Quadrature Spatial Modulation Orthogonal Frequency Division Multiplexing

This paper investigates the application of quadrature spatial modulation (QSM) to orthogonal frequency division multiplexing (OFDM). In comparison to spatial modulation OFDM (SM-OFDM), the proposed QSM-OFDM achieves an enhanced spectral efficiency by decomposing the amplitude and/or phase modulated signal into its real and imaginary components as the transmitted symbols. The index/indices of the activated transmit antenna(s) are employed to convey additional information. These symbols are transmitted orthogonally to eliminate inter-channel interference with little trade-off in synchronization. The average bit error probability for QSM-OFDM and other schemes, including the SM-OFDM, conventional multiple-input multiple-output (MIMO-OFDM), maximal-ratio combining single-input multiple-output (MRC-OFDM), vertical Bell Laboratories layered space-time architecture (VBLAST-OFDM) and Alamouti-OFDM systems are demonstrated using Monte Carlo simulation. The expressions for the receiver computational complexities in terms of the number of real operations are further derived. QSM-OFDM yields a significant signal-to-noise ratio gain of  dB with little trade-off in computational complexity over SM-OFDM, while substantial gains greater than  dB are evident, when compared to other systems

Development of a Grid-Based Rural Electrification Design: A Case Study of Ishashi and Ilogbo Communities in Lagos State, South Western Nigeria

This work presents the development of a grid-based rural electrification design using Ishashi and Ilogbocommunities in Lagos State, South Western Nigeria as case studies. Grid-based and off-grid based methods are two commonly employed rural electrification technologies but in this work grid-based method was employed because of its simplicity, flexibility, sustainability and cost effectiveness. Load audits of Ishashi and Ilogbo were carried out to determine their energy demands. To cater for future expansion of both communities, a fifteen year load growth was calculated using the derived load growth equations. Design equations were used to determine ratings and quantities of substation components required for the electrification. The inter-township connection and township distribution network lengths for both Ishashi and Ilogbo were also determined. The proposed electrical model designs for the two communities were implemented using AutoCAD 2012 Version Software. The energy demand of both Ishashi and Ilogbo were respectively 0.91 MW and 0.61 MW and their estimated fifteen years load growth were 3.26 MW and 2.20 MW respectively. The average load demand of both Ishashi and Ilogbo were respectively 1.31 MW and 0.88 MW using a load factor of 0.4. With the use of average load demand, the inter-township connection and township distribution network lengths of Ishashi (2.65 km and 8.72 km respectively) and Ilogbo (1.13 km and 7.44 km respectively), the required quantities of the major substation components required for implementation of developed electrical model designs were obtained

Labelling diversity for media-based space-time block coded spatial modulation

Abstract: Please refer to full text to view abstract

The Effect of Power factor Improvement on Switching Transients: A Case of FUMMAN Agricultural Products Industry Plc.

Industrial loads are mostly inductive and hence operate at low power factor. Several methods including the installation of capacitor banks are available for improving power factor in order to reduce the kilovolt ampere (kVA) demand of the load and power loss from the power supply system. However, literatures have shown that improvement of power factor has effect on switching transients which is dangerous for industrial loads and operating personnel. In this work, we investigated the effect of improving the power factor of a power system beyond 0.8 (lagging) on switching transient levels using FUMMAN industry power network as a case study. A power factor measuring tool was modelled using the mathematical relation between power factor, reactive power and active power. The modelled equations were simulated Matlab/Simulink software (Version 7.9.0.529 ‘R2009b’). The characteristics of the system under study namely root mean square (r.m.s) voltage, peak steady state voltage, peak transient voltage and kVA demand were measured during the simulation with and without parallel connection of capacitor bank across the system. The result from the analysis showed that FUMMAN industry power network was operating at a lagging power factor of 0.8 with r.m.s voltage of 412.1 V, peak steady state voltage of 582.8 V, peak transient voltage of 701.9 V and kVA demand of 1878 kVA without the capacitor bank. However, when a capacitor bank was connected across the system and the power factor increased from 0.8 (lagging) to 0.9098 (lagging), optimised performance of the system was obtained with a capacitor bank size of 440 kVar. At lagging power factor of 0.9098, the kVA demand of the system was 1650 kVA, r.m.s voltage was 415.5 V and peak transient voltage was 749.5 V. The analysis therefore showed that increasing power factor beyond 0.8 (lagging) using capacitor banks though improves the r.m.s voltage and reduces the power loss but invariably leads to increase in switching transients which is undesired for optimised system performance

Effect of Dynamic Voltage Restorer in Compensating for Voltage Sag and Controlling Harmonics in a Power Distribution System using Fumman Industry as a Case Study

