Sharif Digital Repository

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 study, the simulation of blood flow through a stenosed coronary artery and a bypass graft are discussed using fluid-structure interaction numerical method. Effects of the geometrical parameters of CABG surgery on hemodynamics have been studied. Investigated hemodynamic variables include shear stress on the vessel wall, the velocity profile in high-risk areas and the pathlines. Lower than 0.5 Pa shear stress on intimal layer of arteries causes the formation of plaque on the wall. Angle of 30 degrees and diameter ratio of bypass to host artery of 1:1 are proposed as the optimum geometry. The distance of the anastomosis from the site of occlusion has no effect on surgery. Also,... 

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... 

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... 

Rate splitting multiple access (RSMA) is an efficient approach that divides massages in space and power domain in specific time and frequency in order to control interference. Therefore, in this approach, the goal is linear precoding and power allocation on the transmitter side and successful interference cancellation (SIC) on the receiver side. On the other hand, integrated sensing and communication (ISAC) is an emerging technology in the new generation of communications (six generation) in which the process of sensing and communication can be done by same hardware and in a same frequency band so it can be more cost-effective. we can use RSMA in ISAC system in the applications which we aim... 

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...