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Search Results: 1 - 10 of 462333 matches for " Amr A. Youssef "
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Concircular π-Vector Fields and Special Finsler Spaces  [PDF]
Nabil L. Youssef, Amr Soleiman
Advances in Pure Mathematics (APM) , 2013, DOI: 10.4236/apm.2013.32040

The aim of the present paper is to investigate intrinsically the notion of a concircular π-vector field in Finsler geometry. This generalizes the concept of a concircular vector field in Riemannian geometry and the concept of concurrent vector field in Finsler geometry. Some properties of concircular π-vector fields are obtained. Different types of recurrence are discussed. The effect of the existence of a concircular π-vector field on some important special Finsler spaces is investigated. Almost all results obtained in this work are formulated in a coordinate-free form.

Boards of Directors’ Characteristics and Firm Value: A Comparative Study between Egypt and USA  [PDF]
Wafaa F. Salem, Saad A. Metawe, Amr A. Youssef, Mohamed B. Mohamed
Open Access Library Journal (OALib Journal) , 2019, DOI: 10.4236/oalib.1105323
Purpose This research aims to compare the effect of board of directors’ characteristics on the firm’s value in Egypt as an emerging country and USA as a developed country. Five characteristics have been exposed from the literature review that may influence the enhancement of a firm’s value. In corporate governance, these characteristics are CEO duality, board independence, board size, board meetings and gender diversity. Design The model is developed and 84 Egyptian firms listed on the Egyptian stock exchange and 27 American firms listed on The Dow Jones Industrial Average (DJIA) are utilized in this research for testing this model. The research covers a six-year period (2012-2017). Five main hypotheses and ten sub-hypotheses were derived from the model. GLS regression is used to test these hypotheses. Findings The results of this research revealed that board of directors’ characteristics affects firm value almost in the same way in both Egypt and the USA. The results revealed that board independence, board meetings and gender diversity are positively and significantly related to firm value in both countries. Furthermore, it displayed that board size affected firm value in both the Egyptian and American contexts negatively and significantly. Finally, the results showed that the CEO duality has a positive effect on firm value in the Egyptian setting while it has a negative effect on the firm value in the American setting. This research contributes to the literature on the subject of how corporate governance enhances a firm’s value. Participants in the stock market would benefit from the results when assessing the board of directors’ roles in enhancing the firm’s value. Regulators will be able to use the results of this research to recognize the critical characteristics of corporate governance and to assess the governance practices of the board of directors.
Implementation of High Performance Electronic Circuits for Zero Suppression and Encoding of Digital Signals  [PDF]
Ashraf H. Yahia, Amr Radi, Salwa M. Youssef
Journal of Signal and Information Processing (JSIP) , 2015, DOI: 10.4236/jsip.2015.63022
Abstract: This paper presents a design of a data processing circuit for receiving digital signals from front end-electronic board chips of a specific nuclear detector, encoding and triggering them via specific optical links operating at a specific frequency. Such processed signals are then fed to a data acquisition system (DAQ) for analysis. Very high-speed integrated circuit hardware description language (VHDL) algorithms and codes were created to implement this design using field programmable gate array (FPGA) devices. The obtained data were simulated using international standard simulators.
Numerical Studies of Resonance and Secular Effects of Gravitational Waves  [PDF]
M. H. A. Youssef
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.85013
Abstract: This work deals with the numerical solution of the gravitational waves effects on the orbital elements of the planets in case of commensurability between the wave’s frequency ng and the planet’s mean motion np. Taking Mercury and Pluto as practical examples for low frequency and high frequency, the variations of the orbital elements of Mercury due to resonance of gravitational wave are different and small than the perturbation on Pluto. The amount of changing in the orbital elements under the effects of gravitational waves is different from planet to planet according to the planet’s mean motion np. For low frequency ng, the secular variation in orbital elements will be negative (i.e. decreasing) in the inclination, semi-major axis and the eccentricity (i, a, e) like as Pluto. For high frequency ng like Mercury, the secular variation in all the orbital elements will be positive (i.e. increasing). The perturbation on all the orbital elements of two planets is changing during each revolution except the eccentricity e of Mercury and the mean anomaly M of Mercury and Pluto during the time.
Extensions to the Finite Element Technique for the Magneto-Thermal Analysis of Aged Oil Cooled-Insulated Power Transformers  [PDF]
Jehan Shazly, Amr A. Adly
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2012, DOI: 10.4236/jemaa.2012.44022
Abstract: It is well known that the hot spot temperature represents the most critical parameter identifying the power rating of a transformer. This paper investigates the effect of the degradation of core magnetic properties on temperature variation of aged oil-cooled transformers. Within this work, 2D accurate assessment of time average flux density distribution in an oil insulated-cooled 25 MVA transformer has been computed using finite-element analysis taking into account ageing and stress-induced non-uniform core permeability values. Knowing the core material specific loss and winding details, local core and winding losses are converted into heat. Based upon the ambient temperature outside the transformer tank and thermal heat transfer related factors, the detailed thermal modeling and analysis have then been carried out to determine temperature distribution everywhere. Analytical details and simulation results demonstrating effects of core magnetic properties degradation on hot spot temperatures of the transformer’s components are given in the paper.
Energy β-Conformal Change and Special Finsler Spaces  [PDF]
Amr Soleiman, Amira A. Ishan
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.47132

