Sharif Digital Repository

It is so essential to study a safe dynamics of agricultural mechanical equipment during duty stroke, plus getting a rich information about the nature of the soil under processing and in many cases there are associated simultaneous problems, so the main aim of this study is to create a safe working conditions for such specific equipment to extend their life time span as possible as it could. This study will predict an un-usual working circumstances for agricultural tools including plough of course depending on some automated technologies with fast response supported by smooth working conditions. Simply, the proposed Investigative system consists of a linear potentiometric element with... 

Laminated composite beams are being widely used in engineering applications, including aerospace and automobile where the structures are highly subjected to non-deterministic random loadings, requiring a reliable technique to ensure the stability of structure during operation. A Novel N-layer model of layerwise theory (LWT) for laminated composite beams incorporated with magnetorheological fluid (MR-laminated beams) is developed. In addition, a finite element model of tapered laminated composite beams incorporated with magnetorheological fluid (MR-tapered beam) based on layerwise theory is developed. The dynamic response of the present model for uniform and tapered beams have been compared... 

Detection and classification of arrhythmia is important especially for patients in Emergency care units. Early diagnosis of cardiac arrhythmia makes it possible to choose appropriate anti arrhythmic drugs, and is thus very important for improving arrhythmia therapy. Computer-Assisted Diagnostic (CAD) Systems are used in recent decades in which extracted features and classifiers are the most important factor. In this project, we try to focus on both of these two major factors in heart arrhythmia classification using HRV signal. Therefore, in this project, we try to classify different groups of arrhythmia using HRV signal processing especially the nonlinear processing. Our main aim is to... 

The primary purpose of the present thesis is to understand the dynamic behavior of partially premixed flames of counterflow burners. In this project, work has been done on the previously designed and built counterflow burner. By setting up partially premixed flames in this burner, acoustic excitation of these flames has been done, and finally data acquisition by taking video of the flame and then using image processing to extract the dynamic response of these flames. The flames that we have examined in this project are all in a laminar regime and the fuel used in these flames is also natural gas. The frequencies that we have examined in these flames are 25 and 40 Hz, and these tests were... 

In this study, the modeling of shrink-fit connection was performed by considering the effect of friction on the connection. The behavior of a beam with shrink-fit connection was compared with the results of Adams software and the modeling accuracy was shown. Using both energy and Newton methods, the equations of motion of a rigid rotor consisting of two shafts connected by shrink-fit connection were obtained and the dynamic behavior of the rotor was investigated. Finally, the coupling parameters affecting the vibrations and stability of this rotor were introduced and the effect of each on the system behavior was shown.
 

The present study investigates the effect of MR materials on the vibrations of three-layer pretwisted rotating beams. For this purpose, by considering MR material as the core of the rotating beam and using Hamilton's principle, the equations governing the three-layer rotating beam are extracted. After solving the desired equation, we optimize the dynamic behavior of the three-layer beam at different rotational speeds. Using the Genetic Algorithm optimization tool, the desired beam weight will be minimized and maximum damping will be applied to the desired system. The goal is to find the optimum magnetic field strength for maximum damping in the system at any rotational speed, in addition to... 

In this research, the dynamic behavior of a rotating stiffened cylindrical shell has been investigated using the refined finite element method. Refined FEM means decreasing degrees of freedom based on decoupling the structure to longitudinal and layerwise directions. The refined FEM has been used to solve the 3D rotor dynamics equations. The natural frequencies and the corresponding modes have been calculated and verified for some existed data and problems. In addition, the effects of the shell geometry dimensions on the natural frequencies and mode shapes have been studied. Also, the relationship between the length to radius ratio, radius to thickness ratio, rotational speed, Aspect ratio... 

In this thesis the dynamic behavior of the thick-walled shell with variable thickness is investigated. Such structures are used in a variety of industries including aerospace, oil, gas and petro-chemistry. In this study, the dynamic behavior of a rotating truncated conical thick-shell with various geometries is investigated. For this purpose, modal analysis is performed using the refined finite element method. Then,the natural frequencies and corresponding mode shapes are calculated for several different geometries. Also, the relationship between geometrical variables such as thickness, the ratio of length to radius, ratio of cross-sectional radius and so on, with the natural frequency of... 

In this dissertation, based on the method of recurrence plot and its application in dynamic system analysis we examine the behavior and dynamic analysis of a swirl burner. Though retrospective studies on thermoacoustic instability have been performed on single-blown premixed cone shape flames and several combustion systems but so far this method has not been considered for a real combustion system. There have also been more work on phenomena known as the flame separation from the burner (blowout) and its propagation into the burner (flashback), which is almost conscious of their process. In fact, selecting a single flame has been to eliminate the flame-flame interactions in the... 

This thesis focuses on how the dimensions and location of piezoelectric patches affect thedynamic behavior of multi layered sandwich panels by the use of finite element method (FEM). To accomplish this objective the finite element formulation of the problem, including coupling of electrical and mechanical characteristic equations for piezoelectric patches is derived. Finite element modeling of sandwich panels is presented on the basis of classic theory and also first order shear displacement hypothesis for multi-layered plates. To perform finite element analysis, ABAQUS is utilized and the development procedure of a finite element model by this software is also introduced. After verifying... 

