Sharif Digital Repository

Today, the process of corrosion and compensation of minor injuries, without the need for tracing or any other physical interference, has become one of the subjects of interest to researchers. Inhibitors have been considered as one of the anti-corrosion agents. In this research, safflower extract as a green inhibitor in sodium chloride corrosive environment was used to evaluate the rate of corrosion of mild steel. Also the MoS2 nanoparticles were used as carrier of this green inhibitore in the epoxy coating to allow the activation of the coating in a scratched state in sodium chloride solution of 3.5%. In the first step, the extract of the safflower was prepared to reach the best part of this... 

To protect mild steel against corrosion, an intelligent self-healing epoxy (EP) coating including carbon nanofiber (CNF) modified with polydopamine (PDA)-La (III) complex was successfully fabricated. The high aspect ratio and unique thermal and electrical characteristics of CNF made it an ideal physical barrier against the penetration of corrosive ions. Due to the poor dispersion of CNF, its surface was modified using PDA. PDA, which contains functional groups such as catechol, amine, and imine, can mitigate corrosion reaction by generating the Fe-Catechol complex and also boost the coating's adherence to the metal surface, in addition to anchoring La3+ inorganic corrosion inhibitor.... 

Different definitions of the term ‘subjective well-being’ have been defined by different researchers. While there is no definite definition for this concept, it can be related to one's life evaluation. The issue of citizens’ subjective well-being has not usually been considered in transportation policies, such as reducing single occupancy vehicle. However, subjective well-being reflects the individuals’ quality of life and can be one of the main priorities of any society. This study tries to find the effect of using various modes of travel including passenger car, motorcycle, public transportation and walking on citizens' subjective well-being. Subjective well-being is measured by... 

Nowadays, a large proportion of the power consumption in high-performance multi-processor architectures on chip belongs to connections. Reducing power consumption while maintaining high efficiency in these architectures is one of the main concerns. Networks on Chip (NoC) originally were introduced to improve efficiency, but now, given the importance of power, we must provide some solutions to reduce power consumption, and delay in NOCs. Connections in chip can be divided into three categories: global, intermediate and local, while the length of global connections is almost constant in different scales, local connections are scalable. As a result improving efficiency of a small number of... 

In the present research, a series of bimacrocyclic tweezer anchored through azobenzene moiety were synthesized and characterized by applying IR spectroscopy, 1H and 13C{1H} NMR, fluorescence spectroscopy, UV-visible spectroscopy, mass spectrometry and elemental analysis and in some cases by X-ray crystallography. Firstly, UV-visible spectroscopy established that the irradiation of the tweezers with UV light promoted the trans to cis isomerization. On the other hand, thermal cis-trans isomerization behavior of the azobenzene moiety in tweezers was surveyed in which the cis isomers were formed of the heating at 50 oC for 5 minutes. Where the -OH group was replaced with 4-toluenesulfonyl... 

Graph Theory and Combinatorial Analysis like the other branches of science use the probability for solving their problems. At the first , we will introduce the most common tools from probability used in Discrete Mathematics, such as “The Lovasz Local Lemma”. Most of them are based on Linearity of Expectation, Concentration Theorems and some other innovative methods such as Deletation Method. We will present different examples for these techniques. Also we will introduce “Random Graphs” and their importance. Specially we will explain how to use “Threshold Functions” to obtain different properties about the majority of graphs. Rainbow Connection, is a natural and interesting quantifiable way... 

Computational complexity of graph problems is an important branch in the-oretical computer science. We introduce to some of ideas for computing the complexity of graph problems with some kind and beautiful examples. Next, we show hardness and inapproximability of some problems. Representation number of graphs has been introduce by Pavel Erdos by Number theory. We prove n1−ϵ inapproximability of that. Lucky number η has been studied by Grytczuk et.al . We show for planar and 3-colorable graphs, it is NP-Complete whether η = 2. Note that since a conjecture, for those graphs, 2 ≤ η ≤ 3. Also for each k ≥ 2, we show NP-completeness of η ≤ k for the graphs. Proper orientation number −→ is a... 

CO2 separation from air was investigated in this work. An immobilized liquid membrane (ILM) which contains triethylene glycol (TEG) and diethanolamine (DEA) was used for this purpose. In this kind of membranes a liquid, which improves permeability of gas species through the membrane, fills the pores of a polymeric membrane as support. Because of low vapor pressure of solution, liquid loss was negligible. Transport of CO2 was facilitated due to reversible chemical reaction between CO2 and amine solution. A polyvinylidene fluoride (PVDF) membrane was chosen to have chemical resistance against the solution and prevent destruction of polymer by solution. A flat sheet and hydrophilic PVDF was... 

Nowadays, classic energy supply systems are rapidly shifting towards more efficient, with less pollution, and more economic energy systems. In the meantime, the growing dependence of human activities on energy sources and the reduction of fossil fuels resources as the main source of energy supply at present time, has led to fundamental changes in the energy policy of communities. The use of distributed power generation systems utilizing renewable energy sources is one of the solutions that have been proposed in this regard. This research aims to develop a local energy supply network for a specific rural district using energy sources in place, so that the area is energy self-sufficient and... 

Finding optimize tours on a given sequence of objects has applications in robitic. A tour on a given sequence of objects is a path that touchs or cuts each of them, in order. In STOC′03 it is shown that finding such a shortest path for a sequence of convex polygons is polynomial solvable and it is NP-hard for non-convex polygons with intersections. The complexity of the problem for disjoint polygons is asked as the importest open peoblem. In 2008 an approximation algorithm is presented for this problem. We show that the problem is NP-hard in each Lp norm, even if each polygon consists of two unit line segments. Also, in 2003 the problem, with obstacles has been proposed as a future work. An... 

The air cathode of li-air batteries has been identified as a key factor affecting the overall performance of Li-air batteries. Graphene-based cathodes have been investigated as cathode catalysts for lithium-air batteries due to their high activity in accelerating and facilitating oxygen reduction reaction (ORR). In this study at first, graphene oxide was synthesized using Hummers’ method, and then it has been reduced via hydrothermal methode. To increase electrocatalytic properties of the sample Cobalt oxide nanoparticles has been precipitated on reduced graphene oxide, and it has also been doped with Nitrogen. Three samples of reduced graphene aerogel (GA), Nitrogen doped graphene aerogel... 

In this research, we present a new method for solving layout problems in the cellular manufacturing system. We also analyze the transportation systems using automated guided vehicles (AGVs) and its cost affecting the performance of cellular manufacturing system. For elimination of inter current and traffic problems, we use a new idea of dividing workstations to some non-overlapping closed zones to which independent automated guided vehicles (AGVs) are allocated for internal transfers in each zone. In this research, a combinational mathematical model has been developed for minimizing the cost of material flow intra and inter-loops and minimization of procurement of AGVs for each zone while... 

A New method is proposed to find a mother wavelet for the best localization of acoustic emission (AE) signals generated by leakage in a pipe. At the first step, knowing stochastic nature of acoustic emission signals, a leakage signal in time domain was trapped by monitoring the Short Time Fourier transform (STFT) of AE signal over a relatively long time interval to find frequency traces of leakage AE signal. The trapped signal was used to find a mother wavelet for the best signal localization. Then a novel method for AE signal detection using tuned wavelet is discussed. For this purpose experiments were done in predefined situations to collect signals generated in water filled plastic pipe...