Department of Physical Sciences

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Analysis of Rain Fade Durations on Communication Links at Ka Band in Nigeria
(International Journal of Recent Technology and Engineering (IJRTE), 2020) Willoughby, Alexander
Duration of rain fade events is a major parameter to be considered when designing a communication link. Fading is a phenomenon responsible for intermittent fluctuations of radio signals observed in the tropical region. The prevalence of rain in the tropics accounts for the frequency of fading observed in this region. This study investigates the number of fade events per fade duration interval exceeding attenuation thresholds ranging from 1 dB to 18 dB at 40 GHz. The range of fade durations is from 10 s to 5000 s. The International Telecommunication Union (ITU-RP) propagation model and data from the Tropospheric Data Acquisition Network (TRODAN) were used for the analysis. The eight TRODAN stations, under the Centre for Atmospheric research (CAR), an activity Centre of the National Space Research and Development Agency (NASRDA) in Nigeria, cover the major climatic regions in the sub-Saharan region, namely equatorial, humid tropical and tropical zones (Geo. 4:82 N to 9:58 N). The results show that fade duration decreases as attenuation increases across all the locations. The implication is that heavy rains, causing higher attenuation, occur for shorter time duration. Similarly, higher attenuation depends on raindrops size and rain intensity. Consequently, the frequency of fade events exceeding 1 dB threshold is higher than other thresholds with respect to the fade duration.
Assessment of Five Predictive Models for Solar Radiation in Southwest Nigeria
(Nigerian Journal of Environment and Health, 2021) Willoughby, Alexander
This study compares the accuracies of five predictive models for estimating solar radiation amongst other meteorological parameters in Southwest Nigeria. Twenty-one years of monthly averages of six measured meteorological parameters obtained from six stations in southwest Nigeria have been subjected to five mathematical models for prediction purposes. Solar radiation and sunshine hours have been modelled using the sum of two-Gaussians, the sum of two-Lorentzians, Fourier on four harmonics, sine wave and fourth-order polynomial functions. The fitting accuracies of these models were tested using performance indicators; mean bias error (MBE), root mean square error (RMSE), mean percentage error (MPE), standard error (SE) and the correlation coefficient (R). An evaluation of the models showed that the Gaussian and Lorentzian models are in good agreement with the observed data. However, the Fourier on the fourth harmonics model had the lowest MBE, RMSE and MPE, consequently highest correlation coefficient values, indicating high model accuracy. Thus, the Fourier model has the best correlation with the observed data and is recommended for estimating these variables in the selected locations.
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.
Cathode Materials for Lithium-ion Batteries: A Brief Review
(Journal of New Materials for Electrochemical Systems, 2021-10) Willoughby, Alexander
Layered lithium cobalt oxide (LiCoO2) as a pioneer commercial cathode for lithium-ion batteries (LIBs) is unsuitable for the next generation of LIBs, which require high energy density, good rate performance, improved safety, low cost, and environmental friendliness. LiCoO2 suffers from structural instability at a high level of delithiation and performance degradation when overcharged. Besides, cobalt, a significant constituent of LiCoO2 is more costly and less environmentally friendly than other transition metals. Therefore, alternative cathode materials are being explored to replace LiCoO2 as cathode materials for high-performance LIBs. These new cathode materials, including lithiated transition metal oxides, vanadium pentoxides, and polyanion-type materials, are reviewed in this study. The various challenges hampering the full integration of these cathode materials in commercial LIBs and viable solutions are emphasised.
Characteristics of Rain Fade Slopes on Microwave Communication in Mowe, Nigeria
(Journal of Physics: Conference Series PAPER, 2021) Willoughby, Alexander
In this paper, the rain fade characteristics at Ka-band (30 GHz) in Mowe (Lat 6.80º N, Lon 3.40º E) Nigeria have been presented. The analysis includes both the first- and secondorder statistics of rain rate and rain attenuation, and fade duration and fade slope, respectively. Both parameters are useful for planning the point-to-point microwave link for various communication feeder networks. The estimated fade duration and the fade slope were compared with the ITU-R P.837-5 model. The results of this study would be valuable for improving rain fade mitigation techniques in Nigeria.
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
Design and Construction of Ultraviolet and Incoming Solar Irradiance Sensing Device
(Walailak Journal of Science and Technology, 2021-08-02) Willoughby, Alexander
In-situ measurements of ultraviolet (UV) and solar irradiance is very sparse in Nigeria because of cost, and most researchers estimate them using meteorological parameters. In this work, a low-cost UV and pyranometer device, using locally sourced materials, was developed. The instrument consists of a UV sensor (ML8511), a photodiode (BPW34) housed in a carefully sealed vacuumed glass bulb, the UV and solar irradiance sensor amplifiers, a 16-bit analog-to-digital converter (ADS1115), Arduino mega 2560, liquid crystal display (LCD) and microSD card for data logging. The designed amplifier has an offset voltage of 0.8676 mV. The sensitivity of the irradiance device is 86.819 Wm-2/mV with a correcting factor of 27.77 Wm-2 and a maximum range of 1200 Wm-2. The instrument validation error is 9.67% and a correlation coefficient of 0.89 when compared with a standard SRS100 pyranometer. The UV sensor showed a close response with a correlation of 0.99 in comparison with a standard Skye instrument. From 08:00 to 16:00 local time (LT), there is a very close agreement between the standard device and the developed counterpart, with marginal differences of about 9.6% observed at the two extremes.
