Sharif Digital Repository

Numerous strategies have been applied to deal with the drought crisis such as reusing the effluent wastewater in irrigating crops, sports spaces, parks, health, entertainment purposes etc.Although the common treatment of sewage can eliminate almost 95% to 99% of microorganisms but this level of treatment is not enough for reusing the sewage, due to the existence of Pathogenic microorganisms. Therefore, disinfecting the wastewater effluent is one of the crucial stages of sewage’s treatment for preserving water resources or reusing it. Chlorination is the most common method of disinfecting wastewater. However, using a wastewater which is disinfected through Chlorination has Harmful effect on... 

The existing thesis investigates the removal efficiency of ammonia from wastewater using natural zeolite, and the effects of various parameters on the removal efficiency. The importance of this research is due of the fact that ammonia is among the primary contaminants of wastewater. The common method of removing ammonia is biological processes that have a number of drawbacks. The ion exchange method could be a suitable alternative to the former method. Ammonia removal from wastewater was investigated through both batch and continuous experiments. In these experiments the initial ammonia concentration in the wastewater was chosen to be 1000 mg/L, 100 mg/L. The optimum ammonia removal was... 

Membrane bioreactor (MBR) is a combination of conventional activated sludge (CAS) and membrane filtration which owing to its advantages such as high quality effluent and low excess sludge production, has gained increasing application in wastewater treatment. The major drawback of a MBR is the membrane fouling that reduces the permeate flux, which in turn increases the overall operational costs due to high energy requirements. In existing study, the combination of sludge oxidation and coagulation/flocculation addition was investigated for mitigation of membrane fouling in a membrane bioreactor. Oxidation can facilitate sludge flocculation and hence improve the properties of mixed liquor. The... 

Microalgae is a major problem in water resources due to its adverse influence on water treatment process and water quality like color, odor and taste. In addition microalgae removal is an important process in food and pharmacy industry. Electrocoagulation is a potential method for microalgae removal. Another method for microalgae recovery is membrane treatment. This study is focusing on using both methods separately and simultaneously. To achieve this, the removal of Chlorella Vulgaris, a fresh water microalgae, was used in experiments. In first phase the experiments were solely on electrocoagulation and the effect of several parameters including current density, electrocoagulation duration,... 

Numerical methods in fracture and crack propagation problems usually involve high computational costs. Adaptive finite element method is one of the techniques which can be used to simulate the crack propagation with an acceptable accuracy. In this thesis, various constitutive models are implemented for simulation of fracture, including the linear elastic fracture mechanics, cohesive zone model and continuum damage mechanics. The fracture mechanical evaluation is performed on a general integral technique for non-planar curved cracks in LEFM. In the second model, a bilinear cohesive zone model is applied to implement the traction-separation law. The Lemaitre damage model is employed and the... 

These days usage of prestressed structures in civil projects are increased significantly. One of these structures is prestressed concrete beam. Considering of such charactristics as failure loads , maximum loads, ductility and occurence and extension of cracks in prestressed concrete beams are interested by civil engineering so in this project we try to investigate the effect of increasing in nonprestressed bars with different arrangements in six specimens.
The load enters in static way on each specimen and supports are simple. Considering the results of experiments, ductility increases significantly because of adding longitude and transverse bars and brittle behavior of speciments... 

This study delves into the intricate realm of risk evaluation within the domain of specific financial derivatives, notably options. Unlike other financial instruments, like bonds, options are susceptible to broader risks. A distinctive trait characterizing this category of instruments is their non-linear price behavior relative to their pricing parameters. Consequently, evaluating the risk of these securities is notably more intricate when juxtaposed with analogous scenarios involving fixed-income instruments, such as debt securities. A paramount facet in options risk assessment is the inherent uncertainty stemming from first-order fluctuations in the underlying asset’s volatility. The... 

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... 

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...