Sharif Digital Repository

Active Learning Method (ALM) is a soft computing methodology which has been used for modeling and control. Unlike the good results of ALM’s ability, there is not any analytic expression to prove its power, because ALM’s main operators don’t satisfy fuzzy S-norm & T-norm properties. This problem considered from three viewpoints: Mathematics, Geometry and fuzzy sets. In this paper, we try to introduce two new operators based on morphology to satisfy three conditions: at first, they must be fuzzy S-norm and T-norm to confirm the committal of fuzzy set theory. Secondly, they must satisfy Demorgans law, because they are complement of each other. And finally, they resemble the main operators of... 

Using appropriate box as an artificial boundary condition is one of the critical tasks in geotechnical physical modeling of the soil mass especially under cyclic loading such as earthquakes. In general there are two types of boxes which can simulate boundary conditions of scaled models as rigid or flexible conditions. Main purpose of this study is design and construction of a flexible box in a way that effects of boundary condition have been minimized during tests. Construction of this box is the first step of an investigation project which concern to evaluate the effect of lateral spreading as a result of liquefaction on deep foundations of bridges, piers, harbors by using shake table test... 

Liquefaction induced lateral spreading is defined as the lateral displacement of mildly sloping grounds or those ending in free faces as a result of liquefaction in subsurface soil layers. Damages imposed by lateral spreading on pile foundations supporting different types of structures such as ports, bridges and buildings are usually observed in large earthquakes. These potential damages are of high degree of importance in southern and northern coastal areas of Iran where several ports and critical facilities are located. River banks all over the country where bridge piers exist are also among the areas prone to potential damages. Evaluation of the effects of lateral spreading on existing... 

Liquefaction-induced lateral spreading has imposed severe damages to many important structures supported on pile foundations during past earthquakes. As a result, evaluation of pile response to lateral spreading is an important step towards safe and resistant design of pile foundations against this destructive phenomenon. The boundary conditions for physical modeling in problems of earthquake geotechnical engineering have significant influence on the test results. In order to reduce the undesirable effects of boundaries on the model responses, the flexible containers are used. The flexible containers are those in which the shear stiffness of the walls is proportional to the soil inside. A... 

Nowadays, swift development of cellular network with the increased penetration rate, have made mobile voice channels widely available almost everywhere with higher priority comparing to the other conventional channels, e.g., GPRS, EDGE, HSDPA and etc. Leveraging on this fact two important utilization can be considered. The first one is related to urgent transmitting of vital data. As mentioned earlier, since this channel deems to be available everywhere and, recalling its priority, it is even accessible in congestion condition, it can be exploited as an efficient way to transmit small volume of emergence data urgently. Transforming the crash data on the road is an example of utilizing such... 

The phenomenon of lateral spreading occurs as a consequence of earthquakes induced liquefaction in grounds with mild slopes or ending to an opening. This phenomenon has caused many damages to deep foundations and associated structures. Therefore, it is necessary to study and estimate the forces which may be induced by lateral spreading to these structures. Due to the complex mechanism of the effect of lateral spreading on the piles, various tests have been carried out in the form of shaking table as well as centrifuge tests. According to the results of these tests, the forces applied to the piles are significant and can cause crucial damages to deep foundations. On the other hand, because... 

During the past earthquakes in all over the world, the piles have had serious damages in soils with liquefaction potential. During an earthquake, liquefaction occurs in some parts of ground with mild slope and saturated and soft granular soil. Afterwards lateral spreading induced by liquefaction incurs irreparable damages on structures and piles particularly. Observing these damages, the researchers and engineers have conducted more surveys and investigations to studying the behavior of piles in granular soils with liquefaction potential and also interactions between  soil  and pile.  In  these  researches,  they have  modeled  the  interactions between  soil  and pile.  However  there are ... 

A social network is a social structure made up of individuals (or organizations) called ”nodes”, which are tied by one or more specific types of interdependency. These networks are new forms of distributed larg media which actually plays a critical role in distributing information and news among the people. because of the size and autonomos aspect of these kind od medias, taking control of them seems impossible. with the best hope we could think of some ways to detect information cascades through network.for example we could select a set of nodes as sensor inorder to detect information cascades as effectively as possible. in this thesis we studied cascade detection problem in scenario based... 

Complex networks serve as generic models for many social, technological and biological systems that have been shown to share a number of common structural properties such as power-law degree distribution and small-worldness. These networks determine interactions and influence the spread of diseases, behaviours and ideas. Epidemics and failures like new behaviours ideas and innovations can spread throughout a network and prevent it from doing its functionalities. In this work, we investigate error and attack tolerance of epidemic spreading in complex networks. The main content of this thesis is arranged in three sections as follows: Firstly, the effect of random and systematic failures is... 

Market making is a fundamental trading topic in which an agent creates liquidity in an asset by offering to buy and sell on that security. The challenging problem in market-making is related to inventory risk, which may cause the accumulation of unfavorable positions at the end of the market and create losses. Algorithms are designed for making trades to choose the buying and selling prices and the number of orders by predicting the price to minimize the amount of security in the market maker’s portfolio. In this paper, first, we examine the different market-making algorithms and evaluate their performance in the financial markets of Iran. Then, a model using the reinforcement learning... 

