فهرست مطالب مسعود پدرام

The coastal structures such as wharves withstand severe operational conditions during their service life; hence, they are susceptible to damage and reduction in the stiffness of their elements. In this paper, the performance of a damage detection method based on power spectral density is numerically investigated on the dolphin platform of the oil wharf used for the unloading of crude oil to the refinery. This investigation is held numerically, and the damage is modeled as a percent reduction in stiffness of the elements. For this purpose, the finite-element model of the dolphin is made in the MATLAB software and the effect of surrounding water is considered as the added mass on the elements. To probe the performance of the method on the dolphin model, several assumed damage scenarios with different levels of damage in the structure, are considered. Furthermore, an approach for calculation of the spectral density of excitation using an approximate FRF is introduced. Results prove the success of the method in the identification of the parameters of a stiff coastal structure like a dolphin. Besides, the results from these investigations prove that the added mass significantly affects the damage detection results. The quality and accuracy of the numerical results prove the merits of damage detection by finite-element model updating in the frequency domain. The results of the present study urge the practical assessment of the performance of the method in the future.

An experimental investigation is conducted in the wake of a circular cylinder with two tripwires attached at angle of 140 and 40 degrees measured from the forward stagnation point at Reynolds numbers, Re = 30000. The tripwire diameter is 0.5, 1, 1.5 mm. The effects of the tripwires on drag reduction, mean velocity profile and velocity defect and half width, turbulence intensity profiles and Strouhal number have been examined. The results reveal that for Re=3000, there exits optimum case where the drag coefficients acting on the cylinder all reach some of the drag coefficient of a plain cylinder. At the optimum case the drag coefficient of cylinder is reduced for two-wire cylinder with two different diameters. The results reveal that when we get far from cylinder, the procedure of changes of the peak of mean velocity (w0), and peak of turbulence intensity profiles decrease–increase and increase–decrease, respectively. Also the results of experiment are shown that with a plain cylinder the values of peak of turbulence intensity profiles and velocity defect (w0) are generally decreased compared with those values for tripping wires cylinder.

The effect of installation of turbulence promoter wire on the wake flow characteristics such as average velocity and turbulence intensity about an airfoil is investigated experimentally at a Reynolds number of 3780. The wire is installed at the maximum thickness of NACA0012 airfoil and its diameter is changed to obtain different turbulente flows. This study shows that the width and minimum of velocity profile in the wake is increased by increasing the wire diameter. Also by increasing x/c and the wire diameter, the half width at half depth (b1/2) is increased. The velocity outside of wake region is approximately equal for all cases. This investigation also shows that the drag coefficient is increased by increasing the wire diameter.

Although Jürgen Habermas, critical theoretician of the second generation of Frankfurt school, proposes a comprehensive theory of modernity, he does not heed the nature of the future of art as the first generation of theoreticians did. Since in their view instrumental and technological rationality is irreplaceable, the prominent theoreticians of the first generation, such as Adorno and Marcuse, consider aesthetics and art as a way out of the domination of modern rationality. But Habermas (through reforming rationality and foregrounding its communicative aspect as opposed to its instrumental aspect) reconciles rationality with freedom as the essence of critical theory. He posits aesthetics and art next to each other and not as opposite to rationality. Then he distinguishes the position of art and aesthetics from communicative rationality process, and bestows upon it an aspect different from communicative action. In other words, he eliminates the canonical aspect of art and aesthetics from freedom of thought, which has been focused on by theoreticians such as Adorno and Marcuse.