TiO2 films are extensively used in various applications including optical multi-layers, sensors, photo catalysis, environmental purification, and solar cells etc. These are prepared by both vacuum and non-vacuum methods. In this paper, we present the results on TiO2 thin films prepared by a sol-gel spin coating process in non-aqueous solvent. Titanium isopropoxide is used as TiO2 precursor. The films were annealed at different temperatures up to 3000 C for 5 hours in air. The influence of the various deposition parameters like spinning speed, spinning time and annealing temperature on the thickness of the TiO2 films has been studied. The variation of film thickness with time in ambient atmosphere was also studied. The optical, structural and morphological characteristics were investigated by optical transmittance-reflectance measurements, X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The refractive index and extinction coefficient of the films were determined by envelope technique and spectroscopic ellipsometry. TiO2 films exhibited high transparency (92%) in the visible region with a refractive index of 2.04 at 650 nm. The extinction coefficient was found to be negligibly small. The X-ray diffraction analysis showed that the TiO2 film deposited on glass substrate changes from amorphous to crystalline (anatase) phase with annealing temperature above 2500 C. SEM results show that the deposited films are uniform and crack free.
Wheat is an important food crop of the country. Its productivity lies in a very wide
range due to diverse bio-physical and socio-economic conditions in the growing regions.
Crop cutting and sample surveys are time consuming as well tedious, and procedure of
forecast is delayed. CAPE methodology, which uses remote sensing, ground truth and
prevailing weather, has been very successful, but empirical in nature. In a joint IARI-SAC
Research Programme, possibility of linking the dynamic wheat growth model with the
remote sensing input and other relational database layers was tried. Use of WTGROWS, a
wheat growth model developed at IARI, with the remote sensing and relational databases
is dynamic and can be updated whenever weather, acreage and fertilizer and other inputs
are received. National wheat yield forecast was done for three seasons on meteorological
sub-division scale by using WTGROWS, relational database layers and satellite image.
WTGROWS was run for historic weather dataset (last 25 years), with the relational
database inputs through their associated growth rates and compared with the productivity
trends of the met-subdivision. Calibration factor, for each met-subdivision, were obtained
to capture the other biotic and abiotic stresses and subsequently used to bring down the
yields at each sub-division to realistic scale. The satellite image was used to compute the
acreage with wheat in each sub-division. Meteorological data for each-subdivision was
obtained from IMD (weekly basis). WTGROWS was run with actual weather data obtained upto a given time, and weather normals use for subsequent period, and the forecast was
prepared. This was updated on weekly basis, and the methodology could forecast the
wheat yield well in advance with a great accuracy. This procedure shows the pathway for
Crop Growth Monitoring System (CGMS) for the country, to be used for land use planning
and agri-production estimates, which although looks difficult for diverse agro-ecologies and
wide range of bio-physical and socio-economic characters contributing to differential
A study was undertaken to validate the Wheat Growth Simulator (WTGROWS) in the farmers' fields of Alipur Block of Delhi and linking satellite derived vegetation index with the simulation model to estimate the wheat yield. Date of sowing, management practices and cultivars varied widely among the study sites. Leaf area index (LAI), phenological development and agronomic management (fertilizers and irrigation) were monitored at regular intervals for the 25 field sites selected in the study area. Above ground biomass and grain yield were recorded at harvest. Using the parameters derived for these sites, WTGROWS was run for each of the individual 25 sites. Crop phenology, temporal course of LAI and grain yield of each site was compared with the actual observations. The simulated and actual LAI temporal profile matched well for sites with different dates of sowing, excepting larger deviation noticed in the later stages of the crop growth. The simulated pre-anthesis duration and total above ground biomass were also correlated well with the observed values being mostly within ±15%. There were large discrepancies in simulated and observed grain yield. A satellite image near anthesis of IRS 1D LISS-3 was acquired for the study area. The sites were identified on the image and their vegetation indices were derived. Average grey value in Infrared (IR) and Red (R) band, Ratio Vegetation Index (RVI), Soil Adjusted Vegetation Index (SAVI) and Normalized Difference Vegetation Index (NDVI) were giving significant relation with measured LAI of 5th February which corresponded to crop anthesis stage. The relation between vegetation indices and LAI was logarithmic in nature. This logarithmic relation was incorporated into the WTGROWS to force the LAI to the equation-derived value at particular growth stage and model yield was computed and compared with actual observations.
We report on the investigation of a series of polyaniline based conjugated polymers with rather different backbone structure and energy gap in order to explore the effect of their molecular
architecture on nonlinear optical properties. In particular, we report on the dispersion of x<sup>(3)</sup> in the spectral range covering the rising slope of the optical absorption as well as in off resonance conditions.
Polymer thin film devices are fast emerging as efficient active elements for processing of optical signals for using civil, space and military applications. The requirements for a thin film material to be used in optical processing and communication are the high second and third order non-linear susceptibilities, low propagation loss and variable depth, propagation to allow the same device operate at different wavelength.
Amongst various sol-gel routes to deposit large area WO<SUB>3</SUB> films for electrochromic applications, the one using peroxotungstic acid based precursor solution gives superior electrochromic films. Further improvements in the properties are possible by chemical modification of the precursor material and by controlling the post deposition thermal treatment. Both these parameters affect physical, structural, electrical and as a result electrochromic properties of the films significantly. A detailed study of these properties of the films deposited with precursor solution modified with various organic additives and different thermal parameters was undertaken. X-ray diffraction, electron microscopy and resistance measurements were used to characterize and compare the films. These properties of the films correlated to their electrochromic behavior are reported in this paper.