Sharif Digital Repository

Structural health monitoring (SHM) has been motivated in aircraft and civil industries over the two last decades. Ultrasonic guided wave propagation technique is one of the best damage detection methods in airplane thin wall structures because of their large distance traveling and low attenuation.
In fact by efficient design of sensors pattern one can effectively pick up the changes that happen in propagated signals due to presence of any kind of structural damage. This could be effectively achieved by numerical simulation techniques like finite element modeling. To obtain a damage detection algorithm based on instantaneous baseline data, here, finite element technique is employed for... 

In this thesis the shear strength of pipe shear connector is investigated experimentally and numerically. The numerical analysis uses a nonlinear finite element model of the push-out specimen. The specimens consist of the pipe shear connector, steel beam, concrete slab and embedded steel rebar for concrete confinement. Eight push-out specimens are constructed with different pipe sizes and concrete strength. The results are used in a finite element parametric study to evaluate the strength of such connectors for all practical ranges of pipe size and concrete strength. It is shown that pipe connectors are more effective in transferring shear forces than angle and channel and stud connectors.... 

In this study, novel algorithms are presented for nonlinear parameter varying systems with uncertainty in the model predictive control using heuristic algorithms. To this end, some algorithms are developed which provide the possibility of estimating simultaneously states and control signal of the stochastic nonlinear systems. Then, the model predictive control algorithm is presented for stochastic nonlinear systems with uncertainty to estimate uncertainty and compensate it using ant colony optimization. Next, the model predictive control algorithm is developed for nonlinear system with matched bounded uncertainty using particle swarm optimization. Performance of the developed controllers is... 

Considering the unique characteristics of aluminum alloys in the 5XXX series, such as high strength-to-weight ratio and corrosion resistance, as well as the absence of precipitation hardening, composite fabrication using these alloys has garnered attention. Consequently, friction stir additive manufacturing (FSAM), a novel solid-state layering technique, has been proposed for manufacturing components from these alloys, avoiding the drawbacks associated with traditional melt-based additive manufacture methods. The objective of this research is to produce a five-layer 20mm composite wall in the aluminum 5754 substrate using iron powder via FSAM to achieve desirable mechanical properties. To... 

In this investigation, the behavior of pin loaded composite plates is studied numerically. A failure prediction model is used to predict the ultimate strength considering three different mechanisms of failure: bearing, shearout and net tension. The model consists of two major parts: stress analysis and failure analysis. The main difference between this investigation and others is considering more realistic assumptions in modeling of the problem. As an example, we consider nonlinear behavior in the shear stress/ shear strain relationship of each unidirectional ply and use this model in optimization problem to reach maximum strength. The results are compared with experimental results available... 

The debate over political philosophy has resurfaced five decades after the publication of John Rawls' famous book on the theory of justice. In that book, Rawls criticizes perfectionist states, And considers a state just that leaves the perfection and goodness of human beings to the citizens themselves. And the state can not be the final arbiter and interferor in the good and perfection of the citizens, and the state should never be one-sided in this conflict between the various opinions of the people about the good. Therefore, the state should only provide the means for citizens to be able to pursue their good deeds freely and equally, which is what Rawls calls the precedence of the right... 

To capture what is really done on the computer, we have decided to simulate the behavior of an Intel processor based computer. The main part of a computer is its CPU, so we are have simulated the Intel processors from 8086 to Pentium with MMX, SSEX and 3DNow. To work with hardware and software and going back to these steps for several times, is a time consuming procedure. To avoid falling in such loops, one way is to simulate the hardware and develop the software according to this simulation. This remedy solves time consuming procedure since changing hardware in simulation is quite easy. To simulate the digital systems, we need to have the software codes of the processors. Since the Intel...