Sharif Digital Repository

Soil-structure interaction may have a considerable effect on the response of the superstructure. One of the main steps in analyzing the soil-structure system is determining the soil impedances which vary with frequency. Although it is possible to analyze a dynamic system with complex frequency-dependent property matrices, this cannot be taken into account in most standard general-purpose softwares. In addition, the nonlinear behaviour of the structure can only be studied in time domain. Therefore, in the past two decades efforts have been made to replace the soil media with discrete models having a small number of degrees of freedom (DOFs) and a few springs, dashpots and masses with... 

The use of sandwich panels has become very common in recent engineering designs when the weight of the part or structure is important and we are looking to lose weight while maintaining strength. The mechanical properties of this type of structures, including yield stress, fatigue behavior and estimation of their life, failure modes, natural frequencies and resonance phenomena, etc. are affected by various factors, including geometric and environmental factors. Fatigue is one of the most common failures in these structures. Composite materials have complex structures. In these materials, due to the viscoelastic properties, the fatigue behavior changes with changing stress, stress frequency,... 

1,3-Dipolar cycloaddition reactions constitute one of the most fundamental reactions for construction of five-membered heterocyclic compounds Spiro and dispirooxindoles have become important synthetic targets as these structural frameworks form the core units of many naturally occurring molecules that possess abundant biological activities .In this report we used (E)-Aryl ideneindolinones as unusual dipolarophiles for synthesis of dispirooxindoles. In follow different bifunctional nucleophiles for example 1,3-dicarbonyl, phenol, thioindole can be used in synthesis of benzoxazocines We have reported a new and efficient synthesis of benzoxazocines via unique tandem 1,3-dinucleophilic addition... 

We have reported a new and efficient synthesis of a broad spectrum of heterotetracyclic thiopyranoindole via knovenagel hetero diels alder reaction.Fused pyrimidines have attracted considerable attention in synthetic organic chemistry because of their wide range of biological activities pharmaceutical and therapeutic properties, and antibacterial, antiviral, antitumor, and anti-inflammatory activities. We have reported a new efficient method for synthesis of pyrimidines fused to coumarine, uracile, cyclohexane and triamino pyrimidine structures. The major benefits of the current study are high yields, short reaction times, mild reaction conditions and available materials..We have also... 

The natural tissue of the bones consists of organic and inorganic parts. The bone mineral part contains calcium phosphate and its organic part is mainly of collagen fibers. The combination of these fibers and calcium phosphate makes the bone flexible and resistant to stresses. Many conditions, including osteoporosis and crashes, lead to fractures and cavities in bone. Bone cements are the most used materials used in orthopedic surgeries and spinal cord.The purpose of this study was to synthesis acrylic bone cement with properties determined by ASTM F 451 and Iso5833 for orthopedic applications, including joint replacement. Polymethyl methacrylate polymer was synthesized as the main component... 

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... 

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...