Sharif Digital Repository

The robots that can move on rough terrains are very important especially in rescue operation, exploration of mine and etc. Since contact surfaces between the robot and the ground are unpredictable, the structure of the robot is usually unintelligible and its motion analysis is difficult. In this research, a ring-like shape robot with flexible body is proposed for motion in rough terrain, gradient paths and passing bars. The ring shape has more usages than other shapes for example as a wheel in a larger robot. Also its flexibility helps the motion particularly on rough terrains. This robot consists of a central section for setting equipments and arms around that. Being radially and... 

Nowadays, enormous amounts of data are transferred through data communication networks every day in order to fulfill end users’ demands all over the world.The capacities of the links between network nodes, or in other words, the amount of bandwidth available to carry data is undoubtedly one of the most expensive resources as well as the one of most importance which not only plays an essential role in communicating information packets over such a vast network, but is a major determinant of Quality of Service (QoS) in terms of rapidity as well. The idea of using cache memories to optimize network bandwidth consumption laid the foundation for developing Content Delivery Networks (CDNs). In such... 

This research uses systems dynamics modeling to present an integrated assessment of the energy-economic damage caused by climate change in Iran under different climate scenarios. Implementing these policies will cause a change in the use of global oil, followed by a change in the outlook for oil price changes in the future. Due to the high dependence of the country's economy on fossil fuels, oil price changes affect the country's economy. In the first step of this thesis, the system dynamics method examines the prospect of oil price change in climate scenarios. Then, according to the oil supply and production, in different scenarios, the assessment of the future conditions of the oil market... 

There is a major interest to manufacturers of automobile and aerospace parts towards the tailor-welded blanks (TWBs) to reduce the weight and cost of the parts and improve their performance. In this work, formability of four groups of TWBs (two groups with similar thicknesses and different steels and two groups with similar steels and different thicknesses) are investigated. To produce the TWBs, DX54, E275 and E335 steel sheets were used. The results indicate that the inclined laser beam causes the sample failure from the weld zone in the tensile test. Setting the focal point on the top surface of the sheets results in enhancement of yield strength in comparison to the other positions. ... 

Renewable energy sources have significantly used in recent years and the associated technologies have been widely developed. Grid connection of most renewable technologies, such as photovoltaic and wind turbine, is accomplished using power electronic converters. Control of injected active and reactive power as well as current and frequency control of is, so, implemented through the power converter. Inverter is among the equipments widely used for grid connection The purpose of this project was to design and develop an inverter for grid connection of renewable generation technologies for laboratory use. The inverter is aimed to control both injected active and reactive power. A full-bridge... 

Prediction and calculation of shielding tensors of H, C, F and P nuclei of different molecules has been the subject of much research, because these nuclei have the greatest importance in NMR experiments. The optimum wave functions and calculation method were obtained using empirical models and factorial design. Based on preliminary experiences, the following four factors at two levels were selected: electron correlation, triple-ξ valence shell, diffuse function and polarization function. The wave functions for calculating gas phase 1H and 13C chemical shifts of various types of alcohols, amines and simple hydrocarbons were optimized using empirical model. The B3LYP/6-311+G wave function is... 

Al 5083 is a non-heat treatable alloy that widely used in the aerospace and automotive industry due to its low density and high strength. However, poor wearing behavior and low elastic modulus restrict its engineering applications. Metal matrix composites (MMCs) have advantages of high strength and modulus by reinforcement of second phase. Also, MMCs have excellent dimensional stability, damping capacity and wear, creep and fatigue resistances as compared with the corresponding monolithic alloys. Vast loss in ductility and toughness occurs by non- deformable ceramic reinforcements. For the surface engineering purposes, ceramic particles are added in the surface layers of components, whereas... 

Emission of the greenhouse gases is a great concern and use of lightweight materials in transport vehicles has found a major importance in this respect. Metal/polymer laminated composites are of great interest due to their special mechanical properties and thoughness. Application of metal/polymer sheets is limited because of low bonding strength of metals and polymers in these sheets, which is not sufficient, to endure the stresses and strains during deformation processes such as deep drawing and bending. In this research, roll bonding of AA5052/Polypropylene sheets is investigated and the effects of bonding parameters on strength are evaluated and finally the bonding mechanisms during... 

With the advancement of GPUs and the availability of massive datasets, the main reasons behind the emergence of large language models, human life has been profoundly impacted. Large language models, due to their numerous applications and their increasing development, have influenced various aspects of human life, and this influence continues to grow. As a result, large language models are being used to solve a wide range of problems. However, using these models for problem-solving requires appropriate training data and significant computational resources. Because deep models can be attacked, leading to the extraction of their training data, preserving the privacy of training data in the... 

In this research, the separation of tetracycline (TC) as a pharmaceutical pollutant from water using a nanofiltration membrane process was investigated. For this purpose, a set of polymer-based nanofiltration membranes containing various amounts of the metal-organic framework (MOF-808) which are stable in water, were prepared via the phase inversion method. Due to the hydrophobic nature of the polysulfone and its tendency to fouling in the membrane filtration process, MOF-808 particles were used as agents to enhance the hydrophilicity of the membrane surfaces. In order to achieve this goal, MOF-808 was synthesized via solvothermal method and activated using two different methods:... 

In this study, membrane distillation process was used for treatment of high salinity waters. The focus of this study is to simulate and build a setup of membrane distillation process. Since the membrane distillation process is based on the driving force of the temperature difference, the required temperature is provided by both the use of heaters and the use of solar energy. To increase the feed temperature by solar energy, a black polymer coating on the main membrane is used. The main membrane used in this process is PVDF polymer and the polymer coated on the surface is the PAN polymer. After simulating and constructing the laboratory setup, the influence of a variety of parameters on the... 

Study of the structural flexibility of large-scale wind turbine components on aeroelastic performance is important under the existence of critical atmospheric conditions. Prediction and control the critical deformations, identifying maximum local deformation and modeling the forces involved, are required. Aeroelasticity analysis is a suitable method for studying the coupling effects of wind turbine aerodynamics, dynamics and structures. This research has been done by modeling wind turbine components including blades, hub, nacelle and tower, taking into account aerodynamic couplings, dynamics and structures. Considering the large scale of reference wind turbine, nonlinear equations have added... 

FGM sheets with component or grain size gradient in their thickness direction provide mechanical and physical gradient properties through ND direction. FGMs are fabricated by various methods including centrifugal casting, powder metallurgy, PVD and CVD,all of which suffer from some shortcomings such as porosity of the products, low rate and high cost of production and restrictions on mass production. In this study, 2 and 4 layered Al matrix FGM sheets containing SiC and Al2O3 powders were fabricated by laminating method of Accumulative Roll Bonding(ARB). Two approaches of stacking were chosen as accumulative coupled roll bonding (ACRB) and (ASRB) for initial roll bonding and subsequent...