Assessment of Spatial Exposure to RF Radiation due to GSM 900 and GSM1800 – A Case Study of UCH, Ibadan, Nigeria

An assessment of radiofrequency exposure due to GSM 900 and GSM 1800 was carried out at 30 strategic locations in the University College Hospital (UCH), Ibadan with a frequency selective spectrum analyzer (SPECTRAN HF 60105). The Spectrum analyzer was coupled to a calibrated Omnidirectional antenna to obtain a spatial power density for each location. The mean power densities of 38.37µW/m 2 and 8.68µW/m 2 and maximum power densities of 212.40µW/m 2 and 67.40µW/m 2 were obtained for GSM 900 and GSM 1800 respectively. The standard deviation of 51.3 µW/m 2 and 14.90µW/m 2 were also obtained for GSM 900 and GSM 1800 respectively. GSM 900 and GSM 1800 respectively show compliance level of 0.0047% and 0.00075% with the ICNIRP reference level

EFFECTS OF DEFORMATION ON THE ENERGIES OF METALS

In this work, a model for computing the correlation, binding and cohesive energy of deformed and undeformed metals was developed based on the structureless pseudopotential formalism. Using the developed model, the correlation, binding and cohesive energy of metals were computed and studied. Also, the computed binding and cohesive energy of metals were compared with available experimental values. The results obtained showed that correlation energy increases with increase in electron density parameter. An increase in deformation was found to cause corresponding increase in the correlation energy. The computed binding energy and cohesive energy of metals were in good agreement with experimental values. The results obtained further showed that deformation causes a decrease in the binding energy of metals and it does not cause a significant change in the cohesive energy of metals, although transition metals have high values of cohesive energy compared to alkaline and simple metals. Keywords: Metals, pseudopotential model,cohesive, binding and correlation energy

Calculation Of Positron Annihilation Rates In Metals Using Different Enhancement Factors

Positron annihilation rates in metals were calculated using the enhancement factors of Boronski and Nieminen (1986), Sterne and Kaiser (1991), and the local density approximation by solving the Kohn-Sham type of equation self-consistently for electron-positron densities in metals using an interactive scheme. The experimental and calculated positron annihilation rates in metals exhibit the same trend. The results obtained revealed that there is no significant difference in the positron annihilation rates calculated using the enhancement factors of Boronski and Nieminen (1986) and that of Sterne and Kaiser (1991). Furthermore, the results revealed that the positron annihilation rates calculated using the enhancement factor of the local density approximation were in better agreement with experimental values than the ones calculated using the enhancement factors of the two other models or approximations. This shows that the use of local density approximation is better in the prediction of positron annihilation rates in metals; and that the enhancement factor of the local density approximation explains electron-positron correlation in metals better than other models or approximations. Explanations for the observed discrepancies between the experimental and calculated positron annihilation rates in metals are given. Keywords: Metals, positrons, annihilation rates, enhancement factors Nigerian Journal of Physics Vol. 19 (1) 2007: pp. 1-

Depth profiling of aluminium metal using slow positron beam

Slow positron beam Doppler-broadening technique was used to study depth profiling of aluminium metals sample. The variation of the line-shape parameters with incident positron energy was studied. Also, the depth profile of the S parameter was investigated. The positron implantation profile and backscattering fraction for aluminium sample was studied theoretically using data obtained empirically by Monte Carlo simulation. Results obtained revealed that aluminium metal has high S parameter in the surface and near surface regions and low S parameter in the bulk. The value of the S parameter decreased from the surface region reached a minimum at S = 0.292 and started to increase. While the W parameter increased and reached a value of 0.199 and started to decrease. The calculated positron implantation profile decreased with increase in the energy of the incident positrons but the implantation profile depth increased with an increase in the energy of the incident positrons. The results further revealed that the backscattering fraction increased with increase in the energy of the incident positrons. Keywords: Material, positron annihilation, structure and vacancy Nigerian Journal of Physics Vol. 18 (1) 2006: pp. 19-2

Calculation of the structure factor of liquid metals

Applying the solution of the Percus-Yevick equation to a one component system and using a screened pseudopotential, a model is developed for calculating the structure factor of liquid metals at different temperatures and densities. The model was tested using both simple and non-simple liquid metals. The results obtained were in very good agreement with experimental values for all the metals used to test the model. The model can reproduce the peak positions in the structure factor of liquid metals within the limit of experimental errors. Also the study revealed that the peak positions in the structure factor of liquid metals occur when the screened potential is a minimum. Also, increase in temperature increases the magnitude of the structure factor but does not affect the peak positions. The model can be use to calculate the structure factor of liquid metals at different temperatures and densities. Keywords:One component, structure, factor, screened potential Nigerian Journal of Physics Vol. 18 (1) 2006: pp. 25-3

On The Surface Energy Of Elemental Metals Using The Stabilized Jellium Model

The surface energy of elemental metals was calculated using the stabilized jellium approach. The surface energy of the (111), (100) and (110) faces of the face centred cubic (fcc) and body centred cubic (bcc) metals was also calculated. The calculated surface energy of metals was compared with experimental values and the variation of the calculated and experimental surface energy of metals with electron gas parameter was studied. The surface energy of metals calculated based on the kinetic, electrostatic, exchange-correlation, and pseudopotential components were higher than experimental values. The surface energy calculated without taking the different components into consideration was in perfect agreement with experimental values in the low-density regim. But in the high-density limit, there were discrepancies between the calculated surface energies and experimental values. The discrepancies increased towards the high-density limit. The calculated face dependent surface energy of bcc metals reveal that the (111) face has the highest surface energy while the (110) face has the least surface energy. But for the fcc metals the (110) face has the highest surface energy while the (111) face has the least surface energy. Keywords: Metals, surface energy, stabilized jellium model, electron density parameter Nigerian Journal of Physics Vol. 19 (1) 2007: pp. 9-1

Development of Electron-positron Screened Pseudopotential

In the jellium model, for electron-positron annihilation to take place, the positron must overcome the screened potential of the valence electrons. In this paper, we develop electron-positron screened pseudopotential to explain positron annihilation rate in metals. The results obtained show that there is a trend in the variation of the screened pseudopotential for metals in the same group in the periodic table and also that the higher the positron annihilation rate in a metal the higher the screened pseudopotential experienced before annihilation. Nigeria Journal of Pure and Applied Physics VOLUME 1, AUGUST 2000, pp. 24-2