Symmetries of Quadrupole-Collective Vibrational Motion in Transitional Even-Even 124−134Xenon Nuclei
Pietralla, N; Rainovski, G; Ahn, T; Bauer, C; Leske, J; Möller, O; Möller, T
2010-01-01
Projectile-Coulomb excitation of Xe isotopes has been performed at ANL using the Gammasphere array for the detection of γ-rays. The one-quadrupole phonon 2+ 1,ms mixed-symmetry state (MSS) has been traced in the stable N=80 isotones down to 134Xe. First, the data on absolute E2 andM1 transition rates quantify the amount of F-spin symmetry in these nuclei and provide a new local measure for the pn-QQ interaction. Second, the evolution of the 2+ 1,ms state has been studied along the sequence of stable even-even 124−134Xe isotopes that are considered to form a shape transition path from vibrational nuclei with vibrational U(5) symmetry near N=82 to γ-softly deformed shapes with almost O(6) symmetry. Third, our data on more than 50 absolute E2 transition rates between off-yrast low-spin states of 124,126Xe enable us to quantitatively test O(6) symmetry in these nuclei. As a result we find that O(6) symmetry is more strongly broken in the A=130 mass region than previously thought. The data will be discussed.
Cline, Douglas; Wu, Ching-Yen
2001-10-01
Measured E2 properties are a sensitive and unambiguous probe of the collective shape parameters for quadrupole collective motion in nuclei. Collective motion produces strong correlations of the measured E2 matrix elements that can be related to the E2 properties in the principal axis frame of the rotating nucleus. By analogy with Bohr's quadrupole shape parameters (β,γ), the instantaneous principal axis frame E2 tensor can be expressed in terms of two parameters, Q,δ where E2(2,0)=Q\\cosδ, and E2(2,± 2)=fracQ√2sinδ. The E2 properties can be used to extract the E2 triaxiality parameter δ which can be related to γ by use of a geometrical collective model. The 1965 measurement [1] of the Q_2^+ state in ^114Cd provoked considerable interest in collective triaxial deformation in nuclei and stimulated measurement of Q_2^+ values in many other nuclei in order to probe the centroid of the E2 triaxial deformation. The heavy-ion Coulomb excitation experimental technique, plus the Coulomb excitation least-squares search code GOSIA, made it possible to measure rather complete sets of E2 matrix elements adding a new dimension to the study of triaxiality in nuclear collective motion [2]. This development also made it possible to exploit the rotational invariant technique [3-6] to extract directly from the measured E2 matrix elements, the expectation values of the centroids and fluctuation widths of principal axis E2 parameters for any state. The usefulness, range of validity, and results of this technique for determining the centroids and fluctuation widths for the triaxiality degree of freedom δ in a range of nuclei will be presented. The completeness required is a disadvantage of the rotational invariant technique. A comparison will be made of the use of the full rotational invariant technique with results obtained using restricted E2 data in conjunction with model-dependent analyses or truncation schemes. [1] J. de Boer et al, Phys. Rev. Lett. 14 (1965) 564; [2] D
Quadrupole collectivity with isospin
Energy Technology Data Exchange (ETDEWEB)
Ginocchio, J.N.; Leviatan, A. (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States) Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel))
1994-10-03
We study intrinsic aspects of quadrupole collectivity with conserved isospin in the framework of the interacting boson model (IBM-3) of nuclei. A geometric visualization is achieved by means of a novel type of intrinsic states which are deformed in angular momentum yet have well defined isospin. The energy surface of the general IBM-3 Hamiltonian is derived and normal modes are identified for prolate deformations.
Handheld vibration effects shoulder motion.
Tripp, B L; Eberman, L E; Dwelly, P M
2009-12-01
We explored effects of handheld vibration on glenohumeral motion in competitive overhead-throwing athletes. We used a randomized, blinded pre-test post-test cross-over design. Each arm of each subject experienced 2 conditions (1-control, 1-experimental), each with pre-test and post-test measures; the order of which was randomized. Participants included Division-I baseball and softball players (n=35: age=20+/-2 yr, height=178+/-9 cm, mass=84+/-12 kg, years of sport participation=13+/-4 yrs). During the experimental condition, participants held a vibrating (2.2 mm, 15 Hz, 20 s), 2.55 kg (5.62 lbs) Mini-VibraFlex dumbbell (Orthometric, New York, NY) in neutral glenohumeral rotation. During the control condition, participants held the still dumbbell (0 mm, 0 Hz, 20 s). Participants rested one min after each trial (3). We used a digital protractor to assess range of motion bilaterally, employing a standard technique for measuring maximal internal (IR) and external rotation (ER). Repeated-measures analyses of variance indicated that range of dominant IR increased 6.8% ( P=0.001, ES=0.16) after handheld vibration. Handheld vibration did not affect range of dominant ER ( P>0.05, 1-beta=0.20), non-dominant IR ( P>0.05, 1-beta=0.41), or non-dominant ER ( P>0.05, 1-beta=0.05). Short bouts of handheld vibration increased dominant IR in collegiate baseball and softball athletes. These results suggest that handheld vibration may help maintain glenohumeral IR that is vital to the healthy and competitive throwing shoulder.
Directional motion of liquid under mechanical vibrations
Costalonga, Maxime; Brunet, Philippe; Peerhossaini, Hassan
2014-11-01
When a liquid is submitted to mechanical vibrations, steady flows or motion can be generated by non-linear effects. One example is the steady acoustic streaming one can observe when an acoustic wave propagates in a fluid. At the scale of a droplet, steady motion of the whole amount of liquid can arise from zero-mean periodic forcing. As It has been observed by Brunet et al. (PRL 2007), a drop can climb an inclined surface when submitted to vertical vibrations above a threshold in acceleration. Later, Noblin et al. (PRL 2009) showed the velocity and the direction of motion of a sessile drop submitted to both horizontal and vertical vibrations can be tuned by the phase shift between these two excitations. Here we present an experimental study of the mean motion of a sessile drop under slanted vibrations, focusing on the effects of drop properties, as well as the inclination angle of the axis of vibrations. It is shown that the volume and viscosity strongly affect the drop mean velocity, and can even change the direction of its motion. In the case of a low viscous drop, gravity can become significant and be modulated by the inclination of the axis of vibrations. Contact line dynamic during the drop oscillations is also investigated.
The anomalous quadrupole collectivity in Te isotopes
Qi, Chong
2016-01-01
We present systematic calculations on the spectroscopy and transition properties of even-even Te isotopes by using the large-scale configuration interaction shell model approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behavior, which cannot be reproduced by collective models. Our calculations reproduce well the equally-spaced spectra of those isotopes as well as the constant behavior of the $B(E2)$ values in $^{114}$Te. The calculated $B(E2)$ values for neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The $B(E2)$ of light isotopes can exhibit a nearly constant bevavior upto high spins. We show that this is related to the enhanced neutron-proton correlation when approaching $N=50$.
Quadrupole collectivity in silicon isotopes approaching neutron number N=28
Campbell, C. M.; Aoi, N.; Bazin, D.; Bowen, M. D.; Brown, B. A.; Cook, J. M.; Dinca, D.-C.; Gade, A.; Glasmacher, T.; Horoi, M.; Kanno, S.; Motobayashi, T.; Riley, L. A.; Sagawa, H.; Sakurai, H.; Starosta, K.; Suzuki, H.; Takeuchi, S.; Terry, J. R.; Yoneda, K.; Zwahlen, H.
2007-08-01
Quadrupole deformation parameters, |β|, have been deduced for 36,38,40Si from measured inelastic proton-scattering cross sections. Due to the strong Z=14 subshell gap, low-lying quadrupole collectivity in these nuclei is attributed to the excitation of valence neutrons. Enhanced collectivity at N=26 indicates a reduced N=28 shell gap at large neutron excess in this chain of isotopes. Data are compared to large-scale shell-model calculations and prior Coulomb excitation measurements on 36,38Si.
Low-lying quadrupole collectivity in {sup 136}Xe
Energy Technology Data Exchange (ETDEWEB)
Stahl, Christian; Leske, Joerg; Pietralla, Norbert; Reese, Michael [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Bazzacco, Dino; Farnea, Enrico [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova (Italy); Gadea, Andres [Instituto de Fisica Corpuscular, CSIC-Universitat de Valencia, Valencia (Spain); Gottardo, Andrea [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy); Dipartimento di Fisica e Astronomia dell' Universita degli Studi di Padova, Padova (Italy); John, Philipp Rudolf; Michelagnoli, Caterina [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova (Italy); Dipartimento di Fisica e Astronomia dell' Universita degli Studi di Padova, Padova (Italy); Valiente-Dobon, Jose Javier [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy)
2015-07-01
We present recent results from our investigation of low-lying quadrupole collectivity in the semi-magic N=82 nucleus {sup 136}Xe. An experiment was performed at the Legnaro National Laboratory employing the AGATA demonstrator. Level-lifetimes and B(E2, 0{sup +}{sub 1}→2{sup +}{sub i})-values were determined from Coulomb excitation and by the continuous-angle DSA method exploiting AGATA's position resolution. 2{sup +}{sub i} - states up to i=7 were excited and analyzed.
Bubble oscillations and motion under vibration
O'Hern, Tim; Torczynski, John
2011-01-01
Bubbles under vibration can behave in unusual ways, e.g., moving downward against the force of buoyancy. While the bubble downward motion due to the Bjerknes force is well known at acoustic frequencies close to the bubble resonant frequency, these experiments demonstrate that these effects can be observed at relatively low frequencies as well. Experiments were performed in a thin, quasi-two-dimensional rectangular acrylic box partially filled with 20-cSt PDMS silicone oil with overlying ambient air. The apparatus was subjected to sinusoidal axial vibration that produced breakup of the gas-liquid free surface, producing liquid jets into the air, droplets pinching off from these jets, gas cavities in the liquid from impacts of these droplets, and bubble transport below the interface. Vibration conditions for the attached videos are 280 Hz frequency, 15 g acceleration, and 94 micron peak-to-peak displacement. Behaviors shown in the videos include the following. 1. Free surface breakup into jets and droplets, and...
Communication: Creation of molecular vibrational motions via the rotation-vibration coupling
Energy Technology Data Exchange (ETDEWEB)
Shu, Chuan-Cun [Department of Chemistry, Technical University of Denmark, Building 207, DK-2800 Kongens Lyngby (Denmark); School of Engineering and Information Technology, University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Henriksen, Niels E., E-mail: neh@kemi.dtu.dk [Department of Chemistry, Technical University of Denmark, Building 207, DK-2800 Kongens Lyngby (Denmark)
2015-06-14
Building on recent advances in the rotational excitation of molecules, we show how the effect of rotation-vibration coupling can be switched on in a controlled manner and how this coupling unfolds in real time after a pure rotational excitation. We present the first examination of the vibrational motions which can be induced via the rotation-vibration coupling after a pulsed rotational excitation. A time-dependent quantum wave packet calculation for the HF molecule shows how a slow (compared to the vibrational period) rotational excitation leads to a smooth increase in the average bond length whereas a fast rotational excitation leads to a non-stationary vibrational motion. As a result, under field-free postpulse conditions, either a stretched stationary bond or a vibrating bond can be created due to the coupling between the rotational and vibrational degrees of freedom. The latter corresponds to a laser-induced breakdown of the adiabatic approximation for rotation-vibration coupling.
Communication: creation of molecular vibrational motions via the rotation-vibration coupling
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Henriksen, Niels Engholm
2015-01-01
Building on recent advances in the rotational excitation of molecules, we show how the effect of rotation-vibration coupling can be switched on in a controlled manner and how this coupling unfolds in real time after a pure rotational excitation. We present the first examination of the vibrational...... motions which can be induced via the rotation-vibration coupling after a pulsed rotational excitation. A time-dependent quantum wave packet calculation for the HF molecule shows how a slow (compared to the vibrational period) rotational excitation leads to a smooth increase in the average bond length...... whereas a fast rotational excitation leads to a non-stationary vibrational motion. As a result, under field-free postpulse conditions, either a stretched stationary bond or a vibrating bond can be created due to the coupling between the rotational and vibrational degrees of freedom. The latter corresponds...
Analysis and Modelling of Muscles Motion during Whole Body Vibration
Directory of Open Access Journals (Sweden)
La Gatta A
2010-01-01
Full Text Available The aim of the study is to characterize the local muscles motion in individuals undergoing whole body mechanical stimulation. In this study we aim also to evaluate how subject positioning modifies vibration dumping, altering local mechanical stimulus. Vibrations were delivered to subjects by the use of a vibrating platform, while stimulation frequency was increased linearly from 15 to 60 Hz. Two different subject postures were here analysed. Platform and muscles motion were monitored using tiny MEMS accelerometers; a contra lateral analysis was also presented. Muscle motion analysis revealed typical displacement trajectories: motion components were found not to be purely sinusoidal neither in phase to each other. Results also revealed a mechanical resonant-like behaviour at some muscles, similar to a second-order system response. Resonance frequencies and dumping factors depended on subject and his positioning. Proper mechanical stimulation can maximize muscle spindle solicitation, which may produce a more effective muscle activation.
Vibrational motion in a symmetric, double minimum potential
DEFF Research Database (Denmark)
Spanget-Larsen, Jens
2015-01-01
Molecular vibrational motion in a symmetric, double minimum potential is treated by means of a quartic model potential, by reference to the tables published by Jaan Laane and the results of harmonic analyses for the stationary points. The inversion vibration of ammonia is treated in detail. - Not...... on the harmonic approximation for polyatomic molecules are appended. - Presented at a NORFA Workshop in Hirtshals, Denmark, August 1997....
Manipulation of molecular vibrational motions via pure rotational excitations
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Henriksen, Niels Engholm
2015-01-01
The coupling between different molecular degrees of freedom plays a decisive role in many quantum phenomena, including electron transfer and energy redistribution. Here, we demonstrate a quantum-mechanical time-dependent simulation to explore how a vibrational motion in a molecule can be affected...
Motions of elastic solids in fluids under vibration
DEFF Research Database (Denmark)
Sorokin, V. S.; Blekhman, I. I.; Thomsen, Jon Juel
2010-01-01
Motion of a rigid or deformable solid in a viscous incompressible fluid and corresponding fluid–solid interactions are considered. Different cases of applying high frequency vibrations to the solid or to the surrounding fluid are treated. Simple formulas for the mean velocity of the solid...... are derived, under the assumption that the regime of the fluid flow induced by its motion is turbulent and the fluid resistance force is nonlinearly dependent on its velocity. It is shown that vibrations of a fluid’s volume slow down the motion of a submerged solid. This effect is much pronounced in the case...... of a deformable solid (i.e., gas bubble) exposed to near-resonant excitation. The results are relevant to the theory of gravitational enrichment of raw materials, and also contribute to the theory of controlled locomotion of a body with an internal oscillator in continuous deformable (solid or fluid) media....
Active Damping of Vibrations in High-Precision Motion Systems
Babakhani, B.
2012-01-01
Technology advancements feed the need for ever faster and more accurate industrial machines. Vibration is a significant source of inaccuracy of such machines. A light-weight design in favor of the speed, and avoiding the use of energy-dissipating materials from the structure to omit any source of inaccuracy, contribute to a low structural damping. The goal of this research is to investigate the addition of damping to the rotational vibration mode of a linearly actuated motion system to •achie...
Vibrating-Rocking Motion of Caisson Breakwater Under Breaking Wave Impact
Institute of Scientific and Technical Information of China (English)
王元战; 郑斌
2001-01-01
The possible motions of a caisson breakwater under dynamic load excitation include vibrating, vibrating-sliding andvibrating-rocking motions. The models of vibrating motion and vibrating-sliding motion have been proposed in an earlypaper. In this paper, a model of vibrating-rocking motion of caisson breakwaters under breaking wave impact is presented, which can be used to simulate the histories of vibrating-rocking motion of caisson breakwaters. The effect of rocking motion on the displacement, rotation, sliding force and overturning moment of breakwaters is investigated. In casethe overturning moment exceeds the stability moment ofa caisson, the caisson may only rock. The caisson overturns only in case the rocking angle exceeds the critical angle. It is shown that the sliding force and overturning moment of break-waters can be reduced effectively due to the rocking motion. It is proposed that some rocking motion should be allowedin breakwater design.
Buganu, Petricǎ; Fortunato, Lorenzo
2016-09-01
We review and discuss several recent approaches to quadrupole collectivity and developments of collective models and their solutions with many applications, examples and references. We focus in particular on analytic and approximate solutions of the Bohr hamiltonian of the last decade, because most of the previously published material has been already reviewed in other publications.
Motion control and vibration suppression of flexible lumped systems via sensorless LQR control
Çelebi, Beşir; Celebi, Besir; Çevik, Gülnihal; Cevik, Gulnihal; Mehmet, Berkem; Shoukry Mohammed Khalil, Islam; ŞABANOVIÇ, Asif; SABANOVIC, Asif
2011-01-01
This work attempts to achieve motion control along with vibration suppression of flexible systems by developing a sensorless closed loop LQR controller. Vibration suppression is used as a performance index that has to be minimized so that motion control is achieved with zero residual vibration. An estimation algorithm is combined with the regular LQR to develop sensorless motion and vibration controller that is capable of positioning multi degrees of freedom flexible system point of interest ...
Vibrational motions in rotating nuclei studied by Coulomb excitations
Energy Technology Data Exchange (ETDEWEB)
Shimizu, Yoshifumi R. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics
1998-03-01
As is well-known Coulomb excitation is an excellent tool to study the nuclear collective motions. Especially the vibrational excitations in rotating nuclei, which are rather difficult to access by usual heavy-ion fusion reactions, can be investigated in detail. Combined with the famous 8{pi}-Spectrometer, which was one of the best {gamma}-ray detector and had discovered some of superdeformed bands, such Coulomb excitation experiments had been carried out at Chalk River laboratory just before it`s shutdown of physics division. In this meeting some of the experimental data are presented and compared with the results of theoretical investigations. (author)
Study of quadrupole collectivity in odd mass Po and Bi isotopes
Energy Technology Data Exchange (ETDEWEB)
Pai, H.; Reese, M.; Pietralla, N. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Cortes, M.L. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Gerl, J.; Gorska, M. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Podolyak, Zs. [Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom); Rudolph, D. [Department of Physics, Lund University, SE-22100 Lund (Sweden); Collaboration: S429 PreSPEC-AGATA-Collaboration
2015-07-01
Relativistic Coulomb excitations of odd-mass Po and Bi isotopes were performed during the PreSPEC-AGATA campaign at GSI to study the quadrupole collectivity in the direct vicinity of the heaviest stable doubly-magic nucleus {sup 208}Pb. The PreSPEC-AGATA campaign is the predecessor of the HISPEC (High-resolution In-flight Spectroscopy) experiment in the FAIR context. It was running 2012 and 2014 at GSI. Up to 23 AGATA crystals were used in this campaign, located behind the FRagment Separator. We present the status of the ongoing data analysis and discuss the challenges of data analysis for this type of experiments.
Quadrupole Collectivity beyond N=28: Intermediate-Energy Coulomb Excitation of Ar47,48
Winkler, R.; Gade, A.; Baugher, T.; Bazin, D.; Brown, B. A.; Glasmacher, T.; Grinyer, G. F.; Meharchand, R.; McDaniel, S.; Ratkiewicz, A.; Weisshaar, D.
2012-05-01
We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei Ar47,48 using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced B(E2) transition strengths are confronted with large-scale shell-model calculations in the sdpf shell using the state-of-the-art SDPF-Uand EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.
Kawasaki, Takeshi; Onuki, Akira
2013-03-01
Using molecular dynamics simulation on a glass-forming liquid in three dimensions, we investigate the thermal vibrational motions, the configuration changes caused by stringlike jump motions, and their close correlations. The heterogeneous vibrational motions are visualized in terms of a vibration length Si(t) defined for each particle i. The structure factor for the inhomogeneity of Si(t)2 is also calculated, which exhibits considerable long wavelength enhancement. By examining the birth times of strings, they are shown to appear collectively and intermittently. We show that particles with larger Si(t) tend to trigger jump motions more frequently at later times than those with smaller Si(t). We also show that the particles with fewer bonds tend to have larger Si(t) and participate more frequently in the stringlike motions.
Vibration energy harvesting from random force and motion excitations
Tang, Xiudong; Zuo, Lei
2012-07-01
A vibration energy harvester is typically composed of a spring-mass system with an electromagnetic or piezoelectric transducer connected in parallel with a spring. This configuration has been well studied and optimized for harmonic vibration sources. Recently, a dual-mass harvester, where two masses are connected in series by the energy transducer and a spring, has been proposed. The dual-mass vibration energy harvester is proved to be able to harvest more power and has a broader bandwidth than the single-mass configuration, when the parameters are optimized and the excitation is harmonic. In fact, some dual-mass vibration energy harvesters, such as regenerative vehicle suspensions and buildings with regenerative tuned mass dampers (TMDs), are subjected to random excitations. This paper is to investigate the dual-mass and single-mass vibration harvesters under random excitations using spectrum integration and the residue theorem. The output powers for these two types of vibration energy harvesters, when subjected to different random excitations, namely force, displacement, velocity and acceleration, are obtained analytically with closed-form expressions. It is also very interesting to find that the output power of the vibration energy harvesters under random excitations depends on only a few parameters in very simple and elegant forms. This paper also draws some important conclusions on regenerative vehicle suspensions and buildings with regenerative TMDs, which can be modeled as dual-mass vibration energy harvesters. It is found that, under white-noise random velocity excitation from road irregularity, the harvesting power from vehicle suspensions is proportional to the tire stiffness and road vertical excitation spectrum only. It is independent of the chassis mass, tire-wheel mass, suspension stiffness and damping coefficient. Under random wind force excitation, the power harvested from buildings with regenerative TMD will depends on the building mass only, not
Reiter, P; Blazhev, A A; Nardelli, S; Voulot, D; Habs, D; Schwerdtfeger, W; Iwanicki, J S
We propose to investigate the nucleus $^{128}$Cd neighbouring the r-process "waiting point" $^{130}$Cd. A possible explanation for the peak in the solar r-abundances at A $\\approx$ 130 is a quenching of the N = 82 shell closure for spherical nuclei below $^{132}$Sn. This explanation seems to be in agreement with recent $\\beta$-decay measurements performed at ISOLDE. In contrast to this picture, a beyond-mean-field approach would explain the anomaly in the excitation energy observed for $^{128}$Cd rather with a quite large quadrupole collectivity. Therefore, we propose to measure the reduced transition strengths B(E2) between ground state and first excited 2$^{+}$-state in $^{128}$Cd applying $\\gamma$-spectroscopy with MINIBALL after "safe" Coulomb excitation of a post-accelerated beam obtained from REX-ISOLDE. Such a measurement came into reach only because of the source developments made in 2006 for experiment IS411, in particular the use of a heated quartz transfer line. The result from the proposed measure...
Institute of Scientific and Technical Information of China (English)
WANG; Yuanzhan; HUA; Leina; DONG; Shaowei
2004-01-01
Vibrating, sliding and uplift rocking are three elementary motion types of caisson breakwaters. The dynamic model and the numerical simulation method of vibrating-sliding-uplift rocking coupled motion of caisson breakwaters are developed. The histories of displacement, rotation, sliding force and overturning moment of a caisson breakwater under the excitation of breaking wave impact are calculated for the motion models of vibrating, vibrating-sliding, vibrating-uplift rocking and vibrating-sliding-uplift rocking. The effects of various motion models on the stability of caisson breakwaters are investigated. The feasibility of the dynamic design idea that the sliding motion and the uplift rocking motion of caisson breakwaters are allowed under the excitation of breaking wave impact is discussed.
Institute of Scientific and Technical Information of China (English)
LIAO Yihuan; LI Daokui; TANG Guojin
2011-01-01
This paper is concerned with optimal motion planning for vibration reducing of flee-floating flexible redundant manipulators.Firstly,dynamic model of the system is established based on Lagrange method,and the motion planning model for vibration reducing is proposed.Secondly,a hybrid optimization approach employing Gauss pseudospectral method(GPM) and direct shooting method(DSM),is proposed to solve the motion planning problem.In this approach,the motion planning problem is transformed into a non-linear parameter optimization problem using GPM,and genetic algorithm(GA) is employed to locate the approximate solution.Subsequently,an optimization model is formulated based on DSM,and sequential quadratic programming (SQP) algorithm is used to obtain the accurate solution,with the approximate solution as an initial reference solution.Finally,several numerical simulations are investigated,and the global vibration or residual vibration of flexible link is obviously reduced by the joint trajectory which is obtained by the hybrid optimization approach.The numerical simulation results indicate that the approach is effective and stable to the motion planning problem of vibration reducing.
Institute of Scientific and Technical Information of China (English)
Bian Yushu; Gao Zhihui; Yun Chao
2008-01-01
In order to suppress vibration in flexible manipulators, a new type of manipulator mechanism with controllable local degrees of freedom is proposed. This mechanism consists of a main chain and some branch links. The main chain is of a flexible open-chain configuration with an end-effector installed at its tip, and the rigid branch links are able to perform active movements. It is proved by kinematics and dynamic analysis that, the branch links bear no direct kinematic relation to the main chain, but their independent motions can strongly affect the dynamic behavior and performance of the flexible manipulator. Then comes a new idea of suppressing vibration, in which independent motions of the branch links are used to suppress the undesired vibration of the flexible main chain through dynamic coupling. On this basis, an optimal method for reducing vibration of flexible manipulators is proposed. Finally, the effectiveness of this method is verified by numerical simulations.
Vibrating barrier: a novel device for the passive control of structures under ground motion.
Cacciola, P; Tombari, A
2015-07-08
A novel device, called vibrating barrier (ViBa), that aims to reduce the vibrations of adjacent structures subjected to ground motion waves is proposed. The ViBa is a structure buried in the soil and detached from surrounding buildings that is able to absorb a significant portion of the dynamic energy arising from the ground motion. The working principle exploits the dynamic interaction among vibrating structures due to the propagation of waves through the soil, namely the structure-soil-structure interaction. The underlying theoretical aspects of the novel control strategy are scrutinized along with its numerical modelling. Closed-form solutions are also derived to design the ViBa in the case of harmonic excitation. Numerical and experimental analyses are performed in order to investigate the efficiency of the device in mitigating the effects of ground motion waves on the structural response. A significant reduction in the maximum structural acceleration of 87% has been achieved experimentally.
Active Damping of Vibrations in High-Precision Motion Systems
Babakhani, B.
2012-01-01
Technology advancements feed the need for ever faster and more accurate industrial machines. Vibration is a significant source of inaccuracy of such machines. A light-weight design in favor of the speed, and avoiding the use of energy-dissipating materials from the structure to omit any source of
Energy Technology Data Exchange (ETDEWEB)
Rodriguez-Guzman, R.; Sharma, M.M. [Kuwait University, Physics Department, Kuwait (Kuwait); Robledo, L.M. [Universidad Autonoma de Madrid, Departamento de Fisica Teorica, Madrid (Spain)
2015-06-15
The quadrupole collectivity in Nd, Sm, Gd, Dy, Er, Yb, Hf and W nuclei with neutron numbers 122 ≤ N ≤ 156 is studied, both at the mean field level and beyond, using the Gogny energy density functional. Besides the robustness of the N = 126 neutron shell closure, it is shown that the onset of static deformations in those isotopic chains with increasing neutron number leads to an enhanced stability and further extends the corresponding two-neutron drip lines far beyond what could be expected from spherical calculations. Independence of the mean-field predictions with respect to the particular version of the Gogny energy density functional employed is demonstrated by comparing results based on the D1S and D1M parameter sets. Correlations beyond mean field are taken into account in the framework of the angular momentum projected generator coordinate method calculation. It is shown that N = 126 remains a robust neutron magic number when dynamical effects are included. The analysis of the collective wave functions, average deformations and excitation energies indicate that, with increasing neutron number, the zero-point quantum corrections lead to dominant prolate configurations in the 0{sub 1} {sup +}, 0{sub 2} {sup +}, 2{sub 1} {sup +} and 2{sub 2} {sup +} states of the studied nuclei. Moreover, those dynamical deformation effects provide an enhanced stability that further supports the mean-field predictions, corroborating a shift of the r-process path to higher neutron numbers. Beyond mean-field calculations provide a smaller shell gap at N = 126 than the mean-field one in good agreement with previous theoretical studies. However, the shell gap still remains strong enough in the two-neutron drip lines. (orig.)
Correlating electronic and vibrational motions in charge transfer systems
Energy Technology Data Exchange (ETDEWEB)
Khalil, Munira [Univ. of Washington, Seattle, WA (United States)
2014-06-27
The goal of this research program was to measure coupled electronic and nuclear motions during photoinduced charge transfer processes in transition metal complexes by developing and using novel femtosecond spectroscopies. The scientific highlights and the resulting scientific publications from the DOE supported work are outlined in the technical report.
Energy Technology Data Exchange (ETDEWEB)
Albert, Julian; Falge, Mirjam; Hildenbrand, Heiko; Engel, Volker [Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Emil-Fischer-Str. 42, Campus Nord, Am Hubland, 97074 Würzburg (Germany); Gomez, Sandra; Sola, Ignacio R. [Departamento de Quimica Fisica, Universidad Complutense, 28040 Madrid (Spain)
2015-07-28
We theoretically investigate the photon-echo spectroscopy of coupled electron-nuclear quantum dynamics. Two situations are treated. In the first case, the Born-Oppenheimer (adiabatic) approximation holds. It is then possible to interpret the two-dimensional (2D) spectra in terms of vibrational motion taking place in different electronic states. In particular, pure vibrational coherences which are related to oscillations in the time-dependent third-order polarization can be identified. This concept fails in the second case, where strong non-adiabatic coupling leads to the breakdown of the Born-Oppenheimer-approximation. Then, the 2D-spectra reveal a complicated vibronic structure and vibrational coherences cannot be disentangled from the electronic motion.
The efficacy of airflow and seat vibration on reducing visually induced motion sickness.
D'Amour, Sarah; Bos, Jelte E; Keshavarz, Behrang
2017-06-20
Visually induced motion sickness (VIMS) is a well-known sensation in virtual environments and simulators, typically characterized by a variety of symptoms such as pallor, sweating, dizziness, fatigue, and/or nausea. Numerous methods to reduce VIMS have been previously introduced; however, a reliable countermeasure is still missing. In the present study, the effect of airflow and seat vibration to alleviate VIMS was investigated. Eighty-two participants were randomly assigned to one of four groups (airflow, vibration, combined airflow and vibration, and control) and then exposed to a 15 min long video of a bicycle ride shot from first-person view. VIMS was measured using the Fast Motion Sickness Scale (FMS) and the Simulator Sickness Questionnaire (SSQ). Results showed that the exposure of airflow significantly reduced VIMS, whereas the presence of seat vibration, in contrast, did not have an impact on VIMS. Additionally, we found that females reported higher FMS scores than males, however, this sex difference was not found in the SSQ scores. Our findings demonstrate that airflow can be an effective and easy-to-apply technique to reduce VIMS in virtual environments and simulators, while vibration applied to the seat is not a successful method.
Equations of Motion for the g-LIMIT Microgravity Vibration Isolation System
Kim, Y. K.; Whorton, M. S.
2001-01-01
A desirable microgravity environment for experimental science payloads may require an active vibration isolation control system. A vibration isolation system named g-LIMIT (GLovebox Integrated Microgravity Isolation Technology) is being developed by NASA Marshall Space Flight Center to support microgravity science experiments using the microgravity science glovebox. In this technical memorandum, the full six-degree-of-freedom nonlinear equations of motion for g-LIMIT are derived. Although the motivation for this model development is control design and analysis of g-LIMIT, the equations are derived for a general configuration and may be used for other isolation systems as well.
Effects of vibrational motion on core-level spectra of prototype organic molecules
Energy Technology Data Exchange (ETDEWEB)
Uejio, Janel S.; Schwartz, Craig P.; Saykally, Richard J.; Prendergast, David
2008-08-21
A computational approach is presented for prediction and interpretation of core-level spectra of complex molecules. Applications are presented for several isolated organic molecules, sampling a range of chemical bonding and structural motifs. Comparison with gas phase measurements indicate that spectral lineshapes are accurately reproduced both above and below the ionization potential, without resort to ad hoc broadening. Agreement with experiment is significantly improved upon inclusion of vibrations via molecular dynamics sampling. We isolate and characterize spectral features due to particular electronic transitions enabled by vibrations, noting that even zero-point motion is sufficient in some cases.
Energy Technology Data Exchange (ETDEWEB)
Lan, C. B.; Qin, W. Y. [Department of Engineering Mechanics, Northwestern Polytechnical University, Xi' an 710072 (China)
2014-09-15
This letter investigates the energy harvesting from the horizontal coherent resonance of a vertical cantilever beam subjected to the vertical base excitation. The potential energy of the system has two symmetric potential wells. So, under vertical excitation, the system can jump between two potential wells, which will lead to the large vibration in horizontal direction. Two piezoelectric patches are pasted to harvest the energy. From experiment, it is found that the vertical excitation can make the beam turn to be bistable. The system can transform vertical vibration into horizontal vibration of low frequency when excited by harmonic motion. The horizontal coherence resonance can be observed when excited by a vertical white noise. The corresponding output voltages of piezoelectric films reach high values.
Hubac, Ivan; Babinec, Peter; Polasek, Martin; Urban, Jan; Mach, Pavel; Masik, Jozef; Leszczynski, Jerzy
1998-01-01
The coupling of electronic and vibrational motion is studied by two canonical transformations namely normal coordinate transformation and momentum transformation on molecular Hamiltonian. It is shown that by these transformations we can pass from crude approximation to adiabatic approximation and then to non-adiabatic (diabatic) Hamiltonian. This leads to renormalized fermions and renormalized diabatic phonons. Simple calculations on $H_{2}$, $HD$, and $D_{2}$ systems are performed and compar...
Institute of Scientific and Technical Information of China (English)
Xue-Liang Zhang; Bang-Chun Wen; Chun-Yu Zhao
2012-01-01
In this paper,the synchronization problem of three homodromy coupled exciters in a non-resonant vibrating system of plane motion is studied.By introducing the average method of modified small parameters,we deduced dimensionless coupling equation of three exciters,which converted the problem of synchronization into that of the existence and stability of zero solutions for the average differential equations of the small parameters.Based on the dimensionless coupling torques and characteristics of the corresponding limited functions,the synchronization criterion for three exciters was derived as the absolute value of dimensionless residual torque difference between arbitrary two motors being less than the maximum of their dimensionless coupling torques.The stability criterion of its synchronous state lies in the double-condition that the inertia coupling matrix is positive definite and all its elements are positive as well.The synchronization determinants are the coefficients of synchronization ability,also called as the general dynamical symmetry coefficients.The double-equilibrium state of the vibrating system is manifested by numeric method,and the numeric and simulation results derived thereof indicate the indispensable and crucial role the structural parameters of the vibrating system play in the stability criterion of synchronous operation.Besides,by adjusting its structural parameters,the elliptical motion of the vibrating system successfully met the requirements in engineering applications.
sEMG during Whole-Body Vibration Contains Motion Artifacts and Reflex Activity
Directory of Open Access Journals (Sweden)
Karin Lienhard
2015-01-01
Full Text Available The purpose of this study was to determine whether the excessive spikes observed in the surface electromyography (sEMG spectrum recorded during whole-body vibration (WBV exercises contain motion artifacts and/or reflex activity. The occurrence of motion artifacts was tested by electrical recordings of the patella. The involvement of reflex activity was investigated by analyzing the magnitude of the isolated spikes during changes in voluntary background muscle activity. Eighteen physically active volunteers performed static squats while the sEMG was measured of five lower limb muscles during vertical WBV using no load and an additional load of 33 kg. In order to record motion artifacts during WBV, a pair of electrodes was positioned on the patella with several layers of tape between skin and electrodes. Spectral analysis of the patella signal revealed recordings of motion artifacts as high peaks at the vibration frequency (fundamental and marginal peaks at the multiple harmonics were observed. For the sEMG recordings, the root mean square of the spikes increased with increasing additional loads (p < 0.05, and was significantly correlated to the sEMG signal without the spikes of the respective muscle (r range: 0.54 - 0.92, p < 0.05. This finding indicates that reflex activity might be contained in the isolated spikes, as identical behavior has been found for stretch reflex responses evoked during direct vibration. In conclusion, the spikes visible in the sEMG spectrum during WBV exercises contain motion artifacts and possibly reflex activity.
Studies of quadrupole collectivity in the {gamma}-soft {sup 106}Ru
Energy Technology Data Exchange (ETDEWEB)
Sanchez-Vega, M.; Taylor, R.B.E.; Fogelberg, B.; Lindroth, A. [Uppsala University, Department of Nuclear and Particle Physics, P.O. Box 535, Uppsala (Sweden); Mach, H. [Uppsala University, Department of Nuclear and Particle Physics, P.O. Box 535, Uppsala (Sweden); University of Notre Dame, Institute for Structure and Nuclear Astrophysics, Notre Dame, IN (United States); Aas, A.J. [University of Oslo, Department of Chemistry, P.O. Box 1033, Blindern (Norway); Dendooven, P.; Honkanen, A.; Huhta, M.; Lhersonneau, G.; Oinonen, M.; Parmonen, J.M.; Penttilae, H.; Aeystoe, J. [University of Jyvaeskylae, Department of Physics, P.O. Box 35, Jyvaeskylae (Finland); Persson, J.R. [University of Birmingham, School of Physics and Space Research, Birmingham (United Kingdom); Kurpeta, J. [University of Warsaw, Faculty of Physics, Warsaw (Poland)
2008-02-15
Various alternative models were used to describe the structure of {sup 106}Ru. For example, the General Collective Model (GCM) predicts shape-coexistence for {sup 106}Ru with a spherical and a triaxial minimum and strongly mixed structures, while in the IBA-2 calculations, where {sup 106}Ru was considered as transitional from vibrational U(5) to {gamma}-soft O(6), no need was found to include the shape-coexisting configurations. In order to provide additional constraints on the model interpretations, we have applied the Advanced Time-Delayed (ATD) {beta}{gamma}{gamma}(t) method to measure the level lifetimes of the excited levels in {sup 106}Ru. The new results include the half-lives of T{sub 1/2}=183(3) ps and 7.5(30) ps for the 2{sup +}{sub 1} and 2{sup +}{sub 2} states, respectively. (orig.)
Shell-model configuration-interaction description of quadrupole collectivity in Te isotopes
Qi, Chong
2016-09-01
Systematic calculations on the spectroscopy and transition properties of even-even Te isotopes are carried out by using the large-scale shell-model configuration-interaction approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally spaced pattern whereas the few known E 2 transitions show rotational-like behavior. This cannot be explained by available collective models. My calculations reproduce well the equally spaced spectra of those isotopes as well as the constant behavior for the B (E 2 ) values of 114Te. The calculated B (E 2 ) values of neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The B (E 2 ) of light isotopes can exhibit a nearly constant behavior up to high spins. It is shown that this is related to the enhanced neutron-proton correlation when approaching N =50 .
Nomura, K; Otsuka, T; Shimizu, N; Vretenar, D
2011-01-01
Microscopic energy density functionals (EDF) have become a standard tool for nuclear structure calculations, providing an accurate global description of nuclear ground states and collective excitations. For spectroscopic applications this framework has to be extended to account for collective correlations related to restoration of symmetries broken by the static mean field, and for fluctuations of collective variables. In this work we compare two approaches to five-dimensional quadrupole dynamics: the collective Hamiltonian for quadrupole vibrations and rotations, and the Interacting Boson Model. The two models are compared in a study of the evolution of non-axial shapes in Pt isotopes. Starting from the binding energy surfaces of $^{192,194,196}$Pt, calculated with a microscopic energy density functional, we analyze the resulting low-energy collective spectra obtained from the collective Hamiltonian, and the corresponding IBM-2 Hamiltonian. The calculated excitation spectra and transition probabilities for t...
Vibration Powered RF-Transponder for Sensing Low Frequency Motion Events
Gupta, S. K.; Pinrod, V.; Nadig, S.; Davaji, B.; Lal, A.
2016-11-01
Vibration energy harvesting offers a pathway to developing battery-less sensing solutions to be deployed in wireless sensor network nodes. The integration of the energy harvesters require regulation by power conditioning and control circuitry that consume some of the energy generated, reducing the effective energy available for node function. By designing a unique 3D-printed plastic structure for low frequency sensitivity and mechanical switching, and a lateral PZT bimorph for capturing energy from environmental vibrations, we report a zero-power consumption RF-transponder capable of detecting and reporting motion events without a battery. We have successfully picked up wireless transmissions on an external receiver placed ∼25cm away from the transponder, shaken at 0.75 g and 20 Hz. We have additionally demonstrated the ability to harvest energy from 5 Hz vibrations up to just under 150 Hz. When placed on an oil-based electric generator, which vibrates when operating, the RF-transponder has successfully picked up the differing harmonics to identify the mode of operation as the economy or regular power setting.
Groma, Géza I.; Colonna, Anne; Martin, Jean-Louis; Vos, Marten H.
2011-01-01
The primary energetic processes driving the functional proton pump of bacteriorhodopsin take place in the form of complex molecular dynamic events after excitation of the retinal chromophore into the Franck-Condon state. These early events include a strong electronic polarization, skeletal stretching, and all-trans-to-13-cis isomerization upon formation of the J intermediate. The effectiveness of the photoreaction is ensured by a conical intersection between the electronic excited and ground states, providing highly nonadiabatic coupling to nuclear motions. Here, we study real-time vibrational coherences associated with these motions by analyzing light-induced infrared emission from oriented purple membranes in the 750–1400 cm−1 region. The experimental technique applied is based on second-order femtosecond difference frequency generation on macroscopically ordered samples that also yield information on phase and direction of the underlying motions. Concerted use of several analysis methods resulted in the isolation and characterization of seven different vibrational modes, assigned as C-C stretches, out-of-plane methyl rocks, and hydrogen out-of-plane wags, whereas no in-plane H rock was found. Based on their lifetimes and several other criteria, we deduce that the majority of the observed modes take place on the potential energy surface of the excited electronic state. In particular, the direction sensitivity provides experimental evidence for large intermediate distortions of the retinal plane during the excited-state isomerization process. PMID:21402041
Vibration Measurement Method of a String in Transversal Motion by Using a PSD.
Yang, Che-Hua; Wu, Tai-Chieh
2017-07-17
A position sensitive detector (PSD) is frequently used for the measurement of a one-dimensional position along a line or a two-dimensional position on a plane, but is more often used for measuring static or quasi-static positions. Along with its quick response when measuring short time-spans in the micro-second realm, a PSD is also capable of detecting the dynamic positions of moving objects. In this paper, theoretical modeling and experiments are conducted to explore the frequency characteristics of a vibrating string while moving transversely across a one-dimensional PSD. The theoretical predictions are supported by the experiments. When the string vibrates at its natural frequency while moving transversely, the PSD will detect two frequencies near this natural frequency; one frequency is higher than the natural frequency and the other is lower. Deviations in these two frequencies, which differ from the string's natural frequency, increase while the speed of motion increases.
Cheatham, Scott W; Stull, Kyle R; Kolber, Morey J
2017-08-08
The use of foam rollers to provide soft-tissue massage has become a common intervention among health and fitness professionals. Recently, manufacturers have merged the science of vibration therapy and foam rolling with the development of vibrating foam rollers. To date, no peer reviewed investigations have been published on this technology. The purpose of this study was to compare the effects of a vibrating roller and non-vibrating roller intervention on prone knee flexion passive range of motion (ROM) and pressure pain thresholds (PPT) of the quadriceps musculature. Forty-five recreationally active adults were randomly allocated to one of three groups: vibrating roller, non-vibrating roller, and control. Each roll intervention lasted a total of 2 minutes. The control group did not roll. Dependent variables included prone knee flexion ROM and PPT measures. Statistical analysis included parametric and non-parametric tests to measure changes among groups. The vibrating roller demonstrated the greatest increase in PPT (180kPa, pvibrating roller (112kPa, pcontrol (61kPa, pvibrating roller demonstrated the greatest increase in ROM (7 degrees, pvibrating roller (5 degrees, pcontrol (2 degrees, pvibrating and non-vibrating roller (p=.03) and vibrating roller and control (pvibrating roller and control (pvibrating and non-vibrating roller (p=.31). A significant difference was found between the vibrating roller and control group (pvibrating roller and control (pvibrating roller may increase an individual's tolerance to pain greater than a non-vibrating roller. This investigation should be considered exploratory and a starting point for future research on this technology.
Oliver, Thomas A A; Lewis, Nicholas H C; Fleming, Graham R
2014-07-15
Multidimensional nonlinear spectroscopy, in the electronic and vibrational regimes, has reached maturity. To date, no experimental technique has combined the advantages of 2D electronic spectroscopy and 2D infrared spectroscopy, monitoring the evolution of the electronic and nuclear degrees of freedom simultaneously. The interplay and coupling between the electronic state and vibrational manifold is fundamental to understanding ensuing nonradiative pathways, especially those that involve conical intersections. We have developed a new experimental technique that is capable of correlating the electronic and vibrational degrees of freedom: 2D electronic-vibrational spectroscopy (2D-EV). We apply this new technique to the study of the 4-(di-cyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H-pyran (DCM) laser dye in deuterated dimethyl sulfoxide and its excited state relaxation pathways. From 2D-EV spectra, we elucidate a ballistic mechanism on the excited state potential energy surface whereby molecules are almost instantaneously projected uphill in energy toward a transition state between locally excited and charge-transfer states, as evidenced by a rapid blue shift on the electronic axis of our 2D-EV spectra. The change in minimum energy structure in this excited state nonradiative crossing is evident as the central frequency of a specific vibrational mode changes on a many-picoseconds timescale. The underlying electronic dynamics, which occur on the hundreds of femtoseconds timescale, drive the far slower ensuing nuclear motions on the excited state potential surface, and serve as a excellent illustration for the unprecedented detail that 2D-EV will afford to photochemical reaction dynamics.
Stochastic optimal control of cable vibration in plane by using axial support motion
Institute of Scientific and Technical Information of China (English)
Ming Zhao; Wei-Qiu Zhu
2011-01-01
A stochastic optimal control strategy for a slightly sagged cable using support motion in the cable axial direction is proposed. The nonlinear equation of cable motion in plane is derived and reduced to the equations for the first two modes of cable vibration by using the Galerkin method.The partially averaged 10 equation for controlled system energy is further derived by applying the stochastic averaging method for quasi-non-integrable Hamiltonian systems. The dynamical programming equation for the controlled system energy with a performance index is established by applying the stochastic dynamical programming principle and a stochastic optimal control law is obtained through solving the dynamical programming equation. A bilinear controller by using the direct method of Lyapunov is introduced. The comparison between the two controllers shows that the proposed stochastic optimal control strategy is superior to the bilinear control strategy in terms of higher control effectiveness and efficiency.
Mettu, Srinivas; Chaudhury, Manoj K
2011-08-16
Hysteresis of wetting, like the Coulombic friction at solid/solid interface, impedes the motion of a liquid drop on a surface when subjected to an external field. Here, we present a counterintuitive example, where some amount of hysteresis enables a drop to move on a surface when it is subjected to a periodic but asymmetric vibration. Experiments show that a surface either with a negligible or high hysteresis is not conducive to any drop motion. Some finite hysteresis of contact angle is needed to break the periodic symmetry of the forcing function for the drift to occur. These experimental results are consistent with simulations, in which a drop is approximated as a linear harmonic oscillator. The experiment also sheds light on the effect of the drop size on flow reversal, where drops of different sizes move in opposite directions due to the difference in the phase of the oscillation of their center of mass.
Composite Motion Design Procedure for Vibration Assisted Small-Hole EDM Using One Voice Coil Motor
Directory of Open Access Journals (Sweden)
Jing Cui
2016-01-01
Full Text Available To address the problem of debris accumulation in small-hole electrical discharge machine (EDM and simplify the design of the spindle head, the paper proposes a novel composite motion design procedure integrated high frequency vibration and large stroke feed using one voice coil motor (VCM. Particularly, for the purposes of high servo accuracy and high frequency response of the composite motion, an improved zero-phase-error tracking controller (ZPETC algorithm decoupled with the feedback controller is developed for the process control, in which the feedback parameter adjustment is very simple to reduce the computation complexity. At last, the proposed procedure is validated by the experimental study of the established VCM positioning table; the results verify the efficiency of the proposed method.
VIBRATING-UPLIFT ROCKING MOTION OF CAISSON BREAKWATERS UNDER VARIOUS BREAKING WAVE IMPACT FORCES
Institute of Scientific and Technical Information of China (English)
WANG Yuan-zhan; ZHOU Zhi-rong; YANG Hai-dong
2005-01-01
Overturning is one of principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. The mass-springdashpot model of caisson-foundation system is used to simulate the vibrating-uplift rocking motion of caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave types and the uplift rocking motion on dynamic response behaviors of caisson breakwaters are investigated. It is shown that the dynamic responses of a caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. Though the rotation of a caisson is larger due to the uplift rocking motion, the displacement, the sliding force and the overturning moment of the caisson are significantly reduced. It provides the theoretical base for the design idea that the uplift rocking motion of caisson is allowed in design.
Synchronization of the four identical unbalanced rotors in a vibrating system of plane motion
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
A new mechanism is proposed to implement the synchronization of the four unbalanced rotors in a vibrating system, which consists of a main rigid frame (MRF) and two accessorial rigid frames (ARF). An analytical approach is developed to study the coupling dynamic characteristics of the four unbalanced rotors, which converts the problem of synchronization of the four unbalanced rotors into the existence and the stability of zero solutions for the non-dimensional differential equations of the angular velocity disturbance parameters (NDDEDP). The stability of zero solutions of the NDDEDP is decomposed into that of its generalized system and a system of the three first order differential equations for the disturbance parameters of the phase differences. The coupling dynamic characteristic of the four unbalanced rotors includes the inertia coupling, the stiffness coupling of angular velocity and the load torque coupling. The non-dimensional inertia coupling matrix is symmetric, the non dimensional matrix of the stiffness coupling of angular velocity is antisymmetric and its diagonal elements are all negative. Hence, the general system of the NDDEDP automatically satisfies the generalized Lyapunov equations when the non-dimensional inertia coupling matrix is positive definite and its elements are all positive. Using Routh-Hurwitz criterion the condition of stability of differential equations for the disturbance parameters of the phase differences is obtained. The load torque coupling makes the vibrating system have the dynamic characteristic of selecting motions and self-synchronization of the four unbalanced rotors arises from the dynamic characteristic of selecting motion of the vibrating system. When the two coefficients of coupling cosine effect of phase angles are all greater than 0 and the three indexes of synchronization are all far greater than 1, the vibrating system can implement an elliptical motion of the main rigid frame required in engineering. Numeric
Directory of Open Access Journals (Sweden)
Junji Yoshida
2007-01-01
Full Text Available An image processing technique to capture motions of crowds is proposed and it is applied to understanding pedestrian-induced lateral vibration in a footbridge. Firstly, an outline of recording sequential images of vibration in the bridge is described and, then an image processing for human-head recognition from a single image of crowd is developed. In this method, conventional template matching techniques with human-head templates are extended by employing some selected templates, an updated search-algorithm and a classifier for clustering. Consequently, more than 50% of human-heads could be identified by the proposed method. Then, motions of detected human-heads, together with the bridge response, are tracked. Finally, interaction between the motions of pedestrians and the vibration of the bridge is discussed, with the emphasis on synchronization between the responses of the pedestrians and the bridge.