Different power quality surveys done by researchers identify voltage sags as the most serious power quality problems for industrial customers. Voltage sag can cause serious problems to electric loads that cannot withstand variation in voltage such as adjustable speed drives, process control equipment and computers. This research work investigated the effect of Dynamic Voltage Restorer (DVR) in compensating for voltage sag and controlling harmonics in a power distribution system. A DVR is a power electronic converter base device that is used to regulate the voltage at the load terminals from various power quality problems like sag, swell unbalance etc in the supply voltage. The mathematical equations representing voltage sag and it compensation are presented. To implement the effect of DVR on industrial load network, Fumman Industry was considered as a case study. The DVR was modeled by building the subsystem of each major component. The components are injection transformer, fuzzy logic controller, battery and Pulse Width Modulation (PWM) inverter. Optimization technique was used to determine the appropriate battery size. Simulation was done without and with the DVR using Matlab/Simulink; under three and double phase line-to-ground faults.Simulation results showed that the modeled DVR can work very well against balanced and unbalanced voltage sag caused by fault in industrial distribution systemconsidering the harmonic limits

Power System’s Voltage Stability Improvement Using Static Var Compensator

In alternating current systems, voltage fluctuation is a common phenomenon. Most of the voltage fluctuation problems result from the changes in the system’s reactive power resulting from excessive supply or consumption of reactive power by the elements of the system and the variation in the consumers’ loads. In this paper, the effect of Static Var Compensator (SVC) in stabilizing power system’s voltage through effective reactive power compensation was investigated. Power flow equations involving voltage drop with/without SVC were developed. SVC modeling equations were also developed and used to determine its parameters. Based on the SVC parameters, SIMULINK blocks were used to implement the phase controlled Thyristor–Controlled-Reactor Fixed-Capacitor (TCR-FC) SVC. The Nigerian 28-bus power system used for the study was also modeled using SIMULINK/MATLAB. The 28-bus system was first simulated without SVC and then with two SVCs located at different buses to obtain the bus voltages in both cases. From the bus voltages the total voltage drops for the system with and without SVC were estimated and compared. The compared results clearly showed that, the system’s voltage drop was reduced by 33.78% indicating a significant improvement in the system’s voltage stability when SVCs were applied

Development and Application of a Functional Human Esophageal Mucosa Explant Platform to Eosinophilic Esophagitis.

There is an increasing prevalence of esophageal diseases but intact human tissue platforms to study esophageal function, disease mechanisms, and the interactions between cell types in situ are lacking. To address this, we utilized full thickness human donor esophagi to create and validate the ex vivo function of mucosa and smooth muscle (n = 25). Explanted tissue was tested for contractile responses to carbachol and histamine. We then treated ex vivo human esophageal mucosa with a cytokine cocktail to closely mimic the Th2 and inflammatory milieu of eosinophilic esophagitis (EoE) and assessed alterations in smooth muscle and extracellular matrix function and stiffening. We found that full thickness human esophagus as well as the individual layers of circular and longitudinal muscularis propria developed tension in response to carbachol ex vivo and that mucosa demonstrated squamous cell differentiation. Treatment of mucosa with Th2 and fibrotic cytokines recapitulated the majority of the clinical Eosinophilic Esophagitis Diagnostic Profile (EDP) on fluidic transcriptional microarray. Transforming growth factor-beta-1 (TGFβ1) increased gene expression of fibronectin, smooth muscle actin, and phospholamban (p < 0.001). The EoE cocktail also increased stiffness and decreased mucosal compliance, akin to the functional alterations in EoE (p = 0.001). This work establishes a new, transcriptionally intact and physiologically functional human platform to model esophageal tissue responses in EoE

Enhancing genetic gains in grain yield and efficiency of testing sites of early-maturing maize hybrids under contrasting environments

The major challenges of maize production and productivity in Sub-Saharan Africa (SSA) include Striga hermonthica infestation, recurrent drought, and low soil nitrogen (low N). This study assessed the following: (i) accelerated genetic advancements in grain yield and other measured traits of early-maturing maize hybrids, (ii) ideal test environments for selecting early-maturing multiple-stress tolerant hybrids, and (iii) high-yielding and stable hybrids across multiple-stress and non-stress environments. Fifty-four hybrids developed during three periods of genetic enhancement (2008–2010, 2011–2013, and 2014–2016) were evaluated in Nigeria, The Republic of Benin, and Ghana under multiple stressors (Striga infestation, managed drought, and Low N) and non-stress environments from 2017 to 2019. Under multiple-stress and non-stress environments, annual genetic gains from selection in grain yield of 84.72 kg ha−1 (4.05%) and 61 kg ha−1 (1.56%), respectively, were recorded. Three mega-environments were identified across 14 stress environments. Abuja was identified as an ideal test environment for selecting superior hybrids. The hybrid TZdEI 352 × TZEI 355 developed during period 3 was the most outstanding under multiple-stress and non-stress environments. On-farm testing of this hybrid is required to verify its superior performance for commercialization in SSA. Considerable progress has been made in the genetic improvement of early-maturing maize hybrids for tolerance of multiple stressors and high yield. The identified core testing sites of this study could be used to enhance the testing and selection of promising hybrids