Localized vibrational modes in diamond
Murzaev, R. T.; Bachurin, D. V.; Korznikova, E. A.; Dmitriev, S. V.
2017-03-01
Discrete breather (DB) or, synonymously, intrinsic localized mode (ILM) is a spatially localized and time-periodic vibrational mode in a defect-free nonlinear lattice, e.g., in a crystal lattice. Standing DB and DB clusters (double and triple) are studied in diamond using molecular dynamics method with the AIREBO interatomic potentials. Single DB can be easily excited by applying initial shifts, A0, to a pair of nearest atoms along the valence bond in the opposite directions. Admissible excitation amplitudes are 0.09 ≤A0 /a0 ≤ 0.12, where a0 is the equilibrium interatomic distance. The core of a DB is a pair of nearest carbon atoms oscillating out-of-phase, while the neighboring atoms oscillate with one order of magnitude lower amplitudes. DB frequency is above the top of the phonon spectrum and increases with the oscillation amplitude. DB lives for more than 100 oscillation periods which approximately corresponds to 2 ps. The range of initial amplitudes and other conditions necessary for the excitation of double and triple DB clusters as well as their lifetime are investigated in detail. Two different mechanisms of energy exchange between DBs in the DB clusters are revealed, which is the main result of the present study. Our results contribute to a deeper understanding of the nonlinear lattice dynamics of diamond.
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.
Study of intrinsic localized vibrational modes in micromechanical oscillator arrays.
Sato, M; Hubbard, B E; English, L Q; Sievers, A J; Ilic, B; Czaplewski, D A; Craighead, H G
2003-06-01
Intrinsic localized modes (ILMs) have been observed in micromechanical cantilever arrays, and their creation, locking, interaction, and relaxation dynamics in the presence of a driver have been studied. The micromechanical array is fabricated in a 300 nm thick silicon-nitride film on a silicon substrate, and consists of up to 248 cantilevers of two alternating lengths. To observe the ILMs in this experimental system a line-shaped laser beam is focused on the 1D cantilever array, and the reflected beam is captured with a fast charge coupled device camera. The array is driven near its highest frequency mode with a piezoelectric transducer. Numerical simulations of the nonlinear Klein-Gordon lattice have been carried out to assist with the detailed interpretation of the experimental results. These include pinning and locking of the ILMs when the driver is on, collisions between ILMs, low frequency excitation modes of the locked ILMs and their relaxation behavior after the driver is turned off.
On the benefits of localized modes in anharmonic vibrational calculations for small molecules
Panek, Pawel T
2016-01-01
Anharmonic vibrational calculations can already be computationally demanding for relatively small molecules. The main bottlenecks lie in the construction of the potential energy surface and in the size of the excitation space in the vibrational configuration interaction (VCI) calculations. To address these challanges, we use localized-mode coordinates to construct potential energy surfaces and perform vibrational self-consistent field (L-VSCF) and L-VCI calculations [P. T. Panek, Ch. R. Jacob, ChemPhysChem 15, 3365 (2014)] for all vibrational modes of two prototypical test cases, the ethene and furan molecules. We find that the mutual coupling between modes is reduced when switching from normal-mode coordinates to localized-mode coordinates. When using such localized-mode coordinates, we observe a faster convergence of the $n$-mode expansion of the potential energy surface. This makes it possible to neglect higher-order contributions in the $n$-mode expansion of the potential energy surface or to approximate ...
New approach to Tolman's electronic parameter based on local vibrational modes.
Kalescky, Robert; Kraka, Elfi; Cremer, Dieter
2014-01-06
Tolman's electronic parameter (TEP) derived from the A1-symmetrical CO stretching frequency of nickel-phosphine-tricarbonyl complexes, R3PNi(CO)3, is brought to a new, improved level by replacing normal with local vibrational frequencies. CO normal vibrational frequencies are always flawed by mode-mode coupling especially with metal-carbon stretching modes, which leads to coupling frequencies as large as 100 cm(-1) and can become even larger when the transition metal and the number of ligands is changed. Local TEP (LTEP) values, being based on local CO stretching force constants rather than normal mode frequencies, no longer suffer from mode coupling and mass effects. For 42 nickel complexes of the type LNi(CO)3, it is shown that LTEP values provide a different ordering of ligand electronic effects as previously suggested by TEP and CEP values. The general applicability of the LTEP concept is demonstrated.
Observation of Locked Intrinsic Localized Vibrational Modes in a Micromechanical Oscillator Array
Sato, Masayuki; Hubbard, B. E.; Sievers, A.J.; Ilic, B.; Czaplewski, D. A.; Craighead, H. G.
2003-01-01
The nonlinear vibrational properties of a periodic micromechanical oscillator array have been measured. For sufficiently large amplitude of the driver, the optic mode of the di-element cantilever array becomes unstable and breaks up into excitations ranging over only a few cells. A driver-induced locking effect is observed to eternalize some of these intrinsic localized modes so that their amplitudes become fixed and the modes become spatially pinned.
Observation of locked intrinsic localized vibrational modes in a micromechanical oscillator array.
Sato, M; Hubbard, B E; Sievers, A J; Ilic, B; Czaplewski, D A; Craighead, H G
2003-01-31
The nonlinear vibrational properties of a periodic micromechanical oscillator array have been measured. For sufficiently large amplitude of the driver, the optic mode of the di-element cantilever array becomes unstable and breaks up into excitations ranging over only a few cells. A driver-induced locking effect is observed to eternalize some of these intrinsic localized modes so that their amplitudes become fixed and the modes become spatially pinned.
Molina, Andrew; Smereka, Peter; Zimmerman, Paul M.
2016-03-01
The use of alternate coordinate systems as a means to improve the efficiency and accuracy of anharmonic vibrational structure analysis has seen renewed interest in recent years. While normal modes (which diagonalize the mass-weighted Hessian matrix) are a typical choice, the delocalized nature of this basis makes it less optimal when anharmonicity is in play. When a set of modes is not designed to treat anharmonicity, anharmonic effects will contribute to inter-mode coupling in an uncontrolled fashion. These effects can be mitigated by introducing locality, but this comes at its own cost of potentially large second-order coupling terms. Herein, a method is described which partially localizes vibrations to connect the fully delocalized and fully localized limits. This allows a balance between the treatment of harmonic and anharmonic coupling, which minimizes the error that arises from neglected coupling terms. Partially localized modes are investigated for a range of model systems including a tetramer of hydrogen fluoride, water dimer, ethene, diphenylethane, and stilbene. Generally, partial localization reaches ˜75% of maximal locality while introducing less than ˜30% of the harmonic coupling of the fully localized system. Furthermore, partial localization produces mode pairs that are spatially separated and thus weakly coupled to one another. It is likely that this property can be exploited in the creation of model Hamiltonians that omit the coupling parameters of the distant (and therefore uncoupled) pairs.
Potential energy and vibrational levels for local modes in water and acetylene
Wright, James S.; Donaldson, D. J.
1985-03-01
MRD Cl calculations are given for the potential energy along local X-H streching modes in water and acetylene, out to near dissolution. The Cl data points are accurately fitted by Morse functions up to half the well depth, but generalized (five-parameter) Morse functions are required to fit the whole range of data. The implications for the traetment of vibrational overtone levels are discussed, including a comparison of several treatments. Agreement with experimentally derived mode spectra is good, as is the agreement with bond distances and thermochemistry.
Hahn, Seungsoo
2016-10-01
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.
Low-temperature heat capacity and localized vibrational modes in natural and synthetic tetrahedrites
Lara-Curzio, E.; May, A. F.; Delaire, O.; McGuire, M. A.; Lu, X.; Liu, Cheng-Yun; Case, E. D.; Morelli, D. T.
2014-05-01
The heat capacity of natural (Cu12-x (Fe, Zn, Ag)x(Sb, As)4S13) and synthetic (Cu12-xZnxSb4S13 with x = 0, 1, 2) tetrahedrite compounds was measured between 2 K and 380 K. It was found that the temperature dependence of the heat capacity can be described using a Debye term and three Einstein oscillators with characteristic temperatures that correspond to energies of ˜1.0 meV, ˜2.8 meV, and ˜8.4 meV. The existence of localized vibrational modes, which are assigned to the displacements of the trigonally coordinated Cu atoms in the structure, is discussed in the context of anharmonicity and its effect on the low lattice thermal conductivity exhibited by these compounds.
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.
Institute of Scientific and Technical Information of China (English)
杨忠志; 李慎敏; 唐敖庆
1995-01-01
By using the quasiclassical trajectory method,changes of normal and local mode vibrationalexcitation energies with time are investigated for XH4 （X=C,Si,Ge） molecules.The results demonstrate thatin a CH4 molecule the coupling between C—H stretching vibration and H—C—H bending vibration is relative-ly large so that the energy transfer is fast;while in SiH4 or GeH4 molecules this coupling is relativelysmall and thus an obvious energy relaxation is observed.This implies that there exists approximate local modevibrations for certain vibrational excitation states.
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.)
Henry, Bryan R.; Gough, Kathleen M.
1983-01-01
The theoretical basis for the local mode model is reviewed. The model is applied to gas phase overtone spectra of aromatic molecules to investigate both substituent induced CH bond length changes and conformationally inequivalent hydrogens. The dynamic implications of the local mode model are discussed.
Localized vibrations of graphene nanoribbons
Savin, A. V.; Kivshar, Yu. S.
2016-08-01
Vibrational modes of graphene nanoribbons are studied. It is demonstrated that in an unstretched graphene nanoribbon, localized vibrations (in the form of breathers) can occur only at the edges. The largest number of localized edge oscillations is expected for the nanoribbons with the armchair structure. Stretching of a nanoribbon can lead to the appearance of new types of strongly localized oscillations. When a nanoribbon is stretched, in its oscillatory spectrum a frequency gap appears in which the frequencies of the localized modes are located. An armchair nanoribbon can support localized modes only at its edges, while a highly stretched zigzag nanoribbon can support them both at the edges and inside the nanoribbon.
Naumov, A. V.; Vainer, Yu. G.; Bauer, M.; Kador, L.
2004-12-01
By means of single molecule (SM) spectroscopy we investigated elementary matrix excitations in a disordered solid, i.e., quasi-localized low-frequency vibrational modes (LFMs). To this end we recorded the spectra of single tetra-tert-butylterrylene molecules embedded in an amorphous polyisobutylene matrix in a temperature region, where the LFM contribution to line broadening dominates. The individual param- eters of LFMs in a polymer glass can be determined from the temperature-dependent linewidths of single molecules. The magnitude of the LFM contribution to SM spectra was obtained by the statistical analysis of the distribution of linewidths of SMs. Pronounced distributions of LFM frequencies and SM-LFM coupling constants were found. This result can be regarded as the first direct experimental proof of the localized nature of LFMs.
Jobson, K.W.; Wells, J.P.R.; Schropp, R.E.I.; Vinh, N.Q.; Dijkhuis, J.I.
2008-01-01
We report on picosecond, time-resolved measurements of the vibrational relaxation and decay pathways of the Si–H and Ge–H stretching modes in hydrogenated amorphous silicon-germanium thin films (a-SiGe:H). It is demonstrated that the decay of both modes has a nonexponential shape, attributable to th
Jobson, K. W.; Wells, J. P. R.; Schropp, R. E. I.; Vinh, N. Q.; Dijkhuis, J. I.
2008-01-01
We report on picosecond, time-resolved measurements of the vibrational relaxation and decay pathways of the Si-H and Ge-H stretching modes in hydrogenated amorphous silicon-germanium thin films (a-SiGe: H). It is demonstrated that the decay of both modes has a nonexponential shape, attributable to t
Vibrational Modes of Trumpet Bells
MOORE, T. R.; KAPLON, J. D.; MCDOWALL, G. D.; MARTIN, K. A.
2002-07-01
We report on an investigation of the normal modes of vibration of the bells of several modern trumpets. We describe the results of experiments using electronic speckle-pattern interferometry to visualize the modal structure and we show that the mode frequencies follow a generalized version of Chladni's law.
Instability of vibrational modes in hexagonal lattice
Korznikova, Elena A.; Bachurin, Dmitry V.; Fomin, Sergey Yu.; Chetverikov, Alexander P.; Dmitriev, Sergey V.
2017-02-01
The phenomenon of modulational instability is investigated for all four delocalized short-wave vibrational modes recently found for the two-dimensional hexagonal lattice with the help of a group-theoretic approach. The polynomial pair potential with hard-type quartic nonlinearity ( β-FPU potential with β > 0) is used to describe interactions between atoms. As expected for the hard-type anharmonic interactions, for all four modes the frequency is found to increase with the amplitude. Frequency of the modes I and III bifurcates from the upper edge of the phonon spectrum, while that of the modes II and IV increases from inside the spectrum. It is also shown that the considered model supports spatially localized vibrational mode called discrete breather (DB) or intrinsic localized mode. DB frequency increases with the amplitude above the phonon spectrum. Two different scenarios of the mode decay were revealed. In the first scenario (for modes I and III), development of the modulational instability leads to a formation of long-lived DBs that radiate their energy slowly until thermal equilibrium is reached. In the second scenario (for modes II and IV) a transition to thermal oscillations of atoms is observed with no formation of DBs.
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.
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...
An Abnormal Vibrational Mode of Torsion Pendulum
Institute of Scientific and Technical Information of China (English)
赵亮; 涂英; 顾邦明; 胡忠坤; 罗俊
2003-01-01
In the experiment for the determination of the gravitational constant G, we found an abnormal vibrational mode of the torsion pendulum. The abnormal mode disappeared as a magnetic damper was introduced to the torsion pendulum system. Our experimental results also show that the magnetic damper can be used to suppress the high frequency vibrational noises to torsion pendulums effectively.
Localized Surface Plasmons in Vibrating Graphene Nanodisks
Wang, Weihua; Mortensen, N Asger; Christensen, Johan
2015-01-01
Localized surface plasmons are confined collective oscillations of electrons in metallic nanoparticles. When driven by light, the optical response is dictated by geometrical parameters and the dielectric environment and plasmons are therefore extremely important for sensing applications. Plasmons 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, such as molecules, for future nanophotonic devices.
Vibration mode analysis of the proton exchange membrane fuel cell stack
Liu, B.; Liu, L. F.; Wei, M. Y.; Wu, C. W.
2016-11-01
Proton exchange membrane fuel cell (PEMFC) stacks usually undergo vibration during packing, transportation, and serving time, in particular for those used in the automobiles or portable equipment. To study the stack vibration response, based on finite element method (FEM), a mode analysis is carried out in the present paper. Using this method, we can distinguish the local vibration from the stack global modes, predict the vibration responses, such as deformed shape and direction, and discuss the effects of the clamping configuration and the clamping force magnitude on vibration modes. It is found that when the total clamping force remains the same, increasing the bolt number can strengthen the stack resistance to vibration in the clamping direction, but cannot obviously strengthen stack resistance to vibration in the translations perpendicular to clamping direction and the three axis rotations. Increasing the total clamping force can increase both of the stack global mode and the bolt local mode frequencies, but will decrease the gasket local mode frequency.
Localized Acoustic Surface Modes
Farhat, Mohamed
2015-08-04
We introduce the concept of localized acoustic surface modes (ASMs). We demonstrate that they are induced on a two-dimensional cylindrical rigid surface with subwavelength corrugations under excitation by an incident acoustic plane wave. Our results show that the corrugated rigid surface is acoustically equivalent to a cylindrical scatterer with uniform mass density that can be represented using a Drude-like model. This, indeed, suggests that plasmonic-like acoustic materials can be engineered with potential applications in various areas including sensing, imaging, and cloaking.
Fuzzy Sliding Mode Control of Plate Vibrations
Manu Sharma; Singh, S. P.
2010-01-01
In this paper, fuzzy logic is meshed with sliding mode control, in order to control vibrations of a cantilevered plate. Test plate is instrumented with a piezoelectric sensor patch and a piezoelectric actuator patch. Finite element method is used to obtain mathematical model of the test plate. A design approach of a sliding mode controller for linear systems with mismatched time-varying uncertainties is used in this paper. It is found that chattering around the sliding surface in the sliding ...
Fuzzy Sliding Mode Control of Plate Vibrations
Directory of Open Access Journals (Sweden)
Manu Sharma
2010-01-01
Full Text Available In this paper, fuzzy logic is meshed with sliding mode control, in order to control vibrations of a cantilevered plate. Test plate is instrumented with a piezoelectric sensor patch and a piezoelectric actuator patch. Finite element method is used to obtain mathematical model of the test plate. A design approach of a sliding mode controller for linear systems with mismatched time-varying uncertainties is used in this paper. It is found that chattering around the sliding surface in the sliding mode control can be checked by the proposed fuzzy sliding mode control approach. With presented fuzzy sliding mode approach the actuator voltage time response has a smooth decay. This is important because an abrupt decay can excite higher modes in the structure. Fuzzy rule base consisting of nine rules, is generated from the sliding mode inequality. Experimental implementation of the control approach verify the theoretical findings. For experimental implementation, size of the problem is reduced using modal truncation technique. Modal displacements as well as velocities of first two modes are observed using real-time kalman observer. Real time implementation of fuzzy logic based control has always been a challenge because a given set of rules has to be executed in every sampling interval. Results in this paper establish feasibility of experimental implementation of presented fuzzy logic based controller for active vibration control.
Optimal parameters uncoupling vibration modes of oscillators
Le, K. C.; Pieper, A.
2017-07-01
This paper proposes a novel optimization concept for an oscillator with two degrees of freedom. By using specially defined motion ratios, we control the action of springs to each degree of freedom of the oscillator. We aim at showing that, if the potential action of the springs in one period of vibration, used as the payoff function for the conservative oscillator, is maximized among all admissible parameters and motions satisfying Lagrange's equations, then the optimal motion ratios uncouple vibration modes. A similar result holds true for the dissipative oscillator having dampers. The application to optimal design of vehicle suspension is discussed.
Optimal parameters uncoupling vibration modes of oscillators
Le, Khanh Chau
2016-01-01
A novel optimization concept for an oscillator with two degrees of freedom is proposed. By using specially defined motion ratios, we control the action of springs and dampers to each degree of freedom of the oscillator. If the potential action of the springs in one period of vibration, used as the payoff function for the conservative oscillator, is maximized, then the optimal motion ratios uncouple vibration modes. The same result holds true for the dissipative oscillator. The application to optimal design of vehicle suspension is discussed.
Intermediate vibrational coordinate localization with harmonic coupling constraints
Hanson-Heine, Magnus W. D.
2016-05-01
Optimized normal coordinates can significantly improve the speed and accuracy of vibrational frequency calculations. However, over-localization can occur when using unconstrained spatial localization techniques. The unintuitive mixtures of stretching and bending coordinates that result can make interpreting spectra more difficult and also cause artificial increases in mode-coupling during anharmonic calculations. Combining spatial localization with a constraint on the coupling between modes can be used to generate coordinates with properties in-between the normal and fully localized schemes. These modes preserve the diagonal nature of the mass-weighted Hessian matrix to within a specified tolerance and are found to prevent contamination between the stretching and bending vibrations of the molecules studied without a priori classification of the different types of vibration present. Relaxing the constraint can also be used to identify which normal modes form specific groups of localized modes. The new coordinates are found to center on more spatially delocalized functional groups than their fully localized counterparts and can be used to tune the degree of vibrational correlation energy during anharmonic calculations.
Vibrational modes of thin silicon membranes
Energy Technology Data Exchange (ETDEWEB)
Waitz, Reimar; Schecker, Olivier; Scheer, Elke [Universitaet Konstanz (Germany)
2010-07-01
Membranes with thicknesses of a few hundred nanometers and macroscopic lateral size are interesting systems to study the mechanical properties of solids on various length scales. In our experiment a piezo is used to couple in vibrations, which can be observed with a white light interferometer using stroboscopic light. This way we image transverse modes of frequencies up to 12 MHz. The influence of strain on the the dispersion relation is investigated by applying a pressure difference between both sides of the membrane.
Transition Mode Shapes in a Vibrating Drop
Vukasinovic, Bojan; Smith, Marc K.; Glezer, Ari
2000-11-01
Vertical, time-periodic vibration of a diaphragm has been used to atomize a primary sessile drop into a fine spray of secondary droplets. The evolution and rate of atomization depend on the coupled dynamics of the sessile drop and the piezoelectrically-driven, low-mass diaphragm. The evolution of the free surface of the drop is characterized by the appearance of a hierarchy of surface waves that we investigated using high-speed imaging and laser vibrometry. At low-driving amplitudes, we see the appearance of time-harmonic axisymmetric waves on the drop's free surface induced by the motion of the contact line. As the vibration amplitude increases, azimuthal waves at the subharmonic of the forcing frequency appear around the periphery of the drop and propagate towards its center. A striking lattice mode emerges upon the breakdown of the axisymmetric wave pattern, followed by the appearance of the highly-agitated free surface of the pre-ejection mode shape. Subsequent to the breakdown of the lattice structure, the frequency of the most energetic mode is a subharmonic of the driving frequency. The complex interaction of the fundamental and subharmonic waves ultimately leads to the breakdown of the free surface and the atomization of the drop.
Automatic determination of important mode-mode correlations in many-mode vibrational wave functions.
König, Carolin; Christiansen, Ove
2015-04-14
We introduce new automatic procedures for parameterizing vibrational coupled cluster (VCC) and vibrational configuration interaction wave functions. Importance measures for individual mode combinations in the wave function are derived based on upper bounds to Hamiltonian matrix elements and/or the size of perturbative corrections derived in the framework of VCC. With a threshold, this enables an automatic, system-adapted way of choosing which mode-mode correlations are explicitly parameterized in the many-mode wave function. The effect of different importance measures and thresholds is investigated for zero-point energies and infrared spectra for formaldehyde and furan. Furthermore, the direct link between important mode-mode correlations and coordinates is illustrated employing water clusters as examples: Using optimized coordinates, a larger number of mode combinations can be neglected in the correlated many-mode vibrational wave function than with normal coordinates for the same accuracy. Moreover, the fraction of important mode-mode correlations compared to the total number of correlations decreases with system size. This underlines the potential gain in efficiency when using optimized coordinates in combination with a flexible scheme for choosing the mode-mode correlations included in the parameterization of the correlated many-mode vibrational wave function. All in all, it is found that the introduced schemes for parameterizing correlated many-mode vibrational wave functions lead to at least as systematic and accurate calculations as those using more standard and straightforward excitation level definitions. This new way of defining approximate calculations offers potential for future calculations on larger systems.
[Bone and joint changes caused by exposure to local vibration].
Kir'iakov, V A; Sukhova, A V; Saarkoppel', L M
2011-01-01
The question to include locomotory disorders into set of symptoms of vibration disease due to local vibration is discussed over years. Studies of clinical symptoms of vibration disease in machinery construction workers demonstrated that bone and joint changes risk depends on intensity of vibration factor and length of exposure to local vibration, as well as on work hardiness. The authors specified X-ray criteria of bone and joint disorders and laboratory markers of bone tissue injury under exposure to local vibration.
Hybrid Optimized and Localized Vibrational Coordinates.
Klinting, Emil Lund; König, Carolin; Christiansen, Ove
2015-11-01
We present a new type of vibrational coordinates denoted hybrid optimized and localized coordinates (HOLCs) aiming at a good set of rectilinear vibrational coordinates supporting fast convergence in vibrational stucture calculations. The HOLCs are obtained as a compromise between the recently promoted optimized coordinates (OCs) and localized coordinates (LCs). The three sets of coordinates are generally different from each other and differ from standard normal coordinates (NCs) as well. In determining the HOLCs, we optimize the vibrational self-consistent field (VSCF) energy with respect to orthogonal transformation of the coordinates, which is similar to determining OCs but for HOLCs we additionally introduce a penalty for delocalization, by using a measure of localization similar to that employed in determining LCs. The same theory and implementation covers OCs, LCs, and HOLCs. It is shown that varying one penalty parameter allows for connecting OCs and LCs. The HOLCs are compared to NCs, OCs, and LCs in their nature and performance as basis for vibrational coupled cluster (VCC) response calculations of vibrational anharmonic energies for a small set of simple systems comprising water, formaldehyde, and ethylene. It is found that surprisingly good results can be obtained with HOLCs by using potential energy surfaces as simple as quadratic Taylor expansions. Quite similar coordinates are found for the already established OCs but obtaining these OCs requires much more elaborate and expensive potential energy surfaces and localization is generally not guaranteed. The ability to compute HOLCs for somewhat larger systems is demonstrated for coumarin and the alanine quadramer. The good agreement between HOLCs and OCs, together with the much easier applicability of HOLCs for larger systems, suggests that HOLCs may be a pragmatically very interesting option for anharmonic calculations on medium to large molecular systems.
Lumped Mass Modeling for Local-Mode-Suppressed Element Connectivity
DEFF Research Database (Denmark)
Joung, Young Soo; Yoon, Gil Ho; Kim, Yoon Young
2005-01-01
for the standard element density method. Local modes are artificial, numerical modes resulting from the intrinsic modeling technique of the topology optimization method. Even with existing local mode controlling techniques, the convergence of the topology optimization of vibrating structures, especially...... experiencing large structural changes, appears to be still poor. In ECP, the nodes of the domain-discretizing elements are connected by zero-length one-dimensional elastic links having varying stiffness. For computational efficiency, every elastic link is now assumed to have two lumped masses at its ends......For successful topology design optimization of crashworthy “continuum” structures, unstable element-free and local vibration mode-free transient analyses should be ensured. Among these two issues, element instability was shown to be overcome if a recently-developed formulation, the element...
Institute of Scientific and Technical Information of China (English)
LI Sheng; ZHAO Deyou
2004-01-01
Modal analysis of structural acoustic radiation from a vibrating structure is discussed using structural vibration modes and acoustic radiation modes based on the quadratic form of acoustic power. The finite element method is employed for discretisizing the structure.The boundary element method and Rayleigh integral are used for modeling the acoustic fluid.It is shown that the power radiated by a single vibration mode is to increase the radiated power and the effect of modal interaction can lead to an increase or a decrease or no change in the radiated power, moreover, control of vibration modes is a good way to reduce both vibration and radiated sound as long as the influence of interaction of vibration modes on sound radiation is insignificant. Stiffeners may change mode shapes of a plate and thus change radiation efficiency of the plate's modes. The CHIEF method is adopted to obtain an acoustic radiation mode formulation without the nonuniqueness difficulty at critical frequencies for three-dimensional structures by using Moore-Penrose inverse. A pulsating cube is involved to verify the formulation. Good agreement is obtained between the numerical and analytical solutions. The shapes and radiation efficiencies of acoustic radiation modes of the cube are discussed. The structural acoustic control using structural vibration modes and acoustic radiation modes are compared and studied.
Institute of Scientific and Technical Information of China (English)
吕岿; 童国平; 毛杰健
2012-01-01
The lattice vibration equations of a diatomic chain with an impurity atom and on-site potential are solved. The analytic solutions of local vibration are obtained. The basic features of the effect of on-site potential on the local vibration are given, and the existence forms of localized mode are also discussed. With the on-site potential existence , it is found that the frequency of the high frequency mode and gap vibration mode increase, the degree of locality get better and the new local vibration mode are generated in the acoustic branch and optical branch, which means the disperse relation of the lattice vibration is effected markedly by the on-site potential.%对具有在位势且含杂质的一维双原子链的晶格振动方程组进行求解,得到了局域振动的解析解,给出了在位势对局域振动影响的基本特征,并简要讨论了局域模的存在形式.通过研究发现,在位势的存在使得杂质产生的高频模和隙模的频率升高,局城性变好,于一定条件下在声学支内和光学支内产生新的局域模,从而显著影响了晶格局城振动的色散关系.
Alippi, A.; Biagioni, A.; Germano, M.; Passeri, D.
2008-06-01
Local probing of nonlinear generation of harmonic vibrations has been done on bone plate samples and the evaluation of the nonlinear term is derived from a limited number of cases of bovine thigh bones, that shows that a low level of nonlinearity is present in bone structures. This is consistent with the assumption that in low level nonlinear samples the distribution of harmonic vibrations matches the corresponding power distribution of the fundamental mode.
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 ha
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.
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.
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.
2016-12-01
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.
Revealing subsurface vibrational modes by atom-resolved damping force spectroscopy.
Ashino, Makoto; Wiesendanger, Roland; Khlobystov, Andrei N; Berber, Savas; Tománek, David
2009-05-15
We propose to use the damping signal of an oscillating cantilever in dynamic atomic force microscopy as a noninvasive tool to study the vibrational structure of the substrate. We present atomically resolved maps of damping in carbon nanotube peapods, capable of identifying the location and packing of enclosed Dy@C_{82} molecules as well as local excitations of vibrational modes inside nanotubes of different diameter. We elucidate the physical origin of damping in a microscopic model and provide quantitative interpretation of the observations by calculating the vibrational spectrum and damping of Dy@C_{82} inside nanotubes with different diameters using ab initio total energy and molecular dynamics calculations.
The normal modes of lattice vibrations of ice XI
Zhang, Peng; Wang, Zhe; Lu, Ying-Bo; Ding, Zheng-Wen
2016-07-01
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.
Local vibrational coherences drive the primary photochemistry of vision
Johnson, Philip J. M.; Halpin, Alexei; Morizumi, Takefumi; Prokhorenko, Valentyn I.; Ernst, Oliver P.; Miller, R. J. Dwayne
2015-12-01
The role of vibrational coherence—concerted vibrational motion on the excited-state potential energy surface—in the isomerization of retinal in the protein rhodopsin remains elusive, despite considerable experimental and theoretical efforts. We revisited this problem with resonant ultrafast heterodyne-detected transient-grating spectroscopy. The enhanced sensitivity that this technique provides allows us to probe directly the primary photochemical reaction of vision with sufficient temporal and spectral resolution to resolve all the relevant nuclear dynamics of the retinal chromophore during isomerization. We observed coherent photoproduct formation on a sub-50 fs timescale, and recovered a host of vibrational modes of the retinal chromophore that modulate the transient-grating signal during the isomerization reaction. Through Fourier filtering and subsequent time-domain analysis of the transient vibrational dynamics, the excited-state nuclear motions that drive the isomerization reaction were identified, and comprise stretching, torsional and out-of-plane wagging motions about the local C11=C12 isomerization coordinate.
Ostojic, Bojana; Schwerdtfeger, Peter; Bunker, Phil; Jensen, Per
2016-06-01
We present the results of ab initio calculations for the lower electronic states of the Group 15 (pnictogen) dihydrides, SbH_2 and BiH_2. For each of these molecules the two lowest electronic states become degenerate at linearity and are therefore subject to the Renner effect. Spin-orbit coupling is also strong in these two heavy-element containing molecules. For the lowest two electronic states of SbH_2, we construct the three dimensional potential energy surfaces and corresponding dipole moment and transition moment surfaces by multi-reference configuration interaction techniques. Including both the Renner effect and spin-orbit coupling, we calculate term values and simulate the rovibrational and rovibronic spectra of SbH_2. Excellent agreement is obtained with the results of matrix isolation infrared spectroscopic studies and with gas phase electronic spectroscopic studies in absorption [1,2]. For the heavier dihydride BiH_2 we calculate bending potential curves and the spin-orbit coupling constant for comparison. For SbH_2 we further study the local mode vibrational behavior and the formation of rovibronic energy level clusters in high angular momentum states. [1] X. Wang, P. F. Souter and L. Andrews, J. Phys. Chem. A 107, 4244-4249 (2003) [2] N. Basco and K. K. Lee, Spectroscopy Letters 1, 13-15 (1968)
Effects of induced vibration modes on droplet sliding phenomena
Mejia, Jose Eduardo; Alvarado, Jorge; Yao, Chun-Wei; Dropwise Condensation Collaboration; Engineered Surfaces Collaboration
2016-11-01
An analytical and experimental investigation has been undertaken to understand the effects of induced vibration modes on droplet sliding phenomena. A mathematical model has been postulated which is capable of estimating accurately droplet sliding angles when using hydrophobic and hydrophilic surfaces. The model, which takes into account equilibrium contact angle, contact angle hysteresis, and droplet volume, has been validated using experimental data. The model has been modified to be able to estimate droplet sliding angle when different modes of vibrations are imposed on the surfaces. Experimental results to date reveal that when resonance modes of vibrations are imposed, the droplet sliding angles decrease considerably. The results also indicate that the modified model can be used effectively to relate imposed resonance frequencies to the critical sliding angle of droplets. LSAMP sponsored NSF Fellowship.
An ultrasonic atomizing device using coupled-mode vibration
Toda, Kohji; Akimura, Yoshikazu
1994-10-01
A small, compact ultrasonic atomizing device is composed of a rectangular piezoelectric ceramic bar and a metal plate with minute holes. The resonance arising from the coupling between two vibration modes in the ceramic bar is used for the effective device operation. The best atomizing occurs when one of the coupled-mode resonant frequencies of the atomizing device is equal to that of the device without the metal vibrating plate. For an efficient power usage a self-oscillation type circuit, composed of the atomizing device as a resonant element and a power amplification transistor, is utilized.
Influence of vibration mode on the screening process
Institute of Scientific and Technical Information of China (English)
Dong Hailin; Liu Chusheng; Zhao Yuemin; Zhao Lala
2013-01-01
The screening of particles with different vibration modes was simulated by means of a 3D discrete element method (3D-DEM).The motion and penetration of the particles on the screen deck were analyzed for linear,circular and elliptical vibration of the screen.The results show that the travel velocity of the particles is the fastest,but the screening efficiency is the lowest,for the linear vibration mode.The circular motion resulted in the highest screening efficiency,but the lowest particle travel velocity.In the steady state the screening efficiency for each mode is seen to increase gradually along the longitudinal direction of the deck.The screening efficiency increment of the circular mode is the largest while the linear mode shows the smallest increment.The volume fraction of near-mesh size particles at the underside is larger than that of small size particles all along the screen deck.Linear screening mode has more nearmesh and small size particles on the first three deck sections,and fewer on the last two sections,compared to the circular or elliptical modes.
Longitudinally Vibrating Elastic Rods with Locally and Non-Locally Reacting Viscous Dampers
Directory of Open Access Journals (Sweden)
Şefaatdin Yüksel
2005-01-01
Full Text Available Eigencharacteristics of a longitudinally vibrating elastic rod with locally and non-locally reacting damping are analyzed. The rod is considered as a continuous system and complex eigenfrequencies are determined as solution of a characteristic equation. The variation of the damping ratios with respect to damper locations and damping coefficients for the first four eigenfrequencies are obtained. It is shown that at any mode of locally or non-locally damped elastic rod, the variation of damping ratio with damper location is linearly proportional to absolute value of the mode shape of undamped system. It is seen that the increasing damping coefficient does not always increase the damping ratio and there are optimal values for the damping ratio. Optimal values for external damping coefficients of viscous dampers and locations of the dampers are presented.
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.
Nuclear Schiff moment and soft vibrational modes
Zelevinsky, Vladimir; Auerbach, Naftali
2008-01-01
The atomic electric dipole moment (EDM) currently searched by a number of experimental groups requires that both parity and time-reversal invariance be violated. According to current theoretical understanding, the EDM is induced by the nuclear Schiff moment. The enhancement of the Schiff moment by the combination of static quadrupole and octupole deformation was predicted earlier. Here we study a further idea of the possible enhancement in the absence of static deformation but in a nuclear system with soft collective vibrations of two types. Both analytical approximation and numerical solution of the simplified problem confirm the presence of the enhancement. We discuss related aspects of nuclear structure which should be studied beyond mean-field and random phase approximations.
Hierarchical heterogeneous glassy dynamics of configuration changes and vibration modes
Kawasaki, Takeshi; Shiba, Hayato; Onuki, Akira
2013-02-01
To understand the quantitative properties of dynamic heterogeneities on glassy particle systems, we use the theoretical scheme of bond-breakage which can detect configuration rearrangements corresponding to the structural relaxations. It is compared with the four-point correlation scheme for the results of binary mixtures with molecular dynamics simulations of two dimensional NVE ensembles. From the comparisons in the systems, we find superpositions of heterogeneity of configuration rearrangements and that induced by low-frequency vibration modes. The bond breakage scheme detects the long-time relaxations without short-time vibrations. The four-point scheme detects the mixed dynamics of the both. We find that the results on four-point scheme are sensitive to the influence of such vibration modes which gives rise to detectable system-size effects in physical properties.
Vibrational memory in quantum localized states
Ajili, Y.; Trabelsi, T.; Denis-Alpizar, O.; Stoecklin, T.; Császár, A. G.; Mogren Al-Mogren, M.; Francisco, J. S.; Hochlaf, M.
2016-05-01
The rovibrational eigenenergy set of molecular systems is a key feature needed to understand and model elementary chemical reactions. A unique class of molecular systems, represented by an 4A'' excited electronic state of the [H,S ,N ] - system comprising several distinct dipole-bound isomers, is found to contain both bent and linear minima separated by relatively small barriers. Full-dimensional nuclear-motion computations performed in Jacobi coordinates using three-dimensional potential energy surfaces describing the stable isomers and the related transition states yield rovibrational eigenstates located both below and above the barriers. The rovibrational wave functions are well localized, regardless of whether the state's energy is below or above the barriers. We also show that the states preserve the memory of the isomeric forms they "originate from," which is signature of a strong vibrational memory effect above isomerization barriers.
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.
Raman spectrum of plutonium dioxide: Vibrational and crystal field modes
Naji, M.; Magnani, N.; Bonales, L. J.; Mastromarino, S.; Colle, J.-Y.; Cobos, J.; Manara, D.
2017-03-01
The Raman spectrum of plutonium dioxide is studied both experimentally and theoretically. Particular attention has been devoted to the identification of high-energy modes at 2110 and 2620 c m-1 , whose attribution has so far been controversial. The temperature dependence of both modes suggests an electronic origin for them. Original crystal field (CF) calculations reported in this work show that these two modes can be respectively assigned to the Γ1→Γ5 and Γ1→Γ3 CF transitions within the I54 manifold. These two modes, together with the only vibrational line foreseen by the group theory for the F m -3 m Pu O2 symmetry—the T2 gPu -O stretching mode observed at 478 c m-1 —can thus be used as a Raman fingerprint of fcc plutonium dioxide.
Localization theory of distributed fiber vibration sensor
Institute of Scientific and Technical Information of China (English)
Weimin Chen; Yuanyuan Xie; Peng Zhang; Lei Lin
2009-01-01
Based on Sagnac interferometer, a simple distributed optical fiber sensing system with sub-loop is pre-sented to monitor the vibration applied on the sensing fiber. By introducing a sub-loop, three output beams of interference with different delay time are gotten. Location of the vibration is analyzed through mathematical-physical equations. The vibration frequency, amplitude, and location are theoretically sim-ulated. The results agree well with the previous experiments.
Sensitive acoustic vibration sensor using single-mode fiber tapers.
Li, Yi; Wang, Xiaozhen; Bao, Xiaoyi
2011-05-01
Optical fiber sensors are a good alternative to piezoelectric devices in electromagnetic sensitive environments. In this study, we reported a fiber acoustic sensor based on single-mode fiber (SMF) tapers. The fiber taper is used as the sensing arm in a Mach-Zehnder interferometer. Benefiting from their micrometer dimensions, fiber tapers have shown higher sensitivities to the acoustic vibrations than SMFs. Under the same conditions, the thinnest fiber taper in this report, with a diameter of 1.7 µm, shows a 20 dB improvement in the signal to noise ratio as compared to that of an SMF. This acoustic vibration sensor can detect the acoustic waves over the frequencies of 30 Hz-40 kHz, which is limited by the acoustic wave generator in experiments. We also discussed the phase changes of fiber tapers with different diameters under acoustic vibrations.
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.
Vibrational modes of ultrathin carbon nanomembrane mechanical resonators
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xianghui, E-mail: zhang@physik.uni-bielefeld.de, E-mail: elke.scheer@uni-konstanz.de; Angelova, Polina; Gölzhäuser, Armin [Fakultät für Physik, Universität Bielefeld, 33615 Bielefeld (Germany); Waitz, Reimar; Yang, Fan; Lutz, Carolin; Scheer, Elke, E-mail: zhang@physik.uni-bielefeld.de, E-mail: elke.scheer@uni-konstanz.de [Fachbereich Physik, Universität Konstanz, 78457 Konstanz (Germany)
2015-02-09
We report measurements of vibrational mode shapes of mechanical resonators made from ultrathin carbon nanomembranes (CNMs) with a thickness of approximately 1 nm. CNMs are prepared from electron irradiation induced cross-linking of aromatic self-assembled monolayers and the variation of membrane thickness and/or density can be achieved by varying the precursor molecule. Single- and triple-layer freestanding CNMs were made by transferring them onto Si substrates with square/rectangular orifices. The vibration of the membrane was actuated by applying a sinusoidal voltage to a piezoelectric disk on which the sample was glued. The vibrational mode shapes were visualized with an imaging Mirau interferometer using a stroboscopic light source. Several mode shapes of a square membrane can be readily identified and their dynamic behavior can be well described by linear response theory of a membrane with negligible bending rigidity. By applying Fourier transformations to the time-dependent surface profiles, the dispersion relation of the transverse membrane waves can be obtained and its linear behavior verifies the membrane model. By comparing the dispersion relation to an analytical model, the static stress of the membranes was determined and found to be caused by the fabrication process.
Vibrational modes of the reed in a reed organ pipe
Huber, T. M.; Collins, B. A.; Pineda, M.; Hendrickson, C.
2003-10-01
We will describe a series of measurements of the vibrational modes of the reed in a reed organ pipe. These measurements were performed using a Polytec PSV-300 scanning vibrometer, which allows the vibrational deflection shape to be determined at any frequency. In addition to blowing the reed pipe in a standard fashion, a mechanical driver was used to excite the reed. Using both excitation sources, a number of deflection shapes were observed including simple cantilever, torsional, and higher-order shapes corresponding to higher-order cantilever and torsional modes. As expected, the observed frequencies of the mechanically driven modes were not integer multiples of the fundamental, and were consistent with theoretical predictions. The reed pipe was also excited in a standard manner using an organ blower. This raised integer multiples of the fundamental frequency as high as 20 kHz within two decades of the velocity amplitude of the fundamental. Torsional and other deflection shapes were present, however nonlinear interactions in the system caused them to be shifted from their mechanically driven frequencies. In some cases, significant vibration was observed in the tuning wire and the section of reed above the tuning wire that was previously considered to be clamped.
Vibrational energy transport in molecules and the statistical properties of vibrational modes
Pandey, Hari Datt; Leitner, David M.
2017-01-01
Statistical properties of the eigenmodes computed for two molecules, dodecane and perfluorododecane, are examined and compared with predictions of random matrix theory. The eigenmode statistics of the heat carrying modes of perfluorododecane correspond to Porter-Thomas statistics, whereas those for dodecane do not. Vibrational energy transport in the two molecules is also computed and found to be diffusive in perfluorododecane but not in dodecane, consistent with recent experiments. The correspondence between eigenmode statistics and vibrational energy transport dynamics in molecules as well as thermalization in molecules are discussed.
Wexler, Adam D; Drusová, Sandra; Woisetschläger, Jakob; Fuchs, Elmar C
2016-06-28
In this experiment liquid water is subject to an inhomogeneous electric field (∇(2)Ea≈ 10(10) V m(2)) using a high voltage (20 kV) point-plane electrode system. Using interferometry it was found that the application of a strong electric field gradient to water generates local changes in the refractive index of the liquid, polarizes the surface and creates a downward moving electro-convective jet. A maximum temperature difference of 1 °C is measured in the immediate vicinity of the point electrode. Raman spectroscopy performed on water reveals an enhancement of the vibrational collective modes (3250 cm(-1)) as well as an increase in the local mode (3490 cm(-1)) energy. This bimodal enhancement indicates that the spectral changes are not due to temperature changes. The intense field gradient thus establishes an excited subpopulation of vibrational oscillators far from thermal equilibrium. Delocalization of the collective vibrational mode spatially expands this excited population beyond the microscale. Hindered rotational freedom due to electric field pinning of molecular dipoles retards the heat flow and generates a chemical potential gradient. These changes are responsible for the observed changes in the refractive index and temperature. It is demonstrated that polar liquids can thus support local non-equilibrium thermodynamic transient states critical to biochemical and environmental processes.
Observation of Protein Structural Vibrational Mode Sensitivity to Ligand Binding
Niessen, Katherine; Xu, Mengyang; Snell, Edward; Markelz, Andrea
2014-03-01
We report the first measurements of the dependence of large-scale protein intramolecular vibrational modes on ligand binding. These collective vibrational modes in the terahertz (THz) frequency range (5-100 cm-1) are of great interest due to their predicted relation to protein function. Our technique, Crystals Anisotropy Terahertz Microscopy (CATM), allows for room temperature, table-top measurements of the optically active intramolecular modes. CATM measurements have revealed surprisingly narrowband features. CATM measurements are performed on single crystals of chicken egg-white lysozyme (CEWL) as well as CEWL bound to tri-N-acetylglucosamine (CEWL-3NAG) inhibitor. We find narrow band resonances that dramatically shift with binding. Quasiharmonic calculations are performed on CEWL and CEWL-3NAG proteins with CHARMM using normal mode analysis. The expected CATM response of the crystals is then calculated by summing over all protein orientations within the unit cell. We will compare the CATM measurements with the calculated results and discuss the changes which arise with protein-ligand binding. This work is supported by NSF grant MRI 2 grant DBI2959989.
RESEARCH ON VIBRATION MODES OF THE CHINESE CHIME STONE
Institute of Scientific and Technical Information of China (English)
Zhang Yan-peng; Hou Xun; Lu Ke-qing; Wu Hong-cai
2000-01-01
Nearfield acoustical holography is a powerful tool for imaging of acoustic sources. In this article, the basic theory treating steady-state acoustic radiation with generalized holography has been discussed. By holographic imaging, the vibration characteristics of irregular objects, the Chinese ancient musical instrument, the one-tone chime stone and the two-tone chime stone provided by the Institute of Archaeology, the Museum of Hubei Province, have been researched. The results show that the ancient chime stone has two main vibration modes, which make up the base of sound produced by the instrument. As for the two-tone chime stone, it is not so long and wide as the single-tone chime stone, but thicker and smoother than the single-tone chime stone. When it is excited at different positions, although it radiates sounds of different frequencies, its vibration modes are similar. This may be related to its dimensions and shape. The research is helpful for studying the sound producing system and the radiated field characteristics of the chime stone.
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 .
Electron acceleration by a localized Bernstein mode
Kumar, Asheel
2017-07-01
An analytical framework for electron acceleration by an axially localized large amplitude electron Bernstein mode in a magnetized plasma is developed. The mode is localized due to plasma density profile or magnetic field profile and could be excited by launching an electron cyclotron wave from out side. A mildly pre-accelerated electron beam of finite Larmor radius resonantly interacts with the mode and gains axial energy as well as transverse energy. The scheme is suitable for producing electron beams of energy upto several MeV.
Reynolds stress of localized toroidal modes
Energy Technology Data Exchange (ETDEWEB)
Zhang, Y.Z. [International Center for Theoretical Studies, Trieste (Italy); Mahajan, S.M. [Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies
1995-02-01
An investigation of the 2D toroidal eigenmode problem reveals the possibility of a new consistent 2D structure, the dissipative BM-II mode. In contrast to the conventional ballooning mode, the new mode is poloidally localized at {pi}/2 (or -{pi}/2), and possesses significant radial asymmetry. The radial asymmetry, in turn, allows the dissipative BM-II to generate considerably larger Reynolds stress as compared to the standard slab drift type modes. It is also shown that a wide class of localized dissipative toroidal modes are likely to be of the dissipative BM-II nature, suggesting that at the tokamak edge, the fluctuation generated Reynolds stress (a possible source of poloidal flow) can be significant.
