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elasticity
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Human Motion Imitation and Learning It by Fuzzy Elastic Matching Machine
, M.Sc. Thesis Sharif University of Technology ; Bagheri Shouraki, Saeed (Supervisor)
Abstract
In this thesis, the goal is movement recording by observer and learning it to Fuzzy Elastic Matching Machine (FEMM). For this purpose, first using the camera (Microsoft LifeCam HD-3000), the information specified on the man, taken during the move. After preprocessing performed on the data, Data on each node of the FEMM the classified and is given to special FEMM for that movement and the FEMM to be trained by adaptive neuro fuzzy inference system. During each iteration of training, Sensitivity of FEMM for training new movement information is reduced because the FEMM updated correctly. In test part, one movement among all movements that training in all FEMMs is selected and is done by...
Employing Enriched Meshfree MLSRK Method to Analyze 2D Linear Elastic Fracture Mechanics Problems
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shoja, Hossein (Supervisor)
Abstract
The so-called moving least square reproducing kernel method (MLSRKM), which is a meshfree Galerkin method, has two special properties in comparison with its prior version, say moving least square method (MLSM): (i) stability in preserving completeness conditions to the desired order for a discrete reproducing formula due to implementation of shifted and scaled basis, (ii) use of more accurate quadrature weights in a discrete reproducing form, especially along boundaries. However, because of employing shifted basis in MLSRKM, some of enrichment techniques, specifically in the context of linear elastic fracture mechanics (LEFM) problems, cannot be applied to this method. Therefore, we are...
Monte Carlo Simulation of Asymmetric Elastic Rod Model and Calculation of
Probability of Loop Formation
,
M.Sc. Thesis
Sharif University of Technology
;
Ejtehadi, Mohammad Reza
(Supervisor)
Abstract
Sharply bent DNA plays an important role in many biological processes such as gene regulation, DNA replication and recombination. DNA cyclization experiments are well suited to study of sharply bent DNA, because they are sensitive to strongly bent conformations. Results of these experiments show that short length DNA molecules are more flexible than predicted by elastic rod model. Therefore, based on these experiments, the elastic rod model is not a suitable model for explaining elastic behavior of DNA at small lengths, although it can explain DNA elasticity at large length scales. Recently, it has been shown that a new model called asymmetric elastic rod model can explain high flexibility...
An Appraisal of the Trends of Trade and Transportation of Food Products Among Asia, Europe and Africa
, M.Sc. Thesis Sharif University of Technology ; Vaziri, Manouchehr (Supervisor)
Abstract
In this research, the trends of trade and transportation for the 10 subdivisions of food products and food products as a whole product based upon Standard International Trade Classification, SITC, have been appraised during the time period covering 1965 to 2005 among 125 countries in Asia, Europe and Africa. In this respect, the data of trade for the mentioned goods was gathered and other variables including gross domestic product, population, access to the international waters and area of countries and three transportation networks comprising two multimodal transportation networks and a unimodal network, during the cited period and for 125 countries was gathered. Then, regressions of trade...
3D Resource Allocation in Multi-Core Fibers
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
High-definition video streaming, multimedia file sharing, cloud computing, mobile networks and online gaming, all together, will increase the network traffic enormously every year.Long-haul optical fiber networks form the backbone of the Internet and scaling to higher throughput and lower cost per bit is essential to ensure continued growth of information technologies. For four decades, optical networks have exploited significant progress in physical technologies, including low-loss single-mode fibers (SMFs), high-performance lasers and modulators, and low-noise optical amplifiers. In parallel, communication methods have evolved to multiplex information in various physical dimensions in...
Multiscale Modeling of Microstructure Discontinuities in Saturated Porous Media Using XFEM
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
The main purpose of this study is computational modeling of saturated deformable porous media using multiscale finite element method and explicit modeling of discontinuities such as microcracks at the microscopic scale. The real engineering problems we deal with in the simulation of the phenomenas happening in nature or industrial applications, in contrast to the simplifications being assumed, occur in heterogeneous materials. Although most microscopic heterogeneities are not present in macroscopic scale, they do have their effects on material behavior. In the computational homogenization method, the problem is analyzed coupled in two scales, therefore, the macroscopic behavior of media is...
