Sharif Digital Repository

In recent years, displacement is more considered in comparison with force in design of structures. For example in 2800 standard -3rd edition- it is stated that for the reason that real displacement of structure in linear analysis is not calculable; it is necessary to resonate the lateral displacement of elastic analysis with a coefficient which is related to behavior coefficient of structure. This displacement should be less than allowable limit that is noted in the code. In similar foreign codes importance factor is also noted beside behavior factor in calculation of real lateral displacement of structure. Evaluation of this coefficient for different structures, comparison with suggested... 

Y-based Superconducting compounds (YBCO) with different stoichiometry have been considered by researchers for its transition temperature above the boiling temperature of liquid nitrogen, preparation of high quality samples, simple crystal and electronic structure and other advantages relative to the other high-Tc copper oxide superconductors. Reaching to higher transition temperature has been considered in the recent years. In 2009, new compound of this family with different stoichiometry Y3Ba5Cu8O18(Y358) and transition temperature above 100 K was synthesized which is 10 K higher than maximum transition temperature in this family. Confirming this transition temperature can be help us for... 

The discovery of superconductivity in compounds containing magnetic elements such as Iron, Cobalt and Nickel has attracted the attention of many researchers in last few years. Before the discovery of superconductivity in LaOFeP it was believed that the superconductivity and magnetic properties are in conflict to each other. Untill now, variety of researches in Iran has been done on preparation and characterization of Copper oxide superconductors without any attention to the Iron based superconductors. Accordingly, the main purpose of this thesis is preparation and optimization of LaOFeAs as the basis compound of 1111 Iron based superconductors using the solid state reaction method. This... 

The discovery of the iron-based superconductors attracted much experimental and theoretical attention in the recent years. BaFe2As2 is one of the highlighted materials which is the antiferromagnetic metal (below Neel temperature) and undergoes to superconducting and non-magnetic state by variety of doping, usually accompanied by a structural phase transition. Superconductivity is appeared in this system by doping Co and Ni at the Fe sites which is one of the excited situations in the physics of superconductors, where the magnetic doping suppresses the superconducting state. So, the study of Co doping of the electronic structure of this system, might lead us to better understanding of the... 

Iron based superconductors that are studied more in recent years, have the same and different features with copper oxide high temperature superconductors which they can help in solving problems related to high temperature superconductors. In addition, these compounds have attractive physical characteristics such as superconductivity despite of presence of magnetic Iron element or other magnetic elements like nickel and cobalt (In other superconductivity groups, low doping of magnetic elements destroys superconductivity) and also concurrent presence of magnetic and superconductivity phases. The most reported transition temperature in these compounds is 56.3K in Gd0.8Th 0.2FeAsO compound.... 

Antioxidants are compounds which prevent free radicals from aggregation and formation in body cells. vitamin C, E and carotene are among the most important antioxidant that have reduction properties. free radicals have great chemical reactivity which can react with different types of compound in human body such as lipids, cell membrane and proteins and cause different illnesses. Antioxidants with various mechanisms such as hydrogen atom transfer, single electron transfer SPLET, sequential proton loss electron transfer and radical adduct formation can stable free radicals and also become non-active compounds, antioxidant properties of these compounds related to structure and their functional... 

In the 1950s, Abrikosov predicted the mixed state in superconductors (type II superconductors) which lead to a Noble Prize in 2003 with the experimental verification by shubnikov. Mixed-state is a network of magnetic flux lines with quantized flux (vortices) in superconductors. High-temperature superconductors are of Type II which the existense of vortices in a significant part of the temperature-field phase diagram of them, is an obvious phenomenon. These superconductors provided a proper context for understanding physical phenomena related to vortices and access to experimental data to compare with those provided by statistical mechanics. Vortices can move inside the superconductor by the... 

Buried pipelines might pass slopes that are stable in static condition but slope dicplacements due to dynamic loading can result in pipeline failure. There are various factors that influence 3D slope stability under seismic loading condition.In this dissertation , we used finite element software ABAQUS (ver.6.10) to study pipeline performance in such condition. Dynamic analysis on pipe with burial depth of 1.5m that passes a 3D slope was performed by using the time history of sinusidinal loading. Boundary conidion of slope and pipe affects the slope dicplacement and pipeline performance. In different routes that pipe passes slope, pipeline response to slope displacement has been compared... 

Today, the production of colloquial texts in messengers, search engines, and question and answer systems has increased significantly, while text documents in other fields have a formal tone and style. Thus, there is a need for a system to convert these texts from colloquial form to the formal style. Attention to this need in non-Persian languages has also been recently and seriously felt, but almost at the time of writing, an efficient system has not been offered, and this issue requires more work in Persian than in languages such as English. In general, transferring texts from one form to another falls into the category of natural language processing applications and is called "style... 

