Sharif Digital Repository

The need for independent power generation has been increased in recent years with the growing demand in micro grid systems. Losses in power systems are unavoidable. These losses occur in transmission to distributionnetworks from the generation sites to the end-user loads. Reduction of power losses has been one of the reasons for engineers to be attracted by micro grid systems which include small size independent power generation units. However, in a micro grid with several DGs of different types and with all kinds of loads of variable nature, an optimal power balance in the system has to be achieved. This optimal objective, which results in minimal energy losses over a specific period of... 

The major goal of the power industry is to serve the demand of electricity consumers as reliable as possible but at an affordable cost. Towards the goal, however, the industry faces substantial barriers such as aging infrastructures, growing demand, and limited budgets for reinforcements. A great portion of infrastructures which were built decades ago need to be retired. The growing demand needs system reinforcement and expansion. These, in turn, require considerable amounts of investment which is in contradiction with highly limited budget of the power industry. This critical situation forces the industry to utilize the existing system more efficiently and wisely. To this end, the concept... 

In this thesis, we study the dependence structure between the Tehran Stock Exchange and over-the-counter market, as the two main Iranian capital market institutions. Several constant and time-varying conditional Copula functions are used to model this dependence structure from October 2009 to August 2014. It is shown that, compared to constant conditional copulas, time-varying conditional copulas, provide a better performance. Analyzing the conditional tail dependence of these indices shows an asymmetric dependence structure. Also, investigating the dynamic conditional correlation and conditional tail dependence, using time-varying conditional copulas, reveals large variations and an... 

The present study investigated day of the week effect on stock market returns and the stock market returns and volatility relationship in Tehran Stock Exchange. In this part two regression models is been used and theory that effect of days are meaningful on return and also the theory of meaningfulness and being equal of relation between return and volatility in different days of the week has been examined on index return of all market and on industry indexes in separately. Therefore we have utilized information from time series of total index week days categorized into 8 industries during 2008-2013. The results obtained on weekdays effect on the index of the first model and second model... 

In this study, by dividing spine motion in two part, ordinary movement and initial-final accelerated movement, the commands of CNS are evaluated by optimization methods to find synchronous and time varying synergies. Spine, which is a complex structure of vertebrae and cartilage, has been modeled by a 3D inverted pendulum with a ball and socket joint at L4/L5 incorporated with 18 muscle fascicles. Planning of point-to-point spine motion is performed by optimal control method in combined with cost function of kinematics and kinetic features that available in spine structure. In the second step, coactivation of muscles is predicted by utilizing static optimization along with stability... 

This study investigates consumers’ response to changing the household electricity meter from single stroke case to three stroke case. Existence of different prices in different hours during the day is the advantage of three stroke electricity meters compared to single stroke ones. Electricity bill data of 19,742 subscribers, in Tehran Interior Region 2, during the period 1387 to 1393, has been used to evaluate this policy. Subscribers who always use only single stroke electricity meters or three stroke ones are considered as the control group; and subscribers who have experienced electricity meter change during the period are considered as the experimental group. Changing electricity meters... 

Time-varying media have been in center of attention since recent years for their plethora of applications. Achieving non-reciprocity, one-way propagation, frequency modulation, and signal amplification are some applications of such media which are accessible from microwave to optical frequencies. The aim of this thesis is to first find a method for the analysis of wave propagation in homogeneous time-varying media. To this end, a new formulation is presented based on differential transfer matrices enabling us to find amplitudes, average power, and average energy of a wave in a homogeneous time-varying medium for arbitrary temporal variation of permittivity. In addition,this formulation... 

The demand for independent power generation has been increased in recent years due to the growing demand in distributed networks, losses and power qaulity in power systems. These losses occur in transmission to distribution networks from the generation sites to the end-user loads which have harmonic losses besides fundamental losses.. The non-linear load makes the harmonics flow in the line and create the harmonic losses. However, in a distributed network with several DGs of different types and with all kinds of variable nature loads, an optimal power balance in the system has to be achieved. This optimal objective, which results in minimal energy losses over a specific period of time,... 

This thesis is concerned with the robust control of multiple integrator systems, subjected to input saturation and external disturbance. Since nested saturation method has been demonstrated to be an effective tool for control of a chain of integrators, a feedback law using nested saturation is proposed. In order to deal with disturbance, an extended state observer is applied to nested saturation controller and a comprehensive analysis of stability is also presented. The existence of constant parameters in the proposed controller makes the design conservative which results in performance degradation in some cases at the presence of disturbance. To overcome this issue, an adaptive approach... 

