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The vibration level of a cab affects the passenger's ride comfort and safety significantly. It is of great importance to control the vibration level of cabs under various driving conditions. The associated vibration transfer paths of cabs are studied by using a hierarchical analysis method of a parameter index. The multiobjective design analysis is carried out by using the multiparameter joint optimisation design. Further, the optimal control of the cab vibration level is obtained from a full-condition simulation environment. Additionally, a multibody vehicle model is established. The simulation analysis under multiple working conditions is conducted. The optimal parameter distribution of the cab mounting structure was established by analysing the influence of the design parameters and experimental verification. This greatly improves the comfort of the cab. [ABSTRACT FROM AUTHOR]

In order to study the vibration response of reducer of electric vehicle, a model for the reducer is established in ANSYS Motion, a multi-body dynamics software. Firstly, a 3D model of the reducer is built, including such assemblies as its shaft, gears, bearing, and its case. Secondly, based on the finite element model, the modal simulation is carried out. Finally, under the specified operating condition when the motor speed increases from 0 rpm to 10000 rpm, with using the STFT method, the vibration response of the reducer is obtained through the multi-body dynamics simulation. After comparing the simulation results between different marked nodes, the conclusion indicates that this process can calculate the vibration characteristics of the reducer quickly and accurately and can lay the foundation for the structural optimization in terms of vibration and acoustic properties. [ABSTRACT FROM AUTHOR]

Monitoring vibrations (VMs) of the sea-going ships are necessary to measure and control under the Rules for Classification and Construction of Sea-going Ships of some national registers, such as Russian Maritime Register (RMR) of shipping, Edit 2014. The VM is important and necessary for safety marine diesel engine (MDE) in its technical operation at dangerous levels of torsional, axial or lateral vibrations (TVs, AVs, LVs), which appear in practice at some abnormal regimes, especially on the two-stroke MDE and its main propulsion plant (MPP). This paper presents the results of experimental study for monitoring vibration of the four-stroke MDE, and it's MPP in the sea — trail test of the MV.KN168, designed and manufactured by Hong Ha Shipyard (Haiphong, Vietnam, 2017). The vibration signals were measured and analyzed using Multi-channel Measurement and Monitoring Vibration System (MMMVS) made by Vietnam Maritime University (VMU).The vibration research results on the four-stroke MDE of the MV.KN168 indicated that the vibration levels of the every measured position lie in the allowable limitations. [ABSTRACT FROM AUTHOR]

This article presents a method to achieve the vibration response of wheel–rail beam system on the container crane and to reduce the vibration and improve the trolley speed. To investigate the coupled vibration of a trolley–beam dynamic system, the governing equation is excited to obtain the interaction during the trolley travel on the beam at high speed. We studied the wheel–rail beam system in the container crane and as the structure of the container crane is huge, its beam span is more than 80 m long, the trolley runs on the large elastic beam, the beam deformation will have a significant impact on the structure. The dynamic load produced by the trolley acts on the elastic rail of the beam, which makes major deformation and vibration of the beam. To achieve the procedure of large steel structure on coupling vibration response on the container crane, the model of trolley–beam coupling of large-span elasticity beam with finite element methods and using multi-body dynamic simulation is built. Analysis of trolley–beam coupling is made based on the crawl impact of trolley. We found that the trolley with the elastic wire rope has a real-time dynamic loading effect and it changes the coupled vibration features in the operation. Via analysis on crane vibration of different trolley speed and simulation, the actual artificial frame wave is obtained. The excitation response amplitude by horizontal load has been obtained and it has great effect on the transmissibility performance of the container crane. This study shows that the vibration of the wheel–rail beam system cannot be neglected when increasing the trolley speed on the crane. The vibration response features of partial impact on ground point are done when trolley is running. The measures had been found to reduce the vibration of the container crane operating at high speed. [ABSTRACT FROM AUTHOR]

An active vibration control scheme was proposed based on Macro Fiber Composite (MFC) actuators for the bending and torsional vibration control of large flexible lightweight wing structures. Firstly, a finite element modeling and modal analysis of a flexible wing are carried out. Further, the number, type, and location distribution of the MFC actuators bonded on the supported beam of the wing are designed. Then, the actuated characteristics of the two kinds of MFC actuators required for bending and torsional vibration controls was theoretically analyzed. The simulation model of the overall vibration control system was also finally obtained. Finally, through ANSYS simulation analysis, the vibration control effect of the current control system on the first two-order low-frequency modal response of the wing structure is given. The simulation results show that the proposed active vibration control scheme has specific feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

Flexible sensors at small scales have potential applications in many fields. Until now, the research on high-performance vibration sensors based on soft materials with high sensitivity and precision, fast response and high stability are still in its infancy. In this work, a flexible, wearable and high precision film sensor based on multi-walled carbon nanotube (MWCNT) was prepared via a vacuum filtration process and then encapsulated within polydimethylsiloxane (PDMS). The sensor exhibits an ultrahigh sensitivity with gauge factor of 214.3 at flexural strain of 0.4%. When used to monitor the vibration responses of a carbon-fiber beam induced by the base excitation and impact hammer, the time and frequency responses were comparable with the results obtained by the accelerometer, with difference less than 1\!%. In addition, when the MWCNT/PDMS thin film was employed as an electronic skin sensor attached on the human body to detect human activities, the high sensitivity and repeatability demonstrate a great potential application in monitoring human motion. [ABSTRACT FROM AUTHOR]

The structural vibration and dominant vibration characteristics of the machining process of machine tools have an important influence on the machining quality and efficiency. The dominant vibration characteristics are related to two factors: the dynamic characteristics of the machine tool structure and the excitation characteristics of the system. In the dynamic process of structural vibration, the participations of various modes in a certain frequency domain are often different in the vibration process; that is to say, not all modes can be excited equally, only a certain mode or some of the modes may play a major role in the specific processing conditions and dominate. Thus, these modes are called the dominant vibration modes. Therefore, this paper proposes a method of modal response signal prediction and dominant vibration mode identification under the cutting state of machine tool and studies the dominant vibration characteristics of the machine tool structure under cutting conditions. A dynamic system modeling method based on state space and modal decoupling theory is proposed. The Kalman filter algorithm is used to predict the modal response signal of the machine tool during cutting process, and the modal participation degree is analyzed based on the predicted modal response signal. In this way, the dominant vibration mode of the machine tool structure is analyzed. [ABSTRACT FROM AUTHOR]

