Sharif Digital Repository

In this study, the nonlinear vibrations of an elastic rotor that is under the elastic support and under the follower force caused by the airflow passing through the rotating plane are investigated. The elastic shaft is modeled by the Timoshenko beam theory, which is connected to a motor through a flexible coupling and the motor increases the rotational speed of the rotor by applying torque. Gibbons’ equations have been used to model the misalignment forces. First, the kinetic energy of the rotating system is calculated nonlinearly to take into account the effect of nonlinear terms due to the rotational inertia of the system, and then the potential energy and The work of external forces on... 

Multiple object tracking refers to the detection and following of target object classes in video sequences. In this task, all objects belonging to the target classes in the video are detected simultaneously in each frame, and a unique ID is assigned to each of them throughout the video. In recent years, the use of graph neural networks for solving this problem has received significant attention because these models are suitable tools for discovering and improving the relationships between objects in the scene, which can greatly assist in better object pairing. However, there are various challenges to using graph neural networks, the most important of which is the limitation of input graph... 

The inlet duct is one of the most important components of the waterjet propulsion system, whose hydrodynamic performance is directly related to the capabilities and efficiency of the waterjet propulsion system. In this study, a procedure was proposed to improve the hydrodynamic performance of an inlet duct. According to this proposed procedure, first the basic intake duct geometry of the waterjet propulsion system was prepared using visual programming to simplify the repetition of the design in Rhino design software, and then the numerical analysis of the designed geometry in Star CCM+ commercial software was performed. The simulation results were validated with the results of an... 

In this thesis, we review some methods related to model-free discrete reinforcement learning and their corresponding algorithms. Our main goal is to present existing methods in an integrated and formal setup, without compromising their mathematical accuracy or comprehensibility. We have done our best to fix the inconsistencies existing in notations and definitions appearing in different areas of the vast literature. We discuss dynamic programming methods, including policy iteration and value iteration and temporal difference methods as well as policy-based methods such as policy gradient, advantage actor-critic, TRPO, and PPO. Among value-based methods, we discuss Q-learning and C51 where we... 

Spent fuel assemblies are kept in spent fuel maintenance pools, designed at the vicinity of the reactor, after consuming. As capacity of these pools are limited, fuel assemblies should be transported to outside of the reactor building for maintenance. Transportation cask is used for this reason which is Russian type, named TUK-13, at Bushehr Nuclear Power Plant. The aim of this project is to ensure proper removal of heat from the transportation cask(TUK-13). For this purpose, numerical computational fluid dynamics method is used. The software used in this study is the Comsol. The temperature range suitable for any part of the chamber is different; but the most sensitive and the most... 

Video segmentation means grouping of pixels of the video sequences into spatio-temporal regions which exhibit coherence in both appearance and motion. Due to complexity and spatio-temporal variations, dynamic texture segmentation is a one of the most challenging task in video processing. The problem of dynamic texture segmentation has received considerable attention due to the explosive growth of its applications in video analysis and surveillance systems. In this thesis, two novel approaches have been proposed. The first proposed method is based on generative Dynamic texture models (DTMs) which represent videos as a linear dynamical system. Since DTMs cannot be used for complex videos which... 

Here, we first ivestigate some available nonsmooth algorithms indentilying their drawbacks, and then provide some guidelines to avert these drawbacks. We divide the algorithms to two main classes, first order and second order. The main drawback of the second order class of algorithm is that there does not exist any suitable method to approximate the generalized second order derivative. To solve this problem, we construct a uniform approximation for the generalized Hessian matrix of an SC1 function. Using the discrete gradient and the extended second order derivative, we define the discrete Hessian matrix. We construct a sequence of sets, where each set is composed of discrete Hessian... 

In this thesis, a numerical analysis of micro chamber filling in centrifugal microfluidics is investigated. In the development of micro total analysis systems, it is often necessary to achieve complete and uniform filling of relatively large micro chambers. With centrifugal devices, these large micro chambers must often be orientated perpendicularly to the direction of centrifugal force and are usually bounded by materials with varying surface properties. On the other hand, the mixing characterization of two fluid by centrifugal microfluidic method has been also conducted. The multiphase flow analyses based on Eulerian-Eulerian approach have been conducted and the VOF method was used for ... 

iN This thesis, Design and implementation of a low voltage, low power Delta-Sigma Modulator (DSM) is presented. System level considerations have been discussed thoroughly. In addition a systematic design flow in the context of continuous time delta sigma modulators is provided. While voltage-domain signal processing becomes more difficult in deep sub-micron processes, a finer time resolution is achievable. Time-domain quantizers can ameliorate the design challenges of flash quantizers which arises from lower supply voltages and higher fraction of comparator metastable region. VCO based quantizer such as voltage to frequency and voltage to phase considered as time domain quantizers can be a... 

In recent years in assembly line balancing area many researchers have focused on identifying and modeling real world situations in assembly lines in order to obtain more suitable model. As a result many generalized models have been developed in assembly line balancing area. However, designing efficient algorithms to solve these generalized problems has just begun. In this study it is aimed to design efficient algorithms to solve one of these generalized problems. Specificcally two hybrid genetic algorithms (GA) are proposed to solve assembly line balancing problem with sequence dependent setup times. Scheduling of tasks in the stations has been less considered in the literature of assembly... 

