Owing to the unique features in intensity and phase structures, optical vortex lattices (OVLs) have attracted intensive attention and promoted various applications. However, the power scaling of OVLs always presents a critical challenge. Here we take advantage of the brightness enhancement of coherent beam combining (CBC) technology and propose an architecture for creating OVLs based on the CBC system. In the experiment, by utilizing the stochastic parallel gradient descent algorithm, the dynamic phase noises were compensated. The desired piston phase shifting of each element for tailoring the structured wavefront was implemented by the liquid crystal. When the system in a closed loop, hexagonal close-packed OVL consists of spatially distributed orbital angular momentum, beams can be generated in the far-field. This work is an important step toward future implementation of high-power structured light beams.

Pipeline systems in aircraft are subjected to both hydraulic pump pressure fluctuations and base excitation from the engine. This can cause fatigue failures due to excessive vibrations. Therefore, it is essential to investigate the vibration behavior of the pipeline system under multiexcitations. In this paper, experiments have been conducted to describe the hydraulic pipeline systems, in which fluid pressure excitation in pipeline is driven by the throttle valve, and the base excitation is produced by the shaker driven by a vibration controller. An improved model which includes fluid motion and base excitation is proposed. A numerical MOC-FEM approach which combined the coupling method of characteristics (MOC) and finite element method (FEM) is proposed to solve the equations. The results show that the current MOC-FEM method could predict the vibration characteristics of the pipeline with sufficient accuracy. Moreover, the pipeline under multiexcitations could produce an interesting beat phenomenon, and this dangerous phenomenon is investigated for its consequences from engineering point of view.

Magnetorheological fluid (MRF) porous fabric composite has been demonstrated to improve the shear properties of MRF. Non-woven fabric is manufactured from a multitude of fibers through spinning or melt-blown processing methods. As the fundamental unit of non-woven fabric, fibers without spinning or melt-blown directly influence the shear properties of magnetorheological (MR) materials. However, the effect of unprocessed fiber on the shear properties of MR grease remains uncertain. This study introduces a novel MR grease with fiber threads (MRG-FT) by incorporating fiber threads into MRG. The effects of fiber thread length, mass fraction, and material type on MRG shear stress are investigated. Compared to conventional MRG, the maximum shear stress of MRG-FT is increased by 31.8% under the magnetic field of 0.64 T. A novel Herschel–Bulkley–Fiber (H-B-F) model that considers fiber parameters (tenacity, mass fraction, etc.) is proposed based on the H–B model. To validate the enhancement of MRG by fiber threads, a linear damper based on shear mode has been designed and tested. The results demonstrate a 23.8% increase in the maximum damping force of MRG-FT compared to conventional MRG under an excitation current of 1.6 A. This study reveals the influence of fiber threads, which directly influences the shear properties of MRG upon the application of the magnetic field. The maximum damping force of the MRG can be increased by 23.8% by only 1.5% mass fraction of fibers.

The problem of vibrations of rotating rings has been of interest for its wide applications in engineering, such as the vibratory ring gyroscopes. For the vibratory ring gyroscopes, the vibration of a micro ring is usually actuated and sensed by means of electrostatics. The analytical models of electrostatic microstructures are complicated due to their non-linear electromechanical coupling behavior. Therefore, this paper presents for the first time the free vibration of a rotating ring under uniform electrical field and the results will be helpful for extending our knowledge on the problem of vibrations of rotating rings, helping the design of vibratory ring gyroscopes, and inspiring the feasibilities of other engineering applications. An analytical model, based on thin-ring theory, is derived by means of energy method for a rotating ring under uniformly distributed electrical field. After that, the closed form solutions of the natural frequencies and modes are obtained by means of modal expansion method. Some valuable conclusions are made according to the results of the present analytical model. The electrical field causes not only an electrostatic force but also an equivalently negative electrical-stiffness. The equivalent negative electrical-stiffness will reduce either the natural frequencies or critical speeds of the rotating ring. It is known that the ring will buckle when its rotational speed equals its natural frequencies. The introduction of electrical field will further reduce the buckling speeds to a value less than the natural frequencies. The rotation effect will induce the so-called traveling modes, each one travels either in the same direction as the rotating ring or in the opposite direction with respect to stationary coordinate system. The electrical field will reduce the traveling velocities of the traveling modes.