Abstract In practical environment most of physical systems that are existed, have nonlinear behavior. In most cases the accuracy of these systems, and their responses aren’t acceptable. Therefore to improve the performance of these systems, a modern control methodology must be applied. In the case of nonlinear systems most problems can be divided into two basic types of nonlinear control problems; nonlinear regulation and nonlinear tracking problems. Due to existing of high nonlinearities parts in theses nonlinear systems the use of classical linearization methods don’t provide an acceptable level of accuracy and therefore these problems have gained a great attention in recent years; and there are numbers of methods can be found to solve these nonlinear problems, such as trail and error, feedback linearization, Robust control, Adaptive control, Gain-scheduling and…etc. In This thesis the feedback linearization is choose as a control methodology to solve these problems; The central idea of the feedback linearization approach is to algebraically transform a nonlinear system dynamics into a (fully or partly) linear one, so that linear control techniques can be applied. This differs entirely from conventional linearization (i.e., Jacobian linearization [4]) in that feedback linearization is achieved by exact state transformations and feedback, rather than by linear approximations of the dynamics.
فرج على عبدالسلام بشير (2008)

Abstract The conflict that took place in Libya in 2011, up to the present moment, has greatly affected the electrical power network and resulted in the rise of the voltage instability problem. This was due to loss of the some major transmission lines and certain generation units. Owing to the fact that the southern region of the Libyan network has no generation units, voltage drop phenomena has become a common problem as a result of the long transmission distance, which is approximately 750km. A proposed solution in order to solve this problem is via the utilization of small mobile generation units at the network weak points. This thesis revolves around discussing the voltage instability problem within the Libyan Network and how it can be enhanced when small and mobile generation units are connected to the network weak points. It will also establish and identify where the most weakened buses and regions are so that the mobile units should be connected for the attainment of optimized solution. Moreover, this solution was proposed as it can solve not only the voltage instability problem, but it will also solve the inadequacy in generation issue by circulating additional power within the network. Hence, reduce the load shedding phenomena. Furthermore, the thesis also includes future recommendations to improve and enhance the Libyan network by the addition of new 220kV and 400kV transmission lines that will enable the network to cope with the load growth in the future
ربيع محمد عمر (2014)

Abstract Wireless local area networks (WLANs) have been rapidly developed in recent years. It is used for various applications. VoWLAN, which transmits VoIP data over WLANs, shows its amazing attraction and constitutes one of the most flourishing applications nowadays in WLANs. One of Wireless Local Area Networks (WLAN) main drawbacks, when compared to wired networks, is that WLANs are less predictable and efficient. Wireless physical medium is harder to be controlled than physical wire. WLAN medium is also unlicensed, and thus susceptible to interferences produced by other devices. Therefore, great effort is being done in order to obtain Quality of Service (QoS) in real-time voice communications using WLANs. This topic has opened plenty of new research lines to upgrade current WLAN standards. In this thesis, a study is carried out for the behavior of new Medium Access Control (MAC) protocols defined in IEEE 802.11e draft standard Enhanced Distributed coordination function EDCF as well as for its subsequent modified versions. The Adaptive Enhanced Distributed coordination function AEDCF, designed to support QoS when providing voice communication services between stations in WLAN. Also presents experimental results obtained from simulations, and compare our results with simulations made using IEEE 802.11 standard MAC. The simulation work was done using NS-2 simulator, with the addition of specific modules for 802.11e. A performance comparison is carried out between the modified MAC scheme and IEEE standard MAC scheme, using Experimental simulation models. It is found that the adaptive technique method not only increases the medium utilization ratio and lowers the collision rate by more than 50%, but also enhances vii the overall throughput by around 20% compared with the basic IEEE 802.11DCF technique.
حسين ابراهيم ازويه (2010)