Physicochemical Characterization of Limestone Deposits at Ewekoro, Ogun State, South-West of Nigeria and the Environment Impact

Limestone is the primary constituent raw material for cement manufacture. While most limestone deposits are suitable for cement making, there are some characteristics of limestone which need to be defined in order to establish a usable raw material supply.  These relate to compositional requirements and also the consistency of the deposit in chemical and physical terms. Limestone makes up about 10% of the total volume of all sedimentary rocks. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. The density and porosity of samples from the various locations vary from 2.61g/cm3 to 2.72g/cm3 and 2.70% to 3.80%. The Schmidt hammer rebound number of samples from Ewekoro quarry varies from 32.1 to 33.6. The uniaxial compressive strength of samples from Ewekoro quarry varies from 60.5 MPa to 63.5 MPa thereby classifying the rock as moderate to high strength. The point load strength index is obtained from the LAFARGE laboratory results and varies from 1.239 MPa to 2.185 MPa. The strength classifications fall within the range of moderate to high strength class. Also, the tensile strength, obtained from point load strength ranges from 1.862 MPa to 3.086 MPa. The staining process induces a reaction on the surface of a particular mineral species which results in coloured precipitate characteristic of that mineral. Alizarin red S in NaOH stained the samples purple indicating the presence of magnesium in the carbonate while Alizarin red S in HCL stained the samples red. Physical observation of Ewekoro limestone deposit reveal the rock is highly fossiliferous with the identified fossils indicating deposition in an open shelf environment. Moreover, the limestone deposit was equally observed to be principally mud supported which is indicative of rocks deposited in quiet water and a low energy environment. Keywords: Limestone, Solubility, Ewekoro, Physical and Chemical

Chaos Control in the Nonlinear Bloch Equations using Recursive Active Control

The problem of chaos control in the nonlinear Bloch equations is considered basedon a modified active control technique. In the proposed control scheme a recursive approach and active control mechanism are combined to design control functions that drive the nonliner Bloch equations to a steady state as well as track a desired trajectory in a systematic way. The effeciency of the proposed Recursive Active Control (RAC) is demonstrated with numerical simulations

On the numerical solution of the Gross–Pitaevskii equation

The Gross–Pitaevskii equation is solved using an approach developed for the solution of the Bogoliubov–de Gennes equations for type II superconductivity. The solution is compared with others in the literature and is shown to be easily adapted to the study of an isolated vortex recently discovered in Bose-Einstein Condensation in trapped gases.Journal of the Nigerian Association of Mathematical Physics Vol. 8 2004: pp. 9-1

Numerical simulation of hole injection in high barrier metal-semiconductor short diodes

A numerical investigation is carried out on effects of minority carriers on the transport parameters of one-dimensional metal-semiconductor short diodes under highly injecting conditions. The results show that at a donor concentration Nd=1014 cm-3 and total current density J=0.1 &#956Acm-2, the hole injection ratio,&#955h , decreases rapidly by a factor of more than 80% within 2&#956m semiconductor layer from the interface. Furthermore, a comparison of the two-carrier model adopted in this work with the Schottky model reveals a discrepancy of 30% in the lnJ-V characteristics of a diode of 0.92 eV barrier height. Journal of the Nigerian Association of Mathematical Physics Vol. 8 2004: pp. 69-7