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  • Topological Approach for Analyzing and Modeling the Aerodynamic Hysteresis of an Airfoil
  • Abstract Aerodynamic hysteresis is of practical importance for the flying airfoils. Motivated by the problem of global description on the hysteresis behaviors, this paper proposes a topological approach to analyze and model the hysteresis behaviors exhibited in the airfoil flow from a viewpoint of dynamic system theory. The approach is based on the topological invariant rules of singular points under topological mapping. It is able to theoretically explain such discontinuous hysteresis phenomena, and make consistent and accurate predictions of the hysteresis behaviors in the airfoil flow. The model results have shown that the present model is in good agreement with the…
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  • The Particular Solutions of Chebyshev Polynomials for Reissner Plates under Arbitrary Loadings
  • Abstract Analytical particular solutions of Chebyshev polynomials are obtained for problems of Reissner plates under arbitrary loadings, which are governed by three coupled second-ordered partial differential equation (PDEs). Our solutions can be written explicitly in terms of monomials. By using these formulas, we can obtain the approximate particular solution when the arbitrary loadings have been represented by a truncated series of Chebyshev polynomials. In the derivations of particular solutions, the three coupled second-ordered PDE are first transformed into a single six-ordered PDE through the Hörmander operator decomposition technique. Then the particular solutions of this six-ordered PDE can be found in the…
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  • Boundary Layer Effect in BEM with High Order Geometry Elements Using Transformation
  • Abstract The accurate evaluation of nearly singular integrals is one of the major concerned problems in the boundary element method (BEM). Although the current methods have achieved great progress, it is often possible only for problems defined in the simplest geometrical domains when the nearly singular integrals need to be calculated. However, engineering processes occur mostly in complex geometrical domains, and always, involve nonlinearities of the unknown variables and its derivatives. Therefore, effective methods of dealing with nearly singular integrals for such practical problems are necessary and need to be further investigated. In this paper, a general strategy based on a…
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  • A Computational Approach for Pre-Shaping Voltage Commands of Torsional Micromirrors
  • Abstract Input-shaping is an open-loop control technique for dynamic control of electrostatic MEMS. In MEMS applications, open-loop control is attractive as it computes a priori the required system input to achieve desired dynamic behavior without using feedback. In this work, a 3-D computational electromechanical analysis is performed to preshape the voltage commands applied to electrostatically actuate a torsional micromirror to a desired tilt angle with minimal residual oscillations. The effect of higher vibration modes on the controlled response is also investigated. It is shown that, for some structural design parameters, the first bending mode of the micromirror can have a significant…
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  • Optimization of a Sandwich Structure Using a Genetic Algorithm
  • Abstract A sandwich panel's optimum core height and composite face thickness, under defined loading, have been computed in order to reach the structure's lowest weight and highest stiffness. The Tsai-Hill criterion was used in order to control the support of transverse loading by the panel. Regarding the relationships in the sandwich materials, the studied material was modeled with the MATLAB package. The Genetic Algorithm (GA) that is based on statistics was used. Our goal was to obtain the best methods of the GA in order to present an optimization method for the sandwich structure. Hence, a sensibility analysis was performed. In…
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  • An Integrated Finite Strip Solution for Box Girder Bridges and Slab-on-girder Bridges
  • Abstract In view of the urgent need for an efficient and accurate structural analysis method in bridge design practice, this paper introduces a total integrated analytical solution for multi-span, continuous slab-on-girder and box girder bridges, by modeling the bridge deck and the piers together, using the finite strip method (FSM). FSM has been well accredited for its efficiency in the structural analysis of bridges, reducing the time required for data input and analysis without affecting the degree of accuracy. By using a continuously differentiable smooth series in the longitudinal direction, a complex 3D problem is reduced to a 2D problem using…
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  • Dynamic Instabilities in Slender Space Launch Vehicles under Propulsive Thrust and Aerodynamic Forces
  • Abstract A mechanics based linear analysis of the problem of dynamic instabilities in slender space launch vehicles is undertaken. The flexible body dynamics of the moving vehicle is studied in an inertial frame of reference, including velocity induced curvature effects, which have not been considered so far in the published literature. Coupling among the rigid-body modes, the longitudinal vibrational modes and the transverse vibrational modes due to asymmetric lifting-body cross-section are considered. The model also incorporates the effects of aerodynamic forces and the propulsive thrust of the vehicle. The effects of the coupling between the combustion process (mass variation, developed thrust…
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  • A Dynamical Modeling to Study the Adaptive Immune System and the Influence of Antibodiesin the Immune Memory
  • Abstract Immunological systems have been an abundant inspiration to contemporary computer scientists. Problem solving strategies, stemming from known immune system phenomena, have been successfully applied to chall enging problems of modern computing. Simulation systems and mathematical modeling are also beginning use to answer more complex immunological questions as immune memory process and duration of vaccines, where the regulation mechanisms are not still known sufficiently (Lundegaard, Lund, Kesmir, Brunak, Nielsen, 2007). In this article we studiedin machinaa approach to simulate the process of antigenic mutation and its implications for the process of memory. Our results have suggested that the durability of the…
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  • A Discontinuous Galerkin Meshfree Modeling of Material Interface
  • Abstract A discontinuous Galerkin meshfree formulation is proposed to solve the potential and elasticity problems of composite material where the material interface has to be appropriately modeled. In the present approach the problem domain is partitioned into patches or sub-domains and each patch holds the same material properties. The discretized meshfree particles within a patch are classified as one particle group. Various patches occupied by different particle groups are then linked using the discontinuous Galerkin formulation where an averaged interface flux or traction is constructed based on the fluxes or tractions computed from the adjacent patches. The gradient jump condition across…
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