Liao, Wei-Hsin
2017-04-01
Most of the ambient energy, which was regarded useless in the past, now is under the spotlight. With the rapid developments on low power electronics, future personal mobile devices and remote sensing systems might become self-powered by scavenging energy in different forms from their surroundings. Kinetic energy is one of the promising energy forms in our living environment, e.g., human motions and vibrations. We have proposed an energy flow to clarify the functions of piezoelectric energy harvesting, dissipation, and their effects on the structural damping of vibrating structures. Impedance modeling and analysis were performed. We have designed an improved self-powered switching interface for piezoelectric energy harvesting circuits. With electromagnetic transduction, we also proposed a knee-mounted energy harvester that could convert the mechanical power from knee joints into electricity during walking. On the other hand, we have developed magnetorheological (MR) fluid devices with multiple functions, including rotary actuators and linear dampers. Multifunctional rotary actuator was designed to integrate motor/generator part and MR fluids into a single device. The actuator could function as motor, generator, clutch and brake, with compact size and good energy efficiency. In addition, novel self-sensing MR dampers with power generation, so as to integrate the dynamic sensing, controllable damping and power generation functions, were developed and investigated. Prototypes were fabricated and tested. The developed actuators were promising for various applications. In this paper, related research in energy harvesting done at The Chinese University of Hong Kong and key results will be presented.
The Effect of Whole Body Vibration on Ankle Range of Motion and the H-reflex.
Apple, Stacey; Ehlert, Kelly; Hysinger, Pam; Nash, Cara; Voight, Michael; Sells, Pat
2010-02-01
Limited research suggests that an effect of whole body vibration (WBV) on the central nervous system (CNS) is suppression. An indirect measure used to assess CNS level of activation is the Soleus H-reflex. If true suppression does occur, other factors such as range of motion may be impacted. The purpose of this study was to examine the impact of WBV on H-reflex amplitude and passive ankle dorsiflexion. Twenty-seven healthy volunteers between the ages of 21-41 participated. Subjects were randomly assigned to a control group (n=13) or WBV group (n=14). H-reflex and ankle dorsiflexion measures were assessed before and after a three minute WBV perturbation (40 μHz, amplitude 2-4 mm). These measurements were repeated every five minutes up to twenty minutes following the intervention. The H-reflex amplitude showed a significant decrease (pmotion showed significant interaction (pcontrol group also showed this change, WBV does not appear to be a key cause of suppression. Range of motion was not clinically significant for either group.
Vibrating-Sliding Motion of Caisson Breakwaters Under Various Breaking Wave Impact Forces
Institute of Scientific and Technical Information of China (English)
王元战; 于红霞
2003-01-01
Sliding is one of the principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. Herein, the mass-spring-dashpot model of caisson-base system is used to simulate the vibrating-sliding motion of the caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave impacts and the sliding motion on the dynamic response behaviors of caisson breakwaters are investigated and the calculation of relevant system parameters is discussed. It is shown that the dynamic responses of the caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. The amplitude of dynamic response of the caisson is lower under single peak impact excitation than that under double peak impact or shock-damping oscillation impact excitation. Though the displacement of the caisson is large due to sliding, the rotation, the sliding force and the overturning moment of the caisson are significantly reduced.
New vibration-rotation code for tetraatomic molecules exhibiting wide-amplitude motion: WAVR4
Kozin, Igor N.; Law, Mark M.; Tennyson, Jonathan; Hutson, Jeremy M.
2004-11-01
A general computational method for the accurate calculation of rotationally and vibrationally excited states of tetraatomic molecules is developed. The resulting program is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. The program offers a choice of coordinate systems based on Radau, Jacobi, diatom-diatom and orthogonal satellite vectors. The method includes all six vibrational dimensions plus three rotational dimensions. Vibration-rotation calculations with reduced dimensionality in the radial degrees of freedom are easily tackled via constraints imposed on the radial coordinates via the input file. Program summaryTitle of program: WAVR4 Catalogue number: ADUN Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUN Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: Persons requesting the program must sign the standard CPC nonprofit use license Computer: Developed under Tru64 UNIX, ported to Microsoft Windows and Sun Unix Operating systems under which the program has been tested: Tru64 Unix, Microsoft Windows, Sun Unix Programming language used: Fortran 90 Memory required to execute with typical data: case dependent No. of lines in distributed program, including test data, etc.: 11 937 No. of bytes in distributed program, including test data, etc.: 84 770 Distribution format: tar.gz Nature of physical problem: WAVR4 calculates the bound ro-vibrational levels and wavefunctions of a tetraatomic system using body-fixed coordinates based on generalised orthogonal vectors. Method of solution: The angular coordinates are treated using a finite basis representation (FBR) based on products of spherical harmonics. A discrete variable representation (DVR) [1] based on either Morse-oscillator-like or spherical-oscillator functions [2] is used for the radial coordinates. Matrix elements are computed using an efficient Gaussian quadrature in the angular coordinates and
Estimating Rayleigh wave particle motion from three-component array analysis of ambient vibrations
Poggi, Valerio; Fäh, Donat
2010-01-01
Several methods have been proposed in the past years to extract the Rayleigh wave ellipticity from horizontal-to-vertical spectral ratios of single station ambient noise recordings. The disadvantage of this set of techniques is the difficulty in clearly identifying and separating the contribution of higher modes. In most cases, only the fundamental mode of ellipticity can be identified. Moreover, it is generally difficult to correct for the energy of SH and Love waves present in the horizontal components of the ambient vibration wavefield. We introduce a new methodology to retrieve Rayleigh wave ellipticity using high-resolution frequency-wavenumber array analysis. The technique is applied to the three components of motion and is based on the assumption that an amplitude maximum in the f-k cross-spectrum must represent the true power amplitude of the corresponding signal. In the case of Rayleigh waves, therefore, the ratio between maxima obtained from the horizontal (radial-polarized) and vertical components of motion will also represent the frequency-dependent ellipticity function. Consequently, if we can identify the Rayleigh dispersion curves of several modes on the f-k plane, then the corresponding modal ellipticity patterns can also be separated and extracted. To test the approach, synthetic and real data sets were processed. In all tested cases, a reliable estimation of segments of the fundamental mode ellipticity was obtained. The identification of higher modes is possible in most cases. The quality of results depends on the selected array geometry and the signal-to-noise ratio, with a major improvement achieved by increasing the number of receivers employed during the survey. An experiment conducted in the town of Visp (Switzerland) allowed the retrieval of portions of ellipticity curves up to the second Rayleigh higher mode, using two concentric circular array configurations of 14 and 11 receivers each.
Simulating Rectified Motion of a Piston in a Housing Subjected to Vibrational Acceleration
Clausen, Jonthan; Torczynski, John; Romero, Louis; O'Hern, Timothy
2014-11-01
We employ ALE finite element simulations to investigate the behavior of a piston in a housing subjected to vertical vibrations. The housing is filled with a viscous liquid to damp the piston motion and has bellows at both ends to represent air bubbles present in real systems. The piston has a roughly cylindrical hole along its axis, and a post attached to the housing penetrates partway into this hole. Protrusions from the hole and the post form a gap with a length that varies as the piston moves and forces liquid through this gap. Under certain conditions, nonlinearities in the system can drive the piston to move downward and compress the spring that holds it up against gravity. This behavior is investigated using ALE finite element simulations, and these results are compared with theoretical predictions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
A virtual experiment showing single particle motion on a linearly vibrating screen-deck
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
A virtual sieving experimental simulation system was built using physical simulation principles.The effects of vibration frequency and amplitude,the inclination angle of the screen-deck and the vibration direction angle of screen on single particle kinematics were predicted.Properties such as the average velocity and the average throw height were studied.The results show that the amplitude and the angle of vibration have a great effect on particle average velocity and average height.The vibration frequency ...
Directory of Open Access Journals (Sweden)
Uğbreve;ur Dalli
2011-01-01
Full Text Available An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.
Self-excited multi-scale skin vibrations probed by optical tracking micro-motions of tracers on arms
Chen, Wei-Chia; Chen, Hsiang-Ying; Chen, Yu-Sheng; Tian, Yong; I, Lin
2017-07-01
The self-excited multi-scale mechanical vibrations, their sources and their mutual coupling of different regions on the forearms of supine subjects, are experimentally investigated, using a simple noncontact method, optical video microscopy, which provides 1 μm and 25 ms spatiotemporal resolutions. It is found that, in proximal regions far from the radial artery, the vibrations are the global vibrations of the entire forearm excited by remote sources, propagating through the trunk and the limb. The spectrum is mainly composed of peaks of very low frequency motion (down to 0.05 Hz), low frequency respiration modes, and heartbeat induced modes (about 1 Hz and its harmonics), standing out of the spectrum floor exhibiting power law decay. The nonlinear mode-mode coupling leads to the cascaded modulations of higher frequency modes by lower frequency modes. The nearly identical waveforms without detectable phase delays for a pair of signals along or transverse to the meridian of regions far away from the artery rule out the detectable contribution from the propagation of Qi, some kind of collective excitation which more efficiently propagates along meridians, according to the Chinese medicine theory. Around the radial artery, in addition to the global vibration, the local vibration spectrum shows very slow breathing type vibration around 0.05 Hz, and the artery pulsation induced fundamental and higher harmonics with descending intensities up to the fifth harmonics, standing out of a flat spectrum floor. All the artery pulsation modes are also modulated by respiration and the very slow vibration.
Zhang, Dashan; Guo, Jie; Lei, Xiujun; Zhu, Changan
2016-04-22
The development of image sensor and optics enables the application of vision-based techniques to the non-contact dynamic vibration analysis of large-scale structures. As an emerging technology, a vision-based approach allows for remote measuring and does not bring any additional mass to the measuring object compared with traditional contact measurements. In this study, a high-speed vision-based sensor system is developed to extract structure vibration signals in real time. A fast motion extraction algorithm is required for this system because the maximum sampling frequency of the charge-coupled device (CCD) sensor can reach up to 1000 Hz. Two efficient subpixel level motion extraction algorithms, namely the modified Taylor approximation refinement algorithm and the localization refinement algorithm, are integrated into the proposed vision sensor. Quantitative analysis shows that both of the two modified algorithms are at least five times faster than conventional upsampled cross-correlation approaches and achieve satisfactory error performance. The practicability of the developed sensor is evaluated by an experiment in a laboratory environment and a field test. Experimental results indicate that the developed high-speed vision-based sensor system can extract accurate dynamic structure vibration signals by tracking either artificial targets or natural features.
Abdikarimov, R.; Bykovtsev, A.; Khodzhaev, D.; Research Team Of Geotechnical; Structural Engineers
2010-12-01
Long-period earthquake ground motions (LPEGM) with multiple oscillations have become a crucial consideration in seismic hazard assessment because of the rapid increase of tall buildings and special structures (SP).Usually, SP refers to innovative long-span structural systems. More specifically, they include many types of structures, such as: geodesic showground; folded plates; and thin shells. As continuation of previous research (Bykovtsev, Abdikarimov, Khodzhaev 2003, 2010) analysis of nonlinear vibrations (NV) and dynamic stability of SP simulated as shells with variable rigidity in geometrically nonlinear statement will be presented for two cases. The first case will represent NV example of a viscoelastic orthotropic cylindrical shell with radius R, length L and variable thickness h=h(x,y). The second case will be NV example of a viscoelastic shell with double curvature, variable thickness, and bearing the concentrated masses. In both cases we count, that the SP will be operates under seismic load generated by LPEGM with multiple oscillations. For different seismic loads simulations, Bykovtsev’s Model and methodology was used for generating LPEGM time history. The methodology for synthesizing LPEGM from fault with multiple segmentations was developed by Bykovtev (1978-2010) and based on 3D-analytical solutions by Bykovtsev-Kramarovskii (1987&1989) constructed for faults with multiple segmentations. This model is based on a kinematics description of displacement function on the fault and included in consideration of all possible combinations of 3 components of vector displacement (two slip vectors and one tension component). The opportunities to take into consideration fault segmentations with both shear and tension vector components of displacement on the fault plane provide more accurate LPEGM evaluations. Radiation patterns and directivity effects were included in the model and more physically realistic results for simulated LPEGM were considered. The
Non-resonant dynamic stark control of vibrational motion with optimized laser pulses
DEFF Research Database (Denmark)
Thomas, Esben Folger; Henriksen, Niels Engholm
2016-01-01
The term dynamic Stark control (DSC) has been used to describe methods of quantum control related to the dynamic Stark effect, i.e., a time-dependent distortion of energy levels. Here, we employ analytical models that present clear and concise interpretations of the principles behind DSC. Within...... a linearly forced harmonic oscillator model of vibrational excitation, we show how the vibrational amplitude is related to the pulse envelope, and independent of the carrier frequency of the laser pulse, in the DSC regime. Furthermore, we shed light on the DSC regarding the construction of optimal pulse...... envelopes - from a time-domain as well as a frequency-domain perspective. Finally, in a numerical study beyond the linearly forced harmonic oscillator model, we show that a pulse envelope can be constructed such that a vibrational excitation into a specific excited vibrational eigenstate is accomplished...
Titov, S. V.; Tovbin, Yu. K.
2016-11-01
A molecular model developed earlier for a polar fluid within the lattice gas model is supplemented by considering the vibrational motions of molecules using water as an example. A combination of point dipole and Lennard-Jones potentials from SPC parametrization is chosen as the force field model for the molecule. The main thermodynamic properties of liquid water (density, internal energy, and entropy) are studied as functions of temperature. There is qualitative agreement between the calculation results and the experimental data. Ways of refining the molecular theory are discussed.
Terahertz underdamped vibrational motion governs protein-ligand binding in solution.
Turton, David A; Senn, Hans Martin; Harwood, Thomas; Lapthorn, Adrian J; Ellis, Elizabeth M; Wynne, Klaas
2014-06-03
Low-frequency collective vibrational modes in proteins have been proposed as being responsible for efficiently directing biochemical reactions and biological energy transport. However, evidence of the existence of delocalized vibrational modes is scarce and proof of their involvement in biological function absent. Here we apply extremely sensitive femtosecond optical Kerr-effect spectroscopy to study the depolarized Raman spectra of lysozyme and its complex with the inhibitor triacetylchitotriose in solution. Underdamped delocalized vibrational modes in the terahertz frequency domain are identified and shown to blue-shift and strengthen upon inhibitor binding. This demonstrates that the ligand-binding coordinate in proteins is underdamped and not simply solvent-controlled as previously assumed. The presence of such underdamped delocalized modes in proteins may have significant implications for the understanding of the efficiency of ligand binding and protein-molecule interactions, and has wider implications for biochemical reactivity and biological function.
Janzen, F. C.; Tusset, A. M.; Piccirillo, V.; Balthazar, J. M.; Brasil, R. M. L. R. F.
2015-11-01
This work presents two approaches to the problem of vibration and positioning control of a flexible structural beam driven by a DC motor. The position is controlled by the current applied to the DC motor armature. A Shape Memory Alloy (SMA) actuator controls vibrations of the flexible structural beam. The State Dependent Riccati Equation (SDRE) technique is used to provide a control action which uses sub-optimal control and system local stability search. The robustness of these two controllers is tested by sensitivity analysis to parametric uncertainties. Numerical simulations results are presented to demonstrate the effectiveness of the proposed control strategy.
A modified variation-perturbation approach to zero-point vibrational motion
DEFF Research Database (Denmark)
Åstrand, Per-Olof; Ruud, K.; Sundholm, D.
2000-01-01
We present a detailed investigation of the perturbation approach for calculating zero-point vibrational contributions to molecular properties. It is demonstrated that if the sum of the potential energy and the zero-point vibrational energy is regarded as an effective potential energy, the leading...... contribution to the first-order wave function vanishes in the perturbation approach. Two different perturbation approaches have been investigated numerically by calculations of some magnetic properties for a few diatomic molecules and the results obtained have been compared to the exact numerical results...
Rotation-vibration motion of extremely flexible molecules - The molecular superrotor
Schmiedt, Hanno; Jensen, Per; Schlemmer, Stephan
2017-03-01
This paper treats the low energy rotation-vibration problem in CH5+, an extremely flexible molecule lacking a well-defined structure. Using SO(5) symmetry it determines zeroth order energies, and complete nuclear permutation S5 symmetries, using a five-dimensional model involving rotation and two vibrations (which one might imagine as two different ;cooperative; HCH bends). These two vibrations are presumed to be unhindered by the molecular potential function and their analytical form is not determined. The other ten vibrational degrees of freedom are presumed to be ;rigid; (or averaged over). The general energy expression for this ;rigid superrotor; is obtained as (B / 2) [n1 (n1 + 3) +n2 (n2 + 1) ] where B is the rotational constant and the non-negative integers n1 and n2 satisfy n2 ⩽n1 . The superrotor predictions agree favourably with the available experimental data. Applications of the superrotor model to extremely flexible molecules other than CH5+ are discussed.
The effect of large amplitude motions on the vibrational intensities in hydrogen bonded complexes
DEFF Research Database (Denmark)
Mackeprang, Kasper; Hänninen, Vesa; Halonen, Lauri
2015-01-01
We have developed a model to calculate accurately the intensity of the hydrogen bonded XH-stretching vibrational transition in hydrogen bonded complexes. In the Local Mode Perturbation Theory (LMPT) model, the unperturbed system is described by a local mode (LM) model, which is perturbed by the i......We have developed a model to calculate accurately the intensity of the hydrogen bonded XH-stretching vibrational transition in hydrogen bonded complexes. In the Local Mode Perturbation Theory (LMPT) model, the unperturbed system is described by a local mode (LM) model, which is perturbed...... by the intermolecular modes of the hydrogen bonded system that couple with the intramolecular vibrations of the donor unit through the potential energy surface. We have applied the model to three complexes containing water as the donor unit and different acceptor units, providing a series of increasing complex binding...... energy: H2O⋯N2, H2O⋯H2O, and H2O⋯NH3. Results obtained by the LMPT model are presented and compared with calculated results obtained by other vibrational models and with previous results from gas-phase and helium-droplet experiments. We find that the LMPT model reduces the oscillator strengths...
Brown, T. J.; Mccloud, J. L., III
1980-01-01
Weighted multiple linear regression is used to establish a transfer function matrix relationship between higher harmonic control inputs and transducer vibration outputs for a controllable twist rotor. Data used in the regression were taken from the test of a KAMAN controllable twist rotor conducted in the Ames Research Center's 40- by 80-Foot Wind Tunnel in June 1977. Optimal controls to minimize fixed system vibrational levels are calculated using linear quadratic regulatory theory with a control deflection penalty included in the performance criteria. Control sensitivity to changes in control travel, forward speed, and lift and propulsive forces is examined. It is found that the linear transfer matrix is a strong function of forward speed and a weak function of lift and propulsive force. An open-loop strategy is proposed for systems with limited control travel.
Stable motion of transport vehicles with allowance for the steering system vibrations
Energy Technology Data Exchange (ETDEWEB)
Lobas, V.I.; Verbitskii, V.G. [S.P. Timoshenko Institute of Mechanics, Kiev (Ukraine)
1995-10-01
A new mathematical model is developed for the plane-parallel motion of a system consisting of the frame of a vehicle and a steering system that controls the motion. The stability of straight-line motion is investigated. In most studies on the stability of the straight-line motion of a motor vehicle and a tractor-trailer unit it is assumed that in disturbed motion the driver keeps the steerable wheels in a neutral (unturned) position: the angle {theta} through which the wheels are turned about the axis of the steering knuckle pivot is zero. The validity of the assumption that {theta} = 0 can be argued in only one way, i.e., the torsional stiffness {Kappa} of the steering system is fairly high: if {Kappa} {yields} {infinity}, then {theta} = 0. For finite values of {Kappa} we have {theta} = 0. In that case the variable {theta} is determined by its differential equation, i.e., the number of degrees of freedom of the vehicle increases by one. The dynamic behavior of vehicles in this formulation is considered in this paper.
Graybill, George
2007-01-01
Take the mystery out of motion. Our resource gives you everything you need to teach young scientists about motion. Students will learn about linear, accelerating, rotating and oscillating motion, and how these relate to everyday life - and even the solar system. Measuring and graphing motion is easy, and the concepts of speed, velocity and acceleration are clearly explained. Reading passages, comprehension questions, color mini posters and lots of hands-on activities all help teach and reinforce key concepts. Vocabulary and language are simplified in our resource to make them accessible to str
Altay, G.; Dökmeci, M. C.
2014-09-01
The relative merit of lower-order theories, which have been deduced from the three-dimensional theories of continua, is evaluated with respect to the quantified and un-quantified errors in mathematically modeling the physical response of structural elements. Then, the one-dimensional theories are derived with high accuracy, internal consistency and flexibility from the three-dimensional theory of elasticity in order to govern the nonlinear and incremental motions and stability of a functionally graded rod. First, a kinematic-based method of separation of variables is introduced as a method of reduction, which may lead to the lower-order theories with the same order of errors of the three-dimensional theories, and the nonlinear theories of the rod are derived under Leibnitz's postulate of structural elements by use of Hamilton's principle. A theorem of uniqueness is proved in solutions of the linear equations of the rod by means of the logarithmic convexity argument. Next, the kinematic basis is expressed by the power series expansion in the cross-sectional coordinates using Weierstrass's theorem. Mindlin's method is used so as to derive the equations in an invariant and fully variational form for the small motions superposed on a static finite deformation, the stability analysis and the high-frequency vibrations of the rod. Moreover, the free vibrations of the rod are considered, the basic properties of eigenvalues are examined, and Rayleigh's quotient is obtained. The invariant equations of the rod, which are expressible in any system of orthogonal coordinates, may provide simultaneous approximations on all the field variables in a direct method of solutions. The equations are indicated to contain some of earlier equations of rods, as special cases, and also, the numerical elasticity solution of a sample application is presented.
3D Motions of Iron in Six-Coordinate {FeNO}(7) Hemes by Nuclear Resonance Vibration Spectroscopy.
Peng, Qian; Pavlik, Jeffrey W; Silvernail, Nathan J; Alp, E Ercan; Hu, Michael Y; Zhao, Jiyong; Sage, J Timothy; Scheidt, W Robert
2016-04-25
The vibrational spectrum of a six-coordinate nitrosyl iron porphyrinate, monoclinic [Fe(TpFPP)(1-MeIm)(NO)] (TpFPP=tetra-para-fluorophenylporphyrin; 1-MeIm=1-methylimidazole), has been studied by oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS). The crystal was oriented to give spectra perpendicular to the porphyrin plane and two in-plane spectra perpendicular or parallel to the projection of the FeNO plane. These enable assignment of the FeNO bending and stretching modes. The measurements reveal that the two in-plane spectra have substantial differences that result from the strongly bonded axial NO ligand. The direction of the in-plane iron motion is found to be largely parallel and perpendicular to the projection of the bent FeNO on the porphyrin plane. The out-of-plane Fe-N-O stretching and bending modes are strongly mixed with each other, as well as with porphyrin ligand modes. The stretch is mixed with v50 as was also observed for dioxygen complexes. The frequency of the assigned stretching mode of eight Fe-X-O (X=N, C, and O) complexes is correlated with the Fe-XO bond lengths. The nature of highest frequency band at ≈560 cm(-1) has also been examined in two additional new derivatives. Previously assigned as the Fe-NO stretch (by resonance Raman), it is better described as the bend, as the motion of the central nitrogen atom of the FeNO group is very large. There is significant mixing of this mode. The results emphasize the importance of mode mixing; the extent of mixing must be related to the peripheral phenyl substituents.
Femtosecond Twisting and Coherent Vibrational Motion in the Excited State of Tetraphenylethylene
Lenderink, E; Duppen, K.; Wiersma, D. A.
1995-01-01
The initial dynamics after excitation to the S-1 state of tetraphenylethylene is studied using femtosecond pump-probe spectroscopy. From the rapid spectral changes during the first few hundred femtoseconds, we conclude that a fast ethylenic twisting motion occurs in the excited state within this tim
The efficacy of airflow and seat vibration on reducing visually induced motion sickness
D'Amour, S.; Bos, J.E.; Keshavarz, B.
2017-01-01
Visually induced motion sickness (VIMS) is a well-known sensation in virtual environments and simulators, typically characterized by a variety of symptoms such as pallor, sweating, dizziness, fatigue, and/or nausea. Numerous methods to reduce VIMS have been previously introduced; however, a reliable
Takano, K.; Ito, T.; Masuda, T.; Koketsu, K.; Ramancharla, P. K.; Sangam, R.; Bodige, N.; Dasari, H. C.
2014-12-01
Understanding the vulnerability of built environment in highly seismic areas is an important component of earthquake risk mitigation. As part of Indo-Japan collaborative research project (DISANET) sponsored by JST and JICA, six sets of building vibration sensors have been installed in the Union Territory of Chandigarh, India. The Union Territory of Chandigarh, India is located at South of the Himalayan Frontal Belt (HFT) is in zone IV of the seismic zone map of India (BIS, 2007). In past few decades, this area has experienced several minor earthquakes and a few moderate earthquakes. In spite of being in high seismic zone, most of the buildings in Chandigarh are designed and constructed for gravity loads only disregarding seismic forces. Such kind of buildings may deteriorate in strength even when they are subjected to minor earthquakes. To understand the response of buildings to micro-tremors, vibration sensors were installed in the building of Department of Geology of Panjab University in July 2012. Subsequently 5 more buildings were instrumented by January 2014. For each building, in order to capture the overall vibration of building during earthquake, vibration sensors of 8 or 10 units are installed to the ground floor, top floor and middle floor of the building. These sensors are continuously monitoring the building vibration and recording all data which include the weak ground motion occurring from near to far earthquakes. Through these sensors, over 20 minor ground motions have been recorded during last two years. Even in these weak ground motions, it was possible to confirm the state of the building response caused by earthquakes. In this presentation, we will introduce some building vibration records caused by the weak ground motion of the earthquakes and discuss the important insights drawn from analysis of recorded data.
Guitars, Keyboards, Strobes, and Motors -- From Vibrational Motion to Active Research
Tagg, Randall; Carlson, John; Asadi-Zeydabadi, Masoud; Busley, Brad; Law-Balding, Katie; Juengel, Mattea
2013-01-01
Physics First is offered to ninth graders at high schools in Aurora, CO. A unique new asset of this school system is an embedded research lab called the "Innovation Hyperlab." The goal of the lab is to connect secondary school teaching to ongoing university scientific research, supporting the school district's aim to create opportunities to integrate P-20 (preschool to graduate school) learning. This paper is an example of how we create research connections in the context of introductory physics lessons on vibrations and waves. Key to the process is the use of several different types of technical resources, hence the name "hyperlab." Students learn many practical experimental techniques, reinforcing their knowledge of fundamentals and preparing them to work effectively on open-ended research or engineering projects.
Nuriev, A. N.; Zakharova, O. S.; Zaitseva, O. N.; Yunusova, A. I.
2016-11-01
A rectilinear motion of a two-mass system in a viscous incompressible fluid is considered. The system consists of a shell having the form of an equilateral triangular cylinder and a movable internal mass. The motion of the system as a whole is forced by longitudinal oscillations of the internal mass relative to the shell. This mechanical system simulates a vibration-driven robot, i.e. a mobile device capable to move in a resistive medium without external moving parts. Investigation of the system is carried out by a direct numerical simulation. A comparative analysis of the characteristics of the motion and flow regimes around the vibration-driven robot is carried out for different internal mass oscillation laws.
Yang, Yongchao; Dorn, Charles; Mancini, Tyler; Talken, Zachary; Kenyon, Garrett; Farrar, Charles; Mascareñas, David
2017-02-01
user supervision and calibration. First a multi-scale image processing method is applied on the frames of the video of a vibrating structure to extract the local pixel phases that encode local structural vibration, establishing a full-field spatiotemporal motion matrix. Then a high-spatial dimensional, yet low-modal-dimensional, over-complete model is used to represent the extracted full-field motion matrix using modal superposition, which is physically connected and manipulated by a family of unsupervised learning models and techniques, respectively. Thus, the proposed method is able to blindly extract modal frequencies, damping ratios, and full-field (as many points as the pixel number of the video frame) mode shapes from line of sight video measurements of the structure. The method is validated by laboratory experiments on a bench-scale building structure and a cantilever beam. Its ability for output (video measurements)-only identification and visualization of the weakly-excited mode is demonstrated and several issues with its implementation are discussed.
Ground vibrations and airborne sounds generated by motion of rock in a river bed
Directory of Open Access Journals (Sweden)
C.-J. Huang
2008-10-01
Full Text Available This study investigates how ground vibrations (underground sounds and airborne sounds that are produced by rocks in a river bed differ from each other. Airborne and underground sounds were simultaneously received at three microphones and three geophones, respectively. These sound signals were then analyzed using both the Fast Fourier Transform and the Gabor Transform to represent them in both the frequency and time-frequency domains. Experimental data indicate that the frequency of both airborne and underground sounds produced by the impact of rocks against the river bed is in the range 10–150 Hz. Furthermore, the high-frequency band of underground sounds decays much more rapidly than that of airborne sounds. The spatial decay rate of airborne sounds was also determined and compared with theoretical values. The lower spatial decay rate of airborne sounds than that of underground sounds suggests that monitoring of airborne sounds may be more efficient in the detection of debris flows or other natural hazards that generate both airborne and underground sounds.
Szalay, Viktor
2015-05-07
A new ro-vibrational Hamiltonian operator, named gateway Hamiltonian operator, with exact kinetic energy term, Tˆ, is presented. It is in the Eckart frame and it is of the same form as Watson's normal coordinate Hamiltonian. However, the vibrational coordinates employed are not normal coordinates. The new Hamiltonian is shown to provide easy access to Eckart frame ro-vibrational Hamiltonians with exact Tˆ given in terms of any desired set of vibrational coordinates. A general expression of the Eckart frame ro-vibrational Hamiltonian operator is given and some of its properties are discussed.
Takano, K.; Ito, T.
2010-12-01
There are a lot of buildings which is not experienced severe earthquakes in urban area. In Hanshin-Awaji (Kobe) Earthquake, it was presumed that 80 percent or more of the person was dead immediately after the earthquake by building collapse. Also in Haiti, a lot of buildings deprived of the life of persons. In order to prevent the earthquake damage of urban area, it is the most effective to make the building earthquake-proof. However, there are still a lot of buildings not made earthquake-proof in Japan though 15 years passed since Kobe Earthquake. In order to promote making of the building earthquake-proof, various approaches such as visualization of seismic hazard, education of disaster prevention and legal system for promotion are needed. We have developed the IT Kyoshin(strong motion) Seismometer for Building which is the observation system of the usual weak earthquake ground motion by installing a lot of acceleration sensors in building, and have been setting it up in some buildings of the University of Tokyo. We have also developed the visualization tool that can reproduce the building vibration during earthquake from the observed data. By this tool, we can successfully show where is more shaking in the building or what is the feature of building vibration easily. Such information contributes to not only promotion of making building earthquake-proof but also promotion of disaster prevention action such as fixation of bookshelf, making the safety area in building, etc. In addition, we proposed a concrete technique of the health investigation of buildings by using weak earthquake ground motion. Because there are 20 to 30 felt earthquakes in year in Tokyo area, it is possible to observe these building vibrations by using weak earthquake ground motions. In addition, we have developed the high sensitive ITK sensor which can observe from the microtremor to the felt earthquake in the place without the felt earthquake either.
Lee, Hyoseong; Rhee, Huinam; Oh, Jae Hong; Park, Jin Ho
2016-03-11
This paper deals with an improved methodology to measure three-dimensional dynamic displacements of a structure by digital close-range photogrammetry. A series of stereo images of a vibrating structure installed with targets are taken at specified intervals by using two daily-use cameras. A new methodology is proposed to accurately trace the spatial displacement of each target in three-dimensional space. This method combines the correlation and the least-square image matching so that the sub-pixel targeting can be obtained to increase the measurement accuracy. Collinearity and space resection theory are used to determine the interior and exterior orientation parameters. To verify the proposed method, experiments have been performed to measure displacements of a cantilevered beam excited by an electrodynamic shaker, which is vibrating in a complex configuration with mixed bending and torsional motions simultaneously with multiple frequencies. The results by the present method showed good agreement with the measurement by two laser displacement sensors. The proposed methodology only requires inexpensive daily-use cameras, and can remotely detect the dynamic displacement of a structure vibrating in a complex three-dimensional defection shape up to sub-pixel accuracy. It has abundant potential applications to various fields, e.g., remote vibration monitoring of an inaccessible or dangerous facility.
Wang, Yu
2015-01-01
This study presents the analysis and design of a novel quasi-zero-stiffness (QZS) based vibration sensor system for measuring absolute displacement of vibrating platforms/objects. The sensor system is constructed by using positive and negative-stiffness springs, which makes it possible to achieve an equivalent QZS and consequently to create a broadband vibration-free point for absolute displacement measurement in vibrating platforms. Theoretic analysis is conducted for the analysis and design of the influence of structure parameters on system measurement performance. A prototype is designed which can avoid the drawback of instability in existing QZS systems with negative stiffness, and the corresponding data-processing software is developed to fulfill time domain and frequency domain measurements simultaneously. Both simulation and experiment results verify the effectiveness of this novel sensor system.
Korayem, M. H.; Korayem, A. H.; Hosseini Hashemi, Sh.
2016-02-01
Nowadays, to enhance the performance of atomic force microscopy (AFM) micro-cantilevers (MCs) during imaging, reduce costs and increase the surface topography precision, advanced MCs equipped with piezoelectric layers are utilized. Using the modified couple stress (MCS) theory not only makes the modeling more exhaustive, but also increases the accuracy of prediction of the vibration behavior of the system. In this paper, Hamilton's principle by consideration of the MCS theory has been used to extract the equations. In addition, to discretize the equations, differential quadrature method has been adopted. Analysis of the hysteresis effect on the vibration behavior of the AFM MC is of significant importance. Thus, to model the hysteresis effect, Bouc-Wen method, which is solved simultaneously with the vibration equations of non-uniform Timoshenko beam, has been utilized. Furthermore, a bimodal excitation of the MC has been considered. The results reveal that the hysteresis effect appears as a phase difference in the time response. Finally, the effect of the geometric parameters on the vibration frequency of the system which is excited by combination of the first two vibration modes of the non-uniform piezoelectric MC has been examined. The results indicate the considerable effect of the MC length in comparison with other geometric parameters such as the MC width and thickness.
Nicu, V.P.; Domingos, S.R.; Strudwick, B.H.; Brouwer, A.M.; Buma, W.J.
2015-01-01
A detailed analysis of the computed structure, energies, vibrational absorption (VA) and circular dichroism (VCD) spectra of 30 low-energy conformers of dehydroquinidine reveals the existence of families of pseudo-conformers, the structures of which differ mostly in the orientation of a single
Directory of Open Access Journals (Sweden)
Chunyu Zhao
2009-01-01
Full Text Available The paper focuses on the quantitative analysis of the coupling dynamic characteristics of two non-identical exciters in a non-resonant vibrating system. The load torque of each motor consists of three items, including the torque of sine effect of phase angles, that of coupling sine effect and that of coupling cosine effect. The torque of frequency capture results from the torque of coupling cosine effect, which is equal to the product of the coupling kinetic energy, the coefficient of coupling cosine effect, and the sine of phase difference of two exciters. The motions of the system excited by two exciters in the same direction make phase difference close to π and that in opposite directions makes phase difference close to 0. Numerical results show that synchronous operation is stable when the dimensionless relative moments of inertia of two exciters are greater than zero and four times of their product is greater than the square of their coefficient of coupling cosine effect. The stability of the synchronous operation is only dependent on the structural parameters of the system, such as the mass ratios of two exciters to the vibrating system, and the ratio of the distance between an exciter and the centroid of the system to the equivalent radius of the system about its centroid.
Bravin, E; Sosa, A
2014-01-01
This report summarizes the results of a series of tests performed on the prototype HIE-ISOLDE diagnostic box (HIE-DB) regarding the vibrations and drifts in the transverse position of the scanning blade while moving in and out of beam path in the HIE-ISOLDE short box prototype. To monitor the transverse position of the blade, a series of 0.1 mm diameter holes were drilled on it and their positions were tracked with an optical system. The linear motion actuator was acquired from UHV design (model LSM38-150-SS), and it was adapted to be driven by a brushless EC motor from MAXON. The speed of the scanning blade during the tests was 10 mm/s. The transverse movement of the slit in the direction perpendicular to the movement was lower than 40 m, and is dominated by the displacement of the contact point of the applied force on the lead-screw. An offset on the slit position was observed while changing the direction of movement of the blade, its amplitude being of the order of 30 m. The amplitudes of the displacements...
Directory of Open Access Journals (Sweden)
Chunyu Zhao
2009-01-01
Full Text Available In this paper an analytical approach is proposed to study the feature of frequency capture of two non-identical coupled exciters in a non-resonant vibrating system. The electromagnetic torque of an induction motor in the quasi-steady-state operation is derived. With the introduction of two perturbation small parameters to average angular velocity of two exciters and their phase difference, we deduce the Equation of Frequency Capture by averaging two motion equations of two exciters over their average period. It converts the synchronization problem of two exciters into that of existence and stability of zero solution for the Equation of Frequency Capture. The conditions of implementing frequency capture and that of stabilizing synchronous operation of two motors have been derived. The concept of torque of frequency capture is proposed to physically explain the peculiarity of self-synchronization of the two exciters. An interesting conclusion is reached that the moments of inertia of the two exciters in the Equation of Frequency Capture reduce and there is a coupling moment of inertia between the two exciters. The reduction of moments of inertia and the coupling moment of inertia have an effect on the stability of synchronous operation.
Bravin, E; Sosa, A
2014-01-01
This report summarizes the results of a series of tests performed on the prototype HIE-ISOLDE diagnostic box (HIE-DB) regarding the vibrations and drifts in the transverse position of the scanning blade while moving inside or outside the box. To monitor the transverse position of the blade, a series of 0.1 mm diameter holes were drilled on it and their positions were tracked with an optical system. The linear motion actuator was acquired from UHV design (model LSM38-150-SS), is driven by a stepper motor and has all the guiding mechanisms outside vacuum. The maximum speed of the scanning blade during the tests was 2.5 mm/s. The transverse movement of the slit in the direction perpendicular to the movement was lower than 50 m, and is dominated by the displacement of the contact point of the applied force on the lead-screw. An offset on the slit position was observed while changing the direction of movement of the blade, its amplitude being of the order of 30 m. The amplitudes of the displacements of the transve...
DEFF Research Database (Denmark)
Sorokin, Vladislav
2014-01-01
In the classical papers (see, e.g. P.L. Kapitsa, Pendulum with vibrating axis of suspension. Usp. Fiz. Nauk 44 1 (1954) 7-20 (in Russian)) motion of pendulum with vibrating suspension axis was considered in the case when frequency of external loading is much higher than the natural frequency...... of the pendulum in the absence of this loading. The present paper is concerned with the analysis of inverted pendulums motion at unconventional values of parameters. Case when frequency of external loading and the natural frequency of the pendulum in the absence of this loading are of the same order is studied...... in the stability domain. It is revealed that in the considered range of parameters not only the effective stiffness of the system changes due to the external loading, but also its effective mass. Applicability of the proposed approach for solving non-linear equations without small parameter is demonstrated...
Quadrupole collectivity in {sup 128}Cd
Energy Technology Data Exchange (ETDEWEB)
Boenig, Esther Sabine
2014-07-07
The regions around shell closures, especially around doubly magic nuclei, are of major interest in nuclear structure physics, as they provide a perfect test for nuclear structure theory. The neutron-rich Cd isotopes in the region of {sup 132}Sn are only two protons away from the shell closure at Z=50 and in close proximity to the N=82 magic number. Nevertheless they show an irregular behaviour regarding the excitation energy of the first excited 2{sup +} state. This is not reproduced by shell model calculations, which is astonishing due to the proximity of the shell closures. In order to shed light on the much discussed region around doubly magic {sup 132}Sn, a Coulomb excitation experiment of {sup 128}Cd has been performed at REX-ISOLDE, CERN. The reduced transition strength B(E2;0{sup +}{sub gs} → 2{sup +}{sub 1}), which is a measure of collectivity, and the spectroscopic quadrupole moment Q{sub s}(2{sup +}{sub 1}) as a measure of deformation could be determined for the first time. The results are shown as the continuation of already measured neutron-rich Cd isotopes and are compared to both beyond mean field and shell model calculations, which give different predictions for these observables.
General principles of vibrational spectroscopies
Weckhuysen, B.M.; Schoonheydt, R.A.
2000-01-01
Atoms in molecules and solids do not remain in fixed relative positions, but vibrate about some mean position. This vibrational motion is quantized and at room temperature, most of the molecules in a given sample are in their lowest vibrational state. Absorption of electromagnetic radiation with
Vibration control in accelerators
Energy Technology Data Exchange (ETDEWEB)
Montag, C.
2011-01-01
In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.
Thermal Vibrational Convection
Gershuni, G. Z.; Lyubimov, D. V.
1998-08-01
Recent increasing awareness of the ways in which vibrational effects can affect low-gravity experiments have renewed interest in the study of thermal vibrational convection across a wide range of fields. For example, in applications where vibrational effects are used to provide active control of heat and mass transfer, such as in heat exchangers, stirrers, mineral separators and crystal growth, a sound understanding of the fundamental theory is required. In Thermal Vibrational Convection, the authors present the theory of vibrational effects caused by a static gravity field, and of fluid flows which appear under vibration in fluid-filled cavities. The first part of the book discusses fluid-filled cavities where the fluid motion only appears in the presence of temperature non-uniformities, while the second considers those situations where the vibrational effects are caused by a non-uniform field. Throughout, the authors concentrate on consideration of high frequency vibrations, where averaging methods can be successfully applied in the study of the phenomena. Written by two of the pioneers in this field, Thermal Vibrational Convection will be of great interest to scientists and engineers working in the many areas that are concerned with vibration, and its effect on heat and mass transfer. These include hydrodynamics, hydro-mechanics, low gravity physics and mechanics, and geophysics. The rigorous approach adopted in presenting the theory of this fascinating and highly topical area will facilitate a greater understanding of the phenomena involved, and will lead to the development of more and better-designed experiments.
Vibrations of rotating machinery
Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick
2017-01-01
This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...
Lanzani, Guglielmo; De Silvestri, Sandro
2007-01-01
Vibrational spectroscopy is a powerful investigation tool for a wide class of materials covering diverse areas in physics, chemistry and biology. The continuous development in the laser field regarding ultrashort pulse generation has led to the possibility of producing light pulses that can follow vibrational motion coupled to the electronic transitions in molecules and solids in real time. Aimed at researchers and graduate students using vibrational spectroscopy, this book provides both introductory chapters as well as more advanced contents reporting on recent progress. It also provides a good starting point for scientists seeking a sound introduction to ultrafast optics and spectroscopic techniques.
Riedel, S. A.; Jex, H. R.; Magdaleno, R. E.
1982-01-01
A user-oriented program for exercising the 1980 verson of the biodynamic model BIODYN-80 is described. The user inputs (modifies) some 80-100 variables describing the assumed posture, interface characteristics (e.g., stick "feel" properties), and vestibular characteristics. The computer calculates the transfer functions between vibration input and various selected outputs of interest to the user. Another option is to output the operator's torso-limb-neuromuscular loop transmissibilities as seen at the stick, as required for the PIVIB computer program for computing tracking performance effects of vibration. Applications to some current problems are demonstrated.
Motion Mechanism of Two-Degree-of-Freedom Spherical Motor Using Single PZT Vibrator%单振子二自由度球面马达的运动机理
Institute of Scientific and Technical Information of China (English)
程光明; 郭抗; 孙业明; 曾平; 武迪
2011-01-01
利用矩形板形压电振子的两种振动模态,构建了一种采用单片压电振子驱动球形转子,形成两个旋转自由度的压电球面超声马达,对马达的作用机理进行了仿真分析和试验验证.利用有限元法对马达的矩形板压电振子的振动模态、共振频率进行了分析计算,仿真结果表明矩形板压电振子能够形成振型清晰的B32和B23振动模态,模态频率分别为49.127 kHz和49.756 kHz.对压电振子上每个凸起与球形转子之间的接触点的运动轨迹进行了计算机仿真,并对仿真结果进行了试验验证.分析结果表明各接触点能有效形成时序合理的椭圆运动轨迹,作为支撑足的一组凸起的变形量占作为驱动足的一组凸起的变形量的30%,能够用于驱动球形转子形成二自由度转动.仿真分析和试验结果证明了二自由度球面马达球形转子形成二维运动的作用机理.%A two-degree-of-freedom piezoelectric spherical ultrasonic motor using only one piezoelectric element to drive the rotator was proposed based on two vibration modes of a rectangular plate type piezoelectric vibrator. The motion mechanism of the motor was verified by simulation and experiment. The vibration modes and resonance frequencies of the motor's plate type piezoelectric vibrator were calculated by finite element method. The simulation results show that the piezoelectric vibrator can produce clear vibration shapes in B32 and BB modes, and their modal frequencies are 49.127 kHz and 49.756 kHz, respectively. The motion trajectories of four contact points between the protrusion and the spherical rotor were analyzed with computer simulation, and prototype test was carried out to verify the simulation results. The results indicate that the four contact points can form elliptical trajectories with reasonable timing, which can be used to drive the spherical rotor to form rotation with two-degree-of-freedom, and the deformation of protrusions
Dattani, Nikesh S.
2016-06-01
The state-of-the-art empirical potential, and the state-of-the-art ab initio potential for the b(1^3Π2_u) state of 7,7Li_2 agree with each other that the (v=100,J=0) ro-vibrational state has an outer classical turning point larger than the diameter of most bacteria and many animal cells. The 2015 empirical potential based on a significant amount of spectroscopic data, predicts the (v=100,J=0) level to be bound by only 0.000 000 000 004 cm-1 (0.01 mm. While this discovery occurred during a study of Li_2, the b(1^3Π2_u) states of heavier alkali diatomics are expected to have even larger amplitude vibrational states. While it might be tempting to call these very large molecules ``Rydberg molecules", it is important to remember that this term is already used to describe highly excited electronic states whose energy levels follow a formula similar to that for the famous Rydberg series. The highly delocalized vibrational states are a truly unfamiliar phenomenon. Dattani (2015) http://arxiv.org/abs/1508.07184v1 Musial & Kucharski (2014) Journal of Chemical Theory and Computation, 10, 1200
Vibration enhanced quantum transport
Semião, F L; Milburn, G J
2009-01-01
In this paper, we study the role of a collective vibrational motion in the phenomenon of electronic energy transfer (EET) between chromophores with different electronic transition frequencies. Previous experimental work on EET in conjugated polymer samples has suggested that the common structural framework of the macromolecule introduce correlations in the energy gap fluctuations which cause coherent EET. We present a simple model describing the coupling between the chromophores and a common vibrational mode, and find that vibration can indeed lead to an enhancement in the transport of excitations across the quantum network. Furthermore, in our model phase information is partially retained in the transfer process from a donor to an acceptor, as experimentally demonstrated in the conjugated polymer system. Consequently, this mechanism of vibration enhanced quantum transport might find applications in quantum information transfer of qubit states or entanglement.
Research on cylindrical shell vibration reduction systems
Institute of Scientific and Technical Information of China (English)
XING Xiao-liang; WANG Min-qing
2008-01-01
Longitudinal and horizontal vibration must both be reduced in an effective vibration isolation system. We present a cylindrical shell vibration isolator as a dynamic system composed of four springs and dampers. Vibration is directly produced by the motion of machinery, and more is subsequently generated by harmonic frequencies within their structure. To test the effectiveness of our isolator, we first determined equations for the transmission of vibration from the machine to its cylindrical shell. Damping effects produced by the vibration parameters of our system are then analyzed.
Cartmell, Matthew P.
2016-09-01
The Editor wishes to make the reader aware that the paper "Semi-active control of the rocking motion of monolithic art objects" by R. Ceravolo, M.L. Pecorelli, and L.Z. Fragonara, did not contain a direct citation of the fundamental and original work by D. Konstantinidis and N. Makris entitled "Experimental and analytical studies on the seismic response of free-standing and anchored laboratory equipment", Report No. PEER 2005/07. Pacific Earthquake Engineering Research (PEER) Center, University of California, Berkeley, 2005. The Editor regrets that this omission was not noted at the time that the above paper was accepted and published.
Droplets bouncing over a vibrating fluid layer
Cabrera-Garcia, Pablo
2012-01-01
This is an entry for the Gallery of Fluid Motion of the 65st Annual Meeting of the APS-DFD (fluid dynamics video). This video shows the motion of levitated liquid droplets. The levitation is produced by the vertical vibration of a liquid container. We made visualizations of the motion of many droplets to study the formation of clusters and their stability.
Mechanical vibrations of pendant liquid droplets
Temperton, Robert H.; Smith, Michael I.; Sharp, James S.
2015-01-01
A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependen...
Nicolas, Maxime
2016-01-01
Engineering school; This course is designed for students of Polytech Marseille, engineering school. It covers first the physics of vibration of the harmonic oscillator with damping and forcing, coupled oscillators. After a presentation of the wave equation, the vibration of strings, beams and membranes are studied.
Vibration suppression using smart structures
Garcia, Ephrahim; Inman, Daniel J.; Dosch, Jeffrey
1991-01-01
The control of structures for vibration suppression is discussed in the context of using smart materials and structures. Here the use of smart structures refers to using embedded piezoelectric devices as both control actuators and sensors. Using embedded sensors and actuators allows great improvements in performance over traditional structures (both passive and active) for vibration suppression. The application of smart structures to three experimental flexible structures is presented. The first is a flexible beam, the second is a flexible beam undergoing slewing motion, the third is a ribbed antenna. A simple model of a piezoelectric actuator/sensor is presented. The equations of motion for each structure is presented. The control issues considered as those associated with multi-input, multi-output control, PID control and LQR control implementation. A modern control analysis illustrates the usefulness of smart structures for vibration suppression.
Directory of Open Access Journals (Sweden)
2016-01-01
Full Text Available The paper carried out a comparison of vibration sensors used to measure the vibration condition units with gas turbine engines, with motion sensors, microelectromechanical systems used in modern mobile devices (for example, devices on the platform "Android". It provides opinions on the possibility of assessment of vibration, using sensors of mobile devices.
Cases of coupled vibrations and prametric instability in rotating machines
Luneno, Jean-Claude
2012-01-01
The principal task in this research project was to analyse the causes and consequences of coupled vibrations and parametric instability in hydropower rotors; where both horizontal and vertical machines are involved. Vibration is a well-known undesirable behavior of dynamical systems characterised by persistent periodic, quasi-periodic or chaotic motions. Vibrations generate noise and cause fatigue, which initiates cracks in mechanical structures. Motions coupling can in some cases augment the...
Robust Control of Machine-Tool Vibration in a Lathe
Claesson, Ingvar; Håkansson, Lars; Lagö, Thomas L.
1999-01-01
In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced substantially by active control of the machine-tool vibration. Adaptive fe...
Vibrations and fractional vibrations of rods, plates and Fresnel pseudo-processes
Orsingher, Enzo
2011-01-01
Different initial and boundary value problems for the equation of vibrations of rods (also called Fresnel equation) are solved by exploiting the connection with Brownian motion and the heat equation. The analysis of the fractional version (of order $\
Graff, Karl F
1991-01-01
This highly useful textbook presents comprehensive intermediate-level coverage of nearly all major topics of elastic wave propagation in solids. The subjects range from the elementary theory of waves and vibrations in strings to the three-dimensional theory of waves in thick plates. The book is designed not only for a wide audience of engineering students, but also as a general reference for workers in vibrations and acoustics. Chapters 1-4 cover wave motion in the simple structural shapes, namely strings, longitudinal rod motion, beams and membranes, plates and (cylindrical) shells. Chapter
Moire interferometry for vibration analysis of plates
Asundi, A.; Cheung, M. T.