In this research dynamic modeling of a 3-DOF (degree of freedom) compliant parallel mechanism with flexible intermediate links has been investigated. Unlike conventional rigid mechanisms that gain their mobility from movable joints, the compliant mechanisms transmit or transform through elastic deformation of flexible members (flexible connector and joint), displacement, force, or energy from input into output. Eliminating clearance, friction, wear and demand of lubrication in compliant mechanisms, and having monolithic structure provides high-precision motion with micro/nanometer level resolution for them. Therefore compliant mechanisms play a significant role in modern technologies such as... 

The rapid pace of development of nanoscience and nanotechnology and their applications in various fields have made the study of materials in smaller scales more important than any time ever. Having an insight of materials’ microstructure and the mechanism of different phenomena in the atomic scale will be very beneficent in designing new and advanced materials or modifying the current manufacturing processes. Since molecular dynamics (MD) method has been well known as a mean of studying materials in atomic scale, it has been used in this study to investigate two different phenomena. The selection of the appropriate interatomic potential is of great importance in MD; Embedded Atom Method... 

Fe-29Ni-17Co alloy with commercial name “Kovar” is an alloy with low expansion coefficient. The main specification of this alloy is to maintain this property at the high temperatures that is used in sealing of glass-metal. Achieving to desirable physical properties associated with suitable mechanical properties is the purpose of related industries. However the effect of cold work and heat treatment was studied on the physical properties of this alloy, there is no report about the effect of the hot work. Thus, in this investigation, the effect of the hot work on the physical and mechanical properties of Kovar was studied. At first, slabs of Kovar alloy were cast and remelted. Then,... 

Dynamic modeling and process control, especially the equipment of bioreactors and fermenters, have always faced many challenges due to the complexity and high uncertainty of the kinetics of environmental reactions. Among these, semi-continuous fermentation for bioethanol production is one of the important technologies in biochemical industries. The problem of modeling as well as controlling the use of the main discontinuous and semi-continuous methods of ethanol production is the lack of uniform state conditions and the possibility of aerobic and non-aerobic multiplication conditions in two ways. The main goal of this research is to obtain a new method in modeling bioethanol fermentation and... 

Nowadays counting small particles and gathering their morphological information is widely used in many fields as medicine, engineering, etc. One of the best examples of this technology is counting and distinguishing different cells which are considered bioparticles. In this thesis a brief review of different particle counting methods is presented. Among these methods flow cytometry technology is chosen, because of its speed and accuracy. In flow cytometry method cells are conducted to the center of a transparent capillary by sheath flow technique; then laser beam is radiated to the cells. The intensity of the light scattered from the cells is used to determine cell type and count. In... 

The use of wearable surveillance systems and wireless body sensor networks is an economical solution to medical care, which is capable of detecting abnormal conditions early, and by controlling the health status and enabling one to engage in normal and daily activities, improves the patient's quality of life. Information and communication security is very important in this area and its violation may even endanger the life of the patient. The selection and application of the appropriate security mechanism for a wireless body sensor network is subject to consider the requirements and limitations of the network. One of the most important security requirements in this area is the... 

In this project rotational barrier around the C-N bond in 4-ethyle-morpholine- carboxylate has been studied using DNMR spectroscopy. Spectra were taken at variable temperature, and then with simulation of bandshape broadening pattern at coalescence region, rate constants of exchange were obtained for all temperatures. For simulation of line-shape broadening Spinworks software was used, that with two interfaces made possible simulation with two bandshape simulator programs, DNMR and MEXICO. The rate constants obtained from simulations, were used for calculation of thermodynamic activation parameters (∆G#, ∆H#, ∆S# and Ea). ∆G# 298 value of 13.66 Kcal/mol for 4-ethyle-morpholine- carboxylate... 

In this research, various molecular dynamics simulations have been carried out and sensitivity of the crack propagation process to the simulation parameters including the load pattern, maximum applied strain, temperature, loading frequency, and percentage of defects is investigated. Moreover, the crack propagation in poly-crystalline structure is studied using a larger model consisting of several atomic crystals and the effect of the presence of crystals on crack growth is investigated. In the next step, a novel coupling technique is developed in the continuum–atomistic multi-scale analysis of temperature field problems. In this manner, a new thermostat is introduced based on the single-atom... 

In this research, modal incremental dynamic analysis (MIDA) has been investigated on three-dimensional structures with irregular plans. The MIDA method is an incremental static analysis that considers higher modes of the structure. In fact, it is a combination of modal pushover (MPO) and incremental dynamic analysis (IDA) methods that incorporate the advantages of both and is much faster than the IDA method. Compared to constant analyses, incremental analysis is more extensive in terms of results and response to earthquakes. Due to the uncertainties in the nature of future earthquakes, engineers use the IDA method to achieve a broader view of the structure's response under potential... 

Due to unusual response of structures of buildings with irregularity in their architecture to dynamic excitations, to have a comprehensive knowledge of their behavior during earthquakes is of utmost importance. Building irregularities are in general divided into two major categories, namely Irregularity in Plane and Irregularity in Elevation, and one of the forms of the latter is where there is a split in the levels of the building. In this work, through a series of case studies, the effects of P- phenomenon on the behavior of steel split-level building structures were studied. 5, 10 and 15 story buildings with 5 and 6 bays, and level splitting of 30, 60, 90, 120 and 150 cm were studied. All...