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Amylin as a Future Obesity Treatment
Babak Dehestani,Nicholas RS Stratford,Carel W. le Roux 대한비만학회 2021 The Korean journal of obesity Vol.30 No.4
Obesity is defined as abnormal or excessive fat accumulation that contributes to detrimental health impacts. One-third of the population suffers from obesity, and it is important to consider obesity as a chronic disease requiring chronic treatment. Amylin is co-secreted with insulin from β pancreatic cells upon nutrient delivery to the small intestine as a satiety signal, acts upon sub-cortical homeostatic and hedonic brain regions, slows gastric emptying, and suppresses post-prandial glucagon responses to meals. Therefore, new pharmacological amylin analogues can be used as potential anti-obesity medications in individuals who are overweight or obese. In this narrative review, we analyse the efficacy, potency, and safety of amylin analogues. The synthetic amylin analogue pramlintide is an approved treatment for diabetes mellitus which promotes better glycaemic control and small but significant weight loss. AM833 (cagrilintide), an investigational novel long-acting acylated amylin analogue, acts as a non-selective amylin receptor. This calcitonin G protein-coupled receptor agonist can serve as an attractive novel treatment for obesity, resulting in reduction of food intake and significant weight loss in a dose-dependent manner.
Numerical Simulation of Vortex Induced Vibration of A Flexible Cylinder
Hosseini, Mojtaba,Ashrafi, Hamid reza,Beiranvand, Peyman,Dehestani, Ahmad,Dehestani, Kiuomars Korean Society for Fluid machinery 2017 International journal of fluid machinery and syste Vol.10 No.4
Numerical simulations of vortex-induced vibration of a three-dimensional flexible Cylinder under uniform turbulent flow are calculated when Reynolds number is $1.35{\times}104$. In order to achieve the vortex-induced vibration, the three-dimensional unsteady, viscous, incompressible Navier-Stokes equation and LES turbulence model are solved with the finite volume approach, the Cylinder is discretized according to the finite element theory, and its dynamic equilibrium equations are solved by the Newmark method. The fluid-Cylinder interaction is realized by utilizing the diffusion-based smooth dynamic mesh method. Considering VIV system, the variety trends of lift coefficient, drag coefficient, displacement, vertex shedding frequency, phase difference angle of Cylinder are analyzed under different frequency ratios. The nonlinear phenomena of locked-in, phase-switch are captured successfully. Meanwhile, the limit cycle and bifurcation of lift coefficient and displacement are analyzed using trajectory, phase portrait and Poincare sections. The results reveal that: when drag coefficient reaches its minimum value, the transverse amplitude reaches its maximum and the "lock-in" begins simultaneously. In the range of "lock-in", amplitude decreases gradually with increasing of frequency ratio. When lift coefficient reaches its minimum value, the phase difference, between lift coefficient and lateral displacement, undergoes a suddenly change from the "out-of-phase" to the "in-phase" mode. There is no bifurcation of lift coefficient and lateral displacement occurred in three dimensional flexible Cylinder submitted to uniform turbulent flow.
Numerical Simulation of Vortex Induced Vibration of A Flexible Cylinder
Mojtaba Hosseini,Hamid reza Ashrafi,Peyman Beiranvand,Ahmad Dehestani,Kiuomars Dehestani 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.4
Numerical simulations of vortex-induced vibration of a three-dimensional flexible Cylinder under uniform turbulent flow are calculated when Reynolds number is 1.35×104. In order to achieve the vortex-induced vibration, the three-dimensional unsteady, viscous, incompressible Navier-Stokes equation and LES turbulence model are solved with the finite volume approach, the Cylinder is discretized according to the finite element theory, and its dynamic equilibrium equations are solved by the Newmark method. The fluid-Cylinder interaction is realized by utilizing the diffusion-based smooth dynamic mesh method. Considering VIV system, the variety trends of lift coefficient, drag coefficient, displacement, vertex shedding frequency, phase difference angle of Cylinder are analyzed under different frequency ratios. The nonlinear phenomena of locked-in, phase-switch are captured successfully. Meanwhile, the limit cycle and bifurcation of lift coefficient and displacement are analyzed using trajectory, phase portrait and Poincare sections. The results reveal that: when drag coefficient reaches its minimum value, the transverse amplitude reaches its maximum and the “lock-in” begins simultaneously. In the range of “lock-in”, amplitude decreases gradually with increasing of frequency ratio. When lift coefficient reaches its minimum value, the phase difference, between lift coefficient and lateral displacement, undergoes a suddenly change from the “out-of-phase” to the “in-phase” mode. There is no bifurcation of lift coefficient and lateral displacement occurred in three dimensional flexible Cylinder submitted to uniform turbulent flow.
