Vibrational modes of nanolines
Heyliger, Paul R.; Flannery, Colm M.; Johnson, Ward L.
2008-04-01
Brillouin-light-scattering spectra previously have been shown to provide information on acoustic modes of polymeric lines fabricated by nanoimprint lithography. Finite-element methods for modeling such modes are presented here. These methods provide a theoretical framework for determining elastic constants and dimensions of nanolines from measured spectra in the low gigahertz range. To make the calculations feasible for future incorporation in inversion algorithms, two approximations of the boundary conditions are employed in the calculations: the rigidity of the nanoline/substrate interface and sinusoidal variation of displacements along the nanoline length. The accuracy of these approximations is evaluated as a function of wavenumber and frequency. The great advantage of finite-element methods over other methods previously employed for nanolines is the ability to model any cross-sectional geometry. Dispersion curves and displacement patterns are calculated for modes of polymethyl methacrylate nanolines with cross-sectional dimensions of 65 nm × 140 nm and rectangular or semicircular tops. The vibrational displacements and dispersion curves are qualitatively similar for the two geometries and include a series of flexural, Rayleigh-like, and Sezawa-like modes. This paper is a contribution of the National Institute of Standards and Technology and is not subject to copyright in the United States.
Skyrmion Vibration Modes within the Rational Map Ansatz
Lin, W.T.; Piette, B.
2008-01-01
We study the vibration modes of the Skyrme model within the rational map ansatz. We show that the vibrations of the radial profiles and the rational maps are decoupled and we consider explicitly the cases B=1, B=2, and B=4. We then compare our results with the vibration modes obtained numerically by Barnes et al. and show that qualitatively the rational map reproduces the vibration modes obtained numerically but that the vibration frequencies of these modes do not match very well.
Vibration mode shape control by prestressing
Holnicki-Szulc, Jan; Haftka, Raphael T.
1992-01-01
A procedure is described for reducing vibration at sensitive locations on a structure, by induced distortions. The emphasis is placed on the excitation in a narrow frequency band, so that only a small number of vibration modes contribute to the intensity of the forced response. The procedure is demonstrated on an antenna truss example, showing that, with repeated frequencies, it is very easy to move nodal lines of one of the modes.
Lattice vibrational modes and their frequency shifts in semiconductor nanowires.
Yang, Li; Chou, M Y
2011-07-13
We have performed first-principles calculations to study the lattice vibrational modes and their Raman activities in silicon nanowires (SiNWs). Two types of characteristic vibrational modes are examined: high-frequency optical modes and low-frequency confined modes. Their frequencies have opposite size dependence with a red shift for the optical modes and a blue shift for the confined modes as the diameter of SiNWs decreases. In addition, our calculations show that these vibrational modes can be detected by Raman scattering measurements, providing an efficient way to estimate the size of SiNWs.
Two-mode elliptical-core weighted fiber sensors for vibration analysis
Vengsarkar, Ashish M.; Murphy, Kent A.; Fogg, Brian R.; Miller, William V.; Greene, Jonathan A.; Claus, Richard O.
1992-01-01
Two-mode, elliptical-core optical fibers are demonstrated in weighted, distributed and selective vibration-mode-filtering applications. We show how appropriate placement of optical fibers on a vibrating structure can lead to vibration mode filtering. Selective vibration-mode suppression on the order of 10 dB has been obtained using tapered two-mode, circular-core fibers with tapering functions that match the second derivatives of the modes of vibration to be enhanced. We also demonstrate the use of chirped, two-mode gratings in fibers as spatial modal sensors that are equivalents of shaped piezoelectric sensors.
Broadband vibration energy harvester utilizing three out-of-plane modes of one vibrating body
Park, Shi-Baek; Jang, Seon-Jun; Kim, In-Ho; Choi, Yong Je
2017-10-01
In this paper, we introduce the concept, design equation, and realization of a broadband electromagnetic vibrational energy harvester. The spatial vibrating system in the proposed harvester is arranged to have three out-of-plane vibration modes. We devise the design method for its three natural frequencies and accompanying modes and apply it to the broadband energy harvesting by locating three frequencies close to each other. The numerical simulation and the experimental results show that it satisfies the designated frequencies as well as the enhanced bandwidth for power generation.
Evaluation of Bus Vibration Comfort Based on Passenger Crowdsourcing Mode
Directory of Open Access Journals (Sweden)
Hong Zhao
2016-01-01
Full Text Available Vibration comfort is an important factor affecting the quality of service (QoS of bus. In order to make people involved in supervising bus’s vibration comfort and improve passengers’ riding experience, a novel mode of passenger crowdsourcing is introduced. In this paper, comfort degree of bus vibration is calculated from bus’s vibration signals collected by passengers’ smartphones and sent through WiFi to the Boa web server which shows the vibration comfort on the LCD deployed in bus and maybe trigger alarm lamp when the vibration is beyond the threshold. Three challenges here have been overcome: firstly, space coordinate transformation algorithm is used to solve the constant drift of signals collected; secondly, a low-pass filter is designed to isolate gravity from signals real-timely via limited computing resources; thirdly, an embedded evaluation system is developed according to the calculation procedure specified by criterion ISO 2631-1997. Meanwhile, the model proposed is tested in a practical running environment, the vibration data in whole travel are recorded and analyzed offline. The results show that comfort degree of vibration obtained from the experimental system is identical with the truth, and this mode is proved to be effective.
Vibration modes and frequencies of structures
Durling, R. J.; Kvaternik, R. G.
1980-01-01
SUDAN, Substructuring in Direct Analysis, analyzes natural modes and frequencies of vibration of structural systems. Based on direct method of analysis that employs substructures methodology, program is used with structures that may be represented as equivalent system of beam, springs, and rigid bodies.
Relating normal vibrational modes to local vibrational modes: benzene and naphthalene.
Zou, Wenli; Kalescky, Robert; Kraka, Elfi; Cremer, Dieter
2013-07-01
Local vibrational modes can be directly derived from normal vibrational modes using the method of Konkoli and Cremer (Int J Quant Chem 67:29, 1998). This implies the calculation of the harmonic force constant matrix F (q) (expressed in internal coordinates q) from the corresponding Cartesian force constant matrix f (x) with the help of the transformation matrix U = WB (†)(BWB (†))(-1) (B: Wilson's B-matrix). It is proven that the local vibrational modes are independent of the choice of the matrix W. However, the choice W = M (-1) (M: mass matrix) has numerical advantages with regard to the choice W = I (I: identity matrix), where the latter is frequently used in spectroscopy. The local vibrational modes can be related to the normal vibrational modes in the form of an adiabatic connection scheme (ACS) after rewriting the Wilson equation with the help of the compliance matrix. The ACSs of benzene and naphthalene based on experimental vibrational frequencies are discussed as nontrivial examples. It is demonstrated that the local-mode stretching force constants provide a quantitative measure for the C-H and C-C bond strength.
Surface vibrational modes in disk-shaped resonators.
Dmitriev, A V; Gritsenko, D S; Mitrofanov, V P
2014-03-01
The natural frequencies and distributions of displacement components for the surface vibrational modes in thin isotropic elastic disks are calculated. In particular, the research is focused on even solutions for low-lying resonant vibrations with large angular wave numbers. Several families of modes are found which are interpreted as modified surface modes of an infinitely long cylinder and Lamb modes of a plate. The results of calculation are compared with the results of the experimental measurements of vibrational modes generated by means of resonant excitation in duraluminum disk with radius of ≈90 mm and thickness of 16 mm in the frequency range of 130-200 kHz. An excellent agreement between the calculated and measured frequencies is found. Measurements of the structure of the resonant peaks show splitting of some modes. About a half of the measured modes has splitting Δfsplit/fmode at the level of the order of 10(-5). The Q-factors of all modes measured in vacuum lie in the interval (2…3)×10(5). This value is typical for duraluminum mechanical resonators in the ultrasonic frequency range. Copyright © 2013 Elsevier B.V. All rights reserved.
Function generator for synthesizing complex vibration mode patterns
Naumann, E. C.; Hagood, G. J., Jr. (Inventor)
1973-01-01
A simple highly flexible device for synthesizing complex vibration mode patterns is described. These mode patterns can be used to identify vibration mode data. This device sums selected sine and cosine functions and then plots the sum against a linear function.
A Novel Vibration Mode Testing Method for Cylindrical Resonators Based on Microphones
Directory of Open Access Journals (Sweden)
Yongmeng Zhang
2015-01-01
Full Text Available Non-contact testing is an important method for the study of the vibrating characteristic of cylindrical resonators. For the vibratory cylinder gyroscope excited by piezo-electric electrodes, mode testing of the cylindrical resonator is difficult. In this paper, a novel vibration testing method for cylindrical resonators is proposed. This method uses a MEMS microphone, which has the characteristics of small size and accurate directivity, to measure the vibration of the cylindrical resonator. A testing system was established, then the system was used to measure the vibration mode of the resonator. The experimental results show that the orientation resolution of the node of the vibration mode is better than 0.1°. This method also has the advantages of low cost and easy operation. It can be used in vibration testing and provide accurate results, which is important for the study of the vibration mode and thermal stability of vibratory cylindrical gyroscopes.
Hydrogen local vibrational modes in semiconductors
Energy Technology Data Exchange (ETDEWEB)
McCluskey, Matthew D. [Univ. of California, Berkeley, CA (United States). Dept. of Physics
1997-06-01
Following, a review of experimental techniques, theory, and previous work, the results of local vibrational mode (LVM) spectroscopy on hydrogen-related complexes in several different semiconductors are discussed. Hydrogen is introduced either by annealing in a hydrogen ambient. exposure to a hydrogen plasma, or during growth. The hydrogen passivates donors and acceptors in semiconductors, forming neutral complexes. When deuterium is substituted for hydrogen. the frequency of the LVM decreases by approximately the square root of two. By varying the temperature and pressure of the samples, the microscopic structures of hydrogen-related complexes are determined. For group II acceptor-hydrogen complexes in GaAs, InP, and GaP, hydrogen binds to the host anion in a bond-centered orientation, along the [111] direction, adjacent to the acceptor. The temperature dependent shift of the LVMs are proportional to the lattice thermal energy U(T), a consequence of anharmonic coupling between the LVM and acoustical phonons. In the wide band gap semiconductor ZnSe, epilayers grown by metalorganic chemical vapor phase epitaxy (MOCVD) and doped with As form As-H complexes. The hydrogen assumes a bond-centered orientation, adjacent to a host Zn. In AlSb, the DX centers Se and Te are passivated by hydrogen. The second, third, and fourth harmonics of the wag modes are observed. Although the Se-D complex has only one stretch mode, the Se-H stretch mode splits into three peaks. The anomalous splitting is explained by a new interaction between the stretch LVM and multi-phonon modes of the lattice. As the temperature or pressure is varied, and anti-crossing is observed between LVM and phonon modes.
Inhibiting multiple mode vibration in controlled flexible systems
Hyde, James M.; Chang, Kenneth W.; Seering, Warren P.
1991-01-01
Viewgraphs on inhibiting multiple mode vibration in controlled flexible systems are presented. Topics covered include: input pre-shaping background; developing multiple-mode shapers; Middeck Active Control Experiment (MACE) test article; and tests and results.
Optically active vibrational modes of PPV derivatives on textile substrate
Energy Technology Data Exchange (ETDEWEB)
Silva, M.A.T. da, E-mail: seaquinhos@uel.br [Departamento de Fisica, Universidade Estadual de Londrina-UEL, PR 445 Km 380, CP6001, CEP 86051-970 Londrina, Parana (Brazil); Dias, I.F.L. [Departamento de Fisica, Universidade Estadual de Londrina-UEL, PR 445 Km 380, CP6001, CEP 86051-970 Londrina, Parana (Brazil); Santos, E.P. dos; Martins, A.A. [Departamento de Fisica, Universidade Vale do Paraiba-UNIVAP, Avenida Shishima Hifumi, 2911, CEP 12244-000 Sao Jose dos Campos, Sao Paulo (Brazil); Duarte, J.L.; Laureto, E.; Reis, G.A. dos [Departamento de Fisica, Universidade Estadual de Londrina-UEL, PR 445 Km 380, CP6001, CEP 86051-970 Londrina, Parana (Brazil); Guimaraes, P.S.S.; Cury, L.A. [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Minas Gerais, C.P. 702, Belo Horizonte, CEP 30123-970 Minas Gerais (Brazil)
2013-02-15
In this work, MEH-PPV and BDMO-PPV films were deposited by spin-coating on 'dirty' textile substrates of canvas, nylon, canvas with resin, jeans and on glass and the temperature dependence of the optical properties of them was studied by photoluminescence and Raman (300 K) techniques. The temperature dependence of the energy, of the half line width at half height of the purely electronic peak, of the integrated PL intensity and of the Huang-Rhys factor, S=I{sub (01)}/I{sub (00)}, were obtained directly from the PL spectrum. For an analysis of the vibrational modes involved, Raman measurements were performed on substrates with and without polymers deposited and the results compared with those found in the literature. The films of MEH-PPV and BDMO-PPV showed optical properties similar to those films deposited on other substrates such as glass, metals, etc. It was observed an inversion of the first vibrational band in relation to the purely electronic peak with increasing temperature in the films deposited on nylon and canvas. The vibrational modes obtained by Raman were used to compose the simulation of the PL line shape of BDMO-PPV films on canvas and nylon, using a model proposed by Lin [29]. - Highlights: Black-Right-Pointing-Pointer MEH-PPV and BDMO-PPV films were deposited by spin-coating on dirty textile. Black-Right-Pointing-Pointer Their properties were studied by photoluminescence and Raman techniques. Black-Right-Pointing-Pointer We observed inversion of first vibrational band in relation to purely electronic peak. Black-Right-Pointing-Pointer Optically active vibrational modes of PPV derivatives were studied.
Displacement of polarons by vibrational modes in doped conjugated polymers
Anderson, M.; Ramanan, C.; Fontanesi, C.; Frick, A.; Surana, S.; Cheyns, D.; Furno, M.; Keller, T.; Allard, S.; Scherf, U.; Beljonne, D.; D'Avino, G.; von Hauff, E.; Da Como, E.
2017-10-01
Organic pi-conjugated polymers are deemed to be soft materials with strong electron-phonon coupling, which results in the formation of polarons, i.e., charge carriers dressed by self-localized distortion of the nuclei. Universal signatures for polarons are optical resonances below the band gap and intense vibrational modes (IVMs), both found in the infrared (IR) spectral region. Here, we study p -doped conjugated homo- and copolymers by combining first-principles modelling and optical spectroscopy from the far-IR to the visible. Polaronic IVMs are found to feature absorption intensities comparable to purely electronic transitions and, most remarkably, show only loose resemblance to the Raman or IR-active modes of the neutral polymer. The IVM frequency is dramatically scaled down (up to 50%) compared to the backbone carbon-stretching modes in the pristine polymers. The very large intensity of IVMs is associated with displacement of the excess positive charge along the backbone driven by specific vibrational modes. We propose a quantitative picture for the identification of these polaron shifting modes that solely based on structural information, directly correlates with their IR intensity. This finding finally discloses the elusive microscopic mechanism behind the huge IR intensity of IVMs in doped polymeric semiconductors.
Ultrafast Dynamics of Vibration-Cavity Polariton Modes
Owrutsky, Jeff; Dunkelberger, Adam; Fears, Kenan; Simpkins, Blake; Spann, Bryan
Vibrational modes of polymers, liquids, and solvated compounds can couple to Fabry-Perot optical cavity modes, creating vibration-cavity polariton modes whose energy tunes with the cavity length and incidence angle. Here we report the pump-probe infrared spectroscopy of vibration-cavity polaritons in cavity-coupled W(CO)6. At very early times, we observe quantum beating between the two polariton states find an anomalously low degree of excitation. After the quantum beating, we directly observe spectroscopic signatures of excited-state absorption from both polariton modes and uncoupled reservoir modes. An analytical expression for cavity transmission reproduces these signatures. The upper polariton mode relaxes ten times more quickly than the uncoupled vibrational mode and the polariton lifetime depends on the angle of incidence of the infrared pulses. Coupling to an optical cavity gives a means of control of the lifetime of vibration-cavity polaritons and could have important implications for chemical reactivity in vibrationally excited molecules.
Computing Vibration-Mode Matrices From Finite-Element Output
Levy, Roy
1993-01-01
Postprocessing algorithms devised to facilitate vibrational-mode analyses of dynamics of complicated structures. Yields inertia matrices and elastic/rigid-coupling matrices. Such analyses important in simulation and control in active suppression of vibrations in large building or in precise aiming of large antenna.
selective excitation of vibrational modes of polyatomic molecule
Indian Academy of Sciences (India)
Abstract. Mode-selective dynamics of triatomic molecule in the electronic ground state under continuous wave laser pulse is investigated for the discrete vibrational bound states. A non-perturbative approach has been used to analyse the vibrational couplings and dynamics of the molecule. Keywords. Polyatomic molecule ...
Precise Ab-initio prediction of terahertz vibrational modes in crystalline systems
DEFF Research Database (Denmark)
Jepsen, Peter Uhd; Clark, Stewart J.
2007-01-01
We use a combination of experimental THz time-domain spectroscopy and ab-initio density functional perturbative theory to accurately predict the terahertz vibrational spectrum of molecules in the crystalline phase. Our calculations show that distinct vibrational modes found in solid-state materials...
Dunn, Janette L.
2010-01-01
Understanding the normal mode vibrations of a molecule is important in the analysis of vibrational spectra. However, the complicated 3D motion of large molecules can be difficult to interpret. We show how images of normal modes of the fullerene molecule C[subscript 60] can be made easier to understand by superimposing them on images of the normal…
Comparison of different ultrasonic vibration modes for post removal.
Braga, Neilor Mateus Antunes; Silva, Juliana Monteiro da; Carvalho-Júnior, Jacy Ribeiro de; Ferreira, Raquel Conceição; Saquy, Paulo César; Brito-Júnior, Manoel
2012-01-01
This in vitro study compared different ultrasonic vibration modes for intraradicular cast post removal. The crowns of 24 maxillary canines were removed, the roots were embedded in acrylic resin blocks, and the canals were treated endodontically. The post holes were prepared and root canal impressions were taken with self-cured resin acrylic. After casting, the posts were cemented with zinc phosphate cement. The samples were randomly distributed into 3 groups (n=8): G1: no ultrasonic vibration (control); G2: tip of the ultrasonic device positioned perpendicularly to core surface and close to the incisal edge; and G3: tip of the ultrasonic device positioned perpendicularly to core surface at cervical region, close to the line of cementation. An Enac OE-5 ultrasound unit with an ST-09 tip was used. All samples were submitted to the tensile test using an universal testing machine at a crosshead speed of 1 mm/min. Data were subjected to one-way ANOVA and Tukey's post-hoc tests (α=0.05). Mean values of the load to dislodge the posts (MPa) were: G1 = 4.6 (± 1.4) A; G2 = 2.8 (± 0.9) B, and G3= 0.9 (± 0.3) C. Therefore, the ultrasonic vibration applied with the tip of device close to the core's cervical area showed higher ability to reduce the retention of cast post to root canal.
Automobile Road Vibration Reproduction using Sliding Modes
Monsees, G.; Scherpen, J.M.A.
2001-01-01
Sliding mode controllers have a reputation for their robustness against parameter variations, modeling errors and disturbances. They have been successfully applied in several practical situations which demonstrated the potential of sliding mode control for other control problems. However research
Vibration modes of injured spine at resonant frequencies under vertical vibration.
Guo, Li-Xin; Zhang, Ming; Zhang, Yi-Min; Teo, Ee-Chon
2009-09-01
A detailed three-dimensional finite element model of the spine segment T12-Pelvis was developed to investigate dynamic characteristics of whole lumbar spine with injured cases. This study investigates the motion mechanism of the human lumbar spine and the effect of component injuries on adjacent spinal components under whole body vibration. Several investigations have analyzed the influence of injured spines on adjacent spinal components under static loadings. However, it is not clear how the spine injury affects dynamic characteristics of whole lumbar spine and adjacent components of the injured segment under vibration. The T12-Pelvis model was used to obtain the modal vibration modes of the spine at resonant frequencies. Injury conditions of the spine were simulated and tested, including denucleation and/or facetectomy with removal of capsular ligaments. The results indicate the first-order vertical resonant frequency of the intact model is 7.21 Hz. After the denucleation at L4-L5, it decreases by more than 4% compared with the intact condition. All the injured conditions including disc injury and ligament injury decrease the resonant frequency of the spine. Due to the denucleation at L4-L5 the anteroposterior displacements of the vertebrae from L2 to L5 decrease and the vertical displacements of the vertebrae from L1 to L4 increase under vibration. The denucleation also decreases the rotational deformations of the vertebrae from L1 to L5. The material property sensitivity analysis shows intervertebral discs have a dominating effect on variation of vertical resonant frequency of the spine. The denucleation may decrease cushioning effects of adjacent motion segments at the injured level under vibration. The injured condition may increase the vertical displacement amplitudes of the spine above the injured level. All the injured conditions may decrease the resonant frequency of the spine system.
Signature of nonadiabatic coupling in excited-state vibrational modes.
Soler, Miguel A; Nelson, Tammie; Roitberg, Adrian E; Tretiak, Sergei; Fernandez-Alberti, Sebastian
2014-11-13
Using analytical excited-state gradients, vibrational normal modes have been calculated at the minimum of the electronic excited-state potential energy surfaces for a set of extended conjugated molecules with different coupling between them. Molecular model systems composed of units of polyphenylene ethynylene (PPE), polyphenylenevinylene (PPV), and naphthacene/pentacene (NP) have been considered. In all cases except the NP model, the influence of the nonadiabatic coupling on the excited-state equilibrium normal modes is revealed as a unique highest frequency adiabatic vibrational mode that overlaps with the coupling vector. This feature is removed by using a locally diabatic representation in which the effect of NA interaction is removed. Comparison of the original adiabatic modes with a set of vibrational modes computed in the locally diabatic representation demonstrates that the effect of nonadiabaticity is confined to only a few modes. This suggests that the nonadiabatic character of a molecular system may be detected spectroscopically by identifying these unique state-specific high frequency vibrational modes.
Beyond local group modes in vibrational sum frequency generation.
Chase, Hilary M; Psciuk, Brian T; Strick, Benjamin L; Thomson, Regan J; Batista, Victor S; Geiger, Franz M
2015-04-09
We combine deuterium labeling, density functional theory calculations, and experimental vibrational sum frequency generation spectroscopy into a form of "counterfactual-enabled molecular spectroscopy" for producing reliable vibrational mode assignments in situations where local group mode approximations are insufficient for spectral interpretation and vibrational mode assignments. We demonstrate the method using trans-β-isoprene epoxydiol (trans-β-IEPOX), a first-generation product of isoprene relevant to atmospheric aerosol formation, and one of its deuterium-labeled isotopologues at the vapor/silica interface. We use our method to determine that the SFG responses that we obtain from trans-β-IEPOX are almost exclusively due to nonlocal modes involving multiple C-H groups oscillating at the same frequency as one vibrational mode. We verify our assignments using deuterium labeling and use DFT calculations to predict SFG spectra of additional isotopologues that have not yet been synthesized. Finally, we use our new insight to provide a viable alternative to molecular orientation analysis methods that rely on local mode approximations in cases where the local mode approximation is not applicable.
Fundamental vibrational mode in a highly inhomogeneous star
Bastrukov, S. I.; Chang, H. -K.; Wu, E. -H.; Molodtsova, I. V.
2008-01-01
The eigenfrequency problem of fundamental vibrational mode in a highly inhomogeneous star, modeled by self-gravitating mass of viscous liquid with singular density at the center, is considered in juxtaposition with that for Kelvin fundamental mode in the liquid star model with uniform density. Particular attention is given to the difference between spectral equations for the frequency and lifetime of f-mode in the singular and homogeneous star models. The newly obtained results are discussed ...
Starkey, Carl A; Lee, Scott A; Anderson, Anthony
2016-01-01
High-pressure infrared spectroscopy has been used to study the eigenvectors and eigenvalues of the vibrational modes of crystalline adenosine at 298 K by evaluating the logarithmic derivative of the vibrational frequency with respect to pressure: [Formula: see text]. Crystalline samples of molecular materials such as adenosine have vibrational modes that are localized within a molecular unit ("internal" modes) as well as modes in which the molecular units vibrate against each other ("external" modes). The value of the logarithmic derivative is that it is a diagnostic probe of the nature of the eigenvector of these vibrational modes. Stretching modes, which are predominantly internal to the molecule, have low logarithmic derivatives while external modes have higher logarithmic derivatives. Particular attention is paid to modes in the 800-1000 cm(-1) range since modes in that region of the vibrational spectrum are found to be sensitive to the conformation of double-helical DNA. Since the sugar pucker is different for the various conformations of DNA, this fact suggests that these modes involve the motion of atoms in the sugar group. The vibrations of the hydrogen atoms are also of interest to study since the vibrational frequency of hydrogen atoms involved in hydrogen bonds has a negative pressure derivative. Such behavior clearly shows which hydrogen atoms are involved in hydrogen bonding.
The normal modes of lattice vibrations of ice XI
Zhang, Peng; Wang, Zhe; Lu, Ying-Bo; Ding, Zheng-Wen
2016-01-01
The vibrational spectrum of ice XI at thermal wavelengths using the CASTEP code, a first-principles simulation method, is investigated. A dual-track approach is constructed to verify the validity for the computational phonon spectrum: collate the simulated spectrum with inelastic neutron scattering experiments and assign the photon scattering peaks according to the calculated normal vibration frequencies. The 33 optical normal vibrations at the Brillouin center are illustrated definitely from the ab initio outcomes. The depolarizing field effect of the hydrogen bond vibrations at frequencies of 229 cm−1 and 310 cm−1 is found to agree well with the LST relationship. It is a convincing evidence to manifest the LO-TO splitting of hydrogen bonds in ice crystal. We attribute the two hydrogen bond peaks to the depolarization effect and apply this viewpoint to ordinary ice phase, ice Ih, which is difficult to analyse their vibration modes due to proton disorder. PMID:27375199
Mapping vibrational surface and bulk modes in a single nanocube
Lagos, Maureen J.; Trügler, Andreas; Hohenester, Ulrich; Batson, Philip E.
2017-03-01
Imaging of vibrational excitations in and near nanostructures is essential for developing low-loss infrared nanophotonics, controlling heat transport in thermal nanodevices, inventing new thermoelectric materials and understanding nanoscale energy transport. Spatially resolved electron energy loss spectroscopy has previously been used to image plasmonic behaviour in nanostructures in an electron microscope, but hitherto it has not been possible to map vibrational modes directly in a single nanostructure, limiting our understanding of phonon coupling with photons and plasmons. Here we present spatial mapping of optical and acoustic, bulk and surface vibrational modes in magnesium oxide nanocubes using an atom-wide electron beam. We find that the energy and the symmetry of the surface polariton phonon modes depend on the size of the nanocubes, and that they are localized to the surfaces of the nanocube. We also observe a limiting of bulk phonon scattering in the presence of surface phonon modes. Most phonon spectroscopies are selectively sensitive to either surface or bulk excitations; therefore, by demonstrating the excitation of both bulk and surface vibrational modes using a single probe, our work represents advances in the detection and visualization of spatially confined surface and bulk phonons in nanostructures.
Electric field generated by axial longitudinal vibration modes of microtubule.
Cifra, M; Pokorný, J; Havelka, D; Kucera, O
2010-05-01
Microtubules are electrically polar structures fulfilling prerequisites for generation of oscillatory electric field in the kHz to GHz region. Energy supply for excitation of elasto-electrical vibrations in microtubules may be provided from GTP-hydrolysis; motor protein-microtubule interactions; and energy efflux from mitochondria. We calculated electric field generated by axial longitudinal vibration modes of microtubules for random, and coherent excitation. In case of coherent excitation of vibrations, the electric field intensity is highest at the end of microtubule. The dielectrophoretic force exerted by electric field on the surrounding molecules will influence the kinetics of microtubule polymerization via change in the probability of the transport of charge and mass particles. The electric field generated by vibrations of electrically polar cellular structures is expected to play an important role in biological self-organization. 2010 Elsevier Ireland Ltd. All rights reserved.
CO laser photoacoustic spectra and vibrational modes of heroin ...
Indian Academy of Sciences (India)
Abstract. Heroin, morphine and narcotine are very large molecules having 50, 40 and 53 atoms respectively. Moderately high resolution photoacoustic (PA) spectra have been recorded in 9.6 µm and 10.6 µm regions of CO2 laser. It is very difficult to assign the modes of vibrations for PA bands by comparison with ...
laser photoacoustic spectra and vibrational modes of heroin ...
Indian Academy of Sciences (India)
Heroin, morphine and narcotine are very large molecules having 50, 40 and 53 atoms respectively. Moderately high resolution photoacoustic (PA) spectra have been recorded in 9.6 m and 10.6 m regions of CO2 laser. It is very difﬁcult to assign the modes of vibrations for PA bands by comparison with conventional low ...
Computation of expectation values from vibrational coupled-cluster at the two-mode coupling level
DEFF Research Database (Denmark)
Zoccante, Alberto; Seidler, Peter; Christiansen, Ove
2011-01-01
In this work we show how the vibrational coupled-cluster method at the two-mode coupling level can be used to calculate zero-point vibrational averages of properties. A technique is presented, where any expectation value can be calculated using a single set of Lagrangian multipliers computed...... solving iteratively a single linear set of equations. Sample calculations are presented which show that the resulting algorithm scales only with the third power of the number of modes, therefore making large systems accessible. Moreover, we present applications to water, pyrrole, and para-nitroaniline....
Hahn, Seungsoo
2016-10-28
The Hamiltonian matrix for the first excited vibrational states of a protein can be effectively represented by local vibrational modes constituting amide III, II, I, and A modes to simulate various vibrational spectra. Methods for obtaining the Hamiltonian matrix from ab initio quantum calculation results are discussed, where the methods consist of three steps: selection of local vibrational mode coordinates, calculation of a reduced Hessian matrix, and extraction of the Hamiltonian matrix from the Hessian matrix. We introduce several methods for each step. The methods were assessed based on the density functional theory calculation results of 24 oligopeptides with four different peptide lengths and six different secondary structures. The completeness of a Hamiltonian matrix represented in the reduced local mode space is improved by adopting a specific atom group for each amide mode and reducing the effect of ignored local modes. The calculation results are also compared to previous models using C=O stretching vibration and transition dipole couplings. We found that local electric transition dipole moments of the amide modes are mainly bound on the local peptide planes. Their direction and magnitude are well conserved except amide A modes, which show large variation. Contrary to amide I modes, the vibrational coupling constants of amide III, II, and A modes obtained by analysis of a dipeptide are not transferable to oligopeptides with the same secondary conformation because coupling constants are affected by the surrounding atomic environment.
The diffraction signatures of individual vibrational modes in polyatomic molecules
Ryu, Seol; Weber, Peter M.; Stratt, Richard M.
2000-01-01
Though one normally thinks of single-molecule diffraction studies as tools for eliciting molecular geometry, molecular diffraction patterns are really the Fourier transforms of complete molecular wave functions. There is thus at least the possibility of imaging the vibrational wave functions of polyatomic molecules by means of a pump-probe diffraction experiment: the pump laser could prepare a specific vibrational state and an electron or x-ray could then be diffracted off the molecule some short time later. The present paper develops the general theory of diffraction signatures for individual vibrational wave functions in polyatomic molecules and investigates the feasibility of seeing such signatures experimentally using the example of a linear triatomic molecule modeled after CS2. Although aligned molecules in specific vibrational quantum states turn out to exhibit very characteristic diffraction signatures, the signatures of the vibrational wave functions are partially washed out for the complete isotropy expected from gas phase molecules. Nonetheless, it is possible to design a diffraction experiment using a pump-dump sequence with a polarized laser beam which will select a nonisotropic sample of vibrationally excited molecules. We show that the resulting level of anisotropy should enhance the diffraction signature, helping to distinguish different vibrational components. These model calculations therefore suggest the possibility of observing the dynamics of vibrational wave packets using experimentally realizable diffraction techniques.
Energy Technology Data Exchange (ETDEWEB)
Dhote, Sharvari, E-mail: sharvari.dhote@mail.utoronto.ca; Zu, Jean; Zhu, Yang [Department of Mechanical and Industrial Engineering, University of Toronto, 5 King' s College Road, Toronto, Ontario M5S-3G8 (Canada)
2015-04-20
In this paper, a nonlinear wideband multi-mode piezoelectric vibration-based energy harvester (PVEH) is proposed based on a compliant orthoplanar spring (COPS), which has an advantage of providing multiple vibration modes at relatively low frequencies. The PVEH is made of a tri-leg COPS flexible structure, where three fixed-guided beams are capable of generating strong nonlinear oscillations under certain base excitation. A prototype harvester was fabricated and investigated through both finite-element analysis and experiments. The frequency response shows multiple resonance which corresponds to a hardening type of nonlinear resonance. By adding masses at different locations on the COPS structure, the first three vibration modes are brought close to each other, where the three hardening nonlinear resonances provide a wide bandwidth for the PVEH. The proposed PVEH has enhanced performance of the energy harvester in terms of a wide frequency bandwidth and a high-voltage output under base excitations.
Efficient vibration mode analysis of aircraft with multiple external store configurations
Karpel, M.
1988-01-01
A coupling method for efficient vibration mode analysis of aircraft with multiple external store configurations is presented. A set of low-frequency vibration modes, including rigid-body modes, represent the aircraft. Each external store is represented by its vibration modes with clamped boundary conditions, and by its rigid-body inertial properties. The aircraft modes are obtained from a finite-element model loaded by dummy rigid external stores with fictitious masses. The coupling procedure unloads the dummy stores and loads the actual stores instead. The analytical development is presented, the effects of the fictitious mass magnitudes are discussed, and a numerical example is given for a combat aircraft with external wing stores. Comparison with vibration modes obtained by a direct (full-size) eigensolution shows very accurate coupling results. Once the aircraft and stores data bases are constructed, the computer time for analyzing any external store configuration is two to three orders of magnitude less than that of a direct solution.
Vibrational relaxation pathways of AI and AII modes in N-methylacetamide clusters.
Piatkowski, L; Bakker, H J
2010-11-04
We studied the pathways of vibrational energy relaxation of the amide I (~1660 cm⁻¹) and amide II (~1560 cm⁻¹) vibrational modes of N-methylacetamide (NMA) in CCl₄ solution using two-color femtosecond vibrational spectroscopy. We measured the transient spectral dynamics upon excitation of each of these amide modes. The results show that there is no energy transfer between the amide I (AI) and amide II (AII) modes. Instead we find that the vibrational energy is transferred on a picosecond time scale to a common combination tone of lower-frequency modes. By use of polarization-resolved femtosecond pump-probe measurements we also study the reorientation dynamics of the NMA molecules and the relative angle between the transition dipole moments of the AI and AII vibrations. The spectral dynamics at later times after the excitation (>40 ps) reveal the presence of a dissociation process of the NMA aggregates, trimers, and higher order structures into dimers and monomers. By measuring the dissociation kinetics at different temperatures, we determined the activation energy of this dissociation E(a) = 35 ± 3 kJ mol⁻¹.
Yenagi, Jayashree; Shettar, Anita; Tonannavar, J
2011-09-01
FT-Infrared (4000-400 cm(-1)) and NIR-FT-Raman (4000-50 cm(-1)) spectral measurements have been made for 2-chloro- and 2-bromo-3-pyridinecarboxaldehydes. A DFT vibration analysis at B3LYP/6-311++G (d,p) level, valence force-fields and vibrational mode calculations have been performed. Aided by very good agreement between observed and computed vibration spectra, a complete assignment of fundamental vibration modes to the observed absorptions and Raman bands has been proposed. Orientations of the aldehydic group have produced two oblate asymmetric rotamers for each molecule, ON-trans and ON-cis: the ON-trans rotamer being more stable than cis by 3.42 kcal mol(-1) for 2-chloro-3-pyridinecarboxaldehyde and 3.68 kcal mol(-1) for 2-bromo-3-pyridinecarboxaldehyde. High potential energy barrier ca 14 kcal/mol, induced by steric hindrance, restricts rotamers' population to ON-trans only. It is observed that, in the presence of bromine, C-H stretching modes are pronounced; a missing characteristic ring mode in chlorine's presence shows at 1557 cm(-1); the characteristic ring mode at 1051 cm(-1) is diminished; a mixed mode near 707 cm(-1) is enhanced. Further, an observed doublet near 1696-1666 cm(-1) in both IR and Raman spectra is explained on the basis of Fermi resonance between aldehydic carbonyl stretching at 1696 cm(-1) and a combination mode of ring stretch near 1059 cm(-1) and deformation vibration, 625 cm(-1). A strong Raman aldehydic torsional mode at 62 cm(-1) is interpreted to correspond to the dominant ON-trans over cis rotamers population. Copyright © 2011 Elsevier B.V. All rights reserved.
Piezoelectric nonlinear vibration focusing on the second-harmonic vibration mode.
Ozaki, Ryohei; Liu, Yaoyang; Hosaka, Hiroshi; Morita, Takeshi
2018-01-01
Resonant piezoelectric devices are driven under high power condition. In such condition, a nonlinear piezoelectric vibration becomes apparent and this nonlinearity should be taken into account in the design procedure using the finite elemental method (FEM). The purpose of this study is to introduce the nonlinear parameter to the FEM and to establish the method for measuring the nonlinear parameter through evaluating a nonlinear model for a piezoelectric vibration. In a previous study about the nonlinear piezoelectric vibration, the third term was mainly focused on because the third mode vibration affects the fundamental vibration in the case of a simple bar-type transducer. On the other hand, we considered the second nonlinear parameter of the compliance to the piezoelectric constitutive equation. We observed that this parameter affects the vibration amplitude with each position and the velocity at the tip of the transducer with a double frequency at resonant. It was confirmed that two measured nonlinear parameters based on these two relationships were almost same. From these values, we concluded that the proposed model is reasonable. Copyright © 2017. Published by Elsevier B.V.
He, Huijing; Yang, Jiashi; Kosinski, John A
2012-08-01
We study shear-horizontal free vibrations of an elastic cylinder with an oblate elliptical cross section and a traction-free surface. Exact vibration modes and frequencies are obtained. The results show the existence of thickness-shear and thickness-twist modes. The energy-trapping behavior of these modes is examined. Trapped modes are found wherein the vibration energy is largely confined to the central portion of the cross section and little vibration energy is found at the edges. It is also shown that face-shear modes are not allowed in such a cylinder. The results are useful for the understanding of the energy trapping phenomenon in contoured acoustic wave resonators.
Heavy atom vibrational modes and low-energy vibrational autodetachment in nitromethane anions
Energy Technology Data Exchange (ETDEWEB)
Thompson, Michael C.; Weber, J. Mathias, E-mail: weberjm@jila.colorado.edu [JILA, University of Colorado at Boulder, 440 UCB, Boulder, Colorado 80309-0440 (United States); Department of Chemistry and Biochemistry, University of Colorado at Boulder, 215UCB, Boulder, Colorado 80309-0215 (United States); Baraban, Joshua H. [Department of Chemistry and Biochemistry, University of Colorado at Boulder, 215UCB, Boulder, Colorado 80309-0215 (United States); Matthews, Devin A. [Institute for Computational Engineering and Science, University of Texas at Austin, 201 E. 24th St., Austin, Texas 78712 (United States); Stanton, John F. [Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712-0165 (United States)
2015-06-21
We report infrared spectra of nitromethane anion, CH{sub 3}NO{sub 2}{sup −}, in the region 700–2150 cm{sup −1}, obtained by Ar predissociation spectroscopy and electron detachment spectroscopy. The data are interpreted in the framework of second-order vibrational perturbation theory based on coupled-cluster electronic structure calculations. The modes in the spectroscopic region studied here are mainly based on vibrations involving the heavier atoms; this work complements earlier studies on nitromethane anion that focused on the CH stretching region of the spectrum. Electron detachment begins at photon energies far below the adiabatic electron affinity due to thermal population of excited vibrational states.
Xu, Ben; Poduska, Kristin M
2014-09-07
We demonstrate a correlation between how an IR-active vibrational mode responds to temperature changes and how it responds to crystallinity differences. Infrared (IR) spectroscopy was used to track changes in carbonate-related vibrational modes in three different CaCO3 polymorphs (calcite, aragonite, and vaterite) and CaMg(CO3)2 (dolomite) during heating. Of the three characteristic IR-active carbonate modes, the in-plane bending mode (ν4) shows the most pronounced changes with heating in polymorphs that have planar carbonate arrangements (calcite, aragonite, and dolomite). In contrast, this mode is virtually unchanged in vaterite, which has a canted arrangement of carbonate units. We correlate these trends with recent studies that identified the ν4 mode as most susceptible to changes related to crystallinity differences in calcite and amorphous calcium carbonate. Thus, our results suggest that studies of packing arrangements could provide a generalizable approach to identify the most diagnostic vibrational modes for tracking either temperature-dependent or crystallinity-related effects in IR-active solids.
Vibrational relaxation of the bending mode of HDO in liquid D2O.
Bodis, Pavol; Larsen, Olaf F A; Woutersen, Sander
2005-06-23
The vibrational relaxation of the bending mode of HDO in liquid D2O has been studied using time-resolved mid-infrared pump-probe spectroscopy. At short delays, the transient spectrum clearly shows the v = 1 --> 2 induced absorption and v = 1 --> 0 bleaching and stimulated emission, whereas at long delays, the transient spectrum is dominated by the spectral changes caused by the temperature increase in the sample after vibrational relaxation. From the decay of the v = 1 --> 2 induced absorption, we obtain an estimate of 390 +/- 50 fs for the vibrational lifetime, in surprisingly good agreement with recent theoretical predictions. In the v = 0 --> 1 frequency region, the decay of the absorption change involves a second, slower component, which suggests that after vibrational relaxation the system is not yet in thermal equilibrium.
Directory of Open Access Journals (Sweden)
Yizhou Yang
2017-01-01
Full Text Available To diagnose mechanical faults of rotor-bearing-casing system by analyzing its casing vibration signal, this paper proposes a training procedure of a fault classifier based on variational mode decomposition (VMD, local linear embedding (LLE, and support vector machine (SVM. VMD is used first to decompose the casing signal into several modes, which are subsignals usually modulated by fault frequencies. Vibrational features are extracted from both VMD subsignals and the original one. LLE is employed here to reduce the dimensionality of these extracted features and make the samples more separable. Then low-dimensional data sets are used to train the multiclass SVM whose accuracy is tested by classifying the test samples. When the parameters of LLE and SVM are well optimized, this proposed method performs well on experimental data, showing its capacity of diagnosing casing vibration faults.
Modes of vibration in a circular plate with three simple support points.
Chi, C.
1972-01-01
The analytical solutions for the vibrational modes of a thin circular flat plate that is simply supported at three points on the circumference are presented. The mode shapes and corresponding eigenvalues are obtained. Results show that the modes can be grouped into four different types depending on the manner by which they receive the pressure at the supported points. The problem is of the mixed boundary value type in that some portion of the boundary is free while the other portion is simply supported.
Component mode synthesis and large deflection vibrations of complex structures. [beams and trusses
Mei, C.
1984-01-01
The accuracy of the NASTRAN modal synthesis analysis was assessed by comparing it with full structure NASTRAN and nine other modal synthesis results using a nine-bay truss. A NASTRAN component mode transient response analysis was also performed on the free-free truss structure. A finite element method was developed for nonlinear vibration of beam structures subjected to harmonic excitation. Longitudinal deformation and inertia are both included in the formula. Tables show the finite element free vibration results with and without considering the effects of longitudinal deformation and inertia as well as the frequency ratios for a simply supported and a clamped beam subjected to a uniform harmonic force.
Tamayo, Javier; Pini, Valerio; Kosaka, Prisicila; Martinez, Nicolas F; Ahumada, Oscar; Calleja, Montserrat
2012-08-10
There is a need for noninvasive techniques for simultaneous imaging of the stress and vibration mode shapes of nanomechanical systems in the fields of scanning probe microscopy, nanomechanical biological and chemical sensors and the semiconductor industry. Here we show a novel technique that combines a scanning laser, the beam deflection method and digital multifrequency excitation and analysis for simultaneous imaging of the static out-of-plane displacement and the shape of five vibration modes of nanomechanical systems. The out-of-plane resolution is at least 100 pm Hz⁻¹/² and the lateral resolution, which is determined by the laser spot size, is 1-1.5 μm. The capability of the technique is demonstrated by imaging the residual surface stress of a microcantilever together with the shape of the first 22 vibration modes. The vibration behavior is compared with rigorous finite element simulations. The technique is suitable for major improvements in the imaging of liquids, such as higher bandwidth and enhanced spatial resolution.
Effect of instantaneous and continuous quenches on the density of vibrational modes in model glasses
Lerner, Edan; Bouchbinder, Eran
2017-08-01
Computational studies of supercooled liquids often focus on various analyses of their "underlying inherent states"—the glassy configurations at zero temperature obtained by an infinitely fast (instantaneous) quench from equilibrium supercooled states. Similar protocols are also regularly employed in investigations of the unjamming transition at which the rigidity of decompressed soft-sphere packings is lost. Here we investigate the statistics and localization properties of low-frequency vibrational modes of glassy configurations obtained by such instantaneous quenches. We show that the density of vibrational modes grows as ωβ with β depending on the parent temperature T0 from which the glassy configurations were instantaneously quenched. For quenches from high temperature liquid states we find β ≈3 , whereas β appears to approach the previously observed value β =4 as T0 approaches the glass transition temperature. We discuss the consistency of our findings with the theoretical framework of the soft potential model, and contrast them with similar measurements performed on configurations obtained by continuous quenches at finite cooling rates. Our results suggest that any physical quench at rates sufficiently slower than the inverse vibrational time scale—including all physically realistic quenching rates of molecular or atomistic glasses—would result in a glass whose density of vibrational modes is universally characterized by β =4 .
Estimation of the mechanical properties of the eye through the study of its vibrational modes.
Aloy, M Á; Adsuara, J E; Cerdá-Durán, P; Obergaulinger, M; Esteve-Taboada, J J; Ferrer-Blasco, T; Montés-Micó, R
2017-01-01
Measuring the eye's mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral analysis of the eyeball vibrational modes has not been performed yet. Here we develop a new finite difference method to compute both the spheroidal and, specially, the toroidal eigenfrequencies of the human eye. Using this numerical model, we show that the vibrational eigenfrequencies of the human eye fall in the interval 100 Hz-10 MHz. We find that compressible vibrational modes may release a trace on high frequency changes of the intraocular pressure, while incompressible normal modes could be registered analyzing the scattering pattern that the motions of the vitreous humour leave on the retina. Existing contact lenses with embebed devices operating at high sampling frequency could be used to register the microfluctuations of the eyeball shape we obtain. We advance that an inverse problem to obtain the mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio) measuring its normal frequencies is doable. These measurements can be done using non-invasive techniques, opening very interesting perspectives to estimate the mechanical properties of eyes in vivo. Future research might relate various ocular pathologies with anomalies in measured vibrational frequencies of the eye.
Vibrational relaxation pathways of AI and AII modes in N-methylacetamide clusters
Piatkowski, L.; Bakker, H.J.
2010-01-01
We studied the pathways of vibrational energy relaxation of the amide I (~1660 cm-1) and amide II (~1560 cm-1) vibrational modes of N-methylacetamide (NMA) in CCl4 solution using two-color femtosecond vibrational spectroscopy. We measured the transient spectral dynamics upon excitation of each of
Graus, M; Grimm, M; Metzger, C; Dauth, M; Tusche, C; Kirschner, J; Kümmel, S; Schöll, A; Reinert, F
2016-04-08
Electron-phonon coupling is one of the most fundamental effects in condensed matter physics. We here demonstrate that photoelectron momentum mapping can reveal and visualize the coupling between specific vibrational modes and electronic excitations. When imaging molecular orbitals with high energy resolution, the intensity patterns of photoelectrons of the vibronic sidebands of molecular states show characteristic changes due to the distortion of the molecular frame in the vibronically excited state. By comparison to simulations, an assignment of specific vibronic modes is possible, thus providing unique information on the coupling between electronic and vibronic excitation.
Kaeding, T S
2015-06-01
Research in the field of whole body vibration (WBV) training and the use of it in practice might be hindered by the fact that WBV training devices generate and transmit frequencies and/or modes of vibration which are different to preset adjustments. This research project shall clarify how exact WBV devices apply the by manufacturer information promised preset frequency and mode of vibration. Nine professional devices for WBV training were tested by means of a tri-axial accelerometer. The accelerations of each device were recorded under different settings with a tri-axial accelerometer. Beneath the measurement of different combinations of preset frequency and amplitude the repeatability across 3 successive measurements with the same preset conditions and one measurement under loaded condition were carried out. With 3 exceptions (both Board 3000 & srt medical PRO) we did not find noteworthy divergences between preset and actual applied frequencies. In these 3 devices we found divergences near -25%. Loading the devices did not affect the applied frequency or mode of vibration. There were no important divergences measurable for the applied frequency and mode of vibration regarding repeatability. The results of our measurements cannot be generalized as we only measured one respectively at most two devices of one model in terms of a random sample. Based on these results we strongly recommend that user in practice and research should analyse their WBV training devices regarding applied frequency and mode of vibration.
Design for coupled-mode flutter and non-synchronous vibration in turbomachinery
Clark, Stephen Thomas
-in, causing structural limit-cycle oscillations. This research shows that with proper model-coefficient choices, the frequency range of lock-in can be predicted and the conditions for the worst-case, limit-cycle-oscillation amplitude can be determined. This high-amplitude limit-cycle oscillation is found at an off-resonant condition, i.e., the ratio of the fluid-shedding frequency and the natural-structural frequency is not unity. In practice, low amplitude limit-cycle oscillations are acceptable; this research gives insight into when high-amplitude oscillations may occur and suggests that altering a blade's natural frequency to avoid this resonance can potentially make the response worse. The second reduced-order model uses proper orthogonal decomposition (POD) methods to first reconstruct, and ultimately predict, computational fluid dynamics (CFD) simulations of non-synchronous vibration. Overall, this method was successfully developed and implemented, requiring between two and six POD modes to accurately predict CFD solutions that are experiencing non-synchronous vibration. This POD method was first developed and demonstrated for a transversely-moving, two-dimensional cylinder in cross-flow. Later, the method was used for the prediction of CFD solutions for a two-dimensional compressor blade, and the reconstruction of solutions for a three-dimensional first-stage compressor blade. This research is the first to offer a van der Pol or proper orthogonal decomposition approach to the reduced-order modeling of non-synchronous vibration in turbomachinery. Modeling non-synchronous vibration is especially challenging because NSV is caused by complicated, unsteady flow dynamics; this initial study helps researchers understand the causes of NSV, and aids in the future development of predictive tools for aeromechanical design engineers.
Zhao, Libo; Hu, Yingjie; Wang, Tongdong; Ding, Jianjun; Liu, Xixiang; Zhao, Yulong; Jiang, Zhuangde
2016-06-06
Methods to calculate fluid density and viscosity using a micro-cantilever and based on the resonance principle were put forward. Their measuring mechanisms were analyzed and the theoretical equations to calculate the density and viscosity were deduced. The fluid-solid coupling simulations were completed for the micro-cantilevers with different shapes. The sensing chips with micro-cantilevers were designed based on the simulation results and fabricated using the micro electromechanical systems (MEMS) technology. Finally, the MEMS resonant sensor was packaged with the sensing chip to measure the densities and viscosities of eight different fluids under the flexural and torsional vibrating modes separately. The relative errors of the measured densities from 600 kg/m³ to 900 kg/m³ and viscosities from 200 μPa·s to 1000 μPa·s were calculated and analyzed with different microcantilevers under various vibrating modes. The experimental results showed that the effects of the shape and vibrating mode of micro-cantilever on the measurement accuracies of fluid density and viscosity were analyzed in detail.
Directory of Open Access Journals (Sweden)
Libo Zhao
2016-06-01
Full Text Available Methods to calculate fluid density and viscosity using a micro-cantilever and based on the resonance principle were put forward. Their measuring mechanisms were analyzed and the theoretical equations to calculate the density and viscosity were deduced. The fluid-solid coupling simulations were completed for the micro-cantilevers with different shapes. The sensing chips with micro-cantilevers were designed based on the simulation results and fabricated using the micro electromechanical systems (MEMS technology. Finally, the MEMS resonant sensor was packaged with the sensing chip to measure the densities and viscosities of eight different fluids under the flexural and torsional vibrating modes separately. The relative errors of the measured densities from 600 kg/m3 to 900 kg/m3 and viscosities from 200 μPa·s to 1000 μPa·s were calculated and analyzed with different microcantilevers under various vibrating modes. The experimental results showed that the effects of the shape and vibrating mode of micro-cantilever on the measurement accuracies of fluid density and viscosity were analyzed in detail.
Modeling of 1-3 piezoelectric composites operating in thickness-stretch vibration mode
Yang, Z.; Wang, H.; Zhao, C.; Zeng, D.
2015-06-01
For bulk piezoelectric ceramics plates, the fundamental thickness-stretch (TSt) waves are always coupled to the in-plane extension waves and the symmetric thickness-shear waves. The occurrence of these spurious modes in bulk piezoelectric ceramics plates is undesirable as it may interfere with the operation of transducers. 1-3 piezoelectric composites are promising candidates to suppress the spurious modes mentioned above. However, theoretical modelling of multiphase ceramic composite objects is very complex. In this study, a simple analytical TSt vibration model is constructed from three-dimensional equations of linear piezoelectricity. The mechanical damping is considered in the model by introducing a complex elastic constant. The performance of 1-3 piezoelectric composites is analysed and the electrical impedance results from theoretical and experimental analysis are compared. The results show that there is excellent agreement between the experimental electrical impedance and that obtained by the theoretical TSt vibration analysis. This indicates that 1-3 piezoelectric composites can be operated in a nearly pure TSt vibration mode near the fundamental resonance. The analytical model we present is valid for analysing 1-3 piezoelectric composites plates with large aspect ratios quickly and efficiently.
An Electromagnetic MEMS Energy Harvester Array with Multiple Vibration Modes
Directory of Open Access Journals (Sweden)
Huicong Liu
2015-07-01
Full Text Available This paper reports the design, micromachining and characterization of an array of electromagnetic energy harvesters (EHs with multiple frequency peaks. The authors present the combination of three multi-modal spring-mass structures so as to realize at least nine resonant peaks within a single microelectromechanical systems (MEMS chip. It is assembled with permanent magnet to show an electromagnetic-based energy harvesting capability. This is the first demonstration of multi-frequency MEMS EH existing with more than three resonant peaks within a limited frequency range of 189 to 662 Hz. It provides a more effective approach to harvest energy from the vibration sources of multiple frequency peaks.
Weber, F.; Distl, H.
