Sharif Digital Repository

MIMO radar is a next generation radar which transmits arbitrary waveforms at each one of its apertures. It has been shown that design of waveforms for MIMO radars in order to synthesize a desired spatial beampattern, is mapped into a waveform correlation matrix (R) design in the narrowband case. Therefore, waveform design in MIMO radar for beamforming could be broken into two steps, namely correlation matrix design and waveform synthesis for achieving given R. As of now, given a desired beampattern or estimated location information of targets, calculating R has been modeled as an optimization problem like SDP. Also, in some special cases like rectangular beampattern, close form solutions for... 

Ethylene process is one of the most complex systems in petrochemical industries.The first section of the ethylene plant is the cracking furnace.The radiant section of predicted olefin furnaces is symmetrical with respect to a plane through the center line of the furnace and at an angle of 90° with the side walls. There are a total of 24 vertical radiant coils located centrally in the firebox wherein, bottom andside wall burners supply the heat necessary. Each four coils known as a ZONE so, as a result there are six zones, called zone A through F. Failures(rapture, creep, material degradation) rate on the coils decreases from zone A to zone F (A, B, C, D, E and F) respectively.From... 

In this thesis, we simulate the competition between some investment strategies based on dividends with each other and with mean-variance strategy (Markowitz) in an evolutionary finance framework. We perform simulations by two different approaches. In the first one, we use real dividend data and, in the second one we use dividends that are generated according to a dividend factor model. The dividend factor model which relates the dividends to the macro-economic factors is estimated from data using principal component analysis. Our simulations show that in this competition, the evolutionary portfolio rule will eventually hold the total market wealth. According to this simple rule the portfolio... 

For a Banach space E and a compact metric space (X, d), a function F : X → E is a Lipschitz function if there exists k > 0 such that ∥F (x) − F (y)∥ ≤ kd(x, y) for all x, y ∈ X.The smallest such k is called the Lipschitz constant L(F ) for F . The space Lip(X, E) of all Lipschitz functions from X to E is a Banach space under the norm defined by ∥F ∥ = max{L(F ), ∥F ∥∞}, where ∥F ∥∞ = sup{∥F (x)∥ : x ∈ X}.Recent results characterizing isometries on these vector-valued Lipschitz spaces require the Banach space E to be strictly convex. We inves- tigate the nature of the extreme points of the dual ball for Lip(X, E) and use the information to describe the surjective isometries on Lip(X, E) under... 

In this thesis, we deal with the problem of direction of arrival (DOA) using single-snapshot samples taken from multiple source signals by an array of sensors. The array we are looking for in this work is a uniform linear array. There are many ways to solve this problem, including MUSIC and Prony. But one of the few methods that are able to estimate correctly with single-snapshot samples with incomplete uniform linear arrays in compressed sensing base algorithms. In the first step, we can estimate the data of a incomplete uniform linear array by arranging them in the form of low-rank Hankel matrices and using leverage scores and minimizing the weight nuclear norm. If the weight matrices are... 

The purpose of Direction-of-arrival(DOA) estimation in MIMO communication networks is to find the direction of signals that are mixed together and mixed with noise by using an array of multiple receiving antennas. DOA estimation is an important issue in array signal processing. The traditional methods for DOA estimation try to solve this problem with mathematical algorithms. For example, some of these methods are based on parameter estimation; such as DOA estimation methods using maximum likelihood estimation methods. Some of other traditional methods are based on subspace decomposition; Like the famous MUSIC method. The traditional methods of DOA estimation usually have a drawback, and that... 

Economical strategy of developed countries imposes to improve energy efficiency and a rational renewable energies usage in the buildings. Ground source heat pumps are one of the most important tools in the way moving toward this goal. This study focuses on studying the effect of applying different refrigerants in the direct expansion ground source heat exchangers. In order to compare the performance of the ground source heat pumps using different refrigerants, a specific methodology is presented and implemented. First on this study, the thermal performance of a geothermal borehole filled with both CO2 and a zeotropic mixture of CO2 and R32 (20/80) is studied and the quality, temperature, and... 

The rapid development of scientific areas in this modern era makes the process of finding new field of research slow and laborious for prospective scholars. Thus, having a vision of the future could be helpful to pick a right path for doing researches and ensuring that it is worth to invest in. This thesis seeks to predict research trends by using link prediction approaches on keywords network and discusses about the performance of various algorithms in different situations. Moreover, for the last part of the experiments, novel link prediction algorithms are proposed by the author, enhances the accuracy of prediction results. The data set collected from Sciencedirect and Scopus by a strong... 

In this thesis, the impact of both time offsets (TOs) and carrier frequency offsets (CFOs) on the average output signal-to-interference-plus-noise ratio (SINR) of OFDM systems is investigated with a novel and simple approach. First, TOs are partitioned into five cases based on how they occur. Then the mathematical models for different cases are derived. Considering CFOs and benefiting from the obtained models, closed-form expression for the SINR in each case is derived. It is proved that, SINR is independent of the observed subcarrier for the given TO and CFO. Besides, it is shown that the performance of the affected system deteriorates rapidly as the number of subcarriers increases. It is... 

Nowadays increasing demands of Bandwidth, higher data rate and efficiency cause a huge and novel challenges in communicational systems. One of the recent innovative idea to satisfy these increasing demands is Heterogeneous Networks. Compressive deployment of small cell in Heterogeneous Networks can fulfill a large number of satisfactory parameters in wireless networks. After first Presentation of Heterogeneous Networks idea, loads of structure based on them was proposed.In this Research we consider two outstanding and common structure for this technology and analyze the user association and resource allocation problem at their specific structure. The first one is equipped with simple... 

In recent years, base station coordination (also known as network MIMO) has been analyzed as a means of handling inter cell interference. In principle, all base stations might share their CSI and data through backhaul links. Unfortunately, the demands on backhaul capacity and computational power scale rapidly with the number of cells, which makes this approach unsuitable for practical systems. And these problems shift the researches to find ways for turning this idea to an idea that can be used in practical systems. One of the major changes to this idea can be dealing with local CSIT that there would be no need to exchanging CSIT among BSs. The other change that can make the idea to a more... 

The purpose of ranking Persian web pages is to retrieve the highest number of relevant documents related to the search query of Persian language users, with the minimum number of documents returned from the web. Information retrieval is one of the key issues in search engines. In this study, billions of documents were collected from Persian web pages, and due to infrastructure limitations, a few hundred million documents were indexed in a database like Elastic. Now, considering the user’s actual query, relevant documents should be retrieved from the indexed documents. To achieve this goal, a large Persian language model was needed. Existing large language models for Persian were not usable...