Estimating Air Travel Demand in Iran’s Domestic Routes
, M.Sc. Thesis Sharif University of Technology ; Fatemi Ardestati, Farshad (Supervisor) ; DadPay, Ali (Co-Advisor)Vibration and Stability Analysis of Rotor with Initial Bow and Non-Linear Supports
, M.Sc. Thesis Sharif University of Technology ; Dehghani Firouzabadi, Rouhollah (Supervisor)
Abstract
In this study, the effect of the initial bow on vibrations and stability of the rotor with nonlinear supports has been investigated. Using the energy method, the rotor’s equations of motion for the four-degree of freedom Jeffcott rotor and the elastic rotor assuming Tymoshenko beam relations are calculated. It is very important to study the initial bow as one of the common faults in rotating machines that has a great effect on system vibrations. A method was proposed to reduce rotor vibrations and balancing systems. Choosing a way to eliminate machine defects is one of the points considered by rotor dynamic engineers. Many factors can cause a bow in the rotor, some of the most important of...
A Nanoscopic Approach to the Determination of the Elastic Constants of Cubic Crystals in first Strain Gradient Theory
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
In many problems, the traditional elasticity cannot predict phenomenon such as nano-scale defects, surface effects, and stress concentration correctly. For example, analysis near the crack tip, dislocation and inhomogeneity shows inconsistent results because in this case values of stress go to infinity. Therefore for solving these kinds of problems, higher order continuum theories were introduced. The appearance of additional constants in the equations of motion can represent the atomic nature of materials. Furthermore, they can be utilized for determining properties of materials vibration with high frequency, granular materials, and polymers.First strain gradient theory introduced by...
Ab initio DFPT Based Constitutive Modelling of Crystalline Solids within Micromorphic Theory with Application to Nano/Micro-structures
, Ph.D. Dissertation Sharif University of Technology ; Mohammad Shodja, Hossein (Supervisor)
Abstract
To account for certain essential features of material such as micro-structure effects and dispersive behaviour and optical branches in dispersion curves, a fundamental departure from classical elasticity to generalized continuum theories is required. Among the generalized continuum mechanics, micromorphic elasticity is capable of capturing these physical phenomena completely. In the mathematical framework of micromorphic elasticity, in addition to the traditional elastic moduli tensors, some additional tensors are introduced in the pertinent governing equations of motion. A precise evaluation of the numerical values of the aforementioned elastic moduli tensors in the realm of the...
Experimental Study of the Mechanical Behavior of Plastic Concrete Cutoff Walls
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
The seepage through foundation of earth dams causes the serious menaces and the reduction in their efficiency. Therefore essential contrivances must be provided against mentioned problem. One of the common and efficient ways to control the seepage through pervious layers under earth dams is plastic concrete cut off wall which is used as a filling material in dam foundation due to the low permeability, plastic behavior and low enough elastic modulus compatible with the adjusted soil. In addition to the mentioned properties, it is important that plastic concrete have an adequate compressive strength to sustain the lateral and vertical loads. Since the change in the ratio W/C (water to cement)...
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...
Modelling of Elastic and Plastic Deformation Fracture and Crack Propagation in 3D Problems Using Adaptive Finite Element Method
, Ph.D. Dissertation Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
Numerical methods in fracture and crack propagation problems usually involve high computational costs. Adaptive finite element method is one of the techniques which can be used to simulate the crack propagation with an acceptable accuracy. In this thesis, various constitutive models are implemented for simulation of fracture, including the linear elastic fracture mechanics, cohesive zone model and continuum damage mechanics. The fracture mechanical evaluation is performed on a general integral technique for non-planar curved cracks in LEFM. In the second model, a bilinear cohesive zone model is applied to implement the traction-separation law. The Lemaitre damage model is employed and the...