2015-11-01
This paper derives an approximate collocated control solution for the mitigation of multi-mode cable vibration by semi-active damping with negative stiffness based on the control force characteristics of clipped linear quadratic regulator (LQR). The control parameters are derived from optimal modal viscous damping and corrected in order to guarantee that both the equivalent viscous damping coefficient and the equivalent stiffness coefficient of the semi-active cable damper force are equal to their desired counterparts. The collocated control solution with corrected control parameters is numerically validated by free decay tests of the first four cable modes and combinations of these modes. The results of the single-harmonic tests demonstrate that the novel approach yields 1.86 times more cable damping than optimal modal viscous damping and 1.87 to 2.33 times more damping compared to a passive oil damper whose viscous damper coefficient is optimally tuned to the targeted mode range of the first four modes. The improvement in case of the multi-harmonic vibration tests, i.e. when modes 1 and 3 and modes 2 and 4 are vibrating at the same time, is between 1.55 and 3.81. The results also show that these improvements are obtained almost independent of the cable anti-node amplitude. Thus, the proposed approximate real-time applicable collocated semi-active control solution which can be realized by magnetorheological dampers represents a promising tool for the efficient mitigation of stay cable vibrations.
Energy Technology Data Exchange (ETDEWEB)
Tarana, Michal [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440 (United States); Houfek, Karel; Horacek, Jiri [Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University in Prague, V Holesovickach 2, Prague (Czech Republic); Fabrikant, Ilya I. [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588 (United States); Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)
2011-11-15
We present a study of dissociative electron attachment and vibrational excitation processes in electron collisions with the CF{sub 3}Cl molecule. The calculations are based on the two-dimensional nuclear dynamics including the C-Cl symmetric stretch coordinate and the CF{sub 3} symmetric deformation (umbrella) coordinate. The complex potential energy surfaces are calculated using the ab initio R-matrix method. The results for dissociative attachment and vibrational excitation of the umbrella mode agree quite well with experiment whereas the cross section for excitation of the C-Cl symmetric stretch vibrations is about a factor-of-three too low in comparison with experimental data.
Xue, Jianghong; Xia, Fei; Ye, Jun; Zhang, Jianwen; Chen, Shuhua; Xiong, Ying; Tan, Zuyuan; Liu, Renhuai; Yuan, Hong
2017-06-30
This paper presents a multiscale approach to study the nonlinear vibration of fiber reinforced composite laminates containing an embedded, through-width delamination dividing the laminate into four sub-laminates. The equations of motion are established from macroscopic nonlinear mechanics for plates and shells and micro-mechanics of composite material to allow for the influences of large amplitude, membrane stretching in the neutral plane, and the interactions of the sublaminates. Analytical solutions obtained in this paper reveal that the interaction penalty at the interfaces plays a coupling effect between sublaminates, which eventually alters the vibration characters of the four-sublaminate lamina in macroscopic and microscopic mechanism. From a macro perspective, sub-laminates above and below the delamination vibrate in exactly the same mode in spite of their different stiffness and the four-sublaminate lamina has a consistent global vibration mode. In accompanying with the macro vibration, micro buckles occur on the interfaces of the delamination with amplitude about 10(-3) times of that of the global mode. It is found that the vibration frequency is an eigenvalue of the delaminated lamina determined only by the geometry of the delamination. Authentication of the multiscale study is fulfilled by comparing the analytical solutions with the FEA results.
Kumar, Nitin; Neogi, Sanghamitra; Kent, Paul; Bandura, Andrei; Kubicki, James; Wesolowski, David; Sofo, Jorge
2008-03-01
We study the vibrational density of states (VDOS) of a thin water layer on the rutile (110) surface. The VDOS is obtained from the velocity-velocity autocorrelation function calculated from trajectories of large scale ab-initio molecular dynamics simulations. The rutile surface induces a shift to lower frequencies of the stretching modes with respect to pure water. The water vapor surface shows a peak at the vibrational frequency of free hydroxyls. Overall, the average stretching mode vibrational frequency increases with decreasing hydrogen bonding density. This density depends strongly on temperature. The water dissociation percentage at the surface can be correlated with the ratio between the weights of the stretching and the bending modes. Our results are in good agreement with inelastic neutron scattering measurements done on wet titania nanoparticles.
Energy Technology Data Exchange (ETDEWEB)
Fonda, H.N.; Oertling, W.A.; Salehi, A.; Chang, C.K.; Babcock, G.T. (Michigan State Univ., East Lansing (United States))
1990-12-19
The resonance Raman (RR) and infrared (IR) spectra of the Zn, Cu, and Ni complexes of trans-octaethylchlorin (OEC) reveal significant differences in the vibrational-mode properties of metallochlorins and metalloporphyrins. Modes with a contribution from the C{sub a}C{sub m} stretching coordinate are distinguished by their sensitivity to metal substitution and to selective d{sub 2} and d{sub 4} methine deuteration. Comparison of the resonance Raman spectrum of CuOEC with that of CuECI (ECI = etiochlorin I) identifies those modes with a contribution from C{sub b}C{sub b} and C{sub b}C{sub s} stretching and C{sub b}C{sub s} bending coordinates. The results obtained show that there is substantial mixing of C{sub a}C{sub m} and C{sub b}C{sub b} stretching character in the high-frequency modes of MOEC. The suggestion that the symmetry reduction that occurs in metallochlorins relative to metalloporphyrins produces vibrational-mode localization to specific hemispheres or quadrants of the macrocycle has been tested and confirmed by specific d{sub 2} deuteration at the methine carbons. Resonance Raman spectra of CuOEP-d{sub 2} (OEP = octaethylporphyrin) and CuOEP-d{sub 4} establish that, for a delocalized mode, methine d{sub 2} deuteration can be expected to produce half the d{sub 4} shift. For CuOEC, selective deuteration at the {alpha}{beta} and {gamma},{delta} methine positions causes different patterns of frequency shifts that indicate the extent of mode localization.
Ramya, K. R.; Pavan Kumar, G. V.; Venkatnathan, Arun
2012-05-01
The sI type methane clathrate hydrate lattice is formed during the process of nucleation where methane gas molecules are encapsulated in the form of dodecahedron (512CH4) and tetrakaidecahedron (51262CH4) water cages. The characterization of change in the vibrational modes which occur on the encapsulation of CH4 in these cages plays a key role in understanding the formation of these cages and subsequent growth to form the hydrate lattice. In this present work, we have chosen the density functional theory (DFT) using the dispersion corrected B97-D functional to characterize the Raman frequency vibrational modes of CH4 and surrounding water molecules in these cages. The symmetric and asymmetric C-H stretch in the 512CH4 cage is found to shift to higher frequency due to dispersion interaction of the encapsulated CH4 molecule with the water molecules of the cages. However, the symmetric and asymmetric O-H stretch of water molecules in 512CH4 and 51262CH4 cages are shifted towards lower frequency due to hydrogen bonding, and interactions with the encapsulated CH4 molecules. The CH4 bending modes in the 512CH4 and 51262CH4 cages are blueshifted, though the magnitude of the shifts is lower compared to modes in the high frequency region which suggests bending modes are less affected on encapsulation of CH4. The low frequency librational modes which are collective motion of the water molecules and CH4 in these cages show a broad range of frequencies which suggests that these modes largely contribute to the formation of the hydrate lattice.
Vibrational modes of the Cu(100)-c(2x2)-Pd surface
DEFF Research Database (Denmark)
Stoltze, Per; Hannon, J.B.; Ibach, H.
1996-01-01
The vibrational modes of the surface have been measured using electron-energy loss spectroscopy. The measured mode energies are compared to dynamical models with parameters taken from effective medium theory. Strong Pd-Cu interplanar bonding gives rise to nearly degenerate Pd and Cu vibrations (95...... cm(-1)) at the (X) over bar point, despite the large mass difference of the ions. Upon low-temperature annealing of the surface, overlayer islands of pure Cu coalesce and order. These overlayer islands are characterized by a high-energy vibrational mode near 128 cm(-1) which grows in intensity upon...
Dzung Nguyen, Sy; Kim, Wanho; Park, Jhinha; Choi, Seung-Bok
2017-04-01
Vibration control systems using smart dampers (SmDs) such as magnetorheological and electrorheological dampers (MRD and ERD), which are classified as the integrated structure-SmD control systems (ISSmDCSs), have been actively researched and widely used. This work proposes a new controller for a class of ISSmDCSs in which high accuracy of SmD models as well as increment of control ability to deal with uncertainty and time delay are to be expected. In order to achieve this goal, two formualtion steps are required; a non-parametric SmD model based on an adaptive neuro-fuzzy inference system (ANFIS) and a novel fuzzy sliding mode controller (FSMC) which can weaken the model error of the ISSmDCSs and hence provide enhanced vibration control performances. As for the formulation of the proposed controller, first, an ANFIS controller is desgned to identify SmDs using the improved control algorithm named improved establishing neuro-fuzzy system (establishing neuro-fuzzy system). Second, a new control law for the FSMC is designed via Lyapunov stability analysis. An application to a semi-active MRD vehicle suspension system is then undertaken to illustrate and evaluate the effectiveness of the proposed control method. It is demonstrated through an experimental realization that the FSMC proposed in this work shows superior vibration control performance of the vehicle suspension compared to other surveyed controller which have similar structures to the FSMC, such as fuzzy logic and sliding mode control.
Yang, Jingyu; Lin, Jiahui; Liu, Yuejun; Yang, Kang; Zhou, Lanwei; Chen, Guoping
2017-08-01
It is well known that intelligent control theory has been used in many research fields, novel modeling method (DROMM) is used for flexible rectangular active vibration control, and then the validity of new model is confirmed by comparing finite element model with new model. In this paper, taking advantage of the dynamics of flexible rectangular plate, a two-loop sliding mode (TSM) MIMO approach is introduced for designing multiple-input multiple-output continuous vibration control system, which can overcome uncertainties, disturbances or unstable dynamics. An illustrative example is given in order to show the feasibility of the method. Numerical simulations and experiment confirm the effectiveness of the proposed TSM MIMO controller.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Feng; Tominaga, Keisuke, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-0013 (Japan); Hayashi, Michitoshi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp; Wang, Houng-Wei [Center for Condensed Matter Sciences, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China); Kambara, Ohki; Sasaki, Tetsuo [Research Institute of Electronics, Shizuoka University, 3-5-1 Jyohoku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Nishizawa, Jun-ichi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Jun-ichi Nishizawa Memorial Research Center, Tohoku University, 519-1176 Aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)
2014-05-07
The phonon modes of molecular crystals in the terahertz frequency region often feature delicately coupled inter- and intra-molecular vibrations. Recent advances in density functional theory such as DFT-D{sup *} have enabled accurate frequency calculation. However, the nature of normal modes has not been quantitatively discussed against experimental criteria such as isotope shift (IS) and correlation field splitting (CFS). Here, we report an analytical mode-decoupling method that allows for the decomposition of a normal mode of interest into intermolecular translation, libration, and intramolecular vibrational motions. We show an application of this method using the crystalline anthracene system as an example. The relationship between the experimentally obtained IS and the IS obtained by PBE-D{sup *} simulation indicates that two distinctive regions exist. Region I is associated with a pure intermolecular translation, whereas region II features coupled intramolecular vibrations that are further coupled by a weak intermolecular translation. We find that the PBE-D{sup *} data show excellent agreement with the experimental data in terms of IS and CFS in region II; however, PBE-D{sup *} produces significant deviations in IS in region I where strong coupling between inter- and intra-molecular vibrations contributes to normal modes. The result of this analysis is expected to facilitate future improvement of DFT-D{sup *}.
Matsumura, Takeshi; Esashi, Masayoshi; Harada, Hiroshi; Tanaka, Shuji
For future mobile phones based on cognitive radio technology, a compact multi-band RF front-end architecture is strongly required and an integrated multi-band RF filter bank is a key component in it. Contour-mode resonators are receiving increased attention for a multi-band filter solution, because its resonant frequency is mainly determined by its size and shape, which are defined by lithography. However, spurious responses including flexural vibration are also excited due to its thin structure. To improve resonator performance and suppress spurious modes, visual observation with a laser probe system is very effective. In this paper, we have prototyped a mechanically-coupled disk-array filter, which consists of a Si disk and 2 disk-type resonators of higher-order wine-glass mode, and observed its vibration modes using a high-frequency laser-Doppler vibrometer (UHF-120, Polytec, Inc.). As a result, it was confirmed that higher order wine-glass mode vibration included a compound displacement, and that its out-of-plane vibration amplitude was much smaller than other flexural spurious modes. The observed vibration modes were compared with FEM (Finite Element Method) simulation results. In addition, it was also confirmed that the fabrication error, e.g. miss-alignment, induced asymmetric vibration.
Vibrational relaxation in simulated two-dimensional infrared spectra of two amide modes in solution
Dijkstra, Arend G.; Jansen, Thomas la Cour; Bloem, Robbert; Knoester, Jasper
2007-01-01
Two-dimensional infrared spectroscopy is capable of following the transfer of vibrational energy between modes in real time. We develop a method to include vibrational relaxation in simulations of two-dimensional infrared spectra at finite temperature. The method takes into account the correlated
National Aeronautics and Space Administration — There are several ongoing challenges in non-contacting blade vibration and stress measurement systems that can address closely spaced modes and blade-to-blade...
Directory of Open Access Journals (Sweden)
Alexander G. Milekhin
2017-05-01
Full Text Available Nanoantenna-assisted plasmonic enhancement of IR absorption and Raman scattering was employed for studying the vibrational modes in organic molecules. Ultrathin cobalt phthalocyanine films (3 nm were deposited on Au nanoantenna arrays with specified structural parameters. The deposited organic films reveal the enhancement of both Raman scattering and IR absorption vibrational modes. To extend the possibility of implementing surface-enhanced infrared absorption (SEIRA for biological applications, the detection and analysis of the steroid hormone cortisol was demonstrated.
Acoustic vibration modes and electron-lattice coupling in self-assembled silver nanocolumns.
Burgin, J; Langot, P; Arbouet, A; Margueritat, J; Gonzalo, J; Afonso, C N; Vallée, F; Mlayah, A; Rossell, M D; Van Tendeloo, G
2008-05-01
Using ultrafast spectroscopy, we investigated electron-lattice coupling and acoustic vibrations in self-assembled silver nanocolumns embedded in an amorphous Al2O3 matrix. The measured electron-lattice energy exchange time is smaller in the nanocolumns than in bulk silver, with a value very close to that of isolated nanospheres with comparable surface to volume ratio. Two vibration modes were detected and ascribed to the breathing and extensional mode of the nanocolumns, in agreement with numerical simulations.
Vibrational relaxation of the H2O bending mode in liquid water.
Larsen, Olaf F A; Woutersen, Sander
2004-12-22
We have studied the vibrational relaxation of the H(2)O bending mode in an H(2)O:HDO:D(2)O isotopic mixture using infrared pump-probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55+/-10 cm(-1) for the H(2)O bending mode, and a value of 400+/-30 fs for its vibrational lifetime. (c) 2004 American Institute of Physics.
Modeling and analysis of circular flexural-vibration-mode piezoelectric transformer.
Huang, Yihua; Huang, Wei
2010-12-01
We propose a circular flexural-vibration-mode piezoelectric transformer and perform a theoretical analysis of the transformer. An equivalent circuit is derived from the equations of piezoelectricity and the Hamilton's principle. With this equivalent circuit, the voltage gain ratio, input impedance, and the efficiency of the circular flexural-vibration-mode piezoelectric transformer can be determined. The basic behavior of the transformer is shown by numerical results.
Extended and localized vibrational modes in (1-3) Penrose-like piezocomposites
Montero de Espinosa, F.; Torres, M.
1994-09-01
Acoustic vibrational modes of piezocomposites with ceramic bars arranged at the vertices of both perfect Penrose tilings and random Penrose tilings have directly been observed by recording the corresponding standing vibration amplitude pattern. The random Penrose tiling exhibits similar although smoother spectrum than the perfect Penrose one. For both structures, the existence of extended and localized modes is shown. Resonances frequencies at the edges of the spectrum pseudogap correspond to localized and highly entropic modes. As expected, the modes are more localized in the random Penrose tiling case.
Mei, Chuh; Shen, Mo-How
1987-01-01
Multiple-mode nonlinear forced vibration of a beam was analyzed by the finite element method. Inplane (longitudinal) displacement and inertia (IDI) are considered in the formulation. By combining the finite element method and nonlinear theory, more realistic models of structural response are obtained more easily and faster.
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.
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.
Free vibrations of an arbitrary structure in terms of component modes.
Dowell, E. H.
1972-01-01
A method for the analysis of the free vibrations of an arbitrary structure in terms of component modes is presented based upon the use of the normal, free-free modes of the components in a Rayleigh-Ritz analysis with the constraint or continuity conditions
Westra, H.J.R.; Karabacak, D.M.; Brongersma, S.H.; Crego-Calama, M.; Van der Zant, H.S.J.; Venstra, W.J.
2011-01-01
The interactions between parametrically- and directly-driven vibration modes of a clamped-clamped beam resonator are studied. An integrated piezoelectric transducer is used for direct and parametric excitation. First, the parametric amplification and oscillation of a single mode are analyzed by the
Single-molecule electronics: Cooling individual vibrational modes by the tunneling current.
Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C
2016-03-21
Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.
Mode selection of modal expansion method estimating vibration field of washing machine
Jung, B. K.; Jeong, W. B.
2015-03-01
This paper is about a study estimating the vibration and radiated noise of a washing machine by using a mode selection-applied modal expansion method (MEM). MEM is a technique that identifies the vibration field from a portion of eigenvectors (or mode shapes) of a structure, and thus, the selection of the eigenvectors has a big impact on the vibration results identified. However, there have been few studies about selecting the eigenvectors with respect to the structural vibration and radiated noise estimation. Accordingly, this paper proposes the use of a new mode selection method to identify the vibration based on the MEM and then calculate radiated noise of a washing machine. The results gained from the experiment were also compared. The vibration and noise results of numerical analysis using the proposed selection method are in line with the measured results. The selection method proposed in this paper corresponds well with the MEM and this process seems to be applicable to the estimation of various structure vibrations and radiated noise.
Aerial Ultrasonic Source Using Stripe-Mode Transverse Vibrating Plate with Jutting Driving Point
Miura, Hikaru; Ishikawa, Hitoshi
2009-07-01
Ultrasonic sources using a stripe-mode rectangular transverse vibrating plate have been used as acoustic sources emitting intense acoustic waves in air. Because these sources are based on the resonance of transverse vibration, their electric-acoustic conversion rate is as high as 90%, which is a merit. In this study, a vibrating plate with a unique shape was developed to enhance the effectiveness of acoustic sources. It is called a stripe-mode transverse vibrating plate with a jutting driving point. The advantage of this plate shape is that the acoustic source does not interfere with the emission of acoustic waves since the driving point is outside the plate, and there is no need to distinguish between the front and back sides of the vibrating plate. The conditions effective for driving the stripe-mode transverse vibrating plate were clarified. That is, the length of the side parallel to the node lines of the plate is an odd number times the length between the nodes in the stripe mode, and the length of the side perpendicular is at least 6 times but not a multiple of 3 greater than or equal to 15 times, subtracted by 0.5 times, the length between the nodes. Moreover, the length between the driving point and the edge of the plate is a positive integer with a noninteger value of 0.9.
Localization of natural modes of vibration in bladed disks
Bendiksen, O. O.; Valero, N. A.
1987-01-01
A study is presented of the mode localization phenomenon in imperfect blade-disk and blade-shroud-disk assemblies. The results indicate that unshrouded blades mounted on stiff disks are especially susceptible, and even small blade imperfections within manufacturing tolerances are likely to trigger mode localization. Increasing the interblade coupling by adding shrouds or reducing the disk stiffness greatly reduces the localization susceptiblity, although certain modes may still become localized if the shrouds are free to slip.
Finite-temperature hydrogen adsorption and desorption thermodynamics driven by soft vibration modes.
Woo, Sung-Jae; Lee, Eui-Sup; Yoon, Mina; Kim, Yong-Hyun
2013-08-09
It has been widely accepted that enhanced dihydrogen adsorption is required for room-temperature hydrogen storage on nanostructured porous materials. Here we report, based on results of first-principles total energy and vibrational spectrum calculations, finite-temperature adsorption and desorption thermodynamics of hydrogen molecules that are adsorbed on the metal center of metal-porphyrin-incorporated graphene. We have revealed that the room-temperature hydrogen storage is achievable not only with the enhanced adsorption enthalpy, but also with soft-mode driven vibrational entropy of the adsorbed dihydrogen molecule. The soft vibration modes mostly result from multiple orbital coupling between the hydrogen molecule and the buckled metal center, for example, in Ca-porphyrin-incorporated graphene. Our study suggests that the current design strategy for room-temperature hydrogen storage materials should be modified with explicitly taking the finite-temperature vibration thermodynamics into account.
Lee, Scott A; Pinnick, David A; Anderson, A
2014-12-01
High-pressure Raman spectroscopy has been used to study the eigenvectors and eigenvalues of the vibrational modes of crystalline adenosine at 295 K by evaluating the logarithmic derivative of the vibrational frequency with respect to pressure: [Formula: see text]. Crystalline samples of molecular materials such as adenosine will have vibrational modes that are localized within a molecular unit ("internal" modes) as well as modes in which the molecular units vibrate against each other ("external" modes). The value of the logarithmic derivative is found to be a diagnostic probe of the nature of the eigenvector of the vibrational modes. Stretching modes which are predominantly internal to the molecule have low logarithmic derivatives while external modes have higher logarithmic derivatives. Particular interest is paid to the low-frequency (≤150 cm(-1)) modes. Based on the pressure dependence of its logarithmic derivative, a mode near 49 cm(-1) is identified as internal mode. The other modes below 400 cm(-1) have pressure dependences of their logarithmic derivatives consistent with being either (1) modes which are mainly external, meaning that the molecules of the unit cell vibrate against each other in translational or librational motions (or linear combinations thereof), or (2) torsional or bending modes involving a large number of atoms, mainly within a molecule. The modes above 400 cm(-1) all have pressure dependences of their logarithmic derivatives consistent with being mainly internal modes.
Subfemtosecond steering of hydrocarbon deprotonation through superposition of vibrational modes
Alnaser, A. S.; Kübel, M.; Siemering, R.; Bergues, B.; Kling, Nora G.; Betsch, K. J.; Deng, Y.; Schmidt, J.; Alahmed, Z. A.; Azzeer, A. M.; Ullrich, J.; Ben-Itzhak, I.; Moshammer, R.; Kleineberg, U.; Krausz, F.; de Vivie-Riedle, R.; Kling, M. F.
2014-05-01
Subfemtosecond control of the breaking and making of chemical bonds in polyatomic molecules is poised to open new pathways for the laser-driven synthesis of chemical products. The break-up of the C-H bond in hydrocarbons is an ubiquitous process during laser-induced dissociation. While the yield of the deprotonation of hydrocarbons has been successfully manipulated in recent studies, full control of the reaction would also require a directional control (that is, which C-H bond is broken). Here, we demonstrate steering of deprotonation from symmetric acetylene molecules on subfemtosecond timescales before the break-up of the molecular dication. On the basis of quantum mechanical calculations, the experimental results are interpreted in terms of a novel subfemtosecond control mechanism involving non-resonant excitation and superposition of vibrational degrees of freedom. This mechanism permits control over the directionality of chemical reactions via vibrational excitation on timescales defined by the subcycle evolution of the laser waveform.
Electron-Beam Mapping of Vibrational Modes with Nanometer Spatial Resolution.
Dwyer, C; Aoki, T; Rez, P; Chang, S L Y; Lovejoy, T C; Krivanek, O L
2016-12-16
We demonstrate that a focused beam of high-energy electrons can be used to map the vibrational modes of a material with a spatial resolution of the order of one nanometer. Our demonstration is performed on boron nitride, a polar dielectric which gives rise to both localized and delocalized electron-vibrational scattering, either of which can be selected in our off-axial experimental geometry. Our experimental results are well supported by our calculations, and should reconcile current controversy regarding the spatial resolution achievable in vibrational mapping with focused electron beams.
Vibration Method for Tracking the Resonant Mode and Impedance of a Microwave Cavity
Barmatz, M.; Iny, O.; Yiin, T.; Khan, I.
1995-01-01
A vibration technique his been developed to continuously maintain mode resonance and impedance much between a constant frequency magnetron source and resonant cavity. This method uses a vibrating metal rod to modulate the volume of the cavity in a manner equivalent to modulating an adjustable plunger. A similar vibrating metal rod attached to a stub tuner modulates the waveguide volume between the source and cavity. A phase sensitive detection scheme determines the optimum position of the adjustable plunger and stub turner during processing. The improved power transfer during the heating of a 99.8% pure alumina rod was demonstrated using this new technique. Temperature-time and reflected power-time heating curves are presented for the cases of no tracking, impedance tracker only, mode tracker only and simultaneous impedance and mode tracking. Controlled internal melting of an alumina rod near 2000 C using both tracking units was also demonstrated.
Electronic Properties of Si-Hx Vibrational Modes at Si Waveguide Interface.
Bashouti, Muhammad Y; Yousefi, Peyman; Ristein, Jürgen; Christiansen, Silke H
2015-10-01
Attenuated total reflectance (ATR) and X-ray photoelectron spectroscopy in suite with Kelvin probe were conjugated to explore the electronic properties of Si-Hx vibrational modes by developing Si waveguide with large dynamic detection range compared with conventional IR. The Si 2p emission and work-function related to the formation and elimination of Si-Hx bonds at Si surfaces are monitored based on the detection of vibrational mode frequencies. A transition between various Si-Hx bonds and thus related vibrational modes is monitored for which effective momentum transfer could be demonstrated. The combination of the aforementioned methods provides for results that permit a model for the kinetics of hydrogen termination of Si surfaces with time and advanced surface characterizing of hybrid-terminated semiconducting solids.
"Good Vibrations": A workshop on oscillations and normal modes
Barbieri, Sara; Carpineti, Marina; Giliberti, Marco; Rigon, Enrico; Stellato, Marco; Tamborini, Marina
2016-05-01
We describe some theatrical strategies adopted in a two hour workshop in order to show some meaningful experiments and the underlying useful ideas to describe a secondary school path on oscillations, that develops from harmonic motion to normal modes of oscillations, and makes extensive use of video analysis, data logging, slow motions and applet simulations. Theatre is an extremely useful tool to stimulate motivation starting from positive emotions. That is the reason why the theatrical approach to the presentation of physical themes has been explored by the group "Lo spettacolo della Fisica" (http://spettacolo.fisica.unimi.it) of the Physics Department of University of Milano for the last ten years (Carpineti et al., JCOM, 10 (2011) 1; Nuovo Cimento B, 121 (2006) 901) and has been inserted also in the European FP7 Project TEMI (Teaching Enquiry with Mysteries Incorporated, see http://teachingmysteries.eu/en) which involves 13 different partners coming from 11 European countries, among which the Italian (Milan) group. According to the TEMI guidelines, this workshop has a written script based on emotionally engaging activities of presenting mysteries to be solved while participants have been involved in nice experiments following the developed path.
Non-linear vibrational modes in biomolecules: A periodic orbits description
Energy Technology Data Exchange (ETDEWEB)
Kampanarakis, Alexandros [Department of Chemistry, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (FORTH), Vasilika Vouton, Heraklion 71110, Crete (Greece); Farantos, Stavros C., E-mail: farantos@iesl.forth.gr [Department of Chemistry, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (FORTH), Vasilika Vouton, Heraklion 71110, Crete (Greece); Daskalakis, Vangelis; Varotsis, Constantinos [Department of Environmental Science and Technology, Cyprus University of Technology, 31 Archbishop Kyprianos St., P.O. Box 50329, 3603 Lemesos (Cyprus)
2012-05-03
Graphical abstract: Vibrational frequency shifts in Fe{sup IV} = O species of the active site of cytochrome c oxidase are attributed to changes in the surrounding Coulomb field. Periodic orbits analysis assists to find the most anharmonic modes in model biomolecules. Highlights: Black-Right-Pointing-Pointer Periodic orbits are extended to multidimensional potentials of biomolecules. Black-Right-Pointing-Pointer Highly anharmonic vibrational modes and center-saddle bifurcations are detected. Black-Right-Pointing-Pointer Vibrational frequencies shifts in Oxoferryl species of CcO are observed. - Abstract: The vibrational harmonic normal modes of a molecule, which are valid at energies close to an equilibrium point (a minimum, maximum or saddle of the potential energy surface), are extended by periodic orbits to high energies where anharmonicity and coupling of the degrees of freedom are significant. In this way the assignment of the spectra, and thus the extraction of dynamics in highly excited molecules, can be obtained. New vibrational modes emanating from bifurcations of periodic orbits and long living localized trajectories signal the birth and localization of new quantum states. In this article we review and further study non-linear vibrational modes for model biomolecules such as alanine dipeptide and the active site in the oxoferryl oxidation state of the enzyme cytochrome c oxidase. We locate periodic orbits which exhibit high anhamonicity and lead to center-saddle bifurcations. These modes are associated to an isomerization process in alanine dipeptide and to frequency shifts in the oxoferryl observed by modifying the Coulomb field around the Imidazole-Fe{sup IV} = O species.
Energy Technology Data Exchange (ETDEWEB)
Sharpes, Nathan; Kumar, Prashant [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Abdelkefi, Abdessattar; Abdelmoula, Hichem [Department of Mechanical and Aerospace Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Adler, Jan [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Institute of Dynamics and Vibration Research (IDS), Leibniz Universität, Hannover 30167 (Germany); Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)
2016-07-18
Mode shapes in the design of mechanical energy harvesters, as a means of performance increase, have been largely overlooked. Currently, the vast majority of energy harvester designs employ some variation of a single-degree-of-freedom cantilever, and the mode shapes of such beams are well known. This is especially true for the first bending mode, which is almost exclusively the chosen vibration mode for energy harvesting. Two-dimensional beam shapes (those which curve, meander, spiral, etc., in a plane) have recently gained research interest, as they offer freedom to modify the vibration characteristics of the harvester beam for achieving higher power density. In this study, the second bending mode shape of the “Elephant” two-dimensional beam shape is examined, and its interaction with the first bending mode is evaluated. A combinatory mode shape created by using mass loading structural modification to lower the second bending modal frequency was found to interact with the first bending mode. This is possible since the first two bending modes do not share common areas of displacement. The combined mode shape is shown to produce the most power of any of the considered mode shapes.
Study of surface modes on a vibrating electrowetting liquid lens
Strauch, Matthias; Shao, Yifeng; Bociort, Florian; Urbach, H. Paul
2017-10-01
The increased usage of liquid lenses motivates us to investigate surface waves on the liquid's surface. During fast focal switching, the surface waves decrease the imaging quality. We propose a model that describes the surface modes appearing on a liquid lens and predicts the resonance frequencies. The effects of those surface modes on a laser beam are simulated using Fresnel propagation, and the model is verified experimentally.
Synthesis of stiffness and mass matrices from experimental vibration modes.
Ross, R. G., Jr.
1971-01-01
With highly complex structures, it is sometimes desirable to derive a dynamic model of the system from experimental vibration data. This paper presents algorithms for synthesizing the mass and stiffness matrices from experimentally derived modal data in a way which preserves the physical significance of the individual mass and stiffness elements. The synthesizing procedures allow for the incorporation of other mass and stiffness data, whether empirical or based on the analyst's insight. The mass and stiffness matrices are derived for a cantilever beam example and are compared with those obtained using earlier techniques.
Lee, Scott A; Pinnick, David A; Anderson, A
2015-01-01
Raman spectroscopy has been used to study the eigenvectors and eigenvalues of the vibrational modes of crystalline cytidine at 295 K and high pressures by evaluating the logarithmic derivative of the vibrational frequency ω with respect to pressure P: [Formula: see text]. Crystalline samples of molecular materials have strong intramolecular bonds and weak intermolecular bonds. This hierarchy of bonding strengths causes the vibrational optical modes localized within a molecular unit ("internal" modes) to be relatively high in frequency while the modes in which the molecular units vibrate against each other ("external" modes) have relatively low frequencies. The value of the logarithmic derivative is a useful diagnostic probe of the nature of the eigenvector of the vibrational modes because stretching modes (which are predominantly internal to the molecule) have low logarithmic derivatives while external modes have higher logarithmic derivatives. In crystalline cytidine, the modes at 85.8, 101.4, and 110.6 cm(-1) are external in which the molecules of the unit cell vibrate against each other in either translational or librational motions (or some linear combination thereof). All of the modes above 320 cm(-1) are predominantly internal stretching modes. The remaining modes below 320 cm(-1) include external modes and internal modes, mostly involving either torsional or bending motions of groups of atoms within a molecule.
Mitchell, Deborah G; Johnson, Alan M; Johnson, Jeremy A; Judd, Kortney A; Kim, Kilyoung; Mayhew, Maurine; Powell, Amber L; Sevy, Eric T
2008-02-14
Relaxation of highly vibrationally excited 1,2-, 1,3-, and 1,4-difluorobenzne (DFB) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot DFB (E' approximately 41,000 cm(-1)) was prepared by 248 nm excimer laser excitation followed by rapid radiationless relaxation to the ground electronic state. Collisions between hot DFB isomers and CO2 result in large amounts of rotational and translational energy transfer from the hot donors to the bath. The CO2 nascent rotational population distribution of the high-J (J = 58-80) tail of the 00(0)0 state was probed at short times following the excimer laser pulse to measure rate constants and probabilities for collisions populating these states. The amount of translational energy gained by CO2 during collisions was determined using Doppler spectroscopy to measure the width of the absorption line for each transition. The energy transfer probability distribution function, P(E,E'), for the large DeltaE tail was obtained by resorting the state-indexed energy transfer probabilities as a function of DeltaE. P(E,E') was fit to a biexponential function to determine the average energy transferred in a single DFB/CO2 collision and fit parameters describing the shape of P(E,E'). P(E,E') fit parameters for DFB/CO2 and the previously studied C6F6/CO2 system are compared to various donor molecular properties. A model based on Fermi's Golden Rule indicates that the shape of P(E,E') is primarily determined by the low-frequency out-of-plane donor vibrational modes. A fractional mode population analysis is performed, which suggests that for energy transfer from DFB and C6F6 to CO2 the two key donor vibrational modes from which energy leaks out of the donor into the bath are nu11 and nu16. These "gateway" modes are some of the same modes determined to be the most efficient energy transfer modes by quantum scattering studies of benzene/He collisions.
A comparison of several methods for the calculation of vibration mode shape derivatives
Sutter, T. R.; Camarda, C. J.; Walsh, J. L.; Adelman, H. M.
1986-01-01
Four methods for the calculation of derivatives of vibration mode shapes (eigenvectors) with respect to design parameters are reviewed and compared. These methods (finite difference method, Nelson's method, modal method and a modified modal method) are implemented in a general-purpose commercial finite element program and applied to a cantilever beam and a stiffened cylinder with a cutout. A beam tip mass, a beam root height and specific dimensions of the cylinder model comprise the design variables. Data are presented showing the amount of central processor time used to compute the first four eigenvector derivatives for each example problem; errors and rapidity of convergence of the approximate derivative to the exact derivative are taken into account. Nelson's method proved to be most reliable and efficient.
Hu, Junhui; Jong, Januar; Zhao, Chunsheng
2010-01-01
To increase the vibration energy-harvesting capability of the piezoelectric generator based on a cantilever beam, we have proposed a piezoelectric generator that not only uses the strain change of piezoelectric components bonded on a cantilever beam, but also employs the weights at the tip of the cantilever beam to hit piezoelectric components located on the 2 sides of weights. A prototype of the piezoelectric generator has been fabricated and its characteristics have been measured and analyzed. The experimental results show that the piezoelectric components operating in the hit mode can substantially enhance the energy harvesting of the piezoelectric generator on a cantilever beam. Two methods are used and compared in the management of rectified output voltages from different groups of piezoelectric components. In one of them, the DC voltages from rectifiers are connected in series, and then the total DC voltage is applied to a capacitor. In another connection, the DC voltage from each group is applied to different capacitors. It is found that 22.3% of the harvested energy is wasted due to the series connection. The total output electric energy of our piezoelectric generator at nonresonance could be up to 43 nJ for one vibration excitation applied by spring, with initial vibration amplitude (0-p) of 18 mm and frequency of 18.5 Hz, when the rectified voltages from different groups of piezoelectric components are connected to their individual capacitors. In addition, the motion and impact of the weights at the tip of the cantilever beam are theoretically analyzed, which well explains the experimental phenomena and suggests the measures to improve the generator.
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.
Study of surface modes on a vibrating electrowetting liquid lens
Strauch, M.; Shao, Y.; Bociort, F.; Urbach, Paul
2017-01-01
The increased usage of liquid lenses motivates us to investigate surface waves on the liquid's surface. During fast focal switching, the surface waves decrease the imaging quality. We propose a model that describes the surface modes appearing on a liquid lens and predicts the resonance
Phonon Transport at Crystalline Si/Ge Interfaces: The Role of Interfacial Modes of Vibration.
Gordiz, Kiarash; Henry, Asegun
2016-03-16
We studied the modal contributions to heat conduction at crystalline Si and crystalline Ge interfaces and found that more than 15% of the interface conductance arises from less than 0.1% of the modes in the structure. Using the recently developed interface conductance modal analysis (ICMA) method along with a new complimentary methodology, we mapped the correlations between modes, which revealed that a small group of interfacial modes, which exist between 12-13 THz, exhibit extremely strong correlation with other modes in the system. It is found that these interfacial modes (e.g., modes with large eigen vectors for interfacial atoms) are enabled by the degree of anharmonicity near the interface, which is higher than in the bulk, and therefore allows this small group of modes to couple to all others. The analysis sheds light on the nature of localized vibrations at interfaces and can be enlightening for other investigations of localization.
Improved orthogonality check for measured modes. [from ground vibration testing of structures
Berman, A.
1980-01-01
A method is proposed for performing an orthogonality check for normal modes derived from ground vibration testing. The method utilizes partitioned mass and stiffness matrices for a linear undamped representation of a structure. The normalization of the modes by the proposed method inherently includes the effects of significant displacements which were not measured; and the method may allow the use of fewer measurement points than would be necessary with the conventional method.
Vibrational resonance induced by transition of phase-locking modes in excitable systems.
Yang, Lijian; Liu, Wangheng; Yi, Ming; Wang, Canjun; Zhu, Qiaomu; Zhan, Xuan; Jia, Ya
2012-07-01
We study the occurrence of vibrational resonance as well as the underlying mechanism in excitable systems. The single vibration resonance and vibration bi-resonance are observed when tuning the amplitude and frequency of high-frequency force simultaneously. Furthermore, by virtue of the phase diagram of low-frequency-signal-free FitzHugh-Nagumo model, it is found that each maxima of response measure is located exactly at the transition boundary of phase patterns. Therefore, it is the transition between different phase-locking modes that induces vibrational resonance in the excitable systems. Finally, this mechanism is verified in the Hodgkin-Huxley neural model. Our results provide insights into the transmission of weak signals in nonlinear systems, which are valuable in engineering for potential applications.
Pulsed differential holographic measurements of vibration modes of high temperature panels
Evensen, D. A.; Aprahamian, R.; Overoye, K. R.
1972-01-01
Holography is a lensless imaging technique which can be applied to measure static or dynamic displacements of structures. Conventional holography cannot be readily applied to measure vibration modes of high-temperature structures, due to difficulties caused by thermal convection currents. The present report discusses the use of pulsed differential holography, which is a technique for recording structural motions in the presence of random fluctuations such as turbulence. An analysis of the differential method is presented, and demonstration experiments were conducted using heated stainless steel plates. Vibration modes were successfully recorded for the heated plates at temperatures of 1000, 1600, and 2000 F. The technique appears promising for such future measurments as vibrations of the space shuttle TPS panels or recording flutter of aeroelastic models in a wind-tunnel.
Directory of Open Access Journals (Sweden)
Qiang Zhang
2015-01-01
Full Text Available An analytical model on electromechanical coupling coefficient and the length optimization of a bending piezoelectric ultrasonic transducer are proposed. The piezoelectric transducer consists of 8 PZT elements sandwiched between four thin electrodes, and the PZT elements are clamped by a screwed connection between fore beam and back beam. Firstly, bending vibration model of the piezoelectric transducer is built based on the Timoshenko beam theory. Secondly, the analytical model of effective electromechanical coupling coefficient is built based on the bending vibration model. Energy method and electromechanical equivalent circuit method are involved in the modelling process. To validate the analytical model, sandwich type piezoelectric transducer example in second order bending vibration mode is analysed. Effective electromechanical coupling coefficient of the transducer is optimized with simplex reflection technique, and the optimized ratio of length of the transducers is obtained. Finally, experimental prototypes of the sandwich type piezoelectric transducers are fabricated. Bending vibration mode and impedance of the experimental prototypes are tested, and electromechanical coupling coefficient is obtained according to the testing results. Results show that the analytical model is in good agreement with the experimental model.
Mode pattern of internal flow in a water droplet on a vibrating hydrophobic surface.
Kim, Hun; Lim, Hee-Chang
2015-06-04
The objective of this study is to understand the mode pattern of the internal flow in a water droplet placed on a hydrophobic surface that periodically and vertically vibrates. As a result, a water droplet on a vibrating hydrophobic surface has a typical shape that depends on each resonance mode, and, additionally, we observed a diversified lobe size and internal flows in the water droplet. The size of each lobe at the resonance frequency was relatively greater than that at the neighboring frequencies, and the internal flow of the nth order mode was also observed in the flow visualization. In general, large symmetrical flow streams were generated along the vertical axis in each mode, with a large circulating movement from the bottom to the top, and then to the triple contact line along the droplet surface. In contrast, modes 2 and 4 generated a Y-shaped flow pattern, in which the flow moved to the node point in the lower part of the droplet, but modes 6 and 8 had similar patterns, with only a little difference. In addition, as a result of the PIV measurement, while the flow velocity of mode 4 was faster than that of model 2, those of modes 6 and 8 were almost similar.
Observation of sound-induced corneal vibrational modes by optical coherence tomography
Akca, B. Imran; Chang, Ernest W.; Kling, Sabine; Ramier, Antoine; Scarcelli, Giuliano; Marcos, Susana; Yun, Seok H.
2015-01-01
The mechanical stability of the cornea is critical for maintaining its normal shape and refractive function. Here, we report an observation of the mechanical resonance modes of the cornea excited by sound waves and detected by using phase-sensitive optical coherence tomography. The cornea in bovine eye globes exhibited three resonance modes in a frequency range of 50-400 Hz. The vibration amplitude of the fundamental mode at 80-120 Hz was ~8 µm at a sound pressure level of 100 dB (2 Pa). Vibr...
Wang, Ji; Yang, Jiashi; Li, Jiangyu
2007-03-01
Energy trapping has important applications in the design of thickness-shear resonators. Considerable efforts have been made for the effective utilization and improvement of energy trapping with variations of plate configurations, such as adding electrodes and contouring. As a new approach in seeking improved energy trapping feature, we analyze thickness-shear vibrations in an elastic plate with functionally graded material (FGM) of in-plane variation of mechanical properties, such as elastic constants and density. A simple and general equation governing the thickness-shear modes is derived from a variational analysis. A plate with piecewise constant material properties is analyzed as an example. It is shown that such a plate can support thickness-shear vibration modes with obvious energy trapping. Bechmann's number for the existence of only one trapped mode also can be determined accordingly.
Directory of Open Access Journals (Sweden)
Sun Yi-Hang
2017-01-01
Full Text Available In order to detect a mechanical type of structural failure of the circuit breaker, the characteristics of the circuit breaker mechanical vibration signal is analyzed in this paper. A combination of medium voltage circuit breaker based on empirical mode decomposition (EMD amount of energy and support vector machine (SVM theory vibration signal feature vector extraction and analysis of fault classification method is proposed. First, the vibration signal of the circuit breaker is decomposed by EMD, then intrinsic mode function (IMF is obtain. The major fault feature information intrinsic mode functions the amount of energy of the component is obtained by discrete sampling points and the amount of energy. Using the amount of energy of IMF component as a feature vector, the failure of the test sample signal as input feature vector into trained “BT-SVM” support vector machine classification mechanism for fault classification. The differences and fault type of vibration signals can be identified by this method through the experimental analysis.
Energy Technology Data Exchange (ETDEWEB)
Chase, Hilary M.; Chen, Shunli; Fu, Li; Upshur, Mary Alice; Rudshteyn, Benjamin; Thomson, Regan J.; Wang, Hong-Fei; Batista, Victor S.; Geiger, Franz M.
2017-09-01
Inferring molecular orientations from vibrational sum frequency generation (SFG) spectra is challenging in polarization combinations that result in low signal intensities, or when the local point group symmetry approximation fails. While combining experiments with density functional theory (DFT) could overcome this problem, the scope of the combined method has yet to be established. Here, we assess its feasibility of determining the distributions of molecular orientations for one monobasic ester, two epoxides and three alcohols at the vapor/fused silica interface. We find that molecular orientations of nonlocal vibrational modes cannot be determined using polarization-resolved SFG measurements alone.
Space structure vibration modes: How many exist? Which ones are important?
Hughes, P. C.
1984-01-01
This report attempts to shed some light on the two issues raised in the title, namely, how many vibration modes does a real structure have, and which of these modes are important? The surprise-free answers to these two questions are, respectively, an infinite number and the first several modes. The author argues that the absurd subspace (all but the first billion modes) is not a strength of continuum modeling, but, in fact, a weakness. Partial differential equations are not real structures, only mathematical models. This note also explains (1) that the PDE model and the finite element model are, in fact, the same model, the latter being a numerical method for dealing with the former, (2) that modes may be selected on dynamical grounds other than frequency alone, and (3) that long slender rods are useful as primitive cases but dangerous to extrapolate from.
Using input command pre-shaping to suppress multiple mode vibration
Hyde, James M.; Seering, Warren P.
1990-01-01
Spacecraft, space-borne robotic systems, and manufacturing equipment often utilize lightweight materials and configurations that give rise to vibration problems. Prior research has led to the development of input command pre-shapers that can significantly reduce residual vibration. These shapers exhibit marked insensitivity to errors in natural frequency estimates and can be combined to minimize vibration at more than one frequency. This paper presents a method for the development of multiple mode input shapers which are simpler to implement than previous designs and produce smaller system response delays. The new technique involves the solution of a group of simultaneous non-linear impulse constraint equations. The resulting shapers were tested on a model of MACE, an MIT/NASA experimental flexible structure.
Wang, Zhao; Yan, Hong; Li, Qibing; Xu, Kun
2017-12-01
The unified gas-kinetic scheme (UGKS) is a direct modeling method for both continuum and rarefied flow computations. In the previous study, the UGKS was developed for diatomic molecular simulations with translation and rotational motions. In this paper, a UGKS with non-equilibrium translational, rotational, and vibrational degrees of freedom, will be developed. The new scheme is based on the phenomenological gas dynamics model, where the translational, rotational, and vibrational modes get to the equilibrium with different time scales with the introduction of rotational and vibrational collision numbers. This new scheme is tested in a few cases, such as the homogeneous flow relaxation, shock structure, shock tube problem, and flow passing through a circular and semi-circular cylinders. The analytical and DSMC solutions are used for the validation of the UGKS, and reasonable agreements have been achieved.
Vibrational Surface Electron-Energy-Loss Spectroscopy Probes Confined Surface-Phonon Modes
Directory of Open Access Journals (Sweden)
Hugo Lourenço-Martins
2017-12-01
Full Text Available Recently, two reports [Krivanek et al. Nature (London 514, 209 (2014NATUAS0028-083610.1038/nature13870, Lagos et al. Nature (London 543, 529 (2017NATUAS0028-083610.1038/nature21699] have demonstrated the amazing possibility to probe vibrational excitations from nanoparticles with a spatial resolution much smaller than the corresponding free-space phonon wavelength using electron-energy-loss spectroscopy (EELS. While Lagos et al. evidenced a strong spatial and spectral modulation of the EELS signal over a nanoparticle, Krivanek et al. did not. Here, we show that discrepancies among different EELS experiments as well as their relation to optical near- and far-field optical experiments [Dai et al. Science 343, 1125 (2014SCIEAS0036-807510.1126/science.1246833] can be understood by introducing the concept of confined bright and dark surface phonon modes, whose density of states is probed by EELS. Such a concise formalism is the vibrational counterpart of the broadly used formalism for localized surface plasmons [Ouyang and Isaacson Philos. Mag. B 60, 481 (1989PMABDJ1364-281210.1080/13642818908205921, García de Abajo and Aizpurua Phys. Rev. B 56, 15873 (1997PRBMDO0163-182910.1103/PhysRevB.56.15873, García de Abajo and Kociak Phys. Rev. Lett. 100, 106804 (2008PRLTAO0031-900710.1103/PhysRevLett.100.106804, Boudarham and Kociak Phys. Rev. B 85, 245447 (2012PRBMDO1098-012110.1103/PhysRevB.85.245447]; it makes it straightforward to predict or interpret phenomena already known for localized surface plasmons such as environment-related energy shifts or the possibility of 3D mapping of the related surface charge densities [Collins et al. ACS Photonics 2, 1628 (2015APCHD52330-402210.1021/acsphotonics.5b00421].
Vortex-induced vibration of a tension leg platform tendon: multi-mode limit cycle oscillations
Datta, Nabanita
2017-11-01
This paper studies the application of mathematical models to analyze the vortex-induced vibrations of the tendons of a given TLP along the Indian coastline, by using an analytical approach, analyzed using MATLAB. The tendon is subjected to a steady current load, which causes vortex-shedding downstream, leading to cross-flow vibrations. The magnitude of the excitation (lift and drag coefficients) depends on the vortex-shedding frequency. The resulting vibration is studied for possible resonant behavior. The excitation force is quantified empirically, the added mass by potential flow hydrodynamics, and the vibration by normal mode summation method. Non-linear viscous damping of the water is considered. The non-linear oscillations are studied by the phase-plane method, investigating the limit-cycle oscillations. The stable/unstable regions of the dynamic behavior are demarcated. The modal contribution to the total deflection is studied to establish the possibility of resonance of one of the wet modes with the vortex-shedding frequency.
Gribakin, G. F.; Stanton, J. F.; Danielson, J. R.; Natisin, M. R.; Surko, C. M.
2017-12-01
The dominant mechanism of low-energy positron annihilation in polyatomic molecules is through positron capture in vibrational Feshbach resonances (VFR). In this paper, we investigate theoretically the effect of anharmonic terms in the vibrational Hamiltonian on positron annihilation rates. Such interactions enable positron capture in VFRs associated with multiquantum vibrational excitations, leading to enhanced annihilation. Mode coupling can also lead to faster depopulation of VFRs, thereby reducing their contribution to the annihilation rates. To analyze this complex picture, we use coupled-cluster methods to calculate the anharmonic vibrational spectra and dipole transition amplitudes for chloroform, chloroform-d1, 1,1-dichloroethylene, and methanol, and use these data to compute positron resonant annihilation rates for these molecules. Theoretical predictions are compared with the annihilation rates measured as a function of incident positron energy. The results demonstrate the importance of mode coupling in both enhancement and suppression of the VFR. There is also experimental evidence for the direct excitation of multimode VFR. Their contribution is analyzed using a statistical approach, with an outlook towards more accurate treatment of this phenomenon.
Vortex-induced vibration of a tension leg platform tendon: Multi-mode limit cycle oscillations
Datta, Nabanita
2017-12-01
This paper studies the application of mathematical models to analyze the vortex-induced vibrations of the tendons of a given TLP along the Indian coastline, by using an analytical approach, analyzed using MATLAB. The tendon is subjected to a steady current load, which causes vortex-shedding downstream, leading to cross-flow vibrations. The magnitude of the excitation (lift and drag coefficients) depends on the vortex-shedding frequency. The resulting vibration is studied for possible resonant behavior. The excitation force is quantified empirically, the added mass by potential flow hydrodynamics, and the vibration by normal mode summation method. Non-linear viscous damping of the water is considered. The non-linear oscillations are studied by the phase-plane method, investigating the limit-cycle oscillations. The stable/unstable regions of the dynamic behavior are demarcated. The modal contribution to the total deflection is studied to establish the possibility of resonance of one of the wet modes with the vortex-shedding frequency.
Energy Technology Data Exchange (ETDEWEB)
Mugarza, Aitor; Shimizu, Tomoko K.; Ogletree, D. Frank; Salmeron, Miquel
2009-05-07
Tunneling electrons in a scanning tunneling microscope were used to excite specific vibrational quantum states of adsorbed water and hydroxyl molecules on a Ru(0 0 0 1) surface. The excited molecules relaxed by transfer of energy to lower energy modes, resulting in diffusion, dissociation, desorption, and surface-tip transfer processes. Diffusion of H{sub 2}O molecules could be induced by excitation of the O-H stretch vibration mode at 445 meV. Isolated molecules required excitation of one single quantum while molecules bonded to a C atom required at least two quanta. Dissociation of single H{sub 2}O molecules into H and OH required electron energies of 1 eV or higher while dissociation of OH required at least 2 eV electrons. In contrast, water molecules forming part of a cluster could be dissociated with electron energies of 0.5 eV.
Site-selective detection of vibrational modes of an iron atom in a trinuclear complex
Energy Technology Data Exchange (ETDEWEB)
Faus, Isabelle, E-mail: faus@rhrk.uni-kl.de; Rackwitz, Sergej; Wolny, Juliusz A. [University of Kaiserslautern, Department of Physics (Germany); Banerjee, Atanu; Kelm, Harald; Krüger, Hans-Jörg [University of Kaiserslautern, Department of Chemistry (Germany); Schlage, Kai; Wille, Hans-Christian [DESY, PETRA III, P01 (Germany); Schünemann, Volker [University of Kaiserslautern, Department of Physics (Germany)
2016-12-15
Nuclear inelastic scattering (NIS) experiments on the trinuclear complex [{sup 57}Fe{L-N_4(CH_2Fc)_2} (CH{sub 3}CN){sub 2}](ClO{sub 4}){sub 2} have been performed. The octahedral iron ion in the complex was labelled with {sup 57}Fe and thereby exclusively the vibrational modes of this iron ion have been detected with NIS. The analysis of nuclear forward scattering (NFS) data yields a ferrous low-spin state for the {sup 57}Fe labelled iron ion. The simulation of the partial density of states (pDOS) for the octahedral low-spin iron(II) ion of the complex by density functional theory (DFT) calculations is in excellent agreement with the experimental pDOS of the complex determined from the NIS data obtained at 80 K. Thereby it was possible to assign almost each of the experimentally observed NIS bands to the corresponding molecular vibrational modes.
Multiple mode analysis of the self-excited vibrations of rotary drilling systems
Germay, Christophe; Denoël, Vincent; Detournay, Emmanuel
2009-08-01
This paper extends the analysis of the self-excitated vibrations of a drilling structure presented in an earlier paper [T. Richard, C. Germay, E. Detournay, A simplified model to explore the root cause of stick-slip vibrations in drilling systems with drag bits, Journal of Sound and Vibration 305 (3) (2007) 432-456] by basing the formulation of the model on a continuum representation of the drillstring rather than on a characterization of the drilling structure by a 2 degree of freedom system. The particular boundary conditions at the bit-rock interface, which according to this model are responsible for the self-excited vibrations, account for both cutting and frictional contact processes. The cutting process combined with the quasi-helical motion of the bit leads to a regenerative effect that introduces a coupling between the axial and torsional modes of vibrations and a state-dependent delay in the governing equations, while the frictional contact process is associated with discontinuities in the boundary conditions when the bit sticks in its axial and angular motion. The dynamic response of the drilling structure is computed using the finite element method. While the general tendencies of the system response predicted by the discrete model are confirmed by this computational model (for example that the occurrence of stick-slip vibrations as well as the risk of bit bouncing are enhanced with an increase of the weight-on-bit or a decrease of the rotational speed), new features in the self-excited response of the drillstring can be detected. In particular, stick-slip vibrations are predicted to occur at natural frequencies of the drillstring different from the fundamental one (as sometimes observed in field operations), depending on the operating parameters.
