Sharif Digital Repository

Increasing requirements of industries and research institutes to analytical results of interaction soil-foundation related systems, reveals the importance of the dynamic impedance functions than ever before. The dynamic impedance function relations are presented for massless rigid foundations which is possible to obtain dynamic response of foundations for different frequencies and masses accordingly. In this study, the dynamic impedance functions were investigated using physical modeling tests on sandy soil with finite thickness soil stratum over bedrock. The tests were carried out inside a steel container of dimensions 110.8m in length, width and height respectively which was filled into... 

In this thesis will investigate control performance of coupled buildings. Control of this structures will done using friction dampers based on passive and semi-active strategies.
A numerical study is employed to simulate a coupled building equipped with passive friction damper by using OpenSees software framework.
Semi-active friction damper is used on three groups of adjacent buildings. At first, a mathematical model of coupled buildings is established for each group. The variable friction dampers consist of an actuator, which is based on a piezoelectric stack that alters the normal force at the contact area. A clipping control algorithm considered in the numerical study for the... 

Detecting defects in financial statements is crucial because such defects can impact the transparency, accuracy, and reliability of financial reports and influence the decision-making of stakeholders. This study aims to provide a novel approach for identifying defects in the financial statements of companies listed on the Tehran Stock Exchange. In this research, a defect is defined as a difference in data items between audited and unaudited financial statements, which may indicate either unintentional or intentional deviations or signal a potential fraud. The data for this study was automatically collected from the Codal system and includes both audited and unaudited financial reports in the... 

Delay Tolerant Networks (DTNs) are sparse networks in which intermittent connectivity happens due to energy shortage or high mobility and long latency is unavoidable.These networks have a wide range of applications in our daily life such as internet of moving things. In delay tolerant networks, finding an end to end path between source and destination is almost impossible. Therefore, routing can’t be done based on finding an end to end path but it has to be done based on hop by hop sessions. In this thesis, we aim to represent an efficient routing algorithm for delay tolerant networks that can improve delivery probability, delivery cost and delivery latency.Our proposed routing algorithm is... 

This study presents the application of the doubly fed induction generator (DFIG) to reduce the frequency deviation and improve frequency of a power system. This has been done by proposing a wind turbine model and a new fuzzy controller. The fuzzy controller has been suggested to change the speed of the wind turbine rotor and modify the impacts of wind speed fluctuations on the output power. The fuzzy controller parameters are optimized using the genetic algorithm (GA) to achieve the appropriate transient response. A smart controller is combined with fuzzy controller to optimize the usage of wind turbine’s kinetic energy. Furthermore, the DFIG with the proposed controller participates in the... 

Polar codes have received much attention to the extent that they are selected as a channel coding scheme in the 5G standard. The successive cancellation list (SCL) decoder suffers from high decoding Latency and limited Throughput due to its sequential decoding nature. Another polar decoding approach is the iterative belief propagation (BP) decoder which is inherently parallel and allows for better Decoding Latency and Throughput. However, its main drawback is an error-correction performance loss compared to the CRC-aided successive cancellation list (CA-SCL) decoder. From previous works, the CRC-aided belief propagation list (CA-BPL) decoder that benefits from the parallel structure of the... 

Super-resolution means increasing the resolution so that the quality improves. This is defined for both image and video. In this regard, machine-learning based methods, especially convolutional neural networks, have shown great potential in recent years. Finding the right structure that can deliver high speed and accuracy is the key to solving the super-resolution problem.Despite the myriad of methods for image super-resolution, less attention has been paid to its generalization to video. This generalization should be such that more detail is created in the output using adjacent frames.In this dissertation, the existing methods for image and video super-resolution are reviewed, and then a... 

In the proton exchange membrane fuel cells (PEM, the produced water would be divided into two phases of vapor and liquid. distribution of both liquid and vapor phases in different cell layers affects the performance, the efficiency and the life of a fuel cell significantly. Moreover, Nano pores of the cathode catalyst layer are involved with some phenomena such as electrochemical reaction kinetics, heat and mass transfer and interface phase change. One of the most important problems in the performance of fuel cells is distribution of liquid water in the porous areas. Water flooding in fuel cells causes to delay in oxygen transport to active sites in the catalyst layer because the pores of... 

