Sharif Digital Repository

The widespread use of the Android operating system has made it an attractive target for attackers. In the field of malware identification and mitigation, the use of machine learning methods has seen significant advancements due to their ability to identify unknown malware. One of these methods is graph-based techniques in constructing malware detection systems, which have achieved high success rates in identifying malware. However, machine learning methods suffer from the vulnerability of being misled by adversarial examples. One important aspect in both malware detection systems and adversarial attacks is the limitations imposed on software modification. Any changes made to the application... 

Ever-increasing development and growth of information volume is an unprecedented phenomenon. Analyzing and saving such enormous volume of information calls for innovative ideas capable of processing and managing this information. One of the successful projects in this regard done by Apache is known as Hadoop.Hadoop is a popular open-source implementationof MapReduce processing schemefor analysis of large datasets. The heart of Hadoop is MapReduce that is a parallel programming model for data processing on clusters. To handle storage resources across the cluster, Hadoop employs a distributeduser-level filesystem. The Hadoop Distributed File System (HDFS) is written in Java and is designed for... 

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... 

Due to 18000 MW power consumption of cooling systems from the total Iranian electricity consumption in 2016 and hitting a new peak in 2017, the need for finding other alternatives that consume less electrical energy is inevitable. Hence, instead of buildings new power plants, only to meet the demand at the peak of power consumption, using new solutions to reduce consumption seems more beneficial. One way to reduce consumption is to switch to ejector refrigeration systems. One of the main advantages of these systems is their ability to cooling using low-grade waste energies or solar energy (as a heat source below 80℃). However, in absorption systems, the minimum temperature of the heat source... 

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... 

With the increasing tendency of consumers to purchase from online stores and the remarkable growth of this industry in recent years, timely and cost-efficient delivery of goods to the final customer has become one of its major challenges. Accordingly, last-mile delivery has attracted significant attention from both researchers and practitioners. This study addresses a vehicle routing problem that considers customers’ ability to pick up their orders from selected centers and their possible presence at different locations within the planning horizon. This thesis aims to enhance customer satisfaction and reduce distribution costs by employing two innovative vehicle routing approaches. The first... 

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... 

Hayek is one of the most impressive figures of Austrian School of Economics established by Carl Menger. The Thinkers of this school of thought believed that governments should not intervene in the market process. They argued that such interventions would spoil the market performance in resource allocation. Hayek believes that the order which emerges from the market is a spontaneous one; it means no one has designed it, but it has evolutionarily evolved by distinctive agents' actions who had no plan to make it. Hayek's arguments for spontaneous order are based on some epistemological presuppositions such as: "methodological individualism", "methodological subjectivism", "tacit knowledge" and... 

So far, several studies have been conducted on the endurance time method. In general, these studies can be categorized into two categories. The first group of studies are based on the theoretical foundations of this methodology and the second group of researches that use the method of endurance time in different engineering issues of earthquake and engineering, and also compare the results of this method with other conventional methods of seismic analysis.The purpose of this study, which is more in the first category of research, is to optimize the acceleration functions using various Transform, such as Fourier and Wavelet, as well as the use of various optimization algorithms. In optimizing... 

As application demands for online convex optimization accelerate, the need for design-ing new methods that simultaneously cover a large class of convex functions and im-pose the lowest possible regret is highly rising. Known online optimization methods usually perform well only in specific settings, e.g., specific parameters such as the diam-eter of decision space, Lipschitz constant, and strong convexity coefficient, where their performance depends highly on the geometry of the decision space and cost functions. However, in practice, the lack of such geometric information leads to confusion in using the appropriate algorithm. To address these issues, some adaptive methods have been proposed...