Sharif Digital Repository

In the first part, we report a new and simple procedure for preparing reduced graphene oxide /nickel, cobalt hydroxide composite (Ni,Co-OH/rGO/NF via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of Cetyl trimethyl ammonium bromide )CTAB( as a cationic surfactant. In the first step, a piece of nickel foam (NF) is sonicated in a suspension of graphene oxide (GO, 6 mg/L) after dried in an oven, reduced by electrochemically. After that, Ni, Co LDH were co-deposited on the surface of rGO/NF. The resulting modified electrode afforded extremely high specific capacitance of 2133.3 F/g at a current density of 4 A g-1. FE-SEM results showed that... 

Aphron drilling fluids or CGA fluids are the wellknown updated drilling fluids in recent years.this kind of drilling fluids can control the mud loss into the formation and thus reduce formation damage and drilling costs. its structure consists of two phase fluid (gas and liquid) that the aphrons are the micro bubbles with 10 to 100 micrometer diameter that have strong stability in liquid phase compared to foamy drilling fluids. Generally aphron drilling fluids are made of base drilling fluid and surfactants, for more stability, mixed surfactant-polymer additive is so beneficial. in the last two decades, the Lattice-Boltazmann method is introduced for computational fluid dynamic area and... 

In this thesis we ascribe a one graph to groups and investigate the relations between groups structure and graph. Let G be a group. The prime index graph of G, denoted by π(G), is the graph whose vertex set is the set of all subgroups of G and two distinct comparable vertices H and K are adjacent if and only if the index of H in K or the index of K in H is prime.Also, The intersection graph of G denoted by Γ(G), is the graph whose vertex set is the set of all non-trivial proper subgroups of G and two distinct vertices H and K are adjacent if and only if H ⋂ K≠ {e}, where e denoted the identity element of G. We denote the complement of Γ(G) by Λ(G). In this thesis we consider the following... 

With the development of artificial intelligence as well as robotics, affective computing which is about recognizing human emotions by machines and creating artificial emotions in them in order to create a proper social reaction is becoming an important topic. Most of the research in this field has been focused on recognizing and detecting human emotions. In this study, assuming a proper understanding of emotions by artificial intelligence models, an attempt has been made to better clarify the emotional space. In more detail, the goal is to examine the changes in the human emotional state in order to gain better control of his behavior. In this study, by analyzing the feelings of users and... 

This research mainly aims to propose, for the first time, a way of generating text from Abstract Meaning Representation (AMR) in Persian. AMR is a rather new way of representing the meaning of natural language sentences, that captures the various semantic components in a rooted, directed, acyclic graph. Generating text from AMR is a challenging task in natural language processing as some syntactic constructs are abstracted away from the representation, resulting in one single AMR having multiple translations. Considering many applications of generating text from meaning representations in natural language processing it seems inevitable to design some methods for converting such... 

The emergence of lexical knowledge bases such as WordNet and FarsNet foregrounded the importance of semantic annotation of words in the areas of natural language processing and corpus linguistics. The methodology in these knowledge bases is based on semantic relations and dictionary definitions of the words in coverage. Another efficient way to perform semantic annotation is by semantically classifying the lexicon of a language in a taxonomy. In this research, we build a semantic annotation system for the semantic tagging of Persian texts. This system can be used for building tools and softwares for natural language processing in applications such as text summarization, plagiarism detection... 

Tipping points occur in diverse systems in various disciplines such as ecology, climate science, economy, sociology, and engineering. Critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change in the system exist in many subsystems in complex systems. These thresholds are called tipping points, and these subsystems are called tipping elements. Additionally, many systems with tipping points can be modeled as networks of coupled multistable subsystems. Domino-like tippings are called tipping cascades. Considering that these tipping cascades are primarily unprecedented, it is essential to study the dynamics and control of these... 

The concurrent flow of oil and water is a common occurrence in the field of multiphase flow in different fields including petroleum industry. In oil and gas, production engineers often face a situation in which more than one phase is flowing through the producers. In such conditions an accurate assessment of pressure loss inside the well plays a vital role in efficient and effective production planning. Changes in well orientation, wellbore diameter, reservoir and fluid properties as well as fluid flow rates are among parameters in which will affect the flow patterns that can occur inside a well during its life time. These flow patterns are created as a result of a competition between... 

Casing design is one of the most expensive parts in the drilling of oil wells, and any cost reduction with the basic design of these casing strings will significantly reduce the total cost of the operation. In recent years, occurring scenarios-based casing design has become popular; Because in many cases, it eliminates non-occurring scenarios such as gas kick and saves on drilling costs. In this study, we have tried to investigate all scenarios that may occur during the lifetime of the well, whether drilling or production, and for each well, based on its own field information, possible scenarios for each casing part are selected separately and the applying loads are calculated. For this... 

The growing requirements for renewable energy production lead to the development of a new series of systems, including wave and tidal energy conversion systems. Due to their sensitivity and the impact of the aggressive marine environment, the selection of the most adequate location for these systems is a major and very important task. Several factors, such as technological limitations, environmental conditions, administrative and logistic conditions, have to be taken into account in order to support the decision for best location. The aim of the present study is to provide an Atlas of IRAN Offshore Renewable Energy Resources (hereafter called ‘the Atlas’) to map out wave and tidal resources... 

Nowadays, with high performance computers and progress in video recorder devices and their related technologies, price of these devices is being balanced and recording the videos is conventional now. Processing of these videos has been a challenge in industry and science. Control and surveillance of places such as airports and roads and reducing their sizes in memory are some of their research area. Usually one of the initial preprocesses of such applications specially the object tracking is background modeling and background subtraction. This preprocess has an essential effect on the other algorithms that process based on these processes’ results. If this section conducted with fewer... 

TiO2 is known as a photocatalyst in near UV-Visible light region with better efficiency compared to other semiconductor photocatalysts. Many attempts have been done to increase the efficiency of this photocatalyst. also, application of 2D carbon nanostructures namely graphene for increasing the photocatalytic activity of TiO2 has shown positive results.
In this research, we first synthesized Graphene Oxide (GO) suspension by exfolation of graphite oxide suspension. then we fabricated TiO2 thin films on glass substrates by so-called sol-gel method. finally we fabricate Graphene Oxide/TiO2 nanowalls composite films as a photocatalyst in visible light. X-ray photoelectron spectroscopy... 

Among probable hazards in chemical industries: vapor cloud explosion (VCE) is one of the worst and most destructive ones. More than half of the major process inci¬dents, according to the statistics, are VCEs. VCE causes the most serious consequences; therefore, it attracts many attentions to itself. Accordingly, plenty of researches have been done for the purpose of protection against VCE effects. All efforts in this field can be categorized in two different main activities; firstly, prescribing safety distances between groups of hazardous equipment and vulnerable areas, secondly, using facilities which reinforce vulnerable areas against explosion blasts. Regardless to which category is...