Sharif Digital Repository

Ground vibration during pile driving is one the most important factors that limits usage of this kind of piles. It is of great importance to estimate the level of vibration prior to the beginning of pile driving to avoid structural damage or disturbance of building occupants. In this study, an axisymmetric finite element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code ABAQUS, to simulate the full penetration of a pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particles velocity with those measured in the field. The results indicate that the peak... 

Increasing and diversified use of micro electromechanical components necessitates further development of methods for their secure gripping and transfer. In this research, a piezoelectrically driven microgripper including two gripping sets with four arms has been designed. The system can hold and handle microparts from 100 to 150 microns by applying corresponding voltages between 80 to 20 volts. The design is such that after positioning the work piece between the two microgripper arms the piezoelectric comb-drive actuators are activated. Then the two gripping arms are moved toward each other and ultimately grasp the work piece. In order to determine the behavior of the... 

In this work, a model was presented for an MCFC fuel cell with internal reforming and combustion chamber. The model consists of mass and heat transfer equations beside the chemical and electrochemical reaction rate equations. Velocity distribution due to reactions and temperature distribution along the cell is considered. The model has been simulated in steady state form using finite difference method in MATLAB package environment accompanied by the analysis of the dynamic behavior of cell using method of lines in Simulink environment. Simulation results have been validated with experimental data extracted from literature. The last part of the work concerns with sensitivity analysis of some... 

A novel reduced mechanism is introduced which aimed to predicts NOx and CO generation in advanced industrial gas turbine combustors. The survey is initially conducted by considering 25 species in GRI-3 mechanism of Methane oxidation and continued to choose nine of the most important species based on the quasi-steady state analysis. Finally, a new skeletal reduced mechanism with 35 reactions and 20 species is derived using sensitivity analysis, reaction path analysis, and some physical reasons. The overall validity of this mechanism is clearly confirmed by comparing the present predicted results with GRI-3 full mechanism in a PSR reactor. The adiabatic flame temperature and all of the main... 

Considering the extensive developments achieved up to now in the fields of trade and international transportation, as well as the key role of the freight transportation in the economical development of a zone or a country, the present research, titled “A Study of the Trade and Transportation Trends”, was planned. The available data concerning the trade of six types of the goods according to The United Nations Classification (SITC), within the period 1965-2005, have been analyzed in this research. The study has been focused on the Asian Multimodal Network constituted of 31 countries. Trading centre of each country in the selected network is assumed to be located in its capital town. The... 

Tire is one component of the suspension system and has beneficial effects on reducing vibrations caused to the vehicle. This study aims to determine the factors affecting the damping and stiffness of the tire is carried out. The modeling of factors were identified. For testing the modeling effort is to be made to the instruments used to measure the damping and stiffness of the tires. To make the structural static analysis, dynamic and modal was to have sufficient structural strength and the displacements and stresses are sensibly placed. Factors that have influence on the hardness of the ring diameter, the outer diameter of the tire, tire pressure, tire tread depth, tire wall thickness,... 

Atomic force microscope (AFM) has a significant capability of imaging surface topography on an atomic scale. It is also widely used for Nanolithography in MEMS/NEMS (micro/nanoelectromechanical systems). Although the conventional AFMs have a significant capability of nano-scale surface measurements, their probe tips cannot come in close proximity to the sidewalls, no matter how sharp they are. Therefore, no accurate nano-scale measurements at sidewalls and edges can be achieved by these conventional AFMs. In addition, regarding the increasing applications of micro-structures such as micro nozzles, micro gears, micro holes and micro trenches which all of them have sidewalls and edges,... 

pain is one of the most common musculoskeletal (MS) disorders and the most important cause of functional disability in developed and developing countries. Several studies showed that the most important factor in development of the low back pain is loads and stresses in different parts of the spine. While non-invasive measurement of these internal loads and stresses, as a tool to estimate the risk of injury, is very difficult and costly, biomechanical models of the spine are the best meansfor analyzing the risk of injury in various in-vivo activities. In order to develop a spine model, it is necessary to measure the kinematics of the vertebrae for the specified activity. In previous studies,... 

