Sharif Digital Repository

In this dissertation, the buckling and postbuckling analysis of lattice conical shells are presented. The outer skins of the shell may be reinforced by cross-ply laminated composites. The shell is subjected to uniform axial compression and the boundary conditions are simply supported. This problem is solved using two different approaches. At first approach, the main priority is high speed calculations, which is investigated in static and dynamic types of loadings. In the case of static loads, the equilibrium equations are formulated based on the classical theory and von Karman type of nonlinearity. The equations are solved by Galerkin method and a closed-form relation is derived. In the case... 

The hydrogenation of carbon dioxide to methanol represents a promising route for the efficient use of an anthropogenic greenhouse gas, in which catalysts play a key role in carbon dioxide conversion and methanol selectivity. In this study, firstly, CuO-ZnO-Al2O3, CuO-ZnO-ZrO2, CuO-ZnO-ZrO2-Al2O3, CuO-ZnO-Al2O3-CeO2 and CuO-ZnO-ZrO2-CeO2 catalysts were made using co-precipitation method, then these catalysts were characterized by inductively coupled plasma optical emission spectrometry, specific surface area and pore size distribution, X-ray diffraction, Field Emission Scanning Electron Microscopy, temperature programmed reduction. Finally, in order to compare the performance of the catalysts... 

Electrocoagulation (EC) is an effective process in the treatment of oily wastewater, however, only a few studies have explored the parameters affecting the efficient design of the reactors employed in this process. In this study, a statistical investigation on the factors affecting the design of a continuous electrocoagulation reactor was performed by running the tests designed based on the design of experiments (DOE) principles. The explored design variables were current density (30-80 A/m2), reactor residence time (10-30 min), and the ratio of anode surface to the reactor volume (15-45 m2/m3), which were optimized by the response surface method (RSM) to maximize the amount of oil removal... 

In this study, pyrolysis features and corresponding kinetic behavior of non-metallic fractions of the paper-laminated phenol resin printed circuit boards (P-PCB) and fiberglass-reinforced epoxy resin printed circuit boards (E-PCB) were investigated by the use of simultaneous thermogravimetric analysis (TGA/DTG). The kinetic parameters of the P-PCB abs E-PCB during pyrolysis process were estimated from the experimental data by means of three iso-conversional kinetic models, including Friedman, Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) methods. The activation energy range obtained for P-PCB and E-PCB utilizing the Friedman method was within 117–594.1 and 88.42-295.3 kJ.mol-1,... 

Gas-solid fluidized beds are widely used in various industrial processes due to their multiple advantages and applications, such as enhanced heat transfer, improved mixing and separation of solid particles, drying, combustion, particle coating, etc. In many processes, the mixtures of solid particles in the fluidized bed reactors have a distribution of particle sizes or are different in terms of density or shape of particles. Despite the ability of fluidized beds to improve the mixing of particles, the existence of the aforementioned differences can cause separation of particles under certain conditions. Pulsed fluidized beds are beds where the gas flow enters the bed in a pulsating manner.... 

Many fluidized bed reactors contain particles such as catalysts, biomass, etc. that vary in size, density, and shape. Despite the significance of these systems, the multi-component fluidized beds have been less studied compared to single-component systems. An important challenge in multi-component fluidized beds is the occurrence of particle segregation and reduced mixing, which severely diminish the reactor's efficiency. The objective of this study is seeking the relationship between the pressure signals measured in a binary gas-solid fluidized bed and the degree of particle mixing/segregation of dissimilar components at relatively low superficial gas velocities. To this end, pressure... 

In recent years, due to the drawback of rule-based firewalls in detecting unknown attacks, using neural networks has got more attention to be used in firewalls. As the computation load of neural networks are so much there is a need to decrease the processing time and power consumption as they are under load 24/7. Although there have been huge achievements in the usage of graphics processing units (which contain numerous processing cores) in neural networks, their high power consumption has made the scientists think about an alternative to implement neural networks. Field Programmable Gate Array (FPGA) is one of the most serious candidates to be used for implementing neural networks. The goal... 

The gradual depletion of the resources of fossil fuels, as well as the instability of their price in addition to the necessity of mitigation of hazardous air pollutants, are the chief reasons to increase the use of renewable sources. Biodiesel, as one of the best alternatives, can mitigate the emission of air pollutants resulting from fuel combustion. However, using raw biodiesel is not economically viable due to its lower quality in comparison with diesel. In this study, the role of nanoparticles in the improvement of biodiesel characteristics has been investigated. Firstly, biodiesel was produced from waste cooking oil (WCO) using the transesterification reaction, and then ceria and... 

Due to the unique advantages of fluidized beds for solid mixing and heat transfer, they are widely used for the thermal processing of solid fuel particles. In practice, such systems are composed of non-conventional fuel particles such as coal or biomass, which are completely different in shape, size, and density from the bed material such as sand. In such systems, correct understanding of the main fluidization parameters such as the minimum fluidization velocity (Umf) of the bed components plays a key role in the successful design and control of the system. However, the onset of fluidization of irregular particles is not clear as it may vary depending on the physical properties of the... 

The COVID-19 pandemic has increased environmental risks due to widespread face mask use in production, consumption, and disposal. This study uses surgical single-use as a pyrolysis feedstock due to increased demand. This study investigates the conversion of valuable materials from waste through the recycling of surgical single-use masks in a fluidized bed. The first stage of this study focused on identifying and specifying the main components in the filter layers of disposable surgical masks, which were the compounds in the filter layers made of polypropylene. TGA curves investigated thermal behavior of disposable surgical mask layers, revealing pyrolysis feedstock can produce volatile... 

One of the main challenges in managing flow batteries usage is estimating their state of charge. Since The concentration of ions in the battery indicates the battery's charge and, on the other hand, the sensors for measuring the concentration are expensive, observers should be used to estimate the concentrations of the ions in the battery. This work is done by measuring the cell voltage, and finally, using the mathematical model of the battery, the amount of concentrations and state of charge is calculated. In this work, a vanadium flow battery was initially modeled accurately and mechanistically using COMSOL software to replace an actual flow battery in subsequent studies. Also, two... 

RFID systems are available in various applications for indoor and outdoor positioning. Location awareness in public environment and in stores and companies are widely in use. In indoor environment , multipath and fading changes signals specification, so it is difficult to detect the related parameters. In the other hand the necessity of fast and reliable system which support traffic and a large number of users are in demand. RFID which is based on radio frequency signals is developed for this aim.RFID system with asymmetrical link which support UWB and Narrowband signals is suggested for indoor positioning application. RFID passive tag in this system is redesigned in his thesis....