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... 

Let G be a graph with adjacency matrix A and Δ be a diagonal matrix whose diagonal entries are the degree sequence of G. Then the matrices L = Δ− A and Q = Δ+A are called Laplacian matrix and signless Laplacian matrix of G, respectively. The eigenvalues of A, L, and Q are arranged decreasingly and denoted by λ1 ≥ · · · ≥ λn, μ1 ≥ · · · ≥ μn ≥ 0, and q1 ≥ · · · ≥ qn ≥ 0, respectively. The energy of a graph G is defined as E(G) :=
n
i=1
|λi|.
Furthermore, the incidence energy, the signed incidence energy, and the H¨uckel energy of G are
defined as
IE(G) :=
n
i=1
√
qi, LE(G) :=
n
i=1
√
μi, HE(G) :=

2
r
i=1 λi, n=... 

A traffic classifier maps each input stream into a pre-defined traffic class. If the traffic is encrypted using a protocol, such as SSL, or is protected using an encrypted tunnel, it's content would be hidden from the classifier, in which case the common traffic classification methods will be ineffective. Although common security mechanisms which provide information confidentiality to user can't hide all properties of messages, including length and time. Some of the newly presented methods of traffic classification utilize these properties and can actually classify messages without accessing their content. We will study such methods and their limitations in this thesis. Of all the encrypted... 

Drilling Operations constitute more than fifty percent of total costs of well construction operations. Due to this fact, optimization of drilling operations could have significant effect on decrease in total costs of well construction. It is mentioning worthy that there are a variety of parameters which affect drilling operations from the view point of optimization. In many cases several of those aforementioned parameters are contrary in nature. Thus obtaining an integrated approach to optimize the operation by considering these effects is necessity. The goal of this thesis is to investigate different influential parameters of drilling operation optimization and to develop computer-based... 

Scale formation is an unpleasant phenomenon that occurs when the mixed fluids are incompatible. The scales damage the reservoir, wellbore and the surface facilities. They reduce the effective fluid path and increase the pressure drop of the system; so it is necessary to study the precipitation thermodynamics of scale formation, and present a trustable method for banning the scales from precipitation. In this project, it has been tried to study the value of precipitated scale due to the mixing of two incompatible waters (Civand and Sea Water). The results of which are compared with the results of a geochemical software named PHREEQC. Then, the performance of hydro chloridric acid as a scale... 

We report on numerical and intelligent modeling of three-dimensional laminar flow of non-Newtonian fluids driven by axial pressure gradient in annular media consisting of a coaxially rotating inner cylinder. This is an example of a rotating Couette flow with vast applications in food, oil and gas, and chemical engineering industries. We study the dynamics of pressure in and the velocities (in three directions X, Y and Z) of every grid in presence of rotation and without that by means of CFD. Afterward, we develop a novel predictive model based on an Artificial Neural Network (ANN). The hybrid ANN framework is trained and tested by over 100000 data which collected by CFD. We then perform... 

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... 

In this dissertation, we introduced a Fuzzy based representation and comparison method for sequential patterns such as speech and online handwriting. The new model, called Fuzzy Elastic Matching Machine (FEMM), is simpler than traditional HMM based approaches and is not based on the common statistical assumptions of HMM systems. The model was tested on isolated word and phoneme recognition tasks in speech recognition domain and isolated letter recognition in Persian handwriting recognition. We showed that this method is faster than traditional HMM based models and more robust to noise. To train the model, we introduced a Symbiogenesis-based evolutionary training algorithm. This algorithm...