Damage detection and localization analysis have gained increasing importance over the years,due to the growing number of catastrophic events and the associated risks that small,undetected cracks in structures may evol...Damage detection and localization analysis have gained increasing importance over the years,due to the growing number of catastrophic events and the associated risks that small,undetected cracks in structures may evolve into severe failures if not identified in time.In this context,vibration-based methods have been extensively investigated for structural damage detection.Among them,one of the most widely used approaches since its introduction is the curvature method.It has been successfully employed in numerous studies,consistently providing reliable results.However,the use of second-order or higher-order derivatives can be challenging when dealing with experimental data,as these are highly sensitive tomeasurement noise.Conversely,using the first derivative may simplify the analysis while maintaining robustness.Therefore,the present work introduces and experimentally demonstrates an extension of the curvature-based approach,focusing on the integration of the first derivative for damage localization.In particular,both methods based on the use of the second and first derivatives were applied to detect their capability in detecting and localizing the damage.This was tested on a slender truss structure,with induced damages at different locations,equal to just 1.069%of the structure volume.The results,obtained from this real-world case study,show that for certain structures,like slender ones,the use of the first derivative can achieve equal or even superior damage detection performance compared to the traditional second derivative method.Specifically,the comparison was evaluated based on the accuracy in localizing the damage with the twomethods,both froma visual and quantitative point of view,since a deviation indexδwas also introduced.展开更多
In shape optimization,we often seek to optimize the shape of a domain in order to achieve a goal.For example,the sound of a drum depends on the shape of its membrane,via the eigenvalues of the Laplacian.We use the sha...In shape optimization,we often seek to optimize the shape of a domain in order to achieve a goal.For example,the sound of a drum depends on the shape of its membrane,via the eigenvalues of the Laplacian.We use the shape derivative to adjust this shape.The shape derivative for an eigenvalue problem is frequently used in shape optimisation,in particular when we want to min-imise or maximise an eigenvalue,often the first of an elliptic operator,typi-cally the Laplacian,under geometric constraints.This paper gives a simple method for calculating the shape derivative of a Dirichlet eigenvalue,but also the shape derivative of an objective function constrained to an eigenvalue problem.展开更多
The Generalized Polarization Tensors （GPT） is a series of tensors which contain infor- mations on the shape of a domain and its material parameters. The aim of this paper is to provide a method of constructing GPT-v...The Generalized Polarization Tensors （GPT） is a series of tensors which contain infor- mations on the shape of a domain and its material parameters. The aim of this paper is to provide a method of constructing GPT-vanishing structures using shape derivative for two-dimensional conductivity or anti-plane elasticity problem. We assume a multi-coating geometry as a candidate of GPT-vanishing structure. We define a cost functional to min- imize GPT and compute the shape derivative of this functional deriving an asymptotic expansion of the perturbations of the GPTs due to a small deformation of interfaces of the structure. We present some numerical examples of GPT-vanishing structures for several different shaped inclusions.展开更多
Dear Editor,This letter considers the problem of achieving optimal formation control in multiple vertical take-off and landing(VTOL)unmanned aerial vehicles(UAVs).Specifically,the objective is to derive the vehicles t...Dear Editor,This letter considers the problem of achieving optimal formation control in multiple vertical take-off and landing(VTOL)unmanned aerial vehicles(UAVs).Specifically,the objective is to derive the vehicles to the desired formation shape while minimizing the total cost function.Leveraging the backstepping design,a distributed control strategy is proposed that incorporates a dynamic system for generating a reference trajectory and a trajectory tracking controller for each vehicle.展开更多
文摘Damage detection and localization analysis have gained increasing importance over the years,due to the growing number of catastrophic events and the associated risks that small,undetected cracks in structures may evolve into severe failures if not identified in time.In this context,vibration-based methods have been extensively investigated for structural damage detection.Among them,one of the most widely used approaches since its introduction is the curvature method.It has been successfully employed in numerous studies,consistently providing reliable results.However,the use of second-order or higher-order derivatives can be challenging when dealing with experimental data,as these are highly sensitive tomeasurement noise.Conversely,using the first derivative may simplify the analysis while maintaining robustness.Therefore,the present work introduces and experimentally demonstrates an extension of the curvature-based approach,focusing on the integration of the first derivative for damage localization.In particular,both methods based on the use of the second and first derivatives were applied to detect their capability in detecting and localizing the damage.This was tested on a slender truss structure,with induced damages at different locations,equal to just 1.069%of the structure volume.The results,obtained from this real-world case study,show that for certain structures,like slender ones,the use of the first derivative can achieve equal or even superior damage detection performance compared to the traditional second derivative method.Specifically,the comparison was evaluated based on the accuracy in localizing the damage with the twomethods,both froma visual and quantitative point of view,since a deviation indexδwas also introduced.
文摘In shape optimization,we often seek to optimize the shape of a domain in order to achieve a goal.For example,the sound of a drum depends on the shape of its membrane,via the eigenvalues of the Laplacian.We use the shape derivative to adjust this shape.The shape derivative for an eigenvalue problem is frequently used in shape optimisation,in particular when we want to min-imise or maximise an eigenvalue,often the first of an elliptic operator,typi-cally the Laplacian,under geometric constraints.This paper gives a simple method for calculating the shape derivative of a Dirichlet eigenvalue,but also the shape derivative of an objective function constrained to an eigenvalue problem.
文摘The Generalized Polarization Tensors （GPT） is a series of tensors which contain infor- mations on the shape of a domain and its material parameters. The aim of this paper is to provide a method of constructing GPT-vanishing structures using shape derivative for two-dimensional conductivity or anti-plane elasticity problem. We assume a multi-coating geometry as a candidate of GPT-vanishing structure. We define a cost functional to min- imize GPT and compute the shape derivative of this functional deriving an asymptotic expansion of the perturbations of the GPTs due to a small deformation of interfaces of the structure. We present some numerical examples of GPT-vanishing structures for several different shaped inclusions.
基金supported by the National Natural Science Foundation of China(62003214)Guangdong Basic and Applied Basic Research Foundation(2024A1515012681)+1 种基金the Natural Science Foundation of Shanghai(22ZR1443600)Shanghai Pujiang Programme(23PJD064).
文摘Dear Editor,This letter considers the problem of achieving optimal formation control in multiple vertical take-off and landing(VTOL)unmanned aerial vehicles(UAVs).Specifically,the objective is to derive the vehicles to the desired formation shape while minimizing the total cost function.Leveraging the backstepping design,a distributed control strategy is proposed that incorporates a dynamic system for generating a reference trajectory and a trajectory tracking controller for each vehicle.