Pipeline-induced vibration phenomena are caused by waves and currents during the transportation of oil and natural gas pipelines. For this purpose, the multiphysics coupling calculation was employed by considering the influence of fluid flow characteristics in ocean tidal flow environment and mechanical properties of pipeline solid structure on vibration characteristics of S-type pipeline. According to the analysis of the velocity of the fluid domain and the distribution of the stress distribution of the pipeline, combined with the time history and amplitude of the monitoring point and axis of the pipeline, we analyzed the flow-induced vibration response characteristics of the S-transport pipeline. The results show that under the cyclic flow of the two-way tidal basin, the velocity field on the deformation side of the pipeline is lower, the stress at the solid support end is higher than that in the riser region, the time-displacement of the pipeline fluctuates periodically, and the displacement of the pipeline axis increases sharply in the riser pipe section. It exhibits a normal distribution with extreme values at the center of the pipe segment. The maximum single-pass amplitude in the verticality basin is twice that of the parallel basin and the maximum amplitude is about 1D. [ABSTRACT FROM AUTHOR]

Chip and surface roughness (Ra) are the two main problems in ultra-precision machining. In the current research on elliptical vibration cutting (EVC), little is known about the impact of high-frequency tool tip ellipse trajectory deflection on the quality of cutting surfaces. In this paper, effective control of the tool tip ellipse trajectory deflection is achieved by adjusting phase difference. We also explain how tool tip ellipse trajectory changes affect chip and surface roughness. Firstly, an EVC device is optimized to obtain orthogonal vibration output of the tool tip based on the guided wave transmission technique. Secondly, we establish an elliptical trajectory deflection control model of the tool tip. Analysis of the control model shows that (1) when the tool tip amplitude and phase difference are simultaneously adjusted, the tool tip trajectory can be controlled at an angle of deflection with the same elliptical shape; (2) when only phase difference is adjusted, control of the tool tip trajectory is achieved at an angle of deflection with a different elliptical shape. At a phase difference below 90°, elliptical trajectory of the tool tip is considered positive, while at an angle exceeding 90°, the reverse is true. Analysis of cutting characteristics of the tool tip ellipse trajectory deflection controlled by phase difference adjustments and finite element simulation indicate that as the phase difference increases, the continuity of the chip and Ra first becomes better then poorer due to friction force reversal effect. At a phase difference of 60°, elliptical trajectory of the tool tip is positive with an appropriate dynamic plunging angle for optimized quality of the cutting surface. Overall, test results of our cutting experiment are consistent with theoretical reports demonstrating the feasibility and effectiveness of the current work. [ABSTRACT FROM AUTHOR]

Precision milling processes have been widely applied to manufacturing parts in fields including automotive, aerospace, and precision machinery. Vibrations created in the milling process contribute significantly to machining accuracy and quality. While the direct and interaction effects of machining parameters on vibration amplitude have been analyzed statistically, the comprehensive effect considering machine tool non-cutting vibrations has not been fully explored. In this paper, the comprehensive effect of several machining parameters on the process vibration is studied and a cutting vibration signal-based optimization method is proposed. First, taking the frequency response function (FRF) and non-cutting rotating vibration into consideration, the spindle speed–related dynamic load in machining is studied to analyze the influence of machining accuracy. The main factors influencing the process dynamic performance are then studied using orthogonal experimental analysis of the vibration signal in milling. Finally, the comprehensive effect is determined and the optimal selection approach of machining parameters is put forward based on the experimental research of vibration in machining processes. [ABSTRACT FROM AUTHOR]

In this paper, the torsional vibration characteristics of the high-speed and high-power reciprocating compressor shafting is investigated based on the modal superposition method (MSM) and the sensitivity analysis (SA) is implemented for its dynamics modification. Firstly, the torsional vibration system model of the shafting is established by using the finite element method and modern CAD modeling technology. Then, the natural frequencies and mode shapes are solved by transforming the undamped free vibration system into standard eigenvalue problem. The harmonic excitation coefficient matrix is acquired from the periodic non-harmonic excitation by using Fourier expansion. In addition, MSM is used to solve the transient response, and the contribution of each order modal is investigated. Finally, based on SA of natural frequencies relative to structural parameters, a structural dynamics modification is proposed in terms of the actual situation. Results show that the natural frequency of torsional vibration system of the compressor shafting complies with API standard, and resonance hazard will not occur. The major modes that contribute to the torsional vibration response are first three modes, meanwhile the dynamics modification based on SA can effectively suppress the amplitude of torsional vibration. [ABSTRACT FROM AUTHOR]

The aim of the research is to improve knowledge about the behaviour of materials and structures, to develop models and tools useful in the process of design of structures and machines and to capitalize on a technical culture in terms of analysis, design and manufacturing methodologies. We also set out to show the influence of which types of vibrations have an effect on the operation of the crankshaft mechanism of a car engine, as well as their influence on the operation of the camshaft system, all of which are taken into account in any design process in this field. The generalization of the theory of elasticity and the dynamics of viscous fluids led to the creation of the linear theory of viscos-elasticity, the bodies with such a behaviour obeying the principle of overlapping Boltzmann. Thus, mechanical models were built consisting of spring and damping systems, the springs describing the elastic properties of the body, and the dampers on the viscous ones. [ABSTRACT FROM AUTHOR]

