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elasticity
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Stability Analysis of Hybrid Nanotubes Based on the Nonlocal Continuum Theories
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
Strong van der Waals (vdW) potential fields of carbon nanotubes (CNTs) makes them capable to encapsulate some nanostructures inside their hollow space, which leads to the construction of new hybrid nanostructures under specific conditions. Carbon nano-peapods, carbon nanowires and the hybrid of DNA and CNT are the main categories of hybrid nanostructures of CNT. Characteristics of hybrid nanotubes are unique and different from those of CNT. In nanostructures, the lattice spacing between individual atoms is considerable with respect to the structural dimensions. Also, the range of internal characteristic length is relatively close to external ones. So that utilizing the classical continuum...
Analysis of Micro Rotating Disk Based on the Strain Gradient Elestisity
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
In the present study, we analyzed the mechanical behavior of micro rotating disk based on the most general form of strain gradient elasticity. According to the fact that micro rotating disks have an important role in MEMS, it is necessary to present an exact analysis of their mechanical behavior. It is noticed experimentally that materials behave stronger in deformation as they get smaller. The classical continuum theory is not capable to predict such behavior; therefore, it is essential to use one of the non-classical continuum theories to analyze the material in micro scales, which can capture this phenomenon. In this work, the strain gradient theory is utilized to derive the governing...
Numerical Analysis of Channel Flow over an Elastic Bump, Using Lattice Boltzmann Method- A Biological Application
, M.Sc. Thesis Sharif University of Technology ; Taeibi Rahni, Mohammad (Supervisor)
Abstract
In recent years, lattice Boltzmann method (LBM) has been developed to be used as an alternative and promising computational technique to simulate various flows. It originates from classical statistical physics. The ability to simply solve complex flows, simulating of multiphase and multi-component without need to follow the boundaries of different phases, and the inherent ability of parallel processing are notable features of this approach. On the other hand, finite element method (FEM) is widely used in many practical engineering fields, especially in solid mechanics. In this study, in addition to simulating flow over a rigid body, flow over an elastic body is also simulated with a...
Elastic-Plastic Behavior Analysis of Short Fiber Metal Matrix Composites under Thermal Loading
, Ph.D. Dissertation Sharif University of Technology ; Abedian, Ali (Supervisor) ; Mondali, Mahdi (Supervisor)
Abstract
The use of metal matrix composite materials (MMC) in aerospace structures and engine parts has become more frequent recently. These materials are composed of metal matrices reinforced by hard discontinuous ceramic fibers, usually oriented longitudinally within the matrix, and due to the stability of the mechanical properties, including the hardness and the strength at high working temperatures, have found various applications.Stress transfer from the matrix to the fiber is known as the most important mechanism governing the deformation and the fracture response of such MMCs. The stress transfer characteristic of fiber reinforced composite materials under various mechanical and thermal...
Dynamic and Vibration Analysis of Wavy Carbon Nanotube-Reinforced Composites
, M.Sc. Thesis Sharif University of Technology ; Ahmadiyan, Mohammad Taghi (Supervisor) ; Asghari, Mohsen (Supervisor)
Abstract
Characterization and simulation of carbon nanotube-reinforced composites at large scale have been a concern of researchers in the past decade. This is due to the computational complication of considering many embedded carbon nanotubes (CNTs). However a simple meshing of organized CNT distribution in the matrix can ease this obstacle. In this study, a finite element approach is employed to investigate the elastodynamic behavior of a wavy CNT-reinforced composite structure. A three dimensional structure with up to 6400 uniformly distributed wavy CNTs is embedded in a polymer matrix. Each wavy nanotube is represented by a set of beam elements. The effect of nanotube waviness and volume fraction...
Thermoelastic Analysis of Thick-walled FG Cylinders Using the Strain Gradient Elasticity
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor)
Abstract
There are experimental observations that show material response in micro-scale is dependent on some other parameters rather than Lame parameters. Strain gradient elasticity has been recently developed to take into account this characteristic of materials response. In strain gradient elasticity, characteristic length parameters enter the constitutive equations through the elastic strain energy density function. The elastic strain energy density function is assumed to be a function of the gradient of strain tensor in addition to the strain tensor. In this way, new material constant (characteristic length parameters) are introduced and entered into the constitutive equations. In recent years,...
Elastic-Plastic Analysis of Fiber Reinforced Metal Matrix Composite Structures
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Asghari, Mohsen (Supervisor)
Abstract
In this study, an elastic-plastic analysis of fiber reinforced metal matrix composite structures loaded by uniaxial uniform tension in the direction perpendicular to the fiber is carried out by assuming elastic-plastic matrix with kinematic hardening. Representative volume element (RVE) is used for this analysis. The element consists of a combined square field composed of a solid circular cylinder fiber and matrix in plane strain condition. Elastic analysis is carried out using Airy stress function and Michell solution. Unknown coefficients of the Airy stress function are determined by satisfying boundary conditions as well as continuity conditions. The governing equation of plastic zone is...
