have additional degrees of freedom for determining displacements, stresses developed in the bolt rod. The stiffness of the enriched element is formulated based on properties of rock mass, bolt rod and grout, orientation of the bolt and borehole diameter. Decoupling at grout–bolt interface and elasto‐plastic behavior of rock mass have also been incorporated into the EFEM procedures. The results of this method are compared with analytical pull‐out test results presented by Li and Stillborg (Int. J. Rock Mech. Min. Sci. 1999; 36 :1013–1029). In addition, a numerical example of a bolted tunnel is provided to demonstrate the efficacy of the proposed method for practical applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Machine learning techniques applied to prediction of residual strength of clay

Stability with first time or reactivated landslides depends upon the residual shear strength of soil. This paper describes prediction of the residual strength of soil based on index properties using two machine learning techniques. Different Artificial Neural Network (ANN) models and Support Vector Machine (SVM) techniques have been used. SVM aims at minimizing a bound on the generalization error of a model rather than at minimizing the error on the training data only. The ANN models along with their generalizations capabilities are presented here for comparisons. This study also highlights the capability of SVM model over ANN models for the prediction of the residual strength of soil. Based on different statistical parameters, the SVM model is found to be better than the developed ANN models. A model equation has been developed for prediction of the residual strength based on the SVM for practicing geotechnical engineers. Sensitivity analyses have been also performed to investigate the effects of different index properties on the residual strength of soil.     

Linear dichroism in ALD layers of TiO2

We prepare TiO₂ film by ALD and study their electronic properties by soft X-ray absorption spectroscopy (XAS) and photoelectron spectroscopy. We focus on XAS and X-ray linear dichroism to indentify band onset and learn about local distortion of the Ti–O octahedral atomic and about defects which cause Ti-based electronic states within the band gap.