Sharif Digital Repository

The Atomic Energy Organization of Iran (AEOI) has launched a program of low level waste management. This program also includes waste produced at Uranium Conversion Facility (UCF) of Esfahan. The liquid waste, which was generated during the operation of plant and concentrated in lagoon, was characterized for the development of the treatment process. The aim of this study was to recovery of uranium content of liquid waste in the lagoon. The recovery of uranium has the advantage of saving this valuable metal and the avoidance of unacceptable discarding solution to the environment. Uranium may be recovered from an aqueous solution by precipitation, solvent extraction and ion exchange.... 

Underground reservoirs are highly complicated due to the presence of spatial heterogeneities at length scales that span from micrometer in pore structure of the rocks to kilometer in the reservoir models. While large-scale flow units need to be characterized using seismic and well data, detailed displacements of fluids in pore space need to be modeled using thin section analysis and pore network modeling. It is therefore necessary to adopt a multi-scale approach to reservoir description to make best use of all the available data that vary over several orders of magnitude, from micro-scale in pore structure to field scale in reservoir flow models. In this thesis, an integrated framework for... 

Real-time asynchronous data fusion for high-speed phenomena is an important and challenging task in the sensor networks. Examples of data fusion applications in sensor networks are: managing the traffic of maneuvering airplanes and ground vehicles in airside areas of an airport, traffic management in streets and roads, Driver Assistance Systems, guidance of antiaircraft and antimissile missiles. In all the data fusion applications the estimation of the required variables is necessary.
In this research two methods are introduced for real-time asynchronous data fusion, especially for track-to-track fusion of high-speed phenomena in sensor networks. The effectiveness and usability of these... 

Tehran is one of the most polluted megacities in the world, and based on different studies, vehicular sources are responsible for most of the criteria pollutant emissions in this city. The number of vehicles on the streets has been increased drastically leading to growing amount of emission and this trend is continuing. In order to reduce the amount of vehicular emission, it is vital to investigate the factors affecting vehicles emission in this city. This could help to find efficient solutions to improve the situation. Hence, a low-cost methodology to estimate the vehicular emissions is developed. In this... 

Up to now, compared with the comprehensive research for developing robust watermarking algorithms, no equal attention has been devoted to the proposition of benchmarks tailored to assess the watermark robustness. In addition, almost all the state of the art benchmarks only integrate a number of common image processing operations like geometrical transformations to remove watermarks. However, the quality of the processed image is often too degraded to permit further commercial exploitation. Moreover, to the best of our knowledge, the design of these tools does not take into account the statistical properties of the images and watermarks in the design of attacks. In spite of the significant... 

In the present work, trajectory optimization of the Dual-Arm Cam-Lock robot considering kinematic and dynamic redundancy is performed. First, the optimal control problem is solved only considering kinematic redundancy and then is solved considering dynamic redundancy. General form of the dynamic model for the system is developed using Lagrangian relations. Global optimization method is used for redundancy resolution problem. A performance index is defined based on the consumed kinetic energy and is minimized through a desired trajectory using the global optimization method. Formulations of optimal control problem are derived and initial boundary problem is changed to two point boundary value... 

Electron states of diamond vacancy under stress were studied theoretically. The generalized Hubbard model is used to calculate the electrons energy levels. The results shows that the degeneracy of some levels (T, with triple space degeneracy) reduced to levels with lower degeneracy (E, with double space degeneracy and A, without degeneracy). Besides this spiting of degeneracy the energy of all states changed and therefore the transition energy between these states changed too. Jahn-Teller effect was observed  

Due to vast use of Ametryn herbicide in agricultural and even non-agricultural activities and the possibility of contamination of carp and natural water sources by this herbicide, determination of this herbicide in surface and ground water sources is very important. Therefor introducing simple and sensitive method for determination of Ametryn is critical.
This study demonstrate a simple and sensitive colorimetric method for the detection and determination of Ametryn based on aggregation of citrate capped AuNPs. Studied method relies upon shape and distance dependent AuNPs surface plasmon resonance. By replacing the sulfide containing Ametryn herbicide with citrate molecules on AuNPs... 

Ultrasonic flowmeters are one of the common and profitable measurement tools and applied in many industrial fields.Ultrasonic flowmeters work based on transit-time technique. The transit-time utilizes the propagation time of the ultrasonic signal in the fluid. Since ultrasonic signals can also penetrate solid materials, a pair of transducers is installed on the surface of tube. Each transducer works alternatively as both transmitter and receiver of ultrasonic signals.In this study, effect of temperature gradient on flowmeter measurements by applying constant temperature and uniform heat flux on the boundary is investigated numerically for methane gas in laminar flow regime and the results... 

The reaction of oxygen evolution, in other words, the process of water oxidation in the presence of heterogeneous photocatalysts such as g-C3N4, Co/g-C3N4 /rGO, Ni/g-C3N4/rGO, CoNi/g-C3N4 / rGO, Co2Ni1/g-C3N4/rGO, and Co1Ni2 /g-C3N4 /rGO were studied. The characterization of these nanocatalysts was done by XRD, SEM, FT-IR, BET, DRS, CHN, and TGA techniques. Thermogravimetric analysis (TGA) was used to check the thermal stability of these nanocatalysts. The FT-IR spectroscopy was used to identify the functional groups in graphitic carbon nitride and to confirm g-C3N4 synthesis. According to BET results, the pore sizes were determined which were at the nano and macro scale. It was found that... 

