Sharif Digital Repository

In this thesis, we consider Compute and Forward schemes in relay assisted cooperative communication networks. The main problem associated with the compute and Forward scheme is the possible dependency of the relayed equations to the destination, which leads to the outage and thus the very low achievable rate. We propose several approaches to deal with this problem. In the first part of the thesis, we consider a cooperative network consisting of multi users, multi relays, and one common destination with no direct links between the users and the destination. We propose three strategies to lessen the aforementioned problem associated with the conventional compute and forward relaying scheme,... 

Using clean and renewable energy as driving force for vehicles is becoming more and more important because of rising fuel prices and also environmental concerns. Using solar and wind power for direct use in vehicles seems impractical with today’s technology. Compressed air can serve as an intermediate medium to store energy and utilize it for running vehicles. The main purpose of this research was to conceptually design an air driven vehicle with acceptable performance in a city for everyday life. After a brief history, at first step advantages and disadvantages of using air as driving force of vehicle is studied. This study was carried out in different categories including cost, capability... 

Plasma electrolytic oxidation (PEO) is an advanced technique for creating composite/ceramic coatings on lightweight metals such as aluminum, magnesium, and titanium. This study aims to enhance the corrosion resistance of 5052 aluminum alloy by applying a PEO coating incorporating titanium dioxide (TiO₂) nanoparticles. Initially, samples were coated in a silicate-based electrolyte bath (containing 10 g/L sodium metasilicate and 2 g/L potassium hydroxide) at different processing times (5, 10, and 15 minutes) and current densities (0.2, 0.3, 0.4, and 0.5 A/cm²) to determine the optimal coating conditions. Once the optimal parameters were identified, TiO₂ nanoparticles were added to the... 

Stress is an integral aspect of human experiences, manifesting in various situations such as tension, anxiety, and specific diseases. Researchers globally are exploring innovative approaches to control stress, aiming to quantify and detect it. The quantification of stress levels using brain signals is a prominent focus in the field of medical engineering.In most studies, the classification objective revolves around two classes (stress-relaxation) or three classes (stress levels). Typically, these studies employ databases inducing stress and recording brain signals uniformly. While various stress induction methods have been used, the resulting brain connections are less discussed.This project... 

Due to the ever-increasing growth of the ubiquitous computing systems such as RFID, IoT, etc. and their important security concerns specially in the domain of user’s privacy, a great attention from the cryptology community is attracted to the design and analysis of lightweight primitives. Lightweight primitives, including block ciphers, hash functions, stream ciphers, and authenticated encryption schemes, are those ones that are specifically tailored to the devices with extreme limitations in power, area and cost. It is natural that the conventional rules for designing a typical all-purpose primitive can not be used here identically, and designers have to relax the conditions of some... 

Due to water resources restriction and increase in water demand, optimum use of existing available resources is more essential. This needs accurate prediction of streamflow with lag time from one to several months. In recent decades identification of long term climate variables as predictors of hydrological process has made considerable evolution in climatic predictions and several studies have been made in this field. In this research streamflow volume of Dez Dam in dry season (April to August) has been predicted by using multiple regression models and considering seasonal rainfall data, climate indices and ocean-atmospheric variables including surface temperature of adjacent seas and... 

One of the most important applications of plasma is etching of substrates. This process is the key element of microfabrication. In order to improve the microstructures quality, it is necessary to improve plasma etching process. Therefore different methods have been developed to make etching process more efficient. The latest method is Bosch-process etching method. In this project to understand the effect of input parameters, Bosch-process etching of a PMMA substrate is simulated. Based on the governing equations, the problem is divided to four parts. First, by developing a heuristic approach to solve Maxwell’s equations numerically, electric and magnetic fields in the chamber are determined.... 

Study of the recycling of acidic sludge waste produced from oil refineries and its application in road pavements is the one of the most important issues. Disposal of this sludge has always put the nature at risk. In this research, preliminary NPS bitumen was derived through neutralization and processes. NPS was modified by some thermoplastic elastomers such as SEBS, SBS, EVA, … and SBR and NBR rubbers. Also as a ionic and surface modified organoclay, C15A was used in three different weight percent. Rheological and performance behavior of pure bitumen and modified ones was studied using of standard tests for simulating traffic load. Behavior evaluation tests was included dynamic frequency... 

One of the most common spinal surgeries involves spinal fusion or vertebral fixation, which is used to treat various conditions such as intervertebral disc disease, scoliosis (lateral deviation of the spinal column), fractures, infections, or the presence of tumors in the spinal column. In this surgical procedure, the use of pedicle screws and titanium rods prevents motion and friction between two vertebrae. Screws may enter the vertebrae in the wrong position and angle, causing bone weakening, rupture of nerve roots or blood vessels, weakness or lack of sensation in some parts of the body, spinal cord injury, and in severe cases, paralysis of the patient. For this reason, fusion surgery is... 

In this thesis, we analyze the security of symmetric block ciphers using shortcut cryptanalysis, mainly focusing on differential and impossible-differential cryptanalysis. The contributions of this thesis are twofold. First, we evaluate the security of 4 notable block ciphers named TEA, XTEA, Midori, and HIGHT using ad-hoc impossible-differential cryptanalysis in single-key settings. For each cipher, we introduce new impossible differentials in single-key settings, which are later used in the cryptanalysis. The results show that for all of the mentioned block ciphers, we are able to analyze the longest reduced-round versions of them in contrast to each of the previously mounted single-key... 

Transparent coatings with self-cleaning property in visible light spectrum, UV radiation resistance and antimicrobial are highly desirable. Titanium dioxide (TiO2) is used in this research has been widely studied as an efficient photocatalyst by researchers. In this research enhanced visible-light photocatalytic activity is gained with N and Ag co-doped titania. All samples were annealed at 450℃. Finally AgI was loaded TiO2 coating and the results were investigated. Peaks of XRD pattern wereattributed to different diffraction planes of anatase TiO2. Morphology of coatings were analyzed with using FE-SEM. Nano granis size of TiO2 and AgI loaded TiO2 were observed in FE-SEMimages. Nitrogen... 

Alkali-activated fly ash-slag (AAFS) is a new type of sustainable construction material widely studied in recent years for its desirable mechanical properties and low environmental impacts. In this study, the effects of the slag incorporation from 10 to 30% of fly ash are investigated on the strength, pore structure, and transport properties of the AAFS with various levels of fly ash replacements with slag. The unconfined compression and ultrasonic pulse velocity tests were performed to evaluate the mechanical properties of the AAFS concrete. Microstructural and mineralogical changes were studied by porosity, N2-adsorption/desorption, and SEM/EDX tests. Additionally, transport properties... 

Drilling Operations constitute more than fifty percent of total costs of well construction operations. Due to this fact, optimization of drilling operations could have significant effect on decrease in total costs of well construction. It is mentioning worthy that there are a variety of parameters which affect drilling operations from the view point of optimization. In many cases several of those aforementioned parameters are contrary in nature. Thus obtaining an integrated approach to optimize the operation by considering these effects is necessity. The goal of this thesis is to investigate different influential parameters of drilling operation optimization and to develop computer-based... 

At Lake Urmia (LU) greatest extent, it was the largest lake in the Middle East and the sixth-largest saltwater lake on Earth, with a surface area of approximately 5,200 km2. The lake has shrunk to 10% of its former size due to damming of the rivers that flow into it, and the pumping of groundwater from the surrounding area. Moreover, as the lake shriks its potentional to be a major dust sources increases. A Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to investigate and track the extent of dust emission and aerosol concentration over Lake Urmia marginal dust spots in order to identify the affected and critical areas. Also, percent movement, propagation...