In the present research vibration of a porous rectangular plate which is located between two piezo-electromagnetic layers based on two variables sinusoidal shear deformation plate theory and according to nonlocal theory is investigated. The plate is resting on Winkler–Pasternak foundation and was subjected to pre loads. The motion equations have been obtained using Hamilton principle and are solved using analytical Navier's solution method. The effects of porosity coefficient, pores distribution, nonlocal parameter, pre load values, foundation constants and geometric size of the plate have been discussed in details. The results can be used to design more efficient sensors and actuators. [ABSTRACT FROM AUTHOR]

For the integer slot permanent-magnet (PM) driving synchronous motor, the zeroth-mode slot frequency vibration and noise play a significant vibroacoustic role in the low-frequency domain. For conventional analysis in literature, it is usually assumed that the zeroth-mode vibration is caused by the zeroth-order radial force harmonic. But in this paper, the genuine reason for zeroth-mode vibration is proposed and discussed in detail, which is different from the conventional analysis. The teeth chopping effect is proposed and demonstrates that the slot number order radial force is the root of the zeroth-mode vibration of the motor. After the analysis of the zeroth-mode vibration in existing research work is presented, the teeth chopping effect is introduced and described. The amplitudes of the zeroth-order and slot number order forces are compared with an analytical method, while their amplitudes and caused deformations of these forces are calculated with the finite-element method (FEM). Finally, to validate the analytical and FEM results, a 6-pole 36-slot PM driving motor is manufactured and tested, and the results are in good agreement with those of the FEM results. [ABSTRACT FROM AUTHOR]

This paper proposes a scheme to control the low-frequency vibration of pipelines by using magneto-rheological (MR) vibration reduction technology. The state equation and the transfer function of the pipeline system are established, and its stability and the sinusoidal excitation response are analyzed. The prototype of MR damper is developed. The dynamic characteristics of MR damper are tested and the double-sigmoid model of MR damper is established. The two-state control, Proportion Integration Differentiation (PID) control and sliding-mode-variable-structure (SMVS) control methods of pipeline vibration using MR damper are analyzed comparatively, and the vibration control laws are deduced. The simulation analyses are carried out to predict the control effect of different pipeline vibration control algorithms. The verification tests through a semi-active measurement and control platform are carried out, and the feasibility and applicability of different pipeline vibration control strategies are analyzed. The test results show that the three kinds of pipeline vibration control methods based on MR damper can effectively control the pipeline vibration. Especially, SMVS control has the best vibration control effect, the pipeline amplitude drop and the acceleration drop can reach 22.31 dB and 16.34 dB respectively, while the amplitude attenuation rate and the acceleration attenuation rate can reach 92.34% and 84.77%, respectively. [ABSTRACT FROM AUTHOR]

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Stick-slip of the drill string, as one of the critical factors affecting drilling efficiency, has always been a hot topic for experts and scholars in related fields. Serious stick-slip vibration affects the well construction efficiency, drilling cost and even lead to a downhole accident. Therefore, based on the current research, this paper takes a new type of composite vibration tool as the research object, studies the working mechanism of the tool and analyzes the effect of stick-slip reduction. After establishing the multi-degree-of-freedom torsional dynamics model, we obtained the results of torsional vibration dynamics by cases analysis based on working conditions and related mechanical parameters. In addition, the results of the examples, compared with the field experimental data, verify that the vibration shock generated by the new composite tool can effectively reduce the torque fluctuation range of the system, avoid the occurrence of stick-slip phenomenon, improve the ROP (rate of penetration), and make drilling process more stable. This paper can provide reference for the optimization and development of stick-slip technology in drilling engineering, and the theoretical methods can also be developed to study the dynamics of drill string. [ABSTRACT FROM AUTHOR]

In order to research the impact of the vibration on working stability of the vibration compaction system (VCS) and increase the paver's performance, the acceleration responses at the screed surface under the excitation frequencies of the tampers and vibration screed are analyzed via the root mean square acceleration responses (RMSAR) at the bottom of the screed surface. A non-linear dynamic model of the VCS is then established to research the impact of the VCS's dynamic parameters on the performance of paver via the objective functions of the vertical, pitch and roll RMSAR of the vibration screed. The dynamic parameters are then optimized based on a multi-objective genetic algorithm to enhance the paver's performance. The experiment and simulation results show that the dynamic parameters greatly affect the paver's performance. The compression performance is quickly increased, while the working stability and paving quality are reduced with increasing the angular deviations of tampers and excitation frequencies of both the tampers and vibration screed and vice versa. Also, the paver's performance is significantly improved by using the optimal parameters of the VCS. [ABSTRACT FROM AUTHOR]

Nowadays, two-stage mounting system having integral intermediate mass is widely applied and researched to attenuate vibration of marine machinery equipment, while two stage mounting system having distributed intermediate mass which has the feature of lightweight and installation dimension is rarely used and studied. The theoretical models of two types of mounting systems are set up and force transmissibility rate of the two mounting systems are deduced through four-pole parameters method. A scale experimental prototype is established to test the isolation efficiency of the two-stage mounting system having distributed intermediate mass. FEMs of the two systems are established to make a comparison ascertaining the difference between the two about vibration isolation efficiency at the different frequency. The result shows that two stage mounting system having distributed intermediate mass achieve better vibration isolation efficiency and take less space than two-stage mounting system having integral intermediate mass if with equivalent intermediate mass. Two-stage mounting system having distributed intermediate mass can meet the requirements of practical projects and provides a new way for engineer to refer to when meet with machinery equipment vibration problems. [ABSTRACT FROM AUTHOR]

Large thin-walled parts are widely utilized in many different fields such as aircraft manufacturing. However, the vibration caused by the milling force during processing unfortunately affects the processing quality. To reduce the vibration, a multi-point flexible following support head is proposed, which can adjust the supporting force in mirror milling in real time. By installing the milling cutter and support head at the end of the milling robot and support robot, respectively, and allowing them to symmetrically move during processing, the vibration of the thin-walled parts can be suppressed. In this study, the supporting force equations of the multi-point flexible following support head are established. Then, the vibration response of the thin-walled part with two clamped edges and two free edges (CCFF plate) under alternating external loads is analyzed, and the simulation model of the mirror milling vibration is established. The simulation is carried out under the milling condition with and without the support head to verify the vibration suppression effect of the support head. Finally, the mirror milling experiment verifies that the multi-point flexible following support head can decrease the amplitude by 98% compared with milling without a support head, and the processing quality is significantly improved. [ABSTRACT FROM AUTHOR]

