Department of Electrical and Electronic Engineering

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1-Minute Rain Rate Distribution for Communication Link Design Based on Ground and Satellite Measurements in West Africa
(Begell Journal, 2020) Dairo, Oluropo
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 result 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 in 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 is suitable for estimating the 1-minute rain rate statistics required for propagation planning over West Africa.
a-Amylase inhibition, anti-glycation property and characterization of the binding interaction of citric acid with a-amylase using multiple spectroscopic, kinetics and molecular docking approaches
(Elsevier, 2022-05) Dairo, Oluropo
The quest to suppress complications associated with diabetes mellitus is ever increasing, while food addi- tives and preservatives are currently being considered to play additional roles besides their uses in food enhancement and preservation. In the present study, the protective prowess of a common food preserva- tive (citric acid, CA) against advanced glycation end-products (AGEs) formation and its binding interac- tion mechanism with a-amylase (AMY), an enzyme linked with hyperglycemia management, were examined. Enzyme inhibition kinetics, intrinsic fluorescence, synchronous and 3D fluorescence spectro- scopies, ultraviolet–visible (UV–Vis) absorption spectroscopy, Fourier transform-infrared (FT-IR) spec- troscopy, thermodynamics, and molecular docking analyses were employed. Results obtained showed that citric acid decreased a-amylase activity via mixed inhibition (IC50 = 5.01 ± 0.87 mM, Kic = 2.42 mM, Kiu = 160.34 mM) and suppressed AGEs formation (IC50 = 0.795 ± 0.001 mM). The intrinsic fluorescence of free a-amylase was quenched via static mechanism with high bimolecular quenching constant (Kq) and binding constant (Ka) values. Analysis of thermodynamic properties revealed that AMY-CA complex was spontaneously formed (DG < 0), entropy driven (TDS > DH), with involvement of electrostatic forces. UV–Vis, FT-IR and 3D fluorescence spectroscopies affirmed alterations in a- amylase native conformation due to CA binding interaction. CA interacted with His-101, Asp-197, His- 299, and Glu-233 within AMY active site. Our findings indicated that CA could impair formation of AGEs and interact with a-amylase to slow down starch hydrolysis; vital properties in management of type 2 diabetes complications.
Assessment of Five Predictive Models for Solar Radiation in Southwest Nigeria
(LivingScience Foundation, 2020-10) Dairo, Oluropo
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.
Cathode Materials for Lithium-ion Batteries: A brief review
(International Information and Engineering Technology Association (IIETA), 2021) Dairo, Oluropo
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
(IOP Publishing, 2021) Dairo, Oluropo
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 second- order 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.
Development of Ultra Low-Cost Data Acquisition System (DAS) for Developing Countries
(Walailak University, 2022-07-01) Dairo, Oluropo
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 Mega 2560 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 a microSD card. The DAS was tested and examined through intensive experimental work. From the tables and plots obtained from the experiment for standardizing the sensors, it is clear that there is 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 has been eliminated. There is no need for the 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 atmospheric parameters.
Estimation of Rain Fade Durations on Communication Links at Ka Band in Equatorial and Tropical Regions
(Begell Journal, 2020) Dairo, Oluropo
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.
