Sharif Digital Repository

Nowadays, due to the advancement of robotic technologies and development of industrial robots, the robot manipulators are widely used for automation of various manufacturing processes, such as finishing processes. In these applications, the contact has to be made between robot end-effector and environment. Therefore, control of interaction force in the constrained manipulators is an important demand. On the other hand, due to use of gear box and belts for energy transmission in robot joints, robot manipulators have flexible joints. The vibration, generated due to the interaction force and robot joint flexibility, can deteriorate surface roughness in automated finishing processes. In order to... 

Soil liquefaction is a phenomenon in which soil loses much of its strength or stiffness for a generally short time but nevertheless long enough for liquefaction to be the cause of many losses. Thus, many researchers have worked on the factors which affect this phenomenon. Effects of initial static shear stress on liquefaction strength of loose and medium dense Babolsar sand specimens were investigated in this study. Babolsar sand is fine to medium uniform sand classified as SP in USCS. Tests were performed with cyclic simple shear and static triaxial devices. All tests were performed under consolidated undrained conditions. Cyclic simple shear tests were performed under constant vertical... 

The nature of fluid flow in hydrocarbon reservoirs is very complex because of the complicated sedimentary processes. Proper modeling of distribution of these heterogeneities is crucial, affecting all aspect of fluid flow. The conventional approach to investigating the impact of geological uncertainties on the prediction of reservoir performance is to build a detailed geological model using geophysical, geological and petrophysical data, upscale it and finally perform flow simulation. Because of uncertainties in the data, it is necessary to construct a number of possible geological models and then run flow simulations many times to get a reliable model. This approach is computationally very... 

In this project roll channel autopilot of an agile flight vehicle has been studied. In skid-to-turn tactical flight vehicles according to the type of control strategy, for achievment of acceleration commands, the roll angular velocity should be kept near zero. In usual autopilot design, effects of channels on each others is ignored. But three channels of agile flight vehicles have some mutual effects, that consists of kinematic, inertial and aerodynamic couplings. In the case of roll channel dynamics, aerodynamic couplings are dominant and apears because of two factors: roll induced moment and roll cross coupling moment.
After study and aerodynamic modeling of mentioned factors, based... 

Metamaterials, due to their unique structure-dependent properties, exhibit characteristics beyond those of natural materials. One of the design methods for these materials is topology optimization. This research presents a novel topology optimization approach that directly employs convolutional neural networks (CNNs) to determine material distribution within the design domain. The input features of the neural network are physically meaningful attributes that have a direct correlation with the objective function, applied constraints, and optimal structure. This characteristic accelerates the optimization process and enhances the accuracy of the results. The network architecture is inspired by... 

One of the classic problems in the aeroelasticity field is panel Fluttr that occurs in supersonic flow. Panels as wing skins, fuselage missile, and so are prone to this phenomenon, which causes fatigue and structures, will be demolished.In many cases, the wall panels and a full tank of fuel, this in this case, the vibration of the fluid-filled panels will be affected. There is clearly fluid into a tank filled with considering the approximation of incompressible fluid dynamics and vibration modes of the panel will change. In this study, a three-dimensional rectangular tank is considered the high walls on the elastic and supersonic flow passes.Fuel density and structural dimensions of Full... 

This project presents an outline of the crack tip stress fields in the presence of a plastic enclave around a growing fatigue crack using RKPM and Drucker-Prager criterion for pressure sensitive materials such as concrete and rock. Two distinguished features of RKPM are the arbitrarily high order smoothness and the interpolation property of the shape function which has kronecker delta property at the associated nodes. This method has proved to handle extreme material deformation and moving discontinuities. For the frictional materials such as rock in geotechnical engineering, a non-associated or associated Drucker- Prager plasticity model is appropriate for modeling its constitutive... 

In this thesis first a flrxible launch vehicle is modeled and simulated by taking the moment vibrations into consideration, then navigation system and it’s uncertainties which depicts more realistic performance are added up and the guidance is designed based on pitch-programming. Adaptive robust controller is designed and implemented with the approach of sliding mode such that making the system able to keep it’s despite of navigation uncertainties and flexibilities, also controlling the attitude in the framework of adaptivity and robustness  

Roller compacted concrete is a dry concrete with zero slump which is constructed in layers. Roller compacted concrete dams are generally weak in interlayers. The bonding strength and permeability of the interlayer affect the performance of the dam’s structure and its safety. In this study, the mechanical characteristics and the permeability of the interface layer of RCC are investigated by considering three key parameters, including water-to-cement ratio (w/c) of concrete, w/c ratio of bedding mortar and time interval between pouring each layer. More than 300 RCC specimens are prepared. To evaluate the properties of the interface between the mortar and the first layer surface, various tests... 

Water injection is one of the main methods of enhanced oil recovery that its success depends on exact study of main effective parameters. Saturation functions including relative permeability function and capillary pressure function are one of the effective parameters on the success of water injection projects. In many reservoirs there is wide heterogeneity and various layering that have different absolute permeability. These features result in uncertainty to measurement of curves of saturation function. Experimental studies on this field are carried out on the composite cores that show heterogeneity and layering media of reservoir. By Scaling up the saturation functions from single cores to... 

Thermo-acoustic sience is the conversion of heat to power through the sound wave. Thermoacoustic engines for different reasons like easy making, not having moving parts and so high reliablibility of system is in attention for researchers. Also looped-tube thermoacoustic engines are very new in the world and sience and thechnology of them belong to a few companies and for different reasons are replacing different kinds of thermoacoustic engines.They have higher efficiency than other types. They can be made in large scales. They have a larger thermal range. In this research, the numerical study of one, two and four stage looped-tube thermoacoustic engines has investigated with the help of... 

Most of the heavy oil reservoirs contain discontinuous shaly structures which affect fluid flow through porous media as well as oil recovery efficiency during EOR processes. However, selecting the best EOR technique which maximizes the oil recovery remains a topic of debate in the literature. In addition the effect of shale geometrical characteristics including: spacing from wells, discontinuity, orientation, number of shale streaks, shale's spacing and length on oil recovery factor are not well understood. In this work experiments have been performed on one-quarter five-spot glass micromodels. These models have been developed by a new method using laser technology. Generally, this research... 

Permeability is an essential parameter used for reservoir evaluation, simulation and management to optimize oil recovery. The conventional approach to estimate reservoir connectivity, conductivity, sweep efficiency and other critical information for decision-making is to build detailed geological models, which are then upscaled to a coarser grid where flow simulations are run. However, this takes many hours to be carried out even for a single realization practically. In practice, a very small number of realizations are considered and consequently the true uncertainty in the results is very poorly estimated. In this study, a statistical model of isotropic overlying sandbodies is used to... 

Metabonomics is a quantitative measurement of time dependent metabolic interactions for living systems in response to the pathological or genetic variations. NMR spectroscopy has emerged as a key tool for understanding metabolic processes in living systems. In this project, the study of metabolomics was performed as classification and regression on samples of parkinson’s disease, multiple sclerosis disease, celiac disease and crohn’s disease. In classification part, various methods were applied using optimal parameters.classification methods in Parkinson’s disease, multiple sclerosis disease, celiac disease and crohn’s disease were RF, CART, PLS-DA, RF and RF respectively. Based on the...