This paper aimed to study the longitudinal vibration characteristics of the 5000 m mining pipe in the ocean under different working wind conditions, offset angle, damping, and ore bin weight. Based on the finite element method, the mining pipe is simplified into beam element and discretized, and the physical and mathematical models of the mining pipe system are established. The Wilson-θ direct integral method is adopted for numerical calculation. The results show that the longitudinal vibration of the mining pipe is irregular, which presents the phenomenon of oscillation. The vibration amplitude decreases first and then increases from top to bottom, the minimum vibration amplitude appears at 1000 m, and the maximum vibration amplitude appears at the top of the mining pipe. Under the same working wind condition, the overall longitudinal vibration amplitude of the mining pipe can be increased by increasing the ore bin weight and the offset angle, but neither of them can change the frequency of the longitudinal vibration. The closer the excitation frequency generated by different working wind conditions is to the natural frequency, the larger the mining pipe longitudinal vibration amplitude is. The closer the vibration frequency generated by the same excitation frequency is to the natural frequency, the stronger the vibration intensity is, and when damping is added, the vibration intensity decreases faster. [ABSTRACT FROM AUTHOR]

With the development of ship enlargement, the problems of coupling vibration between hull and propulsion system and vibration transmission via bearings are more and more prominent. Based on the theory of shaft vibration and the experimental system for dynamic characteristics of the shaft, an experiment plan about propulsion shaft vibration under dynamic excitations is designed in this paper. The performance of propulsion shaft vibration under hull deformation excitations applied on intermediate and stern bearings is studied. Hydraulic excitations in horizontal and vertical directions on the intermediate bearing and stern bearing of the experimental model of propulsion shaft are considered in this paper to simulate hull deformation on bearings of the ship. Vibration characteristics of the shaft under different excitations are gained and coupling effects are discussed. Moreover, the influences of amplitude and direction of excitations on bearings and the shaft rotation speed on the vibration of propulsion are studied. The results show that aiming at improving the safety and reliability of navigation, the hull deformation, especially the horizontal hull deformation excitation on the intermediate bearing, is not neglectable and should be considered during primary design. Also, rotation speed and resonant frequency are needed to be well designed with the frequencies of hull deformation excitations. [ABSTRACT FROM AUTHOR]

In this paper, we find the violent vibration of the hot rolling mill is induced by the combination of the screw-down system and the strip, explain how the srew-down-strip combined excitation effects the rolling mill, and introduce an effective method to restrain the vibration. First, two experiments, stripless rolling and turning off the screw-down system, are conducted, the first experiment simulates the rolling process without strip and the second experiment simulates the rolling process without the screw-down system, the results indicate that the rolling mill vibration is induced by the srew-down-strip combined excitation. Then, to explain this phenomenon, the mathematical model of the rolling mill under screw-down-strip combined excitation is proposed, we find that few excitation frequency components can induce more response frequency components, therefore it's more possible to approach the natural frequency of the rolling mill. Finally, a vibration suppression method is introduced by eliminating some specified frequency components of the screw-down system with a filter, and the result shows that the vibration decreased by 98.7 %. [ABSTRACT FROM AUTHOR]

This paper presents a study on the natural vibration of circular double-layer graphene sheets (DLGSs) using circular plate theory. The circular DLGSs are assumed to be coupled together through the carbon-carbon van der Waals (vdW) force between their two layers. An analytical solution of coupled governing equations is proposed to predict the natural frequencies of circular DLGSs. The vibration behaviors in circular DLGSs are found to have an in-phase mode (IPM) associated with the classical natural frequency, and an anti-phase mode (APM) owing to the influence of the vdW interaction. The natural frequencies of the IPM are independent of vdW interactions between adjacent layers, while those of the APM depend on the vdW interaction, and are larger. Based on the exact solution, the influences of wavenumbers (m, n) on the natural frequencies of simply supported circular DLGSs are also investigated in detail. [ABSTRACT FROM AUTHOR]

We investigated the vibration properties of integrated nanostructure on crystalline surface. The embedded chain of molecules is parallel to y-axis and takes three different positions: top, hollow, and bridge. The vibrational dynamics of the structure is considered within the harmonic approximation framework. The evanescent and propagating vibrational field of the perfect lattice is determined and interpreted. The presence of the diatomic molecule chain breakdown the translation symmetry in one direction, and gives rise to localized states on its neighborhood. Our study is based on the matching method and the Green functions, the spectral and state densities associated to localized modes are determined and calculated numerically. Our results show that the presence of the inhomogeneity contribute to the creation of new branches of localized vibrational modes, and their number and feature depend strongly on structural parameters of the system and the position of the diatomic chain. [ABSTRACT FROM AUTHOR]

The effect of a lateral electric field on a donor impurity confined in a thin quantum disk is studied theoretically in the framework of mass approximation and using the Ritz variational approach. We show that the binding energy depends on several parameters: the dot size, the position of the donor impurity, the lateral field strength, and its orientation relative to the axis containing the impurity. When the impurity is located at one edge and the electric field is oriented in the opposite direction, the binding energy is considerably reinforced due to the simultaneous additive effects of coulombic potential and electrostatic force. The competition between these effects modifies considerably the probability densities and allows a better comprehension of the binding energy variations. This interesting behavior can contribute to an better understanding of the experimental optical response. [ABSTRACT FROM AUTHOR]

The results of the studies of the propagation of plane harmonic waves and vibrations in an isotropic, elastic solid layer with atomic point defects (interstitial atoms, vacancies, and electron-hole pairs) generated by a pulsed laser beam are presented. The study is based on coupled evolution equations for the elastic displacement of the medium and atomic defect density fields. The defect dynamics are governed by the strain-stimulated generation, diffusion, and annihilation processes. The frequency equations corresponding to the symmetric and antisymmetric elastic-concentration modes of vibration of the layer are obtained. Some limiting cases and special cases of the frequency equations are considered and a procedure for determining the phase velocity and the attenuation (or amplification) constants is discussed. [ABSTRACT FROM AUTHOR]

