Maan Kousa, Hazem Helmi Selmi

كلية الهندسة-جامعة الملك فهد للبترول والمعادن · السعودية

Asynchronous transfer mode (ATM) technology is expected to have an important role in the future evolution of global integrated services communication networks. ATM networks suffer from cell loss. The problem becomes more severe when part of the connection is noisy. In this case error control schemes must be incorporated to recover lost cells. A cell loss recovery scheme for operation over a noisy ATM scheme is analyzed. This scheme is based on the parity check product code (PCPC). A novel algorithm for analyzing the structure of the lost cell patterns in product codes is presented. An upper bound on post decoding cell loss rate in the PCPC is presented. The use of an ARQ scheme on the top of PCPC is also investigated with various retransmission strategies. It was found that the proposed novel algorithm of structural analysis is very useful in identifying the recoverable cell loss patterns, the derived bound on post-decoding cell loss rate is almost exact, and the PCPC is very powerful in recovering lost cells. The advantage of the hybrid ARQ/PCPC over the pure ARQ depends on the retransmission strategy.

فخرية مخدوم, وداد محمد نايف العرفي

كلية التربية-جامعة طيبة · السعودية

فايزة جروني, نجلاء بن خليفة

كلية الحقوق والعلوم السياسية-جامعة الشهيد حمة لخضر - الوادي · الجزائر

مليكة ديبون, اسماء روان, صالح ربوح

معهد علوم وتقنيات النشاطات البدنية والرياضية-جامعة أحمد بن يحيى الونشريسي - تيسمسيلت · الجزائر

Maha El-Amin Ibrahim El-Nima, Siddig Ahmed Ismail FRCP, FACC ,FCCP

كلية الدراسات العليا-جامعة الخرطوم · السودان

This is a prospective study of 51 patients withpericardial effusion, with male to female ratio of 1.3:1, widerange of age (4 to 80 years), and mean age 34.2± 17.2.Most of the patients presented with S.O.B., cough andchest pain. General symptoms of fever, fatigability, andabdominal pain, were also noticed.The diagnosis was obvious clinically, by increasedcardiac dullness and muffled heart sounds in the vast majorityof patients. Chest roentgenogram and echocardiograph are themainstay of the diagnosis. Pericardiocentesis was done for 35patients .Tuberculosis was found to be the commonest, but notthe only, cause. Followed by malignancy, rheumatologicaland idiopathic in order of sequence.Specific echocardiographic findings, i.e. shaggy pericardiumand fibrinous strands, suggesting the likelihood oftuberculosis were noticed .Other echocardiographic finding and morphologicalfeatures of aspirated fluid have no predilection to a specificetiology.

Kicher, Zineddine Belloul, Azizou, Samir Alem

كلية التكنولوجيا-جامعة عبد الرحمان ميرة - بجاية · الجزائر

محمد الزين جيلي, ابتسام بوجلال , ديهية بومراو

كلية الآداب واللغات-جامعة عبد الرحمان ميرة - بجاية · الجزائر

يعد الحجاج تابع للبرهنة في الفكر اليوناني القديم و مرتبط بالخطاب نجد له عدة أساليب و آليات و هي ما وظفناها في بحثنا هذا بين ما هو بلاغي كالاستعارة و التشبيه و الكناية و بين ما هو لغوي و منطقي؛ ما حاد بنا إلى توضيحها من خلال كتابات مصطفى غلفان نظرا لما لعبته من دور فعال في انسجام الخطاب الحجاجي.

