The optical properties of multi-layers thin films, to be used as resonator for Nd:YAG, is studied in this work via computer simulation. The output coupler was designed to be fabricated by successive thin layers to achieve very high transmittance at optical wavelengths around 1064 nm for Nd:YAG laser. In addition, different optical filters were examined to control the transmittance and reflectance for the same laser wavelength. Three samples of dielectric materials composed of HgS/Na3AlF6, HgS/MgF2, and CdS/Na3AlF6 were used and compared with each other in transmittance, reflectance, physical thickness, optical thickness and full width at half maximum. The results showed that the best transmittance was achieved with HgS+Na3AlF6 where the transmittance for 1064 nm increased to 95.74 %.
Since botanicals still remained the most promising tool that could obviate the use of chemical insecticides, this study investigated the biotoxic effect of Acacia auriculiformis and Acalypha goddsefiana powder and oil against Sitophilus oryzae. The powder of the plants were tested at 0.0g (control), 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 and 2.0g dosages while their extracts were prepared at 1, 2, 3, 4 and 5% concentrations per 20g of maize seeds. Solvent control was also prepared for the oil extracts bioassay. Mortality, adult emergence, % inhibition rate and % weight loss were observed. LD50 and LC50 of the powders and oils of the two botanicals were calculated at 48 hours of application. The powders of both plants achieved complete weevil mortality within 72h of application at 2.0g and their effect was significantly (p<0.05) different from other dosages except 1.0g dosage. Also, the extracts of both plant achieved 100% insect mortality within 48h hours of application at 5%. However the powder and oil of A. auriculiformis appeared more effective than that of A. goddsefiana in term of mortality as reflected by their lethal dosage and concentration. However, A. goddsefiana powder and extract appeared more effective than that of A. auriculiformis in term of protectability as they greatly reduced the emergence of the adult weevil and their ability to cause weight loss of the maize grains. Only the higher dosages and concentrations of the plants were able to achieve 100% inhibition rate.
Chemical activation was carried out on the kaolin clay obtained from Kpautagi Area in Niger State using sulfuric and hydrochloric acids. In order to study the effect of acid activation, the physicochemical characteristics of the Kpautagi clay were determined before and after acid modification and the results obtained were subsequently compared. These characteristics include surface morphology, surface functional groups, surface area and pore volume. Characterization results showed that acid modification of Kpautagi kaolin clay with sulphuric and hydrochloric acids improved the surface area of the clay from 7.598m2/g to 15.5cm2/g and 13.2cm2/g respectively and enhancement in pore volume and average pore diameter were also noted. The changes in the characteristics of the clay after acid modification were further supported by the Scanning Electron Microscope (SEM) micrographs and Fourier Transformed Infrared Spectroscope (FTIR) spectra. Therefore, the outcome of this study shows that sulphuric and hydrochloric acid could be used to improve the characteristics of Kpautagi clay but better performance could be achieved employing sulphuric acid.
In this paper we consider the construction of implicit second derivative Runge-Kutta collocation methods designed for the continuous numerical solution of stiff systems of first order initial value problems in ordinary differential equations. These methods are obtained based on the multistep collocation technique, which are shown to be convergent, with improved regions of absolute stability. Although the implementation of the second derivative Runge-Kutta collocation methods remains iterative due to the implicit nature of the methods, the advantage gained makes them suitable for solving stiff systems with eigenvalues of large modulus lying close to the imaginary axis. Some absolute stability characteristics and order of accuracy of the methods are studied. Finally, we show two possible ways of implementing the methods and compare them on some numerical examples found in the literature to demonstrate the high order of accuracy and reliability of the methods.
Identification of the precise nature and attributes of the time series of climatological data is very important and is usually the first step of water resources planning and management. The major objective of this study was to determine the presence or otherwise of trend over time for some selected hydro-climatic components of Kaduna, Nigeria, and deduce the magnitude. Statistical approaches were used to investigate the presence and extent of persistence, trend analysis in hydro-climatic time series. Based on Mann Kendall test, twenty six years of hydro-climatic data were used. The non-parametric Man-Kendall test was used to detect monotonic trends, and the Mann-Kendall slope estimator was used to estimate the magnitude of trend on the variables. An evidence of trend was observed in all variables. Temperature and evaporation variables showed a positive and significant trend over time, while rainfall and stream flow had negative trend though not significant at the 95 % level of confidence. Thus, it could be concluded that the trend of change in temperature around River Kaduna is on the increase, with no significant increase in change of rainfall.
