Department of Physical Sciences

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Seasonal Variations of Radio Refractivity Gradients in Nigeria
(2002) Willoughby, Alexander
Validation of B0 and B1 in the IRI 2001 Model at Low Solar Activity for Ilorin an Equatorial Station
(advances in Space Research, 2008) Willoughby, Alexander
A new set of data obtained at low solar activity from Ilorin, Nigeria (geog. latitude 8.5 N, geog longitude, 4.6 E, dip 4.1 S) is used to validate the IRI 2001 model at low solar activity. The results show in general a good agreement between model and observed B0 at night but an over estimation during daytime. The overestimation is greatest during the morning period (0600LT–1000LT). The model prediction for B1 is fairly good at night and during the day. A dependence of B0 on solar zenith angle v is observed during the daytime. A formulation of the form B0 = A[cos(v)n] is therefore proposed. Values of the constants n and A were determined for the period of low solar activity for this station.
Observation Bio-effect of SW-global Solar Radiation in Ilorin in the Tropics
(Advances in Space Research, Elsevier, 2009) Willoughby, Alexander
The annual variation of global (total) solar radiation measured over four (4) years (1995–1998) at Ilorin (8320 N, 4340 E) was studied and the bio-effects of the variation is herein reported. The weekly averages of the solar radiation flux were obtained and plotted. The profile of the weekly averages of the insolation shows two notable ‘‘wells” corresponding to the harmattan dry season and the rainy season. It was deduced that the duration of the seasons was directly proportional to the sizes of the ‘‘wells”, while the depths of the ‘‘wells” correspond to the severity of the causes of the ‘‘wells”. The fall and rise rates of the depth of the edges of the wells are inversely proportional to the ecological effects of the variation of the radiation. The rates of decrease and increase of the radiation flux affect the depths of the ‘‘wells” and were found to be rapid and shallow for the ‘‘Harmattan Well”, and gentle and deep for the ‘‘Rain Well”. The width (duration), rate of change and depth of the ‘‘Harmattan Well” bring about stress for both animals and plants.
Atmospheric Aerosol Loading at Ilorin, a Tropical Station
(The African Review of Physics, 2014) Willoughby, Alexander
This work reports the inter-annual variability of the seasonally recurring aerosol haze at Ilorin (8°32¢N, 4°34¢E) a central state of Nigeria, which is in the tropical zone. The data consist of observations collected over a period of seven years 1987 –1990 and 1996 - 1998 using the EKO Sun-photometer model SM –120 with “peak hold” and full view 2.4°quartz window and interference filters having peak transmission at the wavelengths 500, 675, 875 and 945nm, respectively. The data coverage presents to us five distinct aerosol seasons viz: 1987/88, 1988/89, 1989/90, 1996/97 and 1997/98. The data collected for all the aerosol seasons were compared wavelength-by-wavelength and month-by-month. Although the regional mean Aerosol Optical Depth (AOD) and Precipitable Water (PW) remains essentially constant in trend for all the data years, they vary from year to year with spread ranging from 0.789 to 1.526 for AOD1, 0.808 to 1.50 for AOD2, 0.814 to 1.178 for AOD3, and 0.340 to 1.480 for the PW. The coefficient of variation determined is between 27.4 and 52.0 for AOD1, 23.9 and 53.2 for AOD2, 25.2 and 52.8 for AOD3 and 12.9 and 39.5 for PW. The Angstrom exponent was also found to vary from about 0.2 to 3.8.
Seasonal Variation of Surface Radio Refractivity and Water Vapour Density for 48 Stations in Nigeria
(Proceeding of the 2015 International Conference on Space Science and Communication, 2015) Willoughby, Alexander
The monthly and seasonal variation of surface refractivity and water vapour density were studied using thirty nine years meteorological data for forty-eight stations in Nigeria. The factors which influence the transmission of radio signals operating within the troposphere are water vapour and refractivity. The results show that the surface refractivity and water vapour density generally have higher values during the rainy season than dry season at all station studied. Furthermore the results show that the value of surface refractivity and water vapour density varies from about 263 N-units and 3 g/m3 in arid region of Nigeria (North East) to about 393 N-units and 23 g/m3 in the coastal area of Nigeria (South West) respectively. For optimal performance of terrestrial radio link across Nigeria it is required to account for the variability of these parameters for optimal systems design.