Azimuthal Asymmetries and Vibrational Modes in Bubble Pinch-off
Schmidt, Laura E
2011-01-01
The pressure-driven inertial collapse of a cylindrical void in an inviscid liquid is an integrable, Hamiltonian system that forms a finite-time singularity as the radius of the void collapses to zero. Here it is shown that when the natural cylindrical symmetry of the void is perturbed azimuthally, the perturbation modes neither grow nor decay, but instead cause constant amplitude vibrations about the leading-order symmetric collapse. Though the amplitudes are frozen in time, they grow relative to the mean radius which is collapsing to zero, eventually overtaking the leading-order symmetric implosion. Including weak viscous dissipation destroys the integrability of the underlying symmetric implosion, and the effect on the stability spectrum is that short-wavelength disturbances are now erased as the implosion proceeds. Introducing a weak rotational flow component to the symmetric implosion dynamics causes the vibrating shapes to spin as the mean radius collapses. The above theoretical scenario is compared to a...
Entanglement Dynamics in Typical Local- and Normal-Mode Molecules
Institute of Scientific and Technical Information of China (English)
HOU Xi-Wen; WAN Ming-Fang; MA Zhong-Qi
2007-01-01
The entanglement dynamics of two stretching vibrations in theoretically typical local- and normal-mode molecules and realistic molecules H2O and SO2 in an algebraic model is studied in terms of the reduced-density linear entropy with initial entangled states taken to be two-mode squeezed vacuum states. It is shown that the behaviour of the entropy in theoretically typical molecules appears to be more regular than that in realistic ones, and that the entropy becomes irregular as the amplitude of two-mode squeezed vacuum states increases. For initial states with a small amplitude, it is demonstrated that the periodicity and the "classical" beat phenomenon of the entropy occur with the beat in theoretically typical molecules being more regular than that in realistic molecules H2O and SO2.
Elastic moduli and vibrational modes in jammed particulate packings
Mizuno, Hideyuki; Saitoh, Kuniyasu; Silbert, Leonardo E.
2016-06-01
When we elastically impose a homogeneous, affine deformation on amorphous solids, they also undergo an inhomogeneous, nonaffine deformation, which can have a crucial impact on the overall elastic response. To correctly understand the elastic modulus M , it is therefore necessary to take into account not only the affine modulus MA, but also the nonaffine modulus MN that arises from the nonaffine deformation. In the present work, we study the bulk (M =K ) and shear (M =G ) moduli in static jammed particulate packings over a range of packing fractions φ . The affine MA is determined essentially by the static structural arrangement of particles, whereas the nonaffine MN is related to the vibrational eigenmodes. We elucidate the contribution of each vibrational mode to the nonaffine MN through a modal decomposition of the displacement and force fields. In the vicinity of the (un)jamming transition φc, the vibrational density of states g (ω ) shows a plateau in the intermediate-frequency regime above a characteristic frequency ω*. We illustrate that this unusual feature apparent in g (ω ) is reflected in the behavior of MN: As φ →φc , where ω*→0 , those modes for ω ω* approach a constant value which results in MN to approach a critical value MN c, as MN-MN c˜ω* . At φc itself, the bulk modulus attains a finite value Kc=KA c-KN c>0 , such that KN c has a value that remains below KA c. In contrast, for the critical shear modulus Gc, GN c and GA c approach the same value so that the total value becomes exactly zero, Gc=GA c-GN c=0 . We explore what features of the configurational and vibrational properties cause such a distinction between K and G , allowing us to validate analytical expressions for their critical values.
Damage Identification Dependence on Number of Vibration Modes Using Mode Shape Curvature Squares
Janeliukstis, R.; Rucevskis, S.; Wesolowski, M.; Chate, A.
2016-09-01
In this paper a damage identification algorithm for multiple damage sites based on mode shape curvature square method of vibration mode shapes in aluminium beam is reported. The required mode shape curvature of a healthy structure was obtained via interpolation of mode shape curvature of a damaged structure with Fourier series functions of different orders. Algorithm employed calculations of standardized damage index distributions over beam coordinate. Finite element simulations of proposed methodology involving various artificial noise levels and reduction of mode shape input data points were validated on the damage identification results of experimentally measured mode shapes which were measured using scanning laser vibrometer. Results show that the algorithm is capable of capturing the areas of damage. The term called damage estimate reliability was introduced in terms of likelihood of the chosen approximation function to capture the location of damage.
Mode localized MEMS transducers with voltage-controlled linear coupling
Manav, M.; Srikantha Phani, A.; Cretu, E.
2017-05-01
Recent studies have demonstrated mode localized resonant micro-electro-mechanical systems (MEMS) sensing devices with orders of magnitude improvement in sensitivity. Avoided crossings or eigenvalue veering is the physical mechanism exploited to achieve the enhancement in sensitivity of devices operating either in vacuum or in air. The mode localized MEMS devices are typically designed to be symmetric and use gap-varying electrostatic springs to couple motions of two or more resonators. The role of asymmetry in the design of devices and its influence on sensitivity is not fully understood. Furthermore, gap-varying electrostatic springs suffer from nonlinearities when gap variation between coupling plates becomes large due to mode localization, imposing limitations on the device performance. To address these shortcomings, this contribution has two principal objectives. The first objective is to critically assess the role of asymmetry in the device design and operation. We show, based on energy analysis, that carefully designed asymmetry in devices can lead to even higher sensitivities than reported in the literature. Our second objective is to design and implement linear, tunable, electrostatic springs, using shaped combs, which allow large vibration amplitudes of resonators thereby increasing the signal to noise ratio. We experimentally demonstrate linear electrostatic coupling in a two oscillator device. Our study suggests that a future avenue for progress in the mode localized resonant sensing technology is to combine asymmetric devices with tunable linear coupling designs.
Selective gating to vibrational modes through resonant X-ray scattering
Couto, Rafael C.; Cruz, Vinícius V.; Ertan, Emelie; Eckert, Sebastian; Fondell, Mattis; Dantz, Marcus; Kennedy, Brian; Schmitt, Thorsten; Pietzsch, Annette; Guimarães, Freddy F.; Ågren, Hans; Gel'Mukhanov, Faris; Odelius, Michael; Kimberg, Victor; Föhlisch, Alexander
2017-01-01
The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.
Light scattering from acoustic vibrational modes in confined structures
Bandhu, Rudra Shyam
The acoustic vibrational modes and their light scattering intensities in confined structures such as supported films, double layer free-standing membrane and sub-micron sized wires on a free-standing membrane have been studied using Brillouin Light Scattering (BLS). Standing wave type acoustic phonons were recently observed in supported thin films of silicon oxy-nitride. We build upon this finding to study the acoustic modes in thin zinc selenide (ZnSe) films on gallium arsenide (GaAs). The surprising behaviour of the Brillouin intensities of the standing wave modes in ZnSe are explained in terms of interference of the elasto-optic scattering amplitudes from the film and substrate. Numerical calculations of the scattering cross-section, which takes into account ripple and elasto-optic scattering mechanism, agrees well with the experimental data. Light scattering studies of standing wave type modes in free-standing polymethyl methacrylate (PMMA) layer on Si3N4 were carried out. In these bilayer structures PMMA is much softer than Si3N 4, a property that leads to confinement of low frequency modes associated with the PMMA layer to within its boundaries. In addition, the flexural and the dilatational modes from the Si3N4 layer are observed and are found to hybridize with the standing wave modes from the PMMA layer. Our study of phonon modes in PMMA wires supported on a free-standing Si3N4 membrane extends our work on free-standing double layer membranes. In recent years there is much interest in the study of phonon modes in nano-scale structures such as wires or dots. Although much theoretical work has been carried out in this direction, no experiments exist that explore the dispersion of the phonon modes in such structures. Brillouin Light scattering is ideally suited for studying phonons in such reduced dimensions and our work represents the first effort in this direction. The spectra reveal modes which are quantized both along the width, as well along the thickness
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.
Localized modes in nonlinear binary kagome ribbons
Belicev, P. P.; Gligoric, G.; Radosavljevic, A; Maluckov, A.; Stepic, M.; Vicencio, R. A.; Johansson, Magnus
2015-01-01
The localized mode propagation in binary nonlinear kagome ribbons is investigated with the premise to ensure controlled light propagation through photonic lattice media. Particularity of the linear system characterized by the dispersionless flat band in the spectrum is the opening of new minigaps due to the "binarism." Together with the presence of nonlinearity, this determines the guiding mode types and properties. Nonlinearity destabilizes the staggered rings found to be nondiffracting in t...
Upper extremity neuromotor dysfunction caused by local vibration
Directory of Open Access Journals (Sweden)
O. A. Shavlovskaya
2015-01-01
Full Text Available Vibration disease (VD (pneumatic hammer disease is a leader among occupational diseases. The prolonged use of vibrating tools is a high occupational health risk. The clinical picture of VD caused by local vibration includes sensorineural and upper extremity locomotor impairments that are polymorphic, polysyndromic, and not always specific. The International List of Occupational Diseases (2010 defines VD using the terms «vibration-induced white finger» (VWF and «hand-arm vibration syndrome» (HAVS. VWF as a manifestation of secondary Raynaud’s syndrome is the most noticeable vascular injury in HAVS. According to the recommendations of the International Labor Organization (2011 and the order of the Ministry of Health of Russia (2012, the clinical manifestations of local vibration include upper extremity polyneuropathy, secondary Raynaud’s phenomenon, and carpal tunnel syndrome (CTS. The paper considers approaches to differentially diagnosing CTS and HAVS, primary and secondary Raynaud’s syndrome, as well as clinical, laboratory, and electrodiagnostic studies. Prolonged exposure to vibration may affect the large myelinated (Ab fibers responsible for tactile touch, pressure, and vibration. Patients with VWF are frequently found to have hyperresponsiveness of the sympathetic nervous system, which affects digital vascular tone and appears as lower fingertip skin temperature. The paper discusses some possible mechanisms for the pathogenesis of vibration neuropathy (e.g. demyelinationof peripheral nerve fiber, as well as the involvement of plasma endothelin-1 in vascular response to cold as one of the components of the pathogenesis of vascular disorders. The central nervous system (cortical reorganization, plasticity phenomenon is believed to be implicated in the development and maintenance of vibration neuropathy.
A novel vibration mode testing method for cylindrical resonators based on microphones.
Zhang, Yongmeng; Wu, Yulie; Wu, Xuezhong; Xi, Xiang; Wang, Jianqiu
2015-01-16
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.
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.
Nonlinear magnetohydrodynamics of edge localized mode precursors
Energy Technology Data Exchange (ETDEWEB)
Guo, Z. B., E-mail: guozhipku@gmail.com [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing (China); WCI Center for Fusion Theory, NFRI, Gwahangno 113, Yusung-gu, Daejeon 305-333 (Korea, Republic of); Wang, Lu [SEEE, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Wang, X. G. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing (China)
2015-02-15
A possible origin of edge-localized-mode (ELM) precursors based on nonlinear ideal peeling-ballooning mode is reported. Via nonlinear variational principle, a nonlinear evolution equation of the radial displacement is derived and solved, analytically. Besides an explosive growth in the initial nonlinear phase, it is found that the local displacement evolves into an oscillating state in the developed nonlinear phase. The nonlinear frequency of the ELM precursors scales as ω{sub pre}∼x{sup 1/3}ξ{sup ^}{sub ψ,in}{sup 2/3}n, with x position in radial direction, ξ{sup ^}{sub ψ,in} strength of initial perturbation, and n toroidal mode number.
Localized modes in nonlinear photonic kagome nanoribbons
Energy Technology Data Exchange (ETDEWEB)
Molina, Mario I., E-mail: mmolina@uchile.cl [Departamento de Física, MSI – Nucleus for Advanced Optics, and Center for Optics and Photonics (CEFOP), Facultad de Ciencias, Universidad de Chile, Santiago (Chile)
2012-10-01
We examine localization of light in nonlinear (Kerr) kagome lattices in the shape of narrow strips of varying width. For the narrowest ribbon, the band structure features a flat band leading to linear dynamical trapping of an initially localized excitation. We also find a geometry-induced bistability of the nonlinear modes as the width of the strip is changed. A crossover from one to two dimensions localization behavior is observed as the width is increased, attaining two-dimensional behavior for relatively narrow ribbons.
Seyf, Hamid Reza; Henry, Asegun
2017-01-01
The solutions to the equations of motions for the atoms in homogenous crystalline solids result in plane wave modulated velocity fields for the normal modes of vibration. However, when a system lacks periodicity, either compositional or structural, the normal modes of vibration can still be determined, but the solutions take on different characters and many modes may be non-plane wave modulated. Previous work has classified the types of vibrations into three primary categories, namely propagons, diffusons and locons. Localized modes can be distinguished by calculation of participation ratio while distinguishing between propagons and diffusons is challenging because both are spatially delocalized. We present a new method that quantifies the extent to which a mode's character corresponds to a propagating mode, e.g., with a plane wave modulation. This then allows for clear and quantitative distinctions between propagons and diffusons. By resolving this issue quantitatively, one can now automate the classification of modes for any arbitrary structure subject to a single constraint that the atoms must vibrate stably around their respective equilibrium sites.
Acute effects of resistance training with local vibration.
Couto, B P; Silva, H R; Filho, A G; da Silveira Neves, S R; Ramos, M G; Szmuchrowski, L A; Barbosa, M P
2013-09-01
The aim of this study was to verify the acute effects of the application of local vibration on upper limbs during resistance training on the number of maximum repetitions, metabolic and hormonal responses. 32 volunteers performed a maximum voluntary contraction test during a lat pulldown exercise. After the test, all volunteers underwent one conventional resistance training session and one resistance training session with local vibration. In both interventions, volunteers performed 4 sets with the highest possible number of repetitions of the lat pulldown exercise at 55% of maximum voluntary contraction. During the vibratory resistance training intervention, vibration was locally applied (20-Hz and 12-mm). During the conventional resistance training, volunteers performed the same procedures without vibration. Blood samples were taken at each experimental session before and 5 min after the end of each intervention. No significant differences were observed in number of maximum repetitions between the series of vibratory and conventional training. Serum testosterone, cortisol and lactate were significantly increased after 2 interventions. Vibratory resistance training induced greater increases in testosterone and lactate concentrations. No significant changes were found in creatine kinase, creatinine or urea concentration. These data indicate that local vibration increases the metabolic and anabolic response to the resistance training, without changing the training volume. © Georg Thieme Verlag KG Stuttgart · New York.
Vibration modes of 3n-gaskets and other fractals
Energy Technology Data Exchange (ETDEWEB)
Bajorin, N; Chen, T; Dagan, A; Emmons, C; Hussein, M; Khalil, M; Mody, P; Steinhurst, B; Teplyaev, A [Department of Mathematics, University of Connecticut, Storrs CT 06269 (United States)
2008-01-11
We rigorously study eigenvalues and eigenfunctions (vibration modes) on the class of self-similar symmetric finitely ramified fractals, which include the Sierpinski gasket and other 3n-gaskets. We consider the classical Laplacian on fractals which generalizes the usual one-dimensional second derivative, is the generator of the self-similar diffusion process, and has possible applications as the quantum Hamiltonian. We develop a theoretical matrix analysis, including analysis of singularities, which allows us to compute eigenvalues, eigenfunctions and their multiplicities exactly. We support our theoretical analysis by symbolic and numerical computations. Our analysis, in particular, allows the computation of the spectral zeta function on fractals and the limiting distribution of eigenvalues (i.e., integrated density of states). We consider such examples as the level-3 Sierpinski gasket, a fractal 3-tree, and the diamond fractal.
Coupled mode parametric resonance in a vibrating screen model
Slepyan, Leonid I
2013-01-01
We consider a simple dynamic model of the vibrating screen operating in the parametric resonance (PR) mode. This model was used in the course of designing and setting of such a screen in LPMC. The PR-based screen compares favorably with conventional types of such machines, where the transverse oscillations are excited directly. It is characterized by larger values of the amplitude and by insensitivity to damping in a rather wide range. The model represents an initially strained system of two equal masses connected by a linearly elastic string. Self-equilibrated, longitudinal, harmonic forces act on the masses. Under certain conditions this results in transverse, finite-amplitude oscillations of the string. The problem is reduced to a system of two ordinary differential equations coupled by the geometric nonlinearity. Damping in both the transverse and longitudinal oscillations is taken into account. Free and forced oscillations of this mass-string system are examined analytically and numerically. The energy e...
Piezoelectric rotational mixer based on a first bending vibration mode.
Mashimo, Tomoaki
2013-10-01
We propose a miniature piezoelectric mixer that can rotate a liquid inside a hole of several millimeters diameter. The mixer has dimensions 14 × 14 × 10 mm with a through-hole (7 mm), and piezoelectric elements bonded to its four identical sides. When the first bending vibration mode of the mixer is excited by ac voltages, rotational flow of liquid is generated by the rotation of an acoustic field (acoustic streaming) in the through-hole. This technology is useful in automating mixing processes such as the mixing by hand of a few drops of blood in medical testing. In this paper, we verify the driving principle experimentally and examine the characteristics of a prototype mixer, including the induced flow velocity, under changes of the amplitude and frequency of the applied voltages. A plastic test tube, used to prevent contamination, is inserted to the through-hole, and the liquid inside the tube is mixed by rotation of the acoustic field.
Institute of Scientific and Technical Information of China (English)
WU Yun-feng; CAI Su-xian; XU Fang; SHI Lei; Sridhar Krishnan
2014-01-01
This paper presents the knee-joint vibration signal processing and pathological localization procedures using the empirical mode decomposition for patients with chondromalacia patellae. The artifacts of baseline wander and random noise were identified in the decomposed monotonic trend and intrinsic mode functions (IMF) using the modeling method of probability density function and the confidence limit criterion. Then, the fluctuation parts in the signal were detected by the signal method turning for count. The results demonstrated that the quality of reconstructed signal can be greatly improved, with the removal of the baseline wander (adaptive trend) and the Gaussian distributed random noise. By detecting the turn signals in the artifact-free signal, the pathological segments related to chondromalacia patellae can be effectively localized with the beginning and ending points of the span of turn signals.
Localization of Vibrating Noise Sources in Nuclear Reactor Cores
Energy Technology Data Exchange (ETDEWEB)
Hultqvist, Pontus
2004-09-01
In this thesis the possibility of locating vibrating noise sources in a nuclear reactor core from the neutron noise has been investigated using different localization methods. The influence of the vibrating noise source has been considered to be a small perturbation of the neutron flux inside the reactor. Linear perturbation theory has been used to construct the theoretical framework upon which the localization methods are based. Two different cases have been considered: one where a one-dimensional one-group model has been used and another where a two-dimensional two-energy group noise simulator has been used. In the first case only one localization method is able to determine the position with good accuracy. This localization method is based on finding roots of an equation and is sensitive to other perturbations of the neutron flux. It will therefore work better with the assistance of approximative methods that reconstruct the noise source to determine if the results are reliable or not. In the two-dimensional case the results are more promising. There are several different localization techniques that reproduce both the vibrating noise source position and the direction of vibration with enough precision. The approximate methods that reconstruct the noise source are substantially better and are able to support the root finding method in a more constructive way. By combining the methods, the results will be more reliable.
The model of local mode analysis for structural acoustics of box structures
Ngai, King-Wah
Structure-borne noise is a new noise pollution problem emerging from railway concrete box structures in Hong Kong. Its low frequency noise with intermittent effect can cause considerable nuisance to neighborhoods. The tonal noise peaks in this low frequency range should be one of the important factors in structure-borne noise analysis. In the acoustic field, the deterministic analysis of all the resonant modes of vibration is generally considered as not practical. Many acoustic experts use the statistical energy analysis as the main tool for the noise investigation whereas the application of the experimental modal analysis in the structural acoustic problem is comparatively rare. In the past, most studies mainly focused on the structure-borne noise measurement and analysis. The detail study of the cause of structure-borne noise is lack, especially for the rectangular concrete box structure. In this dissertation, an experimental and analytical approach is adopted to study a typical concrete box model. This thesis aims at confirming the importance of modal analysis in the structure-borne noise study and then at identifying the local vibration modes along the cross-section of box structure. These local modes are responsible for the structure-borne noise radiation. The findings of this study suggest that the web of viaduct cross-section is not as rigid as assumed in the conventional viaduct design and the web face is likely to be more flexible in the vertical displacement of the concrete viaduct. Two types of local vibration modes along the cross-section are identified: the centre mode and the web mode. At the top panel of the viaduct, the centre mode has movement in the middle but not at the edges. The web mode has movement at the edges with the middle fixed. The combined centre and web mode has been found to be important in the structural acoustics of the concrete box structure. In the actual concrete viaduct, the coincidence frequency is especially low (often around
Saito, Shigeki; Inerbaev, Talgat M.; Mizuseki, Hiroshi; Igarashi, Nobuaki; Note, Ryunosuke; Kawazoe, Yoshiyuki
2006-11-01
First-principles calculations of the crystalline vibrations of a lactose monohydrate crystal in the terahertz (THz) region were performed using periodic density functional theory calculations. The calculated vibrational modes in the THz region were derived from group motions with different sizes: molecules of lactose and crystal water, pyranose rings, and intramolecular frames. The intermolecular modes with large vibrational amplitude of lactose of 17.5-100.6 cm-1 and of crystal-water of 136.1-237.7 cm-1 were clearly separated. This article especially refers to the intermolecular vibrational modes of crystal water with the THz absorption, which provide detectable spectral features of hydrated crystals.
Vibration frequency measurement using a local multithreshold technique.
Ferrer, Belen; Espinosa, Julian; Roig, Ana B; Perez, J; Mas, D
2013-11-01
In this paper, we demonstrate the use of a video camera for measuring the frequency of small-amplitude vibration movements. The method is based on image acquisition and multilevel thresholding and it only requires a video camera with high enough acquisition rate, not being necessary the use of targets or auxiliary laser beams. Our proposal is accurate and robust. We demonstrate the technique with a pocket camera recording low-resolution videos with AVI-JPEG compression and measuring different objects that vibrate in parallel or perpendicular direction to the optical sensor. Despite the low resolution and the noise, we are able to measure the main vibration modes of a tuning fork, a loudspeaker and a bridge. Results are successfully compared with design parameters and measurements with alternative devices.
[Neuroimmune endocrine relationships under exposure to local vibration in workers].
Bodienkova, G M; Kurchevenko, S I
2015-01-01
The studies prove that local vibration in workers alters parameters of immune, nervous, endocrine systems interconnected and demonstrating pathologic process degree. Findings are that workers with long length of service, having no health disorders, increased CNTF level is associated with high TSH, increased IgG level is connected with ACTH growth. In vibration disease, increase of neurospecific protein S-100β is associatedwith lower level of T4. Increase of anti-inflammatory IL-4 is accompanied by high level of T3--that can prove disbalance in main regulatory systems (immune, nervous, endocrine).
Novel 2D representation of vibration for local damage detection
Directory of Open Access Journals (Sweden)
Grzegorz Żak
2014-07-01
Full Text Available In this paper a new 2D representation for local damage detection is presented. It is based on a vibration time series analysis. A raw vibration signal is decomposed via short-time Fourier transform and new time series for each frequency bin are differentiated to decorrelate them. For each time series, autocorrelation function is calculated. In the next step ACF maps are constructed. For healthy bearing ACF map should not have visible horizontal lines indicating damage. The method is illustrated by analysis of real data containing signals from damaged bearing and healthy for comparison.
Localized modes in nonlinear binary kagome ribbons.
Beličev, P P; Gligorić, G; Radosavljević, A; Maluckov, A; Stepić, M; Vicencio, R A; Johansson, M
2015-11-01
The localized mode propagation in binary nonlinear kagome ribbons is investigated with the premise to ensure controlled light propagation through photonic lattice media. Particularity of the linear system characterized by the dispersionless flat band in the spectrum is the opening of new minigaps due to the "binarism." Together with the presence of nonlinearity, this determines the guiding mode types and properties. Nonlinearity destabilizes the staggered rings found to be nondiffracting in the linear system, but can give rise to dynamically stable ringlike solutions of several types: unstaggered rings, low-power staggered rings, hour-glass-like solutions, and vortex rings with high power. The type of solutions, i.e., the energy and angular momentum circulation through the nonlinear lattice, can be controlled by suitable initial excitation of the ribbon. In addition, by controlling the system "binarism" various localized modes can be generated and guided through the system, owing to the opening of the minigaps in the spectrum. All these findings offer diverse technical possibilities, especially with respect to the high-speed optical communications and high-power lasers.
Seismic base isolation by nonlinear mode localization
Energy Technology Data Exchange (ETDEWEB)
Wang, Y. [University of Illinois, Department of Civil and Environmental Engineering, Urbana, IL (United States); Washington University, Department of Civil and Environmental Engineering, St. Louis, MO (United States); McFarland, D.M. [University of Illinois, Department of Aerospace Engineering, Urbana, IL (United States); Vakakis, A.F. [National Technical University of Athens, Division of Mechanics (Greece); Bergman, L.A. [University of Illinois, Department of Mechanical and Industrial Engineering, Urbana, IL (United States)
2005-03-01
In this paper, the performance of a nonlinear base-isolation system, comprised of a nonlinearly sprung subfoundation tuned in a 1:1 internal resonance to a flexible mode of the linear primary structure to be isolated, is examined. The application of nonlinear localization to seismic isolation distinguishes this study from other base-isolation studies in the literature. Under the condition of third-order smooth stiffness nonlinearity, it is shown that a localized nonlinear normal mode (NNM) is induced in the system, which confines energy to the subfoundation and away from the primary or main structure. This is followed by a numerical analysis wherein the smooth nonlinearity is replaced by clearance nonlinearity, and the system is excited by ground motions representing near-field seismic events. The performance of the nonlinear system is compared with that of the corresponding linear system through simulation, and the sensitivity of the isolation system to several design parameters is analyzed. These simulations confirm the existence of the localized NNM, and show that the introduction of simple clearance nonlinearity significantly reduces the seismic energy transmitted to the main structure, resulting in significant attenuation in the response. (orig.)
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.
Mode-specific energy absorption by solvent molecules during CO2 vibrational cooling.
Kandratsenka, Alexander; Schroeder, Jörg; Schwarzer, Dirk; Vikhrenko, Vyacheslav S
2007-04-14
Non-equilibrium molecular dynamics (NEMD) simulations of energy transfer from vibrationally excited CO(2) to CCl(4) and CH(2)Cl(2) solvent molecules are performed to identify the efficiency of different energy pathways into the solvent bath. Studying in detail the work performed by the vibrationally excited solute on the different solvent degrees of freedom, it is shown that vibration-to-vibration (V-V) processes are strongly dominant and controlled by those accepting modes which are close in frequency to the CO(2) bend and symmetric stretch vibration.
Effect of Vibrational Modes on Sand Pressure and Pattern Deformation in the EPC Process
Institute of Scientific and Technical Information of China (English)
A.Ikenaga; G.S.Cho; K.H.Choe; K.W.Lee
2004-01-01
During the EPC (expendable pattern casting) process, one of the essential requirements is to prevent pattern distortion during sand filling and compaction. A new method which vibrates the system in a two-dimensional circular mode has been applied to the EPC process. The molding properties of unbonded sand obtained by this new vibration mode are investigated and compared with those in the one-dimensional vertical mode. For adequate compaction of sand, the circular vibration mode is more effective than the vertical mode. Sand became more fluidized by the circular vibration and the particle pressure coefficient was close to unity. The particle pressure coefficient, which is defined as the ratio of horizontal to vertical sand pressure, is responsible for the effectiveness of sand filling.
Analysis of the Mode of the Periodically Time-varying Vibration Systems
Institute of Scientific and Technical Information of China (English)
WANG Sheng-ze; REN Ji-ge
2007-01-01
By Liapunov reducibility theorem, the periodically time-varying vibration system can be transformed to a linear time-invariant system. Based on the dynamic characteristics of the linear time-invariant system, the mode of the periodically time-varying vibration system has been discussed. The paper defines the mode and analyzes its characteristics. It can be found that the mode of the periodically time-varying system is periodically time-varing but has such characteristics as orthogonality. Finally, a method is given to solve the mode. By solving the eigenvalues and the eigenvectors of the state transition matrix in one period, the periodically time-varying mode can be obtained.
Localized modes in orientation-disordered uniaxial medium
Energy Technology Data Exchange (ETDEWEB)
Wan Zhenzhu; Han Yanling [School of Mathematics and Physics, China University of Geosciences, Wuhan 430074 (China); Wang Hong, E-mail: wanghong745@sohu.com, E-mail: w_pearl2008@163.com [Center of Information and Laboratory, China University of Geosciences, Wuhan 430074 (China)
2011-02-01
Using a 4x4 transfer matrix method, localized modes in orientation-disordered uniaxial medium have been investigated. We confirm that localized modes origin from the randomness of spatial orientation of optical axes. The misalignment of the optical axe provides the opportunity for a rearrangement of the localized modes. The number of localize mode also closely relative to the spatial orientation of optical axis. Numerical results indicate that it is possible to adjust the localized modes through altering the relative orientation of the optical axes of scatterers. This study is an importance for well understanding of localization of light wave and lasing action in anisotropic random media.
Longitudinal-torsional vibration source consisting of two transducers with different vibration modes
Asami, Takuya; Miura, Hikaru
2016-07-01
The planar vibration locus is applicable to, for example, ultrasonic welding, ultrasonic machining, and ultrasonic polishing. In a previous study, we obtained the planar locus using an ultrasonic longitudinal-torsional vibration source that contained a vibration converter comprising diagonal slits to drive two frequencies. It was difficult to obtain only longitudinal or torsional vibration when using an ultrasonic complex vibration source with diagonal slits. Therefore, the versatility of the ultrasonic complex vibration source with diagonal slits was low. We have developed an ultrasonic longitudinal-torsional vibration source in which the longitudinal-torsional vibration can be controlled. The requirements for an ultrasonic vibration source were longitudinal-torsional vibration control and that the source has a planar locus. In this paper, we investigate a new type of vibration source that satisfies these requirements. It consists of two transducers, a longitudinal transducer and a torsional transducer, attached to the ends of a uniform rod with a length of one wavelength of the propagating vibration.
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.
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...
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...
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...
Effects of boundary conditions on vibrating mode of acoustic logging dipole transducer
Institute of Scientific and Technical Information of China (English)
2008-01-01
Acoustic transducer is an important part of acoustic well logging tool. In this paper,ANSYS software package is used to design acoustic dipole transducer and simulate vibrating mode of the dipole transducer in different mechanical boundary conditions. The results show that boundary conditions influence the number of vibrating mode in the same frequency band and the frequency value of the same vibrating mode. Several acoustic dipole transducers are designed according to the results of numerical simulation and laboratory measurements. The basic frequency of vibrating mode of experi-ment has good agreement with that of simulation. The numerical simulation plays a good guidance role in designing,producing and correctly installing the acoustic dipole transducer.
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...
Hirose, Noriaki; Iwasaki, Makoto; Kawafuku, Motohiro; Hirai, Hiromu
In this paper, we present a novel type of feedback compensation for achieving robust vibration suppression of resonant modes in mechatronic systems by the use of allpass filters. In most mechactronic systems, residual vibration must be sufficiently suppressed during precise positioning. In order to achieve the required vibration suppression, the proposed feedback compensation realized using allpass filters is adopted to stabilize the resonant modes without attenuating the gain and to improve the sensitivity characteristics around the resonant modes even when the plant system has high-order vibration modes and time-delay characteristics. The effectiveness of the proposed approach has been verified by carrying out numerical simulations and performing experiments using a prototype.
Flexural Mie Resonances: Localized Surface Platonic Modes
Farhat, M; Chen, P Y; Salama, K N; Bagci, H
2016-01-01
Surface plasmons polaritons were thought to exist only in metals near their plasma frequencies. The concept of spoof plasmons extended the realms of plasmonics to domains such as radio frequencies, magnetism, or even acoustic waves. Here, we introduce the concept of localized surface platonic modes (SPMs). We demonstrate that they can be generated on a two-dimensional clamped (or stress-free) cylindrical surface, in a thin elastic plate, with subwavelength corrugations under excitation by an incident flexural plane wave. Our results show that the corrugated rigid surface is elastically equivalent to a cylindrical scatterer with negatively uniform and dispersive flexural rigidity. This, indeed, suggests that plasmonic-like platonic materials can be engineered with potential applications in various areas including earthquake sensing, or elastic imaging and cloaking.
MULTI-MODE OF VORTEX-INDUCED VIBRATION OF A FLEXIBLE CIRCULAR CYLINDER
Institute of Scientific and Technical Information of China (English)
XIE Fang-fang; DENG Jian; ZHENG Yao
2011-01-01
The vortex-induced vibration of a flexible circular cylinder is investigated at a constant Reynolds number of 1 000.The finite-volume method on moving meshes is applied for the fluid flow,and the Euler-Bemoulli beam theory is used to model the dynamic response of a flexible cylinder.The relationship between the reduced velocity and the amplitude response agrees well with the experimental results.Moreover,five different vibrating modes appear in the simulation.From the comparisons of their vortex structures,the strength of the wake flow is related to the exciting vibrating mode and different vortex patterns arise for different vibrating modes.Only 2P pattern appears in the first vibrating mode while 2S-2P patterns occur in the other vibrating modes if monitoring at different sections along the length of the cylinder.The vibration of the flexible cylinder can also greatly alter the three-dimensionality in the wake,which needs further studies in our future work,especially in the transition region for the Reynolds number from 170 to 300.
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.
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.
Strozzi, Matteo; Smirnov, Valeri V.; Manevitch, Leonid I.; Milani, Massimo; Pellicano, Francesco
2016-10-01
In this paper, the nonlinear vibrations and energy exchange of single-walled carbon nanotubes (SWNTs) are studied. The Sanders-Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration. The SWNT deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported, clamped and free boundary conditions are considered. The circumferential flexural modes (CFMs) are investigated. Two different approaches based on numerical and analytical models are compared. In the numerical model, an energy method based on the Lagrange equations is used to reduce the nonlinear partial differential equations of motion to a set of nonlinear ordinary differential equations, which is solved by using the implicit Runge-Kutta numerical method. In the analytical model, a reduced form of the Sanders-Koiter theory assuming small circumferential and tangential shear deformations is used to get the nonlinear ordinary differential equations of motion, which are solved by using the multiple scales analytical method. The transition from energy beating to energy localization in the nonlinear field is studied. The effect of the aspect ratio on the analytical and numerical values of the nonlinear energy localization threshold for different boundary conditions is investigated. Time evolution of the total energy distribution along the axis of a simply supported SWNT
Directory of Open Access Journals (Sweden)
Ying Zhao
2017-01-01
Full Text Available The low-order vibration modes of a reciprocating compressor were studied by means of numerical simulation and experimental validation. A shell element model, a beam element model, and two solid element models were established to investigate the effects of bolted joints and element types on low-order vibration modes of the compressor. Three typical cases were compared to check the effect of locations of moving parts on the vibration modes of the compressor. A forced modal test with the MRIT (Multiple References Impact Test technique was conducted to validate the simulation results. Among four numerical models, the solid element model with the bolt-pretension method showed the best accuracy compared with experimental data but the worst computational efficiency. The shell element model is recommended to predict the low-order vibration modes of the compressor with regard to effectiveness and usefulness. The sparsely distributed bolted joints with a small bonded region on the contact surface were key bolted joints that had greater impacts on the low-order vibration modes of the compressor than the densely distributed bolted joints. The positions of the moving parts had little effect on the low-order vibration modes of the compressor.
Damage localization under ambient vibration using changes in flexibility
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
In recent years, Structural Health Monitoring (SHM) has emerged as a new research area in civil engineering. Mostexisting health monitoring methodologies require direct measurement of input excitation for implementation. However, in manycases, there is no easy way to measure these inputs - or alternatively to externally excite the structure. Therefore, SHM methodsbased on ambient vibration have become important in civil engineering. In this paper, an approach is proposed based on the DamageLocation Vector (DLV) method to handle the ambient vibration case. Here, this flexibility-matrix-based damage localization methodis combined with a modal expansion technique to eliminate the need to measure the input excitation. As a by-product of thisapproach, in addition to determining the location of the damage, an estimate of the damage extent also can be determined. Finally, anumerical example analyzing a truss structure with limited sensors and noisy measurement is provided to verify the efficacy of theproposed approach.
Effect of the Vibrational Modes on the Ag-Cu Phase Diagram
Institute of Scientific and Technical Information of China (English)
DUAN Su-Qing; ZHAO Xian-Geng; LIU Shao-Jun; MA Ben-Kun
2000-01-01
We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrational free energies by using the method of ab initio inverted interatomic potentials and dynamic matrix; (2) the vibrational free energies determined by a Debye-Griineisen approximation. The Ag-Cu phase diagram is calculated by the cluster variation method. The results show that the solubility at Ag-rich end of the calculated phase diagram considering vibrational modes by using the first method is in better agreement with the experimental.
Wang, Sihong; Niu, Simiao; Yang, Jin; Lin, Long; Wang, Zhong Lin
2014-12-23
A vibration sensor is usually designed to measure the vibration frequency but disregard the vibration amplitude, which is rather challenging to be quantified due to the requirement of linear response. Here, we show the application of triboelectric nanogenerator (TENG) as a self-powered tool for quantitative measurement of vibration amplitude based on an operation mode, the contact-mode freestanding triboelectric nanogenerator (CF-TENG). In this mode, the triboelectrically charged resonator can be agitated to vibrate between two stacked stationary electrodes. Under the working principle with a constant capacitance between two electrodes, the amplitudes of the electric signals are proportional to the vibration amplitude of the resonator (provided that the resonator plate is charged to saturation), which has been illuminated both theoretically and experimentally. Together with its capability in monitoring the vibration frequency, the CF-TENG appears as the triboelectrification-based active sensor that can give full quantitative information about a vibration. In addition, the CF-TENG is also demonstrated as a power source for electronic devices.
Coupling between flexural modes in free vibration of single-walled carbon nanotubes
Directory of Open Access Journals (Sweden)
Rumeng Liu
2015-12-01
Full Text Available The nonlinear thermal vibration behavior of a single-walled carbon nanotube (SWCNT is investigated by molecular dynamics simulation and a nonlinear, nonplanar beam model. Whirling motion with energy transfer between flexural motions is found in the free vibration of the SWCNT excited by the thermal motion of atoms where the geometric nonlinearity is significant. A nonlinear, nonplanar beam model considering the coupling in two vertical vibrational directions is presented to explain the whirling motion of the SWCNT. Energy in different vibrational modes is not equal even over a time scale of tens of nanoseconds, which is much larger than the period of fundamental natural vibration of the SWCNT at equilibrium state. The energy of different modes becomes equal when the time scale increases to the microsecond range.
Coupling between flexural modes in free vibration of single-walled carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Liu, Rumeng; Wang, Lifeng, E-mail: walfe@nuaa.edu.cn [State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing (China)
2015-12-15
The nonlinear thermal vibration behavior of a single-walled carbon nanotube (SWCNT) is investigated by molecular dynamics simulation and a nonlinear, nonplanar beam model. Whirling motion with energy transfer between flexural motions is found in the free vibration of the SWCNT excited by the thermal motion of atoms where the geometric nonlinearity is significant. A nonlinear, nonplanar beam model considering the coupling in two vertical vibrational directions is presented to explain the whirling motion of the SWCNT. Energy in different vibrational modes is not equal even over a time scale of tens of nanoseconds, which is much larger than the period of fundamental natural vibration of the SWCNT at equilibrium state. The energy of different modes becomes equal when the time scale increases to the microsecond range.
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.
Laser-driven localization of collective CO vibrations in metal-carbonyl complexes
Lisaj, Mateusz; Kühn, Oliver
2014-11-01
Using the example of a cobalt dicarbonyl complex it is shown that two perpendicular linearly polarized IR laser pulses can be used to trigger an excitation of the delocalized CO stretching modes, which corresponds to an alternating localization of the vibration within one CO bond. The switching time for localization in either of the two bonds is determined by the energy gap between the symmetric and asymmetric fundamental transition frequencies. The phase of the oscillation between the two local bond excitations can be tuned by the relative phase of the two pulses. The extend of control of bond localization is limited by the anharmonicity of the potential energy surfaces leading to wave packet dispersion. This prevents such a simple pulse scheme from being used for laser-driven bond breaking in the considered example.
Laser-Driven Localization of Collective CO Vibrations in Metal-Carbonyl Complexes
Lisaj, Mateusz
2014-01-01
Using the example of a cobalt dicarbonyl complex it is shown that two perpendicularly polarized IR laser pulses can be used to trigger an excitation of the delocalized CO stretching modes, which corresponds to an alternating localization of the vibration within one CO bond. The switching time for localization in either of the two bonds is determined by the energy gap between the symmetric and asymmetric fundamental transition frequencies. The phase of the oscillation between the two local bond excitations can be tuned by the relative phase of the two pulses. The extend of control of bond localization is limited by the anharmonicity of the potential energy surfaces leading to wave packet dispersion. This prevents such a simple pulse scheme from being used for laser-driven bond breaking in the considered example.
Energy transfer efficiency in the chromophore network strongly coupled to a vibrational mode.
Mourokh, Lev G; Nori, Franco
2015-11-01
Using methods from condensed matter and statistical physics, we examine the transport of excitons through the photosynthetic complex from a receiving antenna to a reaction center. Writing the equations of motion for the exciton creation-annihilation operators, we are able to describe the exciton dynamics, even in the regime when the reorganization energy is of the order of the intrasystem couplings. We determine the exciton transfer efficiency in the presence of a quenching field and protein environment. While the majority of the protein vibrational modes are treated as a heat bath, we address the situation when specific modes are strongly coupled to excitons and examine the effects of these modes on the energy transfer efficiency in the steady-state regime. Using the structural parameters of the Fenna-Matthews-Olson complex, we find that, for vibrational frequencies below 16 meV, the exciton transfer is drastically suppressed. We attribute this effect to the formation of a "mixed exciton-vibrational mode" where the exciton is transferred back and forth between the two pigments with the absorption or emission of vibrational quanta, instead of proceeding to the reaction center. The same effect suppresses the quantum beating at the vibrational frequency of 25 meV. We also show that the efficiency of the energy transfer can be enhanced when the vibrational mode strongly couples to the third pigment only, instead of coupling to the entire system.
Intrinsic localized modes and nonlinear impurity modes in curved Fermi-Pasta-Ulam chain
Indian Academy of Sciences (India)
Ranja Sarkar; Bishwajyoti Dey
2008-06-01
We explore the nature of intrinsic localized modes (ILMs) in a curved FermiPasta-Ulam (FPU) chain and the effects of geometry and second-neighbor interaction on the localization and movability properties of such modes. We determine analytically the structure of the localized modes induced by an isotopic light-mass impurity in this chain. We further demonstrate that a nonlinear impurity mode may be treated as a bound state of an ILM with the impurity.
Roden, Jan; Strunz, Walter T; Whaley, K Birgitta; Eisfeld, Alexander
2012-11-28
Electronic-vibrational dynamics in molecular systems that interact with an environment involve a large number of degrees of freedom and are therefore often described by means of open quantum system approaches. A popular approach is to include only the electronic degrees of freedom into the system part and to couple these to a non-Markovian bath of harmonic vibrational modes that is characterized by a spectral density. Since this bath represents both intra-molecular and external vibrations, it is important to understand how to construct a spectral density that accounts for intra-molecular vibrational modes that couple further to other modes. Here, we address this problem by explicitly incorporating an intra-molecular vibrational mode together with the electronic degrees of freedom into the system part and using the Fano theory for a resonance coupled to a continuum to derive an "effective" bath spectral density, which describes the contribution of intra-molecular modes. We compare this effective model for the intra-molecular mode with the method of pseudomodes, a widely used approach in simulation of non-Markovian dynamics. We clarify the difference between these two approaches and demonstrate that the respective resulting dynamics and optical spectra can be very different.
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
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.
2016-03-01
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.
Pseudospectral calculation of near-dissociative local mode states for the bifluoride anion HF - 2
Bramley, M. J.; Corey, G. C.; Hamilton, I. P.
1995-12-01
Using a recently reported global potential energy surface, we calculate all vibrational levels of the HF-2 anion up to the dissociation threshold. The equilibrium geometry of the bifluoride anion is linear with the H atom between the F atoms. The vibrational wave functions are symmetric or antisymmetric with respect to reflection in a plane bisecting the F-F axis. We focus on nearly degenerate pairs of symmetric and antisymmetric levels lying close to the dissociation energy. Sums and differences of these levels are local mode states for which the H atom is localized on one of the F atoms. These near-dissociative local mode states, which can exist above the threshold for dissociation into F- and HF or FH and F- fragments, have been proposed as candidates for spectroscopic experiments which probe the dynamics and structure of the transition state in the unimolecular dissociation of polyatomic molecules. Energies of the low-lying vibrational levels, as well as those around the dissociation energy, are presented. Wave functions of highly vibrationally excited states, lying slightly below and slightly above the dissociation threshold, are analyzed graphically.
Preparation and vibrational modes of C60·2CHBr3
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
C60·2CHBr3 polycrystalline powder was prepared by the solution method. The vibrational modes of the sample were studied by Raman scattering and infrared adsorption techniques. The Raman spectra showed that the Ag modes were downshifted by 4-5 cm1, while the Hg(1) mode was unshifted. The analyses of the downshifts of the Ag modes revealed that a small amount of electrons were transferred from the hydrogen atoms to the C60 molecules. In the infrared spectra, the F1u modes of the pristine C60 were unshifted after the intercalation with CHBr3. However, the vibrational modes of CHBr3 changed remarkably. The C-Br stretching mode was downshifted by ～4 cm1. The adsorption of the C-H twisting mode was weakened obviously, and the adsorption of the C-H stretching mode was not observed. These results exhibited that there were nonnegligible interactions between CHBr3 and C60 molecules, and that the strongest interaction took place between the hydrogen atoms and the C60 molecules. The interaction should induce not only the changes of the vibrational modes reported here, but also those of the electronic states. So this work should offer important glues to the mechanism of the superconductivity at 117 K of the field-doped C60·2CHBr3.
Influence of the surface structure and vibration mode on the resistivity of Cu films
Zhao, Ya-Ni; Qu, Shi-Xian; Xia, Ke
2011-09-01
The influence of the surface structure and vibration mode on the resistivity of Cu films and the corresponding size effect are investigated. The temperature dependent conductivities of the films with different surface morphologies are calculated by the algorithm based upon the tight-binding linear muffin-tin orbital method and the Green's function technique. The thermal effect is introduced by setting the atomic displacements according to the Gaussian distribution with the mean-square amplitude estimated by the Debye model. The result shows that the surface atomic vibration contributes significantly to the resistivity of the system. Comparing the conductivities for three different vibration modes, we suggest that freezing the surface vibration is necessary for practical applications to reduce the resistivity induced by the surface electron-phonon scattering.
