Sharif Digital Repository

Separation of the effects of the initial horizontal stress and relative density on the cone tip resistance in the sandy soils has been a complicated issue for many years. On the other hand, there is no reliable method for determining the in-situ horizontal effective stress based on the piezocone measurements in the cohesive soils, and the empirical correlations suggested in the literature produce no more than a rough estimation.Considering the aforesaid issues, an attempt is made in this thesis to provide a new innovative solution for determining the in-situ horizontal (effective) stress in the sandy and clayey soils according to the CPT measurements. In this regard, at first, numerical... 

Existing closed form solutions of contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. These solutions cannot be applied for coastal aquifers where seawater intrusion induces a variable velocity field. The Fourier series method is adapted to obtain a semi-analytical solution for contaminant transport in confined coastal aquifer in which the saltwater wedge is in equilibrium with a freshwater discharge flow. The developed method can be applied for different scenarios of contamination. Two scenarios dealing with, respectively, contaminant leakage from a source at the aquifer top surface and aquifer contamination from the landward boundary are... 

The colloidal crystals are formed of spherical particles and can be fabricated using simple and low-cost chemical methods. Optical properties of colloidal crystals should be recognized properly in order to design optical devices based on these nano-structures. Reflection and transmission coefficients of these multilayer structures are very important for understanding their properties. Semi-analytical methods like Fourier Modal method (FMM) can be very useful to obtain their reflection and transmission properties of these multilayer structures. In this thesis, we try to implement Matched Coordinate (MC) and Adaptive Spatial Resolution (ASR) techniques in the FMM. These techniques increase... 

Approximately, 60 percent of the world's populations are living at the distance of 60 kilometers of the coasts. In coastal zones, coastal aquifers are the most important resources of the available freshwater while expected that the short-term or long-term impacts of the climate changes threat such aquifers. In general, it is predicted that climate changes e.g. sea-level rise (SLR) cause to increase seawater intrusion (SWI) in the coastal aquifers. In this study, both continental and island coastal aquifers are considered. The objective of this research is the investigation of SWI behavior occurred in the coastal aquifers due to climatic change parameters and aquifer properties. For... 

Shape Memory Polymers (SMPs) are a class of smart materials capable of remembering multiple shapes, and transitioning between them in response to an external stimulus such as thermal or magnetic induction. SMPs have attracted significant attention of both industrial and academic researchers due to their useful and attractive functionality. This thesis aims to analytically develop Euler-Bernoulli, Timoshenko and von Karman theories for beam bending in small strain regime considering SMP constitutive equations. To properly introduce analytical solution for the problem of beam bending, the constitutive model proposed by Baghani et al. (2012) has been used. For this purpose, three dimensional... 

A semi-analytical solution for rotating axisymmetric disks made of functionally graded materials was previously proposed by Hosseini Kordkheili and Naghdabadi [10]. In the present work the solution is employed to study thermoelastic creep behavior of the functionally graded rotating disks with variable thickness in to the time domain. The rate type governing differential equations for the considered structure are derived and analytically solved in terms of rate of stress and strain as a reduced to a set of linear algebraic equations. The advantage of this method is to avoid simplifications and restrictions which are normally associated with other creep solution techniques in the literature.... 

The growing use of fossil fuels and their impacts on the environmental pollution, mostly originating from internal combustion engines, is one of the important issues in environmentally friendly energy management. One of the key solutions to improve engine performance and reduce exhaust emissions of internal combustion engines is direct injection of bio-fuels. In this regard, in the present study some new biofuels such as Bio-Norouzak, Modified Bio-Ethanol (MBE), and Modified Bio-Diesel (MBF) have been introduced and effects of different parameters on their sprays have been investigated experimentally and analytically. The literature survey shows there is not any comprehensive study on the... 

Nonlinear forced vibrations of thin functionally graded circular and elliptical plates under classical boundary conditions are investigated based on the classical plate theory. The von Kármán strain-displacement relations is employed to include geometrical nonlinearity caused by large transverse displacements of the plate thickness order, and modal expansion in polar and elliptical coordinate along with the perturbation method of multiple scale is used to solve the governing equations. The material properties are graded through the plate thickness according to a power-law distribution of the volume fraction of the constituents. Transverse forcing is supposed to be harmonic with angular... 

In nature, tidal currents are visible in gorges and in saltwater and freshwater collisions. In the study of behavior of different types of flow, it is usually assumed that the pressure is hydrostatic and the equations are solved based on this assumption. In the Approach Controlled regime observed during the double layer in 1993, the modeling performed using the equations derived from this assumption did not fit the results of the experiments. This demonstrates the inability of the hydrostatic pressure assumption to solve this particular regime. Hence, the equations were written on the basis of non-hydrostatic pressure and then the observed results were in accordance with the results of the... 

Based on Hamilton’s principle, a three-dimensional semi-analytical method for the analysis of free vibration of a nano-composite plate within the couple stress theory is developed. Computation of dynamic behavior as well as natural frequencies and mode shapes is interested. In this method, the mechanical displacement functions, in each layer, are defined as product of a base function and a three-dimensional polynomial with unknown coefficients. The base functions are defined with respect to the kinematical boundary condition and the domain geometry. The mode shapes will be obtained and the accuracy of the present approach is demonstrated by comparison it in both classical elasticity and... 

