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Synthesis of Cu and Ce co-doped ZnO nanoparticles: crystallographic, optical, molecular, morphological and magnetic studies

Rawat M., Singh J., Singh J., Singh C., Singh A., Kukkar D., Kumar S.

Materials Science Poland

2017

Vol. 35, No. 2

427--434

In the present research work, crystallographic, optical, molecular, morphological and magnetic properties of Zn1-xCuxO (ZnCu) and Zn1-x-yCeyCuxO (ZnCeCu) nanoparticles have been investigated. Polyvinyl alcohol (PVA) coated ZnCu and ZnCeCu nanoparticles have been synthesized by chemical sol-gel method and thoroughly studied using various characterization techniques. X-ray diffraction pattern indicates the wurtzite structure of the synthesized ZnCu and ZnCeCu particles. Transmission electron microscopy analysis shows that the synthesized ZnCu and ZnCeCu particles are of spherical shape, having average sizes of 27 nm and 23 nm, respectively. The incorporation of Cu and Ce in the ZnO lattice has been confirmed through Fourier transform infrared spectroscopy. Room temperature photoluminescence spectra of the ZnO doped with Cu and co-doped Ce display two emission bands, predominant ultra-violet near-band edge emission at 409.9 nm (3 eV) and a weak green-yellow emission at 432.65 nm (2.27 eV). Room temperature magnetic study confirms the diamagnetic behavior of ZnCu and ferromagnetic behavior of ZnCeCu.

Closed-form Distribution and Analysis of a Combined Nakagami-lognormal Shadowing and Unshadowing Fading Channel

Singh R., Rawat M.

Journal of Telecommunications and Information Technology

2016

nr 4

81--87

The realistic wireless channels face combined (time shared) Nakagami-lognormal shadowing and unshadowing fading because of time varying nature of radio channel and mobile user. These channels can be modeled as time-shared sum of multipath-shadowing and unshadowing Rician distributions. These fading create severe problems in long distance wireless systems where multipath fading is superim-posed on shadowing fading (called multipath-shadowing fading). The multipath effect can be modeled using Rayleigh, Rician, Nakagami-m or Weibull distribution and shadowing effect is modeled using lognormal distribution. In this paper, authors present a new closed-form probability distribution function of a Nakagami-lognormal fading channel. Using this result, the closed-form expression of combined Nakagami-lognormal shadowing and unshadowing fading is presented. The obtained closed-form result facilitates to derive the important performance metrics of a communication system such as amount of fading, outage probability, and average channel capacity in closed-form expressions.

Measurements of radon flux and soil-gas radon concentration along the main central thrust, Garhwal Himalaya, using SRM and RAD7 detectors

Bourai A., Aswal S., Rawat M., Prasad M., Naithani N., Joshi V., Ramola R.C.

Acta Geophysica

2013

Vol. 61, no. 4

950--957

Radon in the Earth’s crust or soil matrix is free to move only if its atoms find their way into pores or capillaries of the matrix. 222Rn atoms from solid mineral grains get into air, filling pores through emanation process. Then 222Rn enters into the atmosphere from air-filled pores by exhalation process. The estimation of radon flux from soil surface is an important parameter for determining the source term for radon concentration modeling. In the present investigation, radon fluxes and soil-gas radon concentration have been measured along and around the Main Central Thrust (MCT) in Uttarkashi district of Garhwal Himalaya, India, by using Scintillation Radon Monitor (SRM) and RAD7 devices, respectively. The soil radon gas concentration measured by RAD7 with soil probe at the constant depth was found to vary from 12 ± 3 to 2330 ± 48 Bq m–3 with geometrical mean value of 302 ± 84 Bq m–3. The significance of this work is its usefulness from radiation protection point of view.