A Cost Effective Solar Charge Controller and Load Driver for DC Home Appliances
(IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE), 2015-10) Willoughby, Alexander
Entropy Generation Analysis for Variable Viscous Couple Stress Fluid Flow through a Channel with Non-Uniform Wall Temperature
(Elsevier, 2016) Osinowo, Muritala
This article addresses the influence of couple stresses in minimizing of entropy generation rate associated with heat transfer irreversibility in the steady flow of a variable viscous fluid through a channel with a non-uniform wall temperature. The flow is induced by a constant axial pressure gradient applied in the flow direction. It is assumed that the fluid viscosity varies linearly with temperature. Analytical expressions for the dimensionless equations governing the fluid velocity and temperature are derived and used to obtain expressions for volumetric entropy generation numbers, irreversibility distribution ratio and the Bejan number in the flow field. Plots for different pertinent parameters entering the velocity and temperature fields are displayed and discussed.
A Solar Powered PWM Charger for Multiport USB Devices
(IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE), 2016-08) Willoughby, Alexander
The circuit presented is a solar photovoltaic PWM charger for charging USB-powered devices. It is intended as a portable and tidier substitute to the commonly assembled petrol generator powered multi-socket AC phone chargers displayed in market stalls in Nigeria. The unit consists of two DC-DC step-down buck converter circuits; the first employs a TL494 switchmode regulator to charge a 12 V/24 Ah battery in constant current, constant voltage mode, while the second is based around multiple MC34063 switchmode ICs, each configured as a 5 V buck converter to run USB devices such as iPads, iPods, MP3 players, Bluetooth devices as well as chargers for mobile phones.
Sectional Investigation of Seasonal Variations of Surface Refractivity and Water Vapour Density over Nigeria
(International Journal of Applied Engineering Research, 2017) Willoughby, Alexander
The accurate knowledge of radio refractive and water vapour density of the troposphere is important in the planning, budgeting and designing of transmission and reception of radiowave signals on earth-space path. Hence, there is the need to adopt more precise techniques to analyze the seasonal variation of refractivity and water vapour density over Nigeria. The seasonal variation of refractivity and water vapour density was studied using thirty-nine years meteorological data for forty-eight (48) stations over Nigeria. The forty-eight stations were grouped into nine vegetation and two major climates in Nigeria. Harmonic analysis approach was used in addition to the monthly mean computation. The results show that Forests zones values of refractivity and water vapour density are higher than Savannahs zones values. The refractivity value increases from about 281 N units at Sudarian Woodland in January to about 383.6 N units at Mangrove station in June. Water vapour density value increases from about 5.18 g/m3 at Brush and Thicket station in November to maximum value of about 22.36 g/m3 at Swamp Forest station in May. Results also show that over 80% variations in refractivity and over 70% variations in water vapour density are revealed in the first three harmonics at all the nine stations. The results indicate that the method of harmonic amplitudes and phases give a more analytical comparison between predictions model and observational data.
Possibility of Cost Effective and Energy Efficient High-Quality Natural White Light Sources with New Nanophosphor
(SPIEDigitalLibrary.org/conference-proceedings-of-spie, 2017-09-18) Willoughby, Alexander
In this paper, we present results authors published initially on the white light emission with broad band (330-465 nm) excitation of the specially prepared nano-phosphor: Eu3+: ZnS which is capped with sodium methyl carboxylate and on pure red-light emission from the nano-phosphor when capped with alpha methyl acrylic acid and prepared in a different method. Then we discuss possible methods of future improvement of the white light emission from the nano-phosphor. We then present the cost effective and energy efficient method of obtaining highest quality natural white light sources using such nano-phosphor and blue or near UV blue light emitting diodes. The latter discussion includes the driving circuit for the white LED and powering the LED by concentrated solar photovoltaics for both lighting and waste heat energy storage for completely clean energy natural white lighting sources.
