Analysis of the Oscillating Mechanism of an Aerial Work Platform Based on ADAMS Hydraulic-Mechanical Coupling Simulation

Rigid model of the aerial work platform and hydraulic model of the oscillating mechanism were established with ADAMS. The simulation of two parameters, cy-linder force and oil chamber pressure, was carried out. The simulation result is useful to the design of the oscillating mechanism.

Bursting phenomena as well as the bifurcation mechanism in a coupled BVP oscillator with periodic excitation

We explore the complicated bursting oscillations as well as the mechanism in a high-dimensional dynamical system.By introducing a periodically changed electrical power source in a coupled BVP oscillator, a fifth-order vector field with two scales in frequency domain is established when an order gap exists between the natural frequency and the exciting frequency.Upon the analysis of the generalized autonomous system, bifurcation sets are derived, which divide the parameter space into several regions associated with different types of dynamical behaviors. Two typical cases are focused on as examples,in which different types of bursting oscillations such as sub Hopf/sub Hopf burster, sub Hopf/fold-cycle burster, and doublefold/fold burster can be observed. By employing the transformed phase portraits, the bifurcation mechanism of the bursting oscillations is presented, which reveals that different bifurcations occurring at the transition between the quiescent states（QSs） and the repetitive spiking states（SPs） may result in different forms of bursting oscillations. Furthermore, because of the inertia of the movement, delay may exist between the locations of the bifurcation points on the trajectory and the bifurcation points obtained theoretically.

A Further Inquiry on the Mechanism of 30-60 Day Oscillation in the Tropical Atmosphere

In a simple semi-geostropic model on the equatorial β-plane, the theoretical analysis on the 30-60 day oscillation in the tropical atmosphere is further discussed based on the wave-CISK mechanism. The convection heating can excite the CISK-Kelvm wave and CISK-Rossby wave in the tropical atmosphere and they are all the low-frequency modes which drive the activities of 30-60 day oscillation in the tropics. The most favorable conditions to excite the CISK-Kelvin wave and CISK-Rossby wave are indicated: There is convection heating but not very strong in the atmosphere and there is weaker disturbance in the lower troposphere.The influences of vertical shearing of basic flow in the troposphere on the 30-60 day oscillation in the tropics are also discussed.

Superconducting membrane mechanical oscillator based on vacuum-gap capacitor

Using the diluted S1813 UV photoresist as a sacrificial layer, we successfully fabricate a superconducting suspended parallel-plate capacitor, in which the top layer of aluminum film acts as a membrane mechanical resonator. Together with a superconducting octagonal spiral inductor, this parallel-plate capacitor constitutes a superconducting microwave resonator. At m K temperature, the transmission characteristic and spectrum of the microwave resonator are measured.Sideband frequencies caused by the vibration of the membrane mechanical resonator are clearly demonstrated. By downconverting with a mixer, the dependence of fundamental frequency and its harmonics on the input microwave power are clearly demonstrated, which is consistent with the numerical simulation.

Quantum State Transfer between a Mechanical Oscillator and a Distant Moving Atom

We propose a scheme for high fidelity quantum state transfer from a mechanical oscillator to a distant moving atom. In the scheme, two optical cavities connected by an optical fiber are interacted effectively through adiabatically eliminating fiber mode under large detuning limit. The quantum state transfer fidelity can be raised asymptotically to 100% by optimizing the Gaussian pulse G(t), the maximum atom-cavity coupling strength Ωmax, and the atomic velocity v. We also show that the affect of dissipation can be obviously depressed by synchronously increasing Ωmax and v.

