Sharif Digital Repository

After the rise of the automotive industry, aluminum wheels have superseded steel counterparts due to their numerous advantages. Foremost among these benefits is their reduced weight, leading to fuel savings and diminished environmental impact. Moreover, aluminum wheels offer enhanced aesthetics and greater strength in comparison to steel alternatives. This thesis focuses on the geometrical optimization of an aluminum wheel model conforming to the standards set by Iran's Department of Standards, aiming to achieve a higher strength-to-weight ratio. While prior research works have mainly focused on weight reduction while maintaining strength within approved standards, this thesis aims at the... 

Electrostatic precipitators are widely used in cement plants to remove impurities and dust from the exhaust gases. The filtration mechanism is based on using high intensity electric fields which first ionize the particles and then absorb them toward the collecting electrodes. The corrosion effect is one of the major problems associated with electrostatic precipitators which not only can negatively affect their operation efficiency but also decreases their life-time through breakage occurrence in the corroded electrodes. One of the commonly used methods to suppress this negative effect and increase the total working hours of the device is to cut the bottom part of the first collecting plate... 

Investigation of possible vibratory responses of dynamical systems around their stable equilibria is an essential step which must be taken before their both design and application. The attained results of such a study can largely help to prevent instability in closed-loop stabilized systems by avoiding excitation of the system in the neighborhood of its resonance. In this paper, nonlinear oscillations of a Rotary Inverted Pendulum (RIP) enjoying a full-state feedback controller is investigated. Lagrange’s equations are employed to derive an accurate 2-DoF mathematical model whose parameters are extracted by both measurement and 3D modeling of the real system components. The perturbative... 

An isopropanol supercritical reducing environment was prepared by fabricating a high temperature, high pressure autoclave, in order to make a hybridized structure of zinc oxide and graphene oxide, entitled as ZnO-G. In this novel structure, the oxygen acts as bridging element between zinc and carbon, that connects a wide band gap semiconductor to a narrow banded one. The hybridization mechanism is studied by FTIR analysis, and morphology is shown by FE-SEM. The micrographs obtained from the thin film show a stacked pile of ZnO-G disks, like a button, dispersed on a crack free layer. In addition, the crystallographic structure was revealed by comparing low angle X-ray diffraction patterns to... 

In this report, a combination of in-situ chemical synthesis and electrolysis methods was applied for the preparation of zinc oxide/graphene quasi core-shell nanoparticles. Pure zinc oxide was also prepared using the same method at different temperatures. The degree of 100 ◦C was selected for synthesizing of ZnO-GO quasi core-shell (zinc oxide as a core and few layer of graphene oxide as a shell). The particle size was 15±2 nm in all samples. In both processes, oxygen was the main reason for the connection between the core and the shell. Unlike chemical process that has all kind of functions in electrolysis process, one kind of function was produced and confirmed by FTIR. XRD patterns also... 

In recent years, many efforts have been made in the field of drug delivery with hydrogel nanoparticles. This class of materials has been at the center of attention in medical science due to their improved physical and biological properties including high amount of water preservation, penetration, bio capampatibility and physical structure similar to outside matrices of tissue. Among various applications in medical sciences, drug delivery based on hydrogels is very attractive. Hydrogels can protect drugs from aggressive environmental factors such as pH and thermal changes, and presence of enzymes. The porosity of hydrogels facilitates drug loading into the gel matrix and provides a... 

This investigation presents synthesis and characterization of pure and monophasic hydroxyapatite (Ca10(PO4)6(OH)2; HA) Nanostructures prepared by coral and oyster shell powders heated at 800 oC for 8 h as precursor via precipitation method. The morphology of HA nanostructures was controlled in the presence of various surfactants such as SDS, CTAB and PVP. The HA Nanorods synthesized by SDS were applied to fabricate bone scaffolds. Particle sizes of the HA Nanoparticles were about 20-30 nm. Pours three-dimensional HA/Ge/CMC scaffolds cross-linked by citric and oxalic acids were synthesized. In order to increase the pore size of the scaffolds, NaCl with medium (180-250 µm) and large (420-500... 

Electrochemical sensing of glucose has received paramount attention in recent years, particularly, the non-enzymatic glucose sensing is one of the trends in the whole biosensing world. In this research, synthesis and evaluation of a hybrid structure of vertical oriented nickel nanorod-reduced graphene oxide sheets as a non-enzymatic glucose sensor were performed. The 3D array of nickel nanorods was synthesized by electrodeposition of nickel sulfate electrolyte in track-etched polycarbonate template with 100 nm pore size and 6-10 μm thickness. The electrodeposition performed in various conditions, and the best result was achieved by application of potential of 3 V for 60 minutes. The shiny... 

Many structural systems may experience some local damage during their lifetime. If the local damage is not identified timely, it may lead to undesirable consequences. Vibration-based damage detection techniques of structures are global methods and are based on the assumption that damage alters both the physical properties, such as mass, stiffness and damping, as well as the dynamic properties of the structures. It is therefore feasible to utilize measured dynamic quantities, such as time histories, frequency response functions (FRFs) and modal parameters, from structural vibration to detect damage. Damage identification based on vibration characteristics is essentially a form of pattern... 

The application of ultra-high performance concrete (UHPC) as an alternative to conventional/ normal concrete (NC) has grown rapidly in recent years. However, there is limited knowledge on its shear behavior, which is essential for developing design guidelines for structural applications. A detailed parametric study was conducted on 38 beam specimens, half of which were made of UHPC and the other half made of NC. To ensure applicability of findings, two types of UHPC mixes were used, a proprietary and a generic mix. Eighteen of the beams were prepared and tested in Tabriz, Iran, while the other 20 were made and tested in Miami, FL. Test parameters included type of concrete (UHPC and NC),... 