Sound power radiation from a vibrating structure in terms of structure-dependent radiation modes
Ji, Lin; Bolton, J. Stuart
2015-01-01
As a good supplement of conventional acoustic radiation modes (a-modes), a set of so-called "structure-dependent radiation modes" (s-modes) is introduced to describe the sound power radiation from a vibrating structure. Differing from a-modes, s-modes are determined by not only the acoustic resistance matrix of the structure but also the frequency-independent normal modes of the structure. Such a new definition has the following main advantages over the conventional one: (1) it can reflect directly the influences of dynamic properties (e.g., boundary conditions) of the structures on its sound power radiation; (2) the number of s-modes generated is generally less than that of a-modes since the former depends on the number of structural modes involved in the vibration while the latter depends on the number of segmented elemental radiators of the structure, and consequently, the demand for large data storage can be greatly alleviated, especially for large structures and/or higher frequency vibrations; (3) the set of s-modes possesses a better convergence than that of a-modes because the higher ordered s-modes can decay more rapidly than the same ordered a-modes. Two baffled, finite, models, i.e., a simple beam and a thin plate, are employed to investigate numerically the acoustic properties of s-modes, and then compared with those of a-modes. It has been shown that the two sets of radiation modes share a very similar frequency-dependent behavior in that the radiation efficiency falls off very rapidly with increasing mode order at low frequency range (typically with kl<1). Meanwhile, the number of s-modes required to describe the total sound power radiation is found to be the same as that of a-modes. Consequently, an appropriate truncation of a-modes can be achieved by using the number of vibrational modes involved. Nevertheless, the odd-ordered (even-ordered) s-modes are found only associated with the odd-numbered (even-ordered) structural modes. In case of only few
Vibration Modes and the Dynamic Behaviour of a Hydraulic Plunger Pump
Directory of Open Access Journals (Sweden)
Tianxiao Zhang
2016-01-01
Full Text Available Mechanical vibrations and flow fluctuation give rise to complex interactive vibration mechanisms in hydraulic pumps. The working conditions for a hydraulic pump are therefore required to be improved in the design stage or as early as possible. Considering the structural features, parameters, and operating environment of a hydraulic plunger pump, the vibration modes for two-degree-of-freedom system were established by using vibration theory and hydraulic technology. Afterwards, the analytical form of the natural frequency and the numerical solution of the steady-state response were deduced for a hydraulic plunger pump. Then, a method for the vibration analysis of a hydraulic pump was proposed. Finally, the dynamic responses of a hydraulic plunger pump are obtained through numerical simulation.
Institute of Scientific and Technical Information of China (English)
ZHOU,Zheng-Yu(周正宇); CHENG,Xue-Li(程学礼); GUO,Li(郭丽)
2002-01-01
On the basis of the computed results got by the Gaussian 94 package at B3LYP/6-311 + +G * * level, the reaction mechanism of CH3O radical with CO has been investigated thoroughly via the vibrational model analysis. And the relationships among the reactants, eight transition states, four intermediates and various products involved this multichannel reaction are elucidated. The vibrational mode analysis shows that the reaction mechanism is reliable.
Indian Academy of Sciences (India)
S Gunasekaran; S Kumaresan; R Arunbalaji; G Anand; S Srinivasan
2008-05-01
The FTIR and FT Raman spectra of dacarbazine were recorded in the regions 4000-400 and 3500-100 cm-1, respectively. The optimized geometry, wavenumber, polarizability and several thermodynamic properties of dacarbazine were studied using ab initio Hartree-Fock, MP2 and DFT methods. A complete vibrational assignment aided by the theoretical harmonic wavenumber analysis was proposed. The calculated harmonic vibrational frequencies were compared with experimental FTIR and FT Raman spectra. Based on the comparison between calculated and experimental results and the comparison with related molecules, assignments of fundamental vibrational modes were made. The X-ray geometry and experimental frequencies were compared with the results of theoretical calculations.
Ulriksen, M. D.; Damkilde, L.
2016-02-01
Contrary to global modal parameters such as eigenfrequencies, mode shapes inherently provide structural information on a local level. Therefore, this particular modal parameter and its derivatives are utilized extensively for damage identification. Typically, more or less advanced mathematical methods are employed to identify damage-induced discontinuities in the spatial mode shape signals, hereby, potentially, facilitating damage detection and/or localization. However, by being based on distinguishing damage-induced discontinuities from other signal irregularities, an intrinsic deficiency in these methods is the high sensitivity towards measurement noise. In the present paper, a damage localization method which, compared to the conventional mode shape-based methods, has greatly enhanced robustness towards measurement noise is proposed. The method is based on signal processing of a spatial mode shape by means of continuous wavelet transformation (CWT) and subsequent application of a generalized discrete Teager-Kaiser energy operator (GDTKEO) to identify damage-induced mode shape discontinuities. In order to evaluate whether the identified discontinuities are in fact damage-induced, outlier analysis is conducted by applying the Mahalanobis metric to major principal scores of the sensor-located bands of the signal-processed mode shape. The method is tested analytically and benchmarked with other mode shape-based damage localization approaches on the basis of a free-vibrating beam and validated experimentally in the context of a residential-sized wind turbine blade subjected to an impulse load.
Yue, Shuai; Wang, Zhuan; Leng, Xuan; Zhu, Rui-Dan; Chen, Hai-Long; Weng, Yu-Xiang
2017-09-01
Low vibrational modes in a range of 80-400 cm-1 for bacteriochlorophyll a are excited and observed as beating dynamics in two-dimensional electronic spectra. A coupled multi-vibrational mode displaced oscillator model is proposed to account for the vibronic coherence. We found that these low frequency vibrational modes are coupled. By comparing the fitted lifetime of the vibrational modes appearing in the beating dynamics for bacteriochlorophyll a and a protein-bound bacteriochlorophyll a dimer B820 probed by transient grating method, it is suggested that the protein scaffold provides a protection effect on the vibronic coherence where no excitonic coherence has be excited.
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.
A fiber micro-vibration sensor based on single-mode fiber ring laser
Institute of Scientific and Technical Information of China (English)
Shenglai Zhen; Renzhu Liu; Benli Yu; Jing Zhang; Baogang Han
2009-01-01
A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric (MZI) detection technique is presented for interrogating laser frequency shift due to the measurand (piezoelectric transducer (PZT) is used to simulate the micro-vibration) induced laser cavity strain from both single- and multi-mode lasers. In the experiment, compared with multi-mode laser sensors, the single-mode laser sensor is proved to be a sensor with high resolution. When the PZT is driven by the analog signal (0.03 rad near 2 kHz), the signal-to-noise ratio (SNR) of output signal from the single-mode laser sensor is close to 55 dB and the sensitivity of the sensor is about 5 x 10-5 rad/Hz1/2.
Vibrational modes of aminothiophenol: a TERS and DFT study.
Merlen, A; Chaigneau, M; Coussan, S
2015-07-15
We report Tip Enhanced Raman Spectroscopy (TERS) mapping and Density Functional (DFT) calculations of aminothiophenol (ATP) grafted on a gold surface. The TERS mapping has demonstrated Raman modes of (ATP) and its dimerised derivative Dimercaptoazobenzene (DMAB). This feature confirms that the plasmon activated chemical reaction of ATP has occurred during TERS measurements. In some specific part of the samples some unidentified Raman modes are observed. We suggest that they could come from intermediate species formed during the conversion of ATP into DMAB. These modes are compared with calculated Raman spectra of some possible intermediate species. These results confirm the high potentiality of TERS measurements for nanochemistry.
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.
Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation
Thenozhi, Suresh; Yu, Wen
2016-04-01
Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.
CO2 laser photoacoustic spectra and vibrational modes of heroin, morphine and narcotine
Indian Academy of Sciences (India)
R L Prasad; S N Thakur; G C Bhar
2002-09-01
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 resolution IR spectra. The ab initio quantum chemical calculations were used for determining the molecular geometries and normal mode frequencies of vibrations of these molecules for assignments of PA spectra.
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.
Energy Technology Data Exchange (ETDEWEB)
Manley, M; Alatas, A; Trouw, F; Leu, B M; Lynn, J W; Chen, Y; Hults, W L
2007-07-02
In an anharmonic crystal, large-amplitude vibrational fluctuations on the scale of the lattice spacing can develop frequencies that do not resonate with the normal modes, causing energy to become trapped in intrinsically localized modes (ILMs)--also called 'discrete breathers' or 'lattice solitons'. This mechanism has been observed in analogous systems on a larger scale, but unambiguous sightings in atomic lattice vibrations, where quantum mechanics may play a role, have proved difficult. Two challenges have hampered progress: (1) the need to separate ILMs from defect modes, and (2) complications that arise at high temperatures, including feature broadening and multiphonon processes. Here we solve these problems by using x-ray and neutron scattering to induce ILM-forming amplitude fluctuations in uranium at low temperatures, thereby creating nonequilibrium ILMs. Creation of ILMs occurs at a discrete energy, indicating an unexpected quantum character to ILM formation and greatly simplifying detection.
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.
Energy Technology Data Exchange (ETDEWEB)
Hanson-Heine, Magnus W. D., E-mail: magnus.hansonheine@nottingham.ac.uk [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
2015-10-28
Carefully choosing a set of optimized coordinates for performing vibrational frequency calculations can significantly reduce the anharmonic correlation energy from the self-consistent field treatment of molecular vibrations. However, moving away from normal coordinates also introduces an additional source of correlation energy arising from mode-coupling at the harmonic level. The impact of this new component of the vibrational energy is examined for a range of molecules, and a method is proposed for correcting the resulting self-consistent field frequencies by adding the full coupling energy from connected pairs of harmonic and pseudoharmonic modes, termed vibrational self-consistent field (harmonic correlation). This approach is found to lift the vibrational degeneracies arising from coordinate optimization and provides better agreement with experimental and benchmark frequencies than uncorrected vibrational self-consistent field theory without relying on traditional correlated methods.
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.
Institute of Scientific and Technical Information of China (English)
ZHANG Neng-hui; WANG Jian-jun; CHENG Chang-jun
2007-01-01
Under the consideration of harmonic fluctuations of initial tension and axially velocity, a nonlinear governing equation for transverse vibration of an axially accelerating string is set up by using the equation of motion for a 3-dimensional deformable body with initial stresses. The Kelvin model is used to describe viscoelastic behaviors of the material. The basis function of the complex-mode Galerkin method for axially accelerating nonlinear strings is constructed by using the modal function of linear moving strings with constant axially transport velocity. By the constructed basis functions, the application of the complex-mode Galerkin method in nonlinear vibration analysis of an axially accelerating viscoelastic string is investigated. Numerical results show that the convergence velocity of the complex-mode Galerkin method is higher than that of the real-mode Galerkin method for a variable coefficient gyroscopic system.
Natural Frequencies and Vibrating Modes for a Magnetic Planetary Gear Drive
Directory of Open Access Journals (Sweden)
Lizhong Xu
2012-01-01
Full Text Available In this paper, a dynamic model for a magnetic planetary gear drive is proposed. Based on the model, the dynamic equations for the magnetic planetary gear drive are given. From the magnetic meshing forces and torques between the elements for the drive system, the tangent and radial magnetic meshing stiffness is obtained. Using these equations, the natural frequencies and the modes of the magnetic planetary gear drive are investigated. The sensitivity of the natural frequencies to the system parameters is discussed. Results show that the pole pair number and the air gap have obvious effects on the natural frequencies. For the planetary gear number larger than two, the vibrations of the drive system include the torsion mode of the center elements, the translation mode of the center elements, and the planet modes. For the planetary gear number equal to two, the planet mode does not occur, the crown mode and the sun gear mode occur.
Same phase drive-type ultrasonic motors using two degenerate bending vibration modes of a disk.
Takano, T; Tomikawa, Y; Kusakabe, C
1992-01-01
Same-phase drive-type ultrasonic motors, using two degenerate bending vibration modes of a disk, are presented. The distinctive feature of the motor is in using the standing wave modes. The motor is not driven by two input signals with different phases, but by input signals with the same phase. Therefore, only one amplifier is sufficient to drive the motor. The experimental results have proved that the motor can yield stable operational characteristics at low speed and high torque.
Calculations of lattice vibrational mode lifetimes using Jazz: a Python wrapper for LAMMPS
Gao, Y.; Wang, H.; Daw, M. S.
2015-06-01
Jazz is a new python wrapper for LAMMPS [1], implemented to calculate the lifetimes of vibrational normal modes based on forces as calculated for any interatomic potential available in that package. The anharmonic character of the normal modes is analyzed via the Monte Carlo-based moments approximation as is described in Gao and Daw [2]. It is distributed as open-source software and can be downloaded from the website http://jazz.sourceforge.net/.
Raman investigation of ro-vibrational modes of interstitial H2 in Si
Koch, S. G.; Lavrov, E. V.; Weber, J.
2012-08-01
A Raman scattering study of ro-vibrational transitions Q(J) of the interstitial H2 in Si is presented. It is shown that the Q(2) mode of para hydrogen is coupled to the TAX phonon of Si. The mode appears in the spectra at temperatures above 200 K. The results presented also suggest that the Q(3) transition of ortho hydrogen is resonantly coupled to the OΓ phonon.
Raman investigation of ro-vibrational modes of interstitial H{sub 2} in Si
Energy Technology Data Exchange (ETDEWEB)
Koch, S.G., E-mail: sandro.koch@physik.tu-dresden.de [Technische Universitaet Dresden, 01062 Dresden (Germany); Lavrov, E.V.; Weber, J. [Technische Universitaet Dresden, 01062 Dresden (Germany)
2012-08-01
A Raman scattering study of ro-vibrational transitions Q(J) of the interstitial H{sub 2} in Si is presented. It is shown that the Q(2) mode of para hydrogen is coupled to the TA{sub X} phonon of Si. The mode appears in the spectra at temperatures above 200 K. The results presented also suggest that the Q(3) transition of ortho hydrogen is resonantly coupled to the O{sub {Gamma}} phonon.
Quantum theory of collective strong coupling of molecular vibrations with a microcavity mode
Pino, Javier del; Feist, Johannes; García-Vidal, Francisco J.
2015-01-01
We develop a quantum mechanical formalism to treat the strong coupling between an electromagnetic mode and a vibrational excitation of an ensemble of organic molecules. By employing a Bloch-Redfield-Wangsness approach, we show that the influence of dephasing-type interactions, i.e., elastic collisions with a background bath of phonons, critically depends on the nature of the bath modes. In particular, for long-range phonons corresponding to a common bath, the dynamics of the "bright state" (t...
Sang, Hongqiang; Yang, Chenghao; Liu, Fen; Yun, Jintian; Jin, Guoguang
2016-12-01
It is very important for robotically assisted minimally invasive surgery to achieve a high-precision and smooth motion control. However, the surgical instrument tip will exhibit vibration caused by nonlinear friction and unmodeled dynamics, especially when the surgical robot system is attempting low-speed, fine motion. A fuzzy neural network sliding mode controller (FNNSMC) is proposed to suppress vibration of the surgical robotic system. Nonlinear friction and modeling uncertainties are compensated by a Stribeck model, a radial basis function (RBF) neural network and a fuzzy system, respectively. Simulations and experiments were performed on a 3 degree-of-freedom (DOF) minimally invasive surgical robot. The results demonstrate that the FNNSMC is effective and can suppress vibrations at the surgical instrument tip. The proposed FNNSMC can provide a robust performance and suppress the vibrations at the surgical instrument tip, which can enhance the quality and security of surgical procedures. Copyright © 2016 John Wiley & Sons, Ltd.
Theory and Normal Mode Analysis of Change in Protein Vibrational Dynamics on Ligand Binding
Energy Technology Data Exchange (ETDEWEB)
Mortisugu, Kei [RIKEN, Japan; Njunda, Brigitte [Computational Molecular Biophysics, Interdisciplinary Center for Scientific Computing (IWR); Smith, Jeremy C [ORNL
2009-12-01
The change of protein vibrations on ligand binding is of functional and thermodynamic importance. Here, this process is characterized using a simple analytical 'ball-and-spring' model and all-atom normal-mode analysis (NMA) of the binding of the cancer drug, methotrexate (MTX) to its target, dihydrofolate reductase (DHFR). The analytical model predicts that the coupling between protein vibrations and ligand external motion generates entropy-rich, low-frequency vibrations in the complex. This is consistent with the atomistic NMA which reveals vibrational softening in forming the DHFR-MTX complex, a result also in qualitative agreement with neutron-scattering experiments. Energy minimization of the atomistic bound-state (B) structure while gradually decreasing the ligand interaction to zero allows the generation of a hypothetical 'intermediate' (I) state, without the ligand force field but with a structure similar to that of B. In going from I to B, it is found that the vibrational entropies of both the protein and MTX decrease while the complex structure becomes enthalpically stabilized. However, the relatively weak DHFR:MTX interaction energy results in the net entropy gain arising from coupling between the protein and MTX external motion being larger than the loss of vibrational entropy on complex formation. This, together with the I structure being more flexible than the unbound structure, results in the observed vibrational softening on ligand binding.
Intermediate energy electron impact excitation of composite vibrational modes in phenol
Energy Technology Data Exchange (ETDEWEB)
Neves, R. F. C. [School of Chemical and Physical Sciences, Flinders University, G.P.O. Box 2100, Adelaide, SA 5001 (Australia); Instituto Federal do Sul de Minas Gerais, Campus Poços de Caldas, Minas Gerais (Brazil); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, Minas Gerais (Brazil); Jones, D. B. [School of Chemical and Physical Sciences, Flinders University, G.P.O. Box 2100, Adelaide, SA 5001 (Australia); Lopes, M. C. A.; Nixon, K. L. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-900, Juiz de Fora, Minas Gerais (Brazil); Oliveira, E. M. de; Lima, M. A. P. [Instituto de Física ‘Gleb Wataghin,’ Universidade Estadual de Campinas, 13083-859 Campinas, São Paulo (Brazil); Costa, R. F. da [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-580 Santo André, São Paulo (Brazil); Varella, M. T. do N. [Instituto de Física, Universidade de São Paulo, C.P. 66318, 05315-970 São Paulo (Brazil); Bettega, M. H. F. [Departamento de Física, Universidade Federal do Paraná, C.P. 19044, 81531-990 Curitiba, Paraná (Brazil); Silva, G. B. da [Universidade Federal de Mato Grosso, Barra do Garças, Mato Grosso (Brazil); Brunger, M. J., E-mail: Michael.Brunger@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, G.P.O. Box 2100, Adelaide, SA 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2015-05-21
We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C{sub 6}H{sub 5}OH). The measurements were carried out at incident electron energies in the range 15–40 eV and for scattered-electron angles in the range 10–90°. The energy resolution of those measurements was typically ∼80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C{sub 6}H{sub 5}OH molecule by electron impact.
Vibrational relaxation of NO stretching modes in ferrous NO and ferric NO in model heme
Park, Jaeheung; Lee, Taegon; Lim, Manho
2013-08-01
Femtosecond IR-pump-IR-probe spectroscopy was used to measure the vibrational lifetimes (T1) of NO stretching modes of ferrous NO near 1600 cm-1 and ferric NO near 1900 cm-1 at room temperature. The T1 of NO bound to the heme, ranging from 3.5 to 34 ps, is much shorter in ferrous NO. The vibrational relaxation (VR) of NO was independent of solvent used and excess imidazole concentration, suggesting that intramolecular VR into the internal vibrational modes of the probed molecule may be the dominant pathway for VR of the bound NO. With estimated T1 of the bound NO, we simulated transient spectra of NO bound to ferrous hemoglobin (HbII) after photodeligation of HbIINO and discussed the influence of the hot band on the determination of the dynamics of geminate rebinding of NO to HbII using the change in the magnitude of the fundamental band.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
We study the effect of electrodes with varying thickness on thickness-twist vibration of a piezoelectric plate resonator of crystals of 6 mm symmetry. An exact theoretical analysis is performed. Results show that non-uniform electrodes have a strong effect on mode shapes, and suggest the possibility of using nonuniform electrodes for strong energy trapping.
Vibration mode of torsion balance and its response to external shock
Institute of Scientific and Technical Information of China (English)
汤洁; 罗俊; 范淑华
1997-01-01
Intrinsic vibration modes of typical torsion balances and their response to the external shock are discussed in detail. The study is important and instructive for improving measurement precision of gravitational experiments employing torsion balances, and gives a reasonable interpretation on detecting earthquake by high precision torsion balance.
Autonomous Control System for a Squeeze Mode Mr Vibration Isolator in an Automotive Engine Mount
Directory of Open Access Journals (Sweden)
Rosół Maciej
2014-09-01
Full Text Available The investigated autonomous control system for a squeeze mode magnetorheological (MR vibration isolator is based on an ultra-low power microcontroller MSP430F5529. The design structure of the control system and the dedicated real-time system are briefly presented and the laboratory testing data are summarised.
A Study of the Temperature Characteristics of Vibration Mode Axes for Vibratory Cylinder Gyroscopes
Directory of Open Access Journals (Sweden)
Xuezhong Wu
2011-08-01
Full Text Available The zero bias stability, which is an important performance parameter for vibratory cylinder gyroscopes, is high sensitive to temperature change. It is considered that the varying temperature makes the vibration mode axes unstable, which has significant influence on the zero bias stability. This paper will investigate this problem in detail. First, the relationships between the angular positions of vibration mode axes and the zero bias are analyzed. Secondly, the thermal-modal model of the cylinder resonator with several defects such as mass imbalance, frequency split (FS, and geometry errors are developed by ANSYS. Simulation results show that with the increase of temperature, angular positions of the vibration mode axes obviously change, which leads to a dramatic zero bias drift. Finally, several major influence factors on the angular position stability of vibration mode axes, including frequency split, geometry errors, thermal elastic modulus coefficient (TEMC and thermal expansion coefficient (TEC are analyzed in detail. Simulation results in this paper will be helpful for deep understanding of the drift principle of zero bias induced by temperature for vibratory cylinder gyroscopes and also be helpful for further temperature compensation or control.
DEFF Research Database (Denmark)
Rødgaard, Martin Schøler; Andersen, Thomas; Andersen, Michael A. E.
2012-01-01
. In this paper an interleaved interdigitated electrode (IDE) multilayer PT utilizing longitude and thickness mode vibration for high step-up and high output voltage is developed, for driving capacitive loads of up to 2.5kV. The PT possesses native soft switching capabilities, enabling the utilization of inductor...
Active Creation of Instrinsically Localized Vibrations in Uranium Using X-Ray and Neutron Scattering
Energy Technology Data Exchange (ETDEWEB)
Manley, M; Alatas, A; Trouw, F; Hults, W; Leu, B; Lynn, J; Chen, Y
2007-08-23
In real materials, nonlinear forces cause the frequencies of vibrating atoms to depend on amplitude. As a consequence, a large-amplitude fluctuation on the scale of the atom spacing can develop a frequency that does not resonate with the normal modes, causing energy to become trapped in an intrinsically localized mode (ILM)--also called 'discrete breather' or 'lattice soliton'. As temperature is increased, entropy is expected to stabilize increased concentrations of these random hotspots. This mechanism, which spontaneously concentrates energy, has been observed in analogous systems on a larger scale, but direct sightings at the atomic scale have proved difficult. Two challenges have hampered progress: (1) the need to separate ILMs from modes associated with crystal imperfections, and (2) complications that arise at high temperatures, including feature broadening and multiphonon processes. Here we solve both of these problems by actively creating ILMs at low temperatures in {alpha}-uranium using high-energy inelastic x-ray and neutron scattering. The ILM creation excitation occurs at energies ten times higher than conventional lattice excitations, cleanly separating it from modes associated with crystal imperfections. The discovery of this excitation not only proves the existence of ILMs in uranium but also opens up a new route for finding ILMs in other materials and, in the process, a new area for spectroscopy.
Single mode optical fiber vibration sensor: design and development
Alanis-Carranza, L. E.; Alvarez-Chavez, J. A.; Perez-Sanchez, G. G.; Sierra-Calderon, A.; Rodriguez-Novelo, J. C.
2016-09-01
This work deals with the design and development of an SMF28-based vibration detector including the fiber segment, the data acquisition via an NI-USB-6212 card, the data processing code in Visual Basic and the signal spectrum obtained via Fourier analysis. The set-up consists of a regulated voltage source at 2.6V, 300mA, which serves as the power source for a 980nm semiconductor laser operating at 150mW which is fiber coupled into a 20m-piece of SMF-28 fiber. Perpendicular to such fiber the perturbations ranged from 1 to 100 kHz, coming from a DC motor at 12 Volts. At the detection stage, a simple analog filter and a commercial photo diode were employed for data acquisition, before a transimpedance amplification stage reconstructed the signal into the National Instruments data acquisition card. At the output, the signals Fourier transformation allows the signal to be displayed in a personal computer. The presentation will include a full electrical and optical characterization of the device and preliminary sensing results, which could be suitable for structural health monitoring applications.
Mode pattern of internal flow in a water droplet on a vibrating hydrophobic surface.
Kim, Hun; Lim, Hee-Chang
2015-06-01
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.
Vibrational mode and sound radiation of electrostatic speakers using circular and annular diaphragms
Huang, Yu-Hsi; Chiang, Hsin-Yuan
2016-06-01
This study modeled two diaphragms comprising a pair of indium tin oxide (ITO) transparent plates sandwiching a vibrating diaphragm to create circular (30 mm radius) and annular (30 mm outer and 3 mm inner radius) push-pull electrostatic speakers. We then measured the displacement amplitudes and mode shapes produced by the devices. Vibration characteristics were used to predict sound pressure levels (SPLs) using the lumped parameter method (LPM) and distributed parameter method (DPM). The two measurement results obtained using a laser system were compared to the SPLs obtained using traditional acoustic measurement (AM) from 20 Hz to 20 kHz in order to verify our predictions. When using LPM and DPM, the SPL prediction results in the first three symmetric modes were in good agreement with the AM results. Under the assumption of linear operations, the DPM and amplitude-fluctuation electronic speckle pattern interferometry (ESPI) techniques proved effective in determining the visualization of mode shape (0,1)-(0,3). The use of ITO plates is a practical technique for the prediction of SPL, as well as measurement of mode shapes. The four evaluation methods, i.e. LPM, DPM, ESPI and AM, present a high degree of consistency with regard to vibrational mode and sound radiation characteristics.
Cavity quantum electrodynamics with Anderson-localized modes
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2010-01-01
by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices....
Localized radio frequency communication using asynchronous transfer mode protocol
Witzke, Edward L.; Robertson, Perry J.; Pierson, Lyndon G.
2007-08-14
A localized wireless communication system for communication between a plurality of circuit boards, and between electronic components on the circuit boards. Transceivers are located on each circuit board and electronic component. The transceivers communicate with one another over spread spectrum radio frequencies. An asynchronous transfer mode protocol controls communication flow with asynchronous transfer mode switches located on the circuit boards.
Spiralling solitons and multipole localized modes in nonlocal nonlinear media
DEFF Research Database (Denmark)
Buccoliero, Daniel; Lopez-Aguayo, Servando; Skupin, Stefan
2007-01-01
We analyze the propagation of rotating multi-soliton localized structures in optical media with spatially nonlocal nonlinearity. We demonstrate that nonlocality stabilizes the azimuthal breakup of rotating dipole as well as multipole localized soliton modes. We compare the results for two differe...... models of nonlocal nonlinearity and suggest that the stabilization mechanism is a generic property of a spatial nonlocal nonlinear response independent of its particular functional form.......We analyze the propagation of rotating multi-soliton localized structures in optical media with spatially nonlocal nonlinearity. We demonstrate that nonlocality stabilizes the azimuthal breakup of rotating dipole as well as multipole localized soliton modes. We compare the results for two different...
Vibrational spectra and DFT calculations of the vibrational modes of Schiff base C18H17N3O2
Antunes, J. A.; Silva, L. E.; Bento, R. R. F.; Teixeira, A. M. R.; Freire, P. T. C.; Faria, J. L. B.; Ramos, R. J.; Silva, C. B.; Lima, J. A.
2012-04-01
The Schiff base 4-{[(1E)-(2-Hydroxyphenyl)methylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (C18H17N3O2) is a synthetic compound with a variety of scientific and technological applications, such as clinic, analytic and pharmacologic. In this work FT-Raman spectrum and FT-infrared spectrum of C18H17N3O2 were investigated at 300 K. Vibrational wavenumber and wave vector have been predicted using Density Functional Theory (B3LYP) calculations with the 6-31 G(d,p) basis set. The description of the normal modes was performed by means of the potential energy distribution. A comparison with experiment allowed us to assign most of the normal modes of the crystal.
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.
Hudecová, Jana; Hopmann, Kathrin H; Bouř, Petr
2012-01-12
Vibrational properties of solutions are frequently simulated with clusters of a solute and a few solvent molecules obtained during molecular dynamics (MD) simulations. The raw cluster geometries, however, often provide unrealistic vibrational band broadening, for both ab initio and empirical force fields. In this work, partial optimization in normal-mode coordinates is used on empirical basis to reduce the broadening. The origin of the error is discussed on a simplified two-dimensional system, which indicates that the problem is caused by the anharmonic MD potential, mode coupling, and neglect of quantum effects. Then the procedure of partial geometry optimization on Raman and Raman optical activity (ROA) spectra is applied and analyzed for the solvated lactamide molecule. Comparison to experiment demonstrates that the normal-mode partial optimization technique with a suitable frequency limit can significantly reduce the broadening error. For lactamide, experimental and simulated vibrational bandwidths are compared; the most realistic theoretical spectra are obtained for partially optimized clusters with the vibrational wavenumber cutoff of about 200 cm(-1).
"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.
Sbai, K.; Rahmani, A.; Fakrach, B.; Chadli, H.; Benhamou, M.
2014-02-01
We study the collective vibrational breathing modes in the Raman spectrum of multiwalled carbon nanotubes (MCNTs). First, a bond polarization theory and the spectral moment's method (SMM) are used to calculate the non-resonant Raman frequencies of the breathing-like modes (BLMs) and the tangential-like ones (TLMs). Second, the Raman active modes of MCNTs are computed for different diameters and numbers of layers. The obtained low frequency modes in MCNTs can be identified to each single-walled carbon nanotubes. These modes that originate from the radial breathing ones of the individual walls are strongly coupled through the concentric tube-tube van der Waals interaction. The calculated BLMs in the low-frequency region are compared with the experimental Raman data obtained from other studies. Finally, special attention is given to the comparison with Raman data on MCNTs composed of six layers.
Tsen, K. T.; Dykeman, Eric C.; Sankey, Otto F.; Tsen, Shaw-Wei D.; Lin, Nien-Tsung; Kiang, Juliann G.
2006-11-01
Low-wavenumber (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.
Dumas, Jean-Charles; Barriga, Pablo; Zhao, Chunnong; Ju, Li; Blair, David G
2009-11-01
High performance vibration isolators are required for ground based gravitational wave detectors. To attain very high performance at low frequencies we have developed multistage isolators for the proposed Australian International Gravitational Observatory detector in Australia. New concepts in vibration isolation including self-damping, Euler springs, LaCoste springs, Roberts linkages, and double preisolation require novel sensors and actuators. Double preisolation enables internal feedback to be used to suppress low frequency seismic noise. Multidegree of freedom control systems are required to attain high performance. Here we describe the control components and control systems used to control all degrees of freedom. Feedback forces are injected at the preisolation stages and at the penultimate suspension stage. There is no direct actuation on test masses. A digital local control system hosted on a digital signal processor maintains alignment and position, corrects drifts, and damps the low frequency linear and torsional modes without exciting the very high Q-factor test mass suspension. The control system maintains an optical cavity locked to a laser with a high duty cycle even in the absence of an autoalignment system. An accompanying paper presents the mechanics of the system, and the optical cavity used to determine isolation performance. A feedback method is presented, which is expected to improve the residual motion at 1 Hz by more than one order of magnitude.
Maneuver and vibration reduction of flexible spacecraft using sliding mode/command shaping technique
Institute of Scientific and Technical Information of China (English)
HU Qing-lei; MA Guang-fu; ZHANG Wei
2006-01-01
A generalized scheme based on the sliding mode and component synthesis vibration suppression (CSVS) method has been proposed for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexible appendages. The proposed control design process is twofold: design of the attitude controller followed by the design of a flexible vibration attenuator. The attitude controller using only the attitude and the rate information for the flexible spacecraft (FS) is designed to serve two purposes: it forces the attitude motion onto a pre-selected sliding surface and then guides it to the state space origin. The shaped command input controller based on the CSVS method is designed for the reduction of the flexible mode vibration, which only requires information about the natural frequency and damping of the closed system. This information is used to discretize the input so that minimum energy is injected via the controller to the flexible nodes of the spacecraft. Additionally, to extend the CSVS method to the system with the on-off actuators, the pulse-width pulse-frequency ( PWPF) modulation is introduced to control the thruster firing and integrated with the CSVS method. PWPF modulation is a control method that provides pseudo-linear operation for an on-off thruster. The proposed control strategy has been implemented on a FS, which is a hub with symmetric cantilever flexible beam appendages and can undergo a single axis rotation. The results have been proven the potential of this technique to control FS.
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.
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.
Nonlinear Control Strategies for Bioprocesses: Sliding Mode Control versus Vibrational Control
Selisteanu, Dan; Petre, Emil; Popescu, Dorin; Bobasu, Eugen
2008-01-01
In this work, two nonlinear high-frequency control strategies for bioprocesses are proposed: a feedback sliding mode control law and a vibrational control strategy. In order to implement these strategies, a prototype bioprocess that is carried out in a Continuous Stirred Tank Bioreactor was considered. First, a discontinuous feedback law was designed using the exact linearization and by imposing a SMC that stabilizes the output of the bioprocess. When some state variables used in the control ...
Liubchenko, P N; Evlashko, Iu P; Dmitruk, L I
2011-01-01
Opposite to the authors of the publication, that dystrophic changes in locomotory apparatus of hands and shoulders girdle could not be considered as vibration disease signs, the article authors believe that hand bone changes--tuberosity of distal finger bones, cystic transparency, local osteoporosis--could be pathogenetic signs of vibration disease, along with vascular and neurologic signs. The authors agree that periarthrosis, miofibrosis, if characterized properly through sanitary and hygienic regulations in new List of Occupational diseases, that will be put into practical medicine in the nearest future, could be considered as second occupational disease in the same patient.
Study on vibrational modes by group theory and infrared spectra by D FT for calcite crystal
Institute of Scientific and Technical Information of China (English)
Danhua Lou; Fengjiu Sun; Lijuan Li
2007-01-01
The factor group symmetry analysis (FSA) method and position symmetry analysis (PSA) method are used to analyze the vibrational modes of calcite (CaCO3) crystal, respectively. With the activated results of infrared and Raman spectra presented, strong points of each method are concluded. The infrared spectra are studied by using dynamics calculations based on density-functional theory (DFT) with the supercell model of calcite crystal. The frequencies of 27 normal modes are achieved, which are consistent with that by the group symmetry analysis very well, and fit with the experimental results better than the lattice dynamical methods.
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.
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.
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.
Tuan, P. H.; Wen, C. P.; Yu, Y. T.; Liang, H. C.; Huang, K. F.; Chen, Y. F.
2014-02-01
Experimentally resonant modes are commonly presumed to correspond to eigenmodes in the same bounded domain. However, the one-to-one correspondence between theoretical eigenmodes and experimental observations is never reached. Theoretically, eigenmodes in numerous classical and quantum systems are the solutions of the homogeneous Helmholtz equation, whereas resonant modes should be solved from the inhomogeneous Helmholtz equation. In the present paper we employ the eigenmode expansion method to derive the wave functions for manifesting the distinction between eigenmodes and resonant modes. The derived wave functions are successfully used to reconstruct a variety of experimental results including Chladni figures generated from the vibrating plate, resonant patterns excited from microwave cavities, and lasing modes emitted from the vertical cavity.
Discrete dissipative localized modes in nonlinear magnetic metamaterials.
Rosanov, Nikolay N; Vysotina, Nina V; Shatsev, Anatoly N; Shadrivov, Ilya V; Powell, David A; Kivshar, Yuri S
2011-12-19
We analyze the existence, stability, and propagation of dissipative discrete localized modes in one- and two-dimensional nonlinear lattices composed of weakly coupled split-ring resonators (SRRs) excited by an external electromagnetic field. We employ the near-field interaction approach for describing quasi-static electric and magnetic interaction between the resonators, and demonstrate the crucial importance of the electric coupling, which can completely reverse the sign of the overall interaction between the resonators. We derive the effective nonlinear model and analyze the properties of nonlinear localized modes excited in one-and two-dimensional lattices. In particular, we study nonlinear magnetic domain walls (the so-called switching waves) separating two different states of nonlinear magnetization, and reveal the bistable dependence of the domain wall velocity on the external field. Then, we study two-dimensional localized modes in nonlinear lattices of SRRs and demonstrate that larger domains may experience modulational instability and splitting.
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
Institute of Scientific and Technical Information of China (English)
CHEN Chao; SHI Yunlai; CHEN Haipeng; ZHAO Chunsheng
2014-01-01
A novel linear ultrasonic motor based on d15 effect of piezoelectric materials was presented. The design idea aimed at the direct utilization of the shear-induced vibration modes of piezoelectric material. Firstly, the inherent electromechanical coupling mechanism of piezoelectric material was investigated, and shear vibration modes of a piezoelectric shear block was specially designed. A driving point’s elliptical trajectory induced by shear vibration modes was discussed. Then a dynamic model for the piezoelectric shear stator was established with finite element (FE) method to conduct the parametric optimal design. Finally, a prototype based on d15 converse piezoelectric effect is manufactured, and the modal experiment of piezoelectric stator was conducted with laser doppler vibrometer. The experimental results show that the calculated shear-induced vibration modes can be excited completely, and the new linear ultrasonic motor reaches a speed 118 mm/s at no-load, and maximal thrust 12.8 N.
De Boeij, W. P.; Pshenichnikov, M. S.; Wiersma, D. A.
1996-01-01
We demonstrate a novel technique for efficient vibrational mode suppression in stimulated photon echo by diagonal time-gating. This is especially important if the system exhibits non-Markovian optical dynamics.
Institute of Scientific and Technical Information of China (English)
Bian Yushu; Gao Zhihui
2013-01-01
Parameter optimization of the controllable local degree of freedom is studied for reducing vibration of the flexible manipulator at the lowest possible cost.The controllable local degrees of freedom are suggested and introduced to the topological structure of the flexible manipulator,and used as an effective way to alleviate vibration through dynamic coupling.Parameters introduced by the controllable local degrees of freedom are analyzed and their influences on vibration reduction are investigated.A strategy to optimize these parameters is put forward and the corresponding optimization method is suggested based on Particle Swarm Optimization (PSO).Simulations are conducted and results of case studies confirm that the proposed optimization method is effective in reducing vibration of the flexible manipulator at the lowest possible cost.
Impact vibration reduction for flexible manipulators via controllable local degrees of freedom
Institute of Scientific and Technical Information of China (English)
Bian Yushu; Gao Zhihui; Deng Yuchun
2013-01-01
When performing operation tasks, the interaction between a flexible manipulator and a grasped object usually results in an impact. In this paper, a new way is suggested to alleviate impact vibration of a flexible manipulator via its structural characteristic when capturing a moving object. Controllable local degrees of freedom are introduced to the topological structure of the flexible manipulator, and used as an effective tool to combat impact vibration through dynamic coupling. A corresponding method is put forward to reduce impact vibration responses of the flexible manip-ulator via the controllable local degrees of freedom. By planning motion of the controllable local degrees of freedom, appropriate control force can be constructed to increase the modal damping and stiffness and eliminate the exciting force simultaneously, thereby reducing impact vibration responses of the flexible manipulator. Simulations are conducted and results are shown to prove the presented method.
Optimization of new magnetorheological fluid mount for vibration control of start/stop engine mode
Chung, Jye Ung; Phu, Do Xuan; Choi, Seung-Bok
2015-04-01
The technologies related to saving energy/or green vehicles are actively researched. In this tendency, the problem for reducing exhausted gas is in development with various ways. Those efforts are directly related to the operation of engine which emits exhausted gas. The auto start/stop of vehicle engine when a vehicle stop at road is currently as a main stream of vehicle industry resulting in reducing exhausted gas. However, this technology automatically turns on and off engine frequently. This motion induces vehicle engine to transmit vibration of engine which has large displacement, and torsional impact to chassis. These vibrations causing uncomfortable feeling to passengers are transmitted through the steering wheel and the gear knob. In this work, in order to resolve this vibration issue, a new proposed magnetorheological (MR) fluid based engine mount (MR mount in short) is presented. The proposed MR mount is designed to satisfy large damping force in various frequency ranges. It is shown that the proposed mount can have large damping force and large force ratio which is enough to control unwanted vibrations of engine start/stop mode.
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.
Detecting magnetic field direction by a micro beam operating in different vibration modes
Institute of Scientific and Technical Information of China (English)
Chen Jie; Qin Ming; Huang Qing-An
2011-01-01
A new method to detect the magnetic field direction by using a silicon structure is presented in this paper. The structure includes a micro beam and an in-plane coil electrode. When the electrode under a magnetic field is applied with an alternating current,the micro beam is actuated under the effect of the Lorentz forces. Magnetic fields of different directions cause different vibration profiles. The direction of the magnetic field is obtained by measuring the vibration amplitudes of the micro beam,which is driven to work at first- and second-order resonant modes. A micro structure has been fabricated using the bulk micromachined silicon process. A laser Doppler vibrometer system is implemented to measure the vibration amplitudes. The experimental results show that the amplitude of the structure,which depends on the different modes,is a sine or cosine function of the angle of the magnetic field. It agrees well with the simulation result. Currently a resolution of 100 for the magnetic field direction measurement can be obtained using the detecting principle.
Institute of Scientific and Technical Information of China (English)
He ZHANG; Xu XIE
2011-01-01
Stay cables,the primary load carrying components of cable-stayed bridges (CSBs),are characterised by high flexibility which increases with the span of the bridge.This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs.Hence,it is essential to account for these effects in the assessment of the dynamics CSBs.In this paper,the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM),while the local vibration of stay cables is analyzed using the substructure method.A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although,in general,a cable's local vibrations are not obvious.The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge.Load impact factors of the main girder and tower are small,and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.
Directory of Open Access Journals (Sweden)
Sova S.G.
2015-03-01
Full Text Available The paper analyzes the differences between domestic and European methodology of hygienic standardization of the local impulse vibration. With the assistance of the vibrometer Octava-101-U there were studied hygienic parameters of pulsed local vibrations in mechanical workshops of the State Enterprise "Antonov" and the State Enterprise "Plant 410 civil aviation" according to the procedure set out in SSN 3.3.6.039-99 "State sanitary norms of general and local production vibration". Levels of pulsed local vibration in the workplace of fitter-assemblers and fitters do not exceed the standards of domestic hygiene standards and, at the same time, ten times higher than the exposure limits of the European system of standards “Health and Sufety Executive” (HSE. Discrepancies between national and European system of regulation and assessment of the harmful effects of local vibration can explain the development of early clinical syndromes in workers of vibration-dangerous enterprises, this makes to pical bringing of Ukrainian hygienic standards to European standards.
Observation of Localized Multi-Spatial-Mode Quadrature Squeezing
Directory of Open Access Journals (Sweden)
C. S. Embrey
2015-07-01
Full Text Available Quantum states of light can improve imaging whenever the image quality and resolution are limited by the quantum noise of the illumination. In the case of a bright illumination, quantum enhancement is obtained for a light field composed of many squeezed transverse modes. A possible realization of such a multi-spatial-mode squeezed state is a field which contains a transverse plane in which the local electric field displays reduced quantum fluctuations at all locations, on any one quadrature. Using a traveling-wave amplifier, we have generated a multi-spatial-mode squeezed state and showed that it exhibits localized quadrature squeezing at any point of its transverse profile, in regions much smaller than its size. We observe 75 independently squeezed regions. The amplification relies on nondegenerate four-wave mixing in a hot vapor and produces a bichromatic squeezed state. The result confirms the potential of this technique for producing illumination suitable for practical quantum imaging.
Cavity quantum electrodynamics with Anderson-localized modes.
Sapienza, Luca; Thyrrestrup, Henri; Stobbe, Søren; Garcia, Pedro David; Smolka, Stephan; Lodahl, Peter
2010-03-12
A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.
Vertical Transport of Subwavelength Localized Surface Electromagnetic Modes
Gao, Fei; Zhang, Youming; Shi, Xihang; Yang, Zhaoju; Zhang, Baile
2015-01-01
Transport of subwavelength electromagnetic (EM) energy has been achieved through near-field coupling of highly confined surface EM modes supported by plasmonic nanoparticles, in a configuration usually staying on a two-dimensional (2D) substrate. Vertical transport of similar modes along the third dimension, on the other hand, can bring more flexibility in designs of functional photonic devices, but this phenomenon has not been observed in reality. In this paper, designer (or spoof) surface plasmon resonators (plasmonic meta-atoms) are stacked in the direction vertical to their individual planes in demonstrating vertical transport of subwavelength localized surface EM modes. Dispersion relation of this vertical transport is determined from coupled mode theory and is verified with near-field transmission spectrum and field mapping with a microwave near-field scanning stage. This work extends the near-field coupled resonator optical waveguide (CROW) theory into the vertical direction, and may find applications ...
IP over ATM Implementation with Local Switch Mode
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
In classical IPOA, the communication of two users between local Asynchronous Transfer Mode(ATM) ports needs a VCC, however, it is not an elegant solution to the ATM access equipments design when the performance of the whole system is considered. Thus, we investigate the way to provide the improved IPOA protocol that uses switching way in local ports. And it is fully compatible with the CIPOA by using the same protocol for ARP and IP forwarding. In addition, we also present the design of one 10/100 Mbit/s auto adaptive IPOA client board with local switch ability idea and CAM mechanism for our project.
Yang, Jingyu; Lin, Jiahui; Liu, Yuejun; Yang, Kang; Zhou, Lanwei; Chen, Guoping
2016-06-01
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.
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.
Institute of Scientific and Technical Information of China (English)
Liang Xi-Xia; Ban Shi-Liang
2004-01-01
@@ Optical vibrations of the lattice and the electron-phonon interaction in polar ternary mixed crystals are studied in the framework of the continuum model of Born and Huang and the random-element-isodisplacement model. A normal-coordinate system to describe the optical vibration in ternary mixed crystals is correctly adopted to derive a new Frohlich-like Hamiltonian for the electron-phonon interaction including the unit-cell volume variation influence.The numerical results for the phonon modes, the electron-phonon coupling constants and the polaronic energies for several typical materials are obtained. It is verified that the nonlinearity of the electron-phonon coupling effects with the composition is essential and the unit-cell volume effects cannot be neglected for most ternary mixed crystals.
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.
Goos-Hänchen effect for optical vibrational modes in a semiconductor structure.
Villegas, Diosdado; Arriaga, J; de León-Pérez, Fernando; Pérez-Álvarez, R
2017-03-29
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.
High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.
Thome, K E; Bongard, M W; Barr, J L; Bodner, G M; Burke, M G; Fonck, R J; Kriete, D M; Perry, J M; Schlossberg, D J
2016-04-29
Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.
Parametric localized modes in quadratic nonlinear photonic structures
DEFF Research Database (Denmark)
Sukhorukov, Andrey A.; Kivshar, Yuri S.; Bang, Ole;
2001-01-01
We analyze two-color spatially localized nonlinear modes formed by parametrically coupled fundamental and second-harmonic fields excited at quadratic (or chi2) nonlinear interfaces embedded in a linear layered structure-a quadratic nonlinear photonic crystal. For a periodic lattice of nonlinear...... interfaces, we derive an effective discrete model for the amplitudes of the fundamental and second-harmonic waves at the interfaces (the so-called discrete chi2 equations) and find, numerically and analytically, the spatially localized solutions-discrete gap solitons. For a single nonlinear interface...... in a linear superlattice, we study the properties of two-color localized modes, and describe both similarities to and differences from quadratic solitons in homogeneous media....