1987-12-01
Moire interferometry is used to locate nodal regions and measure vibration amplitudes of sinusoidally vibrating square plates. The high sensitivity afforded by this technique makes possible the study of plate vibrations at high frequencies and low amplitudes. The initial pattern is modulated by the zero-order Bessel function representing the vibratory motion. The fringe (or fringes) with best contrast indicate the nodal regions, while the higher order fringes, describing loci of points vibrating with the same amplitude, have decreasing contrast which is improved by spatial filtering.
Panesar, Lucy
2007-01-01
Good Vibrations was a market research exercise conducted by Felicity (my alter-ego) and assistants to help develop marketing and packaging for an electro-therapeutic device (vibrator) used to treat hysteria and other female stress related disorders. It was a live art work commissioned by The Live Art Development Agency for East End Collaborations on 6th May 2007 and the South London Gallery for Bonkersfest on 2nd June 2007.
Gupta, Amita; Singh, Ranvir; Ahmad, Amir; Kumar, Mahesh
2003-10-01
Today, vibration sensors with low and medium sensitivities are in great demand. Their applications include robotics, navigation, machine vibration monitoring, isolation of precision equipment & activation of safety systems e.g. airbags in automobiles. Vibration sensors have been developed at SSPL, using silicon micromachining to sense vibrations in a system in the 30 - 200 Hz frequency band. The sensing element in the silicon vibration sensor is a seismic mass suspended by thin silicon hinges mounted on a metallized glass plate forming a parallel plate capacitor. The movement of the seismic mass along the vertical axis is monitored to sense vibrations. This is obtained by measuring the change in capacitance. The movable plate of the parallel plate capacitor is formed by a block connected to a surrounding frame by four cantilever beams located on sides or corners of the seismic mass. This element is fabricated by silicon micromachining. Several sensors in the chip sizes 1.6 cm x 1.6 cm, 1 cm x 1 cm and 0.7 cm x 0.7 cm have been fabricated. Work done on these sensors, techniques used in processing and silicon to glass bonding are presented in the paper. Performance evaluation of these sensors is also discussed.
Duzen, Carl; And Others
1992-01-01
Presents a series of activities that utilizes a leveling device to classify constant and accelerated motion. Applies this classification system to uniform circular motion and motion produced by gravitational force. (MDH)
Optimal parameters uncoupling vibration modes of oscillators
Le, K. C.; Pieper, A.
2017-07-01
This paper proposes a novel optimization concept for an oscillator with two degrees of freedom. By using specially defined motion ratios, we control the action of springs to each degree of freedom of the oscillator. We aim at showing that, if the potential action of the springs in one period of vibration, used as the payoff function for the conservative oscillator, is maximized among all admissible parameters and motions satisfying Lagrange's equations, then the optimal motion ratios uncouple vibration modes. A similar result holds true for the dissipative oscillator having dampers. The application to optimal design of vehicle suspension is discussed.
Chaotic vortex induced vibrations
Energy Technology Data Exchange (ETDEWEB)
Zhao, J.; Sheridan, J. [Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800 (Australia); Leontini, J. S. [Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Lo Jacono, D. [Institut de Mécanique des Fluides de Toulouse (IMFT), CNRS, UPS and Université de Toulouse, 31400 Toulouse (France)
2014-12-15
This study investigates the nature of the dynamic response of an elastically mounted cylinder immersed in a free stream. A novel method is utilized, where the motion of the body during a free vibration experiment is accurately recorded, and then a second experiment is conducted where the cylinder is externally forced to follow this recorded trajectory. Generally, the flow response during both experiments is identical. However, particular regimes exist where the flow response is significantly different. This is taken as evidence of chaos in these regimes.
Anharmonic vibrations in nuclei
Fallot, M; Andrés, M V; Catara, F; Lanza, E G; Scarpaci, J A; Chomaz, Ph.
2003-01-01
In this letter, we show that the non-linearitites of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of the large matrix elements with such three phonon configurations. These effects are studied in two nuclei, 40Ca and 208Pb.
DEFF Research Database (Denmark)
Jönsson, Jeppe; Hansen, Lars Pilegaard
1994-01-01
Human motion can cause various types of periodic or transient dynamic loads. The periodic loads are mainly due to jumping, running, dancing, walking and body rocking. Transient loads primarily result from single impulse loads, such as jumping and falling from elevated positions. The response...... concerned with spectator-induced vertical vibrations on grandstands. The idea is to use impulse response analysis and base the load description on the load impulse. If the method is feasable, it could be used in connection with the formulation of requirements in building codes. During the last two decades...
Quadrupole collectivity in Si isotopes around N=20
Rodríguez-Guzman, R R; Robledo, L M
2001-01-01
The angular momentum projected Generator Coordinate Method using the quadrupole moment as collective coordinate and the Gogny force as the effective interaction is used to describe the properties of the ground state and low-lying excited states of the neutron rich light nuclei 32,34,36Si. It is found that the ground state of the nucleus 34Si is spherical. However, this is not only due to the N=20 shell closure as the ground state of 34Si contains a significant amount of the intruder f7/2 neutron orbital. On the other hand, rather good agreement with experimental data for many observables is obtained.
Quadrupole collectivity of neutron-rich Neon isotopes
Rodríguez-Guzman, R R; Robledo, L M
2003-01-01
The angular momentum projected Generator Coordinate Method, with the quadrupole moment as collective coordinate and the Gogny force (D1S) as the effective interaction, is used to describe the properties of the ground state and low-lying excited states of the even-even Neon isotopes $^{20-34}$Ne, that is, from the stability valley up to the drip-line. It is found that the ground state of the N=20 nucleus $^{30}$Ne is deformed but to a lesser extent than the N=20 isotope of the Magnesium. In the calculations, the isotope $^{32}$Ne is at the drip-line in good agreement with other theoretical predictions. On the other hand, rather good agreement with experimental data for many observables is obtained.
Vibration transmissibility characteristics of smart spring vibration isolation system
Institute of Scientific and Technical Information of China (English)
倪德; 朱如鹏; 陆凤霞; 鲍和云; 付秋菊
2014-01-01
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.
DEFF Research Database (Denmark)
Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen
2012-01-01
In this paper we describe a field study conducted with a wearable vibration belt where we test to determine the vibration intensity sensitivity ranges on a large diverse group of participants with evenly distributed ages and...... lab studies in that we found a decreased detection rate in busy environments. Here we test with a much larger sample and age range, and contribute with the first vibration sensitivity testing outside the lab in an urban public...
Less sickness with more motion and/or mental distraction.
Bos, J E
2015-01-01
BACKGROUND: Motion sickness may reduce passenger comfort and crew performance. Countermeasures are dominated by medication with specific and often undesirable side effects. OBJECTIVE: To shown that sickness due to motion can be reduced by adding an inherent non-sickening vibration and by mental distraction. METHODS: Eighteen blindfolded subjects were exposed to 20 minutes of off-vertical axis rotation (OVAR). Vibration was added by means of a head rest. Effects of OVAR and vibration were test...
Monitoring Vibration of A Model of Rotating Machine
Directory of Open Access Journals (Sweden)
Arko Djajadi
2012-03-01
Full Text Available Mechanical movement or motion of a rotating machine normally causes additional vibration. A vibration sensing device must be added to constantly monitor vibration level of the system having a rotating machine, since the vibration frequency and amplitude cannot be measured quantitatively by only sight or touch. If the vibration signals from the machine have a lot of noise, there are possibilities that the rotating machine has defects that can lead to failure. In this experimental research project, a vibration structure is constructed in a scaled model to simulate vibration and to monitor system performance in term of vibration level in case of rotation with balanced and unbalanced condition. In this scaled model, the output signal of the vibration sensor is processed in a microcontroller and then transferred to a computer via a serial communication medium, and plotted on the screen with data plotter software developed using C language. The signal waveform of the vibration is displayed to allow further analysis of the vibration. Vibration level monitor can be set in the microcontroller to allow shutdown of the rotating machine in case of excessive vibration to protect the rotating machine from further damage. Experiment results show the agreement with theory that unbalance condition on a rotating machine can lead to larger vibration amplitude compared to balance condition. Adding and reducing the mass for balancing can be performed to obtain lower vibration level.
Umesh P. Agarwal; Rajai Atalla
2010-01-01
Vibrational spectroscopy is an important tool in modern chemistry. In the past two decades, thanks to significant improvements in instrumentation and the development of new interpretive tools, it has become increasingly important for studies of lignin. This chapter presents the three important instrumental methods-Raman spectroscopy, infrared (IR) spectroscopy, and...
2009-01-01
Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.
Vibration-enhanced quantum transport
2009-01-01
In this paper, we study the role of collective vibrational motion in the phenomenon of electronic energy transfer (EET) along a chain of coupled electronic dipoles with varying excitation frequencies. Previous experimental work on EET in conjugated polymer samples suggested that the common structural framework of the macromolecule introduces correlations in the energy gap fluctuations that cause coherent EET. Inspired by these results, we present a simple model in which a driven nanomechanica...
Vibrational mechanics nonlinear dynamic effects, general approach, applications
Blekhman, Iliya I
2000-01-01
This important book deals with vibrational mechanics - the new, intensively developing section of nonlinear dynamics and the theory of nonlinear oscillations. It offers a general approach to the study of the effect of vibration on nonlinear mechanical systems.The book presents the mathematical apparatus of vibrational mechanics which is used to describe such nonlinear effects as the disappearance and appearance under vibration of stable positions of equilibrium and motions (i.e. attractors), the change of the rheological properties of the media, self-synchronization, self-balancing, the vibrat
DEFF Research Database (Denmark)
Vendrell, Oriol; Gatti, Fabien; Meyer, Hans-Dieter
2007-01-01
the fundamentals and several overtones of the vibrational motion are computed. The spectrum of H5O2+ is shaped to a large extent by couplings of the proton-transfer motion to large amplitude fluxional motions of the water molecules, water bending and water-water stretch motions. These couplings are identified...... and discussed, and the corresponding spectral lines are assigned. The large couplings featured by H5O2+ do not hinder, however, to describe the coupled vibrational motion by well defined simple types of vibration (stretching, bending; etc.) based on well defined modes of vibration, in terms of which...
Optimal parameters uncoupling vibration modes of oscillators
Le, Khanh Chau
2016-01-01
A novel optimization concept for an oscillator with two degrees of freedom is proposed. By using specially defined motion ratios, we control the action of springs and dampers to each degree of freedom of the oscillator. If the potential action of the springs in one period of vibration, used as the payoff function for the conservative oscillator, is maximized, then the optimal motion ratios uncouple vibration modes. The same result holds true for the dissipative oscillator. The application to optimal design of vehicle suspension is discussed.
Numerical simulations of vibrating sessile drop
Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Craster, Richard; Matar, Omar
2016-11-01
A vibrated drop constitutes a very rich physical system, blending both interfacial and volume phenomena. A remarkable experimental study was performed by M. Costalonga highlighting sessile drop motion subject to horizontal, vertical and oblique vibration. Several intriguing phenomena are observed such as drop walking and rapid droplet ejection. We perform three-dimensional direct numerical simulations of vibrating sessile drops where the phenomena described above are computed using the massively parallel multiphase code BLUE. EPSRC UK Programme Grant MEMPHIS (EP/K003976/1).
Analysis of radial vibrations of poroelastic circular cylindrical shells ...
African Journals Online (AJOL)
DR OKE
When both outer and inner fluids vanish, the considered problem is reduced to the problem of ... The equations of motion of a homogeneous, isotropic poroelastic solid (Biot, 1956) in presence of dissipation b are. 2. 2 ...... Vibration and Control.
Vibration Control of Flexible Spacecraft Using Adaptive Controller
Directory of Open Access Journals (Sweden)
V.I. George
2012-01-01
Full Text Available The aim is to develop vibration control of flexible spacecraft by adaptive controller. A case study will be carried out which simulates planar motion of flexible spacecraft as a coupled hybrid dynamics of rigid body motion and the flexible arm vibration. The notch filter and adaptive vibration controller, which updates filter and controller parameters continuously from the sensor measurement, are implemented in the real time control. The least mean square algorithm using the adaptive notch filter is applied to the flexible spacecraft. This study will show that the adaptive vibration controller successfully stabilizes the uncertain and it will accurately control the vibration of flexible spacecraft. The Least mean square algorithm is applied in flexible spacecraft to attenuate the vibration. The simulation studies are carried out in a Matlab/Simulink environment.
Energy Technology Data Exchange (ETDEWEB)
Eliazar, Iddo I., E-mail: eliazar@post.tau.ac.il [Holon Institute of Technology, P.O. Box 305, Holon 58102 (Israel); Shlesinger, Michael F., E-mail: mike.shlesinger@navy.mil [Office of Naval Research, Code 30, 875 N. Randolph St., Arlington, VA 22203 (United States)
2013-06-10
Brownian motion is the archetypal model for random transport processes in science and engineering. Brownian motion displays neither wild fluctuations (the “Noah effect”), nor long-range correlations (the “Joseph effect”). The quintessential model for processes displaying the Noah effect is Lévy motion, the quintessential model for processes displaying the Joseph effect is fractional Brownian motion, and the prototypical model for processes displaying both the Noah and Joseph effects is fractional Lévy motion. In this paper we review these four random-motion models–henceforth termed “fractional motions” –via a unified physical setting that is based on Langevin’s equation, the Einstein–Smoluchowski paradigm, and stochastic scaling limits. The unified setting explains the universal macroscopic emergence of fractional motions, and predicts–according to microscopic-level details–which of the four fractional motions will emerge on the macroscopic level. The statistical properties of fractional motions are classified and parametrized by two exponents—a “Noah exponent” governing their fluctuations, and a “Joseph exponent” governing their dispersions and correlations. This self-contained review provides a concise and cohesive introduction to fractional motions.
A Continuum Description of Vibrated Sand
Eggers, J; Eggers, Jens; Riecke, Hermann
1999-01-01
The motion of a thin layer of granular material on a plate undergoing sinusoidal vibrations is considered. We develop equations of motion for the local thickness and the horizontal velocity of the layer, where the driving comes from the violent impact of the grains on the surface. A linear stability theory reveals a novel mechanism for the excitation of waves. Comparing both the stability diagram and the dispersion relation with experiment, we are able to check the consistency of our model.
Active Control of Machine-Tool Vibration in a Lathe
Claesson, Ingvar; Håkansson, Lars
1997-01-01
In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration is a frequent problem, which affects the result of the machining, in particular the surface finish. The tool life is also influenced by the vibrations. When the working environment is considered, noise is frequently introduced by dynamic motion between the cutting tool and the workpiece. By proper machine design, e.g. improved stiffness of the machine structure, the problem of relative dynami...
New Damped-Jerk trajectory for vibration reduction
BEAREE, Richard
2014-01-01
This paper derives a jerk-shaped profile to address the vibration reduction of underdamped flexible dynamics of motion system. The jerk-limited profile is a widespread smooth command pattern used by modern motion systems. The ability of the jerk-limited profile to cancel the residual vibration of an undamped flexible mode is clearly explained using an equivalent continuous filter representation and the input shaping formalism. This motivates the design of a new jerk-shaped profile, named Damp...
Experimental Research on the Influence of Vibration on Fingers Mobility
Directory of Open Access Journals (Sweden)
Radu Panaitescu-Liess
2013-09-01
Full Text Available In many industrial activities the human body is exposed to vibrations transmitted through the hand-arm system. A long exposure to these vibrations can cause various health problems of blood vessels, nerves, muscles, bones, joints and upper limb [1]. This paper presents some considerations about the influence of vibration on finger joints mobility. I used a MediTouch system which consists of a motion capture device (an ergonomic glove and a dedicated software.
Active Vibration Control of a Thin Steel Sheet
Yohji Okada; Ken-Ichi Matsuda; Junji Tani
1995-01-01
The commercial rolling process used in the steel industry to manufacture thin steel sheets tends to cause plate vibrations that lower the quality of the surface finish. This article introduces a noncontact method of active vibration control for reducing the flexural vibrations of a thin steel sheet. The proposed electromagnetic method of control has been implemented in a simple experimental setup where the signal from a motion sensor regulates the attractive force of the magnets that produce ...
The Shock and Vibration Digest. Volume 13, Number 3
1981-03-01
Flight, MppIM.it 198U) N8030000 Kay Word«: Vibration •«citation. Human ratpont« Elavan wbiacu wara vibratad on a ihaka- tabla in the tra- quancy...ranga of 2 Hi to 19 Hi to attaM tha complax haad motion inducad by i^ xii machantcat vibration. Accalaratlon ampiltuda Mat tinuioidal and ha)d
Tunneling ionization of vibrationally excited nitrogen molecules
Kornev, Aleksei S.; Zon, Boris A.
2015-09-01
Ionization of molecular nitrogen plays an important role in the process of light-filament formation in air. In the present paper we theoretically investigated tunneling ionization of the valence 3 σg and 1 πu shells in a N2 molecule using a strong near-infrared laser field. This research is based on our previously proposed theory of anti-Stokes-enhanced tunneling ionization with quantum accounting for the vibrationally excited states of the molecules [A. S. Kornev and B. A. Zon, Phys. Rev. A 86, 043401 (2012), 10.1103/PhysRevA.86.043401]. We demonstrated that if the N2 molecule is ionized from the ground vibrational state, then the contribution of the 1 πu orbital is 0.5%. In contrast, for vibrationally excited states with a certain angle between the light polarization vector and the molecule axis, both shells can compete and even reverse their contributions due to the anti-Stokes mechanism. The structure constants of molecular orbitals are extracted from numerical solutions to the Hartree-Fock equations. This approach correctly takes into account the exchange interaction. Quantum consideration of vibrational motion results in the occurrence of the critical vibrational state, the tunneling ionization from which has the maximum rate. The numbers of the critical vibrational states are different for different valence shells. In addition, quantum description of vibrations changes the rate of ionization from the ground vibrational state by 20%-40% in comparison with the quasiclassical results.
Active Control of Parametric Vibrations in Coupled Rotor-Blade Systems
DEFF Research Database (Denmark)
Christensen, Rene Hardam; Santos, Ilmar
2003-01-01
In rotor-blade systems basis as well as parametric vibration modes will appear due to the vibration coupling among flexible rotating blades and hub rigid body motion. Parametric vibration will typically occur when the hub operates at a constant angular velocity. Operating at constant velocity...
Recurrence plot analysis of nonlinear vibrational dynamics in H sub 3 sup + molecule
Babinec, P
2003-01-01
An ab initio classical trajectories obtained from the simulation of vibrational mode dynamics of H sub 3 sup + molecule were analyzed by Fourier transform and recurrence plot analysis. As has been found, at a particular value of energy supplied to vibrational modes (slightly above the zero point energy) the character of vibrational motion changes from regular to chaotic.
Optimal Damping of Stays in Cable-Stayed Bridges for In-Plane Vibrations
DEFF Research Database (Denmark)
Jensen, C.N.; Nielsen, S.R.K.; Sørensen, John Dalsgaard
2002-01-01
Significant vibrations have been reported in stays of recently constructed cable stayed bridges. The vibrations appear as in-plane vibrations that may be caused by rain–wind- induced aeroelastic interaction or by resonance excitation of the cables from the motion of the pylons. The stays of moder...
DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM
Energy Technology Data Exchange (ETDEWEB)
Martin E. Cobern
2004-08-31
The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed.
DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM
Energy Technology Data Exchange (ETDEWEB)
Martin E. Cobern
2004-08-31
The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed.
Vibration Superposition in Tunnel Blasting with Millisecond Delay
Institute of Scientific and Technical Information of China (English)
ZHENG Jun-jie; LOU Xiao-ming; LUO De-pi
2009-01-01
According to explosion dynamics and elastic wave theory,the models of particle vibration velocity for simultaneous blasting and millisecond blasting are built.In the models,influential factors such as delay interval and charge quantity,are considered.The calculated vibration velocity is compared with the field test results,which shows that the theoretical values are close to the experimental ones.Meanwhile,the particle vibration velocity decreases quickly with time due to the damping of rock mass and has a harmonic motion,and the particle vibration velocity of millisecond blasting has short interval.The superposition of particle vibration velocities may reduce vibration because of wave interference,or magnify the surrounding rock response to the blasting-induced vibration.
Theory of vibration protection
Karnovsky, Igor A
2016-01-01
This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...
Mechanical vibration to electrical energy converter
Kellogg, Rick Allen; Brotz, Jay Kristoffer
2009-03-03
Electromechanical devices that generate an electrical signal in response to an external source of mechanical vibrations can operate as a sensor of vibrations and as an energy harvester for converting mechanical vibration to electrical energy. The devices incorporate a magnet that is movable through a gap in a ferromagnetic circuit, wherein a coil is wound around a portion of the ferromagnetic circuit. A flexible coupling is used to attach the magnet to a frame for providing alignment of the magnet as it moves or oscillates through the gap in the ferromagnetic circuit. The motion of the magnet can be constrained to occur within a substantially linear range of magnetostatic force that develops due to the motion of the magnet. The devices can have ferromagnetic circuits with multiple arms, an array of magnets having alternating polarity and, encompass micro-electromechanical (MEM) devices.
Noncommutativity Error Analysis of Strapdown Inertial Navigation System under the Vibration in UAVs
Directory of Open Access Journals (Sweden)
Jizhou Lai
2012-10-01
Full Text Available Noncommutativity error of a strapdown inertial navigation system (SINS in an unmanned aerial vehicle’s (UAV vibration environment is analysed. The traditional analysis of noncommutativity errors is based on a coning motion model, which is inconsistent with a UAV’s vibration environment. In this paper the UAV’s vibration form is discussed and is modelled as a sinusoidal angular vibration and a random angular vibration. Then, SINS motion models under these two forms of vibration are built up and the formulas for the noncommutativity errors are derived separately. In addition, the effect of a multi‐sample algorithm is explored, which is an effective method for compensating for noncommutativity errors in cases of coning motion. Finally, the UAV’s vibration environment is simulated and it is indicated that the simulation results of the SINS’s noncommutativity errors are consistent with theoretical analysis.
Directory of Open Access Journals (Sweden)
H. Bayıroğlu
2012-01-01
Full Text Available Vibrational conveyers with a centrifugal vibration exciter transmit their load based on the jumping method. Common unbalanced-mass driver oscillates the trough. The motion is strictly related to the vibrational parameters. The transition over resonance of a vibratory system, excited by rotating unbalances, is important in terms of the maximum vibrational amplitude produced and the power demand on the drive for the crossover. The mechanical system is driven by the DC motor. In this study, the working ranges of oscillating shaking conveyers with nonideal vibration exciter have been analyzed analytically for superharmonic and subharmonic resonances by the method of multiple scales and numerically. The analytical results obtained in this study agree well with the numerical results.
Institute of Scientific and Technical Information of China (English)
陈俊岭; 阳荣昌; 马人乐
2013-01-01
Shaking table tests of a 1 ∶ 20 scale model of a 3 MW wind turbine tower were carried out under the excitation of near-fault ground motion with fling step.Rolling-ball vibration absorbers were designed to mitigate the tower's dynamic response.A record with fling step from 1999 Chi-Chi earthquake at TCU052 station was chosen and the record without fling step was obtained by filtering the former record through a 4th order Butterworth filter.The nonlinear dynamic responses of the model without absorber were studied and compared with the results from finite element analysis.Then,the effectiveness of oneball vibration absorber and multi-ball vibration absorber with the same total weight was examined under the excitation of the record with fling step.The results show that the near-fault ground motion with fling step greatly magnifies the tower's responses.It should be noted that this effect cannot be neglected when a wind turbine tower is designed and constructed in seismic zones.The ball vibration absorbers can reduce the standard deviations of dynamic responses to about 60％～70％ of those without absorber.The performance of the multi-ball vibration absorber is superior to that of one-ball vibration absorber.%为研究近断层地震滑冲效应脉冲对大功率风力发电塔架结构的影响及应对措施,以丹麦某3 MW风力发电塔为原型制作缩尺模型并设计相应滚球减振器进行模拟地震振动台试验研究,考察其非线性动力响应及振动控制装置的有效性.选取具有滑冲效应脉冲的1999年Chi-Chi地震TCU052台站记录及其过滤修正记录作为输入,对比分析不同输入下无控制装置时模型的响应并建立试验模型的有限元模型对比数值计算结果和试验结果;考察设置滚球减振器后模型在有滑冲效应脉冲记录下的响应,对比分析了在总重相等时单个滚球和多个滚球布置方案下减振器的减振效果.研究表明:近断层地震滑冲效应脉冲
Vibrational and electronic spectroscopic studies of melatonin
Singh, Gurpreet; Abbas, J. M.; Dogra, Sukh Dev; Sachdeva, Ritika; Rai, Bimal; Tripathi, S. K.; Prakash, Satya; Sathe, Vasant; Saini, G. S. S.
2014-01-01
We report the infrared absorption and Raman spectra of melatonin recorded with 488 and 632.8 nm excitations in 3600-2700 and 1700-70 cm-1 regions. Further, we optimized molecular structure of the three conformers of melatonin within density functional theory calculations. Vibrational frequencies of all three conformers have also been calculated. Observed vibrational bands have been assigned to different vibrational motions of the molecules on the basis of potential energy distribution calculations and calculated vibrational frequencies. Observed band positions match well with the calculated values after scaling except Nsbnd H stretching mode frequencies. It is found that the observed and calculated frequencies mismatch of Nsbnd H stretching is due to intermolecular interactions between melatonin molecules.
Vibration signature analysis of multistage gear transmission
Choy, F. K.; Tu, Y. K.; Savage, M.; Townsend, D. P.
1989-01-01
An analysis is presented for multistage multimesh gear transmission systems. The analysis predicts the overall system dynamics and the transmissibility to the gear box or the enclosed structure. The modal synthesis approach of the analysis treats the uncoupled lateral/torsional model characteristics of each stage or component independently. The vibration signature analysis evaluates the global dynamics coupling in the system. The method synthesizes the interaction of each modal component or stage with the nonlinear gear mesh dynamics and the modal support geometry characteristics. The analysis simulates transient and steady state vibration events to determine the resulting torque variations, speeds, changes, rotor imbalances, and support gear box motion excitations. A vibration signature analysis examines the overall dynamic characteristics of the system, and the individual model component responses. The gear box vibration analysis also examines the spectral characteristics of the support system.
Muon motion in titanium hydride
Kempton, J. R.; Petzinger, K. G.; Kossler, W. J.; Schone, H. E.; Hitti, B. S.; Stronach, C. E.; Adu, N.; Lankford, W. F.; Reilly, J. J.; Seymour, E. F. W.
1988-01-01
Motional narrowing of the transverse-field muon spin rotation signal was observed in gamma-TiH(x) for x = 1.83, 1.97, and 1.99. An analysis of the data for TiH1.99 near room temperature indicates that the mechanism responsible for the motion of the muon out of the octahedral site is thermally activated diffusion with an attempt frequency comparable to the optical vibrations of the lattice. Monte Carlo calculations to simulate the effect of muon and proton motion upon the muon field-correlation time were used to interpret the motional narrowing in TiH1.97 near 500 K. The interpretation is dependent upon whether the Bloembergen, Purcell, and Pound (BPP) theory or an independent spin-pair relaxation model is used to obtain the vacancy jump rate from proton NMR T1 measurements. Use of BPP theory shows that the field-correction time can be obtained if the rate of motion of the muon with respect to the rate of the motion for the protons is decreased. An independent spin-pair relaxation model indicates that the field-correlation time can be obtained if the rate of motion for the nearest-neighbor protons is decreased.
A Vibration Control Method for the Flexible Arm Based on Energy Migration
Directory of Open Access Journals (Sweden)
Yushu Bian
2015-01-01
Full Text Available A vibration control method based on energy migration is proposed to decrease vibration response of the flexible arm undergoing rigid motion. A type of vibration absorber is suggested and gives rise to the inertial coupling between the modes of the flexible arm and the absorber. By analyzing 1 : 2 internal resonance, it is proved that the internal resonance can be successfully created and the exchange of vibration energy is existent. Due to the inertial coupling, the damping enhancement effect is revealed. Via the inertial coupling, vibration energy of the flexible arm can be dissipated by not only the damping of the vibration absorber but also its own enhanced damping, thereby effectively decreasing vibration. Through numerical simulations and analyses, it is proven that this method is feasible in controlling nonlinear vibration of the flexible arm undergoing rigid motion.
The role of vibration in tactile speed perception.
Dallmann, Chris J; Ernst, Marc O; Moscatelli, Alessandro
2015-12-01
The relative motion between the surface of an object and our fingers produces patterns of skin deformation such as stretch, indentation, and vibrations. In this study, we hypothesized that motion-induced vibrations are combined with other tactile cues for the discrimination of tactile speed. Specifically, we hypothesized that vibrations provide a critical cue to tactile speed on surfaces lacking individually detectable features like dots or ridges. Thus masking vibrations unrelated to slip motion should impair the discriminability of tactile speed, and the effect should be surface-dependent. To test this hypothesis, we measured the precision of participants in discriminating the speed of moving surfaces having either a fine or a ridged texture, while adding masking vibratory noise in the working range of the fast-adapting mechanoreceptive afferents. Vibratory noise significantly reduced the precision of speed discrimination, and the effect was much stronger on the fine-textured than on the ridged surface. On both surfaces, masking vibrations at intermediate frequencies of 64 Hz (65-μm peak-to-peak amplitude) and 128 Hz (10 μm) had the strongest effect, followed by high-frequency vibrations of 256 Hz (1 μm) and low-frequency vibrations of 32 Hz (50 and 25 μm). These results are consistent with our hypothesis that slip-induced vibrations concur to the discrimination of tactile speed.
Torsional and Bending Vibration Measurement on Rotors Using Laser Technology
MILES, T. J.; LUCAS, M.; HALLIWELL, N. A.; ROTHBERG, S. J.
1999-09-01
Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) was developed for non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. This paper describes comprehensive theory to account for the sensitivity of the LTV's measurements to shaft motion in all degrees of freedom. The optical geometry of the LTV offers inherent immunity to translational motion of the target shaft, either axial or radial. However, its measurements are sensitive to angular lateral vibration of the shaft. The significance of this sensitivity is compared with the instrument noise floor and typical torsional and lateral vibration levels. Optimum alignments of the instrument are then specified to ensure effective immunity to all lateral motion in typical applications. To overcome this problem more reliably, a new technique is proposed permitting unambiguous measurement of pure torsional vibration in situations where use of a single LTV demonstrates unacceptable sensitivity to angular lateral vibrations. Practical application of this technology is demonstrated with torsional vibration measurements from a diesel engine crankshaft. Simultaneously, previously unattained measurements of shaft bending vibration measurements are made. The first bending mode of the crankshaft was identified and its vibration amplitude and damping estimated. This application of laser vibrometry for non-contact measurements of shaft vibration represents a further step forward in the use of this technology for machinery diagnostics.
2010 GRC VIBRATIONAL SPECTROSCOPY AUGUST 1 - AUGUST 6, 2010
Energy Technology Data Exchange (ETDEWEB)
Brooks Pate
2010-08-06
The Vibrational Spectroscopy conference focuses on using vibrational spectroscopy to probe structure and dynamics of molecules in gases, liquids, and at interfaces. The conference explores the wide range of state-of-the-art techniques based on vibrational motion. These techniques span the fields of time-domain, high-resolution frequency-domain, spatially-resolved, nonlinear and multidimensional spectroscopies. The conference highlights the application of these techniques in chemistry, materials, biology, and medicine. The theory of molecular vibrational motion and its connection to spectroscopic signatures and chemical reaction dynamics is the third major theme of the meeting. The goal is to bring together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of molecular systems ranging from small polyatomic molecules to large biomolecules and nanomaterials.
The Axial Nonlinear Vibration Analysis of Ball-screw about Machine Tool Feeding System
Institute of Scientific and Technical Information of China (English)
ZENG Hao-ran; LIU Nian-cong; YANG Jia-rui; CHEN Jian-long; GENG Wei-tao
2016-01-01
The forced state of the ball⁃screw of machine tool feeding system is analyzed. The ball⁃screw is simplified as Timoshenko beam and the differential equation of motion for the ball⁃screw is built. To obtain the axial vibration equation, the differential equation of motion is simplified using the assumed mode method. Axial vibration equation is in form of Duffing equation and has the characteristics of nonlinearity. The numerical simulation of Duffing equation is proceeded by MATLAB/Simulink. The effect of screw length, exciting force and damping coefficient are researched, and the axial vibration phase track diagram and Poincare section are obtained. The stability and period of the axial vibration are analyzed. The limit cycle of phase track diagram is enclosed. Axial vibration has two type⁃center singularity distributions on both sides of the origin. The singularity attracts vibration to reach a stable state, and Poincare section shows that axial vibration appears chaotic motion and quasi periodic motion or periodic motion. Singularity position changes with the vibration system parameters, while the distribution doesn′t change. The period of the vibration is enhanced with increasing frequency and damping coefficient. Test of the feeding system ball⁃screw axial vibration exists chaos movement. This paper provides a certain theoretical basis for the dynamic characteristic analysis of machine feeding system ball⁃screw and optimization of structural parameters.
Physiology responses of Rhesus monkeys to vibration
Hajebrahimi, Zahra; Ebrahimi, Mohammad; Alidoust, Leila; Arabian Hosseinabadi, Maedeh
Vibration is one of the important environmental factors in space vehicles that it can induce severe physiological responses in most of the body systems such as cardiovascular, respiratory, skeletal, endocrine, and etc. This investigation was to assess the effect of different vibration frequencies on heart rate variability (HRV), electrocardiograms (ECG) and respiratory rate in Rhesus monkeys. Methods: two groups of rhesus monkey (n=16 in each group) was selected as control and intervention groups. Monkeys were held in a sitting position within a specific fixture. The animals of this experiment were vibrated on a table which oscillated right and left with sinusoidal motion. Frequency and acceleration for intervention group were between the range of 1 to 2000 Hz and +0.5 to +3 G during 36 weeks (one per week for 15 min), respectively. All of the animals passed the clinical evaluation (echocardiography, sonography, radiography and blood analysis test) before vibration test and were considered healthy and these tests repeated during and at the end of experiments. Results and discussions: Our results showed that heart and respiratory rates increased significantly in response to increased frequency from 1 to 60 Hz (p monkeys passed vibration experiment successfully without any arrhythmic symptoms due to electrocardiography analysis. Conclusion: Our results indicate that vibration in low frequency can effect respiratory and cardiovascular function in rhesus monkey. Keywords: Vibration, rhesus monkey, heart rate, respiratory rate
Ground motion input in seismic evaluation studies
Energy Technology Data Exchange (ETDEWEB)
Sewell, R.T.; Wu, S.C.
1996-07-01
This report documents research pertaining to conservatism and variability in seismic risk estimates. Specifically, it examines whether or not artificial motions produce unrealistic evaluation demands, i.e., demands significantly inconsistent with those expected from real earthquake motions. To study these issues, two types of artificial motions are considered: (a) motions with smooth response spectra, and (b) motions with realistic variations in spectral amplitude across vibration frequency. For both types of artificial motion, time histories are generated to match target spectral shapes. For comparison, empirical motions representative of those that might result from strong earthquakes in the Eastern U.S. are also considered. The study findings suggest that artificial motions resulting from typical simulation approaches (aimed at matching a given target spectrum) are generally adequate and appropriate in representing the peak-response demands that may be induced in linear structures and equipment responding to real earthquake motions. Also, given similar input Fourier energies at high-frequencies, levels of input Fourier energy at low frequencies observed for artificial motions are substantially similar to those levels noted in real earthquake motions. In addition, the study reveals specific problems resulting from the application of Western U.S. type motions for seismic evaluation of Eastern U.S. nuclear power plants.
Andrén, Linus; Håkansson, Lars; Claesson, Ingvar; Lagö, Thomas L.
1999-01-01
In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In the active control system for the control of tool vibration a tool holder construct...
A Vibration Control Method for the Flexible Arm Based on Energy Migration
Yushu Bian; Zhihui Gao; Ming Fan
2015-01-01
A vibration control method based on energy migration is proposed to decrease vibration response of the flexible arm undergoing rigid motion. A type of vibration absorber is suggested and gives rise to the inertial coupling between the modes of the flexible arm and the absorber. By analyzing 1 : 2 internal resonance, it is proved that the internal resonance can be successfully created and the exchange of vibration energy is existent. Due to the inertial coupling, the damping enhancement effect...
A method for regulating strong nonlinear vibration energy of the flexible arm
Yushu Bian; Ming Wang; Zhihui Gao; Baofeng Yuan; Ming Fan
2015-01-01
For an oscillating system, large amplitude indicates strong vibration energy. In this article, modal interaction is used as a useful means to regulate strong nonlinear vibration energy of the flexible arm undergoing rigid motion. A method is put forward to migrate and dissipate vibration energy based on modal interaction. By means of multiple-scale perturbation analysis, it is proven that internal resonance can be successfully established between modes of the flexible arm and the vibration ab...
Dynamics of Vibration Machine with Air Flow Excitation and Restrictions on Phase Coordinates
Vība, J; Beresņevičs, V; Štāls, L; Eiduks, M; Kovals, E.; Kruusmaa, M.
2010-01-01
The objective of presented article is to show possibilities of practical use of air or liquid flow in vibration engineering. Dynamics of vibration machine with constant air or liquid flow excitation is considered. In the first part vibration motion of the machine working head under constant air or liquid flow velocity excitation is investigated. The main idea is to find out optimal control law for variation of additional surface area of vibrating object within limits. The criterion of optimiz...
Interfacial instabilities in vibrated fluids
Porter, Jeff; Laverón-Simavilla, Ana; Tinao Perez-Miravete, Ignacio; Fernandez Fraile, Jose Javier
2016-07-01
Vibrations induce a range of different interfacial phenomena in fluid systems depending on the frequency and orientation of the forcing. With gravity, (large) interfaces are approximately flat and there is a qualitative difference between vertical and horizontal forcing. Sufficient vertical forcing produces subharmonic standing waves (Faraday waves) that extend over the whole interface. Horizontal forcing can excite both localized and extended interfacial phenomena. The vibrating solid boundaries act as wavemakers to excite traveling waves (or sloshing modes at low frequencies) but they also drive evanescent bulk modes whose oscillatory pressure gradient can parametrically excite subharmonic surface waves like cross-waves. Depending on the magnitude of the damping and the aspect ratio of the container, these locally generated surfaces waves may interact in the interior resulting in temporal modulation and other complex dynamics. In the case where the interface separates two fluids of different density in, for example, a rectangular container, the mass transfer due to vertical motion near the endwalls requires a counterflow in the interior region that can lead to a Kelvin-Helmholtz type instability and a ``frozen wave" pattern. In microgravity, the dominance of surface forces favors non-flat equilibrium configurations and the distinction between vertical and horizontal applied forcing can be lost. Hysteresis and multiplicity of solutions are more common, especially in non-wetting systems where disconnected (partial) volumes of fluid can be established. Furthermore, the vibrational field contributes a dynamic pressure term that competes with surface tension to select the (time averaged) shape of the surface. These new (quasi-static) surface configurations, known as vibroequilibria, can differ substantially from the hydrostatic state. There is a tendency for the interface to orient perpendicular to the vibrational axis and, in some cases, a bulge or cavity is induced
Babakhani, B.; de Vries, Theodorus J.A.; van Amerongen, J.
2012-01-01
In this paper, both collocated and noncollocated active vibration control (AVC) of a the vibrations in a motion system are considered. Pole-zero plots of both the AVC loop and the motion-control (MC) loop are used to analyze the effect of the applied active damping on the system dynamics. Using
Adaptive Active Control of Machine-Tool Vibration In a Lathe
Claesson, Ingvar; Håkansson, Lars
1998-01-01
In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and in particular, the surface finish. Tool life is also influenced by vibration. Noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. With proper machine design, i.e. improved stiffness of the machine structure, the problem of relative dynamic motion betw...
Nanoscale piezoelectric vibration energy harvester design
Directory of Open Access Journals (Sweden)
Hamid Reza Foruzande
2017-09-01
Full Text Available Development of new nanoscale devices has increased the demand for new types of small-scale energy resources such as ambient vibrations energy harvesters. Among the vibration energy harvesters, piezoelectric energy harvesters (PEHs can be easily miniaturized and fabricated in micro and nano scales. This change in the dimensions of a PEH leads to a change in its governing equations of motion, and consequently, the predicted harvested energy comparing to a macroscale PEH. In this research, effects of small scale dimensions on the nonlinear vibration and harvested voltage of a nanoscale PEH is studied. The PEH is modeled as a cantilever piezoelectric bimorph nanobeam with a tip mass, using the Euler-Bernoulli beam theory in conjunction with Hamilton’s principle. A harmonic base excitation is applied as a model of the ambient vibrations. The nonlocal elasticity theory is used to consider the size effects in the developed model. The derived equations of motion are discretized using the assumed-modes method and solved using the method of multiple scales. Sensitivity analysis for the effect of different parameters of the system in addition to size effects is conducted. The results show the significance of nonlocal elasticity theory in the prediction of system dynamic nonlinear behavior. It is also observed that neglecting the size effects results in lower estimates of the PEH vibration amplitudes. The results pave the way for designing new nanoscale sensors in addition to PEHs.
Experimental Motion Analysis of Radially Rotating Beams Using High-Speed Camera and Motion Analyzer
Directory of Open Access Journals (Sweden)
K.H. Low
1996-01-01
Full Text Available Although strain gauges can be attached to a system for vibration analysis, wires connected to the strain gauges may disturb the system and affect the accuracy of the strain measurement. As an alternative, this work presents the use of a high-speed camera combined with a motion analyzer to study the motion of rotating flexible beams. One end of the beam is rigidly connected to a motor, while the other end is free. White stickers placed on selected points on a given beam are the reference points in a digitization process. The modes of the vibrating beams can be filmed and analyzed. The vibration parameters, such as deflection and frequency, can be obtained by using a film motion analyzer. The results show that the beam does not behave in a clamped-free or a pinned-free fashion, but instead occurs at an intermediate boundary between these two classical conditions.
Spiridonov, V. P.; Gershikov, A. G.; Altman, A. B.; Romanov, G. V.; Ivanov, A. A.
1981-01-01
Diffraction data on BaI 2, analyzed by a new approach, indicate an anharmonic potential with a barrier of 71(12) cm -1 at a linear geometry. The structural and vibrational parameters were found to be reh(Ba-I o) = 3.150(7)Å, ∠ eIBaI = 148.0(9) °, fq = 0.69(8) mdyn/Å, fqq= 0.14(6) mdyn/Å, k2 = -0.0075(15) mdyn/Å, k4 = 0.0025(9) mdyn/Å 3, v1 = 106(12) cm -1 and v3 = 145(21) cm -1. The bending frequency v2 is predicted to be near 16 cm -1.
Semiactive variable stiffness control for parametric vibration of cables
Institute of Scientific and Technical Information of China (English)
Li Hui; Chen Wenli; Ou Jinping
2006-01-01
In this paper, a semiactive variable stiffness (SVS) device is used to decrease cable oscillations caused by parametric excitation, and the equation of motion of the parametric vibration of the cable with this SVS device is presented.The ON/OFF control algorithm is used to operate the SVS control device. The vibration response of the cable with the SVS device is numerically studied for a variety of additional stiffness combinations in both the frequency and time domains and for both parametric and classical resonance vibration conditions. The numerical studies further consider the cable sag effect.From the numerical results, it is shown that the SVS device effectively suppresses the cable resonance vibration response, and as the stiffness of the device increases, the device achieves greater suppression of vibration. Moreover, it was shown that the SVS device increases the critical axial displacement of the excitation under cable parametric vibration conditions.
Research on algorithm of blade vibration for general wind turbine
Wang, Long; Sun, Lun-ye; Wu, Guang; Li, Xue-bin; Lai, Yong-bin; Zhou, Yi-jun
2016-01-01
Evaluation of vibration characteristics for wind turbine blades is one of the important contents in the wind turbine research. This paper uses the compressible flow equations with the preconditioning technique, based on the finite volume method and combined with the LU-SGS algorithm for solving the flow area; meanwhile adopts the two degree of freedom of vibration equation with the vertical and torsional vibration for blades to simulate the vibration trajectory of blade under the aerodynamic force, uses the motion grid algorithm for changes in grid computing domain. Calculation program was developed autonomous in the C ++ platform, and the development of software correctness was verified by contrast the results of the classic cylindrical examples. Finally, the vibration characteristics of a wind turbine blade was given, and the software developed in this paper can provide technical support for wind turbine blade vibration study.
SIMULATION OF MULTI-SUPPORT MACHINE VIBRATIONS
Directory of Open Access Journals (Sweden)
N. N. Hurski
2009-01-01
Full Text Available The paper considers problems pertaining to simulation of multi-support machine vibrations by means of ADMOS programming product. A mathematical model of the multi-support machine is presented and its main geometric and physical and mechanical parameters are given in the paper. The paper reveals analysis results of the vibration processes and observes variables in time and frequency areas. The investigations have made it possible to obtain amplitude and frequency and statistical characteristics of the machine mass centre acceleration during its motion along various types of roads
Coupling between flexural modes in free vibration of single-walled carbon nanotubes
Directory of Open Access Journals (Sweden)
Rumeng Liu
2015-12-01
Full Text Available The nonlinear thermal vibration behavior of a single-walled carbon nanotube (SWCNT is investigated by molecular dynamics simulation and a nonlinear, nonplanar beam model. Whirling motion with energy transfer between flexural motions is found in the free vibration of the SWCNT excited by the thermal motion of atoms where the geometric nonlinearity is significant. A nonlinear, nonplanar beam model considering the coupling in two vertical vibrational directions is presented to explain the whirling motion of the SWCNT. Energy in different vibrational modes is not equal even over a time scale of tens of nanoseconds, which is much larger than the period of fundamental natural vibration of the SWCNT at equilibrium state. The energy of different modes becomes equal when the time scale increases to the microsecond range.
Coupling between flexural modes in free vibration of single-walled carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Liu, Rumeng; Wang, Lifeng, E-mail: walfe@nuaa.edu.cn [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing (China)
2015-12-15
The nonlinear thermal vibration behavior of a single-walled carbon nanotube (SWCNT) is investigated by molecular dynamics simulation and a nonlinear, nonplanar beam model. Whirling motion with energy transfer between flexural motions is found in the free vibration of the SWCNT excited by the thermal motion of atoms where the geometric nonlinearity is significant. A nonlinear, nonplanar beam model considering the coupling in two vertical vibrational directions is presented to explain the whirling motion of the SWCNT. Energy in different vibrational modes is not equal even over a time scale of tens of nanoseconds, which is much larger than the period of fundamental natural vibration of the SWCNT at equilibrium state. The energy of different modes becomes equal when the time scale increases to the microsecond range.
Vibration-rotation-tunneling dynamics in small water clusters
Energy Technology Data Exchange (ETDEWEB)
Pugliano, N.
1992-11-01
The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm{sup {minus}1} intermolecular vibration of the water dimer-d{sub 4}. Each of the VRT subbands originate from K{sub a}{double_prime}=0 and terminate in either K{sub a}{prime}=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A{prime} rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K{sub a}{prime} quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a{prime} symmetry, and the vibration is assigned as the {nu}{sub 12} acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D{sub 2}O-DOH isotopomer.
Vibration-rotation-tunneling dynamics in small water clusters
Energy Technology Data Exchange (ETDEWEB)
Pugliano, N.
1992-11-01
The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm[sup [minus]1] intermolecular vibration of the water dimer-d[sub 4]. Each of the VRT subbands originate from K[sub a][double prime]=0 and terminate in either K[sub a][prime]=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A[prime] rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K[sub a][prime] quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a[prime] symmetry, and the vibration is assigned as the [nu][sub 12] acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D[sub 2]O-DOH isotopomer.
Brela, Mateusz; Stare, Jernej; Pirc, Gordana; Sollner-Dolenc, Marija; Boczar, Marek; Wójcik, Marek J; Mavri, Janez
2012-04-19
The nature of medium strong intra- and intermolecular hydrogen bonding in 2-hydroxy-5-nitrobenzamide in the crystal phase was examined by infrared spectroscopy and Car-Parrinello molecular dynamics simulation. The focal point of our study was the part of the infrared spectra associated with the O-H and N-H stretching modes that are very sensitive to the strength of hydrogen bonding. For spectra calculations we used an isolated dimer and the fully periodic crystal environment. We calculated the spectra by using harmonic approximation, the time course of the dipole moment function as obtained from the Car-Parrinello simulation, and the quantization of the nuclear motion of the proton for an instantaneous snapshot of the structures in one and two dimensions. Although quantitative assessment of the agreement between the computed and experimental band contour is difficult due to the fact that the experimental band is very broad, we feel that the most reasonable qualitative agreement with the experiment is obtained from snapshot structures and two-dimensional quantization of the proton motion. We have also critically examined the methods of constructing the one-dimensional proton potential. Perspectives are given for the treatment of nuclear quantum effects in biocatalysis.
Beecher, L. C.; Williams, F. T.
1970-01-01
Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.
Control System Damps Vibrations
Kopf, E. H., Jr.; Brown, T. K.; Marsh, E. L.
1983-01-01
New control system damps vibrations in rotating equipment with help of phase-locked-loop techniques. Vibrational modes are controlled by applying suitable currents to drive motor. Control signals are derived from sensors mounted on equipment.
Less sickness with more motion and/or mental distraction
Bos, J.E.
2015-01-01
BACKGROUND: Motion sickness may reduce passenger comfort and crew performance. Countermeasures are dominated by medication with specific and often undesirable side effects. OBJECTIVE: To shown that sickness due to motion can be reduced by adding an inherent non-sickening vibration and by mental dist
Less sickness with more motion and/or mental distraction
Bos, J.E.
2015-01-01
BACKGROUND: Motion sickness may reduce passenger comfort and crew performance. Countermeasures are dominated by medication with specific and often undesirable side effects. OBJECTIVE: To shown that sickness due to motion can be reduced by adding an inherent non-sickening vibration and by mental
Axial Vibration Confinement in Nonhomogenous Rods
Directory of Open Access Journals (Sweden)
S. Choura
2005-01-01
Full Text Available A design methodology for the vibration confinement of axial vibrations in nonhomogenous rods is proposed. This is achieved by a proper selection of a set of spatially dependent functions characterizing the rod material and geometric properties. Conditions for selecting such properties are established by constructing positive Lyapunov functions whose derivative with respect to the space variable is negative. It is shown that varying the shape of the rod alone is sufficient to confine the vibratory motion. In such a case, the vibration confinement requires that the eigenfunctions be exponentially decaying functions of space, where the notion of spatial domain stability is introduced as a concept dual to that of the time domain stability. It is also shown that vibration confinement can be produced if the rod density and/or stiffness are varied with respect to the space variable while the cross-section area is kept constant. Several case studies, supporting the developed conditions imposed on the spatially dependent functions for vibration confinement in vibrating rods, are discussed. Because variation in the geometric and material properties might decrease the critical buckling loads, we also discuss the buckling problem.
Cigeroglu, Ender; Samandari, Hamed
2014-11-01
Nonlinear free vibration analysis of curved double-walled carbon nanotubes (DWNTs) embedded in an elastic medium is studied in this study. Nonlinearities considered are due to large deflection of carbon nanotubes (geometric nonlinearity) and nonlinear interlayer van der Waals forces between inner and outer tubes. The differential quadrature method (DQM) is utilized to discretize the partial differential equations of motion in spatial domain, which resulted in a nonlinear set of algebraic equations of motion. The effect of nonlinearities, different end conditions, initial curvature, and stiffness of the surrounding elastic medium, and vibrational modes on the nonlinear free vibration of DWCNTs is studied. Results show that it is possible to detect different vibration modes occurring at a single vibration frequency when CNTs vibrate in the out-of-phase vibration mode. Moreover, it is observed that boundary conditions have significant effect on the nonlinear natural frequencies of the DWCNT including multiple solutions.
