Comparison of the Structural Configuration of Cobalt Nanoparticles on Titania and Titania Nanotube Supports

In this study, two cobalt based catalyst samples were prepared on titania and titania nanotubes supports using the deposition precipitation method. Their structural configurations were characterized and compared using BET, and TRP analyses. The BET analysis showed that the surface area of TiO2 is much higher than that of TNT which was due to their structural differences. Analyses of the results obtained revealed that the surface area of the 10 % Co/TNT catalyst sample is higher than that of the 10 % Co/TiO2. The TPR analysis showed that it is much easier to reduce 10 % Co/TiO2, than 10 % Co/TNT. This is attributed to be due to the fact that the cobalt particles were adsorbed on the surface of the TiO2, and formed covalent bonds with TNT. Therefore reduction temperature was higher with TNT than TiO2. The investigation of structural changes of these catalysts when they were coated with carbon, using chemical vapour deposition method was also conducted. The catalyst prepared on TNT support showed better properties in terms of average pore diameter, pore volume and surface area than the catalyst sample prepared on TiO2 support when the two samples were exposed to carbon environment for the same period of time. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2488

Thin Layer Drying Kinetics and Modelling of Okra (Abelmoschus Esculentus (L.) Moench) Slices under Natural and Forced Convective Air Drying

The effect of sample thickness (10 and 20 mm), method of drying (open sun, solar and hot air drying) and drying air temperature (50, 60 and 70 oC) on the drying characteristics and kinetics of okra slices were investigated. The results showed that sample thickness, method of drying and drying air temperature significantly (P = 0.05) affected the drying rate and thus the drying time. It was observed that okra slices would dry perfectly within 216 – 240 h, 192 -216 h, and 12 – 19 h under open sun, solar and hot air drying, respectively. Irrespective of the drying method, all the samples dried in the falling rate period with no constant rate period. Four thin-layer semi-empirical mathematical drying models (Newton, Page, Henderson and Pabis, and Logarithmic models) were fitted to the experimental drying curves. The models were compared using the coefficient of determination ( ) and the root mean square error (RMSE). The logarithmic model has shown a better fit to the experimental data obtained from the open sun, solar and hot air drying respectively as relatively compared to other tested models. Correlation between the model parameters and the drying air temperature (under hot air drying) to calculate moisture ratio in relation to the drying time were also determined. The transport of water during drying was described by application of Fick’s diffusion model and the effective moisture diffusivity was estimated. The value ranges from 0.253 to 0.901 × 10-10 m2/s for open sun, 0.31 to 1.01 × 10-10 m2/s for solar drying and 3.29 to 14.7 × 10-10 m2/s for hot air drying, respectively. The Arrhenius-type relationship describes the temperature dependence of effective moisture diffusivity and was determined to be 16.74 kJ/mol and 10.39 kJ/mol for 10 and 20 mm sample sizes, respectively. Keywords: Okra; Open sun drying; Solar drying; Hot air drying; Mathematical modelling; Effective moisture diffusivity.

Mathematical Modelling and Simulation of the Mass and Heat Transfer of Batch Convective Air Drying of Tropical Fruits

In the present study, a mathematical model capable of predicting the instantaneous moisture and temperature distribution inside fruit and vegetable material undergoing shrinkage during drying process has been developed. The model takes into account moisture content and shrinkage of material as well as shrinkage dependent effective diffusivity. The mass transfer and heat equations were solved using a numerical technique. For evaluation and validation purposes, the model was applied to drying data obtained from the drying tests carried out on banana slices. An oven dryer was used to conduct the test. Banana slices of approximately 5 mm thickness and 30 mm diameter were dried over a temperature range of 50 oC and 70 oC for 6 hours. The predicted results compared favourably with the experimental results. Thus, the experimental results validated the model developed. In addition, empirical drying rate equations are developed. The model is therefore capable of predicting dynamic behaviour of drying of fruits undergoing shrinkage and, as such, it can be used as a design tool. Keywords: Drying; Mathematical modelling; Shrinkage; Simulation; Moisture diffusivit