Development of an Electronic Load I-V Curve Tracer to Investigate the Impact of Harmattan Aerosol Loading on PV Module pern2tkformance in Southwest Nigeria
(Solar Energy, 2018) Willoughby, Alexander
in Southwest Nigeria. To this end, a simple, open-source, cost effective electronic load I-V curve tracer was developed to compare the I-V characteristics of a pair of horizontally positioned 80W monocrystalline modules for the duration of the Harmattan period. The control module was regularly cleaned manually and the other module left to accumulate the Harmattan dust deposits. In order to obtain the modules’ characteristic parameters, an Arduino-based pulse width modulation (pwm) duty cycle was implemented to vary simultaneously, the gate-source voltages, VGS, of two power metal-oxide semiconductor field-effect transistors (MOSFETs) acting as fast variable loads for the modules. Experimental results acquired from the prototype circuit demonstrate that this method provides a more accurate approach and faster response than the resistive load tracer method. The prototype instrument was able to measure and reproduce characteristic curves that are obtainable from the more expensive branded products. Resulting curves depict reduction in the short circuit current, ISC, the current at maximum power, IMP, the power output, PMP and the efficiency, η of the dusty module by more than 18% in comparison with the control module over the measurement period.
Development of an Electronic Load IV Curve Tracer to Investigate the Impact of Harmattan Aerosol Loading on PV Module Pern2tkformance in Southwest Nigeria
(Solar Energy, 2018-05-05) Osinowo, Muritala
This study investigates the impact of the seasonal Harmattan aerosol loading on PV module efficiency at a station in Southwest Nigeria. To this end, a simple, open-source, cost effective electronic load I-V curve tracer was developed to compare the I-V characteristics of a pair of horizontally positioned 80W monocrystalline modules for the duration of the Harmattan period. The control module was regularly cleaned manually and the other module left to accumulate the Harmattan dust deposits. In order to obtain the modules’ characteristic parameters, an Arduino-based pulse width modulation (pwm) duty cycle was implemented to vary simultaneously, the gate-source voltages, VGS, of two power metal-oxide semiconductor field-effect transistors (MOSFETs) acting as fast variable loads for the modules. Experimental results acquired from the prototype circuit demonstrate that this method provides a more accurate approach and faster response than the resistive load tracer method. The prototype instrument was able to measure and reproduce characteristic curves that are obtainable from the more expensive branded products. Resulting curves depict reduction in the short circuit current, ISC, the current at maximum power, IMP, the power output, PMP and the efficiency, η of the dusty module by more than 18% in comparison with the control module over the measurement period.
Multi-Technique Analysis of Precipitable Water Vapor Estimates In the Sub-Sahel West Africa
(Heliyon, Elsevier, 2018-08-28) Willoughby, Alexander
Precipitable water vapor (PWV) is an important climate parameter indicative of available moisture in the atmosphere; it is also an important greenhouse gas. Observations of precipitable water vapor in sub-Sahel West Africa are almost non-existent. Several Aerosol Robotic Network (AERONET) sites have been established across West Africa, and observations from four of them, namely, Ilorin (4.34 E, 8.32 N), Cinzana (5.93 W, 13.28 N), Banizoumbou (2.67 E, 13.54 N) and Dakar (16.96 W, 14.39 N) are being used in this study. Data spanning the period from 2004 to 2014 have been selected; they include conventional humidity parameters, remotely sensed aerosol and precipitable water information and numerical model outputs. Since in Africa, only conventional information on humidity parameters is available, it is important to utilize the unique observations from the AERONET network to calibrate empirical formulas frequently used to estimate precipitable water vapor from humidity measurements. An empirical formula of the form PWV ¼ aTd þ b where Td is the surface dew point temperature, a and b are constants, was fitted to the data and is proposed as applicable to the climatic condition of the sub- Sahel. Moreover, we have also used the AERONET information to evaluate the capabilities of well-established numerical weather prediction (NWP) models such as ERA Interim Reanalysis, NCEP-DOE Reanalysis II and NCEP-CFSR, to estimate precipitable water vapor in the sub-Sahel West Africa; it was found that the models tend to overestimate the amount of precipitable water at the selected sites by about 25 %.