Optimization procedure to control the coupling of vibration modes in flexible space structures
Walsh, Joanne L.
1987-01-01
As spacecraft structural concepts increase in size and flexibility, the vibration frequencies become more closely-spaced. The identification and control of such closely-spaced frequencies present a significant challenge. To validate system identification and control methods prior to actual flight, simpler space structures will be flown. To challenge the above technologies, it will be necessary to design these structures with closely-spaced or coupled vibration modes. Thus, there exists a need to develop a systematic method to design a structure which has closely-spaced vibration frequencies. This paper describes an optimization procedure which is used to design a large flexible structure to have closely-spaced vibration frequencies. The procedure uses a general-purpose finite element analysis program for the vibration and sensitivity analyses and a general-purpose optimization program. Results are presented from two studies. The first study uses a detailed model of a large flexible structure to design a structure with one pair of closely-spaced frequencies. The second study uses a simple equivalent beam model of a large flexible structure to obtain a design with two pairs of closely-spaced frequencies.
Lin, Shuyu
2012-01-01
The piezoelectric ultrasonic composite transducer, which can be used in either gas or liquid media, is studied in this paper. The composite transducer is composed of a longitudinal sandwich piezoelectric transducer, a mechanical transformer, and a metal circular plate in flexural vibration. Acoustic radiation is produced by the flexural circular plate, which is excited by the longitudinal sandwich transducer and transformer. Based on the classic flexural theory of plates, the equivalent lumped parameters for a plate in axially symmetric flexural vibration with free boundary conditions are obtained. The radiation impedance of the plate is derived and the relationship between the radiation impedance and the frequency is analyzed. The equivalent circuits for the plate in flexural vibration and the composite transducer are given. The vibrational modes and the harmonic response of the composite piezoelectric transducer are simulated by the numerical method. Based on the theoretical and numerical analysis, two composite piezoelectric ultrasonic transducers are designed and manufactured, their admittance-frequency curves are measured, and the resonance frequency is obtained. The flexural vibrational displacement distribution of the transducer is measured with a laser scanning vibrometer. It is shown that the theoretical results are in good agreement with the measured resonance frequency and the displacement distribution. © 2012 IEEE
On the correlation between phase-locking modes and Vibrational Resonance in a neuronal model
Morfu, S.; Bordet, M.
2018-02-01
We numerically and experimentally investigate the underlying mechanism leading to multiple resonances in the FitzHugh-Nagumo model driven by a bichromatic excitation. Using a FitzHugh-Nagumo circuit, we first analyze the number of spikes triggered by the system in response to a single sinusoidal wave forcing. We build an encoding diagram where different phase-locking modes are identified according to the amplitude and frequency of the sinusoidal excitation. Next, we consider the bichromatic driving which consists in a low frequency sinusoidal wave perturbed by an additive high frequency signal. Beside the classical Vibrational Resonance phenomenon, we show in real experiments that multiple resonances can be reached by an appropriate setting of the perturbation parameters. We clearly establish a correlation between these resonances and the encoding diagram of the low frequency signal free FitzHugh-Nagumo model. We show with realistic parameters that sharp transitions of the encoding diagram allow to predict the main resonances. Our experiments are confirmed by numerical simulations of the system response.
Influence of vibration modes on control system stabilization for space shuttle type vehicles
Greiner, H. G.
1972-01-01
An investigation was made to determine the feasibility of using conventional autopilot techniques to stabilize the vibration modes at the liftoff flight condition for two space shuttle configurations. One configuration is called the dual flyback vehicle in which both the orbiter and booster vehicles have wings and complete flyback capability. The other configuration is called the solid motor vehicle win which the orbiter only has flyback. The results of the linear stability analyses for each of the vehicles are summarized.
Vibration Control of Flexible Mode for a Beam-Type Substrate Transport Robot
Directory of Open Access Journals (Sweden)
Cheol Hoon Park
2013-07-01
Full Text Available Beam-type substrate transport robots are widely used to handle substrates, especially in the solar cell manufacturing process. To reduce the takt time and increase productivity, accurate position control becomes increasingly important as the size of the substrate increases. However, the vibration caused by the flexible forks in beam-type robots interferes with accurate positioning, which results in long takt times in the manufacturing process. To minimize the vibration and transport substrates on the fork as fast as possible, the trajectories should be prevented from exciting the flexible modes of the forks. For this purpose, a fifth-order polynomial trajectory generator and input shaping were incorporated into the controller of the beam-type robot in this study. The flexible modes of the forks were identified by measuring the frequency response function (FRF, and the input shaping was designed so as not to excite the flexible modes. The controller was implemented by using MATLAB/xPC Target. In this paper, the design procedure of input shaping and its effectiveness for vibration attenuation in both “no load” and “load” cases is presented.
Multiple-mode nonlinear free and forced vibrations of beams using finite element method
Mei, Chuh; Decha-Umphai, Kamolphan
1987-01-01
Multiple-mode nonlinear free and forced vibration of a beam is analyzed by the finite element method. The geometric nonlinearity is investigated. Inplane displacement and inertia (IDI) are also considered in the formulation. Harmonic force matrix is derived and explained. Nonlinear free vibration can be simply treated as a special case of the general forced vibration by setting the harmonic force matrix equal to zero. The effect of the higher modes is more pronouced for the clamped supported beam than the simply supported one. Beams without IDI yield more effect of the higher modes than the one with IDI. The effects of IDI are to reduce nonlinearity. For beams with end supports restrained from axial movement (immovable cases), only the hardening type nonlinearity is observed. However, beams of small slenderness ratio (L/R = 20) with movable end supports, the softening type nonlinearity is found. The concentrated force case yields a more severe response than the uniformly distributed force case. Finite element results are in good agreement with the solution of simple elliptic response, harmonic balance method, and Runge-Kutte method and experiment.
Eriksson, T J R; Ramadas, S N; Dixon, S M
2016-02-01
A unimorph flexural transducer design is proposed and tested with regard to mode shapes and frequencies. The transducers consist of a passive metal cap structure, and a thin piezoelectric disc, rigidly bonded to the inside. Extensive finite element (FE) modelling, and experimental 2D, time-resolved displacement measurements were done to characterise the transducers flexural properties, and to compare them to the analytical solutions of thin vibrating plates. Emphasis was put on characterising the passive layer of the unimorph structure, before bonding the piezoelectric element, to understand how the active element affects the behaviour of the flexing plate. A high power Nd:YAG laser was used to actuate the metal plate (non-contact), and the frequency content of the resulting displacement signal was analysed to identify the flexural modes. The non-axisymmetric modes, which are conventionally disregarded because of their unfavourable acoustic properties, were also taken into account. There was excellent agreement between the experimental results and the FE simulation data. There was good agreement with the analytical edge clamped plate model, but with some notable deviations, which have not previously been identified or commented upon. Specifically, the second axisymmetric mode is split into three separate modes, which is not explained by the traditional theory of vibrating plates. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.
Identification of surface species by vibrational normal mode analysis. A DFT study
Zhao, Zhi-Jian; Genest, Alexander; Rösch, Notker
2017-10-01
Infrared spectroscopy is an important experimental tool for identifying molecular species adsorbed on a metal surface that can be used in situ. Often vibrational modes in such IR spectra of surface species are assigned and identified by comparison with vibrational spectra of related (molecular) compounds of known structure, e. g., an organometallic cluster analogue. To check the validity of this strategy, we carried out a computational study where we compared the normal modes of three C2Hx species (x = 3, 4) in two types of systems, as adsorbates on the Pt(111) surface and as ligands in an organometallic cluster compound. The results of our DFT calculations reproduce the experimental observed frequencies with deviations of at most 50 cm-1. However, the frequencies of the C2Hx species in both types of systems have to be interpreted with due caution if the coordination mode is unknown. The comparative identification strategy works satisfactorily when the coordination mode of the molecular species (ethylidyne) is similar on the surface and in the metal cluster. However, large shifts are encountered when the molecular species (vinyl) exhibits different coordination modes on both types of substrates.
Thompson, Lee M; Lasoroski, Aurélie; Champion, Paul M; Sage, J Timothy; Frisch, Michael J; van Thor, Jasper J; Bearpark, Michael J
2014-02-11
A systematic comparison of different environmental effects on the vibrational modes of the 4-hydroxybenzylidene-2,3-dimethylimidazolinone (HBDI) chromophore using the ONIOM method allows us to model how the molecule's spectroscopic transitions are modified in the Green Fluorescent Protein (GFP). ONIOM(QM:MM) reduces the expense of normal mode calculations when computing the majority of second derivatives only at the MM level. New developments described here for the efficient solution of the CPHF equations, including contributions from electrostatic interactions with environment charges, mean that QM model systems of ∼100 atoms can be embedded within a much larger MM environment of ∼5000 atoms. The resulting vibrational normal modes, their associated frequencies, and dipole derivative vectors have been used to interpret experimental difference spectra (GFPI2-GFPA), chromophore vibrational Stark shifts, and changes in the difference between electronic and vibrational transition dipoles (mode angles) in the protein environment.
USE OF WHOLE-BODY VIBRATION AS A MODE OF WARMING UP BEFORE COUNTER MOVEMENT JUMP
Directory of Open Access Journals (Sweden)
Enrique G. Artero
2007-12-01
Full Text Available Whole-body vibration (WBV has been suggested to be particularly effective on the stretch-shortening cycle-based movements, such as the counter movement jump (CMJ test (Issurin, 2005. Nevertheless, the literature on short-term vibration exposure and lower limb explosive performance (measured by CMJ test is contradictory. Either transient improvements (Bosco et al., 2000; Cochrane and Stannard, 2005; Torvinen et al., 2002a or no effects (Torvinen et al., 2002b; Rittweger et al., 2003; Cormie et al., 2006 have been reported after a single WBV exposure ranging from 30 s to 10 min. The present study aimed at better characterizing the use of a single short bout of WBV as a mode of warming up before a CMJ test.A total of 114 university students (37 men, 77 women, aged 19.6 ± 2.0 years signed an informed consent form and volunteered to participate in the study. The study protocol was approved by the Review Committee for Research Involving Human Subjects of our center. Participants were asked to come to the laboratory in three occasions three days apart. First visit: familiarization session aiming to learn the CMJ technique and to experience the vibration stimulus. Second visit: the participants performed three consecutive CMJ with one min rest interval. No significant differences were observed among the jumps, and the highest score was retained. Third visit: the participants were exposed to a single short bout of WBV and immediately after they performed three CMJ with one min rest interval.An infrared contact timing platform (ERGO JUMP Plus - BOSCO SYSTEM, Byomedic, S.C.P., Barcelona, Spain was used to measure "flight" time (t during the vertical jump (accuracy 0.001 s. Maximum height achieved by the body centre of gravity (h was then estimated, i.e. h = g · t2 / 8, where g = 9.81 m/s2. In all occasions, the participants were instructed to abstain from strenuous exercise for the preceding 24 hours.Whole-body vibration was carried out on an oscillating
Approximate natural vibration analysis of rectangular plates with openings using assumed mode method
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Dae Seung Cho
2013-09-01
Full Text Available Natural vibration analysis of plates with openings of different shape represents an important issue in naval architecture and ocean engineering applications. In this paper, a procedure for vibration analysis of plates with openings and arbitrary edge constraints is presented. It is based on the assumed mode method, where natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion. The presented solution represents an extension of a procedure for natural vibration analysis of rectangular plates without openings, which has been recently presented in the literature. The effect of an opening is taken into account in an intuitive way, i.e. by subtracting its energy from the total plate energy without opening. Illustrative numerical examples include dynamic analysis of rectangular plates with rectangular, elliptic, circular as well as oval openings with various plate thicknesses and different combinations of boundary conditions. The results are compared with those obtained by the finite element method (FEM as well as those available in the relevant literature, and very good agreement is achieved.
Energy Technology Data Exchange (ETDEWEB)
Schliesser, A; Anetsberger, G; Riviere, R; Arcizet, O; Kippenberg, T J [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)], E-mail: tjk@mpq.mpg.de
2008-09-15
The inherent coupling of optical and mechanical modes in high finesse optical microresonators provides a natural, highly sensitive transduction mechanism for micromechanical vibration. Using homodyne and polarization spectroscopy techniques, we achieve shot-noise limited displacement sensitivities of 10{sup -19} m Hz{sup -1/2}. In an unprecedented manner, this enables the detection and study of a variety of mechanical modes, which are identified as radial breathing, flexural and torsional modes using three-dimensional finite element modeling. Furthermore, a broadband equivalent displacement noise is measured and found to agree well with models for thermorefractive noise in silica dielectric cavities. Implications for ground-state cooling, displacement sensing and Kerr squeezing are discussed.
Edighoffer, H. H.
1979-01-01
A component mode desynthesis procedure is developed for determining the unknown vibration characteristics of a structural component (i.e., a launch vehicle) given the vibration characteristics of a structural system composed of that component combined with a known one (i.e., a payload). At least one component static test has to be performed. These data are used in conjunction with the system measured frequencies and mode shapes to obtain the vibration characteristics of each component. The flight dynamics of an empty launch vehicle can be determined from measurements made on a vehicle/payload combination in conjunction with a static test on the payload.
Effects of poroelastic coefficients on normal vibration modes in vocal-fold tissues.
Tao, Chao; Liu, Xiaojun
2011-02-01
The vocal-fold tissue is treated as a transversally isotropic fluid-saturated porous material. Effects of poroelastic coefficients on eigenfrequencies and eigenmodes of the vocal-fold vibration are investigated using the Ritz method. The study demonstrates that the often-used elastic model is only a particular case of the poroelastic model with an infinite fluid-solid mass coupling parameter. The elastic model may be considered appropriate for the vocal-fold tissue when the absolute value of the fluid-solid mass coupling parameter is larger than 10(5) kg/m(3). Otherwise, the poroelastic model may be more accurate. The degree of compressibility of the vocal tissue can also been described by the poroelastic coefficients. Finally, it is revealed that the liquid and solid components in a poroelastic model could have different modal shapes when the coupling between them is weak. The mode decoupling could cause desynchronization and irregular vibration of the folds.
Goos-Hänchen effect for optical vibrational modes in a semiconductor structure
Villegas, Diosdado; Arriaga, J.; de León-Pérez, Fernando; Pérez-Álvarez, R.
2017-03-01
We study the tunneling of optical vibrational modes with transverse horizontal polarization that impinge, at a given angle, on a semiconductor heterostructure. We find a large influence of the Goos-Hänchen shift on tunneling times. In particular, a Goos-Hänchen shift larger than the barrier thickness is reported for the first time. The relation between Goos-Hänchen and Hartman effects is also discussed. The identity that equals the dwell time to the sum of transmission and interference times, previously derived for one-dimensional tunneling problems, is extended to the two-dimensional case. Closed-form expressions are developed for the relevant quantities. Instead of using the standard approach, the interference time is computed from the vibrational energy density. The present study could be useful for the design of semiconductor devices.
Yamada, Toshiki; Tominari, Yukihiro; Tanaka, Shukichi; Mizuno, Maya; Fukunaga, Kaori
2014-11-17
The terahertz and infrared frequency vibration modes of room-temperature ionic liquids with imidazolium cations and halogen anions were extensively investigated. There is an intermolecular vibrational mode between the imidazolium ring of an imidazolium cation, a halogen atomic anion with a large absorption coefficient and a broad bandwidth in the low THz frequency region (13-130 cm(-1)), the intramolecular vibrational modes of the alkyl-chain part of an imidazolium cation with a relatively small absorption coefficient in the mid THz frequency region (130-500 cm(-1)), the intramolecular skeletal vibrational modes of an imidazolium ring affected by the interaction between the imidazolium ring, and a halogen anion with a relatively large absorption coefficient in a high THz frequency region (500-670 cm(-1)). Interesting spectroscopic features on the interaction between imidazolium cations and halogen anions was also obtained from spectroscopic studies at IR frequencies (550-3300 cm(-1)). As far as the frequency of the intermolecular vibrational mode is concerned, we found the significance of the reduced mass in determining the intermolecular vibration frequency.
A disk-pivot structure micro piezoelectric actuator using vibration mode B11.
Chu, Xiangcheng; Ma, Long; Li, Longtu
2006-12-22
Micro piezoelectric actuator using vibration mode B(11) (B(mn), where m is the number of nodal circles, n is the nodal diameters) is designed. Different from conventional wobble-type ultrasonic motor using piezoelectric rod or cylinder, piezoelectric disc is used to excite wobble modes and metal cylinder stator is used to amplify the transverse displacement, metal rod rotor is actuated to rotate. The outer diameter of the actuator is 14mm. There are features such as low drive voltage, micromation, and convenient control of wobble state by modifying the structure of stator, etc. Finite element analysis (FEA) of the stator has been made. It is found that the resonant frequency of vibration mode B(11) is 49.03kHz, which is measured at 45.7kHz by the laser vibrometer and impedance analyzer. The rotation speed has been measured, which could be as high as 10,071rpm under an alternating current 100V. Such piezoelectric actuator can be optimized and adjusted to fit practical conditions. It can be applied in the fields of precise instrument, bioengineering and other micro actuator system.
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Tsen Shaw-Wei D
2006-09-01
Full Text Available Abstract Background Recently, a technique which departs radically from conventional approaches has been proposed. This novel technique utilizes biological objects such as viruses as nano-templates for the fabrication of nanostructure elements. For example, rod-shaped viruses such as the M13 phage and tobacco mosaic virus have been successfully used as biological templates for the synthesis of semiconductor and metallic nanowires. Results and discussion Low wave number (≤ 20 cm-1 acoustic vibrations of the M13 phage have been studied using Raman spectroscopy. The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode has been shown to belong to one of the Raman-active axial torsion modes of the M13 phage protein coat. Conclusion It is expected that the detection and characterization of this low frequency vibrational mode can be used for applications in nanotechnology such as for monitoring the process of virus functionalization and self-assembly. For example, the differences in Raman spectra can be used to monitor the coating of virus with some other materials and nano-assembly process, such as attaching a carbon nanotube or quantum dots.
Energy Technology Data Exchange (ETDEWEB)
Zhou, Shui-Ting; Huang, Hong-Wu [Hunan University, Changsha (China); Chiu, Yi-Jui; Yu, Guo-Fei [Xiamen University of Technology, Xiamen (China); Yang, Chia-Hao [Taipei Chengshih University of Science and Technology, Taipei (China); Jian, Sheng-Rui [I-Shou University, Kaohsiung (China)
2017-02-15
The Assumed mode method (AMM) and Finite element method (FEM) were used. Their results were compared to investigate the coupled shaft-torsion, disk-transverse, and blade-bending vibrations in a flexible-disk rotor system. The blades were grouped with a spring. The flexible-disk rotor system was divided into three modes of coupled vibrations: Shaft-disk-blade, disk-blade, and blade-blade. Two new modes of coupled vibrations were introduced, namely, lacing wires-blade and lacing wires-disk-blade. The patterns of change of the natural frequencies and mode shapes of the system were discussed. The results showed the following: first, mode shapes and natural frequencies varied, and the results of the AMM and FEM differed; second, numerical calculation results showed three influencing factors on natural frequencies, namely, the lacing wire constant, the lacing wire location, and the flexible disk; lastly, the flexible disk could affect the stability of the system as reflected in the effect of the rotational speed.
Xu, Pei-Cang; Li, Ru-Bi; Shang, Tong-Ming; Zhou, Jian; Sun, Jian-Hua; You, Jing-Lin
2010-05-01
Silicate melts are special fractal dimension system that is metastable state of near-way order and far-way disorder. In this paper, the size of nanometer aggregation structure and the frequences of phonon vibration like mode in the low dimension silicate series (CaO-Al2O3-SiO2 and Na2-Al2O3-SiO2 series) synthesized via high temperature melting and sol gel methods were measured by means of small-angle X-ray scattering (SAXS), low wavenumber Raman spectrum (LWRS) and high temperature Raman spectrum (HTRS in situ measuring). The nanometer self-similarity aggregation structure(it's size is about a few nm to a few tens nm) and phonic phonon vibration like modes of low temperature silicate gel, high temperature silicate melts and it's quenching glasses phases were obtained. So a quantitative method by HTRS for measuring the aggregation size in the high temperature melts was established. The results showed that the aggregation size of the silicate melts is smaller at high temperature than at room temperature and the number of bridge oxygen in one Si-O tetrahedron in network structure units is decreasing at high temperature. This study work provides important theory and information for deliberating geochemistry characteristic, crystallization & evolution of natural magma and enhancing performance of low dimension silicate matelials.
Pan, Minghao; Yang, Yongmin; Guan, Fengjiao; Hu, Haifeng; Xu, Hailong
2017-01-01
The accurate monitoring of blade vibration under operating conditions is essential in turbo-machinery testing. Blade tip timing (BTT) is a promising non-contact technique for the measurement of blade vibrations. However, the BTT sampling data are inherently under-sampled and contaminated with several measurement uncertainties. How to recover frequency spectra of blade vibrations though processing these under-sampled biased signals is a bottleneck problem. A novel method of BTT signal processing for alleviating measurement uncertainties in recovery of multi-mode blade vibration frequency spectrum is proposed in this paper. The method can be divided into four phases. First, a single measurement vector model is built by exploiting that the blade vibration signals are sparse in frequency spectra. Secondly, the uniqueness of the nonnegative sparse solution is studied to achieve the vibration frequency spectrum. Thirdly, typical sources of BTT measurement uncertainties are quantitatively analyzed. Finally, an improved vibration frequency spectra recovery method is proposed to get a guaranteed level of sparse solution when measurement results are biased. Simulations and experiments are performed to prove the feasibility of the proposed method. The most outstanding advantage is that this method can prevent the recovered multi-mode vibration spectra from being affected by BTT measurement uncertainties without increasing the probe number. PMID:28758952
Resonant electron-impact excitation of vibrational modes in polyatomic molecules
Cartwright, David C.; Trajmar, Sandor
1996-04-01
Measured differential cross sections (DCSs) for electron-impact excitation of bending vibrational modes involving an odd number of vibrational quanta in 0953-4075/29/8/018/img5 by 4 eV incident energy electrons display a strong trend to zero for forward and backward scattering which is characteristic of `symmetry-forbidden' transitions. This DCS behaviour is postulated here to be produced by a Feshbach resonant mechanism involving a low-lying bent excited state of 0953-4075/29/8/018/img5. The model described here identifies three additional low-lying bent excited states of 0953-4075/29/8/018/img5 which could also be parent states for core-excited Feshbach resonances, one of which may play a role in dissociative attachment in this 3.5 - 5.0 eV energy region. The resonant vibrational excitation mechanism proposed here is also believed to be operative in other polyatomic molecules and could be investigated by performing selected electron energy-loss measurements within the lowest energy resonance regions of the molecules 0953-4075/29/8/018/img8 and 0953-4075/29/8/018/img9.
Aouani, Heykel; Šípová, Hana; Rahmani, Mohsen; Navarro-Cia, Miguel; Hegnerová, Kateřina; Homola, Jiří; Hong, Minghui; Maier, Stefan A
2013-01-22
Optical antennas represent an enabling technology for enhancing the detection of molecular vibrational signatures at low concentrations and probing the chemical composition of a sample in order to identify target molecules. However, efficiently detecting different vibrational modes to determine the presence (or the absence) of a molecular species requires a multispectral interrogation in a window of several micrometers, as many molecules present informative fingerprint spectra in the mid-infrared between 2.5 and 10 μm. As most nanoantennas exhibit a narrow-band response because of their dipolar nature, they are not suitable for such applications. Here, we propose the use of multifrequency optical antennas designed for operating with a bandwidth of several octaves. We demonstrate that surface-enhanced infrared absorption gains in the order of 10(5) can be easily obtained in a spectral window of 3 μm with attomolar concentrations of molecules, providing new opportunities for ultrasensitive broadband detection of molecular species via vibrational spectroscopy techniques.
Sub-THz spectroscopic characterization of vibrational modes in artificially designed DNA monocrystal
Sizov, Igor; Rahman, Masudur; Gelmont, Boris; Norton, Michael L.; Globus, Tatiana
2013-11-01
Sub-terahertz (sub-THz) vibrational spectroscopy is a new spectroscopic branch for characterizing biological macromolecules. In this work, highly resolved sub-THz resonance spectroscopy is used for characterizing engineered molecular structures, an artificially designed DNA monocrystal, built from a short DNA sequence. Using a recently developed frequency domain spectroscopic instrument operating at room temperature with high spectral and spatial resolution, we demonstrated very intense and specific spectral lines from a DNA crystal in general agreement with a computational molecular dynamics (MD) simulation of a short double stranded DNA fragment. The spectroscopic signature measured in the frequency range between 310 and 490 GHz is rich in well resolved and reproducible spectral features thus demonstrating the capability of THz resonance spectroscopy to be used for characterizing custom macromolecules and structures designed and implemented via nanotechnology for a wide variety of application domains. Analysis of MD simulation indicates that intense and narrow vibrational modes with atomic movements perpendicular (transverse) and parallel (longitudinal) to the long DNA axis coexist in dsDNA, with much higher contribution from longitudinal vibrations.
Pacheco-Londono, Leonardo C.; Primera-Pedrozo, Oliva M.; Hernandez-Rivera, Samuel P.
2004-12-01
Fully optimized molecular geometry, parameters of reactivity and vibrational spectra of triacetone triperoxide (TATP) and homologue organic peroxides were calculated using B3LYP/6-31G(d,p) method within the Density Functional Theory formalism. Infrared and Raman Spectroscopy were utilized to obtain vibrational spectra of the energetic compound. The model consists in the relation found between the Raman Shift location of the important symmetric stretch ν(O-O) of the organic peroxides and the reactivity of the organic peroxides. A good correlation between the band location in the series studied and the x-y plane polarizability component and the ionization energy was found. Gas phase IR absorption of TATP in air was used for developing stand-off detection schemes of the important organic peroxide in air. The sublimation properties of TATP were measured using two methods: Grazing Angle Probe-Fiber Coupled FTIR and gravimetric on stainless steel surfaces. Sublimation rates, loading concentration values and absorbance band areas were measured and modeled using the persistent IR vibrational signature of the ν(C-O) mode.
Application of empirical mode decomposition method for characterization of random vibration signals
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Setyamartana Parman
2016-07-01
Full Text Available Characterization of finite measured signals is a great of importance in dynamical modeling and system identification. This paper addresses an approach for characterization of measured random vibration signals where the approach rests on a method called empirical mode decomposition (EMD. The applicability of proposed approach is tested in one numerical and experimental data from a structural system, namely spar platform. The results are three main signal components, comprising: noise embedded in the measured signal as the first component, first intrinsic mode function (IMF called as the wave frequency response (WFR as the second component and second IMF called as the low frequency response (LFR as the third component while the residue is the trend. Band-pass filter (BPF method is taken as benchmark for the results obtained from EMD method.
Kwon, Oh Kuen; Hwang, Ho Jung; Park, Jungcheol
2013-12-01
We investigate tunable graphene-nanoribbon (GNR)-resonators actuated in the tangential direction, and their properties are compared to those actuated in the normal direction, via classical molecular dynamics simulations. These GNR-resonators can be tuned both by the initial strain and the gate. The relationships between the frequency-versus-gate and the initial strain in this work are in good agreement with those in previous experimental works. With increasing initial strain, the resonance frequencies are greatly upshifted, whereas the tunable ranges in frequency are greatly decreased. The tunability in the dynamic operating range decreases with increasing initial strain. For very small strains, the GNR-resonators have large dynamic operating ranges in the normal vibration mode, and for large strains, the GNR-resonators have higher operating frequencies in the tangential vibration mode. The resonance frequencies are estimated by a classical continuum model, with tension acting on the GNR-resonators consisting of both initial tension by initial strain and induced tension by gate actuating.
Portnov, Alexander; Epshtein, Michael; Bar, Ilana
2017-06-01
Nonadiabatic processes, dominated by dynamic passage of reactive fluxes through conical intersections (CIs) are considered to be appealing means for manipulating reaction paths. One approach that is considered to be effective in controlling the course of dissociation processes is the selective excitation of vibrational modes containing a considerable component of motion. Here, we have chosen to study the predissociation of the model test molecule, methylamine and its deuterated isotopologues, excited to well-characterized quantum states on the first excited electronic state, S_{1}, by following the N-H(D) bond fission dynamics through sensitive H(D) photofragment probing. The branching ratios between slow and fast H(D) photofragments, the internal energies of their counter radical photofragments and the anisotropy parameters for fast H photofragments, confirm correlated anomalies for predissociation initiated from specific rovibronic states, reflecting the existence of a dynamic resonance in each molecule. This resonance strongly depends on the energy of the initially excited rovibronic states, the evolving vibrational mode on the repulsive S_{1} part during N-H(D) bond elongation, and the manipulated passage through the CI that leads to radicals excited with C-N-H(D) bending and preferential perpendicular bond breaking, relative to the photolyzing laser polarization, in molecules containing the NH_{2} group. The indicated resonance plays an important role in the bifurcation dynamics at the CI and can be foreseen to exist in other photoinitiated processes and to control their outcome.
Baggott, J. E.; Law, D. W.; Lightfoot, P. D.; Mills, I. M.
1986-11-01
In part I of this study [Baggott, Clase, and Mills, Spectrochim. Acta Part A 42, 319 (1986)] we presented FTIR spectra of gas phase cyclobutene and modeled the v=1-3 stretching states of both olefinic and methylenic C-H bonds in terms of a local mode model. In this paper we present some improvements to our original model and make use of recently derived ``x,K relations'' to find the equivalent normal mode descriptions. The use of both the local mode and normal mode approaches to modeling the vibrational structure is described in some detail. We present evidence for Fermi resonance interactions between the methylenic C-H stretch overtones and ring C-C stretch vibrations, revealed in laser photoacoustic spectra in the v=4-6 region. An approximate model vibrational Hamiltonian is proposed to explain the observed structure and is used to calculate the dynamics of the C-H stretch local mode decay resulting from interaction with lower frequency ring modes. The implications of our experimental and theoretical studies for mode-selective photochemistry are discussed briefly.
Leclerc, Lara; Merhie, Amira El; Navarro, Laurent; Prévôt, Nathalie; Durand, Marc; Pourchez, Jérémie
2015-10-15
We investigated the impact of vibrating acoustic airflow, the high frequency (f≥100 Hz) and the low frequency (f≤45 Hz) sound waves, on the enhancement of intrasinus drug deposition. (81m)Kr-gas ventilation study was performed in a plastinated human cast with and without the addition of vibrating acoustic airflow. Similarly, intrasinus drug deposition in a nasal replica using gentamicin as a marker was studied with and without the superposition of different modes of acoustic airflow. Ventilation experiments demonstrate that no sinus ventilation was observed without acoustic airflow although sinus ventilation occurred whatever the modes of acoustic airflow applied. Intrasinus drug deposition experiments showed that the high frequency acoustic airflow led to 4-fold increase in gentamicin deposition into the left maxillary sinus and to 2-fold deposition increase into the right maxillary sinus. Besides, the low frequency acoustic airflow demonstrated a significant increase of 4-fold and 2-fold in the right and left maxillary sinuses, respectively. We demonstrated the benefit of different modes of vibrating acoustic airflow for maxillary sinus ventilation and intrasinus drug deposition. The degree of gentamicin deposition varies as a function of frequency of the vibrating acoustic airflow and the geometry of the ostia. Copyright © 2015 Elsevier B.V. All rights reserved.
Phu, Do Xuan; Choi, Seung-Bok
2015-02-01
In this work, a new high-load magnetorheological (MR) fluid mount system is devised and applied to control vibration in a ship engine. In the investigation of vibration-control performance, a new modified indirect fuzzy sliding mode controller is formulated and realized. The design of the proposed MR mount is based on the flow mode of MR fluid, and it includes two separated coils for generating a magnetic field. An optimization process is carried out to achieve maximal damping force under certain design constraints, such as the allowable height of the mount. As an actuating smart fluid, a new plate-like iron-particle-based MR fluid is used, instead of the conventional spherical iron-particle-based MR fluid. After evaluating the field-dependent yield stress of the MR fluid, the field-dependent damping force required to control unwanted vibration in the ship engine is determined. Subsequently, an appropriate-sized MR mount is manufactured and its damping characteristics are evaluated. After confirming the sufficient damping force level of the manufactured MR mount, a medium-sized ship engine mount system consisting of eight MR mounts is established, and its dynamic governing equations are derived. A new modified indirect fuzzy sliding mode controller is then formulated and applied to the engine mount system. The displacement and velocity responses show that the unwanted vibrations of the ship engine system can be effectively controlled in both the axial and radial directions by applying the proposed control methodology.
Ultrasonic vibration seeds showed improved resistance to cadmium and lead in wheat seedling.
Chen, Yi-ping; Liu, Qiang; Yue, Xiao-zhen; Meng, Zhong-wen; Liang, Jing
2013-07-01
Heavy metals have long-term adverse impacts on the health of soil ecosystems and even exhibit hazardous influences on human health. Literatures have shown that heavy metals could result in the reduction of crops growth and development and finally result in crops production decline. To determine whether or not ultrasonic vibration alleviate damage induced by cadmium and lead in crops, the wheat seeds, which is one of the most important agriculture crops in China and other countries in the world, were exposed to 10 min ultrasonic vibration and then the toxicological effects were investigated. Wheat seeds were soaked for 3 h with water and then the seeds were placed in clean beaker with some water, the beaker were placed in ultrasonic apparatus to vibrate (model, KQ-200VDV; frequency, 45 KHz; power, 160 W). Pretreatment seeds of 80 were sown in dishes (Ø 15 cm). After seeds emergence, the seedlings were thinned to 60 per dish. The dishes with seedlings were placed in a growth chamber maintained at 25 °C, 70% relative humidity and 380 μmol mol(-1) CO2 under dark condition. A 400 μmol m(-2) s(-1) photosynthetically active radiation was provided for 8 h (dark for 16 h) after the seed germination. When the seedlings were 2 days old, the seedlings were subjected to cadmium and lead for 4 days and then some selective biochemical and physiological parameters were measured. (1) Although each doses of ultrasonic vibration could improve seed germination, enhance biosynthesis of protein and chlorophyll and seedlings growth, the optimum dosage of ultrasonic vibration was 10 min. (2) Compared with the controls, cadmium and lead stress led to significant increase in the concentrations of malondialdehyde (MDA) and O(-2) and in the conductivity of electrolyte leakage, but the activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), the glutathione concentration, and the shoot weight were decreased by Cd and Pb stress. In the case of the seeds
Wang, Xiao Hu; Zheng, Chang Cheng; Ning, Ji Qiang
2016-01-01
Transition-metal dichalcogenides (TMDs) nanostructures including nanotubes and monolayers have attracted great interests in materials science, chemistry to condensed matter physics. We present an interesting study of the vibration modes in multi-walled tungsten sulfide (WS2) nanotubes prepared via sulfurizing tungsten oxide (WO3) nanowires which are investigated by confocal micro-Raman spectroscopy. The inter-layer vibration mode of WS2 nanotubes, A1g, is found to be sensitive to the diameter and curvature strain, while the in-plane vibration mode, E12g, is not. A1g mode frequency shows a redshift by 2.5 cm−1 for the multi-layered nanotubes with small outer-diameters, which is an outcome of the competition between the Van der Waals force stiffening and the curvature strain softening. We also show that the Raman peak intensity ratio is significantly different between the 1–2 wall layered nanotubes and monolayer flat sheets. PMID:27620879
Directory of Open Access Journals (Sweden)
Ehsan Maani Miandoab
2013-01-01
Full Text Available Two different control methods, namely, adaptive sliding mode control and impulse damper, are used to control the chaotic vibration of a block on a belt system due to the rate-dependent friction. In the first method, using the sliding mode control technique and based on the Lyapunov stability theory, a sliding surface is determined, and an adaptive control law is established which stabilizes the chaotic response of the system. In the second control method, the vibration of this system is controlled by an impulse damper. In this method, an impulsive force is applied to the system by expanding and contracting the PZT stack according to efficient control law. Numerical simulations demonstrate the effectiveness of both methods in controlling the chaotic vibration of the system. It is shown that the settling time of the controlled system using impulse damper is less than that one controlled by adaptive sliding mode control; however, it needs more control effort.
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Miguel Cruz-Irisson
2013-04-01
Full Text Available The vibrational dispersion relations of porous germanium (pGe and germanium nanowires (GeNWs were calculated using the ab initio density functional perturbation theory with a generalized gradient approximation with norm-conserving pseudopotentials. Both pores and nanowires were modeled using the supercell technique. All of the surface dangling bonds were saturated with hydrogen atoms. To address the difference in the confinement between the pores and the nanowires, we calculated the vibrational density of states of the two materials. The results indicate that there is a slight shift in the highest optical mode of the Ge-Ge vibration interval in all of the nanostructures due to the phonon confinement effects. The GeNWs exhibit a reduced phonon confinement compared with the porous Ge due to the mixed Ge-dihydride vibrational modes around the maximum bulk Ge optical mode of approximately 300 cm−1; however, the general effects of such confinements could still be noticed, such as the shift to lower frequencies of the highest optical mode belonging to the Ge vibrations.
A magnetic damper for first mode vibration reduction in multimass flexible rotors
Kasarda, M. E. F.; Allaire, P. E.; Humphris, R. R.; Barrett, L. E.
1989-01-01
Many rotating machines such as compressors, turbines and pumps have long thin shafts with resulting vibration problems, and would benefit from additional damping near the center of the shaft. Magnetic dampers have the potential to be employed in these machines because they can operate in the working fluid environment unlike conventional bearings. An experimental test rig is described which was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing. With typical control parameter settings, the midspan location reduced the first mode vibration 82 percent, the disk location reduced it 75 percent and the bearing location attained a 74 percent reduction. Magnetic damper stiffness and damping values used to obtain these reductions were only a few percent of the bearing stiffness and damping values. A theoretical model of both the rotor and the damper was developed and compared to the measured results. The agreement was good.
Complex modes of vibration due to small-scale damping in a guitar topplate
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J. A. Torres
2010-04-01
Full Text Available Modal analysis is one of the preeminent methods used by scientists and engineers to study vibrating structures. The frequency responsefunctions obtained through this method, are, in general, complex-valued. There is, however, no agreed-upon interpretation given to thereal and imaginary parts of these functions, even though it is acknowledged that their relative magnitude for different frequencies is relatedto the behaviour of the corresponding modes. A simple model is deduced to describe the shape of the spectrum associated with afinite-length time-signal. There is very good agreement between results obtained using this model and numerical results obtained for,in this case, the vibration of a guitar top-plate using finite element methods. One interpretation of the relative magnitudes of the real and imaginary parts of the frequency response functions is advanced. It is found that stationary-wave behaviour is associated with the dominance of the real or imaginary part; traveling-wave behaviour, on the other hand, occurs when the real and imaginary parts are of the same order of magnitude, as long as the scale of damping is large enough and resonance peaks in the spectrum are close enough.
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Ming-Chang Pai
2012-01-01
Full Text Available Input shaping technique is widely used in reducing or eliminating residual vibration of flexible structures. The exact elimination of the residual vibration via input shaping technique depends on the amplitudes and instants of impulse application. However, systems always have parameter uncertainties which can lead to performance degradation. In this paper, a closed-loop input shaping control scheme is developed for uncertain flexible structures. The algorithm is based on input shaping control and adaptive sliding mode control. The proposed scheme does not need a priori knowledge of upper bounds on the norm of the uncertainties, but estimates them by using the adaptation technique. This scheme guarantees closed-loop system stability, and yields good performance and robustness in the presence of parameter uncertainties and external disturbances as well. Furthermore, it is shown that increasing the robustness to parameter uncertainties does not lengthen the duration of the impulse sequence. Simulation results demonstrate the efficacy of the proposed closed-loop input shaping control scheme.
A simple method for designing structural models with closely spaced modes of vibration
Hallauer, W. L., Jr.; Weisshaar, T. A.; Shostak, A. G.
1978-01-01
A simple method for designing a mathematical model with closely spaced vibration modes is described. The design process begins with a reference model having specified geometry, continuous inertia and stiffness distributions, and degrees of freedom, all of which remain unchanged. Two natural frequencies of this model are then forced together by means of systematic perturbation of the model's discrete inertia and stiffness parameters. There is only one eigenvalue solution per design cycle, and the gradient vector is calculated directly from the resulting modal quantities. The minimization procedure employed is unconstrained. As applications, a cantilevered plane grid model with five degrees of freedom and a bending-torsion-oscillator with eleven degrees of freedom are treated.
Local vibration modes of shallow thermal donors in nitrogen-doped CZ silicon crystals
Energy Technology Data Exchange (ETDEWEB)
Inoue, N. [RIAST, Osaka Prefecture University, Sakai, 599-8570 (Japan) and Nitrogen Measurement WG, JEITA, Tokyo, 101-0062 (Japan)]. E-mail: inouen@riast.osakafu-u.ac.jp; Nakatsu, M. [RIAST, Osaka Prefecture University, Sakai, 599-8570 (Japan); Ono, H. [Japan Fine Ceramics Center, Tokyo, 105-0003 (Japan); Nitrogen Measurement WG, JEITA, Tokyo, 101-0062 (Japan)
2006-04-01
Local vibration mode (LVM) infrared absorption from shallow thermal donors (STD) composed of nitrogen-oxygen complexes in nitrogen-doped CZ silicon crystals was examined. The samples whose STD concentration had been determined were measured. The sample dependence of the peaks at 810 and 1018cm{sup -1} was similar to that of STD but the estimated concentration was slightly higher. New LVM peaks were found at 855, 973, 982, 1002cm{sup -1} and so on. Their magnitude and sample dependence agreed well with those of STD. Annealing temperature dependence of other samples supported the results. Annealing time dependence of STD concentration at 650 deg. C was examined. STD peaks at 250, 242 and those at 240, 234 and 238cm{sup -1} behaved differently, suggesting the presence of two kinds of STD origin.
National Research Council Canada - National Science Library
Jianghong Xue; Fei Xia; Jun Ye; Jianwen Zhang; Shuhua Chen; Ying Xiong; Zuyuan Tan; Renhuai Liu; Hong Yuan
2017-01-01
This paper presents a multiscale approach to study the nonlinear vibration of fiber reinforced composite laminates containing an embedded, through-width delamination dividing the laminate into four sub-laminates...
Naito, Koki; Asami, Takuya; Miura, Hikaru
2015-07-01
Intense aerial acoustic waves can be produced by an ultrasonic source consisting of a transverse vibrating plate and an external jutting driving point. Previously, we studied the dimensional parameters of vibrating plates to produce stripe-mode patterns and thereby determine the plate dimensions that generate high-quality patterns. In this research, we use four transverse vibrating plates as ultrasonic sources to produce intense standing wave fields in air. As a result, an aerial standing wave field was formed in the field surrounded by four vibrating plates. Furthermore, for a total input power of 30 W for the two ultrasonic sources, a very strong (sound pressure level, 167 dB) wave field is obtained.
Dijkstra, Arend G.; Jansen, Thomas la Cour; Knoester, Jasper
2011-01-01
The amide vibrational modes play an important role in energy transport and relaxation in polypeptides and proteins and provide us with spectral markers for structure and structural dynamics of these macromolecules. Here, we present a detailed model to describe the dynamic properties of the amide I
Stretching dependence of the vibration modes of a single-molecule Pt-H-2-Pt bridge
DEFF Research Database (Denmark)
Djukic, D.; Thygesen, Kristian Sommer; Untiedt, C.
2005-01-01
A conducting bridge of a single hydrogen molecule between Pt electrodes is formed in a break junction experiment. It has a conductance near the quantum unit, G(0)=2e(2)/h, carried by a single channel. Using point-contact spectroscopy three vibration modes are observed and their variation upon...
VCD Robustness of the Amide-I and Amide-II Vibrational Modes of Small Peptide Models.
Góbi, Sándor; Magyarfalvi, Gábor; Tarczay, György
2015-09-01
The rotational strengths and the robustness values of amide-I and amide-II vibrational modes of For(AA)n NHMe (where AA is Val, Asn, Asp, or Cys, n = 1-5 for Val and Asn; n = 1 for Asp and Cys) model peptides with α-helix and β-sheet backbone conformations were computed by density functional methods. The robustness results verify empirical rules drawn from experiments and from computed rotational strengths linking amide-I and amide-II patterns in the vibrational circular dichroism (VCD) spectra of peptides with their backbone structures. For peptides with at least three residues (n ≥ 3) these characteristic patterns from coupled amide vibrational modes have robust signatures. For shorter peptide models many vibrational modes are nonrobust, and the robust modes can be dependent on the residues or on their side chain conformations in addition to backbone conformations. These robust VCD bands, however, provide information for the detailed structural analysis of these smaller systems. © 2015 Wiley Periodicals, Inc.
Hsieh, Chih-Chun; Wang, Peng-Shuen; Wang, Jia-Siang; Wu, Weite
2014-01-01
Simultaneous vibration welding of 304 stainless steel was carried out with an eccentric circulating vibrator and a magnetic telescopic vibrator at subresonant (362 Hz and 59.3 Hz) and resonant (376 Hz and 60.9 Hz) frequencies. The experimental results indicate that the temperature gradient can be increased, accelerating nucleation and causing grain refinement during this process. During simultaneous vibration welding primary δ -ferrite can be refined and the morphologies of retained δ-ferrite become discontinuous so that δ-ferrite contents decrease. The smallest content of δ-ferrite (5.5%) occurred using the eccentric circulating vibrator. The diffraction intensities decreased and the FWHM widened with both vibration and no vibration. A residual stress can obviously be increased, producing an excellent effect on stress relief at a resonant frequency. The stress relief effect with an eccentric circulating vibrator was better than that obtained using a magnetic telescopic vibrator.
Mei, Chuh
1987-01-01
A finite element method is presented for the large amplitude vibrations of complex structures that can be modelled with beam and rectangular plate elements subjected to harmonic excitation. Both inplane deformation and inertia are considered in the formulation. Derivation of the harmonic force and nonlinear stiffness matrices for a beam and a rectangular plate element are presented. Solution procedures and convergence characteristics of the finite element method are described. Nonlinear response to uniform and concentrated harmonic loadings and improved nonlinear free vibration results are presented for beams and rectangular plates of various boundary conditions.
Gamallo, Pablo; Francia, Rafael; Martínez, Rodrigo; Sayós, Ramón; González, Miguel
2012-12-06
The dynamics and kinetics of the O((3)P) + CS(X(1)Σ(+)) → CO(X(1)Σ(+)) + S((3)P) chemical laser reaction was studied theoretically in detail for the first time, as a function of collision energy (0.0388-2.0 eV) and rovibrational excitation of CS. This was made using the quasi-classical trajectory (QCT) method and employing the best ab initio analytical ground potential energy surface (1(3)A' PES) available. A broad set of properties was determined, including scalar and vector properties, and the reaction mode. The behaviors observed and the considerable formation of OCS collision complexes were interpreted from some characteristics of the PES (early barrier, shallow minimum in the exit channel, and high exoergicity (mainly channeled into CO vibration; up to ∼81% of the available energy)) and the kinematics. The QCT vibrational and rotational CO populations and the vector properties show a quite good agreement with experiments, but the QCT rate constants disagree. To better account for the kinetics, we performed CASPT2/aug-cc-pVTZ ab initio calculations on the stationary points along the minimum energy path of the ground and first excited (1(3)A'') PESs. The transition state theory, which can be satisfactorily applied here, leads to rate constants (100-2000 K) that are quite close to the measured ones, where comparison is possible (150-300 K). We expect that these results will encourage further theoretical and experimental developments.
Bastida, Adolfo; Soler, Miguel A; Zúñiga, José; Requena, Alberto; Kalstein, Adrián; Fernández-Alberti, Sebastian
2010-11-04
Nonequilibrium molecular dynamics (MD) simulations and instantaneous normal mode (INMs) analyses are used to study the vibrational relaxation of the C-H stretching modes (ν(s)(CH₃)) of deuterated N-methylacetamide (NMAD) in aqueous (D2O) solution. The INMs are identified unequivocally in terms of the equilibrium normal modes (ENMs), or groups of them, using a restricted version of the recently proposed Min-Cost assignment method. After excitation of the parent ν(s)(CH₃) modes with one vibrational quantum, the vibrational energy is shown to dissipate through both intramolecular vibrational redistribution (IVR) and intermolecular vibrational energy transfer (VET). The decay of the vibrational energy of the ν(s)(CH₃) modes is well fitted to a triple exponential function, with each characterizing a well-defined stage of the entire relaxation process. The first, and major, relaxation stage corresponds to a coherent ultrashort (τ(rel) = 0.07 ps) energy transfer from the parent ν(s)(CH₃) modes to the methyl bending modes δ(CH₃), so that the initially excited state rapidly evolves into a mixed stretch-bend state. In the second stage, characterized by a time of 0.92 ps, the vibrational energy flows through IVR to a number of mid-range-energy vibrations of the solute. In the third stage, the vibrational energy accumulated in the excited modes dissipates into the bath through an indirect VET process mediated by lower-energy modes, on a time scale of 10.6 ps. All the specific relaxation channels participating in the whole relaxation process are properly identified. The results from the simulations are finally compared with the recent experimental measurements of the ν(s)(CH₃) vibrational energy relaxation in NMAD/D₂O(l) reported by Dlott et al. (J. Phys. Chem. A 2009, 113, 75.) using ultrafast infrared-Raman spectroscopy.
Energy Technology Data Exchange (ETDEWEB)
Londos, C. A.; Antonaras, G. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece); Chroneos, A. [Materials Engineering, The Open University, Milton Keynes MK7 6AA (United Kingdom); Department of Materials, Imperial College, London SW7 2AZ (United Kingdom)
2013-07-28
The evolution of self-interstitial clusters in silicon (Si), produced by fast neutron irradiation of silicon crystals followed by anneals up to 750 °C, is investigated using localised vibrational mode spectroscopy. A band at 582 cm{sup −1} appears after irradiation and is stable up to 550 °C was attributed to small self-interstitial clusters (I{sub n}, n ≤ 4), with the most probable candidate the I{sub 4} structure. Two bands at 713 and 758 cm{sup −1} arising in the spectra upon annealing of the 582 cm{sup −1} band and surviving up to ∼750 °C were correlated with larger interstitial clusters (I{sub n}, 5 ≤ n ≤ 8), with the most probable candidate the I{sub 8} structure or/and with chainlike defects which are precursors of the (311) extended defects. The results illustrate the presence of different interstitial clusters I{sub n}, at the various temperature intervals of the material, in the course of an isochronal anneal sequence. As the annealing temperature increases, they evolve from first-order structures with a small number of self-interstitials (I{sub n}, n ≤ 4) for the temperatures 50 < T < 550 °C, to second order structures (I{sub n}, 5 ≤ n ≤ 8) with a larger number of interstitials, for the temperatures 550 < T < 750 °C.
Local vibration modes and nitrogen incorporation in AlGaAs:N layers
Energy Technology Data Exchange (ETDEWEB)
Gallardo, E.; Lazic, S.; Calleja, J.M. [Dept. de Fisica de Materiales, Universidad Autonoma de Madrid (Spain); Miguel-Sanchez, J.; Montes, M.; Hierro, A.; Gargallo-Caballero, R.; Guzman, A.; Munoz, E. [Instituto de Sistemas Optoelectronicos y Microtecnologia, Universidad Politecnica de Madrid (Spain); Teweldeberhan, A.M.; Fahy, S. [Tyndall National Institute, Cork (Ireland)
2008-07-01
Raman scattering measurements in dilute AlGaAs:N films grown by plasma-assisted molecular beam epitaxy on (100) GaAs substrates reveal strong local vibration modes (LVM) associated to N complexes. The LVM observed frequencies between 325 and 540 cm{sup -1} are in good agreement with density functional theory supercell calculations of Al{sub n}Ga{sub 4-n}N complexes (n=1,2,3,4). We find that the observed LVMs correspond to all n values including Al{sub 4}N. The LVMs spectra are resonant at energies around 1.85 eV. The values of the extended phonon frequencies of the ternary compound (GaAs and AlAs-like) reveal changes in the N distribution depending on the growth conditions: A transition from random- to non-random nitrogen distribution is observed upon increasing the growth temperature. Our results confirm the preferential bonding of N to Al in AlGaAs:N, due to the higher Al-N bond strength as compared to the Ga-N bond. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Kalanoor, Basanth S; Ronen, Maria; Oren, Ziv; Gerber, Doron; Tischler, Yaakov R
2017-03-31
The low-frequency vibrational (LFV) modes of biomolecules reflect specific intramolecular and intermolecular thermally induced fluctuations that are driven by external perturbations, such as ligand binding, protein interaction, electron transfer, and enzymatic activity. Large efforts have been invested over the years to develop methods to access the LFV modes due to their importance in the studies of the mechanisms and biological functions of biomolecules. Here, we present a method to measure the LFV modes of biomolecules based on Raman spectroscopy that combines volume holographic filters with a single-stage spectrometer, to obtain high signal-to-noise-ratio spectra in short acquisition times. We show that this method enables LFV mode characterization of biomolecules even in a hydrated environment. The measured spectra exhibit distinct features originating from intra- and/or intermolecular collective motion and lattice modes. The observed modes are highly sensitive to the overall structure, size, long-range order, and configuration of the molecules, as well as to their environment. Thus, the LFV Raman spectrum acts as a fingerprint of the molecular structure and conformational state of a biomolecule. The comprehensive method we present here is widely applicable, thus enabling high-throughput study of LFV modes of biomolecules.
Directory of Open Access Journals (Sweden)
Darius Zizys
2015-12-01
Full Text Available The piezoelectric transduction mechanism is a common vibration-to-electric energy harvesting approach. Piezoelectric energy harvesters are typically mounted on a vibrating host structure, whereby alternating voltage output is generated by a dynamic strain field. A design target in this case is to match the natural frequency of the harvester to the ambient excitation frequency for the device to operate in resonance mode, thus significantly increasing vibration amplitudes and, as a result, energy output. Other fundamental vibration modes have strain nodes, where the dynamic strain field changes sign in the direction of the cantilever length. The paper reports on a dimensionless numerical transient analysis of a cantilever of a constant cross-section and an optimally-shaped cantilever with the objective to accurately predict the position of a strain node. Total effective strain produced by both cantilevers segmented at the strain node is calculated via transient analysis and compared to the strain output produced by the cantilevers segmented at strain nodes obtained from modal analysis, demonstrating a 7% increase in energy output. Theoretical results were experimentally verified by using open-circuit voltage values measured for the cantilevers segmented at optimal and suboptimal segmentation lines.