زينب مصطفى حسين, عبدالكريم مخيف عبيس

كلية الهندسة-جامعة بابل · العراق

Power amplifiers have been widely used in wireless communication systems represented by base stations and handsets. They are essential parts in wireless transceivers, where they constitute the output stages of their transmitters. Efficiency and linearity are two factors governing the design of power amplifiers. Efficiency is strongly related to the battery lifetime, whereas linearity is of great importance for accomplishing reliability of amplified signals. Enhancement of efficiency increases the battery lifetime; therefore, it is very important in manufacturing portable products. Increasing needs for highly linearized RF power amplifiers in modern communication systems make microwave designers urgently compelled to introduce new practical linearization techniques. There are three main linearization techniques, which are: feedback, pre-distortion, and feed-forward techniques. Due to good characteristics, unconditional stability, wideband signal capability, and high reduction of distortions compared with other techniques, the feed-forward linearization technique (FFLT) equipped with an additional linearization loop is adopted in this thesis for linearizing four pre-designed RF power amplifiers having 5.8 GHz central frequency and 500 MHz bandwidth. The proposed modification of the feed-forward technique is referred to as the double-loop feed-forward linearization technique. Class-E and class-F topologies with low bias currents and a single DC source are utilized in the design of two low-bias power amplifiers to meet the requirements of handset applications. Low bias currents make them sensitive to low-level RF excitations. These two amplifiers have achieved approximately coinciding rated collector efficiency and power-added efficiency of about 60%. The third power amplifier is designed using low-bias power class-F topology having two DC sources; thus, it is exploited for base station purposes. It has achieved drain efficiency and power-added efficiency of about 60%. The fourth power amplifier is designed as class-A and exploited for base station applications. It has collector efficiency and power-added efficiency exceeding 30%. All of these amplifiers have been formatted with two stages to compensate for the low voltage gain problem. The double-loop feed-forward linearization technique is exploited through four linearization systems, which are: double-loop FFLT using class-E power amplifier for handsets, double-loop FFLT using class-F power amplifier for handsets, double-loop FFLT using class-F power amplifier for base stations, and double-loop FFLT using class-A power amplifier for base stations. All these linearization techniques are demonstrated to provide significant linearization for the processed amplifiers (about 62% for handset applications, 58.6% for the first base station system, and 36.48% for the second base station system) and effective reduction in intermodulation and multiple harmonic distortions. It is demonstrated in each proposed feed-forward system that the double-loop FFLT is more effective than the basic FFLT with respect to linearization capability and distortion cancellation. The simulated results show that the proposed FFLT using class-F amplifier is better than that using class-E configuration with respect to distortion cancellation and improving efficiency, whereas the proposed double-loop FFLT using class-A power amplifier has good linearization and distortion cancellation. All the four RF power amplifiers and the four double-loop feed-forward linearization systems are designed and tested on Advanced Wave Research - Microwave Office (AWR-MWO)

Zineb Hamlati, Imane Benamara, Oussama Touhami

جامعة سعد دحلب البليدة · الجزائر

Elément critique et indispensable de la sécurité des vols, la gestion de la masse et du centrage des aéronefs est une opération importante lors de la préparation d’un vol car un avion mal chargé et mal centré peut tout simplement ne pas réussir à décoller. L’objectif recherché a travers ce projet est la numérisation d’une feuille de centrage d’un B737-800 sous forme d’application Android afin d’accroitre la sécurité, la qualité, la productivité et la simplicité des opérations tout en suivant des étapes simples.

فيصل علاوي, عبد الحميد برحومة

كلية العلوم الاقتصادية والتجارية وعلوم التسيير-جامعة محمد بوضياف - المسيلة · الجزائر

يهدف هذا البحث إلى تسليط الضوء على أهمية إدارة الصيانة في المؤسسة ودورها في ترشيد نفقات أعمال الصيانة، فالأعطال والاختلالات التي تتعرض لها الآلات والمعدات في العمليات التصنيعية أو الخدمية نتيجة الاستغلال أو التقادم التكنولوجي والزمني تجعل من الضروري القيام بعمليات التخطيط ومتابعة التدخلات لضمان استغلال أمثل للآلات والمعدات وبأقل تكلفة.وقد تم التركيز في هذا البحث على أحد المؤسسات العمومية الخدمية وهي بلدية المسيلة، فالاعطاب والاختلالات التي يتعرض لها عتاد البلدية يعيق المهام التي استعمل من اجلها لأداء الخدمات المختلفة لتلبية حاجيات مواطنين.وقد تم التوصل في بحثنا هذا إلى حقيقة مفادها أن مساهمة مصلحة الصيانة في ترشيد نفقات عتاد البلدية يعتبر ضئيلا، فالمصلحة لا تعتمد على نظام معلوماتي يسهل عمليات التدخل في حالة حدوث أعطاب للعتاد، فهي تركز أكثر على أعمال الصيانة العلاجية فقط (التدخل عند حدوث العطب) وليس هناك تخطيط للوقاية منها باعتماد الصيانة الوقائية، كل هذا جعنا نصل إلى نتيجة مفادها أن عملية ترشيد نفقات صيانة عتاد البلدية متواضعة جدا.