Huang, Yunfei; Luan, Huiqin; Sun, Lianwen; Bi, Jingfang; Wang, Ying; Fan, Yubo
2017-08-01
Spaceflight induced bone loss is seriously affecting astronauts. Mechanical stimulation from exercise has been shown to restrain bone resorption as well as improve bone formation. Current exercise countermeasures in space cannot prevent it completely. Active exercise may convert to passive exercise in some ways because of the loss of gravity stimulus and inertia of exercise equipment. The aim of this study was to compare the efficacy of passive exercise or/and local vibration on counteracting the deterioration of the musculoskeletal system, including bone, muscle and tendons in tail-suspended rats. We hypothesized that local vibration could enhance the efficacy of passive exercise on countering bone loss. 40 Sprague Dawley rats were randomly distributed into five groups (n = 8, each): tail-suspension (TS), TS+35 Hz vibration (TSV), TS + passive exercise (TSP), TS + passive exercise coupled with 35 Hz vibration (TSPV) and control (CON). Passive exercise or/and local vibration was performed for 21 days. On day 0 and 21, bone mineral density (BMD) was observed by dual energy X-ray absorptiometry (DXA), and trabecular microstructure was evaluated by microcomputer tomography (μCT) analysis in vivo. Mechanical properties of tibia and tendon were determined by a mechanical testing system. Soleus and bone ash weight was tested by an electronic balance. Results showed that the passive exercise could not prevent the decrease of trabecular BMD, microstructure and bone ash weight induced by TS, whereas vibration and passive exercise coupled with local vibration (PV) could. Biomechanical properties of the tibia and tendon in TSPV group significantly increased compared with TS group. In summary, PV in this study was the best method in preventing weightlessness-induced bone loss. Consistent with our hypothesis, local vibration partly enhanced the effect of passive exercise. Furthermore, this study will be useful in improving countermeasure for astronauts, but also for the
Leguy, Aurélien M A; Frost, Jarvist M; Skelton, Jonathan; Brivio, Federico; Rodríguez-Martínez, Xabier; Weber, Oliver J; Pallipurath, Anuradha; Alonso, M Isabel; Campoy-Quiles, Mariano; Weller, Mark T; Nelson, Jenny; Walsh, Aron; Barnes, Piers R F
2016-01-01
We present Raman and terahertz absorbance spectra of methylammonium lead halide single crystals (MAPbX3, X = I, Br, Cl) at temperatures between 80 and 370 K. These results show good agreement with density-functional-theory phonon calculations.1 Comparison of experimental spectra and calculated vibrational modes enables confident assignment of most of the vibrational features between 50 and 3500 cm-1. Reorientation of the methylammonium cations, unlocked in their cavities at the orthorhombic-to-tetragonal phase transition, plays a key role in shaping the vibrational spectra of the different compounds. Calculations show that these dynamics effects split Raman peaks and create more structure than predicted from the independent harmonic modes. This explains the presence of extra peaks in the experimental spectra that have been a source of confusion in earlier studies. We discuss singular features, in particular the torsional vibration of the C-N axis, which is the only molecular mode that is strongly influenced b...
Sato, M; Shi, W; Shige, S; Ishikawa, T; Soga, Y; Hubbard, B E; Ilic, B; Sievers, A J
2014-01-01
Both low frequency and high frequency impurity modes have been produced in a SiN micromechanical cantilever array by illumination with either an infrared or visible laser. When such laser-induced impurities are placed near a driven intrinsic localized mode (ILM) it is either repelled or attracted. By measuring the linear response spectrum for these two cases it was found that vibrational hopping of the ILM takes place when the natural frequency of the ILM and an even symmetry linear local mode are symmetrically located about the driven ILM frequency so that parametric excitation of these two linear modes is enhanced, amplifying the lateral motion of the ILM. Numerical simulations are consistent with these signature findings. It is also demonstrated that the correct sign of the observed interaction can be found with a harmonic lattice-impurity model but the magnitude of the effect is enhanced in a nonlinear lattice.
Directory of Open Access Journals (Sweden)
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.
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.
Krishna Bhaskar, K.; Meera Saheb, K.
2015-12-01
A simple but accurate continuum solution for the shear flexible beam problem using the energy method involves in assuming suitable single term admissible functions for the lateral displacement and total rotation. This leads to two non-linear temporal differential equations in terms of the lateral displacement and the total rotation and are difficult, if not impossible, to solve to obtain the large amplitude fundamental frequencies of beams as a function of the amplitude and slenderness ratios of the vibrating beam. This situation can be avoided if one uses the concept of coupled displacement field where in the fields for lateral displacement and the total rotation are coupled through the static equilibrium equation. In this paper the lateral displacement field is assumed and the field for the total rotation is evaluated through the coupling equation. This approach leads to only one undetermined coefficient which can easily be used in the principle of conservation of total energy of the vibrating beam at a given time, neglecting damping. Finally, through a number of algebraic manipulations, one gets a nonlinear equation of Duffing type which can be solved using any standard method. To demonstrate the simplicity of the method discussed above the problem of large amplitude free vibrations of a uniform shear flexible hinged beam at higher modes with ends immovable to move axially has been solved. The numerical results obtained from the present formulation are in very good agreement with those obtained through finite element and other continuum methods for the fundamental mode, thus demonstrating the efficacy of the proposed method. Also some interesting observations are made with variation of frequency Vs amplitude at different modes.
Localization and instability in sheared granular materials: Role of friction and vibration
Kothari, Konik R
2016-01-01
Shear banding and stick-slip instabilities have been long observed in sheared granular materials. Yet, their microscopic underpinnings, interdependencies and variability under different loading conditions have not been fully explored. Here, we use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in sheared, dry, granular materials. We consider frictional and frictionless grains as well as presence and absence of acoustic vibrations. Our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the granular network and de-localize slip at these rates. Stick-slip is only observed for frictional grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of...
A pragmatic approach to including complex natural modes of vibration in aeroelastic analysis
CSIR Research Space (South Africa)
Van Zyl, Lourens H
2015-09-01
Full Text Available -proportionally damped • There are two main ground vibration testing methods: Phase separation (“broadband”) and phase resonance (“sine dwell”) • In phase separation testing the test consists of measuring a large number of transfer functions, typically in the order... to the off-diagonal damping matrix terms) appears to be lost. • The sine-dwell method does however leave a record of the input forces and velocities at the excitation positions when the mode was excited. This record is used to determine the off- diagonal...
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A complex number mode analysis approach is proposed for vibration reducing of structural flexible redundant manipulators by utilizing self-motion. In the proposed approach, the self-motion is evaluated to nullify the modal exciting-force of flexural motion, and the approach can be freely used when the degree of freedom of flexural motion is much greater than the available degree of reundancy. The availability and effectiveness of the proposed approach are demonstrated through numerical simulation with a four-link spatial robotic manipulator possessing an end flexible link.
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
isotope substitution is obtained. The stretching dependence for each of the modes allows uniquely classifying them as longitudinal or transversal modes. The interpretation of the experiment in terms of a Pt-H-2-Pt bridge is verified by density-functional theory calculations for the stability, vibrational...
Mirshekari, Mostafa; Pan, Shijia; Zhang, Pei; Noh, Hae Young
2016-04-01
The objective of this paper is to characterize frequency-dependent wave propagation of footstep induced floor vibration to improve robustness of vibration-based occupant localization. Occupant localization is an essential part of many smart structure applications (e.g., energy management, patient/customer tracking, etc.). Exist- ing techniques include visual (e.g. cameras and IR sensors), acoustic, RF, and load-based approaches. These approaches have many deployment and operational requirements that limits their adaptation. To overcome these limitations, prior work has utilized footstep-induced vibrations to allow sparse sensor configuration and non-intrusive detection. However, frequency dependent propagation characteristics and low signal-to-noise ratio (SNR) of footstep-induced vibrations change the shape of the signal. Furthermore, estimating the wave propagation velocity for forming the multilateration equations and localizing the footsteps is a challenging task. They, in turn, lead to large errors of localization. In this paper, we present a structural vibration based indoor occupant localization technique using improved time-difference-of-arrival between multiple vibration sensors. In particular we overcome signal distortion by decomposing the signal into frequency components and focusing on high energy components for accurate indoor localization. Such decomposition leverages the frequency-specific propagation characteristics and reduces the effect of low SNR (by choosing the components of highest energy). Furthermore, we develop a velocity calibration method that finds the optimal velocity which minimizes the localization error. We validate our approach through field experiments in a building with human participants. We are able to achieve an average localization error of less than 0.21 meters, which corresponds to a 13X reduction in error when compared to the baseline method using raw data.
Edge localized mode rotation and the nonlinear dynamics of filaments
Energy Technology Data Exchange (ETDEWEB)
Morales, J. A.; Bécoulet, M.; Garbet, X.; Dif-Pradalier, G.; Huijsmans, G. T. A.; Fil, A.; Nardon, E.; Passeron, C.; Latu, G. [CEA, IRFM, 13108 St. Paul-Lez-Durance (France); Orain, F.; Hoelzl, M. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany); Pamela, S. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Cahyna, P. [Institute of Plasma Physics ASCR, Za Slovankou 1782/3, 182 00 Prague 8 (Czech Republic)
2016-04-15
Edge Localized Modes (ELMs) rotating precursors were reported few milliseconds before an ELM crash in several tokamak experiments. Also, the reversal of the filaments rotation at the ELM crash is commonly observed. In this article, we present a mathematical model that reproduces the rotation of the ELM precursors as well as the reversal of the filaments rotation at the ELM crash. Linear ballooning theory is used to establish a formula estimating the rotation velocity of ELM precursors. The linear study together with nonlinear magnetohydrodynamic simulations give an explanation to the rotations observed experimentally. Unstable ballooning modes, localized at the pedestal, grow and rotate in the electron diamagnetic direction in the laboratory reference frame. Approaching the ELM crash, this rotation decreases corresponding to the moment when the magnetic reconnection occurs. During the highly nonlinear ELM crash, the ELM filaments are cut from the main plasma due to the strong sheared mean flow that is nonlinearly generated via the Maxwell stress tensor.
Edge localized mode rotation and the nonlinear dynamics of filaments
Morales, J. A.; Bécoulet, M.; Garbet, X.; Orain, F.; Dif-Pradalier, G.; Hoelzl, M.; Pamela, S.; Huijsmans, G. T. A.; Cahyna, P.; Fil, A.; Nardon, E.; Passeron, C.; Latu, G.
2016-04-01
Edge Localized Modes (ELMs) rotating precursors were reported few milliseconds before an ELM crash in several tokamak experiments. Also, the reversal of the filaments rotation at the ELM crash is commonly observed. In this article, we present a mathematical model that reproduces the rotation of the ELM precursors as well as the reversal of the filaments rotation at the ELM crash. Linear ballooning theory is used to establish a formula estimating the rotation velocity of ELM precursors. The linear study together with nonlinear magnetohydrodynamic simulations give an explanation to the rotations observed experimentally. Unstable ballooning modes, localized at the pedestal, grow and rotate in the electron diamagnetic direction in the laboratory reference frame. Approaching the ELM crash, this rotation decreases corresponding to the moment when the magnetic reconnection occurs. During the highly nonlinear ELM crash, the ELM filaments are cut from the main plasma due to the strong sheared mean flow that is nonlinearly generated via the Maxwell stress tensor.
Signatures of different vibrational modes in strong-field fragmentation of diiodomethane
Kaderiya, B.; Malakar, Y.; Kanaka Raju, P.; Pearson, W. L.; Ziaee, F.; Jensen, K.; Rajput, J.; Ben-Itzhak, I.; Roles, D.; Rudenko, A.
2016-05-01
The diiodomethane molecule (CH2 I2) has served as a model system for time-domain studies of large-scale bending vibrations and concerted elimination of I2+.Here we present the results of a time-resolved 3D Coulomb explosion imaging experiment on diiodomethane that maps ultrafast dynamics of both, bound and dissociating nuclear wave packets driven by a strong laser field. Measuring yields, kinetic energies and emission angles of coincident ionic fragments as a function of time delay between two 25 fs, 800 nm pump and probe pulses, we track the propagation of different dissociation pathways and visualize vibrational motion of the molecule. Analyzing channel-selective Fourier spectra, we observe signatures of both, bending and stretching vibrations of diiodomethane, and reveal correlation between bending motion (the I-C-I ``scissors'' mode) and different fragmentation pathways, including I2+elimination. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. DOE. K. R. P. and W. L. P. supported by NSF Award No. IIA-143049, K.J. supported by the NSF-REU Grant No. PHYS-1461251.
Relating the radiated piano sound field to the vibrational modes of the soundboard
Hansen, Uwe J.; Bork, Ingolf; Rossing, Thomas D.
2003-10-01
The sound field near a piano sound board is determined by moving a microphone over a grid of points above and below the sound board as well as in a plane in front of the piano using the experimental techniques of modal analysis with soundboard excitation at a bridge point by a swept sine signal. Since the standard modal analysis signal processing technique relies on tracking phase relations between excitation and response, it is possible to relate the sound field in terms of the vibrating structure which radiated it. Animations of sound board motion and sound field pressure variations are shown for the lowest four modes. It is noted that in all modes the locations of maximal excursion correlate with the sound pressure maxima or minima, respectively.
Application of empirical mode decomposition method for characterization of random vibration signals
Directory of Open Access Journals (Sweden)
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.
Investigation of Microstructure, Natural Frequencies and Vibration Modes of Dragonfly Wing
Institute of Scientific and Technical Information of China (English)
H. Rajabi; M. Moghadami; A. Darvizeh
2011-01-01
In the present work, a thorough investigation on the microstructural and morphological aspects of dragonfly wings was carried out using scanning electron microscope. Then, based on this study and the previous reports, a precise three-dimensional numerical model was developed and natural frequencies and vibration modes of dragonfly forewing were determined by finite element method. The results shown that dragonfly wings are made of a series of adaptive materials, which form a very complex composite structure. This bio-composite fabrication has some unique features and potential benefits. Furthermore, the numerical results show that the first natural frequency of dragonfly wings is about 168 Hz and bending is the predominant deformation mode in this stage. The accuracy of the present analysis is verified by comparison of calculated results with experimental data.This paper may be helpful for micro aerial vehicle design concerning dynamic response.
Driven intrinsic localized modes in a coupled pendulum array
Energy Technology Data Exchange (ETDEWEB)
Thakur, R Basu [Department of Physics and Astronomy, Dickinson College, Carlisle, PA 17013 (United States); English, L Q [Department of Physics and Astronomy, Dickinson College, Carlisle, PA 17013 (United States); Sievers, A J [Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853 (United States)
2008-01-07
Intrinsic localized modes (ILMs), also called discrete breathers, are directly generated via modulational instability in an array of coupled pendulums. These ILMs can be stabilized over a range of driver frequencies and amplitudes. They are characterized by a {pi}-phase difference between their centre and wings. At higher driver frequencies, these ILMs are observed to disintegrate via a pulsating instability, and the mechanism of this breather instability is investigated.
Institute of Scientific and Technical Information of China (English)
WANG Jian; GUO Jifeng
2008-01-01
Cylindrical Ultrasonic Motor (CUSM)can be widely used in many fields such as zoom and focus system of cameras,electric curtain and micro-driver of MEMS.This work concentrates on the single-point and the double-point contact modes between the stator and the rotor.which are proved by theory and experiment.There is a critical point of the pre-pressure.When the pre-pressure is below the critical point.the single-point model is suitable;otherwise the double-point model is appropriate.Then the force transferring model is analyzed,and expressions of mechanical characteristics and efficiency of the motor axe put forward.Simulation results are confirmed by experimental ones,which shows that the model is well suited to guide design of the motor.Finally a φ14 mm prototype was fabricated.Its maximum torque is 0.11 Nm.and the no-load speed is about 300 r/min.
Nonlinear simulations of particle source effects on edge localized mode
Energy Technology Data Exchange (ETDEWEB)
Huang, J.; Tang, C. J. [College of Physical Science and Technology, Sichuan University, Chengdu 610065 (China); Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Chen, S. Y., E-mail: sychen531@163.com [College of Physical Science and Technology, Sichuan University, Chengdu 610065 (China); Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Southwestern Institute of Physics, Chengdu 610041 (China); Wang, Z. H. [Southwestern Institute of Physics, Chengdu 610041 (China)
2015-12-15
The effects of particle source (PS) with different intensities and located positions on Edge Localized Mode (ELM) are systematically studied with BOUT++ code. The results show the ELM size strongly decreases with increasing the PS intensity once the PS is located in the middle or bottom of the pedestal. The effects of PS on ELM depend on the located position of PS. When it is located at the top of the pedestal, peeling-ballooning (P-B) modes can extract more free energy from the pressure gradient and grow up to be a large filament at the initial crash phase and the broadening of mode spectrum can be suppressed by PS, which leads to more energy loss. When it is located in the middle or bottom of the pedestal, the extraction of free energy by P-B modes can be suppressed, and a small filament is generated. During the turbulence transport phase, the broader mode spectrum suppresses the turbulence transport when PS is located in the middle, while the zonal flow plays an important role in damping the turbulence transport when PS is located at the bottom.
Nonlinear TeraHertz Coherent Excitation of Vibrational Modes of Liquids
Allodi, Marco A; Blake, Geoffrey A
2015-01-01
We report the first coherent excitation of intramolecular vibrational modes via the nonlinear interaction of a TeraHertz (THz) light field with molecular liquids. A TeraHertz-TeraHertz-Raman pulse sequence prepares the coherences with a broadband, high-energy, (sub)picosecond TeraHertz pulse, that are then measured in a TeraHertz Kerr effect spectrometer via phase-sensitive, heterodyne detection with an optical pulse. The spectrometer reported here has broader TeraHertz frequency coverage and an increased sensitivity relative to previously reported TeraHertz Kerr effect experiments. Vibrational coherences are observed in liquid diiodomethane at 3.66 THz (122 cm$^{-1}$), and in carbon tetrachloride at 6.50 THz (217 cm$^{-1}$), in exact agreement with literature values of those intramolecular modes. This work opens the door to 2D spectroscopies, nonlinear in TeraHertz field, that can study the dynamics of condensed-phase molecular systems, as well as coherent control at TeraHertz frequencies.
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.
Edge-localized mode avoidance and pedestal structure in I-mode plasmas
Energy Technology Data Exchange (ETDEWEB)
Walk, J. R., E-mail: jrwalk@psfc.mit.edu; Hughes, J. W.; Hubbard, A. E.; Terry, J. L.; Whyte, D. G.; White, A. E.; Baek, S. G.; Reinke, M. L.; Theiler, C.; Churchill, R. M.; Rice, J. E. [MIT Plasma Science and Fusion Center, Cambridge, MA 02139-4307 (United States); Snyder, P. B.; Osborne, T. [General Atomics, San Diego, CA 92186-5608 (United States); Dominguez, A [Princeton Plasma Physics Laboratory, Princeton, NJ 08543-0451 (United States); Cziegler, I. [UCSD Center for Momentum Transport and Flow Organization, La Jolla, CA 92093-0417 (United States)
2014-05-15
I-mode is a high-performance tokamak regime characterized by the formation of a temperature pedestal and enhanced energy confinement, without an accompanying density pedestal or drop in particle and impurity transport. I-mode operation appears to have naturally occurring suppression of large Edge-Localized Modes (ELMs) in addition to its highly favorable scalings of pedestal structure and overall performance. Extensive study of the ELMy H-mode has led to the development of the EPED model, which utilizes calculations of coupled peeling-ballooning MHD modes and kinetic-ballooning mode (KBM) stability limits to predict the pedestal structure preceding an ELM crash. We apply similar tools to the structure and ELM stability of I-mode pedestals. Analysis of I-mode discharges prepared with high-resolution pedestal data from the most recent C-Mod campaign reveals favorable pedestal scalings for extrapolation to large machines—pedestal temperature scales strongly with power per particle P{sub net}/n{sup ¯}{sub e}, and likewise pedestal pressure scales as the net heating power (consistent with weak degradation of confinement with heating power). Matched discharges in current, field, and shaping demonstrate the decoupling of energy and particle transport in I-mode, increasing fueling to span nearly a factor of two in density while maintaining matched temperature pedestals with consistent levels of P{sub net}/n{sup ¯}{sub e}. This is consistent with targets for increased performance in I-mode, elevating pedestal β{sub p} and global performance with matched increases in density and heating power. MHD calculations using the ELITE code indicate that I-mode pedestals are strongly stable to edge peeling-ballooning instabilities. Likewise, numerical modeling of the KBM turbulence onset, as well as scalings of the pedestal width with poloidal beta, indicates that I-mode pedestals are not limited by KBM turbulence—both features identified with the trigger for large ELMs
Identification of a wagging vibrational mode of water molecules at the water/vapor interface.
Perry, Angela; Neipert, Christine; Ridley, Christina; Space, Brian; Moore, Preston B
2005-05-01
An improved time correlation function description of sum frequency generation (SFG) spectroscopy was applied to theoretically describe the water/vapor interface. The resulting spectra compare favorably in shape and relative magnitude to extant experimental results in the O-H stretching region of water. Further, the SFG spectra show a well-defined intermolecular mode at 875 cm(-1) that has significant intensity. The resonance is due to a wagging mode localized on a single water molecule. It represents a well-defined population of water molecules at the interface that, along with the free O-H modes, represent the dominant interfacial species.
Sato, M; Imai, S; Fujita, N; Shi, W; Takao, Y; Sada, Y; Hubbard, B E; Ilic, B; Sievers, A J
2013-01-01
An intrinsic localized mode (ILM) represents a localized vibrational excitation in a nonlinear lattice. Such a mode will stay in resonance as the driver frequency is changed adiabatically until a bifurcation point is reached, at which point the ILM switches and disappears. The dynamics behind switching in such a many body system is examined here through experimental measurements and numerical simulations. Linear response spectra of a driven micromechanical array containing an ILM were measured in the frequency region between two fundamentally different kinds of bifurcation points that separate the large amplitude ILM state from the two low amplitude vibrational states. Just as a natural frequency can be associated with a driven harmonic oscillator, a similar natural frequency has been found for a driven ILM via the beat frequency between it and a weak, tunable probe. This finding has been confirmed using numerical simulations. The behavior of this nonlinear natural frequency plays important but different roles as the two bifurcation points are approached. At the upper transition its frequency coalesces with the driver and the resulting bifurcation is very similar to the saddle-node bifurcation of a single driven Duffing oscillator, which is treated in an Appendix. The lower transition occurs when the four-wave mixing partner of the natural frequency of the ILM intersects the topmost extended band mode of the same symmetry. The properties of linear local modes associated with the driven ILM are also identified experimentally for the first time and numerically but play no role in these transitions.
Sato, M.; Imai, S.; Fujita, N.; Shi, W.; Takao, Y.; Sada, Y.; Hubbard, B. E.; Ilic, B.; Sievers, A. J.
2013-01-01
An intrinsic localized mode (ILM) represents a localized vibrational excitation in a nonlinear lattice. Such a mode will stay in resonance as the driver frequency is changed adiabatically until a bifurcation point is reached, at which point the ILM switches and disappears. The dynamics behind switching in such a many body system is examined here through experimental measurements and numerical simulations. Linear response spectra of a driven micromechanical array containing an ILM were measured in the frequency region between two fundamentally different kinds of bifurcation points that separate the large amplitude ILM state from the two low amplitude vibrational states. Just as a natural frequency can be associated with a driven harmonic oscillator, a similar natural frequency has been found for a driven ILM via the beat frequency between it and a weak, tunable probe. This finding has been confirmed using numerical simulations. The behavior of this nonlinear natural frequency plays important but different roles as the two bifurcation points are approached. At the upper transition its frequency coalesces with the driver and the resulting bifurcation is very similar to the saddle-node bifurcation of a single driven Duffing oscillator, which is treated in an Appendix. The lower transition occurs when the four-wave mixing partner of the natural frequency of the ILM intersects the topmost extended band mode of the same symmetry. The properties of linear local modes associated with the driven ILM are also identified experimentally for the first time and numerically but play no role in these transitions.
Institute of Scientific and Technical Information of China (English)
周正宇; 程学礼; 等
2002-01-01
On the basis of the computed results got by the Gaussian 94 package at B3LYP/6-311++G** level,the reaction mechanism of CH3O radical with CO has been investiagted thoroughly via the vibrational model analysis ,And the relationships among the reactants,eight transition states,four intermediates and various products involved this multichannel reation are eluci-dated,The vibrational mode anaysis shows that the reaction mechanism is relialbe.
Analysis of Vibration Mode for H2+F→HF+H Reaction Mechanism: Density functional Theory Calculation
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Three density functional theory methods (DFT) have been used to investigate the H2+F?HF+H reaction comparing with the Hartree-Fock method and Moller-Plesset (MP2) perturbation theory method. Through the analysis of the vibrational mode and vibrational frequency in the reaction process, the reaction mechanism has been discussed. The activation energy, the reorganization energy and rate constant of the ET reaction are calculated at semi-quantitative level.
Excitation of localized modes and mechanism of random lasing forming in random media
Institute of Scientific and Technical Information of China (English)
WANG Hong; LIU Jinsong; WANG Kejia; HAN Yanling
2006-01-01
Laser phenomena in random media have been studied based on the localized theory for lightwave in random media. The relationship between random lasing modes and localized modes has been investigated by directly solving Maxwell equations numerically via the finite difference time domain method. The spatial distribution and the spectra of localized modes are obtained for both passive and active random media. The results show that random lasing modes directly originate from the localized modes inside the random medium. In the presence of gain, any one of the localized modes can be amplified and can serve as random lasing mode.
Vibrational relaxation of the bending mode of shock-heated CO2 by laser-absorption measurements.
Eckstrom, D. J.; Bershader, D.
1972-01-01
Study of the vibrational relaxation characteristics of shock-heated CO2 using a tuned CO2 laser absorption technique. Absorption-coefficient histories were obtained for a single rotational state in each of the -10 0- and -02 0- levels over the temperature range from 500 to 2000 K, and for 21 rotational states of the -10 0- level at 1000 K. These histories have been combined with translational-rotational temperature histories based on interferometer measurements to calculate vibrational relaxation times for the bending mode. The results verify the mutual equilibrium of the bending and symmetric-stretch modes due to Fermi resonance. The bending mode relaxation times are approximately 10% shorter than predicted from interferometer results using the ratio of specific heats. Furthermore, relaxation times based on measurements of different rotational states at 1000 K show a variation with quantum number J, indicating a possible rotational nonequilibrium during the vibration relaxation process.
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.
Mechanism of Edge Localized Mode Mitigation by Resonant Magnetic Perturbations
Bécoulet, M.; Orain, F.; Huijsmans, G. T. A.; Pamela, S.; Cahyna, P.; Hoelzl, M.; Garbet, X.; Franck, E.; Sonnendrücker, E.; Dif-Pradalier, G.; Passeron, C.; Latu, G.; Morales, J.; Nardon, E.; Fil, A.; Nkonga, B.; Ratnani, A.; Grandgirard, V.
2014-09-01
A possible mechanism of edge localized modes (ELMs) mitigation by resonant magnetic perturbations (RMPs) is proposed based on the results of nonlinear resistive magnetohydrodynamic modeling using the jorek code, realistic JET-like plasma parameters and an RMP spectrum of JET error-field correction coils (EFCC) with a main toroidal number n =2 were used in the simulations. Without RMPs, a large ELM relaxation is obtained mainly due to the most unstable medium-n ballooning mode. The externally imposed RMP drives nonlinearly the modes coupled to n =2 RMP which produce small multimode relaxations, mitigated ELMs. The modes driven by RMPs exhibit a tearinglike structure and produce additional islands. Mitigated ELMs deposit energy into the divertor mainly in the structures ("footprints") created by n =2 RMPs, however, slightly modulated by other nonlinearly driven even harmonics. The divertor power flux during a ELM phase mitigated by RMPs is reduced almost by a factor of 10. The mechanism of ELM mitigation by RMPs proposed here reproduces generic features of high collisionality RMP experiments, where large ELMs are replaced by small, much more frequent ELMs or magnetic turbulence. Total ELM suppression was also demonstrated in modeling at higher RMP amplitude.
Localized modes in optics of photonic liquid crystals with local anisotropy of absorption
Belyakov, V. A.; Semenov, S. V.
2016-05-01
The localized optical modes in spiral photonic liquid crystals are theoretically studied for the certainty at the example of chiral liquid crystals (CLCs) for the case of CLC with an anisotropic local absorption. The model adopted here (absence of dielectric interfaces in the structures under investigation) makes it possible to get rid of mixing of polarizations on the surfaces of the CLC layer and of the defect structure and to reduce the corresponding equations to only the equations for light with polarization diffracting in the CLC. The dispersion equations determining connection of the edge mode (EM) and defect mode (DM) frequencies with the CLC layer parameters (anisotropy of local absorption, CLC order parameter) and other parameters of the DMS are obtained. Analytic expressions for the transmission and reflection coefficients of CLC layer and DMS for the case of CLC with an anisotropic local absorption are presented and analyzed. It is shown that the CLC layers with locally anisotropic absorption reduce the EM and DM lifetimes (and increase the lasing threshold) in the way different from the case of CLC with an isotropic local absorption. Due to the Borrmann effect revealing of which is different at the opposite stop-band edges in the case of CLC layers with an anisotropic local absorption the EM life-times for the EM frequencies at the opposite stop-bands edges may be significantly different. The options of experimental observations of the theoretically revealed phenomena are briefly discussed.
Edge localized modes of cold neutrons in periodic condensed media
Belyakov, V. A.
2017-06-01
It is found that for certain energies of discreet cold neutrons, quasi-stationary eigen solutions of the corresponding Schrodinger equation, which are localized in the layer of a periodic medium, exist. The localization time of these solutions is strongly dependent on the layer thickness, being finite for a finite layer thickness and increasing indefinitely upon a infinite growth of the layer thickness as the third power of the layer thickness. The problem has been solved in the two-wave approximation of the dynamic diffraction theory for the neutron propagation direction coinciding with the periodicity axes (normal incidence of the neutron beam on the layer). The expressions for neutron eigenwave functions in a periodic medium, the reflection and transmission coefficients, and the neutron wavefunction in the layer as a function of the neutron energy incident on the layer have been determined. It turns out that for the certain discrete neutron energies, the amplitudes of the neutron wavefunction in the layer reach sharp maxima. The corresponding energies are just outside of the neutron stop band (energies forbidden for neutron propagation in the layer) and determine the energies of neutron edge modes (NEMs) localized in the layer, which are direct analogs of the optical edge modes for photonic crystals. The dispersion equation for the localized neutron edge modes has been obtained and analytically solved for the case of thick layers. A rough estimate for the localization length L is L ( db N)-1, where b is the neutron scattering length, d is the crystal period, and N is the density of nuclei in the crystal. The estimates of the localized thermal neutron lifetime show that acheaving of a lifetime close to the free neutron lifetime seems nonrealistic due to absorption of thermal neutrons and requires a perfect large size crystal. Nevertheless, acheaving the localized neutron lifetime exceeding by 104 times the neutron time of flight through the layer appears as
Effects of local vibration on bone loss in -tail-suspended rats.
Sun, L W; Luan, H Q; Huang, Y F; Wang, Y; Fan, Y B
2014-06-01
We investigated the effects of vibration (35 Hz, 45 Hz and 55 Hz) as countermeasure locally applied to unloading hind limbs on bone, muscle and Achilles tendon. 40 female Sprague Dawley rats were divided into 5 groups (n=8, each): tail-suspension (TS), TS plus 35 Hz/0.3 g vibration (TSV35), TS plus 45 Hz/0.3 g vibration (TSV45), TS plus 55 Hz/0.3 g vibration (TSV55) and control (CON). After 21 days, bone mineral density (BMD) and the microstructure of the femur and tibia were evaluated by μCT in vivo. The biomechanical properties of the femur and Achilles tendon were determined by a materials testing system. Ash weight of bone, isotonic contraction and wet weight of soleus were also investigated. 35 Hz and 45 Hz localized vibration were able to significantly ameliorate the decrease in trabecular BMD (expressed as the percentage change from TS, TSV35: 48.11%, TSV45: 31.09%), microstructure and ash weight of the femur and tibia induced by TS. Meanwhile, 35 Hz vibration significantly improved the biomechanical properties of the femur (57.24% bending rigidity and 41.66% Young's modulus vs. TS) and Achilles tendon (45.46% maximum load and 66.67% Young's modulus vs. TS). Additionally, Young's modulus of the femur was highly correlated with microstructural parameters. Localized vibration was useful for counteracting microgravity-induced musculoskeletal loss. In general, the efficacy of 35 Hz was better than 45 Hz or 55 Hz in tail-suspended rats. © Georg Thieme Verlag KG Stuttgart · New York.
Directory of Open Access Journals (Sweden)
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.
Theoretic base of Edge Local Mode triggering by vertical displacements
Energy Technology Data Exchange (ETDEWEB)
Wang, Z. T. [Southwestern Institute of Physics, Chengdu 610041 (China); College of Physics Science and Technology, Sichuan University, Chengdu 610065 (China); He, Z. X.; Wang, Z. H. [Southwestern Institute of Physics, Chengdu 610041 (China); Wu, N.; Tang, C. J. [College of Physics Science and Technology, Sichuan University, Chengdu 610065 (China)
2015-05-15
Vertical instability is studied with R-dependent displacement. For Solovev's configuration, the stability boundary of the vertical instability is calculated. The pressure gradient is a destabilizing factor which is contrary to Rebhan's result. Equilibrium parallel current density, j{sub //}, at plasma boundary is a drive of the vertical instability similar to Peeling-ballooning modes; however, the vertical instability cannot be stabilized by the magnetic shear which tends towards infinity near the separatrix. The induced current observed in the Edge Local Mode (ELM) triggering experiment by vertical modulation is derived. The theory provides some theoretic explanation for the mitigation of type-I ELMS on ASDEX Upgrade. The principle could be also used for ITER.
Institute of Scientific and Technical Information of China (English)
Demin ZHAO; Jianlin LIU; C Q WU
2015-01-01
The parametric excited vibration of a pipe under thermal loading may occur because the fluid is often transported heatedly. The effects of thermal loading on the pipe stability and local bifurcations have rarely been studied. The stability and the local bifurcations of the lateral parametric resonance of the pipe induced by the pulsating fluid velocity and the thermal loading are studied. A mathematical model for a simply supported pipe is developed according to the Hamilton principle. Two partial differential equations describing the lateral and longitudinal vibration are obtained. The singularity theory is utilized to analyze the stability and the bifurcation of the system solutions. The transition sets and the bifurcation diagrams are obtained both in the unfolding parameter space and the physical parameter space, which can reveal the relationship between the thermal field parameter and the dynamic behaviors of the pipe. The frequency response and the relationship between the critical thermal rate and the pulsating fluid velocity are obtained. The numerical results demonstrate the accuracy of the single-mode expansion of the solution and the stability and local bifurcation analyses. It also confirms the existence of the chaos. The presented work can provide valuable information for the design of the pipeline and the controllers to prevent the structural instability.
Directory of Open Access Journals (Sweden)
Chi-Ying Lin
2017-03-01
Full Text Available In this paper, we report on the use of piezoelectric sensors and actuators for the active suppression of vibrations associated with the motor-driven rotation of thin flexible plate held vertically. Motor-driven flexible structures are multi-input multi-output systems. The design of active vibration-suppression controllers for these systems is far more challenging than for flexible structures with a fixed end, due to the effects of coupling and nonlinear vibration behavior generated in structures with poor damping. To simplify the design of the controller and achieve satisfactory vibration suppression, we treated the coupling of vibrations caused by the rotary motion of the thin flexible plate as external disturbances and system uncertainties. We employed an adaptive fuzzy sliding mode control algorithm in the design of a single-input–single-output controller for the suppression of vibrations using piezoelectric sensors and actuators. We also used a repetitive control system to reduce periodic vibrations associated with the repetitive motions induced by the motor. Experimental results demonstrate that the hybrid intelligent control approach proposed in this study can suppress complex vibrations caused by modal excitation, coupling effects, and periodic external disturbances.
Guicheteau, Jason; Argue, Leanne; Hyre, Aaron; Jacobson, Michele; Christesen, Steven D.
2006-05-01
Raman and surface-enhanced Raman spectroscopy (SERS) studies of bacteria have reported a wide range of vibrational mode assignments associated with biological material. We present Raman and SER spectra of the amino acids phenylalanine, tyrosine, tryptophan, glutamine, cysteine, alanine, proline, methionine, asparagine, threonine, valine, glycine, serine, leucine, isoleucine, aspartic acid and glutamic acid and the nucleic acid bases adenosine, guanosine, thymidine, and uridine to better characterize biological vibrational mode assignments for bacterial target identification. We also report spectra of the bacteria Bacillus globigii, Pantoea agglomerans, and Yersinia rhodei along with band assignments determined from the reference spectra obtained.
Schuler, Manuel J; Hofer, Thomas S; Huck, Christian W
2017-05-17
The performance of the grid-based Numerov procedure for the prediction of fundamental as well as the first vibrational overtone has been systematically probed for harmonic and anharmonic model systems. In addition to monitor the prediction with respect to the spacing of the potential grid the influence of higher order approximations to the second derivative (i.e. stencils) in Schrödingers equation is evaluated. The latter enable a significant increase of the grid-spacing to achieve results of similar accuracy obtained with smaller stencil sizes. Application to the hydroxyl vibrational mode of methanol, phenol and the natural product thymol in vacuum and carbon tetrachloride predicted wavenumbers within less than 1% of experiment. Due to the highly localised character of the OH-vibration the ad hoc construction of the associated normal mode yields results of similar accuracy than those obtained using the analytical normal modes, effectively eliminating the requirement of an analytical normal mode evaluation of the entire system. This property was shown to be of particular advantage when considering explicit solute-solvent contacts, which have been demonstrated to be superior compared to an implicit representation of solvent effects. The combination of the observed findings (i.e. enlarged grid-spacing due to the application of higher order stencils, construction of localised normal modes) is envisaged to be of particular benefit when investigating localised modes in large systems, such as OH or NH groups in large (bio)macromolecules or solid-state surfaces.
Parametric resonance of intrinsic localized modes in coupled cantilever arrays
Kimura, Masayuki; Matsushita, Yasuo; Hikihara, Takashi
2016-08-01
In this study, the parametric resonances of pinned intrinsic localized modes (ILMs) were investigated by computing the unstable regions in parameter space consisting of parametric excitation amplitude and frequency. In the unstable regions, the pinned ILMs were observed to lose stability and begin to fluctuate. A nonlinear Klein-Gordon, Fermi-Pasta-Ulam-like, and mixed lattices were investigated. The pinned ILMs, particularly in the mixed lattice, were destabilized by parametric resonances, which were determined by comparing the shapes of the unstable regions with those in the Mathieu differential equation. In addition, traveling ILMs could be generated by parametric excitation.
Vibrational modes and electrical transport in Sr{sub 2}GdTaO{sub 6}
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Binita, E-mail: binita_ghosh@yahoo.co.in; Dutta, Alo; Sinha, T.P.
2013-12-16
The double perovskite oxide strontium gadolinium tantalate, Sr{sub 2}GdTaO{sub 6} (SGT) is synthesized by solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern of the sample shows monoclinic phase at room temperature. FTIR spectrum shows two primary phonon modes of the sample at around 373 cm{sup −1} and 562 cm{sup −1}. The electronic structure of SGT has been investigated by Vienna ab-initio simulation package. The eigen frequencies of different phonon modes have been calculated and compared with the experimental data observed by Raman spectroscopy. Dielectric properties of the sample are investigated in a temperature range from 303 K to 673 K and in a frequency range of 42 Hz–1 MHz. The relaxation peaks are observed in the frequency dependent spectra for imaginary part of the dielectric constant. The modified Cole–Cole equation is used to describe the relaxation mechanism in SGT. The frequency dependent conductivity spectra follow the Jonscher power law. - Highlights: • Sr{sub 2}GdTaO{sub 6} ceramic is crystallized in monoclinic structure. • DOS and band structure reveals a band gap of about 3.4 eV. • All Raman and FTIR lines in the experimental spectra are assigned to definite vibrations of the structure. • Theoretically calculated frequencies of the different phonon modes are in good agreement with the experimental data. • Activation energy is 0.18 eV.
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.
Differential equation of transverse vibrations of a beam with local stroke change of stiffness
Directory of Open Access Journals (Sweden)
Stanisław Kasprzyk
2007-01-01
Full Text Available The aim of this paper is to derive a differential equation of transverse vibrations of a beam with a local, stroke change of stiffness, and to solve it. The presented method is based on the theory of distributions.
Local anharmonic vibrations strong correlations and superconductivity : a quantum simulation study
Frick, M.; Linden, W. von der; Morgenstern, I.; Raedt, H. de
1990-01-01
We investigate the importance of local anharmonic vibrations of the bridging oxygen in the copper oxide high-Tc materials in the context of superconductivity. For the numerical simulation we employ the projector quantum Monte Carlo method to study the ground state properties of the coupled electron-
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 *}.
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.
Choi, Seung-Bok; Han, Young-Min
2007-06-01
This paper presents vibration control performance of a semi-active electrorheological (ER) seat suspension system using a robust sliding mode controller (SMC). A cylindrical type of ER seat damper is manufactured for a commercial vehicle seat suspension and its field-dependent damping force is experimentally evaluated. A vertical vibration model of human-body is then derived and integrated with the governing equations of the ER seat suspension system. The integrated seat-driver model featured by a high order degree-of-freedom (dof) is reduced through a balanced model reduction method. The SMC is then designed based on the reduced model and the state observer is formulated to estimate feedback states which cannot be directly measured from sensors. By imposing a semi-active actuating condition, the synthesized SMC is experimentally realized. In the experimental implementation, a driver directly sits on the controlled seat. Both vertical displacement and acceleration are measured at seat frame and driver's head, respectively. Control performances are evaluated under various road conditions and compared with those obtained from conventional passive seat suspension system.
Thaunay, Florian; Dognon, Jean-Pierre; Ohanessian, Gilles; Clavaguéra, Carine
2015-10-21
The calculation of infrared spectra by molecular dynamics simulations based on the AMOEBA polarizable force field has recently been demonstrated [Semrouni et al., J. Chem. Theory Comput., 2014, 10, 3190]. While this approach allows access to temperature and anharmonicity effects, band assignment requires additional tools, which we describe in this paper. The Driven Molecular Dynamics approach, originally developed by Bowman, Kaledin et al. [Bowman et al. J. Chem. Phys., 2003, 119, 646, Kaledin et al. J. Chem. Phys., 2004, 121, 5646] has been adapted and associated with AMOEBA. Its advantages and limitations are described. The IR spectrum of the Ac-Phe-Ala-NH2 model peptide is analyzed in detail. In addition to differentiation of conformations by reproducing frequency shifts due to non-covalent interactions, DMD allows visualizing the temperature-dependent vibrational modes.
Lee, Hochan; Lee, Gayeon; Jeon, Jonggu; Cho, Minhaeng
2012-01-12
IR probes have been extensively used to monitor local electrostatic and solvation dynamics. Particularly, their vibrational frequencies are highly sensitive to local solvent electric field around an IR probe. Here, we show that the experimentally measured vibrational frequency shifts can be inversely used to determine local electric potential distribution and solute-solvent electrostatic interaction energy. In addition, the upper limits of their fluctuation amplitudes are estimated by using the vibrational bandwidths. Applying this method to fully deuterated N-methylacetamide (NMA) in D(2)O and examining the solvatochromic effects on the amide I' and II' mode frequencies, we found that the solvent electric potential difference between O(═C) and D(-N) atoms of the peptide bond is about 5.4 V, and thus, the approximate solvent electric field produced by surrounding water molecules on the NMA is 172 MV/cm on average if the molecular geometry is taken into account. The solute-solvent electrostatic interaction energy is estimated to be -137 kJ/mol, by considering electric dipole-electric field interaction. Furthermore, their root-mean-square fluctuation amplitudes are as large as 1.6 V, 52 MV/cm, and 41 kJ/mol, respectively. We found that the water electric potential on a peptide bond is spatially nonhomogeneous and that the fluctuation in the electrostatic peptide-water interaction energy is about 10 times larger than the thermal energy at room temperature. This indicates that the peptide-solvent interactions are indeed important for the activation of chemical reactions in aqueous solution.
Wu, Da-fang; Huang, Liang; Mu, Meng; Wang, Yue-wu; Wu, Shuang
2012-04-01
In order to reduce effective load and lower the launch cost, many light-weight flexible structures are employed in spacecraft. The research of active control on flexible structural vibration is very important in spacecraft design. Active vibration control on a flexible beam with smart material piezoelectric pieces bonded in surface is investigated experimentally using independent modal space control method, which is able to control the first three modes independently. A comparison between the systems responses before and after control indicates that the modal damping of flexible structure is greatly improved after active control is performed, indicating remarkable vibration suppression effect. Dynamic equation of the flexible beam is deducted by Hamilton principle, and numerical simulation of active vibration control on the first three order vibration modes is also conducted in this paper. The simulation result matches experimental result very well. Both experimental and numerical results indicate that the independent modal control method using piezoelectric patch as driving element is a very effective approach to realize vibration suppression, which has promising applications in aerospace field.
Directory of Open Access Journals (Sweden)
Ruo Lin Wang
2014-01-01
Full Text Available This paper presents an experimental study of an adaptive robust sliding mode control scheme based on the Lyapunov’s direct method for active vibration control of a flexible beam using PZT (lead zirconate titanate sensor and actuator. PZT, a type of piezoceramic material, has the advantages of high reliability, high bandwidth, and solid state actuation and is adopted here in forms of surface-bond patches for vibration control. Two adaptive robust sliding mode controllers for vibration suppression are designed: one uses a discontinuous bang-bang robust compensator and the other uses a smooth compensator with a hyperbolic tangent function. Both controllers guarantee asymptotic stability, as proved by the Lyapunov’s direct method. Experimental results verified the effectiveness and the robustness of both adaptive sliding mode controllers. However, from the experimental results, the bang-bang robust compensator causes small-magnitude chattering because of the discontinuous switching actions. With the smooth compensator, vibration is quickly suppressed and no chattering is induced. Furthermore, the robustness of the controllers is successfully demonstrated with ensured effectiveness in vibration control when masses are added to the flexible beam.
Localized Edge Vibrations and Edge Reconstruction by Joule Heating in Graphene Nanostructures
DEFF Research Database (Denmark)
Engelund, Mads; Fürst, Joachim Alexander; Jauho, Antti-Pekka;
2010-01-01
for current-induced edge reconstruction using density functional theory. Our calculations provide evidence for localized vibrations at edge interfaces involving unpassivated armchair edges. We demonstrate that these vibrations couple to the current, estimate their excitation by Joule heating, and argue......Control of the edge topology of graphene nanostructures is critical to graphene-based electronics. A means of producing atomically smooth zigzag edges using electronic current has recently been demonstrated in experiments [Jia et al., Science 323, 1701 (2009)]. We develop a microscopic theory...
Kartapoltseva, N.
2008-01-01
The pathological disorders in the state of the peripheral nerves based on the data of the vibration sensitivity studies were observed to be in both the patients with the vibration-induced diseases as a result of the local vibration exposure and in the patients with an occupational neurosensoric dullness of hearing. This may assume a total effect mechanism of the physical factors on the human organism. In the former case the alterations observedshowed a more pronounced character.
