Saroj Maity - Academia.edu (original) (raw)

Papers by Saroj Maity

It is important to monitor vegetation such as forests in order to understand the impacts of globa... more It is important to monitor vegetation such as forests in order to understand the impacts of global climate change on terrestrial ecosystems and agriculture crops to ensure food security to the people and livestock. Remote sensing data such as polarimetric SAR data plays a useful role in estimating total vegetation cover and biomass. In this study, a radar vegetation index (RVI) were used to separate vegetation from non-vegetated area and the same were used along with SAR backscatter values at different polarizations in C - and L-band to estimate above-ground biomass of a tropical forest. Models based on multi-frequency SAR data including X -, C - and L-band were developed to improve the estimation of forest biomass. Also, the study of agricultural crops using C - and L-band SAR data at different polarization modes revealed that C-band produced better classification results than L-band. However, L-band showed better correlation with crop growth variables. Further, full polarimetric data was found to be better than various modes of hybrid polarimetric data for crop studies.

Colloid and Polymer Science, 1998

Sol and Gel state properties of aqueous gelatin solutions of concentrations 4%, 6%, 8% and 10% (... more Sol and Gel state properties of aqueous gelatin solutions of concentrations 4%, 6%, 8% and 10% (w/v) have been investigated through dielectric relaxation studies done at various temperatures in the range T=20–60 °C carried out over a frequency range f=20 Hz–10 MHz and no relaxation of any nature was observed. The sharp transition observed at the gelation temperature T gel provided an excellent matching with the same measured through differential scanning calorimetry (DSC). The capacitance (C p) values above f=100 kHz became increasingly negative as the gel was melted to the sol state. However, in the gel state C p was found to be almost independent of temperature for frequencies above 100 kHz. At frequencies lower than 10 kHz, C p measured was ∼105 F, implying pronounced interfacial polarization either due to electro-chemical reaction or because of ions getting trapped at some interface within the bulk.

Colloid and Polymer Science, 1999

A Raman spectroscopic study was carried out on water in gelatin at 4% w/v in gel (25 °C) and sol ... more A Raman spectroscopic study was carried out on water in gelatin at 4% w/v in gel (25 °C) and sol (40–60 °C) states at various concentrations (0.5, 1, 5, 10 and 15 mM) of anionic surfactant, sodium dodecyl sulfate (SDS). The in-phase collective stretching mode vibration of hydrogen-bonded -OH oscillators, centered around 3250 cm−1 in a tetrahedral network of water molecules, was observed to be significantly affected by temperature and the presence of SDS. According to our observation this may be due to the thinning of the hydration water around the gelatin molecules due to strong thermal agitation. The peak center of the collective bands of water decreased linearly with SDS concentration in the gel state which implied that with the increase in concentration of SDS, the -OH oscillators gradually lost their attachment to gelatin chains and were replaced by SDS molecules. Ultimately this resulted in a thinning of the hydration layer around the gelatin and the oscillation frequency of -OH oscillators moved towards 3250 cm−1 at 1 mM SDS concentration resulting in increased coupling of -OH oscillators to form the tetrahedral network at the critical micelle concentration (cmc) of SDS. The variation in the peak amplitudes and the systematic reversal of their trend about the cmc axis was surprising. At 40 °C the amplitude of the peak at 3250 cm−1 increased drastically due to a possible coil expansion by about 7–8% which accommodated more interstitial water into the pseudonetwork leading to an increase in the number of nearest neighbors and for about 6% increase in the C value. However, at the cmc the peak amplitude was observed to be independent of temperature. Continuous shifting of the peak center and full width at half-maxima towards lower values was observed with increasing SDS concentrations in the gel state.

