63 research outputs found
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
Labelling diversity for media-based space-time block coded spatial modulation
Abstract: Please refer to full text to view abstract
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
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
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