Exploring the binding interactions of structurally diverse dichalcogenoimidodiphosphinate ligands with α-amylase: Spectroscopic approach coupled with molecular docking
(Elsevier, 2020) Dairo, Oluropo
Postprandial hyperglycemia has orchestrated untimely death among diabetic patients over the decades and regulation of α-amylase activity is now becoming a promising management option for type 2 diabetes. The present study investigated the binding interactions of three structurally diverse dichalcogenoimidodiphosphinate ligands with α-amylase to ascertain the affinity of the ligands for α-amylase using spectroscopic and molecular docking methods. The ligands were characterized using 1H and 31P NMR spectroscopy and CHN analysis. Dis- elenoimidodiphosphinate ligand (DY300), dithioimidodiphosphinate ligand (DY301), and thio- selenoimidodiphosphinate ligand (DY302) quenched the intrinsic fluorescence intensity of α-amylase via a static quenching mechanism with bimolecular quenching constant (Kq) values in the order of x1011 M-1s-1, indicating formation of enzyme-ligand complexes. A binding stoichiometry of n≈1 was observed for α-amylase, with high binding constants (Ka). α-Amylase inhibition was as follow: Acarbose>DY301>DY300>DY302. Values of thermodynamic parameters obtained at temperatures investigated (298, 304 and 310 K) revealed spontaneous complex formation (ΔG<0) between the ligands and α-amylase; the main driving forces were hydrophobic in- teractions (with DY300, DY301, except DY302). UV–visible spectroscopy and Fo ̈rster resonance energy transfer (FRET) affirmed change in enzyme conformation and binding occurrence. Molecular docking revealed ligands interaction with α-amylase via some key catalytic site amino acid residues (Asp197, Glu233 and Asp300). DY301 perhaps showed highest α-amylase inhibition (IC50, 268.11 ± 0.74 μM) due to its moderately high affinity and composition of two sulphide bonds unlike the others. This study might provide theoretical basis for development of novel α-amylase inhibitors from dichalcogenoimidodiphosphinate ligands for management of postprandial hyperglycemia.
Fabrication and Characterization of a Dye-Sensitized Solar Cell using Natural Dye Extract of Rosella (Hibiscus sabdariffa L.) as Photosensitizer
(Nigerian Society of Physical Sciences, 2021) Dairo, Oluropo
The relatively low energy conversion efficiency 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 efficiency of the solar cell. This study demonstrates the suitability of dye extracted from rosella (Hibiscus sabdariffa 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 in DSSCs. 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 μA and an open-circuit voltage of 0.637 V.
Performance Analysis of Temperature Models for Environmental Monitoring in Southwest Nigeria
(LivingScience Foundation, 2019) Dairo, Oluropo
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 for the observed data. Furthermore, the performance indicators such as mean bias error (MBE), root mean square error (RMSE) and mean percentage error (MPE) recorded the lowest values for Fourier on the fourth harmonic model. Similarly, its correlation coefficient, R, was the highest ranging from 0.95 to 1. Consequently, the Fourier model presented the best correlation with the observed data and hence was 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
(LivingScience Foundation, 2020-10) Dairo, Oluropo
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.
Polymer Optical Fibre in Communications and Environmental Monitoring
(URSI Nigeria, 2010-12) Dairo, Oluropo
This paper focuses on niche applications of polymer optical fibre (POF) in modern communication systems and other related areas. The electromagnetic isolation of POF and its relatively high sensitivity compared to conventional sensors has earned it a centre stage in sensing technology. The ability to detect and measure physical parameters such as temperature, humidity and wind speed makes POF suitable for real-time monitoring of environmental and climatic conditions. Other attractive features of POF include a lower cost compared with glass optical fibres, better fracture resistance and flexibility.
Prediction of Rain-Induced Attenuation along Earth-Space Links at Millimeter Wave Bands over West African Region
(Begell Journal, 2021) Dairo, Oluropo
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
(IOP Publishing, 2021) Dairo, Oluropo
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 third-party 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.
Radio refractivity gradients in the lowest 100 m of the atmosphere over Lagos, Nigeria in the rainy-harmattan transition phase
(Elsevier Ltd, 2018) Dairo, Oluropo
Radio engineers and researchers in conjunction with the International Telecommunication Union (ITU) have established the pivotal role of radio refractivity to the propagation of electromagnetic energy in the troposphere. In particular, the refractivity gradient statistics for the lowest 100m in the troposphere are used to determine the probability of occurrence of anomalous propagation conditions known as ducting. The major challenge to characterising the propagation condition over any environment is accessing the data of the lowest boundary layer of the atmosphere, which is highly dynamic and turbulent in evolution. High resolution radiosonde data from the Nigerian Meteorological Agency (NiMet) were used for a synoptic study of the rain-harmattan transition phase. The rain-harmattan transition phase marks the onset of the dry season due to the movement of the intertropical convergence zone interplay between (north-easterly and south-westerly) trade winds and monsoonal circulation. The lowest 100m data were analysed to determine the frequency of ducting per month. Progressive increase in the occurrence of ducting was observed during the rain-harmattan transition phase, which coincides with the West African Monsoon retreat. The results show significant divergence from previous studies, which reported that the tropospheric condition over Lagos (Geo. 6.5°N, 3.3°E), Nigeria, is predominantly super-refractive.