The goal of this thesis is to understand the physical properties of lanthanum based manganites and barium based ruthenates. In order to obtain negative colossal magnetoresistance in manganites and fabrication of barium ruthenate in ordinary condition, the effects of variables such as ionic radii, chemical composition, temperature, magnetic field and processing in manganites and ruthenates systems are investigated. In the first part, the effects of potassium doping on structure, metalinsulator transition and magnetoresistance in )La1-yKy)0.7 Ca0.3 MnO3 and)La1-yKy)0.7 Ba0.3 MnO3 manganites systems are studied. Polycrystalline samples of manganites are synthesized by the sol‐gel method. In the... 

The coexistence of long-range magnetic order and superconductivity in the ruthenocuprate families, Ru1212 and Ru1222 has been studied both theoretically and experimentally. Historically these two different phases are incompatible with each other and in the most previous research reported on the coexistence of these phases, there have been observed separated magnetic and superconducting phases. However in the ruthenocuprate families, there is a single phase with both magnetic and superconducting phase which coexist with each other. It has been determined that superconductivity arises in CuO2 planes, and magnetic orders occur in RuO2. From experimental point of view, we have investigated the... 

Experiments indicate the important role of the electron-phonon interaction and crystal lattice effects on the electronic and superconductivity properties of the unconventional superconductors. Thus, in the theoretical studies of the mechanism of unconventional superconductivity, role of phonons and crystal lattice distortions can not be ignored. Based on this fact, in this dissertation, it has been tried to investigate the effect of phonons and lattice distortions in the electronic properties of some unconventional superconductors. For this purpose, we have used the ab-initio, density functional theory of the ground state and perturbed states, which is the most suitable approach when it is... 

There are two challenging problems with the physical properties of the recently discovered cuprate, Y3Ba5Cu8O19 δ (Y358): (1) the value of its transition temperature (Tc) and (2) its unknown crystal structure. While some reports argue that Tc of Y358 and its crystal structure are completely different from those of the YBa2Cu3O7 δʹ (Y123) compound, other reports indicate the similarity of both transition temperatures and XRD patterns (or crystal structure) of these materials. It has been suggested that these similarities are due to oxygen deficiency (δ) of Y3Ba5Cu8O19 δ or the decomposition of Y358 to Y123. In this thesis, we address these issues. At first, we have tried to answer the... 

After the discovery of high temperature superconductivity in (LaM)2CuO4, different type of cuprate superconductors have been synthesized. Among them, YBCO compounds (e.g. YBa2Cu3O7-δ) have drawn more attention by researchers due to some advantages such as easier conditions of synthesis high quality samples in comparison with the other cuprate superconductors. However, superconductivity properties of these compounds are very sensitive to structural imperfections; hence it is important to study the effect of the microstructure on the behavior of the compounds. The compound YBaCu2Ox (Y112) is one of these microstructures that may form in YBa2Cu3O7-δ (Y123) samples. On the... 

The most important researchers’ purposes in superconductivity are achievement of the room temperature superconductivity and to understand the high temperature superconductivity mechanism. Researchers’ goal in to increase the transition temperature by applying pressure, changing oxygen content, different doping, and changing stoichiometry in the families of the high temperature superconductors. In this research, which has been carried out in the Magnet Research Laboratary of Sharif University of Technology, samples of Y3Ba5Cu8O18, Gd3Ba5Cu8O18, and Pr3Ba5Cu8O18 have been synthesized by the standard solid-state reaction technique, the structure, electrical and magnetic properties of the... 

Physical properties of $Re_1 Ba_2 Cu_3 O_{7-\delta} (Re123)$ high-temperature cuprate superconductors attract many of physicists due to their high transition temperature (above Nitrogen boiling point), relatively simple synthesizing and high critical current density. Among this family, Nd123 and Sm123 single-crystal compounds have the highest transition temperature and critical current density in the magnetic fields less than 2 Tesla. In addition, due to the near ionic radius of Nd and Sm elements, it is possible to synthesize $Nd_{1-x} Sm_x Ba_2 Cu_3 O_{7-\delta} (0 \leq x \leq 1)$ compounds with no significant dislocation. In order to investigate the effects of such doping on electrical... 

The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's... 

In this thesis, we have studied systems called Ruthenates, which are common in possessing Ru element in their chemical compounds. Ruthenates are a group of transition metal oxides which have attracted so attention, especially in last years duo to their rich phase diagram which shows different orbital, charge and spin orderings.They cover a vast range of materials properties, from a Superconductor to Mott Hubbard insulator, from a paramagnetic metal to an antiferromanetic insulator. In these systems, substituting a covalent atom with structure base, leads to a vast variety changing, not only in electronic properties but also in magnetic and structural ones: Although Sr"RuO£ is a...