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Determining the mechanical characteristics of the artery is very essential for the production of vascular implants. In the present work, the mechanical characteristics of arterial walls were investigated by considering plaque and stent in a 3D model. This article aims to investigate the effect of the arterial tissue with the same boundary conditions and restrictions for an artery blocked with the plaque and stent, in creating stress in the tissue. An intravascular stent implantation is a treatment method whose success largely depends on the mechanical characteristics of each vascular component, plaque and stent, and blood flow pressure. For opening up the blood flow in the blocked artery, stents could be used as medical devices. In this research, a stent was designed, and its impact on all three models of elastic, viscoelastic, and hyper-elastic arterial tissue with plaque was studied and compared. An ideal finite element model was made to find the effect of three types of the artery tissue (elastic, viscoelastic, hyper-elastic) with the systolic and diastolic blood flow pressure to observe the stress and the deformation of arteries, plaques, and stents. In addition, for the hyper-elastic model, two Mooney-Rivlin and Ogden models were also investigated. It was found that the type of artery had an effective impact on the result of the stress and the deformation created in the stented artery. Moreover, the results illustrated that considering different models for the artery tissue affected the plaque and stent behavior. Arteries exhibit interesting mechanical behaviors. In the present study, an attempt was made to investigate different mechanical behaviors of arteries with the plaque and stent obstruction. In the examined models, the stress for the artery and plaque was higher in the Ogden model and the lowest one was in the viscoelastic model, and the deformation was higher in the viscoelastic model and lower in the Ogden model. It should be noted that the average stress for the vessel in the Ogden model was about 50% higher than the viscoelastic model. Pathological changes in the walls of the vessels can lead to high-risk cardiovascular diseases such as heart attacks and strokes. Understanding arterial mechanical behaviors provides valuable insight into disease. Therefore, the investigation of different behavioral models helps to evaluate the behavior of the arterial wall by considering the composition and function of the tissue. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, supercritical extraction of nimbin from neem seeds has been studied. In order to investigate the effect of parameters on nimbin extraction yield, a partial differential equation model based on mass conservation principles. The model was solved using MATLAB software. The results were successfully validated with available laboratory experimental data. The optimum values of the operating parameters were obtained using gradient search strategy. Optimization routine was employed to maximize process profit. The optimum value of temperature, pressure, CO2 flow rate and particle diameter were found to be 305K, 177.339 bar, 0.9660 cm3/min and 0.0575 cm, respectively. Finally, a sensitivity analysis was carried out on the different model parameters, and found that process profit is mostly sensitive to neem price. PRACTICAL APPLICATIONS This work uses mathematical optimization as a computational engine to arrive at the best solution for neem extraction in a systematic and efficient way. In the context of neem supercritical fluid extraction (SFE) systems, coupling optimization with suitable simulation modules opens a new avenue of possibilities. It saves money and provides economical benefits. In neem SFE process, measuring parameters and understanding the process are difficult. In this case, modeling can provide virtual environmental for operator practice. [ABSTRACT FROM AUTHOR]

According to the considerable effects of the loading frequency on the cyclic behaviour of the soils and lack of the sufficient and precise data in this field for the unsaturated soils, more attention needs to be paid to the experimental investigations in various loading paths and frequencies. Meanwhile the unsaturated cyclic tests require advanced equipment and need more precision and time. In this paper, the results of two groups of tests which were performed on an unsaturated fine grained soil in the same initial condition are presented and compared during specific stress paths (pre-cycles of loading and during cycles). The tests are performed using the same suction-controlled cyclic triaxial apparatus in the same stress path before loading cycles, but two conditions of the cyclic loading frequencies (slow cyclic tests with the constant suction condition during the cycles and rapid cyclic tests with the unsteady suction condition during the cyclic path). The results show that increase in the loading frequency leads to the considerable increase in the shear modulus of the samples in the same strain levels.

Soil properties can completely change the ground motion characteristics as they travel from the bedrock to the surface because, soil as a low-pass filter, may amplify or deamplify seismic motions in some frequencies on the wave travelling path. Recent studies about the advanced unsaturated soil mechanics clearly shows that dynamic properties of soils, including small-strain shear modulus (Gmax), shear modulus reduction (G/Gmax), and damping ratio (D) curves are affected by changes in the soil suction level. The current study present nonlinear time-dependent analysis of three different unsaturated soils available in the literature with different ranges of nonlinear behaviour that earlier have been studied on unsaturated dynamic models. Since, the earthquake intensity parameters can be used to describe the damage potential of an earthquake, the focus of this paper is to evaluate the impact of the suction variation on the engineering ground motion parameters, including peak values of strong motion, Vmax/Amax, root-mean-square acceleration, Arias intensity, characteristic intensity, cumulative absolute velocity, acceleration spectrum intensity, effective design acceleration, A95 parameter and predominant period separately under the near-field and the far-field seismicity categories.