Zizys, Darius; Gaidys, Rimvydas; Dauksevicius, Rolanas; Ostasevicius, Vytautas; Daniulaitis, Vytautas
2015-12-23
The piezoelectric transduction mechanism is a common vibration-to-electric energy harvesting approach. Piezoelectric energy harvesters are typically mounted on a vibrating host structure, whereby alternating voltage output is generated by a dynamic strain field. A design target in this case is to match the natural frequency of the harvester to the ambient excitation frequency for the device to operate in resonance mode, thus significantly increasing vibration amplitudes and, as a result, energy output. Other fundamental vibration modes have strain nodes, where the dynamic strain field changes sign in the direction of the cantilever length. The paper reports on a dimensionless numerical transient analysis of a cantilever of a constant cross-section and an optimally-shaped cantilever with the objective to accurately predict the position of a strain node. Total effective strain produced by both cantilevers segmented at the strain node is calculated via transient analysis and compared to the strain output produced by the cantilevers segmented at strain nodes obtained from modal analysis, demonstrating a 7% increase in energy output. Theoretical results were experimentally verified by using open-circuit voltage values measured for the cantilevers segmented at optimal and suboptimal segmentation lines.
Seçgin, Abdullah; Saide Sarıgül, A.
2009-03-01
This study introduces a novel scheme for the discrete high-frequency forced vibration analysis based on discrete singular convolution (DSC) and mode superposition (MS) approaches. The accuracy of the DSC-MS is validated for thin beams and plates by comparing with available analytical solutions. The performance of the DSC-MS is evaluated by predicting spatial distribution and discrete frequency spectra of the vibration response of thin plates with two different boundary conditions. The frequency spectra of the time-harmonic excitation forces are in the form of ideal and band-limited white noise so that the natural modes in the frequency band are provoked. The solution exposes high-frequency response behaviour definitely. Therefore, it is hoped with this paper to contribute the studies on the treatment of uncertainties in the high-frequency design applications.
Fry-Petit, A M; Rebola, A F; Mourigal, M; Valentine, M; Drichko, N; Sheckelton, J P; Fennie, C J; McQueen, T M
2015-09-28
For over a century, vibrational spectroscopy has enhanced the study of materials. Yet, assignment of particular molecular motions to vibrational excitations has relied on indirect methods. Here, we demonstrate that applying group theoretical methods to the dynamic pair distribution function analysis of neutron scattering data provides direct access to the individual atomic displacements responsible for these excitations. Applied to the molecule-based frustrated magnet with a potential magnetic valence-bond state, LiZn2Mo3O8, this approach allows direct assignment of the constrained rotational mode of Mo3O13 clusters and internal modes of MoO6 polyhedra. We anticipate that coupling this well known data analysis technique with dynamic pair distribution function analysis will have broad application in connecting structural dynamics to physical properties in a wide range of molecular and solid state systems.
Wang, Yu; Smolarek, Szymon; Kong, Xianggui; Buma, Wybren Jan; Brouwer, Albert Manfred; Zhang, Hong
2010-11-01
Physical and chemical properties of nanoparticles are known to be subject to the surface factors. For their biological/biomedical applications, typically, surface of the nanoparticles has to be modified which inevitably affects their performance. In this work we have studied the interaction between the surface related organic vibrational modes and the luminescent centers--rare earth ions--in one of the most efficient luminescence upconversion nanosystems--NaYF4. Specifically, the surface quenching centers, the surface related luminescent centers, as well as the role of shell properties, are investigated spectroscopically. Our results demonstrate that the surface related high-frequency vibrational modes can be critical to the spectral properties of the nanosystems once the surface is not well separated from the discrete luminescent centers.
Observation of a universal donor-dependent vibrational mode in graphene.
Fedorov, A V; Verbitskiy, N I; Haberer, D; Struzzi, C; Petaccia, L; Usachov, D; Vilkov, O Y; Vyalikh, D V; Fink, J; Knupfer, M; Büchner, B; Grüneis, A
2014-01-01
Electron-phonon coupling and the emergence of superconductivity in intercalated graphite have been studied extensively. Yet, phonon-mediated superconductivity has never been observed in the 2D equivalent of these materials, doped monolayer graphene. Here we perform angle-resolved photoemission spectroscopy to try to find an electron donor for graphene that is capable of inducing strong electron-phonon coupling and superconductivity. We examine the electron donor species Cs, Rb, K, Na, Li, Ca and for each we determine the full electronic band structure, the Eliashberg function and the superconducting critical temperature Tc from the spectral function. An unexpected low-energy peak appears for all dopants with an energy and intensity that depend on the dopant atom. We show that this peak is the result of a dopant-related vibration. The low energy and high intensity of this peak are crucially important for achieving superconductivity, with Ca being the most promising candidate for realizing superconductivity in graphene.
Nordenfelt, Anders
2011-01-01
We demonstrate theoretically the feasibility of selective self-excitation of higher-mode flexural vibrations of graphene nano-ribbons and carbon nanotubes by the means of magnetomotive instability. Apart from the mechanical resonator, the device consists only of a constant voltage source, an inductor, a capacitor, a gate electrode and a constant magnetic field. Numerical simluations were performed on both graphene and carbon nanotubes displaying an overall similar behaviour, but with some dif...
Abstract: Stoichiometry, Vibrational Modes and Structures of Molten Nb2O5-K2S2O7 Mixtures
DEFF Research Database (Denmark)
Boghosian, S.; Borup, F.; Berg, Rolf W.
1998-01-01
High temperature Raman spectroscopy is used tostudy the vibrational modes and structures of the Nb205-K2S207(0 stoichiometry are performed...... in order to characterise the complex(es) formed. The determination of stoichiometry is done following a general procedure which is based on a simple formalism correlating measurements of relative Raman band intensities with the stoichiometry of solutes in molten salt solvents....
Tan, Qing-Hai; Zhang, Xin; Luo, Xiang-Dong; Zhang, Jun; Tan, Ping-Heng
2017-03-01
Two-dimensional transition metal dichalcogenides (TMDs) have attracted extensive attention due to their many novel properties. The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds, while van der Waals interactions combine the layers together. This makes its lattice dynamics layer-number dependent. The evolutions of ultralow frequency ( 50 cm-1) vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes, known as Davydov splitting. Such Davydov splitting can be well described by a van der Waals model, which directly links the splitting with the interlayer coupling. Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials. Project supported by the National Basic Research Program of China (No. 2016YFA0301200), the National Natural Science Foundation of China (Nos. 11225421, 11474277, 11434010, 61474067, 11604326, 11574305 and 51527901), and the National Young 1000 Talent Plan of China.
Analytical aspects of Randomdec analysis. [for vibration modes and nondestructive flaw detection
Reed, R. E.
1979-01-01
Relationships between Randomdec analysis and conventional methods of analysis such as Fourier and modal analysis are shown. The Randomdec signature is described in terms of the Fourier amplitude coefficients. Using this result, the effect of filtering the time history is shown. For a linear, two mode model, signatures are compared to the free response of the system subjected to different initial conditions to show the relationship of displacement and acceleration signatures to the physical system. Detection and location of flaws is also discussed.
Zimmermann, Jörg; Gundogdu, Kenan; Cremeens, Matthew E; Bandaria, Jigar N; Hwang, Gil Tae; Thielges, Megan C; Cheatum, Christopher M; Romesberg, Floyd E
2009-06-11
The spectral position of C-D stretching absorptions in the so-called "transparent window" of protein absorption (1800-2300 cm(-1)) makes them well suited as probes of protein dynamics with high temporal and structural resolution. We have previously incorporated single deuterated amino acids into proteins to site-selectively follow protein folding and ligand binding by steady-state FT IR spectroscopy. Ultimately, our goal is to use C-D bonds as probes in time-resolved IR spectroscopy to study dynamics and intramolecular vibrational energy redistribution (IVR) in proteins. As a step toward this goal, we now present the first time-resolved experiments characterizing the population and dephasing dynamics of selectively excited C-D bonds in a deuterated amino acid. Three differently deuterated, Boc-protected leucines were selected to systematically alter the number of additional C-D bonds that may mediate IVR out of the initially populated bright C-D stretching mode. Three-pulse photon echo experiments show that the steady-state C-D absorption linewidths are broadened by both homogeneous and inhomogeneous effects, and transient grating experiments reveal that IVR occurs on a subpicosecond time scale and is nonstatistical. The results have important implications for the interpretation of steady-state C-D spectra and demonstrate the potential utility of C-D bonds as probes of dynamics and IVR within a protein.
Michotte, Jean-Bernard; Staderini, Enrico; Le Pennec, Deborah; Dugernier, Jonathan; Rusu, Rares; Roeseler, Jean; Vecellio, Laurent; Liistro, Giuseppe; Reychler, Grégory
2016-08-01
Backround: Coupling nebulization with noninvasive ventilation (NIV) has been shown to be effective in patients with respiratory diseases. However, a breath-synchronized nebulization option that could potentially improve drug delivery by limiting drug loss during exhalation is currently not available on bilevel ventilators. The aim of this in vitro study was to compare aerosol delivery of amikacin with a vibrating mesh nebulizer coupled to a single-limb circuit bilevel ventilator, using conventional continuous (Conti-Neb) and experimental inspiratory synchronized (Inspi-Neb) nebulization modes. Using an adult lung bench model of NIV, we tested a vibrating mesh device coupled with a bilevel ventilator in both nebulization modes. Inspi-Neb delivered aerosol only during the whole inspiratory phase, whereas Conti-Neb delivered aerosol continuously. The nebulizer was charged with amikacin solution (250 mg/3 mL) and placed at two different positions: between the lung and exhalation port and between the ventilator and exhalation port. Inhaled, expiratory wasted and circuit lost doses were assessed by residual gravimetric method. Particle size distribution of aerosol delivered at the outlet of the ventilator circuit during both nebulization modes was measured by laser diffraction method. Regardless of the nebulizer position, Inspi-Neb produced higher inhaled dose (p lung and exhalation port (48.7% ± 0.3% of the nominal dose). During simulated NIV with a single-limb circuit bilevel ventilator, the use of inspiratory synchronized vibrating mesh nebulization improves respirable dose and reduces drug loss of amikacin compared with continuous vibrating mesh nebulization.
Kvaternik, R. G.
1975-01-01
Two computational procedures for analyzing complex structural systems for their natural modes and frequencies of vibration are presented. Both procedures are based on a substructures methodology and both employ the finite-element stiffness method to model the constituent substructures. The first procedure is a direct method based on solving the eigenvalue problem associated with a finite-element representation of the complete structure. The second procedure is a component-mode synthesis scheme in which the vibration modes of the complete structure are synthesized from modes of substructures into which the structure is divided. The analytical basis of the methods contains a combination of features which enhance the generality of the procedures. The computational procedures exhibit a unique utilitarian character with respect to the versatility, computational convenience, and ease of computer implementation. The computational procedures were implemented in two special-purpose computer programs. The results of the application of these programs to several structural configurations are shown and comparisons are made with experiment.
Experimental and DFT dimer modeling studies of the H-bond induced-vibration modes of l-β-Homoserine.
Yalagi, Shashikala; Tonannavar, J; Yenagi, Jayashree
2017-06-15
The vibrational spectra for l-β-Homoserine have been measured (IR absorption: 4000-400cm(-1)/Raman spectra: 4000-200cm(-1)). Characteristic vibrational modes of ammonium (-NH3(+)), carboxylate (-CO2(-)) and hydroxyl (-OH) groups across the 3700-1400cm(-1) are all identified to have originated in inter-molecular hydrogen bonding involving these functional groups. DFT calculations at B3LYP/6-311++G(d, p) level have yielded a single neutral monomer in the gas phase. Since as a member of the amino acids which are known to possess zwitterionic structure in condensed phase, the neutral monomer of l-β-Homoserine is optimized to a zwitterionic structure in a water medium. Consideration of two dimer structures, one dimer with -NH‧‧‧O bond and another -OH‧‧‧O bond, has given rise to vibrational modes that satisfactorily fit to all the observed absorption and Raman bands. It is found that the dimer with -OH‧‧‧O bond (binding energy, 8.896kcal/mol) is more tightly bound than the dimer with -NH‧‧‧O bond (8.363kcal/mol). Copyright © 2017 Elsevier B.V. All rights reserved.
Shaw, D J; Panman, M R; Woutersen, S
2009-11-27
Vibrational energy relaxation of the NH-, OH-, and OD-stretching modes in hydrogen-bonded liquids has been investigated by means of infrared pump-probe spectroscopy. The relaxation rates have been determined both in neat liquids and in isotopic mixtures with systematically varied isotope fractions. In all liquids, the vibrational relaxation rate increases as the isotope fraction is increased and reaches a maximum in the neat liquid. The dependence of the relaxation rate on the isotope fraction suggests a relaxation channel in which the vibrational energy is partitioned between accepting modes of two neighboring molecules.
Oversampling in virtual visual sensors as a means to recover higher modes of vibration
Shariati, Ali; Schumacher, Thomas
2015-03-01
Vibration-based structural health monitoring (SHM) techniques require modal information from the monitored structure in order to estimate the location and severity of damage. Natural frequencies also provide useful information to calibrate finite element models. There are several types of physical sensors that can measure the response over a range of frequencies. For most of those sensors however, accessibility, limitation of measurement points, wiring, and high system cost represent major challenges. Recent optical sensing approaches offer advantages such as easy access to visible areas, distributed sensing capabilities, and comparatively inexpensive data recording while having no wiring issues. In this research we propose a novel methodology to measure natural frequencies of structures using digital video cameras based on virtual visual sensors (VVS). In our initial study where we worked with commercially available inexpensive digital video cameras we found that for multiple degrees of freedom systems it is difficult to detect all of the natural frequencies simultaneously due to low quantization resolution. In this study we show how oversampling enabled by the use of high-end high-frame-rate video cameras enable recovering all of the three natural frequencies from a three story lab-scale structure.
Cao, Yan; Sheremetyeva, Natalya; Liang, Liangbo; Yuan, Hui; Zhong, Tingting; Meunier, Vincent; Pan, Minghu
2017-09-01
When layered transition-metal dichalcogenides (TMDs) are scaled down from a three- to a 2D geometry, electronic and structural transitions occur, leading to the emergence of properties not usually found in the bulk. Here, we report a systematic Raman study of exfoliated semi-metallic WTe2 flakes with thickness ranging from few layers down to a single layer. A dramatic change in the Raman spectra occurs between the monolayer and few-layer WTe2 as a vibrational mode centered at ~86.9 cm-1 in the monolayer splits into two active modes at 82.9 and 89.6 cm-1 in the bilayer. Davydov splitting of these two modes is found in the bilayer, as further evidenced by polarized Raman measurements. Strong angular dependence of Raman modes on the WTe2 film thickness reflects that the existence of directional interlayer interaction, rather than isotropic van der Waals (vdw) coupling, is playing an essential role affecting the phonon modes, especially in anisotropic 2D WTe2 material. Therefore, the strong evolution of Raman modes with thickness and polarization direction, can not only be a reliable fingerprint for the determination of the thickness and the crystallographic orientation, but can also be an ideal probe for such strong and directional interlayer interaction.
Vandenrijt, Jean-François; Thizy, Cédric; Georges, Marc P.
2015-08-01
We present investigation of interferometric methods for vibration mode identification to be applied on shakers in industrial environment. We consider long wave infrared ESPI in time-averaged mode with the use of phase-stepping which allows transforming Bessel fringes, typical to the time averaging, into phase values which provide a better way for identification of vibration mode shapes. The use of long laser wavelength allows measuring larger amplitudes of vibrations compared to what is achieved in visible light. Also longer wavelengths allow lower sensitivity to external perturbations. Time-averaged phase-stepped shearography in visible is also used as a compared alternative to LWIR ESPI for working in industrial environments. Although not demonstrated here, an interesting feature for the future investigations on LWIR ESPI is its potentiality of simultaneous temperature measurement during vibrations.
Dynamics of coupled vibration modes in a quantum non-linear mechanical resonator
Labadze, G.; Dukalski, M.S.; Blanter, Y.M.
2016-01-01
We investigate the behaviour of two non-linearly coupled flexural modes of a doubly clamped suspended beam (nanomechanical resonator). One of the modes is externally driven. We demonstrate that classically, the behavior of the non-driven mode is reminiscent of that of a parametrically driven
Hong, Fan; Pang, Chee Khiang
2012-11-01
This paper presents an improved indirect-driven self-sensing actuation circuit for robust vibration control of piezoelectrically-actuated flexible structures in mechatronic systems. The circuit acts as a high-pass filter and provides better self-sensing strain signals with wider sensing bandwidth and higher signal-to-noise ratio. An adaptive non-model-based control is used to compensate for the structural vibrations using the strain signals from the circuit. The proposed scheme is implemented in a PZT-actuated suspension of a commercial dual-stage hard disk drive. Experimental results show improvements of 50% and 75% in the vibration suppression at 5.4kHz and 21kHz respectively, compared to the conventional PI control. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Hu, S.; Mukherjee, A.; Spiro, T.G. (Princeton Univ., NJ (United States))
1993-12-29
Resonance Raman (RR) and FT-IR spectra are reported for nickel(II) 1,5-dihydroxy-1,5-dimethyloctaethylbacteriochlorin [Ni(HOEBC)] and its meso-d[sub 4] isotopomer. All the in-plane skeletal RR-active modes and most IR-active modes are assigned with the aid of a normal mode analysis by using a force field developed for nickel(II) octaethylporphyrin and by scaling the bond stretch force constants to bond lengths revealed in the crystal structure of nickel(II) octaethylbacteriochlorin. The calculated eigenvectors provide insight into the essential vibrational characteristics of metallobacteriochlorins. The RR spectra of Ni(HOEBC) were acquired with a variety of excitation wavelengths, near resonance with the B[sub x], Q[sub x], and Q[sub y] transitions. The enhancement pattern of the observed RR intensities reveals that the B[sub x]- and near-Q[sub y]-resonant spectra are dominated by Franck-Condon-active modes while the Q[sub x]-resonant spectrum is dominated by vibronically active modes. The B[sub x]-resonant spectrum also shows significant vibronic scattering, via coupling between the B[sub x]- and B[sub y]-excited states. Frequencies correlate well among Ni(II) complexes of octaethylporphine (OEP) and hydroporphyrins for modes containing similar local mode contributions, when allowance is made for C[sub beta]-C[sub beta] bond order reduction and the effects of symmetry lowering. Assignments are proposed for the existing RR data on bacteriochlorophyll a. 32 refs., 14 figs., 6 tabs.
Directory of Open Access Journals (Sweden)
J.-J. Sinou
2017-01-01
Full Text Available During the past decades, the problem of friction-induced vibration and noise has been the subject of a huge amount of works. Various numerical simulations with finite elements models have been largely investigated to predict squeal events. Although a nonlinear analysis is more predictive than Complex Eigenvalues Analysis, one of the main drawbacks of the time analysis is the need of large computational efforts. In view of the complexity of the subject, this approach appears still computationally too expensive to be used in industry for finite element models. In this study, the potential of a new reduced model based on a double modal synthesis (i.e., a classical modal reduction via Craig and Bampton plus a condensation at the frictional interface based on complex modes for the prediction of self-excited vibrations of brake squeal is discussed. The effectiveness of the proposed modal reduction is tested on a finite element model of a simplified brake system. It will be shown that numerical results of times analysis by applying the proposed reduction correlate well with those of the nonlinear analysis based on a reference model, hence demonstrating the potential of using adapted modal reductions to predict the squeal propensity and to estimate self-excited vibrations and noise.
Naumann, E. C.
1972-01-01
Vibration tests were carried out on truncated-cone shells with widely spaced ring stiffeners. The models were excited by an air shaker for LF modes and by small electrodynamic shakers for HF modes. The Novozhilov thin shell theory according to which a ring is an assembly of an arbitrary number of segments, each being a short truncated-cone shell of uniform thickness, is used in the analysis of the results. A mobile, noncontacting, displacement-sensitive sensor system developed by the author was used in the tests. Tests results are given for a free-free 60-deg cone and for a clamped-free 60-deg cone. The tests are characterized as having considerable value for the classification of prevalent multimode responses in shells of this type.
Directory of Open Access Journals (Sweden)
Kookhyun Kim
2012-09-01
Full Text Available An approximate method based on an assumed mode method has been presented for the free vibration analysis of a rectangular plate with arbitrary edge constraints. In the presented method, natural frequencies and their mode shapes of the plate are calculated by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion. Characteristic orthogonal polynomials having the property of Timoshenko beam functions which satisfies edge constraints corresponding to those of the objective plate are used. In order to examine the accuracy of the proposed method, numerical examples of the rectangular plates with various thicknesses and edge constraints have been presented. The results have shown good agreement with those of other methods such as an analytic solution, an approximate solution, and a finite element analysis.
A Simple Reduction Process for the Normal Vibrational Modes Occurring in Linear Molecules
McInerny, William
2005-01-01
The students in molecular spectroscopy courses are often required to determine the permitted normal vibrations for linear molecules that belong to particular groups. The reducible group representations generated by the use of Cartesian coordinates can be reduced by the use of a simple algebraic process applied to the group representations. The…
Excess vibrational modes of a crystal in an external non-affine field
Indian Academy of Sciences (India)
Home; Journals; Journal of Chemical Sciences; Volume 129; Issue 7. Excess vibrational ... While the former couples to external stress with familiar consequences, the response of a crystal when nonaffine displacements are enhanced using the thermodynamically conjugate field, is relatively less studied. We examine this ...
Shiba, Hayato; Kawasaki, Takeshi; Onuki, Akira
2012-10-01
We investigate the dynamic heterogeneities of glassy particle systems in the theoretical schemes of bond breakage and four-point correlation functions. In the bond-breakage scheme, we introduce the structure factor S(b)(q,t) and the susceptibility χ(b)(t) to detect the spatial correlations of configuration changes. Here χ(b)(t) attains a maximum at t=t(b)(max) as a function of time t, where the fraction of the particles with broken bonds φ(b)(t) is about 1/2. In the four-point scheme, treating the structure factor S(4)(q,t) and the susceptibility χ(4)(t), we detect superpositions of the heterogeneity of bond breakage and that of thermal low-frequency vibration modes. While the former grows slowly, the latter emerges quickly to exhibit complex space-time behavior. In two dimensions, the vibration modes extending over the system yield significant contributions to the four-point correlations, which depend on the system size logarithmically. A maximum of χ(4)(t) is attained at t=t(4)(max), where these two contributions become of the same order. As a result, t(4)(max) is considerably shorter than t(b)(max).
Zeng, Jianhua; Chen, Lei; Dai, Qiaofeng; Lan, Sheng; Tie, Shaolong
2016-01-21
We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into "coffee" rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly revealed in the anti-Stokes hyper-Raman scattering. Apart from the strong anti-Stokes hyper-Raman scattering, Stokes hyper-Raman scattering with small Raman shifts was detected during the ablation process of thick MoS2 layers. It was also observed by slightly defocusing the excitation light. The detection of anti-Stokes hyper-Raman scattering may serve as a new technique for studying the Raman inactive vibration modes in nanomaterials.
Local vibration of an elastic plate and zero-group velocity Lamb modes.
Prada, Claire; Clorennec, Dominique; Royer, Daniel
2008-07-01
Elastic plates or cylinders can support guided modes with zero group velocity (ZGV) at a nonzero value of the wave number. Using laser-based ultrasonic techniques, we experimentally investigate some fascinating properties of these ZGV modes: resonance and ringing effects, backward wave propagation, interference between backward and forward modes. Then, the conditions required for the existence of ZGV Lamb modes in isotropic plates are discussed. It is shown that these modes appear in a range of Poisson's ratio about the value for which the cutoff frequency curves of modes belonging to the same family intercept, i.e., for a bulk wave velocity ratio equal to a rational number. An interpretation of this phenomenon in terms of a strong repulsion between a pair of modes having a different parity in the vicinity of the cutoff frequencies is given. Experiments performed with materials of various Poisson's ratio demonstrate that the resonance spectrum of an unloaded elastic plate, locally excited by a laser pulse, is dominated by the ZGV Lamb modes.
Saidi, Wissam A
2014-09-04
Defects are ubiquitous in carbon nanotubes (CNTs), despite their large formation energies, and have astounding effects on their physicochemical properties. In this study, we employ density-functional theory (DFT) calculations to study systematically the atomic structure, stability, and characteristic vibrations of pristine and defected zigzag CNTs, where the defects are of the form of Stone-Wales (SW) and diatom vacancies (DV). The DFT optimized structures and the phonon modes are subsequently used in conjunction with a semiempirical bond-polarization model to study the nonresonant Raman spectra. For each defect type, we find two CNT structures with defects parallel or oblique to the tube axis. For the SW defects, the two structures have similar formation energies, whereas for the DV defect, only defects parallel to the tube axis are likely to exist. The results show that the defects induce a blue shift in the radial breathing mode (RBM) of metallic CNTs, whereas this mode is not shifted for semiconducting CNTs. However, the RBM shift or its Raman profile is not sensitive to the defect type. The G-band showed more sensitivity to the defects in the form of a red/blue shift in the frequency, or a partial/complete defragmentation of the G bands.
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Xiaofei Zhang
2018-01-01
Full Text Available Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the low mode and detect near-field optically induced forces (based on the 2nd in-plane mode called the high mode. Particularly, the high mode sensing performance of the QTF-p is an important issue for characterizing the tip-sample interactions and achieving higher resolution microscopic imaging but the related researches are insufficient. Here, we investigate the vibration performance of QTF-p at high mode based on the experiment and finite element method. The frequency spectrum characteristics are obtained by our homemade laser Doppler vibrometer system. The effects of the properties of the connecting glue layer and the probe features on the dynamic response of the QTF-p sensor at the high mode are investigated for optimization design. Finally, compared with the low mode, an obvious improvement of quality factor, of almost 50%, is obtained at the high mode. Meanwhile, the QTF-p sensor has a high force sensing sensitivity and a large sensing range at the high mode, indicating a broad application prospect for force sensing.
Zhang, Xiaofei; Gao, Fengli; Li, Xide
2018-01-24
Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p) sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the low mode) and detect near-field optically induced forces (based on the 2nd in-plane mode called the high mode). Particularly, the high mode sensing performance of the QTF-p is an important issue for characterizing the tip-sample interactions and achieving higher resolution microscopic imaging but the related researches are insufficient. Here, we investigate the vibration performance of QTF-p at high mode based on the experiment and finite element method. The frequency spectrum characteristics are obtained by our homemade laser Doppler vibrometer system. The effects of the properties of the connecting glue layer and the probe features on the dynamic response of the QTF-p sensor at the high mode are investigated for optimization design. Finally, compared with the low mode, an obvious improvement of quality factor, of almost 50%, is obtained at the high mode. Meanwhile, the QTF-p sensor has a high force sensing sensitivity and a large sensing range at the high mode, indicating a broad application prospect for force sensing.
National Aeronautics and Space Administration — The Phase I project successfully demonstrated that the advanced non-contacting stress measurement system (NSMS) was able to address closely spaced modes and...
Model Penilaian dan Pemilihan Trade Show Bagi Industri Kreatif di Sektor Mode
Directory of Open Access Journals (Sweden)
Afrin Fauzya Rizana
2017-07-01
Full Text Available The article identifies the criteria for choosing a trade show and develops a basic model of exhibition selection for creative industry players before deciding to participate in a trade show. It is necessary to ensure that expenses in terms of business, money, and time, will be worth the results. Based on literature review and interviews, six criteria were used, namely location, booth position, organizational reputation, cost estimation, prestige, and reputation of other participants. After selection criteria are identified, then calculations are performed to measure the criteria weight by using the AHP approach. Based on weight calculations, it was found that booth positions had the highest importance weight, followed by trade show location, organizers reputation, cost estimation, prestige and reputation of other participants. The weight value is then used to calculate the trade show's prediction value. The predicted value generated from the model is then compared to the value of the past data. The model has an accuracy rate of 89% and does not have a significant difference between the value generated by the model and the value of the past data.
Chuang, Kuo-Chih; Liou, Hong-Cin; Ma, Chien-Ching
2014-06-01
Compared with piezoelectric ceramics such as lead zirconate titanate (PZT) ceramics, the low density and high compliance of the PVDF films make them a more suitable choice in modal testing, especially for detecting high-frequency modes in flexible or inflatable structures. In this work, dynamic sensing performances of PVDF films for flexible structures in modal testing are examined, with considerations including the repeatability of the impact source, the accuracy of the sensing responses, and the influences of the nodal lines on the frequency spectra of the transient responses. Two flexible plates with different boundary conditions and thickness are considered. Experimental results, compared with FEM computations or theoretical predictions, demonstrate the excellent dynamic sensing performance of the PVDF film in modal testing applications, especially for identification of high-frequency modes on flexible structures.
Vibration suppression in flexible structures via the sliding-mode control approach
Drakunov, S.; Oezguener, Uemit
1994-01-01
Sliding mode control became very popular recently because it makes the closed loop system highly insensitive to external disturbances and parameter variations. Sliding algorithms for flexible structures have been used previously, but these were based on finite-dimensional models. An extension of this approach for differential-difference systems is obtained. That makes if possible to apply sliding-mode control algorithms to the variety of nondispersive flexible structures which can be described as differential-difference systems. The main idea of using this technique for dispersive structures is to reduce the order of the controlled part of the system by applying an integral transformation. We can say that transformation 'absorbs' the dispersive properties of the flexible structure as the controlled part becomes dispersive.
Nonlinear vibration analysis of axially moving strings based on gyroscopic modes decoupling
Yang, Xiao-Dong; Wu, Hang; Qian, Ying-Jing; Zhang, Wei; Lim, C. W.
2017-04-01
A novel idea that applies the multiple scale analysis to a discretized decoupled system of gyroscopic continua is introduced and an axial moving string is treated as an example. First, the invariant manifold method is applied to the discretized ordinary differential equations of the axially moving string. Complex gyroscopic mode functions that agree well with true analytical results are obtained. The gyroscopic modes are subsequently used for the discretized ordinary differential equations with gyroscopic and nonlinear coupling terms that yield a gyroscopically decoupled system. Further the method of multiple scales is used to obtain the equations at a slow scale. This novel procedure is compared to solutions obtained by directly applying the classical multiple scale analysis to the gyroscopically coupled system without decoupling. The modal decoupled system analysis yields better frequency with comparing to the classic method. The proposed methodology provides a novel alternative for nonlinear dynamic analysis of gyroscopic continua.
Sun, Limin; Chen, Lin
2017-10-01
Residual mode correction is found crucial in calibrating linear resonant absorbers for flexible structures. The classic modal representation augmented with stiffness and inertia correction terms accounting for non-resonant modes improves the calibration accuracy and meanwhile avoids complex modal analysis of the full system. This paper explores the augmented modal representation in calibrating control devices with nonlinearity, by studying a taut cable attached with a general viscous damper and its Equivalent Dynamic Systems (EDSs), i.e. the augmented modal representations connected to the same damper. As nonlinearity is concerned, Frequency Response Functions (FRFs) of the EDSs are investigated in detail for parameter calibration, using the harmonic balance method in combination with numerical continuation. The FRFs of the EDSs and corresponding calibration results are then compared with those of the full system documented in the literature for varied structural modes, damper locations and nonlinearity. General agreement is found and in particular the EDS with both stiffness and inertia corrections (quasi-dynamic correction) performs best among available approximate methods. This indicates that the augmented modal representation although derived from linear cases is applicable to a relatively wide range of damper nonlinearity. Calibration of nonlinear devices by this means still requires numerical analysis while the efficiency is largely improved owing to the system order reduction.
Zhao, Yonghong; Li, Zhi; Liu, Jianjun; Hu, Cong; Zhang, Huo; Qin, Binyi; Wu, Yifang
2018-01-01
The characteristic absorption spectra of crystalline urea in 0.6-1.8 THz region have been measured by terahertz time-domain spectroscopy at room temperature experimentally. Five broad absorption peaks were observed at 0.69, 1.08, 1.27, 1.47 and 1.64 THz respectively. Moreover, density functional theory (DFT) calculation has been performed for the isolated urea molecule, and there is no infrared intensity in the region below 1.8 THz. This means that single molecule calculations are failure to predict the experimental spectra of urea crystals. To simulate these spectra, calculations on a cluster of seven urea molecules using M06-2X and B3LYP-D3 are performed, and we found that M06-2X perform better. The observed THz vibrational modes are assigned to bending and torsional modes related to the intermolecular H-bond interactions with the help of potential energy distribution (PED) method. Using the reduced-density-gradient (RDG) analysis, the positions and types of intermolecular H-bond interactions in urea crystals are visualized. Therefore, we can confirm that terahertz spectroscopy can be used as an effective means to detect intermolecular H-bond interactions in molecular crystals.
Charge-sensitive vibrational modes in the (EDT-TTF-OX)2AsF6 chiral molecular conductors
Olejniczak, Iwona; Frąckowiak, Arkadiusz; Matysiak, Jacek; Madalan, Augustin; Pop, Flavia; Avarvari, Narcis
2014-03-01
Infrared and Raman spectra of three chiral molecular conductors (EDT-TTF-OX)2AsF6, comprising of two salts based on enantiopure EDT-TTF-OX donor molecules and one based on their racemic mixture, have been measured as a function of temperature. In the frequency range of the C=C stretching vibrations of EDT-TTF-OX, charge-sensitive modes are identified based on theoretical calculations for neutral and oxidized EDT-TTF-OX using density functional theory (DFT) methods. The positions of C=C stretching modes in both Raman and infrared spectra of the (EDT-TTF-OX)2AsF6 materials are analyzed assuming a linear relationship between the frequency and charge of the molecule. The charge density on the EDTTTF-OX donor molecule is estimated to be +0.5 in all investigated materials and does not change with temperature. Therefore we suggest, that M-I transition observed in (EDT-TTF-OX)2AsF6 chiral molecular conductors at low temperature is not related to the charge ordering mechanism.
Spectral intensities in cubic systems. I. Progressions based upon parity vibrational modes
Energy Technology Data Exchange (ETDEWEB)
Acevedo, R.; Vasquez, S.O. [Department of Basic Chemistry, Faculty of Physical and Mathematical Sciences, University of Chile. Tupper 2069, Casilla 2777, Santiago, Chile (Chile); Meruane, T. [Department of Chemistry, Universidad Metropolitana de Ciencias de la Educacion. Av. J.P. Alessandri 774, Casilla 147, C. Santiago, Chile (Chile); Poblete, V. [Department of Nuclear Materials, Lo Aguirre, Comision Chilena de Energia Nuclear. Amunategui 95, Casilla 188-D, Santiago, Chile (Chile); Pozo, J. [Facultad de Ciencias de la Ingenieria. Universidad Diego Portales. Casilla 298-V, Santiago, Chile (Chile)
1998-12-01
The well-resolved emission and absorption spectra of centrosymmetric coordination compounds of the transition metal ions have been used widely to provide the experimental data against which to test theoretical models of vibronic intensities. With reference to the {sup 2} E{sub g} {yields} {sup 4} A{sub 2g} luminescence transition, at a perfect octahedral site in Cs{sub 2}SiF{sub 6}, over than one hundred vibronic lines are observed with line widths of a few wavenumber spread over some 3000 cm{sup -1}. This paper reports a through examination of both the electronic and vibrational factors, which influences the observed vibronic intensities of the various assigned and identified lines in the spectra of the MnF{sub 6} {sup 2-} complex ion in the Cs{sub 2}SiF{sub 6} cubic lattice. The origin and nature of higher order vibronic interactions are analysed on the basis of a symmetrized vibronic crystal field-ligand polarization model. (Author)
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.
Control of input delayed pneumatic vibration isolation table using adaptive fuzzy sliding mode
Directory of Open Access Journals (Sweden)
Mostafa Khazaee
Full Text Available AbstractPneumatic isolators are promising candidates for increasing the quality of accurate instruments. For this purpose, higher performance of such isolators is a prerequisite. In particular, the time-delay due to the air transmission is an inherent issue with pneumatic systems, which needs to be overcome using modern control methods. In this paper an adaptive fuzzy sliding mode controller is proposed to improve the performance of a pneumatic isolator in the low frequency range, i.e., where the passive techniques have obvious shortcomings. The main idea is to combine the adaptive fuzzy controller with adaptive predictor as a new time delay control technique. The adaptive fuzzy sliding mode control and the adaptive fuzzy predictor help to circumvent the input delay and nonlinearities in such isolators. The main advantage of the proposed method is that the closed-loop system stability is guaranteed under certain conditions. Simulation results reveal the effectiveness of the proposed method, compared with other existing time -delay control methods.
Korayem, Moharam Habibnejad; Nahavandi, Amir
2017-04-01
This paper investigates the vibration of a tapping-mode Atomic Force Microscope (AFM) cantilever covered with two whole piezoelectric layers in a liquid medium. The authors of this article have already modeled the vibration of a cantilever immersed in liquid over rough surfaces. Five new ideas have been considered for improving the results of the previous work. Mass and damping of a cantilever probe tip have been considered. Since the probe tip of an AFM cantilever has a mass, which can itself affect the natural frequency of vibration, the significance of this mass has been explored. Also, two hydrodynamic force models for analyzing the mass and damping added to a cantilever in liquid medium have been evaluated. In modeling the vibration of a cantilever in liquid, simplifications are made to the theoretical equations used in the modeling, which may make the obtained results different from those in the real case. So, two hydrodynamic force models are introduced and compared with each other. In addition to the already introduced DMT model, the JKR model has been proposed. The forces acting on a probe tip have attractive and repulsive effects. The attractive Van der Waals force can vary depending on the surface smoothness or roughness, and the repulsive contact force, which is independent of the type of surface roughness and usually varies with the hardness or softness of a surface. When the first mode is used in the vibration of an AFM cantilever, the changes of the existing physical parameters in the simulation do not usually produce a significant difference in the response. Thus, three cantilever vibration modes have been investigated. Finally, an analytical approach for obtaining the response of equations is presented which solves the resulting motion equation by the Laplace method and, thus, a time function is obtained for cantilever deflection is determined. Also, using the COMSOL software to model a cantilever in a liquid medium, the computed natural
Calculation of exact vibration modes for plane grillages by the dynamic stiffness method
Hallauer, W. L., Jr.; Liu, R. Y. L.
1982-01-01
A dynamic stiffness method is developed for the calculation of the exact modal parameters for plane grillages which consist of straight and uniform beams with coincident elastic and inertial axes. Elementary bending-torsion beam theory is utilized, and bending translation is restricted to one direction. The exact bending-torsion dynamic stiffness matrix is obtained for a straight and uniform beam element with coincident elastic and inertial axes. The element stiffness matrices are assembled using the standard procedure of the static stiffness method to form the dynamic stiffness matrix of the complete grillage. The exact natural frequencies, mode shapes, and generalized masses of the grillage are then calculated by solving a nonlinear eigenvalue problem based on the dynamic stiffness matrix. The exact modal solutions for an example grillage are calculated and compared with the approximate solutions obtained by using the finite element method.
Florián, Jan; Leszczynski, Jerzy; Johnson, Benny G.
1995-04-01
Harmonic force fields, frequencies, and IR and Raman intensities of the intermolecular vibrational modes in the cyclic formamide dimer and the guanine-cytosine and adenine-thymine DNA base pairs were calculated using several ab initio methods, including Hartree-Fock, MP2 and gradient-corrected density functional theory (DFT), with various basis sets. A polar environment was modeled using the polarizable continuum model (SCRF). The effect of electron correlation upon calculated Raman intensities was investigated using DFT. The normal coordinate analysis was carried out in internal coordinates observing C 2h symmetry of the formamide dimer. These coordinates were also generalized for the DNA base pairs, allowing force constants, frequencies and intensities of the characteristic intermolecular vibrational modes to be compared among the H-bonded complexes studied. In addition, coordinates defined in this way are directly related to standard DNA interbase structural parameters as pseudodyad, tilt and propeller twist angles. Extensive coupling of the intramolecular wagging vibrations of the amino groups participating in H-bonding with the tilt and propeller twist vibrations was obtained for the lowest frequency normal modes.
Yang, Yongchao; Dorn, Charles; Mancini, Tyler; Talken, Zachary; Nagarajaiah, Satish; Kenyon, Garrett; Farrar, Charles; Mascareñas, David
2017-03-01
Enhancing the spatial and temporal resolution of vibration measurements and modal analysis could significantly benefit dynamic modelling, analysis, and health monitoring of structures. For example, spatially high-density mode shapes are critical for accurate vibration-based damage localization. In experimental or operational modal analysis, higher (frequency) modes, which may be outside the frequency range of the measurement, contain local structural features that can improve damage localization as well as the construction and updating of the modal-based dynamic model of the structure. In general, the resolution of vibration measurements can be increased by enhanced hardware. Traditional vibration measurement sensors such as accelerometers have high-frequency sampling capacity; however, they are discrete point-wise sensors only providing sparse, low spatial sensing resolution measurements, while dense deployment to achieve high spatial resolution is expensive and results in the mass-loading effect and modification of structure's surface. Non-contact measurement methods such as scanning laser vibrometers provide high spatial and temporal resolution sensing capacity; however, they make measurements sequentially that requires considerable acquisition time. As an alternative non-contact method, digital video cameras are relatively low-cost, agile, and provide high spatial resolution, simultaneous, measurements. Combined with vision based algorithms (e.g., image correlation or template matching, optical flow, etc.), video camera based measurements have been successfully used for experimental and operational vibration measurement and subsequent modal analysis. However, the sampling frequency of most affordable digital cameras is limited to 30-60 Hz, while high-speed cameras for higher frequency vibration measurements are extremely costly. This work develops a computational algorithm capable of performing vibration measurement at a uniform sampling frequency lower than
Directory of Open Access Journals (Sweden)
Emílio Borges
2007-04-01
Full Text Available A simple method to obtain molecular Cartesian coordinates as a function of vibrational normal modes is presented in this work. The method does not require the definition of special matrices, like the F and G of Wilson, neither of group theory. The Eckart's conditions together with the diagonalization of kinetic and potential energy are the only required expressions. This makes the present approach appropriate to be used as a preliminary study for more advanced concepts concerning vibrational analysis. Examples are given for diatomic and triatomic molecules.
A second, low-frequency mode of vibration in the intact mammalian cochlea
Lukashkin, Andrei N.; Russell, Ian J.
2003-03-01
The mammalian cochlea is a structure comprising a number of components connected by elastic elements. A mechanical system of this kind is expected to have multiple normal modes of oscillation and associated resonances. The guinea pig cochlear mechanics was probed using distortion components generated in the cochlea close to the place of overlap between two tones presented simultaneously. Otoacoustic emissions at frequencies of the distortion components were recorded in the ear canal. The phase behavior of the emissions reveals the presence of a nonlinear resonance at a frequency about a half octave below that of the high-frequency primary tone. The location of the resonance is level dependent and the resonance shifts to lower frequencies with increasing stimulus intensity. This resonance is thought to be associated with the tectorial membrane. The resonance tends to minimize input to the cochlear receptor cells at frequencies below the high-frequency primary and increases the dynamic load to the stereocilia of the receptor cells at the primary frequency when the tectorial membrane and reticular lamina move in counterphase.
Huang, Yihua; Huang, Wenjin; Wang, Qinglei; Su, Xujian
2013-07-01
The equivalent circuit model of a piezoelectric transformer is useful in designing and optimizing the related driving circuits. Based on previous work, an equivalent circuit model for a circular flexural-vibration-mode piezoelectric transformer with moderate thickness is proposed and validated by finite element analysis. The input impedance, voltage gain, and efficiency of the transformer are determined through computation. The basic behaviors of the transformer are shown by numerical results.
Directory of Open Access Journals (Sweden)
Yakov Tseytlin
2012-05-01
Full Text Available Flexible structures are the main components in many precision measuring and research systems. They provide miniaturization, repeatability, minimal damping, low measuring forces, and very high resolution. This article focuses on the modeling, development, and comparison of three typical flexible micro- nano-structures: flexible helicoids, atomic force microscopy (AFM cantilevers, and concave notch hinges. Our theory yields results which allow us to increase the accuracy and functionality of these structures in new fields of application such as the modeling of helicoidal DNA molecules’ mechanics, the definition of instantaneous center of rotation in concave flexure notch hinges, and the estimation of the increase of spring constants and resolution at higher mode vibration in AFM cantilevers with an additional concentrated and end extended mass. We developed the original kinetostatic, reverse conformal mapping of approximating contours, and non-linear thermomechanical fluctuation methods for calculation, comparison, and research of the micromechanical structures. These methods simplify complicated solutions in micro elasticity but provide them with necessary accuracy. All our calculation results in this article and in all corresponding referenced author’s publications are in a good agreement with experimental and finite element modeling data within 10% or less.
Kishor Kumar, J; Gunasekaran, S; Loganathan, S; Anand, G; Kumaresan, S
2013-11-01
Glycine is an important amino acid for building up protein synthesis. Single crystal of glycine dimer was grown from aqueous solution by slow evaporation method. Powder X-ray diffraction analysis confirms the crystalline nature of grown crystal. It is interesting to study the molecular structure of a dimer, having well-defined channels formed through amphoterism bonding between CO⋯H bonds with split-valence basis sets, and the conformer is mirror symmetrical, in which the protonated organic cation plays a significant role to have a dimer pattern. Amphiprotic molecules, like dimeric glycine which can either donate or accept a proton (H(+)) from each other. Optical absorption study reveals that the transparency of the crystal in the entire visible region and the cutoff wavelength was found to be 235nm. Powder SHG test and thermogravimetric analysis shows glycine dimer crystal is optically active and thermally stable. The molecular structure, geometry, stability and theoretical vibrational spectra were calculated for glycine as a monomer and as a dimer linked by the amphoterism hydrogen bonding. The theoretical studies were performed using the B3LYP density functional method with the 6-311G (d,p) basis set. The detailed interpretation of the vibrational spectra has been made on the basis of normal coordinate analysis. Copyright © 2013 Elsevier B.V. All rights reserved.
Computation of antenna vibration mode elastic-rigid and effective-weight coefficients
Levy, R.
1992-01-01
A significant amount of both qualitative and quantitative information about structures can be derived from the elastic-rigid structural coupling matrices, and from the effective modal inertias and masses. Typical finite-element analysis programs do not provide this information as part of the regular output. This report presents an easy way to develop the necessary information from ordinary program output, and shows how to deal with alternative origins for the reference coordinate system.
Lee, Eunae; Kang, Jeong Won; Kim, Ki-Sub; Kwon, Oh-Kuen
2016-02-01
Superlubricity in nanoscale graphene structures has been of interest for developing graphene-based nanoelectromechanical systems, as well as for the study of basic mechanical properties. Here, we investigated the translational and rotational motions of a square graphene nanoflake with retracting motions by performing classical molecular dynamics simulations. Our results show that the kinetic energy of the translational motion was exchanged into the kinetic energy of the rotational motion. Thus, square graphene nanoflake oscillators have very low quality factors in translational motions. We discuss that square graphene nanoflakes have great potential to be a core component in nanoelectromechanical systems by detecting their motions with ultrahigh sensitivity to facilitate the development of sensor, memory, and quantum computing.
Schwenke, David W.
1992-01-01
The optimization of the wave functions is considered for coupled vibrations represented by linear combinations of products of functions depending only on a single vibrational coordinate. The functions themselves are optimized as well as configuration list. For the H2O molecule highly accurate results are obtained for the lowest 15 levels using significantly shorter expansions than would otherwise be possible.
Gaynor, James D.; Wetterer, Anna M.; Cochran, Rea M.; Valente, Edward J.; Mayer, Steven G.
2015-01-01
Raman spectroscopy is a powerful experimental technique, yet it is often missing from the undergraduate physical chemistry laboratory curriculum. Tetrachloromethane (CCl[subscript 4]) is the ideal molecule for an introductory vibrational spectroscopy experiment and the symmetric stretch vibration contains fine structure due to isotopic variations…
Energy Technology Data Exchange (ETDEWEB)
Silva, M.D.P.; Silva, F.C. [Departamento de Química, CCET, Universidade Federal do Maranhão, 65085-580 São Luís, MA (Brazil); Sinfrônio, F.S.M. [Departamento de Engenharia Elétrica, CCET, Universidade Federal do Maranhão, 65085-580 São Luís, MA (Brazil); Paschoal, A.R. [Departamento de Física, Universidade Federal do Ceará, Campus do Pici, 60455-760 Fortaleza, CE (Brazil); Silva, E.N. [Departamento de Física, CCET, Universidade Federal do Maranhão, 65085-580 São Luís, MA (Brazil); Paschoal, C.W.A., E-mail: paschoal@ufma.br [Departamento de Física, CCET, Universidade Federal do Maranhão, 65085-580 São Luís, MA (Brazil); Department of Materials Science and Engineering, University of California Berkeley, 94720-1760 Berkeley, CA (United States); Department of Physics, University of California Berkeley, 94720-7300 Berkeley, CA (United States)
2014-01-25
Highlights: • We synthesized mixed spinels by polymeric precursor method. • We investigated the structural and vibrational properties of the mixed. • We investigated the synthesis condition effects in these properties. • We proposed a complete phonon description for CuFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} spinels. -- Abstract: In this work Co–Cu mixed spinel Co{sub 1−x}Cu{sub x}Fe{sub 2}O{sub 4} powders were obtained by polymeric precursors method at several annealing temperatures between 700 and 1200 °C. The samples were characterized by means of X-ray powder diffraction, confirming the ideal inverse spinel structure for CoFe{sub 2}O{sub 4} sample and the tetragonal distorted inverse spinel structure for CuFe{sub 2}O{sub 4} sample. Based on FWHM evaluation, we estimated that crystallite sizes varies between 27 and 37 nm for the non-substituted samples. The optical-active modes were determined by infrared and Raman spectroscopies. The phonon spectra showed a local tetragonal distortion for mixed samples.
Languy, Fabian; Vandenrijt, Jean-François; Thizy, Cédric; Rochet, Jonathan; Loffet, Christophe; Simon, Daniel; Georges, Marc P.
2016-12-01
We present our investigations on two interferometric methods suitable for industrial conditions dedicated to the visualization of vibration modes of aeronautic blades. First, we consider long-wave infrared (LWIR) electronic speckle pattern interferometry (ESPI). The use of long wavelength allows measuring larger amplitudes of vibrations compared with what can be achieved with visible light. Also longer wavelengths allow lower sensitivity to external perturbations. Second, shearography at 532 nm is used as an alternative to LWIR ESPI. Both methods are used in time-averaged mode with the use of phase-stepping. This allows transforming Bessel fringes, typical to time averaging, into phase values that provide higher contrast and improve the visualization of vibration mode shapes. Laboratory experimental results with both techniques allowed comparison of techniques, leading to selection of shearography. Finally a vibration test on electrodynamic shaker is performed in an industrial environment and mode shapes are obtained with good quality by shearography.
Directory of Open Access Journals (Sweden)
Chi Luo
2017-03-01
Full Text Available We study the dynamic behavior of a quartz crystal resonator (QCR in thickness-shear vibrations with the upper surface covered by an array of micro-beams (MBs under large deflection. Through taking into account the continuous conditions of shear force and bending moment at the interface of MBs/resonator, dependences of frequency shift of the compound QCR system versus material parameter and geometrical parameter are illustrated in detail for nonlinear and linear vibrations. It is found that the frequency shift produces a little right (left translation for increasing elastic modulus (length/radius ratio of MBs. Moreover, the frequency right (left translation distance caused by nonlinear deformation becomes more serious in the second-order mode than in the first-order one.
Zhang, Yong; Straub, John E
2009-06-07
The time scales and pathways of vibrational energy relaxation (VER) of the nu(4) and nu(7) modes of three nickel porphyrin models, nickel porphine (NiP), nickel protoporphyrin IX (Ni-heme), and nickel octaethylporphyrin (NiOEP), were studied using a non-Markovian time-dependent perturbation theory at the B3LYP/6-31G(d) level. When NiP is calculated with D(4h) symmetry, it has the planar structure and the same VER properties as ferrous iron porphine (FeP). The porphine cores of both Ni-heme and NiOEP were distorted from a planar geometry, assuming a nonplanar structure, similar to that of the heme structure in cytochrome c. The VER time scales of Ni-heme are found to be similar to those predicted for a planar iron heme, but the derived pathways have distinctly different features. In particular, the strong coupling between the nu(7) mode and the overtone of the approximately 350 cm(-1) gamma(7) mode, observed for planar porphyrins, is absent in both nonplanar nickel porphyrins. Direct energy exchange between the nu(4) and nu(7) modes is not observed in NiOEP, but is found to play an essential role in the VER of the nu(4) mode in Ni-heme. The Ni-heme isopropionate groups are involved in the dominant VER pathways of both the nu(4) and nu(7) modes of Ni-heme. However, in contrast with VER pathways derived in planar iron heme, the isopropionate groups are not observed to play an essential role relative to other side chains in spatially directing the vibrational energy flow.
Rosen, I. G.
1986-01-01
Rayleigh-Ritz methods for the approximation of the natural modes for a class of vibration problems involving flexible beams with tip bodies using subspaces of piecewise polynomial spline functions are developed. An abstract operator-theoretic formulation of the eigenvalue problem is derived and spectral properties investigated. The existing theory for spline-based Rayleigh-Ritz methods applied to elliptic differential operators and the approximation properties of interpolatory splines are used to argue convergence and establish rates of convergence. An example and numerical results are discussed.
Energy Technology Data Exchange (ETDEWEB)
Hauer, Juergen; Buckup, Tiago [Fachbereich Chemie, Physikalische Chemie, Philipps-Universitaet Marburg, Hans-Meerwein-Strasse, D-35043 Marburg (Germany); Motzkus, Marcus [Fachbereich Chemie, Physikalische Chemie, Philipps-Universitaet Marburg, Hans-Meerwein-Strasse, D-35043 Marburg (Germany)], E-mail: motzkus@staff.uni-marburg.de
2008-06-23
Quantum control spectroscopy (QCS) is used as a tool to study, address selectively and enhance vibrational wavepacket motion in large solvated molecules. By contrasting the application of Fourier-limited and phase-modulated excitation on different electronic states, the interplay between the controllability of vibrational coherence and electronic resonance is revealed. We contrast control on electronic ground and excited state by introducing an additional pump beam prior to a DFWM-sequence (Pump-DFWM). Via phase modulation of this initial pump pulse, coherent control is extended to structural evolution on the vibrationally hot ground state (hot-S{sub 0}) and lowest lying excited state (S{sub 1}) of {beta}-carotene. In an open loop setup, the control scenarios for these different electronic states are compared in their effectiveness and mechanism.
Nonclassicality in two-mode BEC
Giri, Sandip Kumar; Sen, Biswajit; Ooi, C H Raymond; Pathak, Anirban
2013-01-01
The operator solution of a completely quantum mechanical Hamiltonian of the Raman processes is used here to investigate the possibility of obtaining intermodal entanglement between different modes involved in the Raman processes (e.g. pump mode, Stokes mode, vibration (phonon) mode and anti-Stokes mode). Intermodal entanglement is reported between a) pump mode and anti-Stokes mode, b) pump mode and vibration (phonon) mode c) Stokes mode and vibration phonon mode, d) Stokes mode and anti-stoke...
