Sharif Digital Repository

Considering the special importance of network flow problems in human life, as well as the complexity of solving these problems in very large scales, there are numerous methods to solve them and the interior point methods are the most important approaches among them. In a number of methods, a preconditioned conjugate gradient solver has been applied for the solution of the Karush-Kuhn-Tucker (KKT) system, in each interior point iteration; therefore, the selection of an appropriate preconditioner is a special issue. In spite of presenting different preconditioners in recent years, discussion and implementation of a particular class of triangulated graph-based preconditioners is our main... 

The subject of this study is design of a linear quadratic Gaussian controller based on identification of dynamic behavior of unmanned model helicopter “Raptor” in its hover flight. To achieve this end, first, the helicopter linear transfer functions are identified with frequency response method by applying specific inputs to the model of Raptor in the X-Plane software and receiving system outputs via Simulink. Next, using the identified dynamic model of the helicopter, an optimum linear controller is designed for hover flight. As an optimum linear controller needs all the state variables, a Kalman filter is utilized to estimate them, using outputs of various sonsors such as GPS and gyro.... 

In this work dynamic behavior of a two body TSS with main satellite as rigid body is studied and effects of tether elasticity and tension on the satellite dynamic are indicated in station keeping phase and circular orbit. Also a simplified modeling is introduced which could be used in nonlinear controller design. Lagrange and extended Lagrange method is used to derive equations of motion. It is shown that longitudinal vibration of tether has small effect on satellite attitude and angular velocity and because of high frequency it can be decoupled from satellite dynamic. In the simplified model, orbital motion is decoupled from equations of TSS and main satellite dynamic. Effect of decoupling... 

Gamma ray spectroscopy has a special place in the industrial applications of nuclear radiation. Currently, the most common device for gamma ray detection and spectroscopy is the sodium iodide scintillation detector. Long life and high efficiency and reasonable price of these detectors are the reasons for the development of the use of these detectors in industries and laboratories. But these detectors in the classification of energy sensitive detectors are considered as detectors with low resolution. The presence of broad peaks in the gamma ray spectrum of this detector increases the possibility of interference of peaks related to different energies and makes it difficult to identify the... 

In recent decades, widespread application of Linear Complementarity Problems in various branches of science has led to many algorithms which have been proposed to solve these problems in the area of mathematics, economics and computer simulation. Ashtiani used Lemke algorithm for the first time to solve Linear Complementarity Problems in his algorithm for solving Traffic Assignment problem. In this study, Projection Gauss-Seidel algorithm along with two other similar algorithms have been studied for solving Linear Complementarity Problems in Ashtiani Complementarity algorithm and the results are compared with Lemke algorithm. Also an analytical method has been proposed for solving specific... 

Trip demand analysis is among the most important parts in comprehensive transportation studies. Developing four stage models including trip generation, trip distribution, mode choice, and assignment are so common in demand analyzing. In this study, trip generation models have been studied and to analyze data, two different methods including OLR and GWR are utilized. This study aims to examine relationship between aggregate zones in order to forecast future trips. Moreover, results of modeling trip generation with two different methods, OLR and GWR, are compared. Comparing different levels of aggregation reveals that as the number of zones decreases, the results get better. Decreasing number... 

Today, with improvements in industries such as the sensitive equipment’ industries and the optics industries which need great precision for their optimum performance, the need for a vibration-free environment is felt more than ever. The main objective in this thesis is the effective reduction of the effects of ambient vibrations on points on an optical concrete table using active control. In this research, other than separating the table with the passive method, the reduction of vibrations with active control and the LQR algorithm is investigated. In order to study the dynamic characteristics of the table and to observe the active control process better and more carefully, finite element... 

Analysis and design of power systems are challenging due to ever increasing dimension of the system and also the nonlinearities involved in the system. The conventional approach is to use linear analysis tools and then investigate the nonlinear impacts by the means of computer simulations. This requires great deal of trial and error and it is not always a timely approach. In this project, we initiate a comprehensive nonlinear analysis for a single-machine infinite-bus system by studying a Hopf bifurcation in its dynamics. We use results of our nonlinear analysis to study how a capacitive compensation such as TCSC works. Subsequently, we design a nonlinear controller for a PSS to have... 

Direct/inverse scattering of high frequency SH-waves by a circular micro-/nano-fiberembedded in an infinite elastic isotropic medium is addressed in the framework of couple stresstheory with micro inertia. The inadequacy of classical theory of elasticity in the problems dealingwith propagation of high frequency waves as well as the problems concerning the elastic fields inthe vicinity of micro-/nano-size defects in which the wavelengths and the size of the defects arecomparable to intrinsic length of the material is well-known. These dilemmas can be remedied byemploying the more accurate higher order continuum theories. So, in the context of couple stresstheory with micro inertia, the... 

Since early civilizations underground water pipes have played a major role on promoting human being life style. Today, centuries after designing water mains equipment, utilizing a water distribution and sewage collection system is matter of great necessity in modern metropolises. In current research the pilot area is located in the city center .the major motivation for opting such area was extraordinary breakage rate which was unseen on other city areas and nearby cities. Data pertaining to four commonly used pipe material were collected. Preliminary data quality analysis was conducted to detect distinct contradictions. On basis of collected data, breakage rate plots were depicted for each... 