The optimization of recycling of used engine oil with clay sample has been studied using Response Surface Methodology. Acid concentration, activation temperature and time were the independent variables considered in optimizing the recycling of used oil and six responses evaluated. The surface characterization of the clay samples was performed using the Fourier Transform Infrared (FTIR) spectra and Brunauer Emmett Teller (BET) analyses. The relationship between independent variables and response was described by a second order polynomial equation. Statistical testing of the model was performed with F-test to obtain the correlation between the experimental data and predicted results for all responses. The adequacy of the model equations were evaluated by the Adjusted and Predicted R2 coefficients observed to be close to each other for all the six responses. Data obtained from recycling used oil using clay sample showed the optimum condition as; activation temperature of 106.80oC, acid concentration of 3M and activation time of 180 minutes. A yield of 66.28% was obtained at optimum condition and characterized fuel qualities found close to fresh oil used as standard in this work. The surface area and adsorption capacity of raw clay and activated clay samples was observed to have increase from 19.8m2/g to 437.83m2/g and 1.41 mg/g to 8.64 mg/g respectively. This difference adequately described the improvement of the adsorption phenomena of the activated clay over raw clay samples.
The present work describes the effect of palm kernel shell ash (PKSA) as reinforcement on the mechanical properties of As-cast aluminium alloy. Recycled aluminium alloy from cylinder of an automotive engine block was degreased by using premium motor spirit (PMS) also known as petrol, washed thoroughly with soap and water and sun dried for 5 days. The palm kernel shell was screened of dirt and other unwanted foreign materials before being roasted in furnace. The ash was further pulverized by laboratory ball mill machine followed by sieving to obtain particle sizes of 106 µm and divided into two parts. One portion was treated with NaOH solution while the other part was left as untreated before they are used to reinforced molten aluminium alloy in predetermined proportions. The newly developed composites were characterized with respect to their mechanical properties in response to the tests that were carried out on them. The results indicate that palm kernel shell ash can be used as potential reinforcing material for automobile applications.
Asbestos has been used for so long as automobile brake lining material because of its good physical and chemical properties. However, due to the health hazard associated with its handling, it has lost favour and several alternative materials are being increasingly used. Asbestos-free brake lining was developed in this work using pulverized cow hooves along with epoxy resin, barium sulphate, graphite and aluminium oxide. This was with a view to exploiting the characteristics of cow hooves, which are largely discarded as waste materials to replace asbestos which has been found to be carcinogenic. Samples of brake linings were produced using compressive moulding in which the physical and mechanical properties of the samples were studied. The results obtained showed that proper bonding was achieved as the percentage by weight of epoxy resin increased and percentage by weight of pulverized cow hooves decreased. The hardness, compressive strength, coefficient of friction, water and oil absorption, relative density and wear rate of the brake linings were determined and compared with existing brake lining properties. The result indicates that pulverized cow hooves can be used as brake lining material for automobiles.
A probability-based procedure for design of concrete mixes with cow-cone ash admixed cement has been developed considering the strength as a random variable. However, the compressive strength of concrete in turn, depends on the properties of its constituent materials: cement, fine aggregate, coarse aggregate and cow-bone ash. The compressive strength data generated experimentally has been analysed using normal-probability distribution functions based on 95% confidence interval. The proposed probability based design was compared to the method of trial mixture. It was observed that for reliability index (β) of 1.3, the proposed probability methodology uses 10.2% less cement content than the method of trial mixture; thus, indicating that the method is conservative. It was also observed that, for concrete grade 25, the proposed methodology gives higher compressive strength at both 7 and 28 days. Hence, the probability-based design procedure was found appropriate and is therefore recommended for the design of concrete mixes with cow-bone ash admixed cement.