http://nopr.niscair.res.in/handle/123456789/11188 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/11198 Title: Effect of LiTiMg ferrite as substrate for linear array of equilateral triangular microstrip patches under external magnetic field <br/> <br/>Authors: Saxena, Naveen Kumar; Kumar, Nitendar; Pourush, P K S <br/> <br/>Abstract: An analysis of a linear array of four microstrip triangular patches modeled on LiTiMg ferrite has been carried out. Here, polycrystalline LiTiMg ferrite, which is synthesized by the solid state reaction technique (SSRT), has been used as a substrate. The comparison of radiation pattern and some other parameters when the antenna array is biased, perpendicularly with varying magnetic field, or unbiased has been presented in this paper. The results obtained are quite different in comparison to other tested ferrites like LiTi and LiTiZn. The results suggest that the proposed antenna will be useful for scanning purpose in defense systems. The electric and magnetic properties of ferrite have also been tested and presented. <br/> <br/>Page(s): 53-56 http://nopr.niscair.res.in/handle/123456789/11197 Title: Downscaling of NWP based meteorological variables for potential applications <br/> <br/>Authors: Singh, Devendra <br/> <br/>Abstract: A general problem with output from weather forecasting models is that modeled variables often do not compare well with ground-based weather variables and complex downscaling procedures are necessary to convert Numerical Weather Prediction (NWP) weather variables into realistic weather variables on the ground. NWP models have now firmly established as major forecasting tool and there is increasing use of Ensemble Prediction Systems (EPS) based probabilistic information in support of decision-making by forecasters as well as other special users. However, the challenges in down scaling the model forecasts, normally applicable for a grid area commensurable with the model resolution, to a meaningful location-specific product are by no means trivial. An attempt has been made in this study to down scale coarse resolution NWP based meteorological parameters to fine resolution products. The meteorological parameters considered for this study are temperature and downward surface shortwave radiation (DSSR) as important for ecological studies at regional scale. The comparisons have been carried out for the DSSR and temperature from satellite with that of <i style="">in situ</i> data. The NWP based fine grid data were found to be in good agreement with satellite and <i style="">in situ</i> data as compared to that of coarse resolution NWP parameters. The variations of these remapped fine grid parameters have also been studied at local and regional scale over India. <br/> <br/>Page(s): 45-52 http://nopr.niscair.res.in/handle/123456789/11196 Title: Investigation of surface energy budget over a humid tropical site at Ile-Ife, Nigeria: A comparison of eddy covariance and Bowen ratio methods <br/> <br/>Authors: Oladosu, O R; Sunmonu, L A <br/> <br/>Abstract: Research grade-data for estimating surface energy budget is still scarce for the humid tropical West African sub-region despite its vital importance in development and validation of the numerical models both at regional and global scales. The present paper examines the surface energy budget data collected over a humid tropical site at Ile-Ife, Nigeria (7.55^oN, 4.56^oE, 296 m) from eddy covariance (EC) and Bowen ratio (BR) methods during February/March and July 2007. The two periods represent transition from dry to wet and entirely wet season, respectively. The differences in the partitioning of the fluxes by both methods were examined. The mean closures were 92.21 and 80.72% for February/March and July, respectively. The EC and BR were found to partition fluxes differently. The BR estimation of sensible heat flux (H_S) was consistently higher than EC while the BR estimation of latent heat flux (H_LE) was higher in the morning hours before sunrise. At sunrise, however, the EC estimation H_LE was higher than that of BR. The difference in net radiation (R_N), ground heat flux (H_G), and soil moisture by both methods were also reported. <br/> <br/>Page(s): 37-44 http://nopr.niscair.res.in/handle/123456789/11195 Title: Diurnal and seasonal variation of GPS-TEC during a low solar activity period as observed at a low latitude station Agra <br/> <br/>Authors: Chauhan, Vishal; Singh, O P; Singh, Birbal <br/> <br/>Abstract: Employing a dual frequency GPS receiver at a low latitude station Agra (geographic lat 27.12⁰N, long 78.89⁰E, dip 41.1⁰), India (located just outside the equatorial anomaly crest), the measurement of ionospheric total electron content (TEC) has been carried out since 24 June 2006. Three years of data for a low solar activity period during 01 August 2006 - 31 July 2009 has been analysed. The temporal, seasonal and solar activity dependence of GPS-TEC data has been studied for the ionospheric region around Agra. The results show that the mean TEC varies from a minimum at 0500 hrs LT (LT=UT+5.5 hrs) to a peak value at about 1400 hrs LT and then decreases. The lowest values of TEC have been observed in winter whereas highest values have been observed in equinox and summer. The variation of the data has been compared with the variation of three solar indices, i.e. EUV flux, 10.7 cm solar radio flux (F_10.7), and sunspot numbers (SSN) during the period of analysis. It is found that all the solar indices show high correlation with day maximum TEC (TEC_max) in the summer than in equinox and low correlation is shown in winter season. It is also found that the data show high correlation with F_10.7 in the two seasons of summer and equinox while the same is found with EUV flux in winter. The correlation of TEC_max and SSN is found to be low as compared to those of F_10.7 and EUV flux in all seasons. The GPS-TEC data obtained at Agra station for the year 2009 has also been compared with global ionospheric maps (GIMs) of TEC and a very good correlation is found between the two. Further, GIMs of TEC have been analysed for five different latitudes along the common meridian of 80⁰E longitude. The present study has been carried out for three months of the year 2009 in each season. The role of equatorial ionization anomaly (EIA) crest is clearly visible on TEC data. These results are significant for Agra station which is a new location in the low latitude sector of Indian region. <br/> <br/>Page(s): 26-36