Sharif Digital Repository

Navigation in various systems for land, air and sea movement has been of special importance for a long time. Determining the location, direction, speed and acceleration of moving has been a vital issue for mankind and it is also a basic prerequisite for starting the control process. Various methods have been used for this problem, the most important of which is the global positioning system. This method is satellite-based and any user from any part of the world can perform positioning. But in some places, such as tunnels or crowded places in the city, where it is not possible to send a signal, other methods are used. Also, in order to reduce errors, we can use the inertial navigation system... 

Passive energy dissipation systems are mechanical devices which could spread input energy, reduce response and decrease possible damage of the structure. Dampers were identified as a strong energy dissipation devices with cost efficiency and easy installation and maintanance. In this study, effects of using friction and metallic yield dampers to reduce structural responses are investigated. In addition, a comparison between these devices for reducing responses are conducted. Two 5 and 10 stories buildings with intermediate steel moment frames with and without damper are modeled and designed. It is seen, using of dampers could be reduce sections’ sizes. Seven pairs of earthquake records... 

One of the most well-established methods of increasing oil production rate from existing fields is infill drilling. However, drilling these depleted reservoirs with conventional high density drilling fluids may cause formationdamage problems and subsequently reduce the expected production rate. To overcome these technical problems, the use of lightweight aphron based fluids isincreasing rapidly in the petroleum industry. Rheological and fluid loss performance of aphron based drilling fluids can be improved in the presence of nanoparticles; however, very limited information is available in this field. Moreover, a thorough knowledge about the hydrodynamic flow behavior of drilling fluids... 

Ship maneuverability is so important from different aspects. According to the regulations of International Maritime Organization (IMO), every vessel has to meet the minimum requirements of mentioned rules. Consequently, prediction of ship maneuverability in early stages of ship design has become to one of the most necessary steps for shipbuilding and design companies. There are a variety of options in order to prediction of maneuverability of vessels, for instance, one important way is Free running model tests which is capable of direct calculation of the required parameters, provided if some certain conditions are met. In this work, firstly, an introduction to the importance of vessel... 

Customer needs of Iran Print Industry have permanently been a secret for all producers, print centers and even many of the customers themselves. This research tries to find the relationship gaps between Iran Print Industry and its Individual /Industrial Customers, by identifying their needs. This will give recommendations on how manufacturers can increase their customers' satisfaction by providing them with what they need. Also it helps find the customers` satisfaction coefficient of the needs, which is a good guide for Customer Relationship Management in this industry.Therefore, manufacturers can spot these results by providing appropriate machines which can achieve these goals and offer... 

The purpose of this research is producing one phase silica superhydrophobic coating by sol-gel method and drying temperature less than 200 degrees. For preparing micrometer and nanometer scaled hierarchical structure based on silica, TEOS precursor and Fumed Silica nanoparticles were used by density of 43/30 cc/lit and 6/52 gr/lit in order to provide desired roughness in the range of 40 nm. Moreover, HMDS surface modifying agent was used for reducing the surface energy of coating, which is not a danger to the environment in comparison to the same substances. The best Contact Angle is 155 degree and the best Sliding Angle is less than 5 degree. For instance, it was created with the... 

In recent years, there are continuous researches on replacing new dielectrics with suitable dielectric properties (including high dielectric coefficient, low loss factor, high breakdown voltage, and high nonlinear coefficient simultaneously). One of these new materials is co-doped titanium oxide with donor and acceptor of electron, which in spite of having high dielectric coefficient and low loss factor. it has low breakdown voltage and researches on improving the disadvantages of this dielectric are ongoing. Due to the structural similarities between tin oxide and titanium oxide, the tin oxide can be an interesting system for studying and improving disadvantages in this field. In this study... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related... 

Social networks play an important role in people’s lives and have substantial economic outcomes. The role of referrals in labor market, mutual funds in developing countries, the spread of diseases and information, advertisements of goods and services, and political campaigns are just a few examples. Here we propose a strategic network formation model and calibrate and test it with Facebook data. The main idea in this model is that people don’t decide on creating links with others based on individual-link cost-benefit analysis, rather they participate in different social groups and creating links with others are a byproduct of this group participation. Our model does well with regard to... 

A liquid crystal is a state of matter composed of highly anisotropic building blocks. When liquid crystals are exposed to surfaces with given shapes and anchoring conditions, the orientation of their molecules gets spatially disordered and topological defects may form in the system. The interplay between liquid crystals and the geometry and topology of the colloidal particles has motivated extensive recent studies.In this thesis, we present the numerical modeling results for two faceted colloidal particles in a thermotropic nematic liquid crystal. To obtain the equilibrium nematic field with a finiteelement method, we numerically minimize the free energy of the system that based on the... 

Providing high bandwidth network infrastructures for ever increasing need of data transport is of great importance. The underling infrastructure for many communication services such as GSM/3G/4G mobile networks and Internet services is Synchronous Digital Hierarchy (SDH) optical transport systems. SDH are standardized protocols that multiplex multiple lower rate digital bit streams, such as E1 and Ethernet, and transfer them synchronously over optical fiber using lasers or LEDs. In addition to high data transfer rates, flexible network management and protection mechanisms have great importance, hence are part of SDH standards. In order to obtain flexible network architecture and protected... 

Development of Smart Grid and deployment of smart meters in large scale has raised a lot of concerns regarding customers’ privacy. Consequently, several schemes have been proposed to overcome the above mentioned issue. These schemes mainly rely on data aggregation as a method of protecting users’ privacy from the grid operators. However, the main problem with most of these schemes is the fact that they require a large amount of processing power at the meter side. This, together with the fact that smart meters don’t usually have a powerful processor, can cause the unavailability of smart meter data at the required time for operators of the grid, and at the same time disables smart meters from... 

Secure routing is a major key to service maintenance in wireless ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. Wormhole attack is one of the most severe active attacks to mobile ad hoc networks. Noting the resource limitations in such networks, nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a... 

Dynamic spectrum access with the aid of cognitive radio (CR) technology is a viable solution to spectrum scarcity. There are many military and emergency applications that require the use of cognitive radio ad-hoc networks (CRAHNs). In these net- works, nodes must first find each other in a wide spectrum and then exchange their desired data. The process of finding each other in a multichannel environment is a challenging task and is usually known as rendezvous. Since rendezvous is the first step in communication, disrupting will disable the nodes from establishing proper communication sessions. That results in a drastic degrade in the performance of the network. Therefore, it is important to... 

Spray-wall impingement is one of the phenomenon that associated in different subject such as spray cooling, combustion chamber and gas turbine. With the impingement of spray to the wall, liquid film begins to form. Wall film characteristics is still an important subject to study. Due to the various stages of liquid film formation from injection of spray till spray-wall impingement, the investigation of this phenomenon is far more complicated. This paper is meant to provide detailed data on spray-wall impingement and wall film formation physics with the help of computational analysis of OpenFOAM . A Lagrangian-Eulerian method based on discrete phase model (DPM) was employed to model... 

Magnesia-Doloma refractories has advantages such as stability in alkaline environments, clean steel production, resistance to acid slag, good cement kiln coating flexibility, low production cost. It also has some weaknesses such as low resistance to thermal shock and quick hydration. In the present study using Birjand Mines Magnesite powders and Dolomites from Zefreh, Esfahan, Magnesia-Doloma clinkers were pressed under the pressure 90 MP and prepared at 1650⁰C in furnace under air atmosphere. The effect of adding 0, 2, 4, 6, and 8% of the Microparticles and Nanoparticles of α-Alumina on microstructure, physical properties, hydration resistance and Thermal shock resistance was studied. Phase...