Sharif Digital Repository

Ray-tracing method is extensively used for wave propagation analysis of indoor and outdoor environment for narrowband systems. The main goal of this research is to extend ray-tracing method for site-specific modeling of wideband electromagnetic propagation. In this thesis, Time-domain reflection and transmission coefficients have been computed for dielectric half-space and dielectric slab with frequency dependent permittivity. First, analytical form of Fresnel reflection coefficient for vertical and parallel polarizations in time-domain have been computed for dispersive half-spaces with lossy, extended Debye, two-pole Debye and multi-pole Debye models. By using these time-domain... 

In the early time of the discovery of the quantum mechanics and some decades after that, various interpretations of quantum mechanics were proposed. However, many years after that, the “indetermenistic” perspective well-known for Copenhagen perspective which was proposed mostly by Bohr and his colleagues became the dominant attitude among physicists. But nearly two decades after the fixation point of the Copenhagen perspective, a new interpretation of quantum mechanics was proposed by Bohm which was nonlocal but deterministic and it could reproduce all the predictions of quantum mechanics.Bohm’s theory responded to the many theoretical and philosophical objections assumed to the Copenhagen... 

Capacitor setting and reconfiguration are of main means of loss reduction and voltage profile improvement in distribution system operation. Cooperation between these two strategies can effectively minimize power losses in distribution system automation. Also, from the medium and long term viewpoint, capacitor placement and reconfiguration can be used for loss reduction and reliability enhancement. In this section, the sum of losses cost, capacitor investment cost and reliability cost should be minimized. Regarding the need to solve two non-linear combinatorial optimization problems simultaneously, metaheuristic algorithms are used in this thesis. Specifically, Elitist Genetic Algorithm,... 

Cogeneration or combined heat and power (CHP) which simultaneously produces electricity and heat energy from sequential use of single fuel source, has been introduced increasingly for industrial, commercial and residential applications due to its high energy efficiency. While the capital costs of CHP systems are comparatively higher than the conventional systems, their proper selection and optimal sizing and also optimal operation could result in shorter capital recovery period and lower cost of energy supply. Essentially the technical, economic and environmental performances of CHP system are closely dependent on its design and operation strategy. This project presents an optimization... 

Today, with the increasing expansion and development of computer networks and information technology, network security has become an important concern for experts and researchers in this field. One of the main elements in the field of information and network security are intrusion detection systems. To maintain the accuracy and quality of these systems, we need to test and evaluate them frequently. The datasets of intrusion detection systems are one of the main tools for evaluating these systems. The quality and accuracy of these systems in detecting anomalies and attacks in the network largely rely on rich and complete data. Also, the main component of this datasets is the traffic data,... 

This mixed-method study explored the intercultural competence of a group of engineering university students in Sharif University of Technology enrolling in a “Listening and Speaking” class, minoring in English. The aims of this study were first to assess the initial ICC level of the participants, second to evaluate the effect of a culture-based syllabus on ICC development of the learners, third to measure the variation of their L1 cultural identity of the students after the course, fourth to discover recursive themes in the assignments and recorded interviews with the participants and fifth to measure the learners’ satisfaction with the developed syllabus. Quantitative data was derived from... 

The goal of this project was study on coordination behavior of the 14-membered macrocyclic ligand of type N2O2 aza-crown while it is attached to fullerene C60 nano-particle. For this purpose, firstly the macrocyclic ligand (Fig 3-1, L1) was synthesized and then was reacted with C60 (Fig 3-1, L2) of which the product was characterized by elemental analysis. Since the product was insoluble in any solvents, further study on its coordination chemistry was impossible. In a second procedure, the macrocyclic ligand was reacted with benzylbromide. The reaction mixture gave two macrocyclic ligands with different number of benzylic pendant groups (Fig 3-1, L3-L4). The products were separated by column... 

Todays, thanks to the positive effects of electric vehicles, (against the vehicles which use patrol as their fuel), reduction of the Earth temperature and its climate change; the manufacturing, sale and use of electric vehicles experience a sharp increase. In addition to decreasing the air pollution, due to their abundant smart implications, they have been dramatically propagated. Massive use of these devices has raised the concern about the loss of the security which is indispensable part of the infrastructure. None of the past publications and works have taken the cyber-attack on the charging price rate and other data into account. In this thesis, charging methods of electric vehicles are... 

The severe wildfires in California, Australia, Canada, and Iran have interrupted the power system operation, caused multiple blackouts, took many lives, and caused damages to power grid infrastructure to the extent of millions and billions of dollars. Most of the recent wildfires occur in the distribution system. Therefore, enhancing power system distribution resilience against wildfire is crucial.To this end, two groups of measures are proposed: the hardening of the power network and the operational measures. The past published papers mainly studied the resilience enhancement strategies against wildfire from an operational perspective. There is a considerable gap between the past works... 

The concept of symmetry has long been the focus of numerous debates in different fields; some have come up with an artistic approach looking for a beautiful notion germane to the concept of symmetry. Others have examined this issue from a philosophical viewpoint and studied the ontology of symmetry and philosophers like Kant moved beyond the limits and have given their symmetry a transcendental position. On the other hand, in an anti-realist position relying on the fact that the goal of science is not truth but merely it’s an empirical adequacy, Van Fraassen argued that “science was rapidly gaining autonomy not only from theology but from all of philosophy, and was exploiting concepts and... 

