Performance improvement of the stochastic-resonance-based tri-stableenergy harvester under random rotational vibration

In this paper,the stochastic-resonance-based tri-stable energy harvester(TEH)is proposed to enhance harvesting performance under random rotational vibration.An electromechanical coupled system interfaced with a standard rectifier circuit driven by colored noise is considered.The stationary probability density function(SPDF)of the harvester is obtained by the improved stochastic averaging.Then,with the adiabatic approximation theory,the analytical expression of signal-to-noise ratio(SNR)for the TEH is deduced to characterize stochastic resonance(SR).To enhance direct current(DC)power delivery from a rotational TEH,the influences of system parameters on SR is discussed.The obtained results suggest that there are damping-induced resonance and noise-intensity-induced SR in the tri-stable system.The TEH has higher harvesting performance under the optimal SR.That is,the optimal parameter combinations can induce optimal SR and maximize harvesting performance.Thus,the stochastic-resonance-based TEH can be optimized to enhance energy harvesting through choosing the optimal parameter.

Effects of the vibrational and rotational excitation of reagent on the stereodynamics of the reaction S (3P) ＋ H2→ SH ＋ H

Quasiclassical trajectory （QCT） calculations are first carried out to study the stereodynamics of the S （3p） ＋ H2 → SH ＋ H reaction based on the ab initio 13Atr potential energy surface （PES） （Lii etal. 2012 J. Chem. Phys. 136 094308）. The QCT-calculated reaction probabilities and cross sections for the S ＋ H2 （v = 0, j = 0） reaction are in good agreement with the previous quantum mechanics （QM） results. The vector properties including the alignment, orientation, and polarization- dependent differential cross sections （PDDCSs） of the product SH are presented at a collision energy of 1.8 eV. The effects of the vibrational and rotational excitations of reagent on the stereodynamics are also investigated and discussed in the present work. The calculated QCT results indicate that the vibrational and rotational excitations of reagent play an important role in determining the stereodynamic properties of the title reaction.

Accurate all-electron calculation on the vibrational and rotational spectra of ground states for O2 and its ions

The potential energy curves, spectroscopic constants, and low-lying vibration–rotation levels of ground-state O2 and its cation O2+ and anion O2- were calculated with the explicitly correlated multireference configuration interaction method.The zeroth-order reference wavefunction was treated with the complete active space multiconfigurational self-consistent field method, in which the active space was carefully selected, and an additional molecular orbital πu was added into the full valence active space.The electron correlation of the 1s core in the oxygen atom was considered in the computations.The Davidson correction on molecular energy was considered to account for higher electron excitation.The relativistic effects, including the scalar relativistic effect and spin–orbit coupling, were considered in the computation of potential energy curves.These physical effects on the spectroscopic constants were examined.The low-lying levels of vibration–rotation spectra of O2 and its ions were determined based on the computed potential energy curves.Comparisons with available experiments were made and excellent agreement was obtained for the vibrational and rotational parameters.The spectroscopic constants and vibration–rotation spectrum of O2-, which is sparse in experiments, were provided.Our study will shed some light on further theoretical and experimental studies on these simple but important molecular systems.

MEASUREMENT OF ANGULAR VIBRATION AMPLITUDE BY ACTIVELY BLURRED IMAGES

A novel motion-blur-based method for measuring the angular amplitude of a high-frequency rotational vibration is schemed. The proposed approach combines the active vision concept and the mechanism of motion-from-blur, generates motion blur on the image plane actively by extending exposure time, and utilizes the motion blur information in polar images to estimate the angular amplitude of a high-frequency rotational vibration. This method obtains the analytical results of the angular vibration amplitude from the geometric moments of a motion blurred polar image and an unblurred image for reference. Experimental results are provided to validate the presented scheme.

Forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by CNTs based on MCST with temperature-variable material properties

In this study, free and forced vibration analysis of nano-composite rotating pressurized microbeam reinforced by carbon nanotubes （CNTs） under magnetic field based on modify couple stress theory （MCST） with temperature-variable material propertiesis presented. Also, the boundary conditions at two ends of nano-composite rotating pressurized microbeam reinforced by CNTs are considered as simply supported. The governing equations are obtained based on the Hamilton＇s principle and then computed these equations by using Navier＇s solution. The magnetic field is inserted in the thickness direction of the nano-composite microbeam. The effects of various parameters such as angular velocity, temperature changes, and pressure between of the inside and outside, the magnetic field, material length scale parameter, and volume fraction of nanocomposite microbeam on the natural frequency and response systemare studied. The results show that with increasing volume fraction of nano-composite microbeam, thickness, material length scale parameter, and magnetic fields, the natural frequency increases. The results of this research can be used for optimization of micro-structures and manufacturing sensors, displacement fluid, and drug delivery.

