Integration of Distributed Generations (DGs) at distribution network levels have changed the structure from being radial to mesh; thereby causing fault currents to be fed from all the sources connected to the network. Another operational... more
Integration of Distributed Generations (DGs) at distribution network levels have changed the structure from being radial to mesh; thereby causing fault currents to be fed from all the sources connected to the network. Another operational requirement is that DGs can get disconnected from the network due to disturbances or maintenance requirements leading to new network topology. This research work has, therefore, proposed an adaptive protection scheme that relies on modern communication infrastructure for its implementation, after optimally siting and sizing of DG and investigation of impact of DG on the protection system and reliability of the system. Herein, modified particle swarm optimization (MPSO) has been deployed for the optimal relay parameters values (operation time, pick up current and time dial settings). Standard communication protocol (IEC 61850) has been chosen to facilitate the communication amongst the various devices in the adaptive protection framework developed.
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Concrete has been identified as one of the most common building material with high embodied energy. Investigations on lightweight concrete using oil palm shell (OPS) as coarse aggregate were attempts to find an alternative material to the... more
Concrete has been identified as one of the most common building material with high embodied energy. Investigations on lightweight concrete using oil palm shell (OPS) as coarse aggregate were attempts to find an alternative material to the use of crushed granite in concrete with a view to reducing environmental pollution resulting from the accumulation of OPS as waste from palm oil mills. This paper investigated some important characteristics of concrete made with OPS as coarse aggregate and rice husk ash (RHA) partially replacing Ordinary Portland Cement (Ashment) as binding agent. The compressive strength of the Ashment:OPS concrete at 28 days was found to be 62% higher than the minimum required strength of 17N/mm and 22% lighter, for structural lightweight concrete recommended by ASTM C330. Ashment:OPS concrete can therefore be used in lightweight structures. The use of this concrete will reduce environmental pollution. This is because the major constituents of the concrete; OPS a...
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This paper presents the position and trajectory tracking control scheme for the ball and plate system (BPS) using the double feedback loop structure (a loop within a loop) for effective control of the system. The inner loop was designed... more
This paper presents the position and trajectory tracking control scheme for the ball and plate system (BPS) using the double feedback loop structure (a loop within a loop) for effective control of the system. The inner loop was designed using linear algebraic method by solving a set of Diophantine equations. The outer inner loop was designed using sensitivity approach. Simulation results showed that the plate was stabilized at 0.3546 seconds, and the ball was able to settle at 1.7087 seconds, when given a circular trajectory of radius 0.4 m with an angular frequency of 1.57 rad/sec, with a trajectory tracking error of 0.0095 m, which shows that the controllers have adaptability, strong robustness and control performance for the ball and plate system.
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Sixty sesame accessions from eight locations in Nigeria were assessed for agro-morphological traits using random amplified polymorphic DNA (RAPD) markers. DNA was isolated using modified cetyltrimethyl ammonium bromide extraction method.... more
Sixty sesame accessions from eight locations in Nigeria were assessed for agro-morphological traits using random amplified polymorphic DNA (RAPD) markers. DNA was isolated using modified cetyltrimethyl ammonium bromide extraction method. The cultivars were assessed for genetic diversity using eight random amplified polymorphic DNA markers. The agronomic assessment was also conducted and the results showed that germination period ranged 3-7 d. Mean 100-seed weight was 3.6±0.3 mg, while mean seed pod was 56 pods per plant, with days to flowering ranging 48-62 d. Seeds size ranged 50.6-79.3 mm, while plant height was 1.4±1.7 m. Dendrogram generated using unweighted pair groups mean arithmetic analysis separated the accessions into six major groups of two clusters and some independent cultivars with a bootstrap value of 45-60%. The polymorphic information content (PIC) values ranged from 0.3-0.9. The RAPD marker OPT-10 showed polymorphic characteristics, while OPB-11 was monomorphic wit...