Elastic Analysis of Brazilian Test of Transversely Isotropic Material
, M.Sc. Thesis Sharif University of Technology ; Eskandari, Morteza (Supervisor)
Abstract
In Former research we determinate elastic response of Brazilian Test of transversely Isotropic material . In Bio-mechanic science surveying mechanical properties and modeling biological organ such as bone , tooth and bio-material such as titanium, zirconium with application in joint replacement is very important . One of method to determine properties of bio-material which mostly has transversely Isotropic behavior is Brazilian Test. Also most rocks has transversely Isotropic behavior, so choosing efficient test is so important. In current issue , load apply in limited area and it is also considered friction in area of jaw loading area .By use of displacement potential function ...
Vibration and Stability Analysis of Multiwall Carbon Nanocones on Elastic Foundation Using Nonlocal Theorem
, Ph.D. Dissertation Sharif University of Technology ; Haddadpour, Hassan (Supervisor) ; Dehghani Firoozabadi, Rouhollah (Supervisor)
Abstract
Carbo nanocones are one of the nanostructures that are investigated and takes a large deal of attention in nanotechnology. In the present study the governing equilibrium equations of motion of carbon nanotubes under external pressure are derived using a nonlocal shell model and first order shear deformation theory. The natural frequency and buckling load are extracted using modal method along with Galerkin technique.Afterthis using both Winkler and Pasternak elastic foundation models, the governing equations of motion of nanocones embedded in the elastic medium extracted using a novel approach with the nonlocal shell model along with Hamilton’s principle. These equations solved using...
Nonlinear Vibration Analysis of Circular Microplate Based on Strain Gradient Theory
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
Nowadays the combination of mechanical and electronic systems in small scales is gaining attention. Micro electro-mechanical systems are widely used in various industries such as car manufacturing and electronic chips. In these devices, the most important and useful mechanical structures are beams and plates. Therefore, investigating the mechanical properties of these structures in very small scales (micro and nano) is of great importance. Decreasing the size to these scales leads to the dependence of the behavior of these structures to size. Accordingly, some theories for prediction of these behaviors have been presented, one of which is the strain gradient theory. This theory is used in...
Impact of Fuel Price Increase on Urban and Interstate Travel Demands
, M.Sc. Thesis Sharif University of Technology ; Samimi, Amir (Supervisor)
Abstract
This study evaluates the impact of fuel price increase on urban and interstate travel demands via the linear regression model. Indeed this study has two aims. First, analyze the effect of fuel price increase on travel demands of two modes of transit ridership (Subway and Bus Rapid Transit), and determine the cross elasticity of demands. To achieve the demands, the origin-destination matrix of each mode was obtained using automated fare collection data and the trip-chaining method. Second, examine the impact of fuel price increase on interstate travel demands and provide the elasticity of vehicle-kilometer traveled with respect to fuel price. The ordinary least-square method was used to...
Eigenfield Theory for Grade Two Flexoelectric Composites with Periodic or Arbitrary Nanostructure and General Anisotropy
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
Studying the behavior of electromechanical systems containing nanostructures, because of their widespread applications in the nanoscience and technology is of great interest. For this purpose, this work is devoted to analytical and exact determination of the electroelastic fields associated with periodic and arbitrary distributions of electromechanical nano inclusions and nano inhomogeneities of various shapes within electroelastic mediums of general anisotropy. Since classical continuum Theories are inadequate in accounting for size affects in nanostructures, a first strain gradient - first electric field gradient theory is applied. The present work considers Piezoelectric and Flexoelectric...
Innovative Theories of Micro and Nano Ellipsoidal Inclusion and Inhomogeneity in Magneto-electro-elastic Media with General Anisotropy
, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
In the current work, the two- and three-dimensional electro-elastic fields of periodically as well as arbitrarily distributed interacting quantum wires (QWRs) and interacting quantum dots (QDs) of arbitrary shapes within a piezoelectric matrix are studied analytically. The lattice mismatch between the QWR/QD and the barrier is accounted through prescribing an initial misfit strain field within the QWR/QD. The distinction between the electro-mechanical properties of the QWR/QD and those of the barrier is treated by introducing a novel electro-mechanical equivalent inclusion method in Fourier space (FEMEIM). Moreover, the theory can readily treat cases where the QWRs/QDs are multi-phase or...