Effects of vibration measurement error on remote sensing image restoration
Sun, Xuan; Wei, Zhang; Zhi, Xiyang
2016-10-01
Satellite vibrations would lead to image motion blur. Since the vibration isolators cannot fully suppress the influence of vibrations, image restoration methods are usually adopted, and the vibration characteristics of imaging system are usually required as algorithm inputs for better restoration results, making the vibration measurement error strongly connected to the final outcome. If the measurement error surpass a certain range, the restoration may not be implemented successfully. Therefore it is important to test the applicable scope of restoration algorithms and control the vibrations within the range, on the other hand, if the algorithm is robust, then the requirements for both vibration isolator and vibration detector can be lowered and thus less financial cost is needed. In this paper, vibration-induced degradation is first analyzed, based on which the effects of measurement error on image restoration are further analyzed. The vibration-induced degradation is simulated using high resolution satellite images and then the applicable working condition of typical restoration algorithms are tested with simulation experiments accordingly. The research carried out in this paper provides a valuable reference for future satellite design which plan to implement restoration algorithms.
Computational Fluid Dynamic Analysis of a Vibrating Turbine Blade
Directory of Open Access Journals (Sweden)
Osama N. Alshroof
2012-01-01
Full Text Available This study presents the numerical fluid-structure interaction (FSI modelling of a vibrating turbine blade using the commercial software ANSYS-12.1. The study has two major aims: (i discussion of the current state of the art of modelling FSI in gas turbine engines and (ii development of a “tuned” one-way FSI model of a vibrating turbine blade to investigate the correlation between the pressure at the turbine casing surface and the vibrating blade motion. Firstly, the feasibility of the complete FSI coupled two-way, three-dimensional modelling of a turbine blade undergoing vibration using current commercial software is discussed. Various modelling simplifications, which reduce the full coupling between the fluid and structural domains, are then presented. The one-way FSI model of the vibrating turbine blade is introduced, which has the computational efficiency of a moving boundary CFD model. This one-way FSI model includes the corrected motion of the vibrating turbine blade under given engine flow conditions. This one-way FSI model is used to interrogate the pressure around a vibrating gas turbine blade. The results obtained show that the pressure distribution at the casing surface does not differ significantly, in its general form, from the pressure at the vibrating rotor blade tip.
Vibrations of liquid drops in film boiling phenomena: the mathematical model
Casal, Pierre
2008-01-01
Flattened liquid drops poured on a very hot surface evaporate quite slowly and float on a film of their own vapour. In the cavities of a surface, an unusual type of vibrational motions occurs. Large vibrations take place and different forms of dynamic drops are possible. They form elliptic patterns with two lobes or hypotrochoid patterns with three lobes or more. The lobes are turning relatively to the hot surface. We present a model of vibrating motions of the drops. Frequencies of the vibrations are calculated regarding the number of lobes. The computations agree with experiments.
Force transmissibility and vibration power flow behaviour of inerter-based vibration isolators
Yang, Jian
2016-09-01
This paper investigates the dynamics and performance of inerter-based vibration isolators. Force / displacement transmissibility and vibration power flow are obtained to evaluate the isolation performance. Both force and motion excitations are considered. It is demonstrated that the use of inerters can enhance vibration isolation performance by enlarging the frequency band of effective vibration isolation. It is found that adding inerters can introduce anti-resonances in the frequency-response curves and in the curves of the force and displacement transmissibility such that vibration transmission can be suppressed at interested excitation frequencies. It is found that the introduction of inerters enhances inertial coupling and thus have a large influence on the dynamic behaviour at high frequencies. It is shown that force and displacement transmissibility increases with the excitation frequency and tends to an asymptotic value as the excitation frequency increases. In the high-frequency range, it was shown that adding inerters can result in a lower level of input power. These findings provide a better understanding of the effects of introducing inerters to vibration isolation and demonstrate the performance benefits of inerter-based vibration isolators.
Controlling the motion of multiple objects on a Chladni plate
2016-01-01
The origin of the idea of moving objects by acoustic vibration can be traced back to 1787, when Ernst Chladni reported the first detailed studies on the aggregation of sand onto nodal lines of a vibrating plate. Since then and to this date, the prevailing view has been that the particle motion out of nodal lines is random, implying uncontrollability. But how random really is the out-of-nodal-lines motion on a Chladni plate? Here we show that the motion is sufficiently regular to be statistica...
Pilot study of vibration stimulation on neurological rehabilitation.
Sui, Jianfeng; Shull, Pete; Ji, Linhong
2014-01-01
Robot-assisted therapy has been proved effective for dyskinesia, and has many unique advantages compared with traditional treatment, such as repeatability, accuracy, objectivity. But some studies show that the effect of the robot-assisted rehabilitation for improving patients' activities of daily life (ADLs) is not obvious. This study introduces a novel auxiliary method-vibration stimulation combined with robots which may improve patients' ADLs. In controlled trials, two kinds of feedback-vibration and visual feedback are applied to prompt subjects for rehabilitation, and electromyographic signals (EMGs) and motion parameters are recorded in real time. Experimental results show that subjects' EMGs using vibration feedback are similar to healthy people, and characteristics of motion are closer to the theoretical value compared with control group. Vibration stimulation may serve as a kind of efficient auxiliary means to improve the efficiency of neurological rehabilitation.
Vibration of the Package of Rods Linked by Spacer Grids
Zeman, V.; Hlaváč, Z.
This paper deals with modelling and vibration analysis of the large package of identical parallel rods which are linked by transverse springs (spacer grids) placed on several level spacings. The vibration of rods is caused by the support plate motion. The rod discretization by FEM is based on Rayleigh beam theory. With respect to cyclic and central package rod symmetry, the system is decomposed to identical revolved rod segments. The modal synthesis method with condensation of the rod segments is used for modelling and determination of steady forced vibration of the whole system. The presented method is the first step to modelling of the nuclear fuel assembly vibration caused by kinematical excitation determined by motion of the support plates which are part of the reactor core.
Orbiting droplets on a vibrated bath
Sampara, Naresh; Burger, Loic; Gilet, Tristan; Microfluidics, university of liege Team
2015-11-01
A millimeter-sized oil droplet can bounce on a vertically vibrated liquid bath for unlimited time. It may couple to the surface wave it emits; leading to horizontal self-propulsion called walking. When several walkers coexist close to one another, they either repel or attract each other, in response to the superposition of the waves they generate. Attraction leads to various bound states, including droplets that orbit around each other. We have experimentally investigated the variety of quantized orbital motions exhibited by two, three and more identical walkers, as a function of forcing acceleration. Each motion is quantified in terms of droplet and wave energy.
Active Suppression Of Vibrations On Elastic Beams
Silcox, Richard J.; Fuller, Chris R.; Gibbs, Gary P.
1993-01-01
Pairs of colocated piezoelectric transducers, independently controlled by multichannel adaptive controller, employed as actuators and sensors to achieve simultaneous attenuation of both extensional and flexural motion. Single pair used to provide simultaneous control of flexural and extensional waves, or two pairs used to control torsional motion also. Capability due to nature of piezoelectric transducers, when bonded to surfaces of structures and activated by oscillating voltages, generate corresponding oscillating distributions of stresses in structures. Phases and amplitudes of actuator voltages adjusted by controller to impede flow of vibrational energy simultaneously, in waves of various forms, beyond locations of actuators. Concept applies equally to harmonic or random response of structure and to multiple responses of structure to transverse bending, torsion, and compression within structural element. System has potential for many situations in which predominant vibration transmission path through framelike structure.
Transverse vibration of nematic elastomer Timoshenko beams
Zhao, Dong; Liu, Ying; Liu, Chuang
2017-01-01
Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.
Vibration of hydraulic machinery
Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong
2013-01-01
Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...
Free and Forced Vibrations of Periodic Multispan Beams
Liping Zhu; Isaac Elishakoff; Lin, Y.K.
1994-01-01
In this study, the following two topics are considered for uniform multispan beams of both finite and infinite lengths with rigid transversal and elastic rotational constraints at each support: (a) free vibration and the associated frequencies and mode shapes; (b) forced vibration under a convected harmonic loading. The concept of wave propagation in periodic structures of Brillouin is utilized to investigate the wave motion at periodic supports of a multispan beam. A dispersion equation and ...
Vibration Therapy in Management of Delayed Onset Muscle Soreness (DOMS).
Veqar, Zubia; Imtiyaz, Shagufta
2014-06-01
Both athletic and nonathletic population when subjected to any unaccustomed or unfamiliar exercise will experience pain 24-72 hours postexercise. This exercise especially eccentric in nature caused primarily by muscle damage is known as delayed-onset muscle soreness (DOMS). This damage is characterized by muscular pain, decreased muscle force production, reduce range of motion and discomfort experienced. DOMS is due to microscopic muscle fiber tears. The presence of DOMS increases risk of injury. A reduced range of motion may lead to the incapability to efficiently absorb the shock that affect physical activity. Alterations to mechanical motion may increase strain placed on soft tissue structures. Reduced force output may signal compensatory recruitment of muscles, thus leading to unaccustomed stress on musculature. Differences in strength ratios may also cause excessive strain on unaccustomed musculature. A range of interventions aimed at decreasing symptoms of DOMS have been proposed. Although voluminous research has been done in this regard, there is little consensus among the practitioners regarding the most effective way of treating DOMS. Mechanical oscillatory motion provided by vibration therapy. Vibration could represent an effective exercise intervention for enhancing neuromuscular performance in athletes. Vibration has shown effectiveness in flexibility and explosive power. Vibration can apply either local area or whole body vibration. Vibration therapy improves muscular strength, power development, kinesthetic awareness, decreased muscle sore, increased range of motion, and increased blood flow under the skin. VT was effective for reduction of DOMS and regaining full ROM. Application of whole body vibration therapy in postexercise demonstrates less pressure pain threshold, muscle soreness along with less reduction maximal isometric and isokinetic voluntary strength and lower creatine kinase levels in the blood.
Analysis of real-time vibration data
Safak, E.
2005-01-01
In recent years, a few structures have been instrumented to provide continuous vibration data in real time, recording not only large-amplitude motions generated by extreme loads, but also small-amplitude motions generated by ambient loads. The main objective in continuous recording is to track any changes in structural characteristics, and to detect damage after an extreme event, such as an earthquake or explosion. The Fourier-based spectral analysis methods have been the primary tool to analyze vibration data from structures. In general, such methods do not work well for real-time data, because real-time data are mainly composed of ambient vibrations with very low amplitudes and signal-to-noise ratios. The long duration, linearity, and the stationarity of ambient data, however, allow us to utilize statistical signal processing tools, which can compensate for the adverse effects of low amplitudes and high noise. The analysis of real-time data requires tools and techniques that can be applied in real-time; i.e., data are processed and analyzed while being acquired. This paper presents some of the basic tools and techniques for processing and analyzing real-time vibration data. The topics discussed include utilization of running time windows, tracking mean and mean-square values, filtering, system identification, and damage detection.
Viridi, Sparisoma; Hidayat, Wahyu; Singarimbun, Alamta; Balkis, Sitti
2011-01-01
A ball supported by a spring is set on top of a plate which is sinusoidal vibrated. The motion is limited to one dimension motion. It is assumed that the spring is an ideal one with zero mass. The vibrating plate is considered much heavier than the ball, so that the ball motion has no influence on the plate motion. Plate vibration frequency is varied around the frequency of ball-spring system. Resonance phenomenon is reported, which needs a phase match condition to occur.
The vibration discomfort of standing people: evaluation of multi-axis vibration.
Thuong, Olivier; Griffin, Michael J
2015-01-01
Few studies have investigated discomfort caused by multi-axis vibration and none has explored methods of predicting the discomfort of standing people from simultaneous fore-and-aft, lateral and vertical vibration of a floor. Using the method of magnitude estimation, 16 subjects estimated their discomfort caused by dual-axis and tri-axial motions (octave-bands centred on either 1 or 4 Hz with various magnitudes in the fore-and-aft, lateral and vertical directions) and the discomfort caused by single-axis motions. The method of predicting discomfort assumed in current standards (square-root of the sums of squares of the three components weighted according to their individual contributions to discomfort) provided reasonable predictions of the discomfort caused by multi-axis vibration. Improved predictions can be obtained for specific stimuli, but no single simple method will provide accurate predictions for all stimuli because the rate of growth of discomfort with increasing magnitude of vibration depends on the frequency and direction of vibration.
Analysis of Piston Slap Motion
Directory of Open Access Journals (Sweden)
Narayan S.
2015-05-01
Full Text Available Piston slap is the major force contibuting towards noise levels in combustion engines.This type of noise depends upon a number of factors such as the piston-liner gap, type of lubricant used, number of piston pins as well as geometry of the piston. In this work the lateral and rotary motion of the piston in the gap between the cylinder liner and piston has been analyzed. A model that can predict the forces and response of the engine block due to slap has been dicussed. The parameters such as mass, spring and damping constant have been predicted using a vibrational mobility model.
Analysis of Piston Slap Motion
Narayan, S.
2015-05-01
Piston slap is the major force contibuting towards noise levels in combustion engines.This type of noise depends upon a number of factors such as the piston-liner gap, type of lubricant used, number of piston pins as well as geometry of the piston. In this work the lateral and rotary motion of the piston in the gap between the cylinder liner and piston has been analyzed. A model that can predict the forces and response of the engine block due to slap has been dicussed. The parameters such as mass, spring and damping constant have been predicted using a vibrational mobility model.
Gap junctional communication in osteocytes is amplified by low intensity vibrations in vitro.
Directory of Open Access Journals (Sweden)
Gunes Uzer
Full Text Available The physical mechanism by which cells sense high-frequency mechanical signals of small magnitude is unknown. During exposure to vibrations, cell populations within a bone are subjected not only to acceleratory motions but also to fluid shear as a result of fluid-cell interactions. We explored displacements of the cell nucleus during exposure to vibrations with a finite element (FE model and tested in vitro whether vibrations can affect osteocyte communication independent of fluid shear. Osteocyte like MLO-Y4 cells were subjected to vibrations at acceleration magnitudes of 0.15 g and 1 g and frequencies of 30 Hz and 100 Hz. Gap junctional intracellular communication (GJIC in response to these four individual vibration regimes was investigated. The FE model demonstrated that vibration induced dynamic accelerations caused larger relative nuclear displacement than fluid shear. Across the four regimes, vibrations significantly increased GJIC between osteocytes by 25%. Enhanced GJIC was independent of vibration induced fluid shear; there were no differences in GJIC between the four different vibration regimes even though differences in fluid shear generated by the four regimes varied 23-fold. Vibration induced increases in GJIC were not associated with altered connexin 43 (Cx43 mRNA or protein levels, but were dependent on Akt activation. Combined, the in silico and in vitro experiments suggest that externally applied vibrations caused nuclear motions and that large differences in fluid shear did not influence nuclear motion (<1% or GJIC, perhaps indicating that vibration induced nuclear motions may directly increase GJIC. Whether the increase in GJIC is instrumental in modulating anabolic and anti-catabolic processes associated with the application of vibrations remains to be determined.
Built-up edge investigation in vibration drilling of Al2024-T6.
Barani, A; Amini, S; Paktinat, H; Fadaei Tehrani, A
2014-07-01
Adding ultrasonic vibrations to drilling process results in an advanced hybrid machining process, entitled "vibration drilling". This study presents the design and fabrication of a vibration drilling tool by which both rotary and vibrating motions are applied to drill simultaneously. High frequency and low amplitude vibrations were generated by an ultrasonic transducer with frequency of 19.65 kHz. Ultrasonic transducer was controlled by a MPI ultrasonic generator with 3 kW power. The drilling tool and workpiece material were HSS two-flute twist drill and Al2024-T6, respectively. The aim of this study was investigating on the effect of ultrasonic vibrations on built-up edge, surface quality, chip morphology and wear mechanisms of drill edges. Therefore, these factors were studied in both vibration and ordinary drilling. Based on the achieved results, vibration drilling offers less built-up edge and better surface quality compared to ordinary drilling.
Effects of vibration on flexibility: a meta-analysis.
Osawa, Y; Oguma, Y
2013-12-01
Exogenous stimulation of skeletal muscle or tendon is often used to improve range of motion. Despite substantial research efforts, however, the effects of vibration on flexibility have not been clarified. In this review, we investigated the effects of acute and chronic intervention programs which used vibration to improve flexibility in young healthy individuals. Effect size was calculated using data from a total of 600 participants in 19 studies before and after the introduction of vibration-based intervention, and a total of 324 participants in 13 studies on the additive effects of vibration compared with the identical conditions without vibration. Sub-group analyses were performed based on intervention period, type of exercise, and type of vibration. Meta-analysis showed that vibration interventions had significant effects on flexibility (standardized mean difference [SMD]=-0.79, 95% confidence interval [CI]=-1.14- -0.43; pvibration on flexibility compared with the identical condition without vibration (SMD=0.25, 95%CI=0.03-0.48; P=0.03), with small heterogeneity (I(2)=0%). The risk of publication bias was low judged from Kendall's τ statistic. We concluded that the use of vibration might lead to additive improvements in flexibility.
Less sickness with more motion and/or mental distraction.
Bos, Jelte E
2015-01-01
Motion sickness may reduce passenger comfort and crew performance. Countermeasures are dominated by medication with specific and often undesirable side effects. To shown that sickness due to motion can be reduced by adding an inherent non-sickening vibration and by mental distraction. Eighteen blindfolded subjects were exposed to 20 minutes of off-vertical axis rotation (OVAR). Vibration was added by means of a head rest. Effects of OVAR and vibration were tested separately and in combination, while the subjects were performing an audio letter memorising task. This task was absent to test the effect of mental distraction. Effects were quantified by rating subjective misery and objective task performance. Sixteen subjects completed the experiment and showed in mutual comparable conditions that head vibration reduced the amount of sickness by 25%, the mental distraction did so by 19%, and the combined effect resulted in a reduction of 39%. Their task performance decreased with increasing sickness. Sickness due to low-frequency motion can be reduced by adding a high-frequency vibration and by mental distraction. The effect of vibration can be understood by assuming an internal model used by the central nervous system to optimise the control of body motion.
Vibration suppression for laminated composite plates with arbitrary boundary conditions
Li, J.; Narita, Y.
2013-11-01
An analysis of vibration suppression for laminated composite plates subject to active constrained layer damping under various boundary conditions is presented. Piezoelectric-fiber-reinforced composites (PFRCs) are used as active actuators, and the effect of PFRC patches on vibration control is reported here. An analytical approach is expanded to analyze the vibration of laminated composites with arbitrary boundary conditions. By using Hamilton's principle and the Rayleigh-Ritz method, the equation of motion for the resulting electromechanical coupling system is derived. A velocity feedback control rule is employed to obtain an effective active damping in the vibration control. The orientation effect of piezoelectric fibers in the PFRC patches on the suppression of forced vibrations is also investigated.
Pettersson, Linus; Håkansson, Lars; Claesson, Ingvar; Olsson, Sven
2001-01-01
In the turning operation chatter or vibration is a common problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lathe...
Active Vibration Control of a Thin Steel Sheet
Directory of Open Access Journals (Sweden)
Yohji Okada
1995-01-01
Full Text Available The commercial rolling process used in the steel industry to manufacture thin steel sheets tends to cause plate vibrations that lower the quality of the surface finish. This article introduces a noncontact method of active vibration control for reducing the flexural vibrations of a thin steel sheet. The proposed electromagnetic method of control has been implemented in a simple experimental setup where the signal from a motion sensor regulates the attractive force of the magnets that produce a damping force on the steel sheet.
DEFF Research Database (Denmark)
Hansen, Flemming Yssing; Taub, H.
2009-01-01
The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass, rotational motion about the principal molecular axes, and an intramolecular motion that may be associated with vibrations and librations as well as molecular conforma......The motion of the atoms in a molecule may be described as a superposition of translational motion of the molecular center-of-mass, rotational motion about the principal molecular axes, and an intramolecular motion that may be associated with vibrations and librations as well as molecular...... conformational changes. We have constructed projection operators that use the atomic coordinates and velocities at any two times, t=0 and a later time t, to determine the molecular center-of-mass, rotational, and intramolecular motions in a molecular dynamics simulation. This model-independent technique...
Mechanical Bed for Investigating Sleep-Inducing Vibration
Directory of Open Access Journals (Sweden)
Hitoshi Kimura
2017-01-01
Full Text Available In running cars or trains, passengers often feel sleepy. Our study focuses on this physiological phenomenon. If a machine can reproduce this phenomenon, it is feasible to put a person, such as an insomnia patient or an infant, to sleep without any harmful effects. The results of our previous study suggest that low-frequency vibration induces sleep. This report describes a new mechanical bed for inducing sleep and discusses the effects of different vibration conditions. The new bed has two active DOFs in the vertical and horizontal directions to examine the anisotropy of sensation. The bed includes three main parts: a vertical driver unit, a horizontal driver unit, and a unique 2-DOF counterweight system to reduce driving force and noise. With regard to motion accuracy, the maximum motion error in the vertical direction lifting 75 kg load was only 0.06 mm with a 5.0 mm amplitude of a 0.5 Hz sinusoidal wave. The results of excitation experiments with 10 subjects showed a significant difference in sleep latency between the conditions with vibration and without vibration. Furthermore, the average latency with insensible vibration (amplitude = 2.4 mm was shorter than that with sensible vibration (amplitude = 7.5 mm. These results suggest the ability of appropriate vibration to induce sleep.
Vibrating fuel grapple. [LMFBR
Chertock, A.J.; Fox, J.N.; Weissinger, R.B.
A reactor refueling method is described which utilizes a vibrating fuel grapple for removing spent fuel assemblies from a reactor core. It incorporates a pneumatic vibrator in the grapple head which allows additional withdrawal capability without exceeding the allowable axial force limit. The only moving part in the vibrator is a steel ball, pneumatically driven by a gas, such as argon, around a track, with centrifugal force created by the ball being transmitted through the grapple to the assembly handling socket.
Methodology for Analysing Controllability and Observability of Bladed Disc Coupled Vibrations
DEFF Research Database (Denmark)
Christensen, Rene Hardam; Santos, Ilmar
2004-01-01
Many bladed rotating machines such as helicopters, turbines and compressors are susceptible to blade faults due to vibration problems. Typically, blade vibrations in this kind of machines are suppressed by using passive mechanical components. However, when passive control techniques...... are not efficient enough to suppress vibration problems, active control techniques might become the only feasible way of avoiding vibration problems. Implementing effectively active vibration control into any machine implies that the controllability and observability have to be analysed in order to determine where...... to place sensors and actuators so that all vibration levels can be monitored and controlled. Due to the special dynamic characteristics of rotating coupled bladed discs, where disc lateral motion is coupled to blade flexible motion, such analyses become quite complicated. The dynamics is described...
A method for regulating strong nonlinear vibration energy of the flexible arm
Directory of Open Access Journals (Sweden)
Yushu Bian
2015-07-01
Full Text Available For an oscillating system, large amplitude indicates strong vibration energy. In this article, modal interaction is used as a useful means to regulate strong nonlinear vibration energy of the flexible arm undergoing rigid motion. A method is put forward to migrate and dissipate vibration energy based on modal interaction. By means of multiple-scale perturbation analysis, it is proven that internal resonance can be successfully established between modes of the flexible arm and the vibration absorber. Through examples and analyses, it is verified that this control method is effective in regulating strong vibration energy and can be used to suppress strong nonlinear vibration of the flexible arm undergoing rigid motion.
Extracting modal parameters of a cable on shaky motion pictures
Hwa Kim, Byeong
2014-12-01
A set of modal parameters of a cable are extracted from a motion picture captured by a digital camera operated with shaking hands. It is difficult to identify the center of the targets attached to the cable surface from the blurred motion image of the cable, because of the high-speed motion of the cable, low sampling frequency of the camera, and the effect of shaking hands on the motion pictures. This paper proposes a multi-template matching algorithm to solve these difficulties. In addition, a sensitivity-based system identification algorithm is proposed for extracting the natural frequencies and the damping ratios from ambient cable vibration data. Three sets of vibration tests are performed to examine the validity of the proposed algorithms. The results show that the proposed approach of using these two algorithms is fairly feasible for extracting modal parameters from severely blurred motion pictures.
Temple, David R; Lee, Beom-Chan; Layne, Charles S
2016-03-01
The sensory re-weighting theory suggests unreliable inputs may be down-weighted to favor more reliable sensory information and thus maintain proper postural control. This study investigated the effects of tibialis anterior (TA) vibration on center of pressure (COP) motion in healthy individuals exposed to support surface translations to further explore the concept of sensory re-weighting. Twenty healthy young adults stood with eyes closed and arms across their chest while exposed to randomized blocks of five trials. Each trial lasted 8 s, with TA vibration either on or off. After 2 s, a sudden backward or forward translation occurred. Anterior-posterior (A/P) COP data were evaluated during the preparatory (first 2 s), perturbation (next 3 s), and recovery (last 3 s) phases to assess the effect of vibration on perturbation response features. The knowledge of an impending perturbation resulted in reduced anterior COP motion with TA vibration in the preparatory phase relative to the magnitude of anterior motion typically observed during TA vibration. During the perturbation phase, vibration did not influence COP motion. However, during the recovery phase vibration induced greater anterior COP motion than during trials without vibration. The fact that TA vibration produced differing effects on COP motion depending upon the phase of the perturbation response may suggest that the immediate context during which postural control is being regulated affects A/P COP responses to TA vibration. This indicates that proprioceptive information is likely continuously re-weighted according to the context in order to maintain effective postural control.
Vibrational properties of uracil
Institute of Scientific and Technical Information of China (English)
WANG Zhiping; ZHANG Fengshou; ZENG Xianghua; ZHOU Hongyu; GU Bin; CHENG Wei
2006-01-01
A semiempirical molecular dynamics model is developed to study the vibrational frequencies of uracil at very low kinetic temperature by using the Fourier transform of velocity autocorrelation function of trajectories of molecular dynamics simulations. The finite difference harmonic method is used to assign the vibrational frequency of each mode. The calculated frequencies are found to be in good agreement with experimental measurements. Moreover, we make up for the lost vibrational modes in experiments self-consistently. A total of 30 vibrational modes and their corresponding frequencies are reported.
1993-01-01
MOOG, Inc. supplies hydraulic actuators for the Space Shuttle. When MOOG learned NASA was interested in electric actuators for possible future use, the company designed them with assistance from Marshall Space Flight Center. They also decided to pursue the system's commercial potential. This led to partnership with InterActive Simulation, Inc. for production of cabin flight simulators for museums, expositions, etc. The resulting products, the Magic Motion Simulator 30 Series, are the first electric powered simulators. Movements are computer-guided, including free fall to heighten the sense of moving through space. A projection system provides visual effects, and the 11 speakers of a digital laser based sound system add to the realism. The electric actuators are easier to install, have lower operating costs, noise, heat and staff requirements. The U.S. Space & Rocket Center and several other organizations have purchased the simulators.
PREFACE: Vibrations at surfaces Vibrations at surfaces
Rahman, Talat S.
2011-12-01
This special issue is dedicated to the phenomenon of vibrations at surfaces—a topic that was indispensible a couple of decades ago, since it was one of the few phenomena capable of revealing the nature of binding at solid surfaces. For clean surfaces, the frequencies of modes with characteristic displacement patterns revealed how surface geometry, as well as the nature of binding between atoms in the surface layers, could be different from that in the bulk solid. Dispersion of the surface phonons provided further measures of interatomic interactions. For chemisorbed molecules on surfaces, frequencies and dispersion of the vibrational modes were also critical for determining adsorption sites. In other words, vibrations at surfaces served as a reliable means of extracting information about surface structure, chemisorption and overlayer formation. Experimental techniques, such as electron energy loss spectroscopy and helium-atom-surface scattering, coupled with infra-red spectroscopy, were continually refined and their resolutions enhanced to capture subtleties in the dynamics of atoms and molecules at surfaces. Theoretical methods, whether based on empirical and semi-empirical interatomic potential or on ab initio electronic structure calculations, helped decipher experimental observations and provide deeper insights into the nature of the bond between atoms and molecules in regions of reduced symmetry, as encountered on solid surfaces. Vibrations at surfaces were thus an integral part of the set of phenomena that characterized surface science. Dedicated workshops and conferences were held to explore the variety of interesting and puzzling features revealed in experimental and theoretical investigations of surface vibrational modes and their dispersion. One such conference, Vibrations at Surfaces, first organized by Harald Ibach in Juelich in 1980, continues to this day. The 13th International Conference on Vibrations at Surfaces was held at the University of
Active Vibration Suppression R&D for the NLC
Frisch, Josef; Hendirckson, Linda; Himel, Thomas; Seryi, Andrei
2001-01-01
The nanometer scale beam sizes at the interaction point in linear colliders limit the allowable motion of the final focus magnets. We have constructed a prototype system to investigate the use of active vibration damping to control magnet motion. Inertial sensors are used to measure the position of a test mass, and a DSP based system provides feedback using electrostatic pushers. Simulation and experimental results for the control of a mechanically simple system are presented.
Rene de Jesus Romero-Troncoso; Gilberto Herrera-Ruiz; Roque Alfredo Osornio-Rios; Luis Morales-Velazquez; Carlos Rodriguez-Donate
2010-01-01
Intelligent robotics demands the integration of smart sensors that allow the controller to efficiently measure physical quantities. Industrial manipulator robots require a constant monitoring of several parameters such as motion dynamics, inclination, and vibration. This work presents a novel smart sensor to estimate motion dynamics, inclination, and vibration parameters on industrial manipulator robot links based on two primary sensors: an encoder and a triaxial accelerometer. The proposed s...
Dynamic behavior of gas bubble in single bubble sonoluminescence - vibrator model
Institute of Scientific and Technical Information of China (English)
QIAN Menglu; CHENG Qian; GE Caoyan
2002-01-01
Single bubble sonoluminescence is a process of energy transformation from soundto light. Therefore the motion equations of near spherical vibration of a gas bubble in anincompressible and viscous liquid can be deduced by Lagrangian Equation with dissipationfunction when the bubble is considered as a vibrator surrounded by liquid. The analyticalsolutions in the bubble expanding, collapsing and rebounding stages can be obtained by solvingthese motion equations when some approximations are adopted. And the dynamic behaviorsof the bubble in these three stages are discussed.
The current status of measurement standards for acoustics and vibration at Inmetro
Ripper, Gustavo Palmeira; Hoffmann, Walter Erico
2002-01-01
ABSTRACT: The Division of Acoustics and Vibration (DIAVI) of INMETRO establishes, validates and maintains the Brazilian national measurement standards used for the realization of the units of physical quantities related to the field of acoustics and vibration. The basic vibration quantity realized by DIAVI is translational acceleration, from which the other motion quantities, i.e., velocity and displacement can be derived. Acoustical physical quantities include sound pressure and sound power...
McNett, Gabriel D; Miles, Ronald N; Homentcovschi, Dorel; Cocroft, Reginald B
2006-12-01
Conventional approaches to measuring animal vibrational signals on plant stems use a single transducer to measure the amplitude of vibrations. Such an approach, however, will often underestimate the amplitude of bending waves traveling along the stem. This occurs because vibration transducers are maximally sensitive along a single axis, which may not correspond to the major axis of stem motion. Furthermore, stem motion may be more complex than that of a bending wave propagating along a single axis, and such motion cannot be described using a single transducer. Here, we describe a method for characterizing stem motion in two dimensions by processing the signals from two orthogonally positioned transducers. Viewed relative to a cross-sectional plane, a point on the stem surface moves in an ellipse at any one frequency, with the ellipse's major axis corresponding to the maximum amplitude of vibration. The method outlined here measures the ellipse's major and minor axes, and its angle of rotation relative to one of the transducers. We illustrate this method with measurements of stem motion during insect vibrational communication. It is likely the two-dimensional nature of stem motion is relevant to insect vibration perception, making this method a promising avenue for studies of plant-borne transmission.
Longitudinal vibrations of mechanical systems with the transportation effect
Directory of Open Access Journals (Sweden)
A. Buchacz
2009-01-01
Full Text Available Purpose: this thesis purpose is a new way of modelling systems working with high speeds of mechanisms. Systems are analyzed with taking into consideration the rotational movement and with criterions of using materials with high flexibility and high precision of work. The dynamical analysis was done with giving into consideration the interaction between working motion and local vibrations. During the motion a model is loaded by longitudinal forces.Design/methodology/approach: equations of motion were derived by the Lagrange method, with generalized coordinates and generalized velocities assumed as orthogonal projections of individual quantities of the rod and manipulators to axes of the global reference frame.Findings: the model of longitudinally vibrating systems in plane motion was derived, after that the model can be transformed to the dynamical flexibility of these systems. Derived equations are the beginning of analysis of complex systems, especially can be used in deducing of the substitute dynamical flexibility of multilinked systems in motion.Research limitations/implications: mechanical systems vibrating longitudinally in terms of rotation were considered in this thesis. Successive problem of the dynamical analysis is the analysis of systems in spatial transportation and systems loaded by transversal forces.Practical implications: effects of presented calculations can be applied into machines and mechanisms in transportation such as: high speed turbines, wind power plant, water-power plants, manipulators, aerodynamics issues, and in different rotors etc.Originality/value: the contemporary analysis of beams and rods were made in a separate way, first working motion of the main system and next the local vibrations. A new way of modelling took into consideration the interaction between those two displacement. There was defined the transportation effect for models vibrating longitudinally in this paper.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The nonlinear dynamic behavior of a rubbing rotor system was studied with a mathematical model established with the eccentricity and interaction between bending and torsional vibrations taken into consideration.The nonlinear vibrational response of a rubbing rotor was analyzed using numerical integral,spectroscopic analysis and Poince mapping method,which made it possible to have better understanding of the vibrational characteristics of partial rubbing and complete circular rubbing rotors.The numerical results reveal the response of torsional vibration mainly takes a form of suporchronous motion,and its frequency decreases as the rotational speed increases when partial rubbing occurs,and the response of torsional vibration is synchronous when complete circular rubbing occurs.The comparison of the dynamics of rubbing rotors with and without the interaction between bending and torsional vibrations shows the interaction between bending and torsional vibrations advances the rotational speed,at which the response of bending vibration changes from a synchronous motion into a quasi-periodic motion,and the interaction between bending and torsional vibrations reduces stability of the rubbing rotor.
Kis, Z.; Janszky, J.; Vinogradov, An. V.; Kobayashi, T.
1996-01-01
The optical Schroedinger cat states are simple realizations of quantum states having nonclassical features. It is shown that vibrational analogues of such states can be realized in an experiment of double pulse excitation of vibrionic transitions. To track the evolution of the vibrational wave packet we derive a non-unitary time evolution operator so that calculations are made in a quasi Heisenberg picture.
DEFF Research Database (Denmark)
Nielsen, Søren R. K.
The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 4th edition of this textbook on linear stochastic vibration...
[Vibration on agricultural tractors].
Peretti, Alessandro; Delvecchio, Simone; Bonomini, Francesco; di Bisceglie, Anita Pasqua; Colosio, Claudio
2013-01-01
In the article, details related to the diffusion of agricultural tractors in Italy are given and considerations about the effects of vibration on operators, the sources of vibration and suggestions to reduce them are presented. The acceleration values observed in Italy amongst 244 tractors and levels of worker exposure are shown by means of histograms. The relevant data variability is discussed.
Eijk, A.
2010-01-01
The methods that need to be employed to develop the better vibration guidelines to assess the integrity of a reciprocating compressor system are discussed. An R&D project of the European Forum of Reciprocating Compressors (EFRC) has been initiated to develop guidelines for vibrations in reciprocatin
DEFF Research Database (Denmark)
Nielsen, Søren R. K.
The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration th...
Mechanical vibration and shock analysis, sinusoidal vibration
Lalanne, Christian
2014-01-01
Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m
Auditory Motion Elicits a Visual Motion Aftereffect
Directory of Open Access Journals (Sweden)
Christopher C. Berger
2016-12-01
Full Text Available The visual motion aftereffect is a visual illusion in which exposure to continuous motion in one direction leads to a subsequent illusion of visual motion in the opposite direction. Previous findings have been mixed with regard to whether this visual illusion can be induced cross-modally by auditory stimuli. Based on research on multisensory perception demonstrating the profound influence auditory perception can have on the interpretation and perceived motion of visual stimuli, we hypothesized that exposure to auditory stimuli with strong directional motion cues should induce a visual motion aftereffect. Here, we demonstrate that horizontally moving auditory stimuli induced a significant visual motion aftereffect—an effect that was driven primarily by a change in visual motion perception following exposure to leftward moving auditory stimuli. This finding is consistent with the notion that visual and auditory motion perception rely on at least partially overlapping neural substrates.
Vibrational Spectroscopy of Biomembranes
Schultz, Zachary D.; Levin, Ira W.
2011-07-01
Vibrational spectroscopy, commonly associated with IR absorption and Raman scattering, has provided a powerful approach for investigating interactions between biomolecules that make up cellular membranes. Because the IR and Raman signals arise from the intrinsic properties of these molecules, vibrational spectroscopy probes the delicate interactions that regulate biomembranes with minimal perturbation. Numerous innovative measurements, including nonlinear optical processes and confined bilayer assemblies, have provided new insights into membrane behavior. In this review, we highlight the use of vibrational spectroscopy to study lipid-lipid interactions. We also examine recent work in which vibrational measurements have been used to investigate the incorporation of peptides and proteins into lipid bilayers, and we discuss the interactions of small molecules and drugs with membrane structures. Emerging techniques and measurements on intact cellular membranes provide a prospective on the future of vibrational spectroscopic studies of biomembranes.
Vicsek, Tamás; Zafeiris, Anna
2012-08-01
We review the observations and the basic laws describing the essential aspects of collective motion - being one of the most common and spectacular manifestation of coordinated behavior. Our aim is to provide a balanced discussion of the various facets of this highly multidisciplinary field, including experiments, mathematical methods and models for simulations, so that readers with a variety of background could get both the basics and a broader, more detailed picture of the field. The observations we report on include systems consisting of units ranging from macromolecules through metallic rods and robots to groups of animals and people. Some emphasis is put on models that are simple and realistic enough to reproduce the numerous related observations and are useful for developing concepts for a better understanding of the complexity of systems consisting of many simultaneously moving entities. As such, these models allow the establishing of a few fundamental principles of flocking. In particular, it is demonstrated, that in spite of considerable differences, a number of deep analogies exist between equilibrium statistical physics systems and those made of self-propelled (in most cases living) units. In both cases only a few well defined macroscopic/collective states occur and the transitions between these states follow a similar scenario, involving discontinuity and algebraic divergences.
Metrology of vibration measurements by laser techniques
von Martens, Hans-Jürgen
2008-06-01
Metrology as the art of careful measurement has been understood as uniform methodology for measurements in natural sciences, covering methods for the consistent assessment of experimental data and a corpus of rules regulating application in technology and in trade and industry. The knowledge, methods and tools available for precision measurements can be exploited for measurements at any level of uncertainty in any field of science and technology. A metrological approach to the preparation, execution and evaluation (including expression of uncertainty) of measurements of translational and rotational motion quantities using laser interferometer methods and techniques will be presented. The realization and dissemination of the SI units of motion quantities (vibration and shock) have been based on laser interferometer methods specified in international documentary standards. New and upgraded ISO standards are reviewed with respect to their suitability for ensuring traceable vibration measurements and calibrations in an extended frequency range of 0.4 Hz to higher than 100 kHz. Using adequate vibration exciters to generate sufficient displacement or velocity amplitudes, the upper frequency limits of the laser interferometer methods specified in ISO 16063-11 for frequencies procedures (i.e. measurement uncertainty 0.05 % at frequencies <= 10 kHz, <= 1 % up to 100 kHz).
2013-01-01
Please note this is a short discount publication. In today's manufacturing environment, Motion Control plays a major role in virtually every project.The Motion Control Report provides a comprehensive overview of the technology of Motion Control:* Design Considerations* Technologies* Methods to Control Motion* Examples of Motion Control in Systems* A Detailed Vendors List
Time-resolved vibrational spectroscopy of a molecular shuttle
Panman, M.R.; Bodis, P.; Shaw, D.J.; Bakker, B.H.; Newton, A.C.; Kay, E.R.; Leigh, D.A.; Buma, W.J.; Brouwer, A.M.; Woutersen, S.
2012-01-01
Time-resolved vibrational spectroscopy is used to investigate the inter-component motion of an ultraviolet-triggered two-station molecular shuttle. The operation cycle of this molecular shuttle involves several intermediate species, which are observable in the amide I and amide II regions of the mid
Hexagons and Interfaces in a Vibrated Granular Layer
Aranson, I S; Vinokur, V M
1998-01-01
The order parameter model based on parametric Ginzburg-Landau equation is used to describe high acceleration patterns in vibrated layer of granular material. At large amplitude of driving both hexagons and interfaces emerge. Transverse instability leading to formation of ``decorated'' interfaces and labyrinthine patterns, is found. Additional sub-harmonic forcing leads to controlled interface motion.
Whole body vibration improves body mass, flexibility and strength in ...
African Journals Online (AJOL)
even without significant weight loss, and a reduction in the risk of colon cancer and ... muscular strength, flexibility, range of motion, bone density, and improved .... by either increasing the amplitude of the vibration from low (L) to high (H), or by ...
Predicting vibration-induced displacement for a resonant friction slider
DEFF Research Database (Denmark)
Fidlin, A.; Thomsen, Jon Juel
2001-01-01
A mathematical model is set up to quantify vibration-induced motions of a slider, sandwiched between friction layers with different coefficients of friction, and equipped with an imbedded resonator that oscillates at high frequency and small amplitude. This model is highly nonlinear, involving non...
Liquid viscosity sensing using nonlinear vibration of a fiberoptic sensor.
Wang, Wei-Chih; Liu, Chao-Shih
2013-07-01
This paper investigates the nonlinear dynamic motion of a vibrating optical fiber viscosity sensor through representative cases of primary and super-harmonic resonance. The results show that a nonlinear effect drastically improves the sensitivity of the viscosity measurement by nearly an order of magnitude from the previously developed linear systems. Experimental results and several applications of the viscosity sensor are also presented.
Characterization of a novel instrument for vibration exercise.
Xu, L; Rabotti, C; Mischi, M
2012-01-01
Vibration exercise (VE) has been suggested as an effective option to improve muscle strength and power performance. Several studies link the effects of vibration training to enhanced neuromuscular stimulation and typically to involuntary reflex mechanisms. However, the underlying mechanisms are still unclear and information for the most appropriate vibration training protocols is limited. This study proposes to realize a new vibration exercise system for the biceps brachii. Amplitude, frequency, and baseline of the vibrating load, which is generated by an electromechanical actuator, can be adjusted dynamically by a feedback control loop. A second-order model is employed to identify the relation between the mechanical load and the input voltage driving the actuator. An adaptive normalized least mean square algorithm is proposed to remove the motion artifacts from the measured electromyography (EMG) data. Our results show a high correlation (0.99) between the second-order model fit and the measured data, permitting accurate control on the supplied load for vibrations up to 80 Hz. Furthermore, preliminary validation with 4 volunteers showed an excellent performance in the motion artifact removal, enabling reliable evaluation of the neuromuscular activation.
A coin vibrational motor swimming at low Reynolds number
Quillen, Alice C; Kelley, Douglas H; Friedmann, Tamar; Oakes, Patrick W
2016-01-01
Low-cost coin vibrational motors, used in haptic feedback, exhibit rotational internal motion inside a rigid case. Because the motor case motion exhibits rotational symmetry, when placed into a fluid such as glycerin, the motor does not swim even though its vibrations induce steady streaming in the fluid. However, a piece of rubber foam stuck to the curved case and giving the motor neutral buoyancy also breaks the rotational symmetry allowing it to swim. We measured a 1 cm diameter coin vibrational motor swimming in glycerin at a speed of a body length in 3 seconds or at 3 mm/s. The swim speed puts the vibrational motor in a low Reynolds number regime similar to bacterial motility, but because of the vibration it is not analogous to biological organisms. Rather the swimming vibrational motor may inspire small inexpensive robotic swimmers that are robust as they contain no external moving parts. A time dependent Stokes equation planar sheet model suggests that the swim speed depends on a steady streaming veloc...
Direct Measurement of Squeezing in the Motion of Trapped Ions
Institute of Scientific and Technical Information of China (English)
ZENG Hao-Sheng; HU Ai-Qin; LIU Qiong; KUANG Le-Man
2005-01-01
@@ We present a simple method that can be used to directly measure the squeezing of the quantum motional states of a trapped ion.Through the use of the interaction between the trapped ion and classical lasers, one can design a required coupling between the internal electronic and external vibrational degrees of freedom of the ion and can transfer information of the expectation value of a vibrational operator to the atomic internal populations.Thus measurement of squeezing on the quantum motional state can directly be realized.By adjusting the phases of the interacting lasers, one can measure the squeezing of both position and momentum quadratures.
Nonlinear Vibration Analysis of Moving Strip with Inertial Boundary Condition
Directory of Open Access Journals (Sweden)
Chong-yi Gao
2015-01-01
Full Text Available According to the movement mechanism of strip and rollers in tandem mill, the strip between two stands was simplified to axially moving Euler beam and the rollers were simplified to the inertial component on the fixed axis rotation, namely, inertial boundary. Nonlinear vibration mechanical model of Euler beam with inertial boundary conditions was established. The transverse and longitudinal motion equations were derived based on Hamilton’s principle. Kantorovich averaging method was employed to discretize the motion equations and the inertial boundary equations, and the solutions were obtained using the modified iteration method. Depending on numerical calculation, the amplitude-frequency responses of Euler beam were determined. The axial velocity, tension, and rotational inertia have strong influences on the vibration characteristics. The results would provide an important theoretical reference to control and analyze the vertical vibration of moving strip in continuous rolling process.
Modeling of cable vibration effects of cable-stayed bridges
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The analysis of dynamic responses of cable-stayed bridges subjected to wind and earthquake loads generallyconsiders only the motions of the bridge deck and pylons. The influence of the stay cable vibration on the responses of the bridgeis either ignored or considered by approximate procedures. The transverse vibration of the stay cables, which can be significant insome cases, are usually neglected in previous research. In the present study, a new three-node cable element has been developed tomodel the transverse motions of the cables. The interactions between the cable behavior and the other parts of the bridgesuperstructure are considered by the concept of dynamic stiffness. The nonlinear effect of the cable caused by its self-weight isincluded in the formulation. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed model.The impact of cable vibration behavior on the dynamic characteristics of cable-stayed bridges is discussed.
Optical measurements of long-range protein vibrations
Acbas, Gheorghe; Niessen, Katherine A.; Snell, Edward H.; Markelz, A. G.
2014-01-01
Protein biological function depends on structural flexibility and change. From cellular communication through membrane ion channels to oxygen uptake and delivery by haemoglobin, structural changes are critical. It has been suggested that vibrations that extend through the protein play a crucial role in controlling these structural changes. While nature may utilize such long-range vibrations for optimization of biological processes, bench-top characterization of these extended structural motions for engineered biochemistry has been elusive. Here we show the first optical observation of long-range protein vibrational modes. This is achieved by orientation-sensitive terahertz near-field microscopy measurements of chicken egg white lysozyme single crystals. Underdamped modes are found to exist for frequencies >10 cm-1. The existence of these persisting motions indicates that damping and intermode coupling are weaker than previously assumed. The methodology developed permits protein engineering based on dynamical network optimization.
Mechanical vibrations of pendant liquid droplets.
Temperton, Robert H; Smith, Michael I; Sharp, James S
2015-07-01
A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependent intensity variations were recorded using the photodiode. These time-dependent variations were Fourier transformed and the frequencies and widths of the mechanical droplet resonances were extracted. A simple model of vibrations in pendant/sessile drops was used to relate these parameters to the surface tension, density and viscosity of the liquid droplets. The surface tension values obtained from this method were found to be in good agreement with results obtained using the standard pendant drop technique. Damping of capillary waves on pendant drops was shown to be similar to that observed for deep liquid baths and the kinematic viscosities obtained were in agreement with literature values for all three liquids studied.
Synthesis of Vibration Waves Based on Wavelet Technology
Directory of Open Access Journals (Sweden)
L.H. Zou
2012-01-01
Full Text Available A novel method to generate time series of vibration waves is proposed in the paper. Considering the frequency band energy as the criterion, synthesis formulas for fluctuating wind pressure and earthquake ground motion are developed in terms of Daubechies wavelet and Harr wavelet respectively. The wavelet reconstruction method is applicable to both stationary and non-stationary process simulation. Theoretically, for non-stationary (such as seismic process synthesis, it has a better non-stationarity in time-frequency domain than the traditional trigonometric series. Influence of wavelet delamination number and wavelet function type is also analyzed. Numerical results show that the synthesis of vibration waves based on wavelet reconstruction method contains main components of vibration, and can reflect the main properties of practical vibrations.
Passive and Active Vibration Control of Renewable Energy Structures
DEFF Research Database (Denmark)
Zhang, Zili
The present thesis deals with fundamental researches on passive and active vibration control of renewable energy structures, and provides useful models for practical applications. Effective and robust vibration control methods have been explored for mitigating the lightly damped edgewise blade...... vibration and lateral tower vibration, with the main focus on structural control devices. Rigorous theoretical modeling of different dynamic system has been established, based on which detailed design and analysis of the proposed control devices can be carried out. This thesis also explores technical...... solutions for wave energy point absorbers, in order to maximize the mean absorbed power and to deliver more smooth power to the grid. A novel suboptimal causal control law has been established for controlling the motion of the point absorber, and a new type of point absorber has also been proposed...
Acoustic monitoring of a ball sinking in vibrated granular sediments
van den Wildenberg, Siet; Léopoldès, Julien; Tourin, Arnaud; Jia, Xiaoping
2017-06-01
We develop an ultrasound probing to investigate the dynamics of a high density ball sinking in 3D opaque dense granular suspensions under horizontal weak vibrations. We show that the motion of the ball in these horizontally vibrated glass bead packings saturated by water is consistent with the frictional rheology. The extracted stress-strain relation evidences an evolution of flow behaviour from frictional creep to inertial regimes. Our main finding is that weak external vibration primarily affects the yield stress and controls the depth of sinking via vibration-induced sliding at the grain contact. Also, we observe that the extracted rheological parameters depend on the size of the probing ball, suggesting thus a non-local rheology.
Vortex induced vibrations of pipe in high waves. Field measurements
Energy Technology Data Exchange (ETDEWEB)
Hansen Ottesen, N.-E.; Pedersen, B.
1999-07-01
Vortex induced vibrations have been measured full scale on an instrumented pipe placed vertically in the crest zone of high and steep waves. The Reynolds numbers were in the range 105 to 106. It was found that the vortex induced vibrations in the wave motion were generated within a reduced velocity range of 4 and 8. The vibrations grew intermittently with the passing waves. The vibrations took place in 2-3 modes simultaneously. One mode, however, dominated over the other. The growths of the VIV using a modal analysis were consistent with a basic correlation length of 3 diameters for a stationary pipe with a linear growth of the correlation length of 10 diameter for each 0.1 diameter amplitude. (au)
Global nonresonant vibrational-photoelectron coupling in molecular photoionization
Poliakoff, Erwin; Das, Aloke; Hardy, David; Bozek, John; Aguilar, Alex; Lucchese, Robert
2009-05-01
Using photoelectron spectroscopy and Schwinger variational scattering theory, we have investigated the coupling between vibrational motion and the exiting photoelectron over extended ranges of photoelectron kinetic energy. Photoelectron spectroscopy is performed with vibrational resolution over uncommonly large ranges of energy (ca. 200 eV). We find clear and significant changes in vibrational branching ratios as a function of photon energy, in direct contradiction to predictions of the Franck-Condon principle. While it is well known that resonances lead to coupling between electronic and vibrational degrees of freedom, nonresonant mechanisms that result in such coupling are not expected or well-documented. Photoelectron spectra are presented for several electronic states of N2^+, CO^+, and NO^+, and we find that valence isoelectronic channels behave very differently, which is also surprising. Theoretical results indicate that Cooper minima are the underlying cause of these effects, and we are currently working to understand the reasons for the sensitivity of the Cooper minima on bond length.