The active rotary inertia driver system for flutter vibration control of bridges and various promising applications

Active control technology has been investigated and applied in numerous building structures and infrastructures since 1972 when it was firstly introduced into the civil engineering field by Professor JTP Yao.Now,half a century has passed,a variety of control systems have been invented and implemented by researchers and engineers from all over the world.The recent years have witnessed remarkable research attempts and progress devoted to the development in this area based on modern control theory.However,there are still some unknown areas which are worthy of being explored in depth.One of such examples is the application of tuned mass dampers(TMD)to the flutter vibration control of long span bridges.Although applications of TMDs to bridges have been sighted in practice,their genuine effectiveness remains a serious question.The issues relating to how the coupled effect of TMD’s linear force being restricted by the rotational velocity of bridge’s deck during wind excitations which may eventually leads to flutter vibrations,remains unanswered.Such unusual phenomena and limitations were initially discovered and reported by the author sixteen years ago when investigating the barge ship crane hook’s swing motion control.In recent years,the author has invented the active rotary inertia driver(ARID)system which now has been granted patents in China,the US,Europe(including the UK,France,and Germany),Russia,Brazil,India,South Africa,Canada,Australia,Japan and Korean,etc.The ARID is an active control system which could exert direct control torque or moment to the target structures with rotational motions or vibrations natures,including and not limited to buildings,bridges or offshore platforms subjected to winds,earthquakes,and waves excitations.Furthermore,the ARID control system and its methodology can also be applicable to various mechanical systems including but not limited to cranes,vehicles,trains,ships,aircrafts,space crafts,satellites,and robotics.In this paper,the theory,modelling,comprehensive parametric analysis and case study of the ARID system for flutter vibration control of bridges will be discussed,as well as its promising applications in other various occasions.

Quasiclassical trajectory theoretical study on the chemical stereodynamics of the O(~1D)+H_2→OH+H reaction and its isotopic variants (HD, D_2)

The quasiclassical trajectory （QCT） method is used to study stereodynamic information about the reaction O （1D）＋H2 --4OH＋H on the DK （Dobbyn and Knowles） （llA;） ab initio potential energy surface （PES）. A wide scale of collision energy （Ec） from 0.05 eV to 0.5 eV is considered in the dynamic calculations. To reveal the rovibrational excitation effect, calculations at a collision energy of 0.52 eV are carried out for the v = 0 - 5, j = 0 and v = 0, j -- 0 - 15 initial states. The two popularly used polarization-dependent differential cross sections （PDDCSs）, dtY0o/doh （0, 0） and dtra0/dtot（2, 0）, and two angular distributions, P（φr） and P（φr） are calculated to obtain an insight into the alignment and the orientation of the product molecules. From the calculations, we can obtain that the alignment of the OH product is weaker at high collision energy and becomes stronger with the increase of initial vibrational level, and it is almost insensitive to the initially rotational excitation. Influences of the mass values of isotopes （HD, D2） on the stereodynamics are also shown and discussed. Comparisons between available theoretical results and experimental results are made and discussed.

Dynamics of a Rotating Sphere on Free Surface of Vibrated Granular Materials

We investigate the rotational dynamics of a low-density sphere on the free surface of a vertically vibrated granular material（VGM）. The dynamical behavior of the sphere is influenced by the external energy input from an electromagnetic shaker which is proportional to ε,where ε is equal to the ratio between the square of the dimensionless acceleration Γ and the square of the vibration frequency f of the container. Empirical results reveal that as the VGM transits from local-to-global convection,an increase in ε generally corresponds to an increase in the magnitudes of the rotational ω（RS） and translational v（CM） velocities of the sphere, an increase in the observed tilting angle θ（bed） of the VGM bed, and a decrease in the time t（wall） it takes the sphere to roll down the tilted VGM bed and hit the container wall. During unstable convection, an increase in ε results in a sharp decrease in the sphere＇s peak and mean ω（RS）,and a slight increase in t（wall）.For the range of ε values covered in this study, the sphere may execute persistent rotation, wobbling or jamming, depending on the vibration parameters and the resulting convective flow in the system.

Simultaneous measurement of vibration amplitude and rotation angle based on a single-channel laser self-mixing interferometer

Based on a single-channel laser self-mixing interferometcr, we present a new silnultaneous measurement of the vibration amplitude and tile rotation angle of objects that both affect the power spectrum containing two peaks of the interferometer signals. The fitted results indicate that the curve of the peak frequency versus the vibration amplitude follows a linear distribution, and the curve of the difference of the two-peak power values versus the angle follows a Gaussian distribution. A vibration amplitude with an error less than 3.0% and a rotation angle with an error less than 11.7% are calculated from the fitted results.

Calculation of the Neutron Direct Inelastic Scattering cross Section of ~ (238) U

In this work, Rotation model and rotation vibration coupled channel optical model (CCOM) were first used to carry out systematic calculation of neutron direct inelastic scattering cross section (DISCS) for the reaction 238 U (n,n′) with an incident energy from 0 01 MeV to 20 0 MeV . The number of coupled energy levels involved in this calculation increased to eight at the first time, namely 0 +, 2 +, 4 +, 6 +, 8 + in the ground rotation band of 238 U and 1 -, 3 -, 5 - in the octupole vibration band with K=0 -. Some physical problems, such as how to get the optical model parameters of deformed nuclei and phonon amplitudes, are discussed.

Laser cooling of internal degrees of freedom of molecules

Optical pumping techniques using laser fields combined with photo-association of ultracold atoms leads to control of tile vibrational and/or rotational population of molecules. In this study, we review tile basic concepts and main steps that should be followed, including the excitation schemes and detection techniques used to achieve to-vibrational cooling of Cs2 molecules. We also discuss the extension of this technique to other molecules. In addition, we present a theoretical model used to support the experiment. These simulations can be widely used for the preparation of various experiments because they allow the optimization of several important experimental parmneters.