Dillman, Kevin L; Shelly, Katherine R; Beck, Warren F
2009-04-30
Ground-state coherent wavepacket motions arising from intermolecular modes with clustered, first-shell solvent molecules were observed using the femtosecond dynamic absorption technique in polar solutions of Zn(II) meso-tetrakis(N-methylpyridyl)porphyrin (ZnTMPyP) with excitation in the Soret absorption band. As was observed previously in bacteriochlorophyll a solution, the pump-probe transients in ZnTMPyP solutions are weakly modulated by slowly damped (effective damping time gamma > 1 ps) features that are assigned to intramolecular modes, the skeletal normal modes of vibration of the porphyrin. The 40 cm(-1) and 215 cm(-1) modes from the metal-doming and metal-solvent-ligand modes, respectively, are members of this set of modulation components. A slowly damped 2-4 cm(-1) component is assigned to the internal rotation of the N-methylpyridyl rings with respect to the porphyrin macrocycle; this mode obtains strong resonance Raman intensity enhancement from an extensive delocalization of pi-electron density from the porphyrin in the ground state onto the rings in the pi* excited states. The dominant features observed in the pump-probe transients are a pair of rapidly damped (gamma modes with solvent molecules. This structural assignment is supported by an isotope-dependent shift of the average mode frequencies in methanol and perdeuterated methanol. The solvent dependence of the mean intermolecular mode frequency is consistent with a van der Waals intermolecular potential that has significant contributions only from the London dispersion and induction interactions; ion-dipole or ion-induced-dipole terms do not make large contributions because the pi-electron density is not extensively delocalized onto the N-methylpyridyl rings. The modulation depth associated with the intermolecular modes exhibits a marked dependence on the electronic structure of the solvent that is probably related to the degree of covalency; the strongest modulations are observed in acetonitrile
Taleb-Mokhtari, Ilham Naoual; Lazreg, Abbassia; Sekkal-Rahal, Majda; Bestaoui, Noreya
2016-01-15
A structural investigation of the organic molecules is being carried out using vibrational spectroscopy. In this study, normal co-ordinate calculations of anomers of the methyl-D-glucopyranoside and methyl-β-D-xylopyranoside in the crystalline state have been performed using the modified Urey-Bradley-Shimanouchi force field (mUBSFF) combined with an intermolecular potential energy function. The latter includes Van der Waals interactions, electrostatic terms, and explicit hydrogen bond functions. The vibrational spectra of the compounds recorded in the crystalline state, in the 4000-500 cm(-1) spectral region for the IR spectra, and in the 4000-20 cm(-1) spectral range for the Raman spectra are presented. After their careful examination, several differences in the intensities and frequency shifts have been observed. The theoretical spectra have been obtained after a tedious refinement of the force constants. Thus, on the basis of the obtained potential distribution, each observed band in IR and in Raman has been assigned to a vibrational mode. The obtained results are indeed in agreement with those observed experimentally and thus confirm the previous assignments made for the methyl-α and β-D-glucopyranoside, as well as for the methyl-β-D-xylopyranoside. Copyright © 2015 Elsevier B.V. All rights reserved.
Kvaternik, R. G.; Durling, B. J.
1978-01-01
The use of the SUDAN computer program for analyzing structural systems for their natural modes and frequencies of vibration is described. SUDAN is intended for structures which can be represented as an equivalent system of beam, spring, and rigid-body substructures. User-written constraint equations are used to analytically join the mass and stiffness matrices of the substructures to form the mass and stiffness matrices of the complete structure from which all the frequencies and modes of the system are determined. The SUDAN program can treat the case in which both the mass and stiffness matrices of the coupled system may be singular simultaneously. A general description of the FORTRAN IV program is given, the computer hardware and software specifications are indicated, and the input required by the program is described.
Full Article: Stoichiometry, Vibrational Modes and Structure of Molten Nb2O5-K2S2O7 Mixtures
DEFF Research Database (Denmark)
Boghosian, S.; Borup, F.; Berg, Rolf W.
1998-01-01
The dissolution reaction of Nb205 in pure molten K2S207 has been studied and high temperature Raman spectroscopy has been used for determining the vibrational and structural properties of the Nb(V) complex(es) formed according to the reaction Nb205 + n S207(2-) -> complex. By means of a recently ...
Bloem, Robbert; Dijkstra, Arend G.; Jansen, Thomas La Cour; Knoester, Jasper
2008-01-01
Population transfer between vibrational eigenstates is important for many phenomena in chemistry. In solution, this transfer is induced by fluctuations in molecular conformation as well as in the surrounding solvent. We develop a joint electrostatic density functional theory map that allows us to
Directory of Open Access Journals (Sweden)
Byung-Keun Song
2017-10-01
Full Text Available This paper presents a new fuzzy sliding mode controller (FSMC to improve control performances in the presence of uncertainties related to model errors and external disturbance (UAD. As a first step, an adaptive control law is designed using Lyapunov stability analysis. The control law can update control parameters of the FSMC with a disturbance estimator (DE in which the closed-loop stability and finite-time convergence of tracking error are guaranteed. A solution for estimating the compensative quantity of the impact of UAD on a control system and a set of solutions are then presented in order to avoid the singular cases of the fuzzy-based function approximation, increase convergence ability, and reduce the calculating cost. Subsequently, the effectiveness of the proposed controller is verified through the investigation of vibration control performances of a semi-active vehicle suspension system featuring a magnetorheological damper (MRD. It is shown that the proposed controller can provide better control ability of vibration control with lower consumed power compared with two existing fuzzy sliding mode controllers.
McMicken, Brady; Parker, James E; Thomas, Robert J; Brancaleon, Lorenzo
2016-09-01
The ability to modify the conformation of a protein by controlled partial unfolding may have practical applications such as inhibiting its function or providing non-native photosensitive properties. A water-soluble porphyrin, meso-tetrakis (p-sulfonatophenyl) porphyrin (TSPP), non-covalently bound to tubulin can be used as a photosensitizer, which upon irradiation can lead to conformational changes of the protein. To fully understand the mechanism responsible for this partial unfolding and determine the amino acid residues and atoms involved, it is essential to find the most likely binding location and the configuration of the ligand and protein. Techniques typically used to analyze atomic position details, such as nuclear magnetic resonance and X-ray crystallography, require large concentrations, which are incompatible with the dilute conditions required in experiments for photoinduced mechanisms. Instead, we develop an atomistic description of the TSPP-tubulin complex using vibrational mode analysis from density functional theory calculations correlated to resonance Raman spectra of the porphyrin paired with docking simulations. Changes in the Raman peaks of the porphyrin molecule correlate with changes in its structural vibrational modes when bound to tubulin. The data allow us to construct the relative geometry of the porphyrin when bound to protein, which are then used with docking simulations to find the most likely configuration of the TSPP-tubulin complex.
Passarello, Marco; Abbate, Sergio; Longhi, Giovanna; Lepri, Susan; Ruzziconi, Renzo; Nicu, Valentin Paul
2014-06-19
The role played by the C*-H based modes (C* being the chiral carbon atom) and the large amplitude motions in the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra is investigated. The example of an adduct of dimethyl fumarate and anthracene, i.e., dimethyl-(+)-(11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate, and two deuterated isotopomers thereof specially synthesized for this goal, are considered. By comparing the experimental and DFT calculated spectra of the undeuterated and deuterated species, we demonstrate that the C*-H bending, rocking, and stretching modes in the VA and VCD spectra are clearly identified in well defined spectroscopic features. Further, significant information about the conformer distribution is gathered by analyzing the VA and VCD data of both the fingerprint and the C-H stretching regions, with particular attention paid to the band shape data. Effects related to the large amplitude motions of the two methoxy moieties have been simulated by performing linear transit (LT) calculations, which consists of varying systematically the relative positions of the two methoxy moieties and calculating VCD spectra for the partially optimized structures obtained in this way. The LT method allows one to improve the quality of calculated spectra, as compared to experimental results, especially in regard to relative intensities and bandwidths.
Kang, Jaeyoung; Krousgrill, Charles M.; Sadeghi, Farshid
2009-07-01
The current study investigates the disc brake squeal by using an annular disc in contact with two pads subject to distributed friction stresses. The disc and pads are modeled as rotating annular and stationary annular sector plates, respectively. Friction stress is described on the deformed disc surface as distributed non-conservative friction-couples and frictional follower forces. From disc doublet-mode and multiple-mode models, the mode-coupling mechanism influenced by disc rotation is examined. In automotive applications, the frictional mode-coupling resulting from friction couple is shown to be the major mechanism for dynamic destabilization, whereas the effects of disc rotation on flutter destabilization are found to be small. On the verge of stop, however, the rotation effects effectively stabilize the steady sliding. This comprehensive brake model has shown that there is a speed corresponding to maximum squeal propensity for each flutter mode.
DEFF Research Database (Denmark)
Dantan, Aurélien; Marler, Joan; Albert, Magnus
2010-01-01
We report on a novel noninvasive method to determine the normal mode frequencies of ion Coulomb crystals in traps based on the resonance enhanced collective coupling between the electronic states of the ions and an optical cavity field at the single photon level. Excitations of the normal modes...... are observed through a Doppler broadening of the resonance. An excellent agreement with the predictions of a zero-temperature uniformly charged liquid plasma model is found. The technique opens up for investigations of the heating and damping of cold plasma modes, as well as the coupling between them....
Mei, Chuh; Shen, Mo-How
1987-01-01
The use of NASTRAN model synthesis capability is illustrated. A classical truss problem is examined and the results are compared to results from other methods to test for accuracy. The problem is examined using both fixed interface modes and free interface modes. The solution is carried out for an applied dynamic load as far as recovery of forces in individual members as a function of time. Another small beam problem is used to compare different means of combining substructures.
Gascooke, Jason R; Lawrance, Warren D
2013-02-28
The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are ∣V3(S1)∣ = 33.4 ± 1.0 cm(-1), ∣V3(S0)∣ = 20.0 ± 1.0 cm(-1), V6(S1) = -10.7 ± 1.0 cm(-1), and V6(S0) = -1.7 ± 1.0 cm(-1). The methyl rotor is also found to couple with van der Waals vibration; specifically, the m(") = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m(") = 1. The coupling constant is determined to be 1.9 cm(-1), which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.
Gascooke, Jason R.; Lawrance, Warren D.
2013-02-01
The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are |V3(S1)| = 33.4 ± 1.0 cm-1, |V3(S0)| = 20.0 ± 1.0 cm-1, V6(S1) = -10.7 ± 1.0 cm-1, and V6(S0) = -1.7 ± 1.0 cm-1. The methyl rotor is also found to couple with van der Waals vibration; specifically, the m″ = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m″ = 1. The coupling constant is determined to be 1.9 cm-1, which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.
Fu, Li; Wang, Zhuguang; Yan, Elsa C Y
2014-09-01
We present a detailed analysis of the molecular origin of the chiral sum frequency generation (SFG) signals of proteins and peptides at interfaces in the N-H stretching vibrational region. The N-H stretching can be a probe for investigating structural and functional properties of proteins, but remains technically difficult to analyze due to the overlapping with the O-H stretching of water molecules. Chiral SFG spectroscopy offers unique tools to study the N-H stretching from proteins at interfaces without interference from the water background. However, the molecular origin of the N-H stretching signals of proteins is still unclear. This work provides a justification of the origin of chiral N-H signals by analyzing the vibrational frequencies, examining chiral SFG theory, studying proton (hydrogen/deuterium) exchange kinetics, and performing optical control experiments. The results demonstrate that the chiral N-H stretching signals at ~3300 cm(-1) originate from the amide group of the protein backbones. This chiral N-H stretching signal offers an in situ, real-time, and background-free probe for interrogating the protein structures and dynamics at interfaces at the molecular level. © 2014 Wiley Periodicals, Inc.
Fu, Hungshin; Qian, Jun; Green, Richard J.; Anderson, Scott L.
1998-02-01
We report a study of vibrational mode effects and differential scattering in reaction of NH3+ with CD3OD, CD3OH, and CH3OD over the collision energy range from 0.1 to 5 eV. At low collision energies, abstraction of both methyl and hydroxyl D atoms is observed with roughly equal probability, even though methyl D-abstraction should be favored on both energetic and statistical grounds. Branching between the two abstraction reactions is controlled by two different hydrogen-bonded complexes. Formation of these complexes is enhanced by NH3+ umbrella bending, unaffected by the NH3+ symmetric stretch, and inhibited by collision energy. Endoergic proton transfer is mediated at low energies by a third hydrogen-bonded complex, formation of which is enhanced by both umbrella bending and the symmetric stretch. Charge transfer (CT) has a significant cross section only when the NH3+ umbrella bend excitation exceeds the endoergicity. Collision energy and symmetric stretching appear to have no effect on CT. At high collision energies all reactions become direct, with near spectator stripping dynamics. In this energy range product branching appears to be controlled by collision geometry and there are no significant vibrational effects.
Directory of Open Access Journals (Sweden)
Sy Dung Nguyen
2017-01-01
Full Text Available This work proposes a novel adaptive type 2 fuzzy sliding controller (AT2FC for vibration control of magnetorheological damper- (MRD- based railway suspensions subjected to uncertainty and disturbance (UAD. The AT2FC is constituted of four main parts. The first one is a sliding mode controller (SMC for specifying the main damping force supporting the suspension. This controller is designed via Lyapunov stability theory. The second one is an interpolation model based on an interval type 2 fuzzy logic system for determination of optimal parameters of the SMC. The third one is a nonlinear UAD observer to compensate for external disturbances. The fourth one is an inverse MRD model (T2F-I-MRD for specifying the input current. In the operating process, an adaptively optimal structure deriving from the SMC is created (called the Ad-op-SMC to adapt to the real status. Working as an actuator, the input current for MRD is then determined by the T2F-I-MRD to generate the required damping force which is estimated by the Ad-op-SMC and the nonlinear observer. It is shown that the obtained survey results reflect the AT2FC’s excellent vibration control performance compared with the other controllers.
DEFF Research Database (Denmark)
Mackeprang, Kasper; Kjærgaard, Henrik Grum
2017-01-01
The local mode perturbation theory (LMPT) model was developed to improve the description of hydrogen bonded XH-stretching transitions, where X is typically O or N. We present a modified version of the LMPT model to extend its application from hydrated bimolecular complexes to hydrogen bonded...... bimolecular complexes with donors such as alcohols, amines and acids. We have applied the modified model to a series of complexes of different hydrogen bond type and complex energy. We found that the differences between local mode (LM) and LMPT calculated fundamental XH-stretching transition wavenumbers...
Mackeprang, Kasper; Kjaergaard, Henrik G.
2017-04-01
The local mode perturbation theory (LMPT) model was developed to improve the description of hydrogen bonded XH-stretching transitions, where X is typically O or N. We present a modified version of the LMPT model to extend its application from hydrated bimolecular complexes to hydrogen bonded bimolecular complexes with donors such as alcohols, amines and acids. We have applied the modified model to a series of complexes of different hydrogen bond type and complex energy. We found that the differences between local mode (LM) and LMPT calculated fundamental XH-stretching transition wavenumbers and oscillator strengths were correlated with the strength of the hydrogen bond. Overall, we have found that the LMPT model in most cases predicts transition wavenumbers within 20 cm-1 of the experimental values.
Kwac, Kijeong; Lee, Hochan; Cho, Minhaeng
2004-01-01
By carrying out molecular dynamics simulations of an N-methylacetamide (NMA) in methanol solution, the amide I mode frequency fluctuation and hydrogen bonding dynamics were theoretically investigated. Combining an extrapolation formula developed from systematic ab initio calculation studies of NMA-(CH3OH)n clusters with a classical molecular dynamics simulation method, we were able to quantitatively describe the solvatochromic vibrational frequency shift induced by the hydrogen-bonding interaction between NMA and solvent methanol. It was found that the fluctuating amide I mode frequency distribution is notably non-Gaussian and it can be decomposed into two Gaussian peaks that are associated with two distinctively different solvation structures. The ensemble-average-calculated linear response function associated with the IR absorption is found to be oscillating, which is in turn related to the doublet amide I band shape. Numerically calculated infrared absorption spectra are directly compared with experiment and the agreement was found to be excellent. By using the Onsager's regression hypothesis, the rate constants of the interconversion process between the two solvation structures were obtained. Then, the nonlinear response functions associated with two-dimensional infrared pump-probe spectroscopy were simulated. The physics behind the two-dimensional line shape and origin of the cross peaks in the time-resolved pump-probe spectra is explained and the result is compared with 2D spectra experimentally measured recently by Woutersen et al. [S. Woutersen, Y. Mu, G. Stock, and P. Hamm, Chem. Phys. 266, 137 (2001)].
Localized Surface Plasmons in Vibrating Graphene Nanodisks
DEFF Research Database (Denmark)
Wang, Weihua; Li, Bo-Hong; Stassen, Erik
2016-01-01
in graphene disks have the additional benefit to be highly tunable via electrical stimulation. Mechanical vibrations create structural deformations in ways where the excitation of localized surface plasmons can be strongly modulated. We show that the spectral shift in such a scenario is determined...... by a complex interplay between the symmetry and shape of the modal vibrations and the plasmonic mode pattern. Tuning confined modes of light in graphene via acoustic excitations, paves new avenues in shaping the sensitivity of plasmonic detectors, and in the enhancement of the interaction with optical emitters...
Sortur, Veenasangeeta; Yenagi, Jayashree; Tonannavar, J; Jadhav, V B; Kulkarni, M V
2008-11-15
Infrared (4000-400 cm(-1)) and Raman (3500-50 cm(-1)) spectral measurements have been made for the solid sample of 7-methyl-4-bromomethylcoumarin. Electronic structure calculations at RHF/6-31G* and B3LYP/6-31G* levels of theory have been performed, giving equilibrium geometries, harmonic vibrational spectra and normal modes. Different orientations of bromomethyl group have yielded only two conformers, of which the most stable one lying lower from the other conformer by approximately 7.99 kJ/mol, is non-planar with no symmetry. A complete assignment of the vibrational modes, aided by the calculations, has been proposed. Coupled vibrations are manifest in many modes. Some spectral features, compared to 6-methyl-4-bromomethylcoumarin, show changes across both IR and Raman spectra, involving mainly skeletal vibrations, and to a lesser degree, methyl and bromomethyl vibrations. Low-frequency vibrations below 150 cm(-1) are assigned to lattice modes.
Vibration analysis of composite laminate plate excited by piezoelectric actuators.
Her, Shiuh-Chuan; Lin, Chi-Sheng
2013-03-01
Piezoelectric materials can be used as actuators for the active vibration control of smart structural systems. In this work, piezoelectric patches are surface bonded to a composite laminate plate and used as vibration actuators. A static analysis based on the piezoelectricity and elasticity is conducted to evaluate the loads induced by the piezoelectric actuators to the host structure. The loads are then employed to develop the vibration response of a simply supported laminate rectangular plate excited by piezoelectric patches subjected to time harmonic voltages. An analytical solution of the vibration response of a simply supported laminate rectangular plate under time harmonic electrical loading is obtained and compared with finite element results to validate the present approach. The effects of location and exciting frequency of piezoelectric actuators on the vibration response of the laminate plate are investigated through a parametric study. Numerical results show that modes can be selectively excited, leading to structural vibration control.
Chang, Chih-Ming; Young, Yi-Ho; Cheng, Po-Wen
2012-12-01
The age-related changes in ocular vestibular-evoked myogenic potentials (oVEMPs) elicited by galvanic vestibular stimulation (GVS) and bone-conducted vibration (BCV) might be attributed to the morphological degeneration of the vestibular system. This study employed GVS and BCV modes for eliciting oVEMPs in healthy subjects to explore the effect of aging on the vestibulo-ocular reflex (VOR) pathway. Sixty-nine healthy subjects (aged 22-69 years) were divided into 5 groups of 12-19 subjects by decades of age. All subjects underwent oVEMPs using GVS and BCV modes. The prevalence and parameters of oVEMPs, including nI latency, pI latency, nI-pI interval, and nI-pI amplitude were measured and compared. The prevalences of GVS-oVEMPs had nonsignificant differences among all age groups, whereas that of BCV-oVEMPs in the over-60 group was significantly lower than those in the under-60 groups. In GVS-oVEMPs, the group over 60 years had significantly longer nI, pI latencies, and smaller amplitudes when compared with those under 60 years. In BCV-oVEMPs, the nI and pI latencies in the over-60 group were significantly longer than those of the under-60 groups, while the nI-pI amplitudes of groups over 50 years were significantly smaller than those of groups under 50 years. All oVEMP parameters exhibited significant differences between GVS- and BCV-oVEMPs in each age group.
Nahavandi, Amir; Korayem, Moharam Habibnejad
2015-10-01
The aim of this paper is to determine the effects of forces exerted on the cantilever probe tip of an atomic force microscope (AFM). These forces vary according to the separation distance between the probe tip and the surface of the sample being examined. Hence, at a distance away from the surface (farther than d(on)), these forces have an attractive nature and are of Van der Waals type, and when the probe tip is situated in the range of a₀≤ d(ts) ≤ d(on), the capillary force is added to the Van der Waals force. At a distance of d(ts) ≤ a₀, the Van der Waals and capillary forces remain constant at intermolecular distances, and the contact repulsive force repels the probe tip from the surface of sample. The capillary force emerges due to the contact of thin water films with a thickness of h(c) which have accumulated on the sample and probe. Under environmental conditions a layer of water or hydrocarbon often forms between the probe tip and sample. The capillary meniscus can grow until the rate of evaporation equals the rate of condensation. For each of the above forces, different models are presented. The smoothness or roughness of the surfaces and the geometry of the cantilever tip have a significant effect on the modeling of forces applied on the probe tip. Van der Waals and the repulsive forces are considered to be the same in all the simulations, and only the capillary force is altered in order to evaluate the role of this force in the AFM-based modeling. Therefore, in view of the remarkable advantages of the piezoelectric microcantilever and also the extensive applications of the tapping mode, we investigate vibrational motion of the piezoelectric microcantilever in the tapping mode. The cantilever mentioned is entirely covered by two piezoelectric layers that carry out both the actuation of the probe tip and the measuringof its position.
Energy Technology Data Exchange (ETDEWEB)
Hardage, Bob [Bureau of Economic Geology
2013-07-01
This 3-year project was terminated at the end of Year 1 because the DOE Geothermal project-evaluation committee decided one Milestone was not met and also concluded that our technology would not be successful. The Review Panel recommended a ?no-go? decision be implemented by DOE. The Principal Investigator and his research team disagreed with the conclusions reached by the DOE evaluation committee and wrote a scientifically based rebuttal to the erroneous claims made by the evaluators. We were not told if our arguments were presented to the people who evaluated our work and made the ?no-go? decision. Whatever the case regarding the information we supplied in rebuttal, we received an official letter from Laura Merrick, Contracting Officer at the Golden Field Office, dated June 11, 2013 in which we were informed that project funding would cease and instructed us to prepare a final report before September 5, 2013. In spite of the rebuttal arguments we presented to DOE, this official letter repeated the conclusions of the Review Panel that we had already proven to be incorrect. This is the final report that we are expected to deliver. The theme of this report will be another rebuttal of the technical deficiencies claimed by the DOE Geothermal Review Panel about the value and accomplishments of the work we did in Phase 1 of the project. The material in this report will present images made from direct-S modes produced by vertical-force sources using the software and research findings we developed in Phase 1 that the DOE Review Panel said would not be successful. We made these images in great haste when we were informed that DOE Geothermal rejected our rebuttal arguments and still regarded our technical work to be substandard. We thought it was more important to respond quickly rather than to take additional time to create better quality images than what we present in this Final Report.
Park, G. Barratt
2014-10-01
Franck-Condon vibrational overlap integrals for the tilde{A} {^1A_u}—{tilde{X}} {^1Σ _g^+} transition in acetylene have been calculated in full dimension in the harmonic normal mode basis. The calculation uses the method of generating functions first developed for polyatomic Franck-Condon factors by Sharp and Rosenstock [J. Chem. Phys. 41(11), 3453-3463 (1964)], and previously applied to acetylene by Watson [J. Mol. Spectrosc. 207(2), 276-284 (2001)] in a reduced-dimension calculation. Because the transition involves a large change in the equilibrium geometry of the electronic states, two different types of corrections to the coordinate transformation are considered to first order: corrections for axis-switching between the Cartesian molecular frames and corrections for the curvilinear nature of the normal modes at large amplitude. The angular factor in the wavefunction for the out-of-plane component of the trans bending mode, ν _4^' ' }, is treated as a rotation, which results in an Eckart constraint on the polar coordinates of the bending modes. To simplify the calculation, the other degenerate bending mode, ν _5^' ' }, is integrated in the Cartesian basis and later transformed to the constrained polar coordinate basis, restoring the conventional v and l quantum numbers. An updated tilde{A}-state harmonic force field obtained recently in the R. W. Field research group is evaluated. The results for transitions involving the gerade vibrational modes are in qualitative agreement with experiment. Calculated results for transitions involving ungerade modes are presented in Paper II of this series [G. B. Park, J. H. Baraban, and R. W. Field, "Full dimensional Franck-Condon factors for the acetylene tilde{A} {^1A_u}—{tilde{X}} {^1Σ _g^+} transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes," J. Chem. Phys. 141, 134305 (2014)].
DEFF Research Database (Denmark)
Olsen, Thomas; Schiøtz, Jakob
2010-01-01
We propose a mechanism which allows one to control the transmission of single electrons through a molecular junction. The principle utilizes the emergence of transmission sidebands when molecular vibrational modes are coupled to the electronic state mediating the transmission. We will show that i....... As an example we perform a density-functional theory analysis of a benzene molecule between two Au(111) contacts and show that exciting a particular vibrational mode can give rise to transmission of a single electron....
Noninvasive monitoring of vocal fold vertical vibration using the acoustic Doppler effect.
Tao, Chao; Jiang, Jack J; Wu, Dan; Liu, Xiaojun; Chodara, Ann
2012-11-01
To validate a proposed method of noninvasively monitoring vocal fold vertical vibration through utilization of the acoustic Doppler effect and the waveguide property of the vocal tract. Validation case-control study. In this device, an ultrasound beam is generated and directed into the mouth. The vocal tract, acting as a natural waveguide, guides the ultrasound beam toward the vibrating vocal folds. The vertical velocity of vocal fold vibration is then recovered from the Doppler frequency of the reflected ultrasound. One subject (age 32, male) was studied and measurements were taken under three modes of vocal fold vibration: breathing (no vibration), whispering (irregular vibration), and normal phonation (regular vibration). The peak-to-peak amplitude of the measured velocity of vocal fold vertical vibration was about 0.16 m/s, and the fundamental frequency was 172 Hz; the extracted velocity information showed a reasonable waveform and value in comparison with the previous studies. In all three modes of phonation, the Doppler frequencies derived from the reflected ultrasound corresponded with the vertical velocity of vocal fold vibration as expected. The proposed method can accurately represent the characteristics of different phonation modes such as no phonation, whisper and normal phonation. The proposed device could be used in daily monitoring and assessment of vocal function and vocal fold vibration. Copyright © 2012 The Voice Foundation. Published by Mosby, Inc. All rights reserved.
Park, G. Barratt; Baraban, Joshua H.; Field, Robert W.
2014-10-01
A full-dimensional Franck-Condon calculation has been applied to the tilde{A} 1Au—tilde{X} ^1Σ _g^+ transition in acetylene in the harmonic normal mode basis. Details of the calculation are discussed in Part I of this series. To our knowledge, this is the first full-dimensional Franck-Condon calculation on a tetra-atomic molecule undergoing a linear-to-bent geometry change. In the current work, the vibrational intensity factors for levels involving excitation in ungerade vibrational modes are evaluated. Because the Franck-Condon integral accumulates away from the linear geometry, we have been able to treat the out-of-plane component of trans bend (ν _4^' ' }) in the linear tilde{X} state in the rotational part of the problem, restoring the χ Euler angle and the a-axis Eckart conditions. A consequence of the Eckart conditions is that the out-of-plane component of ν _4^' ' } does not participate in the vibrational overlap integral. This affects the structure of the coordinate transformation and the symmetry of the vibrational wavefunctions used in the overlap integral, and results in propensity rules involving the bending modes of the tilde{X} state that were not previously understood. We explain the origin of some of the unexpected propensities observed in IR-UV laser-induced fluorescence spectra, and we calculate emission intensities from bending levels of the tilde{A} state into bending levels of the tilde{X} state, using normal bending mode and local bending mode basis sets. Our calculations also reveal Franck-Condon propensities for the Cartesian components of the cis bend (ν _5^' ' }), and we predict that the best tilde{A}-state vibrational levels for populating tilde{X}-state levels with large amplitude bending motion localized in a single C-H bond (the acetylene↔vinylidene isomerization coordinate) involve a high degree of excitation in ν _6^' } (cis-bend). Mode ν _4^' } (torsion) populates levels with large amplitude counter-rotational motion of
DEFF Research Database (Denmark)
Oddo, Alberto; Thomsen, Thomas Thyge; Kjelstrup, Susanne
2016-01-01
. In this study, we investigated the in vitro antibacterial activities of 18 BP100 analogs (four known and 14 new) against the MDR A. baumannii strain ATCC BAA-1605, as well as against a number of other clinically relevant human pathogens. Selected peptides were further evaluated against strains of A. baumannii......Multiple strains of Acinetobacter baumannii have developed multidrug resistance (MDR), leaving colistin as the only effective treatment. The cecropin-α-melittin hybrid BP100 (KKLFKKILKYL-NH2) and its analogs have previously shown activity against a wide array of plant and human pathogens...... that acquired resistance to colistin due to mutations of the lpxC, lpxD, pmrA, and pmrB genes. The novel analogue BP214 showed antimicrobial activity at 1 to 2 μM and a hemolytic 50% effective concentration (EC50) of >150 μM. The lower activity of its enantiomer suggests a dual, specific and nonspecific mode...
Killgore, Jason P; Tung, Ryan C; Hurley, Donna C
2014-08-29
Combining heated-tip atomic force microscopy (HT-AFM) with quantitative methods for determining surface mechanical properties, such as contact resonance force microscopy, creates an avenue for nanoscale thermomechanical property characterization. For nanomechanical methods that employ an atomic force microscope cantilever's vibrational modes, it is essential to understand how the vibrations of the U-shaped HT-AFM cantilever differ from those of a more traditional rectangular lever, for which analytical techniques are better developed. Here we show, with a combination of finite element analysis (FEA) and experiments, that the HT-AFM cantilever exhibits many more readily-excited vibrational modes over typical AFM frequencies compared to a rectangular cantilever. The arms of U-shaped HT-AFM cantilevers exhibit two distinct forms of flexural vibrations that differ depending on whether the two arms are vibrating in-phase or out-of-phase with one another. The in-phase vibrations are qualitatively similar to flexural vibrations in rectangular cantilevers and generally show larger sensitivity to surface stiffness changes than the out-of-phase vibrations. Vibration types can be identified from their frequency and by considering vibration amplitudes in the horizontal and vertical channels of the AFM at different laser spot positions on the cantilever. For identifying contact resonance vibrational modes, we also consider the sensitivity of the resonant frequencies to a change in applied force and hence to tip-sample contact stiffness. Finally, we assess how existing analytical models can be used to accurately predict contact stiffness from contact-resonance HT-AFM results. A simple two-parameter Euler-Bernoulli beam model provided good agreement with FEA for in-phase modes up to a contact stiffness 500 times the cantilever spring constant. By providing insight into cantilever vibrations and exploring the potential of current analysis techniques, our results lay the groundwork
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...
Moradi, H.; Bakhtiari-Nejad, F.; Movahhedy, M. R.
2008-11-01
Dynamic vibration absorbers are used to reduce the undesirable vibrations in many applications such as electrical transmission lines, helicopters, gas turbines, engines, bridges, etc. Tuneable vibration absorbers (TVA) are also used as semi-active controllers. In this paper, the application of a TVA for suppression of chatter vibrations in the boring manufacturing process is presented. The boring bar is modeled as a cantilever Euler-Bernoulli beam and the TVA is composed of mass, spring and dashpot elements. In addition, the effect of spring mass is considered in this analysis. After formulation of the problem, the optimum specifications of the absorber such as spring stiffness, absorber mass and its position are determined using an algorithm based on the mode summation method. The analog-simulated block diagram of the system is developed and the effects of various excitations such as step, ramp, etc. on the absorbed system are simulated. In addition, chatter stability is analyzed in dominant modes of boring bar. Results show that at higher modes, larger critical widths of cut and consequently more material removal rate (MRR) can be achieved. In the case of self-excited vibration, which is associated with a delay differential equation, the optimum absorber suppresses the chatter and increases the limit of stability.
Tensor-decomposed vibrational coupled-cluster theory
DEFF Research Database (Denmark)
Madsen, Niels Kristian; Godtliebsen, Ian Heide; Christiansen, Ove
Vibrational coupled-cluster (VCC) theory is a highly accurate method for obtaining vibrational spectra and properties of small to medium-sized molecules. Calculating the vibrational energy and wave function requires the solution of a set of non-linear equations. We have implemented an array...... of any VCC calculation is the calculation of the error vector from a set of trial amplitudes. For high-order VCC methods this shows steep polynomial scaling w.r.t. the size of the moleule and the number of one-mode basis functions. Both the computational cost and the memory requirements of the VCC solver...
Structural Stability and Vibration
DEFF Research Database (Denmark)
Wiggers, Sine Leergaard; Pedersen, Pauli
This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni......This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....
Directory of Open Access Journals (Sweden)
Jung Jin Park
2016-05-01
Full Text Available Magnetostrictive Fe-Ga and Fe-Al alloys are promising materials for use in bending-mode vibrational energy harvesters. For this study, 50.8 mm × 5.0 mm × 0.5 mm strips of Fe-Ga and Fe-Al were cut from 0.50-mm thick rolled sheet. An atmospheric anneal was used to develop a Goss texture through an abnormal grain growth process. The anneal lead to large (011 grains that covered over 90% of sample surface area. The resulting highly-textured Fe-Ga and Fe-Al strips exhibited saturation magnetostriction values (λsat = λ∥ − λ⊥ of ∼280 ppm and ∼130 ppm, respectively. To maximize 90° rotation of magnetic moments during bending of the strips, we employed compressive stress annealing (SA. Samples were heated to 500°C, and a 100-150 MPa compressive stress was applied while at 500°C for 30 minutes and while being cooled. The effectiveness of the SA on magnetic moment rotation was inferred by comparing post-SA magnetostriction with the maximum possible yield of rotated magnetic moments, which is achieved when λ∥ = λsat and λ⊥ = 0. The uniformity of the SA along the sample length and the impact of the SA on sensing/energy harvesting performance were then assessed by comparing pre- and post-SA bending-stress-induced changes in magnetization at five different locations along the samples. The SA process with a 150 MPa compressive load improved Fe-Ga actuation along the sample length from 170 to 225 ppm (from ∼60% to within ∼80% of λsat. The corresponding sensing/energy harvesting performance improved by as much as a factor of eight in the best sample, however the improvement was not at all uniform along the sample length. The SA process with a 100 MPa compressive load improved Fe-Al actuation along the sample length from 60 to 73 ppm (from ∼46% to ∼56% of λsat, indicating only a marginally effective SA and suggesting the need for modification of the SA protocol. In spite of this, the SA was effective at improving the sensing
Vibration of imperfect rotating disk
Directory of Open Access Journals (Sweden)
Půst L.
2011-12-01
Full Text Available This study is concerned with the theoretical and numerical calculations of the flexural vibrations of a bladed disk. The main focus of this study is to elaborate the basic background for diagnostic and identification methods for ascertaining the main properties of the real structure or an experimental model of turbine disks. The reduction of undesirable vibrations of blades is proposed by using damping heads, which on the experimental model of turbine disk are applied only on a limited number of blades. This partial setting of damping heads introduces imperfection in mass, stiffness and damping distribution on the periphery and leads to more complicated dynamic properties than those of a perfect disk. Calculation of FEM model and analytic—numerical solution of disk behaviour in the limited (two modes frequency range shows the splitting of resonance with an increasing speed of disk rotation. The spectrum of resonance is twice denser than that of a perfect disk.
Oddo, Alberto; Thomsen, Thomas T; Kjelstrup, Susanne; Gorey, Ciara; Franzyk, Henrik; Frimodt-Møller, Niels; Løbner-Olesen, Anders; Hansen, Paul R
2015-11-16
Multiple strains of Acinetobacter baumannii have developed multidrug resistance (MDR), leaving colistin as the only effective treatment. The cecropin-α-melittin hybrid BP100 (KKLFKKILKYL-NH2) and its analogs have previously shown activity against a wide array of plant and human pathogens. In this study, we investigated the in vitro antibacterial activities of 18 BP100 analogs (four known and 14 new) against the MDR A. baumannii strain ATCC BAA-1605, as well as against a number of other clinically relevant human pathogens. Selected peptides were further evaluated against strains of A. baumannii that acquired resistance to colistin due to mutations of the lpxC, lpxD, pmrA, and pmrB genes. The novel analogue BP214 showed antimicrobial activity at 1 to 2 μM and a hemolytic 50% effective concentration (EC50) of >150 μM. The lower activity of its enantiomer suggests a dual, specific and nonspecific mode of action. Interestingly, colistin behaved antagonistically to BP214 when pmrAB and lpxC mutants were challenged. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Downhole vibration causing a drill collar failure and solutions
Directory of Open Access Journals (Sweden)
Quanta Zhu
2017-03-01
Full Text Available In large borehole drilling of some blocks or formations, due to serious downhole vibration, fatigue failure of a drill collar occurs frequently and most washouts and fractures are in thread root. An analysis of the above failure shows that the drill collar fatigue failure is caused by the cyclic bending stress due to serious downhole vibration. Therefore, downhole vibration modes were theoretically analyzed in terms of axial vibration, lateral vibration, stick-slip, and the physical model established by the mechanical vibration field. Then the resonance damage caused by the actual different downhole vibrations and its theoretical basis were analyzed; and according to the downhole drill string lateral vibration and whirling law, the best area to ensure drilling parameter stability based on the given boundary conditions was figured out, and the theory was clarified that in the best area of drilling, the maximum ROP will be achieved by maintaining the drill string stable or eliminating the vibration/stick-slip, meanwhile the stress fatigue of BHA will be reduced or eliminated especially for drill collar. Finally, solutions were provided as follows: (1 According to the special BHA, drilling conditions, together with physical and mathematical models listed above, downhole resonance speed and related parameters to be avoided can be easily figured out. It was also clarified that resonance speed is exactly the vibration speed that need to be avoided; and that the resonance frequency can be avoided with software for vibration analysis in BHA design and application at well sites; (2 V-Stab is a new and efficient tool which can reduce or eliminate downhole lateral vibration and stick-slip.
Prototype observation and influencing factors of environmental vibration induced by flood discharge
Directory of Open Access Journals (Sweden)
Xin Wang
2017-01-01
Full Text Available Due to a wide range of field vibration problems caused by flood discharge at the Xiangjiaba Hydropower Station, vibration characteristics and influencing factors were investigated based on prototype observation. The results indicate that field vibrations caused by flood discharge have distinctive characteristics of constancy, low frequency, small amplitude, and randomness with impact, which significantly differ from the common high-frequency vibration characteristics. Field vibrations have a main frequency of about 0.5–3.0 Hz and the characteristics of long propagation distance and large-scale impact. The vibration of a stilling basin slab runs mainly in the vertical direction. The vibration response of the guide wall perpendicular to the flow is significantly stronger than it is in other directions and decreases linearly downstream along the guide wall. The vibration response of the underground turbine floor is mainly caused by the load of unit operation. Urban environmental vibration has particular distribution characteristics and change patterns, and is greatly affected by discharge, scheduling modes, and geological conditions. Along with the increase of the height of residential buildings, vibration responses show a significant amplification effect. The horizontal and vertical vibrations of the 7th floor are, respectively, about 6 times and 1.5 times stronger than the corresponding vibrations of the 1st floor. The vibration of a large-scale chemical plant presents the combined action of flood discharge and working machines. Meanwhile, it is very difficult to reduce the low-frequency environmental vibrations. Optimization of the discharge scheduling mode is one of the effective measures of reducing the flow impact loads at present. Choosing reasonable dam sites is crucial.
Guedj, Jeremie; Dahari, Harel; Rong, Libin; Sansone, Natasha D; Nettles, Richard E; Cotler, Scott J; Layden, Thomas J; Uprichard, Susan L; Perelson, Alan S
2013-03-05
The nonstructural 5A (NS5A) protein is a target for drug development against hepatitis C virus (HCV). Interestingly, the NS5A inhibitor daclatasvir (BMS-790052) caused a decrease in serum HCV RNA levels by about two orders of magnitude within 6 h of administration. However, NS5A has no known enzymatic functions, making it difficult to understand daclatasvir's mode of action (MOA) and to estimate its antiviral effectiveness. Modeling viral kinetics during therapy has provided important insights into the MOA and effectiveness of a variety of anti-HCV agents. Here, we show that understanding the effects of daclatasvir in vivo requires a multiscale model that incorporates drug effects on the HCV intracellular lifecycle, and we validated this approach with in vitro HCV infection experiments. The model predicts that daclatasvir efficiently blocks two distinct stages of the viral lifecycle, namely viral RNA synthesis and virion assembly/secretion with mean effectiveness of 99% and 99.8%, respectively, and yields a more precise estimate of the serum HCV half-life, 45 min, i.e., around four times shorter than previous estimates. Intracellular HCV RNA in HCV-infected cells treated with daclatasvir and the HCV polymerase inhibitor NM107 showed a similar pattern of decline. However, daclatasvir treatment led to an immediate and rapid decline of extracellular HCV titers compared to a delayed (6-9 h) and slower decline with NM107, confirming an effect of daclatasvir on both viral replication and assembly/secretion. The multiscale modeling approach, validated with in vitro kinetic experiments, brings a unique conceptual framework for understanding the mechanism of action of a variety of agents in development for the treatment of HCV.
He, Xuemei; Yu, Pengyun; Zhao, Juan; Wang, Jianping
2017-10-12
Ultrafast vibrational relaxation and structural dynamics of indigo carmine in dimethyl sulfoxide were examined using femtosecond pump-probe infrared and two-dimensional infrared (2D IR) spectroscopies. Using the intramolecularly hydrogen-bonded C═O and delocalized C═C stretching modes as infrared probes, local structural and dynamical variations of this blue dye molecule were observed. Energy relaxation of the vibrationally excited C═O stretching mode was found to occur through covalent bond to the delocalized aromatic vibrational modes on the time scale of a few picoseconds or less. Vibrational quantum beating was observed in magic-angle pump-probe, anisotropy, and 2D IR cross-peak dynamics, showing an oscillation period of ca. 1010 fs, which corresponds to the energy difference between the C═O and C═C transition frequency (33 cm-1). This confirms a resonant vibrational energy transfer happened between the two vibrators. However, a more efficient energy-accepting mode of the excited C═O stretching was believed to be a nearby combination and/or overtone mode that is more tightly connected to the C═O species. On the structural aspect, dynamical-time-dependent 2D IR spectra reveal an insignificant inhomogeneous contribution to time-correlation relaxation for both the C═O and C═C stretching modes, which is in agreement with the generally believed structural rigidity of such conjugated molecules.
Vibration Characteristics of Roundabout Swing of HAWT Wind Wheel
Directory of Open Access Journals (Sweden)
Jian-long Ma
2016-01-01
Full Text Available Modal testing was used to show that the roundabout swing was a natural vibration mode of the wind wheel of a horizontal-axis wind turbine (HAWT. During the vibration, the blade root was simultaneously subjected to bending and rotary shear stresses. A method for indirect testing and determination of the dynamic frequencies of the typical vibrations of the wind wheel was developed, based on the frequency-holding characteristic of each subsignal during the transmission of the multiple mixed-vibration signals. The developed method enabled simple and accurate acquisition of the dynamic frequencies without destruction of the flow and structural fields. The dynamic vibration stress of the roundabout swing was found to be significantly stronger than those of the first- and second-order flexural vibrations of the blades. By a combination of numerical simulations and tests, it was determined that the pneumatic circumferential force was the primary determinant of the roundabout swing vibration frequencies, the relationship being quadratic. The roundabout swing vibration potentially offers new explanations and analytical pathways regarding the behavior of horizontal-axis wind turbines, which have been found to be frequently involved in fatigue-damage accidents within periods shorter than their design lives.
The Influence of Shaft’s Bending on the Coupling Vibration of a Flexible Blade-Rotor System
Directory of Open Access Journals (Sweden)
Chao-feng Li
2017-01-01
Full Text Available The influence of shaft bending on the coupling vibration of rotor-blades system is nonignorable. Therefore, this paper analyzed the influence of shaft bending on the coupling vibration of rotor-blades system. The vibration mode function of shaft under elastic supporting condition was also derived to ensure accuracy of the model as well. The influence of the number of blades, the position of disk, and the support stiffness of shaft on critical speed of system was analyzed. The numerical results show that there were two categories of coupling mode shapes which belong to a set where the blade’s first two modes predominate in the system: shaft-blade (SB mode and interblade (BB mode due to the coupling between blade and shaft. The BB mode was of repeated frequencies of (Nb-2 multiplicity for number blades, and the SB mode was of repeated frequencies of (2 multiplicity for number blades. What is more, with the increase of the number of blades, natural frequency of rotor was decreasing linearly, that of BB mode was constant, and that of SB mode was increasing linearly. Natural frequency of BB mode was not affected while that of rotor and SB mode was affected (changed symmetrically with the center of shaft by the position of disk. In the end, vibration characteristics of coupling mode shapes were analyzed.
Modeling and Analysis of a Multi-Degree-of-Freedom Micro-Vibration Simulator
Directory of Open Access Journals (Sweden)
Xiaoming Wang
2017-01-01
Full Text Available To reproduce the disturbance forces and moments generated by the reaction/momentum wheel assembly, a multi-degree-of-freedom micro-vibration simulator is proposed. This can be used in the ground vibration experiments of an optical payload replacing the real action/momentum wheel assembly. First, the detailed structure of the micro-vibration simulator is introduced. Then, the complete system kinematic and dynamic models of the micro-vibration simulator are derived. In addition, the disturbance forces and moments produced by the micro-vibration simulator are calculated. Finally, the normal mode analysis and a cosimulation are adopted to verify the validity of this method. The analysis and simulation results show that the micro-vibration simulator can exactly reproduce the disturbance forces and moments with different amplitudes and different frequency ranges.
Low-frequency vibration control of floating slab tracks using dynamic vibration absorbers
Zhu, Shengyang; Yang, Jizhong; Yan, Hua; Zhang, Longqing; Cai, Chengbiao
2015-09-01
This study aims to effectively and robustly suppress the low-frequency vibrations of floating slab tracks (FSTs) using dynamic vibration absorbers (DVAs). First, the optimal locations where the DVAs are attached are determined by modal analysis with a finite element model of the FST. Further, by identifying the equivalent mass of the concerned modes, the optimal stiffness and damping coefficient of each DVA are obtained to minimise the resonant vibration amplitudes based on fixed-point theory. Finally, a three-dimensional coupled dynamic model of a metro vehicle and the FST with the DVAs is developed based on the nonlinear Hertzian contact theory and the modified Kalker linear creep theory. The track irregularities are included and generated by means of a time-frequency transformation technique. The effect of the DVAs on the vibration absorption of the FST subjected to the vehicle dynamic loads is evaluated with the help of the insertion loss in one-third octave frequency bands. The sensitivities of the mass ratio of DVAs and the damping ratio of steel-springs under the floating slab are discussed as well, which provided engineers with the DVA's adjustable room for vibration mitigation. The numerical results show that the proposed DVAs could effectively suppress low-frequency vibrations of the FST when tuned correctly and attached properly. The insertion loss due to the attachment of DVAs increases as the mass ratio increases, whereas it decreases with the increase in the damping ratio of steel-springs.
Frequency Identification of Vibration Signals Using Video Camera Image Data
Directory of Open Access Journals (Sweden)
Chia-Hung Wu
2012-10-01
Full Text Available This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system.
Directory of Open Access Journals (Sweden)
Mudar A. Abdulsattar
2013-04-01
Full Text Available Infrared spectra of hydrogenated diamond nanocrystals of one nanometer length are calculated by ab initio methods. Positions of atoms are optimized via density functional theory at the level of the generalized gradient approximation of Perdew, Burke and Ernzerhof (PBE using 3-21G basis states. The frequencies in the vibrational spectrum are analyzed against reduced masses, force constants and intensities of vibration. The spectrum can be divided into two regions depending on the properties of the vibrations or the gap separating them. In the first region, results show good matching to several experimentally obtained lines. The 500 cm−1 broad-peak acoustical branch region is characterized by pure C–C vibrations. The optical branch is centered at 1185 cm−1. Calculations show that several C–C vibrations are mixed with some C–H vibrations in the first region. In the second region the matching also extends to C–H vibration frequencies that include different modes such as symmetric, asymmetric, wagging, scissor, rocking and twisting modes. In order to complete the picture of the size dependence of the vibrational spectra, we analyzed the spectra of ethane and adamantane. The present analysis shows that acoustical and optical branches in diamond nanocrystals approach each other and collapse at 963 cm−1 in ethane. Variation of the highest reduced-mass-mode C–C vibrations from 1332 cm−1 of bulk diamond to 963 cm−1 for ethane (red shift is shown. The analysis also shows the variation of the radial breathing mode from 0 cm−1 of bulk diamond to 963 cm−1 for ethane (blue shift. These variations compare well with experiment. Experimentally, the above-mentioned modes appear shifted from their exact positions due to overlap with neighboring modes.
Resonant vibration control of rotating beams
DEFF Research Database (Denmark)
Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker
2011-01-01
Rotatingstructures,like e.g.wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor–actuator system, governed by a resonant controller. The theory is here demonstrated...... modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency....
Nanoscale piezoelectric vibration energy harvester design
Foruzande, Hamid Reza; Hajnayeb, Ali; Yaghootian, Amin
2017-09-01
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.
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.
Vibration Attenuation of Plate Using Multiple Vibration Absorbers
Directory of Open Access Journals (Sweden)
Zaman Izzuddin
2014-07-01
Full Text Available Vibrations are undesired phenomenon and it can cause harm, distress and unsettling influence to the systems or structures, for example, aircraft, automobile, machinery and building. One of the approach to limit this vibration by introducing passive vibration absorber attached to the structure. In this paper, the adequacy of utilizing passive vibration absorbers are investigated. The vibration absorber system is designed to minimize the vibration of a thin plate fixed along edges. The plate’s vibration characteristics, such as, natural frequency and mode shape are determined using three techniques: theoretical equations, finite element (FE analysis and experiment. The results demonstrate that the first four natural frequencies of fixed-fixed ends plate are 48, 121, 193 and 242 Hz, and these results are corroborated well with theoretical, FE simulation and experiment. The experiment work is further carried out with attached single and multiple vibration absorbers onto plate by tuning the absorber’s frequency to match with the excitation frequency. The outcomes depict that multiple vibration absorbers are more viable in lessening the global structural vibration.
Strong 4-mode coupling of nanomechanical string resonators
Gajo, Katrin; Schüz, Simon; Weig, Eva M.
2017-09-01
We investigate mechanical mode coupling between the four fundamental flexural modes of two doubly clamped, high-Q silicon-nitride nanomechanical string resonators. Strong mechanical coupling between the strings is induced by the strain mediated via a shared clamping point, engineered to increase the exchange of oscillatory energy. One of the resonators is controlled dielectrically, which results in strong coupling between its out-of-plane and in-plane flexural modes. We show both inter-string out-of-plane-in-plane and 3-mode resonances of the four coupled fundamental vibrational modes of a resonator pair, giving rise to a simple and a multimode avoided crossing, respectively.
Rotation of the apparent vibration plane of a swinging spring at the 1:1:2 resonance
Petrov, A. G.
2017-05-01
Nonlinear spatial vibrations of a mass point on a weightless elastic suspension (pendulum on a spring) are considered. The frequency of vertical vibrations is assumed to be equal to the doubled swinging frequency (the 1:1:2 resonance). In this case, as numerical calculations and experiments show, the vertical vibrations are unstable, which leads to the vertical vibration energy transfer to the pendulum swinging energy. The vertical vibrations of the mass point decay and, after a certain time period, the pendulum starts swinging in a certain vertical plane. This swinging is also unstable, which results in the reverse energy transfer into the vertical vibration mode. The vertical vibrations are again repeated. But after the second transfer of the vertical vibration energy to the pendulum swinging energy, the apparent plane of vibrations rotates by a certain angle. These effects are described analytically; namely, the energy transfer period, the time variations in the amplitudes of both modes, and the variations in the angle of the apparent vibration plane are determined. An asymptotic solution is also constructed for the mass point trajectory in the orbit elements. In projection on the horizonal plane, the mass point moves in a nearly elliptic trajectory. The ellipse semiaxes slowly vary with time, so that their product remains constant, and the major semiaxis slowly rotates at a constant sectorial velocity. The obtained analytic time dependence of the ellipse semiaxes and the precession angle agree well with the results of numerical calculations.
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.
Cooley, Christopher G.
2017-09-01
This study investigates the vibration and dynamic response of a system of coupled electromagnetic vibration energy harvesting devices that each consist of a proof mass, elastic structure, electromagnetic generator, and energy harvesting circuit with inductance, resistance, and capacitance. The governing equations for the coupled electromechanical system are derived using Newtonian mechanics and Kirchhoff circuit laws for an arbitrary number of these subsystems. The equations are cast in matrix operator form to expose the device's vibration properties. The device's complex-valued eigenvalues and eigenvectors are related to physical characteristics of its vibration. Because the electrical circuit has dynamics, these devices have more natural frequencies than typical electromagnetic vibration energy harvesters that have purely resistive circuits. Closed-form expressions for the steady state dynamic response and average power harvested are derived for devices with a single subsystem. Example numerical results for single and double subsystem devices show that the natural frequencies and vibration modes obtained from the eigenvalue problem agree with the resonance locations and response amplitudes obtained independently from forced response calculations. This agreement demonstrates the usefulness of solving eigenvalue problems for these devices. The average power harvested by the device differs substantially at each resonance. Devices with multiple subsystems have multiple modes where large amounts of power are harvested.
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.
Vibrational Relaxation in Neat Crystals of Naphthalene by Picosecond CARS
Hesp, Ben H.; Wiersma, Douwe A.
1980-01-01
Picosecond delayed CARS experiments on totally symmetric modes in naphthalene at 1.5 K are reported. The Raman lineshape of the vibrational excitons is lorentzian and vibrational relaxation can be surprisingly slow. The Raman lineshape of the Ag exciton level of the 766 cm-1 vibrational mode reveals
Symmetry-broken effects on electron momentum spectroscopy caused by adiabatic vibration
Zhu, Yinghao; Ma, Xiaoguang; Lou, Wenhua; Wang, Meishan; Yang, Chuanlu
2017-11-01
The vibronic coupling effect is usually studied by invoking the breakdown of Born-Oppenheimer approximation. The present study shows that the symmetry-broken effect induced by nuclei vibrations can also lead strong impact on the electronic states under the framework of Born-Oppenheimer approximation. This adiabatic-invoking vibrational effect on electron momentum spectroscopy of ethylene (C2H4), ethane (C2H6) and methanol (CH3OH) was studied with quantum mechanical method. The results show that electron momentum spectroscopy of localized electrons, especially core electrons in axial symmetric geometry molecules can be affected unusually and strongly by several asymmetric vibrational modes.
