Sharif Digital Repository

A lack of appendages makes snake motions simpler in some respects than those of other locomoting animals. Most of the researches done in this area has assumed that the normal force distribution of the snake is uniform along its length. But, observations of snake locomotion show that snakes tend to lift their body during movement, which means they dynamically change the distribution of normal force along their body. In this study, we addressed this issue and succeeded in formulating the snake’s normal force distribution systematically. This project has been conducted in two stages. In the first stage, we speculated uniform normal force distribution and verified our snake model by comparing... 

Due to the application of data streams in various data sources such as Web click streams, Web pages, and data generated by sensors and satellites, data streams have attracted a huge attention recently. A data stream is an ordered sequence of points that must be accessed in order and can be read only once or a small number of times. For mining such data, the ability to process in one pass along with limited memory usage is very important. Data stream clustering also has received a huge attention in recent years and numerous algorithms are developed in this field. None of them has paid attention to the feature selection problem as an effective factor in clustering quality especially when the... 

Navigation has been of special importance in various systems for a long time. In fact, determining the location, direction, speed and acceleration of a moving object has been a vital and important issue for mankind. Various methods have been used for this problem, the most important of which is perhaps the use of GPS. But in some situations, such as inside tunnels or places where it is not possible to send signals well, in order to continue navigation, we must use alternative methods such as model-based navigation and INS and in the form of integrated navigation system. Our final goal in this thesis is to prove that the used model-based navigation (based on the proposed dynamic model for the... 

Aerodynamics loads and aeroheating during reentry, are one of the challenging issues in designing One of the main challenges in the design and application of reusable spacecrafts is the aerodynamic and thermal loads acting on their structures during reentry into the atmosphere. For this reason, all the concepts/prototypes presented in the 20th century were either not fully reusable, or were partially canceled, or did not have economic justification. In this report, the aerodynamic loads on the first stage of a launch vehicle during the launch and return phases have been investigated. Due to the fact that the main part of the first stage of the vehicle includes fuel and oxidizer tanks, the... 

The collision of moderately large asteroids and comets also referred to as Near-Earth Objects (NEO's) with earth would have catastrophic consequences. Such events have occurred in the past and may occur again in the future. However, for the first time in known history, humanity may have the technology required to counter this threat. Methods studied for mitigation of this hazard are based on deflecting asteroid's trajectory and are normally divided into two basic categories: high energy impulsive methods, and long-duration low-thrust methods. Two parts of mission to be optimized are the trajectory of spacecraft to reach the target and the deflection strategy which could be analyzed by the... 

The main purpose of the present thesis is to establish a decentralized controller for some car–like multi robots to follow and hunt moving targets. Robots are very similar to actual cars considering geometric dimensions, mass and moment of inertia and so on; and outputs of the controller are steering-wheel and driving-wheel torques appropriately. Dynamics of the moving target is so that it escapes from the robots. Robots are equipped with antenna for getting wireless sensory signals, including range and bearing sensors. Kalman filter is used for estimation the target relative position and speed and robots state variables. The controller is designed for doing the above mentioned group... 

Dead Reckoning navigation, as an infrastructure-independent approach, plays a key role in scenarios where access to the Global Navigation Satellite System (GNSS) is unavailable; however, its performance is consistently affected by the accumulation of errors in inertial measurement unit (IMU) sensors. In this research, a novel approach is proposed to enhance the accuracy of this method. In the first stage, sensor noise modeling is performed using three innovative approaches. The first approach involves a static tuning based on an adaptive Extended Kalman Filter (AEKF). In this method, the discrete process noise covariance matrix is adaptively estimated, and the continuous-time process noise... 

Internet is the largest multi-purpose, self-reliant, complex and distributed computer network across the globe. The nodes of this network are placed in every place like homes, offices, military camps, schools and all other locations by utilizing many different communication protocols, media and capacities. Furthermore, by rapid technology development, there are many newly born applications utilizing internet in new ways such as Internet of Things systems. The explosive growth of technology causing accelerated addition of new nodes to the internet, and any new single node may have several new unpatched vulnerabilities. This is a serious issue for managing this vast chaotic configuration and...