Papers by Himanshu Trivedi
The electronic properties viz. total energy, band gap at Jones-zone face and bulk modulus of ZnS,... more The electronic properties viz. total energy, band gap at Jones-zone face and bulk modulus of ZnS, ZnSc and ZnTc semiconductor compounds with zincblende structure are investigated using higher-order perturbation theory, which includes covalent correction term. For describing the eloction-ion interaction in these semiconductor compounds, our proposed model potential con.si.sting of linear and quadratic type of interaction wiihin the core and Coulombic interaction outside the core is employed. The computed ratio of the covalent bonding term to the second order term ^ comes out to be 6.90% to 13 1% and hence confirms the essentiality of higher-order correction for zincblende-type crystals We have achieved a e^Kl agreement of present findings of total energy, band gap at Jones zone face and bulk modulus with the expemnental data and other such available fheoictical findings Keywords .
Journal of Applied Remote Sensing, 2021
Abstract. Our study demonstrates the potential of Airborne Visible/Infrared Imaging Spectrometer ... more Abstract. Our study demonstrates the potential of Airborne Visible/Infrared Imaging Spectrometer Next Generation (AVIRIS-NG) hyperspectral data and radiative transfer modeling to retrieve the atmospheric carbon dioxide (CO2) concentration from point source emission of one of India’s major coal-fed super thermal power plants at Kota, Rajasthan, India. AVIRIS-NG data with synchronous in situ measurements were collected as a part of the first ISRO-NASA joint airborne hyperspectral science campaign in India. The method utilized in our study includes theoretical simulations of at-sensor radiance in AVIRIS-NG spectral bands through the atmospheric radiative transfer model MODTRAN. Simulations were performed for the specific scene-sensor-atmospheric conditions pertaining to AVIRIS-NG overpass over Kota site. To eliminate the interfering effect of atmospheric water vapor with CO2 concentrations, simulations pertaining to variable water vapor values varying from 0.25 to 4.5 g / cm2 were a...
Thermodynamics of d a n d /-shell liquid metals-a variational approach J K Baria, H J Trivcdi, P ... more Thermodynamics of d a n d /-shell liquid metals-a variational approach J K Baria, H J Trivcdi, P N Gajjar and A R Jam'* D e p a rtm en t of Physics, Sardhi I'atcl U n iv e is ity. V allabh V id ya n a i!a i-3 $ 8 120, India R *m ail. |a y "b a ria @ y a h o o eom R e c e iv e d 2 S Mciv 2003, a a e p i e d 29 M arch 20(N \bstracl. K eccntly proposed potential is used to calculate internal energy (enthalpy), entropy and H c lm h o lt/ free eneigy of d and /-shell liquid "ciaK with the variation al approach T h e param eter o f the potential is determined w ith the standard zero pressuie condition along w ith w t II established l.uitM screening function fo r exchange and c orrelation effect T h e structure factor derived by Percus-Yevick solution for haid sphere nuids. w hich is jur.uten/ed by hard sphere diam eter, is used. A goixl agreement between theoretical investigations and experim ental findings has confirm ed the ability >! the model potential to the liq u id d and J-shell metals kt'V'^nrds ■ P s e u d o p o te n tia l, th e rm o d y n a m ic s , e n tro p y
Journal of the Indian Society of Remote Sensing, 2021
Land surface albedo (LSA) is an important parameter in surface-energy budget studies and process-... more Land surface albedo (LSA) is an important parameter in surface-energy budget studies and process-based models. Availability of LSA on a continental scale from the geostationary platform can be very useful in various applications and modelling activities. A study has been carried out to develop a narrow to broadband albedo conversion algorithm for estimating broadband LSA over India and surrounding from INSAT-3D (I3D) Imager observations. An atmospheric radiative transfer model was used to simulate the at-sensor reflectivity corresponding to two spectral bands of I3D Imager located in visible (0.55–0.75 μm) as well as shortwave infrared (1.55–1.70 μm) regions and a shortwave broadband spectral region (0.40–2.5 μm) for diverse land-atmospheric characteristics by assuming the surfaces as Lambertian targets. Then a mathematical relationship between reflectivity of two Imager bands and a shortwave broadband was developed based upon radiative transfer model simulation results, which yield...