The propagation behavior of Love wave in functionally graded magneto-electro-elastic half-spaces with a quadratic variation is addressed. The magneto-electromechanical coupling factor, the dispersion relations, electric potential, magnetic potential and displacement are obtained analytically for both magneto-electrically open and short conditions. The effect of gradient coefficient on phase velocity, group velocity and magneto-electromechanical coupling factor are plotted and discussed. Research on the wave propagation in magneto-electro-elastic materials is still very limited. This work provides us with a theoretical foundation to design and practically apply SAW devices with high... 

In this study, the interaction between thin plate completely bonded to the transversely isotropic halfspace and a concentrated force applied horizontally (Mindlin-type force) are considered. This problem has been solved analytically. This problem is used as sample for thin solid films and surface coating technology, where the surface of solid is covered by thethin plate for increasing its stiffness. Moreover, this problem is a good sample when homogenous solid is subjected to contact loading and can be seen that mechanical properties of material which is near the solid surface varies; consequently, a two-phase solid is created.Because of the influence of noted inhomogeneity, solid is... 

Hydrodynamics plays a crucial role in defining the performance of fluidized beds. The numerical simulation of fluidized bed is very important in the prediction of its behaviour. From this point of view, in the present study a dynamic two dimensioanl model is developed for the modeling of regenerator system of a UOP fluid catalytic cracking (FCC) unit of Abadan refinery with a high-efficiency regenerator. Of the various modeling and simulation techniques, computational fluid dynamics (CFD) is employed in this thesis. Effects of gas velocity, the transient local solid volume fraction, pressure drop for gas and solid phase, solid holdup distribution and solid circulation pattern have been... 

Privacy preserving data mining helps organizations and companies not only to deal with privacy concerns of customers and regular limitations, but also to benefit from collaborative data mining. Utilizing cryptographic techniques and secure multiparty computation (SMC) are among widely employed approaches for preserving privacy in distributed data mining. The general purpose of secure multiparty computation protocols to compute specific functions on private inputs of parties in a collaborative manner and without revealing their private inputs. Providing rigorous security proof of secure multiparty computation makes it a good choice for privacy preservation, despite of its cryptographic... 

The rapid growth of Android operating system alongside its open-source nature has made it as the most popular operating system of mobile devices. On the other hand, regarding the increasing computational power of mobile devices, a wide variety of applications are coming to this type of devices. Meanwhile unfortunately many malicious softwares trying to keep up with other applications, are targeting this popular operating system. Therefore with regard to the fact that this type of devices usually store private and sensitive information of their users, security of mobile operating systems is considered very important. Having this matter in mind, the goal of this research work has been... 

In this study, a new concrete slab stiffened by concrete pedestals and steel cables is introduced. The slab system is studied by employing both analytical and numerical methods. The steel cables are connected to the edges of slab and the concrete pedestals mounted at the bottom face of slab act as the middle supports of cables. The tension force in the cable and its inclination results in upward forces acting at the bottom face of slab. With the aims of classical theory of thin plates and the superposition technique, the problem of a simply supported rectangular slab stiffened by cables is studied analytically. The obtained results are verified by a numerical modelling implemented in SAP2000... 

The parametric study of a new introduced metallic yielding damper called telescopic damper is addressed. The telescopic damper comprises of three concentric steel pipes connected together by lead shear keys. The inner and outer steel pipes are subjected to axial loading which results in the shear yielding of the embedded lead cylinders. The inner steel pipe has a lock which limits its movement to some certain extent and beyond this limit the outer tube activates. Employing ABAQUS software, the behavior of damper under cyclic loading is studied numerically. The finite element model is verified by available results in the literature. The effects of inner and outer steel pipes thickness,...