Regime Analysis of Critical Raindrop Diameters for Rainfall Attenuation in Southern Africa

The influence of critical raindrop diameters on the specific rainfall attenuation in Durban (29o52'S, 30o58'E), South Africa using various rainfall regimes is analyzed in this paper. Different rain rate values representing drizzle, widespread, shower and thunderstorm are selected for the purpose of analysis over the measured raindrop size distribution. The three-parameter lognormal and gamma DSD models with shape parameter of 2 are used to estimate the parameters required to investigate the drop sizes which produce a major contribution to the total specific rainfall attenuation for the selected rain rate values. The computed total specific attenuation increases with increasing frequencies and rain rates. The highest and prevailing contribution to the specific attenuation occurs at for the stratiform (drizzle or widespread) and convective (shower or thunderstorm) rain types for the models considered. The total percentage fraction formed by drops in the diameter range 0.5 mm ≤ D ≤ 2.5 mm and 1.0 mm ≤ D ≤ 3.0 mm are found to be most critical for the specific rain attenuation for the stratiform (drizzle and widespread)  and convective (shower and thunderstorm) rainfall types especially at higher frequencies

Analysis of Raindrop Diameters for Rainfall Attenuation in Southern Africa

The influence of critical raindrop diameters on the specific rainfall attenuation in Durban (29o52'S, 30o58'E), South Africa using various rainfall regimes is analyzed in this paper. Different rain rate values representing drizzle, widespread, shower and thunderstorm are selected for the purpose of analysis over the measured raindrop size distribution. The three-parameter lognormal and gamma DSD models with shape parameter of 2 are used to estimate the parameters required to investigate the drop sizes which produce a major contribution to the total specific rainfall attenuation for the selected rain rate values. The computed total specific attenuation increases with increasing frequencies and rain rates. The highest and prevailing contribution to the specific attenuation occurs at  for the stratiform (drizzle or widespread) and convective (shower or thunderstorm) rain types for the models considered.  The total percentage fraction formed by drops in the diameter range 0.5 mm ≤ D ≤ 2.5 mm and 1.0 mm ≤ D ≤ 3.0 mm are found to be most critical for the specific rain attenuation for the stratiform (drizzle and widespread)  and convective (shower and thunderstorm) rainfall types especially at higher frequencies

Performance Evaluation of Lighting Fixtures and Installations for Renewable Energy Applications

Energy efficiency has been viewed as the most accessible and cost effective form of alternative energy. While lighting occupies only a percentage in the total electric loads in homes, technological advances in Light Emitting Diodes (LED) are becoming more convincing in their power consumption and lumens output. This paper evaluates the percentage lighting occupied in the total load spectrum on the two main buildings in Osun State University, verifies the light level in the library reading rooms (a place where adequate lighting is imperative) with recommended standards and comparison between the output of Compact Fluorescent Lamps (CFL) and the LEDs. Walk-through Energy audit approach was used to evaluate the percentage lightning occupies which involves identification and grouping of all electrical loads with their respective power rating in Watts. Similarly, illumination level verification campaign was conducted with the use of a digital light meter (sensor based device) connected to a Personal Computer for logging illumination level real time along the aisles and reading cubicles. The same light meter was used for comparing the output of installed CFL and proposed LED. Results indicate that lighting fixtures occupy 12.2% of the load spectrum. The lighting installations also do not conform to global illumination standards for the facility accessed while the output of the LED tested is still low. It is therefore recommended that better LED light sources be considered for efficient energy, reduction in environmental pollution associated with power generation, reduction in power needed to maintain a cooling effect and cost economy. Keywords: CFL, LEDs, lumens, illumination level verification, power sector, environmental pollution

Experimental Assessment of Cellular Mobile Performance along the Railway Corridor

With the ongoing rehabilitation of the railway transportation sector in Nigeria, improvement in the quality and reliability of the services deliverable becomes crucial. Reliable railway communication infrastructure guarantees effective operation and also ensures connectivity for security, safety, maintenance and passenger communication. This work describes today’s network scenario by assessing current cellular performance as it affects a passenger’s experience along the railway corridor. A drive test was conducted on the 6th of July, 2014 between 12:58pm and 07:14pm along the railroad linking Oshogbo and Lagos, Nigeria. The measurement setup consists of four TEMS Mobile Sony Ericsson W995 phones, a Personal Computer, a GPS receiver, and a power bank. The measurement was useful in the assessment of coverage, capacity and Quality of Service (QoS) of four mobile radio networks namely: Airtel, Globacom, Etisalat and MTN in the GSM 900 MHz and 1800 bands. Results reveal that no single mobile network service operator consistently serviced the train throughout the 6-hour trip. Also, the results obtained from the drive test represents a true picture of mobile network condition and can be useful in decision making in several areas - from planning and design through optimization and maintenance of the system, with the goal of maximizing quality, capacity and coverage for all mobile networks for improved service delivery on our railway infrastructure. Keywords: Railway communication; GSM; Performance of Cellular mobil

