Vol. 6 Issue 1

E.H. Twizell and A.Q.M Khaliq
A family of numerical methods is developed for the numerical solution of fourth order parabolic partial differential equations in one space variable with time dependent boundary conditions. The methods arise from a two-step, one parameter family for the numerical solution of systems of second order ordinary differential equations with time dependent source terms. Global extrapolation procedures in time only and in both space and time are discussed

M.S. Abu-Salih and A.A. Shamseldin
We investigate Bayesian estimation of P(X

W.A. Bassali, M.N.Y. Anwar
Exact expressions in infinite series are given for the small deflections, moments and shears in a thin isotropic circular plate subject to normal paraboloidal loading distributed over the area of a concentric ellipse and supported at the four corners of a concentric rectangle whose sides are parallel to the axes of the ellipse. Limiting cases are investigated. Numerical results are presented in the form of tables and graphs illustrating variation of the deflection, moments and shears along various radii in the first quadrant of the plate

D.A. Al-Sammerrai and F.M. Sammerrai and Z.S. Salih
Two aromatic extracts separated from light (grade 40) and heavy (grade 60) petroleum oil distillates by a selective solvent (furfural) were subjected to nitration followed by catalytic reduction to their corresponding amine derivatives. Only the polyaromatic constituents of the extracts underwent these reactions. The effectiveness of various concentrations of the products obtained in inhibiting oxidation of a mineral oil sample under oxidizing conditions was studied statistically by differential scanning calorimetry (DSC) and dynamically by a catalytic oxidation test procedure. The results obtained from these two methods of evaluation, indicated that, the petroleum derived from aromatic amine compounds imparted good antioxidant protection to the mineral oil

Selim F, Estefan
A safe and profitable method of utilizing phosphogypsum byproduct has been devised involving pretreatment of the sample to minimize impurity content, followed by reaction of the residual phosphogypsum with ammonium carbonate to produce ammonium sulphate fertilizer. The prepared fertilizer was subjected to some physico-chemical tests which proved it to be of good quality, suitable for modulating the pH of the highly alkaline Egyptian soil.

Abdulrahman I. Al-Mansour
Under the conditions where (PhMe2Si)3CSiMe2Cl is inert towards a range of organolithium reagents, the secondary organosilicon chloride (PhMe2Si)3CSiMeHCl reacts with MeLi, EtLi or LiBu^n to give (PhMe2Si)3CSiMe2H, (PhMe2Si)3CSiMeEtH or (PhMe2Si)3CSiMeBu^n H, respectively, but not with LiBu^t. Similar results are obtained from reaction of (Me3Si)3CSiMeHCl with organolithium reagents

H. Sofrata
Large central air conditioning systems, located in a hot and humid environment typical of the Gulf, can be a useful source of high quality water. Moisture condensing on the cooling coils could be collected and treated for use as drinking water. The system considered is as follows: The return air to the cooling coils is divided into two streams. One, after mixing with fresh ventilating air, is passed over the cooling coil at a low dew point to condense the maximum amount of vapous. This cooled stream is then mixed with the second hot stream, to provide air for the conditioned space at the required comfort condition. A method is outlined for estimating the amount of condensation. Daily outputs, per 1000 cfm of air, have been calculated for atmospheric conditions prevailing at Jeddah and Dhahran at different times of the year. The results have been applied to a typical school building to show that a useful amount of potable water is produced.

A.A. Al-Arainy, N.H. Malik and L.N. Abdul-Al
Corona and gap type discharges occurring at high voltage hardware generate appreciable electromagnetic interference (EMI). This work is concerned with the level of interference generated at substations located in the Central Region of Saudi Arabia. The contribution of substation hardware to the overall power system EMI was found by measuring the EMI frequency spectrum under a power line near and away from the substation. Two areas in the central region namely Riyadh and Qassim, were considered. Some differences were observed between the substations in the two areas. The results of these measurements are analysed in the paper.

N. Mansour, A. Piepke, A. Moussavi, H. Sanchez, J. Metzinger, H.V. Klapdor, T. Baymoy, and Z. Awwad
The high spin level structures of 152,153Ho were studied experimentally with the 122Sn (35Cl, xyzy) in-beam reaction. In 152Ho a completely new level scheme was constructed up to Ex ≈ 7.9 MeV and Jπ = 27+ including some isomers. In 153Ho about twenty so far unknown transitions were found in comparison with a recent report. The structures in both nuclei are discussed in comparison with the neighbouring nuclei.

N.A. Razik
In X-ray diffractometry, precision lattice constant determination requires corrections to the measured 2θ- angles for instrumental, sample-dependent and random errors. The external standard method could correct for instrumental errors while the analytical least squares method could eliminate other sources of errors. It was, therefore, suggested that to obtain higher accuracy the externally calibrated 2θ-values should be refined by the analytical method. When applied to X-ray diffractometric data from Cu Al2 powder material (θ-phase) which has a tetragonal crystal structure, the lattice constants a0 and c0 were obtained as 0.60675 ± 0.00011 and 0.48775 ± 0.00006 nm, respectively. The internal standard method could correct for systematic errors. To minimize random errors, least squares formulae were developed for the tetragonal system. When applied to the internally calibrated 2θ-values of Cu Al2, the lattice constants a0 and c0 were obtained as 0.60695 ± 0.00010 and 0.48725 ± 0.00009 nm, respectively. The weighted average values of the lattice constants of CuAl2, at 298 K, corrected for most aberrations to peak positions were estimated as 0.60686 ± 0.00007 and 0.48760 ± 0.00005 nm. These values were considered as refinements of earlier published data.