Mechanism analysis of non-sinusoidal oscillation of continuous casting mold synchronously driven by double servomotors

Due to the disadvantages of complexity,high maintenance and vast investment of the electro-hydraulic servo oscillator,a new mechanical device synchronously driven by double servomotors was proposed. The working principle of the non-sinusoidal oscillator was analyzed and the model of the oscillator was validated via simulation software.Then,taking advantage of resonance technology,the hinging force and moment were calculated. The results showed that the hinging force and driving moment reduced,which was useful in reducing the impact of the hinge and prolonging the service life of the bearing. Besides,the best initial spring pressure was 0. 9 times the mold gravity,which improved the oscillation system stability and reduced the load fluctuation and servomotor driving power.

On The Analysis of Labyrinth Seal Flow Induced Vibration by Oscillating Fluid Mechanics Method

A numerical model and a solution method to analyze the labyrinth seal now induced vibration by Oscillating Fluid Mechanics Method (OFMM) are presented in this paper, including the basic equations and solution procedure to determine the oscillating velocity, pressure and the dynamic characteristic coefficients of Labyrinth seal such as the stiffness coefficients and damping coefficients. The results show that this method has the advantages of both less time cousuming and high accuracy. In addition,it can be applied to the field diagnosis of the vibration of the axis of turbomachinery system.

Two-phase sink vortex suction mechanism and penetration dynamic characteristics in ladle teeming process

At the late stage of continuous casting（CC）ladle teeming,sink vortex can suck the liquid slag into tundish,and cause negative influences on the cleanliness of molten steel.To address this issue,a twophase fluid mechanical modeling method for ladle teeming was proposed.Firstly,a dynamic model for vortex suction process was built,and the profiles of vortex flow field were acquired.Then,based on the level set method（LSM）,a two-phase 3Dinterface coupling model for slag entrapment was built.Finally,in combination with high-order essentially non-oscillatory（ENO）and total variation diminishing（TVD）methods,a LSM-based numerical solution method was proposed to obtain the 3Dcoupling evolution regularities in vortex suction process.Numerical results show that the vortex with higher kinetic energy can form an expanded sandglass-shape region with larger slag fraction and lower rotating velocity;there is a pressure oscillation phenomenon at the vortex penetration state,which is caused by the energy shock of two-phase vortex penetration coupling.

Propagation and Mechanisms of the Quasi-Biweekly Oscillation over the Asian Summer Monsoon Region

The propagation and underlying mechanisms of the boreal summer quasi-biweekly oscillation（QBWO）over the entire Asian monsoon region are investigated,based on ECMWF Interim reanalysis（ERA-Interim）data,GPCP precipitation data,and an atmospheric general circulation model（AGCM）.Statistical analyses indicate that the QBWO over the Asian monsoon region derives its main origin from the equatorial western Pacific and moves northwestward to the Bay of Bengal and northern India,and then northward to the Tibetan Plateau（TP）area,with a baroclinic vertical structure.Northward propagation of the QBWO is promoted by three main mechanisms：barotropic vorticity,boundary moisture advection,and surface sensible heating（SSH）.It is dominated by the barotropic vorticity effect when the QBWO signals are situated to the south of 20°N.During the propagation taking place farther north toward the TP,the boundary moisture advection and SSH are the leading mechanisms.We use an AGCM to verify the importance of SSH on the northward propagation of the QBWO.Numerical simulations confirm the diagnostic conclusion that the equatorial western Pacific is the source of the QBWO.Importantly,the model can accurately simulate the propagation pathway of the QBWO signals over the Asian monsoon region.Simultaneously,sensitivity experiments demonstrate that the SSH over northern India and the southern slope of the TP greatly contributes to the northward propagation of the QBWO as far as the TP area.

Oscillating Disturbance Propagation in Passages of Multi-Stage Hydrogen Turbine

The propagation of oscillating disturbances with various frequencies in multi stage turbine passages in a rocket is analyzed using the oscillating fluid mechanics theorem and the parametric polynomial method. The results show that oscillating disturbances can be rapidly dissipated when the disturbance occurs at the inlet except for very high frequency oscillation such as 50 kHz. Dangerous low frequency oscillations occur at the outlet. The effects of the flow parameter variations on the oscillating disturbance propagation are also studied. The analysis will facilitate safe operation of the whole rocket system.

