Separate Control of High Frequency Electro-hydraulic Vibration Exciter

The working frequency of the conventional electro-hydraulic vibration exciters,which consist of a servo valve and a hydraulic cylinder,is generally restricted within a narrow range due to limited frequency response capability of the servo valve itself.To counteract such restriction,a novel scheme for an electro-hydraulic vibrator,controlled by a two-dimensional valve（2D valve） and a bias valve in parallel,is therefore proposed.The frequency,amplitude and offset are independently controlled by rotary speed,axial sliding of the spool of the 2D valve and axial sliding of the spool of the bias valve.The principle of separate control was presented and the regulation approach of frequency,amplitude and offset was discussed.A mathematical model of the hydraulic power mechanism for the proposed vibration exciter was established to investigate the relationship between the amplitude and the axial sliding of the 2D valve＇ spool,as well as that between the offset and the axial sliding of the bias valve＇s spool at various frequencies.An experimental system was built to validate the theoretical analysis.It is verified that the 2D exciter is capable of working smoothly in a frequency range of 5- 200 Hz.And its frequency,amplitude and offset can be controlled respectively by either closed loop or open loop method.There is a linear relationship between the output amplitude and the spool axial opening of the 2D valve until a point when the flow rate becomes saturate and the amplitude remains constant.The offset displacement of the cylinder＇s piston is linearly proportional to the axial displacement of the spool of the bias valve,when the valve opening is less than 25%.Thereafter,the slop of the offset curve decreases and tends to saturate.The proposed electro-hydraulic vibration controlled by the 2D valve not only facilitates the realization of high-frequency electro-hydraulic vibration,the high-accuracy of vibration can also be achieved by means of independent controls to the frequency,amplitude and offset.

Crossed Molecular Beam Study of H＋CH4 and H＋CD4 Reactions： Vibrationally Excited CH3/CD3 Product Channels

We study the H＋CH4/CD4-＋H2/HD＋CH3/CD3 reactions using the time sliced velocity map ion imaging technique. Ion images of the CH3/CD3 products were measured by the （2＋1） resonance enhanced multi-photon ionization （REMPI） detection method. Besides the CH3/CD3 products in the ground state, ion images of the vibrationally excited CH3/CD3 products were also observed at two collision energies of 0.72 and 1.06 eV. It is shown that the angular distribution of the products CH3/CD3 in vibrationally excited states gradually vary from backward scattering to sideways scattering as the collision energy increases. Compared to the CH3/CD3 products in the ground state, the CH3/CD3 products in vibrationally excited states tend to be more sideways scattered, indicating that larger impact parameters play a more important role in the vibrationally excited product channels.

Quantitative behavior of vibrational excitation in AC plasma assisted dry reforming of methane

Quantitative behavior of non-equilibrium excitation by direct electron impact in low-temperature dry reforming of methane was investigated by integrated studies of experimental validation and kinetic modeling.A plasma chemistry kinetic mechanism incorporating the reactions involving vibrational excitation of CH4,CO2,H2 and CO molecules as well as the low temperature He/CH4/CO2 conversion pathways was developed and validated.The calculation results showed that at lower E/N values(<150 Td)large population of energized electrons generated in a He/CH4/CO2 discharge resulted in an intensification of vibrational excitation.Despite the large generation of vibration,the vibrationally excited molecules in a 0.5/0.25/0.25 of He/CH4/CO2 discharge mixture were easy to relax,due to the strong coupling of the vibration of different molecules in a gas mixture.The results showed that the moderate levels of the vibrational excitation,such as CO2(v10,11,...,18)and CO(v9,10),presented most efficient in the stimulation of species generation including CO,CH2 O,CH3 OH,C2 H4 and C2 H6.Specifically,under conditions of E/N of 108 Td,14.9%of CO formation was estimated from the recombination of CO2(v)with CH3 and H,CO2(v)+CH3→CH3 O+CO,CO2(v)+H→CO+OH.Also,4.8%of C2 H4 formation was from the recombination reaction CH4(v)+CH→C2 H4+H.These results highlight the strong roles of vibrational states in a complex plasma chemistry system.

