Cognitive and Energy Harvesting-Based D2D Communication in Cellular Networks: Stochastic Geometry Modeling and Analysis

While cognitive radio enables spectrum-efficient wireless communication, radio frequency (RF) energy harvesting from ambient interference is an enabler for energy-efficient wireless communication. In this paper, we model and analyze cognitive and energy harvesting-based D2D communication in cellular networks. The cognitive D2D transmitters harvest energy from ambient interference and use one of the channels allocated to cellular users (in uplink or downlink), which is referred to as the D2D channel, to communicate with the corresponding receivers. We investigate two spectrum access policies for cellular communication in the uplink or downlink, namely, random spectrum access (RSA) policy and prioritized spectrum access (PSA) policy. In RSA, any of the available channels including the channel used by the D2D transmitters can be selected randomly for cellular communication, while in PSA the D2D channel is used only when all of the other channels are occupied. A D2D transmitter can communicate successfully with its receiver only when it harvests enough energy to perform channel inversion toward the receiver, the D2D channel is free, and the $\mathsf{SINR}$ at the receiver is above the required threshold; otherwise, an outage occurs for the D2D communication. We use tools from stochastic geometry to evaluate the performance of the proposed communication system model with general path-loss exponent in terms of outage probability for D2D and cellular users. We show that energy harvesting can be a reliable alternative to power cognitive D2D transmitters while achieving acceptable performance. Under the same $\mathsf{SINR}$ outage requirements as for the non-cognitive case, cognitive channel access improves the outage probability for D2D users for both the spectrum access policies.Comment: IEEE Transactions on Communications, to appea

The Impact of Privatisation on the Performance of Firms in Egypt

The objective of this paper is to evaluate the Egyptian privatisation programme in terms of firms' performance. By relaying on 15 years of data, which cover the period 1991/1992 till 2004/2005; this paper empirically investigates whether the operating efficiency of privatised firms improves following privatisation through comparing pre- and post-privatisation performance in terms of operating efficiency indicators, and level of employment. To reach the research objective, several statistical techniques, such as parametric t-test, the non-parametric and Wilcoxon signed-rank test are performed. The results from this analysis indicate clearly that there are significant increases in operating efficiency indicators as well as significant declines in the level of employment in the firms under investigation. Keywords: Privatisation, Performance Measure

The Effect of Corporate Governance on Mutual Fund Dividend Policy: Evidence from Egypt

The purpose of this paper is to investigate whether mutual fund governance has an effect on fund dividend policy in the Egyptian Stock Market. Using a final sample of 27 mutual funds between 2004 and 2013, this paper applies a Structural Equation Modelling technique to solve the potential endogeneity problem between internal governance measures and dividend policy. The empirical evidence shows a positive correlation between governance quality and dividend policy measured by dividend yield. The results are consistent with the notion that shareholders of firms with better governance quality are able to force managers to disgorge more cash through dividends, thereby reducing what is left for expropriation by opportunistic manager. No significant association was found between board independency and dividend policy, because firms with higher number of independent directors are more restricted to pay higher dividends. This study provides additional evidence of the applicability of the Outcome Model in the emerging market of Egypt. It was found that the payment of higher dividend was considered necessary to attract capital during this transitional period. Keywords: Corporate Governance, Dividend Policy, Mutual Fund, Endogeneity. JEL Classification G34, G35, G23, C3

Matrix isolation studies of transition metal halides and main group Lewis acid‒base complexes

The main purpose of this work was to synthesise and study the binary fluorides of nickel, cobalt and chromium, and the binary halides of palladium and molybdenum in solid argon matrices. Both UV/vis spectroscopy and FTIR spectroscopy were employed to identify the products formed. Additionally, this work also investigated the reaction between SiF4 with alkyl phosphines.In the beginning, the work focused on isolation of atomic nickel, cobalt, molybdenum, and palladium in neat argon matrices. The FTIR data revealed the interaction of nickel and fluorine atoms in solid argon matrix and the formation of nickel fluoride molecules NiF, NiF2, and NiF4 and also provided evidence for the formation of NiF3 molecules. Moreover, cobalt atoms trapped in a matrix of argon doped with fluorine yielded the formation of CoF, CoF2, CoF3, CoF4, and Co2F2 molecules. Furthermore, molybdenum fluoride species in an argon matrix have been obtained, which is the first observation of the vibrational modes for MoF and MoF2 in matrices. The geometry of MoF2 species was assigned to be bent with a bond angle of 132°. In addition, FTIR data indicated the formation of matrix isolated chromium fluorides in solid argon matrix. The study succeeded in the characterisation of CrF and CrF6 molecules, as well as the previously identified CrF2, CrF3, CrF4 and CrF5. The IR band related to CrF6 is observed at 757 cm−1. A computational study suggested that PdCl2 is linear.The reaction between SiF4 and PMe3 at cryogenic temperatures led to the formation of a SiF4−PMe3 complex and indicated the formation of two different species. The reaction between SiF4 and PEt3 revealed the formation of a 1:1 adduct of trigonal bipyramid structure with axial PEt3 of SiF4.PEt3 and a 1:2 complex of trans–[SiF4.(PEt3)2] structure. The results were supported by computational data

Market Efficiency and Arbitrage Opportunities: The Case of Egyptian Global Depository Receipts

