Accurate solutions to initial value systems of ordinary differential equations may be approximated efficiently by Runge-Kutta methods or linear multistep methods. Each of these has limitations of one sort or another. In this paper we consider, as a middle ground, the derivation of continuous general linear methods for solution of stiff systems of initial value problems in ordinary differential equations. These methods are designed to combine the advantages of both Runge-Kutta and linear multistep methods. Particularly, methods possessing the property of A-stability are identified as promising methods within this large class of general linear methods. We show that the continuous general linear methods are self-starting and have more ability to solve the stiff systems of ordinary differential equations, than the discrete ones. The initial value systems of ordinary differential equations are solved, for instance, without looking for any other method to start the integration process. This desirable feature of the proposed approach leads to obtaining very high accuracy of the solution of the given problem. Illustrative examples are given to demonstrate the novelty and reliability of the methods.
In this paper, an indirect adaptive fuzzy excitation and static VAR (unit of reactive power, volt-ampere reactive) compensator (SVC) controller is proposed to enhance transient stability for the power system, which based on input-output linearization technique. A three-bus system, which contains a generator and static VAR compensator (SVC), is considered in this paper, the SVC is located at the midpoint of the transmission lines. Simulation results show that the proposed controller compared with a controller based on tradition linearization technique can enhance the transient stability of the power system under a large sudden fault, which may occur nearly at the generator bus terminal.
The present paper was concerned with the design and application of a novel electronic system based on the well-known NE-555 timers. The proposed system was proved to be very useful for direct measurements of some commonly used physical quantities such as temperature, force, light, and relative humidity. The measured quantities were shown to be in the laboratory range, i.e., from -60°C up to 60°C, from 0 gm up to 300 gm; from 0 lux up to 13,000 lux; and from 21.0% up to 88.0%, respectively. Finally, theoretical and experimental results were shown to be in close agreement.
Properties of high-volume fly ash concrete incorporating san fibres are presented in this paper. For this investigation, initially, three concrete mixtures were made with 35%, 45%, and 55% of Class F fly as partial replacement of cement. After this, three percentages (0.25, 0.50, and 0.75%) of san fibres (25 mm length) were added in each of the fly ash concrete mixtures. San is a natural bast fibre, and is also known as Sunn Hemp (Botanical name: Crotalaria Juncea). It is grown in Indian Sub-Continent, Brazil, Eastern and Southern Africa, and also in some parts of U.S.A. Tests were performed for compressive strength, splitting tensile strength, flexural strength, and impact strength at the ages of 28, 91 and 365 days. Tests were also performed for fresh concrete properties. 28 days test results indicated that san fibres reduced the compressive strength of high-volume fly ash concrete by 2 to 13%, increased splitting tensile strength by 6 to 26%, flexural strength by 5 to 14%, and enhanced impact strength tremendously (by 100 to 300%) depending upon the fly ash content and fibre percentage. Later age (91 and 365 days) results showed continuous increase in strength properties of high-volume fly ash concrete. This was probably be possible due to the pozzolanic action of fly ash, leading to more densification of the concrete matrix, and development of more effective bond between fibres and fly ash concrete matrix.
The effect of varied firing temperature on the mechanical properties of fired masonry bricks samples produced from Ipetumodu clay was investigated. The clay sample was characterized using scanning electron microscopy (SEM) for the evaluation of the morphology of the sample using secondary electron imaging; and the phases/compositions of the samples using energy-dispersive X-ray (EDX) analysis, X-ray diffractometer (XRD), X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS). The brick samples of standard dimensions were prepared from the clay slurry. The prepared samples were sun dried for 72 hours and then fired at varied temperature (held for an hour) and then allowed to cool to room temperature in the furnace. The mechanical properties (compression strength, shear strength, modulus of rupture, density and hardness) of the samples were then investigated. It was observed that the mechanical properties of the fired brick samples varied with varying firing temperature due to phase changes/chemical reaction between the phases in the clay sample. It was concluded that the optimum mechanical property for brick samples within the temperature range considered is obtained at 950oC.
This study was designed to assess the quality of selected hand dug wells in Maikunkele area of Niger State, Nigeria using Water Quality Index (WQI). ten hand dug wells were randomly selected in Maikunkele area of Bosso Local Government and were tested for nine (9) parameters of National Sanitation Foundation (NSF) using standard analytical procedures. WQI results indicated that the quality of the selected well water samples were medium except for sample 2 that was extremely bad. The findings also revealed that all the samples except samples 2 and 3 had high coliform levels as high as 91 coliform/100cm3. This was an indication of faecal contamination substantiating the proximity of some of the wells to septic systems. The nitrate levels in all the samples exceeded the Maximum Contaminant Level (MCL) of WHO, EPA, APHA and the Nigerian Drinking Water Standards. Based on the results obtained, the quality of the well water samples was therefore not suitable for human consumption without adequate treatment. Regular monitoring of groundwater quality, abolishment of unhealthy waste disposal practices and introduction of modern techniques were highly recommended.