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 Ultra Low-Cost Data Acquisition System (DAS) for Developing Countries
(Walailak Journal, 2021) Willoughby, Alexander
The Data Acquisition System (DAS) is an important equipment in measurement systems especially in weather monitoring and also very crucial in many areas such as agricultural, communication, transportation, sport and industrial processes. This work proposes a weather monitoring system based on an Arduino Mega2560 microcontroller board. The microcontroller has the ability to monitor, record and display the information of atmospheric sensor parameters connected to its analogue and digital pins. The outputs of analogue sensors are connected to the microcontroller through separate ADC for sampling. An LCD attached to the microcontroller displays the measured parameters. For analysis, the data is stored in excel format and can be copied directly from microSD card. The DAS was tested and examined through intensive experimental work. The tables and plots obtained from the experiment for standardizing the sensors, it is clear that there is a close conformity between the data collected by the developed system and the existing standard systems. The need for extra cost baud rate and expensive third-party computer software for interfacing to download data from the logger have been eliminated. There is no need of internet for any linking or configuration. It is evident that the DAS is of better choice in terms of cost and maintenance. The system will be helpful in monitoring and recording of atmospheric parameters.
Estimation of Rain Fade Durations on Communication Links at Ka Band in Equatorial and Tropical Regions
(Telecommunications and Radio Engineering, Begell House, 2020) Willoughby, Alexander
Duration of rain fade events is a major parameter to be considered when designing a communication link. Fading is a phenomenon responsible for intermittent fluctuations of radio signals observed in the tropical region. The prevalence of rain in the tropics accounts for the frequency of fading observed in this region. Despite, the efforts of researchers to help systems designers give due consideration to fade mitigation techniques in other parts of the world, there is still a dearth of fade duration data from the African equatorial and tropical regions. Hence, this study estimates the number of fade events per fade duration interval exceeding attenuation thresholds ranging from 1 dB to 18 dB at ka-Band (26.5 GHz−40 GHz), leading to nonavailability of satellite systems during raining events in the African equatorial regions. The range of fade durations is from 10 s to 5000 s. The International Telecommunication Union (ITU-RP) propagation model and data from the Tropospheric Data Acquisition Network (TRODAN) were used for the analysis. The eight TRODAN observatories, under the Centre for Atmospheric Research (CAR), cover the major climatic regions in the sub-Saharan region, namely equatorial, humid tropical and tropical zones (Geo. 4.82єN to 9.58єN). Fade duration decreases latitudinally as the attenuation threshold increases from low to higher latitudes. The equatorial region suffers the highest frequency of fade events while the tropical zones recorded the lowest. In addition, the 10 s fade duration recorded the highest occurrence of fade events. The implication is that heavy rains, causing higher attenuation, occur for a shorter time duration. Similarly, higher attenuation depends on raindrops size and rain intensity. Consequently, the number of fade events exceeding 1 dB threshold is higher than other thresholds with respect to the fade duration.
Fabrication and Characterization of a Dye-Sensitized Solar Cell using Natural Dye Extract of Rosella (Hibiscus sabdari a L.) as Photosensitizer
(Journal of the Nigerian Society of Physical Sciences, 2021) Willoughby, Alexander
The relatively low energy conversion e ciency of dye-sensitized solar cells (DSSCs) is a key challenge hindering the commercialization of the solar cell. The photochemical performance of the dye used as a photosensitizer for the DSSC greatly determines the e ciency of the solar cell. This study demonstrates the suitability of dye extracted from rosella (Hibiscus sabdari a L.) flowers as a photosensitizer for a DSSC. The natural dye was extracted using the acid water extraction method and was characterized using FTIR spectroscopy and UV–vis spectrophotometry.The absorption spectra of the dye were examined to determine the aptness of the dye as a photosensitizer inDSSCs. The IR absorption spectra of the extracted dye confirmed both amine and hydroxyl compounds as functional groups in the natural dye, which established the suitability of the dye as a photosensitizer in DSSCs.The UV-vis absorption spectra of the natural dye within the visible region illustrate that the aqueous extract from rosella flowers has stable absorption of visible light, thus validating the natural dye as a good candidate for photosensitizer in a DSSC. The fabricated DSSC delivered a short-circuit current of 5 A and an open-circuit voltage of 0.637 V.
An IoT-Based Home Automation and Weather Monitoring System
(International Journal of Research and Innovation in Applied Science (IJRIAS), 2022-03) Willoughby, Alexander
This paper reports an IoT-based home automation and weather monitoring system developed for remote control of household appliances and weather monitoring. The proposed system comprises a Wi-Fi enabled ESP32 microcontroller as the network gateway, a relay module, and a DHT11 sensor for monitoring temperature and humidity. The status of the household devices and the weather data are continuously collected and stored in a MySQL database, which is set up on the IoT platform. A user interface was created using two different protocols - HyperText Transfer Protocol (HTTP) and Message Queuing Telemetry Transport (MQTT). The IoT-based home automation and weather monitoring system is designed to be low cost, user-friendly and can remotely control home appliances and monitor weather data over the internet.
