http://nopr.niscair.res.in/handle/123456789/4506 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/4535 Title: Broadband aperture-coupled equilateral triangular microstrip array antenna <br/> <br/>Authors: Mulgi, S N; Pushpanjali, G M; Konda, R B; Satnoor, S K; Hunagund, P V <br/> <br/>Abstract: The aperture-coupled equilateral triangular microstrip array antenna comprising parasitic element and slot for broadband operation is designed and presented. An experimental study is carried out to see the effect of slot placed in the parasitic and radiating elements for enhancing the impedance bandwidth. The four-element aperture-coupled equilateral triangular microstrip array antenna (FAEMA) using a common parasitic element in the form of gap-coupled between the two radiating element gives an impedance bandwidth of 18.46%. If the slot is placed at the center of all elements of FAEMA, the impedance bandwidth is found to be 18.57%. However, this bandwidth is enhanced to 19.04% by placing the slot at the center of radiating elements of FAEMA. Further, the bandwidth is increased from 19.04 to 19.07% by placing a slot at the center of parasitic element of FAEMA. This bandwidth is 38% more when compared to four-element array antenna without using parasitic elements. The gain, azimuthal radiation patterns and input impedance of proposed antennas are studied and reported. Details of the antenna design are given and experimental results are discussed. <br/> <br/>Page(s): 174-179 Fri, 29 May 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/4534 Title: Multi dimensional scaling of geomagnetic Sq (H) variations <br/> <br/>Authors: Sridharan, M; Selvaraj, R Samuel <br/> <br/>Abstract: The dominant relationship in respect of geomagnetic solar quiet day variations (Sq) among the six Indian geomagnetic observatories is analysed by employing multidimensional scaling. This is a powerful technique for data analysis to identify the proximity and dominance relationship between data points of different classes. <br/> <br/>Page(s): 165-173 Fri, 29 May 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/4533 Title: Study of Z-R relationship over Gadanki for different rainfall rates <br/> <br/>Authors: Jaiswal, R Sen; Uma, S; Santhakumaran, A <br/> <br/>Abstract: In this paper, Z-R relationship for different rain fall rates over Gadanki has been studied over a period of four years 1998-2001. The basic data set consists of rainfall rates and reflectivities derived from disdrometer during this period. The study has been carried out for rainfall rates R≤ 0.5 mmh^-1, 0.5< r≤ 4.0 mmh^-1, 4< r≤ 10 mmh^-1, 10< r≤ 50 mmh^-1 and R> 50 mmh^-1. The study shows that Z-R relationship varies for different rainfall rates. The various functional relations between reflectivity and rainfall rate are obtained. </r≤></r≤10></r≤> <br/> <br/>Page(s): 159-164 Fri, 29 May 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/4532 Title: Imaging observations of upper mesospheric nightglow emissions from Tirunelveli (8.7^oN) <br/> <br/>Authors: Narayanan, V Lakshmi; Gurubaran, S; Emperumal, K <br/> <br/>Abstract: An all-sky airglow imager was installed at the equatorial site Tirunelveli (8.7^oN, 77.8^oE geographic; 1.34^oN magnetic dip) during January 2007 to study the small-scale dynamics occurring in the mesosphere-lower thermosphere (MLT) region. The instrument details are presented in the paper along with methods of information retrieval from the recorded data. The presence of a variety of small-scale mesospheric dynamical events, observed with the instrument, is demonstrated. Preliminary results on the observed features, viz. the quasi-monochromatic gravity waves and instability features, such as ripples and mesospheric bores, are presented in the paper. <br/> <br/>Page(s): 150-158 Fri, 29 May 2009 22:58:59 GMT