Sharif Digital Repository

The purpose of this thesis is to control the attitude of a tail-sitter UAV in transition phase (from hover to cruise and vice versa). This UAV has a pusher shrouded fan propulsive. Due to the fact that in transition phase the dynamic model of the UAV is associated with a significant uncertainties and the stability is more important than the performance, robust controller has been used. The propulsion part of the tail-sitter UAV can be assumed as a separate ducted fan UAV. In the first step both UAVs have been designed. then, in order to have an accurate model of UAV, the dynamics of actuators, including the engine and servo motor, has been identified. Then, modeling and verification for both... 

The aim of these notes is to describe an exciting chapter in the recent development of quantum cohomology. Guided by ideas from physics, a remarkable structure on the solutions of certain rational enumerative geometry problems has been found: the solutions are coefficients in the multiplication table of a quantum cohomology ring. Associativity of the ring yields non-trivial relations among the enumerative solutions. In many cases, these relations suffice to solve the enumerative problem. For example, let $N_d$ be the number of degree $d$, rational plane curves passing through $3d$ − $1$ general points in $\mathbb{P}^2$. Since there is a unique line passing through 2 points, $N_1 = 1$. The... 

Today, innovation plays an essential role in the economic growth of countries. By evaluating technological capabilities, different approaches have considered important effects of innovation on the economic ability and superiority of countries either directly or indirectly. In recent years, the Global Innovation Index (GII) has been employed as a common framework in this respect. It consists of five components, including “institutions,” “human capital and research,” “infrastructure,” “market sophistication,” and “business sophistication,” as the inputs, and two components, including the “knowledge and technology outputs” and “creative outputs” as the outputs of innovation. The present study... 

Data analysis is the science of extracting human-understandable knowledge from data. Massive data analysis is usually associated with the challenges of Volume, Velocity, Variety, Veracity and Value. These challenges are often referred to as 5V. With increasing processing power and reducing its cost in the last decade, massive data analysis methods have been used in various fields such as market, insurance and health, telecommunications and network, web search engines, intelligent transportation, etc. In this dissertation, we have tried to extract applied knowledge by using massive data analysis platforms and algorithms as well as traffic data. In this dissertation, a mathematical model for... 

Emotion recognition from speech signals has become one of the most popular researches in recent years. In order to increase human-machine interaction, a proper connection must be established between them. To achieve this goal, a machine must be able to understand the situation and respond accordingly. Part of this process involves understanding the user's emotional state. In recent years, various methods have been proposed to increase the efficiency of the speech emotion recognition system. These methods include collecting various audio databases, extracting efficient features from speech signals, using feature selection algorithms, designing different classifiers, as well as combining... 

New technology-based firms (NTBFs) are the driving force behind creating innovation and technology in countries and can play a crucial role in job creation and economic growth. These companies also facilitate technology transfer and strengthen the absorptive capacity of national innovation systems. Therefore, given the externalities of these companies, as well as their significant role in promoting innovation, governments around the world implement policies to support these firms. In Iran, the Vice President for Science and Technology has implemented policies to support NTBFs since 2013. Recently, a few studies have been carried out to evaluate these policies. However, the number of these... 

Having adequate information about water and weather condition is critical for many areas of governance, specially in the context of increasing rates of climate change and uncertainty related to different weather conditions. Open water data and data dissemintation decision making in Iran is facing many challenges, while the number of users and variety of services based on these data and information is increasing. Based on the review of the documents in this study, the most problems that have been reported for developed countries in the field of collecting, processing and using these data and information are the technical challenges related to the large volume of raw data and the need for... 

In the ship designing, it is preferable to access to a good performance in waves and low efficiency loss. Accordingly, modeling and estimation of added resistance would be an important issue. Added resistance in wave is an important part of ship's performance due to many technical and economic effects on the ship's performance. With understanding and awareness of the added resistance that comes from ship accident to the waves, we can reduce this parameter by changing in specifications and hull form of ships. Designers are also interested in optimizing the ship from this aspect. In previous works, added resistance in waves was obtained from experimental, numerical and analytical methods. In... 