The main aim of the present paper is to establish an intrinsic investigation of the energy β-conformal change of the most important special Finsler spaces, namely, Ch-recurrent, Cv-recurrent, C0-recurrent, Sv-recurrent, quasi-C-reducible, semi-C-reducible, C-reducible, P-reducible, C2-like, S3-like, P2-like and h-isotropic, ···, etc. Necessary and sufficient conditions for such special Finsler manifolds to be invariant under an energy β-conformal change are obtained. It should be pointed out that the present work is formulated in a prospective modern coordinate-free form.

Linear Connections and Curvature Tensors in the Geometry of Parallelizable Manifolds
Nabil L. Youssef,Amr M. Sid-Ahmed
Mathematics , 2006, DOI: 10.1016/S0034-4877(07)00020-1
Abstract: In this paper we discuss curvature tensors in the context of Absolute Parallelism geometry. Different curvature tensors are expressed in a compact form in terms of the torsion tensor of the canonical connection. Using the Bianchi identities some other identities are derived from the expressions obtained. These identities, in turn, are used to reveal some of the properties satisfied by an intriguing fourth order tensor which we refer to as Wanas tensor. A further condition on the canonical connection is imposed, assuming it is semi-symmetric. The formulae thus obtained, together with other formulae (Ricci tensors and scalar curvatures of the different connections admitted by the space) are calculated under this additional assumption. Considering a specific form of the semi-symmetric connection causes all nonvanishing curvature tensors to coincide, up to a constant, with the Wanas tensor. Physical aspects of some of the geometric objects considered are mentioned.
The Effect of Board of Directors Characteristics on Firm’s Financial Performance: An Empirical Study on the Most Active Firms in the Egyptian Stock Exchange  [PDF]
Ashraf Mohamed Abdel Atty, Mohamed Moustafasoliman, Amr E. Youssef
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1104993
This paper seeks examining the effect of Board of Directors Characteristics on firm’s financial performance in Egypt, using a sample of 50 more active Egyp-tian companies listed on the Egyptian Stock Exchange of the non-financial sector covering the period of three financial years from 2012 to 2017. Board of Directors Structure is represented by CEO Duality, Board Size, Board Meet-ings, Independence board members and Gender Diversity. Return on Assets (ROA), Return on Equity (ROE) and Tobin’s Q is used as a proxy for Firm fi-nancial Performance. In this research, correlation and regression analysis are used to examine the relationship between Corporate Governance and firm’s fi-nancial performance.
Combined distal tibial rotational osteotomy and proximal growth plate modulation for treatment of infantile Blount’s disease
Amr A Abdelgawad
World Journal of Orthopedics , 2013, DOI: 10.5312/wjo.v4.i2.90
Abstract: Infantile Blount’s disease is a condition that causes genu varum and internal tibial torsion. Treatment options include observation, orthotics, corrective osteotomy, elevation of the medial tibial plateau, resection of a physeal bar, lateral hemi-epiphysiodesis, and guided growth of the proximal tibial physis. Each of these treatment options has its disadvantages. Treating the coronal deformity alone (genu varum) will result in persistence of the internal tibial torsion (the axial deformity). In this report, we describe the combination of lateral growth modulation and distal tibial external rotation osteotomy to correct all the elements of the disease. This has not been described before for treatment of Blount’s disease. Both coronal and axial deformities were corrected in this patient. We propose this combination (rather than the lateral growth modulation alone) as the method of treatment for early stages of Blount’s disease as it corrects both elements of the disease and in the same time avoids the complications of proximal tibial osteotomy.
Vibration of Nano Beam Induced by Ramp Type Heating  [PDF]
Hamdy M. Youssef, Khaled A. Elsibai
World Journal of Nano Science and Engineering (WJNSE) , 2011, DOI: 10.4236/wjnse.2011.12006
Abstract: The non-Fourier effect in heat conduction and the coupling effect between temperature and strain rate, became the most significant effects in the nano-scale beam. In the present study, a generalized solution for the generalized thermoelastic vibration of a bounded nano-beam resonator induced by ramp type of heating is developed and the solutions take into account the above two effects. The Laplace transforms and direct method are used to determine the lateral vibration, the temperature, the displacement, the stress and the energy of the beam. The effects of the relaxation time and the ramping time parameters have been studied with some comparisons.
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