Sharif Digital Repository

In this study, HSS and double angle braces subjected to cyclic loading in order to study the buckling and post buckling behavior have been investigated by Finite Element method. The results of FE analysis are fairly in good agreement with experiments. Analysis demonstrate that when local buckling occurs in middle span, subsequently, strain rises severely. Accordingly, this strain jumping causes early fracture in braces. Therefore, local buckling can be one of the primary reasons of fracture in braces. As a result, local buckling must be considered one of the primary limit state of Performance-Based design of steel braces. In addition, finding a way to predict local buckling can help us to... 

To create applications for smart environments we can select from a huge variety of sensors that measure environmental parameters within the premises. Capacitive proximity sensors use weak electric fields to recognize conductive objects, such as the human body. They can be unobtrusively applied or even provide information when hidden from view which make these sensor more popular. Furthermore, these sensors are low cost, precise and low power. In this thesis, we study the construction and operation of capacitive sensors and the challenges of using them. Then we use them to produce smart devices. Smart flooring is used on the ground and it can be used to track people or fall detection. Smart... 

The use of protons and charged particles such as carbon in the treatment of cancerous tumors is one of the new methods of external radiation therapy. Proton therapy can achieve almost the same tumor dose coverage as traditional photon therapy with a greatly reduced dose to the normal organ. The radiation deviations caused by the magnetic field are an effective factor in reducing the dose of vital organs without sacrificing the dose coverage of tumors; Therefore, a new method of proton therapy, called magnetic field-modulated proton therapy, has been proposed, in which the Bragg peak positions of proton beams can be modulated under the cover of predesigned magnetic fields inside cancer... 

e study of the brain’s neural activity is an active research area in computational neuroscience aiming to provide insights about the functionality of the brain as well as dysfunctions that underlie disorders. Functional Magnetic Resonance Imaging (fMRI) plays an important role in brain studies by providing non-invasive records of neural activities during a specific task with location sensitivity. Recent advances in statistics and machine learning offer powerful tools for paern recognition and processing of fMRI data. In this thesis, we decode information recorded via fMRI from the visual cortex to reconstruct images presented to subjects. Current reconstruction methods face numerous... 

High-frequency oscillations of the frontal cortex are involved in functions of the brain that fuse processed data from different sensory modules or bind them with elements stored in the memory. These oscillations also provide inhibitory connections to neural circuits that perform lower-level processes. Deficit in the performance of these oscillations has been examined as a marker for Alzheimer’s disease (AD). Additionally, the neurodegenerative processes associated with AD, such as the deposition of amyloid-beta plaques, do not occur in a spatially homogeneous fashion and progress more prominently in the medial temporal lobe in the early stages of the disease. This region of the brain... 

Silica nanoparticles is one of the most important mineral particles. In this study, Sodium silicate, Sulfuric acid and Sodium aluminate is used in order to synthesis of the modified Silica nanoparticles. The effects of temperature, reaction time and the molar ratio of regents were tested and optimized. Synthesized nanoparticles were characterized by use of XRD, FT-IR and SEM techniques. The results show that by controlling the reaction conditions, nanoparticles with an average size of 26.2 nm is obtained. The increase of temperature and reaction time alters the structure of the particles of amorphous state to a crystalline needles. The particle surface modification process was performed by... 

Human action recognition is one of the most attended topics in computer vision and robotics.One of the flavors of this problem relates to the situation in which the task of action recognition is carried out by data from several cameras. Different approaches have been proposed for combining information. Various reduction methods have been introduced to decrease the processing load. All of the methods in this particular field of study can be divided into two linear and non-linear methods. In the linear methods, we don’t pay attention to the non-linear structure of the data, and these kind of approaches are not reliable. Furthermore, combining different actions data is done before the dimension... 

WO3 is known as a photocatalyst in the visible light region, but with lower efficiency compared to more interesting semiconductor photocatalysts such as TiO2 and ZnO. Many attempts have been done to increase the efficiency of this photocatalyst by incorporating metal and metal oxide nanoparticles or recently carbon nanotubes.On the other hand, application of graphene, as an unrolled carbon nanotube, for increasing the photocatalytic activity of TiO2 and ZnO has shown positive results. Furthermore, it was reported that such semiconductor photocatalysts (and very recently WO3) can photocatalytically reduce the chemically exfoliated graphene oxide sheets under UV-vis irradiation.
In this... 

Graphene is a one layer atom thickness and zero energy gap so for using it in nano electronic and transistors baised on graphene it's energy gap should be opened.one of the methods for opening graphene band gap is creating nano scale boundaries or synthesize graphene nanoribbons. One of the new methods for graphene nanoribbon synthesize is longitudinal opening of carbon nanotube. In this thesis graphene nanoribbons synthesize with this method and analyze with AFM and Raman spectroscopy. Carbon nanotubes also have energy gap and IR absorption recently they used for living cell destruction. In this thesis we synthesize graphene nanoribbons and analyzing their optical absorption and use it for... 