Multispectral, Hyperspectral, and Ultraspectral Remote Sensing Technology, Techniques and Applications VI, 2016
Satellite based multispectral imagery contains various quantitative information related to surfac... more Satellite based multispectral imagery contains various quantitative information related to surface and atmosphere. To extract the accurate information about surface, we need to correct atmospheric influence which is introduced by the atmosphere. Atmospheric correction of multispectral satellite imagery is an important prerequisite to derive geophysical parameters from satellite data. In this study surface reflectance is retrieved using the Scheme for Atmospheric Correction of Resourcesat-2 (SACRS2). The SACRS2 is physics based atmospheric correction scheme developed at Space Applications Centre (SAC), ISRO based on radiative transfer model 6SV (The Second Simulation of the Satellite Signal in the Solar Spectrum vector version). SACRS2 method is easily applicable for atmospheric correction of multispectral data. A detail analysis has been carried out to retrieve surface reflectance from Resourcesat-2 AWiFS, LISS-3 and LISS-4 data using SACRS2 method. The retrieved surface reflectance from SACRS2 for AWiFS, LISS-3 and LISS-4 have been compared with in-situ measurements. The comparison showed a good match of reflectance derived by SACRS2 scheme with the in-situ measurements.
Journal of the Indian Society of Remote Sensing, 2013
Spectral features of plant species in the visible to SWIR (0.4–2.5 μm) region have been studied e... more Spectral features of plant species in the visible to SWIR (0.4–2.5 μm) region have been studied extensively, but scanty attention has been given to plant thermal infrared (TIR: 4–14 μm) properties. This paper presents preliminary results of a study that was conducted first time in India to measure radiance and emissivity properties of eight plant species in TIR spectral region in the field conditions using a FTIR (Fourier Transform Infrared) field spectroradiometer working in 4–14 μm at an agriculture experimental farm. Several spectral features in the emissivity spectra of plant species were observed that are probably related to the leaf chemical constituents, such as cellulose and xylan (hemicellulose) and structural aspects of leaf surface like abundance of trichomes and texture. Observations and results from the field measurements were supported by the laboratory measurements like biochemical analysis. These preliminary field emissivity measurements of leaves in TIR show that there is useful spectral information that may be detectable by field-based instrument. More detailed field and laboratory measurements are underway to explore this research theme.
Abstract. Recently proposed model potential which combines both linear and quadratic types of int... more Abstract. Recently proposed model potential which combines both linear and quadratic types of interactions is employed for the investigation of some properties like the total en-ergy, equation of state and bulk modulus of AlP, AlAs and AlSb semiconductor compounds using higher-order perturbation theory. The model potential parameter is determined us-ing zero pressure condition. The ratio of the covalent bonding term Ecov to the second-order term E2 is 6.77 % to 11.85 % which shows that contribution from higher order terms are important for zinc-blende-type crystals. The calculated numerical results of the total energy, energy band gap at Jones-zone face and bulk modulus of these compounds are in good agreement with the experimental data and found much better than other such theoretical ¯ndings. We have also studied pressure{volume relations of these compounds. The present study is carried out using six di®erent screening functions along with latest screening function proposed by Sar...
A correction to this paper has been published: https://doi.org/10.1007/s12524-021-01393-8
Semiconductor physics, quantum electronics and optoelectronics
Some electronic, thermodynamical and mechanical properties of Si 1-x Ge x solid solution with an ... more Some electronic, thermodynamical and mechanical properties of Si 1-x Ge x solid solution with an arbitrary (atomic) concentration (x) are studied using the pseudo-alloy atom model. This work is based on the pseudopotential theory of covalent crystals and on the higher-order perturbation scheme with the application of our proposed model potential. We have used the latest local field correction function proposed by Sarkar et al. alongwith other four local-field correction functions of Hartree, Taylor, Utsumi et al. and Farid et al. to study Si-Ge system. The total energy of the Si 1-x Ge x solid solutions is investigated and compared with available experimental data. The calculated numerical values of the heat of solution for Si-Ge system are small and positive. The positive sign of the heat of solution predicts that, at low temperatures, the phase mixture will be more stable than the disordered solid solution. Like the case of simple metals, it is seen that a graph of the ratio of the heat of formations and x(1−x) against x is linear. The bulk modulus of Si 1-x Ge x is also investigated with different concentrations x of Ge. We have found in the present study that the bulk modulus decreases linearly with an increase in the concentration x.
Land Surface and Cryosphere Remote Sensing III, 2016
The higher-order perturbation theory based on pseudopotential is used to calculate total energy, ... more The higher-order perturbation theory based on pseudopotential is used to calculate total energy, band gap at Jones-zone face and bulk modulus of CdS, CdSe and CdTe binary semiconductor compounds. The covalent correction term, which is approximately equal to third and fourth-order perturbation energy, is used in the present study. The ratio of covalent bond correction energy to second-order perturbation energy is about 15% and hence it is essential to study the electronic properties of semiconductor materials. Present theoretical results are found better than other available theoretical findings and good agreements of present finding of total energy, band gap at Jones-zone face and bulk modulus with the experimental data are achieved.
