Sharif Digital Repository

The aim of this thesis is to introduce some algebraic topologies methods and apply them on fining the chromatic number of some famous graphs and also hypergraphs. In the first part, we will use a mixture of two well-known technics, Tucker lemma and Discrete Morse theory to find an upper bound for the chromatic number of s-stable Kneser for some specific vector s. to find the sharper upper bound, we will deviate our strategy and use another approach by finding an edge-labeling and apply some theorems in POSET algebraic topology. In this way, we also find a connection between Young diagrams and the numbers of spheres in the box complex related to Kneser graphs and hypergraph. Actually, we can... 

Fossil fuels provide the most needs of the world's energy, however, continues to lead to two key problems. The first problem is their limitation, and the second problem is the creation of serious environmental issues. Therefore, the need for renewable energy sources is felt more than ever.As an energy source, hydrogen is the lightest, most efficient and cleanest fuel. One of its unique properties is efficiency, the production of electricity by fuel cells through the electrochemical process, has far greater efficiency than of mechanical energy production from fossil fuels in internal combustion engines or energy production in thermal power plants. A fuel cell is a device that converts... 

Study of dams' behavior and their safety against earthquakes has been interesting due to the high rate of failure. In the past, this study was just about linear analysis of dams. However, the weakness of concrete in tensile strength results in cracks in body of dams. Therefore, the nonlinear analysis of these huge structures seems to be so important. Many researches have been done in this field to model dam-reservoir-foundation with effects of concrete nonlinearity. In spite of the fact that gravity dams' safety depends on cracking status and consequently on nonlinear behavior of concrete, we cannot reach accurate and suitable results for dynamic behavior of concrete dams because these... 

In Endurance Time method structures are subjected a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specified spectrum, intensifies with time. So they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this study applicability of Endurance Time method for evaluating collapse potential of buildings is investigated. A set of steel moment frames is used for collapse assessment. The process of using Endurance Time method in collapse evaluation is explained with consideration of uncertainty effects. collapse fragility curves and collapse... 

Endurance Time (ET) method is a dynamic analysis method in which the structure is subjected to an intensifying accelerogram and its response is recorded at different times.On the other hand a new method for designing earthquake resistant structures is Performance-Based Design (P-BD) method. P-BD is a methodology in which structural design criteria are expressed in terms of achieving a set of different performance objectives. In this research the application of ET method and target curve (which is defined based on ET method concepts) in the performance-based design has been studied.Correlating time in ET method and earthquake return period, the design,assessment and retrofitting of different... 

Endurance Time (ET) method is a relatively general analysis method based on time history analysis for evaluation of structure systems under dynamic excitations resulted from earthquakes. Assessment criterion in this method is based on time of endurance of structure versus applied acceleration function and don't use parameters such as stiffness, lateral strength, period of structure and other dynamic characteristics straightly. Upper time of endurance means better operation. In this method, if assumed damage index stays under allowable limit until determined time of endurance then the structure assumed acceptable. In this study, nonlinear analysis of anchored and unanchored (on rigid base)... 

Metallic implants are often used in the open reduction and internal fixation of fractures. Open reduction and internal fixation are commonly used in cases of trauma when the bone cannot be healed using external methods such as casting. The locking compression plate combines the conventional screw holes, which use non-locking screws, with locking screw holes, which use locking head screws. This allows for more versatility in the application of the plate.
In the present work, the stress (von-mises) and deformation of a locking compression plate fixed across a transverse fracture (2-mm gap) at the midshaft of femur was evaluated by Ansys software. Femur model is divided to two part... 

Researches in last decades have shown that biological cell’s functionality is related to the way of their deformation in response to forces and stresses exerted on the cell. Therefore designing microsensors with easy and economical applicationswhich are capable for determining cell mechanical properties seems to be logical. In this project using an electrostatically actuated microbeam with both clamped ends equipped with an indenter at midpoint to transmit force on the cell, proposed as a technique to apply axial load on the cell. Inthis research by implementation of approximated methods for solving nonlinear algebraic and differential equations, governing on microbeam deflection, it has... 

Since the early 1980s, it is well-known that the dynamic properties of structures are effected by flexibility of the underlying soil due to Soil-Structure Interaction (SSI). As a result, the soil-structure systems usually has a longer natural period and higher damping ratio that structure would have in the fixed-base state. The importance of SSI effect as well as the complexity of the phenomenon have made it the subject of several researches for the last four decades. It also has found its way into some seismic codes and provisions as simplified guidelines.In the present paper, a simplified 3DOF model is suggested as the soil-structure system by replacing the structure by a SDOF model using... 

The actual value of structures should not be evaluated only based on initial cost, because failure cost and economical losses due to corrosion and natural hazards can be catastrophic. When a long life Performance of a structure is expected, life cycle cost analysis is the best way to assess and compare economic value of different design choices. The main purpose of this work is investigating the effect of shear walls in limit state cost and total cost . Results demonstrate that shear walls can reduce limit state cost up to 70 percent . Furthermore the influence of increasing thickness of shear walls and effect of reducing dead loads in total life cycle cost is discussed. It is shown that... 

Monumental structures are cultural and aesthetic bases in every nation, and our duty to maintaining these valuable remnants is obvious clearly. Meanwhile, the vaults have essential role as main elements in the Islamic architecture, and evaluation of their performance as well as retrofitting with regard to placing in earthquake-prone regions has high importance. Therefore, in this dissertation, performance of spherical and pointed domes are evaluated. Hence, 13 traditional Iranian domes are modeled with linear and non-linear material behavior in ABAQUS finite element software to verifying effect of their geometries in seismic performance. Base on Complex behavior of these models, they...