Sharif Digital Repository

In the behavior of many convex optimization problems with random constraints in high dimensions, sudden changes or phase transitions have been observed in terms of the number of constraints. A well-known example of this is the problem of reconstructing a thin vector or a low-order matrix based on a number of random linear observations. In both cases, methods based on convex optimization have been developed, observed, and proved that when the number of observations from a certain threshold becomes more (less), the answer to the problem with a probability of close to one (zero) is correct and the original matrix is reconstructed. Recently, results have been obtained that explain why this... 

A particular kind of concentric bracing system composed of three members arranged in y-shaped geometry is examined in this thesis. The non-straight diagonal strut of this off-centre bracing causes eccentricity to the system and is connected to the frame corner through a third member. Providing adequate openings in braced bays accompanied by improved energy dissipation are resulted in positive attitude toward using y-bracing frame as a lateral load resisting system. However, lacking of specific design codes could be problematic for engineers. To overcome this incompetency, seismic performance factors including the response modification coefficient, the system overstrength factor, and... 

There are several algorithms in the literature to solve the problem of finding an optimal path between two points in a region. Such path satisfies certain constraints while optimizing the objective function. There are many factors in building, or finding, such paths in the real world, whose considerations complicate the solution procedure. This led the researchers to seriously consider meta-heuristics to solve the problem. This study hybridizes several suitable and effective meta-heuristic algorithms to solve the routing problem on a given topography. In this hybrid meta-heuristic algorithm an Ant System finds a horizontal path between the two points under considerations on the topography. A... 

Due¬ to the volatile nature of material prices, projecting highway construction costs are proven to be very difficult, leading to many challenges in cost estimation process. Bid preparations as well as project planning and control processes are also negatively affected by the concerns about the inaccuracy of cost projections. There is a growing body of evidence that suggests the use of inaccurate cost estimate can result in bid loss or profit loss for contractors and hidden price contingencies, delayed or cancelled projects, inconsistency in budgets and unsteady flow of projects for owner organizations. Analysis of historical data indicates that a relationship between construction materials... 

Domed roofs were commonly used in buildings with large areas. These roofs played an important role in the Iranian architecture and had a great effect on the buildings cooling loads. Solar energy absorption causes the roof temperature to increase in comparison with its ambient atmosphere. Wind flow removes some of the heat from the roof, and the rest goes thorough the roof and enters the building.The eometrical configuration of these domed roofs causes the wind velocity to increase over them, resulting in an increase in the convection heat transfer coefficient. Also, the heat transfer of the roof is accentuated by the fact that the area of a domed configuration is considerably greater than a...