In this paper, the modelling of Thyristor Controlled Phase Angle Regulator ‘TCPAR’ for power flow studies and the role of that modelling in the study of Flexible Alternating Current Transmission Systems ‘FACTS’ for power flow control are discussed. In order to investigate the impact of TCPAR on power systems effectively, it is essential to formulate a correct and appropriate model for it. The TCPAR, thus, makes it possible to increase or decrease the power forwarded in the line where it is inserted in a considerable way, which makes of it an ideal tool for this kind of use. Knowing that the TCPAR does not inject any active power, it offers a good solution with a less consumption. One of the adverse effects of the TCPAR is the voltage drop which it causes in the network although it is not significant. To solve this disadvantage, it is enough to introduce a Static VAR Compensator ‘SVC’ into the electrical network which will compensate the voltages fall and will bring them back to an acceptable level.
In this study we use sex-structure approach to examine the effect of complacent sexual behaviour (risky sexual activities) on the rate of infection of HIV/AIDS in a population. We partitioned the population into two classes (male and female) represented by to express our model equation as a set of differential equations. We were able to express the number of AIDS cases (male and female) as linear functions that depend on the number of AIDS patient present in the population. We were also able to determine the equilibra states of the model. We found that the Basic Reproduction Number (R0, which is the number of secondary infections due to introduction of infective into the population) of both female and male partitions of the population is given as R0=sqrt(R0fRom).
Picoseconds Nd – YAG laser was used in this work to irradiate pure samples of Aluminum (Al) and produce plasma. The plasma plume was deposited as thin films, using Laser Induced Forward Transfer (LIFT) technique, on two different types of substrate; the first one from copper and the second one from agate (SiO2). The thin films were characterized using scanning electron microscope (SEM) and Energy Dispersive Analysis of X-rays (EDAX), in addition to scratch and scotch-tape for adhesion test. The effects of laser power density, the target thickness and the type of substrate on the homogeneity and adhesion of the films were investigated. The best conditions were: 2∙1013 W/cm2 laser power density, 2 µm target thickness and agate substrate. Al thin films with high quality were deduced using these conditions.
The results of a study that considered the use of regression analysis that may have correlation between index properties and California Bearing Ratio (CBR) of some lateritic soil within Osogbo town of South Western Nigeria have been presented. For an appreciable conclusion to be established, lateritic soil samples were collected from eight (8) different borrow pits within the town and various laboratory tests including Atterberg Limits, Gradation analysis, California Bearing Ratio, Compaction and Specific Gravity were performed on the soil samples.Various linear relationships between index properties and CBR of the samples were investigated and predictive equations estimating CBR from the experimental index values were developed. The findings indicate that good correlation exists between the two groups (i.e Index properties and CBR values). However, the values of the CBR computed from the models are only to be used for preliminary in view of simplicity and economy and not acceptable alternatives to laboratory testing because of the anisotropic nature of lateritic soil and its heterogeneity.
Optimal Power Flow (OPF) is one of the main functions of Power system operation. It determines the optimal settings of generating units, bus voltage, transformer tap and shunt elements in Power System with the objective of minimizing total production costs or losses while the system is operating within its security limits. The aim of this paper is to propose a novel methodology (BCGAs-HSA) that solves OPF including both active and reactive power dispatch It is based on combining the binary-coded genetic algorithm (BCGAs) and the harmony search algorithm (HSA) to determine the optimal global solution. This method was tested on the modified IEEE 30 bus test system. The results obtained by this method are compared with those obtained with BCGAs or HSA separately. The results show that the BCGAs-HSA approach can converge to the optimum solution with accuracy compared to those reported recently in the literature.
New series of N-[3-(1H-6-nitroindazol-1-yl)-propyl]-2-(substituted phenyl)-4-oxo-5-(substitutedbenzylidene)-1,3-thiazolidine-carboxamide, compounds 5(a-j) have been synthesized. Structures of all synthesized compounds were confirmed by chemical and spectral analyses such as IR, 1H-NMR, 13C-NMR and FAB-Mass. All the final synthesized compounds 5(a-j) were screened for their antibacterial, antifungal, antitubercular and anti-inflammatory activities.
