Sharif Digital Repository

In recent years, the usage of Internet bandwidth has been increased by emerging applications such as Video on Demand (VoD).As the popularity of VoD increases among the Internet users, some new problems like bandwidth limitations and congestion embark. For solving mentioned problems, Content Delivery Networks (CDN) has been introduced. Using CDN approaches either in ISP or organization is also known as Telco CDN. Generally implementing CDN approaches to process all requests either in ISP or organization can cause bottleneck. On the other hand, Software Defined Networks (SDN) could bring us new tools and opportunities which enables us to implement novel methods to confront these problems.... 

Deep Neural Networks (DNNs) are widely used as a promising machine learning method in different applications and come with intensive computation and storage requirements. In recent years, several pieces of prior work have proposed different accelerators to improve DNNs processing. We observe that although the state-of-the-art DNN accelerators effectively process some network layers of certain shapes, they fail to keep computation resources fully utilized for many other layers. The reason is twofold: first, the mapping algorithm is unable to employ all compute cores for processing some layer types and dimension sizes, and second, the hardware cannot perform data distribution and aggregation... 

A typical problem in applied mathematics and science is to estimate the future state of a dynamical system given its current state. One approach aimed at understanding one or more aspects determining the behavior of the system is mathematical modeling. This method frequently entails formulation of a set of equations, usually a system of partial or ordinary differential equations. Model parameters are then measured from experimental data or estimated from computer simulation or other methods. Solutions to the model are then studied through mathematical analysis and numerical simulation usually for qualitative fit to the dynamical system of interest and any relative time-series data that is... 

With increasing number of processors on a chip, the role of interconnections becomes more important in both power consumption and bandwidth. As a result, in MultiProcessor System-on-Chip architectures, the design constraints will shift from "Computational Constraints" to "Communicational Constraints". Nowadays, optical information transfer is introduced as a suitable substitution for electrical interconnections in chips, which can eliminate their problems. Many different optical networks have been presented so far. These networks can be divided into two subcategories. Networks of the first category use an electrical infrastructure as well as optical one. Hence, the scalability of scheme is... 

In 2008, a decentralized and distributed payment solution called Bitcoin was born. Since then, it has made the payment industry think about banks and companies on the one hand and government authorities on the other. By using mathematics and cryptography, Bitcoin was able to eliminate the need for trust and in this way it was able to eliminate intermediaries such as banks. In traditional financial affairs such as banks, the user must trust the bank and everything relies on the bank’s servers. While Bitcoin stores the history of transactions in a public and distributed ledger. This ledger is encrypted so that the state of the blockchain is always reliable. In Bitcoin’s decentralized and... 

As the number of processing cores on a single chip continues to grow, the need for a high bandwidth, low power communication structure, will be the most important requirement of the next generation chip multiprocessors. Today, a major part of power consumption in multicore architectures belongs to interconnects. Due to these facts, reducing power consumption, as well as supporting high performance, is of major concern in these architectures. Optical interconnects have the potential to replace electrical wires to solve the bottleneck of communications in integrated circuits. Various routers and architectures with different points of view, have been recently designed considering existing... 

Hybrid CDN-P2P architecture has been introduced to combine scalability advantage of P2P and reliability of CDN networks. Although it has been proved that CDN-P2P is more efficient than other architectures for live video streaming, there is still the question, “How is it possible to be more efficient in providing higher service quality?” Quality degradation in P2P and Hybrid CDN-P2P is mainly connected to the lack of exploiting role of peers’ heterogeneity in the system. Most of currently deployed live video streaming systems don’t adapt to bandwidth of the peers and just send one version of video to all users. To tackle this issue, many researches combine P2P solution with scalable video... 

According to the increasing amount of data exchanged among data centers, the need for speeding up and bandwidth and reduced power consumption has been increased. The information show that about 77% of the data is moved into the data centers. On the other hand, 10% of data center’s power consumption is used to data transmission. Improving the interconnection network of data centers can play an important role in reducing power consumption and speeding up. In recent years, optical interconnects have gained attention as a promising solution. Nevertheless, offering an all-optical and efficient architecture is an important issue. In this study, we intend to provide a multi-stage, all-optical... 

In the Pay-TV industry, it is necessary to limit access of unauthorized users. Conditional Access System (CAS) is the solution. In the Pay-TV, the ability of instant join and leave operation is desirable for users. On the other hand, this characteristic is in contradiction with growth of user number.
Previous proposed conditional access systems address the requirement of pay-TV from several aspects. Key distribution management is on of them which plays a key role in the security and efficiency of a conditional access system. Re-examining the process of key distribution management make it possible to find a way to provide a greater flexibility for the users.
The purpose of this... 

Simulation of biophysical neural networks enables the interpretation and integration of fast-growing and different experimental datasets. The widely used NEURON simulator allows molecular-to-network simulation. However, it is still a very hard challenge to create large-scale models and operate parallel simulations applying NEURON. SUNY Downstate developed the NetPyNE means networks using Python and NEURON, which was funded by the New York State Department of Health and some other institutions. NetPyNE is a Python-based tool that enables the development of data-driven multi-scale network models in NEURON through both programmatic and graphical interfaces. It is a powerful tool for parallel... 