Institute of Scientific and Technical Information of China (English)
Gu Yujiong; He Chengbing; Yang Kun; Zhang Jianqiang
2004-01-01
With the establishment of the nonlinear coupled lateral and torsion vibration equations of rub-impact Jeffcott rotor and through numerical simulations,the influences on lateral and torsion vibration behavior by rotor-to-stator clearance are analyzed,which prove that there is strong impact on coupled lateral and torsion vibration behavior.Smaller the clearance is,more complex the motion of rotor is.When the clearance is larger,the frequency spectrum of rub-impact rotor is mainly composed of 1/2X,1/3X and 1/4X components.With the decrease of clearance,quasi-periodic and chaotic motions will be present.Under different clearances,the bifurcation diagrams of lateral and torsion vibrations can be divided into rub-free zone,rub-light zone and three complex motion zones in which the motion trend of lateral vibration is similar to that of the torsion vibration.Compared with the lateral vibration,the torsion vibration is of more motion forms and more abundant frequency components in amplitude spectrum.
Optomechanical proposal for monitoring microtubule mechanical vibrations
Barzanjeh, Sh.; Salari, V.; Tuszynski, J. A.; Cifra, M.; Simon, C.
2017-07-01
Microtubules provide the mechanical force required for chromosome separation during mitosis. However, little is known about the dynamic (high-frequency) mechanical properties of microtubules. Here, we theoretically propose to control the vibrations of a doubly clamped microtubule by tip electrodes and to detect its motion via the optomechanical coupling between the vibrational modes of the microtubule and an optical cavity. In the presence of a red-detuned strong pump laser, this coupling leads to optomechanical-induced transparency of an optical probe field, which can be detected with state-of-the art technology. The center frequency and line width of the transparency peak give the resonance frequency and damping rate of the microtubule, respectively, while the height of the peak reveals information about the microtubule-cavity field coupling. Our method opens the new possibilities to gain information about the physical properties of microtubules, which will enhance our capability to design physical cancer treatment protocols as alternatives to chemotherapeutic drugs.
Smart actuators for active vibration control
Pourboghrat, Farzad; Daneshdoost, Morteza
1998-07-01
In this paper, the design and implementation of smart actuators for active vibration control of mechanical systems are considered. A smart actuator is composed of one or several layers of piezo-electric materials which work both as sensors and actuators. Such a system also includes micro- electronic or power electronic amplifiers, depending on the power requirements and applications, as well as digital signal processing systems for digital control implementation. In addition, PWM type micro/power amplifiers are used for control implementation. Such amplifiers utilize electronic switching components that allow for miniaturization, thermal efficiency, cost reduction, and precision controls that are robust to disturbances and modeling errors. An adaptive control strategy is then developed for vibration damping and motion control of cantilever beams using the proposed smart self-sensing actuators.
Analysis of potential helicopter vibration reduction concepts
Landgrebe, A. J.; Davis, M. W.
1984-01-01
Several recent helicopter vibration reduction research programs are described. Results of studies of blade design parameters in rotor vibratory response and of an advanced blade design for reduced vibration are examined. An optimization approach to develop a general automated procedure for rotor blade design is described, and analytical results for an articulated rotor operating at a steady 160 kt flight condition are reported. The use of a self-adaptive controller to implement higher harmonic control in closed-loop fashion is addressed, and a computer simulation used to evaluate and compare the performance of alternative algorithms included in the generic active controller is discussed. Results are presented for steady level flight conditions, short-duration maneuvers, blade stresses and rotor performance, blade-appended aeroelastic devices, vibratory airloads, wake-induced blade airloads, and airloads from blade motions, the interaction of rotor and fuselage, and the interaction of rotor and empennage.
Vibration-induced displacement using high-frequency resonators and friction layers
DEFF Research Database (Denmark)
Thomsen, Jon Juel
1998-01-01
A mathematical model is set up to quantify vibration-induced motions of a slider with an imbedded resonator. A simple approximate expression is presented for predicting average velocities of the slider, agreeing fairly well with numerical integration of the full equations of motion. The simple...... expression can be used to the estimate influence of system parameters, and to plan and interpret laboratory experiments....
Energy Technology Data Exchange (ETDEWEB)
Hougen, J.T. [NIST, Gaithersburg, MD (United States)
1993-12-01
The goal of this project is to use spectroscopic techniques to investigate in detail phenomena involving the vibrational quasi-continuum in a simple physical system. Acetaldehyde was chosen for the study because: (i) methyl groups have been suggested to be important promotors of intramolecular vibrational relaxation, (ii) the internal rotation of a methyl group is an easily describle large-amplitude motion, which should retain its simple character even at high levels of excitation, and (iii) the aldehyde carbonyl group offers the possibility of both vibrational and electronic probing. The present investigation of the ground electronic state has three parts: (1) understanding the {open_quotes}isolated{close_quotes} internal-rotation motion below, at, and above the top of the torsional barrier, (2) understanding in detail traditional (bond stretching and bending) vibrational fundamental and overtone states, and (3) understanding interactions involving states with multiquantum excitations of at least one of these two kinds of motion.
Microscopic derivation of nuclear rotation-vibration model, axially symmetric case
Gulshani, Parviz
2015-01-01
We derive from first principles the successful phenomenological hydrodynamic model of Bohr-Davydov-Faessler-Greiner for rotation-vibration motion of an axially symmetric deformed nucleus. The derivation is not limited to small oscillation amplitude, and provides microscopic expressions for the interaction operators among the rotation, vibration, and intrinsic motions, for the moment of inertia, vibration mass, and for the deformation variables. The method uses canonical transformations to collective co-ordinates, followed by a constrained variational method, with the associated constraints imposed on the wavefunction rather than on the particle co-ordinates. The approach yields three self-consistent, time-reversal invariant, cranking-type Schrodinger equations for the rotation-vibration and intrinsic motions, and a self-consistency equation. For deformed harmonic oscillator mean-field potentials, these equations are solved in closed forms for the energies, moments of inertia, quadrupole moments and transition...
Chaotic vibrations of tubes with nonlinear supports in crossflow
Energy Technology Data Exchange (ETDEWEB)
Cai, Y.; Chen, S.S.
1992-12-01
By means of the unsteady flow theory and a bilinear mathematical model, a theoretical study is presented for chaotic vibrations associated with the fluidelastic instability of nonlinearly supported tubes in a crossflow. A series of effective tools, including phase portraits, power spectral density, Poincar`e maps, Lyapunov exponent, fractal dimension, and bifurcation diagrams, are utilized to distinguish periodic and chaotic motions when the tubes vibrate in the instability region. Results show periodic and chaotic motions in the region corresponding to the fluid damping controlled instability. Nonlinear supports, with symmetric or asymmetric gaps, significantly affect the distributions of periodic, quasiperiodic and chaotic motions of the tube with various flow velocity in the instability region of the TSP(tube-support-plate)-inactive mode.
Chaotic vibrations of tubes with nonlinear supports in crossflow
Energy Technology Data Exchange (ETDEWEB)
Cai, Y.; Chen, S.S.
1992-01-01
By means of the unsteady flow theory and a bilinear mathematical model, a theoretical study is presented for chaotic vibrations associated with the fluidelastic instability of nonlinearly supported tubes in a crossflow. A series of effective tools, including phase portraits, power spectral density, Poincar'e maps, Lyapunov exponent, fractal dimension, and bifurcation diagrams, are utilized to distinguish periodic and chaotic motions when the tubes vibrate in the instability region. Results show periodic and chaotic motions in the region corresponding to the fluid damping controlled instability. Nonlinear supports, with symmetric or asymmetric gaps, significantly affect the distributions of periodic, quasiperiodic and chaotic motions of the tube with various flow velocity in the instability region of the TSP(tube-support-plate)-inactive mode.
Chaotic vibrations of nonlinearly supported tubes in crossflow
Energy Technology Data Exchange (ETDEWEB)
Cai, Y.; Chen, S.S.
1992-02-01
By means of the unsteady-flow theory and a bilinear mathematical model, a theoretical study is presented for chaotic vibrations associated with the fluidelastic instability of nonlinearly supported tubes in a crossflow. Effective tools, including phase portraits, power spectral density, Poincare maps, Lyapunov exponent, fractal dimension, and bifurcation diagrams, are utilized to distinguish periodic and chaotic motions when the tubes vibrate in the instability region. The results show periodic and chaotic motions in the region corresponding to fluid-damping-controlled instability. Nonlinear supports, with symmetric or asymmetric gaps, significantly affect the distribution of periodic, quasiperiodic, and chaotic motions of a tube exposed to various flow velocities in the instability region of the tube-support-plate-inactive mode.
Vibrating wire alignment technique
Xiao-Long, Wang; lei, Wu; Chun-Hua, Li
2013-01-01
Vibrating wire alignment technique is a kind of method which through measuring the spatial distribution of magnetic field to do the alignment and it can achieve very high alignment accuracy. Vibrating wire alignment technique can be applied for magnet fiducialization and accelerator straight section components alignment, it is a necessary supplement for conventional alignment method. This article will systematically expound the international research achievements of vibrating wire alignment technique, including vibrating wire model analysis, system frequency calculation, wire sag calculation and the relation between wire amplitude and magnetic induction intensity. On the basis of model analysis this article will introduce the alignment method which based on magnetic field measurement and the alignment method which based on amplitude and phase measurement. Finally, some basic questions will be discussed and the solutions will be given.
NIF Ambient Vibration Measurements
Energy Technology Data Exchange (ETDEWEB)
Noble, C.R.; Hoehler, M.S., S.C. Sommer
1999-11-29
LLNL has an ongoing research and development project that includes developing data acquisition systems with remote wireless communication for monitoring the vibrations of large civil engineering structures. In order to establish the capability of performing remote sensing over an extended period of time, the researchers needed to apply this technology to a real structure. The construction of the National Ignition Facility provided an opportunity to test the data acquisition system on a large structure to monitor whether the facility is remaining within the strict ambient vibration guidelines. This document will briefly discuss the NIF ambient vibration requirements and summarize the vibration measurements performed during the Spring and Summer of 1999. In addition, a brief description of the sensors and the data acquisition systems will be provided in Appendix B.
NIF Ambient Vibration Measurements
Energy Technology Data Exchange (ETDEWEB)
Noble, C.R.; Hoehler, M.S., S.C. Sommer
1999-11-29
LLNL has an ongoing research and development project that includes developing data acquisition systems with remote wireless communication for monitoring the vibrations of large civil engineering structures. In order to establish the capability of performing remote sensing over an extended period of time, the researchers needed to apply this technology to a real structure. The construction of the National Ignition Facility provided an opportunity to test the data acquisition system on a large structure to monitor whether the facility is remaining within the strict ambient vibration guidelines. This document will briefly discuss the NIF ambient vibration requirements and summarize the vibration measurements performed during the Spring and Summer of 1999. In addition, a brief description of the sensors and the data acquisition systems will be provided in Appendix B.
Flow induced vibrations of the CLIC X-Band accelerating structures
Charles, Tessa; Boland, Mark; Riddone, Germana; Samoshkin, Alexandre
2011-01-01
Turbulent cooling water in the Compact Linear Collider (CLIC) accelerating structures will inevitably induce some vibrations. The maximum acceptable amplitude of vibrations is small, as vibrations in the accelerating structure could lead to beam jitter and alignment difficulties. A Finite Element Analysis model is needed to identify the conditions under which turbulent instabilities and significant vibrations are induced. Due to the orders of magnitude difference between the fluid motion and the structure’s motion, small vibrations of the structure will not contribute to the turbulence of the cooling fluid. Therefore the resonant conditions of the cooling channels presented in this paper, directly identify the natural frequencies of the accelerating structures to be avoided under normal operating conditions. In this paper a 2D model of the cooling channel is presented finding spots of turbulence being formed from a shear layer instability. This effect is observed through direct visualization and wavelet ana...
Fitts' law model and target size of pointing devices in a vibration environment.
Liu, Chi No; Lin, Chiuhsiang Joe; Chao, Chin Jung
2007-12-01
This study examined models of Fitts' law and effective target widths of three pointing devices in vibration environments. From a research institute 10 employees, ages 26 to 31 years were recruited as paid subjects. Pointing tasks consisted of four square target sizes, four movement distances, and four target angles and were performed on a motion platform using a touch screen, a mouse, and a track ball. The platform simulated two levels of sea wave vibration environments besides a static one. Analysis showed effective target widths increased with vibration, indicating increased variability of the pointing task under vibration. The increase in the track ball was smaller, indicating resistance to motion disturbance. The study also suggests an enlarged target (button) size for the touch screen under the vibration environment. The findings have implications in motor control and human-computer interfacing.
Directory of Open Access Journals (Sweden)
Jingli Du
2013-01-01
Full Text Available Cable-driven parallel manipulators are one of the best solutions to achieving large workspace since flexible cables can be easily stored on reels. However, due to the negligible flexural stiffness of cables, long cables will unavoidably vibrate during operation for large workspace applications. In this paper a finite element model for cable-driven parallel manipulators is proposed to mimic small amplitude vibration of cables around their desired position. Output feedback of the cable tension variation at the end of the end-effector is utilized to design the vibration attenuation controller which aims at attenuating the vibration of cables by slightly varying the cable length, thus decreasing its effect on the end-effector. When cable vibration is attenuated, motion controller could be designed for implementing precise large motion to track given trajectories. A numerical example is presented to demonstrate the dynamic model and the control algorithm.
Electronic transport in fullerene C20 bridge assisted by molecular vibrations.
Yamamoto, Takahiro; Watanabe, Kazuyuki; Watanabe, Satoshi
2005-08-01
The effect of molecular vibrations on electronic transport is investigated with the smallest fullerene C20 bridge, utilizing the Keldysh nonequilibrium Green's function techniques combined with the tight-binding molecular-dynamics method. Large discontinuous steps appear in the differential conductance when the applied bias voltage matches particular vibrational energies. The magnitude of the step is found to vary considerably with the vibrational mode and to depend on the local electronic states besides the strength of electron-vibration coupling. On the basis of this finding, a novel way to control the molecular motion by adjusting the gate voltage is proposed.
Structure-borne sound structural vibrations and sound radiation at audio frequencies
Cremer, L; Petersson, Björn AT
2005-01-01
Structure-Borne Sound"" is a thorough introduction to structural vibrations with emphasis on audio frequencies and the associated radiation of sound. The book presents in-depth discussions of fundamental principles and basic problems, in order to enable the reader to understand and solve his own problems. It includes chapters dealing with measurement and generation of vibrations and sound, various types of structural wave motion, structural damping and its effects, impedances and vibration responses of the important types of structures, as well as with attenuation of vibrations, and sound radi
Saito, Shigeki; Inerbaev, Talgat M.; Mizuseki, Hiroshi; Igarashi, Nobuaki; Note, Ryunosuke; Kawazoe, Yoshiyuki
2006-11-01
First-principles calculations of the crystalline vibrations of a lactose monohydrate crystal in the terahertz (THz) region were performed using periodic density functional theory calculations. The calculated vibrational modes in the THz region were derived from group motions with different sizes: molecules of lactose and crystal water, pyranose rings, and intramolecular frames. The intermolecular modes with large vibrational amplitude of lactose of 17.5-100.6 cm-1 and of crystal-water of 136.1-237.7 cm-1 were clearly separated. This article especially refers to the intermolecular vibrational modes of crystal water with the THz absorption, which provide detectable spectral features of hydrated crystals.
Energy Technology Data Exchange (ETDEWEB)
Philip J. Reid
2009-09-21
The conference focuses on using vibrational spectroscopy to probe structure and dynamics of molecules in gases, liquids, and interfaces. The goal is to bring together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of systems.
Attenuation of cryocooler induced vibration in spaceborne infrared payloads
Veprik, A.; Twitto, A.
2014-01-01
Recent advancement of operational responsive space programs calls for a development of compact, reliable, low power and vibration free cryogenic cooling for sophisticated infrared payloads. The refrigeration in a typical closed cycle split Stirling linear cryocooler is achieved by a cyclic compression and expansion of a gaseous working agent due to a synchronized reciprocation of electro-dynamically and pneumatically actuated compressor and expander pistons. Attenuation of the cryocooler induced vibration usually relies on the concept of actively assisted momentum cancellation. In a typical dual-piston compressor this objective is achieved by actively synchronizing the motion of oppositely moving piston assemblies; a typical single-piston expander may be counterbalanced by a motorized counter-balancer. The above approach produces complexity, weight, size, high incurred costs and affects reliability. The authors analyze the case of passive attenuation the vibration export induced by the split Stirling linear cryocooler comprised of inline mounted single-piston compressor and expander. Placement of all the moving components onto a common axis results in a single axis consolidation of vibration export and enables use of single tuned dynamic absorber and low frequency vibration mount. From theoretical analysis and full-scale testing, the performance of such vibration protection arrangement is similar to known systems of active vibration cancellation.
Poiseuille flow-induced vibrations of two cylinders in tandem
Lin, Jianzhong; Jiang, Renjie; Chen, Zhongli; Ku, Xiaoke
2013-07-01
Laminar flows past two tandem cylinders which are free to move transversely in a parallel-wall channel were studied numerically by the lattice Boltzmann method. With fixed Reynolds number Re=100, blockage ratio β=1/4 and structural damping ξ=0, the effect of streamwise separation between two cylinders at a range of S/D=[1.1, 10] on the motions of cylinders and fluids was studied for both mass ratios of m(*)=1 and m(*)=0.1. A variety of distinct vibration regimes involving periodic, quasi-periodic and non-periodic vibrations with corresponding flow patterns were observed. A detailed analysis of the vibration amplitudes, vibration frequencies and relative equilibrium positions for both mass ratios demonstrated that as S/D increases, the interaction of the two cylinders first enhances and then reduces. In the strong coupling regime, both cylinders oscillate periodically around the centerline of the channel with large vibration amplitudes and high vibration frequencies. By comparing with the case of an isolated cylinder, a further study indicated that the gap flow plays an important role in such a dynamic system, and the vortex cores formation behind the front cylinder causes the interaction of the cylinders decouple rapidly. Based on the present observations, such a dynamic model system can be considered as a novel type of vortex-induced vibrations (VIV) and is expected to find applications in fluid mixing and heat transfer.
Energy Technology Data Exchange (ETDEWEB)
Hirata, A. [Kumamoto Industries Univ, Kumamoto (Japan); Yamamoto, M. [Asahi Chemical Industry Co. Ltd., Tokyo (Japan); Inaba, C. [Nishimatsu Construction Co. Ltd., Kanagawa (Japan); Kaneko, K. [Hokkaido Univ (Japan)
1997-08-01
For avoiding the generation of public hazard due to ground vibration causes by blasting in tunneling, it is important to devise a blasting method for ensuring the level of the ground vibration caused thereby under a limit, and an exact predication of ground vibration before blasting is desirable. In this study, the characteristics of the ground vibration caused by tunnel blasting are analyzed, and a summary of amplitude spectra calculating method is described. A theoretical analysis method for predicting the vibration level is proposed based on spectrum-multiplicative method. Vibration caused by multistage blasting in tunneling is most strong and deemed as important. When observing the process of elastic wave motion caused by multistage blasting being measured, the process can be divided into three element processes in frequency area as vibration source spectrum, transmission attenuation spectrum and frequency response function vibrating test, and, with the multiplication of them, the amplitude spectra at an observation portion can be estimated. 12 refs., 12 figs.
Pettersson, Linus; Håkansson, Lars; Claesson, Ingvar; Olsson, Sven
2001-01-01
In the turning operation chatter or vibration is a frequent problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lat...
Torsional Vibrations of a Cantilever with Lateral Friction in a Resonance Friction Microscope
Institute of Scientific and Technical Information of China (English)
CHEN Jian-Song; GE Yun; ZHANG Hui
2012-01-01
A model of fundamental torsional vibration of a cantilever with lateral friction is presented by using the harmonic balance method. The model demonstrates that the torsional vibration has close relations with the lateral friction threshold, the lateral contact stiffness and the torsional vibration amplitude of the cantilever. When the threshold is larger than a product of the stiffness and the vibration amplitude, the lateral friction is a linear force with the amplitude. If the lateral friction threshold is less than the product, the motions of the tip on the sample can be stick-slip or slip motions. The results are useful to optimize and to manipulate the fundamental flexural vibration of the piezo-cantilever, and give an insight into the tribological characterization of the interface in a resonance friction microscope.%A model of fundamental torsional vibration of a cantilever with lateral friction is presented by using the harmonic balance method.The model demonstrates that the torsional vibration has close relations with the lateral friction threshold,the lateral contact stiffness and the torsional vibration amplitude of the cantilever.When the threshold is larger than a product of the stiffness and the vibration amplitude,the lateral friction is a linear force with the amplitude.If the lateral friction threshold is less than the product,the motions of the tip on the sample can be stick-slip or slip motions.The results are useful to optimize and to manipulate the fundamental flexural vibration of the piezo-cantilever,and give an insight into the tribological characterization of the interface in a resonance friction microscope.
Elastic vibrations of spheroidal nanometric particles
Hernández-Rosas, Juan; Picquart, Michel; Haro-Poniatowski, Emmanuel; Kanehisa, Makoto; Jouanne, Michel; François Morhange, Jean
2003-11-01
Particles of nanometric size show low-frequency vibrational modes that can be observed by Raman spectroscopy. These modes involve the collective motion of large numbers of atoms and it is possible to calculate their frequency using elasticity theory. In this work a simple model for oblate-shaped nanoparticles is developed and compared with experimental results obtained in bismuth nanoparticles. It is found that the agreement between theory and experiment is improved in comparison to the spherical model usually employed. However for the smallest particles the elastic model is no longer valid and lattice discreteness has to be considered.
Elastic vibrations of spheroidal nanometric particles
Energy Technology Data Exchange (ETDEWEB)
Hernandez-Rosas, Juan [Departamento de FIsica, Universidad Autonoma Metropolitana Iztapalapa, Apartado Postal 55-534, Mexico, DF 09340 (Mexico); Picquart, Michel [Departamento de FIsica, Universidad Autonoma Metropolitana Iztapalapa, Apartado Postal 55-534, Mexico, DF 09340 (Mexico); Haro-Poniatowski, Emmanuel [Departamento de FIsica, Universidad Autonoma Metropolitana Iztapalapa, Apartado Postal 55-534, Mexico, DF 09340 (Mexico); Kanehisa, Makoto [Laboratoire de Physique des Milieux Desordonnes et Heterogenes, UMR CNRS 7603, Universite Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Jouanne, Michel [Laboratoire de Physique des Milieux Desordonnes et Heterogenes, UMR CNRS 7603, Universite Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Morhange, Jean Francois [Laboratoire de Physique des Milieux Desordonnes et Heterogenes, UMR CNRS 7603, Universite Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France)
2003-11-12
Particles of nanometric size show low-frequency vibrational modes that can be observed by Raman spectroscopy. These modes involve the collective motion of large numbers of atoms and it is possible to calculate their frequency using elasticity theory. In this work a simple model for oblate-shaped nanoparticles is developed and compared with experimental results obtained in bismuth nanoparticles. It is found that the agreement between theory and experiment is improved in comparison to the spherical model usually employed. However for the smallest particles the elastic model is no longer valid and lattice discreteness has to be considered.
Vibrational frequencies and structural determination of tetraazidogermane
Jensen, James O.
2003-10-01
The vibrational frequencies and corresponding normal mode assignments of tetraazidogermane are examined theoretically using the Gaussian98 set of quantum chemistry codes. All normal modes were successfully assigned to one of seven types of motion predicted by a group theoretical analysis (NNN asymmetric stretch, NNN symmetric stretch, GeN stretch, NNN bend, GeNN bend, NGeN bend, and NGeNN torsion) utilizing the S 4 symmetry of the molecule. The molecular orbitals of Ge(N 3) 4 are examined.
Vibrational frequencies and structure determination of silylgermane
Jensen, James O.
2003-11-01
The normal mode frequencies and corresponding vibrational assignments of silylgermane are examined theoretically using the GAUSSIAN 98 set of quantum chemistry codes. All normal modes were successfully assigned to one of seven types of motion predicted by a group theoretical analysis (SiH stretch, GeH stretch, SiGe stretch, HSiH bend, HGeH bend, SiH 3 wag/GeH 3 wag and SiGe torsion) utilizing the C3 v symmetry of the molecule. Predicted infrared and Raman intensities are presented. Molecular orbitals are presented and bonding is examined in terms of the molecular orbitals.
Ultrasonic Vibration Electrical Discharge Machining in Gas
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A new method of ultrasonic vibration electrical discharge machining(UEDM) in gas is proposed in this paper. In UEDM in gas, the gap between tool electrode and workpiece is small(about 0.01mm), and the voltage between them is higher than EDM in liquid, so short circuit is easy to take place. It is very important for improving the MRR to avoid short circuit. Therefore, some measures have been taken, a rotation and a planetary motion are superimposed upon the tool electrode. During UEDM in gas, workpiece is vi...
INTELLIGENT INTEGRATION CONTROL OF ROTATING DISK VIBRATION
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The rotating disk is a basic machine part that is u sed widely in industry. The motion equation is transformed into the dynamic equa tion in real modal space. The personating intelligent integration is introduced to improve the existing control method. These modes that affect the transverse v ibration mainly are included to simulate the vibration of rotating disk, and two methods are applied separately on condition that the sensor and the ac tuator are collocated and non-collocated. The results obtained by all-sided si mulations show that the new method can obtain better control effect, especially when the sensor and the actuator are non-collocated.
INTERACTION OF A FLOATING ELLIPTIC CYLINDER WITH A VIBRATING CIRCULAR CYLINDER
Institute of Scientific and Technical Information of China (English)
SUN Ren; CHWANG Allen T.
2006-01-01
The nonlinear hydrodynamic interaction between a floating elliptic cylinder and a vibrating circular cylinder immersed in an infinite fluid was investigated. By taking the added masses of the two-cylinder system into account, the dynamical equations of motion were formulated from the Lagrange equations of motion. The dynamical behaviors of these two cylinders were analyzed numerically for some typical situations, and the results show that the presence of a vibrating circular cylinder has a significant influence on the planar motion of a floating elliptic cylinder. The hydrodynamic interaction between them results in complicated nonlinear behaviors of the floating cylinder. It is found that oscillatory motion of the elliptic cylinder takes place in response to the vibrating mode of the circular one.
DEFF Research Database (Denmark)
Korreman, Stine Sofia
2012-01-01
This review considers the management of motion in photon radiation therapy. An overview is given of magnitudes and variability of motion of various structures and organs, and how the motion affects images by producing artifacts and blurring. Imaging of motion is described, including 4DCT and 4DPET...
Ambiguity in Tactile Apparent Motion Perception.
Directory of Open Access Journals (Sweden)
Emanuela Liaci
Full Text Available In von Schiller's Stroboscopic Alternative Motion (SAM stimulus two visually presented diagonal dot pairs, located on the corners of an imaginary rectangle, alternate with each other and induce either horizontal, vertical or, rarely, rotational motion percepts. SAM motion perception can be described by a psychometric function of the dot aspect ratio ("AR", i.e. the relation between vertical and horizontal dot distances. Further, with equal horizontal and vertical dot distances (AR = 1 perception is biased towards vertical motion. In a series of five experiments, we presented tactile SAM versions and studied the role of AR and of different reference frames for the perception of tactile apparent motion.We presented tactile SAM stimuli and varied the ARs, while participants reported the perceived motion directions. Pairs of vibration stimulators were attached to the participants' forearms and stimulator distances were varied within and between forearms. We compared straight and rotated forearm conditions with each other in order to disentangle the roles of exogenous and endogenous reference frames.Increasing the tactile SAM's AR biased perception towards vertical motion, but the effect was weak compared to the visual modality. We found no horizontal disambiguation, even for very small tactile ARs. A forearm rotation by 90° kept the vertical bias, even though it was now coupled with small ARs. A 45° rotation condition with crossed forearms, however, evoked a strong horizontal motion bias.Existing approaches to explain the visual SAM bias fail to explain the current tactile results. Particularly puzzling is the strong horizontal bias in the crossed-forearm conditions. In the case of tactile apparent motion, there seem to be no fixed priority rule for perceptual disambiguation. Rather the weighting of available evidence seems to depend on the degree of stimulus ambiguity, the current situation and on the perceptual strategy of the individual
Temperature-independent vibrational dynamics in an organic photovoltaic material.
Pensack, Ryan D; Banyas, Kyle M; Asbury, John B
2010-09-30
Ultrafast orientational motion and spectral diffusion of the carbonyl stretch vibration of the functionalized fullerene, PCBM, blended with the conjugated polymer, CN-MEH-PPV, are examined with two-dimensional infrared and polarization-resolved IR pump probe spectroscopy. In previous contributions from our group, the carbonyl stretch frequency of PCBM has been used as a local vibrational reporter to measure the temperature dependence of the time scale for dissociation of charge transfer excitons in CN-MEH-PPV:PCBM polymer blends. It was found that the rate of charge separation is independent of temperature, indicating that charge separation occurs through an activationless pathway. This assignment was supported by the observation at room temperature that thermal fluctuations do not give rise to spectral diffusion of the carbonyl stretch vibration on the picosecond and longer time scale. In this contribution, we examine the temperature dependence of the carbonyl vibrational dynamics to determine whether thermal fluctuations might give rise to spectral diffusion at other temperatures. We find that the time scale for fast wobbling-in-cone orientational motion is independent of temperature on the subpicosecond time scale. Similarly, spectral diffusion is not observed on the picosecond and longer time scale at all temperatures examined confirming our earlier interpretation of the frequency shift dynamics exclusively in terms of charge separation. Interestingly, the half angle characterizing the wobbling-in-cone orientational motion does increase at higher temperature due to increased free-volume resulting from thermal expansion of the polymer blend.
Local vibrational coherences drive the primary photochemistry of vision
Johnson, Philip J. M.; Halpin, Alexei; Morizumi, Takefumi; Prokhorenko, Valentyn I.; Ernst, Oliver P.; Miller, R. J. Dwayne
2015-12-01
The role of vibrational coherence—concerted vibrational motion on the excited-state potential energy surface—in the isomerization of retinal in the protein rhodopsin remains elusive, despite considerable experimental and theoretical efforts. We revisited this problem with resonant ultrafast heterodyne-detected transient-grating spectroscopy. The enhanced sensitivity that this technique provides allows us to probe directly the primary photochemical reaction of vision with sufficient temporal and spectral resolution to resolve all the relevant nuclear dynamics of the retinal chromophore during isomerization. We observed coherent photoproduct formation on a sub-50 fs timescale, and recovered a host of vibrational modes of the retinal chromophore that modulate the transient-grating signal during the isomerization reaction. Through Fourier filtering and subsequent time-domain analysis of the transient vibrational dynamics, the excited-state nuclear motions that drive the isomerization reaction were identified, and comprise stretching, torsional and out-of-plane wagging motions about the local C11=C12 isomerization coordinate.
Energy scavenging from environmental vibration.
Energy Technology Data Exchange (ETDEWEB)
Galchev, Tzeno (University of Michigan); Apblett, Christopher Alan; Najafi, Khalil (University of Michigan)
2009-10-01
The goal of this project is to develop an efficient energy scavenger for converting ambient low-frequency vibrations into electrical power. In order to achieve this a novel inertial micro power generator architecture has been developed that utilizes the bi-stable motion of a mechanical mass to convert a broad range of low-frequency (< 30Hz), and large-deflection (>250 {micro}m) ambient vibrations into high-frequency electrical output energy. The generator incorporates a bi-stable mechanical structure to initiate high-frequency mechanical oscillations in an electromagnetic scavenger. This frequency up-conversion technique enhances the electromechanical coupling and increases the generated power. This architecture is called the Parametric Frequency Increased Generator (PFIG). Three generations of the device have been fabricated. It was first demonstrated using a larger bench-top prototype that had a functional volume of 3.7cm3. It generated a peak power of 558{micro}W and an average power of 39.5{micro}W at an input acceleration of 1g applied at 10 Hz. The performance of this device has still not been matched by any other reported work. It yielded the best power density and efficiency for any scavenger operating from low-frequency (<10Hz) vibrations. A second-generation device was then fabricated. It generated a peak power of 288{micro}W and an average power of 5.8{micro}W from an input acceleration of 9.8m/s{sup 2} at 10Hz. The device operates over a frequency range of 20Hz. The internal volume of the generator is 2.1cm{sup 3} (3.7cm{sup 3} including casing), half of a standard AA battery. Lastly, a piezoelectric version of the PFIG is currently being developed. This device clearly demonstrates one of the key features of the PFIG architecture, namely that it is suitable for MEMS integration, more so than resonant generators, by incorporating a brittle bulk piezoelectric ceramic. This is the first micro-scale piezoelectric generator capable of <10Hz operation. The
An experimental analysis of a vibrating guitar string using high-speed photography
Whitfield, Scott B.; Flesch, Kurt B.
2014-02-01
We use high-speed photography (1200 frames/s) to investigate the vibrational motion of a plucked guitar string over several cycles. We investigate the vibrational pattern for plucking the string at two different locations along the string's length, and with different initial amplitudes. The vibrational patterns are then compared to a standing wave model of the string vibrations. We find excellent agreement between the observed vibrational patterns and the model for small-initial-amplitude displacement of the string. For larger amplitude displacements, the qualitative behavior of the string's vibrational pattern differs significantly from the small-amplitude displacement. This behavior may be due to the presence of inharmonicity, as suggested by its incorporation into the model calculations.
Suppression of wind-induced vibrations of a seesaw-type oscillator by means of a dynamic absorber
Lumbantobing, H.
2003-01-01
In this paper the suppression of wind-induced vibrations of a seesaw-type oscillator by means of a dynamic absorber is considered. With suppression the shift of the critical flow velocity to higher values as well as the reduction of vibration amplitudes is meant. The equations of motion are derived
Modeling of the Archery Bow and Arrow Vibrations
Directory of Open Access Journals (Sweden)
I. Zaniewski
2009-01-01
Full Text Available Vibration processes in the compound and open kinematical chain with an external link, as a model of an archery bow and arrow system, are evaluated. A mechanical and mathematical model of bend oscillations of the system during accelerate motion of the external link is proposed. Correlation between longitudinal acceleration and natural frequencies is obtained. There are recommendations regarding determination of virtual forms to study arrow vibrations and buckling. The models and methods have been adapted for realization into the engineering method using well-known mathematical software packages.
Pott, J.-U.
2011-09-01
MPIA is the PI institute of the MCAO-supported Fizeau imager LINC-NIRVANA at the LBT, and a partner of the E-ELT first light NIR imager MICADO (both SCAO and MCAO assisted). LINC-NIRVANA is a true pathfinder for future ELT-AO imagers both in terms of size and technology. I will present our vibration control strategies, involving accelerometer based real-time vibration measurements, feedforward and feedback optical path control, predictive filtering, vibration sensitive active control of actuators, and the development of a dynamical model of the entire telescope. Our experiences, made with LINC-NIRVANA, will be fed into the MICADO structural AO design to reach highest on-sky sensitivity.
Analysis of mechanical systems with transversal vibrations in transportation
Directory of Open Access Journals (Sweden)
A. Buchacz
2008-12-01
Full Text Available Purpose: of this article are modelling and dynamic analysis of mechanical systems during the rotationalmovement. Nowadays technical problems are tied with high speeds of mechanisms, high precision of work,using lower density materials, and many other high demands for elements of work. Objective of this paper wasthe analysis with giving into consideration the interaction between working motion and local vibrations. Themodel is loaded by transverse forces and transformed to the global reference frame.Design/methodology/approach: derived equations of motion were made by the Lagrange equations methodwith generalized coordinates and generalized velocities assumed as orthogonal projections of individualcoordinates and velocities of each beam to axes of the global reference frame.Findings: systems of equations of motion of transversally vibrating systems in two-dimensional motion willbe put to use to derivation of the dynamical flexibility of these systems and complex systems. Those equationsare the beginning of the analysis of complex systems. They can also be used to derivation of the substitutedynamical flexibility of n-linked systems.Research limitations/implications: mechanical systems vibrating transversally in terms of two-dimensionalmotion were considered in the thesis. The consecutive problem of dynamical analysis is modelling of systemsin spatial motion and also the analysis of systems loaded by longitudinal forces.Practical implications: mathematical effects of this article can be put to use into many mechanisms andmachines running in rotational transportation. For example applications are: high speed turbines, wind powerplants, rotors, manipulators and in aerodynamics issues, etc. Of course results should be adopted and modifiedto appropriate system.Originality/value: High demands for parameters of work of mechanisms and machines are the postulation fornew research and new ways of modelling and analyzing those type systems. The example way
Effect of vibration on forward split flexibility and pain perception in young male gymnasts.
Sands, William A; McNeal, Jeni R; Stone, Michael H; Haff, G Gregory; Kinser, Ann M
2008-12-01
Serious stretching in many sports involves discomfort and is often an early ceiling on improvements. To continue investigation of the use of vibration to enhance acute range of motion while assessing the influence of vibration and stretching on pressure-to-pain threshold perception. Ten young male gymnasts were assessed for split range of motion. One side split was randomly assigned as the experimental condition, and the other side split was assigned as the control. Both side splits were performed on a vibration device; the experimental condition had the device turned on and the control condition was performed with the device turned off. In addition, the athletes were assessed for pressure-to-pain transition using an algometer on the biceps femoris (stretched muscle) and vastus lateralis (nonstretched muscle) bilaterally. Pre-post difference scores between the vibrated split (most improved) and the nonvibrated split were statistically different (P=.001, 95% confidence interval of the difference 2.3 to 5.8 cm). Following the stretching protocol, the force values for the pressure-to-pain threshold comparing the vibrated and nonvibrated biceps femoris muscle were not statistically different. The nonstretched vastus lateralis muscle also showed no statistical difference in pressure-to-pain threshold between the vibration and nonvibration conditions. This study showed that vibration improved split range of motion over stretching alone, but did not show a difference in pressure-to-pain perception in either the stretched or nonstretched muscles.
Institute of Scientific and Technical Information of China (English)
彭利平; 刘初升; 宋宝成; 武继达; 王帅
2015-01-01
Demand for large vibrating screen is huge in the mineral processing industry. As bending and random vibration are not considered in a traditional design method for beam structures of a large vibrating screen, fatigue damage occurs frequently to affect the screening performance. This work aims to conduct a systematic mechanics analysis of the beam structures and improve the design method. Total motion of a beam structure in screening process can be decomposed into the traditional followed rigid translation (FRT), bending vibration (BV) and axial linear-distributed random rigid translation (ALRRT) excited by the side-plates. When treated as a generalized single-degree-of-freedom (SDOF) elastic system analytically, the BV can be solved by the Rayleigh’s method. Stochastic analysis for random process is conducted for the detailed ALRRT calculation. Expressions for the mechanics property, namely, the shearing force and bending-moment with respect to BV and ALRRT, are derived, respectively. Experimental and numerical investigations demonstrate that the largest BV exists at the beam center and can be nearly ignored in comparison with the FRT during a simplified engineering design. With the BV and FRT considered, the mechanics property accords well with the practical situation with the maximum error of 6.33%, which is less than that obtained by traditional method.
Kaliski, S
2013-01-01
This book gives a comprehensive overview of wave phenomena in different media with interacting mechanical, electromagnetic and other fields. Equations describing wave propagation in linear and non-linear elastic media are followed by equations of rheological models, models with internal rotational degrees of freedom and non-local interactions. Equations for coupled fields: thermal, elastic, electromagnetic, piezoelectric, and magneto-spin with adequate boundary conditions are also included. Together with its companion volume Vibrations and Waves. Part A: Vibrations this work provides a wealth
DEFF Research Database (Denmark)
Thomsen, Jon Juel
dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... phenomena and work with advanced tools such as perturbation analysis and bifurcation analysis. Explaining theory in terms of relevant examples from real systems, this book is user-friendly and meets the increasing interest in non-linear dynamics in mechanical/structural engineering and applied mathematics...
Vibrational spectroscopy of resveratrol
Billes, Ferenc; Mohammed-Ziegler, Ildikó; Mikosch, Hans; Tyihák, Ernő
2007-11-01
In this article the authors deal with the experimental and theoretical interpretation of the vibrational spectra of trans-resveratrol (3,5,4'-trihydroxy- trans-stilbene) of diverse beneficial biological activity. Infrared and Raman spectra of the compound were recorded; density functional calculations were carried out resulting in the optimized geometry and several properties of the molecule. Based on the calculated force constants, a normal coordinate analysis yielded the character of the vibrational modes and the assignment of the measured spectral bands.
Ying, Z. G.; Ni, Y. Q.; Ye, S. Q.
2014-02-01
Magneto-rheological visco-elastomer (MRVE) is used to construct sandwich plates for micro-vibration control. The micro-vibration response of a sandwich plate with an MRVE core under stochastic support motion excitation is studied to evaluate the vibration suppression capability. The dynamic behavior of MRVE in micro-vibration is characterized by a non-homogeneous complex modulus dependent on the vibration frequency and controllable by an applied magnetic field, in which the effect of the localized magnetic field distribution is considered. The partial differential equations for the coupled transverse and longitudinal motions of the sandwich plate are derived from the dynamic equilibrium, constitutive and geometric relations. A frequency-domain solution method for the stochastic micro-vibration response of sandwich plates is developed based on the Galerkin method and random vibration theory. The partial differential equations are first converted into ordinary differential equations according to the Galerkin method. Then the expressions for the frequency-response function, response power spectral density and root-mean-square velocity spectrum in terms of the one-third octave frequency band for micro-vibration are obtained. Finally, numerical results are given to illustrate the high response reduction capacity of the MRVE sandwich plate under stochastic support motion excitation, and the influence of the MRVE parameters and localized magnetic field placement on the micro-vibration response.
The coupled motions of bubbles in ultrasonic field
Institute of Scientific and Technical Information of China (English)
WANG Chenghui; LIN Shuyu
2012-01-01
The dynamic responses of bubbles in ultrasonic field include the radial vibration, translation, and their interactions. Based on the radial vibration modal where the secondary radiation of neighboring bubbles was considered, and interaction forces of bubbles, the coupled motions of two bubbles with different size in a plane ultrasonic field was simulated numerically. The results show that the radial vibration of a big bubble has natural properties and its translation velocity is rapid relatively. The behavior and distribution of bubbles was observed experimentally by using high speed photography. It is shown that the big bubbles translate rapidly in bubble clouds and vibrate radially with small-amplitude. On the other hand, the phenomena of attraction and coalescence among bubbles is observed, which may attribute to the effects of secondary radiation between neighboring bubbles.
Jitterbot: A Mobile Millirobot Using Vibration Actuation
Directory of Open Access Journals (Sweden)
John Burkhardt
2011-06-01
Full Text Available Microrobotics is a rapidly growing field with promising applications in microsurgery and microassembly. A challenge in these systems is providing power and control signals to the robot. This project explores crawling robots that are powered and controlled through a global mechanical vibration field. Structures within the robot will cause it to respond to particular frequencies with different motion modalities. A prototype, dubbed the “jitterbot”, was cut out of a 0.75 mm sheet of steel using electric discharge machining (EDM, and has a total footprint of approximately 30 mm × 20 mm in the xy-plane. The “robot” has a tripod body (8 mm × 16 mm with three small legs, and two suspended masses that are designed for specific resonance frequencies. The robot was tested on a plate that was vibrated vertically at frequencies ranging from 20 to 2,000 Hz. For particular resonant frequencies, the robot moves forward and turns in either a clockwise or counterclockwise direction. Finite element modeling confirms that the mechanism for motion is a rocking mode that is influenced by two arms that are suspended mass springs tuned to different frequencies. This lays the groundwork for further miniaturization.
Vibration analysis of bimodulus laminated cylindrical panels
Khan, K.; Patel, B. P.; Nath, Y.
2009-03-01
This paper deals with the flexural vibration behavior of bimodular laminated composite cylindrical panels with various boundary conditions. The formulation is based on first order shear deformation theory and Bert's constitutive model. The governing equations are derived using finite element method and Lagrange's equation of motion. An iterative eigenvalue approach is employed to obtain the positive and negative half cycle free vibration frequencies and corresponding mode shapes. A detailed parametric study is carried out to study the influences of thickness ratio, aspect ratio, lamination scheme, edge conditions and bimodularity ratio on the free vibration characteristics of bimodulus angle- and cross-ply composite laminated cylindrical panels. It is interesting to observe that there is a significant difference between the frequencies of positive and negative half cycles depending on the panel parameters. Through the thickness distribution of modal stresses for positive half cycle is significantly different from that for negative half cycle unlike unimodular case wherein the stresses at a particular location in negative half cycle would be of same magnitude but of opposite sign of those corresponding to positive half cycle. Finally, the effect of bimodularity on the steady state response versus forcing frequency relation is studied for a typical case.
Nonlinear frequency response analysis of structural vibrations
Weeger, Oliver; Wever, Utz; Simeon, Bernd
2014-12-01
In this paper we present a method for nonlinear frequency response analysis of mechanical vibrations of 3-dimensional solid structures. For computing nonlinear frequency response to periodic excitations, we employ the well-established harmonic balance method. A fundamental aspect for allowing a large-scale application of the method is model order reduction of the discretized equation of motion. Therefore we propose the utilization of a modal projection method enhanced with modal derivatives, providing second-order information. For an efficient spatial discretization of continuum mechanics nonlinear partial differential equations, including large deformations and hyperelastic material laws, we employ the concept of isogeometric analysis. Isogeometric finite element methods have already been shown to possess advantages over classical finite element discretizations in terms of higher accuracy of numerical approximations in the fields of linear vibration and static large deformation analysis. With several computational examples, we demonstrate the applicability and accuracy of the modal derivative reduction method for nonlinear static computations and vibration analysis. Thus, the presented method opens a promising perspective on application of nonlinear frequency analysis to large-scale industrial problems.
Resonance Photon Generation in a Vibrating Cavity
Dodonov, V V
1998-01-01
The problem of photon creation from vacuum due to the nonstationary Casimir effect in an ideal one-dimensional Fabry--Perot cavity with vibrating walls is solved in the resonance case, when the frequency of vibrations is close to the frequency of some unperturbed electromagnetic mode: $\\omega_w=p(\\pi c/L_0)(1+\\delta)$, $|\\delta|\\ll 1$, (p=1,2,...). An explicit analytical expression for the total energy in all the modes shows an exponential growth if $|\\delta|$ is less than the dimensionless amplitude of vibrations $\\epsilon\\ll 1$, the increment being proportional to $p\\sqrt{\\epsilon^2-\\delta^2}$. The rate of photon generation from vacuum in the (j+ps)th mode goes asymptotically to a constant value $cp^2\\sin^2(\\pi j/p)\\sqrt{\\epsilon^2-\\delta^2}/[\\pi L_0 (j+ps)]$, the numbers of photons in the modes with indices p,2p,3p,... being the integrals of motion. The total number of photons in all the modes is proportional to $p^3(\\epsilon^2-\\delta^2) t^2$ in the short-time and in the long-time limits. In the case of st...
Vibrations of tube arrays in transversal flow
Energy Technology Data Exchange (ETDEWEB)
Gibert, R.J.; Villard, B. (C.E.N. Saclay, Gif-sur-Yvette (France)); Chabrerie, J. (Ste Fives-Cail-Babcok, La Courneuve, (France)); Sagner, V. (Ste Bertin, Plaisir (France))
1981-01-01
The vibrations induced in tube arrays by a transversal flow are of great practical interest because of their destructive effects especially on heat exchangers. Though turbulence can significantly excite the tubes by itself, most intense vibrations are still caused by two fluid-elastic phenomena: - The << lock-in >> effect: The basic phenomenon consists of a generation and a synchronization of vortex shedding by a transversal tube motion when its frequency approaches the shedding frequency and when its level is large enough. The so modified vortex shedding generates much more intense vibrations. The lock-in effects is well known for a single cylinder. Less results have been obtained for bundles. - The whirling instability: In a tube row or a bundle, quasi-steady forces are generated by the displacements of the tubes in the flow field. Adjacent tubes are disymmetrically coupled by these forces and instability can appear beyond a critical flow velocity. For the tube rows H.J. Connors has shown that the phenomena are characterized by a coefficient c (which is a function of the pitch).
Dancing drops over vibrating substrates
Borcia, Rodica; Borcia, Ion Dan; Helbig, Markus; Meier, Martin; Egbers, Christoph; Bestehorn, Michael
2017-04-01
We study the motion of a liquid drop on a solid plate simultaneously submitted to horizontal and vertical harmonic vibrations. The investigation is done via a phase field model earlier developed for describing static and dynamic contact angles. The density field is nearly constant in every bulk region (ρ = 1 in the liquid phase, ρ ≈ 0 in the vapor phase) and varies continuously from one phase to the other with a rapid but smooth variation across the interfaces. Complicated explicit boundary conditions along the interface are avoided and captured implicitly by gradient terms of ρ in the hydrodynamic basic equations. The contact angle θ is controlled through the density at the solid substrate ρ S , a free parameter varying between 0 and 1 [R. Borcia, I.D. Borcia, M. Bestehorn, Phys. Rev. E 78, 066307 (2008)]. We emphasize the swaying and the spreading modes, earlier theoretically identified by Benilov and Billingham via a shallow-water model for drops climbing uphill along an inclined plane oscillating vertically [E.S. Benilov, J. Billingham, J. Fluid Mech. 674, 93 (2011)]. The numerical phase field simulations will be completed by experiments. Some ways to prevent the release of the dancing drops along a hydrophobic surface into the gas atmosphere are also discussed in this paper.
Vibration Propagation in Spider Webs
Hatton, Ross; Otto, Andrew; Elias, Damian
Due to their poor eyesight, spiders rely on web vibrations for situational awareness. Web-borne vibrations are used to determine the location of prey, predators, and potential mates. The influence of web geometry and composition on web vibrations is important for understanding spider's behavior and ecology. Past studies on web vibrations have experimentally measured the frequency response of web geometries by removing threads from existing webs. The full influence of web structure and tension distribution on vibration transmission; however, has not been addressed in prior work. We have constructed physical artificial webs and computer models to better understand the effect of web structure on vibration transmission. These models provide insight into the propagation of vibrations through the webs, the frequency response of the bare web, and the influence of the spider's mass and stiffness on the vibration transmission patterns. Funded by NSF-1504428.
Vibration mechanism of fuel rod in axial flow
Energy Technology Data Exchange (ETDEWEB)
Kang, Heung Seok; Yoon, Kyung Ho; Kim, Hyung Kyu; Song, Kee Nam
1998-08-01
This is a review on the previous researches for the vibration of fuel rod induced by axial flow. The analysis methods are classified into three categories accordingly as the researchers postulate the vibration to be self-excited, forced and parametric; the self-excited mechanism by Burgreen and Quinn, the forced one by Reavis, Gorman, kanazawa, and S. Chen, and the parametric one by Y. Chen. Quinn supposed that the centrifugal force by flow exaggerated the natural bow in the cylinder, and the flexural force by it diminished the bow by turns; this interactive motion leaded cylinder to vibration. The supporters to the forced mechanism considered the forces arising from pressure perturbation within the boundary layers as vibrating sources. Y. Chen insisted that the cylinder could only be excited to vibration in resonance by the small oscillation of mean flow velocity. The previous studies were based on the simple boundary conditions such as hinged-hinged or fixed-fixed single span. Therefore, for the moreaccurate prediction of the fuel rod vibration in reactor, the further studies need to reflect the actual boundary conditions of the fuel rod like axial force and continuous supports by grids. (author). 25 refs.