WHALE OPTIMIZATION ALGORITHM FOR OPTIMAL LOCATION AND SIZING OF RENEWABLE DISTRIBUTED GENERATION

Renewable generation is a viable source of clean and smart energy in a modern distribution network. Thus, the synergy between photovoltaic and small-hydropower yields a complementary and uninterruptible power output. However, location and sizing mostly affect operational output. This paper presents a combined Voltage Stability Index estimation (VSI) and Whale Optimization Algorithm (WOA) for the optimal allocation of renewable-based energy sources. The nodes voltage stability index is ranked to signal the whale optimization selection of candidate solution agents at each algorithm iterations. Thereby turning the Distributed Generation (DG) node selection into non-random mode to improve simulation time and performance. The WOA technique is modeled using the hunting activities of whales and analysed on IEEE 33 bus systems. The results confirm the algorithm’s improved performance of 89% voltage improvement and 48.50 power loss reduction for single PV integration. The technique ensures efficient network resource management for improved output

Quantification of Rain Induced Artifacts on Digital Satellite Television Reception

The presence of artifacts on the high definition television (TV) content and the eventual loss of the digital TV signals to rain is still a major concern to satellite operators, digital satellite television (DSTV) and terrestrial television content providers. In this paper, the artifacts present in a typical DSTV signal is examined on a practical direct-to-home (DTH) link at Osun State University, Osogbo, Nigeria (7.77°N, 4.60°E), received via EUTELSAT W4/W7 at 12.245 GHz. The degrading effect is assessed using a subjective experimental approach, which is based on the quantification of the artifacts ruining user’s Quality of Experience (QoE) during rainfall events. Results indicate that the thunderstorm rainfall is accountable for the impairment, while pixilation was observed as a dominant artifact appearing before the loss and shortly at the recovery of the DSTV signal.http://dx.doi.org/10.4314/njt.v34i4.1

Experimental Assessment of Cellular Mobile Performance along the Railway Corridor

With the ongoing rehabilitation of the railway transportation sector in Nigeria, improvement in the quality and reliability of the services deliverable becomes crucial. Reliable railway communication infrastructure guarantees effective operation and also ensures connectivity for security, safety, maintenance and passenger communication. This work describes today’s network scenario by assessing current cellular performance as it affects a passenger’s experience along the railway corridor. A drive test was conducted on the 6th of July, 2014 between 12:58pm and 07:14pm along the railroad linking Oshogbo and Lagos, Nigeria. The measurement setup consists of four TEMS Mobile Sony Ericsson W995 phones, a Personal Computer, a GPS receiver, and a power bank. The measurement was useful in the assessment of coverage, capacity and Quality of Service (QoS) of four mobile radio networks namely: Airtel, Globacom, Etisalat and MTN in the GSM 900 MHz and 1800 bands. Results reveal that no single mobile network service operator consistently serviced the train throughout the 6-hour trip. Also, the results obtained from the drive test represents a true picture of mobile network condition and can be useful in decision making in several areas - from planning and design through optimization and maintenance of the system, with the goal of maximizing quality, capacity and coverage for all mobile networks for improved service delivery on our railway infrastructure

Review of Rain Attenuation Measurements On Earth - Space Links in Nigeria

Due to the prevailing impact of rain on microwave and millimetre wave propagation in tropical climates, fade margins derived from experimental campaigns would provide more practical estimates for planning. In this paper, the extent of work done on the experimental assessment of the attenuation induced by rain on practical earth-space links in Nigeria is presented. The cumulative rain rate distributions derived from the instantaneous precipitation indices for propagation modelling and the estimation of fade margin is presented for Ile-Ife, Akure, Ilorin, Ota, Osogbo and Ogbomoso. Results reveals the spatial variability of the point rainfall rate across these stations. Although the stations engaged with measurement on rain attenuation are limited in number, preliminary results from new stations are presented, while addition data from ongoing campaigns will provide a robust indices for modelling the digital DTH links and for evaluating the performance of pre-existing models over Nigeria

Compact automatic modulation recognition using over-the-air signals and FOS features

The recent deployment of automatic modulation recognition (AMR) for cognitive radio (CR) systems has significantly enhanced spectrum sensing capabilities. The utilization of real-time over-the-air digital radio frequency (RF) data for the development of a digital spectrum sensing model based on the automatic modulation classification (AMC) is presented in this study as a step for incorporating opportunistic spectrum sensing onto the NomadicBTS architecture. Some digital modulation techniques were studied for second- generation (2G) through fourth-generation (4G) technology. The raw RF signal dataset was digitized and curated, while non-complex first-order statistical (FOS) features were used with algorithms based on the Scaled conjugate gradient (SCG) and Levenberg-Marquardt (LM) to find the best learning algorithm for the generated AMR model. The results show that the developed AMR model has a very high likelihood of correctly classifying signals, with distinct patterns for each of the features of FOS. The results are compared to reveal a least mean square error (MSE) of 0.0131 with a maximum accuracy of 93.5 percent when the model was trained with seventy (70) neurons in the hidden layer using the LM method. The best model's accuracy will allow for the most precise identification of spectrum holes in the bands under consideratio