Kinetic roles of vibrational excitation in RF plasma assisted methane pyrolysis

A combined experimental and simulational work was carried out in this paper to investigate the kinetic effects of non-equilibrium excitation by direct electron impact on low temperature pyrolysis of CH4 in a RF dielectric barrier discharge.Special attention was placed on the vibrational chemistry of CH4 and some other important products including H2,C2H2,C2H4,C2H6 and C3H8 largely produced in CH4/He discharge under an intermediate reduced electric field ranging 51-80 Td.A detailed kinetic mechanism incorporating a set of electron impact reactions,electron-ion recombination reactions,negative ions attachment reactions,charge exchange reactions,reactions involving vibrationally excited molecules and the relaxation process of vibrationally excited species was assembled and experimentally validated.The modeling results showed a reasonable agreement with the experimentally measured results in terms of CH4 conversion and products production including C2 hydrocarbons and hydrogen.A linear increasing trend of methane conversion with increasing plasma power input was discovered,which suggested a strong dependence of molecular excitation on energy input.Both the CH4/He mole ratio and the reactor temperature play significant roles in CH4 conversion and major products production.The experimental results showed that the selectivity of value-added products C2H4 and H2 keeps essentially unchanged with increasing energy input,mostly because the contribution CH4 ionization and He excitation effectively compete with vibrational excitation and dissociation of CH4 molecule with the E/N value increasing.The calculated results showed that the typical relaxation time of vibrational states is comparable to the gas-kinetics time in a CH4/He discharge mixture,thus the vibrationally excited molecules can significantly accelerate chemical reactions through an effective decrease of activation energy.The path flux analysis revealed that the vibrationally excited molecules CH4(v)and H2(v)enhanced chain propagation reactions,such as CH4(v)+H→CH3+H2,CH4(v)+CH→C2 H4+H,and H2(v)+C→CH+H,further stimulating the production of active radicals and final products.Specifically,H2(v)+C→CH+H was responsible for 7.9%of CH radical formation and CH4(v)+CH→C2 H4+H accounted for 31.4%of total C2 H4 production.This kinetic study provides new sights in demonstrating the contribution of vibrationally excited molecules in RF plasma assisted methane pyrolysis.

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.

Study of highly excited vibrational dynamics of HCP integrable system with dynamic potential methods

Highly excited vibrational dynamics of phosphaethyne(HCP)integrable system are investigated based on its dynamic potentials.Taking into consideration the 2:1 Fermi resonance between H–C–P bending vibrational mode and C–P stretching vibrational mode,it is found that the effects of H–C stretching vibrational mode on vibrational dynamic features of the HCP integrable system are significant and regularly vary with Polyad numbers(P number).The geometrical profiles of the dynamic potentials and the corresponding fixed points are sensitive to the variation of H–C stretching vibrational strength when P numbers are small,but are not sensitive when P numbers become larger and the corresponding threshold values become lower.The phase space trajectories of different energy levels in a designated dynamic potential(P=28)were studied and the results indicated that the dynamic potentials govern the various dynamic environments in which the vibrational states lie.Furthermore,action integrals of the energy levels contained in dynamic potential(P=28)were quantitatively analyzed and elucidated.It was determined that the dynamic environments could be identified by the numerical values of the action integrals of trajectories of phase space,which is equivalent with dynamic potentials.

Effect of ro-vibrational excitation of NeH^+ on the stereodynamics for the reactions H+NeH^+(v=1-3,j=1,3,5) →H_2^++Ne

The stereodynamics of the abstraction reaction H^＋ NeH^＋（v = 1-3,j = 1,3,5） → H2^＋ ＋ Ne is studied theoretically with a quasi-classical trajectory method on a new ab initio potential energy surface [ S J,Zhang P Y,Han K L and He G Z 2012 J.Chem.Phys.132 014303].The effects of vibrational and rotational excitation of reagent molecules on the polarization of the product are investigated.The reaction cross sections,the distributions of P（θr）,P（φr）,and polarizationdependent differential cross sections（PDDCSs） are calculated.The obtained cross sections indicate that the title reaction is a typical barrierless atom（ion）-ion（molecule） reaction.The initial vibrational excitation and rotational excitation of reagent molecules have distinctly different influences on stereodynamics of the title reaction,and the possible reasons for the differences are presented.

