Suppression of thermal postbuckling and nonlinear panel flutter motions of variable stiffness composite laminates using piezoelectric actuators

Variable stiffness composite laminates(VSCLs)are promising in aerospace engineering due to their designable material properties through changing fiber angles and stacking sequences.Aiming to control the thermal postbuckling and nonlinear panel flutter motions of VSCLs,a full-order numerical model is developed based on the linear quadratic regulator(LQR)algorithm in control theory,the classical laminate plate theory(CLPT)considering von Kármán geometrical nonlinearity,and the first-order Piston theory.The critical buckling temperature and the critical aerodynamic pressure of VSCLs are parametrically investigated.The location and shape of piezoelectric actuators for optimal control of the dynamic responses of VSCLs are determined through comparing the norms of feedback control gain(NFCG).Numerical simulations show that the temperature field has a great effect on aeroelastic tailoring of VSCLs;the curvilinear fiber path of VSCLs can significantly affect the optimal location and shape of piezoelectric actuator for flutter suppression;the unstable panel flutter and the thermal postbuckling deflection can be suppressed effectively through optimal design of piezoelectric patches.

On modal energy in civil structural control

A new control strategy based on modal energy criterion is proposed to demonstrate the effectiveness of the control system in reducing structural earthquake responses. The modal control algorithm combining LQR(linear quadratic regulator) control algorithm is adopted in the discrete time-history analysis. The various modal energy forms are derived by definition of the generalized absolute displacement vector. A preliminary numerical study of the effectiveness of this control strategy is carried out on a 20-storey framed steel structural model. The controlled performance of the model is studied from the perspectives of both response and modal energy. Results show that the modal energy-based control strategy is very effective in reducing structural responses as well as in consuming a large amount of modal energy,while augmentation of additional generalized control force corresponding to the modes that contain little modal energy is unnecessary,as it does little help to improve the controlled structural performance.

Jurisprudential Foundation of the Alogithmic Enforcement and Regulation of Law in an Intelligent Society:Taking the Automated Copyright Infringement Monitoring of the Online Content Sharing Platform as an Example

cyber-space has become increasingly important for human activities,and intelligent algorithms are widely used in cyber-space,we are rapidly entering an intelligent society.Now,algorithmic enforcement and regulations of law have posed non-negligible issues.As algorithmic enforcement of copyright law was introduced earlier than that of other laws,it provides a helpful observation perspective.The worldwide practice of copyright enforcement has gradually departed from traditional"safe harbor provisions,"and has emphasized prior examination of shared contents uploaded by Internet service providers'(ISPs)users through the following three dimensions:automated infringement detection algorithms voluntarily used by the ISPs,heavier judicial liability of ISPs,and updated legislation principles.Thus,innovations and development have stimulated new mechanisms and regulations for enforcing copyright in cyberspace.Algorithmic enforcement of copyright law in an intelligent society is essential and meaningful.The copyright regulation mechanisms should be guided by jurisprudential principles and concepts featuring the principles of(a)legitimate and efficient flow of information,(b)balance between and among algorithmic power,public power and private rights,(c)boosting the sharing economy and the new gig economy,and(d)promoting social governance philosophy of"coconstruction,co-governance and sharing."These principles are meaningful for creation of a new mechanism for balancing interests between ISPs and their users,and for introducing the pluralistic co-governance mechanism beyond simply practicing"filtering obligations."In addition,these principles are significant for improving a certification with credibility of copyright status and ownership,and for advancing a mechanism for onlinecollegiate-panel dispute resolution.

Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding （GMAW） processes is presented. Solution of non.linear transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process （constant voltage） and for pulsed processes with U/I and Ill- modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.

A modified Gillespie algorithm for E.coli gene regulation systems

The dynamics of complex gene regulation systems can be simulated by the Gillespie algorithm. The classic Gillespie algorithm is appropriate to simulate a stochastic