European Polymer Journal, 1998

ABSTRACT Polarized static laser light scattering experiments have been reported on dilute sols, s... more ABSTRACT Polarized static laser light scattering experiments have been reported on dilute sols, semi-dilute sols and gels of gelatin in the concentration range of 0.05% to 10% (w/v) at various ionic strengths. The static structure factor S(q) and the helix contents χ of the gelling solutions have been deduced from the measured intensity of scattered light, IVV(q) data and compared with optical rotatory dispersion (ORD) measurements. Below the threshold gelation concentration c*, S(q)∼q−d with d=2.15±0.08 in conformity with Guinier results. Above this concentration, at any temperature, S(q) could be empirically described as S(q)=(1−χ)exp(−q2Rg2/3)+χ exp(−q2L2); for Rg being the radius of gyration of gelatin chain and L being the length of the triple helices formed. In the gel state, this yielded two characteristic length scales; one corresponding to Rg (at large q) and another corresponding to L (at small q) as opposed to the single length scale Rg observed in all sol states.

Physical Review E, 1998

A photon correlation spectroscopy study carried out on semidilute 4% (wt./vol) aqueous gelatin so... more A photon correlation spectroscopy study carried out on semidilute 4% (wt./vol) aqueous gelatin sols and gels with the anionic surfactant sodium dodecyl sulphate (SDS) showed three relaxation processes in the dynamic structure factor data. First an exponential process S(q,t)~exp(-Dfq2t) at t<=20 mus, referred to as the collective mode, was observed, followed by an intermediate power-law regime S(q,t)~t-alpha(q) at 20 mus>=t<=1

IEEE Transactions on Geoscience and Remote Sensing, 2004

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2011

A polarimetric model has been developed to study the temporal growth of different vegetation cano... more A polarimetric model has been developed to study the temporal growth of different vegetation canopies, and their architecture. Eigen decomposition and coherency matrices are analyzed for completely polarimetric Radarsat-2 data. Polarimetric indices have been formulated using co and cross polarized backscattering coefficients, eigen values and eigen vectors. The polarization indices are used to completely understand the difference between polarized scattering signatures of vegetation in HH and VV polarizations. In this study, two decomposition techniques have been used like Freeman-Durden and H/A/α and their volume scattering and entropy components in conjunction with co and cross polarized indices are analyzed. This qualitative evaluation of vegetation parameters and growth stage are found to work better with polarimetric complex SAR data rather than using amplitude imagery.

It is important to monitor vegetation such as forests in order to understand the impacts of globa... more It is important to monitor vegetation such as forests in order to understand the impacts of global climate change on terrestrial ecosystems and agriculture crops to ensure food security to the people and livestock. Remote sensing data such as polarimetric SAR data plays a useful role in estimating total vegetation cover and biomass. In this study, a radar vegetation index (RVI) were used to separate vegetation from non-vegetated area and the same were used along with SAR backscatter values at different polarizations in C - and L-band to estimate above-ground biomass of a tropical forest. Models based on multi-frequency SAR data including X -, C - and L-band were developed to improve the estimation of forest biomass. Also, the study of agricultural crops using C - and L-band SAR data at different polarization modes revealed that C-band produced better classification results than L-band. However, L-band showed better correlation with crop growth variables. Further, full polarimetric data was found to be better than various modes of hybrid polarimetric data for crop studies.

Colloid and Polymer Science, 1998

Sol and Gel state properties of aqueous gelatin solutions of concentrations 4%, 6%, 8% and 10% (... more Sol and Gel state properties of aqueous gelatin solutions of concentrations 4%, 6%, 8% and 10% (w/v) have been investigated through dielectric relaxation studies done at various temperatures in the range T=20–60 °C carried out over a frequency range f=20 Hz–10 MHz and no relaxation of any nature was observed. The sharp transition observed at the gelation temperature T gel provided an excellent matching with the same measured through differential scanning calorimetry (DSC). The capacitance (C p) values above f=100 kHz became increasingly negative as the gel was melted to the sol state. However, in the gel state C p was found to be almost independent of temperature for frequencies above 100 kHz. At frequencies lower than 10 kHz, C p measured was ∼105 F, implying pronounced interfacial polarization either due to electro-chemical reaction or because of ions getting trapped at some interface within the bulk.

