Sharif Digital Repository

Nowadays, multi-agent robotic systems are implemented to perform various operations such as military mission, search and rescue operations, etc. One of the most interested robotic platforms for multi-agent systems is quadrotor aerial robot. In this paper, a team of quadrotors is prepared to perform a formation flight toward a specified target in order to catch and transport it on a desired path. Therefore, at first, trajectory tracking control of the quadrotor has been studied and two types of controllers have been introduced: Hierarchical controller and Non-hierarchical controller. Coordinate free structure of the hierarchical controller provides distinctive properties and guarantees... 

Activated carbon, as an adsorbent with a high adsorption capacity and low cost, has many applications in liquid and gas adsorption processes. Among the adsorption of liquid phase, there are examples of drinking water purification, wastewater treatment, food industry, brewery, chemical separation (acids, amines, glycerin and glycols), enzymes ... and in adsorption from the gas phase there are examples of removing toxic compounds Containing sulfur and recycling sulfur, purifying biogas, use in gas masks, etc. Various materials can be used as raw material to make activated carbon. Materials such as walnut, almonds, coconut, pine, corn, etc. In this thesis, a feasibility study on the production... 

Massive MIMO systems are systems, where the base station has many number of antenna so each user’s channel is orthogonal to one another.These systems have some valuable advantages such as reduction of energy needed for transmission and significant improvement in spectral efficiency, which makes them be suitable for next generation of wireless communication systems. Another advantage of Massive MIMO systems is inherent resistance against passive eavsdroppers due to having a directed power radiation in direction of the desired user. However another physical layer attack threat these systems: attacking in pilot phase then eavsdropping in downlink phase which must taken care of in physical... 

The dRGT theory of massive gravity is a consistent theory of interacting massive spin 2 particles. As an effective field theory compared to observational data, its UV cutoff is rather low. Namely, unitarity is violated at low energies in scattering of longitudinal modes. In this dissertation, we give a brief review of the dRGT theory and its challenges. Of particular interest is the question of its UV completion in a more consistent model. Then, we show that this theory can be obtained from a topological gauge theory in one higher dimension. After dimensional reduction and symmetry breaking via boundary conditions, we obtained four dimensional effective field theories including the dRGT plus... 

Experiments conducted in recent two decades indicated critical behavior in neural activity at different scales. Theoretically occurrences of these critical and power-law behavior can significantly facilitate brain activities correspondent to computation and memory tasks, but attaining the critical point essentially demands externally fine-tuning which has not been established yet. This fine-tuning often lies with placing system at transition point. Recent studies of group showed that a transition from synchronous to asynchronous phase could be achievable by a change in external parameters. At the very transition point, neuronal avalanches statistically demonstrate a power-law behavior which... 

Recently, to improve the dynamic behavior of Reinforced Concrete (RC) slabs under impact load, the methods of externally bonding Glass Fiber Reinforced Polymer (GFRP) sheets to slab and internally reinforcing concrete by steel fibers have been proposed. Nevertheless, it is required to investigate the comparison between these two methods on response of RC slabs under impact loads. In this study, the influence of volume fraction of steel fibers, the number of GFRP sheet layers (one or two) and the arrangement of GFRP sheets (covering the whole or parts of surface), are examined. Performance of fourteen mm concrete slabs including one plain slab, one steel RC slab, three steel RC slabs... 

A new one-dimensional, time dependent aerothermodynamic mathematical model and computer simulation of the gas turbine engine has been developed and is introduced herein. This code simulates the transient and dynamic operation of the gas turbine engine bye solving conservation equations, expressed as one dimensional, time dependent Euler equations, with turbomachinery source terms. The various component models, which provide the turbomachinery source terms to Euler equations, are described. Bye incorporating both explicit and implicit equation solvers, transient simulation of the gas turbine engine can be conducted efficiently while maintaining the capability of simulating dynamic events.... 

Contraction sections are an integral part of all wind tunnels, whether designed for basic fluid flow research or model testing. The location of the contraction, just upstream of the test section, makes it very important to achieve a high quality contraction design. The effect of a contraction on unsteady velocity variations is significant to increase the mean velocity. Furthermore, contraction has a suitable role on the turbulence reduction in a wind tunnel. The contraction itself further reduces the turbulence in terms of percentage of the wind speed. This is due to the increase of the wind speed by a factor equal to the contraction ratio. In this research, to investigation flow quality in... 

Transonic speed is one of the most important flight regimes. There are two main significances related to it. First, all of the supersonic air vehicles should pass through this regime to reach to their final speed. Second, nowadays most of the commercial airplanes fly in nearsonic speeds. According to nonlinear nature of the flow through the speeds, the related researchers haven’t been successful in development of a comprehensive theory as well as subsonic and supersonic ones. So, transonic flow is one of the most critical regimes in wind tunnel testing. In order to eliminate the shock-boundary layer interaction and wave cancellation, perforated walls and side suction are used in test section... 

The unsteady phenomena occur in rotors of helicopters, wind turbines and compressors. Investigation of the unsteady flow is a very important test, since it can affect and restrict the performance of rotors of helicopters and wind turbine's blades when operating at high angles of attack. Dynamic tests, such as pitching and plunging oscillations are one of the best methods for studying these phenomena due to the complexity of the unsteady flows. In analyzing the results of dynamic tests one must consider the interference effects of wind tunnel walls. Different investigations show that in dynamic tests, the interference effects of flow field around the model, wind tunnel walls and support of...