Performance Analysis of Temperature Models for Environmental Monitoring in Southwest Nigeria
(Nigerian Journal of Environment and Health, 2019) Willoughby, Alexander
Temperature is a major meteorological parameter driving most of the atmospheric processes vis-`a-vis climate change. Therefore, a consistent model is necessary to achieve sustainable development goal 13 (SDG 13) known as climate action. Long-term monthly averages of surface temperature obtained from six southwest states in Nigeria were subjected to five mathematical models, namely the sum of two-Gaussians, the sum of two-Lorentzians, Fourier on four harmonics, Sine wave and Fourth-order polynomial functions. Statistical tools were used to examine the accuracy and fitness of the models. The evaluation showed that the Gaussian and Lorentzian models are good fits of the observed data. Furthermore, the performance indicators such as mean bias error (MBE), root mean square error (RMSE), mean percentage error (MPE) recorded the lowest values for Fourier on the fourth harmonic model. Similarly, its correlation coe cient, R, was the highest ranging from 0.95 to 1. Consequently, the Fourier model presented the best correlation with the observed data and hence recommended for predicting the temperature at the selected locations
Rain Fade Analysis at C, Ka and Ku Bands in Nigeria
(iiste.org, 2019) Sanyaolu, Modupe
Rain fade has continued to be a major concern to communication systems designers. The effect of these dynamic fluctuations of the received signal due to rain is very pronounced in the tropical region. This paper pertains to the analysis of rain fades at C, Ku and Ka bands at some selected stations covering the main geographical zones of Nigeria. The ITU-RP propagation model was used to calculate the fade depth at 6 GHz, 8 GHz, 12 GHz, 16 GHz, 20 GHz, 30 GHz and 40 GHz. The rain fade correlate with signal attenuation. Attenuation distributions for percentages of time for signal unavailability were also estimated. The results show that values of attenuation for vertically and circularly polarized signals are less than those of the horizontal polarization at all the frequencies. It is found that rain fade is less severe in the Northern part of the country and is most severe in the southern part of Nigeria, with Port Harcourt, Lagos and Nsukka experiencing the highest rain impairment
Development of a Low-Cost Pyrometer using Locally Sourced Materials
(International Journal for Scientific Research & Development, 2019) Osinowo, Muritala
Measurement of solar irradiance in-situ was very scanty in this part the world most research estimate using atmospheric weather parameter. In this work a low-cost pyranometer using locally sourced materials was developed. Instrument or device consists of photodiode (BPW34) housed inside 40 with bulb that is perfectly seal, solar irradiance sensor amplifier, 16-bit analog-to-digital converter (ADS1115), arduino mega2560, and liquid crystal display (LCD) and microSD card shield. The design amplifier has offsetting voltage of 0.8676 mV. The sensitivity of solar irradiance was amplifier 868.19 Wm-2V-1 with correct factor 27.77 Wm-2. The output range of developed instrument is between 0.1 mV to 1.4 V with maximum 1200 Wm-2. The possible error of the instrument is 9.67%. The result obtained when compared SRS100 pyranometer is 0.89. The result obtained from collected data shows that from 8.15 to 16.00, local time, the response was very good with little difference at early hour of day around up to 8.30 am and around 4.30 pm downward.