Colloid and Polymer Science, 1999

A Raman spectroscopic study was carried out on water in gelatin at 4% w/v in gel (25 °C) and sol ... more A Raman spectroscopic study was carried out on water in gelatin at 4% w/v in gel (25 °C) and sol (40–60 °C) states at various concentrations (0.5, 1, 5, 10 and 15 mM) of anionic surfactant, sodium dodecyl sulfate (SDS). The in-phase collective stretching mode vibration of hydrogen-bonded -OH oscillators, centered around 3250 cm−1 in a tetrahedral network of water molecules, was observed to be significantly affected by temperature and the presence of SDS. According to our observation this may be due to the thinning of the hydration water around the gelatin molecules due to strong thermal agitation. The peak center of the collective bands of water decreased linearly with SDS concentration in the gel state which implied that with the increase in concentration of SDS, the -OH oscillators gradually lost their attachment to gelatin chains and were replaced by SDS molecules. Ultimately this resulted in a thinning of the hydration layer around the gelatin and the oscillation frequency of -OH oscillators moved towards 3250 cm−1 at 1 mM SDS concentration resulting in increased coupling of -OH oscillators to form the tetrahedral network at the critical micelle concentration (cmc) of SDS. The variation in the peak amplitudes and the systematic reversal of their trend about the cmc axis was surprising. At 40 °C the amplitude of the peak at 3250 cm−1 increased drastically due to a possible coil expansion by about 7–8% which accommodated more interstitial water into the pseudonetwork leading to an increase in the number of nearest neighbors and for about 6% increase in the C value. However, at the cmc the peak amplitude was observed to be independent of temperature. Continuous shifting of the peak center and full width at half-maxima towards lower values was observed with increasing SDS concentrations in the gel state.

European Polymer Journal, 1998

ABSTRACT Polarized static laser light scattering experiments have been reported on dilute sols, s... more ABSTRACT Polarized static laser light scattering experiments have been reported on dilute sols, semi-dilute sols and gels of gelatin in the concentration range of 0.05% to 10% (w/v) at various ionic strengths. The static structure factor S(q) and the helix contents χ of the gelling solutions have been deduced from the measured intensity of scattered light, IVV(q) data and compared with optical rotatory dispersion (ORD) measurements. Below the threshold gelation concentration c*, S(q)∼q−d with d=2.15±0.08 in conformity with Guinier results. Above this concentration, at any temperature, S(q) could be empirically described as S(q)=(1−χ)exp(−q2Rg2/3)+χ exp(−q2L2); for Rg being the radius of gyration of gelatin chain and L being the length of the triple helices formed. In the gel state, this yielded two characteristic length scales; one corresponding to Rg (at large q) and another corresponding to L (at small q) as opposed to the single length scale Rg observed in all sol states.

Physical Review E, 1998

A photon correlation spectroscopy study carried out on semidilute 4% (wt./vol) aqueous gelatin so... more A photon correlation spectroscopy study carried out on semidilute 4% (wt./vol) aqueous gelatin sols and gels with the anionic surfactant sodium dodecyl sulphate (SDS) showed three relaxation processes in the dynamic structure factor data. First an exponential process S(q,t)~exp(-Dfq2t) at t<=20 mus, referred to as the collective mode, was observed, followed by an intermediate power-law regime S(q,t)~t-alpha(q) at 20 mus>=t<=1

IEEE Transactions on Geoscience and Remote Sensing, 2004

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2011

A polarimetric model has been developed to study the temporal growth of different vegetation cano... more A polarimetric model has been developed to study the temporal growth of different vegetation canopies, and their architecture. Eigen decomposition and coherency matrices are analyzed for completely polarimetric Radarsat-2 data. Polarimetric indices have been formulated using co and cross polarized backscattering coefficients, eigen values and eigen vectors. The polarization indices are used to completely understand the difference between polarized scattering signatures of vegetation in HH and VV polarizations. In this study, two decomposition techniques have been used like Freeman-Durden and H/A/α and their volume scattering and entropy components in conjunction with co and cross polarized indices are analyzed. This qualitative evaluation of vegetation parameters and growth stage are found to work better with polarimetric complex SAR data rather than using amplitude imagery.