Asian Journal of Research and Reviews in Physics

In this study, we revisit the concept of classical capacitor theory-and derive possible new explanations of the definition charge stored in a capacitor. We introduce the capacity function with respect to time to describe the charge storage in a classical capacitor and a fractional capacitor. Here we will describe that charge stored at any time in a capacitor as ‘convolution integral’ of defined capacity function of a capacitor and voltage stress across it which comes from causality principle. This approach, however, is different from the conventional method, where we multiply the capacity and voltage functions to obtain charge stored. This new concept is in line with the observation of charge stored as a step function and the relaxation current in form of impulse function for ‘ideal geometrical capacitor’ of constant capacity; when an uncharged capacitor is impressed with a constant voltage stress.  Also this new formulation is valid for a power-law decay current that is given by ‘universal dielectric relaxation law’ called as ‘Curie von-Schweidler law’, when an uncharged capacitor is impressed with a constant voltage stress. This universal dielectric relaxation law gives rise to fractional derivative relating voltage stress and relaxation current that is formulation of ‘fractional capacitor’. A ‘fractional capacitor’ we will discuss with this new concept of redefining the charge store definition i.e. via this ‘convolution integral’ approach, and obtain the loss tangent value. We will also show how for a ‘fractional capacitor’ by use of ‘fractional integration’ we can convert the fractional capacity a constant that is in terms of fractional units (Farads per sec to the power of fractional number); to normal units of Farads. From the defined capacity function, we will also derive integrated capacity of capacitor. We will also give a possible physical explanation by taking example of porous and non-porous pitchers of constant volume holding water and thus, explaining the various interesting aspects of classical capacitor and a fractional capacitor that we arrive with this new formulation; and also relates to a capacitor breakdown theory-due to electrostatic forces.

In this study, the effect of modifying boron doping concentration on the optical properties, electrical properties and microstructural images of TiO₂ thin films was investigated by the sol-gel technique by grinding TiO₂ powder with a boron compound at a wavelength range of 250 nm to 850 nm. The SEM micro-images revealed the homogenous, continuous and nanocrystalline surface morphology: 10% is the tolerable amount of boron doping concentration into the TiO₂ for achieving sphere-like nanostructures materials with low agglomeration. The XRD spectra of the B-TiO₂ films showed anatase peaks of greater intensities when compared to the pure TiO₂ film. All the films illustrate extinction coefficient in the visible region of solar spectra corresponding to the low absorption, and absorption peaks established in the ultraviolet region near 330nm with the optical transmittance varied from over 52 - 96% in the UV-Vis wavelength range. Diffuse reflectance absorption spectra analysis indicated that the incorporation of B into TiO₂ material results in a substantial red shift and the absorption extends significantly into the visible range. The optical band gap energy values of the thin films were found to be 3.38, 3.35, 3.28, 3.26, and 3.36eV. This showed a low probability of raising the electron across the mobility gap with the photon energy in the visible region. The refractive index values varied between 1.891 and 1.922 depending on the percentage content of boron. Moreover, the imaginary part of the dielectric constant increase slowly, whereas the real part increases sharply and the optical conductivity was found to increase with the increase in boron addition.