Recent investigations on construction engineering have determined that repairing of Reinforced Concrete (RC) by means of fiber reinforced polymer (FRP) composites is an effective method of retrofitting existing columns. The main research in this thesis focuses on the repair of concrete specimens which are damaged and their initial strength has been reduced. To achieve this purpose, through experimental procedures, the effect of confining damaged concrete cylinders by FRP, has been investigated. The experimental program included three parameters: type of fibers (glass or carbon), type of confining (full or partial), and the number of layers. First concrete cylinders were made and loaded to... 

In recent years considerable effort has been made to advance the hardware Artificial Neural Networks where in most cases, many neurons are placed on a VLSI chip. This research attempts to build individual neurons and connect them to build a hybrid of analog and digital neural network. In fact, every neuron is an AVR microcontroller which has a number of inputs and outputs. The data transfer between neurons are done by both analog (PWM- ADC) and digital (UART). In the first part, the necessary voltage source and programmer and how to build are discussed. Next A\D convertor, PWM technique, UART and their usage in this project are demonstrated. After that, the neurons are calibrated to improve... 

3D bioprinting is an additive manufacturing method that facilitates the deposition of the desired cells and biomaterials at any pre-defined location. This technique also enables control over the internal structure and external dimensions of printed constructs. Among various biomaterials used as bioinks, the bioinks derived from decellularized extracellular matrixes (dECMs) have attracted significant attention due to their bioactivity and being a rich source of biochemical cues. Here in this study, the decellularized amnion membrane (dAM) has been selected as the main component of the bioink formulation because of its biocompatibility, low immunogenicity, antibacterial property, abundance,... 

Theranostic liposomes have recently found a broad range of applications in nanomedicine due to stability, the high solubility of biomacromolecules, bioavailability, efficacy, and low adverse effects. However, the limitations of liposomes concerning the short systemic circulation in the body, limited controllability of the release rate, and the inability of in vivo imaging remain challenging. Herein, the development of novel hybrid ultrasound-activated piezoelectric nanoparticles based on a hybrid liposome nanocarrier composed of poly(vinylidene fluoride‐trifluoroethylene), graphene quantum dots (GQDs), and Silibinin (a hydrophobic drug) is presented. The hybrid nanoparticles are an... 

Tissue engineering has the potential to revolutionize our health care system. Conceptually, lost or malfunctioning tissues will be replaced by man-made biological substitutes to restore, maintain, or improve function. Tissue engineering has already shown great promise to contribute to treatments of a myriad of diseases including osteoarthritis, cancer, diabetes, skin burns, cardiovascular conditions and various traumatic injuries. Tissue engineering is a highly multidisciplinary discipline that demands integration of knowledge, tools and skills from biology, chemistry, engineering and medicine. Integrating nano- and microtechnologies into clinically sized implants represents a major... 

Aerobic oxidation plays important role in industrial processes and pollutant remediation. The catalysts accelerating oxidation reaction rate are included thermal (typical) catalysts such as Pt or Au on oxide supports and photocatalysts such as TiO2 or ZnO. Although well-studied Au/TiO2 system have been under deep
investigations but Au/ZnO system have less investigated because Au/ZnO has low activity relative to Au/ZnO. Gold nanoparticles supported on ZnO nanostructures were prepared through a simple chemical-thermal method and characterized by SEM, TEM, XRD, BET and photo luminescence (PL) spectroscopy. Effect of
annealing temperature on catalytic activity of these Au/ZnO... 

Hyperthermia (also called thermal therapy or thermotherapy) is defined as a type of cancer treatment in which body tissue is exposed to high temperatures, to damage and kill cancer cells, or to make cancer cells more sensitive to the effects of radiation and certain anticancer drugs. The temperature increase required by hyperthermia can be achieved via different heat sources, such as electromagnetic radiation waves (radiofrequency or microwave, ultrasound waves and electrical current. These techniques have shown good results, however, the major problem with present conventional methods is reaching homogenous heat distribution and therapeutic temperatures in the deep region of the tumor to be... 

Polycaprolactone (PCL) scaffolds and its composites containing bioactive glass particles (45S5) and TiO2 nanostructures with pre-defined and controlled external and internal architecture were prepared via an indirect three-dimensional (3D) printing process. The scaffolds had an interconnected structure with macro- (400-500 μm) and micro- (~25 μm) pores. Bioactivity, mechanical behavior and kinetics of tissue growth in 3D scaffolds were studied. The size effect of biogactive glass particles (6 μm, 250 nm, <100 nm) and morphology of titania nanostructures (spherical, tube, leaf-like, and flower-like particles) were elaborated. The biogactive glass particles with different sizes were prepared... 

Superparamagnetic iron oxide nanoparticles (SPION) with proper surface coatings are increasingly being evaluated for clinical applications such as hyperthermia, drug delivery, magnetic resonance imaging, transfection, and cell/protein separation. Since the particles with various sizes exhibit different flow rates in the same environment (same capillary size), it is essential to use particles of a desirable size for targeted drug delivery and imaging. Particles of different sizes may be exposed to different viscosities and behave differently, particularly with regard to their velocities as they move through capillaries. In the present work, SPION with different size, purity, shape and... 

In this study, the behavior of diagonally stiffened steel plate shear wall systems which have a new configuration of stiffeners is investigated. This dissertation is divided into three main sections which contain experimental studies, finite element analysis and developing design equations. In the section on experimental studies, 5 single-bay, single-story, one-third scale specimens were tested. An unstiffened specimen as a control sample and two other specimens with different configuration of stiffeners were constructed and tested to study the effect of diagonal stiffeners. Based on the observations during the tests, it was decided to add and study two other specimens too, including one...