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Search Results: 1 - 10 of 408235 matches for " Ahmad M. Harb "
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Control of Instable Chaotic Small Power System  [PDF]
Samir M. Al Shariff, Ahmad M. Harb
Journal of Power and Energy Engineering (JPEE) , 2015, DOI: 10.4236/jpee.2015.32001
Abstract: In this paper, we aim to control an instable chaotic oscillation in power system that is considered to be small system by using a linear state feedback controller. First we will analyze the stability of the mentioned power system by means of modern nonlinear theory (Bifurcation and Chaos). Our model is based on a three bus power system that consists of multi generators containing both dynamic and static loads. They are considered to be in the form of an induction motor in parallel with a capacitor, as well as a combination of constant power along with load impedance, PQ. We consider the load reactive power as the control parameter. At this stage, after changing the control parameter, the study showed that the system is experiencing a subcritical Hopf bifurcation point. This leads to a chaos within the system period doubling path. We then discuss the system controllability and present that the all chaotic oscillations fade away through the linear controller that we impose on the system.
Fault Classification and Localization in Power Systems Using Fault Signatures and Principal Components Analysis  [PDF]
Qais H. Alsafasfeh, Ikhlas Abdel-Qader, Ahmad M. Harb
Energy and Power Engineering (EPE) , 2012, DOI: 10.4236/epe.2012.46064
Abstract: A vital attribute of electrical power network is the continuity of service with a high level of reliability. This motivated many researchers to investigate power systems in an effort to improve reliability by focusing on fault detection, classification and localization. In this paper, a new protective relaying framework to detect, classify and localize faults in an electrical power transmission system is presented. This work will extract phase current values during ( )th of a cycle to generate unique signatures. By utilizing principal component analysis (PCA) methods, this system will identify and classify any fault instantaneously. Also, by using the curve fitting polynomial technique with our index pattern obtained from the unique fault signature, the location of the fault can be determined with a significant accuracy.
On Slide Mode Control of Chaotic Rikitake Two-Disk Dynamo—Chaotic Simulations of the Reversals of the Earth’s Magnetic Field  [PDF]
Ahmad Harb, Nabil Ayoub
International Journal of Modern Nonlinear Theory and Application (IJMNTA) , 2014, DOI: 10.4236/ijmnta.2014.33015

The modern nonlinear theory, bifurcation and chaos theory are used in this paper to analyze the dynamics of the Rikitake two-disk dynamo system. The mathematical model of the Rikitake system consists of three nonlinear differential equations, which found to be the same as the mathematical model of the well-known Lorenz system. The study showed that under certain value of control parameter, the system experiences a chaotic behaviour. The experienced chaotic oscillation may simulate the reversal of the Earth’s magnetic field. The main objective of this paper is to control the chaotic behaviour in Rikitake system. So, a nonlinear controller based on the slide mode control theory is designed. The study showed that the designed controller was so effective in controlling the unstable chaotic oscillations.

Bifurcation and Chaos Theory in Electrical Power Systems: Analysis and Control
Ahmad M. Harb,Issa Batarseh,Lamine M. Mili,Mohamed A. Zohdy
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/573910
An Experimental Simulation of a Design Three-Port DC-DC Converter  [PDF]
Samir Al Sharif, Ahmad Harb, Haibing Hu, Issa Batarseh
Circuits and Systems (CS) , 2014, DOI: 10.4236/cs.2014.510026
Abstract: Traditional DC-DC converter topologies interface two power terminals: a source and a load. The construction of diverse and flexible power management and distribution (PMAD) systems with such topologies is governed by a tight compromise between converter count, efficiency, and control complexity. The broader impact of the current research activity is the development of enhanced power converter systems suitable for a wide range of applications. Potential users of this technology include the designers of portable and stand-alone systems such as laptops, hand-held electronics, and communication repeater stations. High power topology options support the evolution of clean power technologies such as hybrid-electric vehicles (HEV’s) and solar vehicles. DC-DC converter is considered as an advanced environmental issue since it is a greenhouse emission eliminator. By utilizing the advancement of these renewable energy sources, we minimize the use of fossil fuel. Thus, we will have a cleaner and pollution free environment. In this paper, a three-port DC-DC converter is designed and discussed. The converter was built and tested at the energy research laboratory at Taibah University, Al Madinah, KSA.
Improvement of PV/T Based Reverse Osmosis Desalination Plant Performances Using Fuzzy Logic Controller  [PDF]
Mahmoud Ammous, Sana Charfi, Ahmad Harb, Maher Chaabene
International Journal of Modern Nonlinear Theory and Application (IJMNTA) , 2016, DOI: 10.4236/ijmnta.2016.51002
Abstract: Photovoltaic based reverse osmosis desalination systems (PV/RO) present an effective method of water desalination especially in remote areas. The increase of the feed water temperature leads to an amelioration of the plant performances. Photovoltaic Thermal Collector (PV/T) represents an ideal power source as it provides both electric and thermal energies for the reverse osmosis process. Nevertheless, PV/T based RO plants should be controlled in order to solve operation problems related to electrical efficiency, reverse osmosis membrane, produced water and the rejected salts. This paper suggests a fuzzy logic controller for the flow rate of the circulating fluid into the PV/T collectors so as to ameliorate the system performances. The designed controller has improved the PV/T field electrical efficiency and preserved the reverse osmosis membrane which upgrades the system productivity. LABVIEW software is used to simulate the controlled system and validate the effectiveness of the controller.