Comparison of Item Parameter Estimates of Traditional True Score Theory and Modern Mental Theory in Oyo State Junior Secondary School Certificate Mathematics Examination

The study compared the Traditional True Score Theory (TTST), and Modern Mental Test Theory (MMTT) estimated item parameter indices to the ability of examinees in Junior Secondary School Certificate Examination (JSSCE) in Mathematics. This is with the view of providing empirical justification on the appropriateness of decisions made statistically from psychometric tests. The study adopted a descriptive survey design. A sample of 600 students was randomly selected from a population of 95,419 students who sat for the 2016 JSSCE Mathematics Paper 1 in Oyo State, Nigeria. An adoption version of the 2016 Oyo State JSSCE Mathematics Paper 1 titled Mathematics Test (MT) instrument was utilized for information aggregation. Data collected were analyzed using SPSS and BILOG-MG software packages. The effects indicated that the difficulty indices of Mathematics test items based on TTST ranged from 0.00 to 0.65. The discrimination indices ranged from 0.00 to 0.41. Fifty-two items (86.67%) on the MT items had moderate item difficulty (0.200 ≤ p ≤ 0.620). On the other hand, 42 (70%) on the items discriminate poorly (0.10 ≤ D ≤ 0.29). Regarding MMTT results, item difficulty parameter ranged between 0.216 and 7.988 for 2PLM while the discrimination parameter ranged between 0.100 - 0.729 respectively. Furthermore, there was a negative relationship between the difficulty indices of MMTT and TTST models (r = -0.702, p < .01). The concomitance correlation for discrimination was positive (0.646, p <. 01). The study concluded that the Oyo State 2016 JSSC Mathematics examination was of a moderate psychometric quality irrespective of the theoretical measurement model used in the appraisal. KEYWORDS:     Keywo Traditional True Score Theory, Modern Mental Test Theory, Item Difficulty, Item Discriminatio

Comparative Analysis of Classical Test Theory and Item Response Theory Based Item Parameter Estimates of Senior School Certificate Mathematics Examination

The study compared Classical Test Theory (CTT) and Item Response Theory (IRT)-estimated item difficulty and item discrimination indices in relation to the ability of examinees in Senior School Certificate Examination (SSCE) in Mathematics with a view to providing empirical basis for informed decisions on the appropriateness of statistical and psychometric tests. The study adopted ex-post-facto design. A sample of 6,000 students was selected from the population of 35,262 students who sat for the NECO SSCE Mathematics Paper 1 in 2008 in Osun State, Nigeria. An instrument consisting of 60-multiple-choice items, May/June 2008 NECO SSCE Mathematics Paper 1 was used. Three sampling plans: random, gender and ability sampling plans were employed to study the behaviours of the examinees scores under the CTT and IRT measurement frameworks. BILOG-MG 3 was used to estimate the indices of item parameters and SPSS 20 was used to compare CTT- and IRT-based item parameters. The results showed that CTT-based item difficulty estimates and oneparameter IRT item difficulty estimates were comparable (the correlations were generally in the -0.702 to -0.988 range in large sample and -0.622 to - 0.989 range in small sample). Results also indicated that CTT-based and two-parameter IRT-based item discrimination estimates were comparable (the correlations were in the 0.430 to 0.880 ranges in large sample and 0.531 to 0.950 range in small sample). The study concluded that CTT and IRT were comparable in estimating item characteristics of statistical and psychometric tests and thus could be used as complementary procedures in the development of national examination

Comparison of the structural configuration of Cо nanoparticles on Ti02 and TNT supports

In this study, two cobalt based catalyst samples were prepared on titania and tita- nia nanotubes supports using the deposition precipitation method. Their structural con- figurations were characterized and compared using BET, and TRP analyses. The BET analysis showed that the surface area of TiO2 is much higher than that of TNT which was due to their structural differences. Analyses of the results obtained revealed that the surface area of the 10%Co/TNT catalyst sample is higher than that of the 10%Co/TiO2. The TPR analysis showed that it is much easier to reduce 10%Co/TiO2, than 10%Co/TNT. This is attributed to be due to the fact that the cobalt particles were ad- sorbed on the surface of the TiO2, and formed covalent bonds with TNT. Therefore reduction temperature was higher with TNT than TiO2. The investigation of structural changes of these catalysts when they were coated with carbon, using chemical vapour deposition method was also conducted. The catalyst prepared on TNT support showed better properties in terms of average pore diameter, pore volume and surface area than the catalyst sample prepared on TiO2 support when the two samples were exposed to carbon environment for the same period of time. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2060