Vector correlations study of the reaction N(~2D) + H_2(X^1Σ_g^+) →NH(a^1?) + H(~2S) with different collision energies and reagent vibration excitations

Vector correlations of the reaction N（2D） ＋H2（X1∑g＋） NH（a1△）→ ＋ H（2S） are studied based on a recent DMBE- SEC PES for the first excited state ofNH2 [J. Phys. Chem. A 114 9644 （2010）] by using a quasi-classical trajectory method. The effects of collision energy and the reagent initial vibrational excitation on cross section and product polarization are investigated for v = 0-5 and j = 0 states in a wide collision energy range （10-50 kcal/mol）. The integral cross section could be increased by H2 vibration excitation remarkably based on the DMBE-SEC PES. The different phenomena of differential cross sections with different collision energies and reagent vibration excitations are explained. Particularly, the NH molecules are scattered mainly in the backward hemisphere at low vibration quantum number and evolve from backward to forward direction with increasing vibration quantum number, which could be explained by the fact that the vibrational excitation enlarges the H-H distance in the entrance channel, thus enhancing the probability of collision between N atom and H atom. A further study on product polarization demonstrates that the collision energy and vibrational excitation of the reagent remarkably influence the distributions of P（Or）, P（（Pr）, and P（Or, （Pr）.

A Strategy for Magnifying Vibration in High-Energy Orbits of a Bistable Oscillator at Low Excitation Levels

This work focuses on how to maintain a high-energy orbit motion of a bistable oscillator when subjected to a low level excitation. An elastic magnifier （EM） positioned between the base and the bistable oscillator is used to magnify the base vibration displacement to significantly enhance the output characteristics of the bistable oscillator. The dimensionless electromechanical equations of the bistable oscillator with an EM are derived, and the effects of the mass and stiffness ratios between the EM and the bistable oscillator on the output displacement are studied. It is shown that the jump phenomenon occurs at a lower excitation level with increasing the mass and stiffness ratios. With the comparison of the displacement trajectories and the phase portraits obtained from experiments, it is vMidated that the bistable oscillator with an EM can effectively oscillate in a high-energy orbit and can generate a superior output vibration at a low excitation level as compared with the bistable oscillator without an EM.

High order correlation polarization potential for vibrational excitation scattering of diatomic molecules by low-energy electrons

This paper introduces a correlation-polarization potential with high order terms for vibrational excitation in electron-molecule scattering. The new polarization potential generalizes the two-term approximation so that it can better reflect the dependence of correlation and polarization effects on the position coordinate of the scattering electron. It applies the new potential on the vibrational excitation scattering from N2 in an energy range which includes the ^2Ⅱg shape resonance. The good agreement of theoretical resonant peaks with experiments shows that polarization potentials with high order terms are important and should be included in vibrational excitation scattering.

Effect of reagent vibrational excitation and isotope substitution on the stereo-dynamics of the Ba+HF→BaF+H reaction

Based on an extended London-Eyring-Polanyi-Sato （LEPS） potential energy surface （PES）, the Ba q-HF reaction has been studied by the quasi-classical trajectory （QCT） method. The reaction integral cross section as a function of collision energy for the Ba q- HF --＊ BaF q- H reaction is presented and the influence of isotope substitution on the differential cross sections （DCSs） and alignments of the product＇s rotational angular momentum have also been studied. The results suggest that the integral cross sections increase with increasing collision energy, and the vibrational excitation of the reagent has great influence on the DCS. In addition, the product＇s rotational polarization is very strong as a result of heavy-heavy-light （HHL） mass combination, and the distinct effect of isotope substitution on the stereodynamics is also revealed.

Effects of a reagent’s rotational and vibrational excitations on reaction O(~3P) + H_2 (ν=0,3,j = 0,3,5,7,9,12,15) → OH+H

To investigate the effect of a reagent＇s rotational and vibrational excitations on the stereo-dynamics of the reaction product, the title reaction is theoretically simulated using the quasi-classical trajectory （QCT） method on the 3A~ and 3Aq potentiM energy surfaces （PESs）. The reaction cross section is considered as the only scalar property in this work at four different collision energies. Furthermore the vector properties including two polarization-dependent differential cross sections （PDDCSs）, the angular distributions of product＇ rotational momentum are discussed at one fixed collision energy. Effects of reagents＇ rotational excitation on the reaction do exist regularly.