Influence of Polystyrene on Behavior of Light-Weight Concrete
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor) ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Normal aggregates are replaced by polystyrene beads (EPS) due to their low unit weight. EPS concrete is known for its low density and environmentally friendly properties apart from having various pros such as better heat and sound isolation, affordability, and ease of construction. EPS grain size can also affect the compressive strength, and the tensile strength of EPS concrete compression is also inversely related to EPS grain diameter. The EPS concrete has four different percentages of EPS; 0%, 25%, 50%, and 75%. Each EPS percentage has six different unit weights; 15,20,25,30,35 and 40 kg/m3. In the present study 19 different types of mixing designs were used, the one with no EPS beads has...
Impact of Inflation on Household’s Saving within the Framework of Expenditure System
, M.Sc. Thesis Sharif University of Technology ; Nili, Masoud (Supervisor)
Abstract
In this thesis the impact of inflation on urban household saving is investigated. For calculating sensitivity of saving respect to price changing of different groups of commodities, firstly we divided household cost to two separated groups of durable and nondurable and then by defining total income as summation of monetary and nonmonetary income of households, We consider saving as total income minuses nondurable consumption. Finally we estimated the “Extended Linear Expenditure System” model base on the prepared data. Since inflation is result of unequal changes in prices of goods and services, the approach of expenditure system allows us to assess unequal changes in prices for eight...
Joint Functional Split and Resource Allocation Optimization in Elastic Optical Fronthaul
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Hadi, Mohammad (Co-Supervisor)
Abstract
Dynamic reconfigurability in optical and mobile networks can facilitate heterogeneous service provisioning while utilizing minimal resources. This allows cost-efficient service delivery resulting in increased revenues for network operators. Deployment of elastic mobile and optical networks is a key driver for enabling reconfigurability in modern networks. Elastic optical networks can be utilized as the fronthaul portion of new generation of mobile networks. Such elastic optical fronthaul networks facilitate joint reconfiguration of flexible radio and optical elements and provide considerable performance improvements. This thesis focuses on the joint dynamic selection of functional splits and...
Energy Efficiency in Elastic Optical Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor)
Abstract
Telecommunications operators look forward to network virtualization to reduce capital and operational expenditures. Optimal performance of the virtualized networks requires efficient resource allocation. On the other hand, in recent years, traffic growth and its dynamic behavior are two main drivers for the development of elastic optical networks. In this research, the problem of resource allocation for virtualized network function requests over an elastic optical network is investigated. Due to the high cost of energy consumption, energy efficiency is considered as the objective of the resource allocation problem. Conventional pure static and dynamic solutions are not suitable for efficient...
Improving Architecture of Elastic Optical Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor)
Abstract
Optical telecommunications, and especially optical fiber-based telecommunications, have been one of the most important leading factors in advancing information technology. This age seems to have an insatiable appetite for information in a way that every two years we see a two-fold increase in the traffic of optical networks.The focus of this thesis is in the area of backbone optical networks. We know that companies operating in this field spend a huge amount of money to set up and maintain optical networks. One aspect of reducing costs in optical networks is the use of grooming to reduce the cost of using network equipment.Different heuristic algorithms for optimization are proposed for this...
Efficient Routing and Resource Allocation in Optical Burst Switched Networks based on WDM/OCDMA and Elastic Bandwidth Optical OFDMA
, Ph.D. Dissertation Sharif University of Technology ; Salehi, Jawad (Supervisor)
Abstract
Fiber optic networks are the most attractive technology to deal with the ever increasing demands for high rate transmission with guaranteed quality of service and affordable costs. Optical-to-electrical (O/E) and electrical-to-optical (E/O) conversion at intermediate routers are the restricting processes in current optical networks. There is a great interest to remove O/E and E/O conversion at intermediate routers to achieve an all-optical transmission between source and destination. Optical circuit switched (OCS) networks are the first generation of all-optical networks, which are restricted due to its limitation such as being connection oriented, low bandwidth utilization, and coarse...
Investigation of Local Buckling in Marine Pipelines under External Pressure
, M.Sc. Thesis Sharif University of Technology ; Fallah Rajabzadeh, Famida (Supervisor) ; Seef, Mohammad Saeed (Co-Advisor)
Abstract
To keep up with the growing demands for energy, the oil and gas industry ventures into deeper waters. This increases complexity of offshore projects. Part of this complexity is due to the resistance of a pipeline against local buckling collapse due to external pressure that is more significant in higher pipe laying depth and consequently higher external pressure. Pipeline response to external pressure is an important factor in design of marine pipeline.Local buckling of a pipeline is the buckling behaviour within the pipeline cross section. Other types of buckling behaviour such as upheaval and lateralbuckling are not in the scope of this thesis.In this thesis, the installing pipeline is...