Journal of agrometeorology
Minimum and maximum air temperatures (hereafter called Ta min and Ta max) are important climatolo... more Minimum and maximum air temperatures (hereafter called Ta min and Ta max) are important climatological variables and accurate mapping its spatial-temporal distribution is useful in wide range of applications in the field of ecology, hydrology and atmospheric sciences. Air temperature (Ta) has been traditionally measured at large number of meteorological stations. However such meteorological measurements are not usually available with enough spatial density for accurate research purposes (Vogt et al., 1997; Willmott et al., 1991). The spatio-temporal pattern of near surface Ta is complex because it is affected by properties that vary greatly in both space and time (Prihodko and Goward, 1997). Satellite-based remote sensing technique is an alternative to provide spatially distributed information, because of its capability of systematic and synoptic coverage over a large geographical area (Czajkowski et al., 1997; Goward et al., 1994). The satellite-derived Land Surface Temperature (Ts...
International Journal of Applied Earth Observation and Geoinformation
This paper presents a method called SACRS2, a scheme for atmospheric correction of RS2-AWiFS (Res... more This paper presents a method called SACRS2, a scheme for atmospheric correction of RS2-AWiFS (Resourcesat2-Advanced Wide Field Sensor) data. The SACRS2 is a computationally fast scheme developed from a physics-based detailed radiative transfer model 6SV for correcting large amount of data from the high-repetivity AWiFS sensor. The method is based on deriving a set of equations with coefficients which depend on the spectral bands of the RS2-AWiFS sensor through forward signal simulations by 6SV. Semi-empirical formulations provided in the SMAC method with a few improvements have been used to describe various atmospheric interactions. A total of 112 coefficients for different equations are determined using the best fit equations against the computations of the 6SV. After the specific coefficients for the RS2-AWiFS spectral bands are determined, the major inputs of the scheme are raw digital numbers recorded by RS2-AWiFS sensor, atmospheric columnar water vapour content, ozone content, aero...
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2014
Remote sensing measurements from space born sensors are strongly attenuated by the scattering and... more Remote sensing measurements from space born sensors are strongly attenuated by the scattering and absorption processes through atmospheric molecules, aerosols and gases (ozone, water vapour, oxygen etc). The process of removing the atmospheric interference from the satellite-level signal is called atmospheric correction. Atmospheric correction can be performed through various methods such as, empirical method, semi-physical method, detailed radiative transfer models. Various methods exist for atmospheric correction of available global sensors such as NOAA-AVHRR, MODIS-Terra/Aqua, MERIS, Landsat-TM/ETM etc. However, there was no method available for atmospheric correction of the IRS data sets. A new physics-based model called Scheme for Atmospheric Correction of ResourceSat-2 AWiFS data (SACRS2) has been developed at Space Applications Centre (SAC) specifically tuned for the RS2-AWiFS sensor. This model has been developed from theoretical signal simulations using the 6SV (The Second ...
INSAT-3D is the new generation Indian Earth observation satellite to be launched by ISRO in near ... more INSAT-3D is the new generation Indian Earth observation satellite to be launched by ISRO in near future. It will provide enhanced observations of land, ocean and atmosphere through two payloads namely Imager and Sounder from geostationary orbit. The Imager payload is designed to sense solar-reflected and radiant energy from the Earth through six channels covering visible (VIS: 0.55-0.75µ m), shortwave infrared (SWIR: 1.551.70µm), middle infrared (MIR: 3.8-4.0µm), water vapor infrared (WVIR: 6.5-7.1µm) and thermal infrared (TIR1: 10.3-11.3µm and TIR2: 11.5-12.5µm) spectral regions. The TIR1 and TIR2 are two thermal channels that can be used to derive a key geophysical parameter- land surface temperature (LST) through a split-window algorithm. To derive LST from various satellite-based sensors several types of split-window (SW) algorithms have been developed in the past 25 years; however, SW algorithm for Indian sensor has not been attempted. A study has been conducted with the object...
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2014
Land Surface Temperature (LST) is an important parameter in the land surface processes on regiona... more Land Surface Temperature (LST) is an important parameter in the land surface processes on regional and global scale. The Land Surface Temperature Diurnal (LSTD) cycle of different land cover is an excellent indicator of the surface processes and their interaction with planetary boundary layer. The Kalpana-1 very high resolution radiometer (VHRR) LST product is available with 30 minute spatial resolution and 0.1 degree temporal resolution. A study was carried out with an objective to determine the LSTD parameters directly from K1-VHRR monthly averaged LST observations over Indian landmass. In this analysis, a harmonic function is fitted to LSTD from the K1-VHRR observations, where cosine term describing the effect of sun and exponential term represents decay of LST during nighttime. Using LSTD parameters, one can directly know the temperature amplitude, residual temperature and time of maximum temperature for each pixel. The LSTD parameters fitting accuracy in root mean square error (RMSE) and coefficient of determination (R 2) ranges between 0.5-2.5 K and 0.90-0.99 respectively for most of the pixels over Indian landmass. These LSTD parameters may bring new insight for estimation of thermal inertia and also useful in cloud screening algorithms.