Qiu, Zhi-cheng; Zhang, Si-ma
2016-10-01
A kind of non-contact vibration measurement method for a two-connected flexible piezoelectric plate using laser sensors is proposed. Decoupling of the bending and torsional vibration on measurement and driving control is carried out via using two laser displacement sensors and piezoelectric actuators. The fuzzy fast terminal sliding mode controller (FFTSMC) is investigated to suppress both the larger and the smaller amplitude vibrations quickly. In order to alleviate the chattering phenomenon and enhance the control effect, the fuzzy logic adaptive algorithm is used to adjust the switching control gain for softening the signum function adaptively. To verify the non-contact measurement method and the designed controller, the experimental setup is built up. Experiments on active vibration control using the designed FFTSMC are conducted, compared with the classical proportional derivative (PD) control algorithm. The experimental identification results demonstrate that the laser displacement sensors can detect the low-frequency bending and torsional vibration effectively, after using the decoupling method. Furthermore, the designed FFTSMC can suppress both bending and torsional vibration more quickly than the designed PD controller owing to the adjustment of the switching control gains and the softening factors, especially for the small amplitude residual vibrations.
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.
Rossit, C. A.; Laura, P. A. A.
2001-12-01
An exact solution for the title problem is obtained by means of the classical eigenfunction approach. The natural frequencies are computed for a wide range of the intervening mechanical and geometric parameters. Normal modes of transverse vibration are plotted for some cases of practical interest. The problem is technically important in several areas of applied science and technology.
Parnis, J. Mark; Thompson, Matthew G. K.
2004-01-01
An introductory undergraduate physical organic chemistry exercise that introduces the harmonic oscillator's use in vibrational spectroscopy is developed. The analysis and modeling exercise begins with the students calculating the stretching modes of common organic molecules with the help of the quantum mechanical harmonic oscillator (QMHO) model.
The structure of filled skutterudites and the local vibration behavior of the filling atom
Zhou, Xiaojuan; Zong, Peng-an; Chen, Xihong; Tao, Juzhou; Lin, He
2017-02-01
Both of atomic pair distribution function (PDF) and extended x-ray absorption fine structure (EXAFS) experiments have been carried out on unfilled and Yb-filled skutterudites YbxCo4Sb12 (x=0, 0.15, 0.2 and 0.25) samples. The structure refinements on PDF data confirm the large amplitude vibration of Yb atom and the dependence of Yb vibration amplitude on the filling content. Temperature dependent EXAFS experiment on filled skutterudites have been carried out at Yb LⅢ-edge in order to explore the local vibration behavior of filled atom. EXAFS experiments show that the Einstein temperature of the filled atom is very low (70.9 K) which agrees with the rattling behavior.
The structure of filled skutterudites and the local vibration behavior of the filling atom
Energy Technology Data Exchange (ETDEWEB)
Zhou, Xiaojuan [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Dongguan Institute of Neutron Science, Dongguan 523808 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zong, Peng-an [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Chen, Xihong [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Tao, Juzhou, E-mail: taoj@ihep.ac.cn [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Dongguan Institute of Neutron Science, Dongguan 523808 (China); Lin, He, E-mail: linhe@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Science, Shanghai 201204 (China)
2017-02-15
Both of atomic pair distribution function (PDF) and extended x-ray absorption fine structure (EXAFS) experiments have been carried out on unfilled and Yb-filled skutterudites Yb{sub x}Co{sub 4}Sb{sub 12} (x=0, 0.15, 0.2 and 0.25) samples. The structure refinements on PDF data confirm the large amplitude vibration of Yb atom and the dependence of Yb vibration amplitude on the filling content. Temperature dependent EXAFS experiment on filled skutterudites have been carried out at Yb L{sub Ⅲ}-edge in order to explore the local vibration behavior of filled atom. EXAFS experiments show that the Einstein temperature of the filled atom is very low (70.9 K) which agrees with the rattling behavior.
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.
Directory of Open Access Journals (Sweden)
Mehran Roohnia
2015-06-01
Full Text Available Studying the influence of defect on the dynamic behavior of wood in order to detect the local heterogeneities is of great importance in non-destructive testing of wood. The natural heterogeneities in wood are oriented in a volume. However, onedimensional models are still used in dynamic characterization of wooden beams. The aim of this study was to experimentally investigate the effects of the orientation and position of an artificial defect on the flexural vibration frequencies. Different batches of Fagus orientalis specimens were drilled in the radial direction at five positions along the specimen. Dynamic tests in free flexural vibration were performed on the specimens before and after drilling both in the longitudinal-radial (LR and longitudinal-tangential (LT bending plan. The behavior in free flexural vibration was found to be different depending on the position and orientation of heterogeneity. When the drilling axis lies in the bending plane (LR, the weakening of frequency was maximal at the location of an antinode of vibration. On the contrary, the frequency offset was maximal in the place of a vibration node when the drilling axis was orthogonal to the bending plane (LT.
Modal approach for vibration of a structure with local constraints%局部约束结构振动的模态研究
Institute of Scientific and Technical Information of China (English)
李金录; 丁千
2015-01-01
Braking process of a brake disc is a vibration problem with local contacting,local contact has an influence on the modes and natural frequencies of the disc system.The method of local discontinuous basis function can be used to estimate the modes of the system accurately.Here,a brake disc contacted by a brake boot or a friction block was simplified as a one-dimensional beam with loop structures.Its equation of motion was established.Firstly,the free vibration modes of the beam without contact defined as the reference modes were calculated.Then the contact of the friction block was simplified as several linear springs.Using the continuous conditions,the system's modes were calculated and orthogonalized with the reference modes,they were taken as the supplements of the reference modes and named the local discontinuoas basis functions.They were used to calculate the system response.Based on the discontinuous mode analysis,vibration of the brake disk under action of external excitation is calculated.The results showed that the local discontinuous basis function method is more accurate than the traditional modal method;the local contact of the friction piece can restrain the vibration symmetry of the brake disc to lead to disappearance of sine or cosine modes;nonlinear stiffness and friction make the vibration be wave type.This study laid a foundation for studying unstable vibration mechanism of structures with friction using the local discontinuous basis function method.%制动盘／摩擦块系统的制动过程属于局部接触振动问题。摩擦块局部接触（约束）会对系统模态及固有频率造成影响，进而影响制动噪声的产生。将刹车盘简化为一维循环梁结构，并建立了在摩擦块作用下的运动方程。首先计算无接触时梁自由振动的模态（参考模态）。然后用线性弹簧代替局部接触，列写出连续条件并计算模态，得到所谓局部非连续基函数。将局部非连续基函数
Localized surface plate modes via flexural Mie resonances
Farhat, M.
2017-05-11
Surface-plasmon polaritons are naturally generated upon excitation of metals with high-frequency electromagnetic waves. However, the concept of spoof plasmons has made it possible to generate plasmoniclike effects in microwave electrodynamics, magnetics, and even acoustics. Similarly, in this paper, the concept of localized surface plate modes (SPMs) is introduced. It is demonstrated that SPMs can be generated on a two-dimensional (clamped or stress-free) cylindrical surface with subwavelength corrugations, which resides on a thin elastic plate, under excitation by an incident flexural plane wave. Numerical characterization of this corrugated rigid structure shows that it is elastically equivalent to a cylindrical scatterer with dispersive but uniformly negative flexural rigidity. This, indeed, suggests that plasmoniclike elastic materials can be engineered with potential applications in various areas including earthquake sensing and elastic imaging and cloaking.
Mode localization in the cooperative dynamics of protein recognition
Copperman, J.; Guenza, M. G.
2016-07-01
The biological function of proteins is encoded in their structure and expressed through the mediation of their dynamics. This paper presents a study on the correlation between local fluctuations, binding, and biological function for two sample proteins, starting from the Langevin Equation for Protein Dynamics (LE4PD). The LE4PD is a microscopic and residue-specific coarse-grained approach to protein dynamics, which starts from the static structural ensemble of a protein and predicts the dynamics analytically. It has been shown to be accurate in its prediction of NMR relaxation experiments and Debye-Waller factors. The LE4PD is solved in a set of diffusive modes which span a vast range of time scales of the protein dynamics, and provides a detailed picture of the mode-dependent localization of the fluctuation as a function of the primary structure of the protein. To investigate the dynamics of protein complexes, the theory is implemented here to treat the coarse-grained dynamics of interacting macromolecules. As an example, calculations of the dynamics of monomeric and dimerized HIV protease and the free Insulin Growth Factor II Receptor (IGF2R) domain 11 and its IGF2R:IGF2 complex are presented. Either simulation-derived or experimentally measured NMR conformers are used as input structural ensembles to the theory. The picture that emerges suggests a dynamical heterogeneous protein where biologically active regions provide energetically comparable conformational states that are trapped by a reacting partner in agreement with the conformation-selection mechanism of binding.
The non-linear evolution of edge localized modes
Energy Technology Data Exchange (ETDEWEB)
Wenninger, Ronald
2013-01-09
Edge localized modes (ELMs) are instabilities in the edge of tokamak plasmas in the high confinement regime (H-mode). Without them the edge transport in ordinary H-mode plasmas is too low to establish a stationary situation. However in a future device large unmitigated ELMs are believed to cause divertor power flux densities far in excess of tolerable material limits. Hence the size of energy loss per ELM and the resulting ELM frequency must be controlled. To proceed in understanding how the ELM size is determined and how ELM mitigation methods work it is necessary to characterize the non-linear evolution of pedestal erosion. In order to achieve this experimental data is compared to the results of ELM simulations with the code JOREK (reduced MHD, non-linear) applying a specially developed synthetic magnetic diagnostic. The experimental data are acquired by several fast sampling diagnostics at the experiments ASDEX Upgrade and TCV at a large number of toroidal/poloidal positions. A central element of the presented work is the detailed characterization of dominant magnetic perturbations during ELMs. These footprints of the instability can be observed most intensely in close temporal vicinity to the onset of pedestal erosion. Dominant magnetic perturbations are caused by current perturbations located at or inside the last closed flux surface. In ASDEX Upgrade under certain conditions dominant magnetic perturbations like other H-mode edge instabilities display a similarity to solitons. Furthermore - as expected - they are often observed to be correlated to a perturbation of electron temperature. In TCV it is possible to characterize the evolution of the toroidal structure of dominant magnetic perturbations. Between growing above the level of background fluctuations and the maximum perturbation level for all time instance a similar toroidal structure is observed. This rigid mode-structure is an indication for non-linear coupling. Most frequently the dominant toroidal
Velizhanin, Kirill A; Kilina, Svetlana; Sewell, Thomas D; Piryatinski, Andrei
2008-10-23
Numerical studies of vibrational energy transport and associated (non)linear infrared and Raman response in polyatomic materials require knowledge of the multidimensional vibrational potential-energy surface and the ability to perform normal-mode analysis on that potential. The presence of translational symmetry, as in crystals, leads to the observed dispersion of the unit cell normal modes and has to be accounted for in calculations of energy transfer rates and other spectroscopic quantities. Here we report on the implementation of a computational approach that combines the generalized supercell method and density functional theory electronic structure calculations to investigate the vibrational structure in translationally symmetric materials containing relatively large numbers of atoms in the unit cell (58 atoms in the present study). The method is applied to calculate the phonon and vibron dispersion relations and the vibrational density of states in pentaerythritol tetranitrate (PETN) molecular crystal which is an important energetic material. The results set the stage for future investigations of vibrational energy transport and associated nonlinear spectroscopic signatures in this class of materials.
Muntean, Cristina M; Bratu, Ioan; Hernanz, Antonio
2017-07-20
Vibrational band shape analysis through time correlation function concept is widely used to obtain experimental information on the molecular dynamics of medium-size molecules in different environments. Interesting details are revealed by extending this technique to biomolecules such as functional groups of the nucleic acids in media approaching the physiological conditions. In this work a study into the UV resonance Raman (UVRR) vibrational half bandwidths of functional groups in LacDNA, upon lowering the pH (pH 6.4, pH 3.45) and in the presence of Mn(2+) and Ca(2+) ions, respectively, was of interest. The corresponding global relaxation times have been derived. Also, the 793 cm(-1) UVRR band, corresponding to ν (backbone O-P-O, dT) oscillator of LacDNA in aqueous solutions, was selected for band shape-analysis. Vibrational relaxation appears as the dominant relaxation process for this mode, with vibrational dephasing being the most efficient for this oscillator. Current theories developed for vibrational dephasing have been applied to this profile, and relevant relaxation parameters have been obtained and discussed. To our knowledge this is the first study on DNA oligomers vibrational band shape analysis through time correlation function concept.
Letellier, R; Ghomi, M; Taillandier, E
1989-02-01
A calculated approach based on the Higgs method for assigning the vibration modes of an infinite helicoidal polymeric chain has been performed on the basis of a reliable valence force field. The calculated results allowed the phosphate-backbone marker modes of the A and B forms, to be interpreted. In the dynamic models used, the bases have been omitted and no interchain interaction was considered. The calculation can also interprete quite satisfactorily the characteristic Raman peaks and infrared bands in the 1250-700 cm-1 spectral region arising from the sugar or sugar-phosphate association and reproduce their evolution upon the B----A DNA conformational transition. They clearly show that the phosphate-backbone modes in the above mentioned spectral region constitute the optical branches of the phonon dispersion curves with no detectable variation in the first Brillouin-zone.
Institute of Scientific and Technical Information of China (English)
ZHANG; Yimin; (张义民); WANG; Shun; (王; 顺); LIU; Qiaoling; (刘巧伶); WEN; Bangchun; (闻邦椿)
2003-01-01
Based on the generalized probabilistic finite element method, this paper presents an approximate solution technique for general multi-degree-of-freedom nonlinear random vibration systems with random parameters. The fourth-moment technique, maximum entropy theory and incomplete probability information theory are employed to systematically develop a reliability analysis method for dynamic random structural systems with correlation failure modes under unavailable joint probability density functions of basic random variables. The first passage problem of multi-degree-of-freedom nonlinear random vibration systems is solved.
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.
de Albuquerque, S. S.; dos Santos, J. L. L.; de Moura, F. A. B. F.; Lyra, M. L.
2015-05-01
In this work, we study the vibrational modes and energy spreading in a harmonic chain model with diluted second-neighbors couplings and correlated mass-spring disorder. While all nearest neighbor masses are coupled by an elastic spring, second neighbors springs are introduced with a probability pD. The masses are randomly distributed according to the site connectivity m_i=m_0≤ft(1+1/n_iα\\right) , where ni is the connectivity of the site i and α is a tunable exponent. We show that maximum localization of the vibrational modes is achieved for α ≃ 3/4. The time-evolution of the energy wave-packet is followed after an initial localized excitation. While the participation number remains finite, the energy spread is shown to be sub-diffusive after a displacement and super-diffusive after an impulse excitation. These features are related to the development of a power-law tail in the wave-packet distribution. Further, we unveil that the spring dilution leads to the emergence of a resonant localized state which is signaled by a van Hove singularity in the density of states.
Highly localized clustering states in a granular gas driven by a vibrating wall
Livne, Eli; Meerson, Baruch; Sasorov, Pavel V.
2000-01-01
An ensemble of inelastically colliding grains driven by a vibrating wall in 2D exhibits density clustering. Working in the limit of nearly elastic collisions and employing granular hydrodynamics, we predict, by a marginal stability analysis, a spontaneous symmetry breaking of the extended clustering state (ECS). 2D steady-state solutions found numerically describe localized clustering state (LCSs). Time-dependent granular hydrodynamic simulations show that LCSs can develop from natural initia...
Local Classical and Quantum Criticality due to Electron-Vibration Interaction
2009-01-01
We study the local classical and quantum critical properties of electron-vibration interaction, represented by the Yu-Anderson model. It exhibits an instability, similar to the Wentzel-Bardeen singularity, whose nature resembles to weakly first order quantum phase transitions at low temperatures, and crosses over to Gaussian behaviour with increasing temperature. We determine the dominant energy scale separating the quantum from classical criticality, study the effect of dissipation and analy...
Picosecond infrared studies of H$^{-}$ local modes in LaF$_{3}$
Wells, J P R; Bradley, I V; Pidgeon, C R
2001-01-01
Three-beam normalised pump-probe measurements for the Z-localised vibrational mode of H/sup -/ in LaF/sub 3/ yield a 10 K population decay time (T/sub 1/) of 49 ps. The temperature decrease of this T /sub 1/ time is fitted to two-phonon anharmonic decay together with one-phonon absorption to the 351 cm/sup -1/ higher (X, Y)-mode. Two- pulse vibrational echo measurements yield a homogeneous line width of 0.3 cm/sup -1/. (8 refs).
Vibrational Autodetachment in Nitroalkane Anions
Adams, Christopher L.; Weber, J. Mathias
2010-06-01
Nitroalkanes have electron affinities ge 1370 cm-1, well below the excitation energies for CH stretching modes, with the excess charge localized on the nitro group. Upon absorption of an IR photon in a CH stretching vibrational mode, the absorbed energy is redistributed in the molecule. If enough energy is transferred to the NO2 stretching/wagging modes, the excess electron residing on the nitro group is emitted. Vibrational autodetachment (VAD) spectra encode information regarding intramolecular vibrational relaxation (IVR) processes leading up to electron emission. We present VAD photoelectron spectroscopy of polyatomic molecular anions and discuss how a VAD photoelectron spectrum can be modeled.
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
Modeling the antisymmetric and symmetric stretching vibrational modes of aqueous carboxylate anions.
Sutton, Catherine C R; Franks, George V; da Silva, Gabriel
2015-01-05
The infrared spectra of six aqueous carboxylate anions have been calculated at the M05-2X/cc-pVTZ level of theory with the SMD solvent model, and validated against experimental data from the literature over the region of 1700 cm(-1) to 1250 cm(-1); this region corresponds to the stretching modes of the carboxylate group, and is often interrogated when probing bonding of carboxylates to other species and surfaces. The anions studied here were formate, acetate, oxalate, succinate, glutarate and citrate. For the lowest energy conformer of each anion, the carboxylate moiety antisymmetric stretching peak was predicted with a mean signed error of only 4 cm(-1) using the SMD solvent model, while the symmetric peak was slightly overestimated. Performing calculations in vacuum and scaling was found to generally over-predict the antisymmetric vibrational frequencies and under predict the symmetric peak. Different conformers of the same anion were found to have only slightly different spectra in the studied region and the inclusion of explicit water molecules was not found to significantly change the calculated spectra when the implicit solvent model is used. Overall, the use of density functional theory in conjunction with an implicit solvent model was found to result in infra-red spectra that are the best reproduction of the features found experimentally for the aqueous carboxylate ions in the important 1700 cm(-1) to 1250 cm(-1) region. The development of validated model chemistries for simulating the stretching modes of aqueous carboxylate ions will be valuable for future studies that investigate how carboxylate anions complex with multivalent metal cations and related species in solution.
Stable and Vibrational Octupole Modes in Mo, Xe, Ba, La, Ce and Nd
Energy Technology Data Exchange (ETDEWEB)
Gore, P.M.; Hamilton, J.H.; Hwang, J.K.; Jones, E.F.; Peker, L.K.; Ramayya, A.V.; Zhang, X.Q.; Zhu, S.J.
1998-05-18
Evidence is presented for stable octupole deformation in neutron-rich nuclei, bounded by Z = 54-58 and N = 85-92. To either side of this region negative parity bands built on more vibrational type octupole modes are observed in {sup 140}Ba and {sup 152,154}Nd. The largest stable octupole deformation ({beta}{sub s} {approximately} 0.1) is found in {sup 144}Ba{sub as}. The theoretically predicted quenching ({beta}{sub s} {approximately} 0) of stable octupole deformation at higher spins is found in {sup 140}Ba. There is good agreement between theory and experiment for the strongly varying electric dipole moments as a function of mass for {sup 142-141}Ba. In odd-A {sup 142}Ba and odd-Z {sup 140}La, we observe parity doublets, two pairs of positive and negative parity bands with opposite spins. In {sup 145}La a strong coupled ground band with symmetric shape coexists with the asymmetric octupole shape which stabilizes above about spin 19/2. In {sup 145,147}La a strong reduction in E2 strength around 25/2 from band crossing is observed. The isotope {sup 109}Mo was identified and a new region of stable uctpole deformation is identified in {sup 107,108}Mo centered around N = 64-66 as earlier predicted. This is the first case of stable uctpole deformation involving only one pair of orbitals.
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.
Theory of the normal modes of vibrations in the lanthanide type crystals
Energy Technology Data Exchange (ETDEWEB)
Acevedo, Roberto [Instituto de Ciencias Basicas. Facultad de Ingenieria, Universidad Diego Portales, Avenida Ejercito 441, Santiago (Chile); Soto-Bubert, Andres, E-mail: roberto.acevedo@umayor.cl
2008-11-01
For the lanthanide type crystals, a vast and rich, though incomplete amount of experimental data has been accumulated, from linear and non linear optics, during the last decades. The main goal of the current research work is to report a new methodology and strategy to put forward a more representative approach to account for the normal modes of vibrations for a complex N-body system. For illustrative purposes, the chloride lanthanide type crystals Cs{sub 2}NaLnCl{sub 6} have been chosen and we develop new convergence tests as well as a criterion to deal with the details of the F-matrix (potential energy matrix). A novel and useful concept of natural potential energy distributions (NPED) is introduced and examined throughout the course of this work. The diagonal and non diagonal contributions to these NPED-values, are evaluated for a series of these crystals explicitly. Our model is based upon a total of seventy two internal coordinates and ninety eight internal Hooke type force constants. An optimization mathematical procedure is applied with reference to the series of chloride lanthanide crystals and it is shown that the strategy and model adopted is sound from both a chemical and a physical viewpoints. We can argue that the current model is able to accommodate a number of interactions and to provide us with a very useful physical insight. The limitations and advantages of the current model and the most likely sources for improvements are discussed in detail.
Energy Technology Data Exchange (ETDEWEB)
Balasubramanian, K
2004-03-17
We have presented a group theoretical analysis of the vibrational modes and rovibronic levels of a novel extended aromatic C{sub 48}N{sub 12} azafullerene. The nuclear spin multiplets and statistical weights of {sup 14}N spin-1 bosons, vibrational and rotational analysis and computed vibrational spectra are provided. We have also predicted the properties of the {sup 3}A{sub u}, {sup 3}E{sub g}, and {sup 3}E{sub u} excited states of C{sub 48}N{sub 12} that lie 1.9 eV above the {sup 1}A{sub g} ground state, and that the {sup 3}E{sub g} and {sup 3}E{sub u} states would undergo Jahn-Teller distortion into chiral structures with no symmetry and an achiral structure with C{sub i} symmetry.
Chen, Hung-Yi; Liang, Jin-Wei; Wu, Jia-Wei
2013-07-02
This paper presents an intelligent control strategy to overcome nonlinear and time-varying characteristics of a diaphragm-type pneumatic vibration isolator (PVI) system. By combining an adaptive rule with fuzzy and sliding-mode control, the method has online learning ability when it faces the system's nonlinear and time-varying behaviors during an active vibration control process. Since the proposed scheme has a simple structure, it is easy to implement. To validate the proposed scheme, a composite control which adopts both chamber pressure and payload velocity as feedback signal is implemented. During experimental investigations, sinusoidal excitation at resonance and random-like signal are input on a floor base to simulate ground vibration. Performances obtained from the proposed scheme are compared with those obtained from passive system and PID scheme to illustrate the effectiveness of the proposed intelligent control.
Directory of Open Access Journals (Sweden)
Jia-Wei Wu
2013-07-01
Full Text Available This paper presents an intelligent control strategy to overcome nonlinear and time-varying characteristics of a diaphragm-type pneumatic vibration isolator (PVI system. By combining an adaptive rule with fuzzy and sliding-mode control, the method has online learning ability when it faces the system’s nonlinear and time-varying behaviors during an active vibration control process. Since the proposed scheme has a simple structure, it is easy to implement. To validate the proposed scheme, a composite control which adopts both chamber pressure and payload velocity as feedback signal is implemented. During experimental investigations, sinusoidal excitation at resonance and random-like signal are input on a floor base to simulate ground vibration. Performances obtained from the proposed scheme are compared with those obtained from passive system and PID scheme to illustrate the effectiveness of the proposed intelligent control.
Intrinsic Localized Modes in Optical Photonic Lattices and Arrays
Christodoulides, Demetrios
Discretizing light behavior requires optical elements that can confine optical energy at distinct sites. One possible scenario in implementing such arrangements is to store energy within low loss high Q-microcavities and then allow photon exchange between such components in time. This scheme requires high-contrast dielectric elements that became available with the advent of photonic crystal technologies. Another possible avenue where such light discretization can be directly observed and studied is that based on evanescently coupled waveguide arrays. As indicated in several studies, discrete systems open up whole new directions in terms of modifying light transport properties. One such example is that of discrete solitons. By nature, discrete solitons represent self-trapped wavepackets in nonlinear periodic structures and result from the interplay between lattice diffraction (or dispersion) and material nonlinearity. In optics, this class of self-localized states has been successfully observed in both one- and two-dimensional nonlinear waveguide arrays. In recent years such photonic lattices have been implemented or induced in a variety of material systems, including those with cubic (Kerr), quadratic, photorefractive, and liquid-crystal nonlinearities. In all cases the underlying periodicity or discreteness can lead to new families of optical solitons that have no counterpart whatsoever in continuous systems. Interestingly, these results paved the way for observations in other physical systems obeying similar evolution equations like Bose-Einstein condensates. New developments in laser writing ultrashort femtosecond laser pulses, now allow the realization of all-optical switching networks in fully 3D environments using nonlinear discrete optics. Using this approach all-optical routing can be achieved using blocking operations. The spatio-temporal evolution of optical pulses in both normally and anomalously dispersive arrays can lead to novel schemes for mode
Energy Technology Data Exchange (ETDEWEB)
Chen, Shun-Li; Fu, Li; Chase, Zizwe A.; Gan, Wei; Wang, Hong-Fei
2016-11-10
Vibrational spectral lineshape contains important detailed information of molecular vibration and reports its specific interactions and couplings to its local environment. In this work, recently developed sub-1 cm-1 high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) was used to measure the -C≡N stretch vibration in the 4-n-octyl-4’-cyanobiphenyl (8CB) Langmuir or Langmuir-Blodgett (LB) monolayer as a unique vibrational probe, and the spectral lineshape analysis revealed the local environment and interactions at the air/water, air/glass, air/calcium fluoride and air/-quartz interfaces for the first time. The 8CB Langmuir or LB film is uniform and the vibrational spectral lineshape of its -C≡N group has been well characterized, making it a good choice as the surface vibrational probe. Lineshape analysis of the 8CB -C≡N stretch SFG vibrational spectra suggests the coherent vibrational dynamics and the structural and dynamic inhomogeneity of the -C≡N group at each interface are uniquely different. In addition, it is also found that there are significantly different roles for water molecules in the LB films on different substrate surfaces. These results demonstrated the novel capabilities of the surface nonlinear spectroscopy in characterization and in understanding the specific structures and chemical interactions at the liquid and solid interfaces in general.
Multi-mode traffic-induced vibrations in composite ladder-deck bridges under heavy moving vehicles
Camara, A.; Ruiz-Teran, A. M.
2015-10-01
Composite (steel-concrete) ladder-decks represent one of the most common solutions in road bridges nowadays. In these structures the Serviceability Limit State (SLS) of vibrations is traditionally ignored or roughly addressed by means of simple static deflection-based approaches, inherently assuming that the vibrations are controlled by the fundamental longitudinal mode. This work demonstrates that a wide range of high-order vibrational modes, involving the transverse flexure of the slab between longitudinal girders, govern the accelerations recorded in the deck and inside the vehicles. In addition, a new methodology for analysing the Vehicle-Bridge Interaction is proposed, including the approaching platforms, the transition slabs, and the bridge joints. The results suggest that the riding comfort for vehicle users is specially affected by direct effects on the wheels, like the road roughness and possible construction misalignments at the bridge joints, as well as low-frequency vibrations coming from the deck in short or slender bridges. The filtering effects resulting from the average of the response in time and in space when calculating the root mean square acceleration are also explored, and new design parameters are provided. In addition, several structural features (such as the depth and spacing of the longitudinal and transverse steel beams, the thickness of the concrete slab, and the stiffness of the cantilever cross beams at the diaphragm sections) have been studied, and a set of new design criteria has been established. It has been demonstrated that the transverse flexibility of the deck (specially influenced by the support conditions and the slab thickness) is critically important for the users' (pedestrians and vehicle passengers) comfort, as it controls the aforementioned high-order vibrational modes which govern the dynamic response.
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.
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.
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.
Receptivity of plane Poiseuille flow to local micro-vibration disturbance on wall
Directory of Open Access Journals (Sweden)
Wei-dong CAO
2015-04-01
Full Text Available The receptivity of plane Poiseuille flow to local single-period micro-vibration disturbances with different phases at the top and bottom walls was investigated through direct numerical simulation of three-dimensional incompressible Navier-Stokes equations. Results show that the disturbance presents a symmetrical distribution in the spanwise direction when the micro-vibration on the wall ends, and the initial disturbance velocities and spatial distribution of the disturbance structure are different at the top and bottom walls. The disturbance’s velocity, amplitude, and high- and low-speed streaks increase with time, and the amplitude of streamwise disturbance velocity is larger than those of spanwise and vertical disturbance velocities. However, no significant Tollmien-Schlichting wave was found in the flow field. The number of disturbance vortex cores gradually increases with the disturbance area. High-speed disturbance fluid concentrates near the wall and its normal velocity largely points to the wall, while low-speed disturbance fluid largely deviates from the wall. Furthermore, the streamwise velocity profiles near the top and bottom walls both become plump because of the existence of the disturbances, and the streamwise velocity profiles show a trend of evolving into turbulent velocity profiles. The shear stress near the wall increases significantly. The local micro-vibration disturbance on the wall in plane Poiseuille flow can induce the development of a structure similar to turbulent spots.
Energy Technology Data Exchange (ETDEWEB)
Fry-Petit, A. M., E-mail: mcqueen@jhu.edu, E-mail: afry@fullerton.edu; Sheckelton, J. P.; McQueen, T. M., E-mail: mcqueen@jhu.edu, E-mail: afry@fullerton.edu [Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218 (United States); Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218 (United States); Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Rebola, A. F.; Fennie, C. J. [Department of Applied Physics, Cornell University, Ithaca, New York 14853 (United States); Mourigal, M.; Valentine, M.; Drichko, N. [Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)
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, LiZn{sub 2}Mo{sub 3}O{sub 8}, this approach allows direct assignment of the constrained rotational mode of Mo{sub 3}O{sub 13} clusters and internal modes of MoO{sub 6} 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.
Institute of Scientific and Technical Information of China (English)
Ta Na; Qiu Jiajun; Cai Ganhua
2005-01-01
Zero mode natural frequency (ZMNF) is found during experiments. The ZMNF and vibrations resulted by it are studied. First, calculating method of the ZMNF excited by electromagnetic in vibrational system of coupled mechanics and electrics are given from the view of magnetic energy.Laws that the ZMNF varies with active power and exciting current are obtained and are verified by experiments. Then, coupled lateral and torsional vibration of rotor shaft system is studied by considering rest eccentricity, rotating eccentricity and swing eccentricity. Using Largrange-Maxwell equation when three phases are asymmetric derives differential equation of the coupled vibration. With energy method of nonlinear vibration, amplitude-frequency characteristics of resonance are studied when rotating speed of rotor equals to ZMNF. The results show that ZMNF will occur in turbine generators by the action of electromagnetic. Because ZMNF varies with electromagnetic parameters,resonance can occur when exciting frequency of the rotor speed is fixed whereas exciting current change. And also find that a generator is in the state of large amplitude in rated exciting current.
Habibnejad Korayem, Alireza; Habibnejad Korayem, Moharam; Ghaderi, Reza
2014-12-01
In this article, the vibrational behavior of a microcantilever (MC) with an extended piezoelectric layer in the air ambient undergoes examination. To model the vibrational motion of this type of cantilever, the Hamilton's principle has been used. For this purpose, the MC vibrational equation has been derived by the assumption of the continuous beam based on the Euler-Bernoulli beam theory. By adopting the finite element method (FEM), the MC differential equation has been solved. In the present simulation not only van der Waals and contact forces but also the capillary forces resulting from the condensation of the water vapors in air on MC tip have been considered. The results illustrate that the force between the sample surface and the probe affects the MC amplitude; furthermore, it causes the reduction in the resonance frequency. In addition, to reduce the time delay during topography from the surface roughness, it is better to select MCs with larger width and length and smaller thickness. Furthermore, the results indicate that the best imaging takes place when the vibration is in its second vibrational mode. Finally, the effects of MC geometric parameters on the time delay between the starting moment of surface roughness and the moment of variation in the MC amplitude (surface roughness topography) have been analyzed.
Piezoelectric generator based on torsional modes for power harvesting from angular vibrations
Institute of Scientific and Technical Information of China (English)
CHEN Zi-guang; HU Yuan-tai; YANG Jia-shi
2007-01-01
Torsional vibration of a circular piezoelectric shell of polarized ceramics mounted on a rotationally vibrating base is analyzed. The shell is properly electroded and connected to a circuit such that an electric output is generated. The structure analyzed represents a piezoelectric generator for converting mechanical energy from angular vibrations to electrical energy. Analytical expressions and numerical results for the output voltage, current, power, efficiency and power density are given.
Impurity-induced local modes in one-dimensional dusty plasma chains
Institute of Scientific and Technical Information of China (English)
Ren Yong-Chao; Wang Xin-Shang; Wang Xiao-Gang
2012-01-01
The effects of impurity on eigenmodes in one-dimensional dusty plasma lattices are studied.It is found that local modes can be excited besides lattice waves,due to the existence of an impurity particle.The dispersion relations of the modes are derived accordingly.Properties of the lattice and local modes are also analyzed and discussed,particularly for their symmetric features and conditions of the mode excitation.
Structural Damage Localization by Outlier Analysis of Signal-processed Mode Shapes
DEFF Research Database (Denmark)
Ulriksen, Martin Dalgaard; Damkilde, Lars
2016-01-01
analysis is conducted by applying the Mahalanobis metric to major principal scores of the sensor-located bands of the signal-processed mode shape. The method is tested analytically on the basis of a free-vibrating beam and experimentally in the context of a residential-sized wind turbine blade subjected...
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.
Field-Line Localized Destabilization of Ballooning Modes in Three-Dimensional Tokamaks
Willensdorfer, M.; Cote, T. B.; Hegna, C. C.; Suttrop, W.; Zohm, H.; Dunne, M.; Strumberger, E.; Birkenmeier, G.; Denk, S. S.; Mink, F.; Vanovac, B.; Luhmann, L. C.; ASDEX Upgrade Team
2017-08-01
Field-line localized ballooning modes have been observed at the edge of high confinement mode plasmas in ASDEX Upgrade with rotating 3D perturbations induced by an externally applied n =2 error field and during a moderate level of edge localized mode mitigation. The observed ballooning modes are localized to the field lines which experience one of the two zero crossings of the radial flux surface displacement during one rotation period. The localization of the ballooning modes agrees very well with the localization of the largest growth rates from infinite-n ideal ballooning stability calculations using a realistic 3D ideal magnetohydrodynamic equilibrium. This analysis predicts a lower stability with respect to the axisymmetric case. The primary mechanism for the local lower stability is the 3D distortion of the local magnetic shear.
Nonlinear localized modes in PT-symmetric optical media with competing gain and loss
Energy Technology Data Exchange (ETDEWEB)
Midya, Bikashkali, E-mail: bikash.midya@gmail.com [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108 (India); Roychoudhury, Rajkumar, E-mail: rroychoudhury123@gmail.com [Advanced Center for Nonlinear and Complex Phenomena, Kolkata 700075 (India)
2014-02-15
The existence and stability of the nonlinear spatial localized modes are investigated in parity-time symmetric optical media characterized by a generic complex hyperbolic refractive index distribution with competing gain and loss profile. The exact analytical expression of the localized modes are found for all values of the competing parameter and in the presence of both the self-focusing and self-defocusing Kerr nonlinearity. The effects of competing gain/loss profile on the stability structure of these localized modes are discussed with the help of linear stability analysis followed by the direct numerical simulation of the governing equation. The spatial localized modes in two-dimensional geometry as well as the transverse power-flow density associated with these localized modes are also examined. -- Highlights: • Existence of localized modes is investigated in PT-symmetric complex potentials. • Exact analytical expression of the localized modes is obtained. • Effect of gain/loss profile on the stability of these localized modes is discussed. • Localized modes in 2D and associated transverse power-flow density are also examined.
Nonlinear localized modes in PT-symmetric Rosen-Morse potential well
Midya, Bikashkali
2013-01-01
We report the existence and properties of localized modes described by nonlinear Schroedinger equation with complex PT-symmetric Rosen-Morse potential well. Exact analytical expressions of the localized modes are found in both one dimensional and two-dimensional geometry with self-focusing and self-defocusing Kerr nonlinearity. Linear stability analysis reveals that these localized modes are unstable for all real values of the potential parameters although corresponding linear Schroedinger eigenvalue problem possesses unbroken PT-symmetry. This result has been verified by the direct numerical simulation of the governing equation. The transverse power flow density associated with these localized modes has also been examined.
Advanced tip design for liquid phase vibration mode atomic force microscopy
Energy Technology Data Exchange (ETDEWEB)
Muramatsu, Hiroshi; Yamamoto, Yuji [School of Bionics, Tokyo University of Technology, 1404-1 Katakura, Hachioji, Tokyo 192-0982 (Japan); Shigeno, Masatsugu; Shirakawabe, Yoshiharu; Inoue, Akira [Technology Center, Seiko Instruments Inc., 563 Takatsukashinden, Matsudo, Chiba 271-2222 (Japan); Kim, Woo-Sik [Department of Chemical Engineering, Kyunghee University, Kyungki-Do 449-701 (Korea, Republic of); Kim, Seung Jin; Chang, Sang-Mok [Department of Chemical Engineering, Hadan 840, Saha-Gu, Busan 604-714 (Korea, Republic of); Kim, Jong Min [Department of Chemical Engineering, Hadan 840, Saha-Gu, Busan 604-714 (Korea, Republic of)], E-mail: jmkim3@dau.ac.kr
2008-03-24
We have fabricated polymer tips for atomic force microscopy in order to elucidate the effects of tip length and shape on cantilever vibration damping in liquids. The vibration damping is investigated by measuring the vibration amplitude of cantilevers as a function of tip-sample distance. The cantilever with a short tip provides a higher damping effect over long tip-sample distances. When the vibration amplitude was rescaled to show the effect of the cantilever width on oscillation damping, the vibration amplitude of cantilevers with various tip lengths was similarly obtained in a long distance range over 50 {mu}m. This similarity is explained by an acoustic damping model in which an acoustic wave is generated by the cantilever. Finally, the results indicate a cantilever with a sufficiently long tip compared to the cantilever width can dramatically reduce the long-range damping effect in a liquid environment.
Wang, Zheng; Liu, Chao; Li, Erwen; Chakravarty, Swapnajit; Xu, Xiaochuan; Wang, Alan X.; Fan, D. L.; Chen, Ray T.
2017-02-01
Raman scattering spectroscopy is a unique tool to probe vibrational, rotational, and other low-frequency modes of a molecular system and therefore could be utilized to identify chemistry and quantity of molecules. However, the ultralow efficient Raman scattering, which is only 1/109 1/1014 of the excitation light due to the small Raman scattering cross-sections of molecules, have significantly hindered its development in practical sensing applications. The discovery of surface-enhanced Raman scattering (SERS) in the 1970s and the significant progress in nanofabrication technique, provide a promising solution to overcome the inherent issues of Raman spectroscopy. It is found that In the vicinity of nanoparticles and their junctions, the Raman signals of molecules can be significantly improved by an enhancement factor as high as 1010, due to the ultrahigh electric field generated by the localized surface plasmons resonance (LSPR), where the intensity of Raman scattering is proportional to the |E|4. In this work, we propose and demonstrate a new approach combining LSPR from nanocapsules with densely assembled silver nanoparticles (NC-AgNPs) and guidemode- resonance (GMR) from dielectric photonic crystal slabs (PCSs) for SERS substrates with robustly high performance.
Flexural vibration band gaps in thin plates with two-dimensional binary locally resonant structures
Institute of Scientific and Technical Information of China (English)
Yu Dian-Long; Wang Gang; Liu Yao-Zong; Wen Ji-Hong; Qiu Jing
2006-01-01
The complete flexural vibration band gaps are studied in the thin plates with two-dimensional binary locally resonant structures, i.e. the composite plate consisting of soft rubber cylindrical inclusions periodically placed in a host material. Numerical simulations show that the low-frequency gaps of flexural wave exist in the thin plates. The width of the first gap decreases monotonically as the matrix density increases. The frequency response of the finite periodic thin plates is simulated by the finite element method, which provides attenuations of over 20dB in the frequency range of the band gaps. The findings will be significant in the application of phononic crystals.
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.
Saleeb, A. F.; Prabhu, M.; Arnold, S. M. (Technical Monitor)
2002-01-01
Recently, a conceptually simple approach, based on the notion of defect energy in material space has been developed and extensively studied (from the theoretical and computational standpoints). The present study focuses on its evaluation from the viewpoint of damage localization capabilities in case of two-dimensional plates; i.e., spatial pattern recognition on surfaces. To this end, two different experimental modal test results are utilized; i.e., (1) conventional modal testing using (white noise) excitation and accelerometer-type sensors and (2) pattern recognition using Electronic speckle pattern interferometry (ESPI), a full field method capable of analyzing the mechanical vibration of complex structures. Unlike the conventional modal testing technique (using contacting accelerometers), these emerging ESPI technologies operate in a non-contacting mode, can be used even under hazardous conditions with minimal or no presence of noise and can simultaneously provide measurements for both translations and rotations. Results obtained have clearly demonstrated the robustness and versatility of the global NDE scheme developed. The vectorial character of the indices used, which enabled the extraction of distinct patterns for localizing damages proved very useful. In the context of the targeted pattern recognition paradigm, two algorithms were developed for the interrogation of test measurements; i.e., intensity contour maps for the damaged index, and the associated defect energy vector field plots.
Kong, Xiangxi; Zhang, Xueliang; Chen, Xiaozhe; Wen, Bangchun; Wang, Bo
2016-05-01
In this paper, self- and controlled synchronizations of three eccentric rotors (ERs) in line driven by induction motors rotating in the same direction in a vibrating system are investigated. The vibrating system is a typical underactuated mechanical-electromagnetic coupling system. The analysis and control of the vibrating system convert to the synchronization motion problem of three ERs. Firstly, the self-synchronization motion of three ERs is analyzed according to self-synchronization theory. The criterions of synchronization and stability of self-synchronous state are obtained by using a modified average perturbation method. The significant synchronization motion of three ERs with zero phase differences cannot be implemented according to self-synchronization theory through analysis and simulations. To implement the synchronization motion of three ERs with zero phase differences, an adaptive sliding mode control (ASMC) algorithm based on a modified master-slave control strategy is employed to design the controllers. The stability of the controllers is verified by using Lyapunov theorem. The performances of the controlled synchronization system are presented by simulations to demonstrate the effectiveness of controllers. Finally, the effects of reference speed and non-zero phase differences on the controlled system are discussed to show the strong robustness of the proposed controllers. Additionally, the dynamic responses of the vibrating system in different synchronous states are analyzed.
Hu, Qinglei
2010-09-01
This paper presents a dual-stage control system design method for the rotational maneuver control and vibration stabilization of a flexible spacecraft. In this design approach, the sub-systems of attitude control and vibration suppression are designed separately using the low order model. Based on the sliding mode control (SMC) theory, a discontinuous attitude control law in the form of the input voltage of the reaction wheel is derived to control the orientation of the spacecraft, incorporating the L 2-gain performance criterion constraint. The resulting closed-loop system is proven to be uniformly ultimately bounded stability and the effect of the external disturbance on both attitude quaternion and angular velocity can be attenuated to the prescribed level as well. In addition, an adaptive version of the control law is designed for adapting the unknown upper bounds of the lumped disturbance such that the limitation of knowing the bound of the disturbance in advance is released. For actively suppressing the induced vibration, strain rate feedback control method is also investigated by using piezoelectric materials as additional sensors and actuators bonded on the surface of the flexible appendages. Numerical simulations are performed to show that rotational maneuver and vibration suppression are accomplished in spite of the presence of disturbance and uncertainty.
Zhang, Yuyuan; Improta, Roberto; Kohler, Bern
2014-01-28
UV-pump/broadband-mid-IR-probe transient absorption (TA) experiments and ab initio quantum mechanical (QM) calculations were used to investigate the photophysics in heavy water of the neutral and acid forms of guanosine 5'-monophosphate (GMP and GMPD(+), respectively). Excited GMP undergoes ultrafast internal conversion (IC) and returns to the electronic ground state in less than one picosecond with a large amount of excess vibrational energy. The spectroscopic signals are dominated by vibrational cooling - a process in which the solute dissipates vibrational energy to the solvent. For neutral GMP, cooling proceeds with a time constant of 3 ps. Following IC, at least some medium-frequency modes such as the carbonyl stretch and an in-plane ring vibration are excited, suggesting that the vibrational energy distribution is non-statistical. This is consistent with predicted structural changes upon passage through the S1/S0 conical intersection. GMPD(+) differs from GMP by a single deuteron at the N7 position, but has a dramatically longer lifetime of 200 ps. Vibrational cooling of the S1 state of GMPD(+) was monitored via several medium-frequency modes that were assigned using QM calculations. These medium-frequency modes are also vibrationally excited in a non-statistical fashion. Excitation of these modes is in line with the change in geometry at the S1 minimum of GMPD(+) predicted by QM calculations. Furthermore, these modes relax at different rates, fully consistent with QM calculations, which predict that excited vibrational states of the carbonyl stretch couple strongly to the D2O solvent and thus deactivate via intermolecular energy transfer (IET). In contrast, the ring stretch couples strongly to other ring modes of the guanine chromophore and appears to decay via intramolecular vibrational energy redistribution (IVR).
Investigation of ELM [edge localized mode] Dynamics with the Resonant Magnetic Perturbation Effects
Energy Technology Data Exchange (ETDEWEB)
Pankin, Alexei Y.; Kritz, Arnold H.
2011-07-19
Topics covered are: anomalous transport and E x B flow shear effects in the H-mode pedestal; RMP (resonant magnetic perturbation) effects in NSTX discharges; development of a scaling of H-mode pedestal in tokamak plasmas with type I ELMs (edge localized modes); and divertor heat load studies.
Features of the repetition frequency of edge localized modes in EAST
DEFF Research Database (Denmark)
Jiang, M.; Xiao, C.; Xu, G.S.
2012-01-01
This paper presents the features of the edge localized modes (ELMs) observed in the 2010 experimental campaign on the Experimental Advanced Superconducting Tokamak (EAST). The first high-confinement mode (H-mode) at an H-factor of HIPB98(y, 2)~1 has been obtained with about 1 MW lower hybrid wave...
John, Kevin D.; Miskowski, Vincent M.; Vance, Michael A.; Dallinger, Richard F.; Wang, Louis C.; Geib, Steven J.; Hopkins, Michael D.
