Multiyear Analysis of Ground-Based Sunphotometer (AERONET) Aerosol Optical Properties and Its Comparison with Satellite Observations over West Africa

The Sahelian West Africa Long 20W 20E Lat 0 30N by its climatological and geographical conditions is a key region for the characterization of global atmospheric aerosol optical properties This study evaluates the spatial and temporal variation of the Aerosol Optical Depth AOD440nm aerosol particle size characterization Angstrom exponent 440-675nm at four locations Agoufou Banizoumbou Cape Verde and Ilorin over a period of January 2005 to December 2009 Results of the day-to-day AOD440nm variations as well as the seasonal and annual variations are presented in order to establish the aerosol climatology in the region We compared satellite derived data of Total Ozone Mapping Spectrometer - Aerosol Index TOMSAI MODIS Terra and Aqua with those of ground-based Sunphotometer AERONET measurements In general there exits good relationship between MODIS Terra and Aqua and the ground-based AERONET measurements with correlation coefficients R2 0 8 reported in all stations However low coefficients as low as 0 40 were obtained in all the stations for regressions between TOMS AI and ground-based Sunphotometer AERONET dat

Malaria and pneumonia occurrence in Lagos, Nigeria: Role of temperature and rainfall

The role of climatic parameters in the prevalence and severity of some common diseases is being speculated in the face of changing climate of the world. We investigate this supposition by expounding the relationship between malaria, pneumonia, rainfall and air temperature over Lagos, Nigeria. This study uses temperature and rainfall data of 60 years and 14 years record of reported cases of malaria and pneumonia infection. Significant climatic change was detected in both rainfall and air temperature when standard method of change detection was applied. While rainfall showed a decreasing trend resulting into drier conditions, temperature tends to increase resulting into warmer environment. Temperature spells were found to increase in frequency during the last two decades, and there are tendencies for further increment given the current rate of increasing temperature. Air temperature and malaria correlation coefficient was high and positive in the months of February and December ranging between 40 and 95% but high and negative only in November. Coefficient of correlation between rainfall and pneumonia was high in the range of 50 and 90% and positive in February, May, July and August. The months of March, April, June, September, October and December also showed positive correlation but the coefficients are so weak and insufficient (<20%) to justify reasonable relationship between the variables in these months. We conclude that climatic parameters, rainfall and air temperature, have profound influence on both malaria and pneumonia occurrence and are responsible directly for intractable increase of the diseases.Key words: Malaria occurrence, change points, climate- disease, pneumonia

Estimating the wind energy potential over the coastal stations of Nigeria using power law and diabatic methods

The suitability of two coastal stations in Nigeria for wind energy generation is presented in this study. To estimate the wind speeds at the desired height 70 m for standard wind turbine, two methods; namely power law relationship and diabatic evaluation have been considered. It was found that the diabatic evaluation method performed better because certain physical conditions of farm site are included in the method. Thus when potential site data are not available diabatic method can provide a good approximation of wind speeds. Comparing the energy potential of the two coastal stations, Lagos and Calabar in this study, it was found that Lagos has stronger wind speeds than Calabar especially during peak periods. The atmospheric condition most suitable to obtain maximum wind speeds was also found to be during stable condition. Stable condition occurs mostly in the night time.Keywords: Wind potential energy, wind turbine, power law, diabatic evaluation

Spatial, seasonal and inter-seasonal variations of thunderstorm frequency over Nigeria

Using a 10-year daily data thunderstorm and dry thunder (thunder without precipitation) that spans from 1991-2000, the spatial, seasonal and inter-seasonal variations of thunderstorm frequency have been investigated with results which include the production of seasonal and inter-seasonal maps of dry thunder (thunder without precipitation) and thunderstorm frequencies. Results showed that there exists a latitudinal belt of reduced thunderstorm activity between 8 and 10°N. Also, due to absence of little dry season (LDS) over the south-eastern part of the country, they do not experience double maxima of thunderstorm activity. Hence, the weather over the country has been observed as not following the latitudinal divides. Also, the thunderstorm activities over the country are more prominent over the coast, but gradually decrease towards the inland with anomaly over Ilorin and Yola. Though, several authors have carried out series of researches on the thunderstorm activities but none have been able to look at the seasonal and inter-seasonal variations of thunderstorm frequency over Nigeria. Hence, the need to look into this aspect came as a result of the fact that thunderstorm activities is one of the most contributing systems to total precipitation in Nigeria.Key words: Thunderstorm, seasonal, frequency, latitude, Nigeria

Design and Fabrication of a Low Cost Fluidized Bed Reactor

Many farmers now use the dryer as a part of their normal grain-harvesting system even during wet seasons. This helps in reducing spoilage. However, most available dryers are expensive to purchase and maintain. This work therefore is an attempt to develop a simple low cost drying bed that can lead to reduced drying time. The fluidized bed designed and fabricated in this work consists of the drying column, fluidized plate, the inlet and outlet unit, the heating unit and the fan. The evaluation considered the drying time and temperature in achieving quality. The drying efficiency and the amount of moisture reduced per time and were investigated using rice and wheat with moisture contents of 23% and 33% respectively. The dryer has shorter drying times and efficiencies of 89% and 90% for rice and wheat respectively. Keywords: Fluidized Bed, Grain Drying, Low Cost Design

