Abstract Voice over IP (VoIP) uses the Internet Protocol (IP) to transmit voice as packets over an IP network, like the Internet, Intranets and Local Area Networks (LAN). Here the voice signal is digitized, compressed and converted to IP packets and then transmitted over the IP network. However, at the receiving end, some packets may be missed in its way due to network congestion. This packets loss degrades the quality of speech at the receiving end of a voice transmission system in the IP network. Since the voice transmission is a real time process, the receiver cannot request for retransmission of the missing packets. High speed networks provide real time variable bit rate service with packet loss requirements. The burstiness of the correlated traffic makes dynamic buffer management highly desirable to satisfy the Quality of Service (QoS) requirements. This thesis presents an algorithm to improve and optimize the Adaptive Buffer Allocation Scheme to deal with input traffic based on loss of consecutive packets in data streams and buffer occupancy levels. Buffer is designed to allow the input traffic to be partitioned into different priority classes, and based on the input traffic behavior it controls the threshold dynamically. This scheme allows input packets to enter into buffer if its occupancy level is less than the threshold value for priority of that packet. The threshold is dynamically varied in runtime based on packet loss behavior. The performance evaluation is carried out using simulation and is carried out for two and multiple priority classes of the input traffic "real time and non real time classes". The simulation results show that the Modified Adaptive Partial Buffer Sharing (ADPBS) has better performance than Adaptive Partial Buffer Sharing under the same traffic conditions.
اسماء احمد الكيش (2010)

نظرا لأهمية مشروع النهر الصناعي في نقل المياه من جنوب ليبيا إلى شمالها حيث الطلب الزائد للمياه، وبما أنه يعتبر المصدر الأساسي للمياه في معظم المناطق الساحلية، فقد قمنا بدراسة المرحلة الأولى لهذا المشروع وذلك باعتبارها من أقدم مراحل مشروع النهر الصناعي. حيث أن المرحلة الأولى نقلت المياه لمدة تزيد عن 20 عاما ومازالت حتى يومنا هذا، وقد تعرضت هذه المرحلة للعديد من المشاكل الهيدروليكية أدت إلى توقفها في بعض الأحيان، وحيت أن هذه المرحلة سيتم توصيلها بمرحلة جديدة في المستقبل القريب حيث سيتم وصل منظومة (الكفرة- تازربو) بمنظومة (السرير- سرت / تازربو- بنغازي) من هنا بداء التساؤل، هل تستطيع المرحلة الأولى استيعاب وتحمل هذا العبء؟ والعديد من التساؤلات الأخرى حول منظومة المرحلة الأولى وقد أجبنا في هذا البحث على البعض منها. حيث قمنا بدراسة مخزون المياه الجوفية المستخدمة ومن ثم كيفية نقلها إلى المناطق الشمالية بواسطة منظومة متكاملة ولكي نستطيع دراسة الخصائص الهيدروليكية قمنا بدراسة المكونات الأساسية للمنظومة مثل الأنابيب والمضخات والصمامات والخزانات وغيرها من المنشآت الهيدروليكية الأخرى في هذا المشروع، ومن ثم توجهنا إلى دراسة الخصائص الهيدروليكية كدراسة الفاقد الكلي داخل الأنابيب وتأثير زيادة خشونة الأنبوب تبعاً للمدة الزمنية الطويلة التي أستخدم فيها، ورسم خط الميل الهيدروليكي ومعرفة الضغوط التي تتعرض لها المنظومة ومقارنة الخصائص الهيدروليكية للوضع الحالي بالوضع المستقبلي وكذلك دارسة البدائل المتاحة كتغيير نوع الأنابيب من نوع PCCPإلى نوع GRP ومدى تأثيرها على المنظومة، حيث ثم الاستعانة ببعض برامج الكمبيوتر كبرنامج ,MATLAB,AFT,EXCEL في عملية التحليل والتقييم الهيدروليكي للمنظومة، وبعد ذلك تطرقنا إلى المشاكل والظواهر التي واجهت المشروع كظاهرة القفزة الهيدروليكية ومشكلة التآكل في الأنابيب، وغيرها من المشاكل الهيدروليكية التي تم تسليط الضوء عليها. Abstract The main task of man-made project is to transfer water from south part of Libya to the costal belt, since it is the primary source of water in costal partial of Libya; we have studied the first phase of this project which considered being oldest stage of the River Project. This stage is still delivering water for period over 20 years, and encountered many problems that led to the obstruction in some cases. Which including connection of a new in the near (KUFRA-TAZERBO) and (SARIR-SIRT/TAZERBO-BENGHAZI) system. However there is an important question, dose the first phase can carry this burden? And a lot of other questions regarding the system. In this study we have to answer some enquires. Where we studied the groundwater storage used and how to transfer to the north area by an integrated system, and in order for us to study the hydraulic characteristics of system, we studied the basic components of the system such as pipes, pumps, valves, tanks and some other facilities. From there, we proceed to study the characteristics of hydraulic for instance overall losses in the pipes and the effect of roughness increase in the pipe according to the long use, drawing of hydraulic grade line slop and acknowledging the pressures which the system exposed to, and to comparing the hydraulic characteristics for the current state to the future state. Then, study the available alternatives such as changing the type of pipes and their impact on the system. We have to utilize some of the software such as Excel, AFT, Mat lab, in analyzing and evaluating the process of the hydraulic system. Our next step was dealing with the problems and phenomena’s that have faced the project hydraulic jump phenomenon and the problem of pipes corrosion, and other hydraulic problems that we study.
ماجدة سالم الزيادي (2012)

Abstract: Modern PET/CT clinics consist of a scanner room housing PET/CT unit and a control area, two or more waiting rooms where patients rest prior to scanning, and a hot lab where doses are prepared. The 511 keV photons from the PET positron emitting isotopes are the source term for the waiting rooms and the hot lab, while both the 511 keV photons and the polyenergtic spectrum of x-rays from the CT unit must be considered in the scanning roomThis study is intended to estimate dose distribution resulting from using a FDG procedure (555 MBq). The dose distribution is evaluated in injection room, waiting room, and scanning room using two methods. The first method is the analytical method whids is based on AAPM report № 108, while in the second method the dose distribution was simulated using the Monte Carlo code EGSXYZnrc .In the Monte Carlo method some parameters such as the optimal number of histories and the cut off energy of the electron are found to have a significant effect on the results. These parameters are tested and those values with less statistical error are adapted for the calculations.A good agreement between the two methods has been achieved. The dose distribution in the uptake room , waitting room and the scanning room appears to be below the annually dose limit and does not exceed 1% at the adjacent areas.
مريومة البهلول القرقني (2009)