King Fahd

Economical Feasibility of Utilizing Photovoltaics for Water Pumping in Saudi Arabia

Energy and water are the two major need of the globe which need to be addressed for the sustenance of the human beings on this planet. All the nations, no matter most populous, developed and developing need to diversify the means and ways of producing energy and at the same time guarding the environment. This study aims at techno economical feasibility of producing energy using PV solar panels and utilizing it to pump-water at Dhahran, Riyadh, Jeddah, Guriat, and Nejran regions in Saudi Arabia. The solar radiation data from these stations was used to generate electricity using PV panels of 9.99 kW total capacity. Nejran region was found to be most economical in terms of minimal payback period and cost of energy and maximum internal rate of return whereas PV power production was concerned. Water-pumping capacity of the solar PV energy system was calculated at five locations based on the PV power production and Goulds model 45J series of pumps. Monthly total and annual total water pumping capacities were determined. Considering the capital cost of combined solar PV energy system and the pump unit a cost analysis of water pumping for a well of 50 m total dynamic head (TDH) was carried out. The cost of water pumping was found to vary between 2 and 3 /m3.

Matrix Structure Evolution and Nanoreinforcement Distribution in Mechanically Milled and Spark Plasma Sintered Al-SiC Nanocomposites

Development of homogenous metal matrix nanocomposites with uniform distribution of nanoreinforcement, preserved matrix nanostructure features, and improved properties, was possible by means of innovative processing techniques. In this work, Al-SiC nanocomposites were synthesized by mechanical milling and consolidated through spark plasma sintering. Field Emission Scanning Electron Microscope (FE-SEM) with Energy Dispersive X-ray Spectroscopy (EDS) facility was used for the characterization of the extent of SiC particles’ distribution in the mechanically milled powders and spark plasma sintered samples. The change of the matrix crystallite size and lattice strain during milling and sintering was followed through X-ray diffraction (XRD). The density and hardness of the developed materials were evaluated as function of SiC content at fixed sintering conditions using a densimeter and a digital microhardness tester, respectively. It was found that milling for 24 h led to uniform distribution of SiC nanoreinforcement, reduced particle size and crystallite size of the aluminum matrix, and increased lattice strain. The presence and amount of SiC reinforcement enhanced the milling effect. The uniform distribution of SiC achieved by mechanical milling was maintained in sintered samples. Sintering led to the increase in the crystallite size of the aluminum matrix; however, it remained less than 100 nm in the composite containing 10 wt.% SiC. Density and hardness of sintered nanocomposites were reported and compared with those published in the literature.

Genetic -Based Fuzzy Logic Controller for Satellites Stabilized by Reaction Wheels and Gravity Gradient

In this paper, a systematic technique is proposed to design an optimal distributed fuzzy logic controller (FLC) for the attitude control of satellites stabilized by reaction wheels and gravity gradient. A single FLC with two inputs and one output is used for the pitch motion while a distributed controller with fou r FLCs is proposed for the roll and yaw motions to take into consideration the dynamic coupling between roll and yaw. The control action for yaw is determined by the yaw dynamics as well as the roll dynamics and similarly for the roll. The rules, the distr ibution of membership function of the FLC, and the linking parameters of the distributed controller are determined based on solving a constraint optimization problem using the genetic algorithms. To get accurate pointing, long -life time, and fast response for the satellite, the deviation of the satellite from its nominal position, the consumed power, and the time of deviation are included in the optimization objective function. With the use of multiple initial conditions in determining the objective functio n, the designed controller is shown to be stable with a satisfactory performance in a broad range of the operating conditions. Nomenclature

On the Representation of D.G. Seminear-rings

Some results about the representation of d.g. seminear-rings are given. While not all d.g. seminear-rings are faithful, it seems that there are conditions under which the d.g. seminear-rings are. To every (non-faithful) d.g. seminear-ring (S;T), we associate a faithful d.g. seminear-ring ( ‚ S; ‚ T) and prove the existence of such a d.g. seminear-ring. Finally, we show how adjoining an identity to a given d.g. seminear-ring will give the faithfulness we desire. 2000 Mathematics Subject Classiflcation: 16Y30, 16Y60

CURRENT-CONTROLLED SAWTOOTH GENERATOR

A simple current-controlled sawtooth generator is presented. Both the amplitude and the frequency of the generated sawtooth can be current-controlled. The circuit uses off-the-shelf components. Experimental results are included.

Polynomial Equation in Radicals

Necessary and sucient conditions for a radical class of rings to satisfy the polynomial equation (R(x)) = ( (R))(x) have been investigated. The interrelationship of polynomial equation, Amitsur property and polynomial extensibility is given. It has been shown that complete analogy of R.E. Propes result for radicals of matrix rings is not possible for polynomial rings.

On Predicting the Next Term of a Sequence

When introducing sequences to students, the first skill we teach them is how to predict the next term of a sequence given the first few terms, usually the first three, four or five terms. In this note, we intend to show that given some terms of a sequence, the next term is not uniquely determined in most cases. We will also show under which condition can the next term be determined uniquely.

OPTIMAL ESTIMATION OF HARMONICS IN POWER SYSTEM USING INTELLIGENT TECHNIQUES

This paper presents a new algorithm for harmonic estimation in power systems. It utilizes separable least squares (SLS) technique to estimate the magnitude and phase angle of the harmonics by analyzing the waveform. As well as hybrid techniques have been utilized in this paper to estimate harmonics, real coded genetic algorithm (RCGA) and particle swarm optimization (PSO) utilized to estimate the phase of the harmonics, alongside a least square (LS) method used to estimate harmonics amplitude. The three techniques are analyzed and the results are compared in terms of percentage of error and processing time for finding suitable efficient technique to estimate harmonics.

Managing Failures of Aircraft Systems by Coapplication of Parametric and Nonparametric Methods

Analysis of failures that occur in an actual operational environment is very important for the maintenance service providers and manufacturers to offer specific maintenance solutions or product improvements tailored to the customers’ needs and to survive in the highly competitive aviation market. There are mainly two methodologies for failure analysis: Parametric approach and nonparametric approach. Practitioners usually prefer one of these methodologies alone for monitoring or predicting the failure trends. However, each methodology has its own strengths and weaknesses for any application. Therefore, it may be useful to view these methods as being complementary for obtaining the most benefit from the failure analysis. This paper brings the parametric and nonparametric methodologies together for extracting valuable management information from the field failures of aircraft systems with an example of auxiliary power unit application. Opportunities of coapplication of the methodologies are described for identifying failure trends and unusual behaviors and revealing hidden information that may otherwise not be detected by the application of only one of those methodologies.

A PROBABILISTIC PROOF OFTHE SERIES REPRESENTATION OF THE MACDONALD FUNCTION WITH APPLICATIONS

A series representation of the Macdonald function is obtained using the properties of a probability density function and its moment generating function. Some applications of the result are discussed and an open problem is posed.