1998-12-28
The nature of the skeletal vibrational modes of complexes of the type M(2)(C&tbd1;CR)(4)(PMe(3))(4) (M = Mo, W; R = H, Me, Bu(t)(), SiMe(3)) has been deduced. Metrical data from X-ray crystallographic studies of Mo(2)(C&tbd1;CR)(4)(PMe(3))(4) (R = Me, Bu(t)(), SiMe(3)) and W(2)(C&tbd1;CMe)(4)(PMe(3))(4) reveal that the core bond distances and angles are within normal ranges and do not differ in a statistically significant way as a function of the alkynyl substituent, indicating that their associated force constants should be similarly invariant among these compounds. The crystal structures of Mo(2)(C&tbd1;CSiMe(3))(4)(PMe(3))(4) and Mo(2)(C&tbd1;CBu(t)())(4)(PMe(3))(4) are complicated by 3-fold disorder of the Mo(2) unit within apparently ordered ligand arrays. Resonance-Raman spectra ((1)(delta-->delta) excitation, THF solution) of Mo(2)(C&tbd1;CSiMe(3))(4)(PMe(3))(4) and its isotopomers (PMe(3)-d(9), C&tbd1;CSiMe(3)-d(9), (13)C&tbd1;(13)CSiMe(3)) exhibit resonance-enhanced bands due to a(1)-symmetry fundamentals (nu(a) = 362, nu(b) = 397, nu(c) = 254 cm(-)(1) for the natural-abundance complex) and their overtones and combinations. The frequencies and relative intensities of the fundamentals are highly sensitive to isotopic substitution of the C&tbd1;CSiMe(3) ligands, but are insensitive to deuteration of the PMe(3) ligands. Nonresonance-Raman spectra (FT-Raman, 1064 nm excitation, crystalline samples) for the Mo(2)(C&tbd1;CSiMe(3))(4)(PMe(3))(4) compounds and for Mo(2)(C&tbd1;CR)(4)(PMe(3))(4) (R = H, D, Me, Bu(t)(), SiMe(3)) and W(2)(C&tbd1;CMe)(4)(PMe(3))(4) exhibit nu(a), nu(b), and nu(c) and numerous bands due to alkynyl- and phosphine-localized modes, the latter of which are assigned by comparisons to FT-Raman spectra of Mo(2)X(4)L(4) (X = Cl, Br, I; L = PMe(3), PMe(3)-d(9))(4) and Mo(2)Cl(4)(AsMe(3))(4). Valence force-field normal-coordinate calculations on the model compound Mo(2)(C&tbd1;CH)(4)P(4), using core force constants transferred from a calculation
Yue, Sheng-Ying; Zhang, Xiaoliang; Qin, Guangzhao; Yang, Jiayue; Hu, Ming
2016-09-01
The past few years have witnessed a rapid evolution of hybrid organic-inorganic perovskite solar cells as an unprecedented photovoltaic technology with both relatively low cost and high-power conversion. The fascinating physical and chemical properties of perovskites are benefited from their unique crystal structures represented by the general chemical formula A M X3 , where the A cations occupy the hollows formed by the M X3 octahedra and thus balance the charge of the entire network. Despite a vast amount of theoretical and experimental investigations have been dedicated to the structural stability, electrical, and optical properties of hybrid halide perovskite materials in relation to their applications in solar cells, the thermal transport property, another critical parameter to the design and optimization of relevant solar cell modules, receives less attention. In this paper, we evaluate the lattice thermal conductivity of a representative methylammonium lead triiodide perovskite (CH3NH3PbI3 ) with direct nonequilibrium ab initio molecular dynamics simulation. Resorting to full first-principles calculations, we illustrate the details of the mysterious vibration of the methylammonium cluster (CH3NH3+ ) and present an unambiguous picture of how the organic cluster interacting with the inorganic cage and how the collective motions of the organic cluster drags the thermal transport, which provide fundamental understanding of the ultralow thermal conductivity of CH3NH3PbI3 . We also reveal the strongly localized phonons associated with the internal motions of the CH3NH3+ cluster, which contribute little to the total thermal conductivity. The importance of the CH3NH3+ cluster to the structural instability is also discussed in terms of the unconventional dispersion curves by freezing the partial freedoms of the organic cluster. These results provide more quantitative description of organic-inorganic interaction and coupling dynamics from accurate first
Assimilation of Mode-S EHS aircraft observations with a local EnKF
Lange, Heiner; Janjic, Tijana
2016-04-01
Aircraft observations of wind and temperature collected by airport surveillance radars (Mode-S EHS) were assimilated in COSMO-KENDA (Kilometre-scale ENsemble Data Assimilation) which couples an Ensemble Kalman Filter to a 40 member ensemble of the convection permitting COSMO-DE (Consortium for Small-Scale Modelling) model. The number of observing aircrafts in Mode-S EHS was about 15 times larger than in the AMDAR system. Between both aircraft observation systems, comparable observation error standard deviations in wind and a larger error in temperature were diagnosed a posteriori using analysis/forecast residuals in observation space (Desrozier's method). With the high density of Mode-S EHS observations, a reduction of temperature and wind error in forecasts of one and three hours was found mainly in the flight level and less near the surface. The amount of Mode-S EHS data was reduced by random thinning to test the effect of a varying observation density. With the current data assimilation setup, a saturation of the forecast error reduction was apparent when more than 50 percent of the Mode-S EHS data were assimilated. Forecast kinetic energy spectra indicated that the reduction in error is related to analysis updates on all scales resolved by COSMO-DE. Evolution (every 15 minutes) of forecast kinetic energy spectra compared to the control experiment showed different behavior of COSMO-DE model depending on amount of data assimilated.
Coupled flexural-longitudinal vibration of delaminated composite beams with local stability analysis
Szekrényes, András
2014-09-01
A novel analytical model is developed to solve the problem of free vibration of delaminated composite beams. The beam with a single delamination was modelled by six equivalent single layers by establishing the kinematic continuity in the undelaminated portion of the system. In the delaminated region the layers were captured by the traditional theories. First, Timoshenko beam theory is applied to solve the problem, then by reducing the model, the corresponding Euler-Bernoulli solution is presented. Both the free and constrained models were considered. The most important aspect of the present analysis is that the beams of the delaminated region are subjected to normal forces, as well. That is the essential reason for leading to a coupled flexural-longitudinal vibration problem. It is also concluded that delamination buckling can take place if the normal force is compressive in one of the half-periods of the vibration and reaches a critical value. The problem was also investigated experimentally by modal hammer and sweep excitation tests on beams made of E-glass/polyester in order to measure the natural frequencies and mode shapes. The comparison of the analytical and experimental results indicates the importance of the independent rotations provided by Timoshenko beams over the simple beam theory. The delamination buckling of the beams was captured based on the static stability analysis in the first step. Further results show that the problem is more complex than it was thought before, e.g., some nonlinearity, time-dependent stiffness as well as parametric excitation aspects were discovered during the present analysis.
Robot-assisted assessment of vibration perception and localization on the hand.
Lambercy, Olivier; Kim, Yeongmi; Gassert, Roger
2013-03-01
Sensory perception is crucial for motor learning and the control of fine manipulations. However, therapy after stroke still strongly focuses on the training of motor skills. Sensory assessments are often left out or provide only very subjective data from poorly controlled stimuli. This paper presents a vibration detection/localization test with the Robotic Sensory Trainer, a device that focuses entirely on the assessment and training of sensory function of the hand, with the aim of gaining insights into the prevalence and severity of sensory deficits after stroke, and to provide semiobjective data on absolute and difference perception thresholds in patients. An initial feasibility study investigated localization performance and reaction time during the discrimination of vibration stimuli presented in four locations on the dominant and nondominant hands of 13 healthy volunteers. High correct detection rates were observed (mean ± SD of 99.6% ± 0.6%), touch screen PC Robotic Sensory Trainer which were found to be significantly different between stimulus locations on the dominant hand. Average correct detection rates were not statistically different between dominant and nondominant hand. These data will serve as baseline for future measurements on elderly and stroke subjects, and suggest that data from the nonimpaired hand could be used to identify and assess sensory deficits in the affected hand of stroke patients.
Nonlinear localized modes in PT-symmetric optical media with competing gain and loss
Midya, Bikashkali
2014-01-01
The existence and stability of the nonlinear spatial localized modes are investigated in parity-time symmetric optical media characterized by a generic complex hyperbolic refractive index distribution with competing gain and loss profile. The exact analytical expressions of the localized modes are found for all values of the competing parameter and in the presence of both the self-focusing and self-defocusing Kerr nonlinearity. The effect of competing gain/loss profile on the stability structure of these localized modes are discussed with the help of linear stability analysis followed by the direct numerical simulation of the governing equation. The spatial localized modes in two-dimensional geometry as well as the transverse power-flow density associated with these localized modes are also examined.
He, Xiping; Yao, Jing; Zhang, Haidao; Liu, Doudou; Li, Jiaxing
2015-04-01
The flexural vibration characteristics of a rectangular plate in stripe mode, driven at its center by a different longitudinal vibration ultrasonic transducer (LVUT) with different excitation area are investigated. The variation in the nodal lines and corresponding resonant frequency of the rectangular plate under different excitation area are calculated by using finite element method (FEM). The results show that the resonant frequency increases with the excitation area of the LVUT increasing, and the nodal lines bend obviously when the radius r of excitation area is greater than a certain value. The experimental tests are carried out by the aid of Polytec PSV-400 Scanning laser Vibrometer, and the results agree well those of numerically calculated. It indicates that the larger excitation area of longitudinal transducer may affect the ultrasonic field radiated by the rectangular plate.
Huang, Qingjiu; Fukuhara, Yasuyuki; Chen, Xuedong
In this paper, we proposed a robust control method based on the virtual suspension model for keeping the posture stability and decreasing the tiny vibration of the robot body when it is walking on irregular terrain. Firstly, we developed a six-legged walking robot for this study based on stable theory of wave gaits and CAD dynamic model. Secondly, in order to keep the posture stability of body when robot walks, we designed a virtual suspension model with one degree of freedom, which has virtual spring and damper, for the direction of the center of gravity, the pitch angle, and the roll angle of body respectively. And then, in order to decrease the tiny vibration of body when robot walks, we proposed an active suspension control by using sliding mode control based on a virtual suspension model. These proposed methods are discussed using the walking experimental results of the developed six-legged walking robot.
Changes in EMG activity in the upper trapezius muscle due to local vibration exposure
Astrom, Charlotte; Lindkvist, Markus; Burstrom, Lage; Sundelin, Gunnevi; Karlsson, J. Stefan
2009-01-01
Exposure to vibration is suggested as a risk factor for developing neck and shoulder disorders in working life. Mechanical vibration applied to a muscle belly or a tendon can elicit a reflex muscle contraction, also called tonic vibration reflex, but the mechanisms behind how vibration could cause m
DEFF Research Database (Denmark)
Neves, Miguel M.; Sigmund, Ole; Bendsøe, Martin P.
2002-01-01
The problem of determining highly localized buckling modes in perfectly periodic cellular microstructures of infinite extent is addressed. A double scale asymptotic technique is applied to the linearized stability problem for a periodic structure built from linearly elastic microstructures...... to design materials with optimal elastic properties that are less prone to localized instability in the form of local buckling modes at the scale of the micro structure. Copyright (C) 2002 John Wiley Sons, Ltd....
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 mixtures at 450-700 oC under static equilibria conditions. Band assignments and Raman band intensity correlations with complex 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....
Energy Technology Data Exchange (ETDEWEB)
Garofalo, A. M., E-mail: garofalo@fusion.gat.com; Burrell, K. H.; Meneghini, O.; Osborne, T. H.; Paz-Soldan, C.; Smith, S. P.; Snyder, P. B.; Turnbull, A. D. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Eldon, D.; Grierson, B. A.; Solomon, W. M. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States); Hanson, J. M. [Columbia University, 2960 Broadway, New York, New York 10027-6900 (United States); Holland, C. [University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0417 (United States); Huijsmans, G. T. A.; Liu, F.; Loarte, A. [ITER Organization, Route de Vinon sur Verdon, 13067 St Paul Lez Durance (France); Zeng, L. [University of California Los Angeles, P.O. Box 957099, Los Angeles, California 90095-7099 (United States)
2015-05-15
For the first time, DIII-D experiments have achieved stationary quiescent H-mode (QH-mode) operation for many energy confinement times at simultaneous ITER-relevant values of beta, confinement, and safety factor, in an ITER-like shape. QH-mode provides excellent energy confinement, even at very low plasma rotation, while operating without edge localized modes (ELMs) and with strong impurity transport via the benign edge harmonic oscillation (EHO). By tailoring the plasma shape to improve the edge stability, the QH-mode operating space has also been extended to densities exceeding 80% of the Greenwald limit, overcoming the long-standing low-density limit of QH-mode operation. In the theory, the density range over which the plasma encounters the kink-peeling boundary widens as the plasma cross-section shaping is increased, thus increasing the QH-mode density threshold. The DIII-D results are in excellent agreement with these predictions, and nonlinear magnetohydrodynamic analysis of reconstructed QH-mode equilibria shows unstable low n kink-peeling modes growing to a saturated level, consistent with the theoretical picture of the EHO. Furthermore, high density operation in the QH-mode regime has opened a path to a new, previously predicted region of parameter space, named “Super H-mode” because it is characterized by very high pedestals that can be more than a factor of two above the peeling-ballooning stability limit for similar ELMing H-mode discharges at the same density.
Ahmad, Javaid; Cheng, Shaohong; Ghrib, Faouzi
2016-02-01
Suppressing unfavorable stay cable vibrations using cross-ties is becoming more popular on cable-stayed bridges though the mechanics of the formed cable network is yet fully understood. In practice, the main task in designing cross-ties or cable networks is to choose the cross-tie installation location, stiffness and number based on the main cable properties in the network. To have a more comprehensive picture of how to choose these design parameters to achieve higher in-plane network stiffness while minimizing the number of excited local modes, it is imperative to examine dynamic behavior of cable networks with general configurations. In the current study, an analytical model of a general cable network consisting of multiple main cables interconnected by multiple lines of transverse flexible cross-ties will be developed. A new term, defined as the local mode cluster, will be introduced to assess the severity of local mode excitation. Criteria for identifying the presence of local mode cluster will be proposed. A parametric study will be conducted to evaluate the impact of cross-tie installation location, stiffness and number on the network modal response. Results obtained from the present study will provide deeper insight into the selection of these system parameters to achieve the combined benefits of increasing network in-plane stiffness and minimizing the excitation of local modes.
Wang, Xiao Hu; Zheng, Chang Cheng; Ning, Ji Qiang
2016-09-01
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.
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.
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…
Algebraic Hamiltonian for Vibrational Spectra of Stibine
Institute of Scientific and Technical Information of China (English)
HOU Xi-Wen
2004-01-01
@@ An algebraic Hamiltonian, which in a limit can be reduced to an extended local mode model by Law and Duncan,is proposed to describe both stretching and bending vibrational energy levels of polyatomic molecules, where Fermi resonances between the stretches and the bends are considered. The Hamiltonian is used to study the vibrational spectra of stibine (SbH3). A comparison with the extended local mode model is made. Results of fitting the experimental data show that the algebraic Hamiltonian reproduces the observed values better than the extended local mode model.
Benedetti, Maria Grazia; Boccia, Gennaro; Cavazzuti, Lorenzo; Magnani, Elena; Mariani, Elisabetta; Rainoldi, Alberto; Casale, Roberto
2017-07-18
Quadriceps weakness has been associated with knee osteoarthritis (OA). High-frequency localized muscle vibration (LMV) has been proposed recently for quadriceps strengthening in patients with knee OA. The purpose of this study was (a) to investigate the clinical effectiveness of high-frequency LMV on quadriceps muscle in patients with knee OA and (b) to disentangle, by means of surface electromyography (sEMG), the underlying mechanism. Thirty patients, aged between 40 and 65 years, and clinically diagnosed with knee OA were included in this randomized, controlled, single-blinded pilot study. Participants were randomly assigned to two groups: a study group treated with LMV, specifically set for muscle strengthening (150 Hz), by means of a commercial device VIBRA, and a control group treated with neuromuscular electrical stimulation. Clinical outcome was measured using the Western Ontario and McMaster Universities Osteoarthritis Index, Visual Analogue Scale, knee range of motion, Timed Up and Go test, and Stair climbing test. To assess changes in muscle activation and fatigue a subgroup of 20 patients was studied with the use of sEMG during a sustained isometric contraction. The LMV group showed a significant change in Western Ontario and McMaster Universities Osteoarthritis Index score, Visual Analogue Scale score, Timed Up and Go test, Stair Climbing Test, and knee flexion. These improvements were not significant in patients treated with neuromuscular electrical stimulation. sEMG analysis suggested an increased involvement of type II muscle fibers in the group treated with LMV. In conclusion, the present study supports the effectiveness of local vibration in muscle function and clinical improvement of patients with knee OA.
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.
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 Sb(q,t) and the susceptibility χb(t) to detect the spatial correlations of configuration changes. Here χb(t) attains a maximum at t=tbmax as a function of time t, where the fraction of the particles with broken bonds φb(t) is about 1/2. In the four-point scheme, treating the structure factor S4(q,t) and the susceptibility χ4(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 χ4(t) is attained at t=t4max, where these two contributions become of the same order. As a result, t4max is considerably shorter than tbmax.
Satellites of Xe transitions induced by infrared active vibrational modes of CF4 and C2F6 molecules.
Alekseev, Vadim A; Schwentner, Nikolaus
2011-07-28
Absorption and luminescence excitation spectra of Xe/CF(4) mixtures were studied in the vacuum UV region at high resolution using tunable synchrotron radiation. Pressure-broadened resonance bands and bands associated with dipole-forbidden states of the Xe atom due to collision-induced breakdown of the optical selection rules are reported. The spectra display in addition numerous satellite bands corresponding to transitions to vibrationally excited states of a Xe-CF(4) collisional complex. These satellites are located at energies of Xe atom transition increased by one quantum energy in the IR active v(3) vibrational mode of CF(4) (v(3) = 1281 cm(-1)). Satellites of both resonance and dipole-forbidden transitions were observed. Satellites of low lying resonance states are spectrally broad bands closely resembling in shape their parent pressure-broadened resonance bands. In contrast, satellites of dipole-forbidden states and of high lying resonance states are spectrally narrow bands (FWHM ∼10 cm(-1)). The satellites of dipole-forbidden states are orders of magnitude stronger than transitions to their parent states due to collision-induced breakdown of the optical selection rules. These satellites are attributed to a coupling of dipole-forbidden and resonance states induced by the electric field of the transient CF(4) (v(3) = 0 ↔ v(3) = 1) dipole. Similar satellites are present in spectra of Xe/C(2)F(6) mixtures where these bands are induced by the IR active v(10) mode of C(2)F(6). Transitions to vibrationally excited states of Xe-CF(4)(C(2)F(6)) collision pairs were also observed in two-photon LIF spectra.
High Confinement Mode in the KSTAR Device and Control of Accompanying Edge Localized Mode
Energy Technology Data Exchange (ETDEWEB)
Kim, Jay Hyun; Jeon, Young Mu; Xiao, Weiwen; Yoon, Si Woo; Bae, Young Soon; Ko, Won Ha; Lee, Sang Gon [National Fusion Research Institute, Daejeon (Korea, Republic of); Ahn, Joon Wook [Oak Ridge National Laboratory, Oak Ridge (United States); Yun, Gun Su [Pohang University of Science and Technology, Pohang (Korea, Republic of)
2011-10-15
ELMy high confinement mode (H-mode) discharges have been achieved in the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak with the combined auxiliary heating of neutral beam injection (NBI) and electron cyclotron resonance heating (ECRH) since the 3{sup rd} campaign in 2010. The minimum external heating power required was about 0.9 MW at a line-averaged density higher than 1.4x10{sup 19} m{sup -3} and a toroidal field of 2 T. A clear increase of electron and ion temperatures in the pedestal was observed in the H-mode phase while the core ion temperature did not change notably. The toroidal rotation also increased over all radii in the H-mode phase. The measured ELM frequency was around 30{approx}50 Hz and the drop of the total energy appeared to be less than 5 %. Between large ELM spikes, small/grassy ELMs were also identified when mixed heating of NBI and ECRH was applied. On the basis of the H-mode achievement in the 3{sup rd} campaign, the 4{sup th} campaign experiments were focused on the ELM control by various methods such as resonant magnetic perturbation (RMP), supersonic molecular beam injection (SMBI), vertical jogging of plasma column, and edge current drive. Abrupt burst of stored energy due to ELM is harmful to plasma facing component especially in reactor scale devices like international thermonuclear experimental reactor (ITER). The aforementioned ELM control experiments were supported by advanced diagnostics such as electron cyclotron emission imaging (ECEI) and X-ray imaging crystal spectroscopy (XICS). In the 3{sup rd} campaign, the ECEI observed the evolution of filamentary ELM structures in 2D and the XICS measured the plasma rotation profile enhanced by H-mode. Furthermore, the analyses based on advanced diagnostics are in progress for investigating the underlying physics of edge/pedestal characteristics when applying ELM control methods
Park, G Barratt; Baraban, Joshua H; Field, Robert W
2014-10-07
A full-dimensional Franck-Condon calculation has been applied to the Ã (1)Au-X̃ 1Σg+ 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 (ν4('')) in the linear X̃ 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 ν4('') 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 X̃ 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 Ã state into bending levels of the X̃ 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 (ν5('')), and we predict that the best Ã-state vibrational levels for populating X̃-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 ν6(') (cis-bend). Mode ν4(') (torsion) populates levels with large amplitude counter-rotational motion of the two hydrogen atoms.
Institute of Scientific and Technical Information of China (English)
LI De-Jun; MI Xian-Wu; DENG Ke; TANG Yi
2006-01-01
In the classical lattice theory, solitons and locaLized modes can exist in many one-dimensional nonlinear lattice chains, however, in the quantum lattice theory, whether quantum solitons and localized modes can exist or not in the one-dimensional lattice chains is an interesting problem. By using the number state method and the Hartree approximation combined with the method of multiple scales, we investigate quantum solitons and localized modes in a one-dimensional lattice chain with the nonlinear substrate potential. It is shown that quantum solitons do exist in this nonlinear lattice chain, and at the boundary of the phonon Brillouin zone, quantum solitons become quantum localized modes, phonons are pinned to the lattice of the vicinity at the central position j = j0.
Hui, Xiaonan; Zhang, Weite; Jin, Xiaofeng; Chi, Hao; Zhang, Xianmin
2015-01-01
The topological charge of an electromagnetic vortex beam depends on its wavefront helicity. For mixed vortex beams composed of several different coaxial vortices, the topological charge spectrum can be obtained by Fourier transform. However, the vortex beam is generally divergent and imperfect. It makes it significant to investigate the local topological charges, especially in radio frequency regime. Fourier transform based methods are restrained by the uncertainty principle and cannot achieve high angular resolution and mode resolution simultaneously. In this letter, an analysis method for local topological charges of vortex beams is presented based on the empirical mode decomposition (EMD). From EMD, the intrinsic mode functions (IMFs) can be obtained to construct the bases of the electromagnetic wave, and each local topological charge can be respectively defined. With this method the local value achieves both high resolution of azimuth angle and topological charge, meanwhile the amplitudes of each OAM mode...
MISR Level 1B1 Local Mode Radiance Data V002
National Aeronautics and Space Administration — This is the Local Mode Level 1B1 Product containing the DNs radiometrically scaled to radiances with no geometric resampling (Suggested Usage: The MISR Instrument...
Infrared Spectroscopic Study of Vibrational Modes in Methylammonium Lead Halide Perovskites.
Glaser, Tobias; Müller, Christian; Sendner, Michael; Krekeler, Christian; Semonin, Octavi E; Hull, Trevor D; Yaffe, Omer; Owen, Jonathan S; Kowalsky, Wolfgang; Pucci, Annemarie; Lovrinčić, Robert
2015-08-06
The organic cation and its interplay with the inorganic lattice underlie the exceptional optoelectronic properties of organo-metallic halide perovskites. Herein we report high-quality infrared spectroscopic measurements of methylammonium lead halide perovskite (CH3NH3Pb(I/Br/Cl)3) films and single crystals at room temperature, from which the dielectric function in the investigated spectral range is derived. Comparison with electronic structure calculations in vacuum of the free methylammonium cation allows for a detailed peak assignment. We analyze the shifts of the vibrational peak positions between the different halides and infer the extent of interaction between organic moiety and the surrounding inorganic cage. The positions of the NH3(+) stretching vibrations point to significant hydrogen bonding between the methylammonium and the halides for all three perovskites.
Non-local Lee-Wick modes in the fermionic Myers-Pospelov model
Lopez-Sarrion, Justo
2011-01-01
General solutions and dispersion relations are given explicitly in the Lorentz invariance violating fermionic sector of the Myers and Pospelov theory. We quantize the theory and identify Lee-Wick modes due to the higher time-derivative terms. We analyze the non local character of these modes and discuss the loss of microcausality.
Localized bulk electron heating with ICRF mode conversion in the JET tokamak
DEFF Research Database (Denmark)
Mantsinen, M.J.; Mayoral, M.-L.; Eester, D. Van
2004-01-01
Ion cyclotron resonance frequencies (ICRF) mode conversion has been developed for localized on-axis and off-axis bulk electron heating on the JET tokamak. The fast magnetosonic waves launched from the low-field side ICRF antennas are mode-converted to short-wavelength waves on the high-field side...
Dynamic localization and Bloch oscillations in the spectrum of a frequency mode-locked laser.
Longhi, Stefano
2005-04-01
It is shown that a frequency mode-locked laser with a sinusoidal sweep of modulation frequency around a mode-locking condition represents an ideal optical system for observing in the spectral domain the phenomena of dynamic localization and Bloch oscillations of electrons in an ideal solid placed in an external ac electric field.
DEFF Research Database (Denmark)
Migliucci, P.; Naulin, Volker
2010-01-01
Fast magnetic pickup coils are used in forward modeling to match parameters in a simple edge localized mode (ELM) filament model. This novel method allows us to determine key parameters for the evolution of the ELM filaments, as effective mode number, radial and toroidal velocities, and average...
Energy Technology Data Exchange (ETDEWEB)
Lee, J.; Yun, G. S., E-mail: gunsu@postech.ac.kr; Lee, J. E.; Kim, M.; Choi, M. J.; Lee, W. [Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Park, H. K. [Ulsan National Institute of Science and Technology, Ulsan 689-798 (Korea, Republic of); Domier, C. W.; Luhmann, N. C. [University of California at Davis, Davis, California 95616 (United States); Sabbagh, S. A.; Park, Y. S. [Columbia University, New York, New York 10027 (United States); Lee, S. G.; Bak, J. G. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of)
2014-06-15
A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle α{sub *} of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α{sub *} is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.
Energy Technology Data Exchange (ETDEWEB)
Xiao, Y.; Wang, H.; George, S.J.; Smith, M.C.; Adams, M.W.W.; Jenney, F.E., Jr.; Sturhahn, W.; Alp, E.E.; Zhao, J.; Yoda, Y.; Dey, A.; Solomon, E.I.; Cramer, S.P.; Experimental Facilities Division (APS); Univ. of California; LBNL; Stanford Univ.; Univ. of Georgia; SPring-8
2005-10-26
We have used {sup 57}Fe nuclear resonance vibrational spectroscopy (NRVS) to study the Fe(S{sub cys})4 site in reduced and oxidized rubredoxin (Rd) from Pyrococcus furiosus (Pf). The oxidized form has also been investigated by resonance Raman spectroscopy. In the oxidized Rd NRVS, strong asymmetric Fe-S stretching modes are observed between 355 and 375 cm{sup -1}; upon reduction these modes shift to 300-320 cm{sup -1}. This is the first observation of Fe-S stretching modes in a reduced Rd. The peak in S-Fe-S bend mode intensity is at {approx}150 cm{sup -1} for the oxidized protein and only slightly lower in the reduced case. A third band occurs near 70 cm{sup -1} for both samples; this is assigned primarily as a collective motion of entire cysteine residues with respect to the central Fe. The {sup 57}Fe partial vibrational density of states (PVDOS) were interpreted by normal mode analysis with optimization of Urey-Bradley force fields. The three main bands were qualitatively reproduced using a D{sub 2d} Fe(SC){sub 4} model. A C{sub 1} Fe(SCC){sub 4} model based on crystallographic coordinates was then used to simulate the splitting of the asymmetric stretching band into at least 3 components. Finally, a model employing complete cysteines and 2 additional neighboring atoms was used to reproduce the detailed structure of the PVDOS in the Fe-S stretch region. These results confirm the delocalization of the dynamic properties of the redox-active Fe site. Depending on the molecular model employed, the force constant KFe-S for Fe-S stretching modes ranged from 1.24 to 1.32 mdyn/Angstrom. KFe-S is clearly diminished in reduced Rd; values from {approx}0.89 to 1.00 mdyn/Angstrom were derived from different models. In contrast, in the final models the force constants for S-Fe-S bending motion, HS-Fe-S, were 0.18 mdyn/Angstrom for oxidized Rd and 0.15 mdyn/Angstrom for reduced Rd. The NRVS technique demonstrates great promise for the observation and quantitative
Damage localization by statistical evaluation of signal-processed mode shapes
DEFF Research Database (Denmark)
Ulriksen, Martin Dalgaard; Damkilde, Lars
2015-01-01
in the spatial mode shape signals, hereby potentially facilitating damage detection and/or localization. However, by being based on distinguishing damage-induced discontinuities from other signal irregularities, an intrinsic deficiency in these methods is the high sensitivity towards measurement noise....... The present article introduces a damage localization method which, compared to the conventional mode shape-based methods, has greatly enhanced robustness towards measurement noise. The method is based on signal processing of spatial mode shapes by means of continuous wavelet transformation (CWT...
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...
Levi, E. K.; Irish, E. K.; Lovett, B. W.
2016-04-01
The interplay between an open quantum system and its environment can lead to both coherent and incoherent behavior. We explore the extent to which strong coupling to a single bosonic mode can alter the coherence properties of a two-level system in a structured environment. This mode is treated exactly, with the rest of the environment comprising a Markovian bath of bosonic modes. The strength of the coupling between the two-level system and the single mode is varied for a variety of forms for the bath spectral density in order to assess whether the coherent dynamics of the two-level system are modified. We find a clear renormalization of the site population oscillation frequency that causes an altered interaction with the bath. This leads to enhanced or reduced coherent behavior of the two-level system, depending on the form of the spectral density function. We present an intuitive interpretation, based on an analytical model, to explain the behavior.
Experiment study of edge localized mode with plasma vertical jogging in HL-2A tokamak
Wu, N.; Chen, S. Y.; Song, X. M.; Mou, M. L.; Huang, J.; Wang, Z. T.; Tang, C. J.; Song, X.; Xia, F.; Jiang, M.; HL-2A Team
2017-09-01
The effect of plasma vertical jogging on edge localized modes (ELMs) is investigated in HL-2A tokamak. During the experiment, plasma jogging with a period of about 75 ms is performed, and the results show that both the ELM amplitude and period decrease when the plasma moves upward, which are qualitatively explained by the simulation based on the theory of peeling-ballooning mode including the resistivity effect. The upward movement of plasma causes a change in pedestal parameters, and then the dominant toroidal mode shifts to a relatively high-n mode with the effects of resistivity and diamagnetic, which lead to smaller ELM amplitudes.
Mode Localization in the Cooperative Dynamics of Protein Recognition
Copperman, J
2015-01-01
The biological function of proteins is encoded in their structure and expressed through the mediation of their dynamics. Local fluctuations are known to initiate biologically relevant pathways as they cooperatively enhance the dynamics in specific regions in the protein. Those biologically active regions provide energetically-comparable conformational states that can be trapped by a reacting partner. We analyze this mechanism as we calculate the dynamics of monomeric and dimerized HIV protease, and free Insulin Growth Factor II Receptor (IGF2R) domain 11 and its IGF2R:IGF2 complex. We adopt a newly developed coarse-grained model, the Langevin Equation for Protein Dynamics (LE4PD), which predicts dynamical relevant mechanisms with high accuracy. Both simulation-derived and experimental NMR conformers are the input structural ensembles for the LE4PD. The use of the experimental NMR conformers requires minimal computational resources.
Excitations and management of the nonlinear localized gap modes
Indian Academy of Sciences (India)
Bishwajyoti Dey
2015-11-01
We discuss about the theory of nonlinear localized excitations, such as soliton and compactons in the gap of the linear spectrum of the nonlinear systems. We show how the gap originates in the linear spectrum using examples of a few systems, such as nonlinear lattices, Bose–Einstein condensates in optical lattice and systems represented by coupled nonlinear evolution equations. We then analytically show the excitation of solitons and compacton-like solutions in the gap of the linear spectrum of a system of coupled Korteweg–de Vries (KdV) equations with linear and nonlinear dispersions. Finally, we discuss about the theory of Feshbach resonance management and dispersion management of the soliton solutions.
Excitation Thresholds for Nonlinear Localized Modes on Lattices
Weinstein, M I
1999-01-01
Breathers are spatially localized and time periodic solutions of extended Hamiltonian dynamical systems. In this paper we study excitation thresholds for (nonlinearly dynamically stable) ground state breather or standing wave solutions for networks of coupled nonlinear oscillators and wave equations of nonlinear Schrödinger (NLS) type. Excitation thresholds are rigorously characterized by variational methods. The excitation threshold is related to the optimal (best) constant in a class of discr ete interpolation inequalities related to the Hamiltonian energy. We establish a precise connection among $d$, the dimensionality of the lattice, $2\\sigma+1$, the degree of the nonlinearity and the existence of an excitation threshold for discrete nonlinear Schrödinger systems (DNLS). We prove that if $\\sigma\\ge 2/d$, then ground state standing waves exist if and only if the total power is larger than some strictly positive threshold, the context of DNLS. We also discuss upper and lower bounds for excitation threshol...
Nonlinear localized flatband modes with spin-orbit coupling
Gligorić, G; Hadžievski, Lj; Flach, S; Malomed, B
2016-01-01
We report the coexistence and properties of stable compact localized states (CLSs) and discrete solitons (DSs) for nonlinear spinor waves on a flatband network with spin-orbit coupling (SOC). The system can be implemented by means of a binary Bose-Einstein condensate loaded in the corresponding optical lattice. In the linear limit, the SOC opens a minigap between flat and dispersive bands in the system's bandgap structure, and preserves the existence of CLSs at the flatband frequency, simultaneously lowering their symmetry. Adding onsite cubic nonlinearity, the CLSs persist and remain available in an exact analytical form, with frequencies which are smoothly tuned into the minigap. Inside of the minigap, the CLS and DS families are stable in narrow areas adjacent to the FB. Deep inside the semi-infinite gap, both the CLSs and DSs are stable too.
Modulating toroidal flow stabilization of edge localized modes with plasma density
Cheng, Shikui; Banerjee, Debabrata
2016-01-01
Recent EAST experiments have demonstrated mitigation and suppression of edge localized modes (ELMs) with toroidal rotation flow in higher collisionality regime, suggesting potential roles of plasma density. In this work, the effects of plasma density on the toroidal flow stabilization of the high-$n$ edge localized modes have been extensively studied in linear calculations for a circular-shaped limiter H-mode tokamak, using the extended MHD code NIMROD. In the single MHD model, toroidal flow has a weak stabilizing effects on the high-$n$ modes. Such a stabilization, however, can be significantly enhanced with the increase in plasma density. Furthermore, our calculations show that the enhanced stabilization of high-$n$ modes from toroidal flow with higher edge plasma density persists in the 2-fluid MHD model. These findings may explain the ELM mitigation and suppression by toroidal rotation in higher collisionality regime due to the enhancement of plasma density obtained in recent EAST experiments.
新型压电行走机构的振动模态分析%Analysis on theVibration Mode of Novel Piezoelectric
Institute of Scientific and Technical Information of China (English)
张亚秋; 吴文福; 韩峰
2009-01-01
ANSYS was used to analysis the vibration mode of the mechanism by the floating piezoelectric vibration device which was developed by us.Analysis showed different working frequency with different vibration mode.when the working frequency was 934 Hz,the mechanism was sliding forward or backward; when the working frequency was 670 Hz,the mechanism was moving forward because of the "local elliptical motion" of both the bottom of the drive-feet,when the working frequency was 1 176 Hz,the mechanism was sliding forward or jumping; when the working frequency was 327 Hz,the mechanism was moving to the side or twisting in situ; when the working frequency was 498 Hz,the mechanism was rotating in situ.These theoretic analyses would more or less guide the following practical application.%利用自行研制的浮动式压电振动机构,运用有限元分析软件ANSYS对机构振动模态进行了有限元分析发现,不同的工作频率其振动模态不同.当工作频率为934 Hz时,机构出现向前的滑移动或倒移动;工作频率为670 Hz时,在2个驱动足的底部形成"局部椭圆运动",机构向前移动;工作频率为1 176 Hz时,机构为向前滑移动或跳移动;工作频率为327 Hz时,机构出现侧移动或原地扭动;工作频率为498 Hz时,机构原地转动.这些理论上的分析对实际过程中的应用起到了一定的指导作用.
Finite-width effects for the localized edge modes in zigzag graphene nanoribbons
Akbari-Sharbaf, Arash; Cottam, Michael G.
2016-06-01
A matrix formalism is used to derive the analytical Green's functions describing correlations between any two atomic sites on a zigzag (ZZ) graphene nanoribbon, incorporating modified electronic hopping values between edge sites that may be distinct from the hopping between interior sites. An analysis of the poles of our Green's functions shows two distinct types of localized edge modes in the electronic spectrum. The first of these, the "zero" mode, is a topologically induced mode arising from the bipartite honeycomb lattice structure of graphene and is always present along ZZ edges. The second type of localized edge mode is present at edges when the edge-to-bulk hopping ratio deviates significantly from unity. The correlations between edge sites are found to exhibit strikingly different features when mediated by the zero edge mode compared with mediation by the "modified" edge mode. In particular, the zero-mode spectral intensity for correlations between two atomic sites along opposite edges can be comparable in strength with that between two sites on the same edge of a finite-width ribbon, before it eventually tends to zero as the ribbon width tends to infinity. This remarkable behavior shows a strong dependence on the sublattice labels of the sites and is in contrast with properties of the modified hopping edge modes. The explicit form of our analytical expressions for the electronic spectrum enables us to predict the zero-mode properties (including frequency, spatial attenuation, and intensity) when the hopping values along ZZ edges are modified.
Xu, X. Q.; Xia, T. Y.; Yan, N.; Liu, Z. X.; Kong, D. F.; Diallo, A.; Groebner, R. J.; Hubbard, A. E.; Hughes, J. W.
2016-05-01
The high-fidelity BOUT++ two-fluid code suite has demonstrated significant recent progress toward integrated multi-scale simulations of tokamak pedestal, including Edge-Localized-Mode (ELM) dynamics, evolution of ELM cycles, and continuous fluctuations, as observed in experiments. Nonlinear ELM simulations show three stages of an ELM event: (1) a linear growing phase; (2) a fast crash phase; and (3) a slow inward turbulence spreading phase lasting until the core heating flux balances the ELM energy loss and the ELM is terminated. A new coupling/splitting model has been developed to perform simulations of multi-scale ELM dynamics. Simulation tracks five ELM cycles for 10 000 Alfvén times for small ELMs. The temporal evolution of the pedestal pressure is similar to that of experimental measurements for the pedestal pressure profile collapses and recovers to a steep gradient during ELM cycles. To validate BOUT++ simulations against experimental data and develop physics understanding of the fluctuation characteristics for different tokamak operation regimes, both quasi-coherent fluctuations (QCFs) in ELMy H-modes and Weakly Coherent Modes in I-modes have been simulated using three dimensional 6-field 2-fluid electromagnetic model. The H-mode simulation results show that (1) QCFs are localized in the pedestal region having a predominant frequency at f ≃300 -400 kHz and poloidal wavenumber at kθ≃0.7 cm-1 , and propagate in the electron diamagnetic direction in the laboratory frame. The overall signatures of simulation results for QCFs show good agreement with C-Mod and DIII-D measurements. (2) The pedestal profiles giving rise to QCFs are near the marginal instability threshold for ideal peeling-ballooning modes for both C-Mod and DIII-D, while the collisional electromagnetic drift-Alfvén wave appears to be dominant for DIII-D. (3) Particle diffusivity is either smaller than the heat diffusivity for DIII-D or similar to the heat diffusivity for C-Mod. Key I-mode
PREFACE: Vibrations at surfaces Vibrations at surfaces
Rahman, Talat S.
2011-12-01
Central Florida, Orlando, in March 2010. Several speakers at this meeting were invited to contribute to the special section in this issue. As is clear from the articles in this special section, the phenomenon of vibrations at surfaces continues to be a dynamic field of investigation. In fact, there is a resurgence of effort because the insights provided by surface dynamics are still fundamental to the development of an understanding of the microscopic factors that control surface structure formation, diffusion, reaction and structural stability. Examination of dynamics at surfaces thus complements and supplements the wealth of information that is obtained from real-space techniques such as scanning tunneling microscopy. Vibrational dynamics is, of course, not limited to surfaces. Surfaces are important since they provide immediate deviation from the bulk. They display how lack of symmetry can lead to new structures, new local atomic environments and new types of dynamical modes. Nanoparticles, large molecules and nanostructures of all types, in all kinds of local environments, provide further examples of regions of reduced symmetry and coordination, and hence display characteristic vibrational modes. Given the tremendous advance in the synthesis of a variety of nanostructures whose functionalization would pave the way for nanotechnology, there is even greater need to engage in experimental and theoretical techniques that help extract their vibrational dynamics. Such knowledge would enable a more complete understanding and characterization of these nanoscale systems than would otherwise be the case. The papers presented here provide excellent examples of the kind of information that is revealed by vibrations at surfaces. Vibrations at surface contents Poisoning and non-poisoning oxygen on Cu(410)L Vattuone, V Venugopal, T Kravchuk, M Smerieri, L Savio and M Rocca Modifying protein adsorption by layers of glutathione pre-adsorbed on Au(111)Anne Vallée, Vincent Humblot
Localized modes in dissipative lattice media: An overview
He, Yingji; Mihalache, Dumitru
2014-01-01
We overview recent theoretical studies of the dynamics of one- and two-dimensional spatial dissipative solitons in models based on the complex Ginzburg-Landau equations with the cubic-quintic combination of loss and gain terms, which include imaginary, real, or complex spatially periodic potentials. The imaginary potential represents periodic modulation of the local loss and gain. It is shown that the effective gradient force, induced by the inhomogeneous loss distribution, gives rise to three generic propagation scenarios for one-dimensional (1D) dissipative solitons: transverse drift, persistent swing motion, and damped oscillations. When the lattice-average loss/gain value is zero, and the real potential has spatial parity opposite to that of the imaginary component, the respective complex potential is a realization of the parity-time symmetry. Under the action of lattice potentials of the latter type, 1D solitons feature unique motion regimes in the form of transverse drift and persistent swing. In the 2D...
Localized modes in dissipative lattice media: an overview.
He, Yingji; Malomed, Boris A; Mihalache, Dumitru
2014-10-28
We give an overview of recent theoretical studies of the dynamics of one- and two-dimensional spatial dissipative solitons in models based on the complex Ginzburg-Landau equations with the cubic-quintic combination of loss and gain terms, which include imaginary, real or complex spatially periodic potentials. The imaginary potential represents periodic modulation of the local loss and gain. It is shown that the effective gradient force, induced by the inhomogeneous loss distribution, gives rise to three generic propagation scenarios for one-dimensional dissipative solitons: transverse drift, persistent swing motion, and damped oscillations. When the lattice-average loss/gain value is zero, and the real potential has spatial parity opposite to that of the imaginary component, the respective complex potential is a realization of the parity-time symmetry. Under the action of lattice potentials of the latter type, one-dimensional solitons feature motion regimes in the form of the transverse drift and persistent swing. In the two-dimensional geometry, three types of axisymmetric radial lattices are considered, namely those based solely on the refractive-index modulation, or solely on the linear-loss modulation, or on a combination of both. The rotary motion of solitons in such axisymmetric potentials can be effectively controlled by varying the strength of the initial tangential kick. © 2014 The Author(s) Published by the Royal Society. All rights reserved.
Goos-Hänchen shift and localization of optical modes in deformed microcavities.
Unterhinninghofen, Julia; Wiersig, Jan; Hentschel, Martina
2008-07-01
Recently, an interesting phenomenon of spatial localization of optical modes along periodic ray trajectories near avoided resonance crossings has been observed [Wiersig, Phys. Rev. Lett. 97, 253901 (2006)]. For the case of a microdisk cavity with elliptical cross section, we use the Husimi function to analyze this localization in phase space. Moreover, we present a semiclassical explanation of this phenomenon in terms of the Goos-Hänchen shift, which works very well even deep in the wave regime. This semiclassical correction to the ray dynamics modifies the phase-space structure such that modes can localize either on stable islands or along unstable periodic ray trajectories.
Felici, A.; Trombetta, C.; Abundo, P.; Foti, C.; Rosato, N.
2012-10-01
Mechanical vibrations application is increasingly common in clinical practice due to the effectiveness induced by these stimuli on the human body. Local vibration (LV) application allows to apply and act only where needed, focusing the treatment on the selected body segment. An experimental device for LV application was used to generate the vibrations. The aim of this study was to detect and analyze the metabolic effects induced by LV on the brachial bicep muscle by means of an oximeter. This device monitors tissue and muscle oxygenation using NIRS (Near Infrared Spectroscopy) and is able to determine the concentration of haemoglobin and oxygen saturation in the tissue. In a preliminary stage we also investigated the effects induced by LV application, by measuring blood pressure, heart rate, oxygen saturation and temperature. These data confirmed that the effects induced by LV application are actually localized. The results of the measurements obtained using the oximeter during the vibration application, have shown a variation of the concentrations. In particular an increase of oxygenate haemoglobin was shown, probably caused by an increased muscle activity and/or a rise in local temperature detected during the application.
Zeng, Jianhua; Chen, Lei; Dai, Qiaofeng; Lan, Sheng; Tie, Shaolong
2016-01-01
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.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
Computer simulation structure and vibrations of small metal cluster on the Cu (111) surface
Borisova, Svetlana D.; Rusina, Galina G.
2015-10-01
Vibrational properties of the small tetrahedral cluster of Co on the Cu (111) surface are studied by using tight-binding second moment approximation interatomic interaction potentials. It was shown that interaction of the clusters with substrate leads to arising of frustrated translation and frustrated rotation in-plane polarized vibrational modes localized on the cluster atoms. The Co4 cluster on the surface the high frequency modes remain strongly localized and mixed with the nearest neighbor atoms vibrations.
Computer simulation structure and vibrations of small metal cluster on the Cu (111) surface
Energy Technology Data Exchange (ETDEWEB)
Borisova, Svetlana D., E-mail: svbor@ispms.tsc.ru; Rusina, Galina G., E-mail: rusina@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk 634050 (Russian Federation)
2015-10-27
Vibrational properties of the small tetrahedral cluster of Co on the Cu (111) surface are studied by using tight-binding second moment approximation interatomic interaction potentials. It was shown that interaction of the clusters with substrate leads to arising of frustrated translation and frustrated rotation in-plane polarized vibrational modes localized on the cluster atoms. The Co{sub 4} cluster on the surface the high frequency modes remain strongly localized and mixed with the nearest neighbor atoms vibrations.
Substituent Effects on the Low-Frequency Vibrational Modes of Benzoic Acid and Related Compounds
Institute of Scientific and Technical Information of China (English)
GE Min; ZHAO Hong-Wei; WANG Wen-Feng; YU Xiao-Han; LI Wen-Xin
2007-01-01
Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm-1 at room temperature with terahertz time-domain spectroscopy (THz-TDS). These substances can be distinguished easily based on the terahertz absorption spectra. The measurements suggested that even minor changes in the molecular configuration and chemical composition lead to distinct differences in THz spectrum. Density functional theory (DFT)method was used to assist the analysis and assignment of the individual THz absorption spectra of benzoic acid and its methyl derivatives. Observed THz responses of samples can be assigned to the collective vibrations associated with intermolecular hydrogen bonds.
