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)

كأي منشأ أخر يتعرض إلى أحمال خارجية وظروف جوية متغيرة مثل درجات الحرارة والرطوبة ومعدل سقوط الأمطار, تظهر أضرار على سطح الرصف الإسفلتي تقلل من كفائتة وأحيانا تجعله غير صالح للاستخدام. ومن هذه الحالة تُعتبر برامج الصيانة الخطوة الهامة والضرورية بعد إنشاء الطريق للمحافظة عليه. ولتحديد أفضل وسائل الصيانة و/أو إعادة التأهيل لا بد من إجراء تقييم لحالة الطريق لمعرفة الأضرار الموجودة بالطريق وأسبابها وجود منهجية لتقييم حالة سطح الطريق تساعد على تشخيص حالة سطح الرصف الإسفلتي بطريقة علمية وذلك ليتم الاختيار المناسب لطريقة الصيانة أو إعادة التأهيل تم في هذه الدراسة البحث والإطلاع على العديد من المراجع والطرق المتبعة في الولايات المتحدة الأمريكية وكندا لتقييم حالة سطح الرصف الإسفلتي وتحديد الطرق الأكثر تدقيقاًً والتي أمكن الحصول عليها وقد تم اختيار عدد ثلاث طرق أساسية لهذه الدراسة تم في هذا البحث تطبيق ثلاثة طرق (طريقة نورث كالورينا, وطريقة أوهايو, وطريقة الجمعية الأمريكية للمقاييس واختبارات الموادASTM)) ) لتقييم حالة سطح الرصف الإسفلتي على العديد من القطاعات النموذجية والتي تم اختيارها من عدة طرق بجنوب الجماهيرية ومن خلال النتائج المتحصل عليها لتقييم العديد من الطرق المحلية بجنوب الجماهيرية وذلك باستخدام الطرق القياسية الداخلة بالدراسة تم مناقشة النتائج المتحصل عليها والمقارنة بينها وبين حالة سطح الرصف الإسفلتي الحالي اهتم الجزء الأخير من هذا البحث بتقديم خلاصة للعمل الذي تم في هذه الدراسة وكذلك تقديم مقترح مسودة منهجية لتقييم حالة سطح الرصف الإسفلتي للتطبيق داخل الجماهيرية, ويقدم في الختام توصية بالإجراءات المكملة لهذا البحث. Abstract As any other structures subjected to external loads and environmental changes as temperature, humidity and intensity of rainfall that reduce it is performance and sometimes it becomes uncomfortable and unsafe for use. And programs of a maintenance is important and necessary after construction of the road to keep it convenient for use. An evaluation of road condition must be proceeded before the maintenance to determine the distresses and its causes in order to know the required remedies, to promote level of services for the road and to provide safety and comfortability, and maintain road network and allocate its expenses earlier to elongate its design life. A specific techniques for maintenance should be followed firstly for of asphaltic pavement surface condition to lead to an appropriate choice of the road maintenance or rehabilitation.In this study, several methodologies were studied and reviewed such as the methods used in the United States and Canada for the evaluation of the asphaltic pavement surface condition and methods with the most details and that could be obtained where have been selected (North Carolina, Ohio, and American Society of standards and testing materials method (ASTM)).The selected methods were applied to evaluate the asphaltic pavement surface condition on many typical sections of roads in dry and hot region in south of Great Jamahiriya.From the results obtained for the evaluation of many local roads in south of Great Jamahiriya, using the selected methods in this study, have been discussed and compared with the existent condition.A summary of the work done in this study and the proposal of draft methodology for evaluation of asphaltic pavement surface condition to be applied in Great Jamahiriya, and finally present recommendations for complement actions of this research.
الهاشمي محمد عبد النبي (2010)

Almost all Libyan industries (both private and public) have struggled with many difficulties during the past three decades due to many problems. These problems have created a strongly negative impact on the productivity and utilization of many companies within Libya. This paper studies the current awareness and implementation levels of Just-In-Time (JIT) within the Libyan Textile private industry. A survey has been applied in this study using an intensive detailed questionnaire. Based on the analysis of the survey responses, the results show that the management body within the surveyed companies has a modest strategy towards most of the areas that are considered as being very crucial in any successful implementation of JIT. The results also show a variation within the implementation levels of the JIT elements as these varies between Low and Acceptable levels. The paper has also identified limitations within the investigated areas within this industry, and has pointed to areas where senior managers within the Libyan textile industry should take immediate actions in order to achieve effective implementation of JIT within their companies. arabic 17 English 88
ٌRajab HOKOMA(7-2010)