Motional Quantum State Engineering Via a Single Laser-ion Interaction
Institute of Scientific and Technical Information of China (English)
ZHENG Shibiao
2001-01-01
We propose a scheme to prepare superpositions of several Fock states for the one-dimensional motion of a trapped ion. In the scheme the ion is simultaneously excited by N+1 laser beams, with the nth laser tuned to the nth upper vibrational sideband. After a short interaction time, a measurement of the internal state may project the vibrational motion onto a superposition of the first N+1 Fock states. The scheme can be easily generalized to synthesize entangled states for the two-dimensional ion motion.
Controlling the motion of multiple objects on a Chladni plate
Zhou, Quan; Sariola, Veikko; Latifi, Kourosh; Liimatainen, Ville
2016-09-01
The origin of the idea of moving objects by acoustic vibration can be traced back to 1787, when Ernst Chladni reported the first detailed studies on the aggregation of sand onto nodal lines of a vibrating plate. Since then and to this date, the prevailing view has been that the particle motion out of nodal lines is random, implying uncontrollability. But how random really is the out-of-nodal-lines motion on a Chladni plate? Here we show that the motion is sufficiently regular to be statistically modelled, predicted and controlled. By playing carefully selected musical notes, we can control the position of multiple objects simultaneously and independently using a single acoustic actuator. Our method allows independent trajectory following, pattern transformation and sorting of multiple miniature objects in a wide range of materials, including electronic components, water droplets loaded on solid carriers, plant seeds, candy balls and metal parts.
Wear of connector contacts exposed to relative motion
Wilk, R. A.
Connectors play a significant role in the performance, cost, and reliability of electronic equipment. In connection with the development of the system interconnection design, a factor which is often overlooked is related to the importance of connector selection and mounting to minimize relative motion between contacts during vibration encountered in handling, transportation, and service. This motion can lead to the loss of protective coatings (gold and nickel) due to frictional wear. If this happens, fretting corrosion of the base metals may occur. The produced damage can adversely affect performance due to increased joint resistance, eventually causing intermittent contacts. The present investigation is concerned with the study of different style contacts (tuning fork, box, and circular) to determine their endurance and wear characteristics when exposed to relative motion created by vibration. All contacts investigated were fabricated from brass, beryllium copper, or phosphor bronze, and had .00127 mm minimum gold plating over .00127 mm minimum nickel plating.
Vibration measurements of high-heat-load monochromators for DESY PETRA III extension
Energy Technology Data Exchange (ETDEWEB)
Kristiansen, Paw, E-mail: paw.kristiansen@fmb-oxford.com [FMB Oxford Ltd, Unit 1 Ferry Mills, Oxford OX2 0ES (United Kingdom); Horbach, Jan; Döhrmann, Ralph; Heuer, Joachim [DESY, Deutsches Elektronen-Synchrotron Hamburg, Notkestrasse 85, 22607 Hamburg (Germany)
2015-05-09
Vibration measurements of a cryocooled double-crystal monochromator are presented. The origins of the vibrations are identified. The minimum achieved vibration of the relative pitch between the two crystals is 48 nrad RMS and the minimum achieved absolute vibration of the second crystal is 82 nrad RMS. The requirement for vibrational stability of beamline optics continues to evolve rapidly to comply with the demands created by the improved brilliance of the third-generation low-emittance storage rings around the world. The challenge is to quantify the performance of the instrument before it is installed at the beamline. In this article, measurement techniques are presented that directly and accurately measure (i) the relative vibration between the two crystals of a double-crystal monochromator (DCM) and (ii) the absolute vibration of the second-crystal cage of a DCM. Excluding a synchrotron beam, the measurements are conducted under in situ conditions, connected to a liquid-nitrogen cryocooler. The investigated DCM utilizes a direct-drive (no gearing) goniometer for the Bragg rotation. The main causes of the DCM vibration are found to be the servoing of the direct-drive goniometer and the flexibility in the crystal cage motion stages. It is found that the investigated DCM can offer relative pitch vibration down to 48 nrad RMS (capacitive sensors, 0–5 kHz bandwidth) and absolute pitch vibration down to 82 nrad RMS (laser interferometer, 0–50 kHz bandwidth), with the Bragg axis brake engaged.
Active low-frequency vertical vibration isolation system for precision measurements
Wu, Kang; Li, Gang; Hu, Hua; Wang, Lijun
2017-01-01
Low-frequency vertical vibration isolation systems play important roles in precision measurements to reduce seismic and environmental vibration noise. Several types of active vibration isolation systems have been developed. However, few researches focus on how to optimize the test mass install position in order to improve the vibration transmissibility. An active low-frequency vertical vibration isolation system based on an earlier instrument, the Super Spring, is designed and implemented. The system, which is simple and compact, consists of two stages: a parallelogram-shaped linkage to ensure vertical motion, and a simple spring-mass system. The theoretical analysis of the vibration isolation system is presented, including terms erroneously ignored before. By carefully choosing the mechanical parameters according to the above analysis and using feedback control, the resonance frequency of the system is reduced from 2.3 to 0.03 Hz, a reduction by a factor of more than 75. The vibration isolation system is installed as an inertial reference in an absolute gravimeter, where it improved the scatter of the absolute gravity values by a factor of 5. The experimental results verifies the improved performance of the isolation system, making it particularly suitable for precision experiments. The improved vertical vibration isolation system can be used as a prototype for designing high-performance active vertical isolation systems. An improved theoretical model of this active vibration isolation system with beam-pivot configuration is proposed, providing fundamental guidelines for vibration isolator design and assembling.
Vibration characteristics of ultrasonic complex vibration for hole machining
Asami, Takuya; Miura, Hikaru
2012-05-01
Complex vibration sources that use diagonal slits as a longitudinal-torsional vibration converter have been applied to ultrasonic motors, ultrasonic rock drilling, and ultrasonic welding. However, there are few examples of the application of these sources to ultrasonic machining in combination with an abrasive. Accordingly, a new method has been developed for machining of holes in brittle materials by using the ultrasonic longitudinal and torsional vibration of a hollow-type stepped horn with a diagonal slit vibration converter. In this paper, we compared vibration of a uniform rod and a hollow-type stepped horn, both with diagonal slits, when the conditions of the diagonal slits are constant.
Vibration Sensitive Keystroke Analysis
Lopatka, M.; Peetz, M.-H.; van Erp, M.; Stehouwer, H.; van Zaanen, M.
2009-01-01
We present a novel method for performing non-invasive biometric analysis on habitual keystroke patterns using a vibration-based feature space. With the increasing availability of 3-D accelerometer chips in laptop computers, conventional methods using time vectors may be augmented using a distinct fe
Development of vibrating insoles
Hijmans, J.M.; Geertzen, J.H.B.; Schokker, B.; Postema, K.
2007-01-01
The objective of this study was to describe the development of vibrating insoles. Insoles, providing a subsensory mechanical noise signal to the plantar side of the feet, may improve balance in healthy young and older people and in patients with stroke or diabetic neuropathy. This study describes th
... ENTCareers Marketplace Find an ENT Doctor Near You Dizziness and Motion Sickness Dizziness and Motion Sickness Patient ... vision or speech, or hearing loss. What is dizziness? Dizziness can be described in many ways, such ...
The effects of vibration-reducing gloves on finger vibration.
Welcome, Daniel E; Dong, Ren G; Xu, Xueyan S; Warren, Christopher; McDowell, Thomas W
2014-01-01
Vibration-reducing (VR) gloves have been used to reduce the hand-transmitted vibration exposures from machines and powered hand tools but their effectiveness remains unclear, especially for finger protection. The objectives of this study are to determine whether VR gloves can attenuate the vibration transmitted to the fingers and to enhance the understanding of the mechanisms of how these gloves work. Seven adult male subjects participated in the experiment. The fixed factors evaluated include hand force (four levels), glove condition (gel-filled, air bladder, no gloves), and location of the finger vibration measurement. A 3-D laser vibrometer was used to measure the vibrations on the fingers with and without wearing a glove on a 3-D hand-arm vibration test system. This study finds that the effect of VR gloves on the finger vibration depends on not only the gloves but also their influence on the distribution of the finger contact stiffness and the grip effort. As a result, the gloves increase the vibration in the fingertip area but marginally reduce the vibration in the proximal area at some frequencies below 100 Hz. On average, the gloves reduce the vibration of the entire fingers by less than 3% at frequencies below 80 Hz but increase at frequencies from 80 to 400 Hz. At higher frequencies, the gel-filled glove is more effective at reducing the finger vibration than the air bladder-filled glove. The implications of these findings are discussed.
Active vibration control of structures undergoing bending vibrations
Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor)
1995-01-01
An active vibration control subassembly for a structure (such as a jet engine duct or a washing machine panel) undergoing bending vibrations caused by a source (such as the clothes agitator of the washing machine) independent of the subassembly. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the structure such that vibrations in the plate induced by the AC signal cause canceling bending vibrations in the structure and such that the plate is compressively pre-stressed along the structure when the structure is free of any bending vibrations. The compressive prestressing increases the amplitude of the canceling bending vibrations before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction.
Damonte, Kathleen
2004-01-01
One thing scientists study is how objects move. A famous scientist named Sir Isaac Newton (1642-1727) spent a lot of time observing objects in motion and came up with three laws that describe how things move. This explanation only deals with the first of his three laws of motion. Newton's First Law of Motion says that moving objects will continue…
Vibrating Wingstroke Mechanism Project
National Aeronautics and Space Administration — This proposed work will develop a new method and mechanism for generating wing stroke motion of any shape and orientation. The mechanism will provide power, lift and...
Frame junction vibration transmission with a modified frame deformation model.
Moore, J A
1990-12-01
A previous paper dealt with vibration transmission through junctions of connected frame members where the allowed frame deformations included bending, torsion, and longitudinal motions [J.A. Moore, J. Acoust. Soc. Am. 88, 2766-2776 (1990)]. In helicopter and aircraft structures the skin panels can constitute a high impedance connection along the length of the frames that effectively prohibits in-plane motion at the elevation of the skin panels. This has the effect of coupling in-plane bending and torsional motions within the frame. This paper discusses the transmission behavior through frame junctions that accounts for the in-plane constraint in idealized form by assuming that the attached skin panels completely prohibit inplane motion in the frames. Also, transverse shear deformation is accounted for in describing the relatively deep web frame constructions common in aircraft structures. Longitudinal motion in the frames is not included in the model. Transmission coefficient predictions again show the importance of out-of-plane bending deformation to the transmission of vibratory energy in an aircraft structure. Comparisons are shown with measured vibration transmission data along the framing in the overhead of a helicopter airframe, with good agreement. The frame junction description has been implemented within a general purpose statistical energy analysis (SEA) computer code in modeling the entire airframe structure including skin panels.
Effectiveness of using wearable vibration therapy to alleviate muscle soreness.
Cochrane, Darryl J
2017-03-01
To examine the acute and short-term effect of a wearable vibration device following strenuous eccentric exercise of the elbow flexors. Physically active males (n = 13) performed vibration therapy (VT) and control following eccentric exercise. The arms were randomised and counterbalanced, separated by 14 days. 15 min of VT (120 Hz) was applied immediately and 24, 48, and 72 h after eccentric exercise while the contralateral arm performed no VT (control). Muscle (isometric and concentric) strength, range of motion, electromyography (EMG), muscle soreness and creatine kinase were taken pre-exercise, immediately and 24, 48, and 72 h post-eccentric exercise. Additionally, the acute effect of VT of muscle strength, range of motion, EMG, muscle soreness was also investigated immediately after VT. In the short-term VT was able to significantly reduce the level of biceps brachii pain at 24 h (p motion at 24 h (p control. Acutely, following VT treatment muscle pain and range of motion significantly improved (p motion; however, there was no improvement of muscle strength recovery compared to control following eccentric exercise of the elbow flexors.
Primarily nonlinear effects observed in a driven asymmetrical vibrating wire
Hanson, Roger J.; Macomber, H. Kent; Morrison, Andrew C.; Boucher, Matthew A.
2005-01-01
The purpose of the work reported here is to further experimentally explore the wide variety of behaviors exhibited by driven vibrating wires, primarily in the nonlinear regime. When the wire is driven near a resonant frequency, it is found that most such behaviors are significantly affected by the splitting of the resonant frequency and by the existence of a ``characteristic'' axis associated with each split frequency. It is shown that frequency splitting decreases with increasing wire tension and can be altered by twisting. Two methods are described for determining the orientation of characteristic axes. Evidence is provided, with a possible explanation, that each axis has the same orientation everywhere along the wire. Frequency response data exhibiting nonlinear generation of transverse motion perpendicular to the driving direction, hysteresis, linear generation of perpendicular motion (sometimes tubular), and generation of motion at harmonics of the driving frequency are exhibited and discussed. Also reported under seemingly unchanging conditions are abrupt large changes in the harmonic content of the motion that sometimes involve large subharmonics and harmonics thereof. Slow transitions from one stable state of vibration to another and quasiperiodic motions are also exhibited. Possible musical significance is discussed. .
DEFF Research Database (Denmark)
Zhang, Zili; Nielsen, Søren R. K.; Basu, Biswajit
2015-01-01
Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g. This facilit......Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g...... studied in the numerical simulation. It is shown that the one-mode model is able to predict the sloshing force and the damped structural response accurately, since the primary damping effect on the structure is achieved by the first sloshing mode of the fluid. Although it is unable to predict the fluid...
Sang, Hongqiang; Yang, Chenghao; Liu, Fen; Yun, Jintian; Jin, Guoguang
2016-12-01
It is very important for robotically assisted minimally invasive surgery to achieve a high-precision and smooth motion control. However, the surgical instrument tip will exhibit vibration caused by nonlinear friction and unmodeled dynamics, especially when the surgical robot system is attempting low-speed, fine motion. A fuzzy neural network sliding mode controller (FNNSMC) is proposed to suppress vibration of the surgical robotic system. Nonlinear friction and modeling uncertainties are compensated by a Stribeck model, a radial basis function (RBF) neural network and a fuzzy system, respectively. Simulations and experiments were performed on a 3 degree-of-freedom (DOF) minimally invasive surgical robot. The results demonstrate that the FNNSMC is effective and can suppress vibrations at the surgical instrument tip. The proposed FNNSMC can provide a robust performance and suppress the vibrations at the surgical instrument tip, which can enhance the quality and security of surgical procedures. Copyright © 2016 John Wiley & Sons, Ltd.
Institute of Scientific and Technical Information of China (English)
Yuefang Wang; Lihua Huang; Xuetao Liu; Keren Wang
2005-01-01
The Hamiltonian dynamics is adopted to solve the eigenvalue problem for transverse vibrations of axially moving strings. With the explicit Hamiltonian function the canonical equation of the free vibration is derived. Non-singular modal functions are obtained through a linear, symplectic eigenvalue analysis, and the symplectic-type orthogonality conditions of modes are derived. Stability of the transverse motion is examined by means of analyzing the eigenvalues and their bifurcation, especially for strings transporting with the critical speed. It is pointed out that the motion of the string does not possess divergence instability at the critical speed due to the weak interaction between eigenvalue pairs. The expansion theorem is applied with the non-singular modal functions to solve the displacement response to free and forced vibrations. It is demonstrated that the modal functions can be used as the base functions for solving linear and nonlinear vibration problems.
Lateral vibration effects in atomic-scale friction
Energy Technology Data Exchange (ETDEWEB)
Roth, R. [Climate and Environment Physics, Physics Institute, University of Bern, Bern (Switzerland); Oeschger Centre for Climate Change Research, University of Bern, Bern (Switzerland); Fajardo, O. Y.; Mazo, J. J. [Departamento de Física de la Materia Condensada and Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Meyer, E. [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Gnecco, E. [Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, 28049 Madrid (Spain)
2014-02-24
The influence of lateral vibrations on the stick-slip motion of a nanotip elastically pulled on a flat crystal surface is studied by atomic force microscopy measurements on a NaCl(001) surface in ultra-high vacuum. The slippage of the nanotip across the crystal lattice is anticipated at increasing driving amplitude, similarly to what is observed in presence of normal vibrations. This lowers the average friction force, as explained by the Prandtl-Tomlinson model with lateral vibrations superimposed at finite temperature. Nevertheless, the peak values of the lateral force, and the total energy losses, are expected to increase with the excitation amplitude, which may limit the practical relevance of this effect.
Robust structural design against self-excited vibrations
Spelsberg-Korspeter, Gottfried
2013-01-01
This book studies methods for a robust design of rotors against self-excited vibrations. The occurrence of self-excited vibrations in engineering applications if often unwanted and in many cases difficult to model. Thinking of complex systems such as machines with many components and mechanical contacts, it is important to have guidelines for design so that the functionality is robust against small imperfections. This book discusses the question on how to design a structure such that unwanted self-excited vibrations do not occur. It shows theoretically and practically that the old design rule to avoid multiple eigenvalues points toward the right direction and have optimized structures accordingly. This extends results for the well-known flutter problem in which equations of motion with constant coefficients occur to the case of a linear conservative system with arbitrary time periodic perturbations.
The Seventh International Conference on Vibration Problems ICOVP 2005
İnan, Esin; ICOVP-2005
2007-01-01
This volume presents the Proceedings of the Seventh International Conference on Vibration Problems, held in Istanbul, Turkey, 05-09 September 2005. As with the earlier conferences in the ICOVP series, the purpose of ICOVP-2005 was to bring together scientists with different backgrounds, actively working on vibration-related problems of engineering both in theoretical and applied fields. The main objective did not lie, however, in reporting specific results as such, but rather in joining/exchanging different languages, questions and methods developed in the respective disciplines, and to thus stimulate a broad interdisciplinary research. The topics, indeed, vary from the effect of ground motion on the stochastic response of suspension bridges to coupling effects between different vibrations in rotor-blade systems. All lectures delivered at the Conference are recorded in their full text. Audience: Scientists, researchers and graduate students in physics and engineering
Evolution of photoelectron-vibrational coupling with molecular complexity
Energy Technology Data Exchange (ETDEWEB)
Poliakoff, E D [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Lucchese, R R [Department of Chemistry, Texas A and M University, College Station, TX 77843 (United States)
2006-11-15
We review how electronic and vibrational degrees of freedom become coupled in molecular photoionization, and describe effects that emerge as the molecular complexity increases. Molecular photoionization is frequently influenced by the temporary trapping of the continuum electron in the field of the target molecules, which is referred to as a shape resonance, as it depends on the shape of the potential experienced by the exiting photoelectron. Such resonances couple electronic and vibrational motion, and the nature of the coupling can vary widely for polyatomic molecules. We show how vibrationally resolved photoelectron spectra acquired as a function of energy can be used to elucidate such coupling. The experiments are analysed using physically realistic and computationally tractable Schwinger variational theory, and the systems studied to date can be well understood using an independent-particle, adiabatic nuclei framework. As a result, simple and intuitive pictures emerge, even when dealing with scattering phenomena involving complex molecular targets and potentials.
Grey forecasting model for active vibration control systems
Lihua, Zou; Suliang, Dai; Butterworth, John; Ma, Xing; Dong, Bo; Liu, Aiping
2009-05-01
Based on the grey theory, a GM(1,1) forecasting model and an optimal GM(1,1) forecasting model are developed and assessed for use in active vibration control systems for earthquake response mitigation. After deriving equations for forecasting the control state vector, design procedures for an optimal active control method are proposed. Features of the resulting vibration control and the influence on it of time-delay based on different sampling intervals of seismic ground motion are analysed. The numerical results show that the forecasting models based on the grey theory are reliable and practical in structural vibration control fields. Compared with the grey forecasting model, the optimal forecasting model is more efficient in reducing the influences of time-delay and disturbance errors.
NON-LINEAR FORCED VIBRATION OF AXIALLY MOVING VISCOELASTIC BEAMS
Institute of Scientific and Technical Information of China (English)
Yang Xiaodong; Chen Li-Qun
2006-01-01
The non-linear forced vibration of axially moving viscoelastic beams excited by the vibration of the supporting foundation is investigated. A non-linear partial-differential equation governing the transverse motion is derived from the dynamical, constitutive equations and geometrical relations. By referring to the quasi-static stretch assumption, the partial-differential non-linearity is reduced to an integro-partial-differential one. The method of multiple scales is directly applied to the governing equations with the two types of non-linearity, respectively. The amplitude of near- and exact-resonant steady state is analyzed by use of the solvability condition of eliminating secular terms. Numerical results are presented to show the contributions of foundation vibration amplitude, viscoelastic damping, and nonlinearity to the response amplitude for the first and the second mode.
Forced vibration of a shear thickening fluid sandwich beam
Wei, Minghai; Hu, Gang; Jin, Lu; Lin, Kun; Zou, Dujian
2016-05-01
The forced vibration of a sandwich beam integrating a shear thickening fluid (STF) core and with conductive skins subjected to a periodic excitation was investigated theoretically in this study. The rheological properties of the STF material including viscosity, plasticity, and elasticity may be changed under the periodic vibration, and hence they were considered. The governing equation of motion was derived based on the complex stiffness method and some key parameters were derived based on the Timoshenko beam theory. Effects of the excitation frequency, the excitation amplitude, the excitation location, and the skin/core thickness ratio on the nature frequency of the sandwich beam were investigated. It was found that the STF core has a significant effect on the dynamic property of the sandwich beam. Based on the findings, integrating the STF core in a sandwich beam can reduce the vibration of the beam.
Development and evaluation of a generic active helicopter vibration controller
Davis, M. W.
1984-01-01
A computerized generic active controller is developed, which alleviates helicopter vibration by closed-loop implementation of higher harmonic control (HHC). In the system, the higher harmonic blade pitch is input through a standard helicopter swashplate; for a four-blade helicopter rotor the 4/rev vibration in the rotorcraft is minimized by inducing cyclic pitch motions at 3, 4, and 5/rev in the rotating system. The controller employs the deterministic, cautious, and dual control approaches and two linear system models (local and global), as well as several methods of limiting control. Based on model testing, performed at moderate to high values of forward velocity and rotor thrust, reductions in the rotor test apparatus vibration from 75 to 95 percent are predicted, with HHC pitch amplitudes of less than one degree. Good performance is also noted for short-duration maneuvers.
Smoothing Motion Estimates for Radar Motion Compensation.
Energy Technology Data Exchange (ETDEWEB)
Doerry, Armin W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-07-01
Simple motion models for complex motion environments are often not adequate for keeping radar data coherent. Eve n perfect motion samples appli ed to imperfect models may lead to interim calculations e xhibiting errors that lead to degraded processing results. Herein we discuss a specific i ssue involving calculating motion for groups of pulses, with measurements only available at pulse-group boundaries. - 4 - Acknowledgements This report was funded by General A tomics Aeronautical Systems, Inc. (GA-ASI) Mission Systems under Cooperative Re search and Development Agre ement (CRADA) SC08/01749 between Sandia National Laboratories and GA-ASI. General Atomics Aeronautical Systems, Inc. (GA-ASI), an affilia te of privately-held General Atomics, is a leading manufacturer of Remotely Piloted Aircraft (RPA) systems, radars, and electro-optic and rel ated mission systems, includin g the Predator(r)/Gray Eagle(r)-series and Lynx(r) Multi-mode Radar.
Rolling Shutter Motion Deblurring
Su, Shuochen
2015-06-07
Although motion blur and rolling shutter deformations are closely coupled artifacts in images taken with CMOS image sensors, the two phenomena have so far mostly been treated separately, with deblurring algorithms being unable to handle rolling shutter wobble, and rolling shutter algorithms being incapable of dealing with motion blur. We propose an approach that delivers sharp and undis torted output given a single rolling shutter motion blurred image. The key to achieving this is a global modeling of the camera motion trajectory, which enables each scanline of the image to be deblurred with the corresponding motion segment. We show the results of the proposed framework through experiments on synthetic and real data.
Improved Active Vibration Isolation Systems
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The control force, feedback gain, and actuator stroke of several active vibration isolation systems were analyzed based on a single-layer active vibration isolation system. The analysis shows that the feedback gain and actuator stroke cannot be selected independently and the active isolation system design must make a compromise between the feedback gain and actuator stroke. The performance of active isolation systems can be improved by the joint vibration reduction using an active vibration isolation system with an adaptive dynamic vibration absorber. The results show that the joint vibration reduction method can successfully avoid the compromise between the feedback gain and actuator stroke. The control force and the object vibration amplitude are also greatly reduced.
Animal Communications Through Seismic Vibrations
Energy Technology Data Exchange (ETDEWEB)
Hill, Peggy (University of Tulsa)
2001-05-02
Substrate vibration has been important to animals as a channel of communication for millions of years, but our literature on vibration in this context of biologically relevant information is only decades old. The jaw mechanism of the earliest land vertebrates allowed them to perceive substrate vibrations as their heads lay on the ground long before airborne sounds could be heard. Although the exact mechanism of vibration production and the precise nature of the wave produced are not always understood, recent development of affordable instrumentation to detect and measure vibrations has allowed researchers to answer increasingly sophisticated questions about how animals send and receive vibration signals. We now know that vibration provides information used in predator defense, prey detection, recruitment to food, mate choice, intrasexual competition, and maternal/brood social interactions in a variety of insect orders, spiders, crabs, scorpions, chameleons, frogs, golden moles, mole rats, kangaroos rats, wallabies, elephants and bison.
Variational approach to anharmonic collective motion
Bertsch, George F
1996-01-01
We derive large-amplitude collective equations of motion from the variational principle for the time-dependent Schroedinger equation. These equations reduce to the well-known diabatic formulas for vibrational frequencies in the small amplitude limit. The finite amplitude expression allows departures from harmonic behavior of giant resonances to be simply estimated. The relative shift of the second phonon falls with nuclear mass A as A^(-4/3) in the three modes we consider: monopole, dipole, and quadrupole. Numerically the effect is very small in heavy nuclei, as was found with other approaches.
MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations
Directory of Open Access Journals (Sweden)
Felix Weber
2016-12-01
Full Text Available This paper describes a semi-active vibration absorber (SVA concept based on a real-time controlled magnetorheological damper (MR-SVA for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD. Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.
Simulation of the screening process on a circularly vibrating screen using 3D-DEM
Institute of Scientific and Technical Information of China (English)
Zhao Lala; Zhao Yuemin; Liu Chusheng; Li Jun; Dong Hailin
2011-01-01
A numerical study of the motion particulates follow along a circularly vibrating screen deck was done using the three dimensional Discrete Element Method (DEM).The motion of the particles was analyzed.The effects of vibration amplitude,throwing index,and screen deck inclination angle on the screening process are discussed.The results show that the average velocity of the particles increases along the longitudinal direction of the deck.The screening efficiency is highest when the vibration amplitude,throwing index,and screen deck inclination angle are 3-3.5 mm,2.7 and 15°,respectively.This work is helpful for developing a deep understanding of particle motion and for optimizing screen separator designs.
Design and verification of a novel hollow vibrating module for laser machining.
Wang, Zhaozhao; Jang, Seungbong; Kim, EunHee; Jeon, Yongho; Lee, Soo-Hun; Lee, Moon G
2015-04-01
If a vibration module is added on laser machining system, the quality of surface finish and aspect ratio on metals can be significantly enhanced. In this study, a single mobility model of vibrating laser along the path of laser beam was put forward. In order to realize the desired unidirectional motion, a resonance type vibration module with optical lens was designed and manufactured. This cylindrical module was composed of curved-beam flexure elements. The cylindrical coordinate system was established to describe the relationship of a curved-beam flexure element's motion and deformation. In addition, the stiffness matrix of the curved-beam element was obtained. Finite element method and dynamical modeling were provided to analyze the resonance frequency and the displacement of the motion. The feasibility of the design was demonstrated with the help of experiments on frequency response. Experimental results show good agreement with theoretical analysis and simulation predictions.
Shen, Shixin (Cindy); House, Ronald A.
2017-01-01
Résumé Objectif Permettre aux médecins de famille de comprendre l’épidémiologie, la pathogenèse, les symptômes, le diagnostic et la prise en charge de la maladie des vibrations, une maladie professionnelle importante et courante au Canada. Sources d’information Une recherche a été effectuée sur MEDLINE afin de relever les recherches et comptes rendus portant sur la maladie des vibrations. Une recherche a été effectuée sur Google dans le but d’obtenir la littérature grise qui convient au contexte canadien. D’autres références ont été tirées des articles relevés. Message principal La maladie des vibrations est une maladie professionnelle répandue touchant les travailleurs de diverses industries qui utilisent des outils vibrants. La maladie est cependant sous-diagnostiquée au Canada. Elle compte 3 éléments : vasculaire, sous la forme d’un phénomène de Raynaud secondaire; neurosensoriel; et musculosquelettique. Aux stades les plus avancés, la maladie des vibrations entraîne une invalidité importante et une piètre qualité de vie. Son diagnostic exige une anamnèse minutieuse, en particulier des antécédents professionnels, un examen physique, des analyses de laboratoire afin d’éliminer les autres diagnostics, et la recommandation en médecine du travail aux fins d’investigations plus poussées. La prise en charge consiste à réduire l’exposition aux vibrations, éviter les températures froides, abandonner le tabac et administrer des médicaments. Conclusion Pour assurer un diagnostic rapide de la maladie des vibrations et améliorer le pronostic et la qualité de vie, les médecins de famille devraient connaître cette maladie professionnelle courante, et pouvoir obtenir les détails pertinents durant l’anamnèse, recommander les patients aux cliniques de médecine du travail et débuter les demandes d’indemnisation de manière appropriée. PMID:28292812
Floyd, Lisa M.; Holmes, Taylor C.; Dean, Jesse C.
2013-01-01
Tendon vibration can alter proprioceptive feedback, one source of sensory information which humans can use to produce accurate movements. However, the effects of tendon vibration during functional movement vary depending on the task. For example, ankle tendon vibration has considerably smaller effects during walking than standing posture. The purpose of this study was to test whether the effects of ankle tendon vibration are predictably influenced by the mechanical demands of a task, as quantified by peak velocity. Twelve participants performed symmetric, cyclical ankle plantarflexion/dorsiflexion movements while lying prone with their ankle motion unconstrained. The prescribed movement period (1s, 3s) and peak-to-peak amplitude (10°, 15°, 20°) were varied across trials; shorter movement periods or larger amplitudes increased the peak velocity. In some trials, vibration was continuously and simultaneously applied to the right ankle plantarflexor and dorsiflexor tendons, while the left ankle tendons were never vibrated. The vibration frequency (40, 80, 120, 160 Hz) was varied across trials. During trials without vibration, participants accurately matched the movement of their ankles. The application of 80 Hz vibration to the right ankle tendons significantly reduced the amplitude of right ankle movement. However, the effect of vibration was smaller during more mechanically demanding (i.e. higher peak velocity) movements. Higher vibration frequencies had larger effects on movement accuracy, possibly due to parallel increases in vibration amplitude. These results demonstrate that the effects of ankle tendon vibration are dependent on the mechanical demand of the task being performed, but cannot definitively identify the underlying physiological mechanism. PMID:24136344
Development of enhanced piezoelectric energy harvester induced by human motion.
Minami, Y; Nakamachi, E
2012-01-01
In this study, a high frequency piezoelectric energy harvester converted from the human low vibrated motion energy was newly developed. This hybrid energy harvester consists of the unimorph piezoelectric cantilever and a couple of permanent magnets. One magnet was attached at the end of cantilever, and the counterpart magnet was set at the end of the pendulum. The mechanical energy provided through the human walking motion, which is a typical ubiquitous presence of vibration, is converted to the electric energy via the piezoelectric cantilever vibration system. At first, we studied the energy convert mechanism and the performance of our energy harvester, where the resonance free vibration of unimorph cantilever with one permanent magnet under a rather high frequency was induced by the artificial low frequency vibration. The counterpart magnet attached on the pendulum. Next, we equipped the counterpart permanent magnet pendulum, which was fluctuated under a very low frequency by the human walking, and the piezoelectric cantilever, which had the permanent magnet at the end. The low-to-high frequency convert "hybrid system" can be characterized as an enhanced energy harvest one. We examined and obtained maximum values of voltage and power in this system, as 1.2V and 1.2 µW. Those results show the possibility to apply for the energy harvester in the portable and implantable Bio-MEMS devices.
Longitudinal Vibration of CNTs Viscously Damped in Span
Directory of Open Access Journals (Sweden)
Mustafa Arda
2017-07-01
Full Text Available In this study, longitudinal vibration of a carbon nanotube with an attached damper has been investigated using the nonlocal stress gradient elasticity theory. Equations of motions have been solved analytically and frequencies of clamped-clamped and clamped-free nanotubes have been obtained explicitly in terms of damping coefficient, nonlocal parameter, the attachment point of damper and nanotube length. The nonlocal effects have important effects on the dynamics of a CNT with an attached damper.
The Shock and Vibration Digest. Volume 16, Number 8
1984-08-01
have been examined [57]. the problem of shallow shells by using the Ritz method with algebraic polynomial trial functions Nonlinear analysi. A number...investigate the motion. Nonlinear differential equations have been vibrational behavior of turbine blades [42]. Experi- converted into nonlinear algebraic ...22 (4), Mech., Trans. ASME, 48 (3), pp 559-562 pp 247-264 (1980). (1981). 120. Tadws, R.N. and Rotman , M., "Dynamic Re- 130. Genta, G., Gola, M., et
Cross flow induced vibrations in staggered arrays of cylindrical structures
Energy Technology Data Exchange (ETDEWEB)
Marn, J.
1991-12-31
Flow induced vibrations cause by instability is the subject of this investigation. The bulk of the work performed is theoretical in nature, the comparison with some of existing experimental data is given for each of four models described. First model encompasses the effects of prescribed motion on the cylinder. Such circumstances occur in the case of vortex shedding initiated instability. The reduced velocity within the cylinder array is low and there is no coupling between the adjacent cylinders. Second model assumes certain form of vibration and corresponding behavior of the perturbed velocity field in temporal and one of spatial coordinates thus transforming partial differential equations into ordinary differential equations and takes into account the motion of the neighboring cylinder. This corresponds to fluid elastic controlled instabilities. The resulting equations are solved analytically. The model is used for better understanding of the equations of cylinder motion as well as for quick estimates of threshold of instability. Third model relaxes an assumption about the form of vibration in spatial direction and uses the vorticity formulation of equation of fluid motion to account for fluid-solid interaction. This model analysis is of two phase (air-water mixture) flow. The void fraction distribution is found to be the single most decisive factor to determine the onset of instability for such a domain. In conclusion, two distinct mechanism were found to be responsible for flow induced vibration caused instabilities, (1) outside source controlled periodic excitation (such as vortex shedding) -- described by the first model and (2) fluid elastic forces -- described by second, third and fourth models. For the values of reduced velocity below 0.7 first model is proposed, for the values above 0.7, the rest.
The Shock and Vibration Digest. Volume 13, Number 5
1981-05-01
Gierice E.E.Ungar The Shock and Vibration Digett I* a monthly publication of the Shock and Vibratlo,, Information Center. The goal of the Digett ...of Multi- 99. Spanos, P-T.D., "Numerical Simulations of a Story Buildings Subjected to Ground Motion," Van der Pol Oscillator," Computing Math. Bull...analysis. The (called the 0-Modl) for displacement-time analysis of technique is illustrated by its application to a small hori- multi- story reinforced
Controlled Dynamics of Interfaces in a Vibrated Granular Layer
Aranson, I S; Kwok, W; Karapetrov, G; Welp, U; Crabtree, G W; Vinokur, V M; Tsimring, L S
1999-01-01
We present experimental study of a topological excitation, {\\it interface}, in a vertically vibrated layer of granular material. We show that these interfaces, separating regions of granular material oscillation with opposite phases, can be shifted and controlled by a very small amount of an additional subharmonic signal, mixed with the harmonic driving signal. The speed and the direction of interface motion depends sensitively on the phase and the amplitude of the subharmonic driving.
Using Vibrations to Probe and Control Photoisomerization in Liquids
2014-08-07
toward the conical intersection. Resonance Raman scattering experiments show that the C=C stretching vibration of the central ethylenic bond has a...Figure 1, that controls the passage of the system towards the conical intersection. Because crossing the barrier takes substantially longer than the...teristic times for motion on the excited- and ground-state surfaces. The excited molecule moves to the conical intersection in about 300 fs and takes
Vibrational vs. electronic coherences in 2D spectrum of molecular systems
Butkus, Vytautas; Valkunas, Leonas; Abramavicius, Darius
2012-01-01
The two-dimensional spectroscopy has recently revealed oscillatory behavior of excitation dynamics in molecular systems. However, in the majority of cases it is strongly debated if excitonic or vibrational wavepackets, or evidences of quantum transport have been observed. In this letter, the method for distinguishing between vibrational and excitonic wavepacket motion is presented, based on the phase and amplitude relationships of oscillations of distinct peaks, which has been revealed using fundamental analysis of two-dimensional spectrum of two representative systems.
Dynamics Behavior Research on Variable Linear Vibration Screen with Flexible Screen Face
Changlong Du; Kuidong Gao; Jianping Li; Hao Jiang
2014-01-01
In order to enable the variable linear vibration screen with ideal movement behavior of screen surface and efficient screening capacity, five-freedom dynamic model and stability equations of the variable linear vibration screen were established based on power balance method and Hamilton principle. The motion behaviour of screen face was investigated, and − 0.10 m ≤ xf ≤ − 0.04 m was confirmed as the best range of exciting position. With analysis of stability equations, the stable requirement ...
Connor, Jerome
2014-01-01
This innovative volume provides a systematic treatment of the basic concepts and computational procedures for structural motion design and engineering for civil installations. The authors illustrate the application of motion control to a wide spectrum of buildings through many examples. Topics covered include optimal stiffness distributions for building-type structures, the role of damping in controlling motion, tuned mass dampers, base isolation systems, linear control, and nonlinear control. The book's primary objective is the satisfaction of motion-related design requirements, such as restrictions on displacement and acceleration. The book is ideal for practicing engineers and graduate students. This book also: · Broadens practitioners' understanding of structural motion control, the enabling technology for motion-based design · Provides readers the tools to satisfy requirements of modern, ultra-high strength materials that lack corresponding stiffness, where the motion re...
The behaviour of lubricated EHD contacts subjected to vibrations
Zhang, X.; Glovnea, R. P.
2017-02-01
Machine components containing contacts working in elastohydrodynamic (EHD) conditions are often subjected to vibrations. These may be originated from the mechanism or machine the contact is part of, the surrounding environment and within the contact itself. The influence of vibrations upon the behaviour of elastohydrodynamic films has been studied experimentally in a number of papers, but a comprehensive study of the effect of the parameters of the oscillatory motion upon the film thickness has not been carried out yet. In this study the authors evaluate the effect of the frequency of the oscillatory motion upon the EHD film thickness. Optical interferometry is used to measure lubricant film thickness in a ball-on-flat disc arrangement. A high – speed camera records the interferometric images for later analysis and conversion into film thickness maps. The disc runs at a constant angular velocity while the ball is driven by the traction forces developed in the EHD film. In steady state conditions, this would ensure pure rolling conditions, however in the present investigation the ball is subjected to harmonic vibrations in a direction perpendicular to the plane of the film. The contact under study is lubricated by basic oils and the temperature is kept at a constant value of 60°C. The aim of this paper is to understand how vibrations influence the lubricant film formation.
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A complex number mode analysis approach is proposed for vibration reducing of structural flexible redundant manipulators by utilizing self-motion. In the proposed approach, the self-motion is evaluated to nullify the modal exciting-force of flexural motion, and the approach can be freely used when the degree of freedom of flexural motion is much greater than the available degree of reundancy. The availability and effectiveness of the proposed approach are demonstrated through numerical simulation with a four-link spatial robotic manipulator possessing an end flexible link.
Hydroelastic Vibrations of Ships
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Folsø, Rasmus
2002-01-01
A formula for the necessary hull girder bending stiffness required to avoid serious springing vibrations is derived. The expression takes into account the zero crossing period of the waves, the ship speed and main dimensions. For whipping vibrations the probability of exceedance for the combined...... wave- and whipping induced bending moment is derived under the assumption that the maximum peak value in a whipping sequence occurs simultaneously with a peak in sagging wave-induced bending moment, but that the magnitudes of these two peaks are statistically independent. The expression can be written...... as the usual Rayleigh distribution for the wave response multiplied by a factor independent of the significant wave height. Finally, the springing and whipping predictions are compared with model test results....
Laser induced structural vibration
Koss, L. L.; Tobin, R. C.
1983-01-01
A technique is described for exciting structural vibration by using a focussed laser beam to vaporize material from a target attached to the structure. The rapid ejection of material results in an impulsive reaction to the target which is transmitted to the structure. The method has been studied with a Nd: glass laser, operated in the long pulse mode, in combination with a bismuth target attached in turn to a ballistic pendulum and cantilever beam. The specific mechanical energy was found to be proportional to the laser pulse energy raised to a power in the range 2.5-2.9. The highest efficiency of energy transfer achieved for the first vibrational mode of the cantilever was about 2 millipercent for the maximum laser pulse energy used, 1.5 J, the signal to noise ratio then being about 40 dB.
Vibration Characteristics of a Building Structure from a Natural Frequency Point of View
Directory of Open Access Journals (Sweden)
Katsumi Kurita
2015-05-01
Full Text Available To investigate vibration characteristics of the building, the natural frequency of the building was estimated using microtoremor and strong motion. In case estimated using microtoremor data, the natural frequency was 2.40Hz in the minor axis of the building. However, in case estimated using strong motion data, the average of them was 2.28Hz that is lower than that of microtremor. From a time series analysis on strong motion data, the natural frequency indicates high value before the part of principal motion, it drops to a lower on the part of principal motion. And it goes back with the decreasing acceleration amplitude of motion. It means that the natural frequency of the structure depends on the peak acceleration amplitude. Therefore, it is difficult to evaluate a health index only using the change of the natural frequency estimated by strong motion data. It means that it needs to use another parameter together.
Measurement of rabbit eardrum vibration through stroboscopic digital holography
Energy Technology Data Exchange (ETDEWEB)
De Greef, Daniël; Dirckx, Joris J. J. [University of Antwerp, Laboratory of BioMedical Physics, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)
2014-05-27
In this work, we present a setup for high-power single shot stroboscopic digital holography and demonstrate it in an application on rabbit eardrum vibration measurement. The setup is able to make full-field time-resolved measurements of vibrating surfaces with a precision in the nanometer range in a broad frequency range. The height displacement of the measured object is visualized over the entire surface as a function of time. Vibration magnitude and phase maps can be extracted from these data, the latter proving to be very useful to reveal phase delays across the surface. Such deviations from modal motion indicate energy losses due to internal damping, in contrast to purely elastic mechanics. This is of great interest in middle ear mechanics and finite element modelling. In our setup, short laser pulses are fired at selected instants within the surface vibration period and are recorded by a CCD camera. The timing of the pulses and the exposure of the camera are synchronized to the vibration phase by a microprocessor. The high-power frequency-doubled Nd:YAG laser produces pulses containing up to 5 mJ of energy, which is amply sufficient to record single-shot holograms. As the laser pulse length is 8 ns and the smallest time step of the trigger electronics is 1 μs, vibration measurements of frequencies up to 250 kHz are achievable through this method, provided that the maximum vibration amplitude exceeds a few nanometers. In our application, middle ear mechanics, measuring frequencies extend from 5 Hz to 20 kHz. The experimental setup will be presented, as well as results of measurements on a stretched circular rubber membrane and a rabbit's eardrum. Two of the challenges when measuring biological tissues, such as the eardrum, are low reflectivity and fast dehydration. To increase reflectivity, a coating is applied and to counteract the undesirable effects of tissue dehydration, the measurement setup and software have been optimized for speed without
Vibrational stability of graphene
Directory of Open Access Journals (Sweden)
Yangfan Hu
2013-05-01
Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.
Vibration Induced Microfluidic Atomization
Yeo, Leslie; Qi, Aisha; Friend, James
2008-11-01
We demonstrate rapid generation of micron aerosol droplets in a microfluidic device in which a fluid drop is exposed to surface vibration as it sits atop a piezoelectric substrate. Little, however, is understood about the processes by which these droplets form due to the complex hydrodynamic processes that occur across widely varying length and time scales. Through experiments, scaling theory and numerical modelling, we elucidate the interfacial destabilization mechanisms that lead to droplet formation. Droplets form due to the axisymmetric break-up of cylindrical liquid jets ejected as a consequence of interfacial destabilization. Their 10 μm size correlates with the jet radius and the instability wavelength, both determined from a viscous-capillary dominant force balance and confirmed through a numerical solution. With the exception of drops that spread into thin films with thicknesses on the order of the boundary layer dimension, the free surface is always observed to vibrate at the capillary-viscous resonance frequency despite the surface vibration frequency being several orders larger. This is contrary to common assumptions used in deriving subharmonic models resulting in a Mathieu equation, which has commonly led to spurious predictions in the droplet size.
Katarina Anthony
2015-01-01
In preparation for the civil engineering work on the HL-LHC, vibration measurements were carried out at the LHC’s Point 1 last month. These measurements will help evaluate how civil engineering work could impact the beam, and will provide crucial details about the site’s geological make-up before construction begins. A seismic truck at Point 1 generated wave-like vibrations measured by EN/MME. From carrying out R&D to produce state-of-the-art magnets to developing innovative, robust materials capable of withstanding beam impact, the HL-LHC is a multi-faceted project involving many groups and teams across CERN’s departments. It was in this framework that the project management mandated CERN's Mechanical and Materials Engineering (EN/MME) group to measure the propagation of vibrations around Point 1. Their question: can civil engineering work for the HL-LHC – the bulk of which is scheduled for LS2 – begin while the LHC is running? Alth...
Cavity-enhanced optical detection of carbon nanotube Brownian motion
Stapfner, S; Hunger, D; Weig, E M; Reichel, J; Favero, I
2012-01-01
Optical cavities with small mode volume are well-suited to detect the vibration of sub-wavelength sized objects. Here we employ a fiber-based, high-finesse optical microcavity to detect the Brownian motion of a freely suspended carbon nanotube at room temperature under vacuum. The optical detection resolves deflections of the oscillating tube down to 50pm/Hz^1/2. A full vibrational spectrum of the carbon nanotube is obtained and confirmed by characterization of the same device in a scanning electron microscope. Our work successfully extends the principles of high-sensitivity optomechanical detection to molecular scale nanomechanical systems.
Directory of Open Access Journals (Sweden)
Haoyun Tang
2016-01-01
Full Text Available The irregular wave condition, especially the oblique irregular wave condition, is the actual circumstances when trimaran is sailing in sea. In order to identify the characteristic of the wave-induced hydroelastic vibration in irregular waves, as well as investigate the change of vibration in different oblique irregular wave conditions, trimaran model tests were conducted to measure vibrations, wave impact, and motion under different azimuth and wave height. The vibration on main hull, side hull, and cross-desk is measured and analyzed separately to observe the influence of irregular wave in different structural parts. The longitudinal vibration, transverse vibration, and torsion are also included in the model tests measurement to investigate the relationship between these vibration deformation components and parameters of the irregular waves. The wave-induced hydroelastic vibrations and whipping effect is extracted and analyzed to find influence of whipping and springing on the total vibration. Based on the analysis, the dangerous positions and the critical waves condition is introduced to ensure that the subsequent structural strength assessment is more reliable.
LOCALISED MUSCLE TISSUE OXYGENATION DURING DYNAMIC EXERCISE WITH WHOLE BODY VIBRATION
Directory of Open Access Journals (Sweden)
Daniel Robbins
2012-06-01
Full Text Available Despite increasing use of whole body vibration during exercise an understanding of the exact role of vibration and the supporting physiological mechanisms is still limited. An important aspect of exercise analysis is the utilisation of oxygen, however, there have been limited studies considering tissue oxygenation parameters, particularly during dynamic whole body vibration (WBV exercise. The aim of this study was to determine the effect of adding WBV during heel raise exercises and assessing changes in tissue oxygenation parameters of the lateral gastrocnemius using Near Infra Red Spectroscopy (NIRS. Twenty healthy subjects completed ten alternating sets of 15 heel raises (vibration vs. no vibration. Synchronous oxygenation and motion data were captured prior to exercise to determine baseline levels, for the duration of the exercise and 20 sec post exercise for the recovery period. Both vibration and no vibration conditions elicited a characteristic increase in deoxyhaemoglobin and decreases in oxyhaemoglobin, total haemoglobin, tissue oxygenation index and normalised tissue haemoglobin index which are indicative of local tissue hypoxia. However, the addition of vibration elicited significantly lower (p < 0. 001 depletions in oxyhaemoglobin, total haemoglobin, normalised tissue haemoglobin index but no significant differences in deoxyhaemoglobin. These findings suggest that addition of vibration to exercise does not increase the cost of the exercise for the lateral gastrocnemius muscle, but does decrease the reduction in local muscle oxygenation parameters, potentially resulting from increased blood flow to the calf or a vasospastic response in the feet. However, further studies are needed to establish the mechanisms underlying these findings
Experimental Study on Interfacial Area Transport of Two-Phase Flow under Vibration Conditions
Directory of Open Access Journals (Sweden)
Xiu Xiao
2017-01-01
Full Text Available An experimental study on air-water two-phase flow under vibration condition has been conducted using double-sensor conductivity probe. The test section is an annular geometry with hydraulic diameter of 19.1 mm. The vibration frequency ranges from 0.47 Hz to 2.47 Hz. Local measurements of void fraction, interfacial area concentration (IAC, and Sauter mean diameter have been performed along one radius in the vibration direction. The result shows that local parameters fluctuate continuously around the base values in the vibration cycle. Additional bubble force due to inertia is used to explain lateral bubble motions. The fluctuation amplitudes of local void fraction and IAC increase significantly with vibration frequency. The radial distribution of local parameters at the maximum vibration displacement is specifically analyzed. In the void fraction and IAC profiles, the peak near the inner wall is weakened or even disappearing and a strong peak skewed to outer wall is gradually observed with the increase of vibration frequency. The nondimensional peak void fraction can reach a maximum of 49% and the mean relative variation of local void fraction can increase to more than 29% as the vibration frequency increases to 2.47 Hz. But the increase of vibration frequency does not bring significant change to bubble diameter.
Piezoelectric actuators in the active vibration control system of journal bearings
Tůma, J.; Šimek, J.; Mahdal, M.; Pawlenka, M.; Wagnerova, R.
2017-07-01
The advantage of journal hydrodynamic bearings is high radial load capacity and operation at high speeds. The disadvantage is the excitation of vibrations, called an oil whirl, after crossing a certain threshold of the rotational speed. The mentioned vibrations can be suppressed using the system of the active vibration control with piezoactuators which move the bearing bushing. The motion of the bearing bushing is controlled by a feedback controller, which responds to the change in position of the bearing journal which is sensed by a pair of capacitive sensors. Two stacked linear piezoactuators are used to actuate the position of the bearing journal. This new bearing enables not only to damp vibrations but also serves to maintain the desired bearing journal position with an accuracy of micrometers. The paper will focus on the effect of active vibration control on the performance characteristics of the journal bearing.
Effectiveness of Stationary Humans and Tuned Mass Dampers in Controlling Floor vibrations
DEFF Research Database (Denmark)
Pedersen, Lars
2006-01-01
and the vibrating floor. The paper presents results of controlled tests made with a vibrating test floor carrying stationary crowds of people and how these results are employed in the context of formulating a model for the passive damping mechanism generated by stationary humans. The paper illustrates...... a dynamic excitation generated by humans in motion. The vibration levels are compared with those expected if the else wise empty structures were fitted with a tuned mass damper so as to illustrate the effectiveness of the crowd in mitigating floor vibrations. Since a stationary crowd of people changes......Floor vibrations can be annoying to stationary humans (sitting or standing) on a floor, and therefore codes and standards specify threshold values for floor acceleration levels. For very responsive floors if can be necessary to fit the floor with a passive damping source (such as a tuned mass...