Sustainable and renewable energy sources are of fundamental importance in the development of strategic and sustainable economies. Therefore, in recent decades, water electrolysis has been widely used to produce pure hydrogen and oxygen without emitting carbon materials and is considered as a method for producing electrical energy alongside other renewable sources (such as wind and solar energy). Here, we report the synthesis of CoFe double-layered hydroxides (CoFe-LDHs) and their application as electrocatalysts for water splitting in alkaline environments. CoFe-LDHs were prepared via a new hydrothermal route from the metal-organic framework MIL-88A (MOF). The Co to Fe ratio in LDHs was... 

Emissions of carbon dioxide (CO2) from fossil fuels are a potential issue for the global climate. One way to meet this challenge is to electrochemically convert CO2 molecules to reduced carbon species such as formates, alcohols, hydrocarbons, etc., which is a difficult process due to the poor kinetics of CO2 reduction. Therefore, the use of catalysts, while preventing undesirable side reactions, can also play an important role in reducing CO2. In this study, a two-step synthesis of CuS (1, 5, 12, 24 hr) @ Cu-MOF has been reported as an advanced electrocatalyst for CO2 reduction in neutral pH environments. Bismuth has been used to improve the electrocatalytic properties of the samples. Bi-CuS... 

Lead-acid batteries have been used for over 150 years as a reliable means of storing electrical energy. These batteries have a variety of applications due to their high safety, reliable performance, and relatively easy manufacturing process, including in car starters, car lighting and combustion, electric vehicles (especially electric bicycles), and the resulting electrical energy storage. From renewable sources or pulsed power supplies in hybrid electric vehicles. Despite increasing advances in the performance and design of these batteries, there are still problems in this area. One of the most important of these is the electrolysis of water as a side reaction, which leads to the production... 

Electrochemical water splitting which consists of two half-reactions, namely; the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), is an important process in electrochemical energy storage and sustainable production of energy. Therefore, the development of cost-effective and efficient electrocatalysts for water splitting has attracted a lot of interest. In this work, a new nanocomposite was prepared from cobalt diselenide and cerium (IV) oxide derived from calcination of a cerium-based metal-organic framework (Ce-MOF), via hydrothermal and electrodeposition methods. The structure and morphology of synthesized materials were investigated by XRD, FE-SEM, EDX, and BET... 

The sluggish kinetics of oxygen evolution and reduction on the surface of electrodes is a major problem for the widespread use of devices that are based on sustainable, renewable and clean technologies, such as fuel cells and metal–air batteries. Therefore, the development of efficient and cost–effective materials for the oxygen evolution (OER: Oxygen Evolution Reaction) and reduction reactions (ORR: Oxygen Reduction Reaction) is highly desirable. In recent years, Metal–organic frameworks (MOFs) and their derivatives, have drawn considerable attention as potential catalysts and electrocatalyst due to their high surface area and porous structure. In this study, cerium (IV) oxide was... 

The sluggish kinetics of oxygen evolution and reduction on the surface of electrodes is a major problem for the widespread use of devices that are based on sustainable, renewable and clean technologies, such as fuel cells and metal–air batteries. Therefore, the development of efficient and cost–effective materials for the oxygen evolution (OER: Oxygen Evolution Reaction) and reduction reactions (ORR: Oxygen Reduction Reaction) is highly desirable. In recent years, Metal–organic frameworks (MOFs) and their derivatives, have drawn considerable attention as potential catalysts and electrocatalyst due to their high surface area and porous structure. In this study, cerium (IV) oxide was... 

Global warming and the excessive carbon dioxide emissions from the use of fossil fuels have created many problems for the Earth’s climate. One way to deal with this problem is to convert the photoelectrochemical conversion of water molecules into hydrogen gas, which does not enter the environment due to te burning of pollution, but due to the poor syntheetics of water oxidation in the water fisssions process, this reaction determines the speed and needto be examined to improve the water fissions process.The study examined and reported the two – stage synthesis of Fe2O3@NiCo2O4 as an advanced photoelectrocatalyst for water oxidation in the pH environment of the game. Hematite semiconductor... 

Emissions of carbon dioxide (CO2) from fossil fuels are a potential issue for the global climate. One way to address this challenge is to electrochemically convert CO2 molecules into carbon-reduced species such as alcohols, hydrocarbons, formates and other valuable products, which is a difficult process due to the slow kinetics of CO2 reduction. Therefore, the use of proper electrocatalyst while preventing undesirable adverse reactions can play an important role in the electrochemical reduction of CO2. In this study, synthesis of bimetallic Bi2O3@CuS composite as an advanced electrocatalyst for CO2 reduction in neutral pH environments has been investigated and reported. Bismuth oxide has... 

Photoelectrochemical (PEC) water splitting is exceedingly promising for converting solar energy into molecular hydrogen as a clean and sustainable fuel. However, the overall rate of water splitting reaction is severely limited by the sluggish kinetics of the anodic half-reaction, namely, the oxygen evolution reaction (OER). Bismuth vanadate (BiVO4) is a popular photoanode for PEC water splitting due to its high stability, low cost, narrow band gap (2.4 eV), high visible-light absorption, and environmental compatibility. However, BiVO4 suffers from poor charge transfer, fast recombination of electron-hole pairs, and inferior catalytic activity toward OER. An effective strategy to overcome... 

Hydrogen gas was introduced as a fuel with high energy density and environmentally friendly, and the electrolysis of water is one of the widely used methods to produce this gas. In order to reduce the energy required for this process, the introduction of electrocatalysts with high activity and stable is on the agenda. In this research, the electrocatalytic performance of a composite of MgCo2O4 and Ni3S2 on a nickel foam substrate was investigated in order to produce oxygen in an alkaline environment. To prepare MgCo2O4 compound, hydrothermal method and Ni3S2 compound, electrochemical deposition method with the help of cyclic voltammetry technique was used. According to the results of XRD...