Trigger finger presenting secondary to leiomyoma: a case report
Ziad Harb, Quamar Bismil, David M Ricketts
Journal of Medical Case Reports , 2009, DOI: 10.1186/1752-1947-3-7284
Abstract: A 39-year-old Caucasian man presented with a fairly typical presentation of trigger finger. During surgical treatment, the lesion was excised and sent for histology, which showed tissue consistent with a leiomyoma. The patient made an uneventful recovery.Trigger finger is a common condition that is usually easily diagnosed and managed. However, it is important to appreciate that uncommon conditions, such as leiomyoma, can present with what is sometimes considered trivial disease, and one should always consider the differential diagnoses even when faced with relatively benign conditions.Trigger finger is a common condition, first described by Notta in 1850, characterised by painful clicking and locking of a digit. The underlying cause is a failure of normal tendon gliding in the A1 pulley region of the tendon sheath. This is usually associated with a proliferation of chondrocytes (stenosing tensosynovitis). We present a case of trigger finger secondary to a leiomyoma; a previously unreported condition.A 39-year-old, right-handed Caucasian male office worker presented with a three-month history of painful locking and clicking of his right ring finger. There was no history of trauma and he was otherwise fit and well. On examination, he had a tender mass on the volar aspect of the metacarpophalangeal joint as he actively flexed and extended the ring finger, and there was a small, palpable lump overlying the fourth metacarpophalangeal joint.A diagnosis of trigger finger was made; however, the palpable lump was significantly larger than usually found with a Notta's nodule. An X-ray of the right hand was unremarkable and an ultrasound scan revealed an elliptical soft tissue mass associated with the flexor tendons and A1 pulley.At surgical exploration under general anaesthesia, a circumscribed soft tissue mass, 1.5 cm in diameter, was found infiltrating the A1 pulley and flexor digitorum superficialis (FDS) (Figure 1). The lesion was excised en masse, protecting the neurova
Adaboost Ensemble with Genetic Algorithm Post Optimization for Intrusion Detection
Hany M. Harb,Abeer S. Desuky
International Journal of Computer Science Issues , 2011,
Abstract: This paper presents a fast learning algorithm using Adaboost ensemble with simple genetic algorithms (GAs) for intrusion detection systems. Unlike traditional approaches using Adaboost algorithms, it proposed a Genetic Algorithm post optimization procedure for the found classifiers and their coefficients removing the redundancy classifiers which cause higher error rates and leading to shorter final classifiers and a speedup of classification. This approach has been implemented and tested on the NSL-KDD dataset and its experimental results show that the method reduces the complexity of computation, while maintaining the high detection accuracy. Moreover, the method improves the processing time, so it is especially appealing for the real-time processing of the intrusion detection system.
Selecting Optimal Subset of Features for Student Performance Model
Hany M. Harb,Malaka A. Moustafa
International Journal of Computer Science Issues , 2012,
Abstract: Educational data mining (EDM) is a new growing research area and the essence of data mining concepts are used in the educational field for the purpose of extracting useful information on the student behavior in the learning process. Classification methods like decision trees, rule mining, and Bayesian network, can be applied on the educational data for predicting the student behavior like performance in an examination. This prediction may help in student evaluation. As the feature selection influences the predictive accuracy of any performance model, it is essential to study elaborately the effectiveness of student performance model in connection with feature selection techniques. The main objective of this work is to achieve high predictive performance by adopting various feature selection techniques to increase the predictive accuracy with least number of features. The outcomes show a reduction in computational time and constructional cost in both training and classification phases of the student performance model.
An Optimality-Theoretic Account of English Loanwords in Hawaiian  [PDF]
Mustafa Ali Harb
Open Journal of Modern Linguistics (OJML) , 2016, DOI: 10.4236/ojml.2016.63025
Abstract: The purpose of this paper is to provide an Optimality-Theoretic (henceforth OT) account of the linguistic phenomenon of borrowing. In particular, it examines English loanwords in Hawaiian from a constraint-based analysis as opposed to a rule-based analysis. Data necessary for this study consisted of some randomly selected Hawaiian words. These loanwords were carefully examined as to realize their phonological changes and how they can be accounted for from an OT standpoint. Several phonological changes, mainly those of the syllable structure of Hawaiian, were examined along with accompanying phonological processes (e.g., epenthesis, degemination, etc.) where applicable. The proposed ranking hierarchy that, the argument goes, could account for all English loanwords in Hawaiian is like this: ∑{NO CODA >> MAX-IO >> *CC >> DEP-IO}, a state of affairs which confirmed our intuition that the syllable structure of the borrowing language (Hawaiian) prevails over the syllable structure of the donor language (English). In order to establish the ranking argument, comparative tableaux are used. Violations tableaux are also used to demonstrate how the winning configuration beats competitive candidate forms.
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