Tuned liquid column dampers for mitigation of edgewise vibrations in rotating wind turbine blades
DEFF Research Database (Denmark)
Zhang, Zili; Basu, Biswajit; Nielsen, Søren R.K.
2015-01-01
, with the consideration of both the space limitation inside the blade and the constraint of the liquid motion. The edgewise modal load for the 2-DOF model has been calculated from a more sophisticated 13-DOF aeroelastic wind turbine model, which includes the coupling of the blade-tower-drivetrain vibration......Edgewise vibrations in wind turbine blades are lightly damped, and large amplitude vibrations induced by the turbulence may significantly shorten the fatigue life of the blade. This paper investigates the performance of tuned liquid column dampers (TLCDs) for mitigating edgewise vibrations...... in rotating wind turbine blades. Normally, the centrifugal acceleration at the outboard portion of a rotating blade can reach to a magnitude of 7–8 g, which makes it possible to use a TLCD with a very small mass for suppressing edgewise vibrations effectively. The parameters of the TLCD to be optimized...
Vibration of a delaminated beam-plate relative to buckled states
Yin, W.-L.; Jane, K. C.
1992-07-01
Free vibrations of delaminated beam-plates with respect to postbuckled referential states are studied. If the postbuckling deformation of the referential state is symmetric with respect to the mid-point, then the symmetric and antisymmetric vibration modes are uncoupled. Short delaminations which do not significantly degradate the overall stiffness of the beam-plate have little effect on the lowest modes of vibration and their frequencies, while the presence of a long delamination generally introduces additional vibration frequencies, the associated mode shapes of which show out-of-phase motions of the upper and lower delaminated layers. These new vibration modes and frequencies depend sensitively on the delamination length and location and on the magnitude of the postbuckling load. Hence their detection may indicate the presence and the nature of internal delamination damage.
[The potentials for errors in the hygienic assessment of the general vibrations in tractors].
Ivanovich, E; Goranova, L; Enev, S
1991-01-01
The data for the parameters of the general vibrations in tractors are comparatively scanty and contradictory. In the present work are analyzed the most frequently met omissions and errors in the measurement and evaluation of the general vibrations, as well as the factors, which can effect the intensity of the general vibrations; constructive and technological peculiarities, technical state, rate of machine amortization, construction, damping qualities, and regulation of the seat, motion velocity, relief, type of the performed agricultural activity. The necessity for taking under consideration these factors in measuring the general vibrations and the hygiene interpretation of the data, as well as precise report on the daily, weekly and general exposure, in view of defining the total vibration loading, is underlined.
Vibration band-gap properties of three-dimensional Kagome lattices using the spectral element method
Wu, Zhi-Jing; Li, Feng-Ming; Zhang, Chuanzeng
2015-04-01
The spectral element method (SEM) is extended to investigate the vibration band-gap properties of three-dimensional (3D) Kagome lattices. The dynamic stiffness matrix of the 3D element which contains bending, tensional and torsional components is derived. The spectral equations of motion of the whole 3D Kagome lattice are then established. Comparing with frequency-domain solutions calculated by the finite element method (FEM), the accuracy and the feasibility of the SEM solutions are verified. It can be shown that the SEM is suitable for analyzing the vibration band-gap properties. Due to the band-gap characteristics, the periodic 3D Kagome lattice has the performance of vibration isolation. The influences of the structural and material parameters on the vibration band-gaps are discussed and a new type of 3D Kagome lattice is designed to obtain the improved vibration isolation capability.
Quantum teleportation from light beams to vibrational states of a macroscopic diamond
Hou, P.-Y.; Huang, Y.-Y.; Yuan, X.-X.; Chang, X.-Y.; Zu, C.; He, L.; Duan, L.-M.
2016-05-01
With the recent development of optomechanics, the vibration in solids, involving collective motion of trillions of atoms, gradually enters into the realm of quantum control. Here, building on the recent remarkable progress in optical control of motional states of diamonds, we report an experimental demonstration of quantum teleportation from light beams to vibrational states of a macroscopic diamond under ambient conditions. Through quantum process tomography, we demonstrate average teleportation fidelity (90.6+/-1.0)%, clearly exceeding the classical limit of 2/3. The experiment pushes the target of quantum teleportation to the biggest object so far, with interesting implications for optomechanical quantum control and quantum information science.
Dynamical potential approach to dissociation of H-C bond in HCO highly excited vibration
Institute of Scientific and Technical Information of China (English)
Fang Chao; Wu Guo-Zhen
2009-01-01
The highly excited vibrational levels of HCO in the electronic ground state, X1A', are employed to determine the coefficients of an algebraic Hamiltonian, by which the dynamical potential is derived and shown to be very useful for interpreting thc intramolecular vibrational relaxation (IVR) which operates via the HCO bending motion. The IVR inhibits the dissociation of H atom and enhances the stochastic degree of dynamical character. This approach is from a global viewpoint on a series of levels classified by the polyad number which is a constant of motion in a certain dynamical domain. In this way, the seemingly complicated level structure shows very regular picture, dynamically.
Directory of Open Access Journals (Sweden)
Rene de Jesus Romero-Troncoso
2010-04-01
Full Text Available Intelligent robotics demands the integration of smart sensors that allow the controller to efficiently measure physical quantities. Industrial manipulator robots require a constant monitoring of several parameters such as motion dynamics, inclination, and vibration. This work presents a novel smart sensor to estimate motion dynamics, inclination, and vibration parameters on industrial manipulator robot links based on two primary sensors: an encoder and a triaxial accelerometer. The proposed smart sensor implements a new methodology based on an oversampling technique, averaging decimation filters, FIR filters, finite differences and linear interpolation to estimate the interest parameters, which are computed online utilizing digital hardware signal processing based on field programmable gate arrays (FPGA.
Rodriguez-Donate, Carlos; Morales-Velazquez, Luis; Osornio-Rios, Roque Alfredo; Herrera-Ruiz, Gilberto; de Jesus Romero-Troncoso, Rene
2010-01-01
Intelligent robotics demands the integration of smart sensors that allow the controller to efficiently measure physical quantities. Industrial manipulator robots require a constant monitoring of several parameters such as motion dynamics, inclination, and vibration. This work presents a novel smart sensor to estimate motion dynamics, inclination, and vibration parameters on industrial manipulator robot links based on two primary sensors: an encoder and a triaxial accelerometer. The proposed smart sensor implements a new methodology based on an oversampling technique, averaging decimation filters, FIR filters, finite differences and linear interpolation to estimate the interest parameters, which are computed online utilizing digital hardware signal processing based on field programmable gate arrays (FPGA).
Cazzulani, Gabriele; Resta, Ferruccio; Ripamonti, Francesco
2012-04-01
Large mechanical structures are often affected by high level vibrations due to their flexibility. These vibrations can reduce the system performances and lifetime and the use of active vibration control strategies becomes very attractive. In this paper a combination of resonant control and a disturbance estimator is proposed. This solution is able to improve the system performances during the transient motion and also to reject the disturbance forces acting on the system. Both control logics are based on a modal approach, since it allows to describe the structure dynamics considering only few degrees of freedom.
Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation
Directory of Open Access Journals (Sweden)
Shi-Jian Zhu
2014-01-01
Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.
Raffo, Antonio; Costanzo, Sandra; Di Massa, Giuseppe
2017-01-01
A vibration sensor based on the use of a Software-Defined Radio (SDR) platform is adopted in this work to provide a contactless and multipurpose solution for low-cost real-time vibrations monitoring. In order to test the vibration detection ability of the proposed non-contact method, a 1 GHz Doppler radar sensor is simulated and successfully assessed on targets at various distances, with various oscillation frequencies and amplitudes. Furthermore, an SDR Doppler platform is practically realized, and preliminary experimental validations on a device able to produce a harmonic motion are illustrated to prove the effectiveness of the proposed approach. PMID:28075345
Theory and Normal Mode Analysis of Change in Protein Vibrational Dynamics on Ligand Binding
Energy Technology Data Exchange (ETDEWEB)
Mortisugu, Kei [RIKEN, Japan; Njunda, Brigitte [Computational Molecular Biophysics, Interdisciplinary Center for Scientific Computing (IWR); Smith, Jeremy C [ORNL
2009-12-01
The change of protein vibrations on ligand binding is of functional and thermodynamic importance. Here, this process is characterized using a simple analytical 'ball-and-spring' model and all-atom normal-mode analysis (NMA) of the binding of the cancer drug, methotrexate (MTX) to its target, dihydrofolate reductase (DHFR). The analytical model predicts that the coupling between protein vibrations and ligand external motion generates entropy-rich, low-frequency vibrations in the complex. This is consistent with the atomistic NMA which reveals vibrational softening in forming the DHFR-MTX complex, a result also in qualitative agreement with neutron-scattering experiments. Energy minimization of the atomistic bound-state (B) structure while gradually decreasing the ligand interaction to zero allows the generation of a hypothetical 'intermediate' (I) state, without the ligand force field but with a structure similar to that of B. In going from I to B, it is found that the vibrational entropies of both the protein and MTX decrease while the complex structure becomes enthalpically stabilized. However, the relatively weak DHFR:MTX interaction energy results in the net entropy gain arising from coupling between the protein and MTX external motion being larger than the loss of vibrational entropy on complex formation. This, together with the I structure being more flexible than the unbound structure, results in the observed vibrational softening on ligand binding.
A new vibration isolation bed stage with magnetorheological dampers for ambulance vehicles
Chae, Hee Dong; Choi, Seung-Bok
2015-01-01
The vibration experienced in an ambulance can lead to secondary injury to a patient and discourage a paramedic from providing emergency care. In this study, with the goal of resolving this problem, a new vibration isolation bed stage associated with magnetorheological (MR) dampers is proposed to ensure ride quality as well as better care for the patient while he/she is being transported. The bed stage proposed in this work can isolate vibrations in the vertical, rolling and pitching directions to reflect the reality that occurs in the ambulance. Firstly, an appropriate-sized MR damper is designed based on the field-dependent rheological properties of MR fluid, and the damping force characteristics of a MR damper are evaluated as a function of the current. A mechanical model of the proposed vibration isolation bed stage is then established to derive the governing equations of motion. Subsequently, a sliding mode controller is formulated to control the vibrations caused from the imposed excitation signals; those signals are directly measured using a real ambulance subjected to bump-and-curve road conditions. Using the controller based on the dynamic motion of the bed stage, the vibration control performance is evaluated in both the vertical and pitch directions. It is demonstrated that the magnitude of the vibration in the patient compartment of the ambulance can be significantly reduced by applying an input current to the MR dampers installed for the new bed stage.
Flight vibrations and bleeding in helicoptered patients with pelvic fracture.
Carchietti, Elio; Cecchi, Adriana; Valent, Francesca; Rammer, Raphael
2013-01-01
Depending on their amplitude and frequency, vibrations may facilitate bleeding and worsen the prognosis of patients with pelvic fractures transported by helicopter emergency medical services (HEMS). We measured the range of frequencies and amplitudes of forced vibrations produced by the helicopter used by the HEMS of the Italian Friuli Venezia Giulia region on the pelvis of transported persons. We performed 3 flight tests with 3 different volunteers (mass 70, 80, and 90 kg, respectively) loaded on the helicopter's stretcher and recorded the amplitudes and frequencies of vibrations through a triaxis sensor placed on the HEMS stretcher in the pelvis area. The flight profile planned was identical for each of the 3 iterations. Over the whole flight, the frequencies of vibration were between 26.4 and 53.5 Hz, and the greastest amplitude was 0.035 mm. The vibrations recorded in the helicopter may facilitate bleeding in unstable fractures. In the management of patients with pelvic fractures, HEMS crews should provide prehospital care that includes the use of specific splinting devices in addition to the spinal board, which allows an early immobilization of fractures and the limitation of pelvic motion.
Energy Technology Data Exchange (ETDEWEB)
Wang, Hesheng [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China); Chen, Weidong, E-mail: wdchen@sjtu.edu.cn [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China); Xu, Lifei; He, Tao [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China)
2015-10-15
Highlights: • Vision-based online vibration estimation method for a flexible arm is proposed. • The vibration signal is obtained by image processing in unknown environments. • Vibration parameters are estimated by short-time Fourier transformation. - Abstract: The vibration should be suppressed if it happens during the motion of a flexible robot or under the influence of external disturbance caused by its structural features and material properties, because the vibration may affect the positioning accuracy and image quality. In Tokamak environment, we need to get the real-time vibration information on vibration suppression of robotic arm, however, some sensors are not allowed in the extreme Tokamak environment. This paper proposed a vision-based method for online vibration estimation of a flexible manipulator, which is achieved by utilizing the environment image information from the end-effector camera to estimate its vibration. Short-time Fourier Transformation with adaptive window length method is used to estimate vibration parameters of non-stationary vibration signals. Experiments with one-link flexible manipulator equipped with camera are carried out to validate the feasibility of this method in this paper.
Semiactive Vibration Control for Horizontal Axis Washing Machine
Directory of Open Access Journals (Sweden)
Barış Can Yalçın
2015-01-01
Full Text Available A semiactive vibration control method is developed to cope with the dynamic stability problem of a horizontal axis washing machine. This method is based on adjusting the maximum force values produced by the semiactive suspension elements considering a washing machine’s vibration data (three axis angular position and three axis angular acceleration values in time. Before actuation signals are received by the step motors of the friction dampers, vibration data are evaluated, and then, the step motors start to narrow or expand the radius of bracelets located on the dampers. This changes the damping properties of the damper in the suspension system, and thus, the semiactive suspension system absorbs unwanted vibrations and contributes to the dynamic stability of the washing machine. To evaluate the vibration data, the angular position and angular acceleration values in three axes are defined in a function, and the maximum forces produced by semiactive suspension elements are calculated according to the gradient of this function. The relation between the dynamic stability and the walking stability is also investigated. A motion (gyroscope and accelerometer sensor is installed on the top-front panel of the washing machine because a mathematical model of a horizontal axis washing machine suggests that the walking behavior starts around this location under some assumptions, and therefore, calculating the vibrations occurring there is crucial. Semiactive damping elements are located under the left and right sides of the tub. The proposed method is tested during the spinning cycle of washing machine operation, increasing gradually from 200 rpm to 900 rpm, which produces the most challenging vibration patterns for dynamic stability. Moreover, the sound power levels produced by the washing machine are measured to evaluate the noise performance of the washing machine while the semiactive suspension system is controlled. The effectiveness of the
Random vibrations theory and practice
Wirsching, Paul H; Ortiz, Keith
1995-01-01
Random Vibrations: Theory and Practice covers the theory and analysis of mechanical and structural systems undergoing random oscillations due to any number of phenomena— from engine noise, turbulent flow, and acoustic noise to wind, ocean waves, earthquakes, and rough pavement. For systems operating in such environments, a random vibration analysis is essential to the safety and reliability of the system. By far the most comprehensive text available on random vibrations, Random Vibrations: Theory and Practice is designed for readers who are new to the subject as well as those who are familiar with the fundamentals and wish to study a particular topic or use the text as an authoritative reference. It is divided into three major sections: fundamental background, random vibration development and applications to design, and random signal analysis. Introductory chapters cover topics in probability, statistics, and random processes that prepare the reader for the development of the theory of random vibrations a...
VIBRATION ISOLATION SYSTEM PROBABILITY ANALYSIS
Directory of Open Access Journals (Sweden)
Smirnov Vladimir Alexandrovich
2012-10-01
Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.
Theory of vibrational cooling in molecular crystals: Application to crystalline naphthalene
Hill, Jeffrey R.; Dlott, Dana D.
1988-07-01
The process of vibrational cooling (VC) is theoretically investigated in the molecular crystal naphthalene. Specificially we consider the process where a highly excited vibration cools by emitting lower energy vibrations (vibrational relaxation, or VR) and phonons. We also consider the subsequent cooling of emitted optic phonons by emission of acoustic phonons. Using previously determined vibrational lifetimes [J. R. Hill et al., J. Chem. Phys. 88, 949 (1988)], a consistent transition rate matrix is obtained which describes VR of all vibrations and optic phonons at all temperatures. Then a Master equation is solved numerically to obtain the time dependent vibrational populations of all states following impulse excitation of a high frequency vibration. These results are compared to a previously derived analytic model for VC in molecular crystals [J. R. Hill and D. D. Dlott, J. Chem. Phys. 89, 830 (1988)]. In that theory, which is shown to be in good agreement with the naphthalene calculation, the excess vibrational excitation moves to lower energy states and broadens as time increases. The motion toward lower energy states is described by a temperature independent ``vibrational velocity'' (emitted energy per unit time). In naphthalene, the vibrational velocity is V0 ≊9 cm-1 /ps. The VC process occurs on a time scale as much as an order of magnitude longer than an individual VR step. Although VR is highly temperature dependent, VC is not. The VC calculations are used to predict the decay from the initial state, the time dependent populations of transient vibrational excitations, and the return to the vibrationless ground state. All these quantities are directly related to experimental observables such as incoherent anti-Stokes Raman scattering and hot luminescence.
Scavenging energy from the motion of human lower limbs via a piezoelectric energy harvester
Fan, Kangqi; Yu, Bo; Zhu, Yingmin; Liu, Zhaohui; Wang, Liansong
2017-03-01
Scavenging energy from human motion through piezoelectric transduction has been considered as a feasible alternative to batteries for powering portable devices and realizing self-sustained devices. To date, most piezoelectric energy harvesters (PEHs) developed can only collect energy from the uni-directional mechanical vibration. This deficiency severely limits their applicability to human motion energy harvesting because the human motion involves diverse mechanical motions. In this paper, a novel PEH is proposed to harvest energy from the motion of human lower limbs. This PEH is composed of two piezoelectric cantilever beams, a sleeve and a ferromagnetic ball. The two beams are designed to sense the vibration along the tibial axis and conduct piezoelectric conversion. The ball senses the leg swing and actuates the two beams to vibrate via magnetic coupling. Theoretical and experimental studies indicate that the proposed PEH can scavenge energy from both the vibration and the swing. During each stride, the PEH can produce multiple peaks in voltage output, which is attributed to the superposition of different excitations. Moreover, the root-mean-square (RMS) voltage output of the PEH increases when the walking speed ranges from 2 to 8 km/h. In addition, the ultra-low frequencies of human motion are also up-converted by the proposed design.
Energy Technology Data Exchange (ETDEWEB)
Hildreth, E.C.
1984-01-01
This book examines the measurement of visual motion and the use of relative movement to locate the boundaries of physical objects in the environment. It investigates the nature of the computations that are necessary to perform this analysis by any vision system, biological or artificial. Contents: Introduction. Background. Computation of the Velocity Field. An Algorithm to Compute the Velocity Field. The Computation of Motion Discontinuities. Perceptual Studies of Motion Measurement. The Psychophysics of Discontinuity Detection. Neurophysiological Studies of Motion. Summary and Conclusions. References. Author and Subject Indexes.
DEFF Research Database (Denmark)
Jensen, Rasmus Ramsbøl; Benjaminsen, Claus; Larsen, Rasmus
2015-01-01
The application of motion tracking is wide, including: industrial production lines, motion interaction in gaming, computer-aided surgery and motion correction in medical brain imaging. Several devices for motion tracking exist using a variety of different methodologies. In order to use such devices...... offset and tracking noise in medical brain imaging. The data are generated from a phantom mounted on a rotary stage and have been collected using a Siemens High Resolution Research Tomograph for positron emission tomography. During acquisition the phantom was tracked with our latest tracking prototype...
Computer analysis of railcar vibrations
Vlaminck, R. R.
1975-01-01
Computer models and techniques for calculating railcar vibrations are discussed along with criteria for vehicle ride optimization. The effect on vibration of car body structural dynamics, suspension system parameters, vehicle geometry, and wheel and rail excitation are presented. Ride quality vibration data collected on the state-of-the-art car and standard light rail vehicle is compared to computer predictions. The results show that computer analysis of the vehicle can be performed for relatively low cost in short periods of time. The analysis permits optimization of the design as it progresses and minimizes the possibility of excessive vibration on production vehicles.
Characterisation of walking loads by 3D inertial motion tracking
Van Nimmen, K.; Lombaert, G.; Jonkers, I.; De Roeck, G.; Van den Broeck, P.
2014-09-01
The present contribution analyses the walking behaviour of pedestrians in situ by 3D inertial motion tracking. The technique is first tested in laboratory experiments with simultaneous registration of the ground reaction forces. The registered motion of the pedestrian allows for the identification of stride-to-stride variations, which is usually disregarded in the simulation of walking forces. Subsequently, motion tracking is used to register the walking behaviour of (groups of) pedestrians during in situ measurements on a footbridge. The calibrated numerical model of the structure and the information gathered using the motion tracking system enables detailed simulation of the step-by-step pedestrian induced vibrations. Accounting for the in situ identified walking variability of the test-subjects leads to a significantly improved agreement between the measured and the simulated structural response.
The Hierarchy of Fast Motions in Protein Dynamics
Mazur, A K
1998-01-01
For many biological applications of molecular dynamics (MD) the importance of good sampling in conformational space makes it necessary to eliminate the fastest motions from the system in order to increase the time step. An accurate knowledge of these motions is a necessary prerequisite for such efforts. It is known that harmonic vibrations of bond lengths and bond angles produce the highest frequencies in proteins. There are also fast anharmonic motions, such as inter-atomic collisions, which are probably most important when bond lengths and bond angles are fixed. However, the specific time scales corresponding to all these limitations are not known precisely. In order to clarify the above issue this paper analyses time step limiting factors in a series of numerical tests by using an internal coordinate molecular dynamics approach, which allows chosen internal coordinates to be frozen. It is found that, in proteins, there is a rather complicated hierarchy of fast motions, with both harmonic and anharmonic eff...
A simple model for strong ground motions and response spectra
Safak, Erdal; Mueller, Charles; Boatwright, John
1988-01-01
A simple model for the description of strong ground motions is introduced. The model shows that response spectra can be estimated by using only four parameters of the ground motion, the RMS acceleration, effective duration and two corner frequencies that characterize the effective frequency band of the motion. The model is windowed band-limited white noise, and is developed by studying the properties of two functions, cumulative squared acceleration in the time domain, and cumulative squared amplitude spectrum in the frequency domain. Applying the methods of random vibration theory, the model leads to a simple analytical expression for the response spectra. The accuracy of the model is checked by using the ground motion recordings from the aftershock sequences of two different earthquakes and simulated accelerograms. The results show that the model gives a satisfactory estimate of the response spectra.
Vibrational memory in quantum localized states
Ajili, Y.; Trabelsi, T.; Denis-Alpizar, O.; Stoecklin, T.; Császár, A. G.; Mogren Al-Mogren, M.; Francisco, J. S.; Hochlaf, M.
2016-05-01
The rovibrational eigenenergy set of molecular systems is a key feature needed to understand and model elementary chemical reactions. A unique class of molecular systems, represented by an 4A'' excited electronic state of the [H,S ,N ] - system comprising several distinct dipole-bound isomers, is found to contain both bent and linear minima separated by relatively small barriers. Full-dimensional nuclear-motion computations performed in Jacobi coordinates using three-dimensional potential energy surfaces describing the stable isomers and the related transition states yield rovibrational eigenstates located both below and above the barriers. The rovibrational wave functions are well localized, regardless of whether the state's energy is below or above the barriers. We also show that the states preserve the memory of the isomeric forms they "originate from," which is signature of a strong vibrational memory effect above isomerization barriers.
A first course in vibrations and waves
Samiullah, Mohammad
2015-01-01
This book builds on introductory physics and emphasizes understanding of vibratory motion and waves based on first principles. The book is divided into three parts. Part I contains a preliminary chapter that serves as a review of relevant ideas of mechanics and complex numbers. Part II is devoted to a detailed discussion of vibrations of mechanical systems. This part covers a simple harmonic oscillator, coupled oscillators, normal coordinates, beaded string, continuous string, standing waves, and Fourier series. Part II ends with a presentation of stationary solutions of driven finite systems. Part III is concerned with waves. Here, the emphasis is on the discussion of common aspects of all types of waves. The applications to sound, electromagnetic, and matter waves are illustrated. The book also includes examples from water waves and electromagnetic waves on a transmission line. The emphasis of the book is to bring out the similarities among various types of waves. The book includes treatment of reflection a...
Energy bursts in vibrated shallow granular systems
Rivas, N.; Risso, D.; Soto, R.; Cordero, P.
2011-03-01
In a mixture of two species of inelastic spheres of equal size but different mass, placed in a vertically vibrated shallow box (large horizontal dimensions and height comparable to the grains' size), there is spontaneous segregation. Once the system is at least partly segregated energy bursts recurrently take place: the horizontal kinetic energy of the heavy particles, that normally is small, suddenly increases an order of magnitude. An explanation of these events is provided based on the existence of a fixed point for an isolated particle bouncing with only vertical motion between the top and bottom plates. Energy bursts occur when clusters of heavy particles start a chain reaction of collisions that transfer vertical energy to horizontal energy producing an expansion of the cluster.
Lattice Vibrations in Chlorobenzenes:
DEFF Research Database (Denmark)
Reynolds, P. A.; Kjems, Jørgen; White, J. W.
1974-01-01
Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K...... by consideration of electrostatic forces or by further anisotropy in the dispersion forces not described in the atom‐atom model. Anharmonic effects are shown to be large, but the dominant features in the temperature variation of frequencies are describable by a quasiharmonic model....
Vibrations of Poroelastic Plates: Mixed Displacement-Pressure Modelisation and Experiments
2009-01-01
International audience; This paper presents the equations of motion of air saturated rectangular poroelastic plates. The model is based on a mixed displacement-pressure formulation of Biot's theory. Two equations of motion are obtained and solved with the Galerkin method for any boundary conditions. These equations take into account the solid-fluid coupling effects. Simulations of the bending vibrations of a rectangular water saturated sandstone and air saturated acoustic foam are performed f...
Off-axis Modal Active Vibration Control Of Rotational Vibrations
Babakhani, B.; de Vries, Theodorus J.A.; van Amerongen, J.
Collocated active vibration control is an effective and robustly stable way of adding damping to the performance limiting vibrations of a plant. Besides the physical parameters of the Active Damping Unit (ADU) containing the collocated actuator and sensor, its location with respect to the
Vibrational relaxation and vibrational cooling in low temperature molecular crystals
Hill, Jeffrey R.; Chronister, Eric L.; Chang, Ta-Chau; Kim, Hackjin; Postlewaite, Jay C.; Dlott, Dana D.
1988-01-01
The processes of vibrational relaxation (VR) and vibrational cooling (VC) are investigated in low temperature crystals of complex molecules, specifically benzene, naphthalene, anthracene, and durene. In the VR process, a vibration is deexcited, while VC consists of many sequential and parallel VR steps which return the crystal to thermal equilibrium. A theoretical model is developed which relates the VR rate to the excess vibrational energy, the molecular structure, and the crystal structure. Specific relations are derived for the vibrational lifetime T1 in each of three regimes of excess vibrational energy. The regimes are the following: Low frequency regime I where VR occurs by emission of two phonons, intermediate frequency regime II where VR occurs by emission of one phonon and one vibration, and high frequency regime III where VR occurs by evolution into a dense bath of vibrational combinations. The VR rate in each regime depends on a particular multiphonon density of states and a few averaged anharmonic coefficients. The appropriate densities of states are calculated from spectroscopic data, and together with available VR data and new infrared and ps Raman data, the values of the anharmonic coefficients are determined for each material. The relationship between these parameters and the material properties is discussed. We then describe VC in a master equation formalism. The transition rate matrix for naphthalene is found using the empirically determined parameters of the above model, and the time dependent redistribution in each mode is calculated.
Motion compensator for holographic motion picture camera
Kurtz, R. L.
1973-01-01
When reference beam strikes target it undergoes Doppler shift dependent upon target velocity. To compensate, object beam is first reflected from rotating cylinder that revolves in direction opposite to target but at same speed. When beam strikes target it is returned to original frequency and is in phase with reference beam. Alternatively this motion compensator may act on reference beam.
Spectroscopic Interpretation: The High Vibrations of CDBrClF
Jung, C; Taylor, H S
2004-01-01
We extract the dynamics implicit in an algebraic fitted model Hamiltonian for the deuterium chromophore's vibrational motion in the molecule CDBrClF. The original model has 4 degrees of freedom, three positions and one representing interbond couplings. A conserved polyad allows in a semiclassical approach the reduction to 3 degrees of freedom. For most quantum states we can identify the underlying motion that when quantized gives the said state. Most of the classifications, identifications and assignments are done by visual inspection of the already available wave function semiclassically transformed from the number representation to a representation on the reduced dimension toroidal configuration space corresponding to the classical action and angle variables. The concentration of the wave function density to lower dimensional subsets centered on idealized simple lower dimensional organizing structures and the behavior of the phase along such organizing centers already reveals the atomic motion. Extremely li...
Dynamical flexibility of discretecontinuous vibrating mechatronic system
Directory of Open Access Journals (Sweden)
A. Buchacz
2008-06-01
Full Text Available Purpose: The application of approximate method for solving the task of assignment the frequency-modal analysis and characteristics of flexibly vibrating mechatronic system, because for considered case of boundary conditions exact and approximate methods for the coordinates are equivalent.Design/methodology/approach: Formulate and solve the problem in the form of a set of differential equations of motion and state equations of the considered mechatronic model of an object Galerkin’s method was used. The considered flexibly vibrating mechanical system is a continuous beam, clamped at one of its ends. An integral part of the mechatronic system is a transducer perfectly bonded to the beam surface.Findings: The parameters of the transducer exert an important influence on the values of natural frequencies and on the form of the characteristics of the discussed mechatronic system.Research limitations/implications: The linear mechanical subsystem and linear electrical subsystem of the mechatronic system were analyzed and the theory Euler-Bernoulli is used for the beam; however, this approach is sufficient for such systems.Practical implications: Global approach is presented in the domain of frequency spectrum analysis. The methods of analysis and the obtained results my give grounds for designing and investigating this type of mechatronic systems.Originality/value: The mechatronic system created from mechanical and electric subsystems with electromechanical bondage has been considered. This approach is different from those considered so far.
Transition Mode Shapes in a Vibrating Drop
Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari
2000-11-01
Vertical, time-periodic vibration of a diaphragm has been used to atomize a primary sessile drop into a fine spray of secondary droplets. The evolution and rate of atomization depend on the coupled dynamics of the sessile drop and the piezoelectrically-driven, low-mass diaphragm. The evolution of the free surface of the drop is characterized by the appearance of a hierarchy of surface waves that we investigated using high-speed imaging and laser vibrometry. At low-driving amplitudes, we see the appearance of time-harmonic axisymmetric waves on the drop's free surface induced by the motion of the contact line. As the vibration amplitude increases, azimuthal waves at the subharmonic of the forcing frequency appear around the periphery of the drop and propagate towards its center. A striking lattice mode emerges upon the breakdown of the axisymmetric wave pattern, followed by the appearance of the highly-agitated free surface of the pre-ejection mode shape. Subsequent to the breakdown of the lattice structure, the frequency of the most energetic mode is a subharmonic of the driving frequency. The complex interaction of the fundamental and subharmonic waves ultimately leads to the breakdown of the free surface and the atomization of the drop.
Vibration energy harvesting for unmanned aerial vehicles
Anton, Steven R.; Inman, Daniel J.
2008-03-01
Unmanned aerial vehicles (UAVs) are a critical component of many military operations. Over the last few decades, the evolution of UAVs has given rise to increasingly smaller aircraft. Along with the development of smaller UAVs, termed mini UAVs, has come issues involving the endurance of the aircraft. Endurance in mini UAVs is problematic because of the limited size of the fuel systems that can be incorporated into the aircraft. A large portion of the total mass of many electric powered mini UAVs, for example, is the rechargeable battery power source. Energy harvesting is an attractive technology for mini UAVs because it offers the potential to increase their endurance without adding significant mass or the need to increase the size of the fuel system. This paper investigates the possibility of harvesting vibration and solar energy in a mini UAV. Experimentation has been carried out on a remote controlled (RC) glider aircraft with a 1.8 m wing span. This aircraft was chosen to replicate the current electric mini UAVs used by the military today. The RC glider was modified to include two piezoelectric patches placed at the roots of the wings and a cantilevered piezoelectric beam installed in the fuselage to harvest energy from wing vibrations and rigid body motions of the aircraft, as well as two thin film photovoltaic panels attached to the top of the wings to harvest energy from sunlight. Flight testing has been performed and the power output of the piezoelectric and photovoltaic devices has been examined.
Nemirovsky, Ricardo; Tierney, Cornelia; Wright, Tracy
1998-01-01
Analyzed two children's use of a computer-based motion detector to make sense of symbolic expressions (Cartesian graphs). Found three themes: (1) tool perspectives, efforts to understand graphical responses to body motion; (2) fusion, emergent ways of talking and behaving that merge symbols and referents; and (3) graphical spaces, when changing…
Summers, M. K.
1977-01-01
Described is a novel approach to the teaching of projectile motion of sixth form level. Students are asked to use an analogue circuit to observe projectile motion and to graph the experimental results. Using knowledge of basic dynamics, students are asked to explain the shape of the curves theoretically. (Author/MA)
Naderyan, Vahid; Hickey, Craig J.; Raspet, Richard
2016-02-01
Wind noise is a problem in seismic surveys and can mask the seismic signals at low frequency. This research investigates ground motions caused by wind pressure and shear stress perturbations on the ground surface. A prediction of the ground displacement spectra using the measured ground properties and predicted pressure and shear stress at the ground surface is developed. Field measurements are conducted at a site having a flat terrain and low ambient seismic noise. Triaxial geophones are deployed at different depths to study the wind-induced ground vibrations as a function of depth and wind velocity. Comparison of the predicted to the measured wind-induced ground displacement spectra shows good agreement for the vertical component but significant underprediction for the horizontal components. To validate the theoretical model, a test experiment is designed to exert controlled normal pressure and shear stress on the ground using a vertical and a horizontal mass-spring apparatus. This experiment verifies the linear elastic rheology and the quasi-static displacements assumptions of the model. The results indicate that the existing surface shear stress models significantly underestimate the wind shear stress at the ground surface and the amplitude of the fluctuation shear stress must be of the same order of magnitude as the normal pressure. Measurement results show that mounting the geophones flush with the ground provides a significant reduction in wind noise on all three components of the geophone. Further reduction in wind noise with depth of burial is small for depths up to 40 cm.
Diffractive Imaging of Coherent Nuclear Motion in Isolated Molecules
Energy Technology Data Exchange (ETDEWEB)
Yang, Jie; Guehr, Markus; Shen, Xiaozhe; Li, Renkai; Vecchione, Theodore; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Hartmann, Nick; Hast, Carsten; Hegazy, Kareem; Jobe, Keith; Makasyuk, Igor; Robinson, Joseph; Robinson, Matthew S.; Vetter, Sharon; Weathersby, Stephen; Yoneda, Charles; Wang, Xijie; Centurion, Martin
2016-10-03
Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 Å and temporal resolution of 230 fs full width at half maximum. The method is not only sensitive to the position but also the shape of the nuclear wave packet.
Diffractive Imaging of Coherent Nuclear Motion in Isolated Molecules
Yang, Jie; Shen, Xiaozhe; Li, Renkai; Vecchione, Theodore; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Hartmann, Nick; Hast, Carsten; Hegazy, Kareem; Jobe, Keith; Makasyuk, Igor; Robinson, Joseph; Robinson, Matthew S; Vetter, Sharon; Weathersby, Stephen; Yoneda, Charles; Wang, Xijie; Centurion, Martin
2016-01-01
Observing the motion of the nuclear wavepackets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wavepacket in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 {\\AA} and temporal resolution of 230 fs full-width at half-maximum (FWHM). The method is not only sensitive to the position but also the shape of the nuclear wavepacket.
Sabanovic, Asif
2011-01-01
"Presents a unified approach to the fundamental issues in motion control, starting from the basics and moving through single degree of freedom and multi-degree of freedom systems In Motion Control Systems, Šabanovic and Ohnishi present a unified approach to very diverse issues covered in motion control systems, offering know-how accumulated through work on very diverse problems into a comprehensive, integrated approach suitable for application in high demanding high-tech products. It covers material from single degree of freedom systems to complex multi-body non-redundant and redundant systems. The discussion of the main subject is based on original research results and will give treatment of the issues in motion control in the framework of the acceleration control method with disturbance rejection technique. This allows consistent unification of different issues in motion control ranging from simple trajectory tracking to topics related to haptics and bilateral control without and with delay in the measure...
Stochastic ground motion simulation
Rezaeian, Sanaz; Xiaodan, Sun; Beer, Michael; Kougioumtzoglou, Ioannis A.; Patelli, Edoardo; Siu-Kui Au, Ivan
2014-01-01
Strong earthquake ground motion records are fundamental in engineering applications. Ground motion time series are used in response-history dynamic analysis of structural or geotechnical systems. In such analysis, the validity of predicted responses depends on the validity of the input excitations. Ground motion records are also used to develop ground motion prediction equations(GMPEs) for intensity measures such as spectral accelerations that are used in response-spectrum dynamic analysis. Despite the thousands of available strong ground motion records, there remains a shortage of records for large-magnitude earthquakes at short distances or in specific regions, as well as records that sample specific combinations of source, path, and site characteristics.
Directory of Open Access Journals (Sweden)
Yushu Bian
2013-01-01
Full Text Available Due to the presence of system flexibility, impact can excite severe large amplitude vibration responses of the flexible robotic manipulator. This impact vibration exhibits characteristics of remarkable nonlinearity and strong energy. The main goal of this study is to put forward an energy-based control method to absorb and attenuate large amplitude impact vibration of the flexible robotic manipulator. The method takes advantage of internal resonance and is implemented through a vibration absorber based on the transfer and dissipation of energy. The addition of the vibration absorber to the flexible arm generates a coupling effect between vibration modes of the system. By means of analysis on 2:1 internal resonance, the exchange of energy is proven to be existent. The impact vibrational energy can be transferred from the arm to the absorber and dissipated through the damping of the absorber. The results of numerical simulations are promising and preliminarily verify that the method is feasible and can be used to combat large amplitude impact vibration of the flexible manipulator undergoing rigid motion.
A programmable broadband low frequency active vibration isolation system for atom interferometry
Tang, Biao; Zhou, Lin; Xiong, Zongyuan; Wang, Jin; Zhan, Mingsheng
2014-09-01
Vibration isolation at low frequency is important for some precision measurement experiments that use atom interferometry. To decrease the vibrational noise caused by the reflecting mirror of Raman beams in atom interferometry, we designed and demonstrated a compact stable active low frequency vibration isolation system. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. With the help of field programmable gate array-based control subsystem, the vibration isolation system performed flexibly and accurately. When the feedback is on, the intrinsic resonance frequency of the system will change from 0.8 Hz to about 0.015 Hz. The vertical vibration (0.01-10 Hz) measured by the in-loop seismometer is reduced by an additional factor of up to 500 on the basis of a passive vibration isolation platform, and we have proved the performance by adding an additional seismometer as well as applying it in the atom interferometry experiment.
Active Vibration Suppression of a 3-DOF Flexible Parallel Manipulator Using Efficient Modal Control
Directory of Open Access Journals (Sweden)
Quan Zhang
2014-01-01
Full Text Available This paper addresses the dynamic modeling and efficient modal control of a planar parallel manipulator (PPM with three flexible linkages actuated by linear ultrasonic motors (LUSM. To achieve active vibration control, multiple lead zirconate titanate (PZT transducers are mounted on the flexible links as vibration sensors and actuators. Based on Lagrange’s equations, the dynamic model of the flexible links is derived with the dynamics of PZT actuators incorporated. Using the assumed mode method (AMM, the elastic motion of the flexible links are discretized under the assumptions of pinned-free boundary conditions, and the assumed mode shapes are validated through experimental modal test. Efficient modal control (EMC, in which the feedback forces in different modes are determined according to the vibration amplitude or energy of their own, is employed to control the PZT actuators to realize active vibration suppression. Modal filters are developed to extract the modal displacements and velocities from the vibration sensors. Numerical simulation and vibration control experiments are conducted to verify the proposed dynamic model and controller. The results show that the EMC method has the capability of suppressing multimode vibration simultaneously, and both the structural and residual vibrations of the flexible links are effectively suppressed using EMC approach.
A programmable broadband low frequency active vibration isolation system for atom interferometry.
Tang, Biao; Zhou, Lin; Xiong, Zongyuan; Wang, Jin; Zhan, Mingsheng
2014-09-01
Vibration isolation at low frequency is important for some precision measurement experiments that use atom interferometry. To decrease the vibrational noise caused by the reflecting mirror of Raman beams in atom interferometry, we designed and demonstrated a compact stable active low frequency vibration isolation system. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. With the help of field programmable gate array-based control subsystem, the vibration isolation system performed flexibly and accurately. When the feedback is on, the intrinsic resonance frequency of the system will change from 0.8 Hz to about 0.015 Hz. The vertical vibration (0.01-10 Hz) measured by the in-loop seismometer is reduced by an additional factor of up to 500 on the basis of a passive vibration isolation platform, and we have proved the performance by adding an additional seismometer as well as applying it in the atom interferometry experiment.
Dynamics Behavior Research on Variable Linear Vibration Screen with Flexible Screen Face
Directory of Open Access Journals (Sweden)
Changlong Du
2014-08-01
Full Text Available In order to enable the variable linear vibration screen with ideal movement behavior of screen surface and efficient screening capacity, five-freedom dynamic model and stability equations of the variable linear vibration screen were established based on power balance method and Hamilton principle. The motion behaviour of screen face was investigated, and − 0.10 m ≤ xf ≤ − 0.04 m was confirmed as the best range of exciting position. With analysis of stability equations, the stable requirement of vibration screen was obtained: the direction angle of exciting force should be 0 ≤ θ ≤ 45°. Screening processes of variable linear vibration screen with flexible screen face, variable linear vibration screen with fixed screen face and linear vibration screen were investigated and compared by numerical simulation method, the results show that variable linear vibration screen with flexible screen face have such characteristics as higher intensity of projection and efficient screening. The correctness of theoretical research and simulation research were verified through experiment, and all of the work would provide some guidance for designing and studying variable linear vibration screen with flexible screen face.
Vibrations and Stability: Solved Problems
DEFF Research Database (Denmark)
Thomsen, Jon Juel
Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003.......Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003....
Studies Of Vibrations In Gearboxes
Choy, Fred K.; Ruan, Yeefeng F.; Tu, Yu K.; Zakrajsek, James J.; Oswald, Fred B.; Coy, John J.; Townsend, Dennis P.
1994-01-01
Three NASA technical memorandums summarize studies of vibrations in gearboxes. Directed toward understanding and reducing gearbox noise caused by coupling of vibrations from meshing gears, through gear shafts and their bearings, to surfaces of gearbox housings. Practical systems in which understanding and reduction of gearbox noise beneficial include helicopter, car, and truck transmissions; stationary geared systems; and gear-driven actuator systems.
Vibrational spectra of ordered perovskites
Corsmit, A.F.; Hoefdraad, H.E.; Blasse, G.
1972-01-01
The vibrational spectra of the molecular M6+O6 (M = Mo, Te, W) group in ordered perovskites of the type Ba2M2+M6+O6 are reported. These groups have symmetry Oh, whereas their site symmetry is also Oh. An assignment of the internal vibrations is presented.
Motion-mode energy method for vehicle dynamics analysis and control
Zhang, Nong; Wang, Lifu; Du, Haiping
2014-01-01
Vehicle motion and vibration control is a fundamental motivation for the development of advanced vehicle suspension systems. In a vehicle-fixed coordinate system, the relative motions of the vehicle between body and wheel can be classified into several dynamic stages based on energy intensity, and can be decomposed into sets of uncoupled motion-modes according to modal parameters. Vehicle motions are coupled, but motion-modes are orthogonal. By detecting and controlling the predominating vehicle motion-mode, the system cost and energy consumption of active suspensions could be reduced. A motion-mode energy method (MEM) is presented in this paper to quantify the energy contribution of each motion-mode to vehicle dynamics in real time. The control of motion-modes is prioritised according to the level of motion-mode energy. Simulation results on a 10 degree-of-freedom nonlinear full-car model with the magic-formula tyre model illustrate the effectiveness of the proposed MEM. The contribution of each motion-mode to the vehicle's dynamic behaviour is analysed under different excitation inputs from road irregularities, directional manoeuvres and braking. With the identified dominant motion-mode, novel cost-effective suspension systems, such as active reconfigurable hydraulically interconnected suspension, can possibly be used to control full-car motions with reduced energy consumption. Finally, discussion, conclusions and suggestions for future work are provided.
The origins of vibration theory
Dimarogonas, A. D.
1990-07-01
The Ionian School of natural philosophy introduced the scientific method of dealing with natural phenomena and the rigorous proofs for abstract propositions. Vibration theory was initiated by the Pythagoreans in the fifth century BC, in association with the theory of music and the theory of acoustics. They observed the natural frequency of vibrating systems and proved that it is a system property and that it does not depend on the excitation. Pythagoreans determined the fundamental natural frequencies of several simple systems, such as vibrating strings, pipes, vessels and circular plates. Aristoteles and the Peripatetic School founded mechanics and developed a fundamental understanding of statics and dynamics. In Alexandrian times there were substantial engineering developments in the field of vibration. The pendulum as a vibration, and probably time, measuring device was known in antiquity, and was further developed by the end of the first millennium AD.
Force Limited Vibration Testing Monograph
Scharton, Terry D.
1997-01-01
The practice of limiting the shaker force in vibration tests was investigated at the NASA Jet Propulsion Laboratory (JPL) in 1990 after the mechanical failure of an aerospace component during a vibration test. Now force limiting is used in almost every major vibration test at JPL and in many vibration tests at NASA Goddard Space Flight Center (GSFC) and at many aerospace contractors. The basic ideas behind force limiting have been in the literature for several decades, but the piezo-electric force transducers necessary to conveniently implement force limiting have been available only in the last decade. In 1993, funding was obtained from the NASA headquarters Office of Chief Engineer to develop and document the technology needed to establish force limited vibration testing as a standard approach available to all NASA centers and aerospace contractors. This monograph is the final report on that effort and discusses the history, theory, and applications of the method in some detail.
Rectification of SEMG as a tool to demonstrate synchronous motor unit activity during vibration.
Sebik, Oguz; Karacan, Ilhan; Cidem, Muharrem; Türker, Kemal S
2013-04-01
The use of surface electromyography (SEMG) in vibration studies is problematic since motion artifacts occupy the same frequency band with the SEMG signal containing information on synchronous motor unit activity. We hypothesize that using a harsher, 80-500 Hz band-pass filter and using rectification can help eliminate motion artifacts and provide a way to observe synchronous motor unit activity that is phase locked to vibration using SEMG recordings only. Multi Motor Unit (MMU) action potentials using intramuscular electrodes along with SEMG were recorded from the gastrocnemius medialis (GM) of six healthy male volunteers. Data were collected during whole body vibration, using vibration frequencies of 30 Hz, 35 Hz, 40 Hz or 50 Hz. A computer simulation was used to investigate the efficacy of filtering under different scenarios: with or without artifacts and/or motor unit synchronization. Our findings indicate that motor unit synchronization took place during WBV as verified by MMU recordings. A harsh filtering regimen along with rectification proved successful in demonstrating motor unit synchronization in SEMG recordings. Our findings were further supported by the results from the computer simulation, which indicated that filtering and rectification was efficient in discriminating motion artifacts from motor unit synchronization. We suggest that the proposed signal processing technique may provide a new methodology to evaluate the effects of vibration treatments using only SEMG. This is a major advantage, as this non-intrusive method is able to overcome movement artifacts and also indicate the synchronization of underlying motor units.
Xu, Lin; Rabotti, Chiara; Mischi, Massimo
2013-03-01
Vibration exercise (VE) has been suggested as an effective methodology to improve muscle strength and power performance. Several studies link the effects of vibration training to enhanced neuromuscular demand, typically ascribed to involuntary reflex mechanisms. However, the underlying mechanisms are still unclear, limiting the identification of the most appropriate vibration training protocols. This study concerns the realization of a new vibration exercise system for the upper limbs. Amplitude, frequency, and baseline of the vibrating force, which is generated by an electromechanical actuator, can be adjusted independently. A second order model is employed to identify the relation between the generated force and the input voltage driving the actuator. Our results show a high correlation (0.99) between the second order model fit and the measured data, ensuring accurate control on the supplied force. The level of neuromuscular demand imposed by the system on the targeted muscles can be estimated by electromyography (EMG). However, EMG measurements during VE can be severely affected by motion artifacts. An adaptive least mean square algorithm is proposed to remove motion artifacts from the measured EMG data. Preliminary validation with seven volunteers showed excellent motion artifact removal, enabling reliable evaluation of the neuromuscular activation.
Vibration Response and Power Flow Characteristics of a Flexible Manipulator with a Moving Base
Directory of Open Access Journals (Sweden)
Yufei Liu
2015-01-01
Full Text Available Flexible manipulator generally can be modeled as a coupling system with a flexible beam and a rigid moving base. This paper investigates the vibration responses and power flow of a flexible manipulator with a moving base (FMMB. Considering the motion characteristics of the rigid base, the moving base is modeled to have a motion with disturbances, and the dynamic model of the FMMB is established. With the dynamic model, vibration responses of the FMMB for the rigid base having disturbance velocities and accelerations are specifically presented. Subsequently, to investigate the effect of the disturbances on the vibration energy distributions of the FMMB, power flow of the FMMB is exhibited. To verify the dynamic model, an ADAMS physical model of the FMMB is constructed. It reveals that the motion characteristics of the rigid base have a noticeable effect on the vibration responses and power flow of the FMMB and should be considered. The results are significant and contribute to the vibration control of flexible manipulators.
A nonlinear piezoelectric energy harvester for various mechanical motions
Energy Technology Data Exchange (ETDEWEB)
Fan, Kangqi, E-mail: kangqifan@gmail.com [School of Mechano-Electronic Engineering, Xidian University, Xi' an 710071 (China); Department of Electrical and Computer Engineering, University of Alberta, Edmonton T6G 2V4 (Canada); Chang, Jianwei; Liu, Zhaohui; Zhu, Yingmin [School of Mechano-Electronic Engineering, Xidian University, Xi' an 710071 (China); Pedrycz, Witold [Department of Electrical and Computer Engineering, University of Alberta, Edmonton T6G 2V4 (Canada)
2015-06-01
This study presents a nonlinear piezoelectric energy harvester with intent to scavenge energy from diverse mechanical motions. The harvester consists of four piezoelectric cantilever beams, a cylindrical track, and a ferromagnetic ball, with magnets integrated to introduce the magnetic coupling between the ball and the beams. The experimental results demonstrate that the harvester is able to collect energy from various directions of vibrations. For the vibrations perpendicular to the ground, the maximum peak voltage is increased by 3.2 V and the bandwidth of the voltage above 4 V is increased by more than 4 Hz compared to the results obtained when using a conventional design. For the vibrations along the horizontal direction, the frequency up-conversion is realized through the magnetic coupling. Moreover, the proposed design can harvest energy from the sway motion around different directions on the horizontal plane. Harvesting energy from the rotation motion is also achieved with an operating bandwidth of approximately 6 Hz.