It is believed that the carbon dioxide emissions are likely to be the dominant drivers of climate change over the coming century. Geological sequestration in saline aquifers is a potential technology for mitigating carbon dioxide emission in atmosphere. In this study, computer simulation is combined with experimental design to perform sensitivity analysis and estimation of carbon dioxide sequestration in saline aquifers. For this purpose, horizontal permeability, vertical to horizontal permeability ratio, porosity, depth, pressure gradient, temperature gradient, water salinity, formation thickness, diffusivity coefficient, dip, irreducible water saturation, water Corey exponent, gas Corey... 

Producing from Gas Condensate Reservoirs under dew point pressure and at constant temperature may have a complex behavior because of existing two phase system and liquid around the well. Zones with different mobility generate as a zone away from the well containing only gas, a zone having liquid around the well and finally a zone with capillary effect. Existence of condensate around well reduces gas relative permeability and as a result productivity index of well decreases. In fact these condensate acts like an additional skin and because of some complex processes, investigating of these behaviors can be difficult.
Well testing analysis in Natural Fractured reservoir is generally based... 

With the growing development of urban communities and population, the demand for water and treated sewage water has grown significantly. The environmental damage of polluted water has resulted in passing of new and strict environmental laws on wastewater discharge recently. In the present research, a hybrid system involving a power, heat and cool cogeneration and a carbon dioxide capture system has been designed for a typical wastewater treatment plant. The plant is optimized from economic and environmental criteria. The anaerobic digester is modeled using the ADM1 model. The biogas is directed into the hydrogen sulfide removal filter to remove the impurities and into the heat exchanger to... 

Nowadays, the world is full of multi criteria decision problems and all the people should make decisions in different situations. Sometimes, the result of a decision problem is so important as a wrong decision may result in a loss that cannot be compensated. Therefore a decision making tool seems as a must. On the other hand, in this era of rapid social and technological change leading to increasing life complexity, sensitivity analysis is an important issue in all decision making processes. Analytic Hierarchy Process and Analytic Network Process, as two common tools for multi criteria decision making, are widely used throughout the past decade in different fields. Designing the model and... 

In this work, a comprehensive dynamic model has been used for styrene emulsion polymerization in a semi-batch reactor to predict the evolution of product particle size and molecular weight distributions under non-isothermal condition. Method of moments has been applied for solving the population balance equations and the results are compared with the results obtained from finite-volume method as a precise technique. A sensitivity analysis respect to perturbation in initial values of various reagents, species and the reactor temperature has been performed to identify suitable manipulated variables for closed-loop control of the reactor. The detailed model is used to generate optimal feed... 

Vertical milling machine is one of the most common machine tools for precision parts production. The static deflection of the machine tool and thus the displacement of the tool, is due to the high machining forces is the most important factor in reducing the dimensional Precision of the work piece. Also, the overlap of the frequency range of operation with the natural frequencies causes an undesirable resonance phenomenon. Reducing the strain energy of the column and thus the reducing the displacement of the tool, and increasing the first natural frequency of the milling machine, given that the frequency range of operating is below the first frequency, is a desirable change that can be... 

Modeling and simulating accurate patterns which are adapted to our real world is a hard and complicated task. The most important thing for these models is finding any explicite solution, or, finding any solution that is precise as much as possible. The knowledge of financial mathematics by gathering several sciences such as: probabilities, stochastic analysis, numerical analysis, and stochastic differential equations, attempt to determine such exact solutions, or, try to appoximate the explicit answers as precise as possible; in the world of financial trades and contracts. Moreover; one of the most important requirements to control the risk of these financial cotracts, and, then to optimize... 

To achieve the highest amount of FOPT during reservoir life and the most net present value, the parameters that are effective in the production of the field are adjusted to be the best performance. In order to achieve these conditions, the reservoir model and the surface will be checked integrated so that the optimal mode of each parameter is determined in interaction with other parameters, so the first integrated model of the reservoir and the surface and then optimizing the target functions of cumulative production and the net present value is performed using the genetic algorithm.Since the number of parameters of reservoir model and surface in the studied field in this study is high,... 

Face recognition, which is one of the most important biometrics, has always been one of the main challenges in many security issues, such as verifying the identity of customers of financial institutions and passengers at the airport, and such issues have many applications in daily life. Face recognition has always been an important issue in computer vision and pattern recognition. Currently, several methods based on deep networks have shown great results in face recognition, among which the following can be mentioned.1.The deep face was introduced by Facebook in 2014; 2.Face-net was presented by Google in 2015 ;3.VGGFace was presented by Oxford University in 2015; 4.Openface was presented by...