Sharif Digital Repository

In the last few decades, due to population growth and lack of habitable space, the need for construction of taller buildings with more stories has become an important topic. Design of these high-rise structures include different complex tasks in which the finance of the project is the most important parameter. In order to find an efficient and financially feasible design, engineers have always been looking for new approaches and materials. One of the structural systems to be used for tall buildings is the outrigger system. In this system, the surrounding columns are connected to the central core by deep beams or walls to reduce the core forces. In other words, in this method, a new load... 

In this thesis, we investigate the achievable secrecy rate in a relay channel where the source and the destination wish to keep the information confidential from an untrusted relay (potential eavesdropper). The relay has no energy supply, and harvests its required energy for relaying from its received signals. For radio-frequency (RF) Energy Harvesting (EH) at the relay,we adopt power splitting (PS) and time switching (TS) approach. We study the problem of achieving positive secrecy rates between the transmitter and the receiver while making use of an untrusted relay. Energy limitation at the relay makes the problem more interesting. Because,the relay must choose either to eavesdrop the... 

Device to device communication (D2D) in cellular networks is seen as a promising thechnology to assist local communication services. It offers several gains including cellular traffic offloading gain and proximity gain of devices that allows high data rate, low power consumption, low delays and the reuse gain when cellular and D2D links are allowed to utilize same radio resources simultaneously. D2D communication is one of the key enabler for fifth generation (5G) networks. Major bottleneck in the operation of D2D communication is energy. The direct D2D communication can result in energy inefficiency as the battery powered devices are required to perform energy consuming tasks on their own... 

In this thesis, we evaluate the maximum stable throughput of a cognitive multi-hop IEEE 802.11-based WLAN overlaid on a cellular network. In the considered scenario, the secondary users operate in the downlink or uplink frequency band of primary network and transmit their data in free primary channels using OFDM technique. The activity of primary nodes is modeled independently by ON-OFF alternating states. To model the scenario, each secondary user is modeled with an open queueing network. The queueing network can model the transmission of data as well as the effect of primary users. By writing the traffic equations of the queueing network and applying the stability conditions, we are able... 

In this thesis the effect of frame aggregation mechanism in maximizing throughput in Wireless Local Area Networks (WLANs) have been investigated. Frame aggregation has become a part of the IEEE 802.11 standard as the amendment IEEE 802.11n. First, we have a quick review on access control layer in IEEE 802.11 standard then illustrate the necessity of frame aggregation. Afterwards, we propose an analytical model for the analysis of an IEEE 802.11n network comprised of an Access Point (AP) and several conventional nodes, all in the coverage area of each other. This analytical model focuses on downlink throughput; therefore only AP uses frame aggregation and the other nodes use basic IEEE 802.11... 

Collaborative fltering (CF) is one of the best and widely employed approaches in Recommender systems (RS). This approach tries to fnd some latent features for users and items so it would predict user rates with these features. Early CF methods used matrix factorization to learn users and items latent features. But these methods face cold start as well as sparsity problem. Recent years methods employ side information along with rating matrix to learn users and items latent features. On the other hand, deep learning models show great potential for learning effective representations especially when auxiliary information is sparse. Due to this feature of deep learning, we use deep learning to... 

The transportation is one of the important components in the economies of different countries. In the maritime transportation network, the demand is usually not balanced in different routes, and this imbalance results to accumulation of containers in a node. In order to sustain the problem, firms have to reposition empty equipment from a surplus location to a shortage location, which causes the problem of “Empty Repositioning Problem”. In this study, pricing strategies in one transportation market with two locations are considered; while there is ERP problem in issue. The problem is solved by Bertrand game method. The research is divided into two parts of the monopoly network and the duopoly... 

Navigation is the science of determining the velocity and attitude of a moving object in every given moment. There have been many methods for navigation. Nowadays with the advancement of technology, advanced navigation systems have been developed. Although each of these navigation systems have their pros and cons, in order to improve the overall performance of the system and to solve their problems, these systems are integrated.The goal of this project is to present an integrated cascade method to decrease error and also decrease dependence on GPS. In this project, INS, DVL & GPS are integrated with the cascade method.To achieve this, INS-GPS and INS-DVL integration are first performed. The... 

In this research, a nanocomposite blend of polyamide 6/polystyrene containing polyaniline-coated carbon nanotubes was fabricated via melt blending method, aiming to achieve electrical conductivity in the range of static dissipation. The effect of weight percentage of nanofillers and surface modification of carbon nanotubes with polyaniline on the electrical properties and microstructure of the nanocomposite was investigated. To promote compatibility between the immiscible polyamide 6 and polystyrene polymers, PS-g-MA compatibilizer was utilized, and its effect on the morphology of the nanocomposite blend was examined. Additionally, the influence of weight percentage of nanofillers and the... 

In recent decades, especially with the increase of greenhouse gases and global warming, land degradation has become one of the important global environmental issues. Land degradation has significant impacts on soil performance, vegetation cover, crops, and even the dispersion of dust particles. Land degradation is a complex phenomenon that is affected by multiple factors. Thus, it is necessary to identify these factors and then assess the degree of vulnerability and resilience to it globally. Proper indicators can clarify the integration and effective linkage between related parameters. This study aims to develop a Land Degradation Vulnerability Index (LDVI) using parameters such as... 

Drought is a common phenomena which has a lot of unwanted conse-quences on human being life and environment. Drought forecasting plays a significant role in water resources and environmental systems. Considering IRAN inappropriate location which is on the arid and semi-arid area of the earth and Widespread damages which are related to drought during recent years in iran; importance of developing an accurate model by using new technologies becomes quite inevitable. In the last decay Neural Networks have appeared very useful in non-Stationary and non-linear time Series forecasting and modeling.
This study is about to use conjunctive model of adaptive neuro fuzzy inference system and... 

Deteriorated old urban neighborhoods usually have no access to appropriate municipal services, and have small-sized buildings, densely populated areas, and earthquake-prone structures. Residents in these areas do not have the will and financial ability to renovate their aged properties. A questionnaire survey of the citizens living in the deteriorated areas of the City of Tehran showed that 80% of households do not have a positive monthly financial balance and cannot afford the cost of reconstructing their properties. Serious drawbacks of previous attempts to renovate deteriorated areas, including lack of adequate government funding, and adding to the dependence of local citizens on... 

Design methods and technologies for the implementation of earthquake-resistant buildings in recent years has made remarkable progress. The control and energy dissipation systems such as seismic isolation systems in buildings, according to their history hands-on experience in the world, have shown good performance against seismic hazards, hence they have been considered by scientists and engineers. Most of the energy dissipation systems have limitations such as service life,durability, maintenance , need to change and modifying the structure geometry after the earthquake. In recent years the use of shape memory alloys to improve the behavior of base isolation is considered. Shape memory...