Enhanced ionization of vibrational hot carbon disulfide molecules in strong femtosecond laser fields

By using a heated molecular beam in combination with a time-of-flight mass spectrometer, we experimentally study the ionization of vibrational-hot carbon disulfide（CS2） molecules irradiated by a linearly polarized 800-nm 50-fs strong laser field. The ion yields are measured in a laser intensity range of 7.0 × 10^（12） W/cm^2–1.5 × 10^（14） W/cm^2 at different molecular temperatures of up to 1400 K. Enhanced ionization yield is observed for vibrationally excited CS2 molecules.The results show that the enhancement decreases as the laser intensity increases, and exhibits non-monotonical dependence on the molecular temperature. According to the calculated potential energy curves of the neutral and ionic electronic states of CS2, as well as the theoretical models of molecular strong-field ionization available in the literature, we discuss the mechanism of the enhanced ionization of vibrational-hot molecules. It is indicated that the enhanced ionization could be attributed to both the reduced ionization potential with vibrational excitation and the Frank–Condon factors between the neutral and ionic electronic states. Our study paves the way to understanding the effect of nuclear motion on the strongfield ionization of molecules, which would give a further insight into theoretical and experimental investigations on the interaction of polyatomic molecules with strong laser fields.

HIGHER VIBRATIONAL EXCITATION OF OH(Х~зП,v)FROM THE REACTION OF O(D)WITH TETRAMETHYLSILANE

The vibrational excited OH(X~ Ⅱ,v=1—4)was observed by time-resolved FTIR emission spectroscopy.The nascent species were produced by a reaction of O(~1D) and Si(CH_3).The effect of beery Si atom blocking the energy migration was identified.

Nonlinear parametrically excited vibration and active control of gear pair system with time-varying characteristic

In the present work, we investigate the nonlinear parametrically excited vibration and active control of a gear pair system involving backlash, time-varying meshing stiffness and static transmission error. Firstly, a gear pair model is established in a strongly nonlinear form, and its nonlinear vibration characteristics are systematically investigated through different approaches. Several complicated phenomena such as period doubling bifurcation, anti period doubling bifurcation and chaos can be observed under the internal parametric excitation. Then, an active compensation controller is designed to suppress the vibration, including the chaos. Finally, the effectiveness of the proposed controller is verified numerically.

Analysis on Pseudo Excitation of Random Vibration for Structure of Time Flight Counter

Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated and coupling random vibration in rocket or shuttle launching,the new staging white noise mathematical model is deduced according to the practical launch environment.This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter（ToFC）.The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level.Considering stiffness of fixture structure,the random vibration experiments are conducted in three directions to compare with the revised PEM.The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained.The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results.The maximum error is within 9%.The reasons of errors are analyzed to improve reliability of calculation.This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.

AN SCF-CI STUDY OF HIGHLY EXCITED VIBRATIONAL STATES OF BENT TRIATOMIC MOLECULES AND ITS APPLICATION TO O_(3)

A self-consistent-field—configuration interaction(SCF-CI)procedure of studying highly excited vibrational states of bent triatomic molecules is suggested and its application to O_3 is investigated.

Vibration transmissibility characteristics of smart spring vibration isolation system

The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.

Influence of vibration on the lubrication effect of a splash-lubricated gearbox

In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the gearbox in a moving reference system is described,as well as computational fluid dynamics(CFD)simulations of the gearbox with different vibration directions.The effects of rotational speed,oil-immersion depth,and different oil-injection volume rates on lubrication and efficiency are discussed.We propose a method of evaluating the internal lubrication condition of a splash-lubricated gearbox and quantitatively compare the effects of different operating parameters on lubrication and efficiency.Finally,our experiment to verify the feasibility of the simulation method is described.The results show that with vibration,the churning loss and oil supply for the bearings are significantly higher than those under static conditions.In addition,among different vibrational directions,lateral vibration has the greatest influence on the lubrication condition and efficiency of the gearbox.For the studied railway-vehicle gearbox,the best lubrication condition is achieved at a rotational speed of 1600 r/min and an oil-immersion depth of two times the tooth height(2.Oh).Rotational speed is the operating parameter that has the most significant effect on the lubrication and efficiencyofthegearbox.