Sharif Digital Repository

In some high voltage applications it is necessary for high voltage power supply (HVPS) to operate over a wide load and gain range. For instance a HVPS may be used to supply various microwave tubes. Our goal in this thesis is to design a HVPS which can provide a DC voltage between 0-15 KV and 0-5 KW. In convetional approaches, operating over wide load and gain range necessitates the switching frequency or duty cycle to swing over a wide range. This approach may disturb soft switching, consequently switching loss will increase. The control process will be more complex too. the wide swing range of switching frequency means that the HVPS needs to operate with low switching frequency too.... 

In this study, biosorption of selenium by Pseudomonas putida bacteria was investigated in both single and binary uptake systems. Bacteria cells were immobilized in the chitosan beads, to study impact of microorganism entrapment on the sorption capacity of the fabricated adsorbent. Uptake capacity increased by the entrapped bacterial weight percent up to 20 wt. %; but thereafter, sorption capacity gradually leveled off with an increase in the loading percentage of the bacterial cells.The effects of the three process variables including pH (2-6), biomass dosage (0.5-2.5 g/L) and initial concentration of selenium (50-250 mg/L) on the uptake performance of adsorbent were investigated, and... 

In this research, the separation of tetracycline (TC) as a pharmaceutical pollutant from water using a nanofiltration membrane process was investigated. For this purpose, a set of polymer-based nanofiltration membranes containing various amounts of the metal-organic framework (MOF-808) which are stable in water, were prepared via the phase inversion method. Due to the hydrophobic nature of the polysulfone and its tendency to fouling in the membrane filtration process, MOF-808 particles were used as agents to enhance the hydrophilicity of the membrane surfaces. In order to achieve this goal, MOF-808 was synthesized via solvothermal method and activated using two different methods:... 

Ducted fan vertical take-off and landing (VTOL) aerial vehicles have drawn many attentions in the world because of their capability to offer high power to weight ratio for a certain vehicle diameter relative to open rotors or helicopters. However, due to inherent uncertainties in dynamics and inefficient and poor quality responses, significant control challenges are still unsolved and exciting fields for research. In the current study, a nonlinear dynamic model is proposed for the controller design purpose. This model is validated against simulation by performing several standard scenarios. An adaptive control method, named model reference (MRAC), is utilized to design a perfect controller... 

In this thesis we want to discuss about a new approach about information. Using this approach, Scott Muller builds his formalism on two basic concepts: distinguishablity and symmetry. His claim is that there is an inverse relation between symmetry and information. It means that if we have a symmetric system we need less information (Than an asymmetric system) to describe it. Here, we are going to explore the role and significance of symmetry in probabilistic distributions of the double-slit experiment, and we want to show if there is a predetermined relation between symmetry and information or not.
 

In this work, A new hybrid approach is presented to optimize a trajectory of Micromechanical Flying Insect in an obstacle reach environment. Here, a singleobjective Evolutionary Algorithm is utilize for finding solutions corresponding to multiple conflicting goals, which include minimizing the length of the path while maximizing safety margin by avoiding hard and non-moving obstacles. On the other hand, dynamic constraints of Micromechanical Insect such as maximum and minimum attitude angles and speed should be taken into account. In order to reduce the computational cost, a novel hybrid two-layer procedure is suggested for trajectory optimization. In the first layer, the algorithm generates... 

Identification of dynamic behavior and extraction of mathematical model for aerial vehicle is important in design, test and evaluation processes. Due to explosion of unmanned vehicles industry in recent years, many innovative aerial concepts is introduced. Coanda-effect air vehicle is one of these novel ideas which is similar to flying saucers. In this study, an experimental scale model of this air vehicle is designed, built and tested with purpose of identifying the linear dynamic model of the vehicle, using the frequency domain identification methods. Performing the system Identification in hover requires a stable hovering capability in the vehicle. Given the inherent instabilities of... 

Undoubtedly, the concept of information has an outstanding role in our description of physical systems and biological processes. In the framework of pragmatic approach, information is a useful notion through which any physical event gets its significance. In this approach, information can be understood and recognized while it is capable of producing new information. Thus, the meaning of information depends on our recognition and understanding as conscious beings. Accordingly, the following question may arise: where is the role of conscious being in the emergence of physical properties in Nature? To answer this fundamental question, we first investigate how information enters the physics, in... 

In this study the concept of the origin of life, as an important question, is investigated and reviewed.Then the possibility of the beginning of life from an extraterrestrial origin is studied via spectroscopy methods to analyze the role of the cosmic waves.Moreover, by considering the similarity between the chirality of the essential amino acids and extraterrestrial amino acids, found in meteors the various methods for studying the structure of molecules, as well as the possibility of the transfer of the central elements of life from space to the earth are reviewed in details.Finally, we suggest how chirality might be emerged due to the interaction of the molecule with the environment,... 

Although quantum mechanics has thrilled a multitude of successes since its birth, it has also generated puzzles that persist to this day. These puzzles are largely connected with the role of measurement in quantum mechanics. Therefore, we are dealing with individual phenomena and that our possibilities of handling the measuring instruments allow us only to make a choice between the different complementary types of phenomena. Within the framework of delayed-choice experiments, the choice between complementary types of phenomena is postponed to the moments after the preparation of system is a superposition state. Regarding the probability theory, we have concluded that the delayed-choice... 

The formation flight of satellites corresponds to a group of small satellites, performing the mission of a presumed larger and more expensive satellite. Usually mission designers tend to put these satellites in such orbital configurations that their trajectories do not intersect. Although a stable configuration in a certain collision-free orbit is desirable for long term purposes, most of the missions including maneuvers like forming or changing a configuration and inserting new satellites need to be planned using a proper path planning algorithm. In this thesis, a path planning algorithm is suggested that acquires the optimal and impact-free trajectories for a group of satellites for...