Sharif Digital Repository

3D bioprinting technology is a promising approach for corneal stromal tissue regeneration. At first, two different concentrations of GelMA macromer (7.5% and 12.5%) were tested for corneal stroma bioprinting. Due to high macromer concentrations, 12.5% GelMA was stiffer than 7.5% GelMA, which made it easier to handle. In terms of water content and optical transmittance of the bioprinted scaffolds, we observed that scaffold with 12.5% GelMA concentration was closer to the native corneal stroma tissue. Subsequently, cell proliferation, gene and protein expression of human corneal stromal cells encapsulated in the bioprinted scaffolds were investigated. Cytocompatibility in 12.5% GelMA scaffolds... 

According to the literature survey, the thermal decomposition of ammonium uranyl carbonate (AUC) is affected by different factors such as its purity and environmental conditions. Thermal treatment of this compound in the air atmosphere results in the production of at least three oxide forms of uranium (UO3, U3O8 and UO2) with different stoichiometric structure. The aim of this project was to study the effects of those parameters which play role in the decomposition of AUC and the production of UO2 compound in the presence of ammonia atmosphere. Therefore, an atmosphere control furnace was designed and constructed to establish the gas in the atmosphere of furnace chamber. On the other hand,... 

Accurate and fast attitude estimation of a rigid body plays an essential role in the performance of a vehicle’s control system, especially aerospace vehicles. Ample works have been done to increase the accuracy and speed of the attitude estimation process, but all have been developed according to a model-based approach. This approach assumes that the torques acting on the body have a known dynamical model that is used for the attitude estimation. The purpose of the present research is to estimate the attitude via a model-free approach, i. e. dynamics of the torques acting on the body are no longer assumed to be known, and its learning is the next step. Thus, the problem formulation of this... 

Optical Wireless Communication is believed to have a great potential in establishing point to point connection and have attracted an unexpected growth in research , applications and market. Furthermore, Optical wireless systems have recently emerged as a new means of communication, especially in places where electromagnetic interferences is of utmost concern such as in passenger planes and hospitals and in other communications applications where cost could is of concern. In this thesis we build upon previously introduced wireless optical code-division multiple –access communication. In the context of an OCDMA system we begin our study by considering synchronization circuit via a... 

Today, cancer mortality is one of the most important problems, even considering the scientific advances that offer more effective solutions to treat some diseases, providing a way to prevent and treat this disease is one of the most important issues that engineers have considered. This is achieved by designing a controller to minimize the size of the cancer tumor population, increase healthy cells, optimize treatment time, and drug dose.To achieve this goal, pharmacokinetic, pharmacodynamic, tumor growth, and healthy cell growth models, and mathematical models for subsystems that affect tumor growth, such as the angiogenic system, have been studied to develop a single mathematical model. In... 

Environmental management with emphasis on protecting environment is today one of the most important problems for customers, governments, employees and competitors, and international and global pressures has required organizations to produce environmentally consistent products and services. This challenge has resulted in emergence of a new concept namely green supply change management in the realm of business which is a combination of environmental thinking and supply chain, which will be followed by competitive advantages for firms. This approach has widely attracted the attention of industries, governments and institutions relevant to environment. The aim of this study is to identify main... 

Electrodeposition of composite coatings containing nano particles is very important because this technique is simple and economic. In this research, in order to produce a coating with high hardness and wear resistance, Ni-Co/WC nano composite was co-deposited. Watt’s based bath containing cobalt and tungsten carbide was used and parameters such as preparation of solution, concentration of ingredients and current density were controlled and adjusted. Surface morphology, microstructure and mechanical properties of coatings were studied by SEM and AFM microscopes. Mechanism of electrodeposition was investigated by cyclic voltametry, cronoamperometry and cronopotentiometry techniques and... 

Modern pipelined processors use a memory array named Branch Target Buffer (BTB) to reduce the performance penalty due to conditional braches by predicting path of the branch and keeping useful history-based information for future accesses. Today BTB is a fixed size and small memory array located near the processor. By the way, BTB, in the best case, should be large enough to accommodate all conditional branches throughout the running program. Moreover, small size BTB presents much fast access and is practical on-chip storage for a system with limited power budget.
Considering role in the memory hierarchy, on the other hand, the system performance is highly correlated to the L1 data cache... 