Development of a Low-Cost Soil Heat Flux and Temperature Profile with Logger
(International Journal of Advances in Scientific Research and Engineering, 2019-07-26) Osinowo, Muritala
Variation of soil temperature and soil heat flux measurements from a locally fabricated and calibrated device were analyzed and compared with a standard device. The soil heat flux consists of two-disc aluminum plates, dielectric material and two thermocouples such that each thermocouple was sandwiched between the aluminum plates and one side of the dielectric material. The sizes of the aluminum plates and the dielectric material were 32 mm in diameter and their thickness is 2.5 mm. Differential temperature between two thermocouples attached to two aluminum plates separated by a thermal insulator was used to measure the soil heat flux values. The thermocouples amplifier module AD8495 and then combined with a 16-bit Analog to Digital Converter (ADS1115) for a good measurement resolution was employed for the signal conditioning. A semiconductor sensor DS18B20 was used to measure the soil temperature. The microSD shield was included for storing data and DS3232, a Real Time Clock (RTC) module for timekeeping. Arduino mega 2560 microcontroller was used to coordinate the whole active and display the activities on LCD. The soil heat flux sensor was calibrated using the principle of thermal conduction over the surface area by heating with a known heat source. The thermal conductivity of heat flux is given by 3.3407 (WV-1m-1) from the empirical deduction. The temperature sensing unit was checked for accuracy by inserting it inside a calorimeter with the mercury-in-glass thermometer and the correlation obtained was 0.92. The soil heat flux and temperature sensing unit were compared with that of standard Campbell device. The correlation obtained for soil heat flux and temperature were 0.89 and 0.95 respectively. The result obtained when installed at the Redeemer’s University, Ede, Nigeria, the variation of soil heat flux and temperature when placed at the same level of 10 cm into the soil gave the same value. The maximum peak of heat flux density usually occurs at about 13:00 pm to 15:00 pm with values around 260 W/m2 at 10 cm. The logging interval can be preset to any rate from 30 seconds and above.
Variability of GPS-Derived Ionospheric TEC over Nigeria during a Year of Low Solar Activity
(Canadian Journal of Physics, 2020) Willoughby, Alexander
An investigation on the diurnal and seasonal variability of ionospheric Total Electron Content (TEC) over Nigeria is carried out in this study using Global Positioning System (GPS) observable. Nigeria coordinates fall within the trough of equatorial ionisation anomaly region of African sector. The TEC data used were obtained from the ground-based GPS receiver stations of the Nigerian GNSS network of stations (NIGNET). The stations with their respective geomagnetic latitudes are: Abuja (􀀀1:64 ), Yola (􀀀1:32 ), Zaria (􀀀0:13 ), Kebbi (0:72 ). The results of the diurnal analysis of the relative variability index (VD) revealed higher nighttime values than daytime values. The diurnal variation of VD also showed two conspicuous peaks: the postmidnight and the post-sunset. The diurnal-seasonal variation does not reveal any consistent pattern (no particular season leads the others throughout). On the average, considering all the seasons together maximum TEC variability occurred in Zaria (62%) and least in Yola (54%). Seasonally, maximum VD was recorded during March equinox and the least was recorded during December equinox.
1-Minute Rain Rate Distribution for Communication Link Design Based on Ground and Satellite Measurements in West Africa
(Begell House, Inc., 2020) Sanyaolu, Modupe
West Africa is in the tropical region and it is characterized by intense rainfall. Rain is a significant factor causing signal degradation on microwave links due to its variability; it causes scattering, absorption, and refraction of electromagnetic waves. Experimental studies have shown that rainfall intensities above 64 mm/h at 0.01% in this region results in noticeable digital television signal fading, squelching and complete outages. Hence the need for estimating rain rate distribution across West Africa. This paper analyzed the rain rate from six countries in West Africa, namely Benin, Cameroon, Cote d'Ivoire, Ghana, Nigeria, and Togo. Three locations were selected in each country. Rain data were obtained from the Tropical Rain Measuring Mission-Precipitation Radar (TRMM-PR) and the Global Precipitation Measurement (GPM) missions, and Tropospheric Data Acquisition Network (TRODAN) weather stations in Nigeria. This study used ITU-R and Moupfouma models for the conversion of the 5-minute rain rate to 1-minute integration time at a probability of exceedance ranging from 1% to 0.001%. The cumulative rain rate distribution from the measured rain rate is presented alongside the predictions of the models. ITU-R and Moupfouma predicted similar results at 0.1% probability of exceedance. ITU-R overestimates the rain rate above 0.01% probability of exceedance. On the other hand, the Moupfouma models prediction plots at 0.01% overlap for all locations, indicating that there will be a signal loss at 0.01% probability of exceedance across these locations. The result shows that the 5-minute conversion provides satisfactory performance and suitable for estimating the 1-minute rain rate statistics required for propagation planning over West Africa.
Variability of GPS-derived Ionospheric TEC over Nigeria During a Year of Low Solar Activity
(Canadian Journal of Physics, 2020) Akinyemi, Gbenga

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