Measurement of radioactive contamination in some commonly consumed foodstuffs within the six area councils of Abuja, Nigeria was conducted in this study by means of a very sensitive and portable 3M/3-X Geiger Müller counter-based environmental radiation dosimeter. Eight different food samples were randomly selected in each of the sample locations making a total of 48 foodstuffs samples surveyed across the six area councils. The results obtained show that, the range of radiation dose levels in the analyzed samples varied from 0.01590.0001 to 0.34070.0002 μSvy^-1 at Bwari; 0.14900.0001 to 0.39020.0002 μSvy^-1 at AMAC; 0.00950.0001 to 0.02090.0001 μSvy^-1 at Gwagwalada; 0.00570.0001 to 0.01330.0002  μSvy^-1 at Kuje; 0.02740.0001 to 0.22710.0002 μSvy^-1 at Abaji; Kwali was between 0.01820.0001 and 0.35030.0002 μSvy^-1, and their corresponding arithmetic mean are 0.16900.0001 μSvy^-1, 0.22560.0001 μSvy^-1, 0.01330.0001 μSvy^-1, 0.00880.0001 μSvy^-1, 0.13600.0001 μSvy^-1 and 0.12370.0001 μSvy^-1, which gives estimated annual effective dose rates of 0.18850.0003 mSvy^-1, 0.25760.0001 mSvy^-1, 0.11700.0001 mSvy^-1, 0.07710.0001 mSvy^-1, 0.15530.0002 mSvy^-1, and 0.14120.0001 mSvy^-1 for Bwari, AMAC, Gwagwalada, Kuje, Abaji and Kwali area councils respectively. This finding reveals that the obtained values were sufficiently less than the maximum recommended global average exposure dose limit for environmental background (2.4 mSvy^-1) and general public dose limit (1.0 mSvy^-1). The radiation dose levels and dose rates associated with the intake of foodstuffs across the area councils are, therefore, relatively low and may not pose any immediate radiological health hazard to the populace, as deterministic radiation effects occur only in extreme cases.

Aims: To investigate The effect of concentration on organic solar cell efficiency.

Study Design:  Polymer and natural dye Eriochrome black T were deposited on ITO glass substrate, and then the resulted cells were tested for  characteristics.

Place and Duration of Study: International University of Africa Faculty of Pure and applied science-Department of Physics collaboration with University Medical Science and Technology- Alawia Centre and  AlNilain University – Faculty of Science and Technology – Department of Physics, between March 2016 and May 2017.

Methodology: we have dye of different colour, we select three colours the dye, and then UV-visible spectrometer used for absorption spectra. After that, the relation between absorption and wavelength, absorption coefficient, and energy band gap were found graphically. Finally, cells were designed on ITO glass substrate by using spin coating deposition. Characteristics measured.  

Results: The relation between the Eriochrome black T concentration of dye for three samples are 6.67, 6.03, and 5.43 g/L, and the corresponding efficiencies for dark blue are 0.091, 0.090 and 0.229 respectively. The efficiencies of yellow Eriochrome Black T are 0.228, 0.193 and 0.181. And the efficiencies of red Eriochrome Black T are 0.246, 0.235 and 0.193. The decreases of efficiency due to the decreases of Eriochrome Black T concentration is related to the direct relation between Eriochrome Black T concentration and solar cell.

Conclusion: The efficiency of dye-sensitised solar cells can be increased by increasing the Eriochrome Black T dye concentrations at least within the examined range. The Eriochrome Black T dye type also affect efficiency. This includes the transparency of the Eriochrome Black T dye beside the value of the Fermi energy. In addition to the relative positions of highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbits (LUMO) to nearby layers.

The problem of transient MHD natural convective flow past a vertical plate with thermal radiation, cross-diffusion and zero suction effects is investigated. The governing one-dimensional spatial and non-linear partial differential equations of the Boussineq form are non-dimensionalized to, among others, bring out the necessary parameters. The evolving dimensionless equations are transformed into ordinary differential equations using the similarity transformation, and linearized using the regular perturbation expansion series solutions. The linearization leads to the zeroth and first order equations, and are solved semi-analytically using the Mathematica 11.0 computational software. Expressions for the temperature, concentration, velocity, Nusselt number, Sherwood number and Skin friction are obtained, computed and presented graphically. The analysis of results, amidst others, shows that the increase in the Dufour number increases the temperature, but decreases the Nusselt number; the increase in the Soret number decreases the concentration, but increases the Sherwood number; the increase in the Prandtl number decreases the temperature and concentration, but increases the Nusselt number and Sherwood number; the increase in the Hartmann number decreases the velocity and skin friction. These results are benchmarked with the existing reports in literatures, and are in good agreement.