Sharif Digital Repository

In this research, Al-20Si-5Fe-2X (X=Cu,Ni,Cr) alloys were produced by gas atomizing and melt spinning processes. Microstructure and growth morphology of powder and ribbons were investigated using optical microscopy, scanning electron microscopy and transmission electron microscopy, then, analyzed by solidification models. Powder and chopped ribbons were hot pressed at 400°C/250 MPa and microstructural variations, mechanical properties and thermal coefficient expansion were evaluated after consolidation. Results show that relatively high cooling rate in gas-atomized powders lead to refinement of the microstructure and formation of semi-equilibrium δ intermetallic phase. As the powder particle... 

In this study a systematic effort was made to study and compare electrochemical oxidation behavior of iodide on Pt, carbon and carbon supported polyorthoaminophenol film electrodes. All of the electrochemical experiments were performed in acidic, basic and nuteral aqueous solutions and the applied electrochemical techniques included Chronoamperometry (CA) and Cyclic voltammetry (CV). Effects of concentration and scan rate of potential on the cyclic voltammetry of KI was studied at the previously mentioned electrodes. Current-time and log current-potential curves were analyezed quantitavely in order to determine kinetic parameters. Carbon supported polyorthoaminophenol electrode was prepared... 

Most countries regard to parameters such as equipment, cost, facilities, manpower, geographical conditions and environmental regulations select one (or combination) of the methods of burning in incinerators and burial in the landfill for municipal solid waste management. Both methods have undesirable environmental effects and are dangerous. Composting is another proposed option for solid waste management that is more consistent with the environment. In this process, different bacterial species transfer organic materials under aerobic conditions to the products such as CO2, H2O, minerals and compost. One of the effective and economical method for solid waste management is vermicomposting... 

The applications of science and technology of materials grows rapidly nowadays One of the major aspect of this science discuss about the growth of thin films via deposition of molecules and atoms. By this way we can diagnose physical and chemical properties of thin films whose applications in electronics, computer, microelectronic industry, material engineering telecommunications and so advances every day. In this way we smell out the process of the growth of diamond like carbon (DLC) thin films whose importance is extended nowadays. By acknowledgement of variables that influence the dynamics of film formation we make a big jump in attaining the optical, physical and electrical properties of... 

In this research ,Al-20Si-5Fe-3Cu-1Mg-XMn alloys were produced by gas atomizing and melt spinning processes. Microstructure and growth morphology of powder and ribbons were investigated using optical microscopy , scanning electron microscopy. powders were hot pressed at 400ºC/250Mpa and microstractural variations, mechanical properties were evaluated after consolidation. Results show that relatively high cooling rate in gas-atomized powders lead to refinement of microstructure and formation of semi-equilibrium δ intermetallic phase . As the powder particle size decrease , the growth morphology changes from primary silicon + euthectic to euthectic + primary dendritic aluminum . Mn changed the... 

Nanotechnology is an efficient method suitable for fabrication and production of minimal single dimensional nanometric structures. Such materials and systems can be logically designed that lead to new and optimized biological, chemical and physical properties and characteristics due to their size. Nucleation and growth –appearance of a new phase out of an old phase – is a ubiquitous phenomenon in nature. Fundamental understanding of nanoparticles nucleation and growth mechanism allows more control on form, size and composition and allows tuning of the above said properties easily with use of different reactive conditions as a result of this ability . Nanoparticles of titania are one of... 

The chemical vapor deposition (CVD) of graphene from methane on a copper substrate is the most promising method for production of large-area graphene films. There have been long-standing challenges in this field such as controlling the graphene coverage, film quality, the number of layers, and the nucleation density of graphene domain. These challenges can be overcome by developing a fundamental understanding of the graphene growth process. The main aim of this study is to control nucleation density of graphene domains. Chemical vapor deposition (CVD) graphene is polycrystalline, and grain boundaries in graphene film have been identified to degrade the properties of graphene as a membrane... 

Cardiovascular diseases are the major cause of death worldwide. Atherosclerosis is one of the major types of cardiovascular diseases in which fibrous and fatty materials, called plaque, build up inside the artery and cause partial or total occlusion of the artery. Intravascular balloon angioplasty with or without stenting is the most common treatment of this disease. In 2010, approximately 954000 stent implantations were performed in the United States. The major issue associated with stenting is reclosure or renarrowing of the transverse section of the artery termed in-stent restenosis (ISR). Unfortunately, nearly one–third of the patients
who receive stent implantation require further... 

Crystallization of Aluminum Hydroxide is the most important section of the Alumina production processes as the product yield and crystal size distribution (CSD) of this stage strongly affects the whole Alumina production process. In this work to simulate the crystallization in industrial steady precipitation tanks two Population Balance based models developed. First one is the Coupled CFD-Population Balance Model which considers the effects of flow hydrodynamics on crystallization kinetics and CSD. For development of this model the computational fluid dynamics software ANSYS FLUENT has been used. The two phase flow field has been simulated using Eulerian granular multiphase model coupled... 

Research in the field of medical science goes back decades and significant progress has been made in understanding the behavior of organs and living tissues. Consequently, scientists need to work towards identifying how to mathematically model the mechanical behavior of these living organisms. If we consider any living entity, we can see that they are a product of atoms, molecules, cells, tissues, and/or organs. Differential geometry and continuum mechanics indicate that during the growth process these organisms are influenced by the phenomena of aging, remodeling and morphogenesis. The majority of research in this area, i.e. the study of these important phenomena in living tissues, has... 

Cardiovascular diseases are one of the leading causes of death in the world. Identifying the mechanical behavior of arteries and their growth and remodeling under applied loadings can help to better understand the progression of the disease and provide more effective clinical interventions. Therefore, many researchers in recent decades have turned their attention to modeling the process of stress-mediated growth and remodeling in soft tissues. Among the most important models proposed to study this process are the constrained mixture model proposed by Humphrey et al. and the volumetric growth model proposed by Hoger et al.. The constrained mixture model is based on the continuous turnover of...