Background: Soft tissue sarcomas are a rare group of heterogeneous tumours that consist of several neoplasia which differentiate into different cell lines. They could arise from the mesodermal or ectodermal embryonic germ layers.... more
Background: Soft tissue sarcomas are a rare group of heterogeneous tumours that consist of several neoplasia which differentiate into different cell lines. They could arise from the mesodermal or ectodermal embryonic germ layers. Rhabdomyosarcoma is the most common soft tissue tumour in the paediatric age group in most studies, while in adults, malignant fibrous histocytoma, liposarcoma and fibrosarcoma are seen to be more predominant. The study aims to highlight the histological patterns, clinical presentation, associated risk factors and the patients’ performance status at presentation.Methods: This is a 5-year retrospective between the period of 2010 to 2015 of all cancer patients diagnosed with soft tissue sarcoma, seen in the department of radiotherapy and oncology, a tertiary health centre in Sokoto Nigeria. Data collected included socio-demographic, histological type, clinical features, and performance status.Results: A total of 123 patients were reviewed during the study per...
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This study presents the transient stability enhancement capability of Unified power flow controller (UPFC) as an effective Flexible AC Transmission System (FACTS) device in a multi-machine power system. The test system was a reduced... more
This study presents the transient stability enhancement capability of Unified power flow controller (UPFC) as an effective Flexible AC Transmission System (FACTS) device in a multi-machine power system. The test system was a reduced Nigerian 330kV power system and the focus was on the effect of disturbances on the largest generating unit (Egbin) in the system. The analysis was conducted by simulating a 3-phase fault at two locations; on the terminal of the largest generator unit at Egbin bus and the bus with the largest load at Ikeja–west. The response of the system in both cases was compared with and without the device in operation. Simulations were carried out using the Power System Simulation for Engineering (PSS/E) software. Results showed that, with the UPFC in the network, system transient stability was enhanced considering that critical clearing time of the system was increased from 380ms to 590ms when the fault was at Egbin generator terminal and from 470ms to 510ms followin...
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Thermosensitive alginate–poloxamer (ALG–POL) copolymer with an optimal POL content was synthesized, and it was used to combine with silk fibroin (SF) for building ALG–POL/SF hydrogels with dual network structure. Mesoporous bioactive... more
Thermosensitive alginate–poloxamer (ALG–POL) copolymer with an optimal POL content was synthesized, and it was used to combine with silk fibroin (SF) for building ALG–POL/SF hydrogels with dual network structure. Mesoporous bioactive glass (BG) nanoparticles (NPs) with a high level of mesoporosity and large pore size were prepared and they were employed as a vehicle for loading insulin-like growth factor-1 (IGF-1). IGF-1-loaded BG NPs were embedded into ALG–POL/SF hydrogels to achieve the controlled delivery of IGF-1. The resulting IGF-1-loaded BG/ALG–POL/SF gels were found to be injectable with their sol-gel transition near physiological temperature and pH. Rheological measurements showed that BG/ALG–POL/SF gels had their elastic modulus higher than 5kPa with large ratio of elastic modulus to viscous modulus, indicative of their mechanically strong features. The dry BG/ALG–POL/SF gels were seen to be highly porous with well-interconnected pore characteristics. The gels loaded with ...
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Introduction : cerebrospinal meningitis (CSM) is an epidemic-prone vaccine preventable disease associated with high mortality and morbidity, especially in developing countries like Nigeria. It is regarded as a priority disease in the... more
Introduction : cerebrospinal meningitis (CSM) is an epidemic-prone vaccine preventable disease associated with high mortality and morbidity, especially in developing countries like Nigeria. It is regarded as a priority disease in the Integrated Disease Surveillance and Response (IDSR) system in Nigeria. We analyzed surveillance data to describe the epidemiology of CSM in Kebbi State, 2015 - 2016. Methods : we reviewed surveillance data abstracted from Kebbi State IDSR data-base for the years 2015 - 2016. A suspected case of CSM was defined as: any person with sudden onset of fever (>38.5oc rectal or 38oc axillary) and one of the following signs: neck stiffness, altered consciousness or other meningeal signs. A confirmed case was defined as a suspected case confirmed by isolation of Neisseria meningitidis from Cerebro-spinal fluid (CSF) or blood. We computed frequencies and proportions. Results : a total of 2088 suspected cases of CSM were reported during the period under review with a cumulative attack rate of 48.6/100,000 and 2.3/100,000 in 2015 and 2016 respectively. Mean age was 12.9 ± 9.5 years. Males constituted 1183 (56.7%) of the reported cases. Persons aged 10-15 years accounted for the highest number of cases 720 (34.5%). All patients were treated with Intra-muscular or Intra-venous Ceftriaxone according to the national treatment guidelines. Only 140 (6.7%) patients, had their CSF samples taken of which 76 (54.3%) were positive for Neisseria meningitides serotype C. Ninety three of the total patients died during the reporting period (case fatality rate 4.5%). Amongst those that died, only 2 (2.2%) were laboratory confirmed. One thousand two hundred and fifty four (60.1%) of the cases had a single dose of Meningococcal polysaccharide vaccine, 803 (38.5%) were unvaccinated. Conclusion : the laboratory component of the surveillance system and the vaccination coverage were poor. We recommended further improvement in laboratory surveillance and vaccination activities in the State.