Point defect cavity was constructed in a two-dimensional phononic crystal plate. It was excited by a small piezo chip in the cavity, and the vibrations of each point defect mode were detected by an optical interferometer. Point defect modes on 2D phononic crystal plate in vacuum, air, and with water loaded were investigated theoretically and experimentally. It is shown that the Q factors of the point defect modes are determined by inner attenuation, bandgap effects, and medium. The SSS mode (breathing mode) has highest Q factor in vacuum and air among nine modes thanks to low inner attenuation and low energy leakage. By selectively loading the PC with water on one side, the point defect modes with shear movement surfaces suffer lower attenuation and still have rather high Q factors. These conclusions will help to design a new kind of resonator or sensor. [ABSTRACT FROM AUTHOR]

Hyper-Raman scattering is used to investigate the vibrations in two prototypical relaxors, PbMg1/3 Nb2/3 O3 and PbMg1/3 Ta2/3 O3 (PMT). First-order scattering from polar modes is clearly observed. Most of the triply-degenerate cubic vibrations are split into doublets and their frequencies compare very well to that of PbTiO3 in its tetragonal phase. Their shape and scattering intensities are sensitive to the local chemical ordering and ferroelectric distortions. For example, the tendency toward 1:1 local ordering on the B-site in PMT is clearly evidenced. These results demonstrate the strong potentiality of hyper-Raman scattering as structural probe of complex perovskites. [ABSTRACT FROM AUTHOR]

In recent years, the concept of utilizing the phenomenon of vibration mode-localization as a paradigm of mechanical sensing has made profound impact in the design and development of highly sensitive micro- and nanomechanical sensors. Unprecedented enhancements in sensor response exceeding three orders of magnitude relative to the more conventional resonant frequency shift based technique have been both theoretically and experimentally demonstrated using this new sensing approach. However, the ultimate limits of detection and in consequence, the minimum attainable resolution in such mode-localized sensors still remain uncertain. This paper aims to fill this gap by investigating the limits to sensitivity enhancement imposed on such sensors, by some of the fundamental physical noise processes, the bandwidth of operation and the noise from the electronic interfacial circuits. Our analyses indicate that such mode-localized sensors offer tremendous potential for highly sensitive mass and stiffness detection with ultimate resolutions that may be orders of magnitude better than most conventional micro- and nanomechanical resonant sensors. [ABSTRACT FROM AUTHOR]

We consider the localized vibrational modes that can exist at the edge of a semi-infinite plate and at the end of a semi-infinite bar of small thickness. It is known that for certain special values of Poisson’s ratio σ these modes are perfectly localized, are uncoupled to bulk modes, and thus do not lose energy by acoustic radiation. We show that for other values of σ it is possible to modify the shape of the end of the plate or bar in a way such that a perfectly localized edge mode is formed. Finally, we discuss the effect of this localization phenomenon on the vibrational modes of plates and bars of finite length. [ABSTRACT FROM AUTHOR]

The damping behavior of bent fiber near-field scanning optical microscopy (NSOM) probes operating in tapping mode oscillation is investigated in air and water. We show that the significant drop in probe quality factor Q, which occurs at the air-water interface, is due to meniscus damping. As the probe is immersed in water viscous damping adds to the meniscus damping. Damping effects which lead to a progressive drop in the peak tapping mode resonance frequency are accounted for by additional torsional modes of probe vibration. Understanding the damping processes should lead to the design of high sensitivity NSOM probes for scanning soft biological samples under liquid. [ABSTRACT FROM AUTHOR]

A precise knowledge of the frequency responses, velocity dispersion, and distinct vibration modes in multilayer piezoelectric structures would permit the optimization of new designs for electromechanical sensor, actuator, and surface acoustic wave (SAW) filter devices under broad and narrow band conditions. In this paper, the singular-value decomposition technique, combined with the global matrix method and scaling procedure, are applied for studying the solutions of shear stationary waves in symmetric multilayer composite piezoelectric systems. This approach eliminates numerical instabilities sometimes appearing in the analysis of this type of piezoelectric systems, by using a multiple scaling strategy in the global matrix processing. The dispersion curves of the surface velocities, obtained by application of the proposed approach, have shown the presence of clearly separated odd and even bands in such a type of piezoelectric devices, which is explained by considering the eigenstates of the system. Details of this bands pattern are calculated and analyzed. [ABSTRACT FROM AUTHOR]

In this paper, we presented a modified rectangular cymbal transducer used as the vibration energy harvesting device based on 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 single crystal. The vibration modes of the device were analyzed and the electrical properties were studied systematically. Under a cyclic force of 0.55 N (peak value), a high peak voltage of 45.7 V and maximum power of 14 mW were measured at 500 Hz with a proof mass of 17.0 g. The power density of the transducer is more than three times as high as that of the Pb(ZrxTi1-x)O3 (PZT) ceramic cymbal transducer. The results demonstrate the potential of the device in energy harvesting applied to low-power portable electronics and wireless sensors. [ABSTRACT FROM AUTHOR]

This paper reports on structural, optical, vibrational, and morphological properties of cobalt-doped CdS thin films, prepared by 90 keV Co+ implantation at room temperature. In this work, we have used cobalt concentration in the range of 0.34–10.8 at. %. Cobalt doping does not lead to the formation of any secondary phase, either in the form of metallic clusters or impurity complexes. However, with increasing cobalt concentration a decrease in the optical band gap, from 2.39 to 2.26 eV, is observed. This reduction is addressed on the basis of band tailing due to the creation of localized energy states in association with Urbach energy calculations. In addition, implantation gives rise to grain growth and increase in the surface roughness. Size and shape fluctuations of individual CdS grains, at higher fluences, give rise to inhomogeneity in strain. The results are discussed in the light of ion-matter interaction in the keV regime. [ABSTRACT FROM AUTHOR]

