Sharif Digital Repository

Alloy 6061 is derived from a combination of aluminum with elements such as magnesium and silicon. Due to its high corrosion resistance, excellent machinability, and high strength, this alloy is widely used in various industries, including aerospace, automotive, and the manufacturing of mechanical parts for airplanes. Butt resistance welding is one type of resistance welding employed for joining various components, such as train rails, construction rebar, automobile rims, as well as in aerospace, petrochemical, and marine industries. Butt resistance welding is a process that can be either fusion-based or solid-state. In this process, similar or dissimilar metals are joined by bringing them to... 

The rank effect means that investors are more likely to sell the best or worst positions in their portfolio in terms of returns. According to this effect, the probability of selling a stock in a prominent position (first or last) is higher than other stocks in the portfolio. Apart from being a behavioral bias, the rank effect is that the decision to sell a stock depends on how it is compared and ranked with the rest of the portfolio. In this study, we examine the rank effect on the trading behavior of Iranian mutual funds for the period 1390-1399 and find that it is significant. First in a statistical and univariate form, and then by including other variables such as firm-specific... 

Popular usage of composite materials in aerospace, civil and defense industries in the last decades has been the cause for paying more attention to optimization of composites tailoring. Due to inherent complexity of composite problems, i.e. discrete nature, complex interrelationship of design variables, existence of so many local optimum points, and etc., gradient base methods of optimization are found to be incapable and as a result using other powerful methods seems inevitable. Nowadays Genetic algorithm (GA) as an evolutionary technique is used for tackling composite problems. The success of a genetic algorithm can be quantified by estimating the cost, time required and the quality of... 

Since concepts in quantum information theory has recently been applied to characterize states in many-body systems, we survey entanglement of the ground states in the S = 1/2 antiferromagnetic Heisenberg ladder systems and 2D square lattices. The Lancz¨os method for exact diagonalization of quantum spin models are used to find the ground states. Moreover, effect of defect in ladder on entanglement and ground state energy are studied  

Self-regulated learning, though having swept educational psychology's literature like a tidal wave (Boekaerts, 1999), and also, compared to other constructs such as metacognition and learning strategies, has remained comparatively uncharted in L2 research. One preliminary step to chart this concept is to develop questionnaires for it. With these and other things in mind, the principal purpose of this study was to develop a questionnaire in English and Persian to measure self-regulated language learning capacity and behavior of Iranian EFL learners. The development of the questionnaire was guided by two pilots (412 participants), content validation through expert judgment, cognitive... 

An algebraic number field is a finite extension of Q. Let K be an algebraic number field. Each element 2 K satisfies an equation n + a1n1 + ::: + an with coefficients a1; :::; an 2 Q and is an algebraic integer if it satisfies such an equation with coefficients a1; :::; an 2 Z. algebraic integers form a subring.Let K be an algebraic number field of degree n. Let OK denote the ring of integers of K. The field K is said to possess a power basis if there exists an element 2 OK such that OK = Z + Z + + Zn1. A field having a power basis is called monogenic. In this thesis we consider that there exists infinitely many dihedral quintic fields with a power basis that is shown by lavallee [18]  

In this thesis, first of all we introduce the Anderson model, Multifractality, and conformal field theory. Then we try to determine some critical and scaling quantities for the critical wave functions in the 2D systems with spin-orbit interactions We implement a correction-to-scaling analysis by introducing an irrelevant exponent which leads to a proper and sharp evaluation of the critical parameters including correlation exponent, rescaled localization length and the critical disorder. Then, we survey the multifractal properties of this model and obtain some multifractal exponent in the critical point. Finally, we will survey the existence of the conformal invariance symmetry in it. Our... 

Synthesis and Investigation of Effect of Pr Doping on the Compound Y_(3-x) 〖Pr〗_x 〖Ba〗_5 〖Cu〗_8 O_(19-δ)-FInvestigation of doping of the parent compounds with different elements is important to understand the origin of high-Tc superconductivity. Several research groups have attempted to improve the properties of superconductivity and better understand the superconductivity mechanism of cuprate through doping different elements. In this research, at first, optimization of Y_3 〖Ba〗_5 〖Cu〗_8 O_(19-δ) F_z samples with z=0.2 ,0.4 ,0.6 ,0.8 ,1 ,2 ,3 ,4 have been done. By doping fluorine instead of oxygen, we expected an increase in the transition temperature, based on some the reports. But after... 

For the sake of decrease in energy and force of earthquake, seismic isolators are used. Regular seismic isolators are too heavy and damaged by chemical materials, therefore in this research a new approach is used that steel shim plates replaced by carbon and polyamide fibers. The aim of this research is to obtain the dynamic and mechanical properties of carbon and polyamide fiber reinforced isolators in comparison with steel reinforced isolators. In this approach, firstly some specimens have been designed and manufactured, then compresional and cyclic shear tests were carried out on them. All three type isolators are cylindrical and have identical diameter and height. The steel, carbon fiber... 

Quantum thermodynamics is a new field of study in physics, which by considering the fundamentals of statistical mechanics, open quantum system, quantum information and mesoscopic system aims at the investigation of quantum systems from a thermodynamical point of view. To achieve these aims, a better understanding of the relations between quantum and thermodynamics fundamentals is essential. Energy and correlation are two key concepts in statistical mechanics and quantum thermodynamics (and information), respectively, that studying the relation between them will shed light on the fundamentals of quantum thermodynamics. As generating any correlation in quantum systems with initial heat state... 

Examining and improving driving behavior leads to a reduction in road accidents. Driver behavior is generally divided into two categories: aggressive and safe. Driving culture can be enhanced by identifying aggressive behavior and informing drivers directly. This information is used to assign safe drivers to the missions of transport fleet management companies and organizations. Also, this information is used by insurance companies or traffic police to apply discounts or fines. In any case, the detection and notification of aggressive behaviors would reduce accidents and improve the lives and mental safety of passengers and drivers. The detection of driving events is an introduction to the... 

Internet is the largest multi-purpose, self-reliant, complex and distributed computer network across the globe. The nodes of this network are placed in every place like homes, offices, military camps, schools and all other locations by utilizing many different communication protocols, media and capacities. Furthermore, by rapid technology development, there are many newly born applications utilizing internet in new ways such as Internet of Things systems. The explosive growth of technology causing accelerated addition of new nodes to the internet, and any new single node may have several new unpatched vulnerabilities. This is a serious issue for managing this vast chaotic configuration and...