mohammad shirzad

Vortex-induced vibration is a critical phenomenon that occurs in offshore structures and causes fatigue and damage to these structures. Previous studies show that these structures show complex and sometimes non-linear behavior. This study uses a rigid cylinder with non-linear support to evaluate the hydrodynamic parameters in these systems. The amount of non-linearity of the support has been changed, and its effect on the hydrodynamic parameters of the system has been investigated. The displacement and velocity of the cylinder were obtained by solving the two-dimensional Reynolds averaged Navier-Stokes and cylinder motion equations. The lift, potential, and vortex coefficients were calculated. Finally, the Strouhal number was determined. The results show that the system's behavior consists of two branches. In branch 1, the motion amplitude of the cylinder is small, but in branch 2, its amplitude is multiplied. By increasing the non-linearity of the support, the range of branch 2 becomes smaller, and the velocity of the cylinder oscillation increases. Raising the support non-linearity reduces the lift force and Strouhal number

Vortex-induced vibrations may cause chaotic behavior in offshore structures. Chaos reduces the life of these structures by causing fatigue. In this research, assuming a nonlinear support, the dynamic behavior of these structures has been investigated. The support nonlinearity was changed by using different types of springs. The displacement and lift force signals were obtained by simultaneously solving the two-dimensional Reynolds averaged Navier-Stokes equations and the cylinder motion equation. Then, chaos detection tests were applied to the signals. The results show that the behavior of the system consists of two branches. The second branch's amplitude is multiple times the amplitude of the first branch. At the starting point of the second branch, the cylinder behavior and the lift force are chaotic. As the support nonlinearity increases, the length of the second branch decreases, but the degree of chaotic behavior of the cylinder and the lift force increases.

Flow-mediated dilation (FMD) is considered a marker of endothelial cell dysfunction (ECD) and has been mostly evaluated in coronary artery disease. The role of ECD in the pathogenesis of pulmonary hypertension (PH) is not well-known. This study sought to evaluate the relationship between FMD and PH.
In this cross-sectional study, the FMD of the brachial artery was measured in 40 confirmed PH patients. Meanwhile, echocardiographic findings, the 6-minute walk test (6MWT), and serum pro-brain natriuretic peptide (pro-BNP) level were evaluated. Overall, 20 patients accomplished all evaluations, and their data were analyzed using SPSS software (version 23).
There was an inverse relationship between pro-BNP and 6MWT (r<0, P<0.05). A significant direct relationship was observed between left ventricular ejection fraction and FMD (P=0.031). Right ventricular (RV) dilation was significantly correlated with pro-BNP (P=0.046). There was a significant direct correlation between RV function and FMD and a significant inverse relationship between pro-BNP and FMD (P=0.05). The independent t-test showed no relationship between FMD and syncope (P=0.75).
Endothelial cell function, which can be evaluated by FMD, was involved in patients with PH. The FMD and 6MWT were helpful as objective prognostic markers in PH. Furthermore, pro-BNP was a noninvasive indicator in the diagnosis of RV systolic dysfunction.

Recovery of cobalt(II) from aqueous solution by polymer inclusion membrane with dinonyl-naphtalenesulfonic acid (DNNSA) as the ion carrier and plasticized with 4 different plasticizer was investigated. Carrier concentration as an important parameter in recovery efficiency was studied and the membrane composed of 15% (wt/wt) of carrier was found to be the most efficient. The studies included effects of nature of plasticizers. Transport accross membranes plasticized with dioctyl adipate, dioctyl phthalate, triethyl phosphate, tributyl phosphate in 8 hours were investigated and dioctyl adipate was selected as the best. The FTIR characterization showed that the membrane constituents remains as pure substance after synthesis. Recovery of cobalt(II) ions increased with increasing of rate of mixing up to 200 rpm and after that became constant. The effect of pH on recovery was investigated between 3-7.5 and the most efficient pH was 5. Finally, the kinetics was studied with optimized parameters by investigation of cobalt concentration of source phase as a function of time and were found to follow first-order kinetics.