Sharif Digital Repository

Oxygen enriched combustion is one of the attractive combustion technologies to control pollution and improve combustion in diesel engines. In the present work after an introduction to membrane seperation and membrane seperators for oxygen-nitrogen from air, a simulation of combustion chamber by GT-Power and membrane COMSOL Multiphysics was used to study the impact of oxygen enrichment on combustion, pollution and performance parameters with 23, 25 and 27% levels of enrichment. Increasing the oxygen engine content with the air leads to faster burn rates and the ability to burn more fuel at the same stoichiometry. These effects have the potential to decrease specific fuel consumption and... 

Wireless sensor networks have many applications, vary in size, and are deployed in a wide variety of areas. They are often deployed in potentially adverse or even hostile environment so security issues are of much concern in these networks. Key management is a fundamental security issue in sensor networks. In this thesis, we are mainly focusing on key establishment and group rekeying schemes aspects of key management. Due to limited resources of sensor networks, key pre-distribution schemes are currently viewed as the most promising solution. Key predistribution in sensor networks refers to the problem of distributing secret keys among sensor nodes prior to deployment. Recently, many key... 

By increasing speed gap between microprocessors and off-chip Last Level Cache, Optimization in Last Level Cache makes improvement in system performance. With development of new generation of multi-core processors and sharing LLC between these cores, the so called issue of Memory Wall has caused an incremental effect of LLC on system performance. There are three approaches to use this memory more efficiently:
1. Increasing cache capacity
2. Making cache hierarchical and adding different layers to hierarchy
3. Improvement of replacement algorithms in cache memory
The first approach has not been used in regard with limitation of technology and growth of access time due to... 

With the rapid development of wireless communication standards, the co-existence of multiple standards in a single chip becomes inevitable. It is also fueling interest in analog to digital converters (ADCs) that are reconfigurable over a wide range of bandwidths and resolutions with adaptive power consumption. Employing such ADCs rather than using multiple individually power-optimized ADCs results in a great reduction of silicon area. Hence, a reconfigurable ADC can reduce time to market, and save costs.
This thesis addresses the challenges exists in conventional reconfigurable methods, and presents a novel reconfiguration methodology for changing resolution in pipeline ADCs. The... 

Considering that automobile weigth reduction in industry is important, improvement the strength of low carbon steel sheets is important. These sheets can be supported the service condition in lower thicknesses. Bulk nano-structured materials have been mostly attracted in materials science due to their unique physical and mechanical properties. Severe plastic deformation (SPD) is one of the most efficient methods to produce ultra fine grained or nano-structured materials. Materials produced by SPD are of great importance because of (1) non-porous structure, (2) great mechanical properties such as high strength and toughness and (3) proper dimension for mechanical and physical testing. ... 

Brazing is a crucial process for repairing and manufacturing high-temperature components made of precipitation-hardened superalloys. Boron-containing filler metals are amongst the most common filler metals used for repairing and joining superalloys. Although boron is an effective MPD in such filler metals, the formation of brittle boride intermetallics in the joining area (Athermal solidification zone and diffusion affected zone), due to the low solubility of boron in the matrix of superalloys, is inevitable. Isothermal Solidification is known as an effective technique for removing boride compounds in the joining area of brazed components. but as the time of isothermal solidification... 

Molybdenum disilicide is an intermetallic compound in Mo-Si binary system that has very applications because of its individual properties. High melting point of MoSi2 limits the fabrication of this compound by conventional methods. Nowadays modern techniques such as Mechanical Alloying are used for synthesis of Molybdenum disilicide. In this investigation the MoSi2 has been synthesized from the elemental powders by Mechanically activated Self propagating Reaction method and the effect of milling atmosphere on synthesis efficiency is discussed  

The foregoing note is a Ph.D. Thesis in Material Science and Engineering entitled "Leaching of hydrometallurgical treatment residue of zinc concentrate and Indium solvent extraction of solution". This research includes three stages of Roasting, Leaching, and solvent extraction. The scientific fundamentals and research background in all three domains have been studied. Investigations on the Roasting of zinc sulfide concentrate showed that in order to prevent the ingestion of indium into the zinc ferrit structure, the alkaline roasting process with 15% calcium oxide at 850 0C and 150 min prevented the ingression of 80% of the indium into the ferritic structure. The results of studies on the... 

