Sharif Digital Repository

With the recent developments in power electronics and electrical drives, there is a need for precise position sensors today more than ever. Having high precision and high reliability in harsh environments, resolvers are the most preferred position sensors among other types of prevalent position detectors. In order to control linear machines, which are widely used in different industries, linear resolvers are employed. This project aims to propose a structure for tubular variable reluctance resolvers, formulate an analytical model for and optimize the proposed structure. In addition to having an acceptable precision, the proposed model should be less time-consuming compared with finite... 

This project aims to study a situation in which several projects must be selected. The decision makers should select a subset of these projects taking into account the limitation of resources and scheduling. Project selection models generally do not consider schedule of project activities as part of selection process. On the other hand, except the cases where only one project is under process in each period, prioritizing the selected projects is not optimal not considering their scheduling. Projects scheduling in project activities level may increase the complexity of decision making for portfolio selection and expand the area of search for selection of projects portfolio. Therefore, all the... 

In many industries, including oil and gas industries, power plants, refineries, petrochemicals, steel and cement industries, industrial complexes and consumer industries, there are tanks for storing materials. It is necessary to measure level of products while they are stored in tanks of different sizes. Ultrasonic is one of the non-contact and accurate measurement technologies that can provide a suitable solution for liquid tank monitoring. The purpose of this thesis is to design and build the electronic parts (transmitter and receiver circuits) of an ultrasonic system that is capable of detecting levels at a distance of less than 5 meters with an accuracy of 0.5 % full scale. In this... 

Nowadays, with the increasing need of various industries and applications to directly create linear motion, linear resolvers are attracting more attention than ever. Achieving high accuracy as well as measuring absolute position leads to the introduction of a new generation of resolvers, called multi-turn resolvers. Usually, a multi-turn resolver consisted of two individual resolvers in one frame, while using a common core for both resolvers can help to make the multi-turn sensor smaller, cheaper, and lighter. Nevertheless, the studies conducted on linear and multi-turn resolvers are very limited. Therefore, this research proposes an integrated core linear variable reluctance multi-turn... 

By generalizing dictionary learning (DL) algorithms to Multidimensional (MD) mode and using them in applications where signals are inherently multidimensional, such as in three-dimensional (3D) Inverse Synthetic Aperture Radar (ISAR) imaging, it is possible to achieve much higher speed and less computational complexity. In this thesis, the formulation of the Multidimensional Dictionary Learning (MDDL) problem is expressed and six algorithms are proposed to solve it. The first one is based on the method of optimum directions (MOD) algorithm for 1D dictionary learning (1DDL), which uses alternating minimization and gradient projection approach. As the MDDL problem is non-convex, the second... 

In this research, oscillation in control loop caused by control valve stiction, external harmonic disturbance, poor controller tuning or their combination, is recognized and compensated. In control valve stiction based study, flaws in one of the important modeling methods are described and some modifications are proposed. For diagnosis of oscillation source, signal is decomposed to its fundamental modes and oscillation in each mode is investigated. Then, from the existence of harmonics in decomposed modes, stiction is diagnosed. Also, relation between peak differences in autocorrelation functions of other modes, results to external harmonic disturbance or poor controller tuning as... 

In Private Equity funds, the manager (known as general partner) collects funds from the investors (known as limited partners) and invests them over a certain time horizon. Assuming that both parties seek to maximize their interests, a situation arises in which the manager does not consider the best interests of the investors. The manager's compensation package is one of the important parts of corporate governance, which consists of four components: management fee, performance based fees (or carried interest), hurdle rate and proceeds distribution method. In this research, first by conducting a semi-structured interview with 15 experts in the PE ecosystem and publishing a questionnaire, the... 

In this work, an analytical model has been proposed for rectifiers used in RFID & WSN applications. Body effect has been considered in this model, as well as the effect of transistor size and number of stages on the output voltage of the rectifier. Using proposed equations for both rectifier circuit and the matching network, the power harvesting system is optimized by means of co-designing the rectifier and the matching network. The results of the proposed model are in good agreement with the simulation results.
Finally, A Rectifier circuit which is designed to generate 1-V dc across a capacitive load is presented. Simulation results show that the sensitivity of this power harvesting... 

n this article, we find necessary conditions for the existence of Ito Integral in a Banach space with respect to compensated Poisson random measure (cPrm). Ito integrals with values on M-type 2 Banach spaces F of the above form exist for all measurable, adapted functions f square integrable w.r.t. β ⊗ d t (f ∈ M2T;_(E/F)),with β being Lévy measure associated with cPrm, and have strong second moments. We show that, for general separable Banach spaces F, an inequality of the type resulting for M-type 2 Banach spaces with constant depending on cPrm is necessary and sufficient for the existence of Ito integral having second moment finite for all f ∈ M2 T;_(E/F). It is shown that M2 T;_(E/F) is... 

In last years, many researches are focoused on improving of suspension systems because of their importance in automotive afavourable performance. One of these advanced suspension systems are Magnetorheological suspension with nonlinear dynamic system and complicated behavior like Hysteresis Loops, so their modeling are notable.
In the first chapter as introduction, suspension systems and their aims are expressed briefly. Then Magnetorheological suspension structure and its function are mentioned. After review of researches that has done about its modeling and control , in the third chapter, different types of classic and generalized Prandtl-Ishlinskii models are introduced and... 

In this thesis, we model and analyze coherent optical OFDM systems which are highly concerned as future fiber optic communication. To this end, we first introduce various applications of that in optical communication systems and investigate its probes and cones. In the rest of the thesis, we characterize the mathematical structure of the nonlinear phase noise and discuss the previous methods of compensation of that and propose some new ways of nonlinear phase noise compensation and equalization. And as we discuss each method we also investigate its computational complexity and BER performance. We propose three new phase noise compensation method, considering optical phase conjugation, we...