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Search Results: 1 - 10 of 150279 matches for " Nabil H. Abbasy "
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Low Voltage Ride through Control Capability of a Large Grid Connected PV System Combining DC Chopper and Current Limiting Techniques  [PDF]
Ronald Ntare, Nabil H. Abbasy, Karim H. M. Youssef
Journal of Power and Energy Engineering (JPEE) , 2019, DOI: 10.4236/jpee.2019.71004
Abstract: This paper presents the development and performance capability of a comprehensive Low voltage ride through (LVRT) control scheme that makes use of both the DC chopper and the current limiting based on the required reactive power during fault time. The study is conducted on an 8.5 MW single stage PV power plant (PVPP) connected to the Rwandan grid. In the event of fault disturbance, this control scheme helps to overcome the problems of excessive DC-link voltage by fast activation of the DC chopper operation. At the same instance, AC current is limited to the maximum rating of the inverter as a function of the injected reactive current. This helps overcome AC-over- current that may possibly lead to damage or disconnection of the inverter. The control scheme also ensures voltage support and power balance through the injection of reactive current as per grid code requirements. Selected simulations using MATLAB are carried out in the events of different kinds of fault caused voltage dips. Results demonstrate the effectiveness of the proposed LVRT control scheme.
Calculation of Open Water Evaporation as a Climate Parameter  [PDF]
Nabil H. Swedan
Journal of Water Resource and Protection (JWARP) , 2018, DOI: 10.4236/jwarp.2018.108043
Abstract: Calculation of open water evaporation is important for hydrology, industry, agriculture, environment, and other fields. The available methods of calculating evaporation are based on field or laboratory experiments and should not be used for scale-up to open water evaporation for similitude relationships cannot be correctly obtained. The methods are thus unjustified scientifically. In addition, surface evaporation is not a local phenomenon that is a function of independent meteorological parameters. These are in fact dependent parameters, and the solar energy exchanged with the surface of the earth is the only independent variable for open water evaporation. Contrary to the existing methods, meteorological records and measurements are therefore not required. Many parts of the world do not have full or partial records available. For these, the available methods are likely not to be useful. In addition, future meteorological records or measurements cannot be made available for evaporation projection in a warming world. This may well place a limit on using the existing methods. The work presented in this manuscript reveals a new understanding of evaporation as a climate parameter instead and can be calculated as such. Minimal to no meteorological records or measurements may be required. The advantages of the proposed method are scientific justification, simplicity, accuracy, versatility, low to virtually no cost, and can be used to map present and future evaporation in a short period of time.
A Note on the Size-Sensitive Packing Lemma
Nabil H. Mustafa
Computer Science , 2015,
Abstract: We show that the size-sensitive packing lemma follows from a simple modification of the standard proof, due to Haussler and simplified by Chazelle, of the packing lemma.
Operative Dept, School of Dentistry, Isfahan University of Medical Sciences and Healtb Services, Isfahan, Iran
Journal of Research in Medical Sciences , 2001,
Abstract: Introduction. Dental erosion is a multifactorial lesion (acids, nutrition consisting of sour lemon, soft drinks and alchole) and is result of gradual dissolution of dental tissue according a mechanicochemical procedure. The purpose of this study is evaluation the prevalence of dental erosion in battery workers as a high risk job in Isfahan city. Methods. In this study, 332 battery worker were selected randomly. They were between 15-65 years old. each person examined and had to fill a questionnair separately. The results were analyzed by the SPSS software. Results. 27.1 percent of patients had dental erosion in buccal and lingual surfaces. Severity and frequency of dental errosion was related to age and work exerience and nutrition (sour lemon, soft drink and alcohole). There wasn"t any relationship between dental plaque dental erosion. Discussion. The results of this study accomodates partially or fully other studies results. It is needed to arrange programs to aware the battery workers of acid dangers and its effects on teeth and respiratory system.
Unsteady Numerical Simulation of Cavitation in Axial Turbine
Nabil H. Mostafa,Mohamed Adel
CFD Letters , 2012,
Abstract: A 3-D numerical study has been carried out in order to study the unsteady, turbulent, void growth and cavitation simulation inside the passage of the axial flow turbine. In this study a 3D Navier-Stokes code was used (CFDRC, 2008) to model the two-phase flow field around a four blades axial turbine. The governing equations are discretized on a structured grid using an upwind difference scheme. The numerical simulation used the standard k-ε turbulence model to account for the turbulence effect. The numerical simulation of void growth and cavitation in an axial turbine was studied under unsteady calculating. Pressure distribution and vapour volume fraction were completed versus time at different condition. The computational code has been validated by comparing the predicated numerical results with the previous studies. The comparison shows good agreement.