TiO2 is known as a photocatalyst in near UV-Visible light region with better efficiency compared to other semiconductor photocatalysts. Many attempts have been done to increase the efficiency of this photocatalyst. also, application of 2D carbon nanostructures namely graphene for increasing the photocatalytic activity of TiO2 has shown positive results.
In this research, we first synthesized Graphene Oxide (GO) suspension by exfolation of graphite oxide suspension. then we fabricated TiO2 thin films on glass substrates by so-called sol-gel method. finally we fabricate Graphene Oxide/TiO2 nanowalls composite films as a photocatalyst in visible light. X-ray photoelectron spectroscopy... 

Graphene nanogrids fabricated by graphene nanoribbons obtained through oxidative unzipping of multi-walled carbon nanotubes, used as two-dimensional selective templates for accelerated differentiation of human mesenchymal stem cells (hMSCs), isolated from umbilical cord blood, into osteogenic lineage. The biocompatible and hydrophilic graphene nanogrids showed high actin cytoskeleton proliferations that coinciding with patterns of the nanogrids. The amounts of proliferations found are slightly better than proliferation on hydrophilic graphene oxide (GO) sheets, and significantly higher than non-uniform proliferations on hydrophobic reduced graphene oxide (rGO) sheets and polydimethylsiloxane... 

One atom thick layer of pure carbon in bonded and hexagonal lattice is named graphene. graphene has unique mechanical, optical, thermal and electrical properties and because of these properties has grabbed attention. graphene has been made from high pure graphite by different methods such as CVD(chemical vapor deposition) , chemical exfoliation , micromechanical cleavage and colloidal suspension. through these methods, green methods for synthesis of graphene, using eco-friendly reductants during synthesis of graphene instead of hydrazine and recently using waste(not graphite) are attractive for synthesis of graphene. Following this idea , a group has produced graphene from wastes such as... 

Graphene oxide is a single sheet of Carbon atoms which has been arranged on a two-dimensional honeycomb lattice. Functional groups such as epoxy, carboxyl and carbonyl are located on basal plane and at the edges of graphene oxide and they localize electrons on the surface of graphene oxide and open band gap in its band structure. Pure graphene has zero band gap, so existence of fluorescence properties is unlikely; but graphene oxide has fluorescence properties due to band gap in its band structure. Fluorescence properties of graphene have been used in live cell imaging and drug delivery, so study and increasing of fluorescence properties is significantly important. The purpose of this... 

Graphene is a two dimensional lattice which is created from carbon atoms. Having special feature, it has such various medical usage, for example in diagnosing and treating cancer. Adding a particular factor to graphene could improve their efficiency. In comparis on with graphene itself, graphene oxide and reduced graphene oxide are much more successful in diagnosing and treating than others because of their higher hygroscopic. Recent studies state that hydrogenized combinations including hydrogenized graphene show desired results. Due to its higher hygroscopic and the possibility of adherence to the cells, hydrogenized graphene could be very effective in diagnosing and treating the sarcomas.... 

This study discusses about mass customization and optimization of supply network in which both goal considering to set the flow of raw material and final product to satisfy the customer demand. The mass customization is more important concept in this study, so that this goal is placed to the first objective. In this research, the model which contained both goal is presented. The model focus on mass customization and try to satisfy various products demand, which constitute 3 kind of speed demands. Each product can satisfy in 3 way: fast, normal, slow.In the first model the new approach present in which the speed affects all of supplying, manufacturing and distributing system. The system try... 

Knowledge Based Firms are considered to be important for the economic development of a country in regards to both employment growth and innovative activity. The latter is believed to contribute significantly to the increase in productivity and therefore the competitiveness of Iran’s economy. This study contributes to the above literature by investigating the factors that are believed to treat the growth of such firms in Iran. The purpose of this study is to identify functional risks of vital signs monitors via Fault Tree Analysis (FTA) method to use as a guide for manufacturers to identify and control hazards. Therefore, 30 knowledge based firms were selected as sample. Then, based on a... 

The Internet is often used for communication-based applications such as online banking, stock trading, and shopping where service interruption is unacceptable. Thus, analysis of the impact of the failures of hardware, software, and related services’ performance quality of the service provided to users is of importance to designers and managers in these functions. In this study, we developed a strategy to the design of a dynamic combination of file servers with the aim of providing reliability and SLA. At first, we examine the reasons for the violation of service level in file host services and datacenters, and then we introduce the criteria to measure the violation of service level on the... 

Nowadays, tissue engineering and stem cells-based therapies have outlined a promising prospect in neural networks regeneration. But it usually requires biocompatible and conductive scaffolds for culturing neural stem cells and directing their differentiation toward the neurons. Graphene due to its unique physical and chemical properties has attracted much interest in tissue engineering. For this purpose, in this study biocompatible graphene oxide foams have been used for neural stem cell culturing. For the first time, graphene oxide foam were fabricated by precipitation of chemically exfoliated graphene oxide sheets in an aqueous suspension onto the PET substrate at ~80 oC under UV... 

Today’s organizations always encounter limitations on the way of achieving their goals. Budget constraint, inventory constraints, capital constraints are issues which complicates management decision making.
Global market has enabled manufacturers compete globally. Even position their factories in other countries and use of competitive advantages and other markets demand. This is why decision making in production and manufacturing domain has been complicated. Decision making in production and manufacturing should become faster and more precise in order to keep market competitiveness. Organization should make long term or strategic decisions and short term decisions about keeping the...