Searching for More Efficient Dynamic Programs

Computational models of human language often involve combinatorial problems. For instance, a probabilistic parser may marginalize over exponentially many trees to make predictions. Algorithms for such problems often employ dynamic programming and are not always unique. Finding one with optimal asymptotic runtime can be unintuitive, time-consuming, and error-prone. Our work aims to automate this laborious process. Given an initial correct declarative program, we search for a sequence of semantics-preserving transformations to improve its running time as much as possible. To this end, we describe a set of program transformations, a simple metric for assessing the efficiency of a transformed program, and a heuristic search procedure to improve this metric. We show that in practice, automated search---like the mental search performed by human programmers---can find substantial improvements to the initial program. Empirically, we show that many speed-ups described in the NLP literature could have been discovered automatically by our system.

Modelling the drinking Water Turbidity of Al-Sin Purification Plant using Dynamic Neural Networks

Modelling the relationship between drinking water turbidity and other indicators of water quality in Al-Sin drinking water purification plant using Dynamic Artificial neural networks could help in the implementation of the stabilization for the performance of the plant because these neural networks provide efficient tool to deal with the complex, dynamic and non-linear nature of purification processes. They have the ability to response to various instant changes in parameters influencing water purification. In this research, four models of feed-forward back-propagation dynamic neural network were designed to predict the effluent turbidity from Al-Sin drinking water purification plant. The models were built based on turbidity, pH and conductivity of raw water data while the effluent turbidity data were used for verify the performance accuracy of each network. The results of this research confirm the ability of dynamic neural networks in modeling and simulating the non-linearity behavior of water turbidity as well as to predict its values. They can be used in Al-Sin drinking water purification plant in order to achieve the stabilization of its performance.

A Study of the effect of meteorological variables on the dynamics of several air pollutants

Meteorological elements affect the dynamics of air pollutants, where these elements can play an important role in dispersing and transferring air pollutants as well as to photochemical reactions of secondary air pollutants. This study was conducted to analyze the effect of several meteorological variables on the concentrations of some air pollutants (Co, NO2, SO2, O3, PM10) at two sites in Damascus city, by using the Pearson correlation coefficient.

The Effect of Potential Energy during Acceleration Phase on Vessel stability

The under keel clearance (UKC) is considered as one of the most important factor which governs the navigation safety in restricted waterways. However, the notion of safe under keel clearance is directly related to ship sinkage. The recent researches to evaluate ship sinkage show that it is related to vessel potential energy. The curve of vessel displacement in heave motion as function of potential energy shows that a ship has three equilibrium positions; stable equilibrium position represents steady squat and unstable equilibrium position which can be considered as a virtual bottom for a ship, the third stable equilibrium position does not have any physical signification, since it lies below the bottom. The principal goal of this paper is to develop a mathematical model for vessel motion during acceleration phase by considering several assumptions. Then, analyze the conversion of kinetic energy to potential energy at the unstable equilibrium position during acceleration phase. By taking into account the period during which the vessel accelerates as well as the vessel speed at the end of the acceleration phase. The results show that ship stability could be affected by the oscillations generated at the end of this phase.

The Prolog's strength in writing the experts systems

In this research, we try to show the major features of prolog which make it a strong expressive language about writing the expert systems and the traditional languages lacks them as Pascal language. We also provide expert system, the purpose of it is the Inventory Control by apply the Fixed-Order Quantity Model, and we clearified concept of the static and dynamic data in Prolog. Finally, we compared between the databases in prolog and some of their quires with Access and SQL. Expert systems are considered as one of the main applications of artificial intelligence, which are known as knowledge based systems. And the expert systems are computer applications which embody some non-algorithmic expertise for solving certain types of problems. For example, the problems which provide advice, analysis, classification, diagnostic, explanation, teaching, or designing…etc.

النمو السكاني الصفري في نموذج خطي لديناميكية السكان

يؤدي النموذج الخطي المتقطع للنمو السكاني (نموذج LESLIE) دوراً هاماً في ديناميكية السكان النظرية و التطبيقية. و بمناقشة موجزة لهذا النموذج يمكننا معرفة الحالة التي يمكن أن يتزايـد بهـا السكان الإناث في مجتمع سكاني ما متوقف عن النمو، فيمـا إذا انخفضـت معـدلات الخصـوبة العمرية_النوعية و بشكل تناسبي مباشر عن مستوى الإحـلال (معـدل إعـادة التكـاثر الصـافي 1=NRR) لجيلين متعاقبين و تحت افتراض ثبات الوفاة بمرور الزمن. توصل (Keyfitz) عام ١٩٧١ إلى وضع سكاني مقارب لنموذج سكاني ديناميكي مسـتمر الـذي وضعه (Lotka) ، لنفترض ثبات الوضع الأولي للسكان فتعطي النتيجة حداً أدنى للمجتمع السكاني المتوقف نهائياً، و الذي يكون تركيبه العمري ذا نموٍ سكاني صفري، مع الأخـذ بالحسـبان الفتـرة الزمنية، و التي بها يقترب الوضع المفترض من وضع المجتمع السكاني المتوقف. و أخيراً سنوضح التحليل الجبري للنمو الصفري من خلال نموذج العمليات العشوائية المتعددة.

دراسة بتروغرافية، جيوكيميائية، و بترولوجية لفونوليت شائع في جنوب سورية مساهمة في فهم جيوديناميكية شمال الصفيحة العربية

تثير حركية و جيوديناميكية الفالق السوري الكبير و البركنة المرافقة لهما اهتمامات كبيرة لدى الاختصاصيين على الأصعدة كافة: المحلية، و الإقليمية، و العالمية. و تكاد هذه الاهتمامات تتمركز حول طبيعة الحركة من جهة، و طبيعة المواد البركانية، و عمرها، و ما يرافقها من حشوات معطفية من جهة أخرى، و هذا ما يفسر غزارة الدراسات المنشورة في السنوات العشر الأخيرة، سواء التكتونية منها أم البترولوجية. و تلقي هذه الدراسة لعرق من الفونوليت في بازلت جنوب سورية، شائع الانتشار عالميًا، الضوء على جيوديناميكية شمال الصفيحة، العربية و ارتباطها بالحركات الإقليمية، لا سيما انفتاح البحر الأحمر و امتداداته نحو الشمال في العقبة، و السويس، عبر دراسات متكاملة حقلية، و بتروغرافية، و جيوكيميائية، و بترولوجية و تأريخ زمني .