Al /Al3Ti in-situ composite have been fabricated by mechanical alloying and two-step hot pressing of powders containing Al and 20%wt Ti. Samples were characterized by using optical microscopy, density measurement, brinel hardness, XRD analysis. An increasing density was observed with increasing pressure until certain pressure and after that the density of composite decreased, which can be attributed to the increase in the level of porosity level and the amount of forming Al3Ti. The samples that hot pressed under cycle 5 and 6, showed the most volume fraction of in-situ phases on the matrix. The wear behavior of Al based composites reinforced with in situ Al3Ti particles has been investigated... 

Age-related macular degeneration (AMD) is the most common cause of vision loss in those aged over 50. There are two main types of AMD, Wet and Dry form. Wet AMD is more severe though more treatable. There are three conventional treatments for AMD including laser therapy, surgery and intravitreal injection of anti-VEGF into the eye. Delivery of drugs to the posterior segment of the eye is still challenging and several implants and devices are currently under investigation for their ability to stimulate the retina, producing visual percepts. The application of intravitreal bevacizumab (Avastin) has expanded tremendously from the time of its introduction into ophthalmic care since 3 years ago.... 

Enhancement of photocatalytic characteristics of semiconductors have been always a challenge for the researchers. Doping semiconductors for adjusting their energy gap and changing their morphology in order to increase their effective surface area and reaction sites are examples of their endeavor to overcome the challenge. In this research, nanostructured Aluminum Titanate powder was synthesized with Sol-Gel process and by altering synthesis parameters, the best synthesis condition to get the best possible band gap was discovered. Moreover, we examined the photocatalytic properties of the recently developed material “tialite”, which were not studied before and also evaluated the effect... 

In this thesis, manganese oxide nanoparticles with about 5 nm size were synthesized via solvothermal to maximize surface and active sites for proton relaxation. The synthesized nanoparticles were coated with gentisic acid to acquire suitable colloidal stability and biocompatibility. The nanoparticles showed low cytotoxicity in MTT assay. Electrosteric mechanisim was employed for colloidal stability. This mechanisim doesn’t need high surface charge and thick coat which are vital for particles functionality. Then by cell culture eliminating and adding protamine sulfade, nanoparticles uptake were increased tremendously. In this thesis for first time Prussian blue was utilized for staining... 

Photodynamic therapy that has been developed over last century, now has become more widely used medical tool for the treatment of various diseases such as cancer. This technique involves delivery of photosensitizing drugs, irradiation of light and motivation of drugs. The limitation of light penetration in body tissue, may resolve by application of upconversion nanoparticles. Upconverting nanoparticles could help treatment of cancer tumors in deep or critical points of body by converting high penetrating Near-Infrared emissions to higher energy visible emissions. In the present work, rare earth elements doped TiO2 nanoparticles are synthesized. The photodynamic properties of rare earth... 

In the present research, a novel method for the fabrication of Al/Al3 Ti-Al2O3 composites and nanocomposites based on the thermal degradation of the refectory ceramic “Aluminium Titanate (AT)” or Al2TiO5 by powder metallurgy route. This research encompasses some precise subsequent steps. At first stage, nanostructured aluminium titanate nanofibers and particles were synthesized via a citrate sol gel process in which citric acid was used as a chelating agent. At second step, the possible chemical reactions between Al and aluminium titanate were taken into consideration both in powder form and in bulk form. Thermal analysis results indicated that it is feasible to decompose aluminium titanate... 

The aim of this project is the surface modification of super para magnetic iron oxide (SPIONs), leading to oriented covalent bonding of antibody(AB) to these nanoparticles (NPs) and improve the efficiency of cell separation at MACS columns. For this purpose, SPIONs synthesized by co-precipitation method, and the stability of colloidal NPs then was provided by coating with Dextran . We used TGA to measure weight percentage of dextran. Some properties like particle size, hydrodynamic diameter, presence of coating and superparamagnetic properties were characterized by XRD (16 nm), FTIR, DLS (73 nm), TEM (20nm) and VSM (≈76/78 emu/g) method, respectively. Then we tried to immobilize AB on NPs... 

Sonodynamic therapy has been developed over the last century, now it has become more widely used as a medical tool for the treatment of various diseases such as cancer. This technique involves delivery of sonosensitizing drugs, irradiation of ultrasound waves and motivation of drugs. In this thesis surface modification process with polymer and biocompatible surfactant on TiO2 nanoparticles has been done due to stabilization of TiO2 nanoparticles in neutral pH which is similar to inside-body situation. In the last step, for cancer therapy, doxorubicin as a cancer drug was loaded on TiO2 which was surface modified by PVA. The results revealed the best ratio of (PVA: TiO2), (SDS: TiO2), (SDS:...