Improving Rule Base Quality to Enhance Production Systems Performance  [PDF]
Nabil Arman
International Journal of Intelligence Science (IJIS) , 2013, DOI: 10.4236/ijis.2013.31001
Abstract: Production systems have a special value since they are used in state-space searching algorithms and expert systems in addition to their use as a model for problem solving in artificial intelligence. Therefore, it is of high importance to consider different techniques to improve their performance. In this research, rule base is the component of the production system that we aim to focus on. This work therefore seeks to investigate this component and its relationship with other components and demonstrate how the improvement of its quality has a great impact on the performance of the production system as a whole. In this paper, the improvement of rule base quality is accomplished in two steps. The first step involves re-writing the rules having conjunctions of literals and producing a new set of equivalent rules in which long inference chains can be obtained easily. The second step involves augmenting the rule base with inference short-cut rules devised from the long inference chains. These inference short-cut rules have a great impact on the performance of the production system. Finally, simulations are performed on randomly generated rule bases with different sizes and goals to be proved. The simulations demonstrate that the suggested enhancements are very beneficial in improving the performance of production systems.
The Impact of Human Parvovirus B19 Co-Infection on Liver Function of HCV Infected Patients  [PDF]
Mohamed Nabil, Mohammed H. Saiem Al-Dahr, Waleed Abu Al-Soud, Omar Alfaruok
Open Journal of Applied Sciences (OJAppS) , 2019, DOI: 10.4236/ojapps.2019.91003
Abstract: Background: Human Parvovirus B19 is most known for causing disease in the pediatric population but can also affect adults. Human co-infection with Parvovirus B19 could deteriorate the prognosis of patient with chronic ill-ness.

Objectives: This paper attempts to determine the prevalence of Parvovirus B19 in HCV infected patients and to evaluate the impact of Parvovirus B19 on liver enzymes activity of Hepatitis C patients. Study Design: The study population includes 74 chronic HCV (patient group) and 49 cases without viral hepatitis (control group). Nucleic acid of Parvovirus B19 was detected in Serum samples by nested polymerase chain reaction (nested-PCR) method. Results: Parvovirus B19-DNA infection was detected in 28.0% of chronic HCV patients. Parvovirus B19-HCV co-infection caused increasing in Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) activity than in B19-negative HCV patients. Conclusion: We conclude that Parvovirus B19 acted synergistically with HCV by increasing the levels alanine ami-notransferase (ALT) and Aspartate aminotransferase (AST).

Levetiracetam Extended Release as Adjuvant Therapy for the Control of Partial-onset Seizures
Hasan H. Sonmezturk and Nabil J. Azar
Journal of Central Nervous System Disease , 2012, DOI: 10.4137/JCNSD.S4126
Abstract: Extended release (XR) formulation of levetiracetam (LEV) is approved by the Food and Drug Administration as an add-on to other antiepileptic drugs (AEDs) for adults with partial onset seizures. This is based on class-I evidence demonstrating significant seizure reduction in once daily dosing. Keppra-XR is marketed with the brand name of Keppra XR since 2008 (UCB Pharma). Its original immediate release (IR) formulation has been in the market since 2000. LEV has a unique molecular structure which is chemically unrelated to existing AEDs. The precise mechanism of action is unknown. Animal studies showed binding to synaptic vesicle protein SV2A, thought to be involved in modulating synaptic neurotransmitter release. LEV-IR is proven effective as adjunctive therapy for partial-onset seizures, primary generalized tonic-clonic seizures and myoclonic seizures. It was shown to be equivalent to carbamazepine as first-line treatment for partial-onset seizures. The extended release formulation added advantages such as better tolerance and increased compliance.
Levetiracetam Extended Release as Adjuvant Therapy for the Control of Partial-onset Seizures
Hasan H. Sonmezturk,Nabil J. Azar
Journal of Central Nervous System Disease , 2011,
QPTAS for Geometric Set-Cover Problems via Optimal Separators
Nabil H. Mustafa,Rajiv Raman,Saurabh Ray
Computer Science , 2014,
Abstract: Weighted geometric set-cover problems arise naturally in several geometric and non-geometric settings (e.g. the breakthrough of Bansal-Pruhs (FOCS 2010) reduces a wide class of machine scheduling problems to weighted geometric set-cover). More than two decades of research has succeeded in settling the $(1+\epsilon)$-approximability status for most geometric set-cover problems, except for four basic scenarios which are still lacking. One is that of weighted disks in the plane for which, after a series of papers, Varadarajan (STOC 2010) presented a clever \emph{quasi-sampling} technique, which together with improvements by Chan \etal~(SODA 2012), yielded a $O(1)$-approximation algorithm. Even for the unweighted case, a PTAS for a fundamental class of objects called pseudodisks (which includes disks, unit-height rectangles, translates of convex sets etc.) is currently unknown. Another fundamental case is weighted halfspaces in $\Re^3$, for which a PTAS is currently lacking. In this paper, we present a QPTAS for all of these remaining problems. Our results are based on the separator framework of Adamaszek-Wiese (FOCS 2013, SODA 2014), who recently obtained a QPTAS for weighted independent set of polygonal regions. This rules out the possibility that these problems are APX-hard, assuming $\textbf{NP} \nsubseteq \textbf{DTIME}(2^{polylog(n)})$. Together with the recent work of Chan-Grant (CGTA 2014), this settles the APX-hardness status for all natural geometric set-cover problems.
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