This research examines the effect of the financial crisis on the behavior of the Egyptian GDR’s and their underlying stocks in Egypt. There were ten stocks tested that represent three main sectors which are; the financial sector, the telecom sector and the constructions sector. We found out that there are very low arbitrage opportunities between those two markets, and that these arbitrage opportunities were minimized during the previous crisis. Moreover we found out that the price behavior of the securities changed during the financial crisis, and they showed that the selling pressure appeared on the Egyptian stocks and not the GDR's. Keywords: GDR, Arbitrage, Cross listin

The Effect of Board Structure on Stock Picking and Market Timing Abilities of the Egyptian Mutual Fund Managers: Evidence from Financial Crisis

This paper seeks to examine the effect of mutual fund governance on stock selection and market timing abilities. This paper applies a Structural Equation Modelling technique to solve the potential endogeneity problem between internal governance measures and stock selection and market timing. The main conclusion of this paper is to provide evidence through robust statistical analysis around the usefulness of governance attributes Egyptian mutual funds stock selection and market timing abilities. Accordingly, the financial crisis demonstrates a need to modify some recommendations contained in the OECD methodology for evaluating the implementation of the OECD Principles of Corporate Governance. This paper find that board size and proportion of independent directors is negatively associated with stock selection, and proportion of directors holding zero shares is positively associated with stock selection. Keywords: Corporate Governance, Mutual Fund, Endogeneity

Dually-Polarized Microwave Components Based on Polarization-Selective Coupling for Green Wireless Systems

RÉSUMÉ Avec le développement rapide et continu de technologies et de réseaux sans fil de nouvelle génération tels que la 5G et avec les ressources limitées d'énergie et de spectre disponibles pour soutenir ces développements sans fil rapides, l'exploration des bandes millimétriques sous-utilisées devient incontournable. Il devient de plus en plus crucial de se concentrer sur la réduction de la consommation d'énergie dans les futurs systèmes sans fil. Le moyen le plus efficace de réception d'énergie d'onde électromagnétique est de capturer complètement les deux composantes orthogonales de son vecteur de champ de propagation en relation avec la diversité de polarisation. De plus, l'utilisation d'ondes bi-polarisées permet l'amélioration d'une capacité de transmission via la réception simultanée de deux canaux orthogonaux. Cette thèse montre comment proposer et exploiter le concept très original de la diversité de polarisation sur la bande de fréquences mmW qui a été assignée aux applications sans fil. Auparavant, la diversité de polarisation était mise en oeuvre dans des profils non planaires, ce qui compliquait son intégration avec l'application de carte de circuit imprimé (PCB). Par conséquent, la motivation principale de cette thèse est de mettre en oeuvre la diversité de polarisation dans les profils planaires aux bandes de fréquence récemment assignées autour de 28 GHz et 38 GHz pour être intégrée dans la cinquième génération (5G) de communication sans fil. Ceci est fait en développant la théorie du fonctionnement et de la procédure de conception des composants MMW à double polarisation. La nouveauté présentée dans ce travail de thèse réside dans le développement d'un principe de fonctionnement permettant de concevoir et de mettre en évidence une classe de composants mmW bi-polarisés, à savoir les coupleurs 3dB, les coupleurs 0dB et les déphaseurs. Cela permet le développement de réseaux de formation de faisceau bi-polarisés tels que la matrice de Butler et les systèmes de télédétection à polarisation, basés sur une jonction à six ports à double polarisation. Une procédure de conception analytique complète est présentée avec des vérifications à travers des simulations pleine onde et des mesures de prototypes. La diversité de polarisation a été un facteur essentiel dans la performance et l'amélioration de la capacité de divers systèmes sans fil, y compris les réseaux cellulaires. Par conséquent, la conception et le développement de structures d'alimentation d'antenne bi-polarisées dans la bande mmW sont indispensables.----------ABSTRACT With the rapid and continuous development of new generation wireless technologies and networks such as 5G and with the limited enabling energy and spectrum resources available in support of such fast-moving wireless developments, exploring the underutilized millimeter-wave (mmW) bands becomes inescapable. It becomes more and more crucial to focus on the reduction of energy use in future wireless systems. The most efficient way of electromagnetic wave energy reception is to fully capture the two orthogonal components of its propagating field vector in connection with polarization diversity. In addition, the use of dually-polarized waves allows the enhancement of a transmission capability via the simultaneous reception of two orthogonal channels. This thesis shows how to propose and exploit the highly original concept of polarization diversity over the mmW frequency band which has been assigned for wireless applications. Previously, the polarization diversity was implemented within non-planar profiles which complicates its integration with the printed circuit board (PCB) application. Therefore, the main motivation of this thesis is to implement the polarization diversity within planar profiles at the recently assigned frequency bands around 28 GHz and 38 GHz to be suitable for integration in the fifth generation (5G) of wireless communication. This is done by developing the theory of operation and design procedure of dually-polarized mmW components. The novelty presented in this thesis work lies in developing a principle of operation to come up with the design and demonstration of a class of dually-polarized mmW components, namely 3dB couplers, 0dB couplers and phase shifters. This allows the development of dually-polarized beamforming networks such as Butler matrix and polarization-inclusive remote sensing systems based on a dually-polarized six-port junction. A full analytical design procedure is presented with verifications through full-wave simulations and prototype measurements. Polarization diversity has been an essential factor in the performance and capacity enhancement of various wireless systems including cellular networks. Accordingly, the design and development of dually-polarized antenna feeding structures in the mmW band is a must. Firstly, as the basic dual-polarized device, a compact orthomode transducer (OMT) design in the Ka-band is proposed. The novelty of the proposed OMT stems from a distinct concept of handling dually-polarized signals based on a polarization selective coupler (PSC)