Energy Technology Data Exchange (ETDEWEB)
Stichternath, A.; Schweitzer-Stenner, R.; Dreybrodt, W. (Univ. of Bremen (Germany)); Mak, R.S.W.; Li, X.Y. (Hong Kong Univ. of Science and Technology (Hong Kong)); Sparks, L.D.; Shelnutt, J.A. (Sandia National Lab., Albuquerque, NM (United States) Univ. of New Mexico, Albuquerque (United States)); Medforth, C.J.; Smith, K.M. (Univ. of California, Davis (United States))
1993-04-15
We have employed Raman dispersion, FT Raman, and FT-IR spectroscopy to identify a large number of resonance Raman lines of Ni(II) octaethyltetraphenylporphyrin dissolved in CS[sub 2]. The Raman depolarization dispersion technique was used to derive the symmetry of the normal modes giving rise to the observed Raman lines. By combining this information and the already available normal coordinates of Ni(II) tetraphenylporphyrin and Ni(II) octaethylporphyrin, many of the Raman-modes of the macrocycle could be assigned. Some resonance-enhanced Raman lines were found to arise from vibrations of the ethyl and phenyl substituents. They were identified by comparing resonance Raman, FT Raman, and FT infrared spectra of the Ni(II) octaethyltetraphenylporphyrin and its d[sub 20] isotopomer. All Raman lines normally referred to as core-size markers are found to be significantly shifted to lower frequencies with respect to their positions in Ni(II) octaethylporphyrin, in accordance with earlier findings (Shelnutt et al., J. Am. Chem. Soc. 113, 4077, 1991). This suggests that the molecule is in a highly nonplanar conformation. This notion is further corroborated by the strong dispersion of the depolarization ratio observed for nearly all A[sub 1g] and A[sub 2g] modes of the macrocycle. 27 refs., 13 figs., 2 tabs.
Quantum correlation dynamics in photosynthetic processes assisted by molecular vibrations
Energy Technology Data Exchange (ETDEWEB)
Giorgi, G.L., E-mail: g.giorgi@inrim.it [INRIM, Strada delle Cacce 91, I-10135 Torino (Italy); Roncaglia, M. [INRIM, Strada delle Cacce 91, I-10135 Torino (Italy); Raffa, F.A. [Politecnico di Torino, Dipartimento di Scienza Applicata e Tecnologia, Corso Duca degli Abruzzi 24, I-10129 Torino (Italy); Genovese, M. [INRIM, Strada delle Cacce 91, I-10135 Torino (Italy)
2015-10-15
During the long course of evolution, nature has learnt how to exploit quantum effects. In fact, recent experiments reveal the existence of quantum processes whose coherence extends over unexpectedly long time and space ranges. In particular, photosynthetic processes in light-harvesting complexes display a typical oscillatory dynamics ascribed to quantum coherence. Here, we consider the simple model where a dimer made of two chromophores is strongly coupled with a quasi-resonant vibrational mode. We observe the occurrence of wide oscillations of genuine quantum correlations, between electronic excitations and the environment, represented by vibrational bosonic modes. Such a quantum dynamics has been unveiled through the calculation of the negativity of entanglement and the discord, indicators widely used in quantum information for quantifying the resources needed to realize quantum technologies. We also discuss the possibility of approximating additional weakly-coupled off-resonant vibrational modes, simulating the disturbances induced by the rest of the environment, by a single vibrational mode. Within this approximation, one can show that the off-resonant bath behaves like a classical source of noise.
Multiple Rabi Splittings under Ultrastrong Vibrational Coupling.
George, Jino; Chervy, Thibault; Shalabney, Atef; Devaux, Eloïse; Hiura, Hidefumi; Genet, Cyriaque; Ebbesen, Thomas W
2016-10-07
From the high vibrational dipolar strength offered by molecular liquids, we demonstrate that a molecular vibration can be ultrastrongly coupled to multiple IR cavity modes, with Rabi splittings reaching 24% of the vibration frequencies. As a proof of the ultrastrong coupling regime, our experimental data unambiguously reveal the contributions to the polaritonic dynamics coming from the antiresonant terms in the interaction energy and from the dipolar self-energy of the molecular vibrations themselves. In particular, we measure the opening of a genuine vibrational polaritonic band gap of ca. 60 meV. We also demonstrate that the multimode splitting effect defines a whole vibrational ladder of heavy polaritonic states perfectly resolved. These findings reveal the broad possibilities in the vibrational ultrastrong coupling regime which impact both the optical and the molecular properties of such coupled systems, in particular, in the context of mode-selective chemistry.
Bauer, C.; Gensch, M.; Heberle, J.
2012-05-01
We aim at investigating proteins under irradiation with intense THz radiation tuned into resonance to specific vibrational modes. This approach is much in analogy to recent experiments that showed selective vibrational control in Complex materials [1, 2, 3]. To achieve the necessary sensitivity for protein dynamics we combine a novel time-resolved IR difference spectroscopic setup with uniquely intense, tuneable narrow bandwidth THz radiation (1.2 - 75 THz) of the free electron laser FELBE.
Alleviation of Buffet-Induced Vibration Using Piezoelectric Actuators
National Research Council Canada - National Science Library
Morgenstern, Shawn D
2006-01-01
.... The objective of this research was to determine the most critical natural modes of vibration for the F-16 ventral fin and design piezoelectric actuators capable of reducing buffet-induced ventral fin vibration...
Raman active modes of NiSi crystal
Energy Technology Data Exchange (ETDEWEB)
Wan Li, E-mail: liwan_china@yahoo.com.c [Department of Physics, Wenzhou University (China); Tang Bo; Cheng Xinhong; Ren Yiming; Zhang Xuefei; Xu Dapeng; Luo Haijun; Huang Yunmi [Department of Physics, Wenzhou University (China)
2009-08-01
Raman scattering intensities of the NiSi Raman-active modes have been calculated with three Raman measurement configurations, which can be used for the symmetry assignment of the NiSi Raman peaks. Raman-active vibrations of the NiSi crystal have also been theoretically studied. Results show that the lattices with A{sub g} and B{sub 2g} modes vibrate only in the plane normal to the NiSi[0 1 0] direction while the lattices with B{sub 1g} and B{sub 3g} modes vibrate only along the NiSi[0 1 0] axis. Based on such study, the relationship between the anisotropic strain distribution in the NiSi thin film and the Raman peak shifts has been briefly discussed.
Quartz-enhanced photoacoustic spectroscopy exploiting tuning fork overtone modes
Sampaolo, A.; Patimisco, P.; Dong, L.; Geras, A.; Scamarcio, G.; Starecki, T.; Tittel, F. K.; Spagnolo, V.
2015-12-01
We report on a quartz-enhanced photoacoustic sensor (QEPAS) based on a custom-made quartz tuning fork (QTF) to operate in both the fundamental and the first overtone vibrational mode resonances. The QTF fundamental mode resonance falls at ˜3 kHz and the first overtone at ˜18 kHz. Electrical tests showed that the first overtone provides a higher quality factor and increased piezoelectric current peak values, with respect to the fundamental flexural mode. To evaluate the QTF acousto-electric energy conversion efficiency, we operated the QEPAS in the near-IR and selected water vapor as the target gas. The first overtone resonance provides a QEPAS signal-to-noise ratio ˜5 times greater with respect to that measured for the fundamental mode. These results open the way to employing QTF overtone vibrational modes for QEPAS based trace gas sensing.
Naumann, E. C.; Catherines, D. S.; Walton, W. C., Jr.
1971-01-01
Experimental and analytical investigations of the vibratory behavior of ring-stiffened truncated-cone shells are described. Vibration tests were conducted on 60 deg conical shells having up to four ring stiffeners and for free-free and clamped-free edge constraints and 9 deg conical shells, for two thicknesses, each with two angle rings and for free-free, free-clamped, and clamped-clamped edge constraints. The analytical method is based on linear thin shell theory, employing the Rayleigh-Ritz method. Discrete rings are represented as composed of one or more segments, each of which is a short truncated-cone shell of uniform thickness. Equations of constraint are used to join a ring and shell along a circumferential line connection. Excellent agreement was obtained for comparisons of experimental and calculated frequencies.
Endres, Christian; Caselli, Paola; Martin-Drumel, Marie-Aline; McCarthy, Michael C.; Pirali, Olivier; Wehres, Nadine; Schlemmer, Stephan; Thorwirth, Sven
2016-06-01
Vibrational spectra of small organic nitriles, propionitrile and n-butyronitrile, have been investigated at high spectral resolution at the French national synchroton facility SOLEIL using Fourier-transform far-infrared spectroscopy (< 700 cm-1). The Automated Spectral Assignment Procedure (ASAP) has been used for line assignement and accurate determination of rotational level energies, in particular, of the ν20=1 and the ν12=1 states of propionitrile. The analysis does not only confirm the applicability of the ASAP in the treatment of (dense) high-resolution infrared spectra but also reveals some of its limitations which will be discussed in some detail. M. A. Martin-Drumel, C. P. Endres, O. Zingsheim, T. Salomon, J. van Wijngaarden, O. Pirali, S. Gruet, F. Lewen, S. Schlemmer, M. C. McCarthy, and S. Thorwirth 2015, J. Mol. Spectrosc. 315, 72
Versluis, Michel; Palanchon, P.; Goertz, D.; van der Meer, S.M.; Chin, C.T.; Lohse, Detlef; de Jong, N.
2004-01-01
We have investigated surface vibrations generated by ultrasound excitation of individual unencapsulated micron-sized bubbles. In addition, we present surface modes (n=2 and 3) observed for phospholipid-coated ultrasound contrast agents excited through excitation of radial modes at frequencies
Blade Vibration Measurement System
Platt, Michael J.
2014-01-01
The Phase I project successfully demonstrated that an advanced noncontacting stress measurement system (NSMS) could improve classification of blade vibration response in terms of mistuning and closely spaced modes. The Phase II work confirmed the microwave sensor design process, modified the sensor so it is compatible as an upgrade to existing NSMS, and improved and finalized the NSMS software. The result will be stand-alone radar/tip timing radar signal conditioning for current conventional NSMS users (as an upgrade) and new users. The hybrid system will use frequency data and relative mode vibration levels from the radar sensor to provide substantially superior capabilities over current blade-vibration measurement technology. This frequency data, coupled with a reduced number of tip timing probes, will result in a system capable of detecting complex blade vibrations that would confound traditional NSMS systems. The hardware and software package was validated on a compressor rig at Mechanical Solutions, Inc. (MSI). Finally, the hybrid radar/tip timing NSMS software package and associated sensor hardware will be installed for use in the NASA Glenn spin pit test facility.
Stability of normal modes of a polyatomic molecule under laser-induced modification of its geometry
Kornev, Aleksei S.; Chernov, Vladislav E.; Zon, Boris A.
2017-12-01
We show that the normal modes of a polyatomic molecule in a laser field coincide, to the first order in the field intensity, with the normal modes of free molecule. In the same approximation, we find analytical expressions for the field-modified equilibrium normal coordinates and field-modified harmonic vibrational frequencies.
Large electron transfer rate effects from the Duschinsky mixing of vibrations
DEFF Research Database (Denmark)
Sando, Gerald M.; Spears, Kenneth G; Hupp, Joseph T
2001-01-01
vibrations are very important. The Duschinsky effect arises when two electronic states have vibrational normal mode coordinate systems that are rotated and translated relative to each other. We use a conventional quantum rate model for ET, and the examples include 6-8 vibrations, where two vibrational modes...
Smart accelerometer. [vibration damage detection
Bozeman, Richard J., Jr. (Inventor)
1994-01-01
The invention discloses methods and apparatus for detecting vibrations from machines which indicate an impending malfunction for the purpose of preventing additional damage and allowing for an orderly shutdown or a change in mode of operation. The method and apparatus is especially suited for reliable operation in providing thruster control data concerning unstable vibration in an electrical environment which is typically noisy and in which unrecognized ground loops may exist.
Electronic and Vibrational Coherences in Algal Light-Harvesting Proteins
Directory of Open Access Journals (Sweden)
Scholes Gregory D.
2013-03-01
Full Text Available We present broadband two-dimensional electronic spectra of a lightharvesting protein from photosynthetic algae. Analysis of the spectra show that the amplitude of the main cross peak oscillates as a function of the waiting time period. Both electronic coupling and intramolecular vibrational modes, and their mixture, can lead to such oscillations. Using predictions based on models of four-level systems, we describe ways to distinguish electronic from vibrational contributions to the coherence and find that both types of coupling contribute to the measured dynamics.
Xu, Zhenlong; Tong, Jie; Wu, Fugen
2018-03-01
Magnetorheological elastomers (MREs) are used as cladding in three-dimensional locally resonant acoustic metamaterial (LRAM) cores. The metamaterial units are combined into a vibration isolator. Two types of LRAMs, namely, cubic and spherical kernels, are constructed. The finite element method is used to analyze the elastic band structures, transmittances, and vibration modes of the incident elastic waves. Results show that the central position and width of the LRAM elastic bandgap can be controlled by the application of an external magnetic field; furthermore, they can be adjusted by changing the MRE cladding thickness. These methods contribute to the design of metamaterial MRE vibration isolators.
Strong enhancement of vibrational relaxation by Watson-Crick base pairing.
Woutersen, Sander; Cristalli, Gloria
2004-09-15
We have studied the ultrafast dynamics of NH-stretch vibrational excitations in Watson-Crick base pairs consisting of adenine and uracil derivatives. To estimate the influence of the A:U hydrogen bonding on the vibrational dynamics, we have also studied the uracil derivative in monomeric form. The vibrational relaxation of the NH-stretching mode is found to occur much faster in the Watson-Crick base pair than in monomeric uracil. From the delay dependence of the transient vibrational spectra, it can be concluded that both in base-paired and monomeric uracil, the energy relaxation takes place in two steps, the first step being a rapid transfer of energy from the NH-stretching mode to an accepting mode, the second step the relaxation of this accepting mode. The transient spectra show evidence that in the base pair the hydrogen bond between the nucleobases acts as the accepting mode, and that the hydrogen bonding between the bases is responsible for the extremely fast vibrational relaxation in this system.
Numerical Modal Analysis of Vibrations in a Three-Phase Linear Switched Reluctance Actuator
Directory of Open Access Journals (Sweden)
José Salvado
2017-01-01
Full Text Available This paper addresses the problem of vibrations produced by switched reluctance actuators, focusing on the linear configuration of this type of machines, aiming at its characterization regarding the structural vibrations. The complexity of the mechanical system and the number of parts used put serious restrictions on the effectiveness of analytical approaches. We build the 3D model of the actuator and use finite element method (FEM to find its natural frequencies. The focus is on frequencies within the range up to nearly 1.2 kHz which is considered relevant, based on preliminary simulations and experiments. Spectral analysis results of audio signals from experimental modal excitation are also shown and discussed. The obtained data support the characterization of the linear actuator regarding the excited modes, its vibration frequencies, and mode shapes, with high potential of excitation due to the regular operation regimes of the machine. The results reveal abundant modes and harmonics and the symmetry characteristics of the actuator, showing that the vibration modes can be excited for different configurations of the actuator. The identification of the most critical modes is of great significance for the actuator’s control strategies. This analysis also provides significant information to adopt solutions to reduce the vibrations at the design.
1975-02-01
thoumgh the pinhole into the diverging -:tine bhown in Fig. 4 and then on into the coiicon chai her. The remaining flow is pumped out through an anular ...molecules are prepared under single collision conditions in opposed high velocity flows , one of which contains H20 or CO2 while the other contains a...molecular collision partner. Hyperthermal vclocity flows are required since the threshold activation energy of the 11 0 and CO V modes are 0. 466 and
Vibrating soap films An analog for quantum chaos on billiards
Arcos, E; Cuatlayol, P A; Prian, M L H; Méndez-Sánchez, R A; Hernández-Saldaña, H
1998-01-01
We present an experimental setup based on the normal modes of vibrating soap films which shows quantum features of integrable and chaotic billiards. In particular, we obtain the so-called scars -narrow linear regions with high probability along classical periodic orbits- for the classically chaotic billiards. We show that these scars are also visible at low frequencies. Finally, we suggest some applications of our experimental setup in other related two-dimensional wave phenomena.
Vibration Analysis of AN Induction Motor
WANG, C.; LAI, J. C. S.
1999-07-01
With the advent of power electronics, variable speed induction motors are finding increasing use in industries because of their low cost and potential savings in energy consumption. However, the acoustic noise emitted by the motor increases due to switching harmonics introduced by the electronic inverters. Consequently, the vibro-acoustic behaviour of the motor structure has attracted more attention. In this paper, considerations given to modelling the vibration behaviour of a 2·2 kW induction motor are discussed. By comparing the calculated natural frequencies and the mode shapes with the results obtained from experimental modal testing, the effects of the teeth of the stator, windings, outer casing, slots, end-shields and support on the overall vibration behaviour are analyzed. The results show that when modelling the vibration behaviour of a motor structure, the laminated stator should be treated as an orthotropic structure, and the teeth of the stator could be neglected. As the outer casing, end-shields and the support all affect the vibration properties of the whole structure, these substructures should be incorporated in the model to improve the accuracy.
Macroscopic (and microscopic massless modes
Directory of Open Access Journals (Sweden)
Michael C. Abbott
2015-05-01
Full Text Available We study certain spinning strings exploring the flat directions of AdS3×S3×S3×S1, the massless sector cousins of su(2 and sl(2 sector spinning strings. We describe these, and their vibrational modes, using the D(2,1;α2 algebraic curve. By exploiting a discrete symmetry of this structure which reverses the direction of motion on the spheres, and alters the masses of the fermionic modes s→κ−s, we find out how to treat the massless fermions which were previously missing from this formalism. We show that folded strings behave as a special case of circular strings, in a sense which includes their mode frequencies, and we are able to recover this fact in the worldsheet formalism. We use these frequencies to calculate one-loop corrections to the energy, with a version of the Beisert–Tseytlin resummation.
Energy Technology Data Exchange (ETDEWEB)
Tiryaki, B. [Hacettepe University (Turkey). Dept. of Mining Engineering
2003-12-01
The paper examines the prediction and optimisation of machine vibrations in longwall shearers. Underground studies were carried out at the Middle Anatolian Lignite Mine, between 1993 and 1997. Several shearer drums with different pick lacing arrangements were designed and tested on double-ended ranging longwall shearers employed at the mine. A computer program called the Vibration Analysis Program (VAP) was developed for analysing machine vibrations in longwall shearers. Shearer drums that were tested underground, as well as some provided by leading manufacturers, were analyzed using these programs. The results of the experiments and computer analyses are given in the article. 4 refs., 9 figs.
Ultrafast electronic relaxation and vibrational dynamics in a polyacetylene derivative
Kobayashi, Takayoshi; Iiyama, Tsugumasa; Okamura, Kotaro; Du, Juan; Masuda, Toshio
2013-04-01
Real-time vibrational spectra in a polyacetylene derivative, poly[o-TFMPA([o-(trifluoromethyl) phenyl]acetylene)] in a broad electronic spectral region were observed using a sub-7-fs laser. Using the frequencies and initial phases of vibrational modes obtained by the spectroscopy, the assignment of the wavepackets was made. From the first moment, Huang-Rhys parameters were determined for six most prominent modes, which characterize the potential hypersurface composed of multi-dimensional vibrational mode spaces.
The Study of Dynamical Potentials of Highly Excited Vibrational States of HOBr
Directory of Open Access Journals (Sweden)
Chao Fang
2013-03-01
Full Text Available The vibrational nonlinear dynamics of HOBr in the bending and O–Br stretching coordinates with anharmonicity and Fermi 2:1 coupling are studied with dynamical potentials in this article. The result shows that the H–O stretching vibration mode has significantly different effects on the coupling between the O–Br stretching mode and the H–O–Br bending mode under different Polyad numbers. The dynamical potentials and the corresponding phase space trajectories are obtained when the Polyad number is 27, for instance, and the fixed points in the dynamical potentials of HOBr are shown to govern the various quantal environments in which the vibrational states lie. Furthermore, it is also found that the quantal environments could be identified by the numerical values of action integrals, which is consistent with former research.
Monitoring Gold Nanoparticle Growth in Situ via the Acoustic Vibrations Probed by Four-Wave Mixing.
Wu, Jian; Xiang, Dao; Gordon, Reuven
2017-02-21
We monitor in situ gold nanoparticle growth in aqueous solution by probing the acoustic vibrations with four-wave mixing. We observe two acoustic vibrational modes of gold nanoparticles from the nonlinear optical response: an extensional mode with longitudinal expansion and transverse contraction and a breathing mode with radial expansion and contraction. The mode frequencies, which show an inverse dependence on the nanoparticle diameter, allow one to monitor the nanoparticle size and size distribution during synthesis. The information about the nanoparticle size and size distribution calculated on the basis of the mode frequencies agrees well with the results obtained from the electron microscopy analysis, validating the four-wave mixing technique as an accurate and effective tool for in situ monitoring of colloidal growth.
Vibrationally coupled electron transport through single-molecule junctions
Energy Technology Data Exchange (ETDEWEB)
Haertle, Rainer
2012-04-26
vibrational effects have a profound influence on the transport characteristics of a single-molecule contact and play therefore a fundamental role in this transport problem. Our findings demonstrate that vibrationally coupled electron transport through a molecular junction involves two types of processes: (i) transport processes, where an electron tunnels through the molecular bridge from one lead to the other, and (ii) electron-hole pair creation processes, where an electron tunnels from one of the leads onto the molecular bridge and back to the same lead again. Transport processes directly contribute to the electrical current flowing through a molecular contact and involve both excitation and deexcitation processes of the vibrational modes of the junction. Electron-hole pair creation processes do not directly contribute to the electrical current and typically involve only deexcitation processes. Nevertheless, they constitute a cooling mechanism for the vibrational modes of a single-molecule junction that is as important as cooling by transport processes. As the level of vibrational excitation determines the efficiency of electron transport processes, they have an indirect influence on the electrical current flowing through the junction. As we show, however, this influence can be substantial, in particular, if the molecule is coupled asymmetrically to the leads. Accounting for all these processes and their complex interrelationship, we analyze a number of intriguing transport phenomena, including rectification, negative differential resistance, anomalous peak broadening, mode-selective vibrational excitation and vibrationally induced decoherence. Moreover, we show that higher levels of vibrational excitation are obtained for weaker electronic-vibrational coupling. Thus, based on physical grounds, we establish a relation between the weak electronic-vibrational coupling limit and the limit of large bias voltages, where the level of vibrational excitation in a molecular junction
Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef
2014-10-01
The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.
Vibration-induced coherence enhancement of the performance of a biological quantum heat engine.
Chen, Hong-Bin; Chiu, Pin-Yi; Chen, Yueh-Nan
2016-11-01
Photosynthesis has been a long-standing research interest due to its fundamental importance. Recently, studies on photosynthesis processes also have inspired attention from a thermodynamical aspect when considering photosynthetic apparatuses as biological quantum heat engines. Quantum coherence is shown to play a crucial role in enhancing the performance of these quantum heat engines. Based on the experimentally reported structure, we propose a quantum heat engine model with a non-Markovian vibrational mode. We show that one can obtain a performance enhancement easily for a wide range of parameters in the presence of the vibrational mode. Our results provide insights into the photosynthetic processes and a design principle mimicking natural organisms.
Vibration-induced coherence enhances the performance of a biological quantum heat engine
Chen, Hong-Bin; Chen, Yueh-Nan
2016-01-01
Photosynthesis has been the long-standing research interest due to its fundamental importance. Recently, studies on photosynthesis processes also inspire attention from thermodynamical aspect when considering photosynthetic apparatuses as biological quantum heat engines. Quantum coherence is shown to play a crucial role in enhancing the performance of these quantum heat engines. Based on the experimentally reported structure, we propose a quantum heat engine model with a non-Markovian vibrational mode. We show that one can obtain a performance enhancement easily for a wide range of parameters in the presence of the vibrational mode. Our results suggest new insights into the photosynthetic processes and a design principle mimicking natural organisms.
Mukherjee, Nandini; Perreault, William E.; Zare, Richard N.
2017-07-01
We present a multi-color ladder excitation scheme that exploits Stark-induced adiabatic Raman passage to selectively populate a highly excited vibrational level of a molecule. We suggest that this multi-color coherent ladder excitation provides a practical way of accessing levels near the vibrational dissociation limit as well as the dissociative continuum, which would allow the generation of an entangled pair of fragments with near-zero relative kinetic energy. Specifically, we consider four- and six-photon coherent excitation of molecular hydrogen to high vibrational levels via intermediate vibrational levels, which are pairwise coupled by two-photon resonant interaction. Using a sequence of three partially overlapping, single-mode, nanosecond laser pulses we show that the sixth vibrational level of H2, which is too weakly coupled to be easily accessed by direct two-photon Raman excitation from the ground vibrational level, can be efficiently populated without leaving any population stranded in the intermediate level. Furthermore, we show that the fourteenth vibrational level of H2, which is the highest vibrational level in the ground electronic state with a binding energy of 22 meV, can be efficiently and selectively populated using a sequence of four pulses. The present technique offers the unique possibility of preparing entangled quantum states of H atoms without resorting to an ultracold system.
Hohenemser, K. H.; Crews, S. T.
1973-01-01
The experiments with progressing/regressing forced rotor flapping modes have been extended in several directions and the data processing method has been considerably refined. The 16 inch hingeless 2-bladed rotor model was equipped with a new set of high precision blades which removed previously encountered tracking difficulties at high advance ratio, so that tests up to .8 rotor advance ratio could be conducted. In addition to data with 1.20 blade natural flapping frequency data at 1.10 flapping frequency were obtained. Outside the wind tunnel, tests with a ground plate located at different distances below the rotor were conducted while recording the dynamic downflow at a station .2R below the rotor plane with a hot wire anemometer.
Shaft mode shape demonstration
Grissom, R.
1985-01-01
The dynamic response of a rotating machine is directly influenced by its geometric configuration and all aspects of the rotor construction. These determine two significant parameters, mass distribution and stiffness, which yield a spectrum of natural frequencies and mode shapes. The mode shapes can be presented as snapshots of the characteristic amplitude/phase reponse patterns of the shaft, due to the major forcing function of unbalance, at different rotative speeds. To demonstrate the three shaft mode shapes of the rotor rig using the Shaft Mode Demonstrator and oscilloscopes. The synchronous (1X) amplitude and phase of the rotor vibration in the vertical direction from several points along the shaft is displayed on corresponding points of the demonstrator. Unfiltered vibration from vertical and horizontal probe pairs is displayed on the oscilloscopes in orbit format for a dynamic presentation of the mode shape.
Quenching of self-excited vibrations
Verhulst, F.
2005-01-01
Stable normal-mode vibrations in engineering can be undesirable and one of the possibilities for quenching these is by embedding the oscillator in an autoparametric system by coupling to a damped oscillator. There exists the possibility of destabilizing the undesirable vibrations by a suitable
Vibration fatigue using modal decomposition
Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha
2018-01-01
Vibration-fatigue analysis deals with the material fatigue of flexible structures operating close to natural frequencies. Based on the uniaxial stress response, calculated in the frequency domain, the high-cycle fatigue model using the S-N curve material data and the Palmgren-Miner hypothesis of damage accumulation is applied. The multiaxial criterion is used to obtain the equivalent uniaxial stress response followed by the spectral moment approach to the cycle-amplitude probability density estimation. The vibration-fatigue analysis relates the fatigue analysis in the frequency domain to the structural dynamics. However, once the stress response within a node is obtained, the physical model of the structure dictating that response is discarded and does not propagate through the fatigue-analysis procedure. The structural model can be used to evaluate how specific dynamic properties (e.g., damping, modal shapes) affect the damage intensity. A new approach based on modal decomposition is presented in this research that directly links the fatigue-damage intensity with the dynamic properties of the system. It thus offers a valuable insight into how different modes of vibration contribute to the total damage to the material. A numerical study was performed showing good agreement between results obtained using the newly presented approach with those obtained using the classical method, especially with regards to the distribution of damage intensity and critical point location. The presented approach also offers orders of magnitude faster calculation in comparison with the conventional procedure. Furthermore, it can be applied in a straightforward way to strain experimental modal analysis results, taking advantage of experimentally measured strains.
A Novel Control System Design for Vibrational MEMS Gyroscopes
Directory of Open Access Journals (Sweden)
Qing Zheng
2007-04-01
Full Text Available There are two major control problems associated with vibrational MEMS gyroscopes: to control two vibrating axes (or modes of the gyroscope, and to estimate a time-varying rotation rate. This paper demonstrates how a novel active disturbance rejection control addresses these problems in the presence of the mismatch of natural frequencies between two axes, mechanical-thermal noises, Quadrature errors, and parameter variations. A demodulation approach based on the estimated dynamics of the system by an extended state observer is used to estimate the rotation rate. The simulation results on a Z-axis MEMS gyroscope show that the controller is very effective by driving the output of the drive axis to a desired trajectory, forcing the vibration of the sense axis to zero for a force-to-rebalance operation and precisely estimating the rotation rate.
Vibrations of Damaged Functionally Graded Cantilever Beams
Byrd, Larry W.; Birman, Victor
2008-02-01
The paper discusses closed-form solutions of the problems of free and forced vibrations of a functionally graded cantilever FGM beam with and without damage. The mode of damage considered in the paper is represented by cracks that are perpendicular to the axis of the beam. Notably, such mode of damage was observed in experiments on representative FGM beams. Forced vibrations considered in the paper were generated by a kinematic excitation of the clamped end of the beam.
Sweeping shunted electro-magnetic tuneable vibration absorber: Design and implementation
Turco, E.; Gardonio, P.
2017-10-01
This paper presents a study on the design and implementation of a time-varying shunted electro-magnetic Tuneable Vibration Absorber for broad-band vibration control of thin structures. A time-varying RL-shunt is used to harmonically vary the stiffness and damping properties of the Tuneable Vibration Absorber so that its mechanical fundamental natural frequency is continuously swept in a given broad frequency band whereas its mechanical damping is continuously adapted to maximize the vibration absorption from the hosting structure where it is mounted. The paper first recalls the tuning and positioning criteria for the case where a classical Tuneable Vibration Absorber is installed on a thin walled cylindrical structure to reduce the response of a resonating flexural mode. It then discusses the design of the time-varying shunt circuit to produce the desired stiffness and damping variations in the electro-magnetic Tuneable Vibration Absorber. Finally, it presents a numerical study on the flexural vibration and interior sound control effects produced when an array of these shunted electro-magnetic Tuneable Vibration Absorbers are mounted on a thin walled cylinder subject to a rain-on-the-roof stochastic excitation. The study shows that the array of proposed systems effectively controls the cylinder flexural response and interior noise over a broad frequency band without need of tuning and thus system identification of the structure. Therefore, the systems can be successfully used also on structures whose physical properties vary in time because of temperature changes or tensioning effects for example.
Analytical design method of a device for ultrasonic elliptical vibration cutting.
Huang, Weihai; Yu, Deping; Zhang, Min; Ye, Fengfei; Yao, Jin
2017-02-01
Ultrasonic elliptical vibration cutting (UEVC) is effective in ultraprecision diamond cutting of hard-brittle materials and ferrous metals. However, its design is quite empirical and tedious. This paper proposes an analytical design method for developing the UEVC device which works at the Flexural-Flexural complex-mode to generate the elliptical vibration. For such UEVC device, the resonant frequencies of the two flexural vibrations are required to be the same. In addition, the nodal points of the two flexural vibrations should be coincident so that the device can be clamped without affecting the vibrations. Based on the proposed analytical design method, an UEVC device was first designed. Modal analysis of the designed UEVC device was performed by using the finite element method, which shows that the resonant frequencies coincide well with the targeted ones. Then a prototype UEVC device was fabricated, and its vibration characteristics were measured by an impedance analyzer and a laser displacement sensor. Experimental results indicate that the designed UEVC device can generate elliptical vibration with the resonant frequencies closed to the target ones. In addition, the vibration trajectory can be precisely tuned by adjusting the phase difference and the amplitude of the applied voltage. Simulation and experimental results validated the effectiveness of the analytical design method.
Vibration response of misaligned rotors
Patel, Tejas H.; Darpe, Ashish K.
2009-08-01
Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.
Golubkova, O. S.; Kataeva, T. S.; Shchepkin, D. N.; Asfin, R. E.
2017-06-01
Infrared reflection-absorption spectra of thin films of α-crystalline hexafluoroethane deposited on a gold-plated copper mirror are measured at temperatures of 70 and 80 K. The bands corresponding to strong in the dipole absorption vibrations ν5 and ν10 have complex contours, the shape of which is explained in terms of the resonant dipole-dipole interaction between identical spectrally active molecules of the crystal. Splittings of the complex ν5 and ν10 bands are explained taking into account two effects: the Davydov splitting and the LO-TO splitting of the strong modes. Bands of the asymmetric 13C12CF6 isotopologue in the absorption spectrum of the crystal exhibit an anomalously large isotope shift as compared with the shift in the spectrum of free molecules. This anomaly is explained by intermolecular resonant dipole-dipole interaction of asymmetric 13C12CF6 isotopologue with molecules of the environment, consisting of the most abundant 12C2F6 isotopologue. The correctness of the given interpretation is confirmed calculating these three effects in the model of resonant dipole-dipole interaction.
Numerical Investigation of Flapwise-Torsional Vibration Model of a Smart Section Blade with Microtab
National Research Council Canada - National Science Library
Li, Nailu; Balas, Mark J; Yang, Hua; Jiang, Wei; Magar, Kaman T
2015-01-01
... the microtab control capability on flutter instability case and divergence instability case. The effectiveness of the microtab is investigated with the scenarios of different output controllers and actuation deployments for both instability cases. The numerical results show that the microtab can effectively suppress both vibration modes with the appropriate choice of the output feedback controller.
Three-dimensional free vibration analysis of thick laminated circular ...
African Journals Online (AJOL)
Dr Oke
mechanical systems is understanding the free vibration behavior of different plate components. The dynamic response of complex engineering systems is intimately linked with plate response frequencies as well as vibration mode shapes. A thorough analysis of free vibration data is often useful in arriving at the resonant ...
Ultrafast vibrations of gold nanorings
DEFF Research Database (Denmark)
Kelf, T; Tanaka, Y; Matsuda, O
2011-01-01
We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We...
FEM Updating of Tall Buildings using Ambient Vibration Data
DEFF Research Database (Denmark)
Ventura, C. E.; Lord, J. F.; Turek, M.
2005-01-01
Ambient vibration testing is the most economical non-destructive testing method to acquire vibration data from large civil engineering structures. The purpose of this paper is to demonstrate how ambient vibration Modal Identification techniques can be effectively used with Model Updating tools...... and the corresponding mode shapes. The degree of torsional coupling between the modes was also investigated. The modal identification results obtained from ambient vibration measurements of each building were used to update a finite element model of the structure. The starting model of each structure was developed from...... an ambient vibration modal identification....
Directory of Open Access Journals (Sweden)
Xingmou Liu
2016-01-01
Full Text Available This paper presents a time–frequency analysis of the vibration of transformer under direct current (DC bias through Hilbert–Huang transform (HHT. First, the theory of DC bias for the transformer was analyzed. Next, the empirical mode decomposition (EMD process, which is the key in HHT, was introduced. The results of EMD, namely, intrinsic mode functions (IMFs, were calculated and summed by Hilbert transform(HT to obtain time-dependent series in a 2D time–frequency domain. Lastly, a test system of vibration measurement for the transformer was set up. Three direction (x, y, and z axes components of core vibration were measured. Decomposition of EMD and HHT spectra showed that vibration strength increased, and odd harmonics were produced with DC bias. Results indicated that HHT is a viable signal processing tool for transformer health monitoring.
Broadband Radiation Modes: Estimation and Active Control
Berkhoff, Arthur P.
In this paper we give a formulation of the most efficiently radiating vibration patterns of a vibrating body, the radiation modes, in the time domain. The radiation modes can be used to arrive at efficient weighting schemes for an array of sensors in order to reduce the controller dimensionality.
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.
Energy Technology Data Exchange (ETDEWEB)
Wang, Xue B.; Woo, Hin-koon; Wang, Lai S.
2005-08-01
We demonstrate vibrational cooling of anions via collisions with a background gas in an ion trap attached to a cryogenically controlled cold head (10 ? 400 K). Photoelectron spectra of vibrationally cold C60- anions, produced by electrospray ionization and cooled in the cold ion trap, have been obtained. Relative to spectra taken at room temperature, vibrational hot bands are completely eliminated, yielding well resolved vibrational structures and a more accurate electron affinity for neutral C60. The electron affinity of C60 is measured to be 2.683 ? 0.008 eV. The cold spectra reveal complicated vibrational structures for the transition to the C60 ground state due to the Jahn-Teller effect in the ground state of C60-. Vibrational excitations in the two Ag modes and eight Hg modes are observed, providing ideal data to assess the vibronic couplings in C60-.
Membrane Vibration Analysis Above the Nyquist Limit with Fluorescence Videogrammetry
Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.; Pappa, Richard S.
2004-01-01
A new method for generating photogrammetric targets by projecting an array of laser beams onto a membrane doped with fluorescent laser dye has recently been developed. In this paper we review this new fluorescence based technique, then proceed to show how it can be used for dynamic measurements, and how a short pulsed (10 ns) laser allows the measurement of vibration modes at frequencies several times the sampling frequency. In addition, we present experimental results showing the determination of fundamental and harmonic vibration modes of a drum style dye-doped polymer membrane tautly mounted on a 12-inch circular hoop and excited with 30 Hz and 62 Hz sinusoidal acoustic waves. The projected laser dot pattern was generated by passing the beam from a pulsed Nd:YAG laser though a diffractive optical element, and the resulting fluorescence was imaged with three digital video cameras, all of which were synchronized with a pulse and delay generator. Although the video cameras are capable of 240 Hz frame rates, the laser s output was limited to 30 Hz and below. Consequently, aliasing techniques were used to allow the measurement of vibration modes up to 186 Hz with a Nyquist limit of less than 15 Hz.
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...... was applied in order to correct for anharmonic effects. Calculations based on the atom‐atom model for van der Waals' interaction and on general potential parameters for the aromatic compounds agree reasonably well with the experimental observations. There is no substantial improvement in fit obtained either...
High frequency vibration characteristics of electric wheel system under in-wheel motor torque ripple
Mao, Yu; Zuo, Shuguang; Wu, Xudong; Duan, Xianglei
2017-07-01
With the introduction of in-wheel motor, the electric wheel system encounters new vibration problems brought by motor torque ripple excitation. In order to analyze new vibration characteristics of electric wheel system, torque ripple of in-wheel motor based on motor module and vector control system is primarily analyzed, and frequency/order features of the torque ripple are discussed. Then quarter vehicle-electric wheel system (QV-EWS) dynamics model based on the rigid ring tire assumption is established and the main parameters of the model are identified according to tire free modal test. Modal characteristics of the model are further analyzed. The analysis indicates that torque excitation of in-wheel motor is prone to arouse horizontal vibration, in which in-phase rotational, anti-phase rotational and horizontal translational modes of electric wheel system mainly participate. Based on the model, vibration responses of the QV-EWS under torque ripple are simulated. The results show that unlike vertical low frequency (lower than 20 Hz) vibration excited by road roughness, broadband torque ripple will arouse horizontal high frequency (50-100 Hz) vibration of electric wheel system due to participation of the three aforementioned modes. To verify the theoretical analysis, the bench experiment of electric wheel system is conducted and vibration responses are acquired. The experiment demonstrates the high frequency vibration phenomenon of electric wheel system and the measured order features as well as main resonant frequencies agree with simulation results. Through theoretical modeling, analysis and experiments this paper reveals and explains the high frequency vibration characteristics of electric wheel system, providing references for the dynamic analysis, optimal design of QV-EWS.
Vibration Analysis of Composite Beams with Sinusoidal Periodically Varying Interfaces
Li, Botong; Liu, Chein-Shan; Zhu, Liangliang
2017-12-01
As an increasing variety of composite materials with complex interfaces are emerging, we develop a theory to investigate composite beams and shed some light on new physical insights into composite beams with sinusoidal periodically varying interfaces. For the natural vibration of composite beams with continuous or periodically varying interfaces, the governing equation has been derived according to the generalised Hamiltonian principle. For composite beams having different boundary conditions, we transform the governing equations into integral equations and solve them by using the sinusoidal functions as test functions as well as the basis of the vibration modes. Due to the orthogonality of the sinusoidal functions, expansion coefficients in closed form can be found. Therefore, the proposed iterative schemes, with the help of the Rayleigh quotient and boundary functions, can quickly find the eigenvalues and free vibration modes. The obtained natural frequencies agree well with those obtained using the finite element method. In addition, the proposed method can be extended easily to laminated composite beams in more general cases or complex components and geometries in vibration engineering. The effects of different material properties of the upper and lower components and varying interface geometry function on the frequency of the composite beams are examined. According to our investigation, the natural frequency of a laminated beam with a continuous or periodically varying interface can be changed by altering the density or elastic modulus. We also show the responses of the frequencies of the components to the varying periodic interface.
Experimental Modal Analysis on Vibrations in the Building Construction
成瀬, 治興; 佐野, 泰之; 北畠, 弘基
1996-01-01
This paper describes some results of vibration propagation characteristics of two rooms next door to each other in the actual building construction (including floor, walls, and upstairfloor) by experimental modal analysis. In addition, we investigate about vibration response of measuring points by forced response and sensitivity analysis. The results are summarized as follows. The vibration of lower modes gives larger effect to vibration propagation characteristics of building construction th...
Another approach to vibrational analysis of stepped structures
CSIR Research Space (South Africa)
Fedotov, I
2006-01-01
Full Text Available Hz. First resonance is a pendulum mode at which the stepped bar vibrates as “rigid” pendu- lum. All other modes are “longitudinal”. Geometry of the bar was specially chosen so that vibration amplitude of the junction between the cylindrical...
Rotor Vibration Reduction via Active Hybrid Bearings
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2002-01-01
The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... with experiment, and simulations show the feasibility of controlling shaft vibration through this active device....
DESIGN OF VIBRATION AND NOISE CONTROL SYSTEM FOR FLEXIBLE STRUCTURES
Directory of Open Access Journals (Sweden)
В. Макаренко
2012-04-01
Full Text Available In the article the control system is created, which is able to reduce steady-state vibration response of thinwalled flexible structure in the wide band of low frequencies. It is supposed, that the flexible structure is subject to external harmonic force with variable frequencies, and parameters of that force are available for the usage by the control system. The control system is based on pattern search algorithm and suggestion about the dependence of signal, which is formed by the control system, from the steady-state vibration response of the flexible structure. Developed software allows to use pattern search algorithm as the control system for plate vibration in real-time. The influence on control system operation of signal delay of executive device of compensating path and transition process after the change of control signal parameters is done by the usage of the additional idle time. During idle time the control signal is supported. It has parameters that have taken place before the beginning of idle mode. Step reset option for resuming of search after the long-term steady-state vibration of flexible structure do not derange control system operation, because step change take place only after polling cycle termination. The efficiency of proposed system is illustrated experimentally on the example of clamped plate. Experimental results analysis showed the necessity of multiple compensating devices application for vibration reduction in wide frequency range.
Vibrational Properties of a Monolayer Silicene Sheet Studied by Tip-Enhanced Raman Spectroscopy
Sheng, Shaoxiang; Wu, Jiang-bin; Cong, Xin; Li, Wenbin; Gou, Jian; Zhong, Qing; Cheng, Peng; Tan, Ping-heng; Chen, Lan; Wu, Kehui
2017-11-01
Combining ultrahigh sensitivity, spatial resolution, and the capability to resolve chemical information, tip-enhanced Raman spectroscopy (TERS) is a powerful tool to study molecules or nanoscale objects. Here we show that TERS can also be a powerful tool in studying two-dimensional materials. We have achieved a 109 Raman signal enhancement and a 0.5 nm spatial resolution using monolayer silicene on Ag(111) as a prototypical 2D material system. Because of the selective enhancement on Raman modes with vertical vibrational components in TERS, our experiment provides direct evidence of the origination of Raman modes in silicene. Furthermore, the ultrahigh sensitivity of TERS allows us to identify different vibrational properties of silicene phases, which differ only in the bucking direction of the Si-Si bonds. Local vibrational features from defects and domain boundaries in silicene can also be identified.
Vibrational spectra, theoretical calculations, and structure of 4-silaspiro(3,3)heptane.
Ocola, Esther J; Medders, Cross; Cooke, Joel M; Laane, Jaan
2014-09-15
Theoretical computations have been carried out for 4-silaspiro(3,3)heptane (SSH) in order to calculate its structure and vibrational spectra. SSH was found to have two puckered four-membered rings with dihedral angles of 34.2° and a tilt angle of 9.4° between the two rings. The puckering and tilting reduce the D2d symmetry to C2. Nonetheless, the vibrational assignments can be done quite well on the basis of D2d symmetry. This is confirmed by the fact that all but the lowest E vibrations show insignificant splitting into A and B modes of C2 symmetry. However, the observed splittings of the lowest frequency modes do confirm the lower conformational symmetry. The calculated infrared and Raman spectra were compared to the experimental spectra collected for the vapor, liquid, and solid states, and the agreement is excellent. Copyright © 2014 Elsevier B.V. All rights reserved.
Vibrational spectra, theoretical calculations, and structure of 4-silaspiro(3,3)heptane
Ocola, Esther J.; Medders, Cross; Cooke, Joel M.; Laane, Jaan
2014-09-01
Theoretical computations have been carried out for 4-silaspiro(3,3)heptane (SSH) in order to calculate its structure and vibrational spectra. SSH was found to have two puckered four-membered rings with dihedral angles of 34.2° and a tilt angle of 9.4° between the two rings. The puckering and tilting reduce the D2d symmetry to C2. Nonetheless, the vibrational assignments can be done quite well on the basis of D2d symmetry. This is confirmed by the fact that all but the lowest E vibrations show insignificant splitting into A and B modes of C2 symmetry. However, the observed splittings of the lowest frequency modes do confirm the lower conformational symmetry. The calculated infrared and Raman spectra were compared to the experimental spectra collected for the vapor, liquid, and solid states, and the agreement is excellent.
Energy Technology Data Exchange (ETDEWEB)
Lindenmaier, Rodica; Scharko, Nicole K.; Tonkyn, Russell G.; Nguyen, Kiet T.; Williams, Stephen D.; Johnson, Timothy J.
2017-07-25
Xylenes contain a blend of the ortho-, meta-, and para- isomers, and all are abundant contaminants in the ground, surface waters, and air. To better characterize xylene and to better enable its detection, we report high quality quantitative vapor-phase infrared spectra of all three isomers over the 540-6500 cm^{-1} range. All fundamental vibrational modes are assigned based on these vapor-phase infrared spectra, liquid-phase infrared and Raman spectra, along with density functional theory (DFT), ab initio MP2 and high energy-accuracy compound theoretical model (W1BD) calculations. Both MP2 and DFT predict a single conformer with C_{2v} symmetry for ortho-xylene, and two conformers each for meta- and para-xylene, depending on the preferred orientations of the methyl groups. For meta-xylene the two conformers have C_{s} and C_{2} symmetry, and for para-xylene these conformers have C_{2v} or C_{2h} symmetry. Since the relative population of the two conformers is approximately 50% for both isomers and predicted frequencies and intensities are very similar for each conformer, we made an arbitrary choice to discuss the C_{s} conformer for meta-xylene and the C_{2v} conformer for para-xylene. We report integrated band intensities for all isomers. Using the quantitative infrared data, we determine the global warming potential values of each isomer and discuss potential bands for atmospheric monitoring.
Fonari, A.
2015-12-10
We establish a reliable quantum-mechanical approach to evaluate the vibrational properties of donor-acceptor molecular crystals. The anthracene-PMDA (PMDA = pyromellitic dianhydride) crystal, where anthracene acts as the electron donor and PMDA as the electron acceptor, is taken as a representative system for which experimental non-resonance Raman spectra are also reported. We first investigate the impact that the amount of nonlocal Hartree-Fock exchange (HFE) included in a hybrid density functional has on the geometry, normal vibrational modes, electronic coupling, and electron-vibrational (phonon) couplings. The comparison between experimental and theoreticalRaman spectra indicates that the results based on the αPBE functional with 25%-35% HFE are in better agreement with the experimental results compared to those obtained with the pure PBE functional. Then, taking αPBE with 25% HFE, we assign the vibrational modes and examine their contributions to the relaxation energy related to the nonlocal electron-vibration interactions. The results show that the largest contribution (about 90%) is due to electron interactions with low-frequency vibrational modes. The relaxation energy in anthracene-PMDA is found to be about five times smaller than the electronic coupling.
Energy Technology Data Exchange (ETDEWEB)
Fonari, A.; Corbin, N. S.; Coropceanu, V., E-mail: jean-luc.bredas@kaust.edu.sa, E-mail: coropceanu@gatech.edu [School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 (United States); Vermeulen, D.; McNeil, L. E. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3255 (United States); Goetz, K. P.; Jurchescu, O. D. [Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109-7507 (United States); Bredas, J. L., E-mail: jean-luc.bredas@kaust.edu.sa, E-mail: coropceanu@gatech.edu [School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 (United States); Solar and Photovoltaics Engineering Research Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)
2015-12-14
We establish a reliable quantum-mechanical approach to evaluate the vibrational properties of donor-acceptor molecular crystals. The anthracene-PMDA (PMDA = pyromellitic dianhydride) crystal, where anthracene acts as the electron donor and PMDA as the electron acceptor, is taken as a representative system for which experimental non-resonance Raman spectra are also reported. We first investigate the impact that the amount of nonlocal Hartree-Fock exchange (HFE) included in a hybrid density functional has on the geometry, normal vibrational modes, electronic coupling, and electron-vibrational (phonon) couplings. The comparison between experimental and theoretical Raman spectra indicates that the results based on the αPBE functional with 25%-35% HFE are in better agreement with the experimental results compared to those obtained with the pure PBE functional. Then, taking αPBE with 25% HFE, we assign the vibrational modes and examine their contributions to the relaxation energy related to the nonlocal electron-vibration interactions. The results show that the largest contribution (about 90%) is due to electron interactions with low-frequency vibrational modes. The relaxation energy in anthracene-PMDA is found to be about five times smaller than the electronic coupling.
Mode Shape Analysis of Multiple Cracked Functionally Graded Timoshenko Beams
Directory of Open Access Journals (Sweden)
Tran Van Lien
Full Text Available Abstract The present paper addresses free vibration of multiple cracked Timoshenko beams made of Functionally Graded Material (FGM. Cracks are modeled by rotational spring of stiffness calculated from the crack depth and material properties vary according to the power law throughout the beam thickness. Governing equations for free vibration of the beam are formulated with taking into account actual position of the neutral plane. The obtained frequency equation and mode shapes are used for analysis of the beam mode shapes in dependence on the material and crack parameters. Numerical results validate usefulness of the proposed herein theory and show that mode shapes are good indication for detecting multiple cracks in Timoshenko FGM beams.
Ergonomic Evaluation of Vibrations of a Rototiller with New Blade
Directory of Open Access Journals (Sweden)
H Gholami
2017-10-01
Full Text Available Introduction One of the most important problems arising with operation of the conventional rototillers is severe vibration of the machine handle which is transmitted to the user’s hands, arms and shoulders. Long period exposure of the hand-transmitted vibration may cause various diseases such as white finger syndrome. Therefore in this study, vibrations of a new type of rototiller with ridged blades were investigated at the position of handle/hand interface in different working conditions. Finally, the maximum allowable exposure time to the rototiller users in continuous tillage operation was obtained according to ISO 5349-1. Materials and Methods Experiments were carried out in one of the farms with silty clay soil texture, located in Sari city, Mazandaran province, Iran. Vibration measurements were performed according to ISO 5349-1 and ISO 5349-2 standards in two different modes, including in situ mode and tillage mode. Vibrational parameters were obtained in three blade rotational speeds, i.e., low speed (140-170 rpm, medium speed (170-200, and high speed (200-230. Blade rotational speed varied by changing engine speed using the throttle control lever. In each experiment, different vibrational values were individually recorded in three directions (x, y, and z. Experimental design and data analysis were performed in a Randomized Complete Block Design with three replications using the SPSS16 software. Results and Discussion Based on the obtained results in this study, the RMS of acceleration increased by increasing in rotational speed for all of the conducted experiments. The reason is that number of cutting per unit of time and consequently the frequency of changing in the dynamic forces exerting on the blades dramatically increases with increasing the rotational speed of the blades. Noteworthy is that in most cases the variation of acceleration in the tillage mode showed similar trend with vibrational values in the idling mode. This
Nyawako, Donald; Reynolds, Paul; Hudson, Emma
2016-04-01
Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented. The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.
Rinck, Philipp M.; Sitzberger, Sebastian; Zaeh, Michael F.
2017-06-01
In vibration assisted machining, an additional high-frequency oscillation is superimposed on the kinematics of the conventional machining process. This generates oscillations on the cutting edge in the range of a few micrometers, thereby causing a high-frequency change in the cutting speed or the feed. Consequently, a reduction of cutting forces, an increase of the tool life as well as an improvement of the workpiece quality can be achieved. In milling and grinding it has been shown that these effects are already partially present in the case of a vibration excitation in axial direction relative to the workpiece, which is perpendicular to the cutting direction. Further improvements of the process results can be achieved by superimposing a vibration in cutting direction and thus modifying the cutting speed at high frequency. The presented work shows the design of an ultrasonic actuator that enables vibration-assisted milling and grinding with ultrasonically modulated cutting speed. The actuator system superimposes a longitudinal torsional ultrasonic oscillation to the milling or grinding tool. It uses a bolt clamped Langevin transducer and a helically slotted horn, which degenerates the longitudinal vibration into a combined longitudinal torsional (L-T) vibration at the output surface. A finite element analysis is used to determine the vibration resonance frequency and mode shapes to maximize the torsional output. Afterwards, the simulation has been experimentally validated.
A new compound control method for sine-on-random mixed vibration test
Zhang, Buyun; Wang, Ruochen; Zeng, Falin
2017-09-01
Vibration environmental test (VET) is one of the important and effective methods to provide supports for the strength design, reliability and durability test of mechanical products. A new separation control strategy was proposed to apply in multiple-input multiple-output (MIMO) sine on random (SOR) mixed mode vibration test, which is the advanced and intensive test type of VET. As the key problem of the strategy, correlation integral method was applied to separate the mixed signals which included random and sinusoidal components. The feedback control formula of MIMO linear random vibration system was systematically deduced in frequency domain, and Jacobi control algorithm was proposed in view of the elements, such as self-spectrum, coherence, and phase of power spectral density (PSD) matrix. Based on the excessive correction of excitation in sine vibration test, compression factor was introduced to reduce the excitation correction, avoiding the destruction to vibration table or other devices. The two methods were synthesized to be applied in MIMO SOR vibration test system. In the final, verification test system with the vibration of a cantilever beam as the control object was established to verify the reliability and effectiveness of the methods proposed in the paper. The test results show that the exceeding values can be controlled in the tolerance range of references accurately, and the method can supply theory and application supports for mechanical engineering.