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Chitosan(CH)-polylactide(PLA) copolymers containing varied PLA percentages were synthesized using a group-protection method and one of them with solubility in water-based solvents was used to prepare CH-PLA/hyaluronic acid (HA) complex... more
Chitosan(CH)-polylactide(PLA) copolymers containing varied PLA percentages were synthesized using a group-protection method and one of them with solubility in water-based solvents was used to prepare CH-PLA/hyaluronic acid (HA) complex microspheres for the delivery of transforming growth factor-β1 (TGF-β1). An emulsification processing method was developed for producing TGF-β1-loaded CH-PLA/HA microspheres using sodium tripolyphosphate (TPP) as ionic crosslinker and the size of the microspheres was devised to the micron level in order to achieve high encapsulating efficiency. The encapsulating efficiency, swelling property and release administration of the microspheres could be synergistically regulated by PLA component, the applied TPP dose and the incorporated HA amount. In comparison to CH/HA microspheres, the CH-PLA/HA microspheres had greatly reduced TGF-β1 release rates and were able to administrate the TGF-β1 release at controlled rates over a significant longer period of tim...
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This paper seeks to assess the reactions of Nigeria’s stock market to monetary policy innovations during the period of global financial crisis on the basis of monthly data over the period January, 2007 to August, 2011. In particular,... more
This paper seeks to assess the reactions of Nigeria’s stock market to monetary policy innovations during the period of global financial crisis on the basis of monthly data over the period January, 2007 to August, 2011. In particular, stock market return was regressed against major monetary policy instruments; money stock (M1, and M2) and monetary policy rate (MPR). The theoretical
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... 11 November 1982 A LOCAL CONTROL STRATEGY FOR POWER SYSTEMS IN TRANSIENT EMERGENCY STATE PART II: IMPLEMENTATION AND TEST RESULTS BY SIMULATION Usman 0. Aliyu, Member AH El-Abiad, Fellow Electrical Engineering Department ...
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Effects of unwanted distortions on power system network voltage and current phasor quantities during faults could adversely affect the reliability and discrimination of protective relays. This paper is principally concerned with the... more
Effects of unwanted distortions on power system network voltage and current phasor quantities during faults could adversely affect the reliability and discrimination of protective relays. This paper is principally concerned with the digital relaying concept based on multi-state Kalman filtering approach to minimise such problems. It seeks to characterise the effects of noise, harmonics and DC offset distortions on Kalman
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In this paper, the implementations of some specific transient stabilizing control means, exemplified by dynamic braking resistor, forced excitation and fast turbine valving, are investigated from the view-point of their potential effects... more
In this paper, the implementations of some specific transient stabilizing control means, exemplified by dynamic braking resistor, forced excitation and fast turbine valving, are investigated from the view-point of their potential effects on the torsional stresses in a turbine generator shaft system. For the purpose of this study, a state space digital simulation model of one machine infinite bus system
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This paper presents the comparative application of two metaheuristic approaches: differential evolution (DE) and particle swarm optimization (PSO) to the solution of the reactive power and voltage control problem. Efficient distribution... more
This paper presents the comparative application of two metaheuristic approaches: differential evolution (DE) and particle swarm optimization (PSO) to the solution of the reactive power and voltage control problem. Efficient distribution of reactive power in an electric network leads to minimization of the system losses and improvement of the system voltage profile. It can be achieved by varying the excitation
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The goal of reactive power dispatch is to minimize the system losses and improve the system voltage profiles at all times. This is achieved by adjusting various generating units' excitation systems continuously, discrete tap... more
The goal of reactive power dispatch is to minimize the system losses and improve the system voltage profiles at all times. This is achieved by adjusting various generating units' excitation systems continuously, discrete tap positions of on-load tap changers of transformers as well as switching of correct doses of inductors or capacitors. This is a mixed integer non-linear optimization problem.
