Sharif Digital Repository

Nowadays in Iran service providers, are using copper lines in access networks. They rent these lines from a governmental telecommunication company during a complicated and time consuming process. In this thesis, the most common access technologies have been analyzed in order to find an alternative solution for copper lines. Based on the studies in this thesis, it is clear that Wimax technology can be an appropriate solution comparing with Wi-Fi and 3G from the point of quality and speed. The UNIDO methodology has been used in this economical assessment (feasibility study). In this methodology, all the running and fixed costs and revenue as well, have been estimated. In the next step,... 

This thesis is a research in the technology for paper production from waste paper (non – wood fibers ) , then feasibility study a economical justification for setting up a factory for producing duplex board , with technical and financial study has been performed inaccordance to UNIDO Standard . In packing industries with a capacity 7500 tons per year and the raw material for this process is waste paper. In this thesis paper pulp that needs for board production can be implemented by solving waste paper in the water. This method therefore pollution free and does not have any negative effects on the environment even a considerable amount of water which is extracted from the pulp, istreatment... 

Regarding complexity and wide range use of distribution network structures, loss reduction is possible in case of complete knowledge and suitable approaches. Loss reduction not only can grow GDP but also can improve economic growth. It should have schedule and plan wisely. Thus, in this research, first a region called Yusef Abad in Tehran was selected then the network was assessed completely. During the assessment, the research team determines causes of energy loss and load loss and then measured amount of each one. Then, the loss share of each element of the network determined. Elements of the network consist of transformers, conductors and meters. Then possible solutions for loss reduction... 

Cement, as the basis of industrial development, plays a magnificent role in construction of residential buildings, storage dam projects, industrial factories, roads, agricultural projects, airports, power plants, … In this thesis, the feasibility study of Khomein cement factory has been accomplished. The amount of production assumed as 1 million tons per year. The construction period assumed as 3 years and we suppose that the production plan takes 80 percent of full capacity in the first year, 90 percent in the second year and finally it takes the full capacity in the third year of production. The needed capital has been estimated as 1530 billion Rials and the working capital has been... 

Aabsal Co. was established in north east of Tehran in 1956, under the name of Loab Iran Private LTD.  Co.  and  continued  its  activity  in  manufacturing  enameled  dishes,  bowl,  tea  pots  and  etc.  until 1964. In  this  thesis  we  have  paid  attention  to  basics  of  TPM  and  how  to  implement  PM  procedures.  First we have paid attention to all the maintenance forms and how these forms work together in the company, and then the relationship between departments sections like manufacturing and maintenance are considered. Finally we have attempted to implement TPM. For this purpose we have taken a section of the factory as a pilot plant and have started to implement TPM there to... 

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... 

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... 

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... 

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... 

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... 

Light propagation through turbid media, such as biological tissues, experience scattering due to inhomogeneous distribution of refractive indices of their microscopic structure. Scattering and diffusion of light not only limit many optical imaging techniques, but are also big challenges for telecommunication, spectroscopy, and other optical techniques. Recently many new imaging methods are developed that work in strongly scattering media such as optical coherence tomography, diffusion tomography, and laser speckle velocimetry. In this thesis, we have studied how wavefront shaping techniques can tackle the problem of scattering. By spatially shaping the wavefront of the incident beam, using... 

The effects of biosurfactants on sandstone rocks are known in the literature. However, there are few examples of experimental works in Iranian carbonate reservoirs dealing with the effects of biosurfactants under reservoir conditions. This thesis discusses the effect of an efficient biosurfactant produced from Pseudomonas aeroginosa MRo1, a bacterial strain isolated from oil excavation areas in southern Iran, on the recovery of residual oil trapped within carbonate rocks was investigated. The MRO1 could reduce surface tension from 72 to 28 dyne/cm. It also could reduce Interfacial tension from 18.382 to 5.646 dyne/cm.
In a core holder set-up bearing four limestone- and...