The hierarchical multi-scale approach is one of the most powerful techniques that takes the advantage of different scales and succeeds the limitations of each method in a way that the large systems in coarse-scale can be simulated with atomic precision. In this thesis, the hierarchical atomistic-continuum multi-scale method is developed for modeling the phenomena with non-homogenous deformation, large deformation and plastic behavior. In this regard at first, an atomistic-based higher-order continuum model is formulated in the framework of nonlinear finite element method to present the geometrically nonlinear behavior of nano-structures. The efficiency of higher-order Cauchy-Born hypothesis... 

The increased need for experimental verification of the seismic performance of conventional and novel structural systems has resulted in highly sophisticated dynamic test procedures. Hybrid simulation is one of the most efficient experimental methods for assessment of dynamic and rate-dependent behavior of large-scale structural systems under earthquake excitation. Compared to earthquake simulations using shake tables, hybrid simulation may have significant advantages in terms of cost, scale, geometry, and required physical mass of structures. However, recent hybrid simulations have been limited to simplified structural models with only a few degrees of freedom. Currently, the major... 

Ball bearings diagnosis increases the efficiency and reliability of industrial machinery. Data driven is one of the most effective and highly applicable method in this field. In this way, it is usually assumed that the sensor is mounted on the bearing housing, but in many cases there is no direct access to some of the machine bearings, and in such cases, the bearing can not be monitored and checked. In this project, with simplifications in order to inaccessible bearings diagnostic, a shaft with several supports is considered. The purpose of this project is to diagnose the bearing by the sensors located on the other bearing's housing. In order to achieve this goal, continuous wavelet... 

Due to its extensive applications in imaging, data security, medication, etc., Terahertz has attaracted an ever-inceasing attention. Design and implementation of Terahertz sources and circuits as waveguide, filters, etc. in this band have attracted attention. The unique elec-tric characteristics of graphene, like showing plasmonic characteristics in Terahertz frequency band, made this recently recognized matter a promising one to build super-integrated plas-monic circuits in Terahertz band. In this text, the first section represents an introduction for a number of graphene waveguides as well as studying the effective refractive index method to analyze graphene waveguides. Due to the small... 

Agriculture accounts for 70% of global freshwater consumption. However, precise data on irrigation water use (IWU) at the regional scale is often lacking, which hampers the development of effective water management plans. This study aims to estimate irrigation water use (IWU) by integrating remote sensing soil moisture (SM) and actual evapotranspiration (ET) data into a root-zone soil water model. Since irrigation influences both SM and actual ET, increases in SM and ET following irrigation events can be leveraged to frequently retrieve IWU from remotely sensed data. In this regard, we first developed an irrigation-free soil water model simulating root-zone SM dynamics during non-growing... 

Fault Induced delayed voltage Recovery (FIDVR) is a phenomenon that occurs due to the behavior of motor loads such as A/C loads during voltage drop due to fault occurrence in the transmission, sub-transmission and distribution network. The electric motors used in air conditioning systems have a constant torque and inertia, and may therefore be stalled due to voltage drops And after the fault clearing, by dragging high reactive power and a current of 5 or 6 times the rated current, it leads to a continued voltage drop and a slowdown in the voltage recovery process. After a while, the thermal protection devices of the motors can cause significant load losses and subsequently increase the... 

With the rapid growth of Internet popularity, web applications are growing in usage and complexity, and therefore, are attractive targets for attackers. Increasing number of services and amount of information stored in the Internet, stimulates attackers to focus on these kind of applications. On the other hand, security specialists are deploying different solutions to mitigate such threats. One of these solutions are Honeypot systems. In contrast with other security solutions, honeypots are not designed to defend against attackers directly. Honeypots, rather, are planned to gather data about what attackers do. This information can help security administrators to learn and understand... 

Network forensic analysts employ Payload Attribution Systems (PAS) as an investigative tool. With such tool large amount of network traffic, including full packet payload, is summarized and stored. Hence an investigator could query the system for a specific string and see whether any packets transmitted previously in the network contained that specific string. Wildcards are an important type of query that allows the investigator to locate strings in the payload when only part of the string is known. In this thesis we present a new payload attribution technique, named character based bloom filter, which in addition to improving on previously proposed techniques is able to support wildcard... 

Bearing capacity of foundations is one of the most controversial issues in foundation engineering. In this study regarding to the previous researches which has done by the other researchers the bearing capacity factors of a footing has calculatedusing finite element method. On the next step of this study some footings has modeled on different positions near slopes with different angles and bearing capacity of them has calculated, then some strip foundation has modeled and bearing capacity of them has calculated and compared with the values of the footings in this study and strip foundations of the other researches. Furthermore some foundations have modeled on the solpe and bearing capacity... 

Due to the data centers rapid growth and introduction of a new basic type of massive data processing platforms which requires accelerators to speedup computation and enhance the efficiency and reduce power consumption, using accelerators is inevitable. Communication and data transfer time between software and hardware is the most of time spent on the use of accelerators. By optimizing this part of the hardware / software platform, we have achieved substantial results in this area. The aim of our study is to organize a survey of real accelerator characteristics. To figure out its defects and main drawbacks, in addition to improving the overall efficiency of system. The implementation of...