Directory of Open Access Journals (Sweden)
Daniel Tirelli
2014-01-01
Full Text Available A new passive device for mitigating cable vibrations is proposed and its efficiency is assessed on 45-meter long taut cables through a series of free and forced vibration tests. It consists of a unilateral spring attached perpendicularly to the cable near the anchorage. Because of its ability to change the cable dynamic behaviour through intermittent activation, the device has been called state switched inducer (SSI. The cable behaviour is shown to be deeply modified by the SSI: the forced vibration response is anharmonicc and substantially reduced in amplitude whereas the free vibration decay is largely sped up through a beating phenomenon. The vibration mitigation effect is mainly due to the activation and coupling of various vibration modes, as evidenced in the response spectra of the equipped cable. This first large-scale experimental campaign shows that the SSI outperforms classical passive devices, thus paving the way to a new kind of low-cost vibration mitigation systems which do not rely on dissipation.
Understanding the effect of hammering process on the vibration characteristics of cymbals
Kuratani, F.; Yoshida, T.; Koide, T.; Mizuta, T.; Osamura, K.
2016-09-01
Cymbals are thin domed plates used as percussion instruments. When cymbals are struck, they vibrate and radiate sound. Cymbals are made through spin forming, hammering, and lathing. The spin forming creates the basic shape of the cymbal, which determines its basic vibration characteristics. The hammering and lathing produce specific sound adjustments by changing the cymbal's vibration characteristics. In this study, we study how hammering cymbals affects their vibration characteristics. The hammering produces plastic deformation (small, shallow dents) on the cymbal's surface, generating residual stresses throughout it. These residual stresses change the vibration characteristics. We perform finite element analysis of a cymbal to obtain its stress distribution and the resulting change in vibration characteristics. To reproduce the stress distribution, we use thermal stress analysis, and then with this stress distribution we perform vibration analysis. These results show that each of the cymbal's modes has a different sensitivity to the thermal load (i.e., hammering). This difference causes changes in the frequency response and the deflection shape that significantly improves the sound radiation efficiency. In addition, we explain the changes in natural frequencies by the stress and modal strain energy distributions.
Two methods for estimating aeroelastic damping of operational wind turbine modes from experiments
DEFF Research Database (Denmark)
Hansen, Morten Hartvig; Thomsen, Kenneth; Fuglsang, Peter
2006-01-01
show that turbine vibrations related to the first two tower bending modes can be excited by blade pitch and generator torque variations. However, the excited turbine vibrations are not pure modal vibrations and the estimated damping is therefore not the actual modal damping. The second method is based......The theory and results of two experimental methods for estimating the modal damping of a wind turbine during operation are presented. Estimations of the aeroelastic damping of the operational turbine modes (including the effects of the aerodynamic forces) give a quantitative view of the stability...... characteristics of the turbine. In the first method the estimation of modal damping is based on the assumption that a turbine mode can be excited by a harmonic force at its natural frequency, whereby the decaying response after the end of excitation gives an estimate of the damping. Simulations and experiments...
Study of the vibration of bulkhead-stiffened cylindrical shells by laser-based methods
Zhu, Ninghui
studied. The relationship between natural frequency loci veering, mode shape localization of steady state vibration and pass- stop-band behavior of wave propagation are established in stiffened cylindrical shell structures. It is hoped that this finding can be used to emphasis the importance of mode localization when the numerical models are applied to the study of dynamic behavior of real engineering structures. Finally, a novel laser-based vibration measurement system is developed. Rather than using a photographic camera as in conventional speckle photography, this system utilizes a CCD camera and an interfaced computer to perform the digital speckle image processing. Several algorithms are developed or found to extract the mode shapes related to the vibration of objects from captured digital speckle images. The algorithms can be generally categorized into the following aspects as spatial domain filtering (e.g., image edge detection operation), spectrum domain filtering (e.g., Fourier transform operation), spatial domain correlation and image blurring model. The computer generated or processed images can provide a Chladni-like pattern showing the mode shapes of vibrating objects. This new laser-based vibration measurement technique not only inherits the common merits shared by conventional optical schemes such as whole-field, non-contact and non-destruction, but also possesses its unique features of noise-resistance, simplicity, flexibility and, most of all, practicability. The feasibility of this new technique had been proven by successful field tests at the shipyard of General Dynamic Electric Boat Division.
Chatter vibrations of high-performance motorcycles
Sharp, R. S.; Watanabe, Y.
2013-03-01
Motorcycle racing teams occasionally experience speed-limiting vibrations of around 25 Hz frequency in mid-corner. The nature of the vibrations has not been closely defined yet and the mechanics are currently not properly understood. Conventional motorcycle-dynamics models are shown here to reveal the existence of a vibration mode that aligns with the experience being referred to, suggesting some explanations. Root loci for variations in speed or cornering vigour, demonstrating modal characteristics for small perturbations from trim states, are employed to indicate how the mode responds to changes in operation and design. Modal participation is examined for a lightly damped case. Influences on the natural frequency and damping of the mode are found and a way of stabilising the mode is suggested.
Active damping of the 1D rocking mode
Babakhani, B.; de Vries, Theodorus J.A.
Active damping of a rotational vibration mode in the linear guidance of a precision machine in a one dimensional (1D) setting is considered in this paper. This so-called rocking mode presents itself in machines having linear actuation. The limitation this vibration mode imposes on the machine
Kinetic theory for DNA melting with vibrational entropy
Sensale, Sebastian; Peng, Zhangli; Chang, Hsueh-Chia
2017-10-01
By treating DNA as a vibrating nonlinear lattice, an activated kinetic theory for DNA melting is developed to capture the breakage of the hydrogen bonds and subsequent softening of torsional and bending vibration modes. With a coarse-grained lattice model, we identify a key bending mode with GHz frequency that replaces the hydrogen vibration modes as the dominant out-of-phase phonon vibration at the transition state. By associating its bending modulus to a universal in-phase bending vibration modulus at equilibrium, we can hence estimate the entropic change in the out-of-phase vibration from near-equilibrium all-atom simulations. This and estimates of torsional and bending entropy changes lead to the first predictive and sequence-dependent theory with good quantitative agreement with experimental data for the activation energy of melting of short DNA molecules without intermediate hairpin structures.
Partanen, Sanna T; Novikov, Dmitry K; Popov, Alexander N; Mursula, Anu M; Hiltunen, J Kalervo; Wierenga, Rik K
2004-09-24
The crystal structure of Delta3-Delta2-enoyl-CoA isomerase from human mitochondria (hmEci), complexed with the substrate analogue octanoyl-CoA, has been refined at 1.3 A resolution. This enzyme takes part in the beta-oxidation of unsaturated fatty acids by converting both cis-3 and trans-3-enoyl-CoA esters (with variable length of the acyl group) to trans-2-enoyl-CoA. hmEci belongs to the hydratase/isomerase (crotonase) superfamily. Most of the enzymes belonging to this superfamily are hexamers, but hmEci is shown to be a trimer. The mode of binding of the ligand, octanoyl-CoA, shows that the omega-end of the acyl group binds in a hydrophobic tunnel formed by residues of the loop preceding helix H4 as well as by side-chains of the kinked helix H9. From the structure of the complex it can be seen that Glu136 is the only catalytic residue. The importance of Glu136 for catalysis is confirmed by mutagenesis studies. A cavity analysis shows the presence of two large, adjacent empty hydrophobic cavities near the active site, which are shaped by side-chains of helices H1, H2, H3 and H4. The structure comparison of hmEci with structures of other superfamily members, in particular of rat mitochondrial hydratase (crotonase) and yeast peroxisomal enoyl-CoA isomerase, highlights the variable mode of binding of the fatty acid moiety in this superfamily.
Spinning optical resonator sensor for torsional vibrational applications measurements
Ali, Amir R.; Gatherer, Andrew; Ibrahim, Mariam S.
2016-03-01
Spinning spherical resonators in the torsional vibrational applications could cause a shift in its whispering gallery mode (WGM). The centripetal force acting on the spinning micro sphere resonator will leads to these WGM shifts. An analysis and experiment were carried out in this paper to investigate and demonstrate this effect using different polymeric resonators. In this experiment, centripetal force exerted by the DC-Motor on the sphere induces an elastic deformation of the resonator. This in turn induces a shift in the whispering gallery modes of the sphere resonator. Materials used for the sphere are polydimethylsiloxane (PDMS 60:1 where 60 parts base silicon elastomer to 1 part polymer curing agent by volume) with shear modulus (G≍1kPa), (PDMS 10:1) with shear modulus (G≍300kPa), polymethylmethacrylate (PMMA, G≍2.6×109GPa) and silica (G≍3×1010 GPa). The sphere size was kept constant with 1mm in diameter for all above materials. The optical modes of the sphere exit using a tapered single mode optical fiber that is coupled to a distributed feedback laser. The transmission spectrum through the fiber is monitored to detect WGM shifts. The results showed the resonators with smaller shear modulus G experience larger WGM shift due to the larger mechanical deformation induced by the applied external centripetal force. Also, the results show that angular velocity sensors used in the torsional vibrational applications could be designed using this principle.
DEFF Research Database (Denmark)
Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen
2012-01-01
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...
Damping and energy dissipation in soft tissue vibrations during running.
Khassetarash, Arash; Hassannejad, Reza; Enders, Hendrik; Ettefagh, Mir Mohammad
2015-01-21
It has been well accepted that the vibrations of soft tissue cannot be simulated by a single sinusoidal function. In fact, these vibrations are a combination of several vibration modes. In this study, these modes are extracted applying a recently developed method namely, partly ensemble empirical mode decomposition (PEEMD). Then, a methodology for estimating the damping properties and energy dissipation caused by damping for each mode is used. Applying this methodology on simulated signals demonstrates high accuracy. This methodology is applied to the acceleration signals of the gastrocnemius muscle during sprinting and the differences between the damping properties of different vibration modes were identified. The results were 1) the damping property of high-frequency mode was higher than that for low-frequency modes. 2) All identified modes were in under damped condition, therefore, the vibrations had an oscillatory nature. 3) The damping ratios of lower modes are about 100% increased compared to higher modes. 4) The energy dissipation occurred in lower modes were much more than that for higher mode; According to the power spectrum of the ground reaction force (GRF), which is the input force into the body, the recent finding supports the muscle tuning paradigm. It is suggested that the damping properties and energy dissipation can be used to distinguish between different running conditions (surface, fatigue, etc.). Copyright © 2014 Elsevier Ltd. All rights reserved.
Transient vibration of wind turbine blades
Li, Yuanzhe; Li, Minghai; Jiang, Feng
2017-09-01
This article aims to the transient vibration of wind turbine blades. We firstly introduce transient vibration and previous studies in this area. The report then shows the fundamental equations and derivation of Euler Equation. A 3-D beam are created to compare the analytical and numerical result. In addition we operate the existing result and Patran result of a truncation wedge beam, especially the frequencies of free vibration and transient vibration. Transient vibration cannot be vanished but in some case it can be reduced.
Molecular vibration-sensing component in human olfaction.
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Simon Gane
Full Text Available Whether olfaction recognizes odorants by their shape, their molecular vibrations, or both remains an open and controversial question. A convenient way to address it is to test for odor character differences between deuterated and undeuterated odorant isotopomers, since these have identical ground-state conformations but different vibrational modes. In a previous paper (Franco et al. (2011 Proc Natl Acad Sci USA 108:9, 3797-802 we showed that fruit flies can recognize the presence of deuterium in odorants by a vibrational mechanism. Here we address the question of whether humans too can distinguish deuterated and undeuterated odorants. A previous report (Keller and Vosshall (2004 Nat Neurosci 7:4, 337-8 indicated that naive subjects are incapable of distinguishing acetophenone and d-8 acetophenone. Here we confirm and extend those results to trained subjects and gas-chromatography [GC]-pure odorants. However, we also show that subjects easily distinguish deuterated and undeuterated musk odorants purified to GC-pure standard. These results are consistent with a vibrational component in human olfaction.
Vibrational coupling in plasmonic molecules.
Yi, Chongyue; Dongare, Pratiksha D; Su, Man-Nung; Wang, Wenxiao; Chakraborty, Debadi; Wen, Fangfang; Chang, Wei-Shun; Sader, John E; Nordlander, Peter; Halas, Naomi J; Link, Stephan
2017-10-31
Plasmon hybridization theory, inspired by molecular orbital theory, has been extremely successful in describing the near-field coupling in clusters of plasmonic nanoparticles, also known as plasmonic molecules. However, the vibrational modes of plasmonic molecules have been virtually unexplored. By designing precisely configured plasmonic molecules of varying complexity and probing them at the individual plasmonic molecule level, intramolecular coupling of acoustic modes, mediated by the underlying substrate, is observed. The strength of this coupling can be manipulated through the configuration of the plasmonic molecules. Surprisingly, classical continuum elastic theory fails to account for the experimental trends, which are well described by a simple coupled oscillator picture that assumes the vibrational coupling is mediated by coherent phonons with low energies. These findings provide a route to the systematic optical control of the gigahertz response of metallic nanostructures, opening the door to new optomechanical device strategies. Published under the PNAS license.
Gradient Index Devices for the Simultaneous Focusing of the S0 and A0 Lamb Modes
Jin, Yabin; Pennec, Yan; Pan, Yongdong; Djafari-Rouhani, Bahram
2015-01-01
Gradient index devices for the simultaneous control of the S 0 and A 0 Lamb modes are presented and numerically analysed. It is found a special relationship between the refractive indexes for these two modes which allows their simultaneous control by means of graded phononic crystals and thickness variations of the plate. A flat gradient index lens and a circular Luneburg lens are designed. Numerical simulations show that the performance of these devices is good for the two modes in a broadband frequency region, and that this approach can be used to design more advanced refractive devices for the total control of guided vibrational modes.
Directory of Open Access Journals (Sweden)
Jianfeng Zhang
2015-01-01
Full Text Available During the operation process of the high voltage circuit breaker, the changes of vibration signals can reflect the machinery states of the circuit breaker. The extraction of the vibration signal feature will directly influence the accuracy and practicability of fault diagnosis. This paper presents an extraction method based on ensemble empirical mode decomposition (EEMD. Firstly, the original vibration signals are decomposed into a finite number of stationary intrinsic mode functions (IMFs. Secondly, calculating the envelope of each IMF and separating the envelope by equal-time segment and then forming equal-time segment energy entropy to reflect the change of vibration signal are performed. At last, the energy entropies could serve as input vectors of support vector machine (SVM to identify the working state and fault pattern of the circuit breaker. Practical examples show that this diagnosis approach can identify effectively fault patterns of HV circuit breaker.
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Kongming Guo
2017-05-01
Full Text Available The aim of this paper is to suppress the random spatial vibration of the face sheet of a lightly damped truss core sandwich panel structure. Because broad-bandwidth vibration energy is concentrated in resonance peaks for lightly damped structures, an independent modal resonant shunt control method is utilized to add damping ratios to the chosen modes. In this method, each piezoelectric transducer is connected to a single resonant shunt which is tuned to control the vibration of a single mode. An H2 norm sensitivity-based modal criterion is proposed in order to determine which modes to control under a given bandwidth of excitation and input-output condition. Numerical simulation is implemented while control strategies with different controlled modes are compared. The result shows that the independent modal resonant shunt control method can suppress random vibration response of the face sheet by using only a few piezoelectric transducers, and the proposed modal criterion can be used to determine which modes to control.
Margasahayam, Ravi N.; Meyer, Karl A.; Nerolich, Shaun M.; Burton, Roy C.; Gosselin, Armand M.
2004-01-01
The Crawler Transporter (CT), designed and built for the Apollo Program in the 1960's and surpassing its initial operational life, has become an integral part of the Space Shuttle Program (SSP). The CT transports the Space Shuttle Vehicle (SSV) stack, atop the Mobile Launch Platform (MLP), from the Vehicle Assembly Building (VAB) to the launch pad. This support structure provides hydraulic jacking, leveling and load equalization for the 12 million pound stack on its 3.5-5.0 mile rollout to the launch pad. Major elements of the SSV, consisting of the orbiter, solid rocket boosters (SRB) and external tank (ET) have required fatigue analyses as part of the mission life certification. Compared to rollout vibration, the SSV sees relatively high vibration loads during launch, ascent, descent and landing phases of the mission. Although preliminary measured SRB vibration levels during rollout were of low amplitude and frequency, the duration of the rollout phase is typically high, from 5-6 hours. As part of an expanded mission life assessment, additional certification effort was initiated to define fatigue load spectra for rollout. This study addresses the CT vibration analyses in support of the rollout fatigue study. Structural models developed for modal and vibration analyses were used to identify unique CT, CT/MLP and CT/MLP/SRB vibration characteristics for comparison to instrumented rollout tests. Whereas the main structural and vibration characteristics of the SSV are well defined, minimum analytical and vibration test data on the Crawler Transporter were available. Unique vibration characteristics of the CT are attributable to the drive mechanism, hydraulic jacking system, structural framing and the CT-to-MLP support pad restraints. Initial tests performed on the CT/MLP/SRB configuration showed reasonable correlation with predicted mode shapes and frequencies.
DEFF Research Database (Denmark)
Stokbro, Kurt
1999-01-01
We report a first principles study of the structure and the vibrational properties of the Si(100)-H(2 x 1) surface in an electric field. The calculated vibrational parameters are used to model the vibrational modes in the presence of the electric field corresponding to a realistic scanning...... at room temperature). We calculate the implications for current induced desorption of H using a recently developed first principles model of electron inelastic scattering. The calculations show that inelastic scattering events with energy transfer n (h) over bar omega, where n>1, play an important role...
Shehu, Abubakar; Mohammed, Aliyu; Magaji, Rabiu Abdussalam; Muhammad, Mustapha Shehu
2016-04-01
Research on the effects of Mobile phone radio frequency emissions on biological systems has been focused on noise and vibrations as auditory stressors. This study investigated the potential effects of exposure to mobile phone electromagnetic field radiation, ringtone and vibration on anxiety-like behaviour and oxidative stress biomarkers in albino wistar rats. Twenty five male wistar rats were randomly divided into five groups of 5 animals each: group I: exposed to mobile phone in switched off mode (control), group II: exposed to mobile phone in silent mode, group III: exposed to mobile phone in vibration mode, group IV: exposed to mobile phone in ringtone mode, group V: exposed to mobile phone in vibration and ringtone mode. The animals in group II to V were exposed to 10 min call (30 missed calls for 20 s each) per day for 4 weeks. Neurobehavioural studies for assessing anxiety were carried out 24 h after the last exposure and the animals were sacrificed. Brain samples were collected for biochemical evaluation immediately. Results obtained showed a significant decrease (P electromagnetic radiation, vibration, ringtone or both produced a significant effect on anxiety-like behavior and oxidative stress in young wistar rats.
Improved Predictions for Geotechnical Vibrations
Macijauskas, Darius
2015-01-01
In urban areas where the infrastructure is dense and construction of new structures is near existing and sensitive buildings, frequently vibrations, caused by human activities, occur. Generated waves in the soil may adversely affect surrounding buildings. These vibrations have to be predicted a priori by using currently available knowledge of the soil dynamics. Current research, conducted by Deltares research institute, showed that the reliability of methods for prediction of m...
Jha, Omkant; Yadav, T. K.; Yadav, R. A.
2018-01-01
Structural and vibrational studies for the most stable conformer of dopamine {4-(2-Aminoethyl) benzene-1, 2-diol} have been carried out at the DFT/B3LYP/6-311 ++G** level using the Gaussian 09 software. The IR and Raman spectra have been recorded and analyzed in light of the computed vibrational parameters using the DFT and the PEDs computed with the help of the GAR2PED software. Some of the fundamentals have considerably changed frequencies in going from benzene to dopamine. Except the rocking and wagging modes of the NH2 group the other four modes are pure group modes. The rocking and wagging modes of the NH2 group show mixing with the other modes. The two Osbnd H stretching vibrations are highly localized modes. The Kekule phenyl ring stretching mode is found to remain almost unchanged. The HOMO-LUMO study suggests the existence of charge transfer within the molecule and the energy gap supports the pharmacological active property of the dopamine molecule. The NBO analysis has been carried out to understand the proper and improper hydrogen bonding.
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...
Vibration Analysis of a Split Path Gearbox
Krantz, Timothy L.; Rashidi, Majid
1995-01-01
Split path gearboxes can be attractive alternatives to the common planetary designs for rotorcraft, but because they have seen little use, they are relatively high risk designs. To help reduce the risk of fielding a rotorcraft with a split path gearbox, the vibration and dynamic characteristics of such a gearbox were studied. A mathematical model was developed by using the Lagrangian method, and it was applied to study the effect of three design variables on the natural frequencies and vibration energy of the gearbox. The first design variable, shaft angle, had little influence on the natural frequencies. The second variable, mesh phasing, had a strong effect on the levels of vibration energy, with phase angles of 0 deg and 180 deg producing low vibration levels. The third design variable, the stiffness of the shafts connecting the spur gears to the helical pinions, strongly influenced the natural frequencies of some of the vibration modes, including two of the dominant modes. We found that, to achieve the lowest level of vibration energy, the natural frequencies of these two dominant modes should be less than those of the main excitation sources.
Pin-pin resonance as a reference in determining ballasted railway track vibration behaviour
De Man, A.P.
2000-01-01
Pin-pin resonance is one of the most significant preferred vibration modes of beams, which are supported at equal distances, such as rails at sleepers in railway track structures do. Pin-pin resonance is a vibration that appears in one basic (first) mode and several higher modes, however the basic
Modeling and analysis of the in-plane vibration of a complex cable-stayed bridge
Cao, D. Q.; Song, M. T.; Zhu, W. D.; Tucker, R. W.; Wang, C. H.-T.
2012-12-01
The in-plane vibration of a complex cable-stayed bridge that consists of a simply-supported four-cable-stayed deck beam and two rigid towers is studied. The nonlinear and linear partial differential equations that govern transverse and longitudinal vibrations of the cables and transverse vibrations of segments of the deck beam, respectively, are derived, along with their boundary and matching conditions. The undamped natural frequencies and mode shapes of the linearized model of the cable-stayed bridge are determined, and orthogonality relations of the mode shapes are established. Numerical analysis of the natural frequencies and mode shapes of the cable-stayed bridge is conducted for various symmetrical and non-symmetrical bridge cases with regards to the sizes of the components of the bridge and the initial sags of the cables. The results show that there are very close natural frequencies when the bridge model is symmetrical and/or partially symmetrical, and the mode shapes tend to be more localized when the bridge model is less symmetrical. The relationships between the natural frequencies and mode shapes of the cable-stayed bridge and those of a single fixed-fixed cable and the single simply-supported deck beam are analyzed. The results, which are validated by commercial finite element software, demonstrate some complex classical resonance behavior of the cable-stayed bridge.
Wind Turbine Rotors with Active Vibration Control
DEFF Research Database (Denmark)
Svendsen, Martin Nymann
This thesis presents a framework for structural modeling, analysis and active vibration damping of rotating wind turbine blades and rotors. A structural rotor model is developed in terms of finite beam elements in a rotating frame of reference. The element comprises a representation of general...... formulation. The element provides an accurate representation of the eigenfrequencies and whirling modes of the gyroscopic system, and identifies lightly damped edge-wise modes. By adoption of a method for active, collocated resonant vibration of multi-degree-of-freedom systems it is demonstrated...... that these are geometrically well separated. For active vibration control in three-bladed wind turbine rotors the present work presents a resonance-based method for groups of one collective and two whirling modes. The controller is based on the existing resonant format and introduces a dual system targeting the collective...
Acoustical analysis of gear housing vibration
Seybert, A. F.; Wu, T. W.; Wu, X. F.; Oswald, Fred B.
1991-01-01
The modal and acoustical analysis of the NASA gear-noise rig is described. Experimental modal analysis techniques were used to determine the modes of vibration of the transmission housing. The resulting modal data were then used in a boundary element method (BEM) analysis to calculate the sound pressure and sound intensity on the surface of the housing as well as the radiation efficiency of each mode. The radiation efficiencies of the transmission housing modes are compared with theoretical results for finite, baffled plates. A method that uses the measured mode shapes and the BEM to predict the effect of simple structural changes on the sound radiation efficiency of the modes of vibration is also described.
Madsen, Niels Kristian; Godtliebsen, Ian H; Losilla, Sergio A; Christiansen, Ove
2018-01-14
A new implementation of vibrational coupled-cluster (VCC) theory is presented, where all amplitude tensors are represented in the canonical polyadic (CP) format. The CP-VCC algorithm solves the non-linear VCC equations without ever constructing the amplitudes or error vectors in full dimension but still formally includes the full parameter space of the VCC[n] model in question resulting in the same vibrational energies as the conventional method. In a previous publication, we have described the non-linear-equation solver for CP-VCC calculations. In this work, we discuss the general algorithm for evaluating VCC error vectors in CP format including the rank-reduction methods used during the summation of the many terms in the VCC amplitude equations. Benchmark calculations for studying the computational scaling and memory usage of the CP-VCC algorithm are performed on a set of molecules including thiadiazole and an array of polycyclic aromatic hydrocarbons. The results show that the reduced scaling and memory requirements of the CP-VCC algorithm allows for performing high-order VCC calculations on systems with up to 66 vibrational modes (anthracene), which indeed are not possible using the conventional VCC method. This paves the way for obtaining highly accurate vibrational spectra and properties of larger molecules.
Madsen, Niels Kristian; Godtliebsen, Ian H.; Losilla, Sergio A.; Christiansen, Ove
2018-01-01
A new implementation of vibrational coupled-cluster (VCC) theory is presented, where all amplitude tensors are represented in the canonical polyadic (CP) format. The CP-VCC algorithm solves the non-linear VCC equations without ever constructing the amplitudes or error vectors in full dimension but still formally includes the full parameter space of the VCC[n] model in question resulting in the same vibrational energies as the conventional method. In a previous publication, we have described the non-linear-equation solver for CP-VCC calculations. In this work, we discuss the general algorithm for evaluating VCC error vectors in CP format including the rank-reduction methods used during the summation of the many terms in the VCC amplitude equations. Benchmark calculations for studying the computational scaling and memory usage of the CP-VCC algorithm are performed on a set of molecules including thiadiazole and an array of polycyclic aromatic hydrocarbons. The results show that the reduced scaling and memory requirements of the CP-VCC algorithm allows for performing high-order VCC calculations on systems with up to 66 vibrational modes (anthracene), which indeed are not possible using the conventional VCC method. This paves the way for obtaining highly accurate vibrational spectra and properties of larger molecules.
Zhang, D. P.; Lei, Y.; Shen, Z. B.
2017-09-01
The effect of longitudinal magnetic field on vibration response of a sing-walled carbon nanotube (SWCNT) embedded in viscoelastic medium is investigated. Based on nonlocal Euler-Bernoulli beam theory, Maxwell's relations, and Kelvin viscoelastic foundation model, the governing equations of motion for vibration analysis are established. The complex natural frequencies and corresponding mode shapes in closed form for the embedded SWCNT with arbitrary boundary conditions are obtained using transfer function method (TFM). The new analytical expressions for the complex natural frequencies are also derived for certain typical boundary conditions and Kelvin-Voigt model. Numerical results from the model are presented to show the effects of nonlocal parameter, viscoelastic parameter, boundary conditions, aspect ratio, and strength of the magnetic field on vibration characteristics for the embedded SWCNT in longitudinal magnetic field. The results demonstrate the efficiency of the proposed methods for vibration analysis of embedded SWCNTs under magnetic field.
Zhang, D. P.; Lei, Y.; Shen, Z. B.
2017-12-01
The effect of longitudinal magnetic field on vibration response of a sing-walled carbon nanotube (SWCNT) embedded in viscoelastic medium is investigated. Based on nonlocal Euler-Bernoulli beam theory, Maxwell's relations, and Kelvin viscoelastic foundation model, the governing equations of motion for vibration analysis are established. The complex natural frequencies and corresponding mode shapes in closed form for the embedded SWCNT with arbitrary boundary conditions are obtained using transfer function method (TFM). The new analytical expressions for the complex natural frequencies are also derived for certain typical boundary conditions and Kelvin-Voigt model. Numerical results from the model are presented to show the effects of nonlocal parameter, viscoelastic parameter, boundary conditions, aspect ratio, and strength of the magnetic field on vibration characteristics for the embedded SWCNT in longitudinal magnetic field. The results demonstrate the efficiency of the proposed methods for vibration analysis of embedded SWCNTs under magnetic field.
Earthquake and ambient vibration monitoring of the steel-frame UCLA factor building
Kohler, M.D.; Davis, P.M.; Safak, E.
2005-01-01
Dynamic property measurements of the moment-resisting steel-frame University of California, Los Angeles, Factor building are being made to assess how forces are distributed over the building. Fourier amplitude spectra have been calculated from several intervals of ambient vibrations, a 24-hour period of strong winds, and from the 28 March 2003 Encino, California (ML = 2.9), the 3 September 2002 Yorba Linda, California (ML = 4.7), and the 3 November 2002 Central Alaska (Mw = 7.9) earthquakes. Measurements made from the ambient vibration records show that the first-mode frequency of horizontal vibration is between 0.55 and 0.6 Hz. The second horizontal mode has a frequency between 1.6 and 1.9 Hz. In contrast, the first-mode frequencies measured from earthquake data are about 0.05 to 0.1 Hz lower than those corresponding to ambient vibration recordings indicating softening of the soil-structure system as amplitudes become larger. The frequencies revert to pre-earthquake levels within five minutes of the Yorba Linda earthquake. Shaking due to strong winds that occurred during the Encino earthquake dominates the frequency decrease, which correlates in time with the duration of the strong winds. The first shear wave recorded from the Encino and Yorba Linda earthquakes takes about 0.4 sec to travel up the 17-story building. ?? 2005, Earthquake Engineering Research Institute.
Yeh, Po Ying; Le, Yevgeniya; Kizhakkedathu, Jayachandran N; Chiao, Mu
2008-10-01
A micromachined vibrating membrane is used to remove adsorbed proteins on a surface. A lead zirconate titanate (PZT) composite (3 x 1 x 0.5 mm) is attached to a silicon membrane (2,000 x 500 x 3 microm) and vibrates in a flexural plate wave (FPW) mode with wavelength of 4,000/3 microm at a resonant frequency of 308 kHz. The surface charge on the membrane and fluid shear stress contribute in minimizing the protein adsorption on the SiO(2) surface. In vitro characterization shows that 57 +/- 10% of the adsorbed bovine serum albumin (BSA), 47 +/- 13% of the immunoglobulin G (IgG), and 55.3~59.2 +/- 8% of the proteins from blood plasma are effectively removed from the vibrating surface. A simulation study of the vibration-frequency spectrum and vibrating amplitude distribution matches well with the experimental data. Potentially, a microelectromechanical system (MEMS)-based vibrating membrane could be the tool to minimize biofouling of in vivo MEMS devices.
Development of a Self-Powered Magnetorheological Damper System for Cable Vibration Control
Directory of Open Access Journals (Sweden)
Zhihao Wang
2018-01-01
Full Text Available A new self-powered magnetorheological (MR damper control system was developed to mitigate cable vibration. The power source of the MR damper is directly harvested from vibration energy through a rotary permanent magnet direct current (DC generator. The generator itself can also serve as an electromagnetic damper. The proposed smart passive system also incorporates a roller chain and sprocket, transforming the linear motion of the cable into the rotational motion of the DC generator. The vibration mitigation performance of the presented self-powered MR damper system was evaluated by model tests with a 21.6 m long cable. A series of free vibration tests of the cable with a passively operated MR damper with constant voltage, an electromagnetic damper alone, and a self-powered MR damper system were performed. Finally, the vibration control mechanisms of the self-powered MR damper system were investigated. The experimental results indicate that the supplemental modal damping ratios of the cable in the first four modes can be significantly enhanced by the self-powered MR damper system, demonstrating the feasibility and effectiveness of the new smart passive system. The results also show that both the self-powered MR damper and the generator are quite similar to a combination of a traditional linear viscous damper and a negative stiffness device, and the negative stiffness can enhance the mitigation efficiency against cable vibration.
Numerical investigation on vibration and noise induced by unsteady flow in an axial-flow pump
Energy Technology Data Exchange (ETDEWEB)
Chen, Eryun; Ma, Zui Ling; Yang, Ai Ling; Nan, Guo Fang [School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai (China); Zhao, Gai Ping [School of Medical Instruments and Food Engineering, University of Shanghai for Science and Technology, Shanghai (China); Li, Guo Ping [Shanghai Marine Equipment Research Institute, Shanghai (China)
2016-12-15
Full-scale structural vibration and noise induced by flow in an axial-flow pump was simulated by a hybrid numerical method. An unsteady flow field was solved by a large eddy simulation-based computational fluid dynamics commercial code, Fluent. An experimental validation on pressure fluctuations was performed to impose an appropriate vibration exciting source. The consistency between the computed results and experimental tests were interesting. The modes of the axial-flow pump were computed by the finite element method. After that, the pump vibration and sound field were solved using a coupled vibro-acoustic model. The numerical results indicated that the the blade-passing frequency was the dominant frequency of the vibration acceleration of the pump. This result was consistent with frequency spectral characteristics of unsteady pressure fluctuation. Finally, comparisons of the vibration acceleration between the computed results and the experimental test were conducted. These comparisons validated the computed results. This study shows that using the hybrid numerical method to evaluate the flow-induced vibration and noise generated in an axial-flow pump is feasible.
Vibrational dynamics of aniline(Ar)1 and aniline(CH4)1 clusters
Nimlos, M. R.; Young, M. A.; Bernstein, E. R.; Kelley, D. F.
1989-11-01
The first excited electronic state (S1) vibrational dynamics of aniline(Ar)1 and aniline(CH4)1 van der Waals (vdW) clusters have been studied using molecular jet and time resolved emission spectroscopic techniques. The rates of intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) as functions of vibrational energy are reported for both clusters. For vibrational energy in excess of the cluster binding energy, both clusters are observed to dissociate. The dispersed emission spectra of these clusters demonstrate that aniline(Ar)1 dissociates to all energetically accessible bare molecule states and that aniline(CH4)1 dissociates selectively to only the bare molecule vibrationless state. The emission kinetics show that in the aniline(Ar)1 case, the initially excited states have nanosecond lifetimes, and intermediate cluster states have very short lifetimes. In contrast, the initially excited aniline(CH4)1 states and other intermediate vibrationally excited cluster states are very short lived (golden rule, and the density of vdW vibrational states is the most important factor in determining the relative [aniline(Ar)1 vs aniline(CH4)1] rates of IVR; (2) IVR among the vdW modes is rapid; and (3) VP rates can be calculated by a restricted vdW mode phase space Rice-Ramsberger-Kassel-Marcus theory. Since the density of vdW states is three orders of magnitude greater for aniline(CH4)1 than aniline(Ar)1 at 700 cm-1, the model predicts that IVR is slow and rate limiting in aniline(Ar)1, whereas VP is slow and rate limiting in aniline(CH4)1. The agreement of these predictions with the experimental results is very good and is discussed in detail.
Engine gearbox fault diagnosis using empirical mode ...
Indian Academy of Sciences (India)
This paper presents engine gearbox fault diagnosis based on empirical mode decomposition (EMD) and Naı¨ve Bayes algorithm. In this study, vibration signals from a gear box are acquired with healthy and different simulated faulty conditions of gear and bearing. The vibration signals are decomposed into a finite number ...
Optimization design of high power ultrasonic circular ring radiator in coupled vibration.
Xu, Long; Lin, Shuyu; Hu, Wenxu
2011-10-01
This paper presents a new high power ultrasonic (HPU) radiator, which consists of a transducer, an ultrasonic horn, and a metal circular ring. Both the transducer and horn in longitudinal vibrations are used to drive a metal circular ring in a radial-axial coupled vibration. This coupled vibration cannot only generate ultrasound in both the radial and axial directions, but also focus the ultrasound inside the circular ring. Except for the radial-axial coupled vibration mode, the third longitudinal harmonic vibration mode with relative large vibration amplitude is also detected, which can be used as another operation mode. Overall, the HPU with these two vibration modes should have good potential to be applied in liquid processing, such as sonochemistry, ultrasonic cleaning, and Chinese herbal medicine extraction. Copyright © 2011 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Robby Christian
2015-03-01
A distinct pattern of phase differences was observed for each of the vibration models. The developed fuzzy logic module demonstrated successful recognition of the vibration frequencies, modes, orders, directions, and phase differences within 0.4 ms for the beam and shell mode vibrations.
Communication: creation of molecular vibrational motions via the rotation-vibration coupling
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Henriksen, Niels Engholm
2015-01-01
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......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...
Fujisaki, Hiroshi; Yagi, Kiyoshi; Kikuchi, Hiroto; Takami, Toshiya; Stock, Gerhard
2017-01-01
Performing comprehensive quantum-chemical calculations, a vibrational Hamiltonian of acetylbenzonitrile is constructed, on the basis of which a quantum-mechanical "tier model" is developed that describes the vibrational dynamics following excitation of the CN stretch mode. Taking into account 36 vibrational modes and cubic and quartic anharmonic couplings between up to three different modes, the tier model calculations are shown to qualitatively reproduce the main findings of the experiments of Rubtsov and coworkers (2011), including the energy relaxation of the initially excited CN mode and the structure-dependent vibrational transport. Moreover, the calculations suggest that the experimentally measured cross-peak among the CN and CO modes does not correspond to direct excitation of the CO normal mode but rather reflects excited low-frequency vibrations that anharmonically couple to the CO mode. Complementary quasiclassical trajectory calculations are found to be in good overall agreement with the quantum calculations.
Single mode variable-sensitivity fiber optic sensors
Murphy, K. A.; Fogg, B. R.; Gunther, M. F.; Claus, R. O.
1992-01-01
We review spatially-weighted optical fiber sensors that filter specific vibration modes from one dimensional beams placed in clamped-free and clamped-clamped configurations. The sensitivity of the sensor is varied along the length of the fiber by tapering circular-core, dual-mode optical fibers. Selective vibration mode suppression on the order of 10 dB was obtained. We describe experimental results and propose future extensions to single mode sensor applications.
Energy Technology Data Exchange (ETDEWEB)
Nojarov, R.; Faessler, A. (Tuebingen Univ. (Germany, F.R.). Inst. fuer Theoretische Physik)
1990-06-01
Realistic microscopic RPA calculations for {sup 156}Gd with a deformed Woods-Saxon mean field, quadrupole-quadrupole, spin-spin and symmetry-restoring residual interactions show that the purely collective scissors mode of the two-rotor model is fragmented over orbital isovector 1{sup +} states, lying at 2-7 MeV. The strongest experimentally observed magnetic dipole state is interpreted as performing a low-collective scissors-type of geometrical motion. This conclusion evolves from the identification of the above state with the strongest RPA excitation, which reproduces well the experimental energy, B(M1) value and (e, e') form factor, has the largest overlap with the scissors state and can be represented as a low-collective scissors type vibration. (orig.).
Hand-Arm vibration assessment among tiller operator
Directory of Open Access Journals (Sweden)
P. Nassiri
2013-08-01
Result: Results of the present study indicated that in all measured situations, exposure to hand arm vibration was higher than the standard limit suggested by Iranian occupational health committee and there was risk of vibration-induced disorders. The maximum exposure to vibration is in plowing ground. Exposure to hand arm vibration in three modes of plowing, transmission and natural, were respectively 16.95, 14.16 and 8.65 meters per second squared. Additionally, in all situations, vibration exposure was highest in the X-axis in comparison with Z- and Y-axes. .Conclusion: This study emphasizes on the need to provide intervention and controlling and managing strategies in order to eliminate or reduce vibration transmitted from tiller to operators hand and arm and also prevent to serious problems including neurovascular disorders, discomfort and white finger syndrome. Meanwhile, more studies are necessary to identify the sources of vibration on different models of tiller.
Rabi-vibronic resonance with large number of vibrational quanta
Glenn, R.; Raikh, M. E.
2011-01-01
We study theoretically the Rabi oscillations of a resonantly driven two-level system linearly coupled to a harmonic oscillator (vibrational mode) with frequency, \\omega_0. We show that for weak coupling, \\omega_p \\ll \\omega_0, where \\omega_p is the polaronic shift, Rabi oscillations are strongly modified in the vicinity of the Rabi-vibronic resonance \\Omega_R = \\omega_0, where \\Omega_R is the Rabi frequency. The width of the resonance is (\\Omega_R-\\omega_0) \\sim \\omega_p^{2/3} \\omega_0^{1/3} ...
Vibrational spectra of nickel metalloporphyrins: An algebraic approach
Indian Academy of Sciences (India)
... molecules. In view of the considerable amount of experimental activity in this area, one needs theoretical models within which to interpret experimental data. Using Lie algebraic method, the vibrational energy levels of nickel metalloporphyrins like Ni(OEP), Ni porphyrin and Ni(TPP) are calculated for 16 vibrational modes.
Resonant vibration control of three-bladed wind turbine rotors
DEFF Research Database (Denmark)
Krenk, Steen; Svendsen, Martin Nymann; Høgsberg, Jan Becker
2012-01-01
Rotors with blades, as in wind turbines, are prone to vibrations due to the flexibility of the blades and the support. In the present paper a theory is developed for active control of a combined set of vibration modes in three-bladed rotors. The control system consists of identical collocated...
Modelling, structural, thermal, optical and vibrational studies of a ...
Indian Academy of Sciences (India)
sis of all the fundamental vibration modes using the VEDA. 4 program [21]. Scaling factors used in this study were taken from literature [22]. In order to take into account the effect of intermolecular interactions on geometrical parameters and vibrational spectroscopy, we have considered an appropriate cluster model built up ...
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.
Anti noise system and method using broadband radiation modes
Berkhoff, Arthur P.
2002-01-01
Anti noise system and method, in particular for suppressing sound radiated from a structure, using a formulation of the most efficiently radiating vibration patterns of a vibrating body, the radiation modes, in the time domain. The radiation modes can be used to arrive at efficient weighting schemes
Coupled rotor/airframe vibration analysis
Sopher, R.; Studwell, R. E.; Cassarino, S.; Kottapalli, S. B. R.
1982-01-01
A coupled rotor/airframe vibration analysis developed as a design tool for predicting helicopter vibrations and a research tool to quantify the effects of structural properties, aerodynamic interactions, and vibration reduction devices on vehicle vibration levels is described. The analysis consists of a base program utilizing an impedance matching technique to represent the coupled rotor/airframe dynamics of the system supported by inputs from several external programs supplying sophisticated rotor and airframe aerodynamic and structural dynamic representation. The theoretical background, computer program capabilities and limited correlation results are presented in this report. Correlation results using scale model wind tunnel results show that the analysis can adequately predict trends of vibration variations with airspeed and higher harmonic control effects. Predictions of absolute values of vibration levels were found to be very sensitive to modal characteristics and results were not representative of measured values.
Vibrational Raman spectra of hydrogen clathrate hydrates from density functional theory
Ramya, K. R.; Venkatnathan, Arun
2013-03-01
Hydrogen clathrate hydrates are promising sources of clean energy and are known to exist in a sII hydrate lattice, which consists of H2 molecules in dodecahedron (512) and hexakaidecahedron (51264) water cages. The formation of these hydrates which occur in extreme thermodynamic conditions is known to be considerably reduced by an inclusion of tetrahydrofuran (THF) in cages of these hydrate lattice. In this present work, we employ the density functional theory with a dispersion corrected (B97-D) functional to characterize vibrational Raman modes in the cages of pure and THF doped hydrogen clathrate hydrates. Our calculations show that the symmetric stretch of the H2 molecule in the 51264H2.THF cage is blueshifted compared to the 51264H2 cage. However, all vibrational modes of water molecules are redshifted which suggest reduced interaction between the H2 molecule and water molecules in the 51264H2.THF cage. The symmetric and asymmetric O-H stretch of water molecules in 512H2, 51264H2, and 51264H2.THF cages are redshifted compared with the corresponding guest free cages due to interactions between encapsulated H2 molecules and water molecules of the cages. The low frequency modes contain contributions from contraction and expansion of water cages and vibration of water molecules due to hydrogen bonding and these modes could possibly play an important role in the formation of the hydrate lattice.
Nonlinear thermoelectric properties of molecular junctions with vibrational coupling
DEFF Research Database (Denmark)
Leijnse, Martin Christian; Wegewijs, M. R.; Flensberg, Karsten
2010-01-01
We present a detailed study of the nonlinear thermoelectric properties of a molecular junction, represented by a dissipative Anderson-Holstein model. A single-orbital level with strong Coulomb interaction is coupled to a localized vibrational mode and we account for both electron and phonon...... conditions, which are found to be qualitatively changed by the presence of the vibrational mode. Based on this study of a generic model system, we discuss the desirable properties of molecular junctions for thermoelectric applications....
A seismic vertical vibrator driven by linear motors
Noorlandt, R.P.; Drijkoningen, G.G.; Schneider, R.M.
2012-01-01
In this paper we present a newly developed vertical seismic vibrator driven by linear motors. We explain the different components the vibrator consists of. We show that the harmonic distortion of the linear-motor vibrator signal is very small. We also show that, without applying a feedback loop on
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.
Investigation of structure and vibrational properties of cyclobutane pirimidine dimer
Directory of Open Access Journals (Sweden)
Petković Milena M.
2013-01-01
Full Text Available We performed a theoretical analysis of the structure and vibrational properties of cyclobutane pyrimidine dimer, which is the main product in a photochemical reaction involving two molecules of 1-methylthymine. Thymine is a pyrimidine base that has the highest yield of the dimerization photoproducts. Methylation in position one was chosen because in this position thymine is linked to sugar in DNA. The calculations were performed at the B3LYP/cc-pVTZ level with a Gaussian program package. All molecular geometries were optimized without symmetry constraints in vacuum and D2O. Vibrational frequencies were calculated in the harmonic approximation. It was shown that there are two stable isomers, CPD(cis-syn and CPD(trans-syn. CPD(trans-syn is more stable both in vacuum and in D2O. By dissolving these molecules in D2O, both structures become more stable, although the stabilization of the less stable isomer is more pronounced due to its larger dipole moment. Thus, the difference in stability of the two isomers in D2O is almost two times lower than in vacuum. Because of the similarity of the two isomers’ structures, the difference in their vibrational spectra is not pronounced. Within the harmonic approximation, there is only a slight difference in the C=O and C-H stretching region. The difference in the N-H stretching region is more pronounced; in the CPD(cis-syn molecule the two bonds vibrate separately, whereas in the CPD(trans-syn the two modes couple, and this coupling results in symmetric and asymmetric N-H stretching. The observation shows that a slight difference in geometry can be reflected in the shape of the infrared spectra. A more detailed analysis of the vibrational properties would involve computation of anharmonic coupling terms, which would enable a more precise determination of the peak positions.
Ding, Zhenyang; Yao, X Steve; Liu, Tiegen; Du, Yang; Liu, Kun; Han, Qun; Meng, Zhuo; Chen, Hongxin
2012-12-17
We present a novel method to achieve a space-resolved long- range vibration detection system based on the correlation analysis of the optical frequency-domain reflectometry (OFDR) signals. By performing two separate measurements of the vibrated and non-vibrated states on a test fiber, the vibration frequency and position of a vibration event can be obtained by analyzing the cross-correlation between beat signals of the vibrated and non-vibrated states in a spatial domain, where the beat signals are generated from interferences between local Rayleigh backscattering signals of the test fiber and local light oscillator. Using the proposed technique, we constructed a standard single-mode fiber based vibration sensor that can have a dynamic range of 12 km and a measurable vibration frequency up to 2 kHz with a spatial resolution of 5 m. Moreover, preliminarily investigation results of two vibration events located at different positions along the test fiber are also reported.
Energy trapping of thickness-extensional modes in thin film bulk acoustic wave filters
Directory of Open Access Journals (Sweden)
Zinan Zhao
2016-01-01
Full Text Available This paper presents the thickness-extensional vibration of a rectangular piezoelectric thin film bulk acoustic wave filter with two pairs of electrodes symmetrically deposited on the center of the zinc oxide film. The two-dimensional scalar differential equations which were first derived to describe in-plane vibration distribution by Tiersten and Stevens are employed. The Ritz method with trigonometric functions as basis functions is used based on a variational formulation developed in our previous paper. Free vibration resonant frequencies and corresponding modes are obtained. The modes may separate into symmetric and antisymmetric ones for such a structurally symmetric filter. Trapped modes with vibrations mainly under the driving electrodes are exhibited. The six corner-type regions of the filter neglected by Tiersten and Stevens for an approximation are taken into account in our analysis. Results show that their approximation can lead to an inaccuracy on the order of dozens of ppm for the fundamental mode, which is quite significant in filter operation and application.
Free-Vibration Analysis of Structures
Gupta, K. K.
1984-01-01
Unified numerical procedure for free-vibration analysis of structures developed and incorporated into EIGSOL computer program. Dynamic response analysis of primary importance in design of wide range of practical structures such as space-craft, buildings, and rotating machineries. Procedure determines natural frequencies and associated modes in structural design.
Numerical investigation of vortex shedding and vortex-induced vibration for flexible riser models
Directory of Open Access Journals (Sweden)
Zheng-Shou Chen
2010-06-01
Full Text Available The numerical study about the vortex-induced vibration and vortex shedding in the wake has been presented. Prior to the numerical simulation of flexible riser systems concerning engineering conditions, efficiency validating of the proposed FSI solution method have been performed. The comparison between numerical simulation and published experimental data shows that the CFD method designed for FSI solution could give acceptable result for the VIV prediction of flexible riser/pipe system. As meaningful study on VIV and vortex shedding mode with the focus on flexible riser model systems, two kinds of typical simulation cases have been carried out. One was related to the simulation of vortex visualization in the wake for a riser model subject to forced oscillation, and another was related to the simulation of fluid-structure interaction between the pipes of coupled multi-assembled riser system. The result from forced oscillation simulation shows that the vortex-induced vibration with high response frequency but small instantaneous vibration amplitude contributes to vortex conformation as much as the forced oscillation with large normalized amplitude does, when the frequency of forced oscillation was relatively high. In the multi-assembled riser systems, it has been found that the external current velocity and the distance between two pipes are the critical factors to determine the vibration state and the steady vibration state emerging in quad-pipe system may be destroyed more easily than dual-pipe system.
The shear mode of multilayer graphene
Tan, P. H.; Han, W. P.; Zhao, W. J.; Wu, Z. H.; Chang, K.; Wang, H.; Wang, Y. F.; Bonini, N.; Marzari, N.; Pugno, N.; Savini, G.; Lombardo, A.; Ferrari, A. C.
2012-04-01
The quest for materials capable of realizing the next generation of electronic and photonic devices continues to fuel research on the electronic, optical and vibrational properties of graphene. Few-layer graphene (FLG) flakes with less than ten layers each show a distinctive band structure. Thus, there is an increasing interest in the physics and applications of FLGs. Raman spectroscopy is one of the most useful and versatile tools to probe graphene samples. Here, we uncover the interlayer shear mode of FLGs, ranging from bilayer graphene (BLG) to bulk graphite, and suggest that the corresponding Raman peak measures the interlayer coupling. This peak scales from ~43 cm-1 in bulk graphite to ~31 cm-1 in BLG. Its low energy makes it sensitive to near-Dirac point quasiparticles. Similar shear modes are expected in all layered materials, providing a direct probe of interlayer interactions.
Features of vibrations of structural inhomogeneous solid media
Karimbaev, Telman; Baishagirov, Khairulla; Nurgaliyeva, Saltanat
2017-09-01
Homogeneous or quasi-homogeneous classic models of deformation are generally used at a mathematical de-scription of deformation composite materials (CM). These theories, however, are limited within initial conditions and do not cover the most important properties of CM: heterogeneity of inertia and elasticity of components, their interaction when deforming, etc. Among the models that complement the classical theories, it is possible to allocate the so-called theory of mixture where CM is considered as two (or more) interacting homogeneous continuum. Therefore, the model increase of motion freedom degrees of the particles of such heterogeneous medium allows each component of CM to show their inertial properties. This leads to the identification of such exclusive features as "bifurcation of fre-quencies", i.e., to description of motion on each form of normal modes at two different frequencies. In the research this phenomenon was investigated by the analysis of biquadratic equation obtained at solving the proper value problem of heterogeneous medium, and was verified by testing the normal mode of frequencies of blades made of CM. In the particular case there was received a simple calculation formula for determination of bar technical frequencies from CM on the basis of the characteristic equation of natural vibrations. In this case the numerical results for the lower forms of the vibration normal mode coincide with the experimental data for homogeneous medium. The characteristic equation contains the introduced physical parameters of the two-component theory; therefore, it describes the other forms of vibration. However, in this case the freedom of structural fluctuations of CM each component is limited to their coupling and interaction, providing continuity and shared the compound materials.
Anti-vibration characteristics of rubberised reinforced concrete beams
Rahman, M; Al-Ghalib, A; Mohammad, FA
2014-01-01
The flexural and vibration properties were examined in order to evaluate the anti-vibration characteristics of rubber modified reinforced concrete beam. The rubberised mixtures were produced by replacing 5, 7.5, and 10 % by mass of the fine aggregate with 1–4 mm scrap truck tyre crumb rubber particles. A series of reinforced concrete beam (1,200 × 135 × 90 mm3) was tested in a free vibration mode and then subsequently in a four point flexural tests. The input and output signals from vibration...
Directory of Open Access Journals (Sweden)
Dae Seung Cho
2014-12-01
Full Text Available A simple and efficient vibration analysis procedure for stiffened panels with openings and arbitrary boundary conditions based on the assumed mode method is presented. Natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange's equations of motion, where Mindlin theory is applied for plate and Timoshenko beam theory for stiffeners. The effect of stiffeners on vibration response is taken into account by adding their strain and kinetic energies to the corresponding plate energies whereas the strain and kinetic energies of openings are subtracted from the plate energies. Different stiffened panels with various opening shapes and dispositions for several combinations of boundary conditions are analyzed and the results show good agreement with those obtained by the finite element analysis. Hence, the proposed procedure is especially appropriate for use in the preliminary design stage of stiffened panels with openings.
Analysis of changes of vibrational properties of water in the presence of disaccharides
Branca, C; Maisano, G; Migliardo, F; Romeo, G; Bennington, S M; Fak, B; Bellocco, E; Lagana', G
2002-01-01
Results of inelastic neutron scattering (INS) measurements performed by the MARI spectrometer (ISIS, UK) on aqueous solutions of sucrose and alpha,alpha-trehalose are reported. To get some insight into the effects of disaccharides on the hydrogen-bond network of water, we investigated the intramolecular O-H stretching modes. The obtained spectra show that, contrary to sucrose, the presence of trehalose affects significantly the pure-water O-H stretching mode. The observed changes can be related to the presence of heavier vibrating units, namely to the higher hydration number of trehalose with respect to sucrose. (orig.)
Siddick, M M; Ackland, G J; Morrison, C A
2006-08-14
We present a methodology for extracting phonon data from ab initio Born-Oppenheimer molecular dynamics calculations of molecular crystals. Conventional ab initio phonon methods based on perturbations are difficult to apply to lattice modes because the perturbation energy is dominated by intramolecular modes. We use constrained molecular dynamics to eliminate the effect of bond bends and stretches and then show how trajectories can be used to isolate and define in particular, the eigenvalues and eigenvectors of modes irrespective of their symmetry or wave vector. This is done by k-point and frequency filtering and projection onto plane wave states. The method is applied to crystalline ammonia: the constrained molecular dynamics allows a significant speed-up without affecting structural or vibrational modes. All Gamma point lattice modes are isolated: the frequencies are in agreement with previous studies; however, the mode assignments are different.
