Sharif Digital Repository

In this research with Finite Element Methods in ABAQUS, numerical modeling has done in three-dimensions, which can be used to determine the effect of different factors on the surface settlement. Also, various factors such as geotechnical conditions, tunnel diameter,tunnel depth, the impact of the thickness of the segments and the amount of eccentricity of the structure relative to the longitudinal axis of the tunnel considered in this study. Face Pressure Supports, and Grout Injection Pressures are taken into account, too.Tunnel drilling causes a change in the displacement area and creates a changing zone around the tunnel. In this regard, not only adjacent buildings will be affected by... 

Suction caisson is a relatively new technology which was introduced about 30 years ago for the first time and after several investigations, was found its position in the oil industry and construction of anchorages, during previous decade. So nowadays, it is the most effective and economical choice as the mooring of offshore structures in comparison with the other foundations. Suction caisson is a hollow cylinder with an open bottom and a closed top. After placement on the seafloor, the caisson first penetrates into the soil by its self weight and then inserts into the ground by pumping water out of it. Although many researchers have attempted to understand the behavior of suction caissons... 

A large number of structures subjected to the seismic loading have been damaged or have experienced failure in different parts such as the pile structure or even in the entire structure due to unanticipated effects of the soil-pile-structure interaction.The complexity of problems regarding the soil-pile-structure interaction is an influencing factor in prediction of the behavior of structure during the earthquakes. In this study, the effect of the interaction on the dynamic response of bridges was investigated using the finite element software ABAQUS. The primary purpose of this study, as previously described, is to study the effects of the soil-structure interaction on a bridge located on a... 

Train-induced vibrations can disturb the residential areas close to the rail as well as making ground-borne noises that can create problems for sensitive apparatus and devices. To reduce these problems, there need to be an evaluation of the amplitude of the ground-borne vibrations. The goal in this study is creating a suitable finite difference model in order to predict the intensity of train induced vibrations propagating inside or on the surface of the soil using FLAC (Fast Lagrangian Analysis of Continua) software as well as assessing the effectiveness of recycled shredded tires in reducing the surface vibrations by using these material as the filler for vibration isolation trenches. The... 

Determination of soil bearing capacity has been a subject for both geotechnical engineers and designers for a long time and a variety of relationships have been proposed to determine the ultimate bearing capacity of homogeneous soils. One of the most primitive equations in bearing capacity of foundations, which was Based on prandtl's (1920) bearing capacity, with some modifications, was proposed by Terzaghi. In many lands, the soft clay layer Located in a low depth of subsurface soil profile. Either the foundation should be laid in greater depth on the stiff clay or a layer of compacted sand can be used to improve the ultimate bearing capacity. Most of the recent works, which have done so... 

In this research with Finite Element Method in ABAQUS, a Number of Numerical modeling has done in two-dimensions, which can be used to determic the effect of different factors on the seismic vulnerability of tunnels. Also, varios factor such as Geotechnical conditions, tunnel depth, tunnel thickness and ground water is considered in this study.One of the parameters considered in designing tunnels is the ability of the tunnel’s lining to withstand the seismic and geotechnical loads. Each section of the tunnels are designed according to the maximum stress witch created due to the earthquake. this stress’s created in tunnels can be devided in to 3 category : the axial force,the Shear force and... 

Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of... 

Numerous structures which are involved in seismic soil-pile-structure interaction have been damaged، failure in piles or even collapsed that can’t predict. Because of difficult modeling in soil، pile، structure interaction prediction the response of structure is impossible. In this study with using the finite element Abaqus software tries to understand the effect of soil pile structure interaction in structure response. By using the time history of Elcentro، structure with different boundary conditions were analyzed and the response of them were compared. Models have different boundary condition such as fixed base، pile groups and pile raft. Also in this study the effect of mat in... 

Investigating the behavior of piled-raft foundations is a three-dimensional problem. The shape and location of the piles in the raft as well as the complex interaction of the soil-structure in these foundations should be analyzed in a three-dimensional fashion to indicate the real behavior of this type of foundations. The soil must also be analyzed in a nonlinear state to achieve the correct bearing capacity of these foundations. In this research, a nonlinear 3D analysis was performed using FLAC3D to investigate the behavior of piled-raft foundations, and the effect of various factors such as the length, arrangement and number of the piles, the loading level and the thickness of the raft, on... 

The purpose of designing the foundation is to transfer the load of the structure to the subsoil without creating shear failure and additional settlement in the soil. Therefore, choosing the appropriate bearing capacity is an important point that should be considered in any project. Determining the bearing capacity of foundations is one of the topics that has long been considered by researchers and geotechnical engineering designers. For this reason, its design is not considered a new issue, but the application of new methods and the development of computers, raises new perspectives on this issue that justifies new studies.Most of the recent study, which have done so far on bearing capacity,... 