With the increasing number of applications in internal combustion engines, environmental impact and air pollution caused by emissions has been much attention. Natural gas is a promising fuel for limiting pollution laws in many countries. The use of fuel with a higher ratio of hydrogen gas to carbon pollution reduction motor. In this context and with regard to development policy and also due to the diversity basket NGV fuel, fuel injection, has been modeled analytically and numerically in a direct injection engine. In this study, an analytical model for spray injection fuel delivery and is dissolved. The resolution of the method of separation of variables is taken. The effect of the nozzle... 

Circular cylindrical shells have been widely used in many engineering structures such as spacecraft, submarines, offshores, and storage tanks. Their high stiffness-to-weight ratio and load-carrying capability make them well suited for use in civil and aerospace structures. The consecutive development of material engineering along with the increasing demands for lightweight, heat-resistant, and high strength structures have led to the usage of advanced materials namely functionally graded (FG) materials in designing such structures. In this thesis, the nonlinear static analysis of thin FG cylindrical shells is carried out using the Donnell’s shell theory with first-order approximation and the... 

In the present study, buckling and free vibration of two joined conical shells made from isotropic and generally laminated composites are presented. The joined conical shells can be considered as the general case that can be used in analysis of single cylindrical and conical shells, joined cylindrical-conical shells, joined cylinder-plates or cone-plates, cylindrical and conical shells with stepped thicknesses, annular plates, laminates with ply drop-off or any case that the stiffness of the laminate changes in the shell. Governing equations are obtained using thin-walled shallow shell theory of Donnell type and Hamilton’s principle. The joining of shells is exerted using various methods and... 

Among scientific fields of study, mathematical programming has high status and its importance has led researchers to develop accurate models and effective solving approaches to addressing optimization problems. In particular, meta-heuristic algorithms are approximate methods for solving optimization problems whereby good (not necessarily optimum) solutions can be generated via their implementation. In this study, we propose a population-based meta-heuristic algorithm according to chemotherapy method to cure cancers that mainly search the infeasible region. As in chemotherapy, Chemotherapy Science Algorithm (CSA) tries to kill inappropriate solutions (cancers and bad cells of the human body);... 

Nowadays, the study of flow and heat transfer in turbine engines has become critical due to their increasing use and importance in various engineering industries. The critical issue of blade burning in the first row of turbine’s blades illuminates the critical roles of numerical and experimental activities in reducing these undesirable effects. Since blade cooling is directly related to the secondary air system, one important issue in blade burning research is to utilize the conjugate heat transfer approach. As Known, an increase of about 1% in the mass flow of air entering into the secondary air system would cause an increase of about 0.5% in the engine specific fuel consumption (SFC),... 

Hydrocarbon reservoirs may be classified on the basis of their drive mechanisms. In the reservoirs adjoined by water aquifers, waterdrive may be the primary production mechanism. The invasion of reservoir rock by aquifer water may have a significant impact on reservoir performance. Therefore, water influx into hydrocarbon reservoirs must be predicted accurately as a function of time, pressure history at the reservoir/aquifer interface, reservoir/aquifer size ratio, and aquifer characteristics.To forecast the performance in a waterdrive reservoir, an aquifer model simulating the fluid flow in the aquifer and flow from the aquifer into the reservoir is needed. Robust techniques for analysis of... 

Pump and treat is one of the oldest and mostly used methods in remediation of groundwater. Although this method has been criticized recently, it is still widely be used. The systems typically use one or more extraction and injection wells to hydraulically control the contamination plume. The purpose of studying a pump and treat system is to determine the appropriate location and discharge for the wells in the way that the contamination could be pumped out. In this study after reviewing some existing solutions for delineation the capture zone of single well a method to delineate the capture zone for arbitrary located wells is presented. This method can delineate a three dimensional capture... 

In this thesis, the quasi-two-dimensional modeling of polymer electrolyte membrane fuel cell cathode side is presented as a single phase. Polymer membrane fuel cell modeling equations are solved in the equations of continuity, momentum, and chemical species are potential equation. In this report, for modeling the electrochemical reaction in the catalyst layer of the relationship Baltr-Vollmer is used. The present analytical solution based on two fixed pressure gradient and the velocity dependent pressure gradient is developed. Momentum and continuity equations in the model with separation, velocity and pressure field is achieved. By comparing the results of the modeling analysis with... 

Advanced reservoir characterization methods can yield geological models at a very fine resolution, containing 1011-1018 cells while the common reservoir simulators can handle much fewer numbers of cells due to computer hardware limitations. The process of coarsening the fine-scale model to simulation models is known as upscaling. There are three fundamental steps in the procedure of upscaling, i.e. defining the coarse grid geometry, calculating the average properties for the generated coarse grid and simulation of the two-phase flow equations on the generated coarse-scale model. In this thesis, the focus will be on investigating the applicability of optimization in the context of coarse grid... 

In this thesis the effects of vibro absorbing coating on vibration behavior of an aluminum sheet and also on a stiffened aluminum panel are investigated using experimental approach. Since there wasn't any information available about the used coating, to find its viscoelastic material properties, the method mentioned in ASTM E756-05 standard is employed and corresponding tests are performed.
In the next step, an analytical solution developed for the aluminum sheet with viscoelastic coating and the obtained results compared with experimentation, in order to find its prediction accuracy for loss in “loss factor” of the system in presence of coating.
To study the effect of...