Asian Journal of Research and Reviews in Physics

Atmospheric concentrations of ⁷Be and ²¹²Pb were measured for 11 years (2008 – 2018) in Dar es Salaam, Tanzania. The mean activity concentrations of ⁷Be and ²¹²Pb were found to be within the range of 1.29 – 5.71 mBq/m³ and 10.85 – 50.06 mBq/m³, respectively. The annual mean activity concentrations of ⁷Be and ²¹²Pb were 4.72 ± 1.18 mBq/m³ and 29.76 ± 13.63 mBq/m³, respectively. Distinct annual trends were depicted on ⁷Be and ²¹²Pb, suggesting that the two radionuclides were affected differently with atmospheric conditions. Monthly atmospheric concentrations of ⁷Be showed a strong seasonal variation trend with the highest in January and February and lowest in April. ²¹²Pb depicted the highest concentration during June and July and lowest in January and December. The regression analysis for ⁷Be and ²¹²Pb activity concentrations together with number of meteorological parameters revealed that the relative humidity, rainfall, air temperature, absolute humidity and wind speed are the most significant parameters affecting radionuclides activity concentrations in the atmosphere. The sunspot numbers show 66.7% of its variability with ⁷Be activity concentration which further suggesting that other parameters may influence its variation. ²¹²Pb, on the other hand, shows only 27.3% of its variability which clearly indicates that the existence of cosmic rays does not affect its activity concentration in the atmosphere.

We discussed in this paper a fractional model arising in flow of three different incompatible fluids through a porous medium with mean microtubule pressure. The method adopted for obtaining the solution is the regular perturbation technique for the analytical solution and for the transformation of the boundary conditions. The results are in decent agreement with the findings of researched work reviewed in this paper.

Ramganga river is the main tributary of holy river Ganga and navigates through various cities of Uttarakhand and Uttar Pradesh of India. Its water quality is very important because a lot of population is directly connected to this river. Wavelet transforms is a new analytical tool to analyze non-stationary signals/data because it captures the localized time frequency information of a signal. In wavelet transforms, the Approximation gives the low frequency terms and average behaviour of any data, while Detail gives the high frequency terms and differential behaviour of any data.  The trend represents the slowest part of the signal and corresponds to the greatest scale value. As the scale increases, the resolution decreases, producing a better estimate of the unknown trend of the signal. The dissolved oxygen and biological oxygen demand data of station Kannauj, Uttar Pradesh from October 2015 to June 2020 are studied and processed by Haar wavelet transforms. The statistical parameters like skewness, kurtosis and correlation coefficient are determined and discussed. The strong agreement between wavelet analytical and statistical results is obtained.

Optical filters used specifically for special functions to block a particular wavelength or range of wavelength and transmit the rest of the spectrum have received research attention for the past few eras. Recently, optical filter based on multilayer coating are more focused due to potential to manipulate filter properties by changing layer thickness in order to apply in various fields. This Quarter wave stack (QWS) model design is one of the approaches to design optical filter such as edge filter. However, to obtain desire minimum specification need an optimization. Therefore, in this study aims to design optical edge filter based QWS model by optical matrix method in Octave software. In this design, MoS₂ and Si are being choose for high (H) and low (L) refractive index materials respectively. The optimum twenty-four (24) number of layers are determined by calculating maximum transmittance obtained. The Rayleigh wavelength ( λ_ex ) of 405 nm ,532 nm and 633 nm are selected and ‘glass|12HL|air’ configuration is set for the design simulation.  Then, the cut-on wavelength (λ_cut-_on) and cut-off wavelength ((λ_cut-_off) of successful designed optical edge filter are measured. The result shows that the cut-on wavelength of 408.11 nm, 536 nm and 640.25 nm with minimum effective transmission (MET) of 32.3%, 31.3% and 32% respectively are obtained. In conclusion, this present study shows the deviation between the calculated value and simulation of about 0.2 nm,1.7 nm and 1.15 nm for each λ_ex of 405 nm, 532 nm and 633 nm is determined.  But for λ_cut-_off, the value obtained are much higher than the calculated value. The MET of each filter is 32.3% ,31.3% and 32% for Rayleigh wavelength respectively.

Polymer optical fibre (POF) temperature sensors are rapidly replacing conventional temperature sensors owing to their unique and attractive features, such as small size, immunity to electromagnetic interference, multiplexing, and remote sensing capabilities. The recent developments in temperature sensing using polymer optical fibres are presented. Polymer optical fibre (POF) temperature sensors of various types: macro-bend fibre sensors, microfibre resonators, fibre Bragg grating, Fabry-Perot interferometers, and POF sensors coated with zinc oxide nanorods are discussed. This study also includes dual-parameter sensors to demonstrate intrinsic sensitivities of polymer fibres to temperature, relative humidity, and strain. The prospects and challenges of POF temperature sensors in the automotive industry, biomedical sector, chemical industry, and electrical power applications are also highlighted. This review aims to help researchers in this field identify areas of further work towards improving the accuracy and operating range of POF temperature sensors.