One of the most common devices for terahertz (THz) wave generation and detection is a Terahertz photoconductive antenna. Impedance matching between the antenna and the photoconductive material is a primary factor to obtain high optical-THz conversion efficiency. Because of the time dependant conductivity of the photoconductive material, impedance mismatching is an obstacle for generating high power THz pulses. Moreover, the range of laser power (when using Ti:Sapphire) from the excitation source varies from a few tens of milliwatts to a few watts while the radiated THz power as compared to this laser pump power is very low (in the order of a few μW); this means a low power conversion... 

The integration of radar and communication functionalities into a unified Joint Radar-Communication (JRC) system offers enhanced spectral efficiency and reduced hardware complexity. Recognized as a key enabler for next-generation wireless networks, JRC systems require a careful balance between radar and communication demands, where waveform design plays a pivotal role in achieving this equilibrium. Although waveform design has been extensively studied separately in radar and communication domains, the requirements of modern networks necessitate a unified approach that simultaneously addresses the needs of both systems. This thesis advances waveform design methodologies for JRC systems,... 

In recent years, due to urban expansion and population growth, number of floors and excavations depth has increased. Stabilization of excavations is one of the most important issues in geotechnical engineering. Today, one of the most widely used methods that is used in deep excavations is brace soil by steels and pretension them. In this thesis tries to evaluate static behavior of flexible supporting structures with pretension anchors by using PLAXIS2D, FLAC3D and GEOSTUDIO softwares. The objective of this modeling is better understanding the static behavior of walls, comparing the two and three dimensional modeling and the effect of corners of excavation on deformation. The results shows... 

In this thesis a waveguiding structure is introduced and analyzed for terahertz applications. The proposed structure is called Inhomogeneous Parallel-Plate Ladder Waveguide (IPPLWG). This waveguide is formed by locating a periodic structure inside parallel-plate waveguide.This periodic structure itself consists of a array of metallic posts surrounded by silicon. The combination of metallic posts and silicon have the capability of guiding and confining of EM waves in terahertz band. IPPLWG can be used in implementing the passive terahertz devices such as filters and couplers. The main objective in this thesis is to characterize the IPPLWG for potential applications. Because IPPLWG has open... 

In this dissertation, the application of frequency and space diversities in radar target parameter estimation are investigated. On this basis, multi-frequency signal is used to improve the range resolution, array structure is used to increase the angle estimation accuracy and the merger of the multi-frequency signal and array structure are used to increase the maximum number of targets that can be uniquely identified.Considering the desirable properties of multi-frequency signals such as high bandwidth efficiency, high range resolution achievement without chip length decrease and …, there has been increased interest in the vast area of research on the design of such signals that has... 

Target recognition techniques based on micro Doppler phenomenon are popular because they are applicable even on low resolution radars, in contrast to other techniques such as High Resolution Range Profile (HRRP) which need high resolution in range or angle. Usually, main purpose of such techniques is generating robust features against target initial state, velocity, aspect angle, etc. rather than features which exactly identify a target. Main approaches in the literature are based on time-frequency transforms (TFT) such as spectrogram in order to generate features to classify targets, but in this thesis, we propose a totally different method using Recurrence Plot for generating features... 

In this study TiO2/SiO2 thin films were prepared by sol-gel method from Tetra isopropylortho Titanate(TIPT) as the principle of TiO2 material with Tera ethoxysilane(TEOS) as the principle of SiO2 material to achieve high scratch-resistant , antibacterial and self-cleaning surface area under the effect of various percentage of SiO2 . Film deposition was carried out using a dip-coating technique and heat-treatment was used at 700ºC to achieve crystalline of films with excellent adherence the of substrate.
The surface morphology of the films has been observed by Scanning Electron Microscope (SEM) and the tribological properties of the surface were investigated by Atomic Force Microscope... 

Proton precession magnetometers are one of the most sensitive scalar magnetic sensors. Their function is based on Zeeman effect and also nuclear magnetic resonance phenomena. In this project we have designed and implemented needed coils, swithching and signal detection circuits. Because of extremely high sensitivity of this sensor to induced noises and also gradient of earth’s magnetic fileld, detection of precession signal needs design of low noise electronic circuits with special EMC considerations. The implemented system in this project contains different blocks, such as switching circuit and its related control unit, amplifier, filter and frequency meter. Using this system, the obtained... 

Effective field theory is a practical method for model building and explaining experimental/observational data. These theories are constructed based on knowing low energy degrees of freedom and symmetries (accidental or fundamental). By construction, these theories are applicable up to a cut-off scale and their predictions beyond that are not reliable. For applications to higher energies a UV completion is needed through which modifications are applied or new heavy degrees of freedom are introduced. In order to complete a theory in a Wilsonian approach, scattering amplitudes must satisfy some constraints. These constraints are derived from basic assumptions like Lorentz invariance,... 

Many processes and real world systems indicate nonlinear behavior and operate either naturally in multiple regions or in a wide range of operation space. Modelling and control of these systems by nonlinear methods needs to have a deep insight. Furthermore, the nonlinear methods leads to complexity issues. To overcome these problems, multi-model methods are introduced which consist of two steps, decomposition and combination. In decomposition step, the complex system is divided into a set of simple models; in the combination step, the behavior of local models are combined. How to decompose to local models and how to combine them are two main questions in this area which not answered...