Sharif Digital Repository

In recent years, there have been many concerns about the environment. One of them is the increase in greenhouse gases that cause warming and air pollution. On the other hand, fossil fuels are running out, so we need to look for clean alternative fuels. One of these options is hydrogen gas, which can be produced with the help of electrocatalysts and the water splitting reaction. In the electrolysis of water, the oxygen evolution reaction (OER) limits the reaction kinetics, so the synthesis of efficient electrocatalysts is important. As a result, the goal of this work is the synthesis of a cheap electrocatalyst using transition metals. The basic compound used for this work was a cobalt-based... 

In recent years, providing clean water and addressing pollution caused by toxic organic compounds—especially phenolic compounds—have become major global challenges. Among these hazardous pollutants, 4-nitrophenol (4-NP) is of particular concern due to its high toxicity and carcinogenic potential, making it a priority for removal from water sources. In this study, two types of nanocomposites photocatalysts, including titanium dioxide nanotubes (TNT) and titanium dioxide nanodandelions (TND) doped with 5 wt% bismuth vanadate (BiVO4), were synthesized and applied for the photocatalytic degradation of 4-NP under visible light irradiation. To identify the structural and surface characteristics of... 

The quest for sustainable energy solutions has positioned hydrogen as a pivotal alternative fuel due to its clean emission profile, producing only water vapor and heat. However, efficient hydrogen storage remains a formidable challenge due to its low energy density at standard conditions. Metal-Organic Frameworks (MOFs) offer a promising solution due to their high surface area, tunable pore structures, and reversible adsorption properties. This study leverages computational screening and machine learning (ML) methodologies to identify high-capacity MOFs for hydrogen storage. We utilized a large dataset of known and hypothetical MOFs from comprehensive databases and employed advanced neural... 

The global energy outlook has been altered as a result of mounting concerns regarding fossil fuels. Electrocatalysts have become a favorable alternative for renewable energy production processes, particularly in the fields of hydrogen evolution reactions (HER) and oxygen evolution (OER). This study focuses on the production and enhancement of nanocatalysts, specifically materials based on ZIF-67, for the purpose of water splitting. The initial phase included the synthesis of the ZIF-67 structure through the simple room-temperature coprecipitation process, utilizing cerium as a dual-metal component. The molarity of the cerium was optimized in the ZIF-67 framework to achieve the most desirable... 

In this study, in order to photocatalytic degradation of 4-nitrophenol, which is one of the most hazardous organic pollutants in water, heterostructured photocatalyst NiFe-LDH/XB-doped g-C3N4 Nanosheets (NiFe-LDH/XBCNN) was investigated. A series of NiFe-LDH/XBCNN nanocomposites with different X content (100 mg, 200 mg, 300 mg and 400 mg) were synthesized by hydrothermal method. Time, pH, catalyst dose, initial pollutant concentration and H2O2 effect were studied. NiFe-LDH/300BCNN was an optimal nanocomposite that degraded 97.11% of 4-nitrophenol within 150 minutes under visible light and under optimal conditions (pH=11, 50 mg of catalyst, initial concentration of pollutant equal to 20... 

In this advanced research, titanium dioxide nanotubes were initially synthesized using the hydrothermal method. Subsequently, they were coated with polyaniline, polyindole, or a combination of both polymers using oxidative polymerization. The application of these composites for the removal of the organic pollutant 4-nitrophenol in wastewater was investigated under visible light irradiation from a 250-watt sodium lamp and in the presence of hydrogen peroxide as an oxidizing agent. To characterize the synthesized photocatalysts, various tests were conducted, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS),... 

High-capacity electrode materials are crucial for enhancing the performance of supercapacitors. Transition metal sulfides are considered promising materials for supercapacitor applications due to their high theoretical capacity and good electrical conductivity. Additionally, cerium oxide improves the performance of supercapacitors due to stable reversible oxidation states and greatly supported the faradaic redox reaction. In this study, ceria nanosheets incorporated with MCoS (M=Mn, Zn, Cu) were synthesized successfully through a facile hydrothermal method by sulfidation of MCo LDH/CeO2. The structural and morphological characteristics were analyzed using X-ray diffraction, scanning electron... 

The main goal of this thesis is the design and development of a rehabilitation device for helping patients “to improve blood circulation” & retain and recover their abilities if possible that were lost during the stroke or a accident like that (my research in karaj/iran shows that it is possible by just movement of the specific body part). The focus is on hand in this thesis because Injuries to the hand are common and can be very debilitating since our hands are our primary means for interacting with our world. For rehabilitation in case of human hand there are several practices that should be done for patients either in home or in a rehabilitation center, time and money that is supposed to... 

In the past few decades, shaking tables are widely used to evaluate system response of structures under seismic excitations. These devices are used without any fundamental research performed on a shaking table system as an entity model. In most of these studies for simplicity, it is assumed that there exist no considerable vibration and displacement around the shaking tables, and no attention is paid to the peripheral substances such as soil settled under the foundation.
In this thesis, result of ambient vibration test on shaking table system (solid deck, concrete foundation and soil layer) has been presented. Precise sensors known as low frequency and high accuracy accelerometers have... 

Out of several ground improvement techniques available, stone columns have been widely used. This technique has been successfully applied to increase the bearing capacity and to reduce the settlement for foundation of structures like liquid storage tanks, earthen embankments, raft foundations, etc., where a relatively large settlement is permissible. This technique has, generally, been proven successful in increasing the stiffness of weak soils, upgrading their safe bearing capacity, and reducing their total and differential settlements, as well as speeding up their consolidation process. The beneficial effects of stone column installation in weak deposits is manifested in the form of... 

Laminar forced convection flow through a channel partially filled with a porous material was numerically studied in this thesis. The Navier-Stokes and Brinkman-Forchheimer equations were used to model the fluid flow in the free and porous regions, respectively. Coupling of the pressure and velocity fields was resolved using the SIMPLEC algorithm. The local thermal equilibrium was adopted in the energy equation. The effects of the thermal conductivity ratio, Darcy number, porosity, Reynolds number and height of the porous insert on velocity and temperature field were investigated. The results show that the flow behavior and its associated heat transfer are susceptible to the variation of the... 

In the present study, a new version of haptic devices is presented in which user’s hand is in contact with the device just while collision with virtual surface. In this system, the position of user’s finger can be traced by using a camera and the haptic device follows user’s finger at the distance of about two centimeters. While the haptic device approaches to the virtual surface, gradually reduces its speed and stops about two centimeters distant of virtual plane. Then user’s hand collides with the haptic device which is static. Greater fidelity, transparency, more stability and also no need to large actuators are of the advantages of this system. In this project, first we present a new... 

In this thesis we try to find optimized parameters for imaging and manipulation of a biosample with AFM. For this we have prepared a numerous Molecular Dynamics simulation and find some reliable result. So, first we have focused on imaging process in Non contact mode (the less harmful mode). Then we headed into the manipulation process. The main problem about manipulating a biosample is the environment. In imaging section, the process of imaging a biomolecule by AFM is modeled using molecular dynamics simulations. Since the large normal force exerted by the tip on the biosample in contact and tapping modes may damage the sample structure and produce irreversible deformation, the non-contact...