| 1 |
Author(s):
Sunusi Sani Adamu.
Page No : 1-11
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MODELLING OF SELF EXCITATION PROCESS IN INDUCTION GENERATORS
Abstract
The present energy crisis has led to renewed interest in the use of induction machines in energy conversion applications. This is due to certain advantages they posses; simple construction, rugged and low in cost. Moreover, they can easily be coupled to many types of motive power sources, as such, can be utilised in rural areas in developing countries and also in distributed generation applications. In such situations, the reliability of the self excitation is of paramount importance. This work develops a model to study the effect of machine parameters and other operating conditions on the transient excitation process of induction generators. Both linear and nonlinear models of the machine in quasi-stationary dq-reference frame are developed and simulated in Matlab/ Simulink environment. The developed linear model predicted the voltage build-up but is unbounded. On the other hand, the nonlinear model, where saturation of the mutual flux is considered, presents a more realistic picture. The study concludes that sufficient remanent magnetism, no load starting and ensuring low stator resistance and leakage reactances paths can improve the reliability of the voltage build up
| 2 |
Author(s):
Sadiku L. Umar, Abdussamad U. Jibia.
Page No : 12-19
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TRANSIENT MULTIEXPONENTIAL DATA ANALYSIS USING THE MATRIX PENCIL METHOD
Abstract
Many problems exist in nature in which experimental data can be accurately modeled by a sum of damped exponential
functions with real decay rates. Several methods have been reported for estimating such data. In this paper,
matrix pencil method is used to postprocess the deconvolved data resulting from the application of modified Gardner
transform to the transient multiexponential data signal. Processing of such data using other parametric methods
has been previously reported. Although the results are not very good, the approach is promising as further
modifications on it are expected to improve on the results. The problem of nonstationarity of the deconvolved data
persists.
| 3 |
Author(s):
Abdussamad U. Jibia.
Page No : 20-27
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PERFORMANCE COMPARISON OF TWO DECONVOLUTION TECHNIQUES IN THE ANALYSIS OF EXPONENTIAL DECAY CURVES
Abstract
The paper presents the application of two deconvolution methods, namely Multiparameter Deconvolution (MPD) and
Exponential Compensation Deconvolution (ECD) in the analysis of a sum of damped exponentials. The data signal
was first converted to a convolution integral using Modified Gardner transform. The integral was converted to a
convolution sum and the two methods were used to deconvolve it. The resulting deconvolved data was truncated and
modelled using three parametric models. The results show that MPD outperforms ECD at all SNRs using the appropriate
parametric models.
| 4 |
Author(s):
Onidare Samuel O., Faruk Nasir, Bello Olayiwola W., Muhammad Mujahid Y., Sowande Olugbenga, A. Ayeni Adeseko.
Page No : 28-39
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PRACTICAL ERROR BOUNDS OF EMPIRICAL MODELS AT VHF/UHF BANDS
Abstract
Empirical path loss models are widely used to predict signal propagation behavior in an environment. In this paper, a multi-transmitter scenario was used to bound the errors of five widely used empirical propagation path loss models in predicting radio waves propagation in the UHF and VHF bands in Ilorin metropolis, Nigeria. A drive test was conducted using a dedicated Agilent N9342C spectrum analyzer along seven different routes that span urban and open areas. Three transmitters were utilized in the campaign (National Television Authority NTA Ilorin, Harmony FM and Unilorin FM). The prediction error, root mean square error (RMSE), skewness of the error distribution and the relative error were further computed and presented. Furthermore, the performance of the models were also cor-related with their design parameters and constraints. The analysis reveals that, of the five models investigated, the error bounds of the ECC model is very high, hence its accuracy for Ilorin terrain, while the three models of Cost-231, Hata and Ilorin (a localized model) were below the acceptable tolerable values for the metrics used and the Egli model falls within a reasonable range of the acceptable values of 6-7dB for urban areas and 10-15dB for Suburban and rural areas. For example, while the ECC model recorded RMSE values of 54.11dB, 52.23dB and 52.41dB for the three transmitters, the corresponding values for the Hata model were; 7.9 dB, 8.37 dB and 10.13 dB, for the COST 231 model: 8.46 dB, 10.09 dB and 9.66 dB and for the Ilorin model, the RMSE values were; 8.51 dB, 8.50 dB and 10.57 dB. The RMSE values obtained for the Egli model are 16.77 dB, 14.50 dB and 10.90 dB respectively. Finally, it was found that the error distribution for each model followed the terrain profile of the routes.