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In this paper, the application of a novel and computationally enhances genetic algorithm (GA) for solving the reactive power dispatch problem is presented. In order to attain a significant reduction in the computational time of GA, a... more
In this paper, the application of a novel and computationally enhances genetic algorithm (GA) for solving the reactive power dispatch problem is presented. In order to attain a significant reduction in the computational time of GA, a systematic procedure of reactive power control device pre-selection mechanism is herein proposed to choose a-priori subsets of the available control devices, which maximally
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In this paper, a micro-genetic based approach to the optimization of reactive power and voltage profiles improvement and real power loss minimization is presented. The reactive power control devices such as generators, tap positions of... more
In this paper, a micro-genetic based approach to the optimization of reactive power and voltage profiles improvement and real power loss minimization is presented. The reactive power control devices such as generators, tap positions of on-load tap changer of transformers, shunt reactors are used to correct voltage limits violations while simultaneously reducing the system real power losses. Genetic algorithms (GAs)
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An optimal transient controller for a synchronous generator in a multi-machine power system is designed using the concept of flatness-based feedback linearization in this paper. The computation of the flat output and corresponding... more
An optimal transient controller for a synchronous generator in a multi-machine power system is designed using the concept of flatness-based feedback linearization in this paper. The computation of the flat output and corresponding controller for reduced order model of the synchronous generator is presented. The required feedback gains used to close the linearization loop is optimized using particle swarm optimization for maximum damping. Typical results obtained for transient disturbances on a two-area, four-generator power system equipped with the proposed controller on one generator and conventional power system stabilizers on the remaining generators are presented. The effectiveness of the flatness-based controller for multi-machine power systems is discussed.
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The aim of this study is to obtain a computer based model that can simulate and optimize the performance of an existing industrial fluid catalytic cracking (FCC) unit in steady state. The objective of this unit is to convert residues into... more
The aim of this study is to obtain a computer based model that can simulate and optimize the performance of an existing industrial fluid catalytic cracking (FCC) unit in steady state. The objective of this unit is to convert residues into high added value products (Fuel ...
The main focus of this paper is on the application of genetic algorithm (GA) to search for an optimal solution to a realistically formulated economic dispatch (ED) problem. GA is a global search technique based on principles inspired from... more
The main focus of this paper is on the application of genetic algorithm (GA) to search for an optimal solution to a realistically formulated economic dispatch (ED) problem. GA is a global search technique based on principles inspired from the genetic and evolution mechanism observed in natural biological systems. A major drawback of the conventional GA (CGA) approach is that
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In determining the correct operation of relays of a protection scheme, proper representation of instrument transformers and their behavior in conditions where there can be transient is very critical. This paper presents a simulation model... more
In determining the correct operation of relays of a protection scheme, proper representation of instrument transformers and their behavior in conditions where there can be transient is very critical. This paper presents a simulation model for assessing the transient performance of capacitive voltage transformers (CVTs). In order to test the validity of the developed model, four CVT operational conditions are
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This work presents a novel load frequency control design approach for a two-area power system that relies on unsupervised and supervised learning neural network structure. Central to this approach is the prediction of the load disturbance... more
This work presents a novel load frequency control design approach for a two-area power system that relies on unsupervised and supervised learning neural network structure. Central to this approach is the prediction of the load disturbance of each area at every minute interval that is uniquely assigned to a cluster via unsupervised learning process. The controller feedback gains corresponding to
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The generator maintenance scheduling problem is formulated as a 0-1 integer linear program. Although previous papers have considered a rigorous integer programming approach intractable, an algorithm of this type is developed which (1) is... more
The generator maintenance scheduling problem is formulated as a 0-1 integer linear program. Although previous papers have considered a rigorous integer programming approach intractable, an algorithm of this type is developed which (1) is guaranteed to find a schedule satisfying problem constraints, if one exists; (2) is guaranteed to find the optimal feasible schedules; and (3) will accept any of