According to increasingly utilization of different frequency spots, RF receivers are allways under the threats of compression and desensitization because of large out-of-band or in-band blockers. The IC technologies afford fast, low-resistance switches as scaling keeps going on. With this mind, the Linear Periodic Time Varying circuits, in which the switches play the most dominant role, will be a sensible candidate for the concerns of blocker detection and rejection. Furthermore, nowadays’ receivers should be reconfigureable so as to be tunable at different frequency bands and satisfy contrastive standards. In this regard, the LPTV filters provide vast range of tunablity not only with... 

The purpose of this thesis is design of an adaptive tracking control for input-quantized strict-feedback fractional order nonlinear systems with unknown dynamics and asymmetric time-varying output constraints. The controller design is achieved by using a hysteretic quantizer to avoid chattering and not needing the quantization parameters. The fuzzy logic method has been used to solve the problem of unknown dynamics. Also, due to the asymmetric time-varying output constraints, the Barrier Lyapunov function has been used. In this thesis, less restrictive assumptions have been considered than the work performed in previous researches.By utilizing the adaptive backstepping approach and based on... 

In economies with high inflation rates, investors are concerned about their purchasing power and assets’ value. Traders are interested to choose optimal portfolios in terms of risk and return. In recent years, the Iranian stock market and real estate experienced a quiet long period of boom with high rates of return. In this study, we estimate and analyze the equi-correlation between the returns in the markets. For this purpose, we use the monthly data of real estate prices in Tehran and the Tehran Stock Exchange Index for a twenty-four-year period, applying the DCC technique. Our results reveal that the long-term correlation between these two markets is not strong, leading us to suggest them... 

Epsilon-near-zero media have attracted considerable attention in the last decade due to their exceptional behavior in wave propagation. The purpose of this research project is to analyze time-periodic ENZ structures. To this end, layered structures consisting of plasmonic metal and dielectric layers are used to achieve the epsilon-near-zero effect in a specific frequency range, and by time-variations of the dielectric layers, an effective time-varying (TV) ENZ is achieved. A method based on transfer matrix method is developed to analyze such structures while they are undergoing time-variations, and primarily under normal incident waves. Various structures based on such TV layered structures... 

We study the phenomenon of parametric amplification and instability in the context of time-varying electromagnetic structures, particularly dielectric slabs with periodically modulated permittivity. These structures show particular promise inasmuch as they are capable of very large amplifications when illuminated by an electromagnetic wave of half the modulation frequency. Successive studies have corroborated this finding but none have yet been able to ascertain the nature of amplification in such devices. On top of that, the problem of instability in time-periodic slabs has either been disregarded altogether or it has been subjected to loose analysis, leading to mere speculations which are... 

This thesis presents a resonant time-periodic structure based on the Fabry-Perot resonator for frequency comb generation. Time-periodic structures cannot generate a frequency comb by themselves because side-harmonic amplitudes are really weak. However, due to resonant structure, it is expected that the side-harmonics, which are generated because of the time-periodic part of the structure, are increased if they are close to the main modes of the structure. But the results show that, generally, the amplitude of side harmonics, which are close to the main mode, is increased and far side-harmonics don't have remarkable amplitudes. However, we will show that if the modulation frequency of the... 

Metagrating is a new concept for wavefront manipulation that, unlike phase gradient metasurfaces, does not suffer from low efficiency and also has a less complicated fabrication process. However, they have some drawbacks, which we are trying to resolve in this thesis. First, a compound metallic grating is proposed for anomalous reflection. We propose an analytical method for analyzing the electromagnetic response of this grating and show that the structure can have unprecedented near-to-unitary efficiency. Next, two-dimensional (2D) metagratings are proposed for diffraction pattern control. We first present an analytical method for diffraction analysis of 2D compound metallic grating. As a... 

In today's world we are dealing with many devices and processes with the goal of efficiency and performance improvement. In many processes particularly chemical ones, the goal is to control the output according to its constraints in the way that the performance is economically efficient, such as reducing energy consumption and energy loss and increasing efficiency. In order to control a process with economical goals, an economical cost function is used and after determination of optimal values a controller is used to guide the process so can achieve them. Model predictive control (MPC) is very common in this economic control Due to advantages such as considering the problem constraints. In...