Since 1906, after the earthquake of Messina in Italy, Italian engineers start developing a new method for increasing the resistance of a structure during an earthquake. With the limitation of time and technology, this method was acceptable for the time period. By developing the accelerographs and seismographs and the methods to process big data, new methods are developed and are being used in designing structures; new technologies allow engineers to analyze the performance of structures with ease. The studies in this research indicates that achieving the safety indices in any design require utilizing all dynamic properties of a structure such as period, stiffness and damping. In this... 

In this study, effect of a single concentrated moving mass on thin linear and nonlinear rectangular plates is investigated. The present research focuses on the dynamic behavior of thin plates traversed by a moving mass. Although vast amount of literature is available regarding the modeling of plates with geometric and material nonlinearity as well as evaluation of the inertial components of the external moving mass, but actually no one has addressed implementation of dynamic effects of moving mass for a nonlinear plate. Due to scientific significance of inertial effects in most cases, the external dynamic loading is considered as a moving mass. However, moving force loading is also taken... 

The behavior of pile foundations during earthquakes is one of the most important factors that affect the performance of structures. Therefore, a large number of studies have been performed on the behavior of pile foundations under dynamic loading. A lot of procedures for the analysis and design of piles under earthquake loading have been developed, especially after the earthquakes which took place in 1964 in Niigata and Alaska. They introduced two major mechanisms for the failure of pile foundations in liquefiable grounds: Bending mechanism and buckling mechanism.In this research the focus is the evaluation of pile failure under buckling mechanism. A fully coupled three-dimensional dynamic... 

The behavior of pile foundations under earthquake loading is an important issue that affects the performance of structures. Design procedures have been developed for evaluating pile behavior under earthquake loading; however, the application of these procedures to cases involving liquefiable ground is uncertain. The performance of piles in liquefied soil layers is much more complex than that of non-liquefying soil layers because not only the superstructure and the surrounding soil exert different dynamic loads on pile, but also the stiffness and shear strength of surrounding soil diminishes over time due to both non-linear behavior of soil and pore water pressure generation. In this... 

Structural elements are exposed to different types of loading which may cause excessive deformations during their life cycle. These deflections may cause damage to the structure .Therefore; reduction of dynamic response of structures can be achieved by exploiting active control system.
In this research, the dynamic behavior of prestressed Eulthemer Bernollli concrete beam under moving Load, support excitation and multi support excitation, controlled by active tendon is studied.The control algorithm employed in this thesis is closed loop linear classical optimal control with displacement-velocity feedback. R and Q matrices are chosen in order to balance the source energy consumption and... 

The use of public transportation in metropolises has developed due to the increase in the population and the need for within-city transportation. Among public transportation service, the use of city subways has attracted more public interest due to its speed, safety, and matching with the environment. Also, one solution for reducing the between-city transit distances,decreasing the accidents and above all, saving the time of the travel is building tunnels and underground lines. Design and construction of underground structures (tunnels),in comparison with surfacestructures, has more complex conditions and considerations that require special studies. One challenging problem fortunnel... 

An understanding of the effect of degree of cementation on static and dynamic behaviour of cemented soils is becoming increasingly important in design and analysis of geotechnical engineering problems. Naturally cemented coarse-grained soils are widely present in many parts of the world. Misunderstanding of the behaviour of such soils could lead to underestimate or overestimate of the soil parameters. Previous studies conducted by Haeri and his co-workers show that most of the alluvial deposit of Tehran, the capital city of Iran, has a soil with cemented nature. The amount and characteristics of the cementation of the deposit varies in different parts from highly cemented in the north to... 

Nowadays using traditional hollow clay brick in buildings to make walls and partitionsisvery common. Non-load-bearing walls in buildings are used as architectural elements for design purposes and protecting the people that are inside the building from cold , heat and sound pollution .Due to the new technologies and developing building codes interms of structure , non-load-bearing walls behaviour that is always neglected seems necessary to be considered. In this research we have investigated the static and dynamic behaviour of a patented non-load-bearing wall made up of a claybrick system with specially-designed-precision grooved faces that eliminates conventional cement mortar and results... 

The commercially available finite element software, FLAC, was used to provide better understanding of the static and dynamic behavior of tieback and anchored walls. Many of the codes dealing with the design of these structures use empirical methods to estimate the amount of deformation under static conditions. Therefore, in terms of static behavior, this thesis mainly focuses on the deformation patterns of the wall and the retained soil. Mohr-Coulomb elasto-plastic constitutive model was used; however, in elastic part the nonlinear Duncan-Change was implemented. The efforts made for better representation of soil behavior resulted in the suggestion of a modification to Duncan-Chang’s... 

There are several factors affecting the behavior and response of a pile under lateral loads. These factors can be divided into two main categories: geometrical factors (e.g. dimensions of the pile, soil, and mesh scheme) and material properties (e.g. shear modulus, bulk modulus, soil elasticity, soil density, and shear strength). Studying the effects and importance of these factors in the final response of the pile (i.e. ultimate forces and displacements) can help design engineers in optimization of their designs. Given the importance of the subject and the possibility of using numerical methods and computer technology to evaluate the behavior of piles, this research attempts to use finite...