A stress-function variational approach toward CFRP -concrete interfacial stresses in bonded joints
Samadvand, Hojjat,Dehestani, Mehdi Techno-Press 2020 Advances in concrete construction Vol.9 No.1
This paper presents an innovative stress-function variational approach in formulating the interfacial shear and normal stresses in an externally bonded concrete joint using carbon fiber-reinforced plastic (CFRP) plies. The joint is subjected to surface traction loadings applied at both ends of the concrete substrate layer. By introducing two interfacial shear and normal stress functions on the CFRP-concrete interface, based on Euler-Bernoulli beam idea and static stress equations of equilibrium, the entire stress fields of the joint were determined. The complementary strain energy was minimized in order to solve the governing equation of the joint. This yields an ordinary differential equation from which the interfacial normal and shear stresses were proposed explicitly, satisfying all the multiple traction boundary conditions. Lamination theory for composite materials was also employed to obtain the interfacial stresses. The proposed approach was validated by the analytic models in the literature as well as through a comprehensive computational code generated by the authors. Furthermore, a numerical verification was carried out via the finite element software ABAQUS. In the end, a scaling analysis was conducted to analyze the interfacial stress field dependence of the joint upon effective issues using the devised code.
Implementation of bond-slip effects on behaviour of slabs in structures
S.S. Mousavi,M. Dehestani 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.16 No.2
Employing discrete elements for considering bond-slip effects in reinforced concrete structures is very time consuming. In this study, a new modified embedded element method is used to consider the bond-slip phenomenon in structural behavior of reinforced concrete structures. A comprehensive parametric study of RC slabs is performed to determine influence of different variables on structural behavior. The parametric study includes a set of simple models accompanied with complex models such as multi-storey buildings. The procedure includes the decrease in the effective stiffness of steel bar in the layered model. Validation of the proposed model with existing experimental results demonstrates that the model is capable of considering the bond-slip effects in embedded elements. Results demonstrate the significant effect of bond-slip on total behavior of structural members. Concrete characteristic strengths, steel yield stress, bar diameter, concrete coverage and reinforcement ratios are the parameters considered in the parametric study. Results revealed that the overall behavior of slab is significantly affected by bar diameter compared with other parameters. Variation of steel yield stress has insignificant impact in static response of RC slabs; however, its effect in cyclic behavior is important.
Mechanical behavior of steel-concrete composite decks with perfobond shear connectors
Hamed Allahyari,Mehdi Dehestani,Morteza H.A. Beygi,Bahram Navayi Neya 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.17 No.3
Exodermic deck systems are new composite steel grid deck systems which have been used in various projects during the past decade. One of the eminent features of this system is considerable reduction in the structure weight compared to the ordinary reinforced concrete decks and also reduction in construction time by using precast Exodermic decks. In this study, dynamic properties of the Exodermic deck bridges with alternative perfobond shear connectors are investigated experimentally. In order to evaluate the dynamic properties of the decks, peak picking and Nyquist circle fit methods are employed. Frequencies obtained experimentally are in good agreement with the results of the finite-element solution, and the experimental results show that the first mode is the most effective mode among the obtained modes. The first four modes are the rigid translational motion modes, and the next two modes seem to be rigid rotational motion modes around a horizontal axis. From the 7th mode onwards, modes are flexible. The range of damping ratios is about 0.5%. Furthermore, the static behavior of the Exodermic decks under a static load applied at the center of the decks was investigated. Failure of the decks under positive bending was punching-shear. The bending strength of the decks under negative bending was about 50 percent of their strength under positive bending. In addition, the weight of an Exodermic deck is about 40% of that of an equivalent reinforced concrete slab.