In this paper, an integrated approach is proposed for non-recursive formulation of connection coefficients of different orthogonal functions in terms of a generic orthogonal function. The application of these coefficients arises when the product of two orthogonal basis functions are to be expressed in terms of single basis functions. Two significant advantages are achieved; one, the non-recursive formulations avoid memory and stack overflows in computer implementations; two, the integrated approach provides for digital hardware once-designed can be used for different functions. Computational savings achieved with the proposed non-recursive formulation vis-à-vis recursive formulation, reported in the literature so far, have been demonstrated using MATLAB PROFILER.
An ensemble Monte Carlo simulation is used to compare high field electron transport in bulk GaN, AlN and InN. For all materials we found that electron velocity overshoot only occurs when the electric field is increased to a value above a certain critical field .This critical field is strongly dependent on the material parameters. For example about 0.74×107 Vm-1 for the case of InN, 2.79×107 Vm-1 for AlN and 1.74×107 Vm-1 for GaN. At higher electric fields the drift velocity decreases eventually saturating at around 2.03×105 ms-1 for both GaN and AlN and 1.8×105 ms-1 for InN.
The induction machine, because of its robustness and low-cost, is commonly used in the industry. Nevertheless, as every type of electrical machine, this machine suffers of some limitations. The most important one is the working temperature which is the dimensioning parameter for the definition of the nominal working point and the machine lifetime. Due to a strong demand concerning thermal monitoring methods appeared in the industry sector. In this context, the adding of temperature sensors is not acceptable and the studied methods tend to use sensorless approaches such as observators or parameters estimators like the extended Kalman Filter (EKF). Then the important criteria are reliability, computational cost ad real time implementation.
The ultraviolet (UV) irradiations are used to solve the bacteriological problem of the drinking water quality. A discharge-gas lamp is used to produce this type of irradiation. The UV lamp is fed by photovoltaic (PV) energy via electronic ballast composed by an inverter, a transformer and resonant circuit (RLC). The aim of this work is to give a useful global model of the system. In particular, we introduce the complicated UV lamp model and the water disinfection kinetics, where the radiant energy flux emitted by the discharge-gas lamp and the arc voltage are a complex functions of the current and time. This system is intended to be mainly used in rural zones, the photovoltaic modules as source of energy is an adequate solution. To optimise the power transfer from the PV array to ballast and UV lamp, a Maximum Power Point Tracking (MPPT) device may be located between PV array and the loads. In this paper, we developed a bond-graph model which gives the water quality from UV flow, gas type, pressure, lamp current and geometrical characteristic. Finally reliable simulations are established and compared with experimental tests.
Liquid-Liquid Extraction is one of the most significant unit operations used widely in the chemical industry for the separation of liquid-liquid mixture with the aid of an extracting solvent. There are different contacting patterns for the said purpose viz. co-current, counter current and crosscurrent and also a variety of equipments are encountered. This paper deals with the simulation of counter current liquid-liquid extraction operation for the special case of immiscible solvent using MATLAB. In this paper seven case studies have been studied and the results obtained are compared with the literature and it was found that results are in good agreement with the literature available.
The inhibition potentials of lignin extract of sun flower was investigated by evaluating the corrosion behaviour of medium carbon low alloy steel immersed in 1M H2SO4 solution containing varied concentration of the extract. Mass loss, corrosion rate, and adsorption characterization were utilized to evaluate the corrosion inhibition and adsorption properties of the extract. The results revealed that the lignin extract is an efficient inhibitor of corrosion in mild steel immersed in 1M H2SO4. The corrosion rates were observed to decrease with increase in concentration of lignin extract but increase with temperature. The activation energies and the negative free energy of adsorption obtained from the adsorption studies indicate that the lignin extract is physically adsorbed on the surface of the steel and that the adsorption is strong, spontaneous and fit excellently with the assumptions of the Langmuir adsorption isotherm.
This paper presents and compares the impact of SSSC on measured impedance for single phase to ground fault condition. The presence of Static Synchronous SSSC on a transmission line has a great influence on the ZRelay in distance protection. The protection of the high voltage 220 kV single circuit transmission line in eastern Algerian electrical transmission networks is affected in the case with resistance fault RF. The paper investigate the effect of Static Synchronous Series Compensator (SSSC) on the measured impedance (Relay) taking into account the distance fault point (n) and fault resistance (RF). The resultants simulation is performed in MATLAB software environment.