Sharif Digital Repository

Recent advances in storage and processing have provided the ability of automatic gathering of information which in turn leads to fast and contineous flow of data. The data which are produced and stored in this way are named data streams. It has many applications such as processing financial transactions, the recorded data of various sensors or the collected data by web sevices. Data streams are produced with high speed, large size and much dynamism and have some unique properties which make them applicable in precise modeling of many real data mining applications. The main challenge of data streams is the occurrence of concept drift which can be in four types: sudden, gradual, incremental or... 

This research aims to introduce a new integrated fault tolerant attitude control system of satellites based on the neural networks. First, a linear controller and an optimal controller are designed assuming that no fault occurs in the reaction wheels of the satellite. It is obvious that these controllers are not able to respond properly when a fault occurs. Therefore, artificial neural networks are employed in the fault tolerant controller design. Neural networks are well-known for their adaptiveness and the ability to learn the dynamics of a system. Therefore, they can be used to predict the faulty conditions. In this research two approaches are examined to deal with the faulty conditions.... 

People use social networks to share millions of stories every day, but these stories rarely become viral. Can we estimate the probability that a story becomes a u/rof cascade? If so, can we find a set of users that are more likely to trigger viral cascades? There are many factors influenced the message virality. In this thesis, we investigate the effect of graph structure, diffusion pattern as well as the message text on virality measure. Finally, the authors solve both source localization and inferring COVID-19 network via propsed methods.First, the authors investigate probability estimation and maximization of cascade virality. In this section, we develop an efficient viral cascade... 

IoE devices are going to integrate with our environment. It has been predicted that there would be more than 6 connected devices per each person by 2020. Currently what obstruct this technology from continuing its evolusion path, is its dependence on Ultra Low-Power devices, and for this reason there is a huge concenteration on Radio-Frequency standards which can make devices more power efficient. Within these standards, Bluetooth Low Energy (BLE) attracted designers consentration for its similarities with conventional Bluetooth and its dominance in cellphones and other portable devices.In this project, we have attempted to design a trasmitter for BLE standard based on an All Digital Phase... 

The harmful environmental effects of gases resulting from the combustion of sulfur compounds in fuel, poisoning of catalysts, corrosion of equipment, as well as the intensification of environmental considerations and new standards adopted for the maximum amount of sulfur, have made the desulfurization of fuels important; Meanwhile, the desulfurization method using hydrogen has a high potential to remove sulfur compounds. For example, diesel fuel contains a variety of impurities such as sulfur, nitrogen (basic and Non-basic), and aromatic compounds, the sulfur in diesel fuel causes many problems related to environmental pollution and corrosion of engine components. Also, due to the high... 

PE pipes and specially PE100 are commonly used for the transportation of drinking water, transferred water was mostly disinfected by disinfectants such as chlorine, chlorine dioxide and chloramine. Long-term contact with water containing disinfectants led to morphological and mechanical changes and followed by oxidative degradation and failure. Antioxidants are stabilizers which are used in PE pipes to postpone oxidation and increase the durability of these pipes. Migration of antioxidants is possible during the terms of service, in this case antioxidants can be washed by water and left the pipe. As a result, the loss of antioxidants decreases the stability of pipes and leads to oxidative... 

Sign language is an essential means of communication for millions of people around the world and serves as their primary language. However, most communication tools and technologies are designed for spoken and written languages, which can create barriers and limitations for the deaf community. By creating a sign language recognition system, we can bridge this communication gap and enable people who use sign language as their primary mode of expression to communicate better with people and their surroundings. This sign language recognition system increases the quality of education, the quality of health services, improves public interactions and creates equal opportunities for the deaf... 

Damage identification in uniform structures using Lamb waves has been studied by the researchers; however, as most of the industrial structures are not uniform, it is necessary to study more complex structures. In this thesis, a method of identifying notch specifications as damage in a symmetric stepped beam with arbitrary number of steps using Lamb wave propagation is presented. Initially, the study will examine and compare the Lamb wave propagation in uniform, symmetric stepped and asymmetric stepped beams. In the first stage, a method for detection of damage location in symmetric stepped beam is presented. This method is based on mode conversion phenomenon of Lamb wave modes. Moreover,...