Rain Fade Analysis at C, Ka and Ku Bands in Nigeria
(IISTE, 2019) Dairo, Oluropo
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 correlates 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.
Recent developments in polymer optical fiber strain sensors: A short review
(Springer Nature, 2021) Dairo, Oluropo
Polymer optical fiber (POF) strain sensors have attracted increasing attention owing to the unique features of polymer over silica such as lower Young’s modulus, larger elastic strain limit, higher fracture toughness, bio-compatibility, and lower production cost. Several POF strain sensors have been developed in recent years for applications in various technological fields, including structural health monitoring in civil construction and aerospace industries, biomedicine, and robotics. The principles of operation, prospects and challenges of the POF strain sensors are discussed in this article under five broad categories: POF fiber Bragg grating sensors, intensity-based POF sensors, multimodal interference-based sensors, Brillouin-frequency-based sensors, and Fabry–Perot cavity sensor. This review aims to highlight areas where further research is required for improving the performance and operating range of POF strain sensors.
The Response of the Equatorial Ionosphere over Nigeria to a Geomagnetic Storm Event
(Pleiades Publishing, 2021) Dairo, Oluropo
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 condi- tion’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.
Statistical Analysis of Tropospheric Scintillation of Satellite Communication Signals using Karasawa and ITU-R Models
(IEEE, 2017) Dairo, Oluropo
The climatology of the tropics coupled with its deep convective evolution at the equatorial troposphere has continued to draw significant attention to the effects of scintillation on satellite communication signals. The dearth of signal degradation data perceived as scintillation fade depth is pronounced in the tropics. In particular, the effect of tropospheric scintillation on two major satellite providers, namely NigComSat-1R and Eutelsat, was considered. Karasawa and ITU-R statistical models were used. Twelve months of data were collected from the Tropospheric Data Acquisition Network stations with geo-spatial coverage representing Nigerian climatic zones. The variability is 􏰀9% for both models in the monsoon climate, and ~158%–180% in warm semi-arid climate for both ITU-R and Karasawa, respectively. Scintillation intensity was highest in the monsoon climate with values of 1.31dB, 1.51dB and 18.72 dB using ITU-R, and 0.88 dB, 1.06 dB and 27.05 dB using Karasawafor Eutelsat, NigComSat-1R and low elevation satellites.
Tropospheric Scintillation Effects on Satellite Links from X-band to Q-band over Nigerian Climatic Zones using Karasawa and ITU-R Models
(Begell Journal, 2020) Dairo, Oluropo
The tropospheric scintillation of satellite communication signals has continued to draw the attention of radio engineers. The effect and prevalent paucity of Earth-space tropospheric scintillation data in Africa are remarkable. The parameters of NigComSat-1R and Eutelsat-36B satellites were used for this modelling from X- to Q-band during the West African monsoon (WAM). The low error rates of Karasawa and ITU-R models reported for the tropical climates made them appropriate for this study. In situ data from the Tropospheric Data Acquisition Network stations spanning three climatic regions in Nigeria, namely Tropical Monsoon, Geo. 6.5o N, 3.5o E; Tropical Savanna, Geo. 8.99o N, 7.38o E; and the Sahel, Geo. 9.35o N, 12.5o E. The scintillation variability is lowest in the tropical monsoon climate and highest in the Sahel climate using both models. However, the ITU-R model recorded higher scintillation fade depths (SFDs) of 37.19 dB, 2.91 dB, and 2.52 dB, for low elevation, NigComSat-1R and Eutelsat-36B satellites respectively, over the tropical monsoon climatic zone, than Karasawa model, which recorded SFDs of 34.07 dB, 1.31 dB, and 1.09 dB for the respective satellites. The observed scintillation intensity increased with increasing carrier frequency, low elevation angle and small receiving antenna. High variability of the scintillation intensity characterizes the onset of WAM and post-monsoon months.

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