African Journals On-line
Nigeria Journal of Pure and Applied Physics

Volume 2 Number 1 August 2003
Abstracts

QUANTIFICATION OF SPECTRUM UTILIZATION

V. S. A. Adeloye

Department of Electrical Engineering, University of Ilorin, Ilorin. Nigeria.

Abstract. Given basic technical details such as transmitter power, location, antenna type, height and gain, the coverage area of the transmitter is estimated. For a bandwidth, B, and transmission period, T, of a radio communication transmitter, an equation is derived to substantially reduce the effect of assumptions and approximations of the expression, BAT, (which generally defines spectrum utilization, U) on the quantification of spectrum utilization, U. The derived expression is applied to VHF television transmitters in Nigeria.

DELINEATION OF FAULT ASSISTED AQUIFER USING TRIPOTENTIAL WENNER ARRAY-TECHNIQUE AROUND ITA-ONIYAN INDUSTRIAL LAYOUT, AKURE, NIGERIA

G. M. OLAYANJU

Department of Applied Geophysics, Federal University of Technology, P.M.B. 704, Akure, Nigeria

Abstract. Concealed fault assisted aquifer has been located by the tripotential resistivity survey with Wenner electrode configuration. The interpretations of data acquired were made in terms of comparison of the filtered and unfiltered Wenner alpha-apparent resistivity space sections, ratio profiles and computer aided qualitative interpretation of the alpha-apparent resistivity curves. The results of the study demonstrated that in order to be able to site borehole for underground water supply for both domestic and industrial uses in the study area, the well will have to be located along observed bedrock depression of high degree of fracturing, jointing and fissuring which will provide secondary porosity and permeability of the underlying crystalline bedrock. Although, high resistivity contrast of resistivity values at large electrode spacing seems to make the interpretation of the space sections and ratio sections difficult, filtered data however ensure a reasonable data integrity.

SOLAR ACTIVITY AND TOTAL COLUMN OZONE VARIATION IN LAGOS, NIGERIA

A.B. Rabiu and T.V. Omotosho

Department of Physics, Federal University of Technology, Akure, Nigeria

Abstract. Impacts of solar activity on the total column ozone variation within an interval of four years (1993-1997) have been investigated at an equatorial station of Lagos (06°33' N, 03°21' E) Nigeria. The linear regression analysis shows a significant negative correlation between mean total column ozone and solar activity both at monthly level (r = -0.0652, r² = 0.0043) and annual level (r = -0.2671, r² = 0.07138). Significant negative correlation (r = -3798, r² = 0.1375) exists between the two variables during low solar activity. The total column ozone decreases with increasing solar activity. Linear fits of the data were proposed. The data length needs to be extended and more data points created in equatorial regions.

SOLUTION GROWTH, CHARACTERIZATION AND POSSIBLE APPLICATIONS OF BERYLLIUM FLUORIDE (BeF₂) THIN FILMS DEPOSITED AT 320K AND AT pH of 7 - 12

*P. A. ILENIKHENA and **C.E. OKEKE,

* Department of Physics, University of Benin, Benin City, Nigeria

**Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria.

Abstract. Solution growth technique (SGT) was successfully used to deposit good quality BeF₂ thin films on glass slides at 320K for 3 hours and at pH of 7 – 12. The bath constituents were beryllium nitrate-4-water, and sodium fluoride as starting materials, sodium hydroxide as complexing agent and ethelemediamine tetra-acetate to vary the pH values. Effects of pH and bath constitutions were also investigated. Our numerous investigations reveal that beryllium fluoride thin films were produced only in alkaline medium. The deposited thin films modify the optical properties of the glass substrates at various wavelength regions. Average transmittance (T) values ranges from 0.615 – 0.904, reflectance (R) from 0.052 – 0.175, coefficient of absorption (a) (0.106 – 0.486) x10^-4 cm^-1 and refractive index (n) from 1.59 – 2.43. Values of solid-state properties such as band gap (E_g) range from 2.22-2.66 eV, electrical conductivity (s) from 0.73 – 1.26) X10^-5 (W-cm)^-1 and film thickness (t) from 465 - 214Å. Films with refractive index (n) lower than 1.8 have high transmittance (T) and low reflectance (R) while those with refractive index (n) greater than 1.8 have low transmittance (T) and high reflectance (R). The possible applications of the deposited beryllium fluoride (BeF₂) thin film in optical, architectural, agricultural and electronics industries were also discussed.

