An open-plus-closed-loop (OPCL) control problem for the chaotic motion of a 3D rigid pendulum subjected to a constant gravitationM force is studied. The 3D rigid pendulum is assumed to be consist of a rigid body supported by a fixed and frictionless pivot with three rotational degrees. In order to avoid the singular phenomenon of Euler's angular velocity equation, the quaternion kinematic equation is used to describe the motion of the 3D rigid pendulum. An OPCL controller for chaotic motion of a 3D rigid pendulum at equilibrium position is designed. This OPCL controller contains two parts: the open-loop part to construct an ideal trajectory and the closed-loop part to stabilize the 3D rigid pendulum. Simulation results show that the controller is effective and efficient. 相似文献
Lattice Boltzmann equation method is used to simulate the coherent vortex motions and interactions and the heat transfer characteristics of jets in cross flow (JICFs) via TD2G9 model. After validation, the characteristics of cross flow under different Reynolds numbers are illustrated, including the mean profiles, the Reynolds stress tensor, the vortex and temperature fields, the temperature gradients near the walls, and the coherent correlation of vortex motions. The results show that the velocity profiles in JICF can be characterized by three basic regions, which are mainly caused by the mergence of JICF with the main flow. The temperature gradient near the walls can also be categorized by four basic regions, which are caused mainly by the impulse of JICFs too. Coherent vortex motions are found in JICF for Re = 3000, which are proved by strong periodic correlation of flow variables over a fixed area. 相似文献
In this paper, we consider the existence of positive solutions to a three-point boundary value problem for second order dynamic equations with derivative on time scales.Applying Leggett-Williams fixed point theorem, we obtain at least three positive solutions to the problem. An example is also presented to illustrate the applications of the results obtained. 相似文献
Four fluorimetric probes had been developed to rapidly detect 2,4,6-trinitrophenol (TNP). They were designed and synthesized on the basis of 1,3,4-thiadiazole framework combining calculation with experiment. Among them, SK-1 displayed strong blue emission with fluorescence quantum yield as high as 63.6% in solution. Further evaluation demonstrated that SK-1 displays good selectivity and high sensitivity for rapid and visual detection of TNP. It brought significant changes in both colour and fluorescence emission spectrum. The detection limit was as low as 38 nM. Quenching mechanism was confirmed as photo-induced electron transfer (PET) by nuclear magnetic titration and DFT calculations. What’s more, application in real water samples and solid phase paper tests illustrated the practical significance of detection of TNP in both vapor and solution.
Emissions by magnetic polarons and spin-coupled d-d transitions in diluted magnetic semiconductors(DMSs)have become a popular research field due to their unusual optical behaviors.In this work,high-quality NiI2(Ⅱ)-doped CdS nanobelts are synthesized via chemical vapor deposition(CVD),and then characterized by scanning electron microscopy(SEM),x-ray diffraction,x-ray photoelectron spectroscopy(XPS),and Raman scattering.At low temperatures,the photoluminescence(PL)spectra of the Ni-doped nanobelts demonstrate three peaks near the band edge:the free exciton(FX)peak,the exciton magnetic polaron(EMP)peak out of ferromagnetically coupled spins coupled with FXs,and a small higher-energy peak from the interaction of antiferromagnetic coupled Ni pairs and FXs,called antiferromagnetic magnetic polarons(AMPs).With a higher Ni doping concentration,in addition to the d-d transitions of single Ni ions at 620 nm and 760 nm,two other PL peaks appear at 530 nm and 685 nm,attributed to another EMP emission and the d-d transitions of the antiferromagnetic coupled Ni2+-Ni2+pair,respectively.Furthermore,single-mode lasing at the first EMP is excited by a femtosecond laser pulse,proving a coherent bosonic lasing of the EMP condensate out of complicated states.These results show that the coupled spins play an important role in forming magnetic polaron and implementing related optical responses. 相似文献
Based on single-lane traffic model, a two-lane traffic model is presented considering the velocity difference control signal. The stability condition of the model is obtained by the control theory. The delayed feedback control signal is added to the two-lane model, and the corresponding stability condition is derived again. The numerical simulations show that as the stability conditions are satisfied, the small disturbance will not amplify with and without control signal. In the meantime, the stability is strengthened as the control signal is considered. So the control signal would suppress the traffic disturbance successfully. 相似文献