Pshenichnikov, Maxim S.; Boeij, Wim P. de; Wiersma, Douwe A.
1996-01-01
In this contribution we show that enhanced mode suppression can be obtained by time-gating the stimulated photon echo (SPE) at the conventional echo time and in phase with the wave packet dynamics. This novel technique is demonstrated on a dye solution of DTTCI in ethylene glycol. As it was directly
Catalytic mechanism of LENR in quasicrystals based on localized anharmonic vibrations and phasons
Dubinko, Volodymyr; Irwin, Klee
2016-01-01
Quasicrystals (QCs) are a novel form of matter, which are neither crystalline nor amorphous. Among many surprising properties of QCs is their high catalytic activity. We propose a mechanism explaining this peculiarity based on unusual dynamics of atoms at special sites in QCs, namely, localized anharmonic vibrations (LAVs) and phasons. In the former case, one deals with a large amplitude (~ fractions of an angstrom) time-periodic oscillations of a small group of atoms around their stable positions in the lattice, known also as discrete breathers, which can be excited in regular crystals as well as in QCs. On the other hand, phasons are a specific property of QCs, which are represented by very large amplitude (~angstrom) oscillations of atoms be-tween two quasi-stable positions determined by the geometry of a QC. Large amplitude atomic motion in LAVs and phasons results in time-periodic driving of adjacent potential wells occupied by hydrogen ions (protons or deuterons) in case of hydrogenated QCs. This drivin...
Geometrical structure, multifractal spectra and localized optical modes of aperiodic Vogel spirals.
Trevino, Jacob; Liew, Seng Fatt; Noh, Heeso; Cao, Hui; Dal Negro, Luca
2012-01-30
We present a numerical study of the structural properties, photonic density of states and bandedge modes of Vogel spiral arrays of dielectric cylinders in air. Specifically, we systematically investigate different types of Vogel spirals obtained by the modulation of the divergence angle parameter above and below the golden angle value (≈137.507°). We found that these arrays exhibit large fluctuations in the distribution of neighboring particles characterized by multifractal singularity spectra and pair correlation functions that can be tuned between amorphous and random structures. We also show that the rich structural complexity of Vogel spirals results in a multifractal photonic mode density and isotropic bandedge modes with distinctive spatial localization character. Vogel spiral structures offer the opportunity to create novel photonic devices that leverage radially localized and isotropic bandedge modes to enhance light-matter coupling, such as optical sensors, light sources, concentrators, and broadband optical couplers.
Fine structure of type-I edge-localized modes in the steep gradient region.
Kurzan, B; Murmann, H D; Neuhauser, J
2005-09-30
Fast, high resolution multichannel Thomson scattering is used to quantitatively determine plasma perturbations induced by type-I edge-localized modes (ELMs) in the low-field side edge of ASDEX Upgrade H-mode plasmas. 2D snapshots of temperature and density, deduced from the laser light scattered in a vertically elongated, poloidal array of 5 x 10 scattering volumes, are obtained in the hot, steep edge gradient zone, which is difficult to access by other diagnostics. Local maxima and minima with large amplitude are identified during ELMs and even in the precursor phase, both in density and temperature. Interpreting these structures as footprints of approximately field aligned helical modes in accordance with previous experimental and theoretical work, toroidal mode numbers between 8 and 20 are obtained, roughly consistent with corresponding scrape-off layer and divertor measurements.
Isotope effect in normal-to-local transition of acetylene bending modes.
Ma, Jianyi; Xu, Dingguo; Guo, Hua; Tyng, Vivian; Kellman, Michael E
2012-01-07
The normal-to-local transition for the bending modes of acetylene is considered a prelude to its isomerization to vinylidene. Here, such a transition in fully deuterated acetylene is investigated using a full-dimensional quantum model. It is found that the local benders emerge at much lower energies and bending quantum numbers than in the hydrogen isotopomer HCCH. This is accompanied by a transition to a second kind of bending mode called counter-rotator, again at lower energies and quantum numbers than in HCCH. These transitions are also investigated using bifurcation analysis of two empirical spectroscopic fitting Hamiltonians for pure bending modes, which helps to understand the origin of the transitions semiclassically as branchings or bifurcations out of the trans- and cis-normal bend modes when the latter become dynamically unstable. The results of the quantum model and the empirical bifurcation analysis are in very good agreement.
Optimizing Vibrational Coordinates To Modulate Intermode Coupling.
Zimmerman, Paul M; Smereka, Peter
2016-04-12
The choice of coordinate system strongly affects the convergence properties of vibrational structure computations. Two methods for efficient generation of improved vibrational coordinates are presented and justified by analysis of a model anharmonic two-mode Hessian and numerical computations on polyatomic molecules. To produce optimal coordinates, metrics which quantify off-diagonal couplings over a grid of Hessian matrices are minimized through unitary rotations of the vibrational basis. The first proposed metric minimizes the total squared off-diagonal coupling, and the second minimizes the total squared change in off-diagonal coupling. In this procedure certain anharmonic modes tend to localize, for example X-H stretches. The proposed methods do not rely on prior fitting of the potential energy, vibrational structure computations, or localization metrics, so they are unique from previous vibrational coordinate generation algorithms and are generally applicable to polyatomic molecules. Fitting the potential to the approximate n-mode representation in the optimized bases for all-trans polyenes shows that off-diagonal anharmonic couplings are substantially reduced by the new choices of coordinate system. Convergence of vibrational energies is examined in detail for ethylene, and it is shown that coupling-optimized modes converge in vibrational configuration interaction computations to within 1 cm(-1) using only 3-mode couplings, where normal modes require 4-mode couplings for convergence. Comparison of the vibrational configuration interaction convergence with respect to excitation level for the two proposed metrics shows that minimization of the total off-diagonal coupling is most effective for low-cost vibrational structure computations.
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.
Ota, Norio
2015-01-01
Void induced di-cation coronene C23H12++ is a possible carrier of the astronomically observed polycyclic aromatic hydrocarbon (PAH). Based on density functional theory, multiple spin state analysis was done for neutral void coronene C23H12. Singlet spin state was most stable (lowest total energy). By the Jahn-Teller effect, there occurs serious molecular deformation. Point group D6h of pure coronene transformed to C2 symmetry having carbon two pentagons. Advanced singlet stable molecules were di-cation C23H12++ and di-anion C23H12- -. Molecular configuration was almost similar with neutral C23H12. However, electric dipole moment of these two charged molecules show reversed direction with 1.19 and 2.63 Debey. Calculated infrared spectrum of C23H12++ show a very likeness to observed one of two astronomical sources of HD44179 and NGC7027. Harmonic vibrational mode analysis was done for C23H12++. At 3.2 micrometer, C-H stretching at pentagons was featured. From 6.4 to 8.7 micrometer, C-C stretching mode was obser...
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.
Data-based matched-mode source localization for a moving source.
Yang, T C
2014-03-01
A data-based matched-mode source localization method is proposed in this paper for a moving source, using mode wavenumbers and depth functions estimated directly from the data, without requiring any environmental acoustic information and assuming any propagation model. The method is in theory free of the environmental mismatch problem because the mode replicas are estimated from the same data used to localize the source. Besides the estimation error due to the approximations made in deriving the data-based algorithms, the method has some inherent drawbacks: (1) It uses a smaller number of modes than theoretically possible because some modes are not resolved in the measurements, and (2) the depth search is limited to the depth covered by the receivers. Using simulated data, it is found that the performance degradation due to the afore-mentioned approximation/limitation is marginal compared with the original matched-mode source localization method. The proposed method has a potential to estimate the source range and depth for real data and be free of the environmental mismatch problem, noting that certain aspects of the (estimation) algorithms have previously been tested against data. The key issues are discussed in this paper.
On a common critical state in localized and diffuse failure modes
Zhu, Huaxiang; Nguyen, Hien N. G.; Nicot, François; Darve, Félix
2016-10-01
Accurately modeling the critical state mechanical behavior of granular material largely relies on a better understanding and characterizing the critical state fabric in different failure modes, i.e. localized and diffuse failure modes. In this paper, a mesoscopic scale is introduced, in which the organization of force-transmission paths (force-chains) and cells encompassed by contacts (meso-loops) can be taken into account. Numerical drained biaxial tests using a discrete element method are performed with different initial void ratios, in order to investigate the critical state fabric on the meso-scale in both localized and diffuse failure modes. According to the displacement and strain fields extracted from tests, the failure mode and failure area of each specimen are determined. Then convergent critical state void ratios are observed in failure area of specimens. Different mechanical features of two kinds of meso-structures (force-chains and meso-loops) are investigated, to clarify whether there exists a convergent meso-structure inside the failure area of granular material, as the signature of critical state. Numerical results support a positive answer. Failure area of both localized and diffuse failure modes therefore exhibits the same fabric in critical state. Hence, these two failure modes prove to be homological with respect to the concept of the critical state.
Using a local gyrokinetic code to study global ITG modes in tokamaks
Abdoul, P A; Roach, C M; Wilson, H R
2015-01-01
In this paper the global mode structures of linear ion-temperature-gradient (ITG) modes in tokamak plasmas are obtained by combining results from the local gyrokinetic code GS2 with analytical theory. Local gyrokinetic calculations, using GS2, are performed for a range of radial flux surfaces, ${x}$, and ballooning phase angles, ${p}$, to map out the local complex mode frequency, ${\\Omega_{0}(x,p)=\\omega_{0}(x,p)+i\\gamma_{0}(x,p)}$ for a single toroidal mode number, ${n}$. Taylor expanding ${\\Omega_{0}}$ about ${x=0}$, and employing the Fourier-ballooning representation leads to a second order ODE for the amplitude envelope, ${A\\left(p\\right)}$ , which describes how the local results are combined to form the global mode. We employ the so-called CYCLONE base case for circular Miller equilibrium model. Assuming radially varying profiles of ${a/L_{T}}$ and ${a/L_{n}}$, peaked at ${x=0}$, and with all other equilibrium profiles held constant, ${\\Omega_{0}(x,p)}$ is found to have a stationary point. The reconstruc...
Kartaschew, Konstantin; Baldus, Sabrina; Mischo, Meike; Bründermann, Erik; Awakowicz, Peter; Havenith, Martina
2016-09-01
Cold atmospheric-pressure plasma show promising antimicrobial effects, however the detailed biochemical mechanism of the bacterial inactivation is still unknown. We investigated, for the first time, plasma-treated Gram-positive Bacillus subtilis and Gram-negative Escherichia coli bacteria with Raman and infrared microspectroscopy. A dielectric barrier discharge was used as a plasma source. We were able to detect several plasma-induced chemical modifications, which suggest a pronounced oxidative effect on the cell envelope, cellular proteins and nucleotides as well as a generation of organic nitrates in the treated bacteria. Vibrational microspectroscopy is used as a comprehensive and a powerful tool for the analysis of plasma interactions with whole organisms such as bacteria. Analysis of reaction kinetics of chemical modifications allow a time-dependent insight into the plasma-mediated impact. Investigating possible synergistic effects between the plasma-produced components, our observations strongly indicate that the detected plasma-mediated chemical alterations can be mainly explained by the particle effect of the generated reactive species. By changing the polarity of the applied voltage pulse, and hence the propagation mechanisms of streamers, no significant effect on the spectral results could be detected. This method allows the analysis of the individual impact of each plasma constituent for particular chemical modifications. Our approach shows great potential to contribute to a better understanding of plasma-cell interactions.
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)
Duffy, Daniel J.; Quenneville, Jason; Baumbaugh, T. M.; Kitchener, S. A.; McCormick, R. K.; Dormady, C. N.; Croce, T. A.; Navabi, A.; Stidham, Howard D.; Hsu, Shaw L.; Guirgis, Gamil A.; Deng, Shiping; Durig, James R.
2004-02-01
Ab initio calculations are reported for three of four possible conformers of 1,3-dichloropropane. The fourth conformer, with C s symmetry, has a predicted enthalpy difference of more than 1500 cm -1 from the most stable conformer from each calculation regardless of the basis set used, so there is little chance of observing it. Thus, there is no evidence in the infrared or Raman spectrum of the presence of a fourth conformer. The order of stability given by the ab initio calculations is C 2(GG)>C 1(AG)>C 2v(AA)>C s(GG'), where A indicates the anti form for one of the CH 2Cl groups and G indicates the gauche conformation for the other CH 2Cl group relative to the plane of the carbon atoms. Almost every band observed can be confidently assigned to one or another of the conformers. Many observed bands proved to be of a composite nature, with several nearly coincident vibrations of different conformers contributing to the band contour. Nonetheless, a complete assignment of fundamentals is possible for the most stable C 2 conformer, and 5 of the fundamentals of the C 2v conformer and 13 those of the C 1 conformer can be confidently assigned.
Local modes analysis of a rotating marine ship propeller with higher order harmonic elements
Feng, Chen; Yong, Chen; Hongxing, Hua
2016-09-01
An annular harmonic finite element for the computation of the local modes of a pretwisted ship propeller is developed. The elements take into account both the gyroscopic effect and centrifugal stiffening of the propeller blades. The displacement field is expressed by a truncated Fourier series along the angle and by polynomial shape functions in the radial direction. As an example, the dynamic behaviour, i.e. the nature frequency and local modes, of a ship propeller is studied, and compared with ANSYS, both of which have good consistency.
Localized modes in orientation-disordered one-dimensional media with uniaxial scatterers
Institute of Scientific and Technical Information of China (English)
Yingmao Xie; Zhengdong Liu
2008-01-01
Localized modes in one-dimensional (1D) media with uniaxial scatterers that are assumed to be order in spatial location but disorder in spatial orientation of their optical axis are investigated. Based on the holistic effect model in random laser, I.e., the random laser is due to the interaction of the complex localized modes in active random media with local aperiodic quasi-structure with appropriate pump light, a physical model on this type of random media is found. Its disorder degree is defined by D = no/ne. Then, the typical transmission spectrum through the random media and the light field intensity distribution corresponding to the defect modes in photonic band-gap are calculated numerically by means of the transfer matrix method, and the condition that the localized mode appears is discussed. Results show that the medium disorder plays an important role in determining the lightwave state. The localized state appears when the medium disorder is strong enough, and a new mechanism creating random laser phenomenon is brought forward.
An efficient approach to optimize the vibration mode of bar-type ultrasonic motors.
Zhu, Hua; Li, Zhirong; Zhao, Chunsheng
2010-04-01
The electromechanical coupled dynamic model of the stator of the bar-type ultrasonic motor is derived based on the finite element method. The dynamical behavior of the stator is analyzed via this model and the theoretical result agrees with the experimental result of the stator of the prototype motor very well. Both the structural design principles and the approaches to meet the requirements for the mode of the stator are discussed. Based on the pattern search algorithm, an optimal model to meet the design requirements is established. The numerical simulation results show that this optimal model is effective for the structural design of the stator.
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.
Zhao, Jinfeng; Bonello, Bernard; Boyko, Olga
2016-05-01
We have investigated the focusing of the lowest-order antisymmetric Lamb mode (A0) behind a positive gradient-index (GRIN) acoustic metalens consisting of air holes drilled in a silicon plate with silicon pillars erected on one face of the lens. We have analyzed the focusing in the near field as the result of the coupling between the flexural resonant mode of the pillars and the vibration mode of the air/silicon phononic crystal. We highlight the role played by the polarization coherence between the resonant mode and the vibration of the plate. We demonstrate both numerically and experimentally the focusing behind the lens over a spot less than half a wavelength, paving a way for performance of acoustic lenses beyond the diffraction limit. Our findings can be easily extended to other types of elastic wave.
National Aeronautics and Space Administration — ATA Engineering, Inc. proposes an STTR program to develop innovative tools and methods that will significantly improve the accuracy of random vibration response...
Quantum information processing in localized modes of light within a photonic band-gap material
Vats, N; John, S; Vats, Nipun; Rudolph, Terry; John, Sajeev
1999-01-01
The single photon occupation of a localized field mode within an engineered network of defects in a photonic band-gap (PBG) material is proposed as a unit of quantum information (qubit). Qubit operations are mediated by optically-excited atoms interacting with these localized states of light as the atoms traverse the connected void network of the PBG structure. We describe conditions under which this system can have independent qubits with controllable interactions and very low decoherence, as required for quantum computation.
Local group modes and the dynamics of intramolecular energy transfer across a heavy atom
Lopez, Vicente; Fairen, Victor; Lederman, Steven M.; Marcus, R.A
1986-01-01
The dynamics of energy transfer is discussed for a model system in which two ligands are separated by a heavy atom. Numerical and analytical results are given for the case that each ligand is a CC. In the quasiperiodic regime, the dynamics are interpreted using perturbation theory. Local group modes involved in an intramolecular energy localization which can occur in this regime are identified. An approximate separation of the primarily ligand–ligand motions from the primarily ligand–metal–li...
40万吨矿砂船全船和局部振动研究%Global and Local Vibration Research on 400,000DWT Ore Carrier
Institute of Scientific and Technical Information of China (English)
张新伟; 吴小康; 陆利平
2011-01-01
Based on Finite-element method, a study of global and local vibration of 400,000dwt ore carrier is performed in this paper. The research performs the added mass by using fluid-solid coupled method; adopts static condensed method to process component mode analysis; and caries on Holden method to load propeller induced pressure. The calculation results conclude that multiple spots of hull appear heavy vibration character due to the condition without main engine top bracing installation. Based on this conclusion, a scheme of adding top bracing is proposed. The whole ship performance satisfies and meets the requirement of ISO 6954 well after the proposal has been performed.%通过有限元法对一艘40万吨矿砂船进行了全船和局部的振动性能预报.在预报过程中通过流固耦合方法添加附连水,用界面位移综合法进行局部模态分析,并用Holden法加载螺旋桨激励.计算中发现:因为主机未加横撑而引起的船体多处剧烈振动.最终提出了添加横撑的方案.该方案能使40万吨矿砂船振动性能改良,满足ISO6954标准.
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.
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
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.
An ab initio potential function for the ν13 vibrational mode of 1,3-butadiene
Senent, M. L.
1995-06-01
The restricted potential of the ν13 torsional mode of 1,3-butadiene has been determined from ab initio calculations. The relative energy and geometry of the second rotamer were calculated with the optimized couple cluster method with double substitutions. This ab initio level provides that the second stable structure attaches to a gauche form situated at 140.8°. The potential energy function was obtained by fitting to a symmetry-adapted Fourier series the total electronic energies of several selected conformations. These energies were calculated by the Möller-Plesset perturbation theory up to the second order (MP2) with full and partial optimization of the geometry. Torsional Raman band positions and fundamental frequencies were determined from the periodic potentials with a good agreement with experimental data. The convenience of performing fully optimized calculations to determine the restricted function is also refuted.
Entanglement of resonantly coupled field modes in cavities with vibrating boundaries
Andreata, M A; Dodonov, V V
2002-01-01
We study time dependence of various measures of entanglement (covariance entanglement coefficient, purity entanglement coefficient, normalized distance coefficient, entropic coefficients) between resonantly coupled modes of the electromagnetic field in ideal cavities with oscillating boundaries. Two types of cavities are considered: a three-dimensional cavity possessing eigenfrequencies $\\omega_3=3\\omega_1$, whose wall oscillates at the frequency $\\omega_w=2\\omega_1$, and a one-dimensional (Fabry--Perot) cavity with an equidistant spectrum $\\omega_n= n\\omega_1$, when the distance between perfect mirrors oscillates at the frequencies $\\omega_1$ and $2\\omega_1$. The behaviour of entanglement measures in these cases turns out to be completely different, although all three coefficients demonstrate qualitatively similar time dependences in each case (except for some specific situations, where the covariance entanglement coefficient, based on traces of covariance submatrices, seems to be essentially more sensitive ...
Explicit Correlated Exciton-Vibrational Dynamics of the FMO Complex
Schulze, Jan
2015-01-01
The coupled exciton-vibrational dynamics of a 3-site FMO model is investigated using the numerically exact multilayer multiconfiguration time-dependent Hartree approach. Thereby the vibrational mode specific coupling to local electronic transitions is adapted from a discretized experimental spectral density. The solution of the resulting time-dependent Schr\\"odinger equation including three electronic and 450 vibrational degrees of freedom is analyzed in terms of excitonic populations and coherences. Emphasis is put onto the role of specific ranges of vibrational frequencies. It is observed that modes between 160 and 300 cm$^{-1}$ are responsible for the subpicosecond population and coherence decay.
Institute of Scientific and Technical Information of China (English)
Jumpei; TAYAMA; Motohiro; BANNO; Kaoru; OHTA; Keisuke; TOMINAGA
2010-01-01
We have studied vibrational dynamics of the T1u mode of the CN stretching mode of [Ru(CN)6 ]4- in D2O by infrared(IR) nonlinear spectroscopy such as an IR three-pulse photon echo experiment and polarization-sensitive IR pump-probe spectroscopy. The isotropic component of the pump-probe signal shows a bi-exponential decay with time constants of 0.8 ps and 20.8 ps. The fast and slow components correspond to the rapid equilibration between the T1u mode and the Raman active modes of the CN stretching mode and the vibrational population relaxation from the v=1 state of the T1u mode,respectively. Anisotropy of the pump-probe signal decays with a time constant of 3.1 ps,which is due to the time evolution of the superposition states of the triply degenerate T1u modes. Three pulse photon echo measurements showed that the time correlation function of the frequency fluctuation decays bi-exponentially with time constants of 80 fs and 1.4 ps. These time constants depend only on the solute and are independent of the solvent,whereas the amplitudes depend on both the solute and solvent.
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.
Intrinsic localized modes of a classical discrete anisotropic Heisenberg ferromagnetic spin chain
Energy Technology Data Exchange (ETDEWEB)
Lakshmanan, M., E-mail: lakshman@cnld.bdu.ac.in [Centre for Nonlinear Dynamics, Department of Physics, Bharathidasan University, Tiruchirapalli 620 024 (India); Subash, B. [Centre for Nonlinear Dynamics, Department of Physics, Bharathidasan University, Tiruchirapalli 620 024 (India); Saxena, Avadh [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2014-03-01
We report several exact intrinsic localized mode solutions of the classical spin evolution equation of a one-dimensional anisotropic Heisenberg ferromagnetic spin chain in terms of Jacobian elliptic functions. These include one, two and three spin excitations. All these solutions have smooth anticontinuum limits. Their linear stability and semiclassical quantization are also discussed briefly.
Local probing of Bloch mode dispersion in a photonic crystal waveguide
Engelen, R.J.P.; Engelen, Rob J.P.; Karle, Tim J.; Gersen, H.; Korterik, Jeroen P.; Krauss, Thomas F.; Kuipers, L.; van Hulst, N.F.
2005-01-01
The local dispersion relation of a photonic crystal waveguide is directly determined by phase-sensitive near-field microscopy. We readily demonstrate the propagation of Bloch waves by probing the band diagram also beyond the first Brillouin zone. Both TE and TM polarized modes were distinguished in
Local complementary inputs as drivers of entry mode choices : The case of US investments in Brazil
Hennart, J.M.A.; Sheng, H.H.; Pimenta, G.
2015-01-01
The theory of entry mode choice has modeled that choice as solely determined by the foreign investor. Hennart's bundling model, on the other hand, argues that foreign entry into a host market involves the bundling of intangibles contributed by the foreign investor with local complementary inputs con
All-solid-state cavity QED using Anderson-localized modes in disordered photonic crystal waveguides
DEFF Research Database (Denmark)
Lodahl, Peter; Sapienza, Luca; Nielsen, Henri Thyrrestrup;
2010-01-01
We employ Anderson-localized modes in deliberately disordered photonic crystal waveguides to confine light and enhance the interaction with matter. A 15-fold enhancement of the decay rate of a single quantum dot is observed meaning that 94% of the emitted single photons are coupled to an Anderson...
Local complementary inputs as drivers of entry mode choices : The case of US investments in Brazil
Hennart, J.M.A.; Sheng, H.H.; Pimenta, G.
The theory of entry mode choice has modeled that choice as solely determined by the foreign investor. Hennart's bundling model, on the other hand, argues that foreign entry into a host market involves the bundling of intangibles contributed by the foreign investor with local complementary inputs
A local constitutive model with anisotropy for various homogeneous 2D biaxial deformation modes
Luding, S.; Perdahcioglu, E.S.
2011-01-01
A local constitutive model for granular materials with anisotropy is proposed and applied to different biaxial box deformation modes. The simplified version of the model (in the coordinate system of the biaxial box) involves only scalar values for hydrostatic and shear stresses, for the isotropic an
Contact parameter identification for vibrational response variability prediction
DEFF Research Database (Denmark)
Creixell Mediante, Ester; Brunskog, Jonas; Jensen, Jakob Søndergaard
2018-01-01
industry, where the vibrational behavior of the structures within the hearing frequency range is critical for the performance of the devices. A procedure to localize the most probable contact areas and determine the most sensitive contact points with respect to variations in the modes of vibration...
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)
Ali Bagherian
2016-01-01
Conclusion: It may be concluded that the cotton-roll vibration method can be more helpful than the routine topical anesthesia in reducing behavioral pain reactions in children during local anesthesia administration.
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.
Small Al clusters on the Cu(111) surface: Atomic relaxation and vibrational properties
Rusina, G. G.; Borisova, S. D.; Chulkov, E. V.
2010-11-01
The relaxation and vibrational properties of both Al clusters and the (111) surface of a copper sub-strate were studied using the interatomic interaction potentials obtained in a tight-binding approximation. The presence of small aluminum clusters led to modification of the vibrational states of the substrate, a shift of the Rayleigh mode, and excitation of new Z-polarized modes. Hybridized modes localized on the cluster adatoms and the neighboring atoms of the substrate were found in the phonon spectrum. The localized dipole-active modes of the cluster and their strong hybridization with vibrations of the substrate points to desorption stability of the tri- and heptaatomic clusters.
Vibrational Spectroscopy of CH/CD Stretches in Propadiene: An Algebraic Approach
Institute of Scientific and Technical Information of China (English)
Joydeep Choudhury; Nirmal Kumar Sarkar; Srinivasa Rao Kaxumuri; Ramendu Bhattacharjee
2009-01-01
Using Hamiltonian based on Lie algebraic method, the stretching vibrational modes of C3H4 and C3D4 molecules are calculated up to higher overtones. The model appears to describe C-H and C-D stretching modes with less number of parameters. The locality parameter ξ confirms the highly local behaviour of the stretching modes of these molecules.
Mitigating impact of thermal and rectified radio-frequency sheath potentials on edge localized modes
Energy Technology Data Exchange (ETDEWEB)
Gui, B. [Institute of Plasma Physics Chinese Academy of Sciences, Hefei (China); Lawerence Livermore National Lab, Livermore, California 94550 (United States); Xu, X. Q. [Lawerence Livermore National Lab, Livermore, California 94550 (United States); Myra, J. R.; D' Ippolito, D. A. [Lodestar Research Corporation, Boulder, Colorado 80301 (United States)
2014-11-15
The mitigating impact of thermal and rectified radio frequency (RF) sheath potentials on the peeling-ballooning modes is studied non-linearly by employing a two-fluid three-field simulation model based on the BOUT++ framework. Additional shear flow and the Kelvin-Helmholtz effect due to the thermal and rectified RF sheath potential are induced. It is found that the shear flow increases the growth rate while the K-H effect decreases the growth rate slightly when there is a density gradient, but the energy loss of these cases is suppressed in the nonlinear phase. The stronger external electrostatic field due to the sheaths has a more significant effect on the energy loss suppression. From this study, it is found the growth rate in the linear phase mainly determines the onset of edge-localized modes, while the mode spectrum width in the nonlinear phase has an important impact on the turbulent transport. The wider mode spectrum leads to weaker turbulent transport and results in a smaller energy loss. Due to the thermal sheath and rectified RF sheath potential in the scrape-off-layer, the modified shear flow tears apart the peeling-ballooning filament and makes the mode spectrum wider, resulting in less energy loss. The perturbed electric potential and the parallel current near the sheath region is also suppressed locally due to the sheath boundary condition.
Camelin, P; Marconi, M; Giudici, M
2016-01-01
We show that the pumping current is a convenient parameter for manipulating the temporal Localized Structures (LSs), also called localized pulses, found in passively mode-locked Vertical-Cavity Surface-Emitting Lasers. While short electrical pulses can be used for writing and erasing individual LSs, we demonstrate that a current modulation introduces a temporally evolving parameter landscape allowing to control the position and the dynamics of LSs. We show that the localized pulses drifting speed in this landscape depends almost exclusively on the local parameter value instead of depending on the landscape gradient, as shown in quasi-instantaneous media. This experimental observation is theoretically explained by the causal response time of the semiconductor carriers that occurs on an finite timescale and breaks the parity invariance along the cavity, thus leading to a new paradigm for temporal tweezing of localized pulses. Different modulation waveforms are applied for describing exhaustively this paradigm. ...
On the exploitation of mode localization in surface acoustic wave MEMS
Hanley, T. H.; Gallacher, B. J.; Grigg, H. T. D.
2017-05-01
Mode localization sensing has been recently introduced as an alternative resonant sensing protocol. It has been shown to exhibit several advantages over other resonant methods, in particular a potential for higher sensitivity and rejection of common mode noise. This paper expounds the principles of utilising surface acoustic waves (SAW) to create a mode localization sensor. A generalised geometry consisting of a pair of coupled resonant cavities is introduced and an analytical solution found for the displacement fields within the cavities. The solution is achieved by coupling the internal cavity solutions using a ray tracing method. The results of the analytical solution are compared to a numerical solution found using commercial finite element method (FEM) software; exact agreement is found between the two solutions. The insight gained from the analytical model enables the determination of critical design parameters. A brief analysis is presented showing analogous operation to previous examples of mode localization sensors. The sensitivity of the device is shown to depend nonlinearly on the number of periods in the array coupling the two cavities.
Adaptive Model-Based Mine Detection/Localization using Noisy Laser Doppler Vibration Measurements
Energy Technology Data Exchange (ETDEWEB)
Sullivan, E J; Xiang, N; Candy, J V
2009-04-06
The acoustic detection of buried mines is hampered by the fact that at the frequencies required for obtaining useful penetration, the energy is quickly absorbed by the ground. A recent approach which avoids this problem, is to excite the ground with a high-level low frequency sound, which excites low frequency resonances in the mine. These resonances cause a low-level vibration on the surface which can be detected by a Laser Doppler Vibrometer. This paper presents a method of quickly and efficiently detecting these vibrations by sensing a change in the statistics of the signal when the mine is present. Results based on real data are shown.
Kirk, A.; Chapman, I. T.; Harrison, J.; Liu, Yueqiang; Nardon, E.; Saarelma, S.; Scannell, R.; Thornton, A. J.; the MAST Team
2013-01-01
The application of resonant magnetic perturbations (RMPs) with a toroidal mode number of n = 4 or n = 6 to lower single null plasmas in the MAST tokamak produces up to a factor of 5 increase in edge-localized mode (ELM) frequency and reduction in plasma energy loss associated with type-I ELMs. A threshold current for ELM mitigation is observed above which the ELM frequency increases approximately linearly with current in the coils. Despite a large scan of parameters, complete ELM suppression has not been achieved. The results have been compared with modelling performed using either the vacuum approximation or including the plasma response. During the ELM mitigated stage clear lobe structures are observed in visible-light imaging of the X-point region. The size of these lobes is correlated with the increase in ELM frequency observed. The characteristics of the mitigated ELMs are similar to those of the natural ELMs suggesting that they are type-I ELMs which are triggered at a lower pressure gradient. The application of the RMPs in the n = 4 and n = 6 configurations before the L-H transition has little effect on the power required to achieve H-mode while still allowing the first ELM to be mitigated.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Pei [Manchester Univ. (United Kingdom); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Baboi, Nicoleta [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Jones, Roger M. [The Cockcroft Institute, Daresbury (United Kingdom)
2012-06-15
An electron beam entering an accelerating cavity excites a wakefield. This wakefield can be decomposed into a series of multi-poles or modes. The dominant component of the transverse wakefield is dipole. This report summarizes the higher order mode (HOM) signals of the third harmonic cavities of FLASH measured at various stages: transmission measurements in the single cavity test stand at Fermilab, at CMTB (Cryo- Module Test Bench) and at FLASH, and beam-excited measurements at FLASH. Modes in the first two dipole bands and the fifth dipole band have been identified using a global Lorentzian fit technique. The beam-pipe modes at approximately 4 GHz and some modes in the fifth dipole band have been observed as localized modes, while the first two dipole bands, containing some strong coupling cavity modes, propagate. This report also presents the dependence of the localized dipole modes on the transverse beam position. Linear dependence for various modes has been observed. This makes them suitable for beam position diagnostics. These modes, together with some propagating, strong coupling modes, have been considered in the design of a dedicated electronics for beam diagnostics with HOMs for the third harmonic cavities.
Control System Damps Vibrations
Kopf, E. H., Jr.; Brown, T. K.; Marsh, E. L.
1983-01-01
New control system damps vibrations in rotating equipment with help of phase-locked-loop techniques. Vibrational modes are controlled by applying suitable currents to drive motor. Control signals are derived from sensors mounted on equipment.
Zhong, Min; Liu, Shui Jie; Xu, Bang Li; Wang, Jie; Huang, Hua Qing
2017-10-01
In this paper, we design and simulate a metamaterials absorbers based on the resonance of the local surface plasmon (LSP) mode. The damping constant of gold layer is optimized in simulations to eliminate the effect of the inappropriate material parameters on the electromagnetic properties of the proposed metamaterial absorber. The horizontal distance between two metal particles is optimized in simulations and a perfect absorption resonance peak is achieved due to the strong coupling of LSP modes. A new absorption peak is obtained when the horizontal distance is 0 nm. The vertical distance between the new metal particles and the bottom metal layer is reduced, which leads to the absorption peak reduce based on the reduction of the intensity of LSP modes. A new absorption peak is obtained when the new metallic particle and the bottom gold layer form a whole structure.
Effect of localized microstructural evolution on higher harmonic generation of guided wave modes
Choi, Gloria; Liu, Yang; Yao, Xiaochu; Lissenden, Cliff J.
2015-03-01
Higher harmonic generation of ultrasonic waves has the potential to be used to detect precursors to macroscale damage of phenomenon like fatigue due to microstructural evolution contributing to nonlinear material behavior. Aluminum plates having various plastic zone sizes were plastically deformed to different levels. The fundamental shear horizontal mode was then generated in the plate samples via a magnetostrictive transducer. After propagating through the plastic zone the primary wave mode (SH0) and its third harmonic (sh0) were received by a second transducer. Results of a parallel numerical study using the S1-s2 Lamb mode pair, where sensitivity to changes in third order elastic constants were investigated, are described within the context of the experimental results. Specimens used within both studies are geometrically similar and have double edge notches for dog bone samples that introduce localized plastic deformation. Through both studies, the size of the plastic zone with respect to the propagation distance and damage intensity influence the higher harmonics.
Stabilizing effects of resistivity on low-n edge localized modes in NSTX
Banerjee, Debabrata; Maingi, Rajesh
2016-01-01
The stabilizing effects of enhanced edge resistivity on the low-n edge localized modes (ELMs) are reported for the first time in the context of ELM suppression in H-mode discharge due to Lithium-conditioning in the National Spherical Torus Experiment (NSTX). Here n is the toroidal mode number. Linear stability analysis of the corresponding experimental equilibrium suggests that the change in the equilibrium plasma density profile alone due to Lithium-conditioning may be insufficient for a complete suppression of ELMs. The enhanced resistivity due to the increased effective electric charge number Z eff after Lithium-conditioning can account for additional stabi- lization effect necessary for full ELM suppression. Remarkably, such a stabilizing effect of enhanced edge resistivity on the low-n ELMs only exists when two-fluid effects are considered in the MHD model.
A stochastic, local mode study of neon-liquid surface collision dynamics.
Packwood, Daniel M; Phillips, Leon F
2011-01-14
Equations of motion for a fast, light rare gas atom passing over a liquid surface are derived and used to infer the dynamics of neon collisions with squalane and perfluorinated polyether surfaces from experimental data. The equations incorporate the local mode model of a liquid surface via a stochastic process and explicitly account for impulsive collisional energy loss to the surface. The equations predict angular distributions for scattering of neon that are in good quantitative agreement with experimental data. Our key dynamical conclusions are that experimental angular distributions derive mainly from local mode surface topography rather than from structural features of individual surface molecules, and that the available data for these systems can be accounted for almost exclusively by single collisions between neon atoms and the liquid surface.
Nonlinear nano-scale localized breather modes in a discrete weak ferromagnetic spin lattice
Energy Technology Data Exchange (ETDEWEB)
Kavitha, L., E-mail: louiskavitha@yahoo.co.in [Department of Physics, School of Basic and Applied Sciences, Central University of Tamil Nadu (CUTN), Thiruvarur 610 101, Tamil Nadu (India); Max-Planck Institute for the Physics of Complex Systems, Dresden (Germany); The Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Parasuraman, E. [Department of Physics, Periyar University, Salem 636 011, Tamil Nadu (India); Center for Nanoscience and Nanotechnology, Periyar University, Salem 636 011, Tamil Nadu (India); Gopi, D. [Department of Chemistry, Periyar University, Salem 636 011, Tamil Nadu (India); Center for Nanoscience and Nanotechnology, Periyar University, Salem 636 011, Tamil Nadu (India); Prabhu, A. [Department of Physics, Periyar University, Salem 636 011, Tamil Nadu (India); Vicencio, Rodrigo A. [Departamento de Física and MSI-Nucleus on Advanced Optics, Center for Optics and Photonics (CEFOP), Facultad de Ciencias, Universidad de Chile, Santiago 7800003 (Chile); Max-Planck Institute for the Physics of Complex Systems, Dresden (Germany)
2016-03-01
We investigate the propagation dynamics of highly localized discrete breather modes in a weak ferromagnetic spin lattice with on-site easy axis anisotropy due to crystal field effect. We derive the discrete nonlinear equation of motion by employing boson mappings and p-representation. We explore the onset of modulational instability both analytically in the framework of linear stability analysis and numerically by means of molecular dynamics (MD) simulations, and a perfect agreement was demonstrated. It is also explored that how the antisymmetric nature of the canted ferromagnetic lattice supports highly localized discrete breather (DBs) modes as shown in the stability/instability windows. The energy exchange between low amplitude discrete breathers favours the growth of higher amplitude DBs, resulting eventually in the formation of few long-lived high amplitude DBs. - Highlights: • The effects of DM and anisotropy interaction on the DB modes are studied. • The antisymmetric nature of the canted ferromagnetic medium supports the DB modes. • Dynamics of ferromagnetic chain is governed by boson mappings and p-representation.
Spectral gaps and mode localization in Fibonacci chains of metal nanoparticles.
Dal Negro, Luca; Feng, Ning-Ning
2007-10-29
In this paper we study the spectral, localization and dispersion properties of dipolar modes in quasi-periodically modulated nanoparticle chains based on the Fibonacci sequence. By developing a transfer matrix approach for the calculation of resonant frequencies, oscillation eigenvectors and integrated density of states (IDS) of spatially-modulated dipole chains, we demonstrate the presence of large spectral gaps and calculate the pseudo-dispersion diagram of Fibonacci plasmonic chains. The presence of plasmonic band-gaps and localized states in metal nanoparticle chains based on quasi-periodic order can have a large impact in the design and fabrication of novel nanophotonics devices.
Coalescence of Anderson-localized modes at an exceptional point in 2D random media
Bachelard, Nicolas; Arlandis, Julien; Touzani, Rachid; Sebbah, Patrick
2014-01-01
In non-hermitian systems, the particular position at which two eigenstates coalesce under a variation of a parameter in the complex plane is called an exceptional point. A non-perturbative theory is proposed which describes the evolution of modes in 2D open dielectric systems when permittivity distribution is modified. We successfully test this theory in a 2D disordered system to predict the position in the parameter space of the exceptional point between two Anderson-localized states. We observe that the accuracy of the prediction depends on the number of localized states accounted for. Such an exceptional point is experimentally accessible in practically relevant disordered photonic systems
Camelin, P.; Javaloyes, J.; Marconi, M.; Giudici, M.
2016-12-01
We show that the pumping current is a convenient parameter for manipulating the temporal localized structures (LSs), also called localized pulses, found in passively-mode-locked vertical-cavity surface-emitting lasers. While short electrical pulses can be used for writing and erasing individual LSs, we demonstrate that a current modulation introduces a temporally evolving parameter landscape allowing one to control the position and the dynamics of LSs. We show that the localized pulse drifting speed in this landscape depends almost exclusively on the local parameter value instead of depending on the landscape gradient, as shown in quasi-instantaneous media. This experimental observation is theoretically explained by the causal response time of the semiconductor carriers that occurs on a finite time scale and breaks the parity invariance along the cavity, thus leading to a different paradigm for temporal tweezing of localized pulses. Different modulation waveforms are applied for describing exhaustively this paradigm. Starting from a generic model of passive mode locking based upon delay differential equations, we deduce the effective equations of motion for these LSs in a time-dependent current landscape.
Capture and release of traveling intrinsic localized mode in coupled cantilever array
Kimura, Masayuki; Hikihara, Takashi
2009-01-01
A method to manipulate intrinsic localized mode (ILM) is numerically discussed in a nonlinear coupled oscillator array, which is obtained by modeling a microcantilever array. Prior to the manipulation, coexistence and dynamical stability of standing ILMs are first investigated. The stability of coexisting ILMs is determined by a nonlinear coupling coefficient of the array. In addition, the global phase structure, which dominates traveling ILMs, is also changed with the stability. It makes pos...
Localized Mode Enhanced Coupler Based on Quasi-One-Dimensional Photonic Crystal Microstrip
Institute of Scientific and Technical Information of China (English)
LI Yun-Hui; JIANG Hai-Tao; HE Li; LI Hong-Qiang; ZHANG Ye-Wen; CHEN Hong
2004-01-01
We propose a novel localized mode enhanced (LME) coupler based on quasi-one-dimensional photonic crystal microstrips, which is promising to be applied in wavelength division multiplexed microwave communication systems. Compared to the traditional microstrip coupler, the LME structure has two advantages: high efficiency and frequency selectivity. Even in a relatively far coupling distance, this structure can still achieve a high efficiency about 50%. The frequency selectivity can be realized by simply tuning the distance between two transmission lines.
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…
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…
Local phonon mode in thermoelectric Bi{sub 2}Te{sub 2}Se from charge neutral antisites
Energy Technology Data Exchange (ETDEWEB)
Tian, Yao [Department of Physics and Institute of Optical Sciences, University of Toronto, Toronto, Ontario M5S 1A7 (Canada); Osterhoudt, Gavin B.; Burch, Kenneth S., E-mail: ks.burch@bc.edu [Department of Physics, Boston College, 140 Commonwealth Ave., Chestnut Hill, Massachusetts 02467-3804 (United States); Jia, Shuang; Cava, R. J. [Department of Chemistry, Princeton University, Princeton, New Jersey 08540 (United States)
2016-01-25
Local modes caused by defects play a significant role in the thermal transport properties of thermoelectrics. Of particular interest are charge-neutral defects that suppress thermal conductivity, without significantly reducing electrical transport. Here, we report a temperature dependent Raman study that identifies such a mode in a standard thermoelectric material, Bi{sub 2}Te{sub 2}Se. One of the modes observed, whose origin has been debated for decades, was shown most likely to be an antisite defect induced local mode. The anomalous temperature independent broadening of the local mode is ascribed to the random arrangement of Se atoms. The temperature renormalization of all modes is well explained by an anharmonic model–Klemens's model.
Savoia, Antonella; Landi, Simone; Vannini, Fulvio; Baldi, Alfonso
2013-06-01
In recent years, there has been an upsurge in the application of low-level laser therapy in various medical diseases. Additionally, vibration therapy is a new and effective measure to prevent muscular atrophy and osteoporosis, along with some general health-related beneficial effects of exercise on skeletal muscles such as improvement of endothelial function and an increased enzyme capacity of energy metabolism. The aim of this study was to evaluate the application of a 635 nm and 0.040 W exit power per multiple diode laser in combination with vibration therapy for the application of non-invasive reduction of circumference in patients with localized adiposity and cellulite. The study enrolled men and women (N = 33) aged 18-64 years with localized adiposity or fibrous cellulite. The evaluation parameters were: photographic evaluation, perimetric evaluation, blood tests, ecographic evaluation, histological evaluation, and subjective and objective tests. The results produced were statistically analyzed and resulted in a significant reduction of fat thickness when compared to the measurement prior to the treatment (P cellulite.
Tondreau, Gilles; Deraemaeker, Arnaud
2014-12-01
This paper deals with the experimental application of modal filters for automated damage localization using dynamic strain measurements. Previously developed for damage detection, the extension of modal filtering to damage localization consists in splitting a very large network of dynamic strain sensors into several independent local sensor networks. An efficient signal processing coupled to control charts allows a fully automated data-based damage localization once the modal filters are initialized. The method is tested experimentally on a small clamped-free steel plate and a 3.78 m long steel I-beam, both instrumented with a network of cheap piezoelectric patches to measure the dynamic strains. A removable damage is introduced at different positions by means of a small removable damage device. For both applications, the method can successfully detect and locate all damage cases considered, showing the potentiality of the method for field applications.
Vibration-assisted resonance in photosynthetic excitation energy transfer
Irish, E K; Lovett, B W
2013-01-01
Coherent quantum energy transfer, as observed in photosynthetic pigment-protein complexes, is inhibited by energetic disorder. While this difficulty can be overcome to some extent by the addition of environmental noise, it has recently has begun to be appreciated that discrete intra- and/or intermolecular vibrational modes may play an important role in quantum dynamics. We present a microscopic mechanism by which intramolecular vibrational modes create resonant energy transfer pathways, enhancing the efficiency of both coherent and dephasing-assisted transfer. The principles of this vibration-assisted resonance are illustrated in a simple model based on one energy-transfer branch of the well-characterised Fenna-Matthews-Olson complex. Despite its simplicity, this model captures the interplay between strong electronic coupling that produces delocalised exciton states and resonance-enhanced weak coupling to local vibrational modes. Analytical and numerical results show that intramolecular vibrations can enhance...
Directory of Open Access Journals (Sweden)
Yasser Al Hamidi
2016-04-01
Full Text Available Piezoelectric tube actuators are extensively used in scanning probe microscopes to provide dynamic scanning motions in open-loop operations. Furthermore, they are employed as micropositioners due to their high bandwidth, high resolution and ease of excitation. However, these piezoelectric micropositioners exhibit badly damped vibrations that occur when the input excites the dynamic response, which tends to degrade positioning accuracy and performance. This paper deals with vibrations’ feedforward control of a multi-degrees of freedom (DOF piezoelectric micropositioner in order to damp the vibrations in the direct axes and to reduce the cross-couplings. The novelty in this paper relative to the existing vibrations feedforward controls is the simplicity in design approach, the minimal number of shaper impulses for each input required to damp all modes of vibration at each output, and the account for the strong cross-couplings which only occur in multi-DOF cases. A generalization to a multiple degrees of freedom actuator is first proposed. Then simulation runs on a 3-DOF piezoelectric tube micropositioner have been effectuated to demonstrate the efficiency of the proposed method. Finally, experimental tests were carried out to validate and to confirm the predicted simulation.