A bottom-up appraisal of the technically installable capacity of biogas-based solid oxide fuel cells for self power generation in wastewater treatment plants

This paper proposes a bottom-up method to estimate the technical capacity of solid oxide fuel cells to be installed in wastewater treatment plants and valorise the biogas obtained from the sludge through an efficient conversion into electricity and heat. The methodology uses stochastic optimisation on 200 biogas profile scenarios generated from industrial data and envisages a Pareto approach for an a posteriori assessment of the optimal number of generation unit for the most representative plant configuration sizes. The method ensures that the dominant role of biogas fluctuation is included in the market potential and guarantees that the utilization factor of the modules remains higher than 70% to justify the investment costs. Results show that the market potential for solid oxide fuel cells across Europe would lead up to 1,300 MW of installed electric capacity in the niche market of wastewater treatment and could initiate a capital and fixed costs reduction which could make the technology comparable with alternative combined heat and power solutions

NEW HEURISTICS FOR MINIMISING TOTAL COMPLETION TIME AND THE NUMBER OF TARDY JOBS CRITERIA ON A SINGLE MACHINE WITH RELEASE TIME

<p>ENGLISH ABSTRACT: This paper considers the bi-criteria scheduling problem of simultaneously minimising the total completion time and the number of tardy jobs with release dates on a single machine. Since the problem had been classified as NP-Hard, two heuristics (HR9 and HR10) were proposed for solving this problem. Performance evaluations of the proposed heuristics and selected solution methods (HR7 and BB) from the literature were carried out on 1,100 randomly generated problems ranging from 3 to 500 jobs. Experiment results show that HR7 outperformed HR10 when the number of jobs (n) is less than 30, while HR10 outperformed HR7 for n≥ 30.</p><p>AFRIKAANSE OPSOMMING: In hierdie artikel word die bi-kriteria-skeduleringsprobleem bestudeer waar die totale voltooiingstyd en die aantal take wat laat is op ‘n enkele masjien geminimiseer moet word. Verskeie heuristieke word voorgestel en getoets om sodoende die beste benadering te identifiseer.</p&gt

Pattern of Corneal Opacity in Ibadan, Nigeria

Background: The prevalence and causes of corneal blindness vary from one region of the world to another. There is even variation within the developing countries of Africa. Method: A retrospective review of 675 patients with corneal scarring out of the 3,753 new patients corneal scarring in patients attending the eye clinic of the University College Hospital (UCH) Ibadan over a 5year period. Results: Subjects in age groups 0 to 10years and 21 to 30years were mostly affected. Males were more affected with a ratio of 3:1. Most presentations were in the months of January to March and July to September. Almost half (48.99%) of the patients had uniocular blindness and no case of bilateral blindness from corneal opacity was found. The main causes of corneal opacity were trauma (51.1%) and microbial keratitis (26.70%) both of which are avoidable causes of blindness. No case of trachomatous corneal scarring was found in the group studied. Conclusion

A PERISHABLE INVENTORY MODEL WITH UNKNOWN TIME HORIZON

Abstract-Traditionally, the time (planning) horizon over which the inventory for a particular item will be controlled is often assumed to be known (finite or infinite) and the total inventory cost is usually obtained by summing up the cost over the entire time horizon. However, in some inventory situations the period over which the inventory will be controlled are difficult to predict with certainty, as the inventory problems may not live up to or live beyond the assumed planning horizon, thereby affecting the optimality of the model. This paper presents a deterministic perishable inventory model for items with linear trend in demand and constant deterioration when time horizon is unknown, unspecified or unbounded. The heuristic model obtains replenishment policy by determining the ordering schedule to minimize the total cost per unit time over the duration of each schedule. A numerical example and sensitivity analysis are given to illustrate the model

Presumed optic disc melanocytoma in a young Nigerian: a diagnostic challenge

Optic disc melanocytoma (ODM) is a rare, benign, deeply pigmented ocular tumor arising from melanocytes within the optic disc or from any part of the uvea. It occurs more in dark skinned individuals and females. We report a 17‑year‑old female who presented to our outpatient department with a history of poor distant vision from childhood, worse in the right eye. Ocular examination revealed visual acuity of 6/36 and 6/18 in the right and left eyes, respectively, which improved to 6/9 bilaterally with a pinhole. There was a relative afferent pupillary defect in the right eye, and a posterior segment examination of same eye showed a raised pigmented optic disc lesion occupying the inferior two-thirds of the optic disc and obscuring the lower disc margin. Both the anterior and posterior segments of the left eye were normal. A diagnosis of presumed ODM was made. Spectacles were prescribed, and the patient was counseled on regular follow‑up to monitor progression. ODM should be considered in patients presenting with a pigmented optic disc lesion. Regular follow‑up with fundus photography is advocated.Keywords: Melanocytoma, optic disc, pigmented ocular tumo