The extraordinary ability of the human brain to solve various problems has led scientists to simulate models of the human brain. One of these simulated models is artificial neural networks. Today, the power of artificial neural networks is not overlooked. The ability of artificial neural networks to solve various types of issues led us to use the thesis to solve some of the graph-based problems. Quite accurately, this graph-based problem is a matter of identifying the source of rumor in a network. In many graph networks, whether natural networks such as the network of neurons in the human brain or synthetic ones such as the types of social networks, it is possible that a rumor spreads across... 

In this thesis, we propose a new compressed-sensing-based algorithm for unmixing of hyperspectral data, and show that the reconstruction quality could be significantly improved. In addition, we illustrate that by utilizing this approach, we can achieve an approximate estimation of the Point Spread Function (PSF) of the hyperspectral images. In this way, we first assume that the PSF belongs to a specific family of functions, such as Gaussian, then, by sweeping the parameters of the assumed PSF, we obtain the abundance coefficient matrix of the reconstructed image. Now, by choosing the sparsest coefficient matrix as the best one, we estimate the corresponding PSF. Then, we further investigate... 

Achieving various data rates over a wide range of applications and in a multiple-access scenario should be done under certain power and bandwidth constraints. Emerging UWB communications has opened a novel perspective against different wireless network challenges, especially overwhelming data rates. In the research field, we begin our thesis with exposition of UWB, narrowband interference and spread time codes. We elaborate on the properties of spread time codes through frequency domain analysis of a reusable multiple-access scheme. Evaluating the variance of ISI, MAI and RUI, we demonstrate the spread time codes behave in an optimum manner, i.e., the most RUI resistibility, along with all... 

The average annual turnover of Iranian mutual funds is 330 percent during the years 2011 to 2017. Such a high-volume trading imposes substantial transaction costs on the funds and their investors. Transaction costs comprise four different types of costs: In addition to taxes and commissions, there are other transaction costs originating from bid-ask spread and price impact, which need more complicated procedures to assess. By using high-frequency data and the information in the fund’s seasonal financial statements, the transaction costs of fifteen Iranian mutual funds are estimated. These funds spent 11 percent of their value on the trading costs per anum. Furthermore, the relation between... 

The phenomenon of soil liquefaction has caused significant damage to deep foundations of engineering structures such as bridges and buildings in past earthquakes. In recent years, many researchers have studied the effects of soil liquefaction on the pile response, but there are still many unknowns that require further research and study. The present study is part of a comprehensive research that involves several Ph.D. and master students at Sharif University of Technology (SUT). In this study, the effects of soil liquefaction on two pile 2×2 groups (one with a lumped mass and another without) in a level ground with a sloping bed were investigated. A surface non-liquefied layer was also... 

Selective laser sintering is an additive manufacturing technique based on fusion of powder bed, wherein after spreading a powder layer, a focused laser beam directs onto selected points of powder bed to fuse powder particles together. This process is repeated layer by layer until the final part is created. Although utilization of blade as a conventional powder spreading (CPS) mechanism has a good compression ability, the fixed contact line between blade and powder bed surface results in improper powder flowability and increasing shear forces applied on underneath layer. In this study, in order to obtain the basis for conducting practical experiments, discrete element simulation of powder... 

The lateral movement of a liquefiable layer on gently slopes is the most visible and devastating type of liquefaction-induced ground failure. Occurrence of liquefaction in sloping ground causes large deformations on ground surface, which may lead to several meters in some cases. Recent earthquakes have shown that this phenomenon causes severe damages to coastal structures, piers of bridges and life-lines, by exerting large lateral forces. In this research, a fully coupled two-dimensional dynamic analysis has been used to simulate the lateral spreading phenomenon and to evaluate the magnitude of deformations occurred in liquefiable soils. The critical state bounding surface elastic-plastic... 

Lateral spreading due to liquefaction and resulting destruction of buildings is important in Iran because of high seismicity and important infrastructure near south and north coasts of Iran. Lateral spreading is vast lateral movement of sloping ground or level ground ending in an opening like river which is caused by earthquake inducedliquefaction. For considering the effects of lateral spreading during design of deep foundations of structures in a susceptible area, one needs to determine the lateral loads on piles under lateral spreading. Present study investigates the behavior of a 3x3 pile group against lateral loads due to lateral spreading with numerical methods using OpenSees software.... 

Human brain is one of the most wonderful complex machine which is designed for ever. A huge complex network, composed of neurons as tiny biological and chemical processors which are distributed and work together as a super parallel system to do control and vital activities of human body. Today the main secrecies of operation mechanism in individual neurons as fundamental elements of brain are reasonably understood, but network interactions of this wonderful processors and full understanding of information coding in brain seems elusive and remains as a big challenge in many interdisciplinary fields of science, from biology to cognitive science and engineering.
Thus human brain learning... 

One of the risk factors of financial assets is liquidity. Identifying factors affecting liquidity helps us to predict stock liquidity and to control the risk of investing. The purpose of this research is to identify these factors in Tehran Stock Exchange. We use the data of 48 companies between1388 and 1392. Our results show that the liquidity follows a weekly and a monthly cycle. Stock return, market return, stock return volatility, market return volatility and trading volume are among the factors which affect stock liquidity. In addition, the reaction of liquidity changes to positive or negative stock return is asymmetric, and the effect of negative stock return is more influential. Our...