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Mukherjee J.,Visva Bharati University | Ray S.,Visva Bharati University | Ghosh P.B.,Institute of Engineering and Management
Ecological Modelling

Hooghly-Matla estuarine system receives a major load of carbon from adjacent mangrove forest in the form of litterfall throughout the year. Keeping in view, the crucial role of carbon, a seven compartment model has been proposed to study the dynamics of carbon in this estuarine system. Different forms of carbon present in soil (as soil organic carbon (SOC), soil inorganic carbon (SIC)) and in water (as dissolved inorganic carbon (DIC), dissolved carbon dioxide (DCO2), dissolved bicarbonate (DBC), dissolved organic carbon (DOC) and particulate organic carbon (POC)) are taken as state variables. Litter biomass, dissolved oxygen, primary productivity, community respiration, temperature of water, pH of water and soil, air-water exchange of carbon dioxide and conversion rates among different forms of carbon are considered as graph time functions. The data used in the present model are collected for over two years from our own field works and experiments. Other sensitive rate parameters which are not possible to collect from survey or experiment, calibrated following standard procedure. Sensitivity analysis is performed along with calibration. Model simulation results are validated with observed data. Results show seasonal variations of litterfall and which is the main source of SOC pool and ultimately transported to the estuary. Other than litterfall, the death of organisms in soil and water enriches the SOC and POC respectively. pH of water is governing factor and depending on this factor, DIC is converted to DCO2 and DBC, which are taken up by phytoplankton during photosynthesis. Mineralization rate of SOC to SIC and uptake rate of DCO2 and DBC are the sensitive parameters. © 2012 Elsevier B.V. Source

Mandal S.,T D B College | Mandal S.,Visva Bharati University | Ray S.,Visva Bharati University | Ghosh P.B.,Institute of Engineering and Management
Ecological Modelling

The Sundarban mangrove ecosystem is one of the fragile and dynamic mangrove systems of the world. This ecosystem consists of many islands both virgin and reclaimed in nature. The present study compares the contribution of mangrove litterfall on nitrogen dynamics of Sagar Island (reclaimed) and Lothian Island (virgin). Though, both islands bear similar mangrove species, the dynamics of nitrogen in soil and water is different. Modeling of the virgin island is needed to determine the parameter values governing the transformation of nitrogen in soil and water. Here, a seven compartment nitrogen based model is constructed and applied to Lothian Island. The state variables, physical and chemical factors are retained same as in the reclaimed island model. The experiments and survey works were carried out on both islands for two consecutive years. Sensitivity analysis is performed followed by model calibration and validation. Chi square, root mean square error and average bias are calculated between simulated and observed results of both islands. Sensitivity analysis indicated that the loss rate of soil organic nitrogen as humic acid and fulvic acid is the most sensitive parameter for both systems. The model results indicated that microbial degradation rates are higher in the Lothian Island than Sagar Island while the leaching rates are lower in former and higher in the latter. The concentration of dissolved inorganic nitrogen in the creeks of Sagar Island is higher due to anthropogenic input. Detritus in the estuarine system of Sagar Island is decreased by 44%, if litter biomass is reduced to 50%. This effect is 55% in case of Lothian Island, when litter biomass is reduced to 50%. The model depicts that both systems are governed by nutrient and detritus derived from degradation of mangrove litterfall. If the litter biomass of Sagar and Lothian islands is reduced to 50%, DIN of the system is affected by 48% and 50%, respectively. This model will act as a tool for environment managers to take necessary steps regarding conservation of mangroves and restoration of creeks in the Sundarban mangrove ecosystem. © 2012 Elsevier B.V. Source

Saha S.,Institute of Engineering and Management
International Journal of Systems Science

We explore the impact of channel structure on the manufacturer, the distributer, the retailer and the entire supply chain by considering three different channel structures in radiance of with and without coordination. These structures include a traditional retail channel and two manufacturer direct channels with and without consistent pricing. By comparing the performance of the manufacturer, the distributer and the retailer, and the entire supply chain in three different supply chain structures, it is established analytically that, under some conditions, a dual channel can outperform a single retail channel; as a consequence, a coordination mechanism is developed that not only coordinates the dual channel but also outperforms the non-cooperative single retail channel. All the analytical results are further analysed through numerical examples. © 2014 Taylor & Francis. Source

Banerjee S.,Institute of Engineering and Management
Springer Proceedings in Physics

This paper mainly deals with an efficient method to solve the forward and the backward problem for 2D diffraction tomography. The method described here is a direct method which leads to faster reconstruction of the body’s complex refractive index profile. The method is based upon Born approximation which holds for weakly scattering bodies. The method involves a new type of mapping from real space to K space. The reconstructed image of the body is studied for different noisy environment and for different resolution in K space. Also suitable forward and inverse formula is presented. © Springer India 2015. Source

Saha S.,Institute of Engineering and Management | Goyal S.K.,Concordia University at Montreal
International Journal of Production Economics

In this paper three unlike coordinating contracts namely (i) joint rebate contract (ii) wholesale price discount contract and (iii) cost sharing contract are proposed for two echelon supply chain coordination perspective under stock and price induced demand. It is found analytically that the manufacturer's and the retailer's preferences among three contractual forms are not always aligned. By applying bargaining theory, it is established that stock elasticity plays an important role to select coordination contract and a threshold value stock elasticity is also determined, below which cost sharing contract is not feasible. It is also found that the retailer with higher bargaining power always prefers wholesale price discount contract among considered three contracts. Results are illustrated analytically as well as numerically. © 2015 Elsevier B.V. All rights reserved. Source

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