Analysis of Main Types of Vibrations at a Bridge for Passer-Byes
Directory of Open Access Journals (Sweden)
Attila Nagy
2010-10-01
Full Text Available The present paper deals with the dynamic mode analysis in different situations at a bridge projected for passer-byes, with the help of the AxisVM software. From the multiple studied modes of vibrations we are going to present the main vibrations which appear due to the self-weight of the bridge, due to complex forces (different loads, and also due to seismic forces (mode 1 and mode 9.
Tunable Passive Vibration Suppressor
Boechler, Nicholas (Inventor); Dillon, Robert Peter (Inventor); Daraio, Chiara (Inventor); Davis, Gregory L. (Inventor); Shapiro, Andrew A. (Inventor); Borgonia, John Paul C. (Inventor); Kahn, Daniel Louis (Inventor)
2016-01-01
An apparatus and method for vibration suppression using a granular particle chain. The granular particle chain is statically compressed and the end particles of the chain are attached to a payload and vibration source. The properties of the granular particles along with the amount of static compression are chosen to provide desired filtering of vibrations.
Indian Academy of Sciences (India)
We make music by causing strings, membranes, or air columns to vibrate. Engineers design safe structures by control- ling vibrations. I will describe to you a very simple vibrating system and the mathematics needed to analyse it. The ideas were born in the work of Joseph-Louis Lagrange (1736–1813), and I begin by quot-.
1984-01-01
The methods used to determine the lower natural frequencies and their corresponding mode shapes of the NASA-LSS Astromast (Unmodified Test Structure), and the mass integrals associated with the mode shapes are illustrated. The test structure is modeled as a cantilever beam with 91 lumped masses and without the tip mass on the free end of the bram. This uncouples the torsion and bending modes and allows for them to be determined separately. The frequency range was limited to an upper bound of 100 rad/sec (15.92 Hz.). In this range from 0.-100. rad/sec, three bending frequencies and one torsion frequency was found.
H/sub 3/ /sup +/: Ab initio calculation of the vibration spectrum
Energy Technology Data Exchange (ETDEWEB)
Carney, G.D.; Porter, R.N.
1976-11-01
The vibration spectrum of H/sub 3/ /sup +/ is calculated from the representation of a previously reported (J. Chem Phys. 60, 4251 (1974)) ab initio potential-energy surface in a fifth degree Simons--Parr--Finlan (SPF) expansion. Morse- and harmonic-oscillator basis functions are used to describe the motions of the three oscillators and the Harris--Engerholm--Gwinn quadrature technique is used to obtain matrix elements of the Hamiltonian in the basis of vibrational configurations. Our variational method is thus analogous to configuration--interaction calculations for electronic states. The ground state is found to have a zero-point energy of 4345 cm/sup -1/ and a vibrationally averaged geometry of R/sub 1/=R/sub 2/=0.91396 A, theta=60.0012degree, where theta is the angle between the two equivalent bonds. The transition frequencies for the E and A/sub 1/ fundamentals are nu-bar/sub E/=2516 cm/sup -1/ and nu-bar/sub A/=3185 cm/sup -1/ and those for the corresponding first overtones of the bending mode are 2nu-bar/sub E/=5004 +- 4 cm/sup -1/ and 2nu-bar/sub A/=4799 cm/sup -1/. The first overtone of the breathing mode is 6264 cm/sup -1/. The first-excited A/sub 1/ vibration state is metastable with a dipole--radiation lifetime of 3 sec. Transition frequencies, Einstein coefficients, and lifetimes are reported for a total of 21 transitions. Analysis of results for Dunham number and normal-coordinate expansions in comparison with those for SPF expansion show the latter to be superior for ab initio vibrational calculations. A scheme for possible direct measurement of the fundamental A/sub 1/ and E vibrational bands is suggested. (AIP)
Nonlinear Analysis of Cable Vibration of a Multispan Cable-Stayed Bridge under Transverse Excitation
Directory of Open Access Journals (Sweden)
Kun Lin
2014-01-01
Full Text Available The nonlinear vibrations of cable in a multispan cable-stayed bridge subjected to transverse excitation are investigated. The MECS (multielements cable system model, where multielements per cable stay are used, is built up and used to analyze the model properties of the multispan cable-stayed bridges. Then, a simplified two-degrees-of-freedom (2-DOFs model, where the tower or the deck is reduced to a beam, is proposed to analyze the nonlinear dynamic behaviors of the beam and cable. The results of MECS model analysis show that the main tower in the multispan cable-stayed bridge is prone to the transverse vibration, and the local vibration of cables only has a little impact on the frequency values of the global modes. The results of simplified model analysis show that the energy can be transformed between the modes of the beam and cable when the nature frequencies of them are very close. On the other hand, with the transverse excitation changing, the cable can exhibit richer quasi-periodic or chaotic motions due to the nonlinear terms caused by the coupled mode between the beam and cable.
Evolutionary conservation of protein vibrational dynamics.
Maguid, Sandra; Fernandez-Alberti, Sebastian; Echave, Julian
2008-10-01
The aim of the present work is to study the evolutionary divergence of vibrational protein dynamics. To this end, we used the Gaussian Network Model to perform a systematic analysis of normal mode conservation on a large dataset of proteins classified into homologous sets of family pairs and superfamily pairs. We found that the lowest most collective normal modes are the most conserved ones. More precisely, there is, on average, a linear correlation between normal mode conservation and mode collectivity. These results imply that the previously observed conservation of backbone flexibility (B-factor) profiles is due to the conservation of the most collective modes, which contribute the most to such profiles. We discuss the possible roles of normal mode robustness and natural selection in the determination of the observed behavior. Finally, we draw some practical implications for dynamics-based protein alignment and classification and discuss possible caveats of the present approach.
Directory of Open Access Journals (Sweden)
Jiann-Shing Shieh
2012-11-01
Full Text Available Falls are unpredictable accidents and resulting injuries can be serious to the elderly. A preventative solution can be the use of vibration stimulus of white noise to improve the sense of balance. In this work, a pair of vibration shoes were developed and controlled by a touch-type switch which can generate mechanical vibration noise to stimulate the patient’s feet while wearing the shoes. In order to evaluate the balance stability and treatment effect of vibrating insoles in these shoes, multivariate multiscale entropy (MMSE algorithm is applied to calculate the relative complexity index of reconstructed center of pressure (COP signals in antero-posterior and medio-lateral directions by the multivariate empirical mode decomposition (MEMD. The results show that the balance stability of 61.5% elderly subjects is improved after wearing the developed shoes, which is more than 30.8% using multiscale entropy. In conclusion, MEMD-enhanced MMSE is able to distinguish the smaller differences between before and after the use of vibration shoes in both two directions, which is more powerful than the empirical mode decomposition (EMD-enhanced MSE in each individual direction.
Calculation of the vibrational properties of LiMgAs.
Mellouki, A; Bennecer, B; Kalarasse, F
2009-07-29
We have studied the vibrational properties of the filled tetrahedral semiconductor LiMgAs and its binary analog AlAs by using the plane-wave pseudopotential method within density functional theory. The calculated lattice constants for the studied compounds are in good agreement with previous theoretical and experimental results. The phonon dispersion curves and phonon density of states are calculated by using density functional perturbation theory. The sound speeds in different directions are quantitatively similar in LiMgAs and AlAs. The assignment of the zone center modes to the relative motion of the atoms shows that the lower optic modes are due to the Mg-As pair vibrations, while for the upper ones the Li-Mg pair dominates, which is attributed to the smaller Mg atom mass. The longitudinal interatomic force constant of Mg-As is about 66% higher than that of Li-As, showing the relatively high covalency of the former bond.
Calculation of the vibrational properties of LiMgAs
Energy Technology Data Exchange (ETDEWEB)
Mellouki, A; Bennecer, B; Kalarasse, F, E-mail: b_bennacer@hotmail.co [Physics Laboratory at Guelma, Faculty of Science and Engineering, University of Guelma, PO Box 401, Guelma 24000 (Algeria)
2009-07-29
We have studied the vibrational properties of the filled tetrahedral semiconductor LiMgAs and its binary analog AlAs by using the plane-wave pseudopotential method within density functional theory. The calculated lattice constants for the studied compounds are in good agreement with previous theoretical and experimental results. The phonon dispersion curves and phonon density of states are calculated by using density functional perturbation theory. The sound speeds in different directions are quantitatively similar in LiMgAs and AlAs. The assignment of the zone center modes to the relative motion of the atoms shows that the lower optic modes are due to the Mg-As pair vibrations, while for the upper ones the Li-Mg pair dominates, which is attributed to the smaller Mg atom mass. The longitudinal interatomic force constant of Mg-As is about 66% higher than that of Li-As, showing the relatively high covalency of the former bond.
An adaptive left-right eigenvector evolution algorithm for vibration isolation control
Wu, T. Y.
2009-11-01
The purpose of this research is to investigate the feasibility of utilizing an adaptive left and right eigenvector evolution (ALREE) algorithm for active vibration isolation. As depicted in the previous paper presented by Wu and Wang (2008 Smart Mater. Struct. 17 015048), the structural vibration behavior depends on both the disturbance rejection capability and mode shape distributions, which correspond to the left and right eigenvector distributions of the system, respectively. In this paper, a novel adaptive evolution algorithm is developed for finding the optimal combination of left-right eigenvectors of the vibration isolator, which is an improvement over the simultaneous left-right eigenvector assignment (SLREA) method proposed by Wu and Wang (2008 Smart Mater. Struct. 17 015048). The isolation performance index used in the proposed algorithm is defined by combining the orthogonality index of left eigenvectors and the modal energy ratio index of right eigenvectors. Through the proposed ALREE algorithm, both the left and right eigenvectors evolve such that the isolation performance index decreases, and therefore one can find the optimal combination of left-right eigenvectors of the closed-loop system for vibration isolation purposes. The optimal combination of left-right eigenvectors is then synthesized to determine the feedback gain matrix of the closed-loop system. The result of the active isolation control shows that the proposed method can be utilized to improve the vibration isolation performance compared with the previous approaches.
Analysis of Free Pendulum Vibration Absorber Using Flexible Multi-Body Dynamics
Directory of Open Access Journals (Sweden)
Emrah Gumus
2016-01-01
Full Text Available Structures which are commonly used in our infrastructures are becoming lighter with progress in material science. These structures due to their light weight and low stiffness have shown potential problem of wind-induced vibrations, a direct outcome of which is fatigue failure. In particular, if the structure is long and flexible, failure by fatigue will be inevitable if not designed properly. The main objective of this paper is to perform theoretical analysis for a novel free pendulum device as a passive vibration absorber. In this paper, the beam-tip mass-free pendulum structure is treated as a flexible multibody dynamic system and the ANCF formulation is used to demonstrate the coupled nonlinear dynamics of a large deflection of a beam with an appendage consisting of a mass-ball system. It is also aimed at showing the complete energy transfer between two modes occurring when the beam frequency is twice the ball frequency, which is known as autoparametric vibration absorption. Results are discussed and compared with findings of MSC ADAMS. This novel free pendulum device is practical and feasible passive vibration absorber in the mitigation of large amplitude wind-induced vibrations in traffic signal structures.
Vibration analysis of cryocoolers
Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira; Koyama, Tomohiro; Li, Rui
2004-05-01
The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas.
Vibration analysis of cryocoolers
Energy Technology Data Exchange (ETDEWEB)
Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Koyama, Tomohiro; Rui Li [Sumitomo Heavy Industries Ltd., Tokyo (Japan)
2004-05-01
The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas. (Author)
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...
A miniaturized ferrule-top optical cantilever for vibration measurement
Li, J.; Xu, S. M.; Sun, J. N.; Tang, Y. Q.; Dong, F. Z.
2017-04-01
In this paper, we propose techniques to design and fabricate polymer micro-cantilevers for attachment onto the end of standard single mode fibers using laser machining. The polymer cantilever is fabricated by laser micro-machining a sheet of polymer into the required shape and then bonded onto the top of a ceramic ferrule by photo resist as a flat supporting and bonding layer. The dimension of resulting cantilever is 1.2 mm long, 300 μm wide, and 25 μm thick. In this work we describe the fabrication of single sensors, however the process could be scaled to offer a route towards mass production. Cantilever vibration caused by vibration signal are monitored by a DFB laser based phase interrogation system. Proof-of-concept experiments show that the sensor is capable of detecting vibration signal with a frequency range of 0-800Hz. By using thinner polymer sheet and machining longer cantilever, the frequency response range can be extended up to a few kHz.
Analytical calculation of vibrations of electromagnetic origin in electrical machines
McCloskey, Alex; Arrasate, Xabier; Hernández, Xabier; Gómez, Iratxo; Almandoz, Gaizka
2018-01-01
Electrical motors are widely used and are often required to satisfy comfort specifications. Thus, vibration response estimations are necessary to reach optimum machine designs. This work presents an improved analytical model to calculate vibration response of an electrical machine. The stator and windings are modelled as a double circular cylindrical shell. As the stator is a laminated structure, orthotropic properties are applied to it. The values of those material properties are calculated according to the characteristics of the motor and the known material properties taken from previous works. Therefore, the model proposed takes into account the axial direction, so that length is considered, and also the contribution of windings, which differs from one machine to another. These aspects make the model valuable for a wide range of electrical motor types. In order to validate the analytical calculation, natural frequencies are calculated and compared to those obtained by Finite Element Method (FEM), giving relative errors below 10% for several circumferential and axial mode order combinations. It is also validated the analytical vibration calculation with acceleration measurements in a real machine. The comparison shows good agreement for the proposed model, being the most important frequency components in the same magnitude order. A simplified two dimensional model is also applied and the results obtained are not so satisfactory.
Vibration-based monitoring and diagnostics using compressive sensing
Ganesan, Vaahini; Das, Tuhin; Rahnavard, Nazanin; Kauffman, Jeffrey L.
2017-04-01
Vibration data from mechanical systems carry important information that is useful for characterization and diagnosis. Standard approaches rely on continually streaming data at a fixed sampling frequency. For applications involving continuous monitoring, such as Structural Health Monitoring (SHM), such approaches result in high volume data and rely on sensors being powered for prolonged durations. Furthermore, for spatial resolution, structures are instrumented with a large array of sensors. This paper shows that both volume of data and number of sensors can be reduced significantly by applying Compressive Sensing (CS) in vibration monitoring applications. The reduction is achieved by using random sampling and capitalizing on the sparsity of vibration signals in the frequency domain. Preliminary experimental results validating CS-based frequency recovery are also provided. By exploiting the sparsity of mode shapes, CS can also enable efficient spatial reconstruction using fewer spatially distributed sensors. CS can thereby reduce the cost and power requirement of sensing as well as streamline data storage and processing in monitoring applications. In well-instrumented structures, CS can enable continued monitoring in case of sensor or computational failures.
Fuzzy Semiactive Vibration Control of Structures Using Magnetorheological Elastomer
Directory of Open Access Journals (Sweden)
Xuan Bao Nguyen
2017-01-01
Full Text Available In this research, a novel variable stiffness vibration isolator that uses magnetorheological elastomers (MREs accompanied with a fuzzy semiactive vibration control was developed. Firstly, the viscoelastic characteristics of MREs in shear mode were clarified systematically in order to achieve a mathematical basis for the controller development. Secondly, the fuzzy semiactive vibration control with a strategy based on the Lyapunov theory and dynamic characteristic of MREs was proposed for minimizing the movement of the isolator. In the conventional semiactive algorithm, the command applied current of MRE-based isolator is set at either minimum or maximum value which causes high acceleration and jerk peaks periodically, thus leading to the degeneration of the overall system quality. However, the fuzzy semiactive algorithm presented here is able to produce the sufficient applied current and thus viscoelastic force is desirably produced. The effectiveness of the developed isolator was evaluated numerically by MATLAB simulation and experimentally in comparison with the performances of a passive system and a system with on-off type semiactive controller. The results showed that the developed controller was successful in overcoming the disadvantages of conventional on-off semiactive control.
Extraction of the mode shapes of a segmented ship model with a hydroelastic response
Directory of Open Access Journals (Sweden)
Yooil Kim
2015-11-01
Full Text Available The mode shapes of a segmented hull model towed in a model basin were predicted using both the Proper Orthogonal Decomposition (POD and cross random decrement technique. The proper orthogonal decomposition, which is also known as Karhunen-Loeve decomposition, is an emerging technology as a useful signal processing technique in structural dynamics. The technique is based on the fact that the eigenvectors of a spatial coherence matrix become the mode shapes of the system under free and randomly excited forced vibration conditions. Taking advantage of the sim-plicity of POD, efforts have been made to reveal the mode shapes of vibrating flexible hull under random wave ex-citation. First, the segmented hull model of a 400 K ore carrier with 3 flexible connections was towed in a model basin under different sea states and the time histories of the vertical bending moment at three different locations were meas-ured. The measured response time histories were processed using the proper orthogonal decomposition, eventually to obtain both the first and second vertical vibration modes of the flexible hull. A comparison of the obtained mode shapes with those obtained using the cross random decrement technique showed excellent correspondence between the two results.
Communication: Reactivity borrowing in the mode selective chemistry of H + CHD3 → H2 + CD3.
Ellerbrock, Roman; Manthe, Uwe
2017-12-28
Quantum state-resolved reaction probabilities for the H + CHD3 → H2 + CD3 reaction are calculated by accurate full-dimensional quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree approach and the quantum transition state concept. Reaction probabilities of various ro-vibrational states of the CHD3 reactant are investigated for vanishing total angular momentum. While the reactivity of the different vibrational states of CHD3 mostly follows intuitive patterns, an unusually large reaction probability is found for CHD3 molecules triply excited in the CD3 umbrella-bending vibration. This surprising reactivity can be explained by a Fermi resonance-type mixing of the single CH-stretch excited and the triple CD3 umbrella-bend excited vibrational states of CHD3. These findings show that resonant energy transfer can significantly affect the mode-selective chemistry of CHD3 and result in counter-intuitive reactivity patterns.
Vibrational spectroscopy in the electron microscope.
Krivanek, Ondrej L; Lovejoy, Tracy C; Dellby, Niklas; Aoki, Toshihiro; Carpenter, R W; Rez, Peter; Soignard, Emmanuel; Zhu, Jiangtao; Batson, Philip E; Lagos, Maureen J; Egerton, Ray F; Crozier, Peter A
2014-10-09
Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample--that is, for 'aloof' spectroscopy that largely avoids radiation damage.
Yousefi Rizi, Fereshteh; Setarehdan, Seyed Kamaledin; Behnam, Hamid; Alizadeh Sani, Zahra
2014-07-01
This study aims to non-invasively extract the vibrations of the carotid wall and evaluate the changes in the carotid artery wall caused by age and obesity. Such evaluation can increase the possibility of detecting wall stiffness and atherosclerosis in its early stage. In this study, a novel method that uses a phase-tracking method based on the continuous wavelet transform calculates the carotid wall motion from the ultrasound radio frequency signals. To extract the high-frequency components of the wall motion, wall vibration, the empirical mode decomposition was then used. The posterior wall (intima-media) motion and vibration were extracted for 54 healthy volunteers (mean age: 33.87 ± 14.73 years), including 13 overweight subjects (body mass index > 25) and 14 female participants using their radio frequency signals. The results showed that the dominant frequency of the wall vibration correlates with age (r = -0.5887, p analysis further demonstrated that the dominant frequency of the vibration in the radial direction of the carotid wall decreases by age and is lower in overweight subjects. Besides, the peak-to-peak amplitude of the wall vibration showed significant correlations with age (r = -0.5456, p vibrations and systolic/diastolic blood pressure and sex. Our proposed measures were certified using the calculated arterial stiffness indices. The average power spectrum of the elderly subjects'wall motion in the frequency range of the wall vibration (>100 Hz) is decreased more in comparison with the young subjects. Our results revealed that the proposed method may be useful for detecting the stiffness and distortion in the carotid wall that occur prior to wall thickening caused by age as an early-stage atherosclerotic sign. © IMechE 2014.
DEFF Research Database (Denmark)
Sandvik, Kjetil; Laursen, Ditte
2014-01-01
User interaction with radio and television programmes is not a new thing. However, with new cross-media production concepts such as X Factor and Voice, this is changing dramatically. The second-screen logic of these productions encourages viewers, along with TV’s traditional one-way communication...... mode, to communicate on interactive (dialogue-enabling) devices such as laptops, smartphones and tablets. Using the TV show Voice as our example, this article shows how the technological and situational set-up of the production invites viewers to engage in new ways of interaction and communication....... More specifically, the article demonstrates how online comments posted on the day of Voice’s 2012 season finale can be grouped into four basic action types: (1) Invitation to consume content, (2) Request for participation, (3) Request for collaboration and (4) Online commenting. These action types...
Free vibrations of circular cylindrical shells
Armenàkas, Anthony E; Herrmann, George
1969-01-01
Free Vibrations of Circular Cylindrical Shells deals with thin-walled structures that undergo dynamic loads application, thereby resulting in some vibrations. Part I discusses the treatment of problems associated with the propagation of plane harmonic waves in a hollow circular cylinder. In such search for solutions, the text employs the framework of the three-dimensional theory of elasticity. The text explains the use of tables of natural frequencies and graphs of representative mode shapes of harmonic elastic waves bounding in an infinitely long isotropic hollow cylinder. The tables are
Resonant vibration control of wind turbine blades
DEFF Research Database (Denmark)
Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker
2010-01-01
The paper deals with introduction of damping to specific vibration modes of wind turbine blades, using a resonant controller with acceleration feedback. The wind turbine blade is represented by three-dimensional, two-node finite elements in a local, rotating frame of reference. The element....... The efficiency of the resonant controller is demonstrated for a representative turbine blade exposed to turbulent wind loading. It is found that the present explicit tuning procedure yields close to optimal tuning, with very limited modal spill-over and effective reduction of the vibration amplitudes....
Dhote, Sharvari; Yang, Zhengbao; Zu, Jean
2018-01-01
This paper presents the modeling and experimental parametric study of a nonlinear multi-frequency broad bandwidth piezoelectric vibration-based energy harvester. The proposed harvester consists of a tri-leg compliant orthoplanar spring (COPS) and multiple masses with piezoelectric plates attached at three different locations. The vibration modes, resonant frequencies, and strain distributions are studied using the finite element analysis. The prototype is manufactured and experimentally investigated to study the effect of single as well as multiple light-weight masses on the bandwidth. The dynamic behavior of the harvester with a mass at the center is modeled numerically and characterized experimentally. The simulation and experimental results are in good agreement. A wide bandwidth with three close nonlinear vibration modes is observed during the experiments when four masses are added to the proposed harvester. The current generator with four masses shows a significant performance improvement with multiple nonlinear peaks under both forward and reverse frequency sweeps.
Do Scaphoideus titanus (Hemiptera: Cicadellidae) nymphs use vibrational communication?
Chuche, Julien; Thiéry, Denis; Mazzoni, Valerio
2011-07-01
Small Auchenorrhyncha use substrate-borne vibrations to communicate. Although this behaviour is well known in adult leafhoppers, so far no studies have been published on nymphs. Here we checked the occurrence of vibrational communication in Scaphoideus titanus (Hemiptera: Cicadellidae) nymphs as a possible explanation of their aggregative distributions on host plants. We studied possible vibratory emissions of isolated and grouped nymphs, as well as their behavioural responses to vibration stimuli that simulated presence of conspecifics, to disturbance noise, white noise and predator spiders. None of our synthetic stimuli or pre-recorded substrate vibrations from nymphs elicited specific vibration responses and only those due to grooming or mechanical contacts of the insect with the leaf were recorded. Thus, S. titanus nymphs showed to not use species-specific vibrations neither for intra- nor interspecific communication and also did not produce alarm vibrations when facing potential predators. We conclude that their aggregative behaviour is independent from a vibrational communication.
Self-excited and subharmonic vibrations in a pilot rotor
Kumenko, A. I.; Kostyukov, V. N.; Kuzminykh, N. Yu.; Timin, A. V.
2017-08-01
The paper reviews the publications on low-frequency vibration in power plants. It is noted that the regulatory literature poorly defines the issues of rating and diagnosing self-excited and subharmonic vibrations. Analysis of the literature and ISO standards shows that despite the considerable experience gained by specialists in low-frequency vibration control, a number of issues, such as subharmonic resonances and nonlinear properties of complicated multi-seated rotor systems supported by journal bearings, are still understudied and require further calculations and experiments. The paper presents some results obtained in experiments of low-frequency vibrations for a rotor supported by journal bearings and having a residual deflection. The experimental results confirmed the classical hysteresis of self-excited vibrations - the difference in the boundaries of self-excited vibrations during ascent and descent is about 4 Hz. The arears of appearance and disappearance of subharmonic vibrations are shown using the spectral characteristics of vibrations and cascade spectra.
Investigation of Apple Vibration Characteristics Using Finite Element Modal Analysis
Directory of Open Access Journals (Sweden)
R Mirzaei
2013-02-01
Full Text Available The most important quality indicator of fruits is the flesh firmness which is well correlated to their young’s modulus. In this research variation of vibration characteristics (shape modes, natural frequency of apple due to change of material characteristics (density, young's models, Poisson ratio and apple volume was investigated using Finite Element simulation. An image processing technique was used to obtain an unsymmetrical and non-spherical geometric model of apple. The exact three-dimensional shape of the fruit was created by determining the coordinates of apple surface and forming uneven rotational curvatures. Modal analysis with no boundary constraints has been applied. The first 20 Eigen frequencies and the corresponding mode shape were determined. Six rigid body modes possess zero resonant frequency which is related to the degree of freedom of a rigid body in space indicated the validity of finite element model. The modal analysis results showed that resonant frequency increased by increasing young's modulus of the fruit, while it decreased by increasing apple density. First mode torsion has a mean resonant frequency of 584 Hz. Variations of natural frequency due to change in young's modulus, density, and Poisson ratio were 80%, 11% and 4%, respectively. Coefficient of variation of resonant frequency in response to changing young's modulus was 2-3 times of that of density which shows the greatest effect of young modulus changes on natural frequency of fruits. Consequently with determination of fruits' natural frequency, their young modulus and firmness can be estimated.
Entropy in sound and vibration: towards a new paradigm.
Le Bot, A
2017-01-01
This paper describes a discussion on the method and the status of a statistical theory of sound and vibration, called statistical energy analysis (SEA). SEA is a simple theory of sound and vibration in elastic structures that applies when the vibrational energy is diffusely distributed. We show that SEA is a thermodynamical theory of sound and vibration, based on a law of exchange of energy analogous to the Clausius principle. We further investigate the notion of entropy in this context and discuss its meaning. We show that entropy is a measure of information lost in the passage from the classical theory of sound and vibration and SEA, its thermodynamical counterpart.
Vibrational spectrum of CF4 isotopes in an algebraic model
Indian Academy of Sciences (India)
n this paper the stretching vibrational modes of CF4 isotopes are calculated up to first overtone using the one-dimensional vibron model for the first time. The model Hamiltonian so constructed seems to describe the C–F stretching modes accurately using a relatively small set of well-defined parameters.
Videokymography : High-speed line scanning of vocal fold vibration
Svec, JG; Schutte, HK
A digital technique for high-speed visualization of vibration, called videokymography, was developed and applied to the vocal folds. The system uses a modified video camera able to work in two modes: high-speed (nearly 8,000 images/s) and standard (50 images/s in CCIR norm). In the high-speed mode,
Reducing Transmitted Vibration Using Delayed Hysteretic Suspension
Directory of Open Access Journals (Sweden)
Lahcen Mokni
2011-01-01
Full Text Available Previous numerical and experimental works show that time delay technique is efficient to reduce transmissibility of vibration in a single pneumatic chamber by controlling the pressure in the chamber. The present work develops an analytical study to demonstrate the effectiveness of such a technique in reducing transmitted vibrations. A quarter-car model is considered and delayed hysteretic suspension is introduced in the system. Analytical predictions based on perturbation analysis show that a delayed hysteretic suspension enhances vibration isolation comparing to the case where the nonlinear damping is delay-independent.
Calculated low-energy electron-impact vibrational excitation cross sections for CO2 molecule
Laporta, V; Celiberto, R
2016-01-01
Vibrational-excitation cross sections of ground electronic state of carbon dioxide molecule by electron-impact through the CO2-(2\\Pi) shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume decoupling between normal modes and employ the local complex potential model for the treatment of the nuclear dynamics, usually adopted for the electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and comparison with data present in the literature is discussed.
Flexural vibrations and resonance of piezoelectric cantilevers with a nonpiezoelectric extension.
Shen, Zuyan; Shih, Wan Y; Shih, Wei-Heng
2007-10-01
A piezoelectric cantilever (PEC) is a flexural transducer consisting of a piezoelectric layer [e.g., lead zirconate titanate (PZT)] bonded to a nonpiezoelectric layer (e.g., stainless steel). A PEC with a thin nonpiezoelectric extension has two distinctive sections, each with a different thickness, different axial density, and elastic-modulus profiles and has been increasingly used as an in-situ biosensor. It has the advantages of dipping only the nonpiezoelectric extension part in an aqueous solution without electrically insulating the piezoelectric section as well as serving as the bonding pad for receptor immobilization. In this study, we examined the effect of the thin nonpiezoelectric extension on the flexural resonance spectrum and resonance vibration waveforms of PEC; in particular, how the length ratio between the piezoelectric section and the nonpiezoelectric extension section affects the resonance frequencies and resonance peak intensities of PEC. Theoretical resonance frequencies and resonance vibration waveforms were obtained using an analytical transcendental equation we derived by solving the flexural wave equation. Both experimental and theoretical results showed that the two-section structure distorted the flexural vibration waveforms from those of PEC without an extension. As a result, the higher-mode resonance peaks of PEC with a nonpiezoelectric extension could be higher than the first resonance peak due to the two-section structure. With PEC that has a piezoelectric section of 0.25-mm thick PZT bonded to 0.07 mm thick stainless steel of various length 11 and a 0.07-mm thick nonpiezoelectric extension of length l2, we showed that the first-mode-to-second-mode resonance peak intensity ratio had a maximum of 5.6 at l1/l2 = 0.75 and the first-mode-to-second-mode resonance frequency ratio a minimum of 2.2 at 11/12 = 1.8. These findings will undoubtedly help optimize the design and performance of PEC.
Near-threshold vibrational excitation of acetylene by positron impact
de Oliveira, Eliane M.; Lima, Marco A. P.; Sanchez, Sergio D.'A.; Varella, Márcio T. Do N.
2010-01-01
We report vibrational excitation cross sections for C-C and C-H symmetric stretch modes of acetylene by positron impact. The contribution of these infrared inactive modes to the annihilation parameter is also addressed. The Feshbach projection operator approach was employed to vibrationally resolve e+-acetylene scattering phase shifts obtained with the Schwinger multichannel method. The present results point out a virtual state pole at the equilibrium geometry of acetylene that becomes a bound state as either bond is stretched, in qualitative agreement with previous calculations for small hydrocarbons. The vibrational couplings are stronger for the C-C mode, giving rise to a bound state pole within the Franck-Condon region of the vibrational ground state. These bound and virtual states give rise to sharp threshold structures (vibrational resonances) in both the vibrational excitation cross sections and the annihilation parameter (Zeff). We found fair agreement between the present calculations and previously reported e+-acetylene vibrational excitation cross sections.
Vibrational Excitation Can Control Tropospheric Chemistry
National Research Council Canada - National Science Library
Geoffrey Tyndall
2012-01-01
.... However, on page 1066 of this issue, Glowacki et al. show that a strikingly different product distribution can be obtained in the oxidation of acetylene depending on whether the radicals contain high amounts of internal (vibrational...
Piezoelectrically forced vibrations of rectangular SC-cut quartz plates
Lee, P. C. Y.; Lin, W. S.
1998-06-01
A system of two-dimensional first-order equations for piezoelectric crystal plates with general symmetry and with electroded faces was recently deduced from the three-dimensional equations of linear piezoelectricity. Solutions of these equations for AT-cut plates of quartz were shown to give accurate dispersion curves without corrections, and the resonances predicted agree closely with the experimental data of Koga and Fukuyo [I. Koga and H. Fukuyo, J. Inst. Electr. Commun. Eng. Jpn. 36, 59 (1953)] and that of Nakazawa, Horiuchi, and Ito (M. Nakazawa, K. Horiuchi, and H. Ito, Proceedings of the 1990 IEEE Ultrasonics Symposium, pp. 547-555). In this article, these equations are employed to study the free as well as the forced vibrations of doubly rotated quartz plates. Solutions of straight-crested vibrational modes varying in the x1 and x3 directions of SC-cut quartz plates of infinite extent are obtained and from which dispersion curves are computed. Comparison of those dispersion curves with those from the three-dimensional equations shows that the agreement is very close without any corrections. Resonance frequencies for free vibrations and capacitance ratios for piezoelectrically forced vibrations are computed and examined for various length-to-thickness or width-to-thickness ratios of rectangular SC-cut quartz plates. The capacitance ratio as a function of forcing frequency is computed for a rectangular AT-cut quartz and compared with the experimental data of Seikimoto, Watanabe, and Nakazawa (H. Sekimoto, Y. Watanabe, and M. Nakazawa, Proceedings of the 1992 IEEE Frequency Control Symposium, pp. 532-536) and is in close agreement.
Improving Robustness of Tuned Vibration Absorbers Using Shape Memory Alloys
Directory of Open Access Journals (Sweden)
Mohammad H. Elahinia
2005-01-01
Full Text Available A conventional passive tuned vibration absorber (TVA is effective when it is precisely tuned to the frequency of a vibration mode; otherwise, it may amplify the vibrations of the primary system. In many applications, the frequency often changes over time. For example, adding or subtracting external mass on the existing primary system results in changes in the system’s natural frequency. The frequency changes of the primary system can significantly degrade the performance of TVA. To cope with this problem, many alternative TVAs (such as semiactive, adaptive, and active TVAs have been studied. As another alternative, this paper investigates the use of Shape Memory Alloys (SMAs in passive TVAs in order to improve the robustness of the TVAs subject to mass change in the primary system. The proposed SMA-TVA employs SMA wires, which exhibit variable stiffness, as the spring element of the TVA. This allows us to tune effective stiffness of the TVA to adapt to the changes in the primary system's natural frequency. The simulation model, presented in this paper, contains the dynamics of the TVA along with the SMA wire model that includes phase transformation, heat transfer, and the constitutive relations. Additionally, a PID controller is included for regulating the applied voltage to the SMA wires in order to maintain the desired stiffness. The robustness analysis is then performed on both the SMA-TVA and the equivalent passive TVA. For our robustness analysis, the mass of the primary system is varied by ± 30% of its nominal mass. The simulation results show that the SMA-TVA is more robust than the equivalent passive TVA in reducing peak vibrations in the primary system subject to change of its mass.
Directory of Open Access Journals (Sweden)
Xiuting Sun
2016-01-01
Full Text Available The nonlinear effect incurred by time delay in vibration control is investigated in this study via a vibration absorber coupled with a continuous beam structure. The stability of the vibration absorber coupled structure system with time-delay coupling is firstly studied, which provides a general guideline for the potential time delay to be introduced to the system. Then it is shown that there is a specific region for the time delay which can bring bifurcation modes to the dynamic response of the coupling system, and the vibration energy at low frequencies can be transferred or absorbed due to the bifurcation mode and the vibration in the corresponding frequency range is thus suppressed. The nonlinear mechanism of this vibration suppression incurred by the coupling time delay is discussed in detail, which provides a novel and alternative approach to the analysis, design, and control of vibration absorbers in engineering practice.
Conformational and vibrational reassessment of solid paracetamol
Amado, Ana M.; Azevedo, Celeste; Ribeiro-Claro, Paulo J. A.
2017-08-01
This work provides an answer to the urge for a more detailed and accurate knowledge of the vibrational spectrum of the widely used analgesic/antipyretic drug commonly known as paracetamol. A comprehensive spectroscopic analysis - including infrared, Raman, and inelastic neutron scattering (INS) - is combined with a computational approach which takes account for the effects of intermolecular interactions in the solid state. This allows a full reassessment of the vibrational assignments for Paracetamol, thus preventing the propagation of incorrect data analysis and misassignments already found in the literature. In particular, the vibrational modes involving the hydrogen-bonded Nsbnd H and Osbnd H groups are correctly reallocated to bands shifted by up to 300 cm- 1 relatively to previous assignments.
[Raman, FTIR spectra and normal mode analysis of acetanilide].
Liang, Hui-Qin; Tao, Ya-Ping; Han, Li-Gang; Han, Yun-Xia; Mo, Yu-Jun
2012-10-01
The Raman and FTIR spectra of acetanilide (ACN) were measured experimentally in the regions of 3 500-50 and 3 500-600 cm(-1) respectively. The equilibrium geometry and vibration frequencies of ACN were calculated based on density functional theory (DFT) method (B3LYP/6-311G(d, p)). The results showed that the theoretical calculation of molecular structure parameters are in good agreement with previous report and better than the ones calculated based on 6-31G(d), and the calculated frequencies agree well with the experimental ones. Potential energy distribution of each frequency was worked out by normal mode analysis, and based on this, a detailed and accurate vibration frequency assignment of ACN was obtained.
A small-scale study of magneto-rheological track vibration isolation system
Li, Rui; Mu, Wenjun; Zhang, Luyang; Wang, Xiaojie
2016-04-01
A magneto-rheological bearing (MRB) is proposed to improve the vibration isolation performance of a floating slab track system. However, it's difficult to carry out the test for the full-scale track vibration isolation system in the laboratory. In this paper, the research is based on scale analysis of the floating slab track system, from the point view of the dimensionless of the dynamic characteristics of physical quantity, to establish a small scale test bench system for the MRBs. A small scale MRB with squeeze mode using magneto-rheological grease is designed and its performance is tested. The major parameters of a small scale test bench are obtained according to the similarity theory. The force transmissibility ratio and the relative acceleration transmissibility ratio are selected as evaluation index of system similarity. Dynamics of these two similarity systems are calculated by MATLAB experiment. Simulation results show that the dynamics of the prototype and scale models have good similarity. Further, a test bench is built according to the small-scale model parameter analysis. The experiment shows that the bench testing results are consistency with that of theoretical model in evaluating the vibration force and acceleration. Therefore, the small-scale study of magneto-rheological track vibration isolation system based on similarity theory reveals the isolation performance of a real slab track prototype system.
Arivazhagan, M.; Anitha Rexalin, D.
2013-03-01
The FT-IR and FT-Raman vibrational spectra of ninhydrin have been recorded in the range 4000-400 cm-1and 3600-50 cm-1, respectively. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry, vibrational frequencies, atomic charges, dipole moment, rotational constants and several thermodynamic parameters in the ground state are calculated using ab initio HF and density functional B3LYP methods with 6-311++G(d,p) basis set combination. In order to find the most optimized geometry, the energy calculations are carried out for various possible conformers. Keto and enol forms of ninhydrin are also studied. The condensed summary of the principal NBOs shows the occupancy, orbital energy and the qualitative pattern of delocalization interactions of ninhydrin. The calculated HOMO-LUMO energies reveal that charge transfer occurs within the molecule. The predicted first hyperpolarizability also shows that the ninhydrin molecule have good optical quality and nonlinear optical (NLO) behavior. With the help of specific scaling procedures, the observed vibrational wave numbers in FT-IR and FT-Raman spectra are analyzed and assigned to different normal modes of the molecule.
Pazderková, Markéta; Profant, Václav; Hodačová, Jana; Sebestík, Jaroslav; Pazderka, Tomáš; Novotná, Pavlína; Urbanová, Marie; Safařík, Martin; Buděšínský, Miloš; Tichý, Miloš; Bednárová, Lucie; Baumruk, Vladimír; Maloň, Petr
2013-08-22
We investigate amide nonplanarity in vibrational optical activity (VOA) spectra of tricyclic spirodilactams 5,8-diazatricyclo[6,3,0,0(1,5)]undecan-4,9-dione (I) and its 6,6',7,7'-tetradeuterio derivative (II). These rigid molecules constrain amide groups to nonplanar geometries with twisted pyramidal arrangements of bonds to amide nitrogen atoms. We have collected a full range vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra including signals of C-H and C-D stretching vibrations. We report normal-mode analysis and a comparison of calculated to experimental VCD and ROA. The data provide band-to-band assignment and offer a possibility to evaluate roles of constrained nonplanar tertiary amide groups and rigid chiral skeletons. Nonplanarity shows as single-signed VCD and ROA amide I signals, prevailing the couplets expected to arise from the amide-amide interaction. Amide-amide coupling dominates amide II (mainly C'-N stretching, modified in tertiary amides by the absence of a N-H bond) transitions (strong couplet in VCD, no significant ROA) probably due to the close proximity of amide nitrogen atoms. At lower wavenumbers, ROA spectra exhibit another likely manifestation of amide nonplanarity, showing signals of amide V (δ(oop)(N-C) at ~570 cm(-1)) and amide VI (δ(oop)(C'═O) at ~700 cm(-1) and ~650 cm(-1)) vibrations.
Keersmaekers, Lissa; Keustermans, William; De Greef, Daniël; Dirckx, Joris J. J.
2016-06-01
We developed a setup in which the strings of the violin are driven electromagnetically, and the resulting vibration of the instrument is measured with digital stroboscopic holography. A 250mW single mode green laser beam is chopped using an acousto-optic modulator, generating illumination pulses of 2% of the vibration period. The phase of the illumination pulse is controlled by a programmable function generator so that digital holograms can be recorded on a number of subsequent time positions within the vibration phase. From these recordings, the out of plane motion as a function of time is reconstructed in full field. We show results of full-field vibration amplitude and vibration phase maps, and time resolved full-field deformations of the violin back plane. Time resolved measurements show in detail how the deformation of the violin plane changes as a function of time at different frequencies. We found very different behavior under acoustic stimulation of the instrument and when using electromagnetic stimulation of a string. The aim of the work it to gather data which can be used in power flow calculations to study how the energy of the strings is conducted to the body of the violin and eventually is radiated as sound.
Energy Technology Data Exchange (ETDEWEB)
Keersmaekers, Lissa; Keustermans, William, E-mail: william.keustermans@uantwerpen.be; De Greef, Daniël; Dirckx, Joris J. J. [University of Antwerp, Laboratory of Biophysics and Biomedical Physics, Groenenborgerlaan 171, 2020 Antwerp (Belgium)
2016-06-28
We developed a setup in which the strings of the violin are driven electromagnetically, and the resulting vibration of the instrument is measured with digital stroboscopic holography. A 250 mW single mode green laser beam is chopped using an acousto-optic modulator, generating illumination pulses of 2% of the vibration period. The phase of the illumination pulse is controlled by a programmable function generator so that digital holograms can be recorded on a number of subsequent time positions within the vibration phase. From these recordings, the out of plane motion as a function of time is reconstructed in full field. We show results of full-field vibration amplitude and vibration phase maps, and time resolved full-field deformations of the violin back plane. Time resolved measurements show in detail how the deformation of the violin plane changes as a function of time at different frequencies. We found very different behavior under acoustic stimulation of the instrument and when using electromagnetic stimulation of a string. The aim of the work it to gather data which can be used in power flow calculations to study how the energy of the strings is conducted to the body of the violin and eventually is radiated as sound.
Sikdar, Siddhartha; Shah, Jay P; Gilliams, Elizabeth; Gebreab, Tadesse; Gerber, Lynn H
2008-01-01
Myofascial trigger points (MTrPs) are palpable hyperirritable nodules in skeletal muscle that are associated with chronic musculoskeletal pain. The goal of this study was to image MTrPs in the upper trapezius muscle using 2D gray scale ultrasound (US) and vibration sonoelastography (VSE) for differentiating the soft tissue characteristics of MTrPs compared to surrounding muscle. MTrPs appeared as hypoechoeic elliptically-shaped focal regions within the trapezius muscle on 2D US. Audio-frequency vibrations (100-250 Hz) were induced in the trapezius muscle of four volunteers with clinically identifiable MTrPs, and the induced vibration amplitudes were imaged using the color Doppler variance mode, and were further quantified using spectral Doppler analysis. Spectral Doppler analysis showed that vibration amplitudes were 27% lower on average within the MTrP compared to surrounding tissue (p0.05). Color variance imaging consistently detected a focal region of reduced vibration amplitude, which correlated with the hypoechoeic region identified as an MTrP (r =0.76 for area). Real-time 2D US identifies MTrPs, and VSE is feasible for differentiating MTrPs from surrounding tissue. Preliminary findings show that MTrPs are hypoechoeic on 2D US and the relative stiffness of MTrPs can be quantified using VSE. Ultrasound offers a convenient, accessible and low-risk approach for identifying MTrPs and for evaluating clinical observations of palpable, painful nodules.
Model Indepedent Vibration Control
Yuan, Jing
2010-01-01
A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is
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...
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...
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...
Gearbox vibration diagnostic analyzer
1992-01-01
This report describes the Gearbox Vibration Diagnostic Analyzer installed in the NASA Lewis Research Center's 500 HP Helicopter Transmission Test Stand to monitor gearbox testing. The vibration of the gearbox is analyzed using diagnostic algorithms to calculate a parameter indicating damaged components.
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
Energy Technology Data Exchange (ETDEWEB)
Montanini, Roberto, E-mail: rmontanini@unime.it; Quattrocchi, Antonino, E-mail: aquattrocchi@unime.it [University of Messina, Dept. of Engineering, Contrada di Dio, Messina (Italy)
2016-06-28
A cantilever-type resonant piezoelectric generator (RPG) has been designed by gluing a PZT patch working in d{sub 31} mode onto a glass fibre reinforced composite cantilever beam with a discrete mass applied on its free end. The electrical and dynamic behaviour of the RPG prototype has been investigated by carrying out laboratory tests aimed to assess the effect of definite design parameters, specifically the electric resistance load and the excitation frequency. Results showed that an optimum resistance load exists, at which power generation is maximized. Moreover, it has been showed that power generation is strongly influenced by the vibration frequency highlighting that, at resonance, output power can be increased by more than one order of magnitude. Possible applications include inertial resonant harvester for energy recovery from vibrating machines, sea waves or wind flux and self-powering of wireless sensor nodes.
Development of vibrational analysis for detection of antisymmetric shells
Esmailzadeh-Khadem, S; Rezaee, M
2002-01-01
In this paper, vibrational behavior of bodies of revolution with different types of structural faults is studied. Since vibrational characteristics of structures are natural properties of system, the existence of any structural faults causes measurable changes in these properties. Here, this matter is demonstrated. In other words, vibrational behavior of a body of revolution with no structural faults is analyzed by two methods of I) numerical analysis using super sap software, II) Experimental model analysis, and natural frequencies and mode shapes are obtained. Then, different types of cracks are introduced in the structure, and analysis is repeated and the results are compared. Based on this study, one may perform crack detection by measuring the natural frequencies and mode shapes of the samples and comparing with reference information obtained from the vibration analysis of the original structure with no fault.
Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection.
Luo, Dong; Ibrahim, Zainah; Ma, Jianxun; Ismail, Zubaidah; Iseley, David Thomas
2016-12-16
In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering.
Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection
Directory of Open Access Journals (Sweden)
Dong Luo
2016-12-01
Full Text Available In this study, tapered polymer fiber sensors (TPFSs have been employed to detect the vibration of a reinforced concrete beam (RC beam. The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM system in civil engineering.
Efficiency of Nearly Periodic Structures for Mitigation of Ground Vibration
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard; Peplow, Andrew; Bucinskas, Paulius
2017-01-01
be introduced by periodic inclusions or changes to the ground surface geometry. However, for vibration mitigation in the context of real civil-engineering problems related to ground-borne noise from railways, for example, the excitation is not strictly harmonic and a steady state of the response is usually......Periodic structures are known to produce passbands and stopbands for propagation of vibration energy within the frequency domain. Sources vibrating harmonically at a frequency within a passband can lead to propagation of energy through propagating modes over long distances. However, sources...... vibrating at a frequency within a stopband excite only nearfields in the form of attenuating and evanescent modes, and the energy decays with distance. The decay phenomena are due to destructive interference of waves reflected and scattered by interfaces or obstacles placed periodically within or between...
Vibration Analysis Of a Self-Excited Elastic Beam
Directory of Open Access Journals (Sweden)
M. A. Barrón-M
2010-08-01
Full Text Available The vibration behavior and the energy exchange among the normal modes of a clamped-free self-excited elasticbeam are analyzed in this work. To model this kind of beam, the damping term of a van der Pol oscillator is directlyadded to the equation of a linear elastic beam, yielding a single nonlinear partial differential equation. To solve thisequation, a spectral method is employed. Three vibration modes are considered in the analysis, and the values of theself-exciting constant are varied in order to cover from linear to nonlinear vibration behavior. Multiple frequencies ofthe nonlinear beam are determined through the power spectral density of the beam free-end time series. Given thatthis relatively simple model mimics at least in a qualitative way some key issues of the fluid-structure problem, it couldbe potentially useful for fatigue studies and vibration analysis of rotating blades in turbomachinery.
Damping of wind turbine tower vibrations
DEFF Research Database (Denmark)
Brodersen, Mark Laier; Pedersen, Mikkel Melters
Damping of wind turbine vibrations by supplemental dampers is a key ingredient for the continuous use of monopiles as support for offshore wind turbines. The present thesis consists of an extended summary with four parts and appended papers [P1-P4] concerning novel strategies for damping of tower...... in a stroke amplifying brace, which amplifies the displacement across the damper and thus reduces the desired level of damper force. For optimal damping of the two lowest tower modes, a novel toggle-brace concept for amplifying the bending deformation of the tower is presented. Numerical examples illustrate...... that a minimum of three braces in a symmetric circumferential configuration are needed to introduce homogeneous damping in the two lowest vibration modes, independent of the rotor direction. A novel hybrid viscous damper concept is described in the second part. The hybriddamper consists of a viscous dash...
Directory of Open Access Journals (Sweden)
Gang Tang
2016-06-01
Full Text Available In the condition monitoring of roller bearings, the measured signals are often compounded due to the unknown multi-vibration sources and complex transfer paths. Moreover, the sensors are limited in particular locations and numbers. Thus, this is a problem of underdetermined blind source separation for the vibration sources estimation, which makes it difficult to extract fault features exactly by ordinary methods in running tests. To improve the effectiveness of compound fault diagnosis in roller bearings, the present paper proposes a new method to solve the underdetermined problem and to extract fault features based on variational mode decomposition. In order to surmount the shortcomings of inadequate signals collected through limited sensors, a vibration signal is firstly decomposed into a number of band-limited intrinsic mode functions by variational mode decomposition. Then, the demodulated signal with the Hilbert transform of these multi-channel functions is used as the input matrix for independent component analysis. Finally, the compound faults are separated effectively by carrying out independent component analysis, which enables the fault features to be extracted more easily and identified more clearly. Experimental results validate the effectiveness of the proposed method in compound fault separation, and a comparison experiment shows that the proposed method has higher adaptability and practicability in separating strong noise signals than the commonly-used ensemble empirical mode decomposition method.
Hydrogen Bonds and Vibrations of Water on (110) Rutile
Energy Technology Data Exchange (ETDEWEB)
Kumar, Nitin [ORNL; Neogi, Sanghamitra [Pennsylvania State University; Kent, Paul R [ORNL; Bandura, Andrei V. [St. Petersburg State University, St. Petersburg, Russia; Wesolowski, David J [ORNL; Cole, David R [ORNL; Sofo, Jorge O. [Pennsylvania State University
2009-01-01
We study the relation between hydrogen bonding and the vibrational frequency spectra of water on the (110) surface of rutile (α-TiO2) with three structural layers of adsorbed water. Using ab-initio molecular dynamics simulations at 280, 300 and 320K, we find strong, crystallographically-controlled adsorption sites, in general agreement with synchrotron X-ray and classical MD simulations. We demonstrate that these sites are produced by strong hydrogen bonds formed between the surface oxygen atoms and sorbed water molecules. The strength of these bonds is manifested by substantial broadening of the stretching mode vibrational band. The overall vibrational spectrum obtained from our simulations is in good agreement with inelastic neutron scattering experiments. We correlate the vibrational spectrum with different bonds at the surface in order to transform these vibrational measurements into a spectroscopy of surface interactions.
Directory of Open Access Journals (Sweden)
João Carlos Silva Ramos
1999-09-01
Full Text Available We analyse vibrational frequencies of 168 compounds with the AM1 model concerning its experimentally observed gaseous frequencies. Stretching of CH, NH, OH and CO bonds, its related bending frequencies, and the CC frame movements are the studied vibrations. The results show problems with the AM1 vibrational splittings. Often symmetric stretching frequencies, like in CH3, CH2 and NH3, appear switched with the corresponding antisymmetrical ones. Among the studied vibrations many stretchings are overestimated, while bendings oscillate around experimental values. Fluorine stretchings, NN, OO, CH, double and triples CC bonds and cyclic hydrocarbon breathing modes are always overestimated while torsions, umbrella modes and OH/SH stretching are, in average, underestimated. Graphical analysis show that compounds with the lowest molecular masses are the ones with the largest difference to the experimental values. From our results it is not possible to fit confortably the calculated frequencies by a simple linear relationship of the type, n(obs=a*n(AM1. Better aggreement is obtained when different curves are adjusted for the stretching and bending modes, and when a complete linear function is used. Among our studies the best obtained statistical results are for CH, NH and OH. The conclusions obtained in this work will improve the AM1 calculated frequencies leading to accurate results for these properties.
Acoustic vibration problem for dissipative fluids
Lepe, Felipe; Meddahi, Salim; Mora, David; Rodríguez, Rodolfo
2016-01-01
In this paper we analyze a finite element method for solving a quadratic eigenvalue problem derived from the acoustic vibration problem for a heterogeneous dissipative fluid. The problem is shown to be equivalent to the spectral problem for a noncompact operator and athorough spectral characterization is given. The numerical discretization of the problem is based on Raviart-Thomas finite elements. The method is proved to be free of spurious modes and to converge with optimal order. Finally, w...
Optomechanical proposal for monitoring microtubule mechanical vibrations
Czech Academy of Sciences Publication Activity Database
Barzanjeh, Sh.; Salari, V.; Tuszynski, J. A.; Cifra, Michal; Simon, C.
2017-01-01
Roč. 96, č. 1 (2017), č. článku 012404. ISSN 2470-0045 R&D Projects: GA ČR(CZ) GA15-17102S Grant - others:AV ČR(CZ) SAV-15-22 Program:Bilaterální spolupráce Institutional support: RVO:67985882 Keywords : Vibrational modes * Microtubule * Resonance frequencies Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.366, year: 2016
Free Vibration Analysis of Functionally Graded Beams
Khalane Sanjay Anandrao; R. K. Gupta; P. Ramachandran; G. Venkateswara Rao
2012-01-01
Free vibration analysis of functionally graded beams is carried out for various classical boundary conditions. Two separate finite element formulations, one based on Euler-Bernoulli beam theory and other based on Timoshenko beam theory are developed. Principle of virtual work is used to obtain the finite element system of equations. Numerical results are provided to demonstrate the effect of transverse shear on the natural frequencies and mode shapes for different length-to-thickness ratios a...