Papers

The undoped and Eu doped 0.5BaO.0.5 ZnO-Al2O3: xEu phosphors were prepared by the method of high temperature solid state reaction in air atmosphere. The phase formations of the samples were confirmed by taking powder XRD. Monoclinic phases of barium zinc oxides were identified. The mechanoluminescence (ML) studies of the samples were carried out via impulsive deformation technique (impact method). The ML emissions observed during the deformation of samples consist of two peaks such that intensity of second peak is relatively lower than the first. A large difference in ML decay timings were observed in undoped and Eu doped samples. Significant increase in ML intensities were observed due to Eu doping up to 0.3mole % and beyond that concentration of Eu the ML emission intensity decreases considerably. The decay constant of 0.5BaO.0.5 ZnO-Al2O3:0.3Eu is fairly good and also the sample showed a linear rise in intensity with impact velocity. All these suggest the suitability of the sample for stress sensing applications.

In this paper, an unsteady magnetohydrodynamic (MHD) natural convection heat transfer flow of electrically conductive non-Newtonian Casson fluid over a stretching sheet through vertical porous plate with an influence of heat generation and viscous dissipation is investigated. Similarity transformations are employed to transform the governing partial differential equations into ordinary differential equations. The transformed equations are then solved numerically by Runge-Kutta and shooting methods. The heat flow characteristics for different values of the parameters namely Casson fluid parameter, unsteadiness parameter, Eckert number, heat generation parameter, permeability porous parameter and Prandtl number are studied and discussed in detail. The increase of permeability porous parameter reduces the velocity field and enhances the fluid temperature. The heat generation source leads to an increase in thermal boundary layer thickness. The higher viscous dissipative heat causes an increase in the fluid temperature.

Exposure due to natural radiation is of particular importance because it accounts for the largest contribution (nearly 85 %) to the total collective dose of the world population. Uranium is a heavy metal that is not only radiologically harmful but also a well-known nephrotoxic element. In the present study, about 30 water samples were collected from open-wells ,Bore well and supplied water from taps, from the coastal region of Porakad, Allapuzha District. The Uranium concentration in the water samples was analyzed by light-emitting diode (LED)-based Ultraviolet (UV) fluorimeter (Quantalase Enterprises Pvt. Ltd, Indore, Madhya Pradesh, India). The associated age dependent Uranium intake was estimated by taking the prescribed water intake values. Most of the water samples had the Uranium concentration below the standards set by United States Environmental Protection Agency (30 ppb).

Halo and Full Halo CMEs (Coronal Mass Ejections) events observed by Solar and Heliospheric observatory (SOHO) mission are used to study their effects on cosmic ray intensity variations during 2009 to 2012, which correspond to ascending phase of recent solar cycle 24. It is found that the speed of HCMEs (Halo Coronal Mass Ejections) are significantly negative correlated with cosmic ray intensity. All the FHCMEs (Full Halo Coronal Mass Ejections) having the linear speed  1000 km/s produce transient decrease in cosmic ray intensity on short-term basis. The results of analysis indicated that the magnitude of decrease in cosmic ray intensity is large for high speed FHCMEs (Full Halo Coronal Mass Ejections) in comparison with low speed FHCMEs (Full Halo Coronal Mass Ejections).

Cellular phone technology has made radical changes in global telecommunication scenario with exponential growth in cell phones and base towers. The effect of non-ionizing electromagnetic radiations on human health is a subject of serious concern with the enormous installation of base stations. With a view to study the near field areas of base stations, we selected certain locations in southern districts of Kollam and Trivandrum in Kerala state, India. We assessed the power density of radio frequency waves from mobile towers using a handheld pocket digital LCD microwave leakage radiation detector. The area near the mobile towers were divided into concentric circles, each with increasing radii of 5m maximum. The survey was carried out in various towns having large population. The power density and Specific Absorption Rate (SAR) rates were determined from the field measurements. The present study was conducted only to near field and ground level radiations.