Cobalt micromagnetic particles with an average size of ≈1.6 μm and varying total mass of the powder were assembled on patterned media with perpendicular magnetization by acoustic vibrations onto designed shapes reflecting the primary material. The replicas were studied with scanning electron microscopy, vibrating sample magnetometry, and ferromagnetic resonance spectroscopy. Their properties were significantly influenced by the shape anisotropy induced through the parent molds. A tendency in the development of the physical characteristics of the replicas was observed as their geometrical parameters changed. [ABSTRACT FROM AUTHOR]

Free vibrations of zigzag single-wall carbon nanotubes (SWCNTs) of aspect ratio (length/diameter) ∼6 and with ends traction-free have been studied using molecular mechanics (MM) simulations with the MM3 potential. It is found that the frequencies of inextensional (the Love and the Rayleigh) modes of an (n, 0) SWCNT saturate at the circumferential wave number of either (n-1)/2 or n/2 where n is odd or even. This is explained in terms of its molecular structure. Since the frequencies of the inextensional modes of vibration of a thin cylinder made of an isotropic linear elastic material do not saturate with an increase in the circumferential wave number, a continuum structure cannot represent all modes of vibration of a zigzag SWCNT. This result is independent of the value assigned to the wall thickness of the SWCNT. We have also found values of material and geometric parameters of a shell and a hollow cylinder by equating their frequencies of the inextensional, the radial breathing, the axial and the torsional modes of vibrations to the corresponding ones of a zigzag SWCNT, and by taking their mean diameter and length equal to those of the SWCNT. The frequencies of the extensional modes of oscillations of the two continuum structures for various axial half wave numbers and circumferential wave numbers are found to match well with those of the SWCNT obtained from the MM simulations. However, the frequencies of the inextensional modes of the continuum structures deviate noticeably from those of the SWCNT, and this deviation increases with an increase in the circumferential wave number. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effect of material property changes in the spinal components on the resonant frequency characteristics of the human spine. Several investigations have reported the material property sensitivity of human spine under static loading conditions, but less research has been devoted to the material property sensitivity of spinal biomechanical characteristics under a vibration environment. A detailed three-dimensional finite element model of the human spine, T12- pelvis, was built and used to predict the influence of material property variation on the resonant frequencies of the human spine. The simulation results reveal that material properties of spinal components have obvious influences on the dynamic characteristics of the spine. The annulus ground substance is the dominant component affecting the vertical resonant frequencies of the spine. The percentage change of the resonant frequency relative to the basic condition was more than 20% if Young's modulus of disc annulus is less than 1.5 MPa. The vertical resonant frequency may also decrease if Poisson's ratio of nucleus pulposus of intervertebral disc decreases. [ABSTRACT FROM AUTHOR]

We report the energy dependence of strong collisions of CO2 with highly vibrationally excited azulene for two initial energies, E=20 390 and 38 580 cm-1. These studies show that both the distribution of transferred energy and the energy transfer rates are sensitive to the azulene energy. Highly excited azulene was prepared in separate studies by absorption of pulsed excitation at λ=532 or 266 nm, followed by rapid radiationless decay from S1 or S4 to vibrationally excited levels of the ground electronic state. The appearance of scattered CO2 (0000) molecules with Erot>1000 cm-1 was monitored by high-resolution transient IR absorption at λ=4.3 μm. The average rotational and translational energies of the scattered CO2 molecules double when the azulene energy is increased by a factor of 2. The rate of energy transfer in strong collisions increases by nearly a factor of 4 when the azulene energy is doubled. The energy transfer probability distribution function for ΔE>3000 cm-1 at each initial energy is an exponential decay with curvature that correlates with the energy dependence of the state density, in excellent agreement with predictions from GRETCHEN, a model based on Fermi’s golden rule to describe collisional quenching of highly excited molecules. [ABSTRACT FROM AUTHOR]

We report the energy dependence of strong collisions of CO2 with highly vibrationally excited azulene for two initial energies, E=20 390 and 38 580 cm-1. These studies show that both the distribution of transferred energy and the energy transfer rates are sensitive to the azulene energy. Highly excited azulene was prepared in separate studies by absorption of pulsed excitation at λ=532 or 266 nm, followed by rapid radiationless decay from S1 or S4 to vibrationally excited levels of the ground electronic state. The appearance of scattered CO2 (0000) molecules with Erot>1000 cm-1 was monitored by high-resolution transient IR absorption at λ=4.3 μm. The average rotational and translational energies of the scattered CO2 molecules double when the azulene energy is increased by a factor of 2. The rate of energy transfer in strong collisions increases by nearly a factor of 4 when the azulene energy is doubled. The energy transfer probability distribution function for ΔE>3000 cm-1 at each initial energy is an exponential decay with curvature that correlates with the energy dependence of the state density, in excellent agreement with predictions from GRETCHEN, a model based on Fermi’s golden rule to describe collisional quenching of highly excited molecules. [ABSTRACT FROM AUTHOR]

The use of vibration as a training intervention has been suggested for more than a decade. Following the initial promising studies, a large number of investigations have been conducted to understand the acute and chronic effects of this novel training modality mainly using special populations, sedentary, physically active, and aged individuals. There is a small number of studies involving athletes. For this reason it is at the moment very difficult to provide safe and effective training guidelines to athletes. We discuss the current findings related to the effectiveness on elite athletes and provide some guidance on practical applications. Vibration is without a doubt an interesting intervention; however, more needs to be done to understand the physiological mechanisms involved in the adaptive responses to vibration exercise. Furthermore, more studies are needed to establish a doseresponse relationship to vibration training to provide indications on safe and effective vibration training prescriptions. [ABSTRACT FROM AUTHOR]