Barbarien, Joeri; Munteanu, Adrian; Verdicchio, Fabio; Andreopoulos, Yiannis; Cornelis, Jan P.; Schelkens, Peter
2004-11-01
Modern video coding applications require transmission of video data over variable-bandwidth channels to a variety of terminals with different screen resolutions and available computational power. Scalable video coding is needed to optimally support these applications. Recently proposed wavelet-based video codecs employing spatial domain motion compensated temporal filtering (SDMCTF) provide quality, resolution and frame-rate scalability while delivering compression performance comparable to that of the state-of-the-art non-scalable H.264-codec. These codecs require scalable coding of the motion vectors in order to support a large range of bit-rates with optimal compression efficiency. Scalable motion vector coding algorithms based on the integer wavelet transform followed by embedded coding of the wavelet coefficients were recently proposed. In this paper, a new and fundamentally different scalable motion vector codec (MVC) using median-based motion vector prediction is proposed. Extensive experimental results demonstrate that the proposed MVC systematically outperforms the wavelet-based state-of-the-art solutions. To be able to take advantage of the proposed scalable MVC, a rate allocation mechanism capable of optimally dividing the available rate among texture and motion information is required. Two rate allocation strategies are proposed and compared. The proposed MVC and rate allocation schemes are incorporated into an SDMCTF-based video codec and the benefits of scalable motion vector coding are experimentally demonstrated.
Directory of Open Access Journals (Sweden)
Chi-Ying Lin
2017-03-01
Full Text Available In this paper, we report on the use of piezoelectric sensors and actuators for the active suppression of vibrations associated with the motor-driven rotation of thin flexible plate held vertically. Motor-driven flexible structures are multi-input multi-output systems. The design of active vibration-suppression controllers for these systems is far more challenging than for flexible structures with a fixed end, due to the effects of coupling and nonlinear vibration behavior generated in structures with poor damping. To simplify the design of the controller and achieve satisfactory vibration suppression, we treated the coupling of vibrations caused by the rotary motion of the thin flexible plate as external disturbances and system uncertainties. We employed an adaptive fuzzy sliding mode control algorithm in the design of a single-input–single-output controller for the suppression of vibrations using piezoelectric sensors and actuators. We also used a repetitive control system to reduce periodic vibrations associated with the repetitive motions induced by the motor. Experimental results demonstrate that the hybrid intelligent control approach proposed in this study can suppress complex vibrations caused by modal excitation, coupling effects, and periodic external disturbances.
The Stability Conditions of the Pump Structure Vibration
Directory of Open Access Journals (Sweden)
Nassir Hassan Abdul Hussain Al Hariri
2012-01-01
Full Text Available The general approach of this research is to assume that the small nonlinearity can be separated from the linear part of the equation of motion. The effect of the dynamic fluid force on the pump structure system is considered vibrates at its natural frequency but the amplitude is determined by the initial conditions. If the motion of the system tends to increase the energy of the pump structure system, the vibration amplitude will increase and the pump structure system is considered to be unstable. A suitable MATLAB program was used to predict the stability conditions of the pump structure vibration. The present research focuses on fluid pump problems, namely, the role played by damping coefficient C, damping factor D and angular speed ? (termed the ratio ( and the determining stability of a centrifugal pump structure. The data demonstrate substantial rotor dynamic effects, a destabilizing chart appears to be inversely proportional to the D, C, and ?, and resonance changes significantly with flow rate.
Optimal vibration control of curved beams using distributed parameter models
Liu, Fushou; Jin, Dongping; Wen, Hao
2016-12-01
The design of linear quadratic optimal controller using spectral factorization method is studied for vibration suppression of curved beam structures modeled as distributed parameter models. The equations of motion for active control of the in-plane vibration of a curved beam are developed firstly considering its shear deformation and rotary inertia, and then the state space model of the curved beam is established directly using the partial differential equations of motion. The functional gains for the distributed parameter model of curved beam are calculated by extending the spectral factorization method. Moreover, the response of the closed-loop control system is derived explicitly in frequency domain. Finally, the suppression of the vibration at the free end of a cantilevered curved beam by point control moment is studied through numerical case studies, in which the benefit of the presented method is shown by comparison with a constant gain velocity feedback control law, and the performance of the presented method on avoidance of control spillover is demonstrated.
Influence of vibration mode on the screening process
Institute of Scientific and Technical Information of China (English)
Dong Hailin; Liu Chusheng; Zhao Yuemin; Zhao Lala
2013-01-01
The screening of particles with different vibration modes was simulated by means of a 3D discrete element method (3D-DEM).The motion and penetration of the particles on the screen deck were analyzed for linear,circular and elliptical vibration of the screen.The results show that the travel velocity of the particles is the fastest,but the screening efficiency is the lowest,for the linear vibration mode.The circular motion resulted in the highest screening efficiency,but the lowest particle travel velocity.In the steady state the screening efficiency for each mode is seen to increase gradually along the longitudinal direction of the deck.The screening efficiency increment of the circular mode is the largest while the linear mode shows the smallest increment.The volume fraction of near-mesh size particles at the underside is larger than that of small size particles all along the screen deck.Linear screening mode has more nearmesh and small size particles on the first three deck sections,and fewer on the last two sections,compared to the circular or elliptical modes.
VIBRATION MEASUREMENTS IN A RHIC QUADRUPOLE AT CRYOGENIC TEMPERATURES.
Energy Technology Data Exchange (ETDEWEB)
JAIN, A.; AYDIN, S.; HE, P.; ANERELLA, M.; GANETIS, G.; HARRISON, M.; PARKER, B.; PLATE, S.
2005-10-17
One of the concerns in using compact superconducting magnets in the final focus region of the ILC is the influence of the cryogen flow on the vibration characteristics. As a first step towards characterizing such motion at nanometer levels, a project was undertaken at BNL to measure the vibrations in a spare RHIC quadrupole under cryogenic conditions. Given the constraints of cryogenic operation, and limited space available, it was decided to use a dual head laser Doppler vibrometer for this work. The performance of the laser vibrometer was tested in a series of room temperature tests and compared with results from Mark L4 geophones. The laser system was then used to measure the vibration of the cold mass of the quadrupole with respect to the outside warm enclosure. These measurements were carried out both with and without the flow of cold helium through the magnet. The results indicate only a minor increase in motion in the horizontal direction (where the cold mass is relatively free to move).
Random vibration movements of liquid nanosized Pb inclusions in Al
Energy Technology Data Exchange (ETDEWEB)
Johnson, E.; Andersen, J.S.; Levinsen, M.; Steenstrup, S.; Prokofjev, S.; Zhilin, V.; Dahmen, U.; Radetic, T.; Turner, J.H
2004-07-15
Transmission electron microscopy has been used to study the behavior of liquid nanosized Pb inclusions in Al ribbons made by rapid solidification. In situ heating experiments carried out in the temperature range from around 375 to 450 deg. C have shown that liquid inclusions with sizes from around 10-50 nm, that are trapped on dislocations, perform random vibrations around their positions of attachment with vibration periods of some fractions of seconds. The amplitudes of the vibrations in directions perpendicular to the dislocations are a few nanometers, while the motion in directions parallel to the dislocations can be more than an order of magnitude larger. Under conditions where two or more inclusions, attached to a dislocation line, display one-dimensional random motion the inclusions are rarely seen to coalesce. Movement of the inclusions has been monitored by video and shorter sequences have been digitized and analyzed frame-by-frame. The analysis shows that the step lengths have Gaussian distributions indicative of random walks. Fractal analysis of the paths shows that the fractal dimension is close to two which agrees well with the observations that the inclusions carry out linear random walks in a confined space.
Road vehicle-induced vibration control of microelectronics facilities
Institute of Scientific and Technical Information of China (English)
Guo Anxin; Xu Youlin; Li Hui
2005-01-01
A hybrid control platform is investigated in this paper to mitigate microvibrations to a group of vibrationsensitive equipment installed in a microelectronics facility subject to nearby road vehicle-induced horizontal and vertical ground motions. The hybrid control platform, on which microelectronics equipment is installed, is mounted on a building floor through a series of passive mounts and controlled by hydraulic actuators in both horizontal and vertical directions. The control platform is an elastic body with significant bending modes of vibration, and a sub-optimal control algorithm is used to manipulate the hydraulic actuators with actuator dynamics included. The finite element model and the equations of motion of the coupled platform-building system are then established in the absolute coordinate to facilitate the feedback control and performance evaluation of the platform. The horizontal and vertical ground vibrations at the base of the building induced by nearby moving road vehicles are assumed to be stationary random processes. A typical three-story microelectronics building is selected as a case study. The case study shows that the vertical vibration of the microelectronics building is higher than the horizontal. The use of a hybrid control platform can effectively reduce both horizontal and vertical microvibrations of the microelectronics equipment to the level which satisfies the stringent microscale velocity requirement specified in the Bolt Beranek & Newman (BBN) criteria.
Inflation and Cyclotron Motion
Greensite, Jeff
2016-01-01
We consider, in the context of a braneworld cosmology, the motion of the universe coupled to a four-form gauge field, with constant field strength, defined in higher dimensions. It is found, under rather general initial conditions, that in this situation there is a period of exponential inflation combined with cyclotron motion in the inflaton field space. The main effect of the cyclotron motion is that conditions on the flatness of the inflaton potential, which are typically necessary for exponential inflation, can be evaded. There are Landau levels associated with the four-form gauge field, and these correspond to quantum excitations of the inflaton field.
Microgravity Active Vibration Isolation System on Parabolic Flights
Dong, Wenbo; Pletser, Vladimir; Yang, Yang
2016-07-01
The Microgravity Active Vibration Isolation System (MAIS) aims at reducing on-orbit vibrations, providing a better controlled lower gravity environment for microgravity physical science experiments. The MAIS will be launched on Tianzhou-1, the first cargo ship of the China Manned Space Program. The principle of the MAIS is to suspend with electro-magnetic actuators a scientific payload, isolating it from the vibrating stator. The MAIS's vibration isolation capability is frequency-dependent and a decrease of vibration of about 40dB can be attained. The MAIS can accommodate 20kg of scientific payload or sample unit, and provide 30W of power and 1Mbps of data transmission. The MAIS is developed to support microgravity scientific experiments on manned platforms in low earth orbit, in order to meet the scientific requirements for fluid physics, materials science, and fundamental physics investigations, which usually need a very quiet environment, increasing their chances of success and their scientific outcomes. The results of scientific experiments and technology tests obtained with the MAIS will be used to improve future space based research. As the suspension force acting on the payload is very small, the MAIS can only be operative and tested in a weightless environment. The 'Deutsches Zentrum für Luft- und Raumfahrt e.V.' (DLR, German Aerospace Centre) granted a flight opportunity to the MAIS experiment to be tested during its 27th parabolic flight campaign of September 2015 performed on the A310 ZERO-G aircraft managed by the French company Novespace, a subsidiary of the 'Centre National d'Etudes Spatiales' (CNES, French Space Agency). The experiment results confirmed that the 6 degrees of freedom motion control technique was effective, and that the vibration isolation performance fulfilled perfectly the expectations based on theoretical analyses and simulations. This paper will present the design of the MAIS and the experiment results obtained during the
Nonlinear dynamic vibration absorbers with a saturation
Febbo, M.; Machado, S. P.
2013-03-01
The behavior of a new type of nonlinear dynamic vibration absorber is studied. A distinctive characteristic of the proposed absorber is the impossibility to extend the system to infinity. The mathematical formulation is based on a finite extensibility nonlinear elastic potential to model the saturable nonlinearity. The absorber is attached to a single degree-of-freedom linear/nonlinear oscillator subjected to a periodic external excitation. In order to solve the equations of motion and to analyze the frequency-response curves, the method of averaging is used. The performance of the FENE absorber is evaluated considering a variation of the nonlinearity of the primary system, the damping and the linearized frequency of the absorber and the mass ratio. The numerical results show that the proposed absorber has a very good efficiency when the nonlinearity of the primary system increases. When compared with a cubic nonlinear absorber, for a large nonlinearity of the primary system, the FENE absorber shows a better effectiveness for the whole studied frequency range. A complete absence of quasi-periodic oscillations is also found for an appropriate selection of the parameters of the absorber. Finally, direct integrations of the equations of motion are performed to verify the accuracy of the proposed method.
Meng, Deshan; Wang, Xueqian; Xu, Wenfu; Liang, Bin
2017-05-01
For a space robot with flexible appendages, vibrations of flexible structure can be easily excited during both orbit and/or attitude maneuvers of the base and the operation of the manipulators. Hence, the pose (position and attitude) of the manipulator's end-effector will greatly deviate from the desired values, and furthermore, the motion of the manipulator will trigger and exacerbate vibrations of flexible appendages. Given lack of the atmospheric damping in orbit, the vibrations will last for quite a while and cause the on-orbital tasks to fail. We derived the rigid-flexible coupling dynamics of a space robot system with flexible appendages and established a coupling model between the flexible base and the space manipulator. A specific index was defined to measure the coupling degree between the flexible motion of the appendages and the rigid motion of the end-effector. Then, we analyzed the dynamic coupling for different conditions, such as modal displacements, joint angles (manipulator configuration), and mass properties. Moreover, the coupling map was adopted and drawn to represent the coupling motion. Based on this map, a trajectory planning method was addressed to suppress structure vibration. Finally, simulation studies of typical cases were performed, which verified the proposed models and method. This work provides a theoretic basis for the system design, performance evaluation, trajectory planning, and control of such space robots.
Mode-selective vibrational modulation of charge transport in organic electronic devices
Bakulin, Artem A.
2015-08-06
The soft character of organic materials leads to strong coupling between molecular, nuclear and electronic dynamics. This coupling opens the way to influence charge transport in organic electronic devices by exciting molecular vibrational motions. However, despite encouraging theoretical predictions, experimental realization of such approach has remained elusive. Here we demonstrate experimentally that photoconductivity in a model organic optoelectronic device can be modulated by the selective excitation of molecular vibrations. Using an ultrafast infrared laser source to create a coherent superposition of vibrational motions in a pentacene/C60 photoresistor, we observe that excitation of certain modes in the 1,500–1,700 cm−1 region leads to photocurrent enhancement. Excited vibrations affect predominantly trapped carriers. The effect depends on the nature of the vibration and its mode-specific character can be well described by the vibrational modulation of intermolecular electronic couplings. This presents a new tool for studying electron–phonon coupling and charge dynamics in (bio)molecular materials.
Non-planar vibrations of a string in the presence of a boundary obstacle
Singh, Harkirat; Wahi, Pankaj
2017-02-01
We analyze planar and non-planar motions of a string vibrating against a unilateral curved obstacle. Our model incorporates the change in tension due to stretching of the string, which introduces nonlinear coupling between motions in mutually perpendicular directions, as well as the wrapping nonlinearity due to the presence of the obstacle. The system of equations has been discretized by assuming functional form of the displacements which satisfies all the geometrical boundary conditions. This discretized system is then used to investigate the various motions possible both in the absence as well as the presence of the obstacle. In the absence of the obstacle, there are infinitely many planar and two non-planar motions viz. a circular trajectory and a precessing elliptical trajectory for a fixed magnitude of the disturbance. In contrast, the string has only one planar motion when the obstacle is present and two non-planar motions, either an oscillating orbit or a whirling orbit depending on the magnitude of the initial disturbance. To obtain the transition from oscillating to whirling orbits, we perform a stability analysis of the planar motion using Floquet theory. This analysis reveals that there exists a critical amplitude below which the planar motion is neutrally stable and the typical trajectories are ellipses with major and minor radii changing both in magnitude and direction. Beyond the critical amplitude, the planar motion is unstable and we get whirling trajectories which are precessing ellipses again with varying major and minor radii. We further study the effect of changing obstacle parameters on the critical amplitude, and obtain the stability boundaries in the space spanned by the obstacle parameters and the amplitude of the planar vibration. We obtain some interesting values of the obstacle parameters for which small and large amplitude planar motions are stable resulting in oscillating ellipses while motions with intermediate amplitudes are unstable
Ambient Vibration Test on Reinforced Concrete Bridges
Directory of Open Access Journals (Sweden)
Idris Nurul Shazwin
2016-01-01
Full Text Available An investigation was carried out to determine dynamic characteristic of reinforced concrete (RC bridges by using ambient vibration test (AVT. The ambient vibration sources on bridges may come from traffic, wind, wave motion and seismic events. AVT describes the dynamic characteristics of the bridge and ground by measuring the natural frequencies using highly sensitive seismometer sensor. This test is beneficial due to light weight equipment and smaller number of operator required, cheap and easy to be handled. It is able to give a true picture of the bridge dynamic behavior without any artificial force excitation when vibration data is recorded. A three-span reinforced concrete bridge located in Sri Medan, Batu Pahat, Johor was measured by using microtremor equipment consist of three units of 1 Hz eigenfrequency passive sensors used in this test was performed in normal operating condition without excitation required from any active sources or short period noise perturbations. Ten measurements were conducted on the bridge deck and ten measurements on the ground surface in order to identify the natural frequencies of the bridge. Several peak frequencies were identified from three components of Fourier Amplitude Spectra (FAS in transverse (North-South, longitudinal (East-West and vertical (Up-Down direction as well as squared average Horizontal to Vertical Spectral Ratio (HVSR of ground response, computed by using Geopsy software. From the result, it was expected the bridge have five vibration modes frequencies in the range of 1.0 Hz and 7.0 Hz with the first two modes in the transverse and longitudinal direction having a frequency 1.0 Hz, the third mode is 2.2 Hz in transverse direction, fourth and fifth mode is 5.8 Hz and 7.0 Hz. For ground natural frequencies are in range 1.0 Hz to 1.3 Hz for North-South direction and 1.0 Hz to 1.6 Hz for East-West direction. Finally the results are compared with several empirical formulas for simple
DOWNHOLE VIBRATION MONITORING AND CONTROL SYSTEM
Energy Technology Data Exchange (ETDEWEB)
Martin E. Cobern
2003-04-01
The project continues to advance approximately per the revised (14-month) schedule. Tasks 1-3 (Modeling, Specification and Design) are all essentially complete. Work has begun on designing the test equipment for the Test and Evaluation (Tasks 4 & 5.) One of the intents of this project is to not only dampen vibration above the damper, but to also dampen vibrations below the damper. This is accomplished by smoothing out the discontinuities as the bit drills ahead. The model has the capability to simulate the drilling looking at the depth of cut along the discontinuities. It can also look at the amount of time that the bit is in contact with the formation. It is found that under some conditions the vibrations increased the discontinuities due to resonant conditions. In the ideal situation, the damper reduces the discontinuities and smooths out the drilling. APS looked at a wide range of spring stiffness and damping properties to determine the optimum damper. Spring rates of 10,000 lb/in to 60,000 lbs/in were analyzed. The best compromise is at 30,000 lb/in for the 6 3/4 inch tool. Low spring rates would require large displacements for the damper, while stiff springs do not provide enough motion for the damper. Several damping concepts were analyzed: (1) The first thought was to have a damper providing high damping in the upward direction and low damping in the downward direction. It was found that this increased the vibration by wallowing out the troughs of the discontinuities leading to increased displacements at the bit. (2) Another method investigated was having increased damping at high acceleration levels and less damping at lower acceleration levels. This gave improved results. (3) Constant damping so far provides the damping situation. With the proper damping level the damper can smooth out the discontinuities and provide smooth drilling. However, the damping values are different for different drilling conditions. Different WOB and ROP require different damping
Han, Dongjia; Xue, Bing; Du, Juan; Kobayashi, Takayoshi; Miyatake, Tomohiro; Tamiaki, Hitoshi; Xing, Xin; Yuan, Wei; Li, Yanyan; Leng, Yuxin
2016-09-21
Quantum coherences between excitonic states are believed to have a substantial impact on excitation energy transfer in photosynthetic systems. Here, the excitonic and vibrational coherence relaxation dynamics of artificially synthetic chlorosomes are studied by a sub 7 fs negative-time-delay laser spectroscopy at room temperature. The results provide direct evidence for the quantum coherence of the excitonic dephasing time of 23 ± 1 fs at physiologically relevant temperatures, which is significant in the initial step of energy transfer in chlorosome or chlorosome-like photosynthetic systems. Meanwhile, coherent molecular vibrations in the excited state are also detected without the effect of wave-packet motion in the ground state, which shows that the excited state wave-packet motion contributes greatly to the vibrational modes of ∼150 and ∼1340 cm(-1) in artificial chlorosome systems.
Multiple-support seismic response of Bosporus Suspension Bridge for various random vibration methods
Directory of Open Access Journals (Sweden)
Süleyman Adanur
2016-06-01
Full Text Available This paper presents a study about the spatial variability effects of ground motions on the dynamic behavior of a suspension bridge by a random vibration based spectral analysis approach and two response spectrum methods. Bosphorus Suspension Bridge built in Turkey and connects Europe to Asia in Istanbul is selected as a numerical example. The spatial variability of ground motions between the support points is taken into account with a coherency function that characterizes the incoherence, wave-passage and site-response effects. Power spectral density function and response spectrum values used in random vibration analyses are determined depending on the recordings of August 17, 1999, Kocaeli, Turkey earthquake. From the results, it can be observed that the structural responses for each random vibration analysis depend largely on the intensity and frequency contents of power spectral density functions.
Influence of severe vibrations on the visual perception of video sequences
Stern, Adrian; Fisher, E.; Rotman, Stanley R.; Kopeika, Norman S.
2000-12-01
There are two kinds of video image sequence distortions caused by vibration of the camera. The first is the vibration of the line-of-sight causing location changes of the scene in successive frames. The second effect is the blur of each frame of the sequence due to frame motion during its exposure. In this work, the relative effects of these two types of degradations on the ability of observers to recognize targets are investigated. This study is useful for evaluating the amount of effort required to compensate each effect. We found that the threshold contrast needed to recognize a target in a vibrating video sequence under certain conditions is more affected by the motion blur of each frame than the oscillation of the line-of-sight. For digital sequence restoration methods, this study determines the required precision of the deblurring and registration processes. It shows that the deblurring process should not be neglected as it often is.
Vibration Measurements to Study the Effect of Cryogen Flow in Superconducting Quadrupole.
Energy Technology Data Exchange (ETDEWEB)
He,P.; Anerella, M.; aydin, S.; Ganetis, G. Harrison, M.; Jain, A.; Parker, B.
2007-06-25
The conceptual design of compact superconducting magnets for the International Linear Collider final focus is presently under development. A primary concern in using superconducting quadrupoles is the potential for inducing additional vibrations from cryogenic operation. We have employed a Laser Doppler Vibrometer system to measure the vibrations in a spare RHIC quadrupole magnet under cryogenic conditions. Some preliminary results of these studies were limited in resolution due to a rather large motion of the laser head as well as the magnet. As a first step towards improving the measurement quality, a new set up was used that reduces the motion of the laser holder. The improved setup is described, and vibration spectra measured at cryogenic temperatures, both with and without helium flow, are presented.
Electromagnetic Vibration Energy Harvester Using Springless Proof Mass and Ferrofluid as a Lubricant
Chae, S. H.; Ju, S.; Choi, Y.; Jun, S.; Park, S. M.; Lee, S.; Lee, H. W.; Ji, C.-H.
2013-12-01
This paper presents an electromagnetic energy harvester using an array of rectangular permanent magnets as springless proof mass and ferrofluid as a lubricating material. Lateral motion of the multi-pole magnet array generates voltage across an array of copper windings formed under the aluminum channel in response to low frequency external vibrations such as human-body-induced motion. A proof-of-concept device has been fabricated and output voltage has been measured at various input frequencies and accelerations provided by a vibration exciter. Device with ferrofluid lubrication generated maximum open-circuit voltage of 0.47V at 3g vibration at 12Hz, which is 8% higher than that of the device without lubricant. Maximum output power of 71.26μW has been obtained at 40.8Ω with the device with ferrofluid lubrication.
Designing Motion Gesture Interfaces in Mobile Phones for Blind People
Institute of Scientific and Technical Information of China (English)
任向实
2014-01-01
Despite the existence of advanced functions in smartphones, most blind people are still using old-fashioned phones with familiar layouts and dependence on tactile buttons. Smartphones support accessibility features including vibration, speech and sound feedback, and screen readers. However, these features are only intended to provide feedback to user commands or input. It is still a challenge for blind people to discover functions on the screen and to input the commands. Although voice commands are supported in smartphones, these commands are difficult for a system to recognize in noisy environments. At the same time, smartphones are integrated with sophisticated motion sensors, and motion gestures with device tilt have been gaining attention for eyes-free input. We believe that these motion gesture interactions offer more efficient access to smartphone functions for blind people. However, most blind people are not smartphone users and they are aware of neither the affordances available in smartphones nor the potential for interaction through motion gestures. To investigate the most usable gestures for blind people, we conducted a user-defined study with 13 blind participants. Using the gesture set and design heuristics from the user study, we implemented motion gesture based interfaces with speech and vibration feedback for browsing phone books and making a call. We then conducted a second study to investigate the usability of the motion gesture interface and user experiences using the system. The findings indicated that motion gesture interfaces are more efficient than traditional button interfaces. Through the study results, we provided implications for designing smartphone interfaces.
Refocusing vibrating targets in SAR images
Wang, Qi; Santhanam, Balu; Pepin, Matthew; Atwood, Tom; Hayat, Majeed M.
2012-06-01
In synthetic-aperture radar (SAR) returned signals, ground-target vibrations introduce a phase modulation that is linearly proportional to the vibration displacement. Such modulation, termed the micro-Doppler effect, introduces ghost targets along the azimuth direction in reconstructed SAR images that prevents SAR from forming focused images of the vibrating targets. Recently, a discrete fractional Fourier transform (DFrFT) based method was developed to estimate the vibration frequencies and instantaneous vibration accelerations of the vibrating targets from SAR returned signals. In this paper, a demodulation-based algorithm is proposed to reconstruct focused SAR images of vibrating targets by exploiting the estimation results of the DFrFT-based vibration estimation method. For a single-component harmonic vibration, the history of the vibration displacement is first estimated from the estimated vibration frequency and the instantaneous vibration accelerations. Then a reference signal whose phase is modulated by the estimated vibration displacement with a delay of 180 degree is constructed. After that, the SAR phase history from the vibration target is multiplied by the reference signal and the vibration-induced phase modulation is canceled. Finally, the SAR image containing the re-focused vibration target is obtained by applying the 2-D Fourier transform to the demodulated SAR phase history. This algorithm is applied to simulated SAR data and successfully reconstructs the SAR image containing the re-focused vibrating target.
Schnick, Jeffrey W.
1994-01-01
Presents an exercise that attempts to correct for the common discrepancies between theoretical and experimental predictions concerning projectile motion using a spring-loaded projectile ball launcher. Includes common correction factors for student use. (MVL)
Projectile Motion with Mathematica.
de Alwis, Tilak
2000-01-01
Describes how to use the computer algebra system (CAS) Mathematica to analyze projectile motion with and without air resistance. These experiments result in several conjectures leading to theorems. (Contains 17 references.) (Author/ASK)
Lamb, William G.
1985-01-01
Explains a projectile motion experiment involving a bow and arrow. Procedures to measure "muzzle" velocity, bow elastic potential energy, range, flight time, wind resistance, and masses are considered. (DH)
Mathisson's helical motions demystified
Costa, L Filipe O; Zilhão, Miguel
2012-01-01
The motion of spinning test particles in general relativity is described by Mathisson-Papapetrou-Dixon equations, which are undetermined up to a spin supplementary condition, the latter being today still an open question. The Mathisson-Pirani (MP) condition is known to lead to rather mysterious helical motions which have been deemed unphysical, and for this reason discarded. We show that these assessments are unfounded and originate from a subtle (but crucial) misconception. We discuss the kinematical explanation of the helical motions, and dynamically interpret them through the concept of hidden momentum, which has an electromagnetic analogue. We also show that, contrary to previous claims, the frequency of the helical motions coincides exactly with the zitterbewegung frequency of the Dirac equation for the electron.
Travelers' Health: Motion Sickness
... Disease Directory Resources Resources for Travelers Adventure Travel Animal Safety Blood Clots Bug Bites Business Travel Cold ... motion sickness. Adding distractions—controlling breathing, listening to music, or using aromatherapy scents such as mint or ...
Galus, Pamela J.
2002-01-01
Presents a variety of activities that support the development of an understanding of Newton's laws of motion. Activities use toy cars, mobile roads, and a seat-of-nails. Includes a scoring rubric. (DDR)
Grambo, Gregory
1998-01-01
Presents activities on persistence of vision that involve students in a hands-on approach to the study of early methods of creating motion pictures. Students construct flip books, a Zoetrope, and an early movie machine. (DDR)
Energy Technology Data Exchange (ETDEWEB)
Teng, L.C.
1989-01-01
The magnetic field in an accelerator or a storage ring is usually so designed that the horizontal (x) and the vertical (y) motions of an ion are uncoupled. However, because of imperfections in construction and alignment, some small coupling is unavoidable. In this lecture, we discuss in a general way what is known about the behaviors of coupled motions in two degrees-of-freedom. 11 refs., 6 figs.
Vibration analysis of defective graphene sheets using nonlocal elasticity theory
Namin, S. F. Asbaghian; Pilafkan, R.
2017-09-01
Many papers have studied the free vibration of graphene sheets. However, all this papers assumed their atomic structure free of any defects. Nonetheless, they actually contain some defects including single vacancy, double vacancy and Stone-Wales defects. This paper, therefore, investigates the free vibration of defective graphene sheets, rather than pristine graphene sheets, via nonlocal elasticity theory. Governing equations are derived using nonlocal elasticity and the first-order shear deformation theory (FSDT). The influence of structural defects on the vibration of graphene sheets is considered by applying the mechanical properties of defective graphene sheets. Afterwards, these equations solved using generalized differential quadrature method (GDQ). The small-scale effect is applied in the governing equations of motion by nonlocal parameter. The effects of different defect types are inspected for graphene sheets with clamped or simply-supported boundary conditions on all sides. It is shown that the natural frequencies of graphene sheets decrease by introducing defects to the atomic structure. Furthermore, it is found that the number of missing atoms, shapes and distributions of structural defects play a significant role in the vibrational behavior of graphene. The effect of vacancy defect reconstruction is also discussed in this paper.
A cylindrical standing wave ultrasonic motor using bending vibration transducer.
Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun
2011-07-01
A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200V(rms).
Directory of Open Access Journals (Sweden)
D. Tsaousis
2008-01-01
Full Text Available Ever since the first century A.D. there have been relative descriptions of known devices as well as manufactures for the creation of perpetual motion machines. Although physics has led, with two thermodynamic laws, to the opinion that a perpetual motion machine is impossible to be manufactured, inventors of every age and educational level appear to claim that they have invented something «entirely new» or they have improved somebody else’s invention, which «will function henceforth perpetually»! However the fact of the failure in manufacturing a perpetual motion machine till now, it does not mean that countless historical elements for these fictional machines become indifferent. The discussion on every version of a perpetual motion machine on the one hand gives the chance to comprehend the inventor’s of each period level of knowledge and his way of thinking, and on the other hand, to locate the points where this «perpetual motion machine» clashes with the laws of nature and that’s why it is impossible to have been manufactured or have functioned. The presentation of a new «perpetual motion machine» has excited our interest to locate its weak points. According to the designer of it the machine functions with the work produced by the buoyant force
Molecular vibrations the theory of infrared and Raman vibrational spectra
Wilson, E Bright; Cross, Paul C
1980-01-01
Pedagogical classic and essential reference focuses on mathematics of detailed vibrational analyses of polyatomic molecules, advancing from application of wave mechanics to potential functions and methods of solving secular determinant.
Vibrational Spectroscopy of Methyl benzoate
Maiti, Kiran Sankar
2014-01-01
Methyl benzoate (MB) is studied as a model compound for the development of new IR pulse schemes with possible applicability to biomolecules. Anharmonic vibrational modes of MB are calculated on different level (MP2, SCS, CCSD(T) with varying basis sets) ab-initio PESs using the vibrational self-consistent field (VSCF) method and its correlation corrected extensions. Dual level schemes, combining different quantum chemical methods for diagonal and coupling potentials, are systematically studied and applied successfully to reduce the computational cost. Isotopic substitution of {\\beta}-hydrogen by deuterium is studied to obtain a better understanding of the molecular vibrational coupling topology.
Magnetic damping of ski vibrations
Energy Technology Data Exchange (ETDEWEB)
Yonnet, J.-P. [CNRS, St. Martin d' Heres (France). Lab. d' Electrotech. de Grenoble; Patton, A.C.; Philippe; Arnould; Bressan, C. [CNRS, St. Martin d' Heres (France). Lab. d' Electrotech. de Grenoble]|[Skis Dynastar S.A., Sallanches (France)
1998-07-01
An original damping device has been developed to reduce ski vibrations. Ski movement is transmitted to a conductive sheet situated in a multipole magnetic field created by permanent magnets. The conductive sheet is simultaneously submitted to eddy current and friction forces, giving the damping effect. The eddy current damper is more efficient for high frequency than for low frequency vibrations and consequently is very well adapted to ski vibrations. Bench and snow tests show the positive effects of the damper, which will be commercially available before the end of this year. (orig.)
Vibrational Autodetachment in Nitroalkane Anions
Adams, Christopher L.; Weber, J. Mathias
2010-06-01
Nitroalkanes have electron affinities ge 1370 cm-1, well below the excitation energies for CH stretching modes, with the excess charge localized on the nitro group. Upon absorption of an IR photon in a CH stretching vibrational mode, the absorbed energy is redistributed in the molecule. If enough energy is transferred to the NO2 stretching/wagging modes, the excess electron residing on the nitro group is emitted. Vibrational autodetachment (VAD) spectra encode information regarding intramolecular vibrational relaxation (IVR) processes leading up to electron emission. We present VAD photoelectron spectroscopy of polyatomic molecular anions and discuss how a VAD photoelectron spectrum can be modeled.
Initial Test Results from a 3-axis Vibrating Ring Gyroscope
Energy Technology Data Exchange (ETDEWEB)
Gallacher, B J; Neasham, J A; Burdess, J S; Harris, A J [INSAT University of Newcastle upon Tyne NE1 7RU (United Kingdom)
2006-04-01
There are several application areas where the simultaneous measurement of rates of rotation about three mutually orthogonal axes is required. In this paper the principle features of a 3-axis vibrating ring gyroscope are described. The fabrication process for the gyroscope is presented and employs standard MEMS techniques. The modal properties for the ring are measured experimentally using laser vibrometry and electrostatic sensing and compared with the design predictions. In operation as a rate gyroscope it is necessary to excite the primary motion of the gyroscope and control is amplitude. As Q-factors of vibratory gyroscope are typically of the order 10{sup 3}-10{sup 4} slight variations in environmental conditions will perturb the natural frequency of the primary mode significantly. To ensure the primary motion of the gyroscope is maintained with constant amplitude a control scheme employing both frequency tracking and amplitude control is required. An electronic control system using digital signal processing (DSP) has been developed to ensure excitation of the primary motion occurs at resonance with controlled amplitude. The control scheme employs an embedded processor to generate the drive frequency (via a D/A converter) and to monitor the primary vibration (via an A/D converter). Experimental results from the control scheme highlighting its effectiveness over conventional PLL approaches are presented.
Vibration characteristics analysis of rotating shrouded blades with impacts
Ma, Hui; Xie, Fangtao; Nai, Haiqiang; Wen, Bangchun
2016-09-01
A dynamic model of rotating shrouded blades with impacts among adjacent shrouded blades is established considering the effects of the centrifugal stiffening, spin softening and Coriolis force, and the model is validated using finite element method. In the proposed model, the shrouded blade is simplified as a cantilever Euler-Bernoulli beam with a mass point at the free end, and the flexural dynamic stiffness of shrouded blade is selected as contact stiffness during collision. Based on the developed model, the effects of symmetric and asymmetric shroud gaps, rotational speeds, and aerodynamic force amplitudes on the dynamic characteristics of shrouded blades are analyzed through Newmark-β numerical method. The results indicate that (1) the vibro-impact responses of shrouded blades under some asymmetric gaps are more complicated than that under symmetric gap. (2) With the increase of rotational speed from 6000 to 10,000 rev/min, the system vibration experiences from period-three motion, through chaotic motion, finally to period-one motion during collision process because the increasing rotational speed changes the flexural dynamic stiffness of rotating blade. (3) The vibration displacements of shrouded blades increase linearly, and impact force increases linearly with the increase of aerodynamic force amplitude.
Preparation of Motional Mesoscopic Superpositions of Squeezed Coherent States of N Trapped Ions
Institute of Scientific and Technical Information of China (English)
YANG Wen-Xing; XIE Xiao-Tao; LI Jia-Hua; CHEN Chang-Yong
2005-01-01
A scheme is proposed to generate arbitrary, discrete superpostions of squeezed coherent states of the squeezed center of mass of N trapped ions along a straight line in phase space. The scheme is based on a resonant bichromatic excitation of each trapped ion that generates displacement and squeezing in the vibrational motion conditioned to each internal state. In this paper, we also show that such a method can be used for the engineering of motional quantum states.
Morita, Akihiro; Kato, Shigeki
2001-11-01
In this Letter we discuss in the case of pyrazinyl radical the effect of the large amplitude motion on the charge polarization. The extra hydrogen of pyrazinyl radical is nonplanar at the equilibrium geometry, whereas it is delocalized in the vibrational ground state along the wagging direction. The large amplitude motion of the hydrogen triply enhances the effective out-of-plane polarizability of the ground state. This augmented charge polarization could play a considerable role in the diffusion dynamics in solutions.
Experimental Investigations on Microcracks in Vibrational and Conventional Drilling of Cortical Bone
Directory of Open Access Journals (Sweden)
Yu Wang
2013-01-01
Full Text Available Bone drilling is widely used in orthopedic surgery. Microcracks will be generated in bone drilling, which may cause fatigue damages and stress fractures. Fresh bovine cortical bones were drilled via vibrational and conventional ways. Drilling operations were performed by a dynamic material testing machine, which can provide the vibration while maintaining uniform feed motion. The drill site and bone debris were observed through scanning electron microscope (SEM. The experimental results showed that fewer and shorter micro-cracks were formed in vibrational drilling than those formed in conventional way. And the surface morphology of bone debris from two different drilling ways was also quite different. It is expected that vibrational drilling in orthopedic surgery operation could decrease the microdamage to the bone, which could lower the incidence of stress fracture and contribute to the postoperative recovery.
Vibration induced sliding: theory and experiment for a beam with a spring-loaded mass
DEFF Research Database (Denmark)
Miranda, Erik; Thomsen, Jon Juel
1998-01-01
The study sets up a simple model for predicting vibration induced sliding of mass, and provides quantitative experimental evidence for the validity of the model. The results lend confidence to recent theoretical developments on using vibration induced sliding for passive vibration damping......, and contributes to a further understanding of this nonlinear phenomenon. A mathematical model is set up to describe vibration induced sliding for a base-excited cantilever beam with a spring-loaded pointmass. Approximations simplify the model into two nonlinear ordinary differential equations, describing motions...... of the system at near-resonant excitation of a single beam mode. This simplified model is studied numerically and analytically, and tested against laboratory experiments. The experiments provide evidence that the simplified mathematical model retains those features of the real system that are necessary...
Analytical and experimental studies of flow-induced vibration of SSME components
Chen, S. S.; Jendrzejczyk, J. A.; Wambsganss, M. W.
1987-01-01
Components of the Space Shuttle Main Engines (SSMEs) are subjected to a severe environment that includes high-temperature, high-velocity flows. Such flows represent a source of energy that can induce and sustain large-amplitude vibratory stresses and/or result in fluidelastic instabilities. Three components are already known to have experienced failures in evaluation tests as a result of flow-induced structural motion. These components include the liquid-oxygen (LOX) posts, the fuel turbine bellows shield, and the internal inlet tee splitter vane. Researchers considered the dynamic behavior of each of these components with varying degrees of effort: (1) a theoretical and experimental study of LOX post vibration excited by a fluid flow; (2) an assessment of the internal inlet tee splitter vane vibration (referred to as the 4000-Hz vibration problem); and (3) a preliminary consideration of the bellows shield problem. Efforts to resolve flow-induced vibration problems associated with the SSMEs are summarized.
Off-resonant vibrational excitation: Orientational dependence and spatial control of photofragments
DEFF Research Database (Denmark)
Machholm, Mette; Henriksen, Niels Engholm
2000-01-01
-dependent response to the IR fields is due to the anharmonicity of the potential. A subsequent ultraviolet laser pulse in resonance at the outer turning point of the vibrational motion can then dissociate the oscillating molecules, all with the same orientation, leading to spatial control of the photofragment......Off-resonant and resonant vibrational excitation with short intense infrared (IR) laser pulses creates localized oscillating wave packets, but differs by the efficiency of the excitation and surprisingly by the orientational dependence. Orientational selectivity of the vibrational excitation...... of randomly oriented heteronuclear diatomic molecules can be obtained under simultaneous irradiation by a resonant and an off-resonant intense IR laser pulse: Molecules with one initial orientation will be vibrationally excited, while those with the opposite orientation will be at rest. The orientation...
Asymptotic Method and Numerical Analysis for Self-Excited Vibration in Rolling Mill with Clearance
Directory of Open Access Journals (Sweden)
Hongguang Li
2001-01-01
Full Text Available In this paper, a dynamic model is proposed for analysis of nonlinear vibrations of rolling mills with fixed and time-varying clearances. Self-excited vibrations of the system that is basically involved with piece-wise nonlinearity and discontinuities are investigated via asymptotic method. It is shown by numerical results obtained for the nonlinear system with a time-varying clearance that different forms of nonlinear vibrations appear to be periodic, quasi-periodic and chaotic. Influence of the system parameters on the nonlinear vibration behaviors is examined by applying the Poincare sections, the bifurcation diagram and the largest Lyapunov exponent. New phenomena are observed in nonlinear motions of the rolling mill mechanism and are of significant importance for design of this type of mechanical systems.
Ro-vibrational averaging of the isotropic hyperfine coupling constant for the methyl radical
Energy Technology Data Exchange (ETDEWEB)
Adam, Ahmad Y.; Jensen, Per, E-mail: jensen@uni-wuppertal.de [Fakultät Mathematik und Naturwissenschaften, Physikalische und Theoretische Chemie, Bergische Universität Wuppertal, D-42097 Wuppertal (Germany); Yachmenev, Andrey; Yurchenko, Sergei N. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
2015-12-28
We present the first variational calculation of the isotropic hyperfine coupling constant of the carbon-13 atom in the CH{sub 3} radical for temperatures T = 0, 96, and 300 K. It is based on a newly calculated high level ab initio potential energy surface and hyperfine coupling constant surface of CH{sub 3} in the ground electronic state. The ro-vibrational energy levels, expectation values for the coupling constant, and its temperature dependence were calculated variationally by using the methods implemented in the computer program TROVE. Vibrational energies and vibrational and temperature effects for coupling constant are found to be in very good agreement with the available experimental data. We found, in agreement with previous studies, that the vibrational effects constitute about 44% of the constant’s equilibrium value, originating mainly from the large amplitude out-of-plane bending motion and that the temperature effects play a minor role.
Impact vibration reduction for flexible manipulators via controllable local degrees of freedom
Institute of Scientific and Technical Information of China (English)
Bian Yushu; Gao Zhihui; Deng Yuchun
2013-01-01
When performing operation tasks, the interaction between a flexible manipulator and a grasped object usually results in an impact. In this paper, a new way is suggested to alleviate impact vibration of a flexible manipulator via its structural characteristic when capturing a moving object. Controllable local degrees of freedom are introduced to the topological structure of the flexible manipulator, and used as an effective tool to combat impact vibration through dynamic coupling. A corresponding method is put forward to reduce impact vibration responses of the flexible manip-ulator via the controllable local degrees of freedom. By planning motion of the controllable local degrees of freedom, appropriate control force can be constructed to increase the modal damping and stiffness and eliminate the exciting force simultaneously, thereby reducing impact vibration responses of the flexible manipulator. Simulations are conducted and results are shown to prove the presented method.
Verrier, N; Gross, M
2015-01-01
Sideband holography can be used to get fields images (E0 and E1) of a vibrating object for both the carrier (E0) and the sideband (E1) frequency with respect to vibration. We propose here to record E0 and E1 sequentially, and to image the correlation E1E * 0 . We show that this correlation is insensitive the phase related to the object roughness and directly reflect the phase of the mechanical motion. The signal to noise can be improved by averaging the correlation over neighbor pixel. Experimental validation is made with vibrating cube of wood and with a clarinet reed. At 2 kHz, vibrations of amplitude down to 0.01 nm are detected.
Coupled rotor-flexible fuselage vibration reduction using open loop higher harmonic control
Papavassiliou, I.; Friedmann, P. P.; Venkatesan, C.
1991-01-01
A fundamental study of vibration prediction and vibration reduction in helicopters using active controls was performed. The nonlinear equations of motion for a coupled rotor/flexible fuselage system have been derived using computer algebra on a special purpose symbolic computer facility. The trim state and vibratory response of the helicopter are obtained in a single pass by applying the harmonic balance technique and simultaneously satisfying the trim and the vibratory response of the helicopter for all rotor and fuselage degrees of freedom. The influence of the fuselage flexibility on the vibratory response is studied. It is shown that the conventional single frequency higher harmonic control is capable of reducing either the hub loads or only the fuselage vibrations but not both simultaneously. It is demonstrated that for simultaneous reduction of hub shears and fuselae vibrations a new scheme called multiple higher harmonic control is required.
Time-resolved vibrational spectroscopy of a molecular shuttle.
Panman, Matthijs R; Bodis, Pavol; Shaw, Danny J; Bakker, Bert H; Newton, Arthur C; Kay, Euan R; Leigh, David A; Buma, Wybren Jan; Brouwer, Albert M; Woutersen, Sander
2012-02-14
Time-resolved vibrational spectroscopy is used to investigate the inter-component motion of an ultraviolet-triggered two-station molecular shuttle. The operation cycle of this molecular shuttle involves several intermediate species, which are observable in the amide I and amide II regions of the mid-IR spectrum. Using ab initio calculations on specific parts of the rotaxane, and by comparing the transient spectra of the normal rotaxane with that of the N-deuterated version, we can assign the observed vibrational modes of each species occurring during the shuttling cycle in an unambiguous way. The complete time- and frequency-dependent data set is analyzed using singular value decomposition (SVD). Using a kinetic model to describe the time-dependent concentrations of the transient species, we derive the absorption spectra associated with each stage in the operation cycle of the molecular shuttle, including the recombination of the charged species.
Optimal Energy Harvesting from Vortex-Induced Vibrations of Cables
Antoine, G O; Michelin, S
2016-01-01
Vortex-induced vibrations (VIV) of flexible cables are an example of flow-induced vibrations that can act as energy harvesting systems by converting energy associated with the spontaneous cable motion into electricity. This work investigates the optimal positioning of the harvesting devices along the cable, using numerical simulations with a wake oscillator model to describe the unsteady flow forcing. Using classical gradient-based optimization, the optimal harvesting strategy is determined for the generic configuration of a flexible cable fixed at both ends, including the effect of flow forces and gravity on the cable's geometry. The optimal strategy is found to consist systematically in a concentration of the harvesting devices at one of the cable's ends, relying on deformation waves along the cable to carry the energy toward this harvesting site. Furthermore, we show that the performance of systems based on VIV of flexible cables is significantly more robust to flow velocity variations, in comparison with ...
Tunable transport of drops on a vibrating inclined fiber
Bick, Alison; Sauret, Alban; Stone, Howard A
2015-01-01
Transport of liquid drops in fibrous media occurs in various engineering systems such as fog harvesting or cleaning of textiles. The ability to tune or to control liquid movement can increase the system efficiency and enable new engineering applications. In this Letter, we experimentally investigate how partially wetting drops on a single fiber can be manipulated by vibrating the fiber. We show that a sliding motion along the fiber or a dripping of the drop can be triggered by standing waves. We identify the conditions on the drop volume, the fiber tilt angle and the amplitude and frequency of oscillations to observe these different behaviors. Finally, we experimentally illustrate that vibrations can be used to control the transport and the collection of water drops along a fiber using a combination of the sliding and dripping transitions.
Model reduction and analysis of a vibrating beam microgyroscope
Ghommem, Mehdi
2012-05-08
The present work is concerned with the nonlinear dynamic analysis of a vibrating beam microgyroscope composed of a rotating cantilever beam with a tip mass at its end. The rigid mass is coupled to two orthogonal electrodes in the drive and sense directions, which are attached to the rotating base. The microbeam is driven by an AC voltage in the drive direction, which induces vibrations in the orthogonal sense direction due to rotation about the microbeam axis. The electrode placed in the sense direction is used to measure the induced motions and extract the underlying angular speed. A reduced-order model of the gyroscope is developed using the method of multiple scales and used to examine its dynamic behavior. © The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Approximate Series Solutions for Nonlinear Free Vibration of Suspended Cables
Directory of Open Access Journals (Sweden)
Yaobing Zhao
2014-01-01
Full Text Available This paper presents approximate series solutions for nonlinear free vibration of suspended cables via the Lindstedt-Poincare method and homotopy analysis method, respectively. Firstly, taking into account the geometric nonlinearity of the suspended cable as well as the quasi-static assumption, a mathematical model is presented. Secondly, two analytical methods are introduced to obtain the approximate series solutions in the case of nonlinear free vibration. Moreover, small and large sag-to-span ratios and initial conditions are chosen to study the nonlinear dynamic responses by these two analytical methods. The numerical results indicate that frequency amplitude relationships obtained with different analytical approaches exhibit some quantitative and qualitative differences in the cases of motions, mode shapes, and particular sag-to-span ratios. Finally, a detailed comparison of the differences in the displacement fields and cable axial total tensions is made.
Assements of Level of Comfort on a Vibrating Structure
DEFF Research Database (Denmark)
Pedersen, Lars
2008-01-01
The serviceability limit state of structures is subject to increasing attention. Flooring-systems may encounter vertical vibrations that may be perceived as annoying by stationary persons sitting or standing on the structure. This can happen on office floors, on grand stands etc. where humans...... in motion (for instance people walking or jumping) can bring the structure into vibration. The paper looks into human perception of decaying oscillations of floors by doing experiments with a test floor with stationary humans atop. An impulsive load is directed to the floor, and after the decay, the persons...... on the floor are asked to rate the level of discomfort on a scale from 1 to 10, and to assess the size of floor displacement (the initial amplitude of the decay). Tests are carried out with different numbers of people present on the test floor, and with different initial amplitudes of the decay. The paper...
Vibration and Acoustic Radiation from Submerged Spherical Double-Shell
Institute of Scientific and Technical Information of China (English)
陈军明; 黄玉盈; 陈应波
2003-01-01
Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employed to introduce the forces and moments applied by the attachments, and by means of expanding field quantities as the Legendre series, a semi-analytic solution is derived for the solution to the vibration and acoustic radiation from a submerged spherical double-shell. This solution has a satisfying computational effectiveness and precision for arbitrary frequency range excitation. It is concluded that the internal plates attached to shells can change significantly the mechanical and acoustical characteristics of shells, and make the coupling system have a very rich resonance frequency spectrum. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.
Position Command Shaping for Vibration Suppression Considering Target Position Correction
Yamamoto, Masafumi; Ito, Kazuaki; Iwasaki, Makoto; Matsui, Nobuyuki
This paper presents a command shaping technique based on a minimum jerk control approach considering a target position correction during motion, for the fast and precise positioning in vibratory mechatronic systems. The positioning controller is designed by a 2-degrees-of-freedom control: a feedback compensator is synthesized by H∞ control design to ensure the robust stability, while a feedforward compensator suppresses the vibration in response based on a coprime factorization expression of the plant mechanism. The command shaping, on the other hand, eliminates the corresponding vibration components of the primary and secondary modes in the position command, where the continuity of jerk component in the command can be ensured against the target position correction. The effectiveness of the proposed shaping technique has been verified by experiments using a table drive system on machine stand.