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Emission characteristics of dry and wet loamy sand soil layered pack at microwave frequencies

2014-01-22T16:54:08Z

Title: Emission characteristics of dry and wet loamy sand soil layered pack at microwave frequencies Authors: Calla, O P N; Singh, R K Abstract: The emissivity estimated at different moisture content and at different frequencies is reported for a typical loamy sand soil. It is observed that the emissivity of soil pack depends on frequency as well as on moisture content and the depth of layer at which moisture is present. The estimated emissivity also shows dependence on look angle and polarization. The estimated values of emissivity can be used for designing passive remote sensing instruments. Page(s): 285-292

An adaptive polynomial path loss model at UHF frequencies for mobile railway communications

2014-01-19T16:49:24Z

Title: An adaptive polynomial path loss model at UHF frequencies for mobile railway communications Authors: Ravindra, K; Sarma, A D; Prasad, M V S N Abstract: Study of channel behaviour for efficient spectral usage has been the key aspect in the design of third generation (3G) mobile communications systems. This paper deals with modelling of UHF signals acquired in a moving train corresponding to a distance of 180 km in northern India starting from New Delhi to Sharanpur, covering various environmental zones. A new sixth order adaptive polynomial model is proposed to further model the deviation of earlier adaptive three coefficient model. The standard deviations of the predictions made by the proposed model from the experimental data are within 2.1 dB throughout the region of experimentation in contrast to a maximum of 24 dB reported earlier. Page(s): 278-284

Chemical composition of size-separated aerosols at two rural locations in the Himalayan region

2014-01-18T16:51:58Z

Title: Chemical composition of size-separated aerosols at two rural locations in the Himalayan region Authors: Safai, P D; Rao, P S P; Momin, G A; Ali, K; Tiwari, S; Naik, M S; Kuniyal, J C Abstract: Size-separated atmospheric aerosols were collected at Kothi (a hill top) and Mohal (a valley), situated at the foothills of western Himalayas during the summer season of 1999. Bimodal distribution of aerosols was observed at both the locations. However, at Kothi, fine size particles dominated (62%), whereas at Mohal, coarse size particles contributed more (75%). The SO₄ and NO₃ particles together contributed ~ 30% of the total measured chemical composition of aerosols. Burning of biomass and emissions from tourist vehicles could be the main local sources for these components. However, aerosols showed alkaline nature (Σ^-Σ⁺ ratio< 1) due to the neutralizing effect of some cations such as Ca and NH₄. Page(s): 270-277

Radio visibility at microwave frequencies

2014-01-22T16:54:36Z

Title: Radio visibility at microwave frequencies Authors: Karmakar, P K; Maiti, M; Mitra, A Abstract: Radio visibility through water vapour has been studied over Calcutta at microwave/ millimetre wave frequencies. Due to large abundance of water vapour over Calcutta, the integrated water vapour content restricts the radio visibility approximately up to 5 km at different microwave/millimetre wave frequencies. The present study has been restricted to only the total absorption (dB) part of the propagation parameters of radio waves. The vertical layers of atmosphere have been divided into 10m slabs with the assumption that the meteorological parameters remain unchanged quantitatively within any of these slabs. The height at which the variation of total absorption (dB) is less than or equal to 1% of that of the immediate preceding height (which is one slab thickness less), is, here, defined as 1% height limit. It has been found that beyond this height the radio receivers at microwave/millimetre wave frequency suffer no appreciable change in the total absorption. Page(s): 264-269