• The combination of numerical simulation and test methods is considered. • A new set of evaluation methods for the leakage acceleration signal is proposed. • The influence of pressure and leakage size on acceleration signal is investigated. • Joint time domain and frequency domain to evaluate leakage acceleration signal. • Multiple characteristic frequencies are used to characterize the leakage signal. In the leak detection of water pipelines, interference and environmental noise directly affect the effectiveness of leak detection and the accuracy of leak point location, so it is necessary to study the real signal. Previous studies mostly rely on a single test to improve the positioning accuracy by collecting vibration signals for denoising, but denoising will also affect the real signal, and the actual detection situation is complex, so it is difficult to deal with all working conditions only through the test. With the rapid development of computer technology, the combination of numerical simulation and experiment is expected to solve this problem. Therefore, this paper takes the acceleration signal as the research object, collects and simulates the leakage signals under different pressure strengths by combining experiments with numerical simulation, and verifies the feasibility and accuracy of a numerical simulation model. The generation of leakage vibration acceleration under different pressure and different leakage hole radius is simulated. Research findings: a. the leakage signal energy has a power function relationship with the pressure and an exponential function relationship with the leakage radius; b. the characteristic frequency is the variable of the characteristics of pipeline and leakage hole, which is independent of the pressure; c. the power of each peak frequency has a step-by-step change trend with the energy of the signal; d. the power of acceleration signal concentrates to a higher frequency with the increase of pressure and the decrease of leakage radius. This study provides a basis for identifying, detecting, and extracting leakage signals in a real noise environment, helps to improve the accuracy of acoustic emission signal detection, and can provide a theoretical basis for pipeline leakage detection research. [ABSTRACT FROM AUTHOR]

In aero-engine, spatially parallel pipelines are prone to damage under the harmonic excitation produced by rotors, thus there is an urgent need for vibration reduction research. This paper presents a finite element modeling method for parallel pipelines based on pipe-solid element coupling and performs clamp layout optimization with the objective of reducing the stress response. The modeling idea can be described as follows: the regions of the pipeline with higher stress, such as single and dual clamps and bend sections, are modeled using solid elements, while other regions are modeled using pipe elements, and the different parts are coupled together to complete the overall modeling. An optimization model is created with clamp positions as design variables and the objective function is set as reducing stress response under the resonance condition of the fundamental frequency excitation. The procedure for solving the optimization model is provided based on genetic algorithms. A case study is conducted on a parallel pipeline system with one dual clamp and four single clamps. The rationality of the created spatial parallel pipeline model based on pipe-solid element coupling is demonstrated through a constructed pipeline test system. The model is shown to provide sufficient accuracy while having higher computational efficiency compared with a full 3D solid element model. Furthermore, the stress reduction optimization is performed, and a clamp layout that minimizes the maximum resonant stress of the parallel pipeline system is obtained. • A dynamic model of spatial parallel pipeline based on pipe-solid elements coupling is established. • By changing the material parameters of the local structure (metal rubber) to replace the bolt pre-tensioning effect. • Based on the adjustment of clamps layout, an optimization model with the goal of stress reduction established. • The correctness of the basic model is verified by experiments, and the optimization model is solved and analyzed. [ABSTRACT FROM AUTHOR]

• Reveal the vibration change process of the converter transformer under charging closing and no-load operation. • Both charging closing and tap changer switching will produce shock vibration, and no-load vibration will be affected by excitation inrush current, voltage and winding turns. • The characteristic parameters of pulse factor, offset factor and odd-even harmonic ratio are proposed to identify different no-load operating states. The converter transformer plays a key role in the HVDC transmission project. It will be put back into the power grid after a power outage for maintenance. The transient overvoltage and excitation inrush current during charging and closing will cause shock vibration and affect the stability of the internal mechanical structure. In addition, the on-load tap-changer (OLTC) shifting operation after closing will also lead to changes in the vibration characteristics. Because of insufficient research on vibration during closing transient and no-load operation, this paper measures the transient vibration change process during no-load closing and tap-changer action in a ± 800 kV converter station. Furthermore, the influence of voltage and winding turns changes on no-load vibration is also analyzed, and multi-characteristic parameters of vibration impulse factor, offset factor, and odd–even harmonic ratio are extracted to realize no-load state identification. The results show that the no-load vibration increases with the increase of the voltage, and decreases with the increase of the number of turns of the grid-side winding. More importantly, both the charging closing and the tap-changer action will produce vibration and shock components, and the maximum transient vibration exceeds 90 m/s2, which is 35.7 times that of the steady-state. Odd harmonic components of 50 Hz, such as 150 Hz, 250 Hz, etc., will appear in the vibration spectrum under the action of the 2nd, 4th, and other even harmonics in the excitation inrush current. While the non-excitation inrush current is mainly an even multiple of 50 Hz. The research results reveal the vibration characteristics of the converter transformer during closing transient and no-load operation, and provide a theoretical reference for the evaluation and identification of the converter transformer under all operating conditions. [ABSTRACT FROM AUTHOR]

The development of full-field, accurate vibration testing techniques has been vastly valued by the academic and engineering community. However, due to the limited data transmission speed of digital cameras, the contradiction between speed and resolution remains in the traditional full-field vibration measurement systems based on image measurement, failing to acquire high-resolution images at high-speed simultaneously. In this paper, a high-speed and high-resolution full-field vibration displacement measurement system is established based on the grid CCD moiré method. A periodic grid is arranged on the surface of the sample as a deformation carrier, and the periodic pixel of the digital camera is used as a reference grating that 'enlarges' the grid on the surface of the sample to form a grid CCD moiré with a geometry significantly larger than the original, capturing images for deformation analysis. This approach lowers the requirement of digital image resolution for high-resolution deformation measurement, reducing the contradiction between speed and resolution in full-field vibration measurement. In this paper, the principle and implementation of full-field vibration measurement using the CCD moiré method are introduced, and the experiment results of full-field in-plane vibration displacement measurement are included, verifying the effectiveness and reliability of the system. • A full-field vibration displacement measurement system is established based on CCD moiré method. • A series of experiments are used to verify the measurement accuracy and advantages of the grid CCD moiré method. • An experimental study of in-plane full-field vibration displacement measurement based on the CCD moiré method is conducted. [ABSTRACT FROM AUTHOR]

