Assessment of Radio Coverage in Indian Cities Using FDTD

Prediction of Radio coverage has seen a massive surge of research in recent years. In this paper we attempt to predict the radio coverage of an extremely complicated urban scenario using a very sophisticated mathematical model called Finite-Difference Time-Domain (FDTD). FDTD technique helps us to model an urban area, with different obstacles, by numerically implementing the Maxwell’s equations. This enables us to find the electric and magnetic field strength of different regions. As the simulation is based on basic laws of electromagnetic theory, all the physical phenomena occurring in an urban space are taken into consideration. We use particular electromagnetic parameters such as, electric permittivity, magnetic permeability and electrical conductivity of the materials which form the obstacles. They are aided with the transmission data i.e Transmission power and frequency for deriving the radio power. The simulation is based on a 2 dimensional model of FDTD. This greatly increases our accuracy in complicated scenarios. This also helps us in finding the specific regions that are under very high exposure to radio signals and thereby accessing the risk of health hazards in such regions. In a last few decades, there has been a surge of research and novelty in prediction of radio power and radio coverage in different regions. The requirement of effective algorithms and proper platforms for simulations has been a prime driving cause. There are a number of models in place for determining radio power in a particular area. But the current tools are based on empirical and semi-empirical models for easier algorithms and short running time. These models have shown effective results in rural and semi-urban scenarios. But they seem to fail in extremely complicated urban scenarios, where all the obstacles must be accurately modelled. In these scenarios, we must take all possible physical phenomena, such as reflection, refraction, diffraction, transmissions and scattering, into consideration

Room Temperature Mott Hopping and Spin pumping Characterization of Amorphous Gd-alloyed Bi2Se3

Disordered films have gained intense interest because of their possibility for spintronics applications by benefiting from other exotic transport properties. Here, we have fabricated disordered Gd-alloyed Bi_x Se_(1-x) (BSG) thin films by magnetron sputtering methods and have investigated their magneto-transport and spin-torque properties. Structural characterizations show a mainly amorphous feature for the 8nm thick BSG film, while Bi rich crystallites are developed inside the 16nm thick BSG film. The bulk resistivity of BSG film is found to be relatively high, up to 6x10^4 uOhm.cm, with respect to the resistivity of the polycrystalline Bi_x Se_(1-x) film. Temperature dependent resistivity measurements display the evident character of a variable range hopping transport from 80K to 300K. Spin pumping transport characterizations have been performed on the BSG(t)/CoFeB(5 nm) bilayer structures with different thickness of BSG (t= 6, 8, 12, 16 nm). The possible various origins of the spin-to-charge conversion are related to extrinsic effects. Our study provides a new experimental direction, beyond crystalline solids, to the search for strong SOC systems in amorphous solids and other engineered random systems