The Wedderburn rank reduction formula and the ABS algorithms are powerful methods for developing matrix factorizations and many fundamental numerical linear algebra processes such as Gramm- Schmidt, conjugate direction and Lanczos methods. Esmaeili, Mahdavi-Amiri and Spedicato introduced a class of integer ABS algorithms for solving linear systems of Diophantine equations. In a recent work, Khorramizadeh and Mahdavi-Amiri have also presented a new class of extended integer ABS algorithms for solving linear Diophantine systems by computing an integer basis for the null space while controlling the growth of intermediate results. Here, we propose new approches to develop a new class of extended... 

In this thesis, we consider a system containing fluid equations, structure equations, and equations of these two materials’ common interface in three dimensions and on the regular domains. We suppose that the solid which is described by the Lamé system of linear elasticity, moves inside an incompressible viscous fluid in three dimensions, and the fluid obeys the incompressible Navier-Stokes equations in a time-dependent domain. At the fluid–solid interface, natural conditions are imposed, continuity of the velocities and of the Cauchy stress forces. The fluid and the solid are coupled through these conditions. By this interaction, the fluid deforms the boundary of the solid which in turn... 

Most of the robust or optimal controllers can produce extremely fragile controllers [1], in the sense that vanishingly small perturbations of the coefficients of the designed controller destabilize the closed-loop control system. Modern control methods, including robust control, lead to high order controllers.Often times a reduced order controller is implemented. As a result, need for low order control design reducing controller’s ensitivity is tangible. Based on studies carried out, properties of normal matrices can be employed to define a fragility measure. In this thesis, a new convex criterion measuring controller fragility is defined. Then, a more resilient reduced order controller can... 

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... 

The design and implementation of the hybrid control method for a three-pole active magnetic bearing (AMB) is proposed in this paper. The system is inherently nonlinear and conventional nonlinear controllers are a little complicated while the proposed hybrid controller has a piecewise linear form, i.e., linear in each sub-region. A state-feedback hybrid controller is designed in this study and the unmeasurable states are estimated by an observer. The gains of the hybrid controller are obtained by the LQR method in each sub-region. To evaluate the performance, the designed controller is implemented on an experimental setup. The experimental results show that the proposed method can efficiently... 

In recent years, the widespread investigation on multi-transition metal oxides that with two or more transition metal oxides, have been increased rapidly for electrochemical application due to low cost, high conductivity and good electrochemical performance other than single metal oxides. In this project, CuCo2O4 nanoparticles were firstly fabricated by decomposing of CuCo-MOF as the template. The as prepared samples were used to synthesis a new nanocomposite of MoS2 and CuCo2O4. The best ratio of the two component were optimized to prepare the best electrocatalyst for Hydrogen evolution reaction (HER). The structure of prepared nanocomposite were investigated by various techniques such as... 

The use of myriad pesticides in agriculture crops has promoted the demand of developing rapid and sensitive probes for the detection and discrimination of diverse pesticides, which are usually used together. In this work, a colorimetric sensor array has been designed for identification and discrimination of Thiometon (TM) and Phosalone (PS) as organophosphate pesticides and Prothioconazole (PC) as a triazole pesticide. For this purpose, two different plasmonic nanoparticles including unmodified gold nanoparticles (AuNPs) and unmodified silver nanoparticles (AgNPs) were used as sensing elements. The principle of the proposed strategy relied on the aggregation of AuNPs and AgNPs through the... 

Traffic accidents are one of the main causes of death in Iran. Between 2005 to 2019, 20,000 people were killed and 300,000 were injured on average annually. About 65 percent of all traffic fatalities over the past seven years has been on intercity roads. Finding patterns of accidents on specific days, such as holidays, would help the planners prevent traffic accidents. In this study, using police accident data, traffic counts of Road Maintenance and Transportation Organization, and meteorological data of Iran Meteorological Organization during 2011 to 2018, we study the effect of official holidays, and the days before, after and between two holidays on the rate and severity of road accidents... 

Terrestrial water storage change is an important factor in a region ecosystem studies and climate variability effects. Terrestrial water storage is composed of water on vegetation surfaces, in the biomass, in the unsaturated soil or rock zone, as groundwater, snow and ice, and as surface water in rivers, lakes, reservoirs and wetlands. There was no possibility to monitor and estimate this volume of water and it's changes during past decade because of lack of global processing system. After a successful launch, the GRACE mission developed by NASA is currently mapping the variations of the gravity field of the Earth over its lifetime.
The aim of this study is to investigate Terrestrial... 

Standard model of cosmology successfully describes the properties of the universe on large scales. General relativistic perturbation theory accurately describes how the initial fluctuations created in the inflation era grew larger and became the seeds of structure formation later in the radiation and matter dominated era. However, linear perturbation theory breaks at the scales of approximately 10Mpc. In such scales, the gravitational effects are non-linear and we should use standard pertubation theory to find the corrections to the linear power spectrum. In this thesis, I calculated these non-linear contributions analytically and proved the stability of the linear point which is believed to...