Dynamic Response of Mold Oscillator Interacting with Steel Slabs

A mathematical model to show the dynamic response of the mold oscillator was suggested. The model con- sidered a frictional interaction between the mold oscillator and slab as several connected nodes. The governing equation considered the slab as a multi-degree-of-freedom （DoF） system, and included a hysteresis model to describe elastic-plastic behavior of the slab; the mold oscillator was given two DoF by utilizing pressure and displacement experiment data. Simulations indicate that the mold and slab execute various vibrations, and that mold oscillation marks are caused by a stick-and-slip phenomenon during intervals, in which the slab contacting the mold moves downward compared to the other slab （negative strip time）. The slab shows the formation of mold oscillation marks to previous formation criterion equally when the mold velocity is faster than the casting speed about downward. The oscillation mark will grow up over 2 Hz exciting frequency with constant 4 mm stroke in simulations. Finally, the negative strip time was compared to the frictional force, hysteresis variable, and plastic force to investigate formation mechanism of the oscillation marks.

Second-order magnetic field gradient-induced strong coupling between nitrogen-vacancy centers and a mechanical oscillator

We consider a cantilever mechanical oscillator(MO) made of diamond. A nitrogen-vacancy(NV) center lies at the end of the cantilever. Two magnetic tips near the NV center induce a strong second-order magnetic field gradient. Under coherent driving of the MO, we find that the coupling between the MO and the NV center is greatly enhanced. We studied how to generate entanglement between the MO and the NV center and realize quantum state transfer between them. We also propose a scheme to generate two-mode squeezing between different MO modes by coupling them to the same NV center. The decoherence and dissipation effects for both the MO and the NV center are numerically calculated using the present parameter values of the experimental configuration. We have achieved high fidelity for entanglement generation, quantum state transfer, and large twomode squeezing.

Chimera state in a network of nonlocally coupled impact oscillators

Chimera state is a peculiar spatiotemporal pattern,wherein the coherence and incoherence coexist in the network of coupled identical oscillators.In this paper,we study the chimera states in a network of impact oscillators with nonlocal coupling.We investigate the effects of the coupling strength and the coupling range on the network behavior.The results reveal the emergence of the chimera state for significantly small values of coupling strength,and higher coupling strength values lead to unbounded motions in the oscillators.We also study the network in the case of excitation failure.We observe that the coupling helps in the maintenance of an oscillatory motion with a lower amplitude in the failed oscillator.

Interactive Power Oscillation and Its Suppression Strategy for VSG-DSG Paralleled System in Islanded Microgrid

A virtual synchronous generator(VSG)can provide inertial support through renewables and energy storage.It generally operates in parallel with a diesel generator(DSG)in an islanded microgrid.However,unforeseen interactive power oscillations occur in the paralleled system when loads fluctuate.These may also burn out the VSG owing to its low overcurrent capacity.The mechanism and suppression strategy of the power oscillation of a VSG-DSG paralleled system are investigated.It reveals that the interactive power oscillation is caused essentially by the physical difference and parameter mismatch between the VSG and DSG.Then,the elimination condition of oscillation generation is derived.Subsequently,a comprehensive suppression control strategy based on virtual inductance and dynamic mutual damping technology is proposed.Finally,the experimental results verify the effectiveness of the proposed method.

Micro/nano Scale Mechanics and Intelligent Material-The First Creative Research Group in Mechanics

As the first Creative Research Group sponsored by Division of Mechanics of Department of Mathematical and Physical Sciences of NSEC, a project team, including two CAS members （Porf. Kezhi Huang, Prof. Wei Yang） and two Changjiang scholars （Prof. Quanshui Zheng, Prof. Daining Pang） from Tsinghua University, focused their research on ＂Micro/nanoscale mechanics and smart materials＂, and progressed in the following：