Correlation between body mass index and waist circumference in Nigerian adults: implication as indicators of health status

Background. Anthropometric measures have been widely used for body weight classification in humans. Waist circumference has been advanced as a useful parameter for measuring adiposity. This study evaluated the correlation between body mass index (BMI) and waist circumference and examined their significance as indicators of health status in adults. Design and Methods. The subject included 489 healthy adults from Ota, Nigeria, aged between 20 and 75 years, grouped into early adulthood (20-39 years), middle adulthood (40-59 years) and advanced adulthood (60 years and above). Weight, height and abdominal circumference were measured. BMI was calculated as weight kg/height2 (m2) and World Health Organization cut-offs were used to categorize them into normal, underweight, overweight and obese. Results. Abnormal weight categories accounted for 60 % of the subjects (underweight 11 %, overweight 31%, and obese 18%). The waist circumference of overweight and obese categories were significantly (P<0.05) higher than the normal weight category. There was no significant difference between waist circumference of underweight and normal subjects. The correlation coefficient values of BMI with waist circumference (r=0.63), body weight (r=0.76) and height (r=-0.31) were significant (P<0.01) for the total subjects. Conclusions. The study indicates that waist circumference can serve as a positive indicator of overweight and obesity in the selected communities; however, it may not be used to determine underweight in adults. Regular BMI and waist circumference screening is recommended as an easy and effective means of assessing body weight and in the prevention of weight related diseases in adults

New trends in under-five mortality determinants and their effects on child survival in Nigeria: A review of childhood mortality data from 1990-2008

Under-five mortality in Nigeria has been reported to be on the decline, but the dynamics are yet to receive adequate attention. Thus the main objective of this study was to assess these factors and quantify their relative contributions to under-five mortality between 1990 and 2008. The Nigeria Demographic and Health Survey data for 1990, 2003 and 2008 were re-analysed to assess the trends in determinants of under-five mortality.Cox Regression model was applied to determine the relative contributions of each factor to the under-five mortality risk.The results showed there were improvements in maternal education (8.6%), childhood vaccination (17.7%), use of oral rehydration therapy (13.9%) and medical treatment of childhood illnesses(17.5%) over the 19-year period. There were declines in proportions with birth interval less than 24months (3.9%), access to improved sources of drinking water (24.2%), improved toilet facilities (9.0%) antenatal care (4.5%), skilled delivery (3.0%) while maternal age at childbirth remained unchanged. These factors increased the death hazards by 4.6% between 1990-2003 but decreased them by 12% between 2003 and 2008. It was concluded that Nigeria has recorded very minimal improvements in birth spacing and antenatal/delivery care. Poor access to potable drinking water and sewage disposal, and short birth intervals,are among the factors fueling childhood mortality risks. Further improvements in these environmental and health practices as well as other factors are recommended as strategies for promoting child survival in Nigeria

Impact of Interest Rate on Portfolio Management in Nigeria

This study carried out an investigation on the impact of interest rate on portfolio management in Nigeria. Specifically the study analyzed the impact of interest rate on both long term and short term portfolio investments in Nigeria using secondary data sourced from Central bank of Nigeria statistics bulletin and National bureau of statistics for the periods covering 1985 to 2014. The study employed the techniques of co-integration and error correction model, it was discovered that on the long run interest rate specifically prime lending rate significantly influenced portfolio management both on long and short term basis and that total savings exert significant positive impact on the portfolio investment both on long and short term basis. Hence the study recommended that monetary authorities should ensure that the nexus between interest rate and portfolio management is taken into consideration in the process of policy formulations