Sharif Digital Repository

Axial compression systems are widely used in many aerodynamic applications. However, the operability of such systems is limited at low mass flow rates by fluid dynamic instabilities. These instabilities lead the compressor to rotating stall or surge. In some instances, a combination of rotating stall and surge, called modified surge, has also been observed. In this research Moore – Greitzer model that the principle of constant speed mode checks as a base case has been considered and the developed condition of this model in which the dynamic model of the shaft will also respect and shaft rotational speed as a basis for state shall consider, has been analyzed.
In this study the effect of... 

Experimental identification (EI) of aircraft static and dynamic characteristics is usually performed for design process verification, its compliance against the existing regulations as well as to extraction of its exact stability and performance characteristics. EI is mostly performed via flight and/or wind tunnel testing of a scaled model of the aircraft under scrutiny. In this regard, the purpose of this thesis is design and development of a 5DoF Table Top Platform (TTP) for Aircraft transfer function identifications as well as some of its key derivatives. The proposed TTP can also function as the motion part of a miniature simulator. The PPT is designed in two parts that is comprised of... 

In urban rail (subway) substations, high voltage dc (750 V) is usually used to feed the traction motors of the wagons. This type of feeding raises issues, including the creation of stray currents in different parts of the structure. The cause of the stray current is the voltage difference between the two points of the rails, caused by the current flowing inside the rails. These currents accelerate the corrosion process in and around metallic equipment. One of the most dangerous issues is the corrosion of gas pipes near the subway that has caused disasters in the past. The stray current cannot be eliminated and its maximum reduction requires high costs. For this reason, different standards... 

Today, factors such as the growing energy consumption in the world, followed by the reduction of fossil fuel reserves, and more importantly, the global warming phenomenon due to excessive consumption of fossil fuels have caused attention towards clean energy, especially solar energy, to increase significantly. Researchers throughout the world are looking for solar cells with high efficiency and stability, and of course affordable. In today's world, one of the materials that has grabbed the researchers' attention is perovskite. The reason behind this is that in the last decade, there has been a significant increase in the efficiency of perovskite solar cells to surpass that of Silicon solar... 

Growing production of cement and concrete in developing countries like Iran in addition to high amounts of energy consumption and pollutants formation through production of cement has motivated researchers to partially replace it with suitable additive materials. In this study, the chemo-physical and microstructural properties of rice husk ash as an agricultural waste and its performance in cement mixtures as a pozzolan is experimantally investigated. Parameters influencing the pozzolanic properties of this material that are studied include the effect of acid leaching before pyro-processing, heating rate, retention time, and grinding time. Additionally, this material is compared with other... 

Artemia (brine shrimp) is a genus of crustaceans that lives in saltwater and due to having unique features, in producing the food and nutrients needed for larvae and other types of farmed sea creatures, is of great importance. In its natural environment under certain conditions, Artemia produces cysts that float at the water surface and are driven ashore by wind and waves. These cysts are inactive and do not develop further as long as they are kept dry. Upon immersion in seawater, the biconcave cysts hydrate and become spherical and, within the shell, the embryo resumes its interrupted metabolism. After about 20 h the outer membrane of the cyst breaking and the embryo appears, surrounded by... 

Wall systems are an essential part of the buildings and their capacity should be properly considered in their design. However, the seismic behavior of building systems with in-filled walls and their interaction is a very complex issue, yet to be understood. Using the in-filled walls in the buildings without including them in the design process changes the whole behavior of the structural system as well as their failure mechanism under earthquake excitations. On the other hand, there have been extensive researches on rehabilitation of the structures with in-filled walls or designing them as the main or one of the lateral load carrying systems against seismic input. In this research, first the... 

According to prediction of ITRS, power consumption and bandwidth of processors' interconnection, will be the most major bottleneck of the System-on- Chips (SoCs) in the future. Therefore, in MultiProcessor System-on-Chip (MPSoC) architectures, the design constraints will be altered from "Computational Constraints" to "Communicational Constraints". There are three kinds of communications in the surface of the chip: Global, median and local. The main difference between global and local connections is that the length of latter one will be changed with technology. In other words, it is scalable like processor's elements while the length of global connections is practically constant. Even though... 

Opportunities for creating value are shifting from managing tangible assets to managing knowledge based strategies that deploy on organizations' tangible assets: customer relationship, innovative products and services, high quality, and responsive operation processes, information technology and databases and employee capability skills and innovation" (Strategy Focused Organization, Norton, Kaplan; 1996). As organizations' value creating process shifts, learning has become one of the most important factors in value creation, and as a consequence dynamic capabilities creation. This research is concentrated on Electric Distribution Companies in Tehran region and studies knowledge management as... 

Nowadays competition in business world has increased drastically. Under these competitive circumstances, it is the supply chains that compete against each other rather than individual firms. Accordingly trying to achieve integrated and synchronized management of activities within a supply chain has become inevitable. Recently researchers have found interest in a particular problem in a supply chain and that is to minimize inventory and routing costs in a supply chain. This problem is known as Inventory Routing Problem (IRP) and has been intensely examined in past few years. In this thesis we will try to expand this well-known problem in pricing dimension. We call this new problem “Inventory... 

Human body is subjected to body accelerations or vibrations in several circumstances. During gravitational changes, the hydrostatic pressure gradient along the body axis changes, and then body fluids are redistributed. Prolonged exposure to high level external acceleration may lead to serious or even fatal situations on account of disturbances in blood flow. Due to physiological importance of body acceleration many theoretical investigations have been carried out for the flow of blood under the influence of body acceleration. In this study, the mechanical loads that pilots experience during flight are considered. The aim of the present study is to investigate the effects of mechanical... 

IoT security is an important step in the rapid development of its applications and ser-vices. Many security protocols have been defined to maintain security at higher communication layers, such as the transport layer and the application layer, but with the advent of quantum computers due to high-speed parallel computing, the previous methods are no longer secure and we have to establish security at lower layers such as the physical layer. The efficiency of IoT devices depends on the reliability of their message transmission. Cyber-attacks such as data injection, eavesdropping and man-in-the-middle can lead to security challenges. In this study, we propose a new deep learning based component... 

It is undeniable that there is a great disagreement in the every field of religion. Reductionists argue that awareness of disagreements reduces the justification and rationality of beliefs, including religious beliefs. In contrast, non-reductionists believe that while reductionism may be true in other domains, it is not necessarily true in religion, because religious beliefs have characteristics that can deny a reductionist argument. They are in the realm of religion. In this thesis, I will discuss issues related to those characteristics that can deny reductionist argument in the realm of religion. In this thesis, I try to show that the arguments and responses presented in defense of the... 

Master curves describe the behavior of asphalt binders over a wide range of temperatures and loading frequencies which are utilized by various predictive models in design and analysis procedure of asphalt mixtures. Frequency sweep test is extensively used for construction of master curves within the temperature range of 4 ̊C to 82◦̊C and frequency range of 0.01 to 30 Hz. There is a concern that master curves are unable to accurately represent the low temperature (below 4 C) behavior of binders. In this study a new cyclic loading pattern for the bending beam rheometer (BBR) test was utilized to conduct the low temperature tests and generate an isotherm compliance curve for incorporating the...