PRELIMINARY STUDY OF THE TRENDS IN MONOVACANCY FORMATION ENERGY OF METALS

A. M. Ukpong and I. A. Fuwape,

Department of Physics, Federal University of Technology, Akure, P. M. B. 704, Akure, Nigeria.

Abstract. The monovacancy formation energy has been calculated for the various metal series of the periodic table within the local density approximation of the density functional theory. The calculations were done using the full potential Kohn-Korringa-Rostoker (FP-KKR) approach and the ab initio relaxed core pseudopotential in combination with the supercell approach. The results obtained from these calculations are in good agreement with experimental values obtained from positron annihilation rates. An interpretation of the trends in the variation of the formation energies through these metal series is also presented.

NATURAL RADIONUCLIDES CONTENT OF SOME LOCAL CEREALS IN AKURE, SOUTH WESTERN NIGERIA

A. M. AROGUNJO

Department of physics, Federal University of Technology Akure. Ondo State, Nigeria.

Abstract. The natural radionuclides contents of cowpea (Vigna unguiculata L walp), guinea corn (Sorghum bicolor L), rice (Oryza sativa L) and soyabean (Glycin max L) have been investigated. The specific activities ranged from 36.4 ± 13.5 Bqkg^-1 to 186.9 ± 23.1 Bqkg^-1 for ⁴⁰K, 0.2 ± 0.1 Bqkg^-1 to 1.4 ± 0.5 Bqkg^-1 for ²³⁸U, and 0.3 ± 0.1 Bqkg^-1 to 1.8 ± 0.7 Bqkg^-1 for ²³²Th. Cesium - 137 was not detected in any of the cereals investigated.

MATHEMATICAL MODELLING OF ALUMINUM SURFACE WHEN DIPPED IN MOLTEN METAL

G. A. Osinkolu and D. A. Pelemo

Division of Material Science and Electronics, Centre for Energy Research and Development

Obafemi Awolowo University, Ile-Ife, Nigeria

Abstract. A mathematical model is presented to describe the undulating surface of aluminium casting during an industrial process involving the dipping of the mould, at a particular velocity, into the molten metal. The problem of air gap formation between the mould and the casting was also considered. Below certain value of the mould velocity the shape of the casting as well as its thickness remain practically unchanged with changes in mould velocities. The undulating surface disappears when the mould temperature is in excess of 120^oC.

ELECTRICAL PROPERTIES OF ANTIMONY (Sb) METAL CONTACTS TO SILICON (Si) THIN FILMS

S. S. OLUYAMO

Department of Physics, Federal University of Technology, Akure, Nigeria

Abstract. The study investigates the behaviour of the contacts formed by Antimony (Sb) metal to Silicon (Si) thin films for electric field values 10 – 100V/m. Measurements of I-v characteristics were obtained at temperatures 303, 313, 323, 333, 343 and 353K respectively. The results show linear I – V relationship over a specified range of voltage (10 – 60V) and at higher voltage (>60V), there was deviation from linear behaviour for each of the temperature. The electrical surface conductance of the samples increases with temperature while the saturation current density decreases with temperature. Nonetheless, the study revealed very little increase in the values of the barrier heights with increasing temperature.

SOME ASPECTS OF THE SEDIMENT TRANSPORT CAPACITIES OF OGBESE AND OWENA RIVERS

C.S. OKOLI

Department of Civil Engineering, Federal University of Technology, Akure

Abstract. In this paper, the effect of sediment transport capacities of Ogbese and Owena Rivers were examined. The data were obtained from field investigations carried out on the two rivers respectively. The result obtained is in the form of power law relationship. Calibrating yield the values for k₁ and k₂ which are the erosivily coefficients. When tested, the predicted models for the two rivers performed well when compared with the established models (R² = 0.998, 0.929). It is concluded that models which will be useful for scientific and engineering applications on the two rivers have been developed.

DESIGN AND CONSTRUCTION OF AN INFRARED ACTIVATED ENTRANCE AND EXIT COUNTING DEVICE

A. S. Adekola, A. M. Arogunjo, K. D. Adedayo and S. B. Eniafe

Department of Physics, Federal University of Technology, P. M. B. 704, Akure, Nigeria

Abstract. This paper presents the design procedure and construction of a low powered entrance and exit counting device. It uses infrared activated transmitter and receiver. The particular circuits that have been employed have been constructed using available components. The counter is capable of counting solid objects to a maximum value of nine thousand nine hundred and ninety nine.