Sharif Digital Repository

In wireless communication systems increasing the gain of antennas is seminal to increase in coverage and data transmission rate, and reducing the possible errors. One of the main factors for improving the antenna gain is matching the polarizations of the transmitter and the receiver antennas. Towards this end, both the transmitter and the receiver antennas should have the same axial ratio, specific direction and polarizations. As far as the flexibility of the direction angle between the transmitter and the receiver is concerned, the so-called circular polarization is preferred do the linear polarization. The antennas with circular polarizations are prominently utilized in satellites,... 

Nowdays a large number of companies are faced with Big Data processing. Due to the lack of budget or time, it may not be possible to process all the input data. Data variety is one of the main features of Big Data. Considering Data variety can help us to solve the problem of resource capacity. In this research, we focused on the impact of data variety on the performance of Big Data processing. In the first part, we offer a solution for increasing the performance of progressive Big Data processing. We provide a simple low-overhead mechanism to quickly assess the significance of each data portion, and show its effectiveness in finding the best ranking of data portions. We continue by... 

Microelectrode array technology is a broad platform for studying and characterization of the electrophysiological properties of excitable tissues derived from both brain and heart in vitro. Microelectrode arrays can either record or stimulate cells by accessing multiple sites of neural networks and cell tissues and detect signals from all sources around each electrode simultaneously. By using recorded signals, one can detect cell potential changes and its minor fluctuations. Unlike intracellular recording techniques, the noninvasive interface of microelectrode arrays with cells provides durable studying of neural networks and cell tissues. Using related microelectronics fabrication... 

This study has focused on the important problem of landing on a planet as an important current and future space mission. In this regard, dynamics modeling and integrated state estimation and control problems have been investigated in different views. To this aim, first a novel concurrent representation for translational and rotational kinematics has been developed based on the extension of modified Rodrigues parameters to dual space. This parameter set, called dual modified Rodrigues parameters (DMRP), is then utilized to establish an integrated roto-translational dynamic. The proposed DMRP-based kinematics and dynamics have been verified via comparison to traditional methods of... 

Currently, quantum noise stands as one of the foremost challenges in the realization of quantum algorithms and the development of quantum technologies. Consequently, finding methods to eliminate or reduce the impact of noise is imperative. This thesis explores the possibility of correcting the expectation values of observables on a quantum system, specifically a qubit quantum system experiences quantum noise, given partial knowledge of the noise. We begin by reviewing essential background information, including some of the most common methods for correcting noise, with a particular focus on the noise deconvolution technique. Subsequently, we introduce our method for correcting the... 

The increasing number of road accidents and fatalities have yielded the introduction of several solutions by related industries such as automobile manufacture. Proposed solutions can be classified into two categories: passive, such as airbags, and active such as ABS ad ITS-based technologies. Inter vehicles communication let the communication between vehicles(V2V) or between vehicles and road infrastructure (V2I) by relying on DSRC technology and standards. Intelligent Transportation System (ITS) has three main types of applications namely safety, traffic and commercial. Safety applications are the main goal of vehicular communication, and real time guarantee in safety applications is so... 

Solute-solvent and solvent-solvent interactions were investigated in mixtures of ethylammonium propionate with methanol, ethanol, isopropanol and propanol. Solvatochromic parameters, including normalized polarity ( ), polarity/dipolarizability (p*), hydrogen-bond donor (a), and hydrogen-bond acceptor (ß) abilities, were determined in these mixtures. Parameters showed synergetic effects in mixtures of ionic liquid and alcohols due to the preferential solvation. General polarity shows an ideal behavior in all mixtures, polarity/dipolarizability exhibit increasing profile in all mixtures preferential salvation caused nonideal behavior for hydrogen-bond acceptor parameter Solvent... 

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... 

In this study insitu Al-Al3Ti-Al2O3 nanocomposite has been fabricated based on thermal decomposition of tialite (Al2TiO5) precursor in aluminium matrix through powder metallurgy method. Also the effect of high energy mechanical milling and hot extrusion on this procedure has been investigated. In the first step nano-structured tialite were synthesized through citrate sol gel methods. Then, different volume fraction of tialte was mixed with aluminium by high energy vibratory milling. The results of X-ray differaction analysis, scanning electron microscopy and differential thermal analysis showed that mechanical milling can degrade stability of tialite and cause strain-induced decomposition,...