Design optimization of ships by taking maneuverability in account has great influence on the performance of the vessels. Thus providing a method to predict the behavior of vessel in the design process is very important. Ship maneuverability is remarkable from different aspects of view. Especially in high speed vessels of various applications and missions’ good maneuverability would be a positive rating for it. For example, military vessels in specific situations need to change the speed and direction and this is a crucial capability of them. Also in accordance to the rules of IMO all of the vessels should perform maneuvering trials and fulfil the minimum requirements. Accordingly, this issue... 

Aircraft Range extension is a very common modification for today’s aircraft. Using the conformal fuel tanks is an appropriate method for today’s military and civil aircraft. In this thesis, a Design method has been developed for designing these tanks using DSM, CFD and DOE. The main goal in developing the method was to be able to consider these tanks as an add-on feature for the aircraft, which can be designed after the aircraft production. The main aspects of designing the tanks was to identify the consequences of adding the tanks to the aircraft. Due to limited resources, only the Longitudinal static and dynamic stability of the aircraft has been considered.The method introduced here shows... 

Blind image steganalysis is a technique used for detecting the existence of the data hidden in an image, where no information about the stenographic algorithm is available or usable. In this way, an important problem is to find sensitive features which make noticeable statistical distinction between cover and stego images. New steganalysis methods based on multi-resolution transform, specifically the wavelet and the contourlet transforms, have been proposed in this thesis in order to enhance the detection accuracy of system especially at low embedding rates. In fact, multi-resolution transforms are powerful space-frequency analysis tools that have been found quite successful in detection of... 

Widespread transfer of digital files over networks provides a hidden channel to transfer secret messages. Current steganalysis schemes need to work on a complete image for doing the detection job that starts when the image is entirely transferred, so are often restricted to an offline process. This restriction is serious when existence of the hidden message carriers on the network is shorter than the time required for the detection process. In this thesis, we propose a structurally fast detection method to detect the data hidden in an image passing through network. We use two of most powerful steganalysis algorithms for steganalysis of images that proposed by 1) Fridrich and Pevny and 2) Liu... 

Over recent years, ever increasing developing computer architecture and computer science made increase ability of computers for data processing and creating intelligent systems without human supervision. One of major and important usages of this systems is automatic supervise and analysis on video scene by image and video processing, machine vision and machine learning techniques. Developing this systems and increasing number of installed surveillance cameras on cities made employment of this systems for supervise on urban traffic events.Automatic number plate recognition, anomaly detection, accident detection, traffic sign detection and recognition and etc are example of Intelligent Traffic... 

One of the actions taken to mitigate the climate change is research, development and demonstration (RD&D) investments in renewable energy technology. In addition to domestic R&D spending, the importation of foreign technologies, as a main channel of technology transfer, is another option to obtain renewable energy technologies in order to achieve climate objectives. In this study, a panel dataset of 28 OECD member countries from 2011 to 2020 is analysed, using the OLS, fixed-effects, and two-system system GMM methods, to assess the impacts of public spending on renewable energy RD&D and the import of renewable energy technologies on the energy-related CO2 emissions. To fully capture the the... 

In order to survive in the competitive market, companies should increase the availability of plants. In order to increase the availability of a system, the occurrence of failures should be decreased. It is not possible to eliminate all of failures simultaneously. It means, it is not cost effective and logical to concentrate on elimination of all failures. In Addition, the cause of some failures might not be eliminated. So, the occurrence of those failures should be postponed to the later time as much as possible. Therefore, the critical failure modes should be identified to be concentrated for further analysis. Ultimately; the root causes of these failures should be explored and if it is... 

Due to the developments in technology, digital equipments, networks, storage devices, a lot of videos have been produced so far. Due to the dayly high growth rate of videos and their data, organizing and managing of them is difficult for applications such as interactive television, digital libraries, video surveillance, etc.However, for these kinds of usage from videos, at first the video will need to decompose into a hierarchical structure such as shot, scene, subscenes, scene and story unit. In order to achieve these goals, after the determination of shot boundaries and the allocation of key frames for each shot, similarity between each two shots are measured using key frames. According to...