ISPRS Journal of Photogrammetry and Remote Sensing, 2014
ABSTRACT Indian geostationary satellite Kalpana-1 (K1) offers a potential to capture the diurnal ... more ABSTRACT Indian geostationary satellite Kalpana-1 (K1) offers a potential to capture the diurnal cycle of land surface temperature (LST) through thermal infrared channel (10.5–12.5 μm) observations of the Very High Resolution Radiometer (VHRR) sensor. A study was carried out to retrieve LST by adapting a generalized single-channel (SC) algorithm (Jiménez-Muñoz and Sobrino, 2003) for the VHRR sensor over India. The basis of SC algorithm depends on the concept of Atmospheric Functions (AFs) that are dependent on transmissivity, upwelling and downwelling radiances of the atmosphere. In the present study AFs were computed for the VHRR sensor through the MODTRAN simulations based upon varying atmospheric and surface inputs. The AFs were fitted with the atmospheric columnar water vapour content and a set of coefficients was derived for LST retrieval. The K1-LST derived with the SC algorithm was validated with (a) in situ measurements at two sites located in western parts of India and (b) the MODIS LST products. Comparison of K1-LST with the in situ measurements demonstrated that SC algorithm was successful in capturing the prominent diurnal variations of 283–332 K in the LST at desert and agriculture experimental sites with a rmse of 1.6 K and 2.7 K, respectively. Inter comparison of K1-LST and MODIS LST showed a reasonable agreement between these two retrievals up to LST of 300 K, however a cold bias up to 7.9 K was observed in MODIS LST for higher LST values (310–330 K) over the hot desert region.
Pramana, 2005
Recently proposed model potential which combines both linear and quadratic types of interactions ... more Recently proposed model potential which combines both linear and quadratic types of interactions is employed for the investigation of some properties like the total energy, equation of state and bulk modulus of AlP, AlAs and AlSb semiconductor compounds using higher-order perturbation theory. The model potential parameter is determined using zero pressure condition. The ratio of the covalent bonding term Ecov to the secondorder term E2 is 6.77% to 11.85% which shows that contribution from higher order terms are important for zinc-blende-type crystals. The calculated numerical results of the total energy, energy band gap at Jones-zone face and bulk modulus of these compounds are in good agreement with the experimental data and found much better than other such theoretical findings. We have also studied pressure-volume relations of these compounds. The present study is carried out using six different screening functions along with latest screening function proposed by Sarkar et al. It is found from the present study that effect of exchange and correlation is clearly distinguishable.
Physica B: Condensed Matter, 2005
Recently proposed model potential for describing the electron–ion interaction is employed to calc... more Recently proposed model potential for describing the electron–ion interaction is employed to calculate total energy, energy band gap at Jones-zone face at X, equation of state and bulk modulus of GaP, GaAs and GaSb compounds using higher-order perturbation theory. The covalent correction term corresponding to third- and fourth-order perturbation energy terms are used to take account of covalent bonding effect in such semiconductors. The significant value of the covalent bonding term shows the essentiality of higher-order correction for zincblende-type crystals. We have employed five different screening functions alongwith the latest screening function proposed by Sarkar et al. in the present work. The numerical results for the total energy, energy band gap at Jones-zone face and bulk modulus of these compounds are in good agreement with the experimental data and found better than other such theoretical findings. The pressure and bulk modulus at different volumes are obtained by using such higher-order perturbation theory with the application of our model potential. The pressure obtained by this method is compared with pressure obtained by equations proposed by Murnarghan and Vinet et al. The present study also shows that the incorporation of different screening functions generates distinct effects.
Journal of Earth System Science, 2011
INSAT-3D is the new generation Indian satellite designed for improved Earth observations through ... more INSAT-3D is the new generation Indian satellite designed for improved Earth observations through two payloads-Imager and Sounder. Study was conducted with an aim of simulating satellite level signal over land in the infrared channels of the Imager payload using a radiative transfer model MODTRAN. Satellite level at-sensor radiance corresponding to all four infrared channels of INSAT-3D Imager payload is obtained using MODTRAN and sensitivity of at-sensor radiance was inferred as a function of input parameters namely, surface temperature, emissivity, view angle and atmospheric water vapour, which is helpful in understanding the signal simulation scheme needed for retrieving a very critical parameter namely, land surface temperature.
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Papers by Himanshu Trivedi