Sharif Digital Repository

Recently, computer scientists and economists have defined many joint problems and cooperate widely in various areas. Importance of this interconnection is clear for everybody, now. New works have been conducted, nowadays, to use the daily - increasing web-based social networks in viral marketing for improving companies profits. The main problem which is proved to be NP-Complete in this context is about discovering k most influential nodes in a network. In this dissertation, we generalize the problem to a group-based version and we we use group-based advertising to achieve our main goal. A new algorithm called Group-Based Diffusion technique is proposed in this thesis for solving this problem... 

Origin-destination (OD) matrix is one of the most important sources of information used in planning and management of transportation networks. Estimation of a precise OD matrix is a fundamental component for enabling the administrative authorities to optimize the use of their transportation network. Traditionally, urban planners use direct approaches including household questionnaires to estimate OD matrices. These methods are time-consuming and costly. Strategies that are more recent like Bluetooth, Wi-Fi, and RFID scanners and detectors include deficient precision and the additional cost of accessories. Exploiting GPS technology in spite of its high locating accuracy, due to user... 

Visual odometry(VO) is the process of estimating the egomotion of an agent(e.g., vehicle, human, and robot) using the input of a single or multiple cameras attached to it. Application domains include robotics, wearable computing, augmented reality, and automotive. The term was chosen for its similarity to wheel odometry, which incrementally estimates the motion of a vehicle by integrating the number of turns of its wheels over time. Likewise, VO operates by incrementally estimating the pose of the vehicle through examination of the changes that movements induces on the images of its onboard cameras. For the VO to work effectively, there should be sufficient illumination in the environment... 

In neural systems of living organism, moreover than differences in anatomic structure of cells, there is also differences in physiological functions of analogous cells.Specification and categorization of neurons based on physiological functions is one of objectives of neuroscience. Study of cognitive behaviors and systematic study of neural system, modeling and practical applications in neural prosthesis design are some of applications of categorizing neural cells. Neural signals can be studied by Spike rate of a single neuron activity or Local Field Potential (LFP) of a finite number of neurons. In previous studies neurons of first visual cortex are divided into two groups of simple and... 

In this study, for the first time, a comprehensive and online framework for active control of beams subjected to the moving mass is presented. In active control problems, comprehensive knowledge of system states is required to determine the control force, but it is not possible to measure all system states in practice with a limited number of sensors. In this regard, Kalman filters are introduced to control systems to help improve the performance of control systems as observers of system states. However, in the case of beams subjected to the moving mass, due to the moving nature of the passing mass, in addition to system states, it is also important to identify the input load. In previous... 

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,... 

An important class of applications which have been rapidly growing recently is the one that create and use time series data. These types of data sets are ordered based on the timestamps associated to their data items. In practice, traditional relational databases are unable to satisfy the requirements of these data sets; however, NoSQL databases with column-wide data structure are appropriate infrastructure for them. These databases are very efficient in read and write operations (especially for time series data, which are ordered) and are able to store unstructured data. Time series data may contain valuable and sensitive information; hence, they should be protected from the information...