Sharif Digital Repository

Isogeometric Analysis method is a newly introduced method for the analysis of problems governed by partial differential equations. The method has some features in common with the finite element method and some in common with the mesh-less methods. This method uses the Non-Uniform Rational B-Splines (NURBS) functions as basis function for analysis. With this basis functions, the refinement procedure is much easier than the classical finite element method by eliminating the need to communicate with the CAD model. Modeling cracks in classical finite element method requires very fine mesh near the crack tip. One can model crack propagation by means of classical finite element, using an updating... 

In the recent years, the enhancing of utilization of polymeric materials, especially in packaging application, became the serious concern because of the problems of their recycling. One of efficient ways for solving this problem is usage of biodegradable polymers. Thermoplastic starch (TPS) is one the alternative materials which is produced in gelatinization process by plasticizers. However, using of TPS because of its low mechanical properties, poor processability and high water absorption is not applicable and it is necessary to improve that. One of the strategy in order to improving the TPS properties is blending with other polymers, such as polylactic acid (PLA) which the biodegradable... 

In Iran, the Iranian Nuclear Waste Management Company (INWMC) is responsible for safe disposal of low-level radioactive waste which results from different processes of nuclear fuel cycle and other radioactive-related activities. The safety assessment program is essential to ensure safe isolation of radioactive waste from the biosphere for long periods of time. Usually, the ground water scenario is considered as the main scenario of radionuclides migration from repository to the biological environment. Thus, it is required to measure the transport parameters of radionuclides in the porous media (soil) around the disposal site. In this research, laboratory scale columns, filled with Nain... 

This research presents an innovative analytical solution to static, free vibration and buckling of an isotropic, homogeneous Mindlin plate with uniform thickness. This method satisfies all classical boundary conditions including free, simply supported and clamped as well as non-classical ones. Moreover, Mindlin plates on Winkler foundation of arbitrary stiffness function are investigated. In this study, the deflection and rotation of straight normal line of the plate about x and y axes are represented as the functions of sine and cosine Fourier series, accompanied by auxiliary functions. These auxiliary functions are of great importance because these functions satisfy arbitrary boundary... 

In the recent years, the world has been faced with a spectacular increase in variety and usage of electronic and electric devices. Unfortunately, the highly increasing march of technology reduces the time of their usage, causing a high degree of electric and electronic waste. Nonetheless, these E-waste enjoys a high percentage in precious metals such as Cadmium, Copper, Nickle, Zinc, Barium, Beryllium, Aluminum, Gold, Silver, Platinum, and so forth. With this in mind, they can be named as “secondary mines”, enjoying higher in degree of these metals even than natural mines. Therefore, extraction and recovery of the very metals are of great importance. Nowadays, using microorganisms in order... 

In this research, the issue of outsourcing control calculations to servers or external computing parties for non-ideal situations has been discussed. Due to the confidentiality of the information of the control systems, it is necessary to guarantee and maintain the privacy of the data from sensors to the actuators. In this research, secure multi-party computation using secret sharing has been utilized to establish the privacy of these data and simultaneously outsource control computing. In other words, the goal is to design a secure controller by means of secure multi-party computations. One of the most important challenges in the design of controllers that use communication channels to send... 

Colon cancer is one of the most common and dangerous cancers, with a high mortality rate. Early diagnosis and accurate prediction of this disease are crucial for effective treatment of patients. This study aims to predict and diagnose colon cancer at an early stage using gene expression data. The main challenges in this field include the high dimensionality of gene expression data, the limited number of samples, and imbalanced data. Previous research has utilized feature selection methods to identify genes associated with colon cancer and applied machine learning algorithms to predict this cancer. In this thesis, we examine a feature selection method that utilizes Kullback-Leibler divergence... 

In this study, various methods of speech time scale modification are inspected and the most important one is modified. First, a brief review on all existing methods for audio time scale modification and its applications is presented in introduction section. As will be noted, the presented method could be classified in three classes of Time domain, Phase-vocoder and signal model. In next chapter a review on Time-domain methods is presented and its advantages and disadvantages have been addressed. Afterward, a review on Phase-vocoder and Signal-model methods is expressed in chapter 3 and 4 respectively. Considering the complexity and extent material relating to these techniques, the research... 

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...