Accurate Analytical Formulation of the Electro-elastic Fields of the Nanosized Quantum Wires and Guantum Dots in Piezoelectric Media with General Anisotropy
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
The electro-elastic fields of nano-sized piezoelectric structures are considered based on the non-classical continuum theory. Nowadays because of increasing the application of piezoelectric materials in nano technology and exclusive properties of this kind of materials, they can use as the ingredients of electromechanical systems. Therefore, the determination of induced electro-mechanical fields is important. In this study the constitutive equations based on non-classical continuum theory and general anisotropy for the elastic, piezoelectric and dielectric tensors are considered, and the electromechanical fields are determined using the micromechanical method. Furthermore, the size effects...
Estimating Demand Elasticity of Tap30 Company
, M.Sc. Thesis Sharif University of Technology ; Madanizadeh, Ali (Supervisor) ; Joshaghani, Hosein (Supervisor)
Abstract
Access to the data of Tap30, a ride-hailing company in Iran, has allowed us to estimate the demand elasticity of online taxis. As Tap30 divides Tehran into 256 regions for pricing from Jan to June 2018, we assumed that unobservable consumer characteristics near borders are the same for adjacent regions. We used the Regression Discontinuity method to compare ride requests of people who live on two sides of borders and estimated the demand elasticity of Tap30. This research concludes that by 10 percent increase in price, the demand decreases about 3.5 percent on average in 1 hour time period. On the other hand, in 6 hours time period, the demand decreases about 7.5 percent on average by 10...
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...
Forward and Inverse Problem of Seismic Waves
, M.Sc. Thesis Sharif University of Technology ; Moghadasi, Reza (Supervisor)
Abstract
Applying of seismic waves and analysing of its reflections is of effective ways in exploration of the internal structur of the Earth. In this method the Earth is considered as a elastic body that seismic waves are propagated in it. In this thesis the how of creation and propagation of seismic waves is modeld at first and then the inverse problem, exploration of the internal structure of the Earth from observed data, is considered
Calculating Interface Energy, Residual Stresses and Elastic Constants of Non-magnetic FCC Metals
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shoja, Hossein (Supervisor)
Abstract
The investigation of interface residual stress and interface elastic moduli tensors plays a crucial role in enhancing the conventional theory of elasticity. These considerations allow us to account for size effects and eliminate nonphysical singularities near defects. The primary objective of this study is to comprehensively calculate interface energy, residual stress components, and interface elastic moduli tensors for various interfaces between non-magnetic fcc metals using density functional theory (DFT). We achieve this by performing ab initio DFT calculations to determine the interface energies for different coherent interfaces among these metals. Subsequently, these energies are...
Dynamic Behavior Beam and Plate on Foundation under Moving Mass
, Ph.D. Dissertation Sharif University of Technology ; Mofid, Massoud (Supervisor)
Abstract
The behavior of a beam under moving mass has been always interested in the dynamic of structures. In this study, the dynamic response of beam and plate with general boundary conditions under moving mass were investigated using the Dynamic Green Function. Since the majority of previous studies did not consider the Coriolis acceleration, therefore, this acceleration was used in the present study. Boundary conditions are modeled by the rotational and translational restraint. By moving close to the spring constants of the rotational and translational restraint to extreme values (zero and/or infinity), the boundary conditions can be attained for the desired combinations of end boundary conditions...
design, Analysis and Motion Control of Microrobot Based on Cantilever Rotary Beams Due to Piezoelectric Actuation
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, Mohammad Taghi (Supervisor)
Abstract
With regard to daily developments in micro and nanotechnology , the use of micro robots, In a different of applications increased extensively. The aim of this research was to introduce a mobile micro robot and analysis its behavior. this micro robot has several microlegs which are formed from microbeam mechanism and piezoelectric actuators. The degrees of freedom by taking any micro beam, any of these microlegs are able to move in a three-dimensional space. The mechanism used in this research for each of the microrobot legs, as was the consecutive series and its increase, in manor motor .In this research, unlike the previous tasks, piezoelectric actuators are considered as end effectors and...