| 5 |
Author(s):
Ogork, Egbe-Ngu Ntui, Omofonma, Godwin.
Page No : 40-48
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DURABILITY ASSESSMENT OF POLYPROPYLENE HIGH STRENGTH CONCRETE IN MARINE ENVIRONMENT
Abstract
This paper assesses the effect of polypropylene fibres (PPF) on the durability of high strength concrete exposed to marine environment. The polypropylene fibres were obtained from northern bag manufacturing co. Ltd, Kano, Nigeria and were characterized. The compressive strength of PPF high strength concrete was investigated on grade 50 and 60 concrete of mix ratio of 1: 1.13: 2.39 and 1: 0.82: 1.75 with water cement ratio of 0.38 and 0.34, respectively. Chopped polypropylene fibres of 35 mm long were added to the concrete mix at 0, 0.1, 0.2 and 0.3 %, respectively by volume of concrete. A total of thirty six 150 x 150 x 150 mm cubes of each grade of PPF high strength concrete were tested for compressive strength at 7, 28 and 56 days of curing in clean water. Also twelve 150 x 150 x 150 mm cubes of each grade of concrete were tested for water absorption after curing for 28 days, and a further twelve cubes of each grade of concrete were initially cured in clean water for 28 days before exposure to Sea water for 28 days and tested in compression. The results of the investigations showed that addition of up to 0.2 % PPF increased the compressive strength and resistance of high strength concrete exposed to marine environment. The water absorption of high strength concrete decreased with increase in PPF addition.
| 6 |
Author(s):
Lawan, I., Ali, M.A., Abubakar, M.S..
Page No : 49-62
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PERFORMANCE EVALUATION OF AN INTEGRATED GROUNDNUT OIL EXTRACTION MACHINE
Abstract
An integrated groundnut oil extraction machine previously development at the Department of Agricultural Engineering, Bayero University Kano was evaluated. Throughput capacity (kg/hr), extraction rate (Lit/hr) and extraction efficiency (%) were used as performance indicators, while variety of groundnut seeds (Manipintar and Ex-Dakar), kneading speed on the paste (200, 111 and 73 rpm) and quantity of groundnut seeds (24, 16.8 and 12 kg) were used as experimental factors. The experiment was conducted using 2x3x3 factorial in completely randomized design (CRD) and the treatments were replicated three (3) times. Thus, a total of fifty four (54) experiments were conducted with the samples at 2.52 and 2.69% (db) moisture content for Manipintar and Ex-Dakar variety respectively. The oil content of the samples obtained were 50.40 and 49.20% for Manipintar and Ex-Dakar variety respectively. Results revealed that the highest throughput capacity achieved was 24.45 kg/hr with combination of V2 (Ex-Dakar Variety), KS (200 rpm) and Q1 (24 kg). The highest extraction rate achieved was 7.90 Lit/hr with combination of of V1 (Manipintar Variety), KS1 (200 rpm) and Q1 (24 kg). Also, the highest extraction efficiency of 78.59% was achieved with combination of V1 (Manipintar Variety), KS1 (200 rpm) and Q3 (12 kg). Comparing the results with what was obtained using the traditional method represents 552, 852 and 21% increase in throughput capacity, extraction rate and extraction efficiency respectively.