Perovskite solar cells with 25.5% efficiency and fast and cheap manufacturing process are among the most promising technologies in this field to replace silicon cells. Despite the challenges of stability and toxicity to these cells, their manufacturing technology has recently shifted to the development of large-scale manufacturing methods in module dimensions. In the present study, the fabrication of perovskite cells in large dimensions to achieve the perovskite module has been aimed and studied that to achieve this, the method of large-scale spraying and printing using the vacuum system was used to create cell-forming films and, consequently, to make the final cell and module. To... 

Natural language generation is one of the burgeoning areas of Nautural Langauge Processing/Computational Linguistics in which the primary concern is to automatically generate sentences in human languages. Based on the type of the input they receive, NLG systems can be divided into two categories: text-to-text and data-to-text. Systems of the first type are usually a part of machine translation systems. The latter type, which is the subject of the current research, deals with language generation based on inputs other than raw text, such as databases, images, videos, audio and so on. This project is an attempt to create an image-to-text system. This is the first research on data-to-text NLG... 

The electronic health system plays a crucial role in modern healthcare, facilitating efficient data management, secure information exchange, and improved patient care. However, existing systems often face challenges related to security, privacy, scalability, and interoperability. The primary objectives of this study are proposing a system that ensures data security, patient and peer privacy, scalability, data integrity, deniability, traceability, secure data sharing, access control, transparency, real-time monitoring, and security in the drug supply chain. To achieve these objectives, we have proposed a system that encompasses a wide range of requirements of healthcare system. To enhance... 

The Internet of Things is one of those concepts that, while it has gained significant importance in recent years in scientific and industrial communities, still faces various challenges, such as power consumption and scalability. In networks powered by batteries, it is necessary to optimize power consumption to extend the network's lifespan to the maximum possible extent. Additionally, considering the large number of connected devices in the Internet of Things network, it is essential to optimize the number of devices connected per gateway, ultimately reducing the need for fewer gateways in a network. In this research, we utilized simulation-based methods to extract output parameters of a... 

Blockchains are not scalable by design, and it is known to be the most important barrier in the way of development of these systems. One of the main approaches to this problem is sharding, that is under development in industry and academia. Sharding scales the system up by reducing redundancy, that makes blockchains vulnerable in terms of security. In this paper, we will study the effect of sharding on availability of these systems, and will show that sharding can magnify the unavailability of the service, and introduce an adversary threat model that takes real concerns of availability in today’s Internet like DoS attacks into account. We also introduce a basic unavailability-resistant... 

Model-Driven Engineering (MDE) methodologies play an important role in developing software systems. The main focus in MDE methodologies is on constructing and refining the models of the system based on meta-models of specific domains. MDE methodologies' proliferation in the software industry has been mainly due to their capabilities in automatic generation of code and other artifacts throughout the development process. This removes the need for constructing extra structures and repetitively performing certain practices during the development process. MDE methodologies also enable software solutions to be implemented based on various platforms and technologies. Moreover, they offer... 

Software Defined Networking (SDN) is an emerging paradigm which makes the network programmable by separating the control plane from data plane and makes both planes to work independently. There is a centralized controller and a programmable data plane in these networks architecture and forwarding data packets is realized by programming the data plane via an open interface called OpenFlow. OpenFlow is a communication protocol between control and data planes. The centralized architecture of these networks provides a global view of the underlying network to upper applications and brings numerous advantages such as routing, traffic engineering and QoS control. Despite these advantages there are... 

Blockchain systems are considered a subclass of distributed systems and have drawn a lot of attention from academia in recent years. The deployment of these systems in various contexts has been the focus of extensive studies. Because of their design, which places a strong focus on security and decentralization, blockchain systems have some challenges. The most prominent challenge is the one that involves scalability. A blockchain's scalability refers to its capacity to achieve a target throughput and solid performance in confirming transactions with an ever-increasing workload or number of nodes in the network. A solid performance suggests that the blockchain system can sustain its... 

The purpose of this thesis is to improve the protocols for recording and transmitting medical data in terms of security and performance using blockchain technology. The approach we take in this Thesis differs in three respects from most articles written in this field. The first is that unlike those who look at the blockchain as a black box and take advantage of only its positive features, we consider the details and challenges it creates for us and solve them in order to use it. The second important point is to justify the use of blockchain in this design. It can be seen in many designs that the use of this technology is useless according to their model and goals. Finally, one of the most... 

Aautomatic image annotation that assigns some labels to input images and provides a textual description for the contents of images has become an active field in machine vision community. To design an annotation system, we need a dataset that contains images and labels for them. However, a large amount of manual efforts is required to annotate all images in a dataset. To reduce the demand of annotation systems on the labeled images, one solution is to exploit useful information embedded into the unlabeled images and incorporate them into learning process. In machine learning community, semi-supervised learning (SSL) has been introduced with the aim of incorporating unlabeled samples into the...