The type of consumers’ perceptions of brands is a key factor in establishing long-term business-consumer relationships. As a result, building strong brand perceptions is a principal priority for companies today. Research in brand image has long been one of the main areas in marketing research, because it plays a vital role in building brand equity. Concerning the rise in the number of product categories and the number of similar brands, firms have felt a need to know their brand images among competing brands from the consumer’ s point of view in order to invest in their brands and approach their brand images to the consumer’ s preferable image. Because of the fact that the brand image... 

Taking advantage of aluminum and its alloys in industry is increasing. A common method in metal forming is hot forming. In this condition a precise prediction of flow behaviour of the alloy is necessary to achieve a product of desirable mechanical and physical properties. In this situation, influence of parameters such as chemical composition, temperature, strain, strain rate as well as recovery and recrystallization phenomena should be considered and by using a suitable model, the metal behavior prediction is possible. Distribution of coherent Al3Sc dispersoids in high volume fraction accompany with Al6Mn result in strengthening to this alloy. Because of the high stacking fault energy,... 

This thesis concerns the modeling of precipitation processes aimed at predicting product particle characteristics especially particle size distribution. A mixing-precipitation model (based on SFM) linked to the population balance is used for a single-feed semi-batch precipitation process to describe the mixing effects on the final particle-size distribution (PSD) and mean size, considering the agglomeration mechanism. The model describes mixing on two zones: the feed and bulk zone with different levels of super saturation. To solve a full population balance equation containing nucleation, growth and agglomeration, discretization method was performed witch is more accurate and low... 

The aim of this study is the fabrication of 3D porous PCL scaffolds contain core-shell fibers for cartilage tissue engineering. The novel fabrication method is co-axial wet electrospinning simultaneously. These tablets like scaffolds have superior porosity and pore sizes for cell culturing and cell-cell interaction as they have good mechanical properties for cartilage tissue engineering in comparison to 2D electrospun scaffolds. The structure of these 3D scaffolds is mimicking the ECM of cartilage. This study presents the coaxial electrospinning of PCL nanofibers encapsulated with bovine serum albumin and platelet rich plasma for demonstration of controlled release and bioactivity retention,... 

Expansion of using social networks for reading and sharing news on the one hand, allows for quick and easy access to the news, but on the other hand, increases the spread of fake news and misleads many users. Therefore, identifying the fake news and attempting to mitigate its spreading on social networks is one of the major research areas in recent years. An important issue in this regard is reducing the time gap between news release time and identifying it as fake and starting to take action. Many researches has been done on detection of fake news, but since there is a trade-off between minimizing the time gap and maximizing accuracy, work on these models continues. There are also different... 

Friction Stir Spot Welding as a solid state process is able to solve some of the disadvantages of fusion welding processes. On the other hand, this welding method has disadvantages such as low connection surface due to the hole left by the pin and poor resistance to fatigue loading. In this study, a method called friction stir spot welding via consumable pin was used so that the hole caused by the pin no longer remains at the welding site. The process is done in such a way that first a hole is made in the center of the overlap of the sheets. The rotating tool, in which the consumable pin is made of 6061 aluminum alloy with a diameter equal to the diameter of the hole is lowered at a... 

In this study, an accurate numerical solution of the two-dimensional incompressible viscous flows is performed by using the spectral difference method on structured grids. The system of equations to be solved here is the preconditioned incompressible Navier-Stokes equations in the primitive variable formulation with the artificial compressibility approach. In the spectral difference method, two sets of the structured points, namely, “solution points” and “flux points” are defined in each cell for supporting the reconstruction of desirable order of accuracy. Here, the formulation of the spectral difference method is derived and the representative form of the solution and flux points for... 

Al-20Si-5Fe-3Cu-1Mg–xCr (X=0, X=1.5) ribbons were produced by melt-spinning technique at the rotating speed of 20 and 40 ms-1. The thickness of ribbons were 40 to 80 and 15 to 35 μm, respectively. The properties of as-melt spun and as-cast specimen were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-Ray diffractometry (XRD) and the microhardness method. It was found that at the air side of ribbons the microstructure was dendritic while at the wheel side it was featureless. The microstructure of ribbons at two rotating speed showed a homogenous distribution of Si particles embedded in an α-Al matrix. XRD investigations exhibited the absence of any intermetallic...