The geometries and the harmonic vibrational frequencies have been computed for the N[sub 3][sup +](X [sup 3]Σ[sub g][sup -],ã [sup 1]Δ[sub g],b [sup 1]Σ[sub g][sup +],Ã [sup 3]Π[sub u],1 [sup 1]Π[sub u]), N[sub 3][sup ·](X [sup 2]Π[sub g],Ã [sup 2]Σ[sub u][sup +],1 [sup 2]Σ[sub g][sup +]), and N[sub 3][sup -](X [sup 1]Σ[sub g][sup +]) systems using the full-valence complete active space self-consistent-field (CASSCF) vectors. The systems N[sub 3][sup +](Ã [sup 3]Π[sub u],1 [sup 1]Π[sub u]) and N[sub 3][sup ·](X [sup 2]Π[sub g]) possess two distinct real frequencies for the bending modes. The energy for both components increases upon bending and these states are subject to the type A Renner–Teller effect. The energetics and the dynamical properties have been studied at the complete active space second order perturbation theory (CASPT2) and the multireference singles and doubles configuration interaction (MRSD–CI) levels of theory. The spin–orbit coupling constants, A[sub SO] in N[sub 3][sup +](Ã [sup 3]Π[sub u]) and N[sub 3][sup ·](X [sup 2]Π[sub g]) are obtained by employing the atomic mean field spin–orbit Hamiltonian and these are about 3 cm[sup -1] from the experiment. The nuclear quadrupole coupling constants at various nitrogen centers have been predicted in all the systems by employing the CASSCF, the CASPT2 and the MRSD–CI-ino (iterative natural orbital procedure) methods. The magnetic hyperfine coupling constants (hfcc’s) have been computed for the various [sup 14]N’s in N[sub 3][sup +](X [sup 3]Σ[sub g][sup -],Ã [sup 3]Π[sub u]) and N[sub 3][sup ·](X [sup 2]Π[sub g],Ã [sup 2]Σ[sub u][sup +],1 [sup 2]Σ[sub g][sup +]) at the configuration selected MRSD–CI-ino level of theory using weighted threshold criteria for the configuration selection. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Vibrational predissociation spectroscopy is used to obtain infrared spectra of the Cl[sup -]–C[sub 6]H[sub 6], Br[sup -]–C[sub 6]H[sub 6], and I[sup -]–C[sub 6]H[sub 6] complexes in the region of the benzene CH stretch vibrations (2800–3200 cm-1). The infrared spectra of the three dimers are similar, each exhibiting several narrow bands (full width at half maximum <10 cm-1) that are only slightly redshifted from the absorptions of the free benzene molecule. Ab initio calculations predict that the most stable form of the three complexes is a planar C[sub 2v] structure in which the halide is hydrogen bonded to two adjacent CH groups. The planar C[sub 2v] structure in which the halide is linearly H bonded to a single CH group is predicted to be slightly less stable than the bifurcated form. Comparisons between experimental and theoretically predicted infrared spectra confirm that the bifurcated structure is indeed the most stable conformer for all three complexes. Ab initio calculations show that the electron density transfer from the halide to the benzene is not limited to the σ*(CH) orbitals adjacent to the halide, but extends to the σ domain of the benzene ring, consistent with the moderate shift of the CH stretch frequencies. The presence of weak satellite bands is explained in terms of Fermi resonances reminiscent of the benzene Fermi tetrad or hot bands involving the in-plane intermolecular bend vibration. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Experimental and theoretical studies explore the reactivity of the symmetric and the antisymmetric stretching vibrations of monodeuterated methane (CH[sub 3]D). Direct infrared absorption near 3000 cm[sup -1] prepares CH[sub 3]D molecules in three different vibrationally excited eigenstates that contain different amounts of symmetric C–H stretch (ν[sub 1]), antisymmetric C–H stretch (ν[sub 4]), and bending overtone (2ν[sub 5]) excitation. The reaction of vibrationally excited CH[sub 3]D with photolytic chlorine atoms (Cl, [sup 2]P[sub 3/2]) yields CH[sub 2]D products mostly in their vibrational ground state. Comparison of the vibrational action spectra with the simulated absorption spectra and further analysis using the calculated composition of the eigenstates show that the symmetric C–H stretching vibration (ν[sub 1]) promotes the reaction seven times more efficiently than the antisymmetric C–H stretching vibration (ν[sub 4]). Ab initio calculations of the vibrational energies and eigenvectors along the reaction coordinate demonstrate that this difference arises from changes in the initially excited stretching vibrations as the reactive Cl atom approaches. The ν[sub 1] vibration of CH[sub 3]D becomes localized vibrational excitation of the C–H bond pointing toward the Cl atom, promoting the abstraction reaction, but the energy initially in the ν[sub 4] vibration flows into the C–H bonds pointing away from the approaching Cl atom and remains unperturbed during the reaction. A simple model using vibrational symmetries and vibrational adiabaticity predicts a general propensity for the greater efficiency of the symmetric stretch for accelerating the reaction in the vibrationally adiabatic limit. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effect of vibrational relaxation on the photodesorption dynamics of NO from a Pt(111) surface has been investigated theoretically. Although this system has been studied in many previous works, the relaxation of NO stretching vibration due to the interaction with electron–hole pairs in metals has not been included in conventional models. Although the relaxation lifetimes of the first-excited vibrational state of diatomic molecules adsorbed on metal surfaces are generally in the range 0.1–1 ps, the desorption dynamics of NO is complete in about 1 ps. Therefore, it is considered that the vibrational relaxation can influence the vibrational state of this stretching mode during the desorption process. We described the desorption dynamics by using the time propagation of the density matrix. The effects of vibrational relaxation were included by using a Redfield-type model. We also investigated the validity of the parameters for dynamical calculations by ab initio methods. As a result, we obtained physically reasonable results for the desorption probability, mean translational energy, and vibrational state distribution for the desorbed NO molecules. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]