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 %.
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.
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
Performance Evaluation of Rainfall Models and Associated Precipitation Oscillations in the Southwestern Climate System of Nigeria
(Nigerian Journal of Environment and Health, 2020) Willoughby, Alexander
The study explored the spatio-temporal evolution of rainfall and precipitable water oscillations using data of over two decades. The monthly averages of rainfall and precipitable water were obtained from six locations in the southwestern climatic region of Nigeria. The data were analysed using five mathematical models namely the sum of two-Gaussians, the sum of two-Lorentzian, Fourier on four harmonics, sine wave and fourth-order polynomial functions for prediction purposes. The performances of these models were evaluated using the mean bias error (MBE), root mean square error (RMSE), mean percentage error (MPE), standard error (SE) and the correlation coefficient (R). The performance indicators of the models showed that the Gaussian and Lorentzian models are in good agreement with the observed data. However, the Fourier on fourth harmonics model had the lowest MBE, RMSE and MPE, consequently highest correlation coefficient values, indicating high model accuracy. Thus, the Fourier model has the best correlation with the observed data and is recommended for estimating these variables in the selected locations.
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.
Prediction of Rain-Induced Attenuation along Earth-Space Links at Millimeter Wave Bands over West African Region
(Telecommunications and Radio Engineering, Begell House, 2021) Willoughby, Alexander
The present work characterizes the degree of rain-induced attenuation on 15–80 GHz earth-space communication links. Eutelsats 36B and 36C, and NigComSat-1R satellite links over five West African countries were considered through the International Telecommunication Union Radiocommunication Sector (ITU-R) [International Telecommunications Union (ITU)], Bryant, and Syjatogor rain attenuation models. Three locations were selected in each country for the analysis using 2013–2017 rain data obtained from the Global Precipitation Measurement (GPM) missions. ITU-R predicted higher attenuation values than the other two models; while Svjatogor values were close to ITU-R, and the Bryant model predicted the lowest. At 99.99% signal availability, rain attenuation along the earth-space link over the five countries ranged between 22.1 and 34.2 dB for Ku-band (15 GHz) but exceeded the satellites’ link margins at Ka-band (30 GHz). At 0.1% unavailability, the range is 6–21 dB across all the locations for V-band (60 GHz), which implies that the satellites can sustain 99.9% of signal availability across the countries. However, for 99.99% and 99.9% signal availability at W-band, earth-space links can experience a total outage across the selected stations. Some locations in the northern parts can have 99% availability, which is an ~ 87 h/yr outage. Hence, the result could be a benchmark for planning trans-horizon radio communication links across West Africa.
Preliminary Results of Measurements Obtained from a Low-Cost Arduino-Based Surface Weather Data Acquisition System for Radio Meteorology
(Journal of Physics: Conference Series, 2021) Willoughby, Alexander
Surface weather monitoring is crucial for radio meteorology, agricultural, communication, and industrial processes. However, there is a dearth of weather data in Ede, Osun State, Nigeria (Lat 7.736º N, Lon 4.435º E). The proposed weather monitoring system used the Arduino Mega2560 microcontroller to measure, record and display the atmospheric parameters. Analog sensors for pressure, temperature, relative humidity, and wind speed were interfaced with the microcontroller through an ADC for digital signal conversion and data logging. An LCD connected to the microcontroller displays the measured parameters. The weather data were stored in excel format on a microSD card. The data were compared with that of a nearby weather station. The plots showed a close agreement with the data collected from the nearby station. The system eliminates the need for extra cost baud rate and expensive thirdparty software for interfacing. Besides, there is no need for an internet connection for configuration. Hence, this data acquisition system (DAS) could be a better choice in cost and maintenance than the off-the-shelf weather stations. The DAS was programmed to derive the surface radio refractivity from the meteorological parameters and the corresponding radio refractivity gradients over Ede.
The Response of the Equatorial Ionosphere over Nigeria to a Geomagnetic Storm Event
(Geomagnetism and Aeronomy, Pleiades Publishing, Ltd.,, 2021) Willoughby, Alexander
Abstract—The total electron content (TEC) data obtained from the ground-based GPS receiver stations of the Nigerian GNSS network of stations (NIGNET) have been used in this study to analyse the response of equatorial and low-latitude ionosphere to strong geomagnetic storms that occurred on October 25, 2011. The stations and their respective geomagnetic latitudes are Lagos (−3.03°), Yola (−1.32°) and Birnin Kebbi (0.72°). The storm caused enhancements in TEC (positive storm effect) in comparison with the quiet condition’s TEC across all the stations during both the main and the recovery phases. During the storm of October 25, recorded maximum enhancements in TEC were 181.86%, 142.34% and 181.24% in Kebbi, Yola and Lagos respectively.The magnitude of the ionospheric irregularities was higher at the night (October 25) of the main phase of the geomagnetic storm than the night (October 24) before the storm onset.

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