Energy Technology Data Exchange (ETDEWEB)
Fan, G.W. (3-I Scientific Development Inc., Tempe, AZ (United States)); Nelson, H.D. (Texas Christian Univ., Fort Worth (United States)); Crouch, P.E.; Mignolet, M.P. (Arizona State Univ., Tempe (United States))
1993-04-01
The complex mode and balanced realization methods are used separately to obtain reduced-order models for general linear asymmetric rotor systems. The methods are outlined and then applied to a typical rotor system represented by a 52 degree-or-freedom finite element model. The accuracy of the two methods is compared for this model and the complex model method is found to be more accurate than the balanced realization method for the desired frequency bandwidth and for models of the same reduced order. However, with some limitations, it is also shown that the balanced realization method can be applied to the reduced-order complex mode model to obtain further order reduction without loss of model accuracy. A Linear-Quadratic-Regulator-based least-squares output feedback control procedure is developed for the vibration control of rotor systems. This output feedback procedure eliminates the requirement of an observer for the use of an LQ regulator, and provides the advantage that the rotor vibration can be effectively controlled by monitoring only one single location along the rotor shaft while maintaining an acceptable performance. The procedures presented are quite general and may be applied to a large class of vibration problems including rotordynamics.
Orain, François; Bécoulet, M.; Morales, J.; Huijsmans, G. T. A.; Dif-Pradalier, G.; Hoelzl, M.; Garbet, X.; Pamela, S.; Nardon, E.; Passeron, C.; Latu, G.; Fil, A.; Cahyna, P.
2015-01-01
The dynamics of a multi-edge localized mode (ELM) cycle as well as the ELM mitigation by resonant magnetic perturbations (RMPs) are modeled in realistic tokamak X-point geometry with the non-linear reduced MHD code JOREK. The diamagnetic rotation is found to be a key parameter enabling us to reproduce the cyclical dynamics of the plasma relaxations and to model the near-symmetric ELM power deposition on the inner and outer divertor target plates consistently with experimental measurements. Moreover, the non-linear coupling of the RMPs with unstable modes are found to modify the edge magnetic topology and induce a continuous MHD activity in place of a large ELM crash, resulting in the mitigation of the ELMs. At larger diamagnetic rotation, a bifurcation from unmitigated ELMs—at low RMP current—towards fully suppressed ELMs—at large RMP current—is obtained.
Active control of edge localized modes with a low n perturbation fields in the JET tokamak
Energy Technology Data Exchange (ETDEWEB)
Liang, Y., E-mail: y.liang@fz-juelich.d [Association EURATOM-FZJ, Forschungszentrum Juelich GmbH, Institute of Energy Research IEF-4: Plasma Physics, Partner in the Trilateral Euregio Cluster, 52425 Juelich (Germany); Jachmich, S. [Association EURATOM-Belgian State, Koninklijke Militaire School - Ecole Royale Militaire, B-1000 Brussels (Belgium); Koslowski, H.R. [Association EURATOM-FZJ, Forschungszentrum Juelich GmbH, Institute of Energy Research IEF-4: Plasma Physics, Partner in the Trilateral Euregio Cluster, 52425 Juelich (Germany); Nardon, E. [EURATOM-UKAEA Fusion Association, Culham Science Centre, OX14 3DB Abingdon, OXON (United Kingdom); Alfier, A. [Associazione EURATOM-ENEA sulla Fusione, Consorzio RFX Padova (Italy); Baranov, Y. [EURATOM-UKAEA Fusion Association, Culham Science Centre, OX14 3DB Abingdon, OXON (United Kingdom); De La Luna, E. [Asociacion EURATOM-CIEMAT, Avenida Complutense 22, E-28040 Madrid (Spain); Vries, P. de [EURATOM-UKAEA Fusion Association, Culham Science Centre, OX14 3DB Abingdon, OXON (United Kingdom); Eich, T. [Association EURATOM-Max-Planck-Institut fuer Plasmaphysik, D-85748 Garching (Germany); Esser, H.G.; Harting, D. [Association EURATOM-FZJ, Forschungszentrum Juelich GmbH, Inst. of Energy Research IEF-4: Plasma Physics, Partner in the Trilateral Euregio Cluster, 52425 Juelich (Germany); Kiptily, V. [EURATOM-UKAEA Fusion Association, Culham Science Centre, OX14 3DB Abingdon, OXON (United Kingdom); Kreter, A. [Association EURATOM-FZJ, Forschungszentrum Juelich GmbH, Inst. of Energy Research IEF-4: Plasma Physics, Partner in the Trilateral Euregio Cluster, 52425 Juelich (Germany); Gerasimov, S.; Gryaznevich, M.P.; Howell, D. [EURATOM-UKAEA Fusion Association, Culham Science Centre, OX14 3DB Abingdon, OXON (United Kingdom); Sergienko, G. [Association EURATOM-FZJ, Forschungszentrum Juelich GmbH, Inst. of Energy Research IEF-4: Plasma Physics, Partner in the Trilateral Euregio Cluster, 52425 Juelich (Germany)
2009-06-15
Active control of edge localized modes (ELMs) by using static external magnetic perturbation fields with low toroidal mode number, n, has been demonstrated for both, ITER baseline (q{sub 95}approx3) and high beta advanced tokamak scenarios at the JET tokamak. During the application of the low n field the ELM frequency increased by a factor up to approx4-5. Reduction in carbon erosion and ELM peak heat fluxes on the divertor target by roughly the same factor as the increase of the ELM frequency has been observed. The frequency of the mitigated ELMs using a low n field is found to increase proportional to the total input heating power. Compensation of the density pump-out effect observed when the external low n field is applied has been achieved by gas fueling in low triangularity plasmas.
20-MHz B-mode ultrasound in monitoring the course of localized scleroderma (morphea).
Hoffmann, K; Gerbaulet, U; el-Gammal, S; Altmeyer, P
1991-01-01
Ultrasonographic methods have recently provided us with the means for objective and non-invasive monitoring of the dynamics of chronic skin diseases. We examined 34 patients with localized scleroderma (morphea) using a 20-MHz B-mode ultrasound scanner (DUB 20, Taberna pro Medicum, Lüneburg). In patients with plaque-type and linear band-type localized scleroderma intraindividual comparison of sclerotic skin with corresponding areas of healthy skin showed thickening of the corium. The increase in corium thickness was between 2% and 251%. The extent of the difference in corium thickness between sclerotic and healthy skin depended on the location-originally thin skin showed a greater degree of sclerosis. We also frequently found enhanced reflexes in the lower corium and hyperechoic, widened bands of connective tissue traversing the subcutaneous fatty tissue from the corium-subcutis border in the direction of the muscle fascia. 20 patients were examined several times in the course of one year. In nine patients we found ultrasonographic evidence of regression (decrease in thickness 26%) and in nine the ultrasound examination showed progression (increase in thickness 28%). 20-MHz B-mode ultrasound imaging is a suitable non-invasive method for monitoring the course and treatment of localized scleroderma. Its routine use is strongly recommended.
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.
An ASAP treatment of vibrationally excited S2O: The ν3 mode and the ν3 + ν2 - ν2 hot band
Thorwirth, S.; Martin-Drumel, M. A.; Endres, C. P.; Salomon, T.; Zingsheim, O.; van Wijngaarden, J.; Pirali, O.; Gruet, S.; Lewen, F.; Schlemmer, S.; McCarthy, M. C.
2016-01-01
The fundamental S-S stretching mode ν3 of disulfur monoxide, S2O, located at 679 cm-1, has been investigated using Fourier-transform far-infrared spectroscopy at the SOLEIL synchrotron facility. A spectroscopic analysis has been performed using an Automated Spectral Assignment Procedure (ASAP) which permits accurate determination of more than 2000 energy levels from ν3. In addition, the ν3 + ν2 - ν2 hot band was observed for the first time and some 500 corresponding energy levels were assigned. The high-resolution synchrotron study was complemented with pure rotational spectra of S2O in the (v1, v2, v3) = (0, 0, 1) vibrational state observed in the frequency range from 250 to 280 GHz using a long-path absorption cell. From these combined measurements, extensive molecular parameter sets have been determined and precise band centers have been derived for both vibrational bands.
Dong, Weibing; Wang, Hongxin; Olmstead, Marilyn M; Fettinger, James C; Nix, Jay; Uchiyama, Hiroshi; Tsutsui, Satoshi; Baron, Alfred Q R; Dowty, Eric; Cramer, Stephen P
2013-06-17
The tetraethylammonium salt of the transition-metal complex FeCl4(-) has been examined using inelastic X-ray scattering (IXS) with 1.5 meV resolution (12 cm(-1)) at 21.747 keV. This sample serves as a feasibility test for more elaborate transition-metal complexes. The IXS spectra were compared with previously recorded IR, Raman, and nuclear resonant vibrational spectroscopy (NRVS) spectra, revealing the same normal modes but with less strict selection rules. Calculations with a previously derived Urey-Bradley force field were used to simulate the expected Q and orientation dependence of the IXS intensities. The relative merits of IXS, compared to other photon-based vibrational spectroscopies such as NRVS, Raman, and IR, are discussed.
Kreisbeck, Christoph; Kramer, Tobias; Aspuru-Guzik, Alán
2014-09-09
The accurate simulation of excitonic energy transfer in molecular complexes with coupled electronic and vibrational degrees of freedom is essential for comparing excitonic system parameters obtained from ab initio methods with measured time-resolved spectra. Several exact methods for computing the exciton dynamics within a density-matrix formalism are known but are restricted to small systems with less than 10 sites due to their computational complexity. To study the excitonic energy transfer in larger systems, we adapt and extend the exact hierarchical equation of motion (HEOM) method to various high-performance many-core platforms using the Open Compute Language (OpenCL). For the light-harvesting complex II (LHC II) found in spinach, the HEOM results deviate from predictions of approximate theories and clarify the time scale of the transfer process. We investigate the impact of resonantly coupled vibrations on the relaxation and show that the transfer does not rely on a fine-tuning of specific modes.
DEFF Research Database (Denmark)
Kreisbeck, Christoph; Kramer, Tobias; Aspuru-Guzik, Alán
2014-01-01
The accurate simulation of excitonic energy transfer in molecular complexes with coupled electronic and vibrational degrees of freedom is essential for comparing excitonic system-parameters obtained from ab-initio methods with measured time-resolved spectra. Several exact methods for computing...... the exciton dynamics within a density-matrix formalism are known, but are restricted to small systems with less than ten sites due to their computational complexity. To study the excitonic energy transfer in larger systems, we adapt and extend the exact hierarchical equation of motion (HEOM) method to various...... coupled vibrations on the relaxation and show that the transfer does not rely on a fine-tuning of specific modes....
混合隔振系统自适应模糊滑模控制%Adaptive Fuzzy Sliding-mode Controller for Hybrid Vibration Isolation Systems
Institute of Scientific and Technical Information of China (English)
杨理华; 朱石坚; 楼京俊; 李棒
2014-01-01
针对机械设备被动隔振在低频段隔振效果较差的问题，建立磁致伸缩作动器的电—磁—机转化数学模型，提出一种基于自适应模糊滑模控制算法，并用李雅普诺夫方法证明控制器的稳定性，将该控制策略与磁致伸缩作动器应用于混合隔振系统中。仿真结果表明：在单频、多频及随即激励条件下，自适应模糊滑模控制器具有良好的动态特性和鲁棒性，能够提高系统隔振效率并拓宽隔振频段，有效减小传至基础的力。%Aiming at the problem of poor vibration isolation effect of passive vibration isolators of mechanical equip-ment in low frequency range, an electric-magnetic-mechanical conversion model for magnetostrictive actuators is estab-lished, and an adaptive fuzzy sliding-mode control algorithm is proposed. The stability of the controller is proved by Lyapu-nov method. Then, the control strategy and the magnetostrictive actuator are used in a hybrid vibration isolation system. The simulation results show that in whatever conditions of single frequency excitation, multi-frequency excitation or random ex-citation, the adaptive fuzzy sliding-mode controller has good dynamic characteristics and robustness. This property can also be used to improve the isolation efficiency and broaden the vibration isolation frequency band of the hybrid system, and ef-fectively reduce the force transmitted to the foundation of the mechanical equipment.
Jaber, Abobaker M; Ismail, Mohd Tahir; Altaher, Alsaidi M
2014-01-01
This paper mainly forecasts the daily closing price of stock markets. We propose a two-stage technique that combines the empirical mode decomposition (EMD) with nonparametric methods of local linear quantile (LLQ). We use the proposed technique, EMD-LLQ, to forecast two stock index time series. Detailed experiments are implemented for the proposed method, in which EMD-LPQ, EMD, and Holt-Winter methods are compared. The proposed EMD-LPQ model is determined to be superior to the EMD and Holt-Winter methods in predicting the stock closing prices.
Resistive Reduced MHD Modeling of Multi-Edge-Localized-Mode Cycles in Tokamak X -Point Plasmas
Orain, F.; Bécoulet, M.; Huijsmans, G. T. A.; Dif-Pradalier, G.; Hoelzl, M.; Morales, J.; Garbet, X.; Nardon, E.; Pamela, S.; Passeron, C.; Latu, G.; Fil, A.; Cahyna, P.
2015-01-01
The full dynamics of a multi-edge-localized-mode (ELM) cycle is modeled for the first time in realistic tokamak X -point geometry with the nonlinear reduced MHD code jorek. The diamagnetic rotation is found to be instrumental to stabilize the plasma after an ELM crash and to model the cyclic reconstruction and collapse of the plasma pressure profile. ELM relaxations are cyclically initiated each time the pedestal gradient crosses a triggering threshold. Diamagnetic drifts are also found to yield a near-symmetric ELM power deposition on the inner and outer divertor target plates, consistent with experimental measurements.
Capture and release of traveling intrinsic localized mode in coupled cantilever array.
Kimura, Masayuki; Hikihara, Takashi
2009-03-01
A method to manipulate intrinsic localized mode (ILM) is numerically discussed in a nonlinear coupled oscillator array, which is obtained by modeling a microcantilever array. Prior to the manipulation, coexistence and dynamical stability of standing ILMs are first investigated. The stability of coexisting ILMs is determined by a nonlinear coupling coefficient of the array. In addition, the global phase structure, which dominates traveling ILMs, is also changed with the stability. It makes possible to manipulate a traveling ILM by adjusting the nonlinear coupling coefficient. The capture and release manipulation of the traveling ILM is shown numerically.
Directory of Open Access Journals (Sweden)
Abobaker M. Jaber
2014-01-01
Full Text Available This paper mainly forecasts the daily closing price of stock markets. We propose a two-stage technique that combines the empirical mode decomposition (EMD with nonparametric methods of local linear quantile (LLQ. We use the proposed technique, EMD-LLQ, to forecast two stock index time series. Detailed experiments are implemented for the proposed method, in which EMD-LPQ, EMD, and Holt-Winter methods are compared. The proposed EMD-LPQ model is determined to be superior to the EMD and Holt-Winter methods in predicting the stock closing prices.
Pedestal and E r profile evolution during an edge localized mode cycle at ASDEX Upgrade
Cavedon, M.; Pütterich, T.; Viezzer, E.; Laggner, F. M.; Burckhart, A.; Dunne, M.; Fischer, R.; Lebschy, A.; Mink, F.; Stroth, U.; Willensdorfer, M.; Wolfrum, E.; the ASDEX Upgrade Team
2017-10-01
The upgrade of the edge charge exchange recombination spectroscopy diagnostic at ASDEX Upgrade has enabled highly spatially resolved measurements of the impurity ion dynamics during an edge-localized mode cycle (ELM) with unprecedented temporal resolution, i.e. 65 μs. The increase of transport during an ELM induces a relaxation of the ion, electron edge gradients in impurity density and flows. Detailed characterization of the recovery of the edge temperature gradients reveals a difference in the ion and electron channel: the maximum ion temperature gradient {{\
Institute of Scientific and Technical Information of China (English)
石锋; Helei; Dong
2014-01-01
Ba[(Zn1-xMgx)1/3Ta（2/3）]O3（BZMT,x=0,0.2,0.4,0.6,0.8,and 1.0）solid solution ceramics were synthesized by a conventional solid-state sintering technique.Vibration spectra（Raman spectroscopy and Fourier trans form far-infrared reflection spectroscopy）and X-ray diffraction（XRD）were employed to evaluate the correla tion between microstructures and phonon modes of these solid solutions.Spectroscopic and structural data show sensitivity to structural evolution of samples with Mg2+concentration,and a 1:2 ordered phase appears when x≥0.2.The unit cell parameters decrease with increasing Mg2+content.The ordering degree reaches a relative maximum value in the range of Mg2+content,0.4≤x<0.6.The phonon modes were assigned,and the correlation of phonon vibrations in the microstructure were analyzed.The position and width of the phonon modes were determined and correlated to the ionic radii for the different atoms substituted in the B’-site.
Sliding Mode Vibration Control of Single Flexible Manipulator%单连杆柔性机械臂的滑模振动控制
Institute of Scientific and Technical Information of China (English)
刘业松
2014-01-01
基于Lagrange方程和假设模态法，推导出单连杆柔性机械臂的动力学模型，应用微分几何输出重定义的方法，将电动机转角和振动模态变量的线性组合作为柔性机械臂系统的控制输出量，使柔性机械臂系统在平衡点附近转变为易于控制的最小相位系统。设计了一种滑模控制器，实现了柔性机械臂的振动抑制，仿真试验结果表明了该方法的有效性。%The dynamics model of single flexible manipulator was derived based on the Lagrange equation and assumed mode method.Applied differential geometry output redefinition method,the linear combination of motor angle and vibration mode variable was used as the control output,and then the original system near the equilibrium point was rewritten as a minimum-phase system easy to be controlled.A sliding mode controller to realize vibration suppression was designed,and the simulation results showed it has the effectiveness.
Energy Technology Data Exchange (ETDEWEB)
Wang, Xian-Qu [Institute of Fusion Science, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang, Rui-Bin; Meng, Guo [State Key Lab of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China)
2016-07-15
The destabilization of ideal internal kink modes by trapped fast particles in tokamak plasmas with a “shoulder”-like equilibrium current is investigated. It is found that energetic particle branch of the mode is unstable with the driving of fast-particle precession drifts and corresponds to a precessional fishbone. The mode with a low stability threshold is also more easily excited than the conventional precessional fishbone. This is different from earlier studies for the same equilibrium in which the magnetohydrodynamic (MHD) branch of the mode is stable. Furthermore, the stability and characteristic frequency of the mode are analyzed by solving the dispersion relation and comparing with the conventional fishbone. The results suggest that an equilibrium with a locally flattened q-profile, may be modified by localized current drive (or bootstrap current, etc.), is prone to the onset of the precessional fishbone branch of the mode.
Localization and fractal spectra of optical phonon modes in quasiperiodic structures
Anselmo, D. H. A. L.; Dantas, A. L.; Medeiros, S. K.; Albuquerque, E. L.; Freire, V. N.
2005-04-01
The dispersion relation and localization profile of confined optical phonon modes in quasiperiodic structures, made up of nitride semiconductor materials, are analyzed through a transfer-matrix approach. The quasiperiodic structures are characterized by the nature of their Fourier spectrum, which can be dense pure point (Fibonacci sequences) or singular continuous (Thue-Morse and Double-period sequences). These substitutional sequences are described in terms of a series of generations that obey peculiar recursion relations and/or inflation rules. We present a quantitative analysis of the localization and magnitude of the allowed band widths in the optical phonons spectra of these quasiperiodic structures, as well as how they scale as a function of the number of generations of the sequences.
铁路车桥耦合振动模态法分析%Coupling vibration analysis of vehicle-bridge by mode method
Institute of Scientific and Technical Information of China (English)
杨仕若; 曾庆元
2011-01-01
The free vibration mode of the truss girder bridge and normal coordinates are taken as displacement functions of the bridge vibration.By coupling the vehicle and the truss girder bridge as one composite system, the total potential energy of the vehicle and the truss girder bridge under normal coordinates are calculated.Based on the principle of the total potential energy with stationary value in elastic system and the set-in-right-position rule for forming structural matrices, the vibration equations of vehicle-bridge are established in time-varying system.The calculation results are compared with the ones by non-mode method.The minimum error of the results by the two methods is 0.16％.The mode method could reduce the degrees of freedom of the vehicle-bridge system, thus it reduces the computing time considerably.%以钢桁梁桥自由振动的模态和正则坐标作为桥跨结构振动的位移函数,将列车-钢桁梁桥作为一个系统,计算正则坐标下钢桁梁桥及车辆的总势能.基于弹性系统的总势能值不变原理及形成矩阵的对号入座法则,建立了车桥时变系统在正则坐标下的振动方程,有效减少了车桥振动的自由度和计算工作量.以某铁路为例,计算了连续钢桁梁桥车桥系统的振动响应,并用模态法和非模态法进行对比,最小误差为0.16%.
CALCULATIONS OF STRETCHING VIBRATIONAL ENERGYLEVELS OF THE CH3I MOLECULE BY A NONLINEAR MODEL
Institute of Scientific and Technical Information of China (English)
ZHU JUN; GOU QING-QUAN
2001-01-01
A nonlinear model, i.e. the quantized discrete self-trapping equation, is applied to calculate the highly excited CH stretching vibrational energy levels of the CH3I molecule in the liquid phase at the electronic ground state up to n=8. The obtained results agree well with the experimental data and with those obtained from local mode model calculations. We note that the dominant feature of the methyl CH stretching vibrational energy levels of the CH3I molecule is a pattern of local mode pairs. When n ＞ 7, all the vibrational energy of the CH3 group can nearly be localized on a single CH bond.
Local measurement for structural health monitoring
Institute of Scientific and Technical Information of China (English)
G.Z.Qi; Guo Xun; Qi Xiaozhai; W. Dong; P.Chang
2005-01-01
Localized nature of damage in structures requires local measurements for structural health monitoring. The local measurement means to measure the local, usually higher modes of the vibration in a structure. Three fundamental issues about the local measurement for structural health monitoring including (1) the necessity of making local measurement, (2) the difficulty of making local measurement and (3) how to make local measurement are addressed in this paper. The results from both the analysis and the tests show that the local measurement can successfully monitor the structural health status as long as the local modes are excited. Unfortunately, the results also illustrate that it is difficult to excite local modes in a structure.Therefore, in order to carry structural health monitoring into effect, we must (1) ensure that the local modes are excited, and (2) deploy enough sensors in a structure so that the local modes can be monitored.
Institute of Scientific and Technical Information of China (English)
Liu Yang; Tang Yi
2008-01-01
By means of the Glauber's coherent state method combined with multiple-scale method,this paper investigates the localized modes in a quantum one-dimensional Klein-Gordon chain and finds that the equation of motion of annihilation operator is reduced to the nonlinear Schr(o)dinger equation.Interestingly,the model can support both bright and dark small amplitude travelling and non-travelling nonlinear localized modes in different parameter spaces.
Lv, Wei; Henry, Asegun
2016-10-01
Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.
Boukahil, A.; Huber, D. L.
1989-09-01
The harmonic magnon modes in a one-dimensional Heisenberg spin glass having nearest-neighbor exchange interactions of fixed magnitude and random sign are investigated. The Lyapounov exponent is calculated for chains of 107-108 spins over the interval 0<=ω<=4J. In the low-frequency regime, ω<~0.1J, an anomalous behavior for the density of states ρ(ω)~ω-1/3 is established, consistent with earlier results obtained by Stinchcombe and Pimentel using transfer-matrix techniques; at higher frequencies, gaps appear in the spectrum. At low frequencies, the localization length diverges as ω-2/3. A formal connection is established between the spin glass and the one-dimensional discretized Schrödinger equation. By making use of the connection, it is shown that the theory of Derrida and Gardner, which was developed for weak potential disorder, can account quantitatively for the distribution and localization of the low-frequency magnon modes in the spin-glass model.
Lv, Wei; Henry, Asegun
2016-10-21
Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.
Mode decomposition methods for flows in high-contrast porous media. Global-local approach
Ghommem, Mehdi
2013-11-01
In this paper, we combine concepts of the generalized multiscale finite element method (GMsFEM) and mode decomposition methods to construct a robust global-local approach for model reduction of flows in high-contrast porous media. This is achieved by implementing Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) techniques on a coarse grid computed using GMsFEM. The resulting reduced-order approach enables a significant reduction in the flow problem size while accurately capturing the behavior of fully-resolved solutions. We consider a variety of high-contrast coefficients and present the corresponding numerical results to illustrate the effectiveness of the proposed technique. This paper is a continuation of our work presented in Ghommem et al. (2013) [1] where we examine the applicability of POD and DMD to derive simplified and reliable representations of flows in high-contrast porous media on fully resolved models. In the current paper, we discuss how these global model reduction approaches can be combined with local techniques to speed-up the simulations. The speed-up is due to inexpensive, while sufficiently accurate, computations of global snapshots. © 2013 Elsevier Inc.
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.
Vibrational properties of uracil
Institute of Scientific and Technical Information of China (English)
WANG Zhiping; ZHANG Fengshou; ZENG Xianghua; ZHOU Hongyu; GU Bin; CHENG Wei
2006-01-01
A semiempirical molecular dynamics model is developed to study the vibrational frequencies of uracil at very low kinetic temperature by using the Fourier transform of velocity autocorrelation function of trajectories of molecular dynamics simulations. The finite difference harmonic method is used to assign the vibrational frequency of each mode. The calculated frequencies are found to be in good agreement with experimental measurements. Moreover, we make up for the lost vibrational modes in experiments self-consistently. A total of 30 vibrational modes and their corresponding frequencies are reported.
Characterization of small, Type V edge-localized modes in the National Spherical Torus Experiment
Energy Technology Data Exchange (ETDEWEB)
Maingi, Rajesh [ORNL; Bell, M. [Princeton Plasma Physics Laboratory (PPPL); Fredrickson, E. [Princeton Plasma Physics Laboratory (PPPL); Lee, K. C. [Princeton Plasma Physics Laboratory (PPPL); Maqueda, R. J. [Nova Photonics, Princeton, NJ; Snyder, P. [General Atomics, San Diego; Tritz, K. [Johns Hopkins University; Zweben, S. J. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Biewer, Theodore M [ORNL; Bush, Charles E [ORNL; Boedo, J. [University of California, San Diego; Brooks, N. H. [General Atomics, San Diego; Delgado-Aparicio, L. [Johns Hopkins University; Domier, C. W. [University of California, Davis; Gates, D. [Princeton Plasma Physics Laboratory (PPPL); Johnson, D. W. [Princeton Plasma Physics Laboratory (PPPL); Kaita, R. [Princeton Plasma Physics Laboratory (PPPL); Kaye, S. M. [Princeton Plasma Physics Laboratory (PPPL); Kugel, H. [Princeton Plasma Physics Laboratory (PPPL); LaBlanc, B. P. [Princeton Plasma Physics Laboratory (PPPL); Luhmann, N. C. [University of California, Davis; Menard, J. [Princeton Plasma Physics Laboratory (PPPL); Mueller, D. [Princeton Plasma Physics Laboratory (PPPL); Park, H. [Princeton Plasma Physics Laboratory (PPPL); Raman, R [University of Washington, Seattle; Roquemore, A. L. [Princeton Plasma Physics Laboratory (PPPL); Sabbagh, S. A. [Columbia University; Soukhanovskii, V. A. [Lawrence Livermore National Laboratory (LLNL); Stevenson, T. [Princeton Plasma Physics Laboratory (PPPL); Stutman, D. [General Atomics, San Diego
2006-01-01
There has been a substantial international research effort in the fusion community to identify tokamak operating regimes with either small or no periodic bursts of particles and power from the edge plasma, known as edge-localized modes (ELMs). While several candidate regimes have been presented in the literature, very little has been published on the characteristics of the small ELMs themselves. One such small ELM regime, also known as the Type V ELM regime, was recently identified in the National Spherical Torus Experiment [M. Ono, S. M. Kaye, Y.-K. M. Peng et al., Nucl. Fusion 40, 557 (2000)]. In this paper, the spatial and temporal structure of the Type V ELMs is presented, as measured by several different diagnostics. The composite picture of the Type V ELM is of an instability with one or two filaments that rotate toroidally at ~5-10 km/s, in the direction opposite to the plasma current and neutral beam injection. The toroidal extent of Type V ELMs is typically ~5 m, whereas the cross-field (radial) extent is typically 10 cm (3cm), yielding a portrait of an electromagnetic, ribbon-like perturbation aligned with the total magnetic field. The filaments comprising the Type V ELM appear to be destabilized near the top of the H-mode pedestal and drift radially outward as they rotate toroidally. After the filaments come in contact with the open field lines, the divertor plasma perturbations are qualitatively similar to other ELM types, albeit with only one or two filaments in the Type V ELM versus more filaments for Type I and Type III ELMs. Preliminary stability calculations eliminate pressure driven modes as the underlying instability for Type V ELMs, but more work is required to determine if current driven modes are responsible for destabilization.
Buchanan, Evan G; James, William H; Choi, Soo Hyuk; Guo, Li; Gellman, Samuel H; Müller, Christian W; Zwier, Timothy S
2012-09-07
Single-conformation infrared spectra in the amide I and amide II regions have been recorded for a total of 34 conformations of three α-peptides, three β-peptides, four α/β-peptides, and one γ-peptide using resonant ion-dip infrared spectroscopy of the jet-cooled, isolated molecules. Assignments based on the amide NH stretch region were in hand, with the amide I/II data providing additional evidence in favor of the assignments. A set of 21 conformations that represent the full range of H-bonded structures were chosen to characterize the conformational dependence of the vibrational frequencies and infrared intensities of the local amide I and amide II modes and their amide I/I and amide II/II coupling constants. Scaled, harmonic calculations at the DFT M05-2X/6-31+G(d) level of theory accurately reproduce the experimental frequencies and infrared intensities in both the amide I and amide II regions. In the amide I region, Hessian reconstruction was used to extract local mode frequencies and amide I/I coupling constants for each conformation. These local amide I frequencies are in excellent agreement with those predicted by DFT calculations on the corresponding (13)C = (18)O isotopologues. In the amide II region, potential energy distribution analysis was combined with the Hessian reconstruction scheme to extract local amide II frequencies and amide II/II coupling constants. The agreement between these local amide II frequencies and those obtained from DFT calculations on the N-D isotopologues is slightly worse than for the corresponding comparison in the amide I region. The local mode frequencies in both regions are dictated by a combination of the direct H-bonding environment and indirect, "backside" H-bonds to the same amide group. More importantly, the sign and magnitude of the inter-amide coupling constants in both the amide I and amide II regions is shown to be characteristic of the size of the H-bonded ring linking the two amide groups. These amide I/I and
Directory of Open Access Journals (Sweden)
MIHAIL PRICOP
2016-06-01
Full Text Available Vulnerable and critical mechanical systems are bearings and drive belts. Signal analysis of vibration highlights the changes in root mean square, the frequency spectrum (frequencies and amplitudes in the time- frequency (Short Time Fourier Transform and Wavelet Transform, are the most used method for faults diagnosis and location of rotating machinery. This article presents the results of an experimental study applied on a di agnostic platform of rotating machinery through three Wavelet methods: (Discrete Wavelet Transform -DWT, Continuous Wavelet Transform -CWT, Wavelet Packet Transform -WPT with different mother wavelet. Wavelet Transform is used to decompose the original sig nal into sub -frequency band signals in order to obtain multiple data series at different resolutions and to identify faults appearing in the complex rotation systems. This paper investigates the use of different mother wavelet functions for drive belts and bearing fault diagnosis. The results demonstrate the possibility of using different mother wavelets in rotary systems diagnosis detecting and locating in this way the faults in bearings and drive belts.
Taleb-Mokhtari, Ilham Naoual; Lazreg, Abbassia; Sekkal-Rahal, Majda; Bestaoui, Noreya
2016-01-01
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.
Rishard, Mohamed Z M; Irwin, Richard M; Laane, Jaan
2007-02-08
Our previously published infrared and Raman spectra of 1,3-disilacyclobutane (13DSCB) and its 1,1,3,3-d4 isotopomer have been reexamined and partially reassigned on the basis of DFT and ab initio calculations. The calculations confirm previous microwave work that the CSiC angles in the ring are unexpectedly larger than the SiCSi angles. This may arise from the partial charges on the ring atoms. The calculations are in excellent agreement with the observed spectra in both frequency and intensity. They also demonstrate that this molecule has CH2 wagging and twisting vibrations with frequencies below 1000 cm-1, about 200 cm-1 lower than expected. These unprecedented low values can be explained by the decreased slope in the potential energy curves for these vibrations as the sideways motions of the CH2 groups result in attractive forces between the positively charged hydrogens on the carbon atoms and the negatively charged hydrogens on the silicon atoms. The theoretical calculations also confirm the previous conclusions that the individual molecules (vapor) have C2v symmetry whereas in the solid the molecules become planar with D2h symmetry. The vibrational coupling between the ring-angle bending mode and the SiH2 in-phase rocking, which is present for the C2v structure, is forbidden for D2h and hence disappears.
Directory of Open Access Journals (Sweden)
Lihua Liang
2017-01-01
Full Text Available An adaptive sliding mode controller based on fuzzy input design is presented, in order to reduce the roll motion of surface vessel fin stabilizers with shock and vibration of waves. The nonlinearities and uncertainties of the system including feedback errors and disturbance induced by waves are analyzed. And the lift-feedback system is proposed, which improves the shortage of conventional fin angle-feedback. Then the fuzzy input-based adaptive sliding mode control is designed for the system. In the controller design, the Lyapunov function is adopted to guarantee the system stability. Finally, experimental results demonstrate the superior performance of the controller designed using fuzzy input, when compared to the PID controller used in practical engineering.
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 co
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 ...
Nonlinear localized modes in dipolar Bose–Einstein condensates in two-dimensional optical lattices
Energy Technology Data Exchange (ETDEWEB)
Rojas-Rojas, Santiago, E-mail: srojas@cefop.cl [Center for Optics and Photonics and MSI-Nucleus on Advanced Optics, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Departamento de Física, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Naether, Uta [Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Delgado, Aldo [Center for Optics and Photonics and MSI-Nucleus on Advanced Optics, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Departamento de Física, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Vicencio, Rodrigo A. [Center for Optics and Photonics and MSI-Nucleus on Advanced Optics, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago (Chile)
2016-09-16
Highlights: • We study discrete two-dimensional breathers in dipolar Bose–Einstein Condensates. • Important differences in the properties of three fundamental modes are found. • Norm threshold for existence of 2D breathers varies with dipolar interaction. • The Effective Potential Method is implemented for stability analysis. • Uncommon mobility of 2D discrete solitons is observed. - Abstract: We analyze the existence and properties of discrete localized excitations in a Bose–Einstein condensate loaded into a periodic two-dimensional optical lattice, when a dipolar interaction between atoms is present. The dependence of the Number of Atoms (Norm) on the energy of solutions is studied, along with their stability. Two important features of the system are shown, namely, the absence of the Norm threshold required for localized solutions to exist in finite 2D systems, and the existence of regions in the parameter space where two fundamental solutions are simultaneously unstable. This feature enables mobility of localized solutions, which is an uncommon feature in 2D discrete nonlinear systems. With attractive dipolar interaction, a non-trivial behavior of the Norm dependence is obtained, which is well described by an analytical model.
Lin, C S; Lim, H S; Wang, Z K; Ng, S C; Kuok, M H; Adeyeye, A O
2011-03-01
An understanding of the spin dynamics of nanoscale magnetic elements is important for their applications in magnetic sensing and storage. Inhomogeneity of the demagnetizing field in a non-ellipsoidal magnetic element results in localization of spin waves near the edge of the element. However, relative little work has been carried out to investigate the effect of the applied magnetic fields on the nature of such localized modes. In this study, micromagnetic simulations are performed on an equilateral triangular nanomagnet to investigate the magnetic field dependence of the mode profiles of the lowest-frequency spin wave. Our findings reveal that the lowest-frequency mode is localized at the base edge of the equilateral triangle. The characteristics of its mode profile change with the ground state magnetization configuration of the nanotriangle, which, in turn, depends on the magnitude of the in-plane applied magnetic field.
Relationship of edge localized mode burst times with divertor flux loop signal phase in JET
Energy Technology Data Exchange (ETDEWEB)
Chapman, S. C., E-mail: S.C.Chapman@warwick.ac.uk [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry (United Kingdom); Max Planck Institute for the Physics of Complex Systems, Dresden (Germany); Dendy, R. O. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry (United Kingdom); Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire (United Kingdom); JET-EFDA, Culham Science Centre, Abingdon, Oxfordshire (United Kingdom); Todd, T. N.; Webster, A. J.; Morris, J. [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire (United Kingdom); JET-EFDA, Culham Science Centre, Abingdon, Oxfordshire (United Kingdom); Watkins, N. W. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry (United Kingdom); Max Planck Institute for the Physics of Complex Systems, Dresden (Germany); Centre for the Analysis of Time Series, London School of Economics, London (United Kingdom); Department of Engineering and Innovation, Open University, Milton Keynes (United Kingdom); Calderon, F. A. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry (United Kingdom); JET-EFDA, Culham Science Centre, Abingdon, Oxfordshire (United Kingdom)
2014-06-15
A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM.
Impact of intrinsic localized modes of atomic motion on materials properties
Energy Technology Data Exchange (ETDEWEB)
Manley, M E
2010-01-20
Recent neutron and x-ray scattering measurements show intrinsic localized modes (ILMs) in metallic uranium and ionic sodium iodide. Here, the role ILMs play in the behavior of these materials is examined. With the thermal activation of ILMs, thermal expansion is enhanced, made more anisotropic, and, at a microscopic level, becomes inhomogeneous. Interstitial diffusion, ionic conductivity, the annealing rate of radiation damage, and void growth are all influenced by ILMs. The lattice thermal conductivity is suppressed above the ILM activation temperature while no impact is observed in the electrical conductivity. This complement of transport properties suggests that ILMs could improve thermoelectric performance. Ramifications also include thermal ratcheting, a transition from brittle to ductile fracture, and possibly a phase transformation in uranium.
Enhanced toroidal flow stabilization of edge localized modes with increased plasma density
Cheng, Shikui; Zhu, Ping; Banerjee, Debabrata
2017-09-01
Toroidal flow alone is generally thought to have an important influence on tokamak edge pedestal stability, even though theoretical analysis often predicts merely a weak stabilizing effect of toroidal flow on the edge localized modes (ELMs) in experimental parameter regimes. For the first time, we find from two-fluid MHD calculations that such a stabilization, however, can be significantly enhanced by increasing the edge plasma density. Our finding resolves a long-standing mystery whether or how toroidal rotation can indeed have an effective influence on ELMs, and explains why the ELM mitigation and suppression by toroidal rotation are more favorably achieved in higher collisionality regime in recent experiments. The finding suggests a new control scheme on modulating toroidal flow stabilization of ELMs with plasma density, along with a new additional constraint on the optimal level of plasma density for the desired edge plasma conditions.
An approach to the damping of local modes of oscillations resulting from large hydraulic transients
Energy Technology Data Exchange (ETDEWEB)
Dobrijevic, D.M.; Jankovic, M.V.
1999-09-01
A new method of damping of local modes of oscillations under large disturbance is presented in this paper. The digital governor controller is used. Controller operates in real time to improve the generating unit transients through the guide vane position and the runner blade position. The developed digital governor controller, whose control signals are adjusted using the on-line measurements, offers better damping effects for the generator oscillations under large disturbances than the conventional controller. Digital simulations of hydroelectric power plant equipped with low-head Kaplan turbine are performed and the comparisons between the digital governor control and the conventional governor control are presented. Simulation results show that the new controller offers better performances, than the conventional controller, when the system is subjected to large disturbances.
Directory of Open Access Journals (Sweden)
Abobaker M. Jaber
2014-01-01
Full Text Available Empirical mode decomposition (EMD is particularly useful in analyzing nonstationary and nonlinear time series. However, only partial data within boundaries are available because of the bounded support of the underlying time series. Consequently, the application of EMD to finite time series data results in large biases at the edges by increasing the bias and creating artificial wiggles. This study introduces a new two-stage method to automatically decrease the boundary effects present in EMD. At the first stage, local polynomial quantile regression (LLQ is applied to provide an efficient description of the corrupted and noisy data. The remaining series is assumed to be hidden in the residuals. Hence, EMD is applied to the residuals at the second stage. The final estimate is the summation of the fitting estimates from LLQ and EMD. Simulation was conducted to assess the practical performance of the proposed method. Results show that the proposed method is superior to classical EMD.
Localized Majorana-Like Modes in a Number-Conserving Setting: An Exactly Solvable Model.
Iemini, Fernando; Mazza, Leonardo; Rossini, Davide; Fazio, Rosario; Diehl, Sebastian
2015-10-09
In this Letter we present, in a number conserving framework, a model of interacting fermions in a two-wire geometry supporting nonlocal zero-energy Majorana-like edge excitations. The model has an exactly solvable line, on varying the density of fermions, described by a topologically nontrivial ground state wave function. Away from the exactly solvable line we study the system by means of the numerical density matrix renormalization group. We characterize its topological properties through the explicit calculation of a degenerate entanglement spectrum and of the braiding operators which are exponentially localized at the edges. Furthermore, we establish the presence of a gap in its single particle spectrum while the Hamiltonian is gapless, and compute the correlations between the edge modes as well as the superfluid correlations. The topological phase covers a sizable portion of the phase diagram, the solvable line being one of its boundaries.
Generation of localized modes in an electrical lattice using subharmonic driving.
English, L Q; Palmero, F; Candiani, P; Cuevas, J; Carretero-González, R; Kevrekidis, P G; Sievers, A J
2012-02-24
We show experimentally and numerically that an intrinsic localized mode (ILM) can be stably produced (and experimentally observed) via subharmonic, spatially homogeneous driving in the context of a nonlinear electrical lattice. The precise nonlinear spatial response of the system has been seen to depend on the relative location in frequency between the driver frequency, ω(d), and the bottom of the linear dispersion curve, ω(0). If ω(d)/2 lies just below ω(0), then a single ILM can be generated in a 32-node lattice, whereas, when ω(d)/2 lies within the dispersion band, a spatially extended waveform resembling a train of ILMs results. To our knowledge, and despite its apparently broad relevance, such an experimental observation of subharmonically driven ILMs has not been previously reported.
Suppression of edge localized mode crashes by multi-spectral non-axisymmetric fields in KSTAR
Kim, Jayhyun; Park, Gunyoung; Bae, Cheonho; Yoon, Siwoo; Han, Hyunsun; Yoo, Min-Gu; Park, Young-Seok; Ko, Won-Ha; Juhn, June-Woo; Na, Yong Su; The KSTAR Team
2017-02-01
Among various edge localized mode (ELM) crash control methods, only non-axisymmetric magnetic perturbations (NAMPs) yield complete suppression of ELM crashes beyond their mitigation, and thus attract more attention than others. No other devices except KSTAR, DIII-D, and recently EAST have successfully achieved complete suppression with NAMPs. The underlying physics mechanisms of these successful ELM crash suppressions in a non-axisymmetric field environment, however, still remain uncertain. In this work, we investigate the ELM crash suppression characteristics of the KSTAR ELMy H-mode discharges in a controlled multi-spectral field environment, created by both n=2 middle reference and n=1 top/bottom proxy in-vessel control coils. Interestingly, the attempts have produced a set of contradictory findings, one expected (ELM crash suppression enhancement with the addition of n = 1 to the n = 2 field at relatively low heating discharges) and another unexpected (ELM crash suppression degradation at relatively high heating discharges) from the earlier findings in DIII-D. This contradiction indicates the dependence of the ELM crash suppression characteristics on the heating level and the associated kink-like plasma responses. Preliminary linear resistive MHD plasma response simulation shows the unexpected suppression performance degradation to be likely caused by the dominance of kink-like plasma responses over the island gap-filling effects.
Ansari, R.; Arjangpay, A.
2014-09-01
The meshless local Petrov-Galerkin (MLPG) method is implemented to analyze the free vibration and axial buckling characteristics of single-walled carbon nanotubes (SWCNTs) with different boundary conditions. To this end, a nonlocal shell model accounting for the small scale effect is used. In the theoretical formulations, a variational form of the Donnell shell equations is constructed over a local sub-domain which leads to derivation of the mass, stiffness and geometrical stiffness matrices. Comprehensive results for the resonant frequencies and critical axial buckling loads of SWCNTs are presented. The influences of boundary conditions, nonlocal parameter and geometrical parameters on the mechanical behavior of SWCNTs are fully investigated. The results obtained from the present numerical scheme are shown to be in good agreement with those from exact solution for simply-supported SWCNTs and those of molecular dynamics simulations. It is shown that the natural frequencies and critical axial buckling loads of SWCNTs are strongly dependent on the small scale effect and geometrical parameters.
Huang, Yuanyuan; Hou, Panyu; Yuan, Xinxing; Chang, Xiuying; Zu, Chong; He, Li; Duan, Luming; CenterQuantum Information, IIIS, Tsinghua University, Beijing 100084, PR China Team; Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA Team
2016-05-01
Quantum teleportation is of great importance to various quantum technologies, and has been realized between light beams, trapped atoms, superconducting qubits, and defect spins in solids. Here we report an experimental demonstration of quantum teleportation from light beams to vibrational states of a macroscopic diamond under ambient conditions. In our experiment, the ultrafast laser technology provides the key tool for fast processing and detection of quantum states within its short life time in macroscopic objects consisting of many strongly interacting atoms that are coupled to the environment, and finally we demonstrate an average teleportation fidelity (90 . 6 +/- 1 . 0) % , clearly exceeding the classical limit of 2/3. Quantum control of the optomechanical coupling may provide efficient ways for realization of transduction of quantum signals, processing of quantum information, and sensing of small mechanical vibrations. Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, PR China.
Vibrational properties of the Pt(111)- p(2 × 2)-K surface superstructure
Rusina, G. G.; Eremeev, S. V.; Borisova, S. D.; Chulkov, E. V.
2008-08-01
The vibrational spectra of the Pt(111)- p(2 × 2)-K ordered surface superstructure formed on the platinum surface upon adsorption of 0.25 potassium monolayer are calculated using the interatomic interaction potentials obtained within the tight-binding approximation. The surface relaxation, the dispersion of surface phonons, the local density of surface vibrational states, and the polarization of vibrational modes of adatoms and substrate atoms are discussed. The theoretical results are in good agreement with the recently obtained experimental data.
Localized Modes of the Linear Periodic Schr\\"{o}dinger Operator with a Nonlocal Perturbation
Dohnal, Tomá?; Reichel, Wolfgang
2008-01-01
We consider the existence of localized modes corresponding to eigenvalues of the periodic Schr\\"{o}dinger operator $-\\partial_x^2+ V(x)$ with an interface. The interface is modeled by a jump either in the value or the derivative of $V(x)$ and, in general, does not correspond to a localized perturbation of the perfectly periodic operator. The periodic potentials on each side of the interface can, moreover, be different. As we show, eigenvalues can only occur in spectral gaps. We pose the eigenvalue problem as a $C^1$ gluing problem for the fundamental solutions (Bloch functions) of the second order ODEs on each side of the interface. The problem is thus reduced to finding matchings of the ratio functions $R_\\pm=\\frac{\\psi_\\pm'(0)}{\\psi_\\pm(0)}$, where $\\psi_\\pm$ are those Bloch functions that decay on the respective half-lines. These ratio functions are analyzed with the help of the Pr\\"{u}fer transformation. The limit values of $R_\\pm$ at band edges depend on the ordering of Dirichlet and Neumann eigenvalues ...
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....